Studies of Fractal Microstructure in Nanocarbon Polymer Composites.

The in situ study of fractal microstructure in nanocarbon polymers is an actual task for their application and for the improvement in their functional properties. This article presents a visualization of the bulk structural features of the composites using pulsed acoustic microscopy and synchrotron X-ray microtomography. This article presents details of fractal structure formation using carbon particles of different sizes and shapes-exfoliated graphite, carbon platelets and nanotubes.

Three-Dimensional Study of Polymer Composite Destruction in the Early Stages.

The investigation of destruction processes in composite materials is a current problem for their structural application and the improvement of their functional properties. This work aimed to visualize structural changes induced in layered carbon fiber reinforced plastics (CFRP) with the help of synchrotron X-ray microtomography. This article presents the details of destructive processes in the early stages of the deformation of reinforced polymers under uniaxial stretching, investigated at the micro level.

Noninvasive high-frequency acoustic microscopy for 3D visualization of microstructure and estimation of elastic properties during hydrolytic degradation of lactide and ε-caprolactone polymers.

The monitoring of degradation processes' kinetics in polymers is one of the attractive possibilities of ultrasound technique applications that provide non-destructive imaging of polymers' internal microstructure and measurements of elastic properties. In this work, biodegradable polymers and copolymers based on L,L-lactide, D,L-lactide and ε-caprolactone have been studied at different stages of hydrolysis at 37 °C by high-frequency (100 and 200 MHz) ultrasound. The acoustic microscopy technique has been developed to reveal changes in the internal microstructure and bulk sound speed in polymer samples over a hydrolysis period of 25 weeks.

Noninvasive ultrasound imaging for assessment of intact microstructure of extracellular matrix in tissue engineering.

Development of artificial tissues or organs is one of the actual tasks in regenerative medicine that requires observation and evaluation of intact volume microstructure of tissue engineering products at all stages of their formation, from native donor tissues and decellularized scaffolds to recipient cell migration in the matrix. Unfortunately in practice, methods of vital noninvasive imaging of volume microstructure in matrixes are absent. In this work, we propose a new approach based on high-frequency acoustic microscopy for noninvasive evaluation and visualization of volume microstructure in tissue engineering products.

Postapproval Community Hospital Experience in the United States with Left Atrial Appendage Closure Device (Watchman).

Background: To review the procedural safety and postimplantation complications of Watchman device implanted at 2 community hospitals for primary prevention of systemic embolization in patients with nonvalvular atrial fibrillation (NVAF) who were not candidates for long-term oral anticoagulation (OAC).

Methods: This was a retrospective case series of 48 patients carried out in 2 community hospitals in the United States. Patients with NVAF who had a CHADS2 higher than 2 or CHADS2VASc2 (congestive heart failure, hypertension, age ≥75 years, diabetes mellitus, prior stroke or transient ischemic attack [TIA] or thromboembolism, vascular disease, age 65-74 years, and female gender) score of 3 or higher and were not candidates for long-term OAC.

Drug Therapy in Adult Congenital Heart Disease.

Adults with congenital heart disease are at risk for atrial and ventricular arrhythmias that can lead to an increased morbidity as well as mortality. When catheter ablation is not an option or unsuccessful, antiarrhythmic drugs are the mainstay of treatment. There is limited data on the use of antiarrhythmics in this population.

Optical Properties of Pyrolytic Carbon Films Versus Graphite and Graphene.

We report a comparative study of optical properties of 5-20 nm thick pyrolytic carbon (PyC) films, graphite, and graphene. The complex dielectric permittivity of PyC is obtained by measuring polarization-sensitive reflectance and transmittance spectra of the PyC films deposited on silica substrate. The Lorentz-Drude model describes well the general features of the optical properties of PyC from 360 to 1100 nm.

Addressing the controversy of rate-versus-rhythm control in atrial fibrillation.

Atrial fibrillation is the most common sustained cardiac arrhythmia and significantly increases patient risk of stroke, cardiomyopathy, and mortality. Rate versus rhythm control as the "best" treatment strategy remains an issue of considerable, ongoing debate. A multitude of clinical trials have compared the 2 strategies and have not shown any benefit of one approach over the other.

Cerebral Embolization During AF Ablation -Pathophysiology, Prevention and Management.

Catheter based ablation therapy has evolved as an invaluable tool in the management of symptomatic patients with atrial fibrillation (AF). The procedure of AF ablation requires instrumentation in the systemic circulation predisposing to various concerns that can result in systemic embolization. We will describe the reported incidence of these events and refer to the various pathophysiologic explanations for their occurrence.

Novel oral anticoagulants for stroke prevention in patients with atrial fibrillation: dawn of a new era.

Atrial fibrillation (AF) is an important cause of ischemic stroke and is the underlying cause of > 20% of all strokes, with increasing age being a risk factor. Until recently, warfarin was the only available oral anticoagulant used to decrease this risk in patients with AF. However, there are several disadvantages of warfarin use, such as the requirement for monitoring the international normalized ratio, its wide range of drug-food interactions, and its narrow therapeutic index.

Dabigatran: a new chapter in anticoagulation.

For the last 60 years warfarin has been the cornerstone for chronic anticoagulation in prevention of ischemic strokes and systemic embolization. Warfarin therapy has several limitations including frequent monitoring and various food and significant drug interactions, which make it a less than ideal chronic oral anticoagulant. The continued search for safe, effective, medications with predictable pharmacokinetic profiles has led to newer alternatives.

