On the role of injection in kinetic approaches to nonlinear particle acceleration at non-relativistic shock waves

The dynamical reaction of the particles accelerated at a shock front by the first order Fermi process can be determined within kinetic models that account for both the hydrodynamics of the shocked fluid and the transport of the accelerated particles. These models predict the appearance of multiple solutions, all physically allowed. We discuss here the role of injection in selecting the real solution, in the framework of a simple phenomenological recipe, which is a variation of what is sometimes referred to as thermal leakage. In this context we show that multiple solutions basically disappear and when they are present they are limited to rather peculiar values of the parameters. We also provide a quantitative calculation of the efficiency of particle acceleration at cosmic ray modified shocks and we identify the fraction of energy which is advected downstream and that of particles escaping the system from upstream infinity at the maximum momentum. The consequences of efficient particle acceleration for shock heating are also discussed

Antimatter production in supernova remnants

We calculate the energy spectra of cosmic rays (CR) and their secondaries produced in a supernova remnant (SNR), taking into account the time-dependence of the SNR shock. We model the trajectories of charged particles as a random walk with a prescribed diffusion coefficient, accelerating the particles at each shock crossing. Secondary production by CRs colliding with gas is included as a Monte Carlo process. We find that SNRs produce less antimatter than suggested previously: The positron/electron ratio and the antiproton/proton ratio are a few percent and few $\times 10^{-5}$, respectively. Moreover, the obtained positron/electron ratio decreases with energy, while the antiproton/proton ratio rises at most by a factor of two above 10 GeV.Comment: 8 pages, 8 eps figures; extended version of arXiv:1004.1118; v2: minor corrections, matches published versio

Fluorescent styryl dyes of the RH series affect a potential drop on the membrane/solution boundary

AbstractThe effects of the adsorption of the fluorescent potential-sensitive dyes RH-421, RH-237 and RH-160 on the bilayer lipid membrane were studied. It was shown that a dipole potential drop, positive in the hydrophobic part of the membrane, arose due to the dye adsorption. The dye adsorption led to a considerable increase of the rate constant of hydrophobic anion translocation through the membrane, but did not affect their partition coefficient between membrane and water. It implies that the region of the membrane where the potential drops is located deeper than the adsorption plane of hydrophobic ions. The values of the boundary potential differences were estimated by two independent methods with unilateral and bilateral application of the dyes to lipid bilayer membranes. The results suggest that RH dye molecules penetrate through the lipid bilayers. The values of ζ-potential in liposomes did not change on dye adsorption. Hence, dye molecules are adsorbed in a form that does not change the surface charge. We estimated the effects of the electric field of dye dipole layer on an individual dipole located in the same layer and on ion transport through a membrane protein Na+/K+-ATPase. It turned out that the local electric field of each dye dipole decayed so rapidly that a neighbouring dye molecule did not feel it. It also appeared that RH dyes could have but a minor effect on the electrogenic transport performed by the sodium pump in the examined range of dye concentrations

Experimental comparison of 2-methylimidazole nitration by nitric acid and nitrate salts of alkali metals

The processes of nitration of 2-methylimidazole to produce 2-methyl-4(5)-nitroimidazole are considered in this paper. The processes of nitration by mixture of nitric and sulfuric acids and nitrate salts of alkali metals were compared. It was found the nitration of nitrate salts of alkali metal proceeds smoother. The yield of the desired product 2-methyl-4(5)-nitroimidazole was 85 % and 95% in case of nitric acid and nitrate salt.</jats:p

On the Structure and Scale of Cosmic Ray Modified Shocks

Strong astrophysical shocks, diffusively accelerating cosmic rays (CR) ought to develop CR precursors. The length of such precursor $L_{p}$ is believed to be set by the ratio of the CR mean free path $\lambda$ to the shock speed, i.e., $L_{p}\sim c\lambda/V_{sh}\sim cr_{g}/V_{sh}$, which is formally independent of the CR pressure $P_{c}$. However, the X-ray observations of supernova remnant shocks suggest that the precursor scale may be significantly shorter than $L_{p}$ which would question the above estimate unless the magnetic field is strongly amplified and the gyroradius $r_{g}$ is strongly reduced over a short (unresolved) spatial scale. We argue that while the CR pressure builds up ahead of the shock, the acceleration enters into a strongly nonlinear phase in which an acoustic instability, driven by the CR pressure gradient, dominates other instabilities (at least in the case of low $\beta$ plasma). In this regime the precursor steepens into a strongly nonlinear front whose size scales with \emph{the CR pressure}as $L_{f}\sim L_{p}\cdot(L_{s}/L_{p})^{2}(P_{c}/P_{g})^{2}$, where $L_{s}$ is the scale of the developed acoustic turbulence, and $P_{c}/P_{g}$ is the ratio of CR to gas pressure. Since $L_{s}\ll L_{p}$, the precursor scale reduction may be strong in the case of even a moderate gas heating by the CRs through the acoustic and (possibly also) the other instabilities driven by the CRs.Comment: EPS 2010 paper, to appear in PPC

