This is absolutely correct. Radian is in fact just another symbol for 1.
Thus : 1 rad = 1
From the official SI documentation
(http://www.bipm.org/en/si/si_brochure)(section 2.2 - table 3) :
The radian and steradian are special names for the number one that
may be used to convey information
James Holton wrote:
No No No! This is not what I meant at all!
I am not suggesting the creation of a new unit, but rather that we name
a unit that is already in widespread use. This unit is A^2/(8*pi^2)
which has dimensions of length^2 and it IS the unit of B factor. That
is, every PDB file
On Sun, 2009-11-22 at 23:33 -0800, Dale Tronrud wrote:
I could be describing my angle as
1.5 radians, 1.5 degrees, or 1.5 cycles (or 1.5 of the mysterious
grad on my calculator).
I thought that use of degrees is based on dividing a circle into 360
parts - roughly one per day (then in
...@jiscmail.ac.uk] On Behalf Of Ian
Tickle
Sent: Sunday, November 22, 2009 10:57 AM
To: CCP4BB@JISCMAIL.AC.UK
Subject: Re: [ccp4bb] units of the B factor
Back to the original problem: what are the units of B and
u_x^2? I haven't been able to work that out. The first
wack is to say the B occurs
: Re: [ccp4bb] units of the B factor
Back to the original problem: what are the units of B and
u_x^2? I haven't been able to work that out. The first
wack is to say the B occurs in the term
Exp( -B (Sin(theta)/lambda)^2)
and we've learned that the unit of Sin(theta)/lamda is 1
Zitat von marc.schi...@epfl.ch:
Dale Tronrud wrote:
While it is true that angles are defined by ratios which result in
their values being independent of the units those lengths were measured,
common sense says that a number is an insufficient description of an
angle. If I tell you I
Marc SCHILTZ wrote:
Hi James
I must confess that I do not understand your point. If you read a
value from the last column of a PDB file, say 27.34, then this really
means :
B = 27.34 Å^2
for this atom. And, since B=8*pi^2*U, it also means that this atom's
mean square atomic displacement
Ed,
For instance, if angles are measured in degrees and x1
sin x ~ pi * x / 180
sin x ~ x
Your equations cannot simultaneously be true in fact the 1st one is
obviously wrong, the 2nd is right. In the 1st case I think you meant
(substituting 'x*deg' for 'x' in your correct 2nd equation):
coordinate systems!
-Original Message-
From: CCP4 bulletin board [mailto:ccp...@jiscmail.ac.uk] On Behalf Of Ian
Tickle
Sent: Sunday, November 22, 2009 10:57 AM
To: CCP4BB@JISCMAIL.AC.UK
Subject: Re: [ccp4bb] units of the B factor
Back to the original problem: what are the units
without them!
Cheers
-- Ian
-Original Message-
From: owner-ccp...@jiscmail.ac.uk
[mailto:owner-ccp...@jiscmail.ac.uk] On Behalf Of James Holton
Sent: 23 November 2009 16:35
To: CCP4BB@jiscmail.ac.uk
Subject: Re: [ccp4bb] units of the B factor
Just because something
[mailto:owner-ccp...@jiscmail.ac.uk] On Behalf Of James Holton
Sent: 23 November 2009 16:35
To: CCP4BB@jiscmail.ac.uk
Subject: Re: [ccp4bb] units of the B factor
Just because something is dimensionless does not mean it is
unit-less.
The radian and the degree are very good examples
16:35
To: CCP4BB@jiscmail.ac.uk
Subject: Re: [ccp4bb] units of the B factor
Just because something is dimensionless does not mean it is
unit-less.
The radian and the degree are very good examples of this.
Remember, the
word unit means one, and it is the quantity of something that we
give
-Original Message-
From: owner-ccp...@jiscmail.ac.uk
[mailto:owner-ccp...@jiscmail.ac.uk] On Behalf Of James Holton
Sent: 23 November 2009 19:07
To: CCP4BB@jiscmail.ac.uk
Subject: Re: [ccp4bb] units of the B factor
So... how do you measure or report a solid angle without invoking
...@jiscmail.ac.uk] On Behalf Of Ian
Tickle
Sent: Sunday, November 22, 2009 10:57 AM
To: CCP4BB@JISCMAIL.AC.UK
Subject: Re: [ccp4bb] units of the B factor
Back to the original problem: what are the units of B and
u_x^2? I haven't been able to work that out. The first
wack is to say the B occurs
Holton
Sent: 23 November 2009 19:07
To: CCP4BB@jiscmail.ac.uk
Subject: Re: [ccp4bb] units of the B factor
So... how do you measure or report a solid angle without invoking the
steradian? sterdegrees?
