Bulletin of the American Physical Society
APS March Meeting 2015
Volume 60, Number 1
Monday–Friday, March 2–6, 2015; San Antonio, Texas
Session A4: Undergraduate Research/Society of Physics Students I |
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Sponsoring Units: APS Chair: Crystal Bailey, American Physical Society Room: Mayor Cockrell Room 004 |
Monday, March 2, 2015 8:00AM - 8:12AM |
A4.00001: Detergent Stabilized Nanopore Formation Kinetics of an Anthrax Protein Kelby Peterson This summer research project funded through the Society of Physics Students Internship Program and The National Institute of Standards and Technology focused on optimization of pore formation of Protective Antigen protein secreted by Bacillus Anthraces. This experiment analyzes the use of N-tetradecylphosphocholine (FOS-14 Detergent) to stabilize the water soluble protein, protective antigen protein (PA63) to regulate the kinetics of pore formation in a model bilayer lipid membrane. The FOS-14 Detergent was tested under various conditions to understand its impact on the protein pore formation. The optimization of this channel insertion is critical in preparing samples of oriented for neutron reflectometry that provide new data to increase the understanding of the protein's structure. [Preview Abstract] |
Monday, March 2, 2015 8:12AM - 8:24AM |
A4.00002: Lipid membrane structure and dynamics in the presence of tamoxifen and antimicrobial peptides Samuel Hebenstreit, Nawal Khadka, Jianjun Pan Lipids are organic molecules composed of hydrophobic fatty acid tails and hydrophilic head groups that can form a multitude of structures, including lipid vesicles which provides an excellent model representing cell membranes. In this study, we examine the effects of antimicrobial peptides and drugs on lipid vesicles. Fourier transform infrared spectroscopy measurements are performed with and without the antimicrobial peptide. A change in absorbance corresponding to the wavenumber regimes associated with the stretching of the carbonyl and phosphate groups is observed. Also, a dye leakage assay is performed with vesicles composed of neutral and charged lipids. Calcein dye is enclosed within these vesicles in solution. Different concentrations of the active and inactive antimicrobial peptides, and tamoxifen are incubated with the vesicles. Concentration dependent dye leakage is determined by measuring fluorescence intensity before and after the addition of the peptides and tamoxifen. Different leakage behavior is observed for the active and inactive peptides, and the lipid composition of the vesicle is found to have a large effect. [Preview Abstract] |
Monday, March 2, 2015 8:24AM - 8:36AM |
A4.00003: Amphiplex Formation Shannon Petersen, Jennifer Laaser, Timothy Lodge Polymer-micelle complexes are currently under heavy investigation due to their potential applications in targeted drug delivery and gene therapy, yet the dynamics of the complex formation is still relatively unstudied. By varying the ratios of poly(styrene sulfonate) chains and cationic poly(dimethylaminoethyl methacrylate)-b-poly(styrene) micelles and the ionic strength of the system, we created a variety of complex configurations of different sizes and charges. The complexes were characterized dynamic light scattering and zeta potential measurements which provided information regarding the hydrodynamic radius, distribution of sizes, and effective charge. [Preview Abstract] |
Monday, March 2, 2015 8:36AM - 8:48AM |
A4.00004: Biomimetic Photonic Crystals based on Diatom Algae Frustules Jonathan Mishler, Andrew Alverson, Joseph Herzog Diatom algae are unicellular, photosynthetic microorganisms with a unique external shell known as a frustule. Frustules, which are composed of amorphous silica, exhibit a unique periodic nano-patterning, distinguishing diatoms from other types of phytoplankton. Diatoms have been studied for their distinctive optical properties due to their resemblance of photonic crystals. In this regard, diatoms are not only considered for their applications as photonic crystals, but also for their use as biomimetic templates for artificially fabricated photonic crystals. Through the examination and measurement of the physical characteristics of many scanning electron microscope (SEM) images of diatom frustules, a biomimetic photonic crystal derived from diatom frustules can be recreated and modeled with the finite element method. In this approach, the average geometries of the diatom frustules are used to recreate a 2-dimensional photonic crystal, after which the electric field distribution and optical transmission through the photonic crystal are both measured. The optical transmission is then compared to the transmission spectra of a regular hexagonal photonic crystal, revealing the effects of diatom geometry on their optical properties. Finally, the dimensions of the photonic crystal are parametrically swept, allowing for further control over the transmission of light through the photonic crystal. [Preview Abstract] |
Monday, March 2, 2015 8:48AM - 9:00AM |
