Thermal fatigue effects on the temperature distribution inside IGBT modules for zone engine aeronautical applications

This work examines the thermal fatigue effects on the temperature distribution inside IGBT modules for aeronautical applications. Exactly, they are used in a very different application where temperature cycling due to the working environment is the most limiting fact. In this case, it is concluded that solder delamination does not present any restriction to module lifetime at short term (up to 60% of total delaminated area). In addition, it is proposed only determining the delaminated area behind devices, which is the main responsible of the thermal temperature increase.     

The Future of Mixing Research

This paper is the result of a plenary discussion session held at the 11^th European Conference on Mixing. Three perspectives on mixing research are explored: that of the industrialist, the equipment manufacturer, and the academic researcher. There was strong agreement that, while the one dimensional problems are reasonably well understood and many engineers thus perceive that mixing is simple, current practice actually requires us to address complex, multi‐dimensional problems with interactions between mixing, reaction, multi‐phase physics, surface phenomena, and transport phenomena. Understanding these multi‐scale, multi‐mechanism problems requires models which include interactions between the phenomena, and allow the effects of these interactions to emerge. Developing these models will require us to shift our perspective on mixing from one of equipment design to one of the mixing field as a fundamental physical mechanism.     

Laplace spectra as fingerprints for image recognition

In the area of image retrieval from data bases and for copyright protection of large image collections there is a growing demand for unique but easily computable fingerprints for images. These fingerprints can be used to quickly identify every image within a larger set of possibly similar images. This paper introduces a novel method to automatically obtain such fingerprints from an image. It is based on a reinterpretation of an image as a Riemannian manifold. This representation is feasible for gray value images and color images. We discuss the use of the spectrum of eigenvalues of different variants of the Laplace operator as a fingerprint and show the usability of this approach in several use cases. Contrary to existing works in this area we do not only use the discrete Laplacian, but also with a particular emphasis the underlying continuous operator. This allows better results in comparing the resulting spectra and deeper insights in the problems arising. We show how the well known discrete Laplacian is related to the continuous Laplace-Beltrami operator. Furthermore, we introduce the new concept of solid height functions to overcome some potential limitations of the method.     

Abnormal carnitine distribution in the muscles of patients with idiopathic inflammatory myopathy

OBJECTIVE: To analyze the levels of free carnitine and carnitine esters in the muscles of patients with inflammatory myopathies. METHODS: Six men and 7 women with inflammatory myopathy and 25 age-matched healthy controls were studied. Free carnitine and carnitine esters in muscle homogenates were measured by a radiochemical procedure. Muscle histochemical staining and measurement of respiratory chain enzyme activity were also performed. RESULTS: Eleven patients had muscle carnitine insufficiency. Five of them had subsarcolemmal oxidative accumulations, 5 had lipid droplets, and 4 had defects of the respiratory chain enzyme complexes. CONCLUSION: Abnormal distribution of muscle carnitine is present in patients with inflammatory myopathies and could impair muscle function. Coexistent mitochondrial dysfunction may contribute to carnitine insufficiency.     

Microtiter plate binding assay for cholinergic compounds utilizing the nicotinic acetylcholine receptor.

A receptor-based binding assay for the determination of cholinergic compounds of the nicotinic acetylcholine receptor has been developed. By conducting the assay in a 96-well microtiter plate, the method is suitable for large-scale screening in drug development. Solid-phase extraction of the enzyme label significantly simplifies the assay protocol compared to earlier methods. The assay is based on immobilization of biotin-BSA on the microtiter which takes up avidin-labeled peroxidase due to avidin-biotin interaction. To perform the assay, a ligand (the analyte) and a biotin alpha-bungarotoxin conjugate (alpha Bgt-biotin) sequentially bind to a vesicle bound nicotinic acetylcholine receptor. This is done either in a test tube, assay I, or in a biotinylated microtiter well, assay II. Avidin-HRP is then added to this mixture; free alpha Bgt-biotin conjugate and immobilized biotin-BSA compete for the avidin sites. After the assay solution has been aspirated off, bound enzyme activity is determined which is directly related to the amount of alpha Bgt-biotin added. Dose-response curves of cholinergic compounds and Scatchard plots were generated to evaluate the apparent binding constants. Kinetic studies were conducted for the purpose of optimization. The final assay can be performed in under 4 h with a minimum of sample handling.     

Conversion process of chlorine containing polysilanes into silicon carbide

The crystallization of pyrolysed chlorine containing polycarbosilanes (PCS) into silicon carbide is suggested to begin at about 1000 °C by X-ray diffraction experiments. The crystallite size and the crystallite amount were also estimated from the X-ray diffraction patterns. Electron spin resonance, nuclear magnetic resonance and Raman-spectroscopy were used to describe the structure of the material. In addition to these methods a combustion method was used to investigate the carbon and the oxygen contents.