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At least 37 records · Page 2Linked to original sources
PubMedDate not supplied

Applicability of the latissimus dorsi muscle in situ as a biomechanical energy source.

The purpose of this study was to assess the applicability of the latissimus dorsi muscle in situ as an energy source for a circulatory assist device. A pneumatic chamber, devised by the authors, was inserted beneath the muscle and compressed by contractions of the muscle so that muscle contractile power was converted into pneumatic pressure. The optimal insertion position of the chamber beneath the latissimus dorsi muscle, and the influence of chamber size on generated pneumatic pressure, were investigated. The pneumatic chamber functioned better when it was placed in a proximal position (third intercostal space) than in a middle or distal position. Using a mock circuit, the performance of the pneumatic chamber as an energy source for a circulatory assist device was evaluated. The pneumatic chamber was able to generate power sufficient to drive a right ventricular assist device as far as stroke work was involved. When the pneumatic chamber was operated with a high afterload, it could even be an energy source for aortic counterpulsation.

Animals↗
PubMed1976

Radiographic aspects of permanent cardiac pacemakers.

Radiographic findings in patients with permanent cardiac pacemakers are described, and recent advances in pulse generator and lead design are presented. Emphasis is placed on those findings which are related to (a) complications of cardiac pacing, (b) radiographic configurations of new energy sources and lead/electrode systems, and (c) a new system of pulse generator identification.

Bioelectric Energy Sources↗
PubMedDate not supplied

Implantable power-sources: a review.

It has now been 25 years since the first pacemakers were implanted. It is indeed fascinating to see the breadth and the vision of the early investigators on both sides of the ocean, most of them friends of the author, in the almost desperate search for a power source that would enable the pacemaker to last as long as the expected lifetime of the average patient. Every conceivable method of power generation, power storage, and energy conservation was studied. The result was an orderly transition from zinc-mercury batteries, to lithium-iodine batteries, to the newest lithium oxyhalide systems of the coming decade, all of which coincided with tentative sidesteps into rechargeable batteries and nuclear batteries. This paper traces this 25 years of progress and salutes the many investigators who have brought the implantable pacemaker and its power source to their present state of acceptance by the medical profession.

Bioelectric Energy Sources↗
PubMed2002

Elemental characterization of microorganism granules by EFTEM in the tube wall of a deep-sea vent invertebrate.

Microorganisms colonizing the exoskeletons of the tube worm Riftia pachyptila are described at the ultrastructural level. The prokaryotic cells from the worm tube wall differ from those colonizing the exoskeleton outer surface in the presence of an electron dense granule. The morphology and distribution of these bacteria-like cells are described. Prokaryotic organisms are assembled in nodules which increased in size in the oldest part of the exoskeleton. The aspect, location and elemental composition of the intracellular granules are determined. Most of them (100 nm in diameter) are located close to the cell membrane and exhibit a homogeneous and amorphous content. EDX and EFTEM microanalyses show that these structures contain phosphorus, oxygen and iron. All together these data suggest that these granules are iron polyphosphates. These structures may act as energy sources for making ATP during anoxic conditions as existing in hydrothermal environments.

Adenosine Triphosphate↗
PubMedDate not supplied

A gait-powered autologous battery charging system for artificial organs.

The quality of life of patients relying on electrically powered artificial organs is currently restricted by the limited energy availability provided by portable batteries. As these patients become increasingly ambulatory, and are developing more active lifestyles, this limitation grows more apparent. Coincidentally, these patients may themselves be capable of generating electrical power as a consequence of their physical activity. Extraction of this latent autologous energy could, in turn, be used to augment charging of internal batteries--thus untethering the patient from external power for extended periods of time. In this study, the viability of deriving energy associated with natural human ambulation has been evaluated. The kinematic components of gait were evaluated to identify the largest useful forces and moments that may be harnessed as an energy source, while presenting minimal "perceived" work for the patient. It was found that the ground reaction forces associated with the heel strike and toe-off phases of the gait represent the greatest potential for usable energy. This study uses a piezoelectric array within the midsole of the shoe for the conversion of mechanical to electric energy. This power could then be easily coupled in tandem with existing transcutaneous transformers for augmenting or temporarily replacing external power sources.

