Cooling of Dense Gas by H2O Line Emission and an Assessment of its Effects in Chondrule-Forming Shocks

We consider gas at densities appropriate to protoplanetary disks and calculate its ability to cool due to line radiation emitted by H2O molecules within the gas. Our work follows that of Neufeld & Kaufman (1993; ApJ, 418, 263), expanding on their work in several key aspects, including use of a much expanded line database, an improved escape probability formulism, and the inclusion of dust grains, which can absorb line photons. Although the escape probabilities formally depend on a complicated combination of optical depth in the lines and in the dust grains, we show that the cooling rate including dust is well approximated by the dust-free cooling rate multiplied by a simple function of the dust optical depth. We apply the resultant cooling rate of a dust-gas mixture to the case of a solar nebula shock pertinent to the formation of chondrules, millimeter-sized melt droplets found in meteorites. Our aim is to assess whether line cooling can be neglected in chondrule-forming shocks or if it must be included. We find that for typical parameters, H2O line cooling shuts off a few minutes past the shock front; line photons that might otherwise escape the shocked region and cool the gas will be absorbed by dust grains. During the first minute or so past the shock, however, line photons will cool the gas at rates ~ 10,000 K/hr, dropping the temperature of the gas (and most likely the chondrules within the gas) by several hundred K. Inclusion of H2O line cooling therefore must be included in models of chondrule formation by nebular shocks.Comment: Accepted for publication in The Astrophysical Journa

Incorporation of a Late-forming Chondrule into Comet Wild 2

We report the petrology, O isotopic composition, and Al-Mg isotope systematics of a chondrule fragment from the Jupiter-family comet Wild 2, returned to Earth by NASA's Stardust mission. This object shows characteristics of a type II chondrule that formed from an evolved oxygen isotopic reservoir. No evidence for extinct 26Al was found, with (26Al/ 27Al)0 < 3.0 x 10^-6. Assuming homogenous distribution of 26Al in the solar nebula, this particle crystallized at least 3 Myr after the earliest solar system objects--relatively late compared to most chondrules in meteorites. We interpret the presence of this object in a Kuiper Belt body as evidence of late, large-scale transport of small objects between the inner and outer solar nebula. Our observations constrain the formation of Jupiter (a barrier to outward transport if it formed further from the Sun than this cometary chondrule) to be more than 3 Myr after calcium-aluminum-rich inclusionss.Comment: Accepted for publication in ApJ

Women Workers of St. Petersburg in the Late 19th — early 20th Centuries

The article is devoted to the analysis of the conditions of labor activity, as well as the peculiarities of family life and everyday life of women employed at the enterprises of the factory industry of St. Petersburg in the late 19th — early 20th centuries. At the present stage of development of Russia, there is still a high proportion of female labor in industry, which determines the relevance of the problem under study in order to take into account the historical experience in regulating the complex sphere of labor relations. The question of the main factors in the formation of the female labor force in St. Petersburg during the post-reform period is raised in the article. The industries in which female labor was most widely represented are identified. Issues related to the peculiarities of the professional activity of female workers (working conditions, level of wages, problems of social protection, etc.) are discussed in detail. The circumstances of private, personal life are analyzed, the influence of material factors in the life of workers on the family life is revealed. It is concluded that the contradictions between the new status of a woman, who is able to independently determine her own fate, and the preservation of her unequal position in society, led to the wide participation of women workers in the political life of St. Petersburg during the First World War and the 1917 revolution

A Critical Examination of the X-Wind Model for Chondrule and Calcium-rich, Aluminum-rich Inclusion Formation and Radionuclide Production

Meteoritic data, especially regarding chondrules and calcium-rich, aluminum-rich inclusions (CAIs), and isotopic evidence for short-lived radionuclides (SLRs) in the solar nebula, potentially can constrain how planetary systems form. Intepretation of these data demands an astrophysical model, and the "X-wind" model of Shu et al. (1996) and collaborators has been advanced to explain the origin of chondrules, CAIs and SLRs. It posits that chondrules and CAIs were thermally processed < 0.1 AU from the protostar, then flung by a magnetocentrifugal outflow to the 2-3 AU region to be incorporated into chondrites. Here we critically examine key assumptions and predictions of the X-wind model. We find a number of internal inconsistencies: theory and observation show no solid material exists at 0.1 AU; particles at 0.1 AU cannot escape being accreted into the star; particles at 0.1 AU will collide at speeds high enough to destroy them; thermal sputtering will prevent growth of particles; and launching of particles in magnetocentrifugal outflows is not modeled, and may not be possible. We also identify a number of incorrect predictions of the X-wind model: the oxygen fugacity where CAIs form is orders of magnitude too oxidizing; chondrule cooling rates are orders of magnitude lower than those experienced by barred olivine chondrules; chondrule-matrix complementarity is not predicted; and the SLRs are not produced in their observed proportions. We conclude that the X-wind model is not relevant to chondrule and CAI formation and SLR production. We discuss more plausible models for chondrule and CAI formation and SLR production.Comment: Accepted for publication in The Astrophysical Journa

