2,272 research outputs found

    Application of the EXtrapolated Efficiency Method (EXEM) to infer the gamma-cascade detection efficiency in the actinide region

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    The study of transfer-induced gamma-decay probabilities is very useful for understanding the surrogate-reaction method and, more generally, for constraining statistical-model calculations. One of the main difficulties in the measurement of gamma-decay probabilities is the determination of the gamma-cascade detection efficiency. In [Nucl. Instrum. Meth. A 700, 59 (2013)] we developed the Extrapolated Efficiency Method (EXEM), a new method to measure this quantity. In this work, we have applied, for the first time, the EXEM to infer the gamma-cascade detection efficiency in the actinide region. In particular, we have considered the 238U(d,p)239U and 238U(3He,d)239Np reactions. We have performed Hauser-Feshbach calculations to interpret our results and to verify the hypothesis on which the EXEM is based. The determination of fission and gamma-decay probabilities of 239Np below the neutron separation energy allowed us to validate the EXEM

    Fragmentation of spherical radioactive heavy nuclei as a novel probe of transient effects in fission

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    Peripheral collisions with radioactive heavy-ion beams at relativistic energies are discussed as an innovative approach for probing the transient regime experienced by fissile systems evolving towards quasi-equilibrium. A dedicated experiment using the advanced technical installations of GSI, Darmstadt, permitted to realize ideal conditions for the investigation of relaxation effects in the meta-stable well. Combined with a highly sensitive experimental signature, it provides a measure of the transient effects with respect to the flux over the fission barrier. Within a two-step reaction process, 45 proton-rich unstable spherical isotopes produced by projectile-fragmentation of a stable 238U beam have been used as secondary projectiles. The fragmentation of the radioactive projectiles on lead results in nearly spherical compound nuclei which span a wide range in excitation energy and fissility. The decay of these excited systems by fission is studied with a dedicated set-up which permits the detection of both fission products in coincidence and the determination of their atomic numbers with high resolution. The width of the fission-fragment nuclear charge distribution is shown to be specifically sensitive to pre-saddle transient effects and is used to establish a clock for the passage of the saddle point. The comparison of the experimental results with model calculations points to a fission delay of (3.3+/-0.7).10-21s for initially spherical compound nuclei, independent of excitation energy and fissility. This value suggests a nuclear dissipation strength at small deformation of (4.5+/-0.5).1021s-1. The very specific combination of the physics and technical equipment exploited in this work sheds light on previous controversial conclusions.Comment: 38 pages, 15 figure

    The Impact of Panay Unified Services for Health Project

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    Recognizing the necessity of good health in the attainment of personal and social welfare, the Panay Unified Services for Health Project exemplifies the emerging concept of health care delivery designed to meet the basic health needs of the poorest rural population. Analysis of collected data in a survey of households in 52 depressed barangays of 21 municipalities in Aklan, Antique, Capiz and Iloilo indicates that emphasis of health care projects on sickness prevention and health education are important to achieve their health care goals. In conjunction to the above, the role of barangay health workers should not be undermined especially their role in educating rural folks regarding health beliefs and practices.health sector

    Contribución al conocimiento del abejaruco común Merops apiaster en la provincia de Sevilla

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    Se describen en este estudio dos colonias de nidificación del abejaruco común Merops apiaster, situadas en diferentes zonas de la provincia de Sevilla. Para el estudio se hace una descripción de las zonas donde se localizan las dos colonias estudiadas y tarnbién se han definido una serie de variables respecto a la disposición y estructura de la galeria de nidificación: disposición del nido sobre el terreno, ejes horizontal y vertical de la galeria de nidificación, distancia horizontal y vertical entre galerias adyacentes, y longitud de la galeria de nidificación. Los resultados obtenidos muestran que la colonia 1 presenta una gran variabilidad en la distribución de las galerías de nidificación con una alta densidad de individuos. En el caso de la colonia 2, presenta homogeneidad en la distribución de las galeria de nidificación, con una baja densidad de población.In the present work, two colonies of bee eaters Merops apiaster, located in different zones of the province of Seviile, both on cliffs, have been described. A primary description of two areas of study is made and two sets of variables have been defined, one in regard to nest relative position -vertical and horizontal distance between adjacent galleries, and in relation to ground levels- and the other related to the structure of the nesting gailery -horizontal and vertical axes, and length. Results showed the colony by river Guadiamar presents high values both variability in the distribution of nesting holes and population density. The colony by river Guadalquivir presents homogeneity in the distribution of nesting holes and low population density

    Meandering periods and asymmetries in light curves of Miras: Observational evidence for low mass-loss rates

