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排序方式: 共有515条查询结果,搜索用时 347 毫秒
341.
Ludwig Weißflog Klaus Wienhold Klaus-Dieter Wenzel Gerrit Schüürmann 《Environmental Sciences Europe》1994,6(2):75-80
Air pollution in the region Leipzig-Halle was investigated using two-year-old pine needles (Pinus sylvestris L.) at 39 sites of a biomonitoring net covering an area of ca. 7 500 km2. The concentration values of Al, Ca, Cr, Fe, K, Mg, Mn, Pb and V characterize the immission patterns of the period 1990/91. The method is less suited for Cu, Ni and Zn due to the transfer route soil-pine, and for Cd due to the small total content. There are significant spatial and element-specific variations which require distinct evaluation of the pollution situation. The city of Leipzig itself is a significant source for Pb, Cr, Fe and V emission. Mainly as far as the centre of the region is concerned, the Pb concentration values are beyond those of heavily contaminated reference sites. The bioindication system is also applicable for comparable regions in Eastern Europe where the pine is the dominating conifer type. Immission trends can be monitored over ecologically relevant periods of time. 相似文献
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The gas-transport function of red blood cells which have incorporated inositol hexaphosphate is significantly improved by fusion with effector-loaded lipid vesicles. “Right-shifts” of the O2-binding curves of inositol hexaphosphate-loaded red blood cells with half-saturation pressures at 37 °C up to 98 mmHg are observed. The transformation of 56% of the intracellular haemoglobin into the low affinity state corresponds to an optimum increase of the O2-release capacity of 270%. The CO2 transport is also correspondingly enhanced. The treated red blood cells show no inositol hexaphosphate depletion during a reasonable time. 相似文献
344.
Colin G. Jones Klaus Wyser Anders Ullerstig Ulrika Willén 《Ambio-人类环境杂志》2004,33(4):191-200
作为ARCMIP国际计划的一部分,罗斯比中心区域气候模型(RCA2)针对整个北冰洋地区的气候作了数值模拟整合,并与来自sHEBA数据集的观测资料作了比较,RCA2标准模型对北极冬季的云量和长波辐射的模拟较实况偏多.通过引入新的云量参数化方案(该参数化方案显著地改进了云量的年循环)减少了这部分误差,确定了介于晴空向下大气长波辐射与云层底部的长波辐射的补偿率,利用可以更准确描述冰晶与太阳辐射相互作用的辐射方案修正了模型,从而使得模型对云-太阳辐射间的相互作用的描述更接近实际.在模拟晴空辐射部分,由于太阳辐射大气透射率过大,经常在边界层云的顶部产生正偏差.引入真实海冰和积雪两种表面反照率的时间变化,对准确模拟地面能量净收支是至关重要的.同样,为了准确模拟北极圈地区近地面的热力学过程,将雪面温度作为预报量引入模型中也似乎是必不可少的. 相似文献
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Wierrani F Kubin A Loew HG Henry M Spängler B Bodner K Grünberger W Ebermann R Alth G 《Die Naturwissenschaften》2002,89(10):466-469
We report the development of a novel simple experimental method which allows the comparison of new photosensitizers based on their production of reactive oxygen species. A high-performance liquid chromatography (HPLC) assay permits the monitoring of several substances (sensitizer, reactant and oxidized end product) simultaneously on a single chromatogram. Photoreactions were monitored throughout their course by the HPLC assay surveying the sensitizers' efficiency of singlet oxygen production by the oxidative decomposition of luminol. Several photosensitizers were tested: Rose Bengal, Methylene Blue, Protoporphyrin IX, Photosan III, Photofrin, Hypericin and Pseudohypericin. Additionally, photoreactions were monitored by a standard pO2 detection system. The measurements of the two detection methods were strongly correlated. Rose Bengal proved to be the most efficient photosensitizer, clearly decreasing the luminol concentration and causing a corresponding increase in aminophthalic acid. Our experiments show that when factors necessary for photochemical reactions are absent or are blocked (antioxidants), no reaction can be detected. 相似文献
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