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Articles 1 - 28 of 28
Full-Text Articles in Chemistry
Studies On Electrochemical Hydrogen Isotope Separation, Liyanage Mayura Sankalpa Silva
Studies On Electrochemical Hydrogen Isotope Separation, Liyanage Mayura Sankalpa Silva
All Dissertations
Graphene-integrated Proton Exchange Membrane (PEM) electrochemical cells have emerged as a novel area of scientific investigation in the realm of hydrogen isotope separation. Chemical Vapor Deposited (CVD) graphene has been especially useful due to its large-scale production capability for scaling-up purposes. The research described in this dissertation explores the role that inadvertent introduction of cations, notably ammonium and copper, during the CVD graphene transfer onto PEM substrates, such as Nafion, might play in affecting hydrogen ion transport and isotope separation in PEM electrochemical cells. An extensive review of existing literature exposed a gap concerning unintentional cation introductions during graphene transfer, …
Computational And Experimental Investigations Of Alkali Cation Interactions At The Rutile – Water Interface, Isaac Johnston
Computational And Experimental Investigations Of Alkali Cation Interactions At The Rutile – Water Interface, Isaac Johnston
All Dissertations
Overall, the objective of this dissertation was to investigate the degree of sorption for the alkali cations on rutile to ascertain the impact of different cation properties, such as ion size and charge density, on sorption mechanics as well as probe how the ion may alter the surface – aqueous interface. Initial molecular dynamic simulations and batch experiments showed minimal surface sorption for any alkali cation at relatively low concentrations while simultaneously suggesting the enthalpy of deprotonation shifts slightly in the presence of the alkali cations at different ionic strengths. The cations are likely causing small reorientations of the near-surface …
Isolation And Characterization Of Extracellular Vesicles From Various Biological Matrices Using Capillary-Channeled Polymer (C-Cp) Fiber Solid-Phase Extraction Spin-Down Tips, Kaylan Jackson
All Dissertations
A number of recent works have emphasized the need to isolate nanometer-scale analytes, like extracellular vesicles (EVs), from various biologically-relevant fluids. Exosomes are a subset of small EVs that range from 30-200 nm in diameter that serve as biomolecular snapshots of their cell of origin containing mother cell-specific DNA, miRNA, mRNA, and proteins. As critical components of intercellular communication, exosomes and other EVs play significant roles in many physiological and pathological processes. Diverse populations of these vesicles can be collected from biofluids, including blood, saliva, and urine, from cell culture conditioned media and primary cells, and even from plant …
Development Of Plasmonic And X-Ray Luminescence Nanoparticles For Bioimaging And Sensing Applications, Meenakshi Ranasinghe
Development Of Plasmonic And X-Ray Luminescence Nanoparticles For Bioimaging And Sensing Applications, Meenakshi Ranasinghe
All Dissertations
This dissertation discusses the development of plasmonic and X-ray luminescence nanoparticles (~100 nm) to use in bioimaging and sensing applications. The nanoparticles have interesting optical properties compared to their atomic levels and bulk materials. The optical properties of nanomaterials can be controlled by changing size, shape, crystal structure, etc. Also, they have a large surface area that can be functionalized with biomolecules. Therefore, the optical properties and biofunctionalized nanomaterials are useful in biomedical applications such as targeted drug delivery, bioimaging, and sensing. The overall theme is to use nanoparticles with interesting optical properties compared to their atomic levels and bulk …
Isolation Of Proteins And Extracellular Vesicles Via Capillary-Channeled Polymer Fiber Stationary Phases, Lacey Billotto
Isolation Of Proteins And Extracellular Vesicles Via Capillary-Channeled Polymer Fiber Stationary Phases, Lacey Billotto
All Theses
