[3dem] 3dem Digest, Vol 94, Issue 5

J Mantell J.Mantell at bristol.ac.uk
Thu Jun 4 00:14:40 PDT 2015


Hi William,

If everything is OK on the fluorescent screen, then it seems the problem is
occurring post screen/pre camera. This may be unrelated but on our system
of FEI T20 and Eagle camera, it is very important to select the post
specimen shutter (ie mechanical and part of camera system), rather than
pre-specimen shutter (extreme gun tilt), when doing room temp tomography.
If the pre-specimen shutter is left on, say after a low dose session, then
I sometimes see this effect that looks like astigmatism and it can even
randomly appear half way through the day, thus looking confusingly like
some charge build up problem. For cryo tomography it is not a problem as
both pre and post shutters are employed.

Regards,

Judith Mantell

*Judith Mantell*

Electron Microscopy Specialist
Wolfson Bioimaging Facility
Faculty of Medical and Veterinary Sciences
Medical Sciences Building
University of Bristol
Bristol. BS8 1TL

0117 3312178

On 3 June 2015 at 20:01, <3dem-request at ncmir.ucsd.edu> wrote:

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> Today's Topics:
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>    1. Image distortion issues (William Nicolas)
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> ----------------------------------------------------------------------
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> Message: 1
> Date: Wed, 3 Jun 2015 19:04:18 +0200
> From: William Nicolas <wjnicolas at hotmail.com>
> To: 3dem at ncmir.ucsd.edu
> Subject: [3dem] Image distortion issues
> Message-ID: <BLU436-SMTP165AF703875DBE82F2C1944A7B40 at phx.gbl>
> Content-Type: text/plain; charset="utf-8"
>
> Hello everyone,
>
> I am actually having trouble with coating my grids with gold particles to
> use as fiducial markers prior to tilt series acquisition.
>
> I usually use outdated secondary antibodies linked to 5nm gold particles
> but it went out. I thus bought a gold particle solution from BBI solution
> and can?t get the parameters straight.
> I tested different concentrations and different ways to put them on my
> grid and have found optimal settings.
>
> The problem is now that I want to use them on 200nm thick HM20 embedded
> sample slices which are deposited on a slot-grid coated with formvar, I
> have  distorted images on the camera BUT not on the fluorescent screen.
> The beads and image seems to be stretched in one direction and it is not
> astigmatism nor sample drifting. I thought of charges building up on the
> surface of the sample, distorting the electrons that are transmitted, maybe
> because of the BBI solutions liquid media?
>
> Do you have a solution to prevent charges from building up on the surface
> of my sample ?
>
> Thanks in advance.
>
> Regards,
>
> William Nicolas, PhD student, CNRS UMR 5200
>
>
>
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> End of 3dem Digest, Vol 94, Issue 5
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