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caltechETD 檢索結果共 5156 筆,本頁資料從第 133 筆到第 144 筆

Oxidation is one of the most fundamental and important processes in nature. It would be advantageous to chemically replicate the high substrate specificity and selectivity observed in oxidative enzymes. Several such synthetic processes have been developed that involve the transfer of a heteroatom to a substrate in an asymmetric fashion. Enantioselective oxidative dehydr....

By Raissa M. Trend--California Institute of Technology--2006-02-28
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The work presented in this thesis utilizes the combination of near-IR photometry and spectroscopic redshifts to estimate the stellar masses of distant field galaxies in order to characterize their assembly history since z~1. The primary data set for this analysis comes from an extensive near-IR survey conducted at Palomar Observatory that includes over 12,000 galaxies d....

By Kevin Bundy--California Institute of Technology--2006-02-28
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The von Economo neurons are one of the few known specializations to hominoid cortical microcircuitry. The recent emergence of this cell type, as well as its localization to subregions of the frontal cortex, suggest its involvement in sophisticated cognitive behaviors. Studies of this cell may thus provide insights into human uniqueness and origin and may additionally be....

By Karli Kiiko Watson--California Institute of Technology--2006-02-27
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Selective visual attention provides an effective mechanism to serialize perception of complex scenes in both biological and machine vision systems. In extension of previous models of saliency-based visual attention by Koch & Ullman (Human Neurobiology, 4:219-227, 1985) and Itti et al. (IEEE PAMI, 20(11):1254-1259, 1998), we have developed a new model of bottom-up salien....

By Dirk Walther--California Institute of Technology--2006-02-23
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Biological signaling pathways employ a vast array of integral membrane proteins that process and interpret the chemical, electrical, and mechanical signals that are delivered to cells. Among these proteins, ligand gated ion channels (LGIC) are therapeutic targets for Alzheimerâs disease, Schizophrenia, drug addiction, and learning and memory. High-resolution structural....

By Amanda Leigh Cashin--California Institute of Technology--2006-02-23
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Self-motion estimation is a vital problem for autonomous robots, frequently and appropriately addressed by vision algorithms. Most approaches involve repeating some local calculation over the entire imaging array, such as detection of locally salient features. A simple and local calculation can be efficiently implemented on the same chip as the photo-sensing array, thus....

By Ania Karolina Mitros--California Institute of Technology--2006-02-15
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Chapter one describes studies of the voltage-dependent hydration and conduction properties of the hydrophobic pore of the mechanosensitive channel of small conductance, MscS. A detailed picture of water and ion properties in small pores is important for understanding the behavior of biological ion channels. Several recent modeling studies have shown that small, hydropho....

By Steven Adrian Spronk--California Institute of Technology--2006-02-13
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A complete understanding of the deformation mechanisms of BMGs and their composites requires investigation of the microstructural changes and their interplay with the mechanical behavior. In this dissertation, the deformation mechanisms of a series of Vitreloy glasses and their composites are experimentally investigated over a wide range of strain rates and temperatures....

By Min Tao--California Institute of Technology--2006-02-13
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The problem of proximal bodies in hypersonic flow is encountered in several important situations, both natural and man-made. The present work seeks to investigate one aspect of this problem by exploring the forces experienced by a secondary body when some part of it is within the shocked region created by a primary body travelling at hypersonic speeds. An analytical met....

By Stuart Jon Laurence--California Institute of Technology--2006-02-04
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Ingestion of arsenic (As) in drinking water can lead to several chronic illnesses, including bladder, lung, and skin cancers. Due to natural weathering reactions, As is present in many drinking water sources throughout the United States and other countries. The U.S. drinking water standard has recently been revised from 50 micrograms L-1 to 10 micrograms L-1, thus requi....

By Megan Alameda Ferguson--California Institute of Technology--2006-01-31
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Due to thermal fluctuations, systems at small length scales are remarkably different than their large length scale counterparts. For example, bacterial viruses (phages) have thousands of nanometers of DNA packed inside a hollow capsid of tens of nanometers. This tight compaction leads to large forces on the phage DNA (tens of piconewtons). These forces can be subsequent....

By Mandar Mukund Inamdar--California Institute of Technology--2006-01-23
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High pressure experimental methods are demonstrated for studying pressure-dependent material properties and solid phases unattainable at ambient pressure with synchrotron nuclear resonance techniques. The phonon density of states (DOS) of nanocrystalline 57Fe was measured under pressures up to 28 gigapascals (2.8 x 10^5 atm) using the nuclear resonant inelastic x-ray sc....

By Alexander B. Papandrew--California Institute of Technology--2006-01-23
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