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# Senior Capstone Projects

Toward the end of the junior year, each physics major is paired up with a faculty member to develop a significant and individualized research project that will be undertaken during the student’s senior year.

Rochester Institute of Technology College of Science

## Browse Capstone Projects

Height Dependence of Flow in Sheared Granular Materials

## Height Dependence of Flow in Sheared Granular Materials

Granular materials are composed of many macroscopic solid particles and display solid and fluid-like characteristics. One area of interest is particle behavior under shear, when forces are applied parallel to the surface causing particles to flow over each other. I measure the effects of 2-D shear over long periods by filming particles in an annulus while inducing shear from the top. For this Capstone research project, I improved the experimental apparatus and gathered data to investigate pile stiffness and the flowing and non-flowing regimes for a mixture of circular particles. I also investigated the effect of a few elliptical particles in a mixture of circles. We measure a length scale associated with the penetration depth of motion imposed at the top and find this depth grows linearly with increased pressure. The slope of this line is inversely related to pile stiffness, and we observe shorter piles to have a lower slope indicating a greater stiffness.

Student Author: Daniel Gysbers

Published: 2018

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Generating Si and III-V Nanowire Arrays for Solar Cell Applications Via MacEtch Fabrication

## Generating Si and III-V Nanowire Arrays for Solar Cell Applications Via MacEtch Fabrication

The process of MacEtch introduces an inexpensive semiconductor substrate etching technique that can be completed in a fume hood with no addition of complex lab tools. Surface features developed via MacEtch are characterized by high aspect ratios with high crystalline quality at precise locations. By developing solar cells via MacEtch fabrication and utilizing substrate surface features, production cost can be lowered while device performance can be improved. Thus far, a catalytic Au layer of (48 ±7) nm thickness has been deposited via electroplating and surface features of interest have been generated via MacEtch. Optical measurements of reflectance are pending.

Student Author: Alex Kolberg

Published: 2018

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Inertia Versus Elasticity in Flow of Polymer Solutions Around a Sharp Bend

## Inertia Versus Elasticity in Flow of Polymer Solutions Around a Sharp Bend

Abstract: Fluid dynamic simulations using the FENE-P model of polymer physics are compared to those of a incompressible Newtonian fluid base case in order to under- stand how the four dimensionless numbers, Re, De, El, and *β* affect vortices in a right- angle bend geometry. It is shown that increasing Re, De, or lower *β* will cause vortices to grow in size. It is also shown that elasticity delays the formation of inertial vortices. Two phase space diagrams, one for De vs. Re and one for *β* vs. El, were made to show the range of values where inertial, elastic, and no vortices form.

Student Author: Brian Wojcik

Published: 2018

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Titanium Thin Films on Silicon

## Titanium Thin Films on Silicon

Producing effective catalytic surfaces is an ever-important part of energy production and storage. This study attempts to examine potentially effective catalytic surfaces through the deposition of titanium thin films on Boron-doped silicon substrates. Ti-tanium is sublimated onto the substrate, and then annealed. Through the annealing process titanium silicides start to form, which are studied via Auger emission spec-tropscopy (AES) or x-ray photoelectron spectroscopy (XPS). So as to avoid oxidation, the deposition chamber and spectrometer are both under ultra-high vacuum (UHV), reaching pressures of 10^{-9} Torr. AES and XPS provide crucial information about the chemical composition of the surface, and can also provide a depth profile of the chem-ical composition. As the incident electron or x-ray beam interacts with the electrons on the surface, there are emissions detected that are very sensitive to their constituent atoms. A precise categorization of the chemical properties of these materials will help us work towards creating more effective catalysts.

Student Author: Conner Brown

Published: 2018

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Exchange Bias of Permalloy Based Ferromagnetic Multilayers Compared to Their Alloy

## Exchange Bias of Permalloy Based Ferromagnetic Multilayers Compared to Their Alloy

Throughout the duration of this capstone project, a transverse magneto-optic Kerr effect apparatus was brought to working status after several months of being o-line through use of manuals and past documentation. Once calibrated, the system was used to start analyzing the exchange bias of multilayer samples consisting of permalloy-based ferromagnets interacting with an antiferromagnet. Results of the data are conflicting as to whether the multilayer structure makes any difference in the exchange bias, however more data must be taken to approve or disavow the results.

Student Author: Frank Schooner

Published: 2018

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The Roles of Math Skills and Tools in Scientific Academia and Industry

## The Roles of Math Skills and Tools in Scientific Academia and Industry

This research investigated the kinds of high-level goal driven math activities and math processes, as well as mathematical tools, that are found within two disciplinary cultures: science and engineering workplaces in industry and physics research workplaces in academia. Semi-structured interviews, done with participants from both cultures, were transcribed by a third party transcription service and then analyzed to explore what types of high-level goal driven math activities and math processes are found in RIT physics PhD research and in the Photonics workforce around the Rochester area. Two different interview protocols were used: one for graduate students doing physics PhD research and the other for engineers and technicians in scientific industry. Key features of math usage were identified through a method of emergent coding, where relevant themes were coded by going through each transcribed interview and highlighting all instances of math usage. In total, there are 10 interviews (375 minutes) with PhD students and 22 interviews (1,345 minutes) with engineers and technicians from industry. Analysis of the data showed that both the PhD and industry main codes and subcodes could be rearranged into categories, which enabled direct comparisons to be made between the two cultures. The high-level goal driven math activities are represented by the main codes, while the math processes are represented by the subcodes. Prevalent high-level goal driven math activities found within PhD research include: “sense making”, “modeling”, “answering research questions with evidence”, and “calculations”. Prevalent high-level goal driven math activities found within the Photonics workforce include: “sense making”, “modeling”, “design and fabrication”, “maximizing efficiency”, and “getting a number”. Connected to each of these math activities are math processes that were also identified; these will be discussed in further detail later in the paper. With regards to math tools, the PhD findings were also categorized into tasks that used analytical math, computational math, or both. Due to minimal emphasis on the usage of math tools within the industry interview protocol, a direct categorization of analytical or computational math tools was not done for the industry data. Instead, the types of math tools in industry will addressed with a brief discussion later in the paper. The ultimate goal of this research is to add foundation to physics education research on workplace studies, as well as make implications on current physics curriculum design.

Student Author: Kingston Chen

Published: 2018

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Modeling Double Networks According to Rigidity Percolation Theory to Study

## Modeling Double Networks According to Rigidity Percolation Theory to Study

Articular cartilage (AC) is a soft tissue that covers the ends of bones, providing a smooth cushion and shock absorption at the joints.1 Adult AC has very few cells, and can be thought of as a network-like matrix made of fibers. This matrix has a double network structure, and is made of a stiff network of collagen fibers and a flexible network of proteins called aggrecan. As a material, AC is remarkable. It is only a few millimeters thick, yet can withstand large forces over 100-200 million loading cycles without fracturing. Here we investigate the structure-function properties underlying the fracture toughness of AC by using a framework that combines a double network model of cartilage with rigidity percolation theory. We study how the stiffness, stress-strain properties, toughness, and crack propagation in the double network depend on its composition and on loading conditions. Our results may help to formulate a quantitative criterion for crack propagation in soft tissues that have a double network structure.

Student Author: Leo Sutter

Published: 2018

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Construction of a Laboratory Apparatus to Investigate Fluid Flows and Instabilities

## Construction of a Laboratory Apparatus to Investigate Fluid Flows and Instabilities

The goal of this project was to build a working laboratory device that demonstrates fluid flow properties and will be useful in future undergraduate lab experiments. An experimental apparatus was built containing the fluid to be studied and this fluid is driven by a both a current and a magnetic field. Tracker particles placed in the fluid allow for study of fluid motion via a camera recording. The particles are then tracked using image processing software and their trajectories are analyzed. The analyzed trajectories are used to investigate instabilities and discern where they occur. The apparatus is designed to produce interesting qualitative and quantitative observations about the physics of fluid flow.

Student Author: Rifet Musedinovic

Published: 2018

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Apparatus for Measurement of Basic Ferromagnetic Properties

## Apparatus for Measurement of Basic Ferromagnetic Properties

The goal of the project was to develop a simple and robust system that demonstrates the basic properties of ferromagnetism that could be used as an Advanced Lab experiment at RIT or elsewhere. Ideally the apparatus would be simple in construction and use, and will show the magnetization of some material as a function of temperature. This allows for a simple introduction to a common magnetic phase transition through exploration of the Curie Temperature of a ferromagnetic material. Using an inductive bridge, the magnetometer was completed, tested, and performed accurately as anticipated.

Student Author: Zachary Assenmacher

Published: 2018

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The Effects of Sublimation on the Response Function of an Active Galactic Nuclei’s Dusty Torus

## The Effects of Sublimation on the Response Function of an Active Galactic Nuclei’s Dusty Torus

Abstract: Probing the structure of active galactic nuclei provides significant challenges, as they are not resolvable by current telescopes. This paper focuses on implementing pure graphite clouds into TORMAC, a simulation of the response of the infrared emission of the AGNs dusty torus to variations in the AGN luminosity. The torus surrounding the AGN’s accretion disk absorbs and reemits light from the disk, TORMAC simulates this reverberation response. The dust emission spectra of individual clouds are calculated by another code called DUSTY and built into a grid which is read by TORMAC. Dust sublimation can significantly affect the torus response, by changing the composition of clouds near the inner edge. These effects were modeled by implementing a two-component cloud population in TORMAC, clouds start with a mixture of silicate and graphite dust grains, with a range of sizes, but transition to clouds containing only large graphite grains when they reach a critical temperature. The new version was tested and a set of models computed and compared with one-component models. Sublimation affects the reverberation response light curves by smoothing out features and increasing the brightness at shorter wavelengths.

Student Author: Bryanne McDonough

Published: 2018

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Frequency Control and Gyroscopic Stabilization of Levitated Graphene Nanoplatelets

## Frequency Control and Gyroscopic Stabilization of Levitated Graphene Nanoplatelets

The study of nanoscale systems has been of great interest in recent years, with applications ranging from bridging the gap between quantum and macroscopic effects to high precision force sensing. Levitating these systems provides the advantage of reducing the coupling to the surrounding environment, allowing for even greater measurement sensitivity. Driving these levitated systems at high frequencies can further increase their sensitivity, stabilizing them via gyroscopic effects. We consider a graphene nanoplatelet levitated in a quadrupole ion trap and driven by a circularly polarized laser. An oscillatory electric field is then applied and the rotation of the platelet is locked to the frequency of the field. The frequency locking stabilizes the axis of rotation of the platelet over time to be normal to the surface of the platelet. Properties of the platelet such as its dimensions, dipole moment, and charge can be determined from the optical signal obtained. In this paper we investigate the use of this system as a mass measurement device, the phase shifts this use imparts on the platelet, and the stability of the interactions between the platelet and an external magnetic field. We investigate potential causes for an experimentally observed cooling effect, and present a method of heating the translational degrees of freedom.

Student Author: Wyatt Wetzel

Published: 2018

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Strengths of Wet Non Uniform Granular Materials

## Strengths of Wet Non Uniform Granular Materials

A granular material is a conglomerate of discrete macroscopic particles. Sand, a granular material of the size 200-300 microns, that is wet, can support more weight than dry sand. When silt, another granular material of the size 20-40 microns, is added to this wet sand, the structure collapses under less weight. The strength, or how much weight a column of granular material can support, depends on the ratio of sand and silt as well as the percent moisture in the sample. The strength can be measured directly or by measuring the angle of repose. The angle of repose can be found by using the process of column collapse, which is allowing a column of granular material to collapse and form a pile. Columns that don’t collapse have a force applied to the top, and this force will be the strength of the piles that don’t naturally collapse. Both of these techniques are used to determine the relative strengths of different silt to sand ratios. During capstone 2, Granular materials are sent flowing down a vibrating ramp. A hyperspectral camera is used to observe the flow, and the camera creates an image cube. The image cube generated is a preliminary piece of data that will set the groundwork for a new series of experiments.

Student Author: Ryan Warner

Published: 2017

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Hypermassive Black Holes and Lineless Quasars

## Hypermassive Black Holes and Lineless Quasars

The relationship between a quasars relative emission line strength (equivalent width) from the broad line region (BLR) and their central black hole’s mass (M* _{BH)}* is not well studied. I created a program to model the spectrum of quasars for varying central black hole mass in attempt to study this relation and compare my results to data observed by the Sloan Digital Sky Survey (SDSS). It was expected that we would find an inverse relation of equivalent width vs MBH but the SDSS data showed, instead, a wide distribution of H

_{beta}, H

_{alpha}, and CIV

_{1549}equivalent width for varying M

_{BH}. Many factors including the Eddingtion ratio, inclination angle, dust sublimation and host galaxy contamination could be attributed to the distribution that was observed. I am confident that we understand why a wide distribution was observed, and is due to the possibility that the relative emission line strength changes statistically with black hole mass. This would conceal the relationship that the thin accretion disk model predicts. Using my model along with a locally optimally emitting cloud (LOC) ionization model I show that quasars with hypermassive black holes, M

_{BH}> 10

^{10}M

_{}, can be identified by their red color and weak broad emission lines. This is in contrast to how the SDSS DR7 quasar catalog flags candidates by finding blue objects with strong broad emission lines.

Student Author: Shawn Foster

Published: 2017

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Spin Squeezing the Coherent States of a Single Molecule Magnet

## Spin Squeezing the Coherent States of a Single Molecule Magnet

In this second part of the Capstone project, we further develop the concept of spin squeezing on coherent states by adopting the model of single molecule magnets. Whereas the first part was focused on numerical simulations and modeling, this paper develops analytic results by making use of a series of approximations and by considering special cases. We give simple, closed form expressions that model some aspects of squeezing, including minimum squeezing and fractional squeezing time. Lastly we present a framework for the incorporation of tunneling in spin squeezing through perturbation theory.

Student Author: Stefano Marin

Published: 2017

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X-Ray Diffraction and 2D Area Detectors

## X-Ray Diffraction and 2D Area Detectors

The installation of a 2D area detector is vital for future experimentation involving x-ray diffraction. A detector utilizing a multi-wire proportional chamber was analyzed for viability, interfaced with a computer, refurbished and calibrated. It was determined the detector is capable of observing x-rays produced by an x-ray tube and scan diffraction patterns. Additionally, meaningful scan data can be exported and analyzed. The dimensions of the active area of the detector was determined to be 11.5 cm by 11.5 cm. The efficiency relative to a photo-multiplying tube (PMT) was improved from 0.1% to 60.0 %. This was done by servicing the detector, meaning that the xenon-hydrogen gas blend in the detector was exchanged for an argon-methane blend. After the gas exchange, the detector was again checked for viability by exploring parameters needed to observe a diffraction pattern and scanning various known powder samples and comparing them with scans taken with a point detector under the same conditions. Now that the detector has been determined to be in working order, a variety of sample structures can be studied via x-ray diffraction for numerous research purposes. This new technology allows for expedited sample since the detector has the ability to take scans quicker than the point detector currently in use, however there is some resolution loss.

Student Author: Amy Florio

Published: 2017

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Modeling the Spread of Infectious Diseases Through Territorial Random Walks

## Modeling the Spread of Infectious Diseases Through Territorial Random Walks

The dynamics of the territories of a population of territorial mammals will be modeled as arising from the interaction between a member of the population and the scent markers of the others. The interactions between two members of the population will then be used to model the spread of a non-debilitating disease through the population. These two aspects will be modeled with a variation of constrained random walks.

Student Author: Samuel Washburn

Published: 2017

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Development of Machine Learning Algorithm to Categorize Neutrino-Proton Elastic Scattering and Neutron-Proton Elastic Scattering in MINERvA

## Development of Machine Learning Algorithm to Categorize Neutrino-Proton Elastic Scattering and Neutron-Proton Elastic Scattering in MINERvA

One of the goals of MINERvA is to gather data on the scattering cross section of the neutrino incident on a hadron. For this purpose, it is necessary to filter the desired neutrino interactions from interactions of other particles. MINERvA is able to detect neutral current elastic scattering of neutrinos and protons due to the movement of the charged proton through scintillation strips. How-ever, these neutrino-proton collisions are mixed with neutron-proton collisions due to the presence of neutrons in the incident beam. The energies deposited from the scattering form different patterns between neutrino and neutron scattering. It is necessary due to the large amount of scattering data produced by MINERvA to develop an algorithm to filter out the neutron scattering to prevent them from polluting further analysis. The ROOT Data Analysis Toolkit was used to generate a basic neural network to categorize the events. After this method was deemed ineffective, a Convolutional Neural Network based on LeNet was developed and executed using Caffe. The LeNet network generated a categorization accuracy of 0.974 with our simple toy model and an accuracy of 0.9075 with more realistic Monte Carlo simulations from Fermilab. The best cut was determined to be at 0.47for the output node value. The purity and efficiency of the classification at this cut were determined to be 0.93 and 0.89, respectively.

Student Author: Aidan Thorn

Published: 2017

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Galaxy Classification Schemes focusing on Early Universe Galaxies

## Galaxy Classification Schemes focusing on Early Universe Galaxies

Galaxy mergers in the early universe may help researchers understand the evolution of galaxies and predict the processes driving galaxy growth and formation. Existing galaxy classification methods perform poorly when trying to detect galaxy mergers at high redshifts. The current best practice is to use extensive visual classification to classify galaxies based on estimated morphology. While visual classification is the most robust system currently available, this method is impractical for extremely large data sets due to the required human effort. This paper outlines the results of our improvements on existing methods of locating mergers and irregular galaxies in large datasets in an automated fashion. The first method is performing the Gini vs M20 classification on different sets of galaxies grouped by wavelength. This method is just as effective as the standard analysis with significant improvement. The second method is a system in which we perform two component Sérsic fits on a galaxy image and measure the differences in properties between the two Sérsic components. This method is unsuccessful in locating mergers without significant human intervention and tuning. The third method is to determine the Gini coefficient of the residual of an automated Sérsic t and plot it against the Intensity statistic. This method shows significant promise for being able to locate irregular and merger galaxies in large datasets.

