Fate of turbid glacial inflows in a hydroelectric reservoir.

Turbidity from glacial meltwater limits light penetration with potential ecological consequences. Using profiles of temperature, conductivity, and turbidity, we examine the physical processes driving changes in the epilimnetic turbidity of Carpenter Reservoir, a long and narrow, glacier-fed reservoir in southwest British Columbia, Canada. Following the onset of permanent summer stratification, the relatively dense inflows plunged into the hypolimnion, and despite the high glacial load entering the reservoir, the epilimnion cleared due to particle settling.

An extreme case of platypnoea-orthodeoxia syndrome.

An 80-year-old female presented with progressive breathlessness, worse on sitting or standing and relieved by lying flat. Subsequent investigations identified a patent foramen ovale (PFO) with right-to-left flow across the interatrial septum (IAS). A diagnosis of platypnoea orthodeoxia syndrome secondary to inter-atrial shunting was made.

Hemiarch replacement with concomitant antegrade stent grafting of the descending thoracic aorta versus total arch replacement for treatment of acute DeBakey I aortic dissection with arch tear†.

Objectives: For acute DeBakey I aortic dissection with arch tear, conventional distal reconstruction entails total arch replacement (TAR). Some surgeons at our institution have utilized an alternative reconstructive strategy-primary arch tear repair and transverse hemiarch reconstruction (THR) with concomitant antegrade thoracic endovascular aortic repair (TEVAR). We assessed early and mid-term outcomes comparing these two surgical strategies for arch tear management.

A model of ischemic mitral regurgitation in pigs with three-dimensional echocardiographic assessment.

Background And Aim Of The Study: Ischemic mitral regurgitation (IMR), the incidence of which is increasing, results from annular and subvalvular remodeling after myocardial infarction (MI). Although a sheep model of IMR has been used extensively over the past two decades, the ventricular, coronary and leaflet anatomy in sheep is significantly different from that in humans. In contrast, pigs are more similar to humans with regard to these parameters, and therefore may serve as a better animal to test emerging new technologies designed to treat IMR.

Extended order parameter and conjugate field for the dynamic phase transition in a Ginzburg-Landau mean-field model in an oscillating field.

We present numerical evidence for an extended order parameter and conjugate field for the dynamic phase transition in a Ginzburg-Landau mean-field model driven by an oscillating field. The order parameter, previously taken to be the time-averaged magnetization, comprises the deviations of the Fourier components of the magnetization from their values at the critical period. The conjugate field, previously taken to be the time-averaged magnetic field, comprises the even Fourier components of the field.

A meta-analysis comparing muscle-sparing and posterolateral thoracotomy.

We compared outcomes of posterolateral thoracotomy vs muscle-sparing thoracotomy after open thoracic operations. Twelve trials were included, comprising 571 patients in the muscle-sparing thoracotomy group and 512 patients in the posterolateral thoracotomy group. There was significantly improved shoulder internal rotation (weighted mean difference, -1.

A meta-analysis assessing the benefits of concomitant pleural tent procedure after upper lobectomy.

A meta-analysis comparing outcomes of upper lobectomies with or without pleural tenting was performed. Five trials comprising 396 patients were selected. There was significantly reduced duration of hospital stay, chest drain use, and air leak in the pleural tenting group compared with the group without the pleural tent.

Sutureless mitral valve replacement: initial steps toward a percutaneous procedure.

Purpose: Transcatheter mitral valve replacement would represent a major advance in heart valve therapy. Such a device requires a specialized anchoring and sealing technology. This study was designed to test the feasibility of a novel mitral valve replacement device (the sutureless mitral valve [SMV]) designed to anchor and seal in the mitral position without need for sutures.

Random phenotypic variation of yeast (Saccharomyces cerevisiae) single-gene knockouts fits a double pareto-lognormal distribution.

Background: Distributed robustness is thought to influence the buffering of random phenotypic variation through the scale-free topology of gene regulatory, metabolic, and protein-protein interaction networks. If this hypothesis is true, then the phenotypic response to the perturbation of particular nodes in such a network should be proportional to the number of links those nodes make with neighboring nodes. This suggests a probability distribution approximating an inverse power-law of random phenotypic variation.

Electrophysiology and ablation of arrhythmias.

Major advances in diagnosis and treatment of arrhythmias have created the subspecialty of cardiac electrophysiology. This article reviews supraventricular and ventricular arrhythmias and outlines the indications and process of electrophysiological testing, arrhythmia mechanism and their treatment by catheter ablation.

Posterior leaflet augmentation in ischemic mitral regurgitation increases leaflet coaptation and mobility.

Background: Restoring leaflet coaptation is the primary objective in repair of ischemic mitral regurgitation (IMR). The common practice of placing an undersized annuloplasty ring partially achieves this goal by correcting annular dilation; however, annular reduction has been demonstrated to exacerbate posterior leaflet tethering. Using a sheep model of IMR, we tested the hypothesis that posterior leaflet augmentation (PLA) combined with standard annuloplasty sizing increases leaflet coaptation more effectively than undersized annuloplasty alone.

An ovine model of pulmonary insufficiency and right ventricular outflow tract dilatation.

Background And Aim Of The Study: The treatment of pulmonary insufficiency (PI) following reconstructive surgery of the right ventricular outflow tract (RVOT) in repair of the tetralogy of Fallot remains a significant challenge. The study aim was to establish an ovine model of dilated RVOT and PI, and to quantify the degree of PI and right ventricular remodeling over an eight-week period, using magnetic resonance imaging (MRI).

