New and rare lichens for Russia and the Caucasus from high mountainous Dagestan (East Caucasus)

Five species of lichenized ascomycetes are reported from high mountainous Dagestan. Acarospora laqueata, Lecania ochronigra and Protoparmelia placentiformis are new to Russia and the Caucasus (the last two). Anamylopsora pulcherrima is the first record of the genus and species for the North Caucasus. Buellia centralis is the first record for the Caucasus and second for Russia. Our records considerably extended information about geography and ecology of presented species especially the very rare species Buellia centralis, Lecania ochronigra and Protoparmelia placentiformis. The characteristic features of specimens with information of their morphology, anatomy, ecology and world distribution are given

STRUCTURAL AND TECHNOLOGICAL PARAMETERS AFFECTING THE BIPOLAR STATIC INDUCTION TRANSISTOR (BSIT ) RESISTANCE

Aim. The aim of the study is to determine the impact of structural and technological parameters on the resistance of the bipolar static induction transistor.Methods. The paper provides a comparative analysis of the advantages of bipolar static induction transistor compared to the bipolar power transistors, MOSFETs and insulated-gate bipolar transistor (IGBT). Considered are structural and technological parameters that influence the resistance of BSIT-transistor.Result. As a result of experimental study on silicon substrates were formed test prototypes of BSIT transistor structure, are presented calculation and experimental works. Obtained are the resistance dependencies of the transistor cell on the thickness of the epitaxial film; the resistance dependencies of BSIT transistor cell on the effective gate length for different values of the impurity concentration in the epitaxial film; dependencies resistance of the transistor cell on the gate length at different values of the epitaxial film thickness; the resistance dependencies of BSIT transistor cell on the distance between the mask for the p-region and the gate; dependencies on the multiplication the cell resistance by its area on the gate length.Conclusion. When increasing the gate length (Lk) and the mask length for the p-region (lp +) in the transistor structure, the resistance decreases and the dependence of multiplication of the cell resistance by its area Q on the gate length has this case the minimum

Interband electron Raman scattering in a quantum wire in a transverse magnetic field

Electron Raman scattering (ERS) is investigated in a parabolic semiconductor quantum wire in a transverse magnetic field neglecting by phonon-assisted transitions. The ERS cross-section is calculated as a function of a frequency shift and magnetic field. The process involves an interband electronic transition and an intraband transition between quantized subbands. We analyze the differential cross-section for different scattering configurations. We study selection rules for the processes. Some singularities in the Raman spectra are found and interpreted. The scattering spectrum shows density-of-states peaks and interband matrix elements maximums and a strong resonance when scattered frequency equals to the "hybrid" frequency or confinement frequency depending on the light polarization. Numerical results are presented for a GaAs/AlGaAs quantum wire.Comment: 8 pages, 5 figure

