Thanks Gerard for all those explanations, I'm particularly convinced by
the last one.
Poor of me, who believed that the "B" stood for Boltzman or something
like that, I now have the correct answer!
Cheers
Virgile
Gerard DVD Kleywegt a écrit :
May be too trivial, I was just wondering
what "B" stands for in the term "B-factor".
i don't really know, but i do have some wild theories, none of which
are necessarily based in fact:
- the B-factor is also called the Debye-Waller factor. now, someone
assumed that peter debye was french (instead of dutch) and that his
name should be written "de Bye"; hence the B as the "first" letter in
his name (something similar happened to monsieur luzzati whose
oft-abused 1952 paper is headed "Par V. Luzzati" which probably led
some people to believe he was swedish and that "Par" was his first
name. once "P.V. Luzzati" made it into the x-plor manual (e.g.,
http://nmr.cit.nih.gov/xplor-nih/xplorMan/node484.html) mis-citations
of this kind mushroomed, mostly by people who couldn't read the
original paper because it was in french, in which language "par" means
(written) "by")
- there was a lot of buzz when the concept was first introduced which
led to associations with bees; hence "bee-factor" or, shortened,
"B-factor"
- they wanted to call it "A-factor" first, but realised that the A
could be mistaken for the indefinite article which they definitively
didn't want. i mean, how cool is "a factor" ? hence the B-factor
- the name follows the same path as that of the programming language
"C" (which was simply the third version of a draft, where the earlier
versions had been called "A" and "B"), but they got it right in only
two tries. the first draft ("A-factor") was correct down to a factor
of pi. once the bug had been removed, the second version (that we
still use today) was called the "B-factor"
- around 1920, there was a heated debate as to whether or not a
thermal factor was really necessary or merely a modernistic luxury.
this discussion was held in the carrier-pigeon-based predecessor of
the ccp4 bulletin board (little-known fact: a lot of carrier pigeons
had been bred by the british for communication duties during world war
I and they found good jobs after the war in operating various bulletin
boards) where a classically trained crystallographer semi-facetiously
titled the thread "thermal factors - to be or not to be ?". When the
debate subsided and the need for a new factor was agreed upon, it was
only logical to call it the "B-factor" (actually, it was first called
the "2B-factor" which differed from the modern B-factor by a factor of
2, but this was deemed too confusing)
- the name "B-factor" was first coined by george sheldrick. by
coincidence, he had just exhausted all the possible Fortran variable
names starting with A (A, A1, A2, A3, ...) when he was about to
implement isotropic thermal factor refinement in SHELX53. so the
logical (and bold, if painful) step george took was to make this
parameter the first in a (for him) whole new universe of Fortran
variable names: B
- it was invented by sacha baron cohen's great-grandfather. indeed,
"B-factor" is an anagram of "Borat FC" ("fc" meaning "football club")
i'm sure other ccp4bb-ers can come up with better explanations
--dvd
******************************************************************
Gerard J. Kleywegt
[Research Fellow of the Royal Swedish Academy of Sciences]
Dept. of Cell & Molecular Biology University of Uppsala
Biomedical Centre Box 596
SE-751 24 Uppsala SWEDEN
http://xray.bmc.uu.se/gerard/ mailto:[EMAIL PROTECTED]
******************************************************************
The opinions in this message are fictional. Any similarity
to actual opinions, living or dead, is purely coincidental.
******************************************************************
begin:vcard
fn:Virgile ADAM
n:ADAM;Virgile
org:European Synchrotron Radiation Facility;Macromolecular Crystallography Group
adr:BP 220;;6, rue Jules Horowitz;Grenoble CEDEX 9;;38043;FRANCE
email;internet:[EMAIL PROTECTED]
title:Cryobench team
tel;work:+33-(0)4-76-88-27-72
tel;fax:+33 (0)4-76-88-26-24
url:http://www.esrf.fr/UsersAndScience/Experiments/MX/Cryobench/
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end:vcard
