Plasma and electrode emissions from a 1 kW hydrogen-nitrogen arcjet thruster

Arc root behavior affects the energy transfer and nozzle erosion in an arcjet thruster. To investigate the development of arc root attachment in 1 kW class N2 and H2-N2 arcjet thrusters from the time of ignition to the stably working condition, a kinetic series of end-on view images of the nozzle obtained by a high-speed video camera was analyzed. The addition of hydrogen leads to higher arc voltage levels and the determining factor for the mode of arc root attachment was found to be the nozzle temperature. At lower nozzle temperatures, constricted type attachment with unstable motions of the arc root was observed, while a fully diffused and stable arc root was observed at elevated nozzle temperatures.

NADPH oxidase-mediated generation of reactive oxygen species: A new mechanism for X-ray-induced HeLa cell death

Oxidative damage is an important mechanism in X-ray-induced cell death. Radiolysis of water molecules is a source of reactive oxygen species (ROS) that contribute to X-ray-induced cell death. In this study, we showed by ROS detection and a cell survival assay that NADPH oxidase has a very important role in X-ray-induced cell death. Under X-ray irradiation, the upregulation of the expression of NADPH oxidase membrane Subunit gp91(phox) was dose-dependent. Meanwhile, the cytoplasmic subunit p47(phox) was translocated to the cell membrane and localized with p22(phox) and gp91(phox) to form reactive NADPH oxidase. Our data Suggest, for the first time, that NADPH oxidase-mediated generation of ROS is an important contributor to X-ray-induced cell death. This suggests a new target for combined gene transfer and radiotherapy.

Biphasic regulation of H2O2 on angiogenesis implicated NADPH oxidase

ROS (reactive oxygen species) take an important signalling role in angiogenesis. Although there are several ways to produce ROS in cells, multicomponent non-phagocytic NADPH oxidase is an important source of ROS that contribute to angiogenesis. In the present work, we examined the effects of H2O2 on angiogenesis including proliferation and migration in HUVECs (human umbilical vein endothelial cells), new vessel formation in chicken embryo CAM (chorioallantoic membrane) and endothelial cell apoptosis, which is closely related to anti-angiogenesis. Our results showed that H2O2 dose-dependently increased the generation of O-2(-) (superoxide anion) in HUVECs, which was suppressed by DPI (diphenylene iodonium) and APO (apocynin), two inhibitors of NADPH oxidase. H2O2 at low concentrations (10 mu M) stimulated cell proliferation and migration, but at higher concentrations, inhibited both. Similarly, H2O2 at 4 nmol/cm(2) strongly induced new vessel formation in CAM, while it suppressed at high concentrations (higher than 4 nmol/cm(2)). Also, H2O2 (200 similar to 500 mu M) could stimulate apoptosis in HUVECs. All the effects of H2O2 on angiogenesis could be suppressed by NADPH oxidase inhibitors, which suggests that NADPH oxidase acts downstream of H2O2 to produce O-2(-) and then to regulate angiogenesis. In summary, our results suggest that H2O2 as well as O-2(-) mediated by NADPH oxidase have biphasic effects on angiogenesis in vitro and in vivo.

Composite electrode for unitized regenerative proton exchange membrane fuel cell with improved cycle life

To improve the cycle life of unitized regenerative fuel cells (URFCs), an electrode with a composite structure has been developed. The cycle life and polarization curves for both fuel cell and electrolysis modes of URFC operation were investigated. The cycle life of URFCs was improved considerably and the performance was fairly constant during 25 cycles, which illustrates that the composite electrode is effective in sustaining the cyclic performance of URFCs. It shows the URFCs with such an electrode structure are promising for practical applications. (C) 2004 The Electrochemical Society.

The study on a PVC membrane electrode for gemfibrozil

In this paper, a poly(vinyl chloride) (PVC) membrane electrode is prepared for gemfibrozil, 2, 2-dimethyl-5(2,5-xylyloxy) valeric acid, based on its ion pair complexes with hexadecyltrioctyl ammonium iodide (HTOA). The membrane composition of the electrode was optimized by using the sequential level elimination method for orthogonal experimental design. The electrode has a Nernstian response range from 2.5 X 10(-5) to 0.1 mol/l with an average slope of 55.3 mV/decade. The limit of detection is 7.1 X 10(-6) mol/l. The electrode responses were not affected by pH in the range 10.0-12.3. A Na2B4O7-Na2CO3 buffer of pH = 11.0 was selected as the background electrolyte solution for potentiometric measurements. The electrode was used for determining gemfibrozil in pharmaceutical preparations with satisfactory results.

Calibration of a solid-state copper ion-selective electrode in cupric ion buffers containing chloride

It is shown that near-Nernstian calibration slopes can be obtained with a Cu1.8Se electrode in a range of cupric ion buffers in spite of a high chloride content. Best results are obtained with the ligands ethylenediamine, glycine and histidine. The onset of cupric ion toxicity towards marine organisms falls within the pCu calibration range obtained with glycine, and the Cu1.8Se electrode could, therefore, be useful for monitoring cupric ion activity in bioassays in sea-water media.