排序方式: 共有100条查询结果,搜索用时 15 毫秒
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Jan Plue Pieter De Frenne Kamal Acharya Jrg Brunet Olivier Chabrerie Guillaume Decocq Martin Diekmann Bente J. Graae Thilo Heinken Martin Hermy Annette Kolb Isgard Lemke Jaan Liira Tobias Naaf Anna Shevtsova Kris Verheyen Monika Wulf Sara A. O. Cousins 《Global Ecology and Biogeography》2013,22(10):1106-1117
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The biomass allocation pattern in plants is known to depend on the below and above-ground resource availabilities. In a herbaceous
multi-species stand, it can be expected that the effects of nutrient and light availability on plants’ general space-use strategy
are fundamentally different. We hypothesized that nutrient status alters the amount of biomass produced per unit canopy volume
(biomass density), but not so much the biomass vertical distribution pattern. Changes in light availability, in contrast,
should affect the vertical distribution pattern of biomass but not biomass density. We were also interested in whether the
effect of resource manipulation on a plant’s space-use strategy depends on its basic morphological characteristics (growth
form).
The results from a four-year permanent plot experiment in a species-rich grassland, with fertilization and additional illumination
from mirrors applied to 40 × 40 cm plots, showed that our main hypothesis was correct. Fertilization significantly affected
biomass density above as well as below-ground, while additional illumination generally did not. Light addition altered the
vertical distribution pattern of above-ground biomass, which remained unaffected by the fertilizer treatment. 相似文献
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Baldursdóttir SG Kjøniksen AL Karlsen J Nyström B Roots J Tønnesen HH 《Biomacromolecules》2003,4(2):429-436
Interactions between photoexcited riboflavin (RF), promoted by irradiation in the range of 310-800 nm, and alginate have been studied in air equilibrated aqueous solutions with the aid of rheological methods. Light irradiation of RF causes under aerobic conditions fragmentation of alginate and a decrease in the shear viscosity and other rheological parameters of its solutions. The decrease is most pronounced in concentrated polymer solutions. The photochemical degradation of alginate is inhibited in the presence of the quenchers/scavengers d-mannitol, glutathione, potassium iodide, and sodium azide and in excess oxygen. The addition of thiourea to alginate-RF solutions leads to enhanced degradation of the polymer. Significant shear-thinning effects and deviations from the Cox-Merz rule are observed at higher polymer concentrations. 相似文献
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Marina Gabriela Monteiro Carvalho Mori da Cunha Silvia Zia Fanny Oliveira Arcolino Marianne Sylvia Carlon Diego Vilibaldo Beckmann Ney Luis Pippi Dominguita Luhers Gra?a Elena Levtchenko Jan Deprest Jaan Toelen 《PloS one》2015,10(8)
Objectives
Mesenchymal stem cells derived from human amniotic fluid (hAFSCs) are a promising source for cellular therapy, especially for renal disorders, as a subpopulation is derived from the fetal urinary tract. The purpose of this study was to evaluate if hAFSCs with a renal progenitor phenotype demonstrate a nephroprotective effect in acute ischemia reperfusion (I/R) model and prevent late stage fibrosis.Methods
A total of 45 male 12-wk-old Wistar rats were divided into three equal groups;: rats subjected to I/R injury and treated with Chang Medium, rats subjected to I/R injury and treated with hAFSCs and sham-operated animals. In the first part of this study, hAFSCs that highly expressed CD24, CD117, SIX2 and PAX2 were isolated and characterized. In the second part, renal I/R injury was induced in male rats and cellular treatment was performed 6 hours later via arterial injection. Functional and histological analyses were performed 24 hours, 48 hours and 2 months after treatment using serum creatinine, urine protein to creatinine ratio, inflammatory and regeneration markers and histomorphometric analysis of the kidney. Statistical analysis was performed by analysis of variance followed by the Tukey’s test for multiple comparisons or by nonparametric Kruskal-Wallis followed by Dunn. Statistical significance level was defined as p <0.05.Results
hAFSCs treatment resulted in significantly reduced serum creatinine level at 24 hours, less tubular necrosis, less hyaline cast formation, higher proliferation index, less inflammatory cell infiltration and less myofibroblasts at 48h. The treated group had less fibrosis and proteinuria at 2 months after injury.Conclusion
hAFSCs contain a renal progenitor cell subpopulation that has a nephroprotective effect when delivered intra-arterially in rats with renal I/R injury, and reduces interstitial fibrosis on long term follow-up. 相似文献6.
