期刊文献+
共找到407篇文章
< 1 2 21 >
每页显示 20 50 100
Evidence on the causes of the rising levels of COD_(Mn) along the middle route of the South-to-North Diversion Project in China:The role of algal dissolved organic matter 被引量:14
1
作者 Chao Wang Hong Zhang +3 位作者 Pei Lei Xiaokang Xin Aijing Zhang Wei Yin 《Journal of Environmental Sciences》 SCIE EI CAS CSCD 2022年第3期281-290,共10页
As the biggest inter-basin water transfer scheme in the world,the South-to-North Water Diversion Project(SNWD) was designed to alleviate the water crisis in North China.The main channel of the middle route of the SNWD... As the biggest inter-basin water transfer scheme in the world,the South-to-North Water Diversion Project(SNWD) was designed to alleviate the water crisis in North China.The main channel of the middle route of the SNWD is of great concern in terms of the drinking water quality.In this study,we tested the hypothesis that the dissolved organic matter(DOM) derived from the planktonic algae causes the rising levels of COD_(Mn) along the middle route by monitoring data on water quality(2015-2019,monthly resolution).The results showed that algal density in the main channel increased along the channel and was significantly correlated with COD_(Mn)(p <0.01).Five fluorescent components of DOM,including tyrosine-like(14.85%),tryptophan-like(22.48%),microbial byproduct-like(26.34%),fulvic acid-like(11.41%),and humic acid-like(24.92%) components,were detected.The level of tyrosine-like components increased along the channel and was significantly correlated with algal density(p<0.01),indicating that algae significantly changed the level of DOM in the channel.Algal decomposition and metabolism were found to be the main mechanisms that drive the changes in COD_(Mn).Therefore,controlling algal density would be an important measure to prevent further increase in CODMn and for the guarantee of excellent water quality. 展开更多
关键词 Dissolved organic matter(DOM)Algae COD_(Mn) South-to-North Diversion Project Danjiangkou reservoir Three-dimensional fluorescence excitation emission matrix spectroscopy(3D-EEMs)
原文传递
Penalty model for delay of bidding section construction period in South-to-North Water Diversion Eastern Route Project from perspective of programs 被引量:2
2
作者 Jing-chun FENG Ya-fang REN +2 位作者 Zhong-nan DUAN Zhan-jun LIU Hai-yang LI 《Water Science and Engineering》 EI CAS 2012年第3期350-360,共11页
According to the multi-project and program management theory, this paper analyzes the program generation principle and establishes a program based on progress goals. On the basis of the present situation of calculatio... According to the multi-project and program management theory, this paper analyzes the program generation principle and establishes a program based on progress goals. On the basis of the present situation of calculation of penalty for delay of the bidding section construction period with the critical path method, we studied the effects of contractor-induced delay of the bidding section construction period in detail, including the effects on the construction period of the bidding section itself, the earliest start times of the next bidding section and other subsequent bidding sections, and the construction period of the program, and then constructed a penalty model for delay of the bidding section construction period from the perspective of programs. Using the penalty model, we conducted a practical analysis of penalty for delay of the construction period of the Baoying station program in the South-to-North Water Diversion Project. The model can help determine the amount of penalty for delay of the construction period in bidding sections scientifically and reasonably, 展开更多
