Proton acceleration in analytic reconnecting current sheets

Particle acceleration provides an important signature for the magnetic collapse that accompanies a solar flare. Most particle acceleration studies, however, invoke magnetic and electric field models that are analytically convenient rather than solutions of the governing magnetohydrodynamic equations. In this paper a self-consistent magnetic reconnection solution is employed to investigate proton orbits, energy gains, and acceleration timescales for proton acceleration in solar flares. The magnetic field configuration is derived from the analytic reconnection solution of Craig and Henton. For the physically realistic case in which magnetic pressure of the current sheet is limited at small resistivities, the model contains a single free parameter that specifies the shear of the velocity field. It is shown that in the absence of losses, the field produces particle acceleration spectra characteristic of magnetic X-points. Specifically, the energy distribution approximates a power law ~ξ-3/2 nonrelativistically, but steepens slightly at the higher energies. Using realistic values of the “effective” resistivity, we obtain energies and acceleration times that fall within the range of observational data for proton acceleration in the solar corona

Indeterminacy and instability in Petschek reconnection

We explain two puzzling aspects of Petschek's model for fast reconnection. One is its failure to occur in plasma simulations with uniform resistivity. The other is its inability to provide anything more than an upper limit for the reconnection rate. We have found that previously published analytical solutions based on Petschek's model are structurally unstable if the electrical resistivity is uniform. The structural instability is associated with the presence of an essential singularity at the X-line that is unphysical. By requiring that such a singularity does not exist, we obtain a formula that predicts a specific rate of reconnection. For uniform resistivity, reconnection can only occur at the slow, Sweet-Parker rate. For nonuniform resistivity, reconnection can occur at a much faster rate provided that the resistivity profile is not too flat near the X-line. If this condition is satisfied, then the scale length of the nonuniformity determines the reconnection rate

Acesso das pequenas empresas russas aos mercados de contratos públicos: análise de dados

The aim of this study was to assess the current extent of participation by Russian small enterprises in regional public procurement. We discussed how legislation affects the volume of contracts awarded to small enterprises. We calculated the number of contracts per 100 small enterprises, how much the number and value of such contracts account for in the total number and value of contracts concluded with all suppliers per region, as well as what is the average value of contracts per small enterprise and the average value of one such contract. In order to ensure benchmarking for enterprises located in different regions, such enterprises were assessed on the basis of relative indicators. This study used official statistics accumulated with regard to all public procurement in the regions. The data on the number of contracts and their value for the period from 2010 to 2014 were used. For the purposes of empirical data analysis, the normal distribution probability density functions set for all the indicators in question were used. The findings of this study and the tools used for assessing the extent of participation by small enterprises in public procurement can be used when researching entrepreneurship, as well as to justify the contract system development programs in Russia. Such information is important for entrepreneurs, as it enables them to assess the feasibility and consequences of participation in public procurement.El objetivo de este estudio fue evaluar el grado actual de participación de las pequeñas empresas rusas en la contratación pública regional. Discutimos cómo la legislación afecta el volumen de contratos adjudicados a pequeñas empresas. Calculamos el número de contratos por cada 100 pequeñas empresas, cuánto representan el número y el valor de dichos contratos en el número y el valor total de los contratos celebrados con todos los proveedores por región, así como también cuál es el valor promedio de los contratos por cada pequeña empresa y el valor promedio de uno de esos contratos. Con el fin de garantizar la evaluación comparativa para las empresas ubicadas en diferentes regiones, dichas empresas se evaluaron sobre la base de indicadores relativos. Este estudio utilizó estadísticas oficiales acumuladas con respecto a todas las contrataciones públicas en las regiones. Se utilizaron los datos sobre el número de contratos y su valor para el período de 2010 a 2014. A los efectos del análisis de datos empíricos, se utilizaron las funciones de densidad de probabilidad de distribución normal establecidas para todos los indicadores en cuestión. Las conclusiones de este estudio y las herramientas utilizadas para evaluar el grado de participación de las pequeñas empresas en la contratación pública se pueden utilizar al investigar el espíritu empresarial, así como para justificar los programas de desarrollo de sistemas contractuales en Rusia. Dicha información es importante para los empresarios, ya que les permite evaluar la viabilidad y las consecuencias de la participación en la contratación pública.O objetivo deste estudo foi avaliar o atual grau de participação das pequenas empresas russas nas compras públicas regionais. Discutimos como a legislação afeta o volume de contratos concedidos a pequenas empresas. Nós calculamos o número de contratos por 100 pequenas empresas, que representam o número eo valor desses contratos no número total eo valor total dos contratos com todos os fornecedores por região, bem como o que o valor médio de contratos para cada empresa de pequeno porte e o valor médio de um desses contratos. Para garantir benchmarking para empresas localizadas em diferentes regiões, essas empresas foram avaliadas com base em indicadores relativos. Este estudo utilizou estatísticas oficiais acumuladas em relação a todas as compras públicas nas regiões. Foram utilizados os dados sobre o número de contratos e seu valor para o período de 2010 a 2014. Para fins de análise empírica dos dados, foram utilizadas as funções de densidade de probabilidade de distribuição normal estabelecidas para todos os indicadores em questão. As conclusões deste estudo e os instrumentos utilizados para avaliar o grau de participação das pequenas empresas nos contratos públicos podem ser utilizados na investigação do empreendedorismo, bem como para justificar os programas de desenvolvimento de sistemas contratuais na Rússia. Esta informação é importante para os empresários, pois permite avaliar a viabilidade e as consequências da participação em contratos públicos

