Weighted exponential regression for characterizing radionuclide concentrations in soil depth profiles

Radium concentration was determined in 23 types of bottled mineral waters, commercially available in Romania. Using the Lucas cells with the device Luk 3A, the radium concentration was determined directly, after the radon balanced with radium. From these measurements, the corresponding annual effective ingestion dose was determined.     

Some synthetic approaches to ropinirole (sk&f 101468-a): A potent dopamine receptor agonist

Three new routes to ropinirole (SK&F 101468-A, 1 ) are described each involving the preparation of 3-chlorooxindole intermediates of type 3 from β-nitrostyrenes as the pivotal step. The superiority of sulphonate esters 17a-c as direct precursors to 1 over the bromide 11 is also described.     

Cyclisation of dienes using phosphorus-centred radicals to form organophosphorus adducts

Reaction of various dienes with phosphites or related phosphorus hydrides, under free radical cyclisation conditions, affords cyclic organophosphorus adducts. This quick, mild and technically clean approach affords 5- and 6-ring carbocycles and heterocycles in good to excellent yield.     

Characterisation of novel anodes for solid oxide fuel cells based on oxygen-excess perovskite related structures

Mixed oxides belonging to the La₂Sr_n–2Ti_nO_3n+1 family have been targeted as potential materials for high performance anodes in fuel cells. The most important feature of these ompounds is the existence of excess oxygen along preferential directions. Substitution by lower valence cations might lead to a removal of this excess oxygen along preferential directions and therefore possibly increase the potential for ionic conductivity. High total conductivity (>1 S·cm⁻¹) was found after reduction for some compounds within this family of compounds. The activation energy varied with the structure and the more disordered the structure (thicker perovskite blocks), the lower the activation energy was found. Paper presented at the 8th EuroConference on Ionics, Carvoeiro, Algarve, Portugal, Sept. 16 – 22, 2001.     

Metalorganic vapour phase epitaxy of mercury cadmium telluride

The present review covers the fundamental factors involved in the the metalorganic vapour phase epitaxy of mercury cadmium telluride. In addition recent significant developments which could have an important influence on the future of the technology are discussed. The topics covering these developments include growth techniques, photoepitaxy, in-situ monitoring, “new” precursors, substrates and layer quality. The review highlights the advanced nature of the technology, which inspite of currently-addressed limitations has an important future.     

The effect of a magnetic field on the rheodynamic behavior of ferromagnetic suspensions

In this work a simplified analytical model and the results of an experimental investigation of the influence of an external magnetic field on the rheological characteristics of a suspension of iron particles in silicon oil is presented. The particles of iron were approximately of a circular shape, from 3 to 5 μm, with a maximum concentration of 10¹⁰ particles/cm³. The viscosity of the carrying fluid varied from 80 to 240 cP.The experimental channel was located in a closed circuit of forced circulation of the ferromagnetic suspension. The entire length of 750 mm was placed in an area of a homogeneous magnetic field, with the velocity vector of the suspension being perpendicular to the direction of the magnetic field. The strength of the magnetic field could be changed continually from 0 to 9000 G.The results obtained are shown in the form of parametrical dependencies of the rheological characteristics of the ferromagnetic suspension. With that, the concentration of the solid phase of the suspension is parametrically changed, along with the strength of the external magnetic field and the viscosity of the carrying fluid.In the range of parameters studied, the external magnetic field leads to a Bingham character of behavior of the ferromagnetic suspension.