> "important". The > answer to the last question appears to be "never". The > "background"-subtracted spot intensities really are the square of the > Fourier transform of the AVERAGE electron density in a unit > cell. Yes, > the arithmetic average. Does not matter where the background comes > from. This is another beer I owe Colin.
James, without knowing more about the innards of your random-number generator, it's not clear to me how the random number sequence that you generate simulates the correlated displacements that are responsible for DS, i.e. either between atoms related by lattice translations in adjacent unit cells (-> 'acoustic' DS), or between atoms in pseudo-rigid groups within the same unit cell (-> 'optic' DS), or even correlations between the displacements of electrons on the same atom (-> 'Einstein' DS). Surely the whole purpose of a 'normal' random number generator is to avoid correlations in the generated sequence. Of course, in practice for a sufficiently long sequence of software-generated random numbers it's impossible to avoid correlations, but even then it's extremely unlikely any correlations that are accidentally produced by defects in the algorithm will simulate the physical situation. You would surely have to deliberately design in the correlations to produce meaningful results. Unless you are properly simulating the set of correlated displacements that give rise to DS, it's hardly surprising that you don't see any DS effects in the measured intensities. I think we can take it that DS effects are real! 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
