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Kinetic modeling of high-temperature oxidation of pure Mg

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Journal of magnesium and Alloys 2020年第3期8卷 819-831页

作者： sa ma Fangzhou Xing Na Ta Lijun Zhang State Key Laboratory of Powder Metallurgy Central South UniversityChangshaHunan 410083P.R.China max-Planck-Institut fiir Eisenforschung GmbH Max-Planck-Straβe 140237DusseldorfGermany

A variety of experimental tracer diffusivities of Mg and O in magnesium oxide available in the literature were first *** mobilities including bulk and short-circuit diffusion of Mg and O were then obtained by means of the CALPhaD(Calculation of Phase Diagram)***,the diffusion-controlled kinetic model of oxidation in a gas-MgO-Mg environment was developed based on the moving boundary model and Fick's law,coupling with the modified thermodynamic description of MgO.A mathematical expression for parabolic rate constant kp of the oxide scale was derived for magnesia and correlated with the thermodynamic and diffusion kinetic *** evaluated kp results were in line with the experimental ***,the oxidation process of pure magnesium at 673 K was model-predicted,and the predicted evolution of the oxide thicknesses agreed very well with the experimental *** was indicated that the grain boundaries diffusion of magnesium cations predominated the high temperature oxidation process.

关键词： MgO Diffusion Oxidation Atomic mobility CALPhaD Wagner's model

Effects of human disturbance on nest placement of the woodpigeon (Columba palumbus): a case study from the Middle Atlas, Morocco

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Integrative Zoology 2014年第3期9卷 349-359页

作者： saâd haNANE Forest Research Center High Commissariat for WaterForests and Desertification ControlRabat-AgdalMorocco

The woodpigeon(Columba palumbus)is a common and widespread bird in Morocco(North Africa).I examined,over 2 years(2010 and 2011),the breeding density and nest placement of this game species in relation to nest site habitat and degree of human *** study area was in the Middle Atlas Tighboula mountain forest,Morocco,in a disturbed and an undisturbed *** data collected in the 2 study sites,I aimed to identify the factors influencing the placement of nests within holm oak trees(Quercus rotundifolia)and their densities.I found that habitat structures,influenced by grazing disturbance,have affected nesting density and the location of nests of this *** place their nests in a higher position(3.42±0.19 m)when disturbance intensity is high and lower(1.68±0.1 m)when disturbance intensity is low,and show higher nesting density in less disturbed zone(3.1±0.4 nests/ha)than in highly disturbed zones(1.4±0.2 nests/ha).Grazing disturbance could pose a threat to population persistence at a broader scale and could potentially reduce the abundance of this species by altering the composition and the structure of the forest nesting *** multi-scale studies are needed to assess the effects of different levels of grazing disturbance on woodpigeon nest density and placement,and to enhance our knowledge of the breeding behavior of this game species under variable environments.

关键词： breeding density Columba palumbus holm oak Middle Atlas Morocco nest location woodpigeon

A　NEW　INGENOL　ESTER　FROM　EUPHORBIA　PETIOLATA

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Chinese Chemical Letters 1996年第5期7卷 439-440页

作者： Shi, YP ma, B Jia, ZJ Lahham, J saleh, sa LANZHOU UNIV INST ORGAN CHEMSTATE KEY LAB APPL ORGAN CHEMLANZHOU 730000PEOPLES R CHINA

Abstract: A new monoester of the tetracyclic diterpene ingenol was isolated from Euphorbia petiolata and its structure was elucidated by spectroscopic methods and chemical transformationas ingenol-3-O-(2'E, 4'Z)-tetra...

