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Hydrogen
Kinds of Hydrogen Terms modified by Hydrogen Selected AbstractsMELATONIN PROTECTS AGAINST HYDROGEN PEROXIDE-INDUCED GASTRIC INJURY IN RATSCLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 4 2009Ahmed M Mohamadin SUMMARY 1Melatonin (MT) is a pineal hormone that is also abundant in the gut and has a well known role in scavenging oxygen free radicals. The aim of the present study was to evaluate the potential protective effects of MT against H2O2 -induced gastric lesions in rats. 2An experimental model of gastric ulceration was established in rats using 15% H2O2. Melatonin (12.5, 25 or 50 mg/kg, intagastrically) was administered to rats 30 min before H2O2 challenge. 3Intragastric administration of H2O2 resulted in haemorrhagic lesions in the fundic area of the stomach. Furthermore, H2O2 induced gastric oxidative stress, as indicated by depletion of reduced glutathione (GSH), inhibition of glutathione peroxidase (GPx) activity and elevation of malonedialdehyde (MDA) levels. These effects were accompanied by decreased gastric tissue levels of prostaglandin (PG) E2 and nitric oxide (NO), as well as increased levels of tumour necrosis factor (TNF)-,. Administration of MT (12.5, 25 or 50 mg/kg) 30 min before H2O2 significantly attenuated the development of gastric lesions in a dose-dependent manner. The protective effects of MT were accompanied by significant inhibition of the H2O2 -induced reduction in gastric content of GSH and GPx activity and elevation in MDA levels. Furthermore, MT antagonized H2O2 -induced reduction of gastric PGE2 and NO levels and elevation of TNF-,. 4In conclusion, MT protects rat gastric mucosa against H2O2 -induced damage. The observed protective effects of MT can be attributed, at least in part, to its anti-oxidant properties, preservation of PGE2 and NO levels, as well as inhibition of TNF-, induction in gastric tissues. [source] Control of Oxidative Reactions of Hemoglobin in the Design of Blood Substitutes: Role of the Ascorbate,Glutathione Antioxidant SystemARTIFICIAL ORGANS, Issue 2 2009Jan Simoni Abstract Uncontrolled oxidative reactions of hemoglobin (Hb) are still the main unresolved problem for Hb-based blood substitute developers. Spontaneous oxidation of acellular ferrous Hb into a nonfunctional ferric Hb generates superoxide anion. Hydrogen peroxide, formed after superoxide anion dismutation, may react with ferrous/ferric Hb to produce toxic ferryl Hb, fluorescent heme degradation products, and/or protein-based free radicals. In the presence of free iron released from heme, superoxide anion and hydrogen peroxide might react via the Haber,Weiss and Fenton reactions to generate the hydroxyl radical. These highly reactive oxygen and heme species may not only be involved in shifting the cellular redox balance to the oxidized state that facilitates signal transduction and pro-inflammatory gene expression, but could also be involved in cellular and organ injury, and generation of vasoactive compounds such as isoprostanes and angiotensins. It is believed that these toxic species may be formed after administration of Hb-based blood substitutes, particularly in ischemic patients with a diminished ability to control oxidative reactions. Although varieties of antioxidant strategies have been suggested, this in vitro study examined the ability of the ascorbate,glutathione antioxidant system in preventing Hb oxidation and formation of its ferryl intermediate. The results suggest that although ascorbate is effective in reducing the formation of ferryl Hb, glutathione protects heme against excessive oxidation. Ascorbate without glutathione failed to protect the red blood cell membranes against Hb/hydrogen peroxide-mediated peroxidation. This study provides evidence that the ascorbate,glutathione antioxidant system is essential in attenuation of the pro-oxidant potential of redox active acellular Hbs, and superior to either ascorbate or glutathione alone. [source] Current Awareness in Contrast Media and Molecular ImagingCONTRAST MEDIA & MOLECULAR IMAGING, Issue 2 2010Article first published online: 20 APR 2010 In order to keep subscribers up-to-date with the latest developments in their field, John Wiley & Sons are providing a current awareness service in each