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Azzu, Vian. "Deactivation of mitochondrial uncoupling proteins". Thesis, University of Cambridge, 2009. https://www.repository.cam.ac.uk/handle/1810/252159.
Pełny tekst źródłaDevadas, P. "Catalyst deactivation in propane aromatization". Thesis(Ph.D.), CSIR-National Chemical Laboratory, Pune, 1997. http://dspace.ncl.res.in:8080/xmlui/handle/20.500.12252/3145.
Pełny tekst źródłaO'Toole, Ann Marie. "Thermal deactivation of Pseudomonas aeruginosa biofilms". Thesis, University of Iowa, 2015. https://ir.uiowa.edu/etd/1715.
Pełny tekst źródłaArteaga, Colina Geomar Daniel. "Deactivation of Pt/(gamma)-A12O3 during hydrocarbon reactions : mechanism of initial deactivation stages and carbonaceous residue characterisation". Thesis, University of Aberdeen, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.521157.
Pełny tekst źródłaSteiner, Petr. "Kinetic and Deactivation Studies of Hydrodesulfurization Catalysts". Doctoral thesis, Norwegian University of Science and Technology, Department of Chemical Engineering, 2002. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-94.
Pełny tekst źródłaHydrodesulfurization is an important part of the hydrotreating process. More stringent regulations on the quality of fuels bring new requirements to the catalytic processes. The removal of sulfur has become a key issue in the oil refining and this work aims to address several aspects of the process.
Kinetic studies of the hydrodesulfurization reaction over conventional (molybdenum-based) and new (Pt/Y-zeolite) catalysts are reported. The hydrodesulfurization of both the real oil (light gas oil from Statoil Mongstad refinery) and model compounds (thiophene and dibenzothiophene) over a NiMo/γ-Al2O3 catalyst were studied. In a high-pressure study of the light gas oil, substituted alkyl-DBTs were found to be the most difficult to desulfurize and the order of reactivity was found to be DBT > 4-MDBT > 4,6-DMDBT. Steric hindrance together with electronic effects were identified as possible reasons for this behavior. The difference in reactivities of the individual compounds was found to decrease with the increasing reaction temperature. A gas chromatograph equipped with the atomic emission detector (GC-AED) was used for the analysis of the individual components of the oil.
The initial deactivation and the steady-state kinetics were studied during the HDS of thiophene at atmospheric pressure. Unpromoted Mo/γ-Al2O3, CoMo/γ-Al2O3, NiMo/γ-Al2O3, and phosphorus modified NiMo/γ-Al2O3 were used for the deactivation study, while NiMo/γ-Al2O3,CoMo/γ-Al2O3, and Pt/Y-zeolite (with three different pretreatments) were used for the steadystate study. Several experiments related to the deactivation of Mo/γ-Al2O3 and NiMo/γ-Al2O3 catalysts prepared with the chelating agent (NTA) were also performed and NTA was found to have no significant effect on the activity of the catalysts.
In the deactivation study, a fast initial decrease in the activity was observed on all the catalysts. However, nickel promoted catalysts were found to be more resistant to deactivation than unpromoted ones. The presence of phosphorus slightly increased the activity of the catalyst towards the thiophene HDS, but had no effect on the deactivation behavior. Several methods to regenerate the catalyst were investigated. During the resulfiding experiments, a difference between Mo/γ-Al2O3 and NiMo/γ-Al2O3 was observed. Deactivation of the Mo catalyst was more severe with increasing temperature, while for the NiMo catalyst the opposite behavior was observed. Carbon deposition on catalysts followed the similar trend: More carbon was observed on the Mo catalyst at higher temperatures, while the opposite is true for NiMo. The restoration of the activity of NiMo was complete, while the reactivation of the Mo catalyst was only partial. The results from the reactivation experiments with pure H2 and inert gas (helium) suggest that several mechanisms of the restoration of activity exist: Resulfiding of the desulfided active sites, hydrogenation and removal of the deposited carbonaceous species, and the desorption of the reactants and products from the active sites of the catalyst. Based on the observed results, the higher hydrogenation activity of nickel is assumed to be the reason for the behavior. Hydrogenation causes the faster removal of the deposited carbonaceous species and this leads to the conclusion that the desulfiding of the active sites and the adsorption of the reaction species is significantly less pronounced on the NiMo/γ-Al2O3 catalyst.
