检索结果-南通市图书馆

Stability and Hopf bifurcation of a delayed ratio-dependent predator-prey system

Acta Mechanica Sinica 2011年第2期27卷 285-296页

作者： wan-yong wang Li-Jun Pei School of Aerospace Engineering and Applied Mechanics Tongji University 200092 Shanghai China Department of Mathematics Zhengzhou University 450001 Zhengzhou China

Since the ratio-dependent theory reflects the fact that predators must share and compete for food, it is suitable for describing the relationship between predators and their preys and has recently become a very important theory put forward by biologists. In order to investigate the dynamical relationship between predators and their preys, a so-called Michaelis-Menten ratio-dependent predator-prey model is studied in this paper with gestation time delays of predators and preys taken into consideration. The stability of the positive equilibrium is investigated by the Nyquist criteria, and the existence of the local Hopf bifurcation is analyzed by employing the theory of Hopf bifurcation. By means of the center manifold and the normal form theories, explicit formulae are derived to determine the stability, direction and other properties of bifurcating periodic solutions. The above theoretical results are validated by numerical simulations with the help of dynamical software WinPP. The results show that if both the gestation delays are small enough, their sizes will keep stable in the long run, but if the gestation delays of predators are big enough, their sizes will periodically fluc-tuate in the long term. In order to reveal the effects of time delays on the ratio-dependent predator-prey model, a ratiodependent predator-prey model without time delays is considered. By Hurwitz criteria, the local stability of positive equilibrium of this model is investigated. The conditions under which the positive equilibrium is locally asymptotically stable are obtained. By comparing the results with those of the model with time delays, it shows that the dynamical behaviors of ratio-dependent predator-prey model with time delays are more complicated. Under the same conditions, namely, with the same parameters, the stability of positive equilibrium of ratio-dependent predator-prey model would change due to the introduction of gestation time delays for predators and preys. Moreover, w

关键词： Time delays · Stability · Hopf bifurcation · Normal form · Center manifold

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Effects of Nitrogen Application in Different Wheat Growth Stages on the Floret Development and GrainYield of Winter Wheat

引用

Agricultural Sciences in China 2002年第10期1卷 1156-1161页

作者： ZHU Yun-ji, wang Chen-yang, GUO Tian-cai, CUI Jin-mei, XIA Guo-jun, LIU wan-dai and wang yong-hua( The National Engineering Research Centre for Wheat, Zhengzhou 450002, P. R . China ) The National Engineering Research Centre for Wheat Zhengzhou 450002 P.R.China

The study was carried out on the effect of nitrogen application in different wheat growth stage on the floret development, the photosynthetic rate, the yield and its components of winter wheat. The result indicated that nitrogen application in the pistil-stamen primordium formation stage and the tetrad formation stage of wheat growth prolonged the duration of floret development, promoted the balance growth of floret and reduced the floret decadence number, thus increased the grain number per spike. Nitrogen application in the middle and in the late stages of wheat development increased the photosynthetic ability of the plant leaves in the later stage, and also lengthened the peak of grain filling stage, thus enhanced the grain weight and yield of wheat significantly.

关键词： Winter wheat Nitrogen application Development of floret Grain yield

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Mutual regulation of microglia and astrocytes after Gas6 inhibits spinal cord injury

引用

Neural Regeneration Research 2025年第2期20卷 557-573页

作者： Jiewen Chen Xiaolin Zeng Le wang Wenwu Zhang Gang Li Xing Cheng Peiqiang Su yong wan Xiang Li Department of Spine Surgery The First Affiliated HospitalSun Yat-sen UniversityGuangzhouGuangdong ProvinceChina Guangdong Province Key Laboratory of Orthopedics and Traumatology GuangzhouGuangdong ProvinceChina

