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Showing papers by "Chinese Academy of Sciences published in 2000"


Journal ArticleDOI
TL;DR: In this paper, the authors collected monthly surface air temperature data from almost every meteorological station on the Tibetan Plateau (TP) since their establishment, and analyzed the temperature series to show that the main portion of the TP has experienced statistically significant warming since the mid-1950s, especially in winter, but the recent warming in the central and eastern TP did not reach the level of the 1940s warm period until the late 1990s.
Abstract: Adequate knowledge of climatic change over the Tibetan Plateau (TP) with an average elevation of more than 4000 m above sea level (a.s.l.) has been insufficient for a long time owing to the lack of sufficient observational data. In the present study, monthly surface air temperature data were collected from almost every meteorological station on the TP since their establishment. There are 97 stations located above 2000 m a.s.l. on the TP; the longest records at five stations began before the 1930s, but most records date from the mid-1950s. Analyses of the temperature series show that the main portion of the TP has experienced statistically significant warming since the mid-1950s, especially in winter, but the recent warming in the central and eastern TP did not reach the level of the 1940s warm period until the late 1990s. Compared with the Northern Hemisphere and the global average, the warming of the TP occurred early. The linear rates of temperature increase over the TP during the period 1955‐1996 are about 0.16°C:decade for the annual mean and 0.32°C:decade for the winter mean, which exceed those for the Northern Hemisphere and the same latitudinal zone in the same period. Furthermore, there is also a tendency for the warming trend to increase with the elevation in the TP and its surrounding areas. This suggests that the TP is one of the most sensitive areas to respond to global climate change. Copyright © 2000 Royal Meteorological Society.

1,532 citations


Journal ArticleDOI
TL;DR: In this article, the chemical state of oxygen, aluminum and zinc in Al-doped ZnO (ZAO) films was investigated by X-ray photoelectron spectroscopy (XPS), as well as the transition zone of the film-to-substrate, by auger electron spectrography (AES), showing that zinc remains mostly in the formal valence states of Zn2+.

1,180 citations


Journal ArticleDOI
06 Mar 2000-Talanta
TL;DR: Is a simple and reliable method for the dissolution of granite and the determination of 38 elements by inductively coupled plasma mass spectrometry, and the recoveries for most of these elements in granite ranged from 90 to 110%.

994 citations


Journal ArticleDOI
TL;DR: In this paper, ordered semiconductor ZnO nanowire arrays embedded in anodic alumina membranes (AAM) were fabricated by generating alumina templates with nanochannels, electrodepositing Zn in them, and then oxidizing the Zn nanowires arrays.
Abstract: Ordered semiconductor ZnO nanowire arrays embedded in anodic alumina membranes (AAM) were fabricated by generating alumina templates with nanochannels, electrodepositing Zn in them, and then oxidizing the Zn nanowire arrays. The polycrystalline ZnO nanowires with the diameters ranging from 15 to 90 nm were uniformly assembled into the hexagonally ordered nanochannels of the AAM. Photoluminescence (PL) measurements show a blue PL band in the wavelength range of 450–650 nm caused by the singly ionized oxygen vacancy in ZnO nanowires.

975 citations


Journal ArticleDOI
TL;DR: The history of the East Asian monsoon is an alternation between dominance by the dry-cold winter and warm-humid summer monsoons as mentioned in this paper, and high-resolution eolian sequences preserved in the Chinese Loess Plateau reveal evidence indicating that the pulsed uplift of the Tibetan Plateau at about 3.4 and 7.2 Ma may have played an important role in inducing climate change.

948 citations


Journal ArticleDOI
15 Sep 2000-Science
TL;DR: A high-resolution ice core record from Dasuopu, Tibet, reveals that this site is sensitive to fluctuations in the intensity of the South Asian Monsoon, and suggests a large-scale, plateau-wide 20th-century warming trend that appears to be amplified at higher elevations.
Abstract: A high-resolution ice core record from Dasuopu, Tibet, reveals that this site is sensitive to fluctuations in the intensity of the South Asian Monsoon. Reductions in monsoonal intensity are recorded by dust and chloride concentrations. The deeper, older sections of the Dasuopu cores suggest many other periods of drought in this region, but none have been of greater intensity than the greatest recorded drought, during 1790 to 1796 A.D. of the last millennium. The 20th century increase in anthropogenic activity in India and Nepal, upwind from this site, is recorded by a doubling of chloride concentrations and a fourfold increase in dust. Like other ice cores from the Tibetan Plateau, Dasuopu suggests a large-scale, plateau-wide 20th-century warming trend that appears to be amplified at higher elevations.

