Search

Background. The object of the study is a symmetrical current source for bioimpedance measurements. The subject of the study is to determine the ways of occurrence of errors in the measurement of bioimpedance. The aim is to develop a method for reducing parasitic leakage of high-frequency current in the process of bioimpedance measurement. Materials and methods. To determine the sources of measurement error, the idea of the paths of parasitic leakage currents into the ground is used. Results. A method is proposed to eliminate the parasitic effect of leakage current from the measuring object into the ground. As a result, the bioimpedance measurement circuit is insensitive to any types of leakage currents from the measuring object into the ground. Conclusions. The proposed symmetrical current source for bioimpedance measurements makes it possible to completely eliminate the influence of parasitic leakage current from the measuring object into the ground, which positively affects the accuracy and reliability of determining the parameters of the human body.

Modulation of electric currents through single-molecule junctions is usually achieved by synthesis of molecules with desired functionalities, in conjunction with suitable molecule–electrode contacts through specific anchoring groups. An alternative to this approach, barely explored so far, is to use structured electrodes, where conductivity could eventually be controlled by changing the specific anchoring site within the very same electrode. Here, we theoretically investigate how to exploit the pronounced anisotropy of corrugated graphene deposited on Ru(0001) (Gr/Ru) to tailor single-molecule conductivity in 4-aminophenyl and 4-aminobenzonitrile. We show that currents induced in the upper and lower anchoring positions in the Gr/Ru moiré are substantially different, irrespective of the chosen molecule. The magnitude of these currents can differ by as much as an order of magnitude at specific bias voltages. We also show that both molecules display rectifying properties, which can differ by up to a factor of five in different anchoring sites. Interestingly, the observed modulations strongly depend on the chemical binding nature between the molecule and the electrode, (strong) covalent bond for 4-aminophenyl and (weak) physisorption for 4-aminobenzonitrile. All this suggests that Gr/Ru can be an ideal electrode to modulate single-molecule electric conductivity under experimental conditions that are available in many laboratories. [Display omitted] • Gr/Ru electrodes can be used to tailor single-molecule conductivity. • Molecule–electrode interaction strongly affects the current. • The asymmetry of the junction influences the rectification ratio. • Transport properties are not affected by the quantum dot located at the hill-site. [ABSTRACT FROM AUTHOR]

Designing proper frontend electronics is critical in the development of highly sophisticated electrode systems. Multielectrode arrays for measuring electrical signals or impedance require multichannel readout systems. Even more challenging is the differential or ratiometric configuration with simultaneous assessment of measurement and reference channels. In this work, an eight-channel frontend was developed for contacting a 2×8 electrode array (8 measurement and 8 reference electrodes) with a large common electrode to the impedance gain-phase analyzer Solartron 1260 (S-1260). Using the three independent and truly parallel monitor channels of the S- 1260, impedance of trapped cells and reference material was measured at the same time, thereby considerably increasing the performance of the device. The frontend electronics buffers the generator output and applies a potentiostatic signal to the common electrode of the chip. The applied voltage is monitored using the current monitor of the S-1260 via voltage/current conversion. The frontend monitors the current through the electrodes and converts it to a voltage fed into the voltage monitors of the S-1260. For assessment of the 8 electrode pairs featured by the chip, a relay-based multiplexer was implemented. Extensive characterization and calibration of the frontend were carried out in a frequency range between 100 Hz and 1 MHz. Investigating the influence of the multiplexer and the frontend electronics, direct measurement with and without frontend was compared. Although differences were evident, they have been negligible below one per cent. The significance of measurement using the complex S-1260-frontend-electrode was tested using Kohlrausch's law. The impedance of an electrolytic dilution series was measured and compared to the theoretical values. The coincidence of measured values and theoretical prediction serves as an indicator for electrode sensitivity to cell behavior. Monitoring of cell behavior on the microelectrode surface will be shown as an example. [ABSTRACT FROM AUTHOR]

Three dual alloy ingots were processed by electroslag remelting with 1500 A, 1800 A and 2100 A. The compositions and inclusions of ingots were analyzed by means of various analytical techniques. The results show that the segregation becomes severer with the increase of current. With the current increasing, the proportion of inclusions with large size, the T.[O] and sulfur content in the ingot increase, showing a worse cleanliness due to the severer electrode surface oxidation and shorter interaction time between slag pool and film of molten steel at the electrode tip. The single (Mn,Cr)S inclusion can precipitate in transition zone of each ingot and NiCrMoV zone of ingot with 1800 A and 2100 A due to higher sulfur content and the solute segregation during solidification. The ingot processed by ESR with 1500 A performed a balanced quality. [ABSTRACT FROM AUTHOR]

