Heat flux from the catalyst layer of a fuel cell

We report exact solutions to the problem of heat transport in the catalyst layer (CL) of a fuel cell. The solutions are obtained for the low- and high-current regimes of CL operation. The approximate equation for the heat flux from the CL valid for the whole range of current densities is suggested. This equation is suitable for CFD calculations of heat transport in cells and stacks. Heat fluxes from the catalyst layers of PEMFC, HT-PEMFC and DMFC are discussed.     

The Annual Black Start Service Selection Analysis of ERCOT Grid

This paper evaluates ERCOT's existing annual Black Start service selection analysis and subsequently presents novel selection procedures. ERCOT procures Black Start resources annually through a competitive process. It selects and awards contracts to qualifying resources after completing a Black Start unit selection analysis, which selects a group of Black Start resources that meet a set of system selection criteria consisting of system reliability and minimum cost parameters. A current analysis methodology exists, but due to its inherent limitations, it is very labor intensive. Further analysis methodology development is performed to streamline the selection process, enable additional functions, reduce the manual intervention of personnel, and overall to improve the selection analysis. This paper analyzes the current Black Start automatic program analysis, and proposes new methodologies, programming improvements, and enhanced user ability.     

Gas Phase Initial Oxidation of Incoloy 800 Surfaces

The surface oxidation of Incoloy 800 was studied using dilute O₂ gas at temperatures of 300 °C. Samples with two differing grain sizes were studied using time-of flight secondary ion mass spectrometry (ToF–SIMS) and X-ray photoelectron spectroscopy (XPS) as primary analysis tools. A multi-layered oxide film was detected and was composed of an exterior gamma-Fe₂O₃ with a Cr₂O₃ layer at the oxide–metal interface also containing significant concentrations of NiCr₂O₄. Minor concentrations of another spinel oxide, NiFe₂O₄ were distributed throughout the film. The kinetics of oxidation growth was found to follow a direct logarithmic relationship for both grain sizes, suggesting that the oxide would be a suitably protective. Very small oxide nodules formed at later stages, particularly for the small grained samples. A protocol for assessment of XPS spectral envelopes is advanced. The method measures the percent residual intensities remaining after spectral subtraction of reference spectra and appears to be an effective means for screening of possible components.     

Mu and alpha EEG rhythms during the arrest reaction in microgravity

Mu and alpha oscillations (8–12 Hz) are the most prominent electroencephalographic rhythms observed in awake, relaxed subjects. Different cortical sources may participate in these oscillations and appear to be modulated by the sensorimotor context and functional demands. In microgravity, the marked reduction in multimodal graviceptive inputs to cortical networks participating in the representation of space could be expected to affect these spontaneous rhythms. Here, we report the results of an experiment conducted over the course of 3 space flights, in which we quantified the power of the mu and alpha rhythms in relation to the arrest reaction (i.e. in 2 distinct physiological states: eyes open and eyes closed). We observed that the power of the spontaneous mu and alpha rhythms recorded in the eyesclosed state in the sensorimotor areas (mu rhythm) and in the parieto-occipital cortex (alpha rhythm) increased in microgravity. The suppression coefficient produced by eye-opening/ closure state transition also increased in microgravity. These results are discussed in terms of current theories on the source and the physiological significance of these EEG rhythms.     

A scanning tunneling microscope that operates at high pressures and high temperatures (430 K) and during catalytic reactions

We describe the construction and operation of a scanning tunneling microscope (STM) designed in our laboratory that is contained in a reaction cell and allows operation throughout a wide range of pressures (ultra-high vacuum-atmospheric) and temperatures (300–425 K). This thermally compensated, double piezo tube design is entirely mechanically clamped. Samples are inertially translated and can be easily transferred in and out of the STM. With this microscope, we have investigated the stability of Pt(110) as a function of oxygen and hydrogen pressure and temperature.     

Vitamin C blocks inflammatory platelet-activating factor mimetics created by cigarette smoking

Cigarette smoking within minutes induces leukocyte adhesion to the vascular wall and formation of intravascular leukocyte-platelet aggregates. We find this is inhibited by platelet-activating factor (PAF) receptor antagonists, and correlates with the accumulation of PAF-like mediators in the blood of cigarette smoke-exposed hamsters. These mediators were PAF-like lipids, formed by nonenzymatic oxidative modification of existing phospholipids, that were distinct from biosynthetic PAF. These PAF-like lipids induced isolated human monocytes and platelets to aggregate, which greatly increased their secretion of IL-8 and macrophage inflammatory protein-1alpha. Both events were blocked by a PAF receptor antagonist. Similarly, blocking the PAF receptor in vivo blocked smoke-induced leukocyte aggregation and pavementing along the vascular wall. Dietary supplementation with the antioxidant vitamin C prevented the accumulation of PAF-like lipids, and it prevented cigarette smoke-induced leukocyte adhesion to the vascular wall and formation of leukocyte-platelet aggregates. This is the first in vivo demonstration of inflammatory phospholipid oxidation products and it suggests a molecular mechanism coupling cigarette smoke with rapid inflammatory changes. Inhibition of PAF-like lipid formation and their intravascular sequela by vitamin C suggests a simple dietary means to reduce smoking-related cardiovascular disease.     

Characterization of the influence of fabrication methods on microstructure failure

Single-crystal silicon microstructures, of identical design, exhibit different failure rates (following fabrication or mechanical shock testing) due to various processes. The microstructures fabricated with a boron diffusion and subsequent removal of the boron-diffused layer have a higher survival rate to the fabrication process and to mechanical shock. The survival rate (a survivor has an intact proof mass and beam) through the process is increased by 26.5%. At a 3680g shock, the boron-diffused devices have a 2.3% lower failure rate but the difference is not statistically significant. These results have been developed with wafer-level shock testing, which permits bulk testing of many samples in a cost-effective manner.