issue of the journal. The bibliography contains newly published material in the field of Contrast Media and Molecular Imaging. Each bibliography is divided into 15 sections: 1 Reviews; 2 General; Contrast Agents: 3 Chemistry; 4 Technique; 5 Experimental; 6 Applications; Molecular Imaging: 7 Carbon; 8 Fluorine; 9 Gallium; 10 Hydrogen; 11 Indium; 12 Iodine; 13 Phosphorus; 14 Technetium; 15 Others. Within each section, articles are listed in alphabetical order with respect to author. If, in the preceding period, no publications are located relevant to any one of these headings, that section will be omitted. [source] Current Awareness in Contrast Media and Molecular ImagingCONTRAST MEDIA & MOLECULAR IMAGING, Issue 1 2010Article first published online: 22 FEB 2010 In order to keep subscribers up-to-date with the latest developments in their field, John Wiley & Sons are providing a current awareness service in each issue of the journal. The bibliography contains newly published material in the field of Contrast Media and Molecular Imaging. Each bibliography is divided into 15 sections: 1 Reviews; 2 General; Contrast Agents: 3 Chemistry; 4 Technique; 5 Experimental; 6 Applications; Molecular Imaging: 7 Carbon; 8 Fluorine; 9 Gallium; 10 Hydrogen; 11 Indium; 12 Iodine; 13 Phosphorus; 14 Technetium; 15 Others. Within each section, articles are listed in alphabetical order with respect to author. If, in the preceding period, no publications are located relevant to any one of these headings, that section will be omitted. [source] Current Awareness in Contrast Media and Molecular ImagingCONTRAST MEDIA & MOLECULAR IMAGING, Issue 1 2008Article first published online: 11 MAR 200 In order to keep subscribers up-to-date with the latest developments in their field, John Wiley & Sons are providing a current awareness service in each issue of the journal. The bibliography contains newly published material in the field of Contrast Media and Molecular Imaging. Each bibliography is divided into 15 sections: 1 Reviews; 2 General; Contrast Agents: 3 Chemistry; 4 Technique; 5 Experimental; 6 Applications; Molecular Imaging: 7 Carbon; 8 Fluorine; 9 Gallium; 10 Hydrogen; 11 Indium; 12 Iodine; 13 Phosphorus; 14 Technetium; 15 Others. Within each section, articles are listed in alphabetical order with respect to author. If, in the preceding period, no publications are located relevant to any one of these headings, that section will be omitted. [source] Current Awareness in Contrast Media and Molecular ImagingCONTRAST MEDIA & MOLECULAR IMAGING, Issue 6 2006Article first published online: 8 DEC 200 In order to keep subscribers up-to-date with the latest developments in their field, John Wiley & Sons are providing a current awareness service in each issue of the journal. The bibliography contains newly published material in the field of Contrast Media and Molecular Imaging. Each bibliography is divided into 15 sections: 1 Reviews; 2 General; Contrast Agents: 3 Chemistry; 4 Technique; 5 Experimental; 6 Applications; Molecular Imaging: 7 Carbon; 8 Fluorine; 9 Gallium; 10 Hydrogen; 11 Indium; 12 Iodine; 13 Phosphorus; 14 Technetium; 15 Others. Within each section, articles are listed in alphabetical order with respect to author. If, in the preceding period, no publications are located relevant to any one of these headings, that section will be omitted. [source] Current Awareness in Contrast Media and Molecular ImagingCONTRAST MEDIA & MOLECULAR IMAGING, Issue 5 2006Article first published online: 10 OCT 200 In order to keep subscribers up-to-date with the latest developments in their field, John Wiley & Sons are providing a current awareness service in each issue of the journal. The bibliography contains newly published material in the field of Contrast Media and Molecular Imaging. Each bibliography is divided into 15 sections: 1 Reviews; 2 General; Contrast Agents: 3 Chemistry; 4 Technique; 5 Experimental; 6 Applications; Molecular Imaging: 7 Carbon; 8 Fluorine; 9 Gallium; 10 Hydrogen; 11 Indium; 12 Iodine; 13 Phosphorus; 14 Technetium; 15 Others. Within each section, articles are listed in alphabetical order with respect to author. If, in the preceding period, no publications are located relevant to any one of these headings, that section will be omitted. [source] Pressure