307 research outputs found
Evaluation of the professional aptitude of a student for internship at the enterprise
The competences declared by educational standards and the labor functions declared by professional standards for compliance with each other are analyzedПроанализированы компетенции, заявленные образовательными стандартами и трудовые функции, заявленные профессиональными стандартами на предмет соответствия друг друг
Critical exponents for 3D O(n)-symmetric model with n > 3
Critical exponents for the 3D O(n)-symmetric model with n > 3 are estimated
on the base of six-loop renormalization-group (RG) expansions. A simple
Pade-Borel technique is used for the resummation of the RG series and the Pade
approximants [L/1] are shown to give rather good numerical results for all
calculated quantities. For large n, the fixed point location g_c and the
critical exponents are also determined directly from six-loop expansions
without addressing the resummation procedure. An analysis of the numbers
obtained shows that resummation becomes unnecessary when n exceeds 28 provided
an accuracy of about 0.01 is adopted as satisfactory for g_c and critical
exponents. Further, results of the calculations performed are used to estimate
the numerical accuracy of the 1/n-expansion. The same value n = 28 is shown to
play the role of the lower boundary of the domain where this approximation
provides high-precision estimates for the critical exponents.Comment: 10 pages, TeX, no figure
Membrane fusion mediated by ricin and viscumin
AbstractThe ribosome inactivating plant proteins (RIPs) ricin and viscumin but not Ricinus communis agglutinin are able induce vesicle–vesicle fusion. A model is suggested in which the toxicity of the RIPs is partially determined by their fusogenicity. Herein, fusion is hypothesized to allow the RIPs to leak across endocytic vesicles to approve their access to cytoplasmic ribosomes
125Te spin-lattice relaxation in a candidate to Weyl semimetals WTe2
The tungsten ditelluride WTe2 was suggested to belong to the Weyl semimetal family. We studied 125Te spin-lattice relaxation and NMR spectra in a WTe2 single crystal within a large range from 28 K up to room temperature. Measurements were carried out on a Bruker Avance 500 NMR pulse spectrometer for the crystalline c axis directed in parallel and perpendicular to the magnetic field. Relaxation proved to be single-exponential. The relaxation time varied depending on the sample position in magnetic field and frequency offset. The relaxation rate increased about linearly with temperature below 70 K, however the dependence became nearly quadratic at higher temperatures. The relaxation rate within the total temperature range was fitted using a theoretical model developed in Ref. [41] for Weyl semimetals and assuming the decrease of the chemical potential with increasing temperature. The results obtained for 125Te spin-lattice relaxation evidence in favor of the topological nontriviality of the WTe2 semimetal. The 125Te NMR spectra agreed with the occurrence of nonequivalent tellurium sites and varied insignificantly with temperature. © 2020 The Author(s)The authors acknowledge the financial support from RFBR , grants 19-57-52001 , 19-29-03004 , and 19-07-00028 . The work was partly supported by Minobrnauki of Russia (“Spin” No. AAAA-A18-118020290104-2 ) and Russian Government (contract No. 02.A03.21.0006 ). Measurements were partly carried out using the equipment of the Research park of St. Petersburg State University
Scaling of Particle and Transverse Energy Production in 208Pb+208Pb collisions at 158 A GeV
Transverse energy, charged particle pseudorapidity distributions and photon
transverse momentum spectra have been studied as a function of the number of
participants (N_{part}) and the number of binary nucleon-nucleon collisions
(N_{coll}) in 158 A GeV Pb+Pb collisions over a wide impact parameter range. A
scaling of the transverse energy pseudorapidity density at midrapidity as
N_{part}^{1.08 \pm 0.06} and N_{coll}^{0.83 \pm 0.05} is observed. For the
charged particle pseudorapidity density at midrapidity we find a scaling as
N_{part}^{1.07 \pm 0.04} and N_{coll}^{0.82 \pm 0.03}. This faster than linear
scaling with N_{part} indicates a violation of the naive Wounded Nucleon Model.Comment: 13 pages, 16 figures, submitted to European Physical Journal C
(revised results for scaling exponents
Centrality Dependence of Neutral Pion Production in 158 A GeV Pb + Pb Collisions
The production of neutral pions in 158AGeV Pb+Pb collisions has been studied
in the WA98 experiment at the CERN SPS. Transverse momentum spectra are studied
for the range 0.3 GeV/c < mT-m0 < 4.0 GeV/c. The results for central collisions
are compared to various models. The centrality dependence of the neutral pion
spectral shape and yield is investigated. An invariance of the spectral shape
and a simple scaling of the yield with the number of participating nucleons is
