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Search Results: 1 - 10 of 507307 matches for " Carlos Alejandro Echeverría "
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Black corals (Cnidaria: Anthozoa: Antipatharia): first records and a new species from the Brazilian coast
Echeverría,Carlos Alejandro;
Revista de Biología Tropical , 2002,
Abstract: a new species, cirripathes secchini (cnidaria: antipatharia) from the abrolhos area (babia, brazil) is describes and constitutes the first record to this genus from brazil. two other species (antipathes hirta, first record from the southwestern atlantic; and antipathes fernandezi, first record from the atlantic ocean) are compared to the most recent redescriptions and new data on the size distribution of the characters is provided. to the present there are only two records of the order antipatharia from brazil.
Black corals (Cnidaria: Anthozoa: Antipatharia): first records and a new species from the Brazilian coast
Carlos Alejandro Echeverría
Revista de Biología Tropical , 2002,
Abstract: A new species, Cirripathes secchini (Cnidaria: Antipatharia) from the Abrolhos area (Babia, Brazil) is describes and constitutes the first record to this genus from Brazil. Two other species (Antipathes hirta, first record from the Southwestern Atlantic; and Antipathes fernandezi, first record from the Atlantic Ocean) are compared to the most recent redescriptions and new data on the size distribution of the characters is provided. To the present there are only two records of the order Antipatharia from Brazil. Se describe una nueva especie, Cirripathes secchini (Cnidaria: Antipatharia) proveniente de la región de Abrolhos (Bahia, Brasil), que constituye además el primer registro de este género en Brasil. Otras dos especies (Antipathes hirta, primer registro en el Océano Atlántico sur-occidental; Antipathes fernandezi, primer registro en el Océano Atlántico) se comparan a sus redescripciones más recientes y se agregan nuevos datos sobre la distribución de tama o de sus caracteres taxonómicos. Hasta el momento existen apenas dos registros del orden Antipatharia en Brasil.
Spatial and temporal distribution of the gastropod Heleobia australis in an eutrophic estuarine system suggests a metapopulation dynamics  [PDF]
Carlos Alejandro Echeverría, Raquel A. F. Neves, Leandro A. Pessoa, Paulo C. Paiva
Natural Science (NS) , 2010, DOI: 10.4236/ns.2010.28108
Abstract: Hydrobiidae is one of the most diverse taxa among limnic and estuarine mollusks. Patterns of spatial and seasonal distribution of Heleobia australis were studied in ten stations over two years, in the urban eutrophic bay of Guanabara, Rio de Janeiro, Brazil. Spatial dispersal strategies in adults of this species, analyzed in the laboratory, revealed three patterns: 1) mobility on soft sediments; 2) mobility on hard substrata; and 3) the ability to lift from the bottom to the surface, to again sink down. This facilitate species movement from one location to another by surface currents or attached to floating debris. Thus, individuals are able to escape from an impacted area and further re-colonize other patches after recovering from local impacts. The hypothesis of metapopulation dynamics (source– sink) was analyzed. Two stations with high and constant numbers of individuals were grouped and tested as possible ‘sources’. The number of specimens in the remaining stations was highly variable, even with the complete disappearance and posterior highly dense re-occurrence of the mollusk, whereby these were tested as possible ‘sinks’. Results derived from nested ANOVA supported the hypothesis of metapopulation dynamics in the case of H. australis adults, ex-pressed through opportunistic-species domi- nation of a highly impacted estuarine system, such as Guanabara Bay.
Recovery Process on Soft-Bottom Macrobenthic Communities after Artificial Disturbance in Tropical Polluted Estuary (Guanabara Bay, Rio de Janeiro, Brazil)  [PDF]
Cecília do Valle Pinto Pereira, Leandro Amaro Pessoa, Marcos Aurélio Vasconcelos de Freitas, Carlos Alejandro Echeverría
Open Journal of Marine Science (OJMS) , 2013, DOI: 10.4236/ojms.2013.34018
Abstract:

The regime of disturbance with natural or anthropogenic origin can lead to the destabilization or even to a mass mortality of benthic communities. Due to the heterogeneity of the disturbance there is a formation of patches in different stages of ecological succession. The aim of this study is to follow and describe the resilience in artificial disturbed sediment in a polluted bay in Rio de Janeiro. The sediment was collected, sterilized and placed inside corers (10 cmdiameter ×15 cmheight) in the same place where it was collected. We allocated the samples in two structures, the difference between them was that one was placed closed to the bottom and the other was placed50 cmheight. We found 2352 organisms distributed in 14 taxons. The class Polychaeta and the order Amphipoda showed the highest density in all the survey and treatments. We identified the factors influencing the scenarium: different mechanisms of dispersal, the position of the structures and life history of each group. Disturbance can be the main cause of the patch’s diversity found in estuaries and coastal areas. Because of this, monitoring of selected areas becomes an important tool to understand the regime of disturbance as a key factor structuring benthic communities in soft sediment, also suggesting a metapopulation dynamics.

Study of the copper corrosion mechanism in the presence of propionic acid vapors
Echavarría, Alejandro;Echeverría, Felix;Arroyave, Carlos;Gil, Harveth;
Journal of the Brazilian Chemical Society , 2009, DOI: 10.1590/S0103-50532009001000011
Abstract: the interaction mechanism between copper and propionic acid vapors is shown. exposures were carried out to various pollutant concentrations and times. cathodic scan, x-ray diffraction (xrd) and scanning electrode microscope (sem) were used to quantify the degree of deterioration. the results obtained were explained by the following mechanism: a cuprite (cu2o) layer covers the copper surface immediately; this compound in presence of adsorbed water is oxidized to tenorite (cuo). the hydration of the tenorite layer benefits the formation of a hydroxide compound such as cuo?xh2o. as the pollutant level is increased, insoluble basic propionate is formed (cu(oh)x(ch3ch2 coo)2-x). higher concentrations of propionic acid acidify the monolayers and a new compound cu(ch3ch2coo)2?h 2o begins to precipitate at low ph, this is the main constituent of the green olive patina formed under these conditions. this mechanism agrees, in general terms, with those proposed in previous works to study the interaction between copper and the acetic and formic acids.
