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Log reduction is a measure of how thoroughly a decontamination process reduces the concentration of a contaminant. It is defined as the common logarithm of the ratio of the levels of contamination before and after the process, so an increment of 1 corresponds to a reduction in concentration by a factor of 10.
Biogenic sulfide corrosion is a bacterially mediated process of forming hydrogen sulfide gas and the subsequent conversion to sulfuric acid that attacks concrete and steel within wastewater environments. The hydrogen sulfide gas is biochemically oxidized in the presence of moisture to form sulfuric acid.
Z-value is a term used in microbial thermal death time calculations. It is the number of degrees the temperature has to be increased to achieve a tenfold (i.e. 1 log 10 ) reduction in the D-value . The D-value of an organism is the time required in a given medium, at a given temperature, for a ten-fold reduction in the number of organisms.
In microbiology, in the context of a sterilization procedure, the D-value or decimal reduction time (or decimal reduction dose) is the time (or dose of an antimicrobial drug) required, at a given condition (e.g. temperature) or set of conditions, to achieve a one-log reduction, that is, to kill 90% of relevant microorganisms. [1]
In 90 days, exposure to the fungus resulted in a mass reduction of 7.2% in the concrete. Aspergillus niger was the second worst offender out of the three, followed by Fusarium, which can lower the mass of concrete by 6.2 grams in a single year, as well as cause the pH to down from 12 to 8 in the same time frame. [6]
2, portlandite) produced by Portland cement hydration in concrete to form calcium carbonate (CaCO 3) while releasing a water molecule in the following reaction: CO 2 + Ca(OH) 2 → CaCO 3 + H 2 O. Exception made of the water molecule, the carbonation reaction is essentially the reverse of the process of calcination of limestone taking place in ...
The initiation time is related to the rate at which carbonation propagates in the concrete cover thickness.Once that carbonation reaches the steel surface, altering the local pH value of the environment, the protective thin film of oxides on the steel surface becomes instable, and corrosion initiates involving an extended portion of the steel surface.
Heat is applied by baking in a dry heat oven that is designed specifically for the depyrogenation process. Although endotoxins are relatively thermally stable, sufficient heating (250 °C for 30 min) results in a 3-log reduction of endotoxin levels. Due to the high temperature levels, this method is also not suitable when purifying proteins.