期刊文献+
共找到20,080篇文章
< 1 2 250 >
每页显示 20 50 100
Short-term silicone oil tamponade on retinal structure and function in rhegmatogenous retinal detachment:a randomized controlled trial
1
作者 Zi-Ye Chen Yu-Qing Wu +7 位作者 Bao-Yi Liu Yuan Ma Zhuang-Ling Lin Run-Ping Duan Lan Jiang Chinling Tsai Zhuo-Jun Xu Tao Li 《International Journal of Ophthalmology(English edition)》 2026年第1期83-89,共7页
AIM:To investigate the effects of shortening the duration of silicone oil tamponade on retinal structure and function in patients undergoing silicone oil removal(SOR)after surgery for primary rhegmatogenous retinal de... AIM:To investigate the effects of shortening the duration of silicone oil tamponade on retinal structure and function in patients undergoing silicone oil removal(SOR)after surgery for primary rhegmatogenous retinal detachment(RRD).METHODS:A total of 58 eligible patients were enrolled and randomly assigned to two groups based on tamponade duration:the short-term group(30-45d)and the conventional group(≥90d).Comprehensive evaluations were performed before and after SOR,including slitlamp examination,best-corrected visual acuity(BCVA)measurement,intraocular pressure(IOP)testing,optical coherence tomography(OCT),optical coherence tomography angiography(OCTA),microperimetry,electroretinography(ERG),and visual evoked potential(VEP)assessment.RESULTS:A total of 33 patients(23 males and 10 females;33 eyes)were enrolled in the short-term SO tamponade group with mean age of 52.45±9.35y,and 25 patients(15 males and 10 females;25 eyes)were enrolled in the conventional SO tamponade group with mean age of 50.80±12.06y.Compared with the conventional group,the short-term silicone oil tamponade group had a significantly lower incidence of silicone oil emulsification and cataract progression,with no significant difference in retinal reattachment success rate.Structurally,short-term tamponade was associated with increased thickness of the retinal ganglion cell layer(RGCL)in the nasal and superior macular regions and improved recovery of superficial retinal vascular density in these areas.Functionally,the shortterm group showed better BCVA and retinal sensitivity both before and 1mo after SOR;additionally,the P100 amplitude in VEP tests was significantly increased in this group.CONCLUSION:Shortening the duration of silicone oil tamponade effectively reduces damage to retinal structure and function without compromising the success rate of retinal reattachment in patients with primary RRD. 展开更多
关键词 silicone oil tamponade rhegmatogenous retinal detachment silicone oil removal retinal structure retinal function PROGNOSIS
原文传递
Research progress on the structure and physiological functions of PKG
2
作者 Meng-Jie Peng Chao Li +1 位作者 Xiang-Xiang Zhang Xiao-Jun Han 《Biomedical Engineering Communications》 2025年第3期13-22,共10页
Protein Kinase G(PKG)is an important intracellular signal transduction enzyme,and its activity is modulated by cyclic guanosine monophosphate(cGMP).PKG plays a pivotal role in various significant physiological process... Protein Kinase G(PKG)is an important intracellular signal transduction enzyme,and its activity is modulated by cyclic guanosine monophosphate(cGMP).PKG plays a pivotal role in various significant physiological processes,including vascular smooth muscle relaxation,myocardial cell function regulation,neuron growth,and synaptic plasticity,et al.In recent years,the role of PKG in diseases has gradually attracted attention,and the abnormalities in its signaling pathway are closely related to the occurrence and development of cardiovascular and neurological diseases.Although PKG has been widely studied,its complex functions in different physiological systems and potential innovative applications still need to be further explored.This article reviews the purification techniques for PKG,discusses the advantages and disadvantages of different extraction methods,summarizes the structure and activation mechanism of each domain of PKG,and analyzes the physiological functions of PKG in organisms,especially the well-established roles in the cardiovascular system,nervous system,and endocrine system.The emerging therapeutic applications of PKG are also reviewed.In addition,the challenges of this field are proposed at the end. 展开更多
关键词 protein kinase G plasmid expression technology structural domain activation mechanism physiological function
在线阅读 下载PDF
3D Printing of Tough Hydrogel Scaffolds with Functional Surface Structures for Tissue Regeneration
3
作者 Ke Yao Gaoying Hong +11 位作者 Ximin Yuan Weicheng Kong Pengcheng Xia Yuanrong Li Yuewei Chen Nian Liu Jing He Jue Shi Zihe Hu Yanyan Zhou Zhijian Xie Yong He 《Nano-Micro Letters》 SCIE EI CAS 2025年第2期18-45,共28页
