检索结果-南通市图书馆

胺基化树脂负载Pd(0)对Heck反应催化性能的研究

在线全文

学校读者我要写书评

暂无评论

化学学报 2005年第16期63卷 1469-1473页

作者：杨元法曾朝霞罗孟飞李巧玲黄朝表浙江师范大学物理化学研究所浙江省固体表面反应化学重点实验室金华321004 浙江大学分析测试中心杭州310028

将氯球用胺化剂、乙二胺、胍进行胺化后负载氯化钯,在乙醇溶液中用硼氢化钾还原,制备了含胺功能基树脂负载钯(0)的催化剂;研究了催化剂对含各种取代基碘代苯与丙烯酸的Heck芳基化反应催化性能.结果表明,该类催化剂具有良好的催化活性和... 详细信息

将氯球用胺化剂、乙二胺、胍进行胺化后负载氯化钯,在乙醇溶液中用硼氢化钾还原,制备了含胺功能基树脂负载钯(0)的催化剂;研究了催化剂对含各种取代基碘代苯与丙烯酸的Heck芳基化反应催化性能.结果表明,该类催化剂具有良好的催化活性和重复使用性能,其中用乙二胺功能化树脂负载的Pd(0)催化剂在90℃重复使用17次时能保持良好的催化活性.催化剂反应前后的SEM形貌图和过滤液的活性试验表明催化剂活性组分Pd(0)在反应中有沥取(leaching)现象.

关键词：胺化树脂负载型钯催化剂 Heck反应循环使用催化性能负载树脂胺基化 Heck芳基化反应重复使用性能

Vertical gradients of neutral winds observed by ICON and estimated by the Horizontal Wind Model during the geomagnetic storm on August 26−28,2021

在线全文

学校读者我要写书评

暂无评论

Earth and Planetary Physics 2025年第1期9卷 69-80页

作者： JiaWei Wu chao Xiong YuYang huang YunLiang Zhou Department of Space Physics School of Electronic InformationHubei Luojia LaboratoryWuhan UniversityWuhan 430072China

The Michelson Interferometer for Global High-resolution Thermospheric Imaging(MIGHTI)onboard the Ionospheric Connection Explorer(ICON)satellite offers the opportunity to investigate the altitude profile of thermospheric *** this study,we used the red-line measurements of MIGHTI to compare with the results estimated by Horizontal Wind Model 14(HWM14).The data selected included both the geomagnetic quiet period(December 2019 to August 2022)and the geomagnetic storm on August 26-28,*** the geomagnetic quiet period,the estimations of neutral winds from HWM14 showed relatively good agreement with the observations from *** to the ICON observations,near the equator,zonal winds reverse from westward to eastward at around 06:00 local time(LT)at higher altitudes,and the stronger westward winds appear at later LTs at lower *** around 16:00 LT,eastward winds at 300 km reverse to westward,and vertical gradients of zonal winds similar to those at sunrise hours can be *** the middle latitudes,zonal winds reverse about 2-4 h *** winds vary more significantly than zonal winds with seasonal and latitudinal *** to the ICON observations,in the northern low latitudes,vertical reversals of meridional winds are found at 08:00-13:00 LT from 300 to 160 km and at around 18:00 LT from 300 to 200 km during the June *** reversals of meridional winds are found at 04:00-07:00 LT from 300 to 160 km and at 22:00-02:00 LT from 270 to 200 km during the December *** the southern low latitudes,meridional wind reversals occur at 08:00-11:00 LT from 200 to 160 km and at 21:00-02:00 LT from 300 to 200 km during the June *** the December solstice,reversals of the meridional wind appear at 20:00-01:00 LT below 200 km and at 06:00-11:00 LT from 300 to 160 *** the northern middle latitudes,the northward winds are dominant at 08:00-14:00 LT at 230 km during the June *** winds persist until

关键词： horizontal neutral winds vertical gradients Ionospheric Connection Explorer satellite Horizontal Wind Model 14 geomagnetic storm

