The multi-structure of oxidized-reduced tungsten carbide surface(s)

The XPS of bulk tungsten carbide, partially oxidized WC surfaces at 373 and 573 K as well as tungsten trioxide have been reported. Bulk WC has been prepared from WO₃ as a starting material in a mixture of CH₄ (20%) and H₂ (80%) at 1150 K for 4 h, while partially oxidized WC surfaces were prepared by oxygen chemisorption on a clean WC surface at 200 K, then the temperatures were raised to 373 and 573 K respectively. The XPS of a freshly prepared WC reveals the presence of a small amount of WO₃ on the surface and a slightly higher concentration in the bulk. The oxygen-exposed fresh WC surfaces and surfaces treated at temperatures higher than 373 K show the presence of WO₃ in a considerable quantity depending on the length and the treatment temperature. Ar⁺ bombardment of this partially oxidized surface reduces WO₃ to WO₂ and W(0), while WC is partially reduced to W(0). Isomerization reactions of alkanes on oxygen-exposed WC surface occurs in reality on a composite surface structure containing WC, WO₃, WO₂ and elemental W(0).     

Measurevent of the Transient Effects of a Gamtma-Flux on the Energy Resolution of Surface-Barrier Silicon Detectors

The energy resolutions of surface barrier n-type silicon detectors counting al pha-particles were measured under the disturbance of 1.25 MeV gamma-fluxes ranging from 2.3 x 107 to 3.8 x 108 photons cm-2 sec-1 and for detectors having different total thicknesses and resistivities. The results obtained confirm the existence of a zone about 100 micron wide and external to the depletion layer of partially depleted detectors which contributes to worsen the energy resolution of the gamma-irradiated detectors by diffusion rrocesses. It is also pointed out that the energy resolution of the detectors under gamma irradiation varies with the time constants of the amplifying circuit quite differently from what is obser ved in the absence of gamma irradiation.     

Design Impact on Airflow Patterns in Fluidization Units

The airflow behavior in a fluidization unit was integrally studied by means of experimental work and computational fluid dynamics simulation. The computational domain included the gas inlet pipe, plenum, perforated plate, fluidization chamber, and air outlet pipe. Different scenarios were simulated to allow distinguishing the best way to represent perforated‐plate distributors and elucidate the impact of the grid design on the fluidization performance. The simulated pressure drop across the distributor and the plenum flow pattern were in concordance with the experimental data. It was found that the distance between the peripheral holes and walls has a great impact on the airflow downstream the distributor.     

The substrate specificity of a recombinant cysteine protease from Leishmania mexicana: application of a combinatorial peptide library approach

The substrate specificity of CPB2.8DeltaCTE, a recombinant cysteine protease from Leishmania mexicana, was mapped by screening a fluorescence-quenched combinatorial peptide library. Results from library screening indicated a preference for Arg or Lys in the S(3) subsite and for hydrophobic residues, both aliphatic and aromatic, in S(2). The S(1) subsite exhibited a specificity for the basic residues Arg and Lys. Generally, the specificity of the primed subsites was less strict compared with the non-primed side which showed preference for Arg, Lys and Ala in S'(1), Arg, Pro and Gly in S'(2) and Lys, Arg and Ser in S'(4). By contrast, a strict preference for the basic residues Arg and Lys was found for S'(3). Overall, there was a trend for basic residues in alternating subsites and smaller residues in the primed sites compared with the non-primed sites. In addition, there were strict requirements for the amino acids in subsites S(3)--S(1). Fluorescence-quenched peptides from the library with the highest on-resin cleavage were resynthesised and their kinetics of hydrolysis by CPB2.8DeltaCTE assessed in solution phase assays. Several good substrates containing the quintessential dipeptide particular to cathepsin-L-like enzymes, -F-R/K-, in P(2) and P(1) were identified (e.g. Y(NO(2))-EKFR down arrow RGK-K(Abz)G, Abz=2-aminobenzoyl; k(cat)K(m)(-1)=4298 mM(-1)s(-1)). However, novel substrates containing the dipeptide -L/I-Q- in P(2) and P(1) were also well hydrolysed (e.g. Y(NO(2))-YLQ down arrow GIQK-K(Abz)G; k(cat)K(m)(-1)=2583 mM(-1)s(-1)). The effect of utilising different fluorescent donor--quencher pairs on the value of k(cat)K(m)(-1) was examined. Generally, the use of the Abz/Q-EDDnp donor--quencher pair (EDDnp=N-(2,4-dinitrophenyl)ethylenediamine) instead of K(Abz)/Y(NO(2)) resulted in higher k(cat)K(m)(-1) values for analogous substrates.     

