Re: dWater as sheath plus ARIA question

Alice

I don't think that is quite right.  We use distilled water in our 
CyAn and can not see any difference compared to saline.  Anyway, the 
light will not bounce off the interface due to the refractive index 
difference but will just be bent (i.e. refracted) slightly.  This is 
the effect of trying to hit a fish underwater with a spear when you 
are standing in air.	Remember that the amount light is bent 
(refracted) is also a function of the angle of the incident 
light.	Going back to the fish.  If you stand directly over the fish 
the light is not bent at all and he is easy to hit.  If you stand on 
the bank and the fish is several feet out in the water away from the 
bank the effect will be large due to the increased angle you are 
looking through.  Thus hitting the refractive index interface 
straight on (which is what we are doing) will give you no 
refraction.  Also the refractive index of physiological saline is 
almost the same as water.  I don't think the difference in refractive 
index between water (1.332) and physiological saline (1.333) is 
enough to see although maybe I haven't looked closely enough.

Larry

At 01:04 PM 2/16/2006, you wrote:
>To Howard et al,
>As Howard said, you cannot use distilled water in the sheath stream 
>if you are sorting as
>distilled water will not take the charge needed for sorting.
>
>But, even for non-sorting applications,  I have always thought 
>(although have not tested)
>that using distilled water as sheath fluid will raise	background 
>signals --- because
>light will bounce off the interface between the core stream and the 
>sheath fluid  (they
>no longer have the same refractive index).
>
>Is this incorrect?
>
>Alice
>
>Alice L. Givan, Director
>Englert Cell Analysis Laboratory
>of the Norris Cotton Cancer Center
>Dartmouth Medical School
>Lebanon, NH 03756 USA
>tel 603-650-7661
>fax 603-650-6130
>givan@dartmouth.edu
>www.dartmouth.edu/~celllab

Larry W. Arnold, Ph.D.
Research Professor and Director, Flow Cytometry Facility
Department of Microbiology and Immunology
CB# 7290
University of North Carolina
Chapel Hill, NC 27599
Phone: 919-966-1530
FAX: 919-962-8103