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While traditional Magnetic Resonance Imaging is used to visualize the structure of the body, Functional Magnetic Resonance Imaging (fMRI) measures neural activity in the brain and spinal cord, providing a mechanism to study brain function. When an area of the brain is active, it uses oxygen faster than inactive regions. Blood-oxygen-level dependent (BOLD) fMRI is a method of locating active areas of the brain at a given time, by visualizing changes in local magnetic susceptibility of blood. A statistical analysis of fMRI data after repeated actions or thoughts could be used to localize these actions or thoughts in the brain. A number of techniques are available for analysis of fMRI data, but several challenges remain, notably in choosing which data are suitable for analysis. This project endeavors to understand the challenges in statistical analysis of fMRI data, and to study new methods of analyzing data.

Current work on dark matter points toward Weakly Interacting Massive Particles (WIMPs) as the leading candidate. As suggested by their name, these particles do not interact electrically with matter but rather through their gravitational fields. WIMPs are detected in the <10keV region that coincides with a background of spallation neutrons. These spallation neutrons occur when a high-energy neutron (~60MeV) collides with the Pb shielding around the detector. The difference between a neutron and WIMP detection is the number of events recorded in a small, approximately 25 microsecond, time frame. The spallation neutrons are detected in “bundles”, whereas WIMPs will create single isolated events. A new gadolinium-loaded water detector is currently being designed and built to detect these low energy background neutrons. Results from Monte Carlo simulations will create "benchmark" measurements of background neutrons that penetrate our shielding and mimic the signal created by a WIMP.

Chemotherapeutic agents have been found to be increasingly effective at fighting the growth of cancerous tumors. However, they can also have a devastating impact on healthy tissue and prove to be fatal to the patient. Polymer nanoparticles have recently been used experimentally to increase the precision of drug delivery by encapsulating drugs until the site of the tumor is reached. Environmental variables such as pH balance and hydrodynamic forces unique to such sites can then be used to increase the drug release rate. While the entropy of monomer-monomer interactions for a polymer chains are well understood, polymer chain-chain interactions within the nanoparticle are required to capture the mechanical properties of polymer nanoparticles. This project will seek to theoretically and computationally elucidate the entropic, and enthalpic, interactions within a polymer nanoparticle and develop a discrete model of polymer nanoparticle mechanics. The resulting models will help us understand how polymer swelling near more acidic tumor sites, or hemodynamic stresses which arise due to the irregular vasculature of the tumor, can influence the release of anti-cancer drugs from these nanoparticles.

The practicality and safety of hydrogen fuel cell vehicles has been scrutinized since the design originated. This project will investigate the unique situations under which hydrogen fuel leaks can ignite and possibly cause an explosion. Various metals found in fuel cell vehicles can act as catalysts to ignite hydrogen outside normal flammability limits. This has been shown extensively with high surface area tubular platinum catalysts used for propulsion purposes. Tubular reactors can be used to investigate the effect of residence time on the ignition of a hydrogen leak. The critical conditions for hydrogen ignition can be found by varying the flow parameters through tubular catalysts of the various metals found in fuel cell vehicles.

This project will focus on the design and development of a tubular reactor to test ignition propensity for hydrogen/air mixtures under different conditions. The apparatus will include temperature control, fuel composition regulation and velocity control. The goals are to develop a working test apparatus and complete initial ignition tests on a catalyst tube. If time allows, tests will be completed for varying temperature, fuel consumption, flow rate, and surface to volume ratio of the tube. Additional materials can then be tested that may come into contact with leaking hydrogen fuel. The critical ignition conditions can then be investigated to identify high-risk situations and advance safety considerations in all hydrogen powered devices.

A great deal of problem solving in physics comes from our physical intuition. While this intuition may come more natural to some individuals as opposed to others, it certainly can be improved through experience. Through fundamentally introductory questions with counter intuitive twists, an investigation on problem solving methods will be attempted. I will observe the responses of beginner (Physics 122 students), intermediate (Physics 325 students) and expert (professors/grad students) physics problem solvers to observe just how prevalent certain misconceptions may be among physicists.

