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Early millet use in West Liaohe area during early-middle Holocene

Science china Earth Sciences 2016年第8期59卷 1554-1561页

作者： MA ZhiKun YANG XiaoYan zhang chi SUN YongGang JIA Xin School of Archaeology and Museology Peking University Laboratory of Land Surface Pattern and Simulation Institute of Geographic Sciences and Natural Resources ResearchChinese Academy of Sciences History and Culture Institute Chifeng University Laboratory of Earth Surface Process and Environment School of Geographic and Oceanographic SciencesNanjing University

It is generally recognized that millet agriculture originated in northern china. However, the domestication process of foxtail millet(Setaria italica) and broomcorn millet(Panicum miliaceum) is still poorly understood. Based on statistical and morphological analyses of ancient millet starch grains, a tangible hypothesis has been proposed for the long-term domestication of green foxtail millet(S. viridis). However, the hypothesis requires validation by evidence from more regions and more archaeological finds. The West Liaohe region is one of the earliest regions of millet cultivation. Here, we report ancient starch grains recovered from 12 stone grinding tools from eight sites of the Xiaohexi culture(before 8.5 ka BP), Xinglongwa culture(8.2–7.4 ka BP), Zhaobaogou culture(7.0–6.4 ka BP), and Hongshan culture(6.5–5.0 ka BP) in the West Liaohe region of china. Our results indicate that the proportion of millet starch grains with wrinkled surfaces and rough edges, which are diagnostic of wild millet grasses, decreased from 13.0% to 3.4% from the Xiaohexi culture to the Hongshan culture. Millet starch grains measuring >16.8 ?m, a size class recorded only in domesticated foxtail millet, increased from 55.0% to 62.1%. These millet data imply that the process of millet domestication in the West Liaohe region began in the Xiaohexi period and continued up to the Hongshan period.

关键词： Plant domestication West Liaohe region Agricultural origin Neolithic Age Starch grain analysis

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On-surface stereoconvergent synthesis, dimerization and hybridization of organocopper complexes

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Science china Chemistry 2019年第1期62卷 126-132页

作者： chi zhang Qiang Sun Huihui Kong Chunxue Yuan Wei Xu Interdisciplinary Materials Research Center College of Materials Science and Engineering Tongji University

Despite the vital role of stereoconvergent synthesis in modern chemistry, the on-surface stereoconvergent synthesis of organometallic complexes involving transformation among several stereoisomers to one specific form has been few reported. By combination of high-resolution scanning tunneling microscopy(STM) imaging/manipulation and density functional theory(DFT) calculations, we have displayed the stereoconvergent synthesis of organocopper complexes via the Cu-alkene interaction and further dimerization into H-shaped motifs, in which two cis-forms and one trans-form are involved, and the specific adsorption configuration of one cis-form is revealed to be the key for such a synthesis. Furthermore, the generality of the dimerization of organocopper complexes has also been verified by codeposition of two similar molecular precursors, and the hybridized K-shaped motifs(made up of two kinds of organocopper complexes) have been successfully achieved. These findings may provide atomic-scale insights into the synthesis of specific stereoisomers in the fields of pharmaceuticals, biochemistry and organometallic chemistry.

关键词： scanning tunneling microscopy density functional theory surface chemistry organometallic complex stereoconvergent synthesis

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Precipitate Behavior in Fe–20Cr–30Ni–2Nb Austenitic Heat-Resistant Steel

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Acta Metallurgica Sinica(English Letters) 2015年第4期28卷 424-429页

作者： Hiroki Ishikawa chi zhang Sheng-Wei Chen Zhi-Gang Yang School of Materials Science and Engineering Tsinghua University Department of Chemistry and Materials Science Tokyo Institute of Technology

In this study, the precipitation behavior of a new austenitic heat-resistant steel （Fe-20Cr-30Ni-2Nb, in at%） was investigated. The effects of alloying addition of boron （B） and lanthanum （La） on the microstructure of the austenitic steel were scrutinized using SEM, EPMA, TEM, and XRD. The results showed that the addition of B enhanced the precipitation of bar-type Laves phase. A small precipitate with high La concentration was observed at the grain boundary in the alloy without aging; similar precipitates without La also presented in region adjacent to the La single phase. This result indicates that La can exist independently and does not contribute to the formation of new compounds. However, in both B- and La-modified alloy, B appeared in the precipitate free zone. In the alloy containing both B and La, only Fe2Nb Laves- phase precipitates, as indicated by the XRD result.

