28,268 research outputs found
Fermi detected blazars seen by INTEGRAL
Multiwavelength observations are essential to constrain physical parameters
of the blazars observed by Fermi/LAT. Among the 187 AGN significantly detected
in public INTEGRAL data above 20 keV by the imager IBIS/ISGRI, 20 blazars were
detected. 15 of these sources allowed significant spectral extraction. They
show hard X-ray spectra with an average photon index of 2.1+-0.1 and a hard
X-ray luminosity of L(20-100 keV) = 1.3e46 erg/s. 15 of the INTEGRAL blazars
are also visible in the first 16 months of the Fermi/LAT data, thus allowing to
constrain the inverse Compton branch in these cases. Among others, we analyse
the LAT data of four blazars which were not included in the Fermi LAT Bright
AGN Sample based on the first 3 months of the mission: QSO B0836+710, H
1426+428, RX J1924.8-2914, and PKS 2149-306. Especially for blazars during
bright outbursts, as already observed simultaneously by INTEGRAL and Fermi
(e.g. 3C 454.3 and Mrk 421), INTEGRAL provides unique spectral coverage up to
several hundred keV. We present the spectral analysis of INTEGRAL and Fermi
data and demonstrate the potential of INTEGRAL observations of Fermi detected
blazars in outburst by analysing the combined data set of the persistent radio
galaxy Cen A.Comment: 5 pages, 5 figures, 2009 Fermi Symposium, eConf Proceedings C09112
Impact of foregrounds on Cosmic Microwave Background maps
We discuss the possible impact of astrophysical foregrounds on three recent
exciting results of Cosmic Microwave Background (CMB) experiments: the WMAP
measurements of the temperature-polarization (TE) correlation power spectrum,
the detection of CMB polarization fluctuations on degree scales by the DASI
experiment, and the excess power on arcminute scales reported by the CBI and
BIMA groups. A big contribution from the Galactic synchrotron emission to the
TE power spectrum on large angular scales is indeed expected, in the lower
frequency WMAP channels, based on current, albeit very uncertain, models; at
higher frequencies the rapid decrease of the synchrotron signal may be, to some
extent, compensated by polarized dust emission. Recent measurements of
polarization properties of extragalactic radio sources at high radio frequency
indicate that their contamination of the CMB polarization on degree scales at
30 GHz is substantially below the expected CMB E-mode amplitude. Adding the
synchrotron contribution, we estimate that the overall foreground contamination
of the signal detected by DASI may be significant but not dominant. The excess
power on arc-min scales detected by the BIMA experiment may be due to
galactic-scale Sunyaev-Zeldovich effects, if the proto-galactic gas is heated
to its virial temperature and its cooling time is comparable to the Hubble time
at the epoch of galaxy formation. A substantial contamination by radio sources
of the signal reported by the CBI group on scales somewhat larger than BIMA's
cannot be easily ruled out.Comment: 10 pages, 5 figures, to appear in proc. int. conf. "Thinking,
Observing and Mining the Universe", Sorrento, Sept. 200
Realization of Universal Optimal Quantum Machines by Projective Operators and Stochastic Maps
Optimal quantum machines can be implemented by linear projective operations.
In the present work a general qubit symmetrization theory is presented by
investigating the close links to the qubit purification process and to the
programmable teleportation of any generic optimal anti-unitary map. In
addition, the contextual realization of the N ->M cloning map and of the
teleportation of the N->(M-N) universal NOT gate is analyzed by a novel and
very general angular momentum theory. An extended set of experimental
realizations by state symmetrization linear optical procedures is reported.
These include the 1->2 cloning process, the UNOT gate and the quantum
tomographic characterization of the optimal partial transpose map of
polarization encoded qubits.Comment: 11 pages, 7 figure
Transient increases in intracellular calcium and reactive oxygen species levels in TCam-2 cells exposed to microgravity
The effects of microgravity on functions of the human body are well described, including alterations in the male and female reproductive systems. In the present study, TCam-2 cells, which are considered a good model of mitotically active male germ cells, were used to investigate intracellular signalling and cell metabolism during exposure to simulated microgravity, a condition that affects cell shape and cytoskeletal architecture. After a 24 hour exposure to simulated microgravity, TCam-2 cells showed 1) a decreased proliferation rate and a delay in cell cycle progression, 2) increased anaerobic metabolism accompanied by increased levels of intracellular Ca(2+), reactive oxygen species and superoxide anion and modifications in mitochondrial morphology. Interestingly, all these events were transient and were no longer evident after 48 hours of exposure. The presence of antioxidants prevented not only the effects described above but also the modifications in cytoskeletal architecture and the activation of the autophagy process induced by simulated microgravity. In conclusion, in the TCam-2 cell model, simulated microgravity activated the oxidative machinery, triggering transient macroscopic cell events, such as a reduction in the proliferation rate, changes in cytoskeleton-driven shape and autophagy activation
Single Superconducting Split-Ring Resonator Electrodynamics
We investigate the microwave electrodynamic properties of a single
superconducting thin film split-ring resonator (SRR). The experiments were
performed in an all-Nb waveguide, with Nb wires and Nb SRRs. Transmission data
showed a high-Q stopband for a single Nb SRR ( at 4.2 K)
below , and no such feature for a Cu SRR, or closed Nb loops, of similar
dimensions. Adding SRRs increased the bandwidth, but decreased the insertion
loss of the features. Placing the Nb SRR into an array of wires produced a
single, elementary negative-index passband ( at 4.2 K).
