1,772 research outputs found
A Study of the LXeGRIT Detection Efficiency for MeV Gamma-Rays during the 2000 Balloon Flight Campaign
LXeGRIT - Liquid Xenon Gamma-Ray Imaging Telescope - is the first prototype
of a Compton telescope for \MeV \g-ray astrophysics based on a LXe time
projection chamber. One of the most relevant figures of merit for a Compton
telescope is the detection efficiency for \g-rays, which depends on diverse
contributions such as detector geometry and passive materials, trigger
efficiency, dead time, etc. A detailed study of the efficiency of the LXeGRIT
instrument, based both on laboratory measurements and Monte Carlo simulations,
is presented in this paper.Comment: 20 pages, 15 figures; submitted to NIM
Compton Imaging of MeV Gamma-Rays with the Liquid Xenon Gamma-Ray Imaging Telescope (LXeGRIT)
The Liquid Xenon Gamma-Ray Imaging Telescope (LXeGRIT) is the first
realization of a liquid xenon time projection chamber for Compton imaging of
MeV gamma-ray sources in astrophysics. By measuring the energy deposit and the
three spatial coordinates of individual gamma-ray scattering points, the
location of the source in the sky is inferred with Compton kinematics
reconstruction. The angular resolution is determined by the detector's energy
and spatial resolutions, as well as by the separation in space between the
first and second scattering. The imaging response of LXeGRIT was established
with gamma-rays from radioactive sources, during calibration and integration at
the Columbia Astrophysics Laboratory, prior to the 2000 balloon flight mission.
In this paper we describe in detail the various steps involved in imaging
sources with LXeGRIT and present experimental results on angular resolution and
other parameters which characterize its performance as a Compton telescope.Comment: 22 pages, 20 figures, submitted to NIM
Gator: a low-background counting facility at the Gran Sasso Underground Laboratory
A low-background germanium spectrometer has been installed and is being
operated in an ultra-low background shield (the Gator facility) at the Gran
Sasso underground laboratory in Italy (LNGS). With an integrated rate of ~0.16
events/min in the energy range between 100-2700 keV, the background is
comparable to those of the world's most sensitive germanium detectors. After a
detailed description of the facility, its background sources as well as the
calibration and efficiency measurements are introduced. Two independent
analysis methods are described and compared using examples from selected sample
measurements. The Gator facility is used to screen materials for XENON, GERDA,
and in the context of next-generation astroparticle physics facilities such as
DARWIN.Comment: 14 pages, 6 figures, published versio
Note sulla didattica del progetto
RIFLESSIONI SUL PROGETTO ARCHITETTONICO DALLE ESPERIENZE DI ALCUNI DOCENTI DELLA FACOLTĂ DI ARCHITETTURA DI PALERM
Design and Performance of the XENON10 Dark Matter Experiment
XENON10 is the first two-phase xenon time projection chamber (TPC) developed
within the XENON dark matter search program. The TPC, with an active liquid
xenon (LXe) mass of about 14 kg, was installed at the Gran Sasso underground
laboratory (LNGS) in Italy, and operated for more than one year, with excellent
stability and performance. Results from a dark matter search with XENON10 have
been published elsewhere. In this paper, we summarize the design and
performance of the detector and its subsystems, based on calibration data using
sources of gamma-rays and neutrons as well as background and Monte Carlo
simulations data. The results on the detector's energy threshold, energy and
position resolution, and overall efficiency show a performance that exceeds
design specifications, in view of the very low energy threshold achieved (<10
keVr) and the excellent energy resolution achieved by combining the ionization
and scintillation signals, detected simultaneously
Embedded Through-Section shear strengthening technique using steel and CFRP bars in RC beams of different percentage of existing stirrups
The Embedded Through-Section (ETS) technique is a promising technique for the shear strengthening of
existing (RC) elements. According to this technique, holes are drilled through the beam section, and bars of steel
or FRP material are introduced into these holes and bonded to the concrete with adhesive materials. An
experimental program was carried out with RC T-cross section beams strengthened in shear using the ETS steel
bars and ETS CFRP rods. The research is focused on the evaluation of the ETS efficiency on beams with
different percentage of existing internal transverse reinforcement (Ïsw=0.0%, Ïsw=0.1% and Ïsw=0.17%). The
effectiveness of different ETS strengthening configurations was also investigated. The good bond between the
