Coronary artery stents revolutionized the practice of interventional cardiology after they were first introduced in the mid-1980s. Since then, there have been significant developments in their design, the most notable of which has been the introduction of drug-eluting stents. This paper reviews the benefits, risks, and current status of Food and Drug Administration-approved drug-eluting stents.
A stiffness reduction approach is presented in this paper, which utilises Linear Buckling Analysis (LBA) and Geometrically Nonlinear Analysis (GNA) in conjunction with developed stiffness reduction functions for the design of columns and beam-columns in steel frames. The proposed stiffness reduction approach obviates the need to model member imperfections and to make member buckling checks. While LBA with appropriate stiffness reduction provides inelastic buckling loads of columns, GNA with stiffness reduction is performed for the prediction of beam-column failure. In addition to regular members, the accuracy and practicality of the method is illustrated for irregular members. For the latter case, results indicate that the proposed stiffness reduction method provides more accurate strength predictions in comparison to traditional design approaches. The influence of moment gradient on the development of plasticity (i.e. stiffness reduction) is accounted for by incorporating simple moment gradient factors into the stiffness reduction expressions originally derived for members under uniform bending. The accuracy of the proposed stiffness reduction approach is verified against results obtained through non-linear finite element modelling for all of the considered cases.
The prediction of the likely future state of cementitious materials has been the focus of research for many decades and has expanded to match the availability of computational power and of codes and data.The field has traditionally been divided into two activities and even communities; high and low temperature methods.By tradition, each community has favoured its own models, codes and data but recent developments are leaving this boundary less distinct than in the past.To compound this, is the wider adoption of methods complementary to thermodynamics, which makes modelling high temperature cement chemistry an exciting area in which to conduct research.What follows, is a very personal view of the major advances in modelling cement chemistry at high temperatures, the needs and drivers to model development and an equally personal speculation about areas of fruitful research and development in the foreseeable future.
Background Software to compute angiography-derived fractional flow reserve (angio-FFR) have been validated against pressure wire–derived fractional flow reserve (PW-FFR) with an area under the receiver-operating characteristic curve (AUC) of 0.93 to 0.97. Objectives The aim of this study was to investigate diagnostic accuracies of 5 angio-FFR software/methods by an independent core lab in a prospective cohort of 390 vessels with carefully documented sites of PW-FFR and pressure wire–derived instantaneous wave-free ratio. Methods One “matcher investigator” colocalized on angiography the sites of pressure wire measurement with angio-FFR measurements and provided the same 2 optimal angiographic views and frame selection to independent analysts who were blinded to invasive physiological results and results from other software. The results were anonymized and randomly presented. The AUC of each angio-FFR was compared with 2-dimensional quantitative coronary angiography (QCA) percent diameter stenosis (%DS) using a 2-tailed paired comparison of AUC. Results All 5 software/methods yielded a high proportion of analyzable vessels (A: 100%, B: 100%, C: 92.1%, D: 99.5%, and E: 92.1%). The AUCs for predicting fractional flow reserve ≤0.8 for software A, B, C, D, E, and 2-dimensional QCA %DS were 0.75, 0.74, 0.74, 0.73, 0.73, and 0.65, respectively. The AUC for each angio-FFR was significantly greater than that for 2-dimensional QCA %DS. Conclusions This head-to-head comparison by an independent core lab demonstrated that the diagnostic accuracy of various angio-FFR software for predicting PW-FFR ≤0.80 was useful, with a higher discrimination compared with 2-dimensional QCA %DS; however, it did not reach the diagnostic accuracy previously reported in validation studies of various vendors. Therefore, the intrinsic clinical value of “angiography-derived fractional flow reserve” requires confirmation in large clinical trials.
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