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2019

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Articles 931 - 960 of 1773

Full-Text Articles in Chemistry

Development Of A New Analytical Method For Separation And Quantitative Determination Of Synthetic Cathinones In Urine Using Gas Chromatography Tandem Mass Spectrometry, Jasim Ali Ali Alzaabi Apr 2019

Development Of A New Analytical Method For Separation And Quantitative Determination Of Synthetic Cathinones In Urine Using Gas Chromatography Tandem Mass Spectrometry, Jasim Ali Ali Alzaabi

Chemistry Theses

This thesis is concerned with a new class of drugs known as synthetic cathinones, which overruns the drug markets in recent years as “legal highs” drugs, under different commercial names such as bath salts. All synthetic cathinone derivatives consist of a chiral center and usually sold out as a racemic mixture. Usually, one of the two enantiomers will have stronger central nervous system (CNS) stimulatory activity and the other one may have no significant CNS activity or addictive properties. A new sensitive and selective analytical method was developed for the simultaneous determination of ten synthetic cathinones enantiomers in spiked urine …

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Multi-Instrument Surface Characterization Of Display Glass, Cody Vic Cushman Apr 2019

Multi-Instrument Surface Characterization Of Display Glass, Cody Vic Cushman

Theses and Dissertations

Flat panel displays (FPDs) are microfabricated devices that are often fabricated on specialized glass substrates known as display glass. The surface chemistry of the outer few nanometers of display glass can have an important influence on FPD performance and yield. Dsiplay glass surface characterization is difficult because (i) display glass surface composition varies significantly from its bulk composition; (ii) high-surface area forms of glass, such as fibers and powders, may not have the same surface composition as melt-formed planar surfaces, and (iii) the surface composition of display glass may be altered through exposure to chemical treatments commonly used during flat …

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Study Of The Effects Of Silver Ions And Silver Nanoparticles On Embryonic Development, Martha Sharisha Johnson Apr 2019

Study Of The Effects Of Silver Ions And Silver Nanoparticles On Embryonic Development, Martha Sharisha Johnson

Biomedical Sciences Theses & Dissertations

This dissertation focuses on the study of the toxicity of metal nanoparticles (NPs) and their ions on the development of zebrafish embryos, aiming to understand unique biological effects of NPs and ions, and design new in vivo assays to characterize the toxicity of these metal NPs and metal ions. Currently, the underlying molecular mechanisms of biological effects of nanomaterials are partially understood. Some studies assume that the toxic effects of NPs can be attributed to the release of their ions. We investigate the effects of silver NPs (Ag NPs) and silver ions (Ag+ ions) on the embryonic development of zebrafish …

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Charge-Transfer Or Excimeric State? Exploring The Nature Of The Excited State In Cofacially Arrayed Polyfluorene Derivatives, Ainur Abzhanova, Lena V. Ivanova, Denan Wang, Tushar S. Navale, Sameh H. Abdelwahed, Maxim Vadimovich Ivanov, Sergey V. Lindeman, Rajendra Rathore, Scott A. Reid Apr 2019

Charge-Transfer Or Excimeric State? Exploring The Nature Of The Excited State In Cofacially Arrayed Polyfluorene Derivatives, Ainur Abzhanova, Lena V. Ivanova, Denan Wang, Tushar S. Navale, Sameh H. Abdelwahed, Maxim Vadimovich Ivanov, Sergey V. Lindeman, Rajendra Rathore, Scott A. Reid

Chemistry Faculty Research and Publications

It is well known that upon electronic excitation various π-stacked dimers readily exhibit excimer formation, facilitated by a perfect sandwich-like arrangement between the chromophores. However, it is unclear whether such a dimer is also capable of electron transfer upon excitation, if a strong electron-donating group is covalently attached. In this work, we probe the nature of the excited state in a series of cofacially arrayed polyfluorene derivatives with electron-rich aromatic donor attached via a methylene linker. Our studies show that in all cases excimer formation is energetically favorable, and promotion of a charge-transfer state in such systems is possible but …

