Dissertations / Theses on the topic 'Hydrogen sulphide'
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Lawrence, Nathan S. "Electrochemical detection of hydrogen sulphide." Thesis, University of Oxford, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.275271.
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White, Benjamin J. O. "The vascular effects of hydrogen sulphide." Thesis, University of Nottingham, 2012. http://eprints.nottingham.ac.uk/12447/.
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In recent years it has become apparent that hydrogen sulphide (H2S) is an important biological mediator. In the vasculature, it produces complex responses: contraction in some blood vessels, relaxation in others, via multiple mechanisms. This thesis examined the relationship between H2S and oxygen in determining vascular responsiveness, and was conducted using porcine splenic and mesenteric arteries. Studies were also conducted using porcine splenic veins, since few studies have examined venous function. Additionally, studies were extended to the resistance vasculature by determining responses to a H2S donor in small arteries isolated from the rat mesentery. Porcine vessels were set up in an isometric tension recording system and rat small mesenteric arteries were set up in a pressure myograph. Vessels were pre-contracted and responses to the H2S donor, NaHS, were generated in the presence and absence of putative inhibitors, under either 95% O2:5% CO2, 95% air:5% CO2 or 95% N2:5% CO2 gassing conditions. Generally, in both porcine arteries and veins, when gassing with higher oxygen levels (95% O2:5% CO2 or 95% Air:5% CO2), NaHS induced contractile responses, whereas gassing with a lower oxygen level (95% N2:5% CO2), NaHS induced vasorelaxation. At higher O2 levels, removal of the endothelium or, the nitric oxide (NO) synthase inhibitor L-NAME, significantly attenuated contractile response in all porcine vessels. This suggests an interaction between endothelium-derived NO and NaHS, whereby the removal of the vasorelaxatory influence of NO resulted in contraction. In porcine arteries, relaxation at lower O2 levels was attenuated by glibenclamide, suggesting that NaHS activated KATP channels to cause relaxation. In porcine veins, removal of the endothelium or, L-NAME, abolished NaHS-induced relaxation, showing this relaxation occurred via the release of endothelium-derived NO. In rat mesenteric small arteries responses to NaHS did not change with different O2 levels and NaHS-induced vasodilatation that was abolished by desensitization of sensory nerves with capsaicin or the presence of BIBN 4096. These observations suggest NaHS-induced vasodilatation is mediated via release of CGRP from sensory nerves. Thus, responses to NaHS in large conduit arteries and veins, are sensitive to the prevailing level of O2 the tissue is exposed to. At more physiological levels of O2 the predominant response is a vasorelaxation, mediated by either, activation of KATP channels in arteries or, the release of NO in veins. In small arteries, the predominant response is a vasodilator response, involving the release of neuropeptides from sensory nerves. The predominance of a vasorelaxant/vasodilator response is consistent with the observation that mice which lack the capacity to generate endogenous H2S are hypertensive.
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Deuchar, Christopher Norton. "The detection and measurement of hydrogen sulphide." Thesis, University of Nottingham, 2003. http://eprints.nottingham.ac.uk/10223/.
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Gas measurement techniques for hydrogen sulphide (H2S) have been investigated, with particular reference to the monitoring of average ambient concentrations and also the rapidly changing concentrations which may be associated with vehicle pollution. Two new techniques have been identified, and new equipment built and tested, for H2S determination. The first of these is designed to measure long term average concentrations of H2S and the second to evaluate rapidly changing peak concentrations over very short periods of time. The implementation of catalytic converters in modern petrol driven motor vehicles has resulted in undesirable emissions of hydrogen sulphide gas. The reasons for these emissions are discussed. Ambient concentrations of H2S have been measured at the roadside and the average contribution originating from vehicular emissions on major roads determined. Results are presented which confirm the elevation of hydrogen sulphide concentrations at the road side of an average of single figure parts per billion. Peak H2S concentrations of up to 100 ppb were also measured at the roadside and within motor vehicles. The peaks were of very short duration and therefore of only minimal contribution to average ambient concentrations. Measurements of H2S concentrations at a variety of locations have also been made,and results are presented, of comparisons between areas with no source of H2S nearby, roadside sites and other possible H2S sources such as sewage treatment works and landfill sites. Known H2S concentrations, in excess of 500 ppm from a point source on a landfill site, were found to diminish rapidly toward zero, within 150 m of the source. This demonstrated the high reactivity of H2S and therefore the importance of measuring H2S concentration as closely as possible to the emission source. Consequently, this high reactivity is particularly important in the consideration of roadside and 'on-road' monitoring of H2S.
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Azzam, A. A. A. "A linelist for the hydrogen sulphide molecule." Thesis, University College London (University of London), 2013. http://discovery.ucl.ac.uk/1404058/.
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The main aim of this study is to calculate a high temperature line list for H_2^32S. The results will form an important addition to the databases used for space applications, as well as laboratory investigations and pollution studies. The Dvr3d program suite is used to calculate the bound ro-vibrational energy levels, and dipole moment transition intensities. The most accurate available potential energy surface is empirically determined. This surface is used in our calculations after refining it by fitting to the up-to-date experimental data. For accurate line intensities, an accurate dipole moment surface (DMS) is needed. Constructing an accurate DMS for H_2S is well known to be difficult. A systematic ab initio study for the DMS has been performed. Different methods were tested in conjunctions with different basis sets taking into account the relativistic corrections and core-valence effects. The resulting (ATY2013) line list should be valid from 0 to 9000 cm^−1 and for temperature up to 2000 K. ATY2013 with cut off intensity of order 10^−31 cm^−1/(molecule×cm^−2) contains ∼36×10^6 transitions at 2000 K. In addition, the pure rotational transition frequencies of H_2S in natural abundance in its ground and first excited vibrational states have been recorded at room temperature at 0.005 cm^−1 resolution in the region 45 to 360 cm^−1 with a globar continuum source at SOLEIL synchrotron. 2400 rotational transitions are assigned to ground vibrational state of the four isotopologues H_2^32S, H_2^33S, H_2^34S and H_2^36S where 65% of them are new. 91 rotational transitions of H_2^36S were identified for the first time, as well as 406 rotational lines of H_2^32S and H_2^34S in their first excited bending vibrational state were recorded and analysed for the first time.
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Hsu, Anna. "Hydrogen sulphide (H2S) and the cardiovascular system." Thesis, King's College London (University of London), 2012. http://kclpure.kcl.ac.uk/portal/en/theses/hydrogen-sulphide-h2s-and-the-cardiovascular-system(53365106-ee0f-4a29-a626-c9f80e5cef80).html.
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Hydrogen sulfide (H2S) has relatively recently been added to a list of endogenously produced gaseous signalling molecules. Our understanding of the science of H2S has advanced rapidly in recent years as exemplified by the fact that within a mere 10 years a range of H2S releasing drugs have already been discovered and some indeed are entering clinical trials. However, the precise biological roles of endogenous H2S are not fully understood. In this respect, slow releasing H2S donors, such as GYY4137, have played a part in elucidating the complex roles of this gas in the body and are also beginning to show promise as possible therapeutics in inflammation - an area in which the function of H2S remains ambiguous. This thesis attempts to provide some additional clarity to the biological significance endogenous H2S. The first part of this work examines the release of endothelial cell derived H2S in vitro and the consequences of knocking out nitric oxide synthase on tissue H2S biosynthesis in mice. As part of this study, I show that the methods currently utilised to measure H2S are insufficiently sensitive/reliable to demonstrate the release of H2S synthesis from endothelial cells in vitro. In addition, data reported herein has demonstrated that knocking out endothelial cell nitric oxide synthase (eNOS) results in a presumably compensatory increase in tissue H2S synthesising activity associated with increased protein levels of the H2S synthesising enzyme, cystathionine-γ-lyase (CSE). The second part of this thesis examines the role of H2S in inflammation and provides further evidence for its anti-inflammatory activity both in vitro and in vivo. In addition, this thesis has shown the ‘added benefit’ of slow-releasing H2S donors (c.f. 3 conventional sulpide salt based donors) in that the H2S released from slow-releasing donors is sustained and does not instantaneously expose cells to potentially cytotoxic amounts of H2S. Identifying a need for additional slow releasing H2S donors attempts were made to examine the H2S releasing ability and antioxidant capacity of a library of additional compounds. As a result of this work, a novel compound, ZJ802 was shown to exhibit more potent antioxidant ability than the currently commercially available H2S donors and was further shown to exhibit anti-inflammatory activity both in vitro and in vivo. Overall, the roles of H2S in physiology are not clear. Current methods to detect H2S are flawed. Thus, the necessity for pharmacological tools, such as slow releasing H2S donors and selective H2S synthesising enzyme inhibitors, cannot be overemphasised. Whilst the possible use of H2S donors in the clinic has been raised there is still a need for more detailed preclinical, pharmacokinetic and long term drug safety and toxicological studies.
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Idriss, Ahmed. "Corrosive effect of hydrogen sulphide on cement mortar." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0018/NQ55626.pdf.
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Babcock, Kevin Brian. "Alkali carbonate-sulfide electrolytes for medium temperature hydrogen sulfide removal." Thesis, Georgia Institute of Technology, 1986. http://hdl.handle.net/1853/12959.
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Barbosa, Vera Lucia. "Biological treatment of hydrogen sulphide by activated sludge diffusion." Thesis, Cranfield University, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.422391.
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Picton, Rhian. "Hydrogen sulphide toxicity : an aetiological factor in ulcerative colitis." Thesis, University of Birmingham, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.395590.
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Le, Trionnaire Sophie. "Hydrogen sulphide: a novel mediator of diabetic microvascular dysfunction?" Thesis, Exeter and Plymouth Peninsula Medical School, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.657595.
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Hydrogen sulfide (H2S) has been proposed as a novel endogenous regulator of vascular tone and inflammation. Novel slow release H2S donors (SRHOs) (e.g. GYY4137) have been shown to regulate blood pressure in experimental/genetically induced hypertension, and to inhibit tissue damage, oedema and inflammatory signalling in sepsis and arthritis. All these conditions involve perturbed mitochondrial function, oxidative stress and eventually apoptotic cell death. In the literature, the majority of studies pertaining to the vascular effects of H2S have been limited to the use of simple sulfide salts, NaSH and Na2S, which release H2S far too quickly to be physiologically relevant. Indeed, a study comparing NaSH and GYY 4137 showed that the level of H2S released from NaSH was rapidly high (400I-lM in the first 20min) and declined dramatically until disappearance. In contrast, H2S release from GYY4137 was low and continuous in time (-40I-lM up to 7 days). Therefore, to circumvent this problem, our team has designed several novel SRHOs, such as GYY4137, AP39, AP123, AP67 and AP72. These compounds offer the advantage over sulfide salts (i) to be not toxic (ii) to release H2S in a slow and sustained manner, (iii) to exert their effects at considerably lower H2S concentrations, and (iiii) to selectively target the mitochondria (in the case of AP39 and AP123). The latter combine a mitochondria-targeting moiety (triphenylphosphonium), a C2-C18 linker and H2S releasing moieties (dithiolethione or 4-hydroxythiobenzamide respectively). Preliminary experiments on these mitochondria-targeting SRHO showed a C1Q linker to be optimal; therefore AP39 and AP123 were chosen. Human cerebral microvascular endothelial cells (hCMEC/03) were exposed to oxidative stress agents, mitochondrial toxins and apoptosis inducing drugs in the presence/absence of the SRHOs. Cell toxicity was assessed using alamarBlue and flow cytometry, whereas cytosolic/mitochondrial reactive oxygen species (ROS) generation was estimated using H20CFOA, MitoSOX Red and Oihydroethidium fluorescence (spectrophotometry, flow cytometry). Mitochondrial membrane potential (~4Jm) was assessed using TMRM. Western immunoblotting and fluorescence activity assays were used to determine caspase3/7 activation/activity. Quantification of cytochrome c release from the 3 mitochondria was also attempted. Intracellular levels of ATP were assessed by the luciferase activity assay. Some antioxidant assays were finally used to determine whether the potential antioxidant effects of the SRHDs would be due to any scavenging effect. Cell viability was significantly preserved by all SRHDs. Besides, the potency of cytoprotection was substantially increased by the targeting mitochondria SRHD (AP39/AP123) from the j..IM to the nM range. The collapse of L14Jm normally observed in toxic conditions was inhibited by SRHDs. Overall "ROS" generation was markedly decreased after treatment with SRHDs. AP67 and AP72 inhibited caspase 3/7 activity when apoptosis was induced by staurosporine/etoposide. Cytochrome c release was positively modulated with our donors, as well as the ATP synthesis. These data suggest that SRHDs can inhibit/reverse oxidative stressmediated cellular injury, and highlight the increased potency of the mitochondria- targeting H2S donors AP39 and AP123 compared to GVY4137, AP67 and AP72. The measurement of the antioxidant capacity in cell-free system of the SRHDs showed (i) no scavenging effect of AP39 and AP123, confirming their release of H2S only in the mitochondria (ii) a scavenging effect of GVY4137, AP67 and AP72 only for high concentrations (>250j..lM), confirming that the antioxidant effects of these SRHDs in our cell system was unlikely due to any scavenging effect. Strategies increasing H2S bioavailability, in particular targeting mitochondria, may represent a new therapeutic opportunity to limit mitochondrial dysfunction.
