(last updated on January 26, 2007)
Clicking on the project title will call up a PowerPoint or pdf file of the student's final poster presentation, if one is available.
Ross Anderson with Harihara Baskaran, Jean Welter & Robert Brown
Modeling Oxygen Diffusion Through an Inhomogeneous Growing Cartilage Matrix
Once cartilage, a cushioning tissue in a joint, has failed, the mobility of the patient is significantly inhibited due to pain caused by bone-bone interaction. Cartilage lacks a vascular system, and the ability to mobilize repair cells, and thus da ma ge is cumulat ive . The current solution is to replace the joint with a plastic-metal composite prosthetic joint. These can last up to 20 years without maintenance, but for younger patients this is not a permanent solution, and usually ends the career of athletes. Biological cartilage repair may make it possible to delay or prevent prosthetic replacement, restore mobility, and to some degree , athletic ability.
This project focuses on a critical tissue engineering problem found in the artificial construction and replacement of joint cartilage. Specifically, it is currently very challenging to grow large sections of cartilage because the interior can not be properly supplied with nutrients. Two parallel approaches to this problem are to improve delivery of nutrients to the construct and to reduce the demands of the cells inside. We are studying the first approach in this project by using a combination of a biological model system and computer modeling to understand the diffusion of oxygen and nutrients into a growing cartilage disk. In the biological system, we induce stem cell differentia tion to create cartilage cells through a series of manipulations. Stem cells have much higher metabolic demands than cartilage cells. C omputer modeling of oxygen diffusion into the cartilage will help us understand the needs of the se cells during the transition from stem cells to cartilage cells. Using the finite element modeling program Femlab (Comsol, Burlington M assachusetts ), we have created a baseline model of our bioreactor system and the growing cartilage construct, illustrating diffusion through the cartilage construct as a function of time. The model is based on the Navier-Stokes e quations describing momentum balance and Fickian diffusion equation describing species transport. We intend to enhance this basic model by varying the diffusivity of the construct in the model as a function of time and space, and including functions for time dependent species consumption. Experimental verification will be accomplished by using a fiber optic oxygen sensor system to measure the concentration of oxygen at specific points in the construct.
The computer model developed in this project will define the oxygen requirements of the construct under a variety of culture conditions and will allow us to predict the effects of modifications to the bioreactor system.
Joshua Ball with Harsh Mathur
The Efficiency of Adiabatic Quantum Computing
Adiabatic quantum computing is a newly proposed method developed to solve exact cover and other NP-complete problems. Classically, NP-complete problems can only be solved in exponential time. However, numerical simulations of the adiabatic quantum computer on a classical computer suggest that this method can solve exact cover in polynomial time. In this project we aim to improve the simulation of the adiabatic quantum computer in order to test the algorithm with larger input problems. We will also study exact cover or other NP-complete problems analytically and look for special cases where the method could fail to solve the problem in polynomial time.
Frank Calma with John Ruhl (project started January 2006)
Magnetic Bearing for Cosmic Microwave Polarimetry
Balloon borne polarimetry experiments such as the BOOMERANG experiment require adjustable polarimetry apparatus with low frictional loss or heat discharge. One such design is to use a bearing containing a half wave-plate polarimeter. Unfortunately, typical mechanical and electromagnetic designs have prohibitive heat costs and characteristic oscillations that are extremely difficult to dampen or remove.
One possible solution to this issue is the use of high temperature superconductors. The use of high temperature superconductors can be self damping, and heat and frictional loss is then only a result of eddy currents.
The purpose of this project will be to design, build and test a 6” superconducting magnetic bearing. The bearing will be designed to rotate a 10 kilogram mass at a 20 Hz. operating frequency, with the intent to achieve a coefficient of friction m <10 6 , and adequate damping and stiffness to oppose vibration.
James Garrison with Tanmay Vachaspati
An Investigation of Classically-Forbidden Quantum Detection and its Application to Island Cosmology
Island cosmology is a cosmological model that is an alternative to the inflationary paradigm. In island cosmology, the universe is initially void of matter but filled with cosmological constant. Quantum fluctuations of an existing field then have some probability of violating the null energy condition, suddenly making the Hubble length scale very small with an island of matter. This island then evolves according to the Friedman-Robertson-Walker model, which is generally thought to describe the universe in which we live. The mechanism behind the null energy condition is analogous to the observation of a quantum particle in a classically forbidden region, such as under a potential energy barrier during quantum tunneling. The present study will explore the nature of detection and measurement in quantum mechanics. Then, we will attempt to determine restraints on other internal degrees of freedom when a particle is detected under the barrier. In other words, if quantum tunneling occurs in the x direction, can conclusions be made about the nature of the wavefunction in the y and z directions? We will then attempt to extend these conclusions to the infinite number of modes present in a quantum field and relate our findings to island cosmology.
