1,324 research outputs found
Three-body treatment of the penetration through the Coulomb field of a two-fragment nucleus
On the basis of the Faddeev integral equations method and the Watson-
Feshbach concept of the effective (optical) interaction potential, the first
fully consistent three-body approach to the description of the penetration of a
charged particle through the Coulomb field of a two-particle bound complex
(composed of one charged and one neutral particles) has been developed. A
general formalism has been elaborated and on its basis, to a first
approximation in the Sommerfeld parameter, the influence of the nuclear
structure on the probability of the penetration of a charged particle (the
muon, the pion, the kaon and the proton) through the Gamow barrier of a
two-fragment nucleus (the deuteron and the two lightest lambda hypernuclei,
lambda hypertriton and lambda hyperhelium-5, has been calculated and studied.Comment: LaTeX, 30 pages, 4 eps figure
A RAVE investigation on Galactic open clusters I. Radial velocities and metallicities
Context. Galactic open clusters (OCs) mainly belong to the young stellar population in the Milky Way disk, but are there groups and complexes of OCs that possibly define an additional level in hierarchical star formation? Current compilations are too incomplete to address this question, especially regarding radial velocities (RVs) and metallicities ([M/H]).
Aims. Here we provide and discuss newly obtained RV and [M/H] data, which will enable us to reinvestigate potential groupings of open clusters and associations.
Methods. We extracted additional RVs and [M/H] from the RAdial Velocity Experiment (RAVE) via a cross-match with the Catalogue of Stars in Open Cluster Areas (CSOCA). For the identified OCs in RAVE we derived (RV) over bar and ([M/H]) over bar from a cleaned working sample and compared the results with previous findings.
Results. Although our RAVE sample does not show the same accuracy as the entire survey, we were able to derive reliable (RV) over bar for 110 Galactic open clusters. For 37 OCs we publish (RV) over bar for the first time. Moreover, we determined ([M/H]) over bar for 81 open clusters, extending the number of OCs with ([M/H]) over bar by 69
Моделювання зіткнення літаків з використанням методики істотних вибірок
We introduce the model of movement of two conflicting aircrafts and state the problem, we apply the importance sampling technique and elaborate an algorithm of collision modeling based on normal distributions, a small simulation studyРассмотрена модель движения двух конфликтующих самолетов. Предложены методика важных выборок и алгоритм моделирования столкновения самолетов, основанный на нормальном распределенииРозглянуто модель руху двох конфліктуючих літаків. Запропоновано методику істотних вибірок і алгоритм моделювання зіткнення літаків, заснований на нормальному розподіл
Properties of pattern formation and selection processes in nonequilibrium systems with external fluctuations
We extend the phase field crystal method for nonequilibrium patterning to
stochastic systems with external source where transient dynamics is essential.
It was shown that at short time scales the system manifests pattern selection
processes. These processes are studied by means of the structure function
dynamics analysis. Nonequilibrium pattern-forming transitions are analyzed by
means of numerical simulations.Comment: 15 poages, 8 figure
Reconstruction of N2O and CH4 content by dial measurements at wavelengths of overtone CO laser
The paper presents the results of laboratory experiments on measurement of absorption and extinction of radiation of the overtone СО laser at wavelengths used for sensing of methane and N2O in the mid-IR spectral range with the differential absorption (DIAL) method, as well as the concentrations of the studied gases reconstructed from the analysis of experimentally obtained absorption coefficients
Histone H3 Acetylation is Asymmetrically Induced Upon Learning in Identified Neurons of the Food Aversion Network in the Mollusk Helix Lucorum
Regulation of gene expression is an essential step during long-term memory formation. Recently, the involvement of DNA-binding transcription factors and chromatin remodeling in synaptic plasticity have been intensively studied. The process of learning was shown to be associated with chromatin remodeling through histone modifications such as acetylation and phosphorylation. We have previously shown that the MAPK/ERK (mitogen-activated protein kinase/extracellular signal-regulated kinase) regulatory cascade plays a key role in the food aversion conditioning in the mollusk Helix. Specifically, command neurons of withdrawal behavior exhibit a learning-dependent asymmetry (left–right) in MAPK/ERK activation. Here, we expanded our molecular studies by focusing on a potential MAPK/ERK target – histone H3. We studied whether there is a learning-induced MAPK/ERK-dependent acetylation of histone H3 in command neurons RPa(2/3) and LPa(2/3) of the right and left parietal ganglia and whether it is asymmetrical. We found a significant learning-dependent increase in histone H3 acetylation in RPa(2/3) neurons but not in LPa(2/3) neurons. Such an increase in right command neurons depended on MAPK/ERK activation and correlated with a lateralized avoidance movement to the right visible 48 h after training. The molecular changes found in a selective set of neurons could thus represent a lateralized memory process, which may lead to consistent turning in one direction when avoiding a food that has been paired with an aversive stimulus
A Search for EUV Emission from Comets with the Cosmic Hot Interstellar Plasma Spectrometer (CHIPS)
We have obtained EUV spectra between 90 and 255 \AA of the cometsC/2002 T7
(LINEAR), C/2001 Q4 (NEAT), and C/2004 Q2 (Machholz) near their perihelion
passages in 2004 with the Cosmic Hot Interstellar Plasma Spectrometer (CHIPS).