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Wood, Christine Frances. "An analytical study of hydrogen sulphide in the environment." Thesis, University of Aberdeen, 1990. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU024242.
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The occurrence of hydrogen sulphide in the environment, the reasons for concern about the levels which may be present, particularly on off-shore installations, and methods for determining the gas in air are reviewed. The original aim of this project was to explain the reasons for the variations in the levels of naturally occurring hydrogen sulphide over the estuary of the Don at Aberdeen. The monitoring work required a reliable method: as the published methods were all problematical, much effort was expended in improving the Ethylene Blue method and investigating the range of trapping solutions. The final optimised method has been published (Analyst 1988, 113, 1635). An alternative method for standardising H2S in air gas mixes has also been developed and used on commercial samples. Microbiological studies have shown that sulphate-reducing bacteria were not present in the sediments of the Don estuary in 1988 (but were present in sediments from the Forth estuary) and further, that the Don sediments would not support growth of SRB's, which in part explains why there has been effectively no release of H2S from the estuary in recent years. Attempts have been made to correlate the H2S emission events with changes in river water quality over the last ten years, but no obvious clues have become evident.
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Hunter, James Philip. "The role of hydrogen sulphide in ischaemia reperfusion injury." Thesis, University of Leicester, 2015. http://hdl.handle.net/2381/35951.
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Warm ischaemic injury occurs when an organ or region of the body is starved of oxygenated blood under normothermic conditions. Two important clinical examples of warm ischaemia are donation after circulatory death (DCD) kidney transplantation and abdominal aortic aneurysm (AAA) repair. The tissue injury that results from warm ischaemia can lead to organ dysfunction, which has important clinical consequences. In kidney transplantation warm ischaemic injury can lead to delayed graft function, increased rates of primary non-function and poorer long-term outcomes. In open AAA repair occlusion of the abdominal aorta leads to remote injury to organs such as the kidneys. Renal failure following AAA repair can cause significant morbidity including the need for renal replacement therapy. Hydrogen sulphide (H2S) is an endogenously produced gas that been shown to be protective against ischaemia-reperfusion injury. The aims of this thesis were twofold. First, the effect of H2S on ischaemia-reperfusion injury in a porcine model of direct renal ischaemia was assessed. Second, the effect of H2S on inflammation and remote renal injury was assessed using a rodent model of aortic occlusion. This research demonstrated that hydrogen sulphide, delivered as an exogenous agent, preserved renal function and reduced inflammation in a large animal model of renal warm ischaemia. Furthermore, in a rodent model of remote renal injury hydrogen sulphide also reduced systemic and renal inflammation but had no effect on renal function. In addition, there were no significant side effects from the administration of hydrogen sulphide.
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Gostelow, P. "The modelling of odours from sewage treatment works." Thesis, Cranfield University, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.248506.
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Lazarevic, David Andrew. "In-situ Removal of Hydrogen Sulphide from Landfill Gas : Arising from the Interaction between Municipal Solid Waste and Sulphide Mine Environments within Bioreactor Conditions." Thesis, KTH, Industriell ekologi, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-32770.
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This project was compiled in co-operation with the Royal Institute of Technology, Stockholm and Veolia Environmental Services (Australia) at the Woodlawn Bioreactor in NSW, Australia. Hydrogen sulphide is an unwanted component of landfill gas, raising occupational health and safety concerns, whilst leading to acid gas corrosion of power generation equipment and increased emissions of SOx, a primary constituent of acidification. Australian governmental requirements to place a periodic cover over the unused proportion of the tipping surface of landfills and bioreactors create an interesting opportunity for the removal of the hydrogen sulphide component of landfill gas. Using waste materials containing a high concentration of metals as waste cover can enhance the precipitation of sulphur in the form of metal sulphides. The reduction of sulphate via sulphate reducing bacteria is prevalent in sites that have a sizeable inflow of sulphate. The Woodlawn Bioreactor is located in an area where the influence of sulphate has a critical influence of bioreactor performance and production of hydrogen sulphide. Through a series of experimental bioreactors it was established that from the use of metalliferous periodic waste covers, the hydrogen sulphide component of landfill gas was maintained at an extremely low level when compared to the levels of hydrogen sulphide produced in waste under the influence of high sulphate loads with no waste cover.www.ima.kth.se
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Lawrie, Catriona H. "Study of the reaction between hydrogen sulphide and zinc oxide." Thesis, University of Edinburgh, 1990. http://hdl.handle.net/1842/11041.
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Experiments were conducted to study the absorption reaction of hydrogen sulphide with zinc oxide forming zinc sulphide and water. The reaction is of commercial importance for the removal of hydrogen sulphide from reactor feed streams and from natural gas. Most of the experiments were performed on a commercial ICI zinc oxide-based absorbent prepared by calcination of basic zinc carbonate but a number of experiments were also performed on samples of basic zinc carbonate or of zinc oxide prepared by different treatments. The reactions were carried out in a shallow bed flow reactor containing 0.2-0.6g of absorbent at a pressure just above atmospheric and at temperatures in the range 0 to 450C. Feed gases containing 0.06-0.7% v/v hydrogen sulphide and 0-0.5% v/v water in nitrogen were used. On-line gaseuos analysis was performed using a Thermal Conductivity Detector with complementary information provided by sulphur analysis and electron microprobe analysis of the discharged partially sulphided absorbent. The specific reaction rate was observed to be very high initially but to decline to a much slower pseudo-steady state (pss) rate. The pattern of this decline was found to be a function of particle size, with larger particles exhibiting slower, diffusion-limited rates in the initial period but higher pss rates than smaller particles. This latter result was attributed to an enhanced water concentration in the centre of larger particles. Microprobe analysis indicated uniform sulphiding at about 20% absorbent conversion whereas at low conversions an outer sulphided shell surrounds a central unreacted core. The conversion of the absorbent at pss (in the range 9-23%) was observed to increase with increasing partial pressures of water and of hydrogen sulphide in the feed. A marked dependence of the pss rate upon water partial pressure and a decrease in the rate with increasing temperature were observed and interpreted as indicative of an autocatalytic reaction. The role of water in facilitating solid rearrangement is consistent with the results of interrupted experiments which showed enhanced water adsorption and reaction rate after isolation. The pss rate was found to be insensitive to hydrogen sulphide concentration in the range studied. There appears to be an optimal calcination temperature of the absorbent precursor although this may not correspond with the temperature yielding maximal specific surface area. The effects of some impurities in the commercial absorbent were also investigated.
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Rava, Eleonora Maria Elizabeth. "Management of hydrogen sulphide generation at a Kraft paper mill." Diss., Pretoria : [s.n.], 2008. http://upetd.up.ac.za/thesis/available/etd-09152008-113200/.
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Aguilar, Luis Felipe. "Development of Sulfur Tolerant Materials for the Hydrogen Sulfide Solid Oxide Fuel Cell." Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/6979.
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One of the major technical challenges towards a viable H2S//Air SOFC is to identify and develop anode materials that are electronically conductive, chemically and electrochemically stable, and catalytically active when exposed to H2S-rich environments. The corrosive nature of H2S renders most traditional state-of-the-art SOFC anode materials (Ni, Pt, Ag) useless for long-term cell performance even at very low sulfur concentrations. In my doctoral thesis work, a new class of perovskite-based anodes was developed for potential use in SOFCs operating with H2S and sulfur-containing fuels. Cermets from this family of materials have shown excellent chemical stability and electrochemical performance at typical SOFC operating conditions. As an added benefit, they appear to preferentially oxidize H2S over hydrogen, as suggested by open circuit voltage, impedance spectra, and cell performance measurements obtained using various H2S-H2-N2 fuel mixtures. Cell power output values were among the highest reported in the literature and showed no significant deterioration during 48-hour testing periods. Impedance measurements indicated overall cell resistances decreased with increasing temperature and H2S content of the fuel. This behavior is starkly different from that of contemporary SOFC anodes, where the presence of H2S usually increases overall polarization resistance and ultimately destroys the cell. Results are promising due to the drastic improvement in sulfur tolerance compared to the current generation of SOFC power systems.
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Weaver, Dan. "Electrochemical removal of hydrogen sulfide from multicomponent gas streams." Diss., Georgia Institute of Technology, 1988. http://hdl.handle.net/1853/11154.
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Zezin, Denis. "The solubility of gold in water-hydrogen sulphide vapours: an experimental study." Thesis, McGill University, 2011. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=96970.
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This thesis presents the results of an experimental study of the solubility of Au in reduced sulphur-bearing vapours at elevated temperature and pressure, as well as the PVTx properties of H2O-H2S gas mixtures. The solubility of gold was measured in pure H2S gas and H2O-H2S gas mixtures. Results of the experiments demonstrate that the fugacity of gold increases with the fugacity of H2S, and that reactions involving the formation of volatile sulphide species control the solubility of gold in the gas phase. The results obtained for pure H2S gas indicate that solvation of sulphide gold species by molecules of H2S significantly increases the dissolution of gold, whereas the experiments with H2O-H2S vapour mixtures showed that this dissolution is further enhanced by hydration of the gold sulphide. The reactions of formation of solvated and hydrated gaseous complexes AuS(H2S)n and AuS(H2O)m are interpreted to control the solubility of gold in H2O-H2S gas mixtures. Equilibrium constants and the solvation or hydration numbers (n or m) for these reactions were determined by minimizing the errors between the results for an optimized solvation/hydration model and the experimental data. The fugacity of H2S and H2O required for the model calculation were determined from the experimentally determined PVTx properties of the H2O-H2S fluid mixtures; the latter were modeled using cubic equations of state with composition- and density-dependent mixing rules and adjusted binary interactions parameters.Under the experimental conditions of this study, i.e., temperatures from 300 to 400 °C, pressures up to 265 bar, and hydrogen fugacity constrained by the reaction H2+S=H2S, the solubility of gold in reduced sulphur-bearing vapour is relatively high (up to 1 ppb), and the results obtained provide strong evidence that H2S plays an important role in the vapour transport of gold. As most natural hydrothermal vapours are water rich (>90% H2O), gold will be transported in the vapour dominantly as an hydrated gold sulphide, provided that there is sufficient reduced sulphur (H2S) in the vapour for complexation. The stoichiometry and stability of the gold complexes determined in this study represent an important contribution to our knowledge of the chemical properties of volatile metal species and permit accurate modeling of vapour-related processes involved in the mobilization, transport and deposition of gold in magmatic hydrothermal systems, notably those of epithermal environments.Cette thèse présente les résultats d'une étude expérimentale sur la solubilité de l'or dans des vapeurs contenant du souffre à l'état réduit à haute pression et température, ainsi que les propriétés PVTx de mélanges gazeux de H2O-H2S. La solubilité de l'or a été mesurée dans du H2S gazeux pur et dans des mélanges gazeux de H2O-H2S. Les résultats de cette expérience démontrent que la fugacité de l'or augmente avec la fugacité de H2S, et que les réactions qui mènent à la production d'espèces volatiles de souffre contrôlent la solubilité de l'or dans la phase gazeuse. Les résultats obtenus pour le gaz de sulfure d'hydrogène à l'état pur indiquent que la solvatisation des espèces de sulfure d'or par les molécules de sulfure d'hydrogène augmente de façon significative la dissolution de l'or, alors que les résultats issus des expériences utilisant des mélanges gazeux de H2O et de H2S montrent que cette dissolution est davantage augmentée par l'hydratation du sulfure d'or. Nous proposons que les réactions de formation de solvates et hydratée complexes gazeux AuS(H2S)n et AuS(H2O)m contrôlent la solubilité de l'or dans des mélanges de H2O-H2S. Les constantes d'équilibre ainsi que le degré de solvatisation ou d'hydratation (n ou m) pour ces réactions furent déterminés par minimisation de l'erreur entre les résultats obtenus d'un modèle de solvatation/hydratation optimisé et les données expérimentales. Les fugacités de H2S et de H2O requises pour les calculs du dit modèle furent établies en utilisant les propriétés de PVTx expérimentalement déterminées pour les mélanges fluides de H2O-H2S; ces dernières furent modélisées en utilisant des équations d'état cubiques avec des lois de mélange sur la dépendance de composition et densité, ainsi que des paramètres sur les interactions binaires spécialement ajustées.Dans les conditions de cette étude, c'est- à -dire à 300-400 °C et à des pressions jusqu'à 265 bars, la fugacité de l'hydrogène étant contrainte par la réaction chimique H2+S=H2S, la solubilité de l'or dans des vapeurs de soufre à l'état réduit est relativement élevée (jusqu'à 1 ppb), et les résultats démontrent que le sulfure d'hydrogène joue un rôle important dans le transport de l'or par la vapeur. La plupart des vapeurs hydrothermales dans la nature sont riches en eau (>90% H2O), donc l'or sera transporté par la vapeur sous la forme de sulfure d'or hydraté si il y a assez de sulfure d'hydrogène à l'état réduit pour qu'il y ait complexation. La stœchiométrie et la stabilité des complexes d'or déterminés dans cette étude représentent une contribution essentielle à la caractérisation des propriétés chimiques sur les espèces métalliques volatiles et permettent une modélisation précise des processus à l'état vapeur et inhérents à la mobilisation, le transport et le dépôt de l'or dans des systèmes hydrothermaux magmatiques, en particulier les environnements épithermaux.
