Magnetic-field-dependent zero-bias diffusive anomaly in Pb oxide-n-InAs structures: Coexistence of two- and three-dimensional states

The results of experimental and theoretical studies of zero-bias anomaly (ZBA) in the Pb-oxide-n-InAs tunnel structures in magnetic field up to 6T are presented. A specific feature of the structures is a coexistence of the 2D and 3D states at the Fermi energy near the semiconductor surface. The dependence of the measured ZBA amplitude on the strength and orientation of the applied magnetic field is in agreement with the proposed theoretical model. According to this model, electrons tunnel into 2D states, and move diffusively in the 2D layer, whereas the main contribution to the screening comes from 3D electrons.Comment: 8 double-column pages, REVTeX, 9 eps figures embedded with epsf, published versio

Electron localization in sound absorption oscillations in the quantum Hall effect regime

The absorption coefficient for surface acoustic waves in a piezoelectric insulator in contact with a GaAs/AlGaAs heterostructure (with two-dimensional electron mobility $\mu= 1.3\times 10^5 cm^2/V\cdot s)$ at T=4.2K) via a small gap has been investigated experimentally as a function of the frequency of the wave, the width of the vacuum gap, the magnetic field, and the temperature. The magnetic field and frequency dependencies of the high-frequency conductivity (in the region 30-210 MHz) are calculated and analyzed. The experimental results can be explained if it assumed that there exists a fluctuation potential in which current carrier localization occurs. The absorption of the surface acoustic waves in an interaction with two-dimensional electrons localized in the energy "tails" of Landau levels is discussed.Comment: RevTeX 6 pages+6 EPS pic

Interaction effects and phase relaxation in disordered systems

This paper is intended to demonstrate that there is no need to revise the existing theory of the transport properties of disordered conductors in the so-called weak localization regime. In particular, we demonstrate explicitly that recent attempts to justify theoretically that the dephasing rate (extracted from the magnetoresistance) remains finite at zero temperature are based on the profoundly incorrect calculation. This demonstration is based on a straightforward evaluation of the effect of the electron-electron interaction on the weak localization correction to the conductivity of disordered metals. Using well-controlled perturbation theory with the inverse conductance $g$ as the small parameter, we show that this effect consists of two contributions. First contribution comes from the processes with energy transfer smaller than the temperature. This contribution is responsible for setting the energy scale for the magnetoresistance. The second contribution originates from the virtual processes with energy transfer larger than the temperature. It is shown that the latter processes have nothing to do with the dephasing, but rather manifest the second order (in $1/g$) correction to the conductance. This correction is calculated for the first time. The paper also contains a brief review of the existing experiments on the dephasing of electrons in disordered conductors and an extended qualitative discussion of the quantum corrections to the conductivity and to the density of electronic states in the weak localization regime.Comment: 34 pages, 13 .eps figure

Immune-Complex Mimics as a Molecular Platform for Adjuvant-Free Vaccine Delivery

Protein-based vaccine development faces the difficult challenge of finding robust yet non-toxic adjuvants suitable for humans. Here, using a molecular engineering approach, we have developed a molecular platform for generating self-adjuvanting immunogens that do not depend on exogenous adjuvants for induction of immune responses. These are based on the concept of Immune Complex Mimics (ICM), structures that are formed between an oligomeric antigen and a monoclonal antibody (mAb) to that antigen. In this way, the roles of antigens and antibodies within the structure of immune complexes are reversed, so that a single monoclonal antibody, rather than polyclonal sera or expensive mAb cocktails can be used. We tested this approach in the context of Mycobacterium tuberculosis (MTB) infection by linking the highly immunogenic and potentially protective Ag85B with the oligomeric Acr (alpha crystallin, HspX) antigen. When combined with an anti-Acr monoclonal antibody, the fusion protein formed ICM which bound to C1q component of the complement system and were readily taken up by antigen-presenting cells in vitro. ICM induced a strong Th1/Th2 mixed type antibody response, which was comparable to cholera toxin adjuvanted antigen, but only moderate levels of T cell proliferation and IFN-γ secretion. Unfortunately, the systemic administration of ICM did not confer statistically significant protection against intranasal MTB challenge, although a small BCG-boosting effect was observed. We conclude that ICM are capable of inducing strong humoral responses to incorporated antigens and may be a suitable vaccination approach for pathogens other than MTB, where antibody-based immunity may play a more protective role

Regional Differences in Life Expectancy in Russia Through the Lens of Epidemiological Transition

Received 16 February 2024. Accepted 13 May 2024. Published online 21 July 2024.An immense territory of Russia with several climatic zones and, accordingly, a fundamentally different styles of life, inevitably results in pronounced varieties in the levels and structure of mortality across the regions of the country. Since the scale and sustainability of differences in mortality in Russia can be considered an entire epidemiological epoch, the evaluation of them through the lens of epidemiological transition seems methodologically appropriate. Regional differences are regarded as a kind of projection of evolution in time, though taking into account modern realities. The analysis of regional differences in mortality is based on such indicators as life expectancy, structure of mortality, i.e., predominantly endogenous to exogenous causes of death ratio, as well as the average age of death from predominantly endogenous causes calculated on the basis of life tables by cause of death. The study showed that according to the periodization of epidemiological transition only Moscow and St. Petersburg are at the final phase of the 3rd stage and are moving to the 4th stage of epidemiological development. Meanwhile, the burden of exogenous and preventable pathologies precludes the completion of the 3rd stage in the regions with high life expectancy according to Russian criteria. The stadial nature of epidemiologic development of Russian regions is currently conditioned by socio-economic and medical determinants, with more pressing medical determinants in regions with high and medium levels of life expectancy and socio-economic factors prevailing in regions with low life expectancy

Реологические свойства эпоксидного олигомера, наполненного стеклянными микрошариками

Specific features of the flow of filled and highly filled composites with a filler having monofractional structure (glass microspheres) on the basis of epoxy oligomers were investigated in two modes: at a constant shear rate and at a constant shear stress.Исследованы особенности течения наполненных и высоконаполненных композиций на основе эпоксидного олигомера с наполнителем монофракционного состава (стеклянные микрошарики) в двух режимах: при постоянной скорости сдвига; при постоянном напряжении сдвига

Post-Covid disorders of nervous system: personal experience

Introduction. In the COVID-19 pandemic, high lethality as well as long-term outcomes are getting more and more relevant. According to the accumulated study results, COVID-19 affects the nervous system both directly and indirectly. Objective: to study the variants of post-COVID syndrome based on the data from the State Novosibirsk Regional Clinical Hospital from July 2020 to February 2022. Materials and methods. We have performed post hoc analysis of the medical records of 1,500 patients with a past history of COVID-19 admitted following various neurological disorders manifested from July 2020 to February 2022. Results. While temporary and pathogenetic association with past COVID-19 was revealed in 455 patients, primary involvement of the central nervous system was reported in 91.6% of cases, primary involvement of the peripheral nervous system in 8.1% of cases, and musculoskeletal disorder (idiopathic myodystrophy) in 0.3% of cases. Conclusion. Prevalence of the neurological variants of post-COVID syndrome is still unknown. However, patients with severe COVID-19 are more susceptible to neurological complications during the following six months

The impact of the covid-19 pandemic on women’s menstrual and reproductive functions

The aim of the study - to find out the impact of recovering from COVID-19 and different types of vaccination on the women's reproductive healthЦель исследования – выяснить влияние перенесённой коронавирусной инфекции и различных видов вакцинации на состояние репродуктивной системы женщи