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    Some Miras -- long-period variables in late evolutionary stages -- have meandering pulsation periods and light curve asymmetries, the causes of which are still unclear. We aim to understand better the origin of these phenomena by investigating a sample of solar-neighbourhood Miras. We characterised this group of stars and related their variability characteristics to other stellar parameters. We analysed observations from several databases to obtain light curves with maximum time span and temporal coverage for a sample of 548 Miras. We determined their pulsation period evolution over a time span of many decades, searched for changes in the periods, and determined the amplitude of the period change. We also analysed the Fourier spectra with respect to possible secondary frequency maxima. The sample was divided into two groups with respect to the presence of light curve bumps. IR colours and indicators of the third dredge-up were collected to study the sample stars' mass-loss and deep mixing properties. Our analysis revealed one new star, T~Lyn, with a continuously changing period. The group of Miras with meandering period changes is exclusively made up of M-type stars. The Fourier spectra of the meandering period Miras have no prominent additional peaks, suggesting that additional pulsation modes are not the cause of the meandering periods. We confirm that bumps are more common among S and C Miras and show, for the first time, that Miras with bumps have lower mass-loss rates than those with regular, symmetric light curves. Also Miras with meandering period changes have relatively little mass loss. We conclude that Miras with strongly changing periods or asymmetries in their light curves have relatively low dust mass-loss rates. Meandering period changes and light curve asymmetries could be connected to He-shell flashes and third dredge-up episodes.Comment: 13 pages (plus 13 pages Appendix), 14 Figures, accepted for publication in A&

    Effects of water activity on the performance of potassium sorbate and natamycin as preservatives against cheese spoilage moulds

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    peer-reviewedThis work investigated the effects of the food preservatives potassium sorbate and natamycin, combined with different levels of ionic (sodium chloride) and non-ioinic (glycerol) water activity (aw), on growth of fungi involved in cheese spoilage. In general, the combined effect of water stress and presence of preservatives enhanced fungal inhibition. However, some doses of potassium sorbate (0.02%) and natamycin (1, 5 and 10 ppm) were able to stimulate growth of Aspergillus varians, Mucor racemosus, Penicillium chrysogenum and P. roqueforti at aw values in the range of 0.93–0.97. P. solitum was the only species whose growth was consistently reduced by any doses of preservative. The results also showed that sodium chloride and glycerol differentially affected the efficacy of preservatives. This study indicates that aw of cheese is a critical parameter to be considered in the formulation of preservative coatings used against fungal spoilage

    Mitochondrial membrane lipid remodeling in pathophysiology: A new target for diet and therapeutic interventions

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    Mitochondria are arbiters in the fragile balance between cell life and death. These organelles present an intricate membrane system, with a peculiar lipid composition and displaying transverse as well as lateral asymmetry. Some lipids are synthesized inside mitochondria, while others have to be imported or acquired in the form of precursors. Here, we review different processes, including external interventions (e.g., diet) and a range of biological events (apoptosis, disease and aging), which may result in alterations of mitochondrial membrane lipid content. Cardiolipin, the mitochondria lipid trademark, whose biosynthetic pathway is highly regulated, will deserve special attention in this review. The modulation of mitochondrial membrane lipid composition, especially by diet, as a therapeutic strategy for the treatment of some pathologies will be also addressed.Work at the authors laboratory is supported by the Portuguese Foundation for Science and Technology and FEDER/COMPETE (research Grants PTDC-QUI-QUI-101409-2008; PTDC/QUI-BIQ/ 103001/2008 and Pest-C/SAU/LA0001/2013-2014). J.P.M. acknowledges FCT for Ph.D. Grant SFRH/BD/37626/2007

    Estudio de la Curva de Crecimiento en la Gallina Utrerana

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    Utilizando el modelo de Gompertz se compararon las curvas de crecimiento de pollos de las tres variedades de la raza Utrerana: La Utreana Negra, la Perdiz y la Franciscana. El estudio se realizó alojando los animales en cautividad en el Centro Agropecuario Provincial de la Diputación de Córdoba. Se observó que la variedad Franciscana alcanzó un mayor peso a la madurez con 2870.3 g, seguida de la varidad Negra y, finalmente, de la variedad Perdiz con 2504.7 y 2181.8 g., respectivamente. En lo que respecta a la velocidad de crecimiento de la raza, la variedad Franciscana mostró las mayores tasas de crecimiento hasta el punto de inflexión, en tanto que los menores índices de crecimiento a partir de dicho punto lo obtuvo la variedad Perdiz. El punto de inflexión se alcanzó a los 62.16, 59.31 y 60.82 días por este orden, para la variedad Franciscana, Negra y Pediz. Los pesos en ese punto fueron de 1056.03g para la variedad Franciscana, 921.52 g para la Negra y 802.72 g para la Perdiz
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