Ian Tickle wrote:
James, I think you misunderstood, no-one is suggesting that
we
Ian,
On Mon, 2009-11-23 at 17:34 +, Ian Tickle wrote:
Ed,
For instance, if angles are measured in degrees and x1
sin x ~ pi * x / 180
sin x ~ x
Your equations cannot simultaneously be true in fact the 1st one is
obviously wrong, the 2nd is right. In the 1st case I think you
Nice
Scott
On Mon, Nov 23, 2009 at 1:07 PM, Ed Pozharski epozh...@umaryland.eduwrote:
Ian,
On Mon, 2009-11-23 at 17:34 +, Ian Tickle wrote:
Ed,
For instance, if angles are measured in degrees and x1
sin x ~ pi * x / 180
sin x ~ x
Your equations cannot simultaneously be
James,
I don't think that you are re-phrasing me correctly. At least I can
not understand how your statement relates to mine.
You simply have to tell us whether a value of 27.34 read from the last
column of a PDB file means :
(1) B = 27.34 Å^2 , as I (and hopefully some others) think, or
Not at all !
If I want to compute the sinus of 15 degrees, using the series
expansion, I write
X = 15 degrees = 15 * pi/180 = 0.2618
because, 1 degree is just a symbol for the unitless, dimensionless
number pi/180.
I plug this X into the series expansion and get the right result.
Marc
-- Ian
-Original Message-
From: owner-ccp...@jiscmail.ac.uk
[mailto:owner-ccp...@jiscmail.ac.uk] On Behalf Of James Holton
Sent: 23 November 2009 16:35
To: CCP4BB@jiscmail.ac.uk
Subject: Re: [ccp4bb] units of the B factor
Just because something is dimensionless does not mean it is
unit
I would like to apologize to everyone for creating such a busy thread
(an what could perhaps be construed as an occasionally belligerent
tone), but I really do want to know the right answer to this! I am
trying to model radiation damage from first principles, and in such
models you cannot
be better off without them!
Cheers
-- Ian
-Original Message-
From: owner-ccp...@jiscmail.ac.uk
[mailto:owner-ccp...@jiscmail.ac.uk] On Behalf Of James Holton
Sent: 23 November 2009 16:35
To: CCP4BB@jiscmail.ac.uk
Subject: Re: [ccp4bb] units of the B factor
Just because
Quoting James Holton jmhol...@lbl.gov:
Now the coefficients of a Taylor polynomial are themselves values of the
derivatives of the function being approximated. Each time you take a
derivative of f(x), you divide by the units (and therefore dimensions)
of x. So, Pete's coefficients below: 1,
James,
I could not help typing something!
Consider a circle of radius R, its circumstance L is then 2*Pi*R.
Both R and L have the same unit, the 2*Pi angle is unitless.
SI defines the unit of angle to be Ran just because this unitless
number is different because it is obtained by the length of
angle then you absolutely must state that, but I would advise sticking
to the SI unit.
Cheers
-- Ian
-Original Message-
From: James Holton [mailto:jmhol...@lbl.gov]
Sent: 23 November 2009 19:53
To: Ian Tickle
Subject: Re: [ccp4bb] units of the B factor
.. and if you have 1234
to propose,
insinuate, proselytize or enforce it in any way, for now...
Artem
-Original Message-
From: CCP4 bulletin board [mailto:ccp...@jiscmail.ac.uk] On Behalf Of Dale
Tronrud
Sent: Monday, November 23, 2009 1:33 AM
To: CCP4BB@JISCMAIL.AC.UK
Subject: Re: [ccp4bb] units of the B factor
Interesting that the IUCr committee report that Ian pointed
out stated
we recommend that the use of B be discouraged. Hmm... Good
luck with
that!
You seem to be implying, if I understand you correctly, that the IUCr
report recommends that the use of the equivalent isotropic B be
Back to the original problem: what are the units of B and
u_x^2? I haven't been able to work that out. The first
wack is to say the B occurs in the term
Exp( -B (Sin(theta)/lambda)^2)
and we've learned that the unit of Sin(theta)/lamda is 1/Angstrom
and the argument of
sides of a right triangle
-Original Message-
From: CCP4 bulletin board [mailto:ccp...@jiscmail.ac.uk] On Behalf Of Ian
Tickle
Sent: Sunday, November 22, 2009 10:57 AM
To: CCP4BB@JISCMAIL.AC.UK
Subject: Re: [ccp4bb] units of the B factor
Back to the original problem: what are the units
as 499 sec. Those people in general relativity are great
at manipulating coordinate systems!
