Influence of the preliminary annealing conditions on step motion at the homoepitaxy on the Si(100) surface

In this paper, the motion of steps SA and SB on the Si(100) surface in the process of Si Molecular beam epitaxy (MBE) is explored. The study was carried out by means of the reflection intensity dependence behavior analysis of reflection high-energy electron diffraction (RHEED) corresponding to the (2×1) and (1×2) reconstructions. Superstructural rearrangement from a two-domain to a single-domain surface is associated with the bilayer step formation, which occurs due to the different motion rates of the steps SA and SB. Based on the research conducted, the conditions under which the step doubling occurs were determined. A behavior analysis of the diffraction reflection intensity dependences showed that an increasing of preliminary annealing time and temperature facilitates to the faster convergence of the steps SA and SB, but to the slower recovery of the initial surface. The presented experimental results indicate that step movement rate difference depends on the step A edge kink density

Computer modeling of coupled electromagnetic, temperature and magnetohydrodynamic fields in the induction heating and melting devices

Computer modeling is necessary part of design new induction heating and melting devices [1]. One of the complicated technologies when it is necessary to simulate coupled electromagnetic, temperature and magnetohydrodynamic fields is heating and melting of titanium alloys in the alternating electromagnetic field. Thermal processing of titanium alloys in the inductor has some features that it is necessary to take into account on the designing of the advanced technology and equipment. Low thermal conductivity and high temperature losses at the surface result in maximum temperature inside of the billet that could under appropriate conditions exceed melting point. In this way it is possible to obtain liquid phase of titanium alloy inside of the billet and protect it from the contact with surrounding atmosphere. To get this it is necessary to choose the right regime of processing, frequency of current, power and thermal conditions. At the same time precise heating with very strong execution of the temperature profile during the heating time are essential for thermal processing of titanium alloys in this technology [2]. Mathematical model comprising computation of electromagnetic, temperature, MHD fields after getting melt zone and dynamic of its growth was developed. The calculation of the melting process has been carried out by the method “enthalpy-porosity” with application of models of turbulent currents k-ω SST in a non-static setting. Electromagnetic forces and heat sources have been defined by solving a harmonic task by the method of finite elements on a vector magnetic potential in the system “inductor – load” for each iteration of the hydrodynamic task. Experiments confirmed need in simulation of MHD fields to receive good coincidence. Using of the developed models for simulation of electromagnetic processing billets make it easy to develop and implement optimal heat processing systems for the crucibleless induction melting of titanium alloys.The calculations on the basis of the model and the analysis of physical processes with non-crucible melting of titanium alloys have also been carried out

SOME FEATURES OF CURRENT TECHNOGENIC MOVEMENTS OF THE EARTH’S CRUST

We describe the history of studying the current crustal movements by various methods and discuss technogenic effects recorded at large water-reservoir zones and mineral deposits in Siberia. Initially, classical surveying techniques aimed to obtain high-accuracy ground-based measurements of height, tilt and direction. Modern geodesy techniques and methods for measuring absolute gravity are now available to investigate displacement, deformation, tilt and other phenomena taking place on the Earth’s surface. These methods are used to estimate kinematic parameters of the crust areas (e.g. rates of subsidence and horizontal movements) and to monitor fluid motions in mineral deposits. Such data are critical for ensuring a proper management of the mineral deposits. In this article, we analyse technogenic processes observed in the Ust Balyk oil-gas field, the Zapolyarny gas deposit, the water-reservoir zone at the Sayano-Shushenskaya hydroelectric power station (SSHPS) on the Yenisei river, and large open-pit mines in the Kuzbass basin. Our analysis is based on surface displacement rates estimated from the data collected in different periods of observations at large man-made facilities. In the study of the hydro technical objects, we estimated the displacement rates at 5.0 mm per year. In the northern areas of the West Siberian petroleum basin, subsidence rates amounted to 20–25 mm per year in the early 2000s. These estimates were supported by the high-accuracy gravity measurements showing an increase up to 6–7 microGal per year in the oil-gas field development areas. We assess a possibility of triggering effects related to weak seismicity due to a high stress accumulation rate (1 KPa per hour) in the SSHPS area. A connection between earth tides and catastrophic events, such as gas emissions in high amounts on mining sites, is discussed. Having analysed the surface monitoring records taken in South Primorye in September 2017, we conclude that underground nuclear explosions in North Korea in this period did not cause any significant displacement of the surface in this most southerly region of the Russian Far East territories