Characterization studies show differences between standard and NTA-based catalysts. The higher amount of carbon on the NTA catalysts is attributed to the presence of the carboncontaining precursor - NTA. The changes in the surface area and the pore volume were observed only during the sulfiding process. In the case of standard catalysts the surface area and the pore volume decreased, while for the NTA-based catalysts the opposite is true. No change in the surface area and the pore volume with the increasing time on stream indicates that the deactivation is not due to structural changes of the catalyst. The amount of sulfur was found to be constant during the time on stream for all the catalysts.
In the steady-state study of the HDS of thiophene, CoMo and NiMo catalysts were found to be equally active. The activity of the Pt/Y-zeolite catalyst was found to be comparable to conventional catalysts when based on the amount of active material, but a fast deactivation was observed. The product selectivities during the HDS of thiophene were found to be the same for all standard catalysts, but slightly different for the Pt/Y-zeolite catalyst. This was attributed to a higher hydrogenation activity of the Pt/Y-zeolite catalyst.
The inhibition effect of other sulfur compounds and aromatics on the high-pressure hydrodesulfurization of dibenzothiophene (DBT), the so-called “matrix effect” was studied. Thiophene and DMDS have the same inhibiting effect on the total conversion of DBT, but differences exist in the effect on the selectivities of the products at low concentrations. The results indicate that the inhibiting effect of H2S on the direct desulfurization route is stronger than the effect of thiophene on the hydrogenation pathway. In the study of aromatics, both toluene and naphthalene affect the total conversion of DBT. Naphthalene was found to be a much stronger inhibitor and inhibits mainly the direct desulfurization pathway, while the hydrogenation route is more affected by the presence of toluene.
Rashchi, Fereshteh. "Deactivation of Pb-contaminated sphalerite by polyphosphate". Thesis, McGill University, 2000. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=36828.
Pełny tekst źródłaA mechanism of lead interaction is proposed: at weakly acidic to mildly alkaline conditions Pb2+ and PbOH+ adsorb on sphalerite and react with xanthate to form PbX2 and Pb(OH)X; at high pH, hydrophilic Pb(OH)2(s) precipitates depress flotation.
Various candidate deactivators were compared using microflotation. The reagents were diethylenetriamine (DETA), sodium bicarbonate (NaHCO3), silica sol (SS), sodium phosphate (Na3PO4·12H 2O) and sodium polyphosphate (NaPO3)n. The latter had the strongest effect and was selected for detailed study. The mechanism of polyphosphate action was investigated by SEM and XPS. The results show that polyphosphate acted to remove Pb ("clean") from the sphalerite by forming soluble complexes.
The polyphosphate (PP) to lead (Pb) ratio in the complexes was determined from conductometric titration of lead nitrate vs. polyphosphate. It was found that initially a precipitate formed with PP/Pb of 1/3. The precipitate dissolved in excess polyphosphate, resulting in a variety of complexes with PP/Pb of 1/2, 1/1, 3/2, 2/1, and 3/1. Knowing the amount of Pb to be removed and taking the lowest PP/Pb ratio, 1/2, the quantity of polyphosphate required to solubilize the Pb can be calculated.
McQueen, Paul. "Catalysis deactivation in staged direct coal liquefaction". Thesis, Heriot-Watt University, 1996. http://hdl.handle.net/10399/746.
Pełny tekst źródłaMandani, Faisal Mohammad. "Kinetic and deactivation studies during catalytic dehydrogenation". Thesis, University of Salford, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.305913.
Pełny tekst źródłaPaweewan, Boontham. "Coking and deactivation of zeolite-based catalysts". Thesis, University of Cambridge, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.624350.