Student Author: Samuel Zimmerman

Published: 2017

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In-Situ X-Ray Photon Correlation Spectroscopy of Ag Nanocubes in Electrolyte on the Pt (111) Surface

## In-Situ X-Ray Photon Correlation Spectroscopy of Ag Nanocubes in Electrolyte on the Pt (111) Surface

The study of catalysis, and chemical conversion in the presence of active metals is of particular interest to many groups. It is interesting not just to study these interactions, but study them in conditions similar to the conditions that can be useful to us. The movement of Ag nanocubes on the surface of a Pt (111) crystal submersed in perchlorate solution was studied in-situ. Synchrotron radiation was used to preform X-Ray Photon Correlation Spectroscopy to quantify the movement of the cubes in solution with different applied potentials to the electrochemical cell which housed the solution. The order of the cubes on the surface of the Pt crystal allowed us to use the Ag (002)peak as the starting point for the measurement. Movement of the individual cubes becoming more or less ordered was able to be seen in the peak itself due to the coherent properties of the x-rays used. A model of the diffraction patterns from multiple cubes together has been developed in order to recreate what was seen at the Synchrotron. This model operates by calculating the diffraction of one cube and the array theorem to quickly generate the diffraction pattern from any other cube in the system. Two different scenarios which seem to be reasonable explanations of what happened in the lab were explored.

Student Author: Christian Cammarota

Published: 2017

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Measuring the Exchange Bias of Various Ferromagnetic Hetero-structures

## Measuring the Exchange Bias of Various Ferromagnetic Hetero-structures

During the course of the Capstone project we were successfully able to setup, and test a fast magnetooptical Kerr effect magnetometer. We added automatic rotation capabilities into the apparatus, and vastly improved speeds of taking data. We then took scans on over 45 different samples and were successfully able to quantify their magnetic properties, and see if our model of exchange bias held up. We concluded that the introduction of materials with different crystal structures induced anisotropy in permalloy, a nickel-iron alloy, and that the exchange bias field is inversely proportional to thickness. We also found that samples with a gradient for their ferromagnet layer had no directional dependence on their magnetic properties.

Student Author: Tighe Bailey

Published: 2017

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Photon Recycling and Open Circuit Voltage Enhancement in Thin Film GaAs Solar Cells

## Photon Recycling and Open Circuit Voltage Enhancement in Thin Film GaAs Solar Cells

Radiative recombination is a fundamental loss mechanism in semiconductor based solar cells, and is dominant in direct band gap materials like Gallium Arsenide. To reduce this loss, we employ substrate removal as a means to enhance photon recycling, or the reabsorption of emitted photons. Optimal cell design and photon recycling were investigated with the simulation program PC1D. The fabrication process for upright and inverted single junction GaAs solar cells was performed and analyzed for its ability to create a successful photon recycling effect. Under AM0 illumination, we measured an open circuit voltage of 1.12 V on the inverted structure, a 120 mV increase compared to the upright control. This result is direct evidence of photon recycling in the device, proving the intended result of substrate removal. Based on our simulation, this corresponds to a reduction in the effective radiative recombination coefficient by a factor of 100, and a PR factor of 99%.

Student Author: George McMurdy

Published: 2017

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Removing the Astrophysical Gravitational Wave Foreground: Comparing the Efficacies of Signal Deletion and Signal Subtraction with Respect to Gravitational Wave Telescope Parameters

## Removing the Astrophysical Gravitational Wave Foreground: Comparing the Efficacies of Signal Deletion and Signal Subtraction with Respect to Gravitational Wave Telescope Parameters

Gravitational waves from astrophysical sources have been detected and the next generation of gravitationalwave telescopes might be able to detect gravitational waves from cosmological background sources. However we expect that these cosmological background signals will be obscured by a substantial astrophysical background which will make analyzing the cosmological background prohibitively difficult. In this paper we assess techniques for removing resolved astrophysical sources from gravitational wave data for the purpose of reducing the astrophysical background and easinganalysis of the cosmological gravitational wave background.

Student Author: Thomas Kilmer

Published: 2017

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Silicon Nanofabrication by Carbon Nanotube-Assisted Chemical Etching

## Silicon Nanofabrication by Carbon Nanotube-Assisted Chemical Etching

Metal-assisted chemical etching (MACE) is a solution-based, room-temperature, and anisotropic etching technique that is routinely used for fabrication of semiconductor nano-/micro-structures. In the conventional MACE process, a semiconductor is interfaced with a patterned noble metal film, which acts as a catalyst to promote local oxidation of the semiconductor when introduced into an etching solution containing an oxidant and an acid. The locally oxidized semiconductor phase is then preferentially etched by the acid in the MACE solution, allowing the catalyst layer to sink into the semiconductor to generate nano-/micro-features along its path. Here, use of patterned carbon-nanotube (CNT) films as an alternative to noble metal catalysts in the MACE method for the fabrication of Si micropillar arrays is investigated for the first time. Vertical and lateral etching trends are analyzed as a function of oxidant concentration, dimensions of the patterned CNT catalytic layer, and duration of the etching process. Chemical analysis of the resultant Si micropillars is performed using Raman spectroscopy, Auger electron spectroscopy, and energy-dispersive X-ray spectrometry. Post-etch features demonstrate maximum etching rates between 73 - 90 nm/min Physical models are provided to demonstrate interpretations of the etching trends. It is concluded that the CNT films do not degrade over time in the etch solution and that they can serve as effective alternatives to conventional MACE catalysts. Based upon these observations, the carbon nanotube assisted chemical etching (CNT-ACE) process can be employed for the fabrication of semiconductor nanostructures with applications in electronics, optoelectronics, and photovoltaics.

Student Author: Ian Kecskes

Published: 2017

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Nonlinear Solutions and Effects for Gravitational Radiation using Various Approximations

## Nonlinear Solutions and Effects for Gravitational Radiation using Various Approximations

Solutions to the *Einstein field equations* (EFE) are seldom discovered due to its nonlinear attributes. To circumvent this dilemma, physicists employ perturbation theory to find approximate forms of the EFE, which to the first-order neglects all nonlinear contributions caused by the perturbation. Linear solutions are appropriate in weak gravitational fields but are often paradoxical and lack self-consistency, even failing to predict work done by gravity. With recent experimental detection of *gravitational waves* (GWs) as our motivation, we are exploring the effect of these higher-order perturbations for solutions in vacuum and simple models, such as compact binaries. The higher order perturbations that are neglected in the linear EFE may yield significant results that can be observed and utilized in the emerging field of GW astronomy.

Student Author: Thomas Larned

Published: 2017

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Initial Data Problems with Binary Black Holes

## Initial Data Problems with Binary Black Holes

Black hole binary systems are the primary sources of observable gravitational waves for LIGO, the Laser Interferometer Gravitational Wave Observatory. In fact, the first detection of gravitational waves, by LIGO, was of a binary black hole merger. Numerical simulations of these systems require initial data to represent the physically possible configurations of the system; however, because of singularities at the centers of the black holes, the source terms in the constraint equations are not smooth, or infinitely differentiable. This can prevent numerical solutions from converging rapidly, especially those that use spectral methods such as the Lorene class package used by many people. This project’s purpose is to numerically solve the initial data problem for such a system more simply by setting the singularities in the black holes to finite functions through the introduction of a multiplicative factor to the constraint equations.

The behavior of the original code has been inspected by looking at the root mean square, rms, error of

∇^{2}*u* in a simplistic system under various conditions. This rms error was calculated by performing 4th order finite differencing on the* u* output by the Lorene system and comparing it to the exact equation the system attempts to solve. Initial analysis includes several regions of space, different finite differencing grid resolutions, and some alterations to the solution method’s shell spacings and resolutions before adding in the “stung” term. The results show an innate error from the solution method through the saturation of rms with increasing finite differencing resolution. This can be at least partially remedied by increasing the resolution of the LORENE shells, but is nearly unaffected by more strategic placements of the shells at a single resolution. Once a geometric stung term of order r^{3} was implemented rms error dropped by 2-3 orders of magnitude and computational requirements fell by 30%.

Student Author: Joshua Dubinsky

Published: 2017

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X-ray Spectral Analysis of the "Changing-Look" Active Galaxy NGC6418

## X-ray Spectral Analysis of the "Changing-Look" Active Galaxy NGC6418

NGC6418 is a Seyfert 1 Active Galactic Nucleus (AGN) that has exhibited qualities of a rare "changing-look"galaxy. Optical observations in the B and V optical bands have demonstrated that 3:6 and 4:5* μm* fluxes lag behind the optical continuum with large variations in intrinsic luminosity. This behavior could be consistent with dust obscuration from a clumpy torus or a dust cloud traversing the line of sight. Recent observational data from the X-ray Multi-mirror Mission (XMM)Newton telescope verifies the previously obtained data from *Chandra*. The most recent survey of NGC6418 indicates that its X-ray spectrum has transitioned back into one similar to a Seyfert Type1 with a low hydrogen column density. It is expected that XMM-Newton observations of the optical spectrum will give additional insight into the mechanism of the "changing-look" characteristics.

Student Author: Lucas Shadler

Published: 2017

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Relativistic Sunyaev Zel’dovich Effect in the mm and sub-mm range

## Relativistic Sunyaev Zel’dovich Effect in the mm and sub-mm range

The Sunyaev-Zeldovich effect is a spectral distortion of the Cosmic Microwave Background (CMB)due to inverse Compton scattering with electrons in the intercluster medium of large hot galaxyclusters. For λ<1.3 mm, there is an increase in the intensity of light emitted by the CMB, and the strength of this increment is directly related to the temperature of the galaxy cluster. For extremely hot clusters,k_{b}T >5 keV, relativistic scattering effects start to become noticeable. We observed 9 hot galaxy clusters with data taken in the sub-mm range by SPIRE on the Herschel Space Observatory. To analyze this data to extract the SZ intensity, we have to subtract the sub-mm background using source subtraction methods. In order to determine the significance of these results, we compare the data to maps with simulated sub-mm background. We find that some clusters match up to the simulations better than others, due to various properties of each cluster

Student Author: Nicholas Bitten

Published: 2017

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Measurement of the magnetocaloric effect in Ni2MnGa based Heusler alloys

## Measurement of the magnetocaloric effect in Ni2MnGa based Heusler alloys

Some magnetic materials exhibit a change in temperature when magnetized. If this magnetocaloric effect were large enough it would be of practical interest, as this temperature change could be used for entirely solid-state refrigeration. Heusler alloys like Ni_{2}MnGa_{1-x} have shown promise, with a large magnetocaloric effect near their structural (martensite) transition. This study has investigated variants of this alloy of the form Ni_{2}MnGa_{1-x} and Ni_{2}Mn_{1-x}Cu_{x}Ga. Bulk magnetization measurements were taken to locate the samples’ structural and magnetic transitions. *ΔT* was measured directly by suddenly immersing the samples in an external field at various temperatures.

Student Author: Alexander Madden

Published: 2016

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Coplanar waveguide ferromagnetic resonance (CPW-FMR) spectroscopy of ferromagnetic/normal metal bilayers

## Coplanar waveguide ferromagnetic resonance (CPW-FMR) spectroscopy of ferromagnetic/normal metal bilayers

This paper contains a brief background and practical approach of using coplanar waveguide ferromagnetic resonance (CPW-FMR) spectroscopy to characterize the properties of ferromagnetic/normal metal (FM/NM) bilayers. The first part will serve as introduction to the applications of using FMR to understand how applying a normal metal to a ferromagnet will affect the ferromagnets magnetization dynamics. A background to FMR spectroscopy and spin pumping will be provided as well as a detailed explanation of the experimental setup. Experimentally, the effect that a copper spacer has on the Gilbert damping parameter α of the bilayer Py/Ir, has been examined. The presence of the copper spacing causes a decrease in α showing that the loss of angular momentum is due to the spin mixing conductance gmix of the interface between Py and Ir. A value of g_{mix}= 1.54 x 10^{19} m^{-2} was measured.

Student Author: Derek Joyce

Published: 2016

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Modeling the mechanics and crack formation in biopolymer networks in soft tissue

## Modeling the mechanics and crack formation in biopolymer networks in soft tissue

The goal of this project is to study the mechanical response and formation of cracks in biopolymer networks in soft tissue using numerical simulations, with articular cartilage (AC) as the motivating experimental system. AC of adult mammals has very few cells and the extracellular matrix primarily determines its mechanical response. This matrix can be thought of as a double network of collagen fibers and proteoglycans (PG), with spatially varying concentration and organization. The collagen fibers are stiff and resist tension and compression forces, while the PG are flexible and control swelling and hydration. To study this system, we constructed a microscopic model made of two interconnected disordered polymer networks: a network of stiff fibers and a network of comparatively flexible fibers. Each network has fiber stretching and bending elasticity chosen to qualitatively mimic the experimental system. We study the mechanical response of this double network as a function of the concentration and stiffness of the individual components, as well as the strength of the connection between them, using rigidity percolation theory. The results may provide insights into the mechanical response of disordered and multi-component soft and biological materials.

Student Author: Joshua Carroll

Published: 2016

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In-Situ X-ray Studies of the Au (111) and (001) Surfaces in Electrolyte and Gas Phase Environments

## In-Situ X-ray Studies of the Au (111) and (001) Surfaces in Electrolyte and Gas Phase Environments

The behavior of atoms and molecules on metallic surface catalysts play an important role in how these complex surfaces function during chemical reactions. However, there are still large gaps found in the understanding of how exactly the collective nature of these atomic structures, along with their dynamics, contribute to a surface’s catalytic properties. Here we present in-situ x-ray scattering measurements of the Au (111) and Au (001) surfaces when exposed to weak NaF electrolyte and Ar, O_{2}, and H_{2} gas environments respectfully. Crystal truncation rod (CTR) measurements were taken to investigate how the surface structure of Au (111) changed while interacting with the electrolyte solution. X-ray photon correlation spectroscopy (XPCS) was used to examine adaptations to the surface dynamics of Au (001) while reacting with O_{2} and H_{2} gases. On the Au (111) surface, the population sizes of the hexagonal and reconstructed \herringbone” domains were found to share a hysteresis relationship with applied voltage. Here, the (00L), (10L), (01L) hexagonal CTRs were measured and revealed that the surface layer of Au (111) relaxes away from the surface and becomes more disordered when the reconstruction is present. Residual Gas Analyzer (RGA) and XPCS data from the Au (001) surface at high temperature (~1080 K) revealed that a water shift reaction occurs when exposed to H_{2} and O_{2}, which causes highly non-linear dynamics to occur on the surface. Future work will go towards relating the surface structure and dynamics of Au in an attempt to gain a better understand for why catalytic surfaces behave as they do.

Student Author: John C. Collini

Published: 2016

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Parameter Estimation of Eccentric Orbit Binaries from Gravitational Wave Signatures

## Parameter Estimation of Eccentric Orbit Binaries from Gravitational Wave Signatures

We have finally entered the era of gravitational wave astronomy. With the sighting of GW150914, it has become a more urgent problem than ever to be able to use gravitational waves to better under- stand our universe. This project is about the further development of tools to extract astrophysical data, in particular eccentricity, from gravitational wave signals. Starting from orbit data, we create a pipeline to test the effectiveness of parameter estimation techniques on compact binaries with eccentric orbits. We have been able to begin to study the effectiveness of these parameter estimation techniques. Initial results seem to indicate that they can effectively isolate the eccentricity of a binary system.

Student Author: Jackson T. Henry

Published: 2016

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The Gas Kinematics and Composition Within the Inner Kiloparsec of NGC4593

## The Gas Kinematics and Composition Within the Inner Kiloparsec of NGC4593

Gas flow at the center of galaxies provides the fuel for the activity in their active galactic nuclei. By studying these gas flows, the accretion and the feedback processes around the black hole can be investigated, thus providing a better understanding of the relation between black holes and their host galaxies. This investigation was performed on active galaxy NGC4593 by analyzing 2-D spectroscopic data of its inner kiloparsec. The data was used to measure the emission line flux, the velocity, and the velocity dispersion of the gas. These provided information on the gas velocity field, local turbulence, mass flow rates, and ionization mechanisms within this innerkiloparsec. From this investigation, it was concluded that the center ( ≈ inner 1 arcsecond) contains a high electron density and is ionized by a Seyfert AGN, while the outermost regions contain low electron densities and are ionized by the AGN as well as HII regions. The velocity field is dominated by rotation but out outflows are apparent when a stellar rotation model is subtracted.

Student Author: John Reuter

Published: 2016

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Photometric Analysis of the Contact Binary HH UMa

## Photometric Analysis of the Contact Binary HH UMa

Light curves in the B,V,R, and I bands for the low-mass eclipsing binary HH UMa were created by obtaining and analyzing data from the Rochester Institute of Technology (RIT) Observatory and the Kitt Peak National Observatory. Science and calibration images were obtained using the 0.9 meter WIYN telescope at Kitt Peak and the 12 inch Meade telescope at RIT. Light curves were extracted from these images, and times of the primary and secondary minima were calculated and combined with the times of minima from previous works to create an O-C diagram. It was found that the orbital period of the system is lengthening by (10± 4)X10^{10} days/day. The mechanism causing the period to increase remains unknown; however, it is possible that magnetic braking is contributing to this increase.

Student Author: Kaitlin Schmidt

Published: 2016

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Theoretical Analysis and Experimental Examination of the Hong-Ou-Mandel Effect using Periodically-Poled Potassium Titanyl Phosphate

## Theoretical Analysis and Experimental Examination of the Hong-Ou-Mandel Effect using Periodically-Poled Potassium Titanyl Phosphate

In this paper, we discuss the theoretical principles and experimental results of a Hong-Ou-Mandel system using a fiber-coupled Periodically-Poled Potassium Titanyl Phosphate crystal. The output produced by a lossless beam splitter whose input is a pair of correlated photons is analyzed; the equivalence between this optical element in free-space and a half-wave plate in a collinear system is shown. The construction of the experimental system and the optical elements needed to reproduce this experiment in a partially fiber-based collinear environment are discussed. The spectral width of the photons generated by spontaneous parametric down-conversion is shown to be narrower than originally predicted, and conclusions are drawn from there.