关键词 program establishment program management bidding section construction period critical path method (CPM) penaly model South-to-North Water Diversion Project
在线阅读 下载PDF
Influence of Microstructure and Sintering Routes on Transport Properties of Apatite Materials for Fuel Cells
3
作者 A.Chesnaud C.Estournes G.Dezannau 《复旦学报(自然科学版)》 CAS CSCD 北大核心 2007年第5期680-,共1页
1 Results Oxy-apatite materials are thought as zirconia-substitutes in Solid Oxide Fuel Cells due to their fast ionic conduction. However, the well known difficulties related to their densification prevent them from b... 1 Results Oxy-apatite materials are thought as zirconia-substitutes in Solid Oxide Fuel Cells due to their fast ionic conduction. However, the well known difficulties related to their densification prevent them from being used as such. This study presents strategies to obtain oxy-apatite dense materials and the influence of elaboration route on transport properties. Particular emphasis is put on the microstructure effect on ion conduction. By the combined use of freeze-drying and conventional or spark p... 展开更多
关键词 oxy-apatite ion conductor ELECTROLYTE Spark-Plasma Sintering fuel cells
在线阅读 下载PDF
A Catalyst for Change
4
作者 ZAMIR AHMED AWAN 《ChinAfrica》 2025年第8期30-31,共2页
China’s Five-Year Plans balance stability and market vitality,o#ering a forward-looking model for social progress and economic transformation China’s Five-Year Plans(FYPs)represent a rare combination of strategic fo... China’s Five-Year Plans balance stability and market vitality,o#ering a forward-looking model for social progress and economic transformation China’s Five-Year Plans(FYPs)represent a rare combination of strategic foresight and adaptive governance.Over the past 70 years,this planning mechanism has served as both a compass and a roadmap,allowing China not only to stay true to its long-term objectives but also to recalibrate policies in response to evolving domestic and international environments. 展开更多
关键词 adaptive governanceover CATALYST market vitality planning mechanism recalibrate policies social progress strategic foresight five year plans
原文传递
Development of La_(2-x)Ce_(x)O_(2)CO_(3) solid solution for low-concentration phosphate removal and recovery:manipulating Ce ratio and valence to boost phosphate capture
5
作者 Jingzhang Liu Lei Bi +4 位作者 Xinzong Xiao Wenzhong Tang Qiong Wang Mei Du Maoyong Song 《Journal of Environmental Sciences》 2025年第10期213-224,共12页
The removal and recovery of low-concentration phosphates from water have become crucial due to the dual challenges of eutrophication and the phosphorus crisis.Herein,we engineered a highly efficient and recyclable pho... The removal and recovery of low-concentration phosphates from water have become crucial due to the dual challenges of eutrophication and the phosphorus crisis.Herein,we engineered a highly efficient and recyclable phosphate trapping agent of La_(2-x)CexO_(2)CO_(3) solid solution.The incorporation of Ce enhances the surface area and surface potential of La_(2-x)CexO_(2)CO_(3),providing abundant adsorption sites for phosphate.Surprisingly,we found that adjusting the Ce proportion affects the carbonate content,thereby influencing the anion-exchange capacity between