869 research outputs found
Fermi-LAT upper limits on gamma-ray emission from colliding wind binaries
Context: Colliding wind binaries (CWBs) are thought to give rise to a
plethora of physical processes including acceleration and interaction of
relativistic particles. Observation of synchrotron radiation in the radio band
confirms there is a relativistic electron population in CWBs. Accordingly, CWBs
have been suspected sources of high-energy gamma-ray emission since the COS-B
era. Theoretical models exist that characterize the underlying physical
processes leading to particle acceleration and quantitatively predict the
non-thermal energy emission observable at Earth. Aims: We strive to find
evidence of gamma-ray emission from a sample of seven CWB systems: WR 11, WR
70, WR 125, WR 137, WR 140, WR 146, and WR 147. Theoretical modelling
identified these systems as the most favourable candidates for emitting
gamma-rays. We make a comparison with existing gamma-ray flux predictions and
investigate possible constraints. Methods: We used 24 months of data from the
Large Area Telescope (LAT) on-board the Fermi Gamma Ray Space Telescope to
perform a dedicated likelihood analysis of CWBs in the LAT energy range.
Results: We find no evidence of gamma-ray emission from any of the studied CWB
systems and determine corresponding flux upper limits. For some CWBs the
interplay of orbital and stellar parameters renders the Fermi-LAT data not
sensitive enough to constrain the parameter space of the emission models. In
the cases of WR140 and WR147, the Fermi-LAT upper limits appear to rule out
some model predictions entirely and constrain theoretical models over a
significant parameter space. A comparison of our findings to the CWB eta Car is
made.Comment: 9 pages, 3 figure
How to use current practice, risk analysis and standards to define hospital-wide policies on the safe use of infusion technology
Infusion therapy is widely used in hospitals. It is well known that medication errors constitute one of the highest risks to patient safety, leading to numerous adverse events concerning incorrect application of infusion technology. Both clinical practice and in vitro studies show that infusion of multiple medications via one access point induces unwanted phenomena such as backflow and an incorrect system response to interventions. Within the Metrology for Drug Delivery project, we addressed the role of infusion devices in drug delivery. We surveyed current practices for application in hospitals to provide input to standards and quality norms for the materials used in infusion technology. Furthermore, we organized meetings with clinicians and other relevant stakeholders to set up a risk analysis-based infusion policy, accompanied by easy to access operating procedures on infusion technology. It was found difficult to establish clear-cut infusion safety guidelines based on quantitative data because of the many different application areas and stakeholders. However, both the expert team and the survey indicated the value of multidisciplinary qualitative discussion for defining best practices. We advise to incorporate specific requirements on infusion devices in protocols and standards, adjusted to specific applications, to ensure safe use of infusion technology
Gamma-ray follow-up studies on Eta Carinae
Observations of high energy gamma rays recently revealed a persistent source
in spatial coincidence with the binary system Eta Carinae. Since modulation of
the observed gamma-ray flux on orbital time scales has not been reported so
far, an unambiguous identification was hitherto not possible. Particularly the
observations made by the Fermi Large Area Telescope (LAT) posed additional
questions regarding the actual emission scenario owing to the existence of two
energetically distinct components in the gamma-ray spectrum of this source,
best described by an exponentially cutoff power-law function (CPL) at energies
below 10 GeV and a power-law (PL) component dominant at higher energies. The
increased exposure in conjunction with the improved instrumental response
functions of the LAT now allow us to perform a more detailed investigation of
location, spectral shape, and flux time history of the observed gamma-ray
emission.
For the first time, we are able to report a weak but regular flux decrease
over time. This can be understood and interpreted in a colliding-wind binary
scenario for orbital modulation of the gamma-ray emission. We find the spectral
shape of the gamma-ray signal in agreement with a single emitting particle
population in combination with significant absorption by gamma-gamma pair
production.
Studying the correlation of the flux decrease with the orbital separation of
the binary components allows us to predict the behaviour up to the next
periastron passage in 2014.Comment: 11 pages, 9 figure
Породы песчаники – редкие материалы высокой крепости – уникальные фрикционные материалы
Розглядаються питання при підготовці до відпрацювання пологих вугільних пластів на
великих глибинах в умовах шахти «Довжанська Капітальна» ТОВ "ДТЕК Свердловантрацит". Проведено дослідження вміщуючих підготовчу виробку порід. Запропоновано можливості проектування комплексного видобутку супутніх корисних компонентів при підготовці Антрацитівського пластів до видобутку.The questions in preparation for mining of shallow coal seams at great depths in the mine
"Dolzhanskaya Capital" LLC "DTEK Sverdlovantratsit." Investigations of host rocks of underground working. Suggested the possibility of designing an integrated co-production of useful components in preparation Antratsitovskogo of flat seam to production
Use of Dipeptidyl Peptidase-4 Inhibitors and the Reporting of Infections: A Disproportionality Analysis in the World Health Organization VigiBase