关键词： Precipitation free zone Grain boundary Phase transformation Microstructure Fe-20Cr-30Ni-2Nb austenitic heat-resistant steel

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The role of mergers and gas accretion in black hole growth and galaxy evolution

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Research in Astronomy and Astrophysics 2021年第8期21卷 293-302页

作者： Tian-chi zhang Qi Guo Yan Qu Liang Gao Key Laboratory for Computational Astrophysics National Astronomical ObservatoriesChinese Academy of SciencesBeijing 100101China School of Astronomy and Space Science University of Chinese Academy of SciencesBeijing 100049China Institute of Computational Cosmology Department of PhysicsUniversity of DurhamSouth RoadDurham DH13LEUK

We use a semi-analytic galaxy formation model to study the co-evolution of supermassive black holes(SMBHs) with their host *** the coalescence of SMBHs is not important,the quasarmode accretion induced by mergers plays a dominant role in the growth of *** play a more important role in the growth of SMBH host galaxies than in the SMBH *** is the combined contribution from quasar mode accretion and mergers to the SMBH growth and the combined contribution from starburst and mergers to their host galaxy growth that determine the observed scaling relation between the SMBH masses and their host galaxy *** also find that mergers are more important in the growth of SMBH host galaxies compared to normal galaxies which share the same stellar mass range as the SMBH host galaxies.

关键词： methods:numerical galaxies:evolution (galaxies:)quasars:supermassive black holes

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Pylorus- and vagus-nerve-preserving partial gastrectomy (D2 dissection)

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chinese Journal of Cancer Research 2013年第4期25卷 457-459页

作者： Jian zhang Liang Cao Zhenglin Wang chi zhang Xiang Hu Department of Gastrointestinal Surgery First Affiliated Hospital of Dalian Medical University

Pylorus- and vagus nerve-preserving partial gastrectomy is important in improving the prognosis of early gastric cancer surgery, reducing surgical complications and improving the quality of life for such patients. In the present case, pylorus- and vagus nerve-preserving partial gastrectomy was performed using the bipolar electrocautery dissection technique combined with D2 dissection along the lesser sac.

关键词： Gastric cancer gastrectomy vagus nerve pylorus

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Study on Hydrodynamic Characteristics of Wave Turbulent Bottom Boundary Layer Using A Large-Sized Wave Flume

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china Ocean Engineering 2021年第5期35卷 759-766页

作者： zhang Hong-qian XIE Ming-xiao zhang chi LI Shao-wu zhang Hua-qing SUN Yu-chen State Key Laboratory of Hydraulic Engineering Simulation and Safety Tianjin UniversityTianjin 300072China Tianjin Research Institute for Water Transport Engineering M.O.T..Tianjin 300456China State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering Hohai UniversityNanjing 210098China

