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Showing papers on "Oxygen published in 1979"



Journal ArticleDOI
TL;DR: In this paper, the authors investigated the interaction of tin oxide surface with oxygen, water vapor, and hydrogen using temperature-programmed desorption (TPD) chromatograms of oxygen.

736 citations


Journal ArticleDOI
TL;DR: Suspensions of cultured C 1300 neuroblastoma cells, sarcoma 180 ascites tumor cells, and Tetrahymena pyriformis cells provide direct evidence that in intact cells mitochondrial oxidative phosphorylation is oxygen dependent throughout the physiological range of oxygen tension.

362 citations


Journal ArticleDOI
TL;DR: In this paper, the authors used the experimental data to calculate the rate of sulphate formation in water droplets under atmospheric conditions for each of the three oxidants, i.e., ozone, ozone and hydrogen peroxide.

330 citations


Journal ArticleDOI
TL;DR: Experimental evidence is presented indicating that ascorbate is a ‘02 scavenger, and it is suggested that the inhibition of methylene blue-catalyzed photoinactivation of Escherichia coli ribosomes was mediated via the scavenging of ‘ 02 by asCorbate.

225 citations


Journal ArticleDOI
TL;DR: In this article, the interaction of O2 and N2O in the low pressure range with a Cu(111) surface and of CO with adsorbed oxygen have been studied with ellipsometry, Auger electron spectroscopy and LEED.

203 citations



Journal ArticleDOI
TL;DR: A mathematical model was developed to take into account diffusion through an unstirred solvent layer which increases in thickness with time which can account quantitatively both for the dependence of the apparent rate of uptake on O2 concentration and for the shape of the observed time courses.

195 citations


Journal ArticleDOI
TL;DR: The photo-activity of TiO2 (anatase P. 25) samples with a "fully hydroxylated surface" was studied in the presence of oxygen as discussed by the authors, where photo-adsorption of oxygen was observed in the early stages of u.v. illumination reducing the pressure to < 0.1 N m −2.
Abstract: The photo-activity of TiO2(anatase P. 25) samples with a “fully hydroxylated surface” was studied in the presence of oxygen. Photo-adsorption of oxygen was observed in the early stages of u.v. illumination reducing the pressure to < 0.1 N m–2. After this fast adsorption, slow photo-desorption of oxygen was detected continuing for several hours. Thermal removal of water and hydroxyl groups reduced photo-adsorption and the process became diffusion controlled. Rehydration restored fast photo-adsorption and first order kinetics. Photo-desorption of water accompanied photo-adsorption of oxygen on these “fully hydrated surfaces”. A mechanism involving the formation of OH· radicals and their reaction to give H2O2, which decomposes leading to oxygen photo-desorption, is proposed to explain these facts.

178 citations


Journal ArticleDOI
TL;DR: In this article, the authors measured the activation energy for ordering of oxygen atoms in a disordered state at 100 K and orders irreversibly into an apparent (2 × 2) surface structure upon heating to T⩾ 150 K.

176 citations


Journal ArticleDOI
01 Jun 1979-Blood
TL;DR: Experiments with the cell-free O2- -forming system suggested that this decline in respiratory burst activity at low pH was due to inefficient activation of the O2-- -forming enzyme under acidic conditions.

Journal ArticleDOI
TL;DR: In this article, a photochemical model of the early terrestrial atmosphere is used to find oxygen profiles as a function of the hydrogen and carbon monoxide outgassing rates from volcanoes and the rate of oxidation of the earth's crust.
Abstract: A photochemical model of the early terrestrial atmosphere is used to find oxygen profiles as a function of the hydrogen and carbon monoxide outgassing rates from volcanoes and the rate of oxidation of the earth's crust. Steady state solutions for the amount of O2 in the atmosphere are possible only when the combined loss rate from all three processes can balance the production of oxygen from photodissociation of H2O, followed by escape of hydrogen to space. If limiting flux controls the escape rate, then the production rate of oxygen atoms depends linearly upon the water vapor mixing ratio at the tropopause. Evidence is presented which indicates that the hydrogen outgassing alone was sufficient to overwhelm the production of oxygen, leading to ground level O2 mixing ratios of the order of 10−12 times the present atmospheric level (PAL) or below. The O2 mixing ratio increases rapidly with altitude up to a peak of 10−5 PAL at 60 km owing to the presence of CO2. Present-day concentrations of N2, CO2, and H2O are assumed in the calculation. The effect of possible temperature variations upon the H2O content is discussed.

