4,419 research outputs found
1WHSP: an IR-based sample of 1,000 VHE -ray blazar candidates
Blazars are the dominant type of extragalactic sources at microwave and at
-ray energies. In the most energetic part of the electromagnetic
spectrum (E>100GeV) a large fraction of high Galactic latitude sources are
blazars of the High Synchrotron Peaked (HSP) type, that is BL Lac objects with
synchrotron power peaking in the UV or in the X-ray band. HSP blazars are
remarkably rare, with only a few hundreds of them expected to be above the
sensitivity limits of currently available surveys. To find these very uncommon
objects, we have devised a method that combines ALLWISE survey data with
multi-frequency selection criteria. The sample was defined starting from a
primary list of infrared colour-colour selected sources from the ALLWISE all
sky survey database, and applying further restrictions on IR-radio and IR-X-ray
flux ratios. Using a polynomial fit to the multi-frequency data (radio to
X-ray) we estimated synchrotron peak frequencies and fluxes of each object. We
assembled a sample including 992 sources, which is currently the largest
existing list of confirmed and candidates HSP blazars. All objects are expected
to radiate up to the highest -ray photon energies. In fact, 299 of
these are confirmed emitters of GeV -ray photons (based on Fermi-LAT
catalogues), and 36 have already been detected in the TeV band. The majority of
sources in the sample are within reach of the upcoming Cherenkov Telescope
Array (CTA), and many may be detectable even by the current generation of
Cherenkov telescopes during flaring episodes. The sample includes 425
previously known blazars, 151 new identifications, and 416 HSP candidates
(mostly faint sources) for which no optical spectra is available yet. The full
1WHSP catalogue is on-line at http://www.asdc.asi.it/1whsp/ providing a direct
link to the SED building tool where multifrequency data can be easily
visualised
Nitrogen fluorescence in air for observing extensive air showers
Extensive air showers initiate the fluorescence emissions from nitrogen
molecules in air. The UV-light is emitted isotropically and can be used for
observing the longitudinal development of extensive air showers in the
atmosphere over tenth of kilometers. This measurement technique is
well-established since it is exploited for many decades by several cosmic ray
experiments. However, a fundamental aspect of the air shower analyses is the
description of the fluorescence emission in dependence on varying atmospheric
conditions. Different fluorescence yields affect directly the energy scaling of
air shower reconstruction. In order to explore the various details of the
nitrogen fluorescence emission in air, a few experimental groups have been
performing dedicated measurements over the last decade. Most of the
measurements are now finished. These experimental groups have been discussing
their techniques and results in a series of Air Fluorescence Workshops
commenced in 2002. At the 8 Air Fluorescence Workshop 2011, it was
suggested to develop a common way of describing the nitrogen fluorescence for
application to air shower observations. Here, first analyses for a common
treatment of the major dependences of the emission procedure are presented.
Aspects like the contributions at different wavelengths, the dependence on
pressure as it is decreasing with increasing altitude in the atmosphere, the
temperature dependence, in particular that of the collisional cross sections
between molecules involved, and the collisional de-excitation by water vapor
are discussed.Comment: 12 pages, 17 figures, 2 tables, International Symposium on Future
Directions in UHECR Physics, 13-16 February 2012, CERN, Geneva (Switzerland);
the updated version corrects for a typo in Eq. (1
From QCD lattice calculations to the equation of state of quark matter
We describe two-flavor QCD lattice data for the pressure at finite
temperature and zero chemical potential within a quasiparticle model. Relying
only on thermodynamic selfconsistency, the model is extended to nonzero
chemical potential. The results agree with lattice calculations in the region
of small chemical potential.Comment: 5 eps figure
Chromophoric azo reagents for amino acid and peptide labeling
Four carboxylic azo dyes are presented as new markers with spectroscopic absorption peaks ranging from 400 to 500 nm for amino acid and peptide labeling at their N-terminus. Labeling can also be performed at side chain residues as it is exemplified with lysine and serine.Fundação para a Ciência e Tecnologia
Quark matter in compact stars?
Ozel, in a recent reanalysis of EXO 0748-676 observational data
(astro-ph/0605106), concluded that quark matter probably does not exist in the
center of compact stars. We show that the data is actually consistent with the
presence of quark matter in compact stars.Comment: 4 pages, LaTeX; New title and overall rewrite to reflect version
published in Nature. Conclusions unchange
Strange quark matter in explosive astrophysical systems
Explosive astrophysical systems, such as supernovae or compact star binary
mergers, provide conditions where strange quark matter can appear. The high
degree of isospin asymmetry and temperatures of several MeV in such systems may
cause a transition to the quark phase already around saturation density.
Observable signals from the appearance of quark matter can be predicted and
studied in astrophysical simulations. As input in such simulations, an equation
of state with an integrated quark matter phase transition for a large
temperature, density and proton fraction range is required. Additionally,
restrictions from heavy ion data and pulsar observation must be considered. In
this work we present such an approach. We implement a quark matter phase
transition in a hadronic equation of state widely used for astrophysical
simulations and discuss its compatibility with heavy ion collisions and pulsar
data. Furthermore, we review the recently studied implications of the QCD phase
transition during the early post-bounce evolution of core-collapse supernovae
and introduce the effects from strong interactions to increase the maximum mass
of hybrid stars. In the MIT bag model, together with the strange quark mass and
the bag constant, the strong coupling constant provides a parameter
to set the beginning and extension of the quark phase and with this the mass
and radius of hybrid stars.Comment: 6 pages, 5 figures, talk given at the International Conference on
Strangeness in Quark Matter (SQM2009), Buzios, Brasil, September 28 - October
2, 2009, to be published in Journal Phys.
Comparaciones indirectas en los informes de evaluación de medicamentos en la web del grupo GENESIS de la SEFH
An active comparator was present in 95% of the 337 analysed reports; 50% included a
direct comparative study vs comparator. In 114 reports (34%), an IC was used; 69% of the ICs
were made by the report author. Most ICs were narrative and none were adjusted. An IC could
have been made in an additional 16% of the cases and possibly in 24% more.
Conclusions: Most evaluated drugs have an active comparator but studies comparing them
directly are not as common. ICs could be included in more reports along with quality control
criteria.
© 2011 SEFH. Publishe
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