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Monitoring Silver Nanoparticle Aggregation In Situ By Integrating Particle Impact Voltammetry And Uv-Vis Spectroscopy, Laela Ezra , '19 Apr 2019

Monitoring Silver Nanoparticle Aggregation In Situ By Integrating Particle Impact Voltammetry And Uv-Vis Spectroscopy, Laela Ezra , '19

Senior Theses, Projects, and Awards

Engineered nanomaterials (ENMs) have been increasingly used for a variety of purposes. Silver nanoparticles (AgNPs) are the most widely-used ENM to date. AgNPs undergo many transformations while in solution and in biologically relevant environments, so the development of techniques to analyze the extent of these transformations is crucial. The transformation of interest for this work is AgNP aggregation. There exist techniques to monitor aggregation of AgNPs and other ENMs (such as scanning electron microscopy) but often these instruments cannot measure aggregation in situ: some cannot monitor aggregation in real-time, and none are suited for fieldwork. Two methods that can characterize …

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Diastereoselective Cyclizations Of Enantiopure Planar Chiral N-Oxazolidinoyl Diene Iron(0) Tricarbonyl Complexes, Colin C. Howell , '19 Apr 2019

Diastereoselective Cyclizations Of Enantiopure Planar Chiral N-Oxazolidinoyl Diene Iron(0) Tricarbonyl Complexes, Colin C. Howell , '19

Senior Theses, Projects, and Awards

Iron(0) tricarbonyl diene complexes have long been established as effective stereodirecting groups due to their planar chirality and the steric bulk of the iron fragment. If initial diastereoselective complexation can be achieved, these molecules are therefore capable of acting as scaffolds for the stereoselective synthesis of architecturally complex products. The Paley laboratory uses chiral auxiliaries, most recently oxazolidinones, bound to acyclic dienes to assure diastereoselective complexation, before exploring the potential of diverse diastereomeric chemistry on the diene periphery. In this work we report progress on the development of an asymmetric, intramolecular rhodium(II)-catalyzed C-H insertion adjacent to the diene to form …

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Site-Directed Spin Label Epr Studies Of The Interaction Between The Influenza A Proteins (M1 And M2) Involved In Viral Assembly, Abigail J. Wong-Rolle , '19 Apr 2019

Site-Directed Spin Label Epr Studies Of The Interaction Between The Influenza A Proteins (M1 And M2) Involved In Viral Assembly, Abigail J. Wong-Rolle , '19

Senior Theses, Projects, and Awards

Influenza A presents a significant concern for public health as it is the cause of seasonal outbreaks and global pandemics. The influenza A proteins, matrix protein 1 (M1) and matrix protein 2 (M2), have been shown to be essential for the propagation of new viruses, especially through their roles in viral assembly and budding. The M2 cytoplasmic tail interacts with the M1 protein, recruiting it to the viral budding site and enabling proper packaging of the viral genome. The Howard lab has previously characterized residues 50-70 in the M2 cytoplasmic tail and the M2 protein’s conformational equilibria by sitedirected spin …

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Diastereoselective Synthesis Of Cyclopentenes Via Rhii-Catalyzed C-H Insertion Directed By A Planar Chiral N-Oxazolidinoyl Iron(0) Tricarbonyl Diene Complex, Benjamin G. Hejna , '19 Apr 2019

Diastereoselective Synthesis Of Cyclopentenes Via Rhii-Catalyzed C-H Insertion Directed By A Planar Chiral N-Oxazolidinoyl Iron(0) Tricarbonyl Diene Complex, Benjamin G. Hejna , '19

