Lead conductors

Pacemakers are among the most reliable electronic devices ever built device survival probabilities of 99.9% (excluding normal battery depletion) at 10 years are not unheard of. But despite intensive quality assurance efforts by manufacturers, the devices do remain subject to occasional failures the annual pacemaker replacement rate due to generator malfunction has been estimated at roughly one per 1000 devices implanted, a marked improvement in reliability since the early 1980s (Maisel et al. 2006 Maisel 2006). There have been multiple major advisories and recalls issued by the FDA regarding pacing leads, with more of these because of problems with the lead insulation than with the lead conductor. 

Within a pacemaker lead, the flow of electrons from the connector lead pin to the cathode electrode is relatively unimpeded, because the materials used for modem lead conductors have a very low resistance of the order of 5-50 Q. This is necessary to prevent wastage in delivery of energy to the cathode. For instance, a very high resistance conductor would act like a radiator generating heat in the conductor thus, the current or number of electrons eventually delivered to the cathode would be markedly attenuated. Similarly, partial lead fractures or complete lead fractures with the fractured ends in contact with each other will result in very high resistances. In both of these cases, despite the production of an adequate voltage, the current or electron density reaching the distal end of the conductor may be inadequate for the stimulation of the myocardium. This situation can be explained by Ohm s Law ... 

Fig. U Schematic of a bipolar lead illustrating the factors involved in determining system impedance. The arrows denote current flow. Resistance to current flow occurs at the lead conductor (conductor resistance), at the cathode-tissue interface (cathode impedance and polarization), in the myocardium (tissue impedance) and at the anode (anode impedance). The largest contributors to system impedance are the cathode impedance and polarization effects.

The pacing lead conductor is composed of wire that conducts the electrical current from the pulse generator to the stimulating electrode and the sensed cardiac signals (intrinsic or evoked) from the electrode(s) to the sensing amplifier of the pulse generator. Unipolar leads require one conductor, whilst bipolar... 

Subclavian puncture may result in lead conductor fracture. Medtronic News 1986-1987 16 27. 

Inspect the entire length of the lead for lack of integrity, such as fracture, compression, or crimp. Intermittent or complete failure to capture or sense or output could be secondary to lead conductor coU fracture or loss of insulation integrity. Attempt to follow each lead along its course, assessing the conductor coil. Also, inspect for any crimping of the lead as it passes under the clavicle. 

Sensing Problems Sensing problems in the lead/lCD system, such as T-wave sensing, double counting of pacing stimuli, and lead/conductor failure, were reviewed earlier. Real-time measurements and marker channels are very useful in this setting. The chest radiograph will identify some types of lead problems (Chap. 18). In some cases, implantation of a new lead is required unfortunately. 

Fig. 5 Examples of various types of lead conductors and their insulation A. a unipolar single-filar conductor coil, B. parallel single-filar conductor cods, C. coaxial multifilar conductor cods, and D. a multifilament microcable...

Fig. 6 A 0.5 -inch-long grooved cobalt mandrel is inserted into tubing, which is sealed on both ends with medical adhesive. The grooves are intended to simulate the spaces between pacemaker lead conductor coils. A 1-mm-diameter hole is made in one end to assure ingress of exudate/transudate. Samples are tied together in strings, identified with a colored glass bead, and implanted in the subcutis of rabbits as shown in Fig. 3. After optical microscopic examination, the samples may be analyzed by FTIR, HPLC molecular weight, SEM, and other suitable techniques...

Mozumi, T., T. Ikeuchi, N. Fukuda, A. Ametani, and S. Sekioka. 2002. Experimental formulas of surge impedance for grounding lead conductors in distribution lines. lEEJ Trans. PE 122-B (2) 223-231. 

At sufficiently high frequency, the electromagnetic skin depth is several times smaller than a typical defect and induced currents flow in a thin skin at the conductor surface and the crack faces. It is profitable to develop a theoretical model dedicated to this regime. Making certain assumptions, a boundary value problem can be defined and solved relatively simply leading to rapid numerical calculation of eddy-current probe impedance changes due to a variety of surface cracks. 

Ionic conductors arise whenever there are mobile ions present. In electrolyte solutions, such ions are nonually fonued by the dissolution of an ionic solid. Provided the dissolution leads to the complete separation of the ionic components to fonu essentially independent anions and cations, the electrolyte is tenued strong. By contrast, weak electrolytes, such as organic carboxylic acids, are present mainly in the undissociated fonu in solution, with the total ionic concentration orders of magnitude lower than the fonual concentration of the solute. Ionic conductivity will be treated in some detail below, but we initially concentrate on the equilibrium stmcture of liquids and ionic solutions. 

