NetNotes


if you’re not careful (shaking the can or not holding it upright, espe- cially when full), the liquid is expelled and can leave residue. Some cans also contain bittering agent! (I always try to pick the ones that don’t, I don’t know about the Newport stuff, try to find an MSDS). I would just clean it with an ethanol swab or tissue. Zdenek Svindrych zdedenn@gmail.com


Stains from compressed air are common, especially if you have


the can upside down when you try to dust. Usually it is some oil leſt over from the manufacturing/packaging process that was dissolved in the r134a while under pressure. I’ve never had trouble cleaning it off of lenses using methanol/lens paper. Remove the filter, get some forceps and lens paper, and wipe it off. Michael Giacomelli mgia- come@ur.rochester.edu


Te main vendors of dichroic mirrors both recommend using


alcohol+lens paper for cleaning: https://www.chroma.com/support/technical-support/cleaning-


handling-and-orientation https://www.semrock.com/cleaning-optical-filters.aspx. Fol-


lowing their recommendations is probably a good idea here. If you want to try more advanced cleaning methods, I would reserve them for when alcohol (or acetone) do not work. Michael Giacomelli mgia- come@ur.rochester.edu


Tank you everyone for your great insights and advice. I will


contact the manufacture to confirm with them how I should pro- ceed with cleaning the mirror. One thing we have in our lab is “First Contact” polymer cleaning kit from Newport (https://www.new- port.com/f/polymer-optic-cleaning-kits). Would you think that this would be safe to use for cleaning dichroic mirrors in general or might this be riskier than directly using solvents like acetone or methanol? Tanks. Steven Hou shou@partners.org


First contact works well if you know how to use it. It takes some


playing around with the layer thickness to get it right. If you don’t know what you are doing you end up with bits of First Contact stuck to your optic. I would start with isopropyl and/or methanol alcohols first, forceps, and a proper optics cleaning tissue. Craig Brideau craig. brideau@gmail.com


Electron Microscopy


Microscopy Listserver Heat Polymerizing LR White Popoffs (Thread Started April 10, 2019) I would like to use LR White resin to popoff a de-paraffinized


tissue section from a slide and then perform immuno labeling for EM. Te problem is that I have not found a good way to heat polym- erize the LR White without introducing air into the BEEM capsule that is upside down on the slide. I have used gelatin capsules with LR white for embedding pieces of tissue and it has worked well but gela- tin capsules will not work upside down on the slide. Te resin flows out. Has anyone attempted this and had success? Gayle Schneider gayle_schneider@urmc.rochester.edu


Two thoughts occur: First, leave the gelatin capsule right-side up, overfill it enough to


get a convex surface, put a thin layer of LR White on the section, just enough to infiltrate the section and exclude air from the tissue, then put the slide on the capsule upside-down (section down). Given the


60


sizes of gelatin capsules and paraffin sections, you should be able to use 3 or 4 capsules and so balance the slide. Better, collect the sections on 22 mm square coverslips. Second, use BEEM capsules but first coat the outside with an


oxygen impermeable coating. Dip the BEEM capsule in an epoxy resin and polymerize, or perhaps (clear) fingernail polish. Overfill the BEEM capsule and mount the sections on the BEEM capsule as above, but aſter getting the section mounted on top of the capsule, invert the capsule so its upside-down on the section, as is usually done. Phil Oshel oshel1pe@cmich.edu


I had to do this once and almost lost my mind….people don’t


laugh. Try it the other way around. Line up the capsules in a holder and fill with LR White to the top until it makes a dome shape above the end of the capsule. Now lay the slide with the tissue downward on top of the capsule. Some LR White will run down but that is Ok. Tis worked for us. Aſter polymerized, carefully cut away the area around the capsule. Lita Duraine duraine@bcm.edu


For me, BEEM capsules deform when LR-White is heat polymer-


ized. Surrounding the tissue with a gasket, then applying a sheet of aclar film over the top might work, aſterwards the hardened resin/ tissue could be glued onto a resin stub. See this paper: “A Novel Technique for Flat-Embedding Cryo-


fixed Plant Specimens in LR White Resin.” Joseph Mowery Joseph. Mowery@ars.usda.gov


Microscopy Listserver LaB6 or CeB6? (Thread Started February 26, 2019) I would like to hear from the pros and cons of the cathode CeB6 in


comparison to the LaB6? Erico Freitas ericotadeu@ufmg.br CeB6 is a little bit more expensive than a LaB6, this would be the


only disadvantage I could think about… It is less sensitive to contami- nation than LaB6, yet you will still need a clean ultra-high vacuum in the gun (although not as low as a FEG). CeB6 has the advantage that it requires a lower evaporation temperature and it has a lower work function (2.7 eV for LaB6 vs 2.4 eV for CeB6). Terefore, you will get a longer lifetime with CeB6 over LaB6, and a slightly better brightness. If you can afford a CeB6, go for it! Julien Allaz julien.allaz@erdw.ethz.ch


I have not used one, but I think it would be quite comparable. I am


used to LaB6 filaments in higher end research microscopes. I have only ever heard of CeB6 in desktop microscopes. CeB6 should be better than tungsten and maybe just a little worse than LaB6. If it is in a desktop microscope, I would be more concerned about the other design details. How is the rest of the column? How does it compare to a regular research microscope? For our service lab, we run a field emitter on an FEI Quanta that is now rated at 1 nm resolution. We routinely push 100kx (based on a 5-inch Polaroid reference). If you based it on the image enlarged to the computer monitor, we would be pushing 300kx. How does that compare to your spec? Warren Straszheim wesaia@iastate.edu


Hi Warren, Tanks for your reply. We have been using a LaB6


emitter in our TEM Tecnai ST20. We have also used Denka and Kim- ball. We had a look at the LaB6 and CeB6 specs and found out that they are pretty much the same, but CeB6 has a lower vapor pressure, perhaps a lower work function, and it might have a longer life. But what puzzled us is that neither Kimball nor Denka produce CeB6 fila- ments, so we were wondering about its quality, though we would like to give it a try. Erico Freitas ericotadeu@ufmg.br


www.microscopy-today.com • 2019 July


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