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2007

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Articles 601 - 630 of 658

Full-Text Articles in Chemistry

Synthesis And Evaluation Of Derivatives And Analogs Of Xanthene Dyes, Xiangyang Xu Jan 2007

Synthesis And Evaluation Of Derivatives And Analogs Of Xanthene Dyes, Xiangyang Xu

LSU Doctoral Dissertations

Xanthene dyes are one of the oldest synthetic dyes. Fluorescein was first synthesized by von Baeyer in 1871. Since its discovery, it has been extensively studied. Fluorescein can exist as four different ionic forms (cationic form, neutral form, monoanionic form and dianionic form). Under physiological conditions (pH 7.4), fluorescein mainly exists as the dianionic form which grants it large quantum yield and excellent solubility in water. This renders fluorescein and its derivatives useful for studies in biological media. Cysteine (Cys) and homocysteine (Hcy) are of the few amino acids which contain sulfur and both of them are believed to be …

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Stereochemical And Regiochemical Trends In The Selective Spectrophotometric Detection Of Biological Molecules, Shan Jiang Jan 2007

Stereochemical And Regiochemical Trends In The Selective Spectrophotometric Detection Of Biological Molecules, Shan Jiang

LSU Doctoral Dissertations

Useful mechanistic studies to date concerning sugar detection by arylboronic acid chemosensors have mainly involved the elucidation of equilibrium constants and the role of boron-nitrogen interactions in signal transduction. However, several discreet sugarboronate complexes exist in solution. This is due to the complex equilibria between isomeric species of even the simplest monosaccharides. Relatively few reports have been devoted to a systematic study of the structures of each of the corresponding individual sugar-boronate complexes. We have investigated some of the precise regio- and stereochemical features of the various equilibrating sugar isomers that induce selective signal transduction. As a result of this …

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Synthesis And Properties Of Isoporphyrins And Related Derivatives For Application In Photodynamic Therapy, Sandra Celinah Mwakwari Jan 2007

Synthesis And Properties Of Isoporphyrins And Related Derivatives For Application In Photodynamic Therapy, Sandra Celinah Mwakwari

LSU Doctoral Dissertations

Isoporphyrins are tautomers of porphyrins with an interrupted macrocyclic conjugation owing to the presence of a sp3 hybridized meso-carbon. Due to their absorption at long wavelengths (~800nm), isoporphyrins are potential candidates as photosensitizers in photodynamic therapy (PDT), a ternary modality of cancer treatment. They are also of biological interest due to their unique redox properties among porphyrin derivatives and could be a new class of near-IR dyes. Isoporphyrins are known to be unstable with respect to transformation back to the fully conjugated porphyrin chromophore except when the meso-carbon is geminally substituted and for this reason a detailed study of this …

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Design, Synthesis, And Conformational Studies Of Peptides Containing α,α-Disubstituted Amino Acids, Jia Wang Jan 2007

Design, Synthesis, And Conformational Studies Of Peptides Containing α,α-Disubstituted Amino Acids, Jia Wang

LSU Doctoral Dissertations

Cα,α-disubstituted amino acids (ααAAs) are widely utilized to conformationally constrain peptides. Several pentapeptides containing dipropylglycine (Dpg) at alternating positions and their α-amino acid counterpart L-norvaline (Nva) analogues were synthesized to fully investigate the impact of Dpg on peptide backbone structure in aqueous solution. CD, VCD and NMR spectral analysis suggest that Dpg containing peptides adopt more ordered structures relative to their Nva containing analogues. The central residues (Ala, Thr, Tyr, Val) and the charged side-chains of Glu and Lys play important roles in the degree of peptide folding. Hydrophobic and branched residues (Val, Tyr) at the …

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Copper(Ii) Oxide Mediated Formation And Stabilization Of Combustion Generated Persistent Free Radicals, Hieu Truong Jan 2007

Copper(Ii) Oxide Mediated Formation And Stabilization Of Combustion Generated Persistent Free Radicals, Hieu Truong