carbonate and phosphate.Specifically,at 3% Ce content(3%-CeL),the carbonate ratio is maximized,resulting in an optimal sorption capacity(196.4mg P/g)and a rapid removal rate(under 40min)for phosphate,unaffected by interfering ions.Remarkably,3%-CeL achieved nearly 100%phosphate removal efficiency in diverse water samples from sewage treatment plants,rivers,reservoirs,and groundwater.After five adsorption-desorption cycles,the phosphate removal and recovery efficiency of 3%-CeL remained above 90%.Mechanistic studies revealed that 3%Ce content yielded the highest proportion of Ce^(4+)/Ce^(3+),enabling greater carbonate binding for anion-exchange.This study proposes a high-performance phosphate trapping agentwith broad applicability for treating actual waters and provides a new perspective on enhancing low-concentration phosphate removal in La-based materials through manipulating Ce ratio and valence. 展开更多
关键词 La_(2-x)CexO_(2)CO_(3) Anion exchange Adsorption Low concentration of phosphate Phosphate removal and recycle
原文传递
Magnetic Activity and Differential Rotation of HIP12653
6
作者 Amina Boulkaboul Lotfi Yelles Chaouche +1 位作者 Alessandro C.Lanzafame Yassine Damerdji 《Research in Astronomy and Astrophysics》 2025年第12期1-19,共19页
We present a spectroscopic and photometric study of HIP 12653 to investigate its magnetic cycle and differential rotation.Using HARPS archival spectra matched with MARCS-AMBRE theoretical templates,we derive the stell... We present a spectroscopic and photometric study of HIP 12653 to investigate its magnetic cycle and differential rotation.Using HARPS archival spectra matched with MARCS-AMBRE theoretical templates,we derive the stellar parameters(Teff,logg,FeH,and vsini)of the target.The S-index,an activity indicator based on the emission of the CaⅡH&K lines,is fitted to determine the magnetic cycle and rotation periods.We refine the magnetic cycle period to 5799.20±0.88 days and suggest the existence of a secondary,shorter cycle of674.6922±0.0098 days,making HIP 12653 the youngest star known to exhibit such a short activity cycle.During the minimum activity phase,a rotation period of 4.8 days is estimated.This is notably different from the 7 day period obtained when measurements during minimum activity are excluded,suggesting that these two periods are rotation periods at different latitudes.To explore this hypothesis,we introduce a novel light curve fitting method that incorporates multiple harmonics to model different spot configurations.Applied to synthetic light curves,the method recovers at least two rotation periods close to the true input values(within three times their uncertainties)in 92.1%of cases.The inferred rotation shear shows a median deviation of 0.0011±0.0003 and a standard deviation of 0.0177±0.0002 from the true value.Applying this approach to TESS photometric data from 2018 to2023,we detect three distinct rotation periods—4.8 days,5.7 days,and 7.7 days,(along with a signal at 3.75 days interpreted as its first harmonic)—consistent with spots located at different latitudes.Assuming a solar-like differential rotation,we estimate an inclination of 34.0°±1.8°and a rotational shear ofα=0.38±0.01.These results confirm the 4.8 day period and demonstrate that differential rotation can be constrained by tracking rotation period changes across different phases of the magnetic cycle. 展开更多
关键词 stars:activity (stars:)starspots stars:rotation stars:chromospheres stars:individual(HIP12653)
