Oxygen uptakes

Oxygen uptake measurements can give considerable mechanistic information. In normal peroxyl radical reactions the G(02-uptake) will range between 3 x 10 7 and 6 x 10 7 mol J1 (Table 8.2). The lower value will be found when half of the 02 is reformed (for example, the formate system), the higher value when all 02 is consumed during the decay of the peroxyl radicals. As soon as G(02-uptake) exceeds the upper limit of 6 x 10 7 mol J, a chain reaction must prevail [examples are some polymers including poly(U)]. However, there is also the interesting situation that G(02-uptake) is below 3 x 10 7 mol JThis means that some of the radicals do not react with 02. A case in point are the OH-induced reactions of purines (Chap. 10.3). 

Poly(methyl vinyl ether) 110 Janik etal. (2000) 

Ditto calculated from the above data 3.3 Isildar et al. (1982) 

Because electrode measurements of O2 uptake can detect intra- and extracellular oxidase activity, this assay can be used to measure the respiratory burst elicited by soluble and particulate stimuli. What is somewhat surprising is that, during stimulation of neutrophils with agonists such as fMet-Leu-Phe, the activated O2 uptake profile is biphasic (Fig. 5.11c). A rapid burst of O2 uptake (which coincides with measurements of cytochrome c reduction) is followed by a more sustained activity of lower magnitude. 

By the late 1920s quantitative micro-determination of oxygen uptake had been developed in Warburg s laboratory in Berlin based on a manometric technique introduced by Barcroft and Haldane (1902). With this equipment evolution of carbon dioxide or uptake of oxygen could be monitored Carbon dioxide produced in respiration was absorbed by potassium hydroxide. If bicarbonate buffer was used, acid production caused carbon dioxide to be released. Krebs and others from 

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Now here is a post from a very influential chemist named Spice-boy who has contributed quite a bit to this science (hypothetically of course). She decided to go ahead and apply the idea of using benzoquinone as the oxygen source. If this works it would mean that one would not have to use a balloon of O2 at all. thus making the entire apparatus much more simpler and causing an increase in the efficiency of oxygen uptake and transfer by the system. So let s see what Spiceboy dreamt might happen if this were actually applied ... 

Fig. 1. The relationship between rate of oxygen uptake and dissolved oxygen, concentration where is the critical oxygen concentration.

As the oxygen uptake or F/M iacreases, the dissolved oxygen must be iacreased to provide sufficient driving force to penetrate the floe. Minimum concentrations of nitrogen and phosphoms are necessary in the effluent. 

The synergistic effect of a hydroperoxide decomposer, eg, dilauryl thiodipropionate [123-28-4] (34), and a radical scavenger, eg, tetrakis[methylene(3,5-di-/ f2 butyl-4-hydroxyhydrocinnamate)]methane (9), ia protecting polypropylene duting an oxygen-uptake test at 140°C is shown ia Table 3. 

Since oxygen uptake is tested in a closed system, loss of volatilization is minimal. This type of test is not reUable for estimating service life under conditions in which the polymer is exposed to air movement. 

Finally, candidate lubricants containing the antioxidants are tested in fleets of automobiles for thousands of miles. The engines are dismantled and examined for wear and coatings of varnish and other deposits. The lubricant is evaluated for sludge, viscosity, acidity, etc. Since evaluation in automobiles is expensive and time-consuming it is reserved for only the most promising candidates. Oxygen uptake tests are also used to measure oxidative stabiUty (28). 

A.ctive driers promote oxygen uptake, peroxide formation, and peroxide decomposition. At an elevated temperature several other metals display this catalytic activity but are ineffective at ambient temperature. Active driers include cobalt, manganese, iron, cerium, vanadium, and lead. 

A plot of the specific respiration rate ( 02 versus the specific growth rate coefficient [L is linear, with the intercept on the ordinate equal to the oxygen uptake rate for cell maintenance. A formulation of this is ... 

As the oxygen transfer rate under steady-state conditions must equal oxygen uptake, K a may be calculated ... 

A useful index of process performance is the oxygen uptake rate, OUR, that is calculated from the difference in oxygen concentration of the inlet air and the exiting gas. Also important is the respiration ratio defined as the carbon dioxide evolved divided by the oxygen consumed. 

Decline (linear with increasing CoHb level) in maximal oxygen uptake of healthy young men undergoing strenuous exercise decrements in visual perception, manual dexterity, and performance of complex sensorimotor tasks... 

Figure 7.4. Schematic relationship showing effect of pro-oxidants, antioxidants and oxidation retarders on the oxygen uptake of a polymer...

The shape of the curves is of some interest. An induction period is noted during which no oxygen uptake, i.e. oxidation, is observed. At the end of this induction period, when in effect antioxidant moieties have been consumed, oxygen uptake is rapid unless some retardation mechanism is at work. 

Table 10.8 Comparison oE antioxidants in polyethylene in both the absence and presence of copper powder and carbon black (data based on ICI literature). Induction time assessed from oxygen uptake measurements using a Barcroft manometer...

Polypropylene differs from polyethylene in its chemical reactivity because of the presence of tertiary carbon atoms occurring alternately on the chain backbone. Of particular significance is the susceptibility of the polymer to oxidation at elevated temperatures. Some estimate of the difference between the two polymers can be obtained from Figure 1J.7, which compares- the rates of oxygen uptake of eaeh polymer at 93°C. Substantial improvements can be made by the inclusion of antioxidants and such additives are used in all commercial compounds. Whereas polyethylene cross-links on oxidation, polypropylene degrades to form lower molecular weight products. Similar effects are noted... 

Livingston, A.G., Gikas, P., Viability of immobilised cells use of specific ATP levels and oxygen uptake rates.. Immobilised Cells Basics and Applications, Ed. Wijfells, R.H., Buitelaar, R.M., Bucke, C., Tramper, J., Progess in Biotech. 11, pp.264-271, 1996. 

Oxygen uptake rate (OUR) The actual rate at which oxygen utilization takes place and is given by ( o/Yo2) C, , where p is specific growth... 

Oxygen uptake Rate of oxygen transfer from air resident in the pulmonary... 

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