Damped and sub-damped Lyman-α absorbers in z > 4 QSOs

We present the results of a survey of damped (DLA, log N(H I) > 20.3) and sub-damped Lyman-α systems (19.5 2.55 along the lines-of-sight to 77 quasars with emission redshifts in the range 4 19.5 were detected of which 40 systems are damped Lyman-α systems for an absorption length of ΔX = 378. About half of the lines of sight of this homogeneous survey have never been investigated for DLAs. We study the evolution with redshift of the cosmological density of the neutral gas and find, consistent with previous studies at similar resolution, that Ω_(DLA,HI) decreases at z > 3.5. The overall cosmological evolution of Ω_(HI) shows a peak around this redshift. The H I column density distribution for log N(H I) ≥ 20.3 is fitted, consistent with previous surveys, with a single power-law of index α ~ −1.8 ± 0.25. This power-law overpredicts data at the high-end and a second, much steeper, power-law (or a gamma function) is needed. There is a flattening of the function at lower H I column densities with an index of α ~ −1.4 for the column density range log N(H I) = 19.5−21. The fraction of H I mass in sub-DLAs is of the order of 30%. The H I column density distribution does not evolve strongly from z ~ 2.5 to z ~ 4.5

Aproveitamento sustentável de recursos geotérmicos no campo geotérmico da Ribeira Grande, São Miguel, Açores

ABSTRACT: The use of geothermal resources for power production on São Miguel Island has almost 40 years of accumulated experience. In the last decade, the stable power output from Pico Vermelho and Ribeira Grande geothermal plants have been providing up to 44% of the electricity needs of São Miguel Island. Throughout the history of the project, EDA RENOVÁVEIS has been carefully monitoring the Ribeira Grande reservoir conditions and well discharges to assess the resource response to the production load. The results from the last 10 years of monitoring data indicate that production did not cause any significant impact on the reservoir pressure or temperature and it can be maintained in the long-term without the risk of over-exploiting the geothermal resource.RESUMO: O uso de recursos geotérmicos para produção de eletricidade na ilha de São Miguel tem quase 40 anos de experiência acumulada. Na última década, a estabilidade da produção das centrais geotérmicas do Pico Vermelho e da Ribeira Grande tem garantido até 44% das necessidades de energia elétrica da ilha de São Miguel. Ao longo da história do projeto, a EDA RENOVÁVEIS tem promovido a monitorização do reservatório geotérmico da Ribeira Grande, bem como dos parâmetros de produção dos poços geotérmicos, com vista a avaliar a resposta do recurso ao esforço de exploração. Os resultados dos últimos 10 anos de monitorização indicam que a exploração do recurso geotérmico não causou impacto significativo quer na pressão, quer na temperatura do reservatório, prevendo-se que esta poderá manter-se a longo prazo sem o risco de sobre-exploração do recurso geotérmico.info:eu-repo/semantics/publishedVersio

Experimental observation of quantum entanglement in low dimensional spin systems

We report macroscopic magnetic measurements carried out in order to detect and characterize field-induced quantum entanglement in low dimensional spin systems. We analyze the pyroborate MgMnB_2O_5 and the and the warwickite MgTiOBO_3, systems with spin 5/2 and 1/2 respectively. By using the magnetic susceptibility as an entanglement witness we are able to quantify entanglement as a function of temperature and magnetic field. In addition, we experimentally distinguish for the first time a random singlet phase from a Griffiths phase. This analysis opens the possibility of a more detailed characterization of low dimensional materials

Comparison of 120Sn(6He,6He)120Sn and 120Sn(alpha,alpha)120Sn elastic scattering and signatures of the 6He neutron halo in the optical potential

Cross sections of $^{120}$Sn($\alpha$,$\alpha$)$^{120}$Sn elastic scattering have been extracted from the $\alpha$ particle beam contamination of a recent $^{120}$Sn($^6$He,$^6$He)$^{120}$Sn experiment. Both reactions are analyzed using systematic double folding potentials in the real part and smoothly varying Woods-Saxon potentials in the imaginary part. The potential extracted from the $^{120}$Sn($^6$He,$^6$He)$^{120}$Sn data may be used as the basis for the construction of a simple global $^6$He optical potential. The comparison of the $^6$He and $\alpha$ data shows that the halo nature of the $^6$He nucleus leads to a clear signature in the reflexion coefficients $\eta_L$: the relevant angular momenta $L$ with $\eta_L \gg 0$ and $\eta_L \ll 1$ are shifted to larger $L$ with a broader distribution. This signature is not present in the $\alpha$ scattering data and can thus be used as a new criterion for the definition of a halo nucleus.Comment: 13 pages, 7 figures, accepted for publication in Phys. Rev.

Controle da brusone nas folhas de arroz de terras altas em resposta ao tratamento de sementes e época de plantio.

O presente trabalho objetivou estudar a influência da época de plantio e tratamento de sementes em duas cultivares melhoradas de arroz de terras altas e uma linhagem promissora.bitstream/CNPAF/18764/1/pqfoco55.pd

Influência da época de plantio no controle da brusone em folhas de arroz de terras altas.

O presente trabalho objetivou estudar a influencia da época de plantio, da cultivar e do tratamento de sementes sobre a severidade da brusone nas folhas das novas cultivares de terras altas, melhoradas para alta qualidade de grãos.bitstream/item/59066/1/Foco-56.pd

Cosmic String Wakes in Scalar-Tensor Gravities

The formation and evolution of cosmic string wakes in the framework of a scalar-tensor gravity are investigated in this work. We consider a simple model in which cold dark matter flows past an ordinary string and we treat this motion in the Zel'dovich approximation. We make a comaprison between our results and previous results obtained in the context of General Relativity. We propose a mechanism in which the contribution of the scalar field to the evolution of the wakes may lead to a cosmological observation.Comment: Replaced version to be published in the Classical and Quantum Gravit