Whether they are collaborating with faculty at Rhodes or participating in one of the many NSF sponsored Research Experiences for Undergraduates programs, students are encouraged and supported in the presentation of their research. It is not unusual for a graduating senior physics major to have attended several national meetings and given formal presentations to both research audiences in their field of work as well as general audiences in a seminar presentation
Research with Faculty
Areas of interest for Rhodes physics faculty and their collaborations with students
Dr. Shubho Banerjee
- Iionic fluids
- Lipid membranes
Dr. Brent Hoffmeister
- Ultrasonic Backscatter for Clinical Bone Assessment
Ultrasound is being used increasingly as a diagnostic tool for bone diseases such as osteoporosis. Commercial ultrasonic devices use through transmission techniques that require two ultrasonic transducers to be placed on either side of the bone. This severely restricts areas accessible to ultrasonic interrogation. We are developing backscatter techniques that require only a single transducer. We have found that high frequency (5-10 MHz) backscatter correlates significantly with bone mineral density and mechanical properties of bone.
- Effect of Medical Implants on Magnetically Induced Currents in the Body
Patients who receive MRI scans are exposed to electrical currents that are induced in their bodies by the rapidly switched gradient magnetic fields. These currents are believed to be too weak to cause serious problems such as cardiac stimulation. However the effect of plastic and metal implants on these currents is not known. We have developed an experimental apparatus to study these effects. We have found that that plastic implants can have a very large effect, and we are focusing our attention on this because (unlike metal implants) no one else is considering it. We also have developed a theoretical model based on Coulomb′s Law and Faraday′s law that agrees well with our experiments.
- Ultrasonic Characterization of the Curing Process of Cement
Ultrasound is well known for its nondestructive testing (NDT) applications. We are using ultrasonic techniques to characterize the curing process of various types of cement. This has included bone cement, and structural cement modified with fly ash (a waste product of coal powered electrical plants). Ultrasonic speed of sound and attenuation (measured as a function of time during curing) have proven very sensitive to changes in the properties of these cements as they cure.
Many students have contributed significantly to my research, and I am grateful to them for their hard work. These students are listed below along with brief descriptions of their contributions.
- David Johnson ’07 - David performed ultrasonic backscatter measurements of human cancellous bone in the frequency range 0.6-15 MHz
- John Janeski ’07 - John performed ultrasonic backscatter measurements of human cancellous bone in the frequency range 5-10 MHz
- Brian Steinert ’06 - Brian mechanically tested specimens of human bone used in ultrasonic studies.
- Daniel Keedy ’06 - Daniel performed ultrasonic backscatter measurements of human cancellous bone in the frequency range 0.6-15 MHz.
- Taylor Whaley ’05 and Chip Hartigan ’05 - Taylor and Chip analyzed videos of surgically exposed heart to study how the heart responded mechanically to weak AC electrical stimuli
- Garney Caldwell ’05 - Chad performed ultrasonic backscatter measurements of cancellous bone in the frequency range 2.5-7.5 MHz.
- Drew Shores ’05 - Drew developed an experimental and theoretical model to describe how weak electrical currents induced in the body during MRI scans interact with plastic medical implants.
- John Sexton ’04 - John measured the area and wall thickness of the left ventricle of the heart during weak AC electrical stimuli.
- Stu Johnston ’03 - Stu processed ultrasound images of the heart during weak electrical stimulation.
- Chad Jones ’03- Chad performed ultrasonic backscatter measurements of cancellous bone in the frequency range 2.5-7.5 MHz.
- Tom O’Hara ’03 - Tom analyzed ultrasound “M-mode” images of the heart during weak AC electrical stimulation. He also developed a computer model to simulate M-mode data.
- Julie Auwarter ’01 - Julie worked on two main projects. The first involved monitoring the curing process of bone cement with ultrasound. The second involved ultrasonic measurements of bone before and after the marrow was removed.
- Andy Whitten ’00 - Andy performed ultrasonic measurements of cancellous bone in the frequency range 1-3 MHz.
- Steve Smith ’00 - Steve studied ultrasound images of the heart during electrical defibrillation shocks.
- Will McKinney ’00 - Will studied ultrasound images of the heart during weak electrical stimulation.
Dr. Anne Viano
My current research projects are in the area of biomaterials- materials that are used in the human body to recover or enhance function. Metal alloys, plastics, and animal-derived materials are currently used in a variety of applications from artificial joints to new heart valves to new lenses for the eyes.