LSU Doctoral Dissertations

Biologically damaging semiquinone-type radicals have been reported in cigarette smoke, their likely origin being hydroquinone (HQ) and catechol (CT) molecular precursors contained by the tobacco. Since other biomass contains HQ and CT-type species, it is likely that combustion of other biomass will also form semiquinone-type radicals. All hydrocarbon fuels will form phenol and substituted phenol that can form substituted phenoxyl radicals. Because each of these radicals has the potential to be environmentally persistent and biologically active, their formation and stabilization from various molecular precursors was studied with the focus on surface-bound radicals formed in association with combustion-generated fly-ash particles. Comprehensive …

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The Spectral And Photophysical Characterization Of Water Solubilizing Metal Phthalocyanines For Highly Sensitive Detection In Biological Studies, Vera Tamisha Verdree Jan 2007

The Spectral And Photophysical Characterization Of Water Solubilizing Metal Phthalocyanines For Highly Sensitive Detection In Biological Studies, Vera Tamisha Verdree

LSU Doctoral Dissertations

Efforts to improve the technology for DNA analyses stimulated the work presented here to develop a series of fluorescent probes that would aid in the increased multiplexing capabilities allowing the ability to detect multiple targets in a single measurement. Typically, spectral discrimination has been used to identify each DNA fragment in sequencing or diagnostic applications by means of unique emission properties from several labeling dyes. This has been accomplished with labels that fluoresce in the visible region. The limitations with these dyes is the broad emission profile making discrimination difficult, high intrinsic biological fluorescence and structural differences of the dyes …

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Probing The Association Behavior Of Hydrophobic Organic Compounds With Dissolved Humic Materials, Hadi M. Marwani Jan 2007

Probing The Association Behavior Of Hydrophobic Organic Compounds With Dissolved Humic Materials, Hadi M. Marwani

LSU Doctoral Dissertations

The association mechanism between hydrophobic organic compounds (HOC) and dissolved humic materials (DHM) has continued to be one of the interesting areas in environmental applications. The goal of the research reported in this dissertation is to investigate the association behavior of HOC with DHM. The first part of this research involves steady-state fluorescence measurements of these multi-component systems to study the effect of DHM content on the association mechanism of HOC, in particular using pyrene as a model. Results showed that steady-state fluorescence alone may not provide enough information about the quenching mechanism of pyrene with DHM. Lifetime based fluorescence …

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Chiral Analyses Using Molecualr Micelles And Multiple Regression Modeling In Chromatographic And Spectroscopic Methods, Alicia Williams Snearl Jan 2007

Chiral Analyses Using Molecualr Micelles And Multiple Regression Modeling In Chromatographic And Spectroscopic Methods, Alicia Williams Snearl

LSU Doctoral Dissertations

Multiple regression modeling techniques allow for rapid and accurate prediction of migration times and resolution values for micellar electrokinetic chromatography (MEKC) as well as the development of quick screening methods using steady-state fluorescence spectroscopy. All studies reported in this dissertation include optimization of calibration models and predictions of dependent variables by the use of validation samples. The root-mean-square percent relative error (RMS%RE) is used as a figure of merit for characterizing the performance of the calibration models. MEKC separations of achiral and chiral analytes were performed using an achiral molecular micelle, poly(sodium N-undecylenic sulfate), and chiral molecular micelles, poly(sodium N-undecanoyl-L-leucylvalinate) …

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Shear Responses Of Poly(Ethylene Oxide)-Laponite Nanocomposite Hydrogels, Elena Loizou Jan 2007

Shear Responses Of Poly(Ethylene Oxide)-Laponite Nanocomposite Hydrogels, Elena Loizou

LSU Doctoral Dissertations

This research seeks to understand the structure and shear responses of poly(ethylene oxide)-Laponite nanocomposite hydrogels and to relate the macroscopic physical properties to the nanoscopic structural changes. Understanding that relationship is necessary, in order to tailor material properties to specific applications. Information on the structure at rest on multiple length scales was obtained by combining microscopic and neutron scattering techniques. The structural changes that occur in response to a shear field were explored using rheology and neutron scattering. These structures were examined as a function of polymer molecular weight, polymer and clay concentrations, and sample preparation method. While the sample …

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Structural Manipulation Of Pyrrole-Terminated Dendrimers To Create A More Efficient Encapsulation/Release System, Henry Wiggins Jan 2007

