.AC.UK] On Behalf Of Colin Nave
Sent: 15 May 2013 22:17
To: ccp4bb
Subject: Re: [ccp4bb] Fwd: Re: [ccp4bb] reference for "true multiplicity"?
Times up!
The 3rd case I had in mind was the presence of anisotropy of the anomalous
scattering in the presence of a polarised beam. John Helli
guess it would also apply to Latin) language.
Colin
-Original Message-
From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf Of Colin Nave
Sent: 15 May 2013 10:21
To: ccp4bb
Subject: Re: [ccp4bb] Fwd: Re: [ccp4bb] reference for "true multiplicity"?
Oh – I seemed to ha
The traditional benefit was in reducing absorbtion errors. This obviously
depends on crystal path, and seeing it is hard to model well, one way to
mitigate the errors was to average equivalents collected at different
settings. The error was still there, but assuming random distribution about
the tr
Oh – I seemed to have diverted Frank’s thread.
Fortunately most languages themselves are highly redundant, with following
characters and words being quite predictable. The entropy and redundancy of
English language was analysed by Shannon (with the help of his wife) and he
obtained figures of
One day many years ago, my Ph.D. students all appeared wearing T-shirts
with the logo
"We want more redundancy". They had clearly got the message about how to
do sulfur
SAD phasing, but were completely unaware of the usual meaning of the
word in the UK!
George
--
Prof. George M. Sheldrick FRS
ments
under different conditions, the effect of these systematic errors
will be minimised.
Can anyone suggest other sources of error which would be mitigated
by having different paths through the crystal. I don't think
radiation damage (mentioned by several people) is one.
Colin
From
e) is one.
>
> Colin
>
> From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf Of Frank
> von Delft
> Sent: 14 May 2013 14:23
> To: ccp4bb
> Subject: [ccp4bb] Fwd: Re: [ccp4bb] reference for "true multiplicity"?
>
> George points out that the
Behalf Of Frank von
Delft
Sent: 14 May 2013 14:23
To: ccp4bb
Subject: [ccp4bb] Fwd: Re: [ccp4bb] reference for "true multiplicity"?
George points out that the quote I referred to did not make it to the BB --
here we go, read below and learn, it is a most succinct summary.
phx
--
y having
> different paths through the crystal. I don't think radiation damage
> (mentioned by several people) is one.
>
> Colin
>
> From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf Of Frank
> von Delft
> Sent: 14 May 2013 14:23
> To: ccp4bb
> Subje
Colin wrote:
> Can anyone suggest other sources of error which would be mitigated by having
> different paths through the crystal. I don't think radiation damage
> (mentioned by several people) is one.
Suggestion : any source of error which does not obey the crystal symmetries
will benefit from
K] On Behalf Of Frank von
Delft
Sent: 14 May 2013 14:23
To: ccp4bb
Subject: [ccp4bb] Fwd: Re: [ccp4bb] reference for "true multiplicity"?
George points out that the quote I referred to did not make it to the BB --
here we go, read below and learn, it is a most succinct summary.
phx
--
George points out that the quote I referred to did not make it to the BB
-- here we go, read below and learn, it is a most succinct summary.
phx
Original Message
Subject:Re: [ccp4bb] reference for "true multiplicity"?
Date: Tue, 14 May 2013 09:25:22
"Precision does not trump accuracy" is something Michael Blum told me.
Also Charles Wheelan wrote in his recently published "Naked Statistics": “But
no amount of precision can make up for inaccuracy.”
I myself have been pleasantly surprised at how low multiplicity can be nowadays
and still d
We know that our scaling models do not completely describe and compensate for
all systematic errors, for various reasons including radiation damage (which is
hard to model). This can be seen by scaling together data collected about
different axes, where typically the merging statistics between d
It's not about multiplicity, it's about scaling. See quote I sent
earlier. phx.
On 14/05/2013 10:40, Felix Frolow wrote:
I guess that in a standpoint to reduce errors it is easy to improve
statistical errors by longer counting or by using multiple observations.
However the real enemy at the
I guess that in a standpoint to reduce errors it is easy to improve statistical
errors by longer counting or by using multiple observations.
However the real enemy at the gate is a systematic error which require special
skills and experience to detect and to eliminate.
I never understood why to m
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Hi Frank,
I would not call it 'axiomatic' but 'statistics' to reduce the
(stochastic) error by several independent measurements. You can
probably give any statistics textbook as a reference.
In real life, though, you have to compromise with radiation
Dear Frank,
We did extensive testing of this approach at the beginning of this
millenium - see
Acta Cryst. D59 (2003) 393 and 688 - but never claimed that it was our idea.
Best wishes,
George
On 05/14/2013 06:50 AM, Frank von Delft wrote:
Hi, I'm meant to know this but I'm blanking, so I'll
Hi, I'm meant to know this but I'm blanking, so I'll crowdsource instead:
Anybody know a (the) reference where it was showed that the best SAD
data is obtained by collecting multiple revolutions at different crystal
offsets (kappa settings)? It's axiomatic now (I hope!), but I remember
seeing
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