> -----Original Message----- > From: marc.schi...@epfl.ch [mailto:marc.schi...@epfl.ch] > Sent: 12 January 2009 22:35 > To: Ian Tickle > Cc: CCP4BB@JISCMAIL.AC.UK > Subject: Re: [ccp4bb] structure (factor) amplitude > > Ian Tickle wrote: > > OK, limiting the vote to people whom I think we can assume know what > vaguely they're talking about, i.e. Acta Cryst. / J. Appl. Cryst. > authors, and using the IUCr search engine we get 553 hits for > "structure > amplitude" and 256 for "structure factor amplitude" > > But be warned that not all Acta Cryst. authors give the term > "structure amplitude" the meaning that you think they do, i.e. a > shortcut version for "structure factor amplitude" !
Actually it seems that "structure amplitude" in the |F| sense was historically derived as a shortcut version of "magnitude of the structure amplitude factor", not of "structure factor amplitude" which is obviously derived directly from "structure factor". Similarly "structure factor" was derived as a shortcut version of "structure amplitude factor", but it has now unfortunately acquired at least 2 entirely different meanings as you point out. The term "structure amplitude" clearly goes back a long way, it's much older than "structure factor amplitude", and originally meant something else entirely, as Gerard pointed out, so again we have ambiguous terminology! "Structure factor amplitude" (or maybe "modulus" or "magnitude" would be better to avoid the historical ambiguities surrounding the term "amplitude") has the clear advantage that it is relatively recent terminology and hasn't had time yet to acquire ambiguous meanings, so I would vote for it on that count alone! Cheers -- Ian 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
