Field examination of temperature and oxygen relationships in mushroom composting stacks dash consideration of stack oxygenation based on utilisation and supply

1989 ◽  
Vol 29 (5) ◽  
pp. 741 ◽  
Author(s):  
FC Miller ◽  
ER Harper ◽  
BJ Macauley
Keyword(s):  
Natural Convection ◽  
Oxygen Uptake ◽  
Phase I ◽  
Oxygen Concentration ◽  
Physical Factors ◽  
Activity Data ◽  
Gaseous Diffusion ◽  
Oxygen Concentrations

Temperature and oxygen concentration in Phase I composting stacks were investigated in the field. that both determine and are consequences of biological Investigations focused on various physical factors activity. Data indicate that oxygen concentrations in Phase I stacks are affected by convection, gaseous diffusion and utilisation rates, but that these rates vary significantly spatially and temporally. When stack temperatures exceed 60�C, biological rates of activity, and therefore oxygen uptake, decrease, allowing oxygen to penetrate well into the centres of stacks. While natural convection is commonly used to explain stack oxygenation, this is an over simplification that does not adequately describe stack oxygen concentrations.

Influence of some factors on oxygen uptake of canine cardiac Purkinje fibers

1963 ◽  
Vol 204 (1) ◽  
pp. 5-8 ◽  
Author(s):  
Kalman Greenspan ◽  
Paul F. Cranefield
Keyword(s):  
Oxygen Uptake ◽  
Oxygen Concentration ◽  
Diffusion Limitation ◽  
Purkinje Fibers ◽  
Ambient Oxygen ◽  
Cardiac Purkinje Fibers ◽  
Lower Oxygen ◽  
Wet Weight ◽  
Oxygen Tensions ◽  
Oxygen Concentrations

The rate of oxygen uptake of quiescent Purkinje fibers of the dog's heart was determined using a flow respirometer and oxygen polarography. At ambient oxygen concentrations of 60% or higher the rate of uptake was 0.739 mm3/mg wet weight per hr at 35 C. The temperature coefficient over the range 25–35° was 2.3. The uptake was independent of the ambient oxygen concentration at oxygen concentrations equal to or greater than 60% of an atmosphere. In lower oxygen concentrations the rate of uptake was found to be depressed. The depression of uptake in the lower oxygen tensions is probably the result of diffusion limitation; it may, however, reflect dependence of resting uptake on oxygen concentration.

Respiratory differences associated with culture aeration in Azotobacter vinelandii

1989 ◽  
Vol 35 (10) ◽  
pp. 918-924 ◽  
Author(s):  
Jay B. Peterson
Keyword(s):  
Nitrogen Fixation ◽  
Oxygen Uptake ◽  
Oxygen Concentration ◽  
Azotobacter Vinelandii ◽  
Partial Explanation ◽  
Respiration Rates ◽  
Carbon Substrates ◽  
Moderate Agitation ◽  
Different Levels ◽  
Oxygen Concentrations

Respiratory oxygen uptake of nitrogen-fixing Azotobacter vinelandii cells was altered by culturing at different levels of culture agitation (aeration). Cells were grown at low agitation or moderate agitation and with three different carbon substrates. The low-agitation cultures had much lower dissolved-oxygen concentrations than moderate-agitation cultures at the stage of growth at which they were studied. The respiration systems of cells from the moderate-agitation cultures had lower apparent affinities (higher Ks (O2) values) for oxygen than cells grown at low agitation. The higher Ks (O2)) values were dependent on the presence of Ca2+ and (or) Mg2+ in the medium. In low-agitation cultures, the oxygen concentrations were below the Ks (O2 values and the respiration rates in the cultures were therefore well below the maximal respiration (Vmax) rates. The oxygen concentrations in moderate-agitation cultures were above the Ks (O2) values and the culture respiration rates were much higher. The culture oxygen concentration relative to the Ks (O2) had a much greater effect on culture respiration rate than did the Vmax. It is proposed that changes in the respiration system resulting from culture agitation (aeration) reflect an "oxygen-sensing mechanism" that regulates respiration. This would provide at least a partial explanation for the increased respiration rates with increased culture oxygen concentration in A. vinelandii.Key words: Azotobacter, oxygen, respiration, nitrogen fixation.

