Thermal Characterization of Fine Fibers Using an Improved Direct Electrical Heating Method

The transient electrothermal technique has been shown to be an important method for the thermal characterization of fine fibers. However, this study shows that the accuracy of this method hinges on the proper consideration of several sample parameters including the initial electrical resistance and the emissivity of the sample. Such consideration is verified through measurement of platinum samples with various lengths. A multi-level heating scheme is proposed to mitigate the high sensitivity to the initial sample electrical resistance resulting in a demonstrated precision uncertainty of \({<}3~\%\) . Using a recently expanded thermal model accounting for heretofore neglected heat losses, the emissivity of the sample may be measured simultaneously with thermal conductivity. The influence of the vacuum level is demonstrated by the results of measurements at two vacuum levels \({<}0.001\hbox { Pa}\) (diaphragm plus turbo pumps) and \({\sim } 2\hbox { Pa}\) (regular rotary vane pump). Neglecting these considerations can produce seemingly viable measurement results having significant bias error. Based on the characteristics of the expanded model, a new approach is presented that takes advantage of the simplicity of the reduced model, which neglects lateral heat losses from the sample, to obtain sample thermal properties that are independent of heat loss effects. Lastly, several experimental results validate the new model.     

Cloning and characterization of a novel upstream untranslated exon of the mouse Fgf-1 gene

Several recent studies have reported that there is an imbalance of increased oxidant status and decreased antioxidant system in women with preeclampsia and that factor might contribute to the pathogenesis of the disease. The following study examined blood levels of some of the antioxidants (glutathione, glutathione-peroxidase and -SH groups) as markers of lipid peroxidation in women with preeclampsia compared with normal gestation. Blood levels of these antioxidants were found significantly decreased in women with preeclampsia, which allowed us to speculate that there were abnormally increased levels of lipid peroxides. We believe that lipid peroxides are toxic compounds that damage endothelial cells, increase peripheral vasoconstriction and increase thromboxane synthesis and decrease prostacyclin synthesis. We consider that lipid peroxides are not the cause but the effect of oxidative stress induced by ischaemic placenta and leukocytes activation, so the contribute but not induce pathogenesis in preeclampsia.     

Principles for the safety evaluation of flavouring substances

This paper reviews efforts by various organizations to develop principles and procedures for the safety evaluation of flavouring substances. Critical factors considered in safety evaluation of these substances include their level of human intake, ease of metabolism to innocuous end-products and the margin of safety between no-observed-effect levels in animal studies and human intakes. These factors form the basis for the principles and criteria laid out in this paper.     

Accuracy-speed relationships of a robotic filament winding cell

Filament winding is a process in which tensioned resio-impregnated continuous fibers are placed on specified paths of a rotating mandrel to cover the entire surface thus forming a composite component. Traditionally, filament winding is carried out on multi-saris numerically controlled lathe-like machines. This paper describes the evaluation of a robot based filament winding cell consisting of an industrial robot (ASEA IRB 6/2) and an in-house fabricated mandrel drive mechanism, both being coordinated by a personal computer. As in many manufacturing processes, tradeoffs exist between accuracy and speed. The accuracy vs speed relationships of the robotic winding cell were experimentally determined for discrete, fine and medium movement modes while traversing a segmented delivery eye path for a cylindrical mandrel in three configurations (in-line, offset and angled with respect to the axis of rotation). The results show that the robot winding cell is appropriate for very accurate winding of fiber strands if the mandrel axis is concentric with the mandrel drive axis and the discrete mode (i.e. low speed) of the robot is used. For high speed wet winding all three configurations can be accurately wound in the discrete and fine modes.