Jonathan Glicoes with Dan Akerib & Richard Schnee
Investigation of Background Rejection in the Search for Dark Matter
The Cryogenic Dark Matter Search (CDMS) experiment seeks to demonstrate the existence of dark matter in the form of Weakly Interacting Massive Particles (WIMPS). In order to attempt to distinguish potential WIMPS from other particle interactions a stacked array of transition edge phonon sensors operating at 10-50 mK are utilized. Due to the nature and sensitivity of these detectors they are highly susceptible to background noise from latent radiation and high energy perturbations from gamma rays. The goal of this project is to characterize these background signals utilizing calibration data so that better analysis techniques may be utilized to increase the expected signal to noise ratio of the CDMS experiment.
Edward Hawkins with Hiroyuki Fujita, Xiaoyu Yang & Robert Brown
Constructing a Birdcage Coil, Facilitating Freedom from the MRI Cage
Magnetic Resonance Imaging (MRI) represents the marriage of medicine and physics, producing images of the human body which are astoundingly accurate while employing only non-invasive shifting magnetic fields as detectors. Because the idea for medical imaging evolved from applying spatial mapping to existing Nuclear Magnetic Resonance (NMR) technology only a few decades ago, MRI has typically been performed with immense and intimidating machines which surround the person being imaged. Also, to accumulate the best images, an ideal subject would be motionless and extremely cold, both of which are at odds with imaging a living person. To better fit the special conditions ideal for imaging people, the need is great for more specialized coils. One particularly pertinent idea is to insert a microcoil in a catheter and use it to image blood vessels and other tubes within the body in vivo . Before clinical trials of prototypes can begin, images of blood vessels from cadavers must be validated using a more conventional external coil. While there are many possibilities, the birdcage coil is an elegant choice because of its uniquely uniform internal field; it is especially efficient at increasing the signal to noise ratio (SNR) because this field is tuned to rotate at the frequency of hydrogen atoms precessing in the large static magnetic field used in imaging. This project will numerically simulate, construct, and tune a birdcage coil for use in testing prototype microcoils. In so doing, we hope to uncover peculiar and new aspects of the problem of imaging the singularly difficult human physiology.
Joseph Kolthammer with Kathy Kash
Near-Atmospheric Thermal Gradient Growth of Single Crystal Gallium Nitride
Gallium nitride (GaN) is a highly desirable wide bandgap semiconductor with myriad optoelectronic applications. Reliable GaN growth has in the past been limited to reactions at 10 kbar or greater pressures; a near-atmospheric process features much easier implementation. The first objective of this project is the construction of a reactor to support the growth of a polycrystalline GaN seed crust from a molten gallium phase using ammonia as the nitrogen source. The seed crust will form at the top of the melt in a small graphite crucible. Numerical modeling indicates that under the influence of a thermal gradient, and the consequent solubility gradient, single crystal GaN may grow into the melt from the polycrystalline seed, like a stalactite from a cave ceiling. Upon successful synthesis, the material will be characterized with a variety of techniques. A reliable thermal gradient growth mechanism would be applicable in the experimental growth of many other semiconductors, and the growth process could easily be enlarged to production scale.
Ben Lawrie with Arnold Dahm
Fabrication and Characterization of an InSb Hot-Electron Bolometer
For this project, hot-electron bolometers of various meander line geometries will be investigated. Several geometries will be modeled analytically, and then constructed using a laser milling machine. The thickness of the InSb, the number of lines in the meander pattern, and the spacing between the lines will be varied in order to find the bolometer with the best sensitivity. It has been suggested that spiral geometries have particularly high sensitivity, though fabrication of a spiral pattern may be quite difficult. If time and funds permit however, a spiral meander line will be cut and compared against the other geometries. Because the skin depth of the InSb depends on frequency, the sensitivity will also be compared against the frequency of the microwaves.
Chris Muscatello with Tanmay Vachaspati
Propagation of Charged Particles with Spin in Helical Magnetic Fields
The study of cosmic rays and their origin has both cosmological and astrophysical implications. Some previous works dealt with the propagation of charged particles through large-scale randomly distributed astrophysical magnetic fields. Magnetic fields are known to exist in all astrophysical systems and are theorized to exist in the early universe. More specifically, helical magnetic fields exist in a number of astrophysical systems such as jets emanating from galactic centers and possibly the early universe. The current interest is to study the propagation of charged particles with spin in helical magnetic fields and to determine if the results can be used as a probe of magnetic helicity.
