Microstructure of high velocity oxy-fuel sprayed Ti2AlC coatings

The microstructure formation and phase transformations in Ti₂AlC-rich coatings deposited by High Velocity Oxy-fuel spraying of Maxthal 211^? powders is presented. High resolution electron microscopy analysis, using both scanning and transmission electron microscopy with energy dispersive spectrometry and energy filtering, combined with X-ray diffraction reveals that the coatings consist of Ti₂AlC grains surrounded by regions of very small TiC grains embedded in Ti _x Al _y . The composition of the Ti _x Al _y depends on its surrounding and varies with size and distribution of the adjacent TiC grains. Impact of spray parameters on coating microstructure is also discussed. Two spray parameters were varied; powder size distribution and flame power. They were found to greatly affect the coating microstructure. Increasing powder size and decreasing flame power increase the amount of Ti₂AlC, but produces thinner coatings with lower cohesion. Larger powder size will also decrease oxygen incorporation.     

Use of the DIAS model to predict unrecognised hypoglycaemia in patients with insulin-dependent diabetes

The Diabetes Advisory System (DIAS) is a model of human glucose metabolism implemented in a causal probabilistic network. It handles data on insulin dose, carbohydrate intake and blood glucose concentration to predict hourly blood glucose concentrations and thus provide an indication of blood glucose values between home blood tests. DIAS was used to predict blood glucose profiles in eight patients with well-controlled insulin-dependent diabetes, who are at increased risk of hypoglycaemia (abnormally low blood glucose levels). DIAS predicted nocturnal hypoglycaemia in six patients and daytime hypoglycaemia in one patient. The occurrence of nocturnal hypoglycaemia was not recognised by the patient or suspected by their doctor but was subsequently confirmed by blood testing in five patients. It is known that unrecognised nocturnal hypoglycaemia is common in patients with well-controlled diabetes. The ability of DIAS to identify such periods of hypoglycaemia with reasonable accuracy illustrates how the advanced technology it employs may provide reliable decision support to clinicians.     

GM1 ganglioside attenuates the development of vacuous chewing movements induced by long-term haloperidol treatment of rats

Tardive dyskinesia (TD) is a serious side-effect of long-term treatment with neuroleptics. To investigate if TD may be a result of neuroleptic-induced excessive stimulation of striatal glutamate receptors, the effect of the anti-excitotoxic GM1 ganglioside was studied in a rat model of TD. In an acute experiment each of four groups of rats was treated with GM1 20 mg/kg SC+saline IP, saline SC+haloperidol 1.2 mg/kg IP, GM1 SC+haloperidol IP, or saline SC+saline IP. In a subsequent long-term experiment lasting 16 weeks, each of the four groups was treated as in the acute experiment, with the exception that haloperidol was injected IM as decanoate 38 mg/kg every 4 weeks, and the controls received vehicle injections. The behavior was videotaped and scored at intervals during both experiments, including 16 weeks after cessation of the long-term treatment. Haloperidol induced a significant increase in vacuous chewing movements (VCM) and immobility both in the acute and in the long-term experiment. Other categories of behaviour (rearing, moving, sitting) were significantly affected only in the acute experiment. GM1 did not affect any of the acute behavioural effects of haloperidol, but significantly reduced VCM in the long-term experiment. The effects on VCM of haloperidol and GM1 persisted for at least 8 weeks after cessation of the long-term treatment. These results suggest that long-lasting changes in striatal function induced by excessive glutamate receptor stimulation may be a mechanism for the development of VCM in rats and perhaps also for TD in humans.     

Characterization of evaporated gold-indium films on semiconductors

Evaporated Au-In films with total thicknesses in the range 200–6000 Å have been studied by backscattering of 1.5 MeV He⁺ ions, SEM, X-ray diffraction and with the electron microprobe. Both Si and GaAs were used as substrates, and the atomic percentage of Au in the films was less than 30. A fast diffusion within the films was observed which resulted in the formation of the AuIn₂ phase at room temperature. The compositional structure and the annealing behaviour of the films have been studied in the temperature range 25°–600°C. A model for the annealing behaviour of the films is presented. The Au-In films have been used for ohmic contacts to GaAs and a correlation between the resistance of such contacts and the alloying behaviour is attempted.     

A model of the endogenous glucose balance incorporating the characteristics of glucose transporters

This paper describes the development and preliminary test of a model of the endogenous glucose balance that incorporates the characteristics of the glucose transporters GLUT1, GLUT3 and GLUT4. In the modeling process the model is parameterized with nine parameters that are subsequently estimated from data in the literature on the hepatic- and endogenous- balances at various combinations of blood glucose and insulin levels. The ability of the resulting endogenous balance to fit blood glucose measured from patients was tested on 20 patients. The fit obtained with this model compared favorably with the fit obtained with the endogenous balance currently incorporated in the DIAS system.     

On the (non-)optimality of Michell structures

Optimal analytical Michell frame structures have been extensively used as benchmark examples in topology optimization, including truss, frame, homogenization, density and level-set based approaches. However, as we will point out, partly the interpretation of Michell’s structural continua as discrete frame structures is not accurate and partly, it turns out that limiting structural topology to frame-like structures is a rather severe design restriction and results in structures that are quite far from being stiffness optimal. The paper discusses the interpretation of Michell’s theory in the context of numerical topology optimization and compares various topology optimization results obtained with the frame restriction to cases with no design restrictions. For all examples considered, the true stiffness optimal structures are composed of sheets (2D) or closed-walled shell structures (3D) with variable thickness. For optimization problems with one load case, numerical results in two and three dimensions indicate that stiffness can be increased by up to 80 % when dropping the frame restriction. For simple loading situations, studies based on optimal microstructures reveal theoretical gains of +200 %. It is also demonstrated how too coarse design discretizations in 3D can result in unintended restrictions on the design freedom and achievable compliance.