Showing papers on "Oxygen published in 1988"
TL;DR: Transient increases in neural activity cause a tissue uptake of glucose in excess of that consumed by oxidative metabolism, acutely consume much less energy than previously believed, and regulate local blood flow for purposes other than oxidative metabolism.
Abstract: Brain glucose uptake, oxygen metabolism, and blood flow in humans were measured with positron emission tomography, and a resting-state molar ratio of oxygen to glucose consumption of 4.1:1 was obtained. Physiological neural activity, however, increased glucose uptake and blood flow much more (51 and 50 percent, respectively) than oxygen consumption (5 percent) and produced a molar ratio for the increases of 0.4:1. Transient increases in neural activity cause a tissue uptake of glucose in excess of that consumed by oxidative metabolism, acutely consume much less energy than previously believed, and regulate local blood flow for purposes other than oxidative metabolism.
1,725 citations
TL;DR: During stepwise restoration of oxygen flow, the phosphorescence images showed marked heterogeneous patterns of tissue reoxygenation, which indicated that there were regional inequalities in oxygen delivery.
Abstract: The imaging of phosphorescence provides a method for monitoring oxygen distribution within the vascular system of intact tissues. Isolated rat lives were perfused through the portal vein with media containing palladium coproporphyrin, which phosphoresced and was used to image the liver at various perfusion rates. Because oxygen is a powerful quenching agent for phosphors, the transition from well-perfused liver to anoxia (no flow of oxygen) resulted in large increases of phosphorescence. During stepwise restoration of oxygen flow, the phosphorescence images showed marked heterogeneous patterns of tissue reoxygenation, which indicated that there were regional inequalities in oxygen delivery.
524 citations
TL;DR: Salin et al. as discussed by the authors reviewed the production of oxyradicals and intermediates by chloroplasts as well as the means of protection are discussed in this review and concluded that these highly reactive intermediates pose the threat of toxicity unless neutralized by scavenger substrates or enzymes.
Abstract: Salin, M. L. 1988. Toxic oxygen species and protective systems of the chloroplast. -Physiol. Plant. 72: 681–689.
As a consequence of living in an environment enriched in oxygen, which they themselves at least partially generate, photosynthetic organisms are exposed to large fluxes of oxyradicals and reactive oxygen species. Among these are superoxide, hydrogen peroxide, hydroxyl radical and singlet oxygen. These highly reactive intermediates pose the threat of toxicity unless neutralized by scavenger substrates or enzymes. The production of oxyradicals and intermediates by chloroplasts as well as the means of protection are discussed in this review.
455 citations
TL;DR: The oxygen dependence of mitochondrial oxidative phosphorylation is such that mitochondria could function in their proposed role of tissue oxygen sensors for regulation of such diverse functions as local blood flow and electrical activity in the carotid body.
383 citations
TL;DR: In this paper, the ionic transference number was nearly unity between 600 and 900°C for the samarium oxide-doped ceria-samarium oxide system with a fluorite structure.
Abstract: Ionic conduction of oxygen in the ceria-samarium oxide system was investigated as a function of temperature, partial pressure of oxygen and the oxide composition, together with its crystal structure, density and defect structure. The ionic conductivity of (CeO2)1−x(SmO1.5)x was the highest in ZrO2-, ThO2- and CeO2-based oxide systems. The system CeO2-SmO1.5 consisted of the solid solution with a fluorite structure atx<50 at.%. The ionic transference number was nearly unity between 600 and 900°C. With an increase in Sm2O3 content, the ionic conductivity gradually decreased due to a decrease in mobility of oxygen ions. The samarium oxide-doped ceria was less reducible than pure and alkaline earth oxide-doped ceria.
332 citations
TL;DR: In this paper, the oxygen semipermeability of CoO3-based perovskite-type oxides was investigated by partial substitution of A site and B site cations, Ba and Cu being the most effective substituents, respectively.