Student Author: Ryan E. Scott

Published: 2016

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Imaging Magnetic Domains and Microstructure of Ni Bearing Heusler Alloys

## Imaging Magnetic Domains and Microstructure of Ni Bearing Heusler Alloys

Magnetic Heusler alloys based upon Ni_{2}MnGa exhibit a wealth of phenomena, including both a structural phase transition (cubic to tetragonal) as well as a ferromagnetic phase transition. Adjusting the chemical composition as well as sample preparation techniques allows placement of both of these phase transitions near ambient temperatures. The complex interplay between structural and magnetic propertied is poorly understood. In this work, imaging techniques were used to investigate both the microstructure and the magnetic domain pattern for several alloys. Both gallium deficient and copper bearing Ni_{2}MnGa alloys were imaged using both magnetic force microscopy and light microscopy. The light microscopy was extended to allow the investigation of magnetic domains by placing a thin layer of ferrofluid over the sample. Techniques to prepare samples for imaging and for imaging samples were developed. Images were taken of certain samples in an attempt to gather information about the effect of sample preparation on magnetic domains and microstructure, and our ability to image them. This work should set a basis for future work with similar alloys in this laboratory.

Student Author: Mollie Corrigan

Published: 2016

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Rheology of U-Shaped Granular Particles

## Rheology of U-Shaped Granular Particles

We study the response of cylindrical samples of U-shaped granular particles (staples) to extensional loads. Samples exhibit characteristic slide-slip behavior, elongating at a slow, constant rate interrupted by strain bursts (events). These events correspond to particles rearranging and re-entangling. Previous research on samples of constant cross-sectional area found a Weibullian weakest-link theory could explain the distribution of yield points. We now vary the cross-sectional area, and find that the average particle number density sets the upper bound on the failure stress (force/area). Analyzing stress instead of force collapses the data for all cross-sections into a single curve, indicating that the forces scale with cross-sectional area. Fourier transforms of the fluctuating stress scale inversely with frequency for all cross-sections, which is consistent with the power spectra seen in systems with irregular force fluctuations between events. The stress and strain rates during events exhibit behavior reminiscent of avalanche dynamics. The slip and stress drop rate profiles for events with short durations show the characteristic parabolic shape predicted by theory, while longer events deviate from the predicted curves. Slip and stress rate curves for individual events also exhibit the scaling collapse predicted by mean field theory.

Student Author: Matthew S. Hill

Published: 2016

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Orbital angular momentum in the regenerative regime of cavity optomechanics

## Orbital angular momentum in the regenerative regime of cavity optomechanics

The regenerative regime (or laser `heating’ region) is an active area of research within the field of cavity optomechanics, as it provides routes to create effects analogous to optical lasing with mechanical systems. Our goal is to investigate several phenomena present in the regenerative regime and generalize to systems including orbital angular momentum (OAM). The dynamics of a single ion in a harmonic trap are derived and shown to be the result of stimulated emission of phonons; these results are used as a stepping stone to investigate more complicated optomechanical systems. The dynamics and multistability of such an optomechanical system are derived and analyzed for simple cases and then generalized to cases where the input laser-light possesses OAM. It is noted that several of the results and beginning equations in this paper are present in the literature; however, a great deal of time was spent during the capstone process filling in the details necessary to derive the equations and results, so that while much of the math has been left out for readability, it is present in the student’s capstone notebook and provided the bulk of the student’s efforts throughout the capstone process.

Student Author: Tyler Godat

Published: 2016

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Granular Shear on Particles in the Annular Planar Couette Geometry

## Granular Shear on Particles in the Annular Planar Couette Geometry

We study systems of granular circles and ellipses under shear within the annular planar Couette geometry. Small plastic rings and ellipses will serve as the granular medium which should over time form shear transformational zones (STZ) which are analogous to dislocations in crystalline solids in their ability to lead to shear. These STZs are theorized to produce non-affine transformations of a set of particles that in this system are possible to observe by imaging the particles over time and tracking their locations. The movements are then able to be fitted to a linear transformation, the square residual of which is a quantified measurement of the non-affine part of the particle movements and suggests the presence of STZs. Under annular planar Couette ow we are able to probe essentially arbitrarily large pure shears which is ideal for analyzing the creation and movement of STZs under different conditions as well as global properties of the system such is particle packing fraction and velocities. The annular planar Couette geometry has been shown to be an effective system for observing sheared granular materials and can now be used to collect data.

Student Author: Alexander Hensley

Published: 2015

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Calculating Black Hole Quasinormal Mode Frequencies

## Calculating Black Hole Quasinormal Mode Frequencies

For the past six decades, the detection of gravitational waves has been long sought after. A component is the study of the quasinormal modes, modes of energy being dissipated in a perturbed object, and frequencies of black holes under perturbation. Although numerical methods of calculating quasinormal mode frequencies have had some success in the past, they are often time consuming and inefficient in calculating quasinormal modes. In this Capstone paper, the WKB approximation and a continued fractions method are used as semi-analytical approaches to calculating quasinormal mode frequencies. The results from the WKB method are comparable to other semi-analytic results for lower lying modes and the results from the continued fraction method are successfully reproduced as another semi-analytic method.

Student Author: Matthew Beach

Published: 2015

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Magnetic and Structural Properties in Non-Stoichiometric Gallium Deficient Ni2MnGa1-x Heusler Alloys

## Magnetic and Structural Properties in Non-Stoichiometric Gallium Deficient Ni2MnGa1-x Heusler Alloys

Vibrating sample magnetometry as well as x-ray diraction techniques were used to determine the magnetic and structural properties of gallium deficient Ni_{2}MnGa_{1-x} Heusler alloys. Magnetic properties include phase transition temperatures as well as magnetization as a function of field and temperature. Structural properties include crystal structure in different phases, lattice constant, and polycrystalline domain behavior while transitioning between phases. These data allow correlations between magnetic and structural behaviors.

Student Author: Anthony Ruffino

Published: 2015

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Students’ use of models as tools for sensemaking in the lab

## Students’ use of models as tools for sensemaking in the lab

Modeling is a key scientific practice, that allows for understanding to be shared through the sharing of these models. Models are also sensemaking tools used to increase understanding of a particular subject. This study focused on how students in upper-division physics laboratory courses use models as tools to make sense of the apparatus and data acquired in a lab experiment. The lab in question was a two-week laboratory on Johnson noise using the TeachSpin NF1-A Noise Fundamentals apparatus. Interviews with students were conducted in order to map out their understanding of the lab. The data from the interviews was then qualitatively analyzed using coding techniques. The students’ understanding of the apparatus was compared to an expert understanding map in order to determine where gaps occurred in their understanding of the apparatus and data. From this, it was determined that students with stronger, more complete models were more apt to have a complete understanding of the data while less accurate and less complete models tended towards a less accurate and less complete understanding of the data.

Student Author: Michael D. Rinkus

Published: 2015

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Static and Quasielastic Light Scattering of Bile Salt Micelles

## Static and Quasielastic Light Scattering of Bile Salt Micelles

The micelle formation of taurodeoxycholate (TDC), one of the bile salts, and dioleoyl phosphatidylcholine (DOPC), a pure form of lecithin, was studied with static and dynamic light scattering. TDC and DOPC are two of the compounds that are present in physiological bile, and play essential roles in the digestion of fats and the formation of gallstones. In large enough concentrations, TDC and DOPC form micelles in aqueous solution. Both the molecular mass (M_{w}) and hydrodynamic radius (R_{H}) of TDC and mixed TDC/DOPC micelles were measured as functions of concentration at 30°C. For pure TDC, R_{H} increased from 2.6 nm at low concentrations to close to 8 nm at high concentrations. Mixed micelles were observed to grow with dilution from approximately 100,000 g/mol at high concentrations to 370000 g/mol at low concentrations, consistent with previous studies that used a mixture lecithin components. A thermodynamic theory of mixed micellar growth is being developed, which, to date, can qualitatively predict growth with dilution.

Student Author: Avery Thompson

Published: 2015

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Design of a Temperature Controlled Mach-Zehnder Interferometer for Measuring Properties of Binary Liquid Solutions

## Design of a Temperature Controlled Mach-Zehnder Interferometer for Measuring Properties of Binary Liquid Solutions

Design of an experimental apparatus that may expedite measurements of temperature-dependent liquid-liquid phase transitions is outlined. Construction and tests of an interferometer that measures the concentration gradient within an optical cell is outlined. Theoretical designs for a temperature control system for the interferometer are described in detail. Phase separation behavior is observed in a concentration gradient of bovine calf lens γ crystallin.

Student Author: Nathan Cawley

Published: 2015

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Geometric Phases in Single Molecule Magnets

## Geometric Phases in Single Molecule Magnets

The characterization of the material properties of Single Molecule Magnets (SMMs) has grown in importance over the last few decades, with the rise of novel applications such as high-density magnetic storage and quantum computation. Many of the applications require the probing of SMMs with spectroscopic methods that make use of electromagnetic radiation. The interaction with these time- dependent fields leads to energy shifts, which can be attributed to the geometric phase acquired by the system or the Bloch-Siegert shift. We model an SMM by a giant spin Hamiltonian, and use Floquet perturbation theory to find the geometric phase shifts. The location where the phase shift between two levels is zero is useful for performing accurate spectroscopies, whereas the regions where relative phase differences exist are useful in applications like quantum computing. Using the same giant spin Hamiltonian, we can use Floquet theory and Salwen perturbation theory to determine the Bloch-Siegert shift and therefore a modified version of the Rabi formula for transition probabilities between the energy states E_{α}→E_{α±1}, E_{α} →E_{α±3}, and E_{α}→ E_{α → }E_{α±5 , }where α is the index of an initial state. The shifted eigenvalues and modified transition probabilities can be useful in spectroscopies where accurate values for the energy-splitting between magnetic states need to be determined.

Student Author: Brian Canchola Fenochio

Published: 2015

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Analyzing Global Mean Climate Change with a Two-Box Model

## Analyzing Global Mean Climate Change with a Two-Box Model

A “Two-Box” mathematical model is developed in order to analyze the temperature response of the Earth’s climate system as external forcings perturb it from radiative balance. By fitting to the instrumental temperature record, a set of bounds consistent with common literature can be placed on the equilibrium climate sensitivity of the system, as well as the time frame in which the response is realized. These results provide insight as to how the Earth reacts to changes in its energy budget, back up common figures derived from large climate simulations, and aid in making the conclusions drawn in policy-relevant research a bit more accessible.

Student Author: Pierce Donovan

Published: 2015

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Optical Photometry of Tidal Distortion in Compact Object Binary Systems

## Optical Photometry of Tidal Distortion in Compact Object Binary Systems

A photometric study of tidal deformation in closely orbiting binary systems, with a goal of deriving system parameters from the light curve. Featured is the short period binary *KPD*1930 + 2752 located in the Cygnus constellation using measurements from the RIT observatory. Analysis of *KPD* from nine independent nights of observation is presented along with post processing data analysis strategies specific to this set of long term measurements. A dynamic model of stellar morphology in the presence of the local potentials is discussed with the intention of further development based on these and future measurements. The final light curve as it stands for *KPD* is measured. Observations of cataclysmic binary FIRST* J*102346:6 + 003841 from Kitt Peak National Observatory is presented. A full computational simulation of a distorting binary in the presence of local potentials is described as it applies to *KPD* and fitted to the best available data, yielding fit mass value of (1.08 ±0.15)M⊙ .Future expansions and applications are outlined.

Student Author: Brandon B. Miller

Published: 2015

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Determination of the Neutron Scattering Background to the Neutrino Neutral-Current Elastic Scattering in the MINERvA Detector

## Determination of the Neutron Scattering Background to the Neutrino Neutral-Current Elastic Scattering in the MINERvA Detector

The MINERvA experiment seeks to measure rates of neutral-current elastic scattering of neutrinos on protons. The final state for this process is an isolated measurable proton track. This signal is mimicked by a proton that is knocked out of its nucleus by an incoming neutron generated by the NuMI beam line. By comparing the rock muon data to a simulation and then re-weighting the simulation, a reliable characterization of the neutron spectrum can be generated. With this characterization the neutron elastic scattering can be filtered out so that a reliable and more accurate neutrino neutral-current scattering measurement is left.

Student Author: Robert L. Masti

Published: 2015

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Propagating Waves in a Suspended Slinky

## Propagating Waves in a Suspended Slinky

This project took place in the lab examining generated waves in a suspended Slinky. Sending pulses or continuously driven displacements along a horizontally oriented Slinky allowed me to observe node locations and measure wave speeds of standing waves. With the added complexity of a position dependent mass density and tension, suspending the Slinky vertically allowed me to observe node locations that were no longer equally spaced and a position dependent wave speed. A driver made from 80/20 construction pieces, a power drill, an offset pin, and a slide piece that connected to the spring generated continuous forced oscillations that set up longitudinal and transverse standing waves. The normal mode frequencies and wave speeds for these waves were theoretically calculated and experimentally determined for comparison. In the horizontal orientation the resulting wave speed for longitudinal standing waves was (2.72±0.06) m/s , which came within 1% of the actual wave speed (2.69±0.01) m/s . The resulting wave speed for transverse standing waves was (3.0±0.2) m/s ,which came within 4.6% of the actual wave speed (2.86±0.01) m/s . In both cases the wave speeds agreed with the theoretical values within the uncertainties. In the vertical orientation the wave speed was not constant and so the fundamental frequency of the spring was compared. The fundamental frequency of the open ended suspended Slinky was (0.42±0.02) H*z* which came within 0:3% of the theoretical value (0.421±0.001) Hz. The fundamental frequency of the closed ended suspended Slinky was (0.950±0.05) H*z* which came within 4.7% of the theoretical value (0.905±0.001) H*z*. In each case the values agreed within the uncertainties.

Student Author: Christopher Valant

Published: 2015

Project Page

Imaging of Pt Nanocrystals on SrTiO3 Substrate: Coherent X-ray Diffraction and Scanning Microscopy Studies

## Imaging of Pt Nanocrystals on SrTiO3 Substrate: Coherent X-ray Diffraction and Scanning Microscopy Studies

Imaging of nano-scale structures, particularly those in real-world environments, presents a significant challenge. X-ray Coherent Diffractive Imaging (CDI) provides one avenue of accessing the structural information of a nano-scaled sample in a harsh environment. However, while this problem has been solved for Au and Pb nano-crystals in clean, vacuum environments, much work remains before it can be rapidly employed in other systems. Our efforts center on determining the real-space structure of Pt nanocrystals grown on a SrTiO_{3} substrate using a combination of CDI and atomic force scanning microscopy (AFM). X-ray speckle patterns are produced by coherent diffraction of the crystals at different orientations. In principal these speckle patterns can be transformed back to real space coordinates to calculate the crystal structure using CDI algorithms. Microscopy provides complementary information allowing us to simulate the speckled diffraction patterns from real-space images of the actual particles. This dual approach of using both real and reciprocal space information to solve the structures should lead to a practical set of algorithms and procedures whereupon the samples can be imaged quickly in the environments and conditions of interest.

Student Author: Travis Douglas

Published: 2015

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Migration and Segregation in Three Dimensional Cellular Co-cultures: Role of Differential Cell Adhesion and Elasticity

## Migration and Segregation in Three Dimensional Cellular Co-cultures: Role of Differential Cell Adhesion and Elasticity

The biophysics of cell co-cultures, i.e. a binary system of cell populations, is of great interest in many biological processes including formation of embryos, and tumor progression. During these processes, different types of cells with different physical properties are mixed with each other, with important consequences for cell-cell interaction, aggregation, and migration. The role of the differences in their physical properties in their collective behavior remains poorly understood. Furthermore, until recently, most experiments and theoretical models of collective cell migration have focused on two dimensional systems. Under physiological conditions, however, cells often have to navigate three dimensional and conned micro environments. I have modeled cell co-culture systems by extending previous two-dimensional Brownian Dynamics simulation of a binary system of interacting, active, and deformable particles to a conned three-dimensional system. I compare results from the model with experiments done by our collaborators. Findings may provide insights into how the differences in cells’ physical properties such as elasticity, propensity for cell-cell adhesion, and self-propulsion speeds of two cell types influence emergent collective properties such as cell aggregation and differential migration experimentally observed in co-cultures of breast cancer cells and healthy breast epithelial cells.

Student Author: Daniel Kolbman

Published: 2015

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Tidal Love Numbers of Neutron Stars in an External Tidal Field

## Tidal Love Numbers of Neutron Stars in an External Tidal Field

I explore the reaction of Neutron stars to an external tidal field. First, the simpler problem of perturbations in a Schwarzschild spacetime is explored as a stepping stone to understanding a perturbed Tolman-Oppenheimer-Volko (TOV) spacetime. These perturbations can be separated into two types: odd and even. In this paper the equations of motion for the odd perturbations are derived. The mathematical tools and procedures developed here are then extended to study of tidal deformations in neutron stars (NS_{s}). For example, binary neutron stars will tidally perturb each other, producing deformations in their shape and therefore the surrounding spacetime. The even* l* = 2 perturbations to the TOV background are studied. These perturbations are related to the a Post Newtonian deformation of the star and the tidal Love numbers to this perturbation are derived. The relationship between these tidal Love numbers and properties of the neutron star, namely its equation of state and compactness are explored.

Student Author: Travis Robson

Published: 2015

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Structural and Magnetic Properties of the Martensite Phase in Ni2MnGa0.87 Based Alloys

## Structural and Magnetic Properties of the Martensite Phase in Ni2MnGa0.87 Based Alloys

Heusler alloys are of particular importance to physics and engineering because of their unique magnetic and structural properties. They exhibit a ferromagnetic phase transition as well as a structural transformation from cubic lattice to a tetragonal lattice. These alloys have real world application and can be used in magnetic refrigeration. It was found that in Ni_{2}MnGa_{0.87}, the expansion during this structural transition was (26±4)μm using interferometry techniques and (10±4) μm using a strain gauge. The temperature at which this transition occurred was found to be 295°K. The Curie temperature was found on average to be at 359°K. It was shown that annealing the sample decreased its coercivity by 73% and increased its magnetic saturation by 22%. A light microscope was to image the magnetic domain. These domains are thought to be on the order of a few micrometer in width.

Student Author: Gregory Jones

Published: 2015

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Static and Quasielastic Light Scattering of Early Native Aggregates of Bovine Eye Lens Alpha Crystallin

## Static and Quasielastic Light Scattering of Early Native Aggregates of Bovine Eye Lens Alpha Crystallin

We have used size exclusion chromatography and light scattering to study aggregation of α-crystallin aggregation from bovine cortical extracts. For the peak alpha fraction we did obtain a hydrodynamic radius of 11.6 nm and molecular weight of 7:34X10^{5}g/mol. We have shown that molecular weight and hydrodynamic radius decrease with increasing elution volume. We plotted our data as molecular weight as a function of hydrodynamic radius along with a dimer model for alpha crystallin. The

model generally followed the data but a closer t would be ideal.

