465 research outputs found
Muons tomography applied to geosciences and volcanology
Imaging the inner part of large geological targets is an important issue in
geosciences with various applications. Dif- ferent approaches already exist
(e.g. gravimetry, electrical tomography) that give access to a wide range of
informations but with identified limitations or drawbacks (e.g. intrinsic
ambiguity of the inverse problem, time consuming deployment of sensors over
large distances). Here we present an alternative and complementary tomography
method based on the measurement of the cosmic muons flux attenuation through
the geological structures. We detail the basics of this muon tomography with a
special emphasis on the photo-active detectors.Comment: Invited talk at the 6th conference on New Developments In
Photodetection (NDIP'11), Lyon-France, July 4-8, 2011; Nuclear Instruments
and Methods in Physics Research Section A, 201
Neutron-skin thickness of Pb, and symmetry-energy constraints from the study of the anti-analog giant dipole resonance
The Pb(,) Pb reaction at a beam energy of
30 MeV has been used to excite the anti-analog of the giant dipole resonance
(AGDR) and to measure its -decay to the isobaric analog state in
coincidence with proton decay of IAS. The energy of the transition has also
been calculated with the self-consistent relativistic random-phase
approximation (RRPA), and found to be linearly correlated to the predicted
value of the neutron-skin thickness (). By comparing the
theoretical results with the measured transition energy, the value of 0.190
0.028 fm has been determined for of Pb, in
agreement with previous experimental results. The AGDR excitation energy has
also been used to calculate the symmetry energy at saturation (
MeV) and the slope of the symmetry energy ( MeV), resulting in
more stringent constraints than most of the previous studies.Comment: 6 pages, 5 figures. arXiv admin note: text overlap with
arXiv:1205.232
Level densities and thermodynamical properties of Pt and Au isotopes
The nuclear level densities of Pt and Au below the
neutron separation energy have been measured using transfer and scattering
reactions. All the level density distributions follow the constant-temperature
description. Each group of isotopes is characterized by the same temperature
above the energy threshold corresponding to the breaking of the first Cooper
pair. A constant entropy excess and is observed in
Pt and Au with respect to Pt and Au,
respectively, giving information on the available single-particle level space
for the last unpaired valence neutron. The breaking of nucleon Cooper pairs is
revealed by sequential peaks in the microcanonical caloric curve
Completing the nuclear reaction puzzle of the nucleosynthesis of 92Mo
One of the greatest questions for modern physics to address is how elements
heavier than iron are created in extreme, astrophysical environments. A
particularly challenging part of that question is the creation of the so-called
p-nuclei, which are believed to be mainly produced in some types of supernovae.
The lack of needed nuclear data presents an obstacle in nailing down the
precise site and astrophysical conditions. In this work, we present for the
first time measurements on the nuclear level density and average strength
function of Mo. State-of-the-art p-process calculations systematically
underestimate the observed solar abundance of this isotope. Our data provide
stringent constraints on the NbMo reaction rate,
which is the last unmeasured reaction in the nucleosynthesis puzzle of
Mo. Based on our results, we conclude that the Mo abundance
anomaly is not due to the nuclear physics input to astrophysical model
calculations.Comment: Submitted to PR
Statistical properties of Pu, and Pu(n,) cross section calculation
The level density and gamma-ray strength function (gammaSF) of 243Pu have
been measured in the quasi-continuum using the Oslo method. Excited states in
243Pu were populated using the 242Pu(d,p) reaction. The level density closely
follows the constant-temperature level density formula for excitation energies
above the pairing gap. The gammaSF displays a double-humped resonance at low
energy as also seen in previous investigations of actinide isotopes. The
structure is interpreted as the scissors resonance and has a centroid of
omega_{SR}=2.42(5)MeV and a total strength of B_{SR}=10.1(15)mu_N^2, which is
in excellent agreement with sum-rule estimates. The measured level density and
gammaSF were used to calculate the 242Pu(n,gamma) cross section in a neutron
energy range for which there were previously no measured data.Comment: 9 pages, 8 figure
Carbon fragmentation measurements and validation of the GEANT4 nuclear reaction models for hadrontherapy
Nuclear fragmentation measurements are necessary when using heavy-ion beams in hadrontherapy to predict the effects of the ion nuclear interactions within the human body. Moreover, they are also fundamental to validate and improve the Monte Carlo codes for their use in planning tumor treatments. Nowadays, a very limited set of carbon fragmentation cross sections are being measured, and in particular, to our knowledge, no double-differential fragmentation cross sections at intermediate energies are available in the literature. In this work, we have measured the double-differential cross sections and the angular distributions of the secondary fragments produced in the C-12 fragmentation at 62 A MeV on a thin carbon target. The experimental data have been used to benchmark the prediction capability of the GEANT4 Monte Carlo code at intermediate energies, where it was never tested before. In particular, we have compared the experimental data with the predictions of two GEANT4 nuclear reaction models: the Binary Light Ions Cascade and the Quantum Molecular Dynamic. From the comparison, it has been observed that the Binary Light Ions Cascade approximates the angular distributions of the fragment production cross sections better than the Quantum Molecular Dynamic model. However, the discrepancies observed between the experimental data and the Monte Carlo simulations lead to the conclusion that the prediction capability of both models needs to be improved at intermediate energies
Clinical outcomes in patients treated for coronary in-stent restenosis with drug-eluting balloons: Impact of high platelet reactivity.
BACKGROUND: The impact of high platelet reactivity (HPR) on clinical outcomes after elective percutaneous coronary interventions (PCI) with drug-eluting balloons (DEB) due to in-stent restenosis (ISR) is unknown. OBJECTIVE: We sought to evaluate the prognostic importance of HPR together with conventional risk factors in patients treated with DEB. METHODS: Patients treated with DEB due to ISR were enrolled in a single-centre, prospective registry between October 2009 and March 2015. Only patients with recent myocardial infarction (MI) received prasugrel, others were treated with clopidogrel. HPR was defined as an ADP-test >46U with the Multiplate assay and no adjustments were done based on results. The primary endpoint of the study was a composite of cardiovascular mortality, MI, any revascularization or stroke during one-year follow-up. RESULTS: 194 stable angina patients were recruited of whom 90% were treated with clopidogrel. Clinical characteristics and procedural data were available for all patients; while platelet function testing was performed in 152 subjects of whom 32 (21%) had HPR. Patients with HPR had a higher risk for the primary endpoint (HR: 2.45; CI: 1.01-5.92; p = 0.03). The difference was primarily driven by a higher risk for revascularization and MI. According to the multivariate analysis, HPR remained a significant, independent predictor of the primary endpoint (HR: 2.88; CI: 1.02-8.14; p = 0.04), while total DEB length and statin treatment were other independent correlates of the primary outcome. CONCLUSION: HPR was found to be an independent predictor of repeat revascularization and MI among elective patients with ISR undergoing PCI with DEB
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