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Matthew Ashby (Senior Thesis, August 2016, Advisor: Michael Ware )

Abstract

We compare the behavior of light scattered by free electrons in an intense laser focus to quantum electrodynamics (QED) predictions. We are primarily interested in what happens to the radiation field when the electron wave packets spread to the scale of the driving-laser wavelength. As the wave packet expands in the laser focus, different parts of the wave packet oscillate out of phase with each other. The question naturally arises whether the different parts of the wave packet will interfere with each other in such a way as to suppress the radiative process. A classical model predicts this suppression; however, it goes against QED. In our experiment a large vacuum chamber is backfilled with helium. These helium atoms become electron donors as the atoms are ionized in an intense laser focus. The electrons from the helium atoms drift forward at a good fraction of the speed of light, red-shifting the signal. We use a series of filters to isolate the light from the free electrons from the background noise in the vacuum chamber. In comparing the data from our experiment with various predictions, we found evidence supporting the QED model as we did not observe radiative suppression.

Merrill Asp (Senior Thesis, April 2016, Advisor: Mark Transtrum )

Abstract

Adaptation is an important biological function that can be achieved through networks of enzyme reactions. These networks can be modelled by systems of coupled differential equations. There has been recent interest in identifying what aspect of a network allows it to achieve adaptation. We ask what design principles are necessary for a network to adapt to an external stimulus. We use an information geometric approach that begins with a fully connected network and uses automated model reduction to remove unnecessary combinations of components, effectively constructing and tuning the network to the simplest form that still can achieve adaptation. We interpret the simplified network and combinations of parameters that arise in our model reduction to identify minimal mechanisms of adaptation in enzyme networks, and we consider the applications of these methods to other fields.

Cameron Bell (Capstone, April 2016, Advisor: )

Abstract

Creativity is a process of connection, not of synthesis. Great ideas are characterized by the combination of known concepts - for example, brownie waffles. The genius is neither in the brownies nor the waffles, but in the combination of the two. Theoretically, a computer could make the connections for us, researching and suggesting other products, industries, and fields whose methods could be of use in our processes of development. Using latent semantic indexing, we have mathematically mapped semantic relationships among the documents on Wikipedia and developed a tool that compares documents, allowing us to work on finding these valuable creative connections, or intuitive leaps. Though this could be done much faster with existing technologies like Google, our model needed to be fully customized for specific applications.

Kendall Berry (Senior Thesis, April 2016, Advisor: Richard Vanfleet )

Abstract

X-ray spectroscopy effectively gives insight into material development and other fields by detecting characteristic x-ray emissions from a sample. Measurement of lower Z-number elements is limited by poor transmission through the detector-sample chamber interface, or x-ray window. A thinner, more transmissive window would allow detection of these elements, but it would also need additional support to withstand the required differential pressures. A process for fabricating submicron-thick nanoporous polymer support membranes was developed using electron beam lithography, thermal nickel evaporation, and reactive ion etching. Bulge testing the resulting films gave insight into material strength and properties. Preliminary results are inconclusive but seem to indicate that membranes similar to the ones fabricated here may be able to serve as support structures for more transmissive x-ray windows.

Joel Bradley (Senior Thesis, April 2016, Advisor: Eric Hintz )

Abstract

The High Mass X-Ray Binary KRL2007B-367 is observed in the Johnson B, V, R, and I filters from 2010 to 2012 and is analyzed in the optical for periodicity. Although there may be some hints of variability, KRL2007B-367 is for the most part stable. An uncatalogued star that is in the same field, referred to as star Fey, shows sporadic changes in magnitude. It is proposed that star Fey could possibly be the correct optical counterpart of the High Mass X-Ray Binary System. This is because star Fey shows much more variability in magnitude, and may show signs of periodicity. These are signs of evidence one would look for in a High Mass X-Ray Binary System. Even if this conclusion is incorrect, star Fey is still an object worth studying in the future since it shows interesting properties.

Matt Burbidge (Senior Thesis, April 2016, Advisor: Gus Hart )

Abstract

The 1998 Nobel prize was given to Kohn and Pople for their development of Density Functional Theory. DFT has been developed into a powerful tool that allows one to do quantum-mechanical calculations. Typical DFT calculations require a numerical integral over the occupied electron states in the material. Even though this integral is a small piece of the overall calculation, it is a primary source of error. Through the use of a simple toy problem, we will explain the fundamentals of the integration problem. We will introduce some of the attempts at resolving it and explore their effectiveness in current DFT codes as well as our own attempts. The resolution of this integration problem for metals will result in millions of CPU hours saved for a typical computational materials scientist.

Dan Crunkleton (Senior Thesis, April 2016, Advisor: Scott Bergeson )

Abstract

We measure the time-dependent plasma density of a neutral strongly-coupled plasma formed using strong-field ionization of atoms. The plasma is generated by focusing a Ti:Sapphire laser with a 70 femtosecond pulse duration into a gas jet. The ion temperature of our plasma is proportional to the plasma density through disorder-induced heating. The electron temperature can be determined from the measured plasma expansion. We measure the time-dependent densities of He, Ne and Ar plasmas using interferometry. We show that the relative plasma expansion is accurately described by a simple model.

