952 resultados para Suspended matter of the mud bank
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Land cover change constitutes one of main way of alteration of soil organic matter in both quantitative and qualitative terms. The goal of this study was to compare the carbon stock and the isotopic signature of the organic matter in the soil of areas with different land use,covered with forest and grass (pasture). The study area is located at Sorocaba, SP, Brazil. Using un-deformed soil samples, we measured the carbon content and bulk density. The isotopic signature of soil carbon was determined through the analysis of isotopic ratio (12)C/(13)C. The pasture soil stocks 48% less carbon than the soil covered by natural forest. The isotopic signature indicated that 42.2% of organic matter of the soil covered by pasture is originated from grasses. This characterizes a highly degradation of organic matter in the environment, both quantitatively and qualitatively. Hence, some guidelines of recuperation are described in order to restore the soil organic matter, structure and porosity.
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Israël est l’un des pays développés les plus féconds dans le monde et maintient un taux de fécondité stable depuis 1995. Il a échappé à la chute spectaculaire de la fécondité qui a été observée dans la plupart des pays occidentaux. Le taux de fécondité était de 2,96 enfants par femme en 2009 (Statistical Abstract of Israel, 2010, tableau 3.14). Le maintien d’une si forte fécondité pourrait être dû à l’immigration et à la “guerre démographique” qui sévit entre les différentes communautés vivant dans le pays (Sardon, 2006). Toutefois, on observe une différence significative entre les niveaux de fécondité des juifs d’Israël et de Cisjordanie depuis plusieurs années. Les études qui portent sur la fécondité en Israël sont faites au niveau national, ce qui ne fournit aucune explication sur cette différence. Pour ces raisons, l’étude de la fécondité en Israël mérite une attention particulière. Ce projet vise à identifier les différents facteurs qui ont une incidence sur la fécondité des femmes juives vivant en Israël et en Cisjordanie. Il contribuera à une meilleure compréhension des comportements liés à la fécondité de la population juive de la Cisjordanie et peut fournir des indices sur les mécanismes complexes qui régissent les relations entre Juifs et Arabes dans les territoires occupés. Grâce aux données recueillies dans l’Enquête sociale générale de 2004 d’Israël,des analyses descriptives et explicatives ont été produites. Dans un premier temps, les facteurs qui ont un impact sur la fécondité dans chaque région ont été déterminés et par la suite, une analyse de l’importance de ces facteur sur la fécondité a été produite. Le nombre d’enfants nés de femmes âgées de 20 à 55 ans constitue la variable d’intérêt et les variables explicatives retenues sont les suivantes: religiosité, éducation, revenu familial mensuel, statut d’emploi, pays d’origine, âge et état matrimonial. Cette étude a montré que les femmes juives qui résident en Cisjordanie ont un nombre prévu d’enfants de 13% supérieur à celui des femmes juives qui résident en Israël lorsque l’on contrôle toutes les variables. Il est notamment montré que la religion joue un rôle important dans l’explication de la forte fécondité des femmes juives dans les deux régions, mais son impact est plus important en Israël. L’éducation joue également un rôle important dans la réduction du nombre prévu d’enfants, en particulier en Cisjordanie. Tous ces facteurs contribuent à expliquer les différents niveaux de fécondité dans les deux régions, mais l’étude montre que ces facteurs ne permettent pas une explication exhaustive de la forte fécondité en Israël et en Cisjordanie. D’autres forces qui ne sont pas mesurables doivent avoir une incidence sur la fécondité telles que le nationalisme ou la laïcisation, par exemple.
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OBJETIVO: Nosso objetivo foi investigar se o uso do solo do ambiente terrestre adjacente influencia a estrutura das assembleias fitoplanctônicas (composição, riqueza, diversidade e abundância) e biomassa (clorofila-a) em um riacho de Cerrado durante diferentes períodos do ano. MÉTODOS: Os trabalhos de campo foram realizados trimestralmente durante dois anos. RESULTADOS: As variáveis físico-químicas que melhor indicaram as diferenças nas condições da água foram condutividade, oxigênio dissolvido e transparência. Também houve um notável aumento na concentração de nitrogênio, fósforo e material em suspensão na água durante o verão devido aos efeitos da pluviosidade. As assembleias fitoplanctônicas foram compostas por 64 espécies. Cryptophyceae foi o grupo mais abundante, seguido por Bacillariophyceae. Para ambos os anos, a riqueza e a diversidade foram maiores durante a primavera e no outono, enquanto que a abundância do fitoplâncton e a concentração de clorofila-a foram mais elevados durante o outono e verão. A análise de agrupamento e a analise de correspondência canônica mostraram que a sazonalidade e o uso do solo são fatores importantes na estruturação das assembleias ao longo do ano. As alterações nas assembleias fitoplanctônicas ocorreram provavelmente em função da variação na intensidade e freqüência da mistura da água e da entrada de nutrientes oriundo do sistema terrestre adjacente para o aquático. CONCLUSÃO: A estrutura das assembleias fitoplanctônicas mostrou ser altamente influenciada pelo uso do solo, corroborando com a hipótese inicial do trabalho.
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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A complete section of an unconsolidated sedimentary sequence about 5 m thick was sampled in the western margin of the Campeche Bank with use of gravity cores. The sequence forms a flat sea bottom at depth of 51-53 m and rests on a consolidated basement composed of coral limestones and carbonate sandstones. Initiation of deposition of unconsolidated sediments in this area is related to a sea transgression caused by sea level rise that followed the Würm glaciation stage about 10-11 ky ago. Analysis of grain size and chemical compositions of sediments and study of biogenic carbonate remains made it possible to outline environmental changes in this region during the last 10 ky.
