Seasonal migration of cirrus clouds over the Asian Monsoon regions and the Tibetan Plateau measured from MODIS/Terra

IEECAS SKLLQG

稀土离子对甲醇电氧化的影响

直接甲醇燃料电池(DMFC)是以固体聚合物为电解质,阳极以液相甲醇或蒸气相甲醇进料,阴极以空气或氧气为氧化剂.DMFC具有原料甲醇易储存、电池的理论电压高和能量效率高等特点,适于作电动车电源和便携式电源,具有广阔的发展前景.然而,在DMFC中,甲醇的阳极氧化涉及6个电子的传递过程,比氢气的氧化更困难,由于存在较高的阳极过电位,使得电池的实际输出电压低于理论电压;更为重要的是甲醇的部分氧化中间产物(CO)易使电催化剂中毒,因此,高效的阳极电催化剂一直是DMFC中的重要研究领域之一[1~7].目前解决这一问题的途径主要集中在对电催化剂的研究和改进上,如性能较好的Pt/Metal(oxide),即Pt复合金属或金属氧化物催化剂.稀土元素Ln系位于元素周期表中的B族,具有丰富的d轨道和f轨道电子,因此可以作为催化剂中的第二种金属元素加以研究.将稀土元素及其氧化物用于较低温度(250℃)下催化CO的化学氧化反应已早有研究[8].目前,已经有将Rh/Sm和Pt/Sm合金应用于CO的催化氧化反应的研究报道[9].本文选择几种稀土离子作为添加剂,研究了稀土离子对甲醇电氧化反应的影响.1实验部分1.1试剂与仪器甲醇(优级纯),...

The contribution of trace elements from seawater to chimneys: a case study of the native sulfur chimneys in the sea area off Kueishantao, northeast of Taiwan Island

Hydrothermal fluid containing abundant matter erupts from seafloor, meets ambient cold seawater and forms chimneys. So the main matter origins of chimneys are seawater and matter which are taken by hydrothermal fluid from deep reservoir. However, because of seawater's little contribution to the forming of chimneys, it is usually covered by the abundant matter which is taken by hydrothermal fluid. Therefore, chimneys formed in ordinary deep seawater hydrothermal activity, containing complex elements, cannot be used to study the seawater's contribution to their formation. While the native sulfur chimneys, formed by hydrothermal activity near the sea area off Kueishantao, are single sulfur composition (over 99%), and within chimneys distinct layers are seen. Different layers were sampled for trace element determination, with Inductively Coupled Plasma Mass Spectrometry (ICP-MS). By analyzing the data, we consider C-layer (secondary inner-layer) as the framework layer of the chimney which formed early (Fig. 4), and its trace elements derive from hydrothermal fluid. While the trace elements within A, B, D layers have undergone later alteration. A, B layers are affected by seawater and D layer by hydrothermal fluid. The increase of trace elements of A and B layers was calculated using C layer as background. Based on the known typical volume of chimneys of the near sea area off Kueishantao, we calculated the volume of seawater that contributed trace element to chimneys formation to be about 6.37 x 10(4) L. This simple quantified estimate may help us better understand the seafloor hydrothermal activity and chimneys.

羟基自由基降解琼胶及其产物的活性研究

琼胶是一种从石花菜等红藻中提取的，目前生产工艺和结构等方面研究比较成熟的海藻多糖，广泛应用于医药、仪器等行业。但是，海藻多糖因为具有分子量大，粘度大，溶解度较小的等特点，而使其应用范围受到限制。利用降解的手段对其进行修饰，降低分子量和粘度，改善溶解性，可以拓展其应用范围。并且根据文献报道，琼 胶寡糖具有一些特殊的生物活性，如抗氧化性，抗炎症等。因此，对琼胶降解的研究具有生要意义。本研究中，为了选择一种合适的降解方法，进行了几种水解方法的尝试，其中包括在不同湿度和酸度下盐酸水解，过氧化氢和醋酸催化水解，Fenton体系羟基自由基降解。对于酸水解和Fenton体系氧化还原降解方法，通过粘度法对反应的速度进行了比较，表明氧化还原降解反应中琼胶的粘度降低比较快，并且具有代表性和新意，确定为本实验的降解琼胶的方法并对氧化还原降解所得的产物进行了活性实验。通过模仿自然界普遍存在的氧化还原降解反应，利用Vc诱导的Fenton体系产生的羟基自由基氧化还原降解琼胶得到低分子量的琼胶。降解产物经过高速离心、60％乙醇沉淀，除去分子量比较大的降解产物和磷酸盐，得到可溶于60％乙醇的分子量估计小于3000的降争产物，其产率为85％。利用经Sephadex-G25凝胶色谱分离所香的不同分子量的级分进行分子量和α－葡萄糖苷酶抑制活性关系的实验。降解产物对α－葡萄糖苷酶的抑制率和各级分的浓度呈线性正相关，并且各级分的IC_(50)则随着分子量的降低而降低。另外，对所得的降解产物混合物进行了红外吸收光谱、质子去偶核磁共震碳谱和负离子基质辅助激光诱导－飞行时间质谱结构分析。结果表明，氧化还原降解反应的专一性差，在得到寡糖的同时，在光谱图中出现一些比较复杂的副产物的结构信息。最后，根据MTT法的原理，以有体皮肤成纤维细胞为材料，通过紫外线辐射产生自由基造成氧化损伤，研究降解产物对成纤维细胞的保护作用。当无紫外线辐射时，降解产物对成纤维细胞具有显著的促进生长增殖作用：当经UVa、UBb辐射时则可以显著地表现出对损伤的保护作用，并且这种促进生长和保护作用呈显著的量效关系，表明降解产物具有清除基自由基的作用。但是，因为氧化还原降解以应的机理尚不十分明的以及琼羟胶的特殊结构，使得反应的副产物很难预测，也就使得分离工作难以进行，所以，根据目前所得的信息，尚不能确定是降解产物的什么级分产生的以上两种生物活性。

