Александр Степанович Попов — изобретатель радио

Biographical details of Alexander Stepanovich Popov are stated in the paper, years of education in religious schools, seminary, St. Petersburg University. It was the University where he became an educated engineer-electrician. Repeating Hertz’s experiments and improving them A. S. Popov created the first in the world radio receiver. That is why May, 7 the date of publication of A. S. Popov of his invention is considered to be the birthday of radio. A. S. Popov was one of the originators of radioengineering industry and education in Russia.Излагаются биографические сведения об Александре Степановиче Попове, годы обучения в духовных училищах, духовной семинарии, Санкт-Петербургском университете. Именно в университете он становится высокообразованным инженером-электриком. Повторяя опыты Г. Герца и усовершенствуя их, А. С. Попов постепенно приходит к созданию первого в мире радиоприемника. Именно поэтому 7 мая — дата опубликования Поповым своего изобретения — считается днем рождения радио. А. С. Попов стоял также у истоков организации радиопромышленности и радиотехнического образования в России

The role of fragmentation in interaction of meteoroids with the Earth's atmosphere

As a rule, when analyzing the mechanism of quasi continuous fragmentation (QCF) it is assumed that fragments separated from the parent meteoroid (PM) are of equal initial mass. In reality, this may not be so. A major difficulty is the lack of observational data on the function of the fragment initial mass distribution and so one must resort to theoretical modeling. A discrete distribution is considered which excluded to a certain extent some mathematical difficulties. The calculation results are given and discussed

Angular momentum dependent friction slows down rotational relaxation under non-equilibrium conditions

It has recently been shown that relaxation of the rotational energy of hot non-equlibrium photofragments (i) slows down significantly with the increase of their initial rotational temperature and (ii) differs dramatically from the relaxation of the equilibrium rotational energy correlation function, manifesting thereby breakdown of the linear response description [Science 311, 1907 (2006)]. We demonstrate that this phenomenon may be caused by the angular momentum dependence of rotational friction. We have developed the generalized Fokker-Planck equation whose rotational friction depends upon angular momentum algebraically. The calculated rotational correlation functions correspond well to their counterparts obtained via molecular dynamics simulations in a broad range of initial non-equilibrium conditions. It is suggested that the angular momentum dependence of friction should be taken into account while describing rotational relaxation far from equilibrium

Jurkat/A4 cells with multidrug resistance exhibit reduced sensitivity to quercetin

Background: While multidrug resistance of cancer cells is a well-known phenomenon, little is known on the cross resistance between cytotoxic chemotherapeutical agents and unrelated substances such as natural flavonoids. Aim: To compare the effects of cytotoxic drug, vepeside and natural flavonoid, quercetin in Jurkat cells and their multidrug-resistant subline Jurkat/A4, in particular to analyze the effector mechanisms of apoptosis and the profiles of several pro- and antiapoptotic proteins in these cells upon exposure to vepeside or quercetin. Methods: Apoptosis and poly (ADP-ribose) polymerase cleavage were assessed by flow cytometry. Expression of apoptosisrelated proteins was analyzed by Western blotting. Results: Jurkat/A4 cells are less sensitive to antiproliferative effects of quercetin as compared with the parental Jurkat cell line. While vepeside as well as quercetin initially induces apoptosis in both cell lines, the following survival of the exposed cells is essentially different. In resistant Jurkat/A4 cells, vepeside or quercetin treatment activates significantly less caspase-9 and -3 as compared with that in the parental cells. The expression of Bad and BNip1 proteins in Jurkat/A4 cells is lower than in the parental cell line. At the same time, XIAP and CAS levels in Jurkat/A4 cells increase. Upon apoptosis induction, XIAP and CAS levels in Jurkat cells decrease, this effect being negligible in resistant cells. Conclusion: Multidrug-resistant Jurkat/A4 cells exhibit reduced sensitivity to cytotoxic effects of quercetin. The expression profile of Jurkat/A4 cells is characterized by the increased levels of XIAP and CAS representing the endogenous inhibitors of apoptosis

The pseudo-spin symmetry in Zr and Sn isotopes from the proton drip line to the neutron drip line

