278 research outputs found
Hydrodynamical and radio evolution of young supernova remnant G1.9+0.3 based on the model of diffusive shock acceleration
The radio evolution of, so far the youngest known, Galactic supernova remnant
(SNR) G1.9+0.3 is investigated by using three-dimensional (3D) hydrodynamic
modelling and non-linear kinetic theory of cosmic ray (CR) acceleration in
SNRs. We include consistent numerical treatment of magnetic field amplification
(MFA) due to resonant streaming instability. Under the assumption that SNR
G1.9+0.3 is the result of a Type Ia supernova explosion located near the
Galactic Centre, using widely accepted values for explosion energy 10
erg and ejecta mass 1.4 , the non-thermal continuum radio emission
is calculated. The main purpose of this paper is to explain radio flux
brightening measured over recent decades and also predict its future temporal
evolution. We estimate that the SNR is now 120 yr old, expanding in an
ambient density of 0.02 cm, and explain its steep radio spectral index
only by means of efficient non-linear diffusive shock acceleration (NLDSA). We
also make comparison between simulations and observations of this young SNR, in
order to test the models and assumptions suggested. Our model prediction of a
radio flux density increase of 1.8 per cent yr during the past
two decades agrees well with the measured values. We synthesize the synchrotron
spectrum from radio to X-ray and it fits well the VLA, MOST, Effelsberg,
Chandra and NuSTAR measurements. We also propose a simplified evolutionary
model of the SNR in gamma rays and suggest it may be a promising target for
gamma-ray observations at TeV energies with the future generation of
instruments like Cherenkov Telescope Array. SNR G1.9+0.3 is the only known
Galactic SNR with the increasing flux density and we present here the
prediction that the flux density will start to decrease approximately 500 yr
from now. We conclude that this is a general property of SNRs in free expansion
phase.Comment: 16 pages, 11 figures, 1 table; corrected typos, updated reference
Identification of deep trap levels from thermally stimulated current spectra of semi-insulating CdZnTe detector material
Deep trap levels in the semi-insulating (SI) CdZnTe detector material were characterized by simultaneous multiple peak analysis based on thermally stimulated current (TSC) measurements. In our TSCs that have been published previously electron hole pairs were created through the use of proton beam irradiation. Charge carriers were captured in deep traps and afterward released by thermal emission, which was recorded in the 90–300 K range. We showed that the obtained TSC spectra could be well fitted with a unique set of 14 different deep traps, which were all simultaneously and completely characterized. The obtained trap data are in good accordance with earlier deep trap characterizations of the other authors obtained on similar SI CdZnTe materials using different methods
Updated radio relation for Galactic supernova remnants
We present updated empirical radio surface-brightness-to-diameter
() relation for supernova remnants (SNRs) in our Galaxy. Our original
calibration sample of Galactic SNRs with independently determined distances
(Pavlovic et al. 2013, hereafter Paper I) is reconsidered and updated with data
which became available in the past two years. The orthogonal fitting procedure
and probability-density-function-based (PDF) method are applied to the
calibration sample in the plane. Orthogonal regression
keeps and relations invariant. Our previous Monte Carlo
simulations verified that the slopes of the empirical relation
should be determined by using orthogonal regression. Updated calibration sample
contains 65 shell SNRs. 6 new Galactic SNRs are added to the sample from Paper
I, one is omitted and distances are changed for 10 SNRs. The slope derived here
is slightly steeper () than slope in Paper I
(). The PDF method relies on data points density maps which
can provide more reliable calibrations that preserve more information contained
in the calibration sample. We estimate distances to five new faint Galactic
SNRs discovered for the first time by Canadian Galactic Plane Survey and
obtained distances of 2.3, 4.0, 1.3, 2.9 and 4.7 kiloparsecs for G108.5+11.0,
G128.5+2.6, G149.5+3.2, G150.8+3.8 and G160.11.1, respectively. The updated
empirical relation is used to estimate distances of 160 shell Galactic SNRs and
new results change their distance scales up to 15 per cent, compared to results
from Paper I. The PDF calculation can provide even few times higher or lower
values in comparison with orthogonal fit, as it uses totally different
approach. However, in average, this difference is 32, 24 and 18 per cent for
mode, median and mean distances.Comment: 17 pages, 3 figures, Accepted for publication in Serbian Astronomical
Journa
Ultrasound diagnostics of carotid and vertebral arteries
Stroke is the third leading cause of death and themain cause ofmajor
disability worldwide.Each yearmore than 700,000 people experience
a new or recurrent stroke and on average someone dies every 4min of
a stroke (1). In Serbia stroke is the first cause of death among women
and the second one among men.
