Showing papers on "Oxygen published in 1983"

The Solubility of Oxygen and Ozone in Liquids

Abstract: This review covers the solubility of oxygen and ozone in liquids as a function of temperature and pressure. Solubility data for individual systems were critically evaluated and recommended or tentative values presented in many cases. The trend of solubilities in homologous series or related solvents is discussed. Liquids include water; seawater; aqueous salt solutions; mixed solvents; hydrocarbons; organic compounds containing oxygen, halogen, sulfur, nitrogen, or silicon; olive oil; and human blood. For ozone, only its solubility in water is presented. Key words: aqueous solutions; biological fluids; gas solubility; hydrocarbons; mixed solvents; organic solvents; oxygen; ozone; seawater; water.

Correction for the Presence of Intravascular Oxygen-15 in the Steady-State Technique for Measuring Regional Oxygen Extraction Ratio in the Brain: 1. Description of the Method:

Abstract: The oxygen-15 steady-state inhalation technique provides quantitative values of regional cerebral blood flow, fractional oxygen extraction, and oxygen utilisation. These last two, however, have been found to be higher than those reported using arteriovenous difference techniques. On theoretical grounds, this overestimation is due to the signal from nonextracted intravascular oxygen-15. In this paper, a method is presented to correct for this intravascular component utilising a measurement of regional cerebral blood volume. The statistical penalty imposed as a result of this correction is defined.

Assessment of chlorination by human neutrophils

Abstract: On phagocytosing a microorganism, the neutrophil zpolymor-phonuclear leukocyte, PMN) consumes oxygen at a sharply elevated rate1. The oxygen is used to kill the microorganism, presumably being used to produce a potent oxidizing agent or agents. Candidates for these bactericidal agents are singlet oxygen, hydroxyl radical and chlorinating agents (that is, species containing ‘active’ Cl in a formal +1 oxidation state: HOCl, Cl2, N-chloroamides, and so on)1–5. We now report a semiquantitative assay for PMN-generated active chlorine based on its trapping with 1,3,5-trimethoxybenzene (TMB). Using this assay, we have found that at least 28% of the oxygen consumed by stimulated normal human PMNs is converted to active chlorinating agents.

Oxygen Microelectrode That Is Insensitive to Medium Chemical Composition: Use in an Acid Microbial Mat Dominated by Cyanidium caldarium.

Abstract: A novel oxygen microelectrode with a tip diameter of 2 to 20 μm was constructed which could function satisfactorily under a variety of environmental conditions and in a variety of media, including human blood serum, citric acid at pH 2.5, moist air, and paraffin oil. Measurement of oxygen by this electrode does not require stirring of the medium. Electrodes could be made so that the 90% response time necessary to detect changes in oxygen concentration was less than 0.2 s, and response was linear with oxygen concentration. To demonstrate the performance of the electrode, oxygen and photosynthesis profiles of an acid microbial mat (pH 2.8) dominated by the eucaryotic alga Cyanidium caldarium were made. Photosynthetic rates as high as 95 mmol of O2 dm−3 h−1 were measured within the most active 0.1-mm layer, which was ca. 0.2 mm below the surface of the microbial mat. The total photosynthetic activity was 47 mmol of O2 m−2 h−1. Vertical profiles of photosynthesis at different light intensities showed that the microalgae within the mat were not photoinhibited at bright sunlight (2,090 μEinsteins m−2 s−1).

Carbon monoxide oxidation on the Pt(111) surface: Temperature programmed reaction of coadsorbed atomic oxygen and carbon monoxide

Abstract: Carbon dioxide formation from coadsorbed atomic oxygen and molecular carbon monoxide has been characterized using temperature programmed reaction spectroscopy over a wide range of initial oxygen and carbon monoxide coverages. The experiments were performed in an apparatus containing Auger electron spectroscopy, low energy electron diffraction, and a multiplexed mass spectrometer for the temperature programmed reaction experiments. A single reaction limited CO2 peak is observed in the 320–340 K temperature range over a wide range of initial atomic oxygen and molecular CO coverages, suggesting that a single reaction mechanism dominates. The activation energy for CO2 formation ranges from 166 kJ/mol (40 kcal/mol) for small surface concentrations of reactive adsorbed atomic oxygen and CO (0.4×1014/cm2) to 68 kJ/mol (17 kcal/mol) for larger surface concentrations of reactive adsorbed atomic oxygen and CO (2.5×1014/cm2). Low energy electron diffraction results indicate that adsorbed atomic oxygen forms islands ...