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Nuttall, Robert Horan. "Aqueous hydrogen sulphide corrosion of iron, iron/chromium and iron/nickel alloys." Thesis, Robert Gordon University, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358471.
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Burke, Adrian Alan. "Removal of hydrogen sulfide from hot fuel gas using an electrochemical membrane system." Diss., Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/11702.
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Ariyaratnam, Priyadharshanan. "The effect of oxygen, temperature and hydrogen sulphide on the human pulmonary circulation." Thesis, University of Hull, 2014. http://hydra.hull.ac.uk/resources/hull:8922.
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Introduction: The human pulmonary circulation is poorly understood at a physiological level which is a shame given that the pathology affecting it, particularly pulmonary artery hypertension, can have detrimental effects not only in the lungs but on the heart. Pulmonary artery hypertension in its acute or chronic form carries a high mortality. Few centres have the luxury to utilise human tissue to study this phenomenon. My thesis looks at the effect of certain stimuli such as oxygen, temperature and hydrogen sulphide to discern their role in governing pulmonary artery reactivity at both the tissue and organ level. Methods: Tissue was supplied from lungs taken from patients with lung cancer following resection of the tumour during surgery. I used a combination of isolated arterial ring models in organ baths and isolated perfused lung models to study the factors governing pulmonary arterial tone and pulmonary artery pressures at a tissue and organ level respectively. Results: At the tissue level, hypoxia caused nitric-oxide independent dilation of human pulmonary arteries whilst hyperoxia caused a vasoconstriction. This hyperoxic vasoconstriction is dependent on both voltage gated calcium-channels in the cell membrane as well as release from intracellular calcium stores. It is also dependent on oxygen-free radicals. Hypothermia blunts this vasoconstrictive response to hyperoxia as well as endothelin-1 and potassium chloride-mediated pulmonary smooth muscle contraction. Hydrogen sulphide dilates pulmonary arteries. At the organ level, oxygen changes either via the perfusate or the ventilator do not affect pulmonary artery pressures. Both hypothermia and hydrogen sulphide reduce both pulmonary artery pressures and bronchial pressures. Conclusions: Compensatory mechanisms within the pulmonary circulation may compensate for hypoxic vasodilation and hyperoxic vasoconstriction or there may be a systemic component to entities such as “hypoxic pulmonary vasoconstriction” seen in animal models. Hydrogen sulphide may provide a possible treatment avenue for pulmonary artery hypertension.
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Wannerberg, Karin. "Evaluation of Odomin and potential factors reducing the hydrogen sulphide levels in sewage systems." Thesis, KTH, Maskinkonstruktion (Inst.), 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-175675.
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Xylem Inc. develops pumps and integrated solutions for sewages systems. A new concept has been designed to reduce the levels of hydrogen sulphide, H2S, in wastewater. H2S is a toxic, stinking gas that smells at levels above 0.002-0.2 ppm. Recommended exposure level is 15 ppm for 15 minutes. The gas is soluble in water and arises with both increasing temperatures and long retention times. Levels of H2S normally differ between 0-1000 ppm, depending on the time of year. The new concept, a pre-chamber installed upstream a pump station, is called Odomin. Inside Odomin H2S is oxidized to sulphuric acid, H2SO4, on moist surfaces. A plate is used to splash thewastewater onto the moist surfaces surrounding the plate. This master thesis aims to find the reduction rate, in terms of H2S, between Odomin 65 and the pump sump and to evaluate three factors that have possibility to improve the performance of Odomin 65. The investigated factors are 1) a sacrificial anode made from carbon steel 2) a reduced area of the inlet which increases the splash effect and 3) an increased inner area to increase themoist surfaces inside Odomin. The evaluation is made with 23 factorial design. The analysis indicates that no factor affect the daily mean value with a significance at 5%. The sacrificial anode is the one factor showing a reduction by the levels of H2S in the pump sump for both mean and extreme values. The general reduction rate is 5.33 and this can be increased with 55% by using the splash. The tests were affected by several influences that impact the trustworthiness of the results. Therefore this analysis needs additional investigations in order to be verified.Xylem Inc. utvecklar pumpar och lösningar för avloppssystem. De har utvecklat ett nytt koncept för att reducera halten av svavelväte, H2S, i avloppsvattnet. H2S är en giftig, illaluktande gas med kännbar lukt vid 0.002-0.2 ppm. Rekommenderat är att utsättas för högst 15 ppm under 15 minuter. Gasen är löslig i vatten och nivåerna ökar med både höga temperaturer och långa uppehållstider i ledningarna. Normalt sätt kan nivåerna av H2S variera mellan 0-1000 ppm, beroende på årstid. Det nya konceptet som kallas Odomin är en för-kammare som installeras uppströms till en pumpstation. I Odomin oxideras H2S till svavelsyra, H2SO4, på våta ytor. Genom att avloppsvattnet kaskaderar på en platta kan gasen komma i kontakt med våta ytor kring plattan. Examensarbetet syftar till att hitta reduktionstalet mellan Odomin 65 och pumpsumpen samt utvärdera 3 faktorer som kan förbättra effekten av Odomin. De undersökta faktorerna är 1) en offeranod av kolstål 2) en minskad inloppsarea för att öka kaskadet och 3) en ökad inre area, för att öka andelen våta ytor, i Odomin. De 3 faktorerna utvärderas med faktorförsök (factorial design). Utvärderingen ger indikationen att ingen av de tre faktorerna påverkar det dagliga medelvärdet på en 5 % signifikansnivå. Offeranoden är den faktor som tenderar minska både medelvärdet och extremvärdet i pump sumpen. Reduktionen av H2S mellan Odomin 65 och pump sumpen är 5.33 och analysen visar att en ökad kaskadeffekt kan öka reduktionen med 55 %. Testerna influeras av flera yttre faktorer vilket påverkar resultatens trovärdighet. Denna analys bör därför repeteras för att resultaten ska kunna verifieras.
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Tazzari, V. "SINTESI DI NUOVE MOLECOLE PER IL TRATTAMENTO DI PATOLOGIE INFIAMMATORIE." Doctoral thesis, Università degli Studi di Milano, 2012. http://hdl.handle.net/2434/170506.
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Recently, the role of hydrogen sulphide (H2S) a well known toxic gas with reducing properties has received a great interest. It has been found that H2S is produced in consistent quantity in the mammalian tissues and it exerts several physiological effects that suggest its role as a regulating mediator. H2S is involved in the regulation of the muscular tone, of the myocardial contractility, in the inflammatory processes, in the neurotransmission and in insulin secretion. Reduced levels of H2S were observed in several animal models of artery and pulmonary hypertension, damages of gastric mucosa and hepatic cirrhosis. Exogenous H2S inhibits inflammation, improves cardiac dysfunctions associated to ischemia/reperfusion and reduces the gastric damage induced by anti-inflammatory drugs. On the other hand, if not properly controlled and in excessive doses, endogenous H2S may contribute to tissue inflammation through stimulation of related converting enzymes (CBA and CBS).
H2S has also an active role in the redox imbalance processes. In particular this gas mediator influences the activation of cellular inflammatory processes interacting with signalling mechanisms, transcription factors and neutralizing ROS. Moreover it has been reported that it has cytoprotective properties due to GSH production in several tissues.
On this basis, it is clear the utility of molecules capable to modulate the plasma and tissue concentration of H2S especially in pathologies characterised by disorders of GSH homeostasis and increase of oxidative stress as it happens in neurodegenerative diseases, cystic fibrosis and other severe lung pathologies, but also in cardiovascular diseases (such as metabolic syndrome) etc.
An interesting and innovative approach is the synthesis of hybrid molecules that combine the structure of a known drug with a sulfurated moiety able to in vivo slowly release H2S. Therefore, the purpose of this thesis was the synthesis of hybrid compounds active in neurodegenerative diseases (PD), such as sulfurated derivatives of L-DOPA and H2S-releasing drugs active on the peripheral circulatory system, such as sulfurated derivatives of phosphodiesterase 5 (PDE-5) inhibitors, in order to improve the efficacy and tolerability of the parent compound. Cysteine hybrid compounds coupled to dithiolethiones, addressed to treatment of specific metabolic conditions such as hyperhomocysteinemia, were also synthesized.
The pharmacological studies conducted until now show that the H2S-releasing drugs, described in this thesis, by in vivo H2S releasing and modulating, have important antioxidant, anti-inflammatory and cytoprotective properties, while maintaining the pharmacological profile of the original drug. These data confirm the potential usefulness of new compounds in the treatment of many different diseases in which there is an inflammatory and / or a redox imbalance component.
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Peterson, David Ross. "The study of intermediate temperature solid state fuel cell utilizing hydrogen sulfide as the fuel." Diss., Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/10983.
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Gil, Folch Víctor. "Neural inhibitory mechanisms regulating colonic mechanical activity: role of adenosine triphosphate, nitric oxide and hydrogen sulphide." Doctoral thesis, Universitat Autònoma de Barcelona, 2013. http://hdl.handle.net/10803/125873.
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La neurotransmissió inhibitòria participa en el control de l’activitat motora del còlon. Els neurotransmissors inhibitoris hiperpolaritzen la membrana del múscul llis, generant un potencial d'unió inhibitori (”Inhibitory Junction Potential” IJP) que és la base electrofisiològica de la relaxació muscular. Així, l’adenosina trifosfat (ATP), l’òxid nítric (NO) i el sulfur d’hidrogen (H2S) són molècules de senyalització que poden exercir aquest control. L’objectiu d’aquesta tesi doctoral ha estat valorar la participació de l’ATP, el NO i el H2S en la transmissió neuromuscular inhibitòria en el còlon humà i de rata. El hidrogensulfur de sodi (NaHS) va ser utilitzat com font de H2S.
Els antagonistes específics dels receptors P2Y1 van inhibir completament el component purinèrgic de l’IJP en el còlon humà i de rata (rang de potència: MRS2500>MRS2279>MRS2179). El β-NAD va produir hiperpolarització i relaxació de la musculatura del còlon humà. Tanmateix, la relaxació no va ser bloquejada pels antagonistes P2Y1. En el còlon de rata es va observar que l’alliberament de neurotransmissors inhibitoris produïa la generació d’IJP espontanis i un potencial de membrana muscular hiperpolaritzat. Mitjançant MRS2500 es va posar de manifest que els receptors P2Y1 participaven en la gènesi dels IJP espontanis. El Nω-nitro-L-arginina (L-NNA) va permetre establir que l'estat de hiperpolarització tònic del potencial de membrana era d'origen nitrèrgic. L’ús d’apamina, spadina i ODQ va permetre valorar la participació dels canals de potassi de baixa conductància activats per calci (SKCa), els canals de potassi relacionats amb TWIK tipus 1 (TREK1) i la via de la guanilat ciclasa (GC) sobre la neurotransmissió purinèrgica i nitrèrgica. L’apamina va bloquejar tots dos components amb diferents nivells d'afinitat. L’ODQ només va bloquejar la neurotransmissió nitrèrgica. D’altra banda, tot i posar de manifest la presència de canals TREK1 en el còlon de rata, la spadina, un blocador de TREK1, no va bloquejar cap dels components. L’expressió dels enzims de síntesi del H2S es va determinar immunohistoquímicament en l’epiteli, el múscul i les neurones del còlon de rata. A més, es va demostrar que el teixit de rata era capaç de produir enzimàticament H2S. Tot i que en alguns casos es van observar efectes no específics dels inhibidors dels enzims de síntesi del H2S, aquestos van produir despolarització de les cèl·lules musculars i un increment de l’activitat mecànica del còlon. En segments de còlon de rata, el NaHS administrat per serosa va causar un efecte dual sobre els patrons de motilitat. El NaHS va inhibir les contraccions d'alta amplitud, mentre que va incrementar les contraccions de baixa amplitud. El NaHS va inhibir els potencials d'unió excitador i va hiperpolaritzar el múscul. Tanmateix, l’H2S no va alterar el marcapassos colònic situat a nivell del plexe submucós. El NaHS via luminal no va modificar la motilitat del còlon.