Modeling of competitive interactions: basic regularities. Part 2.

Objective: to analyze the general patterns of political dynamics (primarily in interstate relations) caused by the presence of competition between the key political actors.Methods: methods of mathematical dynamic modeling are used to study competitive interactions.Results: the work is the second part of the article devoted to the analysis of general patterns of socio-economic and political dynamics. This part of the study analyzes the issues of competition of social systems, general features of competitive interactions based on the study of the basic mathematical model describing competition in socio-economic and political spheres. It has been shown that the basic mathematical model of competition allows describing the features of geopolitical dynamics both in terms of competition and in terms of partnership.Scientific novelty: the results of analysis and mathematical modeling allow identifying the patterns of geopolitical dynamics and determining the conditions under which the implementation of various options for global development is possible.Practical significance: comprehension of the conditions of transition from one mode of geopolitical interaction to another increases the validity of the geopolitical dynamics forecast

Modeling of competitive interactions: basic regularities. Part 1

Objective: to analyze the general patterns of socio-economic and political dynamics (both within society and in interstate relations) caused by the presence of competition between key economic and political actors.Methods: methods of mathematical dynamic modeling were used to study competitive interactions.Results: the attitude to competition as a social phenomenon is ambiguous. It is considered either as a positive (for example, in market economy studies), or as a negative (for example, when considering interstate conflicts) factor. The paper attempts to analyze the general features of competitive interactions based on the study of the basic mathematical model describing competition in socio-economic and socio-political spheres. Using the basic mathematical model, various regimes of competitive interactions are considered; the conditions for the transition from one regime to another are determined; examples of the implementation of these modes in the economy are given.Scientific novelty: in the course of the research using mathematical modeling, the main attention was paid to the so-called non-robust (according to A. A. Andronov) cases of the implementation of competitive interaction, which have rarely been considered in the scientific literature so far, but are often found in real life.Practical significance: the results of analysis and mathematical modeling allow establishing the conditions under which competition stimulation contributes to economic development and under which it leads to crisis situations

Russia in the Context of the Global Crisis

The article examines the features of the current situation in the world and the existing threats to Russia in its confrontation with the collective West. It is shown that the current global crisis is caused by the change of historical epochs and the transformation of the world system into a qualitatively new state. The old patterns stop working, it’s time to design the future. In these conditions, Russia has a chance to propose its own world order project and become one of the leaders in the new historical reality. But this requires a purposeful and wise policy.Aim. The aim of this article is to analyze the current situation in the world and substantiate Russia’s policy in the current conditions.Tasks. During the research, the following tasks were solved: modeling and forecasting world dynamics in the 21st century, identifying global trends, analyzing the features of the current crisis situation; analysis of the modern confrontation between the collective West and Russia; analysis of the tasks that Russia faces in the short, medium and long term, and justification of ways to solve them.Methods. The methodology for solving these problems is based on the identification of patterns of historical development using modern methods of modeling and forecasting world dynamics, developed at Lomonosov Moscow State University under the guidance of Academician V. A. Sadovnichy.Results. The results of mathematical modeling have shown that humanity is currently moving to a fundamentally new phase of historical development, when the old economic and social technologies (liberal capitalism, classical socialism) no longer work. There is a transition of human society into a new phase state, the shape of which has not yet been determined. In these conditions, we are not talking about forecasting, but about designing the future in new historical conditions. The struggle of world projects begins. Russia’s strategy should be formed on the basis of understanding the specifics of the current situation.Conclusions. The current global crisis creates serious threats to Russia’s development, exacerbates the pressure on it from the collective West. However, at the same time, new opportunities are opening up for Russia: it gets a chance to propose its own world order project and become one of the leaders in the new historical reality. To realize this chance, a purposeful and wise policy is needed. The article suggests a number of measures to implement this policy