5,347 research outputs found
On the role of recombination in common-envelope ejections
The energy budget in common-envelope events (CEEs) is not well understood,
with substantial uncertainty even over to what extent the recombination energy
stored in ionised hydrogen and helium might be used to help envelope ejection.
We investigate the reaction of a red-giant envelope to heating which mimics
limiting cases of energy input provided by the orbital decay of a binary during
a CEE, specifically during the post-plunge-in phase during which the spiral-in
has been argued to occur on a time-scale longer than dynamical. We show that
the outcome of such a CEE depends less on the total amount of energy by which
the envelope is heated than on how rapidly the energy was transferred to the
envelope and on where the envelope was heated. The envelope always becomes
dynamically unstable before receiving net heat energy equal to the envelope's
initial binding energy. We find two types of outcome, both of which likely lead
to at least partial envelope ejection: "runaway" solutions in which the
expansion of the radius becomes undeniably dynamical, and superficially
"self-regulated" solutions, in which the expansion of the stellar radius stops
but a significant fraction of the envelope becomes formally dynamically
unstable. Almost the entire reservoir of initial helium recombination energy is
used for envelope expansion. Hydrogen recombination is less energetically
useful, but is nonetheless important for the development of the dynamical
instabilities. However, this result requires the companion to have already
plunged deep into the envelope; therefore this release of recombination energy
does not help to explain wide post-common-envelope orbits.Comment: 17 pages, 10 figures, submitted to MNRAS. Comments are welcom
Determination of the Fragmentation Parameters of the Multi-charge Component of Primary Cosmic Rays
Determination of fragmentation parameters of multicharge component of primary cosmic ray
On the upper limit of antinuclei content in cosmic rays
Upper limit of antinuclei content in cosmic ray
The Formation of Low-Mass Double White Dwarfs through an Initial Phase of Stable Non-Conservative Mass Transfer
Although many double white dwarfs (DWDs) have been observed, the evolutionary
channel by which they are formed from low-mass/long-period
red-giant-main-sequence (RG-MS) binaries remains uncertain. The canonical
explanations involve some variant of double common-envelope (CE) evolution,
however it has been found that such a mechanism cannot produce the observed
distribution. We present a model for the initial episode of mass transfer (MT)
in RG-MS binaries, and demonstrate that their evolution into double white
dwarfs need not arise through a double-CE process, as long as the initial
primary's core mass (Md,c) does not exceed 0.46M. Instead, the first
episode of dramatic mass loss may be stable, non-conservative MT. We find a
lower bound on the fraction of transferred mass that must be lost from the
system in order to provide for MT, and demonstrate the feasibility of this
channel in producing observed low-mass (with M < 0.46M) DWD
systems.Comment: 2 pages, 1 figure, Conference Proceedings for the International
Conference on Binaries, Mykonos, Greec
Supernova Ia: a Converging Delayed Detonation Wave
A model of a carbon-oxygen (C--O) presupernova core with an initial mass 1.33
M_\odot, an initial carbon mass fraction 0.27, and with an average mass
growth-rate 5 x 10^{-7} M_\odot/yr due to accretion in a binary system was
evolved from initial central density 10^9 g/cm^3, and temperature 2.05 x 10^8 K
through convective core formation and its subsequent expansion to the carbon
runaway at the center. The only thermonuclear reaction contained in the
equations of evolution and runaway was the carbon burning reaction 12C + 12C
with an energy release corresponding to the full transition of carbon and
oxygen (with the same rate as carbon) into 56Ni. As a parameter we take
\alpha_c - a ratio of a mixing length to the size of the convective zone. In
spite of the crude assumptions, we obtained a pattern of the runaway acceptable
for the supernova theory with the strong dependence of its duration on
\alpha_c. In the variants with large enough values of \alpha_c=4.0 x 10^{-3}
and 3.0 x 10^{-3} the fuel combustion occurred from the very beginning as a
prompt detonation. In the range of 2.0 x 10^{-3} >= \alpha_c >= 3.0 x 10^{-4}
the burning started as a deflagration with excitation of stellar pulsations
with growing amplitude. Eventually, the detonation set in, which was activated
near the surface layers of the presupernova (with m about 1.33 M_\odot) and
penetrated into the star down to the deflagration front. Excitation of model
pulsations and formation of a detonation front are described in detail for the
variant with \alpha_c=1.0 x 10^{-3}.Comment: 13 pages, 11 figures, to appear in Astronomy Letter
Trends and perspectives in business psychology. What are the outcomes of the fifth International scientific-practical conference “Business psychology: theory and practice”?
The article analyzes the current state, trends and development prospects of business psychology based on the Fifth International Scientific and Practical Conference “Business Psychology: Theory and Practice (HSE, Moscow, Russia), which was held November, 30 — December, 1, 2018. The conference was prepared and held by the master’s program “Psychology in Business”, which is the domestic scientific and practical center for the development of business psychology — a new branch in applied psychology. Presentations, their discussion, workshops showed a growing interest of researchers and practitioners to business psychology. There has been a tendency to search for a deeper psychological validation of business psychological tools, search for integrated approaches that can be the basis for the development of business psychological practice. A more clear understanding of the structure of business psychology from the perspective of personal, organisational, social, cultural factors of business management was indicated. The strengths of business psychologists were identified in the context of their ability to solve problems systematically and rely on an interdisciplinary approach. The prospects for the development of business psychology are the following: the expansion of geography and subject areas of research and practical activities of business psychology on the development of new approaches in management and organisational consulting
ANALOGIES BETWEEN APHASIC AND POETIC SPEECH PHENOMENA WITHIN THE RANGE OF THEIR THEORETICAL PROBABILITY
It is generally comprehended that pathological phenomena have their analogies in the norm. Performing a study of poetical speech allows for certain identification of formal analogy between paronyms, neologisms (coinages?), new word groups, iterations, etc, as well as well known aphasic phenomena. Such a comparison suggests their consideration (examining) as manifestations of specific prevalence and disbalance, in one case (the poetic speech), and dysfunction in the other case (the aphasic speech), of certain speech-forming and brain mechanics. This kind of study does not concern the radical difference in the subject and product of speech, and the communication resultant in poetic and aphasic speech
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Origin of the ungrouped achondrite NWA 4518: mineralogy and geochemistry of FeNi-metal
Ungrouped achondrite NWA 4518 is an ultramafic breccia with abundant siderophile rich IIA-like metal. Its silicate chemistry is similar to that of WINs, HEDs, and silicate inclusions of IIE irons. Oxygen isotopic composition is nearby IAB-IIICD-WIN
On the estimate of the sigma^(I = 1)_(KN)(0)-term value from the energy level shift of kaonic hydrogen in the ground state
Using the experimental data on the energy level shift of kaonic hydrogen in
the ground state (the DEAR Collaboration, Phys. Rev. Lett. 94, 212302 (2005))
and the theoretical value of the energy level shift, calculated within the
phenomenological quantum field theoretic approach to the description of strong
low-energy anti-K N and anti-K NN interactions developed at Stefan Meyer
Institut fuer subatomare Physik in Vienna, we estimate the value of the
sigma^(I = 1)_(KN)(0)-term of low-energy anti-K N scattering. We get sigma^(I =
1)_(KN)(0) = (433 +/- 85) MeV. This testifies the absence of strange quarks in
the proton structure.Comment: 7 pages, no figure
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