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At least 199 records · Page 11Linked to original sources
PubMed2006

Effect of electrode potential on electrode-reducing microbiota.

The benthic microbial fuel cell (BMFC) generates power by coupling oxidation of fuels naturally residing in marine sediments with reduction of oxygen in overlying waters. A central feature of BMFCs is spontaneous colonization of the anode by mineral-reducing microorganisms indigenous to marine sediments that catalyze the power-generating anodic reactions. Described here is a preliminary investigation of how the anode potential affects this feature. Different oxidative potentials were applied to a set of anodes under conditions known to promote anode enrichment of acetate oxidizing/mineral reducing microorganisms. In-situ analysis of current, acetate consumption, and reducing ability of the anode colonies suggest thatthe microorganisms conserve a significant portion (as much as 95%) of potential energy liberated from oxidation of acetate and reduction of the anode for their own metabolic benefit. The implication of this result with respect to BMFCs, and other MFCs utilizing electrode-reducing microbial catalysts, is that although the microorganisms enable long-term stability of such fuel cells, they may significantly impact efficiency of power output per equivalent of fuel consumed.

Acetates↗
PubMed1989

Do electrode and lead design differences for permanent cardiac pacing translate into clinically demonstrable differences? (Comparison of sintered platinum and activated vitreous and porous carbon electrodes).

A randomized prospective study was undertaken to compare the electrical performances of three permanent, endocardial, tined pacing leads with different electrode designs--sintered platinum, vitreous carbon, and porous carbon. Ninety-nine patients received one of the leads (S80 31; 423S 32; S100 36). Acute R wave amplitude and ST elevation of the native endocardial electrogram, voltage threshold, impedance, and current flow at four pulse durations (0.25-1.0 msec) were measured. Voltage thresholds were measured noninvasively at each of four pulse durations at 2 days and 1, 3, and 6 months after implantation. No significant differences were found in sensing properties, or current flow at threshold at 0.5 msec pulse duration. The 423S lead had a significantly higher impedance at threshold and both a higher impedance and lower current flow at 5 V. No significant differences in threshold voltages were found between the three leads at any pulse duration, at any of the assessed times after implantation. Six-month thresholds for the S80, 423S, and S100 leads were 1.18 +/- 0.35, 1.17 +/- 0.29, and 1.06 +/- 0.38 V respectively at 0.5 msec pulse duration. Differences between 'high performance' pacing leads need to be of a greater order of magnitude before they can be exploited to give any real clinical advantage to patients.

Aged↗
PubMed1977

Detector electrode introduced by mediastinoscopy for atrial triggered cardiac pacing. A follow-up of electrode function in 82 patients.

An atrial detector electrode was introduced by mediastinoscopy in 82 patients requiring permanent cardiac pacing. There were no complications. An adequate P wave was recorded in 80 patients. During the following week, the P wave became ineffective in 5 patients; angina occurred in 2 and atrial arrhythmias in 2. Atrially triggered ventricular pacing established in 73 patients and was followed in 71 patients for a period of 1 to 113 months. In 17 cases, it had to be terminated because of an ineffective or unstable P wave,in 6 cases because of atrial arrhythmias, and in 4 cases because of advanced age and recurrent infections. The method is technically simple and place little stress on the patient.

Adult↗
PubMed2000

Recommendations for measurement of and conventions for reporting sodium and potassium by ion-selective electrodes in undiluted serum, plasma or whole blood. International Federation of Clinical Chemistry and Laboratory Medicine (IFCC). IFCC Scientific Division Working Group on Selective Electrodes.

Ion-selective electrodes (ISEs) respond to ion-activity and therefore do not sense substance concentration directly. However, it is recognized that sodium and potassium in plasma will continue to be expressed for clinical purposes in terms of substance concentration (mmol/l). A convention is proposed whereby for routine clinical purposes results of ISE measurements of sodium and potassium in undiluted plasma should be reported in terms of substance concentration (mmol/l). In specimens with normal concentrations of plasma water, total CO2, lipids, protein and pH, the values will concur with the total substance concentration as determined for example by flame atomic emission spectrometry (FAES) or ISE measurements on diluted samples. In specimens with abnormal concentrations of plasma water, the results will differ. However, under these circumstances, measurements of sodium and potassium by ISE in the undiluted sample will more appropriately reflect the activity of sodium and potassium and are therefore clinically more relevant than the determination in diluted samples. Detailed recommendations are made about practical procedures to achieve this. The recommended name for this quantity is the substance concentration of ionized sodium or ionized potassium in plasma, as opposed to total sodium or total potassium determined by, e.g. FAES, or ISE measurements on diluted samples.

Calibration↗
PubMed1996

Recommendation on mean molar activity coefficients and single ion activity coefficients of solutions for calibration of ion-selective electrodes for sodium, potassium, and calcium determination. IFCC Scientific Division Working Group on Selective Electrodes.

