Mechanical properties, microstructure and crystallographic texture of magnesium AZ91-D alloy welded by Friction Stir Welding (FSW)

The objective of the study was to characterize the properties of a magnesium alloy welded by friction stir welding (FSW). The results led to a better understanding of the relationship between this process and the microstructure and anisotropic properties of alloy materials. Welding principally leads to a large reduction in grain size in welded zones due to the phenomenon of dynamic recrystallization. The most remarkable observation was that crystallographic textures appeared from a base metal without texture in two zones: the thermo-mechanically affected and stir welded zones. The latter zone has the peculiarity of possessing a marked texture with two components on the basal plane and the pyramidal plane. These characteristics disappeared in the TMAZ, which had only one component following the basal plane. These modifications have been explained by the nature of the plastic deformation in these zones, which occurs at a moderate temperature in the TMAZ and high temperature in the SWZ

Verification of conicoidal concave surfaces by keratometry

Purpose: To investigate the possibility of using a keratometer to check the specification of the conicoidal back surface of rigid contact lenses. Methods: A conicoidal surface can be described by quoting two parameters. The most useful for the contact lens practitioner are the apical radius (curvature) and the P-value (asphericity). A keratometer was used to measure calibrated aspheric concave surfaces with the surfaces tilted in relation to the keratometer optical axis in order to acquire sagittal radii of curvature for various regions across the concave surface. The known surface characteristics were used to apply a correction factor to the results in order to allow derivation of the surface apical radius and P-value by keratometry. Results: The 95% confidence limits suggest an estimate to within —0.014 to +0.011 mm for apical radius and —0.011 to +0.009 for the P-value compared to the results derived by form Talysurf analysis. The coefficient of repeatability was 0.029 mm for apical radius and 0.031 for the P-value. Conclusions: The investigation supports the notion that the keratometer could be used to check both the curvature and the asphericity of conicoidal back surface rigid contact lenses

Platelets, aspirin, and cardiovascular disease.

Aspirin was first synthesised 100 years ago and its preparation and marketing is generally reckoned to have been the foundation of the pharmaceutical industry. For most of the time since then it has been used for the relief of pain and fever. The modern phase of aspirin use commenced with the reporting in 1974 of a randomised controlled trial in the secondary prevention of death by low-dose aspirin given to patients who had suffered a myocardial infarct. Reports of other trials followed and an overview of the first six trials was presented to the inaugural meeting of the Society for Clinical Trials in Philadelphia in 1980. There have been two further major overviews and the most recent, based on 145 trials, established that low-dose aspirin reduces vascular events by around one third. It has been estimated that, used appropriately, aspirin could prevent 100,000 premature deaths each year worldwide, at a cost of about 250 Pounds ($400) per life saved, and about 80 Pounds ($130) per cardiovascular event prevented. The evidence indicates that it is seriously underused at present. The aspirin story continues and trials are in progress to test other possible uses of aspirin, in vascular dementia, colorectal cancer, and cataract