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Field topologies in ideal and near-ideal magnetohydrodynamics and vortex dynamics

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Science china(Physics,Mechanics & Astronomy) 2015年第1期58卷 12-31页

作者： LOW b.c. High Altitude Observatory National Center for Atmospheric Research

Magnetic field topology frozen in ideal magnetohydrodynamics （MHD） and its breakage in near-ideal MHD are reviewed in two parts, clarifying and expanding basic concepts. The first part gives a physically complete description of the frozen field topology derived from magnetic flux conservation as the fundamental property, treating four conceptually related topics： Eulerian and La- grangian descriptions of three dimensional （3D） MHD, chandrasekhar-Kendall and Euler-potential field representations, magnetic helicity, and inviscid vortex dynamics as a fluid system in physical contrast to ideal MHD. A corollary of these developments clar- ifies the challenge of achieving a high degree of the frozen-in condition in numerical MHD. The second part treats field-topology breakage centered around the Parker Magnetostatic Theorem on a general incompatibility of a continuous magnetic field with the dual demand of force-free equilibrium and an arbitrarily prescribed, 3D field topology. Preserving field topology as a global con- straint readily results in formation of tangential magnetic discontinuities, or, equivalently, electric current-sheets of zero thickness. A similar incompatibility is present in the steady force-thermal balance of a heated radiating fluid subject to an anisotropic thermal flux conducted strictly along its frozen-in magnetic field in the low-fl limit. In a weakly resistive fluid the thinning of current sheets by these general incompatibilities inevitably results field notwithstanding the small resistivity. Strong Faraday in sheet dissipation, resistive heating and topological changes in the induction drives but also macroscopically limits this mode of energy dissipation, trapping or storing free energy in self-organized ideal-MHD structures. This property of MHD turbulence captured by the Taylor hypothesis is reviewed in relation to the Sun＇s corona, calling for a basic quantitative description of the breakdown of flux conservation in the low-resistivity li

关键词： magnetic topology magnetic reconnection current sheets magnetic helicity thermal conduction solar corona magnetohy-drodynamics interstellar clouds

biofabrication of nanocomposite-based scaffolds containing human bone extracellularmatrix for the differentiation of skeletal stem and progenitor cells

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bio-Design and Manufacturing 2024年第2期7卷 121-136页

作者： Yang-Hee Kim Janos M.Kanczler Stuart Lanham Andrew Rawlings Marta Roldo Gianluca Tozzi Jonathan I.Dawson Gianluca cidonio Richard O.c.Oreffo Faculty of Medicine Bone and Joint Research GroupCentre for Human DevelopmentStem Cells and RegenerationInstitute of Developmental SciencesUniversity of SouthamptonSouthampton SO166YDUK School of Pharmacy and biomedical Science University of PortsmouthPortsmouth PO12DTUK School of Engineering Faculty of Engineering and ScienceUniversity of GreenwichGreenwich ME44TBUK center for Life Nano-and Neuro-Science(cLN2S) Italian Institute of Technology00161 RomeItaly

Autograft or metal implants are routinely used in skeletal ***,they fail to provide long-term clinical resolution,necessitating a functional biomimetic tissue engineering *** use of native human bone tissue for synthesizing a biomimeticmaterial inkfor three-dimensional(3D)bioprintingof skeletal tissueis anattractivestrategyfor ***,human bone extracellular matrix(bone-EcM)offers an exciting potential for the development of an appropriate microenvironment for human bone marrow stromal cells(HbMScs)to proliferate and differentiate along the osteogenic *** this study,we engineered a novel material ink(LAb)by blending human bone-EcM(b)with nanoclay(L,Laponite®)and alginate(A)polymers using extrusion-based *** inclusion of the nanoﬁller and polymeric material increased the rheology,printability,and drug retention properties and,critically,the preservation of HbMScs viability upon *** composite of human bone-EcM-based 3D constructs containing vascular endothelial growth factor(VEGF)enhanced vascularization after implantation in an ex vivo chick chorioallantoic membrane(cAM)*** inclusion of bone morphogenetic protein-2(bMP-2)with the HbMScs further enhanced vascularization and mineralization after only seven *** study demonstrates the synergistic combination of nanoclay with biomimetic materials(alginate and bone-EcM)to support the formation of osteogenic tissue both in vitro and ex vivo and offers a promising novel 3D bioprinting approach to personalized skeletal tissue repair.