Pełny tekst źródłaHu, Ing-Feng. "Activation and deactivation of glassy carbon electrodes /". The Ohio State University, 1986. http://rave.ohiolink.edu/etdc/view?acc_num=osu148726339902366.
Pełny tekst źródłaGillan, Claire. "Deactivation of precious metal steam reforming catalysts". Thesis, University of Glasgow, 2010. http://theses.gla.ac.uk/2069/.
Pełny tekst źródłaDixon, Emma Victoria. "Mechanisms of immunoglobulin deactivation by Streptococcus pyogenes". Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:ec80e3f9-0c73-4d39-bc68-c39b927365d4.
Pełny tekst źródłaMishra, Dhananjay. "Electrochemical Deactivation of Nitrate, Arsenate, and Trichloroethylene". Diss., The University of Arizona, 2006. http://hdl.handle.net/10150/194084.
Pełny tekst źródłaZamy, Jean-Paul A. "An investigation of the hydrogenation of phenol over supported palladium catalysts". Thesis, University of Reading, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.270212.
Pełny tekst źródłaMatheson, Martyn. "In-situ characterisation of reforming catalysts undergoing deactivation". Thesis, Brunel University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.263516.
Pełny tekst źródłaThomson, Steven James. "Deactivation gating and pharmacology of hERG potassium channel". Thesis, University of Leicester, 2012. http://hdl.handle.net/2381/11071.
Pełny tekst źródłaSantamaria, Ramiro J. M. "Deactivation and regeneration of fixed bed catalytic reactors". Thesis, University of Salford, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.356187.
Pełny tekst źródłaLarsson, Ann-Charlotte. "Study of Catalyst Deactivation in Three Different Industrial Processes". Doctoral thesis, Växjö : Växjö University Press, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:vxu:diva-1058.
Pełny tekst źródłaRussell, Nigel Vincent. "Thermal deactivation and reactivity of high temperature coal chars". Thesis, Imperial College London, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302505.
Pełny tekst źródła劉毅廷 i Ngai-ting Lau. "An infected zone model for the deactivation of catalysts". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1990. http://hub.hku.hk/bib/B31209786.
Pełny tekst źródłaWalser, Moritz, Rico Fischer, Thomas Goschke, Clemens Kirschbaum i Franziska Plessow. "Intention Retrieval and Deactivation Following an Acute Psychosocial Stressor". Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-133421.
Pełny tekst źródłaBelghazi, Ahmed. "The initial deactivation of a coal liquid hydrocracking catalyst". Thesis, University of Nottingham, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239409.
Pełny tekst źródłaSnyder, Daniel Joseph. "Deactivation Diagram Development for Naval Ship System Vulnerability Analysis". Thesis, Virginia Tech, 2019. http://hdl.handle.net/10919/90220.
Pełny tekst źródłaMaster of Science
As the development of new ships becomes more technically complex due to the increased incorporation of redundant and interdependent ship systems, there is a greater need for advanced tools to support future ship system design. Ship operational capabilities rely on the resiliency of onboard systems in all situations, included damaged conditions, and require comprehensive design evaluation to identify weaknesses in system concepts. This thesis details the development of a computational approach to ship system analysis using precomputed deactivation diagrams for early-stage naval ship system design. Deactivation diagrams are a unique way of looking at the interconnectivity of system components and offer a consolidated view of complex network architecture to significantly simplify and accelerate subsequent analyses. Developments in computational algorithms for ship system connectivity presented in this thesis aid in the automated development of deactivation diagrams and support system flow and vulnerability analyses with particular regard to ongoing work on the Virginia Tech (VT) Naval Ship Design Concept and Requirements Exploration (C&RE) process. Additional thesis development work referencing the U.S. Navy’s Leading-Edge Architecture for Prototyping Systems (LEAPS) database framework has demonstrated the capability for generating deactivation diagrams from complex LEAPS ship system databases and paved the way for future incorporation of LEAPS into research work at VT.