Andrew Davis (Senior Thesis, April 2016, Advisor: Richard Vanfleet )

Abstract

Here we demonstrate the fabrication of two types of fluid filters developed using carbon-nanotube-templated microfabrication (CNT-M). The first of these are high strength microsieves for both liquid and gas filtration. The sieves were fabricated by growing patterned forests of vertically aligned carbon nanotubes followed by an infiltration of the forest with nanocrystalline carbon. The process is compatible with the fabrication of sieves with pore sizes from below one micron up to tens of microns. Straight, vertical channels result in low flow resistance and the high strength carbon material is compatible with high pressure filtering. Initial filtration testing on sample sieves with 5 micron pores showed greater than 99.5% removal efficiencies of 6 micron particles. The second filter type also uses an adaptation of CNT-M to make high throughput filters by hierachically patterning the structure to achieve ultrahigh surface areas. These filters have pores on the order of 50-100 nm and therefore are compatible with bacterial filtration. Preliminary flow testing has shown flow rates of over 180 times greater than standard Millipore mixed cellulose ester sterilizing disk filters.

Michael Denison (Capstone, April 2016, Advisor: Timothy Leishman )

Abstract

Anechoic chambers are typically qualified by comparing sound pressures at several radial distances from a sound source and verifying that they follow the spherical spreading law within specified tolerances. While this technique is useful, it may not sufficiently characterize free-field variations at fixed radial distances and numerous angular positions, as are commonly used for directivity, sound power, and other important acoustical measurements. This paper discusses a technique to detect angular field deviations in anechoic chambers. It incorporates a loudspeaker in an altazimuth mount, an adjustable-radius boom arm, and a precision microphone. The boom arm and microphone remain in line with the loudspeaker driver axis at a fixed radius while the system rotates to specified azimuthal angle increments. In an ideal free-field environment, the frequency-response function from the loudspeaker input signal to the microphone output signal should remain consistent—regardless of the system orientation. However, in typical anechoic chambers, they vary. Standard deviation calculations over many angles reveal frequency-dependent departures from the ideal, especially for narrow-band data. The results show the impact of these discrepancies for multiple-angle measurements and how they change with radial distance from the source.

Jacob Embley (Senior Thesis, April 2016, Advisor: John Colton )

Abstract

Electron spin states in silicon carbide have shown potential for use as qubits. A qubit requires a quantum state that will remain coherent over a sufficiently long period of time. By measuring spin coherence times for electrons in silicon vacancies, we not only investigate their potential for use as qubits, but we better understand the factors which lead to their eventual decoherence. Using a combination of experimental techniques, including optically detected magnetic resonance and spin echo, we measured electron spin coherence times for two samples of proton-irradiated 4H-silicon carbide. Each sample was studied over a range of temperatures. Results indicate that the longest coherence times for each sample exist at the lowest temperature (8 K). While in general higher temperatures resulted in shorter coherence times, results also show a range of temperature from 60 K to 160 K for which the trend was reversed.

Cory Finlinson (Capstone, August 2016, Advisor: )

Abstract

VocalEyes is a mobile application that gives real-time visual feedback for singers. VocalEyes will eventually include five aspects of singing: phonation mode, vowel, placement, pitch, and vibrato. Vowel and phonation mode feedback have both been implemented, with supervised machine learning models being used to estimate vowel and phonation mode values. This work can be seen as a synthesis of work done in all five areas to provide a useful, all-in-one solution for automated singing feedback. Initial user testing has been performed with generally positive feedback.

Forrest Glines (Senior Thesis, April 2016, Advisor: David Neilsen )

Abstract

Simulating binary star mergers in full relativistic magnetohydrodynamics with general relativity is computationally expensive, with production level simulations taking up to two months using traditional algorithms. These speeds are insufficient to explore the parameter space of binary star mergers. Following recent trends in chip manufacture, CPU speeds are unlikely to increase and speed up simulation times. In order to shorten simulation times new algorithms that take advantage of newer, faster computing architectures such as GPUs are required. This thesis presents GMHD, a relativistic magnetohydrodynamics code that runs on NVIDIA GPUs faster than other codes on CPUs. It implements a high-resolution shock-capturing algorithm using the piecewise-parabolic method and a total variation bounded method based on the Osher-Chakrabarthy method. The accuracy of the fluid methods are tested simulating the shock tube problem and the Kelvin-Helmholtz instability. Both methods accurately mode solution. This thesis also presents tests demonstrating the weak and strong scalability of the code tests to hundreds of GPUs. GMHD shows the viability and usefulness of using GPUs and forms a basis for future work on large scale simulations of binary mergers.

