The effect of the electric field on the nucleation of the nanometer periodic structure of adatoms in GaAs semiconductor under the action of laser irradiation

In the paper, the effect of the electric field on the conditions of formation and on the period of the surface superlattice of adatoms in $n$-GaAs semiconductor is investigated. It is established that in GaAs semiconductor, an increase in the electric field strength, depending on the direction, leads to an increase or decrease of the critical temperature (the critical concentration of adatoms), at which the formation of self-organized nanostructure is possible. It is shown that in strongly alloyed $n$-GaAs semiconductor, an increase of the electric field strength leads to a monotonous change (decrease or increase depending on the direction of the electric field) of the period of self-organized surface nanostructures of adatoms.Comment: 9 pages, 4 figures. arXiv admin note: text overlap with arXiv:1512.0780

Path-integral approach to mutual information calculation for nonlinear communication channel with small second dispersion at large signal-to-noise power ratio

We consider the information fiber optical channel modeled by the nonlinear Schrodinger equation with additive Gaussian noise. Using path-integral approach and perturbation theory for the small dimensionless parameter of the second dispersion, we calculate the conditional probability density functional in the leading and next-to-leading order in the dimensionless second dispersion parameter associated with the input signal bandwidth. Taking into account specific filtering of the output signal by the output signal receiver, we calculate the mutual information in the leading and next-to-leading order in the dispersion parameter and in the leading order in the parameter signal-to-noise ratio (SNR). Further, we find the explicit expression for the mutual information in case of the modified Gaussian input signal distribution taking into account the limited frequency bandwidth of the input signal.Comment: 42 pages, 5 figure

Possible predictors of depressive syndrome in patients with chronic obstructive pulmonary disease.

Recently, the problem of depressive syndrome in COPD patients often attracts the attention of doctors and scientists. It is important to study the relationship between the presence of the depressive syndrome, on the one hand, and the clinical and functional characteristics of COPD patients on the other, in order to determine the categories of patients inclined to develop a depressive syndrome. The purpose of the study: to determine the relationship between the presence of depressive syndrome in COPD patients with the severity of their clinical symptoms of COPD and the level of functional impairments. 52 COPD patients of clinical groups C and D were examined. Depending on the presence of depressive syndrome patients were divided into two subgroups: a subgroup 1 – 15 COPD patients with concomitant depressive syndrome, a subgroup 2 – 37 people without it. The examination included general clinical and functional methods. It was determined that the development of depressive syndrome in COPD patients can be affected by the high severity of clinical symptoms of COPD in general, decreased tolerance to physical activity, long duration of the disease, poor quality of life. At the same time, the levels of functional indicators, in particular, OFV1 and SpO2, may not have a significant relationship with the occurrence of depressive syndrome, even in patients with severe COPD

Experiences of women who have lost young children to AIDS in KwaZulu-Natal, South Africa: a qualitative study

Background AIDS continues to be the leading cause of death in South Africa. Little is known about the experiences of mothers who have lost a young child to AIDS. The purpose of this qualitative study was to explore the attitudes and experiences of women who had lost a young child to HIV/AIDS in KwaZulu-Natal Province, South Africa. Methods In-depth interviews were conducted with 10 women who had lost a child to AIDS. The average age of the deceased children was six years. Interviews were also conducted with 12 key informants to obtain their perspectives on working with women who had lost a child to AIDS. A thematic analysis of the transcripts was performed. Results In addition to the pain of losing a child, the women in this study had to endure multiple stresses within a harsh and sometimes hostile environment. Confronted with pervasive stigma and extreme poverty, they had few people they could rely on during their child\u27s sickness and death. They were forced to keep their emotions to themselves since they were not likely to obtain much support from family members or people in the community. Throughout the period of caring for a sick child and watching the child die, they were essentially alone. The demands of caring for their child and subsequent grief, together with daily subsistence worries, took its toll. Key informants struggled to address the needs of these women due to several factors, including scarce resources, lack of training around bereavement issues, reluctance by people in the community to seek help with emotional issues, and poverty. Conclusions The present study offers one of the first perspectives on the experiences of mothers who have lost a young child to AIDS. Interventions that are tailored to the local context and address bereavement issues, as well as other issues that affect the daily lives of these mothers, are urgently needed. Further studies are needed to identify factors that promote resilience among these women

Polymerization of Lactic Acid Using Microwave and Conventional Heating

The polymerization of lactic acid (LA) has been investigated by two methods: conventional heating and under microwave irradiation. The reactions of polymerization have been carried out in two stages: at the beginning water is removed and oligomer is obtained; then, the catalysts/co-catalysts are added and reactions are carried out. Tin octoate, toluene sulfonic acid, 2-aminopropanoic acid (alanine) have been investigated as polymerization catalysts and the derivatives of 2,4,6,8- tetramethilol -2,4,6,8- tetraazabicyclo[3.3.0]octane -3,7-dion (Tetraol), comprising atoms of Mg, Zn, Al have been synthesized for the first time. The structure of the synthesized catalyst has been investigated using the method of IR, {1}H NMR. It has been shown that the process of obtaining polylactic acid (PLA) by microwave irradiation proceeds hundreds of times faster. PLA samples synthesized by this method have the same optical characteristics as the PLA obtained by conventional heating