基于DNA QDs@PDA荧光共振能量转移的半胱氨酸传感器

在线全文

学校读者我要写书评

暂无评论

分析化学 2020年第1期48卷 83-89页

作者：陈飘飘邢怡晨刘洋郑姗黄朝表浙江师范大学化学与生命科学学院浙江师范大学行知学院

建立了基于DNA量子点(DNA QDs)与聚多巴胺(PDA)荧光共振能量转移(FRET)检测半胱氨酸的方法。DNA QDs发射的荧光被PDA分子吸收,发生FRET,导致DNA QDs的荧光猝灭,使DNA QDs处于荧光"关闭"状态。当存在半胱氨酸时,从多巴胺(DA)向PDA的自发... 详细信息

建立了基于DNA量子点(DNA QDs)与聚多巴胺(PDA)荧光共振能量转移(FRET)检测半胱氨酸的方法。DNA QDs发射的荧光被PDA分子吸收,发生FRET,导致DNA QDs的荧光猝灭,使DNA QDs处于荧光"关闭"状态。当存在半胱氨酸时,从多巴胺(DA)向PDA的自发氧化聚合反应将被阻断,使DNA QDs的荧光恢复,处于荧光"开启"状态,且DNA QDs荧光的恢复程度与溶液中半胱氨酸的浓度相关,基于此构建了半胱氨酸荧光传感器。检测半胱氨酸的线性方程为y=0.0181x-0.0185,线性范围为10.0～100.0μmol/L,检出限为1.7μmol/L(S/N=3,n=10),此传感器对半胱氨酸具有良好的选择性,常见氨基酸及生物硫醇小分子均无干扰。将本方法用于人尿样中半胱氨酸的测定,回收率为98.6%～105.9%。

关键词： DNA量子点共振能量转移聚多巴胺半胱氨酸

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

铝对荞麦和金荞麦根系分泌物的影响

水土保持学报 2005年第2期19卷 106-109页

作者：王芳黄朝表刘鹏姚小芳浙江师范大学化学与生命科学学院浙江金华321004

以荞麦和金荞麦为实验材料,用砂培方法研究Al胁迫下荞麦和金荞麦根系分泌电解质、糖和氨基酸的变化。结果表明,Al胁迫条件下,电解质外渗率、糖类随Al3 + 浓度升高而增加;在低浓度Al3 + 作用下,随处理浓度的升高,氨基酸分泌量增加,当处... 详细信息

以荞麦和金荞麦为实验材料,用砂培方法研究Al胁迫下荞麦和金荞麦根系分泌电解质、糖和氨基酸的变化。结果表明,Al胁迫条件下,电解质外渗率、糖类随Al3 + 浓度升高而增加;在低浓度Al3 + 作用下,随处理浓度的升高,氨基酸分泌量增加,当处理浓度高于相应浓度时,氨基酸分泌量随浓度升高而减少。Al胁迫使荞麦和金荞麦根系分泌物的种类和浓度发生改变。

关键词：根系分泌物金荞麦 Al^3+ 电解质外渗率氨基酸实验材料胁迫条件分泌量铝低浓度

在线全文

学校读者我要写书评

暂无评论

浙江及邻近地区蛇足石杉依存环境的初步研究

热带亚热带植物学报 2005年第3期13卷 211-216页

作者：李沛玲黄朝表郭水良钟艳斌浙江师范大学化学与生命科学学院浙江金华321004

对浙江及邻近地区产的蛇足石杉(Huperzia serrata)7个种群的自然环境进行野外观察,测定了土壤含水量、电导率、有机质含量、pH值,植株和土壤中K、Ca、Mg、Fe、Zn、Cu、Mn、Na、Al、Pb、Cd11种元素的含量,以及植株中石杉碱甲(HupA)含量... 详细信息

