The nonlinear effects in 2DEG conductivity investigation by an acoustic method

The parameters of two-dimensional electron gas (2DEG) in a GaAs/AlGaAs heterostructure were determined by an acoustical (contactless) method in the delocalized electrons region ($B\le$2.5T). Nonlinear effects in Surface Acoustic Wave (SAW) absorption by 2DEG are determined by the electron heating in the electric field of SAW, which may be described in terms of electron temperature $T_e$. The energy relaxation time $\tau_{\epsilon}$ is determined by the scattering at piezoelectric potential of acoustic phonons with strong screening. At different SAW frequencies the heating depends on the relationship between $\omega\tau_{\epsilon}$ and 1 and is determined either by the instantaneously changing wave field ($\omega\tau_{\epsilon}$$<1$), or by the average wave power ($\omega\tau_{\epsilon}$$>1$).Comment: RevTeX, 5 pages, 3 PS-figures, submitted to Physica Status Sol.(Technical corrections in PS-figs

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

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

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

The Role of Native Language and the Fundamental Design of the Auditory System in Detecting Rhythm Changes

Accepted December 13, 2018Purpose: We investigated whether rhythm discrimination is mainly driven by the native language of the listener or by the fundamental design of the human auditory system and universal cognitive mechanisms shared by all people irrespective of rhythmic patterns in their native language. Method: In multiple experiments, we asked participants to listen to 2 continuous acoustic sequences and to determine whether their rhythms were the same or different (AX discrimination). Participants were native speakers of 4 languages with different rhythmic properties (Spanish, French, English, and German) to understand whether the predominant rhythmic patterns of a native language affect sensitivity, bias, and reaction time in detecting rhythmic changes in linguistic (Experiment 2) and in nonlinguistic (Experiments 1 and 2) acoustic sequences. We examined sensitivity and bias measures, as well as reaction times. We also computed Bayes factors in order to assess the effect of native language. Results: All listeners performed better (i.e., responded faster and manifested higher sensitivity and accuracy) when detecting the presence or absence of a rhythm change when the 1st stimulus in an AX test pair exhibited regular rhythm (i.e., a syllable-timed rhythmic pattern) than when the 1st stimulus exhibited irregular rhythm (i.e., stress-timed rhythmic pattern). This result pattern was observed both on linguistic and nonlinguistic stimuli and was not modulated by the native language of the participant. Conclusion: We conclude that rhythm change detection is a fundamental function of a processing system that relies on general auditory mechanisms and is not modulated by linguistic experience.The authors acknowledge support from Spanish Ministry of Economy and Competitiveness Grant PSI2017-82563-P (awarded to A. G. S.), the “Severo Ochoa” Programme for Centres/Units of Excellence in R&D Grant SEV-2015-490 (BCBL), and the Basque Foundation for Science Grant IKERBASQUE (awarded to A. G. S. and M. O.). D. M. G. was supported by Grant PIA/Basal FB0003 from the Chilean Research Council. L. P. was supported by the Spanish Ministry of Economy and Competitiveness via Juan de la Cierva fellowship

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

ТЕХНОГЕННЫЕ РАДИОНУКЛИДЫ В ПРИЗЕМНОМ СЛОЕ АТМОСФЕРЫ ВСЛЕДСТВИЕ АВАРИИ НА АЭC «ФУКУСИМА»

The article presents information about the main observation results of radiometric departments of the Federal Service for Hydrometeorology and Environmental Monitoring for changes in the radiation situation on the territory of Russia following the accident at the Fukushima NPP. The obtained experimental data allowed to conclude that the volumetric activities of radionuclides in the near-the-ground  atmospheric layer were by 3 to 6 orders of magnitude below the permissible volumetric activity set by Radiation Safety Standards (NRB-99/2009), and the correction to the density of soil contamination by cesium-137 was by 2 to 3 orders of magnitude less than the decrease of the density of contamination with this isotope of the global origin due to radioactive decay.В статье приведена информация об основных результатах наблюдений радиометрических подразделений Федеральной службы по гидрометеорологии и мониторингу окружающей среды за изменением радиационной обстановки на территории России вследствие аварии на АЭС «Фукусима». Полученные экспериментальные данные позволили сделать заключение о том, что объемные актив- ности радионуклидов в приземном слое атмосферы были на 3–6 порядков ниже допустимой объем- ной активности, установленной Нормами радиационной безопасности (НРБ-99/2009), а добавка к плотности загрязнения почвы цезием-137 – на 2–3 порядка меньше убыли плотности загрязнения этим изотопом глобального происхождения за счет радиоактивного распада