Abstract The luminosity of lightning channel is closely related to the lightning current. In the present paper, a lightning channel luminosity detection system (LCLDS), comprising of an avalanche photodiode module, a neutral density filter, an extension tube and an adjustable horizontal slit, is assembled. By using the impulse current generator, lightning impulse currents with different amplitudes and also different waveforms were produced in a 15-mm open-air gap between two graphite-rod electrodes. The luminosity and the current of discharge channel were measured synchronously. The experiments looking into the influencing factors of luminosity measurement, including the alignment of the silt and the slit width, were carried out. Obtained results show that the slit opening center of LCLDS should be aligned to the center of the discharge gap. Otherwise, in the case of improper alignment, the measured luminosity waveforms associated with the same injected current might be quite different in the amplitudes as well as in the waveforms. Moreover, the peak luminosity increases linearly with increasing slit width, whereas the luminosity waveforms are practically unaffected, implying that, in the practical application, the slit width can be adjusted to alter the luminosity signal output according to the actual need. Obtained results here can establish the foundation to develop the correlation between the current and the corresponding luminosity in the future. Highlights • The slit opening center of lightning channel luminosity detection system should be aligned to the center of the discharge gap. • The humps of luminosity waveforms found in the lightning flashes is due to improper alignment. • Peak luminosity increases linearly with increasing slit width. [ABSTRACT FROM AUTHOR]

Influence of surfacing modes on welding-technological properties of different types of high-alloyed flux-cored strips was studied. Electrode metal melting, surfacing, loss factors, as well as the efficiency of electrode material melting and deposition rate, were determined. As the objects of study, the flux-cored strips PL-AN-101 and PL-AN-179 made on a shel strip-sheath, as well as the strip PL-AN-111 on the bes on nickel sheath, widely applied in industry, were selected. Surfacing of samples for investigations was performed in A-874N machine with AD-167 attachment and VDU-1201 power source in a wide range of modes: current of 600–900 A, voltage of 32–40 V, speed of 32–55 m/h. Obtained results are presented graphically. It is found that alongside the surfacing modes, the filler-powder composition and sheath strip material have a significant effect on the characteristics of welding-technological properties of flux-cored strips and chemical composition and hardness of deposited metal, respectively. In surfacing with PL-AN-111 strip with a nickel sheath, having a high ohmic resistance, the more intensive heating of the flux-cored strip at the stickout takes place, and, consequently, the coefficient of electrode material melting is increased. Melting efficiency was lower in surfacing with PL-AN-101 and PL-AN-179 strips. At current rise, losses for burn-out and spattering become greater for PL-AN-111 strip, and change only slightly for PL-AN-101 strip, while for PL-AN-179 strip they decrease abruptly in the current range of 900–1200 A because of the specifics of powder-filler composition. Values of melting and surfacing factors, as well as melting and deposition efficiency decrease with increase of process speed for all the strip types. For PL-AN-111 strip, however, these values change only slightly. [ABSTRACT FROM AUTHOR]

Purpose: This study evaluates the effects of active electrode cooling, via internal fluid circulation, on the irreversible electroporation (IRE) lesion, deployed electric current and temperature changes using a perfused porcine liver model. Materials and methods: A bipolar electrode delivered IRE electric pulses with or without activation of internal cooling to nine porcine mechanically perfused livers. Pulse schemes included a constant voltage, and a preconditioned delivery combined with an arc-mitigation algorithm. After treatment, organs were dissected, and treatment zones were stained using triphenyl-tetrazolium chloride (TTC) to demonstrate viability. Results: Thirty-nine treatments were performed with an internally cooled applicator and 21 with a non-cooled applicator. For the constant voltage scenario, the average final electrical current measured was 26.37 and 29.20 A for the cooled and uncooled electrodes respectively (). The average final temperature measured was 33.01 and 42.43 °C for the cooled and uncooled electrodes respectively (). The average measured ablations (fixed lesion) were 3.88-by-2.08 cm and 3.86-by-2.12 cm for the cooled and uncooled electrode respectively (, ). Similarly, the preconditioned/arc-mitigation scenario yielded an average final electrical current measurement of a 41.07 and 47.20 A for the cooled and uncooled electrodes respectively (). The average final temperature measured was 34.93 and 44.90 °C for the cooled and uncooled electrodes respectively (). The average measured ablations (fixed lesion) were 3.67-by-2.27 cm and 3.58-by-2.09 cm for the cooled and uncooled applicators (). Conclusions: The internally-cooled bipolar applicator offers advantages that could improve clinical outcomes. Thermally mitigating internal perfusion technology reduced tissue temperatures and electric current while maintaining similar lesion sizes. [ABSTRACT FROM AUTHOR]

