期刊文献+
共找到82,917篇文章
< 1 2 250 >
每页显示 20 50 100
Increasing Threat of Scarcity Prompts Rise in Water Recycling
1
作者 Chris Palmer 《Engineering》 SCIE EI CAS CSCD 2024年第2期6-8,共3页
In January 2018,construction wrapped on Salesforce Tower(Fig.1),a 61-story office building that now dominates the skyline of San Francisco,CA,USA.In addition to being the tallest building in the city,Salesforce Tower ... In January 2018,construction wrapped on Salesforce Tower(Fig.1),a 61-story office building that now dominates the skyline of San Francisco,CA,USA.In addition to being the tallest building in the city,Salesforce Tower is the largest structure in the world with an onsite water recycling system.Built by the Australian com-pany Aquacell(Milton,NSW,Australia),the system cleans 113 m^(3)of sewage,sink,shower,and other wastewater each day for use in irrigation and flushing toilets,saving an estimated 35000 m?of water anmually[1].The building is just one of dozens in San Fran-cisco outitted with their own water recycling systems,thanks to a city mandate enacted in 2015[1]. 展开更多
关键词 cycling WASTEWATER recycling
下载PDF
Single-cell transcriptomics reveals cell atlas and identifies cycling tumor cells responsible for recurrence in ameloblastoma
2
作者 Gan Xiong Nan Xie +17 位作者 Min Nie Rongsong Ling Bokai Yun Jiaxiang Xie Linlin Ren Yaqi Huang Wenjin Wang Chen Yi Ming Zhang Xiuyun Xu Caihua Zhang Bin Zou Leitao Zhang Xiqiang Liu Hongzhang Huang Demeng Chen Wei Cao Cheng Wang 《International Journal of Oral Science》 SCIE CAS CSCD 2024年第2期251-264,共14页
Ameloblastoma is a benign tumor characterized by locally invasive phenotypes,leading to facial bone destruction and a high recurrence rate.However,the mechanisms governing tumor initiation and recurrence are poorly un... Ameloblastoma is a benign tumor characterized by locally invasive phenotypes,leading to facial bone destruction and a high recurrence rate.However,the mechanisms governing tumor initiation and recurrence are poorly understood.Here,we uncovered cellular landscapes and mechanisms that underlie tumor recurrence in ameloblastoma at single-cell resolution.Our results revealed that ameloblastoma exhibits five tumor subpopulations varying with respect to immune response(IR),bone remodeling(BR),tooth development(TD),epithelial development(ED),and cell cycle(CC)signatures.Of note,we found that CC ameloblastoma cells were endowed with stemness and contributed to tumor recurrence,which was dominated by the EZH2-mediated program.Targeting EZH2 effectively eliminated CC ameloblastoma cells and inhibited tumor growth in ameloblastoma patient-derived organoids.These data described the tumor subpopulation and clarified the identity,function,and regulatory mechanism of CC ameloblastoma cells,providing a potential therapeutic target for ameloblastoma. 展开更多
关键词 inhibited cycling eliminated
下载PDF
TuBG1 promotes hepatocellular carcinoma via ATR/P53-apoptosis and cycling pathways
3
作者 Yan Zhang Zhen-Zhen Wang +4 位作者 An-Qi Han Ming-Ya Yang Li-Xin Zhu Fa-Ming Pan Yong Wang 《Hepatobiliary & Pancreatic Diseases International》 SCIE CAS CSCD 2024年第2期195-209,共15页
Background:As reported,γ-tubulin(TuBG1)is related to the occurrence and development of various types of malignant tumors.However,its role in hepatocellular cancer(HCC)is not clear.The present study was to investigate... Background:As reported,γ-tubulin(TuBG1)is related to the occurrence and development of various types of malignant tumors.However,its role in hepatocellular cancer(HCC)is not clear.The present study was to investigate the relationship between TuBG1 and clinical parameters and survival in HCC patients.Methods:The correlation between TuBG1 and clinical parameters and survival in HCC patients was ex-plored by bioinformatics analysis.Immunohistochemistry