Ppm O2 Research Articles

Influence of long-term hypoxia on the energy metabolism of the haemoglobin-containing bivalve Scapharca inaequivalvis: critical O2 levels for metabolic depression.

The oxygen consumption rate of Scapharca inaequivalvis measured under normoxic conditions over 48 h showed a significant daily cycle with lowest values occurring shortly after the dark period; all hypoxia exposure experiments were carried out during the declining part of the cycle. Animals were exposed to a constant level of hypoxia for a 12-h period in a series of 14 experiments, each at a different oxygen tension. The oxygen consumption was measured continuously, and the extent of accumulation of end-products (succinate and propionate), and the inhibitory effect of adenosine triphosphate on phosphofructokinase were determined at the end of exposures. All three parameters (oxygen consumption, end-product accumulation, phosphofructokinase inhibition) showed a remarkable correlation with major changes occurring between 2.5 and 1.5 ppm (7 and 4 kPa) O2. The oxygen consumption rates showed a drop to 6% of the normoxic rate, but a consistent low consumption remained below 2 ppm (5.5 kPa) which partly recovered over the 12-h exposure period by about three-fold. Succinate and propionate accumulated progressively between 2.5 and 1.5 ppm (7 and 4 kPa); at [O2] less than 1.5 ppm (4 kPa) the concentration did not increase further, indicating that anaerobic metabolism had reached a maximum. Over the same range, phosphofructokinase showed an increased sensitivity for adenosine triphosphate, the lower inhibitor concentration at 50% Vmax value pointing to depression of glycolytic rate. Despite the activation of anaerobic metabolism and the evident depression of aerobic metabolism, simple calculation demonstrates that Scapharca inaequivalvis relies mainly on aerobic metabolism even during severe hypoxia.(ABSTRACT TRUNCATED AT 250 WORDS)

Carbondioxide affects the growth rate of ?oxygen limited?Escherichia coli at low concentrations of oxygen

It is shown that addition of 1% CO2 in Argon, containing traces of oxygen (<30 ppm O2) to a described mineral salts medium leads to deblockage of the normal “oxygen limited” growth pattern ofEscherichia coli (ATCC 1524).

Shock tube measurements of the reactions of CN with O and O2

AbstractThe rate coefficients of the reactionsequation imageandequation imagewere determined in a series of shock tube experiments from CN time histories recorded using a narrow‐linewidth cw laser absorption technique. The ring dye laser source generated 388.44 nm radiation corresponding to the CN B2Σ+(v= 0) ←X2Σ+(v= 0) P‐branch bandhead, enabling 0.1 ppm detection sensitivity.Reaction (1) was measured in shock‐heated gas mixtures of typically 200 ppm N2O and 10 ppm C2N2in argon in the temperature range 3000 to 4500 K and at pressures between 0.45 and 0.90 atm.k1was determined using pseudo‐first order kinetics and was found to be 7.7 × 1013(±20%) [cm3mol−1s−1]. This value is significantly higher than reported by earlier workers. Reaction (2) was measured in two regimes. In the first, nominal gas mixtures of 500 ppm O2and 10 ppm C2N2in argon were shock heated in the temperature range 2700 K to 3800 K and at pressures between 0.62 and 1.05 atm.k2was determined by fitting the measured CN profiles with a detailed mechanism. In the second regime, gas mixtures of 500 ppm O2and 1000 ppm C2N2in argon were shock heated in the temperature range 1550 to 1950 K and at pressures between 1.19 and 1.57 atm. Using pulsed radiation from an ArF excimer laser at 193 nm, a fraction of the C2N2was photolyzed to produce CN. Pseudo‐first order kinetics were used to determinek2. Combining the results from both regimes,k2was found to be 1.0 × 1013(±20%) [cm3mol−1s−1].

