Inactive Electrode Research Articles

Vitreal Oxygenation in Retinal Ischemia Reperfusion

To study the feasibility of anterior vitreal oxygenation for the treatment of acute retinal ischemia. Twenty rabbits were randomized into an oxygenation group, a sham treatment group, and a no treatment group. Baseline electroretinography (ERG) and preretinal oxygen (Po(2)) measurements were obtained 3 to 5 days before surgery. Intraocular pressure was raised to 100 mm Hg for 90 minutes and then normalized. The oxygenation group underwent vitreal oxygenation for 30 minutes using intravitreal electrodes. The sham treatment group received inactive electrodes for 30 minutes while there was no intervention for the no treatment group. Preretinal Po(2) in the posterior vitreous was measured 30 minutes after intervention or 30 minutes after reperfusion (no treatment group) and on postoperative days (d) 3, 6, 9, and 12. On d14, rabbits underwent ERG and were euthanatized. Mean final (d12) Po(2) was 10.64 ± 0.77 mm Hg for the oxygenation group, 2.14 ± 0.61 mm Hg for the sham group, and 1.98 ± 0.63 mm Hg for the no treatment group. On ERG, scotopic b-wave amplitude was significantly preserved in the oxygenation group compared with the other two groups. Superoxide dismutase assay showed higher activity in the operated eyes than in the nonoperated control eyes in the sham treatment group and no treatment group only. Histopathology showed preservation of retinal architecture and choroidal vasculature in the oxygenation group, whereas the sham-treated and nontreated groups showed retinal thinning and choroidal atrophy. In severe total ocular ischemia, anterior vitreal oxygenation supplies enough oxygen to penetrate the retinal thickness, resulting in rescue of the RPE/choriocapillaris that continues to perfuse, hence sparing the retinal tissue from damage.

Dielectrophoretic assembly of carbon nanotube-based NEMS devices using floating electrodes

We present a floating-electrode dielectrophoresis (DEP) approach for optimizing the assembly of individual carbon nanotubes (CNTs). A versatile four-electrode structure employing the properties of floating-electrode DEP and optimal nanoelectrode geometry is described, which can be used to realize various NEMS devices. Finite element modeling (FEM) was used to investigate the influence of inactive electrodes on the electric fields and assembly behaviors of nanotubes (NTs). Experimental findings show that the DEP technique assisted by floating electrodes improves the alignment precision and achieves directional deposition of CNTs on multiple electrodes.

Plasticity in human motor cortex is in part genetically determined

Brain plasticity refers to changes in the organization of the brain as a result of different environmental stimuli. The aim of this study was to assess the genetic variation of brain plasticity, by comparing intrapair differences between monozygotic (MZ) and dizygotic (DZ) twins. Plasticity was examined by a paired associative stimulation (PAS) in 32 healthy female twins (9 MZ and 7 DZ pairs, aged 22.6±2.7 and 23.8±3.6 years, respectively). Stimulation consisted of low frequency repetitive application of single afferent electric stimuli, delivered to the right median nerve, paired with a single pulse transcranial magnetic stimulation (TMS) for activation of the abductor pollicis brevis muscle (APB). Corticospinal excitability was monitored for 30 min following the intervention. PAS induced an increase in the amplitudes of the motor evoked potentials (MEP) in the resting APB, compared to baseline. Intrapair differences, after baseline normalization, in the MEP amplitudes measured at 25-30 min post-intervention, were almost double for DZ (1.25) in comparison to MZ (0.64) twins (P =0.036). The heritability estimate for brain plasticity was found to be 0.68. This finding implicates that genetic factors may contribute significantly to interindividual variability in plasticity paradigms. Genetic factors may be important in adaptive brain reorganization involved in motor learning and rehabilitation from brain injury.