Diagnóstico de Muerte The diagnosis of death
Carlos Echeverría B,Alejandro Goic G,Manuel Lavados M,Carlos Quintana V
Revista médica de Chile , 2004,
Abstract: This paper undertakes an analysis of the scientific criteria used in the diagnosis of death and underscores the importance of intellectual rigor in the definition of medical concepts, particularly regarding such a critical issue as the diagnosis of death. Under the cardiorespiratory criterion, death is defined as the irreversible cessation of the functioning of an organism as a whole and the tests used to confirm this criterion (negative life-signs) are sensitive and specific. In this case, cadaverous phenomena appear immediately following the diagnosis of death. On the other hand, doubts have arisen concerning the theoretical and the inner consistency of the criterion of brain death, since it does not satisfy the definition of the irreversible cessation of the functioning of an organism as a whole , nor the requirement of total and irreversible cessation of all functions of the entire brain, including the brain stem . There is evidence to the effect that the tests used to confirm this criterion are not specific enough. It is clear that brain death marks the beginning of a process that eventually ends in death, though death does not occur at that moment. From an ethical point of view, the conflict arises between the need to provide an unequivocal diagnosis of death and the possibility of saving a life through organ transplantation. The sensitive issue of brain death calls for a more thorough and in-depth discussion among physicians and the community at large (Rev Méd Chile 2004; 132: 95-107).
A new mini box corer for sampling muddy bottoms in antarctic shallow waters
Echeverría, Carlos Alejandro;Lavrado, Helena Passeri;Campos, Lúcia;Paiva, Paulo Cesar de;
Brazilian Archives of Biology and Technology , 2009, DOI: 10.1590/S1516-89132009000300015
Abstract: a new mini box corer (mbc-geamb) was developed for bottom sampling in antarctic shallow waters down to 100 m depth from a small vessel. it consists of a detachable stainless steel box with a total sampling area of 0.0625 m2, and a closing arm with a detachable blade without an external frame. mbc allowed stratified bottom sampling and good quality samples comparable to those obtained through diving. a comparison between the mbc-geamb and a 0.056 m2van veen grab (vv) was undertaken for the benthic macrofaunal composition in admiralty bay, king george island (antarctica). mbc and vv samples were taken from three depths (20, 30 and 60m) in two sites. total densities sampled with the mbc were up to 10 times higher than those obtained with van veen grab. vv samples might lead to faunistic abundance underestimation compared to the mbc samples. besides, mbc showed a higher performance on discriminating different sites as regards total macrofaunal density. it is suggested that mbc could be employed as an efficient remote sampling device for shallow-waters where direct sampling by scuba was not advisable.
Diagnóstico de Muerte
Echeverría B,Carlos; Goic G,Alejandro; Lavados M,Manuel; Quintana V,Carlos; Rojas O,Alberto; Serani M,Alejandro; Vacarezza Y,Ricardo;
Revista médica de Chile , 2004, DOI: 10.4067/S0034-98872004000100015
Abstract: this paper undertakes an analysis of the scientific criteria used in the diagnosis of death and underscores the importance of intellectual rigor in the definition of medical concepts, particularly regarding such a critical issue as the diagnosis of death. under the cardiorespiratory criterion, death is defined as ?the irreversible cessation of the functioning of an organism as a whole? and the tests used to confirm this criterion (negative life-signs) are sensitive and specific. in this case, cadaverous phenomena appear immediately following the diagnosis of death. on the other hand, doubts have arisen concerning the theoretical and the inner consistency of the criterion of brain death, since it does not satisfy the definition of ?the irreversible cessation of the functioning of an organism as a whole?, nor the requirement of ?total and irreversible cessation of all functions of the entire brain, including the brain stem?. there is evidence to the effect that the tests used to confirm this criterion are not specific enough. it is clear that brain death marks the beginning of a process that eventually ends in death, though death does not occur at that moment. from an ethical point of view, the conflict arises between the need to provide an unequivocal diagnosis of death and the possibility of saving a life through organ transplantation. the sensitive issue of brain death calls for a more thorough and in-depth discussion among physicians and the community at large (rev méd chile 2004; 132: 95-107).
Experiencia subjetiva del tiempo y su influencia en el comportamiento: revisión y modelos
Vásquez Echeverría, Alejandro;
Psicologia: Teoria e Pesquisa , 2011, DOI: 10.1590/S0102-37722011000200011
Abstract: since the beginning of psychology researchers have tried to explain the subjective experience of time on cognitions, emotions and behavior. as it is one of the most complex and influential dimensions of the mind, it has been approached from different conceptions without a common consensual framework. this article attempts to contribute to the systematization of the psychology of time expanding a fourfold model, which emphasizes life-time perception or time iii. publications were selected that were either relevant in the history of psychology or had a good citation index. an explanatory model of time iii is proposed that incorporates discussion and debate and which intends to integrate various existing models encountered in the literature.
President Nicolas Sarkozy's Mediterranean Union: Leaving the Barcelona Process Behind?
Carlos Echeverría
UNISCI Discussion Papers , 2007,
Abstract: In this analysis we want to explore the possibilities offered by the initiative, still French to a great extent, but already approached by Italy and Spain, for building a smaller Euro-Mediterranean space than the current one, taking into account not only its possibilities but also the obstacles for dialogue and cooperation proposals in the region.
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