Journal ArticleDOI
TL;DR: In this article, the mechanism of thermal oxidation of silicon in dry oxygen was studied using 18O as the tracer, and the results suggest that the oxide grows mainly through long-range migration of oxygen, favoring models based on the transport of molecular oxygen.
Abstract: The mechanism of thermal oxidation of silicon in dry oxygen was studied using 18O as the tracer. SiO2 layers first grown in natural oxygen (1300–3000 A) were further grown in highly 18O‐enriched oxygen for 8.5 h at 930 °C. 18O profiling was carried out using the 629‐keV narrow resonance in the nuclear reaction 18O(p,α) 15N. The resulting SiO2 films consist of two 18O‐rich layers, 7% near the SiO2 surface and 93% near the Si‐SiO2 interface, while the bulk 18O concentration is very low. The results suggest that the oxide grows mainly through long‐range migration of oxygen, favoring models based on the transport of molecular oxygen.

Journal ArticleDOI
TL;DR: Results indicate a singlet oxygen-mediated process that generates upon irradiation with near ultraviolet light reactive oxygen species on which the in vitro nematicidal activity depends.

Journal ArticleDOI
TL;DR: An extremely sensitive near-infrared spectrophotometer that uses a thermoelectrically cooled lead sulfide detector, optimized optics, and a boxcar integrator as a data processor is reported.
Abstract: The direct observation of dye-photosensitized 1268-nm emission of the 1Δg → 3Σg transition of molecular oxygen in liquid solution at room temperature is reported. Singlet oxygen was photosensitized by UV excitation of perfluorobenzophenone in fluorocarbon solvent, by 3,4-benzpyrene and hematoporphyrin in carbon tetrachloride, and by methylene blue in water. Also reported is the development of an extremely sensitive near-infrared spectrophotometer that uses a thermoelectrically cooled lead sulfide detector, optimized optics, and a boxcar integrator as a data processor.

Journal ArticleDOI
TL;DR: Using the resting lamb as a model, the mechanisms that are called into play during this period to maintain oxygen delivery are studied, finding that at rest cardiac output varies as a result of the changing need for oxygen.
Abstract: After birth a decrease in hemoglobin concentration occurs while high metabolic demands are imposed on the infant by the extrauterine environment. Using the resting lamb as a model, we studied the mechanisms that are called into play during this period to maintain oxygen delivery. Measurements were made of oxygen consumption, arterial and mixed venous blood oxygen contents, cardiac output, hemoglobin concentration, percent fetal hemoglobin, 2,3-diphosphoglycerate, and hemoglobin oxygen affinity during the first two postnatal months. There was a rapid decrease in hemoglobin concentration after birth and concomitant decrease in hemoglobin oxygen affinity, changes similar to those described in humans. Cardiac output and oxygen consumption were both very high immediately after birth and declined in parallel, so that arteriovenous oxygen content difference was constant. Thus at rest cardiac output varies as a result of the changing need for oxygen. This relationship is independent of hemoglobin concentration or oxygen affinity within the normal range. If, however, oxygen demands were increased, oxygen delivery might be compromised by a limited ability to increase oxygen extraction during the immediate newborn period or when hemoglobin concentration is lowest.

Journal ArticleDOI
TL;DR: The multicell spheroid in vitro tumor model was used to study the effects of diffusion limitations of metabolites on the development of necrosis in a tumor-like environment and it was found that an unknown mechanism controls the formationmore » of Necrosis when the oxygen diffusion distance is less than approximately 80 ..mu..m.
Abstract: The multicell spheroid in vitro tumor model was used to study the effects of diffusion limitations of metabolites on the development of necrosis in a tumor-like environment. Chinese hamster V79-171b cells were grown in suspension as multicellular spheroids in different oxygen or glucose concentrations to diameters where they developed central necrosis surrounded by an outer rim of viable cells. The range of oxygen concentrations used in the gas phase was 1 to 20.3%, in equilibrium with complete nutrient medium. For each oxygen concentration the thickness of the rim of viable cells was determined from measurements of histological sections. The square of the thickness of the viable rims of spheroids grown at different oxygen concentrations between 5 and 20.3% increased linearly with the theoretically derived oxygen diffusion distance, showing that the oxygen diffusion distance is a main factor controlling, either directly or indirectly, the development of necrosis in this concentration range. The data were interpreted as meaning spheroids grown at more than 5% O/sub 2/ contain a very small proportion of cells which were severely hypoxic or anoxic. The viable rim thickness was relatively less affected during growth at less than 5% oxygen, implying that an unknown mechanism controls the formationmore » of necrosis when the oxygen diffusion distance is less than approximately 80 ..mu..m. Although alterations in the glucose concentration had some effect on viable rim thickness at these low oxygen concentrations, the effect was much less than expected if glucose alone were responsible for controlling viability in this outer region.« less