Capillary-channeled polymer (C-CP) fiber stationary phases have been developed by the Marcus lab as an alternative approach to traditional, commercially-available silica-based supports for biomacromolecule separations. C-CP columns are created with natural and synthetic base polymers in a variety of chemistries and shapes, allowing for customization of separations, while providing low material costs and ease of construction. The stationary phase is virtually nonporous with respect to the size of proteins and can operate under high linear velocities (~100 mm s-1) while maintaining relatively low backpressures. As a result of these hydrodynamic benefits, low flow resistance at high volume flow …
Radioluminescence Based Biochemical Sensing And Imaging Strategies To Measure Local Drug Release And Ph, Gretchen B. Schober
Radioluminescence Based Biochemical Sensing And Imaging Strategies To Measure Local Drug Release And Ph, Gretchen B. Schober
All Dissertations
In this dissertation we describe methods for measuring infection relevant biochemical analytes using radioluminescent and ultrasound luminescent materials. Films and nanoparticles fabricated with europium doped gadolinium oxysulfide (Gd2O2S:Eu3+) are used to quantitatively measure radiolabeled pharmaceutical concentration, specifically tritium labeled vancomycin (3H-vancomycin). Europium and dysprosium doped strontium aluminate is used to fabricate an ultrasound modulated, pH sensing film. These methods are indicated for theranostic evaluation of implant associated infection. Bacterial biofilms are inherently resistant to traditional antibiotic treatment and can coat biomedical implants. These biofilm related infections are difficult or impossible to eradicate …
Analyses Of Multivitamins In Nutraceuticals By Reverse Phase Hplc With Dad, Elsd And Ms, Hsiang-Chi Huang
Analyses Of Multivitamins In Nutraceuticals By Reverse Phase Hplc With Dad, Elsd And Ms, Hsiang-Chi Huang
All Theses
ABSTRACT
Vitamins are essential to human beings and support long-term healthy lifestyle. They exist widely in food, but in small amount. Hence, dietary supplements and fortified food products are more and more popular in the nutritional markets. According to the Infant Formula Act of 1980, the range of each of the nutrients should fall within a specific range or above the required minimum, so there is an increasing interest of accurate measurement of vitamins, particularly the B-group vitamins. However, traditional methods for vitamin B analyses are time-consuming and often in poor accuracy. As a result, rapid and reliable analytical methods …
Sample Preparation Techniques For The Improvement Of Analytical Measurements: Capillary-Channeled Polymer Fibers Employed In Protein Solid Phase Extraction Applications And Characterization Of Active Components In Botanical Dietary Supplements, Carolyn Burdette
All Dissertations
The task of sample preparation encompasses many challenges and demands for analytical techniques. Appropriate preparative steps can be the determining factor between successful measurements and failures. Too little preparation can lead to the inability to detect analytes due to low concentrations, insufficient extraction of analytes, and/or strong matrix effects; exhaustive preparation steps increases analysis times, the potential for analyte losses, and the difficulty to obtain consistent reproducible results. Discussed here are several examples of analytical techniques where sample preparation is critical and can be used to improve existing techniques. Capillary-channeled polymer (C-CP) fibers used for solid phase extraction (SPE) protein …
Surface Modifications Of Capillary-Channeled Polymer (C-Cp) Fibers For Applications In Highly Selective Separations, Jennifer Pittman
Surface Modifications Of Capillary-Channeled Polymer (C-Cp) Fibers For Applications In Highly Selective Separations, Jennifer Pittman
All Dissertations
High Performance Liquid Chromatography (HPLC) is a key component in the purification and separation of biological samples. Stationary phases in HPLC are generally silica based porous particles or monoliths designed with high surface area and high capacities in mind. However, in the field of macromolecule separations, specifically proteins, the porous based stationary phases have inherent issues that include slow mass transfer, high operating back pressures, and analyte carryover. Recent research has looked to non-porous polymeric materials as stationary phases in HPLC to overcome these challenges. Specifically, fibrous based polymer stationary phases exhibit significant benefits for macromolecules that include improved mass …