Student Author: James B. Molnar

Published: 2015

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Approximating the Energy Spectrum of Bound States in One-Dimensional Quantum-Scale Double Heterostructures

## Approximating the Energy Spectrum of Bound States in One-Dimensional Quantum-Scale Double Heterostructures

In this study, the problem of electron/hole confinement in one-dimensional double heterostructures is investigated. At the quantum scale, these structures are represented as one-dimensional finite square wells, and solution to the Schrödinger equation for this potential does not result in a closed form analytic expression for the bound state energy levels. A computational model was constructed to calculate exact solutions, against which models could be analyzed and validated. This simulation was also used to generate a large database of solutions that new models could be fit to empirically. The results of this analysis were used to construct a new model, with the shortcomings of previous models in mind. This study ultimately proposes a very simple piecewise expression for energy derived from first order series expansions at both ends of the interval. The resulting approximation outperforms previous models, despite being of lesser or comparable complexity.

Student Author: Jacob Popham

Published: 2015

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Classical Rotational Dynamics of a Rattleback

## Classical Rotational Dynamics of a Rattleback

The rattleback, or celt, is an interesting toy based on rotational physics. Perhaps its most interesting characteristic is that it reverses its rotation when it is spun in a specific direction. This reversal may be traced to its shape and the interaction between its oscillation and rotation. Many different theoretical models have been proposed for describing rattleback dynamics, especially the curious behavior of rotational reversal. This paper reviews the one suggested by William Case and Sahar Jalal in “The rattleback revisited,” Am. J. Phys. 82, 654 (2014). In that paper, the analysis is limited to analytically examining the response of the physical system. In our work, we examine the model of Case and Jalal computationally, and explore its implications.

Student Author: Joshua Aaron Schussler

Published: 2015

Project Page

Brownian dynamics of soft colloidal spheres in a monolayer of stier colloids.

## Brownian dynamics of soft colloidal spheres in a monolayer of stier colloids.

We have studied the mechanical response and dynamics of a binary system of active and deformable

colloidal particles using Langevin Dynamics simulations. We have characterized their motility by

studying the evolution of particle congurations, trajectories, and correlation functions with time.

Our study has sought to provide an understanding of the interplay of mechanical and statistical

mechanical properties, and its consequences for the collective and individual particle dynamics in

such systems. Of particular interest is problems of cellular dynamics: recent experiments demon-

strate remarkable changes during tumor progression in the mechanical stiness of cells and their

interaction with their surroundings. An intriguing experimental result in this area has suggested

that the mismatch in the elastic and adhesive properties between cancer cells and cells that have not

yet undergone malignant transformation may lead to enhanced cancer cell motility in a binary cell

population. By combining these theoretical frameworks to study active systems and cell mechanics,

we hope to obtain insights about the role that a mechanical mismatch in cellular properties plays

in cancer cell migration.

Student Author: Julian Butcher

Published: 2014

Project Page

Epitaxial Au on MgO Single Crystal Substrates

## Epitaxial Au on MgO Single Crystal Substrates

Physical Vapor Deposition (PVD) and annealing proves sucient for some degree of epitaxial gold

(Au) nanoparticles on Magnesium Oxide (MgO). MgO single crystals cut along the principal faces

(001), (011), (111) served as substrates to the Au that would be deposited using electron beam

sputtering; a form of PVD. After annealing, X-ray diraction (XRD) revealed two specular Au

peaks that turned out to be powder rings on all substrates except for one. Au (002) showed epitaxy

on MgO(001) after annealing to 900^{o}C. In addition, samples were analyzed using Nanoscope software

to measure average particle size and depths. Several other features of the nanoparticles are outlined

here including an ascending Au(111) peak. Au nanoparticles have achieved a great deal of interest

recently for their potential use as catalysts, and in surface chemistry1 as their ability to do so is

dependant on their size and surface properties. CO oxidation using Au nanoparticles is currently

a topic of interest.

Student Author: Timothy Pulliam

Published: 2014

Project Page

AC Susceptibility of Heusler Alloys

## AC Susceptibility of Heusler Alloys

Using a previously constructed AC susceptometer a heating and cooling system was constructed that

enables a temperature range from 90 to 400 K. Preliminary data on a sample of Ni_{2}MnGa_{1−x}Zn_{x}

for x=0.074 show anomalies in the magnetic susceptibility at the Curie temperature as well as the

structural martensitic transformation temperature. The heating and cooling process was automated

using Matlab as the control software. Experiments were also performed with another sample where

x=0.033. The martensite temperature transitions were found to be independent of changes in

amplitude and frequency for this material.

Student Author: Danielle E. Campbell

Published: 2014

Project Page

Modeling the deformability of a cell in a conning channel

## Modeling the deformability of a cell in a conning channel

Recent experimental studies have shown that cancer cells deform more easily than healthy cells of

the same type when migrating through narrow channels. We aim to understand and characterize

this enhanced deformability^{2-5} by studying the interplay between the micromechanics of the cell

nucleus, which is the largest and stiest of all cellular organelles, and the rest of the cell. To do

so, a static computational model of a cell has been developed. Using Matlab2013, the deformation

energy of the cell is calculated and minimized under constraints due to the cell's surroundings. For

example, square walls have been added that are narrower than the cell's diameter to mimic ow

through a narrow channel. By studying the new, changed shape of the cell in the channel and the

associated aspect ratio as a function of the elastic moduli of various cellular components such as

the nucleus and cytoskeleton, we hope to obtain new insights into the rate limiting steps for cell

deformability and migration through narrow constrictions.

Student Author: Jake Shechter

Published: 2014

Project Page

Using an Elastic Tracking Method to Find Steep Tracks in the MINERvA Neutrino Detector

## Using an Elastic Tracking Method to Find Steep Tracks in the MINERvA Neutrino Detector

The Minerva neutrino detector currently does not have a good algorithm that will nd short or

steep (greater than 70^{o}) particle tracks. We have spent time creating an algorithm that will allow a

steep track to be found with a fairly high accuracy by utilizing the elastic tracking method proposed

by Gyulassy and Harlander^{12}, as well as a modication to this design. The results of this is an

algorithm that is able to nd single steep tracks of a specied particle in the detector.

Student Author: Andrew James Carley

Published: 2014

Project Page

Seaching for Structural Patterns in the Distribution of Classical Dwarf Galaxies Orbiting the Milky Way

## Seaching for Structural Patterns in the Distribution of Classical Dwarf Galaxies Orbiting the Milky Way

The observed distribution of dwarf galaxies around the Milky Way (MW) is not consistent with

expectations from cosmological simulations. These galaxies are integrated back in time in order

to gain insight on the origin of this polar structure. The simulation code was written by Chang

& Chakrabarti (2011) in Fortran 90, and uses a gravitational potential well for the MW based on

theoretical models and a fourth order Runge-Kutta method to integrate the dynamical equations

of motion. The masses of dwarf galaxies are uncertain and aect our results. A mass based on

observed stellar content was used for most satellites. The total dark matter mass is motivated both

by cosmological simulations as well as the observed velocity dispersion, but is not used in simulation.

A method for sampling a distribution using a quantile function of a normal distribution was made

which recovers a gaussian curve. A way of tting points to a plane is tested and used for the galaxies

in the analysis. 1000 sets of data are collected in a monte carlo method of accounting for error.

Findings of analysis inconsistent with the results found in Metz and Kroupa 2008.

Student Author: Nelson Silva

Published: 2014

Project Page

Quantum Dynamics of a Coupled Oscillator-Rotor System

## Quantum Dynamics of a Coupled Oscillator-Rotor System

The interaction of light elds with mechanical systems in the quantum regime is currently of sub-

stantial interest to the physics community. The subject is related to explorations of fundamental

physics as well as innovation of next-generation sensing and information processing technologies.

Along these lines, we study the quantum dynamics of a mechanical rotor coupled to a single-mode

electric eld (supported by an optical cavity) modeled as a harmonic oscillator. Specic cases,

where the rotor can provide either a permanent or an induced dipole moment will be investigated.

Particularly, the time evolution of the optical photon number, and the rotor angular momentum,

alignment and orientation will be investigated.

Student Author: Bryan Ek

Published: 2014

Project Page

X-ray Spectral Analysis of Planetary Nebulae

## X-ray Spectral Analysis of Planetary Nebulae

This project analyzes Chandra X-ray Observatory (CXO) observations of planetary nebulae (PNe)

to determine the temperature of the X-ray emitting gas, and determine whether the composition

of the gas can be determined by fitting to the model. Pressure in the X-ray emitting region (“hot

bubble”) is also calculated. The PNe examined here are part of the Chandra Planetary Nebula

Survey (ChanPlaNS) of nearby (D > 1.5 kpc) PNe.

Student Author: Kayla R. Emerson

Published: 2014

Project Page

Characterization of a Tunable Bandpass Filter for Astronomy

## Characterization of a Tunable Bandpass Filter for Astronomy

Bandpass lters are a standard tool in astronomy for acquiring data over a specic wavelength

regime. The pass band of a conventional bandpass lter is meant to be \xed," meaning there is only

one pass band per physical lter. This is useful for comparing data sets, but is a practical hindrance

for observers who require more than a few pass bands, because each pass band is represented by a

physical lter. Tunable lters transmit a pass band of light centered about one wavelength that can

be changed by tilting the lter with respect to the incoming light. The purpose of this research is to

investigate a class of tunable bandpass lters for use in astronomy. Some aspects to be investigated

are the light throughput as a function of angle, image shift and distortion and overall image quality.

Student Author: Michael Every

Published: 2014

Project Page

Magnetic Properties of Ni2MnGa based Heusler Alloys

## Magnetic Properties of Ni2MnGa based Heusler Alloys

Subtle compositional variations of Heusler alloys, based on Ni_{2}MnGa, change the temperature at

which various crystalline phase transitions occur. The goal was to the shift the martensite transition

of the material to a temperature at or near room temperature (300 K). Low eld magnetization

data shows the signature behavior of the martensite transition. To measure the magnetization as

a function of temperature, a thermal controller was constructed to insulate the sample from the

laboratory environment and to facilitate the adjustment of the sample's temperature from near

liquid nitrogen temperature to a peak of around 500 K, with a smooth variation across the room

temperature boundary. The apparatus consisted of a vacuum jacket around the sample, and inline

gas heater and a liquid nitrogen heat exchanger coil. Data was taken on three dierent Heusler

alloys, each with a dierent zinc content. One of the samples exhibited a transition temperature at

the goal temperature, yet it was a sample where the zinc was left absent.

Student Author: Ian F. Ferralli

Published: 2014

Project Page

Cells for High Resolution Electric-Field NMR

## Cells for High Resolution Electric-Field NMR

An NMR phantom is a calibration tool used on NMR systems in order to probe how eective a

system is at producing images of the subject. In order to be used to calibrate multiple systems,

the phantom must be able to change its NMR signal dynamically. This involves altering the spin-

spin relaxation time (T_{2}) of a liquid in the phantom. Recent research suggests that it is possible

to generate this change in T_{2} by applying a strong, uniform electric eld perpendicular to the

magnetic eld produced by the NMR system. We intended to design an MMR probe that applies

this electromagnetic eld conguration to a test cell while maintaining high eld resolution.

Student Author: Andrew Ferris

Published: 2014

Project Page

Characterizing a lattice for dielectrics in an optical resonator

## Characterizing a lattice for dielectrics in an optical resonator

We consider a superposition of two identical, counter-propagating Hermite-Gaussian modes in an

optical resonator as a potential lattice for conning an array of small dielectric particles. We

choose to study a dielectric cube in this context due to symmetry. The intra-cavity intensity and

maximal intensity points are rst calculated, applying appropriate approximations. We then dene

the gradient force experienced by a single dielectric, responsible for the connement. From this

force we derive a potential landscape for the dielectric and calculate trapping depths. Using a series

expansion to approximate the potential, we calculate an eective frequency in each direction near a

potential minimum. Further we calculate the scattering force experienced by the dielectric, which

can contribute to trap instability. From these results we determine the axial displacement of the

dielectric from equilibrium. The scattering cross-section of a dielectric cube for a beam at normal

incidence is then calculated. Related photon scattering that occurs due to the dielectric is also

calculated. Using axial displacement, photon scattering rates, and pressure-dependent damping, we

show the proposed trap is indeed stable. We then determine the general expression for the mode

volume occupied by two identical, counter-propagating HG_{m,n} modes. Lastly we characterize the

optomechanical coupling that occurs between the optical mode and the dielectric.

Student Author: Okechukwu S. Igbokwe

Published: 2014

Project Page

Stellar Structure in Scalar-Tensor Gravity

## Stellar Structure in Scalar-Tensor Gravity

Einstein's theory of General Relativity (GR) is currently our most successful theory of gravity. It has

been well tested outside of matter in the weak-eld limit. GR is not as well tested, however, inside

of matter and in strong eld regimes. Therefore theories that deviate from GR in matter, while

obeying weak-eld constraints, are important alternatives to explore. Such theories could possibly

lead to observable signatures in stellar pulsations while avoiding solar system constraints. This

project is intended as a rst step towards using asteroseismology and gravitational wave detection

to constrain such theories. We rst model static, spherically symmetric stars in both Newtonian

gravity and GR. After, we investigate stars in scalar-tensor gravity. We present the derivation of the

stellar structure equations and discuss methods we use to solve them numerically. We explore specic

models characterized by exponential coupling functions and use the Parametrized Post Newtonian

parameters to put constraints on the asymptotic behavior of the scalar eld. We show that in

certain models these constraints are enough to prevent deviations from GR and begin work towards

exploring models where, even with these constraints, we can still see deviations in the strong eld

regime.

Student Author: David Anderson

Published: 2014

Project Page

Coherent X-ray Scattering from Ag(001) Surfaces in Electrochemical Environments

## Coherent X-ray Scattering from Ag(001) Surfaces in Electrochemical Environments

Using X-ray Photon Correlation Spectroscopy (XPCS) and Crystal Truncation Rod (CTR) scatter-

ing, we have examined behavior of single crystal surfaces of Ag(001) in electrochemical solutions.

XPCS analysis allows for measurements of the Ag surface dynamics, while CTR scattering analysis

allows for measurements of the structure of the system. Using these techniques, along with ex-situ

Atomic Force Microscopy (AFM) data and cyclic voltametry data, we have investigated relation-

ships between the dynamics of the Ag surface and the distribution of water molecules above the

surface. We have demonstrated that the water distribution is potential dependent and developed a

model to describe this dependence. We have also proposed a model to describe the system dynamics

in terms of applied potential.

Student Author: Robert Karl, Jr.

Published: 2014

Project Page

Development of a Mach-Zehnder Interferometer for the Measurement of the Coexistence Curve

## Development of a Mach-Zehnder Interferometer for the Measurement of the Coexistence Curve

Measuring the coexistence curve of various macromolecular systems is an ever-growing research area

in the study of biophysics. Although this is a popular field, collection of data for one coexistence

curve can take approximately three months and an excessive amount of sample. This paper describes

development of a new method to find information about the coexistence curve using a Mach-Zehnder

interferometer. Our new method will be a noticeably quicker method to collect data on gradients

of macromolecular systems while also using less sample. Here we describe the preliminary steps

towards the development of a Mach-Zehnder based coexistence curve measurement apparatus.

Student Author: Justin Bartlett

Published: 2014

Project Page

Investigation of O2 Interactions with the Au (001) Single Crystal Facet

## Investigation of O2 Interactions with the Au (001) Single Crystal Facet

The interaction of oxygen on the Au (001) single crystal facet has been investigated at high temper-

ature and at atmospheric pressures using *in-situ* synchrotron-based surface X-ray diraction and

scattering techniques. The surface X-ray scattering is highly sensitive to the arrangement of the

surface Au atoms, and clearly indicates the relative fraction of the surface in the \hex" phase and

the disordered bulk (1x1) phase. It has been demonstrated that oxygen exposure lifts the surface

reconstruction in a reproducibly and reversibly manner that is dependent upon both pressure and

temperature. A pressure-temperature phase diagram has been constructed, where the relation be-

tween the coverage and temperature follows a simple power law over 2 decades in P and T, and the

critical exponent is determined to be 1:4 +/- 0:2. The activation energies associated with the cataly-

sis have been experimentally measured and compared with a system of coupled partial dierential

equations that model the absorption kinetics and the surface reconstruction.

Student Author: Andrew C. Loheac

Published: 2014

Project Page

Magnetocaloric Measurements in Heusler Alloys

## Magnetocaloric Measurements in Heusler Alloys

Heusler alloys are a class of ferromagnetic intermetallic alloys with unusual magnetic and thermal properties. They exhibit an unusually large magnetocaloric effect, a change in temperature caused magnetization of the sample by a magnetic field. They undergo structural and magnetic phase transitions at different temperatures, depending on composition. In this study we examine the magnetocaloric effect at different temperatures. We intend to examine a N i2MnGa alloy. The magnetocaloric effect is observed to decrease with increasing temperature. It does so linearly, with a unitless slope of -0.02.

Student Author: Spencer Allen

Published: 2013

Project Page

Faculty Discourse in Physics Curriculum

## Faculty Discourse in Physics Curriculum

Faculty discourse in a variety of course subjects, all involving mathematical topics, was recorded and analysed using an emergent coding method. The Symbolic Form construct is shown to be a useful too for interpreting discourse, with two new symbolic forms, Compound Form and Sum-toZero Form, being discovered. Transcript analysis, defined as the exchanges between parties, both verbal and non-verbal, that set parameters and guide the interaction, also reveals distinct classroom frames. Examples are presented where an instructor intentionally or unintentionally changes the frame, as well as describing two new frames termed Instructor as Learner and Rule Based. This research establishes the legitimacy of qualitative discourse analysis as a research tool in the postsecondary physics classroom and establishes new foundational markers for subsequent research to use in analysing classroom practice.

