923 resultados para Study of Library and Information Science


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Mode of access: Internet.

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Mode of access: Internet.

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Latest issue consulted: Vol. 598 (Mar. 2005)

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"March 1980".

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Includes bibliographies and index.

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A new model for Archaean granitoid magmatism is presented which reconciles the most important geochemical similarities and differences between tonalite-trondhjemite-granodiorite (TTG) and potassic granitoids. Trace element abundances reveal a strong arc magmatism signature in all studied granitoids from Barberton Mountain Land. Characteristic features include HFSE depletion as well as distinct enrichment peaks of fluid-sensitive trace elements such as Pb in N-MORB normalisation, clearly indicating that all studied granitoids are derived from refertilised mantle above subduction zones. We envisage hydrous basaltic (s.l.) melts as parental liquids, which underwent extensive fractional crystallisation. Distinctive residual cumulates evolved depending on initial water content. High-H2O melts crystallised garnet/amphibole together with pyroxenes and minor plagioclase, but no olivine. This fractionation path ultimately led to TTG-like melts. Less hydrous basaltic melts also crystallised garnet/amphibole, but the lower compatible element content indicates that olivine was also a liquidus phase. Pronounced negative Eu-anomalies of the granitic melts, correlating with Na, Ca and Al, indicate plagioclase to be of major importance. In the context of our model, the post-Archaean disappearance of TTG and concomitant preponderance of granites (s.l.), therefore, is explained with secular decrease of aqueous fluid transport into subduction zones and/or efficiency of deep fluid release from slabs.

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Recent studies have revealed marked differences in the basal dendritic structure of layer III pyramidal cells in the cerebral cortex of adult simian primates. In particular, there is a consistent trend for pyramidal cells of increasing complexity with anterior progression through occipitotemporal cortical visual areas. These differences in pyramidal cell structure, and their systematic nature, are believed to be important for specialized aspects of visual processing within, and between, cortical areas. However, it remains unknown whether this regional specialization in the pyramidal cell phenotype is unique to simians, is unique to primates in general or is widespread amongst mammalian species. In the present study we investigated pyramidal cell structure in the prosimian galago (Otolemur garnetti). We found, as in simians, that the basal dendritic arbors of pyramidal cells differed between cortical areas. More specifically, pyramidal cells became progressively more spinous through the primary (V1), second (V2), dorsolateral (DL) and inferotemporal ( IT) visual areas. Moreover, pyramidal neurons in V1 of the galago are remarkably similar to those in other primate species, in spite of large differences in the sizes of this area. In contrast, pyramidal cells in inferotemporal cortex are quite variable among primate species. These data suggest that regional specialization in pyramidal cell phenotype was a likely feature of cortex in a common ancestor of simian and prosimian primates, but the degree of specialization varies between species. Copyright (C) 2005 S. Karger AG, Basel.

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Study objective: Low birth weight predicts cardiovascular disease in adulthood, and one possible explanation is that children with lower birth weight consume more fat than those born heavier. Therefore, the objective of this study was to investigate associations between birth weight and childhood diet, and in particular, to test the hypothesis that birth weight is inversely related to total and saturated fat intake. Design: Prospective cohort study. Setting: South west England. Participants: A subgroup of children enrolled in the Avon longitudinal study of parents and children, with data on birth weight and also diet at ages 8, 18, 43 months, and 7 years ( 1152, 998, 848, and 771 children respectively). Main results: Associations between birth weight and diet increased in strength from age 8 to 43 months, but had diminished by age 7 years. Fat, saturated fat, and protein intakes were inversely, and carbohydrate intake was positively associated with birth weight at 43 months of age, after adjusting for age, sex, and energy intake. After adjustment for other confounders, all associations were weakened, although there was still a suggestion of a relation with saturated fat ( -0.48 (95% CI -0.97, 0.02) g/day per 500 g increase in birth weight. Similar patterns were seen in boys and girls separately, and when the sample was restricted to those with complete data at all ages. Conclusions: A small inverse association was found between birth weight and saturated fat intake in children at 43 months of age but this was not present at 7 years of age. This study therefore provides little evidence that birth weight modifies subsequent childhood diet.