Hydrogel scaffolds have numerous potential applications in the tissue engineering field.However,tough hydrogel scaffolds implanted in vivo are seldom reported because it is difficult to balance biocompatibility and hi... Hydrogel scaffolds have numerous potential applications in the tissue engineering field.However,tough hydrogel scaffolds implanted in vivo are seldom reported because it is difficult to balance biocompatibility and high mechanical properties.Inspired by Chinese ramen,we propose a universal fabricating method(printing-P,training-T,cross-linking-C,PTC&PCT)for tough hydrogel scaffolds to fill this gap.First,3D printing fabricates a hydrogel scaffold with desired structures(P).Then,the scaffold could have extraordinarily high mechanical properties and functional surface structure by cycle mechanical training with salting-out assistance(T).Finally,the training results are fixed by photo-cross-linking processing(C).The tough gelatin hydrogel scaffolds exhibit excellent tensile strength of 6.66 MPa(622-fold untreated)and have excellent biocompatibility.Furthermore,this scaffold possesses functional surface structures from nanometer to micron to millimeter,which can efficiently induce directional cell growth.Interestingly,this strategy can produce bionic human tissue with mechanical properties of 10 kPa-10 MPa by changing the type of salt,and many hydrogels,such as gelatin and silk,could be improved with PTC or PCT strategies.Animal experiments show that this scaffold can effectively promote the new generation of muscle fibers,blood vessels,and nerves within 4 weeks,prompting the rapid regeneration of large-volume muscle loss injuries. 展开更多
关键词 3D printing Tough hydrogel scaffold functional surface structure Tissue regeneration BIOMATERIALS
在线阅读 下载PDF
Insights into microbial actions on hydraulic concrete structures:Effects of ammonia and sulfate on community structure,function and biofilm morphology
4
作者 Longfei Wang Wentao Zhuo +6 位作者 Tao He Zongyi Peng You Mou Minyue Wan Xinnan Pan Yi Li Zhengjian Yang 《Journal of Environmental Sciences》 2025年第11期430-442,共13页
Microbial corrosion of hydraulic concrete structures(HCSs)has received increasing research concerns.However,knowledge on the morphology of attached biofilms,as well as the community structures and functions cultivated... Microbial corrosion of hydraulic concrete structures(HCSs)has received increasing research concerns.However,knowledge on the morphology of attached biofilms,as well as the community structures and functions cultivated under variable nutrient levels is lacking.Here,biofilm colonization patterns and community structures responding to variable levels of ammonia and sulfate were explored.From field sampling,NH_(4)^(+)-N was proven key factor governing community structure in attached biofilms,verifying the reliability of selecting target nutrient species in batch experiments.Biofilms exhibited significant compositional differences in field sampling and incubation experiments.As the nutrient increased in batch experiments,the growth of biofilms gradually slowed down and uneven distribution was detected.The proportions of proteins and β-d-glucose polysaccharides in biofilms experienced a decrease in response to elevated levels of nutrients.With the increased of nutrients,themass losses of concretes exhibited an increase,reaching a highest value of 2.37%in the presence of 20 mg/L of ammonia.Microbial communities underwent a significant transition in structure and metabolic functions to ammonia gradient.The highest activity of nitrification was observed in biofilms colonized in the presence of 20 mg/L of ammonia.While the communities and their functions remained relativelymore stable responding to sulfate gradient.Our research provides novel insights into the structures of biofilms attached on HCSs and the metabolic functions in the presence of high level of nutrients,which is of significance for the operation and maintenance of hydraulic engineering structures. 展开更多
关键词 Hydraulic concrete structures Community structure Nutrient levels functional prediction Microbial action
原文传递
Deep Embedding of Literature Logical Structure in LBL-RBL Pedagogy:A Novel Pathway to Enhance Thesis Proposal Competency in Neuropathophysiology Courses
5
作者 Rongrong Mao Guangya He +1 位作者 Heng Tan Qian Wang 《Journal of Contemporary Educational Research》 2025年第7期48-55,共8页
