Annular Electrode Research Articles

Differences between jejunal myoelectric activity after a meal and during phase 2 of migrating motor complexes in healthy humans.

Using an intraluminal probe with six pairs of annular electrodes, the myoelectric activity of the proximal jejunum was recorded during 48-hr sessions in 16 healthy volunteers receiving evening and noon meals (1000 kcal) and breakfast (400 kcal). In 10 subjects receiving no drug, the characteristics of the migrating motor complexes (period, duration of each phase, velocity of propagation of phase 3, duration of the postprandial disruption) varied markedly between subjects but were relatively constant from the first to the second day of recording. Single spike bursts propagated at a rate of 2-5 cm/sec, clusters of 3-10 spike bursts propagated at a rate of 0.5-1 cm/sec, and similar clusters recurring repetitively each 1.5-2 min were observed after the meals and very rarely in the fasted state during phase 2 of nocturnal migrating motor complexes. In six subjects, oral administration of codeine (50 mg) 1 hr before a meal induced migrating motor complexes in the postprandial state, with characteristics similar to that observed in the fasted state except a longer duration of phase 2. Single spike bursts and isolated and repetitive clusters of spike bursts were observed during phase 2 of the codeine-induced migrating motor complexes and after meals preceded by placebo, but very rarely during the phase 2 of nocturnal (fasted state) migrating motor complexes. It is concluded that the patterns of jejunal contractions consisting of propagated single spike bursts and isolated or repetitive spike bursts characterize the postprandial state in healthy humans and are dependent upon digesta flow.

A microwave induced plasma operated at atmospheric and low pressure as an ion source for a mass separator

The stabilized capacitive plasma (SCP) is a 27 MHz discharge in helium at atmospheric pressure used as atomic emission source for element specific detection (ESD) in gas chromatography. The discharge is sustained in a liquid-cooled fused-silica tube surrounded by two annular electrodes. The introduction of small amounts of various gases (H 2 , O 2 , N 2 , CO 2 , Ar) into the helium plasma leads to significant changes in the spectral emission pattern and the emission intensity of important analyte lines

Atomic emission gas chromatographic detection—chemical and spectral interferences in the stabilized capacitive plasma (SCP)

The stabilized capacitive plasma (SCP) is a 27 MHz discharge in helium at atmospheric pressure used as atomic emission source for element specific detection (ESD) in gas chromatography. The discharge is sustained in a liquid-cooled fused-silica tube surrounded by two annular electrodes. The introduction of small amounts of various gases (H 2, O 2, N 2, CO 2, Ar) into the helium plasma leads to significant changes in the spectral emission pattern and the emission intensity of important analyte lines. The analytes were introduced into the plasma at constant flow using a diffusion device and by chromatographic separation of test mixtures. Both a monochromator and a polychromator system were used to detect spectral emission in the near-infrared region.

Electric field coupling to quantum dot diodes

We have fabricated two different structures in the GaAs/AlGaAs heterojunction system to quantify the transfer characteristics of the quantum dot subjected to external, local electric fields. The first structure is a single quantum dot diode with an annular field electrode placed adjacent to the double-barrier structure by a self-aligned fabrication process. A second structure consists of a pair of independently contacted quantum dot diodes separated by several hundred angstroms. The fabrication processes and transport properties for both of these structures are described. We have also attempted for the first time to form quantum dots in InGaAs/AlAs system lattice matched to InP and have observed that strong conductance fluctuations not related to lateral size quantization can occur. These fluctuations arise from the formation of rotation-induced finite superlattices.

Intraluminal Multiple Electric Impedance Procedure for Measurement of Gastrointestinal Motility

A new catheter‐related procedure for high‐resolution measurements of gastrointestinal motility is presented. The method is based on simultaneous acquisition of the electric impedance in the surrounding body volume conductor from a number of annular electrodes, successively arranged on the catheter. The impedance of a volume conductor around the catheter, consisting of a bolus, the organ wall, body fluids, and so forth, has a characteristic value for each segment and phase of contraction wave, as theoretical and experimental investigations revealed. A calculation on the basis of a simplified model reveals that the impedance changes as a logarithmic function of the bolus thickness, in which the highest sensitivity is advantageously obtained at a small lumen size and utilizing unipolar or bipolar electrode setups. The high resolution in time, space, and amplitude of the changes in the bolus shape allow us to use this impedance method for evaluation of functional stages in each measuring segment and of the beginning, end, and type of contraction wave, as well as their characteristics. The unique mechanical properties of the catheter (thinner than 3 mm, several meters long, flexible, closed surface) and the ability to distribute more than 32 measuring segments of different lengths on the catheter make this procedure suitable even for long‐term physiologic and pathologic studies of gastrointestinal motility.

