检索结果-南通市图书馆

atmospheric nitrogen deposition affects forest plant and soil system carbon:nitrogen:phosphorus stoichiometric flexibility:A meta-analysis

在线全文

学校读者我要写书评

暂无评论

Forest Ecosystems 2024年第3期11卷 307-317页

作者： Xiyan Jiang Xiaojing wang Yaqi Qiao Yi Cao Yan Jiao An yang Mengzhou Liu Lei Ma Mengya Song Shenglei Fu key laboratory of Geospatial Technology for the Middle and Lower Yellow River Regions College of Geography and Environmental ScienceHenan UniversityKaifeng475004China Henan key laboratory of Integrated Air Pollution Control and Ecological Security College of Geography and Environmental ScienceHenan UniversityKaifeng475004China Henan Dabieshan National Field Observation and Research Station of Forest Ecosystem Henan UniversityZhengzhou450046China

Background:Nitrogen(N)deposition affects forest stoichiometric flexibility through changing soil nutrient availability to influence plant ***,the effect of N deposition on the flexibility of carbon(C),N,and phosphorus(P)in forest plant-soil-microbe systems remains ***:We conducted a meta-analysis based on 751 pairs of observations to evaluate the responses of plant,soil and microbial biomass C,N and P nutrients and stoichiometry to N addition in different N intensity(050,50–100,>100 kg·ha^(-1)·year^(-1)of N),duration(0–5,>5 year),method(understory,canopy),and matter(ammonium N,nitrate N,organic N,mixed N).Results:N addition significantly increased plant N:P(leaf:14.98%,root:13.29%),plant C:P(leaf:6.8%,root:25.44%),soil N:P(13.94%),soil C:P(10.86%),microbial biomass N:P(23.58%),microbial biomass C:P(12.62%),but reduced plant C:N(leaf:6.49%,root:9.02%).Furthermore,plant C:N:P stoichiometry changed significantly under short-term N inputs,while soil and microorganisms changed drastically under high N *** N addition primarily affected plant C:N:P stoichiometry through altering plant N content,while understory N inputs altered more by influencing soil C and P *** N significantly influenced plant and soil C:N and C:P,while ammonia N changed plant N:*** C:P and soil C:N were strongly correlated with mean annual precipitation(MAT),and the C:N:P stoichiometric flexibility in soil and plant under N addition connected with soil ***,N addition decoupled the correlations between soil microorganisms and the ***:N addition significantly increased the C:P and N:P in soil,plant,and microbial biomass,reducing plant C:N,and aggravated forest P ***,these impacts were contingent on climate types,soil layers,and N input *** findings enhance our comprehension of the plant-soil system nutrient cycling mechanisms in forest ecosystems and plant strategy responses to N deposition.

关键词： C:N:P stoichiometry Meta-analysis Forest ecosystem Nitrogen addition form Nutrient cycles

Wear Behavior of Cu Matrix Composites Reinforced with Mixture of Carbon and Carbon Nanotubes

在线全文

学校读者我要写书评

暂无评论

Journal of Wuhan university of Technology(Materials Science) 2009年第2期24卷 254-257页

作者：姜金龙 School of Science Lanzhou University of Technology State key laboratory of Solid Lubrication Lanzhou Institute of Chemical Physics Chinese Academy of Sciences

In order to improve wear resistance and decrease the cost, carbon and carbon nanotubes reinforced copper matrix composites were fabricated by the power metallurgy method. The effects of carbon （carbon and carbon nanotubes） volume fraction and applied load on the friction coefficient and wear rate under dry sliding of the composites were investigated at room temperature. By scanning electron microscopy （SEM）, the worn surfaces and debris were observed, and wear mechanism was also analyzed and discussed. The experimental wear process consists of the run-in, steady wear and severe wear process with the increasing of sliding distance. Both the friction coefficient and wear rate of the composites first decrease and then increase with the increasing of carbon volume fraction. The minimum friction coefficient and wear rate are obtained when carbon is 4.0vo1%. The wear mechanisms of the composites change from the adhesive wear and delamination wear to abrasive wear with the increasing of carbon volume fraction.