A4.00005: Employing Multiple Spectroscopic Techniques Simultaneously to Observe Protein Unfolding Michael Crowe, Ben Kelty, Justin Link A protein's function is directly related to its native, folded structure. In order to study the structure of proteins, the unfolding process may be characterized. In our study, by using the spectroscopic techniques of circular dichroism (CD), absorption, and fluorescence simultaneously, we examined the unfolding of horse heart cytochrome c, a well-studied, model protein by gradually increasing the concentration of the chemical denaturant, guanidine hydrochloride. The signal changes from these modalities over the course of the unfolding reaction provides some of the thermodynamic properties like Gibbs free energy for insight into the stability of the protein. This allows us to compare the three techniques under the exact same conditions. The objective of this session is to present recent work in developing a protocol to observe the unfolding of cytochrome c using fluorescence, absorbance, and CD simultaneously. [Preview Abstract] |
Monday, March 2, 2015 9:00AM - 9:12AM |
A4.00006: The Effect of Magnetic Fields on the Quorum Sensing-Regulated Luminescence of \textit{ Vibrio fischeri} Addie Barron, Steve Hagen, Minjun Son Quorum sensing (QS) is a mechanism by which bacteria communicate through the secretion and detection of extracellular signaling molecules known as autoinducers. This research focuses on the quorum sensing regulated bioluminescence of \textit{Vibrio fischeri}, a marine bacterium that lives in symbiosis with certain fish and squid species. Previous studies of \textit{V. harveyi}, a close relative of \textit{V. fisheri}, indicate that a strong magnetic field has a positive effect on \textit{V.harveyi} bioluminescence. However the effect of magnetic fields on quorum sensing-regulated luminescence is in general poorly understood. We grew \textit{V. fischeri} in solid and liquid growth media, subject to strong static magnetic fields, and imaged the bioluminescence over a period of forty-eight hours. Luminescence patterns were analyzed in both the spatial and time dimensions. We find no indication that a magnetic field influences \textit{Vibrio fischeri} luminescence either positively or negatively. [Preview Abstract] |
Monday, March 2, 2015 9:12AM - 9:24AM |
A4.00007: Electron mobility in liquid-gated graphene biosensors Christina Harmon, Morgan Brown, Ethan Minot, Michael Crosser We report measurements of the electron mobility in liquid-gated graphene. Graphene field-effect transistor (GFET) biosensors are more sensitive to changes in external fields when the mobility is high; therefore, increasing mobility will improve sensitivity. Mobility can be calculated from the ratio of sheet conductivity to carrier density. Sheet conductivity was measured using a van der Pauw geometry and carrier density was determined from measurements of the liquid-gate capacitance. We show that mobility improves after the graphene surface is cleaned by an annealing process. [Preview Abstract] |
Monday, March 2, 2015 9:24AM - 9:36AM |
A4.00008: Detecting a Protein in its Natural Environment with a MOSFET Transistor Benjamin Perez, Arvind Balijepalli Our group's goal is to make a MOSFET transistor that has a nanopore through it. We want to have proteins flow through this device and examine their structure based on the modulation they cause on the current. This process does not harm the protein and allows the protein to be studied in its natural environment. The electric field and electric potential of a point charge were computed within a nano-transistor. The simulations were used to see if the point charge had enough influence on the current to cause a modulation. The point charge did cause a rise in the current making the modulation concept a viable one for medical applications. COMSOL metaphysics software was used to perform all simulations. [Preview Abstract] |
Monday, March 2, 2015 9:36AM - 9:48AM |
A4.00009: Topological Properties of Some Integrated Circuits for Very Large Scale Integration Chip Designs S. Swanson, M. Lanzerotti, G. Vernizzi, J. Kujawski, A. Weatherwax This talk presents topological properties of integrated circuits for Very Large Scale Integration chip designs. These circuits can be implemented in very large scale integrated circuits, such as those in high performance microprocessors. Prior work considered basic combinational logic functions [1] and produced a mathematical framework based on algebraic topology for integrated circuits composed of logic gates [2]. Prior work also produced an historically-equivalent interpretation of Mr. E. F. Rent's work for today's complex circuitry in modern high performance microprocessors, where a heuristic linear relationship was observed between the number of connections and number of logic gates [2]. This talk will examine topological properties and connectivity of more complex functionally-equivalent integrated circuits. References: [1] E. Hiteshue, K. Irvin, M. Lanzerotti, G. Vernizzi, J. Kujawski, A. Weatherwax, ``Topological Properties of Basic Combinational Logic Functions for Very Large Scale Integrated Circuits,'' in 2014 Proc. APS Mtg., Denver, CO, 2014. [2] G. Vernizzi, M. Y. Lanzerotti, J. Kujawski, A. Weatherwax, ``Topological Constraints for E. F. Rent's Work on Microminiature Packaging and Circuitry,'' IBM Jnl. Res. Dev., vol. 58, no. 2/3, pp. 13:1-17, Mar/May 2014. [Preview Abstract] |
Monday, March 2, 2015 9:48AM - 10:00AM |
