检索结果-南通市图书馆

在线全文

学校读者我要写书评

暂无评论

波导双圆极化分离器

微波 1986年第4期 44-52页

作者：陈顺生南京工学院

在波导定向滤波器的基础上,本文提出了一种双模式波导圆极化分离器,并对它进行了分析和设计。阐述了这种圆极化分离器的工作原理,导出了构成圆极化分离器的必要条件。通过实验测试,对比了各种耦合孔形状与尺寸对分离器性能的影响,并定... 详细信息

在波导定向滤波器的基础上,本文提出了一种双模式波导圆极化分离器,并对它进行了分析和设计。阐述了这种圆极化分离器的工作原理,导出了构成圆极化分离器的必要条件。通过实验测试,对比了各种耦合孔形状与尺寸对分离器性能的影响,并定性地证明了本文所得出的结论。

关键词：圆极化分波器双圆极化分离器波导分波器定向滤波器椭圆极化测定器驻波测试器天线馈源网络

Hypoxic and temporal variation in the endocrine disrupting toxicity of perfluorobutanesulfonate in marine medaka(Oryzias melastigma)

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Journal of Environmental sciences 2024年第2期136卷 279-291页

作者： Baili sun Jing Li Yachen Bai Xiangzhen Zhou Paul K.s.Lam Lianguo chen state Key Laboratory of Freshwater Ecology and Biotechnology Institute of HydrobiologyChinese Academy of SciencesWuhan 430072China University of Chinese Academy of sciences Beijing 100049China Office of the President Hong Kong Metropolitan University30 Good Shepherd StreetKowloonHong Kong SARChina

Perfluorobutanesulfonate(PFBs)is an emerging pollutant capable of potently disrupting the sex and thyroid endocrine systems of ***,the hypoxic and temporal variation in PFBs endocrine disrupting toxicity remain largely *** the present study,adult marine medaka were exposed to environmentally realistic concentrations of PFBs(0 and 10μg/L)under normoxia or hypoxia conditions for 7 days,aiming to explore the interactive behavior between PFBs and *** addition,PFBs singular exposure was extended till 21days under normoxia to elucidate the time-course progression in PFBs *** results showed that hypoxia inhibited the growth and caused the suspension of egg spawn regardless of PFBs *** regard to the sex endocrine system,7-day PFBs exposure led to an acute stimulation of transcriptional profiles in females,which,subsequently,recovered after the 21-day *** potency of hypoxia to disturb the sex hormones was much stronger than PFBs.A remarkable increase in estradiol concentration was noted in medaka blood after hypoxia *** in sex endocrinology of coexposed fish were largely determined by hypoxia,which drove the formation of an estrogenic *** further enhanced the endocrine disrupting effects of ***,the hepatic synthesis of vitellogenin and choriogenin,two commonly used sensitive biomarkers of estrogenic activity,failed to initiate in response to the estrogen *** to sex endocrine system,disturbances in thyroidal axis by PFBs or hypoxia were relatively ***,the present findings will advance our toxicological understanding about PFBs pollutant under the interference of hypoxia.

关键词： Perfluorobutanesulfonate(PFBs) Aquatic hypoxia Temporal toxicity Combined exposure Endocrine disruption Marine medaka

Integrated stratigraphy and Mineralogy of the Doushantuo Formation in Weng’an,south China,and Implications for Ediacaran Phosphogenesis

在线全文

学校读者我要写书评

暂无评论

Journal of Earth science 2024年第2期35卷 476-503页

作者： Liangxuan Jiao Zhenbing she Dominic Papineau Yaguan Zhang Matthew s.Dodd Kenan Cao Qun chen Guoyong chen state Key Laboratory of Biogeology and Environmental Geology China University of GeosciencesWuhan430078China school of Earth sciences China University of GeosciencesWuhan430047China London Centre for Nanotechnology University College London17-19 Gordon StreetLondonWC1E 6BTUK Department of Earth sciences University College LondonLondonWC1E 6BTUK Centre for Planetary science University College London and Birkbeck CollegeLondonWC1E 7HXUK Innovation Center of Ore Resources Exploration Technology in the Region of Bedrock Ministry of Natural Resources of People’s Republic of China’Guiyang550000China Guizhou Bureau of Geology and Mineral Exploration and Development Guiyang550000China

