Magnetic domain confinement by anisotropy modulation

The spin configuration in a magnet is in general a "natural" consequence of both the intrinsic properties of the material and the sample dimensions. We demonstrate that this limitation can be overcome in a homogeneous ferromagnetic film by engineering an anisotropy contrast. Substrates with laterally modulated single-crystal and polycrystalline surface regions were used to induce selective epitaxial growth of a ferromagnetic Ni film. The resulting spatially varying magnetic anisotropy leads to regular perpendicular and in-plane magnetic domains, separated by a new type of magnetic wall---the "anisotropy constrained" magnetic wall.     

Non-isothermal polymer melt flow in sudden expansions

This paper presents numerical results for laminar, incompressible and non-isothermal polymer melt flow in sudden expansions. The mathematical model includes the mass, momentum and energy conservation laws within the framework of a generalized Newtonian formulation. Two constitutive relations are adopted to describe the non-Newtonian behavior of the flow, namely Cross and Modified Arrhenius Power-Law models. The governing equations are discretized using the finite difference method based on central, second-order accurate formulas for both convective and diffusive terms. The pressure–velocity coupling is treated by solving a Poisson equation for pressure. The results are presented for two commercial polymers and demonstrate that important flow parameters, such as pressure drop and viscosity distribution, are strongly affected by heat transfer features.     

Preparation and thermal characterization of inclusion complex of Brazilian green propolis and hydroxypropyl-β-cyclodextrin

The propolis produced in Southeastern Brazil is known as green propolis (BGP) because of its color and the most important plant source is Baccharis dracunculifolia. Several authors reported biological activities such as antiulcer, anti-inflammator, antimutagenic, antifungal/antibacterial, antileishmanial/antiplasmodial for the BGP. For this reason, BGP has been extensively employed in food and beverages, thus helping improve health and preventing diseases. Some authors related that the biological activities of BGP are mostly due to its high levels of prenylated ρ-coumaric acids derivatives, mainly artepillin C. The inclusion complex between Brazilian green propolis (BGP) with hydroxypropyl-β-cyclodextrin (HP-β-CD) was prepared and its characterization was investigated by different analytical techniques (X-ray diffraction, Fourier transform infrared spectroscopy, and thermogravimetry) and suggesting that propolis was molecularly dispersed in the HP-β-CD matrix. The increasing solubility of chemical constituents was determined using quantitation methods for total flavonoids and polyphenols. Furthermore, it was developed a method for the quantitation and identification of the main compounds by high-performance liquid chromatography in order to evaluate the increasing water solubility of each constituent in aqueous BGP extract (aromadendrin, isosakuranetin, and artepillin C). The antioxidant activity was evaluated by chemical assay 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging.     

Non-Associativity in the Clifford Bundle on the Parallelizable Torsion 7-Sphere

In this paper we discuss generalized properties of non-associativity in Clifford bundles on the 7-sphere S ⁷. Novel and prominent properties inherited from the non-associative structure of the Clifford bundle on S ⁷ are demonstrated. They naturally lead to general transformations of the spinor fields on S ⁷ and have dramatic consequences for the associated Ka?-Moody current algebras. All additional properties concerning the non-associative structure in the Clifford bundle on S ⁷ are considered. We further discuss and explore their applications.     

Post-buckling behaviour of slender structures with a bi-linear bending moment-curvature relationship

Certain classes of slender structures of complex cross-section or fabricated from specialised materials can exhibit a bi-linear bending moment-curvature relationship that has a strong influence on their global structural behaviour. This condition may be encountered, for instance, in (a) non-linear elastic or inelastic post-buckling problems if the cross-section stiffness may be well approximated by a bi-linear model; (b) multi-layered structures such as stranded cables, power transmission lines, umbilical cables and flexible pipes where the drop in the bending stiffness is associated with an internal friction mechanism. This paper presents a mathematical formulation and an analytical solution for such slender structures with a bi-linear bending moment versus curvature constitutive behaviour and subjected to axial terminal forces. A set of five first-order non-linear ordinary differential equations are derived from considering geometrical compatibility, equilibrium of forces and moments and constitutive equations, with hinged boundary conditions prescribed at both ends, resulting a complex two-point boundary value problem. The variables are non-dimensionalised and solutions are developed for monotonic and unloading conditions. The results are presented in non-dimensional graphs for a range of critical curvatures and reductions in bending stiffness, and it is shown how these parameters affect the structure's post-buckling behaviour.     

Stable weakly shadowable volume-preserving systems are volume-hyperbolic

We prove that any C1-stable weakly shadowable volume-preserving diffeomorphism defined on a compact manifold displays a dominated splitting E ⊕ F. Moreover, both E and F are volume-hyperbolic. Finally, we prove the version of this result for divergence-free vector fields. As a consequence, in low dimensions, we obtain global hyperbolicity.     

Electrochemical study of butylate: application to the analysis of water

A biochemical gas-sensor (bio-sniffer) was constructed for convenient measurement of odourless hydrogen peroxide (H₂O₂) vapour, which is harmful to skin and mucous membranes. An enzyme-immobilized membrane was fabricated by spreading the mixture of catalase and photo-crosslinkable polymer on a dialysis membrane. An H₂O₂ biosensor was constructed by attaching this catalase-immobilized membrane to the sensitive top of a Clark-type oxygen electrode, and the oxygen generation from the decomposition of H₂O₂ catalysed by catalase was measured amperometrically. This biosensor was first applied to the measurement of H₂O₂ solution and was able to quantify the concentrations of H₂O₂ solution from 0.02 to 10.0?mmol?L^?1. Then, this biosensor was applied to gaseous phase as a bio-sniffer and was able to detect the odourless H₂O₂ vapour with the calibration range from 0.5 to 30?ppm, where the threshold limit value assigned by the American Conference of Governmental Industrial Hygienists (1?ppm) is covered.