Ionization and Transitions in Dense HydrogenCONTRIBUTIONS TO PLASMA PHYSICS, Issue 3-4 2005W. Ebeling Abstract Shock experiments with fluid hydrogen have shown that a transition from insulating behavior to metal-like conductivity occurs at pressures beyond 100 GPa. This requires the development of new methods to describe the transition region of dense plasmas. The traditional approach due to Saha is based on the assumption of chemical equilibrium between charged and neutral components. This is equivalent to minimizing the free energy with respect to the composition. Here we improve an expression for the free energy developed recently to determine Hugoniot curves and isentropes in dense hydrogen and deuterium plasma in the regions of partial dissociation and partial ionization. We show that at high pressures the influence of the excluded volume occupied by neutral species is crucial for the transition to full ionization. We present curves for several thermodynamic functions for the region 5000 K < T < 20000 K and 0.6 g/cm3 < , < 1 g/cm3. The influence of the effective radii of the neutral species is crucial in the transition region. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Thermodynamics of Hydrogen and Hydrogen-Helium Plasmas: Path Integral Monte Carlo Calculations and Chemical PictureCONTRIBUTIONS TO PLASMA PHYSICS, Issue 3-4 2005V. S. Filinov Abstract In this paper we study thermodynamic properties of hydrogen and hydrogen-helium mixtures with the help of the direct path integral Monte Carlo simulations. The results are compared with available theoretical and experimental methods based, in particular, on chemical picture. We investigate the effects of temperature ionization in low-density hydrogen plasma. We also present a number of calculated isotherms for hydrogenhelium mixture with the mass concentration of helium Y = 0.234 in the range from 104 K to 2 · 105 K. In the density region where a sharp conductivity rise have been observed experimentally the simulations give indications for one or two plasma phase transitions, in accordance with earlier theoretical predictions. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] The Equation of State of Fluid HydrogenCONTRIBUTIONS TO PLASMA PHYSICS, Issue 3-4 2005D. Kremp Abstract A review is given about some selected aspects of the development of the equation of state of hydrogen. Recent results are presented for low temperature fluid hydrogen. Reaction Ensemble Monte Carlo data determined thus are combined with Path Integral Monte Carlo results to give an Hugoniot covering the entire pressure range. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Thermodynamic Properties and Plasma Phase Transition in dense HydrogenCONTRIBUTIONS TO PLASMA PHYSICS, Issue 5-6 2004V. S. Filinov Abstract The internal energy and equation of state of dense hydrogen are investigated by direct path integral Monte Carlo method simulations which are further improved in comparison to our previous results. Data for four isotherms , T = 10, 000K, 30, 000K, 50, 000K, and 100, 000K , are presented. For T = 10, 000K it is shown that the internal energy is lowered due to droplet formation for densities of the order 1023cm,3 giving direct support for the existence of a plasma phase transition in megabar hydrogen. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Hydrogen- and carbon-related defects in heavily carbon-doped GaAs induced degradation under minority-carrier injectionELECTRONICS & COMMUNICATIONS IN JAPAN, Issue 5 2010Hiroshi Fushimi Abstract GaAs/AlGaAs heterojunction bipolar transistors (HBTs) have attracted much attention because of their high-speed performance. However, long-term operation seriously degrades the device characteristics: the current gain decreases and the low-bias-leakage current increases. This degradation has long been an issue in GaAs-based devices operated under minority-carrier injection, such as laser diodes. The cause of degradation is thought to lie in the carbon-doped base, but this is not yet certain. In this paper the degradation of HBTs is described, especially that of GaAs/AlGaAs HBTs with a heavily carbon-doped base layer. Two types of device degradation are found, namely, hydrogen-related degradation and carbon-related degradation. The mechanisms governing the degradation