Christian Perez with Arnold Dahm (project started January 2005, finished in December 2005 )
Quantum Computation: From Electron to Qubit
The characterization of electron states for quantum computing with electrons on liquid He requires several proprietary components. Two of those are a low-T, low noise microwave bolometer and submicron electrode array for electron localization and control of the confinement potential. This project will investigate the feasibility of constructing an InSb hot electron bolometer from commercial materials using standard fabrication technologies. If possible, several prototypes will be constructed and tested. The electrode array (or pad) design, field calculations, signal analysis, and fabrication process is the main goal. Once these are implemented, proof of principle tests and single qubit gate operations will be attempted.
Salem Ritenour with Corbin Covault (project started January 2006)
Cosmic Ray Showers: Detectors, Simulation, and Reconstruction
The arrival of cosmic rays into earth's atmosphere poses a variety of scientific conundrums. One can examine these problems by devising methods of deducing the Entergy, arrival direction, and composition of the rays. Our approach will be to examine the effects of particle interaction during cosmic ray showers. Such rays might penetrate an atom through the electron region causing minimal deflection. In the event that the ray strikes a nucleus, it will become deflected and energy will be released due to the collision, causing the genesis of secondary particles. One expects this procedure to repeat numerous times before the shower reaches the ground. Furthermore, the angle of incidence of the particles with respect to the ground introduces measurement uncertainties via the variance in the dispersion of the front of particles. This angle can, in principle, lead one to a particular region of space to which the rays originated, provided that a significant portion of the rays were not severely deflected before entering the atmosphere, most likely due to the presence of a magnetic field.
Although still under construction, the Pierre Auger project is capable of acquiring data via detectors comprising photomultiplier tubes housed in water tanks on the plains of Argentina. Moving near the speed of light in air, the secondary particles will exceed the local speed of light in water upon entering the tank due to the difference in indices of refraction between air and water. A flash of light will result, which the detectors will record. If a significant number of detectors report a flash within a few nanoseconds, it can be deduced with fair certainty that a cosmic ray shower occurred. Through examining the differences in timing and pulse-height data from each individual detector, one can infer the arrival direction of the shower.
An important step toward building such detectors is the testing of the Tank Power Control Board, which is capable of evenly distributing power gathered from solar cells throughout the day and night. The High Energy Astrophysics group at Case Western Reserve University is undertaking the testing of such boards for the entire Auger Project. We will further examine the technical specifications of the boards in hope of specifying more precise error bounds for their operating properties. Detailed tolerance testing and analysis will assist in discerning to what extent variations in the specifications would have upon reconstructed quantities such as energy and arrival direction.
In the event that the examination of the power control boards is completed in due time, we will extend the research to consider other uncertainties in timing determinations at individual detector stations. This might include errors in data relay such as GPS timing drifts, miscalculated timing offsets, spurious or missed triggers, and/or event mismerging. For each of these examples, we will develop numerical simulations and compare them to actual data in order to minimize the impact of these errors on uncertainties in arrival directions.
Brian Tinker with William Fickinger (project started January 2006)
History of Acoustics Research in the Physics Department
The Case Physics Department has a rich history of research in acoustics, which peaked during the early 20th century. In particular, the department head, Dayton Miller, invented the phonodeik, the predecessor to modern oscilloscopes, which could photographically record sound waves. The department still has much of the original equipment purchased by Miller, including pieces designed by German acoustician Karl Rudolf König. This project will explore the history of acoustics research in the department. Key pieces of equipment will be identified and detailed, and a website will be created presenting this information.
Benjamin Titus with John Ruhl (project started January 2006)
Development and Testing of Millimeter-wave Half-Wave Plates (draft abstract)
In the project titled “Development and Testing of millimeter-wave Half-Wave Plates” we are testing a half-wave plate polarization rotator using birefringent sapphire crystals made by two different manufacturers. One of our goals is to determine if we can satisfy our needs using the less expensive crystals. We are testing the polarization properties as a function of frequency. Sapphire has a large index of refraction which leads to a large amount of reflection, this can cause unwanted interference. In order to reduce reflections we are also testing the performance of quarter-wave fused quartz anti-reflection coating as a function of frequency. We will take data and fit it to numerical models of half-wave plate/A.R coating systems. These tests are aimed at developing prototype half-wave plates that will be used by professor John Ruhl in future research on the Cosmic Microwave Background.
Colleen Woodward with Ken Singer
Lasing and Nonlinear Optics in Polymeric 1-D Photonic Crystals
New techniques have been used to create high quality multilayer polymer films, forming one-dimensional photonic crystals. Films doped with active species will be used to study stimulated emission and other linear and nonlinear optical properties. These properties may include lasing, second harmonic generation, and linear and nonlinear transmission.