Abstract: Oxygen semipermeability of LnCoO3-based perovskite-type oxides changed drastically by the partial substitution of A site and B site cations, Ba and Cu being the most effective substituents, respectively. Host rare earth cations (Ln) also affected the oxygen semipermeability, which increased with a decrease in ionic radius of Ln.
296 citations
01 Jan 1988
TL;DR: In this paper, Dioxygen complexes with transition metals have been used for the extraction of DIOxygen from biological Oxygen Carriers and for the transport of Diooxygen to transition metals.
Abstract: Opening Remarks- Dioxygen Complexes with Transition Metals- Bonding of Dioxygen to Transition Metals- Oxygen Binding by the Metalloproteins Hemerythrin, Hemocyanin, and Hemoglobin- Metal Oxo Complexes and Oxygen Activation- Kinetics of Formation of Biological Oxygen Carriers- Synthetic Dioxygen Carriers for Dioxygen Transport- Formation and Degradation of Cobalt Dioxygen Complexes- Reversible Complexes for the Recovery of Dioxygen- Summary - Dioxygen Complexes with Transition Metals- Oxygen Activation by Transition Metals- Summary - Oxygen Activation by Transition Metals- The Chemistry and Activation of Dioxygen Species (02, 02-, and H00H) in Biology- Oxygen Activation by Neutrophils- Mechanisms of Dioxygen Activation in Metal-Containing Monooxygenases: Enzymes and Model Systems- Radical Cation Pathways for Selective Catalytic Oxidation by Molecular Oxygen- Vanadium Catalyzed Autoxidation of Hydrogen Sulfide- Copper Catalyzed Oxidative Carbonylation of Methanol to Dimethyl Carbonate- Dependence of Reaction Pathways and Product Distribution on the Oxidation State of Palladium Catalysts for the Reactions of Olefinic and Aromatic Substrates with Molecular Oxygen- Oxygen Activation and Oxidation Reactions on Metal Surfaces- Methane Oxidation at Metal Oxide Surfaces- The Activation of Oxygen by Metal Phosphorus Oxides - The Vanadium Phosphorus Oxide Catalyst- The Oxidation of Organic Compounds by Metal Complexes in Zeolites- Abstracts of Posters- Kinetics and Mechanisms of Degradation of Binuclear Cobalt Dioxygen Complexes- Methane Activation over Lanthanide Oxides- Dioxygen Affinities of Some Synthetic Cobalt Schiff Base Complexes- Temporal Analysis of Products (TAP): A Unique Catalyst Evaluation System with Sub-Millisecond Time Resolution- Dioxygen Insertion into Metal-Carbon Bonds of Metalloporphyrins: Formation and Characterization of Alkylperoxy Metalloporphyrins- Iron Porphyrin Catalyzed Air Oxidation of Aldehydes and Alkenes- Oxidative Dimerization of Methane over Sodium-Promoted Calcium Oxides- Synthesis and Metal Ion Affinities of a Binucleating Polyamine: Reversible Formation of a Cobalt Dioxygen Complex- Potentiometric Determination of Stabilities of Cobalt(II) Complexes of Polyamine Schiff Bases and Their Dioxygen Adducts- Catalysis of Cobalt Schiff Base Complexes for the Oxygenation of Olefins Mechanisms for the Ketonization Reaction- Selective Oxidation of Saturated Hydrocarbons by the Gif and Gif-Orsay Systems- The Formation, Characterization, and Reactivity of the Oxene Adduct of Tetrakis(2,6-dichlorophenyl)porphinato-Iron(III) Perchlorate in Acetonitrile- Preparation and Characterization of a Binuclear Iron(III)- Hydroxo-y-hydroperoxy Complex [(Ph3PO)4(HO)FeIII(HOOH)FeIII(OH)(OPPh3)4](C1O4)4- Autoxidation of FeII(dihydroxyphenanthroline)3- Phosphine-Ruthenium(II)-Aquo Redox Chemistry: The Aerobic Catalytic Oxidation of Cyclohexene- The Oxidation of Organic Substrates by Molecular Oxygen Catalysis by Ru(III) and Ru(III)-EDTA- Oxygenation of Tryptophane Catalyzed by Polyamine Cobalt Dioxygen Complexes- Resonance Raman Spectroscopy of the Fe(IV)=0 Group in Peroxidase Intermediates- Reaction of Dioxygen with Synthetic Copper(I) Compounds of Biological Relevance- Thorough Elucidation of Oxygenation- and Oxidation-Mechanisms of Iron(II) Porphyrin on the Basis of a New Hypothesis for an Electron-Transfer Pathway- IUCCP Description
294 citations
TL;DR: In this article, the crystal structure of the 84K superconductor Bi 2 Sr 2 CaCu 2 O 8+δ is described, as is the stabilization of 110K superconductivity via partial Pb/Bi substitution with long time annealing.
