801 research outputs found
Recent outburst of the young star V1180 Cas
We report on the ongoing outburst of the young variable V1180 Cas, which is
known to display characteristics in common with EXor eruptive variables. We
present results that support the scenario of an accretion-driven nature of the
brightness variations of the object and provide the first evidence of jet
structures around the source. We monitored the recent flux variations of the
target in the Rc, J, H, and K bands. New optical and near-IR spectra taken
during the current high state of V1180 Cas are presented, in conjunction with
H2 narrow-band imaging of the source. Observed near-IR colour variations are
analogous to those observed in EXors and consistent with excess emission
originating from an accretion event. The spectra show numerous emission lines,
which indicates accretion, ejection of matter, and an active disc. Using
optical and near-IR emission features we derive a mass accretion rate of ~3 E-8
Msun/yr, which is an order of magnitude lower than previous estimates. In
addition, a mass loss rate of ~4 E-9 and ~4 E-10 Msun/yr are estimated from
atomic forbidden lines and H2, respectively. Our H2 imaging reveals two bright
knots of emission around the source and the nearby optically invisible star
V1180 Cas B, clearly indicative of mass-loss phenomena. Higher resolution
observations of the detected jet will help to clarify whether V1180 Cas is the
driving source and to determine the relation between the observed knots.Comment: Accepted as Letter in A&A; 4 pages, 3 figure
Study of acute and subacute action of iron-molybdenum nanocluster polyoxometalates
There were no significant deviations from the norm in the functional state of the liver, kidneys, and pancreas in the study of the acute toxicity of iron-molybdenum buckyballs intended for targeted drug delivery. No accumulation of nanoparticles or deviation from the norm in any investigated parameter was detected in the study of subacute toxicity. © 2013 Pleiades Publishing, Ltd
Magnetized Particle Capture Cross Section for Braneworld Black Hole
Capture cross section of magnetized particle (with nonzero magnetic moment)
by braneworld black hole in uniform magnetic field is considered. The magnetic
moment of particle was chosen as it was done by \citet{rs99} and for the
simplicity particle with zero electric charge is chosen. It is shown that the
spin of particle as well as the brane parameter are to sustain the stability of
particles circularly orbiting around the black hole in braneworld i.e. spin of
particles and brane parameter try to prevent the capture by black hole.Comment: 7 pages, 4 figures, Accepted for publication in Astrophysics & Space
Scienc
A Practical Method to Test the Safety of HV/MV Substation Grounding System
The adequacy of a Grounding System (GS) to the safety conditions has to be periodically tested by measurements. The test methods and techniques used to verify the electrical characteristics of the GS include the measurements of step and touch voltages. The goal of the test is to verify that touch voltage and step voltage remain below a safe value in all the zones of the installation. The measurements can present some operational difficulties. The purpose of this paper is to present the procedure, step-by-step, of a practical method of measuring touch/step voltages in grounding systems located in urban or industrial areas with reduced accessibility. The suggested method uses auxiliary current electrodes located at short distances. This paper demonstrates by test measurements done in a real case that the method provides conservative results
Influence of LV Neutral Grounding on Global Earthing Systems
International Standards define a Global Earthing System as an earthing net created interconnecting local Earthing Systems (generally through the shield of MV cables and/or bare buried conductors). In Italy the Regulatory Authority for Electricity and Gas requires Distributors to guarantee the electrical continuity of LV neutral conductor. This requirement has led to the standard practice of realizing “reinforcement groundings” along the LV neutral conductor path and at users’ delivery cabinet. Moreover, in urban high load scenarios (prime candidates to be part of a Global Earthing System), it is common that LV distribution scheme creates, trough neutral conductors, an effective connection between grounding systems of MV/LV substations, modifying Global Earthing System consistency. Aim of this paper is to evaluate the effect, in terms of electrical safety, of the above mentioned LV neutral distribution scheme when an MV-side fault to ground occurs. At this purpose simulations are carried out on a realistic urban test case and suitable evaluation indexes are proposed
The brightest gamma-ray flaring blazar in the sky: AGILE and multi-wavelength observations of 3C 454.3 during November 2010
Since 2005, the blazar 3C 454.3 has shown remarkable flaring activity at all
frequencies, and during the last four years it has exhibited more than one
gamma-ray flare per year, becoming the most active gamma-ray blazar in the sky.