are discussed in the framework of the recombination-enhanced defect reaction (REDR) and charge state effect (CSE). © 2010 Wiley Periodicals, Inc. Electron Comm Jpn, 93(5): 33,41, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecj.10208 [source] Hydrogen peroxide-induced oxidative stress responses in Desulfovibrio vulgaris HildenboroughENVIRONMENTAL MICROBIOLOGY, Issue 10 2010Aifen Zhou Summary To understand how sulphate-reducing bacteria respond to oxidative stresses, the responses of Desulfovibrio vulgaris Hildenborough to H2O2 -induced stresses were investigated with transcriptomic, proteomic and genetic approaches. H2O2 and induced chemical species (e.g. polysulfide, ROS) and redox potential shift increased the expressions of the genes involved in detoxification, thioredoxin-dependent reduction system, protein and DNA repair, and decreased those involved in sulfate reduction, lactate oxidation and protein synthesis. A gene coexpression network analysis revealed complicated network interactions among differentially expressed genes, and suggested possible importance of several hypothetical genes in H2O2 stress. Also, most of the genes in PerR and Fur regulons were highly induced, and the abundance of a Fur regulon protein increased. Mutant analysis suggested that PerR and Fur are functionally overlapped in response to stresses induced by H2O2 and reaction products, and the upregulation of thioredoxin-dependent reduction genes was independent of PerR or Fur. It appears that induction of those stress response genes could contribute to the increased resistance of deletion mutants to H2O2 -induced stresses. In addition, a conceptual cellular model of D. vulgaris responses to H2O2 stress was constructed to illustrate that this bacterium may employ a complicated molecular mechanism to defend against the H2O2 -induced stresses. [source] Hydrogen ,leakage' during methanogenesis from methanol and methylamine: implications for anaerobic carbon degradation pathways in aquatic sedimentsENVIRONMENTAL MICROBIOLOGY, Issue 4 2007Niko Finke Summary The effect of variations in H2 concentrations on methanogenesis from the non-competitive substrates methanol and methylamine (used by methanogens but not by sulfate reducers) was investigated in methanogenic marine sediments. Imposed variations in sulfate concentration and temperature were used to drive systematic variations in pore water H2 concentrations. Specifically, increasing sulfate concentrations and decreasing temperatures both resulted in decreasing H2 concentrations. The ratio of CO2 and CH4 produced from 14C-labelled methylamine and methanol showed a direct correlation with the H2 concentration, independent of the treatment, with lower H2 concentrations resulting in a shift towards CO2. We conclude that this correlation is driven by production of H2 by methylotrophic methanogens, followed by loss to the environment with a magnitude dependent on the extracellular H2 concentrations maintained by hydrogenotrophic methanogens (in the case of the temperature experiment) or sulfate reducers (in the case of the sulfate experiment). Under sulfate-free conditions, the loss of reducing power as H2 flux out of the cell represents a loss of energy for the methylotrophic methanogens while, in the presence of sulfate, it results in a favourable free energy yield. Thus, hydrogen leakage might conceivably be beneficial for methanogens in marine sediments dominated by sulfate reduction. In low-sulfate systems such as methanogenic marine or freshwater sediments it is clearly detrimental , an adverse consequence of possessing a hydrogenase that is subject to externally imposed control by pore water H2 concentrations. H2 leakage in methanogens may explain the apparent exclusion of acetoclastic methanogenesis in sediments dominated by sulfate reduction. [source] Perchlorate reduction by a novel chemolithoautotrophic, hydrogen-oxidizing bacteriumENVIRONMENTAL MICROBIOLOGY, Issue 10 2002Husen Zhang Summary Water treatment technologies are needed that can remove perchlorate from drinking water without introducing organic chemicals that stimulate bacterial growth in water distribution systems. Hydrogen is an ideal energy source for bacterial degradation of perchlorate as it leaves no organic residue and is sparingly