Artificial Organs↗
PubMedDate not supplied

Alternative energy sources for surgical atrial ablation.

As less complex modifications of the Maze procedure have been developed, a number of energy sources have been introduced to facilitate the creation of electrically isolating lesions within the atria. These include cryoablation, radiofrequency, microwave, laser, and focused ultrasound. Although each of these sources works slightly differently, the goal of all thermal sources is to heat tissue to a temperature (50 degrees C) above which irreversible electrical isolation occurs. These sources have been utilized both endocardially in arrested heart procedures as well as epicardially in the beating heart setting. There are several obstacles to the use of these sources epicardially, mostly related to the heat sink effect of endocardial blood. Several recent modifications have been introduced that will hopefully increase the efficacy of these sources in beating heart applications.

Atrial Fibrillation↗
PubMed2004

Confessions of a bioenergy advocate.

Feedstocks that deserve serious consideration for fuels and chemicals are sugarcane, corn, trees and algae. Commercialization of biomass refining is imminent but the wild claims of those who think that bioenergy can replace much of our dependence on foreign oil are appalling. It is naive to view biomass as the panacea for the coming energy crisis because there is not enough in practical locations and the costs involved in retrieving and refining it will be relatively high. The world will not run out of energy, but cheap energy might disappear, with its economics clouded by a myriad of subsidies for the competing energy sources and by world politics. This assessment of biomass supply and conversion technologies provides global perspectives and exposes some alternatives to be so impractical that they are almost fraudulent.

Bioelectric Energy Sources↗
PubMedDate not supplied

Efficacy of a biomechanical counterpulsation device powered by skeletal muscle for right heart assist.

A valveless, single-orifice counterpulsation device powered by skeletal muscle was applied to the pulmonary artery for right heart assist. Latissimus dorsi muscles of six dogs had been electrically conditioned for four months in advance (Group 1); the muscles of eight dogs were not preconditioned (Group 2). A polyvinyl chloride balloon was placed beneath the latissimus dorsi muscle and connected to the left pulmonary artery using a noncollapsing graft. Latissimus dorsi muscle was paced synchronously to the cardiac cycle to produce pulmonary artery diastolic augmentation. Percent changes in diastolic augmentation pressure (% DAP) in the main PA was measured. Percent DAP after 180 min assistance was 91 +/- 10% in Group 1, whereas it decreased to 17 +/- 12% in Group 2 (p less than 0.001). These results demonstrate that electrically conditioned skeletal muscle is effective as a power source in right heart assist.

Animals↗
PubMed1976

Rechargeable silver-modified mercuric oxide-zinc cell for cardiac pacemakers.

Tests were conducted on rechargeable mercury-zinc pacemaker batteries under simulated and actual biologic conditions, using a variety of discharge rates and charging schedules. In tests on 96 cells at a 6.4 milliampere (ma) discharge, recharging once every 15 months of simulated pacing at a 25 microampere (mua) drain, the earliest cell failure occurred after an equivalent of 50 years of pacing. The mean pacing equivalent for all 96 cells was more than 140 years. In 6.4 ma discharge tests on 24 cells, recharging once every 8 days of simulated pacing, only 1 cell in 24 failed after an equivalent of more than 500 years of pacing (actual time 2 years). In tests on 13 cells pacing at a 200 mua drain without recharging, the simulated mean duration of pacing before total discharge was 4.8 years. Seven other cells at a 200 mua drain with periodic recharging continue to function normally after more than 7 years of actual time, simulating 56 years of pacing at a 25 mua drain. Cardiac pacemakers using the rechargeable mercury-zinc cell have been implanted in animals for more than 2 1/2 years and in patients for more than 1 year with all units continuing to function satisfactorily. It has been demonstrated unequivocally that a rechargeable mercury-zinc pacemaker will function continuously for more than 4 years without recharging and that periodic recharging will extend pacing life far beyond that predicted for lithium and nuclear primary power sources.

