Structural and transport properties of GaAs/delta<Mn>/GaAs/InxGa1-xAs/GaAs quantum wells

We report results of investigations of structural and transport properties of GaAs/Ga(1-x)In(x)As/GaAs quantum wells (QWs) having a 0.5-1.8 ML thick Mn layer, separated from the QW by a 3 nm thick spacer. The structure has hole mobility of about 2000 cm2/(V*s) being by several orders of magnitude higher than in known ferromagnetic two-dimensional structures. The analysis of the electro-physical properties of these systems is based on detailed study of their structure by means of high-resolution X-ray diffractometry and glancing-incidence reflection, which allow us to restore the depth profiles of structural characteristics of the QWs and thin Mn containing layers. These investigations show absence of Mn atoms inside the QWs. The quality of the structures was also characterized by photoluminescence spectra from the QWs. Transport properties reveal features inherent to ferromagnetic systems: a specific maximum in the temperature dependence of the resistance and the anomalous Hall effect (AHE) observed in samples with both "metallic" and activated types of conductivity up to ~100 K. AHE is most pronounced in the temperature range where the resistance maximum is observed, and decreases with decreasing temperature. The results are discussed in terms of interaction of 2D-holes and magnetic Mn ions in presence of large-scale potential fluctuations related to random distribution of Mn atoms. The AHE values are compared with calculations taking into account its "intrinsic" mechanism in ferromagnetic systems.Comment: 15 pages, 9 figure

Electronic structure and optical properties of Ca2Si films grown on silicon different oriented substrates and calculated from first principles

The work considered the growth, optical properties and emerging interband transitions in Ca2Si films grown on silicon substrates with (111), (001), and (110) orientations at two temperatures (250 °C and 300 °C) using the sacrificial-template method. The optimum temperature for MBE single-phase growth of Ca2Si is 250 °C. Calculations of optical functions from the transmission and reflection spectra were carried out within the framework of a two-layer model and by the Kramers–Kronig method. It is shown that the main peaks in the experimental reflection spectra and the optical conductivity calculated according to Kramers–Kronig are in good agreement with each other. Comparison of ab initio calculations of the energy band structure and optical properties of a Ca2Si single crystal and two-dimensional Ca2Si layers with experimental data in the region of high-energy transitions showed good coincidence

Formation, structure, and optical properties of single-phase CaSi and CaSi2 films on Si substrates

In this paper, we report on optimizing the conditions for subsequently growing single-phase films of calcium monosilicide (CaSi) and calcium disilicide (CaSi2) on single-crystal silicon by reactive deposition epitaxy (RDE) and molecular beam epitaxy (MBE). The temperature range for the growth of CaSi films (400–500 °C) was determined, as well as the temperature range (600–680°C) for the growth of CaSi2 films on silicon with three orientations: (111), (100) and (110). The minimum temperatures for the epitaxial growth of CaSi films by the RDE method and CaSi2 films by the MBE method were determined, amounting to, respectively, T = 475 °C and T = 640 °C. An increase in the ratio of Ca to Si deposition rates to 26 made it possible to grow a large-block CaSi2 epitaxial film with the hR6 structure by the MBE method at T = 680 °C. Raman spectra and reflection spectra from single-phase epitaxial CaSi and CaSi2 films on silicon were recorded and identified for the first time. The correspondence between the experimental reflection spectra and the theoretically calculated reflection spectra in terms of amplitude and peak positions at photon energies of 0.1–6.5 eV has been established. Single-phase CaSi and CaSi2 films retain transparency in the photon energy range 0.4–1.2 eV

Объемная капнография: возможности применения в пульмонологической практике

The aim of this review was to analyze abilities of a novel diagnostic method intended to measure the lung function. Volumetric capnography is one of the most promising tools for assessing pulmonary function. This method reflects CO2 elimination pattern at the exhaled air volume. Changes in CO2 portion at the tidal volume are related to the integrated evaluation of the respiratory function and could be expressed as the following parameters: emphysema index, the dead space volume, phases 2 and 3 slopes, etc. Possible use of the volumetric capnography for diagnosis of chronic obstructive pulmonary disease, asthma, emphysema, and other respiratory diseases is discussed in the article. This method is simple, non-invasive, and safe. Diagnostic value of the volumetric capnography needs further investigation in order to implement this method in clinical practice.Необходимость изучения новых методов диагностики и оценки параметров дыхания пациента продиктована широким распространением заболеваний респираторной системы. Одним из перспективных инструментов оценки легочной функции является метод объемной капнографии, отражающий особенности паттерна элиминации углекислого газа (CO2) в объеме выдоха, при помощи которого анализируется динамика выделения CO2 по отношению к дыхательному объему и представляется интегральная оценка функционального состояния органов дыхания в виде следующих расчетных показателей: индекс эмфиземы, объем «мертвого» пространства, наклон фаз 2 и 3 и т. п. В обзоре освещены вопросы, касающиеся возможностей применения метода объемной капнографии в клинической практике, в частности при диагностике хронической обструктивной болезни легких (ХОБЛ), бронхиальной астмы (БА), эмфиземы и других заболеваний легких. Продемонстрировано, что неинвазивный, безопасный и простой в использовании метод объемной капнографии может использоваться для оценки параметров дыхания у пациентов с ХОБЛ, БА и эмфиземой легких, однако требуется дальнейшее изучение его диагностических возможностей с целью последующего внедрения в пульмонологическую практику

Ca silicide films—promising materials for silicon optoelectronics

Single-phase films of semiconductor and semimetallic calcium silicides (Ca2Si, CaSi, and CaSi2), as well as films with a significant contribution of Ca5Si3 and Ca14Si19 silicides, were grown on single-crystal silicon and sapphire substrates. The analysis of the crystal structure of the grown films was carried out and the criterion of their matching with silicon and sapphire substrates was determined. Some lattice-matching models were proposed, and the subsequent deformations of the silicide lattices were estimated. Film’s optical functions, including the optical transparency, were calculated from the optical spectroscopy data and an extended comparison was performed with the results of ab initio calculations. The real limits of the optical transparency for the films on sapphire substrates were established. The maximum transparency limit (3.9 eV) was observed for the CaSi film. Based on an analysis of the photoelectric properties of Ca2Si/Si diodes on n- and p-type silicon substrates, a perspective of their applications in silicon optoelectronics was discussed

Комплексный подход к прогнозированию клещевых нейроинфекций

Here, we propose a method of forecasting the development of the heavy forms of the tick-borne encephalitis using diagnostic tables. The method is based on evaluation of the patients with syndrome of endogenous intoxication using immunological and biochemical data along with evaluation of the clinical manifestations. We also propose an advanced form of the method that includes data based on the genotype of OAS1 — the gene, coding oligonucleotidesynthetase needed for immune response to RNA viruses. OAS1 genotype is an important risk factor since the differences in catalytic activity of OAS1 isoenzymes result in different susceptibility to the virus of the tick-borne encephalitis.В данной работе предлагается метод прогнозирования развития тяжелого течения очаговых форм клещевого энцефалита с помощью диагностической таблицы. Метод основан на оценке у больных синдрома эндогенной интоксикации с применением иммунологических и биохимических исследований, а также оценке клинических проявлений. Предлагается дополнение метода данными по генотипированию гена OAS1, кодирующего олигонуклеотидсинтетазу, необходимую для иммунного ответа на РНК-вирусы. Генотип OAS1 является важным фактором риска, так как различия в каталитической активности изоферментов OAS1 приводят к различиям в восприимчивости к вирусу клещевого энцефалита