Oxygen induced adhesion degradation at metal/polyimide interface

The role of oxygen in affecting the adhesive bonding at the metal/polyimide (polyimide-on-metal) interface has been studied. Both pyromellitic dianhydride (PMDA) -oxydianiline (ODA) and biphenyl-tetracarboxylic dianhydride(BPDA) -p-phenylene diamine (PDA) based poly(amic acid) precursors were cast and fully imidized on metal surfaces of Cr, Cu, Ni, Co, Cu/Ni, and Cu/Co in a nitrogen atmosphere. The peel strengths at the polyimide-on-metal interface were measured, using a 90° peel test, immediately after curing, and then remeasured after annealing in either nitrogen (N2−≤100 ppm O2 ) or air (N2 –21% O2 ) at 350 °C for 1 h. Very little or no change in peel strength was measured after these samples were annealed in nitrogen, while significant adhesion degradations were measured on all metals after annealing in air. The loss of polyimide (PI) adhesion to the Cu or Co surface is attributed to metal catalyzed thermal–oxidative degradation of the PI at the metal/PI interface, as characterized by polyimide thickness reduction, Fourier transform infrared and x-ray photoelectron spectrometries. The rate of degradation of the PMDA-ODA films on Cu or Co is several times faster than that of the BPDA-PDA films. The degradation products were characterized as CO2, CO, Cu carboxylate salts and a nitrile moiety entrapped in partially degraded PI films. The extent of degradation was found to increase with increasing oxygen content in the annealing ambient or with decreasing PI thickness, indicating that oxygen diffusion through the PI overcoating to the metal/PI interface plays a critical role in promoting degradation. On the Cr and Ni surfaces, such metal catalyzed degradation was not detected with our techniques, while some adhesion strength was still retained, a significant loss in adhesion strength was observed. This is probably due to oxidation of the metal underlayer causing debonding at the originally well adhered metal/PI interface. When all testing variables were held constant, the peel strength of a well adhered metal/PI joint is shown to increase with increasing peeling rate (crosshead speed). An increase of up to ∼40% in peel strength was measured when the crosshead speed was increased from a low speed of 0.05 mm/min to 10 mm/min. The locus of fracture of the as-cured films was cohesive, i.e., the fractured surface was located within PI, while for the thermal–oxidative degraded joint the failure mode was changed to adhesive.

The winter environment of painted turtles, Chrysemys picta: temperature, dissolved oxygen, and potential cues for emergence

Water, bottom, and presumed hibernaculum temperatures and dissolved oxygen concentrations were examined over four winter seasons (1981–1985) in a shallow pond near Ann Arbor, Michigan, where a population of painted turtles, Chrysemys picta, overwinter. The minimum presumed hibernaculum temperature varied considerably from year to year (3.7–6.3 °C) and was correlated with the severity of the winter. Turtles hibernating at this site would not have been exposed to temperatures below freezing even in the severest winter. Ice covered the pond continuously for an average of 92 (56–117) days and subsequently, dissolved oxygen fell precipitously, the water becoming severely hypoxic (&lt; 1 ppm O2) for an average of 43 (39–46) days. The timing of emergence varied annually (March 1 to April 14) and was correlated with the severity of the winter. Thus, it appears that photoperiod or a circannual rhythm is not a proximate cue for arousal. Emergence generally occurred after the ice cover was completely melted, when water and bottom temperatures were increasing steadily and the vertical temperature gradient had collapsed or reversed. The annual variability in physical conditions demonstrated in this study strongly suggests that studies involving hibernation in aquatic ecosystems are best conducted over several winters.

Cell inactivation and cell cycle inhibition as induced by extreme hypoxia: the possible role of cell cycle arrest as a protection against hypoxia‐induced lethal damage

Cycling mammalian cells that are rendered extremely hypoxic (less than 4 ppm O2) tend to accumulate in a pre-DNA-synthesis stage. It is not clear whether or not this is the result of an active regulation by the cells. In the present study we have rendered cells, synchronized by mitotic selection, extremely hypoxic over a relatively long period of time (up to 48 h). We have recorded cell cycle progression during hypoxia as well as cell inactivation depending on where in the cell cycle the cells were located when the hypoxic treatment was started. Three main conclusions are drawn: 1 the cell cycle arrest in late-G1 is complete even during a long-lasting (24 h) hypoxic treatment: 2 while cells in early- and mid-S are completely arrested and quickly inactivated under hypoxic conditions, cells in late-S, G2 and mitosis are able to continue cell cycle progression and divide; 3 whether the cells are located in G2, mitosis or early-G1 at the onset of hypoxia, they were able to survive relatively long-lasting hypoxic treatment. The present results are in favour of the view that the pre-DNA-synthetic arrest induced by extreme hypoxia may function to rescue the cells from severely damaging effects that would appear if the cells were able to initiate DNA synthesis.

Fluoromisonidazole. A metabolic marker of myocyte hypoxia.

