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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Pyrolysis and ignition behavior of coal, cattle biomass, and coal/cattle biomass blends

Martin, Brandon Ray 15 May 2009 (has links)
Increases in demand, lower emission standards, and reduced fuel supplies have fueled the recent effort to find new and better fuels to power the necessary equipment for society’s needs. Often, the fuels chosen for research are renewable fuels derived from biomass. Current research at Texas A&M University is focused on the effectiveness of using cattle manure biomass as a fuel source in conjunction with coal burning utilities. The scope of this project includes fuel property analysis, pyrolysis and ignition behavior characteristics, combustion modeling, emissions modeling, small scale combustion experiments, pilot scale commercial combustion experiments, and cost analysis of the fuel usage for both feedlot biomass and dairy biomass. This paper focuses on fuel property analysis and pyrolysis and ignition characteristics of feedlot biomass. Deliverables include a proximate and ultimate analysis, pyrolysis kinetics values, and ignition temperatures of four types of feedlot biomass (low ash raw manure [LARM], low ash partially composted manure [LAPC], high ash raw manure [HARM], and high ash partially composted manure [HAPC]) as well as blends of each biomass with Texas lignite coal (TXL). Activation energy results for pure samples of each fuel using the single reaction model rigorous solution were as follows: 45 kJ/mol (LARM), 43 kJ/mol (LAPC), 38 kJ/mol (HARM), 36 kJ/mol (HAPC), and 22 kJ/mol (TXL). Using the distributed activation energy model the activation energies were 169 kJ/mol (LARM), 175 kJ/mol (LAPC), 172 kJ/mol (HARM), 173 kJ/mol (HAPC), and 225 kJ/mol (TXL). Ignition temperature results for pure samples of each of the fuels were as follows: 734 K (LARM), 745 K (LAPC), 727 (HARM), 744 K (HAPC), and 592 K (TXL). There was little difference observed between the ignition temperatures of the 50% blends of coal with biomass and the pure samples of coal as observed by the following results: 606 K (LARM), 571 K (LAPC), 595 K (HARM), and 582 K (HAPC).
2

Synthesis of nitrogen-containing carbon nanotubes on copper catalyst

Chiu, Hsiu-yu 21 July 2009 (has links)
none
3

Characterization of Fluoropolymer Powders Made By Supercritical Assisted Mixing With Crystalline Additives

Atem-Tambe, Ntoh 01 January 2005 (has links)
This research project investigates a new technique to efficiently mix crystalline solid additives with polymers by gentle ball milling with steel balls in the presence of carbon dioxide (C02) at 17 to 30°C and 1300 to 2500 psig. As the ball milling system is agitated, the steel balls transfer mechanical energy to the fluoropolymer and additive thereby converting them to powders. C02 is added into the chamber to expand the polymer and make it amenable to impregnation by the additive. At the end of the mixing process, a free flowing powder is produced consisting of the additive coated with fluoropolymer. The additives were extracted from the powders and intrinsic viscosity measurements were done on the remnant fluoropolymer. Viscosity studies showed that the virgin and post-ball milled fluoropolymers had similar intrinsic viscosities, hence similar molecular weights within experimental error limits. This implies that most of the polymer chains were simply disentangled during the mixing process and not broken. Differential Scanning Calorimetry (DSC) and Thermal Gravimetric Analysis (TGA) were done on the virgin polymer, the additives and the fabricated powders to determine the loading levels and to ascertain if there were any changes to the physical properties of the polymer. Scanning electron micrographs showed that some of the powder particles had additive particles stuck on the surface, but when these additives were washed off the surface of the powders with a suitable solvent that did not dissolve the polymer, DSC analysis showed the presence of additive incorporated into the polymer matrix.
4

Regulation of Arabidopsis TGA transcription factors by cysteine residues : implication for redox control

Chubak, Catherine 26 May 2006
The Arabidopsis TGA family of basic leucine zipper transcription factors regulate the expression of pathogenesis-related genes and are required for resistance to disease. Members of the family possess diverse properties in respect to their ability to transactivate and interact with NPR1, the central regulator of systemic acquired resistance in Arabidopsis. Two TGA factors, TGA1 and TGA2, have 83 % amino acid similarity but possess differing properties. TGA1 does not interact with NPR1 but is able to transactivate, while TGA2 interacts with NPR1 but is unable to transactivate. This study uses these two TGA factors to identify amino acids that are responsible for their function. <p>Four cysteines residues within TGA1 were targeted for study by site-directed mutagenesis and the resulting mutants were tested for interaction with NPR1 in yeast. The construct containing a mutation of cysteine 260 (Cys-260) interacted well with NPR1, while those with mutations at Cys-172 or Cys-266 interacted poorly. The Cys-260 mutant also displayed the greatest decrease in transactivation potential in yeast, while mutation of Cys-172 or Cys-266 resulted in smaller decreases. Mutation of Cys-287 had no effect on NPR1 interaction or transactivation. Combining various point mutations in a single protein did not increase NPR1 interaction or transactivation levels, indicating that Cys-260 is crucial for regulating TGA1 properties. Cysteines possess the unique ability of forming reversible disulfide bonds which have been shown to regulate several mammalian cellular processes. The observation that mutation of a single TGA1 cysteine (Cys-260) greatly alters the proteins properties provides a convincing argument that oxidoreduction of this residue is important for its regulation, possibly through the formation of a disulfide bond with either Cys-172 or Cys-266. <p>To test whether other members of the TGA family could be regulated by oxidoreduction, several TGA2 constructs were created that introduced Cys at positions corresponding to those found in TGA1. When tested in yeast none were able to transactivate but continued to interact with NPR1.
5

