850 research outputs found

    Research of regional growth and development theories

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    Исследование теорий регионального экономического рост

    Conductivity, weak ferromagnetism and charge instability in αMnS\alpha-MnS single crystal

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    The temperature dependence of resistivity, magnetization and electron-spin resonance of the αMnS\alpha- MnS single crystal were measured in temperature range of 5K<T<550K5 K < T < 550 K. Magnetization hysteresis in applied magnetic field up to 0.7 T at T=5K,77K,300KT=5 K, 77 K, 300 K, irreversible temperature behavior of magnetization and resistivity were found . The obtained data were explained in terms of degenerate tight binding model using random phase approximation. The contribution of holes in t2gt_{2g} and ege_g bands of manganese ions to the conductivity, optical absorbtion spectra and charge instability in αMnS\alpha -MnS were studied. Charge susceptibility maxima resulted from the competition of the on-site Coulomb interaction between the holes in different orbitals and small hybridization of sub-bands were calculated at T=160K,250K,475KT=160 K, 250 K, 475 K.Comment: 6 pages, 12 figure

    Організація фізичного виховання школярів спеціальних медичних груп

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    Актуальність дослідження зумовлена невизначеністю системи організації фізичного виховання школярів спеціальних медичних груп. Завдання дослідження – узагальнити досвід теорії й практики з проблеми організації та методики проведення уроків фізичної культури з учнями спеціальних медичних груп. Найбільш ефек-тивний вплив на покращання здоров’я дітей можна здійснювати, проводячи заняття учнів спеціальної медичної групи на уроках фізичної культури, які проводяться окремою підгрупою за розкладом уроків основної медичної групи, та заняття учнів спеціальної медичної групи на уроках фізичної культури, що проводяться в позаурочний час. Отже, на сьогодні не розв’язаною залишається проблема організації уроків фізичної культури з учнями спеціальної медичної групи. Наявні підходи до проведення таких занять мають переваги та недоліки об’єктивного й суб’єктивного характеру. The research actuality is caused by the vagueness of the system of organization of physical education of schoolchildren in special medical groups. Research task: to generalize the experience of theory and practice of organization and methodology of conducting lesson of physical culture with students of special medical groups. The most effective influence on improvement of children health can made by organizing physical culture lessons for schoolchildren in special medical groups which are conducted to a separate group on the lessons curriculum of basic medical group and the lessons for students of the special medical groups which are organized in after-school time. It is consequently that nowadays a problem of organization of physical culture lessons with the students of. special medical groups stays unsolved Existent methods of organization of such lessons have advantages and disadvantages of objective and subjective character

    Particle Acceleration and Magnetic Dissipation in Relativistic Current Sheet of Pair Plasmas

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    We study linear and nonlinear development of relativistic and ultrarelativistic current sheets of pair plasmas with antiparallel magnetic fields. Two types of two-dimensional problems are investigated by particle-in-cell simulations. First, we present the development of relativistic magnetic reconnection, whose outflow speed is an order of the light speed c. It is demonstrated that particles are strongly accelerated in and around the reconnection region, and that most of magnetic energy is converted into "nonthermal" part of plasma kinetic energy. Second, we present another two-dimensional problem of a current sheet in a cross-field plane. In this case, the relativistic drift kink instability (RDKI) occurs. Particle acceleration also takes place, but the RDKI fast dissipates the magnetic energy into plasma heat. We discuss the mechanism of particle acceleration and the theory of the RDKI in detail. It is important that properties of these two processes are similar in the relativistic regime of T > mc^2, as long as we consider the kinetics. Comparison of the two processes indicates that magnetic dissipation by the RDKI is more favorable process in the relativistic current sheet. Therefore the striped pulsar wind scenario should be reconsidered by the RDKI.Comment: To appear in ApJ vol. 670; 60 pages, 27 figures; References and typos are fixe

    Winds, B-Fields, and Magnetotails of Pulsars

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    We investigate the emission of rotating magnetized neutron stars due to the acceleration and radiation of particles in the relativistic wind and in the magnetotail of the star. We consider that the charged particles are accelerated by driven collisionless reconnection. Outside of the light cylinder, the star's rotation acts to wind up the magnetic field to form a predominantly azimuthal, slowly decreasing with distance, magnetic field of opposite polarity on either side of the equatorial plane normal to the star's rotation axis. The magnetic field annihilates across the equatorial plane with the magnetic energy going to accelerate the charged particles to relativistic energies. For a typical supersonically moving pulsar, the star's wind extends outward to the standoff distance with the interstellar medium. At larger distances, the power output of pulsar's wind E˙w\dot{E}_w of electromagnetic field and relativistic particles is {\it redirected and collimated into the magnetotail} of the star. In the magnetotail it is proposed that equipartition is reached between the magnetic energy and the relativistic particle energy. For such conditions, synchrotron radiation from the magnetotails may be a significant fraction of E˙w\dot{E}_w for high velocity pulsars. An equation is derived for the radius of the magnetotail rm(z)r_m(z^\prime) as a function of distance zz^\prime from the star. For large distances zz^\prime, of the order of the distance travelled by the star, we argue that the magnetotail has a `trumpet' shape owing to the slowing down of the magnetotail flow.Comment: 11 pages, 4 figures, accepted for publication in Ap