Animals↗
PubMedDate not supplied

Atrial ablation for the surgical treatment of atrial fibrillation: principles and limitations.

This article reviews the development of procedures designed to eradicate atrial fibrillation by creating nonincisional lesions in the atria. Percutaneous interventional and surgical data are reviewed and analyzed. A major limitation of the surgical approaches, which utilize a variety of energy sources, appears to be the difficulty in achieving transmurality in all patients. A second limitation is related to a poor understanding of the underlying mechanisms of atrial fibrillation, and the consequent uncertainty as to the ideal lesion configurations necessary to counter these mechanisms. The article also discusses the various types of clinical atrial fibrillation, and discusses the differences between endocardial and epicardial application of thermal energy sources. Finally, atrial contractility is addressed, and the authors conclude that the ideal procedure will achieve a balance between conversion to normal sinus rhythm and the preservation of atrial contractility.

Atrial Fibrillation↗
PubMed1993

The bioelectrical source in computing single muscle fiber action potentials.

Generally, single muscle fiber action potentials (SFAPs) are modeled as a convolution of the bioelectrical source (being the transmembrane current) with a weighting or transfer function, representing the electrical volume conduction. In practice, the intracellular action potential (IAP) rather than the transmembrane current is often used as the source, because the IAP is relatively easy to obtain under experimental conditions. Using a core conductor assumption, the transmembrane current equals the second derivative of the IAP. In previous articles, discrepancies were found between experimental and simulated SFAPs. Adaptations in the volume conductor slightly altered the simulation results. Another origin of discrepancy might be an erroneous description of the source. Therefore, in the present article, different sources were studied. First, an analytical description of the IAP was used. Furthermore, an experimental IAP, a special experimental SFAP, and a measured transmembrane current scaled to our experimental situation were applied. The results for the experimental IAP were comparable to those with the analytical IAP. The best agreement between experimental and simulated data was found for a measured transmembrane current as source, but differences are still apparent.

Action Potentials↗
PubMed2002

Effect of initial carbon sources on the electrochemical detection of glucose by Gluconobacter oxydans.

An electrochemical system consisted of Gluconobacter oxydans as a microorganism and 2-hydroxy-1,4-naphthoquinone (HNQ) as a mediator has been setup to examine the effect of initial carbon sources on the detection of glucose. Catalytic current due to the oxidation of glucose was observed only when both G. oxydans and HNQ were present. From amperometric measurements, it was found that the sensitivity strongly depended on the initial carbon sources. The sensitivity was highest for the cells cultured in a fructose-containing medium and decreased in the order, mannitol > sucrose > glucose > galactose > glycerol. The difference in sensitivity was explained by considering the current rising pattern at an initial stage of a microbial fuel cell constructed with the same components. The rising time, not the fuel cell efficiency, could directly be related to the sensitivity order. A sensor where G. oxydans was confined at the vicinity of the electrode by the semipermeable membrane was constructed. A linear response over a millimolar range of glucose concentration was observed with a cell grown in galactose-containing medium. This work demonstrates that the initial carbon source play an important role on glucose sensoring and should be considered in a real application.

Bioelectric Energy Sources↗
PubMed1991

Estimates of neuronal current distributions.

The main purpose of measurements of the magnetic field produced by cerebral electrical activity is to locate this activity or to determine its distribution in the brain. In this paper, methods to locate or otherwise characterize source currents in the brain are briefly discussed. It is emphasized that the optimal source estimation method depends crucially on the availability of prior information and on the questions one wants to resolve with the measurements.

Bioelectric Energy Sources↗