A sol-gel method for growing superconducting MgB2 films

In this paper we report a new sol-gel method for the fabrication of MgB2 films. Polycrystalline MgB2 films were prepared by spin-coating a precursor solution of Mg(BH_4)_2 diethyl ether on (001)Al2O3 substrates followed with annealing in Mg vapor. In comparison with the MgB2 films grown by other techniques, our films show medium qualities including a superconducting transition temperature of Tc ~ 37 K, a critical current density of Jc(5 K, 0 T) ~ 5 {\times} 10^6 A cm^{-2}, and a critical field of H_{c2}(0) ~ 19 T. Such a sol-gel technique shows potential in the commercial fabrication of practically used MgB2 films as well as MgB2 wires and tapes.Comment: 8 pages, 5 figure

Formation of MgB2 at low temperatures by reaction of Mg with B6Si

Formation of MgB2 by reactions of Mg with B6Si and Mg with B were compared, the former also producing Mg2Si as a major product. Compared to the binary system, the ternary reactions for identical time and temperature were more complete at 750 C and below, as indicated by higher diamagnetic shielding and larger x-ray diffraction peak intensities relative to those of Mg. MgB2 could be produced at temperatures as low as 450 C by the ternary reaction. Analyses by electron microscopy, x-ray diffraction, and of the upper critical field show that Si does not enter the MgB2 phase.Comment: Submitted to Supercond. Sci. Techno

Effects on residual stresses of annealing parameters in high-temperature ZrO2 insulation coatings on Ag/Bi-2212 superconducting tapes using finite element method

In the present work, we focus on effects of residual stresses of annealing parameters and fracture behavior in high-temperature ZrO2 insulation coatings on Ag/Bi-2212 superconducting tapes using the finite element method. High-temperature ZrO2-based insulation ceramic coatings were produced on Ag and Ag/AgMg sheathed Bi-2212 superconducting tapes by the reel-to-reel sol-gel technique for magnet technology. The samples produced were characterized using scanning electron microscopy (SEM). These coatings are exposed to thermal loading under several annealing conditions. The residual stresses in 8-mum-thick coatings, as well as changes during thermal cycling, were simulated by finite element analysis (FEA). It was found that the shear stress values of ZrO2 coatings in the interface were very low, and the maximum shear stress was 47 Pa for 8-mum-thick coatings. It was determined that the highest fracture intensity was 1.09 x 10(-4) MN m(-3/2), and the fracture intensity decreased as a function of distance from the initial crack. (C) 2002 Elsevier Science Ltd. All rights reserved

Assemblage of drug release modules: Effect of module shape and position in the assembled systems on floating behavior and release rate

The aim of this work was to study the clindamycin release kinetics from floating delivery systems consisting of two modules assembled in void configuration, according to the modified release technology platform known as Dome Matrix®. Two modules differently shaped, i.e., female and male, formulated as swellable matrices and containing clindamycin, were assembled by friction interlocking. Then, by stacking additional female modules without drug on the assembled two-module floating system, modulation of clindamycin release rate and kinetics was attained. The additional modules stacked on the assembled system acted as a transient barrier to clindamycin release from the void configuration. Inertness, dissolution/erosion or swelling behavior characterized their performance as matrices in simulated gastric fluid. In particular, we found that stacking additional barrier modules on the bases of void configuration, the drug release rate and kinetics of the assembled system were modified in dependence on the composition of module added. In particular, the quickly soluble module exerted an influence on the release rate in the late time of delivery. The swellable module produced a significant reduction in release rate of void assembly, but the release mechanism remained the same. Finally, the inert module led to a substantial linearization of the release profile with a minimal reduction in release rate

Permeation Studies of Indomethacin from Different Emulsions for Nasal Delivery and Their Possible Anti-Inflammatory Effects

The purpose of this research was to develop an emulsion formulation of indomethacin (IND) suitable for nasal delivery. IND was incorporated into the oil phases of oil in water (O/W) and water in oil (W/O) emulsions. For this purpose, different emulsifying agents (Tween 80, Span 80 and Brij 58) were used in two emulsion formulations. When the effects of several synthetic membranes (nylon, cellulose, cellulose nitrate) were compared with the sheep nasal mucosa, the cellulose membrane and sheep nasal mucosa showed similar permeation properties for O/W emulsion (P > 0.05). To examine the absorption characteristics of IND, the anti-inflammatory properties of intravenous solution of IND, intranasal O/W emulsions of IND (with or without enhancers) and intranasal solution of IND (IND-Sol) were investigated in rats with carrageenan-induced paw edema. When citric acid was added to the nasal emulsion, the anti-inflammatory activity was similar to that of intravenous solution (P > 0.05). Finally, it was concluded that, intranasal administration of IND emulsion with citric acid may be considered as an alternative to intravenous and per oral administrations of IND to overcome their adverse effects