We present for the first time the multi-wavelength AGILE, SWIFT, INTEGRAL, and
GASP-WEBT data collected in order to explain the extraordinary gamma-ray flare
of 3C 454.3 which occurred in November 2010. On 2010 November 20 (MJD 55520),
3C 454.3 reached a peak flux (E>100 MeV) of F_gamma(p) = (6.8+-1.0)E-5 ph/cm2/s
on a time scale of about 12 hours, more than a factor of 6 higher than the flux
of the brightest steady gamma-ray source, the Vela pulsar, and more than a
factor of 3 brighter than its previous super-flare on 2009 December 2-3. The
multi-wavelength data make a thorough study of the present event possible: the
comparison with the previous outbursts indicates a close similarity to the one
that occurred in 2009. By comparing the broadband emission before, during, and
after the gamma-ray flare, we find that the radio, optical and X-ray emission
varies within a factor 2-3, whereas the gamma-ray flux by a factor of 10. This
remarkable behavior is modeled by an external Compton component driven by a
substantial local enhancement of soft seed photons.Comment: Accepted for publication in ApJ Letters. 18 Pages, 4 Figures, 1 Tabl
Dissecting the long-term emission behaviour of the BL Lac object Mrk 421
We report on long-term multiwavelengthmonitoring of blazar Mrk 421 by the GLAST-AGILE
Support Program of the Whole Earth Blazar Telescope (GASP-WEBT) collaboration and
Steward Observatory, and by the Swift and Fermi satellites. We study the source behaviour in
the period 2007–2015, characterized by several extreme flares. The ratio between the optical,
X-ray and γ -ray fluxes is very variable. The γ -ray flux variations show a fair correlation with
the optical ones starting from 2012.We analyse spectropolarimetric data and find wavelengthdependence
of the polarization degree (P), which is compatible with the presence of the
host galaxy, and no wavelength dependence of the electric vector polarization angle (EVPA).
Optical polarimetry shows a lack of simple correlation between P and flux and wide rotations of
the EVPA.We build broad-band spectral energy distributions with simultaneous near-infrared
and optical data from the GASP-WEBT and ultraviolet and X-ray data from the Swift satellite.
They show strong variability in both flux and X-ray spectral shape and suggest a shift of
the synchrotron peak up to a factor of ∼50 in frequency. The interpretation of the flux and
spectral variability is compatible with jet models including at least two emitting regions that
can change their orientation with respect to the line of sight.http://10.0.4.69/mnras/stx2185Accepted manuscrip
Диагностическая и прогностическая ценность диффузионно-взвешенного изображения печени при магнитно-резонансной томографии у пациентов с алкогольной болезнью печени
The aim of the study was to assess the diagnostic and prognostic value of a diffusion-weighted image of the liver with magnetic resonance imaging in patients with alcoholic liver disease.Material and methods. A total of 113 patients with alcoholic liver disease (ALD) were examined. Among them, 65 (57.5%) are men and 48 (42.5%) are women. The mean age of patients is 46.3 ± 5.2 years. The structure of the instrumental algorithm for examining patients was presented: ultrasound of the abdominal cavity organs with clinical elastography – 98 (86.7%) patients, MRI of the liver with the mandatory inclusion of the DWI liver sequence in the protocol (n = 113). The b-factor values of 100/600/1000 were used for the liver DWI sequence. Liver biopsy was chosen as the reference method in 65 (57.5%) patients.Results. The patients were monitored for 12 months. At the first stage, the qualitative characteristics of the liver DWI sequence were assessed: no or there is a diffusion limitation. At the second stage, the quantitative indicators of the DWI sequence were assessed in the form of calculating the measured diffusion index and coefficient. In order to standardize the technique of liver DWI on MRI in patients with ALD, the results were compared with the data of clinical elastography (p < 0.01) and liver biopsy (p < 0.05). Upon admission and monitoring of patients (after 1, 3, 6, 9 months), a high correlation was found in the assessment of comparing the quantitative indicators of DWI with clinical elastography (r = 0.873) and an average correlation with biopsy data (r = 0.715).Conclusions. There was a high correlation between the limitation of liver diffusion on MRI and negative clinical and laboratory dynamics (r = 0.889) and in the absence of limitation of diffusion in the liver and positive clinical and laboratory dynamics (r = 0.885). DWI of the liver on MRI in patients with ALD has a high diagnostic and prognostic value in assessing abnormal abstinence regimen (AUROC = 0.903 (95% CI 0.871–0.911)). Diagnostic and prognostic significance of the developed criteria for DWI of the liver at MRI in patients with ABD at admission: for a qualitative assessment AUROC = 0.844 (95% CI 0.801–0.869), quantitative – AUROC = 0.908 (95% CI 0.875–0.911); with dynamic observation: for a qualitative assessment AUROC = 0.939 (95% CI 0.901–0.955), quantitative – AUROC = 0.919 (95% CI 0.871–0.931).