Study on Mechanism of Formation of Volcanic Rock in North Altay by Using Rare Earths

The characteristics of rare earth elements in the Devonian and Carboniferous volcanic rocks were studied in the north Altay. And the mechanism of formation of volcanic rocks were discussed by using the rare earth elements. The correlativity of rare earth elements and major elements shows that the fractional crystallization is undistinguishable during the formation of Devonian and Carboniferous volcanic rocks, and the mechanism of formation of volcanic rocks may be the partial melting. The further study of the relationship of manifold rare earth elements shows that the mechanism of formation of Devonian and Carboniferous volcanic rocks in the north Altay is the partial melting. And the result also shows that the rare earth elements in the Devonian and Carboniferous volcanic rocks inherited the characteristics of those in its source materiels.

The natural basis of the formation of the dual-nuclei structural model

The dual-nuclei spatial structure is composed of a regional central city, a port city and their spat ial relations in certain regions. In general, this spatial structure c ould be found in most of the coastal regions or regions along big rivers. In terms of the mechanism, the dual-nuclei structure is the result of the s patial interaction and the complementary characteristics of the center city and the port city. The 'marginal function' of the port city and its relationship with the central city has long been discussed in th e literature. On the one hand, drainage area is the main natural geo graphical background of the formation of the dual-nuclei spatial structure; the refore, we can build a theoretical geographic structure that is based on the drainage area. On the other hand, vicissitude of the coastline al so has important influence on the formation of the dual-nuclei spatial structure. It is especially meaningful if we can notice this when w e examine deeply the research on the spatial structure of delta.

Temporal and spatial variations of the Huanghe River mouth bars

On the basis of the bathymetric records of 371 survey sections in the present Huanghe mouth area from 1996 to 2001, the temporal and spatial variations of the Huanghe mouth bars were studied by using GIS technology. The variation of the mouth bars is closely related to the water and sediment discharges from the Huanghe River to the sea that has been decreasing drastically in recent years, and to coastal hydrodynamic regimes. The characteristics of the mouth bars are unique in contrast with those of other estuaries in the world. (1) The mouth bars of the Huanghe River consist of many small sandbars. Usually the sandbars are of ellipse-shape with the long axis of about 1~6 km, and short axis of about 1~4 km. The long axis is parallel to the principal direction of tidal current, and the short axis is variable, depending on the local dynamics. The crest of the sandbars is only about 0.4 m below the water surface at low tide. They are distributed within an area of 20 km2, not far from the river mouth area. The present mouth bars are in small-medium size, quite different from the large one formed during the 1970s and 1980s, when the river sediment discharge was several times larger than that after 1996. (2) The scale of a river mouth bar is related to the river discharge of that year. In 1997 sediment discharge from the Huanghe River was 42 Mt, and the mouth bar consisted of several small scattered sandbars. In 1998 the size of mouth bars was much larger than that in 1997, as the sediment discharge from the Huanghe River increased to 363 Mt. Variation of the mouth bars largely depends on the sediment discharge with a correlation coefficient of 0.78. The calculation of the volume of the mouth bar area shows that about 30%~40% of the river's into-sea sediment is deposited in the mouth bar area. (3) Compared with other large estuaries in the world, the Huanghe mouth bars have three unique features in responding to its high sediment concentration: small size, steep slope gradient and shallow crest depth.

Surfactant-free synthesis of metallic bismuth spheres by microwave-assisted solvothermal approach as a function of the power level

In the present work, the synthesis of micro- and nano-sized spheres of metallic bismuth by microwave-assisted solvothermal method is reported. The synthesis method was carried out at different power levels and at a unique frequency of microwave irradiation. The sphere sizes were controlled by the microwave power level and the concentration of dissolved precursor. Structural and morphological characterization was performed by SEM, HRTEM, EELS and XRD. The results demonstrated that rhombohedral zero valent Bi spheres were synthesized after microwave radiation at 600 and 1200 W. However, if the power level is decreased to 120 W, a monoclinic phase of Bi203 is obtained with a flake-like morphology. In comparison with a conventional hydrothermal process, the microwave-assisted solvothermal approach provides many advantages such as shorter reaction time, optimum manipulation of morphologies and provides a specific chemical phase and avoids the mixture of structural phases and morphologies which is essential for further applications such as drug delivery or functionalization with organic materials, thanks to its biocompatibility.