421 resultados para CONCHA PERLIFERA


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Pós-graduação em Agronomia (Proteção de Plantas) - FCA

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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Pós-graduação em Agronomia (Proteção de Plantas) - FCA

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Direct borohydride fuel cells (DBFCs) are attractive energy generators for powering portable electronic devices, mainly due to their high energy density and number of electrons per borohydride ion. However, the lack of a highly efficient electrocatalyst for the borohydride oxidation reaction limits the performance of these devices. The most commonly studied electrocatalysts for this reaction are composed of gold and platinum. Nevertheless, for these metals, the borohydride electrooxidation reaction mechanism (BOR) is not completely understood, and the total oxidation reaction, involving eight electrons per BH4- species, competes with parallel reactions, with a lower number of exchanged electrons and/or with heterogeneous chemical hydrolysis. Considering the above-mentioned issues, this work presents recent advances in the knowledge of the BOR pathways on polycrystalline (bulk) Au and Pt electrocatalysts. It presents the studies of the BOR reaction on Au and Pt electrodes using in situ Fourier Transform Infrared Spectroscopy (FUR), and on-line Differential Electrochemical Mass Spectrometry (DEMS). The spectroscopic and spectrometric data provided physical evidence of intermediate species and the formation of H-2 in the course of the BOR as a function of the electrode potential. These results enabled to advance in the knowledge about the BOR pathways on Au and Pt electrocatalysts. (C) 2012 Elsevier Ltd. All rights reserved.

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The habenular nuclei are diencephalic structures present in Vertebrates and they form, with the associated fiber systems, a part of the system that connects the telencephalon to the ventral mesencephalon (Concha M. L. and Wilson S. W., 2001). In representative species of almost all classes of Vertebrates the habenular nuclei are asymmetric, both in terms of size and of neuronal and neurochemical organization, although different types of asymmetry follow different evolutionary courses. Previous studies have analyzed the spread and diversity of the asymmetry in species for which data are not clear (Kemali M. et al., 1980). Notwithstanding that, it’s still not totally understood the evolution of the phenomenon, and the ontogenetic mechanisms that have led to the habenular asymmetry development are not clear (Smeets W.J. et al., 1983). For the present study 14 species of Elasmobranchs and 15 species of Teleostean have been used. Brains removed from the animals have been fixed using 4% paraformaldehyde in phosphate buffer; brains have been analyzed with different tecniques, and I used histological, immunohistochemical and ultrastructural analysis to describe this asymmetry. My results confirm data previously obtained studying other Elasmobranchs species, in which the left habenula is larger than the right one; the Teleostean show some slightly differences regarding the size of the habenular ganglia, in some species, in which the left habenular nucleus is larger than the right. In the course of studies, a correlation between the habits of life and the diencephalic asymmetry seems to emerge: among the Teleostean analyzed, the species with benthic life (like Lepidorhombus boscii, Platichthys flesus, Solea vulgaris) seem to possess a slight asymmetry, analogous to the one of the Elasmobranchs, while in the other species (like Liza aurata, Anguilla anguilla, Trisopterus minutus) the habenulae are symmetrical. However, various aspects of the neuroanatomical asymmetries of the epithalamus have not been deepened in order to obtain a complete picture of the evolution of this phenomenon, and new searches are needed to examine the species without clear asymmetry, in order to understand the spread and the diversity of the asymmetry among the habenulae between the Vertebrates.

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Independencia Bay can be considered as one of the most productive invertebratc fishing grounds worldwide. One of the most important exploited species is the scallop (Argopecten purpuratus) with strong catching fluctuations related to El Nino and La Nina events and to inadequate Management strategies. During strong warming periods annual landings reach up to 50000 t in an area of about 150 km**2 and during cold years they remain around 500 to 1000 t. This study analyses the changes in scallop landings at Independencia Bay observed during the last two decades and discusses the main factors affecting the scallop proliferations during the EI Nino events. In this way data on landings, sea surface temperature and those related to growth, reproduction, predation, mean density and oxygen concentration from published and unpublished Papers are used. The relationship between annual catches and average water temperature over the preceding reproductive period of the scallop over the past 20 year's period, showed that scallop production is affected positively only with strong EI Nino such as those of 1983 and 1998. Our review showed that the scallop stock proliferation can be traced to the combined effect of (1) an increase in reproductive output through an acceleration of gonad maturation and a higher spawning frequency; (2) a shortening of the larval period and an increase in larval survival; (3) an increase in the individual growth performance; (4) an increase in the juvenile and adult survival through reduction of predator biomass; (5) an increase in carrying capacity of the scallop banks due to elevated oxygen levels.

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Se evaluó el nivel de conocimiento de la nueva Ley de bosque nativo y fomento forestal que poseen los pequeños propietarios forestales en dos territorios de la Cordillera de Nahuelbuta, en Chile. Para ello, se aplicó una encuesta a 53 personas (10 de las viviendas), que abordó cinco temas centrales: (1) uso del bosque nativo, (2) participación en redes sociales y acceso a la información, (3) conocimiento general de la Ley, (4) conocimiento respecto a la administración y (5) fomento de la Ley. Los resultados mostraron que: (1) el bosque nativo es usado para obtener productos madereros y no madereros, (2) las redes sociales y especialmente la radio son fundamentales para la transferencia de información, (3) tanto el conocimiento general de la Ley como (4) el nivel de conocimiento respecto de la administración de la Ley es insuficiente, y (5) se desconocen los trámites que deben efectuarse para obtener los beneficios de la Ley. Se concluye que: (1) el nivel de conocimiento de la Ley es insuficiente, (2) es fundamental estimular el uso de los instrumentos de esta Ley en la totalidad del territorio, de modo de garantizar el uso sustentable del recurso, y (3) la difusión de los beneficios de la Ley debe considerar las formas de comunicación tradicionales, el nivel de educación y la cultura de los espacios rurales

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La vindicación de la Guerra Civil española por parte de los intelectuales exiliados se convierte en las memorias y autobiografías en una deuda ética frente a la desmemoria de gran parte del interior del país y, sobre todo, en un campo de reconstrucción identitaria de un sujeto que ha quedado definido por un pasado perdido y por una obligatoria readaptación a la sociedad que lo acoge. La narración de la Guerra Civil en Vida en claro (1944) de José Moreno Villa, Recuerdos y olvidos (1988) de Francisco Ayala, Memoria de la melancolía (1970) de María Teresa León, Quan érem capitans (1974) de Teresa Pàmies, Una mujer por los caminos de España (1952) de María Lejárraga y Memorias habladas, memorias armadas (1990) de Concha Méndez recuperan los arduos sucesos bélicos para entretejerlos con el rescate y reubicación del yo.