International audiencePollen data from China for 6000 and 18,000 C-14 yr BP Were compiled and used to reconstruct palaeovegetation patterns, using complete taxon lists where possible and a biomization procedure that entailed the assignment of 645 pollen taxa to plant functional types. A set of 658 modern pollen samples spanning all biomes and regions provided a comprehensive test for this procedure and showed convincing agreement between reconstructed biomes and present natural vegetation types, both geographically and in terms of the elevation gradients in mountain regions of north-eastern and south-western China. The 6000 C-14 yr BP map confirms earlier studies in showing that the forest biomes in eastern China were systematically shifted northwards and extended westwards during the mid-Holocene. Tropical rain forest occurred on mainland China at sites characterized today by either tropical seasonal or broadleaved evergreen/warm mixed forest. Broadleaved evergreen/warm mixed forest occurred further north than today, and at higher elevation sites within the modern latitudinal range of this biome. The northern limit of temperate deciduous forest was shifted c. 800 km north relative to today. The 18,000 C-14 yr BP map shows that steppe and even desert vegetation extended to the modem coast of eastern China at the last glacial maximum, replacing today's temperate deciduous forest. Tropical forests were excluded from China and broadleaved evergreen/warm mixed forest had retreated to tropical latitudes, while taiga extended southwards to c. 43 degreesN

The history of the east Asian monsoon has been reconstructed from proxy records from the aeolian loess-palaeosol sequence in the Loess Plateau. It has been suggested that the monsoonal atmospheric circulation was initiated abruptly at 2.6 M yr BP. From about 1.2 M yrBP, the climate was characterized by contrasts between dry-cold periods brought on by the northwesterly monsoon and humid-warm periods brought about by the southeasterly monsoon. The periodic changes related to the earth’s orbital cycles have been clearly identified. Since about 0.6 M yr BP, the monsoonal climatic variations have become extremely pronounced and these correlate well with the marine isotope stages. The three-step shift in the east Asian monsoon towards greater variation seems to have been caused by the accelerated uplifting of the Tibetan Plateau. Climatic change during the last interglacial-glacial cycle recorded in the loess seems to match the SPECMAP δ18O record exactly. Six episodes of extremely strong dustfall events (brought on by the strengthened northwesterly monsoon winds) have been identified during the last glaciation. The ages of these episodes seem to match the Heinrich events in the North Atlantic and the Dansgaard-Oeschger events in Greenland. It is therefore suggested that the atmospheric circulation in east Asia is very sensitive to climatic change in high latitudes and has been responsive to global climatic change over the last 2.6 M yr. Millennial-scale climatic variations have also been identified in the Holocene loess. The article concludes by suggesting areas of research that might be undertaken in order to improve our understanding of the Chinese loess and of the evolution of the east Asian monsoon.

We report on the optical properties of ZnWO(4) planar waveguides created by ion implantation, and the effect annealing has on these structures. Planar optical waveguides in ZnWO(4) crystals are fabricated by 5.0 MeV carbon ion implantation with a fluence of 1 × 10(15) ions/cm(2) or 500 keV helium ion implantation with the a fluence of 1 × 10(16) ions/cm(2). The thermal stability was investigated by 60 minute annealing cycles at different temperatures ranging from 260°C to 550°C in air. The guided modes were measured by a model 2010 prism coupler at wavelengths of 633 nm and 1539 nm. The reflectivity calculation method (RCM) was applied to simulate the refractive index profile in these waveguides. The near-field light intensity profiles were measured using the end-face coupling method. The absorption spectra show that the implantation processes have almost no influence on the visible band absorption.

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13 ternary Cu-Mg-Si alloys were prepared by means of the powder metallurgy method. Phase equilibria at 500 and 700 o C of the Cu-Mg-Si system were determined using X-ray diffraction analysis (XRD). The existence of 3 ternary compounds in this system was verified: CuMgSi_Sigma (Cu 16 Mg 6 Si 7), Tau (Cu 3 Mg 2 Si), and Laves ((Cu 0.8 Si 0.2) 2 (Mg 0.88 Cu 0.12)). A thermodynamic modeling for the Cu-Mg-Si system was then conducted on the basis of the experimental data obtained in this work and those critically reviewed from the literature. The complex phase relationship between Laves phase and other phases has been successfully modeled in this work. Comparisons between the calculated and the measured phase diagrams show that most of the experimental data can be reproduced by the presently obtained thermodynamic parameters.