对浙江及邻近地区产的蛇足石杉(Huperzia serrata)7个种群的自然环境进行野外观察,测定了土壤含水量、电导率、有机质含量、pH值,植株和土壤中K、Ca、Mg、Fe、Zn、Cu、Mn、Na、Al、Pb、Cd11种元素的含量,以及植株中石杉碱甲(HupA)含量。结果表明,蛇足石杉种群多分布于海拔350-1700m的山地密林下或沟谷阴湿土中,郁闭度、年均降雨量、空气相对湿度均较大;环境中土壤含水量为10%-30%,pH值4.57-5.31,电导率0.061-0.385mscm-1,有机质含量6.18%-9.75%;蛇足石杉对K、Ca、Zn和Na的需要程度较高,对Pb、Cu、Cd3种重金属元素的富集能力较强,在人工栽培中应注意协调各元素的合理配给;蛇足石杉较适宜生长的环境条件为:土壤电导率以及pH值相对较低;郁闭度高,年均降雨量和空气相对湿度较大。基于土壤理化性质,对7个种群分布点进行除趋势对应分析,表明石杉碱甲含量高的磐安种群分布点具有特殊性,提示环境条件对蛇足石杉中HupA含量有较大的影响。

关键词：蛇足石杉环境土壤元素

Nitrogen addition promotes soil carbon accumulation globally

在线全文

学校读者我要写书评

暂无评论

Science China Life Sciences 2025年第1期 284-293页

作者： Xuemei Yang Suhui Ma Erhan huang Danhua Zhang Guoping Chen Jiangling Zhu Chengjun Ji biao Zhu Lingli Liu Jingyun Fang Institute of Ecology College of Urban and Environmental Sciencesand Key Laboratory for Earth Surface Processes of the Ministry of EducationPeking University Ministry of Education Key Laboratory for Transboundary Ecosecurity of Southwest China School of Ecology and Environmental ScienceYunnan University State Key Laboratory of Vegetation and Environmental Change Institute of BotanyChinese Academy of Sciences

Soil is the largest carbon(C) reservoir in terrestrial ecosystems and plays a crucial role in regulating the global C cycle and climate *** nitrogen(N) deposition has been widely considered as a critical factor affecting soil organic carbon(SOC) storage, but its effect on SOC components with different stability remains unclear. Here, we analyzed extensive empirical data from 304 sites worldwide to investigate how SOC and its components respond to N addition. Our analysis showed that N addition led to a significant increase in bulk SOC(6.7%), with greater increases in croplands(10.6%) and forests(6.0%) compared to grasslands(2.1%). Regarding SOC components, N addition promoted the accumulation of plant-derived C(9.7%–28.5%) over microbial-derived C(0.2%), as well as labile(5.7%) over recalcitrant components(–1.2%), resulting in a shift towards increased accumulation of plant-derived labile C. Consistently, N addition led to a greater increase in particulate organic C(11.9%) than mineral-associated organic C(3.6%), suggesting that N addition promotes C accumulation across all pools, with more increase in unstable than stable pools. The responses of SOC and its components were best predicted by the N addition rate and net primary productivity. Overall, our findings suggest that N enrichment could promote the accumulation of plant-derived and non-mineral associated C and a subsequent decrease in the overall stability of soil C pool, which underscores the importance of considering the effects of N enrichment on SOC components for a better understanding of C dynamics in soils.

关键词：

同方期刊数据库

Thermally triggered topological polymerization in diacetylene-functionalized covalent organic framework toward enhanced memristive properties

在线全文

学校读者我要写书评

暂无评论

Science China Chemistry 2025年

作者： Panke Zhou Yuxing huang Ziyue Yu Cong Zhang Qian Chen Yiping Li chao Lin Xiong Chen State Key Laboratory of Photocatalysis on Energy and Environment Key Laboratory of Advanced Carbon-Based Functional MaterialsCollege of Chemistry Fuzhou University

