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Articles 1 - 30 of 40
Full-Text Articles in Physical Sciences and Mathematics
Strategies To Resolve The Three-Dimensional Structure Of The Genome Of Small Single-Stranded Icosahedral Viruses, Eduardo Sanz Garcia
Strategies To Resolve The Three-Dimensional Structure Of The Genome Of Small Single-Stranded Icosahedral Viruses, Eduardo Sanz Garcia
Theses and Dissertations
The aim of this study is the three-dimensional structural characterization of the genome packaging inside viral capsids via cryo-electron microscopy and three-dimensional reconstruction. The genome of some single-stranded viruses can be densely packaged within their capsid shells. Several stretches of the genome are known to adopt stable secondary structures, however, to date, little is known about the three-dimensional organization of the genome inside their capsid shells. Two techniques have been developed to facilitate the structural elucidation of genome packaging: the asymmetric random-model method, and the symmetry-mismatch, random model method. Both techniques were successfully tested with model and experimental data. The …
Chemical Vapor Deposition Of Silanes And Patterning On Silicon, Feng Zhang
Chemical Vapor Deposition Of Silanes And Patterning On Silicon, Feng Zhang
Theses and Dissertations
Self assembled monolayers (SAMs) are widely used for surface modification. Alkylsilane monolayers are one of the most widely deposited and studied SAMs. My work focuses on the preparation, patterning, and application of alkysilane monolayers. 3-aminopropyltriethoxysilane (APTES) is one of the most popular silanes used to make active surfaces for surface modification. To possibly improve the surface physical properties and increase options for processing this material, I prepared and studied a series of amino silane surfaces on silicon/silicon dioxide from APTES and two other related silanes by chemical vapor deposition (CVD). I also explored CVD of 3-mercaptopropyltrimethoxysilane on silicon and quartz. …
High Flow Air Sampling For Field Detection Using Gas Chromatography-Mass Spectrometry, Jacolin Ann Murray
High Flow Air Sampling For Field Detection Using Gas Chromatography-Mass Spectrometry, Jacolin Ann Murray
Theses and Dissertations
The ability to rapidly detect and identify hazardous analytes in the field has become increasingly important. One of the most important analytical detection methods in the field is gas chromatography-mass spectrometry (GC-MS). In this work, a hand-portable GC-MS system is described that contains a miniature toroidal ion trap mass analyzer and a low thermal mass GC. The system is self-contained within the dimensions of 47 x 36 x 18 cm and weighs less than 13 kg. Because the instrument has a small footprint, it was used as the detector for an automated near-real-time permeation testing system. In permeation testing, materials …
Work Towards The Isolation And Characterization Of The Muscle Isoform Of Glucose 1,6-Bisphosphatase, Caleb J. Hiller
Work Towards The Isolation And Characterization Of The Muscle Isoform Of Glucose 1,6-Bisphosphatase, Caleb J. Hiller
Theses and Dissertations
Glucose 1,6-bisphosphate is an important small molecule involved in the regulation of glycolysis. Four enzymes synthesize this compound. One enzyme is known to degrade it, glucose 1,6-bisphosphatase. Other groups have produced work that indicates that there are two isoforms of this enzyme, one predominant in the brain and one in the muscle. This thesis contains the work performed in attempts to isolate and characterize the muscle isoform of glucose 1,6-bisphosphatase. While this enzyme was not isolated, much was learned about it and the results from this work may help in the future identification of this enzyme.