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Objectives: The objectives of this study were to examine the extent of clustering of smoking, high levels of television watching, overweight, and high blood pressure among adolescents and whether this clustering varies by socioeconomic position and Cognitive function. Methods: This study was a cross-sectional analysis of 3613 (1742 females) participants of an Australian birth cohort who were examined at age 14. Results: Three hundred fifty-three (9.8%) of the participants had co-occurrence of three or four risk factors. Risk factors clustered in these adolescents with a greater number of participants than would be predicted by assumptions of independence having no risk factors and three or four risk factors. The extent of clustering tended to be greater in those from lower-income families and among those with lower cognitive function. The age-adjusted ratio of observed to expected cooccurrence of three or four risk factors was 2.70 (95% confidence interval [Cl], 1.80-4.06) among those from low-income families and 1.70 (95% Cl, 1.34-2.16) among those from more affluent families. The ratio among those with low Raven's scores (nonverbal reasoning) was 2.36 (95% Cl, 1.69-3.30) and among those with higher scores was 1.51 (95% Cl, 1.19-1.92); similar results for the WRAT 3 score (reading ability) were 2.69 (95% Cl, 1.85-3.94) and 1.68 (95% Cl, 1.34-2.11). Clustering did not differ by sex. Conclusion: Among adolescents, coronary heart disease risk factors cluster, and there is some evidence that this clustering is greater among those from families with low income and those who have lower cognitive function.

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Reasons for performing study: Obtaining magnetic resonance images of the inner hoof wall tissue at the microscopic level would enable early accurate diagnosis of laminitis and therefore more effective therapy. Objectives: To optimise magnetic resonance imaging (MRI) parameters in order to obtain the highest possible resolution of the structures beneath the equine hoof wall. Methods: Magnetic resonance microscopy (MRM) was performed in front feet from 6 cadaver horses using T-2-weighted fast spin echo (FSE-T-2), and T-1-weighted gradient echo (GRE-T-1) sequences. Results: In T-2 weighted FSE images most of the stratum medium showed no signal, however the coronary, terminal and sole papillae were visible. The stratum lamellatum was clearly visible and primary epidermal lamellae could be differentiated from dermal lamellae. Conclusion: Most structures beneath the hoof wall were differentiated. Conventional scanners for diagnostic MRI in horses are low or high field. However this study used ultra-high field scanners currently not available for clinical use. Signal-to-noise ratio (SIN) increases as a function of field strength. An increase of spatial resolution of the image results in a decreased SIN. SIN can also be improved with better coils and the resolution of high field MRI scanners will increase as technology develops and surface array coils become more readily available. Potential relevance: Although MR images with microscopic resolution were obtained ex vivo, this study demonstrates the potential for detection of lamellar pathology as it occurs. Early recognition of the development of laminitis to instigate effective therapy at an earlier stage and may improve the outcome for laminitic horses. Clinical MR is now readily available at 3 T, while 4 T, 7 T and 9 T systems are being used for human whole body applications.

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GCMC simulations are applied to the adsorption of sub-critical methanol and ethanol on graphitized carbon black at 300 K. The carbon black was modelled both with and without carbonyl functional groups. Large differences are seen between the amounts adsorbed for different carbonyl configurations at low pressure prior to monolayer coverage. Once a monolayer has been formed on the carbon black, the adsorption behaviour is similar between the model surfaces with and without functional groups. Simulation isotherms for the case of low carbonyl concentrations or no carbonyls are qualitatively similar to the few experimental isotherms available in the literature for methanol and ethanol adsorption on highly graphitized carbon black. Isosteric heats and adsorbed phase heat capacities are shown to be very sensitive to carbonyl configurations. A maximum is observed in the adsorbed phase heat capacity of the alcohols for all simulations but is unrealistically high for the case of a plain graphite surface. The addition of carbonyls to the surface greatly reduces this maximum and approaches experimental data with carbonyl concentration as low as 0.09 carbonyls/nm(2).