was used for the verification.The molecular function of TuBG1 was measured using colony formation,scratch assay,trans-well assay and flow cytometry.Gene set enrichment analysis(GSEA)was used to pick up the enriched pathways,followed by investigating the target pathways using Western blotting.The tumor-immune system interactions and drug bank database(TISIDB)was used to evaluate TuBG1 and immunity.Based on the TuBG1-related immune genes,a prognostic model was constructed and was further validated internally and externally.Results:The bioinformatic analysis found high expressed TuBG1 in HCC tissue,which was confirmed us-ing immunohistochemistry and Western blotting.After silencing the TuBG1 in HCC cell lines,more G1 arrested cells were found,cell proliferation and invasion were inhibited,and apoptosis was promoted.Furthermore,the silence of TuBG1 increased the expressions of Ataxia-Telangiectasia and Rad-3(ATR),phospho-P38 mitogen-activated protein kinase(P-P38MAPK),phospho-P53(P-P53),B-cell lymphoma-2 associated X protein(Bax),cleaved caspase 3 and P21;decreased the expressions of B-cell lymphoma-2(Bcl-2),cyclin D1,cyclin E2,cyclin-dependent kinase 2(CDK2)and CDK4.The correlation analysis of immunohistochemistry and clinical parameters and survival data revealed that TuBG1 was negatively corre-lated with the overall survival.The constructed immune prognosis model could effectively evaluate the prognosis.Conclusions:The increased expression of TuBG1 in HCC is associated with poor prognosis,which might be involved in the occurrence and development of HCC. 展开更多
关键词 TuBG1 Hepatocellular carcinoma APOPTOSIS Cell cycling IMMUNOMODULATORS
下载PDF
Enhanced High-Temperature Cycling Stability of Garnet-Based All Solid-State Lithium Battery Using a Multi-Functional Catholyte Buffer Layer
4
作者 Leqi Zhao Yijun Zhong +2 位作者 Chencheng Cao Tony Tang Zongping Shao 《Nano-Micro Letters》 SCIE EI CAS CSCD 2024年第7期59-73,共15页
The pursuit of safer and high-performance lithium-ion batteries(LIBs)has triggered extensive research activities on solid-state batteries,while challenges related to the unstable electrode-electrolyte interface hinder... The pursuit of safer and high-performance lithium-ion batteries(LIBs)has triggered extensive research activities on solid-state batteries,while challenges related to the unstable electrode-electrolyte interface hinder their practical implementation.Polymer has been used extensively to improve the cathode-electrolyte interface in garnet-based all-solid-state LIBs(ASSLBs),while it introduces new concerns about thermal stability.In this study,we propose the incorporation of a multi-functional flame-retardant triphenyl phos-phate additive into poly(ethylene oxide),acting as a thin buffer layer between LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)(NCM811)cathode and garnet electro-lyte.Through electrochemical stability tests,cycling performance evaluations,interfacial thermal stability analysis and flammability tests,improved thermal stability(capacity retention of 98.5%after 100 cycles at 60℃,and 89.6%after 50 cycles at 80℃)and safety characteristics(safe and stable cycling up to 100℃)are demonstrated.Based on various materials characterizations,the mechanism for the improved thermal stability of the interface is proposed.The results highlight the potential of multi-functional flame-retardant additives to address the challenges associated with the electrode-electrolyte interface in ASSLBs at high temperature.Efficient thermal modification in ASSLBs operating at elevated temperatures is also essential for enabling large-scale energy storage with safety being the primary concern. 展开更多
关键词 Solid-state battery Cathode electrolyte interlayer Flame-retardant additive cycling stability Interfacial stability
下载PDF