Factors associated with the efficiency of maintenance therapy in patients with metastatic colorectal cancer

Objective: to evaluate tolerability and efficacy of maintenance treatment in the absence of progression after 16 weeks of first-line therapy in patients with unresectable metastatic colon cancer.Materials and methods. We have analyzed medical case histories of patients with metastatic colorectal cancer who underwent treatment in the department of clinical pharmacology and chemotherapy of N. N. Blokhin Russian Cancer Research Center from 2007 to 2015 years. Inclusion criteria were the following: 16–24 weeks of first-line chemotherapy with no signs of progression and the inability to perform metastasectomy. Progression-free survival was the main criterion for effectiveness in our study.Results. 160 (44.5 %) of 359 treated patients met the inclusion criteria. 102 (63.7 %) patients were followed up, while the other 58 (36.3 % – comparison group) patients underwent maintenance chemotherapy. Grade I–II toxic reactions and grade III complications associated with first-line chemotherapy were insignificantly more common in the group of patients left on maintenance chemotherapy: 72.4 % and 37.9 % versus 57.8 % and 24.5 % in the comparison group, p = 0.07 and p = 0.07 respectively. The frequency of grade I–II toxic reactions and grade III complications in the second-line treatment did not differ between treatment groups (p = 0.9 and p = 0.8). The median of progression-free survival in observation group and comparison group was 4, and 6 months (odds ratio (OR) 0.6; p = 0.009), and life expectancy – 23 and 31 months (OR 0.75; p = 0.1), respectively. Statistically significant differences between groups with respect to achieving the objective response and/or normalization of carcinoembryonic antigen level were revealed: median of progression-free survival was 13 (n = 26 of 57; 45.6 %) and 4 months (n = 31 of 57, 54.4 %), respectively (HR 0.38; p = 0.002), median of life expectancy – 34 months versus 26 months (OR 0.37; p = 0.3). Conclusions. Carrying out maintenance therapy is associated with increased incidence of grade III complications during the first-line treatment, but does not affect the tolerability of the second-line treatment. Supportive chemotherapy with fluoropyrimidines remains to be the most effective in patients with favorable prognostic factors such as normalization of carcinoembryonic antigen and/or achievement of the objective response on the background of first-line chemotherapy

The effectiveness of splinting prostheses in the complex rehabilitation of patients with periodontal pathology

То assess the effectiveness of splinting prostheses in treatment parodontopathies conducted the examination and treatment of 32 patients with chronic generalized periodontitis of moderate to severe. All patients underwent comprehensive dental rehabilitation with clasp splinting prostheses. The dental status of patients was recorded before treatment and after 6 and 12 months after splinting. Focusing a study found that the treatment of periodontal disease sufficiently long and consists of several stages. It can be effective only if the multi-disciplinary approach with participation of experts of the therapeutic, surgical, orthodontic, orthopedic, and further include physiotherapy.Для оценки эффективности применения шинирующих протезов в комплексном лечении пародонтопатий проводилось обследование и лечение 32 пациентов с диагнозом хронический генерализованный пародонтит средней и тяжелой степени тяжести. Всем пациентам была проведена комплексная стоматологическая реабилитация с использованием бюгельных шинирующих протезов. Стоматологический статус пациентов регистрировался до лечения, через 6 и 12 месяцев после шинирования. Ориентируясь результаты исследования, установлено, что лечение заболеваний пародонта достаточно длительное и состоит из нескольких этапов. Оно может быть эффективном только при условии мультидисциплинарного подхода с участием специалистов терапевтического, хирургического, ортодонтического, ортопедического профилей, а также дополнительно включать в себя физиотерапевтическое лечение