strengthening ETS bars and the surrounding concrete allowed the yield initiation of the ETS steel bars and the
attainment of high tensile strains in the ETS CFPR rods, leading to significant increase of shear capacity, whose
level was strongly influenced by the inclination of the ETS bars and the percentage of internal transverse
reinforcement.The authors wish to acknowledge Elletipi S.r.l. (Ferrara, Italy) for supporting the experimental program, Interbau
S.r.l. (Milano, Italy) for applying the ETS strengthening system, BASF company Italy for providing the CFRP
rods and the ENDIF Geomatic Group (University of Ferrara, Italy) for monitoring the experimental program, as
well as the support provided by FCT (PTDC/ECM/114511/2009). The authors wish also acknowledge the
Engineering Department of the University of Ferrara for its financial support
RC beams strengthened in shear using the Embedded Through-Section technique: experimental results and analytical formulation
The Embedded Through-Section (ETS) is a recent strengthening technique that has been developed to retrofit existing
reinforced concrete (RC) elements with shear reinforcement deficiencies. This technique is based on the execution of holes
drilled through the element cross section, in which steel or fiber reinforced polymer (FRP) bars are inserted and bonded to the
surrounding concrete with an epoxy adhesive. An experimental program was carried out with RC T-cross section beams
strengthened in shear using steel ETS bars. The influence of the inclination and shear strengthening ratio of ETS on the shear
strengthening efficiency was evaluated, as well as the interaction of ETS bars with existing steel stirrups. Two different
analytical models are presented in this paper in order to calculate the contribution of ETS to shear resistance. The first model
follows an empirical approach (experimental-based approach), while the second model takes into account the physical and
mechanical principles of the technique (mechanical-based approach). The predictive performance of both models is assessed
by using the experimental results.The authors wish to acknowledge the support provided by the CutInov project QREN n. 38780 supported by ADI, and by the Engineering Department of the University of Ferrara
The contribution of legal medicine in clinical risk management
Background: In advanced health services, a main objective is to promote the culture of safety and clinical risk management. In this regard, the reporting of sentinel events fits within a perspective of error analysis, attempting to propose solutions aimed at preventing a new occurrence of the harmful event. The purpose of this study is to analyze the contribution of medico-legal litigation in the management of clinical risk and to propose an organizational model so as to coordinate the intervention of clinical risk management and medico-legal services. Methods: Retrospective review of 206 cases of medico-legal litigation, settled against a Hospital of a North-eastern city in Italy from January 1, 2014 and December 31, 2015. Results: Approximately 20% of cases, that are classifiable as "sentinel events", were not reported due to various factors. The reason that these events are under-reported is mainly due to the latency between the event itself and its manifestation as a serious damage to health as well as the discomfort in reporting the events of this kind, which is still widespread among healthcare workers. The systematic research of the available documentation for medico-legal purposes permits the acquisition of more information concerning the clinical event, thereby increasing the number and accuracy of the reports to the clinical risk unit. Conclusion: The analysis of medico-legal litigation is a valid tool to enhance the reporting of "sentinel events". One possible proposal is the implementation of an organizational model to establish a rapid procedure for the reporting of sentinel events during the evaluation of medico-legal litigations
Detection of Noble Gas Scintillation Light with Large Area Avalanche Photodiodes (LAAPDs)
Large Area Avalanche Photodiodes (LAAPDs) were used for a series of
systematic measurements of the scintillation light in Ar, Kr, and Xe gas.
Absolute quantum efficiencies are derived. Values for Xe and Kr are consistent
with those given by the manufacturer. For the first time we show that argon
scintillation (128 nm) can be detected at a quantum efficiency above 40%.
Low-pressure argon gas is shown to emit significant amounts of non-UV
radiation. The average energy expenditure for the creation of non-UV photons in
argon gas at this pressure is measured to be below 378 eV.Comment: 16 pages, 7 figure
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