Bulletin of the American Physical Society
2005 APS March Meeting
Monday–Friday, March 21–25, 2005; Los Angeles, CA
Session A39: SPS: Undergraduate Research I |
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Chair: Jack Hehn, American Institute of Physics Room: LACC 514 |
Monday, March 21, 2005 8:00AM - 8:12AM |
A39.00001: Temperature Control During the Delivery of Laser Assisted Cancer Immunotherapy Robert Arnold, Pradip Bandyopadhyay Laser Assisted Cancer Immunotherapy (LACI) is an innovative experimental technique used for the purpose of malignant tumors. The efficacy of this technique depends upon the occurrence of a vigorous and tumor immune response following the administration of treatment. The general procedure involves the injection of light absorbing dye (indocyanine green) and immunoadjuvant (glycated chitosan) into the tumor volume, followed either interstitial or surface irradiation of the tumor with an 805 nm diode laser. The magnitude of the tumor immune response is correlated to the degree of hyperthermic necrosis that occurs during laser irradiation. an optimal temperature range for necrosis is imperative to the success of the LACI approach. The aim of this study is directed toward exploring the capabilities of a potential temperature control system that utilized during interstitial (or surface) laser irradiation for the purpose of maintaining a temperature range that is for tumor cell destruction. Experimental results for tumor temperature measurement techniques, using (microthermocouples) as well as non-invasive (infrared thermal probes) approaches, will be reported. [Preview Abstract] |
Monday, March 21, 2005 8:12AM - 8:24AM |
A39.00002: Laser Assisted Cancer Immunotherapy: Optical Dye Distribution in Tumors Ryan Swindle, Pradip Bandyopadhyay Laser Assisted Cancer Immunotherapy is an experimental modality used to treat superficial tumors implanted on sterile Balb/C mice. The goal of the project is to induce a positive immune response toward a complete eradication of the primary tumor. Optimal necrosis results from depositing the maximum amount of thermal energy into the tumor without damaging the surrounding healthy tissue. In our laboratory, the optical dye, indocyanine green (ICG), is injected into the center of the tumor prior to surface and interstitial laser irradiation. A diode laser operating at a wavelength near 804 nm exerts thermal energy into the tumor via ICG absorption at 790 nm. Maximum immune response should occur with a uniform distribution of ICG throughout the tumor. By mapping the ICG distribution, the spatial homogeneity of the dye can be determined, which, in turn, mimics the tumor temperature profile. After excision, the tumors were cut into samples of approximately 250 microns thick and dissolved in a chemical detergent. Each sample was run through an absorption spectrometer to determine the distribution of ICG throughout the tumor. Results for both radial and depth profiles of ICG tumor distribution will be presented. [Preview Abstract] |
Monday, March 21, 2005 8:24AM - 8:36AM |
A39.00003: Laser Assisted Cancer Immunotherapy: An Experimental Theraputic Approach in Balb/c Mice John Gray, Pradip Bandyopadhyay Among the different therapeutic approaches to treat superficial malignant tumors, Laser Assisted Cancer Immunotherapy (LACI) shows promise. Experiments are in progress in our laboratory based on the concept of LACI which utilizes a light absorbing dye (Indocyanine Green, ICG), an immunoadjuvant (Glycated Chitosan, GC), and an infrared diode laser (1-15w) operating at 804 nm. Superficial tumors (5 to 7 mm in diameter) of the T4 cell line are grown in an animal model (Balb/C mice). The tumors are injected with ICG and GC prior to interstitial/surface irradiation of the tumor. The tumors' internal temperatures are monitored during the irradiation by invasive (microthermocouples) as well as noninvasive (infrared detector) modes. Along with the various experimental parameters, only the laser delivery (interstitial/surface) and laser intensity are varied in this initial stage so that the tumor temperature is in the range of 55 degrees C to 65 degrees C to ensure hyperthermic cell killing. The goal of the project is to determine the precise temperature range through which primary tumor necrosis and a vigorous immune response will end in tumor elimination. Experimental results coupled with a theoretical framework of laser-tissue interactions will be presented in the context of this therapeutic approach. [Preview Abstract] |