Halo Ion Trap Mass Spectrometry: Design, Instrumentation, And Performance, Miao Wang
Halo Ion Trap Mass Spectrometry: Design, Instrumentation, And Performance, Miao Wang
Theses and Dissertations
New ion trap mass spectrometry (ITMS) instrumentation, the toroidal IT and halo IT, were developed to meet the significant growth in on-site analysis applications. The miniature toroidal IT mass analyzer was operated with radio frequency (RF) trapping voltages of 3 kVp-p or less. Despite its reduced dimensions, it has roughly the same ion trapping capacity as conventional 3D quadrupole ITs. Unit-mass resolved spectra for n-butylbenzene, xenon, and naphthalene were obtained. The desired linear mass scale was obtained using conventional mass-selective instability scan combined with resonance ejection. The halo IT was also based on toroidal trapping geometry and microfabrication technology, consisting …
Functionalization Of Diamond And Its Application In High Performance Liquid Chromatography And Solid Phase Extraction, Gaurav Saini
Functionalization Of Diamond And Its Application In High Performance Liquid Chromatography And Solid Phase Extraction, Gaurav Saini
Theses and Dissertations
The primary focus of my work was to chemically functionalize diamond as normal and reversed phases for solid phase extraction (SPE) and high performance liquid chromatography (HPLC). Diamond was functionalized with -NH2 groups via self-limiting adsorption of an amine-containing polymer, polyallylamine (PAAm), onto oxidized diamond particles. The chemical stability of these particles was improved by thermal curing or chemical crosslinking with 1,2,5,6-diepoxycyclooctane. The reversed phase material for SPE was synthesized by reacting amine-functionalized diamond particles with long chain alkyl and a perfluorinated isocyanate. Unlike commercially available silica, functionalized diamond particles were stable under extreme pH conditions (pH 0-14). Functionalized diamond …
Electronic Structure Based Classification Of Neurotransmitters And Related Drugs, Amrita Jha
Electronic Structure Based Classification Of Neurotransmitters And Related Drugs, Amrita Jha
Theses and Dissertations
A fundamental understanding of the relationship between structure and activity of neurotransmitters in the human brain is of vital importance for the design targeted drugs. Using density functional theory and hybrid exchange correlation energy functionals we have studied the structure-activity-relationships of some important neurotransmitters and selected drugs by calculating their absolute hardness (η) and absolute electronegativity (χ). A plot of the η- χ diagram allowed us to assign them into three distinct groups, namely, (i) Acetylcholine analogs (positively charged structure), (ii) GABA analogs (zwitterionic structures) and (iii) monoamines. The results suggest that brain stem is chemically soft because of distribution …
Polymeric Monolithic Stationary Phases For Capillary Hydrophobic Interaction Chromatography, Yuanyuan Li
Polymeric Monolithic Stationary Phases For Capillary Hydrophobic Interaction Chromatography, Yuanyuan Li
Theses and Dissertations
Rigid poly[hydroxyethyl acrylate-co-poly(ethylene glycol) diacrylate] (Poly(HEA-co-PEGDA) monoliths were synthesized inside 75-µm i.d. capillaries by one-step UV-initiated copolymerization using methanol and ethyl ether as porogens. The optimized monolithic column was evaluated for hydrophobic interaction chromatography (HIC) of standard proteins. Six proteins were separated within 20 min with high resolution using a 20 min elution gradient, resulting in a peak capacity of 54. The performance of this monolithic column for HIC was comparable or superior to the performance of columns packed with small particles. Monoliths synthesized solely from PEGDA were also found to show excellent performance in HIC …
Axial Temperature Gradients In Gas Chromatography, Jesse Alberto Contreras
Axial Temperature Gradients In Gas Chromatography, Jesse Alberto Contreras
Theses and Dissertations
The easiest and most effective way to influence the separation process in gas chromatography (GC) is achieved by controlling the temperature of the chromatographic column. In conventional GC, the temperature along the length of the column is constant at any given time, T(t). In my research, I investigated the effects of temperature gradients on GC separations as a function of time and position, T(t,x), along the column. This separation mode is called thermal gradient GC (TGGC). The research reported in this dissertation highlights the fundamental principles of axial temperature gradients and the separation potential of the TGGC technique. These goals …