Perfluoroalkyl Phosphonic And Phosphinic Acid Electrolytes For Proton Exchange Membrane Fuel Cells, Mahesha Herath
Perfluoroalkyl Phosphonic And Phosphinic Acid Electrolytes For Proton Exchange Membrane Fuel Cells, Mahesha Herath
All Dissertations
Perfluorinated sulfonic acid polymers have been considered as the state-of-art membrane materials for proton exchange membrane fuel cells. A major technical issue with these polymers is that they do not function well at temperatures above 80 °C and at low humidities. Therefore, research has been focused on developing PEM materials that can operate independent of hydration requirements. The operation of fuel cells at high temperature (e.g. 120 oC) increases fuel cell system efficiency due to faster electrode kinetics and better CO tolerance. This dissertation will describe a study of proton-transport rates and mechanisms under anhydrous and aqueous conditions using a …
Chemical Characterization Of Botanical Products: Comprehensive Speciation By Liquid Chromatography Particle Beam Mass Spectrometry, Joaudimir Castro Georgi
Chemical Characterization Of Botanical Products: Comprehensive Speciation By Liquid Chromatography Particle Beam Mass Spectrometry, Joaudimir Castro Georgi
All Dissertations
The dietary supplement industry has expanded and many of these supplements have become an important aspect of people's everyday lives. In 1994, the U.S. Dietary Supplement Health and Education Act (DSHEA) classified numerous nutraceutical/botanical products as dietary supplements because of their beneficial medicinal properties and provided the necessary regulation to the supplement producers. Since then, the interest of the scientific community towards dietary supplements has grown intensively and numerous studies have been carried out in order to understand the chemical behavior of the active molecules in the human body. The development towards analytical methods for the quantification of the active …
Comparison Of Rna Quality From Stressed And Unstressed Recombinant Escherichia Coli, Mary Alice Salazar
Comparison Of Rna Quality From Stressed And Unstressed Recombinant Escherichia Coli, Mary Alice Salazar
All Theses
High quality, intact RNA is required for DNA microarray studies, cloning, and reverse transcriptase polymerase chain reaction (rt-PCR) analysis. There are several analytical methods used to assess the RNA quality. The RNA Integrity Number (RIN) from the Agilent Bioanalyzer is one quality control assay used to evaluate RNA. For recombinant Escherichia coli cultured under stressful conditions the RNA profiles obtained using the Agilent Bioanalyzer indicate RNA degradation; however, RNA obtained and purified in parallel from unstressed recombinant cultures indicate acceptable RNA values without significant degradation. We proposed that for stressed E. coli the RIN value is not necessarily indicative of …
Synthesis, Modification Of Mesoporous Carbons And Their Application In Polymer Electrolyte Membrane Fuel Cells, Bing Liu
All Dissertations
Mesoporous carbon materials of carbon xerogel (CX) and silica-templated carbon (MC) were synthesized and explored as catalyst supports alternative to the most-commonly-used carbon black (CB) support, for polymer-electrolyte-membrane fuel cell (PEMFC) application. Pt catalyst was loaded on these carbons and electrodes were fabricated from them. These Pt-loaded carbon supports were characterized with XRD, TEM, ex-situ and in-situ cyclic voltammetry, etc. The fabricated electrodes were evaluated in single-cell testing in comparison with commercial CB-supported Pt catalyst fabricated electrodes. The experimental results showed that CX-supported Pt catalyst had close or better performance than that of CB-supported Pt, possibly due to CX's 3-D …
Synthesis And Characterization Of Metallic, Core-Shell And Composite Nanoparticles, Amar Kumbhar
Synthesis And Characterization Of Metallic, Core-Shell And Composite Nanoparticles, Amar Kumbhar
All Dissertations