在线阅读 下载PDF
Numerical implication of water-soil leakage induced by longitudinal tunnel segment dislocation opening in saturated strata
7
作者 Fan Chen Junfeng Sun +2 位作者 Hao Xiong Zhen-Yu Yin Xiangsheng Chen 《Journal of Rock Mechanics and Geotechnical Engineering》 2025年第12期7570-7589,共20页
Water-soil leakage due to the longitudinal dislocation opening of tunnel segments in high-permeable soil strata is crucial for ensuring the longevity of underground tunnel infrastructures.This research delves into thi... Water-soil leakage due to the longitudinal dislocation opening of tunnel segments in high-permeable soil strata is crucial for ensuring the longevity of underground tunnel infrastructures.This research delves into this complex phenomenon employing coupled computational fluiddynamics(CFD),discrete element method(DEM),and finiteelement method(FEM),considering varied tunnel buried depths and dislocation opening sizes.Two critical areas susceptible to water-soil leakage have been identified,including an‘ellipsoid’shaped area at the tunnel top and a soil sliding area perpendicular to the tunneling direction.With a narrow segment opening(3 d_(50)),the fineloss remains below 2%across various buried depths,whereas it escalates to 7.4%-30%with increasing buried depth under a slightly wider opening(3.8d_(50)).The proposed three-dimensional(3D)ellipsoid model is used to delineate the leakage region and quantify over 98%ground soil loss due to dislocation opening.Furthermore,the research reveals that soil sliding induced by water-soil leakage significantly decreases the structural shear stress on the waists and inverts of the tunnel segment,while the soil arching at the top of the tunnel would mitigate the stress release,particularly at the lower dislocated tunnel segment. 展开更多
关键词 Tunnel segment dislocation Water-soil leakage Computational fluiddynamics(CFD) Discrete element method(DEM) Finite element method(FEM) Tunnel loading Structure analysis
在线阅读 下载PDF
Quantifying unseen woody biomass and diversity in understorey trees and shrubs at the extremes of water availability in the Miombo ecoregion
8
作者 Hermane Diesse John L.Godlee +7 位作者 Nichola Knox Jonathan Muledi Leena Naftal David Nkulu Ben Nkomba Gabriel Uusiku Kyle Dexter Vera De Cauwer 《Forest Ecosystems》 2025年第3期482-494,共13页
The Miombo ecoregion covers eastern and southern Africa,with variations in plant species composition,structure,and biomass across a broad precipitation gradient.Most studies of woody plant communities focus exclusivel... The Miombo ecoregion covers eastern and southern Africa,with variations in plant species composition,structure,and biomass across a broad precipitation gradient.Most studies of woody plant communities focus exclusively on larger overstorey trees(≥5 or≥10cm stem diameter),overlooking the contribution of small trees and shrubs in the understorey,which can comprise a significant portion of total biomass and diversity.Here,we evaluate the contribution of both large overstorey and small understorey woody plants to species diversity and above-ground biomass(AGB),with 17 plots(0.5-1ha)across five sites representing both extremes of rainfall gradient spanning the Miombo ecoregion,in northeast Namibia(500-700mm mean annual precipitation,MAP)and southern Democratic Republic of Congo(DRC)(>1,200mm MAP).Mean AGB per site ranged from 21 to 119Mg·ha^(-1),increasing with rainfall,while the proportional AGB contribution of small trees,saplings,and