Integrated Affinity Column Capillary Electrophoresis Microdevices For Biomarker Analysis, Weichun Yang
Integrated Affinity Column Capillary Electrophoresis Microdevices For Biomarker Analysis, Weichun Yang
Theses and Dissertations
In this dissertation, microfluidic systems that integrate antibody-based sample preparation methods with electrophoretic separation are developed to analyze multiple biomarkers in a point-of-care setting. To form an affinity column, both monolith materials and wall-coated channels were explored. I successfully demonstrated that monolith columns can be prepared in microfluidic devices via photopolymerization. The selectivity of monolith columns was improved by immobilizing antibodies on the surface. These affinity columns can selectively enrich target analytes and reduce the signal of contaminant proteins up to 25,000 fold after immunoaffinity extraction. These results clearly demonstrate that microchip affinity monoliths can selectively concentrate and purify target …
Synthesis And Characterization Of An Oligothiophene-Ruthenium Complex And Synthesis And Optical Properties Of Oligothiophene-Ruthenium Complexes Bound To Cdse Nanoparticles, Nathan A. Bair
Theses and Dissertations
Oligothiophenes are of increasing interest in organic based electronic devices in part due to their high electron and hole mobilities. In an organic photovoltaic (OPV) device, the electronic properties of oligothiophenes make them advantageous as charge transfer junctions. To serve as charge transfer junctions, oligothiophenes must be functionalized to bind to the donor and acceptor parts of the device. The donor and acceptor parts are different materials and the synthesis of asymmetric oligothiophenes is of great interest. Previous researchers in our lab synthesized four asymmetric oligothiophenes, two with two thiophene subunits and two with four. Each set of oligothiophenes contained …
Ribosomal Synthesis Of N-Methylated Peptides, Sara Ahadi
Ribosomal Synthesis Of N-Methylated Peptides, Sara Ahadi
Theses and Dissertations
Natural peptide products isolated from various organisms often contain N-methylated backbones. Such a modification of backbone of the peptide changes its conformational rigidity. This modification improves the biological properties of the peptide, such as improved target affinity, proteolytic stability or membrane permeability. Therefore synthesis of N-methylated peptide libraries is valuable in screening for drug-like peptides suitable for therapeutic uses. Protein synthesis using recombinant elements (PURE) and Flexizyme were used in order to reassign specific codons to N-methyl amino acids. mRNA-dependent translation system enable us to make our desired peptides with N-methyl amino acids. This technology is a convenient tool for …
Adsorption Studies By Pulsed Streaming Potentials In Microfluidic Channels, Thutrang Nguyen
Adsorption Studies By Pulsed Streaming Potentials In Microfluidic Channels, Thutrang Nguyen
Theses and Dissertations
In this work, an instrument for measuring pulsed streaming potentials was constructed and optimized for analytical and teaching applications. This thesis is divided in three chapters, the first one deals with the construction of the instrument, the second describes a microfluidic experiment designed for undergraduate and high school students using this instrument, and the third one shows an application of pulsed streaming potential measurements in the detection of heparin. Streaming potential is the electric field generated when a liquid is forced to flow by a pressure gradient through a channel or other stationary charged surfaces.1,2 These measurements were done in …
Synthesis, Functionalization And Characterization Of Dual Mode Nanoparticles For Biomedical Applications, Farah Radwan
Synthesis, Functionalization And Characterization Of Dual Mode Nanoparticles For Biomedical Applications, Farah Radwan
Theses and Dissertations
Three different approaches were used to prepare dual mode nanoparticles using a previously described reverse micelle technique. Superparamagnetic Fe@FeOx core shell nanoparticles were chosen to be the magnetic component for all three dual mode systems. In the first type of particles, 2- amino-1,3- propane diol (APD) was used as a functionalization ligand to stabilize the surface of the particles and its functional amino group also provided a binding site for the attachment of a fluorescent probe. The TEM analysis showed that the APD coated particles have a size range of 8-13 nm while XPS and MALDI measurements confirmed the presence …
