Instabilities in asymmetric nuclear matter

The existence of phase transitions from liquid to gas phases in asymmetric nuclear matter (ANM) is related with the instability regions which are limited by the spinodals. In this work we investigate the instabilities in ANM described within relativistic mean field hadron models, both with constant and density dependent couplings at zero and finite temperatures. In calculating the proton and neutron chemical potentials we have used an expansion in terms of Bessel functions that is convenient at low densities. The role of the isovector scalar $\delta$-meson is also investigated in the framework of relativistic mean field models and density dependent hadronic models. It is shown that the main differences occur at finite temperature and large isospin asymmetry close to the boundary of the instability regions.Comment: 13 pages, 5 figures; to appear in Phys. Rev.

Análises genéticas aplicadas à seleção de búfalos (Bubalus bubalis) para carne de qualidade.

A carne de búfalo é considerada um alimento nobre, tanto pelo seu valor nutricional, como pelos aspectos sensoriais extremamente desejáveis. A utilização de técnicas de biologia molecular nos estudos de genoma bubalino permite identificar indivíduos com genótipos favoráveis para a produção de carne. Dentre os genes de interesse para programas de melhoramento genético de bubalinos podemos citar o gene da leptina, associado a características de interesse pecuário como a deposição de gordura na carcaça, produção de leite, capacidade de consumo, conversão alimentar, bem como características reprodutivas. O objetivo do presente trabalho foi caracterizar e selecionar pares de primers para PCR-RFLP provenientes de estudos do genoma bubalino para o gene da leptina. Três pares de iniciadores foram desenhados com base na sequência da região promotora e exon 1 do gene da leptina bubalina depositada no Genbank (AY495586), para a amplificação por PCR de fragmentos a partir do DNA genômico extraído de sangue bubalino. A visualização do produto amplificado pela eletroforese em gel de agarose indicou que a PCR realizada com o primer LEPTBU1 apresentou banda bem definida de 474 pb, sem bandas inespecíficas. Em resumo, o primer LEPTBU1 é sensível e específico para identificar e caracterizar o fragmento do gene da leptina em bubalinos

RPA approach to rotational symmetry restoration in a three-level Lipkin model

We study an extended Lipkin-Meshkov-Glick model that permits a transition to a deformed phase with a broken continuous symmetry. Unlike simpler models, one sees a persistent zero-frequency Goldstone mode past the transition point into the deformed phase. We found that the RPA formula for the correlation energy provides a useful correction to the Hartree-Fock energy when the number of particle N satisfies N > 3, and becomes accurate for large N. We conclude that the RPA correlation energy formula offers a promising way to improve the Hartree-Fock energy in a systematic theory of nuclear binding energies.Comment: RevTex, 11 pages, 3 postscript figure

Radiocarbon and blue optically stimulated luminescence chronologies of the Oitavos consolidated dune (Western Portugal)

The dune of Oitavos, the underlying paleosol, and Helix sp. gastropod shells found within the paleosol were dated using a combination of radiocarbon and blue optically stimulated luminescence (OSL). The organic component of the paleosol produced a significantly older age (~20,000 cal BP) than the OSL age measurement (~15,000 yr), while 14C age measurements on the inorganic component and the gastropods produced ages of ~35,000 yr and ~34,000 yr, respectively. Rare-earth element analyses provide evidence that the gastropods incorporate geological carbonate, making them an unreliable indicator of the age of the paleosol. We propose that the 14C age of the small organic component of the paleosol is also likely to be unreliable due to incorporation of residual material. The OSL age measurement of the upper paleosol (~15,000 yr) is consistent with the age for the base of the dune (~14,500 yr). The younger OSL age for the top of the dune (~12,000 yr) suggests that it was built up by at least 2 sand pulses or that there was a remobilization of material at the top during its evolution, prior to consolidation

Monitoring natural organic matter in surface water by UV spectroscopy : effects of calcium, magnesium and pH value

The aim of this study was to evaluate the effects of dissolved magnesium and calcium ions on the determination of humic substances in water by spectrophotometry at 254 nm. Quantifications were carried out for different pH values, both with and without filtration of the samples. The smallest effects were observed for unfiltered samples and neutral pH values.Fundação para a Ciência e a Tecnologia (FCT) - Project POCI-2010, measure IV.3 and reference n.º SFRH / BD / 18565 / 2004