No abstract is provided for this article.
Numerical analysis of the local buckling behaviour and ultimate cross-sectional strength of tubular elliptical profiles in compression has been performed. After validating the model against previous experimental results, a parametric study comprising a total of 270 elliptical sections was conducted in order to examine the influence of cross-section aspect ratio, geometric imperfections and local slendernesses. The obtained ultimate capacities, load–deformation responses and failure modes are discussed. It was found that for lower cross-section aspect ratios the behaviour of The Elliptical Hollow Sections (EHS) was similar to that of cylindrical shells across a number of metrics; as the aspect ratio increased, more plate-like stable postbuckling behaviour was observed. A design method has been proposed for Class 4 EHS members that reflects the reduction in capacity due to local buckling with increasing slenderness, but also recognises the improved postbuckling stability with increasing aspect ratio.
This chapter reflects on the fact whether it could be possible to scaffold a vessel without using a permanent metallic implant to keep the vessel largely patent. Scaffold was the word used by Ulrich Sigwart to describe the stenting process since at that time the word "stent" was not even mentioned in any dictionary of the English language. Back in the Netherlands, Wim van der Giessen and the author kept working on the concept of developing a stent with a biostable polymer with the major Dutch corporation AkzoNobel. The results of this scaffold implantation in the coronaries of the pig model were very satisfactory and were published in the Journal of Interventional Cardiology in 1992. They created a working group to test a family of bioresorbable polymers and biostable polymers, all attached on the external surface of a Wictor stent.
Paper presented at the Institute of Materials conference on cement and concrete, Held 2-2 September 1999, University of Keele.\n
No abstract is provided for this article.
Theophylline has been used for several decades in the treatment of asthma and remains the most widely prescribed anti-asthma drug worldwide, although the development of newer anti-asthma medications, especially inhaled steroids, has resulted in declining use of theophylline in industrialized countries. Theophylline is now considered to be a bronchodilator, but it is increasingly recognized that theophylline has other anti-asthma activities, which may be more important. Theophylline, even at low plasma concentrations, inhibits the late asthmatic reaction following allergen challenge. These clinical pharmacological observations are substantiated by experimental animal and in vitro data showing that theophylline has several anti-inflammatory activities relevant to asthma. These include the inhibition of cytokine synthesis and release, the inhibition of inflam- matory cell activation and microvascular leakage, and the prevention of airway hyperresponsiveness induced by airway inflammation. Theophylline appears to have immunomodulatory effects, even at relatively low plasma concentrations. Based on these considerations, theophylline can be regarded as a useful altern- ative to other anti-inflammatory drugs for the chronic treatment of mild to mod- erate asthma. Theophylline should be used at lower doses to achieve plasma concentrations of 5-10 mg·l-1, which will avoid the risk of side-effects. Further studies are required to evaluate the role of low-dose theophylline as an adjunct to low-dose inhaled steroids in the management of chronic asthma. It may now be appropriate to re-evaluate the role of theophylline in asthma management.
