消落带是位于水陆交错带的一种特殊生态系统.消落带土壤作为生态系统中氮、磷元素重要的“源”与“汇”,在生物地球化学循环研究中具有重要意义.该研究基于中国知网CNKI以及Web of Science数据库检索近10年三峡消落带土壤氮、磷研究文献...消落带是位于水陆交错带的一种特殊生态系统.消落带土壤作为生态系统中氮、磷元素重要的“源”与“汇”,在生物地球化学循环研究中具有重要意义.该研究基于中国知网CNKI以及Web of Science数据库检索近10年三峡消落带土壤氮、磷研究文献,提取w(TN)、w(TP)数据并进行统计,从宏观尺度上分析w(TN)、w(TP)的时空分布特征.结果表明:①高程分布上,当高程高于155 m时,土壤w(TN)(0.75~1.17 g kg)随着高程增加呈下降趋势,土壤w(TP)未发生显著变化(0.53~0.60 g kg);当高程低于155 m时,土壤w(TN)处于较低水平(0.66~0.86 g kg),但w(TP)维持较高水平(0.60~0.76 g kg).②时间分布上,消落带土壤w(TN)整体呈现逐年递减的趋势,Pearson相关系数为-0.64,但是w(TP)没有显著变化.③地区分布上,三峡上游库区消落带土壤w(TP)出现显著高值,下游库区w(TN)出现显著高值.研究显示:不同高程土壤受植物残体分解等因素影响,在落干期w(TN)上升,在浸没期向上覆水体释放TN;水位调节导致的淹没强度变化对消落带土壤中TN产生淋溶作用,而对TP的影响较小;对于消落带上游地区应更关注土壤中高w(TP)带来的环境风险,而对于消落带下游地区应更关注因水土流失和非点源输出导致的高w(TN)所致环境风险.展开更多
Fluorescence detection is widely used in biology and medicine,while the realization of on-chip fluorescence detection is vital for the portable and point-of-care test(POCT)application.In this Letter,we propose an effi...Fluorescence detection is widely used in biology and medicine,while the realization of on-chip fluorescence detection is vital for the portable and point-of-care test(POCT)application.In this Letter,we propose an efficient fluorescence excitation and collection system using an integrated GaN chip consisting of a slot waveguide and a one-dimensional photonic crystal(1D PC)waveguide.The slot waveguide is used to confine the excitation light for intense light–sample interaction,and the one-trip collection efficiency at the end of slot waveguide is up to 14.65%.More interestingly,due to the introduction of the 1D PC waveguide,the fluorescence signal is directly filtered out,and the excitation light is reflected to the slot waveguide for multiple excitations.Its transmittances for the designed exciting wavelength of 520 nm and the fluorescent wavelength of 612 nm are 0.2%and 85.4%,respectively.Finally,based on numerical analysis,the total fluorescence collection efficiency in our system amounts to 15.93%.It is the first time,to our knowledge,that the concept of an all-in-one-chip fluorescence detection system has been proposed,which paves the way for on-chip fluorescence excitation and collection,and may find potential applications of miniaturized and portable devices for biomedical fluorescence detection.展开更多
文摘消落带是位于水陆交错带的一种特殊生态系统.消落带土壤作为生态系统中氮、磷元素重要的“源”与“汇”,在生物地球化学循环研究中具有重要意义.该研究基于中国知网CNKI以及Web of Science数据库检索近10年三峡消落带土壤氮、磷研究文献,提取w(TN)、w(TP)数据并进行统计,从宏观尺度上分析w(TN)、w(TP)的时空分布特征.结果表明:①高程分布上,当高程高于155 m时,土壤w(TN)(0.75~1.17 g kg)随着高程增加呈下降趋势,土壤w(TP)未发生显著变化(0.53~0.60 g kg);当高程低于155 m时,土壤w(TN)处于较低水平(0.66~0.86 g kg),但w(TP)维持较高水平(0.60~0.76 g kg).②时间分布上,消落带土壤w(TN)整体呈现逐年递减的趋势,Pearson相关系数为-0.64,但是w(TP)没有显著变化.③地区分布上,三峡上游库区消落带土壤w(TP)出现显著高值,下游库区w(TN)出现显著高值.研究显示:不同高程土壤受植物残体分解等因素影响,在落干期w(TN)上升,在浸没期向上覆水体释放TN;水位调节导致的淹没强度变化对消落带土壤中TN产生淋溶作用,而对TP的影响较小;对于消落带上游地区应更关注土壤中高w(TP)带来的环境风险,而对于消落带下游地区应更关注因水土流失和非点源输出导致的高w(TN)所致环境风险.
基金supported by the National Natural Science Foundation of China(Nos.61875083 and 61535005)the Social Development Project of Jiangsu Province(No.BE2019761)the Key Research and Development Program of Shandong Province(No.2020CXGC011304).
文摘Fluorescence detection is widely used in biology and medicine,while the realization of on-chip fluorescence detection is vital for the portable and point-of-care test(POCT)application.In this Letter,we propose an efficient fluorescence excitation and collection system using an integrated GaN chip consisting of a slot waveguide and a one-dimensional photonic crystal(1D PC)waveguide.The slot waveguide is used to confine the excitation light for intense light–sample interaction,and the one-trip collection efficiency at the end of slot waveguide is up to 14.65%.More interestingly,due to the introduction of the 1D PC waveguide,the fluorescence signal is directly filtered out,and the excitation light is reflected to the slot waveguide for multiple excitations.Its transmittances for the designed exciting wavelength of 520 nm and the fluorescent wavelength of 612 nm are 0.2%and 85.4%,respectively.Finally,based on numerical analysis,the total fluorescence collection efficiency in our system amounts to 15.93%.It is the first time,to our knowledge,that the concept of an all-in-one-chip fluorescence detection system has been proposed,which paves the way for on-chip fluorescence excitation and collection,and may find potential applications of miniaturized and portable devices for biomedical fluorescence detection.