The Ediacaran–Cambrian Phosphogenic Episode is the Earth’s first true phosphogenic event and resulted in worldwide phosphate deposits,which occurred during the processes of the Neoproterozoic Oxygenation *** Ediacaran Doushantuo Formation(ca.635–551 Ma)of Weng’an area in central Guizhou,south China,contains two economic phosphorite beds(the Lower and Upper Phosphorite Beds).This paper presents a detailed stratigraphic,sedimentological and mineralogical study of multiple outcrop and drill core sections of the Doushantuo Formation across the Weng’an area,and identified 11 lithofacies and 4 types of phosphatic *** differences in lithofacies and grain types between the upper and lower phosphate deposits are observed,indicating that the two sets of phosphate deposits are the products of two distinct phosphogenic *** Lower Phosphorite Bed mainly consists of banded and laminated phosphorites,contains micro-oncoids formed by microbially-mediated precipitation and peloids formed by in-situ chemically oscillating reactions,indicating a biochemical and chemical enrichment of phosphorus to sediments during the Early Ediacaran *** Upper Phosphorite Bed is mainly composed of carbonaceous,massive,and stromatolitic phosphorites,contains bioclasts(phosphatized spheroidal fossils),and intraclasts formed by hydrodynamic agitation,suggesting that the major accesses of phosphorus to sediments were the remineralization of organic *** of the two economic phosphorite beds was controlled by two sea-level *** differences have also been documented in contemporaneous phosphate-bearing successions in Brazil and Mangolia,indicating a significant shift in global phosphogenic mechanism during the early and middle Ediacaran,which may be due to the changes in redox conditions in seawater,associated with the Neoproterozoic Oxygenation *** regional active P-cycle processes could produce more free oxygen,which may have contributed to the up

关键词： phosphorite lithofacies phosphatic grains phosphogenic paragenesis phosphorus cycle mineralogy

structural basis for polyuridine tract recognition by sARs-CoV-2 Nsp15

在线全文

学校读者我要写书评

暂无评论

Protein & Cell 2024年第7期15卷 547-552页

作者： Fumiaki Ito Hanjing Yang Z.Hong Zhou Xiaojiang s.chen Molecular and Computational Biology Department of Biological SciencesUniversity of Southern CaliforniaLos AngelesCA 90089United States Department of Microbiology Immunology and Molecular GeneticsUniversity of CaliforniaLos AngelesCA 90095United States California Nanosystems Institute University of CaliforniaLos AngelesCA90095United States Genetic Molecular and Cellular Biology ProgramKeck School of MedicineUniversity of Southern CaliforniaLos AngelesCA 90089United States Norris Comprehensive Cancer Center University of Southern CaliforniaLos AngelesCA 90089United States Center of Excellence in NanoBiophysics University of Southern CaliforniaLos AngelesCA 90089United States

Dear Editor,Coronaviruses have evolved a wide array of tactics to evade host antiviral *** host cells detect invading foreign nucleic acids including viral genome and viral replication intermediates,they activate interferon(IFN)signaling via cytoplasmic pattern recognition receptors(Kang et al.,2002;Kato et al.,2006).Remarkable stealth activities exhibited by coronaviruses are facilitated by a series of non-structural proteins(Nsps),such as Nsp15(Deng and Baker,2018;Deng et al.,2019;Hackbart et al.,2020),which is a uridine-specific endoribonuclease that mediates evasion of host detection of viral double-stranded RNA(dsRNA)(Bhardwaj et al.,2004;Deng et al.,2017;Frazier et al.,2021;Ivanov et al.,2004).Nsp15 targets a polyuridine[poly(U)]tract on the coronavirus negative strand RNA(Hackbart et al.,2020).Nsp15 limits the abundance and length of poly(U)within the negative strand RNA 5ʹ-extension by trimming down the initially synthesized poly(U)lead sequence to the optimal length that can suppress dsRNA formation but still serves as a template for poly(A)tail of the positive strand genome of the coronaviruses(Hofmann and Brian,1991).