Graduate students universally struggle with vague topics,insufficient innovation,and logical gaps in research proposals,highlighting the need for structured scientific training.This study presents an innovative pedago... Graduate students universally struggle with vague topics,insufficient innovation,and logical gaps in research proposals,highlighting the need for structured scientific training.This study presents an innovative pedagogical model embedding scholarly literature’s logical architecture into LBL-RBL hybrid teaching,implemented in Kunming Medical University’s Neuropathophysiology course.Targeting the complexity of neurological disease mechanisms,the course integrates lecture-based learning(LBL)and research-based learning(RBL)through a small-cohort framework featuring personalized literature-logic embedding→targeted lecture reinforcement→multi-round proposal iteration.Faculty deconstructed domain literature to establish a three-phase training system(“Logic Demonstration-Methodology Mapping-Proposal Embedding”),systematically merging academic logic with research methodology over 9 weeks.Results demonstrate that this problem-driven approach creates authentic scientific inquiry scenarios,activating student knowledge co-construction and collaborative exploration.It successfully enables dynamic competency progression through“cognitive deconstruction→methodological practice→proposal refinement,”significantly enhancing proposal rigor and innovation.This study offers a scalable dual-track solution for cultivating advanced scientific capabilities in medical graduate education. 展开更多
关键词 Literature logical structure LBL-RBL pedagogy Thesis proposal Neuropathophysiology Research competency cultivation
在线阅读 下载PDF
Neuroplasticicity mechanism of acupuncture for pain-induced emotions: From function to structure
6
作者 Hong-yu LU Bao-jin WANG +2 位作者 Cui MA An-guo LIU Xing-ke YAN 《World Journal of Acupuncture-Moxibustion》 2025年第4期276-282,共7页
Pain-induced emotions are the negative moods caused by pain,such as depression and anxiety.Acupunc-ture can effectively relieve pain-induced emotions,and its mechanism is closely related to the regulation of neuroplas... Pain-induced emotions are the negative moods caused by pain,such as depression and anxiety.Acupunc-ture can effectively relieve pain-induced emotions,and its mechanism is closely related to the regulation of neuroplasticity.Neuroplasticity is composed of two types,functional neuroplasticity and structural neuroplasticity.(1)Acupuncture improves functional neuroplasticity by inhibiting the activation of mi-croglia and astrocytes,regulating the expression of neurotransmitters and receptors,modulating cellular signal transduction pathways,and optimizing synaptic transmission efficiency.(2)Acupuncture improves structural neuroplasticity by modulating neuronal synaptic plasticity,inhibiting neuronal apoptosis,and up-regulating the expression of the BDNF/TrKB/CREB signaling pathway.Additionally,acupuncture up-regulates the expression of brain-derived neurotrophic factors to improve both the functional and struc-tural neuroplasticity,thus relieves pain-induced emotions.The above discovery provides an approach to the mechanism research of acupuncture for pain-induced emotions. 展开更多
关键词 ACUPUNCTURE Pain-induced emotions NEUROPLASTICITY functional neuroplasticity structural neuroplasticity
原文传递
Ordered structures with Schottky heterojunction functional unit regulate immune response and osteogenesis
7
作者 Peng Yu Maofei Ran +7 位作者 Heying Ran Xuebin Yang Youzhun Fan Zhengao Wang Zhengnan Zhou Jinxia Zhai Zefeng Lin Chengyun Ning 《Journal of Materials Science & Technology》 2025年第10期276-287,共12页
Mimicking the electric microenvironment of natural tissue is a promising strategy for developing biomedical implants. However, current research has not taken biomimetic electrical functional units into consideration w... Mimicking the electric microenvironment of natural tissue is a promising strategy for developing biomedical implants. However, current research has not taken biomimetic electrical functional units into consideration when designing biomedical implants. In this research, ordered structures with Schottky heterojunction functional unit (OSSH) were constructed on titanium implant surfaces for bone regeneration regulation. The Schottky heterojunction functional unit is composed of periodically distributed titanium microdomain and titanium oxide microdomain with different carrier densities and surface potentials. The OSSH regulates the M2-type polarization of macrophages to a regenerative immune response by activating the PI3K-AKT-mTOR signal pathway and further promotes osteogenic differentiation of rat bone marrow mesenchymal stem cells. This work provides fundamental insights into the biological effects driven by the Schottky heterojunction functional units that can electrically modulate osteogenesis. 展开更多
关键词 Ordered structures with functional unit MACROPHAGE Implant OSTEOGENESIS Electric microenvironment
原文传递
Structure-function insights of natural Ganoderma polysaccharides:advances in biosynthesis and functional food applications
8
作者 Zhou-Wei Wu Xue-Fang Zhao +5 位作者 Chen-Xi Quan Xiao-Cui Liu Xin-Yu Tao Yu-jie Li Xing-Rong Peng Ming-Hua Qiu 《Natural Products and Bioprospecting》 2025年第2期143-175,共33页