Student Author: Jonathan Lindine

Published: 2013

Project Page

Numerical Modeling of Neutron Stars

## Numerical Modeling of Neutron Stars

Here we present our findings after 20 weeks of research on the numerical modeling of neutron stars. We successfully modeled white dwarves in the extreme relativistic and non-relativistic limits as degenerate gasses and obtained results which agree with our guiding AJP article [1]. We then proceeded to treat neutron stars as a degenerate gas of non-interacting neutrons and found a maximum mass of around .7 solar masses in good agreement with the result of Oppenheimer and Volkoff’s 1939 result. In order to obtain a more accurate model of a neutron star we first create our own model for the interaction potential between 2 neutrons, using this model, we approximate the neutron star as having a HCP lattice structure, and then calculate the energy due to nucleon interactions in said lattice to produce a nuclear equation of state. We calculate the speed of sound inside our neutron stars, and find that the nuclear equation of state derived from our nuclear potential satisfies causality. Using this lattice model we find the maximum mass of a neutron star to be around 1.5 solar masses.

Student Author: Jonathan Beaumariage

Published: 2013

Project Page

Infrared Properties of Optically Polarized AGN

## Infrared Properties of Optically Polarized AGN

In the investigation of a unified model of active galactic nuclei, it has been found that many Seyfert 1 galaxies exhibit optical polarization characteristics similar to Seyfert 2 galaxies. This indicates that polarization is dependent upon the orientation of the nucleus. The dusty torus is the cause of the orientation-dependent obscuration as well as being the source of the infrared emission. Therefore, we expect the different optical polarization classes to have distinct infrared spectral energy distributions. Data from the Spitzer Space Telescope and the 2 Micron All-Sky Survey of a sample of galaxies containing both Seyfert 1 and Seyfert 2 galaxies was analyzed to determine if there are any correlations between the infrared properties and the optical polarization properties.

Student Author: Marc A. Magagnoli

Published: 2013

Project Page

Optorotational coupling of a dielectric particle to a Laguerre-Gaussian mode

## Optorotational coupling of a dielectric particle to a Laguerre-Gaussian mode

We propose to theoretically derive the coupling of a dielectric particle to the standing Laguerre Gaussian (LGl,p) mode of an optical resonator. This will involve the investigation of the potential landscape presented by the optical mode to the dielectric, including the depth of the well in which the dielectric is trapped, as well as the frequency and anharmonicity of dielectric oscillation. Also, we will study the effect of the dielectric on the optical beam, in terms of scattering of photons and the consequent effect on the finesse of the optical cavity. Lastly, we will derive in an approximate analytic form the coupling between the angular motion of the dielectric and the optical beam carrying orbital angular momentum. This is an essential step in designing a sensor which can detect angular motion of small particles.

Student Author: Michael Eggleston

Published: 2013

Project Page

Observing the Martensitic Transition of Heusler Alloys

## Observing the Martensitic Transition of Heusler Alloys

The affect Sn and Zn doping had on the martensitic transition of N i2MnGa was investigated. Experimentally, it was found that Sn doping lowered the martensite temperature while Zn doping raised the martensite temperature. Being able to alter the temperature at which this transition occurs is important for real world applications.

Student Author: Edward R. Marsten

Published: 2013

Project Page

Special Relativistic Orbits of a Two-Body System

## Special Relativistic Orbits of a Two-Body System

Special relativity allows for many orbital trajectories that are unfamiliar to classical mechanics [1]. In this project, these orbits will be simulated for a two body system with a potential that is proportional to 1/r. We were able to produce simulations for the one-body case that matched the analytical solutions obtained by Dr. Boyer[1] and conserved energy to an acceptable level. Additionally the chosen integration method was able to produce accurate results for some two-body orbits with a large mass ratio. However, when this integration technique was applied to the general two-body case it failed to reproduce classical trajectories for the non-relativistic limit and did not conserve energy to an acceptable level for most relativistic orbits.

Student Author: Joel W. Newbolt

Published: 2013

Project Page

Investigating Electron-induced Eefects in Semiconductors Using Deep-level Transient

## Investigating Electron-induced Eefects in Semiconductors Using Deep-level Transient

Solar radiation is well known to degrade the performance of semiconductor devices. When high energy particles interact with a semiconductor they create or increase the number of traps, also known as deep levels, in the band structure. These defects interfere with with the conduction of current and make the device less efficient. One way of studying these defects is using deep-level transient spectroscopy (DLTS). Samples were characterized pre and post irradiation by 1 MeV electrons at a fluence of 6x1014 cm−2 for aluminum gallium arsenide and 1x1015 cm−2 for gallium arsenide. The first sample studied was aluminum gallium arsenide (AlGaAs) which was found to have native defects with activation energies of 0.37 ± 0.03 eV, 0.43 ± 0.02 eV and 0.76 ± 0.03 eV. After irradiation these peaks remained at the same energy, but the trap densities all increased by nearly a factor of two. An n-type gallium arsenide (GaAs) sample was also studied. Pre-irradiation the GaAs sample was found to only have one native defect at 0.77 ± 0.03 eV. Post-irradiation, a new defect was detected at 0.26 ± 0.03 eV. These defects were compared to literature to attempt to gain an understanding of the mechanisms of their creation.

Student Author: Justin R. Shellenberger

Published: 2013

Project Page

Quantum Correlation of Photons

## Quantum Correlation of Photons

Polarization-entangled photon pairs were used to demonstrate the nonlocal character of quantum mechanics. These photon pairs were generated using spontaneous parametric downconversion with a diode laser and two nonlinear crystals. The quantum polarization state of these photons was tuned to a Bell state, capable of disproving hidden variable theories by violating the Clauser, Horne, Shimony, and Holt version of the Bell inequality. In this experiment, S was found to be 2.268 ± 0.053, which is inconsistent with the hidden variable theory proposed by Einstein, Podolsky, and Rosen which predicts that S = 2. A similar setup was used to investigate the quantum nature of light using the Hong-Ou-Mandel effect. If two identical photons are incident on opposing input modes of a beamsplitter, intuition suggests that there are four possible output modes with either photon being transmitted or reflected. However, quantum mechanics predicts that there are only two possible output modes in which the photons exit the beamsplitter together. This results from the wave-like nature of light and is a quintessential part of quantum mechanics.

Student Author: Dylan A. Heberle

Published: 2013

Project Page

An Optomechanical System with Simultaneous Linear and Quadratic Couplings

## An Optomechanical System with Simultaneous Linear and Quadratic Couplings

Optomechanical systems are composed of optical cavities and mechanical oscillators. The typical optomechanical interaction relies on a coupling that is linear in the displacement of the mechanical oscillator. However, recent experiments have shown that higher order couplings can be achieved as well. In this article, we present the study of an optomechanical system with simultaneous linear and quadratic coupling, whose electromechanical analog has been experimentally realized. In this work we treat the system simply, by neglecting external driving and dissipation. We derive the exact spectrum of the closed system Hamiltonian and the corresponding unitary time evolution operator. We calculate the time evolved state and phonon statistics with the cavity field initially in a coherent state and the oscillator in its ground state as in recent experiments. We show that the periodic disentanglement between the mechanical oscillator and the optical field that only occurs in systems with linear coupling can be traced back to the fact that linear coupling does not change the eective mechanical trapping frequency, while quadratic coupling does. We also calculate and plot the Wigner function for the mechanical oscillator under (a) unitary time evolution and (b) conditional measurement of photon number. We expect our results to be useful for optomechanical spectroscopy, non-classical state engineering, and further study on optomechanical entanglement.

Student Author: Hao Shi

Published: 2013

Project Page

Simulations of Hexagonal 2D Ferromagnetic Systems

## Simulations of Hexagonal 2D Ferromagnetic Systems

A numerical φ^{4} model was built to simulate 2-D ferromagnetic domains. The goal of the simulation was to accurately model the evolution of magnetic domains. The simulation uses two staggered square lattices to create a hexagonal lattice. This hexagonal lattice allowed us to more accurately model the domains compared to the conventional square lattice. The simulation proceeds until the lattice converges to a steady state, as determined by the magnetization. The parameter space includes variables to model the potential well, a dipolar RKKY interaction, and a small local random field to break symmetry. After getting a working steady state simulation, the parameter space of the variables *a* and *k* were investigated. *a* is a parameter in our Hamiltonian that controls how much each dipole in the domain resists spin flipping, and *k* is a parameter in our potential that effects how fast the potential decays. We found that *k* values around 1.0 produced the most realistic domain patterns, and that varying a did not present significant effects beyond blurring of the domain lines. The steady state simulation was then modified to simulate an applied external field. This allows for experimental hysteresis loops to be recreated, and for an investigation into what happens when a hysteresis reversal curve exits the main hysteresis loop.

Student Author: Zachary Howard

Published: 2013

Project Page

The Effects of Device Area on the Yield of Working Devices

## The Effects of Device Area on the Yield of Working Devices

With low working device yields, < 1%, research came to a halt. To overcome this problem the manufacturing process was analyzed. The aspect chosen to study was the device area, an aspect deemed critical at many OPV conferences. Device area literature studies were conducted to show whether a smaller device area would increase our device yield. The data collected from these studies did not show a correlation between smaller device areas and a higher working device yield and proved inconclusive. An experimental approach was taken to test whether smaller areas would produce greater yields. A new mask was made to accommodate for smaller device areas. Benefits of the new mask included 84 more devices per batch, an increase of 400%, smaller device areas, and a much more efficient evaporation process. The new mask has been tested once, due to time constraints, and data from this test does not match the outcomes of a greater working device yield for smaller device areas. More testing and analysis will be conducted in the ensuing weeks.

Student Author: Ross Spinelli

Published: 2013

Project Page

AC Susceptiblity of Heusler Alloys

## AC Susceptiblity of Heusler Alloys

Using a previously constructed AC susceptometer, analysis will be done for a Heusler alloy series. A heating and cooling system will be constructed for the existing apparatus to enable a temperature range from 77K to 450K. The analysis will be completed by looking at the Curie temperatures, magnetization, and martensite transitions of the Heusler alloy series, as a function of AC field strength and frequency.

Student Author: Danielle E. Trost

Published: 2013

Project Page

Planetary Nebula Morphology

## Planetary Nebula Morphology

There is some debate among astronomers on the theories behind planetary nebulae morphology. It is not entirely clear the amount of effect by which magnetic fields, stellar-rotation and binarity influence the morphology of nebulae, as most planetary nebulae show deviation from axial symmetry. By using Kitt Peak’s 0.9 meter WIYN telescope and observing a set list of binary targets, we aim to search for remnants of planetary nebulae in order to clarify constraints on the binarity influence required to produce them.

Student Author: Jack Wong

Published: 2013

Project Page

Construction of a Torsion Balance

## Construction of a Torsion Balance

The thrust stand is a piece of equipment designed to measure small forces, such as those applied by a small thruster or light reecting off of a surface; such forces are often in the micro-Newton range, and cannot be reliably detected by other instruments. No thrust stand currently exists in the RIT labs; as such, this projects purpose is to create the initial prototype for one. (Completion of the stand is beyond the scope of this pro ject.) Since the start of Capstone I, a very basic torsion balance has been constructed, and attempts have been made to experimentally determine its abilities; the values are very rough, however, since the initial version of the balance was intended to only get

order-of-magnitude accuracy and to display the general qualitative characteristics of the balance. In addition, a small collection of equations has been derived which appear to describe the balance’s behavior accurately.

Student Author: Gregory S. Janesch

Published: 2013

Project Page

Chaos in a Double Pendulum with Distributed Mass

## Chaos in a Double Pendulum with Distributed Mass

The goal of this project is to investigate chaos in a double pendulum composed of two plates,

which exhibits similar behavior a simple double pendulum, but at different energies. This project

was inspired by a project by M. Rafat et al. in 2008, but aims to go into significantly more depth

in the model, and explores a somewhat different pendulum. During the first part of this project,

a simulation was created to model a simple double pendulum. Also, the actual pendulum to be

investigated was constructed. In the second part of this project, the simulation was be adapted to

the pendulum to be investigated. Data were collected for both the model and the actual pendulum,

and some matching was done between model and experimental data.

Student Author: Joshua Kahn

Published: 2013

Project Page

Diversity of Faculty Practice in Active-Learning Classrooms

## Diversity of Faculty Practice in Active-Learning Classrooms

Professors use many different approaches in teaching University Physics classes. At RIT 24 different professors teach 34 sections of University Physics per quarter, with the possibility of having up to 42 students in each class. Considering all of these professors have different backgrounds and training, this leads to students being taught in very different ways. This project is looking at how much variation is occurring in the classroom environment, including time spent on different instructional methods, student engagement, and RTOP results looking to see if variations correspond to different material being taught, be it within a single section or across University Physics III classes observed. These aspects are also compared across instructional room and professor. Interviews are also being conducted so faculty ideas can be compared across the classes as well as being compared with observations.

Student Author: Tricia Chapman

Published: 2012

Project Page

Spectral Variations and the Optimization of Solar Cell Band Gaps: Antireflection Coatings and Air Mass

## Spectral Variations and the Optimization of Solar Cell Band Gaps: Antireflection Coatings and Air Mass

The goal of this study is to computationally optimize the power of a multi-junction solar cell with antireflection coatings. Considerations must be made to account for spectral variations in the solar spectrum that occur over a full day and a full year which factors in the effect due to changes in air mass as well as making considerations to minimize the amount of reflected light on the surface of the solar cell. This and requiring current matching between cell layers will allow for optimal operating voltage, specifications for antireflection coating, and set of energy band gaps to be chosen.

Student Author: Alexander Marshall

Published: 2012

Project Page

Nonlinear Behavior in an Electronic Oscillator

## Nonlinear Behavior in an Electronic Oscillator

Dr. Mark Koepke, a plasma physicist who studies the ionosphere, found that the nonlinear plasma waves in the ionosphere behaved similarly to the nonlinear waves in a unijunction transistor oscillator. In 1991, Drs. Koepke and Hartley published a paper in the Physical Review A that highlighted their research entitled Experimental verification of periodic pulling in a nonlinear oscillator. The purpose of this Capstone Project will be to extend and verify the results obtained in their paper, including the effect that Koepke describes as periodic pulling. Periodic pulling is a partial entrainment of a nonlinear oscillator driven by a periodically varying voltage source.

Student Author: Steven M. Christopher

, Student Author: John J. Zelinski

Published: 2012

Project Page

Quantum Random Walks in Photonic Waveguide Lattices: A Progress Review

## Quantum Random Walks in Photonic Waveguide Lattices: A Progress Review

Here an analysis of both single and two photon field states evolving in a waveguide lattice is presented. The analysis is easily extendable to an arbitrary single-mode number state. Whereas the evolution of a single photon field state mimics the behavior of a classical field state, simulations of two photon field states reveal quantum interference and provide a continuous analogue to the HongOu-Mandel effect in a set of two or more adjacent waveguides. In addition, simulations in MATLAB of a two-photon system with a higher number of waveguides demonstrate quantum interference in a random walk, producing drastically different behavior than any similar situation from a classical perspective.

Student Author: Christopher A. Mullarkey

Published: 2012

Project Page

Chaotic dynamics of a driven pendulum

## Chaotic dynamics of a driven pendulum

An theoretical analysis and construction of a chaotic pendulum from the ground up, using the general structure and key features of the pendulum apparatus detailed in Robert DeSerio’s paper, “Chaotic pendulum: The complete attractor”. The framework of the pendulum has been established, key electronics have been acquired, and machining of several unique mechanical parts have been completed. Assembly of the apparatus and design of additional required mechanical parts are in progress. Computational simulations using MATLAB programming with fourth order Runge-Kutta numerical integration techniques have been written. Raw outputs of the simulations have been generated for a range of systems with varying parameters. Beginning stages of data acquisition programming using LabVIEW has also been written. Continued improvement of the simulation and data acquisition code is in progress. Theory of the chaotic pendulum and it’s dynamics has been established. The system of differential equations of motion have been derived for the pendulum being constructed, and theoretical phase spaces have been explored. Further exploration into theory has been postponed in favor of the previously mentioned construction and simulation of the pendulum.

Student Author: James Downey

Published: 2012

Project Page

Quantum Random Walks in Photonic Waveguide Lattices: A Progress Review

## Quantum Random Walks in Photonic Waveguide Lattices: A Progress Review

Here an analysis of both single and two photon field states evolving in a waveguide lattice is presented. The analysis is easily extendable to an arbitrary single-mode number state. Whereas the evolution of a single photon field state mimics the behavior of a classical field state, simulations of two photon field states reveal quantum interference and provide a continuous analogue to the HongOu-Mandel effect in a set of two or more adjacent waveguides. In addition, simulations in MATLAB of a two-photon system with a higher number of waveguides demonstrate quantum interference in a random walk, producing drastically different behavior than any similar situation from a classical perspective.

Student Author: Christopher A. Mullarkey

Published: 2012

Project Page

Quantum Properties of Light

## Quantum Properties of Light

It is well known that light displays both a wave-like and particle-like behavior. The particle nature, quantum in behavior, has inherent properties and effects unexplainable by classic physics. To view these quantum tendencies, a truly single photon source is required, which is to say the photons are anti-bunched. One of the most promising methods for producing single photons is through spontaneous parametric down-conversion (SPD) in a non-linear crystal, such as, beta barium borate (BBO). A strong pump beam is illuminated through the crystal, which through the non-linear susceptibility of the crystal produces two new photons which are strongly correlated in energy and momentum. Here we investigate these correlations and the dependence on the orientation of the BBO crystal. We found that there is a strong correlation between simultaneous coincidences, with a time delay caused by a difference in path length. The rotation of the BBO or of the pump polarization, by use of a half wave plate, produces a sinusoidal effect on the signal intensity (number of counts). Also, if a BBO crystal is tilted or twisted, the position of cones (rails) alters positively and negatively linear, respectively. Finally, using the results, we plan on testing entanglement by disproving Bell’s Inequality, and further test correlations in coincidences through a Hanbury Brown Twiss setup.

Student Author: Alexander J. Dunn

Published: 2012

Project Page

Quantum Random Walks in Photonic Waveguide Lattices: A Progress Review

## Quantum Random Walks in Photonic Waveguide Lattices: A Progress Review

Here an analysis of both single and two photon field states evolving in a waveguide lattice is presented. The analysis is easily extendable to an arbitrary single-mode number state. Whereas the evolution of a single photon field state mimics the behavior of a classical field state, simulations of two photon field states reveal quantum interference and provide a continuous analogue to the HongOu-Mandel effect in a set of two or more adjacent waveguides. In addition, simulations in MATLAB of a two-photon system with a higher number of waveguides demonstrate quantum interference in a random walk, producing drastically different behavior than any similar situation from a classical perspective.

