Fluoroscopic and electrical assessment of a series of defibrillation leads:prevalence of externalized conductors

Introduction : Insulation defects with externalized conductors have been reported in the St. Jude Riata(®) family of defibrillation leads (St. Jude Medical, Sylmar, CA, USA). The objective of the Northern Ireland Riata(®) lead screening program was to identify insulation defects and externalized conductors by systematic fluoroscopic and electrical assessment in a prospectively defined cohort of patients. We sought to estimate the prevalence, identify risk factors, and determine the natural history of this abnormality. Methods : All patients with a Riata(®) lead under follow-up at the Royal Victoria Hospital were invited for fluoroscopic imaging and implantable cardioverter-defibrillator lead parameter checks. Fluoroscopic images were read independently by two cardiologists and the presence of externalized conductors was classified as positive, negative, or borderline. Results: One hundred and sixty-five of 212 patients with a Riata lead were evaluated by fluoroscopy and lead parameter measurements. The mean duration after implantation was 3.98+/-1.43 years. After screening 25 (15%) patients were classified as positive, 137 (83%) negative, and three (1.8%) borderline. Time since implantation (P = 0.001), presence of a single coil lead (P = 0.042), and patient age (P = 0.034) were significantly associated with externalized conductors. The observed rate of externalized conductors was 26.9% for 8-French and 4.7% for 7-French leads. No leads that were identified prospectively with externalized conductors had electrical abnormalities. Seven of 25 (28%) patients had a defective lead extracted by the end of this screening period. Conclusion: A significant proportion (15%) of patients with a Riata lead had an insulation breach 4 years after implantation. High-resolution fluoroscopic imaging in at least two orthogonal views is required to identify this abnormality. (PACE 2012;35:1498-1504).

Characterization of physio-chemical processes and hydration kinetics in concretes containing supplementary cementitious materials using electrical property measurements

The current study monitors both the short- and long-term hydration characteristics of concrete using discretized conductivity measurements from initial gauging, through setting and hardening, the latter comprising both the curing and post-curing periods. In particular, attention is directed to the near-surface concrete as it is this zone which protects the steel from the external environment and has a major influence on durability, performance and service-life. A wide range of concrete mixes is studied comprising both plain Portland cement concretes and concretes containing fly-ash and ground granulated blast furnace slag. The parameter normalised conductivity was used to identify four distinct stages in the hydration process and highlight the influence of supplementary cementitious materials (SCM) on hydration and hydration kinetics. A relationship has been presented to account for the temporal decrease in conductivity, post 10-days hydration. The testing procedure and methodology presented lend itself to in-situ monitoring of reinforced concrete structures. (c) 2013 Elsevier Ltd. All rights reserved.

Characterisation of Passive Intermodulation in Passive RF Devices with X-parameter

A novel approach to the modelling of passive intermodulation (PIM) generation in passive components with distributed weak nonlinearities is outlined. Based upon the formalism of X-parameters, it provides a unified framework for co-design of antenna beamforming networks, filters, combiners, phase shifters and other passive and active devices containing nonlinearities at RF front-end. The effects of discontinuities and complex circuit layouts can be efficiently evaluated with the aid of the equivalent networks of the canonical nonlinear elements. The main concepts are illustrated by examples of numerical simulations of PIM generation in the transmission lines and comparison with the measurement results.

Structural and electrical anisotropy of (001)-, (116)-, and (103)-oriented epitaxial SrBi2Ta2O9 thin films on SrTiO3 substrates grown by pulsed laser deposition

Epitaxial SrBi2Ta2O9 (SBT) thin films with well-defined (001), (116), and (103) orientations have been grown by pulsed laser deposition on (001)-, (011)-, and (111)-oriented Nb-doped SrTiO3 substrates. X-ray diffraction pole figure and phi -scan measurements revealed that the three-dimensional epitaxial orientation relation SBT(001)parallel to SrTiO3(001), and SBT[1(1) over bar 0]parallel to SrTiO3[100] is valid for all cases of SET thin films on SrTiO3 substrates, irrespective of their orientations. Atomic force microscopy images of the c-axis-oriented SET revealed polyhedron-shaped grains showing spiral growth around screw dislocations. The terrace steps of the c-axis-oriented SET films were integral multiples of a quarter of the lattice parameter c of SBT (similar to 0.6 nm). The grains of (103)-oriented SET films were arranged in a triple-domain configuration consistent with the symmetry of the SrTiO3(111) substrate. The measured remanent polarization (2P(r)) and coercive field (2E(c)) of (116)-oriented SBT films were 9.6 muC/cm(2) and 168 kV/cm, respectively, for a maximum applied electric field of 320 kV/cm. Higher remanent polarization (2P(r)=10.4 muC/cm(2)) and lower coercive field (2E(c)=104 kV/cm) than those of SBT(116) films were observed in (103)-oriented SET thin films, and (001)-oriented SET revealed no ferroelectricity along the [001] axis. The dielectric constants of (001)-, (116)-, and (103)-oriented SBT were 133, 155, and 189, respectively. (C) 2000 American Institute of Physics.

Pseudolikelihood equations for Potts MRF model parameter estimation on higher order neighborhood systems

This letter presents pseudolikelihood equations for the estimation of the Potts Markov random field model parameter on higher order neighborhood systems. The derived equation for second-order systems is a significantly reduced version of a recent result found in the literature (from 67 to 22 terms). Also, with the proposed method, a completely original equation for Potts model parameter estimation in third-order systems was obtained. These equations allow the modeling of less restrictive contextual systems for a large number of applications in a computationally feasible way. Experiments with both simulated and real remote sensing images provided good results.

