Reactions of ethanol over CeO2 and Ru/CeO2 catalysts

The reaction of ethanol has been investigated on Ru/CeO2 in steady state conditions as well as with temperature programmed desorption (TPD). High resolution transmission electron microscopy (HRTEM) images indicated that the used catalyst contained Ru particles with a mean size of ca. 1.5 nm well dispersed on CeO2 (of about 12–15 nm in size). Surface uptake of ethanol was measured by changing exposure to ethanol followed by TPD. Saturation coverage is found to be between 0.25 and 0.33 of a monolayer for CeO2 that has been prior heated with O2 at 773 K. The main reactions of ethanol on CeO2 during TPD are: re-combinative desorption of ethanol; dehydrogenation to acetaldehyde; and dehydration to ethylene. The dehydration to ethylene occurs mainly in a small temperature window at about 700 K and it is attributed to ethoxides adsorbed on surface-oxygen defects. The presence of Ru considerably modified the reaction of ceria towards ethanol. It has switched the desorption products to CO, CO2, CH4 and H2. These latter products are typical reforming products. Ethanol steam reforming (ESR) conducted on Ru/CeO2 indicated that optimal reaction activity is at about 673 K above which CO2 production declines (together with that of H2) due to reverse water gas shift. This trend was well captured during ethanol TPD where CO2 desorbed about 50 K below than CO on both oxidized and reduced Ru/CeO2 catalysts.Peer ReviewedPostprint (author's final draft

Oxidation of Low Valent Sulphur Compounds with Lead Tetraacetate: Part II- Potentiometric Determination of Pb(IV) Acetate by Reduction with Thiosulphate or Metabisulphite

195-19

Incorporation of tic particulates on AISI 4340 low alloy steel surfaces via tungsten inert gas arc melting

Surface cladding utilizes a high energy input to deposit a layer on substrate surfaces providing protection against wear and corrosion. In this work, TiC particulates were incorporated by melting single tracks in powder preplaced onto AISI 4340 low alloy steel surfaces using a Tungsten Inert Gas (TIG) torch with a range of processing conditions. The effects of energy input and powder content on the melt geometry, microstructure and hardness were investigated. The highest energy input (1680 J/mm) under the TIG torch produced deeper (1.0 mm) and wider melt pools, associated with increased dilution, compared to that processed at the lowest energy (1008 J/mm). The melt microstructure contained partially melted TiC particulates associated with dendritic, cubic and globular type carbides precipitated upon solidification of TiC dissolved in the melt; TiC accumulated more near to the melt-matrix interface and at the track edges. Addition of 0.4, 0.5 and 1.0 mg/mm2 TiC gave hardness values in the resolidified melt pools between 750 to over 1100Hv, against a base hardness of 300 Hv; hardness values are higher in tracks processed with a greater TiC addition and reduced energy input

Highly acid-durable carbon coated Co3O4 nanoarrays as efficient oxygen evolution electrocatalysts

Most oxygen evolution reaction (OER) electrocatalysts are not stable in corrosive acids. Even the expensive RuO2 or IrO2, the most acid-resistant oxides, can be dissolved at an oxidative potential. Herein, we realize that the failures of OER catalysts are mostly caused by the weak interface between catalysts and the substrates. Hence, the study of the interface structure between catalysts and substrates is critical. In this work, we observe that the cheap OER catalysts Co3O4 can be more durable than the state-of-the-art RuO2 if the interface quality is good enough. The Co3O4 nanosheets deposited on carbon paper (Co3O4/CP) is prepared by electroplating of Co-species and followed by a two-step calcination process. The 1st step occurs in vacuum in order to maintain the surface integrity of the carbon paper and converts Co-species to Co(II)O. The 2nd step is a calcination in ambient conditions which enables the complete transformation of Co(II)O to Co3O4 without degrading the mechanical strength of the Co3O4-CP interface. Equally important, an in situ formation of a layer of amorphous carbon on top of Co3O4 further enhances the OER catalyst stability. Therefore, these key advances make the Co3O4 catalyst highly active toward the OER in 0.5 M H2SO4 with a small overpotential (370 mV), to reach 10 mA/cm2. The observed long lifetime for 86.8 h at a constant current density of 100 mA/cm2, is among the best of the reported in literature so far, even longer than the state-of-art RuO2 on CP. Overall, our study provides a new insight and methodology for the construction of a high-performance and high stability OER electrocatalysts in corrosive acidic environments