It has recently been observed [1, 2] that radioactive decay of certain isotopes [Praesodymium-140 (140Pr) and Promethium-142 (142Pm)] exhibit an oscillatory exponential time dependence in a marked departure from the simple exponential behavior that is normally observed. A recent theoretical study [3] of electrons tunneling off the surface of liquid helium predicted that electronic tunneling decay could show oscillatory exponential behavior due to quantum interference between the decaying electronic state and a nearby unoccupied "phantom" state. This mechanism is quite general and should also apply to other quantum systems including atomic nuclei. The purpose of this project is to adapt the theory of ref [3] to the problem of nuclear beta decay via K-capture and to determine whether it can account for the oscillations observed by ref [1].

[1] Litvinov, Yu. A. et al. Phys. Lett. B 644, 162-168 (2008)
[2] Walker, Philip M. Nature 453, 864-865 (12 June 2008)
[3] S. Duki and H. Mathur arXiv:0804.2210v1, (14 April 2008)

Pressure gain combustion is a developing area of research that attempts to achieve more efficient aircraft engines, which typically suffer pressure loss across the combustor. If instead, the pressure can be increased, more work is extracted and more thrust is generated. One way to attain pressure gain is by using resonant pulsed combustion. The NASA Glenn Research Center experiment uses a commercially available pulsejet for this purpose. The pulsejet allows for high frequency pulsed combustion (220Hz) instead of continuous combustion, which aircraft currently employ. The pulsejet is a relatively simple design with only one moving part: a reed valve that opens and closes with each combustion cycle. The valve is also self-actuating, meaning its operation is driven by the physical processes that occur in the chamber during combustion. However, the valve has a notoriously short lifetime and its design is outdated. Given the tremendous stresses from high frequency blasts, as well as the high temperature and pressure conditions, the reed valves at Glenn have lasted a maximum of 20 seconds. The conditions inside the pulsejet and the current valve will be modeled and an improved valve will be designed. If the design proves successful compared to model, it will be fabricated and tested at the Glenn facility. With new materials, technology, and testing, there is good potential for an improved reed valve design and thus, a significant advancement in pulsejet combustors.

Vibrato is a series of expressive pitch oscillations produced by left hand movements on the violin and viola. This project aims to investigate the variations in vibrato waveforms between college-level and professional violinists and violists. First, pedagogical and scientific definitions of an effective vibrato will be compared, and various waveforms will be electronically synthesized for aural evaluation. Then, many (n > 10) college-level players will be audio- and video-recorded. These audio tracks, as well as excerpts taken from available professional recordings, will be digitally analyzed; the video footage will then be used to motivate biomechanical explanations for aural differences among players. These investigations will hopefully result in a refined definition of an effective vibrato, ultimately streamlining teaching methods.

In the last decade OSETI, the Optical Search for Extraterrestrial Intelligence, has come to be seen as an attractive means of looking for signals from other intelligent lifeforms. The High Energy Astrophysics group is developing a new experiment for Optical SETI that we hope will exceed the performance of previous and current projects. Our approach will be to use a large Fernel lens and small PMTs which will improve the overall signal-to-noise ratio. To obtain signals and differentiate between potential messages and other light pulses, we will need to build a detector that operates in the nanosecond range. The threshold for this device will need to be tuned so as to cut out background noise and light flashes associated with Cherenkov radiation due to high energy cosmic rays in the atmosphere.

Much research is done on antennas made of high conductance material, including measuring the radiation pattern and gain of antennas. However, this project will investigate antennas made of materials with a low conductance, or lossy materials, concentrating on the effects that different antenna dimensions and geometries have on the behavior of the gain as a function of conductivity of an antenna for different antenna structures. Numerical simulation methods such as finite difference time domain (FDTD) will be used to model the structure of the antenna, the propagation of electromagnetic (EM) waves, and the interactions between the antenna and the EM waves.