基于多目标权重分析的草地适宜放牧率探讨

依据生态系统服务的理念，首次发展了生态系统服务指数（ESI），试图通过对生态系统服务功能的综合考虑，提出科学的适宜放牧率的评价方法。本研究利用美国北达科他州立大学中部草原研究站17年长期放牧试验数据，选取植物多样性Shannon-Wiener指数、地上净初级生产力、土壤表层含水量和单位面积家畜增重4个指标，通过对不同指标分别赋予不同的权重，计算不同管理目标下ESI及其稳定性，并对单目标管理与多目标管理进行了比较研究。结果表明，对于北美混合普列里（Prairie）草地，围封不利用或建立自然保护区，虽然生态系统比较稳定，但既不能有效的提高植物多样性、初级生产力和土壤水分含量等生态功能，又没有畜产品产出；而在重牧或极重牧处理下虽然获得了较大的畜产品生产，但导致了草地生态系统的退化和较大的系统不稳定性。因此，这2种管理方式在实践中都是不可取的。应用生态系统服务指数综合考虑，认为应该权衡各项生态功能和生产功能，此时轻牧或中牧是最适宜的。因此，ESI的建立避免了单项指标的评价偏差，使得适宜放牧率的确定更加合理。

甘肃胡麻地方种质资源品质特性研究

对甘肃省116份胡麻地方品种的重要品质指标--粗脂肪、硬脂酸、棕榈酸、油酸、亚油酸、亚麻酸含量和碘值进行测定,并根据这些品质指标对供试品种进行聚类分析.结果显示:(1)供试品种粗脂肪含量平均值为37.48%,变异系数3.8%;硬脂酸、油酸含量平均值分别为5.32%和29.05%,变异系数分别为19.5%和11.6%;棕榈酸、亚麻酸、亚油酸含量平均值分别为5.9%、48.76%、10.95%,变异系数分别为8.4%、8%、8%;平均碘价175.60,变异系数2.76%;(2)聚类分析结果显示,116个品种聚为7大类,其中:b亚组群硬脂酸和油酸含量最高,而亚麻酸含量最低;d亚组群品种亚麻酸含量最高;e亚组群粗脂肪含量和碘价最高,油酸含量最低;f亚组群硬脂酸含量最低;g亚组群棕榈酸含量最高,碘价最低.

Phylogeography of the Qinghai-Tibetan Plateau endemic Juniperus przewalskii (Cupressaceae) inferred from chloroplast DNA sequence variation

The vegetation of the northeast Qinghai-Tibetan Plateau is dominated by alpine meadow and desert-steppe with sparse forests scattered within it. To obtain a better understanding of the phylogeography of one constituent species of the forests in this region, we examined chloroplast trnT-trnF and trnS-trnG sequence variation within Juniperus przewalskii, a key endemic tree species. Sequence data were obtained from 392 trees in 20 populations covering the entire distribution range of the species. Six cpDNA haplotypes were identified. Significant population subdivision was detected (G(ST) = 0.772, N-ST = 0.834), suggesting low levels of recurrent gene flow among populations and significant phylogeographic structure (N-ST > G(ST), P < 0.05). Eight of the nine disjunct populations surveyed on the high-elevation northeast plateau were fixed for a single haplotype (A), while the remaining, more westerly population, contained the same haplotype at high frequency together with two low frequency haplotypes (C and F). In contrast, most populations that occurred at lower altitudes at the plateau edge were fixed or nearly fixed for one of two haplotypes, A or E. However, two plateau edge populations had haplotype compositions different from the rest. In one, four haplotypes (A, B, D and E) were present at approximately equivalent frequencies, which might reflect a larger refugium in the area of this population during the last glacial period. Phylogenetic analysis indicated that the most widely distributed haplotype A is not ancestral to other haplotypes. The contrasting phylogeographic structures of the haplotype-rich plateau edge area and the almost haplotype-uniform plateau platform region indicate that the plateau platform was recolonized by J. przewalskii during the most recent postglacial period. This is supported by the findings of a nested clade analysis, which inferred that postglacial range expansion from the plateau edge followed by recent fragmentation is largely responsible for the present-day spatial distribution of cpDNA haplotypes within the species.

洱海沉积物孔隙水中溶解有机质的三维荧光光谱特征

文章应用三维荧光光谱技术对洱海沉积物孔隙水中的溶解有机质进行了研究。结果表明,所有样品均含有4个明显的荧光峰,其中A和C为类腐殖酸荧光,B和D为类蛋白荧光。荧光强度在沉积物-水界面特别强,在1cm处急剧下降,之后随着沉积深度呈上升趋势。孔隙水溶解有机质均具有强的类蛋白荧光,揭示了溶解有机质中含有大量色氨酸、酪氨酸等芳环结构的类蛋白物质,并且在早期成岩过程中随着沉积深度呈积累趋势;类蛋白荧光与类腐殖酸荧光之间具有一定的相关关系,r(A,C)值在0.94-1.79之间,随着沉积深度逐渐下降,r(D,B)值在0.9-1.75之间,与r(A,C)值极为接近,且随着沉积深度有着类似的变化趋势,说明在洱海沉积物孔隙