Fluoromisonidazole is metabolically trapped in viable hypoxic cells in vitro. This property is the basis for the hypothesis that [18F]fluoromisonidazole can be used to detect hypoxic tissues noninvasively using positron emission tomography. To assess the potential usefulness of this compound as a marker for hypoxic myocardium, we measured the accumulation of [3H]fluoromisonidazole in isolated adult rat myocytes under normoxic, hypoxic (5,000 ppm O2), and anoxic conditions. Both anoxia and hypoxia caused a marked increase in [3H]fluoromisonidazole accumulation. Relative to uptake during normoxia, uptake during anoxia was increased by 8.4-fold at 60 minutes and 26.5-fold at 180 minutes (p less than 0.001). During hypoxia, uptake was increased by 4.4-fold at 60 minutes and by 15.3-fold at 180 minutes (p less than 0.0001) and occurred in the absence of significant cell injury as measured by release of creatine kinase and changes in cell morphology. Additional studies demonstrated a slow oxygen-insensitive efflux of fluoromisonidazole or labeled metabolite(s) from myocytes reincubated in drug-free medium. We conclude that fluoromisonidazole is avidly retained in hypoxic myocytes and thus may be suitable for noninvasive detection of hypoxic myocardium using positron emission tomography.

Cesium sorption on mylonite

As part of the laboratory support program for the field migration experiment at the Grimsel Test Site (GTS) in the Swiss Alps, the sorption behaviour of cesium on Grimsel mylonite was studied. Batch sorption experiments were carried out in N2 atmosphere (<3 ppm O2). The adsorption isotherms were reversible and non-linear for cesium concentrations of between 3.2·10−8 and 5.0·10−4M. Two different sites appear to be involved in sorption depending on whether Cs loading was high (10−6–10−3 meq/g) or low (10−7–10−6 meq/g). At low Cs loadings adsorption was considered to occur mainly at the crystal edges of mica particles. Selectivity coefficients for exchange between cesium and potassium were calculated for different Cs loadings. It was suggestd that by varying the potassium concentration of the solution and by making some assumptions, a Kd value for cesium at the migration site could be estimated. Data were fitted to both Freundlich and Dubinin-Radushkevich isotherms. The empirical Freundlich parameters enabled a site distribution function to be calculated and a mean energy of sorption of about 12 kJ/mol was found using Dubinin-Radushkevich isotherms approach.

Influence of annealing ambients on ZrSi2 formation

The formation of zirconium silicide was studied in many kinds of annealing ambients, i.e., Ar-H2, Ar-O2, N2-O2, Ar-N2-O2, and Ar-air. When the ambient involves both N2 and O2, such as Ar-N2-O2 and N2-O2, in the range of [N2]/([N2] +[O2])>0.9, the film resistivity becomes higher than that of the Ar-O2 case, even at the same O2 concentration. This is because a thick ZrOxNy layer is formed on the ZrSi2 layer. When the ratio of [N2]/([N2] + [O2]) in the Ar-N2-O2 ambient is less than 0.9, the films are partially peeled off from the substrate. The resistivity of a film annealed in the Ar-air ambient is very high at even a few ppm O2. This is because the film peels off and then the oxidation of the peeled film is accelerated by a small amount of H2O in air.

Damage tolerance and supportability aspects of ARALL laminate aircraft structures: Gunnink J.W. Compos. Struct. 1988, 10, (1), 83–104

Slow strain rate stress corrosion tests have been performed on a nuclear reactor pressure vessel steel in pure water at temperatures from 150 to 288°C and at various oxygen contents. The variation of cracking susceptibility correlates with the electrochemical potential, and cracking occurs for this temperature range if the rest potential is greater than about −0.2 V(SHE). It was confirmed that the oxygen in the water acts as a chemical potentiostat, which drives the steel into or out of the cracking range, by showing that cracking could be prevented in 45 ppm O2 water at 288°C by applying cathodic polarization. Cracking could also be induced in < 5 ppb O2 content water by applying anodic potentials. Large IR drops occurred in the potentiostatically controlled tests and it is probable that the potential need only be moved slightly from the cracking potential to induce a significant reduction in the susceptibility to cracking. The cracking potential correlates well with the Fe3O4Fe2O3 boundary for high temperature potential-pH data. It is probable that the mechanism of stress corrosion cracking requires that both Fe2O3 and Fe3O4 can form in the crack enclave. By replotting the potential-pH data in the form of the required oxygen for a given potential against temperature, it is shown that the oxygen content for inducing cracking agrees closely with the Fe3O4-Fe2O3 boundary at temperatures from 150°C to 288°C and that in this temperature range cracking is more likely to be associated with an anodic dissolution mechanism than by hydrogen-assisted cracking.

