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Статті в журналах з теми "Active oxidants"
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Guo, Mian, Yong-Min Lee, Shunichi Fukuzumi, and Wonwoo Nam. "Biomimetic metal-oxidant adducts as active oxidants in oxidation reactions." Coordination Chemistry Reviews 435 (May 2021): 213807. http://dx.doi.org/10.1016/j.ccr.2021.213807.
Повний текст джерела
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Wu, Ru Feng, You Cheng Xu, Zhenyi Ma, Fiemu E. Nwariaku, George A. Sarosi, and Lance S. Terada. "Subcellular targeting of oxidants during endothelial cell migration." Journal of Cell Biology 171, no. 5 (December 5, 2005): 893–904. http://dx.doi.org/10.1083/jcb.200507004.
Повний текст джерелаАнотація:
Endogenous oxidants participate in endothelial cell migration, suggesting that the enzymatic source of oxidants, like other proteins controlling cell migration, requires precise subcellular localization for spatial confinement of signaling effects. We found that the nicotinamide adenine dinucleotide phosphate reduced (NADPH) oxidase adaptor p47phox and its binding partner TRAF4 were sequestered within nascent, focal complexlike structures in the lamellae of motile endothelial cells. TRAF4 directly associated with the focal contact scaffold Hic-5, and the knockdown of either protein, disruption of the complex, or oxidant scavenging blocked cell migration. An active mutant of TRAF4 activated the NADPH oxidase downstream of the Rho GTPases and p21-activated kinase 1 (PAK1) and oxidatively modified the focal contact phosphatase PTP-PEST. The oxidase also functioned upstream of Rac1 activation, suggesting its participation in a positive feedback loop. Active TRAF4 initiated robust membrane ruffling through Rac1, PAK1, and the oxidase, whereas the knockdown of PTP-PEST increased ruffling independent of oxidase activation. Our data suggest that TRAF4 specifies a molecular address within focal complexes that is targeted for oxidative modification during cell migration.
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Wu, Chiung-Ta, Chen-Yu Chang, Yi-Ying Li, and Po-Hsiung Lin. "Feasibility study for the production of multi-oxidants from the desalination of seawater brine." Water Quality Research Journal 54, no. 3 (September 20, 2018): 242–48. http://dx.doi.org/10.2166/wcc.2018.160.
Повний текст джерелаАнотація:
Abstract The primary goals of this study are to compare the efficiency of multiple oxidants that are produced using different commercially available anodes and separators and to optimize the reaction conditions for the recovery of multiple oxidants from brine. The brine produced in the desalination plants in Taiwan is the concentrated seawater that is recovered after the reverse osmosis process. The main component in the solution is NaCl. On average, chlorine concentration is approximately 3–5% by weight, which is slightly higher than the concentration for normal seawater. This concentrated brine can be used as raw material for the electrolyte to extract mixed disinfectant solutions. This study uses different catalytic electrolyzers to compare the efficiency with which multiple oxidants are produced using anodes that are coated in precious metal. A ruthenium-coated titanium anode generates the largest amount of active chlorine (chlorine dioxide). In terms of the diaphragms that are tested, the DuPont Nafion NE-2030 ion film produces active chlorine most efficiently. If no other chemicals are added to the brine (salinity 11.3%), Cl2 (302–376 mg L−1) is the primary oxidant generated from the original brine, and ClO2 (3.7–7.2 mg L−1) is the minor product in batch electrolysis. This article has been made Open Access thanks to the kind support of CAWQ/ACQE (https://www.cawq.ca).
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Kamceva, Gordana, Zorica Arsova-Sarafinovska, Tatjana Ruskovska, Milka Zdravkovska, Lidija Kamceva-Panova, and Elisaveta Stikova. "Cigarette Smoking and Oxidative Stress in Patients with Coronary Artery Disease." Open Access Macedonian Journal of Medical Sciences 4, no. 4 (October 28, 2016): 636–40. http://dx.doi.org/10.3889/oamjms.2016.117.
Повний текст джерелаАнотація:
AIM: To determine whether cigarette smoking, as a risk factor for CAD, affects oxidative stress.MATERIAL AND METHODS: The study included patients with CAD divided according to smoking status and number of cigarettes smoked during a whole day. In all subjects were examined biological markers of oxidative stress (concentration of oxidants and activity of antioxidant enzymes).RESULTS: The study included 300 patients with CAD, with an average age of 62.97 ± 11.18 years, with a predominance of males. Of the total, 34.0% were active smokers, and 43.0% were non-smokers. The number of the most active smokers smoked cigarettes 1-20/day. In terms of concentration of oxidants (MDA and HP) it has not proved a significant difference between smokers versus non-smokers. Over the activity of antioxidant enzymes (SOD, CAT and GPX) statistically significant difference was found in the activity of GPX and among active smokers with CAD and non-smokers with CAD (p = 0.039).CONCLUSION:Smoking as a risk factor for CAD is closely associated with increased oxidative stress and the number of cigarettes smoked plays an important role in increasing the level of oxidative damage and reduced antioxidant defence.AIM: To determine whether cigarette smoking, as a risk factor for CAD, affects (anti)oxidant status.MATERIAL AND METHODS: The study included patients with CAD, divided according to their smoking status and the number of cigarettes smoked during a day. Biological markers of oxidative stress (concentration of oxidants and activity of antioxidant enzymes) were measured in all subjects.RESULTS: The study included 300 patients with CAD, (average age of 63 ± 11 years), predominantly males. Of the total, 34.0% were active smokers, 23.0% were former smokers, and 43.0% were non-smokers. Most of the active smokers smoked 1-20 cigarettes/day. In terms of concentration of oxidants (MDA and HP) there was not a significant difference between smokers versus non-smokers. As for the activity of antioxidant enzymes (SOD, CAT and GPX), a statistically significant difference was found in the activity of GPX among the active smokers with CAD and the non-smokers with CAD (p = 0.039). CONCLUSION: Smoking as a risk factor for CAD is closely associated with increased oxidative stress, and the number of cigarettes smoked plays an important role in increasing the level of oxidative damage and reducing antioxidant defence.
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Jang, Jaeyoun, Myoseon Jang, Wilton Mui, Carrie A. Delcomyn, Michael V. Henley, and John D. Hearn. "Formation of Active Chlorine Oxidants in Saline-Oxone Aerosol." Aerosol Science and Technology 44, no. 11 (September 30, 2010): 1018–26. http://dx.doi.org/10.1080/02786826.2010.507612.
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Collman, James P., Allis S. Chien, Todd A. Eberspacher, and John I. Brauman. "Multiple Active Oxidants in Cytochrome P-450 Model Oxidations." Journal of the American Chemical Society 122, no. 45 (November 2000): 11098–100. http://dx.doi.org/10.1021/ja000961d.
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Patel, K. D., G. A. Zimmerman, S. M. Prescott, R. P. McEver, and T. M. McIntyre. "Oxygen radicals induce human endothelial cells to express GMP-140 and bind neutrophils." Journal of Cell Biology 112, no. 4 (February 15, 1991): 749–59. http://dx.doi.org/10.1083/jcb.112.4.749.
Повний текст джерелаАнотація:
The initial step in extravasation of neutrophils (polymorphonuclear leukocytes [PMNs]) to the extravascular space is adherence to the endothelium. We examined the effect of oxidants on this process by treating human endothelial cells with H2O2, t-butylhydroperoxide, or menadione. This resulted in a surface adhesive for PMN between 1 and 4 h after exposure. The oxidants needed to be present only for a brief period at the initiation of the assay. Adhesion was an endothelial cell-dependent process that did not require an active response from the PMN. The adhesive molecule was not platelet-activating factor, which mediates PMN adherence when endothelial cells are briefly exposed to higher concentrations of H2O2 (Lewis, M. S., R. E. Whatley, P. Cain, T. M. McIntyre, S. M. Prescott, and G. A. Zimmerman. 1988. J. Clin. Invest. 82:2045-2055), nor was it ELAM-1, an adhesive glycoprotein induced by cytokines. Oxidant-induced adhesion did not require protein synthesis, was inhibited by antioxidants, and, when peroxides were the oxidants, was inhibited by intracellular iron chelators. Granule membrane protein-140 (GMP-140) is a membrane-associated glycoprotein that can be translocated from its intracellular storage pool to the surface of endothelial cells where it acts as a ligand for PMN adhesion (Geng, J.-G., M. P. Bevilacqua, K. L. Moore, T. M. McIntyre, S. M. Prescott, J. M. Kim, G. A. Bliss, G. A. Zimmerman, and R. P. McEver. 1990. Nature (Lond). 343:757-760). We found that endothelial cells exposed to oxidants expressed GMP-140 on their surface, and that an mAb against GMP-140 or solubilized GMP-140 completely blocked PMN adherence to oxidant-treated endothelial cells. Thus, exposure of endothelial cells to oxygen radicals induces the prolonged expression of GMP-140 on the cell surface, which results in enhanced PMN adherence.