关键词： C/Cu matrix composite power metallurgy wear behavior

Modification of POSS and their tribological properties and resistant to space atomic oxygen irradiation as lubricant additive of multialkylated cyclopentanes

在线全文

学校读者我要写书评

暂无评论

Friction 2024年第5期12卷 884-896页

作者： Xingwei wang Chaoyang ZHANG Chen ZHAO Yijing LIANG Ming ZHANG Wufang yang Bo YU Qiangliang YU Meirong CAI Feng ZHOU Weimin LIU State key laboratory of Solid Lubrication Lanzhou Institute of Chemical PhysicsChinese Academy of SciencesLanzhou730000China Shandong laboratory of Yantai Advanced Materials and Green Manufacturing Yantai264000China

Developing functional additive resistant to space atomic oxygen(AO)irradiation through simple molecular design and chemical synthesis to enhance the lubricating performance of multialkylated cyclopentanes(MACs)oil is a significant ***,sulfur-containing polyhedral oligomere silsesquioxane(POSS)were synthesize via a click-chemistry reaction of octavinyl polyhedral oligomeric with alkyl *** reduce-friction(RF),anti-wear(AW)properties and anti-AO irradiation of POSS-S-R as MACs base oil additives in atmospheric and simulated space environments were systematically investigated for the first *** demonstrate that POSS-S-R not only possesses outstanding anti-AO irradiation capacity but also effectively improves the RF and AW of MACs in atmospheric or simulated space *** improvement is due to the excellent anti-AO irradiation properties of the POSS structure itself and the high load-carrying ability of silicon-containing and sulfur-containing compounds generated by tribo-chemical reactions,which effectively separates the direct contact of the friction *** believe that this synthesized POSS-S-R is a promising additive for space lubricants.

关键词： POSS additive reduce-friction anti-wear multialkylated cyclopentanes(MACs) resistant atomic irradiation

Formation of the [M+NH_4]^+ Ious of Some Mouo-and Di-saccharides in Fast Atom Bombardment Mass Spectrometry

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

Chinese Chemical Letters 1997年第10期8卷 879-882页

作者： Jian Jun ZHAI Fau Zhi ZHAO Deug Gang HUANG Yao Zu CHEN (State key laboratory of Applied Organic Chemistry , lanzhou university , lanzhou 730000Department of Chemistry , Zhejiang university , Hangzhou 310027)Jin Skan GUO(gansu Institute of Plast State key Lab. of Appl. Organ. Chem. Lanzhou University Lanzhou 730000 China Department of Chemistry Zhejiang University Hangzhou 310027 China gansu Inst. of Plastics and Leather Lanzhou 730000 China

In positive-ion fast atom bombardment (FAB) mass spectrometry, when mono- and di- saccharides are mixed with an appropriate amount of NH4Cl, a highly abundan peak [M+NH4]+appers in FAB mass spectra . From the adduct ... 详细信息

关键词： Mass Atom Ious of Some Mouo-and Di-saccharides in Fast Atom Bombardment Mass Spectrometry M+NH4 Formation of the NH

Epidemiological Characteristics of Human Parainfluenza Viruses Infections-china,2019-2023