soluble. We describe here the isolation of a perchlorate-respiring, hydrogen-oxidizing bacterium (Dechloromonas sp. strain HZ) that grows with carbon dioxide as sole carbon source. Strain HZ is a Gram-negative, rod-shaped facultative anaerobe that was isolated from a gas-phase anaerobic packed-bed biofilm reactor treating perchlorate-contaminated groundwater. The ability of strain HZ to grow autotrophically with carbon dioxide as the sole carbon source was confirmed by demonstrating that biomass carbon (100.9%) was derived from CO2. Chemolithotrophic growth with hydrogen was coupled with complete reduction of perchlorate (10 mM) to chloride with a maximum doubling time of 8.9 h. Strain HZ also grew using acetate as the electron donor and chlorate, nitrate, or oxygen (but not sulphate) as an electron acceptor. Phylogenetic analysis of the 16S rRNA sequence placed strain HZ in the genus Dechloromonas within the , subgroup of the Proteobacteria. The study of this and other novel perchlorate-reducing bacteria may lead to new, safe technologies for removing perchlorate and other chemical pollutants from drinking water. [source] Borrowing Hydrogen: Indirect "Wittig" Olefination for the Formation of C,C Bonds from AlcoholsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 19 2006Phillip J. Black Abstract The successful development of an indirect three-step domino sequence for the formation of C,C bonds from alcohol substrates is described. An iridium-catalysed dehydrogenation of alcohol 1 affords the intermediate aldehyde 2. The desired C,C bond can then be formed by a facile Wittig olefination, yielding the intermediate alkene 3. In the final step the alkene is hydrogenated to afford the indirect Wittig product, the alkane 4. The key to this process is the concept of borrowing hydrogen; hydrogen removed in the initial dehydrogenation step is simply borrowed by the iridium catalyst. Functioning as a hydrogen reservoir, the catalyst facilitates C,C bond formation before subsequently returning the borrowed hydrogen in the final step. Herein we present full details of our examination into both the substrate and reaction scope and the limitations of the catalytic cycle. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Effect of Hydrogen on Fatigue Strength of High-Strength Steels in the VHCF Regime,ADVANCED ENGINEERING MATERIALS, Issue 7 2009Yongde Li Diffusible hydrogen or non-diffusible hydrogen can decrease the fatigue strength of high-strength steels. The hydrogen influence factor f(C) describes the hydrogen damage level of fatigue strength. Fatigue strength decreases with increasing non-diffusible hydrogen content in the range 1 ppm,<,Ci,<,3.0,ppm. Fatigue strength decreases significantly with increasing diffusible hydrogen content in the range 1 ppm,<,Cr,<,3.0,ppm, but shows almost no obvious change in the range 3.0 ppm,<,Cr,<,10.0,ppm. [source] Hydrogen Production via Autothermal Reforming of Diesel FuelFUEL CELLS, Issue 3 2004J. Pasel Abstract Hydrogen, for the operation of a polymer electrolyte fuel cell, can be produced by means of autothermal reforming of liquid hydrocarbons. Experiments, especially with ATR 4, which produces a molar hydrogen stream equivalent to an electrical power in the fuel cell of 3,kW, showed that the process should be preferably run in the temperature range between 700,° and 850,°. This ensures complete hydrocarbon conversion and avoids the formation of considerable amounts of methane and organic compounds in the product water. Experiments with commercial diesel showed promising results but insufficient long-term stability. Experiments concerning the ignition of the catalytic reaction inside the reformer proved that within 60,s after the addition of water and hydrocarbons the reformer reached 95% of its maximum molar hydrogen flow. Measurements, with respect to reformer start-up, showed that it takes approximately 7,min. to heat up the monolith to a temperature of 340,° using an external heating device. Modelling is performed, aimed at the modification of the mixing chamber of ATR Type 5, which will help to amend the homogeneous blending of diesel fuel with air and water in the mixing chamber. [source] A Review of Mathematical Models for Hydrogen and Direct Methanol Polymer Electrolyte Membrane Fuel CellsFUEL