In recent years, single-element 2-D atom crystal materials have aroused extensive interest in many applications. Blue phosphorus, successfully synthesized on Au (111) substrate by molecular beam epitaxy not long ago, shows unusual geometrical and electronic structures. We investigate the electronic structures and transport properties of zigzag blue phosphorene nanoribbons (ZBPNRs) by using a first-principles method, which can be obviously tuned via different groups (i.e., -H, -O, and -OH) passivation on both edges. The ZBPNRs-H and ZBPNRs-OH present a wide-gap semiconductor property, while the ZBPNRs-O are metallic. Interestingly, the current–voltage (${I}$ – ${V}$) curves of ZBPNRs-O show a negative differential resistive (NDR) effect, which is independent on the ribbon width. The electric current through the ZBPNRs-O mainly flows along both the outside zigzag phosphorus chains through the P-P bond current. By modifying both the edges with various functional groups, the ZBPNRs can display some important functional characteristics and become a candidate of NDR devices. [ABSTRACT FROM AUTHOR]

A finite difference model of a four-electrode tissue conductivity measurement system was developed and shown to be within 10% of theory. The model is useful for explaining the behavior of conductivity measurement electrodes in tissue.

Accumulation of interfacial space charge in oil-paper interface is a critical issue in insulation diagnostics of transformers. This interfacial charge mainly accumulates due to the conductivity difference of oil and paper. Accumulation of interfacial charge leads to localized field enhancement, which further leads to partial discharges and acceleration in the aging of insulation. Therefore, from the point of view of transformer insulation diagnostics, assessment of interfacial charge is very important. However, it is not easy to estimate interfacial space charge behavior from the transformer diagnostics methods currently in use. In case of Polarization-Depolarization Current (PDC) measurement, a well known method for transformer condition monitoring, the effect of interfacial charge is reflected in the non-linearity of current response during polarization and de-polarization. During de-polarization process, a part of the interfacial charge accumulated during polarization period is absorbed by the electrodes producing a current, which is difficult to separate using conventional linear dielectric theory. In this paper, an attempt has been made to separate this current component from de-polarization current through considering charge de-trapping mechanism. Terming this current component as de-trapping current, its relationship with other parameters of transformer insulation is discussed. The developed methodology has been applied on several practical transformers. It was observed that the time constant of de-trapping current is related to the paper conductivity, oil conductivity, dissipation factor and age of the insulation. [ABSTRACT FROM PUBLISHER]

An indirect resistance spot welding process with single-side electrode access was developed for automotive applications. The variable controls of electrode force and welding current during welding were studied in order to achieve the promotion of weld nugget formation and the suppression of expulsion without sacrificing the productivity and design flexibility of automobiles. The welding experiments were performed on lapped test coupons of 0.7-mm- thick cold-rolled sheet with tensile strength of 270 N/mm² and 1.6-mm-thick cold-rolled sheet with tensile strength of 980 N/mm² using a resistance spot welding system consisting a servo-motor-controlled welding gun and an inverter DC power supply. Welding experiments verified that the occurrence of expulsion and formation of molten nugget were significantly influenced by the heat generation and melting process at an initial period during welding and manageable by applying the variable patterns of electrode force and welding current. When welding was performed under the large shunting condition simply with the constant force and current pattern of 400 N in electrode force, the appropriate current range was less than 1 kA. On the other hand, it extended to 2.6 kA when performed with the variable force and current pattern of 800 N in force and 4 kA in current at the first stage and 400 N in force at the second stage, confirming the fact that the variable pattern successfully suppressed the expulsion and promoted the nugget formation. Numerical simulations were conducted to compare the difference in welding phenomena between the constant force and current pattern and the variable force and current pattern and clarified that the effect of variable force and current pattern on the promotion of nugget formation and the suppression of expulsion. [ABSTRACT FROM AUTHOR]