Method for operating a production well in an oxygen driven in-situ combustion oil recovery process

Abstract: A method for operating a production well during an oxygen driven in-situ combustion oil recovery process comprising continuously injecting an inert gas such as nitrogen or carbon dioxide into the bottom of the production well at a predetermined low injection rate, preferably 0.1 to 2 MSCF/day, and continuously monitoring the oxygen concentration of the produced effluent gas and the bottomhole temperature of the production well. In the event that the oxygen content of the effluent gas increases to a value within the range of 5 to 20 volume percent or the bottomhole temperature of the production well increases to a value within the range of 200° to 300° F., the injection rate of the inert gas into the bottom of the production well is increased to a maximum rate until the oxygen concentration of the effluent gas and the bottomhole temperature are reduced to a safe level.

Diffusivity of oxygen in silicon at the donor formation temperature

Abstract: We present data on oxygen diffusivity in silicon for the temperature range 270–400 °C. The diffusivity is determined from the recovery kinetics of a stress induced dichroism in the 9‐μm oxygen infrared absorption band. We combine our data for well dispersed oxygen (i.e., crystals heat treated at 1350 °C for 20 h), with Mikkelsen’s recent mass transport work at higher temperature to obtain the diffusivity, D=0.17 exp (−2.54/kT), for the range 330–1240 °C. We have also found that the oxygen atomic hopping times can be as much as 100 times faster in crystals that have not received the 1350 °C heat treatment.

Chemoautotrophic growth of a marine Beggiatoa in sulfide-gradient cultures

Abstract: A recently isolated strain of Beggiatoa, MS-81-6 (cf. alba), was tested for chemoautotrophic growth in semi-solid (0.2% agar) sulfide/oxygen gradient cultures. The organism grew in a horizontal layer, the distance from the air/medium interface depending on sulfide concentrations and changing with time. Optimal growth as a gradient organism was based on a preference for reduced oxygen concentrations and a limited sulfide tolerance in combination with gliding motility. In gradient cultures chemoautotrophic growth was demonstrated by the following criteria: (1) biomass yield (protein) increased with increasing sulfide concentration, and estimated molar growth yields agreed with those for other sulfide-grown chemoautotrophs; (2) approximately 90% of total cell carbon and protein carbon were fixed from carbon dioxide; (3) the CO2-fixing enzyme, ribulosebisphosphate carboxylase, was present in cell-free extracts at a level typical of chemoautotrophs; (4) acidification of the medium, apparently linked to utilization of internal So granules, accompanied the later phase of growth. The ability to grow on acetate in the absence of a source of reduced sulfur renders the organism facultatively chemoautotrophic.

Oxygen chemisorption and oxide formation on Si(111) and Si(100) surfaces

Abstract: We have used photoemission techniques with synchrotron radiation to study the adsorption of oxygen on the Si(111)‐(7×7) and Si(100)‐(2×1) surfaces at room temperature in the submonolayer and monolayer regimes. High resolution Si 2p core‐level spectra, valence‐band spectra, work‐function, and Fermi‐level pinning positions have been measured for exposures between 1 and 1000 L and after annealing at 700 °C. Four oxidation states have been detected for the silicon surface atoms with Si 2p core‐level shifts of 0.9, 1.9, 2.6, and 3.4 eV which are assigned to silicon atoms bonded to 1, 2, 3, and 4 oxygen atoms. Both (111) and (100) surfaces are characterized by about the same sticking coefficient, a simple adsorption process for 1‐L exposures, the quenching of the surface states after 15 L and a saturation of the amount of oxygen after 100 L. Significant differences exist in the initial bonding geometries for the (111) and (100) surfaces. After 15‐L exposure, oxygen atoms are incorporated below the Si (111)‐(7×7...

