Gerard,
You are absolutely right. My apology for the confusion. Keep on
reading, looks like that James called |F| "geometrical structure
factor", which probably is not commonly used anymore.
-- Jianghai
On Jan 12, 2009, at 1:45 PM, Gerard Bricogne wrote:
Dear Jacob and Jianghai,
The trouble with this "King James version" is that what he calls
the
"structure amplitude" A is the amplitude of the scattered
electromagnetic
wave! If you look at equation (2.3) on p.27, the expression for A is
first
of all complex (!), and refers for each atom to its "scattering
power",
denoted phi[j]. This phi[j] is subsequently expressed in equation
(2.11) in
terms of some physical constants, of the squared atomic form factor,
and of
the polarisation factor, allowing A to be written in terms of the
"structure
factor" F defined in the familiar manner and of these other factors.
Therefore, what Ewald and James call the "structure amplitude"
is NOT
AT ALL the amplitude (or modulus) of the structure factor, and
therefore
these venerable authors cannot be brought into the debate in this way!
With best wishes,
Gerard.
--
On Mon, Jan 12, 2009 at 12:58:27PM -0500, Jianghai Zhu wrote:
JPK beats me on this one. Here is the quote from R. W. James, "The
Optical
Principles of the Diffraction of X-rays".
"We shall call A the 'structure amplitude', a name introduced by
Ewald, to
denote the fact that its value depends essentially on the structure
of the
group associated with each lattice-point. It is the amplitude, at
unit
distance, of the wave scattered by the unit group of s points."
-- Jianghai
++++++++++++++++++++
Jianghai Zhu, PhD
Immune Disease Institute
Dept. of Pathology
Harvard Medical School
3 Blackfan Circle, CLSB
Boston, MA 02115
Tel: 617-713-8224
Fax: 617-713-8232
++++++++++++++++++++
On Jan 12, 2009, at 12:43 PM, Jacob Keller wrote:
[King?] James says "structure amplitude."
(1950 ed., Ch II, 1a (p27))
JPK
*******************************************
Jacob Pearson Keller
Northwestern University
Medical Scientist Training Program
Dallos Laboratory
F. Searle 1-240
2240 Campus Drive
Evanston IL 60208
lab: 847.491.2438
cel: 773.608.9185
email: j-kell...@northwestern.edu
*******************************************
----- Original Message ----- From: "Ethan Merritt"
<merr...@u.washington.edu>
To: <CCP4BB@JISCMAIL.AC.UK>
Sent: Monday, January 12, 2009 10:59 AM
Subject: Re: [ccp4bb] structure (factor) amplitude
On Monday 12 January 2009 02:42:43 Ian Tickle wrote:
Also I did a 'Google vote' for the two terms. 'Structure
amplitude' has
11300 hits. 'Structure factor amplitude' has only 4750. So all
round I
would say that 'structure amplitude' wins by a considerable
margin.
The field of crystagooglography is relatively young,
and standard procedures have not yet been established :-)
Here's what I get:
+"structure factor amplitude" 18,000 hits
+"structure amplitude" 17,100 hits
Ethan
Cheers
-- Ian
-----Original Message-----
From: owner-ccp...@jiscmail.ac.uk
[mailto:owner-ccp...@jiscmail.ac.uk] On Behalf Of Pavel Afonine
Sent: 11 January 2009 03:01
To: Ethan A Merritt
Cc: CCP4BB@jiscmail.ac.uk
Subject: Re: [ccp4bb] structure (factor) amplitude
On 1/10/2009 5:14 PM, Ethan A Merritt wrote:
On Saturday 10 January 2009, Bernhard Rupp wrote:
Dear All,
I am getting conflicting comments on the use of
'structure factor amplitude'
vs. just
'structure amplitude'
for |F|.
???
That's just... odd.
|F| is the amplitude of F.
But no way F is a "structure".
I agree. If F is a structure factor then |F| is a structure
factor amplitude. "structure amplitude" doesn't make much
sense...
Pavel.
Disclaimer
This communication is confidential and may contain privileged
information intended solely for the named addressee(s). It may
not be
used or disclosed except for the purpose for which it has been
sent. If
you are not the intended recipient you must not review, use,
disclose,
copy, distribute or take any action in reliance upon it. If you
have
received this communication in error, please notify Astex
Therapeutics
Ltd by emailing i.tic...@astex-therapeutics.com and destroy all
copies
of the message and any attached documents.
Astex Therapeutics Ltd monitors, controls and protects all its
messaging
traffic in compliance with its corporate email policy. The Company
accepts no liability or responsibility for any onward
transmission or
use of emails and attachments having left the Astex Therapeutics
domain.
Unless expressly stated, opinions in this message are those of the
individual sender and not of Astex Therapeutics Ltd. The recipient
should check this email and any attachments for the presence of
computer
viruses. Astex Therapeutics Ltd accepts no liability for damage
caused
by any virus transmitted by this email. E-mail is susceptible to
data
corruption, interception, unauthorized amendment, and tampering,
Astex
Therapeutics Ltd only send and receive e-mails on the basis that
the
Company is not liable for any such alteration or any consequences
thereof.
Astex Therapeutics Ltd., Registered in England at 436 Cambridge
Science
Park, Cambridge CB4 0QA under number 3751674
--
Ethan A Merritt
Biomolecular Structure Center
University of Washington, Seattle 98195-7742
--
===============================================================
* *
* Gerard Bricogne g...@globalphasing.com *
* *
* Global Phasing Ltd. *
* Sheraton House, Castle Park Tel: +44-(0)1223-353033 *
* Cambridge CB3 0AX, UK Fax: +44-(0)1223-366889 *
* *
===============================================================
