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Sun Apr 10 20:52:34 EST 2005

> An article in Brain Research uses some units I've never run into before,
> and I've exhausted my limited resources in my office and my colleagues'
> offices.  The authors are from Leipzig, Munich, and Quebec if that's a
> clue. 

Ah, yes, good ol' Brain Research.

> Apparently referring to concentrations of tritiated amino acids and 
> glucose or 14C tagged mannitol, etc., the authors use the units:

> TBq mmol(-1)  and GBq mmol(-1)

> where (-1) is of course an exponent.  What are these TBq and GBq?
> I'm guessing T is tera and G is giga.  I've no clue as to the Bq.

This is the becquerel, the SI unit for the activity of radioactive
materials.  One becquerel = 1 event per second.  Most of us are more
accustomed to seeing curies used in this context:
	1 curie = 3.70 x 10**10 = 37 GBq
Hence we usually deal with milli- and microcuries rather than
becquerels, perhaps because we are more comfortable with milli
and micro than with tera and giga :-).

> Later, referring to a permeability surface area product (the paper is 
> about transfer across the blood-brain barrier) they use the units:

> ml/hg/min
> I've often seen the PS product as ml/g/min, but what's 'hg'?

Well, my guess is that this is hectograms, which is units of 100.
The alternative is that it is a typo (it is Brain Research after
all), but since the authors have demonstrated their knowledge of,
um, arcane units of measure, I'd be inclined to go with the former
hypothesis.  Is there any way to check by recalculating their

Steve Matheson   Program in Neuroscience   University of Arizona
sfm at neurobio.arizona.edu

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