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Talukder, Saranika, Kendra L. Kerrisk, Gianfranco Gabai, and Pietro Celi. "Role of oxidant–antioxidant balance in reproduction of domestic animals." Animal Production Science 57, no. 8 (2017): 1588. http://dx.doi.org/10.1071/an15619.
Повний текст джерелаАнотація:
Reproductive process leads to dynamic changes in metabolism and energy consumption, which may be responsible for the excessive production of free radicals (oxidants) that are generated during the physiological process of oxygen consumption. As the ovary is a metabolically active organ, it produces oxidants. Growing follicles, granulose cells of Graffian follicles and ovulated follicles all produce both enzymatic and non-enzymatic antioxidants to preserve themselves from the oxidative damage of oxidants. Oxidants and antioxidants are involved in several reproductive functions such as the regulation of follicular fluid environment, folliculogenesis, steroidogenesis, corpus luteum function, and luteolysis. In this article, the currently available literature is reviewed in relation to the roles of oxidants and oxidative stress in both normal and abnormal reproductive physiological processes.
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Nalian, Armen, and Alexei V. Iakhiaev. "Possible mechanisms contributing to oxidative inactivation of activated protein C: Molecular dynamics study." Thrombosis and Haemostasis 100, no. 07 (2008): 18–25. http://dx.doi.org/10.1160/th07-12-0750.
Повний текст джерелаАнотація:
SummaryActivated protein C (APC) is a serine protease, an effector enzyme of the natural anticoagulant pathway. APC is approved for treatment of severe sepsis characterized by the increased concentrations of H2O2 and hypochlorite. We found that treatment of APC with these oxidants markedly inhibits the cleavage of the APC-specific chromogenic substrate, suggesting that oxidants can induce changes in the structure of the active site of APC. Resistance of oxidant-treated APC to chemical digestion with cyanogen bromide (CNBr) implies that methionine oxidation can at least in part be responsible for inhibition of APC. Since methionine residues, the main targets of oxidants in APC, are not included in the active site, we hypothesize that oxidation induces allosteric changes in the architecture of the catalytic triad of APC. Using molecular dynamics (MD) simulations we found that methionine oxidation alters the distance between cSer 195Oγ and cHis57 Nε2 atoms placing them in positions unfavorable for the catalysis. At the same time, neither distances between Cα atoms of the catalytic triad cAsp102-cHis57-cSer195, nor the overall structure of APC changed significantly after oxidation of the methionine residues. Disruption of the H-bond between Nδ1 of cHis57 and carboxyl group of cAsp 102, which can take place during the hypochlorite-induced modification of cHis57,dramatically changed the architecture of the catalytic triad in oxidized APC. This mechanism could contribute to APC inactivation by hypochlorite concurrently with methionine oxidation. These are novel findings, which describe potentially pathophysiologically relevant changes in the functional stability of APC exposed to the oxidative stress.
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Pardini, Ronald S. "Toxicity of oxygen from naturally occurring redox-active pro-oxidants." Archives of Insect Biochemistry and Physiology 29, no. 2 (1995): 101–18. http://dx.doi.org/10.1002/arch.940290203.
Повний текст джерелаДисертації з теми "Active oxidants"
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Wright, Paul F. A. "Systemic oxidant stress and its effects on hepatotoxicity /." Title page, contents and abstract only, 1988. http://web4.library.adelaide.edu.au/theses/09PH/09phw952.pdf.
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Colclough, Nicola. "Studies of the formation and reaction of active oxidant species in metalloporphyrin models for peroxidases." Thesis, University of York, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358210.
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Rolle, Clarence J. "Selective aerobic oxidations catalyzed by manganese(III) complexes using redox-active ligands." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/42827.
Повний текст джерелаАнотація:
Selective oxidations are important for the functionalization of compounds in organic synthesis and chemical industry. Using O2 as a terminal e- acceptor would be ideal because it is cheap and environmentally friendly, but aerobic oxidations are often prone to unselective free radical autoxidation. Recently developed palladium catalysts use O2 as a selective multi-electron oxidant for various organic transformations. Although these methods are powerful and sophisticated, the lower cost of base metals makes them attractive as potential alternatives. The challenge is to develop methods for effecting multi-electron transformations at metals that typically prefer one electron changes. To this end, the development of manganese(III) complexes containing redox-active ligands as catalysts for selective oxidase-type oxidation of organic substrates was pursued. Bis(tetrabromocatecholato) manganese(III) complexes were shown to aerobically oxidize catechols to form quinones and H2O2. This reactivity was extended to other alcohol and amine substrates. In these reactions, the non-innocent tetrabromocatecholate ligands may impart a multi-electron character to the metal. To directly probe the intermediacy of ligand-centered radicals in catalytic turnover, a series of structurally similar manganese(III) complexes with aminophenol-derived ligands were prepared and characterized. The capacity of these ligands to undergo low-energy redox changes, allowed for isolation of an electron transfer series spanning two redox states without a change in oxidation state at the metal center. The ligand-centered redox events were a key feature in aerobic homocoupling of Grignard reagents.
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Peltoniemi, M. (Mirva). "Mechanism of action of the glutaredoxins and their role in human lung diseases." Doctoral thesis, University of Oulu, 2007. http://urn.fi/urn:isbn:9789514285165.
Повний текст джерелаАнотація:
Abstract
Glutaredoxins (Grx) are small thiol disulphide oxidoreductases with a conserved active site sequence -CXXC/S- and a glutathione (GSH) binding site. They catalyze the reduction of protein disulphides, preferring protein-GSH mixed disulphides as substrates. The accumulation of protein-GSH mixed disulphides has been observed during oxidative stress, where they may serve both a regulatory and an antioxidant function by protecting the enzymes from irreversible oxidation. Once oxidative stress has been removed the GSH-protein mixed disulphides are reduced by GSH or, more efficiently, by Grx.
The present study showed for the first time that Grx1 and Grx2 can be detected in healthy human lung. Highly specific expression of Grx1 was observed in alveolar macrophages, but it could also be detected from sputum supernatant. Grx1 levels in alveolar macrophages were lower in selected inflammatory diseases than in control lung samples. Grx1 was also mainly negative in the fibrotic areas in usual interstitial pneumonia, an aggressive fibrotic lung disease. Overall, the present study suggests that Grx1 is a potential redox modulatory protein regulating the intracellular as well as extracellular homeostasis of glutathionylated proteins and GSH not only in healthy lung, but also in inflammatory and fibrotic lung diseases.
In order to study the mechanism of action of glutaredoxins in vitro, a new real-time fluorescence-based method for measuring the deglutathionylation activity of glutaredoxins using a glutathionylated peptide as a substrate was developed. The first reaction intermediate in the deglutathionylation reaction was shown to be exclusively Grx-GSH mixed disulphide and this specificity was solely dependent on the unusual γ-linkage present in glutathione. The study also demonstrated the role of conserved residues in the proximity of proposed GSH binding site to the GSH binding specificity of E. coli Grx1. Opening the binding groove and removing charged residues enabled Grx to form more readily mixed disulfides with other molecules besides GSH. Different members of the PDI family showed considerably lower activity levels compared to glutaredoxins and, in contrast to the glutaredoxin-GSH mixed disulphide, the only intermediate in the PDI catalysed reaction was PDI-peptide mixed disulphide.