La neurotransmissió purinèrgica al còlon humà i de rata es produeix a través del receptor P2Y1. L’ATP i el NO són alliberats per les neurones inhibitòries del plexe mientèric i tenen funcions complementàries en el còlon. D'una banda, l’ATP exerceix una acció fàsica sobre el potencial de membrana i l’activitat mecànica, mentre que el NO té una acció tònica. Ambdues respostes nitrèrgica i purinèrgica son en part sensibles a apamina, suggerint que els canals SKCa poden esta involucrats en les dues vies. El NO exerceix el seu efecte sobre el potencial de membrana a través de l’activació de la via de GC però no activa els canals TREK1. El H2S és produït i alliberat endògenament en el còlon de rata i pot actuar com una molècula de senyalització amb acció moduladora sobre la motilitat colònica. El seu mecanisme d’acció implica una inhibició de la neurotransmissió colinèrgica i hiperpolarització muscular.Inhibitory neuromuscular transmission is involved in the control of colonic motility. Inhibitory neurotransmitters cause membrane hyperpolarization of smooth muscle, that is, an inhibitory junction potential (IJP) which is the electrophysiological basis of muscle relaxation. Thus, adenosine triphosphate (ATP), nitric oxide (NO) and hydrogen sulphide (H2S) are signalling molecules which can exert this control. The aim of this thesis was to evaluate the role of ATP, NO and H2S in inhibitory neuromuscular transmission in the rat and human colon. Sodium hydrosulphide (NaHS) was used as the source of H2S. Specific P2Y1 receptor antagonists completely inhibited the purinergic component of the IJP in the human and rat colon (potency range: MRS2500> MRS2279> MRS2179). β-NAD produced smooth muscle hyperpolarization and relaxation in the human colon. However, the relaxation was not blocked by P2Y1 antagonists. In the rat colon, it was observed that the release of inhibitory neurotransmitters produced both spontaneous IJP and a sustained muscle hyperpolarization. MRS2500 revealed that P2Y1 receptors were responsible for spontaneous IJP. Nω-nitro-L-arginine (L-NNA) allowed us to establish that the tonic state of muscle hyperpolarization was nitrergic in origin. Apamin, spadin and ODQ were used to assess the involvement of small-conductance calcium-activated potassium channels (SKCa), TWIK-related potassium channels 1 (TREK1) and the guanylate cyclase (GC) pathway on purinergic and nitrergic neuromuscular transmission. Apamin blocked both components with a different relative sensitivity. ODQ only blocked nitrergic neuromuscular transmission. Furthermore, even though the presence of TREK1 channels was revealed in rat colon, none of the components was blocked by spadin, an effective TREK1 channel inhibitor. The expression of H2S-producing enzymes was determined by immunohistochemistry in the epithelium, muscle and nerve cells in the rat colon. In addition, it was demonstrated that the rat tissue was able to enzymatically produce H2S. Although in some cases the effects of H2S-producing enzymes inhibitors were not specific, they caused muscle depolarization and an increase in colonic mechanical activity. In segments of rat colon, NaHS caused a dual effect on motility patterns when administered via serosa. NaHS inhibited propulsive contractions whereas it caused an increase in the amplitude of ripples. NaHS inhibited cholinergic excitatory junction potentials and hyperpolarized smooth muscle cells. However, NaHS did not modify the colonic pacemaker located at the level of the submucosal plexus. Luminal addition of NaHS did not modify motility patterns. Purinergic neurotransmission in the rat and human colon is mediated by P2Y1 receptors. ATP and NO are released by myenteric plexus inhibitory neurons and have complementary functions in the colon. I.e. ATP produces a phasic action on membrane potential and mechanical activity and NO has a tonic effect. Both purinergic and nitrergic responses are in part apamin sensitive suggesting a possible involvement of SKCa in both pathways. NO effects on membrane potential are produced by GC activation but TREK1 channels are not involved. In the rat colon, H2S is produced and released endogenously and it might be a signalling molecule modulating action on colonic motility. H2S mechanism of action involves inhibition of neurally mediated cholinergic responses and muscle hyperpolarization.
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Partlo, Lisa Ann. "The effects of repeated exposure to moderate concentrations of hydrogen sulphide on learning and memory in the rat." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape10/PQDD_0035/NQ38496.pdf.
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BALLESTEROS, ADRIANA FORERO. "EVALUATION OF THE RESISTANCE TO SULPHIDE STRESS CORROSION CRACKING AND HYDROGEN EMBRITTLEMENT OF API 5L -X80 GIRTH WELDS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2009. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=32706@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCOORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
FUNDAÇÃO DE APOIO À PESQUISA DO ESTADO DO RIO DE JANEIRO
PROGRAMA DE SUPORTE À PÓS-GRADUAÇÃO DE INSTS. DE ENSINO
BOLSA NOTA 10
A susceptibilidade à corrosão sob tensão em aços para dutos é dependente de uma série de eventos que vão desde a manufatura do aço, fabricação do tubo, montagem dos dutos e tipo de substância transportada pelo duto. O procedimento de soldagem envolvido na montagem dos dutos pode modificar as propriedades mecânicas do metal de base na região da zona termicamente afetada (ZTA), assim como as propriedades metalúrgicas e de resistência à corrosão, tornando potencialmente a região da junta soldada com maior probabilidade de incidência de corrosão sob tensão.Este trabalho tem como objetivo estudar a resistência à corrosão sob tensão em presença de sulfeto e fragilização pelo hidrogênio, em soldas circunferenciais de tubo API 5L X80. Foram realizados: -Ensaios de acordo com norma NACE TM0177/96, Método A -Ensaios de Baixa Taxa de Deformação (BTD) de acordo com a norma ASTM G129-00/2006, em solução contendo Tiossulfato de Sódio. Os resultados mostraram que o metal base foi considerado aprovado segundo os requisitos dos testes NACE TM0177/96. Porém as juntas soldadas originadas nos diferentes processos de soldagem estudados apresentaram susceptibilidade à corrosão sob tensão em presença de sulfeto e fragilização pelo hidrogênio, segundo o mesmo critério, fraturando em um período inferior a 720h. Esta susceptibilidade foi comprovada com os resultados dos ensaios de tração BTD, tendo sido constatada uma queda significativa no limite de resistência, alongamento e tempo de ruptura, em comparação aos ensaios realizados ao ar na mesma taxa de deformação. O mecanismo de fratura predominante nos ensaios foi fratura transgranular.
The susceptibility of pipeline steels to stress corrosion cracking (SCC) depends on a series of factors ranging from the manufacture of the steel, the pipe fabrication, the assembly of the pipeline and the type of substances to be transported. Additionally, the welding procedures adopted during the production of the tubes and for construction of the pipelines (field welding), can modify the properties of the base metal in the heat affected zone (HAZ), potentially rendering this region susceptible to sulphide stress corrosion cracking and hydrogen embrittlement.This study evaluates the resistance of girth welds in API 5LX80 pipes to hydrogen embrittlement and also to stress corrosion cracking in the presence of sulphides. The evaluation was performed according to NACE TM0177/96, Method A, applying the criterion of fracture/no fracture, and slow strain rate tensile tests (SSRT) were undertaken using a sodium thiosulphate solution according to the ASTM G29 standard. According to the requirements of the NACE TM0177/96 test, the base metal was considered approved. The weld metal exhibited susceptibility to SCC in the presence of sulphides, failling in a period of less than 720h. The susceptibility of the welded joint to SCC in the presence of sulphides was confirmed by the results obtained with SSRT tensile tests, where a significant decrease in the ultimate tensile strength, elongation and time to fracture were observed. The mechanism of fracture for the tests was predominantly transgranular.
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Elsey, David Jonathan. "Roles and mechanisms of action of the L-cysteine cystathionine-gamma-lyase hydrogen sulphide pathway in the heart." Thesis, Cardiff University, 2009. http://orca.cf.ac.uk/55820/.
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Hydrogen sulphide (H2S) is a naturally occurring gas and originally the primary focus of research was to investigate its toxicity. In 1989 a physiological role of H2S was proposed after endogenous levels were detected in the rat brain and normal human post-mortem tissue. This discovery has led to an explosion of interest in H2S as a biological mediator. Identification of H2S synthesising enzymes in the cardiovascular system has led to a number of studies examining specific regulatory actions of H2S. The hypothesis underlying the studies in this thesis was that H2S synthesising enzymes exist in the myocardium and the resulting H2S provides cardioprotection against ischaemia-reperfusion injury. This was investigated using a broad range of experimental techniques including Langendorff isolated perfused rat heart models, biochemical H2S stimulation and detection assays, PCR, and Western blotting. The principal findings can be summarised as follows: 1. Rat myocardium has the potential to express both CSE and CBS H2S synthesising enzymes, due to the confirmed detection of mRNA. 2. Furthermore it was possible to exogenously stimulate the CSE enzyme, with its substrate L-cysteine, to produce H2S gas which limited infarct size during regional ischaemia-reperfusion. 3. Endogenous H2S levels were up-regulated during ischaemia-reperfusion, consistent with an endogenous protective role within the myocardium. 4. Simple and complex H2S/thiol containing compounds produced cardioprotection during regional ischaemia-reperfusion, with a mechanism that involves PI3k and Akt activation, implicating recruitment of downstream kinases within the RISK pathway. The studies presented have provided a significant advancement in understanding the involvement of H 2S in cardioprotection during ischaemia-reperfusion. It has also raised questions such as the exact mechanism of action of H2S donor/thiol containing compounds and highlighted the need for more robust H2S donors. The scope for H2S as an endogenous mediator also stems beyond that of cardioprotection, as the range of body systems and cell types are continually expanding.
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Guedes, Sales Daniella. "Etude des mécanismes d'endommagement d'aciers martensitiques associés au SSC (Sulphide Stress Cracking)." Thesis, La Rochelle, 2015. http://www.theses.fr/2015LAROS041.
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Dans le cadre de ces travaux, il a clairement été établi que l’hydrogène piégé ou diffusible pouvait avoir une forte influence sur les propriétés mécaniques des matériaux. Cependant, cet effet varie de façon importante en fonction de leur microstructure, leur composition chimique et leur traitement thermique. En effet, les aciers martensitiques trempés/revenus dédiés à des tubes pour des milieux sous-service présentent, de par leur structure, différents types de pièges tels que les dislocations, les joints de grains, les précipités, les inclusions, les lacunes et d’autres interfaces qui jouent un rôle important dans les mécanismes endommageants. Ces aciers de haute résistance mécanique, lorsqu’ils sont soumis à des contraintes mécaniques et à un environnement agressif (qui dépend de la pression en H2S et du pH de la solution) peuvent rompre à cause du phénomène de Sulphide Stress Cracking (SSC). Ce dernier est une forme de fragilisation par l’hydrogène (FPH) qui inclut un amorçage de fissure suivi d’une étape de propagation conduisant à la rupture, dont la contribution de l’hydrogène reste encore mal comprise. En parallèle de l’impact de la microstructure de l’acier, les champs de contrainte et déformation subis par le matériau modifient les effets induits par l’hydrogène. C’est pourquoi un montage de perméation sous contrainte a été utilisé afin de pouvoir réaliser des essais mécaniques jusqu’à rupture sous flux d’hydrogène et les comparer au comportement du matériau lorsque celui-ci est sollicité à l’air ou dans un environnement H2S. Ainsi, l’impact sur le comportement mécanique du flux d’hydrogène mais également de son piégeage peut être étudié. Dans ce cadre, des éprouvettes plates et axisymétriques, lisses et entaillées ont été employées. Les informations expérimentales obtenues dans ce travail ont servi à alimenter un modèle numérique qui a permis de caractériser localement l’état mécanique et les concentrations d’hydrogène piégé et diffusible dans le matériau. Ceci a rendu possible la définition d’un critère local de ruptureThe findings of this work established that the diffusible and trapped hydrogen could have a strong influence on the mechanical properties of materials. However, this effect varies significantly with the materials’ microstructure, chemical composition, and heat treatment. Due to their structure, quenched and tempered martensitic steels (developed for tubes suitable for sour service environments) have different types of traps such as dislocations, grain boundaries, precipitates, inclusions, vacancies and other interfaces that play an important role in the damage mechanisms. These high strength steels may break due to Sulphide Stress Cracking (SSC) if subjected to mechanical stress and an aggressive environment (which depends on the H2S partial pressure and pH solution). This phenomenon is a form of hydrogen embrittlement (HE) that includes a crack initiation followed by a propagation step leading to failure. However the hydrogen contribution is still insufficiently understood. In addition to the impact of the microstructure on the steel, the stress and the deformation fields in the material also modify the effects induced by hydrogen. To investigate this event, electrochemical permeation tests under stress were used to perform mechanical tests under hydrogen flux until failure is reached. The results were compared to those mechanically loaded in air or in a H2S environment. This enabled the examination of the impact of the hydrogen flux and trapping on the mechanical behavior of martensitic steel. In this framework, flat and axisymmetric, smooth and notched specimens were employed. Experimental data obtained in this work were used to provide a numerical model that enables the locally characterization of the mechanical condition and the concentrations of trapped and diffusible hydrogen in the material. These outcomes enabled us to determine a local failure criterion
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Gatty, Hithesh K. "MEMS-based electrochemical gas sensors and wafer-level methods." Doctoral thesis, KTH, Mikro- och nanosystemteknik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-172955.
