Collective behaviour in two-dimensional cobalt nanoparticle assemblies observed by magnetic force microscopy

The use of magnetic nanoparticles in the development of ultra-high-density recording media is the subject of intense research. Much of the attention of this research is devoted to the stability of magnetic moments, often neglecting the influence of dipolar interactions. Here, we explore the magnetic microstructure of different assemblies of monodisperse cobalt single-domain nanoparticles by magnetic force microscopy and magnetometric measurements. We observe that when the density of particles per unit area is higher than a determined threshold, the two-dimensional self-assemblies behave as a continuous ferromagnetic thin film. Correlated areas (similar to domains) of parallel magnetization roughly ten particles in diameter appear. As this magnetic percolation is mediated by dipolar interactions, the magnetic microstructure, its distribution and stability, is strongly dependent on the topological distribution of the dipoles. Thus, the magnetic structures of three-dimensional assemblies are magnetically soft, and an evolution of the magnetic microstructure is observed with consecutive scans of the microscope tip.     

Reduction of CO2 on bismuth modified Pt(1 1 0) single-crystal surfaces. Effect of bismuth and poisoning intermediates on the rate of hydrogen evolution

The reduction of CO₂ on bismuth modified Pt(1 1 0) single crystal surfaces has been studied voltammetrically. The effect of bismuth and the amount of formed CO species on the rate of hydrogen evolution has also been investigated. A decrease in the rate of CO₂ reduction is observed due to the modification of the surface with bismuth adsorption. This decrease goes beyond the simple third body effect expected from the blockage of active sites on the platinum surface after bismuth adsorption. However, the hydrogen evolution reaction is relatively insensitive to the presence of adsorbed species, in contrast with previous result reported for Pt(1 1 1) and Pt(1 0 0) surfaces.     

Calcium carbonate thermal decomposition in white-body wall tile during firing. I. Kinetic study

This study examines the thermal decomposition of calcium carbonate, contained in disk-shaped test pieces formed from a mixture of raw materials of a similar composition and characteristics to those of the mixtures customarily used for the manufacture of white-body wall tile.The experiments were conducted under isothermal conditions at different temperatures in the range 825–950 °C in an air stream free of carbon dioxide.The experimental results have been interpreted using the Shrinking Unreacted Core kinetic model, assuming that, at low conversion degrees, the process is only controlled by the chemical reaction step of CaCO₃ decomposition, while at high conversion degrees the diffusion of the resulting CO₂ through the porous structure of the reacted ceramic layer also affects the process. The derived equations, which relate the conversion degree of calcium carbonate in the ceramic body to residence time, temperature, and initial porosity of the test pieces, allow the experimental results to be satisfactorily reproduced.     

Sulcotrione soil metabolism in summer corn crops

The IL-15 receptor alpha subunit (IL-15Ralpha) mediates high-affinity binding of IL-15, a pleiotropic cytokine implicated in the development of innate immune cells. We have generated IL-15Ralpha null (IL-15Ralpha-/-) mice to understand the role of IL-15Ralpha in immune development and function. IL-15Ralpha-/- mice are markedly lymphopenic despite grossly normal T and B lymphocyte development. This lymphopenia is due to decreased proliferation and decreased homing of IL-15Ralpha-/- lymphocytes to peripheral lymph nodes. These mice are also deficient in natural killer cells, natural killer T cells, CD8+ T lymphocytes, and TCRgammadelta intraepithelial lymphocytes. In addition, memory phenotype CD8+ T cells are selectively reduced in number. Thus, IL-15Ralpha has pleiotropic roles in immune development and function, including the positive maintenance of lymphocyte homeostasis.     

Carbon monoxide oxidation and nitrous oxide reduction on Rh/Pt(1 1 1) electrodes

Rhodium adlayers on Pt(1 1 1) substrates have been prepared by electrodeposition from dilute Rh³⁺ acidic solutions. Resulting deposition rates are lower than 0.03 ML min⁻¹. Pseudomorphic growth of the first monolayer has been confirmed by scanning tunneling microscopy (STM) as well as the formation of small compact islands in the submonolayer range. Carbon monoxide oxidation and nitrous oxide reduction have been studied on Rh/Pt(1 1 1) electrodes. The oxidation of carbon monoxide is catalyzed by the presence of very low coverages of rhodium as demonstrated by the negative shift of the CO oxidation profile. Results are compatible with a bifunctional mechanism for catalysis including CO diffusion in the Pt domains toward the edges of the islands (splitting of the voltammetric oxidation profile). The reduction of nitrous oxide occurs at different potential and with different rates on Pt domains, at the center of the Rh islands and at their edges, being the latter sites especially active. In any case, the adsorptive and catalytic activity of the adlayers differ from those of the bulk Pt(1 1 1) and Rh(1 1 1) electrodes. The existence of strain in the film together with a diminution in the coordination number for adatoms at the edges of the islands are considered to be at the origin of the observed behavior.     

Isoxaben soil biodegradation in pear tree orchard after repeated high dose application

Dose uniformity within the treatment volume for tangent breast irradiation can be significantly improved through dynamic compensating collimation using all four independent jaws to define a superposition of sequentially reduced Enhanced dynamic wedge fields. The enhanced dynamic wedge angle is determined which optimizes dose uniformity in the central axis transverse plane, then the sequential reduction of the superior and inferior jaws is determined to optimize the sagittal dose uniformity. This technique could be applied under computer control through a record and verify system.     

Synthesis of planar inductors in low temperature co-fired ceramic technology

A simple bisection algorithm for the synthesis of planar inductors using a fast electromagnetic analysis algorithm is presented in this work. Both bisection and electromagnetic analysis algorithms are based on a set of heuristic and physical rules obtained from the study of the electromagnetic behavior of these planar devices. With this procedure, the benefits are two fold: (i) the number of iterations is kept moderately low in the synthesis loop, and (ii) the analysis at each iteration step is speed up without compromising accuracy. The algorithm is applied to the development of an inductor library for a low temperature co-fired ceramic process technology.     

Interfacial chemistry of humidity-induced adhesion loss of chlorinated rubber on rusted steel substrates

The effect of the exposure to the humidity of a chlorinated rubber coating applied to pre-rusted mild steel has been investigated from the interfacial chemistry and adhesion point of view. X-ray photoelectron spectroscopy (XPS) data suggest that the locus of failure changes with the time of exposure to the humidity. The adhesion strength values are strongly dependent on the time of exposure. The presence of a pre-rusted layer on the mild steel has a detrimental effect on the formation of bonds between the metallic substrate and the coating after the curing process. After 1 day of exposure, the adhesion values increase nearly twice compared to the non-exposed system. XPS data suggest the presence of an important coating residue on the interfacial substrate surface. The locus of adhesion loss is probably within the coating closest to the substrate. After 30–60 days of exposure, adhesion again shows low values, the locus of adhesion loss being now inside the transformed pre-corroded layer.