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Effect of rare-earth doping on adsorption of carbon atom on ferrum surface and in ferrum subsurface:A first-principles study

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Journal of Rare Earths 2021年第9期39卷 1144-1150页

作者： Yang Yang Xiang Zhou Faqing Pan Zuju ma Rongjian sa Jun Zheng Qimin Wang Key Laboratory of Green Fabrication and Surface Technology of Advanced Metal materials(Ministry of Education) Research Center of Modem Surface and Interface EngineeringAnhui University of TechnologyMaanshan 243002China School of materials Science and Engineering Anhui University of TechnologyMaanshan 243002China Institute of Oceanography Ocean CollegeMinjiang UniversityFuzhou 350108China School of Electromechanical Engineering Guangdong University of TechnologyGuangzhou 510006China

The adsorption of carbon atom on Fe surface and in Fe subsurface with and without rare earth(La and Ce)substitution in the surface layer and subsurface layer was studied by first-principles *** carbon atom is predicted to adsorb at hollow and long bridge site on Fe(100)and Fe(110),***,the carbon atom shifts to occupy preferentially hollow site on both Fe(100)and Fe(110)with rare earth atom doping at surface *** lower adsorption energies involved with stronger adsorption abilities were obtained for carbon atoms on Fe surface with rare earth doping at surface layer,which was determined by the electronic structure of the surface *** La atom was pulled out the surface after carbon adsorption due to strong interaction of La-C,which is consistent with the more charge *** the subsurface region,the carbon atom prefers to occupy at octahedral site with rare earth doping at surface layer in Fe *** strong adsorption energies of the carbon atoms on Fe surface and in Fe subsurface with rare earth pose relevant insights into the interaction between carbon and rare earth,which helps to understanding the influence mechanism of rare earth in carburizing.

关键词： Carburizing Rare earth First-principles Adsorption energy Electronic structure

PYRIDINATION OF POLY(VINYL CHLORIDE) via A HOMOLYTIC PATHWAY

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Chinese Journal of Polymer Science 2007年第3期25卷 297-302页

作者： sad Moulay Zakia Zeffouni Laboratoire de Chimie-Physique Moléculaire et macromoléculaire Faculté des Sciences de l'Ingénieur Département de Chimie IndustrielleUniversité Sad Dahlab de BlidaRoute de SoumaB. P. 270Blida 09000Algeria

PVC was subjected to a chemical modification aiming at replacing the chlorine atoms by pyridine groups via a homolytic route. Pyridine groups were peculiarly affixed to the PVC matrix via a carbon-carbon bond rather than a carbonnitrogen one. PVC was first iodinated using the Conant-Finkelstein reaction, followed by the application of the homolytic conditions of Minisci to generate pyridinated PVC with a varying degree of substitution. The extent of substitution was not high; the reaction on 30% iodinated PVC afforded a degree of modification no greater than 3%.

关键词： Conditions of Minisci Iodinated PVC Pyridinated PVC

Changes in plant community diversity and aboveground biomass along with altitude within an alpine meadow on the Three-River source region

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Chinese Science Bulletin 2012年第27期57卷 3573-3577页

作者： sa WenJun AN LiZhe sa Wei Institute of Botany Science School of Life SciencesLanzhou UniversityLanzhou 730000China School of Life Science Qinghai UniversityXining 810008China

The grassland is an important component of terrestrial ecosystems and plays a significant role in biodiversity and ecosystem *** the present study,the changes of plant species diversity and aboveground biomass productivity were examined along with the altitude in natural alpine grassland in the source region of three rivers on the Qinghai-Tibetan *** experimental locations were selected with altitudes ranging from 3862 to 4450 m above sea level(a.s.l.).The results indicated that Kobresia pygmaea meadow,Kobresia humilis meadow and salix cupularis shrub meadow had higher indices of diversity and aboveground *** distribution of species diversity,richness and aboveground biomass showed similarly unimodal patterns across the altitude gradient with the highest indices appeared at mid-altitudes *** changing trend of species diversity,richness and evenness also showed significant unimodal patterns with total aboveground biomass,and the highest species diversity occurred at intermediate level of *** research would provide a valuable reference for the protection of grassland biodiversity and maintaining of the grazing ecosystem function in the source region of the Three Rivers.

