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 indivíduos geneticamente predispostos, o desenvolvimento do estado de insulino-resistência. Neste estado, são necessárias concentrações de insulina mais elevadas para que se obtenha uma normal resposta metabólica nos tecidos-alvo, ocasionando o desenvolvimento de hiperinsulinismo. Em consequência da multiplicidade de acções da insulina, a insulino-resistência está associada a disfunção de vários tecidos,orgãos e sistemas (Síndrome X), tendo por consequência, entre outras, um aumento do risco de patologia vascular aterosclerótica. Neste artigo, são revistas as alterações a nível do controlo da pressão arterial, endotélio vascular, metabolismo lipídico e sistema fibrinolítico, consequentes ao estado de insulino resistência e a forma como, junto com o hiperinsulinismo, aceleram o processo da aterogénese. São, igualmente, abordadas algumas das armas terapêuticas capazes de combater aquele estado e, assim, reduzir a morbilidade e mortalidade associadas à 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 $\chi^2$ analysis of neutron elastic scattering data off $^{40}$Ca, $^{90}$Zr and $^{208}$Pb at energies $E \approx 5-40$ 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