A4.00010: Exploration of Whispering Gallery Modes in an Optically Trapped Aerosol Droplet Angela Ludvigsen, Lowell McCann Optical traps use a laser beam to catch and hold small transparent objects. Past observations of optically trapped aqueous aerosol droplets have shown that the droplet moves between two or more stable positions depending upon the power of the trapping laser. It is hypothesized that this movement coincides with a resonance of the light with the droplet called a Whispering Gallery Mode. When the resonance occurs, additional forces act on the droplet. To investigate this behavior, Raman scattered light from the droplet is measured using a spectrometer while simultaneously recording the droplet's position. The Raman spectrum exhibits a series of peaks that appear due to the very spherical shape of the droplet called Cavity Enhanced Raman Spectroscopy. The location and spacing of the peaks are related to the diameter and the optical properties of the droplet. In order to achieve an accurate determination of the radius from this spectrum, the magnitude of the electric and magnetic fields of the light scattered off the droplet are calculated. This allows for a precise measurement of the droplet's radius at the moment that the droplet moves between stable positions. [Preview Abstract] |
Monday, March 2, 2015 10:00AM - 10:12AM |
A4.00011: Measuring the Temperature of the Ithaca College MOT Cloud using a CMOS Camera Jonathan Smucker, Bruce Thompson We present our work on measuring the temperature of Rubidium atoms cooled using a magneto-optical trap (MOT). The MOT uses laser trapping methods and Doppler cooling to trap and cool Rubidium atoms to form a cloud that is visible to a CMOS Camera. The Rubidium atoms are cooled further using optical molasses cooling after they are released from the trap (by removing the magnetic field). In order to measure the temperature of the MOT we take pictures of the cloud using a CMOS camera as it expands and calculate the temperature based on the free expansion of the cloud. Results from the experiment will be presented along with a summary of the method used. [Preview Abstract] |
Monday, March 2, 2015 10:12AM - 10:24AM |
A4.00012: Investigation of Nanowire Thickness and Enhancement Characteristics Cameron Saylor, Desalegn Debu, Eric Novak, Joseph Herzog This work investigates of the effect of nanowire thickness on the optical enhancement of nanowire. We present a study that shows there is potential in altering the thickness of plasmonic structures to improve their optical field enhancement. The study was performed using a finite element method computational electromagnetic analysis, which allows for the thickness and width of the nanowire and wavelength of the incident light to be changed, and the corresponding effects on the optical enhancement characteristics of the structure to be measured. The nanowire was modeled using a two-dimensional cross-section that approximates the nanowire as being infinitely long, with the incident light polarized perpendicular to the length of the nanowire. Preliminary results suggest that lower nanowire thickness provide the highest optical enhancement. The effects of the material and thickness of the adhesion layer on the optical enhancement of the nanowire are also investigated. [Preview Abstract] |
Monday, March 2, 2015 10:24AM - 10:36AM |
A4.00013: Nonlinear Interactions between Slender Structures and Axial Flow Li Du For decades, dynamic behaviors of a slender structure with axial flow have been extensively studied. However, the governing equation based on expansions of small quantities is complicatedly-expressed and can be inappropriate as amplitude becomes considerably large. In this research, we are dedicated to finding an approach to study the nonlinear dynamics of a fluid-conveying slender strcture with arbitrary amplitude. By introducing the \emph{Intrinsic Coordinate}, we find a concise way to describe the configuration of the system. Differential relations of such coordinate are studied and the rigorous nonlinear equation of motion is derived. Then rather than small-deflection approximation, linear dynamics are studied using \emph{Argand Diagram} under a weaker condition named low-varying approximation. Nonlinear properties including Hopf bifurcation, limit-cycle motion and vibration frequencies are studied theoretically and experimentally. [Preview Abstract] |
Monday, March 2, 2015 10:36AM - 10:48AM |
A4.00014: ABSTRACT WITHDRAWN |
Monday, March 2, 2015 10:48AM - 11:00AM |
A4.00015: The Importance of Science Policy and its Challenges Benjamin Preis I worked for physicist and Congressman Bill Foster (D-IL) as the Mather Public Policy Intern through the American Institute of Physics and the Society of Physics Students during the summer of 2014. This internship is meant to connect undergraduate physics students with the policy process in Washington DC. As a Mather Public Policy Intern, I worked for Congressman Foster researching policy initiatives such as science funding, STEM education, and environmental regulations. This talk will discuss my experience and many of the things that I learned as an undergraduate physicist working on Capitol Hill. For example, through my experience with the internship, I attended lectures and hearings that illuminated for me how members of Congress conceive of scientific research. I also met with many physicists on Capitol Hill working to improve government interest in physics research --- AAAS Fellows, Members of Congress, and Government Relations Specialists --- and I will talk about how I saw physicists impacting governmental policies relating to scientific research and development. This internship is part of the Society of Physics Students internship program and was funded by the John and Jane Mather Foundation for Science and the Arts. [Preview Abstract] |
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