The most direct effect of defects on tire properties of a material usually derive from altered ionic conductivity and diffusion properties. So-called superionic conductors materials which have an ionic conductivity comparable to that of molten salts. This h conductivity is due to the presence of defects, which can be introduced thermally or the presence of impurities. Diffusion affects important processes such as corrosion z catalysis. The specific heat capacity is also affected near the melting temperature the h capacity of a defective material is higher than for the equivalent ideal crystal. This refle the fact that the creation of defects is enthalpically unfavourable but is more than comp sated for by the increase in entropy, so leading to an overall decrease in the free energy... 

Lead is a bluish-white metal of bright luster, is very soft, highly malleable, ductile, and a poor conductor of electricity. It is very resistant to corrosion lead pipes bearing the insignia of Roman emperors, used as drains from the baths, are still in service. It is used in containers for corrosive liquids (such as sulfuric acid) and may be toughened by the addition of a small percentage of antimony or other metals. 

These ion lasers are very inefficient, partly because energy is required first to ionize the atom and then to produce the population inversion. This inefficiency leads to a serious problem of heat dissipation, which is partly solved by using a plasma tube, in which a low-voltage high-current discharge is created in the Ar or Kr gas, made from beryllium oxide, BeO, which is an efficient heat conductor. Water cooling of the tube is also necessary. 

Fig. 4. Submersible oil well pump cable. A, SoHd copper conductor B, EPR-based insulation C, chemical barrier D, lead sheath E, filler E, galvanised...

Dispersion-strengthened copper is made by dispersing a thoria or alumina phase through copper powder. The resulting P/M product retains its strength at elevated temperatures. It is used, for example, as the conductor or lead wine that supports the hot filament inside incandescent lamps. 

Electronic Applications. The PGMs have a number of important and diverse appHcations in the electronics industry (30). The most widely used are palladium and mthenium. Palladium or palladium—silver thick-film pastes are used in multilayer ceramic capacitors and conductor inks for hybrid integrated circuits (qv). In multilayer ceramic capacitors, the termination electrodes are silver or a silver-rich Pd—Ag alloy. The internal electrodes use a palladium-rich Pd—Ag alloy. Palladium salts are increasingly used to plate edge connectors and lead frames of semiconductors (qv), as a cost-effective alternative to gold. In 1994, 45% of total mthenium demand was for use in mthenium oxide resistor pastes (see Electrical connectors). 

The lead—acid battery is comprised of three primary components the element, the container, and the electrolyte. The element consists of positive and negative plates connected in parallel and electrically insulating separators between them. The container is the package which holds the electrochemically active ingredients and houses the external connections or terminals of the battery. The electrolyte, which is the Hquid active material and ionic conductor, is an aqueous solution of sulfuric acid. 

Betts Electrolytic Process. The Betts process starts with lead bullion, which may carry tin, silver, gold, bismuth, copper, antimony, arsenic, selenium, teUurium, and other impurities, but should contain at least 90% lead (6,7). If more than 0.01% tin is present, it is usually removed from the bullion first by means of a tin-drossing operation (see Tin AND TIN ALLOYS, detinning). The lead bullion is cast as plates or anodes, and numerous anodes are set in parallel in each electrolytic ceU. Between the anodes, thin sheets of pure lead are hung from conductor bars to form the cathodes. Several ceUs are connected in series. 

Soldering materials are alloys that are composed primarily of tin and lead (qv), and have low melting temperatures relative to the conductor metals which are being soldered (see Lead alloys Tin and tin alloys). Welding requires sufficientiy high temperatures for the fusion of metals. 

We developed a sensor for determination of content of phosphorars in metallurgical melts. In quality of ion conductor used orthophosphate of calcium which pressed in tablets 010 mm. Tablets (mass 1-2 g) annealed at a temperature 400°C during 7-10 h. Tablets melts then in a quartz tube and placed the alloy of iron containing 1 mass % P. Control of sensor lead on Fe - P melts. Information on activities (effective concentration) of phosphorars in Fe - P melts was received. It is set that the isotherm of activity of phosphorars shows negative deviations from the Raouls law. Comparison them with reliable literary inforiuation showed that they agree between itself. Thus, reliable data on activities (effective concentration) of phosphorars in metallic melts it is possible to received by created electrochemical sensor for express determination. 

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