Interaction between light and chilling temperature on the inhibition of photosynthesis in chilling-sensitive plants†

Abstract: . Fully expanded leaves of 25°C grown Phaseolus vulgaris and six other species were exposed for 3 h to chilling temperatures at photon flux densities equivalent to full sunlight. In four of the species this treatment resulted in substantial inhibition of the subsequent quantum yield of CO2 uptake, indicating reduction of the photochemical efficiency of photosynthesis. The extent of inhibition was dependent on the photon flux density during chilling and no inhibition occurred when chilling occurred at a low photon flux density. No inhibition occurred at temperatures above 11.5°C, even in the presence of the equivalent of full sunlight. This interaction between chilling and light to cause inhibition of photosynthesis was promoted by the presence of oxygen at normal air partial pressures and was unaffected by the CO2 partial pressure present when chilling occurred in air. When chilling occurred at low O2 partial pressures, CO2 was effective in reducing the degree of inhibition. Apparently, when leaves of chilling-sensitive plants are exposed to chilling temperatures in air of normal composition then light is instrumental in inducing rapid damage to the photochemical efficiency of photosynthesis.

Evidence for oxygen-dependent and -independent leishmanicidal activity

Abstract: Human peripheral blood monocytes were cultivated for 1-30 d before assay for H2O2 release or challenge with Leishmania donovani promastigotes (LDP) or amastigotes (LDA). 1-d cells readily generated H2O2 in response to both phorbol myristate acetate triggering (1,013 +/- 58 nmol/mg protein . 90 min) and LDP ingestion, and killed 50% of LDP within 6 h, and 90% by 24 h. In contrast, the same cells released little H2O2 during LDA ingestion, killed no LDA at 6 h and less than 30% by 24 h, and supported intracellular LDA replication. Monocyte-derived macrophages (cells first cultivated for greater than or equal to 7 d) generated less than 125 nmol H2O2/mg . 90 min after phorbol myristate acetate triggering, killed neither LDP nor LDA, and permitted both forms to replicate. The addition of mitogen- or antigen-stimulated lymphokines, however, prevented the decline in monocyte oxidative capacity, enhanced macrophage H2O2 release by more than sixfold, and, in parallel, induced 1-d monocytes to kill LDA and cultivated macrophages to display both promastigocidal and amastigocidal activity. In comparison to 1-d monocytes and lymphokine-activated macrophages from normal donors, the same cells from patients with chronic granulomatous disease (CGD) or normal cells whose oxidative activity had been impaired by catalase pretreatment or glucose deprivation exerted considerably less or no antileishmanial activity during the early (6-24 h) postphagocytic period. By 48 h after infection, however, 1-d CGD monocytes and oxidatively impaired normal cells killed 40 and greater than 80% of LDP, respectively. Although a longer period of lymphokine stimulation was required and the resulting antileishmanial effects were not as rapid as with normal cells, activated CGD monocytes and macrophages also eventually achieved promastigocidal and amastigostatic activity. These results indicate that human mononuclear phagocytes utilize both oxygen-dependent and -independent mechanisms to achieve activity against ingested Leishmania, and also demonstrate (a) the differential susceptibilities of the two forms of L. donovani to intracellular killing, (b) the key role of oxygen intermediates in effective mononuclear phagocyte antimicrobial activity, (c) the capacity of lymphocyte products to enhance oxygen-dependent as well as -independent pathways, and (d) the vulnerability of the monocyte-derived macrophage to Leishmania infection in the absence of lymphokine stimulation.

Adrenergic regulation of haemoglobin oxygen affinity in rainbow trout red cells

Abstract: Adrenaline (initial concentration 5×10−6 M) caused an increase in haemoglobin oxygen affinity of rainbow trout red cells incubated in vitro in physiological saline. The increase was more pronounced at low than at high extracellular pH values. Adrenaline also induced an increase in intracellular pH, swelling of red cells and a metabolic decrease in cellular ATP concentration. The most important reason for increased oxygen affinity was the increase in intracellular pH resulting, to a great extent, from decreased concentration of impermeable polyanions, ATP and haemoglobin, in the cell. In addition, the decrease in cellular ATP concentration as such increases oxygen affinity of haemoglobin.

