234 research outputs found
Population of ground and lowest excited states of Sulfur via the dissociative recombination of SH+ in the diffuse interstellar medium
Our previous study on dissociative recombination of ground state SH into
states of SH is extended by taking into account the contribution of
states recently explored by quantum chemistry methods. Multichannel
quantum defect theory is employed for the computation of cross sections and
rate coefficients for dissociative recombination, but also for vibrational
excitation. Furthermore, we produce the atomic yields resulting from
recombination, quantifying the generation of sulfur atoms in their ground
(\mbox{P}) and lowest excited (\mbox{D}) states respectively.Comment: 9 pages, 8 figures, 3 table
Demonstration and Comparison of Operation of Photomultiplier Tubes at Liquid Argon Temperature
Liquified noble gases are widely used as a target in direct Dark Matter
searches. Signals from scintillation in the liquid, following energy deposition
from the recoil nuclei scattered by Dark Matter particles (e.g. WIMPs), should
be recorded down to very low energies by photosensors suitably designed to
operate at cryogenic temperatures. Liquid Argon based detectors for Dark Matter
searches currently implement photo multiplier tubes for signal read-out. In the
last few years PMTs with photocathodes operating down to liquid Argon
temperatures (87 K) have been specially developed with increasing Quantum
Efficiency characteristics. The most recent of these, Hamamatsu Photonics Mod.
R11065 with peak QE up to about 35%, has been extensively tested within the R&D
program of the WArP Collaboration. During these testes the Hamamatsu PMTs
showed superb performance and allowed obtaining a light yield around 7
phel/keVee in a Liquid Argon detector with a photocathodic coverage in the 12%
range, sufficient for detection of events down to few keVee of energy
deposition. This shows that this new type of PMT is suited for experimental
applications, in particular for new direct Dark Matter searches with LAr-based
experiments
Methods for reduced cost and lower sample prep volumes for genetic analysis applications
As the cost of NGS has decreased, the library preparation cost has become a larger portion of the total expenditure. This is especially true for high-throughput applications, such as single-cell analysis. Therefore, there is a need to develop methods that can not only study the transcriptomes of single cells, but can also feasibly analyze large numbers of single cells.
Miniaturizing the sample preparation volume provides the opportunity for significant cost savings. Using TTP Labtech’s mosquito liquid handlers, reagent and sample quantities can be scaled down to picogram values
The flaring blazars of the first 1.5 years of the AGILE mission
We report the AGILE gamma-ray observations and the results of the
multiwavelength campaigns on seven flaring blazars detected by the mission:
During two multiwavelength campaigns, we observed gamma-ray activity from two
Flat Spectrum Radio Quasars of the Virgo region, e.g. 3C 279 and 3C 273 (the
latter being the first extragalactic source simultaneously observed with the
gamma-ray telescope and the hard X ray imager of the mission). Due to the large
FOV of the AGILE/GRID instrument, we achieved an almost continuous coverage of
the FSRQ 3C 454.3. The source showed flux above 10E-6 photons/cm2/s (E > 100
MeV) and showed day by day variability during all the AGILE observing periods.
In the EGRET era, the source was found in high gamma-ray activity only once. An
other blazar, PKS 1510-089 was frequently found in high gamma-ray activity. S5
0716+71, an intermediate BL Lac object, exhibited a very high gamma-ray
activity and fast gamma-ray variability during a period of intense optical
activity. We observed high gamma-ray activity from W Comae, a BL Lac object,
and Mrk 421, an high energy peaked BL Lac object. For this source, a
multiwavelength campaign from optical to TeV has been performed
Detection of Gamma-ray Emission from the Eta-Carinae Region
We present the results of extensive observations by the gamma-ray AGILE
satellite of the Galactic region hosting the Carina nebula and the remarkable
colliding wind binary Eta Carinae (Eta Car) during the period 2007 July to 2009
January. We detect a gamma-ray source (1AGL J1043-5931) consistent with the
position of Eta Car. If 1AGL J1043-5931 is associated with the Eta Car system
our data provide the long sought first detection above 100 MeV of a colliding
wind binary. The average gamma-ray flux above 100 MeV and integrated over the
pre-periastron period 2007 July to 2008 October is F = (37 +/- 5) x 10-8 ph
cm-2 s-1 corresponding to an average gamma-ray luminosity of L = 3.4 x 10^34
erg s-1 for a distance of 2.3 kpc. We also report a 2-day gamma-ray flaring
episode of 1AGL J1043-5931 on 2008 Oct. 11-13 possibly related to a transient
acceleration and radiation episode of the strongly variable shock in the
system.Comment: 5 pages, 4 figure, accepted for publication in ApJ Letter
AGILE detection of delayed gamma-ray emission from GRB 080514B
GRB 080514B is the first gamma ray burst (GRB), since the time of EGRET, for
which individual photons of energy above several tens of MeV have been detected
with a pair-conversion tracker telescope. This burst was discovered with the
Italian AGILE gamma-ray satellite. The GRB was localized with a cooperation by
AGILE and the interplanetary network (IPN). The gamma-ray imager (GRID)
estimate of the position, obtained before the SuperAGILE-IPN localization, is
found to be consistent with the burst position. The hard X-ray emission
observed by SuperAGILE lasted about 7 s, while there is evidence that the
emission above 30 MeV extends for a longer duration (at least ~13 s). Similar
behavior was seen in the past from a few other GRBs observed with EGRET.
