867 research outputs found
Topics in Energy Release and Particle Acceleration in the Heliosphere
No full textThis thesis investigates both the release of energy in solar flares, and the acceleration and transport of particles in various astrophysical situations. While numerical simulations are central to this thesis, these are always motivated by analytical arguments.
A review of flare energy release is given in Chapter 2, with results presented in Chapters 3 and 4. The main goal of the flare work is to investigate the effect of viscosity on energy release rates. Scaling arguments and exact solutions of the magnetohydrodynamic equations are used to interpret the results of two-dimensional numerical simulations of magnetic reconnection. The results support viscous energy dissipation accounting for a significant fraction of flare energy release.
Chapter 5 contains an introduction to astrophysical particle acceleration, using the Fokker-Planck formulation. The theory introduced in this chapter is used to study electron transport in solar flare loops (Section 5.5). A key aspect of the analysis is the expression of the Fokker-Planck equation as a system of stochastic differential equations. A generalisation to the flare loop hard X-ray emission prediction of Conway et al. (1998) is obtained, giving a stronger dependence on density for dispersed initial distributions.
Chapter 6 uses the methods of the previous chapter to study the acceleration of cosmic-rays at the heliospheric termination shock. The applicability of the focused acceleration mechanism of Schlickeiser and Shalchi (2008) is examined using numerical simulations, which are interpreted using analytical arguments based on averaging the stochastic equations. The results show significant limitations in assuming a near-isotropic distribution, a requirement for the focused acceleration mechanism. In addition, momentum diffusion provides a significant effect that cannot be neglected. The theory is extended to include focused deceleration and pure momentum diffusion
The Disciples of A.R Kovalevsky: Yu.G. Litvinenko
No full textВ статье освещается жизнь и научное наследие Ю.Г. Литвиненко (1929-1990) -одного из ведущих украинских индологов, ученика выдающегося ориенталиста А.П. Ковалевскго. Научное наследие Ю.Г Литвинвнко условно разделено на четыре рубрики; 1) труды по истории рабочего движения в Британской Индии; 2) сочинения гю истории индийского коммунистического движения; 3) работы по истории национально-освободительного движения народов Индии: 4) индологические публикации в Украинской советской энциклопедии. Автор пришел к выводу, что хотя Ю.Г Литвиненко и не выдвинул фундаментальных концепций истории индийского рабочего и национально-освободительного движения, внес посильный вклад в становление и развитие украинской индологии.The life and scientific heritage of one of thB leading Ukrainian indologist, a disciple of the prominent orientalist A.P. Kovalevsky, Yu.G. Litvinenko (1929-1990). There are studied in the article Yu.G. Litvinenko’s scientific heritage is conditionally divided into four parts: 1) works from the history of the labour movement in the British India; 2) essays on the history of Indian communist movement; 3) studies on the history of national liberation movement of Indian peoples; 4) indological publications in the Ukrainian Soviet Encyclopedia. The author concluded that though Yu.G. Litvinenko has not promoted any fundamental conception of the history of the Indian labour and national liberation movement he had made certain contributions in rise and development of Ukrainian indology
The Disciples of A.R Kovalevsky: Yu.G. Litvinenko
No full textВ статье освещается жизнь и научное наследие Ю.Г. Литвиненко (1929-1990) -одного из ведущих украинских индологов, ученика выдающегося ориенталиста А.П. Ковалевскго. Научное наследие Ю.Г Литвинвнко условно разделено на четыре рубрики; 1) труды по истории рабочего движения в Британской Индии; 2) сочинения гю истории индийского коммунистического движения; 3) работы по истории национально-освободительного движения народов Индии: 4) индологические публикации в Украинской советской энциклопедии. Автор пришел к выводу, что хотя Ю.Г Литвиненко и не выдвинул фундаментальных концепций истории индийского рабочего и национально-освободительного движения, внес посильный вклад в становление и развитие украинской индологии.The life and scientific heritage of one of thB leading Ukrainian indologist, a disciple of the prominent orientalist A.P. Kovalevsky, Yu.G. Litvinenko (1929-1990). There are studied in the article Yu.G. Litvinenko’s scientific heritage is conditionally divided into four parts: 1) works from the history of the labour movement in the British India; 2) essays on the history of Indian communist movement; 3) studies on the history of national liberation movement of Indian peoples; 4) indological publications in the Ukrainian Soviet Encyclopedia. The author concluded that though Yu.G. Litvinenko has not promoted any fundamental conception of the history of the Indian labour and national liberation movement he had made certain contributions in rise and development of Ukrainian indology
