Showing papers on "Oxygen published in 1968"
541 citations
467 citations
TL;DR: In this paper, the oxygen isotope behavior in the sulfate-water system is studied. But the relationship between sulfate ion exchange rates and water is not discussed. But it is shown that sulfate reducing bacteria preferentially metabolize oxygen-16 relative to dissolved sulfate by about 4.6% in both pure and natural cultures.
Abstract: Fundamental data on oxygen isotope behavior in the sulfate-water system are given. Oxygen exchange rates between sulfate ions and water are very slow and show a marked pH dependence. Of the order of 10/sup +3/ to 10/sup +5/ years are required to closely approach isotopic equilibrium at earth surface conditions. Oxygen isotope fractionation experiments yielded the following relationships: Ln alpha = 3878/(t+2) -0.0034 anhydrite water (and) Ln alpha = 3251/(t+2) -0.0056 dissolved sulfate water. During progressive evaporation of saturated CaSO/sub 4/ solution the gypsum formed tends to concentrate oxygen-18 relative to dissolved sulfate by 2%. Sulfate reducing bacteria preferentially metabolize oxygen-16 by about 4.6% in both pure and natural cultures. Oxidation of sulfide to sulfate in natural environments is a complex process making use of both water oxygen and molecular oxygen.
459 citations
TL;DR: The data strongly suggest that with anoxia, the observed rise in organic phosphate content of the red cell is responsible for increased availability of oxygen to tissues.
Abstract: The relationship between oxygen dissociation and 2,3-diphosphoglycerate (2,3-DPG) in the red cell has been studied in subjects moving from low to high altitude and vice versa. Within 24 hr following the change in altitude there was a change in hemoglobin affinity for oxygen; this modification therefore represents an important rapid adaptive mechanism to anoxia. A parallel change occurred in the organic phosphate content of the red cell. While this study does not provide direct evidence of a cause-effect relationship, the data strongly suggest that with anoxia, the observed rise in organic phosphate content of the red cell is responsible for increased availability of oxygen to tissues.
391 citations
TL;DR: In eight subjects exposed to hypoxia at high altitude the oxyhemoglobin dissociation curve was shifted to the right, the half saturation oxygen tension at pH 7.40 being changed from 26.7 to 30.2 mm Hg on the average, and the decreased affinity of hemoglobin for oxygen appeared within 12 hours after exposure to Hypoxia.
Abstract: In eight subjects exposed to hypoxia at high altitude the oxyhemoglobin dissociation curve was shifted to the right, the half saturation oxygen tension at pH 7.40 being changed from 26.7 to 30.2 mm Hg on the average. The decreased affinity of hemoglobin for oxygen appeared within 12 hours after exposure to hypoxia. The shift was confirmed in short exposure experiments using simulated high altitude in a low pressure chamber. At prolonged carbon monoxide exposure the expected shift of the oxygen dissociation curve to the left occurred, but no adaptive changes were found. The physiological implication of these differences are discussed. It is suggested that the rapid shift to the right at high altitude may be a physiological regulation.
344 citations
TL;DR: In Initiation of growth of nitrogen-fixing Azotobacter species was prevented by efficient aeration but proceeded normally with gentle aeration; addition of CO2 to the air did not relieve inhibition, suggesting two mechanisms exist in the cell to protect the oxygen-sensitive components of nitrogenase from oxygen.
