944 resultados para pollen grains
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In this article we present a phenomenological model which simulates very well the mag¿ netic relaxation behavior experimentally observed in small magnetic grains and single domain particles. In this model, the occurrence of quantum tunneling of magnetization below a certain temperature is taken into account. Experimental results for different materials are presented to illustrate the most important behavior deduced from our model
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Référence bibliographique : Weigert, 182
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Selostus: Viljelyalojen muutosten vaikutus hunajan siitepölysisältöön
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Flavor is the main limiting factor affecting soybean acceptability in the Occidental countries. The purpose of this study was to determine the effetcs of isoflavones on soybean flavor. Differences in beany flavor and astringency of soymilk and cooked whole soybean grains, prepared with cultivars IAS 5 and BR-36 (136 and 54 mg of total isoflavones /100 g of sample, respectively) with pre-soaking and pre-heating of grains, were sensorially analised, by an unstructured category scale of ascending intensity. Differences in isoflavone contents for both soybean cultivars were maintained in the two products, despite the pre-treatments in the processing. Pre-soaking of grains intensified beany flavor in the soymilk, reducing the perception of astringency, which is caused by the aglucones that were developed in reduced amounts.The whole soybeans grains cooked under pressure (1.5 kgf/cm² at 127°C) presented reduced levels of isoflavones malonyl-glucosides. Due to thermal instability, these compounds were converted to conjugated glucosides, genistin and daidzin. In the cooked whole soybean grains, no aglucones were formed and consequently it was not possible to detect differences in astringency. Results suggest that pre-heating of grains promote better flavor in soybean products.
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[Acte. 1716-08-18]
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Selostus: Esitutkimus kauran röyhyn sisäisestä vaihtelusta jyvän täyttymisen käynnistyessä
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The role of competition for light among plants has long been recognized at local scales, but its potential importance for plant species' distribution at larger spatial scales has largely been ignored. Tree cover acts as a modulator of local abiotic conditions, notably by reducing light availability below the canopy and thus the performance of species that are not adapted to low-light conditions. However, this local effect may propagate to coarser spatial grains. Using 6,935 vegetation plots located across the European Alps, we fit Generalized Linear Models (GLM) for the distribution of 960 herbs and shrubs species to assess the effect of tree cover at both plot and landscape grain sizes (~ 10-m and 1-km, respectively). We ran four models with different combinations of variables (climate, soil and tree cover) for each species at both spatial grains. We used partial regressions to evaluate the independent effects of plot- and landscape-scale tree cover on plant communities. Finally, the effects on species' elevational range limits were assessed by simulating a removal experiment comparing the species' distribution under high and low tree cover. Accounting for tree cover improved model performance, with shade-tolerant species increasing their probability of presence at high tree cover whereas shade-intolerant species showed the opposite pattern. The tree cover effect occurred consistently at both plot and landscape spatial grains, albeit strongest at the former. Importantly, tree cover at the two grain sizes had partially independent effects on plot-scale plant communities, suggesting that the effects may be transmitted to coarser grains through meta-community dynamics. At high tree cover, shade-intolerant species exhibited elevational range contractions, especially at their upper limit, whereas shade-tolerant species showed elevational range expansions at both limits. Our findings suggest that the range shifts for herb and shrub species may be modulated by tree cover dynamics.
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This study quantified vitamin C, E and β-carotene in samples of fresh bee-collected pollen and correlating them with the botanical origin. Vitamin content varied between 13.5 and 42.5 µg/g for vitamin E; 56.3 and 198.9 µg/g for β-carotene and 273.9 and 560.3 µg/g for vitamin C. It was concluded that the botanical origin and collecting season influenced the vitamin contents. There is a relationship between the vitamins and its botanical origin: Raphanus sp and Macroptilium sp, Mimosa caesalpineafolia with β-carotene; Raphanus sp, Eucalyptus sp, Macroptilium sp, Mimosa caesalpineafolia with vitamin E and Anadenanthera sp, Arecaceae type and Philodendron sp with vitamin C.
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This study evaluated the stability of vitamins C, E and β-carotene in six samples of bee pollen after their process, and in a one-year period of storage. After the pollen's process, there was a 67.1% increase for vitamin C (p <0.05), an 18.7% loss for vitamin E and 15.6% for β-carotene. Storage in freezer was the most efficient condition for the vitamins conservation; the loss in storage at room temperature (exposed or protected from light) was similar. Vitamin E appears to be better preserved during storage when compared to vitamin C and β-carotene.