ABSTRACT
Silver nanoparticles exhibit size, shape and the surrounding dielectric medium dependent optical properties (scattering and absorption) in the visible spectral region. These optical properties can be explained in terms of the collective oscillation of the 'free conduction band electrons' or 'surface plasmons' induced by an external electromagnetic field. Dipole and Quadrupole Plasmon resonances have been observed for silver particles less than 100nm in diameter prepared using various synthetic techniques. However higher order resonances have been elusive due to lack of experimental techniques to prepare colloidal solutions of large silver nanoparticles in the size range above 100nm. Controlled hydrogen reduction …
Development Of A Fluorescent Probe For Determination Of Water Transport In Subcellular Organelles, Adriana Chaurra-Arboleda
Development Of A Fluorescent Probe For Determination Of Water Transport In Subcellular Organelles, Adriana Chaurra-Arboleda
All Dissertations
Water transport has been widely studied in a variety of cells and isolated membranes. However, the intrinsic complexity related with the study of intracellular processes has delayed the development of an analytical technique for the study of water transport in subcellular compartments of living cells. This study represents the development and application of a ratiometric fluorescent probe to study water transport in endocytic organelles of intact living cells. The probe is based on the use of a D2O-sensitive fluorophore, Lucifer yellow dextran (LY-dex), together with a D2O-insensitive fluorophore, Alexa fluor 546 dextran (AF546-dex), used as an …
Fundamental Aspects Of Small Molecules And Macromolecules On Poly(Ethylene Terephthalate) Capillary-Channeled Polymer Fibers, Christine Straut
Fundamental Aspects Of Small Molecules And Macromolecules On Poly(Ethylene Terephthalate) Capillary-Channeled Polymer Fibers, Christine Straut
All Dissertations
Stationary phases and adsorbents are continually being developed to enhance separations in high performance liquid chromatography (HPLC). Polymeric stationary phases have gained popularity due to their ability to be employed over a large pH range and because they are more chemically robust when compared to silica based phases. Capillary-channeled polymer (C-CP) fibers are an alternative to traditional porous packed bed beads. These fibers have a unique geometry with increased the surface area/volume ratios when compared to cylindrical fibers. Very unique characteristics are realized in the use of the C-CP fibers, including drastically reduced backpressures and selection of solute-surface interaction through …
Investigation Of Photophysical And Photochemical Processes In Conjugated Polymer Nanoparticles By Single Particle And Ensemble Spectroscopy, Craig Szymanski
Investigation Of Photophysical And Photochemical Processes In Conjugated Polymer Nanoparticles By Single Particle And Ensemble Spectroscopy, Craig Szymanski
All Dissertations
Single molecule imaging has emerged as a powerful tool in a range of applications, but the field is limited by a lack of fluorescent probes with sufficient brightness and photostability for many demanding applications such as tracking of single biomolecules in cells and tissues at video rate with 1 nm spatial resolution. Conjugated polymers hold great promise as a solution to these issues, with a high density of π electrons and variety of chemistries, allowing efficient and tunable absorption of light. This dissertation describes the development and characterization of a novel type of nanoparticle composed of conjugated polymer called CPdots. …
Synthesis, Characterization, And Application Of Ag Nanostructures, Stephen Hudson
Synthesis, Characterization, And Application Of Ag Nanostructures, Stephen Hudson
All Dissertations
Noble metal nanoparticles (NPs) have been used for many centuries; however their properties were not truly scrutinized until Michael Farady's investigations in the 1850's. Advances in the field of nanotechnology over the last three decades have enabled insights into the properties of materials as their dimensions are reduced to the nanoscale. The repercussions of these insights are seen in many modern applications.