Walser, Moritz, Rico Fischer, Thomas Goschke, Clemens Kirschbaum i Franziska Plessow. "Intention Retrieval and Deactivation Following an Acute Psychosocial Stressor". Public Library of Science, 2013. https://tud.qucosa.de/id/qucosa%3A27510.
Pełny tekst źródłaShirakawa, Takashi. "Deactivation of STAT6 through serine 707 phosphorylation by JNK". Kyoto University, 2011. http://hdl.handle.net/2433/142114.
Pełny tekst źródłaLau, Ngai-ting. "An infected zone model for the deactivation of catalysts /". Hong Kong : [University of Hong Kong], 1990. http://sunzi.lib.hku.hk/hkuto/record.jsp?B12986355.
Pełny tekst źródłaZanlongo, Sebastian A. "Multi-Robot Coordination and Scheduling for Deactivation & Decommissioning". FIU Digital Commons, 2018. https://digitalcommons.fiu.edu/etd/3897.
Pełny tekst źródłaHorne, Andrew James. "Insights into Kv1.2 activation and deactivation using voltage clamp fluorimetry". Thesis, University of British Columbia, 2010. http://hdl.handle.net/2429/27083.
Pełny tekst źródłaFleischer, Jacklyn Gabriella. "Deactivation of the LPS antagonist eritoran by HDL-associated apolipoproteins". Thesis, University of British Columbia, 2010. http://hdl.handle.net/2429/27100.
Pełny tekst źródłaNew, Michael Dean. "Deactivation of automation in aircraft systems using dynamic function allocation". Thesis, Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/28792.
Pełny tekst źródłaGranestrand, Jonas. "Material characterization for studying thermal deactivation of automotive SCR catalysts". Thesis, KTH, Skolan för kemivetenskap (CHE), 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-147524.
Pełny tekst źródłaSharp, James Alexander. "Deactivation of non-melt laser annealed boron ultra-shallow junctions". Thesis, University of Surrey, 2007. http://epubs.surrey.ac.uk/844056/.
Pełny tekst źródłaSherborne, Grant John. "Catalyst deactivation in copper-catalysed C-N cross-coupling reactions". Thesis, University of Leeds, 2017. http://etheses.whiterose.ac.uk/17595/.
Pełny tekst źródłaMarafi, Meena A. "Studies on the deactivation and reactivation of spent hydroprocessing catalyst". Thesis, Aston University, 1996. http://publications.aston.ac.uk/9600/.
Pełny tekst źródłaRichards, D. S. "The deactivation of singlet molecular oxygen in the gaseous phase". Thesis, Keele University, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.355614.
Pełny tekst źródłaReardon, Kenneth Frederick Bailey James E. Bailey James E. "Deactivation and regeneration kinetics during bioconversions by immobilized Clostridium acetobutylicum /". Diss., Pasadena, Calif. : California Institute of Technology, 1988. http://resolver.caltech.edu/CaltechETD:etd-11072007-104847.
Pełny tekst źródłaWest, Andrew. "Green techniques in reversible-deactivation radical polymerization : alternative synthetic methodologies". Thesis, The University of Sydney, 2010. https://hdl.handle.net/2123/28902.
Pełny tekst źródłaCarron, David. "FISCHER-TROPSCH SYNTHESIS IN SUPERCRITICAL PHASE CARBON DIOXIDE: DEACTIVATION STUDIES". OpenSIUC, 2011. https://opensiuc.lib.siu.edu/theses/643.
Pełny tekst źródłaLøvik, Ingvild. "Modelling, estimation and optimization of the methanol synthesis with catalyst deactivation". Doctoral thesis, Norwegian University of Science and Technology, Department of Chemical Engineering, 2001. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-1175.
Pełny tekst źródłaThis thesis studies dynamic modelling, estimation and optimization of the methanol synthesis with catalyst deactivation. Conversion of natural gas is of special interest in Norway for both economic and political reasons. In June 1997 Statoil opened a methanol plant at Tjeldbergodden. It is among the largest in the word with a capacity of 830 000 metric tons per year, which equals 1/4 of Europe's capacity. Methanol is today mainly used as a building block to produce chemical intermediates, and it is also a promising fuel for fuel cells.