M. E. Gold Dahl (Senior Thesis, April 2016, Advisor: Scott Bergeson )

Abstract

We report a precision measurement of the frequency interval between two well-known atomic transitions. The frequency of the Rb-87 5s^2 S1/2 F=2->5p^2 P3/2^0 F=2/3 crossover transition is known to +-0.005 MHz. The frequency of the Cs-133 6s^2 S1/2 F=4->6p^2 P3/2^0 F=3,4,5 transitions are also known to +-0.005 MHz. Using a partially-stabilized optical frequency comb, we reproduce this measurement in our lab within an error of 0.02 +- 0.06 MHz.

Julia Grimes (Capstone, April 2016, Advisor: Robert Davis )

Abstract

For this project we not only wanted to create pre-class exercises that would help introductory level physics students learn basic physics principles before coming to class, but we also wanted to get feedback from the students so that we knew how to make the exercises more useful for their learning. We conducted interviews with students from the Physics 121 and Physics 140 classes and gave pre and post interview surveys to all who were willing to take them. Based on the feedback that we got from the students who were interviewed, the students felt like the idea behind the exercises was great. Even if they found the exercises to be frustrating, they still thought that idea and purpose for making them was very useful and hoped that we would continue to improve them to make them even better for students in the future. The data and feedback we collected gave us an overwhelming response that the students want more explanations and feedback when they are taking the exercises. We also had a majority of students who said that the most useful part of the exercises for them were the videos that gave explanations to the problems that they needed to solve. Along with this feedback, we were able to come up with a list of other helpful aspects students saw, issues they came up against, and changes that they saw we could make to help improve the exercises. This is discussed and presented in the paper.

Dalton Griner (Senior Thesis, August 2016, Advisor: Karine Chesnel )

Abstract

Magnetic nanoparticle technology is changing the world with important applications in healthcare such as more effective cancer treatments and drug delivery systems. To understand the magnetic behavior of Fe3O4 (known as magnetite) nanoparticles when forming assemblies, we have studied them with x-ray diffraction techniques. We used organic solution methods to create nanoparticles with different particle sizes ranging from 5 to 11 nm. Using X-ray Diffraction (XRD) and Transmission Electron Microscopy (TEM), we finely measured the average particle size and distribution. Using the synchrotron at the Stanford Synchrotron Radiation Lightsource (SSRL) at Stanford Linear Accelerator Center (SLAC), X-ray Circular Magnetic Dichroism (XMCD) and X-ray Resonance Magnetic Scattering (XRMS) experiments were conducted at different temperatures and magnetic fields on the freshly made samples. From this data, spin and orbital magnetic moments, as well as magnetic profiles, were extracted that provide information about the magnetic order in the nanoparticle assembly and its dependency on particle size, concentration, and temperature.

Nicholas Harrison (Senior Thesis, April 2016, Advisor: Scott Bergeson )

Abstract

We employ laser interferometry to measure the time-dependent density of a strongly-coupled plasma created in neon. We plot this time-dependent density for peak ionization intensities ranging from 2 to 20.3 times the first ionization intensity. All the scaled expansion data fit onto a similar curve except for the lowest intensity, probably because of ionization impurities. These data support the strongly-coupled plasma expansion model, confirming its dependence on electron velocity and initial plasma radius, and reinforce current theories of plasma dynamics.

Spencer Hart (Senior Thesis, April 2016, Advisor: Gus Hart )

Abstract

High-throughput alloy simulations can greatly increase the rate at which we discover and synthesize new materials by giving narrower focus and clearer direction to physical materials experimentation. In working towards a comprehensive database of potential alloys and their predicted characteristics, we are seeking ways to increase the computational efficiency of our simulations. One main opportunity for improvement is in calculating the energy contribution from electron bands. Determining this energy contribution requires numerically integrating over the occupied regions of the electron bands. For metals in particular, dense sampling of the electron bands is required to achieve sufficient accuracy in the integral (due to the lack of smoothness in the partially filled electron bands of metals). Each sample point requires solving a large eigenvalue problem, leading to longer computation time for denser sampling. This thesis describes attempts to interpolate the electron bands using trigonometric star functions and splines to achieve necessary accuracy with sparser sampling. The findings I present here show that the interpolation methods we have employed do not represent the bands well enough to be used to reduce sampling of the electron bands.

Matthew Healey (Capstone, June 2016, Advisor: Karine Chesnel )

Abstract

It was recently established, through MFM microscopy, that the magnetic domain topology in Co/Pt (cobalt-platinum) multilayered thin films can be influenced by the magnetic history of the material (i.e. the magnetic path which the material has been exposed to). Particularly, it appears that the domain topology at remanence drastically depends on the magnitude of the field previously applied perpendicular to the material. A maximum density of domains is obtained after a magnetic field of appropriate strength has been applied. We are expanding this study by showing that the appropriate field strength necessary for maximum magnetic domain density in a Co/Pt multilayer depends on the thickness of the cobalt layers. By performing MFM microscopy on a sample with thicker (16Å) cobalt layers than the ones used for the preliminary study (8Å), we found that the magnetic domain density is maximized at a greater magnetic field magnitude than for thinner cobalt layers, in agreement with the associated increase of saturation field.