Polarographic oxygen sensors : aquatic and physiological applications

Abstract: I Principles of Sensor Design and Operation.- I.1 Factors Influencing the Stability of Polarographic Oxygen Sensors.- I.2 Calibration and Accuracy of Polarographic Oxygen Sensors.- I.3 A Thermodynamic Consideration of Permeability Coefficients of Membranes.- I.4 Microcoaxial Needle Sensor for Polarographic Measurement of Local O2 Pressure in the Cellular Range of Living Tissue. Its Construction and Properties.- I.5 Electrolytes.- I.6 The Action of Hydrogen Sulfide on Polarographic Oxygen Sensors.- I.7 A Double-Membrane Sterilizable Oxygen Sensor.- I.8 Construction of a Polarographic Oxygen Sensor in the Laboratory.- I.9 A Polarographic Oxygen Sensor Designed for Sewage Work and Field Application.- I.10 Electronic Circuits for Polarographic Oxygen Sensors.- I.11 The Application of a Microprocessor to Dissolved Oxygen Measurement Instrumentation.- II Laboratory Applications of Polarographic Oxygen Sensors.- II.1 An Automated Multiple-Chamber Intermittent-Flow Respirometer.- II.2 The Application of Polarographic Oxygen Sensors for Continuous Assessment of Gas Exchange in Aquatic Animals.- II.3 The Twin-Flow Microrespirometer and Simultaneous Calorimetry.- II.4 Simultaneous Direct and Indirect Calorimetry.- II.5 An Automated, Intermittent Flow Respirometer for Monitoring Oxygen Consumption and Long-Term Activity of Pelagic Crustaceans.- II.6 Sealed Respirometers for Small Invertebrates.- II.7 A Method for the Simultaneous Long-Term Recording of Oxygen Evolution and Chloroplast Migration in an Individual Cell of Acetabularia.- II.8 A Respirometer for Monitoring Homogenate and Mitochondrial Respiration.- II.9 Bacterial Growth and Antibiotics in Animal Respirometry.- II.10 pO2 and Oxygen Content Measurement in Blood Samples Using Polarographic Oxygen Sensors.- II.11 Determination of the In Vivo Oxygen Flux into the Eye.- III Field Applications of Polarographic Oxygen Sensors.- III.l In Situ Measurement of Oxygen Profiles in Lakes: Microstratifications, Oscillations, and the Limits of Comparison with Chemical Methods.- III.2 In Situ Measurement of Oxygen Profiles of Sediments by Use of Oxygen Microelectrodes.- III.3 Methods for Measuring Benthic Community Respiration Rates.- III.4 In Situ Measurement of Community Metabolism in Littoral Marine Systems.- III.5 Deap-Sea Respirometry: In Situ Techniques.- Appendix A Calculation of Equilibrium Oxygen Concentration H. Forstner and E. Gnaiger.- Appendix B Calculation of pO2 in Water Equilibrated with a Mixture of Room Air and Nitrogen.- Appendix C Calculation of Energetic and Biochemical Equivalents of Respiratory Oxygen Consumption E. Gnaiger (With 1 Figure).- Appendix D The Winkler Determination H.L. Golterman (With 1 Figure).- Appendix E Symbols and Units: Toward Standardization E. Gnaiger.

Mechanisms and Products of Photosensitized Degradation of Nucleic Acids and Related Model Compounds

Abstract: The mechanisms and products of photosensitized and singlet oxygen oxidation of nucleic acid model compounds have been investigated using kinetics analysis and product isolation and identification. A competitive kinetics analysis is presented as a simple yet quantitative method for the determination of the role of singlet oxygen in homogeneous chemical reactions. This method is compared to other techniques that have been used in the past including determination of the solvent isotope effect and the effect of singlet oxygen quenchers and variations in oxygen and substrate concentration. The results of competitive kinetics experiments indicate that the photooxidation of dGuo (2′-deoxyguanosine) at pH 7–10 in buffered aqueous solution sensitized by Rose Bengal, Methylene Blue, Thionine or several other dyes proceeds predominantly by a pathway requiring intermediate formation of singlet oxygen. In contrast, dGuo photooxidation under the same conditions sensitized by flavin or pterin derivatives proceeds predominantly by pathways that do not involve singlet oxygen. Most of the primary products of dGuo photooxidation are very unstable and consequently are difficult, if not impossible, to isolate and characterize. However, two compounds have now been isolated that correspond to the addition of a single molecule of oxygen to the purine ring of guanine with the purine ring system still intact. Some of the products formed in the singlet oxygen oxidation of 2′-deoxyguanosine appear to be different than some of the products formed in flavin photosensitized reactions in agreement with kinetic results that indicate that the flavin sensitized reactions proceed by mechanisms that do not involve intermediacy of singlet oxygen. If the unique nature of the products of 2′-deoxyguanosine oxidation by singlet oxygen can be firmly established it may be possible to detect singlet oxygen reactions in vivo by product analysis.