    Strongly anisotropic magnetocaloric effect in a dipolar magnet LiGdF4_4

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    We report the detailed study of the magnetocaloric effect (MCE) in a dipolar-Heisenberg magnet LiGdF4_4 using magnetization measurements performed on a single crystal sample. Entropy variation on isothermal demagnetization from the magnetic field up to 3 T is determined in the temperature range 2-10 K for two principal directions of the applied field (parallel and perpendicular to the tetragonal cc-axis of the crystal). The MCE is found to be highly anisotropic, with the cooling efficiency being up to twice higher at HcH\parallel c. The results are nicely interpreted in the frame of a conventional molecular field approach taking into account considerable anisotropy of the paramagnetic Curie-Weiss temperature. These results are compared to earlier studies of MCE in powder samples of LiGdF4_4 [T. Numazawa et al., AIP Conf. Proc. 850, 1579 (2006)] as well as with analogous data for other well known magnetocaloric materials. Our findings may open new possibilities to enhance the efficiency of magnetic refrigeration in the liquid helium-4 temperature range.Comment: 4 pages, 3 figure

    Locking of the Rotation of Disk-Accreting Magnetized Stars

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    We investigate the rotational equilibrium state of a disk accreting magnetized stars using axisymmetric magnetohydrodynamic (MHD) simulations. In this ``locked'' state, the spin-up torque balances the spin-down torque so that the net average torque on the star is zero. We investigated two types of initial conditions, one with a relatively weak stellar magnetic field and a high coronal density, and the other with a stronger stellar field and a lower coronal density. We observed that for both initial conditions the rotation of the star is locked to the rotation of the disk. In the second case, the radial field lines carry significant angular momentum out of the star. However, this did not appreciably change the condition for locking of the rotation of the star. We find that in the equilibrium state the corotation radius rcor_{co} is related to the magnetospheric radius rAr_A as rco/rA1.21.3r_{co}/r_A\approx 1.2-1.3 for case (1) and rco/rA1.41.5r_{co}/r_A\approx 1.4-1.5 for case (2). We estimated periods of rotation in the equilibrium state for classical T Tauri stars, dwarf novae and X-ray millisecond pulsars.Comment: 10 pages, 9 figures. Accepted by ApJ, will appear in vol. 634, 2005 December

    Microscopic spin Hamiltonian for a dipolar-Heisenberg magnet LiGdF4 from EPR measurements

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    Low-temperature electron paramagnetic resonance measurements are performed on single crystals of LiY_{1-x}Gd_xF_4 with weak x=0.005 and moderate x=0.05 concentration of Gd ions. Modeling of the experimental spectra allows us to precisely determine microscopic parameters of the spin Hamiltonian of the parent LiGdF4 material, including the nearest-neighbor exchange constant. The obtained parameters are further tested by comparing a strongly anisotropic Curie-Weiss temperature obtained for LiGdF4 in our static magnetization measurements with theoretically computed values. We find a fine balance between principal magnetic interactions in LiGdF4, which results in a hidden magnetic frustration presumably leading to a delayed magnetic ordering and an enhanced magnetocaloric effect at low temperatures.Comment: 6 pages, 6 figure

    Pollen quality and pollen productivity of blue honeysuckle species and varieties

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    Studies to assess the pollen quality and pollen productivity of blue honeysuckle were conducted on the ecosystem dendrological territory of the Siberian Botanical garden of TSU (Tomsk). Objects of research: 8 varieties and 4 species of blue honeysuckle – ‘Velvet’, ‘Berel’, ‘Vasyuganskaya’, ‘Zolushka’, ‘Lazurnaya’, ‘Ogneny Opal’, ‘Selena’, ‘Tomichka’, Lonicera altaica, L. edulis, L. kamtschatica, L. turczaninovii. It was found that the ‘Ogneny Opal’ and ‘Velvet’ varieties have low fertility, and the ‘Berel’ and L. edulis have an average fertility. Other varieties and species of honeysuckle have high pollen fertility. The viability of pollen with high values is more than 60 % – ‘Berel’, ‘Vasyuganskaya’, ‘Lazurnaya’, L. turczaninovii, L. kamtschatica, with average values from 40% to 60 % – ‘Selena’, ‘Tomichka’ and L. altaica, with low values – less than 40 % – ‘Velvet’, ‘Zolushka’, ‘Ogneny Opal’ and L. edulis. High pollen productivity – more than 20,000 pollen grains per flower – ‘Tomichka’, L. kamtschatica, L. turczaninovii and L. edulis, average productivity - from 10,000 to 20,000 pollen grains – ‘Berel’, ‘Vasyuganskaya’, ‘Zolushka’, ‘Lazurnaya’, ‘Selena’ and L. altaica, low productivity – less than 10,000 pollen grains per flower – ‘Velvet’, ‘Ogneny Opal’. It is recommended to use at least 10% of varieties with high pollen viability and pollen productivity as pollinators when creating industrial honeysuckle plantations: ‘Lazurnaya’, ‘Vasyuganskaya’, and ‘Berel’
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