CELLS, Issue 1-2 2004K.Z. Yao Abstract This paper presents a review of the mathematical modeling of two types of polymer electrolyte membrane fuel cells: hydrogen fuel cells and direct methanol fuel cells. Models of single cells are described as well as models of entire fuel cell stacks. Methods for obtaining model parameters are briefly summarized, as well as the numerical techniques used to solve the model equations. Effective models have been developed to describe the fundamental electrochemical and transport phenomena occurring in the diffusion layers, catalyst layers, and membrane. More research is required to develop models that are validated using experimental data, and models that can account for complex two-phase flows of liquids and gases. [source] Hydrogen for the Mobility of the Future Results of GM/Opel's Well-to-Wheel Studies in North America and EuropeFUEL CELLS, Issue 3 2003U. Winter Abstract General Motors conducted two well-to-wheel studies for fundamental clarification on the question of which is the cleanest and most environmentally sustainable source of energy for the mobility of the future. In both studies the complete energy chains were analyzed from fuel production using primary energy to the actual consumption of the fuel in the car, i.e. from the well up to the wheels of the vehicle (well to wheel). The aim of the studies was to evaluate total energy consumption on the one hand and, on the other, the total greenhouse gas emissions arising between the production of a fuel and its final use to power an automobile. The results of the studies clearly show that fuel cell vehicles can greatly reduce greenhouse gas emissions from passenger cars or, if they run on hydrogen from renewable energy sources, they can eliminate them entirely. Regenerative fuels, however, will be more expensive than current products. With the fuel cell, because of its superior efficiency (35 , 45% less energy consumption well to wheel), it will be possible to keep individual mobility affordable in the future. [source] Phototrophic Fe(II) oxidation in an atmosphere of H2: implications for Archean banded iron formationsGEOBIOLOGY, Issue 1 2009L. R. CROAL ABSTRACT The effect of hydrogen on the rate of phototrophic Fe(II) oxidation by two species of purple bacteria was measured at two different bicarbonate concentrations. Hydrogen slowed Fe(II) oxidation to varying degrees depending on the bicarbonate concentration, but even the slowest rate of Fe(II) oxidation remained on the same order of magnitude as that estimated to have been necessary to deposit the Hamersley banded iron formations. Given the hydrogen and bicarbonate concentrations inferred for the Archean, our data suggest that Fe(II) phototrophy could have been a viable process at this time. [source] Niches of the pre-photosynthetic biosphere and geologic preservation of Earth's earliest ecologyGEOBIOLOGY, Issue 2 2007NORMAN H. SLEEP ABSTRACT The tree of terrestrial life probably roots in non-photosynthetic microbes. Chemoautotrophs were the first primary producers, and the globally dominant niches in terms of primary productivity were determined by availability of carbon dioxide and hydrogen for methanogenesis and sulfite reduction. Methanogen niches were most abundant where CO2 -rich ocean water flowed through serpentinite. Black smoker vents from basalt supplied comparable amount of H2. Hydrogen from arc volcanoes supported a significant methanogenic niche at the Earth's surface. SO2 from arc volcanoes reacted with organic matter and hydrogen, providing a significant surface niche. Methane ascended to the upper atmosphere where photolysis produced C-rich haze and CO, and H escaped into space. The CO and C-rich haze supported secondary surface niches. None of these ecologies were bountiful; less than 1% of the CO2 vented by ridge axes, arcs, and metamorphism became organic matter before it was buried in carbonate. In contrast, a photosynthetic biosphere leaves copious amounts of organic carbon, locally concentrated in sediments. Black shales are a classic geologic biosignature for photosynthesis that can survive subduction and high-grade metamorphism. [source] Is There a ZnO Face Stable to Atomic Hydrogen?ADVANCED MATERIALS, Issue 17 2009Giovanni Bruno The interaction of atomic hydrogen with ZnO depends on ZnO polarity. O-polar (000,1) ZnO is stable to atomic hydrogen; Zn-polar (0001) ZnO is partially attacked by atomic hydrogen, affording a self-inhibiting reaction that enriches the surface in metallic Zn; nonpolar (11,20) ZnO is completely etched by atomic hydrogen; and the nonpolar (10,10) ZnO is roughened during interaction with atomic hydrogen. [source] Achieving High Density of Adsorbed Hydrogen in Microporous Metal Organic Frameworks,ADVANCED MATERIALS, Issue 22 2005Y. Lee Two microporous metal organic framework structures are shown to possess hydrogen uptake capacities reaching 1.74 and 1.98,wt.