Perceptual threshold and neuronal excitability as long‐term safety evaluation in retinal implants

Abstract Purpose Despite the recent progress of retinal implants the effects of continuing stimulation still remains an open issue. Sofar the established safety limits are based on laboratory findings and clinical observations.This study examined the changes of perceptual threshold over time and its relation to longterm stimulation. The goal of the study was to establish stimulus induced depression of neuronal excitability (SIDNE) measurements as a method to gain further insight on the safety profile of epiretinal implants. Methods As part of a clinical trial a prototype of an epiretinal implant ( IMI Intelligent medical implant) with 61 active platinum electrodes was implanted in a retinitis pigmentosa (RP) patient. The threshold was defined as the level of stimulation intensity at which the patient had a visual perception in a defined probability of 50% using the Best‐PEST method. SIDNE is measured by comparing the thresholds of two electrodes obtained at the beginning and at the end of a stimulation session. One electrode is actively used during the stimulation, the other remains passive. The stimulation is regarded as safe when the threshold raise of active electrodes is not significantly higher than of the inactive electrode. Results The threshold remained stable over the observation period. The threshold raise of the active electrodes never exceeded that of the inactive electrode. Conclusion SIDNE measurement is feasible in epiretinal implants. After prolonged stimulation the thresholds may increase by more than 16 % due to the patients fading concentration, however the stimulation was performed within the safety limits.

Observation of Discrete Au Nanoparticle Collisions by Electrocatalytic Amplification Using Pt Ultramicroelectrode Surface Modification

After growing a thin layer of oxide (PtOx) by anodization of a Pt electrode, it changed from catalytically active for electrochemical NaBH4 oxidation into an inactive electrode. When held at a potential where the oxide film was maintained, collisions of individual 14 nm diameter Au nanoparticles (NPs) that catalyzed NaBH4 oxidation were successfully observed as discrete current pulses (spikes or blips) for each NP interaction with the modified Pt electrode via amplification from NaBH4 oxidation. The current response is affected by NP concentration and the applied potential.

Myocardial electrical impedance as a predictor of the quality of RF-induced linear lesions

Production of complete (i.e. continuous and transmural) cardiac lesions by radiofrequency (RF) ablation can cure certain cardiac arrhythmias. However, a predictor of lesion completeness that is reliable and can be measured intraoperatively is needed in order to maximize effectiveness of ablation therapy. Predictors that require membrane excitation or response to stimulation are not always practical. This study tested whether changes of myocardial impedance across the lesion can predict completeness. RF energy was applied epicardially on perfused rabbit ventricles to produce linear lesions that were complete (n = 25) or incomplete (noncontinuous or nontransmural, n = 25). Before and after creation of each lesion, the magnitude and phase of impedance at 1 kHz were measured with a four-electrode epicardial array across the lesion. For 16 of the lesions, the translesion stimulus-excitation delay was also measured. Lesion completeness was evaluated with 2,3,5-triphenyltetrazolium chloride stain. Complete lesions increased resistivity by 26 Ω cm (21% of the preablation value, p = 0.0007, n = 17) when the inactive RF electrode remained on the epicardium during impedance measurements. When the RF electrode was removed during measurements, the rise of resistivity by complete lesions increased to 58 Ω cm (30% of the preablation value, p = 0.022, n = 8). For incomplete lesions, resistivity did not change significantly. Ablation did not significantly alter the phase of impedance. Accuracies of predictions of lesion completeness by the change in resistivity or the change in translesion stimulus-excitation delay were comparable (Youden's index 0.75 and 0.625, respectively, n = 16). Thus, RF ablation increases myocardial resistivity. The resistivity can predict lesion completeness and may provide an alternative to predictors based on excitation.

Solid-state amperometric CH 4 sensor using, LaGaO 3-based electrolyte

A solid-state amperometric CH 4 sensor using a LaGaO 3-based electrolyte was studied. For this sensor, a combination of active (anode) and inactive (cathode) electrodes for CH 4 oxidation was applied. Among the various active electrode materials studied, Pd mixed with tin-doped In 2O 3 (ITO) was found to be the most active electrode and RuO 2 the most inactive one. The sensitivities of the sensor using La 0.9Sr 0.1Ga 0.8Mg 0.2O 3 (LSGM) electrolyte to CH 4 were approximately 797 µA/decade at 673 K and 188 µA/decade at 873 K. The changes in oxygen pumping current upon exposure to CH 4 could be attributed to the mixed potential generated by the difference in oxidation activity between the active and inactive electrodes.

