Novel non-invasive algorithm to identify the origins of re-entry and ectopic foci in the atria from 64-lead ECGs: A computational study.

Atrial tachy-arrhytmias, such as atrial fibrillation (AF), are characterised by irregular electrical activity in the atria, generally associated with erratic excitation underlain by re-entrant scroll waves, fibrillatory conduction of multiple wavelets or rapid focal activity. Epidemiological studies have shown an increase in AF prevalence in the developed world associated with an ageing society, highlighting the need for effective treatment options. Catheter ablation therapy, commonly used in the treatment of AF, requires spatial information on atrial electrical excitation. The standard 12-lead electrocardiogram (ECG) provides a method for non-invasive identification of the presence of arrhythmia, due to irregularity in the ECG signal associated with atrial activation compared to sinus rhythm, but has limitations in providing specific spatial information. There is therefore a pressing need to develop novel methods to identify and locate the origin of arrhythmic excitation. Invasive methods provide direct information on atrial activity, but may induce clinical complications. Non-invasive methods avoid such complications, but their development presents a greater challenge due to the non-direct nature of monitoring. Algorithms based on the ECG signals in multiple leads (e.g. a 64-lead vest) may provide a viable approach. In this study, we used a biophysically detailed model of the human atria and torso to investigate the correlation between the morphology of the ECG signals from a 64-lead vest and the location of the origin of rapid atrial excitation arising from rapid focal activity and/or re-entrant scroll waves. A focus-location algorithm was then constructed from this correlation. The algorithm had success rates of 93% and 76% for correctly identifying the origin of focal and re-entrant excitation with a spatial resolution of 40 mm, respectively. The general approach allows its application to any multi-lead ECG system. This represents a significant extension to our previously developed algorithms to predict the AF origins in association with focal activities

Influence of Tempering Temperature on Low Cycle Fatigue of High Strength Steel

In this study, the mechanical and low cycle fatigue properties for a heat-treatment steel subjected to quenching and tempering (QT) were evaluated. The steel had a modified chemical composition with respect to a conventional material and was subjected to tempering at various temperatures. It was shown that the material tempered at 250 degrees C exhibited superior fatigue properties in the short life regions. Carbon atom clusters in concentration of 18 at% in martensite were observed using atom probe tomography (APT) for the steel tempered at 250 degrees C. It is believed that these clusters contribute to the improvement of fatigue properties by hindering the motion of dislocations.X111Nsciescopu

Observation of a temperature-induced phase transition on the Si(5 5 12) surface

X11sciescopuskc

EVIDENCE OF METALLIC NATURE OF THE SURFACE BANDS OF AU/SI(557)

We have studied temperature dependence of the two proximal bands, S1 and S2, from the one-dimensional (1D) Au/Si(557) system using angle-resolved photoemission spectroscopy with synchrotron photons. The intriguing feature of these bands reported earlier, metallic S1 and insulating S2 at room temperature [J. R. Ahn, H. W. Yeom, H. S. Yoon, and I. W. Lyo, Phys. Rev. Lett. 91, 196403 (2003)], has neither been reproduced nor understood properly yet. Our band images, however, unambiguously reveal that both bands behave nearly identically with temperature and remain metallic for 83 K <= T <= 300 K as seen by the well-defined Fermi-Dirac edges. We thus exclude the presence of a Peierls-type metal-insulator transition claimed earlier and discuss possible causes for the difference. The metallic nature of these bands is further illustrated by the presence of a satellite peak in the Au 4f(7/2) core level reflecting the 1D plasmon excitation.open119sciescopu

CAPE (caffeic acid phenethyl ester) stimulates glucose uptake through AMPK (AMP-activated protein kinase) activation in skeletal muscle cells

Caffeic acid phenethyl ester (CAPE), a flavonoid-like compound, is one of the major components of honeybee propolis. In the present study, we investigated the metabolic effects of CAPE in skeletal muscle cells and found that CAPE stimulated glucose uptake in differentiated L6 rat myoblast cells and also activated AMPK (AMP-activated protein kinase). In addition, the inhibition of AMPK blocked CAPE-induced glucose uptake, and CAPE activated the Akt pathway in a PI3K (phosphoinositide 3-kinase)-dependent manner. Furthermore, CAPE enhanced both insulin -mediated Akt activation and glucose uptake. In summary, our results suggest that CAPE may have beneficial roles in glucose metabolism via stimulation of the AMPK pathway. (C) 2007 Elsevier Inc. All rights reserved.X1155sciescopu

METAL-INSULATOR TRANSITION-INDUCED ADSORPTION-RESISTANT BEHAVIOR OF SMALL AU NANOPARTICLES

The size-dependent variation of the. electronic and chemical properties of Au nanoparticles formed on native Si oxide surfaces is investigated using. synchrotron radiation photoemission spectroscopy and ultraviolet photoelectron spectroscopy. The adsorption reactivity toward butanethiol adsorption initially increases with decreasing particle size; however, the reactivity of Au nanoparticles becomes gradually lower below a size of similar to 0.8 nm. The photoemission spectral changes suggest a metal-insulator transition, accompanied by negative charge transfer from the nanoparticles to the support, which may be the source of the chemical inertness of small Au nanoparticles.115sciescopu