Determination of Oxygen Solubility in Liquid Foods Using a Dissolved Oxygen Electrode

ABSTRACTA rapid method for determining oxygen solubility in foods was introduced. Fructose, glucose, sucrose, orange juice, apple juice, grape juice, grapefruit juice, lemonade, and tomato juice had similar oxygen solubilities at comparable °Brix readings. The equation: In [ppm O2] = 2.63 − 0.0179 (°Brix) − 0.0190 (°C) estimated to within 5% the oxygen solubility of sugar solutions and fruit juices at temperatures between 4°C and 40°C. At likely food concentrations, citric acid, ascorbic acid, and NaCl reduced oxygen solubility by less than 10%. Tests for component interactions were also conducted. There was no measurable synergism or antagonism between fructose, glucose, and sucrose with or without organic acids.

A Device for Measuring Oxygen Solubility in Fluids and Oxygen Permeation through Polymers having Fluid Contact

ABSTRACTAn apparatus was developed which measured oxygen permeation from a gaseous environment into a liquid medium. Oxygen permeating the package material was detected in the liquid phase by an oxygen electrode. The oxygen permeation of 1 mil oriented polypropylene was 1417 cc/m2 day at 25°C. Slopes of permeation lines were related to the oxygen solubility of various aqueous media. The oxygen solubility of an air‐saturated 1.5% NaCl solution was 7.15 ppm O2. Permeability and solubility values were both within 3% of known standards. The solubility method was used to determine the oxygen concentration of air‐saturated single‐strength tomato juice. At 25°C, the sample contained 7.3 ppm O2.

Low temperature sensitization of type 304 stainless steel pipe weld heat affected zone

Large-diameter Type 304 stainless steel pipe weld heat-affected zone (HAZ) was investigated to determine the rate at which low temperature sensitization (LTS) can occur in weld HAZ at nuclear reactor operating temperatures and to determine the effects of LTS on the initiation and propagation of intergranular stress corrosion cracks (IGSCC). The level of sensitization was determined with the electrochemical potentiokinetic reactivation (EPR) test, and IGSCC susceptibility was determined with constant extension rate tests (CERT) and actively loaded compact tension (CT) tests. Substructural changes and carbide compositions were analyzed by electron microscopy. Weld HAZ was found to be susceptible to IGSCC in the as-welded condition for tests conducted in 8-ppm-oxygen, high-purity water at 288 °C. For low oxygen environments (i.e., 288 °C/0.2 ppm O2 or 180 °C/1.0 ppm O2), IGSCC susceptibility was detected only in weld HAZ that had been sensitized at temperatures from 385 °C to 500 °C. Lower temperature heat treatments did not produce IGSCC. The microscopy studies indicate that the lack of IGSCC susceptibility from LTS heat treatments below 385 °C is a result of the low chromium-to-iron ratio in the carbide particles formed at grain boundaries. Without chromium enrichment of carbides, no chromium depleted zone is produced to enhance IGSCC susceptibility.

Notch Fatigue Crack Initiation in High Temperature Water Environments: Experiments and Life Prediction

Test results, experimental techniques and analytical interpretations are reported from notched compact type (CT) tests of SA 333 Gr. 6 carbon steel to determine quantitatively fatigue initiation lives in high temperature oxygenated water. Parameters explored include environments of air, 0.2 ppm O2 and 8 ppm O2-water at 10.3 MPa (1500 psi), temperatures of 149, 232 and 288° C, frequencies of 0.00021, 0.0021 and 0.021 Hz, notch radii of 0.051 and 0.51 mm and R-values of 0.2, 0.5 and 0.8. Pseudostress amplitudes were calculated elastically and by Neuber notch analysis procedures using a worst case notch concept. Results were compared to ASME Section III fatigue data curves. Test results showed that the fatigue initiation life of carbon steel is substantially lowered as oxygen level is raised, as frequency is lowered or as temperature is raised. No frequency or temperature effect occurred in air. To a lesser extent, a decreasing notch radius or an increased R-value degrade the initiation life. Results compare favorably with interpretations based on environmental fatigue crack growth of this material.

ChemInform Abstract: Effect of Oxygen on the Open‐Circuit Passivity of Fe ‐ 18 Cr.

AbstractThe critical amount of O2 necessary to prevent corrosion by maintaining the open‐circuit passivity of Fe‐18 Cr samples initially passivated at 0.6 V (NHE) in N2‐saturated IN H2SO4 has been determined to be 1.7 ppm O2.