Abstract: Ambient temperature measurements of the crystallographic cell parameters for oxygen deficient Ba 2 YCu 3 O 7−δ prepared by gettered annealing indicate the presence of microscopic differences in the oxygen configuration at fixed δ dependent on annealing temperature. The loss of superconductivity with increasing oxygen deficiency is shown to be due to a step-like increase in length of the plane copper-apical oxygen bond, and not to the orthorhombic to tetragonal transition. The crystal structure of the 84K superconductor Bi 2 Sr 2 CaCu 2 O 8+δ is described, as is the stabilization of 110K superconductivity via partial Pb/Bi substitution with long time annealing.
224 citations
TL;DR: In this article, rate constants and mechanisms for the gas phase reactions of atomic oxygen O(3P) with organic compounds having only saturated C-C bonds are compiled and critically evaluated, and error limits are assigned to all recommended values.
Abstract: Rate constants and mechanisms for the gas phase reactions of atomic oxygen O(3P) with organic compounds having only saturated C–C bonds are compiled and critically evaluated. Data are given for the alkanes, cycloalkanes, haloalkanes, oxygen and nitrogen containing organic compounds, and free radicals. In addition, data are given for some miscellaneous compounds containing boron, silicon, germane, and mercury. From a critical examination of the data, recommended values for rate constants are given over specified temperature intervals or at specified temperatures. Error limits are assigned to all recommended values.
219 citations
TL;DR: Hydrogen peroxide steady state levels of 5 micromolar were determined in soybean (Glycine max) embryonic axes incubated for 2 hours and in axes pretreated with aminotriazole or cyanide, where these levels were 50 and 1micromolar, respectively.
Abstract: Hydrogen peroxide steady state levels of 5 micromolar were determined in soybean (Glycine max) embryonic axes incubated for 2 hours and in axes pretreated with aminotriazole or cyanide, where these levels were 50 and 1 micromolar, respectively. The activities of catalase (105 picomoles H(2)O(2) per minute per axis), peroxidase (10-44 picomoles H(2)O(2) per minute per axis), glutathione peroxidase (3 picomoles H(2)O(2) per minute per axis) and superoxide dismutase (3.5 units per axis), were also determined. Catalase seems to be the most important H(2)O(2) consuming enzyme at the physiological concentration of H(2)O(2). A short treatment with aminotriazole, while substantially increasing H(2)O(2) level, did not affect the growth of the axes. The production of superoxide anion by the mitochondria isolated from soybean axes was measured from the superoxide dismutase-sensitive rate of adrenochrome formation in the presence of NADH or succinate as substrate and amounted to 1.3 and 0.8 nanomole O(2) (-) per minute per milligram protein, respectively. According to the stoichiometry of O(2) (-) and H(2)O(2) dismutation reactions, it is apparent that about 0.9 to 1.5% of the total oxygen uptake proceeds through the formation of the free intermediates of the partial reduction of oxygen.
183 citations
TL;DR: In this article, two alloys, Ti-6Al-2V and Ti-2Al-16V, were simulated with oxygen concentrations from 0.07 to 0.65 wt pct.