关键词： Extracellular matrix Nanoclay bone 3D bioprinting

An abrupt cooling event early in the last interglacial in the northern South china Sea

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Science china Earth Sciences 2001年第10期44卷 865-870页

作者：涂霞郑范王吉良蔡慧梅汪品先 c.bühring M.Sarnthein The South china Sea Institute of Oceanology Chinese Academy of Sciences Guangzhou 510301 China Key Laboratory of Marine Geology Ministry of Education Tongji University Shanghai 200092 China Institut für Geowissenschaften Universitat Kiel Germany

The high-resolution quantitative analysis of the planktonic foraminifera and the δ18O records of the section between 96.49– 137.6 mcd at ODP Site 1144 on the continental slope of northern South china Sea reveals an abrupt cooling event of sea surface temperature (SST) during the last interglacial (MIS 5.5, i.e. 5e). The dropping range of the winter SST may come to 7.5°c corresponding to 1.2‰ of the δ18O value of sea surface water. This event is comparable with those discovered in the west Europe and the northern Atlantic Ocean, but expressed in a more intensive way. It is inferred that this event may have been induced by middle- to low-latitude processes rather than by polar ice sheet change. Since the Kuroshio-index speciesPulleniatina obliquiloculata displayed the most distinct change at the event, it may also be related to the paleoceanographic change of the low-latitude area in the western Pacific Ocean. This event can be considered as one of “Younger Dryas-style coolings” and is indicative of climate variability of the last interglacial stage.

关键词： northern South china Sea last interglacial period sudden cooling event MIS 5.5 climate variability

Surface-modified Ag@Ru-P25 for photocatalytic cO_(2) conversion with high selectivity over cH_(4) formation at the solid–gas interface

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carbon Energy 2024年第1期6卷 182-196页

作者： chaitanya b.Hiragond Sohag biswas Niket SPowar Junho Lee Eunhee Gong Hwapyong Kim Hong Soo Kim Jin-Woo Jung chang-Hee cho bryan M.Wong Su-Il In Department of Energy Science&Engineering Daegu Gyeongbuk Institute of Science and Technology(DGIST)DaeguRepublic of Korea Department of chemical&Environmental Engineering Materials Science&Engineering ProgramDepartment of ChemistryDepartment of Physics&AstronomyUniversity of California-RiversideRiversideCaliforniaUSA Department of Physics and chemistry Daegu Gyeongbuk Institute of Science and Technology(DGIST)DaeguRepublic of Korea NiceScience corporation DaeguRepublic of Korea

Systematic optimization of the photocatalyst and investigation of the role of each component is important to maximizing catalytic activity and comprehending the photocatalytic conversion of cO_(2) reduction to solar fuels.A surface-modified Ag@Ru-P25 photocatalyst with H_(2)O_(2) treatment was designed in this study to convert cO_(2) and H_(2)O vapor into highly selective *** doping followed by Ag nanoparticles(NPs)cocatalyst deposition on P25(TiO_(2))enhances visible light absorption and charge separation,whereas H_(2)O_(2) treatment modifies the surface of the photocatalyst with hydroxyl(–OH)groups and promotes cO_(2) ***-resonance transmission electron microscopy,X-ray photoelectron spectroscopy,X-ray absorption near-edge structure,and extended X-ray absorption fine structure techniques were used to analyze the surface and chemical composition of the photocatalyst,while thermogravimetric analysis,cO_(2) adsorption isotherm,and temperature programmed desorption study were performed to examine the significance of H_(2)O_(2) treatment in increasing cO_(2) reduction *** optimized Ag1.0@Ru1.0-P25 photocatalyst performed excellent cO_(2) reduction activity into cO,cH4,and c2H6 with a~95%selectivity of cH4,where the activity was~135 times higher than that of pristine TiO_(2)(P25).For the first time,this work explored the effect of H_(2)O_(2) treatment on the photocatalyst that dramatically increases cO_(2) reduction activity.

