7,649 research outputs found
Photometric and spectroscopic variability of the FUor star V582 Aurigae
We carried out BVRI CCD photometric observations in the field of V582 Aur
from 2009 August to 2013 February. We acquired high-, medium-, and
low-resolution spectroscopy of V582 Aur during this period. To study the
pre-outburst variability of the target and construct its historical light
curve, we searched for archival observations in photographic plate collections.
Both CCD and photographic observations were analyzed using a sequence of 14
stars in the field of V582 Aur calibrated in BVRI. The pre-outburst
photographic observations of V582 Aur show low-amplitude light variations
typical of T Tauri stars. Archival photographic observations indicate that the
increase in brightness began in late 1984 or early 1985 and the star reached
the maximum level of brightness at 1986 January. The spectral type of V582 Aur
can be defined as G0I with strong P Cyg profiles of H alpha and Na I D lines,
which are typical of FU Orionis objects. Our BVRI photometric observations show
large amplitude variations V~2.8 mag. during the 3.5 year period of
observations. Most of the time, however, the star remains in a state close to
the maximum brightness. The deepest drop in brightness was observed in the
spring of 2012, when the brightness of the star fell to a level close to the
pre-outburst. The multicolor photometric data show a color reversal during the
minimum in brightness, which is typical of UX Ori variables. The corresponding
spectral observations show strong variability in the profiles and intensities
of the spectral lines (especially H alpha), which indicate significant changes
in the accretion rate. On the basis of photometric monitoring performed over
the past three years, the spectral properties of the maximal light, and the
shape of the long-term light curve, we confirm the affiliation of V582 Aur to
the group of FU Orionis objects.Comment: 9 pages, 8 figures, accepted for publication in A&
Capillary Rise in Nanopores: Molecular Dynamics Evidence for the Lucas-Washburn Equation
When a capillary is inserted into a liquid, the liquid will rapidly flow into
it. This phenomenon, well studied and understood on the macroscale, is
investigated by Molecular Dynamics simulations for coarse-grained models of
nanotubes. Both a simple Lennard-Jones fluid and a model for a polymer melt are
considered. In both cases after a transient period (of a few nanoseconds) the
meniscus rises according to a -law. For the polymer melt,
however, we find that the capillary flow exhibits a slip length ,
comparable in size with the nanotube radius . We show that a consistent
description of the imbibition process in nanotubes is only possible upon
modification of the Lucas-Washburn law which takes explicitly into account the
slip length .Comment: 4 pages 4 figure
Multi-site, multi-year monitoring of the oscillating Algol-type eclipsing binary CT Her
We present the results of a multi-site photometric campaign carried out in
2004-2008 for the Algol-type eclipsing binary system CT Her, the primary
component of which shows Delta Scuti-type oscillations. Our data consist of
differential light curves collected in the filters B and V which have been
analysed using the method of Wilson-Devinney (PHOEBE). After identification of
an adequate binary model and removal of the best-matching light curve solution,
we performed a Fourier analysis of the residual B and V light curves to
investigate the pulsational behaviour. We confirm the presence of rapid
pulsations with a main period of 27.2 min. Up to eight significant frequencies
with semi-amplitudes in the range 3 to 1 mmag were detected, all of which
surprisingly lie in the frequency range 43.5-53.5 c\d. This result is
independent from the choice of the primary's effective temperature (8200 or
8700 K) since the light curve models for the binary are very similar in both
cases. This is yet another case of a complex frequency spectrum observed for an
accreting Delta Scuti-type star (after Y Cam). In addition, we demonstrate that
the amplitudes of several of these pulsation frequencies show evidence of
variability on time scales as short as 1-2 years, perhaps even less. Moreover,
our analysis takes into account some recently acquired spectra, from which we
obtained the corresponding radial velocities for the years 2007-2009.
Investigation of the O-C diagram shows that further monitoring of the epochs of
eclipse minima of CT Her will cast a new light on the evolution of its orbital
period.Comment: 13 pages, 13 encapsulated Postscript figures. Tables~3, 4, 9 and 12
will be available in electronic form only. Astronomy and Astrophysics, in
process (2011). Replaced the abstract with its final versio
CLINICAL APPLICATION OF THE HAEMOPERFUSION DEVICES BULSORB 160 COMBINED WITH HAEMODIALYSIS
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Polymer Brushes in Cylindrical Pores: Simulation versus Scaling Theory
The structure of flexible polymers endgrafted in cylindrical pores of
diameter D is studied as a function of chain length N and grafting density
\sigma, assuming good solvent conditions. A phenomenological scaling theory,
describing the variation of the linear dimensions of the chains with \sigma, is
developed and tested by Molecular Dynamics simulations of a bead-spring model.Comment: 35 pages, 38 figure
Advances in surface EMG signal simulation with analytical and numerical descriptions of the volume conductor
Surface electromyographic (EMG) signal modeling is important for signal interpretation, testing of processing algorithms, detection system design, and didactic purposes. Various surface EMG signal models have been proposed in the literature. In this study we focus on 1) the proposal of a method for modeling surface EMG signals by either analytical or numerical descriptions of the volume conductor for space-invariant systems, and 2) the development of advanced models of the volume conductor by numerical approaches, accurately describing not only the volume conductor geometry, as mainly done in the past, but also the conductivity tensor of the muscle tissue. For volume conductors that are space-invariant in the direction of source propagation, the surface potentials generated by any source can be computed by one-dimensional convolutions, once the volume conductor transfer function is derived (analytically or numerically). Conversely, more complex volume conductors require a complete numerical approach. In a numerical approach, the conductivity tensor of the muscle tissue should be matched with the fiber orientation. In some cases (e.g., multi-pinnate muscles) accurate description of the conductivity tensor may be very complex. A method for relating the conductivity tensor of the muscle tissue, to be used in a numerical approach, to the curve describing the muscle fibers is presented and applied to representatively investigate a bi-pinnate muscle with rectilinear and curvilinear fibers. The study thus propose an approach for surface EMG signal simulation in space invariant systems as well as new models of the volume conductor using numerical methods
A hybrid version of the tilted axis cranking model and its application to ^{128}Ba
A hybrid version the deformed nuclear potential is suggested, which combines
a spherical Woods Saxon potential with a deformed Nilsson potential. It removes
the problems of the conventional Nilsson potential in the mass 130 region.
Based on the hybrid potential, tilted axis cranking calculations are carried
out for the magnetic dipole band in ^{128}Ba.Comment: 10 pages 6 figure
Ancient coastlines of the Black Sea and conditions for human presence – Black Sea expedition 2011
Project DO 02-337, an expedition on the RV Akademik, took place during June 2011 with financial support from the Bulgarian Science Fund. The location for this expedition was the Western Black Sea. 17 core and 8 grapple organic seabed samples were taken. The initial core samples were extracted from the submerged shorelines with subsequent ones taken from deeper water. So submerged shoreline was mapped, samples for dating, isotope analysis and pollen sampling were taken.Проект ДО 02-337, експедиція у східну частину Чорного моря на н/с «Академік» відбулася в червні 2011 року за фінансової підтримки Болгарського наукового фонду. Відібрано 17 проб трубкою і 8 проб драгою. Зразки відбиралися із затопленої берегової лінії, відібрано зразки для датування, ізотопного і пилкового аналізів.Проект ДО 02-337, экспедиция в восточную часть Черного моря на н/с «Академик» состоялась в июне 2011 г. при финансовой поддержке Болгарского научного фонда. Отобраны 17 проб трубкой и 8 проб драгой. Образцы отбирались из затопленной береговой линии, отобраны образцы для датирования, изотопного и пыльцевого анализов
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