Active site of RNase: neutron diffraction study of a complex with uridine vanadate, a transition-state analog

Abstract: A complex of RNase A with a transition-state analog, uridine vanadate, has been studied by a combination of neutron and x-ray diffraction. The vanadium atom occupies the center of a distorted trigonal bipyramid, with the ribose oxygen O2' at the apical position. Contrary to expectations based on the straightforward interpretation of the known in-line mechanism of action of RNase, nitrogen NE2 of histidine-12 was found to form a hydrogen bond to the equatorial oxygen O8, while nitrogen NZ of lysine-41 makes a clear hydrogen bond to the apical oxygen O2'. Nitrogen ND1 of histidine-119 appears to be within a hydrogen-bond distance of the other apical oxygen, O7. Two other hydrogen bonds between the vanadate and the protein are made by nitrogen NE2 of glutamine-11 and by the amide nitrogen of phenylalanine-120. The observed geometry of the complex may necessitate reinterpretation of the mechanism of action of RNase.

Nature of oxidizing power of rice roots

Abstract: The oxidizing power of rice roots comprises two components,i. e., oxygen release and enzymatic oxidation as measured by α-naphthylamine oxidation. Microscopic examination of roots shows a columnar arrangement of cells having structural intercellular spaces that may serve as air passage pipes in the tip region of the root. Both oxygen release and α-naphthylamine oxidation were studied as function of atmospheric oxygen concentration, light, temperature of root environment, respiratory inhibitors, and nutritional status of the plant. The results led to the concept that α-naphthylamine oxidation is a part of the respiration, and that the oxygen which is not consumed by respiration is diffused into the surrounding environment. Both processes are governed by molecular oxygen supply from shoots. At 25°C, the oxygen release of 3-week-old seedlings of IR36 was about 9 times greater than the amount of oxygen needed to account for α-naphthylamine oxidation rate.

Corrosion Behavior of SiC / Al Metal Matrix Composites

Abstract: The effect of the phase on the corrosion behavior of metal matrix composites has been studied in , both in the presence and absence of dissolved oxygen. Anodic polarization behavior has been determined, and pitting potentials have been measured for three composite systems: 2024, 6061, and 5456. General corrosion behavior and the effects of anodizing on the corrosion resistance of the composites have been studied by a‐c impedance techniques. The results show that pitting susceptibility is about the same for the composites and their corresponding alloys, except for Al 2024. In this system, the composite is less resistant to pit initiation than the corresponding wrought aluminum alloy. General corrosion is more significantly affected by the presence of oxygen than by the phase. In the absence of oxygen, corrosion resistance is improved for both the alloys and composites. In addition, the corrosion resistance of the composites can be improved by anodizing.

Properties of microcrystalline silicon. IV. Electrical conductivity, electron spin resonance and the effect of gas adsorption

Abstract: For pt.III see ibid., vol.16, p.2005 (1983). Measured values of the electrical conductivity, sigma , and electron spin density (g=2.0057) of microcrystalline silicon can be essentially determined by the extent of the contamination of the samples by oxygen unless special precautions are taken as regards the sample preparation and/or handling. For samples deposited at a floating potential, two kinds of oxygen incorporation are identified: irreversible formation of Si-O bonds on the grain boundaries (and on the sample surface) and a reversible absorption which is probably associated with a nondissociative O2delta - (ads) state. The latter results in a decrease of sigma RT by up to five orders of magnitude, an increase of the activation energy, epsilon a, and of the preexponential factor, sigma 0, as well as in an increase of the electron spin density. A reversible desorption of oxygen leads to an increase of sigma RT up to not less than about 10-2 Omega -1 cm-1 and a decrease of the EPR signal below the detection limit of less than 1016 cm-3. In order to avoid such effects a negative bias has to be applied to the substrate during deposition. Samples of undoped mu c-Si deposited in this way show neither the incorporation of oxygen into the bulk nor significant changes in the dark conductivity even after long-term exposure to air.