关键词： gas-phase cO_(2) reduction H_(2)O_(2) treatment plasmonic nanoparticles solar fuel photocatalyst surface modification

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近期国内塑料市场行情

上海塑料 2002年第2期30卷 49-50页

作者： c.b

一、PE市场目前国内PE市场,各主要品种价格继续反弹,但反弹的空间有限。由于进口货到货量较前阶段略有减少,大庆、吉化等企业也进入检修期,市场供应量略有减少,贸易商借机炒作,使PE市场本不应在需求相对淡季的月份出现反弹。

关键词：塑料市场行情 2002年中国高压聚乙烯低压聚乙烯线性聚烯聚丙烯聚苯乙烯 AbS树脂

Stable Fetal Heart Rate after Phenylephrine Infusion during Spinal Anesthesia for cesarean Delivery

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麻醉与监护论坛 2012年第2期19卷 100-104页

作者： X.G. Guo M. Wang c.b Han Y.N.Qian Department of Anesthesiology First Affiliated Hospital Nanjing Medical University Nanjing Jiangsu Province China Department of Anesthesiology Maternal and Child Health Care Hospital in Wuxi Jiangsu Province China

background:Use of phenylephrine for prevention of hypotension following spinal anesthesia in women undergoing caesarean delivery can improve the fetal oxygen supply and demand balance. The authors hypothesized whether the mechanism underlying this is the stable fetal heart rate and metabolism in the fetus compared with ephedrine. Methods:Sixty women having elective cesarean delivery under spinal anesthesia randomly received ephedrine 4 mg/ml (GroupⅠ) or phenylephrine 50 pg/ml (GroupⅡ) titrated to maintain the systolic.blood pressure near baseline. The fetal heart rate, maternal heart rate and maternal blood pressure were measured at various time points after medicine infusion. At delivery, maternal arterial, umbilical arterial, and umbilical venous blood samples were taken for measurement of blood gases and plasma concentrations of lactate and glucose. Results:compared with baselines, fetal heart rate after ephedrine infusion in groupⅠwas significantly increased (P cantly change (P > 0.05). Umbilical arterial and venous pH and base excess were lower in groupⅠthan in groupⅡ(Pcompared with groupⅡ, umbilical arterial plasma concentrations of lactate (median 4.23 [interquartile range 2.28-6.18] vs 2.23 [1.57-2.89] mmol.l^-1, Pbilical venous concentration of lactate (median and interquartile 3.12 [1.80-4.44] vs 1.78 [1.45-2. 11] mmol.l^-1, P bilical arterial PcO2, and plasma concentrations of glucose were higher in groupⅠ(P conclusions:compared with ephedrine, the fetal heart rate after phenylephrine infusion maintains stable, which may be one of mechanisms that phenylepbrine can improve fetal acid-based status.

关键词：麻醉监护肾上腺素临床

Triple the steady-state reaction rate by decorating the In_(2)O_(3)surface with SiO_(x)for cO_(2)hydrogenation

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Journal of Energy chemistry 2024年第8期95卷 96-105,I0003页

作者： Hao Wang chun Yang Xiaoyan Yu Mingrui Wang Runze Yang Xiaowa Nie ben Hang Yin Alex c.K.Yip chunshan Song Guanghui Zhang Xinwen Guo State Key Laboratory of Fine chemicals Frontier Science Center for Smart MaterialsPSU-DUT Joint Center for Energy ResearchSchool of Chemical EngineeringDalian University of TechnologyDalian 116024LiaoningChina Department of chemistry the Chinese University of Hong KongHong Kong 999077China Paihau-Robinson Research Institute the MacDiarmid Institute for Advanced Materials and NanotechnologyVictoria University of WellingtonWellington 6012New Zealand Department of chemical and Process Engineering The University of CanterburyChristchurch 8041New Zealand

