[RASMB] Abs optics design question

Hayes, David HayesD at MedImmune.com
Thu Jun 3 08:12:27 PDT 2010


Hi Andrew,
My understanding is that it is not just one cell scanned at a time, but
one sector of one cell scanned at each time.  There is one flash of the
lamp for the reference sector and one flash for the lamp for the sample
sector.  At rotor speeds above about 6000 RPM, it is the flash lamp
maximum flash rate (60 flashes per second without overheating) that is
the time limiting factor in collecting absorbance data.  

Besides engineering reasons for choosing the flash lamp back when the
XLA was designed, John Philo did raise the question once if there might
be a molecular downside to having a continuous lamp shining UV on your
sample for the entire time of the experiment (hours).
Tom Laue is the expert on this topic of instrument design, but your
basic idea that collecting absorbance data from every cell at once
should be possible has been confirmed in prototype form by Tom.

Although I know Tom has experienced or heard just about everything, I
thought it would be fun and useful to have a "reminder" thread about
inexplicable design decisions for the XLA and add a few questions of my
own.  

I would also like to know why the XLA engineers placed all the Peltier
heating/cooling plates on a circuit board with uninsulated wire traces,
so that when the board heats or cools too fast it warps and short
circuits (Yes this really happened).  Why couldn't the plates be
connected individually to the metal can or why couldn't there be some
insulation between the metal can and the circuit board just in case it
warps more than the thickness of the Peltier plates?  

Why do we have to run the XLA at 0 speed just to get the diffusion pump
going and get a reliable low vacuum?  Couldn't there just be a switch?

Why does the XLA "wait for diffusion pump cooling" even after we
replaced the diffusion pump with a turbo-molecular pump?

Why can't the interference optics laser be physically connected to the
interference camera to reduce vibration noise?(sorry Tom, you have
apologize about this before, but maybe some newer AUC people haven't
heard)

Why can't analytical cell housings have a built in tightening system
like the counterweight? (People have used hair, white-out "paint", and
kimwipe strips to hold the cells a little tighter in the rotor)

Why can't the manufacturer test the sapphire windows for Low UV
absorbance before selling them to us?

David Hayes


-----Original Message-----
From: rasmb-bounces at rasmb.bbri.org [mailto:rasmb-bounces at rasmb.bbri.org]
On Behalf Of Leech, AP
Sent: Thursday, June 03, 2010 10:39 AM
To: RASMB
Subject: [RASMB] Abs optics design question

Hello all,

This is an idle question about the design of the XL/A (or I)
absorbance optics. Why are the cells scanned one at once?
Would it not be possible to scan them all "simultaneously"
by gating the output from the photomultiplier into a
suitable number of different channels?

Andrew

-- 
Dr Andrew Leech                   *  Laboratory Head
Technology Facility               *  Molecular Interactions Laboratory
Department of Biology (Area 15)   *  Tel   : +44 (0)1904 328723
University of York                *  Fax   : +44 (0)1904 328804
PO Box 373,  York  YO10 5YW       *  Email : apl3 at york.ac.uk
EMAIL DISCLAIMER: http://www.york.ac.uk/docs/disclaimer/email.htm
_______________________________________________
RASMB mailing list
RASMB at rasmb.bbri.org
http://rasmb.bbri.org/cgi-bin/mailman/listinfo/rasmb



To the extent this electronic communication or any of its attachments contain information that is not in the public domain, such information is considered by MedImmune to be confidential and proprietary.  This communication is expected to be read and/or used only by the individual(s) for whom it is intended.  If you have received this electronic communication in error, please reply to the sender advising of the error in transmission and delete the original message and any accompanying documents from your system immediately, without copying, reviewing or otherwise using them for any purpose.  Thank you for your cooperation.



More information about the RASMB mailing list