This paper examines the relationship of the national IQs reported by Lynn & Vanhanen (2002, 2006) to national achievement in mathematics and science among 8th graders in 67 countries. The correlation between the two is 0.92 and is interpreted as establishing the validity of the national IQs. The correlation is so high that national IQs and educational achievement appear to be measures of the same construct. National differences in educational achievement are greater than differences in IQ, suggesting an amplifier effect such that national differences in IQs amplify differences in educational achievement. Controlling for national differences in IQ, slight inverse relationships of educational achievement are observed with political freedom, subjective well-being, income inequality, and GDP. However, public expenditure on education (as % of GDP) was not a significant predictor of differences in educational achievement. 相似文献
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Kasmel J Kaarma H Koskel S Tiit EM 《Anthropologischer Anzeiger; Bericht über die biologisch-anthropologische Literatur》2004,62(1):93-106
A total of 462 schoolgirls aged 7-8 and 17-18 years were examined anthropometrically (45 body measurements and 10 skinfolds) in a cross-sectional study. The data were processed in two age groups: 7-8-year-olds (n = 205) and 17-18-year-olds (n = 257). Relying on average height and weight in the groups, both groups were divided into five body build classes: small, medium, large, pyknomorphous and leptomorphous. In these classes, the differences in all other body measurements were compared, and in both age groups, analogous systematic differences were found in length, width and depth measurements and circumferences. This enabled us to compare proportional changes in body measurements during ten years, using for this ratios of averages of basic measurements and measurement groups in the same body build classes. Statistical analysis by the sign test revealed statistically significant differences between various body build classes in the growth of averages. Girls belonging to the small class differed from the girls of the large class by an essentially greater increase in their measurements. Our results suggest that the growth rate of body measurements of girls with different body build can be studied by the help of body build classification. 相似文献
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Kasari M Padrik P Vaasa A Saar K Leppik K Soplepmann J Uri A 《Analytical biochemistry》2012,422(2):79-88
A novel nonmetal optical probe ARC-1063 whose long-lifetime luminescence is induced by association with the target protein kinase is used for the measurement of the concentration of catalytic subunit of protein kinase A (PKAc) in complicated biological solutions. High affinity (K(D) = 10 pM toward PKAc) and unique optical properties of the probe enable its application for the measurement of picomolar concentrations of PKAc in the presence of high concentrations of other proteins. The described assay is applicable in the high-throughput format with the instrument setups designed for lanthanide-based time-gated (time-resolved) luminescence methods. The assay is used for demonstration that extracellular PKAc (ECPKA) is present in plasma samples of all healthy persons and cancer patients but great care must be taken for procedures of treatment of blood samples to avoid disruption, damage, or activation of platelets in the course of plasma (or serum) preparation and conservation. 相似文献
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There are 10,091 km2 of peatlands in Estonia and human activities may have changed the role of northern peatlands from global sinks to global sources of carbon. The aim of this work was to explain the changes in organic carbon exports from eleven Estonian rivers in the period 1992–2007 in terms of land use change, climate change quantified by trends in stream-water discharge and hydrological droughts and reductions in atmospheric sulfate quantified by change in water chemistry. Direct TOC (total organic carbon) measurements had been initiated in 1998. We used CODKMnO4 (permanganate oxygen consumed) as its surrogate for the whole time span (Spearman’s determination coefficient in six small northern Estonian rivers 0.95 > ρ2 > 0.72; p < 0.01). The Mann–Kendall test revealed significant trends in the TOC proxy in five small rivers in northern Estonia (M–K stat > 2.35; p < 0.05). The trends in the eleven investigated streams correlated closely with the increased 28 ratios of drought days (Spearman’s ρ2 = 0.68; p < 0.01). The correlations with land use compositions, decreases in water discharges and SO4 2? concentrations were insignificant (p > 0.05). We conclude that the main factor in the increase of organic carbon export is the deepening of droughts driven by climate change, magnified by man-made drainage. 相似文献
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Mai Bl?ndal Tiia Ainla Toomas Marandi Aleksei Baburin Jaan Eha 《Cardiovascular diabetology》2012,11(1):1-8