Interactions of acetone with MoO3

Interactions of acetone and acetone/oxygen mixtures with MoO₃ were studied at 215–300 °C by pulse method. It has been shown that acetone is deoxygenated to propylene or oxidized to acetic acid, CO, and CO₂. Moreover a part of acetone is reversibly adsorbed and several minutes are necessary for acetone to be removed with a flow of carrier gas. As the surface is endowed with deoxygenating and oxidizing sites the desorbing acetone leaves the reactor mainly in the form of CO. These results agree with theoretical predictions based on the bond-strength model of active sites, according to which the sites of the first type (conversion of acetone) are localized on (100) face of MoO₃ and those of the second type (adsorption) on (001) and (101) planes. Both types of sites consist of surface anion vacancies and differ in the strength of bonding of oxygen. On the (100) face the bond strength is sufficiently large to break CO bond in acetone. On the other faces the interactions between acetone and surface are much weaker. In this context the application of acetone as poison of other reactions (e.g., conversion of methanol) is discussed.     

Numerical investigation of dynamic shear bands in inelastic solids as a problem of mesomechanics

The main objective of the present paper is to discuss very efficient procedure of the numerical investigation of the propagation of shear band in inelastic solids generated by impact-loaded adiabatic processes. This procedure of investigation is based on utilization the finite element method and ABAQUS system for regularized thermo-elasto-viscoplastic constitutive model of damaged material. A general constitutive model of thermo-elasto-viscoplastic polycrystalline solids with a finite set of internal state variables is used. The set of internal state variables is restricted to only one scalar, namely equivalent inelastic deformation. The equivalent inelastic deformation can describe the dissipation effects generated by viscoplastic flow phenomena. As a numerical example we consider dynamic shear band propagation in an asymmetrically impact-loaded prenotched thin plate. The impact loading is simulated by a velocity boundary condition, which are the results of dynamic contact problem. The separation of the projectile from the specimen, resulting from wave reflections within the projectile and the specimen, occurs in the phenomenon. A thin shear band region of finite width which undergoes significant deformation and temperature rise has been determined. Shear band advance, shear band velocity and the development of the temperature field as a function of time have been determined. Qualitative comparison of numerical results with experimental observation data has been presented. The numerical results obtained have proven the usefulness of the thermo-elasto-viscoplastic theory in the investigation of dynamic shear band propagations.     

Evaluation of an injectable,photopolymerizable three-dimensional scaffold based on <Emphasis Type="SmallCaps">d</Emphasis>,<Emphasis Type="SmallCaps">l</Emphasis>-lactide and ɛ-caprolactone in a tibial goat model

An in situ crosslinkable, biodegradable, methacrylate-encapped porous bone scaffold composed of D: ,L: -lactide, varepsilon-caprolactone, 1,6-hexanediol and poly(ortho-esters), in which crosslinkage is achieved by photoinitiators, was developed for bone tissue regeneration. Three different polymer mixtures (pure polymer and 30% bioactive glass or alpha-tricalcium phosphate added) were tested in a uni-cortical tibial defect model in eight goats. The polymers were randomly applicated in one of four (6.0 mm diameter) defects leaving a fourth defect unfilled. Biocompatibility and bone healing properties were evaluated by serial radiographies, histology and histomorphometry. The pure polymer clearly showed excellent biocompatibility and moderate osteoconductive properties. The addition of alpha-TCP increased the latter characteristics. This product offers potentials as a carrier for bone healing promoter substances.     

Grain growth in ultrafine grained aluminium processed by hydrostatic extrusion

Ultrafine grained materials can be produced by a number of techniques among which one can distinguish hydrostatic extrusion. In aluminium, this method can be used to obtain a structure with the grain size of 300 nm and high fraction of HAGBs (more than 70%). During annealing this structure undergoes significant changes which were evaluated quantitatively. Annealing for 1 h at temperatures up to 200 °C results in normal grain growth whereas at higher temperatures or for longer annealing times a transition from normal to abnormal growth is observed. The activation energy for low temperature regime is 43 kJ/mol whereas for high temperature annealing—128 kJ/mol. The former corresponds to grain boundary diffusion whereas the latter is close to activation energy of self diffusion in aluminium. The change in activation energy well corresponds to the transition in grain growth mechanism from normal to abnormal.     

Development of Microstructure and Properties of Multicomponent MoS2/HA/PEEK Coatings on a Titanium Alloy Via Electrophoretic Deposition and Heat Treatment

Metallurgical and Materials Transactions A - In this study, molybdenum disulfide nanosheets, bioactive hydroxyapatite particles of two types in various amounts, and PEEK 704 microparticles were...     

MSQL: A Query Language for Database Mining

The tremendous number of rules generated in the mining process makes it necessary for any good data mining system to provide for powerful query primitives to post-process the generated rulebase, as well as for performing selective, query based generation. In this paper, we present the design and compilation of MSQL, the rule query language developed as part of the Discovery Board system.     

Two Paralogous Gb3/CD77 Synthases in Birds Show Different Preferences for Their Glycoprotein and Glycosphingolipid Substrates

Most glycosyltransferases show remarkable gross and fine substrate specificity, which is reflected in the old one enzyme-one linkage paradigm. While human Gb3/CD77 synthase is a glycosyltransferase that synthesizes the Galα1→4Gal moiety mainly on glycosphingolipids, its pigeon homolog prefers glycoproteins as acceptors. In this study, we characterized two Gb3/CD77 synthase paralogs found in pigeons (Columba livia). We evaluated their specificities in transfected human teratocarcinoma 2102Ep cells by flow cytofluorometry, Western blotting, high-performance thin-layer chromatography, mass spectrometry and metabolic labelling with ¹⁴C-galactose. We found that the previously described pigeon Gb3/CD77 synthase (called P) can use predominately glycoproteins as acceptors, while its paralog (called M), which we serendipitously discovered while conducting this study, efficiently synthesizes Galα1→4Gal caps on both glycoproteins and glycosphingolipids. These two paralogs may underlie the difference in expression profiles of Galα1→4Gal-terminated glycoconjugates between neoavians and mammals.     

Model of inelastic impact of unit loads

In this study, the authors present a model of the inelastic impact of bodies that takes place during handling of unit loads (cubiform parcels). A modified non‐linear Kelvin model is proposed, in which the relationships between object strains and elastic and damping forces of the impact are represented by power functions. The results of analytical investigations on the proposed model were confirmed by experiments consisting in tests of free fall of the load on rigid ground and on elastic beam. The developed model allows the assessment of the influence of mechanical properties of loads and conveyor‐line deflection mechanisms as well as impact velocity, on the dynamic forces exerted on the manipulated objects during the impact. Copyright © 2008 John Wiley & Sons, Ltd.