We demonstrated the possibility to inscribe long-period fiber gratings (LPFGs) in a B/Ge codoped fiber by using grating periods shorter than 150 μm. We also have arc-induced in the SMF 28 fiber an LPFG in the dispersion turning points by using a grating period of 197 μm. In previous works, the shortest periods were, respectively, of the order of 190 and 320 μm for the same fibers. To achieve such a considerable reduction in the grating periods which enables access to the higher order cladding modes (higher sensitivity), we have developed a high-voltage power supply that allows for a constant and stable electric current ranging from 10.5 up to 21 mA. Computer simulations were used to identify the cladding mode resonances for each grating inscribed in the different fibers. The fabricated LPFGs were characterized as a function of the external refractive index from 1.33 up to 1.42, and an average refractive index sensitivity of –720 nm/RIU in the 1.33–1.41 range was obtained for a 192-μm LPFG without further optimization, such as the use of etching or thin films deposition. [ABSTRACT FROM PUBLISHER]

Electrical bone growth stimulators improve patient outcomes following the spinal fusion surgery, particularly important in high-risk patient populations. The therapeutic electromagnetic field (EMF) effects in tissue were modeled for two Food and Drug Administration (FDA) approved magnetic stimulation devices: 1) Coil A (SpinaLogic, DJO LLC, Vista, CA) and 2) Coil B system (Spinal-Stim, Orthofix Inc., Lewisville, TX). The electric current density induced in the target tissue (spinal vertebra) was compared with that of an FDA approved electric stimulation device (SpinalPak, Biomet, Warsaw, IN). For Coil A and Coil B, the EMF source was current-carrying coils that differed in the design (single coil versus two coaxial coil system) and the current characteristics (continuous 76.6 Hz sinusoid, biased versus intermittent 3850 Hz rectangular pulse bursts repeated at 1.5 Hz, unbiased). The local maximum induced electric field and current density were over 700-fold higher for Coil B system than for Coil A but only half of the values calculated for the reference electric stimulation device. The interaction of the magnetic field and the induced current in the tissue gives rise to local Lorentz force effects expressed as magnetoacoustic pressure (MAP) that for Coil B system reached 5 dB relative to $1~\mu $ Pa of sound pressure level in bone (SPL) (compared with −45 dB for Coil A and absent for capacitive coupling reference device). The analysis broadens the range of possible mechanisms of therapeutic EMF action to include the MAP. [ABSTRACT FROM PUBLISHER]

Goal: We aimed to develop a system for controlled exposure of biological samples to conditions they experience when lightning strikes their habitats. Methods: We based the generator on a capacitor charged via a bridge rectifier and a dc–dc converter, and discharged via a relay, delivering arcs similar to natural lightning strokes in electric current waveform and similarly accompanied by acoustic shock waves. We coupled the generator to our exposure chamber described previously, measured electrical and acoustic properties of arc discharges delivered, and assessed their ability to inactivate bacterial spores. Results: Submicrosecond discharges descended vertically from the conical emitting electrode across the air gap, entering the sample centrally and dissipating radially toward the ring-shaped receiving electrode. In contrast, longer discharges tended to short-circuit the electrodes. Recording at 341 000 FPS with Vision Research Phantom v2010 camera revealed that initial arc descent was still vertical, but became accompanied by arcs leaning increasingly sideways; after 8–12 μs, as the first of these arcs formed direct contact with the receiving electrode, it evolved into a channel of plasmified air and short-circuited the electrodes. We eliminated this artefact by incorporating an insulating cylinder concentrically between the electrodes, precluding short-circuiting between them. While bacterial spores are highly resistant to electric pulses delivered through direct contact, we showed that with arc discharges accompanied by an acoustic shock wave, spore inactivation is readily obtained. Conclusion: The presented system allows scientific investigation of effects of arc discharges on biological samples. Significance: This system will allow realistic experimental studies of lightning-triggered horizontal gene transfer and assessment of its role in evolution. [ABSTRACT FROM PUBLISHER]

The paper presents the technique for computing current?time characteristics of the transient regime, taking place after the pulsed application or change of high voltage, and dynamical current?voltage ones obtained with the voltage sawtooth modulation. The basis of the simulation is the complete set of electrohydrodynamic equations with both the convective and the migration mechanisms of charge transport being taken into account jointly. The numerical calculations were performed using commercial software package COMSOL Multiphysics based on the finite element method. The simulation was carried out for the needle?plane electrode system. The unsteady-state current passage processes, including electrohydrodynamic flow formation, were calculated. The interrelation between the latter and the total current passing through the electrical circuit were investigated. The shape and features of the current?voltage characteristics obtained with the voltage sawtooth modulation were shown to be dependent on the mechanism of charge formation. The qualitative comparison between the simulated dynamical current? voltage characteristics and the original experimental data has shown a good agreement. [ABSTRACT FROM AUTHOR]