843 citations


Journal ArticleDOI
TL;DR: In this paper, a denoising method based on wavelet analysis is applied to feature extraction for mechanical vibration signals, which is an advanced version of the famous soft thresholding denoizing method proposed by Donoho and Johnstone.

823 citations


Journal ArticleDOI
TL;DR: The Global Soil Moisture Data Bank (GSOMoisture) as mentioned in this paper is a web site dedicated to collection, dissemination, and analysis of soil moisture data from around the globe.
Abstract: Soil moisture is an important variable in the climate system. Understanding and predicting variations of surface temperature, drought, and flood depend critically on knowledge of soil moisture variations, as do impacts of climate change and weather forecasting. An observational dataset of actual in situ measurements is crucial for climatological analysis, for model development and evaluation, and as ground truth for remote sensing. To that end, the Global Soil Moisture Data Bank, a Web site (http://climate.envsci.rutgers.edu/soil—moisture) dedicated to collection, dissemination, and analysis of soil moisture data from around the globe, is described. The data bank currently has soil moisture observations for over 600 stations from a large variety of global climates, including the former Soviet Union, China, Mongolia, India, and the United States. Most of the data are in situ gravimetric observations of soil moisture; all extend for at least 6 years and most for more than 15 years. Most of the stat...

821 citations


Journal ArticleDOI
25 Feb 2000-Science
TL;DR: Microstructure analysis suggests that the superplastic extensibility of the nc copper originates from a deformation mechanism dominated by grain boundary activities rather than lattice dislocation, which is also supported by tensile creep studies at room temperature.
Abstract: A bulk nanocrystalline (nc) pure copper with high purity and high density was synthesized by electrodeposition. An extreme extensibility (elongation exceeds 5000%) without a strain hardening effect was observed when the nc copper specimen was rolled at room temperature. Microstructure analysis suggests that the superplastic extensibility of the nc copper originates from a deformation mechanism dominated by grain boundary activities rather than lattice dislocation, which is also supported by tensile creep studies at room temperature. This behavior demonstrates new possibilities for scientific and technological advancements with nc materials.

712 citations


Journal ArticleDOI
TL;DR: The geologic framework of the Qinling orogen was built up through interplay of three blocks, the North China block (including the North Qinling), the South Qinling, and the South China block, separated by the Shangdan and Mianlue sutures as discussed by the authors.

710 citations


Journal ArticleDOI
TL;DR: In this article, problems and measures for the comprehensive control of soil and water loss in the Loess Plateau are proposed and a guide for the reconstruction of ecological and economic development in the region is provided.

Journal ArticleDOI
TL;DR: In this article, the authors reviewed the currents in the South China Sea (SCS) and the interaction between the SCS and its adjacent seas and reviewed the seasonal circulation characteristics of the SW currents.
Abstract: Researches on the currents in the South China Sea (SCS) and the interaction between the SCS and its adjacent seas are reviewed Overall seasonal circulation in the SCS is cyclonic in winter and anticyclonic in summer with a few stable eddies The seasonal circulation is mostly driven by monsoon winds, and is related to water exchange between the SCS and the East China Sea through the Taiwan Strait, and between the SCS and the Kuroshio through the Luzon Strait Seasonal characteristics of the South China Sea Warm Current in the northern SCS and the Kuroshio intrusion to the SCS are summarized in terms of the interaction between the SCS and its adjacent seas

Journal ArticleDOI
TL;DR: A compilation of reliable isotope age data indicates that Cretaceous magmatism in SE China occurred in four major episodes during 136-146 Ma, 122-129 Ma, 101-109 Ma and 87-97 Ma as discussed by the authors.

