Oxygen gradient

MIC depends on the complex structure of corrosion products and passive films on metal surfaces as well as on the structure of the biofilm. Unfortunately, electrochemical methods have sometimes been used in complex electrolytes, such as microbiological culture media, where the characteristics and properties of passive films and MIC deposits are quite active and not fully understood. It must be kept in mind that microbial colonization of passive metals can drastically change their resistance to film breakdown by causing localized changes in the type, concentration, and thickness of anions, pH, oxygen gradients, and inhibitor levels at the metal surface during the course of a... 

Vary the operating parameters and interpret the results in terms of the axial oxygen gradients in the reactor column. 

For oxidation of iron to occur at high temperatures, the oxygen partial pressure must be above that of the dissociation pressure of the appropriate corrosion products. For example, at ca. 700 °C, an oxygen partial pressure of greater than 10 Pa is required for wiistite to form. In air, of course, this condition is readily satisfied, at least initially. As oxidation continues and the film thickens and becomes coherent, an oxygen gradient across the film is established and the composition of the corrosion layer changes. 

Tramper J. Oxygen gradients in animal-cell bioreactors. In Beuvery EC, ed. Animal Cell Technology. 1995 883-891. 

Realizing that it does not matter whether O2 or CO2 reaches the surface, one can assume, as a first approximation, that a linear oxygen gradient determines the oxygen flux. Since it is not a convective problem, one can write a simplified expression as... 

Wishner, K. F., Gowing, M. M., and Gelfman, C. (1998). Mesozooplankton biomass in the upper 1000 m in the Arabian Sea Overall seasonal and geographic patterns and relationship to oxygen gradients. Deep-Sea Res. II45, 2405—2432. 

Figure 6 Oxygen fluxes determined from benthic lander measurements (X) and calculated from microelectrode oxygen gradients measured in the top few centimeters of pore waters (O) as a function of latitude and depth on the northwest US continental margin. Error bars are the standard deviation of replicate measurements (after Archer and Devol, 1992).

Stamler JS, Jia L, Eu JP, McMahon TJ et al (1997) Blood flow regulation by S-nitrosoheittoglobin in the physiological oxygen gradient Science 276 2034-2037. 

Hypoxemia (alveolar-arterial oxygen gradient >30mmHg on room air saturation <94%) 6/10... 

Fig. 8. Schematic plot of oxygen solubility vs. alloy composition illustrating the source of the oxygen gradient that drives the composite growth rate. From Vlach et al. [41].

It must be noted that, even in the case of similar methods, some details in the procedures employed may lead to significantly different results. For example, the much larger oxygen gradient found by Peimbert et al. (1978) probably results from their using the temperature fluctuation scheme (with t2 =. 035). 

The relative change in dissolved or adsorbed concentration of trace metals due to the flux of particles along a dissolved oxygen gradient, 02-01, may be calculated likewise using K s determined under different oxygen conditions. Thus ... 

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