Regulation of Arabidopsis TGA transcription factors by cysteine residues : implication for redox control

Chubak, Catherine 26 May 2006 (has links)
The Arabidopsis TGA family of basic leucine zipper transcription factors regulate the expression of pathogenesis-related genes and are required for resistance to disease. Members of the family possess diverse properties in respect to their ability to transactivate and interact with NPR1, the central regulator of systemic acquired resistance in Arabidopsis. Two TGA factors, TGA1 and TGA2, have 83 % amino acid similarity but possess differing properties. TGA1 does not interact with NPR1 but is able to transactivate, while TGA2 interacts with NPR1 but is unable to transactivate. This study uses these two TGA factors to identify amino acids that are responsible for their function. <p>Four cysteines residues within TGA1 were targeted for study by site-directed mutagenesis and the resulting mutants were tested for interaction with NPR1 in yeast. The construct containing a mutation of cysteine 260 (Cys-260) interacted well with NPR1, while those with mutations at Cys-172 or Cys-266 interacted poorly. The Cys-260 mutant also displayed the greatest decrease in transactivation potential in yeast, while mutation of Cys-172 or Cys-266 resulted in smaller decreases. Mutation of Cys-287 had no effect on NPR1 interaction or transactivation. Combining various point mutations in a single protein did not increase NPR1 interaction or transactivation levels, indicating that Cys-260 is crucial for regulating TGA1 properties. Cysteines possess the unique ability of forming reversible disulfide bonds which have been shown to regulate several mammalian cellular processes. The observation that mutation of a single TGA1 cysteine (Cys-260) greatly alters the proteins properties provides a convincing argument that oxidoreduction of this residue is important for its regulation, possibly through the formation of a disulfide bond with either Cys-172 or Cys-266. <p>To test whether other members of the TGA family could be regulated by oxidoreduction, several TGA2 constructs were created that introduced Cys at positions corresponding to those found in TGA1. When tested in yeast none were able to transactivate but continued to interact with NPR1.
6

Shale characterization using TGA, Py-GC-MS, and NMR

Gips, Jameson Parker 03 February 2015 (has links)
Many of the current analytical techniques originally developed to characterize conventional reservoir rocks and fluid cannot adequately measure shale and source rocks. An example of this is Retort, where it is not feasible to get sufficient fluid from source rock to make useful measurements. The primary interest of this thesis is the exploration of other analytical techniques, two of which are previously unused in the oil and gas industry. These are Thermal Gravimetric Analysis (TGA), Pyrolysis-Gas Chromatography-Mass Spectrometry (Py-GC-MS), and Nuclear Magnetic Resonance (NMR). The techniques proposed offer valuable insight into the properties of the rock. TGA gives accurate weight of a sample as temperature is increased, Py-GC-MS is useful for identifying exact molecules in vaporized fluid, and NMR can be used to characterize viscosity and hydrocarbon chain length. The methods using these techniques can be utilized to further confirm mineralogy of a sample, identify the fluid constituents and quantify their weight, analyze changes in a sample between two different states, and calculate the free fluid saturations of oil and gas in shales. Procedures and results for each of these are presented in this thesis to show methodology and give the reader an idea of its useful applications. / text
7

Resistencia a la Oxidación/Corrosión del Cobre Recubierto con Compuestos de Titanio Mediante Doble Plasma

Oberg Suárez, Héctor Francisco January 2008 (has links)
No description available.
8

Viability of UiO-66 Impregnated with Silver for Carbon Capture

Le, Tin 07 August 2020 (has links)
Carbon dioxide levels have been steadily increasing over the past decades; as of 2019 (411 ppm), CO2 levels are at their highest in over 40 years (330 ppm in 1977); consequently, regulations in certain areas require the reduction of CO2 emissions to combat this trend. For effective carbon capture, we require a sorbent that has high adsorption capacity, stability, and recyclability; in addition, an efficient and economical way to release the captured gas is needed as well. Metal-organic frameworks (MOFs) possess a high surface area for adsorption, but releasing the stored gases requires additional energy input that limits the overall efficiency of carbon capture. Ag/UiO-66 provides a thermally stable complex with a high surface for adsorption of CO2 while the silver nanoparticles utilize light-induced local heating to act as a photoswitch for dynamic release of CO2; visible light in the 400 nm spectrum is used to liberate the captured CO2.
9

