Coherent solvus of disordered alkali feldspar: experiment, atom probe tomography and thermodynamic model.

Unlabelled: At temperatures above about 600 °C, alkali feldspar forms a continuous solid solution between the Na and K end members. Towards lower temperatures a miscibility gap opens, and alkali feldspar of intermediate composition exsolves, forming an intergrowth of relatively more Na-rich and K-rich lamellae. During exsolution, the crystal structure usually remains coherent across the lamellar interfaces, a feature that may be preserved over geological times.

Coherent lamellar intergrowth in alkali feldspar.

A thermodynamic analysis of coherent lamellar intergrowth resulting from the exsolution of initially homogeneous alkali feldspar is presented. In contrast to earlier treatments, where the simplifying assumption of zero strain in the lamellar interfaces was used, our treatment is more general. The elastic stresses and strains associated with coherent lamellar intergrowth of Na-rich and K-rich alkali feldspar are calculated by minimising the overall elastic energy of the lamellar microstructure.

Multicomponent diffusion in ionic crystals: theoretical model and application to combined tracer- and interdiffusion in alkali feldspar.

We present a model for multicomponent diffusion in ionic crystals. The model accounts for vacancy-mediated diffusion on a sub-lattice and for diffusion due to binary exchange of different ionic species without involvement of vacancies on the same sub-lattice. The diffusive flux of a specific ionic species depends on the self-diffusion coefficients, on the diffusion coefficients related to the binary exchanges, and on the site fractions of all ionic species.

[Ultrasound-guided perivascular axillary brachial plexus block. A simple, effective and efficient procedure].

Background: The perivascular axillary plexus block is an easily applicable procedure with a low risk of complications but with a high failure rate. To improve this, the standard procedure was combined with transpectoral sonography to benefit from the advantages of ultrasound, while using a nearly unchanged puncture technique.

Method: The technique developed by the authors is described in this article and the success rate and the time factor were determined in a sample of 86 patients.