Christopher Heaton (Capstone, August 2016, Advisor: Brian Anderson )

Abstract

The purpose of this research is to develop a visual demonstration of time reversal focusing of vibrations in a thin plate. Various plate materials are tested to provide optimal conditions for time reversal focusing. Specifically, the reverberation time in each plate and the vibration coupling efficiency from a shaker to the plate are quantified to illustrate why a given plate provides the best spatially confined focus as well as the highest focal amplitude possible. A single vibration speaker and a scanning laser Doppler vibrometer (SLDV) are used to provide the time reversal focusing. Salt is sprinkled onto the plate surface to allow visualization of the high amplitude, spatially localized time reversal focus; the salt is thrown upward only at the focal position. Spatial mapping of the vibration focusing on the plate using the SLDV is correlated to the visual salt jumping demonstration. The time reversal focusing is also used to knock over an object when the object is placed at the focal position; some discussion of optimal objects to use for this demonstration are given.

Marcus Holden (Senior Thesis, April 2016, Advisor: Joseph Moody )

Abstract

Using the Brigham Young University 16" ROVOR telescope, we have monitored the TeV blazar Markarian 501 for 75 days in 2012 through the Johnson B V R filters. Markarian 501 was stable during this time, serendipitously allowing the opportunity to examine its behavior during long quiescent periods. We unexpectedly discovered a small sinusoidal variation in its magnitude having an amplitude of 0.03 magnitudes and a period of between 113-130 days which is essentially twice the period of the x-ray variation discovered by Abdo, et al. (2011). We present our data and interpret it using a binary orbital model.

Travis Hoyt (Capstone, August 2016, Advisor: Timothy Leishman )

Abstract

The volume velocity of an acoustic source is its rate of sound-induced flow of the medium (typically air) through a specified surface. The measurement of this acoustic flux is used by some industry researchers to evaluate the acoustics of their products. Current experimental methods used to determine the volume velocity of loudspeakers involve tedious and costly procedures such as scanning laser Doppler vibrometry in an anechoic environment that are impractical in most situations. BYU researchers have developed a theoretical method that has been experimentally verified to describe the in situ volume velocity of a single-driver loudspeaker using only electrical data if certain premeasured parameters are known. This work investigates the application of the single-driver theory to multiple-driver loudspeaker arrays such as 12-driver dodecahedrons. The limits of the method were assessed and detailed. The theory, experimental methods, calculations, and results are discussed. Acceptable agreement has been found in multi-driver loudspeakers between the measured values and those predicted by this method within the bandwidths of interest. Experiments demonstrate that the volume velocities of these loudspeakers are fairly insensitive to typical changes in acoustic environments. A single 12-source dodecahedron was prototyped and tested as part of this work.

Rachael Hunter (Senior Thesis, April 2016, Advisor: Eric Hintz )

Abstract

Current variable star research makes corrections for the Earth’s motion, or Heliocentric correction, to improve period accuracy. However, corrections for the star’s radial motion have not been made, until now. We applied a time correction to variable star data to adjust for the radial velocity of the star and improve the period solution accuracy. From this we are investigated the appropriate number of cycles that must be observed before a reliable period can be determined. Using the time corrected data and the changes in the apparent period, for NR Lyr, V839 Cyg, and V894 Cyg, we recovered the actual radial velocity of the stars and produced the most accurate period solutions. These were, -122.224 km/s, -92.1665 km/s, -226.372 km/s, and 0.682314 days, 0.433902 days, 0.571821 days, respectively. We also used a moving source simulation to show a distinct, repeated observed-minus-calculated ( O-C) pattern, and suggested a self-correcting period theory.Our results of this work suggest that radial velocity time corrections should be considered and implemented in variable star research.

Dale Huntington (Capstone, July 2016, Advisor: )

Abstract

In order to address the need of quicker analysis of the calorimetry data obtained in the BYU Biophysics Lab, I developed user friendly Mathematica code (for non-Mathematica users) that will display easily modified graphs of the calorimetry runs and their interpolations, as well as needed information about each scan. This serves to better understand the thermal denaturation process of the protein and can be paired with lipid bilayer fusion data to correlate the state of the protein and the corresponding rates of fusion.

Tanner Ingalls (Capstone, August 2016, Advisor: )

Abstract

Evaluating the success of a team based on Real-Time Performance Management (RTPM) defined by collecting frequent reviews inside of a department. Using Space Monkey as the test Company, we seek to find a mathematical model to gain insight on how a team is performing at their current level. This research can then be used to help re-define the entire performance management process inside of interested companies.

Joseph Lawrence (Senior Thesis, August 2016, Advisor: Bret Hess )

Abstract

Structures of metal on graphene play important roles in batteries and hydrogen storage, and discovery of new structures could improve these applications. Through computational methods, the formation energy of a proposed structure can be calculated. Enumeration is the process of creating lists of possible structures to search for low formation energy. We present an enumeration method that allows for efficient treatment of vacancies and apply it to the case of six sites per two carbon atoms. If the separation between two sites in the lattice is less than a specified distance, the pair is referred to as forbidden. The enumeration skips structures where at least one forbidden pair has both sites non-vacant, speeding up the process exponentially by volume. This allows for enumeration of structures of high volumes that would be impossible using standard methods. The search method is applied to the case of scandium, titanium, yttrium, and zirconium on graphene. We report results of several low-energy structures, many of which do not currently appear in the literature. These structures may be useful in future applications of batteries and hydrogen storage.

