Insights into Nanoscale Electrochemical Reduction in a Memristive Oxide: the Role of Three‐Phase Boundaries

The nanoscale electro‐reduction in a memristive oxide is a highly relevant field for future non‐volatile memory materials. Photoemission electron microscopy is used to identify the conducting filaments and correlate them to structural features of the top electrode that indicate a critical role of the three phase boundary (electrode‐oxide‐ambient) for the electro‐chemical reduction. Based on simulated temperature profiles, the essential role of Joule heating through localized currents for electro‐reduction and morphology changes is demonstrated.     

Experimental measurements of fuel and water crossover in an active DMFC

This study measured polarization curves as well as the high-frequency resistance of active direct methanol fuel cell (DMFC) operates at around 80 °C with active controls of temperature, methanol concentration, airflow rate, and relative humidity. The relative humidity of the air did not have noticeable impacts on the fuel cell unless the operating temperature was near the evaporation temperature of water (100 °C). The hydrophobic water management layer (WML) between the membrane electrode assembly (MEA) and cathode air channel increases the mass transfer resistance and improves the water retention in MEA. Adding a WML increased the peak power density, decreased the ohmic resistance, and improved the fuel efficiency of the fuel cell, especially when it operated near 100 °C. This study also quantitatively measured methanol and water crossover as well as the fuel efficiency at different operating currents. The fuel efficiency increased significantly with the increase of the current density. Using a hydrophobic fuel management layer (FML) between the anode fuel channel and MEA reduced the fuel and water crossover rates and increased the ohmic resistance due to the decrease of the water content of the Nafion membrane. The FML improved fuel efficiency by reducing the methanol crossover. The combination of the FML and WML enabled the steady operation of DMFC using highly concentrated methanol solutions (up to 75 wt%).     

EFFECTS OF H/C RATIO AND MOLECULAR WEIGHT ON MICROCARBON RESIDUE OF VACUUM RESID SUB-FRACTIONS

Studies in the literature have reported correlations of Microcarbon Residue (MCR) either with hydrogen to carbon atomic ratio (H/C) or with the number average molecular weight (M_n). The MCR value can be an indication of die coke yield in a commercial coking process. In this work a single correlation of MCR widi both H/C and M_n has been presented. Vacuum residue distillation fractions from hydroprocessing experiments were separated into five sub-fractions by preparative scale gel permeation chromatography, and characterized in terms of H/C, M„and MCR. In accordance with other correlations it was confirmed that increasing the H/C atomic ratio will decrease coke formation (MCR)- In addition this work has shown that for identical H/C ratio, molecules with smaller M_n values will produce less coke than those with larger M_n; values.     

The ubiquitin-conjugating enzyme Pex4p of Hansenula polymorpha is required for efficient functioning of the PTS1 import machinery

We have cloned the Hansenula polymorpha PEX4 gene by functional complementation of a peroxisome-deficient mutant. The PEX4 translation product, Pex4p, is a member of the ubiquitin-conjugating enzyme family. In H.polymorpha, Pex4p is a constitutive, low abundance protein. Both the original mutant and the pex4 deletion strain (Deltapex4) showed a specific defect in import of peroxisomal matrix proteins containing a C-terminal targeting signal (PTS1) and of malate synthase, whose targeting signal is not yet known. Import of the PTS2 protein amine oxidase and the insertion of the peroxisomal membrane proteins Pex3p and Pex14p was not disturbed in Deltapex4 cells. The PTS1 protein import defect in Deltapex4 cells could be suppressed by overproduction of the PTS1 receptor, Pex5p, in a dose-response related manner. In such cells, Pex5p is localized in the cytosol and in peroxisomes. The peroxisome-bound Pex5p specifically accumulated at the inner surface of the peroxisomal membrane and thus differed from Pex5p in wild-type peroxisomes, which is localized throughout the matrix. We hypothesize that in H. polymorpha Pex4p plays an essential role for normal functioning of Pex5p, possibly in mediating recycling of Pex5p from the peroxisome to the cytosol.     

Performance monitoring in a confusing world: Error-related brain activity, judgments of response accuracy, and types of errors.

The error-related negativity (ERN) represents a neural response, recorded from scalp electrodes, that is associated with monitoring activities. It is most likely generated in the anterior cingulate cortex (ACC). Measures of the ERN, and of behavioral and perceived accuracy, were obtained from participants while they performed a visual 2-choice reaction time task under degraded stimulus conditions. Irrespective of behavioral accuracy, the amplitude of the ERN (measured at the time of the response) covaried with the perceived inaccuracy of the behavior (measured at the end of the trial). Errors due to premature responding (errors perceived as errors) were associated with large ERNs. Errors due to data limitations (errors about which there was uncertainty) were associated with smaller ERNs. These and other results are consistent with the proposal that performance monitoring, as manifested by the ERN, involves a comparison between representations of the appropriate response and the response actually made. (PsycINFO Database Record (c) 2010 APA, all rights reserved)