Structural Manipulation Of Pyrrole-Terminated Dendrimers To Create A More Efficient Encapsulation/Release System, Henry Wiggins

LSU Doctoral Dissertations

This work demonstrates the ability to manipulate the structure of pyrrole-terminated dendrimers by modifying solution conditions which directly affects their encapsulation properties. Investigations were conducted using FTIR and 2D NMR to determine the location of end groups. NMR relaxation studies were conducted at various temperatures and different solution pH to gain an understanding of the relative mobility and rigidity of different areas of the dendrimer. It was found that that the release properties were affected by the solution pH and the presence of salt. Further the effectiveness of retaining molecular guests by oligo-pyrrole terminated dendrimers with a range of oligomer …

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Enhanced Fire Retardancy Of Vinyl Ester Resins By Combination Of Additives, Grace Chigwada, Charles A. Wilkie Jan 2007

Enhanced Fire Retardancy Of Vinyl Ester Resins By Combination Of Additives, Grace Chigwada, Charles A. Wilkie

Chemistry Faculty Research and Publications

In pursuit of fire-retardant materials, vinyl ester resins were combined with commercially available fire retardants at lower loadings than that at which they are usually effective when used alone. The thermal stability and flammability of the various combinations of fire retardants were evaluated by thermogravimetric analysis and cone calorimetric analysis. With some combinations, the 50% degradation temperature was improved by about 5-10ºC Different additives affected the flammability to varying extents and some combinations resulted in an enhanced fire retardancy compared to the additives used alone. The combinations that showed the best reductions in the peak heat release rate (PHRR) were …

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Elementary Reactions Involved In Pollutant-Forming Mechanisms, Cheri Ann Mcferrin Jan 2007

Elementary Reactions Involved In Pollutant-Forming Mechanisms, Cheri Ann Mcferrin

LSU Doctoral Dissertations

The reactions of the hydroxyl radical (OH) with molecular chlorine (Reaction 1), methane (Reaction 2), and propane (Reaction 3) have been studied experimentally using a pulsed laser photolysis/pulsed-laser-induced fluorescence technique over wide ranges of temperatures (297-826, 298-1009, and 296-908 K, respectively) and at pressures between 6.68 and 24.15 kPascals. The rate coefficients for these reactions exhibit no dependence on pressure and exhibit positive temperature dependences that can be represented with modified three-parameter Arrhenius expressions within their corresponding temperature ranges: k1 = 3.59 x 10-16T1.35exp(-745K/T)cm3molecule-1sec-1, k2 = 3.82 x 10-19T2.38 exp(-1136K/T)cm3molecule-1sec-1, and k3 = 6.64 x 10-16T1.46 exp(-271K/T)cm3molecule-1sec-1. For the OH …

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A Thallium Mediated Route To Σ-Arylalkynyl Complexes Of Bipyridyltricarbonylrhenium(I), Brendan J. Liddle, Sergey V. Lindeman, Daniel L. Reger, James R. Gardinier Jan 2007

A Thallium Mediated Route To Σ-Arylalkynyl Complexes Of Bipyridyltricarbonylrhenium(I), Brendan J. Liddle, Sergey V. Lindeman, Daniel L. Reger, James R. Gardinier

Chemistry Faculty Research and Publications

A simple, one-pot preparation of rhenium(I) σ-arylalkynyl complexes is reported using thallium(I) hexafluorophosphate as a halogen abstraction agent. This new route to rhenium σ-alkynyls enjoys higher yields compared to analogous preparations using silver salts by eliminating potential electrochemical degradation pathways.

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Hexabenzo[4.4.4]Propellane:  A Helical Molecular Platform For The Construction Of Electroactive Materials, Paromita Debroy, Sergey V. Lindeman, Rajendra Rathore Jan 2007

Hexabenzo[4.4.4]Propellane:  A Helical Molecular Platform For The Construction Of Electroactive Materials, Paromita Debroy, Sergey V. Lindeman, Rajendra Rathore

Chemistry Faculty Research and Publications

Helical hexabenzo[4.4.4]propellane (a relative of hexaphenylethane) and its derivatives are synthesized and their structures are established by X-ray crystallography. Isolation and X-ray crystallographic characterization of a robust trication-radical salt of hexamethoxypropellane derivative confirms that its framework is stable toward oxidative (aliphatic) C−C bond cleavage. It is also demonstrated that propellane can be easily brominated at the 4,4‘-positions of the biphenyl linkages for its usage as a molecular platform for the preparation of electroactive materials.