Kevin Leete (Senior Thesis, April 2016, Advisor: Kent Gee )

Abstract

Mach stem formation in acoustic shocks is investigated using oxyacetylene balloon explosions conducted a short distance above pavement. As the shock wave propagates away from the blast site it transitions from a regular reflection to irregular reflection. The location of this transition point, as well as the path of the triple point, are experimentally resolved using microphone arrays and a high-speed camera. The measured transition point falls between that predicted from derivations based on weak shock waves and an empirical relationship derived from large-scale explosions. It also agrees well with predicted values based on von Neumann’s three shock theory.

Ryan Lesser (Senior Thesis, April 2016, Advisor: Joseph Moody )

Abstract

Photometric redshifts are routinely obtained for galaxies without spectral emission lines using broadband photometry. However, this method does not work if galaxies have emission. For galaxies with emission, it is theoretically possible to obtain reasonably accurate (< 500 km/s) photometric redshift values using "ramp'' filters. Such filters have a linearly increasing/decreasing transmission through the bandpass, causing the intensity of the image to be a function of the wavelength of the emission line. We have obtained a set of ramp filters tuned for isolating Hα at a redshift range of 3,000-9,000 km/s. The set consists of two filters that are nearly linear in transmission, have opposite slope, and cover the wavelength range from 655-680 nm. We add a 2.1 nm FWHM filter centered on the red side of the ramp filters at 697 nm to measure the continuum. Redshifts are derived from the ratio of the ramp filters indices after the continuum has been removed. We recover the redshifts of a test sample of 16 Sey I and Sey II galaxies with an accuracy of 450 km/s. This value can be improved by increasing the wavelength coverage of the ramp filters and measuring the continuum on the blue side as well.

Shaun Livingston (Capstone, April 2016, Advisor: )

Abstract

I worked with the BYU Engineering Capstone program for my capstone project. We partially designed a training apparatus that will provide instant feedback for softball players on the direction of spin that is applied to a ball to achieve a rise, drop, curve, and screwball. Our design takes the form of a rechargeable training ball that both matches the look and feel of a normal softball and measures the speed and direction of the spin. The design is not yet fully functional but it is intended that from direction in this report the design could be completed and the device will use internal sensors to provide instant feedback on four types of pitches as well as interact with a mobile app via Bluetooth for configuration of the ball and to review historical pitching data. The ball can then be recharged through inductive charging on a cradle.

Eli McArthur (Senior Thesis, June 2016, Advisor: David Neilsen )

Abstract

Minor perturbations resulting from a brief period of inflation at the time of the universe's birth seeded the growth of all structure in the universe. Using Enzo, a research code optimized for running cosmological simulations, we simulate the formation of the universe. We take into account the most current cosmological parameters and plot star formation rates of the universe for halos of varying mass from the beginning of time until today. By simulating star formation of the early universe, we verify that initially minuscule dark matter pockets resulting from inflationary perturbations attract more and more matter as the universe expands. The resulting halos vary in size and have varying degrees of star formation. Additionally, this analysis paves the way for future members of the scientific community to test a new way of identifying population III stars in the cosmic microwave background.

Andrew McClellan (Senior Thesis, April 2016, Advisor: Lawrence Rees )

Abstract

In recent years, there has been a helium-3 shortage, resulting in a need for alternative neutron detectors that can efficiently distinguish between neutrons and gammas. A hybrid liquid organic scintillator and lithium-6 glass neutron detector has been developed and tested to determine its neutron-gamma discrimination capabilities using pulse shape discrimination (PSD). Two liquid scintillators, Eljen EJ-325a and EJ-325UV, were compared. The EJ-325UV lacks a wavelength-shifting phosphor so as to minimize the significance of the absorption of lithium glass light in the scintillator. Principal component analysis (PCA) is explored as a method to improve neutron and gamma region separation. Previous work is extended from single- to correlated-pulse analysis, which declares an event a neutron if a liquid scintillator recoil pulse precedes a lithium capture pulse. It was found that PCA fails to improve region separation and efficiencies, but it does provide quantifiable measures of the significance of PSD parameters in distinguishing between events. The correlated-pulse analysis method reduces the ratio of misidentified gammas by an order of magnitude, but reduces the detector efficiency to less than one percent. The detector utilizing EJ-325UV identified 20-40% more neutrons than the EJ-325a detector. Further analysis is needed to determine the importance of self-absorption in the hybrid detector.