Abstract: Two alloys, Ti-6Al-2V and Ti-2Al-16V, simulating the alpha and beta phases of Ti-6A1-4V, respectively, were prepared with oxygen concentrations from 0.07 to 0.65 wt pct (0.20 to 1.83 at. pct). Their microstructure, deformation behavior, and strength were investigated with X-ray diffraction, microscopy, and mechanical tests to determine the effects of oxygen concentration and heat treatment. In both alloys the hardness increases in identical fashion with the square root of oxygen concentration. The alloys' strengths also depend on heat treatment, but in different ways. Whereas the alpha alloy is non-age-hardenable, the beta alloy's strength can be doubled by aging. The hardening effect of oxygen is generally unaffected by heat treatment, except for the alloys with the highest oxygen concentrations. During aging of the alpha a small amount of Ti3Al can form, and slight age-hardening occurs. The ductility of the alpha alloy is little affected by aging. On the other hand, oxygen causes a change from good ductility at low oxygen concentration (0.07 wt pct) to total brittleness at 0.65 wt pct oxygen, independent of heat treatment. In the beta alloy there are complex phase transformations depending on heat treatment. Its deformation behavior varies from very ductile in solutiontreated and quenched (STQ) condition to totally brittle in aged conditions. The aging embrittlement appears to be caused by alpha and some omega precipitation. Decoration of the beta grain boundaries with precipitates accounts for the intergranular brittle fracture. Oxygen, on the other hand, is not an embrittler, although it reduces the ductility of the beta alloy.
TL;DR: It is concluded that some prevalent biomolecules may afford protection either by preventing singlet oxygen production (urate, L‐ergothioneine) or by intercepting singinglet oxygen once formed (L‐carnosine).
Abstract: — We have compared the relative abilities of some putative biological protectors to block oxidation of 2,5-bis(hydroxymethyl)furan (BHMF)† in illuminated solutions containing the photosensitizer rose bengal and in the separated-surface-sensitizer (S-S-S) system involving pure singlet oxygen (1ΔAgO2). While L-histidine is a well-known quencher of singlet oxygen, free L-histidine is not commonly found in high concentrations in nature. L-Carnosine (β-alanyl-L-histidine), however, is present in the striated muscles of many organisms, most notably mammals, in concentrations up to 40 mM. At neutral pH, carnosine quenched singlet oxygen more effectively than did equimolar histidine, both in solubilized sensitizer studies and in the S-S-S system. In the pure singlet oxygen system, 1 mM carnosine reduced the rate of BHMF oxidation as effectively as 3 mM histidine alone, or a mixture of 3 mM histidine and 3 mMβ-alanine. The fungal product L-ergothioneine (2-thiol-L.-histidine betaine) and its synthetic analogue, 2-thiolhistidine, at 1 mM blocked photosensitized BHMF oxidation using solubilized rose bengal, as did urate at 0.5 mM. All three compounds failed to reduce the rate of BHMF oxidation by singlet oxygen in the S-S-S system, however. Homocarnosine (-γ-aminobutyryl-L-histidine) gave levels of protection against BHMF oxidation identical to histidine, but is present in the central nervous system only at micromolar concentrations. Neither 1 mM imidazole nor 5 mM urea reduced BHMF oxidation in either system. We conclude that some prevalent biomolecules may afford protection either by preventing singlet oxygen production (urate, L-ergothioneine) or by intercepting singlet oxygen once formed (L-carnosine). Such protective devices may be of importance in natural systems.
TL;DR: The isomer product distribution was interpreted in terms of a dual singlet oxygen and radical mechanism, the radical contribution increasing with sensitiser in the order ER = MB < HP ≪ RF, but also showing some dependence on substrate unsaturation.