Cell-Impedance-Controlled Lithium Transport Through Li1 − δMn2O4 with Fractal Surface by Analyses of Experimental PCT and LSV

Lithium transport through the fractal film electrode with partially inactive surface under the cell-impedance-controlled constraint was investigated by employing ac-impedance spectroscopy, potentiostatic current transient (PCT) technique and linear sweep voltammetry (LSV). For this purpose, the totally active and partially inactive film electrodes were obtained by surface modification of film with polyvinylidene fluoride (PVDF) binder. Based upon the perimeter-area relation, the fractal dimension of the partially inactive surface was determined. From the analysis of the ac-impedance spectra obtained from the totally active and partially inactive fractal electrodes, it was found that the charge-transfer kinetics strongly depends upon the surface coverage by active sites θ. All the potentiostatic current transients did not exhibit the generalized Cottrell behavior even before the characteristic time and all the power dependence of the peak current on the potential scan rate deviated from the generalized Randles-Sevčik behavior even above the characteristic scan rate in the linear sweep voltammograms. In particular, as either θ or falls in value, the value of is prolonged and at the same time the value of is reduced as well. From the analyses of the potentiostatic current transients and the linear sweep voltammograms in terms of and , it was experimentally confirmed that the partial inactivity of the surface plays a significant role in the interfacial charge-transfer reaction and subsequent diffusion reaction during the whole lithium intercalation and deintercalation processes.

Room-Temperature Hydrogen Sensors Based on an In3 + -Doped SnP2O7 Proton Conductor

A potentiometric solid-state gas sensor was fabricated using a proton-conducting electrolyte with an active working electrode in order to study its sensing properties for small quantities ( ) of in air at room temperature. The sensor showed electromotive force (emf) response in the negative direction to changes in the concentration. Furthermore, the emf value varied linearly with the logarithm of the concentration, while it was minimally affected by the water-vapor concentration. The sensing mechanism was shown to be based on the mixed potential at the working electrode through measurements of the polarization curves of and air. The electrolyte was also applied in two single-chamber sensors, wherein and carbon were used as active and inactive electrodes, respectively; these electrodes were attached on the opposite surfaces or on the same surface of the electrolyte. Both single-chamber sensors could exhibit comparable sensitivities, compared to the dual-chamber sensor.

Synthesis of PAN/SnCl2 composite as Li-ion battery anode material

A novel process was proposed to synthesize the pyrolytic polyacrylonitrile (PAN)/SnCl2 composite anode material for Li-ion batteries. The preparation started with the dissolution of PAN and SnCl2 in dimethylformamide (DMF), followed by drying of the solution and pyrolysis of the dried mixture of PAN and SnCl2 at 300 °C, leading to homogenous dispersal of SnCl2 in pyrolytic PAN, which becomes conducting polymer matrix. The composite presented stable cycling capacity of about 490 mAh/g. It is demonstrated that SnCl2, which has been considered to be an inactive electrode material, can become active by the proposed composite technique. This paves the promising way to prepare electrode materials for Li-ion batteries.

Theoretical approach to cell-impedance-controlled lithium transport through Li 1 − δMn 2O 4 film electrode with partially inactive fractal surface by analyses of potentiostatic current transient and linear sweep voltammogram