Michael Meehan (Senior Thesis, June 2016, Advisor: John Colton )

Abstract

Titanium-sapphire lasers are useful in condensed matter research because of their ability to be mode-locked, generating ultrafast, regular pulses of coherent radiation. When designing Ti:sapph lasers, their stability in continous wave (CW) operation is often overlooked; however, this feature is often useful and would make a Ti:sapph laser more versatile. We discuss implementing an alternative laser cavity design that provides more stability in CW operation while retaining the ability to be mode-locked.

Cameron Olsen (Senior Thesis, April 2016, Advisor: John Colton )

Abstract

This thesis investigates the reactions of Mn2+ and Co2+ with permanganate as a route for manganese and cobalt oxide nanoparticle synthesis in the protein ferritin. Permanganate serves as the electron acceptor and reacts with Mn2+ and Co2+ in the presence of apoferritin to form manganese and cobalt oxide cores inside the protein shell. Manganese loading into ferritin was studied under acidic, neutral, and basic conditions and the ratios of Mn2+ and permanganate were varied at each pH, while cobalt loading was studied at pH 8.5 only. The manganese and cobalt-containing ferritin samples were characterized by transmission electron microscopy, UV/Vis absorption, and by measuring the band gap energies for each sample. Manganese cores formed in both the acidic and basic conditions, while a mixed cobalt-manganese core formed at the desire pH. New manganese oxide cores formed in the acidic manganese trials and have absorption profiles and band gap energies that are different from the Mn(O)OH cores synthesized by the traditional method of using oxygen. These new manganese cores have indirect band-gap transitions ranging from 1.63 to 1.68 eV, which differ from the band gap energy of 1.53 eV for Mn(O)OH ferritin. In addition, an increased absorption around 370 nm was observed for the new manganese cores, suggestive of MnO2 formation inside ferritin. The mixed cobalt-manganese samples showed band gaps ranging from 1.48 eV up to 1.75 eV, which correlated with the final ratio of cobalt and manganese present in the material.

Brian Ostler (Senior Thesis, April 2016, Advisor: Lawrence Rees )

Abstract

It is often difficult to accurately determine the number of neutrons incident on a detector because of room return, or the scattering of neutrons from nearby material into the detector. We developed a neutron detection platform mounted on a scissor lift so that room return can be minimized in our counting experiments. We measured the neutron counting rate as a function of the height of the platform above a concrete slab located below the lift. This measurement was taken with a Li-6 glass neutron detector used in conjunction with a Li-7 glass detector to subtract gamma background. We used neutrons from a Cf-252 source located at a fixed position on the platform. We found that room return became minimal when the lift was raised to a height of five meters above the concrete. This result is important for helping reduce room return in neutron detection research. With neutron detectors that are sensitive to low energy or thermal neutrons, as is our Li-6 detector, an effective way to account for room return is to have the detector and source beyond five meters from the wall and floor.

Derek Ostrom (Senior Thesis, April 2016, Advisor: Gus Hart )

Abstract

The Wang-Landau algorithm is a relatively new Monte Carlo method and its applications are still being explored. One such application, discussed here, is in cluster expansion calculations. Current Monte Carlo algorithms used in cluster expansions are slow to converge and the Wang- Landau algorithm looks like a faster alternative. We tested the algorithm on simple Ising models and toy 2D binary alloys and then tested it for the first time on a real metal alloy system, AgPd, in UNCLE, the cluster expansion code. I compared the time of simulation and the specific heat graphs produced from the Wang-Landau algorithm with those produced from the Metropolis algorithm on these three models. I found that the specific heat results matched well for the toy cases and for the AgPd case. There was also a significant increase in the speed of the simulation for some runs. I present results along with possible problems for the algorithm’s application in UNCLE and future work to be done.

Katrina Pedersen (Senior Thesis, August 2016, Advisor: Joseph Moody )

Abstract

Identifying the chemical composition of unknown satellites is of great interest for defense applications. A developing method of accomplishing this takes low-resolution spectra of satellites and deconvolves them using known material reflection and absorption properties. Using a suitable diffraction grating in the filter wheel slot, test spectra have been obtained over a variety of sun angles for various geostationary satellites using the ROVOR 16’’ RC Optical telescope. The data are encouraging but the analysis is cumbersome and time-intensive. We are developing a data analysis package based on the commercial image-processing software package Mira, to help automate the data reduction process. Using the Mira scripting language and its file event scripting capabilities, data can be automatically processed with limited user interaction. We report on progress to date.

Reese Petersen (Senior Thesis, April 2016, Advisor: Robert Davis )

Abstract

Dense arrays of carbon nanotubes (CNTs) were covered conformally with 14 nm of nanocrystalline carbon via chemical vapor deposition, followed by 14 nm of hafnium dioxide (HfO2) via atomic layer deposition (ALD) for creating dielectric capacitors with high areal capacitance. These coated carbon nanotube arrays were analyzed via scanning electron microscope imaging, energy dispersive x-ray spectroscopy, and transmission electron microscope imaging. HfO2 was found throughout the array but appeared to be thinner than 14 nm near the bottom of the array. We recommend a lower pyrolytic carbon deposition temperature and shorter CNT arrays for more uniform ALD.

