Bulletin of the American Physical Society
2013 Annual Fall Meeting of the APS New England Section
Volume 58, Number 11
Friday–Saturday, October 11–12, 2013; Bridgewater, Massachusetts
Session D1: Parallel Session: Biophysics & Fundamental Physics |
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Chair: Jeff Williams, Bridgewater State University Room: Science and Mathematics Auditorium CON120 |
Saturday, October 12, 2013 8:00AM - 8:12AM |
D1.00001: A Protein-Based, Ion-Mediated Retinal Implant for the Treatment of Retinal Degenerative Diseases Jordan Greco, Nicole Wagner, Robert Birge Impaired vision or loss of sight due to retinal degenerative diseases, including age-related macular degeneration and retinitis pigmentosa, affect over 30 million people worldwide. Because there is no cure for these diseases and treatments only slow the progression, there is a significant need for the development of retinal implants that restore meaningful vision. A number of research groups are creating electrode-based implants to stimulate the damaged retina, however, these implants are low resolution and require external hardware. We describe here a flexible, high-resolution implant that is comprised of the light-activated protein, bacteriorhodopsin. Bacteriorhodopsin is a transmembrane proton pump that converts light energy into chemical energy for its native organism. The protein is a favorable candidate as the photoactive medium in an implant due to a high thermal and photochemical stability and a high quantum efficiency. The implant is fashioned by using layer-by-layer electrostatic adsorption, thereby creating a multilayer film that generates a directional ion gradient. The implant is placed in a subretinal orientation and converts incident light energy into a pH gradient used to activate the bipolar and ganglion cell network. Extracellular recording experiments have revealed that the ion-mediated implant is capable of reproducibly stimulating the degenerated retinas of P23H rats and demonstrate that the relative activation efficiency directly correlates with light intensity. [Preview Abstract] |
Saturday, October 12, 2013 8:12AM - 8:24AM |
D1.00002: Effect of Electric Field on Tumor Cells Joseph Shahbazian Applied electric field has profound inhibitory effects on the tumor cells. The applied electric field controls the production, reproduction and proliferation and then help to destruct the tumor cells. Here theoretical and numerical result of investigation of the Low intensity AC applied electric field on tumor cells has been shown. [Preview Abstract] |
Saturday, October 12, 2013 8:24AM - 8:36AM |
D1.00003: Separation of DNA by Length using Counter-Rotating Vortices Jennifer Pearce DNA has been observed to be trapped at a convergent stagnation point in simulations based on the lattice-Boltzmann method using a bead-spring model for the DNA. We have successfully separated DNA strands whose lengths differ by 20{\%}. Currently we are investigating parameters that optimize this technique and hope to separate lengths differing by as little as 5{\%}. Mastering this technique could allow advancements in developing microfluidic techniques for DNA amplification based on PCR and purification of the PCR product. Additionally these simulations mimic conditions found in pores of hydrothermal vents, therefore these studies can shed light on the development of the amplification of long strands of DNA preferentially. [Preview Abstract] |
Saturday, October 12, 2013 8:36AM - 8:48AM |
D1.00004: Optical and Photoacoustic Characterization of BODIPY as Novel Molecular Contrast Agent for In Vivo Tomography. Olivier Dantiste, Samir Laoui, Stephanie Bellinger-Buckley, Jonathan Rochford, Chandra Yelleswarapu Proper imaging of tumors and nodules is of utmost important in cancer diagnostics as it provides information about their location and metabolic activities. In contrast to existing clinical imaging Photoacoustic imaging/tomography (PAI) has been developed in the recent past as a key in vivo imaging technique. PAI is a cost effective techniques offering several distinct advantages such as use of non-ionizing near-infrared radiation as source, providing good contrast of biological structures based on optical absorption and low scattering of ultrasound in biological media. PAI is based on the photoacoustic effect, a process in which the target absorbs incident light and release part of that energy which is eventually converted into sound waves. To image objects of interest such as tumors for cancer detection, the photoacoustic signal needs to be significant compared to that of the surrounding tissue. Hence exogenous contrast agents are administered. We are working on developing molecular photoacoustic contrast agents (MPACs) through chemical modification of efficient and established fluorescent probes. Using a bottom-up approach, non-emissive functionalities are being conjugated to well-known BODIPY fluorescent probe so that the absorbed energy is directed into a nonradiative decay pathway. Our optical and photoacoustic characterization of MPACs indicate increase of the photoacoustic response of MPACs, compared to the corresponding fluorescent probes. [Preview Abstract] |