Abstract: — The triplet state characteristics (spectrum, lifetime and quantum yield) for four dye sensi tisers [methylene blue (MB), erythrosin (ER), haematoporphyrin (HP) and riboflavin (RF)] were determined in methanol by laser flash photolysis and singlet oxygen yields (0.60 to 0.48) from time-resolved measurements of the 1270 nm near infrared emission. The reaction of singlet oxygen with four long chain unsaturated phenyl esters [oleate (18: 1), linoleate (18: 2), linolenate (18: 3) and arachidonate (20: 4)] was followed quantitatively using the singlet oxygen luminescence technique and also, after continuous420–700 nm irradiation, by HPLC and other analysis of the isomeric product monohydroperoxides. The overall quantum yield of photooxidation (∼10-2) was shown to be consistent with the observed singlet oxygen quenching constants(2–12 times 104 dm3 mol-1 s-1) for the four esters studied and the singlet oxygen lifetime in methanol (τ∼ 9 μs). The isomer product distribution was interpreted in terms of a dual singlet oxygen and radical mechanism, the radical contribution increasing with sensitiser in the order ER = MB < HP ≪ RF, but also showing some dependence on substrate unsaturation. Evidence is presented for singlet oxygen quenching by MB and RF (kO= 1.6 and 6.0 times 107 dm3 mol-1 s-1) and for the accelerated photobleaching of the dye sensitisers in the presence of the unsaturated esters.
TL;DR: Direct estimates have been gained for the rate constants of the singlet oxygen reactions with a group of sulphur compounds in the pD range 5 to 13, which might be considered as possible candidates for protection against skin photosensitivity side effects associated with the photodynamic therapy of solid tumours and as observed in the disease erythropoietic protoporphyria.
Abstract: — From time-resolved measurements of the decay of singlet molecular oxygen phosphorescence at 1270 nm in D2O, direct estimates have been gained for the rate constants of the singlet oxygen reactions with a group of sulphur compounds in the pD range 5 to 13. In the case of most of the thiols, the results are consistent with singlet oxygen reacting exclusively with the thiolate anions. At the normal physiological pH 7, the apparent rate constants (in units of M-1 s-1) were 8.9 times 106 (cysteine), 2.5 times 106 (N-acetyl cysteine), 2.9 times 106 (glutathione), 3.0 times 105 (2-mercaptoethanol), 2.3 times 107 (ergothioneine) and 2.7 times 106 (2-mercaptopropionyl glycine). For methionine the rate constant, 1.4 times 107, was independent of pD in the range studied. These sulphur compounds, in particular N-acetyl cysteine and ergothioneine, or related compounds, might be considered as possible candidates for protection against skin photosensitivity side effects associated with the photodynamic therapy of solid tumours and as observed in the disease erythropoietic protoporphyria.
TL;DR: In this paper, electrical conductivity measurements were made on Gd 2 (Zr 0.3 Ti 0.7 ) 2 O 7 as a function of temperature, oxygen fugacity and aliovalent dopant concentration using Ca and Ta.
TL;DR: In this paper, a variety of analytical tools have been combined to show that bulk superconducting La2CuO4+δ has a La to Cu ratio of 2.00 (± 0.02) and an oxygen stoichiometry of 4.13 (±0.1).
Abstract: A variety of analytical tools have been combined to show that bulk superconducting La2CuO4+δ has a La to Cu ratio of 2.00 (±0.02) and an oxygen stoichiometry of 4.13 (±0.1). The combination of these analytical results and magnetization data with a model leads us to suggest that the excess charged oxygen is introduced as O-2.
TL;DR: In this article, the order of redox potentials was determined and a reaction sequence including enzymatic oxidation, coupled oxidations and the formation of caftaric acid and catechin copolymers was proposed.
Abstract: Oxidation of caftaric acid, catechin, epicatechin, epicatechin gallate, procyanidins B1 to B4 and 2-S-glutathionyl caftaric acid (GRP) in grape must-like model solutions containing grape polyphenoloxidase was monitored by HPLC. Caftaric acid was degraded faster than catechin, epicatechin, and epicatechin gallate. Procyanidins and GRP were oxidized very slowly when incubated alone with the enzyme. Oxidation of two-component mixtures in the presence of polyphenoloxidase was studied. Caftaric acid induced coupled oxidation of other compounds. The order of redox potentials was determined. Oxidation of catechin-caftaric acid mixtures was studied, and the oxygen consumption measured. A reaction sequence including enzymatic oxidation, coupled oxidations and the formation of caftaric acid and catechin copolymers was proposed.
