Browsing by Subject "electrical"
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Item Analysis of programmable molecular electronic systems(Texas A&M University, 2007-09-17) Ma, YuefeiThe continuing scaling down in size of microelectronics devices has motivated the development of molecular electronic devices, often called moletronics, which use molecules to function as electronic devices. One of the moletronics is the programmable molecular array. In this device, disordered arrays of metallic islands are interlinked by molecules. It is addressed by a small number of input/output leads located on the periphery of the device. In this dissertation, a thorough investigation of the programmable molecular array is performed. First, theoretical calculations for single molecules are carried out. The effect of bias voltage on the electron transmission through the molecule is reported. Next, electrical measurements are conducted on programmable molecular arrays. Negative differential resistance and memory phenomena are found. The electrical characteristics of the programmable molecular array populated with different molecules indicate that the metallic islands contribute to the above phenomena. The electrical conductance through the metallic islands is investigated, and conformational change of the metallic islands under bias is reported. Furthermore, a scenario is proposed to use molecular vibronics and electrostatic potential to transport and process signals inside the programmable molecular array. Simulated results are presented.Item Impact of Climate Change on Long Term Nuclear Power Plant Operation(2010-10-12) Redwine, Adam B.The present work examines the potential impact of changes in climatic conditions on the long-term functioning of nuclear power plants. Nuclear power plants are potentially susceptible to changes both in acute risks, such as severe storm events, and chronic risks, such as detrimental changes in the thermodynamics of plant operation. Extending plant lifetimes well beyond the lengths of operation for which they were originally designed suggests the necessity of studying the impacts such changes might have. Potential threats are examined in light of earlier work performed by Business Continuity Consulting on commission for Enteritgy Nuclear. The fourteen risk drivers identified in that work as threats warranting additional investigation are studied individually, and their relevance and likely impact extrapolated for regions covered by the ten selected sites under examination. Thermodynamic eff ects are simulated with a plant analysis program known as PEPSE (Performance Evaluation of Plant Systems Efficiencies), with which a broad range of modeled environmental and plant conditions are analyzed for potential impacts to plant functioning. Of the fourteen climatic risk drivers considered, changes in drought and ood severity and frequency resulting from climate change were determined to be the most likely detriments to plant operations. Precipitation gures indicate that plants located in the Midwest are particularly susceptible to future drought conditions while those in the Northeast are likely to experience more frequent ooding. Many of the risk drivers specifi ed by the earlier work were only cursorily examined in light of the complex nature of these phenomena and lack of well defi ned correlation to climate change. Other risks were analyzed using the gathered data, but were determined not to pose signi ficant threats to plant operations. In addition to large scale climatic e ffects, changes related to coolant uid temperature rise and plant component efficiency were examined to qualify their e ect on the thermodynamics of the model plant. Plant operating conditions were modeled for a wide range of conditions related to theoretical environmental changes. These examinations showed negligibly small impacts caused by increased coolant water temperature and moderate impact caused by changes in air humidity.Item Visualization of cellular mechanisms regulating differential neuronal synapse formation(Texas A&M University, 2005-11-01) Neunuebel, Joshua PaulOver thirty years ago electrical coupling was observed in embryonic cells prior to chemical communication. This temporal relationship of electrical coupling preceding functional chemical neurotransmission occurs throughout neurogenesis, prompting the idea that gap junctional coupling synchronizes the synaptogenic establishment of functional neural networks. Helisoma neuronal pairs treated with trophic factors exhibit increased electrical coupling and subsequently delay the formation of inhibitory chemical connections. Studies in this thesis addressed the mechanism regulating this inverse relationship between electrotonic and chemical communication. Synaptogenesis between two neurons from the Helisoma buccal ganglia, B110 and B19, were examined using alternative culturing conditions that were either exposed to or deprived of trophic factors. Incubating neuronal pairs in trophic factors induced transient electrical synapses and postponed the formation of chemical connections. In electrically coupled neuronal pairs, presynaptic secretory vesicles were recruited to the sites of presynaptic contact, but did not respond to calcium elevation (i.e., photolytic release of calcium from NP-EGTA) with neurotransmitter release. These and other studies demonstrated that transient electrical coupling does not disrupt calcium handling or postsynaptic responsiveness. Rather, electrotonic coupling delays chemical synaptic transmission by imposing a functional block between the accumulation of presynaptic calcium and the synchronized vesicular release of neurotransmitter.