关键词：植物群落多样性地上生物量海拔高度高寒草甸三江源地区植物物种多样性生态系统功能生物多样性

haLOMETHYLATION OF POLYSTYRENE AND SUBSEQUENT PYRIDINATION VIA A HOMOLYTIC PATHWAY

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Chinese Journal of Polymer Science 2006年第6期24卷 627-635页

作者： sad Moulay Nadia Mehdi Laboratoire de Chimie-Physique Moléculaire et macromoléculaire Faculté des Sciences de l'Ingénieur Departement de Chimie IndustrielleUniversité de BlidaRoute de SoumaB. P. 270Blida 09000Algeria

Chloromethylation of polystyrene （PS） with two different chloromethylating systems methylal/thionyl chloride and paraformaldehyde/trimethylchlorosilane was studied. Soluble chloromethylated polystyrene with a degree of substitution of 89% was obtained. The Conant-Finkelstein reaction on the chloromethylated PS afforded soluble iodomethylated polystyrene with a degree of substitution as high as 96%. The reaction conditions of Minisci were employed to radically pyridinate PS via its iodomethylated derivative. Polyelectrolytes were formed which could be converted to normal polymers by treatment with a 20% aqueous solution of NaOH.

关键词： Chloromethylated polystyrene Conditions of Minisci Iodomethylated polystyrene Pyridinated polystyrene.

Response of photosynthesis,growth,and acorn mass of pedunculate oak to diff erent levels of nitrogen in wet and dry growing seasons

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Journal of Forestry Research 2023年第1期34卷 167-176页

作者： Krunoslav Sever saša Bogdan ŽeljkoŠkvorc Faculty of Forestry and Wood Technology University of ZagrebSvetošimunska 2510000 ZagrebCroatia

The objective was to examine the effects of optimal leaf nitrogen levels>2.0%and suboptimal levels<2.0%,nitrogen nutrition on net photo synthetic rate,stem diameter increment,height growth increment and acorn mass of ... 详细信息

The objective was to examine the effects of optimal leaf nitrogen levels>2.0%and suboptimal levelsmass of pedunculate oak during 2010 in the absence of drought stress and during 2011 under the impact of moderate drought *** to the results,moderate drought stress significantly reduced net photo synthetic rate,stem diameter increment and height growth increment,while acorn mass was not *** nitrogen nutrition significantly reduced the net photo synthetic rate and stem diameter increment only in the wet year,acorn mass in both wet and dry years,while height growth increment was not significantly reduced by suboptimal nitrogen nutrition in either *** results indicate that optimal nitrogen levels can stimulate photo synthetic rate and stem diameter increment of pedunculate oak only in the absence of moderate drought ***,the results show that moderate drought stress is a more dominant stressor for photosynthesis and growth of pedunculate oak than suboptimal nitrogen nutrition,while for acorn development,it is the more dominant stressor.

关键词： Quercus robur L. Drought stress Net photosynthic rate Stem diameter increment Height growth increment Acorn mass

Ecoregional height-diameter models for Scots pine in Turkiye

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Journal of Forestry Research 2024年第6期35卷 49-61页

作者： Fadime sağlam Oytun Emre sakici Department of Forest Engineering Faculty of ForestryKastamonu University37150 KastamonuTurkey

Ecoregion-based height-diameter models were developed in the present study for Scots pine(Pinus sylves-tris L.)stands in Turkiye and included several ecological factors derived from a pre-existing ecoregional classification *** data were obtained from 2831 sample trees in 292 sample *** generalized height–diameter models were developed,and the best model(HD10)was selected according to statistical ***,nonlinear mixed-effects modeling was applied to the best *** R2 for the generalized height‒diameter model(Richards function)modified by Sharma and Parton is 0.951,and the final model included number of trees,dominant height,and diameter at breast height,with a random parameter associated with each ecoregion attached to the inverse of the mean basal *** full model predictions using the nonlinear mixed-effects model and the reduced model(HD10)predictions were compared using the nonlinear sum of extra squares test,which revealed significant differences between ecore-gions;ecoregion-based height–diameter models were thus found to be suitable to *** addition,using these models in appropriate ecoregions was very important for achieving reliable predictions with low prediction errors.

关键词： Tree height Nonlinear mixed-effects modelling Nonlinear sum of extra squares method Ecoregion Scots pine