Polyethylene in Joint Prostheses
Ultrahigh molecular weight polyethylene (UHMWPE) is a major component in large human joint prostheses. It is well suited to play the role of cartilage in these devices due to its excellent biocompatibility and high values of many relevant mechanical properties. One of the key problems associated with use of UHMWPE in prostheses is the release of microscopic polymer particles (wear particles) during use, which can lead to adverse biological reactions such as osteolysis. Although treatments such as gamma-irradiation-induced cross-linking have been developed to reduce wear particle production, very little is known about how these treatments affect the microscopic structure, which is fundamentally related to mechanical properties. We use transmission electron microscopy (TEM) or atomic force microscopy (AFM) to visualize the microstructure of UHMWPE. The polymer chains are ordered and stacked into long, worm-like lamellae which give the material crystalline properties (image above). Between lamella, the chains are randomly oriented, which imparts amorphous (glass-like) qualities to UHMWPE. Our laboratory has developed new analysis techniques that allow a quantification of microstructural parameters, which can be correlated to performance properties of the material.
Biological Interactions and Modification of Implant Alloys
The biological environment inside the human body is a chemically active and corrosive one, and corrosion of metalic alloys that are part of implants in the body releases metal ions into the bloodstream. This can cause toxic, immunological inflammation reactions. Fortunately, most metallic alloys naturally form a protective oxide layer at their surface, and this layer resists corrosion to some extent. The nature and evolution of this corrosion resistance for implant alloys exposed to cellular media is currently being investigated. The attachment of cells to the metal surface, a natural occurrence when these devices are placed in the biological environment, causes structural and chemical changes to the metal surface. These changes alter the protective oxide layer and therefore the ability of the metal to resist corrosion. A change in the corrosion properties of the metal may then affect the ability of cells to attach to the metallic surface. Thus, the corrosion of the metal is somewhat manipulated by the external environment, but at the same time the environment is influenced by the corrosion. We are investigated corrosion of titanium and stainless steel as a function of cell attachment and biological environment, with the aim of providing a better understanding of tissue attachment on metallic implant components, which is necessary in the pursuit of longer-lasting and better-performing implants. The image at the right shows the components of a typical hip implant.
Vibration Reduction in X-ray Capillary Optic Fabrication
Advisor: Donald Bilderback (Cornell University)
Glass capillary optics are used to focus X-rays from synchrotron light sources. The quality of Cornell High Energy Synchrotron Source (CHESS) capillaries matches present generation light sources well, but improvements will be necessary to take advantage of planned facilities, such as the Energy Recovery Linac (ERL). The primary obstacles are small radius profile errors and centerline oscillations in capillaries drawn from constant-diameter glass tubing into an elliptical shape. This project focuses on minimizing mechanical vibrations in the capillary fabrication and analysis system. Capillary errors are compared before and after structural bracing additions; these additions were found to reduce errors and enable the drawing of some of the best capillary optics to date.
SOCKs and Summer Camps
Advisors: Gary White and Donna Hammer (Society of Physics Students)
A large focus of the Society of Physics Students is outreach, both in undergraduate institutions and in the community. Each year, the Society of Physics Students summer interns develop and put together the SPS Outreach Catalyst Kit, or SOCK. The theme of the 2008 kit is “Makin’ Waves” and it includes three topics: polarization, sound waves, and reflection and refraction. Each topic uses fun toys such as long springs, Boomwhackers®, and Jell-O® to engage college students and schoolchildren alike. Development of the SOCK and the society’s focus on outreach is complemented by the opportunity to work with the summer camps at the Materials Research Science and Engineering Center at the University of Maryland.
Brad Taylor ′09
On Stability of Electrostatic Orbits
Advisor: Shubho Banerjee (Rhodes College)
This summer Prof. Banerjee and I analyzed orbital stability between two charged conducting spheres orbiting each other. While similar in manner to the gravitational orbits between planets, electrostatic orbits deviate, as a result of polarization, from typical 1/r2 behavior as the two spheres get closer to each other. Accounting for such a phenomenon with our mathematical understanding of the situation, we find the nature of electrostatic orbits is subtly but fundamentally different from gravitational orbits. We focus on the stability of the orbits.