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Oshikiri, Reona. "Fundamental bases for the improving action of novel enzyme-oxidant combinations in frozen dough." Thesis, Kansas State University, 2013. http://hdl.handle.net/2097/15518.
Повний текст джерелаАнотація:
Master of ScienceDepartment of Grain Science and Industry
J.M. Faubion
The market for frozen goods is expanding and the frozen dough goods sector still has potential to expand its market. It is well known that deterioration in bread quality occurs during frozen dough/bread production. In addition, it is known that dough rheology influences bread quality. To prevent deterioration of bread quality, many additives have been used and researched. Combinations of oxidants (potassium bromate and ascorbic acid) are widely used worldwide. However, potassium bromate may be carcinogenic to humans, and it has been detected in bread after baking. Since it has been prohibited or strictly limited in many countries, many researchers have tried to find a replacement. Ascorbic acid is safe for human intake, and does not persist in bread. However, it is not as effective as potassium bromate. Possible replacements in frozen doughs include oxidant (ascorbic acid)-enzyme combinations. This study evaluated the effects of ascorbic acid-specific enzyme combinations as a replacement for the potassium bromate in frozen dough and related the effects to dough behavior (gluten network strength) as evaluated by dynamic oscillation rheometry. Bread quality was evaluated by test baking. Based on the results from fresh baking studies, potassium bromate can be replaced by an optimum level combination of ascorbic acid and hemicellulase/endo-xylanase. This combination clearly improved loaf volume, and crumb grain over both control and potassium bromate containing doughs. For frozen dough/bread production, the addition of all additives improved bread quality, but ascorbic acid and endo-xylanase containing dough resulted in higher volume, and better crumb structure than did dough containing potassium bromate. Dough rheology experiments show that rheology was affected by both the process and additives. Strain sweeps gave the information about dough stability. Both the additives and proofing improved dough stability. Dough behavior (gluten network strength) was assessed by frequency sweeps. Dough containing ascorbic acid and endoxylanase was most stable during frozen dough processing.
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Barbarroja, Ortiz Paula. "Estudio de la dinámica poblacional y actividad de los organismos nitrificantes en sistemas de depuración de aguas residuales." Doctoral thesis, Universitat Politècnica de València, 2019. http://hdl.handle.net/10251/124063.
Повний текст джерелаАнотація:
[ES] Las estaciones depuradoras de aguas (EDAR) tienen un papel fundamental en la protección del medio ambiente, evitan la llegada de nutrientes (nitrógeno y fósforo) y otros contaminantes a los ecosistemas acuáticos. El sistema más utilizado para la eliminación de nitrógeno en las EDAR es el proceso biológico de nitrificación-desnitrificación vía nitrato. El rendimiento de los sistemas biológicos está directamente relacionado con la estructura de la comunidad bacteriana y su metabolismo.
En este trabajo se monitorizaron las variaciones temporales de las características fisicoquímicas del afluente, los parámetros operacionales y los rendimientos de eliminación del amonio en 6 reactores biológicos con sistemas de fangos activos. Para la caracterización de comunidades involucradas en el proceso de nitrificación se utilizaron diferentes técnicas de biología molecular: hibridación in situ con sondas marcadas con fluoróforos (FISH), secuenciación de segunda generación Illumina y secuenciación de tercera generación SMRT de PacBio, la cual no había sido utilizada hasta la fecha para el análisis de la microbiota de sistemas convencionales de eliminación de nutrientes. Para valorar la actividad de la biomasa nitrificante y de la biomasa heterótrofa se utilizaron técnicas respirométricas y técnicas para la cuantificación del ATP de última generación. Para analizar el gran volumen de datos generado tras la aplicación de las diferentes técnicas, se utilizaron técnicas estadísticas de análisis multivariante, como los modelos de regresión lineal multivariante basados en la distancia (DISTLM). Estas técnicas estadísticas permitieron valorar la contribución de las variables ambientales a la variabilidad observada en la estructura de las comunidades de bacterias nitrificantes, los rendimientos de eliminación del nitrógeno y su actividad.
Las técnicas moleculares empleadas permitieron determinar que Nitrosomonas oligotropha, Nitrospira spp. y Nitrotoga sp. fueron las especies responsable de los procesos de nitrificación en las EDAR analizadas. Los resultados alcanzados con las técnicas FISH e Illumina sobre la estructura de la población de bacterias nitrificantes fueron similares, y permitieron detectar los sesgos de la secuenciación SMRT de PacBio. Los modelos de regresión permitieron valorar la contribución de las bacterias nitrificantes a la eliminación del amonio y cuáles fueron los factores que influían en su abundancia en cada una de las EDAR. La carga orgánica, la concentración de sólidos volátiles, la concentración de oxígeno y la temperatura fueron las variables de mayor influencia en la abundancia de estas especies. Mientras que la carga de fósforo influenció significativamente en su actividad. Este estudio reveló que la aplicación de ozono disminuye significativamente a los rendimientos de eliminación del amonio. Los resultados obtenidos ayudaron a mejorar la comprensión sobre el proceso de nitrificación en cada una de las EDAR y manifiestan la importancia de la dinámica poblacional de las bacterias nitrificantes en los rendimientos de eliminación del amonio en las EDAR. Estos resultados establecen que las técnicas moleculares combinadas con respirometría y los modelos de ordenación multivariante empleados en esta tesis, son una herramienta fiable para la monitorización y el control del proceso de nitrificación en sistemas de eliminación biológica de nitrógeno.
Los resultados de esta tesis sugieren que la medida de los sólidos suspendidos volátiles activos mediante técnicas de determinación de ATP de segunda generación puede mejorar el cálculo de las variables de diseño y control más habituales de las EDAR.[CAT] Les estacions depuradores d'aigües residuals (EDAR) tenen un paper fonamental en la protecció del medi ambient, eviten l'arribada de nutrients (nitrogen i fòsfor) i altres substàncies contaminants als ecosistemes aquàtics. El sistema més utilitzat per a l'eliminació de nitrogen en les EDAR és el procés biològic de nitrificació-desnitrificació via nitrat. El rendiment dels sistemes biològics està directament relacionat amb l'estructura de la comunitat bacteriana i el seu metabolisme. En aquest treball es van monitorar les variacions temporals de les característiques fisicoquímiques de l'afluent, els paràmetres operacionals i els rendiments d'eliminació de l'amoni en 6 reactors biològics amb sistemes de fangs actius. Per a caracteritzar les comunitats involucrades en el procés de nitrificació s'han utilitzat diferents tècniques de biologia molecular: hibridació in situ amb sondes marcades amb fluoròfors (FISH), seqüenciació de segona generació Illumina i seqüenciació de tercera generació SMRT de PacBio, la qual no havia estat utilitzada fins avui per a l'anàlisi de la microbiota dels sistemes convencionals d'eliminació de nutrients. Per a valorar l'activitat de la biomassa nitrificant i de la biomassa heteròtrofa es van utilitzar tècniques respiromètriques i tècniques per a la quantificació de l'ATP d'última generació. Per a analitzar el gran volum de dades generat després de l'aplicació de les diferents tècniques, es van utilitzar tècniques estadístiques d'anàlisi multivariant, com els models de regressió lineal multivariant basats en la distància (DISTLM). Aquestes tècniques estadístiques van permetre valorar la contribució de les variables ambientals a la variabilitat observada en l'estructura de les comunitats de bacteris nitrificants, els rendiments d'eliminació del nitrogen i la seua activitat. Les tècniques moleculars emprades van permetre determinar que Nitrosomonas oligotropha, Nitrospira spp. i Nitrotoga sp resultaren les espècies responsables del procés de nitrificació en les EDAR analitzades. Les tècniques FISH i Illumnina van mostrar resultats molt similars sobre l'estructura de la població de bacteris nitrificants i van permetre detectar els biaixos de la seqüenciació SMRT de PacBio. Els models de regressió van permetre valorar la contribució dels bacteris nitrificants a l'eliminació de l'amoni i quins van ser els factors d'influència en la seua abundància en cadascuna de les EDAR. La concentració de matèria orgànica, sòlids volàtils en suspensió, la concentració d 'oxigen i la temperatura foren les variables amb més influència en l'abundància d'aquestes especies. Així mateix la càrrega de fòsfor va influir en la seua activitat. Aquest estudi va determinar que l 'aplicació ozó va causar una disminució significativa dels rendiments d 'eliminació del amoni. Aquests models van ajudar a millorar la comprensió sobre el procés de nitrificació en cadascuna de les EDAR i ressalten la importància de la dinàmica poblacional dels bacteris nitrificants en el rendiments de l 'eliminació de l 'amoni. Els resultats estableixen que les tècniques moleculars combinades amb respirometría i els models d'ordenació multivariant emprats en aquesta tesi, són una eina fiable per al monitoratge i el control del procés de nitrificació en sistemes d'eliminació biològica de nitrogen. Els resultats d'aquesta tesi suggereixen que la mesura dels sòlids suspesos volàtils actius mitjançant tècniques de determinació d'ATP de segona generació pot millorar el càlcul de les variables de disseny i control més habituals de les EDAR.