DEFINITION of EXTENDED STRUCTURAL DEFECTS IN EPITAXIAL FILMS of ZnTeG‘GaAs GROWN by MBE

The last three decades of the development of solid state physics are characterized by the fact that the main objects of research are increasingly not massive crystals, but thin films, multilayer thin-film systems, conducting filaments and crystallites of small size. Epitaxial films are grown on a substrate of a single crystal of the same or another material. In the first case, the epitaxial layer with the correct technology becomes a natural extension of the substrate. Epitaxial film can be doped with various impurities. To introduce an alloying admixture into the epitaxial film, three methods are used. According to the first method, the necessary admixture is dissolved in the source of the semiconductor material. The second method involves the use of an alloying admixture in an elementary form and its placement in the pipe between the source of the semiconductor material and the substrate. Sometimes the alloying admixture is placed in a separate temperature zone of the working pipe. The third method is to add an alloying admixture to the volatile iodides. Interest in the study of quantum-dimensional structures based on A2B6 materials is due to the possibility of manufacturing on their basis of injection sources of coherent and incoherent radiation, as well as emitters with electronic pumping, covering almost the entire visible range. To clarify the nature of the luminescence centers responsible for the i1c band, we studied the effect on the FL spectra of the buffer ES ZnTe: (I)a thin (5-10 nm) intermediate recrystallized ZnTe layer located between the buffer layer and the substrate (100) GaAs; (ii)the thickness of the buffer layer, as well as (III) the build-up of quantum-dimensional layers CdxZn1-xTeG‘ZnTe (xq0.2-0.4). In addition, the spatial distribution (in buffer depth) of the intensity (I) and spectral position (m) of THE i1c band, as well as temperature dependences of I and m were investigated. At the same time, x-ray diffraction measurements of the swing curves were carried out to control the structural perfection of the ZnTe ES. In the exciton region of the spectrum, there are also intense band I1C hmq2.356 eV and located in close proximity to her far side strip with hmq2.352 eV (I2C) lower intensity. In the samples with quantum layers from the short-wave side of I1C, an additional band IX with hmq2.359 eV is observed. A number of characteristics of the bands in the group I1C different from the corresponding characteristics such as both free and associated excitons. Thus, the change in the technology of growing MBE epitaxial buffer layers ZnTeG‘GaAs: (1) the use of a thin, recrystallized layer ZnTe (d10 nm), as well as (2) an increase in the thickness of the buffer layer leads to an improvement in the structure of the ES, as well as an increase in the total intensity of the FL bands in the exciton spectrum and a decrease in the impurity. The paper also provides with additional information on the nature of the i1c band and the IX band found near it. The difference between the temperature and deformation dependences of the positions of these bands on the corresponding characteristics of the exciton radiation lines, as well as the increase in their intensity with a decrease in deformations made it possible to link these bands with extended defects. Based on these data, as well as the results of x-ray diffraction measurements, it is assumed that the centers responsible for the I1C band are associated with the boundaries of the subunits in the mosaic structure

Исследование параметров, влияющих на пробивное напряжение биполярного транзистора со статической индукцией

The article considers structural and technological parameters affecting breakdown voltage of a BSIT transistor cell. The main objective of the scientific research in that field is optimization of manufacturing techniques of power electronics transistor configurations in order to improve the instrument output characteristics and reliability. One of the key electrical parameters characterizing this instrument is breakdown voltage. In p-n junction at specific value of reverse bias the breakdown effect is present that appears as sharp increase of reverse current in p-n junction. For thermal breakdown to occur the thermal self-heating of the structure is necessary. It takes place in case of considerable reverse current in p-n junction. Typically, thermal breakdown happens after tunnel or avalanche breakdown of p-n junction. Breakdown voltage of real diffused p-n junction is defined by value of avalanche breakdown voltage of spherical part of the junction. Thus, breakdown voltage of p-n of junction strongly depends on its geometry.Исследуется структура биполярного транзистора со статической индукцией (БСИТ). Рассмотрены конструктивно-технологические параметры, влияющие на пробивное напряжение ячейки БСИТ. Исследованы и получены зависимости пробивного напряжения от геометрии прибора

Investigation of conduction band structure, electron scattering mechanisms and phase transitions in indium selenide by means of transport measurements under pressure

In this work we report on Hall effect, resistivity and thermopower measurements in n-type indium selenide at room temperature under either hydrostatic and quasi-hydrostatic pressure. Up to 40 kbar (= 4 GPa), the decrease of carrier concentration as the pressure increases is explained through the existence of a subsidiary minimum in the conduction band. This minimum shifts towards lower energies under pressure, with a pressure coefficient of about -105 meV/GPa, and its related impurity level traps electrons as it reaches the band gap and approaches the Fermi level. The pressure value at which the electron trapping starts is shown to depend on the electron concentration at ambient pressure and the dimensionality of the electron gas. At low pressures the electron mobility increases under pressure for both 3D and 2D electrons, the increase rate being higher for 2D electrons, which is shown to be coherent with previous scattering mechanisms models. The phase transition from the semiconductor layered phase to the metallic sodium cloride phase is observed as a drop in resistivity around 105 kbar, but above 40 kbar a sharp nonreversible increase of the carrier concentration is observed, which is attributed to the formation of donor defects as precursors of the phase transition.Comment: 18 pages, Latex, 10 postscript figure