Invasive inflammation and excessive scar formation are the main reasons for the difficulty in repairing nervous tissue after spinal cord *** and astrocytes play key roles in the spinal cord injury micro-environment and share a close ***,the mechanisms involved remain *** this study,we found that after spinal cord injury,resting microglia(M0)were polarized into pro-inflammatory phenotypes(MG1 and MG3),while resting astrocytes were polarized into reactive and scar-forming *** expression of growth arrest-specific 6(Gas6)and its receptor Axl were significantly down-regulated in microglia and astrocytes after spinal cord *** vitro experiments showed that Gas6 had negative effects on the polarization of reactive astrocytes and pro-inflammatory microglia,and even inhibited the cross-regulation between *** further demonstrated that Gas6 can inhibit the polarization of reactive astrocytes by suppressing the activation of the Yes-associated protein signaling ***,in turn,inhibited the polarization of pro-inflammatory microglia by suppressing the activation of the nuclear factor-κB/p65 and Janus kinase/signal transducer and activator of transcription signaling *** vivo experiments showed that Gas6 inhibited the polarization of pro-inflammatory microglia and reactive astrocytes in the injured spinal cord,thereby promoting tissue repair and motor function ***,Gas6 may play a role in the treatment of spinal cord *** can inhibit the inflammatory pathway of microglia and polarization of astrocytes,attenuate the interaction between microglia and astrocytes in the inflammatory microenvironment,and thereby alleviate local inflammation and reduce scar formation in the spinal cord.

关键词： astrocytes Axl cell polarization Gas6 Hippo signal inflammatory micro-environment intercellular interaction microglia single-cell sequencing spinal cord injury

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Duodenal pseudolymphoma: A case report and review of literature

引用

World Journal of Gastroenterology 2011年第27期17卷 3267-3270页

作者： yong-Heng Huang, Tian-Zhu Long, Zhi-Yu Xiao, Hua Ye, Yun-Le wan, Jie wang yong-Heng Huang, Tian-Zhu Long, Zhi-Yu Xiao, Hua Ye, Yun-Le wan, Jie wang, Department of Hepatobiliary Surgery, Sun Yat-sen Memorial Hospital, Sun Yat-sen University Haizhu District, Guangzhou 510260, Guangdong Province, China yong-Heng Huang Tian-Zhu Long Zhi-Yu Xiao Hua Ye Yun-Le Wan Jie Wang Department of Hepatobiliary Surgery Sun Yat-sen Memorial Hospital Sun Yat-sen University Haizhu District Guangzhou 510260 Guangdong Province China

We report a rare case of duodenal pseudolymphoma without any symptoms. The lesion located in front of the head of the pancreas was found accidentally during a medical examination. The findings of computed tomography and positron emission tomography-computed tomography suggested a stromal tumor or malignant lymphoma. Surgical resection was performed. The lesions were patho- logically diagnosed as duodenal pseudolymphoma.

关键词： Pseudolymphoma Duodenum

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Dative B–N bonds weaven toward two-dimensional purely organic materials for single crystals

引用

Science China Chemistry 2025年第01期 12-14页

作者： Wei-Lei Zhou Siwei wang yong Chen College of Chemistry and Materials Science Inner Mongolia Key Laboratory of Chemistry for Nature Products and Synthesis for Functional Molecules Innovation Team of Optical Functional Molecular Devices Inner Mongolia Minzu University College of Chemistry Nankai University

Molecular topology is one of the important topics to study and understand the relationship between molecular structure and properties [1]. Particularly, two-dimensional (2D) materials with extremely high surface area and ultra-thin morphology have attracted considerable attention due to their unexpected properties in materials and chemistry [2,3].

关键词：

来源：

同方期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Cholesterol metabolism: physiological versus pathological aspects in intracerebral hemorrhage

引用

Neural Regeneration Research 2025年第4期20卷 1015-1030页

作者： Ruoyu Huang Qiuyu Pang Lexin Zheng Jiaxi Lin Hanxi Li Lingbo wan Tao wang Department of Forensic Science School of Basic Medicine and Biological SciencesSuzhou Medicine College of Soochow UniversitySuzhouJiangsu ProvinceChina