shrubs decreased.In dry Namibia,small trees,saplings,and shrubs(<5cm DBH)contributed up to 28.2%of total AGB(mean±standard deviation:18.3%±3.4%),whereas in wet DRC,they contributed only up to 2.5%(2.3%±1.4%).Namibian sites,on average,contained a large proportion of woody species diversity exclusively in small trees and shrubs(<5cm DBH),with 55 species representing 59.4%of the total diversity.In contrast,DRC sites had higher overall small woody plant diversity(66 species)but fewer species found exclusively as small individuals(25.2%),with many saplings that grow to larger trees.Understorey composition also differed,with saplings of overstorey trees dominating in DRC,while shrubs dominated in Namibia.Our findings show that woody biomass and diversity in dry woodlands are substantially underestimated when studies focus only on larger trees.This highlights the need to consider all woody vegetation to better understand woody plant diversity and biomass variation. 展开更多
关键词 Miombo woodlands Plant diversity Overstorey UNDERSTOREY Biomass SHRUBS Stand structure
在线阅读 下载PDF
Innovative Approaches in the Extraction,Identification,and Application of Secondary Metabolites from Plants
9
作者 Amine Assouguem Saoussan Annemer +1 位作者 Mohammed Kara Abderrahim Lazraq 《Phyton-International Journal of Experimental Botany》 2025年第6期1631-1668,共38页
Unlike primary metabolites,secondary metabolites serve critical ecological functions,including plant protection,stress tolerance,and symbiosis.This review focuses on extracting,separating,and identifying the major cla... Unlike primary metabolites,secondary metabolites serve critical ecological functions,including plant protection,stress tolerance,and symbiosis.This review focuses on extracting,separating,and identifying the major classes of secondary metabolites,including alkaloids,terpenoids,phenolics,glycosides,saponins,and coumarins.It describes optimized methods regarding plant selection,extraction by solvents,and purification of the metabolites,highlighting the latest advancements in chromatographic and spectroscopic techniques.The review also describes some of the most important problems,such as the instability of the compounds or diversity of the structures,and discusses emerging technologies that solve these issues.Moreover,it examines the secondary roles of these metabolites in medicine,such as anticancer and antimicrobial drugs,sustainable agriculture biopesticides,and environmental ecology-also known as allelopathy and bioindicators.It combines traditional ethnobotanical approaches with contem-porary science,demonstrating the vital need to protect biodiversity in key ecosystems such as tropical rainforests,mountain regions,coral reefs,and arid zones as a foundation for anticipatory bio-discoveries.It organizes the methodological frameworks and outlines the steps needed to enhance the extraction of bioactive compounds from natural sources. 展开更多
关键词 Plant-derived substances extraction methods spectroscopic methods climate-friendly farming ecological roles biodiversity preservation
在线阅读 下载PDF
Geospatial analysis of neotectonics in the Jebel Gustar Mountain,northeastern Algeria
10
作者 TAIB Hassan HADJI Riheb +3 位作者 ZIGHMI Karim HAMED Younes GENTILUCCI Matteo BEDRI Khaoula 《Journal of Mountain Science》 2025年第2期391-403,共13页