Venous thromboembolism in patients with heart failure: in-hospital and chronic use of anti-coagulants for prevention.

Heart failure (HF) is a common clinical syndrome characterized by high morbidity and frequent hospitalizations. HF is an independent and major risk factor for venous thromboembolism (VTE) and VTE occurring in patients with HF carries a worse prognosis. The present review will focus on short and long term role of anti-coagulants in prevention of venous thrombosis in HF patients.

Atrial fibrillation in patients with heart failure: Role of catheter ablation therapies.

Atrial fibrillation (AF) represents the most common sustained cardiac arrhythmia in patients with heart failure (HF). AF in HF patients is associated with worsening of symptoms and also results in a substantial increase in mortality. Although HF patients in sinus rhythm have a better outcome than patients with AF, several randomized studies investigating pharmacological rhythm control versus rate control have shown no advantage of one strategy over the other in terms of patient outcomes.

Safety and efficacy of dronedarone in the treatment of atrial fibrillation/flutter.

Dronedarone is an amiodarone analog but differs structurally from amiodarone in that the iodine moiety was removed and a methane-sulfonyl group was added. These modifications reduced thyroid and other end-organ adverse effects and makes dronedarone less lipophilic, shortening its half-life. Dronedarone has been shown to prevent atrial fibrillation/flutter (AF/AFl) recurrences in several multi-center trials.

Interatrial conduction correlates with optimal atrioventricular timing in cardiac resynchronization therapy devices.

Background: Echocardiographic optimization of the atrioventricular delay (AV) may result in improvement in cardiac resynchronization therapy (CRT) outcome. Optimal AV has been shown to correlate with interatrial conduction time (IACT) during right atrial pacing. This study aimed to prospectively validate the correlation at different paced heart rates and examine it during sinus rhythm (Sinus).

Suppression of ventricular tachycardia with dronedarone: a case report.

Unlabelled:  

Introduction: Dronedarone is a multichannel blocker with similar electrophysiological properties to amiodarone. Dronedarone has not been studied in humans as an agent to suppress ventricular arrhythmias.

Methods: This case report describes the dramatic antiarrhythmic effects of dronedarone in a patient with nonischemic cardiomyopathy and recurrent ventricular tachycardia, which was resistant to multiple antiarrhythmic agents and endocardial catheter ablation.

Optimal atrioventricular delay in CRT patients can be approximated using surface electrocardiography and device electrograms.

Unlabelled: Electrocardiographic AV Delay Adjustment.

Background: Optimization of the atrioventricular (AV) delay (AVD) may result in an improvement in cardiac resynchronization therapy (CRT) outcome. Previous studies have shown positive correlation between interatrial conduction time measured invasively during the implant procedure and optimal AVD determined postimplant using Doppler echocardiography.

Ranolazine--treatment of ventricular tachycardia and symptomatic ventricular premature beats in ischemic cardiomyopathy.

Premature ventricular complexes (PVCs) are a frequent occurrence in the presence of ischemic heart disease. A very high PVC load can be symptomatic or occasionally result in a cardiomyopathy (CMP). Treatment options include pharmacologic agents and radiofrequency ablation (RFA).

Interatrial conduction measured during biventricular pacemaker implantation accurately predicts optimal paced atrioventricular intervals.

Background: Optimizing atrioventricular (AV) delay during biventricular (BiV) pacemaker implantation can require substantial resources. Hence, a simpler method is desirable. We hypothesized that interatrial conduction time (IACT), measured at the time of BiV device implant, could be a surrogate value for the optimal AV delay.

Thinning and flow of Tibetan crust constrained by seismic anisotropy.

Intermediate-period Rayleigh and Love waves propagating across Tibet indicate marked radial anisotropy within the middle-to-lower crust, consistent with a thinning of the middle crust by about 30%. The anisotropy is largest in the western part of the plateau, where moment tensors of earthquakes indicate active crustal thinning. The preferred orientation of mica crystals resulting from the crustal thinning can account for the observed anisotropy.

Seismic evidence for catastrophic slab loss beneath Kamchatka.

In the northwest Pacific Ocean, a sharp corner in the boundary between the Pacific plate and the North American plate joins a subduction zone running along the southern half of the Kamchatka peninsula with a region of transcurrent motion along the western Aleutian arc. Here we present images of the seismic structure beneath the Aleutian-Kamchatka junction and the surrounding region, indicating that: the subducting Pacific lithosphere terminates at the Aleutian-Kamchatka junction; no relict slab underlies the extinct northern Kamchatka volcanic arc; and the upper mantle beneath northern Kamchatka has unusually slow shear wavespeeds. From the tectonic and volcanic evolution of Kamchatka over the past 10 Myr (refs 3-5) we infer that at least two episodes of catastrophic slab loss have occurred.

Seismic anisotropy: tracing plate dynamics in the mantle.

Elastic anisotropy is present where the speed of a seismic wave depends on its direction. In Earth's mantle, elastic anisotropy is induced by minerals that are preferentially oriented in a directional flow or deformation. Earthquakes generate two seismic wave types: compressional (P) and shear (S) waves, whose coupling in anisotropic rocks leads to scattering, birefringence, and waves with hybrid polarizations.