Senior Theses, Projects, and Awards

Herein is presented a general methodology for the synthesis of cyclopentenes bearing two consecutive, diastereoselectively generated stereocenters by Rhᴵᴵ-catalyzed C-H insertion using a planar chiral N-oxazolidinoyl iron(0) tricarbonyl diene complex as a steric directing group. The majority of this work is dedicated to designing and accessing viable substrates to undergo the aforementioned diastereomerically selective C-H insertion, as well as determination of the absolute stereochemical configuration of the enantiomerically pure product. We hypothesize that the observed stereochemical outcome is caused by the favorability of orienting the substituent on each newly-generated stereocenter away from the sterically bulky iron(0) tricarbonyl fragment. In …

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3-Hydroxyflavones And 3-Hydroxy-4-Oxoquinolines As Carbon Monoxide-Releasing Molecules, Tatiana Soboleva, Lisa M. Berreau Mar 2019

3-Hydroxyflavones And 3-Hydroxy-4-Oxoquinolines As Carbon Monoxide-Releasing Molecules, Tatiana Soboleva, Lisa M. Berreau

Chemistry and Biochemistry Faculty Publications

Carbon monoxide-releasing molecules (CORMs) that enable the delivery of controlled amounts of CO are of strong current interest for applications in biological systems. In this review, we examine the various conditions under which CO is released from 3-hydroxyflavones and 3-hydroxy-4-oxoquinolines to advance the understanding of how these molecules, or derivatives thereof, may be developed as CORMs. Enzymatic pathways from quercetin dioxygenases and 3-hydroxy-4-oxoquinoline dioxygenases leading to CO release are examined, along with model systems for these enzymes. Base-catalyzed and non-redox-metal promoted CO release, as well as UV and visible light-driven CO release from 3-hydroxyflavones and 3-hydroxy-4-oxoquinolines, are summarized. The visible …

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Optical Stability Of 1,1′-Binaphthyl Derivatives, Nikolay V. Tkachenko, Steve Scheiner Mar 2019

Optical Stability Of 1,1′-Binaphthyl Derivatives, Nikolay V. Tkachenko, Steve Scheiner

Chemistry and Biochemistry Faculty Publications

The racemization process of various 1,1′-binaphthyl derivatives is studied by quantum calculations. The preferred racemization pathway passes through a transition state belonging to the Ci symmetry group. The energy barrier for this process is independent of solvation, the electron-withdrawing/releasing power of substituents, or their ability to engage in H-bonds within the molecule. The primary factor is instead the substituent size. The barrier is thus reduced when the −OH groups of 1,1′-bi-2-naphthol are replaced by H. There is a drop in the barrier also when the substituents are moved from the 2,2′ positions to 6,6′, where they will not come …

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An Improved Synthesis Of Adefovir And Related Analogues, Timothy P. O'Sullivan, Et Al Mar 2019

An Improved Synthesis Of Adefovir And Related Analogues, Timothy P. O'Sullivan, Et Al

Physical Sciences Publications

An improved synthesis of the antiviral drug adefovir is presented. Problems associated with current routes to adefovir include capricious yields and a reliance on problematic reagents and solvents, such as magnesium tert-butoxide and DMF, to achieve high conversions to the target. A systematic study within our laboratory led to the identification of an iodide reagent which affords higher yields than previous approaches and allows for reactions to be conducted up to 10 g in scale under milder conditions. The use of a novel tetrabutylammonium salt of adenine facilitates alkylations in solvents other than DMF. Additionally, we have investigated how …

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Synthesis And Metalation Of Internally Alkylated Porphyrinoids, Alissa Nicole Latham Mar 2019

Synthesis And Metalation Of Internally Alkylated Porphyrinoids, Alissa Nicole Latham

Theses and Dissertations

The mechanism behind alkyl migration in palladium(II) benzocarbaporphyrins was investigated through the synthesis of a 23-methylcarbaporphyrin. It was found that palladium insertion led to methyl group migration to C21 and it is proposed that this occurs through an oxidative addition onto the palladium metal center, followed by a reductive elimination to transfer the methyl to the internal carbon. A similar rearrangement was observed when 23-methylcarbaporphyrin was reacted with [Rh(CO)2Cl]2 and resulted in the formation of a rhodium(III) complex containing a three-membered rhodacycle. The syntheses of rhodium(I) and rhodium(III) derivatives of other carbaporphyrins, including 21- and 22-methylbenzo-carbaporphyrins, were probed and four …