If a single fluorescent dye molecule is near the image plane of a far-field microscope, it is possible, by carefully analyzing the image of the particle in an ordinary light microscope, to find the position of the particle in the directions perpendicular to the axis of the microscope to accuracy significantly better than the wavelength of light that is the “Rayleigh limit.” We will examine theoretically how these limits can be improved by interfering light on different paths or with different polarizations, and then examining simultaneously the images that these interferences form. Various schemes for making these interferences will be examined to find which will result in the best signal to noise for various combinations of the 3-dimensional position of the particle and its orientation.

Observations such as galaxy rotation curves, orbital motions of galaxy clusters, and gravitational lensing in the light of Newton’s law of gravity and general relativity overwhelmingly suggest that much of the matter in the universe is invisible. This dark matter is theorized to be a massive particle that interacts with regular baryonic matter via only the gravitational and weak force (WIMP). Due to the nature of the weak force, the probability (should I use cross section?) of a WIMP interacting with baryonic particle is very small, making the search for this particle a challenging experiment. Furthermore, WIMP detector sensitivities to smaller cross sections of WIMP events are limited by the background in the detector. The LUX Dark Matter Experiment addresses these challenges by creating a large volume detector, which increases the fiducial volume and thus increasing the probability of a wimp interacting in the detector. Another method to increase the fiducial volume, water shielding, is used to reduce background events such cosmic rays, hot neutrons, gamma rays, and other radioactive events from reaching the detector. Unfortunately, water can be a source of radiation, since it usually has some concentration of radon. Thus steps are taken to purify water this radon. After this, it is necessary to determine the remaining concentration of radon in the water in order to assess the background. I will be constructing a new system for the radon assay of water in the framework of the LUX Dark Matter experiment. The technique is based on separating radon from the water using a hydrophobic membrane stripping technology and subsequently after purification concentrating it in a carbon trap before sweeping it into an emanation chamber that counts the alpha decays. The target sensitivity for this system is 1 mBq/m3.

Further constraints on cosmological parameters are progressed by determining the abundance of galaxy clusters in the universe. Bayesian analysis is applied to maps generated by the South Pole Telescope (SPT), to locate and classify galaxy clusters using the Sunyaev-Zel'dovich (SZ) effect. The SPT is a 10-meter telescope that can scan a 4000 square degree solid angle at 95 GHz, 150 GHz, and 225 GHz. The SZ effect is the result of CMB radiation passing through galaxy clusters. Tasks include programming an MCMC routine, finding and counting galaxy clusters, and determining the fraction of total clusters were detected.

Artists, particularly M.C. Escher, have made many attractive tessellations of the plane, incidentally illustrating many of the two dimensional space groups. Such pictures may have different space groups or attractiveness based on the patterning and symmetry of various colors in the pictures, and in defects in such symmetries. Many physical systems have "broken" symmetries in which an unspecified state (e.g. color) can be determined by the state of its neighbors, as in antiferromagnetism. Much is known about such ordering in various two dimensional cases, including various statistical models thereof. In this project we will combine art and physics by animating an Escher-like tessellation of the plane, using a Monte-Carlo or similar simulation of a statistical model to change the colors or other attributes of the tessellation. As the formation of long range order in such models, and the resulting potential fractional dimensionality of the patterns is thought to have aesthetic value, this will hopefully achieve all of providing an interesting illustration of two dimensional statistical models, an interesting piece of modifiable art, and a potential screen-saver.

Dark matter exists in earth-mass to solar-mass mini-halos, or clumps. As these clumps move through the galaxy, it is possible that part of the clump may interact with a binary star system, leading to a capture of dark matter by that system. Over time, the mass of the clump can move to the center of the stars in the system. Dark matter does not interact with matter very strongly, so the dark matter particles will simply move into the gravitational center of the stars. Because dark matter is its own anti-particle, the dark matter particles in the center of the stars will annihilate, releasing energy. While this effect would occur in any type of star, it would be more easily observed in a binary system with two white dwarfs, whose luminosities would be low enough that the dark matter annihilation would have a larger proportional effect. The result of this effect is that the distribution of white dwarfs over luminosity will require a correction, with more white dwarfs having relatively higher luminosities than previously thought. For my project, I will be working through the math of this theory and determining how much mass is accreted by the average white dwarf binary system and how this would affect the white dwarf luminosity distribution.

