4,254 research outputs found
Detection of C3O in the low-mass protostar Elias 18
We have performed new laboratory experiments which gave us the possibility to
obtain an estimate of the amount of carbon chain oxides (namely C3O2, C2O, and
C3O) formed after irradiation (with 200 keV protons) of pure CO ice, at 16 K.
The analysis of laboratory data indicates that in dense molecular clouds, when
high CO depletion occurs, an amount of carbon chain oxides as high as 2-3x10^-3
with respect to gas phase carbon monoxide can be formed after ion irradiation
of icy grain mantles. Then we have searched for gas phase C2O and C3O towards
ten low-mass young stellar objects. Among these we have detected the C3O line
at 38486.891 MHz towards the low-mass protostar Elias 18. On the basis of the
laboratory results we suggest that in dense molecular clouds gas phase carbon
chain oxides are formed in the solid phase after cosmic ion irradiation of
CO-rich icy mantles and released to the gas phase after desorption of icy
mantles. We expect that the Atacama Large Millimeter Array (ALMA), thanks to
its high sensitivity and resolution, will increase the number of carbon chain
oxides detected in dense molecular clouds.Comment: 19 Pages, 5 figures, Accepted to Ap
Garigliano nuclear power plant: seismic evaluation of the turbine building
The Italian Garigliano Nuclear Power Plant (NPP) started its energy production in 1963. At present it is in the decommissioning stage. In order to get a proper management of the radioactive waste that will be produced during the dismantling operations it has been considered convenient to convert the turbine building of the plant into a temporary waste repository. This decision posed a remarkable seismic safety assessment issue. As a matter of fact, the challenge was to extend, in satisfactory safety conditions, the use of an important facility that has reached the end of its designed lifetime and to have this extended use approved by nuclear safety agencies. In this context many tasks have been accomplished, of which the most important are:
(a) a new appraisal of site seismic hazard;
(b) the execution of many investigations and testing on the
construction materials;
(c) the set up of a detailed 3D finite element model including the explicit representation of foundation piles and soil;
(d) consideration of soil structure kinematic and dynamic nteraction effects.
This paper describes the adopted seismic safety assessment criteria which are based on a performance objectives design approach. While performance based design is the approach currently recommended by European Regulations to manage seismic risk and it is fully incorporated in the Italian code for conventional buildings, bridges and plants, NPP are not explicitly considered. Therefore it was necessary to delineate a consistent interpretation of prescribed rules in order to properly select the maximum and operating design earthquakes on one side and corresponding acceptable limit states on the other side. The paper further provides an outline of the numerical analyses carried out, of the main results obtained and of the principal retrofitting actions that will be realized
Adult lifelong learning and counselling in life transitions: Challenges for universities.
The paper aims to explore the implications of university lifelong learning on professional and personal transitions (and micro-transitions) and the role of adult counselling in supporting and facilitating them. This is a challenge for Italian Universities as national rules are being implemented in the perspective of a National Lifelong Learning System. In recent decades in Europe different research has analysed the phase betwee
3C 33: another case of photoionized soft X-ray emission in radio galaxies
All the observations available in the Chandra and XMM-Newton archives have
been used to investigate the X-ray spectral properties of 3C 33. In this paper
is presented a complete X-ray analysis of the nuclear emission of this narrow
line radio galaxy. The broad band spectrum of 3C 33 is complex. The hard part
resembles that of Seyfert 2 galaxies, with a heavily obscured nuclear continuum
(N_H~10^23 cm^-2) and a prominent Fe Kalpha line. This represents the nuclear
radiation directly observed in transmission through a cold circumnuclear gas.
On the other hand an unabsorbed continuum plus emission lines seem to fit well
the soft part of the spectrum (0.5-2 keV) suggesting that the jet does not
significantly contribute to the X-ray emission. We discuss the possible
collisional or photoionized origin of the gas that emits the soft X-ray lines.
Our results, strengthened by optical spectroscopy favor the photoionization
scenario.Comment: 7 pages, 5 figures, accepted for publication in A&
Precise half-life measurement of 110Sn and 109In isotopes
The half-lives of 110Sn and 109In isotopes have been measured with high
precision. The results are T1/2 =4.173 +- 0.023 h for 110Sn and T1/2 = 4.167
+-0.018 h for 109In. The precision of the half-lives has been increased by a
factor of 5 with respect to the literature values which makes results of the
recently measured 106Cd(alpha,gamma)110Sn and 106Cd(alpha,p)109In cross
sections more reliable.Comment: 3 pages, 2 figures, accepted for publication in Phys. Rev C as brief
repor
Plasma density profile characterization for resonant plasmawakefield acceleration experiment at SPARC-LAB
Photometry of the Oort Cloud comet C/2009 P1(Garradd): pre-perihelion observations at 5.7 and 2.5 AU
The aim of this paper is to contribute to the characterization of the general properties of the Long Period Comets (LPCs) family, and in particular to report on the dust environment of comet C/2009 P1 (Garradd).
The comet was observed at two epochs pre-perihelion, at ~6 AU and at ~2.5 AU: broad-band images have been used to investigate its coma morphology and properties and to model the dust production rate.
Comet C/2009 P1 (Garradd) is one of the most active and âdust producingâ LPCs ever observed, even at the large heliocentric distance rh~6 AU. Its coma presents a complex morphology, with subtle structures underlying the classical fan-shaped tail, and, at rh~2.5 AU, also jet-like structures and spiralling outflows. In the reference aperture of radius Ï=5°Ă104 km, the R-AfÏ is 3693±156 cm and 6368±412 cm, in August 2010 (rh~6 AU) and July 2011 (rh~2.5 AU), respectively. The application of a first order photometric model, under realistic assumptions on grain geometric albedo, power-law dust size distribution, phase darkening function and grain dust outflow velocity, yielded a measure of the dust production rate for the two epochs of observation of Qd=7.27Ă102 kg/s and Qd=1.37Ă103 kg/s, respectively, for a reference outflow dust velocity of vsmall=25 m/s for small (0.1â10 ”m) grains and vlarge=1 m/s for large (10 ”mâ1 cm) grains.
These results suggest that comet Garradd is one of the most active minor bodies observed in recent years, highly contributing to the continuous replenishment of the Interplanetary Dust Complex also in the outer Solar System, and pose important constraints on the mechanism(s) driving the cometary activity at large heliocentric distances
A collimation system for ELI-NP Gamma Beam System - design and simulation of performance
The purpose of this study was to evaluate the performance and refine the design of the collimation system for the gamma radiation source (GBS) currently being realised at ELI-NP facility. The gamma beam, produced by inverse Compton scattering, will provide a tunable average energy in the range between 0.2 and 20Ă MeV, an energy bandwidth 0.5% and a flux of about 108Ă photons/s. As a result of the inverse Compton interaction, the energy of the emitted radiation is related to the emission angle, it is maximum in the backscattering direction and decreases as the angle increase [1,2]. Therefore, the required energy bandwidth can be obtained only by developing a specific collimation system of the gamma beam, i.e. filtering out the radiation emitted at larger angles. The angular acceptance of the collimation for ELI-NP-GBS must be continuously adjustable in a range from about 700 to 60Ă ĂÂŒrad, to obtain the required parameters in the entire energy range. The solution identified is a stack of adjustable slits, arranged with a relative rotation around the beam axis to obtain an hole with an approximately circular shape. In this contribution, the final collimation design and its performance evaluated by carrying out a series of detailed Geant4 simulations both of the high-energy and the low-energy beamline are presented
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