569 research outputs found
Distribution spatio-temporelle des précipitations de type PMP utilisant un modèle de champ de pluie : application en Suisse
Les précipitations maximales probables (PMP) représentent les pluies extrêmes les plus élevées raisonnablement possibles (période de retour d'environ 10'000 ans) qui sont notamment utilisées pour dimensionner des barrages contre des crues extrêmes. En Suisse, ces précipitations sont représentées sous forme des cartes avec une résolution horizontale de 2 km. Cet article présente la méthode nécessaire pour utiliser les cartes de type PMP dans le but final d'estimer la crue maximale probable (PMF) pour les barrages. Cette méthode a été développée suite aux problèmes rencontrés avec une application inadéquate des PMP. Ces problèmes peuvent être résolus par la distribution spatio-temporelle des PMP avec une résolution affinée conservant les données physiques. La conception de la méthode de distribution spatio-temporelle des précipitations se base sur la création de champ de pluie. Cette méthode a été validée en s'appuyant sur des évènements extrêmes de type supercellulaire et confirme la possibilité de reproduire des structures réelles de pluie en utilisant un algorithme de champ de pluie
Early in vitro selection of eutypine-tolerant plantlets. Application to screening of Vitis vinifera cv. Ugni lanc somaclones
Research Not
Electronic structure and magnetic properties of epitaxial FeRh(001) ultra-thin films on W(100)
Epitaxial FeRh(100) films (CsCl structure, thick), prepared
{\it in-situ} on a W(100) single crystal substrate, have been investigated via
valence band and core level photoemission. The presence of the
temperature-induced, first-order, antiferromagnetic to ferromagnetic
(AF FM) transition in these films has been verified via linear
dichroism in photoemission from the Fe 3 levels. Core level spectra indicate
a large moment on the Fe atom, practically unchanged in the FM and AF phases.
Judging from the valence band spectra, the metamagnetic transition takes place
without substantial modification of the electronic structure. In the FM phase,
the spin-resolved spectra compare satisfactorily to the calculated
spin-polarized bulk band structure.Comment: 7 pages, 5 figure
Microscopic calculations of double and triple Giant Resonance excitation in heavy ion collisions
We perform microscopic calculations of the inelastic cross sections for the
double and triple excitation of giant resonances induced by heavy ion probes
within a semicalssical coupled channels formalism. The channels are defined as
eigenstates of a bosonic quartic Hamiltonian constructed in terms of collective
RPA phonons. Therefore, they are superpositions of several multiphonon states,
also with different numbers of phonons and the spectrum is anharmonic. The
inclusion of (n+1) phonon configurations affects the states whose main
component is a n-phonon one and leads to an appreacible lowering of their
energies. We check the effects of such further anharmonicities on the previous
published results for the cross section for the double excitation of Giant
Resonances. We find that the only effect is a shift of the peaks towards lower
energies, the double GR cross section being not modified by the explicity
inclusion of the three-phonon channels in the dynamical calculations. The
latters give an important contribution to the cross section in the triple GR
energy region which however is still smaller than the experimental available
data. The inclusion of four phonon configurations in the structure calculations
does not modify the results.Comment: Revtex4, to be published in PR
Purification of plasma membrane vesicles from Vitis vinifera cv. Gamay suspension cells by free electrophoresis
Research Not
Evaluation des différentes lois statistiques pour l'estimation des précipitations journalières extrêmes en Suisse
Les précipitations journalières extrêmes centennales ont été estimées à partir de six lois statistiques différentes effectuées sur des séries de mesures pluviométriques à 151 endroits en Suisse pour deux périodes de 50 ans. Ces estimations ont été comparées avec les valeurs journalières maximales mesurées durant les 100 dernières années (1911-2010) afin de tester l’efficacité de ces six lois. Cette comparaison révèle que la loi de Gumbel avec la méthode du maximum de vraisemblance et la loi Log-Normale sont globalement les meilleures pour estimer les précipitations journalières centennales en Suisse alors que les lois Normale et de Weibull les
sous-estiment le plus fortement par rapport aux valeurs journalières maximales mesurées de 1911 à 2010. Mais la loi de Gumbel avec les méthodes des moments et des moindres carrés serait la plus efficace avec celle de Fréchet pour estimer les précipitations journalières centennales dans le futur si l’augmentation des précipitations journalières maximales mesurée de 1911 à 2010 devait se poursuivre
Anharmonic vibrations in nuclei
In this letter, we show that the non-linearitites of large amplitude motions in atomic nuclei induce giant quadrupole and monopole vibrations. As a consequence, the main source of anharmonicity is the coupling with configurations including one of these two giant resonances on top of any state. Two-phonon energies are often lowered by one or two MeV because of the large matrix elements with such three phonon configurations. These effects are studied in two nuclei, 40Ca and 208Pb
New antineutrino energy spectra predictions from the summation of beta decay branches of the fission products
In this paper, we study the impact of the inclusion of the recently measured
beta decay properties of the Tc, Mo, and
Nb nuclei in an updated calculation of the antineutrino energy spectra
of the four fissible isotopes U, and Pu. These
actinides are the main contributors to the fission processes in Pressurized
Water Reactors. The beta feeding probabilities of the above-mentioned Tc, Mo
and Nb isotopes have been found to play a major role in the component
of the decay heat of Pu, solving a large part of the
discrepancy in the 4 to 3000\,s range. They have been measured using the Total
Absorption Technique (TAS), avoiding the Pandemonium effect. The calculations
are performed using the information available nowadays in the nuclear
databases, summing all the contributions of the beta decay branches of the
fission products. Our results provide a new prediction of the antineutrino
energy spectra of U, Pu and in particular of U for
which no measurement has been published yet. We conclude that new TAS
measurements are mandatory to improve the reliability of the predicted spectra.Comment: 10 pages, 2 figure
Nuclear break-up of 11Be
The break-up of 11Be was studied at 41AMeV using a secondary beam of 11Be
from the GANIL facility on a 48Ti target by measuring correlations between the
10Be core, the emitted neutrons and gamma rays. The nuclear break-up leading to
the emission of a neutron at large angle in the laboratory frame is identified
with the towing mode through its characteristic n-fragment correlation. The
experimental spectra are compared with a model where the time dependent
Schrodinger equation (TDSE) is solved for the neutron initially in the 11 Be. A
good agreement is found between experiment and theory for the shapes of neutron
experimental energies and angular distributions. The spectroscopic factor of
the 2s orbital is tentatively extracted to be 0.46+-0.15. The neutron emission
from the 1p and 1d orbitals is also studied
A non-perturbative approach to halo breakup
The theory of weakly bound cluster breakup, like halo nucleus breakup, needs
an accurate treatment of the transitions from bound to continuum states induced
by the nuclear and Coulomb potentials. When the transition probability is not
very small, a non-perturbative framework might be necessary. Nuclear excitation
dominates at small impact parameters whereas the Coulomb potential being long
range acts over a larger impact parameter interval. In this article, we propose
an effective breakup amplitude which meets a number of requirements necessary
for an accurate quantitative description of the breakup reaction mechanism.
Furthermore our treatment gives some insight on the interplay between time
dependent perturbation theory and sudden approximation and it allows to include
the nuclear and Coulomb potentials to all orders within an eikonal-like
framework.Comment: 22 Latex pages, 1 table, 8 eps figures. Accepted for publication on
Nucl. Phys.
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