NetNotes
T ere are many parts of the instrument that shield you from room temperature interference; general lens bulk, water cooling etc. You are more likely to suff er from magnetic fi eld problems than any other in the modern day environment. My only advice, if you worry about specimen stage stability, is to store the specimen rod in the microscope! In this way the few seconds it will take to change the specimen will hardly change the rod temperature, and by the time you are settled in to record images, the rod will be back at “stage temperature”. I have always thought it to be an operating error to store the specimen rod at room temperature, when it needs to be at specimen stage temperature. Working at very high resolution the most unstable unit in my experience is the specimen rod. Remember it is a directional object so a constant driſt direction will be produced. In the good old days, when we used a round specimen cartridge, the specimen driſt problem was very rare, due to the heat transfer being in all directions rather than one! Steve Chapman protrain@
emcourses.com T u Sep 3 T e eff ect on your system will depend on what you are trying to do with it. If you are using the instrument at moderate magnifi cations and not using STEM or EELS then you won’t see too many problems. T e change in temperature relative to your column and electronics temper- ature will induce alignment as well as specimen driſt , for STEM, HRTEM, EELS, etc. this will cause you to lose performance and have issues with stability over extended periods. You say you have a “powerful” a/c system. T e issue may be it is too powerful. A/C systems are designed to generate a stable temperature by operating continually with a certain load; if the load it too small it will constantly cycle on/off cooling causing the exact problem you have. You can test this by increasing the heat load in the room (say a few bar heaters) and seeing if you get an improvement. Not a very green long term solution but could help you justify a change. Another option is putting computer servers in the room as well, these generate lots of extra load. Another potential problem is the location of the temperature sensor relative to the room airfl ow, if it is directly in line with the output fl ow it could be over cooled, tricking the system into thinking it needs to shut off and on. A “ductsock” on the a/c out will take away any heterogeneous fl ow and minimize this problem. Matthew Weyland
matthew.weyland@monash.edu T u Sep 3
TEM: water condensation problem
I’m seeking advice about water condensate inside the console (column and electronic electronics). It seems that there was a brief power interruption during my 10-day vacation, and there was no alternative person to watch and report this incident. When I returned and entered the lab, I found water all around the fl ooring and console. T e power supply was on, the water chiller was operating, the scope was inactive, and the PC had rebooted. On seeking advice from the support center, I was asked to shut the chiller and cut the power to the machine. T e approach seemed to be to dry out all of the system for two or three days and then attempt to diagnose the resulting damage. Mohammed Yousuf
mdyousuf@qu.edu.qa Mon Sep 7
I do not know if this will help but this is my experience. Twice in my career I have had water pour all over an instrument; one from a bust tap creating a fountain in the microscope room, the other from a fi re on upper fl oors, and the extinguisher water ending up on the microscope. I found that with clean water going all over the microscope, aſt er a week of drying out, we had no problems. With the fi re water damage, waiting the same amount of time one circuit board suff ered, this was due to the contamination of the board by media from the building itself being brought down onto the board
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surface. No matter how much cleaning I tried I could not persuade the board to run. It had to be replaced. So clean water should not be a problem, dirty water probably is! Steve Chapman protrain@
emcourses.com Mon Sep 7
TEM: sampling
An ongoing, hair-pulling dispute between me, the microscopist, and almost every person doing research: “Why did you take so many photomicrographs for each sample? Wouldn’t you say two or three photographs would be just as good as the 5 to 10 you took? I, the investi- gator, still can’t get over you embedding 6 blocks and sectioning all those blocks as semi-things!” How do you handle this scenario? How do you demonstrate that more in EM is actually better? Connie Cummings
ultrapathimaging@gmail.com Tue Sep 15
I draw them pictures (I always draw pictures, as if for a child) of their sample size. For TEM, I draw a cell. Then I draw the nucleus and maybe a few other organelles. Then I draw the object of interest, particularly if they are looking for a virus. Then I draw a line through the cell, representing a 60-80 nm section, which clearly misses any of the object of interest. Then I draw a bunch more parallel lines, representing lots more sections, still missing the object of interest. If it’s a cell pellet, I draw more cells, but show that, unless there are a lot of cells and they are ALL showing the object of interest, my paltry 1 mm×2 mm×60 nm section is going to miss it. If it’s a tissue, same problem, probably worse. Explain sample size. For semi-thins, same problem but at a slightly different scale. I just serial-sectioned a small marine organism for somebody who had a pre-conceived notion of how something worked based on a couple of random sections taken from a paraffin block ages ago. And gave a talk about it. The serial resin sections clearly showed something else was going on altogether, and then the intermittent ultrathins blew it all out of the water. This is why I really encourage investi- gators to come and do their own microscopy, so they have a better idea of the context. If they don’t, I take a zillion micrographs and send them all. I hate just giving them a few select micrographs that may or may not reflect my bias (me, biased?). Tina (Weatherby) Carvalho
tina@pbrc.hawaii.edu Tue Sep 15
If you are digital, the memory for the images is practically free! Any professional photographer these days just shoots gazzilions of pictures. Been to a wedding lately? T e photog just sits there, clicking away. My last vacation, I took 1,354 photos in 2 weeks. Aſt er I got home, I realized it was not enough. Experiments are expensive. Specimen prep is expensive. Once you have the object to photograph, take as many photos as you can! John Mardinly
john.mardinly@asu. edu Tue Sep 15
One word: statistics. If that doesn’t work, ask them what a sample
is. T e cell within which the T ing is hidden? So how many cells need to be sampled? From how many diff erent tissues/organisms because the cells vary among tissues and organisms. T e T ing, because they need to know the T ing’s ultrastructure, which may vary by the local micro-environment? How many T ings from how many diff erent micro-environments need to be sampled? Perhaps it’s the tissue, so how many bits of tissue need to be sampled? Phil Oshel oshel1pe@
cmich.edu Tue Sep 15
Your conversation is so refreshing! Connie loves her prepara- tions and shoots many photos, Tina points at the diverse aspects of each sample and John mentions how easier is to get photos in our digital era. So where is the problem if flooded with photos? Are they not all of them unique snapshots of each sample? Why
www.microscopy-today.com • 2016 January
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