Cycling performance of layered oxide cathode materials for sodium-ion batteries
5
作者 Jinpin Wu Junhang Tian +1 位作者 Xueyi Sun Weidong Zhuang 《International Journal of Minerals,Metallurgy and Materials》 SCIE EI CAS CSCD 2024年第7期1720-1744,共25页
Layered oxide is a promising cathode material for sodium-ion batteries because of its high-capacity,high operating voltage,and simple synthesis.Cycling performance is an important criterion for evaluating the applicat... Layered oxide is a promising cathode material for sodium-ion batteries because of its high-capacity,high operating voltage,and simple synthesis.Cycling performance is an important criterion for evaluating the application prospects of batteries.However,facing challenges,including phase transitions,ambient stability,side reactions,and irreversible anionic oxygen activity,the cycling performance of layered oxide cathode materials still cannot meet the application requirements.Therefore,this review proposes several strategies to address these challenges.First,bulk doping is introduced from three aspects:cationic single doping,anionic single doping,and multi-ion doping.Second,homogeneous surface coating and concentration gradient modification are reviewed.In addition,methods such as mixed structure design,particle engineering,high-entropy material construction,and integrated modification are proposed.Finally,a summary and outlook provide a new horizon for developing and modifying layered oxide cathode materials. 展开更多
关键词 sodium-ion battery layered oxide materials cycling performance bulking doping surface coating concentration gradient mixed structure high-entropy
下载PDF
Changes in calcium accumulation and utilization efficiency and their impact on recycling,immobilization,and export across the oil palm cycle
6
作者 Ismael de Jesus Matos Viégas Luma Castro de Souza +4 位作者 Eric Victor de Oliveira Ferreira Milton Garcia Costa Glauco André dos Santos Nogueira Vitor Resende do Nascimento Candido Ferreira de Oliveira Neto 《Oil Crop Science》 CSCD 2024年第3期143-150,共8页
Effective calcium(Ca)management is crucial for optimizing oil palm cultivation and enhancing crop yield.This study aimed to gain insights into the dynamics of Ca concentration,accumulation,exportation,immobilization,a... Effective calcium(Ca)management is crucial for optimizing oil palm cultivation and enhancing crop yield.This study aimed to gain insights into the dynamics of Ca concentration,accumulation,exportation,immobilization,and recycling in various oil palm organs relative to plant age.The experiment was conducted at the Agropalma enterprise site in the northeastern region of Para State,Brazil,evaluating seven plant age treatments:2,3,4,5,6,7,and 8 years old.Employing a completely randomized design with four replications.The results demonstrated an age-related increase in Ca concentration in petioles,rachis,arrows,male inflorescences,peduncles,and fruits.Furthermore,Ca accumulation exhibited an upward trend in all organs with progressing plant age.Notably,the study revealed an enhanced Ca use efficiency across all plant organs in correlation with the age of oil palm cultivation.These findings underscore the dynamic nutritional demands of oil palm,influencing Ca immobilization,cycling,and export throughout its developmental stages. 展开更多
关键词 Elaeis guineensis Jacq Ca cycling Ca export Ca immobilization Ca use efficiency Plant nutrition AMAZON
下载PDF
Identification and Optimisation of Cycling Life Circle in High Density Communities with Public Health Support: A Case Study of Tiantongyuan in Beijing
7
作者 LIANG Weinan HUANG Yi +1 位作者 WANG Zilin ZHOU Xuan 《Journal of Landscape Research》 2024年第5期27-32,37,共7页