Based on the Relativistic continuum Hartree-Bogoliubov (RCHB) theory, the pseudo-spin approximation in exotic nuclei is investigated in Zr and Sn isotopes from the proton drip line to the neutron drip line. The quality of the pseudo-spin approximation is shown to be connected with the competition between the centrifugal barrier (CB) and the pseudo-spin orbital potential (PSOP). The PSOP depends on the derivative of the difference between the scalar and vector potentials $dV/dr$. If $dV/dr = 0$, the pseudo-spin symmetry is exact. The pseudo-spin symmetry is found to be a good approximation for normal nuclei and to become much better for exotic nuclei with highly diffuse potential, which have $dV/dr \sim 0$. The energy splitting of the pseudo-spin partners is smaller for orbitals near the Fermi surface (even in the continuum) than the deeply bound orbitals. The lower components of the Dirac wave functions for the pseudo-spin partners are very similar and almost equal in magnitude.Comment: 22 pages, 9figure

Stresses in Twisted Cylindrical Plugs of Non-homogeneous Material Inserted into a Rigid Medium

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Investigation of thermodynamic properties of organic substances

Scientific and ptactical significance of the investigations in the field of thermodynamics of organic compounds is discussed. The apparatuses and methods used in LTOC (the Laboratory of Thermodynamics of Organic Compounds, Research Institute for Physical Chemical Problems, Belarusian State University) for experimental determination of thermodynamic properties of substances are described. They are adiabatic calorimetry and DSC of the heat bridge type for the measurements of heat capacities and enthalpies of phase transitions in the con-densed state, heat flow differential microcalorimeter of the Calvet type to obtain en-thalpies of evaporation, calorimeters for combustion of organic substances for determination of the enthalpies of combustion and formation, the apparatus for measurements of saturated vapor pressure by the integral effusion Knudsen method. The main results of studies of chemical and phase equilibria,thermodynam-ics of isomerization, improvements of additive methods for calculation of thermo-dynamic properties, investigations of plastic crystals of organic compounds and ionic liquids, calculations by the methods of statistical thermodynamics are re-ported. The information concerning development of the methods of calculation of chemical exergies in LTOC and thermodynamic substantiation of energy and resource saving technologies of organic production of Republic of Belarus is give

Application of photoluminescence and electroluminescence techniques to the characterization of intermediate band solar cells

The intermediatebandsolarcell (IBSC) is a photovoltaic device with a theoretical conversion efficiency limit of 63.2%. In recent years many attempts have been made to fabricate an intermediateband material which behaves as the theory states. One characteristic feature of an IBSC is its luminescence spectrum. In this work the temperature dependence of the photoluminescence (PL) and electroluminescence (EL) spectra of InAs/GaAs QD-IBSCs together with their reference cell have been studied. It is shown that EL measurements provide more reliable information about the behaviour of the IB material inside the IBSC structure than PL measurements. At low temperatures, the EL spectra are consistent with the quasi-Fermi level splits described by the IBSC model, whereas at room temperature they are not. This result is in agreement with previously reported analysis of the quantum efficiency of the solarcell

Laser welding of metal-polymer-metal sandwich panels

In the production of metal-polymer multilayer composite parts, e.g., for automotive applications, the possibilities of thermal joining are limited due to the instability of the polymer core at elevated temperatures. Accordingly, such materials require a special approach to their welding. The three-layered metal-polymer-metal samples were made of DPK 30/50+ZE dual-phase steel as cover sheets that were electrolytic galvanized, and a polypropylene-polyethylene foil as core material, with thicknesses of 0.48/0.3/0.48 mm. The samples were welded on both sides using a 1.06 μm Nd:YAG ROFIN StarWeld Manual Performance laser. Significant improvements of the welding conditions are achieved by machining the edges of materials to be welded. The parameters of laser welding were chosen in such a way that the polymer structure remained almost unchanged. The weld thickness was about 40% of the thickness of each steel layer. It was established that within the selected laser processing parameters the melting occurred uniformly, while the polymer layer practically did not change its structure. Therefore, it can be stated that two-sided joint welding of metal-polymer-metal composite sandwich panels, without significant degradation of the polymer core layer, is feasible