I am trying to make an application of the Brown et al. (2004) formulation for the metabolic theory of ecology to growth data, but I am getting tripped up on the term for temperature dependence. According to them, I should be able to model growth as:
growth = G0*M^-0.25*exp(-E/kT) where G0 is a taxon-specific normalization constant, M is the mass, and the term exp(-E/kT) is the Vant Hoff-Arrhenius relationship for chemical reactivity where E is the activation energy, k is the Boltzmanns constant, and T is the temperature in degrees Kelvin. They suggest that E should be set to 0.65 eV and k is 0.0000862 eV/T. If I assume a temperature of 293 degrees Kelvin (i.e., 20 degrees Celsius), and attempt to solve the Vant Hoff-Arrhenius term then: exp(-E/kT) = exp(-0.65/(0.0000862*293) = exp(-0.65/0.025)=exp(26)= 0.00000000002 So, no matter what terms I plug in for the other parameters growth, or, for that matter, what temperature I use, growth will be really, really, really small (i.e., growth = G0*M^-0.25*0.00000000002, because of the Vant Hoff-Arrhenius term. I want to use a nonlinear model instead of doing the log-transform can I not do that? Where am I going wrong? Any help would be much appreciated! Thanks, Dan ___________________________________________________________________ Daniel C. McEwen, Ph.D. Candidate North Dakota State University Department of Biological Sciences Stevens Hall 233 Fargo, ND 58105-5517 Phone: 701-231-6561 Fax: 701-231-7149 URL: http://www.ndsu.edu/ndsu/biosciences/students/dmcewen/index.html Major advisor: Malcolm G. Butler http://www.ndsu.nodak.edu/ndsu/mbutler/