Core-Shell Nanoparticles: Synthesis, Design, And Characterization, Kyler Carroll
Core-Shell Nanoparticles: Synthesis, Design, And Characterization, Kyler Carroll
Theses and Dissertations
The design of core/shell nanoparticles is of great interest for a wide range of applications. The primary focus of this dissertation is on the design and optimization of two synthetic routes. The first one is an aqueous reduction method using sodium borohydride and sodium citrate. This method was extended to design two types of core/shell nanoparticles, both of which have many applications in bio-sensing, magnetic resonance imaging, and magnetically guided SERS for the identification of environmental threats. The first, Fe/Ag core/shell nanoparticles were designed using a novel one-pot method by varying the AgNO3 addition time in the system. For …
Synthesis Of Glycolipids And Evaluation Of Their Nkt Cell Stimulatory Properties, Yang Liu
Synthesis Of Glycolipids And Evaluation Of Their Nkt Cell Stimulatory Properties, Yang Liu
Theses and Dissertations
Natural killer T (NKT) cells are a subset of T cells that modify a variety of immune responses. NKT cells recognize glycolipid antigen presented by a molecule called CD1d, a nonclassical antigen-presenting molecule. The best known subset of CD1d-dependent NKT cells expresses an invariant T cell receptor Vα (TCR-α) chain. These are referred to as type I or invariant NKT (iNKT) cells. When stimulated by a glycolipid, NKT cells rapidly release large amounts of cytokines. Cytokines released by NKT cells can induce either Th1 or Th2 responses. Th1 cytokines are effective in regulating bacterial, parasitic, and viral infections. But Th1 …
Impact Of Nickel Doping On Hydrogen Storage In Porous Metal-Organic Frameworks, Tanushree Banerjee
Impact Of Nickel Doping On Hydrogen Storage In Porous Metal-Organic Frameworks, Tanushree Banerjee
Theses and Dissertations
A supply of clean, carbon neutral and sustainable energy is the most scientific and technical challenge that humanity is facing in the 21st century. Though there is enough fossil fuels available for a few centuries, their use would increase the level of CO2 in the atmosphere. This would lead to global warming and may pose serious threats such as rising of sea level, change in hydrological cycle, etc. Hence there is a need for an alternative source of fuel that is clean and sustainable. Among the many resources considered as an alternative power source, hydrogen is considered one of the …
Mechanistic Studies On The Electrochemistry Of Proton Coupled Electron Transfer And The Influence Of Hydrogen Bonding, Timothy Alligrant
Mechanistic Studies On The Electrochemistry Of Proton Coupled Electron Transfer And The Influence Of Hydrogen Bonding, Timothy Alligrant
Theses and Dissertations
This research has investigated proton-coupled electron transfer (PCET) of quinone/hydroquinone and other simple organic PCET species for the purpose of furthering the knowledge of the thermodynamic and kinetic effects due to reduction and oxidation of such systems. Each of these systems were studied involving the addition of various acid/base chemistries to influence the thermodynamics and kinetics upon electron transfer. It is the expectation that the advancement of the knowledge of acid/base catalysis in electrochemistry gleaned from these studies might be applied in fuel cell research, chemical synthesis, the study of enzymes within biological systems or to simply advance the knowledge …
Targeting Complex Cyclic Peptides For Synthesis: The Celogentin And Theonellamide Families, Joshua Wayne Robinson
Targeting Complex Cyclic Peptides For Synthesis: The Celogentin And Theonellamide Families, Joshua Wayne Robinson
Theses and Dissertations
Celogentin C and theonellamide F are a class of natural products that have potential antimitotic behavior. They both contain interesting bicyclic structures with unusual linkages within a central moiety. Celogentin C's highly functionalized tryptophan moiety has two unusual linkages, a β-substituted Leu connection to the C6 of the indole structure that makes up the left-hand ring, and a τ-N connection of the imidazole to the C2 of the indole constructing the right-hand ring. This right-hand ring connection was solved via a novel oxidative coupling procedure developed in our group and the left-hand ring was initially constructed via a radical conjugated …
Electronic Structure Of Lithium Tetraborate, David J. Wooten
Electronic Structure Of Lithium Tetraborate, David J. Wooten
Theses and Dissertations
