Bulletin of the American Physical Society
2008 Joint Fall Meeting of the Texas and Four Corners Sections of APS, AAPT, and Zones 13 and 16 of SPS, and the Societies of Hispanic & Black Physicists
Volume 53, Number 11
Friday–Saturday, October 17–18, 2008; El Paso, Texas
Session H3: Medical Physics |
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Chair: Mickey Manciu, The University of Texas at El Paso Room: Union East, 3rd Floor Ray |
Saturday, October 18, 2008 10:30AM - 10:42AM |
H3.00001: Inharmonicity Analysis: A Novel Physical Method for Acoustic Screening of Dysphonia Sam Matteson, Fang-Ling Lu In the United States 6.8{\%} of men, women, and children report current voice problems and approximately 29{\%} will report some problems during their lifetime. Often this dysphonia is due to pathologies of the vocal folds. The authors (a physicist and a speech pathologist) describe an interdisciplinary approach that shows promise of detecting physiological abnormalities of the vocal folds from an analysis of the Fourier spectrum of spoken ``tokens.'' The underlying principle maintains that the normal human vocal fold is a linear oscillator that emits overtones that are very nearly precise integral values of the fundamental. Physiological problems of the vocal folds, however, introduce mechanical non-linearities that manifest themselves as frequency deviations from the ideal harmonic (that is, integral) values. The authors quantify this inharmonicity, describing and illustrating how one can obtain and analyze such data. They outline, as well, a proposed program to assess the clinical sensitivity and significance of the analysis discussed in this work. [Preview Abstract] |
Saturday, October 18, 2008 10:42AM - 10:54AM |
H3.00002: Inhibition of urinary calculi -- a spectroscopic study Felicia Manciu, Jayesh Govani, William Durrer, Layra Reza, Luis Pinales Although a considerable number of investigations have already been undertaken and many causes such as life habits, metabolic disorders, and genetic factors have been noted as sources that accelerate calculi depositions and aggregations, there are still plenty of unanswered questions regarding efficient inhibition and treatment mechanisms. Thus, in an attempt to acquire more insights, we propose here a detailed scientific study of kidney stone formation and growth inhibition based on a traditional medicine approach with \textit{Rotula Aquatica Lour (RAL)} herbal extracts. A simplified single diffusion gel growth technique was used for synthesizing the samples for the present study. The unexpected Zn presence in the sample with \textit{RAL} inhibitor, as revealed by XPS measurements, explains the inhibition process and the dramatic reflectance of the incident light observed in the infrared transmission studies. Raman data demonstrate potential binding of the inhibitor with the oxygen of the kidney stone. Photoluminescence results corroborate to provide additional evidence of Zn-related inhibition. [Preview Abstract] |
Saturday, October 18, 2008 10:54AM - 11:06AM |
H3.00003: MAGIC Gel Dosimetry Rachel Mifflin, Kambiz Shahnazi, Rick Jesseph Proton therapy has proven a very successful tool in treating certain tumors, but a three dimensional view of this fact has not yet been clearly demonstrated. In this experiment we have used MAGIC (Methacrylic and Ascorbic Acid in Gelatin Initiated by Copper) gel to represent brain tissue and gone through normal treatment planning for an Acoustic Neuroma to show the three dimensional dose distributions associated with such a tumor. [Preview Abstract] |
Saturday, October 18, 2008 11:06AM - 11:18AM |
H3.00004: Construction of a cost effective optical tweezers for manipulation of birefringent materials using circularly polarized light Allison McMahon, Toni Sauncy Light manipulation is a very powerful tool in physics, biology, and chemistry. There are several physical principles underlying the apparatus known as the ``optical tweezers,'' the term given to using focused light to manipulate and control small objects. By carefully controlling the orientation and position of a focused laser beam, dielectric particles can be effectively trapped and manipulated. We have designed a cost efficient and effective undergraduate optical tweezers apparatus by using standard ``off the shelf'' components and starting with a standard undergraduate laboratory microscope. Images are recorded using a small CCD camera interfaced to a computer and controlled by LabVIEW$^{TM}$ software. By using wave plates to produce circular polarized light, rotational motion can be induced in small particles of birefringent materials such as calcite and mica. [Preview Abstract] |
Saturday, October 18, 2008 11:18AM - 11:30AM |
H3.00005: Secondary Structure of Nucleic Acids near a Surface Joaquin Ambia-Garrido, B. Montgomery Pettitt While the conformation of Nucleic Acids in the bulk has been widely studied, the influence of a surface on its secondary structure has been limited to some particular cases. Here we present a more general study of the influence of a surface with different conditions into the secondary structure of nucleic acids. The environment is an electrolyte and the salt concentration also plays an important roll. For this porpoise we work in the scope of mean field theory, namely Poisson-Boltzmann. A Monte-Carlo simulation was performed. The DNA strands were modeled by sphere chains. The analytic solution for the interaction energy of spheres is known and simple, which allows us to have multiple strands interacting with the surface and each other. The obtained results are in agreement with all atom simulations previously performed for single molecules and two molecules interacting. The multiple molecules results are unprecedented and give us new insights into these systems. The results are also in agreement with experimental data. The results are particularly interesting regarding the growing new technology of DNA nano-arrays; broadly used in the medial industry. [Preview Abstract] |
Saturday, October 18, 2008 11:30AM - 11:42AM |
H3.00006: Cellular mechanics on the nano-patterned scaffolds Soyeun Park, Justin Mcanally It is expected that modulation in adhesion of cells such as endothelial cells and fibroblasts lead to the changes in cells' viscoelstic properties as well as cell motility through the mechanical signaling mediated by the cellular acto-myosin machinery. The studies on the roles of mechanical parameters, such as stress from spreading restrictions and substrate elasticity, on the mechanical properties have been challenged due to the technical difficulties both in controlling the mechanical properties of the substrate where cells adhere and in precisely determining the mechanical properties. By combining a surface-initiated polymerization and nano-sphere lithography, we successfully grow polymers on a nano-patterned substrate that allows us to direct cellular adhesion sites to controlled nanoareas with defined elastic modulus. In addition, we utilized our AFM-based microrheology that allows us to fully quantify the local viscoelastic moduli by accounting the substrate effect on the thin samples such as adherent cells. Based on the AFM-based microrheology on normal and cancerous fibroblasts, we found that cellular responses such as viscoelastic properties and cell motility are correlated with the cell adhesions. [Preview Abstract] |
Saturday, October 18, 2008 11:42AM - 11:54AM |
H3.00007: Inferring kinetic pathways, rates, and force dependence from nonprocessive optical tweezers experiments: a maximum likelihood approach Bennett Kalafut, Koen Visscher Optical tweezers experiments allow us to probe the role of force and mechanical work in a variety of biochemical processes. However, observable states do not usually correspond in a one-to-one fashion with the internal state of an enzyme or enzyme-substrate complex. Different kinetic pathways yield different distributions for the dwells in the observable states. Furthermore, the dwell-time distribution will be dependent upon force, and upon where in the biochemical pathway force acts. I will present a maximum-likelihood method for identifying rate constants and the locations of force-dependent transitions in transcription initiation by T7 RNA Polymerase. This method is generalizable to systems with more complicated kinetic pathways in which there are two observable states (e.g. bound and unbound) and an irreversible final transition. [Preview Abstract] |
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