806 research outputs found
Observation of superluminal geometrical resonances in Bi2Sr2CaCu2O8+x intrinsic Josephson junctions
We study Fiske steps in small Bi2Sr2CaCu2O8+x mesa structures, containing
only few stacked intrinsic Josephson junctions. Careful alignment of magnetic
field prevents penetration of Abrikosov vortices and facilitates observation of
a large variety of high quality geometrical resonances, including superluminal
with velocities larger than the slowest velocity of electromagnetic waves. A
small number of junctions limits the number of resonant modes and allows
accurate identification of modes and velocities. It is shown that superluminal
geometrical resonances can be excited by subluminal fluxon motion and that
flux-flow itself becomes superluminal at high magnetic fields. We argue that
observation of high-quality superluminal geometrical resonances is crucial for
realization of the coherent flux-flow oscillator in the THz frequency range
Effective attraction between oscillating electrons in a plasmoid via acoustic waves exchange
We consider the effective interaction between electrons due to the exchange
of virtual acoustic waves in a low temperature plasma. Electrons are supposed
to participate in rapid radial oscillations forming a spherically symmetric
plasma structure. We show that under certain conditions this effective
interaction can result in the attraction between oscillating electrons and can
be important for the dynamics of a plasmoid. Some possible applications of the
obtained results to the theory of natural long-lived plasma structures are also
discussed.Comment: 14 pages in LaTeX2e, two columns, 3 eps figures; minimal changes,
some typos are corrected; version published on-line in Proc. R. Soc.
Fractional Models of Cosmic Ray Acceleration in the Galaxy
Possible formulations of the problem of cosmic rays acceleration in the
interstellar galactic medium are considered with the use of fractional
differential equations. The applied technique has been physically justified. A
Fermi result has been generalized to the case of the acceleration of particles
in shock waves in the supernovae remnants fractally distributed in the Galaxy.Comment: 10 page
Improvement of Manufacturing Procedure as Regards Immunosorbents with Magnetic Properties for Chemiluminescent Assay
mc/ml alongside with high specificity. Additionally, experimental works on melioidosis detection in soil samples has testified to the usage of the composite magnetic immunosorbents for ambient environment monitoring against contamination with various microorganisms and for the purpose of indication of particularly dangerous infection agents
lmmuno Histochemical Profile of Endometrium in Patients With Genital Endometriosis
The aim of present study was to investigate the occurence of different lymphocyte
subsets in the endometrium of endometriosis patients and in healthy women on every
day of the menstrual cycle with special emphasis to the proliferative activity of
endometrial cells with Ki-S3 antibody. We also conducted immunohistochemical
studies of T-lymphocytes, B-lympho-cytes, macrophages, natural-killer-cells and also
of antigens class II of the histocompatibility complex (HLA-DR) during the different
phases of the menstrual cycle in endometriosis and non-endometriosis patients
Spin-controlled Mott-Hubbard bands in LaMnO_3 probed by optical ellipsometry
Spectral ellipsometry has been used to determine the dielectric function of
an untwinned crystal of LaMnO_3 in the spectral range 0.5-5.6 eV at
temperatures 50 K < T < 300 K. A pronounced redistribution of spectral weight
is found at the Neel temperature T_N = 140 K. The anisotropy of the spectral
weight transfer matches the magnetic ordering pattern. A superexchange model
quantitatively describes spectral weight transfer induced by spin correlations.
This analysis implies that the lowest-energy transitions around 2 eV are
intersite d-d transitions, and that LaMnO_3 is a Mott-Hubbard insulator.Comment: 4 pages, 4 figure
Nonstandard analysis in electrical engineering. The analysis of the direct current circles with ideal reactive elements
The article proposes the use of ideas and methods of non-standard analysis in the field of theoretical electronics. The article shows that the analysis of DC circuits, including ideal inductances and capacitances, by standard methods of theoretical electrical engineering is too complicated or almost impossible. To solve this problem, it is proposed to extend the methods of non-standard analysis by the tasks of analyzing electrical circuits with ideal reactive elements. The authors have defined a class of non-standard electrotechnical problems aimed at the analysis of DC electrical circuits, including ideal reactive elements — ideal inductances and capacitances. It is shown that the solution of the selected class of problems by standard methods of theoretical electrical engineering is too difficult or almost impossible. It is proposed to extend the methods of non-standard analysis by the tasks of analyzing electrical circuits with ideal reactive elements. The obtained advantages of this approach are confirmed by examples of calculations of electrical circuits with inductances and capacitances, as well as magnetic circuits
Raman spectra of MgB2 at high pressure and topological electronic transition
Raman spectra of the MgB2 ceramic samples were measured as a function of
pressure up to 32 GPa at room temperature. The spectrum at normal conditions
contains a very broad peak at ~590 cm-1 related to the E2g phonon mode. The
frequency of this mode exhibits a strong linear dependence in the pressure
region from 5 to 18 GPa, whereas beyond this region the slope of the
pressure-induced frequency shift is reduced by about a factor of two. The
pressure dependence of the phonon mode up to ~ 5GPa exhibits a change in the
slope as well as a "hysteresis" effect in the frequency vs. pressure behavior.
These singularities in the E2g mode behavior under pressure support the
suggestion that MgB2 may undergo a pressure-induced topological electronic
transition.Comment: 2 figure
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