In recent years,the compact development of high-density cities has sparked ongoing interest in healthy urban environments and public well-being.This study examines the relationship between cycling behaviors and the bu... In recent years,the compact development of high-density cities has sparked ongoing interest in healthy urban environments and public well-being.This study examines the relationship between cycling behaviors and the built environment of streets in Tiantongyuan Community,a typical high-density area in Beijing,China.By observing street spaces and summarizing residents’travel modes and behaviors,the study evaluates the impact of street design on cycling habits.In order to reveal the riding behavior characteristics of residents in different time periods and different street spaces,tools such as track recording APPs and the Gopro Motion Camera are employed to collect street view pictures and riding track data comprehensively,analyzing the various travel purposes of residents in Tiantongyuan community and the riding OD activity tracks of the main entrances and exits of the community.Meanwhile,by conducting the questionnaire survey of residents’travel demands and OD data of Baidu,and utilizing geographic information system(GIS)for data visualization,this study further investigates the distribution characteristics of cycling hotspots,cycling paths and cycling space,accurately identifies the cycling life circle of this community based on the spatial and temporal scales,and further puts forward the optimization strategy of the cycling network.Some cycling-friendly street space optimization strategies are suggested to deeply analyze the mechanism of the built environment of street space in high-density communities on the cycling activities and health of urban residents,with a view to provide accurate data support for the renewal of street cycling space. 展开更多
关键词 Public health High-density neighbourhoods cycling life circle Precision update Tiantongyuan community
下载PDF
Recycling Carbon:A Leap towards Greener Chemicals
8
作者 YAN Fusheng 《Bulletin of the Chinese Academy of Sciences》 2024年第1期22-24,共3页
Imagine a world where carbon dioxide(CO_(2))emissions that contribute to global warming are not only captured but transformed into something valuable.Scientists have now engineered a new method that could make this vi... Imagine a world where carbon dioxide(CO_(2))emissions that contribute to global warming are not only captured but transformed into something valuable.Scientists have now engineered a new method that could make this vision a reality,offering a new twist on carbon fixation. 展开更多
关键词 cycling offering SOMETHING
下载PDF
Swiss cycling brand to pushing the boundaries of sustainability
9
《China Textile》 2024年第3期47-47,共1页
Possenia,a trailblazing newcomer in the cycling industry,proudly announces a groundbreaking achievement:it is Switzerland’s first cycling brand to introduce the bluesign®PRODUCT label,marking an important milest... Possenia,a trailblazing newcomer in the cycling industry,proudly announces a groundbreaking achievement:it is Switzerland’s first cycling brand to introduce the bluesign®PRODUCT label,marking an important milestone in sustainable cycling apparel in Europe.These environmentally conscious,premium cycling essentials are now available on Digitec Galaxus as well as directly through Possenia’s own website. 展开更多
关键词 cycling TRAIL BREAKING
下载PDF
Recycling a Scarce Resource
10
作者 GITONGA NJERU 《ChinAfrica》 2024年第11期42-43,共2页
Caleb Munyao,a 48-year-old middle-scale farmer from Kenya’s eastern region,understands the importance of water better than most.On his 13-hectare farm,where he grows maize,yellow beans,and mangoes,every drop of water... Caleb Munyao,a 48-year-old middle-scale farmer from Kenya’s eastern region,understands the importance of water better than most.On his 13-hectare farm,where he grows maize,yellow beans,and mangoes,every drop of water is precious.Kenya,like many countries in Africa,faces significant challenges in managing its water resources.The country’s water scarcity issues are exacerbated by climate change,rapid urbanisation,and inconsistent rainfall patterns. 展开更多