Volcanic SO2 Effective Layer Height Retrieval for OMI Using a Machine Learning Approach

Information about the height and loading of sulfur dioxide (SO2) plumes from volcanic eruptions is crucial for aviation safety and for assessing the effect of sulfate aerosols on climate. While SO2 layer height has been successfully retrieved from backscattered Earthshine ultraviolet (UV) radiances measured by the Ozone Monitoring Instrument (OMI), previously demonstrated techniques are computationally intensive and not suitable for near-real-time applications. In this study, we introduce a new OMI algorithm for fast retrievals of effective volcanic SO2 layer height. We apply the Full-Physics Inverse Learning Machine (FP_ILM) algorithm to OMI radiances in the spectral range of 310–330 nm. This approach consists of a training phase that utilizes extensive radiative transfer calculations to generate a large dataset of synthetic radiance spectra for geophysical parameters representing the OMI measurement conditions. The principal components of the spectra from this dataset in addition to a few geophysical parameters are used to train a neural network to solve the inverse problem and predict the SO2 layer height. This is followed by applying the trained inverse model to real OMI measurements to retrieve the effective SO2 plume heights. The algorithm has been tested on several major eruptions during the OMI data record. The results for the 2008 Kasatochi, 2014 Kelud, 2015 Calbuco, and 2019 Raikoke eruption cases are presented here and compared with volcanic plume heights estimated with other satellite sensors. For the most part, OMI-retrieved effective SO2 heights agree well with the lidar measurements of aerosol layer height from Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) and thermal infrared retrievals of SO2 heights from the infrared atmospheric sounding interferometer (IASI). The errors in OMI-retrieved SO2 heights are estimated to be 1–1.5 km for plumes with relatively large SO2 signals (>40 DU). The algorithm is very fast and retrieves plume height in less than 10 min for an entire OMI orbit

Extreme 54Cr-rich nano-oxides in the CI chondrite Orgueil -Implication for a late supernova injection into the Solar System

Systematic variations in 54Cr/52Cr ratios between meteorite classes (Qin et al., 2010a; Trinquier et al., 2007) point to large scale spatial and/or temporal isotopic heterogeneity in the solar protoplanetary disk. Two explanations for these variations have been proposed, with important implications for the formation of the Solar System: heterogeneous seeding of the disk with dust from a supernova, or energetic-particle irradiation of dust in the disk. The key to differentiating between them is identification of the carrier(s) of the 54Cr anomalies. Here we report the results of our recent NanoSIMS imaging search for the 54Cr-rich carrier in the acid-resistant residue of the CI chondrite Orgueil. A total of 10 regions with extreme 54Cr-excesses ({\delta}54Cr values up to 1500 %) were found. Comparison between SEM, Auger and NanoSIMS analyses showed that these 54Cr-rich regions are associated with one or more sub-micron (typically less than 200 nm) Cr oxide grains, most likely spinels. Because the size of the NanoSIMS primary O- ion beam is larger than the typical grain size on the sample mount, the measured anomalies are lower limits, and we estimate that the actual 54Cr enrichments in three grains are at least 11 times Solar and in one of these may be as high as 50 times Solar. Such compositions strongly favor a Type II supernova origin. The variability in bulk 54Cr/52Cr between meteorite classes argues for a heterogeneous distribution of the 54Cr carrier in the solar protoplanetary disk following a late supernova injection event. Such a scenario is also supported by the O-isotopic distribution and variable abundances in different planetary materials of other presolar oxide and silicate grains from supernovae

Влияние габаритных параметров цилиндрического экрана на эффективность экранирования