-% at 77,K (1, 2, see Figure). These give the highest adsorbed H2 density reported thus far for metal-organic-based porous materials. The estimated pore volumes are 0.33 and 0.38,cm3,g,1 for 1 and 2. [source] An experimental investigation on manifold-injected hydrogen as a dual fuel for diesel engine system with different injection durationINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 15 2009N. Saravanan Abstract Stringent emission norms and rapid depletion of petroleum resources have resulted in a continuous effort to search for alternative fuels. Hydrogen is one of the best alternatives for conventional fuels. Hydrogen has both the benefits and limitation to be used as a fuel in an automotive engine system. In the present investigation, hydrogen was injected into the intake manifold by using a hydrogen gas injector and diesel was introduced in the conventional, mode which also acts as an ignition source for hydrogen combustion. The flow rate of hydrogen was set at 5.5,l,min,1 at all the load conditions. The injection timing was kept constant at top dead center (TDC) and injection duration was adjusted to find the optimized injection condition. Experiments were conducted on a single cylinder, four stroke, water-cooled, direct injection diesel engine coupled to an electrical generator. At 75% load the maximum brake thermal efficiency for hydrogen operation at injection timing of TDC and with injection duration of 30°CA is 25.66% compared with 21.59% for diesel. The oxides of nitrogen (NOX) emission are 21.7,g,kWh,1 for hydrogen compared with diesel of 17.9,g,k,Wh,1. Smoke emissions reduced to 1 Bosch smoke number (BSN) in hydrogen compared with diesel of 2.2 BSN. Hydrogen operation in the dual fuel mode with diesel exhibits a better performance and reduction in emissions compared with diesel in the entire load spectra. Copyright © 2009 John Wiley & Sons, Ltd. [source] Hydrogen as burner fuel: modelling of hydrogen,hydrocarbon composite fuel combustion and NOx formation in a small burnerINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 11 2005Mustafa Ilbas Abstract The objective of this work is to investigate numerically the turbulent non-premixed hydrogen (H2) and hydrogen,hydrocarbon flames in a small burner. Numerical studies using Fluent code were carried out for air-staged and non-staged cases. The effects of fuel composition from pure hydrogen to natural gas (100%H2, 70%H2+30%CH4, 10%H2+90%CH4, and 100%CH4) were also investigated. The predictions are validated and compared against the experimental results previously obtained and results from the literature. Turbulent diffusion flames are investigated numerically using a finite volume method for the solution of the conservation equations and reaction equations governing the problem. Although, three different turbulence models were tested, the standard k,, model was used for the modelling of the turbulence phenomena in the burner. The temperature and major pollutant concentrations (CO and NOx) distributions are in good agreement with the existing experimental results. Air staging causes rich and lean combustion regions thus lower NOx emissions through the combustor exit. Blending hydrogen with methane causes considerable reduction in temperature levels and thus NO emissions. Increasing the mixture ratio from stoichiometric to leaner mixtures also decreases the temperature and thus NO emissions. Hydrogen may be considered a good alternative fuel for burners, as its use reduces the emission of pollutants, and as it is a renewable synthetic fuel. Copyright © 2005 John Wiley & Sons, Ltd. [source] Palladium-Catalyzed Transformation of Renewable Oils into Diesel ComponentsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 11-12 2010Junxing Han Abstract A size-controlled palladium nanoparticle catalyst prepared by adsorption of colloidal palladium nanoparticles on barium sulfate is efficient and highly selective in transforming vegetable oils into diesel-like fuel. Preliminary kinetic investigations using model compounds indicated that decarboxylation of aliphatic esters on palladium in a hydrogen-rich atmosphere showed a zero-order rate. Hydrogen temperature-programmed desorption measurements revealed that the high-temperature desorption of hydrogen species might be the rate-determining step. [source] Hydrogen,potassium ATPase inhibitors induce relaxation on rabbit prostatic strips in vitroINTERNATIONAL JOURNAL OF UROLOGY, Issue 11 2002Ihsan Bagcivan Summary Background : To determine the relaxant effect of omeprazole and lansaprazole, hydrogen,potassium (H+,K+) ATPase inhibitors, on rabbit prostatic tissue in vitro. Methods : Male New Zealand white rabbits were sacrificed and their prostatic tissues were removed. The prostatic stromal strips were mounted in organ baths and relaxation responses were obtained in precontracted tissues with phenylephrine, carbachol and potassium chloride (KCl). Relaxation responses were controlled in the presence of various antagonists to explain the mechanism for relaxation exerted by omeprazole and lansaprazole. Results : Omeprazole and lansaprazole caused similar relaxation responses in the prostatic strips precontracted with phenylephrine, carbachol and KCl. The addition of prostaglandin synthase inhibitor indomethacin, nitric oxide synthase inhibitor L-NAME, potassium channel blockers, glibenclamide and tetraethylammonium into the organ baths did not change the relaxations induced by omeprazole and lansaprazole in vitro. Conclusion : Omeprazole and lansaprazole cause a relaxation in prostatic stromal tissue precontracted with phenyephrine, carbachol and KC1 in vitro. This relaxant effect is independent of H+,K+ ATPase inhibition. Additionally, cyclooxygenase and nitric oxide pathways do not contribute to this relaxant effect. Further studies are required to determine whether these drugs may have a beneficial effect in the non-operative treatment of benign prostatic hyperplasia. [source] Silica Supported Sodium Hydrogen Sulfate and Amberlyst-15: Two Efficient Heterogeneous Catalysts for Facile Synthesis of Bis- and Tris(1H -indol-3-yl)methanes from Indoles and Carbonyl Compounds[1]ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 5 2003Chimmani Ramesh Abstract Bis- and tris(1H -indol-3-yl)methanes are synthesized in high yields by an electrophilic substitution reaction of indoles with carbonyl compounds under mild reaction conditions using two efficient heterogeneous catalysts, silica supported sodium hydrogen sulfate (NaHSO4,SiO2) and amberlyst-15. The second catalyst can be reused. [source] The effect of toluidine blue on the survival, dormancy and outer membrane porin proteins (OmpC and OmpF) of Salmonella typhimurium LT2 in seawaterJOURNAL OF APPLIED MICROBIOLOGY, Issue 6 2002R. Ozkanca Aims: To study the relationship between changes in the composition of the outer membrane proteins and the survival of Salmonella typhimurium LT2 in filtered autoclaved seawater containing Toluidine Blue (TB) dye as a photosensitizer. Methods and Results: In samples exposed to TB and excited by artificial visible light, the total viable (TVC) and respiring cell counts (RCC) showed that, although the TVC declined to an undetectable level in 6·5 h, the RCC showed that some cells were still capable of respiration. The porin protein composition changed gradually with OmpC and OmpF becoming undetectable by sodium dodecyl sulphate-polyacrylamide gel electrophoresis after 8 h of incubation. Hydrogen peroxide-pretreated cells survived longer compared with the control. Conclusions: Oxidative pretreatment of Salm. typhimurium protects cells from some of the effects of sunlight in the presence of photosensitizers. The changes in porin proteins may play a role in this protection. Significance and Impact of the Study: The study shows that the survival of bacteria under conditions of stress is the result of a linked series of reactions. [source] | ||||||||||||||||||||||||||||||||||||||||||||||||||||