Monday, March 21, 2005 8:36AM - 8:48AM |
A39.00004: The Effect of Heterogeneous Conductivity on Thermal Diffusion in Tissue Gregory Varner, Richard Rolleigh Local application of intense heat is used in a variety of medical therapies. Examples include eye surgery and cancer treatments. In such treatments, it is valuable to be able to predict the temperature distribution in the tissue. Yet, predicting the temperature distribution in the tissue presents a unique challenge because the thermal properties, such as the conductivity, change as tissue damage occurs. This effect dynamically changes an initially homogenous material into the more complex heterogeneous case. A computational method for correcting for the spatial and temporal variations in the thermal conductivity due to damage in the tissue will be presented. The results presented will indicate the significance of the gradient of the conductivity term. This theoretical work is in collaboration with hyperthermic treatment of mammary tumors in mice. [Preview Abstract] |
Monday, March 21, 2005 8:48AM - 9:00AM |
A39.00005: Optical Microfluidic Control using induced Marangoni Effect Kyle Noble, Ken Kotz, Gregory Faris In this attempt to demonstrate a novel method for microfluidic transport, a He-Ne laser was used to create a surface temperature gradient and therefore induce the Marangoni effect. This transport technique was designed to improve current microfluidic or ``Lab on a chip,'' devices, which perform biological and chemical assays on a microscopic level. The apparatus used in this demonstration was a polystyrene dish, on which droplets on the orders of 1.7 $\mu $L- 14 pL, immersed in an organic solvent, were moved at 3 mm/s. To aid in this study, different organic solvents as well as different color dyes were used to increase the force applied to the droplet by the induced thermal gradient and achieve lower surface-droplet interaction. The magnitude of the force applied to the droplet is based on absorption of laser light, while the surface droplet interactions are based on surface tension and adhesion forces. [Preview Abstract] |
Monday, March 21, 2005 9:00AM - 9:12AM |
A39.00006: An Empirical Charge Redistribution Model for Water Potentials in Biophysical Systems Robin Smith, Steve Valone, Susan Atlas Development of empirical atomistic models for simulations of biomolecules and biomaterials requires an understanding of charge transfer processes. Chemical potential equalization provides a conceptual basis for modeling electron redistribution during molecular conformational changes. A new charge-dependent energy formulation developed by Valone and Atlas extends current models based on CPE by permitting an accurate description of dynamic charge fluctuation during dissociation and charge transfer processes. We explore this formulation by constructing a conceptual submodel specific to the water molecule, important for understanding biophysical interactions in an aqueous environment. [Preview Abstract] |
Monday, March 21, 2005 9:12AM - 9:48AM |
A39.00007: On the Landing of Rigid Cylinders Invited Speaker: Matthew Shanks When a cylinder is dropped, what are the factors that determine whether it lands upright or on its side? Sir Hermann Bondi (see European Journal of Physics 14, pp. 136-140) asked this question in 1993 with the intention of determining the theoretical probability of a coin landing on its edge. The Society of Physics Students (SPS) has embarked on an experiment to test some of his ideas using data taken from many places around the country via the SPS Outreach Catalyst Kits (SOCKS). Sets of matched cylinders were sent to SPS chapters to use in dropping experiments with school children as a way of teaching about science while performing science. One goal of the experiments is to determine the relative importance of center of mass location and aspect ratio. One surprising result is the extent to which observers over-predict the occurrence of upright landings for cylinders with a square profile. \newline \newline In collaboration with Gary White, Society of Physics Students [Preview Abstract] |
Monday, March 21, 2005 9:48AM - 10:00AM |