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This thesis describes novel microel ectromechanical system (MEMS) based electrochemical gas sensors and methods of fabrication. This thesis presents the research in two parts. In the first part, a method to handle a thin silicon wafer using an electrochemically active adhesive is described. Handling of a thin silicon wafer is an important issue in 3D-IC manufacturing where through silicon vias (TSVs) is an enabling technology. Thin silicon wafers are flexible and fragile, therefore difficult to handle. In addressing the need for a reliable solution, a method based on an electrochemically active adhesive was developed. In this method, an electrochemically active adhesive was diluted and spin coated on a 100 mm diameter silicon wafer (carrier wafer) on which another silicon wafer (device wafer) was bonded. Device wafer was subjected to post processing fabrication technique such as wafer thinning. Successful debonding of the device wafer was achieved by applying a voltage between the two wafers. In another part of the research, a fabrication process for developing a functional nanoporous material using atomic layer deposition is presented. In order to realize a nanoporous electrode, a nanoporous anodized aluminum oxide (AAO) substrate was used, which was functionalized with very thin layers (~ 10 nm) of platinum (Pt) and aluminum oxide (Al2O3) using atomic layer deposition. Nanoporous material when used as an electrode delivers high sensitivity due to the inherent high surface area and is potentially applicable in fuel cells and in electrochemical sensing. The second part of the thesis addresses the need for a high performance gas sensor that is applicable for asthma monitoring. Asthma is a disease related to the inflammation in the airways of the lungs and is characterized by the presence of nitric oxide gas in the exhaled breath. The gas concentration of above approximately 50 parts-per-billion indicates a likely presence of asthma. A MEMS based electrochemical gas sensor was successfully designed and developed to meet the stringent requirements needed for asthma detection. Furthermore, to enable a hand held asthma measuring instrument, a miniaturized sensor with integrated electrodes and liquid electrolyte was developed. The electrodes were assembled at a wafer-level to demonstrate the feasibility towards a high volume fabrication of the gas sensors. In addition, the designed amperometric gas sensor was successfully tested for hydrogen sulphide concentration, which is a bio marker for bad breath.QC 20150907
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Barba, Daniela. "Simultaneous production of H2 and sulphur by catalytic oxidative decomposition of H2S." Doctoral thesis, Universita degli studi di Salerno, 2018. http://hdl.handle.net/10556/3033.
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2016 - 2017The recovery of hydrogen from H2S has recently attracted attention because of the economic and environmental advantages: hydrogen is an energy source, a raw material for chemical industry and in the near future it could become a significant fuel. A great amount of H2S is obtained as a by-product during the H2 reduction processes and the hydrodesulphurization of petroleum and, due to the stringent environmental regulations, H2S has to been removed before its release in the environment. Hydrogen Sulphide is usually removed by the well-known Claus process, where H2S is oxidized to water and elemental Sulphur by two-step reactions. This process is not profitable from an economic point of view because the price of the Sulphur (the primary product) is depressed and the hydrogen is lost as water. Furthermore, due to the thermodynamic limitations, H2S conversion in the catalytic stage is limited to ~95-97%, as a consequence further treatments of the residual tail gas are necessary. So, an attractive alternative could be to produce simultaneously Sulphur and hydrogen by thermal decomposition of H2S (H2S = H2 +1/2 S2). Unfortunately, this reaction is very endothermic and it is thermodynamically favored only for extremely high temperatures, thus requiring large amounts of energy and subsequent separation stages with high fixed and operating costs. A possible solution could be to couple the decomposition reaction with an exothermic reaction, making the system auto-thermal. For this purpose, the reaction of H2S oxidative decomposition at high temperature was studied; the main objective of this work was to find a catalyst active and selective to Sulphur and H2, depressing the possible SO2 formation related to the presence of the oxygen in the reaction system. First of all, this reaction was studied in homogeneous phase, by varying the main operating conditions such as temperature, O2/H2S, residence time. The results have shown an approach of H2S conversion and H2 yield to equilibrium values only at high temperature (1273−1373 K) but with a SO2 selectivity higher than one expected from equilibrium calculations. Different sulphide-based catalysts supported on Al2O3, both monometallic and bimetallic, were prepared, characterized and tested under different operating conditions. MoS2-based catalysts have shown good results at 1273 K, even at very low contact times (20-40 ms) and at high H2S inlet concentration (40 vol%) in terms of H2S conversion, H2 yield and SO2 selectivity, exhibiting values very close to those expected from the thermodynamic equilibrium. Based on the experimental collected data, a kinetic macroscopic model able to describe the main reactions was also developed and compared with the homogeneous phase reaction system. The results have evidenced that MoS2/Al2O3 catalyst (at 10 wt % MoS2), was able to promote the Claus reaction, besides the H2S decomposition reaction and the partial oxidation to Sulphur, determining a decrease of the SO2 formation. The system was also studied in the presence of CH4 in the feed stream. The results showed that the MoS2-based catalysts has favored the formation of undesired by-products as COS and CS2. Different mono and bimetallic catalysts were also tested and compared. The best results in terms of H2S conversion, H2 yield, and SO2, COS and CS2 selectivity were obtained in the case of the Mo-Fe bimetallic samples. As a consequence, the bimetallic 10 wt% MoS2 - 5 wt% FeS2/Al2O3 sample was tested also in presence of ammonia, ensuring a complete NH3 conversion at 1333 K with a contact time of 1 s. Finally, the active phases were supported on cordierite honeycombs monolith, which were tested for 25 hours at T= 1333 K in presence of a feed stream with a defined composition, representative of a typical refinery stream. The catalytic activity of the structured catalyst was also tested for 30 h of TOS at very high temperatures and very stressing conditions in terms of H2S, NH3, CH4 and Oxygen concentrations. The results showed that also in these conditions, an almost total NH3 conversion is possible without any significative apparent deactivation phenomena, making this catalyst a suitable system for H2S oxidative decomposition in presence of other compounds, such as methane and ammonia. [editedby author]
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Kouroussis, Emilia. "The Elucidation of Hydrogen Sulfide Signalling Through Persulfidation." Thesis, Bordeaux, 2019. http://www.theses.fr/2019BORD0435.
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Le sulfure d’hydrogène (H2S), auparavant considéré comme un gaz toxique, est aujourd’hui reconnu comme gazotransmetteur. De nombreuses études ont révélé le rôle de l’H2S en tant que molécule de signalisation redox contrôlant d’importantes fonctions physiologiques et pathologiques. Le mécanisme sous-jacent proposé pour expliquer ses effets est la persulfidation (P-SSH, aussi connue sous le nom de S-sulfhydration), une modification post-traductionnelle oxydative des thiols de résidus cystéines. La persulfidation des protéines est restée sous-étudiée en raison de son instabilité et de sa réactivité chimique similaire à celle d’autres modifications de la cystéine, faisant d’elle une modification très difficile à marquer sélectivement. De là, nous avons développé une nouvelle méthode chimiosélective en deux étapes, aisément adaptable à des applications diverses, pour la détection et le marquage des protéines persulfidées, connue sous le nom de méthode “Dimedone-switch”. Nous avons confirmé la cinétique et la sélectivité de la méthode, tout en montrant que la persulfidation des protéines est une modification conservée au cours de l’évolution et aussi contrôlée par l’H2S produit dans les voies de transsulfuration et de catabolisme de la cystéine. Nous avons adapté la méthode à une détection directe sur gel à différents organismes-modèles, à la microscopie à fluorescence, à une approche de antibody microarray et à l’analyse protéomique par spectrométrie de masse.Par la suite, nous avons étudié le rôle de l’H2S dans la signalisation redox via la persulfidation. Pour cela, nous avons étudié l’interconnexion entre P-SSH et les modifications séquentielles des thiols de cystéines, à savoir la sulfenylation (P-SOH), la sulfinylation (P-SO2H) et la sulfonylation (P-SO3H), formées lors de l’exposition au stress oxydatif (espèces réactives à l’oxygène). Nos études ont montré une corrélation directe entre P-SSH et ces modifications de manière temporelle et dose-dépendante. Nous avons observé un net décalage de phase dans la réponse entre les deux modifications de cystéines, P-SSH et P-SOH, qui mettent en évidence la présence de “vagues de protection” par la persulfidation des protéines. Couplés à des études mécanistiques montrant la réduction efficace de P-SSH par le système thiorédoxine, ces résultats suggèrent que la persulfidation des protéines est la voie principale par laquelle les acides sulféniques sont reconvertis en thiols originaux, et donc éliminés lors du stress oxydatif. A ce titre, nous avons proposé un mécanisme général (potentiel vestige des temps anciens où la vie a émergé et proliféré dans un environnement riche en H2S) dans lequel la persulfidation figure une boucle de sauvetage face à l’hyper-oxydation des cystéines et au dommage cellulaire oxydatif subséquent.De plus, dans le but de faire la lumière sur l’intérêt biologique de cette protection naturelle des persulfides, nous avons exploré une possible corrélation entre les niveaux de persulfides et le vieillissement. En nous appuyant sur la capacité des persulfides à piéger les oxydants qui s’accumulent, nous avons mené une série d’études visant à obtenir une meilleure compréhension du rôle de la voie de transsulfuration dans la résistance au stress et sur la durée de vie. Nous avons observé une corrélation directe entre la capacité à produire des persulfides et la résistance au stress oxydatif, ainsi qu’une diminution de la persulfidation au cours du vieillissement chez C.elegans, le rat et les cellules humainesHydrogen sulfide (H2S), originally considered a toxic gas, is now a recognised gasotransmitter. Numerous studies have revealed the role of H2S as a redox signalling molecule that controls important physiological/pathophysiological functions. The underlying mechanism postulated to serve as an explanation of these effects is protein persulfidation (P-SSH, also known as S-sulfhydration), an oxidative posttranslational modification of cysteine thiols. Protein persulfidation has remained understudied due to its instability and chemical reactivity similar to other cysteine modifications, making it very difficult to selectively label. Herein, we developed a novel, versatile, two-step chemoselective method for the detection and labelling of protein persulfides, called the Dimedone-switch method. We confirmed the method’s kinetics and selectivity, and showed that protein persulfidation is an evolutionarily conserved modification controlled by H¬2S generated by transsulfuration pathway and cysteine catabolism. We adapted the method for direct in-gel detection in different model organisms, fluorescence microscopy, antibody microarray approach and proteomic analysis by mass spectroscopy.Next, we studied the role of H¬2S in redox signaling through persulfidation. To do this we investigated the interconnection between P-SSH and the sequential modifications of cysteine thiols, sulfenylation (P-SOH), sulfinylation (P-SO2H) and sulfonylation (P-SO3H), formed when exposed to oxidative stress (reactive oxygen species). Our studies showed a direct correlation between P-SSH and these modifications in a time- and dose- dependent manner. We observed a clear phase shifted response between the two cysteine modifications, P-SSH and P-SOH, revealing the presence of ‘protective waves’ of protein persulfidation. Coupled with mechanistic studies showing the efficient reduction of P-SSH by the thioredoxin system, these results suggest that protein persulfidation is the main pathway by which sulfenic acids are resolved under oxidative stress. As such, we proposed a general mechanism (potentially an evolutionary remnant of the times when life emerged and flourished in a H2S environment) in which persulfidation represents a rescue loop from cysteine overoxidation and subsequent oxidative cellular damage.Furthermore, in order to shed light on the biological relevance of this protective nature of persulfides, we explored a possible correlation between persulfide levels and aging. This was explored through a range of studies, from the persulfide’s chemical ability to scavenge the build-up of oxidants, to gaining a better understanding of the role of transsulfuration pathway in stress resistance and lifespan. We observed a direct correlation between ability to make persulfides and oxidative stress resistance, and a decrease in persulfidation with aging, in C. elegans, rats and human cells
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Abdul, Majid Aman Shah Bin. "The influence of selected sulphur containing compounds on retinal cell death : neuroprotective effects of hydrogen sulphide in a glaucoma model." Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:bfb5ec82-9141-4784-94a8-0df3ce9d9471.