This research investigates dynamic earth processes within the South Setifian allochthonous ensemble,providing insights into landscape evolution and seismotectonic activity within the Tellian mountain chain.Focusing on... This research investigates dynamic earth processes within the South Setifian allochthonous ensemble,providing insights into landscape evolution and seismotectonic activity within the Tellian mountain chain.Focusing on the Jebel Gustar and Kef Lahmar area,which includes 14 sub-basins,this research uses a DEM-based technique to assess Holocene activities,lineament characteristics,and stream systems.Five geomorphic indices are used to assess relative active tectonics:the stream lengthgradient index(SL),drainage basin asymmetry(AF),valley-floor width to valley height ratio(VF),drainage basin shape(BS),and mountain front sinuosity(SMF).A weighted overlay of these five indices produces the Index of Relative Active Tectonics(IRAT)map.The findings reveal significant neotectonic activity in the study area,supported by profound basement faulting.This research highlights the morpho-structural processes and neotectonics activity in the Jebel Gustar,providing a framework for investigating the evolution of this structure.Additionally,it enhances comprehension of the interactions between the alpine range's internal zones in Eastern Algeria and the Atlasic domain.This study proposes a systematic approach to evaluate the tectonic and geomorphological dynamics of the South Setif region. 展开更多
关键词 Active tectonics Crustal deformation Holocene activities Geomorphic indices Neotectonic dynamics
原文传递
The Global Boundary Stratotype Section and Point(GSSP)for the base of the Valanginian Stage,the Vergol section(Montbrun-les-Bains,Droe,SE France)and its Standard Auxiliary Boundary Stratotype(SABS),Canda Luenga section(Cehegín,SE Spain)
11
作者 Stéphane Reboulet Miguel Company +19 位作者 Thierry Adatte Roque Aguado François Baudin Jean-François Deconinck Stan Duxbury Ginés de Gea Jacek Grabowski Bruno Granier Daria Ivanova Nico M.M.Janssen Jaap Klein Iskra Lakova Melanie G.Leng Damian G.Lodowski Mathieu Martinez Emanuela Mattioli John M.McArthur Davide Olivero Daniela Reháková JoséMaría Tavera 《Episodes》 2025年第4期479-563,共85页
Following votes by the Valanginian Working Group,the International Subcommission on Cretaceous Stratigraphy and the International Commission on Stratigraphy,the Executive Committee of the International Union of Geolog... Following votes by the Valanginian Working Group,the International Subcommission on Cretaceous Stratigraphy and the International Commission on Stratigraphy,the Executive Committee of the International Union of Geological Sciences unanimously approved in December 2024 the Global Stratotype Section and Point(GSSP)for the Valanginian Stage(Cretaceous System). 展开更多
关键词 standard auxiliary boundary stratotype Valanginian stage commission stratigraphythe cretaceous stratigraphy Vergol section International Subcommission Cretaceous Stratigraphy global boundary stratotype section point Canda Luenga section
在线阅读 下载PDF
Ag掺杂对TiO_2粉末结构的影响 被引量:25
12
作者 何超 于云 +2 位作者 周彩华 胡行方 André LARBOT 《无机材料学报》 SCIE EI CAS CSCD 北大核心 2003年第2期457-464,共8页
采用溶胶-凝胶工艺制备了Ag掺杂的TiO_2粉末.通过XRD、SEM、EDX、DSC-TG、BET氮吸附法等研究了Ag掺杂对TiO2结构的影响,结果发现掺杂的Ag降低了TiO_2锐钛矿向金红石相转变的温度,促进了相转变.适量掺杂时,Ag抑制了锐钛矿粒子的生长,结... 采用溶胶-凝胶工艺制备了Ag掺杂的TiO_2粉末.通过XRD、SEM、EDX、DSC-TG、BET氮吸附法等研究了Ag掺杂对TiO2结构的影响,结果发现掺杂的Ag降低了TiO_2锐钛矿向金红石相转变的温度,促进了相转变.适量掺杂时,Ag抑制了锐钛矿粒子的生长,结果使锐钛矿粒子的粒径降低,TiO2_粉末的比表面积增加. 展开更多
关键词 TIO2 AG 溶胶-凝胶法 掺杂 结构
在线阅读 下载PDF
珠江禁渔对广东鲂资源补充群体的影响分析 被引量:17
13
作者 李跃飞 李新辉 +3 位作者 杨计平 SOVAN Lek 帅方敏 李捷 《水产学报》 CAS CSCD 北大核心 2014年第4期503-509,共7页