Respiratory metabolism of Azotobacter vinelandii cells at oxygen concentrations that initially range from suboptimal to supraoptimal for nitrogenase activity

1991 ◽  
Vol 37 (4) ◽  
pp. 321-325 ◽  
Author(s):  
Jay B. Peterson
Keyword(s):  
Oxygen Uptake ◽  
Oxygen Concentration ◽  
Azotobacter Vinelandii ◽  
Nitrogenase Activity ◽  
Low Oxygen ◽  
Total Oxygen ◽  
Apparent Affinity ◽  
Lower Oxygen ◽  
Effect Of Oxygen ◽  
Oxygen Concentrations

The effects of three low oxygen concentrations on nitrogenase activity, total oxygen uptake, and respiratory parameters (Vmax and Ks(O2) of N2-grown Azotobacter vinelandii were studied in acetylene reduction assays during a 2-h incubation. The cell suspensions were taken from cultures grown at low aeration. Total oxygen uptake was higher with each increment in oxygen concentration. The highest oxygen concentration was initially supraoptimal for nitrogenase activity. The Ks(O2) values, representing the apparent affinity of the respiration system for oxygen, increased during the incubation of cells at the highest oxygen concentration. The Ks(O2) values at the two lower oxygen concentrations decreased and were very similar. A small effect of oxygen on the Vmax was observed. These results show that the metabolism determining the apparent affinity of the system for oxygen responds to the oxygen concentrations. Furthermore, this metabolism did not substantially increase the Ks(O2) unless the oxygen concentration was high enough to inhibit nitrogenase activity, indicating that the two processes may be linked. Key words: Azotobacter, oxygen regulation, nitrogen fixation.

The Effects of Passive and Active Smoking on Brachial and radial Blood Pressure and Some Other Physical Factors in Healthy Young Adults

2017 ◽  
Vol 5 (3) ◽  
pp. 259
Author(s):  
Shireen H. Ramadhan ◽  
Shamil K. Talal ◽  
Wasfiya A. Moner
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Oxygen Saturation ◽  
Oxygen Concentration ◽  
Tobacco Smoke ◽  
Blood Pressure Measurement ◽  
Reference Level ◽  
Physical Factors ◽  
New Device ◽  
Active Smoker

Tobacco smoke is enormously harmful to human health, there’s no safe way to smoke. The primary objective of this study is to analyze the role of tobacco smoke compounds and their ability to damage the cardiovascular system and, in particular, to interfere with blood pressure (Brachial and radial pressure), heart rate and partly on the percentage blood Oxygen saturation. A new device has been manufactured which is unique for measuring the level of smoke, to obtained privies readings, the device had fixed to the first reference level آ and starting up from it. The effect of smoking has been studied on (26) male passive (26) active smoker volunteer, (14) female passive and (14) female active smoker participants. The results has been showed that the blood pressure and heart rate has been increased with increasing the number of cigarettes in both genders for passive and active smokers. However, this effect for male was more pronounced comparing with females for passive and active smokers. In the case of oxygen saturation concentration percentage, for males the change of oxygen concentration percentage was not stable. In other words, it was fluctuated with the number of cigarettes. But for females the oxygen concentration was decreased but not too much. This means that this effect was not pronounced. this study found آ that the most pronounced effect has been shown by male’s comparison to females for both passive and active smokers. As well as in nonsmoker’s males, the relation between heart rate and smoke level is inversely proportional. While in male and female smokers and female nonsmokers the relation is proportional. In all cases the relation between the smoke level and time of smoking is inversely proportional. Finally males& females are affected differently by tobacco use; the sensitivities to smoke for males are higher than in females for passive and active smokers in both brachial and radial blood pressure measurement.