Wave energy dissipation by anisotropic viscosity in magnetic x-points
No full textThe viscous dissipation of axial field disturbances in planar magnetic X-points is examined. It is emphasized that an accurate treatment requires a nonisotropic tensor viscosity whose components are governed by the local magnetic field. Numerical solutions are constructed, which compare the buildup of viscous forces using the tensor formulation against a simplified model based on conventional shear viscosity. The scaling of the global energy-loss rate with the viscosity coefficient is shown to follow for both the traditional shear viscosity and the Braginskii bulk viscosity. This suggests that viscous wave dissipation can occur quite rapidly, in a few tens of Alfvén times. The results imply that large-scale disturbances, generated by magnetic reconnection in the solar corona, should dissipate in a time on the order of a few minutes and significantly contribute to coronal heating
Focused acceleration of cosmic-ray particles in non-uniform magnetic fields
No full textThe Fokker–Planck equation for cosmic-ray particles in a spatially varying guide magnetic field in a turbulent plasma is analyzed. An expression is derived for the mean rate of change of particle momentum, caused by the effect of adiabatic focusing in a non-uniform guide field. Results of an earlier diffusion-limit analysis are confirmed, and the physical picture is clarified by working directly with the Fokker–Planck equation. A distributed first-order Fermi acceleration mechanism is identified, which can be termed focused acceleration. If the forward and backward-propagating waves have equal polarizations, focused acceleration operates when the net cross helicity of an Alfvenic slab turbulence is either negative in a diverging guide field or positive in a converging guide field. It is suggested that focused acceleration can contribute to the formation of the anomalous cosmic-ray spectrum at the heliospheric termination shock
Particle acceleration scalings based on exact analytic models for magnetic reconnection
No full textObservations suggest that particle acceleration in solar flares occurs in the magnetic reconnection region above the flare loops. Theoretical models for particle acceleration by the reconnection electric field, however, employ heuristic configurations for electric and magnetic fields in model current sheets, which are not solutions to the MHD reconnection problem. In the present study, particle acceleration is discussed within the context of a self-consistent MHD reconnection solution. This has the advantage of allowing poorly constrained local parameters in the current sheet region to be expressed in terms of the boundary conditions and electric resistivity of the global solution. The resulting acceleration model leads to energy gains that are consistent with those for high-energy particles in solar flares. The overall self-consistency of the approach is discussed
Modeling sunspot and starspot decay by turbulent erosion
No full textDisintegration of sunspots (and starspots) by fluxtube erosion, originally proposed by Simon and Leighton, is considered. A moving boundary problem is formulated for a nonlinear diffusion equation that describes the sunspot magnetic field profile. Explicit expressions for the sunspot decay rate and lifetime by turbulent erosion are derived analytically and verified numerically. A parabolic decay law for the sunspot area is obtained. For moderate sunspot magnetic field strengths, the predicted decay rate agrees with the results obtained by Petrovay and Moreno-Insertis. The new analytical and numerical solutions significantly improve the quantitative description of sunspot and starspot decay by turbulent erosion
Клинико-анатомические особенности иннервации почечных артерий у больных артериальной гипертензией = Clinical and anatomical features of innervation of the renal arteries in patients with arterial hypertension
No full textGarmazi S., Litvinenko M. A. Клинико-анатомические особенности иннервации почечных артерий у больных артериальной гипертензией = Clinical and anatomical features of innervation of the renal arteries in patients with arterial hypertension. Journal of Education, Health and Sport. 2016;6(2):293-300. eISSN 2391-8306. DOI http://dx.doi.org/10.5281/zenodo.46810
http://ojs.ukw.edu.pl/index.php/johs/article/view/3406
https://pbn.nauka.gov.pl/works/717684
The journal has had 7 points in Ministry of Science and Higher Education parametric evaluation. Part B item 755 (23.12.2015).