In principle, flame photometry measures substance concentration, and ion-selective electrodes (ISEs) measure ion activity. However, the situation regarding the comparison of results from the two techniques when applied to blood plasma is complex. The problem can be approached experimentally from the point of view of calibration of ISEs with concentration calibrators, and similar procedures are adopted for commercial ISE-based clinical analyzers. Nevertheless, there is interest in the evaluation of single ion activities in blood plasma and solutions simulating its ionic composition. Solutions are proposed for calibrating ISEs for the determination of sodium, potassium, and calcium. It is recommended that the values for single ion activities derived from the Pitzer treatment of mixed electrolyte solutions be adopted, because, although this has some empirical features, it has a sounder theoretical basis than the previously used Stokes-Robinson-Bates hydration approach.

Calcium↗
PubMed1990

[Prerequisites for pacemaker electrodes for individual programming of a low stimulation impulse (comparison of an Elgiloy and a steroid-dependent pacemaker electrode)].

The individual programming of cardiac pacemakers to pulse amplitudes of 2.5 volts and less reduces unnecessary energy consumption by the pacing impulse. In order not to impair the safety margin, electrodes must reveal a low chronic pacing threshold associated with a small standard deviation. For 3 months after implantation we investigated these conditions in 10 patients with a steroid-eluting lead and in 10 patients with a conventional elgiloy lead. During the study period patients with a steroid-eluting lead had a significantly lower pacing threshold. Twelve weeks after implantation all steroid-patients had 0.8 volts pacing threshold at 0.5 ms pulse width. In contrast to the conventional lead the steroid-eluting lead had a significantly lower impedance. Since voltage enters squared into the energy consumption formula, patients with a steroid-eluting lead needed significantly less energy for an effective stimulation of the myocardium 4 and 12 weeks after implantation. R-wave amplitude was not different in both groups. Our investigation demonstrates that immediately after implantation all patients with a steroid-eluting lead can be programmed at 2.5 volts pulse voltage or individually even lower. The saved energy results either in an extended pulse generator longevity or allows the implantation of a smaller pulse generator with a reduced battery capacity.

Aged↗
PubMed2005

X-ray absorption spectroscopic study on the electronic structure of Li(1)(-)(x)()CoPO(4) electrodes as 4.8 V positive electrodes for rechargeable lithium ion batteries.

Changes in the electronic structure of olivine Li(1-x)CoPO(4), 4.8 V positive electrode material for lithium ion batteries, were investigated using the X-ray absorption spectroscopy (XAS) technique. The threshold energy in the Co K-edge increased with electrochemical Li removal, indicating the oxidation of cobalt ions due to charge compensation. Moreover, P and O K-edge XAS showed a slight shift in threshold energy with Li removal. Although it is generally believed that the electrons of PO(4) polyanion do not contribute to the oxidation process, present experimental results indicate changes in the electronic structure around PO(4) units. Such results would be interpreted by the idea of the hybridization effect between the Co 3d and O 2p orbitals and of the polarization effect introduced by Li ions.

Journal Article↗
PubMed1998

Effect of a single element subcutaneous array electrode added to a transvenous electrode configuration on the defibrillation field and the defibrillation threshold.

Even with the use of biphasic shocks, up to 5% of patients need an additional subcutaneous lead to obtain a defibrillation safety margin of at least 10 J. The number of patients requiring additional subcutaneous leads may even increase, because recent generation devices have a < 34 J maximum output in order to decrease their size. In 20 consecutive patients, a single element subcutaneous array lead was implanted in addition to a transvenous lead system consisting of a right ventricular (RV) and a vena cava superior lead using a single infraclavicular incision. The RV lead acted as the cathode; the subcutaneous lead and the lead in the subclavian vein acted as the anode. The biphasic defibrillation threshold was determined using a binary search protocol. Patients were randomized as to whether to start them with the transvenous lead configuration or the combination of the transvenous lead and the subcutaneous lead. In addition, a simplified assessment of the defibrillation field was performed by determining the interelectrode area for the transvenous lead only and the transvenous lead in combination with the subcutaneous lead from a biplane chest X ray. The intraoperative defibrillation threshold was reconfirmed after 1 week, after 3 months, and after 12 months. The mean defibrillation threshold with the additional subcutaneous lead was significantly (P = 0.0001) lower (5.7 +/- 2.9 J) than for the transvenous lead system (9.5 +/- 4.6 J). With the subcutaneous lead, the impedance of the high voltage circuit decreased from 48.9 +/- 7.4 omega to 39.2 +/- 5.0 omega. In the frontal plane, the interelectrode area increased by 11.3% +/- 5.5% (P < 0.0001) and in the lateral plane by 29.5% +/- 12.4% (P < 0.0001). The defibrillation threshold did not increase during follow-up. Complications with the subcutaneous electrode were not observed during a follow-up of 15.8 +/- 2 months. The single finger array lead is useful in order to lower the defibrillation threshold and can be used in order to lower the defibrillation threshold.

Aged↗