146 research outputs found

    Branching ratio change in K- absorption at rest and the nature of the Lambda(1405)

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    We investigate in-medium corrections to the branching ratio in K- absorption at rest and their effect on the (positively and negatively) charged pion spectrum. The in-medium corrections are due to Pauli blocking, which arises if the Lambda(1405) is assumed to be a Kˉ\bar{K}-nucleon bound state and leads to a density and momentum dependent mass shift of the Lambda(1405). Requiring that the optical potential as well as the branching ratio are derived from the same elementary T-matrix, we find that the in-medium corrected, density dependent T-matrix gives a better description of the K- absorption reaction than the free, density-independent one. This result suggests that the dominant component of the Lambda(1405) wave function is the KˉN\bar{K}N bound state.Comment: 8 Pages, Revtex with epsf, and embedded 8 ps figure

    Marine wildlife in Brazilian zoohandicrafts: assessing the expansion of an uncontrolled trade

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    The trade of wild animal parts as souvenirs, hereafter termed zoohandicrafts, has witnessed significant growth in Brazil due to increasing tourism and the associated demand for souvenirs. This study aimed to investigate the diversity of marine wildlife traded as zoohandicrafts along the Brazilian coast, identify the prevalent categories for these products, and assess the extent of this trade across the country. Sampling was conducted in 23 markets at tourist destinations, covering 11 states from the Northern, Northeastern, Southeastern, and Southern regions of Brazil, between 2017 and 2022. A total of 160 items or voucher specimens were examined, revealing the presence of 68 invertebrate species and two fishes. Statistical analysis indicated significant variations in the number of species across different categories of use and within the visited states and regions. Several species were found to serve multiple purposes. Whole mollusk shells constituted the most frequently traded item, with 58 identified species. Non-metric multidimensional scaling (NMDS) revealed two distinct groups—one including species with diverse uses in all regions of Brazil and the other encompassing species predominantly associated with decoration and religious purposes—particularly in the Northeastern and Southeastern regions of Brazil. An increasing diversity of species and a lower frequency of use were observed in the Southeastern region, relative to the Northeastern region. Approximately 20% of the species recorded are exclusively from the Indo-Pacific Ocean and are regarded as non-native to Brazil. Only 12 of the species were listed in the International Union for the Conservation of Nature (IUCN) Red List, and two are regulated by the Convention on International Trade in Endangered Species (CITES). This research sheds light on the status of the zoohandicraft trade in Brazil and highlights the lack of regulatory measures, the potential threats posed to biodiversity loss, and the economic importance of these species for people’s livelihoods. Further investigations are required to gain a comprehensive understanding of the actual social, economic, and ecological impacts of the trade in zoohandicrafts in Brazil and to devise strategies that promote both conservation and the socioeconomic wellbeing of all people involved in this commerce, from sourcing, production, distribution, and sale

    The effects of siblings on the migration of women in two rural areas of Belgium and the Netherlands, 1829-1940

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    This study explores the extent to which the presence and activities of siblings shaped the chances of women migrating to rural and urban areas in two rural areas of Belgium and the Netherlands during the second half of the nineteenth and first decades of the twentieth century. Shared-frailty Cox proportional hazard analyses of longitudinal data from historical population registers show that siblings exerted an additive impact on women's migration, independently of temporal and household characteristics. Just how siblings influenced women's migration depended on regional modes of production and on employment opportunities. In the Zeeland region, sisters channelled each other into service positions. In the Pays de Herve, where men and women found industrial work in the Walloon cities, women were as much influenced by their brothers' activities. Evidence is found for two mechanisms explaining the effects of siblings: micro-economic notions of joint-household decision-making and social capital theory

    Position of the Third Na+ Site in the Aspartate Transporter GltPh and the Human Glutamate Transporter, EAAT1

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    Glutamate transport via the human excitatory amino acid transporters is coupled to the co-transport of three Na+ ions, one H+ and the counter-transport of one K+ ion. Transport by an archaeal homologue of the human glutamate transporters, GltPh, whose three dimensional structure is known is also coupled to three Na+ ions but only two Na+ ion binding sites have been observed in the crystal structure of GltPh. In order to fully utilize the GltPh structure in functional studies of the human glutamate transporters, it is essential to understand the transport mechanism of GltPh and accurately determine the number and location of Na+ ions coupled to transport. Several sites have been proposed for the binding of a third Na+ ion from electrostatic calculations and molecular dynamics simulations. In this study, we have performed detailed free energy simulations for GltPh and reveal a new site for the third Na+ ion involving the side chains of Threonine 92, Serine 93, Asparagine 310, Aspartate 312, and the backbone of Tyrosine 89. We have also studied the transport properties of alanine mutants of the coordinating residues Threonine 92 and Serine 93 in GltPh, and the corresponding residues in a human glutamate transporter, EAAT1. The mutant transporters have reduced affinity for Na+ compared to their wild type counterparts. These results confirm that Threonine 92 and Serine 93 are involved in the coordination of the third Na+ ion in GltPh and EAAT1

    A-dependence of phi-meson production in p+A collisions

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    A systematic analysis of the A-dependence of phi-meson production in proton-nucleus collisions is presented. We apply different formalisms for the evaluation of the phi-meson distortion in nuclei and discuss the theoretical uncertainties of the data analysis. The corresponding results are compared to theoretical predictions. We also discuss the interpretation of the extracted results with respect to different observables and provide relations between frequently used definitions. The perspectives of future experiments are evaluated and estimates based on our systematical study are given.Comment: 14 pages, 8 figure

    Nycthemeral and Monthly Occupation of the Fish Assemblage on a Sheltered Beach of Baía Norte, Florianópolis, Santa Catarina State, Brazil

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    Interpreting fish community records is challenging for several reasons, including the lack of past ichthyofauna data, the cyclical temporal variations in the community, and the methodology employed, which usually underestimates fish assemblages. The objective of this study was to describe short-scale and meso-scale (nycthemeral period and months, respectively) temporal variations in the ichthyofauna composition and structure of a sheltered beach of Baía Norte (Florianópolis, Santa Catarina state, Brazil), using a capéchade net. Samples were collected monthly for a period of 48 hours. During the period from December 2010 to November 2011, a total of 19,302 individuals belonging to 89 species and 39 families were captured. The number of individuals that were sampled during the day and/or night was dependent on the sampling month. On average, the daytime assemblage was more abundant and different in structure and composition than the nighttime assemblage. Of the eight species that had the highest Index of Relative Importance (%IRI), five had higher variations (ANOVA F) between the day and night than between the months. This finding reinforced the need for sampling during both the day and night. The capéchade net effectively captured demersal and pelagic individuals in a broad range of sizes
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