检索结果-南通市图书馆

Long-term mercury variations in tree rings of the permafrost forest,northeastern China

Science China Earth Sciences 2022年第7期65卷 1328-1338页

作者： Huhu KANG Xiaohong LIU Junming GUO Qiuliang ZHANG Yabo WANG Jie HUANG Guobao XU Guoju WU wensen ge Shichang KANG State Key Laboratory of Cryospheric Science Northwest Institute of Eco-Environment and ResourcesChinese Academy of SciencesLanzhou 730000China School of geography and Tourism Shaanxi Normal UniversityXi'an 710119China University of Chinese Academy of Sciences Beijing 100049China Forest College Inner Mongolia Agricultural UniversityHohhot 010018China Key Laboratory of Tibetan Environment Changes and Land Surface Processes Institute of Tibetan Plateau ResearchChinese Academy of SciencesBeijing 100101China CAS Center for Excellence in Tibetan Plateau Earth Sciences Chinese Academy of SciencesBeijing 100101China

Permafrost is a potential mercury(Hg)pool released by thawing,which can raise the risk of Hg pollution under global *** rings are useful archives of environment-specific Hg exposure over long *** determined Hg concentrations in tree rings of two dominant tree species(Larix gmelinii *** Pinus sylvestris ***)at permafrost sites in northeastern *** biweighted mean Hg concentrations ranged from 0.36 to 3.96 ng g^(-1) from 1840 to *** tree-ring width had no significant influence on the Hg *** Hg increased slightly before the 1970 s and peaked in the 1990 ***,the pine Hg concentration increased continuously until the 1930 s,decreased rapidly until the 1970 s,then rose to a peak in the late 1980 *** change of Hg concentrations in larch and pine revealed a time offset of 4 to 5 years,which implied possibly high mobility of Hg in pine tree *** Hg concentrations from 1920 to 1960 and subsequent decreases in isolated permafrost forests revealed the local geographical Hg cycling *** Hg concentrations and faster increases in larch suggest the role of additional winter Hg loading for the evergreen pine and species-specific differences in root absorption in response to melting *** results highlight possible geographical impacts on tree-ring Hg records,improve understanding of Hg cycles in permafrost forest,and suggest a need to sample additional species in a range of permafrost environments.

关键词： Tree rings Mercury Long-term variations Larch Pine geographic environment Permafrost forest

来源：

维普期刊数据库

同方期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Tree-ring δ^(15)N of Qinghai spruce in the central Qilian Mountains of China:Is pre-treatment of wood samples necessary?

引用

Journal of Arid Land 2022年第6期14卷 673-690页

作者： WANG Ziyi LIU Xiaohong WANG Keyi ZENG Xiaomin ZHANG Yu ge wensen KANG Huhu LU Qiangqiang School of geography and Tourism Shaanxi Normal UniversityXi'an 710119China State Key Laboratory of Cryospheric Science Northwest Institute of Eco-Environment and ResourcesChinese Academy of SciencesLanzhou 730000China Qilian Mountain National Park Research Center(Qinghai) Xining 810008China School of Earth System Science Tianjin UniversityTianjin 300072China

A knowledge of the tree-ring stable nitrogen isotope ratio(δ^(15)N)can deepen our understanding of forest ecosystem dynamics by indicating the long-term availability,cycling and sources of nitrogen(N).However,the radial mobility of N blurs the interannual variations in the long-term N *** studies of the chemical extraction of tree rings before analysis had produced inconsistent results and it is still unclear whether it is necessary to pre-treat wood samples from specific tree species to remove soluble N compounds before determining theδ^(15)N *** compared the effects of pre-treatment with organic solvents and hot ultrapure water on the N concentration andδ^(15)N of tree rings from endemic Qinghai spruce(Picea crassifolia)growing in the interior of the central Qilian Mountains,China,during the last 60 *** assessed the effects of different preparation protocols on the removal of the labile N compounds and investigated the need to pre-treat wood samples before determining theδ^(15)N values of tree *** trends of the tree-ring N concentration were consistently observed in both the extracted and unextracted wood *** total N removed by extraction with organic solvents was about 17.60%,with a significantly higher amount in the sapwood section(P<0.01).Theδ^(15)N values of tree rings decreased consistently from 1960 to 2019 in both the extracted and unextracted wood *** with organic solvents increased theδ^(15)N values markedly by about 5.2‰and reduced the variations in theδ^(15)N ***,extraction with hot ultrapure water had little effect,with only a slight decrease in theδ^(15)N values of about 0.5‰.Our results showed that the radial pattern in the inter-ring movement of N in Qinghai spruce was not minimized by extraction with either organic solvents or hot ultrapure *** is unnecessary to conduct hot ultrapure water extraction for the wood samples from Qinghai spruce because of its negligible effect on t

关键词： tree rings stable nitrogen isotope ratio(δ^(15)N) nitrogen concentration solvent-extracted wood water-extracted wood wood pre-treatment Qinghai spruce Qilian Mountains

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Ultra-broadband,fast,and polarization-sensitive photoresponse of low-symmetry 2D NdSb_(2)