In this dissertation, properties of novel nanostructures based on Ag NPs are presented and discussed. The exceptional optical properties of Ag NPs stem from the collective oscillations of the conduction electrons known as plasmon resonances. The excitation of …
Fabrication And Optical Properties Of Noble Metal Nanostructures, Mark Kinnan
Fabrication And Optical Properties Of Noble Metal Nanostructures, Mark Kinnan
All Dissertations
Experimental and theoretical results are presented in Chapters 2, 3, and 4 on the effects of dielectric medium, particle size, and interparticle distance, respectively, on plasmon coupling in two-dimensional arrays of silver nanoparticles. The arrays were fabricated via the self-assembly of single crystal particles from c.a. 46 nm to 287 nm on PVP-modified glass substrates. Spin-coated poly(methylmethacrylate) layers were used to immobilize the particles and prevent their surface aggregation. Varying the thickness of the PMMA layer made it possible to change the average dielectric medium between the particles. UV-Visible spectra of different arrays were compared to the corresponding electron microscope …
Synthesis And Electrochemical Studies In Microstructured Media, Jamie Norton
Synthesis And Electrochemical Studies In Microstructured Media, Jamie Norton
All Dissertations
In-situ electrochemical methods involving both oxidative and reductive mediators were employed to modify the oxidation state (doping level) of PEDOT polymers in colloidal PEDOT-coated silica core-shell particles that were prepared as a dispersion encapsulated in a hydrogel matrix. The modifications of the redox states of the PEDOT coating induced a change in the absorbance characteristics. A mediated electron transfer system was employed to ferry charge from the electrodes of the cell to the isolated particles. The mediator diffuses between the electrode surface and the PEDOT-coated particles to accomplish (de)doping. The developed system was a fully self-contained and electrically driven device. …
Preparation And Characterization Of Macroporous Electrodes For Electrochemical Bioassays, Ashwin Rao
Preparation And Characterization Of Macroporous Electrodes For Electrochemical Bioassays, Ashwin Rao
All Dissertations
Applications such as point-of-care medical diagnosis and in-the-field biological warfare agent detection require portable bioassays which are less laborious yet cost effective. Conventional sandwich bioassays see limited use for such applications as it involves time consuming steps of reagent treatment and washings, and are restricted to use inside laboratories. We explore new platforms for sandwich bioassays required by such applications. The platform we have developed is based on electrochemical methods of detection. Flow-through three-dimensional electrodes suitable for use in electrochemical sandwich bioassays were fabricated. A composite of superporous agarose and reticulated vitreous carbon (SPA-RVC) material was used for the fabrication …
Development Of Fullerene Based Sturctures For Photovoltaic And Electronic Applications, Amit Palkar
Development Of Fullerene Based Sturctures For Photovoltaic And Electronic Applications, Amit Palkar
All Dissertations
Solar energy can be envisioned as a long term alternative to rapidly depleting fossil fuels. The energy from the sun can be harnessed by constructing donor-acceptor (D-A) type devices where the incident photon induces the transfer of an electron from the donor to the acceptor. If recombination is prevented, this electron can then be channeled through an external circuit, thus leading to the generation of photocurrent. Porphyrins, which are the naturally occurring pigments in photosynthesis, have been widely established as donors while fullerenes, such as C60 and C70 , due to their unique electron accepting properties, have been …
Lithium-Conducting Ionic Melt Electrolytes From Oligomeric Ethylene Glycols: Synthesis And Characterization, Boutros Hallac
Lithium-Conducting Ionic Melt Electrolytes From Oligomeric Ethylene Glycols: Synthesis And Characterization, Boutros Hallac
All Dissertations
Commercial lithium ion cells consist of electrolytes that undergo salt concentration polarization which is acute upon high discharge currents. This type of polarization occurs as a result of the mobility of more than one ionic species in the presence of an electric field. One way to overcome it is by employing a material that would allow the mobility of one ionic species. This thesis will describe the synthesis and characterization of several fluorosulfonimide and fluorosulfonate based ionic liquids/melts as electrolytes having lithium as the only mobile ion. These materials were prepared by the nucleophilic addition reaction of a deprotonated polyether …
Thermodynaimic Study Of Nucleic Acids Recognition By Aminoglycosides , Hongjuan Xi
Thermodynaimic Study Of Nucleic Acids Recognition By Aminoglycosides , Hongjuan Xi
All Dissertations
ABSTRACT
Since the origin of first aminoglycosides antibiotics, streptomycin, isolated by Selman Waksman about 60 years ago, a number of aminoglycosides antibiotics were discovered to treat different infections. Neomycin class aminoglycosides were found to originally target the A site 16S rRNA in the 30S subunit of the ribosome within the Gram-negative bacteria. In addition to its antibacterial effect, aminoglycosides were also found to binding to various other viral RNA structures such as TAR and RRE of HIV, Group I introns and hammerhead ribozyme, implying its potential to be used as antiviral reagent.