Comparing the Reaction Rates of Plasmonic (Gold) and Non-Plasmonic (Palladium) Metal Particles in Photocatalytic Hydrogen Production

Both Pd and Au metal particles are used in photocatalytic hydrogen generation. Yet while both act as electron sink only gold is poised to respond to visible light due to its plasmonic response. In order to quantitatively gauge their relative contribution into the reaction, the photocatalytic H2 production, from Au/TiO2 and Pd/TiO2 catalysts was studied under UV and UV–Vis light. While under UV light excitation, a weak dependence on the work function of the metal is observed, under UV–Vis light, Au is found to be twice more active than Pd. Under identical UV–Vis light irradiation, the turn over frequency calculated from XPS at.% is found to be 2.8 and 1.8 s−1 for Au and Pd, respectively. The effect is far more pronounced when the rates are normalized to the number of particles of each metal. Both the semiconductor TiO2 (UV light) and the plasmonic metal (visible light) need to be excited for the enhancement to occur; visible light alone causes a negligible reaction rate. Photocurrent measurements further confirmed the difference in the photocatalytic activity under UV and UV–Vis light excitation. Moreover, because of the presence of Au particles responding to visible light the reaction rate is enhanced due to “light penetration depth” effect

Oxidation of Low Valent Sulphur Compounds with Lead Tetraacetate: Part III- Determination of Tri- & Tetrathionates & the Redox Potential of Sulphate- Trithionate System

812-81

Wang Koch-adjusted axial length in SRK/T formula for ocular biometry in high myopia: a prospective study

Background: The aim of this study was to prospectively assess refractive results of cataract surgery in highly myopic eyes using the SRKT formula and Wang Koch-adjusted axial length. Material and methods: Prospectively, we recruited consecutive candidates for cataract surgery having an axial length equal to 27 mm and longer. We performed biometry by using Wang and Koch-adjusted axial length applied to the SRKT formula. The main outcome measures were: mean of refractive error, mean of absolute refractive error, and percentage of eyes that achieved a refractive error of ± 0.5D and ± 1D. Results: Fifteen eyes of nine patients were involved in the study. The mean refractive error was -0.01D ± 0.4D, and the mean absolute refractive error was + 0.35D ± 0.20D. Refractive errors of ± 0.5D and ± 1D were achieved, respectively, in 86.6% and in 100% of eyes. Conclusions: Wang Koch’s axial length adjustment applied to the SRKT formula is a reliable alternative in high myopic cataract patients

A Stable Integrated Photoelectrochemical Reactor for H₂ Production from Water Attains a Solar‐to‐Hydrogen Efficiency of 18 % at 15 Suns and 13 % at 207 Suns

The major challenge in solar water splitting to H_{2} and O_{2} is in making a stable and affordable system for large‐scale applications. We have designed, fabricated, and tested a photoelectrochemical reactor characterized as follows: 1) it comprises an integrated device to reduce the balance of the system cost, 2) it utilizes concentrated sunlight to reduce the photoabsorber cost, and 3) it employs and alkaline electrolyte to reduce catalyst cost and eliminate external thermal management needs. The system consists of an III‐V‐based photovoltaic cell integrated with Ni foil as an O_{2} evolution catalyst that also protects the cell from corrosion. At low light concentration, without the use of optical lenses, the solar‐to‐hydrogen (STH) efficiency was 18.3 %, while at high light concentration (up to 207 suns) with the use of optical lenses, the STH efficiency was 13 %. Catalytic tests conducted for over 100 hours at 100–200 suns showed no sign of degradation nor deviation from product stoichiometry (H_{2}/O_{2}=2). Further tests projected a system stability of years