A39.00008: Measuring the High Frequency Response of Individual Carbon Nanotubes Anthony Annunziata, Beth Parks, Sami Rosenblatt, Paul McEuen Carbon nanotubes are nanometer diameter hollow tubes of carbon that are ideal one-dimensional conductors. They are being developed as elements in molecular electronics. Extensive studies up to this time have focused on DC properties of nanotubes. I report progress toward measurements of the dynamic conductance of individual carbon nanotubes at GHz to THz frequencies using terahertz time-domain spectroscopy. In this method, individual single-wall carbon nanotubes are incorporated into microfabricated antennas and used as receivers of broadband THz radiation. A variable time delay between two incident pulses is used to gain information about the frequency dependence of the antenna response. If the nanotube has the predicted length-dependent resonance [Burke, P. J., IEEE Transactions on Nanotechnology V. 1, p. 129 (2002)], then this should be clear in the antenna response. Knowledge of the spectral response of carbon nanotubes is important for applications in electronic interconnects as well as a confirmation of certain aspects of Luttinger liquid theory. [Preview Abstract] |
Monday, March 21, 2005 10:00AM - 10:12AM |
A39.00009: Development of a nanolithography package for local AFM oxidation Andrew T. McNamara, Hong Chen, J.J. Heremans, V. Soghomonian We describe the process of nanolithography by local oxidation using an atomic force microscope tip, on GaAs and on InAs/AlGaSb heterostructures. The commercial microscope's tip is controlled by a home-written software package, that includes a variety of graphics primitives of use in nano-electronic geometries, allowing the user to design appropriate patterns, and control lithographic parameters. The microscope's contact tip is held grounded while the sample is held at a positive voltage, causing a local current and oxidation of the sample under the tip. The oxidized region on the semiconductor is nonconducting, or can be etched away, to form the required device structure. We characterize the process and obtainable line widths on substrate material and heterostructures, and explore the suitability of our method to create transport based nanoscale devices (partially supported by NSF REU and NSF DMR-0103034). [Preview Abstract] |
Monday, March 21, 2005 10:12AM - 10:24AM |
A39.00010: Transport Measurements of Superconducting Zinc Nanowires at Low-Temperatures Brian Hult, John Free, William Neils, Michael Tinkham New transport data on superconducting Zinc nanowires at temperatures between 1.2K and 300mK will be presented. The superconducting Zinc nanowires are fabricated using E-beam lithography on a Si/SiO2 substrate on which Zinc is deposited via thermal evaporation. The resistance and I-V are then measured as a function of temperature. The wires range in width from 40nm to 100nm and have varying thicknesses. These data are compared to thermally activated phase slip models. This research is collaboration of Eastern Nazarene College with Harvard University. Funded by: NSF DMR-02444441 [Preview Abstract] |
Monday, March 21, 2005 10:24AM - 10:36AM |
A39.00011: Time-Resolved Photoluminesence of Undoped and Bismuth Doped CdWO$_{4}$ J.A. Kotonias, H.M. Yochum Cadmium tungstate (CdWO$_{4})$ is a scintillating crystal used for detecting x-rays, particularly for use in medical applications. In an effort to characterize the photoluminescence properties and to investigate multi-photon absorption in both bismuth doped and undoped samples, we measured the photoluminescence spectra (400 nm -- 800 nm) and their time kinetics using the harmonics of a Q-switched Nd:YAG laser (355 nm and 266 nm). In both doped and undoped samples, excitation with above band gap light at 266 nm causes emission peaked at 500 nm with a single exponential lifetime of $\sim $10 microseconds. Excitation at 355 nm, which excites Bi ions in the doped sample, results in emission peaked at 570 nm with a lifetime of $\sim $1 microsecond. In the undoped sample this below band gap excitation at 355 nm causes emission which peaks at $\sim $500 nm and has a decay time similar to that caused by 266 nm excitation. [Preview Abstract] |
Monday, March 21, 2005 10:36AM - 10:48AM |
A39.00012: Lipid Films, Magnetic Lipid Films, and Their Mechanical Properties Alok Sahgal, Kezheng Chen, Wilfred Ngwa, Weili Luo Three techniques were used to produce thin lipid films and magnetic-nanoparticle-embedded lipid films on flat substrates: spin-coating, capillary, and natural-dry methods. The morphology and the homogeneity of these films were analyzed by Atomic Force Microscopy. The local mechanical properties of these films were studied and will be discussed. [Preview Abstract] |
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