-Original Message-
From: CCP4 bulletin board [mailto:ccp...@jiscmail.ac.uk] On Behalf Of Ian
Tickle
Sent: Sunday, November 22, 2009 10:57 AM
To: CCP4BB@JISCMAIL.AC.UK
Subject: Re: [ccp4bb] units
To avoid the creation of a cumbersome new unit everyone will need to
keep track of, can we just come up with a prefix that means 0.013 of
something? Perhaps we could give it the symbol b and then we could
say the B-factor is 20 bA^2.*
James
*Seemed like 76.92 b humor units when I wrote
This question by the Mad Scientist (here after the MS) has provoked
me to give the topic a lot of thought. I think I can provide some
direction towards the solution, but I'm not adept enough with The
Optical Principles of the Diffraction of X-rays (Which people on this
BB should refer to
On Thu, 19 Nov 2009 23:13:53 -0800, James Holton jmhol...@lbl.gov said:
should we call it? I nominate the Born after Max Born who did
so much fundamental and far-reaching work on the nature of
disorder in crystal lattices. The unit then has the symbol B,
which will make it
I second that... are there committees that ratify these things? phx
James Holton wrote:
Many textbooks describe the B factor as having units of square
Angstrom (A^2), but then again, so does the mean square atomic
displacement u^2, and B = 8*pi^2*u^2. This can become confusing if
one
Hi James,
James Holton wrote:
Many textbooks describe the B factor as having units of square Angstrom
(A^2), but then again, so does the mean square atomic displacement u^2,
and B = 8*pi^2*u^2. This can become confusing if one starts to look at
derived units that have started to come out of
Hi Marc
Not at all, one uses units that are convenient. By your reasoning we
should get rid of Å, atmospheres, AU, light years... They exist not to
be obnoxious, but because they're handy for a large number of people in
their specific situations.
Sounds familiar...
phx
Marc SCHILTZ
I think that you should suggest a new unit of 10^(-11) m, a JHm
perhaps. If it is convenient to have B in A^2 then u^2 should be
in JHm^2.
Adam
On Thu, 19 Nov 2009, James Holton wrote:
Many textbooks describe the B factor as having units of square Angstrom
(A^2), but then again, so does
Hi James
If we're going to sort out the units we need to get the terminology
right too. The mean square atomic displacement already has a symbol U =
u^2 (or to be precise Ueq as we're talking about isotropic
displacements here), and u is conventionally not defined as the RMS
displacement as you
Of course, for SI political correctness we should be using nm^2 anyway. This
would add more confusion to a situation that most people don't worry about
anyway.
Pete
On 20 Nov 2009, at 11:05, Ian Tickle wrote:
Hi James
If we're going to sort out the units we need to get the terminology
Frank von Delft wrote:
Hi Marc
Not at all, one uses units that are convenient. By your reasoning we
should get rid of Å, atmospheres, AU, light years... They exist not to
be obnoxious, but because they're handy for a large number of people in
their specific situations.
Hi Frank,
I think
Eh? m and Å are related by the dimensionless quantity 10,000,000,000.
Vive la révolution!
Marc SCHILTZ wrote:
Frank von Delft wrote:
Hi Marc
Not at all, one uses units that are convenient. By your reasoning we
should get rid of Å, atmospheres, AU, light years... They exist not
to be
...@jiscmail.ac.uk] On Behalf Of Frank von
Delft
Sent: Friday, November 20, 2009 1:11 PM
To: CCP4BB@JISCMAIL.AC.UK
Subject: [ccp4bb] {Spam?} Re: {Spam?} Re: [ccp4bb] {Spam?} Re: {Spam?} Re:
[ccp4bb] units of the B factor
Eh? m and Å are related by the dimensionless quantity 10,000,000,000.
Vive la révolution
Yes, but Å is really only just tolerated.
It has evaded the Guillotine - for the time being ;-)
Frank von Delft wrote:
Eh? m and Å are related by the dimensionless quantity 10,000,000,000.
Vive la révolution!
Marc SCHILTZ wrote:
Frank von Delft wrote:
Hi Marc
Not at all, one uses
What a funny pleasant piece of discussion !
Given any physical quantity Something, having any kind of dimension
(even as awful as inches^2*gallons*pounds^-3)
Would it exist any room for a discussion about the dimension of
2*Something ? And what about 1*Something ?
Philippe Dumas
What a funny pleasant piece of discussion !
Given any physical quantity Something, having any kind of dimension (even
as awful as inches^2*gallons*pounds^-3)
Would it exist any room for a discussion about the dimension of 2*Something
? And what about 1*Something ?
(1) You can always
No No No! This is not what I meant at all!
I am not suggesting the creation of a new unit, but rather that we name
a unit that is already in widespread use. This unit is A^2/(8*pi^2)
which has dimensions of length^2 and it IS the unit of B factor. That
is, every PDB file lists the B
Many textbooks describe the B factor as having units of square Angstrom
(A^2), but then again, so does the mean square atomic displacement u^2,
and B = 8*pi^2*u^2. This can become confusing if one starts to look at
derived units that have started to come out of the radiation damage
field like
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