Zero Width Glass Cutting with CO 2 Laser
Laser cutting of glass in not a novel technique, excellent results have already been achieved by various research institutes. There are several patents concerned with controlled cutting of glass with zero width and other brittle materials in a straight line using CO2 laser beam. Laser beam glass cutting produces a high quality cut edge with minimal microcracking. This is achieved using a controlled cleaving of glass through a combination of heating and cooling. Laser separation of glass with zero width can be summarised by the following steps:
Laser separation of flat glass in electronic-, optic-, display-, and bio-industry (Invited Paper)
Up until now, conventional cutting methods by using metal or diamond wheels have been widely in use in numerous glass industries. Along with the market trend towards clean and more sophisticated process, constraints by the traditional methods have been unavoidable. Hence, laser separation is seen as an alternative and breakthrough solution to many and in this paper, an overview on laser separation as a whole is provided in terms of its process theories and its system as process equipment. Also glass application varieties as well as market requirements are discussed.
Human exposure to methylmercury from crayfish (Procambarus clarkii) in China
Methylmercury (MeHg) accumulation in aquatic food raises global concerns about human exposure to MeHg. Crayfish is the world’s third largest farmed crustacean species and a favorite aquatic food in many countries. However, human health hazard due to MeHg exposure via crayfish consumption is unclear, partly because appropriate survey data are lacking. We report on mercury concentrations and speciation in edible tail muscle of crayfish collected from restaurants in 23 Chinese cities. On average, MeHg constituted 99.1 % of mercury in tail muscle, and MeHg concentrations were comparable with those reported for fish in China. Variation in MeHg concentrations was not attributable to broad geographic region (i.e., provinces) or tail length. For different populations, potential health risk (characterized by hazard quotient or HQ) of MeHg exposure through crayfish consumption depended largely on crayfish consumption rates. In particular, a health hazard (HQ > 1) was found for high-rate consumers (i.e., 95 %ile or higher) in some cities in the middle and lower reaches of the Yangtze River (MLYR), during the peak consumption season. Our results suggest that more attention should be paid to dietary MeHg intake via crayfish consumption in China, particularly for communities with high consumption in MLYR.