Ganoderma polysaccharides(GPs),derived from various species of the Ganoderma genus,exhibit diverse bioactivities,including immune modulation,anti-tumor effects,and gut microbiota regulation.These properties position G... Ganoderma polysaccharides(GPs),derived from various species of the Ganoderma genus,exhibit diverse bioactivities,including immune modulation,anti-tumor effects,and gut microbiota regulation.These properties position GPs as dual-purpose agents for medicinal and functional food development.This review comprehensively explores the structural complexity of six key GPs and their specific mechanisms of action,such as TLR signaling in immune modulation,apoptosis pathways in anti-tumor activity,and their prebiotic effects on gut microbiota.Additionally,the structure-activity relationships(SARs)of GPs are highlighted to elucidate their biological efficacy.Advances in green extraction techniques,including ultrasonic-assisted and enzymatic methods,are discussed for their roles in enhancing yield and aligning with sustainable production principles.Furthermore,the review addresses biotechnological innovations in polysaccharide biosynthesis,improving production efficiency and making large-scale production feasible.These insights,combined with ongoing research into their bioactivity,provide a solid foundation for developing health-promoting functional food products that incorporate GPs.Furthermore,future research directions are suggested to optimize biosynthesis pathways and fully harness the health benefits of these polysaccharides. 展开更多
关键词 Ganoderma polysaccharides extraction techniques structural characteristics Bioactivity biosynthetic pathways functional food applications
在线阅读 下载PDF
Investigation of Near-Surface S-Wave Velocity Structure beneath the Epicenter and adjacent Area of the Jishishan Earthquake by using the Receiver Function
9
作者 Fan-chang Meng Ruo-ge Xu +2 位作者 Hui Sun Bo Li Yun Long 《Applied Geophysics》 2025年第3期647-659,893,共14页
Based on the observational data from 60 short-period stations deployed in the Jishishan M6.2 earthquake epicenter and adjacent regions(Gansu Province,2023),this study inverted the near-surface S-wave velocity structur... Based on the observational data from 60 short-period stations deployed in the Jishishan M6.2 earthquake epicenter and adjacent regions(Gansu Province,2023),this study inverted the near-surface S-wave velocity structure through teleseismic receiver function analysis by using the amplitude of direct P-wave.The results reveal that the epicentral area(Liugou Township and surroundings)exhibits markedly low S-wave velocities of 400-600 m/s,with a mean value of(500±50)m/s.In contrast,intermountain basins-Guanting Basin and Dahejia Basin-demonstrate significantly elevated velocities,exceeding the epicentral zone by 100-300 m/s,with values concentrated at 600-900 m/s.Notably,localized areas such as Jintian Village and Caotan Village maintain stable S-wave velocities of(700±30)m/s.The western margin tectonic belt of Jishishan displays distinctive velocity differentiation:A pronounced velocity gradient zone along the 35.8°N latitude boundary separates northern areas(<550 m/s)from southern regions(>750 m/s).These findings demonstrate significant spatial heterogeneity in shallow S-wave velocity structures,primarily controlled by three factors:(1)topographic-geomorphic units,(2)stratigraphic lithological contrasts,and(3)anthropogenic modifications.The persistent low-velocity anomalies(<600 m/s)in the epicentral zone and northern Yellow River T2 terrace likely correlate with Quaternary unconsolidated sediments,enhanced groundwater circulation,and bedrock weathering.These results provide critical geophysical constraints for understanding both the seismogenic environment of the Jishishan earthquake and its damage distribution patterns.Furthermore,they establish a foundational framework for regional seismic intensity evaluation,site amplification analysis,and secondary hazard risk assessment. 展开更多
关键词 Jishishan Earthquake Dense Seismic Array Receiver function S-Wave Velocity structure
在线阅读 下载PDF
Stable crystal structure prediction using machine learning-based formation energy and empirical potential function
10
作者 Lu Li Jianing Shen +4 位作者 Qinkun Xiao Chaozheng He Jinzhou Zheng Chaoqin Chu Chen Chen 《Chinese Chemical Letters》 2025年第11期563-568,共6页