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Protein-Polymer Conjugates Synthesized Using Water-Soluble Azlactone-Functionalized Polymers Enable Receptor-Specific Cellular Uptake Toward Targeted Drug Delivery, Julia S. Kim, Allison R. Sirois, Analia J. Vazquez Cegla, Eugenie Jumai'an, Naomi Murata, Maren E. Buck, Sarah J. Moore Mar 2019

Protein-Polymer Conjugates Synthesized Using Water-Soluble Azlactone-Functionalized Polymers Enable Receptor-Specific Cellular Uptake Toward Targeted Drug Delivery, Julia S. Kim, Allison R. Sirois, Analia J. Vazquez Cegla, Eugenie Jumai'an, Naomi Murata, Maren E. Buck, Sarah J. Moore

Chemistry: Faculty Publications

Conjugation of proteins to drug-loaded polymeric structures is an attractive strategy for facilitating target-specific drug delivery for a variety of clinical needs. Polymers currently available for conjugation to proteins generally have limited chemical versatility for subsequent drug loading. Many polymers that do have chemical functionality useful for drug loading are often insoluble in water, making it difficult to synthesize functional protein–polymer conjugates for targeted drug delivery. In this work, we demonstrate that reactive, azlactone-functionalized polymers can be grafted to proteins, conjugated to a small-molecule fluorophore, and subsequently internalized into cells in a receptor-specific manner. Poly(2-vinyl-4,4-dimethylazlactone), synthesized using reversible addition–fragmentation chain …

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Synthesis Of Simplified Azasordarin Analogs As Potential Antifungal Agents, Yibiao Wu, Chris Dockendorff Mar 2019

Synthesis Of Simplified Azasordarin Analogs As Potential Antifungal Agents, Yibiao Wu, Chris Dockendorff

Chemistry Faculty Research and Publications

A new series of simplified azasordarin analogs was synthesized using as key steps a Diels–Alder reaction to generate a highly substituted bicyclo[2.2.1]heptane core, followed by a subsequent nitrile alkylation. Several additional strategies were investigated for the generation of the key tertiary nitrile or aldehyde thought to be required for inhibition at the fungal protein eukaryotic elongation factor 2. This new series also features a morpholino glycone previously reported in semisynthetic sordarin derivatives with broad spectrum antifungal activity. Despite a lack of activity against Candida albicans for these early de novo analogs, the synthetic route reported here permits more comprehensive modifications …

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Revisiting Volumes Of Lipid Components In Bilayers, John F. Nagle, Richard M. Venable, Ezekiel Maroclo-Kemmerling, Stephanie Tristram-Nagle Mar 2019

Revisiting Volumes Of Lipid Components In Bilayers, John F. Nagle, Richard M. Venable, Ezekiel Maroclo-Kemmerling, Stephanie Tristram-Nagle

University Faculty Publications and Creative Works

In addition to obtaining the highly precise volumes of lipids in lipid bilayers, it has been desirable to obtain the volumes of parts of each lipid, such as the methylenes and terminal methyls on the hydrocarbon chains and the head group. Obtaining such component volumes from experiment and from simulations is re-examined, first by distinguishing methods based on apparent versus partial molar volumes. Although somewhat different, both these methods give results that are counterintuitive and that differ from results obtained by a more local method that can only be applied to simulations. These comparisons reveal differences in the average methylene …

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Tin Assisted Fully Exposed Platinum Clusters Stabilized On Defect-Rich Graphene For Dehydrogenation Reaction, Jiayun Zhang, Yuchen Deng, Xiangbin Cai, Yunlei Chen, Mi Peng, Zhimin Jia, Zheng Jiang, Pengju Ren, Siyu Yao, Jinglin Xie, Dequan Xiao, Xiao-Dong Wen, Ning Wang, Hongyang Liu, Ding Ma Mar 2019