Polarization and depolarization current measurement is a non-destructive testing method to study the dielectric properties of insulating materials. Two types of mineral oils with different aging times have been studied using both time domain and frequency domain methods separately. In this paper, a novel approach to understanding the correlation between the electric conduction in time domain and frequency domain has been proposed. When the charge carriers drift to the electrodes, they may be blocked and accumulated near the electrode. The amount of charge in the vicinity of electrode has been estimated. In the depolarization period, these charge layers will return to the bulk resulting in a depolarization current. In this paper, an analytical solution to the time dependence of the depolarization current has been developed and used to fit the experimental results. The field and temperature dependence of the polarization and depolarization current have been used to study the characteristics of charge carriers in mineral oil. The calculated conductivity has been used to simulate the frequency response in mineral oil and the simulating results have been compared with the experimental data. [ABSTRACT FROM AUTHOR]

Phototrophic microbial mats are among the most diverse ecosystems in nature. These systems undergo daily cycles in redox potential caused by variations in light energy input and metabolic interactions among the microbial species. In this work, solid electrodes with controlled potentials were placed under mats to study the electron transfer processes between the electrode and the microbial mat. The phototrophic microbial mat was harvested from Hot Lake, a hypersaline, epsomitic lake located near Oroville (Washington, USA). We operated two reactors: graphite electrodes were polarized at potentials of -700 mVAg/AgCl [cathodic (CAT) mat system] and +300 mVAg/AgCl [anodic (AN) mat system] and the electron transfer rates between the electrode and mat were monitored. We observed a diel cycle of electron transfer rates for both AN and CAT mat systems. Interestingly, the CAT mats generated the highest reducing current at the same time points that the AN mats showed the highest oxidizing current. To characterize the physicochemical factors influencing electron transfer processes, we measured depth profiles of dissolved oxygen (DO) and sulfide in the mats using microelectrodes. We further demonstrated that the mat-to-electrode and electrode-to-mat electron transfer rates were light- and temperature-dependent. Using nuclear magnetic resonance (NMR) imaging, we determined that the electrode potential regulated the diffusivity and porosity of the microbial mats. Both porosity and diffusivity were higher in the CAT mats than in the AN mats. We also used NMR spectroscopy for high-resolution quantitative metabolite analysis and found that the CAT mats had significantly higher concentrations of osmoprotectants such as betaine and trehalose. Subsequently, we performed amplicon sequencing across the V4 region of the 16S rRNA gene of incubated mats to understand the impact of electrode potential on microbial community structure. These data suggested that variation in the electrochemical conditions under which mats were generated significantly impacted the relative abundances of mat members and mat metabolism. [ABSTRACT FROM AUTHOR]

This paper presents the results of experimental and numerical studies of the behavior of metallic shaped-charge jets (SCJs) with passage of electric current through them. The possibilities of decreasing or increasing the depth of penetration of SCJs into targets are discussed. It is shown that the penetration capability of SCJs can be decreased or increased by varying the electric pulse parameters. [ABSTRACT FROM PUBLISHER]

The effect of formation protocol including different constant voltage points at low potential, different constant voltage time, and different current were studied in this paper. The electrochemical impedance spectroscopy and stored and cycle performance tests were used to verify the parameter of different formation protocols. The results show that the resistance of solid electrolyte interphase film R drops during the whole potential range except 3.1 to 3.5 V and the diffusion coefficient P which represents the uniformity of anode electrode surface decreases only at this potential range. The effects of different constant voltage points at 3.1 to 3.5 V were studied to increase the uniformity of anode electrode surface and decrease the resistance of the SEI film. The film is more stable at 3.3 V constant voltage than other potentials, and a constant voltage 60 min is enough to form a uniformity and compact passivation layer. With the constant voltage time extending, the P decreases. When the formation current to constant potential is increased, the film is more loose (or porous) and less adhesive. The formation protocol of 0.01 C to 3.3 V constant voltage 60 min shows the best cycling performance, and formation protocol of no constant voltage shows the worst cycling performance. Considering the time and energy consumption, the formation protocol of 0.05 C to 3.3-V constant voltage 60 min is the best. [ABSTRACT FROM AUTHOR]

