Optical Spin Orientation in Strained Superlattices

Optical orientation in the strained semiconductor superlattices is investigated theoretically. The dependence of the features in spin-polarization spectra on the structure parameters is clarified. The value of polarization in the first polarization maximum in the SL structures is shown to grow with the splitting between the hh- and lh- states of the valence band, the joint strain and confinement effects on the hh1- lh1 splitting being strongly influenced by the tunneling in the barriers. In strained structures with high barriers for the holes initial polarization can exceed 95 %. Calculated polarization spectra are close to the experimental spectra of polarized electron emission.Comment: 20 pages, 8 figure

The formation of Uranus and Neptune among Jupiter and Saturn

The outer giant planets, Uranus and Neptune, pose a challenge to theories of planet formation. They exist in a region of the Solar System where long dynamical timescales and a low primordial density of material would have conspired to make the formation of such large bodies ($\sim$ 15 and 17 times as massive as the Earth, respectively) very difficult. Previously, we proposed a model which addresses this problem: Instead of forming in the trans-Saturnian region, Uranus and Neptune underwent most of their growth among proto-Jupiter and -Saturn, were scattered outward when Jupiter acquired its massive gas envelope, and subsequently evolved toward their present orbits. We present the results of additional numerical simulations, which further demonstrate that the model readily produces analogues to our Solar System for a wide range of initial conditions. We also find that this mechanism may partly account for the high orbital inclinations observed in the Kuiper belt.Comment: Submitted to AJ; 38 pages, 16 figure

Venus Express radio occultation observed by PRIDE

Context. Radio occultation is a technique used to study planetary atmospheres by means of the refraction and absorption of a spacecraft carrier signal through the atmosphere of the celestial body of interest, as detected from a ground station on Earth. This technique is usually employed by the deep space tracking and communication facilities (e.g., NASA's Deep Space Network (DSN), ESA's Estrack). Aims. We want to characterize the capabilities of the Planetary Radio Interferometry and Doppler Experiment (PRIDE) technique for radio occultation experiments, using radio telescopes equipped with Very Long Baseline Interferometry (VLBI) instrumentation. Methods. We conducted a test with ESA's Venus Express (VEX), to evaluate the performance of the PRIDE technique for this particular application. We explain in detail the data processing pipeline of radio occultation experiments with PRIDE, based on the collection of so-called open-loop Doppler data with VLBI stations, and perform an error propagation analysis of the technique. Results. With the VEX test case and the corresponding error analysis, we have demonstrated that the PRIDE setup and processing pipeline is suited for radio occultation experiments of planetary bodies. The noise budget of the open-loop Doppler data collected with PRIDE indicated that the uncertainties in the derived density and temperature profiles remain within the range of uncertainties reported in previous Venus' studies. Open-loop Doppler data can probe deeper layers of thick atmospheres, such as that of Venus, when compared to closed-loop Doppler data. Furthermore, PRIDE through the VLBI networks around the world, provides a wide coverage and range of large antenna dishes, that can be used for this type of experiments

Moa-2010-BLG-073L: An m-dwarf with a substellar companion at the planet/brown dwarf boundary

We present an analysis of the anomalous microlensing event, MOA-2010-BLG-073, announced by the Microlensing Observations in Astrophysics survey on 2010 March 18. This event was remarkable because the source was previously known to be photometrically variable. Analyzing the pre-event source light curve, we demonstrate that it is an irregular variable over timescales \u3e200 days. Its dereddened color, (V-I)S, 0, is 1.221 ± 0.051 mag, and from our lens model we derive a source radius of 14.7 ± 1.3 R⊙, suggesting that it is a red giant star. We initially explored a number of purely microlensing models for the event but found a residual gradient in the data taken prior to and after the event. This is likely to be due to the variability of the source rather than part of the lensing event, so we incorporated a slope parameter in our model in order to derive the true parameters of the lensing system. We find that the lensing system has a mass ratio of q = 0.0654 ± 0.0006. The Einstein crossing time of the event, tE = 44.3 ± 0.1 days, was sufficiently long that the light curve exhibited parallax effects. In addition, the source trajectory relative to the large caustic structure allowed the orbital motion of the lens system to be detected. Combining the parallax with the Einstein radius, we were able to derive the distance to the lens, DL = 2.8 ± 0.4 kpc, and the masses of the lensing objects. The primary of the lens is an M-dwarf with ML,1 = 0.16 ± 0.03 M⊙, while the companion has ML,2 = 11.0 ± 2.0 MJ, putting it in the boundary zone between planets and brown dwarfs. © 2013 The American Astronomical Society. All rights reserved