Josh Fuchs ’11
Cooling Effects on Molecular Motor Speeds
Advisor: George Shubeita (University of Texas, Austin)
Molecular motors are the primary transport mechanisms inside the cell. Since the distances cargo is transported is much larger than the motors themselves, the motors physically walk the cargo along microtubules. The work I did was focused on two of these motors, kinesin and dynein, and their motion in Drosophila embryos. In an effort to better characterize the physical motion of these two motors, I investigated whether or not a lower temperature will decrease the speed of the motors.
Travis Rasor ’10
The Mysterious Shapes of Magnetic Liquids
Advisor: Shubho Banerjee (Rhodes College)
A magnetic liquid is a chaotic jumble of constantly moving magnetic particles. The particles are unable to align themselves and exert a detectable magnetic field without first transitioning into a solid. A great amount of research has been done into the creation of a liquid that is orderly (with all the particles in alignment) without becoming a solid. Ordered magnetic liquids have been predicted theoretically, but never observed experimentally. Such a liquid would have magnetic properties and interesting applications. But what would a drop of magnetic liquid look like? Our main goal this summer was to determine the shape of a freely suspended magnetic liquid drop using computer simulations. With Surface Evolver we successfully programmed a working model of a liquid drop and determined several possible shapes for this mythical masterpiece.
Kelsey Dudziak ’11
Introduction to Nuclear Physics and E-GOS method
Advisor: Deseree Meyer (Rhodes College)
Nuclear Physics is a division of physics that deals with the nucleus of the atom. It is a study of the tiny particles, called nucleons, which make up the nucleus and contribute to the structure and the behavior of the nucleus. The E-GOS (E-Gamma Over Spin) method is a method that allows us to empirically determine the structure of a nucleus. We achieve this through comparisons with the ideal limits of a perfect harmonic vibrator and axially symmetric rotor, which are known limits that help determine whether the nucleus takes a spherical shape or a deformed shape. We applied E-GOS method to the yrast bands of nuclei in the Rare-Earth region in order to verify the method because it is a well-known region of nuclei. Finally, we arranged the plots according to increasing nucleon number so that we could see the transition from vibrational to rotational nuclei.
Nuclear shape is commonly described as a function of nucleon number. The closer a nucleus approaches to a closed shell, the more likely the nucleus is to be spherical. A simple way to describe changes in the shape of a specific nucleus is as a function of its angular momentum using the E-Gamma Over Spin (E-GOS) method. We performed an experiment using the ESTU tandem Van de Graff particle accelerator at the Wright Nuclear Structure Laboratory at Yale University. In the experiment, many nuclei in the mass one hundred region were synthesized. A plethora of data was acquired as a result of this experiment, and I have undertaken the task of the analysis process. I will discuss the E-GOS method, which is the framework within which my research is being performed. I will also give a simple introduction into the analysis using gamma-ray spectroscopy and provide a summary and interpretation of results obtained thus far. This work was supported by DOE Grant DE-FG-91ER-40609 and Rhodes CARES.
The Effects of Multipoint High-Velocity Impact Damage on the Residual Properties of Fiber Glass Reinforced Vinyl Ester Composites
Advisor: Dr. Uday Vaidya (University of Alabama at Birmingham)
Composite materials are increasingly used in military applications due to their lightweight and high strength characteristics. Military vehicles and structures often face attacks from bullet fire and fragmentations from blasts. Under such threats, these structures witness multipoint impact damage. This research evaluates the significance of multipoint high velocity impact damage patterns in glass fiber reinforced vinyl ester composite materials. In this approach, sets of composite specimens were fabricated using a Vacuum Assisted Resin Transfer Molding (VARTM) procedure and imposed with either clean drill-hole or ballistics damage. Controlled damage patterns were created to identify the effects of damage type, area, and positioning on the compressive strength and stiffness of the composites. Samples were subjected to Compression After Impact (CAI) testing and to 4-point Flexural Testing to quantify and compare their stress yield values and to identify their residual properties after failure. From the results, it is suggested that increases in the delamination of the material due to initial damage correlate with a decrease in the stress yield in damaged samples. In addition, the positioning of the damaged areas in relation to the loading point is responsible for variations in the location and degree of compression failure in the composites, while damaged areas in closer proximity have been observed to demonstrate more aggressive compression failure after maximum yield.