Lithium transport through the partially inactive fractal Li 1 − δ Mn 2O 4 film electrode under the cell-impedance-controlled constraint was theoretically investigated by using the kinetic Monte Carlo method based upon random walk approach. Under the cell-impedance-controlled constraint, all the potentiostatic current transients calculated from the totally active and partially inactive fractal electrodes hardly exhibited the generalised Cottrell behaviour and they were significantly affected in shape by the interfacial charge-transfer kinetics. In the case of the linear sweep voltammogram determined from the totally active and partially inactive fractal electrodes, all the power dependence of the peak current on the scan rate above the characteristic scan rate deviated from the generalised Randles–Sevčik behaviour. From the analyses of the current transients and the linear sweep voltammograms simulated with various values of the simulation parameters, it was further recognised that the cell-impedance-controlled lithium transport through the partially inactive fractal Li 1 − δ Mn 2O 4 film electrode strongly deviates from the generalised diffusion-controlled transport behaviour of the electrode with the totally active surface, which is attributed to the impeded interfacial charge-transfer kinetics governed by the surface inhomogeneities including the fractal dimension of the surface and the surface coverage by active sites and by the kinetic parameters including the internal cell resistance.

Study of the thickness of the dead Layer below electrodes, deposited by electroless technique, in CdTe nuclear detectors

The semiconductor nuclear detector structure is usually a superposition of several different layers: the metallic electrode, the interface, the depleted zone, the nondepleted one, and finally the second electrode. All inactive layers, and particularly the region below the metallic electrodes, give rise to absorption for photons (X, gamma) and to energy loss for charged particles. As a consequence, the detectors measure lower count rates for photons, particularly at low energies, and lower energies for charged particles. The amount of this effect can be only partially attributed to the inactive metallic electrode; the main part has to be attributed to the highly defected zone below the electrode in the interfacial region. This is a structural drawback which needs to be studied to reduce this effect, e.g., by developing new polishing and deposition techniques, or to perform the appropriate corrections. We have measured the thickness of this dead layer for various solution dilution electroless depositions of Pt electrodes on CdTe devices. These measurements were carried out by using collimated (X, gamma) rays beams impinging at different angles, especially the grazing ones, and comparing the count rates registered at two selected angles, and by measuring Rutherford backscattering spectra and energy loss of 4He ions

Inducción de pseudocrisis mediante la colocación de electrodos inactivos en las regiones malares

Pseudoseizures are paroxysmal disorders of a psychogenic origin with manifestations that are similar to epileptic seizures. They constitute a pathology that is found relatively often in the clinical practice of neurology. In many cases the diagnostic suspicion of their existence is difficult to confirm. The complementary examination that proves to be most useful in diagnosing them is video electroencephalogram (video-EEG).We report the cases of seven patients who were referred to our service with a clinical suspicion of pseudoseizures. Placing electrodes with an inactive surface-coating over the two malar regions during a video-EEG study enabled us to trigger in all patients (by means of suggestion) the appearance of a clinical picture that was similar to those that initially gave rise to the request for an examination. Suggestion was also employed to limit the time they lasted by getting the patient to resolve the episode. In all the cases the trace of the simultaneous electroencephalogram showed no pathological findings.Placing inactive electrodes on malar regions is a method for inducing pseudoseizures that is harmless, easily applicable, readily available and economical, and which has not been reported in the literature. Video-EEG monitoring time is reduced using this approach. It provides evidence that a specific seizure phenomenon can be induced and resolved by suggestion techniques, which is a fact that is very useful in the diagnosis of pseudoseizures.

Regular arrays of microdisc electrodes: simulation quantifies the fraction of ‘dead’ electrodes

Arrays of microdisc electrodes have found widespread use in electroanalysis. These are commonly produced lithographically and practical arrays may contain up to hundreds of individual disc electrodes (e.g. of gold, platinum, indium,...) to maximise sensitivity and minimise limits of detection. Typically, however, the lithographic fabrication process is imperfect resulting in a significant fraction (often tens of percent) of electrochemically inactive electrodes. We demonstrate that a 2-dimensional simulation based on the diffusion domain approximation in conjugation with simple experiments on the ferrocyanide redox couple in aqueous solutions can be used to rigorously 'count' the number of active electrodes in a non-destructive fashion. The agreement with an independent count in which active electrodes are identified via electro-plating with copper followed by ex situ microscopic examination is quantitatively excellent.

