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At least 181 records · Page 10Linked to original sources
PubMed2006

Photomodulation of the electrode potential of a photochromic spiropyran-modified Au electrode in the presence of Zn2+: a new molecular switch based on the electronic transduction of the optical signals.

The electrode potential of a photochromic spiropyran-modified Au electrode could be reversibly modulated by UV/visible light irradiation in the presence of Zn2+, and a new molecular switch and an "AND" logic gate based on this electronic transduction of the optical signals were established.

Benzopyrans↗
PubMed1975

[Electrode problems in pacemaker wearers (experiences with three electrode types) (author's transl)].

3 types of electrodes (Medtronic 6903, EMT 588, MIP 2000) of 123 patients are examined by following criterial 1. rate of dislocation, 2. development of threshold, 3. time of application. We found: The Medtronic has the smallest rate of dislocation, the lowest range of threshold and is quickly placed in the right ventricle. The rate of dislocation of the EMT 588 is still just acceptable and it also has a sufficient low threshold, but in comparison to the other helical-wire electrodes the disadvantage of being rather difficult to place in the right ventricle. The MIP 2000 has not proved to be useful due to its large rate of dislocation.

Electrodes, Implanted↗
PubMed1977

[A simple and reliable atrial pacemaker electrode: technique of transvenous implantation and clinical results with a metal hook electrode (author's transl)].

At present only about 1% of all implanted pacemakers are atrial triggered ones, although an indication for them exists in about 77% of cases. This disproportion is due to an overestimate of the difficulties encountered in fixing the electrode. The electrode developed by Irnich has now been modified to provide good fixation for atrial stimulation, as well as recording of atrial potentials. Preliminary results in 20 patients have been favourable. Over a seven-month observation period there have been no instances of dislocation or loss of effective stimulation.

Electrocardiography↗
PubMed2003

Electrode systems for measuring cardiac impedances using optical transmembrane potential sensors and interstitial electrodes--theoretical design.

The cardiac electrical substrate is a challenge to direct measurement of its properties. Optical technology together with the capability to fabricate small electrodes at close spacings opens new possibilities. Here, those possibilities are explored from a theoretical viewpoint. It appears that with careful measurements from a well-designed set of electrodes one can obtain structural conductivities, separating intracellular from interstitial values, and longitudinal from transverse. Resting membrane resistance also can be obtained.

Body Surface Potential Mapping↗
PubMed1983

Electrode-heart interface: definition of the ideal electrode.

In dual-chamber pacing in order to maintain the advantages of small pulse generator size and volume, and increased longevity, it becomes necessary to reduce pulse generator output. This may be accomplished by optimizing the electrode-heart interface. New electrode designs may reduce polarization losses; perhaps even newer materials should be considered. The results of accumulated data must be applicable to long-term pacing.

Biocompatible Materials↗
PubMed1987

Platinum pacemaker electrodes: origins and effects of the electrode-tissue interface impedance.

Investigation of the unipolar properties of the paced-evoked response requires special measures to eliminate the post-stimulus potential, and this in turn requires a knowledge of the properties of the electrode-tissue interface which is not supplied by any single source in the literature. We have therefore drawn together published information and some of our own experimental results. The behavior of a particular type of pacemaker electrode was investigated in vitro under a range of conditions. The application of DC potentials revealed an extremely nonlinear voltage-current characteristic with conduction thresholds at about +1 V and -1 V. Small signal AC response to applied voltages well within these values (20 mV pk-pk) was found to be linear when a nonpolarizable counterelectrode was used. Nonlinearities were introduced by the use of a stainless steel counterelectrode. The response of an in vitro model of a paced patient to voltage pulses (amplitude 5 V, duration 0.5 ms) was also investigated. We have made extensive use of previously published work to demonstrate the mechanisms underlying these results and also their relationship to each other. We have concluded with some theoretical comments upon the design requirements for a device to eliminate the post-stimulus afterpotential in order to detect the paced-evoked response.

Electric Conductivity↗
PubMed1991

Protein interference with ion-selective electrode measurement depends on reference electrode composition and design.

There is controversy about whether protein interferes with ion measurements using ion-selective electrodes. We have investigated the effects of changes in the salt-bridge composition of five commercially available analysers with open, membrane-restricted or porous frit-restricted reference electrode junctions on measurements of an albumin solution prepared by gel filtration. When the manufacturers' salt bridges were used, instruments with open or membrane-restricted junctions showed apparent increases in the activity of ionized calcium, sodium and potassium in the presence of protein. When the hypertonic bridge solutions were replaced with 150 mmol/L potassium chloride this increase disappeared. The instrument with a porous frit-restricted junction showed no protein effect, but its response to changes in sample sodium chloride concentration in protein-free solution suggested that its junction was functionally equivalent to that formed with an isotonic sodium chloride bridge. Our results emphasize that liquid junction design and composition affect ion measurements in protein-containing solutions and suggest that the use of hypertonic bridge solutions for biological samples needs to be re-examined.