While the percentage of strokes attributed to carotid disease is relatively
low, the overall social and economic burden is high (2). It is, therefore, important to identify and manage carotid atherosclerosis with the aim of stroke prevention.
The presence of an atherosclerotic lesion in the carotid bulb or in the
extracranial internal carotid artery (ICA) is associated with elevated
stroke risk (3). Severalmechanisms are attributable to the increased risk
of cerebrovascular events including decrease in the blood flow resulting
from critical stenosis or occlusion, or the stenotic lesion can also be the
source of thromboembolic events.
In this article the authors are going to focus on some important
aspects of ultrasound diagnostics of extracranial parts of brain arteries
Analysis of lactoferin gene polymophism and its association to milk quality and mammary gland health in Holstein-Friesian cows
Lactoferrin (LTF) is a glycoprotein, a member of transferrin gene family
which plays an important role in immune mechanisms in the mammary glands of
cows. The amount of lactoferrin increases during inflammatory processes and
viral infections. The aim of this investigation was to monitor the
distribution of lactoferrin gene genotypes and its connection to milk quality
and the occurrence of mammary gland diseases in 46 Holstein-Freisian cows of
different age (2-7 years) on a farm near Belgrade. DNA was isolated from
blood samples, and the polymorphism of lactoferrin gene was deterimined by
PCR-RFLP method using the restriction enzyme Eco RI. We found two alelic
forms of this gene in cows included in these experiments (A and B) and two
genotypes (AA and AB) in a ratio 71.7% to 28.3%. The genotype BB was not
found in this sample. In order to determine the degree of differences between
genotypes we used discriminant analysis which has shown that there is a
statistically significant difference between genotypes AA and with respect
to productive parameters. When analyzed separately, the only parameter which
differed significantly (p=0.021) between two genotypes was total milk
production. Individuals with observed genotypes are most similar for the
amount of milk fat (p=0.271). There is no statistically significant
difference in the number of somatic cells in milk samples between the
examined genotypes. [Projekat Ministarstva nauke Republike Srbije, br.
III46002
Supplementary data for article: Krstić, N. M.; Pavlović, V. D.; Novaković, I. T.; Matić, I. Z.; Sladić, D. Synthesis, Characterization and Biological Evaluation of Some Novel P-Heterocyclic Androst-4-Ene Derivatives. Molecular Diversity 2013, 17 (3), 547–561. https://doi.org/10.1007/s11030-013-9455-9
Supplementary material for: [https://doi.org/10.1007/s11030-013-9455-9]Related to published version: [http://cherry.chem.bg.ac.rs/handle/123456789/1376
Structural and electrical properties of ferroelectric poly(vinylidene fluoride) and mechanically activated ZnO nanoparticle composite films
The influence of the mechanical activation of ZnO nanoparticle fillers on the structural and electrical properties of the matrix of poly(vinylidenefluoride)-ZnO (PVDF-ZnO) films was investigated. Transmission electron microscopy and scanning electron microscopy analyses showed that mechanical activation in a high energy planetary ball mill reduces the size of ZnO particles. X-ray diffraction and Raman spectroscopy revealed that PVDF crystallized predominantly as the gamma-phase. Non-activated ZnO filler reduces the degree of the crystallinity of the matrix and promotes crystallization of alpha-phase of PVDF in the film, while the fillers activated for 5 and 10 min induce crystallization of beta-phase, indicating that mechanical activation of the filler can be used as a general method for fabrication of PVDF composites with increased content of piezoelectric beta-phase crystals. Dielectric spectroscopy measurements show that polymer composite with the high content of beta-phase (with ZnO filler activated for 5 min) exhibits the highest value of dielectric permittivity in 150-400 K range of temperatures. Kinetic analysis shows combined effects of increased surface area and increased concentration of surface defects on the interactions between polymer chains and activated nanoparticles
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