关键词： p15 interferon template

同方期刊数据库

The Immense Impact of Reverse Edges on Large Hierarchical Networks

在线全文

学校读者我要写书评

暂无评论

Engineering 2024年第5期36卷 240-249页

作者： Haosen Cao Bin-Bin Hu Xiaoyu Mo Duxin chen Jianxi Gao Ye Yuan Guanrong chen Tamás Vicsek Xiaohong Guan Hai-Tao Zhang MOE Engineering Research Center of Autonomous Intelligent Unmanned systems State Key Laboratory of Intelligent Manufacturing Equipment and TechnologySchool of Artificial Intelligence and AutomationHuazhong University of Science and TechnologyWuhan 430074China school of Mechanical and Aerospace Engineering Nanyang Technological UniversitySingapore 639798Singapore Jiangsu Key Laboratory of Networked Collective Intelligence School of MathematicsSoutheast UniversityNanjing 210096China Department of Computer science Rensselaer Polytechnic InstituteTroyNY 12180USA Department of Electronic Engineering City University of Hong KongHong Kong 999077China Department of Biological Physics Eötvös UniversityBudapest 1117Hungary MOE Key Laboratory for Intelligent Networks and Network security School of Automation Science and EngineeringXi’an Jiaotong UniversityXi’an 710049China

Hierarchical networks are frequently encountered in animal groups,gene networks,and artificial engineering systems such as multiple robots,unmanned vehicle systems,smart grids,wind farm networks,and so *** structure of a large directed hierarchical network is often strongly influenced by reverse edges from lower-to higher-level nodes,such as lagging birds’howl in a flock or the opinions of lowerlevel individuals feeding back to higher-level ones in a social *** study reveals that,for most large-scale real hierarchical networks,the majority of the reverse edges do not affect the synchronization process of the entire network;the synchronization process is influenced only by a small part of these reverse edges along specific *** surprisingly,a single effective reverse edge can slow down the synchronization of a huge hierarchical network by over 60%.The effect of such edges depends not on the network size but only on the average in-degree of the involved *** overwhelming majority of active reverse edges turn out to have some kind of“bunching”effect on the information flows of hierarchical networks,which slows down synchronization *** finding refines the current understanding of the role of reverse edges in many natural,social,and engineering hierarchical networks,which might be beneficial for precisely tuning the synchronization rhythms of these *** study also proposes an effective way to attack a hierarchical network by adding a malicious reverse edge to it and provides some guidance for protecting a network by screening out the specific small proportion of vulnerable nodes.

关键词： synchronizability Large hierarchical networks Reverse edges Information flows Complex networks

Effect of Eu3+,Bi3+,and Li+ doping on luminescent property of GdNbO4

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

Journal of Rare Earths 2024年第1期42卷 66-75页

作者： s.W.Wi Y.s.Lee Department of Physics and Integrative Institute of Basic sciences Soongsil University

We investigated the emission properties of Eu3+-doped GdNbO4-based oxide phosphors,aiming at improving the Eu3+emission by codoping of Bi3+and Li+.Eu3+singly doped,Eu3+and Bi3+doubly doped,and Eu3+,Bi3+,and Li+triply doped GdNbO4were prepared using a high-temperature solid-state reaction *** red-orange emissions from Eu3+in the singly doped samples are significantly improved by the codoping of Bi3+,mainly due to the energy transfer from Bi3+to Eu3+.The additional codoping of Li+is found to increase the Eu3+emission *** improvement might be attributed to the increase in the photoluminescent quantum yield originating from larger grain sizes and better crystallinity.A detailed analysis of the X-ray diffraction pattern and the asymmetric ratio estimated from the photoluminescence spectra show that the local lattice environment around Eu3+in GdNbO4does not change significantly with the codoping of Bi3+and Li+.Our results indicate that Li+doping is a promising way to improve the emission properties of rare-earth ion-doped GdNbO4phosphors.

关键词： Eu 3+ GdNbO 4 Codoping of Li + Photoluminescence sensitizer Rare earths

First evidence for chiral wobbling of triaxial nuclei

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Nuclear science and Techniques 2024年第7期35卷 4-7页

作者： s.Frauendorf Department of Physics and Astronomy University of Notre DameNotre DameIN 46556USA

Chirality(Greek“handiness”)is a property of many com-plex *** molecules exist in two forms,one being the mirror image of the *** for our hands,it is impossible to make the images identical by a suitable *** two forms are called left-handed and *** have the same binding energy,because the electro-magnetic interaction,which holds the molecule together,does not change under a *** properties that are insensitive to the geometry are also the *** different geometry is the reason why the left-handed form turns the polarization plane of transmitted light in one direction by some angle while the right-handed form turns it in the oppo-site direction by the same ***,the geometrical differences between the two species may have other *** two species of the carvon molecule shown in Fig.1 taste quite differently.