However, the latter measurements were affected, during the brightest phases, by
instrumental dead time effects, resulting in only lower limits to the burst
intensity. Thanks to the small dead time of the AGILE/GRID we could assess that
in the case of GRB 080514B the gamma-ray to X-ray flux ratio changes
significantly between the prompt and extended emission phase.Comment: A&A letters, in pres
Multiwavelength observations of 3C 454.3. I. The AGILE 2007 November campaign on the "Crazy Diamond"
[Abridged] We report on a multiwavelength observation of the blazar 3C 454.3
(which we dubbed "crazy diamond") carried out on November 2007 by means of the
astrophysical satellites AGILE, INTEGRAL, Swift, the WEBT Consortium, and the
optical-NIR telescope REM. 3C 454.3 is detected at a level
during the 3-week observing period, with an average flux above 100 MeV of
\phcmsec. The gamma-ray
spectrum can be fit with a single power-law with photon index between 100 MeV and 1 GeV. We detect significant
day-by-day variability of the gamma-ray emission during our observations, and
we can exclude that the fluxes are constant at the 99.6% ()
level. The source was detected typically around 40 degrees off-axis, and it was
substantially off--axis in the field of view of the AGILE hard X-ray imager.
However, a 5-day long ToO observation by INTEGRAL detected 3C 454.3 at an
average flux of about \phcmsec with
an average photon index of between 20--200
keV. Swift also detected 3C 454.3 with a flux in the 0.3--10 keV energy band in
the range \phcmsec{} and a photon index in the
range . In the optical band, both WEBT and REM
show an extremely variable behavior in the band. A correlation analysis
based on the entire data set is consistent with no time-lags between the
gamma-ray and the optical flux variations. Our simultaneous multifrequency
observations strongly indicate that the dominant emission mechanism between 30
MeV and 30 GeV is dominated by inverse Compton scattering of relativistic
electrons in the jet on the external photons from the broad line region.Comment: Accepted for publication in ApJ. Abridged Abstract. 37 pages, 14
Figures, 3 Table
AGILE observation of a gamma-ray flare from the blazar 3C 279
Context. We report the detection by the AGILE satellite of an intense
gamma-ray flare from the gamma-ray source 3EG J1255-0549, associated to the
Flat Spectrum Radio Quasar 3C 279, during the AGILE pointings towards the Virgo
Region on 2007 July 9-13.
Aims. The simultaneous optical, X-ray and gamma-ray covering allows us to
study the spectral energy distribution (SED) and the theoretical models
relative to the flaring episode of mid-July.
Methods. AGILE observed the source during its Science Performance
Verification Phase with its two co-aligned imagers: the Gamma- Ray Imaging
Detector (GRID) and the hard X-ray imager (Super-AGILE) sensitive in the 30 MeV
- 50 GeV and 18 - 60 keV respectively. During the AGILE observation the source
was monitored simultaneously in optical band by the REM telescope and in the
X-ray band by the Swift satellite through 4 ToO observations.
Results. During 2007 July 9-13 July 2007, AGILE-GRID detected gamma-ray
emission from 3C 279, with the source at ~2 deg from the center of the Field of
View, with an average flux of (210+-38) 10^-8 ph cm^-2 s^-1 for energy above
100 MeV. No emission was detected by Super-AGILE, with a 3-sigma upper limit of
10 mCrab. During the observation lasted about 4 days no significative gamma-ray
flux variation was observed.
Conclusions. The Spectral Energy Distribution is modelled with a homogeneous
one-zone Synchrotron Self Compton emission plus the contributions by external
Compton scattering of direct disk radiation and, to a lesser extent, by
external Compton scattering of photons from the Broad Line Region.Comment: Accepted for publication in Astronomy and Astrophysic
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