Phase I and Phase II Oxygen Uptake Kinetics During Atrioventricular Dyssynchrony in Chronotropically Competent Pacemaker Patients

CHEST Journal ◽  
2005 ◽  
Vol 128 (3) ◽  
pp. 1782-1789 ◽  
Author(s):  
Corey R. Tomczak ◽  
Wladyslaw Wojcik ◽  
Edward F.G. Busse ◽  
Robert G. Haennel
Keyword(s):  
Oxygen Uptake ◽  
Phase I ◽  
Phase Ii ◽  
Oxygen Uptake Kinetics ◽  
Uptake Kinetics

Kinetics of oxygen uptake at the onset of exercise in boys and men

1998 ◽  
Vol 85 (5) ◽  
pp. 1833-1841 ◽  
Author(s):  
H. Hebestreit ◽  
S. Kriemler ◽  
R. L. Hughson ◽  
O. Bar-Or
Keyword(s):  
Oxygen Uptake ◽  
Phase I ◽  
Heavy Exercise ◽  
Time Constants ◽  
Analysis Phase ◽  
Methods Of Analysis ◽  
S 100 ◽  
Kinetics Of ◽  
Energy Pathways

The objective of this study was to compare the O2 uptake (V˙o 2) kinetics at the onset of heavy exercise in boys and men. Nine boys, aged 9–12 yr, and 8 men, aged 19–27 yr, performed a continuous incremental cycling task to determine peak V˙o 2(V˙o 2 peak). On 2 other days, subjects performed each day four cycling tasks at 80 rpm, each consisting of 2 min of unloaded cycling followed twice by cycling at 50%V˙o 2 peak for 3.5 min, once by cycling at 100%V˙o 2 peak for 2 min, and once by cycling at 130%V˙o 2 peak for 75 s. O2 deficit was not significantly different between boys and men (respectively, 50%V˙o 2 peak task: 6.6 ± 11.1 vs. 5.5 ± 7.3 ml ⋅ min−1 ⋅ kg−1; 100% V˙o 2 peak task: 28.5 ± 8.1 vs. 31.8 ± 6.3 ml ⋅ min−1 ⋅ kg−1; and 130%V˙o 2 peaktask: 30.1 ± 5.7 vs. 35.8 ± 5.3 ml ⋅ min−1 ⋅ kg−1). To assess the kinetics, phase I was excluded from analysis. Phase IIV˙o 2 kinetics could be described in all cases by a monoexponential function. ANOVA revealed no differences in time constants between boys and men (respectively, 50%V˙o 2 peaktask: 22.8 ± 5.1 vs. 26.4 ± 4.1 s; 100%V˙o 2 peak task: 28.0 ± 6.0 vs. 28.1 ± 4.4 s; and 130%V˙o 2 peak task: 19.8 ± 4.1 vs. 20.7 ± 5.7 s). In conclusion, O2 deficit and fast-componentV˙o 2 on-transients are similar in boys and men, even at high exercise intensities, which is in contrast to the findings of other studies employing simpler methods of analysis. The previous interpretation that children rely less on nonoxidative energy pathways at the onset of heavy exercise is not supported by our findings.

THE ROLE OF OXYGEN IN TISSUE MAINTENANCE: MATHEMATICAL MODELING AND QUALITATIVE ANALYSIS

2008 ◽  
Vol 18 (08) ◽  
pp. 1409-1441 ◽  
Author(s):  
AVNER FRIEDMAN ◽  
BEI HU
Keyword(s):  
Mathematical Modeling ◽  
Free Boundary ◽  
Qualitative Analysis ◽  
Phase I ◽  
Stationary Solution ◽  
Oxygen Concentration ◽  
Existence And Uniqueness ◽  
Symmetric Case ◽  
Special Case

The cells in a tissue occupying a region Ωt are divided according to their cycling phase. The density pi of cells in phase i depends on the spatial variable x, the time t, and the time si since the cells entered in phase i. The pi(x, t, si) and the oxygen concentration w(x, t) satisfy a system of PDEs in Ωt, and the boundary of Ωt is a free boundary. We denote by [Formula: see text] the oxygen concentration on the free boundary and consider the radially symmetric case, so that Ωt = {r < R(t)}. We prove that R(t) is always bounded; furthermore, if [Formula: see text] is small, then R(t) → 0 as t → ∞, and if [Formula: see text] is large, then R(t) ≥ c > 0 for all t. Finally, we prove the existence and uniqueness of a stationary solution in a special case.

