The collapsar model for gamma-ray bursts requires three essential ingredients: a massive core, removal of the hydrogen envelope, and enough angular momentum in the core. We study current massive star evolution models of solar metallicity to determine which massive star physics is capable of producing these ingredients. In particular, we investigate the role of hydrodynamic and magnetic internal...

In the present study, a novel catalyst was well designed by incorporating the tungstophosphoric acid into the magnetic chitosan, as highly stable composite, in which the iron oxides were used the strong super-magnetic core. The prepared composite was characterized by several methods, including FTIR, XRD, SEM, TEM and EDS and its catalytic activity was examined in a facile, green and highly effi...

In this paper, Fe3 O4 @SiO2 core/shell magnetic nanostructure has been synthesized and modified by N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (AEAPTMS). Fe3 O4 @SiO2 was used as a novel adsorbent for separation of hexachloroplatinic acid. X-ray diffraction (XRD), scanning electron microscopy (SEM), and FT-IR technique were used to characterize morphologies and surface texturing of these ads...

Amorphous Fe73B7Si16Nb3Cu1 ribbon was crystallized rapidly by electric current heating under simultaneously applied tensile stress along the ribbon axis. As a result, strong transverse magnetic anisotropy was induced in the ribbon. Dynamic magnetic properties of the ribbons rapidly heated either under the tensile stress or without tensile stress were measured using toroidal cores. Optimal elect...

This paper is a report on the synthesis of the Fe3O4@Ag core-shell with high saturation magnetization of magnetite nanoparticles as the core, by using polyol route and silver shell by chemical reduction. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy analyses confirmed that the particles so produced were monophase. The magnetic properties of the product were investigated by...

In this research controlled coating of magnetite (Fe3O4) nanoparticles with SiO2 was investigated. The Fe3O4 nanoparticles were synthesized via chemical co-precipitation and then coated by silica according to Stober method. Effects of tetra ethyl ortho silicate (TEOS) concentration and ethanol to TEOS on the coating thickness were inves...

Evidence of fast variations in the Earth's core field are seen both magnetic observatory and satellite records. We present here how they have been identified at surface from ground-based records their spatio-temporal structure is now characterised by data. It shown properties mantle boundary extracted through localised global modelling processes, paying particular attention to time scales. Fina...