Tin Assisted Fully Exposed Platinum Clusters Stabilized On Defect-Rich Graphene For Dehydrogenation Reaction, Jiayun Zhang, Yuchen Deng, Xiangbin Cai, Yunlei Chen, Mi Peng, Zhimin Jia, Zheng Jiang, Pengju Ren, Siyu Yao, Jinglin Xie, Dequan Xiao, Xiao-Dong Wen, Ning Wang, Hongyang Liu, Ding Ma

Chemistry and Chemical Engineering Faculty Publications

Tin assisted fully exposed Pt clusters are fabricated on the core-shell nanodiamond@graphene (ND@G) hybrid support (a-PtSn/ND@G). The obtained atomically dispersed Pt clusters, with an average Pt atom number of 3, were anchored over the ND@Gsupport by the assistance of Sn atoms as a partition agent and through the Pt-C bond between Pt clusters and defect-rich graphene nanoshell. The atomically dispersed Pt clusters guaranteed a full metal availability to the reactants, a high thermal stability, and an optimized adsorption/desorption behavior. It inhibits the side reactions and enhances catalytic performance in direct dehydrogenation of n-butane at a low temperature of 450 °C, …

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Production Of Secondary Organic Aerosol During Aging Of Biomass Burning Smoke From Fresh Fuels And Its Relationship To Voc Precursors, A. T. Ahern, E. S. Robinson, D. S. Tkacik, R. Saleh, L. E. Hatch, K. C. Barsanti, C. E. Stockwell, R. J. Yokelson, A. A. Presto, A. L. Robinson, R. C. Sullivan, N. M. Donahue Mar 2019

Production Of Secondary Organic Aerosol During Aging Of Biomass Burning Smoke From Fresh Fuels And Its Relationship To Voc Precursors, A. T. Ahern, E. S. Robinson, D. S. Tkacik, R. Saleh, L. E. Hatch, K. C. Barsanti, C. E. Stockwell, R. J. Yokelson, A. A. Presto, A. L. Robinson, R. C. Sullivan, N. M. Donahue

Chemistry and Biochemistry Faculty Publications

After smoke from burning biomass is emitted into the atmosphere, chemical and physical processes change the composition and amount of organic aerosol present in the aged, diluted plume. During the fourth Fire Lab at Missoula Experiment, we performed smog-chamber experiments to investigate formation of secondary organic aerosol (SOA) and multiphase oxidation of primary organic aerosol (POA). We simulated atmospheric aging of diluted smoke from a variety of biomass fuels while measuring particle composition using high-resolution aerosol mass spectrometry. We quantified SOA formation using a tracer ion for low-volatility POA as a reference standard (akin to a naturally occurring internal standard). …

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Deswelling Induced Morphological Changes In Dual Ph And Temperature Responsive Ultra-Low Crosslinked Poly (N-Isopropyl Acrylamide)-Co-Acrylic Acid Microgels, Molla R. Islam, Maddie Tumbarello, L. Andrew Lyon Mar 2019

Deswelling Induced Morphological Changes In Dual Ph And Temperature Responsive Ultra-Low Crosslinked Poly (N-Isopropyl Acrylamide)-Co-Acrylic Acid Microgels, Molla R. Islam, Maddie Tumbarello, L. Andrew Lyon

Engineering Faculty Articles and Research

Poly(N-isopropylacrylamide) microgels prepared without exogenous cross-linker are extremely “soft” as a result of their very low cross-linking density, with network connectivity arising only from the self-crosslinking of pNIPAm chains. As a result of this extreme softness, our group and others have taken interest in using these materials in a variety of bioengineering applications, while also pursuing studies of their fundamental properties. Here, we report deswelling triggered structural changes in poly(N-isopropylacrylamide-co-acrylic acid) (ULC10AAc) microgels prepared by precipitation polymerization. Dynamic light scattering suggests that the deswelling of these particles not only depends on the collapse of …