Цель исследования: оценка диагностической и прогностической ценности диффузионно-взвешенного изображения (ДВИ) печени при магнитно-резонансной томографии (МРТ) у пациентов с алкогольной болезнью печени (АБП).Материал и методы. Обследовано 113 пациентов с АБП, среди них 65 (57,5%) мужчин и 48 (42,5%) женщин. Средний возраст больных 46,3 ± 5,2 года. Структура инструментального алгоритма обследования пациентов была представлена: УЗИ органов брюшной полости с клинической эластографией – 98 (86,7%) больных, МРТ печени с обязательным включением в протокол последовательности ДВИ печени (n = 113). При последовательности ДВИ печени использовались значения b-фактора 100/600/1000. Референтным методом была выбрана биопсия печени у 65 (57,5%) пациентов.Результаты и обсуждение. Наблюдение за пациентами велось в течение 12 мес. На первом этапе проводилась оценка качественной характеристики последовательности ДВИ печени: нет или есть ограничение диффузии. На втором этапе проводилась оценка количественных показателей последовательности ДВИ в виде расчета измеряемого показателя диффузии и коэффициента. С целью стандартизации методики ДВИ печени при МРТ у больных с АБП результаты были сопоставлены с данными клинической эластографии (p < 0,01) и биопсией печени (p < 0,05). При поступлении и мониторинге за пациентами (через 1, 3, 6, 9 мес) была установлена высокая корреляционная связь в оценке сопоставления количественных показателей ДВИ с клинической эластографией (r = 0,873) и средняя корреляционная связь с данными биопсии (r = 0,715).Выводы. Отмечена высокая корреляционная связь ограничения диффузии печени при МРТ и отрицательной клинико-лабораторной динамики (r = 0,889) и отсутствии ограничения диффузии в печени и положительной клинико-лабораторной динамики (r = 0,885). ДВИ печени при МРТ у пациентов с АБП имеет высокую диагностическую и прогностическую значимость в оценке нарушения режима абстиненции (AUROC = 0,903 (95% ДИ 0,871–0,911)). Диагностическая и прогностическая значимость разработанных критериев ДВИ печени при МРТ у пациентов с АБП при поступлении: для качественной оценки AUROC = 0,844 (95% ДИ 0,801–0,869), количественной – AUROC = 0,908 (95% ДИ 0,875–0,911); при динамическом наблюдении: для качественной оценки AUROC = 0,939 (95% ДИ 0,901–0,955), количественной – AUROC = 0,919 (95% ДИ 0,871–0,931)
AGILE detection of extreme gamma-ray activity from the blazar PKS 1510-089 during March 2009. Multifrequency analysis
We report on the extreme gamma-ray activity from the FSRQ PKS 1510-089
observed by AGILE in March 2009. In the same period a radio-to-optical
monitoring of the source was provided by the GASP-WEBT and REM. Moreover,
several Swift ToO observations were triggered, adding important information on
the source behaviour from optical/UV to hard X-rays. We paid particular
attention to the calibration of the Swift/UVOT data to make it suitable to the
blazars spectra. Simultaneous observations from radio to gamma rays allowed us
to study in detail the correlation among the emission variability at different
frequencies and to investigate the mechanisms at work. In the period 9-30 March
2009, AGILE detected an average gamma-ray flux of (311+/-21)x10^-8 ph cm^-2
s^-1 for E>100 MeV, and a peak level of (702+/-131)x10^-8 ph cm^-2 s^-1 on
daily integration. The gamma-ray activity occurred during a period of
increasing activity from near-IR to UV, with a flaring episode detected on
26-27 March 2009, suggesting that a single mechanism is responsible for the
flux enhancement observed from near-IR to UV. By contrast, Swift/XRT
observations seem to show no clear correlation of the X-ray fluxes with the
optical and gamma-ray ones. However, the X-ray observations show a harder
photon index (1.3-1.6) with respect to most FSRQs and a hint of
harder-when-brighter behaviour, indicating the possible presence of a second
emission component at soft X-ray energies. Moreover, the broad band spectrum
from radio-to-UV confirmed the evidence of thermal features in the optical/UV
spectrum of PKS 1510-089 also during high gamma-ray state. On the other hand,
during 25-26 March 2009 a flat spectrum in the optical/UV energy band was
observed, suggesting an important contribution of the synchrotron emission in
this part of the spectrum during the brightest gamma-ray flare, therefore a
significant shift of the synchrotron peak.Comment: 13 pages, 7 figures, 3 tables. Accepted for publication in Astronomy
and Astrophysic
Bures volume of the set of mixed quantum states
We compute the volume of the N^2-1 dimensional set M_N of density matrices of
size N with respect to the Bures measure and show that it is equal to that of a
N^2-1 dimensional hyper-halfsphere of radius 1/2. For N=2 we obtain the volume
of the Uhlmann 3-D hemisphere, embedded in R^4. We find also the area of the
boundary of the set M_N and obtain analogous results for the smaller set of all
real density matrices. An explicit formula for the Bures-Hall normalization
constants is derived for an arbitrary N.Comment: 15 revtex pages, 2 figures in .eps; ver. 3, Eq. (4.19) correcte
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