Effect Oxygen uptake

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. 

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. 

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... 

Probably the most comprehensive measurements of the effect of voids on rates are those of Cohen "" and his school. They have published data on the oxidation of pure irons for a wide temperature range and for oxygen pressures ranging from 1-3 x 10 "N/m to lOOkN/m. The interactions between void formation and oxygen uptake are complex but only at pressures below 1 3 X 10 N/m do voids have no effect. Some of their results are summarised in Fig. 1.85 over the pressure range 1-3 x 10 N/m to... 

In OIT determinations, the test samples are flushed continuously with oxygen during the course of the measurement [1], This is in contrast to oxygen-uptake measurements that are mostly undertaken in a static oxygen atmosphere (see below). Effects such as dynamic removal of volatile antioxidants in the OIT method can lead to these two methods yielding very different assessments of a polymer formulation s stability [1]. 

The observation of an unusual effect occurring as a consequence of preannealing on the induction time of oxidation of PP stabilized with Irganox 1010 (Figures 19 and 20) needs to be taken into account when searching for correlations between induction periods from chemiluminescence and oxygen uptake for oxidation of PP stabilized with different types of antioxidants. 

It is thought that during fast movement, the pH at the gills may drop too low for efficient oxygen uptake by those hemoglobins that exhibit the Root effect. To ensure a continued oxygen supply, trout and some... 

Freebaim, H. T. Reversal of inhibitory effects of ozone on oxygen uptake of mitochondria. Science 126 303-304, 1957. 

Nobel and Wang reported that the permeability of the outer membranes of chloroplasts was increased by exposure to ozone (at 30 ppm for 5 min). They hypothesized that the effect was lipid oxidation. Freebaim showed that ozone inhibited respiratory activities of isolated mitochondria, and Lee found that the effect of ozone on oxidative phosphorylation was greater than on oxygen uptake. Mudd et reported that the metabolism of UDP-galactose by isolated... 

Figure 2.5 A plot of oxygen uptake after two meals in young adult males. The vertical bars indicate the meal times. The measurements were carried out after physical activity which exaggerates the effect of the meal. The meal was high in carbohydrate.

J. R. Harbour, R. Wolkow and M. L. Hair. (1981) Effect of platinization on the photoproperties of cadmium sulfide pigments in dispersion. Determination by hydrogen evolution, oxygen uptake and electron spin resonance spectroscopy. J Phys Chem 85 4026-4029... 

These optical probes are the most universally applicable in situ devices for on-line biomass monitoring up to now [15,16]. Konstaninov et al. [17] tested several absorbance and scattering sensors for real-time biomass concentration monitoring in mammalian cell cultivation processes and Hatch and Veilleux [18] compared optical density probes with oxygen uptake rates, packed cell volume, and off-line cell mass monitoring in commercial fed-batch fermentations of Saccharomyces cerevisiae [19]. In order to minimize influencing effects, special chemometric data treatment is necessary [20]. 

Mecfianism of Action A cinchona alkaloid that relaxes skeletal muscle by increasing the refractory period, decreasing excitability of motor end plates (curare-like), and affecting distribution of calcium with muscle fiber. Antimalaria Depresses oxygen uptake, carbohydrate metabolism, elevates pH in intracellular organelles of parasites. Therapeutic Effect Relaxes skeletal muscle produces parasite death. Pharmacokinetics Rapidly absorbed mainly from upper small intestine. Protein binding 70%-95%. Metabolized in liver. Excreted in feces, saliva, and urine. Half-life 8-14 hr (adults), 6-12 hr (children). 

The answer is d. (Hardman, p 1019.) Niclosamide is a halogenated salicylanilide derivative. It exerts its effect against cestodes by inhibition of mitochondrial oxidative phosphorylation in the parasites. The mechanism of action is also related to its inhibition of glucose and oxygen uptake in the parasite. 

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