Large Eddy Simulation of Multiple-Stage Ignition Process of n-Heptane Spray Flame

2019 ◽  
Vol 141 (8) ◽  
Author(s):  
Wanhui Zhao ◽  
Lei Zhou ◽  
Wenjin Qin ◽  
Haiqiao Wei
Keyword(s):  
Oxygen Concentration ◽  
Mixture Fraction ◽  
Ignition Process ◽  
Low Oxygen ◽  
Nonpremixed Combustion ◽  
Eddy Simulation ◽  
Spray Flames ◽  
Large Eddy ◽  
Initial Oxygen ◽  
Oxygen Concentrations

Large eddy simulation of n-heptane spray flames is conducted to investigate the multiple-stage ignition process under extreme (low-temperature, low oxygen, and high-temperature, high-density) conditions. At low oxygen concentrations, the first-stage ignition initiates in the fuel-rich region and then moves to stoichiometric equivalence ratio regions by decreasing the initial temperature. It is also clear that at high temperatures, high oxygen concentrations, or high densities, the reactivity of the mixture is enhanced, where high values of progress variable are observed. Analysis of key intermediate species, including acetylene (C2H2), formaldehyde (CH2O), and hydroxyl (OH) in the mixture fraction and temperature space provides valuable insights into the complex combustion process of the n-heptane spray flames under different initial conditions. The results also suggest that C2H2 appears over a wider range in the mixture fraction space at higher temperature or oxygen concentration condition, implying that it mainly forms at the fuel-rich regions. The initial oxygen concentration of the ambient gas has great influence on the formation and oxidization of C2H2, and the maximum temperature depends on the initial oxygen concentration. OH is mainly formed at the stoichiometric equivalence ratio region, which moves to high-temperature regions very quickly especially at higher oxygen concentrations. Finally, analysis of the premixed and nonpremixed combustion regimes in n-heptane spray flames is also conducted, and both premixed and nonpremixed combustion coexist in spray flames.

scholarly journals The FLASH effect depends on oxygen concentration

2020 ◽  
Vol 93 (1106) ◽  
pp. 20190702 ◽  
Author(s):  
Gabriel Adrian ◽  
Elise Konradsson ◽  
Michael Lempart ◽  
Sven Bäck ◽  
Crister Ceberg ◽  
...  
Keyword(s):  
Oxygen Concentration ◽  
Underlying Mechanism ◽  
Oxygen Depletion ◽  
Therapeutic Window ◽  
High Dose ◽  
Dose Rates ◽  
Conventional Dose ◽  
Oxygen Concentrations

Objective: Recent in vivo results have shown prominent tissue sparing effect of radiotherapy with ultra-high dose rates (FLASH) compared to conventional dose rates (CONV). Oxygen depletion has been proposed as the underlying mechanism, but in vitro data to support this have been lacking. The aim of the current study was to compare FLASH to CONV irradiation under different oxygen concentrations in vitro. Methods: Prostate cancer cells were irradiated at different oxygen concentrations (relative partial pressure ranging between 1.6 and 20%) with a 10 MeV electron beam at a dose rate of either 600 Gy/s (FLASH) or 14 Gy/min (CONV), using a modified clinical linear accelerator. We evaluated the surviving fraction of cells using clonogenic assays after irradiation with doses ranging from 0 to 25 Gy. Results: Under normoxic conditions, no differences between FLASH and CONV irradiation were found. For hypoxic cells (1.6%), the radiation response was similar up to a dose of about 5–10 Gy, above which increased survival was shown for FLASH compared to CONV irradiation. The increased survival was shown to be significant at 18 Gy, and the effect was shown to depend on oxygen concentration. Conclusion: The in vitro FLASH effect depends on oxygen concentration. Further studies to characterize and optimize the use of FLASH in order to widen the therapeutic window are indicated. Advances in knowledge: This paper shows in vitro evidence for the role of oxygen concentration underlying the difference between FLASH and CONV irradiation.

Monitoring of Fish Tank Oxygen Concentration Using a Digital Recorder

1971 ◽  
Vol 28 (8) ◽  
pp. 1196-1197 ◽  
Author(s):  
K. R. Scott
Keyword(s):  
Computer Program ◽  
Oxygen Concentration ◽  
Paper Tape ◽  
Operating Conditions ◽  
Digital Recorder ◽  
Fish Tank ◽  
Oxygen Concentrations

A method for monitoring fish tank oxygen concentrations at 10-min intervals is described. The millivolt output from a temperature-compensated oxygen meter is connected to a clocked digital datalogger system having a perforated paper tape output. Results from two widely different sets of operating conditions are analysed and automatically plotted using a prewritten computer program.

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