A study is made of the structure of the power flows in the baths of ore-smelting furnaces, arc furnaces, and electroslag furnaces operating on direct current and low-frequency current. Results are reported from studies of the energy processes which take place in the three main zones of the furnace's working space: the zone occupied by the charge materials and slag, the arc zone, and the zone occupied by materials that are electrically conducting. Data are presented on the industrial use of the proposed generalized approach to developing highly efficient electrode smelting furnaces. [ABSTRACT FROM AUTHOR]

A voltage has been applied to a network of multiwalled carbon nanotubes (MWCNTs) placed between two electrodes. The current flowing through the MWCNTs is found to be responsible of irreversible effects, such as the suppression of radial breathing modes (RBM) in the Raman spectra. Furthermore, we observe a significant modification of the G-band in the Raman spectra for applied voltages higher than 1 V, only if Raman analysis is performed while current is flowing. This is due to a combined effect of current flow and laser beam irradiation that induces extended structural damage in the CNT outer walls. [ABSTRACT FROM AUTHOR]

Abstract: Effects of current and voltage of consumed power on plasma reactor with rotating electrode at different feed flow rates is investigated for the non thermal decomposition of methane using a system of direct current (DC) discharge. Experimental results showed that designed reactor increases not only the concentration of the produced hydrogen in continues condition but also guarantees stable plasma. It is demonstrated that decreasing both electrical voltage and electrical current results in decreasing of methane conversion but on the other hand C2 hydrocarbons selectivity will increase. After the break down voltage, increasing the input power results in increasing electrical current more intensively than increasing electrical voltage. [Copyright &y& Elsevier]

This paper deals with the influence of the dc electric field on the stabilization of the flame created from a poor (lean) mixture of methane and oxygen. In our experiments, the electric field is created between two electrodes in a combustion chamber in which one of the electrodes is a part of a burner. The dc voltage from a high voltage source is applied to both electrodes. A mixture of methane and oxygen with the purity of 99.95% of both gases is used for the combustion process. The burner combustion power is set at 0.5 kW. The observations of the electric field effects on the stabilization of the flame are carried out by increasing the oxygen flow up to the flame extinction. The result of the measurement is the observed electric field influence on the stabilization of the flame that is created from a poor mixture of methane and oxygen. In the experiment, we observe the dependence between flame stabilization and supplied electrical energy. [ABSTRACT FROM PUBLISHER]

High-strength materials can be easily machined by spark erosion process to obtain complex shapes. The discharge energy can be characterized by the current flowing through the dielectric medium in spark erosion process during the machining. The performance measures such as workpiece erosion, tool electrode erosion, and surface finish can be modified by the properties of tool electrode material. This current is determined by the conductivity of the tool electrode material. The erosion process has been experimentally investigated to analyze the effects of tool electrode on machinability of AISI 202 stainless steel in the present study. Copper, brass, and tungsten carbide have been used as the tool electrode with different combinations of electrical input parameters. From the results, it is observed that tool properties of tool electrode material could have an influence on machining characteristics in spark erosion process. Copper tool could give higher material removal rate, whereas tungsten carbide could produce better surface finish after machining process. [ABSTRACT FROM PUBLISHER]

Background Stability of threshold currents during long-term use of phrenic nerve stimulation has been questioned. Methods and Results Between January 5, 1988, and March 5, 2008, 49 patients with functional C2-tetraplegia received an Atrostim PNS (Atrotech Ltd., Tampere, Finland) as treatment of their respiratory insufficiency; a follow-up of 35 of such patients was carried out exclusively in our institution for 6.3 (4.44) 0.04-15.75 years (mean [standard deviation (SD)] range). The device employed four-pole sequential nerve stimulation, which provided four threshold currents subsequently evaluated for each phrenic nerve. Stimulation data were prospectively recorded. The differences between threshold currents recorded 1 year after implantation and the last recorded values were 0.33-0.43 (0.44-0.63) 0-2.9 mA. After having excluded the data of eight patients with values >1 mA (= mean + SD), we registered the differences for the remaining patients of 0.15-0.24 (0.14-0.24) 0-0.95 mA, which is just twice the adjustment accuracy of the device. Out of the eight problem cases one had, and two were suspected to have, surgical trauma; all three nerves recovered. In two cases the values steadily increasing over years might have been caused by unspecific foreign body reaction. Two cases with values >1mA for different durations at different electrodes might be caused by biofilm, and one patient displaying steadily increasing values lived, unwilling to live, only 2 years after the implantation. Conclusion Thus, there was no permanent nerve injury and in 77% of the presented cases threshold currents remained stable. [ABSTRACT FROM AUTHOR]