Journal ArticleDOI
TL;DR: In this article, the effects of preoxidation on catalytic rates and selectivity were found to be sensitive to the structure of the platinum surface, kink sites playing a particularly active role in the enhancement of dehydrogenation and hydrogenation activity by strongly bound oxygen.

Journal ArticleDOI
TL;DR: In this article, the changes in the ellipsometric angles Δ and ψ per oxygen atom upon adsorption and removal of oxygen depend on the coverage θ, the temperature and on the azimuth of the plane of incidence of the light beam.

Journal ArticleDOI
TL;DR: In this paper, it was found that linear Ag+3 clusters are formed upon activation, the ends of which constitute chemisorption sites for hydrogen and oxygen, while one molecule of carbon monoxide was chemisorcised per Ag ion available in the supercage.
Abstract: Carbon monoxide, oxygen and hydrogen were found to be chemisorbed on dehydrated AgA zeolites. This was investigated in detail using volumetric sorption and temperature programmed desorption techniques. Also i.r. and mass spectrometry were used to characterize the solid and the desorbed molecules.It was found that as a result of an auto-reductive process, colour centres are created upon degassing of the zeolite. These centres sorb hydrogen and oxygen dissociatively, while one molecule of carbon monoxide was chemisorbed per Ag ion available in the supercage. It is proposed that linear Ag+3 clusters are formed upon activation, the ends of which constitute chemisorption sites for hydrogen and oxygen.

Journal ArticleDOI
TL;DR: In this article, simultaneous measurements of the nightglow profiles of the O2(b1g+−X3Σg−) A-band, the atomic oxygen green line and the OH (8−3) Meinel band are presented.

Journal ArticleDOI
TL;DR: In situ X-ray photoelectron spectroscopic observation of a silver foil at 473 K exposed to oxygen at pressures up to 0.5 torr has identified three species, characterised by oxygen 1s binding energies of 528.3, 530.3 and 532.5 eV as discussed by the authors.


Journal ArticleDOI
TL;DR: In this paper, the massive Mn oxides were synthesized and their anodic characteristics were investigated in aqueous solutions, and it was suggested that the oxidation process of the electrode surface is a common rate-determining step in both reactions on massive Mn oxide electrodes.

Journal ArticleDOI
TL;DR: Olympic exercise increased oxygen uptake 4-fold, oxygen supply fell below demand during exercise, and considerable anaerobic metabolism resulted, as evidenced by a 9-fold increase in haemolymph lactate concentration.
Abstract: Scaphognathite and heart-pumping frequencies, ventilation volume, cardiac output, oxygen uptake and oxygen transport by haemolymph have been studied in unrestrained Dungeness crabs ( Cancer magister ) before, immediately after, and during recovery from 20 min of enforced exhausting activity. Exercise increased oxygen uptake 4-fold. This increase was achieved by more than 2-fold elevation of both ventilation volume and cardiac output and by greater participation of haemocyanin in oxygen delivery. The elevated ventilation volume resulted entirely from an increase in scaphognathite pumping frequency, while the rise in cardiac output resulted largely from increase in stroke volume. Prior to exercise haemocyanin accounts for less than 50% of the oxygen delivered to the tissues. Following exercise this increases to over 80%, the additional oxygen release being mediated by a depression of prebranchial oxygen tension and a substantial Bohr effect resulting from build up of lactate ion in the haemolymph and subsequent fall in pH. These changes allowed % oxygen extraction from branchial water to be maintained at 28% despite a 2-fold increase in ventilation volume, and allowed an increase in %. oxygen extraction by the tissues. Despite these changes oxygen supply fell below demand during exercise, and considerable anaerobic metabolism resulted, as evidenced by a 9-fold increase in haemolymph lactate concentration. The resulting oxygen debt required 8–24 h for repayment. Aerobic metabolic scope, and mechanisms of increasing oxygen uptake and transport in this crab are compared with those of a range of fish species.

