Possible sources of H2 to H2O enrichment at evaporation of parent chondritic material

One of the results obtained from thermodynamic simulation of recondensation of the source chondritic material is that at 1500-1800 K it's possible to form iron-rich olivine by reaction between enstatite, metallic iron and water vapor in the case of (H2O)/(H2) approximately equal to 0.1. This could be reached if the gas depletion in hydrogen is 200-300 times relative to solar abundance. To get this range of depletion one needs some source material more rich in hydrogen than the carbonaceous CI material which is the richest in volatiles among chondrites. In the case of recondensation at impact heating and evaporation of colliding planetesimals composed of CI material, we obtain insufficiently high value of (H2)/(H2O) ratio. In the present paper we consider some possible source materials and physical conditions necessary to reach gas composition with (H2)/(H2O) approximately 10 at high temperature

Bimodal Brightness Oscillations in Models of Young Binary Systems

We consider a model for the cyclic activity of young binary stars that accrete matter from the remnants of a protostellar cloud. If the orbit of such a binary system is inclined at a small angle to the line of sight, then the streams of matter and the density waves excited in the circumbinary disk can screen the primary component of the binary from the observer. To study these phenomena by the SPH (smoothed particle hydrodynamics) method, we have computed grids of hydrodynamic models for binary systems based on which we have constructed the light curves as a function of the orbital phase.The main emphasis is on investigating the properties of the brightness oscillations. Therefore, the model parameters were varied within the following ranges: the component mass ratio q = M2 : M1 = 0.2 - 0.5 and the eccentricity e = 0 - 0.7. The parameter that defined the binary viscosity was also varied. We adopted optical grain characteristics typical of circumstellar dust. Our computations have shown that bimodal oscillations are excited in binaries with eccentric orbits, provided that the binary components do not differ too much in mass. In this case, the ratios of the periods and amplitudes of the bimodal oscillations and their shape depend strongly on the inclination of the binary plane and its orientation relative to the observer. Our analysis shows that the computed light curves can be used in interpreting the cyclic activity of UX Ori stars.Comment: 14 pages, 5 figures, 1 tabl

Analysis of Peculiarities of the Stellar Velocity Field in the Solar Neighborhood

Based on a new version of the Hipparcos catalogue and an updated Geneva-Copenhagen survey of F and G dwarfs, we analyze the space velocity field of about 17000 single stars in the solar neighborhood. The main known clumps, streams, and branches (Pleiades, Hyades, Sirius, Coma Berenices, Hercules, Wolf 630-alpha Ceti, and Arcturus) have been identified using various approaches. The evolution of the space velocity field for F and G dwarfs has been traced as a function of the stellar age. We have managed to confirm the existence of the recently discovered KFR08 stream. We have found 19 Hipparcos stars, candidates for membership in the KFR08 stream, and obtained an isochrone age estimate for the stream, 13 Gyr. The mean stellar ages of the Wolf 630-alpha Ceti and Hercules streams are shown to be comparable, 4--6 Gyr. No significant differences in the metallicities of stars belonging to these streams have been found. This is an argument for the hypothesis that these streams owe their origin to a common mechanism.Comment: 23 pages, 9 figure

Application of Vector Spherical Harmonics and Kernel Regression to the computations of OMM Parameters

The high quality of Hipparcos data in position, proper motion, and parallax has allowed for studies about stellar kinematics with the aim of achieving a better physical understanding of our galaxy, based on accurate calculus of the Ogorodnikov-Milne model (OMM) parameters. The use of discrete least squares is the most common adjustment method, but it may lead to errors mainly because of the inhomogeneous spatial distribution of the data. We present an example of the instability of this method using the case of a function given by a linear combination of Legendre polynomials. These polynomials are basic in the use of vector spherical harmonics, which have been used to compute the OMM parameters by several authors, such as Makarov & Murphy, Mignard & Klioner, and Vityazev & Tsvetkov. To overcome the former problem, we propose the use of a mixed method (see Marco et al.) that includes the extension of the functions of residuals to any point on the celestial sphere. The goal is to be able to work with continuous variables in the calculation of the coefficients of the vector spherical harmonic developments with stability and efficiency. We apply this mixed procedure to the study of the kinematics of the stars in our Galaxy, employing the Hipparcos velocity field data to obtain the OMM parameters. Previously, we tested the method by perturbing the Vectorial Spherical Harmonics model as well as the velocity vector field.Part of this work was supported by a grant P1-1B2012-47 from UJI.Marco Castillo, FJ.; Martínez Uso, MJ.; Lopez, J. (2015). Application of Vector Spherical Harmonics and Kernel Regression to the computations of OMM Parameters. Astronomical Journal. 149(4):1-11. https://doi.org/10.1088/0004-6256/149/4/129S111149

Влияние диборнола-ГЭК на электрофизиологические параметры в период восстановления кровотока в миокарде кролика