Methods: Five sheep underwent baseline MRI scanning and catheterization.

A novel method for quantifying the in-vivo mechanical effect of material injected into a myocardial infarction.

Background: Infarcted regions of myocardium exhibit functional impairment ranging in severity from hypokinesis to dyskinesis. We sought to quantify the effects of injecting a calcium hydroxyapatite-based tissue filler on the passive material response of infarcted left ventricles.

Methods: Three-dimensional finite element models of the left ventricle were developed using three-dimensional echocardiography data from sheep with a treated and untreated anteroapical infarct, to estimate the material properties (stiffness) in the infarct and remote regions.

Posterior leaflet augmentation improves leaflet tethering in repair of ischemic mitral regurgitation.

Objectives: Ischemic mitral regurgitation results from annular dilatation, leaflet tethering and leaflet flattening. Undersized annuloplasty corrects annular dilatation but worsens leaflet tethering and flattening. This exacerbation of abnormal leaflet geometry may contribute to poor repair results for ischemic mitral regurgitation (IMR).

Melody valve implantation into the branch pulmonary arteries for treatment of pulmonary insufficiency in an ovine model of right ventricular outflow tract dysfunction following tetralogy of Fallot repair.

Background: Transannular patch (TAP) repair of tetralogy of Fallot often results in significant right ventricular outflow tract (RVOT) dilation and distortion. We hypothesized that insertion of Melody valves into the proximal right and left branch pulmonary arteries (PAs) would reduce pulmonary regurgitation fraction (PRF) in an ovine model of pulmonary insufficiency and dilated RVOT.

Methods And Results: Ten sheep underwent baseline cardiac catheterization, surgical pulmonary valvectomy, and TAP placement.

Can we really do without antibiotic prophylaxis for infective endocarditis?

Current guidance recommends against the use of antibiotic prophylaxis around the time of dental intervention for the prevention of infective endocarditis. The authors report the case of a previously well-patient with an asymptomatic isolated ventricular septal defect (VSD) who developed evidence of infective systemic and pulmonary emboli following dental treatment. A diagnosis of severe endocarditis of a previously normal native mitral valve was made.

Quantitative mitral valve modeling using real-time three-dimensional echocardiography: technique and repeatability.

Background: Real-time three-dimensional (3D) echocardiography has the ability to construct quantitative models of the mitral valve (MV). Imaging and modeling algorithms rely on operator interpretation of raw images and may be subject to observer-dependent variability. We describe a comprehensive analysis technique to generate high-resolution 3D MV models and examine interoperator and intraoperator repeatability in humans.

Elimination of ischemic mitral regurgitation does not alter long-term left ventricular remodeling in the ovine model.

Background: The efficacy of annuloplasty for ischemic mitral regurgitation (IMR) has been difficult to establish. Using an established ovine model of IMR, we tested the ability of ring annuloplasty to durably relieve IMR and reverse or limit progression of left ventricular (LV) remodeling during a clinically relevant follow-up period.

Methods: A posterolateral infarction known to result in chronic IMR was initiated in 33 sheep.

Injectable hydrogel properties influence infarct expansion and extent of postinfarction left ventricular remodeling in an ovine model.

A recent trend has emerged that involves myocardial injection of biomaterials, containing cells or acellular, following myocardial infarction (MI) to influence the remodeling response through both biological and mechanical effects. Despite the number of different materials injected in these approaches, there has been little investigation into the importance of material properties on therapeutic outcomes. This work focuses on the investigation of injectable hyaluronic acid (MeHA) hydrogels that have tunable mechanics and gelation behavior.

Computational model for the formation of uniform silver spheres by aggregation of nanosize precursors.

We present results of computational modeling of the formation of uniform spherical silver particles prepared by rapid mixing of ascorbic acid and silver-amine complex solutions in the absence of a dispersing agent. Using an accelerated integration scheme to speed up the calculation of particle size distributions in the latter stages, we find that the recently reported experimental results-some of which are summarized here-can be modeled effectively by the two-stage formation mechanism used previously to model the preparation of uniform gold spheres. We treat both the equilibrium concentration of silver atoms and the surface tension of silver precursor nanocrystals as free parameters, and find that the experimental reaction time scale is fit by a narrow region of this two-parameter space.

Model of nanocrystal formation in solution by burst nucleation and diffusional growth.

The phenomenon of burst nucleation in solution, in which a period of apparent chemical inactivity is followed by a sudden and explosive growth of nucleated particles from a solute species, has been given a widely accepted qualitative explanation by LaMer and co-workers. Here, we present a model with the assumptions of instantaneous re-thermalization below the critical nucleus size and irreversible diffusive growth above the critical size, which for the first time formulates LaMer's explanation of burst nucleation in a manner allowing quantitative calculations. The behavior of the model at large times, t, is derived with the result that the average cluster size, as measured by the number of atoms, grows approximately t, while the width of the cluster distribution grows approximately (sq root)1.

Can tissue adhesives and glues significantly reduce the incidence and length of postoperative air leaks in patients having lung resections?

A best evidence topic in thoracic surgery was written according to a structured protocol. The question addressed was whether the intraoperative use of surgical adhesives in patients undergoing lung resection would reduce the incidence and length of postoperative air leaks. The reported search strategy identified 261 papers of which 12 were considered to represent the best evidence available.