Tomographic imaging and scanning thermal microscopy: thermal impedance tomography

The application of tomographic imaging techniques developed for medical applications to the data provided by the scanning thermal microscope will give access to true three-dimensional information on the thermal properties of materials on a mm length scale. In principle, the technique involves calculating and inverting a sensitivity matrix for a uniform isotropic material, collecting ordered data at several modulation frequencies, and multiplying the inverse of the matrix with the data vector. In practice, inversion of the matrix in impractical, and a novel iterative technique is used. Examples from both simulated and real data are given

Thermal Conductivity of Ordered Mesoporous Nanocrystalline Silicon Thin Films Made from Magnesium Reduction of Polymer-Templated Silica

This paper reports the cross-plane thermal conductivity of ordered mesoporous nanocrystalline silicon thin films between 25 and 315 K. The films were produced by evaporation induced self-assembly of mesoporous silica followed by magnesium reduction. The periodic ordering of pores in mesoporous silicon was characterized by X-ray diffraction and direct SEM imaging. The average crystallite size, porosity, and film thickness were about 13 nm, 25-35%, and 140-340 nm, respectively. The pores were arranged in a face-centered cubic lattice. The cross-plane thermal conductivity of the mesoporous silicon thin films was measured using the 3ω method. It was between 3 and 5 orders of magnitude smaller than that of bulk single crystal silicon in the temperature range considered. The effects of temperature, film thickness, and copolymer template on the thermal conductivity were investigated. A model based on kinetic theory was used to accurately predict the measured thermal conductivity for all temperatures. On the one hand, both the measured thermal conductivity and the model predictions showed a temperature dependence of k proportional to T2 at low temperatures, typical of amorphous and strongly disordered materials. On the other hand, at high temperatures the thermal conductivity of mesoporous silicon films reached a maximum, indicating a crystalline-like behavior. These results will be useful in designing mesoporous silicon with desired thermal conductivity by tuning its morphology for various applications

Médicaments et aliments : approche ethnopharmacologique = Medicines and foods : ethnopharmacological approach

The traditional uses of plants for medicine were studied in North Algerian Sahara. To date, 85 spontaneous medicinal plants have been identified, 35 are reported with the vernacular names and 17, selected because they have common medicinal use in 3 different geographical localities and may serve as an indicator of the major health problems of the populations. (Résumé d'auteur

The fabrication and characterization of polycrystalline CuSn bolometers.

Polycrystalline CuSn thin films can be used as highly reproducible and easily fabricated bolometers for the temperature region of 1.3–3 K, an important range for both phonon pulse experiments and photon and particle detection. We report their fabrication and the dependence of their characteristic parameters on the evaporation melt and deposition conditions. The superconducting transition temperature of the films was determined predominantly by the alloy composition, the normal state resistance by the film thickness, and the bolometer sensitivity by the deposition rate. X-ray diffraction showed that the films were composites of Cu6Sn5 complexes and pure tin regions