Cholesterol is an important component of plasma membranes and participates in many basic life functions,such as the maintenance of cell membrane stability,the synthesis of steroid hormones,and *** plays a key role in the establishment and maintenance of the central nervous *** brain contains 20%of the whole body’s cholesterol,80%of which is located within myelin.A huge number of processes(e.g.,the sterol regulatory element-binding protein pathway and liver X receptor pathway)participate in the regulation of cholesterol metabolism in the brain via mechanisms that include cholesterol biosynthesis,intracellular transport,and *** brain injuries or diseases involving crosstalk among the processes above can affect normal cholesterol metabolism to induce detrimental ***,we hypothesized that cholesterol-related molecules and pathways can serve as therapeutic targets for central nervous system *** hemorrhage is the most severe hemorrhagic stroke subtype,with high mortality and *** cholesterol levels are associated with the risk of intracerebral ***,secondary pathological changes after intracerebral hemorrhage are associated with cholesterol metabolism dysregulation,such as neuroinflammation,demyelination,and multiple types of programmed cell *** cholesterol accumulation in the brain has been found after intracerebral *** this paper,we review normal cholesterol metabolism in the central nervous system,the mechanisms known to participate in the disturbance of cholesterol metabolism after intracerebral hemorrhage,and the links between cholesterol metabolism and cell *** also review several possible and constructive therapeutic targets identified based on cholesterol metabolism to provide cholesterol-based perspectives and a reference for those interested in the treatment of intracerebral hemorrhage.

关键词： cell death cholesterol metabolism intracerebral hemorrhage myelination therapeutic target

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Assessing the corrosion protection property of coatings loaded with corrosion inhibitors using the real-time atmospheric corrosion monitoring technique

引用

International Journal of Minerals,Metallurgy and Materials 2025年第1期32卷 119-126页

作者： Xiaoxue wang Lulu Jin Jinke wang Rongqiao wang Xiuchun Liu Kai Gao Jingli Sun yong Yuan Lingwei Ma Hongchang Qian Dawei Zhang School of Energy and Power Engineering Beihang UniversityBeijing 100191China Beijing Institute of Space Long March Vehicle Beijing 100076China National Materials Corrosion and Protection Data Center University of Science and Technology BeijingBeijing 100083China Institute of Materials Intelligent Technology Liaoning Academy of MaterialsShenyang 110004China Shanghai Spaceflight Precision Machinery Institute Shanghai 201600China

The atmospheric corrosion monitoring(ACM)technique has been widely employed to track the real-time corrosion behavior of metal ***,limited studies have applied ACM to the corrosion protection properties of organic *** study compared a bare epoxy coating with one containing zinc phosphate corrosion inhibitors,both applied on ACM sensors,to observe their corrosion protection properties over *** with artificial damage via scratches were exposed to immersion and alternating dry and wet environments,which allowed for monitoring galvanic corrosion currents in *** the corrosion tests,the ACM currents of the zinc phosphate/epoxy coating were considerably lower than those of the blank epoxy *** trend in ACM current variations closely matched the results obtained from regular electrochemical tests and surface *** alignment highlights the potential of the ACM technique in evaluating the corrosion protection capabilities of organic *** with the blank epoxy coating,the zinc phosphate/epoxy coating showed much-decreased ACM current values that confirmed the effective inhibition of zinc phosphate against steel corrosion beneath the damaged coating.

关键词： atmospheric corrosion monitoring technology corrosion inhibitor coating carbon steel corrosion protection

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Direct and rapid detection of serum amino acid and monoamine neurotransmitters to assist the diagnosis of panic disorder

引用

Science China Chemistry 2025年第01期 377-384页

作者： Shiwen Liu Xuerui wan Meng Zhao Jiaqi wang Weilan Wu Linlin You yonggui Yuan Qian Xu Rong Gao Key Laboratory of Environmental Medicine Engineering Ministry of Education School of Public Health Southeast University Key Laboratory of Modern Toxicology of Ministry of Education Department of Hygienic Analysis and Detection School of Public HealthNanjing Medical University Department of Psychosomatics and Psychiatry Zhongda Hospital School of Medicine Southeast University

