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Soil Macropore Structure Characterized by X-Ray Computed Tomography

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Pedosphere 2003年第4期13卷 289-298页

作者： FENGJie ZHANGJia-Bao ZHUAn-Ning BIJing-Wei InstituteofSoilScience theChineseAcademyofSciencesNanjing210008China CollegeofWaterResourcesandEnvironment HohaiUniversityNanjing2100g8China

Undisturbed soil core with many macropores and disturbed soil core with onlyone macropore (diameter is 10 mm) were probed by X-ray computed tomography (CT). The size, number,shape and continuity of macropores in the transverse and vertical sectionsof soil were characterizedusing CT scanning images. The probability densities of macropores in the transverse section of soilcore exhibited a logarithmic P distribution. Results indicated that CT scanning was a promisingnondestructive method for characterizing macropores in soils.

关键词： CT scanning distribution image macropores

Effect of CO_2 Concentration on Nitrogen Metabolism of Winter Wheat

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Agricultural Sciences in China 2005年第8期4卷 601-608页

作者： MEN Zhong-hua LI Sheng-xiu College of Resources and Environment Sciences Northwest A＆F University Yangling 712100 P.R.China College of Life Science Inner Mongolia University of Science and Technology Baotou 014030 P.R. China

Hoagland＇s solution was used as water culture medium to study the effect of CO2 concentration on nitrate metabolism of wheat under natural light and light-shaded conditions. NO3^-N, NH4^＋-N, nitrate reductase activity, total uptake N by wheat plants during solution cultural period and total N in plants were determined for comprehensive evaluation of the effect. Results showed that under both natural light and light-shaded conditions, addition of CO2 increased NO3^-N uptake and its assimilative capabilities by plants. However, there were some difference between shoots and roots. With increase of CO2 concentration, the concentration of NO3^-N and NH4^＋-N as well as nitrate reductase activity were all decreased for shoots while the difference was not so distinct in roots, and the nitrate reductase activity was not decreased, but increased. Since NO3^-N uptake by plants from the solution and the total N in plants were much higher by CO2 addition, it may be concluded that addition of CO2 has resulted in rise of nitrate absorption, assimilation and metabolism of wheat.

关键词： CO2 concentration Winter wheat Water culture Nitrogen metabolism

DNS and scaling law analysis of compressible turbulent channel flow

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Science China Mathematics 2001年第5期44卷 645-654页

作者：李新亮马延文傅德薰 LNM Institute of Mechanics Chinese Academy of Sciences Beijing China LHD Institute of Mechanics Chinese Academy of Sciences Beijing China

Fully developed compressible turbulent channel flow (Ma = 0.8, Re = 3300) is numerically simulated, and the data base of turbulence is established. The statistics such as density-weighted mean velocity and RMS velocity fluctuations in semi-local coordinates agree well with those from other DNS data. High order statistics (skewness and flatness factors) of velocity fluctuations of compressible turbulence are reported for the first time. Compressibility effects are also discussed. Pressure-dilatation absorbs part of the kinetic energy and makes the streaks of compressible channel flow more smooth. The scaling laws of compressible channel flow are also discussed. The conclusions are: (a) Scaling law is found in the center area of the channel, (b) In this area, ESS is also found, (c) When Mach number is not very high, compressibility has little effect on scaling exponents.

关键词： compressible turbulent flow direct numerical simulation high-order statistics scaling law streaks.

Ammonia Volatilization and Deriitrification Losses from an Irrigated Maize-Wheat Rotation Field in the North China Plain

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Pedosphere 2004年第4期14卷 533-540页

作者： ZHANGYu-Ming CHENDe-Li ZHANGJia-Bao R.EDIS HUChun-Sheng ZHUAn-Ning InstituteofGeneticsandDevelopmentalBiology ChineseAcademyofSciencesShijiazhuang050021（China） DepartmentofResourceManagementandHorticulture InstituteofLandandFoodResourcetheUniversityofMel-bourneParkville3052Victoria（Australia） InstituteofSoilScience ChineseAcademyofSciencesNanjing210008（China）