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Ethanolamine Regulates Cqsr Quorum-Sensing Signaling In Vibrio Cholerae, Samit Watve, Kelsey Barrasso, Sarah A. Jung, Kristen J. Davis, Lisa A. Hawver, Atul Khataokar, Ryan G. Palaganas, Matthew B. Neiditch, Lark Perez, Wai-Leung Ng Mar 2019

Ethanolamine Regulates Cqsr Quorum-Sensing Signaling In Vibrio Cholerae, Samit Watve, Kelsey Barrasso, Sarah A. Jung, Kristen J. Davis, Lisa A. Hawver, Atul Khataokar, Ryan G. Palaganas, Matthew B. Neiditch, Lark Perez, Wai-Leung Ng

College of Science & Mathematics Departmental Research

The pathogen that causes cholera, Vibrio cholerae, uses the cell-cell communication process known as quorum sensing (QS) to regulate virulence factor production and biofilm formation in response to changes in population density and complexity. QS is mediated through the detection of extracellular chemical signals called autoinducers. Four histidine kinases, LuxPQ, CqsS, CqsR and VpsS, have been identified as receptors to activate the key QS regulator LuxO at low cell density. At high cell density, detection of autoinducers by these receptors leads to deactivation of LuxO, resulting in population-wide gene expression changes. While the cognate autoinducers that regulate the activity of …

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In Situ Measurements Of Trace Gases, Pm, And Aerosol Optical Properties During The 2017 Nw Us Wildfire Smoke Event, Vanessa Selimovic, Robert J. Yokelson, Gavin R. Mcmeeking, Sarah Coefield Mar 2019

In Situ Measurements Of Trace Gases, Pm, And Aerosol Optical Properties During The 2017 Nw Us Wildfire Smoke Event, Vanessa Selimovic, Robert J. Yokelson, Gavin R. Mcmeeking, Sarah Coefield

Chemistry and Biochemistry Faculty Publications

In mid-August through mid-September of 2017 a major wildfire smoke and haze episode strongly impacted most of the NW US and SW Canada. During this period our ground-based site in Missoula, Montana, experienced heavy smoke impacts for ∼ 500h (up to 471μ-3 hourly average PM2.5). We measured wildfire trace gases, PM2.5 (particulate matter ≤2.5μm in diameter), and black carbon and submicron aerosol scattering and absorption at 870 and 401nm. This may be the most extensive real-time data for these wildfire smoke properties to date. Our range of trace gas ratios for δNH3 δCO and δC2H4 δCO confirmed that the smoke …

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Photocatalytic Degradation Of Profenofos And Triazophos Residues In The Chinese Cabbage, Brassica Chinensis, Using Ce-Doped Tio2, Xiangying Liu, You Zhan, Zhongqin Zhang, Lang Pan, Lifeng Hui, Kailin Liu, Xuguo Zhou, Lianyang Bai Mar 2019

Photocatalytic Degradation Of Profenofos And Triazophos Residues In The Chinese Cabbage, Brassica Chinensis, Using Ce-Doped Tio2, Xiangying Liu, You Zhan, Zhongqin Zhang, Lang Pan, Lifeng Hui, Kailin Liu, Xuguo Zhou, Lianyang Bai

Entomology Faculty Publications

Pesticides have revolutionized the modern day of agriculture and substantially reduced crop losses. Synthetic pesticides pose a potential risk to the ecosystem and to the non-target organisms due to their persistency and bioaccumulation in the environment. In recent years, a light-mediated advanced oxidation processes (AOPs) has been adopted to resolve pesticide residue issues in the field. Among the current available semiconductors, titanium dioxide (TiO2) is one of the most promising photocatalysts. In this study, we investigated the photocatalytic degradation of profenofos and triazophos residues in Chinese cabbage, Brassica chinensis, using a Cerium-doped nano semiconductor TiO2 (TiO …

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Conducting Polymer Based Gel Electrolytes For Ph Sensitivity, Aditya Jagannath Kashyap Mar 2019