Crystal structure prediction aims to predict stable and easily experimentally synthesized materials,which accelerates the discovery of new materials.It is worth noting that the stability of materials is the basis for ... Crystal structure prediction aims to predict stable and easily experimentally synthesized materials,which accelerates the discovery of new materials.It is worth noting that the stability of materials is the basis for ensuring high performance and reliable application of materials.Among which,the thermodynamic and molecular dynamics stability is especially important.Therefore,this paper proposes a method to predict stable crystal structures using formation energy and Lennard-Jones potential as evaluation indicators.Specifically,we use graph neural network models to predict the formation energy of crystals,and employ empirical formulas to calculate the Lennard-Jones potential.Then,we apply Bayesian optimization algorithms to search for crystal structures with low formation energy and Lennard-Jones potential approaching zero,in order to ensure the thermodynamic stability and dynamics stability of materials.In addition,considering the impact of the bonding situation between atoms in the crystal on the structural stability,this article uses contact map to analyze the atomic bonding situation of each crystal to screen out more stable materials.Finally,the experimental results show that the method we proposed can not only reduce the time for crystal structure prediction,but also ensure the stability of crystal materials. 展开更多
关键词 Crystal structure prediction Machine learning Formation energy Empirical potential function Thermodynamic stability Dynamics stability
原文传递
Ecological Disturbance Caused by Land Use Change in the Karst Area,China:A Combined Structural and Functional Perspective
11
作者 ZHOU Zhongfa SUN Yaopeng +4 位作者 FANG Min SUN Jianwei YANG Pingping KONG Jie DING Shengjun 《Chinese Geographical Science》 2025年第4期755-768,共14页
Land use change is a fundamental factor affecting ecosystem’s structures and functions.However,few studies have explored the ecological disturbance caused by land use change from a combined structural and functional ... Land use change is a fundamental factor affecting ecosystem’s structures and functions.However,few studies have explored the ecological disturbance caused by land use change from a combined structural and functional perspective.In this study,the ecological structural disturbance index(SDI)and functional disturbance index(FDI)were introduced to quantitatively evaluate ecological disturbance caused by land use change in a typical karst area—Huangping County,Guizhou Province,China during 2009–2019.Results show that although the area of ecological land increased during past 10 yr,there had been a fragmentation trend of ecological land.Agricultural occupation was more severe than construction encroachment on ecological land.The grids with negative structural disturbance were consistent with areas of obvious dynamic loss and gain of ecological land.Ecological fragmentation had a greater impact than habitat gain in grids with negative structural disturbance.The ecosystem service functions of supply,adjustment,support,and culture were obviously affected by land use change,and the total FDI reflects the trade-off among them.Negative FDI values were easily observed in the rocky desertification area or water and soil loss area.The combination analysis of the SDI and FDI indicated the characteristic of codirectional ecologically structural and functional disturbance in the majority of grids.The findings improve our understanding of multiple relationships among ecological disturbances and provide valuable information for guiding land use activities. 展开更多
关键词 land use ecological land ecosystem service function ecological structural disturbance index(SDI) functional disturbance index(FDI) karst area Huangping County China
在线阅读 下载PDF
Analysis of the Protein Structure and Function of HpaG_(Xoo) 被引量:2
12
作者 任秀艳 冯雪 +1 位作者 侯志敏 张倩倩 《Agricultural Science & Technology》 CAS 2010年第2期12-14,75,共4页
[Objective] The study was to analyze the structure and function of HpaGXoo and the relationship between the two.[Method] Some related bioinformatics analysis software on internet such as NPSA,Swiss-Model,SAPS and Inte... [Objective] The study was to analyze the structure and function of HpaGXoo and the relationship between the two.[Method] Some related bioinformatics analysis software on internet such as NPSA,Swiss-Model,SAPS and InterPro Scan were adopted to analyze the structure and predict its function.[Result] HpaGXoo consists of 139 amino acids,and has many alpha-helical and coiled structure,no signal peptide on N-terminal and no transmembrane structure.It locates in bacterial cytoplasm.[Conclusion] The study will lay ... 展开更多
关键词 HpaGXoo BIOINFORMATICS structure analysis function prediction
在线阅读 下载PDF
Analysis of Emergy Structure,Function and Efficiency of Agro-ecosystem in Hunan Province 被引量:1
13
作者 朱玉林 李明杰 +2 位作者 侯茂章 龙雨孜 王茂溪 《Agricultural Science & Technology》 CAS 2013年第1期186-192,共7页