ChemInform Abstract: Decomposition of the FeTi1.13 Hydride After Hydrogen Absorption

AbstractThermal decomposition of the FeTi1.13 hydride was investigated after hydrogen absorption ‐ desorption cycling at 50°C in impure H2 containing 680 ppm O2.

Ultrastructural changes in V79 hamster lung fibroblasts during hypoxic exposure.

Cells in tumors that are deprived of their blood supply become hypoxic. These stressed cells adapt to their new environments by altering their metabolic regimen which in time induces cellular structure changes. The morphologic make-up of these O2-deprived cells is the focal point of this electron microscopy study. V-79 hamster lung fibroblast cells grown as monolayer cultures were examined under controlled culture density and oxygen tensions - normal aerobia (2.1 X 10(5) ppm O2), and extreme hypoxia (less than 10 ppm O2). Electron micrographs of these cells demonstrated a loss of structural mitochondrial integrity accompanied with large increases in both mitochondrial and lipid vacuole size following exposure to extreme hypoxia. When these cells were reoxygenated, those mitochondria which had not become degenerate returned to their normal state however, lipids still continued to accumulate in vacuoles for a further 6 h. Addition of 1 mM palmitic acid to aerobic cultures evoked similar lipid and mitochondrial irregularities as were observed in hypoxic cells although, the latter were not as marked. When this saturated fatty acid was added to hypoxic cells no further structural alterations were seen. The cellular changes manifested during this study were subjected to quantitative measurements and these results have given an insight into the scope and variety of ultrastructural changes which have resulted from exposure of cultured cells to hypoxic conditions.

Stress Corrosion Cracking Susceptibility of AISI 316 NG and 316 Stainless Steel in an Impurity Environment

Abstract The relative stress corrosion cracking (SCC) susceptibility of heat-treated AISI 316 nuclear grade (NG) and 316 stainless steel (SS) has been investigated by means of constant extension rate tensile (CERT) tests over a range of strain rates from 10−5 to 10−7 s−1 in simulated boiling water reactor (BWR) environments that contain SO42− as an impurity. It is observed that although AISI 316 NG SS is extremely resistant to intergranular SCC (IGSCC) even when subjected to severe heat treatments, it can become susceptible to transgranular SCC (TGSCC) in the presence of impurities. Sensitized AISI 316 SS, however, is susceptible to IGSCC even in high-purity water containing 0.2 ppm O2, and the addition of an impurity aggravates the IGSCC susceptibility. The SCC results obtained for both materials are discussed in terms of a phenomenological model that incorporates a slip-dissolution mechanism and elastic-plastic fracture mechanics. The results for both IGSCC and TGSCC are demonstrated to be consistent with the slip-dissolution model of Ford.

The Effects of Cellular Glutathione Elevation on the Oxygen Enhancement Ratio

The radiation responses at various oxygen tensions were evaluated in V79 Chinese hamster cells under conditions where their nonprotein thiols, primarily glutathione (GSH), were elevated by 2-oxothiazolidine-4-carboxylate (OTZ). OTZ, when cleaved by intracellular oxoprolinase, provides the cell with cysteine which stimulates GSH synthesis. A 2-hr pretreatment with 10 mM OTZ elevated GSH to 200% of controls. This elevation in GSH offered no protection to aerated cells; however, for O2 tensions less than or equal to 40,000 ppm modest protection was observed as evidenced by an increase in oxygen enhancement ratio. GSH elevation afforded maximal protection between 1000 and 10,000 ppm O2; however, the extent of protection was relatively small (protection factor = 1.3).

Changes in ultrastructure and function of hypoxic V79 fibroblast cells after treatment with misonidazole.

Morphologic and enzymatic changes due to exposure to the radiosensitizing chemical, misonidazole, have been identified in V79 cells grown in a system in which oxygen tensions and culture density have been controlled. Misonidazole prevented the increase in mitochondrial size normally seen during exposure of these cells to conditions of moderate hypoxia (2 X 10(3) ppm O2). Mitochondrial size was also significantly decreased in cells from exponential cultures exposed to 1 mmol/l misonidazole. Morphologic changes to the mitochondria that varied from data reported elsewhere were also noted. Misonidazole caused a significant initial decrease in cytochrome oxidase activity after 4 hours of exposure of aerobic and moderately hypoxic cultures that did not return to normal in chronically hypoxic cells during continued exposure to the drug.