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No abstract is provided for this article.
No abstract is provided for this article.
A variational model is formulated that accounts for the localization of deformation due to buckling under pure bending of thin-walled elastic tubes with circular cross-sections. Previous studies have successfully modelled the gradual process of ovalization of the cross-section with an accompanying progressive reduction in stiffness but these theories have had insufficient freedom to incorporate any longitudinal variation in the tube. Here, energy methods and small-strain nonlinear elastic theory are used to model the combined effects of cross-section deformation and localized longitudinal buckling. Results are compared with a number of case studies, including a nanotube, and it is found that the model gives rise to behaviours that correlate well with some published physical experiments and numerical studies.
No abstract is provided for this article.
Why More Research into Molecular and Cellular Mechanisms of COPD Is Needed. Inflammation in Lung Parenchyma. Small Airways Disease in COPD. Asthma versus COPD: Cellular and Molecular Differences. Airway Mucus Hypersecretion. Macrophages. Neutrophils. Epithelial Cells. T Lymphocytes. Inflammatory Mediators. Oxidative Stress. Proteinases in COPD. Antiproteases. Corticosteroid Resistance in COPD. Molecular Genetics. Mechanisms of Systemic Effects. Mechanisms of Exacerbations of Chronic Obstructive Pulmonary Disease. Mechanisms of Pulmonary Vascular Changes. Therapeutic Implications and Future Developments
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 inflammatory 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 alternative to other anti-inflammatory drugs for the chronic treatment of mild to moderate 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.
Inhaled therapy is the mainstay of modern asthma management, as this optimizes the therapeutic ratio. Short-acting beta 2-agonists are the most effective bronchodilators and when given by inhalation give rapid relief of symptoms, without adverse effects, although there are concerns about overuse of these drugs. Inhaled long-acting beta 2-agonists are useful in some patients. Inhaled anticholinergics are particularly useful in patients with COPD and in the future long-acting drugs, such as tiotropium bromide, will be available. Inhaled glucocorticoids are the most effective therapy in controlling chronic asthma symptoms, and systemic effects are not a problem in the vast majority of patients. Improved inhalation devices and steroids with reduced oral bioavailability have resulted in reduced systemic side effects, which now arise largely from absorption from the lungs. In the future it is likely that new classes of drug will be developed, but whether they will be used by inhalation or given by mouth will depend on the frequency of side effects and the mode of action of the drugs. There are likely to be several improvements in inhaler delivery systems, so that the inhaled route will remain predominant for many years to come.
Optical coherence tomography is a recently introduced intracoronary imaging modality with higher spatial resolution than intravascular ultrasound. For this reason, it is increasingly applied to investigate the characteristics of vulnerable atheromatous plaques and the result of stent implantation, struts coverage and restenosis, as well as in procedural decision-making. OCT is also useful in the field of secondary revascularisation, particularly in assessing implanted stents, evaluating relevant technologies like biodegradable stents, and in studying surgical grafts. In this article we perform a review of current developments and evidence in this area.