OBJECTIVE - Dipeptidyl peptidase-4 (DPP-4) inhibitors are a new class of antidiabetic drugs. They inactivate incretin hormones but also have many other effects throughout the body, among which are effects on the immune system. This might result in an increased infection risk. This study assessed the association between use of DPP-4 inhibitors and the reporting of infections. RESEARCH DESIGN AND METHODS - A nested case-control was conducted using VigiBase, the World Health Organization-Adverse Drug Reactions (WHO-ADR) database. The base cohort consisted of ADRs for antidiabetic drugs (Anatomical Therapeutic Chemical code A10). Cases were defined as ADRs of infection according to the Medical Dictionary for Regulatory Activities (MedDRA) classification system. All other ADRs were considered controls. Reporting odds ratios (RORs) were calculated to estimate the strength of the association between different classes of antidiabetic drugs and the reporting of infections. RESULTS - We identified 305,415 suspected ADRs involving antidiabetic drugs in 106,469 case reports, of which 8,083 involved DPP-4 inhibitors monotherapy. Overall, the reporting of infections was higher for patients using DPP-4 inhibitors compared with users of biguanides (ROR 2.3 [95% CI 1.9-2.7]). Reporting of upper respiratory tract infections (ROR 12.3 [95% CI 8.6-17.5]) was significantly associated with use of DPP-4 inhibitors. CONCLUSIONS - This study indicates an increased reporting of infections, in particular upper respiratory tract infections, for users of DPP-4 inhibitors compared with users of other antidiabetic drugs. However, the limitations of spontaneous reporting systems (e.g., underreporting, the Weber-effect, reporting bias) should be taken into account. Therefore, further research is needed to evaluate this suspicion and the underlying mechanism
First detection of a VHE gamma-ray spectral maximum from a Cosmic source: H.E.S.S. discovery of the Vela X nebula
The Vela supernova remnant (SNR) is a complex region containing a number of
sources of non-thermal radiation. The inner section of this SNR, within 2
degrees of the pulsar PSR B0833-45, has been observed by the H.E.S.S. gamma-ray
atmospheric Cherenkov detector in 2004 and 2005. A strong signal is seen from
an extended region to the south of the pulsar, within an integration region of
radius 0.8 deg. around the position (RA = 08h 35m 00s, dec = -45 deg. 36'
J2000.0). The excess coincides with a region of hard X-ray emission seen by the
ROSAT and ASCA satellites. The observed energy spectrum of the source between
550 GeV and 65 TeV is well fit by a power law function with photon index = 1.45
+/- 0.09(stat) +/- 0.2(sys) and an exponential cutoff at an energy of 13.8 +/-
2.3(stat) +/- 4.1(sys) TeV. The integral flux above 1 TeV is (1.28 +/- 0.17
(stat) +/- 0.38(sys)) x 10^{-11} cm^{-2} s^{-1}. This result is the first clear
measurement of a peak in the spectral energy distribution from a VHE gamma-ray
source, likely related to inverse Compton emission. A fit of an Inverse Compton
model to the H.E.S.S. spectral energy distribution gives a total energy in
non-thermal electrons of ~2 x 10^{45} erg between 5 TeV and 100 TeV, assuming a
distance of 290 parsec to the pulsar. The best fit electron power law index is
2.0, with a spectral break at 67 TeV.Comment: 5 pages, 4 figures, accepted for publication in Astronomy and
Astrophysics letter
Detailed spectral and morphological analysis of the shell type SNR RCW 86
Aims: We aim for an understanding of the morphological and spectral
properties of the supernova remnant RCW~86 and for insights into the production
mechanism leading to the RCW~86 very high-energy gamma-ray emission. Methods:
We analyzed High Energy Spectroscopic System data that had increased
sensitivity compared to the observations presented in the RCW~86 H.E.S.S.
discovery publication. Studies of the morphological correlation between the
0.5-1~keV X-ray band, the 2-5~keV X-ray band, radio, and gamma-ray emissions
have been performed as well as broadband modeling of the spectral energy
distribution with two different emission models. Results:We present the first
conclusive evidence that the TeV gamma-ray emission region is shell-like based
on our morphological studies. The comparison with 2-5~keV X-ray data reveals a
correlation with the 0.4-50~TeV gamma-ray emission.The spectrum of RCW~86 is
best described by a power law with an exponential cutoff at TeV and a spectral index of ~. A static
leptonic one-zone model adequately describes the measured spectral energy
distribution of RCW~86, with the resultant total kinetic energy of the
electrons above 1 GeV being equivalent to 0.1\% of the initial kinetic
energy of a Type I a supernova explosion. When using a hadronic model, a
magnetic field of ~100G is needed to represent the measured data.
Although this is comparable to formerly published estimates, a standard
E spectrum for the proton distribution cannot describe the gamma-ray
data. Instead, a spectral index of ~1.7 would be required, which
implies that ~erg has been transferred into
high-energy protons with the effective density cm^-3. This
is about 10\% of the kinetic energy of a typical Type Ia supernova under the
assumption of a density of 1~cm^-3.Comment: accepted for publication by A&
3.9 day orbital modulation in the TeV gamma-ray flux and spectrum from the X-ray binary LS 5039
New observations of LS 5039, a High Mass X-ray Binary comprising a massive
star and compact object, were carried out with the High Energy Stereoscopic
System of Cherenkov Telescopes (H.E.S.S.) in 2005 at very high energy (VHE)
gamma-ray energies. These observations reveal that its flux and energy spectrum
are modulated with the 3.9 day orbital period of the binary system. This is the
first time in gamma-ray astronomy that orbital modulation has been observed,
and periodicity clearly established using ground-based gamma-ray detectors. The
VHE gamma-ray emission is largely confined to half of the orbit, peaking around
the inferior conjunction epoch of the compact object. For this epoch, there is
also a hardening of the energy spectrum in the energy range between 0.2 TeV and
a few TeV. The flux vs. orbital phase profile provides the first clear
indication of gamma-ray absorption via pair production within an astrophysical
source, a process which is expected to occur if the gamma-ray production site
is situated within ~1 AU of the compact object. Moreover the production region
size must be not significantly greater than the binary separation (~0.15 AU).
Notably, these constraints are also considerably smaller than the collimated
outflows or jets (extending out to ~1000 AU) observed in LS 5039. The spectral
hardening could arise from variations with phase in the maximum electron
energies, and/or the dominant VHE gamma-ray production mechanism.Comment: 8 pages, 8 figures, accepted for publication in Astronomy &
Astrophysic
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