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

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

Left-handed metacomposites containing carbon fibers and ferromagnetic microwires

We investigate the microwave behavior of polymer-based metacomposites containing ferromagnetic microwires and carbon fibers. A notable transmission window is observed from the metacomposite containing 3mm spaced parallel microwire array in 1-7 GHz, verifying a left-handed behavior. In the hybrid metacomposites containing both parallel wires and carbon fibers, such transmission window is preserved with a much higher transmittance due to the improved impedance match and hence decreased reflection loss. The introducing of continuous carbon fibers leads to a remarkable anisotropic behavior: left-handed properties are turned on/off by rotating the electric excitation by 90 degrees. The proposed metacomposites are promising for microwave cloaking and sensing applications for aerospace-graded structural components

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

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

A giant planet beyond the snow line in microlensing event OGLE-2011-BLG-0251

Aims: We present the analysis of the gravitational microlensing event OGLE-2011-BLG-0251. This anomalous event was observed by several survey and follow-up collaborations conducting microlensing observations towards the Galactic bulge. Methods: Based on detailed modelling of the observed light curve, we find that the lens is composed of two masses with a mass ratio q = 1.9 × 10[SUP]-3[/SUP]. Thanks to our detection of higher-order effects on the light curve due to the Earth's orbital motion and the finite size of source, we are able to measure the mass and distance to the lens unambiguously. Results: We find that the lens is made up of a planet of mass 0.53 ± 0.21 M[SUB]J[/SUB] orbiting an M dwarf host star with a mass of 0.26 ± 0.11 M[SUB]⊙[/SUB]. The planetary system is located at a distance of 2.57 ± 0.61 kpc towards the Galactic centre. The projected separation of the planet from its host star is d = 1.408 ± 0.019, in units of the Einstein radius, which corresponds to 2.72 ± 0.75 AU in physical units. We also identified a competitive model with similar planet and host star masses, but with a smaller orbital radius of 1.50 ± 0.50 AU. The planet is therefore located beyond the snow line of its host star, which we estimate to be around ~1-1.5 AU

Microlensig Binaries with Candidate Brown Dwarf Companions

Brown dwarfs are important objects because they may provide a missing link between stars and planets, two populations that have dramatically different formation history. In this paper, we present the candidate binaries with brown dwarf companions that are found by analyzing binary microlensing events discovered during 2004 - 2011 observation seasons. Based on the low mass ratio criterion of q < 0.2, we found 7 candidate events, including OGLE-2004-BLG-035, OGLE-2004-BLG-039, OGLE-2007-BLG-006, OGLE-2007-BLG-399/MOA-2007-BLG-334, MOA-2011-BLG-104/OGLE-2011-BLG-0172, MOA-2011-BLG-149, and MOA-201-BLG-278/OGLE-2011-BLG-012N. Among them, we are able to confirm that the companions of the lenses of MOA-2011-BLG-104/OGLE-2011-BLG-0172 and MOA-2011-BLG-149 are brown dwarfs by determining the mass of the lens based on the simultaneous measurement of the Einstein radius and the lens parallax. The measured mass of the brown dwarf companions are (0.02 +/- 0.01) M_Sun and (0.019 +/- 0.002) M_Sun for MOA-2011-BLG-104/OGLE-2011-BLG-0172 and MOA-2011-BLG-149, respectively, and both companions are orbiting low mass M dwarf host stars. More microlensing brown dwarfs are expected to be detected as the number of lensing events with well covered light curves increases with new generation searches.Comment: 10 pages, 9 figures, 4 table