The overall theme for this thesis is to find the optimal operation of the methanol synthesis when undergoing catalyst deactivation by dynamic optimization. There has been an increase in method development, tool development and industrial use of dynamic optimization in the past decade. Few realistic, large-scale applications with nonlinear, first principle models, exist apart from this thesis.
A rigorous pseudo-steady state model of the total methanol synthesis loop is developed. The model has been verified against a design flow sheet and to some extent, validated against process data. Overall, good agreement was found.
Optimal operation policy of the methanol synthesis is found by dynamic optimization. Both the reactor and the reactor system with recycle are studied, and it is shown that the total reactor system with recycle must be considered to find the optimal operating policy. It is also shown that a heterogeneous reactor model gives different optimal policy and more accurate results than a pseudohomogeneous reactor model. Optimization of the loop leads to USD 3 165 000, or 0.75 per cent, increased profit over four years compared to a selected reference case with a constant operation policy. Optimal operation policy is compared with an operating procedure recommended for the Tjeldbergodden methanol plant. The calculated optimal operation policy gives higher profit. However, there are two important advantages of optimization: The ability to find the optimal operation if some of the variables in the optimization problem change, and the ability to track changes in the process by model updating and repeated optimization.
During modelling and optimization, it became evident that a good industrialscale deactivation model is needed for the methanol synthesis. The sensitivity in the dynamic optimization of the methanol synthesis is analysed with regards to the deactivation model by a first order error propagation - approach. It is found that 20 per cent standard deviation in the deactivation parameters is suffcient for optimization purposes.
A deactivation model for the methanol synthesis catalyst is estimated from historic process data from a methanol plant. A model on the generalized power law form was successfully fitted to process data from a limited period of time. The estimated model is of second order. No measurable effect of water was found, probably because the variations in the feed compositions were too small. The model parameters found are confidential, and are not valid for the total catalyst lifetime because the deactivation process is fast in the beginning and slower after some time. It is necessary to use data from a longer period of time to obtain a model that is valid over the total catalyst lifetime.
The work presented in this thesis serves as a framework for the implementation of dynamic optimization in the control system of a methanol synthesis plant. The dynamic optimization should be implemented in the optimization layer of the control system with feedback to update the activity. A new catalyst deactivation model should be estimated whenever the commercial catalyst type is changed. A shrinking horizon algorithm with repeated optimization is proposed.
The main contribution in this thesis is a realistic, large-scale case study on modelling, estimation and dynamic optimization. Several researchers have studied optimal operation of fixed bed reactors experiencing catalyst deactivation. This work adopts an approach which is more realistic. A rigorous model of the total reactor system with recycle, with varying model parameters and thermodynamic properties is used. A thorough analysis of the process is enployed to formulate the optimization problem. The actual time varying control variables in the reactor system, the recycle rate and coolant temperature, are optimized with regards to an economic objective, and path constrains on the reactor temperature are considered. An optimal operation strategy for the methanol synthesis has not been published before. Similar studies have probably been performed in industry without being published.
Broering, James M. "Quantification of Hofmeister Effects on Enzyme Deactivation and Amyloid Protein Stability". Diss., Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/14077.
Pełny tekst źródłaHamoudi, Safia. "Heterogeneous catalytic oxidation of aqueous phenol, degradation kinetics and catalyst deactivation". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0001/NQ39357.pdf.
Pełny tekst źródłaBaldyga, Lyndsey Michelle. "Effect of Platinum Particle Size on the Sulfur Deactivation of Hydrogenation". Scholar Commons, 2012. http://scholarcommons.usf.edu/etd/3966.
Pełny tekst źródłaSwart, Jurie Christiaan Wessels. "A theoretical view on deactivation of cobalt-based Fischer-Tropsch catalysts". Doctoral thesis, University of Cape Town, 2008. http://hdl.handle.net/11427/5394.
Pełny tekst źródłaOtor, Hope O. "Catalyst Development and Control of Catalyst Deactivation for Carbon Dioxide Conversion". University of Toledo / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1596134702392137.