Current-voltage correlations in interferometers

We investigate correlations of current at contacts and voltage fluctuations at voltage probes coupled to interferometers. The results are compared with correlations of current and occupation number fluctuations at dephasing probes. We use a quantum Langevin approach for the average quantities and their fluctuations. For higher order correlations we develop a stochastic path integral approach and find the generating functions of voltage or occupation number fluctuations. We also derive a generating function for the joint distribution of voltage or occupation number at the probe and current fluctuations at a terminal of a conductor. For energy independent scattering we found earlier that the generating function of current cumulants in interferometers with a one-channel dephasing or voltage probe are identical. Nevertheless, the distribution function for voltage and the distribution function for occupation number fluctuations differ, the latter being broader than that of former in all examples considered here.Comment: 23 pages, 10 figures, minor changes, additional appendix, added reference

Excitonic condensation in a symmetric electron-hole bilayer

Using Diffusion Monte Carlo simulations we have investigated the ground state of a symmetric electron-hole bilayer and determined its phase diagram at T=0. We find clear evidence of an excitonic condensate, whose stability however is affected by in-layer electronic correlation. This stabilizes the electron-hole plasma at large values of the density or inter-layer distance, and the Wigner crystal at low density and large distance. We have also estimated pair correlation functions and low order density matrices, to give a microscopic characterization of correlations, as well as to try and estimate the condensate fraction.Comment: 4 pages, 3 figures, 2 table

ORGAN-SPARING TREATMENT IN PATIENTS WITH SQUAMOUS CELL CARCINOMA OF THE ANAL CANAL

Objective: to improve the results of treatment in patients with squamous cell carcinoma of the anal canal, by creating a new combination treatment option, and to increase the rate of organ-sparing treatment.Subjects and methods. A new combination treatment option for squamous cell carcinoma of the anal canal was created, which involved a combination of radiotherapy and a multiple radio modification program (ultrahigh-frequency (UHF) hyperthermia and local metronidazole (MZ) injection and systemic polychemotherapy) (RF patent No. 2427399 “A treatment option for squamous cell carcinoma of the anal canal” registered on 27 August 2011). To evaluate the created treatment option, the latter was analyzed in 157 patients with Т1–4N0–3M0 squamous cell carcinoma of the anal canal, who had been treated in 1990 to 2012. In 22 patients, radiotherapy was performed in combination with 3–5 sessions of local UHF hyperthermia (thermoradiotherapy (TRT)); 88 patients received the latter in combination with polychemotherapy (thermoradiochemotherapy (TRCT)); in addition to TRCT, 47 patients used MZ (TRCT + MZ).Results. In the TRT, TRCT, and TRCT + MZ groups, organ-sparing treatment was performed in 11 (50 %), 71 (80.7 %), and 44 (93.6 %) patients, respectively. In these groups, the median follow-up was 18.6; 51.7, and 15.5 months, respectively. In the 3 groups, the three-year overall survival rates were 71.4; 90.0, and 96.3 % and the three-year relapse free survival rates were 46.7; 60.6, and 75.0 %, respectively.Conclusion. The created combination thermochemoradiotherapy involving a polymer combination with MZ (TRCT + MZ) makes it possible to achieve organ-sparing treatment in 93.6 % of the patients and to slightly improve 3-year overall and relapse-free survival rates in patients with squamous cell carcinoma of the anal canal who have received organ-sparing treatment although there is only a tendency for statistical survival difference in this patient group