Tunable quantum spin Hall effect in double quantum wells

The field of topological insulators (TIs) is rapidly growing. Concerning possible applications, the search for materials with an easily controllable TI phase is a key issue. The quantum spin Hall effect, characterized by a single pair of helical edge modes protected by time-reversal symmetry, has been demonstrated in HgTe-based quantum wells (QWs) with an inverted bandgap. We analyze the topological properties of a generically coupled HgTe-based double QW (DQW) and show how in such a system a TI phase can be driven by an inter-layer bias voltage, even when the individual layers are non-inverted. We argue, that this system allows for similar (layer-)pseudospin based physics as in bilayer graphene but with the crucial absence of a valley degeneracy.Comment: 9 pages, 8 figures, extended version (accepted Phys. Rev. B

Dirac-screening stabilized surface-state transport in a topological insulator

We report magnetotransport studies on a gated strained HgTe device. This material is a threedimensional topological insulator and exclusively shows surface state transport. Remarkably, the Landau level dispersion and the accuracy of the Hall quantization remain unchanged over a wide density range ($3 \times 10^{11} cm^{-2} < n < 1 \times 10^{12} cm^{-2}$). This implies that even at large carrier densities the transport is surface state dominated, where bulk transport would have been expected to coexist already. Moreover, the density dependence of the Dirac-type quantum Hall effect allows to identify the contributions from the individual surfaces. A $k \cdot p$ model can describe the experiments, but only when assuming a steep band bending across the regions where the topological surface states are contained. This steep potential originates from the specific screening properties of Dirac systems and causes the gate voltage to influence the position of the Dirac points rather than that of the Fermi level.Comment: 12 pages 4 figure

Актуальная тактика ведения детей с бронхиальной астмой

The article is devoted to the problem of timely diagnosis and current principles of management of children with bronchial asthma. Given the  increase in the prevalence of allergic pathology stated over the past  decades, the issues of differential diagnosis, integrated approach to the  treatment and management of children with allergies are extremely  relevant. Strategies of sequential therapy and monitoring of the  patient’s condition, adherence principles are key links in achieving and  maintaining control over bronchial asthma. The publication presents the  main provisions of national clinical guidelines developed and approved  by the professional association «Union of Pediatricians of Russia».Статья посвящена проблеме своевременной диагностики и современным принципам ведения детей с бронхиальной астмой. Учитывая рост распространенности аллергической патологии,  зафиксированный на протяжении последних десятилетий, вопросы дифференциальной  диагностики, комплексного подхода к лечению и ведению детей с аллергией крайне актуальны. Стратегии ступенчатой терапии и мониторинга состояния пациента, принципы приверженности  — ключевые звенья в достижении и поддержании контроля над бронхиальной астмой. В  публикации представлены основные положения национальных клинических рекомендаций,  разработанных и утвержденных профессиональной ассоциацией «Союз педиатров России»

Finishing the euchromatic sequence of the human genome

The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead

Actual Surveillance of Children with Bronchial Asthma

The article is devoted to the problem of timely diagnosis and current principles of management of children with bronchial asthma. Given the  increase in the prevalence of allergic pathology stated over the past  decades, the issues of differential diagnosis, integrated approach to the  treatment and management of children with allergies are extremely  relevant. Strategies of sequential therapy and monitoring of the  patient’s condition, adherence principles are key links in achieving and  maintaining control over bronchial asthma. The publication presents the  main provisions of national clinical guidelines developed and approved  by the professional association «Union of Pediatricians of Russia»

Band structure near the Dirac Point in HgTe quantum wells with critical thickness