There has been much work done in determining temperature correlations in the WMAP cosmic microwave background (CMB) data, through the angular power spectrum data with Fourier parameters and through the two-point correlation data in real parameters. Each technique provides its own insight into the nature of the CMB's anisotropies. In particular, it has been discovered that there is a statistically significant cutoff in angular temperature correlations at large angles compared with the predictions of the concordance model and inflation theory. This indicates an error in the data or the data processing, or a possible violation of statistical isotropy in the CMB. However, no similar studies have yet been done for the polarization data, which has been treated using angular power spectrum techniques alone. We will perform a similar treatment of the correlation in polarization, particularly comparing these results to the expected results from the concordance model.

A local inventor has designed a heat engine to generate electricity from lake water. In his rather unspecific design, the working fluid, a low temperature liquid refrigerant, enters an evaporator where it undergoes a transition to the gaseous phase and absorbs heat from the lake water. The gaseous working fluid is pressurized and circulated through the system by a solar powered compressor. The refrigerant passes through a turbine, generating power, and then condenses and the cycle is repeated.

The basic idea proposed by Mr. Isaacs is not new and belongs to a class of geothermal and ocean energy generating devices that operate either as heat engines or heat pumps. Ocean thermal energy conversion (OTEC) uses the temperature difference that exists between deep and shallow water to run a heat engine to produce electricity. The larger the temperature difference, the greater the efficiency of the system. Evaporation limits surface temperature to about 27 °C and the subsurface water rarely falls below 5 °C. (For this case the Carnot efficiency is about 7%). Typically, designs achieve actual efficiencies of only about 3%.

The objective of this project is to analyze the feasibility and cost-effectiveness of the proposed system and to suggest modifications that would improve the design. The results of the investigation will be used to advise a local charitable foundation as to whether it is worth funding development of this idea.

Detecting Cherenkov radiation is a way to obtain information about the ultra-high-energy cosmic rays that enter the Earth’s atmosphere. By measuring this radiation, we can discover the energy-level and direction of the incoming rays, which can in turn point us to their source. The purpose of this project is to put together a durable and low-cost Cherenkov radiation detector from a non-imaging optical concentrator and a coincidence system. Specifically, all the already-assembled components need to be tested individually and used together to take data. After it is possible to successfully detect Cherenkov radiation with this setup, more such detectors will be created, to be employed in the Auger North Project.

In recent years, a number of studies have attempted to demonstrate the presence of retinotopic maps in occipital, parietal and frontal cortex. The evidence for these maps has come from inspection of color-coded maps based on phase-encoded visual field stimulation. However, this method is qualitative in nature and the maps have not been consistent between groups and subjects, thus leaving the important question of what these mappings look like or whether they even exist unanswered. Our research involves regression analysis of BOLD fMRI data in an attempt to establish a more quantitatively rigorous assessment of the presence of topographical maps on the cortical surface. If time permits, we would like to extend this mapping from the occipital lobe to higher cortical areas, and examine the faithfulness of our mapping for when considering both attended and unattended stimuli.

Dark matter detection requires effective reduction and rejection of background events to accurately detect dark matter interactions. The LUX detector consists of a volume of liquid xenon with photo multiplier tubes inside of a sealed container shielded by a medium such as water or liquid scintillater. Upgrading the current LUX water shield would allow for effective detection of high energy gammas in the MeV range that have gone through small angle Compton scattering to produce an event in the main detector. Detection of the high energy gammas in the shield region will allow vetoing of the 10keV signals produced by the Compton scattering. Additional PMTs will be required to detect these events as the current set up does not have the required sensitivity to detect gammas in the shielding region. Neutron background from both the natural environment and the radioactivity from the PMTs must be rejected to ensure correct detection of dark matter events. Doping the outer water shield with gadolinium will allow for effective neutron detection. Feasibility and performance studies of the new designs will be done using MCNP Monte Carlo.