Student Author: Christopher A. Mullarkey

Published: 2012

Project Page

The electrostatic contribution to the second virial coefficient of γ-crystallin

## The electrostatic contribution to the second virial coefficient of γ-crystallin

This project attempts to extend efforts to produce better models of the interactions between the γ-crystallin molecules found in the eye lens. The ultimate goal is to determine how the non-uniform distributions of acidic and basic—proton donor and proton acceptor—sites and their relative orientations affect these interactions. Although previous research projects have created the code necessary to simulate γ-crystallin pair interactions sans various contributions of lesser significance, the quantity of computations required mitigates the production of enough data to generate a meaningful model. Thus, we are researching various computational methods to optimize simulation performance.

Student Author: David Brenton Allen

Published: January 2015

Project Page

A study of solitons: video analysis of wave propagation in a fluid tank

## A study of solitons: video analysis of wave propagation in a fluid tank

Hydrodynamic soliton creation and propagation is to be studied using video analysis programs and compared to expected analytical results. The underlying theory of soliton creation in shallow water and the descriptive Korteweg-de Vries equation is derived from basic fluid mechanics principles. A description of the experimental apparatus, its construction process and the procedure for video analysis is discussed in detail. A computational method to provide an analytical model for comparison is also described. The creation of a single propagating wave form is discussed and compared to expected results from a similar experiment. The milestones discussed in Capstone Preparation are reviewed and reassigned for development in Capstone II.

Student Author: Joseph M Fabritius

Published: 2012

Project Page

Applications of Quantum Game Theory

## Applications of Quantum Game Theory

Game theory is a theory of decision making. Players employ strategies to optimize payoffs in games. A twoplayer, zero-sum game, such as the coin flip game, can be played using pure or mixed versions of quantum or classical strategies. In strictly classical games, von Neumann's Minimax Theorem guarantees an equilibrium for an appropriate mixed strategy. However, owing to the quantum mechanical superposition principle, quantum strategies allow for payoffs that are not possible in classical games. We examine quantum mechanical two player, zero-sum games of strategy. In particular, we use the PQ Penny Flip game described by Meyer[2] and determine outcomes for various cases involving different quantum strategies. The results show that if the right quantum strategy is used, player Q will always win.

Student Author: Robyn Schwartz

Published: 2012

Project Page

The electrostatic contribution to the second virial coefficient of γ-crystallin

## The electrostatic contribution to the second virial coefficient of γ-crystallin

This project attempts to extend efforts to produce better models of the interactions between the γ-crystallin molecules found in the eye lens. The ultimate goal is to determine how the non-uniform distributions of acidic and basic—proton donor and proton acceptor—sites and their relative orientations affect these interactions. Although previous research projects have created the code necessary to simulate γ-crystallin pair interactions sans various contributions of lesser significance, the quantity of computations required mitigates the production of enough data to generate a meaningful model. Thus, we are researching various computational methods to optimize simulation performance.

Student Author: David Brenton Allen

Published: January 2015

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Ionic strength dependence of γβ crystallin diffusivity and molecular weight at low pH

## Ionic strength dependence of γβ crystallin diffusivity and molecular weight at low pH

In this project, dynamic and static light scattering are being used to study the behaviour of γβ crystallin at low pH and at different ionic strengths, and to find experimentally the molecular weight of such proteins. By using an inverse Debye plot, the molecular weight was found to be (21616 ± 882) g/mol, which agreed with the known value of 20960 g/mol. In addition, the hydrodynamic radius was found to be (2.74 ± 0.07) nm, although it did not agree with a previous measured value of (2.39 ± 0.03) nm, the presence of dust or unexpected formation of dimers might have influenced on the present experiment. Moreover, at pH 4.4, γβ crystallin showed a repulsive interaction between the particles. In Capstone Project II, the ionic strength dependence at low pH will be studied in depth, in order to probe for the possibility of cluster formation analogous to those found for lysozymes .

Student Author: Rafael Herschberg

Published: 2012

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Applications of Quantum Game Theory

## Applications of Quantum Game Theory

Game theory is a theory of decision making. Players employ strategies to optimize payoffs in games. A twoplayer, zero-sum game, such as the coin flip game, can be played using pure or mixed versions of quantum or classical strategies. In strictly classical games, von Neumann's Minimax Theorem guarantees an equilibrium for an appropriate mixed strategy. However, owing to the quantum mechanical superposition principle, quantum strategies allow for payoffs that are not possible in classical games. We examine quantum mechanical two player, zero-sum games of strategy. In particular, we use the PQ Penny Flip game described by Meyer[2] and determine outcomes for various cases involving different quantum strategies. The results show that if the right quantum strategy is used, player Q will always win.

Student Author: Robyn Schwartz

Published: 2012

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Imaging With an Optical Vortex Coronagraph

## Imaging With an Optical Vortex Coronagraph

This experiment explores the use of a vortex coronagraph as a way to get information from a poorly resolved system of light sources. This is done by using two optical fibers as equal intensity point sources of light and measuring the intensity of the light after it passes through the vortex coronagraph. Imaging systems have an angular separation where the point sources are no longer resolvable, but we expect that this system with the optical vortex coronagraph will allow us to get information about the light sources at separations smaller than typically allowed, for example smaller than the Raleigh criterion of 1.22 λ/D .

Student Author: Matthew Hesselink

Published: 2012

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Measurement of Resistance Anomalies In Heusler Alloys

## Measurement of Resistance Anomalies In Heusler Alloys

A Heusler alloy is a ferromagnetic alloy based on a Heusler phase, a solid-state phase of a specific composition with a body centered, L21 crystallographic structure. Utilizing a four point resistance measurement this project has allowed the measurement of resistivity as a function of temperature for the set of Heusler alloys in question (Ni_{2}MnSn, Ni_{2}MnGa and Ni_{2}Mn(SnnGa_{1−n})). Such measurements should yield a discontinuity in a graph of resistance vs. temperature as the sample reaches the Curie Temperature, the temperature at which the metal undergoes a solid state phase transition. Thus far testing has proven to be inconclusive, showing no discontinuity at the desired temperature aside from one instance, before a computational basis of data collection was established.

Student Author: Steven V. Ulrich

Published: 2012

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An exploration in the use of Carbon Nanotube films as Gas Sensors

## An exploration in the use of Carbon Nanotube films as Gas Sensors

Gas sensors are widely used in many industrial, residential, and scientific applications. As technology advances, the call for smaller and more sensitive gas sensors increases. Carbon nanotubes are a fascinating group of nanomaterials that have many unique properties making them well suited for gas sensing applications. Properties such as a high surface area to volume ratio, the ability to be functionalized and unique thermal properties. Sensors consisting of metallic interdigitated electrodes deposited onto thin films of single wall carbon nanotubes were fabricated and tested in three different trace gases, Hydrogen *H2*, Carbon monoxide *CO*, and Ammonia *NH _{3}*. Ammonia exhibited the only response having sensitivities on the order of .4%, These sensitivities are as of yet independent of the presented gas concentration.

Student Author: John Y. Howson

Published: 2012

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NMR Study of Peptide-Palladium Binding Involving Water Suppression Techniques

## NMR Study of Peptide-Palladium Binding Involving Water Suppression Techniques

Certain peptides can interact with metal ions and form them into nanoparticles. The peptide Pd4 will do this with palladium. This project investigates the binding of Pd4 and palladium in intermediate complexes formed en route to nanoparticle formation. Pd4 has 3 variant peptides, related by a change of one or two amino acids, that are also being studied in this project. The intermediate complexes of all four of the peptides have not been well studied. The tool of investigation for this project is nuclear magnetic resonance. First, NMR spectra are collected of Pd4 and variants of Pd4 without any palladium added. A series of titrations will be made with increasing palladium concentration, and NMR spectra will be taken for those titrations. The suppression of signal from H_{2}O must be improved to fairly high degree of success before starting with titration spectra. Currently, the water suppression is almost at the desired level of success.

Student Author: Colin J. Jacob

Published: 2012

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Geometrically cohesive granular materials: rheology of staple piles

## Geometrically cohesive granular materials: rheology of staple piles

The characteristics of U-shaped geometrically cohesive granular materials are investigated. Staples are rolled together in a tumbler to constant packing fraction (about 24% for standard staples) and constant end-velocity tensile tests are conducted. A slide was built to conduct rheology experiments. The force applied to stretch the pile and distance stretched are measured electronically through LabVIEW. A power spectrum of force was shown to have a frequency dependence of *f ^{ −n} *with

*n*= 2.0 ± 0.3 for standard size staples. Preliminary data suggests this holds for other barb ratio (leg length to spine length) staples.

Student Author: Patrick Battaglia

Published: 2012

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Magnetic Investigation of Various Heusler Alloys

## Magnetic Investigation of Various Heusler Alloys

Heusler series are an interesting collection of alloys that exhibit a unique combination of shape, thermal, and electrical properties. For this research, a vibrating sample magnetometer was used to detect the magnetization of the sample alloy, as a function of temperature and applied field strength. Additionally, a temperature controller will be set up to test the sample at controlled temperatures.

Student Author: Raymond Lazott

Published: 2012

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Simulating Stoner-Wohlfarth Magnetic Particles

## Simulating Stoner-Wohlfarth Magnetic Particles

The magnetic behavior of two interacting single-domain magnetic particles is simulated. The particles are fixed in space and are approximated as interacting point dipoles at their centers, while an external field is applied. The resulting magnetization curves of the two interacting magnetic particles are simulated. The magnetization direction of the individual particles is governed by Stoner-Wohlfarth theory.

Student Author: Joseph Caprino

Published: 2012

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pH Dependence of Bovine GammaB Crystallin Virial Coefficient

## pH Dependence of Bovine GammaB Crystallin Virial Coefficient

Recent work has shown that interactions between γ-crystallin proteins located in the eye can contribute to the formation of cataracts. Of the techniques available one of the most useful for measuring the interactions is the second virial coefficient, B_{2}, where the virial coefficients quantify the low concentration deviations from ideal solution thermodynamics. To measure the virial coefficient of the γB-crystallin proteins static light scattering was used. From the light scattering measurements the value of the molecular weight was determined to be (22659 ± 1220) (mean ± std. dev.) grams/mole , which does agrees within twice the standard deviation to the sequenced value of 20992.7 grams/mole for single γB-crystallin proteins. The dimensionless second virial coefficient, B_{2}, at a pH of 4.4 was measured to be (8.11 ± .99) which is greater than that predicted from the model of hard spheres and hard sphere dimers suggesting a more repulsive interaction as expected at this pH from prior work in this lab.

Student Author: Kaho Long

Published: 2012

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An Investigation of the Effects of Varying Growth Conditions on Induim-Arsenide Quantum Dots

## An Investigation of the Effects of Varying Growth Conditions on Induim-Arsenide Quantum Dots

Stranski-Krastanov (SK) grown Indium Arsenide Quantum Dots (InAs QDs) have been studied and their optical and physical properties compared. Four independent experiments were conducted, varying a series of growth parameters, Θ_{c}, InAs coverage, T_{g}, growth temperature, GRI, Growth rate interrupt and V/III ratio. Test structures were analyzed using atomic force microscopy (AFM) evaluated using Scanning Probe Image Processor (SPIP) software and statistical results were compared to optical results using photoluminescence (PL) spectroscopy. It was seen that an increased InAs coverage tended to increase average QD height with subsequent decrease in areal number density with average heights ranging from 1.6±0.5nm to 3.9±0.5nm and areal number densities ranging from (1.28±0.2)x10^{10}cm^{−2} to (3.00±0.2)x10^{10}cm^{−2} . Statistical results from the V/III ratio series showed that increased ratio produced higher number densities with lower average heights, ranging from 1.7±0.3nm to 4.7±0.3nm. PL data showed that a V/III ratio of 12 led to the best optical quality dots. Growth temperature studies showed that higher growth temperature produced lower number densities of dots with higher average heights at each point measured, with heights ranging from 2.5±0.3nm to 5.5±0.3nm and number densities ranging from (0.59±0.01)x1010cm−2 to (2.57±0.1)x1010cm−2 . GRI studies determined that a 30 second interrupt led to both higher densities of dots and higher average heights than a 10 second interrupt with heights ranging from 2.3±0.3nm to 2.5±0.3nm and number densities ranging from (4.3±0.1)x10^{10}cm^{−2} to (7.0±0.1)x10^{10}cm^{−2} .

Student Author: Adam Podell

Published: 2011

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Modifying the DLVO Potential to Incorporate Discrete Embedded Charge Distributions

## Modifying the DLVO Potential to Incorporate Discrete Embedded Charge Distributions

In this paper we discuss a means of modeling the interaction between two charged particles in electrolyte solution which will consider the effects of discrete arrangements of charge embedded within a dielectric. This model builds off the DLVO theory for colloid interaction, using a similar analysis of van der Waals forces, while expanding upon the simple model used for electrostatic forces. The model describes neighboring particles by specifying the locations of individual charged groups in two dielectric spheres and uses a finite difference method to solve for the voltage within both particles and the surrounding electrolyte solution. This method has been used to predict interaction energy between particles with a dipolar distribution of charge in a range of solutions in order the gain insight into how the Debye length, relative dielectric of the molecules, and depth of charge within the dielectric will affect interactions between particles. A method which has been developed to construct the interaction potential between molecules in an efficient manner is also discussed

Student Author: Elias Putzig

Published: 2011

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Detailed Nebular Diagnostics for the Host Galaxy of E1821+643

## Detailed Nebular Diagnostics for the Host Galaxy of E1821+643

Two key features of this active galactic nucleus have motivated this study: the location in a cooling flow and a region of ionized gas that extends to a significant fraction of the host galaxy’s size. We sought to characterize this extended region by analyzing optical emission of ions in the nebulae. Using data from observations with the Gemini North long slit spectrograph, we fit analytical functions to prominent emission lines such as Hα, Hβ, [S II], [O III] and [O I]. Line intensity is computed from fit parameters, from which we determine electron density—we also make use of diagnostic diagrams and empirical relations to establish the source of ionizing radiation. A series of photoionization models were constructed to simulate gas clouds exposed to an ionizing source; by comparing model output and observed data, we infer properties that emission line analysis alone cannot provide. We also analyze how ionization conditions depend on radial distance from the nucleus. We find that observed emission lines cannot be explained by star formation, radiative shocks, or composite galaxies; further, we show that nebular abundances rival or exceed solar values, the clouds become optically thick at the edge of the extended region and that the incident continuum shape is typical of an active galactic nucleus.

Student Author: Sean P. Quinn

Published: 2011

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Interaction between γ-crystallin eye lens proteins

## Interaction between γ-crystallin eye lens proteins

Static light scattering studies were used to better quantify the intermolecular interaction potential between γ-crystallin proteins found in the lens of the eye. Recent work has shown that the interaction potential between α- and γ-crystallin proteins may be responsible for instabilities of protein solution that could contribute to cataracts. To help quantify this interaction strength, the virial coefficients for pure γ solutions have been measured, and further studies would measure pure α and then move on to measure the mixed α–γ solution virial coefficients—the first in a series of corrections to the solution analog of the ideal gas law. In addition to the second virial coefficients, preliminary measurements of the molecular weights of the γ-crystallin have been made. From the light scattering measurements, the value of the molecular weight was determined to be (26462 ± 443) g/mole. Although this disagrees with the well known value of 20960 g/mole for single γB-crystallin proteins, there is reason to believe that the γB solution measured contained mixtures of monomers and dimers. The second dimensionless virial coefficient was measured to be (−3.93 ± .55), and the value for the third dimensionless virial coefficient was not well determined.

Student Author: Summer N Saraf

Published: 2011

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Experimental assay of eye lens alpha-crystallin subunit homopolymers

## Experimental assay of eye lens alpha-crystallin subunit homopolymers

The interactions between the three major groups of structural protein within the mammalian eye lens have been found to affect the formation of cataracts, by either polymeric aggregation or phase separation. The largest and most abundant of these crystallin proteins is α-crystallin, a polydisperse macromolecule composed of approximately forty subunits of two types of peptide chains, αA and αB. More work is needed to characterize the molecular weights and interactions of assembled, separated, and controlled mixtures of aggregates of theα-crystallin subunits, to better identify the role of each subunit in lens transparency. In this Capstone, we explored the efficacy of different subunit refining and reassembly techniques, for the purpose of preparing samples for characterization of protein properties by light scattering. Once subunit disassociation was confirmed, the subunits were separated and identified using cation-exchange gel chromatography and isoelectric focusing electrophoresis, respectively. During the first stage of our project, we re-aggregated the confirmed and separated αA subunit fraction, and made preliminary light scattering measurements of the molecular weight, the second virial coefficient, and the average diameter of the assembled particles. During the second phase of the project we tested reaggregation techniques.

Student Author: Timothy Shank

Published: 2011

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Response of Flammable Analytes investiagated via Zinc Oxide Gas Sensors

## Response of Flammable Analytes investiagated via Zinc Oxide Gas Sensors

Zinc Oxide (ZnO) nanoplatelets and ZnO thin films were tested as hydrogen (H2) sensors. Initially ZnO nanoparticles were drop-casted onto commercial inter-digitated electrodes structures (IDEs). Quality of sensing film was verified via Nomarski microscopy. At 16^{◦}C, the ZnO nanoplatelet sensor achieved a maximum sensitivity of 68.6%. Sensitivity of the ZnO nanoplatelet sensor decreases as carrier gas flow increases and as concentration decreases. Sensitivity of the ZnO nanoplatelet sensor increases as sensor is heated above 100^{◦}C and is significantly increases as the sensor is heated above 150^{◦}C. ZnO nanoplatelet sensors were compared to ZnO thin film sensors. Platinum (Pt) IDEs were fabricated on ZnO thin films via photolithography and metal evaporation in RIT’s Semiconductor & Microsystems Fabrication Laboratory. Two different types of ZnO thin films were used, undoped and Cobalt (Co) doped ZnO and compared. Undoped ZnO sensors yielded a higher sensitivity of 7.8% while Co-doped ZnO sensors resulted in a sensitivity of 4.4%. ZnO nanoplatelet sensors had a surface area of 17110 mm^{2} compared to the 2.04 mm^{2} surface area of ZnO thin film sensors.