Changes in the features due to the superconducting kinetic inductance were
observed. Models for the SRR permeability, and the wire dielectric response,
were used to fit the data.Comment: 4 pages, 3 figures, RevTex, submitted to Applied Physics Letters.
Updated version includes mention of bianisotropy, better looking figures, and
different temperature dat
Teleportation scheme implementing contextually the Universal Optimal Quantum Cloning Machine and the Universal Not Gate. Complete experimental realization
By a significant modification of the standard protocol of quantum state
Teleportation two processes ''forbidden'' by quantum mechanics in their exact
form, the Universal NOT gate and the Universal Optimal Quantum Cloning Machine,
have been implemented contextually and optimally by a fully linear method. In
particular, the first experimental demonstration of the Tele-UNOT Gate, a novel
quantum information protocol has been reported (cfr. quant-ph/0304070). A
complete experimental realization of the protocol is presented here.Comment: 11 pages, 3 figure
Compton processes in the bright AGN MCG+8-11-11
We present preliminary results on the hard X-ray emission properties of the
Seyfert 1.5 galaxy MCG+8-11-11 as observed by INTEGRAL and SWIFT. All the
INTEGRAL IBIS/ISGRI data available up to October 2009 have been analyzed
together with two SWIFT/XRT snapshot observations performed in August and
October 2009, quasi-simultaneously to INTEGRAL pointed observations of
MCG+8-11-11. No correlation is observed between the hard X-ray flux and the
spectral slope, while the position of the high-energy cut-off is found to have
varied during the INTEGRAL observations. This points to a change in the
temperature of the Comptonising medium from a minimum value of kT = 30-50 keV
to values larger than 100-150 keV. There is no significant detection of Compton
reflection, with a 3 sigma upper limit of R < 0.2, and no line has been
detected at 112 keV, as previously claimed from HEAT observations (112 keV flux
F < 2.4e-4 ph/cm^2/s). The variability behaviour of MCG+8-11-11 is found to be
similar to that shown by IC 4329A, with different temperatures of the electron
plasma for similar flux levels of the source, while other bright Seyfert
galaxies present different variability patterns at hard X-rays, with spectral
changes correlated to flux variations (e.g. NGC 4151).Comment: 6 pages, 4 figures. Accepted for publication on PoS (contribution
PoS(INTEGRAL 2010)077), proceedings of the 8th INTEGRAL Workshop "The
Restless Gamma-ray Universe" (September 2010, Dublin, Ireland
The BeppoSAX Deep Surveys
We present the preliminary results of a survey that makes use of several deep
exposures obtained with the X-Ray telescopes of the BeppoSAX satellite. The
survey limiting sensitivity is 5 x 10^-14 cgs in the 2-10 keV band and 7 x
10^-14 cgs in the harder 5-10 keV band. We find that the 2-10 keV LogN-LogS is
consistent with that determined in ASCA surveys. The counts in the 5-10 keV
band imply either a very hard average spectral slope or the existence of a
population of heavily absorbed sources that can hardly be detected in soft
X-ray surveys. A sample of 83 serendipitous sources has been compiled from a
systematic search in 50 MECS images. The analysis of the hardness ratio of this
sample also implies very hard or heavily cutoff spectral shapes.Comment: Invited Talk, to appear in : The Active X-ray Sky: Results from
BeppoSAX and Rossi-XTE, Nuclear Physics B Proceedings Supplements, L. Scarsi,
H. Bradt, P. Giommi and F. Fiore (eds.), Elsevier Science B.V. 9 pages LateX
and 8 ps figures, using espcrc2 and epsfi
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