[3dem] [TEM] amplitude contrast

Sacha De Carlo sacha.decarlo at dectris.com
Tue Aug 15 05:29:04 PDT 2017


...thus my statement with a "may provide" instead of "will" (provide
answers to...).

Alright, let's try this again, forward 8 years (2000), Angert et al,
zero-loss (no inelastic scattering) and of course in a practical sense the
ice thickness and size of the aperture DO influence the contrast (for the
same defocus or in-focus image), but I do not recall other papers where it
was quantified methodically (thoroughly)...

Cheers,
Sacha



On Tue, Aug 15, 2017 at 2:22 PM, Philip Koeck <Philip.Koeck at ki.se> wrote:

> Hi Sacha.
>
>
>
> Thanks for the paper.
>
>
>
> I don’t think Wade says very much about the source of amplitude contrast.
> He lists some possible explanations from other publications in section 2
> of the paper,
>
> but to me it sounds a bit like nobody is really sure.
> Therefore Wade and many others just continue with a phenomenological
> description.
>
> I see many open questions:
> If it’s due to scattering outside the aperture, shouldn’t it depend
> strongly on the aperture size?
> If it’s due to multiple scattering, it must depend strongly on specimen
> thickness.
>
> If it’s due to inelastic scattering, why is it so weak (about 10%)?
> Inelastic scattering has a larger cross section than elastic, I believe.
>
>
>
> All the best,
>
>
>
> Philip
>
>
>
>
>
> *Från:* Sacha De Carlo [mailto:sacha.decarlo at dectris.com]
> *Skickat:* den 15 augusti 2017 13:11
> *Till:* Philip Koeck
> *Kopia:* 3dem at ncmir.ucsd.edu
> *Ämne:* Re: [3dem] [TEM] amplitude contrast
>
>
>
> A good reference which may provide you with an answer... I am sure many
> other people will provide more recent studies...
>
>
>
> Enjoy !
>
>
>
> Best,
>
> Sacha
>
>
>
>
>
>
>
> On Tue, Aug 15, 2017 at 12:55 PM, Philip Koeck <Philip.Koeck at ki.se> wrote:
>
> Dear all.
>
>
>
> Is there any agreement on the cause of amplitude contrast when imaging
> proteins in cryo-TEM?
>
>
>
> Is it the second order term in the expansion of a weak phase object or is
> it due to inelastic scattering or the aperture or something else?
>
>
>
> Al the best.
>
>
>
> Philip
>
>
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-- 
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Sacha De Carlo, Ph.D.
Business Development Manager EM
Phone: +41 56 500 21 90 | Mobile: +41 79 354 47 40 | Email:
sacha.decarlo at dectris.com
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