The electrical conductivity for bulk metal is described by the well-known Drude model. As the size of the metal is reduced to the nanometer scale however, the energy levels become discrete, rather than continuous. The average spacing between adjacent energy levels in a metal nanoparticle is called the Kubo gap, and is related to the Fermi energy of the metal and the size of the nanoparticle. For instance, in a silver nanoparticle of 3-nm diameter containing ~103 atoms, the Kubo gap is around 5-10 meV. Therefore, at room temperature when the thermal energy is greater than this gap, the electrical conductivity will be the same as in bulk metal. As the temperature is lowered however, the Kubo gap becomes significant and the nanoparticle becomes an insulator. Although the DC properties of this metal-to-insulator transition are well understood, the experimental observations and theoretical description for AC conductivity are much less comprehensive. In this project I will investigate the AC conductivity of silver nanoparticles in an interesting frequency range that corresponds with the Kubo gap of the nanoparticles. Conductivity will be measured using terahertz (1 THz ~ 4.2 meV) time-domain spectroscopy based on a mode-locked laser. The frequency dependence of the complex conductivity will be investigated as a function of the sample temperature to understand the metal-to-insulator transition.

The synthesis and study of group II-IV nitride semiconductors is an area of condensed matter physics that has not been rigorously explored. However, growth of group III nitride semiconductors has received a great amount of attention because of their interesting properties. For instance, GaN is a large bandgap group III semiconductor of interest because of its use in optoelectronic devices. This project will attempt to grow ZnSnN2 a group II-IV semiconductor that serves as an analog to the group III conductor InN. The growth will be done from a Zn and Sn melt exposed to nitrogen plasma under high vacuum at temperatures around 400 C, an environment in which InN grows. Because this material has never been grown before, it may be unstable at pressures where the plasma system operates. If material is successfully grown, it will be of interest to measure its properties from crystal structure to electrical bandgaps in order to compare these aspects with the group III counterparts.

An ionomer membrane is the central component of a polymer electrolyte membrane fuel cell. Its purpose is to separate reactants while only allowing one specific ion to pass through it. In the case of a hydrogen fuel cell, the reactants are hydrogen gas and oxygen gas. Hydrogen gas is split into its composite protons and electrons, and the protons are allowed to pass through the membrane. While there is theory for the flow of protons through the membrane, little is really known about the mechanisms at work and their relative strengths. The goal of this project is to determine the importance of the various mechanisms at work in proton transport through the membrane. This will be done by developing a simplified theoretical model of the forces and energies in the substructure of the membrane. This model will then be used to run computer simulations of the membrane under conditions emulating a fuel cell.

Currently the most efficient solar cells are made of silicon and are not a viable technology due to high device fabrication costs. It is hoped that organic semiconductors and hybrid systems with nanostructured inorganic materials can be used to construct less expensive, yet efficient, solar cells. The purpose of this project is to develop a new fabrication approach that would enable self-assembly of organic electron-donor and electron-acceptor molecules into blends of a quasi one-dimensional architecture. We will study exciton dissociation at the donor-acceptor interfaces and transport of electrons and holes along the quasi one-dimensional donor and acceptor channels in photovoltaic device architectures as well as in a number of simpler model geometries. Better understanding these fundamental photo-physical processes would allow for further optimization of the device performance.

The Large Underground Xenon detector requires a very low background environment in its search for weakly interacting massive particles. One contributor to the radioactive background is radon (222Rn) emanates out of materials used in the construction of the detector. A radon emanation counting system will be designed, constructed and tested; this system consists of a radon detector, an emanation chamber and the mechanism required for the effective transfer of radon from the emanation chamber into the detector. The intended goal is to determine the radon emanation rate from samples of several critical LUX components in order to allow the proper selection of materials and to characterize the expected radon background.