Cathodic Pole Research Articles

Display of Solid-State Materials Using Bipolar Electrochemistry

We report the formation and characterization of one-dimensional chemical composition gradients of CdS on Au surfaces using bipolar electrodeposition. When an external electric field is applied across an electrically floating Au electrode immersed in a bipolar electrochemical cell, a position-dependent interfacial potential difference is generated along the length of the Au. This potential gradient can be used to induce variations of chemical composition within thin films electrodeposited onto the Au bipolar electrode (BPE). Thin films formed by bipolar electrodeposition represent continuous one-dimensional solid-state material libraries and were screened using resonance Raman microscopy and Auger electron spectroscopy. As predicted from simple thermodynamic considerations, we observed three distinct deposition zones scanning from the cathodic pole to the midpoint of the BPE: (i) CdS+Cd, (ii) stoichiometric CdS, and (iii) elemental S. Bipolar electrodeposition can be used to generate material libraries rapidly and without direct electrical contact to the substrate using extremely simple instrumentation.

Shortening of distal motor latency in anode distal stimulation

Objective Distal motor latency (DML) is shortened when the anode is held distally instead of the cathode by increasing the stimulus intensity. The objective of this study was to clarify the mechanism responsible for this shortening. Methods In seven healthy subjects, compound muscle action potential (CMAP) was obtained from the thenar muscle by bipolar stimulation of the median nerve at the wrist, and the intensity at which the first motor units were stimulated was defined as the threshold. Bipolar stimulation with extended interpole distance was employed to identify the generating site of the CMAP and F-wave. Results The shortening of DML was dependent on the stimulus intensity and threshold. For the low threshold condition, the CMAP generating site was replaced from the proximal cathodal pole to the distal anodal pole by increasing the stimulus intensity. The generating site of the F-wave remained at the proximal cathodal pole irrespective of stimulus intensity. Conclusions Replacement of the generating site results in the shortening of DML. When the F-wave is recorded after being induced by anode distal stimulation, CMAP should not be simultaneously evaluated. Significance This study clarified the generation sites of CMAP and the F-wave when induced by anode distal stimulation.

Human dermal fibroblasts do not exhibit directional migration on collagen I in direct-current electric fields of physiological strength.

Endogenous electric fields are generated lateral to skin wounds, with the cathodal pole of the field residing in the center of the wound. These fields are thought to be an important mechanism in guiding the migration of keratinocytes and other cells into wounds to effect healing. In this work, human dermal fibroblasts were exposed to direct current electric fields of physiological strength, and their migrational behavior was quantitated. Only random migration of human dermal fibroblasts was observed in direct-current electric fields under conditions that support the directional migration of human epidermal keratinocytes. Additionally, neither the presence of serum nor serum plus additional Mg++ in the experimental medium supported directional migration. Migratory rates of fibroblasts varied depending on the experimental medium used: in serum-containing medium the average velocity was as low as 0.23 micro m/min, while in serum-free keratinocyte medium the average velocity was as high as 0.36 micro m/min. These studies suggest that dermal fibroblasts do not respond to the endogenous electric field of a wound, and use other migratory cues to direct their movement into the wound bed.

A Precision Machining of Gears. Slow-Scanning Field Controlled Electrochemical Honing.

This paper presents a new working method of controllable Electro-Chemical Honing (ECH) of gears as follows. A gear shaped cathode which is meshing with a workpiece gear during machining is exposed as cathode pole only on a strip on the tooth dank. By varying the center distance between the cathode and the gear slowly, the electrolysis zone sweeps over the tooth flank from root to tip (slow scanning as we call it). Since the center distance is varied by a step motor, so the time of dwelling of the pole, and hence the amount of metal removal on different spots of the profile can be controlled by programming. An on-line profile error measuring device is provided. The computer calculates the required discharging time which has a relationship with dwelling time, and sends out the programming to control the metal. removing rate so as to cancel the error or to produce profile correction needed by silent transmission. A mathematical model is built for calculating the required discharging time. Several ground gears with typical profile errors are subjected to trial machining on this working principle. It cancels the profile errors very efficiently. The experiment demonstrates that the machining method can step up the profile accuracy to very high order on the basis of the general accuracy guaranteed by the proceeding operationgear grinding.

放電プラズマ焼結チタン合金の耐食性に及ぼす焼結温度の影響

The present study was conducted in order to analyze the effects of sintering temperature on the microstructure and corrosion resistance of Ti-M (M=Ru, Rh, Pd, Ir, Pt) alloys prepared from titanium and M powders using spark plasma sintering (SPS). In addition, the practicality of the Ti-Ru alloy as a low-cost Ti alloy was discussed. The specimens were prepared at SPS temperatures of 800, 1100 and 1500°C. The microstructure of specimens were investigated using scanning electron microscopy (SEM) and X-ray diffraction. The corrosion resistances of specimens were determined by potentiodynamic polarization measurement at a scanning speed of 0.124 V/min using a 5% HCl solution open to air at 25°C. Measurement was performed at a specimen potential of from −1.0 to 2.0 V and the potential approached noble.At a low SPS temperature, SPS alloys show a particle dispersion microstructure, in which the added element phases and intermetallic compound phases are dispersed in the Ti matrix. These phases affect the corrosion resistance of the alloys. At a high SPS temperature, the added elements and compounds are diffused in the Ti matrix, causing the alloy to approach a solid solution microstructure and increasing the formation of metastable βTi. In particular, at a high SPS temperature, in the Ti-Pt alloy increases slightly the amount of βTi, whereas increases greatly the amount of Ti3Pt. High SPS temperatures reduce the added element phases that serve as the cathodic pole, thus diminishing the cathodic current. In the anodic area, the reduction or dispersion of compound phases reduces the compound active region, thus diminishing the anode current.Furthermore, high SPS temperatures produce similar polarization curves among Ti-M alloys, and provide SPS alloys having the same corrosion resistance equivalent to that of arc-melted alloys. Therefore, no problem is associated with the replacement of Pd with Ru.

