On the Surface Nature of Bimetallic PdZn Particles Supported on a ZnO–CeO<Subscript>2</Subscript> Nanocomposite for the Methanol Steam Reforming Reaction

CO adsorption—as a molecular probe—was studied by transmission IR spectroscopy on pre-reduced Pd and bimetallic PdZn nanoparticles. Palladium was supported (2 wt% Pd) on pure CeO₂, ZnO and a ZnO–CeO₂ composite (atomic ratio Zn:Ce?=?1:2). The Pd 3d_5/2 binding energy shift, together with the formation of metallic zinc were consistent with the development of a PdZn alloy over the zinc-containing supports at increasing reduction temperature, as revealed by XPS. Following H₂ reduction at 623 K the bimetallic particles showed only linear CO adsorption (CO_L) at initial contact time (10 Torr CO, 298 K), giving rise to a convoluted IR band ascribed to different Pd sites, where it was assumed that the Pd–Pd distances were larger than for pure Pd crystallites, indicating the presence of a PdZn alloyed surface. However, for longer exposure time to CO and/or higher superimposed pressure, the appearance of bridge and hollow coordinated CO (CO_B and CO_H, respectively) on the Pd sites suggested the degradation of the PdZn surface alloy, most likely due to the segregation of Pd surface patches. The temperature-programmed, dynamic isobaric adsorption of CO (TPA-CO), under flowing CO(1%)/He on the catalysts pre-reduced at 623 K (that is, for similar conditions to those found in the methanol steam reforming—MSR-process) showed faster desorption of CO_L as compared to CO_B?+?CO_H species for supported Pd/CeO₂, as expected. However, the TPA-CO results on Pd/ZnO–CeO₂ were atypical: even under the superimposed, low CO partial pressure, and for a temperature range similar to those found at high methanol conversion in the MSR reaction, the PdZn bimetallic surface nature was recovered, which could be an explanation of the good selectivity to CO₂ of Pd/ZnO-based catalysts and—in particular—of the catalytically stable Pd/ZnO–CeO₂ materials.

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Critical superparamagnetic/single-domain grain sizes in interacting magnetite particles: implications for magnetosome crystals

Magnetotactic bacteria contain chains of magnetically interacting crystals (magnetosome crystals), which they use for navigation (magnetotaxis). To improve magnetotaxis efficiency, the magnetosome crystals (usually magnetite or greigite in composition) should be magnetically stable single-domain (SSD) particles. Smaller single-domain particles become magnetically unstable owing to thermal fluctuations and are termed superparamagnetic (SP). Previous calculations for the SSD/SP threshold size or blocking volume did not include the contribution of magnetic interactions. In this study, the blocking volume has been calculated as a function of grain elongation and separation for chains of identical magnetite grains. The inclusion of magnetic interactions was found to decrease the blocking volume, thereby increasing the range of SSD behaviour. Combining the results with previously published calculations for the SSD to multidomain threshold size in chains of magnetite reveals that interactions significantly increase the SSD range. We argue that chains of interacting magnetosome crystals found in magnetotactic bacteria have used this effect to improve magnetotaxis.     

Parikh matrices and amiable words

Using the fact that the Parikh matrix mapping is not an injective mapping, the paper investigates some properties of the set of words with the same Parikh matrix; these words are called “amiable”. The presented results extend the results obtained in [A. Atanasiu, Binary amiable words, Int. J. Found. Comput. Sci. 18 (2) (2007) 387–400] for the binary case. In particular it is shown that all the words having the same Parikh matrix can be obtained one from another by applying only two types of transformations. Moreover, the mirrors of two amiable words are also amiable (thus forming a symmetrical class of words).     

Evolution of ion-induced ripple patterns on SiO2 surfaces

The evolution of nanoscale ripple patterns during sub-keV ion sputtering of thermally grown, fused and single crystalline SiO₂ surfaces has been investigated by means of atomic force microscopy. For all three materials, different dependencies of the ripple wavelength and the surface roughness on the ion fluence have been found. Within the Bradley-Harper model of pattern formation, the observed differences are consistent with different amounts of surface and near-surface mass transport by ion-enhanced viscous flow which might result from different surface energies of the SiO₂ specimens.     

