Effect of diffusion on measuring oxygen consumption in oxidation reactions with polarographic membrane-covered probe

The Analyst ◽  
1999 ◽  
Vol 124 (3) ◽  
pp. 343-347 ◽  
Author(s):  
A. Naidja ◽  
P. M. Huang
Keyword(s):  
Oxygen Consumption ◽  
Oxidation Reactions

scholarly journals Methods for Predicting More Confident Lifetimes of Seals in Air Environments

2000 ◽  
Vol 73 (2) ◽  
pp. 265-283 ◽  
Author(s):  
Kenneth T. Gillen ◽  
Mathias Celina ◽  
Michael R. Keenan
Keyword(s):  
Oxygen Consumption ◽  
Oxygen Consumption Rate ◽  
Consumption Rate ◽  
Synergistic Effects ◽  
Tensile Elongation ◽  
Mechanical Strain ◽  
Extensive Study ◽  
Oxidation Reactions ◽  
Arrhenius Behavior ◽  
Degradation Rates

Abstract We have been working for many years to develop improved methods for predicting the lifetimes of polymers exposed to air environments and have recently turned our attention to seal materials. This paper describes an extensive study on a butyl material using elevated temperature compression stress—relaxation (CSR) techniques in combination with conventional oven aging exposures. The results initially indicated important synergistic effects when mechanical strain is combined with oven aging, as well as complex, non-Arrhenius behavior of the CSR results. By combining modeling and experiments, we show that diffusion-limited oxidation (DLO) anomalies dominate traditional CSR experiments. A new CSR approach allows us to eliminate DLO effects and recover Arrhenius behavior. Furthermore, the resulting CSR activation energy (Ea) from 125 to 70 °C is identical to the activation energies for the tensile elongation and for the oxygen consumption rate of unstrained material over similar temperature ranges. This strongly suggests that the same underlying oxidation reactions determine both the unstrained and strained degradation rates. We therefore utilize our ultrasensitive oxygen consumption rate approach down to 23 °C to show that the CSR Ea likely remains unchanged when extrapolated below 70 °C, allowing more confident room temperature lifetime predictions for the butyl seal.

scholarly journals Control of the effective P/O ratio of oxidative phosphorylation in liver mitochondria and hepatocytes

1993 ◽  
Vol 291 (3) ◽  
pp. 739-748 ◽  
Author(s):  
M D Brand ◽  
M E Harper ◽  
H C Taylor
Keyword(s):  
Oxygen Consumption ◽  
Liver Mitochondria ◽  
Substrate Oxidation ◽  
Proton Leak ◽  
Rat Liver Mitochondria ◽  
Protonmotive Force ◽  
Control Analysis ◽  
Control Coefficient ◽  
Oxidation Reactions ◽  
In Cells

The control exerted by substrate oxidation reactions, by ATP turnover and by the proton leak over the oxygen consumption rate, the phosphorylation rate, the proton leak rate and the protonmotive force (delta p) in isolated rat liver mitochondria under a range of conditions between non-phosphorylating (State 4) and maximum phosphorylation (State 3) was investigated by using the top-down approach of metabolic control analysis. The experiments were carried out with saturating concentrations of the substrates succinate, glutamate with malate, or pyruvate with malate. The distribution of control was very similar with each of the three substrates. The effective P/O ratio (i.e. not corrected for leak reactions) was also measured; it varied from zero in State 4 to 80-90% of the maximum theoretical P/O ratio in State 3. Under most conditions control over the effective P/O ratio was shared between proton leak (which had negative control) and the phosphorylating subsystem (which had roughly equal positive control); near State 4, substrate oxidation reactions also acquired some control over this ratio. In resting hepatocytes the effective P/O ratio was only 50% of its maximum theoretical value, corresponding to an effective P/O ratio of only 1.3 for complete oxidation of glucose. The effective P/O ratio for intracellular mitochondrial oxygen consumption was 64% of the maximum value. The control coefficient of the mitochondrial proton leak over the effective P/O ratio in cells was -0.34; the control coefficient of phosphorylation reactions over this ratio was 0.31 and the control coefficient of substrate oxidation reactions over the ratio was 0.03, showing how the coupling efficiency in cells can respond sensitively to agents that change the proton leak or the ATP demand, but not to those that change substrate oxidation.

Oxidation of mine tailings from Rankin Inlet, Nunavut, at subzero temperatures

2001 ◽  
Vol 38 (5) ◽  
pp. 957-966 ◽  
Author(s):  
J L Meldrum ◽  
H E Jamieson ◽  
L D Dyke
Keyword(s):  
Oxygen Consumption ◽  
Pore Water ◽  
Mine Drainage ◽  
Experimental Program ◽  
Unfrozen Water ◽  
Hudson Bay ◽  
Oxidation Reactions ◽  
Subzero Temperatures ◽  
Direct Measurements

Acid-generating sulphidic tailings from a Ni–Cu mine were exposed on the shores of Hudson Bay for 30 years before burial in a drained bedrock basin. To determine if encapsulation in permafrost will maintain the tailings, and their saline pore water, in a chemically inert state, a field and experimental program was employed. Three years after burial, several boreholes were drilled to collect tailings and pore-water samples and to initiate long-term thermal monitoring. Columns charged with pyrrhotite-bearing, unsaturated tailings were studied at temperatures between +30°C and –10°C. Oxygen consumption was measured directly to determine the effect of low temperatures on oxidation rate. Results of the column experiments indicate that significant oxidation of the Rankin Inlet tailings occurs at +30°C, but at lower temperatures this rate is substantially reduced. At –10°C, unfrozen water was still present in the columns, but oxygen consumption was below the detection limit. The highest measured oxygen flux correlates with a temperature increase of 1°C, consistent with exothermic sulphide oxidation reactions. Thermal modeling and direct measurements have shown that the freezing of the tailings in Rankin Inlet is progressing. The tailings are expected to be ice-bonded approximately 15 years after burial.Key words: acid mine drainage, permafrost, tailings, reclamation, sulphides, oxidation