关键词 cycling YELLOW inconsistent
下载PDF
Effect of vinylene carbonate as electrolyte additive on cycling performance of LiFePO_4/graphite cell at elevated temperature 被引量:4
11
作者 宋海申 曹政 +3 位作者 张治安 赖延清 李劼 刘业翔 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2014年第3期723-728,共6页
Effects of film-forming additive on stability of electrode and cycling performance of LiFePO4/graphite cell at elevated temperature were studied. Two 18650 cells with and without VC additive were investigated by galva... Effects of film-forming additive on stability of electrode and cycling performance of LiFePO4/graphite cell at elevated temperature were studied. Two 18650 cells with and without VC additive were investigated by galvanostatic cycling, electrochemical impedance spectroscopy, scanning electron microscopy, energy-dispersive X-ray analysis and Raman spectroscopy. The results show that in the presence of VC additive, dissolution of Fe from LiFePO4 material is greatly depressed and stability of graphite structure is improved; the additive can not only reduce reaction of electrolyte on surface of LiFePO4 electrode but also suppress reduction of solvent and thickening of the solid electrolyte interface (SEI) layer on graphite surface. Electrolyte with VC is considered to be a good candidate for improving cycling performance of the LiFePOa/graphite cell at elevated temperature. 展开更多
关键词 LiFeP04 vinylene carbonate electrolyte additive cycling performance
下载PDF
布鲁菌Cycling探针荧光定量PCR检测方法的建立 被引量:2
12
作者 许邹亮 南文龙 +4 位作者 陆明哲 周洁 谭鹏飞 陈义平 毛开荣 《中国兽医杂志》 CAS 北大核心 2012年第2期13-16,共4页
根据布鲁菌BCSP31基因序列设计布鲁菌通用检测引物和探针,建立了布鲁菌Cycling探针荧光定量PCR检测方法。以构建的含BCSP31基因的质粒标准品10倍递进稀释为模板检测其敏感性,结果显示,本方法能检测约10个拷贝的阳性质粒,且标准曲线的线... 根据布鲁菌BCSP31基因序列设计布鲁菌通用检测引物和探针,建立了布鲁菌Cycling探针荧光定量PCR检测方法。以构建的含BCSP31基因的质粒标准品10倍递进稀释为模板检测其敏感性,结果显示,本方法能检测约10个拷贝的阳性质粒,且标准曲线的线性关系良好。用本方法检测5株不同种的布鲁菌以及猪大肠杆菌K99、巴氏杆菌C48-1、猪链球菌ST171、绿脓杆菌等4株对照菌。结果显示,5株不同种的布鲁菌均出现典型的"S"型扩增曲线,4株对照菌40个循环内均无CT值出现。用本方法和B4/B5-PCR方法对来自布鲁菌病流行地区3个不同牛场的40份血样、奶样和血清样进行平行检测。结果显示,本方法和B4/B5-PCR方法的结果符合率为80.0%。B4/B5-PCR检测为阳性的27份样品经本方法检测均为阳性;B4/B5-PCR检测为阴性的13份样本,经本方法检测,其中8份呈阳性,5份为阴性。本方法的敏感性明显高于B4/B5-PCR方法。试验表明,所建立的Cycling探针荧光定量PCR方法具有敏感、特异、稳定等特点,可用于布鲁菌感染的快速检测。 展开更多
关键词 布鲁菌 cycling探针荧光定量PCR
下载PDF
Effect of sintering temperature on cycling performance and rate performance of LiNi_(0.8)Co_(0.1)Mn_(0.1)O_2 被引量:2
13
作者 李向群 熊训辉 +1 位作者 王志兴 陈启元 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2014年第12期4023-4029,共7页
LiNi0.8Co0.1Mn0.1O2 powder was prepared by mixing LiOH·H2O and co-precipitated Ni0.8Co0.1Mn0.1(OH)2 at a molar ratio of 1:1.05, followed by sintering at different temperatures. The effects of temperature on th... LiNi0.8Co0.1Mn0.1O2 powder was prepared by mixing LiOH·H2O and co-precipitated Ni0.8Co0.1Mn0.1(OH)2 at a molar ratio of 1:1.05, followed by sintering at different temperatures. The effects of temperature on the morphology, structure and electrochemical performance were extensively studied. SEM and XRD results demonstrate that the sintering temperature has large influence on the morphology and structure and suitable temperature is very important to obtain spherical materials and suppresses the ionic distribution. The charge-discharge tests show that the electrochemical performance of LiNi0.8Co0.1Mn0.1O2 powders becomes better with the increase of temperature from 700 ℃ to 750 ℃ and higher temperature will deteriorate the performance. Although both of materials obtained at 750 ℃ and 780 ℃ demonstrate almost identical cyclic stability at 2C rate, which delivers 71.9%retention after 200 cycles, the rate performance of powder calcined at 780 ℃ is much poorer than that at 750 ℃. The XRD results demonstrate that the poor performance is ascribed to more severe ionic distribution caused by higher temperature. 展开更多