The measurement of amino acid and monoamine neurotransmitters（NTs） in serum plays a central role in the identification and monitoring of clinical panic disorder（PD）. However, the strong polarity and chemical heterogeneity of NTs make direct extraction and rapid detection extremely challenging. Herein, we developed a strategy that integrated solid phase extraction based on magnetic Fe3O4coated with polydopamine（Fe3O4@PDA） and direct analysis of mass spectrometry in real time（DART-MS） for quantification of 10 NTs. We systematically investigated the optimal conditions of this strategy to achieve good accuracy and precision. Compared with existing magnetic solid phase extraction methods for NTs detection in biological samples, this strategy could adsorb more targets while having similar adsorption efficiencies, and the total process time was reduced by an average of 69.42%. We rapidly determined the metabolic abnormality of 6 types of NTs in the serum of PD patients and demonstrated their diagnostic accuracy. In addition, an outstanding feature of PD in which tryptophan was more metabolized by the KYN pathway and the 5-hydroxytryptamine pathway was inhibited could be elucidated by this strategy. Our results highlighted the potential ability of Fe3O4@PDA coupled with DART-MS to assist in the clinical diagnosis of PD.

关键词：

来源：

同方期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

基于群论的频率图在旅行商问题中的应用

引用

郑州大学学报（理学版） 2025年第1期57卷 74-80页

作者：王永华北电力大学新能源学院北京102206

针对最小生成树(minimum spanning tree,MST)和旅行商问题(travelling salesman problem,TSP),介绍了完全图上的两类特殊图并定义了这些图上的交运算,每类特殊图和交运算构成一个半群。根据半群性质计算出频率图,分析了最优哈密顿圈(opt... 详细信息

针对最小生成树(minimum spanning tree,MST)和旅行商问题(travelling salesman problem,TSP),介绍了完全图上的两类特殊图并定义了这些图上的交运算,每类特殊图和交运算构成一个半群。根据半群性质计算出频率图,分析了最优哈密顿圈(optimal Hamiltonian cycle,OHC)和MST中边的频率性质,证明了频率图上OHC中边的频率下界,该频率下界用于缩小OHC的搜索空间,降低了TSP的求解难度。此外,采用一些TSP算例验证了频率图上OHC中边的频率性质。

关键词：半群特殊图频率图旅行商问题最小生成树

来源：

维普期刊数据库

同方期刊数据库博看期刊

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

响岩与花岗岩机制砂混凝土性能对比研究

引用

建材世界 2022年第2期43卷 43-47页

作者：万永旺潘延昇中交四航局第一工程有限公司广州510000

该文针对肯尼亚内罗毕快速路项目工程周边河砂紧缺,常用母岩石灰岩、玄武岩、花岗岩等资源距离较远,同时距离较近的响岩机制砂压碎值较高、吸水率较大、坚固性不良等问题,对比研究了响岩和花岗岩机制砂对C30、C50强度等级混凝土拌合物... 详细信息

该文针对肯尼亚内罗毕快速路项目工程周边河砂紧缺,常用母岩石灰岩、玄武岩、花岗岩等资源距离较远,同时距离较近的响岩机制砂压碎值较高、吸水率较大、坚固性不良等问题,对比研究了响岩和花岗岩机制砂对C30、C50强度等级混凝土拌合物性能、力学性能和耐久性能的影响。结果表明:响岩机制砂可以替代花岗岩机制砂配制混凝土,在增大减水剂用量的情况下,响岩机制砂混凝土与花岗岩机制砂混凝土相同强度等级工作性能相当,抗压强度、弹性模量略低于花岗岩机制砂混凝土,抗氯离子渗透能力、抗碳化性能与花岗岩机制砂混凝土相近。

关键词：响岩机制砂拌合物性能力学性能耐久性能

来源：

维普期刊数据库

同方期刊数据库博看期刊评论

在线全文

学校读者我要写书评

暂无评论

欢迎您,

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案：

请选择收藏分类：

通借通还

欢迎您,

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：