Increasing the activity of Fe/N/C catalysts in PEM fuel cell cathodes using carbon blacks with a high-disordered carbon content

Fe/N/C catalysts for the reduction of oxygen in PEM fuel cells were prepared by pyrolyzing three series of iron acetate-impregnated developmental carbon blacks at 950 °C. The carbon supports used were derived from the N234, N330, and N650 commercial furnace grades. In this study, we tried to increase the performance of Fe/N/C-based cathode of PEM fuel cells by using the following two approaches: (1) increasing the number of catalytic sites on the carbon black either by optimizing the structural parameters of the pristine carbon supports or by increasing the initial metal content above 0.2 wt% Fe on the carbon support; (2) increasing the catalyst loading in the cathodic layer of a PEM fuel cell. For (1), we show, on the one hand, that optimizing the structural parameters of the pristine carbon support, in order to increase the number of catalytic sites, has its limits and that these limits have been reached for the present synthesis method of Fe/N/C catalysts. On the other hand, increasing the initial metal content above 0.2 wt% Fe leads to a decrease in catalytic activity. For (2), it is shown that increasing the catalyst loading per cm² of cathode well improves the performance of a cathode based on Fe/N/C catalysts in the kinetic region of the polarization curve. At lower potentials, a large improvement in the performance of these non-precious metal cathodes would occur if the mass transport properties in these electrodes were significantly increased.     

Sorption and degradation of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine in soil

The sorption/desorption and long-term fate of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) was examined using sterilized and nonsterilized soils. Two soils were used that differ mainly by the amount of total organic carbon (TOC): an agricultural topsoil (VT, 8.4% TOC) and a sandy soil (SSL, 0.33% TOC). The adsorption isotherms performed at room temperature were well-described by a linear model, which led to sorption distribution coefficients of 2.5 and 0.7 L kg(-1) for VT and SSL soils, respectively. The organic content of soil did not significantly affect HMX sorption. Over a period of 20 weeks, HMX degraded (60% disappearance) in static anaerobic nonsterile VT soil preparations. In separate experiments using UL-[14C]-HMX, 19% mineralization (liberated 14CO2) was obtained in 30 weeks. In addition, four nitroso derivatives of HMX were detected. Knowing the sorption/desorption behavior and the long-term fate of HMX in soil will help assess the effectiveness of natural attenuation for HMX removal.     

pH-Dependent behaviour of soluble protein aggregates formed during heat-treatment of milk at pH 6.5 or 7.2

The pH-dependent behaviour of soluble protein aggregates produced by the pre-heating of reconstituted skim milk at 90 degrees C for 10 min was studied, in order to understand the role of these aggregates in acid gelation of heated milk. The following milk samples were prepared: (1) control (unheated reconstituted milk, pH 6.5); (2) milk heat-treated at pH 6.5 (mHtd6.5) and (3) milk heat-treated at pH 7.2 (mHtd7.2). They were centrifuged and the supernatants (SPNT 1) pH-adjusted to yield a series of pH values ranging from 6.5 or 7.2 to 4.6 using HCl at 20 degrees C or GDL at 20 and 38 degrees C. pH-Adjusted SPNTs 1 were re-centrifuged. The resulting supernatants (SPNTs 2) were analysed by OD (at 600 and 280 nm) and SDS-PAGE in order to characterise proteins still soluble as a function of pH. Particle size in SPNTs 1 was analysed by Steric Exclusion Chromatography. The OD600 nm revealed that during acidification soluble casein in both control and heat-treated samples exhibits variations in its optical properties or size as previously shown with micellar casein. In heat-treated samples, soluble casein and heat-induced covalent soluble aggregates precipitate at the same pH value. A progressive acidification of the soluble phase did not separate them. Increasing the temperature of acidification from 20 to 38 degrees C resulted in an increase in the precipitation pH of the proteins. However choice of acidifier did not have a significant effect on OD profiles. The soluble covalent aggregates from mHtd7.2 were smaller, more numerous, and had a higher content of kappa-casein than mHtd6.5. Both types of aggregates began to precipitate at the same pH value but precipitation occurred over a narrower pH-range for soluble aggregates prepared from mHtd7.2. This may explain the higher gelation pH of mHtd7.2 compared with mHtd6.5.     