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Practical Synthesis Of Unsymmetrical Tetraarylethylenes And Their Application For The Preparation Of [Triphenylethylene−Spacer−Triphenylethylene] Triads, Moloy Banerjee, Susanna J. Emond, Sergey V. Lindeman, Rajendra Rathore Jan 2007

Practical Synthesis Of Unsymmetrical Tetraarylethylenes And Their Application For The Preparation Of [Triphenylethylene−Spacer−Triphenylethylene] Triads, Moloy Banerjee, Susanna J. Emond, Sergey V. Lindeman, Rajendra Rathore

Chemistry Faculty Research and Publications

We have demonstrated that reactions of diphenylmethyllithium with a variety of substituted benzophenones produces corresponding tertiary alcohols that are easily dehydrated, without any need for purification, to produce various unsymmetrical and symmetrical tetraarylethylenes in excellent yields. The simplicity of the method allows for the preparation of a variety of ethylenic derivatives in multigram (10−50 g) quantities with great ease. The methodology was successfully employed for the preparation of various triphenylethylene (TPE)-based triads (i.e., TPE−spacer−TPE) containing polyphenylene and fluoranyl-based spacers. The ready availability of various substituted tetraarylethylenes allowed us to shed light on the effect of substituents on the oxidation potentials …

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Borazans:  Tunable Fluorophores Based On 2-(Pyrazolyl)Aniline Chelates Of Diphenylboron, Brendan J. Liddle, Rosalice M. Silva, Tyler James Morin, Felipe P. Macedo, Ruchi Shukla, Sergey V. Lindeman, James R. Gardinier Jan 2007

Borazans:  Tunable Fluorophores Based On 2-(Pyrazolyl)Aniline Chelates Of Diphenylboron, Brendan J. Liddle, Rosalice M. Silva, Tyler James Morin, Felipe P. Macedo, Ruchi Shukla, Sergey V. Lindeman, James R. Gardinier

Chemistry Faculty Research and Publications

The reaction between 2-pyrazolyl-4-X-anilines, H(pzAnX), (X = para-OMe (L1), Me (L2), H (L3), Cl (L4), CO2Et (L5), CF3 (L6), CN (L7)) and triphenylboron in boiling toluene affords the respective, highly emissive N,N‘-boron chelate complexes, BPh2(pzAnX) (X = para-OMe (1), Me (2), H (3), Cl (4), CO2Et (5), CF3 (6), CN (7)) in high yield. The …

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Preparation Of Chiral Cholestanofluorene And Its Electron-Rich Derivatives For Isolation Of A Stable Cation−Radical Salt, Paromita Debroy, Ruchi Shukla, Sergey V. Lindeman, Rajendra Rathore Jan 2007

Preparation Of Chiral Cholestanofluorene And Its Electron-Rich Derivatives For Isolation Of A Stable Cation−Radical Salt, Paromita Debroy, Ruchi Shukla, Sergey V. Lindeman, Rajendra Rathore

Chemistry Faculty Research and Publications

A simple and practical synthesis of a variety of chiral fluorene derivatives is described where a cholestane moiety is attached to the carbon 9 of the fluorene ring system from readily available starting materials. An appropriately substituted fluorene derivative (i.e., R = OMe) forms a highly colored (chiral) cation−radical that can be isolated as robust hexachloroantimonate salt. Interestingly, the simplest cholestanofluorene (i.e., R = H) can also be transformed into a dibromo derivative (i.e., R = Br), a precursor to the (poly)cholestanofluorenes where the cholestane moieties will serve not only as groups that impart chirality but also allow them to …

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Electron Transfer Prompted Ejection Of A Tightly Bound K+ From The Ethereal Cavity Of A Hexaarylbenzene-Based Receptor, Ruchi Shukla, Sergey V. Lindeman, Rajendra Rathore Jan 2007