关键词 lithium ion battery LiNi0.8CO0.1Mn0.1O2 sintering temperature cycling performance rate performance
下载PDF
基于FES cycling训练的刺激模式的设计与研究 被引量:2
14
作者 姜洪源 魏伟 马长波 《中国康复医学杂志》 CAS CSCD 北大核心 2007年第2期147-150,共4页
目的:提出一种基于FES cycling训练的刺激模式的设计方法,使训练者在训练过程中腿部肌肉能够协调运动,获得较高的运动效率。方法:对训练中的蹬踏运动结构进行建模,同时结合腿部肌肉运动的动力学模型,对运动中的运动效率进行分析,以运动... 目的:提出一种基于FES cycling训练的刺激模式的设计方法,使训练者在训练过程中腿部肌肉能够协调运动,获得较高的运动效率。方法:对训练中的蹬踏运动结构进行建模,同时结合腿部肌肉运动的动力学模型,对运动中的运动效率进行分析,以运动过程中的平均功率作为目标函数进行优化,获取运动效率最高的刺激模式。结论和结果:得到一种运动效率更高的刺激模式,同时也为不同结构形式的FES cycling刺激模式的设计提供了一种较为通用的方法。 展开更多
关键词 功能性电刺激脚踏车训练系统 刺激模式 动力学 模型
下载PDF
HBx基因缺失突变体(HBx-d382)对L02细胞cyclinD1、cyclinG1和E2F1表达的影响
15
作者 胡志亮 侯周华 +5 位作者 符小玉 陈莉 谢萍 欧阳奕 杨永峰 谭德明 《中国现代医学杂志》 CAS CSCD 北大核心 2011年第33期4114-4117,4121,共5页
目的前期的研究成功构建了稳定表达HBx基因及其缺失突变体(HBx-d382)的L02细胞,分别命名为L02/HBx和L02/HBx-d382,并证实其可导致肝细胞恶性转化。该研究进一步探讨HBx-d382对L02细胞G1期细胞周期调控相关基因cyclinD1,cyclinG1和E2F1... 目的前期的研究成功构建了稳定表达HBx基因及其缺失突变体(HBx-d382)的L02细胞,分别命名为L02/HBx和L02/HBx-d382,并证实其可导致肝细胞恶性转化。该研究进一步探讨HBx-d382对L02细胞G1期细胞周期调控相关基因cyclinD1,cyclinG1和E2F1表达的影响。方法实验分为L02/pcDNA3.0(稳定转染pcDNA3.0)、L02/HBx和L02/HBx-d382(分别稳定转染质粒pcDNA3.0/HBx和pcDNA3.0/HBx-d382)3组。通过实时定量PCR以及wester-blot检测转染HBx基因及其缺失突变体HBx-d382后L02细胞cyclinD1、cyclinG1和E2F1表达的改变。方法实时定量PCR以及wester-blot结果表明稳定表达HBx基因或HBx-d382的L02细胞cyclinD1、cyclinG1和E2F1表达上调,表达HBx-d382的L02细胞上调最为明显。结论 HBx-d382可能通过上调cyclinD1、cyclinG1和E2F1从而影响细胞G1期调控,进一步导致肝细胞恶性转化。 展开更多
关键词 HBX HBx-d382 细胞周期 cyclIN
下载PDF
Microstructure instability of fully lamellar TiAl alloy containing high content of Nb after long-term thermal cycling 被引量:3
16
作者 方璐 丁贤飞 +3 位作者 何建平 张来启 林志 林均品 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2014年第10期3095-3102,共8页
Microstructure instabilities of the fully lamellar Ti-45Al-8.5Nb-(W,B,Y) alloy were investigated by SEM and TEM after long-term thermal cycling(500 and 1000 thermal cycles) at 900 °C. Two major categories of ... Microstructure instabilities of the fully lamellar Ti-45Al-8.5Nb-(W,B,Y) alloy were investigated by SEM and TEM after long-term thermal cycling(500 and 1000 thermal cycles) at 900 °C. Two major categories of microstructure instability were produced in the alloy after the thermal cycling: 1) The discontinuous coarsening implies that grain boundary migrations are inclined to occur in the Al-segregation region after the long-term thermal cycling, especially after 1000 thermal cycles. Al-segregation can be reduced during the process of long-term thermal cycling as a result of element diffusion; 2) The α2 lamellae become thinner and are broken after 1000 thermal cycles caused by the dissolution of α2 lamellae through phase transformation of α2→γ. The γ grains nucleate within the α2 lamellae or(α2+γ) lamellae in a random direction. 展开更多
关键词 TiAl alloys thermal cycling thermal stability discontinuous coarsening
下载PDF
Geological cycling of potassium and the K isotopic response:insights from loess and shales 被引量:13
17
作者 Weiqiang Li Shilei Li Brian L.Beard 《Acta Geochimica》 EI CAS CSCD 2019年第4期508-516,共9页
Shales are a major sink for K into seawater delivered from continental weathering,and are potential recorders of K cycling.High precision K isotope analyses reveal a[0.6%variation in δ^41K values(41K/39K relative to ... Shales are a major sink for K into seawater delivered from continental weathering,and are potential recorders of K cycling.High precision K isotope analyses reveal a[0.6%variation in δ^41K values(41K/39K relative to NIST SRM 3141a)from a set of well characterized postArchean Australian shale(PAAS)samples.By contrast,loess samples have relatively homogenous δ^41K values(-0.5±0.1%),which