755 Journal of Education, Health and Sport eISSN 2391-8306 7
© The Author (s) 2016;
This article is published with open access at Licensee Open Journal Systems of Kazimierz Wielki University in Bydgoszcz, Poland
Open Access. This article is distributed under the terms of the Creative Commons Attribution Noncommercial License which permits any noncommercial use, distribution, and reproduction in any medium,
provided the original author(s) and source are credited. This is an open access article licensed under the terms of the Creative Commons Attribution Non Commercial License
(http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted, non commercial use, distribution and reproduction in any medium, provided the work is properly cited.
This is an open access article licensed under the terms of the Creative Commons Attribution Non Commercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted, non commercial
use, distribution and reproduction in any medium, provided the work is properly cited.
The authors declare that there is no conflict of interests regarding the publication of this paper.
Received: 05.01.2016. Revised 12.02.2016. Accepted: 27.02.2016.
Клинико-анатомические особенности иннервации почечных артерий у больных артериальной гипертензией
Clinical and anatomical features of innervation of the renal arteries in patients with arterial hypertension
Гармази С., Литвиненко М. А.
Garmazi S., Litvinenko M. A.
Одесский национальный медицинский университет, г. Одесса, Украина
Odessa National Medical University, Odessa, Ukraine
Summary
Clinical and anatomical features of innervation of the renal arteries in patients with arterial hypertension
Garmazi S., Litvinenko M.A.
Odessa National Medical University, Odessa, Ukraine
The aim of this study was the clinical and anatomical features of innervation of the renal arteries.
The retrospective analysis of health statistics on the prevalence of resistant hypertension based on the Odessa Regional Mortem Bureau during 2011-2012 was conducted. The analysis of the results of the autopsy and subsequent histological examination of 30 bodies of deceased patients with resistant hypertension II and III stages has been done. The morphometry of renal arteries and their segments was conducted. Fragments of the renal artery were not larger than 1,0x1,0x1,0 cm, fixed in 10% neutral formalin and alcohol after standard wiring block embedded in paraffin. Sections 5.0-8.0 microns (in an amount of at least two sections with each block) were stained by the observation procedures recommended modern guidelines: hematoxylin and eosin, by Van Gieson; by Nissle, by Golgi and by Masson. The evaluation of the histological response rate in the vessels was performed visually and compared to the control group.
The greatest density of accumulation in the nerve ganglia determined adventitia proximal renal arteries, preferably on the frontal surface. Ganglions sizes ranging from 80 to 220 microns, larger than when the ganglia are located in the proximal renal artery. The main part of the sympathetic ganglia, located at a depth of 2-3 mm. Postbifurcation ganglia localization occurs in 32.2% of cases. The degree of fibrosis of the renal artery wall in hypertension does not preclude the implementation of radiofrequency catheter sympathectomy.
Key words: arterial hypertension, renal arteries, innervation, pathomorphology
Finite-time singularity formation at a magnetic neutral line in Hall magnetohydrodynamics
No full textThe formation of a current sheet in a weakly collisional plasma can be modelled as a finite-time singularity solution of magnetohydrodynamic equations. We use an exact self-similar solution to confirm and generalise a previous finding that, in sharp contrast to two-dimensional solutions in standard MHD, a finite-time collapse to a current sheet can occur in Hall MHD. We derive a criterion for the finite-time singularity in terms of initial conditions, and we use an intermediate asymptotic solution for the evolution of an axial magnetic field to obtain a general expression for the singularity formation time. We illustrate the analytical results by numerical solutions
Proton acceleration in analytic reconnecting current sheets
No full textParticle 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
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