[EN] Wastewater treatment plants play an important role in environmental protection. These facilities protect aquatic ecosystems from excessive inputs of nutrients (nitrogen and phosphorous) and other pollutants. The most widespread system of nitrogen removal in wastewater treatment plants is a conventional method involving a biological nitrification-denitrification via nitrate. The efficiency of biological systems is directly related to bacterial community structure and its metabolism. In this work, the temporal variations of influent characteristics, operational parameters and ammonium removal efficiency in 6 bioreactors with activated sludge systems were monitored. To characterize the microbial communities involved in the nitrification process different molecular biology techniques were used: fluorescence in situ hybridization (FISH); second generation sequencing (Illumina), and third generation sequencing (SMRT PacBio). To assess the activity of nitrifying and heterotrophic bacteria, respirometric tests and second-generation ATP determination techniques were used. To analyse the large volume of data generated, statistical multivariate analysis techniques were used, including distance-based multivariate linear regression models (DISTLM). These statistical techniques allowed us to assess the contribution of environmental variables to the variability observed in the nitrifying community structure, in nitrogen removal performance and nitrifying activity. The molecular techniques employed determined that Nitrosomonas oligotropha, Nitrospira spp. and Nitrotoga sp. where the dominant nitrifying bacteria in the monitored WWTP. FISH and Illumnina technique showed very similar results and allowed for the detection of biases in PacBio SMRT sequencing. The regression models determined the contribution of nitrifying bacteria to ammonium oxidation and the factors influencing their abundance and activity. The main factors influencing the nitrifying bacteria abundance were organic load, volatile suspended solids concentration, dissolved oxygen and temperature. The activity of nitrifying bacteria also was influenced by phosphorous loading rate. This study revealed that ozone concentration was the main factor determining the low ammonium removal performance. These models helped to improve our understanding of the nitrification process in each WWTP and highlight the importance of nitrifying bacterial community structure in nitrogen removal performance. The results establish that the molecular techniques combined with respirometry and the multivariate ordering models used in this thesis, are a reliable tool for the monitoring and control of the nitrification process. The results of this thesis suggest that the measurement of active volatile suspended solids by means of second- generation ATP determination techniques can improve calculation of the most common design and control parameters of WWTPs.
A la Entidad de Saneamiento y Depuración de la Región de Murcia (ESAMUR) por la financiación del proyecto “Influencia de las variables operacionales y fisicoquímicas en la dinámica y estructura de la población de bacterias nitrificantes”, al Grupo de Química y Microbiología del Agua del IIAMA. A la Entidad Pública de Saneamiento de Aguas Residuales de la Comunidad Valenciana (EPSAR), por la financiación del proyecto “Estudio integrado del proceso biológico en plantas de tratamiento por fangos activos, análisis de interrelación entre los distintos componentes y optimización de métodos moleculares para la identificación de bacterias formadoras de espumas” al Grupo de Química y Microbiología del Agua del IIAMA
Barbarroja Ortiz, P. (2019). Estudio de la dinámica poblacional y actividad de los organismos nitrificantes en sistemas de depuración de aguas residuales [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/124063
TESIS
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Nqolo, Nandipha Lucia. "Phytochemical study of Rhoicissus tomentosa." Thesis, University of the Western Cape, 2008. http://etd.uwc.ac.za/index.php?module=etd&action=viewtitle&id=gen8Srv25Nme4_3223_1263940394.
Повний текст джерелаАнотація:
This investigation focused on Rhoicissus tomentosa, belonging to the family, Vitaceae in an attempt to assess the phytochemistry of this plant which is widely used by traditional healers in South Africa to ensure the safe delivery during pregnancy and childbirth (Hutchings et al., 1996).
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Abdulkarim, Kayigire Xavier. "Does maternal nicotine exposure during gestation and lactation change the oxidant-antioxidant status of the lungs of the offsprings and is tomato juice protecting the lungs of the offsprings?" Thesis, University of the Western Cape, 2009. http://etd.uwc.ac.za/index.php?module=etd&action=viewtitle&id=gen8Srv25Nme4_1431_1277678988.
Повний текст джерелаАнотація:
Nicotine exposure to the fetus through tobacco smoking or nicotine replacement therapy during the whole period of gestation and lactation causes diverse effects on fetal and neonatal lung development, integrity and maturation which compromise the gas exchange function of the lungs and renders this vital organ susceptible to gradual damage and different diseases in latter life. Maternal nicotine exposure during gestation and lactation results in gradual destruction of the lung parenchyma, and this leads to the combination of many small air sacs in one bigger alveoli which is a sign of emphysema. Many researchers speculated that the way in which, nicotine causes emphysema and other damage, is by inducing the formation of many reactive oxygen species (ROS), and creating an imbalance between the oxidants and the antioxidants of the body, which is termed oxidative stress. The aim of this study was to assess the effects of nicotine exposure on the lung of the fetal and neonate rat during gestation and lactation as gas exchanger, and also to see whether the supplementation of tomato juice containing lycopene, a powerful carotenoid antioxidant could protect the lungs against these effects of maternal nicotine exposure.
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Jolibois, Franck. "Etude théorique de lésions radioinduites de l'ADN : analyses conformationnelles, propriétés électroniques et mécanismes de formation." Université Joseph Fourier (Grenoble), 1997. http://www.theses.fr/1997GRE10157.
Повний текст джерелаАнотація:
Differents facteurs tels les rayonnements uv ou ionisants, les agents oxydants, les radicaux libres, peuvent engendrer des dommages au niveau des bases de l'adn. Ces modifications peuvent avoir une influence notable sur la structure et les proprietes du biopolymere. Afin de mieux comprendre la nature de ces lesions, leur mode de formation et les effets qu'elles peuvent avoir sur l'integrite de l'adn, l'etude de certains degradations de la thymine a ete realisee au moyen des outils de la chimie quantique. La premiere partie de ce travail est consacree a l'etude comparative des proprietes conformationnelles et electroniques de produits d'oxydation du groupement methyle de la thymidine par l'intermediaire d'une methode locale de la dft. Le chapitre suivant traite des intermediaires radicalaires formes par l'addition d'un atome d'hydrogene ou du radical hydroxyle sur la double liaison 5,6 de la thymine. Un protocole general d'etude de la structure et des constantes de couplage hyperfin isotrope rpe, incluant une methode hybride de la dft (b3lyp), les effets du solvant, des vibrations et de la temperature a ete mis en place. Ce protocole a ete applique a l'analyse des produits radicalaires formes par addition de l'atome d'hydrogene. D'autre part, les parametres thermodynamiques et cinetiques des differentes reactions d'addition ont ete determines. Un modele de reactivite en solution est finalement propose pour la comprehension des mecanismes d'addition du radical hydroxyle. La derniere partie concerne l'etude des produits finaux non radicalaires formes par l'addition initiale du radical hydroxyle sur la double liaison 5,6 de la thymine. La comparaison des conformations et des proprietes electroniques des deux isomeres cis d'hydroxyhydroperoxydes de thymine et des deux isomeres cis de la 5,6-dihydrothymidine a ete effectuee.
