Search

In the Western China, soft rocks, in particular, phyllites are very widespread. With the increase of soft rock tunnels in recent years, the secondary lining cracking of newly-built tunnels have fre...

A complete diagonalization energy matrix method (CDM) is proposed for 3d 8 ions in orthorhombic site (D 2 h ) symmetry. As an application, the optical spectra of XF2 : Ni2+ (X = Mg, Zn) is well explained on the basis of both the CDM and the semi-self-consistent field d-orbital (semi-SCF d-orbital) theory. In addition, by establishing the relationship between the optical spectra and local structure, it has been possible to calculate the crystal structure parameters for XF2:Ni2+ from optical measurements on Ni2+ ions. The theoretical results are in good agreement with experimental findings.

Optimizing endothelial cell growth and adhesion on the surface of metallic stents implanted in the vascular system is a fundamental issue in understanding and improving their long-term biocompatibility. The ability of the endothelial cell to attach and adhere to the luminal stent surface as well as the capacity to withstand the significant shear stress associated with blood flow are important determinants. The adhesive characteristics of human umbilical vein endothelial cellsectin (HUVEC) on stent surfaces coated with either Poly-L-Lysine (PLL) or fibron (FN) were compared with uncoated controls. Increasing concentrations of PLL and FN were measured using a micropipette aspiration system. The adhesivenamic properties of HUVECs under static flow conditions were compared to a dy environment on endovascular stents using a parallel-plate-flow chamber. A scanning electron microscope picture was used to measure the number and the adhesive cell ratio as well as the percentage of surface coverage of stent by endothelial cells. The adhesive forces of HUVECs on foreign surfaces coated with PLL and FN were higher compared to uncoated surfaces, and were dependent on incr ing concentrations. These coatings resulted in significant increase of the adhesive force of HUVECs. The influence of substrates on the adhesion of the endothelial cell monolayer under static or dynamic flow conditions was highly significant compared with controls (p

The growth of 174 infants from Hong Kong and 221 infants from Guangzhou from birth to 2 years were compared. Ethnic origins, parental size, and birth weights were similar. Common illnesses in the two groups were upper respiratory tract infection and diarrhoea. The early infant feeding practices were different, with more breastfeeding and earlier introduction of solids in Guangzhou. Compared to those of Hong Kong, Guangzhou babies had lower weight for length in the first year of life. Within the Guangzhou group, babies totally breastfed for the first 2-4 months were heavier than those given rice cereals as supplement and they had less diarrhoea in the first 6 months. Hong Kong infants suffered more diarrhoea than the Guangzhou group. It was concluded that breastfeeding should be promoted and supported in these two cities.

Carbon nanorods and graphene-like nanosheets are catalytically synthesized in a hot filament chemical vapor deposition system with and without plasma enhancement, with gold used as a catalyst. The morphological and structural properties of the carbon nanorods and nanosheets are investigated by field-emission scanning electron microscopy, transmission electron microscopy and micro-Raman spectroscopy. It is found that carbon nanorods are formed when a CH4 + H2 + N2 plasma is present while carbon nanosheets are formed in a methane environment without a plasma. The formation of carbon nanorods and carbon nanosheets are analyzed. The results suggest that the formation of carbon nanorods is primarily a precipitation process while the formation of carbon nanosheets is a complex process involving surface-catalysis, surface diffusion and precipitation influenced by the Gibbs–Thomson effect. The electron field emission properties of the carbon nanorods and graphene-like nanosheets are measured under high-vacuum; it is found that the carbon nanosheets have a lower field emission turn-on than the carbon nanorods. These results are important to improve the understanding of formation mechanisms of carbon nanomaterials and contribute to eventual applications of these structures in nanodevices.