Optimum seismic design of concentrically braced steel frames: concepts and design procedures

A methodology is presented for optimization of the dynamic response of concentrically braced steel frames subjected to seismic excitation, based on the concept of uniform distribution of deformation. In order to obtain the optimum distribution of structural properties, an iterative optimization procedure has been adopted. In this approach, the structural properties are modified so that inefficient material is gradually shifted from strong to weak areas of a structure. This process is continued until a state of uniform deformation is achieved. It is shown that the seismic performance of such a structure is optimal, and behaves generally better than those designed by conventional methods. In order to avoid onerous analysis of the frame models, an equivalent procedure is introduced for performing the optimization procedure on the modified reduced shear-building model of the frames, which is shown to be accurate enough for design purposes

Posttransplant survival is not diminished in heart transplant recipients bridged with implantable left ventricular assist devices

BackgroundThe purpose of this study was to compare posttransplantation morbidity and mortality in orthotopic heart transplant recipients bridged to transplant with a left ventricular assist device with nonbridged recipients. To account for potential differences across device types, we stratified bridge-to-transplant recipients by type of ventricular assist device: extracorporeal (EXTRA), paracorporeal (PARA), and intracorporeal (INTRA).MethodsThe United Network for Organ Sharing provided de-identified patient-level data. The study population included 10,668 orthotopic heart transplant recipients aged 18 years old or older and undergoing transplantation between January 1, 2001, and December 31, 2006. Follow-up data were provided through August 3, 2008, with a mean follow-up time of 3.17 ± 2.15 years (range, 0–8.11 years). The primary outcome was actuarial posttransplant graft survival. Other outcomes of interest included infection, stroke, and dialysis during the transplant hospitalization; primary graft failure at 30 days; transplant hospitalization length of stay; and long-term complications including diabetes mellitus, transplant coronary artery disease, and chronic dialysis. Multivariable Cox proportional hazards regression (backward, P < .15) was used to determine the relationship between groups and overall graft survival, and multivariable logistic regression analysis (backward, P < .15) was used to determine the relationship between groups and secondary outcome measures.ResultsIn multivariable Cox regression analysis, when compared with the nonbridged group, risk-adjusted greater than 90-day graft survival was diminished among the EXTRA group (hazard ratio = 3.54, 2.28–5.51, P < .001), but not the INTRA group (1.04, 0.719–1.51, P = .834) or the PARA group (1.06, 0.642–1.76, P = .809). There were no significant differences in risk-adjusted graft survival across the 4 groups during the 90-days to 1-year or 1- to 5-year intervals. However, at more than 5 years, risk-adjusted graft survival in the INTRA group (0.389, 0.205–0.738, P = .004) was better than in the nonbridged group. The EXTRA, PARA, and INTRA groups all experienced increased risks of infection. The EXTRA group had increased risks of dialysis, stroke, and primary graft failure at 30 days, whereas neither the PARA nor the INTRA group differed from the nonbridged group. Long-term complications did not differ by group.ConclusionThe use of implantable left ventricular assist devices as bridges to transplantation, including both intracorporeal and paracorporeal devices, is not associated with diminished posttransplant survival. However, 90-day survival was diminished in recipients bridged with extracorporeal devices

Nurse Management of Hypertension in Rural Western Kenya: Implementation Research to Optimize Delivery

Background: Hypertension is the leading global risk factor for mortality. Hypertension treatment and control rates are low worldwide, and insufficient human resource capacity is among the contributing factors. Thus, a critical component of hypertension management is to develop novel and effective solutions to the human resources challenge. One potential solution is task redistribution and nurse management of hypertension in these settings. Objectives: The aim of this study is to investigate whether nurses can effectively reduce blood pressure in hypertensive patients in rural western Kenya and, by extension, throughout sub-Saharan Africa. Methods: An initial phase of qualitative inquiry will assess facilitators and barriers of nurse management of hypertension. In addition, we will perform usability and feasibility testing of a novel, electronic tablet-based integrated decision-support and record-keeping tool for the nurses. An impact evaluation of a pilot program for nurse-based management of hypertension will be performed. Finally, a needs-based workforce estimation model will be used to estimate the nurse workforce requirements for stable, long-term treatment of hypertension throughout western Kenya. Findings: The primary outcome measure of the impact evaluation will be the change in systolic blood pressure of hypertensive individuals assigned to nurse-based management after 1 year of follow-up. The workforce estimation modeling output will be the full-time equivalents of nurses. Conclusions: This study will provide evidence regarding the effectiveness of strategies to optimize task redistribution and nurse-based management of hypertension that can be applicable to noncommunicable disease management in low- and middle-income countries

Designing comparative effectiveness trials of surgical ablation for atrial fibrillation: Experience of the Cardiothoracic Surgical Trials Network

ObjectiveSince the introduction of the cut-and-sew Cox maze procedure for atrial fibrillation, there has been substantial innovation in techniques for ablation. Use of alternative energy sources for ablation simplified the procedure and has resulted in dramatic increase in the number of patients with atrial fibrillation treated by surgical ablation. Despite its increasingly widespread adoption, there is lack of rigorous clinical evidence to establish this procedure as an effective clinical therapy.MethodsThis article describes a comparative effectiveness randomized trial, supported by the Cardiothoracic Surgical Clinical Trials Network, of surgical ablation with left atrial appendage closure versus left atrial appendage closure alone in patients with persistent and long-standing persistent atrial fibrillation undergoing mitral valve surgery. Nested within this trial is a further randomized comparison of 2 different lesions sets: pulmonary vein isolation and the full maze lesion set.ResultsThis article addresses trial design challenges, including how best to characterize the target population, operationalize freedom from atrial fibrillation as a primary end point, account for the impact of antiarrhythmic drugs, and measure and analyze secondary end points, such as postoperative atrial fibrillation load.ConclusionsThis article concludes by discussing how insights that emerge from this trial may affect surgical practice and guide future research in this area

Paradoxical euthyroid hormone profile in a case of Graves' disease with cardiac failure

Cardiac failure is an uncommon complication of juvenile hyperthyroidism. We describe an adolescent boy with Graves' disease who developed manifestations of heart failure while on antithyroid medications. There was no evidence of any underlying cardiac disease. He had paradoxical euthyroid hormone profile which rose to hyperthyroid range when the manifestations of the cardiac failure subsided. The case highlights several unusual features of Graves' disease

Experimental behaviour of non-seismical RWS connections with perforated beams under cyclic actions

The use of perforated (in particular cellular and castellated) beams has become widespread as their manufacturing processes keep minimising wasted material and has become cost-effective by reducing self-weight of steel structures, while allowing for larger clear spans. Although their behaviour to time-invariant vertical loads has been extensively investigated and validated in laboratory setups, their response to reversible actions has not been explored to the same extent. This paper presents results of cyclic load tests of beam-column reduced web section (RWS) connections, considering setups representative of what is observed in low-rise buildings in the UK; a region with sparse seismicity. Results show that RWS connections on these frames can achieve stable hysteresis loops without significant strength degradation, due to the simultaneous occurrence of yielding of the critical cross-section and development of a Vierendeel mechanism on the edges of the perforations (web openings). Also, inelastic action is mostly observed within the beam, thus being successful in protecting the beam-column connection. Performance particularly exceeds what is observed for a benchmarking RBS connection styled according to the same underlying assumptions, hinting that RWS connections could be a more suitable solution for structural retrofitting in regions where seismicity is sparse