A POSSIBILITY TO USE ANTIARRHYTHMIC MEDICATIONS FROM II CLASS AND MODULATED KINESITHERAPY AS PRIMARY PREVENTION OF ATRIAL FIBRILLATION IN METABOLIC SYNDROME PATIENTS

Aim. To evaluate the usage of II class antiarrhythmic drugs and modulated kinesitherapy (MK) as primary prevention of atrial fibrillation (AF) in patients with metabolic syndrome (MS) with revelation of short-term risk for this arrhythmia development.Material and methods. We observed 153 patients with MS at the age 58-75 y. o. without AF in anamnesis, but with short-term risk of its development (2 years after examination), defined via comparative analysis of AF course, induced by transesophageal electrocardiostimulation, in dynamic patients observation. All patients, as primary prevention of AF, used antiarrhythmics of the 2nd class, and in side effects development or in contraindications they underwent MK; polyunsaturated fatty acids also used (PUFA).Results. After inclusion to the study 77 (50,33%) of MS patients used II class drugs additionally to therapy, 42 (27,45%) patients underwent MK, and the rest used PUFA. The best clinical effect was found in II class drugs and MK >63,75% and 74,41%, resp. Efficacy of the therapy in this type of patients highly correlated with the improvement of the left ventricle dysfunction, signal-average electrocardiogram, P-wave dispersion and the decrease of the left atrium volume.Conclusion. If the short-term risk of AF found in MS patients, as primary prevention the method of choice is antiarrhythmic therapy II class drugs and MK

Petroleum-related hydrocarbons in deep and subsurface sediments from South-Western Barents Sea

Subsurface sediments from a pockmark area in South-Western Barents Sea have been earlier found to contain elevated levels of petroleum-related polycyclic aromatic hydrocarbons. This work describes a comprehensive analysis of various biomarkers, including the highly source-specific hopanes, in a 4.5 m long gravity core from the same area, together with subsurface sediment samples from other areas in the region without pockmarks present (“background samples”). A clear difference between the pockmark gravity core and the background sediment cores was found, both with regard to genesis and the level of transformation of organic matter. A number of indicator parameters, such as methylphenanthrene index (MPI-1), point towards a significantly higher maturity of hydrocarbons in the pockmark core throughout its length as compared to the other sampled locations. Higher contents of microbial hopanoids (hopenes) may indicate the former presence of petroleum. These findings confirm the hypothesis of a natural hydrocarbon source in the deeper strata present in the studied location with pockmarks