Bulletin of the American Physical Society
2005 58th Gaseous Electronics Conference
Sunday–Thursday, October 16–20, 2005; San Jose, California
Session RW2: Biological Applications of Plasmas |
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Chair: Uwe Kortshagen, University of Minnesota Room: Doubletree Hotel Cedar |
Wednesday, October 19, 2005 1:30PM - 2:00PM |
RW2.00001: Biological Application of Plasma: Sterilization, Surface Treatment, and Tissue Engineering Invited Speaker: The presentation reviews modern achievements in using non- thermal plasma for different applications in biology and medicine. Specific features of non-equilibrium atmospheric pressure discharges attractive for biological and medical applications are to be discussed. Primary attention will be focused on such discharges as: dielectric-barrier discharge (DBD) in homogeneous and streamer modes; RF atmospheric pressure glow discharges (RF APG); corona and pulsed corona discharges; gliding arc discharges. Especially novel discharges in liquids efficient for bio-medical applications are to be discussed. Specific non-thermal plasma applications in biology and medicine will be subdivided into three major groups: different kind of sterilization processes; surface treatment and tissue engineering processes; direct cold plasma applications in medicine. Sterilization processes are to be considered separately for treatment of different surfaces, treatment of air, and treatment of water (and other liquids). Specifics related to bacteria, viruses, spores will be addressed. Disinfection is to be compared with low-temperature burning out and complete disintegration. Major sterilization mechanism related to atoms and radicals (OH et al.), ozone, UV, charged particles, excited molecules (singlet oxygen et al.), micro-shocks are to be discussed. Kinetic modeling of plasma sterilization processes will be demonstrated. Surface treatment and tissue engineering applications will be discussed using as an example DBD bio-printer experiments. Direct plasma-medical applications are to be considered using as examples: non-thermal plasma cauterization and blood coagulation; non-thermal plasma treatment of wounds; and non- thermal plasma treatment of skin deceases. Mechanisms of the non-thermal plasma effects in medicine will be discussed; detailed kinetic modeling of the plasma-medical processes is to be compared with experiments. [Preview Abstract] |
Wednesday, October 19, 2005 2:00PM - 2:30PM |
RW2.00002: Electron attachment to molecules of biological relevance Invited Speaker: Free electron attachment to biomolecules in the electron energy range from about 0 -- 15 eV has been studied. The experiments have been carried out using a homebuilt crossed electron/neutral beams apparatus in combination with a quadrupole mass spectrometer described in detail in [1]. The electrons are monochromatized in a high resolution hemispherical electron monochromator with an energy resolution of about 110 meV in the present experiments. The biomolecules under study include thymine, alanine, glycolaldehydes, thymidine, uridine and uracil. In this presentation we want to focus on one particular experiment, where bond-selective H- ion abstraction by electron attachment to thymine has been studied [2]. This study has been performed using partially deuterated thymine to enable the measurement of electron attachment to certain bonds in the molecule. The results are particularly interesting as certain sites of the isolated molecules are not available (or even not present) when they are incorporated in the DNA structure. Therefore the present results can be used to evaluate the previously reported DEA to isolated undeuterated bases concerning their importance for real DNA environments. In particular the radiation damage due to (dissociative) anionic resonance states are assumed to be critical intermediates leading to DNA strand breaks. To support the experimental results we have also performed quantum chemical studies using the G2(MP2) method. In collaboration with Stephan Denifl, Sylwia Plasinska, Michael Probst, Paul Scheier, and Tilmann Maerk, Institut f\"{u}r Ionenphysik, Leopold-Franzens-Universit\"{a}t Innsbruck. \newline \newline Financial support from the FWF, \"{O}AW, and \"{O}NB (Vienna) and the EU Commission (Brussels) through the EPIC Network is gratefully acknowledged. \newline [1] D.Muigg, G. Denifl, A. Stamatovic, T.D.M\"{a}rk, Chem. Phys. 239 (1998) 409 \newline [2] S. Ptasinska, S. Denifl, V. Grill, T.D. M\"{a}rk, P. Scheier, S. Gohlke, M.A. Huels and E. Illenberger, Bond-Selective H$^{-}$ Ion Abstraction from Thymine. \textit{Angew. Chem. Int. Ed.} \textbf{44} (2005) 1647--1650 [Preview Abstract] |
Wednesday, October 19, 2005 2:30PM - 2:45PM |
RW2.00003: Spatial and Temporal Behavior of Repetitive Plasma Discharges in Saline Solutions Kenneth Stalder, Gagik Nersisyan, William Graham Plasmas formed around multielectrode devices submerged in saline solution were investigated using fast, intensified charge-coupled detector imaging techniques. The images show that synchronous, bipolar, moderate-voltage ($<$300 volts rms) square-wave pulses at 100-kHz frequency applied to the electrodes cause intense and transient plasma regions to form randomly in both space and time on short (10 microsecond) time scales, even though they appear to be more stationary and constant on longer (seconds) time scales. Images from progressively longer exposures show that there is an increasing probability that the electrodes closest to the common ground electrode will develop discharges sometime during this period, but there is also a large variation in the intensity of the discharges surrounding each electrode. These observations support the notion that the dynamic and varying behavior of the thin vapor layer developed around the electrodes influences the nature of the microdischarges.\footnote{K. R. Stalder, D. F. McMillen and J. Woloszko, J. Phys. D: Appl. Phys. \textbf{38} 1728-1738 (2005).} [Preview Abstract] |
Wednesday, October 19, 2005 2:45PM - 3:00PM |
RW2.00004: Electron-impact total ionization cross sections of DNA sugar-phosphate backbone and an additivity principle Winifred Huo, Christopher Dateo The improved binary-encounter dipole (iBED) model [W.M. Huo, Phys. Rev. A64, 042719-1 (2001)] is used to study the total ionization cross sections of the DNA sugar-phosphate backbone by electron impact. Calculations using neutral fragments found that the total ionization cross sections of C3$'$- and C5$'$-deoxyribose- phospate, two conformers of the sugar-phosphate backbone, are close to each other. Furthermore, the sum of the ionization cross sections of the separate deoxyribose and phosphate fragments is in close agreement with the C3$'$- and C5$'$- deoxyribose-phospate cross sections, differing by less than 10\%. The result implies that certain properties of the DNA, like the total singly ionization cross section, are localized properties and a building-up or additivity principle may apply. This allows us to obtain accurate properties of larger molecular systems built up from the results of smaller subsystem fragments. Calculations are underway using a negatively charged sugar- phosphate backbone with a metal counter-ion. [Preview Abstract] |
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