Abstract: SUMMARY: Initiation of growth of nitrogen-fixing Azotobacter species was prevented by efficient aeration but proceeded normally with gentle aeration; addition of CO2 to the air did not relieve inhibition The ratio of oxygen solution rate to concentration of organisms determined whether growth would be inhibited or not Populations growing in media containing fixed nitrogen (NH+
4) showed no unusual sensitivity to oxygen though inhibition could be induced at a P02
value of 06 atm Nitrogen-limited continuous cultures fixed about twice as much N2/g carbon source utilized at 003 atm O2 than at the atmospheric value (02 atm); even at relatively high cell concentrations growth was inhibited at 06 atm O2 Carbon- and phosphate-limited continuous cultures showed even more sensitivity to oxygen when fixing nitrogen but none when growing with NH+
4; excessive oxygen was lethal to phosphate-limited populations These observations suggest that two mechanisms exist in the cell to protect the oxygen-sensitive components of nitrogenase from oxygen: augmented respiration to scavenge excess oxygen and a conformational state of nitrogenase that prevents damage by O2
254 citations
TL;DR: Oxygen consumption, blood flow, perfused capillary surface area, and vasomotor fiber control were quantitatively compared in “white” gastrocnemius and “red” soleus muscles of cats during rest and graded exercise.
199 citations
TL;DR: In this paper, the kinetics of exchange of oxygen-18 between enriched oxygen gas and 38 inorganic oxides and 1 oxy-acid salt has been examined in detail, and possible mechanisms for the two main reactions are discussed.
Abstract: The kinetics of exchange of oxygen-18 between enriched oxygen gas and 38 inorganic oxides and 1 oxy-acid salt has been examined in detail. Most of the exchange reactions occur by a dissociative atomic mechanism confined to the surface layer of oxygen ions. For these there is a strong compensation effect between A0 and E in the rate expression: E shows a systematic fall with increasing size of the unit-crystal cell and related crystal parameters: the plots separate the oxides into structure-dependent groups. The slow stage is the desorption of oxygen. The oxides PbO, PdO, AgO, and CuO exchange the surface layer by a molecular reaction which also occurs to an appreciable extent, together with the atomic mechanism, on a number of other oxides. Na2WO4, V2O5, MoO3, and WO3 exchange the whole of the bulk oxygen with the gas phase by a combination of both mechanisms. SiO2 and GeO2 are inactive. Possible mechanisms for the two main reactions are discussed.
144 citations
TL;DR: Transfer of material across the mud-water interface in lakes and ponds has an important influence on biological activity in both the aquatic and the mud environment, and the Mud environment can usually be described as anaerobic, except for the surface layer.
Abstract: Transfer of material across the mud-water interface in lakes and ponds has an important influence on biological activity in both the aquatic and the mud environment. Oxygen is one of the important components influencing biological activity in both media. The amount of oxygen in any micro-volume has an influence on total biological activity, the nature of the biological population and the products of biological activity. Thus, any description of an environment must include a description of the concentration of oxygen and oxygen transfer. In many aquatic media with a limited amount of suspended, decaying organic matter, or in shallow bodies of water, the oxygen content of the water is high enough that, biologically, the aquatic medium would be described as aerobic. The mixing action of wind and temperature gradients and production of oxygen by photosynthesis maintain a reasonable supply of oxygen in relation to consumption by organisms. However, in the porous (mud) medium, appreciable mixing and phbtosynthesis do not occur and diffusion of oxygen through the liquid phase of the mud is too slow to provide sufficient oxygen for more th'an a thin layer of the surface of the mud if biological activity is at all appreciable, and, as a consequence, the mud environment can usually be described as anaerobic, except for the surface layer. Characteristically, the surface, aerobic layer of the mud will contain little Fe" + and Mn+ +, and CO2 will be the principle end product of biological activity. However, only a few millimeteres away the anaerobic zone begins where high concentrations of Fe' + and Mn+ + and the various organic by-products of anaerobic respiration will be found. Thus, drastic chemical changes in the mud occur over a distance of a few millimetres. In some deep lakes with temperature stratification, consumption of oxygen by organisms in the water and in the mud together deplete the hypolimnion of oxygen. The mud then becomes anaerobic to the interface with the water and large amounts of Fe' +, Mn+ + and phosphate, among other ions, are released to the water. With turnover of the lake and mixing of the water, the lower part of the lake becomes oxygenated and oxidation of the mud surface proceeds until the oxygen in the water is again depleted. The quantity of a material transferred by diffusion phenomena per unit area per unit time is proportional to the diffusion coefficient (characteristic of the medium and the diffusing material) and the concentration gradient. In the mud near the water-mud interface, concentration gradients can be relatively large and hence diffusion of oxidants from
TL;DR: In this article, the authors used the probability of an encounter between a molecule of oxygen and a fluorescent molecule in its excited state, and the energy that would otherwise be emitted as fluorescence is transferred to the oxygen.