Due to interest as neutron detection material, an investigation of Li2B4O7(110) and Li2B4O7(100) was undertaken, utilizing photoemission and inverse photoemission spectroscopic techniques. The measured band gap depended on crystallographic direction with the band gaps ranging from 8.9±0.5 eV to 10.1±0.5 eV. The measurement yielded a density of states that qualitatively agreed with the theoretical results from model bulk band structure calculations for Li2B4O7; albeit with a larger band gap than predicted, but consistent with the known deficiencies of LDA and DFT calculations. …
Characterization Of Stabilized Palladium Nanocatalysts, Meghann Broderick
Characterization Of Stabilized Palladium Nanocatalysts, Meghann Broderick
Theses and Dissertations
Metal nanoparticles have received much interest for their application in catalysis due to high surface-to-volume ratios resulting in more available active sites. Ideally these catalysts are heterogeneous and allow for facile separation from the catalytic reaction mixture making them ideal for industrial application. Dispersed metal nanoparticles are explored due to their high reactivity in solution and are stabilized by surfactants and polymers. However, it is difficult to determine whether or not a catalyst is truly heterogeneous as a certain degree of leaching from the metal nanoparticle is inevitable. Determining the mechanisms involved in nanocatalysis is also a challenge. In this …
Celogentin C And Thioviridamide: Synthetic And Structural Studies, Dmitry Nikolayevich Litvinov
Celogentin C And Thioviridamide: Synthetic And Structural Studies, Dmitry Nikolayevich Litvinov
Theses and Dissertations
Project I Celogentin C, isolated by Kobayashi from the seeds of Celosia argentea in 2001 exhibits strong inhibitory behavior towards polymerization of tubulin – globular protein, which plays crucial role during the cell division cycle. We have attempted synthesis of the left-hand ring of celogentin C via the intramolecular alkylation and the Knoevenagel condensation strategies. Utilizing synthetic methodologies in the field of nitroacetyl chemistry, developed by Kornblum and Rajappa we have successfully prepared the intermolecular Knoevenagel condensation product – the late-stage precursor to the left-hand ring of celogentin C. Synthesis of this key intermediate subsequently led to the preparation of …
Density Functional Studies Of The Stability Of Clusters, Penee Clayborne
Density Functional Studies Of The Stability Of Clusters, Penee Clayborne
Theses and Dissertations
Theoretical studies using the Kohn-Sham density functional formalism have been carried out to identify and investigate the stability of a variety of atomic clusters for their use in cluster assembled materials. The stable behavior found in a cluster system provides a way to classify inorganic clusters. The clusters in this study can be categorized in one of the following, jellium, all-metal aromatic, Zintl analogue or as a covalent metal-carbide. By understanding the electronic structure and ultimately the stable nature of a cluster first, it is proposed one can construct assemblies based on the stable cluster. The methodology presented is a …
Ribosomal Rna Mutations That Inhibit The Activity Of Transfer-Messenger Rna Of Stalled Ribosomes, Jacob N. Crandall
Ribosomal Rna Mutations That Inhibit The Activity Of Transfer-Messenger Rna Of Stalled Ribosomes, Jacob N. Crandall
Theses and Dissertations
In eubacteria, stalled ribosomes are rescued by a conserved quality-control mechanism involving transfer-messenger RNA (tmRNA) and its protein partner SmpB. Mimicking a tRNA, tmRNA enters stalled ribosomes, adds Ala to the nascent polypeptide, and serves as a template to encode a short peptide that tags the nascent protein for destruction. To further characterize the tagging process, we developed two genetic selections that link tmRNA activity to cell death. These negative selections can be used to identify inhibitors of tagging or to identify mutations in key residues essential for ribosome rescue. Little is known about which ribosomal elements are specifically required …
Electrodeposited Silica Thin Films, Debbie Campbell-Rance
Electrodeposited Silica Thin Films, Debbie Campbell-Rance
Theses and Dissertations
Sol-gel derived silica thin film synthesis has gained prominence because of the mild processing conditions and widespread understanding of the chemistry of the process. Traditionally, silicate films are prepared by spin- and dip-coating but these materials lack the desired porosity for sensing, separations and catalysis applications. Electrochemical deposition was proposed to improve the porosity of silicate films. The main aims of this work were threefold. First we wanted to elucidate what parameters influenced film formation during electrodeposition. Then we wanted to understand how these parameters affected the morphology of the materials prepared. These films were characterized by profilometry, AFM, and …