Speech Perception with Mono- and Quadrupolar Electrode Configurations: A Crossover Study

To study the effect of two multipolar electrode configurations on speech perception, pitch perception, and the intracochlear electrical field. Crossover design; within subject. Tertiary referral center. Eight experienced adult cochlear implant users. Each subject used each of three experimental processors for 3 weeks. The following processors were compared that differed only in electrode configuration: 1) monopolar; 2) hybrid quadrupolar, in which half of the current returned to the extracochlear reference electrode and half to two electrodes immediately to the left and right of the active electrode; and 3) flat tripolar +2, which directed all the current to four reference electrodes (two on each side), separated from the active electrode by two inactive electrodes. All the processors used the standard Advanced Bionics HiRes speech-processing strategy, 12 channels, 1,220 pulses per second per channel, and with a pulse width of 33 (micros/phase). The monopolar processors had the largest stimulation efficiency and the smallest dynamic range in linear current units. The reverse was true of flat tripolar +2 processor, whereas the hybrid quadrupolar processor fell in between. Insufficient loudness growth prevented the use of the flat tripolar +2 processor in three subjects. Word recognition did not differ between the clinically used 16-channel monopolar processor and the experimental monopolar processor, regardless of the differences in the number of channels, pulse rate, and duration of experience. Word recognition with the flat tripolar +2 processor was significantly poorer than with the monopolar and hybrid quadrupolar processors; monopolar and quadrupolar processors did not differ. There was no significant interaction between processor type and competing noise type (stationary or fluctuating), but performance at the higher level of fluctuating noise was best with the hybrid quadrupolar processor in almost all the subjects. Pitch scaling showed ceiling performance in five subjects and differed between processors in the two other subjects with imperfect tonotopy. Intracochlear current spread was considerable with the monopolar configuration; it was reduced with the hybrid quadrupolar configuration and virtually absent beyond the active electrodes with the tripolar configuration. More confined configurations reduced the longitudinal width of the electrical field, which was expected to enhance channel separation, but no improvement in word recognition was found. More research is needed to test confined configurations that have enhanced efficiency and to evaluate the fundamental effects of configuration on channel discriminability.

Characteristics of an HC sensor using a Pr 6O 11 electrode

The characteristics of an HC sensor consisting of a gas-detection cell and an oxygen pump cell have been investigated. A Pt active electrode and a Pr 6O 11 inactive electrode were formed on YSZ in the gas-detection cell using a sputtering technique, and the concentration of hydrocarbon gases was determined from the electromotive force generated between these two electrodes. The pump cell was assembled such that the oxygen concentration in the gas-detection space was decreased. At 800 °C, the gas-detection cell showed high output sensitivity for hydrocarbon gases such as CH 4 and C 3H 8. However, the sensitivity was low for H 2 and CO. The sensor output increased when the pump cell was operated in C 3H 8/O 2/N 2. This result shows that decreasing the oxygen concentration in the gas-detection space by using the pump cell is an effective technique for improving the detection sensitivity of the sensor.

Amperometric NO X sensor based on oxygen pumping current by using LaGaO 3-based solid electrolyte for monitoring exhaust gas

An amperometric NO sensor using a LaGaO 3 base solid electrolyte was investigated based on the difference of catalytic activity of the electrode. It was found that oxygen pumping current increased upon exposure to NO when Sr 0.6La 0.4Mn 0.8Ni 0.2O 3 and La 0.5Sr 0.5MnO 3 (LSM 55) were used as active and inactive electrodes for NO oxidation, respectively. Effects of electrolyte on the sensitivity were investigated and the sensitivity to NO becomes higher with increasing oxide ion conductivity for electrolyte. By applying LaGaO 3 doped with Ni or Co, the sensitivity of the sensor becomes 1842 μA per decade of NO concentration at 823 K. The oxygen pumping current linearly increased with increasing NO concentration and the sensor responded NO and recovered to the original level within 1 min. The appearance of mixed potential in potentiometric study suggests that oxidation of NO to NO 2 mainly occurs on Sr 0.6La 0.4Mn 0.8Ni 0.2O 3 electrode. Although oxygen pumping current of this sensor was slightly affected by change in oxygen partial pressure ( P O 2 ), influence by P O 2 change is negligibly small. Cross-sensitivity study revealed that NO in exhaust gas can be selectively detected in presence of coexisting gases.

