Modelling variability of solar activity cycles

Context. Solar activity cycles vary in amplitude and duration. The variations can be at least partly explained by fluctuations in dynamo parameters. Aims. We want to restrict uncertainty in fluctuating dynamo parameters and find out which properties of the fluctuations control the amplitudes of the magnetic field and energy in variable dynamo cycles. Methods. A flux-transport model for the solar dynamo with fluctuations of the Babcock-Leighton type $\alpha$-effect was applied to generate statistics of magnetic cycles for our purposes. The statistics were compared with data on solar cycle periods to restrict the correlation time of dynamo fluctuations. Results. A characteristic time of fluctuations in the $\alpha$-effect is estimated to be close to the solar rotation period. The fluctuations produce asymmetry between the times of rise and descent of dynamo cycles, the rise time being on average shorter. The affect of the fluctuations on cycle amplitudes depends on the phase of the cycle in which the fluctuations occur. Negative fluctuations (decrease in $\alpha$) in the rise phase delay decay of poloidal field and increase the cycle amplitude in toroidal field and magnetic energy. Negative fluctuation in the decline phase reduces the polar field at the end of a cycle and the amplitude of the next cycle. The low amplitude of the 24th solar cycle compared to the preceding 23rd cycle can be explained by this effect. Positive fluctuations in the descent phase enhance the magnetic energy of the next cycle by increasing the seed poloidal field for the next cycle. The statistics of the computed energies of the cycles suggest that superflares of $\ge 10^{34}$ erg are not possible on the Sun.Comment: 8 pages, 11 figures, A&A (accepted

Longitudinal drift of Tayler instability eigenmodes as a possible explanation for super-slowly rotating Ap stars

Rotation periods inferred from the magnetic variability of some Ap stars are incredibly long, exceeding ten years in some cases. An explanation for such slow rotation is lacking. This paper attempts to provide an explanation of the super-slow rotation of the magnetic and thermal patterns of Ap stars in terms of the longitudinal drift of the unstable disturbances of the kink-type (Tayler) instability of their internal magnetic field. The rates of drift and growth were computed for eigenmodes of Tayler instability using stellar parameters estimated from a structure model of an A star. The computations refer to the toroidal background magnetic field of varied strength. The non-axisymmetric unstable disturbances drift in a counter-rotational direction in the co-rotating reference frame. The drift rate increases with the strength of the background field. For a field strength exceeding the (equipartition) value of equal Alfven and rotational velocities, the drift rate approaches the proper rotation rate of a star. The eigenmodes in an inertial frame show very slow rotation in this case. Patterns of magnetic and thermal disturbances of the slowly rotating eigenmodes are also computed. The counter-rotational drift of Tayler instability eigenmodes is a possible explanation for the observed phenomenon of super-slowly rotating Ap stars.Comment: Accepted in A&

Luminescence of Aluminoborosilicate Glasses Doped with Gd3+ Ions

International audienceThe twophoton absorption that leads to the ultraviolet upconversion luminescence in the SiO2–Al2O3–B2O3–Na2O3–Zr2O : Gd3+ glass has been investigated. The inference has been made that no photon cascade emission takes place under excitation by monochromatic light corresponding to the maximum of the absorption band of the Cd3+ ion (204 nm). The mechanisms of concentration quenching and energy transfer between Cd3+ ions and optically active defects of the aluminoborosilicate glass have been discussed

LIPID INFILTRATION OF HEPATOCYTES IN THE MORPHOGENESIS OF CHRONIC HEPATITIS C

The aim of the study was to investigate structurally functional features of lipidic infiltration of hepatocytes in a morphogenesis of chronic hepatitis C. Material and methods. A clinical and morphological study of 199 patients with HCV infection markers (139 men and 60 women aged from 20 till 65 years) was conducted. In all cases, a comprehensive study including analysis of blood biochemical parameters, serological markers of HCV replication in blood and liver, viremia level, number of the infected hepatocytes and HCV genotypes was performed. Diagnostic complex included clinical, biochemical, immunoserological methods. Results and discussion. The results of the analysis of structural and functional features of lipid-containing hepatocytes and indicators of replication of virus particles of chronic hepatitis C are provided. For its reproduction HCV enters into complex relationships with the metabolic apparatus of the cell, in which lipid metabolism and related structures – lipid droplets play an important role. The only structural marker that correlates with indicators of virus replication is subcytolemmal small-vesicular lipid infiltration, which can reflect a virus-induced increase in lipid metabolism in the host cell for the effective production of infectious active viral particles

Использование гипертонического раствора хлорида натрия при операциях в условиях искусственного кровообращения

The paper analyzes the data available in the references on different aspects of using hypertonic sodium chloride solution during surgery under extracorporeal circulation in cardiosurgical care. The hypertonic solution is shown to lower positive fluid balance in the perioperative period, to increase cardiac output with simultaneously decreased vascular resistance, to improve lung oxygenating function, and to normalize tissue blood circulation and neurological status in patients exposed to artificial perfusion. There is evidence for its effect on the immune system and capillary endothelium. It is suggested that it is necessary to study the effect of the hypertonic solution on the incidence of complications and death rates during surgery under extracorporeal circulation and it is proposed to use the solution under long-term extracorporeal circulation. Key words: hypertonic saline, sodium chloride, extracorporeal circulation.Представлен анализ литературы о различных аспектах применения гипертонического раствора хлорида натрия при операциях в условиях искусственного кровообращения в кардиохирургической практике. Показано, что гипертонический раствор уменьшает положительный баланс жидкости в периоперационном периоде, увеличивает сердечный выброс с одновременным снижением сосудистого сопротивления, улучшает оксигенирующую функцию легких, способствует нормализации тканевого кровообращения, а также неврологического статуса у пациентов, подвергшихся искусственной перфузии. Представлены данные о его влиянии на иммунную систему и эндотелий капилляров. Предложена необходимость исследований влияния гипертонического раствора на частоту развития осложнений и летальность при операциях в условиях искусственного кровообращения, а также его использование при длительном искусственном кровообращении. Ключевые слова: гипертонический раствор, хлорид натрия, искусственное кровообращение