11,283 research outputs found
Asymptotic normalization of mirror states and the effect of couplings
Assuming that the ratio between asymptotic normalization coefficients of
mirror states is model independent, charge symmetry can be used to indirectly
extract astrophysically relevant proton capture reactions on proton-rich nuclei
based on information on stable isotopes. The assumption has been tested for
light nuclei within the microscopic cluster model. In this work we explore the
Hamiltonian independence of the ratio between asymptotic normalization
coefficients of mirror states when deformation and core excitation is
introduced in the system. For this purpose we consider a phenomenological rotor
+ N model where the valence nucleon is subject to a deformed mean field and the
core is allowed to excite. We apply the model to 8Li/8B, 13C/13N, 17O/17F,
23Ne/23Al, and 27Mg/27P. Our results show that for most studied cases, the
ratio between asymptotic normalization coefficients of mirror states is
independent of the strength and multipolarity of the couplings induced. The
exception is for cases in which there is an s-wave coupled to the ground state
of the core, the proton system is loosely bound, and the states have large
admixture with other configurations. We discuss the implications of our results
for novae.Comment: 8 pages, 2 figures, submitted to PR
Insulin Resistance and Atherosclerosis
O tipo de vida nas sociedades ocidentais favorece, nos indivĂduos geneticamente predispostos, o desenvolvimento do estado de insulino-resistĂȘncia. Neste estado, sĂŁo necessĂĄrias concentraçÔes de insulina mais elevadas para que se obtenha uma normal resposta metabĂłlica nos tecidos-alvo, ocasionando o desenvolvimento de hiperinsulinismo. Em consequĂȘncia da multiplicidade de acçÔes da insulina, a insulino-resistĂȘncia estĂĄ associada a disfunção de vĂĄrios tecidos,orgĂŁos e sistemas (SĂndrome X), tendo por consequĂȘncia, entre outras, um aumento do risco de patologia vascular aterosclerĂłtica. Neste artigo, sĂŁo revistas as alteraçÔes a nĂvel do controlo da
pressĂŁo arterial, endotĂ©lio vascular, metabolismo lipĂdico e sistema fibrinolĂtico, consequentes ao estado de insulino resistĂȘncia e a forma como, junto com o hiperinsulinismo, aceleram o processo da aterogĂ©nese. SĂŁo, igualmente, abordadas algumas das armas terapĂȘuticas capazes de
combater aquele estado e, assim, reduzir a morbilidade e mortalidade associadas Ă aterosclerose
Energy dependence of non-local potentials
Recently a variety of studies have shown the importance of including
non-locality in the description of reactions. The goal of this work is to
revisit the phenomenological approach to determining non-local optical
potentials from elastic scattering. We perform a analysis of neutron
elastic scattering data off Ca, Zr and Pb at energies MeV, assuming a Perey and Buck or Tian, Pang, and Ma non-local
form for the optical potential. We introduce energy and asymmetry dependencies
in the imaginary part of the potential and refit the data to obtain a global
parameterization. Independently of the starting point in the minimization
procedure, an energy dependence in the imaginary depth is required for a good
description of the data across the included energy range. We present two
parameterizations, both of which represent an improvement over the original
potentials for the fitted nuclei as well as for other nuclei not included in
our fit. Our results show that, even when including the standard Gaussian
non-locality in optical potentials, a significant energy dependence is required
to describe elastic-scattering data.Comment: 6 pages, 3 figures, accepted by Phys. Rev. C Rapid Communicatio
Temperature dependence of the coercive field in single-domain particle systems
The magnetic properties of Cu97Co3 and Cu90Co10 granular alloys were measured
over a wide temperature range (2 to 300K). The measurements show an unusual
temperature dependence of the coercive field. A generalized model is proposed
and explains well the experimental behavior over a wide temperature range. The
coexistence of blocked and unblocked particles for a given temperature rises
difficulties that are solved here by introducing a temperature dependent
blocking temperature. An empirical factor gamma arise from the model and is
directly related to the particle interactions. The proposed generalized model
describes well the experimental results and can be applied to other
single-domain particle system.Comment: 7 pages, 8 figures, revised version, accepted to Physical Review B on
29/04/200
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