Binding Specificity of Recombinant Odorant-Binding Protein Isoforms is Driven by Phosphorylation

Native porcine odorant-binding protein (OBP) bears eleven sites of phosphorylation, which are not always occupied in the molecular population, suggesting that different isoforms could co-exist in animal tissues. As phosphorylation is a dynamic process resulting in temporary conformational changes that regulate the function of target proteins, we investigated the possibility that OBP isoforms could display different binding affinities to biologically relevant ligands. The availability of recombinant proteins is of particular interest for the study of protein/ligand structure-function relationships, but prokaryotic expression systems do not perform eukaryotic post-translational modifications. To investigate the role of phosphorylation in the binding capacities of OBP isoforms, we produced recombinant porcine OBP in two eukaryotic systems, the yeast, Pichia pastoris, and the mammalian CHO cell line. Isoforms were separated by anion exchange HPLC, and their phosphorylation sites were mapped by MALDI-TOF mass spectrometry and compared to those of the native protein. Binding experiments with ligands of biological relevance in the pig, Sus scrofa, were performed by fluorescence spectroscopy on two isoforms of recombinant OBP expressed in the yeast. The two isoforms, differing only by their phosphorylation pattern, displayed different binding properties, suggesting that binding specificity is driven by phosphorylation.     

猫眼观市 主板行情

AMD即将收购ATi的传闻无疑是近期最大的业界新闻，不过此时带来的影响或许并不在显卡业界，因为nVIDIA和ATi的对抗还是会按部就班地进行，反倒是nVIDIA面对芯片组市场的态度可能发生巨大的变化。由于ATi也有芯片组部门，因此未来nVIDIA很可能适当减少对AMD平台的投入．[编者按]     

Windloader KBS - from prototype to the market

The Australian Standard, Minimum Design Loads on Structures: Part 2-Wind Loads (AS 1170.2) has been extensively revised, and many comments made during the public revision have been incorporated. The text has also been represented in a rule-based form using expert systems techniques, providing further input to the SAA Committee work by checking for logical inconsistencies and, in addition, using graphical input to enhance use of the Code and to avoid input errors. The paper will show how AS 11 70.2 (hereafter called the Wind Code) has been transferred into knowledge-based form, pointing out some of the problems that have been encountered and are likely to occur during any similar process:

• A Code text written for manual use will, in general, not be as well organized, complete and logically consistent as a computer software version requires to avoid failure.

• The computer version of the document must be understood by the experts to make validation of the knowledge base possible.

• Only very expensive commercial expert system shells give sufficient support for table handling and advanced mathematics. This has now been overcome by the development of C functions in the CSIRO BX-shell and subsequently ported into the CRYSTAL shell.

• Explanation facilities in the form of pictures, text and line of reasoning have to please both experts and end users.

• A ‘fast track’ for experienced users has to be provided to avoid wasting time with unnecessary questions.

The present version of WINDLOADER, written originally in the CSIRO BX-shell has now been ported to the CRYSTAL (IBM PC-based) shell and also partly to an object-oriented version under the NEXPERT OBJECT shell, interfaced to Hyper-card on a colour Mac II.     

Indigenous Measures of Personality Assessment in Asian Countries: A Review.

This article reviews attempts to develop multidimensional personality measures in Asia and their applications in clinical assessment. Indigenous personality assessment measures in India, Korea, Japan, the Philippines, and Taiwan are examined. These early attempts have not yielded a comprehensive personality measure that integrates a theoretical framework and an empirical program of validation. The Chinese Personality Assessment Inventory (CPAI) is cited as an example to illustrate the process of developing an indigenous measure that meets the testing standards of established assessment instruments. On the basis of the research findings from the CPAI, the authors discuss the relevance of indigenous measures in clinical assessment in native cultures as well as in informing mainstream personality assessment. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Oxidation of steels in liquid lead bismuth: Oxygen control to achieve efficient corrosion protection

Hybrid systems dedicated to waste transmutation are constituted of an accelerator generating a high energy proton flux, a spallation target on which the accelerated proton beam impinges to produce neutrons and a subcritical core. The Pb-Bi eutectic liquid alloy is considered as spallation target material due to its suitable nuclear and physical properties.However, liquid metals can be corrosive towards containment materials (austenitic and Fe9Cr alloys). In the case of liquid lead bismuth alloy, one of the protection means considered against the dissolution of the steels is the in situ protection by the formation of an oxide layer at the steels’ surface.However, in order to ensure the efficient protection of the steels by an oxide layer, the control and the monitoring of the oxygen content in the Pb-Bi alloy is a major issue. The paper recalls, first, the oxygen chemistry in a lead alloy system, in order to propose the oxygen operating window that complies with both the contamination by lead oxide of the coolant and the corrosion control by the promotion of an oxide film on the structure. Results of tests performed in stagnant lead bismuth at high oxygen concentrations are also presented showing the effect of various operating parameters on the oxidation kinetics and on the nature of the oxide layer. An oxidation mechanism and model are also proposed and compared with experimental data.