First-principles study of TMNan (TM= Cr, Mn, Fe, Co, Ni; n = 4-7) clusters

Geometry, electronic structure, and magnetic properties of TMNan (TM=Cr-Ni; n = 4-7) clusters are studied within a gradient corrected density functional theory (DFT) framework. Two complementary approaches, the first adapted to all-electron calculations on free clusters, and the second been on plane wave projector augmented wave (PAW) method within a supercell approach are used. Except for NiNan, the clusters in this series are found to retain the atomic moments of the TM atoms, and the magnetic moment presented an odd-even oscillation with respect to the number of Na atoms. The origin of these odd-even oscillations is explained from the nature of chemical bonding in these clusters. Differences and similarities between the chemical bonding and the magnetic properties of these clusters and the TMNan (TM = Sc, V and Ti; n = 4-6) clusters on one hand, and TM-doped Au and Ag clusters on the other hand, are discussed

Изменчивость гидрохимических характеристик поверхностных вод пролива Шокальского по результатам наблюдений на научно-исследовательском стационаре «Ледовая база Мыс Баранова» в 2018–2019 гг.

In connection with the progressing climate change in the Arctic, it is extremely important to conduct systematic long-term monitoring in the high-latitude Arctic. An important place in the network of monitoring stations is occupied by the research Station «Cape Baranov» Ice base», located on Severnaya Zemlya (in the area of the Shokalsky Strait). The article presents the results of hydrochemical observations at the Ice base from December 02, 2018 to July 15, 2019. 35 hydrochemical stations were operated from the ice of the strait in the seawater layer of 0–110 m. A significant temporal variability of the characteristics in the upper layer (0–10 m) has been recorded. Four phases of variability of the hydrochemical parameters (HP) have been identified. In December (phase 1) the HP values indicate the presence of surface waters, the origin of which we associate with the transformed river waters (TRW) of the Ob and Yenisei, coming from the Kara Sea. From January to mid-April (phase 2) the highest salinity levels and homogeneous HP are observed due to intensive vertical mixing of waters in the autumn-winter period. At the end of April — May (phase 3) there is a slight desalination of the surface layer in the Shokalsky Strait, with HP pointing to the presence of TRW. From June to July, 15 (4th phase), there is a sharp decrease in the salinity, an increase in oxygen and pH, as well as a drop in the concentration of all the biogenic elements. Such HPs indicate both additional desalination from ice and snow melting and the beginning of phytoplankton bloom. An estimation has been carried out of the proportion of TRW and waters formed during sea ice melting. The average integral proportion of TRW in the water column is ~ 4 %, and for melt water this indicator is close to zero. The influence of ice formation on the hydrochemical characteristics of the surface layers is most noticeable in the 1st and 3rd phases. During the period of strong desalination of the surface waters (May —July), the TRW proportion can reach 10 % or more. From July, the contribution of the melting of sea ice is comparable to that of TRW.В соответствии с программой систематического долгосрочного мониторинга климата Арктики на НИС «Ледовая база Мыс Баранова» в 2018–2019 гг. в проливе Шокальского выполнено наблюдение гидрохимических характеристик поверхностных вод и проведен анализ причин их временной изменчивости. Выделены 4 фазы изменчивости характеристик поверхностных вод, обусловленных влиянием речного стока, процессами вертикального перемешивания, образования и таяния льда и функционированием фитопланктона в весенне-летний период. Выполнена оценка доли речных и талых вод в составе поверхностного слоя вод пролива: доля речных вод в столбе воды составляет ~ 4 %, для талых вод этот показатель близок к нулю. В периоды сильного распреснения поверхностных вод (май — июль) доля речных вод достигает десяти и более процентов

Конусно-лучевая компьютерная томография в диагностике плоских деформаций стопы: проспективное исследование