The Survey of HEIs Performance as a Data Source on Higher Education in Russia

Мониторинг эффективности деятельности организаций высшего образования, проводимый с 2012 года, является самым полным источником открытой информации об организационной популяции российских вузов. В настоящее время дискуссия о показателях Мониторинга ведется в ключе их применимости для оценки организаций высшего образования; как вторичный источник сведений для исследователей высшего образования материалы Мониторинга не рассматриваются. Предлагаемая статья должна ликвидировать существующий пробел – в ней данные Мониторинга оцениваются с точки зрения их качества и потенциала для статистического анализа. Качество данных Мониторинга рассматривается авторами через призму основных измерений, таких как точность, актуальность, полнота и согласованность. Техническое удобство данных Мониторинга оценивается с позиции характера распределения переменных, что позволяет понять, какие методы анализа данных могут быть применены к Мониторингу. В завершение авторы дают рекомендации представителям научного сообщества, планирующим использовать данные Мониторинга для исследования российского высшего образования.Annual Survey of Performance of Higher Education Institutions, conducted in Russia since 2012, is the main source of open-access information on Russian universities. The discussion on the indicators of the Survey mainly focuses on their applicability for assessing higher education institutions (HEIs). The Survey, however, is not observed as a possible source of data for researchers in higher education. To remedy this deficiency, this paper evaluates the Survey data in terms of their quality and applicability for statistical analysis. The quality of the data is measured in four dimensions: accuracy, timeliness, completeness, and consistency. The technical convenience of the data is evaluated through the analysis of the variables distribution. The conclusion contains recommendations for researchers, who plan to use the Survey data for studying Russian higher education.Статья подготовлена в рамках гранта РАНХиГС № AAAA-A18-118060590091-8.This research was supported by the RANEPA via grant № AAAA-A18-118060590091-8

Rigor and Ethics in the World of Big-team Qualitative Data: Experiences From Research in International Development

In the large international projects where many qualitative researchers work, generating qualitative Big Data, data sharing represents the status quo. This is rarely acknowledged, even though the ethical implications are considerable and span both process and product. I argue that big-team qualitative researchers can strengthen claims to rigor in analysis (the product) by drawing on a growing body of knowledge about how to do credible secondary analysis. Since this necessitates a full account of how the research and the analysis are done (the process), I consider the structural disincentives for providing these. Debates around credibility and rigor are not new to qualitative research in international development, but they intensify when new actors such as program evaluators and quantitative researchers use qualitative methods on a large scale. In this context, I look at the utility of guidelines used by these actors to ensure the quality of qualitative research. I ask whether these offer pragmatic suggestions to improve its quality, recognizing the common and hierarchized separation between the generation and interpretation of data, or conversely, whether they set impossible standards and fail to recognize the differences between and respective strengths of qualitative and quantitative research

Energy-conserving physics for nonhydrostatic dynamics in mass coordinate models

Motivated by reducing errors in the energy budget related to enthalpy fluxes within the Energy Exascale Earth System Model (E3SM), we study several physics–dynamics coupling approaches. Using idealized physics, a moist rising bubble test case, and the E3SM's nonhydrostatic dynamical core, we consider unapproximated and approximated thermodynamics applied at constant pressure or constant volume. With the standard dynamics and physics time-split implementation, we describe how the constant-pressure and constant-volume approaches use different mechanisms to transform physics tendencies into dynamical motion and show that only the constant-volume approach is consistent with the underlying equations. Using time step convergence studies, we show that the two approaches both converge but to slightly different solutions. We reproduce the large inconsistencies between the energy flux internal to the model and the energy flux of precipitation when using approximate thermodynamics, which can only be removed by considering variable latent heats, both when computing the latent heating from phase change and when applying this heating to update the temperature. Finally, we show that in the nonhydrostatic case, for physics applied at constant pressure, the general relation that enthalpy is locally conserved no longer holds. In this case, the conserved quantity is enthalpy plus an additional term proportional to the difference between hydrostatic pressure and full pressure.</p

The spectral element method (SEM) on variable-resolution grids: evaluating grid sensitivity and resolution-aware numerical viscosity

We evaluate the performance of the Community Atmosphere Model's (CAM) spectral element method on variable-resolution grids using the shallow-water equations in spherical geometry. We configure the method as it is used in CAM, with dissipation of grid scale variance, implemented using hyperviscosity. Hyperviscosity is highly scale selective and grid independent, but does require a resolution-dependent coefficient. For the spectral element method with variable-resolution grids and highly distorted elements, we obtain the best results if we introduce a tensor-based hyperviscosity with tensor coefficients tied to the eigenvalues of the local element metric tensor. The tensor hyperviscosity is constructed so that, for regions of uniform resolution, it matches the traditional constant-coefficient hyperviscosity. With the tensor hyperviscosity, the large-scale solution is almost completely unaffected by the presence of grid refinement. This later point is important for climate applications in which long term climatological averages can be imprinted by stationary inhomogeneities in the truncation error. We also evaluate the robustness of the approach with respect to grid quality by considering unstructured conforming quadrilateral grids generated with a well-known grid-generating toolkit and grids generated by SQuadGen, a new open source alternative which produces lower valence nodes