Hypernuclear structure with the new Nijmegen potentials

Information on level density for nuclei with mass numbers A?20250 is deduced from discrete low-lying levels and neutron resonance data. The odd-mass nuclei exhibit in general 47 times the level density found for their neighboring even-even nuclei at the same excitation energy. This excess corresponds to an entropy of ?1.7kB for the odd particle. The value is approximately constant for all midshell nuclei and for all ground state spins. For these nuclei it is argued that the entropy scales with the number of particles not coupled in Cooper pairs. A simple model based on the canonical ensemble theory accounts qualitatively for the observed properties.

Spin polarized neutron matter and magnetic susceptibility within the Brueckner-Hartree-Fock approximation

The Brueckner-Hartree-Fock formalism is applied to study spin polarized neutron matter properties. Results of the total energy per particle as a function of the spin polarization and density are presented for two modern realistic nucleon-nucleon interactions, Nijmegen II and Reid93. We find that the dependence of the energy on the spin polarization is practically parabolic in the full range of polarizations. The magnetic susceptibility of the system is computed. Our results show no indication of a ferromagnetic transition which becomes even more difficult as the density increases.

Delta(1232) isobar excitations and the ground state of nuclei

The influence of Delta isobar components on the ground-state properties of nuclear systems is investigated for nuclear matter as well as finite nuclei. Many-body wave functions, including isobar configurations and binding energies, are evaluated employing the framework of the coupled-cluster theory. It is demonstrated that the effect of isobar configurations depends in a rather sensitive way on the model used for the baryon-baryon interaction. As examples for realistic baryon-baryon interactions with explicit inclusion of isobar channels we use the local (V28) and nonlocal meson-exchange potentials (Bonn2000) but also a model recently developed by the Salamanca group, which is based on a quark picture. The differences obtained for the nuclear observables are related to the treatment of the interaction, the pi-exchange contributions in particular, at high momentum transfers.

Estimation of temperature effects on fission barriers

An accurate mass formula at finite temperature has been used to obtain a more precise estimation of temperature effects on fission barriers calculated within the liquid drop model.

Antikaon potential in hot and dense matter

The antikaon optical potential in hot and dense nuclear matter is studied within the framework of a coupled-channel self-consistent calculation taking, as bare meson-baryon interaction, the meson-exchange potential of the Jlich group. Typical conditions found in heavy-ion collisions at GSI are explored. As in the case of zero temperature, the angular momentum components larger than L=0 contribute significantly to the finite temperature antikaon optical potential at finite momentum. It is found that the particular treatment of the medium effects has a strong influence on the behavior of the antikaon potential with temperature. Our self-consistent model, in which antikaons and pions are dressed in the medium, gives a moderately temperature dependent antikaon potential which remains attractive at GSI temperatures, contrary to what one finds if only nuclear Pauli blocking effects are included.

Tres arquetips d'inversors en els mercats de valors. Retorn a Keynes

En el present treball, es descriuen tres arquetips d'inversors: l'inversor motivat per l'optimització del seu risc, l'inversor amb esperit d'empresa i l'inversor especulador i intuïtiu, també anomenat irracional. Aquestes modalitats d'inversió es troben presents en el mercat de valors i es poden analitzar i sistematitzar teòricament. El predomini d'aquestes modalitats d'inversió varia segons les èpoques. La bombolla financera és un exemple de predomini de l'inversor irracional i especulatiu. Al final de l'article es mostra com J.M.Keynes va anticipar cada una d'aquestes modalitats d'inversió.

Una nova subespàcie de Pedicularis pyrenaica J. Gay (Scrophulariaceae) als Pirineus Centrals

A new subspecies of Pedicularis pyrenaica J. Gay (Scrophulariaceae) in Central Pyrenees. We describe a new subspecies of Pedicularis pyrenaica (P. pyrenaica subsp. praetermissa) from the Central Pyrenees, which differs from the typical in the shape of the upper lip of the corolla (fusiform, attenuated in a conical beak), as for the larger size of the corolla and the whole plant. We add several comments on the morphological characterization and the habitat of the plant in relation to close taxa

Sobre els trets distintius dels sòls mediterranis

En aquest article es revisen els components de la fertilitat dels sòls mediterramis i es discuteix les seves característiques generals, així com la suposada oligotrofia que sovint se'ls ha atribuït. La tipologia d'aquests sòls i els cicles del N i P presenten alguns trets comuns que vénen determinats per trobar-se en n règim de clima mediterrani, tanmateix existeixen diferències remarcables que es relacionen, sobretot, amb el tipus de roca mare i que expliquen les diferències sovint atribuïdes als sòls de les cinc regions mediterrànies

La diversitat liquènica de Catalunya i Andorra. Estat dels nostres coneixements i propostes per millorar-los

The diversity of lichens of Catalonia and Andorra. The state of the question and proposals to complete our knowledge. After a selection of bibliographical sources, the authors analyse the current level of the knowledge of the lichenic flora of Catalonia and Andorra. Having in mind this situation, they propose some objectives aimed to an optimum field research, as a first step towards a balanced and reasonably complete knowledge of the lichenic biodiversity of the area