3,409 research outputs found
Thermal optical non-linearity of nematic mesophase enhanced by gold nanoparticles – an experimental and numerical investigation
In this work the mechanisms leading to the enhancement of optical nonlinearity of nematic liquid crystalline material through localized heating by doping the liquid crystals (LCs) with gold nanoparticles (GNPs) are investigated. We present some experimental and theoretical results on the effect of voltage and nanoparticle concentration on the nonlinear response of GNP-LC suspensions. The optical nonlinearity of these systems is characterized by diffraction measurements and the second order nonlinear refractive index, n 2 , is used to compare systems with different configurations and operating conditions. A theoretical model based on heat diffusion that takes into account the intensity and finite size of the incident beam, the nanoparticle concentration dependent absorbance of GNP doped LC systems and the presence of bounding substrates is developed and validated. We use the model to discuss the possibilities of further enhancing the optical nonlinearity
Coulomb-oscillator duality in spaces of constant curvature
In this paper we construct generalizations to spheres of the well known
Levi-Civita, Kustaanheimo-Steifel and Hurwitz regularizing transformations in
Euclidean spaces of dimensions 2, 3 and 5. The corresponding classical and
quantum mechanical analogues of the Kepler-Coulomb problem on these spheres are
discussed.Comment: 33 pages, LaTeX fil
Распределение вариантов однонуклеотидного полиморфизма rs6795970 гена SCN10A среди молодого населения Республики Молдова
Distribuția variantelor polimorfismului de un singur nucleotid rs6795970 al genei SCN10A la populația tânără din Republica MoldovaBackground. PR interval reflects atrial and atrioventricular nodal conduction time and is an important determinant of arrhythmia risk. Genome-wide association studies (GWAS) have identified association of nonsynonymous SNP, rs6795970, in the SCN10A gene with PR interval in individuals of European ancestry. Purpose. To estimate the distribution of rs6795970 variants, associated with PR interval in young population of Republic of Moldova. Methods. 1390 young participants from Republic of Moldova with age range: 19-25 years, were genotyped for rs6795970 in the SCN10A gene, using TaqMan technology. Results. The genotype A/A, A/G, G/G distributions of rs6795970 among the young participants were 15%, 48%, 37% respectively (χ2 = 0.161, p = 0.688). The allele frequencies for A and G in young participants were 39% and 61% respectively. Conclusion. The minor allele frequency (MAF) in young Moldavian population was 0.39 for rs679570 and was consistent with 1000 Genomes Project data in the European population – 0.41. 15% of all participants (the AA genotype), may have an increased risk of conduction abnormalities.Распределение вариантов однонуклеотидного полиморфизма rs6795970 гена SCN10A среди молодого населения Республики Молдов
Spectrum Generating Algebras for the free motion in
We construct the spectrum generating algebra (SGA) for a free particle in the
three dimensional sphere for both, classical and quantum descriptions. In
the classical approach, the SGA supplies time-dependent constants of motion
that allow to solve algebraically the motion. In the quantum case, the SGA
include the ladder operators that give the eigenstates of the free Hamiltonian.
We study this quantum case from two equivalent points of view.Comment: 29 pages, 1 figur
THE ORGANIZATION OF THE UNIVERSITY EDUCATIONAL PROCESS IN TERMS OF DIGITALIZATION OF EDUCATION
Purpose: The paper deals with the optimization of the preparation of educational professional programs of higher education to the processes of accreditation and licensing.
Methodology: In this paper, we will consider technical tools that optimize the organization of the management of the university's educational process in the conditions of the “digitalization” of education.
Result: Since the verification of compliance of University educational programs with the requirements of Federal state educational standards is carried out in the process of accreditation examination, it is necessary to optimize the organization of management of the educational process of the University on the basis of computer equipment and software.
Applications: This research can be used for universities, teachers, and students.
