Bulletin of the American Physical Society
Joint Spring 2013 Meeting of the Texas Sections of the APS and AAPT and Zone 13 of the SPS
Volume 58, Number 3
Thursday–Saturday, April 4–6, 2013; Stephenville, Texas
Session D3: General Physics |
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Chair: Carlos Handy, Texas Southern University Room: Science Building 112 |
Friday, April 5, 2013 2:00PM - 2:12PM |
D3.00001: Electron Nuclear Dynamics Simulations of Proton Collisions with Water in Proton Cancer Therapy Jieun Yoo, Austin Privett, Christopher Stopera, Jorge Morales Proton cancer therapy (PCT) uses high-energy proton projectiles to kill cancerous cells. With water composing $\sim$ 70 $\%$ of the human body, the main destructive effects of PCT processes include the radiolysis of water due to proton collisions. Water radiolysis products include radicals and ions formed by fragmentations and ionizations, which can cause damage to the DNA of cells. We conducted electron nuclear dynamics (END) simulations of proton collisions with water clusters (H$_2$O)$_n$ n=1-5, at 100 keV. These clusters represent a progressive approximation to actual bulk water. END is a time-dependent, variational, direct, and non-adiabatic method that simultaneously models the dynamics of electrons and nuclei in a molecular system. In its current implementation, END uses a classical description for the nuclear degrees of freedom and a single determinant quantum mechanical description for the electronic degrees of freedom. We conducted END simulations revealing mechanistic details and calculated cluster-to-proton electron-transfer integral cross sections (ICSs). Comparison of those ICSs with experimental results involving single water molecules shows good agreement. [Preview Abstract] |
Friday, April 5, 2013 2:12PM - 2:24PM |
D3.00002: Quantitative Phase Microscopy of Cellular Fluctuations Modulated by Optogenetic Stimulation Bishorup Banjara, Nelson Cardenas, Samarendra Mohanty Significant progress has been made in the application of optogenetic stimulation as a means to modulate and control cellular functions within chemically-identical groups of cells. High resolution imaging can detect subtle morphological (shape/refractive index) changes in cells subsequent to optogenetic stimulation. Invasive topographical measurement methods such as mainstream AFM and other scanning probe techniques suffer from low temporal resolution and restricted field of view, resulting in reduced throughput. QPM, integrated with optogenetic stimulation incorporates a wide-field, label-free, non-invasive optical imaging technique for all optical stimulation and detection with high spatial and temporal resolution. We dynamically monitored phase of cells, sensitized with and without ChR2, using quantitative phase microscopy with and without light stimulation. The variation of phase in optogenetically stimulated cells (expressing ChR2) was found to be higher than that of the control cells. We report that our method could potentially evaluate effectiveness of various opsins and stimulation parameters including cellular function under different physiological surroundings via spatially-modulated optogenetic stimulation and wide-field quantitative phase imaging. [Preview Abstract] |
Friday, April 5, 2013 2:24PM - 2:36PM |
D3.00003: Polynomial preconditioned GMRES-DR Quan Liu GMRES-DR (Gneralized Minimal Residual algorithm with Deflated Restarting), developed by Dr. Ronald Morgan in 2002, is a well known algorithm in QCD matrix calculation. We did a modified vertion of regular GMRES-DR by combing it with the polynomial conditioning method, which can help improve the eigenvalue spectrum of the lattice QCD matrix, especially for ill-conditioned matrix with small eigenvalues. [Preview Abstract] |
Friday, April 5, 2013 2:36PM - 2:48PM |
D3.00004: Recognizing the Unobservable Properties of the Physical Universe Lionel Hewett Observational science defines the physical universe as consisting of that and only that which can be verified or disproven through experimental observations. Everything else is considered to be metaphysical and subject to a philosophical debate regarding reality. However, as the resolution of a physical observation is probed toward its limit, one finds that the observable properties of the universe must be expressed in terms of unobservable properties. The failure to distinguish between the observable and unobservable properties of the universe results in much of the confusion regarding the various interpretations of quantum mechanics and general relativity. Recognizing this distinction renders an explanation of such phenomena as quantum gravity, entangled states, double-slit experiment, Schrodinger's cat, and the collapse of the wave function of the entire universe. [Preview Abstract] |
Friday, April 5, 2013 2:48PM - 3:00PM |
D3.00005: A Classical Model of Helium James Espinosa, James Woodyard We present a preliminary model of the Helium atom that stays within the Newtonian framework. The three body Coulomb problem is greatly simplified by taking into account the delayed action at a distance character of the electromagnetic force. This time delay is amply represented by our modified Ritzian force law between two charged particles. In addition, we will use chemical and scattering data to arrive at a pictorial model of the atom. From this mechanical picture we will derive its stability, the magnetic properties, ground state energy, and spectra of Helium. We will conclude with a series of models that will be used for the rest of the noble gases. [Preview Abstract] |
Friday, April 5, 2013 3:00PM - 3:12PM |
D3.00006: Electronic structure and charge transfer states of a multichromophoric heptad antenna Luis Basurto, Tunna Baruah, Rajendra Zope A multichromophoric Heptad molecule containing Zn-tetraphenyl porphyrin, BDPY dye, bisphenyl anthracene, and C60 attached to a hexaphenyl -benzene core was synthesized by Gust et al. (J. Phys. Chem. B, 113, 7147 (2009)). The snowflake like molecule behaves like an antenna capturing photons at different wavelengths and transferring the energy to the porphyrin. We present a DFT based study on the ground state of the complex and also on the lowest two charge transfer (CT) states of the complex carried out using a perturbative delta-SCF method. The calculations, done using a mixed all-electron and pseudo-potential approach, show that the ionization potential of the porphyrin and the electron affinity of the C60 in the complex changes significantly from isolated molecules. Our calculated value of the lowest CT state is within 0.2 eV of the experimental estimate. This CT state contains a hole on the porphyrin HOMO and a particle on the C60 LUMO. A comparison of the energetics with experiment indicates that the process probably involves excitation from the HOMO-1 of porphyrin to the porphyrin LUMO followed by electron transfer and hole bubbling up, resulting in a CT state with the hole on the porphyrin HOMO and particle on the C60 LUMO. [Preview Abstract] |
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