Oxygen diffusive uptake rates

Average oxygen uptake rate in a hypothetical clump of microbial mass in which diffusion and simultaneous consumption of oxygen takes place is given by... 

Fig. 6.16 Plots of (a) the ratio between diffusive oxygen uptake rates (DOU) ex-situ and in-situ and (b) oxygen penetration depth ex-situ and in-situ versus water depth from stations off the continental slope off Southwest Africa (from Glud et al. 1994). Solid lines indicate linear regressions. With increasing water depth fluxes appear to be overestimated and oxygen penetration underestimated when measured ex-situ.

Comparison of concentration and activity profiles in counter-diffusion (a) and co-diffusion (b) biofilms.The membrane or substratum is located to the left and the bulk liquid to the right.The solid lines, SI and S2, represent substrate concentrations, for example organics (SI) and oxygen (S2).The dashed line shows activity, i.e., substrate uptake rate. 

Table 15) could in part be due to diiferent solubility and hence concentration of the two catalysts. A second point is that the highest rates of oxygen uptake reported (2 7 x 10 ) are near the diffusion-controlled rates. 

It is interesting to observe that also in these cases, cyanide ion depresses the oxidation rates and that the rates of oxygen uptake with these metal complexes exceed in several cases the limiting rate of oxygen diffusion. 

Kupriyanov et al. determined intracellular p02 in cardiac muscle by the balance between its diffusion from vascular to intercellular space and its uptake by mitochondria [52]. They reasoned that cessation of mechanical work decreased O2 demand and should have reduced the O2 gradient between vascular and intercellular spaces. For their research, they compared the effects of arterial p02 on myoglobin (Mb) oxygenation, O2 uptake, and lactate formation rates in beating and KQ-arrested pig hearts. 

When aUcoxysilanes are extensively polymerized or condensed, they form silicones, which are dissolved in organic solvents, and may be used as water repellents (Bosch, 1972). Commercial silicones have been used extensively in materials conservation (Roth, 1988 Molteni, 1987), either pure or combined with other organic polymers such as polyurethanes (Puterman, 1996) or isocyanate prepolymers (Jansen, 1993). Some of their shortcomings involve high oxygen diffusion rates and high water uptake. 

Since the mass uptake corresponds to the oxygen bound to form peroxide rings, it is a direct measure of the chemical stability to the oxidation the maximum oxidation rate depends on the exposed surface area, which supports the conclusion that oxygen diffusion determines the reaction rate [23],... 

Equation (2.19), which concerns a situation without processes in the biofilm, can be extended to include transformation of a substrate, an electron donor (organic matter) or an electron acceptor, e.g., dissolved oxygen. If the reaction rate is limited by j ust one substrate and under steady state conditions, i.e., a fixed concentration profile, the differential equation for the combined transport and substrate utilization following Monod kinetics is shown in Equation (2.20) and is illustrated in Figure 2.8. Equation (2.20) expresses that under steady state conditions, the molecular diffusion determined by Fick s second law is equal to the bacterial uptake of the substrate. 

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