[Objective] The aim was to explore function and efficiency of emergy input/ output of Hunan agricultural ecosystem to reveal relationship of human being with natural resources and environment. [Method] Emergy structur... [Objective] The aim was to explore function and efficiency of emergy input/ output of Hunan agricultural ecosystem to reveal relationship of human being with natural resources and environment. [Method] Emergy structure, function and efficien- cy of Hunan agricultural ecosystem were analyzed based on input/output data in Hunan Province in 2009 as per emergy theory. [Result] The structure characters of agricultural ecosystem were as follows: Hunan is characterized with traditional agri- culture, depending greatly on both human and animal labor. For industrial accessory emergy, chemical fertilizers make most contribution to the system, and agricultural mechanization is not satisfied. Furthermore, renewable ratio of industrial accessory emergy is lower, and development and potential of green energy is promising. In addition, prices of the products are lower, without consideration of contribution made by natural resources and environment. It also suggested that Hunan agricultural chain is short and added value of products is not high. In general, emergy output of farming and animal husbandry dominates and the prices are lower than those of forestry and fishery. The function of the system was as follows: With lower environ- mental load ratio, the system is overloaded by population and the index of sustain- able development was 5.96, suggesting that the system enjoys vitality and potential, but the economy is undeveloped and the pressure from natural resources and envi- ronment is not high. The emergy output ratio was a little lower than national level in 2009, suggesting Hunan agricultural production is extensive. [Conclusion] The re- search indicated that rapid increase of population should be controlled; surplus labor should be transferred; agricultural structure and products structure should be further adjusted; agricultural technology should be further developed; agdcultural mechaniza- tion and modernization should be improved. 展开更多
关键词 Energy analysis structure function EFFICIENCY Agriculture of Hunan Province introduction
在线阅读 下载PDF
Function and structure of the farmland shelterbelts in northern area of Shanxi Province 被引量:4
14
作者 郭学斌 《Journal of Forestry Research》 SCIE CAS CSCD 2002年第3期217-220,251,共4页
From the 1950s to 1960s, large area of Populus simonii shelterbelts system was established in northern area of Shanxi Province. For reconstructing the old shelterbelts, more attentions should be paid to selecting suit... From the 1950s to 1960s, large area of Populus simonii shelterbelts system was established in northern area of Shanxi Province. For reconstructing the old shelterbelts, more attentions should be paid to selecting suitable tree species and design of logical shelterbelts structure. In order to provide a profound basis for the efficient establishment of shelterbelts, the study on function and structure of the farmland shelterbelts was conducted in Shuozhou and Datong areas, both are semi-arid areas in Northern Shanxi Province during 1996-2001. The wind-control effects of shelterbelts with different structures (close-spaced, wider-spaced, and widest-spaced) were investigated by portable wind vane and anemometer, wet and dry bulb thermometer, ground thermometer, glass service instrument. The results showed that the wind-control capacity of the shelterbelts during the leafing period should be thought as the criteria index in shelterbelts established. The wider-spaced shelterbelt that was made of 4-6 rows of trees, with a spacing of 2.0 m×3.0 m, had the best wind-control result. 展开更多
关键词 SHELTERBELTS Wind-control function Shelterbelts structure
在线阅读 下载PDF
Functional Equilibrium Between Photosynthetic and Above-ground Nonphotosynthetic Structures of Plants: Evidence from a Pruning Experiment with Three Subtropical Tree Species 被引量:4
15
作者 曾波 《Acta Botanica Sinica》 CSCD 2003年第2期152-157,共6页
It is well known that plants have functional equilibrium between their above-ground parts (shoots) and below-ground parts (roots), but whether the above-ground parts of plants have functional equilibrium between their... It is well known that plants have functional equilibrium between their above-ground parts (shoots) and below-ground parts (roots), but whether the above-ground parts of plants have functional equilibrium between their photosynthetic structures (leaves) and non-photosynthetic structures (branches and stem) is unknown. The purpose of this study is to test the hypotheses that: (1) the above-ground parts of plants have functional equilibriums between their photosynthetic structures and non-photosynthetic structures; (2) the maintenance of the equilibriums is guaranteed by the alteration of biomass partitioning to photosynthetic and non-photosynthetic structures. To test these hypotheses, a pruning experiment with four pruning intensities (0%, 20%, 50%, and 70%) were carried out with three subtropical Chinese tree species ( Ficus microcarpa, Ficus virens, Cinnamomum camphora). Pruning treatments were conducted in two successive years. The results were in conformity with the