Modeling of Cylindrical Alkaline Cells: II . Secondary Current Distribution

A secondary current distribution model is presented to examine the reaction distribution at an annular porous electrode. The model is applied to assess the extent of polarization in alkaline cells that arises exclusively from ohmic and kinetic limitations in the system. Variations in the cell performance are traced to differences in the electrode thickness that are used to carry the different capacities in the cells. The reaction distribution in the larger D and C cells is more non‐uniform than in the AA and the AAA cells. Curvature effects are also evaluated with the present model. If the basis of comparison is taken at the electrode/separator interface at the inner radius of the annular domain, then a higher curvature is shown to produce a greater polarization reduction effect.

Effects of Dynamic Electrodes on Sodium Sulfur Cell Performance

The construction and performance of a sodium sulfur cell with dynamic sodium and sulfur electrodes are described. The cell was constructed with a sodium feed into a β″‐alumina tube and a sulfur feed into an annular sulfur electrode. Low‐resistance graphite felt was tightly packed around the β″‐alumina tube. Sodium pentasulfide was removed from the sulfur electrode. The cell was stably charged in the two‐phase region and a high charge acceptance of 95% was obtained. The cell capacity and the discharge voltage increased with the sulfur and sodium feeds. The internal resistance was decreased by thinning the sulfur electrode and using a single zone of low‐resistance graphite felt.

Technology and long-term application of an epineural electrode.

An epineural electrode (ENE) was developed to achieve a controllable, progressive muscle contraction and reduce muscle fatigue during functional electrostimulation. In vitro studies of annular (torus-shaped) electrodes have been carried out to select adequate electrode materials and electrode diameters. We investigated the long-term stability of ENEs using different intensities of current (range: 0.8-1.2 mA) in sheep and rat experiments. Depending upon size and material, ENE tolerates anodic and cathodic impulses of up to 1 msec and 8 mA (peak current). ENEs were used during clinical application in four paraplegic patients (16 channel implants) for stimulation of lower extremities, and in nine quadruplegic patients (eight channel implants) for diaphragm pacing, for a total observation time of 37 patient years. The low rate of clinical complications, including no corrosion of the electrodes or significant loss of nerve fibers, seems related to the small dimensions of the electrode (less than 1 mm2).

Technology and Long-term Application of an Epineural Electrode

An epineural electrode (ENE) was developed to achieve a controllable, progressive muscle contraction and reduce muscle fatigue during functional electrostimulation. In vitro studies of annular (torus-shaped) electrodes have been carried out to select adequate electrode materials and electrode diameters. We investigated the long-term stability of ENEs using different intensities of current (range: 0.8–1.2 mA) in sheep and rat experiments. Depending upon size and material, ENE tolerates anodic and cathodic impulses of up to 1 msec and 8 mA (peak current). ENEs were used during clinical application in four paraplegic patients (16 channel implants) for stimulation of lower extremities, and in nine quadruplegic patients (eight channel implants) for diaphragm pacing, for a total observation time of 37 patient years. The low rate of clinical complications, including no corrosion of the electrodes or significant loss of nerve fibers, seems related to the small dimensions of the electrode (< 1 mm2).