Journal ArticleDOI
TL;DR: In this paper, the vibrational energies of the adsorbed layer with electron energy loss spectroscopy were measured by measuring vibrational energy of an upright CO with a single metal-carbon bond.
Abstract: The adsorption of CO and O2 on the Ru(001) surface and the interaction between CO and chemisorbed oxygen on this surface have been studied by measuring the vibrational energies of the adsorbed layer with electron energy loss spectroscopy. Adsorbed CO shows two vibrational energies that are assigned to the metal–carbon and carbon–oxygen stretching frequencies of an upright CO with a single metal–carbon bond. Oxygen adsorbed on Ru (001) has a single vibrational energy that can be attributed to a mode of atomic oxygen perpendicular to the surface. The variation of the frequency spectrum of CO with CO coverage and with the coverage of oxygen in coadsorption experiments is discussed in terms of direct interadsorbate interactions and indirect through‐bond interactions.

Journal ArticleDOI
01 Nov 1979-Nature
TL;DR: In this article, the authors reported the preparation and the oxygen evolution reaction (OER) electrocatalytic properties of iridium oxide films deposited by reactively sputtering iridium in a humidified oxygen discharge.
Abstract: Oxygen evolution reactions1 are critical to the development of efficient energy conversion and energy storage devices For example, power losses at the oxygen electrodes of commercial water electrolysers2 and H2˙−O2 fuel cells limit their efficiencies to values well below those expected theoretically The power loss of these devices is ≳15% even at low current densities, and much higher in practical operating conditions We report here the preparation and the oxygen evolution reaction (OER) electrocatalytic properties of iridium oxide films deposited by reactively sputtering iridium in a humidified oxygen discharge We find that these sputtered iridium oxide films (SIROFs) have catalytic properties far superior to the best known catalysts for oxygen evolution in acidic aqueous electrolytes at room temperature

Journal ArticleDOI
TL;DR: In this article, the reaction of the ordered-O layer with H2(g) to produce H2O takes place rapidly above 275 K in the 10−8−10−6 Torr range and can be followed quantitatively by observation of the(1, 12) LEED beam intensity.

Journal ArticleDOI
TL;DR: The concept of inappropriate oxygen demand relative to oxygen supply would appear to be central to the patient with coronary artery disease whose oxygen delivery may be compromised, but also to patients with chronic hemodynamic overload (for example, aortic stenosis) whose hypertrophied ventricle is now failing.
Abstract: The utilization of energy by the working heart has been studied extensively over the years. Because the conversion of chemical energy to mechanical work by the heart is highly dependent on oxygen, the oxygen required and the oxygen available for this conversion are considered to form the conceptual framework of the metabolic demand and supply of the heart, respectively. The oxygen requirement of the myocardium, as assessed by the rate of oxygen consumed (MVO 2 ), is a function of the mechanical components of ventricular contraction and include: (1) the force developed and sustained by the muscular wall during its contraction; (2) the rate of force development; and (3) the frequency of generating force in the wall per unit time. The oxygen available to the mitochondria, which satisfies this requirement, is primarily determined by the oxygen delivered per unit of time (that is, coronary flow) and the oxygen extracted. Collectively, the response in flow and oxygen extraction represent the metabolic reserve of the heart. Normally, during increments in work, coronary vascular resistance decreases permitting an increment in flow; oxygen extraction (65 to 70 percent) changes little under these circumstances. However, when the response in coronary vascular resistance is limited or at its optimal value, further increments in oxygen requirements are accompanied by an increase in oxygen extraction to 80 to 85 percent; oxygen extraction may exceed 90 percent in the presence of a reduced oxygen-carrying capacity. Stressed beyond the limits of its metabolic reserve (that is, minimum coronary vascular resistance and maximal oxygen extraction) the oxygen available to the heart becomes insufficient and, hence, an aerobic limit is reached. As a consequence, anaerobic metabolism commences, ventricular performance declines and pulsus alternans appear. The concept of inappropriate oxygen demand relative to oxygen supply would appear to be central not only to the patient with coronary artery disease whose oxygen delivery may be compromised, but also to patients with chronic hemodynamic overload (for example, aortic stenosis) whose hypertrophied ventricle is now failing. Moreover, the implications of an aerobic limit may also explain the limits of hypertrophy.