继我国各大水系实施禁渔期制度之后,珠江水系于2011年4月1日至6月1日实现首次禁渔。广东鲂是珠江中下游地区主要的经济鱼类之一,为分析珠江实施禁渔期制度对广东鲂资源补充群体的影响,于珠江实施禁渔制度前(2006—2010年)和禁渔制度后(2... 继我国各大水系实施禁渔期制度之后,珠江水系于2011年4月1日至6月1日实现首次禁渔。广东鲂是珠江中下游地区主要的经济鱼类之一,为分析珠江实施禁渔期制度对广东鲂资源补充群体的影响,于珠江实施禁渔制度前(2006—2010年)和禁渔制度后(2011—2012年)在珠江下游肇庆江段设立固定采样点,利用定量弶网对流经该江段的广东鲂鱼苗补充群体进行调查。结果显示,禁渔前,珠江广东鲂鱼苗集中出现在4月中下旬至10月中旬,持续时间为(189±11)d,高峰期为6—8月。禁渔期制度实施之后,全年广东鲂鱼苗出现的起始时间变化不大,但是结束时间提前,持续时间略有缩短,4—5月份广东鲂鱼苗密度明显增大。广东鲂鱼苗总量及其在鱼苗补充群体中的比例均有所提高。根据禁渔前广东鲂鱼苗发生量与径流量之间存在的回归关系:LgY=0.988Lnx-4.932(R2=0.365,P<0.01),结合禁渔后实际调查结果,对禁渔的实际作用进行了估算,2011年和2012年由于禁渔分别增加了9.43×108和651.81×108尾广东鲂鱼苗。研究表明,在径流量有保障的前提下,目前的禁渔制度可以有效增加广东鲂鱼苗补充群体资源量。 展开更多
关键词 广东鲂 鱼苗 禁渔 补充群体
在线阅读 下载PDF
西江颗粒直链藻种群生态特征 被引量:17
14
作者 王超 赖子尼 +5 位作者 李跃飞 李新辉 Sovan Lek 洪颐 谭细畅 李捷 《生态学报》 CAS CSCD 北大核心 2012年第15期4793-4802,共10页
西江肇庆段是珠江干流汇入珠三角河网水域的咽喉通道,结合长期定点连续采样和空间季节性调查,重点对2009年西江干流肇庆段的颗粒直链藻(Aulacoseira granulata)的种群生态学特征进行系统分析。结果显示:全年中,颗粒直链藻在总种群中所... 西江肇庆段是珠江干流汇入珠三角河网水域的咽喉通道,结合长期定点连续采样和空间季节性调查,重点对2009年西江干流肇庆段的颗粒直链藻(Aulacoseira granulata)的种群生态学特征进行系统分析。结果显示:全年中,颗粒直链藻在总种群中所占百分比均值为25.37%,与总种群丰度存在极显著正相关关系,这表明颗粒直链藻是西江浮游植物群落的重要优势种。调查期间发现了颗粒直链藻的4种形态,包括原变种(var.granulata)、极狭变种(var.angustissima)、弯曲变种(var.curvata)和极狭变种螺旋变型(var.angustissima f.spiralis)。其中,原变种占有绝对优势地位,其相对百分组成的年均值为91.47%,推测为原变种的形态结构比其它3种形态更容易适应外界环境变化,进而形成优势群体。颗粒直链藻总密度的周年变化呈现明显的双峰型,两个峰值分别出现在8月和11月,主要得益于适宜的水温、相对稳定的水体和较高的营养盐水平,这些均有助于颗粒直链藻的生长繁殖。第一个高峰之前,颗粒直链藻总密度未出现明显的波动,这很可能是由于水体径流量增大导致的稀释作用和频繁降雨导致的水体剧烈波动对颗粒直链藻增长的负作用掩盖了水温上升所带来的益处。从空间分布来看,颗粒直链藻总丰度的最大值一般出现在S1、S5和S6站点,这与营养盐最大值的空间分布格局是一致的。 展开更多
关键词 西江 颗粒直链藻 种群生态特征
在线阅读 下载PDF
温室条件下UV-B辐射对蓝藻结皮生长和超微结构的影响 被引量:9
15
作者 饶本强 吴沛沛 +2 位作者 Alain DAUTA 李敦海 刘永定 《环境科学学报》 CAS CSCD 北大核心 2011年第3期649-657,共9页
UV-B辐射是野外蓝藻结皮经常面临的一种环境胁迫因子.报道了温室条件下UV-B辐射对蓝藻结皮形态、生理和超微结构特征的影响.在本研究中,首先通过接种具鞘微鞘藻和爪哇伪枝藻形成初始蓝藻结皮,接着以初始蓝藻结皮为材料进行3种辐射处理:... UV-B辐射是野外蓝藻结皮经常面临的一种环境胁迫因子.报道了温室条件下UV-B辐射对蓝藻结皮形态、生理和超微结构特征的影响.在本研究中,首先通过接种具鞘微鞘藻和爪哇伪枝藻形成初始蓝藻结皮,接着以初始蓝藻结皮为材料进行3种辐射处理:光合有效辐射、UV-B辐射+光合有效辐射和N-乙酰半胱氨酸+UV-B辐射+光合有效辐射.在各种辐射处理的第0、1、3、6、9和20天分别测定蓝藻结皮的光合活性(Fv/Fm)、叶绿素a、伪枝藻素和胞外多糖含量.同时采用扫描电镜观察辐射处理下结皮的超微结构特征.此外,对结皮的表观形态如结皮颜色、厚度、干重等进行了测定.结果表明UV-B辐射对蓝藻结皮具有持续而明显的负面效应.与对照结皮相比,UV-B辐射下结皮的表观形态受到不利影响,结皮Fv/Fm被完全抑制,单位重量的叶绿素a含量和胞外多糖含量显著降低,而伪枝藻素含量并未受到UV-B辐射抑制,其含量则出现大量增加.电镜观察表明,UV-B辐射导致蓝藻结皮的超微结构遭到明显破坏,表现为藻丝体数量减少,缢缩成条索状,对沙粒的缠绕减弱等.研究还表明,N-乙酰半胱氨酸能够较好地保护UV-B辐射下结皮的光合活性,增加结皮的叶绿素a含量和胞外多糖含量,并有利于结皮表观形态的恢复.本研究探索了蓝藻结皮对UV-B辐射的响应,对于进一步理解蓝藻结皮对UV-B辐射的耐受限度以及应用蓝藻结皮进行荒漠化治理具有重要的理论与实际意义. 展开更多
关键词 蓝藻结皮 UV-B辐射 超微结构 光合活性 叶绿素A 伪枝藻素 胞外多糖 N-乙酰半胱氨酸
原文传递
珠三角河网水域栅藻的时空分布特征 被引量:9
16
作者 王超 李新辉 +5 位作者 赖子尼 曾艳艺 高原 刘乾甫 杨婉玲 LEK Sovan 《生态学报》 CAS CSCD 北大核心 2014年第7期1800-1811,共12页
珠三角河网水域是珠江之水流入南海的必经之地,对2012年该水域浮游植物群落中的栅藻种类丰富度和生物量的时空特征及其环境影响因子进行系统阐析。调查期间共发现栅藻24种(包括变种、变型),其中具刺和无刺种类分别为11种和13种。出现率... 珠三角河网水域是珠江之水流入南海的必经之地,对2012年该水域浮游植物群落中的栅藻种类丰富度和生物量的时空特征及其环境影响因子进行系统阐析。调查期间共发现栅藻24种(包括变种、变型),其中具刺和无刺种类分别为11种和13种。出现率高且生物量贡献率大的物种仅3种,包括被甲栅藻原变种(Scenedesmus armatus var.armatus)、被甲栅藻博格变种双尾变型(S.armatus var.boglariensis f.bicaudatus)和二形栅藻(S.dimorphus),分析认为这3个物种在栅藻种群中的生态优势很可能与其形态特征存在一定的关联。栅藻种类丰富度的季节分布呈现丰水期高于枯水期的特征,空间分布呈现河网中部站位低于外侧站位的特征。此外,种类丰富度的空间分布格局存在季节差异,丰水季节呈现河网中部站位明显低于外侧站位的特征,而枯水季节西江沿线站位种类丰富度明显偏低。分析认为,水温和径流是影响栅藻种类丰富度季节变动的关键因素;同时,径流也是影响总种类丰富度空间分布格局的关键因素,而水温和营养盐是影响不同季节种类丰富度的空间格局的重要因素。栅藻种群生物量的季节分布呈现丰水期高于枯水期的特征,空间分布表现为珠江桥站位的生物量明显高于其它站位。分析认为,径流和水温是决定种群生物量季节变动的关键因素,而营养盐、水体稳定性和盐度是决定生物量空间分布格局的关键因素。栅藻生物量与种类丰富度的关系基本符合单峰模型,且偏重于单峰模型的上升区,丰富了全球多样性模式的分级特征和区域特征。 展开更多
关键词 珠江三角洲 河网 栅藻 时空特征
在线阅读 下载PDF
低成本大孔陶瓷膜支撑体的制备与表征(英文) 被引量:6
17
作者 张小珍 周健儿 +2 位作者 江瑜华 刘志刚 LARBOT André 《硅酸盐学报》 EI CAS CSCD 北大核心 2009年第3期447-452,共6页