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Ganglion cell death in glaucoma is caused by a variety of insults that include ischemia, insufficient neurotrophic support and oxidative stress. Experimental studies were therefore conducted on cell cultures to determine how serum deprivation (to mimic insufficient neurotrophic support) or oxidative glutamate toxicity (GB), cause oxidative stress and induce retinal cell death. Moreover, studies were carried out to deduce whether selected sulphur containing compounds can blunt any negative influences to cells in culture and/or a defined ischaemic insult to the rat retina in situ, as this might suggest their use for the treatment of glaucoma. Serum deprivation and GB caused generation of reactive oxygen species (ROS) and apoptosis-like death to transformed retinal ganglion cells (RGC-5 cells). RGC-5 cells were more susceptible to the detrimental effects of GB than serum deprivation. RGC-5 cells subjected to serum deprivation appear to die by mechanisms that resemble classical apoptosis more closely than that caused by GB and the phase between the maximal generation of ROS and cell death were different. Cell death caused by serum deprivation was caspase-dependent but this was not the case for GB. Moreover, of the two sulphur compounds sulbutiamine and N-acetyl cysteine (NAC), sulbutiamine blunts the effect of serum deprivation more effectively. In addition, the pan caspase inhibitor z-VAD-fmk attenuated the negative effect of serum deprivation to RGC-5 cells while the necroptosis inhibitor (necrostsatin-1) counteracted solely the insult of GB. The sulphur containing compounds, ACS1 and ACS 67 which release hydrogen sulphide (H2S) slowly and NAC (a pro-cysteine GSH precursor) attenuated GB-induced cell death of RGC-5 cells. In contrast, sulbutiamine (a lipophilic thiolic thiamine derivative) was particularly effective in protecting RGC-5 cells from an insult of serum deprivation. Moreover, all of the sulphur compounds directly sequestered different types of ROS but with varying efficiency. Common features by which all tested sulphur containing agents seem to elicit a mode of action include the stimulation of GSH and the antioxidant enzyme glutathione-S-transferase (GST) as well as to scavenge excess free radicals. Moreover, the slow release of H2S from the ACS compounds appears to protect cells from oxidative stress through increasing the level of GSH, modulation of the cystine uptake transporter xCT, stimulation of the oxidative stress related transcription factor Nrf2 and the stimulation of pro-survival signalling pathways. The slow releasing H2S sulphur compound ACS67 also counteracts a number of detrimental influences to the rat retina in situ because of ischemia/reperfusion that includes damage to their ganglion cells. This suggests that such sulphur compounds might find a use in the treatment of glaucoma where ischemia probably plays a part in the disease process.
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Yates, Christopher Lee. "The study of anode materials for an intermediate temperature solid oxide fuel cell utilizing hydrogen sulfide as the fuel." Thesis, Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/10054.
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Maletzky, Erich. "The effects of oxygen deficiency, hydrogen sulphide and turbidity on the rock lobster, Jasus lalandii : implications for diamond dredge-mining in Namibia." Master's thesis, University of Cape Town, 2007. http://hdl.handle.net/11427/6128.
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Includes abstract.Includes bibliographical references (leaves 131-144).
A study was initiated by the Environmental Section of the De Beers Marine Namibia group as part of a pre-feasibility study for a new dredger (a Trailing Suction Hopper Dredger) to be employed for offshore diamond mining along the Namibian south coast. The aims of this study were to assess (a) the potential mining-induced impacts on oxygen and turbidity, and (b) the behavioural responses of the rock lobster Jasus lalandii, to decreased oxygen, elevated hydrogen sulphide and turbidity. For the latter objective, laboratory-based experiments were designed in which juvenile lobsters were exposed to various levels of hypoxia and increased hydrogen sulphide and suspended sediment levels to determine the impacts these stressors may have on the behavioural responses of lobsters.
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Мись, Л. А., Н. А. Струтинська, and В. Ф. Сагач. "Відновлення ендогенного синтезу сірководню сприяє зниженню чутливості мітохондріальної пори до Са2+ при старінні." Thesis, Сумський державний університет, 2017. http://essuir.sumdu.edu.ua/handle/123456789/53950.
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Сірководень (H2S) – газовий трансмітер, який має ендогенне походження і виконує важливу регуляторну роль в організмі людини. Він синтезується з амінокислоти цистеїну такими ферментами: цистатіонін-γ-ліазою, цистатіонін-ß-синтазою та 3-меркаптопіруватсульфуртрансферазою, що кон’югована з цистеїнамінотрансферазою, для яких кофактором є піридоксаль-5-фосфат (П5Ф). Як відомо, однією з основних причин серцево-судинних захворювань при різних патологічних станах і старінні є мітохондріальна дисфункція. Формування неселективної кальційзалежної циклоспорин А-чутливої МП між зовнішньою і внутрішньою мембранами лежить в основі індукції клітинної смерті – апоптозу. Проте роль H2S у регуляції пороутворення в мітохондріях серця остаточно ще не з'ясована.
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Joseph, Christy [Verfasser]. "Neuroprotection by prolonged hypothermia induced by hydrogen sulphide in focal cerebral ischemic rat model: Evidence from electrocortical activity and recruitment of polymorphonuclear cells / Christy Joseph." Greifswald : Universitätsbibliothek Greifswald, 2012. http://d-nb.info/1027393888/34.
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Garcia, Carolina Gil. "Montagem e operação de unidade de adsorção em leito fixo para remoção de H2S de corrente gasosa." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/18/18138/tde-01092014-092813/.
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O H2S é um gás que causa preocupação devido aos efeitos que pode provocar a saúde, a corrosão sobre alguns materiais e a redução do poder calorífero no aproveitamento de biogás, mesmo quando presente em baixas concentrações. O uso de biogás como fonte energética tem crescido nos últimos anos, impulsionando a remoção do sulfeto de hidrogênio, uma vez que a presença de tal gás reduz a capacidade calorífica do biogás e causa danos às instalações. Diante disso, várias técnicas são utilizadas na remoção de H2S, sendo uma delas, a adsorção. Os processos de separação por adsorção são muito utilizados para a remoção de poluentes gasosos de misturas gasosas. Neste trabalho foram realizados experimentos da adsorção do H2S sobre lodo seco, em coluna de leito fixo, para obtenção da capacidade de adsorção dinâmica do lodo e como esta seria afetada pelas variáveis de processo: concentração de alimentação e vazão de alimentação. Para tanto, foi concebida e instalada uma unidade de bancada de adsorção em leito fixo, com facilidades experimentais necessárias para testes dinâmicos, com o emprego da técnica de interpretação de curvas de efluência, um método útil para a avaliação do desempenho de um adsorvente em colunas de leito fixo. Testes preliminares mostraram que a unidade de bancada apresentou versatilidade, podendo ser operada com vazões de até 5 L/ min e concentração de H2S na mistura gasosa de até 500 ppm. Os resultados obtidos mostraram que a capacidade de adsorção do lodo seco foi muito baixa, com valores variando de 3,30 x 10-5 a 2,54 x 10-3 mg de H2S/g de lodo seco e existência de caminhos preferenciais no leito.It is widely known that H2S is a gas which causes preoccupation due to the potential risks to health, corrosion in materials and reduction of the calorific value, even when present in low concentrations. The application of biogas as an energetic source has increased in last years, promoting the hydrogen sulphide removal, so that H2S presence can reduce the biogas energetic capacity and cause damage in the installations. Therefore, many techniques are used to H2S removal, one them is adsorption. The adsorption separation processes are widely used in the removal of pollutants gaseous from gas mixtures. In this work, experiments were performed on the adsorption of H2S the dry sludge in a fixed bed column, aiming to obtain the dynamic adsorption capacity and how this would be affected by the process variables: feed concentration and feed flow rate . For that, we designed and installed a bench unit to fixed bed adsorption with necessary experimental facilities for dynamic tests with the use of the technique of interpretation breakthrough curves, an useful method for evaluating the performance of an adsorbent columns fixed bed . Preliminary tests showed that the bench unit has presented versatility and efficiency and it can be operated at flow rates up to 5 L/min and H2S concentration in the gas mixture up to 500 ppm. The results showed that the adsorption capacity of the dried sludge was very low , with values varied from 3.30 × 10-5 to 2.54 × 10-3 mg H2S/g of dry sludge and the existence of preferential paths in the bed .
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Caizzi, Adriano. "Modelling desulfurization of Biogas from Biomass gasification plants." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020.
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This Thesis originates from the demand of a freeware useful to describe the behavior of a filter for biogas. The whole project was done in an Austrian research institute, BioEnergy2020+, based in Graz. Particular attention is focused on hydrogen sulphide (H2S), which is one of the major biogas pollutants. Concentrations above 140 mg m–3 are harmful for human health.
The first part of the thesis is a brief explanation of why biogas and biomasses are important in an optic of reduction of greenhouse gases in the European Union, then is shown a brief review of the most promising technologies for biogas purification from H2S.
An Impregnated Activated Carbon - Packed Bed Reactor is chosen to do the filtration. To evaluate the calculation, it was used an original script, written in Julia Language. A system of Partial Differential Equations was developed using the finite differences method in order to have the concentration of pollutants in various time-steps. Multiple iterations were made to check the effective duration of the filter and when it needs a regeneration.
The last part shows the results discussion and the comparison with an existing study on H2S pollutant, made with a proprietary software (COMSOL).
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Forgan, Leonard George. "Influence of Oxygen Supply on Metabolism and Energetics in FishMuscles." Thesis, University of Canterbury. Biological sciences, 2009. http://hdl.handle.net/10092/4295.
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The five discrete, but related studies presented in this thesis investigate several aspects of the physiology and biochemistry of whole animals, perfused and isolated tissues from fishes and other vertebrates. Important fundamental questions about tissue metabolism and energy supply and utilisation in relation to oxygen supply, in addition to applied questions relating to commercial harvesting and post-mortem muscle physiology were addressed. Oxyconformance of oxygen consumption (VO2) at low oxygen delivery rates was shown using an isolated, perfused salmon tail preparation, composed primarily of skeletal muscle. Addition of pig red blood cells to the perfusing solution at a haematocrit of 5 or 10%, increasing the capacitance, resulted in oxyregulation of VO2 by the tail tissues. Below c.60 ml O2.kg-1.h-1 of oxygen delivery, VO2 was delivery dependent. Above this value additional oxygen delivery did not increase VO2 of resting muscle above c.35 ml O2 kg-1.h-1. The preparation was validated by measuring mitochondrial activity using MTT and blood flow distribution to the red and white muscle using fluorescent microspheres. Evidence of both O2-independence of VO2 in the vasculature and strict O2-dependence of VO2 in striated muscles of fishes and a mammal is presented using isolated vascular tissue and an in vitro tissue slice model. VO2 by vessels from rat, salmon and hagfish showed varying degrees of independence between PO2s of 15-95 mmHg in vitro (1 mmHg = 0.133 kPa). Above and below these values, VO2 was highly PO2-dependent. VO2 by cardiac and skeletal muscles from rat, salmon, snapper and hagfish were shown to relate linearly to PO2 between zero and 125 mmHg. VO2 in these tissues was highly dependent on tissue type (cardiac, red and white muscle) which correlated with haem protein concentration. The increase in VO2 in muscle slice mitochondria uncoupled with FCCP and DNP ruled out diffusion-limitation as a constraint on VO2.
Mitochondrial activity was constant over time and reoxygenation of the Ringer bathing the tissues after the initial run down in PO2 resulted in VO2 rates that were unchanged from the starting values, demonstrating that the tissues remained viable over time. ATP turnover in red muscle was significantly increased at 100 mmHg relative to 30 mmHg, and increased in both treatments from values at the start. Our data suggest that ATP supply and ATP demand were reduced in conjunction with falling PO2.
