2554
Recently , an electrical - mechanical analog model of heat flow within the brain has been developed from which an expression for CBF has been derived : CBF = Cb / ( tau rho c ) where tau is the thermal decay constant , rho is the density of blood , and c is its specific heat .
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Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: GENE 
Text: {0} 
Answer:
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