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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.
What is often called a "log reduction" (technically a reduction by one order of magnitude) represents a 90% reduction in microbial population. Thus a process that achieves a "6-log reduction" (10 −6 ) will theoretically reduce an initial population of one million organisms to very close to zero.
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]
The aim of sterilization is the reduction of initially present microorganisms or other potential pathogens. The degree of sterilization is commonly expressed by multiples of the decimal reduction time, or D-value , denoting the time needed to reduce the initial number N 0 {\displaystyle N_{0}} to one tenth ( 10 − 1 {\displaystyle 10^{-1 ...
Specialist companies will often advertise a certain log reduction, e.g., 6-log reduction or 99.9999% effective, instead of sterilization. This takes into consideration a phenomenon known as light and dark repair ( photoreactivation and base excision repair , respectively), in which a cell can repair DNA that has been damaged by UV light.
The formal standard reduction potential ′ can be defined as the measured reduction potential of the half-reaction at unity concentration ratio of the oxidized and reduced species (i.e., when C red / C ox = 1) under given conditions. [3] Indeed:
Serial dilution is one of the core foundational practices of homeopathy, with "succussion", or shaking, occurring between each dilution.In homeopathy, serial dilutions (called potentisation) are often taken so far that by the time the last dilution is completed, no molecules of the original substance are likely to remain.