The effects of hydrogen sulphide (H2S) (derived from Na2S) and isoeugenol exposure on activity, VO2 and ventilation frequency (Vf) in a teleost fish are reported. In the H2S treatment group (200 μM Na2S) both resting VO2 and Vf decreased after 30 minutes of exposure, concurrent with narcosis and a loss of equilibrium. These events corresponded with a significant fall in VO2 (33%) and Vf (20%) by 15 minutes, both declining further to a nadir of 40% of resting values at 30 minutes. After flushing, VO2 increased to resting levels, with Vf remaining significantly depressed until 30 minutes of recovery. Recovery was accompanied by regained mobility and equilibrium and significantly increased VO2 and Vf. Isoeugenol anaesthetised fish (0.011 g.L-1) reached stage 4-5 of anaesthesia accompanied by significant decreases in VO2 (45%) and Vf (25%) at 25 minutes, both parameters declining further to around 64% and 38% respectively by 35 minutes. Similar to H2S exposed fish, VO2 increased to resting values after flushing, followed by a significant rise in VO2. Likewise, Vf had risen to resting values post-flushing, subsequently increasing significantly during recovery. Overall, VO2 in relation to resting rate was reduced in the isoeugenol treated animals, while in H2S treated fish, exposure there was increased oxygen usage, possibly associated with a toxic effect. H2S significantly reduced cytochrome c oxidase activity in muscle and gill tissue in vitro between 69-79% at 20 μM and 77-97% at 200 μM Na2S, while isoeugenol had no effect on activity in any tissue. Calorimetric and biochemical profiles of anoxic, post-mortem white muscle from Chinook salmon subjected to rested and exhausted harvesting regimens at their acclimation temperature (10°C) are reported. Prior to harvest rested animals were anaesthetised with 0.012 g.L-1 isoeugenol without disturbance. The muscle of these animals had a high metabolic rate at the time of death, at around 400 μW.g-1, which declined rapidly over the first 12 hours to15 μW.g-1. Exhausted animals were forced to swim and were crowded before capture, resulting in an initial heat output of <10 μW.g-1. Heat output was significantly greater in the rested group at the time of death and for 7 hours post-mortem. In both groups there was an exothermic event, occurring between 4 and 6 hours post-mortem amounting to a rise of around 35 μW.g-1. A one-phase exponential decay model appropriately described the net heat output of the rested profile minus the exhausted data. Rested animals had significantly higher initial cut surface pH (7.5 vs 6.7), tissue glycogen (16 vs 2 μmol.g-1), creatine phosphate (18 vs 0.1 μmol.g-1), ATP (6 vs 3.5 μmol.g-1) and potential energy (30 vs 7 μmol.g-1) than the exhausted group, which had significantly elevated tissue concentrations of lactate (43 vs 18 μmol.g-1) and glucose (5 vs 2 μmol.g-1). Potential energy in the form of ATP, glycogen and creatine phosphate remained elevated for an extended period post-mortem in rested animals while catabolites further down the chain such as inosine, hypoxanthine and uric acid accumulated at similar rates in both groups. We examined the relationship between exogenous and endogenous H2S and oxygen partial pressure in isolated hagfish and lamprey vessels that exhibit profound hypoxic vasoconstriction (HVC). In myography studies, H2S (Na2S) dose-dependently constricted dorsal aortas (DA) and efferent branchial arteries but did not affect ventral aortas or afferent branchial arteries, which was similar to the effects produced by hypoxia. Sensitivity of H2S-mediated contraction in hagfish and lamprey DA was enhanced by hypoxia. HVC in hagfish DA was enhanced by the H2S precursor cysteine and inhibited by amino-oxyacetate (AOA), an inhibitor of the H2S-synthesising enzyme, cystathionine β-synthase, and unaffected by propargyl glycine, an inhibitor of cystathionine λ-lyase. Oxygen consumption (MO2) of hagfish DA was constant between a PO2 of 15 and 115•mmHg, decreased when PO2 <15•mmHg, and increased if PO2 exceeded 115•mmHg. 10 μmol.l-1 H2S increased and concentrations above 100 μmol.l-1 H2S decreased MO2. Consistent with the effects on HVC, cysteine increased and AOA and hydroxylamine, an inhibitor of pyridoxyl 5’-phosphate-dependent enzymes, decreased MO2. These data show that H2S is a monophasic vasoconstrictor of specific cyclostome vessels and because hagfish lack vascular NO, and vascular sensitivity to H2S was enhanced at low PO2, it is unlikely that H2S contractions are mediated by either an H2S-NO interaction or an oxidation product of H2S. These experiments provide additional support for the hypothesis that the metabolism of H2S is involved in oxygen sensing/signal transduction in vertebrate vascular smooth muscle.
Together the findings of this thesis contribute to the understanding of oxygen utilisation and energetics in relation to oxygen supply in a number of tissues. These data further our understanding of respiratory physiology and may have practical applications in the seafood industry.
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Čiutelytė, Rūta. "Biogas yield and quality improvement and purification with natural minerals." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2013. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2013~D_20131004_191808-62516.
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Research goal and objective. To investigate the possibilities of the use of mineral raw materials of local origin for the purification of biogas produced from sewage sludge, by-products and waste and to assess the environmental benefits of the use of biogas in the transport sector. The properties of by-products and waste generated in Lithuania as well as the possibilities of their use in the production of biogas from sewage sludge have been assessed. The potential and properties of local mineral raw materials suitable for the purification of biogas have been assessed. The process of the removal of hydrogen sulphide and carbon dioxide from biogas using natural sorbents has been investigated. It was found that large dolomite resources available in Lithuania allow using this natural raw material for biogas purification because sorbent solutions and suspensions of dolomite powder effectively remove hydrogen sulphide and absorb carbon dioxide from biogas sufficiently quickly. A principal biogas purification technology was developed on the basis of the performed assessment of the process kinetic calculations. Engine perfomance tests were carried out using a mixture of biogas and mineral diesel fuel and exhaust gas emissions were assessed.Darbo tikslas – ištirti gamtinių sorbentų (vietinės kilmės mineralinių žaliavų) panaudojimo biodujų, pagamintų iš nuotekų dumblo, šalutinių produktų ir atliekų, valymui galimybes bei įvertinti biodujų panaudojimo transporto sektoriuje aplinkosauginę naudą. Įvertintos Lietuvoje susidarančių šalutinių produktų ir atliekų savybės bei panaudojimo biodujų gamyboje iš nuotekų dumblo galimybės. Įvertintos vietinės kilmės mineralinių žaliavų, tinkančių biodujų valymui, potencialas ir savybės. Ištirtas biodujų valymo nuo sieros vandenilio ir anglies dioksido procesas, naudojant gamtinius sorbentus. Nustatyta, kad Lietuvoje eantys dideli dolomito ištekliai leidžia panaudoti šią natūralią žaliavą biodujų valymui, nes absorbciniai tirpalai iš dolomito miltelių efektyviai pašalina sieros vandenilį ir pakankamai gerai sugeria anglies dioksidą. Remiantis atliktu proceso kinetinių skaičiavimų įvertinimu buvo parengta principinė biodujų valymo technologija. Atlikti stendiniai variklio bandymai naudojant biodujų ir mineralinio dyzelino mišinį bei įvertintos deginių emisijos.
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De, Beer Deon Johan. "The relationship of weld metal hardness residual stress and susceptible to stress corrosion cracking in hydrogen sulphide environment in A516 Grade 70 carbon steel shielded metal arc welded joint." Diss., University of Pretoria, 2002. http://hdl.handle.net/2263/71679.
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In the petrochemical industry, carbon steels exposed to H2S environments may be susceptible to stress-corrosion cracking. A tensile residual stress and high hardness increases the risk of cracking in H2S environments. NACE SP 0472 limits weld metal hardness to 210 HV10 (200 HB) and heat-affected zone hardness to 250 HV10 to prevent stress-corrosion cracking of carbon steel welds in H2S. The hardness is controlled by the weld thermal cycle or by a post-weld heat treatment. In this project, the effect of hardness on the susceptibility to stress-corrosion cracking was investigated by increasing electrode strength systematically and measuring residual stress in the weld metal in the as-welded state. Samples were manufactured from SA 516 Gr 70, a carbon steel used extensively in the petrochemical industry. Heavily clamped plates were welded to minimise distortion and to maximise residual stress. The weld metal hardness was increased by using E6013, E7018-1, E8018-B2 and E9018-B3 electrodes without a post-weld heat treatment. Mechanical tests included all-weld and transverse tensile tests, impact strength and hardness testing. As the nominal strength of the weld metal increased, the all-weld tensile strength increased from 512 to 829 MPa, while the yield strength increased from 443 to 659 MPa. The average weld metal hardness increased from 177 to 317 HV10. The transverse tensile strength was between 511-517 MPa, while the yield strength (in the transverse direction) was between 360 and 382 MPa. Residual stresses of the welded joint were measured by neutron diffraction in the through-thickness, longitudinal and transverse direction. The Von Mises theorem evaluated the principle residual stress. Results indicate that the residual stress in the weld metal may be up to 99% of the yield strength. For stress-corrosion cracking, the samples were submerged in the standard TM0177-2005 test solution for 30 days. The only sample to crack was the E9018, with an average weld metal hardness of 317 HV10. The study results were consistent with the NACE SP0472 specification and earlier publications.Dissertation (MEng)--University of Pretoria, 2017.
TM2019
Materials Science and Metallurgical Engineering
MEng
Unrestricted
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Grandclerc, Anais. "Compréhension des mécanismes de biodétérioration des matériaux cimentaires dans les réseaux d'assainissement : étude expérimentale et modélisation." Thesis, Paris Est, 2017. http://www.theses.fr/2017PESC1089/document.
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Des détériorations importantes sont observées dans les réseaux d’assainissement en béton en raison de la présence d’hydrogène sulfuré (H2S). Différentes études ont montré qu’un environnement riche en hydrogène sulfuré entraîne, au contact de surfaces cimentaires, la sélection de bactéries sulfo-oxydantes (bactéries capables d’oxyder des composés soufrés réduits), menant à la production d’acide sulfurique. Cet acide détériore localement les réseaux par dissolution et recomposition minéralogique de la matrice cimentaire (formation de gypse et d’ettringite). Les réseaux ne collectent alors plus correctement les eaux usées et ce phénomène provoque donc des travaux de rénovation onéreux. Dans ce contexte, des solutions plus performantes que celles mises en place actuellement doivent être étudiées. L’objectif du projet FUI DURANET dans lequel s’inscrit cette thèse vise à proposer un essai accéléré et à développer un modèle.La mise en place d’essais abiotiques a permis de démontrer que cette première étape n’est pas l’étape limitante du phénomène de biodétérioration. En effet, le pH de surface des matériaux cimentaires adapté au développement microbien est rapidement atteint lorsqu’ils sont mis au contact de l’hydrogène sulfuré à une concentration élevée (100 ppm), quel que soit le matériau cimentaire considéré (mortiers à base de ciments CEM I, CEM III, CEM IV, CEM V, CAC et CSS). La modélisation de l’attaque par l’acide sulfurique et la mise en place d’un essai représentatif et accéléré ont ensuite été abordées pour prédire la durabilité des différents matériaux cimentaires de l’étude. Pour l’essai, différentes techniques d’ensemencement des microorganismes à la surface des matériaux cimentaires ont été comparées, afin de déterminer laquelle mène à la meilleure reproduction des conditions d’un réseau d’assainissement et à l’accélération des mécanismes de biodétérioration la plus importante. Ces essais permettent de préconiser l’utilisation de boues activées contenant un consortium de microorganismes, par rapport à l’utilisation de souches de collection, dont l’activité dépend trop fortement de leur adaptabilité aux conditions environnementales. L’ensemble des résultats, obtenus expérimentalement et par modélisation, montre une meilleure résistance des ciments d’aluminate de calcium et une dégradation très importante des ciments Portland face aux mécanismes mis en jeu, en accord avec les essais in-situImportant deteriorations have been observed in concrete sewers, due to hydrogen sulfide (H2S) presence. H2S is used as nutrients for sulfur-oxidizing bacteria (bacteria able to oxidize the reduced sulfur compounds) and is oxidized into sulfuric acid. This acid attack of concrete leads to cementitious matrix dissolution and expansive products formation (gypsum and ettringite). This phenomenon disturbs the sewer system and conducts to expensive works of rehabilitation. In order to avoid this degradation, a French project named “FUI Duranet” was initiated to propose more efficient solutions. The aim of this thesis is to define a representative and accelerated test as well as a predictive model.Abiotic tests allow stating that this first stage of the biodeterioration mechanisms is not the limiting stage. Indeed, the adapted surface pH of the cementitious materials to bacteria development is quickly reached with a high H2S concentration (100 ppm), whatever the cementitious materials considered (mortars based on CEM I, CEM III, CEM IV, CEM V, CAC, and SSC cements). The chemical-transport modeling of the sulfuric acid attack of cementitious materials and the establishment of a representative and accelerated test have been proposed to predict their service life in these conditions. For the test, different seeding technics have been compared in order to determine which one lead to the better reproduction and acceleration of biodeterioration mechanisms. This test allows recommending the sludge use, which contains a microorganism’s consortium, rather than a collection strain use, whose activity is too dependent on environmental conditions. With the experimental test and the model, the better resistance of the calcium aluminate cement and the important degradation of the Portland cements are quickly confirmed, as highlighted during the field tests
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Maleki, Rahil. "Consequences Analysis of CH4/H2S Release in Offshore Platform." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2018.
Find full textAbstract:
The exploitation and development of offshore oil & gas fields continue to be one of the main source to supply energy worldwide. However, existing and new projects may involve specific geographic areas with safety challenges due to the presence of natural gas, mainly Methane (CH4), containing a certain amount of Hydrogen Sulphide (H2S) in the extracted hydrocarbons (sour gas). Indeed, the combined effect of flammability and toxicity of such gases has the critical potential to increase the hazard level in the offshore installation aggravating the consequences for human and assets.
The present work aims at the consequences analysis related to the release of sour gas (CH4/H2S) on an offshore production facility, by considering different H2S fractions in the gas composition. The analysis was based on the estimation of safety distances for the physical effects of accident scenarios with respect to personnel, equipment and facility structures.
Two different approaches implemented into consequences modelling software, the Process Hazard Analysis Software Tool (PHAST), which is based on integral and lumped parameter model, and the Fire Dynamic Simulator (FDS), which is ascribed to the Computational Fluid Dynamic model, hence based on distributed parameter model.