The results of investigation of the distinctive features of the dynamics of outflow of plasma jets and of formation of electrode spots in the source of a high-purity plasma obtained from a dielectric material at atmospheric pressure by analogy with a capillary discharge have been given. It has been established that the geometry of the electrode-spot distribution is dependent on the height of the dielectric projection above the electrodes, cathode spots appear in the negative half-cycle of the current, the outflowing plasma jet is of an intricate shock-wave and intermittent structure, and the space-time distribution of the shock is determined by the energy stored in the storage system. [ABSTRACT FROM AUTHOR]

Long-term catheters remain a significant clinical problem in urology due to the high rate of bacterial colonization, infection, and encrustation. Minutes after insertion of a catheter, depositions of host urinary components onto the catheter surface form a conditioning film actively supporting the bacterial adhesion process. We investigated the possibility of reducing or avoiding the buildup of these naturally forming conditioning films and of preventing bacterial adhesion by applying different current densities to platinum electrodes as a possible catheter coating material. In this model we employed a defined environment using artificial urine and Proteus mirabilis. The film formation and desorption was analyzed by highly mass sensitive quartz crystal microbalance and surface sensitive atomic force microscopy. Further, we performed bacterial staining to assess adherence, growth, and survival on the electrodes with different current densities. By applying alternating microcurrent densities on platinum electrodes, we could produce a self regenerative surface which actively removed the conditioning film and significantly reduced bacterial adherence, growth, and survival. The results of this study could easily be adapted to a catheter design for clinical use. [ABSTRACT FROM AUTHOR]

Abstract: A frequency-domain method is proposed for the transient analysis of grounding systems with ionized soil. The method involves two stages. First, the grounding system is transformed into a nonlinear equivalent circuit, in which the frequency-domain circuit parameters of the grounding electrodes are extracted by the method of moment (MoM) and the nonlinear part of the equivalent circuit represents the soil ionization. Soil ionization is represented by a nonlinear load whose characteristics can be specified based on either experimental data or theoretical models, without any limitations in the order of nonlinearity. In the second stage the nonlinear equivalent circuit is treated using the arithmetic operator method (AOM). The AOM uses a linear matrix transformation of spectra to perform basic arithmetic operations in the frequency-domain. The main feature of the proposed method is its efficiency in dealing with the nonlinear behavior of soil ionization in the frequency-domain solution of grounding systems by the MoM. It also enables one to consider the actual nonlinear behavior of soil ionization specified by experimental data or appropriate theoretical models. [ABSTRACT FROM AUTHOR]

The results of thermal efficiency on welding using the modified indirect electric arc technique [Ambriz RR, Barrera G, Garcia R. S&I. 2006;11:10-17] of the 6061-T6 aluminium alloy are presented. These values are in the range of 90-94%, depending on the preheat temperature and were obtained by means of a heat balance that considers the heat input, the amount of molten mass of the welding profiles, and welding parameters during the joining, giving particular emphasis to the data collected during the digitalization of the arc current. Also, some dimensionless parameters were employed in order to determine the approximation grade of the molten pool, the heat-affected zone, and their corresponding approximations to the experimental results. [ABSTRACT FROM AUTHOR]

When electrical stimulation is used on wounds, the electrical current has difficulty penetrating areas where there is necrotic tissue. Further, for an irregularly shaped wound, current distribution is poor in some areas of the wound since conventional two-electrode delivery systems provide the greatest current in a line directly between the electrodes. A new stimulator and electrode system is described which uses three electrodes spaced around a wound to disperse current more evenly. The stimulator senses tissue impedance and then redirects current by altering its Thevenin's output impedance for each electrode; each of the three electrodes becomes the active one in sequence while the remaining are the sink electrodes. Eight subjects were examined to test the stimulator. Electrical stimulation was applied to the skin above the quadriceps muscle at currents of 15 mA in six subjects without wounds and in two subjects with wounds. The relationship between electrode position and current dispersion on the skin was examined with a two-electrode vs. a three-electrode system to set stimulation parameters for the computer. The results showed that the three-electrode system could (1) detect areas of the skin with high impedance; (2) compensate by altering the Thevenin's output impedance at each of the three electrodes to shift current to high impedance areas; (3) provide uniform current across the skin as assessed by skin current and blood flow measurements with a laser Doppler flow imager. [ABSTRACT FROM AUTHOR]