Student Author: Wyatt Strong

Published: 2011

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Resistance Measurements in Heusler Alloys

## Resistance Measurements in Heusler Alloys

Heusler alloys are the subject of current interest because many exhibit unusual properties such as spin polarization and strong magnetoresistance. Our ultimate goal was to form these alloys using induction heating and to perform resistivity measurements while varying temperature to determine Curie temperatures. We developed a procedure for producing samples in the induction furnace. We performed above room temperature resistance measurements on Ni_{2}MnGa, but did not observe a transition

Student Author: Melissa Trepanier

Published: 2011

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Imaging Properties of Cylindrically Symmetric Gradient Index Rod Lenses

## Imaging Properties of Cylindrically Symmetric Gradient Index Rod Lenses

Gradient index lenses are being investigated for use in a variety of imaging applications. Their ability to focus light without the requirement of precise surface geometry tolerances makes them an attractive and economical alternative to conventional lenses. Understanding the imaging properties of gradient index lenses will be crucial in deciding which applications will benefit from their use and which new applications will be made possible. In this investigation; a single gradient index rod with a parabolic index profile is used to image a 1951 USAF Resolution Test Target. Contrast data is acquired and an MTF plot is constructed. Transmitted wavefront data is aquired with a commercial optical interferometer, and the wavefront is curve fitted to Zernike polynomials to determine the values of the third order aberration coefficients. The type and severity of image aberrations are analyzed, and potential corrections for such aberrations are proposed, leading to a better understanding of the strengths and limitations of such lenses in imaging applications.

Student Author: Michael J. Andrews

Published: 2011

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Magnetic Measurements and Investigation of Novel Heusler Alloys

## Magnetic Measurements and Investigation of Novel Heusler Alloys

A Heusler alloy is a ferromagnetic metal alloy based on a Heusler phase. Heusler phases are intermetallics with particular composition of at least three constituent metallic elements and a L2_{1} cubic crystal structure. This class of alloys often exhibits unusual magnetic properties, which although they are not fully understood at this point in time, may prove useful. Starting with a nickel sample, basic measurements of the initial permeability, hysteresis loop, and temperature behavior were performed to gain familiarity with the operation of the VSM, or Vibrating Sample Magnetometer, as well as to calibrate it. Once samples of Heusler alloys were obtained, by making new samples in-lab using an RF furnace, measurements of the samples’ magnetic properties were taken. Data was taken on a sample of material with the stoichiometric formula N i_{2}MnGa. This data was then analyzed to determine various magnetic properties of the materials, such as the Curie temperature and the critical exponents β and γ.

Student Author: Matthew J. Wahila

Published: 2011

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Characterization and Shearing of Dense Packings of Granular Materials Through Computational Simulation

## Characterization and Shearing of Dense Packings of Granular Materials Through Computational Simulation

Jamming, a configuration of particles in which (significant) movement is no longer able to happen, is one of the most important areas of study within a granular media. This is the case because it has a vast number of applications not just to granular materials, but also colloids, emulsions, and molecular glasses. Aspects of jamming, such as the rigidity of the jam, vary depending on the type and dimensions of the particles involved. A tangible example of this being how it is possible to stir a bowl of (uncooked) rice with ease, while stirring a bowl of toothpicks, would be much more difficult, resulting in either no motion, or entire clusters of toothpicks moving as a solid. The fundamental difference between these particle types (rice and toothpicks in this case) is the aspect ratio, defined as the ratio of length to diameter of a particle. The study of how aspect ratio results in solid/fluid phase transition among particles has been ongoing but is not yet understood. At first glance, the only readily visible difference between packings of different aspect ratios is the packing fraction or packing density Φ which is the ratio of volume occupied by particles to the total volume available. Our goal is to further characterize this system through applying the use of the dynamic matrix as well as compression and shearing to simulated packings of granular materials in order to better understand the underlying causes of the solid/fluid transition behavior.

Student Author: James Graham

Published: 2011

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Experimental Determination of the Gibbs Free Energy for a Ternary Mixture via a Partial Differential Equation Method and Light Scattering Data

## Experimental Determination of the Gibbs Free Energy for a Ternary Mixture via a Partial Differential Equation Method and Light Scattering Data

Information on the Gibbs free energy of a multi-component liquid greatly facilitates the determination of its thermodynamic behaviour. The goal of this project was to experimentally test a theory for determining the Gibbs free energy of a mixture through light scattering data. [1] The present experiment used a Helium-Neon laser in conjunction with a photomultiplier tube (PMT) to measure the intensity of scattered light and thus determined the Rayleigh ratio of miscible or single-phase solutions at different concentrations. The data were then used to numerically solve the partial differential equation that governs the relation, between the Gibbs free energy and Rayleigh ratio.

Student Author: Oscar D.J. Marcelino

Published: 2011

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Chaos in the Magnetic Dipole Motor

## Chaos in the Magnetic Dipole Motor

In recent years nonlinear systems and chaos have been of great interest to physicists. One system known to exhibit chaos is a magnetic dipole in an oscillating magnetic field. In order to examine the route to chaos in this system, an experimental investigation and a numerical simulation were performed. A NeFeB magnet was used and the system was analyzed at a drive frequency of 2 Hz. The results of these were analyzed using phase space plots, Poincar´e return maps, and bifurcation diagrams. The results are consistent with results by Ballico [1]. In addition, the effects of two types of damping were observed: the air resistance, and frictional damping in the bearings. A detailed investigation into the effects of initial phase of the drive field was also carried out. All of the experimental results found were consistent, within experimental uncertainty, with the simulated, theoretical results.

Student Author: Zachary E. Dell

Published: 2010

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5CB∗ Liquid Crystal Experiment

## 5CB∗ Liquid Crystal Experiment

In a liquid crystal, the Fr´eedericksz transition can be observed to determine properties of the material. This capstone project will attempt to examine how the Fr´eedericksz transition changes with temperature, and therefore how the properties of the material change with temperature. This document will summarize the theory of liquid crystals, derive equations pertaining to the experiment, describe the experiment used to find the properties, and report the results of the experiment.

Student Author: Andrew Drake

Published: 2010

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The Eclipsing Binary Star MR Delphini

## The Eclipsing Binary Star MR Delphini

Some stars when studied show a change in apparent brightness compared to nearby stars. These stars change because the system happens to be a close binary in which two stars are revolving around each other. We monitored one such system, MR Delphini, and we were able to determine some of its parameters. This data uses a combination of different filters and radial velocity measurements to improve upon previous measurements of the system. Both components seem to be of K spectral type (between 4000 and 5000 degrees Kelvin) and fit the qualifications of being main sequence stars. There is also a third component, also of K spectral type, behind these two that affects the overall brightness of the system but does not affect the eclipse itself. We hope that these results will help further not only studies of our system but any close binary system studies. Goals and Motivation The purpose of this project is to find the characteristics of the binary system MR Delphini. These include the period, temperature, size and mass of the stars but also other factors that may be discovered. The motivation for taking on the project in the first place involves learning how to find the aforementioned characteristics but also learning how to observe and take pictures of a binary system using the observatory; clean raw observatory images; use these images to extract data on the system; create a magnitude (brightness) vs. time graph; create as accurate a model of the system as possible. Collecting and modeling this data turns out to be useful on a larger scale as well. There is the obvious point that any other astronomers that want to look at this data later will have more background info. In a more general sense, the projects errors and successes can serve as an example to future astronomers studying eclipsing binary stars. A good system to study must have stars that eclipse each other so as to create a varying magnitude; be visible in Rochester at the time it is being studied; have a short period of revolution so enough measurements can be taken; have reference stars around it of similar apparent magnitude. MR Delphini happens to exhibit these properties and as such this is the reason it was chosen. Eclipsing Binary S

Student Author: Justin Ludwigsen

Published: 2010

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Thermodynamics and Electrostatics of the Eye Lens Protein GammaB Crystallin

## Thermodynamics and Electrostatics of the Eye Lens Protein GammaB Crystallin

In attempt to better understand the liquid-liquid phase transition in the cytoplasm of eye lens cells, which is related to the molecular orgins of cataract, we model the contribution made by electrostatics through computer simulations of the protein GammaB crystallin. There are several factors that complicate the accurate modeling of gamma crystallin electrostatics. These include an inhomogeneous dielectric, ionic screening of charge interactions[1], and the dynamic response of protonatable groups on a protein to the local electrostic potential known as charge regulation [2]. Current models of proteins incorporate ionic screening but charge regulation and are often omitted. A model for the electrostatics of the GammaB Crystallin is developed. A finite difference method using a rectangular grid is developed for solving this model of the GammaB. Also a Metropolis Monte Carlo program for finding the statistics of occupancy for a particular pH is developed and used to calculate titration curves for the GammaB. Additionally, we modeled two proteins and found when they first interacted. Rules of thumb for calculating the potential are discussed as well as the most likely charge configuration of the GammaB at neutral pH

Student Author: K. Michael Martini

Published: 2010

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Behavior of light near massive objects

## Behavior of light near massive objects

The path that light travels is the shortest distance between two points in space and time. Near massive objects, space and time become distorted and curvature occurs. The bending of light occurs because light travels along null geodesics. A metric tensor is a description of the gravitational field in a certain region of space. The metric is used with the geodesic equation in order to get the equations for the path of light. The simplest metric is the Schwarzchild metric which describes a stationary black hole. There are many metrics which are used to describe a mass with differet properties (i.e. rotation, radiation, charged, etc.). The metric that best describes a real system is the Kerr metric, the metric for a rotating mass. This bending of light can be observed on the stellar scale as an increase in the brightness of the background object and can provide insight into the object that is causing the bending.

Student Author: Mark McCoy

Published: 2010

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Modeling Concentrator Solar Cells Using Detailed Balance and Numerical Approaches

## Modeling Concentrator Solar Cells Using Detailed Balance and Numerical Approaches

The conversion efficiency of single and triple junction solar cells were modeled utilizing a detailed balance theory. Simulations were coded in Matlab. Two methods were used to model the triple-junction solar cell. First, using a modified single junction model and second using Lagrange multipliers. Error between the two methods was found to be the smallest at the highest maximum efficiency. Conversion efficiencies of 48.1%, 47.4% and 50.6% were found for 6000K black body, AM0 and AM1.5 spectra respectively. A global Lagrange model was also made and used to model the effects of concentration and temperature on a triple junction cell.

Student Author: Tim Bald

Published: 2010

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Modeling Concentrator Solar Cells Using Detailed Balance and Numerical Approaches

## Modeling Concentrator Solar Cells Using Detailed Balance and Numerical Approaches

The conversion efficiency of single and triple junction solar cells were modeled utilizing a detailed balance theory. Simulations were coded in Matlab. Two methods were used to model the triple-junction solar cell. First, using a modified single junction model and second using Lagrange multipliers. Error between the two methods was found to be the smallest at the highest maximum efficiency. Conversion efficiencies of 48.1%, 47.4% and 50.6% were found for 6000K black body, AM0 and AM1.5 spectra respectively. A global Lagrange model was also made and used to model the effects of concentration and temperature on a triple junction cell.

Student Author: Tim Bald

Published: 2010

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Optical Vortex Coronagraph

## Optical Vortex Coronagraph

The purpose of this experiment was to further the development of the coronagraph in the optical field. The goal was to use a telephoto lens as a telescope and couple it with an optical vortex coronagraph to create a portable coronagraph to use for demonstrations. The strehl ratio of the telephoto lens was calculated to be 0.97 ± 0.03 and the vortex lens was analyzed to decrease the intensity of a laser beam by 24%.

Student Author: Allison Browar

Published: 2010

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Ebb and flow of student knowledge in introductory physics

## Ebb and flow of student knowledge in introductory physics

We have extended an earlier study by Sayre et al.[1] on student learning, forgetting and interference in introductory calculus based physics. Our study took place at Rochester Institute of Technology which has the advantage of offering all three courses of introductory physics each quarter. Each quarter we administered seven tasks covering vectors, kinematics, and basic dynamics to students in intro physics I, covering mechanics, and intro physics III, covering electricity and magnetism. In the Fall quarter, there were five sections of physics I (N = 142) and eight sections of physics III (N = 257) and in the Winter quarter there were 14 sections of physics I (N = 421) and five sections of physics III (N = 144). The important results were that students in different intro physics I courses performed indistinquishably on a Newton’s Third Law task and that interactive engagement sytle of instruction appears to help students retain the scalar nature of electric potential after instruction has ceased.

Student Author: Jessica W. Clark

Published: 2010

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Simulating the Solar System : the Yarkovsky Effect

## Simulating the Solar System : the Yarkovsky Effect

Of the four fundamental forces gravity is the weakest. Yet it binds the massive objects within the Solar System and using Newton's law of gravitation it is possible to accurately predict the orbit of these celestial bodies. However, as modern technology improves at an astounding rate we are able to detect the subtle driving forces within our Solar System. Of these forces is an effect first discovered by Ivan Osipovich Yarkovsky, called the Yarkovsky effect. The effect was measured for the first time on 6489 Golevka in 2003.

Student Author: Kei Kawabata

Published: 2009

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Chaotic Dynamics of an Elastically Bouncing Dumbbell

## Chaotic Dynamics of an Elastically Bouncing Dumbbell

During the course of this research I have written a flexible program to simulate the motion of a dumbbell elastically bouncing on a flat horizontal, frictionless surface. The simulation shows situations of periodic locking, quasi-periodic meandering, and fully chaotic tumbling in the motion of the dumbbell. We consider the degeneracy in time of flight between bounces as a means of identifying these periodic flights. We also map the problem as a billiard bouncing horizontally through a ^{θ} space and calculate the diffusivity of the angle of the dumbbells. We also calculate the Lyapunov exponent of points in the phase space of the dumbbell.

Student Author: Colin Rees

Published: 2009

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Light Scattering Study of a Microemulsion System

## Light Scattering Study of a Microemulsion System

1 Project Goals Light Scattering techniques provide a powerful tool to observe the microscopic world. The properties of a certain microemulsion system are to be studied using both static and dynamic light scattering. These properties include particle size and inter-particle potential. These properties will be measured as a function of particle volume fraction and temperature. It is also desired to reproduce results reported by Chen and Huang [1], in which they found a minimum in the initial decay rate(Γ_{1}) of the intensity autocorrelation function at a volume fraction of .62. 2

Student Author: Kevin Segall

Published: 2009

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Ultraviolet Observations of Star Formation in Brightest Cluster Galaxies

## Ultraviolet Observations of Star Formation in Brightest Cluster Galaxies

Brightest cluster galaxies are above average-sized galaxies located at the center of clusters. Within these galaxies is a cooling plasma that eventually becomes a neutral gas that will form stars. In theory, the plasma cooling rate found from x-ray emissions should equal the star formation rate, but the star formation rate is often an order of magnitude lower than the cooling rate. By analyzing ultraviolet observations from the Hubble Space Telescope, the star formation rate can be calculated and compared to the cooling rate. These calculated star formation rates are lower than other independently calculated values, but this discrepancy can be explained through alternative dust heating sources, varying starburst model initial conditions, and host galaxy dust extinction. Of the three, host galaxy dust extinction plays the most significant role in affecting calculations.

Student Author: Bradford Snios

Published: 2009

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Spatial Infrared Characterization of Solar Cells

## Spatial Infrared Characterization of Solar Cells

The purpose of this project was to find non-uniformities with spatial resolution in solar cells. This was done using the Luminoscopy method [1]. Non-uniformities were found in Gallium Arsenide (GaAs), Indium Gallium Phosphide (InGaP), tandem cells with these 2 materials, and GaAs cells with quantum dots (QD). The non-uniformities include broken fingers, areas of high resistance, areas of low or no radiative recombination, surface defects, and non-uniform QD distribution.

Student Author: A. Vargas

Published: 2009

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Characterization of Concentrator Photovoltaics

## Characterization of Concentrator Photovoltaics

The characterization of quantum dot solar cells (QDSC_{s}) is important as few reports on this subject are available thus far. Presented in this investigation are extracted cell parameters including parasitic resistances and diode characteristics, as well as physical interpretations of these results. Parasitic resistances were obtained from the comparison of dark J-V with J_{sc}-V_{oc} curves (used to find series resistance-R_{s}), and by applying a small reverse bias to produce a measureable current (used to find shunt resistance-Rsh). Fitting curves to the measured J_{sc}-V_{oc} data using a MatLab program yielded diode parameters. The illuminated series resistance (R_{slight}) was also determined by comparing the Jsc-Voc curves to the one sun AM0 illuminated J-V curves. Cells of varying strain compensation level (SC) were investigated under constant temperature conditions, while a second study compared cells of varying QD layers under varying temperature conditions. Rslight and Rsdark were minimized in cells with SC between 9-14Ǻ. Samples with these optimal SC levels also yielded fill factors (FFs) of ~75%, close to that of our baseline. In the 20_{x} QD study, a temperature coefficient of R_{sdark} was found to be -0.19 ΩK-1. Analysis of R_{sh} trends over this same temperature range allowed for the extraction of activation energies which were ~0.4 eV for all but the 5x QD sample (0.6 eV). An optimum range of 9-18Ǻ SCL was found, as well as favorable solar cell performance at higher, realistic operating temperatures. Determining the parasitic resistances and diode parameters associated with QDSC_{s} is essential to understanding what factors contribute to the degradation in cell performance, and what can be done to mitigate these negative effects.

Student Author: Eric Albers

Published: 2009

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The Time Evolution of Non-Singular Primordial Black Holes

## The Time Evolution of Non-Singular Primordial Black Holes

We explore the time evolution of the Mbonye-Kazanas non-singular black hole. The Mbonye-Kazanas solution to the Einstein Field Equations admits two horizons, an outer Schwarzschild-like horizon and an inner de Sitter-like horizon.The analysis models the time evolution of the black hole mass subject to the competition between the Hawking radiation and the black hole accretion during the radiation dominated era of the universe. We find that when the Hawking evaporation process completes, there is a finite mass leftover. This remnant mass asymototically approaches approximately 9.29×10^{26}r_{0} ≈ 1.48×10−8 kg, where r_{0} is the de Sitter radius that we assume is on the order of the Planck length. This mass corresponds to the limiting value of mass necessary for black hole formation to occur. Therefore this work confirms that the Mbonye-Kazanas black hole will not radiate its entire mass through Hawking radiation. We also find benchmark initial masses corresponding to what size NSBH_{s} would be remnant masses (G-lumps) by the end of the radiation dominated era and what size NSBH_{s} would be becoming remnants currently.