The development of stimuli-responsive switching memory devices and the elucidation of their switching mechanisms in specific environments are crucial for advancing the field of molecular electronics. Herein, we propose two distinct two-dimensional covalent organic frameworks (COFs), namely Py-EDA and Py-BDA, incorporating acetylene (-C≡C-) or diacetylene(-C≡C-C≡C-) moieties, respectively, targeting fabricate memory devices exhibiting stimuli-responsive switching *** findings demonstrate that the incorporation of acetylene units effectively modulates the electronic band structure and enhances the degree ofπ-conjugation, resulting in devices that exhibit typical bipolar nonvolatile memory performance. Notably,upon thermal treatment, the memory behavior of the ITO/Py-BDA/Ag device transitions to a write-once-read-many-times(WORM) mode, displaying decreased SET voltage, increased ON/OFF current ratio, and remarkable retention reliability and cycle stability. This switching behavior is attributed to the occurrence of interlayer solid-state topological polymerization at 350℃, leading to the transformation of diacetylene columnar arrays into enyne chains within Py-BDA, thereby further promoting interlayer charge transfer and separation.

关键词：

Quickly obtaining densely dispersed coherent particles in steel matrix and its related mechanical property

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

International Journal of Minerals,Metallurgy and Materials 2025年第1期32卷 111-118页

作者： Xiaoxiao Wang Qingsong huang School of Chemical Engineering Sichuan UniversityChengdu 610065China

Densely distributed coherent nanoparticles(DCN)in steel matrix can enhance the work-hardening ability and ductility of steel *** the routes to this end can be generally classified into the liquid-solid route and the solid-solid ***,the formation of DCN structures in steel requires long processes and complex *** far,obtaining steel with coherent particle enhancement in a short time remains a bottleneck,and some necessary steps remain ***,we show a high-efficiency liquid-phase refining process reinforced by a dynamic magnetic ***-Y-Mn-O particles had an average size of around(3.53±1.21)nm and can be obtained in just around 180 *** small nanoparticles were coherent with the matrix,implying no accumulated dislocations between the particles and the steel *** findings have a potential application for improving material machining capacity,creep resistance,and radiation resistance.

关键词： ferritic steels coherent particles microstructure compression test work hardening

基于硫化镉量子点-二氧化钛复合材料的Hg2+光电化学生物传感器研究

在线全文

学校读者我要写书评

暂无评论

分析化学 2019年第9期47卷 1314-1320页

作者：郑姗刘洋陈飘飘邢怡晨张伟波施娅颖黄朝表浙江师范大学化学与生命科学学院浙江师范大学行知学院

以硫化镉量子点-二氧化钛（CdS QDs/TiO2）复合材料作为光电转换单元,构建了汞离子(Hg2+)光电化学（PEC）生物传感器。将两种不同带隙无机半导体CdS QDs和TiO2偶联以提高电极的性能,当用特定波长的光激发CdS QDs时,处于价带（VB）的电子... 详细信息

以硫化镉量子点-二氧化钛（CdS QDs/TiO2）复合材料作为光电转换单元,构建了汞离子(Hg2+)光电化学（PEC）生物传感器。将两种不同带隙无机半导体CdS QDs和TiO2偶联以提高电极的性能,当用特定波长的光激发CdS QDs时,处于价带（VB）的电子（e-）跃迁至导带（CB）,并在价带上产生空穴（h+）。由于TiO2的导带低于CdS QDs,激发态电子跃迁至TiO2,导致电子-空穴对（e--h+）的空间分离,有效抑制了它们的复合,从而提高了光电转换效率。利用两条互补的短链DNA构建了Hg2+传感器,其中一条富含T碱基的DNA单链因与Hg2+特异性结合形成T-Hg2+-T结构,无法与金纳米粒子标记的另一条DNA单链配对,进而抑制光电流的下降,实现了对Hg2+的灵敏检测。本方法的线性范围为1.0×10-10～1.5×10-7mol/L,检出限为6.0×10-11mol/L（S/N=3）,灵敏度高,选择性好。

关键词：光电化学汞离子(Ⅱ) 生物传感器硫化镉量子点二氧化钛金纳米粒子