在线全文

学校读者我要写书评

暂无评论

china CDC weekly 2024年第12期6卷 235-241,I0003,I0004页

作者： Yixuan Gao Yingwei Ma Daxing Feng Feng Zhang Biao wang Xiaoqing Liu Bing Zhu Hui Xie Linqing Zhao Xiaoru Long Ying Chen Bing wang Jie Jiang Zhen Zhu Yan Zhang Aili cui Baicheng Xia Naiying Mao National key laboratory of Intelligent Tracking and Forecasting for Infectious Diseases National Institute for Viral Disease Control and PreventionChinese Center for Disease Control and PreventionBeijingChina Precision Medicine Research Center Children’s Hospital of ChangchunChangchun CityJilin ProvinceChina Henan Provincial Center for Disease Control and Prevention Zhengzhou CityHenan ProvinceChina laboratory of Viral Diseases Qingdao Municipal Centre for Disease Control and PreventionQingdao CityShandong ProvinceChina Virus laboratory Gansu Provincial Center for Disease Control and PreventionLanzhou CityGansu ProvinceChina Jiangxi Provincial Center for Disease Control and Prevention Nanchang CityGansu ProvinceChina Virus laboratory Guangzhou Women and Children’s Medical CenterGuangzhou Medical UniversityGuangzhou CityGuangdong ProvinceChina Institute for Immunization and Prevention Beijing Center for Disease Prevention and ControlAcademy for Preventive MedicineInstitute of Tuberculosis Control Research and PreventionBeijingChina laboratory of Virology Beijing Key Laboratory of Etiology of Viral Diseases in ChildrenCapital Institute of PediatricsBeijingChina Department of Infection Children’s Hospital of Chongqing Medical UniversityChongqingChina Inner Mongolia Autonomous Region Comprehensive Center for Disease Control and Prevention Hohhot CityInner Mongolia Autonomous RegionChina Shenyang Prefecture Center for Disease Control and Prevention Shenyang CityLiaoning ProvinceChina

Introduction:A retrospective study based on sentinel surveillance was conducted in 10 provinciallevel administrative divisions(PLADs)in china to enhance the understanding of the epidemiological characteristics of human parainfluenza viruses(HPIVs).Methods:From January 2019 to June 2023,respiratory specimens were collected from individuals with acute respiratory infections(ARIs)and screened for four HPIVs serotypes and other common respiratory viruses using multiplex real-time polymerase chain reaction(PCR).This study analyzed the association of HPIVs infections with seasonal patterns,geographical distribution,demographic profiles,clinical features,and co-infection ***:During the study period,a total of 12,866 ARIs were *** overall detection rate of HPIVs was 6.15%,varying from 5.04%in 2022 to 9.70%in *** median age of HPIVs-infected patients was 3 ***2 was more prevalent among individuals aged 5–17 years(42.57%),while HPIV4 was more common in those over 65 years(12.24%).HPIV3(54.16%)and HPIV1(27.18%)were the predominant serotypes,and their prevalence exhibited significant seasonal fluctuations postcoronavirus disease 2019(COVID-19)*** peak of HPIV3 shifted three months later in 2020 compared to 2019 and returned to a summer peak *** peaks of HPIV1 were observed in 2021 following the peak of ***,coinfections were frequent in HPIVs cases(overall rate:22.12%),with human rhinovirus being the most common co-infecting ***:The prevalence of HPIVs in china was predominantly due to HPIV3 and HPIV1,and their seasonal patterns were altered by pandemic ***,continuous surveillance of HPIVs is essential.

关键词： prevalence seasonal Human

Global analysis theory of climate system and its applications

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

Chinese Science Bulletin 2003年第10期48卷 1034-1039页

作者： LI Jianping1,2 & CHOU Jifan2,3 1. LASG, Institute of atmospheric Physics, Chinese Academy of sciences, Beijing 100029, china 2. Department of atmospheric sciences, lanzhou university, lanzhou 730000, china 3. Training Center for china Meteorological Administration, Beijing 100081, china LASG Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029 China Department of atmospheric sciences Lanzhou University Lanzhou 730000 China Training Center for china Meteorological Administration Beijing 100081 China

The idea and main theoretical results of the global analysis theory of climate system are briefly summarized in this paper. A theorem on the global behavior of climate system is given, i.e. there exists a global attractor in the dynamical equations of climate, any state of climate system will be evolved into the global attractor as time increases, indicating the nonlinear adjustment process of climate system to external forcing. The different effects of external forcing, dissipation and nonlinearity on the long-term behavior of solutions are pointed out, and some main applications of the global analysis theory are also introduced. Especially, three applications, the adjustment and evolution processes of climate, the principle of numerical model design and the optimally numerical integration, are discussed.