Study of dimensional parametersʼ influence on shielding properties of cylindrical shields will allow to optimise the fusion process, as well as to reduce production costs by reducing the material used. The purpose of this work was to compare results of theoretical calculation of shielding effectiveness of an infinite cylindrical shield with the data obtained in real conditions.A cylindrical Ni-Fe shield was synthesised by electrochemical deposition with length of 32 cm, diameter of 4.5 cm and shielding thickness of ≈ 100 µm. The cylinder length was then reduced from 32 cm to 6 cm in 4 cm increments and for each cylinder length shielding effectiveness was measured using three-coordinate Helmholtz field-forming system.The measurement results show that the calculation of shielding effectiveness of infinite cylindrical shield is valid for cylinder lengths l ≥ 18–20 cm. Shielding effectiveness is markedly reduced at values of l ˂ 15 cm.Analysis of data obtained allowed to conclude that it is necessary to determine the correction factor when calculating a cylindrical screen shielding efficiencyИзучение влияния габаритных параметров на экранирующие свойства цилиндрических экранов позволит оптимизировать процесс синтеза, а также снизить затраты на производство, за счёт уменьшения используемого материала. Целью данной работы было сравнение результатов теоретического расчёта эффективности экранирования бесконечного цилиндрического экрана и данных, полученных в реальных условиях.Методом электрохимического осаждения был синтезирован цилиндрический экран Ni-Fe, длина которого составила 32 см, диаметр 4,5 см, толщина экранирующего покрытия составила≈ 100 мкм. Затем длина цилиндра уменьшалась от 30 до 6 см с шагом в 4 см, для каждой длины цилиндра была измерена эффективность экранирования с помощью полеобразующей системы трёхкоординатных катушек Гельмгольца.Результаты измерений показали, что расчёт эффективности экранирования бесконечного цилиндрического экрана справедлив при длине цилиндра l ≥ 18–20 см. При значениях l ˂ 15 см эффективность экранирования заметно снижается.Анализ полученных данных позволил сделать вывод о необходимости определения поправочного коэффициента при расчётах эффективности экранирования цилиндрического экрана

Primordial Compositions of Refractory Inclusions

Bulk chemical and oxygen, magnesium and silicon isotopic compositions were measured for each of 17 Types A and B refractory inclusions from CV3 chondrites. After bulk chemical compositions were corrected for non-representative sampling in the laboratory, the Mg and Si isotopic compositions of each inclusion were used to calculate its original chemical composition assuming that the heavy-isotope enrichments of these elements are due to Rayleigh fractionation that accompanied their evaporation from CMAS liquids. The resulting pre-evaporation chemical compositions are consistent with those predicted by equilibrium thermodynamic calculations for high-temperature nebular condensates but only if different inclusions condensed from nebular regions that ranged in total pressure from 10{sup -6} to 10{sup -1} bar, regardless of whether they formed in a system of solar composition or in one enriched in OC dust relative to gas by a factor of ten relative to solar composition. This is similar to the range of total pressures predicted by dynamic models of the solar nebula for regions whose temperatures are in the range of silicate condensation temperatures. Alternatively, if departure from equilibrium condensation and/or non-representative sampling of condensates in the nebula occurred, the inferred range of total pressure could be smaller. Simple kinetic modeling of evaporation successfully reproduces observed chemical compositions of most inclusions from their inferred pre-evaporation compositions, suggesting that closed-system isotopic exchange processes did not have a significant effect on their isotopic compositions. Comparison of pre-evaporation compositions with observed ones indicates that 80% of the enrichment in refractory CaO + Al{sub 2}O{sub 3} relative to more volatile MgO + SiO{sub 2} is due to initial condensation and 20% due to subsequent evaporation for both Type A and Type B inclusions

Method of the decision of tasks of heat conduction on the basis of determination of the front of temperature perturbation

On the basis of an integral method by determination of the front of temperature perturbation the approximate analytical solution of the nonstationary task of heat conduction for infinitely extensive plate is received. In case of the symmetric boundary conditions of the first kind in a stage of the irregular mode of heat exchange. The decision allows to execute assessment of a temperature status of a plate for small and midget values of temporary variable.На основе интегрального метода путем определения фронта температурного возмущения получено приближенное аналитическое решение нестационарной задачи теплопроводности для бесконечно протяженной пластины. При симметричных граничных условиях первого рода в стадии нерегулярного режима теплообмена. Решение позволяет выполнять оценку температурного состояния пластины для малых и сверхмалых значений временной переменной