INTRODUCTION: Flat deformities are one of the most common pathological changes of the feet. Flatfeet is a disease with high social significance, since it not only affects on the quality of life, but is also an important factor in classification of fitness for military service. The main method of diagnosis of these diseases is radiography of the feet in a lateral projection in the standing position. Despite numerous publications describing various methods for assessing the ratio of the bones of the foot, there is no consensus in the scientific community about the exact criteria for flatfoot and its degrees. At the same time, it is noted that the final conclusion is influenced not only by the method of evaluating the finished image, but also by the method of conducting the study. The construction of modern digital X-ray systems in most cases is not adapted for classical X-ray podography, and the study without special devices and the impossibility of strict adherence to the methodology lead to significant distortions of the results. It follows from this that specialized equipment is required for the diagnosis of flatfoot deformities, which allows developing a unified methodology for conducting research and limiting the possibilities of simulations and aggravations.OBJECTIVE: To determine the possibilities of cone-beam computed tomography in the diagnosis of flatfoot deformities in a standing position with a natural load.MATERIALS AND METHODS: This study included 100 patients underwent examination at the S.M.Kirov Military Medical Academy. All patients were examined using the classical radiography and using the cone-beam computed tomograph (CBCT) «ATRISS» (Electron, Russia). Tomograms were evaluated by two methods: using an averaged image and using a thin slice. The study was conducted by two doctors with the determination of the height and angle of the arch of the foot, followed by an assessment of the degree of flatfoot. Statistics. Statistical analysis was performed using Medcalc software (version 18.2.1). The absolute results of measurements for longitudinal and transverse flatfoot obtained by various methods were compared, as well as the time spent on the study (Wilcoxon and Friedman criteria), the degree of correlation between measurements (Spearman’s criterion), as well as the degree of consistency of the conclusions of two experts to identify longitudinal and transverse flat feet (Kappa-Cohen coefficient). RESULTS: Angle measurements in absolute values did not differ significantly between all the methods used (p=0.1803). There were significant differences between measurements of the height of the arch of the foot between the X-ray method and CBCT (p<0.01). In a comparative analysis of radiography and CBCT, two experts noted a high consistency of research results. CBCT made it possible to perform studies with less time (p<0.01). The effective dose for CBCT is significantly higher than for radiography (p<0.01), but does not exceed 0.12 mSv.DISCUSSION: According to the results of the study, it was found that the effectiveness of CBCT in the diagnosis of flatfoot deformities is not worse than classical radiography. At the same time, the CBCT allows you to avoid positioning errors, stacking and cases of attempted simulation. The effective dose for CBCT allows using the technique as a preventive study. Also, CBCT has a high throughput and allows you to get significantly more information in one scan than with radiography.CONCLUSION: CBCT in a standing position with a natural load is not worse then classical radiography techniques in the accuracy of diagnosis of flatfoot deformities. At the same time, the CBCT has extensive postprocessing capabilities, higher throughput, low radiation load, and also reduces the likelihood of methodological errors and cases of aggravation. CBCT is promising in the consciousness of a universal methodology for measuring and classifying of flatfoot with a more precise formulation of setting points for measuring the angles of the arch and deviation of the hallux.ВВЕДЕНИЕ: Плоские деформации являются одними из наиболее часто встречающихся патологических изменений стоп. Плоскостопие является заболеванием с высоким социальным значением, поскольку не только оказывает влияние на качество жизни отдельного человека, но и является важным фактором классификации на различные категории годности к военной службе. Основным методом диагностики этих заболеваний является рентгенография стоп в боковой проекции в условиях естественной нагрузки. Несмотря на многочисленные публикации, в которых описываются различные методики оценки соотношения костей стопы, в научной среде отсутствует единое мнение о точных критериях плоскостопия и его степеней. При этом отмечается, что на итоговое заключение влияет не только способ оценки готового изображения, но и особенности его получения. Конструкция современных цифровых рентгеновских аппаратов в большинстве случаев не приспособлена для проведения классической рентгеновской подографии, а выполнение исследования без специальных устройств и невозможность строгого соблюдения методики приводят к значительным искажениям результатов. Из этого следует, что для диагностики плоских деформаций стоп требуется специализированное оборудование, позволяющее разработать единую методику проведения исследования и ограничивающую возможности симуляций и агграваций.ЦЕЛЬ: Определить возможности конусно-лучевой компьютерной томографии в диагностике плоской деформации стоп в положении стоя с естественной нагрузкой.МАТЕРИАЛЫ И МЕТОДЫ: В данном исследовании принимали участие 100 пациентов, проходивших обследование в Военно-медицинской академии им. С. М. Кирова. Все пациенты были обследованы с использованием классической методики рентгенографии и с использованием конусно-лучевого компьютерного томографа (КЛКТ) «АТРИСС» («Электрон», Россия). Томограммы оценивались двумя методиками: с использованием усредненного изображения и с использованием тонкого среза. Исследование проводилось двумя врачами с определением высоты и угла свода стопы с последующей оценкой степени плоскостопия.Статистика. Статистический анализ проводился с использованием программного обеспечения Medcalc (версия 18.2.1). Сравнивались абсолютные результаты измерений на продольное и поперечное плоскостопие, полученные различными методиками, а также врем, затраченное на исследование (критерии Уилкоксона и Фридмана), степень корреляции между измерениями (критерий Спирмена), а также степень согласованности заключений двух экспертов на выявление продольного и поперечного плоскостопия (коэффициент Каппа-Коэна).РЕЗУЛЬТАТЫ: Измерения углов в абсолютных значениях значимо не различались между всеми используемыми методиками (p=0,1803). Отмечались значимые различия между измерениями высоты свода стопы между рентгенологическим методом и КЛКТ (p<0,01). При сравнительном анализе рентгенографии и КЛКТ двумя экспертами отмечалась высокая согласованность результатов исследований. КЛКТ позволяла выполнять исследования с меньшими затратами времени (р<0,01). Эффективная доза при КЛКТ значимо больше, чем при рентгенографии (р<0,01), но не превышает 0,12 мЗв.ОБСУЖДЕНИЕ: По итогам исследования было установлено, что эффективность КЛКТ в диагностике плоских деформаций стопы не уступает классической рентгенографии. При этом КЛКТ позволяет избежать ошибок позиционирования, укладки и случаев попытки симуляции. Эффективная доза при КЛКТ позволяет использовать методику в качестве профилактического исследования. Также КЛКТ обладает высокой пропускной способностью и позволяет за одно сканирование получить существенно больше информации, чем при рентгенографии.ЗАКЛЮЧЕНИЕ: КЛКТ с вертикальной нагрузкой не уступает классическим методикам рентгенографии в точности диагностики плоских деформаций стопы. При этом КЛКТ обладает широкими возможностями постпроцессорной обработки, более высокой пропускной способностью, низкой лучевой нагрузкой, а также позволяет снизить вероятность методологических ошибок и случаев аггравации. КЛКТ перспективна в сознании универсальной методики измерения и классификации плоскостопия с более точной формулировкой постановки точек для измерения углов свода и отклонения большого пальца стопы