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Podgorski, Matthew Nathanial. "Investigation of the Mechanism of Multiple Cytochrome P450-catalysed Reactions." Thesis, 2019. http://hdl.handle.net/2440/123404.
Повний текст джерелаАнотація:
The cytochrome P450 heme-thiolate enzymes catalyse a multitude of oxidation reactions and, in humans, carry out drug metabolism. P450s perform hydroxylation, epoxidation, N-, O- and Sdealkylation, sulfoxidation, alkyne oxidation and aldehyde oxidation of organic molecules (and many other reactions). These reactions are predominantly performed by the reactive intermediate Compound I, but other intermediates in the catalytic cycle may mediate some types of reactions. It would be appealing to exploit these enzymes as environmentally benign catalysts in the synthesis of fine chemicals. Their widespread use in industrial synthesis is, however, impractical given the high cost of the required cofactor NAD(P)H, but engineering P450s to instead use cheap H₂O₂ would overcome this problem. CYP199A4 is a soluble bacterial P450 enzyme from Rhodopseudomonas palustris HaA2 that favours 4-methoxybenzoic acid and other para-substituted benzoic acids as substrates. It tightly binds these substrates and the para-substituent is rapidly oxidised. This enzyme has been used as a model system to study the mechanism of P450-catalysed reactions. While 4-methoxybenzoic acid is oxidatively demethylated at a rate of 1220 μM (μM-P450)⁻¹ min⁻¹, CYP199A4 displays no detectable activity towards the meta isomer, 3-methoxybenzoic acid. In vitro reactions were performed with a range of other meta-substituted benzoic acids (3-methylthio-, 3-methylamino-, 3- formyl-, 3-methyl-, 3-isopropyl-, 3-tert-butyl- and 3-ethoxy-benzoic acid) to assess whether CYP199A4 had activity towards these substrates. These meta-substituted substrates, except for 3- tert-butylbenzoic acid, were all metabolised by CYP199A4, but with low activity compared to the corresponding para isomers. Compared to the para isomers, the meta isomers had lower binding affinity and induced smaller type I spin-state shifts to high-spin. To rationalise CYP199A4’s preference for para- over meta-substituted benzoic acid substrates and to investigate the requirements for efficient monooxygenase activity, crystal structures were solved of CYP199A4 in complex with 3-methoxy-, 3-methylamino-, 3-methylthio-, and 3- and 4-methyl-benzoic acid. These structures revealed that the heme-bound water ligand to the heme is retained when these substrates bind (water occupancy 21-90%) and is hydrogen-bonded to the heteroatom (N, S, O) of the substrate. The corresponding para isomers displace the iron-bound water. 3-Ethoxybenzoic acid, which has a bulkier meta-substituent, shifted the spin-state to 85% high-spin and in the crystal structure the iron-bound water was removed. The meta-substituent of each substrate is held in close proximity to the iron. 3-Methoxybenzoic acid is positioned near the iron but is not oxidised. This was attributed to the fact that the C-H bonds are oriented away from the heme, whereas those of 4-methoxybenzoic acid are ideally oriented for H-atom abstraction by Cpd I. These results emphasise that close proximity of the methyl carbon to the heme iron does not guarantee that hydroxylation will occur if the C-H bonds are not oriented appropriately for abstraction, and subtle modification of the substrate’s position relative to the heme can abolish catalytic activity. X-ray crystallography, CW and HYSCORE EPR and other experiments were performed to elucidate the binding modes of 4-pyridin-2-yl-, 4-pyridin-3-yl- and 4-imidazol-1-yl-benzoic acid in the CYP199A4 active site. These heterocyclic aromatic compounds are not metabolised and induce substantially different type II UV-Vis spectra. 4-Pyridin-3-yl- and 4-imidazol-1-yl-benzoic acid redshifted the Soret band from 419 to 424 nm. They induced ‘normal’ type II spectra, characterised by a less intense α-band than β-band and an increase in δ-band intensity. The UV-Vis spectra of ferrous CYP199A4 in complex with these ligands indicated that 4-pyridin-3-ylbenzoic acid was directly ligated to the heme iron via the pyridine nitrogen, but the Fe-N bond between the iron and 4-imidazol-1-ylbenzoic acid was ruptured upon heme reduction. 4-Pyridin-2-ylbenzoic acid induced a smaller Soret band red-shift (to 422 nm) when added to the ferric enzyme. It produced an ‘abnormal’ type II spectrum, with no decrease in the α-band intensity. 4-Pyridin-2-ylbenzoic acid also induced a smaller Soret band trough in the difference spectrum than 4-pyridin-3-ylbenzoic acid. HYSCORE EPR and X-ray crystallography revealed that 4-pyridin-3-yl- and 4-imidazol-1-ylbenzoic acid were directly ligated to the ferric heme iron, but 4-pyridin-2-ylbenzoic acid was hydrogen-bonded to the heme-bound water. This study revealed that optical spectroscopy can distinguish between water-bridged and directly bound nitrogen donor ligands. 4-Pyridin-3-yl- and 4-imidazol-1-yl-benzoic acid-bound CYP199A4 were both reduced to the ferrous form by ferredoxin, ferredoxin reductase and NADH. On the other hand, binding of 4-pyridin-2-ylbenzoic acid to CYP199A4 lowered the reduction potential and prevented heme reduction by even the powerful reductant dithionite. This implies that water-bridged nitrogen ligands may in some instances be more effective P450 inhibitors than those that bind directly to the iron. The T252E mutant of CYP199A4 was produced and characterised. This variant was no longer able to operate using NADH but was a more efficient peroxygenase (H₂O₂-utilising enzyme) than the wild-type (WT) enzyme. EPR indicated that the sixth axial ligand to the heme was a mixture of hydroxide and water. Crystal structures showed that this aqua/hydroxo ligand was tightly bound due to strong interactions with the carboxylate of E252. The axial aqua/hydroxo ligand was not displaced by substrates, even sterically bulky substrates, explaining the lack of substrate-induced spin-state shifts and the exceedingly slow rate of electron transfer from the ferredoxin to the P450. Because this ligand is not displaced by substrates, the active species could potentially be generated via light-driven oxidation of the water-bound ferric resting state to Compound I. Type II nitrogen ligands were also unable to displace the aqua/hydroxo ligand. 4-Pyridin-3-ylbenzoic acid, when added to the T252E mutant, induced an ‘abnormal’ type II spectrum, confirming that optical spectroscopy can distinguish between water-bridged and directly bound type II ligands. X-ray crystallography revealed that the T252 → E mutation only subtly altered the orientation of substrates in the CYP199A4 active site. In the absence of substrate, the heme signal of the T252E mutant was rapidly bleached by 50 mM H₂O₂. When substrate was present, the T252E variant remained catalytically active for several hours. The T252E variant was able to perform a range of reactions using H₂O₂ (O-dealkylation, hydroxylation/desaturation, epoxidation, sulfoxidation, alkyne oxidation and aldehyde oxidation). When the surrogate oxygen donor tert-butyl hydroperoxide was substituted for H₂O₂, the T252E mutant had negligible activity. t-BuOOH is presumably too bulky to access the heme iron in this P450. WT CYP199A4 and the T252A and D251N mutants also catalysed these reactions using H₂O₂ but afforded less product over a 4-hour period than the T252E mutant. H₂O₂- and NADH-driven epoxidation of 4-vinylbenzoic acid catalysed by WT and mutant CYP199A4 proceeded with high enantioselectivity, yielding almost exclusively the (S)-enantiomer. In NADH-supported reactions, WT CYP199A4 catalysed O-demethylation of 4- methoxybenzoic acid more efficiently than sulfoxidation of 4-methylthiobenzoic acid. In H₂O₂- driven reactions, the T252E variant had higher activity towards sulfoxidation compared to Odemethylation, hydroxylation, epoxidation, aldehyde oxidation and alkyne oxidation. This may indicate the involvement of a second oxidant in sulfoxidation (e.g. the FeIII–H₂O₂ species), allowing sulfoxidation to occur in the absence of Compound I as proposed by Shaik.Thesis (MPhil) -- University of Adelaide, School of Physical Sciences, 2020
Книги з теми "Active oxidants"
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Lester, Packer, ed. Oxidants and antioxidants. San Diego: Academic Press, 1999.