Abstract: THE energy acquired by matter when it absorbs electromagnetic radiation is normally converted to heat, but in some cases much of the energy may be re-emitted as fluorescence or phosphorescence. Fluorescence is often quenched (that is, its intensity is reduced) in the presence of oxygen. The degree of quenching depends on the probability of an encounter between a molecule of oxygen and a fluorescent molecule in its excited state, and the energy that would otherwise be emitted as fluorescence is transferred to the oxygen. This effect has been used as the basis of a portable instrument to measure the atmospheric oxygen tension (British Patent Application No. 46674/66). Various prototype devices have been constructed and tested.
TL;DR: It was concluded that both release and oxygen burst were dependent upon ATP supplied either from glycolysis or oxidative phosphorylation, and the burst in oxygen uptake seemed not to be linked to ordinary platelet respiration.
TL;DR: Results suggest a subtle, but potentially dangerous, form of oxygen toxicity in cats, which is interpreted in terms of inhibition of carbohydrate metabolism by oxygen and the positive effect of catecholamines on this function.
Abstract: The effect of oxygen on tracheal mucus flow was measured in young cats by a particle-transport technic. Any deviation from ambient oxygen tension in the inspired air, high or low, had an adverse effect on mucus flow; 100 per cent oxygen produced marked impairment. Basal mucus flow was improved, and the adverse oxygen effects were prevented and reversed by epinephrine compounds and adenosine triphosphate. These results, which are interpreted in terms of inhibition of carbohydrate metabolism by oxygen and the positive effect of catecholamines on this function, suggest a subtle, but potentially dangerous, form of oxygen toxicity.
TL;DR: In this paper, the relationship between organic matter and the oxygen minimum layer was studied in the southwest Atlantic and it was concluded that the concentration of oxygen and organic carbon is controlled by the mixing of opposing water masses, at depths in excess of several hundred meters.
TL;DR: The oxygen-transport function of stored blood seems to be related to the intracorpuscular ATP and 2,3-diphosphoglycerate levels.
Abstract: During storage of acid-citrate-dextrose-blood the oxygen affinity of the haemoglobin is increased; i.e. the oxygen dissociation curve is shifted to the left. In the meantime the red cell ATP and 2,3-diphospho-glycerate levels are decreased. In the present investigation it is shown that these changes are reversed by addition of inosine. Thus the oxygen-transport function of stored blood seems to be related to the intracorpuscular ATP and 2,3-diphosphoglycerate levels.
TL;DR: In this article, electrical conductivity and thermogravimetric measurements on single crystalline cobaltous oxide indicate that the electronic and atomic defect concentration is a function of the 1 4 power of the oxygen partial pressure over the temperature range of 900°-1200°C and 10°−10 −4 atm.
TL;DR: Patients with various conditions characterized by an impairment in the oxygen supply system to tissues respond with a diminished affinity of their blood for oxygen, associated with an increase in heme-heme interaction.