may represent the average K composition of upper continental crust.Most of the shales analyzed in this study have experienced K enrichment relative to average continental crust,and the majority of them define a trend of decreasing δ^41K value(from-0.5to-0.7%)with increasing K content and K/Na ratio,indicating cation exchange in clays minerals is accompanied by K isotope fractionation.Several shale samples do not follow the trend and have elevated δ^41K values up to-0.1%,and these samples are characterized by variable Fe isotope compositions,which reflect post-depositional processes.The K isotope variability observed in shales,in combination with recent findings about K isotope fractionation during continental weathering,indicates that K isotopes fractionate during cycling of K between different reservoirs,and K isotopes in sediments may be used to trace geological cycling of K. 展开更多
关键词 K ISOTOPES LOESS SHALE K cycle
下载PDF
Description and Application of a Model for Simulating Regional Nitrogen Cycling and Calculating Nitrogen Flux 被引量:16
18
作者 郑循华 刘春岩 韩圣慧 《Advances in Atmospheric Sciences》 SCIE CAS CSCD 2008年第2期181-201,共21页
A regional nitrogen cycle model, named IAP-N, was designed for simulating regional nitrogen (N) cycling and calculating N fluxes flowing among cultivated soils, crops, and livestock, as well as human, atmospheric an... A regional nitrogen cycle model, named IAP-N, was designed for simulating regional nitrogen (N) cycling and calculating N fluxes flowing among cultivated soils, crops, and livestock, as well as human, atmospheric and other systems. The conceptual structure and calculation methods and procedures of this model are described in detail. All equations of the model are presented. In addition, definitions of all the involved variables and parameters are given. An application of the model in China at the national scale is presented. In this example, annual surpluses of consumed synthetic N fertilizer; emissions of nitrous oxide (N2O), ammonia (NH3) and nitrogen oxide (NOx); N loss from agricultural lands due to leaching and runoff; and sources and sinks of anthropogenic reactive N (Nr) were estimated for the period 1961-2004. The model estimates show that surpluses of N fertilizer started to occur in the mid 1990s and amounted to 5.7 Tg N yr^-1 in the early 2000s. N20 emissions related to agriculture were estimated as 0.69 Tg N yr^-1 in 2004, of which 58% was released directly from N added to agricultural soils. Total NH3 and NOx emissions in 2004 amounted to 4.7 and 4.9 Tg N yr^-1, respectively. About 3.9 Tg N yr^-1 of N was estimated to have flowed out of the cultivated soil layer in 2004, which accounted for 33% of applied synthetic N fertilizer. Anthropogenic Nr sources changed from 2.8 (1961) to 28.1 Tg N yr^-1 (2004), while removal (sinks) changed from to 2.1 to 8.4 Tg N yr^-1. The ratio of anthropogenic Nr sources to sinks was only 1.4 in 1961 but 3.3 in 2004. Further development of the IAP-N model is suggested to focus upon: Ca) inter-comparison with other regional N models; (b) overcoming the limitations of the current model version, such as adaptation to other regions, high-resolution database, and so on; and (c) developing the capacity to estimate the safe threshold of anthropogenic Nr source to sink ratios. 展开更多
关键词 nitrogen cycle nitrous oxide reactive nitrogen MODEL AGRICULTURE China
下载PDF
Biomass production,nutrient cycling and distribution in age-sequence Chinese fir(Cunninghamia lanceolate)plantations in subtropical China 被引量:14
19
作者 Lili Zhou Addo-Danso Daniel Shalom +3 位作者 Pengfei Wu Zongming He Chunhua Liu Xiangqing Ma 《Journal of Forestry Research》 SCIE CAS CSCD 2016年第2期357-368,共12页
