Artículos con la etiqueta ‘Biological Physics (physics.bio-ph)’

Is there enough fertile soil to feed a planet of growing cities?

Por • 19 ago, 2013 • Category: sociologia

We analyze a scaling law for the consumption of agricultural soil by the cities. The nonlinear depen- dence of the size of the city on the number of inhabitants gives rise to an equation for the population dynamics. We found the asymptotic limit of the solution for this equation, given by the carrying capacity in terms of number of inhabitants that can be fed. The carrying capacity as a function of the scaling law exponent is computed numerically, showing that the exponent must be very small to ensure a food sustainability. We suggest a bound for the value of this exponent and analyze the reliability of the scaling law for the major cities.



Extending physical chemistry to populations of living organisms. First step: measuring coupling strength

Por • 7 ene, 2013 • Category: Ambiente

For any system, whether physical or non-physical, knowledge of the form and strength of inter-individual interactions is a key-information. In an approach based on statistical physics one needs to know the interaction Hamiltonian. For non-physical systems, based on qualitative arguments similar to those used in physical chemistry, interaction strength gives useful clues about the macroscopic properties of the system. Even though our ultimate objective is the understanding of social phenomena, we found that systems composed of insects (or other living organisms) are of great convenience for investigating group effects. In this paper we show how to design experiments that enable us to estimate the strength of interaction in groups of insects. By repeating the same experiments with increasing numbers of insects, ranging from less than 10 to several hundreds, one is able to explore key-properties of the interaction. The data turn out to be consistent with a global correlation that is independent of distance (at least within a range of a few centimetres). Estimates of this average cross-correlation will be given for ants, beetles and fruit flies.