62 research outputs found
Role of Fragment Higher Static Deformations in the Cold Binary Fission of Cf
We study the binary cold fission of Cf in the frame of a cluster
model where the fragments are born to their respective ground states and
interact via a double-folded potential with deformation effects taken into
account up to multipolarity . The preformation factors were
neglected. In the case when the fragments are assumed to be spherical or with
ground state quadrupole deformation, the -value principle dictates the
occurence of a narrow region around the double magic Sn, like in the
case of cluster radioactivity. When the hexadecupole deformation is turned on,
an entire mass-region of cold fission in the range 138 - 156 for the heavy
fragment arise, in agreement with the experimental observations.
This fact suggests that in the above mentioned mass-region, contrary to the
usual cluster radioactivity where the daughter nucleus is always a
neutron/proton (or both) closed shell or nearly closed shell spherical nucleus,
the clusterization mechanism seems to be strongly influenced by the
hexadecupole deformations rather than the -value.Comment: 10 pages, 12 figure
Shift of the 2 state of Be in the ternary cold fission of Cf
Recent experimental data indicate that in the ternary cold fission of
Cf the energy of the first excited state of the accompanying light
cluster Be is decreased by an amount ranging between 6 and 26
keV. A model is proposed to calculate the shift of the vibrational 2
state in Be when its heavy companions are the even-even nuclei
Ba and Sr. The stiffness parameters of the -vibrations
are calculated within the self-consistent Hartree-Fock method with BCS pairing
correlations taken into account, and its change is determined by the
interaction of the light cluster with the heavy fragments. The results are
pointing to a dependence of the shift magnitude and signature on the relative
distance between the three clusters and their mutual orientation. Eventually it
is the anharmonic perturbation of the spherical vibrator which is responsible
for obtaining a negative energy shift of the 2 state.Comment: 4 pages, 3 figure
Ternary configuration in the framework of inverse mean-field method
A static scission configuration in cold ternary fission has been considered
in the framework of mean field approach. The inverse scattering method is
applied to solve single-particle Schroedinger equation, instead of constrained
selfconsistent Hartree-Fock equations. It is shown, that it is possible to
simulate one-dimensional three-center system via inverse scattering method in
the approximation of reflectless single-particle potentials.Comment: 8 pages, 1 figure, iopart.cls, to be published in Int.J.Mod.Phys.
Microscopic Enhancement of Heavy-Element Production
Realistic fusion barriers are calculated in a macroscopic-microscopic model
for several soft-fusion heavy-ion reactions leading to heavy and superheavy
elements. The results obtained in such a realistic picture are very different
from those obtained in a purely macroscopic model. For reactions on 208:Pb
targets, shell effects in the entrance channel result in fusion-barrier
energies at the touching point that are only a few MeV higher than the ground
state for compound systems near Z = 110. The entrance-channel fragment-shell
effects remain far inside the touching point, almost to configurations only
slightly more elongated than the ground-state configuration, where the fusion
barrier has risen to about 10 MeV above the ground-state energy. Calculated
single-particle level diagrams show that few level crossings occur until the
peak in the fusion barrier very close to the ground-state shape is reached,
which indicates that dissipation is negligible until very late in the fusion
process. Whereas the fission valley in a macroscopic picture is several tens of
MeV lower in energy than is the fusion valley, we find in the
macroscopic-microscopic picture that the fission valley is only about 5 MeV
lower than the fusion valley for soft-fusion reactions leading to compound
systems near Z = 110. These results show that no significant
``extra-extra-push'' energy is needed to bring the system inside the fission
saddle point and that the typical reaction energies for maximum cross section
in heavy-element synthesis correspond to only a few MeV above the maximum in
the fusion barrier.Comment: 7 pages. LaTeX. Submitted to Zeitschrift fur Physik A. 5 figures not
included here. Complete preprint, including device-independent (dvi),
PostScript, and LaTeX versions of the text, plus PostScript files of the
figures, available at http://t2.lanl.gov/publications/publications.html or at
ftp://t2.lanl.gov/pub/publications/mehe
Potential energy surfaces of superheavy nuclei
We investigate the structure of the potential energy surfaces of the
superheavy nuclei 258Fm, 264Hs, (Z=112,N=166), (Z=114,N=184), and (Z=120,N=172)
within the framework of self-consistent nuclear models, i.e. the
Skyrme-Hartree-Fock approach and the relativistic mean-field model. We compare
results obtained with one representative parametrisation of each model which is
successful in describing superheavy nuclei. We find systematic changes as
compared to the potential energy surfaces of heavy nuclei in the uranium
region: there is no sufficiently stable fission isomer any more, the importance
of triaxial configurations to lower the first barrier fades away, and
asymmetric fission paths compete down to rather small deformation. Comparing
the two models, it turns out that the relativistic mean-field model gives
generally smaller fission barriers.Comment: 8 pages RevTeX, 6 figure
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Education and training programmes for infection prevention and control professionals: mapping the current opportunities and local needs in European countries.
BACKGROUND: Studies have repeatedly highlighted the need for homogenisation of training content and opportunities in infection prevention and control (IPC) across European countries.
OBJECTIVES: To map current training opportunities for IPC professionals, define local needs and highlight differences, across 11 European countries (Cyprus, France, England, Germany, Greece, Italy, Netherlands, Poland, Romania, Spain, Switzerland).
SOURCES: From July 2018 to February 2019, IPC experts directly involved in IPC training and education in their countries and/or internationally were invited to complete a prespecified set of questions in order to provide a detailed description of IPC training opportunities and needs in their country.
CONCLUSIONS: IPC training among nurses and doctors varies greatly across countries, with differences in content and type of training (e.g., standardised curriculum, educational programme, clinical experience) duration, as well as in assessment and recognition/accreditation. The observed heterogeneity in IPC training between European countries can be eliminated through establishment of interdisciplinary region-wide training programmes, with common learning objectives, shared know-how and supported by national and international professional bodies
Toward understanding the post-collisional evolution of an orogen influenced by convergence at adjacent plate margins; Late Cretaceous-Tertiary thermotectonic history of the Apuseni Mountains
The relationship between syn- to post-collisional orogenic shortening and stresses transmitted from other neighboring plate boundaries is important for understanding the kinematics of mountain belts, but has received little attention so far. The Apuseni Mountains are an example of an orogen in the interference zone between two other subduction systems located in the external Carpathians and Dinarides. This interference is demonstrated by the results of a combined thermochronological and structural field study that quantifies the post-collisional latest Cretaceous-Tertiary evolution. The exhumation history derived from apatite fission track and (U-Th)/He thermochronology indicates that the present-day topography of the Apuseni Mountains originates mainly from latest Cretaceous times, modified by two tectonic pulses during the Paleogene. The latter are suggested by cooling ages clustering around ∼45 Ma and ∼30 Ma and the associated shortening recorded along deep-seated fault systems. Paleogene exhumation pulses are similar in magnitude (∼3.5 km) and are coeval with the final collisional phases recorded in the Dinarides and with part of the Carpathian rotation around the Moesian promontory. These newly quantified Paleogene exhumation and shortening pulses contradict the general view of tectonic quiescence, subsidence and overall sedimentation for this time interval. The Miocene collapse of the Pannonian Basin did not induce significant regional exhumation along the western Apuseni flank, nor did the subsequent Carpathian collision. This is surprising in the overall context of Pannonian Basin formation and its subsequent inversion, in which the Apuseni Mountains were previously interpreted as being significantly uplifted in both deformation stages. Copyright 2011 by the American Geophysical Union
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