- When Rontgen discovered a new kind of light, he called it "x-
rays". Now only the Germans call them Rontgen rays.
Thanks for a great essay! Since I have nothing of real value
contribute here, I won't pass over the opportunity to be a
"besserwisser" (as the Swedes say, using a borrowed word...) the
Röntgen moniker has stuck here in northern Europe too: in Swedish:
Röntgenstrålning, in Danish and Norwegian: Røntgenstråling, in Dutch:
Röntgenstraling. Also thanks to Wikipedia, I can inform you that it's
called Röntgengeislun in Icelandic and Röntgensäteily in Finnish.
Eastern Europe seems to have adopted various forms based on "Rentgen",
but I won't pretend I knew that before 5 minutes ago ;-)
Derek
- When the largest protein ever was discovered, it was called
"connectin", but a subsequent paper called it "titin" and the second
name has stuck. I actually can't remember who the "connectin" guy
was ...
- When Joseph Fourier discovered that heat radiated from the earth
could be reflected back by gasses in the atmosphere, he simply named
it by describing it (in French). Now this is (incorrectly) called
the "greenhouse effect". Why not the Fourier effect? Fortunately
for Fourier, a mathematical series was named after him, although he
neither discovered it (Budan did that), nor implemented it (Navier
did that). All Fourier did was present a theorem based on a flawed
premise that turned out to be right anyway.
So, I decided to look up Friedel and Bijvoet in the Undisputed
Source of All Human Knowledge (wikipedia) and found that Friedel's
Law "... is a property of Fourier transforms <http://en.wikipedia.org/wiki/Fourier_transform
> of real functions."
I am willing to believe that. And considering this origin I would
think it appropriate to call (hkl) and (-h-k-l) a "Friedel pair" (or
"Friedel's pair" as it is described in the USAHK). G. Friedel was
indeed a crystallographer, but I doubt he considered more than this
simple centrosymmetric property. Who would care in 1913 which is F+
and F-? The atomic scattering factors had not yet been worked out
at that time. Ewald may have predicted it, but anomalous scattering
was not shown to exist until the classic work of Koster, Knol and
Prins (1930). I guess that goes to show that if you want something
named after you... keep it at one or two authors.
Perhaps it has to do with the original paper getting old enough that
it gets too hard to find. I'm sure in G. Friedel's paper in 1913 he
cited Joseph Fourier's Paper from 1822. Or did he? I wonder if
they were already calling it a Fourier Transform at that time?
Okay, so what, exactly did Bijvoet do? Everyone cites his Nature
paper (1951), but one thing that I was NOT KIDDING about in my April
Fool's joke was that this paper (like so many other high-profile
papers) contains almost no information about how to reproduce the
results. I was also not kidding that boring little details like the
reasoning behind the conclusion (the hand of the microworld) were
relegated to a more obscure journal (the one in the Proc. Royal.
Soc. Amsterdam). I WAS kidding about having found and read that
paper. I have never seen it. Still, Bijvoet did the first
experiment to elucidate the absolute configuration, and he
definitely deserves credit for that.
So, particularly in that light, I would agree that any pair of
reflections that would be equivalent if not for anomalous scattering
effects could be called a "Bijvoet pair". This is because they
contain the information needed to apply Bijvoet's technique.
Something that has always eluded me is who decided which is F+ and
F-? After all, the reciprocal lattice is very very nearly
centrosymmetric. You cannot tell by looking at a single diffraction
image whether that spot at a given X,Y pixel coordinate is F+ or F-,
you need to know the axis convention of the camera. At some point
in writing the CCP4 libraries with their asymmetric unit
definitions, someone must have established a convention. What is
it? To me, the reasoning behind these assignments is, in fact, they
key to assigning the absolute configuration, not the anomalous
scattering effect itself. So, who worked this out? Should we
really be calling them Dodson pairs?
-James Holton
MAD Scientist