Electron Transfer Prompted Ejection Of A Tightly Bound K+ From The Ethereal Cavity Of A Hexaarylbenzene-Based Receptor, Ruchi Shukla, Sergey V. Lindeman, Rajendra Rathore

Chemistry Faculty Research and Publications

Synthesis of a pair of rotamers (9u/9s) of a hexaarylbenzene derivative containing six (cofacially arranged) electroactive 2,5-dimethoxytolyl groups is described. The toroidal electronic stabilization due to the circular arrangement of aryl groups in 9u/9s leads to the observation of multiple (reversible) oxidation waves and lowering of their Eox1 by ∼250 mV relative to model compounds. The binding of K+ to symmetrical rotamer 9s was monitored by an electrochemical method and further confirmed by X-ray crystallography.

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Conserved Amino Acids In Each Subunit Of The Heteroligomeric Trna M1A58 Mtase From Saccharomyces Cerevisiae Contribute To Trna Binding, Sarah G. Ozanick, Janusz M. Bujnicki, Daniel S. Sem, James T. Anderson Jan 2007

Conserved Amino Acids In Each Subunit Of The Heteroligomeric Trna M1A58 Mtase From Saccharomyces Cerevisiae Contribute To Trna Binding, Sarah G. Ozanick, Janusz M. Bujnicki, Daniel S. Sem, James T. Anderson

Chemistry Faculty Research and Publications

In Saccharomyces cerevisiae, a two-subunit methyltransferase (Mtase) encoded by the essential genes TRM6 and TRM61 is responsible for the formation of 1-methyladenosine, a modified nucleoside found at position 58 in tRNA that is critical for the stability of . The crystal structure of the homotetrameric m1A58 tRNA Mtase from Mycobacterium tuberculosis, TrmI, has been solved and was used as a template to build a model of the yeast m1A58 tRNA Mtase heterotetramer. We altered amino acids in TRM6 and TRM61 that were predicted to be important for the stability of the heteroligomer based on …

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Use Of Factor Analysis In Multi‐Electron Spectroelectrochemistry, Michael D. Ryan, Robert L. Keesey Jan 2007

Use Of Factor Analysis In Multi‐Electron Spectroelectrochemistry, Michael D. Ryan, Robert L. Keesey

Chemistry Faculty Research and Publications

Spectroelectrochemistry and voltammetry contain both unique and complementary information. For multielectron transfers, information on each electron exchange is only directly accessible in the voltammetric data if the potentials are well separated so that two distinct waves can be observed. If the E°’s are close together, the voltammetric data will contain the sum of the two exchanges which can only be deconvoluted by modeling the system and solving the appropriate equations. On the other hand, the spectroscopic data contains direct information on each electron exchange even when the E°’s are close together. Unfortunately, this information cannot be readily extracted if the …

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Lanthanide Complexes As Fluorescent Indicators For Neutral Sugars And Cancer Biomarkers, Onur Alpturk Jan 2007

Lanthanide Complexes As Fluorescent Indicators For Neutral Sugars And Cancer Biomarkers, Onur Alpturk

LSU Doctoral Dissertations

Simple water soluble lanthanum and europium complexes are effective at detecting neutral sugars as well as glyco- and phospholipids. In solutions at physiologically relevant pH the fluorescent lanthanum complex binds neutral sugars with apparent binding constants comparable to those of arylboronic acids. Interference from commonly occurring anions is minimal. The europium complex detects sialic acid-containing gangliosides at pH 7.0 over an asialoganglioside. This selectivity is attributed, in large part, to the cooperative complexation of the oligosaccharide and sialic acid residues to the metal center, based on analogous prior studies. In MeOH, lysophosphatidic acid (LPA), a biomarker for several pathological conditions …

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Xanthene/Benzoxanthene Dyes: Novel Synthetic Metholologies, Applications In Molecular Recognition, Cellular Imaging And The Design Of A Tunable White (Rgb) Light Emitter, Youjun Yang Jan 2007

Xanthene/Benzoxanthene Dyes: Novel Synthetic Metholologies, Applications In Molecular Recognition, Cellular Imaging And The Design Of A Tunable White (Rgb) Light Emitter, Youjun Yang