observed for centralities with greater than about 30 participating nucleons
which is most naturally explained by assuming an equilibrated system.Comment: 5 pages, Latex, including 3 eps figures, submitted to Phys.Rev.Lett;
updated pQCD comparison due to new input from the author, updated references,
corrected plotting error in figure
Systematics of Inclusive Photon Production in 158 AGeV Pb Induced Reactions on Ni, Nb, and Pb Targets
The multiplicity of inclusive photons has been measured on an event-by-event
basis for 158 AGeV Pb induced reactions on Ni, Nb, and Pb targets. The
systematics of the pseudorapidity densities at midrapidity (rho_max) and the
width of the pseudorapidity distributions have been studied for varying
centralities for these collisions. A power law fit to the photon yield as a
function of the number of participating nucleons gives a value of 1.13+-0.03
for the exponent. The mean transverse momentum, , of photons determined
from the ratio of the measured electromagnetic transverse energy and photon
multiplicity, remains almost constant with increasing rho_max. Results are
compared with model predictions.Comment: 16 pages including 4 figure
Interferometry of Direct Photons in Central 280Pb+208Pb Collisions at 158A GeV
Two-particle correlations of direct photons were measured in central
208Pb+208Pb collisions at 158 AGeV. The invariant interferometric radii were
extracted for 100<K_T<300 MeV/c and compared to radii extracted from charged
pion correlations. The yield of soft direct photons, K_T<300 MeV/c, was
extracted from the correlation strength and compared to theoretical
calculations.Comment: 5 pages, 4 figure
ОСОБЕННОСТИ ЭЛЕКТРОННОГО СТРОЕНИЯ НАНОСЛОЕВ «КРЕМНИЙ–НА–ИЗОЛЯТОРЕ» И ИХ ВЗАИМОДЕЙСТВИЕ С ИЗЛУЧЕНИЕМ НАНОМЕТРОВОГО ДИАПАЗОНА
Structures with strained and unstrained silicon layers were studied by ultrasoft X−ray emission spectroscopy and X−ray absorption near edge structure spectroscopy with the use of synchrotron radiation techniques the SOI (silicon−on−insulator). Analysis of X−ray data has shown a noticeable transformation of the electron energy spectrum and local partial density of states distribution in valence and conduc- tion bands in the strained silicon layer of the SOI structure. USXES Si L2,3 spectra analysis revealed a decrease of the distance between the L′2v и L1v points in the valence band of the strained silicon layer as well as a shift of the first two maxima of the XANES first derivation spectra to the higher energies with respect to conduction band bottom Ec. At the same time the X−ray standing waves of synchrotron radiation (λ ~ 12−20 nm) are formed in the silicon−on−insulator structure with and without strains of the silicon layer. Moreover the synchrotron radiation grazing angle θ changing by 2° leads to a change of the electromagnetic field phase to the opposite. Методами ультрамягкой рентгеновской эмиссионной спектроскопии и спектроскопии ближней тонкой структуры края рентгеновского поглощения с использованием синхротронного излучения исследованы структуры КНИ (кремний−на−изоляторе) с растянутым и нерастянутым слоями кремния. Выявлена заметная перестройку электронно−энергетического спектра и локальной парциальной плотности состояний как в валентной зоне, так и в зоне проводимости растянутого слоя кремния структуры КНИ. На основе анализа Si L2,3 спектров USXES показано уменьшение энергетического расстояния между точками L′2v и L1v в валентной зоне растянутого слоя кремния, в котором наблюдался и сдвиг первых двух максимумов первой производной спектра XANES в сторону больших энергий относительно дна зоны проводимости Ес. Обнаружено, что при этом стоячие рентгеновские волны синхротронного излучения нанометрового диапазона длин волн (λ ~ 12—20 нм) формируются в структурах кремний−на−изоляторе как с растянутым, так и с нерастянутым нанослоем кремния. Более того, установлено, что изменение угла скольжения синхротронного излучения θ на 2° приводит к смене фазы электромагнитного поля на противоположную.
Central Pb+Pb Collisions at 158 A GeV/c Studied by Pion-Pion Interferometry
Two-particle correlations have been measured for identified negative pions
from central 158 AGeV Pb+Pb collisions and fitted radii of about 7 fm in all
dimensions have been obtained. A multi-dimensional study of the radii as a
function of kT is presented, including a full correction for the resolution
effects of the apparatus. The cross term Rout-long of the standard fit in the
Longitudinally CoMoving System (LCMS) and the vl parameter of the generalised
Yano-Koonin fit are compatible with 0, suggesting that the source undergoes a
boost invariant expansion. The shapes of the correlation functions in Qinv and
Qspace have been analyzed in detail. They are not Gaussian but better
represented by exponentials. As a consequence, fitting Gaussians to these
correlation functions may produce different radii depending on the acceptance
of the experimental setup used for the measurement.Comment: 13 pages including 10 figure
- …