X-Message-Number: 13890
Date: Sat, 10 Jun 2000 14:06:04 -0700
From: Jeff Davis <>
Subject: Re: cryostats and economics of scale

Dr. Ettinger in  #13852, re my post (#13844) about cryostats and economics
of scale, writes:

>Jeff also misspoke himself or erred in a couple of places. For one, he said
>>with two cryostats, one ten times as large as the other, the boil-off per 
>>patient--assuming that the number of patients inside the larger cryostat is 
>>larger: ten times as many--the cost per patient for liquid nitrogen
>>replenishment would be reduced by a factor of ten.

It's a bit embarrassing, but he's right.  So let me go back and try to
clear things up.  

There was a math error, and there was a communications error.
Unfortunately, they went together all too well, distracting from and
perhaps tending to discredit the point I was trying to make.

First, the math error.  When I wrote:

"...assuming that the number of patients inside the larger cryostat is 
proportionately larger: ten times as many..."

Whoops! Seriously wrong.  It should have been "a thousand times as many".

Because--and here's the communications error--when I said that one cryostat
was ten times larger than the other, I was thinking of an increase in
linear dimension by a factor of ten.  Since volume is proportional to the
cube of the linear dimension, an increase in linear dimension by a factor
of ten results in an increase in volume by a factor of a thousand.
However, I rather deftly botched the chance of getting that point across
when I wrote, "ten times larger than the other", which, inevitably and
logically would be interpreted as "ten times greater capacity", which is to
say ten times greater internal volume.

All these numbers making your head spin?  Thinking to yourself, "It's not
really all that interesting to me."?  Well, you're right.  It was my
screw-up.  No need to bother with it.  Or, in the words of Rosanne
Reannadanna, " Nevermind."  

Allow me, however, to quote Dr. Ettinger's from his post:

"Eventually, as Jeff says, economies of scale will reduce liquid 
nitrogen cost per patient, regardless of the system used."

			Best, Jeff Davis

	   "Everything's hard till you know how to do it."
					Ray Charles				

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