Journal ArticleDOI
TL;DR: The ultra fine nanosized TiO2 photocatalysts in anatase, rutile, and both phases were prepared by the hydrolysis of TiCl4 solution as discussed by the authors.
Abstract: The ultra fine nanosized TiO2 photocatalysts in the anatase, rutile, and both phases were prepared by the hydrolysis of TiCl4 solution The resulting materials have been characterized by HREM, XRD, BET and UV–VIS absorption spectroscopy The photoactivity, effective degradation, and the selectivity for complete mineralization of these catalysts were tested in the photocatalytic degradation of phenol For this reaction, the quantum-sized catalyst particles (4 nm) in the anatase phase shows the highest selectivity, the concentrations of p-benzoquinone and hydroquinol as the photocatalytic products were at very low level However, the selectivity of the quantum-sized crystallites in the rutile phase was not improved in comparison with that of catalysts which bandgap corresponding bulk rutile HREM micrographs show the quantum-sized catalysts were crystallized partially or many defects occurred on their crystal planes, they are responsible for their relative low photoactivity Calcination is an effective treatment to increase the photoactivity of nanosized TiO2 photocatalysts resulting from the improvement of crystallinity Mixtures of both phases exhibit higher photoactivity as well as effective degradation in comparison with pure anatase or rutile catalysts To the best of our knowledge, we are first to report that the quantum-sized TiO2 crystallite exhibit high selectivity for complete mineralization in the photocatalytic degradation of phenol solution

Journal ArticleDOI
TL;DR: In this paper, the authors conducted geochemical and Nd isotopic studies on both the basement rocks and Phanerozoic granites from the major tectonic terranes in northern Xinjiang: Altai, Junggar, Tianshan and North Tarim.

Journal ArticleDOI
07 Dec 2000-Nature
TL;DR: This is the first mature non-avian dinosaur to be found that is smaller than Archaeopteryx, and it eliminates the size disparity between the earliest birds and their closest non-Avian theropod relatives.
Abstract: Non-avian dinosaurs are mostly medium to large-sized animals, and to date all known mature specimens are larger than the most primitive bird, Archaeopteryx. Here we report on a new dromaeosaurid dinosaur, Microraptor zhaoianus gen. et sp. nov., from the Early Cretaceous Jiufotang Formation of Liaoning, China. This is the first mature non-avian dinosaur to be found that is smaller than Archaeopteryx, and it eliminates the size disparity between the earliest birds and their closest non-avian theropod relatives. The more bird-like teeth, the Rahonavis-like ischium and the small number of caudal vertebrae of Microraptor are unique among dromaeosaurids and improve our understanding of the morphological transition to birds. The nearly completely articulated foot shows features, such as distally positioned digit I, slender and recurved pedal claws, and elongated penultimate phalanges, that are comparable to those of arboreal birds. The discovery of these in non-avian theropods provides new insights for studying the palaeoecology of some bird-like theropod dinosaurs.

Journal ArticleDOI
12 Oct 2000-Nature
TL;DR: The observation of high concentrations of clinopyroxene, rutile and apatite exsolutions in garnet within eclogites from Yangkou in the Sulu UHP metamorphic belt, China is interpreted as resulting from the high-pressure formation of pyroxene solid solutions in subducted continental material.
Abstract: Determining the depth to which continental lithosphere can be subducted into the mantle at convergent plate boundaries is of importance for understanding the long-term growth of supercontinents as well as the dynamic processes that shape such margins. Recent discoveries of coesite and diamond in regional ultrahigh-pressure (UHP) metamorphic rocks has demonstrated that continental material can be subducted to depths of at least 120 km (ref. 1), and subduction to depths of 150-300 km has been inferred from garnet peridotites in orogenic UHP belts based on several indirect observations. But continental subduction to such depths is difficult to trace directly in natural UHP metamorphic crustal rocks by conventional mineralogical and petrological methods because of extensive late-stage recrystallization and the lack of a suitable pressure indicator. It has been predicted from experimental work, however, that solid-state dissolution of pyroxene should occur in garnet at depths greater than 150 km (refs 6-8). Here we report the observation of high concentrations of clinopyroxene, rutile and apatite exsolutions in garnet within eclogites from Yangkou in the Sulu UHP metamorphic belt, China. We interpret these data as resulting from the high-pressure formation of pyroxene solid solutions in subducted continental material. Appropriate conditions for the Na2O concentrations and octahedral silicon observed in these samples are met at depths greater than 200 km.