Biomass production and nutrient (N, P, K, Ca and Mg) accumulation, distribution and cycling were quantified in young, mature and over-mature (10-, 22-, and 34-year old) Chinese fir [Cunninghamia lanceolate (Lamb.... Biomass production and nutrient (N, P, K, Ca and Mg) accumulation, distribution and cycling were quantified in young, mature and over-mature (10-, 22-, and 34-year old) Chinese fir [Cunninghamia lanceolate (Lamb.) Hook] plantations in southern China. Total stand biomass of young, mature and over-mature stands was 38, 104 and 138 t ha-1 respectively. Biomass production increased significantly with age. Stem wood represented the highest percentage of stand biomass, accounting for 41, 55 and 63 % in the young, mature and over-mature plan- tations respectively. Nutrients concentration was highest in live needles and branches, and lowest in stem wood. The plantations accumulated more N, followed by K, Ca, Mg, and P. Nutrient return amount, nutrient utilization effi- ciency, nutrient turnover time, the ratio of nutrient return and uptake increased with stand age, which implies that young Chinese fir deplete soil nutrients to maintain growth, and efficiently utilize nutrients to decrease dependence on soil nutrients as they age. Harvesting young Chinese fir plantations would therefore lead to high nutrient loss, but prolonging the rotation length could improve soil recovery, and help sustain productivity in the long-term. Improved nutrient return through litterfall as stands get older may also be beneficial to nutrient pool recovery. 展开更多
关键词 Cunninghamia lanceolate BIOMASSPRODUCTION Nutrient distribution Nutrient cycling
下载PDF
Nitrogen cycling of atmosphere-plant-soft system in the typical Calamagrostis angustifolia wetland in the Sanjiang Plain,Northeast China 被引量:13
20
作者 SUN Zhi-gao LIU Jing-shuang 《Journal of Environmental Sciences》 SCIE EI CAS CSCD 2007年第8期986-995,共10页
The nitrogen (N) distribution and cycling of atmosphere-plant-soil system in the typical meadow Calamagrostis angustifolia wetland (TMCW) and marsh meadow Calamagrostis angustifolia wetland (MMCW) in the Sanjian... The nitrogen (N) distribution and cycling of atmosphere-plant-soil system in the typical meadow Calamagrostis angustifolia wetland (TMCW) and marsh meadow Calamagrostis angustifolia wetland (MMCW) in the Sanjiang plain were studied by a compartment model. The results showed that the N wet deposition amount was 0.757 gN/(m^2·a), and total inorganic N (TIN) was the main body (0.640 gN/(m^2·a)). The ammonia volatilization amounts of TMCW and MMCW soils in growing season were 0.635 and 0.687 gN/m^2, and the denitrification gaseous lost amounts were 0.617 and 0.405 gN/m^2, respectively. In plant subsystem, the N was mainly stored in root and litter. Soil organic N was the main N storage of the two plant-soil systems and the proportions of it were 93.98% and 92.16%, respectively. The calculation results of N turnovers among compartments of TMCW and MMCW showed that the uptake amounts of root were 23.02 and 28.18 gN/(m^2·a) and the values of aboveground were 11.31 and 6.08 gN/(m^2·a), the re-translocation amounts from aboveground to root were 5.96 and 2.70 gN/(m^2·a), the translocation amounts from aboveground living body to litter were 5.35 and 3.38 gN/(m^2·a), the translocation amounts from litter to soil were larger than 1.55 and 3.01 gN/(m^2·a), the translocation amounts from root to soil were 14.90 and 13.17 gN/(m^2·a), and the soil (0-15 cm) N net mineralization amounts were 1.94 and 0.55 gN/(m^2·a), respectively. The study of N balance indicated that the two plant-soil systems might be situated in the status of lacking N, and the status might induce the degradation of C. angustifolia wetland. 展开更多
关键词 compartment model nitrogen cycling Calamagrostis angustifolia wetland ecosystem Sanjiang Plain
下载PDF
上一页 1 2 250 下一页 到第
使用帮助 返回顶部