6,629 research outputs found
An Overview of a Grid Architecture for Scientific Computing
This document gives an overview of a Grid testbed architecture proposal for
the NorduGrid project. The aim of the project is to establish an inter-Nordic
testbed facility for implementation of wide area computing and data handling.
The architecture is supposed to define a Grid system suitable for solving data
intensive problems at the Large Hadron Collider at CERN. We present the various
architecture components needed for such a system. After that we go on to give a
description of the dynamics by showing the task flow
IBM: parameter symmetry, hidden symmetries and transformations of boson operators
A symmetry of the parameter space of interacting boson models IBM-1 and IBM-2
is studied. The symmetry is associated with linear canonical transformations of
boson operators, or, equivalently, with the existence of different realizations
of the symmetry algebras of the models. The relevance of the parameter symmetry
to physical observables is discussed.Comment: LATEX, 11 pages including 1 eps figure and 1 table prepared as an eps
figure; a talk given by A. M. Siirokov at XXII Symposium on Nuclear Physics,
Oaxtepec, Morelos, M\'exico, 5--8 January, 1999; to be published in Revista
Mex. Fi
Relation between parameters of dust and parameters of molecular and atomic gas in extragalactic star-forming regions
The relationships between atomic and molecular hydrogen and dust of various
sizes in extragalactic star-forming regions are considered, based on
observational data from the Spitzer and Herschel infrared space telescopes, the
Very Large Array (atomic hydrogen emission) and IRAM (CO emission). The source
sample consists of approximately 300 star-forming regions in 11 nearby
galaxies. Aperture photometry has been applied to measure the fluxes in eight
infrared bands (3.6, 4.5, 5.8, 8, 24, 70, 100, and 160m), the atomic
hydrogen (21cm) line and CO (2--1) lines.
The parameters of the dust in the starforming regions were determined via
synthetic-spectra fitting, such as the total dust mass, the fraction of
polycyclic aromatic hydrocarbons (PAHs), etc. Comparison of the observed fluxes
with the measured parameters shows that the relationships between atomic
hydrogen, molecular hydrogen, and dust are different in low- and
high-metallicity regions. Low-metallicity regions contain more atomic gas, but
less molecular gas and dust, including PAHs. The mass of dust constitutes about
of the mass of molecular gas in all regions considered. Fluxes produced
by atomic and molecular gas do not correlate with the parameters of the stellar
radiation, whereas the dust fluxes grow with increasing mean intensity of
stellar radiation and the fraction of enhanced stellar radiation. The ratio of
the fluxes at 8 and 24m, which characterizes the PAH content, decreases
with increasing intensity of the stellar radiation, possibly indicating
evolutionary variations of the PAH content. The results confirm that the
contribution of the 24m emission to the total IR luminosity of
extragalactic star-forming regions does not depend on the metallicity.Comment: Published in Astronomy Reports, 2017, vol. 61, issue
Position-sensitive detector for the 6-meter optical telescope
The Position-Sensitive Detector (PSD) for photometrical and spectral
observation on the 6-meter optical telescope of the Special Astrophysical
Observatory (Russia) is described. The PSD consists of a position-sensitive
tube, amplifiers of output signals, analog-to-digital converters (ADC) and a
digital logic plate, which produces a signal for ADC start and an external
strob pulse for reading information by registration system. If necessary, the
thermoelectric cooler can be used. The position-sensitive tube has the
following main elements: a photocathode, electrodes of inverting optics, a
block of microchannel plates (MCP) and a position-sensitive collector of
quadrant type. The main parameters of the PSD are the diameter of the sensitive
surface is 25 mm, the spatial resolution is better than 100 (\mu)m in the
centre and a little worse on the periphery; the dead time is near 0.5 (\mu)s;
the detection quantum efficiency is defined by the photocathode and it is not
less than 0.1, as a rule; dark current is about hundreds of cps, or less, when
cooling. PSD spectral sensitivity depends on the type of photocathode and input
window material. We use a multialkali photocathode and a fiber or UV-glass,
which gives the short- wave cut of 360 nm or 250 nm, respectively.Comment: 4 pages, 7 figures, to be published in Nuclear Instruments & Methods
in Physics Researc
Structure of coenopopulations and phytocoenotic confinement of Paeonia tenuifolia L. in floristic complexes of Oka-Don lowland
Paeonia tenuifolia L. is a rare and protected plant of Saratov region classified as 2 (V) vulnerable species. It has been established that in Kalininsky district, Saratov region, this plant is characterized by narrow environmental amplitude and is exerted to anthropogenic impacts, the coenopopulations are isolated from each other. Existence of the species in communities of the meadow–steppe floristic complexes of Kalininsky district has confirmed that peony is heliophyte, xeromesophyte, eutrophic plant and calcicole. Photophily of P. tenuifoliais confirmed first of all by its high abundance and occurrence in open steppe communities. In both coenopopulations of P.tenuifolia, the indices of recovery have been higher than 1 (CP 1 Irec = 3.38, CP 2 Irec = 1.67), that is, the coenopopulations are relatively steady, numerous seeds are generated giving birth to viable individuals. The index of replacement showing the ratio of the density of regrowth to total mature fraction of the population has been higher in CP 1 (Irepl = 0.80) and lower in CP 2 (Irepl = 0.67). Moderate index of maturing evidence long-term existence of the species in the generative state
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