Indium oxide(In_(2)O_(3)),as a promising candidate for cO_(2)hydrogenation to c_(1) products,often suffers from sintering and activity decline,closely related to the undesirable structural evolution under reaction *** on the comprehension of the dynamic evolution,this study presents an efficient strategy to alleviate the agglomeration of In_(2)O_(3)nanoparticles by the surface decoration with highly dispersed silica species(SiO_(x)).Various structural characterizations combined with density functional theory calculations demonstrated that the sintering resulted from the over-reduction,while the enhanced stability originated from the anchoring effect of highly stable In-OSi bonds,which hinders the substantial formation of metallic In(In^(0))and the subsequent agglomeration.0.6Si/In_(2)O_(3)exhibited cO_(2)conversion rate of10.0 mmol g^(-1)h^(-1)at steady state vs.3.5 mmol g^(-1)h^(-1)on In_(2)O_(3)in cO_(2)*** steady-state activity was also achieved on Pd-modified *** to the traditional Pd/In_(2)O_(3)catalyst,the methanol production rate of Pd catalyst supported on 0.6Si/In_(2)O_(3)was enhanced by 23%,showing the potential of In_(2)O_(3)modified by SiO_(x)in serving as a platform *** work provides a promising method to design new In_(2)O_(3)-based catalysts with improved activity and stability in cO_(2)hydrogenation.

关键词： cO_(2)hydrogenation In_(2)O_(3)sintering Dynamic structural evolution Surface SiO_(x)modification DFT simulations

SANc Monte carlo programs for small-angle bhabha scattering

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chinese Physics c 2024年第4期48卷 14-19页

作者： A.b.Arbuzov S.G.bondarenko I.R.boyko L.V.Kalinovskaya A.A.Kampf R.R.Sadykov V.L.Yermolchyk bogoliubov Laboratory of Theoretical Physics JINRDubna141980 Russia Dzhelepov Laboratory of Nuclear Problems JINRDubna141980 Russia Dubna State University Dubna141982 Russia

Luminosity monitoring at e^(+)e^(−)colliders was investigated using SANc Monte carlo event generator ReneSANce and integrator McSANc for simulation of bhabha scattering at low *** are presented for center-of-mass energies of the Z boson resonance and at 240 GeV for the conditions of typical luminosity *** is shown that bremsstrahlung events with extremely low electron scattering angles are relevant to match the precision tags of future electron-positron colliders.

关键词： luminosity bhabha scattering QED Monte carlo simulation

Assessment of Similitude behavior in Natural Frequencies of Printed Turbine blade

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Transactions of Nanjing University of Aeronautics and Astronautics 2024年第4期41卷 488-501页

作者： MUHAMMAD Usman Safdar SHEN Xing EIMAN b.Saheby State Key Lab of Mechanics and control for Aerospace Structures College of AeronauticsNanjing University of Aeronautics and AstronauticsNanjing 210016P.R.China Graduate School Chinese Aeronautical EstablishmentYangzhou 225111P.R.China

Improving structures involves comparing old and new designs on a key *** the percent change in performance is a method to *** paper proposes a cost-effective analogy by generating replicas of additive manufactured aluminum alloy(Al Si10Mg)body-centered c.bic lattice(bcc.based turbine blade(T106c)with the same in poly-lactic acid(PLA)material and their comparison in the context of percent change for natural ***,a cavity is created inside the turbine blade(hollow blade).Natural frequencies are obtained experimentally and numerically by incorporating bcc at 50%and 80%of the cavity length into the hollow blade for both *** cost of manufacturing the metal blades is 90%more than that of the PLA *** two material blade designs show a similar percentage variation,as the first-order mode enhancs more than 5%and the second-order mode more than 4%.To observe the behavior in another material,both blades are analyzed numerically with a nickel-based U-500 material,and the same result is achieved,describing that percent change between designs can be verified using the PLA material.

关键词： AlSi10Mg poly-lactic acid(PLA) U-500 T106c.blade bcc lattice structure