Pełny tekst źródłaSadeqzadeh, Majid. "Deactivation modeling of cobalt Fischer-Tropsch catalysts in different reactor configurations". Thesis, Lille 1, 2012. http://www.theses.fr/2012LIL10172/document.
Pełny tekst źródłaCatalyst deactivation remains a major challenge in Fischer-Tropsch synthesis; as it reduces the catalyst lifetime as well as its productivity. Deactivation can be attributed to certain mechanisms according to the literature. Sintering is proposed in this work to be responsible for the initial deactivation whereas coking is suggested to be the main cause of long-term deactivation. The final objective of this thesis is to develop the mechanistic models which could predict the extent of catalyst deactivation with time. In the first step, the change in the catalyst physico-chemical properties with time on stream is considered. A three-step sintering model is proposed which involves the effect of water acceleration through the formation of surface cobalt oxide layer. This mechanism allows correlating the crystallites growth with certain operating conditions especially the H2O/H2 molar ratio inside the reactor. We have also developed a mechanism for the active site poisoning by carbon deposition for the long-term deactivation. This mechanism helps to evaluate the change in the active sites coverage with time as well the CO, H2, and H2O mole fractions. The two microscopic models are then integrated in the reactor models in order to correlate the change in the catalytic activity with the catalyst properties. We have developed the models dedicated to fixed bed and slurry reactors. The effect of operating conditions on the crystallite size, active sites fraction, and conversion is considered by the simulations. The models are then employed in the laboratory scale reactors to fit the experimental data and to optimize the deactivation constants
Petrova, Olga. "Regulation, activation, and deactivation of soluble guanylate cyclase and NO-sensors". Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLX113/document.
Pełny tekst źródłaThis thesis is devoted to the regulation of soluble guanylate cyclase (sGC), the endogenous nitric oxide (NO) receptor in mammals involved in signal transduction. The enzyme is activated by the binding of NO to its heme and catalyzes the formation of cGMP from GTP. While sGC is present in many mammalian cells, the homologous bacterial domain (H-NOX) is involved in NO detection and metabolism regulation. An important objective was to find sGC inhibitors to slow down tumor progression.The screening of natural compounds from a chemical library, tested on purified sGC activity, revealed six active inhibitors (Ki = 0.2 – 1 µM). Together with two agents for photodynamic therapy (hypericin and hypocrellin) we demonstrated that these inhibitors are allosteric modulators which bind neither to the heme nor to the catalytic and activator sites, revealing a new class of pharmacological compounds targetting the NO/cGMP signaling pathway.The structural transition induced in sGC by stimulator riociguat in synergy with CO was studied by transient absorption spectroscopy to demonstrate coordination changes of the heme. Two different activation states of sGC with CO 6c-heme and 5c-heme exist simultaneously in the presence of the stimulator which induces the breaking of the heme Fe-His bond, as does the sGC natural effector NO. In addition, the effect of isoliquiritigenin, which is sold as a sGC activator, was shown to be actually an inhibitor of sGC.The dynamics of the ligands CO, NO and O2 were measured over 12 orders of magnitude in time in wild type and mutant of a bacterial NO transporter (AXCP). The single mutation Leu16Ala increased 108-fold the CO affinity, ~106-fold the NO affinity and makes this protein reactive to O2. In the case of CO and NO, whose affinities for L16A-AXCP are the largest ever measured, the bimolecular rebinding was absolutely not detectable. Molecular dynamic simulations demonstrated that dissociated CO is constrained to stay within 4 Å from Fe2+ by Ala16, contrarily to wild-type Leu16.The dynamics of O2 in Tt-H-NOX proteins measured by transient absorption spectroscopy confirmed the hypothesis that Tt-H-NOX may not be a NO-sensor stricto sensu but a redox sensor. The properties of the Tt-H-NOX protein are not compatible with the role a mere NO-carrier
Casellas, Soler Josep. "Elucidating deactivation and reaction paths of photosensitive organic systems through computational methods". Doctoral thesis, Universitat Rovira i Virgili, 2016. http://hdl.handle.net/10803/386574.