A novel neural model to electrical load forecasting in transformers

The paper describes a novel neural model to electrical load forecasting in transformers. The network acts as identifier of structural features to forecast process. So that output parameters can be estimated and generalized from an input parameter set. The model was trained and assessed through load data extracted from a Brazilian Electric Utility taking into account time, current, tension, active power in the three phases of the system. The results obtained in the simulations show that the developed technique can be used as an alternative tool to become more appropriate for planning of electric power systems.

Optical and electrical properties of polymerizing plasmas and their correlation with DLC film properties

Diamond-like carbon (DLC) films were grown from radiofrequency plasmas of acetylene-argon mixtures, at different excitation powers, P. The effects of this parameter on the plasma potential, electron density, electron temperature, and plasma activity were investigated using a Langmuir probe. The mean electron temperature increased from about 0.5 to about 7.0 eV while the mean electron density decreased from about 1.2x10(9) to about 0.2x10(9) cm(-3) as P was increased from 25 to 150 W. Both the plasma potential and the plasma activity were found to increase with increasing P. Through actinometric optical emission spectrometry, the relative concentrations of CH, [CH], and H, [H], in the discharge were mapped as a function of the applied power. A rise in [H] and a fall in [CH] with increasing P were observed and are discussed in relation to the plasma characteristics and the subimplantation model. The optical properties of the films were calculated from ultraviolet-visible spectroscopic data; the surface resistivity was measured by the two-point probe method. The optical gap, E(G), and the surface resistivity, rho(s), fall with increasing P. E(G) and rho(s) are in the ranges of about 2.0-1.3 eV and 10(14)-10(16) Omega/square, respectively. The plasma power also influences the film self-bias, V(b), via a linear dependence, and the effect of V(b) on ion bombardment during growth is addressed together with variation in the relative densities of sp(2) and sp(3) bonds in the films as determined by Raman spectroscopy.

Using artificial neural networks for identification of electrical losses in transformers during the manufacturing phase

The paper describes a novel neural model to estimate electrical losses in transformer during the manufacturing phase. The network acts as an identifier of structural features on electrical loss process, so that output parameters can be estimated and generalized from an input parameter set. The model was trained and assessed through experimental data taking into account core losses, copper losses, resistance, current and temperature. The results obtained in the simulations have shown that the developed technique can be used as an alternative tool to make the analysis of electrical losses on distribution transformer more appropriate regarding to manufacturing process. Thus, this research has led to an improvement on the rational use of energy.

A generalized theory of electrical characteristics of schottky barriers for amorphous materials

In the present paper, we discuss a generalized theory of electrical characteristics for amorphous semiconductor (or insulator) Schottky barriers, considering: (i) surface states, (ii) doping impurity states at a single energy level and (iii) energetically distributed bulk impurity states. We also consider a thin oxide layer (≈10 Å) between metal and semiconductor. We develop current versus applied potential characteristics considering the variation of the Fermi level very close to contact inside the semiconductor and decrease in barrier height due to the image force effect as well as potential fall on the oxide layer. Finally, we discuss the importance of each parameter, i.e. surface states, distributed impurity states, doping impurity states, thickness of oxide layer etc. on the log I versus applied potential characteristics. The present theory is also applicable for intimate contact, i.e. metal-semiconductor contact, crystalline material structures or for Schottky barriers in insulators or polymers.

Urbach energy parameter of flash evaporated amorphous gallium arsenide films

The dependence of the optical absorption edge on the deposition crucible temperature is used to investigate the electronic states in As-rich a-GaAs flash evaporated films. The Urbach energy parameter, determined from photothermal deflection spectroscopy (PDS), presents large correlated variations with crucible temperature. The optical and electrical results are consistent with the As under coordinated sites being the more important defect in the material. © 2002 Elsevier Science B.V. All rights reserved.

A simplified method for determining the high frequency induction motor equivalent electrical circuit parameters to be used in EMI effect

The aim of this paper is to present a simple method for determining the high frequency parameters of a three-phase induction motor to be used in studies involving variable speed drives with PWM three-phase inverters, in which it is necessary to check the effects caused to the motor by the electromagnetic interference, (EMI) in the differential mode, as well as in the common mode. The motor parameters determination is generally performed in adequate laboratories using accurate instruments, such as very expensive RLC bridges. The method proposed here consists in the identification of the motor equivalent electrical circuit parameters in rated frequency and in high frequency through characteristic tests in the laboratory, together with the use of characteristic equations and curves, shown in the references to be mentioned for determining the motor high frequency parasite capacitances and also through system simulations using dedicated software, like Pspice, determining the characteristic waveforms involved in the differential and common mode phenomena, comparing and validating the procedure through published papers [01].

Electrical consumers data clustering through optimum-path forest

Non-technical losses identification has been paramount in the last decade. Since we have datasets with hundreds of legal and illegal profiles, one may have a method to group data into subprofiles in order to minimize the search for consumers that cause great frauds. In this context, a electric power company may be interested in to go deeper a specific profile of illegal consumer. In this paper, we introduce the Optimum-Path Forest (OPF) clustering technique to this task, and we evaluate the behavior of a dataset provided by a brazilian electric power company with different values of an OPF parameter. © 2011 IEEE.

Contribution of electrical parameters on the dynamical behaviour of a nonlinear electromagnetic damper

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Theorem for series in three-parameter mittag-leffler function

The new result presented here is a theorem involving series in the three-parameter Mittag-Le er function. As a by-product, we recover some known results and discuss corollaries. As an application, we obtain the solution of a fractional di erential equation associated with a RLC electrical circuit in a closed form, in terms of the two-parameter Mittag-Le er function.

Transformer Operation at Deep Saturation: Model and Parameter Determination

This paper proposes a model that adequately describes the operation of the transformer at deep saturation, suitable for power-electronics applications, and a method for determining its parameters. Simulation and experimental results are presented to confirm the validity of the model and the method.