672 research outputs found
Speckle pattern formation in spatially limited optical systems
The dependences of statistical parameters inherent to speckle patterns on the object roughness and aperture size have been investigated. The experimental results that confirm theoretical dependence quality within the limits of errors were obtained. It has been shown that spatial finiteness of the optical system causes significant changes of transferred field
A comparative morphometric study of the myocardium during the postnatal development in normotensive and spontaneously hypertensive rats
Background: Differences in the size of cardiac muscle cells observed in normal and hypertrophic hearts have been assessed through different methodologies. Spontaneously hypertensive rats are often used as an experimental model of essential hypertension in humans, which allows researchers to study the relation between hypertension and cardiac hypertrophy. It has been shown that ventricular hypertrophy in mammals progresses and ventricular failure develops in the end stage of hypertrophy. The aim of the present study was to analyse a number of morphometric markers and compare them between male normotensive Wistar rats (WR) and male spontaneously hypertensive rats (SHR).
Materials and methods: The total number of male WR was 15, distributed in five age groups, each containing three animals: 2-week-old; 1-month-old; 3-month-old; 6-month-old; 12-month-old. The male SHR were distributed in two age groups, each containing three animals: 1-month-old (young) and 6-month-old (adult).
Results: As aging progressed, both in male normotensive WR and in male SHR we noted a statistically significant increase in the morphometric parameters thickness of the free wall and the cross-sectional area of the cardiomyocytes and their nuclei and a decrease in the cardiomyocytic density in both ventricles. These changes were more pronounced and occurred at an earlier age in SHR.
Conclusions: The present study analyses in detail the alterations in the myocardium of the left and right ventricle, initiated by age-related hypertrophy, as well as hypertrophy induced by arterial hypertension. (Folia Morphol 2018; 77, 2: 253–265
Mobile app for selecting power transformers
The paper is concerned with creating a mobile assistant to design a step-down substation. In that regard, it is spoken in detail about mathematical model, algorithmic decisions and layout arrangements used for creating this app. It also gives valuable information about calculation results that are based on actual data. Moreover, the paper presents application usage guideline for students who prepare their course projects.В докладе рассматривается математическая модель, алгоритмические и компоновочные решения, использованные при создании мобильного ассистента для проектирования понижающей подстанции. Описаны результаты расчетов, выполненных на реальных данных, а также рекомендации по использованию приложения в учебном курсовом проектировании
Determination of surface defects by using the wavefront scanner
The possibility of changes in the polarization state of the laser beam reflected
from inhomogeneity with the refractive index gradient is theoretically shown, which
allows separating the phase shifts related with relief inhomogeneities and local changes
of the surface refractive index. Modification of the wavefront scanner for analyzing the
wavefront of the laser beam reflected from the samples’ surface is considered. The main
idea of the method is to use the focused laser beams with different polarizations for
illuminating separate areas of the surface. The results of detecting test surfaces with
different structures by the wavefront scanner are presented
Magnetization plateaux in dimerized spin ladder arrays
We investigate the ground state magnetization plateaux appearing in spin 1/2
two-leg ladders built up from dimerized antiferromagnetic Heisenberg chains and
dimerized zig-zag interchain couplings. Using both Abelian bosonization and
Lanczos methods we find that the system yields rather unusual plateaux and
exhibits massive and massless phases for specific choices or ``tuning'' of
exchange interactions. The relevance of this behavior in the study of
NH_4CuCl_3 is discussed.Comment: 9 pages, RevTeX, 11 postscript figure
Modelling spectral and timing properties of accreting black holes: the hybrid hot flow paradigm
The general picture that emerged by the end of 1990s from a large set of
optical and X-ray, spectral and timing data was that the X-rays are produced in
the innermost hot part of the accretion flow, while the optical/infrared (OIR)
emission is mainly produced by the irradiated outer thin accretion disc. Recent
multiwavelength observations of Galactic black hole transients show that the
situation is not so simple. Fast variability in the OIR band, OIR excesses
above the thermal emission and a complicated interplay between the X-ray and
the OIR light curves imply that the OIR emitting region is much more compact.
One of the popular hypotheses is that the jet contributes to the OIR emission
and even is responsible for the bulk of the X-rays. However, this scenario is
largely ad hoc and is in contradiction with many previously established facts.
Alternatively, the hot accretion flow, known to be consistent with the X-ray
spectral and timing data, is also a viable candidate to produce the OIR
radiation. The hot-flow scenario naturally explains the power-law like OIR
spectra, fast OIR variability and its complex relation to the X-rays if the hot
flow contains non-thermal electrons (even in energetically negligible
quantities), which are required by the presence of the MeV tail in Cyg X-1. The
presence of non-thermal electrons also lowers the equilibrium electron
temperature in the hot flow model to <100 keV, making it more consistent with
observations. Here we argue that any viable model should simultaneously explain
a large set of spectral and timing data and show that the hybrid
(thermal/non-thermal) hot flow model satisfies most of the constraints.Comment: 26 pages, 13 figures. To be published in the Space Science Reviews
and as hard cover in the Space Sciences Series of ISSI - The Physics of
Accretion on to Black Holes (Springer Publisher
Measurement of and between 3.12 and 3.72 GeV at the KEDR detector
Using the KEDR detector at the VEPP-4M collider, we have measured
the values of and at seven points of the center-of-mass
energy between 3.12 and 3.72 GeV. The total achieved accuracy is about or
better than at most of energy points with a systematic uncertainty of
about . At the moment it is the most accurate measurement of in
this energy range
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