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Electrical Connection (electrical + connection)

Distribution by Scientific Domains

Medical Sciences	72%

Selected Abstracts

Maintenance of Atrial Fibrillation by Pulmonary Vein Tachycardia with Ostial Conduction Block: Evidence of an Interpulmonary Vein Electrical Connection

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 10 2008
SEIICHIRO MATSUO M.D.
We report a case of a 56-year-old man with paroxysmal atrial fibrillation who underwent segmental, ostial pulmonary vein (PV) isolation while in arrhythmia. During isolation of the left superior PV (LSPV), organized electrical activity was seen within the vein, suggestive of a PV tachycardia with a cycle length of 90 ms. Simultaneously, organized electrical activity with a cycle length of 180 ms was seen in the left inferior PV (LIPV), suggestive of 2:1 conduction between the LSPV and the LIPV. Isolation of the LIPV resulted in conversion to sinus rhythm, while confirming isolation of the LSPV by the presence of ongoing PV tachycardia in this vein. This case demonstrates a direct electrical connection between the ipsilateral left PVs, leading to maintenance of atrial fibrillation. [source]

Electrical Connection Between Left Superior and Inferior Pulmonary Veins in a Patient with Paroxysmal Atrial Fibrillation

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 5 2002
YOSHIHIDE TAKAHASHI M.D.
Electrical Connection Between Pulmonary Veins. We report the case of a patient with paroxysmal atrial fibrillation, who underwent pulmonary vein (PV) electrical isolation from the left atrium (LA). Prior to achieving isolation of the left superior PV (LSPV) from the LA, earlier PV potentials were recorded inside the left inferior PV (LIPV) than LA activity during pacing at the distal LSPV. The LSPV finally was isolated by radiofrequency applications at the ostium of the LIPV. The patient had electrical connection between the LSPV and LIPV, and required radiofrequency ablation of the breakthroughs from the LA to LIPV for complete isolation of the LSPV. [source]

Maintenance of Atrial Fibrillation by Pulmonary Vein Tachycardia with Ostial Conduction Block: Evidence of an Interpulmonary Vein Electrical Connection

Electrical Connection Between Left Superior and Inferior Pulmonary Veins in a Patient with Paroxysmal Atrial Fibrillation

Wet etching for improved GaN-based HBT performance

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2005
Jennifer A. Bardwell
Abstract Photoenhanced wet etching of GaN in a peroxydisulfate aqueous solution has been used in npn HBT device fabrication. The wet etch acts as a selective etch for n-type layers, where the p-type layer acts as an etch stop. This allows the use of thinner base layers in an npn structure. No counter electrode or electrical connection to the wafer is required with the approach. We present experimental results on the fabrication of BJTs and HBTs using this self-aligned wet etching. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Wiring Enzymes in Nanostructures Built with Electrostatically Self-Assembled Thin Films

CHEMPHYSCHEM, Issue 1 2005
Ernesto J. Calvo Prof.
Abstract The construction of electrostatically self-assembled intelligent nanostructures on electrodes with redox enzyme layers and redox polymer molecular wires defined in space allowed the analysis of redox charge transport from the redox enzyme to the electrode along nanometric distances. Recent results on the electrical connection of enzymes to electrodes and perspectives of generating electrical signals from molecular recognition in integrated enzyme electrodes are discussed. [source]

Cover Picture: Fabrication of Multicomponent Microsystems by Directed Three-Dimensional Self-Assembly (Adv. Funct.

ADVANCED FUNCTIONAL MATERIALS, Issue 5 2005
Mater.
Abstract Directed three-dimensional self-assembly to assemble and package integrated semiconductor devices is demonstrated by Jacobs and Zheng on p.,732. The self-assembly process uses geometrical shape recognition to identify different components and surface-tension between liquid solder and metal-coated areas to form mechanical and electrical connections. The components (top left) self-assemble in a turbulent flow (center) and form functional multi-component microsystems (bottom right) by sequentially adding parts to the assembly solution. The technique provides, for the first time, a route to enable the realization of three-dimensional heterogeneous microsystems that contain non-identical parts, and connecting them electrically. We have developed a directed self-assembly process for the fabrication of three-dimensional (3D) microsystems that contain non-identical parts and a statistical model that relates the process yield to the process parameters. The self-assembly process uses geometric-shape recognition to identify different components, and surface tension between liquid solder and metal-coated areas to form mechanical and electrical connections. The concept is used to realize self-packaging microsystems that contain non-identical subunits. To enable the realization of microsystems that contain more than two non-identical subunits, sequential self-assembly is introduced, a process that is similar to the formation of heterodimers, heterotrimers, and higher aggregates found in nature, chemistry, and chemical biology. The self-assembly of three-component assemblies is demonstrated by sequentially adding device segments to the assembly solution including two hundred micrometer-sized light-emitting diodes (LEDs) and complementary metal oxide semiconductor (CMOS) integrated circuits. Six hundred AlGaInP/GaAs LED segments self-assembled onto device carriers in two minutes, without defects, and encapsulation units self-assembled onto the LED-carrier assemblies to form a 3D circuit path to operate the final device. The self-assembly process is a well-defined statistical process. The process follows a first-order, non-linear differential equation. The presented model relates the progression of the self-assembly and yield with the process parameters,component population and capture probability,that are defined by the agitation and the component design. [source]