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2
Baraboĭ, V. A. Okislitelʹno-antioksidantnyĭ gomeostaz v norme i patologii. Kiev: Chernobylʹinterinform, 1997.
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3
Kronhausen, Eberhard. Formula for life: The anti-oxidant, free-radical, detoxification program. New York: Morrow, 1989.
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4
International, Conference on Oxygen and Life (3rd 2000 Kyoto Japan). Oxygen and life: Oxygenases, oxidases, and lipid mediators : proceedings of the 3rd International Conference on Oxygen and Life which was held in Kyoto, between 26 and 29 November 2000. Amsterdam: Elsevier, 2002.
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5
1942-, Sies H., ed. Oxidative stress: Oxidants and antioxidants. London: Academic Press, 1991.
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6
(Editor), John N. Abelson, Melvin I. Simon (Editor), and Helmut Sies (Editor), eds. Methods in Enzymology, Volume 299: Oxidants and Antioxidants, Part A (Methods in Enzymology). Academic Press, 1998.
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(Editor), Jens Thiele, and Peter Elsner (Editor), eds. Oxidants and Antioxidants in Cutaneous Biology (Current Problems in Dermatology). S. Karger Publishers (USA), 2001.
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Fuchs, Jürgen. Environmental Stressors in Health and Disease (Oxidative Stress and Disease). CRC, 2001.
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F, Ursini, and Davies Kelvin J. A, eds. The oxygen paradox. Padova, Italy: CLEUP University Press, 1995.
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1957-, Fuchs Jürgen, and Packer Lester, eds. Environmental stressors in health and disease. New York: M. Dekker, 2001.
Знайти повний текст джерелаЧастини книг з теми "Active oxidants"
1
Yang, Xu, Jingbo Yang, Qinhai Hu, Min Xia, and Zucheng Wu. "In-Situ Generation of Active Oxidants in Permeable Reactive Barriers." In Environmental Science and Engineering, 868–73. Singapore: Springer Singapore, 2018. http://dx.doi.org/10.1007/978-981-13-2221-1_99.
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Huck, Peter M., and Daniel Urfer. "A Comparison of the Effects of Different Oxidants/Disinfectants on Biologically Active Drinking Water Filters." In Chemical Water and Wastewater Treatment V, 57–67. Berlin, Heidelberg: Springer Berlin Heidelberg, 1998. http://dx.doi.org/10.1007/978-3-642-72279-0_6.
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Zulfiqar, Abida, Sara Ishaq, and Touqeer Ahmed. "Anti-Oxidant Nutrients and Nutraceuticals in Aging." In Nutrients and Nutraceuticals for Active & Healthy Ageing, 195–216. Singapore: Springer Singapore, 2020. http://dx.doi.org/10.1007/978-981-15-3552-9_9.
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Knowles, P. F., I. Singh, K. D. S. Yadav, F. E. Mabbs, D. Collison, C. E. Cote, D. M. Dooley, and M. A. McGuirl. "Active Site Structures of Copper-Containing Oxidases." In PQQ and Quinoproteins, 283–88. Dordrecht: Springer Netherlands, 1989. http://dx.doi.org/10.1007/978-94-009-0957-1_43.
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Holt, A., and B. A. Callingham. "Location of the active site of rat vascular semicarbazide-sensitive amine oxidase." In Amine Oxidases: Function and Dysfunction, 433–37. Vienna: Springer Vienna, 1994. http://dx.doi.org/10.1007/978-3-7091-9324-2_58.
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Wouters, J., F. Moureau, D. P. Vercauteren, G. Evrard, F. Durant, J. J. Koenig, F. Ducrey, and F. X. Jarreau. "Experimental and theoretical study of reversible monoamine oxidase inhibitors: structural approach of the active site of the enzyme." In Amine Oxidases: Function and Dysfunction, 313–19. Vienna: Springer Vienna, 1994. http://dx.doi.org/10.1007/978-3-7091-9324-2_41.
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Ackenheil, M. "The mechanism of action of antidepressants revised." In Amine Oxidases and Their Impact on Neurobiology, 29–37. Vienna: Springer Vienna, 1990. http://dx.doi.org/10.1007/978-3-7091-9113-2_3.
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Klotz, Lars-Oliver. "Oxidative Stress, Antioxidants, and Chemoprevention: On the Role of Oxidant-Induced Signaling in Cellular Adaptation." In Recent Advances in Redox Active Plant and Microbial Products, 119–46. Dordrecht: Springer Netherlands, 2014. http://dx.doi.org/10.1007/978-94-017-8953-0_5.
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Müller, Th, W. Kuhn, R. Krüger, and H. Przuntek. "Selegiline as immunostimulant — a novel mechanism of action?" In MAO — The Mother of all Amine Oxidases, 321–28. Vienna: Springer Vienna, 1998. http://dx.doi.org/10.1007/978-3-7091-6499-0_33.
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May, T., S. Strauss, and H. Rommelspacher. "[3H] Harman labels selectively and with high affinity the active site of monoamine oxidase (EC 1.4.3.4) subtype A (MAO-A) in rat, marmoset, and pig." In Amine Oxidases and Their Impact on Neurobiology, 93–102. Vienna: Springer Vienna, 1990. http://dx.doi.org/10.1007/978-3-7091-9113-2_12.
Повний текст джерелаТези доповідей конференцій з теми "Active oxidants"
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Krause, T. R., S. Ahmed, and R. Kumar. "Distributed Reforming of Diesel, JP-8, and Other Heavy Hydrocarbon Fuels for Fuel Cell Applications: Challenges and Issues." In ASME 2006 4th International Conference on Fuel Cell Science, Engineering and Technology. ASMEDC, 2006. http://dx.doi.org/10.1115/fuelcell2006-97260.
Повний текст джерелаАнотація:
Reforming diesel, JP-8 (Jet Propellant 8 – standard U.S. military kerosene-based jet fuel), and other heavy hydrocarbon fuels is one option being investigated for providing H2 for distributed mobile and stationary fuel cell systems for military and civilian applications. Unlike natural gas, which is another hydrocarbon fuel being investigated, these fuels are high-boiling-point, multi-component liquids that contain high concentrations of refractory sulfur and aromatic compounds that can negatively impact the efficiency and operating lifetime of the fuel processor. Fuel injection, desulfurization, and carbon deposition are major issues that fuel processor developers must address when designing fuel processors for these fuels. The fuel injection system must prevent direct injection of liquid onto the catalyst surface and poor mixing of the fuel and oxidants (i.e., air and/or steam), both of which can result in excessively high temperatures that can damage or destroy the reforming catalyst. A highly efficient desulfurization process is required that can reduce the sulfur concentration to acceptable levels for both fuel processor and fuel cell catalysts without requiring large amounts of materials or complicated processes, and without generating excessive amounts of disposable waste. Highly active reforming catalysts and the proper choice of operating conditions (i.e., ratio of fuel to oxidant[s], temperature, residence time) are required for effective reforming of aromatic compounds to prevent carbon deposition on the reforming catalyst as well as in the fuel processor downstream of the reformer. In this paper, we will discuss how the chemical and physical properties of these fuels influence the design of the fuel processor focusing on the fuel injection system, the choice of desulfurization process, and the design and operation of the reformer. We will also discuss various approaches and design options for developing highly efficient fuel processors for reforming these fuels for both polymer electrolyte and solid oxide fuel cells.
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Loskutoff, D. J., J. Mimuro, and C. Hekman. "PLASMINOGEN ACTIVATOR INHIBITOR." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1644763.