We obtained contemporaneous data on Comet NEAT Q4 with the X-ray
Observatory ACIS instrument, marking the first simultaneous EUV and X-ray
spectral observations of a comet. The total CHIPS/EUV observing times were 337
ks for Q4, 234 ks for T7, and 483 ks for Machholz and for both CHIPS and
we calculate we have captured all the comet flux in the instrument
field of view. We set upper limits on solar wind charge exchange emission lines
of O, C, N, Ne and Fe occurring in the spectral bandpass of CHIPS. The spectrum
of Q4 obtained with can be reproduced by modeling emission lines of
C, N O, Mg, Fe, Si, S, and Ne solar wind ions. The measured X-ray emission line
intensities are consistent with our predictions from a solar wind charge
exchange model. The model predictions for the EUV emission line intensities are
determined from the intensity ratios of the cascading X-ray and EUV photons
arising in the charge exchange processes. They are compatible with the measured
limits on the intensities of the EUV lines. For comet Q4, we measured a total
X-ray flux of 3.7 ergs cm s, and derive from
model predictions a total EUV flux of 1.5 erg cm
s. The CHIPS observations occurred predominantly while the satellite was
on the dayside of Earth. For much of the observing time, CHIPS performed
observations at smaller solar angles than it was designed for and EUV emission
from the Sun scattered into the instrument limited the sensitivity of the EUV
measurements.Comment: 28 pages total, 4 tables, 7 figures. Accepted by The Astrophysical
Journa
TUBERCULOSIS MENINGITIS IN CHILDREN AND ADOLESCENTS
The article presents the clinical and epidemiological data on tuberculosis meningitis among children in Astrakhan Region. It was found out that among those cases 77.8% were children under 7 years old exposed to tuberculosis in their families, meningitis developed against the background of active respiratory tuberculosis and only 17.4% had post-vaccinal scar out of 85.2% who had BCG vaccination. There were two clinical forms of tuberculosis meningitis: basilar form in 59.2% and meningoencephalitis in 40.8% of patients. Late diagnostics and untimely start of treatment were observed in 88.9% of patients
Spitzer Space Telescope study of disks in the young Orionis cluster
We report new Spitzer Space Telescope observations from the IRAC and MIPS
instruments of the young (~ 3 Myr) sigma Orionis cluster. We identify 336 stars
as members of the cluster using optical and near-infrared color magnitude
diagrams. Using the spectral energy distribution (SED) slopes in the IRAC
spectral range, we place objects in several classes: non-excess stars, stars
with optically thick disks(like classical T Tauri stars), class I
(protostellar) candidates, and stars with ``evolved disks''; the last exhibit
smaller IRAC excesses than optically thick disk systems. In general, this
classification agrees with the location expected in IRAC-MIPS color-color
diagrams for these objects. We find that the evolved disk systems are mostly a
combination of objects with optically thick but non-flared disks, suggesting
grain growth and/or settling, and transition disks, systems in which the inner
disk is partially or fully cleared of small dust. In all, we identify 7
transition disk candidates and 3 possible debris disk systems. As in other
young stellar populations, the fraction of disks depends on the stellar mass,
ranging from ~10% for stars in the Herbig Ae/Be mass range (>2 msun) to ~35% in
the T Tauri mass range (1-0.1 msun). We find that the disk fraction does not
decrease significantly toward the brown dwarf candidates (<0.1 msun). The IRAC
infrared excesses found in stellar clusters and associations with and without
central high mass stars are similar, suggesting that external photoevaporation
is not very important in many clusters. Finally, we find no correlation between
the X-ray luminosity and the disk infrared excess, suggesting that the X-rays
are not strongly affected by disk accretion.Comment: 44pages, 17 figures. Sent to Ap
A study of Jupiter's aurorae with XMM-Newton
We present a detailed analysis of Jupiter's X-ray (0.2-10 keV) auroral
emissions as observed by XMM-Newton in Nov. 2003 and compare it with that of an
Apr. 2003 observation. We discover the existence of an electron bremsstrahlung
component in the aurorae, which accounts for essentially all the X-ray flux
above 2 keV: its presence had been predicted but never detected for lack of
sensitivity of previous X-ray missions. This bremsstrahlung component varied
significantly in strength and spectral shape over the 3.5 days covered by the
Nov. 2003 observation, displaying substantial hardening of the spectrum with
increasing flux. This variability may be linked to the strong solar activity
taking place at the time, and may be induced by changes in the acceleration
mechanisms inside Jupiter's magnetosphere. As in Apr. 2003, the auroral spectra
below 2 keV are best fitted by a superposition of line emission most likely
originating from ion charge exchange, with OVII playing the dominant role. We
still cannot resolve conclusively the ion species responsible for the lowest
energy lines (around 0.3 keV), so the question of the origin of the ions
(magnetospheric or solar wind) is still open. It is conceivable that both
scenarios play a role in what is certainly a very complex planetary structure.
High resolution spectra of the whole planet obtained with the XMM-Newton RGS in
the range 0.5-1 keV clearly separate emission lines (mostly of Fe) originating
at low latitudes on Jupiter from the auroral lines due to O. These are shown to
possess very broad wings which imply velocities of ~5000 km/s. Such speeds are
consistent with the energies at which precipitating and charge exchanging O
ions are expected to be accelerated in Jupiter's magnetosphere. Overall we find
good agreement between our measurements and the predictions of recent models.Comment: 16 pages, 17 figures, to be published in 'Astronomy and Astrophysics
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