以高岭土和白云石为主要原料,通过反应烧结法制备低成本大孔陶瓷膜支撑体,对制备的支撑体进行了结构和性能表征。结果表明:在高岭土中引入质量分数为20%的白云石,可显著抑制高岭土的高温烧结;加入白云石后制备的支撑体在1150~1300℃保... 以高岭土和白云石为主要原料,通过反应烧结法制备低成本大孔陶瓷膜支撑体,对制备的支撑体进行了结构和性能表征。结果表明:在高岭土中引入质量分数为20%的白云石,可显著抑制高岭土的高温烧结;加入白云石后制备的支撑体在1150~1300℃保温1h后,主晶相为莫来石、堇青石和钙长石,平均孔径和抗弯强度随烧成温度升高而增大,而水通量和孔隙率降低;加入20%白云石并在1250℃保温1h制备的大孔支撑体的孔隙率和平均孔径分别为44.6%和4.7μm,抗弯强度和纯净水通量分别达到47.6MPa和10.76m3/(m2·h·bar)。 展开更多
关键词 支撑体 陶瓷膜 高岭土 白云石 表征
原文传递
硬粒小麦品种Waskana和Waskowa对禾谷孢囊线虫(Heterodera filipjevi和H.avenae)的抗性 被引量:7
18
作者 高秀 崔磊 +5 位作者 李洪连 王晓鸣 唐文华 Robert L. CONNER 林小虎 李洪杰 《作物学报》 CAS CSCD 北大核心 2012年第4期571-577,共7页
禾谷孢囊线虫(cereal cyst nematode,CCN)是一类重要的土传小麦病原线虫,危害我国小麦的主要是燕麦孢囊线虫(Heterodera avenae)和菲利普孢囊线虫(H.filipjevi)。我国对这些病原线虫的抗性资源十分缺乏,寻找新抗源是当前抗性育种的重要... 禾谷孢囊线虫(cereal cyst nematode,CCN)是一类重要的土传小麦病原线虫,危害我国小麦的主要是燕麦孢囊线虫(Heterodera avenae)和菲利普孢囊线虫(H.filipjevi)。我国对这些病原线虫的抗性资源十分缺乏,寻找新抗源是当前抗性育种的重要工作。本研究通过3年的田间病圃和温室接种鉴定,发现加拿大的硬粒小麦品种Waskana和Waskowa对H.filipjevi(河南许昌群体,Hfc-1致病型)和H.avenae(河南荥阳群体,Ha43致病型)都表现很强的抗性,单株孢囊数显著少于感病的普通小麦品种矮抗58、石4185和温麦19。显微观察可见,虽然2种线虫的幼虫都能够侵入Waskana和Waskowa的根组织内,但是根内的线虫数量显著少于感病对照普通小麦品种,最终在根系上形成的可见孢囊数量也较少。Waskana和Waskowa对2种病原线虫的抗性为我国抗CCN小麦品种选育提供了有较高利用价值的新抗源。根据南澳大利亚研究所的土传病害检测服务系统对土壤中病原线虫的分子检测结果,抗CCN品种Waskana和Waskowa根际土壤中的线虫虫卵量低于感病小麦品种,因此种植后可能降低土壤中禾谷孢囊线虫危害的风险。 展开更多
关键词 硬粒小麦 禾谷孢囊线虫 HETERODERA filipjevi H.avenae 抗病性
在线阅读 下载PDF
SUBSPECIFIC DIFFERENTIATION OF Paracobitis variegatus WITH COMMENTS ON ITS ZOOGEOGRAPHY 被引量:6
19
作者 杨君兴 陈银瑞 MauriceKottelat 《Zoological Research》 CAS CSCD 1994年第S1期58-67,0,共11页
The distribution of the loach Paracobitis variegatus is confined to upper Yangtze, Huanghe and Nanpanjiang drainages. The number of branched dorsal fin rays, morphology of anterior nostril, colour pattern of head... The distribution of the loach Paracobitis variegatus is confined to upper Yangtze, Huanghe and Nanpanjiang drainages. The number of branched dorsal fin rays, morphology of anterior nostril, colour pattern of head and the length of maxillary barbel indicate that it has differentiated into two subspecies. Both subspecies are isolated geographically: P. variegatus variegatus restricted to the upper Yangtze and the upper Huanghe Rivers, and P. variegatus longidorsalis, new subspecies, to the upper Nanpanjiang River. The subspecific differentiation is supposed to correlated to the sharp uplift of the eastern Yunnan Plateau during late Pleistocene. The taxonomic status of Nemachilus berezowsku Gunther, 1896 and Nemacheilus oxygnathus Regan, 1908 are also discussed and they are considered to be the synonyms of P. variegatus variegatus. 展开更多
关键词 Paracobitis variegatus Subspecific differentiation New subspecies ZOOGEOGRAPHY
在线阅读 下载PDF
来自东亚的黑耳属一新种,亚东黑耳 被引量:7
20
作者 吴芳 赵琪 +3 位作者 杨祝良 叶晟懿 Rivoire Bernard 戴玉成 《菌物学报》 CAS CSCD 北大核心 2020年第7期1203-1214,共12页
"亚东黑耳"是西藏近几年备受关注的一种特色野生珍稀食用菌,但对其分类学地位尚无定论。本文基于分子系统学和形态学研究了东亚、欧洲和北美洲与亚东黑耳相近的黑耳属标本,发现碟形黑耳Exidia recisa是个物种复合群,已知包括... "亚东黑耳"是西藏近几年备受关注的一种特色野生珍稀食用菌,但对其分类学地位尚无定论。本文基于分子系统学和形态学研究了东亚、欧洲和北美洲与亚东黑耳相近的黑耳属标本,发现碟形黑耳Exidia recisa是个物种复合群,已知包括4个种,欧洲有碟形黑耳和浅波黑耳E.repanda两个种,北美洲有钝齿黑耳E.crenata,东亚的为1新种,本文将其描述为亚东黑耳Exidia yadongensis。这4个种在系统发育关系中相近,形态相似,但亚东黑耳的子实体边缘基本是全缘,担孢子大小为12–16×3–4μm(Q=3.62–3.83),而欧洲的碟形黑耳E.recisa和北美洲的钝齿黑耳E.crenata子实体边缘通常锯齿状,担孢子分别为13–15.5×2.8–3.8μm(Q=4.51)和12–14×3–4μm(Q=4.11),浅波黑耳E.repanda具有垫状至波浪状折叠的子实体,区别于其他3个种的盘状至耳状的子实体,其担孢子为12.7–15.7×2.8–3.7μm(Q=4.33–4.57)。此外,亚东黑耳具有树状分枝和叉形的子实层侧丝,但其他3个种只有树状分枝的子实层侧丝。尽管亚东黑耳广泛分布于东亚地区,但由于亚东黑耳的汉语名称已经在中国普遍使用,所以我们提出了上述拉丁学名。 展开更多
关键词 木耳目 分类 系统发育 木生真菌 食用菌
原文传递
上一页 1 2 21 下一页 到第
使用帮助 返回顶部