A drain current model is developed for a symmetrically driven undoped (or lightly doped) symmetric double-gate MOSFET (SDGFET) under the drift-diffusion transport mechanism, with velocity saturation effects being included as an integral part of the model derivation. Velocity saturation effects are modeled by using the Caughey-Thomas engineering model with exponent n = 2. Id-Vd, IdVg, gm-Vg, and gDS-Vd comparisons are made with 2-D device simulation results, and a very good match is found all the way from subthreshold to strong inversion. Gummel symmetry compliance is also shown. [ABSTRACT FROM AUTHOR]

In order to elucidate the mechanism of ethanol oxidation, a simple cylindrical diffusion-surface reaction was developed on a platinum disk electrode. An ethanol electro-oxidation mechanism was proposed, in which electrochemical reactions proceed without adsorption of any electro-oxidation products (C2 type) on the surface. After the simulation of the proposed mechanism, it was seen that the model can explain ethanol electro-oxidation behavior without any surface CO formation. The simulation of the mechanism indicated that the formation of acetaldehyde through the oxidation of bulk ethanol is the rate determining step between 0.6 and 0.75 V vs. RHE. After 0.75 V vs. RHE, the formation of surface acetate through bulk ethanol becomes the rate determining step. According to the proposed oxidation model, around 0.7 V vs. RHE, acetaldehyde coverage becomes the major surface species, and acetate formation starts around 0.7 V vs. RHE. Surface species profiles of the proposed model show that C2 type species play an important role in ethanol electro-oxidation. [ABSTRACT FROM AUTHOR]

Abstract: The combination of pressurized flow and electric field offers, with the use of capillary columns, several options for retention control. However, it has been shown that the utility of this technique is strongly limited by the high electric current that is generated at the high electric field strengths that are needed. We have earlier shown that the high current is a result of locally increased mobile phase ion concentration in the electric field, particularly around the inlet electrode. In this paper, we report that by splitting the mobile phase flow around the inlet electrode a relatively constant ion concentration around the electrode can be obtained and the high currents are there by reduced. [Copyright &y& Elsevier]

Abstract: Objective: Do large stimulation electrodes reduce pain in nerve conduction testing? Methods: Fourteen healthy subjects (6 men, 22–42 years) blinded for study design underwent 8 H-reflex studies, using a large (36×36mm) or a small (6×6mm) electrode, placed on either the patella or the popliteal fossa; either site could be used for the cathode or the anode. Stimulation intensity was adjusted to obtain M- and H-waves. Intensity and other characteristics of pain were noted, as were M- and H-wave parameters. Results: Pain was felt strongest near the smaller electrode when two sizes were used. Large electrodes reduced pain without compromising H- or M-waves. Conclusions: Large stimulation electrodes reduce pain. Significance: The results apply for tests relying on amplitude measurements. [Copyright &y& Elsevier]

We present recent results of an extensive aging test, performed at the CERN Gamma Irradiation Facility, on two bakelite Resistive Plate Chambers (RPC) detectors. With a method based on a model describing the behavior of an RPC exposed to a large particle flux, we have periodically measured the electrode resistivity ρ of the two detectors over 3 years. We observed a large increase of ρ with time, from initial values of about 1010 Ω cm to more than 200×1010 Ω cm. A corresponding degradation of the RPC rate capability, from about 3 kHz/cm2 to less than 200 Hz/cm2, was observed. The reversibility of the process, using a humid gas mixture, has also been studied. [Copyright &y& Elsevier]

The present study describes the result of an improved numerical method applied to our two-electrode spark gap discharge. The time evolution of the ionization current is obtained and mechanisms describing ionization growth in discharge are presented. The effect of E/N has been investigated by changing either the applied gap voltage or by varying the nitrogen gas pressure. Some fluctuations in the exponential ionization growth are noticed which are related to the secondary ionization by the cathode photoelectric emission. Simulated snapshots were obtained that clearly show the image of electron avalanches traversing the discharge gap. My results are compared with other computational methods and they are in good agreement providing higher accuracy in the results. The advantage of my results is that I have considered a more accurate finite-element method for the numerical computation in which. considers the growth of the discharge in both the axial and radial directions with a good stability [ABSTRACT FROM PUBLISHER]