hypothesis, i.e. above-ground parts of trees had functional equilibriums between photosynthetic and non-photosynthetic structures. Pruning decreased instantaneously the mass ratios of photosynthetic structures to non-photosynthetic structures (P/NP) of all three tree species, the reduction in P/NP was strengthened with pruning intensity. However, one year after pruning, the P/NP of all pruned trees increased and were not smaller than those of unpruned trees. In agreement with the expectation, the biomass partitioning of pruned trees was altered, more newly produced above-ground biomass was partitioned to leaf growth and less to branch and stem growth, thus enabled the damaged trees to restore their functional equilibrium between photosynthetic and non-photosynthetic structures. It is clear that the maintenance of functional equilibrium between photosynthetic and non-photosynthetic structures guaranteed by the alteration of biomass partitioning provides plants a good strategy to resist external disturbance and damage. 展开更多
关键词 biomass partitioning functional equilibrium non-photosynthetic structures photosynthetic structures tree
在线阅读 下载PDF
A study on deep structure using teleseismic receiver function in Western Yunnan 被引量:18
16
作者 贺传松 王椿镛 吴建平 《地震学报》 CSCD 北大核心 2004年第3期238-246,共9页
s Western Yunnan is located at the boundary of collision or underthrusting zone of Eurasian plate and is influenced by many times tectonic movements. With very complex geological environment and tectonic background, i... s Western Yunnan is located at the boundary of collision or underthrusting zone of Eurasian plate and is influenced by many times tectonic movements. With very complex geological environment and tectonic background, it is one of the seismically active areas. In the paper, the teleseismic records were selected from 16 national, local and mo-bile stations, including 4 very-wide-band mobile stations of PASSCAL. And nearly 2 000 receiver functions were extracted. Two measuring lines are 650 km and 450 km, respectively and across some major tectonic units in Western Yunnan. It is indicated that Nujiang might be a seam characterized by underthrusting. The western and eastern boundaries of Sichuan-Yunnan rhombus block, i.e., Honghe and Xiaojiang faults, might be an erection seam or collision belt. Panxi tectonic zone still has the characteristics of continental rift valley, that is, the surface is hollow and the upper mantle is upwarping. The tectonic situation in Western Yunnan is of certain regulation with the interlacing distribution of orogenic zone and seam. The crustal thickness decreases gradually from the north to the south and the S wave velocity is globally lower here. 展开更多
关键词 接收函数 反演 S波速度结构 构造关系
在线阅读 下载PDF
Discussion on Structure Evolution and Function Expansion of Agriculture in China 被引量:1
17
作者 刘新 《Agricultural Science & Technology》 CAS 2009年第2期145-148,153,共5页
According to the characteristics of agricultural development during different periods, agricultural development was basically divided into traditional period, planning system period and household contracting pedod to ... According to the characteristics of agricultural development during different periods, agricultural development was basically divided into traditional period, planning system period and household contracting pedod to discuss the related laws of agricultural development in China. The agricultural function expansion during different periods was analyzed in terms of agricultural structure evolution, while structural optimization and function expansion of modem agriculture in China were also studied. The results indicated that during the traditional period, agricultural structure emphasized feeding people and grain production while agricultural function reflected the economic function beyond surviving standard. During the planning system period, a unitary structural mode of agriculture was formed in China, which showed that agriculture was dominated by planting industry and planting industry was dominated by grain, while agriculture executed the mixed economic function beyond surviving and liv- ing standard. During the household contracting period, the industrial structure of agriculture in China gradually became diversification and optimi- zation, but as the economic function of industrial standard, agricultural development was still greatly inhibited. The structural evolution of modem agriculture in China must step forward towards collectivization and scale merit, while ecological function and social function of agriculture increas- ingly become important and the function of agricultural production becomes mere and more diverse. 展开更多
关键词 Agricultural structure Agricultural function Multi-functional agriculture
在线阅读 下载PDF
Logical-Structure Modeling for Conceptual Design
18
作者 孙正兴 张福炎 《Journal of Southeast University(English Edition)》 EI CAS 2001年第1期59-65,共7页