Abstract: Blood from patients with erythrocytosis secondary to arterial hypoxemia due either to congenital heart disease or to chronic obstructive pulmonary disease was shown to have a decreased affinity for oxygen; the average oxygen pressure required to produce 50% saturation of hemoglobin with oxygen was 29.8 mm Hg (average normal, 26.3 mm Hg). Such a displacement of the blood oxygen equilibrium curve promotes the release of oxygen from blood to the tissues. Studies were also performed upon blood from a man with complete erythrocyte aplasia who received all of his red cells by transfusion from presumably normal persons. With mild anemia (hematocrit, 28%), the affinity of his blood for oxygen was slightly diminished (an oxygen pressure of 27.0 mm Hg was required to produce 50% saturation of hemoglobin with oxygen). With severe anemia (hematocrit, 13.5%), however, his blood had a markedly decreased oxygen affinity (an oxygen pressure of 29.6 mm Hg was required to produce 50% saturation of hemoglobin with oxygen). We conclude that patients with various conditions characterized by an impairment in the oxygen supply system to tissues respond with a diminished affinity of their blood for oxygen. Although the mechanism which brings about this adaptation is not known, the displacement of the oxygen equilibrium curve is associated with an increase in heme-heme interaction. The decrease in blood oxygen affinity need not occur during erythropoiesis, but may be imposed upon mature circulating red cells.
TL;DR: An oxygen requirement of isolated intact chloroplasts reducing PGA and nitrate was indicated by lower reaction rates and faster decay of activity under nitrogen than under air.
Abstract: Oxygen was taken up by both intact and broken chloroplasts when catalase was posioned. In confirmation of other work we found that oxygen enters the electron transport chain of isolated chloroplasts by oxidizing the primary photoreductant of system I. In isolated intact chloroplasts this reaction proceeds in addition to oxygen evolution by PGA reduction. The reductant produced by photosystem II does not react with oxygen at a significant rate. In normal leaves oxygen depresses chlorophyll fluorescence. However, this depression does not take place in DCMU poisoned leaves or in a mutant having a nonfunctional photosystem II; furthermore, another mutant with a weakly functioning photosystem I gave only a very small fluorescence depression with oxygen. This shows that the site of interaction of oxygen is at the reducing end of the electron transport chain. This view is supported by the extent of the fluorescence depression in leaves as a function of oxygen concentration which is very similar to the oxygen dependence of oxygen uptake by isolated chloroplasts. An oxygen requirement of isolated intact chloroplasts reducing PGA and nitrate was indicated by lower reaction rates and faster decay of activity under nitrogen than under air.
TL;DR: In this paper, the reactive sputtering of tantalum in mixed argon/oxygen atmospheres at a total pressure of 3.0×10−4 torr was investigated by means of measurements on deposition and growth rates, density, electrical properties and electron diffraction.
Abstract: The reactive sputtering of tantalum in mixed argon/oxygen atmospheres at a total pressure of 3.0×10−4 torr has been investigated by means of measurements on deposition and growth rates, density, electrical properties and electron diffraction. The main controlling factor on all of the parameters was found to be the partial pressure of oxygen.
TL;DR: In this paper, the rate equation for the oxidation of ferrous ions by dissolved oxygen in aqueous solutions in the presence of such chelating agents as EDTA, DTPA, EDTAOH, EDTP, CyDTA and NTA was studied spectrophotometrically.
Abstract: The oxidation of ferrous ions by dissolved oxygen in aqueous solutions in the presence of such chelating agents as EDTA, DTPA, EDTAOH, EDTP, CyDTA and NTA was studied spectrophotometrically. The rate equation for the oxidation reaction is:d[Fe^III]/dt=4k_p[Fe^IIHZ][O_2]+4k_n[Fe^IIZ][O_2] where kp is the rate constant for the (1) reaction; kn, the rate constant for the (2) reaction; FeIIHZ, protonated chelate, and FeIIZ, the normal chelate.&Fe^IIHZ+O_2\xrightarrowk_pFe^IIIZ+HO_2 \labeleq1&Fe^IIZ+O_2\xrightarrowk_nFe^IIIZ+O_2^-\labeleq2The linear relationship between log k and log Rf shown by Eq. (3), was obtained from all the experimental results except for those on the EDTPA and CyDTA systems:logk=0.92+0.13logR_f\labeleq3In Eq. (3), k is 4kp and Rf is KFeIIIL⁄KFeIIHL, for the protonated chelate, while k is 4kn and Rf is KFeIIIL⁄KFeIIL for the normal chelate. In the cases of the DTPA and CyDTA systems, a deviation from the straight line was observed. This can be explained by steric hindrance of the oxygen ...