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Plasminogen activation provides an important source of localized proteolytic activity not only during fibrinolysis, but also during ovulation, cell migration, epithelial cell differentiation, tumor invasion and a variety of other physiological processes. Precise regulation of plasminogen activator (PA) activity thus constitutes a critical feature of many biological processes. This control is achieved in large part through the action of specific PA inhibitors (PAIs). Although 4 distinct PAIs have been detected,1the endothelial cellTderived inhibitor (PAI-1) is the only one that efficiently inhibits both urokinase (Kd=2.3×10−13M; Kassoc =1.6×108 M−1s−1) and single-chaintissue-type PA (tPA; Kd=1.3×lO−15 M Kd=3.9×lO7M−1s−1). It also inhibits trypsin (Kassoc=6.8×106M−1 s−1 ) ancl Plasmin (Kassoc=7.6×l05 M−1 s5 Analysis of the effect of PAI-1 on the rate of plasminogen activation revealed a competitive type of inhibition when urokinase was employed but a linear mixed type of inhibition when single chain tPA was employed. These results suggest that the interaction of PAI-1 with tPA, in contrast to its interaction with urokinase, may involve 2 sites on the tPA molecule.PAI-1 has been purified from medium conditioned by cultured bovine aortic endothelial cells and partially characterized. It is a major biosynthetic product of these cells, accounting for as much as 12% of the total protein released by the cells in 24 h. It has an M of 50,000, an isoelectric point of 4.5-5.0, and is immunologically and biochemically related to the rapidly acting inhibitor present in human platelets and in the plasma of some patients at risk to develop thrombotic problems. Although it is relatively stable to conditions which inactivate most protease inhibitors (acid pH, SDS), it is extremely sensitive to oxidants. The molecular cloning of the PAI-1 gene revealed that the mature human protein is 379 amino acids long, contains an NH2-terminal valine, lacks cysteines and has a methionine at the Pi position of it's reactive center. The conversion of this methionine to methionine sulfoxide may be responsible for the rapid inactivation of PAI-1 by oxidants. Human PAI-1 has extensive (30%) homology with α1-antitrypsin and antithrombin III and is thus a member of the serine proteinase inhibitor (serpin) family; a group of related molecules that control the major protease cascades of the blood. The PAI-1 gene is approximately 12.2 kilobase pairs in length and is organized into nine exons and eight introns.The production of PAI-1 by endothelial cells is stimulated by endotoxin, interleukin-1, tumor necrosis factor, and transforming growth factor β(TGFβ). The cells are extremely sensitive to TGFβwith maximal effects (100-fold stimulation) observed with 1-2 ng/ml. These changes were relatively specific for PAI-1, and could be detected at both the protein and the RNA level. Interestingly, TGFgalso stimulated the amount of PAI-1 present in the extracellular matrix (ECM) of BAEs. PAI-1 was one of the primary ECM components of these cells, constituting 10-20% of the ECM proteins detected after SDS-PAGE.One of the most unusual properties of PAI-1 is that it exists in blood and in various cellular samples in both an active and an inactive (latent) form, the ratio depending on the source. The latent form can be converted into the active one by treatment with denaturants like SDS or guanidine-HCl. Although the majority of the cell-associated PAI-1 is active, it rapidly decays (t1/2=3 h) into the latent form once it is released from the cells. In contrast, the half-life of ECM associated PAI-1 was greater than 24 h. These data suggest that PAI-1 is produced by BAEs in an active form, and is then either released into the medium where it is rapidly inactivated, or released into the subendothelium where it binds to ECM. The specific binding of PAI-1 to ECM protects it from this inactivation.
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Maksymchuk, Pavlo, Kateryna Hubenko, Vladyslav Seminko, and Svetlana Yefimova. "Pro-oxidant action of preliminarily UV-activated orthovanadate nanocrystals." In RAD Conference. RAD Centre, 2021. http://dx.doi.org/10.21175/rad.abstr.book.2021.38.6.
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Vasko, Christopher A., and Christina G. Giannopapa. "Liquid Droplets in Contact With Cold Non-Equilibrium Atmospheric Pressure Plasmas." In ASME 2016 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/pvp2016-63629.
Повний текст джерелаАнотація:
Recently, cold, non-equilibrium atmospheric pressure plasmas (CAPs) and their active chemistry have been extensively investigated to the benefit of a wide array of applications such as biomedical and industrial applications mainly in the area of materials processing and chemical synthesis, amongst many others. In general, these plasmas operate at standard conditions (i.e. 1 atm, 300K), are small (∼ cm) and rather simple to operate in comparison to other plasmas. Their complex chemistry gives rise to a wide array of both stable and transient reactive species: such as O3, H2O2, OH and NOx, next to charged species and (V)UV-radiation. This chemistry is the reason for their wide spread application and has already found many industrial applications from waste water treatment, stain free detergents and industrial scale production of oxidants. In recent years, bactericidal effects of CAPs gained increasing attention for applications such as dermatology, disinfection, dentistry and cancer treatment or stimulated blood coagulation. This paper aims to highlight recent research into new biological applications for complex mission scenarios involving humans in remote locations using CAPs for disinfection, bleaching or wound healing. Results using radiofrequency plasma jets for the inactivation of Pseudomonas aeruginosa are summarized, highlighting the importance of liquid plasma interactions. Work with such a CAP paved the way for a promising application in the field of biomedical applications presented here. It involves surface barrier discharges which can be used to treat larger surfaces compared to jets. Their physical construction, using floating or contained electrodes, offer a convenient way of controlling electrical current on a large scale, 3D treatment of both conducting and insulating surfaces with minimal heating. These devices may be tailored to specific skin treatments, allowing fast and effective treatment of larger skin surfaces while following the shape of the skin. This might reduce the need for bactericidal agents and would be a valuable application to assist humans in remote locations. These emerging technologies could be essential both for human health care under extreme conditions, as well as for research itself (sterilisation of tools and large areas, etc.). Especially in the absence of abundant resources (antibiotic agents, disinfectants and the like) alternative approaches to support humans in isolated locations have to be developed. Applications based on a good understanding of plasma chemistry would empower health care under extreme conditions to efficiently use and manage in situ resources. Their low mass, compact size, low power consumption and high reliability could make them essential use under extreme conditions.
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Magar, Yogesh N., and Raj M. Manglik. "Thermal and Hydrodynamic Modeling of Fully-Developed Convection in Anode-Supported Planar Solid Oxide Fuel Cells." In ASME 2005 International Mechanical Engineering Congress and Exposition. ASMEDC, 2005. http://dx.doi.org/10.1115/imece2005-79986.
Повний текст джерелаАнотація:
Uniform supply of volatile species to an active surface along with the oxidant flow to sustain the surface electrochemical reaction, and its effective cooling in an anode supported solid oxide fuel cell (SOFC) is modeled. Three-dimensional nonlinear partial differential governing equations for the conservation of mass, momentum, energy, species, and electrochemical kinetics for both the anode and cathode ducts for steady laminar, incompressible flow are solved computationally. A planar, tri-layer SOFC module, which consists of porous anode and cathode layers, solid electrolyte and rectangular flow ducts, is considered. The homogenous porous electrode layers are characterized by constant porosity, permeability, and thermal conductivity, and the fluid in these porous layers is considered to be in thermal equilibrium with the solid matrix. The computational results highlight the influence of fuel and oxidant flow duct aspect ratio and porous anode-layer depth on the friction factor and Nusselt number for typical electrochemical loads, and the consequent thermal signatures of the SOFC.
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Parekh, K., R. Mourhatch, and P. B. Aswath. "ZDDP-Additive-Catalyst Interactions in Engine Oil." In World Tribology Congress III. ASMEDC, 2005. http://dx.doi.org/10.1115/wtc2005-64075.
