First Records and First Proven Breeding of Lesser Grey Shrike, \u3ci\u3eLanius minor\u3c/i\u3e, in Mongolia

During a trip to the Dzungarian Gobi in southwestern Mongolia, a group of German birdwatchers found several territorial lesser grey shrikes, Lanius minor, and documented an active nest. The species had not previously been recorded from Mongolia. Observations were made near Bulgan gol (Bulgan river; nest coordinates: 46°6’N 91°32’E, 1190 m a.s.l.) in Khovd aimag (Khovd province) on June 24, 2006. Besides two territorial pairs, of which a female could be photographically documented on the nest, at least four more territorial adults were found within an area of about 1.5 km2. Based on these records, an abundance of 4 pairs/km2 can be assumed for this riparian site, which consists mainly of open meadows with scattered bushes and trees

First Records and First Proven Breeding of Lesser Grey Shrike, \u3ci\u3eLanius minor\u3c/i\u3e, in Mongolia

During a trip to the Dzungarian Gobi in southwestern Mongolia, a group of German birdwatchers found several territorial lesser grey shrikes, Lanius minor, and documented an active nest. The species had not previously been recorded from Mongolia. Observations were made near Bulgan gol (Bulgan river; nest coordinates: 46°6’N 91°32’E, 1190 m a.s.l.) in Khovd aimag (Khovd province) on June 24, 2006. Besides two territorial pairs, of which a female could be photographically documented on the nest, at least four more territorial adults were found within an area of about 1.5 km2. Based on these records, an abundance of 4 pairs/km2 can be assumed for this riparian site, which consists mainly of open meadows with scattered bushes and trees

Collective motion and nonequilibrium cluster formation in colonies of gliding bacteria

We characterize cell motion in experiments and show that the transition to collective motion in colonies of gliding bacterial cells confined to a monolayer appears through the organization of cells into larger moving clusters. Collective motion by non-equilibrium cluster formation is detected for a critical cell packing fraction around 17%. This transition is characterized by a scale-free power-law cluster size distribution, with an exponent $0.88\pm0.07$, and the appearance of giant number fluctuations. Our findings are in quantitative agreement with simulations of self-propelled rods. This suggests that the interplay of self-propulsion of bacteria and the rod-shape of bacteria is sufficient to induce collective motion

A mean-field theory for self-propelled particles interacting by velocity alignment mechanisms

A mean-field approach (MFA) is proposed for the analysis of orientational order in a two-dimensional system of stochastic self-propelled particles interacting by local velocity alignment mechanism. The treatment is applied to the cases of ferromagnetic (F) and liquid-crystal (LC) alignment. In both cases, MFA yields a second order phase transition for a critical noise strength and a scaling exponent of 1/2 for the respective order parameters. We find that the critical noise amplitude $\eta_c$ at which orientational order emerges in the LC case is smaller than in the F-alignment case, i.e. $\eta^{LC}_{C}<\eta^{F}_{C}$. A comparison with simulations of individual-based models with F- resp. LC-alignment shows that the predictions about the critical behavior and the qualitative relation between the respective critical noise amplitudes are correct

A mean-field theory for self-propelled particles interacting by velocity alignment mechanisms

A mean-field approach (MFA) is proposed for the analysis of orientational order in a two-dimensional system of stochastic self-propelled particles interacting by local velocity alignment mechanism. The treatment is applied to the cases of ferromagnetic (F) and liquid-crystal (LC) alignment. In both cases, MFA yields a second order phase transition for a critical noise strength and a scaling exponent of 1/2 for the respective order parameters. We find that the critical noise amplitude $\eta_c$ at which orientational order emerges in the LC case is smaller than in the F-alignment case, i.e. $\eta^{LC}_{C}<\eta^{F}_{C}$. A comparison with simulations of individual-based models with F- resp. LC-alignment shows that the predictions about the critical behavior and the qualitative relation between the respective critical noise amplitudes are correct

A mean-field theory for self-propelled particles interacting by velocity alignment mechanisms

A mean-field approach (MFA) is proposed for the analysis of orientational order in a two-dimensional system of stochastic self-propelled particles interacting by local velocity alignment mechanism. The treatment is applied to the cases of ferromagnetic (F) and liquid-crystal (LC) alignment. In both cases, MFA yields a second order phase transition for a critical noise strength and a scaling exponent of 1/2 for the respective order parameters. We find that the critical noise amplitude $\eta_c$ at which orientational order emerges in the LC case is smaller than in the F-alignment case, i.e. $\eta^{LC}_{C}<\eta^{F}_{C}$. A comparison with simulations of individual-based models with F- resp. LC-alignment shows that the predictions about the critical behavior and the qualitative relation between the respective critical noise amplitudes are correct

Construction of an isotropic cellular automaton for a reaction-diffusion equation by means of a random walk

We propose a new method to construct an isotropic cellular automaton corresponding to a reaction-diffusion equation. The method consists of replacing the diffusion term and the reaction term of the reaction-diffusion equation with a random walk of microscopic particles and a discrete vector field which defines the time evolution of the particles. The cellular automaton thus obtained can retain isotropy and therefore reproduces the patterns found in the numerical solutions of the reaction-diffusion equation. As a specific example, we apply the method to the Belousov-Zhabotinsky reaction in excitable media