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Seriocarpa rhizoides Diehl 1969 was collected in abundance from the calcareous sand of the Josephine Bank (between Portugal and Madeira) during the "Meteor" seamount cruises in 1967. Attachment in this loose soft substratum is effected by fine anchoring strands of the tests. Two irregular series of small polycarp-like hermaphrodite bodies which are embedded in a connective tissue lie directly below the endostyle, forming a tubular compound gonad, but without common ducts. The intermediate nature of the reproductive system with respect to arrangement and structure increases our knowledge about the polygenetic relations of the stylid-genera. Some of the hitherto known ecological facts point to the presumed "seamounts effect" on this species.
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Freshwater chlorophycean algae are characteristic organic-walled microfossils in recent coastal and shelf sediments from the Beaufort, Laptev and Kara seas (Arctic Ocean). The persistent occurrence of the chlorophycean algae Pediastrum spp. and Botryococcus cf. braunii in marine palynomorph assemblages is related to the discharge of freshwater and suspended matter from the large Siberian and North American rivers into the Arctic shelf seas. The distribution patterns of these algae in the marine environments reflect the predominant deposition of riverine sediments and organic matter along the salinity gradient from the outer estuaries and prodeltas to the shelf break. Sedimentary processes overprint the primary distribution of these algae. Resuspension of sediments by waves and bottom currents may transport sediments in the bottom nepheloid layer along the submarine channels to the shelf break. Bottom sediments and microfossils may be incorporated into sea ice during freeze-up in autumn and winter leading to an export from the shelves into the deep sea. The presence of these freshwater algae in sea-ice and bottom sediments in the central Arctic Ocean confirm that transport in sea ice is an important process which leads to a redistribution of shallow water microfossils.
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Louis M'Lane, secretary.
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Errata slip inserted.
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Colour changes in fiddler crabs have long been noted, but a functional interpretation is still lacking. Here we report that neighbouring populations of Uca vomeris in Australia exhibit different degrees of carapace colours, which range from dull mottled to brilliant blue and white. We determined the spectral characteristics of the mud substratum and of the carapace colours of U. vomeris and found that the mottled colours of crabs are cryptic against this background, while display colours provide strong colour contrast for both birds and crabs, but luminance contrast only for a crab visual system. We tested whether crab populations may become cryptic under the influence of bird predation by counting birds overflying or feeding on differently coloured colonies. Colonies with cryptically coloured crabs indeed experience a much higher level of bird presence, compared to colourful colonies. We show in addition that colourful crab individuals subjected to dummy bird predation do change their body colouration over a matter of days. The crabs thus appear to modify their social signalling system depending on their assessment of predation risk.
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The density and spatial distribution of the vacuoles, glial cell nuclei and glial cytoplasmic inclusions (GCI) were studied in the white matter of various cortical and subcortical areas in 10 cases of multiple system atrophy (MSA). Vacuolation was more prevalent in subcortical than cortical areas and especially in the central tegmental tract. Glial cell nuclei widespread in all areas of the white matter studied; overall densities of glial cell nuclei being significantly greater in the central tegmental tract and frontal cortex compared with areas of the pons. The GCI were present most consistently in the external and internal capsules, the central tegmental tract and the white matter of the cerebellar cortex. The density of the vacuoles was greater in the MSA brains than in the control brains but glial cell density was similar in both groups. In the majority of areas, the pathological changes were distributed across the white matter randomly, uniformly, or in large diffuse clusters. In most areas, there were no spatial correlations between the vacuoles, glial cell nuclei and GCI. These results suggest: (i) there is significant degeneration of the white matter in MSA characterized by vacuolation and GCI; (ii) the central tegmental tract is affected significantly more than the cortical tracts; (iii) pathological changes are diffusely rather than topographically distributed across the white matter; and (iv) the development of the vacuoles and GCI appear to be unrelated phenomena. © 2007 Japanese Society of Neuropathology.
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The objective of this study was to determine the degree of white matter pathology in the cerebral cortex in cases of variant Creutzfeldt-Jakob disease (vCJD) and to study the relationships between the white matter and grey matter pathologies. Hence, the pathological changes in cortical white matter were studied in individual gyri of the frontal, parietal, occipital, and temporal cortex in eleven cases of vCJD. Vacuolation (‘spongiform change’), deposition of the disease form of prion protein (PrPsc) in the form of discrete PrP deposits, and gliosis were observed in the white matter of virtually all cortical regions studied. Mean density of the vacuoles in the white matter was greater in the parietal lobe compared with the frontal, occipital, and temporal lobes but there were fewer glial cells in the occipital lobe compared with the other cortical regions. In the white matter of the frontal cortex, vacuole density was negatively correlated with the density of both glial cell nuclei and the PrP deposits. In addition, the densities of glial cells and PrP deposits were positively correlated in the frontal and parietal cortex. In the white matter of the frontal cortex and inferior temporal gyrus, there was a negative correlation between the densities of the vacuoles and the number of surviving neurons in laminae V/VI of the adjacent grey matter. In addition, in the frontal cortex, vacuole density in the white matter was negatively correlated with the density of the diffuse PrP deposits in laminae II/III and V/VI of the adjacent grey matter. The densities of PrP deposits in the white matter of the frontal cortex were positively correlated with the density of the diffuse PrP deposits in laminae II/III and V/V1 and with the number of surviving neurons in laminae V/V1. The data suggest that in the white matter in vCJD, gliosis is associated with the development of PrP deposits while the appearance of the vacuolation is a later development. In addition, neuronal loss and PrP deposition in the lower cortical laminae of the grey matter may be a consequence of axonal degeneration within the white matter.