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Slightly off-topic, and I may have recommended these some time ago on the BB (sorry), but we find these toy turtles very useful for explaining symmetry, particularly screw axes which some students have a really hard time visualizing from 2D diagrams: https://www.amazon.com/Fat-Brain-Toys-FA042-1-Reptangles/dp/B00392NSQ4/ref=sr_1_2?ie=UTF8&qid=1549988668&sr=8-2&keywords=reptangles You can assemble an amazing array of symmetries with these things. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Phoebe A. Rice Dept. of Biochem & Mol. Biol. and Committee on Microbiology https://voices.uchicago.edu/phoebericelab/ From: CCP4 bulletin board <[log in to unmask]> on behalf of Marin van Heel <[log in to unmask]> Reply-To: Marin van Heel <[log in to unmask]> Date: Tuesday, March 5, 2019 at 3:28 PM To: "[log in to unmask]" <[log in to unmask]> Subject: Re: [ccp4bb] Purchasing slides with diffraction gratings for teaching diffraction Dear Pietro I have used many different gratings for the purpose over many years... Ones that I found very rewarding are writeable CDs and DVDs. They often come in a pack "protected" by a empty CD / DVD matrix hat is only plastic with grooves and no silver (or whatever the shiny recording material is). Burnig your own CDs DVDs has gone somwhat out of fashion so you may have a problem finding those transparent ones. But if you have a RED/GREEN laser pointer and empty CD / DVDs all kinds of diffraction experiments are possible. Since DVDs are designed for green/blue lasers, the red laser diffraction rapidly goes evanescent on a DVD. On the other hand a green or blue laser on a CD matrix gives you many diffraction orders on white wall in a dark lecture hall. Nylon flags and other woven materials can give excellent diffraction patterns. Great fun! Decades of students at Imperial and other places (www.brazil-school.org<http://www.brazil-school.org>) enjoyed those crystallography/cryo-EM demos! My two cents, Marin On Tue, Mar 5, 2019 at 6:52 AM Roversi, Pietro (Dr.) <[log in to unmask]<mailto:[log in to unmask]>> wrote: Dear all, I'd like to purchase slides with diffraction gratings for educational purposes. Ideally, to be used with a visible-light laser pointer. And: with 1D and 2D patterns, of variable repeats - so as to be able to illustrate the effect on the spacing in reciprocal space, as it were. I am looking online but not having much joy. Can anyone recommend a good provider to purchase from? Thank you! Pietro Pietro Roversi LISCB Wellcome Trust ISSF Fellow https://bit.ly/2I4Wm5Z Leicester Institute of Structural and Chemical Biology Department of Molecular and Cell Biology, University of Leicester Henry Wellcome Building Lancaster Road, Leicester, LE1 7HB England, United Kingdom Tel. +44 (0)116 2297237 ________________________________ To unsubscribe from the CCP4BB list, click the following link: https://www.jiscmail.ac.uk/cgi-bin/webadmin?SUBED1=CCP4BB&A=1 ________________________________ To unsubscribe from the CCP4BB list, click the following link: https://www.jiscmail.ac.uk/cgi-bin/webadmin?SUBED1=CCP4BB&A=1 ######################################################################## To unsubscribe from the CCP4BB list, click the following link: https://www.jiscmail.ac.uk/cgi-bin/webadmin?SUBED1=CCP4BB&A=1