PHASES High Precision Differential Astrometry of delta Equulei

delta Equulei is among the most well-studied nearby binary star systems. Results of its observation have been applied to a wide range of fundamental studies of binary systems and stellar astrophysics. It is widely used to calibrate and constrain theoretical models of the physics of stars. We report 27 high precision differential astrometry measurements of delta Equulei from the Palomar High-precision Astrometric Search for Exoplanet Systems (PHASES). The median size of the minor axes of the uncertainty ellipses for these measurements is 26 micro-arcseconds. These data are combined with previously published radial velocity data and other previously published differential astrometry measurements using other techniques to produce a combined model for the system orbit. The distance to the system is determined to within a twentieth of a parsec and the component masses are determined at the level of a percent. The constraints on masses and distance are limited by the precisions of the radial velocity data; we outline plans improve this deficiency and discuss the outlook for further study of this binary.Comment: Accepted by AJ. Complete versions of tables 2-7 now available at http://stuff.mit.edu/~matthew1/deltaEquTables/ (removed from astroph server

Multi-band analyses of the bright GRB~230812B and the associated SN2023pel

GRB~230812B is a bright and relatively nearby ($z =0.36$) long gamma-ray burst that has generated significant interest in the community and therefore has been subsequently observed over the entire electromagnetic spectrum. We report over 80 observations in X-ray, ultraviolet, optical, infrared, and sub-millimeter bands from the GRANDMA (Global Rapid Advanced Network for Multi-messenger Addicts) network of observatories and from observational partners. Adding complementary data from the literature, we then derive essential physical parameters associated with the ejecta and external properties (i.e. the geometry and environment) and compare with other analyses of this event (e.g. Srinivasaragavan et al. 2023). We spectroscopically confirm the presence of an associated supernova, SN2023pel, and we derive a photospheric expansion velocity of v $\sim$ 17$\times10^3$ km $s^{-1}$. We analyze the photometric data first using empirical fits of the flux and then with full Bayesian Inference. We again strongly establish the presence of a supernova in the data, with an absolute peak r-band magnitude $M_r = - 19.41 \pm 0.10$. We find a flux-stretching factor or relative brightness $k_{\rm SN}=1.04 \pm 0.09$ and a time-stretching factor $s_{\rm SN}=0.68 \pm 0.05$, both compared to SN1998bw. Therefore, GRB 230812B appears to have a clear long GRB-supernova association, as expected in the standard collapsar model. However, as sometimes found in the afterglow modelling of such long GRBs, our best fit model favours a very low density environment ($\log_{10}({n_{\rm ISM}/{\rm cm}^{-3}}) = -2.16^{+1.21}_{-1.30}$). We also find small values for the jet's core angle $\theta_{\rm core}={1.70^{+1.00}_{-0.71}} \ \rm{deg}$ and viewing angle. GRB 230812B/SN2023pel is one of the best characterized afterglows with a distinctive supernova bump

Ready for O4 II: GRANDMA Observations of Swift GRBs during eight-weeks of Spring 2022

We present a campaign designed to train the GRANDMA network and its infrastructure to follow up on transient alerts and detect their early afterglows. In preparation for O4 II campaign, we focused on GRB alerts as they are expected to be an electromagnetic counterpart of gravitational-wave events. Our goal was to improve our response to the alerts and start prompt observations as soon as possible to better prepare the GRANDMA network for the fourth observational run of LIGO-Virgo-Kagra (which started at the end of May 2023), and future missions such as SM. To receive, manage and send out observational plans to our partner telescopes we set up dedicated infrastructure and a rota of follow-up adcates were organized to guarantee round-the-clock assistance to our telescope teams. To ensure a great number of observations, we focused on Swift GRBs whose localization errors were generally smaller than the GRANDMA telescopes' field of view. This allowed us to bypass the transient identification process and focus on the reaction time and efficiency of the network. During 'Ready for O4 II', 11 Swift/INTEGRAL GRB triggers were selected, nine fields had been observed, and three afterglows were detected (GRB 220403B, GRB 220427A, GRB 220514A), with 17 GRANDMA telescopes and 17 amateur astronomers from the citizen science project Kilonova-Catcher. Here we highlight the GRB 220427A analysis where our long-term follow-up of the host galaxy allowed us to obtain a photometric redshift of $z=0.82\pm0.09$, its lightcurve elution, fit the decay slope of the afterglows, and study the properties of the host galaxy