A case study concerning an actual offshore, multi-level platform for gas production was considered. Large releases from two different process equipment were simulated for three mixtures with different amount of H2S, starting from specific release points.
The results showed that the H2S content is not an effective factor for the safety distance in the case of ignition of the gas cloud, hence in the case of fires. Also, the presence of obstructions slightly affects the damage distances for fires. On the contrary, the safety distance from the release point can be strongly affected by the presence of H2S concentration higher than 1%v.
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Bolyard, Steven Jeffrey. "Monitoring and Modeling to Estimate Hydrogen Sulfide Emissions and Dispersion from Florida Construction and Demolition Landfills to Construct Odor Buffering Distances." Master's thesis, University of Central Florida, 2012. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5134.
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Emissions of hydrogen sulfide (H2S) from construction and demolition (C & D) landfills can result in odors that are a significant nuisance to nearby neighborhoods and businesses. As Florida's population continues to grow and create development pressures, housing is built closer to existing landfills. Additionally, new landfills will be created in the future. This research project was undertaken to develop a detailed modeling methodology for use by counties and other landfill owners to provide them with an objective and scientifically defensible means to establish odor buffer zones around C & D landfills. A technique for estimating methane (and odorous gas) emissions from municipal solid waste (MSW) landfills was recently developed by researchers at the University of Central Florida. This technique was based on measuring hundreds of ambient methane concentrations near the surface of the landfill, and combining that data with matrix inversion mathematics to back-solve the dispersion equations. The technique was fully documented in two peer-reviewed journal articles. This project extends that methodology. In this work the author measured ambient H2S concentrations at various locations in a C & D landfill, and applied those same matrix inversion techniques to determine the H2S emission rates from the landfill. The emission rates were then input into the AERMOD dispersion model to determine H2S odor buffer distances around the landfill. Three sampling trips to one C & D landfill were undertaken, data were taken, and the modeling techniques were applied. One problem encountered was that H2S emissions from C & D landfills are typically about 1000 times smaller than methane emissions (from MSW landfills). Thus, H2S ambient concentrations often are near the detection limits of the instruments, and the data may not be as reliable. However, this approach could be used for any particular C & D landfill if the appropriate amount of data were available to characterize its emissions with some certainty. The graphical tool developed in this work shows isopleths of "H2S" concentrations at various distances, and color codes the isopleths into a "green-yellow-red" scheme (analogous to a traffic signal) that depicts zones where private landowners likely will not detect odors, where they may experience some odors, or where they likely will experience odors. The “likelihood” can be quantified by selecting the Nth highest hourly concentrations in one year to form the plot. In this study, N was conservatively selected as 8. Requiring that concentrations be at or below the 8th highest concentration in a year corresponds to a 99.9% probability of not exceeding that concentration at that distance in any future year. The graphical tool can be applied to any C & D landfill but each landfill is different. So this technique depends on having a fairly good estimate of the rate of emissions of H2S from the landfill in question, and at least one year's worth of hourly meteorological data (wind speed, direction, and stability class) that is representative of the landfill location. The meteorological data can be obtained with relative ease for most locations in Florida; however, the emission data must be obtained from on-site measurements for any given landfill.ID: 031001460; System requirements: World Wide Web browser and PDF reader.; Mode of access: World Wide Web.; Adviser: .; Title from PDF title page (viewed July 8, 2013).; Thesis (M.S.Env.E.)--University of Central Florida, 2012.; Includes bibliographical references (p. 76-77).
M.S.Env.E.
Masters
Civil, Environmental, and Construction Engineering
Engineering and Computer Science
Environmental Engineering
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Kazlauskas, Dainius. "Researches of H2S generation from municipal landfills and systematical evaluation of landfills pollution." Master's thesis, Lithuanian Academic Libraries Network (LABT), 2005. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2005~D_20050614_082554-89323.
Full textAbstract:
In Lithuania the amount of waste generation is increasing every year. According to national strategy, all wastes should be disposed in new regional landfills. Landfills pollutes environment with leachate and landfill gas and odours. Landfill gas consists of odorous compounds and one of them is hydrogen sulphide (H2S). Hydrogen sulphide is highly toxic and affects the nervous system with low threshold. As the landfill gas and leachate generation was word widely investigated before this work, it is not necessary to provide new researches on them. The measurements of H2S generation were provided in Jerubaiciai landfill. For the measurements was used “site-on” measurement method, measurements were provided with equipment GD/MG 7, in 51 measurement points and 2 monitoring wells, during different seasons of the year. Results of the measurement shows, that amount of H2S varies in different areas of landfill and during different seasons. The results of dispersion modeling achieved with dispersion model AERMOD, provided under calm weather conditions and under wind dominated in that session winter speed and direction, during different seasons of the year shows, that H2S spreads from landfill in longest distances from landfill’s section during summer (almost in distance equal to 2.5 km the H2S concentration is higher then Highest Allowable Concentration ). In autumn and spring this distance is equal to 1.5 km, and in winter – 800 m.Susidarančių komunalinių atliekų kiekis Lietuvoje kiekvienais metais didėja. Pagal nacionalinę strategiją, visos komunalinės atliekos Turi būti deponuojamos regioniniuose sąvartynuose, kurie teršia aplinka filtratu iš sąvartyno išsiskiriančiomis dujomis bei kvapais, kurių veina iš sudedamųjų dalių yra sieros vandenilis (H2S). H2S matavimai buvo atlikti Jerubaičių sąvartyne. Iš sąvartyno išsiskiriantis H2S kiekis buvo tiriamas jo išsiskyrimo vietoje, t.y. sąvartyno teritorijoje. Šis matavimo metodas buvo pasirinktas remiantis tuo, kad iš sąvartyno išsiskiriančios taršos dydis ir poveikis priklauso nuo daugelio aplinkos faktorių. Matavimai, naudojant prietaisą GD/MG 7, buvo atlikti 59 matavimo taškuose ir 2 monitoringo šuliniuose, skirtingais metų laikai. Gauti tyrimų rezultatai parodė, kad šios medžiagos kiekis yra skirtingas įvairiose sąvartyno zonose bei įvairiais metų laikais. Norint ištirti H2S sklaidą buvo atliktas skaitmeninis dispersijos modeliavimas naudojant programą AERMOD. Jo metu vienu atveju buvo pasirinktos stabilios meteorologinės sąlygos, o kitu pasirinkti dominuojančios konkrečiu metų laiku vėjo kryptys ir greičiai. Modeliavimo rezultatai parodė, kad vasarą H2S didžiausia leistina koncentracija pasiekiama tik maždaug 2,5 kilometrų, rudenį ir pavasarį 1,5 kilometrų, o žiemą - už 800 metrų atstumu nuo sąvartyno teritorijos.
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Silva, Thiago Nepomuceno. "Avaliação dos efeitos da adição de L-cistina e sais biliares na técnica de H2S na detecção de contaminação fecal em ambientes aquáticos." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/87/87131/tde-19102016-142754/.
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As fontes hídricas disponíveis para o consumo humano vêm sendo comprometidas. Para resolver este problema, várias técnicas de detecção de contaminação fecal foram desenvolvidas. Em 1982, Manja e colegas desenvolveram método H2S que é simples, rápida e de baixo custo e detecta bactérias produtoras de H2S e, assim, a contaminação fecal. Neste trabalho foi analisada a eficácia de detecção de micro-organismos produtores de H2S frente a adição de L-cistina (125mg/L e 250mg/L) e desoxicolato de sódio (DS) (0,1% e 0,3%) e na presença de bactérias não produtoras de H2S para verificar se a presença destas bactérias interferem na detecção dos isolados H2S+. Assim, comparou-se o teste H2S com a membrana filtrante e o Colilert®. Os resultados deste estudo indicam que o meio H2S com adição de 0,3% de desoxicolato de sódio se mostrou mais rápido e sensível. Quando comparado com outras metodologias clássicas, o meio com 0,3% apresentou uma ligeira queda na sensibilidade mas o método H2S se mostrou mais sensível que o Colilert.Water supply for human consumption have been compromised. Several detection methods for fecal contamination have been developed to solve this problem. Manja and co-workers (1982) developed a simple, fast and low-cost method for fecal contamination based on detection of sulfate-reducing bacteria, the H2S method. This work aimed to analyse the detection efficiency of the H2S method under different conditions: with L-cystine (125mg/L e 250mg/L) and sodium deoxycholate (0.1% e 0.3%). Also, non-sulfate-reducing bacteria interference were evaluated. Comparison tests were made through membrane filtration and Colilert®. Our results indicate a faster and more sensible for the 0.3% sodium deoxycholate condition. Compared to other classic methodologies, the 0.3% sodium deoxycholate condition slightly decrease the sensibility. However the H2S method was more sensitive than the Colilert one.
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Gustavsson, Catrin. "On the Interrelation Between Kraft Cooking Conditions and Pulp Composition." Doctoral thesis, Stockholm, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4232.
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Diniz, Polyana Borges França. "Avaliação de mecanismos envolvidos na gastroproteção induzida pelo extrato etanólico da entrecasca da Caesalpinia pyramidalis Tul." Pós-Graduação em Ciências Fisiológicas, 2014. https://ri.ufs.br/handle/riufs/3980.
Full textAbstract:
Caesalpinia pyramidalis, is an endemic plant from the North east of Brazil which present scientifically proven anti-inflamatory, antinociceptive, and gastroprotective activities. This work aimed at evaluating the gastroprotective effect of the extract of Caesalpinia pyramidalis (EECp) bark in acute gastric ulcers induced by ethanol in Wistar rats. The ulcered animals were treated with a dose of 100mg/kg of EECp and L-NAME (nitric acid blocker) and Propargylglycine (hydrogen sulfide blocker). It was evaluated, in all treatments, the role of the gas mediators such as nitric oxide (NO) and hydrogen sulfide (H2S) and also the participation of mast cells and molecules involved in the anti-inflamatory process as iNOS and citocin IL-4. It was observed in the NO evaluation that the treatment with L-NAME was not able to revert the inhibitory effect of EECp on the ulcers induced by ethanol, showing that the EECp does not operate via NO. However, the H2S can operate in the gastro protection of the EECp as its block hindered the gastroprotective effect on the ulcers induced by ethanol. In order to evaluate the mast cells, histological cuts were made with toluidine blue/alcian blue/safranine where different mast cells phenotypes were observed. In all treatments a prevalence of mucous mast cells was observed. The techniques of immunofluorescence and flow cytometry were used to evaluate IL-4 and iNOS. The ulcered animals treated with EECp presented high expression of IL-4 and low expression of iNOS, suggesting an anti-inflammatory activity of EECp. In conclusion, the gastroprotective effect of EECp and its action mechanism are related to H2S in diminishing the oxidative stress, the induced NO synthase, and the positive immunomodulatory effect for IL-4, with the diminution of mucous mast cells during the inflammatory process.A Caesalpinia pyramidalis, planta endêmica da região do Nordeste é utilizada popularmente para tratamento de diversos distúrbios patológicos e possui ação anti-inflamatória, anti-nociceptiva e gastroprotetora. O objetivo desse trabalho foi avaliar o efeito gastroprotetor do extrato da entrecasca da Caesalpinia pyramidalis (EECp) em modelos de úlcera aguda induzidas por etanol em ratos Wistar. Os animais ulcerados foram tratados com EECp na dose de 100 mg/kg, com L-NAME (bloqueador de óxido nítrico) e Propargilglicina (bloqueador de sulfeto de hidrogênio). Para todos os tratamentos foi avaliado o papel de mediadores gasosos como óxido nítrico (NO) e sulfeto de hidrogênio H2S, e também a participação de mastócitos e de moléculas envolvidas no processo inflamatório como a iNOS e a citocina IL-4. Na avaliação dos de NO observamos que o tratamento com L-NAME não foi capaz de reverter o efeito inibitório da EECp sobre as úlceras induzidas por etanol, demonstrando que o EECp não age pela via do NO. Contudo o H2S pode estar atuando na gastroproteção do EECp pois o seu bloqueio impediu o efeito gastroprotetor sobre as úlceras induzidas por etanol. Para avaliação de mastócitos cortes histológicos foram corados com azul de toluidina/ alcian blue/ safranina onde observamos diferentes fenótipos de mastócitos. Observamos um predomínio de mastócitos mucosos em todos os tratamentos. Para a avaliação de IL-4 e de iNOS foram utilizadas as técnicas de imunofluorescência e citometria de fluxo. Observamos que os animais ulcerados tratados com EECp apresentaram alta expressão de IL-4 e baixa expressão de iNOS, sugerindo uma atividade anti-inflamatória da EECp. Pode-se concluir que o efeito gastroprotetor do EECp e o possível mecanismo de ação, está relacionado ao H2S na diminuição do estresse oxidativo, diminuição do NO sintase induzível e com o efeito imunomodulatório positivo para IL-4, como a diminuição de mastócitos mucosos durante o processo inflamatório.