Pełny tekst źródłaEsta tesis estudia computacionalmente los procesos que explican las propiedades fotoquímicas de ciertos compuestos orgánicos. Para ello se han usado métodos ab initio multiconfiguracionales, CASSCF y CASPT2, con los que se describe la topografía de las superficies de energía potencial de los estados de más baja energía y se localizan los caminos de reacción. Se ha estudiado primeramente el mecanismo de fotoisomerización del azobenzeno y su derivado, la fenilazopiridina. El mecanismo de reacción obtenido explica satisfactoriamente por qué el rendimiento cuántico de la isomerización depende de la excitación inicial y del grado de restricción de la rotación interna en estos sistemas. También se ha analizado un protocolo computacional para poder reproducir el espectro de absorción en disolución de sistemas flexibles, usando como ejemplo la fenilazopiridina. Se ha estudiado también la 9-fenilfenalenona. A diferencia del sistema del que deriva, la fenalenona, que presenta un alto rendimiento cuántico de sensitización de oxígeno singlete, el de la 9-fenilfenalenona es muy bajo. Se ha demostrado que eso se debe a que en el segundo la fotoexcitación produce la formación por ciclación de un fotoproducto metaestable que rápidamente revierte en el compuesto original. Este estudio ha supuesto un reto para los métodos computacionales empleados debido a su gran tamaño. Por último se ha estudiado el dehidroescualeno, un carotenoide que interviene en procesos de absorción de energía lumínica de organismos vegetales. El estudio determina la estructura de los estados excitados de baja energía y la influencia de la flexibilidad de este compuesto en las energías de estos estados. Se demuestra que la aproximación de utilizar sólo la conformación más simétrica proporciona buenos resultados a nivel cualitativo pero que, si se busca la reproducción cuantitativa de las observaciones experimentales, se debe tener en cuenta la flexibilidad molecular.
This thesis develops a computational work to study the processes that explain the photochemical properties of some organic compounds. Multiconfigurational ab initio methods, CASSCF and CASPT2 have been used to determine the topography of the potential energy surfaces of the low energy states and locate reaction paths. We have studied first the mechanism of photoisomerization of azobenzene and its derivative phenylazopyridine. The reaction mechanism obtained explains satisfactorily why the isomerization quantum yield depends on the initial excitation and on the degree of the restriction on the internal rotation of these systems. We have also analysed the performance of a computational protocol to reproduce the absorption spectrum of flexible systems in solution, using phenylazopyridine as target system. We have also studied 9-phenylphenalenone. Its parent system, phenalenone, shows a high quantum yield in the process of singlet oxygen sensitization, but the quantum yield of this phenyl derivate for the same process is very low. Our study shows that this difference is due to a side reaction induced by the initial photoexcitation, which produces a metastable photoproduct by cyclisation that turns back quickly to the initial reactant. This study has been a challenge for the computational methods used due to its big size. Finally, we have studied dehidrosqualene, a carotenoid involved in light harvesting processes in vegetables. Our study determines the structure of the low energy excited states and the influence of the flexibility of this compound in the energy of these states. We show that to use only the most symmetric conformation on this flexible compound to calculate the energy of the excited states, give results that qualitatively agree with the experimental observations but, if quantitative agreement is required, the molecular flexibility must be taken into account.
Feller, Andreas. "Reaction mechanism and deactivation pathways in zeolite catalyzed isobutane-2-butene alkylation". [S.l. : s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=967127483.
Pełny tekst źródłaZuazo, Iker. "Deactivation routes in zeolite catalyzed isobutane/2-butene alkylation and regeneration procedures". [S.l. : s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=97204227X.
Pełny tekst źródłaHong, Eock Kee. "Analysis of the hollow fiber membrane reactor using immobilized enzyme with deactivation". Ohio : Ohio University, 1986. http://www.ohiolink.edu/etd/view.cgi?ohiou1183132380.
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