18,782 research outputs found
How important is adapting regional climatic projections to the local environment? A procedure for microclimatic corrections makes the difference for crop growth in a virtual experiment
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Impurity in a granular gas under nonlinear Couette flow
We study in this work the transport properties of an impurity immersed in a
granular gas under stationary nonlinear Couette flow. The starting point is a
kinetic model for low-density granular mixtures recently proposed by the
authors [Vega Reyes F et al. 2007 Phys. Rev. E 75 061306]. Two routes have been
considered. First, a hydrodynamic or normal solution is found by exploiting a
formal mapping between the kinetic equations for the gas particles and for the
impurity. We show that the transport properties of the impurity are
characterized by the ratio between the temperatures of the impurity and gas
particles and by five generalized transport coefficients: three related to the
momentum flux (a nonlinear shear viscosity and two normal stress differences)
and two related to the heat flux (a nonlinear thermal conductivity and a cross
coefficient measuring a component of the heat flux orthogonal to the thermal
gradient). Second, by means of a Monte Carlo simulation method we numerically
solve the kinetic equations and show that our hydrodynamic solution is valid in
the bulk of the fluid when realistic boundary conditions are used. Furthermore,
the hydrodynamic solution applies to arbitrarily (inside the continuum regime)
large values of the shear rate, of the inelasticity, and of the rest of
parameters of the system. Preliminary simulation results of the true Boltzmann
description show the reliability of the nonlinear hydrodynamic solution of the
kinetic model. This shows again the validity of a hydrodynamic description for
granular flows, even under extreme conditions, beyond the Navier-Stokes domain.Comment: 23 pages, 11 figures; v2: Preliminary DSMC results from the Boltzmann
equation included, Fig. 11 is ne
Uninformed sacrifice: evidence against long-range alarm transmission in foraging ants exposed to a localized perturbation
It is well stablished that danger information can be transmitted by ants
through relatively small distances, provoking either a state of alarm when they
move away from potentially dangerous stimulus, or charge toward it
aggressively. There is almost no knowledge if danger information can be
transmitted along large distances. In this paper, we perturb leaf cutting ants
of the species Atta insularis while they forage in their natural evioronment at
a certain point of the foraging line, so ants make a "U" turn to escape from
the danger zone and go back to the nest. Our results strongly suggest that
those ants do not transmit "danger information" to other nestmates marching
towards the danger area. The individualistic behavior of the ants returning
from the danger zone results in a depression of the foraging activity due to
the systematic sacrifice of non-informed individuals.Comment: 5 pages, 2 figure
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