26 INTEREST OF COLONIC ELECTROMYOGRAPHY (EMG) IN CHILDREN

Colonic EMG has not yet been reported in children. 5 children (3 boys, 2 girls, mean age 5.3 ± 3.4 y) with severe irritable bowel syndrome (IBS) underwent a colonic bipolar EMG with a probe with annular electrodes positionned in left colon by colonoscopy. After an overnight fast, a two hour pre- and post-prandial recording was performed (meal : 30 Kcal/kg). Results : the tracing showed the typical colonic patterns : Short Spike Bursts (SSB), Long Spike Bursts (LSB), Migrating Long Spike Bursts (MLSB). As in adults, different patterns were observed, associated with different clinical features of IBS : - in one case with watery diarrhea, low electrical activity with reduced number of SSB during the preprandial period, and a normal postprandial increase of colonic motility. - in two IBS with abdominal pains, intense preprandial spiking activity with repetitive LSB, and decreased activity after feeding. - in two cases with alternate diarrhea and constipation the preprandial electrical activity was normal and the postprandial spiking activity was lowered. These preliminary results individualize several groups of IBS children. Colonic EMG may contribute to diagnostic and therapeutic progress in IBS, and other intestinal dysmotilitics in children.

Axisymmetric problem of electroelasticity for a piezoelectric layer with annular electrodes

Axisymmetric problem of electroelasticity for a piezoelectric layer with annular electrodes

Optimal electrode designs for electrosurgery, defibrillation, and external cardiac pacing.

We have developed a simple and easily modifiable two-dimensional finite element computer model of the human torso, which allows us to predict current delivery from arbitrarily placed and designed electrodes. Using this model, the performance of many variations from the commonly used gelled-pad electrode, applied to a torso of uniform and isotropic resistivity, has been examined by independently varying the thickness, width, and resistivity of the gel layer, as well as the width of the conducting plate. We compared the electrode performances on the basis of their ability to maintain a uniform current density at the electrode-body interface, which is thought to be of critical concern in avoiding burn, pain, and other complications in electrosurgery, external cardiac pacing, and defibrillation. In addition to studying the effects of geometric and electrical design variations, we have isolated two electrode designs of particular importance: 1) a simple plate electrode with a uniformly high resistivity gel layer and intermediate conducting plate width, which could be used for low-energy applications such as external cardiac pacing, and 2) an annular electrode in which the resistivity of the gel varies as a function of distance to the electrode center, which could be used for high-energy applications such as electrosurgery and defibrillation, as well as for external cardiac pacing.

Substantiation of the parameters of a rheographic catheter for intravascular investigations

Catheter impedance rheography is a method of investigating the cariovascular system by measurlng the impedance inslde the heart and vessels. For this purpose special probes, called rheographic or impedance catheters, are used. Such catheters have a channel for transmitting pressure to an external sensor and several pairs of annular electrodes on the proximal end serving for measuring the impedance.

Low pressure arc spraying of reactive materials

In spite of the introduction of low pressure plasma spraying, disadvantages remain in the case of powdered materials because of their large specific surface area. Thus tantalum, for example, is already embrittled before the spraying operation and the gases adsorbed on the very large surface area of the powder compared with that of a wire limit the purity of the coatings even if high purity gases are employed. Low pressure arc spraying, however, combines the advantages of wire spraying with those of spraying in low pressure chambers in that it yields homogeneous chemically pure coatings of low porosity. At the same time, the process is more economical than low pressure plasma spraying. Stable operation of conventional arc spraying heads at low pressure is not possible because the environmental pressure causes considerable enlargement of the arc between the electrodes being burned off. The result is that, among other things, the arc causes seizure of the contact nozzles and melts them off thereby rendering the spray heads unusable. In low pressure arc spraying the melting process takes place in an antechamber maintained at a pressure above atmospheric to ensure a safe burn-off along with appropriate droplet formation. The low pressure acts on the particles emerging from the nozzle and ensures intense degasification. In this way coatings are produced which are outstanding as regards density and adhesion to the substrate. The arc may burn between two or more current-carrying wires or between one centrally arranged wire and an annular backing electrode, located in the nozzle, or the surface of the substrate. By applying a voltage between an annular metallic electrode insert at the underside of the combustion chamber and the base metal, a transferred arc of selectable polarity can additionally be started and maintained as in low pressure plasma spraying. Coatings of titanium and tantalum prepared by low pressure arc spraying are presented. Optical, electron microscopy, metallographic and electrochemical analyses reveal the properties of the coatings.

