6,963 publications from this institution
The pressure drop over a coronary stenosis and the intracoronary Doppler blood flow velocity were measured at rest and during coronary vasodilation. We report the first observation that confirms the validity of fluid dynamic equations to describe the hemodynamics of a coronary stenosis based on quantitative arteriography in a human being. (J Interven Cardiol 1988:1:1)
An experimental and numerical study of the flexural buckling behavior of hot-finished high-strength steel (HSS) square and rectangular hollow section (SHS and RHS, respectively) columns is described in this paper. A total of 30 hot-finished S460 and S690 hollow section column specimens have been tested in compression with pin-ended boundary conditions. Finite element (FE) models have been developed to replicate the experiments and employed in a subsequent parametric study considering a range of member geometries. Based on the test and FE results, the applicability of the current column design curves in European, North American, Chinese and Australian structural steel design standards to hot-finished HSS SHS and RHS columns has been verified by means of reliability analyses.
Corticosteroids are the most effective anti-inflammatory therapy for many chronic inflammatory diseases, such as asthma but are relatively ineffective in other diseases such as chronic obstructive pulmonary disease (COPD). Chronic inflammation is characterised by the increased expression of multiple inflammatory genes that are regulated by proinflammatory transcription factors, such as nuclear factor-kappaB and activator protein-1, that bind to and activate coactivator molecules, which then acetylate core histones to switch on gene transcription. Corticosteroids suppress the multiple inflammatory genes that are activated in chronic inflammatory diseases, such as asthma, mainly by reversing histone acetylation of activated inflammatory genes through binding of liganded glucocorticoid receptors (GR) to coactivators and recruitment of histone deacetylase-2 (HDAC2) to the activated transcription complex. At higher concentrations of corticosteroids GR homodimers also interact with DNA recognition sites to active transcription of anti-inflammatory genes and to inhibit transcription of several genes linked to corticosteroid side effects. In patients with COPD and severe asthma and in asthmatic patients who smoke HDAC2 is markedly reduced in activity and expression as a result of oxidative/nitrative stress so that inflammation becomes resistant to the anti-inflammatory actions of corticosteroids. Theophylline, by activating HDAC, may reverse this corticosteroid resistance. This research may lead to the development of novel anti-inflammatory approaches to manage severe inflammatory diseases.
The cellular action of rapamycin (sirolimus), a natural fermentation product produced by Streptomyces hygroscopicus , is mediated by binding to the FK506 binding protein. By inhibiting a kinase known as the target of rapamycin, it restricts the proliferation of smooth‐muscle cells by blocking cell‐cycle progression at the G1/S transition. The finding that rapamycin possesses both antiproliferative and antimigratory activity suggests that it could contribute to the control of arterial re‐narrowing after percutaneous intervention and control the vascular manifestations of chronic rejection in transplanted hearts. The first clinical trials of implantation of rapamycin‐coated stents in obstructive coronary artery lesions have been reported and, in selected patient groups, it appears that the restenosis process has been abolished. Studies are underway to establish the benefits of rapamycin‐coated stents in day‐to‐day interventional practice, including small vessels, long lesions and patients with multivessel disease. With the addition of novel antiplatelet agents and delivery systems, it is possible that the two major limitations of percutaneous coronary intervention − restenosis and stent thrombosis − will be overcome. Cardiac graft loss due to intimal hyperplasia and accelerated atherosclerosis remains the major limitation to long‐term survival following cardiac transplantation. Animal studies of rapamycin have suggested that this process can be reduced or abolished. Human studies of the efficacy of rapamycin in preventing both acute rejection and allograft arterial disease are in progress. Concerns regarding toxicity, carcinogenicity, delayed healing and endothelialization remain. As with any new agent or technology, we must remain vigilant to late adverse side‐effects. (Intern Med J 2003; 33: 103−109)
This paper presents a comprehensive numerical study into the in-plane member stability and design of normal and high strength steel (NSS and HSS) non-slender welded I-section beam–columns subjected to compression plus uniaxial bending. Finite element (FE) models were firstly developed to replicate the structural performance of welded I-section beam–columns made of different steel grades, as observed in existing tests collected from the literature. The validated FE models were then employed in a comprehensive parametric study to generate extensive numerical data covering a wide range of cross-section geometries, steel grades, member slendernesses and loading combinations. The numerically obtained data were utilised to evaluate the accuracy of the current design methods set out in the European Standards EN 1993-1-1:2005 and EN 1993-1-12:2007 as well as the American Specification AISC 360-16 for both NSS and HSS non-slender welded I-section beam–columns. The comparisons revealed that the codified design methods yield varying levels of accuracy in predicting the ultimate capacities of welded I-section beam–columns depending on the steel grade. To address this issue, new design proposals that are compatible with the European beam–column design framework have been developed, featuring more accurate yield strength-dependent interaction curves anchored to improved resistance predictions for members subjected to isolated loading scenarios (i.e. the compression and bending end points of the interaction curves). The new design proposals have been found to provide more accurate and consistent resistance predictions than the existing codified design provisions for NSS and HSS non-slender welded I-section members under compression plus uniaxial bending. The reliability of the new proposals has been confirmed through statistical analyses according to EN 1990: 2002.
No abstract is provided for this article.
According to pathologic studies, the content of a necrotic core increases in a “linear fashion” as plaque enlarges. In addition, these 2 plaque characteristics have been associated with plaque vulnerability. This study assessed the relation between plaque cross-sectional area (CSA) and content of necrotic core (NC). Twenty-five patients (75 arteries) with acute coronary syndrome were studied. In total, 7,834 CSAs were analyzed. An analysis of plaque CSA in percentiles was performed (median 5.5 mm2, interquartile range 3.7 to 7.8); subsequently, plaque CSA values were categorized as small (≤3.7 mm2), medium (>3.7 to ≤7.8 mm2), and large (>7.8 mm2). There was a difference in content of the NC between arteries within each plaque CSA category. This observation was confirmed in a multivariate analysis in which only 2 variables remained statistically significant, plaque CSA (estimate 1.34, SE 0.05, p <0.0001) and studied artery (left anterior descending coronary artery, estimate 0.29, SE 0.08, p = 0.0003; left circumflex coronary artery, estimate 0.23, SE 0.07, p = 0.0014; and these vs the right coronary artery). In conclusion, the NC and plaque increase in patients with acute coronary syndromes.