Experimental studies were conducted in a super-large wave flume,aiming at uncovering the hydrodynamic characteristics involved in the turbulent wave boundary layer of full scale *** explicit formula of boundary layer thickness on rough turbulent flow was presented based on the measured velocity data of the present study and collected experimental data on wave boundary *** was found that the bottom wave-associated nominal stresses under the conditions of prototype scale tests suppress the vertical turbulence scattering upward over the boundary layer,which accounts for thickening of the boundary layer under wave *** effect has yet not been reported in the literatures using oscillatory U-tube or small-sized wave *** phase inconsistency in the turbulent boundary layer to the free stream velocity(velocity immediately outside the boundary layer)is within15°,which is remarkably smaller than the results from oscillatory U-tubes,as well as the larger wave flume experiment presented by Xie et al.(2021),showing that the coarser bed would further reduce the phase *** intensity of the vertical turbulent component is approximately 1/2 of the horizontal component,which has larger ratio compared with the value of 1/5 reported by previous ***,it was also found that the vertical turbulent energy was approximately 3/4 of the turbulent energy in spanwise directions(y-direction).This means that the turbulent fluctuation has similar order in all three-directions(x,y,z)in a full scale environment and highlights that the turbulent components in all the three directions should not be neglected when calculating the total turbulent energy.

关键词： large wave flume wave boundary layer hydrodynamic mechanism turbulent

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Mechanical and acoustic emission characteristics of anhydrite rock under freeze-thaw cycles

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Journal of Mountain Science 2023年第1期20卷 227-241页

作者： zhang chi JIN Xiao-guang HOU Chao HE Jie School of Civil Engineering Chongqing UniversityChongqing400045China china Railway 14TH Bureau Group Fourth Engineering Corporation Limited Jinan250101China Key Laboratory of New Technology for Construction of Cities in Mountain Area of the Ministry of Education Chongqing UniversityChongqing400045China State Key Laboratory of Coal Mine Disaster Dynamics and Control Chongqing UniversityChongqing400045China

To study the damage mechanisms of anhydrite rock under freeze-thaw cycles, the physicalmechanical properties and the microcracking activities of anhydrite rock were investigated through mass variation, nuclear magnetic resonance, scanning electron microscope tests, and uniaxial compression combined with acoustic emission(AE) tests. Results show that with the increase of freeze-thaw processes,the mass, uniaxial compression strength, and elastic modulus of the anhydrite specimens decrease while the porosity and plasticity characteristics *** example, after 120 cycles, the uniaxial compression strength and elastic modulus decrease by 46.54% and 60.16%, and the porosity increase by 75%. Combined with the evolution trend of stressstrain curves and the detected events, three stages were labeled to investigate the AE characteristics in freeze-thaw weathered anhydrite rock. It is found that with the increase of freeze-thaw cycles, the proportions of AE counts in stage Ⅰ and stage Ⅱ show a decaying exponential trend. Contrarily, the proportion of AE counts in stage Ⅲ displays an exponential ascending trend. Meanwhile, as the freeze-thaw cycles increase, the low-frequency AE signals increase while the intermediate-frequency AE signals decrease. After 120 cycles, the proportion of low-frequency AE signals increases by 168.95%, and the proportion of intermediate-frequency AE signals reduces by 81.14%. It is concluded that the microtensile cracking events occupy a dominant position during the loading process. With the increase of freeze-thaw cycles, the b value of samples *** 120 cycles, b value decreases by 27.2%, which means that the proportion of cracking events in rocks with small amplitude decreases. Finally, it is proposed that the freeze-thaw damage mechanism of anhydrite is also characterized by the water chemical softening effect.

关键词： Freeze-thaw cycles Anhydrite rock Physical and mechanical properties AE characteristics Damage mechanism

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Phase-Field Modeling of Hydrogen Diffusion and Trapping in Steels

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Acta Metallurgica Sinica(English Letters) 2021年第10期34卷 1421-1426页

作者： Jun zhang Jie Su Boning zhang Yi Zong Zhigang Yang chi zhang Hao Chen Key Laboratory for Advanced Materials of Ministry of Education School of Materials Science and EngineeringTsinghua UniversityBeijing 100084China china Iron and Steel Research Institute Beijing 100081China

Hydrogen embrittlement of steels is directly linked to hydrogen diffusion and trapping in the microstructure,which can hardly be precisely measured by modern experimental techniques.A phase-field model,in which a chemical potential well of hydrogen in the grain boundaries is introduced,is proposed to simulate hydrogen diffusion and trapping in the polycrystalline *** was interestingly found that grain boundaries,as connected trap sites,have a complex influence on the effective diffusivity of hydrogen,which are strongly linked to grain boundary diffusivity and binding energy.