Furthermore, previous studies in our laboratory discovered a …
The Glow Discharge - A Multifaceted Optical Emission Source: From Solids Analysis To Metalloproteins, Timothy Brewer
The Glow Discharge - A Multifaceted Optical Emission Source: From Solids Analysis To Metalloproteins, Timothy Brewer
All Dissertations
Glow discharges (GD) are well known for their application to direct solids elemental analysis of metals and alloys by optical emission spectroscopy (GD-OES). The most successful application of GD-OES has been the analysis of solid materials since the GD provides rapid, direct bulk and depth profiling analysis of solids, metals, powders, polymers, glasses and ceramics. However, solids analysis has typically suffered from the lack of true analytical blanks and the inability to study particulate solids in their native state. An approach for the analysis of solid powdered material entrapped in a sol-gel matrix by radio frequency glow discharge optical emission …
Analysis Of Nutraceuticals For Toxic Metals: Development And Validation Of Sample Preparation Method, Julia Cooper
Analysis Of Nutraceuticals For Toxic Metals: Development And Validation Of Sample Preparation Method, Julia Cooper
All Theses
With increasing numbers of health-conscious consumers purchasing nutraceutical supplements, total sales in the nutrition industry have soared to over $200 billion in 2006. It is important to assess the safety of these nutraceutical products, with specific regards to toxic metals, including arsenic, cadmium, lead, and mercury. Because species of these metals may be more toxic than others, they can have hazardous health effects if ingested in excess quantities. The work described in this thesis focuses on the development of a sample preparation method for nutraceutical products, specifically ethanolic tinctures and glycerin-based matrices, and analysis of these products by inductively coupled …
Incorporation Of Capillary-Channeled Polymer (C-Cp) Fibers Into Micropipette Tips For Solid Phase Extraction With Applications In Bioanalysis, Donald Fornea
All Theses
Solid phase extraction (SPE), is a widely used sample preparation method that is currently experiencing a surge in research interest, clever architecture/format development, and stationary phase characterization.1-3 SPE devices commonly exist in syringe, cartridge, disk, and micropipette tip formats.4 Micropipette tip SPE has enhanced the determination of proteins by electrospray ionization (ESI) and matrix assisted laser desorption ionization (MALDI) mass spectrometry (MS) by handling micro-liter volumes of sample and buffer removal/solvent exchange.5-7 Buffers have deleterious effects on ionization taking place in MS sources due to preferential ionization, ion suppression effects, and the formation of adduct species competing for ionization in …
Characterization Of Capillary-Channeled Polymer Fibers As Stationary Phases For High-Performance Liquid Chromatography Of Macromolecules, Dwella Nelson
All Dissertations
Capillary-channeled polymer (C-CP) fibers are being developed and characterized as high-performance liquid chromatography (HPLC) stationary phases for reversed-phase separations of proteins. Conventional porous phases are not well suited for separating large macromolecules due to the slow diffusivity of the molecules, large diffusional distances, and stagnant mobile phase zones within the column. Stationary phases are continually being developed to address the challenges associated with HPLC of proteins and other macromolecules in general. C-CP fiber stationary phases are an alternative to conventional bead technology and offer a variety of chemical and physical advantages. The fibers can be selected for their chemical functionality …