Saturday, October 12, 2013 8:48AM - 9:00AM |
D1.00005: Directed Evolution of a Photochromic Protein for Long-Term Data Storage Nicole Wagner, Jordan Greco, Robert Birge Bacteriorhodopsin has long been known as a protein with comparative advantages for photonic device applications due to its unique photochemistry, excellent thermal stability, and high quantum efficiency. Our recent work has emphasized the use of the long-lived Q state, which is a stable photoproduct with photochemical properties ideal for optical data storage and processing. The formation of the Q state is minimized in the native organism because it eliminates the biological function of the protein. Thus, mutagenesis is necessary to enhance the ability of bacteriorhodopsin to form this photoproduct. We describe here the use of directed evolution to optimize the photochemical properties of the protein, and implement an automated process to characterize microgram protein quantities. Directed evolution is a process by which proteins are optimized toward a specific characteristic via repeated iterations of genetic mutation, screening and differential selection. The mutants are generated via region specific semi-random mutagenesis and are screened with respect to Q state formation and reversion. Next, the efficient Q state mutants are selected to serve as the parent to the next generation of genetic progeny. This process is iterative and builds upon successive improvements to the protein. After six generations of optimization involving over 10,000 mutants, more than ten new proteins have been discovered with excellent Q formation and reversion efficiency, cyclicities and thermal stabilities. [Preview Abstract] |
Saturday, October 12, 2013 9:00AM - 9:12AM |
D1.00006: Measurements of the properties of the Higgs-like boson in the four lepton decay channel with the ATLAS detector using 25 fb$^{-1}$ of proton-proton collision data Stefano Zambito We present an update of the search results and property measurements of the observed Higgs-like boson in the decay channel $H\to ZZ^{(*)}\to\ell^+\ell^-\ell^{+}\ell^{-}$ where $\ell$, $\ell'$ = $e$ or $\mu$, using proton-proton collision data corresponding to integrated luminosities of 4.6 $fb^{-1}$ and 20.7 $fb^{-1}$ at $\sqrt{s}=7$ TeV and $\sqrt{s}=8$ TeV, respectively, recorded with the ATLAS detector at the LHC. A clear excess of events over the background is observed at $m_H = 124.3$ GeV in the combined analysis of the two datasets with a significance of 6.6 standard deviations, corresponding to a background fluctuation probability of $2.7~\times~10^{-11}$. The mass of the Higgs-like boson is measured to be $124.3^{+0.6}_{-0.5}$(stat)$^{+0.5}_{-0.3}$(syst) GeV, and the signal strength (the ratio of the observed cross section to the expected SM cross section) at this mass is found to be $1.7^{+0.5}_{-0.4}$. A study of Higgs boson production mechanisms allows a first measurement of couplings with this channel. A spin-parity analysis is performed. [Preview Abstract] |
Saturday, October 12, 2013 9:12AM - 9:24AM |
D1.00007: Origins of the Electron's Angular Momentum Ernst Wall The electron may be modeled as a point charge revolving at light speed in a Compton wavelength orbit. This provides the electron's mass energy and the Bohr magneton identically, as well as a plausible origin of its de Broglie waves. At the same time, it may be viewed as if it were a photon trapped in that orbit so that the momentum of this ``photon'' is p $=$ E/c$=$mc [1, 2]. If the mass were concentrated at the point charge, its implicit angular momentum would be L$=$rp$=$ (h\textunderscore bar/mc)*mc $=$h\textunderscore bar, where h\textunderscore bar$=$h/(2pi). However, the revolving particle's electric impulse propagates radially inward across the orbit, so one can simplistically postulate that the mean mass over time is uniformly distributed over its surface with a constant angular momentum that is equivalent to a revolving disk. Using this, the electron's overall angular momentum is L$=$ h\textunderscore bar/2. However, there are spinor (360 degree rotation to change sign) and other issues not discussed here that clearly require further investigation [3].\\[4pt] [1] \textbf{The Physics of Tachyons}, Ernst Wall (Hadronic Press, 230 pp., 1995).\\[0pt] [2] Web page www.tachyonmodel.com.\\[0pt] [3] Walter Niblack's spinor comments are much appreciated. Also: Gerhard Hahn's criticism was helpful. [Preview Abstract] |
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