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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.
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]
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.
The difference in meaning between this and the probabilistic sense can be seen from an example: if careful assays before and after indicate that a procedure has inactivated 90% of the biological agents in some unit, then the procedure can be correctly reported to have achieved a 1-log reduction, even though the probability that the unit is ...
The calcium carbonate heals the concrete by solidifying on the cracked concrete surface, mimicking the process by which bone fractures in human body are healed by osteoblast cells that mineralize to reform the bone. [36] Two methods are currently being studied: injection of calcium carbonate precipitating bacteria.
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.
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.
For example, the bacterial species Paracoccus denitrificans engages in denitrification under both oxic and anoxic conditions simultaneously. Upon oxygen exposure, the bacteria is able to utilize nitrous oxide reductase, an enzyme that catalyzes the last step of denitrification. [15]