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myosin on sperm-cell-associated membranes of tobacco ( Nicotiana tabacum L.) - https://link.springer.com/article/10.1007/BF01279082 5. As Jan suggested, control is critical! Zhaojie Zhang zzhang@uwyo. edu T u Mar 23


LM:


need 700-800 nm excitation for Zeiss AxioObserver We need to excite in the 700 to 800 nm range and the Zeiss HPX-120 lamp we have is fi ltered to block wavelengths above 660 nm. Rather than customize the fi lter inside the lamp house, we are looking for an alternative light source for the 700-800 nm range with a liquid light guide or fi ber that we could swap for the Zeiss HPX-120 on the days we need to image infra-red. Are there any simple light sources that fi t this description that cost less than $3k? If not, how about ones that don’t cost much more than this? Michael Cammer michael.cammer@ med.nyu.edu Tue Apr 18


I’d say it depends on how stable you want the line (frequency)


to be. CD-ROM lasers are 780 nm, and super cheap thanks to economies of scale. Getting one coupled to the fi ber of your choice would then be your challenge. Nathan McCorkle nmz787@gmail. com Tue Apr 18


HR-TEM: good reference text


I’m struggling with Williams and Carter (2nd edition, I think) understanding HRTEM. I generally fi nd their text approachable and easy to read, but not the HRTEM material, other than the math. Is there a text or article that is more detailed? Outside of the supposedly HRTEM sources that I have found have lengthy introductions to the basic, non-HR microscope, then brief descriptions of the math of HRTEM. What is a good read? I am a microscopist, with a B.S., so technical is okay, but I want a deep focus on HRTEM, theory and instrumentation. Kleo (Kathleen) Pullin kleopullin@email.arizona. edu Tue Apr 18


Check out the Oxford text: High Resolution Electron Microscopy by Spence. A close second and less graduate-level math is found in Transmission Electron Microscopy and Diff ractory Materials by Fultz and Howe (Springer). You are looking for a discussion of “Pendellosung,” page 631, Fultz and Howe. To explain it to students at U of O that I taught, I built a coupled pendulum, where the one pendulum represents the non-diff racted beam and the other is the Bragg refl ected beam. T e coupling represents the lattice. T e pendulum will stop and start, and that time can represent thickness of the sample. And so white spots in HRTEM, nodes, could be channels between atoms or atoms depending on how thick the sample is (how much time the pendulum swings). Pete Eschbach peter.eschbach@ comcast.net T u Apr 20


SEM: LaB 6 emitters for EDS and WDS


A friend of mine is interested in buying a SEM with a LaB 6 emitter for imaging and, above all, analytical applications: EDS and WDS. However, he was told that LaB 6 emitters are not a good choice for analytical applications in a SEM, mainly due to stability issues, which— if I got it correctly—would require a long wait time before reliable spectra could be acquired. I have no experience with such a machine, so I cannot advise him about this. Maybe some of you can help me. Davide Cristofori dcristofori@unive.it Fri Mar 3 I know of no problems with LaB 6 emitters with regard to stability, provided that the vacuum level in the electron gun is suitable for their use. Could you be confusing the instability problem with cold fi eld emitter instruments, where their natural emission is prone to early


68


and late instabilities during long operating sessions? Steve Chapman protrain@emcourses.com Sat Mar 4 LaB 6 emitters are unanimously considered stable, yet some of you pointed out that the fi lament has to be kept heated in order to assure a stable emission, even when not working, e.g. overnight. I would like to fi gure out how common this approach is, and what the life of LaB 6 emitters are which are operated in this way. It would also be very interesting and useful to know your experience about this point, if you want to share it. Davide Cristofori dcristofori@unive.it Fri Mar 10


Compare FEI 12T and FEI Quanta 400 ESEM, both tungsten emitters (exchangeable). Quanta 400 ESEM has average life = 60-80 hr. When Quanta vented to change specimen, entire column is vented with air (could be better with N 2 , but not oſt en). Tecnai 12T (120kV) has average life = 1000 hr. When you change specimen (single tilt), current condition of fi lament is maintained until vacuum in specimen chamber has recovered. Quanta fi lament is OFF overnight. Tecnai fi lament is under low current and minimum vacuum pressure 24/7 (10 -8 with no break in vacuum in life). Fred Monson fmonson@wcupa. edu Fri Mar 10 LaB 6 emitters, like any other source, outgas when fi rst heated and may then be unstable. A way of getting round this is to run the fi lament at a very low current, just to keep it warm, even if the instrument is not being used. I do not know if they do it now, but JEOL with LaB 6 systems set the fi lament heating at half value when you “turned it off ”. At very low emission there is no source evaporation, so the fi lament life does not suff er. Steve Chapman protrain@emcourses.com Fri Mar 10


To sum up the results of my little survey: it came out that keeping


the LaB 6 fi lament heated, even not at a full range, is quite the standard approach for this emitters. Davide Cristofori dcristofori@unive.it Mon Mar 20


SEM:


Need help in understanding loss of image generation Our Hitachi S-2700 SEM will no longer produce an image. We can only see a series of vertical lines of varying intensity with both secondary electron and backscatter detectors. We do have an electron beam - there are changes in intensity of the vertical lines during adjustment of fi lament current, beam tilt, beam horizon, changes in the lines if we move the specimen. We do lose the image if the HV is turned off on the secondary electron detector. A very similar pattern is seen with the backscatter detector, so it does not appear to be a detector issue. We have exchanged circuit boards and even the entire column (!) from a second identical scope used for parts. A commercial technician was unable to correct the problem. His best guess is that one or more of the lenses are not functioning. Any suggestions as to what the problem is? I can send images off -line. Jeff rey T ompson jthompso@csusb.edu T u Mar 2 Please feel free to send or post images to look at, but most likely, you have a simple defl ection problem. Remember that in SEM lenses are only used to form the beam, but magnifi cation (and formation of image) comes from ratio between area physically scanned by electron beam on surface of the sample and area of the CRT screen (or digital image) representing the image. If you see only vertical lines then chances are that primary electron beam is not scanned in Y direction over the sample, so in every line of image you are seeing information from the same exact line physically scanned by electron beam on the sample. Find a local tech who knows how to use oscilloscope and able to fi gure out amplifi ers driving inductive loads (scan coils). Valery Ray vray@partbeamsystech.com T u Mar 2 I agree with Valery, a defl ection circuit is faulty. A defl ection problem is also possible from the screen circuit. T is can be check by


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