关键词： Hydrogen embrittlement Diffusion Trapping Grain boundaries Phase-field model

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Variation in retained austenite content and mechanical properties of 0.2C–7Mn steel after intercritical annealing

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International Journal of Minerals,Metallurgy and Materials 2016年第2期23卷 161-167页

作者： Chuan Zhao chi zhang Wen-quan Cao Zhi-gang Yang School of Materials Science and Engineering Tsinghua University Institute for Structural Materials Central Iron and Steel Research Institute

The effects of annealing time and temperature on the retained austenite content and mechanical properties of 0.2C-7Mn steel were *** retained austenite content of 0.2C-7Mn steel was compared with that of 0.2C-5Mn *** is found that 0.2C-7Mn steel exhibits a similar variation trend of retained austenite content as 0.2C-5Mn ***,in detail,these trends are different.0.2C-7Mn steel contains approximately 7.5vol%retained austenite after austenitization and *** stability of the reversed austenite in 0.2C-7Mn steel is lower than that in 0.2C-5Mn steel;in contrast,the equilibrium reversed austenite fraction of 0.2C-7Mn steel is substantially greater than that of 0.2C-5Mn ***,the retained austenite content in 0.2C-7Mn steel reaches 53.1vol%.The tensile results show that long annealing time and high annealing temperature may not favor the enhancement of mechanical properties of 0.2C-7Mn *** effect of retained austenite on the tensile strength of the steel depends on the content of retained austenite;in contrast,the 0.2%yield strength linearly decreases with increasing retained austenite content.

关键词： manganese steel annealing austenite mechanical properties

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Influence of upstream solar wind on magnetic field distribution in the Martian nightside ionosphere

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Earth and Planetary Physics 2024年第5期8卷 728-741页

作者： JiaWei Gao ZhaoJin Rong Qi zhang Anna Mittelholz chi zhang Yong Wei Key Laboratory of Earth and Planetary Physics Institute of Geology and GeophysicsChinese Academy of SciencesBeijing 100029China College of Earth and Planetary Sciences University of Chinese Academy of SciencesBeijing 100049China Swedish Institute of Space Physics Kiruna SE-98128Sweden Department of Earth Sciences ETH ZurichZurich 8092Switzerland Center for Space Physics and Department of Astronomy Boston UniversityBostonMA 02215USA

Using over eight years of Mars Atmosphere and Volatile Evolutio N(MAVEN)data,from November 2014 to May 2023,we have investigated the Martian nightside ionospheric magnetic field distribution under the influence of upstream solar wind drivers,including the interplanetary magnetic field intensity(∣BIMF∣),solar wind dynamic pressure(PS W),solar extreme ultraviolet flux(EUV),and Martian seasons(L s).Our analysis reveals pronounced correlations between magnetic field residuals and both∣BIMF∣and PS *** observed with EUV flux and Ls were weaker—notably,magnetic field residuals increased during periods of high EUV flux and at Mars *** find that the IMF penetrates to an altitude of 200 km under a wide range of upstream conditions,penetrating notably deeper under high∣BIMF∣*** analysis also indicates that EUV flux and IMF cone angle have minimal impact on IMF penetration *** findings provide useful constraints on the dynamic nature of Martian atmospheric escape processes and their evolution,suggesting that historical solar wind conditions may have facilitated deeper IMF penetration and higher rates of ionospheric escape than are observed ***,by establishing criteria for magnetic‘quiet’conditions,this study offers new insights into the planet’s magnetic environment under varying solar wind influences,knowledge that should help refine models of the Martian crustal magnetic field.

关键词： Martian magnetic field external magnetic field upstream solar wind drivers IMF penetration altitude magnetic field activity indices

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