Journal ArticleDOI
TL;DR: In this paper, the toxicity of Se can be attributed to metabolic disturbances, in addition to its pro-oxidative effects, which can be explained by the changes in the total chlorophyll concentration.
Abstract: Selenium is an essential element for antioxidation reactions in human and animals. In order to study its biological role in higher plants, ryegrass (Lolium perenne) was cultivated in a soil without Se or amended with increasing dosages of H2SeO4 (0.1, 1.0, 10.0 and 30.0 mg Se kg−1). Ryegrass was harvested twice and the yields were analyzed for antioxidative systems and growth parameters. Selenium exerted dual effects: At low concentrations it acted as an antioxidant, inhibiting lipid peroxidation, whereas at higher concentrations, it was a pro-oxidant, enhancing the accumulation of lipid peroxidation products. The antioxidative effect was associated with an increase in glutathione peroxidase (GSH-Px) activity, but not with superoxide dismutase (SOD) and αα-tocopherol, which was the only tocopherol detected. In the second yield, the diminished lipid peroxidation due to a proper Se addition coincided with promoted plant growth. The oxidative stress found at the Se addition level ≥ 10 mg kg−1 resulted in drastic yield losses. This result indicates that the toxicity of Se can be attributed, in addition to metabolic disturbances, to its pro-oxidative effects. Neither the growth-promoting nor the toxic effect of Se could be explained by the changes in the total chlorophyll concentration.

Journal ArticleDOI
TL;DR: In this paper, a new compilation of heat flow data for the continental area of China has been constructed using both published data (up to 1999) as well as previously unpublished data.

Journal ArticleDOI
01 Mar 2000-Catena
TL;DR: In this paper, the effects of lichens on their mineral substrates can be attributed to both physical and chemical processes, such as hyphal penetration, expansion and contraction of lichen thallus, swelling action of the organic and inorganic salts originating from lichen activity.
Abstract: The evidence presented by numerous investigations of the interface between lichens and their rock substrates strongly suggests that the weathering of minerals can be accelerated by the growth of at least some lichen species. The effects of lichens on their mineral substrates can be attributed to both physical and chemical processes. The physical effects are reflected by the mechanical disruption of rocks caused by hyphal penetration, expansion and contraction of lichen thallus, swelling action of the organic and inorganic salts originating from lichen activity. Lichens also have significant impact in the chemical weathering of rocks by the excretion of various organic acids, particularly oxalic acid, which can effectively dissolve minerals and chelate metallic cations. As a result of the weathering induced by lichens, many rock-forming minerals exhibit extensive surface corrosion. The precipitation of poorly ordered iron oxides and amorphous alumino-silica gels, the neoformation of crystalline metal oxalates and secondary clay minerals have been frequently identified in a variety of rocks colonized by lichens in nature. For a better understanding of the impacts of lichens on environments, further work on the comprehensive involvement of the lichen effects on weathering of natural rocks, deterioration of building stones and stonework, and formation of primitive soils should be carried out.



Journal ArticleDOI
TL;DR: In this paper, the crystal structure and morphology of nanosized Si particles and wires after Li-insertion/extraction electrochemically have been studied by ex-situ XRD, Raman spectroscopy and electronic microscopy.

Journal ArticleDOI
Bojie Fu1, Liding Chen1, Keming Ma1, Huafeng Zhou1, Jun Wang1 
28 Feb 2000-Catena
TL;DR: In this article, the effects of land use changes on soil erosion and the distribution of soil nutrients and moisture were studied at the three spatial scales of total catchment, transect and land use type.
Abstract: Inappropriate land use is one of the main reasons for soil erosion and nutrient loss in the hilly loess area. In the Yangjuangou catchment, which has typical hill and gully topography, the effects of land use changes on soil erosion and the distribution of soil nutrients and moisture were studied at the three spatial scales of total catchment, transect and land use type. Between 1984 and 1996, forest and grassland increased by 36% and 5%, respectively, and slope farmland decreased by 43%. The land use changes decreased annual soil erosion by 24%. The amounts of total N, total P, available N, available P and organic matter of surface soil (0–20 cm) and of moisture in the 0–70 cm soil suggest that a farmland/grassland/forest land use structure from hill foot to hill top has a better capacity for soil conservation and retention of nutrients than other land use structures. The contents of soil nutrients are in the order forest>grassland>slope farmland, and those of soil water are forest