Based on the definition of a logic structure feature to relate logically functional requirements to geometric representation independent upon detailed geometric representation, this paper presents an idea of logical s... Based on the definition of a logic structure feature to relate logically functional requirements to geometric representation independent upon detailed geometric representation, this paper presents an idea of logical structure modeling for computer aided conceptual design and makes attempt to establish a representation formalism of logic structure modeling. The definition and representation of logical structure feature are given and an assembly module definition for supporting top down conceptual design is also proposed. The proposed scheme contributes to several aspects of conceptual design research, especially to provide elementarily a formal methodology for computer aided conceptual design system development and operation. 展开更多
关键词 conceptual design function form transformation logic structure feature representation formalism
在线阅读 下载PDF
Effect of vegetation of transgenic Bt rice lines and their straw amendment on soil enzymes, respiration, functional diversity and community structure of soil microorganisms under field conditions 被引量:21
19
作者 Hua Fang Bin Dong +3 位作者 Hu Yan Feifan Wang Baichuan Wang Yunlong Yu 《Journal of Environmental Sciences》 SCIE EI CAS CSCD 2012年第7期1259-1269,共11页
With the development of transgenic crops, there is an increasing concern about the possible adverse effects of their vegetation and residues on soil environmental quality. This study was carried out to evaluate the po... With the development of transgenic crops, there is an increasing concern about the possible adverse effects of their vegetation and residues on soil environmental quality. This study was carried out to evaluate the possible effects of the vegetation of transgenic Bt rice lines Huachi B6 (HC) and TT51 (TT) followed by the return of their straw to the soil on soil enzymes (catalase, urease, neutral phosphatase and invertase), anaerobic respiration activity, microbial utilization of carbon substrates and community structure, under field conditions. The results indicated that the vegetation of the two transgenic rice lines (HC and TT) and return of their straw had few adverse effects on soil enzymes and anaerobic respiration activity compared to their parent and distant parent, although some transient differences were observed. The vegetation and subsequent straw amendment of Bt rice HC and TT did not appear to have a harmful effect on the richness, evenness and community structure of soil microorganisms. No different pattern of impact due to plant species was found between HC and TT. It could be concluded that the vegetation of transgenic Bt rice lines and the return of their straw as organic fertilizer may not alter soil microbe-mediated functions. 展开更多
关键词 anaerobic respiration enzyme activity functional diversity community structure transgenic Bt rice
原文传递
Independent continuous mapping for topological optimization of frame structures 被引量:10
20
作者 Yunkang Sui Jiazheng Du Yingqiao Guo 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 2006年第6期611-619,共9页
Based on the Independent Continuous Mapping method (ICM), a topological optimization model with continuous topological variables is built by introducing three filter functions for element weight, element allowable s... Based on the Independent Continuous Mapping method (ICM), a topological optimization model with continuous topological variables is built by introducing three filter functions for element weight, element allowable stress and element stiffness, which transform the 0-1 type discrete topological variables into continuous topological variables between 0 and 1. Two methods for the filter functions are adopted to avoid the structural singularity and recover falsely deleted elements: the weak material element method and the tiny section element method. Three criteria (no structural singularity, no violated constraints and no change of structural weight) are introduced to judge iteration convergence. These criteria allow finding an appropriate threshold by adjusting a discount factor in the iteration procedure. To improve the efficiency, the original optimization model is transformed into a dual problem according to the dual theory and solved in its dual space. By using MSC/Nastran as the structural solver and MSC/Patran as the developing platform, a topological optimization software of frame structures is accomplished. Numerical examples show that the ICM method is very efficient for the topological optimization of frame structures. 展开更多
关键词 Frame structures Topological optimization ICM method Filter functions Element elimination
在线阅读 下载PDF
上一页 1 2 250 下一页 到第
使用帮助 返回顶部