LSU Doctoral Dissertations

My graduate work has focused on the development of new fluorophore materials towards addressing several interdisciplinary research problems. Selective detection of sialic acid via a boron-amide interaction. Concentration changes of sialic acid can be monitored ratiometrically in the visible region using a boronic acid based chemosensor. The technique shows great promise for the detection of sialic acid, a critical cell surface residue involved in cancer, graft rejection and virulence in certain bacteria. There is no interference from commonly occurring oligosaccharides, aminosugars and most carboxylic acid-containing compounds. Improved synthetic methodology and studies of novel molecular probe architectures. I have developed a …

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Syntheseses [Sic] And Evaluation Of Porphyrin Derivatives For Applications In Medicine And In Material Science, Erhong Hao Jan 2007

Syntheseses [Sic] And Evaluation Of Porphyrin Derivatives For Applications In Medicine And In Material Science, Erhong Hao

LSU Doctoral Dissertations

Chapter 1 presents a concise introduction to porphyrins, especially on the synthesis of meso-tetraphenylporphyrins, which were synthesized during the course of my research and were used for further purposes in the following chapters. Chapter 2 describes the synthesis of a series of cobaltacarborane-porphyrin conjugates for the boron neutron capture therapy (BNCT) of tumors. Using an efficient and high yield ring-opening reaction, N-substituted porphyrins were also synthesized. The spectroscopic and structural properties of these compounds are presented. These high percentage boron and amphiphilic compounds are promising boron delivery agents for BNCT (prelimary cellular studies using some of these compounds have been …

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Synthesis And Functionalizations Of Tetrapyrrole Derivatives, Lijuan Jiao Jan 2007

Synthesis And Functionalizations Of Tetrapyrrole Derivatives, Lijuan Jiao

LSU Doctoral Dissertations

Chapter 1 of this Dissertation presents a brief overview of the history of tetrapyrrole derivatives and of their fundamental properties. Overviews of porphyrins, benzoporphyrins, chlorins and porphycenes are presented. Work presented in Chapter 2 through Chapter 4 mainly focuses on the syntheses and functionalization of chromophore-extended porphyrin derivatives. Several new synthetic routes for the syntheses and functionalizations of extended porphyrins either at the β-position or at the meso-position of porphyrin are developed. From these improved synthetic routes, the regio-selective syntheses of porphyrin derivatives are described. Chapter 2 mainly focuses on the syntheses of β,β'-fused methylenepropanoporphyrins and related porphyrin dimers. Chapter …

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Chemical Differences Of Atherosclerotic Plaques In Native And Bypass Human Coronary Arteries And Diseased And Non-Diseased Human Aortas, Samuel Jean Washington Jan 2007

Chemical Differences Of Atherosclerotic Plaques In Native And Bypass Human Coronary Arteries And Diseased And Non-Diseased Human Aortas, Samuel Jean Washington

LSU Doctoral Dissertations

ABSTRACT Cardiovascular disease, primarily atherosclerosis involves a number of distinct processes that are associated with plaque development. The use of differential gel electrophoresis to determine differences between proteins produced in native and bypass coronary arteries from the same heart has been studied. The analytical techniques presented in this study to characterize plaque samples include two dimensional gel electrophoresis, sodium dodecylsulfate polyacrylamide gel electrophoresis, mass spectrometry, differential gel electrophoresis, and high performance liquid chromatography. An overview of the stages involved in atherosclerosis and the theories implicated in the manifestation of atherosclerosis was presented. A design study using the Box Behnken method …

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Formation Of In- (2×1) And In Islands On Si (100) - (2×1) By Femtosecond Pulsed Laser Deposition, M. A. Hafez, H. E. Elsayed-Ali Jan 2007

Formation Of In- (2×1) And In Islands On Si (100) - (2×1) By Femtosecond Pulsed Laser Deposition, M. A. Hafez, H. E. Elsayed-Ali

Electrical & Computer Engineering Faculty Publications

The growth of indium on a vicinal Si (100) - (2×1) surface at room temperature by femtosecond pulsed laser deposition (fsPLD) was investigated by in situ reflection high-energy electron diffraction (RHEED). Recovery of the RHEED intensity was observed between laser pulses and when the growth was terminated. The surface diffusion coefficient of deposited In on initial two-dimensional (2D) In- (2×1) layer was determined. As growth proceeds, three-dimensional In islands grew on the 2D In- (2×1) layer. The RHEED specular profile was analyzed during film growth, while the grown In islands were examined by ex situ atomic force microscopy. The full …