TL;DR: Catalase can be assayed very simply with the oxygen cathode, by measuring the initial rate of oxygen release from a solution of hydrogen peroxide or sodium perborate, because the substrate concentration is high enough, and the time short enough, to prevent decreasing rates during the reaction.
TL;DR: In this article, the adsorption of phenol, nitrobenzene, and sodium benzene sulfonate from aqueous solution on several different carbons, including a channel black and adsorbent carbons.
TL;DR: Ethylene was the most effective abscission accelerant examined, with decreasing activity shown by propene, carbon monoxide, acetylene, vinyl fluoride, 1-butene, and 1,3-butadiene.
Abstract: Ethylene was the most effective abscission accelerant examined, with decreasing activity shown by propene, carbon monoxide, acetylene, vinyl fluoride, 1-butene, and 1,3-butadiene. Carbon dioxide inhibited abscission, but its effect was overcome by ethylene. Oxygen was required for abscission as an electron acceptor for respiration and not as a potentiator or activator of the ethylene attachment site. The molecular requirements for abscission were similar to those shown by other workers for other biological processes under the influence of ethylene.
TL;DR: In this article, the quenching of singlet benzene by oxygen was discussed and attributed to triplet benzene with a rate constant of 5 × 10 −11 cm 3 mol −1 sec −1.
TL;DR: In this article, the magnetic properties of a series of discrete trinuclear transition-metal complexes derived from tetradentate Schiff bases have been investigated over the temperature range 80°-400°K.
Abstract: The magnetic properties of a series of discrete trinuclear transition‐metal complexes derived from tetradentate Schiff bases have been investigated over the temperature range 80°–400°K. The complexes contain the groupings of metals CuMCu where M is Cu(II), Ni(II), Co(II), Fe(II), and Mn(II), and the three metal atoms are linked by oxygen bridges. For each grouping of metals, the observed magnetic moments are subnormal, and decrease markedly with decreasing temperatures. These magnetic properties are explained in terms of antiferromagnetic interactions between the central metal atom M and the adjacent copper (II) atoms. The magnetic moments calculated on the basis of this model of discrete antiferromagnetism are found to be in good agreement with the experimental results. Mutual interactions between the terminal copper atoms apparently exist to only a small degree or not at all.
TL;DR: In this paper, the wettability of sapphire single crystals by liquid copper which contained oxygen added as cupric oxide was investigated using the sessile drop technique in vacuum at 1230°C.
Abstract: The wettability of sapphire single crystals by liquid copper which contained oxygen added as cupric oxide was investigated using the sessile drop technique in vacuum at 1230°C. Additions of cupric oxide to copper, varying from 1 to 72% of copper weight, resulted in rapid chemical reaction at the solid-liquid interface with a significant reduction of the contact angle, the final value being dependent on the oxygen in the system. In all cases the interfacial product was CuAlO2. A linear relation between the fourth power of the basal radius of the molten drop and the amount of oxygen present was observed. The initial stage of the reaction could be explained by the formation of a Cu2O layer at the interface, followed by reaction between Cu2O and Al2O3 to form CuAlO2.
TL;DR: Experimental evidence supports a hypothesis that oxygen deficiency may be a causal factor in the formation of chemical attractants for the ambrosia beetle Trypodendron lineatum (Olivier).
Abstract: Experimental evidence supports a hypothesis that oxygen deficiency may be a causal factor in the formation of chemical attractants for the ambrosia beetle Trypodendron lineatum (Olivier). Detectable attractancy can be induced by anaerobic conditions at 20 °C, imposed for 4 hours on fresh sapwood. Maximum attractancy develops within 24 hours of anaerobic processing. The hypothesis proposes that in a log or dying tree stagnation of the translocative and pneumatic systems leads to deficiency of oxygen at the active metabolic centers. The consequent change from oxidative to fermentative metabolism thus induces attractant formation.