Magicity of the 52^{52}Ca and 54^{54}Ca isotopes and tensor contribution within a mean--field approach

We investigate the magicity of the isotopes $^{52}$Ca and $^{54}$Ca, that was recently confirmed by two experimental measurements, and relate it to like--particle and neutron--proton tensor effects within a mean--field description. By analyzing Ca isotopes, we show that the like--particle tensor contribution induces shell effects that render these nuclei more magic than they would be predicted by neglecting it. In particular, such induced shell effects are stronger in the nucleus $^{52}$Ca and the single--particle gaps are increased in both isotopes due to the tensor force. By studying $N=32$ and $N=34$ isotones, neutron--proton tensor effects may be isolated and their role analyzed. It is shown that neutron--proton tensor effects lead to increasing $N=32$ and $N=34$ gaps, when going along isotonic chains, from $^{58}$Fe to $^{52}$Ca, and from $^{60}$Fe to $^{54}$Ca, respectively. The mean--field calculations are perfomed by employing one Skyrme parameter set, that was introduced in a previous work by fitting the tensor parameters together with the spin--orbit strength. The signs and the values of the tensor strengths are thus checked within this specific application. The obtained results indicate that the employed parameter set, even if generated with a partial adjustment of the parameters of the force, leads to the correct shell behavior and provides, in particular, a description of the magicity of $^{52}$Ca and $^{54}$Ca within a pure mean--field picture with the effective two--body Skyrme interaction.Comment: 7 figure

The Metaphysics of Free Will: A Critique of Free Won’t as Double Prevention

The problem of free will is deeply linked with the causal relevance of mental events. The causal exclusion argument claims that, in order to be causally relevant, mental events must be identical to physical events. However, Gibb has recently criticized it, suggesting that mental events are causally relevant as double preventers. For Gibb, mental events enable physical effects to take place by preventing other mental events from preventing a behaviour to take place. The role of mental double preventers is hence similar to what Libet names free won’t, namely the ability to veto an action initiated unconsciously by the brain. In this paper I will propose an argument against Gibb’s account, the causal irrelevance argument, showing that Gibb’s proposal does not overcome the objection of systematic overdetermination of causal relevance, because mental double preventers systematically overdetermine physical double preventers, and therefore mental events are causally irrelevant

Primordial Magnetic Fields and Electroweak Baryogenesis

In this contribution we will shortly review the main mechanism through which primordial magnetic fields may affect the electroweak baryogenesis. It is shown that although strong magnetic fields might enhance the strength of the electroweak phase transition, no benefit is found for baryogenesis once the effect of the field on the sphaleron rate is taken into account. The possible role of hypermagnetic helicity for the electroweak baryogenesis is shortly discussed.Comment: 10 pages, 1 fig. Plenary talk presented at the COSMO99 Conference, Trieste, Italy, 27 Sept - 3 Oct, 199

Importance of Lipid Composition in the Membrane Dynamics of Urothelial Umbrella Cells

The studies on membrane dynamics in urinary bladder umbrella cells were focused on proteins as important factors for maintaining the permeability barrier and their role as pathways modulators for the discoidal/fusiform endocytic vesicles which is one of the main features of the umbrella cells. However, our workgroup has dedicated to the study of lipid membrane composition and its biological impact in the urothelium. We first studied the lipid membrane composition of rat urothelium modified my dietary treatments differentiated in their fatty acid composition. Changes of lipid composition were related to the asymmetric unit membrane organization and permeability. Finally, we observed that the lipid composition was critically related to the intracellular pathways of discoidal/fusiform endocytic vesicles and their content. The purpose of this communication is to summarize the importance of lipids in the membrane organization and permeability of the apical plasma membrane and endocytic vesicles of umbrella cells.Fil: Grasso, Ernesto Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Química Biológica de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Centro de Investigaciones en Química Biológica de Córdoba; Argentin

CR electrons and positrons: what we have learned in the latest three years and future perspectives

After the PAMELA finding of an increasing positron fraction above 10 GeV, the experimental evidence for the presence of a new electron and positron spectral component in the cosmic ray zoo has been recently confirmed by Fermi-LAT. We show that a simple phenomenological model which assumes the presence of a primary electron and positron extra component allows a consistent description of all available data sets. We then describe the most relevant astrophysical uncertainties which still prevent to determine the electron+positron source properties from those data and the perspectives of forthcoming experiments.Comment: 10 pages, 4 figures, Proceeding of the 3th ICATPP Conference on Astroparticle, Particle, Space Physics and Detectors for Physics Applications, Villa Olmo (Como), 3-7 October 2011

Mediterranean agriculture under climate change: adaptive capacity, adaptation, and ethics

In the coming decades, the Mediterranean region is expected to experience various climate impacts with negative consequences on agricultural systems and which will cause uneven reductions in agricultural production. By and large, the impacts of climate change on Mediterranean agriculture will be heavier for southern areas of the region. This unbalanced distribution of negative impacts underscores the significance and role of ethics in such a context of analysis. Consequently, the aim of this article is to justify and develop an ethical approach to agricultural adaptation in the Mediterranean and to derive the consequent implications for adaptation policy in the region. In particular, we define an index of adaptive capacity for the agricultural systems of the Mediterranean region on whose basis it is possible to group its different sub-regions, and we provide an overview of the suitable adaptation actions and policies for the sub-regions identified. We then vindicate and put forward an ethical approach to agricultural adaptation, highlighting the implications for the Mediterranean region and the limitations of such an ethical framework. Finally, we emphasize the broader potential of ethics for agricultural adaptation policy

Diffusion of Ultra High Energy Protons in Galaxy Clusters and Secondary X and Gamma Ray Emissions

In this work we simulate the propagation of Ultra High Energy (UHE) protons in the magnetised intergalactic medium of Galaxy Clusters (GCs). Differently from previous works on the subject, we trace proton trajectories in configurations of the Intra Cluster Magnetic Field (ICMF) which have been extracted from a constrained Magnetic-SPH simulation of the local universe. Such an approach allows us to take into account the effects of several features of the ICMFs, e.g. irregular geometrical structure and field fluctuations due to merger shocks,which cannot be investigated analitically or with usual numerical simulations. Furthermore, we are able to simulate a set of clusters which have properties quite similar to those of GCs observed in the nearby universe. We estimate the time that UHE protons take to get out of the clusters and found that in the energy range 5\times 10^{18} \simleq E \simleq 3 \times 10^{19} \eV proton propagation takes place in the Bohm scattering diffusion regime passing smoothly to a small pitch angle diffusion regime at larger energies. We apply our results to estimate the secondary gamma and Hard X Ray (HXR) emissions produced by UHE protons in a rich GC. We show that the main emission channel is due to the synchrotron HXR radiation of secondary electrons originated by proton photo-pair production scattering onto the CMB. This process may give rise to a detectable signal if a relatively powerful AGN, or a dead quasar, accelerating protons at UHEs is harboured by a rich GC in the local universe.Comment: 27 pages, 13 figure