Venus Express radio occultation observed by PRIDE

Context. Radio occultation is a technique used to study planetary atmospheres by means of the refraction and absorption of a spacecraft carrier signal through the atmosphere of the celestial body of interest, as detected from a ground station on Earth. This technique is usually employed by the deep space tracking and communication facilities (e.g., NASA’s Deep Space Network (DSN), ESA’s Estrack). Aims. We want to characterize the capabilities of the Planetary Radio Interferometry and Doppler Experiment (PRIDE) technique for radio occultation experiments, using radio telescopes equipped with Very Long Baseline Interferometry (VLBI) instrumentation. Methods. We conducted a test with ESA’s Venus Express (VEX), to evaluate the performance of the PRIDE technique for this particular application. We explain in detail the data processing pipeline of radio occultation experiments with PRIDE, based on the collection of so-called open-loop Doppler data with VLBI stations, and perform an error propagation analysis of the technique. Results. With the VEX test case and the corresponding error analysis, we have demonstrated that the PRIDE setup and processing pipeline is suited for radio occultation experiments of planetary bodies. The noise budget of the open-loop Doppler data collected with PRIDE indicated that the uncertainties in the derived density and temperature profiles remain within the range of uncertainties reported in previous Venus’ studies. Open-loop Doppler data can probe deeper layers of thick atmospheres, such as that of Venus, when compared to closed-loop Doppler data. Furthermore, PRIDE through the VLBI networks around the world, provides a wide coverage and range of large antenna dishes, that can be used for this type of experiments