749 research outputs found
Информационные технологии в управлении интеллектуальным капиталом организации
The report examines how organization can use information technologies for management of intellectual capital
On the sensitivity of the energy of vanishing flow towards mass asymmetry of colliding nuclei
We demonstrate the role of the mass asymmetry in the energy of vanishing flow
by studying asymmetric reactions throughout the periodic table and over entire
colliding geometry. Our results, which are almost independent of the system
size and as well as of the colliding geometries indicate a sizable effect of
the asymmetry of the reaction on the energy of vanishing flow
The importance of initial-final state correlations for the formation of fragments in heavy ion collisions
Using quantum molecular dynamics simulations, we investigate the formation of
fragments in symmetric reactions between beam energies of E=30AMeV and 600AMeV.
After a comparison with existing data we investigate some observables relevant
to tackle equilibration: dsigma/dErat, the double differential cross section
dsigma/pt.dpz.dpt,... Apart maybe from very energetic E>400AMeV and very
central reactions, none of our simulations gives evidence that the system
passes through a state of equilibrium. Later, we address the production
mechanisms and find that, whatever the energy, nucleons finally entrained in a
fragment exhibit strong initial-final state correlations, in coordinate as well
as in momentum space. At high energy those correlations resemble the ones
obtained in the participant-spectator model. At low energy the correlations are
equally strong, but more complicated; they are a consequence of the Pauli
blocking of the nucleon-nucleon collisions, the geometry, and the excitation
energy. Studying a second set of time-dependent variables (radii,
densities,...), we investigate in details how those correlations survive the
reaction especially in central reactions where the nucleons have to pass
through the whole system. It appears that some fragments are made of nucleons
which were initially correlated, whereas others are formed by nucleons
scattered during the reaction into the vicinity of a group of previously
correlated nucleons.Comment: 45 pages text + 20 postscript figures Accepted for publication in
Physical Review
A temporal study of oxygen-rich pulsating variable AGB star, T Cep: Investigation on dust formation and dust properties
Pulsation is believed to be the leading cause of dusty mass loss from
Asymptotic Giant Branch (AGB) stars. We present a temporal study of T Cep, a
long-period Mira variable, using seven ISO SWS spectra, covering a 16-month
period over a single pulsation cycle. The observed spectral dust features
change over the pulsation cycle of this Mira. In general, the overall apparent
changes in spectral features can be attributed to changes in the dust
temperature, resulting from the intrinsic pulsation cycle of the central star.
However, not all feature changes are so easily explained. Based on direct
comparison with laboratory spectra of several potential minerals, the dust is
best explained by crystalline iron-rich silicates. These findings contradict
the currently favored dust formation hypotheses.Comment: This article has been accepted for publication in The Astrophysical
Journal. It is tentatively scheduled for the May 10, 2011, v732 -2 issu
Mid-Infrared Imaging and Modelling of the Dust Shell around Post-AGB star HD 187885 (IRAS 19500-1709)
We present 10 and 20 micron images of IRAS 19500-1709 taken with the
mid-infrared camera, OSCIR, mounted on the Gemini North Telescope. We use a 2-D
dust radiation transport code to fit the spectral energy distribution from UV
to sub-mm wavelengths and to simulate the images.Comment: 4 pages, 5 figures. To appear in "Asymmetric Planetary Nebulae III",
eds. M.Meixner, J.Kastner, N.Soker & B.Balick. 2004, ASP Conference Serie
Simulated Annealing Clusterization Algorithm for Studying the Multifragmentation
We present the details of the numerical realization of the recently advanced
algorithm developed to identify the fragmentation in heavy ion reactions. This
new algorithm is based on the Simulated Annealing method and is dubbed as
Simulated Annealing Clusterization Algorithm [SACA]. We discuss the different
parameters used in the Simulated Annealing method and present an economical set
of the parameters which is based on the extensive analysis carried out for the
central and peripheral collisions of Au-Au, Nb-Nb and Pb-Pb. These parameters
are crucial for the success of the algorithm. Our set of optimized parameters
gives the same results as the most conservative choice, but is very fast. We
also discuss the nucleon and fragment exchange processes which are very
important for the energy minimization and finally present the analysis of the
reaction dynamics using the new algorithm. This algorithm is can be applied
whenever one wants to identify which of a given number of constituents form
bound objects.Comment: 36 pages, 15 figures, submitted to Journal of Computational Physic
Recent Advances in Imprinting Disorders.