Ammonia (NH3) volatilization, denitrification loss, and nitrous oxide (N2O) emission were investigated from an irrigated wheat-maize rotation field on the North China Plain, and the magnitude of gaseous N loss from denitrification and NH3 volatilization was assessed. The micrometeorological gradient diffusion method in conjunction with a Bowen Ratio system was utilized to measure actual NH3 fluxes over a large area, while the acetylene inhibition technique (intact soil cores) was employed for measurement of denitrification losses and N2O emissions. Ammonia volatilization loss was 26.62% of the applied fertilizer nitrogen (N) under maize, while 0.90% and 15.55% were lost from the wheat field at sowing and topdressing, respectively. The differences in NH3 volatilization between different measurement events may be due to differences between the fertilization methods, and to differences in climatic conditions such as soil *** losses in the fertilized plots were 0.67%-2.87% and 0.31%-0.49% of the applied fertilizer N under maize and wheat after subtracting those of the controls, respectively. Nitrous oxide emissions in the fertilized plots were approximately 0.08%-0.41% and 0.26%-0.34% of the applied fertilizer N over the maize and wheat seasons after subtracting those of the controls, correspondingly. The fertilizer N losses due to NH3 volatilization were markedly higher than those through denitrification and nitrous oxide emissions. These results indicated that NH3 volatilization was an important N transformation in the crop-soil system and was likely to be the major cause of low efficiencies with N fertilizer in the study area. Denitrification was not a very important pathway of N fertilizer loss, but did result in important evolution of the greenhouse gas N2O and the effect of N2O emitted from agricultural fields on environment should not be overlooked.

关键词： ammonia volatilization denitrification gaseous N loss N_2O emission

Separation of Different Contributions to the Total X-ray Luminosity in Gamma-ray Loud Blazars

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Chinese Journal of Astronomy and Astrophysics 2005年第5期5卷 457-462页

作者： Jun-Hui Fan Gustavo E. Romero Yong-Xiang Wang Jiang-Shui Zhang Center for Astrophysics Guangzhou University Guangzhou 5104001 National Astronomical Observatories Chinese Academy of Sciences Beijing 100012 Instituto Argentino de Radioastronomfa C.C.5 （1894）- Villa Elisa Bs.As. Argentina College of Science and Trade Guangzhou University Guangzhou 511442

The relativistic beaming model has been successfully used to explain many of the observational properties of active galactic nuclei. In this model the total emission is formed by two components, one beamed, one unbeamed. However, the exact contribution from each component in unresolved sources is still not clear. In the radio band, the core and extended emissions are clearly separated. We adopt the method proposed by Kembhavi to separate the two contributions in the X-ray emissions in a sample of 19 gamma-ray loud blazars. It is clearly shown that the beamed emission dominates the X-ray flux and the unbeamed X-ray emission is correlated with the extended radio emission of the considered objects. We also find that the ratio of the beamed to the unbeamed X-ray luminosity is correlated with the X-ray spectral index, an effect that should be a consequence of the underlying X-ray emission mechanism.

关键词： galaxies: active-galaxies - jets - X-rays: galaxies

Multi-proxy evidence for Late Pleistocene-Holocene climatic and environmental changes in Lop-Nur,Xinjiang,Northwest China

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Chinese Journal Of Geochemistry 2008年第3期27卷 257-264页

作者： LUO Chao YANG Dong PENG Zicheng ZHANG Zhaofeng LIU Weiguo HE Jianfeng ZHOU Chenlin School of Earth and Space Science University of Science and Technology of China Hefei 230026 China State Key Laboratory of Loess and Quaternary Geology Institute of Earth Environment Chinese Academy of Sciences Xi＇an 710054 China Department of Geology University of lllinois-Urbana Champaign Urbana IL 61801 U.S.A. Illinois State Geological Survey 615 East Peabody Drive Champaign IL61820 U.S.A.

A 10.35-m-long sediment core from the Luobei depression in Lop-Nur,Xinjiang,Northwest China,provides detailed information about environmental changes during the Late *** samples taken every 5 cm of the core were analyzed for 10 environmental proxies,including magnetic susceptibility,granularity,chroma,carbonate and loss on ignition(LOI),and pH *** chronology data are provided by the uranium/thorium disequi-librium *** sediments of the section were deposited during the last 32000 *** results of analysis of 10 proxies were examined using multivariate statistical analysis,and the principal components were *** to the results,the Late Pleistocene sequence contains four climatic and environmental stages appearing in the cycles of cold-wet and warm-dry *** 10-9 ka BP,it was the earliest warm episode in the *** changes in this district were restricted by global change,as suggested by the analysis of glacial-interglacial *** it was different from the mutative trend of a monsoon region in East China because of its own characteristics,which was the situation of cold-wet and warm-dry climate-environment *** candidate reason may be the uplift of the Tibet Plateau and the westerly wind circulation.

