The purpose of this study was to determine the effect of the dietary antioxidant vitamin E on hepatocarcinogenesis by peroxisome proliferators which, it is hypothesized, induce tumors by increased ...production of hydrogen peroxide or other oxygen radicals. Rats were fed diets containing the peroxisome proliferator ciprofibrate and one of three concentrations (10, 50, or 500 ppm) of alpha-tocopheryl acetate for 6 months or 21 months. The incidence of hepatic tumors and the number and volume of gamma-glutamyl-transpeptidase-positive, ATPase-negative, glucose-6-phosphatase-negative, and glucose-6-phosphatase-positive foci were quantified. No tumors or altered hepatic foci were seen at 6 months, but at 21 months the incidence of hepatic tumors and the number and volume of altered hepatic foci were increased in rats fed higher levels of vitamin E. Indices of oxidative damage--concentrations of malonaldehyde, conjugated dienes, and lipid-soluble fluorescence products--were not affected or were lower in rats fed higher amounts of vitamin E; the enhancing effect of vitamin E on the development of altered hepatic foci and hepatic tumors, therefore, was not related to the induction of cellular oxidative damage. Hepatic peroxisomal fatty acid beta-oxidation and vitamin C concentrations were not affected by vitamin E, whereas the glutathione concentration was decreased in rats fed higher amounts of vitamin E. This study shows that increasing the vitamin E content of the diet enhances ciprofibrate-induced hepatocarcinogenesis, but the mechanism of this effect is unclear.
We have demonstrated multi-walled carbon nanotube (MWCNTs) based sensors, which are capable of detecting alcohol vapor with ultra-low power. We fabricated the Si-substrate sensors using an AC ...electrophoretic technique so as to form bundled MWCNTs sensing elements between Au microelectrodes. The I-V measurement illustrates that we can activate the sensors at the Ohmic region of the sensors (at 10 muA), which is without any overheat effect. The sensors only need an ultra-low power (~1 muW) to detect the alcohol vapor. They exhibit fast, reversible and repeatable response. We have tested the response of the sensors with alcohol concentrations from 10 ppth to 400 ppth (ppth = parts per thousand). Our result shows that there is a linear relation between the resistance of the sensors and alcohol concentration. Also, we can easily reverse the sensor to the initial reference resistance by annealing them at 100-250 muA current within 6 minutes. Moreover, the sensors are selective with respect to flow from air, water vapor, and alcohol vapor. Finally, we have also studied how the temperature of the sensors affects their response towards alcohol vapor. The result shows that the performance of the sensors will deteriorate as the temperature of the sensors increase. Also, the cooling effect of the vapor is not a dominating factor in determining the response of the sensor. Based on our experiments, we prove the feasibility of turning the MWCNTs sensors into a commercialized alcohol sensor with ultra-low power requirements
We have successfully chemically functionalized the multi-walled carbon nanotubes (MWCNTs) with COOH group by the method of oxidation and used AC electrophoresis to formed these bundles MWCNTs between ...Au electrodes on the Si substrate. We then demonstrated that these resistive elements are capable of detecting alcohol vapor using an ultra-low input power of only ∼0.01μW. The sensors exhibit fast, repeatable, highly sensitive, and reversible response. Our results show that the resistances of the sensors vary linearly with alcohol vapor concentration from 5ppth to 100ppth (ppth = part per thousand). We can also easily reverse the initial resistance of the sensors by annealing them in real time at 100-250μA current within 1-6 minutes. We have experimental proof that the functionalized MWCNTs have a much higher sensitivity towards the alcohol vapor than the bare MWCNTs. Based on our experimental results, we prove that MWCNTs sensors, especially for those with proper functionalized groups, are sensitive to a wide range of alcohol vapor and potentially other volatile organic compounds, and are very attractive for commercialization due to their extreme low-power requirements for activation.