Imprinting disorders (ImpDis) are a group of currently 12 congenital diseases with common underlying (epi)genetic etiologies and overlapping clinical features affecting growth, development and metabolism. In the last years it has emerged that ImpDis are characterized by the same types of mutations and epimutations, i.e. uniparental disomies, copy number variations, epimutations, and point mutations. Each ImpDis is associated with a specific imprinted locus, but the same imprinted region can be involved in different ImpDis. Additionally, even the same aberrant methylation patterns are observed in different phenotypes. As some ImpDis share clinical features, clinical diagnosis is difficult in some cases. The advances in molecular and clinical diagnosis of ImpDis help to circumvent these issues, and they are accompanied by an increasing understanding of the pathomechanism behind them. As these mechanisms have important roles for the etiology of other common conditions, the results in ImpDis research have a wider effect beyond the borders of ImpDis. For patients and their families, the growing knowledge contributes to a more directed genetic counseling of the families and personalized therapeutic approaches.COST (BM1208), Bundesministerium für Bildung und Forschung (Network ‘Imprinting Diseases’, 01GM1513B), German Ministry of research and education (01GM1513B)This is the author accepted manuscript. The final version is available from Wiley via http://dx.doi.org/10.1111/cge.1282
Cosmic-ray strangelets in the Earth's atmosphere
If strange quark matter is stable in small lumps, we expect to find such
lumps, called ``strangelets'', on Earth due to a steady flux in cosmic rays.
Following recent astrophysical models, we predict the strangelet flux at the
top of the atmosphere, and trace the strangelets' behavior in atmospheric
chemistry and circulation. We show that several strangelet species may have
large abundances in the atmosphere; that they should respond favorably to
laboratory-scale preconcentration techniques; and that they present promising
targets for mass spectroscopy experiments.Comment: 28 pages, 4 figures, revtex
W Hya : molecular inventory by ISO-SWS
Infrared spectroscopy is a powerful tool to probe the inventory of solid
state and molecular species in circumstellar ejecta. Here we analyse the
infrared spectrum of the Asymptotic Giant Branch star W Hya, obtained by the
Short and Long Wavelength Spectrometers on board of the Infrared Satellite
Observatory. These spectra show evidence for the presence of amorphous
silicates, aluminum oxide, and magnesium-iron oxide grains. We have modelled
the spectral energy distribution using laboratory measured optical properties
of these compounds and derive a total dust mass loss rate of 3E-10 Msol/yr. We
find no satisfactory fit to the 13 micron dust emission feature and the
identification of its carrier is still an open issue. We have also modelled the
molecular absorption bands due to H2O, OH, CO, CO2, SiO, and SO2 and estimated
the excitation temperatures for different bands which range from 300 to 3000K.
It is clear that different molecules giving rise to these absorption bands
originate from different gas layers. We present and analyse high resolution
Fabry-Perot spectra of the three CO2 bands in the 15 micron region. In these
data, the bands are resolved into individual Q-lines in emission, which allows
the direct determination of the excitation temperature and column density of
the emitting gas. This reveals the presence of a warm (about 450K) extended
layer of CO2, somewhere between the photosphere and the dust formation zone.
The gas in this layer is cooler than the 1000K CO2 gas responsible for the
low-resolution absorption bands at 4.25 and 15 micron. The rotational and
vibrational excitation temperatures derived from the individual Q-branch lines
of CO2 are different (450K and 150K, respectively) so that the CO2 level
population is not in LTE.Comment: To appear in Astronomy and Astrophysics A reference is adde
The Spitzer Spectroscopic Survey of S-type Stars
S-type AGB stars are thought to be in the transitional phase between M-type
and C-type AGB stars. Because of their peculiar chemical composition, one may
expect a strong influence of the stellar C/O ratio on the molecular chemistry
and the mineralogy of the circumstellar dust. In this paper, we present a large
sample of 87 intrinsic galactic S-type AGB stars, observed at infrared
wavelengths with the Spitzer Space Telescope, and supplemented with
ground-based optical data. On the one hand, we derive the stellar parameters
from the optical spectroscopy and photometry, using a grid of model
atmospheres. On the other, we decompose the infrared spectra to quantify the
flux-contributions from the different dust species. Finally, we compare the
independently determined stellar parameters and dust properties. For the stars
without significant dust emission, we detect a strict relation between the
presence of SiS absorption in the Spitzer spectra and the C/O ratio of the
stellar atmosphere. These absorption bands can thus be used as an additional
diagnostic for the C/O ratio. For stars with significant dust emission, we
define three groups, based on the relative contribution of certain dust species
to the infrared flux. We find a strong link between group-membership and C/O
ratio. We show that these groups can be explained by assuming that the
dust-condensation can be cut short before silicates are produced, while the
remaining free atoms and molecules can then form the observed magnesium
sulfides or the carriers of the unidentified 13 and 20 micron features.
Finally, we present the detection of emission features attributed to molecules
and dust characteristic to C-type stars, such as molecular SiS, hydrocarbons
and magnesium sulfide grains. We show that we often detect magnesium sulfides
together with molecular SiS and we propose that it is formed by a reaction of
SiS molecules with Mg.Comment: Accepted for publication in A&
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