John Peterson (Capstone, April 2016, Advisor: Lawrence Rees )

Abstract

We investigated the response magnitude across the full spatial extent of two commercially produced 5-inch photomultiplier tubes, the Hamamatsu R1250 and the Adit B133D01S. Each tube was translated by motorized stages across an incident light source. The response of the photomultiplier tube was recorded, as well as the response of a fast photodiode that simultaneously measured a portion of the incident light. Peak height and area responses were analyzed, with constant fraction discrimination implemented to determine the start and stop times of the peaks for the area calculations. The Hamamatsu response varied linearly across the tube, but had responses that varied by up to a factor of 10 when normalized to the center. The Adit was much more uniform, varying only by a factor of 0.3 across the majority of its spatial extent. These results indicate that the Adit is superior for magnitude of response experimental applications.

McKinley Pugh (Senior Thesis, April 2016, Advisor: Dallin Durfee )

Abstract

Extended cavity diode lasers (ECDLs) have a number of useful applications, but they mode hop. We have observed an increase in frequency noise before mode hops in ECDLs. A feedback system using frequency noise instead of amplitude noise has been developed

Alec Raymond (Senior Thesis, April 2016, Advisor: John Ellsworth )

Abstract

We are interested in improving neutron spectrometric capabilities in the energy range of 0.1 to 3 MeV. Current neutron spectrometry technologies do not have good energy resolution in this energy range without the use of either a complicated or a multiple-detector setup. We have developed a stand-alone detector with improved features in this energy range. The detector uses Li6Gd(BO3)3 : Ce crystal in a thin slab of polyvinyl toluene scintillator for capture-gated neutron detection and a second thin slab of solid plastic scintillator for proton recoil detection. Comparisons of proton recoil pulse area to measured time-of-flight data and theoretical neutron energy spectra indicate a useful correlation with neutron energy. The spectrometer we have developed functions as an initial prototype.

Michael Rollins (Capstone, August 2016, Advisor: Timothy Leishman )

Abstract

Schoolteachers have a particularly high rate of voice-problem symptoms. Room acoustics could be a significant reason for this prevalence, but more needs to be known about the effects room acoustics on vocal effort. With increased understanding, rooms could be designed to mitigate unhealthy vocal effort, and by extension, voice problems. The present study attempts to measure the influence of room acoustic parameters on vocal changes by comparing the vocal effort of typical talkers in several distinct acoustic environments. Thirty-two participants were recorded completing a battery of speech tasks in eight widely ranging acoustic conditions. Key vocal parameters were derived from associated recordings and the statistical significance of the influence of the room acoustic parameters on each of the vocal parameters was determined using standard one-way ANOVA tests. It was found that changes in EDT, C50, and %ALcons had highly correlated effects on several vocal parameters, notably smoothed cepstral peak prominence, acoustic vocal quality index (AVQI), and pitch strength. As the EDT increased and C50 and %ALcons decreased, these and other vocal parameters tended toward more dysphonic phonation. There were also gender differences in several vocal parameters, including AVQI, pitch strength, and other vocal effort-related parameters, with females tending to exert more vocal effort. These findings begin to objectify the effect of room acoustics on vocal accommodations and provide grounds for developing future talker-oriented room acoustical standards.

Aaron Skousen (Capstone, April 2016, Advisor: )

Abstract

Currently, families with adult members who have quadriplegic paralysis caused by cerebral palsy or similar conditions have limited options for sharing runs and bike rides. The available trailers and joggers are either too small or extremely expensive. This problem was solved by creating a simple, yet functional, open-source design that these families can use to build their own trailer/jogger at a competitive price. I have created a prototype with my team that demonstrates the desirability of our design, with detailed instructions and drawings that can transfer the open-source design to those who will build the BTJ (Bike Trailer/Jogger). I helped contribute to all aspects of the trailer and was specifically in charge of interfacing the front wheel and the footrest with the rest of the trailer Some important features of our design include: • Simple, triangular frame with a folding hypotenuse that simplifies construction and keeps folding compact. • Suspended fabric seat allows for adaptable design. • Button-release wheels to simplify manufacturing and collapsibility. • Adjustable handlebar to accommodate a wide height range of joggers. • Pre-manufactured tow bar assembly and hitch to decrease build time. • Parking brake and 5-point harness for safety. • Front swivel wheel for easy maneuvering The product that these families want is a bike trailer/jogger (BTJ) that is comfortable for their family member, safe, easy to use, and affordable. My team and I have provided such a product. Some performance measures used to evaluate the BTJ that I made are listed below. Comfort and safety performance measures (* = Critical Success Measure): • *Coefficient of rolling resistance • Lateral tipping angle (measure of stability) Ease-of-use performance measures (* = Critical Success Measure): • Time to set-up / collapse the BTJ • Time to convert the BTJ from bike trailer to jogger • Dimensions of the BTJ • *Weight of the BTJ Models, Tests, and Results Overall, the BTJ has either exceeded or come close to achieving all Target Values. More details are available in Appendix 2. Table 1. Summary of important Performance Measures with Target and Achieved Values. Performance Measure Target Value Achieved Value *Coefficient of Rolling Resistance .02 .0118 *Weight of BTJ 40 lbs 37 lbs *Time to convert the trailer 30 - 60 sec 45 sec As this project concludes, the team has provided a final, clear design. A functional prototype was created that has been demonstrated, validated, and tested. This prototype will be given as a gift to the Mitton family for their support of the project. Parts of the user manual that and drawings are included that I have created.

