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Logarithm

Logarithm

(Science: mathematics) One of a class of auxiliary numbers, devised by john napier, of Merchiston, Scotland (1550-1617), to abridge arithmetical calculations, by the use of addition and subtraction in Place of multiplication and division.

The relation of logarithms to common numbers is that of numbers in an arithmetical series to corresponding numbers in a geometrical series, so that sums and differences of the former indicate respectively products and quotients of the latter; thus 0 1 2 3 4 indices or logarithms 1 10 100 1000 10,000 numbers in geometrical progression Hence, the logarithm of any given number is the exponent of a power to which another given invariable number, called the base, must be raised in order to produce that given number. Thus, let 10 be the base, then 2 is the logarithm of 100, because 10^2 = 100, and 3 is the logarithm of 1,000, because 10^3 = 1,000. Arithmetical complement of a logarithm, the difference between a logarithm and the number ten. Binary logarithms. See binary. Common logarithms, or Brigg's logarithms, logarithms of which the base is 10; so called from henry Briggs, who invented them. Gauss's logarithms, tables of logarithms constructed for facilitating the operation of finding the logarithm of the sum of difference of two quantities from the logarithms of the quantities, one entry of those tables and two additions or subtractions answering the purpose of three entries of the common tables and one addition or subtraction. They were suggested by the celebrated german mathematician Karl Friedrich gauss (died in 1855), and are of great service in many astronomical computations. Hyperbolic, or Napierian, logarithms, those logarithms (devised by john Speidell, 1619) of which the base is 2.7182818; so called from napier, the inventor of logarithms. Logistic or Proportionallogarithms.

Origin: gr. Word, account, proportion _ number: cf. F. Logarithme.


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ratio of product / reactant

Log is a logarithm: explanation in wikipedia: http://en.wikipedia.org/wiki/Logarithm basic maths skills are useful in biology, you know?

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by canalon
Thu Jan 20, 2011 11:52 pm
 
Forum: Molecular Biology
Topic: ratio of product / reactant
Replies: 3
Views: 3193

change in free energy equation

LOG is a mathematical operation. In this case it is the Decimal logarithm (sometimes abbreviated as Log10), not the natural logarithm (generally abbreviated as Ln). It means that 10^(-0.5501)=0.2818 It is quite hard to calculate in your head, or even on ...

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by canalon
Thu Jan 20, 2011 11:48 pm
 
Forum: Molecular Biology
Topic: change in free energy equation
Replies: 1
Views: 1342

ratio of product / reactant

LOL, that's all what you need? Just convert logarithm to normal number? log (10^x) = x ^ here means power, so you can have like: log 100 = log (10^2) = 2 pretty simple, isn't it? (of course, this is decimal logarithm, but the basis can be any)

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by JackBean
Thu Jan 20, 2011 7:30 pm
 
Forum: Molecular Biology
Topic: ratio of product / reactant
Replies: 3
Views: 3193

Doubling time for cells

... : c1 Let them grow during h hours Count them again : c2 The doubling time(in hours)=h*ln(2)/ln(c2/c1) You can use decimal or neperien logarithm. You can use this formula to forcast the cell expension or to calculate the volume to split to get a target concentration after a period of ...

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by snoopline
Fri Nov 10, 2006 1:25 am
 
Forum: Cell Biology
Topic: Doubling time for cells
Replies: 9
Views: 42978

Finding RF?

the distance a molecule travels in a gel is inversely proportional to the logarithm of the molecular weight. --> so you can plot a curve where distance is set out against the logarithm of the molecular weigth and you will get a straight line.

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by sdekivit
Thu Dec 15, 2005 7:58 am
 
Forum: Molecular Biology
Topic: Finding RF?
Replies: 2
Views: 1681


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