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Electrical Stability (electrical + stability)
Selected AbstractsMatters of the heart: the physiology of cardiac function and failureEXPERIMENTAL PHYSIOLOGY, Issue 6 2007Godfrey Smith Heart failure as a result of a myocardial infarction (MI) is a common condition with a poor prognosis. The adaptive changes in the surviving myocardium appear to be insufficient in terms of both mechanical/contractile performance and electrical stability. The modification of the underlying myocardial physiology is complex, varying across the different layers within the wall of the ventricle and within one layer. Two therapeutic strategies are briefly discussed, as outlined here. (i) Enhancing contractility by alteration of the expression of a single protein (e.g. sarco-endoplasmic reticulum Ca2+ ATPase, SERCA) could potentially reverse both mechanical and electrical abnormalities. However, experimental data involving the upregulation of SERCA suggest that the therapeutic range of this approach is narrow. (ii) The use of regular exercise training to improve cardiac performance in heart failure. This appears to act by normalizing a number of aspects of myocardial physiology. [source] High-Performance Programmable Memory Devices Based on Hyperbranched Copper Phthalocyanine Polymer Thin Films,ADVANCED MATERIALS, Issue 9 2008Seungchel Choi Electrically programmable fuse-type polymer memory devices based on hyperbranched copper phthalocyanine polymer thin films are fabricated. The devices have novel write-once-read-many (WORM) memory characteristics, with a high ON/OFF current ratio (of 106) and a high electrical stability, thus opening up the possibility of a low-cost mass production of high-performance, nonvolatile polymer memory devices. [source] Generating heat from conducting polypyrrole-coated PET fabricsADVANCES IN POLYMER TECHNOLOGY, Issue 3 2005Akif Kaynak Abstract Heating effects in polypyrrole-coated polyethyleneterephthalate (PET)-Lycra® fabrics were studied. Chemical synthesis was employed to coat the PET fabrics by polypyrrole using ferric chloride as oxidant and antraquinone- 2-sulfonic acid (AQSA) and naphthalene sulfonic acid (NSA) as dopants. The coated fabrics exhibited reasonable electrical stability, possessed high electrical conductivity, and were effective in heat generation. Surface resistance of polypyrrole-coated fabrics ranged from approximately 150 to 500 ,/square. Different connections between conductive fabrics and the power source were examined. When subjected to a constant voltage of 24 V, the current transmitted through the fabric decreased about 10% in 72 h. An increase in resistance of conductive fabrics subjected to constant voltage was observed. © 2005 Wiley Periodicals, Inc. Adv Polym Techn 24: 194,207, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20040 [source] The Role of Cardiac Tissue Alignment in Modulating Electrical FunctionJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 12 2007CHIUNG-YIN CHUNG M.S. Introduction:,Most cardiac arrhythmias are associated with pathology-triggered ion channel remodeling. However, multicellular effects, for example, exaggerated anisotropy and altered cell-to-cell coupling, can also indirectly affect action potential morphology and electrical stability via changed electrotonus. These changes are particularly relevant in structural heart disease, including hypertrophy and infarction. Recent computational studies showed that electrotonus factors into stability by altering dynamic properties (restitution). We experimentally address the question of how cell alignment and connectivity alter tissue function and whether these effects depend on the direction of wave propagation. Methods and Results:,We show that cardiac cell arrangement can alter electrical stability in an in vitro cardiac tissue model by mechanisms both dependent and independent of the direction of wave propagation, and local structural remodeling can be felt beyond a space constant. Notably, restitution of action potential duration (APD) and conduction velocity was significantly steepened in the direction of cell alignment. Furthermore, prolongation of APD and calcium transient duration was found in highly anisotropic cell networks, both for longitudinal and transverse propagation. This is in contrast to expected correlation between wave propagation direction and APD based on electrotonic effects only, but is consistent with our findings of increased cell size and secretion of atrial natriuretic factor, a hypertrophy marker, in the aligned structures. Conclusion:,Our results show that anisotropic structure is a potent modulator of electrical stability via electrotonus and molecular signaling. Tissue alignment must be taken into account in experimental and computational models of arrhythmia generation and in designing effective treatment therapies. [source] Influence of insulating barrier thickness on the magnetoresistance properties of a magnetic tunnel junction with Zr-alloyed Al oxide barrierPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 8 2004Chul-Min Choi Abstract We have investigated the magnetoresistive properties and thermal and electrical stability of a magnetic tunnel junction (MTJ) with a high-quality, ultra-thin Zr-alloyed Al oxide (ZrAl oxide) barrier of below 1.0 nm. We obtained the highest bias voltage and breakdown voltage of 711 mV and 1.75 V for a 1.6-nm-thick barrier. The resistance drops from 1850 , to 72 , as the ZrAl thickness decreases from 1.6 to 0.6 nm, respectively. A significant TMR (Tunneling Magneto-resistance) value of 17% and a junction resistance of 98 , were obtained for a MTJ with a ZrAl oxide barrier thickness of 0.8 nm. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Copolymers of N -methylpyrrole and 3,4-ethylenedioxythiophene: structural, physical and electronic propertiesPOLYMER INTERNATIONAL, Issue 6 2007Cintia Ocampo Abstract The structural, electric and electronic properties of copolymers derived from mixtures of N -methylpyrrole and 3,4-ethylenedioxythiophene (EDOT) with various concentration ratios have been investigated and, additionally, compared with those of the corresponding homopolymers. The electropolymerization kinetics of all the generated copolymers and the homopolymers was examined in terms of current productivity using chronoamperometry. The chemical structure of the linkages between adjacent monomers and the microstructure of the chains were investigated using Fourier transform infrared spectroscopy and quantum mechanical calculations, respectively. The results indicate that the linkages between monomeric units formed during the anodic copolymerization are of the ,,, type, while the microstructure of the copolymers depends on the EDOT content. Theoretical calculations were also used to examine the electronic properties of the systems under study, while the conductivity and the electrical stability were studied using the sheet-resistance method. Interestingly, the electric properties are consistent with the random and block microstructures predicted for the copolymers with low and high EDOT content, respectively. Copyright © 2006 Society of Chemical Industry [source] The Late Open Infarct-related Artery Hypothesis: Evidence-based Medicine or Not?CLINICAL CARDIOLOGY, Issue 11 2007Martin Brueck M.D. Abstract Randomized clinical trials have clearly shown that early reperfusion of coronary arteries is the established treatment of myocardial infarction preserving left ventricular function and reducing mortality. However, late patency of the infarct-related artery is an independent predictor of survival leading to the late open-artery hypothesis. This concept implies restoration of antegrade blood flow of the infarct-related artery in patients with myocardial infarction to improve survival by mechanisms less time-dependent or even time-independent. Possible explanations for this benefit include improved left ventricular function and electrical stability by perfusion of hibernating myocardium, accelerated infarct healing and limitation of ventricular remodeling. This review focuses on the evidence of late recanalization of occluded infarct-related arteries in patients with coronary artery disease. Copyright © 2007 Wiley Periodicals, Inc. [source] | |||||||||||||