A space efficient solution to the frequent string mining problem for many databases

The frequent string mining problem is to find all substrings of a collection of string databases which satisfy database specific minimum and maximum frequency constraints. Our contribution improves the existing linear-time algorithm for this problem in such a way that the peak memory consumption is a constant factor of the size of the largest database of strings. We show how the results for each database can be stored implicitly in space proportional to the size of the database, making it possible to traverse the results in lexicographical order. Furthermore, we present a linear-time algorithm which calculates the intersection of the results of different databases. This algorithm is based on an algorithm to merge two suffix arrays, and our modification allows us to also calculate the LCP table of the resulting suffix array during the merging.     

Adherence in childhood diabetes: Results of a confirmatory factor analysis.

Tested the equality of the factor pattern of adherence to treatment of childhood diabetes identified by S. B. Johnson et al (see record 1988-05437-001) across 2 independent samples. Samples of 162 and 157 diabetics (aged 6–18 yrs) were studied. Factors 1–4, Exercise, Injection, Diet Type, and Eating/Testing Frequency, were confirmed. Factor 5, Diet Amount, proved to be too complex; the adherence measures comprising this factor (total calories and concentrated sweets consumed) are best treated as separate, single-indicator constructs. Results support a multivariate concept of adherence, offer insight into the nature of the components underlying diabetes adherence, and provide measurement information for reliable component estimation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Couple communication and female problem drinking: A behavioral observation study.

Couples with alcohol and relationship problems often report poor communication, yet little is known about the communication of maritally distressed couples in which the woman abuses alcohol (MDWA couples). Compared with maritally distressed couples without alcohol problems (MDNA) and couples with neither problem (NDNA), MDWA couples showed a distinctive pattern of negative communication. Similar to MDNA men, MDWA men spoke negatively to their partners but listened positively to their partners much like NDNA men. MDWA women listened negatively, much as MDNA women did, but spoke positively, like NDNA women did. The interactions of MDWA couples can be characterized as a male-demand-female-withdraw pattern, which is a gender reversal of the female-demand-male-withdraw pattern often observed in MDNA couples. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Refined Epistemic Entrenchment

Epistemic entrenchment, as presented by Gärdenfors and Makinson (1988) and Gärdenfors (1988), is a formalisation of the intuition that, when forced to choose between two beliefs, an agent will giveup the less entrenched one. While their formalisation satisfactorilycaptures the intuitive notion of the entrenchment of beliefs in a number ofaspects, the requirement that all wffs be comparable has drawn criticismfrom various quarters. We define a set of refined versions of theirentrenchment orderings that are not subject to the same criticism, andinvestigate the relationship between the refined entrenched orderings,the entrenchment orderings of Gärdenfors and Makinson, and AGM theorycontraction (Alchourrón et al., 1985). To conclude, we compare refinedentrenchment with two related approaches to epistemic entrenchment.     

景观规划对景观公约的贡献

第一，地区的特点现在变得越来越重要。在全球化不断发展的今天，景观的保护和发展作为生活质量构成的一部分，已经变得越来越重要了。资源的保护实际上要比物种的保护和生物种类的保护更加重要，因为景观必须要有一个更加全面的想法，这样才能有非常好的景观设计。我们在考虑景观的时候必须要考虑景观的因素和当地的情况。现在我们不断地标准化，不断地趋同、     

Wind turbine performance under icing conditions

The wind energy market is in full growth in Quebec but technical difficulties due to cold climate conditions have occurred for most of the existing projects. Thus, icing simulations were carried out on a 0.2 m NACA 63 415 blade profile in the refrigerated wind tunnel of the Anti‐icing Materials International Laboratory (AMIL). The shapes and masses of the ice deposits were measured, as well as the lift and drag forces of the iced profiles. Scaling was carried out based on the 1.8 MW–Vestas V80 wind turbine technical data, for three different radial positions and two in‐fog icing conditions measured at the Murdochville wind farm in the Gaspé Peninsula. For both icing events, the mass of ice accumulated on the blade profile increased with an increase in the radial position. In wet regime testing (first icing event), glaze formed mostly near the leading edge and on the pressure side. It also accumulated by run‐off on the trailing edge of the outer half of the blade. In dry‐regime testing (second icing event), rime mostly accreted on the leading edge and formed horns. For both icing events, when glaze or rime accreted on the blade profile, lift decreased and drag increased. A load calculation using the blade element theory shows that drag force on the entire blade becomes too large compared to lift, leading to a negative torque and the stop of the wind turbine. Torque reduction is more significant on the outer third of the blade. Setting up a de‐icing system only on the outer part of the blade would enable significant decrease of heating energy costs. Copyright © 2007 John Wiley & Sons, Ltd.