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An Experiment Using A Simple Photoassisted Fuel Cell Designed To Remediate Simulated Wastewater, John Cassidy, Faisa Touati, Kevin Mcguigan Jan 2007

An Experiment Using A Simple Photoassisted Fuel Cell Designed To Remediate Simulated Wastewater, John Cassidy, Faisa Touati, Kevin Mcguigan

Articles

Work in photochemistry work peaked in the 1980’s where there was the prospect of using sunlight shining on suspensions of titanium dioxide in order to catalytically cleave water into hydrogen and oxygen [1-5]. In this way a clean and efficient method of producing hydrogen as a fuel was envisaged. However, there was a requirement to use a rather high energy light to achieve the splitting and it was not as efficient with visible light[5]. Doped TiO2 layers have been used in a three electrode system for formic acid degradation[6]. In this work, the system uses an electrode coated with TiO2 …

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Kinetic Study Of Selective Co Oxidation Over Pt-Co-Ce/Al_2o_3 Catalyst In Hydrogen-Rich Streams, Göktuğ Nezi̇hi̇ Özyönüm, Ayşe Ni̇lgün Akin, Ramazan Yildirim Jan 2007

Kinetic Study Of Selective Co Oxidation Over Pt-Co-Ce/Al_2o_3 Catalyst In Hydrogen-Rich Streams, Göktuğ Nezi̇hi̇ Özyönüm, Ayşe Ni̇lgün Akin, Ramazan Yildirim

Turkish Journal of Chemistry

The kinetics of the selective CO oxidation was studied in a fixed-bed microreactor at atmospheric pressure over Pt-Co-Ce/Al_2O_3 catalyst, which was prepared using the incipient to wetness co-impregnation technique. Intrinsic kinetic data were obtained in the initial rate region using 8 different sets of CO and O_2 concentrations, each at 2 space times, i.e. 2 catalyst loadings, at 110 °C. The kinetic models based on elementary reaction steps were constructed and tested using nonlinear regression analysis with Levenberg-Marquardt algorithm. The alternative models proposed for the similar catalytic systems in the literature were also tested. It was found that Pt-Co-Ce/Al_2O_3 acts …

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Matrix Effects, Development Of Clean-Up And Lc-Techniques Contributing Towards A Reference Lcms Method For The Analysis Of Lipophilic Marine Toxins, Mairead Anne Mcelhinney Jan 2007

Matrix Effects, Development Of Clean-Up And Lc-Techniques Contributing Towards A Reference Lcms Method For The Analysis Of Lipophilic Marine Toxins, Mairead Anne Mcelhinney

Masters

The most widely used reference method in Europe for the detection and monitoring of lipophilic marine toxins is the Mouse Bioassay (MBA) as first described by Yasumoto et al., (1978). The MBA offers a good level of protection to human health and is capable of detecting the overall toxicity of previously known toxins. However, there are drawbacks associated with the use of the MBA as it is both expensive and time consuming and can give false positives due to interferences (Suzuki et al, 1976). The problems associated with the original mouse bioassay have led to several modifications (Yasumoto et al, …

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Structures And Reactivities Of Ionized And Metal Cation-Containing Acetylene Clusters, Paul O. Momoh Jan 2007

Structures And Reactivities Of Ionized And Metal Cation-Containing Acetylene Clusters, Paul O. Momoh

Theses and Dissertations

In this dissertation, the ion mobility technique is used to determine the structures of small acetylene cluster ions, (C2H2)1-3+, mass-selected from the largest ever reported ionized acetylene clusters. The technique is also used to characterize the reaction of acetylene clusters with water in an effort to elucidate thermochemistry and kinetics of some interesting ion-molecule reactions suspected to occur in interstellar clouds and other interplanetary bodies.A combination of ion mobility measurements, collision induced dissociation (CID), and theoretical calculations are used to provide the most conclusive evidence for the frequently hypothesized trimerization of ionized acetylene to form the benzene ion. The results …

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