Conducting Polymer Based Gel Electrolytes For Ph Sensitivity, Aditya Jagannath Kashyap

USF Tampa Graduate Theses and Dissertations

The evaluation of concentration of ions and molecules with the help of biosensors have been regarded as an emerging technology. Bio and chemical sensors have a variety of applications in the field of medicine, military, environmental and food industries alike. With an estimated investment growth of over 4.31% in the development of pH sensors in the next five year, the objective of a developing a robust measurement system is all the more required. The scope of this research is to evaluate the ability of conducting polymer-based gel electrolytes for pH sensitivity, as a function of the transistor characteristics using an …

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Control Strategies For Multi-Evaporator Vapor Compression Cycles, Sunderlin D. Jackson Mar 2019

Control Strategies For Multi-Evaporator Vapor Compression Cycles, Sunderlin D. Jackson

Theses and Dissertations

Next-generation military aircraft must be able to handle highly transient thermal loads that exceed the ability of current aircraft thermal subsystems. Vapor compression cycle systems are a particular refrigeration technology that is an attractive solution for dealing with this challenge, due primarily to their high efficiency. However, there are several barriers to realizing the benefits of vapor cycles systems for controlling thermal loads in military aircraft. This thesis focuses on addressing the challenge of controlling vapor cycles in the presence of highly transient evaporator heat loads. Specifically, a linear quadratic regulator (LQR) is designed for a simple vapor cycle system, …

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Fracture Toughness And Fatigue Crack Growth Rate Characterization Of Inconel 718 Formed By Laser Powder Bed Fusion, Charles C. Hohnbaum Mar 2019

Fracture Toughness And Fatigue Crack Growth Rate Characterization Of Inconel 718 Formed By Laser Powder Bed Fusion, Charles C. Hohnbaum

Theses and Dissertations

Continuing improvement in the field of AM of metals provides the opportunity for direct fabrication of aerospace parts. AM was once used in large part for rapid prototyping but improvements in technology and increases in the knowledge base of AM materials has provided the opportunity for manufacture of AM parts for operational use. The ability to create low numbers of unique parts without having to invest in expensive tooling provides great economic incentive to utilize this technique. IN718 is the most common high temperature alloy used in the aerospace industry and lends itself readily to formation by LPBF. The superior …

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Ultra-Strong Long-Chain Polyamide Elastomers With Programmable Supramolecular Interactions And Oriented Crystalline Microstructures, Lingzhi Song, Tianyu Zhu, Liang Yuan, Jiangjun Zhou, Yaqiong Zhang, Zhongkai Wang, Chuanbing Tang Mar 2019

Ultra-Strong Long-Chain Polyamide Elastomers With Programmable Supramolecular Interactions And Oriented Crystalline Microstructures, Lingzhi Song, Tianyu Zhu, Liang Yuan, Jiangjun Zhou, Yaqiong Zhang, Zhongkai Wang, Chuanbing Tang

Faculty Publications

Polyamides are one of the most important polymers. Long-chain aliphatic polyamides could bridge the gap between traditional polyamides and polyethylenes. Here we report an approach to preparing sustainable ultra-strong elastomers from biomass-derived long-chain polyamides by thiol-ene addition copolymerization with diamide diene monomers. The pendant polar hydroxyl and non-polar butyrate groups between amides allow controlled programming of supramolecular hydrogen bonding and facile tuning of crystallization of polymer chains. The presence of thioether groups on the main chain can further induce metal–ligand coordination (cuprous-thioether). Unidirectional step-cycle tensile deformation has been applied to these polyamides and significantly enhances tensile strength to over 210 …

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Creep Of Nextel 720/Alumina Ceramic Matrix Composite With Diamond-Drilled Effusion Holes At 1200°C In Air And In Steam, Megan L. Harkins Mar 2019

Creep Of Nextel 720/Alumina Ceramic Matrix Composite With Diamond-Drilled Effusion Holes At 1200°C In Air And In Steam, Megan L. Harkins