TL;DR: The shape of the N(2)O profile after the addition of acetylene showed that denitrification (denitrifying activity) was detectable in all anoxic layers of the biofilm.
Abstract: The construction of a microsensor which can be used to measure O2 and N2O simultaneously is described The microsensor exhibited a linear response to both O2 and N2O, and the response to N2O was independent of the O2 concentration and vice versa The N2O detection limit of a microsensor with a tip diameter of 20 μm was around 1 μmol liter−1 The signals for O2 and N2O were affected by hydrogen sulfide, but other interfering agents were not observed in the biofilms and sediments analyzed Microprofiles of O2 and N2O were measured in a biofilm which was exposed to acetylene to block the N2O reductase activity of denitrifying bacteria O2 penetrated about 05 mm into the biofilm and was not affected by acetylene, but the N2O concentration at 14 mm depth increased from 32 to 411 μmol liter−1 after the addition of the inhibitor The shape of the N2O profile after the addition of acetylene showed that denitrification (denitrifying activity) was detectable in all anoxic layers of the biofilm
TL;DR: Heterogeneities in red blood cell velocity, lineal density, SO2, and QO2, assessed by their coefficients of variation, were significantly greater in venular capillaries, and the effect of these heterogeneities under conditions of increased flow and high oxygen consumption was evaluated.
TL;DR: A survey of diffusion data of interstitial oxygen and of the substitutional elements aluminum and vanadium for alpha and beta titanium is presented in this paper, which is based on a survey of literature.
Abstract: A survey of diffusion data of interstitial oxygen and of the substitutional elements aluminum and vanadium is presented for alpha and beta titanium. It is based on a survey of literature. Oxygen is an important interstitial element in titanium alloys. Oxygen’s large chemical affinity to titanium is indicated by Ti—O bond energy of 2.12 eV,1 comparable to the Ti—Ti bond energy of 2.56 eV.2 Oxygen is difficult to eliminate completely from titanium, and commercial titanium alloys usually contain from 0.10 to 0.20 wt pct oxygen. Oxygen significantly affects the mechanical properties of titanium alloys1,3 and is sometimes used as an alloying element. The effects of oxygen on phase transformation ,4,5,6 Youngs modulus,7,8 hardness,9,10 fracture toughness,11 and other mechanical properties12 have been amply documented. Aluminum and vanadium are the most frequently used substitutional alloying elements. Aluminum is an alpha stabilizer and vanadium is a beta stabilizer.
TL;DR: Evidence of cerebral anaerobic glycolysis associated with inadequate oxygen delivery to the brain consistent with either inhibition of cerebral oxidative metabolism or the microcirculatory obstruction envisaged in the "mechanical" hypothesis for cerebral malaria is provided.
TL;DR: The sensitivity of Tc to oxygen sorption and the Ca to Sr ratio has been studied for the homologous series Bi2 in this article, where single phase n=2 samples were equilibrated under a fixed partial pressure of oxygen at temperatures between 300 and 850°C and quenched in liquid nitrogen.