关键词：更新世沉积物气候变化环境代理新疆

Quaternary biogenic opal records in the South China Sea: Linkages to East Asian monsoon, global ice volume and orbital forcing

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Science China Earth Sciences 2007年第5期50卷 710-724页

作者： WANG RuJian JIAN ZhiMin XIAO WenShen TIAN Jun LI JianRu CHEN RongHua ZHENG YuLong CHEN JianFang State Key Laboratory of Marine Geology Tongji University Shanghai 200092 China

Particulate fluxes investigated in the central South China Sea (SCS) during 1993―1996 indicate that opal flux can be used to show primary productivity change, which provides a foundation for tracing the evolutionary relationship between the surface productivity and East Asian monsoon in the SCS during the late Quaternary glacial and interglacial periods. Based on the studies of opal % and their mass accumulation rates (MAR) at the six sites recovered from the SCS during the “Resolution” ODP Leg 184 and “Sonne” 95 cruise of the Sino-Germany cooperation, opal % and their MARs increased evidently in the northern sites since 470―900 ka, and they enhanced and reduced, respectively, during the glacial and interglacial periods. Whereas they increased obviously in the southern sites since 420―450 ka, and they augmented and declined, respectively, during the interglacial and glacial periods. The vari- ability in opal % and their MARs in the late Quaternary glacial cyclicity indicate the “seesaw” pattern of surface productivity in the SCS. The winter monsoon intensified during the glacial periods, surface productivity increased and decreased, respectively, in the northern and southern SCS. The summer monsoon strengthened during the interglacial periods, surface productivity increased and decreased, respectively, in the southern and northern SCS. The cross spectral analyses between the opal % in the northern and southern SCS during the Quaternary and global ice volume (δ 18O) and orbital forcing (ETP) indicate that the East Asian winter and summer monsoons could be ascribed to the different drive mechanisms. On the orbital time scale, the global ice volume change could be a dominant factor for the winter monsoon intension and temporal variations. As compared with the winter monsoon, the correlative summer solar radiation with the obliquity and precession in the Northern Hemisphere could be a mostly controlling factor for the summer monsoon intension and temporal variations.

关键词： biogenic opal surface productivity East Asian monsoon global ice volume orbital forcing ODP Leg 184 Quaternary South China Sea

Preliminary Research on the Size Distribution of Aerosols in Beijing

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Advances in Atmospheric Sciences 2001年第2期18卷 225-230页

作者：张仁健王明星符建中 State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry Institute of Atmospheric Physics Chinese Academy of Sciences Beijing

Number concentration and size distribution of atmospheric aerosols were measured in Beijing by an optical particle counter. The relationship between aerosol size distribution and relative humidity is discussed. The results show that the size distribution, diurnal variation, daily variation of atmospheric aerosols have a good relation to relative humidity and Richardson number. Key words Atmospheric aerosol - Number concentration - Size distribution - Relative humidity - Richardson number This work is financially supported by nkbrsf project (G1999043400), Knowledge Creative project (8-2101 and 82303) founded by TAP, CAS.The authors would like to express their thanks to Prof. Zhang Wen for his work in this observation.

关键词： Atmospheric aerosol Number concentration Size distribution Relative humidity Richardson number

MEMBRANE POTENTIAL——A KEY PARAMETER OF AQUATIC MICROPLANKTON

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Chinese Journal of Oceanology and Limnology 2002年第S1期20卷 74-80页

作者：杨印杰焦念志 Ministry of Education Key Laboratory for Marine Environmental Sciences Center of Marine Environmental Science Xiamen University Xiamen 361005 China

Membrane potential is essential for the uptake of substance and physiological activityin cells; and is an indicator of cell viability and a criterion of aquatic environment. It is also applied toclassification of ecological populations. So membrane potential is a key parameter in studies on aquaticmicroplankton. It can be estimated by microelectrode, radioisotope method, spectro photomeny, flow cy-

关键词： membrane potential aquatic microplankton flow cytometry