THE Exchange Rate Determinants in Morocco: An Empirical Investigation

One of the most important instruments of economic policy of the opened countries is the exchange rate. It is considered both a mean of monetary regulation and a tool of outside competitiveness. Morocco plans to adopt the floating exchange rate regime, in the end of 2009. Indeed, the question which arises today is to know what type of floating exchange rate regime will be applied. Under the economic, technical and institutional factors, we ask if Morocco is ready and able to adopt this regime. In the light of this report, this paper will deal with the impact of the exchange rate policy on the real economy in Morocco through an empirical model called « The Behavioural Equilibrium Exchange Rate » supported by Clark and MacDonald (1997). Firstly, our investigation deals with the efficiency of exchange rate policy adopted by Morocco, secondly, it deals with the capacity of Dirham to resist to the shocks caused by the misalignments and finely, with the Moroccan monetary authorities’ capacity to manage the existing exchange regime. Under using the cointegration method, the error correction model and the analysis of the shocks by using the method of the decomposition of variance, our results confirm that the dynamics of the exchange rate in Morocco is determined by the variables such as the terms of trade, the foreign assets and the foreign debt. Similarly, in terms of short-term fluctuations in the exchange rate and in the analysis of the shocks, the supply and demand dynamics the dirham seems determining.Exchange Rate Policy; Exchange Rate regime; efficiency; shocks and misalignments; Cointegration Tests; Stability; Dirham.

Le kawal, un condiment a base de feuilles fermentees de senna obtusifolia: technologies et valeurs nutritionnelles

De nombreux aliments fermentés à base de légumes-feuilles sont consommés dans le monde, particulièrement en Afrique et en Asie. Ces aliments très répandus, représentent le régime de base en plus de leurs matières premières disponibles et constituent une part importante dans l’alimentation des populations locales. Le kawal obtenu par fermentation naturelle et alcaline des feuilles de Senna obtusifolia encore appelé Cassia obtusifolia, est un aliment très apprécié et largement consommé par les populations au Tchad et au Soudan. Les feuilles de S. obtusifolia occupent une place importante dans le système alimentaire de nombreuses communautés en Afrique. Elles sont riches en acides aminés essentiels et peuvent être considérées comme des produits d’intérêt nutritionnel de par leur valeur protéique. Le kawal contient des quantités appréciables de protéines et est utilisé comme substitut de viande et ou de poisson. Il est également riche en hydrates de carbone et en sels minéraux. La technologie de production du kawal reste traditionnelle avec des équipements rudimentaires et une fermentation incontrôlée. Cependant, cette technique de fermentation bien que traditionnelle permet l’élimination des facteurs antinutritionnels contenus dans les feuilles. Elle contribue aussi à l’amélioration de la valeur nutritionnelle et au développement de composés aromatiques tout en permettant d’augmenter la biodisponibilité des minéraux aboutissant ainsi à un produit qui permet de réduire les problèmes de carences en minéraux chez l’Homme. Les bactéries fermentaires du kawal, principalement celles des genres Bacillus et Lactobacillus du fait de leurs aptitudes probiotiques sont bénéfiques pour la santé humaine. La transformation de ce produit constitue un enjeu économique important en raison des revenus générés et contribue ainsi à la valorisation des ressources végétales et à la sécurité alimentaire des populations. Les technologies de la transformation du kawal n’étant pas bien maitrisées et variant d’une région à l’autre et ou d’une productrice à une autre il est donc indispensable de faire une synthèse sur les technologies de sa transformation et sa valeur nutritionnelle en vue de son amélioration.Mots clés: Kawal, feuilles fermentées, Senna obtusifolia, technologies, valeursnutritionnelle