Abstract: The sensitivity of Tc to oxygen sorption and the Ca to Sr ratio has been studied for the homologous series Bi2.1(CaχSr1−χ)n+1CunO2n+4+δ for n=1, 2 and 3. The n=0 and n=∞ members have been produced as single phase samples but are found to be semiconducting. While single phase n=2 material has been prepared, the n=1 member always displays a small n=2 contribution to the X-ray diffraction pattern. n=3 is only found in multiphase samples. Single phase superconducting samples were equilibrated under a fixed partial pressure of oxygen at temperatures between 300 and 850°C and quenched in liquid nitrogen. It is shown that Tc can be controlled in a reversible and systematic way by varying the oxygen partial pressure and the annealing temperature and consequently the oxygen stoichiometry. The site energy per oxygen sorbed for n=2 is 3.24 eV, only a little less than that for YBa2Cu3O7. However, the volume change on sorption is ten times smaller than that for YBa2Cu3O7, and is manifested as a changing c-axis with the a-axis invariant. This can be interpreted as implying that oxygen sorption occurs within the Bi-O layers. Tc is found to be maximised for a Ca to Sr ratio of 1 to 2 for both n=1 and 2. Thermal expansion data for n=2 material is also reported to illustrate that oxygen sorption does effect the physical properties of these materials.
TL;DR: It was concluded that acclimatization did not increase O2 delivery but rather maintained delivery via increased arterial oxygenation and decreased leg blood flow, which suggested matching of O2 Delivery to tissue O2 demands, with vasoconstriction possibly contributing to the decreased flow.
Abstract: Residence at high altitude could be accompanied by adaptations that alter the mechanisms of O2 delivery to exercising muscle. Seven sea level resident males, aged 22 +/- 1 yr, performed moderate to...
TL;DR: In this article, the average copper charge on the Cu sites in the high temperature superconductor Y1Ba2Cu3O7−x was determined as function of the oxygen vacancy concentration.
Abstract: From XPS core level spectroscopy the average copper charge on the Cu sites in the high temperature superconductor Y1Ba2Cu3O7−x
is determined as function of the oxygen vacancy concentrationx. Analysis of these data leads to the suggestion that there are holes on the oxygen sites in the basal plane of the crystal structure. The probability for holes on these oxygen ions is rather constant for 0≦x≦0.3 with a value of 0.64 and decreases to zero forx=0.5. The dependence of the superconducting transition temperature on the hole concentration is discussed. An energy level diagram for Cu2+ and Cu3+ in YBa2Cu3O7−x
is constructed.
TL;DR: In this paper, the ground electronic state of O(3P) atoms with sulfur containing compounds was evaluated and conservative uncertainty limits were assigned to them where possible, where possible the recommended values of the rate parameters have been assessed.
Abstract: Chemical kinetic data for reactions of O(3P) atoms with sulfur containing compounds are compiled and critically evaluated. Specifically, the reactions considered include the interactions of the ground electronic state of oxygen atoms, O(3P), with S2, SF2, SF5, SOF, S2O, SO, SO2, SO3, SH, H2S, D2S, H2SO4, CS, CS2, COS, CH3SH, C2H5SH, C4H9SH, C5H11SH, CH3SCH3, cy‐CH2SCH2, cy‐CHCHSCHCH, CH3SSCH3, SCF2, SCCl2, and cy‐CF2SCF2S. With one exception, the liquid phase reaction O(3P)+H2SO4→products, all the data considered were for gas phase reactions. Where possible, ‘‘Recommended’’ values of the rate parameters have been assessed and conservative uncertainty limits assigned to them.
TL;DR: In this article, the superconducting properties of YBa 2 Cu 3 O 7−x have been shown to depend markedly on the overall oxygen stoichiometry and on the ordering of oxygen vacancies on the available sites.
Abstract: The superconducting properties of YBa 2 Cu 3 O 7−x have been shown to depend markedly on the overall oxygen stoichiometry and on the ordering of oxygen vacancies on the available sites. YBa 2 Cu 3 O 7−x has been studied in situ by high-temperature neutron powder diffraction in controlled oxygen atmospheres in order to learn the structural properties of the system in thermodynamic equilibrium. Additionally, metastable, oxygen-deficient samples produced by quenching into liquid nitrogen from high temperature and various oxygen partial pressures have been studied at room temperature or low temperature in order to correlate the structural and superconducting properties. Such experiments have shown that a systematic relationship exists between the superconducting transition temperature, T c , the number of oxygen vacancies, and the degree of oxygen vacancy ordering. This brief paper reviews our work in these areas.