The search for a topographic signature of life

Landscapes are shaped by the uplift, deformation and breakdown of bedrock and the erosion, transport and deposition of sediment. Life is important in all of these processes. Over short timescales, the impact of life is quite apparent: rock weathering, soil formation and erosion, slope stability and river dynamics are directly influenced by biotic processes that mediate chemical reactions, dilate soil, disrupt the ground surface and add strength with a weave of roots. Over geologic time, biotic effects are less obvious but equally important: biota affect climate, and climatic conditions dictate the mechanisms and rates of erosion that control topographic evolution. Apart from the obvious influence of humans, does the resulting landscape bear an unmistakable stamp of life? The influence of life on topography is a topic that has remained largely unexplored. Erosion laws that explicitly include biotic effects are needed to explore how intrinsically small-scale biotic processes can influence the form of entire landscapes, and to determine whether these processes create a distinctive topography.     

精密平板检测误差分布及影响因素

讨论高精度平板检测误差分布及实际测量中的影响因素,并提出了减小或消除检测误差的方法     

Methane bubbling from Siberian thaw lakes as a positive feedback to climate warming

Large uncertainties in the budget of atmospheric methane, an important greenhouse gas, limit the accuracy of climate change projections. Thaw lakes in North Siberia are known to emit methane, but the magnitude of these emissions remains uncertain because most methane is released through ebullition (bubbling), which is spatially and temporally variable. Here we report a new method of measuring ebullition and use it to quantify methane emissions from two thaw lakes in North Siberia. We show that ebullition accounts for 95 per cent of methane emissions from these lakes, and that methane flux from thaw lakes in our study region may be five times higher than previously estimated. Extrapolation of these fluxes indicates that thaw lakes in North Siberia emit 3.8 teragrams of methane per year, which increases present estimates of methane emissions from northern wetlands (< 6-40 teragrams per year; refs 1, 2, 4-6) by between 10 and 63 per cent. We find that thawing permafrost along lake margins accounts for most of the methane released from the lakes, and estimate that an expansion of thaw lakes between 1974 and 2000, which was concurrent with regional warming, increased methane emissions in our study region by 58 per cent. Furthermore, the Pleistocene age (35,260-42,900 years) of methane emitted from hotspots along thawing lake margins indicates that this positive feedback to climate warming has led to the release of old carbon stocks previously stored in permafrost.     

壳聚糖乙烯基衍生物的合成及其对鸟嘌呤的印迹识别

以壳聚糖(CS)为原料,通过其活性基团与甲基丙烯酸缩水甘油酯(GMA)反应,制得水溶性的乙烯基壳聚糖衍生物(CS-GMA).用FTIR和XRD对所合成的衍生物进行了分析和表征.在印迹分子鸟嘌呤的存在下,利用该乙烯基壳聚糖衍生物为功能单体和乙二醇二甲基丙烯酸酯(EGDMA)为交联剂,合成了可通过非共价自组装法形成多个识别位点的生物碱基-鸟嘌呤的分子印迹聚合物(MIP).通过静态吸附实验,用紫外分光光度法研究了CS-GMA的分子识别作用.结果表明分子印迹聚合物(MIP)对鸟嘌呤具有较高的识别能力及选择性.     

人体内的腔隙结构及其基础性的生理功能

简述了有关人体科学方面的一个问题:即以人体内存在腔隙结构和腔气的事实为依据,从其基本的物理性质出发讨论了它应具有的一些基础性的生理功能.     

我国消费需求不足的深层次原因及政策建议

城乡居民收入比重下降是我国消费率下降的最主要原因,城乡居民消费倾向下降对消费率下降也有较大影响,城市化率提高是我国消费率变动的唯一正向促进因素。因此,扩大我国居民消费应以提高居民收入比重和加快城市化进程为主要着力点,努力提高居民收入占国民收入的比重,公共支出占政府支出的比重;调整国民收入分配结构、政府支出结构和城乡二元结构;深化户籍制度改革、资源价格和税费改革、垄断性行业改革、税收制度改革。     

模糊优化决策模型及其在产品定价方面的应用

为了凸显模糊优化决策的实际应用价值,研究模糊优化决策方法在某一种产品定价方面的应用。通过实际数据的采集和对相关影响因素的分析,建立了基于互补性优先关系的模糊优化决策模型,并将该模型应用于产品定价。通过对某地一些影楼的套系价格采集,进行数据分析,求出最优解。