Influence of pH on complexing of model beta-d-glucans with zearalenone

Previous studies have shown that isolated beta-(1,3 and 1,6)-D-glucans and related alkali-extracted fractions from the cell wall of Saccharomyces cerevisiae are able to complex with zearalenone in vitro (affinity up to 50%) and thus may reduce the bioavailability of toxins in the digestive tract. The complexation mechanisms involve cooperative interaction between the two chemical entities that can be computed by Hill's model. Various linear or branched soluble or insoluble beta-D-glucans were evaluated to elucidate their roles in the adsorption mechanisms under three pH conditions (3.0, 6.0, and 8.0) found in the digestive tract. A constant quantity of each beta-D-glucans (1 mg/ml) was mixed at 39 degrees C with increasing amounts of zearalenone (2 to 100 microg/ml), and the amount of bound toxin was measured. Acidic and neutral conditions gave the highest affinity rates (64 to 77%) by beta-(1,3)-D-glucans, whereas alkaline conditions decreased adsorption except when beta-(1,6)-D-glucan side chains were branched on beta-(1,3)-D-glucans. Alkaline conditions appear to impede the active three dimensional conformation of beta-D-glucans and favor single helix and/or random coil structures. Study of the equilibrium between beta-D-glucan-bound and free toxins revealed that two types of chemical interactions occur during toxin complexation with beta-D-glucans, identified as weak chemical linkages such as hydrogen and van der Waals bonds.     

Network-controlled mobility within radio access networks based onWLAN technologies

This article presents a network-controlled approach of user terminal mobility within anIP based WirelessLAN Access Network. In a first part, this article makes a review of the mobility support, on the subject of emergingWLAN technologies asHIPERLAN/2 andIEEE 802.11, on the one hand, and, regardingIP networks as currently studied withinIETF, on the other hand. Both types ofIP mobility protocols are presented, either global mobility protocols such as MobileIP, or local mobility management protocols (micro mobility). In the next part, the overall principles of our mobility management approach are explained; this approach is based on the implementation of a new network entity dedicated to the control of user terminal mobility. The last part details a practical implementation of this approach. The implementation is carried out on the basis of Hierarchical MobileIPv6 (HMIPv6). The experimental results confirm the importance to carefully plan and control the user terminal mobility within largeIP based Access Networks, as this brings benefit to the user as well as to the operator.     

Microstructured air-silica fibres: Recent developments in modelling, manufacturing and experiment

The main modelling methods devoted to microstructured air-silica optical fibres (MOFS) are presented and discussed. Then, the specific propagation properties ofMOFS are studied in detail. Characteristics measured on fibres manufactured in our laboratory or reported in the literature are analysed. A large number of potential and demonstrated applications are presented and the obtained performances are discussed. A particular attention is given to hollow-core photonic bandgap fibres and their applications.     

DAILY AVERAGED 2D WATER TEMPERATURE MODEL FOR THE ST. LAWRENCE RIVER

A daily averaged two‐dimensional water temperature model has been developed for the freshwater part of the St. Lawrence River, between Lake St. Louis and Trois‐Rivières (Québec, Canada). The model was first calibrated and validated for the area of Lake St. Pierre, a natural enlargement of the river subject to strong lateral and longitudinal thermal variations. Forecasts from the Global Environmental Multiscale model were used in preference to observations from meteorological stations for model inputs, both to increase the spatial resolution and ultimately to allow the water temperature model to be used in predictive mode. The resulting model provided daily water temperature estimates with an overall root mean square error (RMSE) of 1.18 °C and a Nash–Sutcliffe coefficient of 0.44. Comparisons between Landsat images and simulations demonstrated that the model not only simulated accurate water temperature values but also showed the adequacy of the model in general. It not only simulated local water temperature relatively accurately but also provided a good representation of the spatial water temperature patterns within the study area. The error varied between deep and shallow water areas. In deeper water, the overall RMSE is 0.41 °C, and the modified Nash coefficient rises up to 0.92. Because shallow water areas are subject to greater variations, longer, more spatially dense data sets will be needed to refine the hydrodynamic and thermal budget models for those specific areas. Copyright © 2013 John Wiley & Sons, Ltd.