Calcium Chloride↗
PubMed2001

A contact lens electrode with built-in high intensity white light-emitting diodes. A contact lens electrode with built-in white LEDs.

We determined the clinical usefulness of a new contact lens electrode with built-in, white light-emitting diodes (LEDs) for full-field electroretinograms (ERGs). Three, high-brightness white LEDs were incorporated into a contact lens electrode and served as the source for the stimulus and the background. The stimulus intensity, stimulus duration and background illumination were regulated by a small LED control device. Maximum stimulus and background intensities were 3.9 and 3.6 log cd/m2, respectively. We successfully recorded intensity-response series for scotopic and photopic ERGs. We also recorded a duration-series for photopic ERGs, and ERGs that were comparable to the ISCEV standardized ERGs. The compactness and ease of using this system suggest that it will be clinically useful under different conditions.

Adult↗
PubMed1989

Biological evaluation of the aggressiveness of dust formed during the manufacture of carbon electrodes in the carbon electrode plant.

The biological aggressiveness of five dusts formed during the production of carbon electrodes was evaluated using intraperitoneal, pulmonary and hemolytic tests. The greatest increase in the hydroxyproline level in the lungs of the experimental animals was observed in the group that had been administered dust from the Moulding Shop. Dusts from the Carbon Electrode Plant in Raciborz exhibit weak fibrogenic properties.

Air Pollutants, Occupational↗
PubMedDate not supplied

Electrode system for permanent implantable defibrillators: transvenous catheter and subcutaneous plate electrodes.

The permanently implanted automatic defibrillator offers an alternative treatment for heart patients with high risk of ventricular fibrillation, who cannot be safely treated by surgery or drugs. Because of size and energy requirements, permanently implanted automatic defibrillators are not presently practical for many of these patinets, and sudden death from ventricular fibrillation remains a majof health problem. This study, which determines the optimal electrode configuration of the transvenous catheter when used in conjunction with a subcutaneous plate or disk electrode for transvenous ventricular defibrillation, attempts one of many changes needed to improve the defibrillator's efficiency so that it will be a viable alternative treatment for delicate heart patients.

Animals↗
PubMed1993

[Stable stimulation impedance of steroid electrodes in various impulse amplitudes: indications for low polarization of the electrode-myocardium interface].

The reduction of electrode surface area leads to an increase of pacing impedance which may be caused either by higher tissue resistance or by greater polarization occurring at the electrode-myocardium interface. The impedance of steroid-eluting leads with both 8 mm2 surface area (CapSure 4003, Medtronic n = 12) and with 4 mm2 (030-368, Telectronics, n = 8) were compared to the impedance of a high polarizing Elgiloy lead (PE 60/4 DN, Biotronik; n = 7). All leads were connected to the same unipolar VVI pacemaker (Pasys 8329, Medtronic). Pacing impedance was measured at 0.8, 1.6, 2.5, 5.0, and 8.0 volts pulse amplitude and at 0.05, 0.25, 0.5, 1.0, 2.0 msec pulse duration. Impedance of the Elgiloy lead was constant at 0.05 and 0.25 msec, but increased at longer pulse durations for pulse amplitudes below 5.0 volts. Both steroid-eluting leads had constant impedance at each pulse duration. The impedance of the 4 mm2 lead was significantly higher than of the 8 mm2 lead. In contrast to the Elgiloy lead, impedance of the steroid-eluting leads is not influenced by pulse-dependent factors such as polarization, indicating that the higher impedance of the 4 mm2 steroid-eluting lead is caused by a higher tissue resistance and not by greater polarization.

Aged↗
PubMed1977

[Electrode surface areas, pulse duration and stimulation threshold. Acute and chronic study with endocardial unipolar electrodes (author's transl)].

Acute and chronic voltage-threshold of cardiac stimulation was studied in patients with complete A-V block. Endocardial unipolar electrode with three different cathodial surface areas were used (54, 22 and 12 sqmm), and tested with rectangular stimulus of variable duration (from 0.2 to 3.5 msec.). The results show that the threshold values, at first implantation and at pulse-generator replacements, are low when short-duration stimulus and smaller electrode surface area are used. The practical advantages of this study are evident.

Electric Stimulation↗
PubMed2001

Theoretical Model of Electrode Polarization and AC Electroosmotic Fluid Flow in Planar Electrode Arrays.

Strong frequency-dependent fluid flow has been observed near the surface of microelectrode arrays. Modeling this phenomenon has proven to be difficult, with existing theories unable to account for the qualitative trend observed in the frequency spectra of this flow. Using recent electrode polarization results, a more comprehensive model of the double layer on the electrode surface is used to obtain good theoretical agreement with experimental data. Copyright 2001 Academic Press.

Journal Article↗
PubMed2005

Electrochemical impedance spectroscopy study of a hydrogen electrode reaction at a Zn electrode in a molten LiCl-KCl-LiH system.