Oxygen consumption test to evaluate the diffusive flux into reactive tailings: interpretation and numerical assessment

2011 ◽  
Vol 48 (6) ◽  
pp. 878-890 ◽  
Author(s):  
Mamert Mbonimpa ◽  
Michel Aubertin ◽  
Bruno Bussière
Keyword(s):  
Oxygen Consumption ◽  
Reaction Rate ◽  
Oxygen Flux ◽  
Test Duration ◽  
Oxidation Reactions ◽  
Relative Precision ◽  
Numerical Assessment ◽  
Sulphide Tailings ◽  
Numerical Parametric Study ◽  
Interpretation Method

The oxygen consumption (OC) test is conducted on sulphide tailings by measuring the decline of oxygen concentration in a closed headspace, at the top of a cylinder, as a result of diffusion and oxidation reactions. For a short-duration test, the measurements may be interpreted using a simplified analytical method based on modified Fick’s laws, which provides the combined value of the effective oxygen diffusion (De) and reaction rate (Kr) coefficients of the tailings. This lump value can be used to evaluate the steady-state oxygen flux entering the exposed sulphide tailings. In this paper, a numerical parametric study is performed to investigate the effect of test duration and headspace height, h, on results obtained from OC tests. The assessment also considers tailings with different values of De and Kr. The results indicate that the simplified interpretation method usually tends to underestimate the surface oxygen flux, in proportions that depend on the testing conditions. Results from this study can be used to estimate the relative precision of the oxygen flux for specific conditions, thus helping practitioners decide how to best interpret testing measurements for a given application.

Clinical and Experimental Analysis of 201Thallium Uptake of the Heart

1978 ◽  
Vol 17 (04) ◽  
pp. 142-148
Author(s):  
U. Büll ◽  
S. Bürger ◽  
B. E. Strauer
Keyword(s):  
Oxygen Consumption ◽  
Left Ventricle ◽  
Muscle Mass ◽  
Myocardial Oxygen Consumption ◽  
Animal Experiments ◽  
Left Ventricular ◽  
Left Ventricular Wall ◽  
Ventricular Wall ◽  
Flow Measurements ◽  
Myocardial Flow

Studies were carried out in order to determine the factors influencing myocardial 201T1 uptake. A total of 158 patients was examined with regard to both 201T1 uptake and the assessment of left ventricular and coronary function (e. g. quantitative ventriculography, coronary arteriography, coronary blood flow measurements). Moreover, 42 animal experiments (closed chest cat) were performed. The results demonstrate that:1) 201T1 uptake in the normal and hypertrophied human heart is linearly correlated with the muscle mass of the left ventricle (LVMM);2) 201T1 uptake is enhanced in the inner (subendocardial) layer and is decreased in the outer (subepicardial) layer of the left ventricular wall. The 201T1 uptake of the right ventricle is 40% lower in comparison to the left ventricle;3) the basic correlation between 201T1 uptake and LVMM is influenced by alterations of both myocardial flow and myocardial oxygen consumption; and4) inotropic interventions (isoproterenol, calcium, norepinephrine) as well as coronary dilatation (dipyridamole) may considerably augment 201T1 uptake in accordance with changes in myocardial oxygen consumption and/or myocardial flow.It is concluded that myocardial 201T1 uptake is determined by multiple factors. The major determinants have been shown to include (i) muscle mass, (ii) myocardial flow and (iii) myocardial oxygen consumption. The clinical data obtained from patient groups with normal ventricular function, with coronary artery disease, with left ventricular wall motion abnormalities and with different degree of left ventricular hypertrophy are correlated with quantitated myocardial 201T1 uptake.

Oxygen Consumption in Platelets of Newborn Infants before and after Stimulation by Thrombin.

1976 ◽  
Vol 35 (03) ◽  
pp. 712-716 ◽  
Author(s):  
D. Del Principe ◽  
G Mancuso ◽  
A Menichelli ◽  
G Maretto ◽  
G Sabetta
Keyword(s):  
Oxygen Consumption ◽  
Cord Blood ◽  
Umbilical Cord ◽  
Newborn Infant ◽  
Umbilical Cord Blood ◽  
Newborn Infants ◽  
O2 Consumption ◽  
Adult Control ◽  
Healthy Newborn ◽  
Before And After

SummaryThe authors compared the oxygen consumption in platelets from the umbilical cord blood of 36 healthy newborn infants with that of 27 adult subjects, before and after thrombin addition (1.67 U/ml). Oxygen consumption at rest was 6 mμmol/109/min in adult control platelets and 5.26 in newborn infants. The burst in oxygen consumption after thrombin addition was 26.30 mμmol/109/min in adults and 24.90 in infants. Dinitrophenol did not inhibit the burst of O2 consumption in platelets in 8 out of 10 newborn infants, while the same concentration caused a decrease in 9 out of 10 adult subjects. Deoxyglucose inhibited the burst in O2 consumption in newborn infant and adult platelets by about 50%. KCN at the concentration of 10−4 M completely inhibited basal oxygen consumption but did not completely inhibit the burst after thrombin. At the concentration of 10−3 M, it inhibited both basal O2 consumption and the burst in infants and adult subjects.

Sign in / Sign up

Export Citation Format

Share Document