Competition and cooperation in one-dimensional stepping stone models

Cooperative mutualism is a major force driving evolution and sustaining ecosystems. Although the importance of spatial degrees of freedom and number fluctuations is well-known, their effects on mutualism are not fully understood. With range expansions of microbes in mind, we show that, even when mutualism confers a distinct selective advantage, it persists only in populations with high density and frequent migrations. When these parameters are reduced, mutualism is generically lost via a directed percolation process, with a phase diagram strongly influenced by an exceptional DP2 transition.Comment: 8 pages, 4 figure

Statistical Analysis of Precipitation Events

In the present paper we demonstrate the results of a statistical analysis of some characteristics of precipitation events and propose a kind of a theoretical explanation of the proposed models in terms of mixed Poisson and mixed exponential distributions based on the information-theoretical entropy reasoning. The proposed models can be also treated as the result of following the popular Bayesian approach.Comment: 5 pages, 4 figures; ICNAAM 201

On the kinetic equation approach to pair production by time-dependent electric field

We investigate the quantum kinetic approach to pair production from vacuum by time-dependent electric field. Equivalence between this approach and the more familiar S-matrix approach is explicitly established for both scalar and fermion cases. For the particular case of a constant electric field exact solution for kinetic equations is provided and the accuracy of low-density approximation is estimated.Comment: 8 pages, 4 figure

Defect-Mediated Emulsification in Two Dimensions

We consider two dimensional dispersions of droplets of isotropic phase in a liquid with an XY-like order parameter, tilt, nematic, and hexatic symmetries being included. Strong anchoring boundary conditions are assumed. Textures for a single droplet and a pair of droplets are calculated and a universal droplet-droplet pair potential is obtained. The interaction of dispersed droplets via the ordered phase is attractive at large distances and repulsive at short distances, which results in a well defined preferred separation for two droplets and topological stabilization of the emulsion. This interaction also drives self-assembly into chains. Preferred separations and energy barriers to coalescence are calculated, and effects of thermal fluctuations and film thickness are discussed.Comment: revtex4, 13 pages, 12 figure

Fisher waves in the strong noise limit

We investigate the effects of strong number fluctuations on traveling waves in the Fisher-Kolmogorov reaction-diffusion system. Our findings are in stark contrast to the commonly used deterministic and weak-noise approximations. We compute the wave velocity in one and two spatial dimensions, for which we find a linear and a square-root dependence of the speed on the particle density. Instead of smooth sigmoidal wave profiles, we observe fronts composed of a few rugged kinks that diffuse, annihilate, and rarely branch; this dynamics leads to power-law tails in the distribution of the front sizes.Comment: 4 pages, 2 figures, updat

Guided random walk calculation of energies and <\sq {r^2} > values of the 1Σg^1\Sigma_g state of H_2 in a magnetic field

Energies and spatial observables for the $^1\Sigma_g$ state of the hydrogen molecule in magnetic fields parallel to the proton-proton axis are calculated with a guided random walk Feynman-Kac algorithm. We demonstrate that the accuracy of the results and the simplicity of the method may prove it a viable alternative to large basis set expansions for small molecules in applied fields.Comment: 10 pages, no figure

On the kinetic equation approach to pair production by time-dependent electric field

We investigate the quantum kinetic approach to pair production from vacuum by time-dependent electric field. Equivalence between this approach and the more familiar S-matrix approach is explicitly established for both scalar and fermion cases. For the particular case of a constant electric field exact solution for kinetic equations is provided and the accuracy of low-density approximation is estimated.Comment: 8 pages, 4 figure

Femtosecond photonic viral inactivation probed using solid-state nanopores

We report on detection of virus inactivation using femtosecond laser radiation by measuring the conductance of a solid state nanopore designed for detecting single particles. Conventional methods of assaying for viral inactivation based on plaque forming assays require 24–48 h for bacterial growth. Nanopore conductance measurements provide information on morphological changes at a single virion level.We show that analysis of a time series of nanopore conductance can quantify the detection of inactivation, requiring only a few minutes from collection to analysis. Morphological changes were verified by dynamic light scattering. Statistical analysis maximizing the information entropy provides a measure of the log reduction value. This work provides a rapid method for assaying viral inactivation with femtosecond lasers using solid-state nanopores.First author draf

Peculiarities of hormonal, macro- and microelemental status in wrestlers

Objective: to determine the content of hormones, as well as some macro- and microelements in athletes-wrestlers outside the period of competition and active training.Materials and methods: the study involved 66 athletes-wrestlers and 107 students involved in sports professionally. The level of hormones and vitamin D was determined by the ELISA method. To analyze the content of macro- and microelements, the subjects were cut off a lock of hair from the back of the head in an amount of at least 0.1 g. The studies were carried out on an ICP-MS Agilent 7900 mass spectrometer.Results: levels of cortisol, TSH and T4 are higher, and levels of testosterone, T3 and vitamin D are lower in athletes compared to the control group. An increase in the content of sodium, calcium, potassium, magnesium, cobalt and a decrease in iodine were revealed in fighters from those who were not involved in sports professionally.Conclusion: the data obtained indicate an imbalance in the work of the body’s endocrine systems and impaired adaptation to stress. It is known that the determination of the hormonal status is used to assess the adaptation, the revealed changes in the indicators of vitamin D, macro- and microelements, allow the study of these indicators in order to prevent the syndrome of overtraining of athletes, to maintain and improve sports performance