Study of Electrochemical Inactivity of Nanocomposites Generated Using High-Energy Mechanical Milling

High-energy mechanical milling (HEMM) has been used to generate electrochemically active-inactive nanocomposite anodes for Li-ion applications. However, prolonged milling renders the nanocomposites electrochemically inactive. The causes of electrochemical capacity loss after prolonged HEMM have been studied using different analytical and experimental techniques comprising impedance spectroscopy, four-point probe measurements, high resolution transmission electron microscopy (HRTEM), and X-ray diffraction. The electrical resistivity of the Si/TiN nanocomposites remained unaltered within error even after milling for 18 h. An electrochemically inactive electrode of Si/TiN composite obtained after milling Si and TiN for 9 h exhibited a fivefold increase in charge-transfer resistance in comparison to an electrochemically active electrode obtained after milling for 6 h based on the impedance analysis. The chemical and thermodynamic stability of the Si/TiN system has been confirmed through HRTEM and high-temperature stability experiments. HRTEM and electron energy loss spectroscopy analyses results reveal that some of the Si is embedded in the Si/TiN nanocomposite obtained after prolonged milling. All these results suggest that embedding of Si leads to the electrochemical inactivity of the nanocomposites obtained from prolonged HEMM. © 2004 The Electrochemical Society. All rights reserved.

Improvement of Pulse Amperometric Detection Integrated Automated Flow Injection Analysis of Ethylenethiourea Determination

AbstractImprovement of pulse amperometric detection (PAD) method is demonstrated in determination of ethylenethiourea (imidazolidine‐2‐thione, ETU). The anodic detection of ETU will produce polymeric film on an electrode leading to an inactive electrode surface. Here, the PAD method was used to remove the polymeric film formed on the electrode surface between ETU detection. Further, the scheme was integrated with automated flow injection analysis (AFIA) for determining ETU. The operational parameters of PAD in the AFIA system were discussed thoroughly. The analytical characteristics of the system were evaluated at optimum conditions. The linear range of calibration plot was between 20 to 300 μM (the correlative coefficient, r = 0.999) and the detection limit was 0.9 μM (S/N = 3). The relative standard deviations of detection of 50 μM ETU were 0.82% with and 9.07% without PAD scheme. The results indicate the system is a very promising tool for ETU determination. Finally, the matrix effects of two water samples that were collected from a campus and a farm show good recoveries of 92% and 96%.

Amperometric Solid-State Gas Sensor Using LaGaO3 Based Perovskite Oxide Electrolyte for Detecting Hydrocarbon in Exhaust Gas: II. Improvement of Inactive Electrode Performance

(LSGM) based solid electrolyte coupled with suitable electrodes was demonstrated to be a highly sensitive hydrocarbon sensor in the temperature range of 523-673 K. Sensors were studied in the amperometric mode. Keeping Pt as the active electrode, the various inactive electrode materials were studied. It was seen that (LSC 55) gave the best sensitivity among the studied catalysts. Furthermore, it was found that the performance of the sensor with (LSM 55) showed the highest sensitivity (≈600 μA/decade at 623 K) among all the investigated perovskite oxides for an inactive electrode. The sensitivity of all the sensors was fast, reversible, and the current linearly increased with increasing concentration. Over a broad range of oxygen concentration, the sensitivity was found unaltered. The thickness of the electrolyte played an important role for increasing the sensitivity. The measured value of the open circuit potential in the potentiometric mode was very small; but it confirmed the development of mixed potential between the two electrodes which palyed the key role for changing current in the present amperometric sensor. © 2004 The Electrochemical Society. All rights reserved.