Theses and Dissertations

A recent study evaluated tensile stress-strain and tensile creep behavior of an oxide-oxide composite (Nextel™720/alumina) with laser-drilled effusion holes at 1200°C. It was determined that the presence of laser-drilled holes degraded the mechanical properties and performance of the CMC as a result of damage caused to the composite microstructure by the laser drilling process. Based on these results, the present effort sought to assess the effects of diamond-drilled holes on the mechanical behavior of this CMC. Tensile properties of the N720/A composite at 1200°C in laboratory air were unaffected by the presence of an array of 17 diamond-drilled effusion holes. …

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The Effects Of Reactant Concentration And Air Flow Rate In The Consumption Of Dissolved O2 During The Photochemistry Of Aqueous Pyruvic Acid, Alexis J. Eugene, Marcelo I. Guzman Mar 2019

The Effects Of Reactant Concentration And Air Flow Rate In The Consumption Of Dissolved O2 During The Photochemistry Of Aqueous Pyruvic Acid, Alexis J. Eugene, Marcelo I. Guzman

Chemistry Faculty Publications

The sunlight photochemistry of the organic chromophore pyruvic acid (PA) in water generates ketyl and acetyl radicals that contribute to the production and processing of atmospheric aerosols. The photochemical mechanism is highly sensitive to dissolved oxygen content, [O2(aq)], among other environmental conditions. Thus, herein we investigate the photolysis (λ ≥ 305 nm) of 10–200 mM PA at pH 1.0 in water covering the relevant range 0 ≤ [O2(aq)] ≤ 1.3 mM. The rapid consumption of dissolved oxygen by the intermediate photolytic radicals is monitored in real time with a dissolved oxygen electrode. …

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Cooperative Transport In A Multi-Particle, Multi-Dimensional Flashing Ratchet, Ofer Kedem, Emily A. Weiss Mar 2019

Cooperative Transport In A Multi-Particle, Multi-Dimensional Flashing Ratchet, Ofer Kedem, Emily A. Weiss

Chemistry Faculty Research and Publications

Random and undirected forces are rectified in biological and synthetic systems using ratcheting mechanisms, which employ periodic asymmetric potentials and nonequilibrium conditions to produce useful transport. The density of motors or transported particles is known to strongly affect the nature and efficacy of transport in biological systems, as well as in synthetic ratchets and active swimmer systems. While experimental ratchet implementations typically employ potentials varying in two dimensions (2D), the role of the density of interacting particles in such a system has not been modeled. Prompted by experimental observations and building upon previous simulations, this paper describes the ratcheting process …

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Process Parameter Development Of Additively Manufactured Af9628 Weapons Steel, Erin M. Hager Mar 2019

Process Parameter Development Of Additively Manufactured Af9628 Weapons Steel, Erin M. Hager

Theses and Dissertations

The manufacture of components in Additive Manufacturing processes is limited by the range of materials available. Qualification of materials for Additive Manufacturing is time intensive, and is often specific to a single type of machine. In this study, an approach to selecting power, speed, and hatch spacing values for a newly powderized material, AF9628 weapons steel, is described that results in highly dense (>99.9%) parts on an MLab 200R Cusing. Initial power and speed values used in a weld track study were selected based on a survey of parameters used on similar materials, with a focus on the energy …

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Recycling Aluminum, Steffani Burwitz, Kristin M. Roe, Matthew L. Miller, Madhav P. Nepal, Larry B. Browning, P. Troy White Mar 2019

Recycling Aluminum, Steffani Burwitz, Kristin M. Roe, Matthew L. Miller, Madhav P. Nepal, Larry B. Browning, P. Troy White

iLEARN Teaching Resources

Students will investigate and compare the energy cost to produce aluminum products from aluminum ore and recycled aluminum. Students will perform an electrolysis activity to reinforce the idea that recycling metal requires less energy than mining and refining metals from their original source in the earth.

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