3,080 research outputs found
Probing high-mass stellar evolutionary models with binary stars
Mass discrepancy is one of the problems that is pending a solution in
(massive) binary star research field. The problem is often solved by
introducing an additional near core mixing into evolutionary models, which
brings theoretical masses of individual stellar components into an agreement
with the dynamical ones. In the present study, we perform a detailed analysis
of two massive binary systems, V380 Cyg and Sigma Sco, to provide an
independent, asteroseismic measurement of the overshoot parameter, and to test
state-of-the-art stellar evolution models.Comment: 5 pages, 1 figure, 3 tables; proceedings of the IAU Symposium 307
held in Geneva in June 201
Development of the New Point Scale of Organoleptic Evaluation at Manufacturing Organic Cakes
The article presents the ground of developing the 50-point scale for evaluating cakes by organoleptic parameters. The aim of the article is to create the new point scale of organoleptic evaluation for using at producing organic cakes. It was established, that for today such important parameters as “flavor”, “post-flavor”, “porosity structure” are not always used at the organoleptic evaluation of cakes' quality. The article describes the recipes of four developed cakes, produced of the organic raw materials – “Grechanyk”, based on buckwheat flour, “Zhytnytsa', based on rye flour, “Golden amaranth”, based on amaranth flour and “Hempen delight”, based on hempen flour. For evaluating organoleptic characteristics of cakes, there was presented 50-point scale that includes evaluation of the following parameters: form, surface condition, color of crust, condition and color of crumble, porosity structure, smell, taste, flavor, post-taste, malaxation of crumble. Based on the method of expert evaluations, there were determined significance coefficients for each parameter. Thus, coefficient 0,5 was set for the parameters “porosity structure” and 1,5 for “color” and “smell”, the significance coefficient was equal 1 for a series of other parameters. The developed scale provided the following criteria of cakes evaluation: 45–50 points − "perfectly”, 40–44 points − "well", 30–39 points − "satisfactorily”, lower 30 points – “unsatisfactorily”. Based on the developed scale, the developed cakes were evaluated by the gustatory commission. All developed cakes corresponded to the mark “perfectly” by organoleptic parameters. The highest index of the quality level was inherent to the cake “Grechanyk” " – 0,99 at general sum of points for the gustatory evaluation 49,95. The cake Zhytnytsa corresponded to 0,98 by the quality level, "Hempen delight" – 0,96. The lowest quality level was detected in the cake “Golden amaranth” (0,94),that is caused by the specific taste of amaranth flour
Tkachenko modes as sources of quasiperiodic pulsar spin variations
We study the long wavelength shear modes (Tkachenko waves) of triangular
lattices of singly quantized vortices in neutron star interiors taking into
account the mutual friction between the superfluid and the normal fluid and the
shear viscosity of the normal fluid. The set of Tkachenko modes that propagate
in the plane orthogonal to the spin vector are weakly damped if the coupling
between the superfluid and normal fluid is small. In strong coupling, their
oscillation frequencies are lower and are undamped for small and moderate shear
viscosities. The periods of these modes are consistent with the observed
~100-1000 day variations in spin of PSR 1828-11.Comment: 7 pages, 3 figures, uses RevTex, v2: added discussion/references,
matches published versio
Dissipationless Phonon Hall Viscosity
We study the acoustic phonon response of crystals hosting a gapped
time-reversal symmetry breaking electronic state. The phonon effective action
can in general acquire a dissipationless "Hall" viscosity, which is determined
by the adiabatic Berry curvature of the electron wave function. This Hall
viscosity endows the system with a characteristic frequency, \omega_v; for
acoustic phonons of frequency \omega, it shifts the phonon spectrum by an
amount of order (\omega/\omega_v)^2 and it mixes the longitudinal and
transverse acoustic phonons with a relative amplitude ratio of \omega/\omega_v
and with a phase shift of +/- \pi/2, to lowest order in \omega/\omega_v. We
study several examples, including the integer quantum Hall states, the quantum
anomalous Hall state in Hg_{1-y}Mn_{y}Te quantum wells, and a mean-field model
for p_x + i p_y superconductors. We discuss situations in which the acoustic
phonon response is directly related to the gravitational response, for which
striking predictions have been made. When the electron-phonon system is viewed
as a whole, this provides an example where measurements of Goldstone modes may
serve as a probe of adiabatic curvature of the wave function of the gapped
sector of a system.Comment: 14 page
Vortex states of rapidly rotating dilute Bose-Einstein condensates
We show that, in the Thomas-Fermi regime, the cores of vortices in rotating
dilute Bose-Einstein condensates adjust in radius as the rotation velocity,
, grows, thus precluding a phase transition associated with core
overlap at high vortex density. In both a harmonic trap and a rotating
hard-walled bucket, the core size approaches a limiting fraction of the
intervortex spacing. At large rotation speeds, a system confined in a bucket
develops, within Thomas-Fermi, a hole along the rotation axis, and eventually
makes a transition to a giant vortex state with all the vorticity contained in
the hole.Comment: 4 pages, 2 figures, RevTex4. Version as published; discussion
extended, some references added and update
Modelling of the B-type binaries CW Cep and U Oph: A critical view on dynamical masses, core boundary mixing, and core mass
Context: Intermediate-Mass stars are often overlooked as they are not
supernova progenitors but still host convective cores and complex atmospheres
which require computationally expensive treatment. Due to this, there is a
general lack of such stars modelled by state of the art stellar structure and
evolution codes. Aims: This paper aims to use high-quality spectroscopy to
update the dynamically obtained stellar parameters and produce a new
evolutionary assessment of the bright B0.5+B0.5 and B5V+B5V binary systems CW
Cep and U Oph. Methods: We use new spectroscopy obtained with the Hermes
spectrograph to revisit the photometric binary solution of the two systems. The
updated mass ratio and effective temperatures are incorporated to obtain new
dynamical masses for the primary and secondary. With these, we perform
isochrone-cloud based evolutionary modelling to investigate the core properties
of these stars. Results: We report the first abundances for CW Cep and U Oph as
well as report an updated dynamical solution for both systems. We find that we
cannot uniquely constrain the amount of core boundary mixing in any of the
stars we consider. Instead, we report their core masses and compare our results
to previous studies. Conclusions: We find that the per-cent level precision on
fundamental stellar quantities are accompanied with core mass estimates to
between ~ 5-15%. We find that differences in analysis techniques can lead to
substantially different evolutionary modeComment: 15 pages, 7 figures, two appendices with 4 figures each. Accepted for
publication in Astronomy & Astrophysic
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