关键词： turns Chiral mirror

Tribological behavior of lubricant-impregnated porous polyimide

在线全文

学校读者我要写书评

暂无评论

Friction 2024年第4期12卷 711-725页

作者： Jinbang LI Ningning ZHOU Janet s.s.WONG school of Mechanical Engineering and Mechanics Ningbo UniversityNingbo 315211China Beijing Key Laboratory of Long-life Technology of Precise Rotation and Transmission Mechanisms Beijing Institute of Control EngineeringBeijing 100029China Department of Mechanical Engineering Imperial College LondonLondon SW72AZUK

Porous materials impregnated with lubricants can be used in conditions where limited lubricant is *** this work,three porous polyimides(PPI)with different densities were ***(PAO)impregnated PPI(iPPI)discs were rubbed against steel and sapphire *** operando observations of the iPPI-sapphire contacts show that oil is released under an applied load,forming a meniscus around *** at the outlet is created at high sliding *** amount of released oil increases with increasing PPI *** moduli,E*,estimated based on the actual contact size show that trapped oil in iPPIs contributes to load *** higher speeds,tribological rehydration of the contact occurs in low density iPPI,with that E*rises with *** high density PPIs,high speeds give a constantly high E*which is limited by the viscoelastic properties of the PPI network and possibly the rate of oil *** of iPPI-steel contacts is governed by the mechanical properties of the PPI,the flow of the lubricant,and the roughness of the PPI *** low-and medium-density(highly porous,high roughness)PPIs,large amount of oil is released,and lubrication is mainly via lubricant restricted in the contact in the pores and possibly tribological *** high density(low porosity)PPI,with lower roughness,hydrodynamic lubrication is achieved which gives the lowest *** results show that polymeric porous materials for effective lubrication require the optimization of its surface roughness,stiffness,oil flow,and oil retentions.

关键词： polyimide porous material friction mechanism polymer limited lubrication

Enhancing fatigue performance of AZ31 magnesium alloy components fabricated by cold metal transfer-based wire arc directed energy deposition through LPB

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

Journal of Magnesium and Alloys 2024年第4期12卷 1638-1662页

作者： shambhu Kumar Manjhi srikanth Bontha A.s.s.Balan Department of Mechanical Engineering National Institute of Technology KarnatakaSurathkalSrinivasanagarMangaloreKarnataka 575025India

Cold Metal Transfer-Based Wire Arc Directed Energy Deposition(CMT-WA-DED)presents a promising avenue for the rapid fabrication of components crucial to automotive,shipbuilding,and aerospace ***,the susceptibility to fatigue of CMT-WA-DED-produced AZ31 Mg alloy components has impeded their widespread adoption for critical load-bearing *** this study,a comprehensive investigation into the fatigue behaviour of WA-DED-fabricated AZ31 Mg alloy has been carried out and compared to commercially available wrought AZ31 *** findings indicate that the as-deposited parts exhibit a lower fatigue life than wrought Mg alloy,primarily due to poor surface finish,tensile residual stress,porosity,and coarse grain microstructure inherent in the WA-DED *** Plasticity Burnishing(LPB)treatment is applied to mitigate these issues,which induce significant plastic deformation on the *** treatment resulted in a remarkable improvement of fatigue life by 42%,accompanied by a reduction in surface roughness,grain refinement and enhancement of compressive residual stress ***,during cyclic deformation,WA-DED specimens exhibited higher plasticity and dislocation density compared to both wrought and WA-DED+LPB specimens.A higher fraction of Low Angle Grain Boundaries(LAGBs)in WA-DED specimens contributed to multiple crack initiation sites and convoluted crack paths,ultimately leading to premature *** contrast,wrought and WA-DED+LPB specimens displayed a higher percentage of High Angle Grain Boundaries(HAGBs),which hindered dislocation movement and resulted in fewer crack initiation sites and less complex crack paths,thereby extending fatigue *** findings underscore the effectiveness of LPB as a post-processing technique to enhance the fatigue performance of WA-DED-fabricated AZ31 Mg alloy *** study highlights the importance of LPB surface treatment on AZ31 Mg components produced by CMT-WA-DED to remove surface d

关键词： Wire arc additive manufacturing AZ31 Mg alloy Low plasticity burnishing Low cycle fatigue test strain amplitude