Mercury telluride (HgTe) thin films with a critical thickness of 6.5 nm are predicted to possess a gapless Dirac-like band structure. We report a comprehensive study on gated and optically doped samples by magnetooptical spectroscopy in the THz range. The quasi-classical analysis of the cyclotron resonance allowed the mapping of the band dispersion of Dirac charge carriers in a broad range of electron and hole doping. A smooth transition through the charge neutrality point between Dirac holes and electrons was observed. An additional peak coming from a second type of holes with an almost density-independent mass of around 0.04m0 was detected in the hole-doping range and attributed to an asymmetric spin splitting of the Dirac cone. Spectroscopic evidence for disorder-induced band energy fluctuations could not be detected in present cyclotron resonance experiments

Sweet-Tasting Natural Proteins Brazzein and Monellin: Safe Sugar Substitutes for the Food Industry

This article presents the results of a comprehensive toxicity assessment of brazzein and monellin, yeast-produced recombinant sweet-tasting proteins. Excessive sugar consumption is one of the leading dietary and nutritional problems in the world, resulting in health complications such as obesity, high blood pressure, and cardiovascular disease. Although artificial small-molecule sweeteners widely replace sugar in food, their safety and long-term health effects remain debatable. Many sweet-tasting proteins, including thaumatin, miraculin, pentadin, curculin, mabinlin, brazzein, and monellin have been found in tropical plants. These proteins, such as brazzein and monellin, are thousands-fold sweeter than sucrose. Multiple reports have presented preparations of recombinant sweet-tasting proteins. A thorough and comprehensive assessment of their toxicity and safety is necessary to introduce and apply sweet-tasting proteins in the food industry. We experimentally assessed acute, subchronic, and chronic toxicity effects, as well as allergenic and mutagenic properties of recombinant brazzein and monellin. Our study was performed on three mammalian species (mice, rats, and guinea pigs). Assessment of animals’ physiological, biochemical, hematological, morphological, and behavioral indices allows us to assert that monellin and brazzein are safe and nontoxic for the mammalian organism, which opens vast opportunities for their application in the food industry as sugar alternatives

Amino acid formulas in patients with food allergy

The article presents modern approaches to the use of balanced formulas for nutrition and diet correction in children with various forms of food allergies. The guidelines are based on all available up to date evidence on the efficacy, safety and utility of using such innovative medical technology as specialized amino acid formulas. This formula is the targeted medical intervention for food allergies and confirmed cow's milk protein allergy, and particularly for patients with reduced physical growth and development (growth rates included). The material is based on methodological guidelines on the amino acid formulas usage previously developed by specialist experts of the Union of pediatricians of Russia in 2020

Amino Acid Formulas in Patients with Gastrointestinal Diseases

Modern approaches for the management of children with gastrointestinal pathologies include optimal nutritional support that makes it possible to replete energy failure and restore essential nutrients balance. The article presents key information on gastrointestinal diseases in which modern amino acid formulas can be used to regulate nutritional status. The authors have conducted the extensive analysis of all available for now evidence on the efficacy, safety and utility of using such innovative medical technology as special elemental formula in gastrointestinal tract pathological conditions. This material is the basis for guidlines on the use of amino acid formulas developed by expert specialists of the Union of Pediatricians of Russia in 2020

Giant THz Nonlinearity in Topological and Trivial HgTe-Based Heterostructures

Nonlinear phenomena in the THz spectral domain are important for understanding the optoelectronic properties of quantum systems and provide a basis for modern information technologies. Here, we report a giant THz nonlinearity in high-mobility 2D topological insulators based on HgTe quantum wells, which manifests itself in a highly efficient third harmonic generation. We observe a third harmonic THz susceptibility several times higher than that in bare graphene and many orders of magnitude higher than that in trivial quantum well structures based on other materials. To explain the strong nonlinearity of HgTe-based heterostructures at the THz frequencies, we consider the acceleration of free carriers with a high mobility and variable dispersion. This acceleration model, for which the nonparabolicity of the band dispersion is key, in combination with independently measured scattering time and conductivity, is in good agreement with our experimental data in a wide temperature range for THz fields below the saturation. Our approach provides a route to material engineering for THz applications based on frequency conversion