Piezoelectric thin film ZnO on Si integrated microphone

Recent technology advances in thin film deposition and in fabrication of Si microstructures have made possible the development of a new class of “intelligent” sensors having electronics and sensing element integrated on the same Si chip. The present paper describes a fully integrated microphone which combines high sensitivity, wide frequency range, low power, and low cost of batch processed miniature silicon components. A thin piezoelectric layer of ZnO transforms the mechanical deflection of a thin Si diaphragm into a piezoelectric output voltage. This signal is directly connected to an amplifier built on the same chip. A unique annular electrode design provides cancellation of temperature induced parasitic signal due to the pyroelectric effect in ZnO. Integrated devices were fabricated and tested. Measured performances were: sensitivity of 25 μV/μbar, a signal to noise ratio of 5:1 at 2 μbars, a frequency response of 0.1 Hz to 10 kHz and a power consumption below 40 μW. Further improvements in the onchip electronics should increase the signal to noise ratio by an order of magnitude bringing its value in the range of the conventional hearing aid devices.

Experimental study of the edge effect at an inlaid electrode

Chronoamperometric experiments using an annular inlaid electrode confirm the theoretical relationship between current and electrode geometry under diffusion-controlled conditions. The technique is valuable as a means of measuring diffusion coefficients.

Experimental study of the edge effect at an inlaid electrode

Summary Chronoamperometric experiments using an annular inlaid electrode confirm the theoretical relationship between current and electrode geometry under diffusion-controlled conditions. The technique is valuable as a means of measuring diffusion coefficients.

Development and characterization of an electrochemical cell with improved high-frequency response for voltammetric applications

An electrochemical cell design is described for rapid voltammetric experiments at a hanging mercury drop electrode. The design features contact between the reference electrode and the sample solution by means of an annular ring surrounding the base of the hanging mercury drop electrode hanger. This configuration allows reliable placement with one-time alignment of the reference electrode very close to the working electrode for minimization of uncompensated resistance, in a zone of reduced iR drop due to shielding by the drop hanger assembly. Minimization of uncompensated resistance allows facile improvement of frequency response of the cell by a factor of five to sevenfold over the conventional geometry. The approach affords considerably greater convenience in hanging mercury drops than feasible with the traditional Luggin probe geometry, since the annular reference electrode placement does not block access to the electrode. Performance of the cell design is evaluated and compared to performance with a standard Luggin probe of variable geometry by means of cell transfer function measurements and cyclic voltammetric measurements at high scan rates.

ZnO on Si integrated acoustic sensor

Recent technology advances in thin film deposition and in etching of Si microstructures have made possible the fabrication of a new class of integrated sensors having electronics and sensing element on the same chip. The present paper describes a fully integrated acoustic sensor that combines high sensitivity, wide frequency range and low cost of batch processed miniature silicon components. A sputtered piezoelectric ZnO layer transforms the mechanical deflection of a thin etched Si diaphragm into a piezoelectric charge. This signal is directly connected to the gate of an MOS buffer amplifier through buried contacts. A unique annular electrode design provides cancellation of the temperature-induced parasitic signal due to the pyroelectric effect in ZnO. It also enables connections to be made at the Si/ZnO interface, avoiding step coverage problems and increases the sensitivity by a factor of two over a simple circular electrode design. Integrated devices were fabricated and tested. Measured performances for a 3 mm diameter, 30 μm thick diaphragm were: sensitivity of 25 μV/μbar, a signal-to-noise ratio of 5:1 at 2 μbar, a frequency response of 0.1 Hz to 10 kHz with a 10 10 Ω shunt resistor and a power consumption below 40 microwatts.

Three‐dimensional, farfield measurements of a Gaussian profile ultrasonic transducer

An ultrasonic transducer has been constructed using a concentric array of annular metallic electrodes on a thin circular piezoelectric substrate. The transducer is driven through an impedance matching and weighting network to produce an electric field within the substrate that is an optimized piecewise linear approximation to a two‐dimensional Gaussian function [P.S. Zerwekh and R. O. Claus, IEEE 1981 Ultrason. Symp., Chicago, IL]. In this paper, the calculated farfield Gaussian amplitude distribution is presented and compared to experimental data measured using a microprocessor‐controlled automatic scanning system at a distance of 500 wavelengths in a water tank. This data is also compared with similar analytical and experimental results obtained for a circular piston transducer having only one active surface electrode. Applications of the transducer in acousto‐optical modulation systems and in the ultrasonic inspection of metallic surfaces is discussed. [Work partially supported by NSF and NASA.]