Student Author: Nicholas A. Battista

Published: 2009

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Particle Infall for Radiating Black Holes

## Particle Infall for Radiating Black Holes

The purpose of this work is to determine the limits of particle accretion for a radiating black hole. Using the Vaidya metric under Hawking radiation, the critical initial position for which a particle’s radial position vanishes with the Schwarzschild radius of the black hole is determined for various initial black hole masses. This critical radius is found to depend on the initial mass according to a simple power function. The implications of this result are then discussed, including a derived minimum mass under which a singular black hole loses the ability to accrete mass, as well as how this applies to microscopic black holes as may be produced by the Large Hadron Collider (LHC).

Student Author: Benjamin Farr

Published: 2009

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Random Packings of Spherocylinders

## Random Packings of Spherocylinders

Experimentally, packings of high aspect ratio rods have been shown to exhibit rigidity which is not present in low aspect ratio rods. This project involves creating a computer simulation which can achieve stable, realistic spherocylinder packings in order to examine this behavior, utilizing conjugate gradient techniques in order to minimize the potential energy and thus relinquish rod overlap. Of interest is the relation of the average contact number to the isostatic limit. Also, rigidity can be analysed by studying the dynamical matrix of the system.

Student Author: Tim Green

Published: 2009

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Colloid Osmotic Pressure of Bovine Gamma-B and Gamma-III Crystallins

## Colloid Osmotic Pressure of Bovine Gamma-B and Gamma-III Crystallins

We have constructed a membrane based colloid osmometer and have used it to measure the osmotic pressure of bovine gamma-B and gamma-III crystallins, proteins found in the lens of the eye. Studying these proteins can potentially give a clearer understanding of cataract disease, and how cataracts form. We find in a 0.1M sodium acetate solution the gamma-III second virial coefficients, normalized by particle volume, are 44 ± 20 at pH 4.47 and −16 ± 8 at pH 5.377. For gamma-B in 0.275M sodium acetate buffer the normalized second virial coefficients are 32 ± 16 at pH 4.5 and 4 ± 4 at pH 4.8. While more data are needed, these results are possibly consistent with previous experiments performed with gamma-B and gamma-III, as previous phase separation and neutron scattering data have suggested that at pH 4.5 the net forces between these proteins are repulsive, but become attractive at pH 5.5. To make these results more secure, the physical origin of an observed experimental offset needs to be identified.

Student Author: Benjamin Haehnel

Published: 2009

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High Velocity Gas Flows in Active Galactic Nuclei

## High Velocity Gas Flows in Active Galactic Nuclei

For Active galactic nuclei to accrete matter into a super massive black hole from an accretion disc, angular momentum must be released from the infallling matter. While the physical mechanism is still being determined, radial outflows may play an important part in removing angular momentum from the accreting gas and depositing this mechanical energy in the galactic system. Active galactic nuclei are likely to exhibit strong winds when the accretion disk luminosity approaches the Eddington limit. Studying emission lines from the broad line region near the black hole, the effects of these outflows should be visible in the profile shape. A two Gaussian model, implementing concentric shells of clouds located radially outward from a black hole depicting broad and intermediate velocity dispersion, was able to accurately describe a wide spread of profile shapes and sizes. In particular the velocity dispersion of the two components was correlated as ( ) FWHM _{BC} 3 FWHM _{IC} = 2.8 ± 0. , in agreement with the recent results of Hu et al 2008. It was also found that both components could be either red- or blueshifted; however, they were not correlated. The broad component, in particular, did show an overall redshift in its distribution, but gravitational redshift may account for the net shift. Assuming gravity dominates, the geometry of the intermediate region was then proved to have radius of 8 times the broad radius and a surface area roughly 64 times bigger. The relationship between velocity dispersion and black hole mass also shows that while gravity dictates the size of the intermediate component, it does not fully dominate the broad component of this model. While its strength is unknown, outflows from the active galactic nuclei may be the cause of the discrepancy in this region.

Student Author: G. Hrinda

Published: 2009

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Investigating Ionospheric Radio Propagation

## Investigating Ionospheric Radio Propagation

We constructed an antenna to listen for distant radio signals reflected from clouds of abnormal ionization levels within the ionosphere. Recordings of high-activity events were analyzed to make qualitative inferences of the specific phenomenon of interest, dubbed “sporadic-E” for its dynamic nature. Disturbances in the solar wind were found to be strongly correlated with these events, although no robust causal link could yet be established.

Student Author: Alexander Derby

Published: 2008

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SERIES RESISTANCE MEASUREMENTS OF NANOSTRUCTURED SOLAR CELLS

## SERIES RESISTANCE MEASUREMENTS OF NANOSTRUCTURED SOLAR CELLS

Solar cells are solid state devices designed to take energy from light and generate power, and current research on them is focused on increasing their capability. This project is focused internal resistances. To extract these different characteristics a dark I-V curve and a short circuit current-open circuit voltage current is measured. The latter is accomplished by measuring the cell when sourced at zero voltage and current respectively over a range of light intensities. For this project phase 1 consisted of building a complete experimental apparatus and phase 2 consisted of improving measurements and undergoing a study. The setup is programmed in Labview and can take and log all data automatically. For the study, 28 cells were measured across 4 wafers. 3 wafers consist of dot cells, with 2 being doped with tellurium, and the third baseline wafer contained an intrinsic (un-doped) layer. The doped wafers showed lowest series resistance. However, overall the baseline proved to have the highest average fill factor and efficiency. INTRODUCTION Photovoltaics are solid state devices that can generate electrical power from light, and solar cells are a branch of these devices specifically tuned for sunlight. In 1951 Pearson, Chapin, and Fuller discovered that GaAs semiconductor p-n junctions have 4.5% power conversion efficiency. Since this time, there has been growing interest in similar semiconductor devices, and others which can utilize thin films, organic materials, and multiple junctions.[1][2] Conventional solar cells are nothing more than solid state P-N junctions. In this type of device, semiconductors that have been doped to have different charge carrier concentrations (with electrons as negative carriers and holes as positive) are placed in electrical contact. Before contact, as a result of these different concentrations, these materials have different Fermi levels. When placed next to each other, electrons and holes diffuse across the junction. As they diffuse, an electric field (and thus a potential) is created keeping them at equilibrium. The result of this potential is seen as a shift in the conduction/valence bands. When the semiconduct

Student Author: Elliott C Miller

Published: 2008

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Analysis of Asteroid 755 Quintilla From Ground-Based Observation

## Analysis of Asteroid 755 Quintilla From Ground-Based Observation

Images of the asteroid Quintilla taken by Tracy Davis on April 15, 2004 using the Rochester Institute of Technology Observatory were used to calculate its rotation period and amplitude variation, and to derive a simple shape model. The lightcurve yields a rotation period of 4.58 ± 0.17 hours and amplitude of 0.37 ± 0.08 magnitude. The calculated values agree closely with those previously calculated[1]. Quintilla’s lightcurve has a fairly symmetric shape with a sharp slope upwards and a decline which is shallower. The shape analysis provided inconclusive results, but an ellipsoid with axis ratios of 1:1:1.25 and a deformed ellipsoid with axis ratios 1:1:1.07 modeled in “Maya 2008” provide the best fit and approximate shape respectively. The best fit model correspocds to the smallest χ^{2} and the best approximate shape is the visualization of the model and Quintilla curve. Better estimations can be made by analyzing data taken over a series of aspect angles, instead of a single aspect angle.

Student Author: J. Panzik

Published: 2008

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Experimentally Determining the Effects of a Magnet on a Vibrating Ferrous String

## Experimentally Determining the Effects of a Magnet on a Vibrating Ferrous String

A piezoelectric transducer and videogrammetry were used to determine vibrational properties of a ferrous string when a magnet is introduced near the string. An effort was made to determine additional damping caused by the magnet. Experimental results using the above methods were inconclusive in determining the effects of the magnet on the string.

Student Author: Brian J. Patterson

Published: 2008

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Effects of Relativity in the Global Positioning System

## Effects of Relativity in the Global Positioning System

The Global Positioning System (GPS) is a system that consists of three different segments working together to determine the position of a person with a GPS receiver on the surface of the Earth. In this paper, the effects of Special and General Relativity in the GPS are considered. We intend to explore these relativistic effects and communicate them to a general audience through a museum demonstration.

Student Author: P. Perez

Published: 2008

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ZnO Nanoparticle Gas Sensors

## ZnO Nanoparticle Gas Sensors

ZnO chemical gas sensors were fabricated from prepared ZnO nanoplatelets and their sensitivities to H_{2} gas were investigated under conditions of varying concentration, sensor temperature, and intensity of UV light. It was found that at room temperature and a source voltage of 5V that the ZnO sensor had the best sensitivity of greater than 85% to H_{2} gas at 50ppm and was most sensitive in the absence of UV radiation. At temperatures above room temperature, the ZnO sensor showed sensitivities near 100% to ~50ppm of H_{2} at approximately 130C, where it both responded and recovered faster. Memory effect previously observed was also non-existent at temperatures near and above 100°C. The sensor was also observed to be both slower in response and lower in sensitivity in the absence of UV light in a darkened chamber.

Student Author: Matthew Szeto

Published: 2008

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Carbon Nanotube Fabrication and Characterization Studies

## Carbon Nanotube Fabrication and Characterization Studies

Selective adjustment of variables in the laser ablation and chemical vapor deposition techniques of carbon nanotube production provided insight into why structural diversity is present in the harvested materials. The properties of laser-produced single-walled carbon nanotubes were studied by optical absorption spectroscopy, thermogravimetric analysis, Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy. These materials were compared to those produced using injection chemical vapor deposition. As a carrier gas, argon’s low thermal conductivity allows the production of the larger diameter SWCNTs. Smaller catalyst particle sizes and higher laser power densities resulted in increased SWNCT production. The resulting changes in carbon nanotube quality and diameter distributions, from variations of the experimental parameters, will be discussed.

Student Author: J. Alvarenga

Published: 2008

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AC Susceptibility of Ferromagnetic Materials

## AC Susceptibility of Ferromagnetic Materials

An AC susceptometer with variable temperature was constructed, and used to take measurements to find the Curie temperature of multiple materials. The apparatus was constructed from three coils, one to drive the system and two smaller ones as the pickup coils. A heating system was constructed as well for the system and data was taken for Gadolinium, Alumel and Audio cassette tape. This data was then analyzed and Curie temperatures were obtained. The Curie temperature for Gadolinium found was 20.4 +/- 1.2 °C and for Alumel 158.9 +/- 2.3 °C. The audio cassette tape that was measured was found to have a Curie temperature that was above the limits of the apparatus

Student Author: M. Wallingford

Published: 2008

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Comparing Various Models for Dispersion in Optical Fibers

## Comparing Various Models for Dispersion in Optical Fibers

We have been studying the applicability of two models for dispersion in an optical fiber: a Taylor series expansion of the propagation “constant” and an approximation to the index of refraction using the Sellmeier formulation. By comparing these two models with each other through computational models and also with data from industries such as Corning we are able to determine the differences and similarities on a numerical and physical level. By coupling the time and primary axis of propagation together with the propagation constant we are able to change to co-moving coordinates when using the Taylor Series expansion approach; this is difficult to perform with the Sellmeier approximation because there is no initial propagation constant. When comparing the wave equation for both models, it is easily shown that the Taylor Series model is the simpler as well as the more controllable model. It was also found that the Taylor Series approximation is a more accurate representation to information physical information obtained from outside sources. For these reasons we have concluded that the Taylor Series is a better overall model for dispersion then the Sellmeier approximation, at the current time.

Student Author: Stephen R. Baker

Published: 2008

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Liquid Crystals and the Fréedericksz Transition

## Liquid Crystals and the Fréedericksz Transition

The Fréedericksz transition in liquid crystals is a phase transition based in the competition between structural ordering and ordering along an applied magnetic or electric field. The transition can be examined to determine multiple properties of the material. In this project, two of the three elastic constants of 5CB liquid crystals were found.

Student Author: Daniel Warnow

Published: 2008

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3D Motion Analysis with Videogrammetry

## 3D Motion Analysis with Videogrammetry

This project involved the determination of whether or not an inexpensive two video camera system, the development of which assumes a pinhole camera projection with front image plane and ignores the intrinsic camera calibrations necessary for the standard DLT method [1], could be useful in mechanical analysis. The exploitation of the approximations in projection requires strict camera geometry, however the speed and low cost spent under this emphasis may outweigh the time and costs necessary for more accurate process. The sources of the inadequacies generated by the inexpensive method are to be identified and assessed.

Student Author: Jordan D. Blevins

Published: 2008

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Photon Counting Statistics for Two Characteristic Light Sources

## Photon Counting Statistics for Two Characteristic Light Sources

The statistical nature of two characteristic light sources, a coherent light source and a narrow-band, pseudo-thermal light source, was experimentally studied. A He-Ne laser was used as the coherent light source, and the same laser focused onto a rotating ground glass plate was used for the narrow-band pseudo-thermal light source. The experiment required the design and assembly of an optical setup with counting electronics. The electronics used to collect the data included a photodiode, PMT, MCA, digital oscilloscope, and NIM modules. Different photon count distributions for each light source were observed. The coherent source produced a Poisson distribution and the narrow-band pseudo-thermal source approached a Bose-Einstein distribution.

Student Author: E. Woodward

Published: 2008

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Active Galactic Nuclei and Fossil Nebulae: Modelling the Time Evolution of Luminosity

## Active Galactic Nuclei and Fossil Nebulae: Modelling the Time Evolution of Luminosity

All galaxies have super massive black holes (SMBH) in their cores. Galaxies where the SMBH are receiving fuel (interstellar gas) and radiate strongly from disk accretion are known as Active Galaxies or AGN. Ionizing radiation from the accretion disk photoionizes surrounding gas clouds, which produce a characteristic emission line spectrum. If the fuel supply to the SMBH is interrupted or if the SMBH is removed from the system the AGN fades and the line emission decays. Fossil Nebula are the remnants of inactive AGN if the timescale over which the AGN shuts off is short in comparison to both the recombination timescales of the clouds and the light travel times from the accretion disk to the surrounding clouds. The line emission from these fossil nebulae will evolve with time as the ionized gas recombines. Similar fossil nebulae are expected to occur in the early universe, following the demise of the first generation of massive stars. We model the system as a collection of clouds at different radii and angles with respect to the source ionizing radiation. Using a published theoretical model of the decay of line emission from a single cloud following the fading of the ionizing source, the aim of this project is to follow the time evolution of the total line emission from the nebula. The theoretical model of line emission could be used for comparison with observed line emission of fossil nebula candidates. Possible candidate classes of galactic nuclei are low-ionization nuclear emission line regions (LINERs). The study of the way spectra evolve is important in the further understanding of quasar life-times and the formation of the first stars (population III stars).

Student Author: S. Fernandes

Published: 2008

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Monte Carlo Simulation of effects on anisotropic protein interactions on liquid structure

## Monte Carlo Simulation of effects on anisotropic protein interactions on liquid structure

In this project, I set out to model the behavior of protein molecules in solution. Specifically, I examined the effects that differetn potentials had upon the structure that the proteins made. I simulatd, in two dimenstions, these complex systems using adjustable parameters. In my imulations, I could adjust how much of the simulated area was occupied by particles, and I could vary the definition of the potential. By doing this, I hoped to gain inside into the effects that these parameters had. I compared the results I obtained for the different potentials using graphs of the radial distribution, so that I could see how the simulated particles had arranged themselves after the simulation ran. Unfortunately, I was unable to determine how patchy particles change the radial distribution, but I was able to determine that the program that I had written behaved as expected for two more basic potentials. More time is necessary with this project to reach any more conclusions.

Student Author: P. Gordon

Published: 2008

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Fluorescence Spectroscopy and Transition Probabilities of SingleWalled Carbon Nanotubes

## Fluorescence Spectroscopy and Transition Probabilities of SingleWalled Carbon Nanotubes

One method of estimating quantities of specific single-walled carbon nanotubes in a sample is by using fluorescence spectroscopy. By exciting the nanotube electrons with light and observing the light emitted by the electrons, a map of fluorescence intensity versus both excited and emitted wavelengths is produced. The intensity peaks correspond to electronic transitions in one or more varieties of nanotubes, but to quantify the actual amount of nanotubes present, more information about the energy transitions and their probabilities is required. Using published theoretical values of probabilities of electronic energy transitions in SWNTs and fluorescence intensities, an absorption spectrum was generated and compared to the actual absorption data. The generated spectrum was not consistent with the data, and seemed to overestimate the size of several of the transition peaks present. To get an estimate of transition probabilities that are consistent with the data, the absorption spectrum was fit with a sum of Lorentzian functions, one for each nanotube. Using the peaks from this fit and the fluorescence intensities, transition probabilities were calculated. These had different trends and values from both the theoretical values of probability and a set of published experimental values that also relate to the transition probability.

Student Author: J. Gallagher

Published: 2008

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NMR Studies of the Belousov-Zhabotinsky Oscillatory Reaction

## NMR Studies of the Belousov-Zhabotinsky Oscillatory Reaction

The purpose of this experiment was to verify if with our range of equipment a study of the BZ reaction was possible using the RIT NMR machine, and if so to obtain data on its kinetics. We succeeded in obtaining a calibration curve relating the peak area of malonic acid to concentration, setting up a pulse sequence to collect a desired number of spectra over time, and in importing this data into a Mathematica program for integration. Our results showed that the concentration of malonic acid indeed changes over time, and that after some streamlining and technical setup we anticipate it will be possible to view its oscillations as well as oscillations of other reactants.

Student Author: Michael Harris

Published: 2008

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Experiments in Superconductivity

## Experiments in Superconductivity

The goal of this project is to synthesize the ceramic high temperature superconductor Y Ba_{2}Cu_{3}O_{7} (YBCO) with varying parameters and characterize these samples to determine the effects. Synthesis will be carried our used a dry chemistry approach, and characterization done by attempting to find the critical transition temperatures of each sample as well as demonstraight the samples Meissner state.

Student Author: Casey Jordan

Published: 2008

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