Crystal Undulator As A Novel Compact Source Of Radiation

A crystalline undulator (CU) with periodically deformed crystallographic planes is capable of deflecting charged particles with the same strength as an equivalent magnetic field of 1000 T and could provide quite a short period L in the sub-millimeter range. We present an idea for creation of a CU and report its first realization. One face of a silicon crystal was given periodic micro-scratches (grooves), with a period of 1 mm, by means of a diamond blade. The X-ray tests of the crystal deformation have shown that a sinusoidal-like shape of crystalline planes goes through the bulk of the crystal. This opens up the possibility for experiments with high-energy particles channeled in CU, a novel compact source of radiation. The first experiment on photon emission in CU has been started at LNF with 800 MeV positrons aiming to produce 50 keV undulator photons.Comment: Presented at PAC 2003 (Portland, May 12-16

Prognostic criteria of heart rate variability at the daily monitoring

The data of comparative researches of parameters of heart rate variability on the basis of daily ECG registration with regard circadian oscillations of heart rate. Shown significant reduction in both temporary and spectral indices of daily variability of a heart rhythm in adolescents with scoliosis without significant imbalance parasympathetic and sympathetic departments of ANS. These changes indicate violations of interaction between different parts of ANS in providing functionality driving rhythm and demonstrated reduction of adaptational possibilities of the organism, which leads to a heightened risk of violations of the regulation of the heart rate in this group of adolescentsПриведены данные сравнительного исследования показателей вариабельности сердечного ритма на основе суточной регистрации ЭКГ с учетом циркадных колебаний ритма сердца. Показано достоверное снижение как временных, так и спектральных показателей суточной вариабельности сердечного ритма у подростков со сколиозом без выраженного дисбаланса парасимпатического и симпатического отделов ВНС. Данные изменения указывают на нарушения взаимодействия между различными звеньями ВНС в обеспечении функции вождения ритма и свидетельствуют о снижении адаптационных возможностей организма, что ведет к повышенному риску развития нарушений регуляции сердечного ритма в данной группе подростко

Stationary waves in a superfluid exciton gas in quantum Hall bilayers

Stationary waves in a superfluid magnetoexciton gas in nu = 1 quantum Hall bilayers are considered. The waves are induced by counter-propagating electrical currents that flow in a system with a point obstacle. It is shown that stationary waves can emerge only in imbalanced bilayers in a certain diapason of currents. It is found that the stationary wave pattern is modified qualitatively under a variation of the ratio of the interlayer distance to the magnetic length d/l. The advantages of use graphene-dielectric-graphene sandwiches for the observation of stationary waves are discussed. We determine the range of parameters (the dielectric constant of the layer that separates two graphene layers and the ratio d/l) for which the state with superfluid magnetoexcitons can be realized in such sandwiches. Typical stationary wave patterns are presented as density plotsComment: 17 pages, 8 figure

Nuclear Track Emulsion in Search for the Hoyle’s State in Dissociation of Relativistic 12C Nuclei

Study of production of ensembles of alpha-particle triples associated with the Hoyle state (the second excited state 0+ 2 of the 12 C nucleus) in peripheral dissociation of relativistic 12C nuclei is started. Stacks of pellicles of nuclear track emulsion exposed to 12C of energy from hundreds MeV to few GeV per nucleon serve as the material of the study. The Hoyle state decays are reconstructed via measurements of emission angles of α-particles with accuracy that allows one to identify the unstable 8Be nucleus. A role in the Hoyle state of alpha-particle bonds corresponding to 8Be is determined

The ART-XC telescope on board the SRG observatory

ART-XC (Astronomical Roentgen Telescope - X-ray Concentrator) is the hard X-ray instrument with grazing incidence imaging optics on board the Spektr-Roentgen-Gamma (SRG) observatory. The SRG observatory is the flagship astrophysical mission of the Russian Federal Space Program, which was successively launched into orbit around the second Lagrangian point (L2) of the Earth-Sun system with a Proton rocket from the Baikonur cosmodrome on 13 July 2019. The ART-XC telescope will provide the first ever true imaging all-sky survey performed with grazing incidence optics in the 4-30 keV energy band and will obtain the deepest and sharpest map of the sky in the energy range of 4-12 keV. Observations performed during the early calibration and performance verification phase as well as during the on-going all-sky survey that started on 12 Dec. 2019 have demonstrated that the in-flight characteristics of the ART-XC telescope are very close to expectations based on the results of ground calibrations. Upon completion of its 4-year all-sky survey, ART-XC is expected to detect ~5000 sources (~3000 active galactic nuclei, including heavily obscured ones, several hundred clusters of galaxies, ~1000 cataclysmic variables and other Galactic sources), and to provide a high-quality map of the Galactic background emission in the 4-12 keV energy band. ART-XC is also well suited for discovering transient X-ray sources. In this paper, we describe the telescope, results of its ground calibrations, major aspects of the mission, the in-flight performance of ART-XC and first scientific results.Comment: 19 pages, 30 figures, accepted for publication in Astronomy and Astrophysic

Graphene Bilayer Structures with Superfluid Magnetoexcitons

We study superfluid behavior of a gas of spatially indirect magnetoexcitons with reference to a system of two graphene layers embedded in a multilayer dielectric structure. The system is considered as an alternative of a double quantum well in a GaAs haterostructure. We determine a range of parameters (interlayer distance, dielectric constant, magnetic field and gate voltage) where magnetoexciton superfluidity can be achieved. Temperature of superfluid transition is computed. A reduction of critical parameters caused by impurities is evaluated and critical impurity concentration is determined

Physicochemical Properties and Electrochemical Performance of the La1.7Ca0.3Ni1-yCuyO4+ δ Cathodes

The results of present work demonstrate that the developed La1.7Ca0.3Ni1-yCuyO4+δ-based electrode can be considered as prospective cathode for intermediate temperature solid oxide fuel cells