80 research outputs found
Three-body vs. dineutron approach to two-neutron radiative capture in He
The low-energy behavior of the strength function for the soft dipole
excitation in He is studied theoretically. Use of very large basis sizes
and well-grounded extrapolation procedures allows to move to energies as small
as 1 keV, at which the low-energy asymptotic behavior of the E1 strength
function seems to be achieved. It is found that the low-energy behavior of the
strength function is well described in the effective three-body "dynamical
dineutron model". The astrophysical rate for the ++He+ is calculated. Comparison with the previous calculations is
performed.Comment: 6 pages, 9 figure
Spin-dependent effective interactions for halo nuclei
We discuss the spin-dependence of the effective two-body interactions
appropriate for three-body computations. The only reasonable choice seems to be
the fine and hyperfine interactions known for atomic electrons interacting with
the nucleus. One exception is the nucleon-nucleon interaction imposing a
different type of symmetry. We use the two-neutron halo nucleus 11Li as
illustration. We demonstrate that models with the wrong spin-dependence are
basically without predictive power. The Pauli forbidden core and valence states
must be consistently treated.Comment: TeX file, 6 pages, 3 postscript figure
Isovector soft dipole mode in 6Be
By using the 1H(6Li,6Be)n charge-exchange reaction, continuum states in 6Be
were populated up to E_t=16 MeV, E_t being the 6Be energy above its three-body
decay threshold. In kinematically complete measurements performed by detecting
alpha+p+p coincidences, an E_t spectrum of high statistics was obtained,
containing approximately ~5x10^6 events. The spectrum provides detailed
correlation information about the well-known 0^+ ground state of 6Be at
E_t=1.37 MeV and its 2^+ state at E_t=3.05 MeV. Moreover, a broad structure
extending from 4 to 16 MeV was observed. It contains negative parity states
populated by Delta L=1 angular momentum transfer without other significant
contributions. This structure can be interpreted as a novel phenomenon, i.e.
the isovector soft dipole mode associated with the 6Li ground state. The
population of this mode in the charge-exchange reaction is a dominant
phenomenon for this reaction, being responsible for about 60% of the cross
section obtained in the measured energy range.Comment: 8 pages, 7 figure
Laser processing effect on magnetic properties of amorphous wires
A study was conducted to observe the laser processing effects on the magnetic properties of amorphous wires. Weekly interacting heterogeneous structures with different magnetic properties were formed by the local annealing by argon laser. Favourable changes were observed due to the creation of local stresses and structural interfaces
Radiative capture and electromagnetic dissociation involving loosely bound nuclei: the B example
Electromagnetic processes in loosely bound nuclei are investigated using an
analytical model. In particular, electromagnetic dissociation of B is
studied and the results of our analytical model are compared to numerical
calculations based on a three-body picture of the B bound state. The
calculation of energy spectra is shown to be strongly model dependent. This is
demonstrated by investigating the sensitivity to the rms intercluster distance,
the few-body behavior, and the effects of final state interaction. In contrast,
the fraction of the energy spectrum which can be attributed to E1 transitions
is found to be almost model independent at small relative energies. This
finding is of great importance for astrophysical applications as it provides us
with a new tool to extract the E1 component from measured energy spectra. An
additional, and independent, method is also proposed as it is demonstrated how
two sets of experimental data, obtained with different beam energy and/or
minimum impact parameter, can be used to extract the E1 component.Comment: Submitted to Phys. Rev. C. 10 pages, 7 figure
Kelvin-Helmholtz Instability Associated With Reconnection and Ultra Low Frequency Waves at the Ground: A Case Study
The Kelvin-Helmholtz instability (KHI) and its effects relating to the transfer of energy and mass from the solar wind into the magnetosphere remain an important focus of magnetospheric physics. One such effect is the generation of Pc4-Pc5 ultra low frequency (ULF) waves (periods of 45–600 s). On July 3, 2007 at ∼ 0500 magnetic local time the Cluster space mission encountered Pc4 frequency Kelvin-Helmholtz waves (KHWs) at the high latitude magnetopause with signatures of persistent vortices. Such signatures included bipolar fluctuations of the magnetic field normal component associated with a total pressure increase and rapid change in density at vortex edges; oscillations of magnetosheath and magnetospheric plasma populations; existence of fast-moving, low-density, mixed plasma; quasi-periodic oscillations of the boundary normal and an anti-phase relation between the normal and parallel components of the boundary velocity. The event occurred during a period of southward polarity of the interplanetary magnetic field according to the OMNI data and THEMIS observations at the subsolar point. Several of the KHI vortices were associated with reconnection indicated by the Walén relation, the presence of deHoffman-Teller frames, field-aligned ion beams observed together with bipolar fluctuations in the normal magnetic field component, and crescent ion distributions. Global magnetohydrodynamic simulation of the event also resulted in KHWs at the magnetopause. The observed KHWs associated with reconnection coincided with recorded ULF waves at the ground whose properties suggest that they were driven by those waves. Such properties were the location of Cluster’s magnetic foot point, the Pc4 frequency, and the solar wind conditions.publishedVersio
Matériel didactique pour les cours pratiques et les séminaires au sujet de la " Sécurité du travail dans le secteur médical" pour les étudiants de la 2ème année de la spécialité "Médecine"(niveau de formation du master)
Le but de l'enseignement de la discipline "Sécurité du travail dans le secteur médical" est la formation des futurs professionnels des connaissances et des compétences nécessaires pour assurer la gestion de la sécurité du travail efficace dans le secteur médical et la création de conditions favorables de l'environnement de travail et de la sécurité dans le secteur en vertu de la législation en vigueur et d'autres actes juridiques réglementaires, correspondant aux objectifs finaux de l'étude de la discipline en conformité avec "Standard de la formation supérieure" du cours "222. Médecine.
Theoretical study of the two-proton halo candidate Ne including contributions from resonant continuum and pairing correlations
With the relativistic Coulomb wave function boundary condition, the energies,
widths and wave functions of the single proton resonant orbitals for Ne
are studied by the analytical continuation of the coupling constant (ACCC)
approach within the framework of the relativistic mean field (RMF) theory.
Pairing correlations and contributions from the single-particle resonant
orbitals in the continuum are taken into consideration by the resonant
Bardeen-Cooper-Schrieffer (BCS) approach, in which constant pairing strength is
used. It can be seen that the fully self-consistent calculations with NL3 and
NLSH effective interactions mostly agree with the latest experimental
measurements, such as binding energies, matter radii, charge radii and
densities. The energy of 2s orbital is slightly higher than that
of orbital, and the occupation probability of the
2s orbital is about 20%, which are in accordance with the
shell model calculation and three-body model estimation
Asymptotic normalization coefficients for 8B->7Be+p from a study of 8Li->7Li+n
Asymptotic normalization coefficients (ANCs) for 8Li->7Li+n have been
extracted from the neutron transfer reaction 13C(7Li,8Li)12C at 63 MeV. These
are related to the ANCs in 8B->7Be+p using charge symmetry. We extract ANCs for
8B that are in very good agreement with those inferred from proton transfer and
breakup experiments. We have also separated the contributions from the p_1/2
and p_3/2 components in the transfer. We find the astrophysical factor for the
7Be(p,gamma)8B reaction to be S_17(0)=17.6+/-1.7 eVb. This is the first time
that the rate of a direct capture reaction of astrophysical interest has been
determined through a measurement of the ANCs in the mirror system.Comment: 5 pages, 3 figures, 2 table
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