Electrospray Ionization Mass Spectrometry For The Characterization Of Covalent And Noncovalent Polynuclear Platinum Compounds Interacting With Bio-Molecules, John Mangrum
Theses and Dissertations
Polynuclear platinum compounds represent a new class of potential platinum anticancer therapeutics. Derived from the most widely used platinum anticancer drug, cisplatin, these novel compounds are distinct in their interactions with bio-molecules. The effectiveness of platinum anticancer agents is influenced by three pharmacological factors: (i) their resistance to deactivating sulfur nucleophiles, (ii) the ability to gain cellular entry and efficient cellular uptake, and (iii) the ability to form stable and specific complexes with DNA. BBR 3464, the first multinuclear platinum compound to reach phase II clinical trials, has created a new approach to cancer drug design. Large, highly charged platinum …
Role Of Members Of The Phosducin Gene Family In Protein Translation And Folding, Nana Sono-Koree
Role Of Members Of The Phosducin Gene Family In Protein Translation And Folding, Nana Sono-Koree
Theses and Dissertations
G proteins regulate various physiological processes by way of transducing a wide variety of signals ranging from hormonal to sensory stimuli. Malfunctions in G protein signaling lead to numerous diseases. G protein signaling begins with binding of a ligand to a G protein-coupled receptor resulting in a conformational change that leads to the exchange of a GDP for a GTP on G α. The GTP bound α subunit dissociates for its stable Gβγ dimer partner. G α-GTP and Gβγ control the activity of effector enzymes and ion channels that ultimately orchestrate the cellular response to stimulus. Current reports have shown …
Calculation Of Collisional Cross Sections For The ²P3/2 > ²P1/2 Transition In Alkali-Noble Gas Systems, Samuel D. Butler
Calculation Of Collisional Cross Sections For The ²P3/2 > ²P1/2 Transition In Alkali-Noble Gas Systems, Samuel D. Butler
Theses and Dissertations
Collisional cross sections were calculated as a function of energy for two coupled one dimensional, spherically symmetric potentials. The Split Operator Method was used to propagate an initial Moller state, chosen to be a Gaussian in the asymptotic limit, through a potential. The correlation between the wave packet and Moller final state was calculated at each time step. Using the Channel Packet Method, the correlation function was used to obtain scattering matrix elements. From scattering matrix elements for several different effective potential values and using the Method of Partial Waves, the collisional cross section is calculated for the transition from …
The Material Properties Of Cssnbr3 And Csbr:Sn-1% And Their Potential As Scintillator Detector Material, Neal B. Kleinschmidt
The Material Properties Of Cssnbr3 And Csbr:Sn-1% And Their Potential As Scintillator Detector Material, Neal B. Kleinschmidt
Theses and Dissertations
The search for superior nuclear radiation detection materials is ongoing. Current scintillator materials using Thallium doped Sodium Iodide or Cesium Iodide are the benchmarks for ease of use and quick identification of isotope species. This research aims to explore Cesium Bromide doped with 1% molar tin (CsBr:Sn-1%) and Cesium Tin Bromide (CsSnBr3) as candidate materials for a new scintillator. The techniques of Extended X-Ray Absorption Fine Structure (EXAFS), X-Ray Absorption Near Edge Structure (XANES) and Cathodoluminescence are used to determine the suit- ability of CsSnBr3 and CsBr:Sn-1% with Sn4+ as a potential scintillator materials and explore their …
Optical Properties Of Si, Ge, Gaas, Gasb, Inas, And Inp At Elevated Temperatures, Thomas R. Harris
Optical Properties Of Si, Ge, Gaas, Gasb, Inas, And Inp At Elevated Temperatures, Thomas R. Harris
Theses and Dissertations
Investigation of the optical and electrical behavior of some semiconductors at very high temperatures has not been an area of much study, at least not experimentally. The importance of such research becomes obvious due to the effects of high temperatures on semiconductor devices such as infrared detectors and light emitters. Besides the destructive effects of thermal stress and melting, changes in the optical properties of the material can greatly affect device performance. In this research, the infrared absorption of Si, Ge, GaAs, GaSb, InAs, and InP was measured from 0.6 to 25 μm at temperatures ranging from 295 up to …