Повний текст джерелаАнотація:
The phosphorous content in engine oil is found to be the major cause of the poisoning of Catalytic converters in automobiles, hence environmental regulations limiting the phosphorous level in GF4 and GF5 oils have been introduced. Zinc dialkyl dithiophosphate (ZDDP) being the only major source of phosphorous in current engine oils, is also an indispensable component of the additive package in these oils for it has been the primary anti wear — as well as anti oxidant — additive for over fifty years. Efforts are made to replace the ZDDP with other materials with the same properties which would not be harmful to the environment and also an economically feasible substitute. Another solution to this problem is to reduce the amount of ZDDP used while improving its antiwear performance. Anti-wear action of ZDDP, involves its break down reaction with the steel surface by Zn Fe ion exchange and subsequent formation of an amorphous chemisorbed film containing zinc, phosphorus, oxygen and sulfur and also iron in the form of polyphosphates and sulfates of zinc and iron. The efficiency of this mechanism is reduced by parallel reactions between ZDDP and other additives as well as their antagonistic effects. Introduction of a material with catalytic properties which would reduce the negative effects of the presence of the other additives on the anti wear properties of ZDDP is an option that was explored in this paper. Both triboligical wear tests (Ball on cylinder lubricity evaluation tests) as well as mechanism studies (DSC, FT-IR and NMR) were used to evaluate the performance of ZDDP in the presence of the most common additives (i.e. Anti-oxidants, Detergents and Dispersant). Iron Fluoride is also introduced as a potential additive to improve the efficiency of wear protection mechanism of ZDDP. The improvements observed in the presence of the Iron Fluoride will allow further reducing the amount of ZDDP in engine oils containing this material as an additive [1].
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Khabbazi, Ali Ebrahimi, Andrew Richards, and Mina Hoorfar. "Numerical Analysis of the Effect of Different Channel Geometries and Electrode Materials on the Performance of Microfluidic Fuel Cells." In ASME 2010 8th International Conference on Nanochannels, Microchannels, and Minichannels collocated with 3rd Joint US-European Fluids Engineering Summer Meeting. ASMEDC, 2010. http://dx.doi.org/10.1115/fedsm-icnmm2010-30772.
Повний текст джерелаАнотація:
A typical microfluidic fuel cell is comprised of a Y- or T-shaped microchannel. The fuel and the oxidant streams are introduced from the two different inlets. The anodic and cathodic flows meet each other at the beginning of the main channel and start to travel together along the channel. Due to the fact that the viscous forces dominate the inertia forces in microchannels, the oxidant and the fuel streams establish a side-by-side co-laminar flow which makes the anolyte and catholyte flow together without turbulent mixing. Laminar flow in microfluidic fuel cells plays the role of the membrane in proton exchange membrane (PEM) fuel cells by maintaining the separation of the fuel and oxidant. This eliminates the need for the membrane and overcomes the membrane-related issues such as the ohmic overpotential and water management which are relevant to PEM fuel cells. In addition to the above advantage, the high surface-to-volume ratio of these micron-scale devices contributes to their high power density. This advantage is due to the fact that the electrochemical reactions in fuel cells are surface-based. The electrodes on which the electrochemical reactions are occurring are installed appropriately on the walls of the channel in a way that reacting flows are restricted to the proper electrodes. Since the flow is laminar the performance of the microfluidic fuel cell significantly depends on the device geometry. In this paper, different channel geometries and different electrode configurations are modeled and their performances are compared through the polarization curves. It has been found that the high aspect ratio provides the largest power density. In this work, the performance of the flow-through porous electrode was also modeled and compared against the conventional non-porous electrode microfluidic fuel cells. The flow-through porous electrode design is based on cross-flow of aqueous vanadium redox species through the electrodes into an exit channel, where the waste solutions meet and establish a co-laminar flow. This co-laminar flow of reacted species facilitates ionic charge transfer in a membraneless configuration. It has been found that the flow-through porous architecture provides an increased active surface area which contributes to a higher power density as opposed to the fuel cells with non-porous electrodes.
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Fuerth, D., and A. Bazylak. "Carbon Based Electrodes for Upscaling Microfluidic Fuel Cells." In ASME 2012 10th International Conference on Fuel Cell Science, Engineering and Technology collocated with the ASME 2012 6th International Conference on Energy Sustainability. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/fuelcell2012-91043.
Повний текст джерелаАнотація:
In this work, we present an experimental microfluidic fuel cell with a novel up-scaled porous electrode architecture that provides higher overall power output compared to conventional microfluidic fuel cells and a methodology for electrode material evaluation to inform designs for improved performance. Our proof-of-concept architecture is an up-scaled version of a previously presented flow-through cell with more than nine times the active electrode surface area. We employed 0.04M formic acid and 0.01M potassium permanganate as fuel and oxidant, respectively, dissolved in a 1M sulfuric acid electrolyte. Platinum black was employed as the catalyst for both anode and cathode. Carbon based porous electrodes including felt, cloth, fibre, and foam were compared to traditional Toray carbon paper in order to characterize their respective performances. We also discussed current densities normalized by electrode volume, which is appropriate for comparison of flow-through architectures. The traditional method of current normalization by projected electrode surface area is also presented.
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Shatos, M., J. Doherty, D. Allen, and J. Hoak. "ALTERATIONS IN VASCULAR ENDOTHELIAL CELL FUNCTION BY OXYGEN-FREE RADICALS." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1643365.
Повний текст джерелаАнотація:
The vascular endothelium is a target for oxidant-induced damage in many disease states including hyperoxia, inflammation, ischemia and reperfusion injury. However, little is known concerning oxidant injury to endothelial cells and its relationship to hemostasis. Our studies have focused on the ability of oxygen free radicals to injure and/or alter selected vascular endothelial cell functions pertinent to the regulation of hemostasis. Xanthine and xanthine oxidase, a well-characterized generating system for the production of the superoxide anion radical (O− 2) was used to sublethally injure human umbilical vein endothelial cells (HUVE) in vitro. We examined the effects of a 15 min exposure of HUVE cells to xanthine (50μM), and xanthine oxidase (2.5-100mU) (previously determined to be non-toxic using trypan blue dye exclusion) on platelet adherence, and prostacyclin release using established assays. The antioxidant enzymes superoxide dismutase (SOD) 200μg/ml and catalase 50μg/ml were added to endothelium incubation systems to evaluate any protective effects upon O− 2-induced alterations. All experiments were conducted in a serum-free HEPES-Tyrode's buffer, pH 7.4 incubation system. Our results show that exposure of HUVE cells to sublethal concentrations of oxygen free radical generating systems causes significant enhancement of platelet adherence (65%) to injured endothelium. A 12-fold increase in prostacyclin release resulted after a 15 min treatment with xanthine and xanthine oxidase. The addition of exogenous PGI2 (150nM) to platelet-endothelial systems did not completely prevent the enhanced platelet adherence suggesting that lack of prostacyclin was not completely responsible for the adherence of platelets to O− 2 injured cells. When SOD and catalase, scavengers of O− 2 and H2O− 2, were added to treated cells, platelet adherence decreased by 42-77% and prostacyclin release approached that of control cultures. These data implicate an active participation of activated metabolites of molecular oxygen in the alteration of vascular endothelial cell function.
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Niwa, A., and K. Hamashima. "Effect of M-CrAlY Coating for Corrosion Resistance in Specific High Temperature Atmosphere." In ITSC2010, edited by B. R. Marple, A. Agarwal, M. M. Hyland, Y. C. Lau, C. J. Li, R. S. Lima, and G. Montavon. DVS Media GmbH, 2010. http://dx.doi.org/10.31399/asm.cp.itsc2010p0298.
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Abstract In the glass manufacturing, stainless-steel parts are used in characteristic corrosive reduction atmosphere at high temperature. The reactive products, that are induced by volatilization from the stainless steel surface, cause defects of the glass in this usage. Some thermal spraying coating of thermal-resistant alloys is tested in this study for the protection to the volatilization. It is clarified that, the Ni-Cr-Al-Y film, containing plate-like metal oxide dispersions, shows an outstanding effect as followings; 1) The diffusion rate of Fe from a stainless substrate in this coating film is decreased by the dispersions, and Fe is not detected at surface layer of the coating after a long-term exposure test at high temperature. 2) The reaction between Sn and this coating is not active relatively can, and the further inactivation can be possible by pre-existing heat-treatment in oxidant atmosphere. 3) Both effect (decreasing of Fe diffusion rate and inactivation with Sn) are induced by plate-like Al2O3 particles. These particles are generated by oxidation of Al-content in the coating material.