Background. Intellectual disability (ID) in patients with chronic kidney disease is a relative contraindication for kidney transplantation. Methods. We analysed a retrospective cohort of 16 ...recipients of kidney transplantation with ID and 83 controls. Results. Graft survival at 5 years was similar between patients (81.2%) and controls (80.2%), P = 0.9. Patient survival at 5 years was lower among patients (81.2% versus 94.4%, P < 0.05). Patients had more infection episodes, but no risk factors were identified. Conclusion. Although recipients with ID have lower long-term patient survival, the equivalent graft survival rates support the indication of renal transplantation in such disability.
The very high energy (VHE; E > 100 GeV) blazar Markarian 501 (Mrk 501) has a well-studied history of extreme spectral variability and is an excellent laboratory for studying the physical processes ...within the jets of active galactic nuclei. However, there are few detailed multiwavelength studies of Mrk 501 during its quiescent state, due to its low luminosity. A short-term multiwavelength study of Mrk 501 was coordinated in 2009 March, focusing around a multi-day observation with the Suzaku X-ray satellite and including Delta *g-ray data from VERITAS, MAGIC, and the Fermi Gamma-ray Space Telescope with the goal of providing a well-sampled multiwavelength baseline measurement of Mrk 501 in the quiescent state. The results of these quiescent-state observations are compared to the historically extreme outburst of 1997 April 16, with the goal of examining variability of the spectral energy distribution (SED) between the two states. The derived broadband SED shows the characteristic double-peaked profile. We find that the X-ray peak shifts by over two orders of magnitude in photon energy between the two flux states while the VHE peak varies little. The limited shift in the VHE peak can be explained by the transition to the Klein-Nishina (KN) regime. Synchrotron self-Compton models are matched to the data and the implied KN effects are explored.
We present results from VERITAS observations of the BL Lac object PG 1553+113 spanning the years 2010, 2011, and 2012. The time-averaged spectrum, measured between 160 and 560 GeV, is well described ...by a power law with a spectral index of 4.33 + or - 0.09. We also present the combined gamma -ray spectrum from the Fermi Large Area Telescope and VERITAS covering an energy range from 100MeV to 560 GeV. The data are well fit by a power law with an exponential cutoff at 101.9 + or - 3.2GeV. Given lower limits to the redshift of z > 0.395 based on optical/UV observations of PG 1553+113, the cutoff would be dominated by EBL absorption. Conversely, the small statistical uncertainties of the VERITAS energy spectrum have allowed us to provide a robust upper limit on the redshift of PG 1553+113 of z < or = 0.62. The light curve measured during the 2012 observing season is marginally inconsistent with a steady flux, giving a xsup 2 probability for a steady flux of 0.03%.
VERITAS has been monitoring the very-high-energy (VHE; > 100 GeV) gamma-ray activity of the radio galaxy M 87 since 2007. During 2008, flaring activity on a timescale of a few days was observed with ...a peak flux of (0.70 + or - 0.16) x 10 super(-11) cm super(-2) s super(-1) at energies above 350 GeV. In 2010 April, VERITAS detected a flare from M 87 with peak flux of (2.71 + or - 0.68) x 10 super(-11) cm super(-2) s super(-1) for E > 350 GeV. The source was observed for six consecutive nights during the flare, resulting in a total of 21 hr of good-quality data. The most rapid flux variation occurred on the trailing edge of the flare with an exponential flux decay time of 0.90 sub(-0.15) super(+0.22) days. The shortest detected exponential rise time is three times as long, at 2.87 sub(-0.99) super(+1.65) days. The quality of the data sample is such that spectral analysis can be performed for three periods: rising flux, peak flux, and falling flux. The spectra obtained are consistent with power-law forms. The spectral index at the peak of the flare is equal to 2.19 + or - 0.07. There is some indication that the spectrum is softer in the falling phase of the flare than the peak phase, with a confidence level corresponding to 3.6 standard deviations. We discuss the implications of these results for the acceleration and cooling rates of VHE electrons in M 87 and the constraints they provide on the physical size of the emitting region.
We report the detection of a new TeV gamma-ray source, VER J0521+211, based on observations made with the VERITAS imaging atmospheric Cherenkov Telescope Array. These observations were motivated by ...the discovery of a cluster of > 30 GeV photons in the first year of Fermi Large Area Telescope observations. VER J0521+211 is relatively bright at TeV energies, with a mean photon flux of (1.93 + or - 0.13 sub(stat) + or - 0.78 sub(sys)) x 10 super(-11) cm super(-2) s super(-1) above 0.2 TeV during the period of the VERITAS observations. The source is strongly variable on a daily timescale across all wavebands, from optical to TeV, with a peak flux corresponding to ~0.3 times the steady Crab Nebula flux at TeV energies. Follow-up observations in the optical and X-ray bands classify the newly discovered TeV source as a BL Lac-type blazar with uncertain redshift, although recent measurements suggest z = 0.108. VER J0521+211 exhibits all the defining properties of blazars in radio, optical, X-ray, and gamma-ray wavelengths.
ABSTRACT
We present optical, X-ray, high-energy (⪅30 GeV) and very high energy (⪆100 GeV; VHE) observations of the high-frequency peaked blazar Mrk 421 taken between 2008 May 24 and June 23. A ...high-energy γ-ray signal was detected by
AGILE
with
between June 9 and 15, with
F
(
E
>100 MeV) = 42
+14
−12
× 10
−8
photons cm
−2
s
−1
. This flaring state is brighter than the average flux observed by EGRET by a factor of ∼3, but still consistent with the highest EGRET flux. In hard X-rays (20–60 keV) SuperAGILE resolved a five-day flare (June 9–15) peaking at ∼55 mCrab. SuperAGILE,
RXTE
/ASM and
Swift
/BAT data show a correlated flaring structure between soft and hard X-rays. Hints of the same flaring behavior are also detected in the simultaneous optical data provided by the GASP-WEBT. A
Swift
/XRT observation near the flaring maximum revealed the highest 2–10 keV flux ever observed from this source, of 2.6 × 10
−9
erg cm
−2
s
−1
(i.e. >100 mCrab). A peak synchrotron energy of ∼3 keV was derived, higher than typical values of ∼0.5–1 keV. VHE observations with MAGIC and VERITAS between June 6 and 8 showed the flux peaking in a bright state, well correlated with the X-rays. This extraordinary set of simultaneous data, covering a 12-decade spectral range, allowed for a deep analysis of the spectral energy distribution as well as of correlated light curves. The γ-ray flare can be interpreted within the framework of the synchrotron self-Compton model in terms of a rapid acceleration of leptons in the jet.
The MAGIC telescope reflecting surface Bigongiari, C.; Bastieri, D.; Galante, N. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
02/2004, Volume:
518, Issue:
1
Journal Article
Peer reviewed
The Major Atmospheric Gamma Imaging Cherenkov telescope will achieve an energy threshold lower than any other present IACT
(E
Th
∼30
Gev)
thanks to the largest reflecting surface, a
17
m
diameter, ...f/1, tessellated parabolic reflector. The tiles are
50
cm×50
cm
all-aluminum spherical mirrors with different radii of curvature to best fit the paraboloid. The technology used to make these mirrors and the method used to measure their optical properties, as the focal length, the spot size and the reflectivity, are described. The results of these measurements are shown.
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