Reentry in a Morphologically Realistic Atrial Model

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 9 2001
EDWARD J. VIGMOND Ph.D.
Reentry in Morphologically Realistic Atria.Introduction: Atrial fibrillation is the most common cardiac arrhythmia. In ablation procedures, identification of the reentrant pathways is vital. This has proven difficult because of the complex morphology of the atria. The purpose of this study was to ascertain the role of specific anatomic structures on reentry induction and maintenance. Method and Results: A computationally efficient, morphologically realistic, computer model of the atria was developed that incorporates its major structural features, including discrete electrical connections between the right and left atria, physiologic fiber orientation in three dimensions, muscle structures representing the crista terminalis (CT) and pectinate muscles, and openings for the veins and AV valves. Reentries were induced near the venous openings in the left and right atria, the mouth of the coronary sinus, and the free wall of the right atrium. The roles of certain muscular structures were ascertained by selectively removing the structures and observing how the propagation of activity was affected. Conclusion: (1) The muscular sheath of the coronary sinus acts as a pathway for a reentrant circuit and stabilizes any circuits that utilize the isthmus near the inferior vena cava. (2) Poor trans-CT coupling serves to stabilize flutter circuits. (3) Wall thickness is an important factor in the propagation of electrical activity, especially in the left atrium. (4) The openings of the inferior and superior venae cavae form natural anatomic anchors that make reentry easier to initiate by allowing for smaller ectopic beats to induce reentry. [source]

Design and development of a prototype endocavitary probe for high-intensity focused ultrasound delivery with integrated magnetic resonance imaging

JOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 3 2007
Iain P. Wharton MRCS
Abstract Purpose To integrate a high intensity focused ultrasound (HIFU) transducer with an MR receiver coil for endocavitary MR-guided thermal ablation of localized pelvic lesions. Materials and Methods A hollow semicylindrical probe (diameter 3.2 cm) with a rectangular upper surface (7.2 cm × 3.2 cm) was designed to house a HIFU transducer and enable acoustic contact with an intraluminal wall. The probe was distally rounded to ease endocavitary insertion and was proximally tapered to a 1.5-cm diameter cylindrical handle through which the irrigation tubes (for transducer cooling) and electrical connections were passed. MR compatibility of piezoceramic and piezocomposite transducers was assessed using gradient-echo (GRE) sequences. The radiofrequency (RF) tuning of identical 6.5 cm × 2.5 cm rectangular receiver coils on the upper surface of the probe was adjusted to compensate for the presence of the conductive components of the HIFU transducers. A T1-weighted (T1-W) sliding window dual-echo GRE sequence monitored phase changes in the focal zone of each transducer. High-intensity (2400 W/cm,2), short duration (<1.5 seconds) exposures produced subtherapeutic temperature rises. Results For T1-W images, signal-to-noise ratio (SNR) improved by 40% as a result of quartering the conductive surface of the piezoceramic transducer. A piezocomposite transducer showed a further 28% improvement. SNRs for an endocavitary coil in the focal plane of the HIFU trans-ducer (4 cm from its face) were three times greater than from a phased body array coil. Local shimming improved uniformity of phase images. Phase changes were detected at subtherapeutic exposures. Conclusion We combined a HIFU transducer with an MR receiver coil in an endocavitary probe. SNRs were improved by quartering the conductive surface of the piezoceramic. Further improvement was achieved with a piezocomposite transducer. A phase change was seen on MR images during both subtherapeutic and therapeutic HIFU exposures. J. Magn. Reson. Imaging 2007. © 2007 Wiley-Liss, Inc. [source]

Ageing to arrhythmias: conundrums of connections in the ageing heart

JOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 12 2006
Sandra A. Jones
The proportion of the population that is elderly continues to increase, leading to an increasing need to address problems chiefly associated with old age. Progressive ageing of the heart is associated with an increasing incidence of arrhythmias and disorders of the normal origin of the heartbeat, the sinoatrial node. This intrinsic pacemaker of the heart has an increasing tendency with age to lose its dominant role in pacing the heart, and regulation of heart rate becomes erratic. This ,sick sinus syndrome' is associated with fainting, palpitations, shortness of breath and sudden death. Current treatment of this condition is by implantation of an artificial pacemaker, an intervention increasingly required with age. The current evidence suggests that the normal heartbeat fails due to changes in the expression of critical proteins that ensure the correct production and conduction of the cardiac action potential. Depletion of a protein directly responsible for providing electrical connections between the cells of the heart, connexin 43, appears to leave the normal cardiac pacemaker disconnected and unable to drive the heart. This process may be associated with age-dependent changes in stress-related signalling. Simple interventions such as exercise could impact on the processes hypothesized to be involved and may offer a means to preserve the stability of the electrical activity of the heart into old age without pharmacological manipulation. [source]