引用

Nano Research 2022年第6期15卷 5469-5475页

作者： Gang Li Hanlin Zhang Yong Li Shiqi Yin Xucai Kan wensen Wei Haifeng Du Binghui ge Chao An Mingliang Tian Feng Yan Sanjun Yang Tianyou Zhai Liang Li Institutes of Physical Science and Information Technology Anhui UniversityHefei 230601China Engineering Technology Research Center of Magnetic Materials School of Physics and Materials ScienceAnhui UniversityHefei 230601China Anhui Province Key Laboratory of Condensed Matter Physics at Extreme Conditions High Magnetic Field Laboratory of the Chinese Academy of ScienceHefei 230031China Department of Applied Physics The Hong Kong Polytechnic UniversityKowloonHong Kong 999077China State Key Laboratory of Materials Processing and Die and Mould Technology School of Materials Science and EngineeringHuazhong University of Science and Technology(HUST)Wuhan 430074China

Broadband photodetectors with polarization-sensitive ability have received extraordinary attention for modern optoelectronic *** photodetectors should possess high responsivity,fast response,and good stability,which are rare to meet at the same time in one low-symmetric two-dimentional(2D)*** this work,neodymium diantimonides(RSb_(2)),a member of light rare-earth diantimonides RSb_(2)(R=La–Nd,Sm)with low-symmetry structure,is introduced as a fascinating highly anisotropic 2D material for broadband detection(532 nm to 4μm).The photodetector exhibits a responsivity of 0.49 mA·W^(−1)with 15μs response time at 532 nm and highly stable performance under ambient conditions over 8 ***,we identify the polarization-sensitive photoresponse of the detector and demonstrate a high anisotropic factor~*** addition,strong inplane anisotropy is revealed by anisotropic phonon response and the photodetection mechanism is investigated by scanning photocurrent microscopy *** pioneer work on RSb_(2)paves the way for further exploration of 2D RSb_(2)for high performance polarized photodetectors with fast photothermoelectric response.

关键词： ultra-broadband fast response polarization-sensitive photodetector RSb_(2)

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Observation of Charge Density Wave in Layered Hexagonal Cu1.89Te Single Crystal

引用

Chinese Physics Letters 2023年第1期40卷 37-42页

作者：高文帅陈正韦文森闫超王莎莎汤进张冉冉程礼迅南鹏飞王杰韩玉岩郗传英葛炳辉何林杜海峰宁伟朱相德田明亮 Institutes of Physical Science and Information Technology Anhui UniversityHefei 230601China Anhui Province Key Laboratory of Condensed Matter Physics at Extreme Conditions High Magnetic Field LaboratoryChinese Academy of SciencesHefei 230031China Center for Advanced Quantum Studies Department of PhysicsBeijing Normal UniversityBeijing 100875China Department of physics University of Science and Technology of ChinaHefei 230026China School of Physics and Optoelectronics Engineering Anhui UniversityHefei 230601China

We report comprehensive transport, electron microscopy and Raman spectroscopy studies on transition-metal chalcogenides Cu1.89Te single crystals. The metallic Cu1.89Te displays successive metal-semiconductor transitions at low temperatures and almost ideal linear MR when magnetic field up to 33 T. Through the electron diffraction patterns, the stable room-temperature phase is identified as a 3 × 3 × 2 modulated superstructure based on the Nowotny hexagonal structure. The superlattice spots of transmission electron microscopy and scanning tunneling microscopy clearly show the structural transitions from the room-temperature commensurate Ⅰ phase, named as C-Ⅰ phase, to the low temperature commensurate Ⅱ(C-Ⅱ) phase. All the results can be understood in terms of charge density wave(CDW) instability, yielding intuitive evidences for the CDW formations in Cu1.89Te. The additional Raman modes below room temperature further reveal that the zone-folded phonon modes may play an important role on the CDW transitions. Our research sheds light on the novel electron features of Cu1.89Te at low temperature, and may provide potential applications for future nano-devices.

关键词： structure transitions Crystal

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

胃粘膜癌变过程中bc1-2、p^(53)和Rb基因的表达

引用

重庆医学 2000年第4期29卷 292-293页

作者：张朝军晏才杰葛海燕靳文生第三军医大学新桥医院普外科 400037 第三军医大学大坪医院泌尿外科

目的　研究胃粘膜癌变过程中bc1- 2、p53 和Rb的基因的表达及意义。方法　采用免疫组化方法对 5 0例胃癌 ,18例癌旁肠化生 ,7例癌旁轻中度异型增生及 9例重度异型增生组织中bc1- 2、p53 和Rb基因表达情况进行检测和比较。结果　正常胃... 详细信息

目的　研究胃粘膜癌变过程中bc1- 2、p53 和Rb的基因的表达及意义。方法　采用免疫组化方法对 5 0例胃癌 ,18例癌旁肠化生 ,7例癌旁轻中度异型增生及 9例重度异型增生组织中bc1- 2、p53 和Rb基因表达情况进行检测和比较。结果　正常胃粘膜上皮增殖带干细胞区bc1- 2蛋白呈弱阳性表达 ,异性增生病变中 ,bcl- 2蛋白表达率和表达强度明显大于肠化生病变和正常胃粘膜上皮 (P <0 .0 5 ) ,胃癌组织中表达减少 ,p53 蛋白和Rb蛋白仅在重度异型增生病变和胃癌组织中表达。结论　bcl-2蛋白的表达主要是在胃癌的启动和促进阶段起作用 ,而在已具有恶性表型的细胞中不起关键作用。p53 和Rb基因的改变可能发生在胃粘膜癌变的较后期阶段 ,使胃癌的细胞凋亡受抑。

关键词：胃癌 bc1-2 p^53 基因表达细胞凋亡

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

欢迎您,

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案：

请选择收藏分类：

通借通还

欢迎您,

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：