关键词：整体分析理论气侯体系应用不定性计算法则气侯科学数字模型

Interspecific delimitation and phylogenetic origin of Pugionium(Brassicaceae)

在线全文

学校读者我要写书评

暂无评论

Journal of Systematics and Evolution 2010年第3期48卷 195-206页

作者： 1,2,3Qiu-Shi YU 1Qian wang 1Ai-Lan wang 1Gui-Li WU 3Jian-Quan LIU 1(Division of Molecular Ecology,key laboratory of Arid and Grassland Ecology,School of Life Science,lanzhou university,lanzhou 730000,china) 2(Minqin National Studies Station for Desert Steppe Ecosystem,Minqin 733300,china) 3(gansu Desert Control Research Institute,lanzhou 730070,china) (Division of Molecular Ecology Key Laboratory of Arid and Grassland Ecology School of Life Science Lanzhou University Lanzhou 730000 China) (Minqin National Studies Station for Desert Steppe Ecosystem Minqin 733300 China) (gansu Desert Control Research Institute Lanzhou 730070 China)

Pugionium(Brassicaceae)is a small genus that occurs in central Asian *** interspecific delimitation and taxonomic treatments of this genus are disputed and its phylogenetic origin remains unknown. In the present study,we examined these issues based on morphological and molecular data obtained for the first *** used statistical methods to examine inter-and intraspecific morphological *** results suggest that only two species,namely *** and ***,can be warranted for all examined populations and specimens,whereas three species(***,***,and ***)should be incorporated into P. *** delimitation was further supported by the molecular data:all populations of ***,P. calcaratum,***,and *** shared the same internal transcribed spacer genotype,whereas those from *** had another *** analyses of Pugionium and representative genera of Brassicaceae based on ndhF sequences suggest that this genus is sister to the genus Megacarpaea,which,together,comprise a well-supported lineage with Farsetia,Lobularia,Iberis,and Ionopsidium,whereas the two other genera that were previously suggested to be closely related to this genus(Isatis and Bunias)were placed in the other *** further discuss the origin of Pugionium and suggest that it probably originated in central Asia when the climate became drier from the late Miocene.

关键词： internal transcribed spacer(ITS) interspecific delimitation morphological variation ndhF phyloge- netic origin Pugionium.

Multi-performance evaluation of high-throughput accelerated corrosion test for high-strength low-alloy 921A steel

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Journal of Iron and Steel Research(International) 2024年第5期31卷 1260-1278页

作者： Cong-cong Du Ming-hua Qin Zhan-fang Wu Dong-ling Li Lei Zhao Xiang-yang Li Hai-zhou wang Beijing Advanced Innovation Center for Materials Genome Engineering National Center for Materials Service SafetyUniversity of Science and Technology BeijingBeijing100083China china Iron and Steel Research Institute Group Co. Ltd.Beijing100081China Beijing Advanced Innovation Center for Materials Genome Engineering Central Iron and Steel Research InstituteBeijing100081China

