Gamma Radiation by Neutralino Stars

A new model of gamma radiation (GR) generated by neutralino annihilation in neutralino stars (NeS) is proposed. Diffuse Galactic and extragalactic GR is calculated for this model and is shown to be in a reasonable agreement with observations. The point source component (P) is picked out among nonidentified discrete gamma sources from EGRET catalog. This component is shown to be distributed isotropically and homogeneously, as it should be for NeS. Gamma radiation from significant part of P-sources is supposed to be the direct radiation from individual NeS. This supposition is shown to be in agreement with observations. The comparison of the theory with observed GR gives a possibility to establish some important features of CDM particle.Comment: 12 pages, LaTe

Unfolding and unzipping of single-stranded DNA by stretching

We present a theoretical study of single-stranded DNA under stretching. Within the proposed framework, the effects of basepairing on the mechanical response of the molecule can be studied in combination with an arbitrary underlying model of chain elasticity. In a generic case, we show that the stretching curve of ssDNA exhibits two distinct features: the second-order "unfolding" phase transition, and a sharp crossover, reminiscent of the first-order "unzipping" transition in dsDNA. We apply the theory to the particular cases of Worm-like Chain (WLC) and Freely-Joint Chain (FJC) models, and discuss the universal and model--dependent features of the mechanical response of ssDNA. In particular, we show that variation of the width of the unzipping crossover with interaction strength is very sensitive to the energetics of hairpin loops. This opens a new way of testing the elastic properties of ssDNA.Comment: 7 pages, 4 figures, substantially revised versio

TeV cosmic-ray proton and helium spectra in the myriad model

Recent measurements of cosmic ray proton and helium spectra show a hardening above a few hundreds of GeV. This excess is hard to understand in the framework of the conventional models of Galactic cosmic ray production and propagation. We propose here to explain this anomaly by the presence of local sources (myriad model). Cosmic ray propagation is described as a diffusion process taking place inside a two-zone magnetic halo. We calculate the proton and helium fluxes at the Earth between 50 GeV and 100 TeV. Improving over a similar analysis, we consistently derive these fluxes by taking into account both local and remote sources for which a unique injection rate is assumed. We find cosmic ray propagation parameters compatible with B/C measurements and for which the proton and helium spectra remarkably agree with the PAMELA and CREAM measurements over four decades in energy.Comment: 5 pages, 3 figure

THE INTERNATIONALIZATION DETERMINANTS OF THE SMALL AGRO-FOOD FIRMS: HYPOTHESES AND STATISTICAL TESTS

The purpose of this paper is to establish a link between competition perceived by the small firm manager and the decision to export. Using a sample of 335 small agro-food firms as a basis to our study, the statistical model presented shows a negative connection between the high perceived quality competitiveness and the fact that a firm exports.Agribusiness, International Relations/Trade,

A General Equilibrium Model of the Term Structure of Interest Rates under Regime-switching Risk

This paper incorporates the systematic risk of regime shifts into a general equilibrium model of the term structure of interest rates. The model shows that there is a new source of time-variation in bond term premiums in the presence of regime shifts. This new component is a regime-switching risk premium that depends on the covariations between discreet changes in marginal utility and bond prices across different regimes. A closed-form solution for the term structure of interest rates is obtained under an affine model using log-linear approximation. The model is estimated by Efficient Method of Moments. The regime-switching risk is found to be statistically significant and mostly affect the long-end of the yield curveThe Term Structure, General Equilibrium, Markov Regime Shifts