Novelty/Originality: In this research, the model of the organization of the university educational process in terms of digitalization of education is presented in a comprehensive and complete manner
Close binary stars in the solar-age Galactic open cluster M67
We present multi-colour time-series CCD photometry of the solar-age galactic
open cluster M67 (NGC 2682). About 3600 frames spread over 28 nights were
obtained with the 1.5 m Russian-Turkish and 1.2 m Mercator telescopes.
High-precision observations of the close binary stars AH Cnc, EV Cnc, ES Cnc,
the Scuti type systems EX Cnc and EW Cnc, and some long-period
variables belonging to M67 are presented. Three full multi-colour light curves
of the overcontact binary AH Cnc were obtained during three observing seasons.
Likewise we gathered three light curves of EV Cnc, an EB-type binary, and two
light curves of ES Cnc, a blue straggler binary. Parts of the light change of
long-term variables S1024, S1040, S1045, S1063, S1242, and S1264 are obtained.
Period variation analysis of AH Cnc, EV Cnc, and ES Cnc were done using all
times of mid-eclipse available in the literature and those obtained in this
study. In addition, we analyzed multi-colour light curves of the close binaries
and also determined new frequencies for the Scuti systems. The
physical parameters of the close binary stars were determined with simultaneous
solutions of multi-colour light and radial velocity curves. Finally we
determined the distance of M67 as 857(33) pc via binary star parameters, which
is consistent with an independent method from earlier studies.Comment: 12 pages, 9 Figures, 13 Table
Variability of Active Galactic Nuclei from the Optical to X-ray Regions
Some progress in understanding AGN variability is reviewed. Reprocessing of
X-ray radiation to produce significant amounts of longer-wavelength continua
seems to be ruled out. In some objects where there has been correlated X-ray
and optical variability, the amplitude of the optical variability has exceeded
the amplitude of X-ray variability. We suggest that accelerated particles
striking material could be linking X-ray and optical variability (as in
activity in the solar chromosphere). Beaming effects could be significant in
all types of AGN. The diversity in optical/X-ray relationships at different
times in the same object, and between different objects, might be explained by
changes in geometry and directions of motion relative to our line of sight.
Linear shot-noise models of the variability are ruled out; instead there must
be large-scale organization of variability. Variability occurs on
light-crossing timescales rather than viscous timescales and this probably
rules out the standard Shakura-Sunyaev accretion disk. Radio-loud and
radio-quiet AGNs have similar continuum shapes and similar variability
properties. This suggests similar continuum origins and variability mechanisms.
Despite their extreme X-ray variability, narrow-line Seyfert 1s (NLS1s) do not
show extreme optical variability.Comment: Invited talk given at Euro Asian Astronomical Society meeting in
Moscow, June 2002. 20 pages, 4 figures. References update
Time-Series Photometry of M67: W UMa Systems, Blue Stragglers, and Related Systems
We present an analysis of over 2200 V images taken on 14 nights at the Mt.
Laguna 1 m telescope of the open cluster M67. Our observations overlap but
extend beyond the field analyzed by Gilliland et al. (1991), and complement
data recently published by van den Berg et al. (2002) and Stassun et al.
(2002). We show variability in the light curves of all 4 of the known W UMa
variables on timescales ranging from a day to decades (for AH Cnc). We have
modeled the light curve of AH Cnc, and the total eclipses allow us to determine
q = 0.16 +0.03/-0.02 and i = 86 +4/-8 degrees. The position of this system near
the turnoff of M67 makes it useful for constraining the turnoff mass for the
cluster. We have also detected two unusual features in the light curve of AH
Cnc that may be caused by prominences. We have also monitored cluster blue
stragglers for variability, and we present evidence hinting at low level
variations in the stragglers S752, S968, and S1263, and we place limits on the
variability of a number of other cluster blue stragglers. Finally, we provide
photometry of the sub-subgiant branch star S1063 showing variability on
timescales similar to the orbital period, while the ``red straggler'' S1040
shows evidence of an unexplained drop in brightness at phases corresponding to
the passage of the white dwarf in front of the giant.Comment: 44 pages, 16 figures, AASTeX, accepted for A
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