Termogravimetrisk analys av olika magnetitsliger från LKAB

Hallberg, Dan January 2013 (has links)
LKAB are in a process to complement the existing underground mines in Kiruna and Malmberget with satellite open pit mines to increase the total amount of ore. This work consist of a long chain of activities from prospecting to integration of the new materials in the production. One important link is to examine and estimate the mineral processing and metallurgical properties of the materials and the effect they may have on the process and the product. This work can be carried out in different scales, from micro studies via laboratory and pilot studies up to plant scale tests. In general it is initially a very small amount of material, maybe some kilograms collected from drill cores, there for is it important to have tools and methods that cover all different process areas and experimental scales. This will give the possibility to do necessary classifications of the different materials early in the development chain and thereby increase the efficiency in the working process.In this work, a method to estimate and compare the oxidation properties of different magnetite materials in micro / laboratory scale is presented. Thermo gravimetric analyse has been used to analyse the materials. There is also a method presented that discuss a way to minimise the effect caused by particle size on the results. Finally has a method to numerical present the oxidation curves been developed. This method will make it easier and contribute to a more objective study and comparability of bigger amount of sample data. / <p>Validerat; 20131014 (global_studentproject_submitter)</p>
10

Identification de deux gènes NPR1chez les VITACEAE, analyse de leur diversité de séquences et interactions avec les facteurs de transcription VvTGA / Identification of two NPR1 genes in the VITACEAE family, analyses of their sequence diversity and the interaction with VvTGA transcription factors

Bergeault, Karine 26 November 2010 (has links)
La vigne est soumise à de nombreuses maladies impliquant l'utilisation de produits phytosanitaires en grande quantité dont l'utilisation est néfaste pour l'environnement et la santé des utilisateurs. Un enjeu est donc de développer des méthodes alternatives à la lutte chimique. La protéine codée par le gène NPR1 (Nonexpressor of pathogenesis-related gene 1) joue un rôle clef dans la résistance à large spectre chez les plantes. Des éliciteurs tels que l'acide salicylique ou des agents pathogènes influencent l'activation de NPR1 dans le cytoplasme. La translocation de NPRl dans le noyau et son interaction avec des facteurs de transcription TGA induit l'expression des gênes PR (Pathogenesis-related). Nous avons identifié sept homologues potentiels des gènes NPR1 et TGA chez Vitis vinifera (VvNPR1.1, VvNPR1.2, VvTGA1 à 5). L'étude de la diversité de séquences dans les exons de 15 accessions de Vitaceae indique qu'ils sont soumis à une forte pression de sélection purificatrice. De plus, l'analyse in silico des régions promotrices des VvNPR1 montre la présence, d'éléments cis-régulateurs potentiels, en réponse aux stress biotiques et abiotiques ainsi que des motifs de liaison à des facteurs de transcription. Une étude plus poussée des introns montre quelques éléments transposables et un faible polymorphisme dans six accessions de Vitis vinifera. Ces résultats argumentent en faveur d'une pression de sélection forte agissant sur ces gènes. Ceci nous a mené à formuler des hypothèses fonctionnelles et à réaliser une étude d'interaction avec les facteurs de transcription VvTGA1 et VvTGA4 par la technique du double hybride. Ces derniers n'interagissent pas avec VvNPR 1.1. / Numerous diseases affect grapevine, resulting in the use of phytochemicals in large quantities that are harmful for environment and user's health. In the long term, the aim is to develop alternative methods to chemicals. The protein encoded by NPR1 (Nonexpressor of pathogenesis-related gene 1) plays a pivotal role in conferring broad spectrum pathogen resistance in plants. Activation of NPR 1 in the cytoplasm is influenced by elicitors such as salicylic acid or pathogens associated with the accumulation of reactive oxygen species. Translocation of NPR1 into the nucleus and interaction with TGA transcription factors induce the expression of PR (Pathogenesis-related) genes. Using a candidate gene approach, we have identified seven putative homologs to NPR1 and TGA in the grapevine genome (VvNPR1.1, VvNPR1.2, VvTGA1 to 5). The study of sequence diversity in exons of 15 accessions of the Vitaceae family indicates that these exons are subjected to a strong purifying selection pressure. Moreover, in silico analysis in the promoters of VvNPR1 shows putative cis-regulator elements, in answer to biotic and abiotic stresses as well as link patterns to transcription factors. An intron study shows transposable elements and a low polymorphism in six accessions of Vitis vinifera. These results suggest a strong selection pressure on these genes. Functional hypotheses were formulated, and an interaction study with transcription factors VvTGA1 and VvTGA4 was conducted using a method based on yeast two hybrid, showing that they do not interact with VvNPR1.1.

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