The corrosion behavior of high-strength low-alloy 921A steel in a simulated marine atmospheric environment was studied using a high-throughput experimental *** corrosion behavior,corrosion morphology,and corrosion products of 921A steels were analyzed using various techniques,including corrosion mass loss method,polarization curve,white-light interferometry,scanning electron microscopy,energy-dispersive spectrometry,microbeam X-ray fluorescence spectrometry,X-ray diffraction technique,and X-ray photoelectron *** test results indicated that 921A steel exhibits better corrosion resistance than Q450NQR1 steel in simulated harsh atmospheric environments,as evidenced by a lower corrosion mass loss rate throughout the corrosion *** corrosion products of both steels consisted ofα-FeOOH,Fe_(3)O_(4),andγ-FeOOH,withα-FeOOH being more prevalent in the rust layer of 921A steel than in Q450NQR1 *** inner rust layer of 921A steel also exhibited an appositional enrichment region of Cr,Ni,Mo,and V,leading to its superior corrosion resistance compared to that of Q450NQR1 *** efficacy of high-throughput accelerated corrosion experimental methods was highlighted for evaluating the corrosion resistance of steel materials in harsh environmental *** findings suggest that 921A steel exhibits better corrosion resistance compared to Q450NQR1 steel and has the potential to be more suitable in harsh marine atmospheric *** characterization of the rust layer structures and composition reveals the parallel enrichment of certain elements in the inner rust layer of 921A steel,which enhances its corrosion resistance.

关键词： atmospheric corrosion High-throughput experimental method High-strength low-alloy steel Corrosion characteristics Rust layer Element enrichment

Miocene Bahean stratigraphy in the Longzhong Basin, northern central china and its implications in environmental change

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

Science china Earth sciences 2006年第12期49卷 1270-1279页

作者： LI Jijun1,2, ZHANG Jun1, SONG Chunhui1, ZHAO Zhijun2, ZHANG Yong1, wang Xiuxi 1, ZHANG Jianming1 & cui Qiaoyu1 1. key laboratory of Western china’s Environmental Systems (Ministry of Education) & college of Earth and Environment sciences, lanzhou university, lanzhou 730000, china 2. Jiangsu key laboratory of Environmental Change and Ecological Construction & college of Geography, Nanjing Normal university, Nanjing 210097, china key laboratory of Western china’s Environmental Systems (Ministry of Education) & college of Earth and Environment sciences Lanzhou University Lanzhou China Jiangsu key laboratory of Environmental Change and Ecological Construction & college of Geography Nanjing Normal University Nanjing China

Fossil mammal-riched Neogene strata are widely distributed in the southeast corner of the huge Longzhong Basin at Tianshui, gansu province, northern central china. Hipparion weihoense, a typical member of late Middle Miocene Bahean stage, was recently excavated at Yaodian along a well-exposed outcrop. Owing to the importance of the Bahean stage in the mammalian evolution and its potential for environmental change, we suggested a name of Yaodian Formation for the stratigra- phy, which is correlated to the Bahe Formation at Lantian, Shaanxi. High resolution paleomagnetic dating of the section shows that the Yaodian Formation covers the period between 11.67 Ma and 7.43 Ma, with the site bearing Hipparion weihoense being estimated at about 10.54―10.30 Ma, providing first magnetostratigraphic chronology for the Bahean Stage. The Yaodian Formation consists of fluvial channel deposits (11.67―10.40 Ma) at the bottom, floodplain deposits in the middle (10.40―9.23 Ma) and shallow lake sediments at the top (9.23―7.43 Ma). This upward fining sequence suggests that the relief in nearby mountain ranges such as West Qinling to the south and Huajia Ling to the north was greatly reduced after long-term denudation, fluvial transport capacity was low, and finally the drainage system was disintegrated, replaced with broad-shallow lakes in which only fine sediments like mud and marlite were deposited, indicating an old stage of development of a planation surface. A remarkable shift in ecology and climatic environment was found at 7.4―7.7 Ma when paleoclimate changed from early warm humid to late dry as indicated by sedimentary facies changed from early shallow lake sequence to late eolian red clays and a former coniferous-deciduous mixed forest was replaced by grassland, leading to great growth of Hipparion Fauna of Baodean stage in the region. Therefore, it is estimated that the present high relief of Qinling and drainage pattern did not come into being until Late Pliocene in response

关键词： Bahean stage,magnetostratigraphy,Yaodian Formation,Neogene,Longzhong Basin.