Journal ArticleDOI
TL;DR: In this article, a new technique was introduced to realize surface nanocrystallization (i.e., generation of a surface layer of nanostructures) on a 316L stainless steel by means of ultrasonic shot peening treatment.
Abstract: A new technique was introduced to realize surface nanocrystallization (i.e. generation of a surface layer of nanostructures) on a 316L stainless steel by means of ultrasonic shot peening treatment. The microstructural evolution of the 316L stainless steel was characterized by using X-ray diffraction, scanning electron microscopy and transmission electron microscopy. After the ultrasonic shot peening treatment, obvious grain refinement was observed and a nanocrystalline surface layer was found. The thickness of the nanocrystalline surface layer varies from a few to about 30 μm depending upon the treatment duration and the grain size increases from about 10 nm at the top surface layer, gradually to more than 100 nm at a depth of ≈30 μm. The nanocrystallization mechanism was analyzed in terms of the deformation behavior and TEM observations of the microstructural evolution of the treated samples.

Proceedings ArticleDOI
01 Sep 2000
TL;DR: A new system for personal identification based on iris patterns is presented, which employs the rich 2D information of the iris and is translation, rotation, and scale invariant.
Abstract: A new system for personal identification based on iris patterns is presented in this paper. It is composed of iris image acquisition, image preprocessing, feature extraction and classifier design. The algorithm for iris feature extraction is based on texture analysis using multichannel Gabor filtering and wavelet transform. Compared with existing methods, our method employs the rich 2D information of the iris and is translation, rotation, and scale invariant.

Journal ArticleDOI
Sishen Xie1, Wei Li1, Zhengwei Pan1, B. H. Chang1, Lianfeng Sun1 
TL;DR: In this paper, the aligned and very long carbon nanotubes were prepared by chemical vapor deposition (CVD) of hydrocarbon gas on various substrates, and properties such as tensile strength, Young's modulus, thermal conductivity and third-order optical nonlinearity were analyzed.

Journal ArticleDOI
01 Aug 2000-Geology
TL;DR: In this paper, a 45 km section near Yecheng in the western Kunlun Mountains of the northern Tibetan Plateau was investigated and the change from deposition on distal alluvial plains to proximal fans occurred during the Gilbert reversed chron (45-35 Ma) followed by an increase in sedimentation rate.
Abstract: Neogene redbeds passing upward into upward-coarsening conglomerate and debris-flow deposits at the foot of the Kunlun Mountains record the change in paleoslope related to uplift of the surface of the northern Tibetan Plateau Detailed magnetostratigraphy of a 45 km section near Yecheng in the western Kunlun Mountains shows that the change from deposition on distal alluvial plains to proximal alluvial fans occurred during the Gilbert reversed chron (45–35 Ma) The change in depositional facies was accompanied by an increase in sedimentation rate from an average ∼015 mm/yr between the earliest Oligocene and the earliest Pliocene to 14 mm/yr in the Gauss normal chron (36–26 Ma) We interpret the change in depositional facies and increase in sedimentation rate as indicating that the main uplift of the northwestern Tibetan Plateau began ca 45 Ma

Journal ArticleDOI
01 May 2000-Neuron
TL;DR: NRG suppressed induction of long-term potentiation in the hippocampal CA1 region without affecting basal synaptic transmission, suggesting that NRG signaling may be synaptic and regulated by PSD-95.

Journal ArticleDOI
03 Mar 2000-Science
TL;DR: Stone artifacts from the Bose basin, South China, imply that Acheulean-like tools in the mid-Pleistocene of South China imply that Mode 2 technical advances were manifested in East Asia contemporaneously with handaxe technology in Africa and western Eurasia.
Abstract: Stone artifacts from the Bose basin, South China, are associated with tektites dated to 803,000 ± 3000 years ago and represent the oldest known large cutting tools (LCTs) in East Asia Bose toolmaking is compatible with Mode 2 (Acheulean) technologies in Africa in its targeted manufacture and biased spatial distribution of LCTs, large-scale flaking, and high flake scar counts Acheulean-like tools in the mid-Pleistocene of South China imply that Mode 2 technical advances were manifested in East Asia contemporaneously with handaxe technology in Africa and western Eurasia Bose lithic technology is associated with a tektite airfall and forest burning