143 resultados para 233


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The diet of the Irish hare Lepus timidus hibernicus was investigated in Northern Ireland. Faecal pellets were collected at regular intervals from three contrasting study sites and from a number of randomly selected sites from known land classes. Microhistological techniques were employed to analyse the pellets. Grass species occurred in high percentage frequencies in all samples of faecal pellets and a wide variety of plant species were represented (up to 26 species in one study site). In a stratified, random survey of the presence of hares, areas of lowland intensive agriculture had fewer positive records than expected. It is contended that L. t. hibernicus may not be able to sustain viable populations in areas of intensive agriculture, which are almost exclusively composed of ryegrass Lolium spp.

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At present, optical microscopy studies of minerals, especially diamonds, are hampered by the lack of available high refractive index (> 1.8) immersion fluids. We report here the syntheses and refractive indices of some 1-alkyl-3-methylimidazolium based ionic liquids containing polyhalide anions, which exhibit refractive indices between 1.6 and 2.23, and thus significantly extend the range of minerals which can be studied.

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The role of the serine/threonine protein kinase B (PKB, also known as Akt) is becoming increasingly more evident to researchers investigating diverse cellular processes such as glucose uptake, cell-cycle progression, apoptosis and transcriptional regulation. New roles for PKB/Akt have been described in various organisms and biological processes. From the regulation of ovarian ecdysteroid production in the humble mosquito (Aedes aegypti), through the seasonal, tissue-specific regulation of PKB/Akt during the hibernation of yellow-bellied marmots (Marmota flaviventris), to the control of glucose metabolism and insulin signalling in the mouse (Mus musculus), our knowledge of the function of this protein kinase has expanded greatly in recent years. Significant advances in all aspects of PKB/Akt signalling have occurred in the past 2 years, including biological insights, novel substrates and newly discovered regulatory mechanisms of PKB/Akt. Collectively, these data expand the current models of PKB/Akt signalling and highlight potential directions for PKB/Akt research in the future.

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Because of the different mix design in comparison with traditional concrete and the absence of vibration, different durability characteristics might be expected for self-compacting concrete. The stateof- the-art report, prepared by RILEM Technical Committee TC 205-DSC focuses on the Durability of SCC, by first gathering the available information concerning pore structure, air-void system and transport mechanisms. The available durability results are studied and summarised keeping in mind the fundamental mechanisms and driving forces. All relevant durability issues are considered, like carbonation, chloride penetration, frost resistance, ASR, sulphate attack, thaumasite formation, fire resistance, etc... It is not the intention to give a review on these durability aspects for concrete in general. The aim however is to point at the specifics related to the use of SCC, e.g. due to the addition of a large amount of limestone filler, etc... This paper summarizes the main conclusions of the State-of-the-Art Report.

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Concrete used for underwater repair is often proportioned to spread readily into place and self-consolidate, and to develop high resistance to segregation and water dilution. An investigation was carried out to determine the effect of the dosage of antiwashout admixture, water-cementitious materials ratio (w/cm), and binder composition on the relative residual strength of highly flowable underwater concrete. Two types of antiwashout admixtures were used: a powdered welan gum at 0.07 and 0.15% by mass of binder, and a liquid-based cellulosic admixture employed at a high dosage of 1 to 1.65 L/100 kg of cementitious materials. The w/cms were set at 0.41 and 0.47 to secure adequate performance of underwater concrete for construction and repair. Four binder compositions were used: a Canadian Type 10 cement; a cement with 10% silica fume replacement; a cement with 50% replacement of granulated blast-furnace slag; and a ternary binder containing 6% silica fume and 20% Class F fly ash. Test results indicate that for a given washout mass loss and slump flow consistency, greater relative residual strength can be secured when the dosage of antiwashout admixture is increased, the w/cm is reduced, and a binary binder with 10% silica fume substitution or the ternary binder are employed. Such mixtures can develop relative residual compressive strengths of 85 and 80%, compared to mixtures cast in air, when the value of washout loss is limited to 4 and 6% for mixtures with slump flow values of 450 and 550 mm, respectively.

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