Objective. Dibornol-HES, a water-soluble drug based on the derivative of 2,6-diisobornyl-4-methylphenol Dibornol conjugated with hydroxyethyl starch, can reduce the occurrence and severity of arrhythmias by preventive intravenous administration, but it is unknown whether the drug could reduce the myocardial arrhythmogenicity once ischemia has developed at the developed ischemia.Materials and methods. In the model of acute ischemia / reperfusion of the rabbit heart, the effect of Dibornol-HEC (80 mg/kg body weight of the animal) on the electrophysiological indices characterizing myocardial arrhythmogenicity (global and border dispersion of repolarization) was studied during the restoration of blood flow. In the model of acute ischemia / reperfusion with 64 unipolar epicardial leads, the activation-recovery intervals were measured and global and border dispersion of repolarization in the native rabbits (control group, n = 9) and in the rabbits treated by Dibornol-HES (on the 25th minute of occlusion, the experimental group, n = 6).Results. The introduction of Dibornol-HES did not lead to a change in the electrocardiographic parameters of rabbits. By the 30th minute of the coronary occlusion on the ECG in the animals of the control and the experimental groups, the intervals RR, QT, QTc were shortened (p < 0.05). In the animals of both groups by the 30th minute of coronary occlusion, the global dispersion of repolarization increased (p < 0.05), the boundary dispersion of repolarization also increased (p < 0.05), due to the decrease in the duration of the activation-recovery intervals in the ischemic zone (p < 0.05). During the 30-minute reperfusion the magnitude of the global dispersion of repolarization did not change in animals of the both groups, and the magnitude of the border dispersion of repolarization in the control rabbits decreased (p < 0.05), while in the rabbits treated by Dibornol-HES the border dispersion of repolarization did not changed.Conclusion. In rabbits of the experimental group, the values of the global and border dispersions of repolarization did not differ from those of the animals in the control group. Therefore, the administration to Dibornol-HES just prior to reperfusion does not lead to the decrease in the dispersion of repolarization increased as a result of acute ischemic myocardial damage.Введение. Диборнол-ГЭК, водорастворимый лекарственный препарат на основе производного 2,6-диизоборнил-4-метилфенола диборнола, конъюгированного гидроксиэтилкрахмалом, способен снижать возникновение и тяжесть аритмий при превентивном внутривенном введении. Однако о данных, способен ли препарат снижать аритмогенность миокарда при его введении в момент уже развившейся ишемии, не известно.Цель работы – исследование влияния препарата диборнола-ГЭК на электрофизиологические показатели сердца кролика в период восстановления кровотока в миокарде.Материалы и методы. В модели острой ишемии (реперфузии) сердца кролика изучено действие диборнола-ГЭК (80 мг/кг массы тела животного) на электрофизиологические показатели, характеризующие аритмогенность миокарда (глобальная и пограничная дисперсии реполяризации, длительность интервала «активация–восстановление») в период восстановления кровотока. У нативных кроликов (контрольная группа, n = 9) и кроликов, получавших внутривенно диборнол-ГЭК (на 25-й мин окклюзии, опытная группа, n = 6), в модели острой ишемии (реперфузии) в 64 униполярных эпикардиальных отведениях измерены интервалы «активация – восстановление», величина глобальной и пограничной дисперсии.Результаты. Введение диборнола-ГЭК не приводило к изменению электрокардиографических параметров кроликов. К 30-й мин коронарной окклюзии на электрокардиограмме у животных контрольной и опытной групп выявлено укорочение интервалов RR, QT, QTc (p < 0,05). У животных обеих групп к 30-й мин ишемии глобальная дисперсия реполяризации увеличилась (p < 0,05), пограничная дисперсия реполяризации также увеличилась (p < 0,05) за счет уменьшения длительности интервалов «активация – восстановление» в ишемизированной зоне (p < 0,05). В период 30-минутной реперфузии величина глобальной дисперсии реполяризации не изменялась у животных обеих групп, а величина пограничной дисперсии реполяризации у контрольных кроликов уменьшилась (p < 0,05), в то время как у кроликов, которым вводили диборнол-ГЭК, нет.Заключение. Значения глобальных и пограничных дисперсий реполяризации у кроликов экспериментальной группы не отличались от значений животных в контрольной группе. Поэтому введение диборнола-ГЭК непосредственно перед реперфузией не приводит к уменьшению дисперсии реполяризации, увеличенной в результате острого ишемического повреждения миокарда

Diurnally Entrained Anticipatory Behavior in Archaea

By sensing changes in one or few environmental factors biological systems can anticipate future changes in multiple factors over a wide range of time scales (daily to seasonal). This anticipatory behavior is important to the fitness of diverse species, and in context of the diurnal cycle it is overall typical of eukaryotes and some photoautotrophic bacteria but is yet to be observed in archaea. Here, we report the first observation of light-dark (LD)-entrained diurnal oscillatory transcription in up to 12% of all genes of a halophilic archaeon Halobacterium salinarum NRC-1. Significantly, the diurnally entrained transcription was observed under constant darkness after removal of the LD stimulus (free-running rhythms). The memory of diurnal entrainment was also associated with the synchronization of oxic and anoxic physiologies to the LD cycle. Our results suggest that under nutrient limited conditions halophilic archaea take advantage of the causal influence of sunlight (via temperature) on O2 diffusivity in a closed hypersaline environment to streamline their physiology and operate oxically during nighttime and anoxically during daytime