The hydrogen electrode reaction involving hydride ion, H-, at a Zn electrode is investigated in a molten LiCl-KCl-LiH system at 673 K. The charge-transfer resistances were measured by electrochemical impedance spectroscopy in the overpotential region of 0.10 < or = eta < or = 0.35 V and over the H- concentrations of 1.5 x 10(-4) < or = C(H)- < or = 1.2 x 10(-3) mol cm(-3). The logarithm plot of the charge-transfer resistance against the overpotential at C(H)- = 3.0 x 10(-4) mol cm(-3) gives the symmetry factor, beta, of 0.50 and the exchange current density, j0, of 5.8 x 10(-3)A cm(-2), respectively. Analysis of the dependence of j0 on H- concentration independently gives a beta of 0.55. The reasonable beta values indicate that the H- <==> H(ad)(M) + e- step is rate-determining.

Journal Article↗
PubMed2004

Electroneutrality coupling of electron transfer at an electrode surface and ion transfer across the interface between thin-layer of 1-octyl-3-methylimidazolium bis(perfluoroalkylsulfonyl)imide covering the electrode surface and an outer electrolyte solution.

The electrode reaction of decamethylferrocene (DMFc) dissolved in a thin layer of a room-temperature molten salt (RTMS), 1-octyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (C8mimC1C1N) or 1-octyl-3-methylimidazolium bis(pentafluoroethylsulfonyl)imide (C8mimC2C2N), on a self-assembled monolayer-modified gold electrode is coupled with the ion transfer across the interface between the RTMS and the outer aqueous solution (W) to give a voltammogram whose shape resembles a voltammogram of a simple one-electron transfer process. The electroneutrality of the RTMS layer during the oxidation of DMFc to decamethylferricenium ion is maintained by the concomitant dissolution of C8mim+ ion from the RTMS phase to the W phase, and the reduction of decamethylferricenium ion to DMFc is accompanied by the transfer of either C1C1N- or C2C2N- from RTMS to W. The midpoint potential of the voltammogram varies with the concentration of the salt in the aqueous phase, C8mimCl or LiCnCnN (n = 1 or 2), in a Nernstian manner, showing that the phase-boundary potential between the RTMS and the W is controlled by the partition of these ions. Although the phase-boundary potential across the RTMS / W interface is Nernstian with respect to the ions common to both phases at the equilibrium, the polarization at the RTMS / W interface under current flow distorts the shape of the voltammograms, resulting in a wider peak separation in the voltammogram.

Journal Article↗
PubMed1995

Averaged electrode voltages used to identify nonfunctioning electrodes in cochlear implants: case study.

We present the case of an adult male whose internal cochlear implant unit failed. Several months elapsed following initial stimulation with the implant before the problem was identified and corrected. The sequence of the failure and its detection are detailed. Following reimplantation, the patient did not initially report improved sound quality. However, within a week of the initial stimulation of the second device, he reported being able to identify environmental sounds, and speech began to sound the way he remembered it before he lost his hearing. We suggest a method of detection that might improve the early identification of a nonfunctioning device or of nonfunctioning individual electrodes. Knowledge of specific nonfunctioning electrodes is important in device adjustment, especially for young children.

Audiometry, Pure-Tone↗
PubMed1997

When do sphenoidal electrodes yield additional data to that obtained with antero-temporal electrodes?

The advantage of using sphenoidal (SE) over antero-temporal electrodes (ATE) remains controversial among epileptologists. Yet, in a recently published study of 17 patients with seizures of antero-temporal origin (Kanner et al., 1995), we demonstrated that SE placed under fluoroscopic guidance (FPSE), in order to insure that their recording tips are positioned immediately below the foramen ovale (FO), yielded a significant advantage over SE placed with the standard blind method of insertion (BPSE), in both interictal and ictal recordings. This study was done to test the following hypothesis: FPSE advantage over BPSE and ATE resides in the recording of epileptiform activity with a restricted electric field. We compared spike voltages at FPSE, BPSE and ATE in sets of 5 randomly selected spikes per interictal focus, recorded in the course of separate monitoring studies with BPSE and FPSE. We represented the voltage differences as ratios, VATE/FPSE and VATE/BPSE and calculated a mean ratio for each spike set. The spikes' voltage was almost identical at BPSE and at ATE (mean VATE/BPSE = 0.94), while it was significantly higher at FPSE than at ATE (mean VATE/FPSE = 0.66; P < 0.001, t test). A significantly narrower electric field contour was found among interictal foci in which FPSE yielded additional data during interictal (P < 0.001) and ictal (P = 0.016) recordings. Conversely, VATE/FPSE did not differ from VATE/BPSE among interictal foci where FPSE failed to yield any advantage over BPSE in either interictal (P = 0.240), or ictal (P = 0.311) recordings. These findings prove that SE yield additional localizing data when recording epileptiform activity with a restricted field, provided that its recording tip is positioned below the FO. When distant from FO, SE can be expected to yield comparable data to that obtained with ATE.

Action Potentials↗