Student Research Abstracts: 2007
Justin Hugon ‘09
UHMWPE Creation and Analysis
Ultra High Molecular Weight Polyethylene (UHMWPE) is the most prominent polymer in joint replacements. Significant gravimetric wear analysis has been done on bulk UHMWPE, but little is known about the wear particles created during the wear process. Quantitative analysis and analysis of particles of less than 1µm are particularly lacking. Over the summer, we created a method for wear particle creation and analysis. It involved the use of a wear machine, multiple methods of particle isolation, and imaging with TEM and SEM. We were able to isolate and identify particles smaller than 100nm, which has not been done before. Particle creation and analysis methods will be presented, as well as preliminary data.
Justin LeBlanc ‘09
Gamma-Ray Spectroscopy of 100,101Pd
An experiment was performed using the ESTU tandem Van de Graff particle accelerator at the Wright Nuclear Structure Laboratory at Yale University. In the experiment, a Carbon-12 beam was accelerated into a Zirconium-92 target, and many nuclei in the mass one-hundred region were synthesized. A plethora of data was acquired as a result of this experiment, and I undertook the task of the analysis process. In my talk, I will establish the framework within which my research was performed and give a simple introduction into the analysis that is utilized in the process of gamma-ray spectroscopy.
Jennifer Thompson ‘08
Blast Mitigating Materials: Can they Handle the Pressure?
The purpose of this study is to investigate blast mitigating materials to protect an aircraft during an onboard explosion. The protective layers were mounted to vertical frames of a test panel replicating the internal structure of an aircraft. The completed panels were then clamped to a vacuum tank and a charge of C-4 was detonated at a standoff distance of 6 inches. Two combinations were successful: a sheet of aluminum 2024-T3 coated on one side with a thermoplastic elastomer, and a fiber-metal laminate backed with a Kevlar reinforced elastomer. The aluminum and the fiber-metal laminate were by themselves ineffective in preventing panel rupture, indicating that a stiff layer coupled with an elastic backing allows the protective panel to fracture while preventing rupture of the fuselage skin.
In order to undermine terrorist attacks, the United States has to remain on the cutting edge of bomb detection technology. DNT is an explosive molecule that indicates the presence of TNT, one of the most used explosives in terrorist bombs. Our mission was to detect and identify the presence of DNT using a system of chemical detection called Gas Chromatography (GC) and Solid Phase Micro Extraction (SPME). To test our detection capabilities, we exposed a sample of DNT to our detection system inside of a wind tunnel, where the wind would blow the sample past the SPME detection device. My project for the summer was to characterize how the speed of the wind in the wind tunnel and the temperature of the DNT sample affected our ability to detect DNT. The knowledge this project provides will help protect the lives of troops in Iraq, bolster the security of airports, as well as countless other life-saving scenarios.
Bulk PALS Measurements of P2VP/Silica Nanocomposites
This summer I used a positron source to perform materials science research. Positrons form a bound state with an electron to form Positronium (Ps). Ortho-Ps—the spin triplet state—has a lifetime that is directly proportional to the pore-size and is used as our probe. We investigated various weights of nanocomposites, or polymer samples reinforced with nano-sized metals for enhanced performance. From these lifetime measurements on our P2VP/Silica nanocomposites taken at temperatures between 20 and 170ºC, we are able to extract the pore-size/free volume. Then we can deduce valuable information about the phase transition as well as the mechanical, electronic, and transport properties.
Chase LaFont ‘08
Remote Controllers and Autonomous Vehicles
The purpose of my summer research was to develop a PID controller for a remote control car. We used system based software, MatLab Simulink, to model the dynamics of the car and develop a remote for an autonomous car.
Travis Rasor ‘10
A New Interferometer for Easy Detection of Mysterious Sources
An Interferometer is an instrument used to make sophisticated optical measurements. The aim of the summer project was to test a new interferometer, which--in principle--is a better design than the classic Michelson-Morley set-up. This interferometer is able to analyze light from a single interference pattern produced on a screen using stationary parts, whereas the Michelson-Morley requires a movable mirror adding on another layer of mechanical complexity. This interferometer would be more suitable to analyze infrared light to determine the chemical composition of a source and, therefore, could be used in the detection of explosives.
Finding an Appropriate Sample Size of Ultrasonic Backscatter Measurements
Ultrasonic backscatter measurements show a great deal of promise as a diagnostic tool in the fight against bone disease-especially osteoporosis. However, the site to site variation in a biological specimen can make the mean ultrasound values difficult to obtain. By using a statistical method to determine an appropriate sample size for a given scan, a value can be found that is within a certain level of confidence with the actual mean. Thus standard scanning procedures in ultrasound measurements could be greatly improved by these findings."