Dallin Smith (Senior Thesis, April 2016, Advisor: Karine Chesnel )

Abstract

The study of magnetic nanoparticles has attracted attention for biomedical and nanotechnology research. Magnetite Fe$_{3}$O$_{4}$ is a ferrimagnetic nanoparticle carrying a macro-magnetic spin. When the nanoparticles self-assemble on a membrane, they interact with each other and demonstrate a superparamagnetic behavior. To understand these properties, we use several x-ray techniques: x-ray absorption spectroscopy (XAS), x-ray magnetic circular dichroism (XMCD) and x-ray magnetic resonant scattering (XRMS). With these procedures we can study the electronic structure and obtain a magnetic profile for the nanoparticles. Having acquired such data at the SLAC synchrotron, we examined different nanoparticles sizes and concentrations, at different x-ray energies and various temperatures and under the application of different magnetic field strengths. Models were made to fit the experimental data to outline the physical structure and the magnetic order from the XMCD and XRMS experiments. More importantly, the modeling concluded about the magnetic order of the specific magnetic spin configuration of the nanoparticle assembly, under the application of a given magnetic field at a given temperature.

Erik Swenson (Senior Thesis, April 2016, Advisor: Bret Hess )

Abstract

Because of its status as an emerging energy carrier, methods of hydrogen storage are in high demand. Using computational methods, we explore a very large space of graphene structures with different adsorption configurations of hydrogen and calcium as possible mechanisms for hydrogen storage. We expand our search space further than the traditional search space by a factor of almost 20 using cluster expansion to enumerate structures in a variety of computational cell shapes and sizes. This allows for periodicities not studied previously. We also introduce vacancies in the adsorption configurations and study their effects. We conclude that the cell size and shape is an important parameter in the search for stable structures. We also find that vacancies allow for structures with more than 40% calcium concentration without exhibiting signs of calcium stacking. We present four stable structures that show promise for hydrogen storage applications.

KaeCee Terry (Senior Thesis, April 2016, Advisor: John Ellsworth )

Abstract

A lithium gadolinium borate capture-gated neutron detector was used, in conjunction with time of flight techniques, to determine if paired neutrons are observable within a single detector. Data was verified by analyzing the time delays between detectors, quantifying room return rates, comparing detection rates to statistical probabilities and calculating expected neutron flux. Potentially paired neutrons were detected by our system. Future work is discussed, including improvements to code and source configurations, as well as possible experiments to be conducted.

Darren Torrie (Senior Thesis, April 2016, Advisor: Kent Gee )

Abstract

A recently developed phase and amplitude gradient estimator (PAGE) method for calculating acoustic intensity from multiple pressure measurements [Thomas et al., J. Acoust. Soc. Am. 134, 4058 (2013)] has been tested via anechoic laboratory measurements of the radiation from broadband sources. The measurements determine that the effective frequency bandwidth of valid acoustic intensity calculations can be substantially increased when using the PAGE method over the traditional cross-spectral approaches. Preliminary results are shown for two probe sizes and multiple broadband source configurations.

Clarissa Veach (Senior Thesis, April 2016, Advisor: Robert Davis )

Abstract

Ion-exchange chromatography is a purification method for biological molecules commonly performed on functionalized Si monoliths. A potential method of ion-exchange chromatography is presented using a Si coated CNT structure as the chromatography matrix. Surface area and binding capacity calculations were made to determine the advantage of using these structures in place of those commonly used. It was found that the surface are of the CNT structure is approximately 0.58m^2 for a 1 cm^2 filter area. This results in a binding capacity for the antibody Immunoglobulin G of 5.67*10^14 particles/cm^2. When a quaternary ammonium substituted agarose polymer coating was applied to a Si plate it was found that the thickness was 1.8nm.

Michael Zarian (Senior Thesis, April 2016, Advisor: Mark Transtrum )

Abstract

Fitting non-linear models to data is a notoriously difficult problem. The standard algorithm, known as Levenberg-Marquardt (LM), is a gradient search algorithm based on a trust region approach that interpolates between gradient decent and the Gauss-Newton methods. Algorithms (including LM) often get lost in parameter space and take an unreasonable amount of time to converge, especially for models with many parameters. The computational challenge and bottleneck is calculating the derivatives of the model with respect to each parameter to construct the so-called Jacobian matrix. We explore methods for improving the efficiency of LM by approximating the Jacobian using partial-rank updates. We construct an update method that reduces the computational cost of the standard Levenberg-Marquardt routine by a factor of .64 on average for a set of test problems.