Common molecular mechanisms in field- and agrin-induced acetylcholine receptor clustering.

1. The aggregation of acetylcholine receptors at the developing neuromuscular junction is critical to the development and function of this synapse. In vitro studies have shown that receptor aggregation can be induced by the finding of agrin to the muscle cell surface and by the electric field-induced concentration of a (nonreceptor) molecule at the cathodal cell pole. 2. We report here on the interaction between agrin binding and electric fields with respect to the distribution of receptors and agrin binding sites. 3. (a) Pretreatment of cells with agrin completely blocks the development of field-induced receptor clusters. (b) Field-induced aggregation of receptors precedes the field-induced aggregation of agrin binding sites by approximately 30 min. (c) Electric fields prevent agrin-induced receptor clustering despite the presence of agrin binding sites and freely diffusing receptors. 4. These results indicate that another membrane component-but not the agrin binding site and not the receptor-is required for agrin-induced receptor clustering. They also suggest that electric fields and agrin cause receptor clustering via common molecular mechanisms.

Extracción y caracterización de antígeno micelial de Aspergillus fumigatus

This report describes the standardization and antigen characterisation of a mycelial extract of Aspergillus fumigatus, for the purpose of employing it later in pulmonary aspergillosis diagnostic tests. The mycelial antigen was evaluated using double-immunodiffusion (DD), counterimmunoelectrophoresis (CIE+ID) and enzyme immunoassay (ELISA) techniques, the results were compared with a reference antigen. The protein and carbohydrate concentrations of the mycelial antigen were 8,800 pg1mL and 2,452 pg/mL, respectively, being very similar to the reference antigen. The antigens analysed in the DD presented bands of partial and total identity. No precipitin bands were presented in DD and CIE+ID tests when both antigens with 20 negative sera were run. In the CIE+ID, precipitin bands were obsewed at the anodic and cathodic poles for both antigens. The cut-off value determined in the mycelial antigen ELISA test was 0.352 with a 95% confidence interval. It is possible to conclude that mycelial antigen can be used in diagnostic serological tests.

Direct solution analysis by glow discharge: electrolyte-cathode discharge spectrometry

A new glow discharge atomic emission source was developed for the direct determination of metals in aqueous solutions by applying an atmospheric glow discharge in the air gap (2–6 mm) between an electrolyte solution cathode and a W-rod anode. Cathode sputtering of the solution surface and subsequent excitations occur when the pH of the solution is below 2.5. The spectrum emitted contains the basic atomic lines of the dissolved metals from K 769.9 to Zn 213.8 nm, ion lines of Mg and Ca and strong OH, NH and N2 bands. Boiling of the cathode pole can be avoided by use of a flow-through technique. The electron temperature was found to be around 5000 K. The calibration curves of line intensities versus metal concentrations were linear in the 1–50 ppm range and showed strong positive dependence on the discharge current and on the hydrogen ion concentration of the solution. Pulse modulated operation with time-resolved signal processing promises a substantial increase in the signal-to-background ratio. The flow-through electrolyte acts as a continuously renewed cathode pole, thereby enabling the continuous direct multi-metal assay of solutions. This report is the first discussion on the analytical characteristics of electrolyte-cathode discharge (ELCAD). spectrometry as a new technique for metal monitoring in aqueous solutions.

Electric Field-Induced Redistribution of ACh Receptors on Cultured Muscle Cells: Electromigration, Diffusion, and Aggregation.

Xenopus myoball cultures were used to examine the lateral migration and clustering of acetylcholine receptors in response to electric fields. In contrast to concanavalin A binding sites, which behave in a manner explained by electromigration and diffusion, acetylcholine receptors form stabile aggregates at the cathode-facing cell pole. Interestingly, receptor aggregation continues there after termination of the field. This post-field receptor aggregation is consistent with the action of a specific diffusion-trap mechanism mediated by adhesion or cohesion events on the cell surface. The simplest hypothesis for the triggering of receptor aggregation is that receptors are accumulated in response to the electric field and, once past a threshold density, autoaggregation is initiated. This model was tested by examining field-induced distributions of receptors following enzymatic treatment to reverse the electromigration of receptors. After neuraminidase treatment, and exposure to electric fields, receptor distributions were consistent with reversed electromigration (towards the anodal cell pole) but continued to show receptor aggregation at the cathodal cell pole. We conclude that the diffusion-trapping of acetylcholine receptors requires the participation of non-receptor molecules. In addition to providing a useful experimental tool in these studies, electric fields may play a role in receptor clustering at the neuromuscular junction.

Changes in cell surface anionogenic groups during differentiation ofHerpetomonas samuelpessoai mediated by dimethylsulfoxide

The surface anionic groups of untreated or dimethyl sulfoxide (DMSO)-treated Herpetomonas samuelpessoai cells were analyzed by cell electrophoresis, ultrastructural cytochemistry, and identification of sialic acids using thin-layer chromatography. Differentiation of H. samuelpessoai induced by DMSO treatment caused a significant increase in the net negative surface charge. In flagellates exposed to DMSO, more cationized ferritin, colloidal iron hydroxide, and sendai virus particles bound to the cell surface. Treatment of both untreated and DMSO-treated flagellates with neuraminidase decreased markedly the EPM of cells to the cathodic pole. These findings suggest that sialic acid residues are the major anionogenic groups exposed on the surface of H. samuelpessoai. Thin-layer chromatography showed that N-acetyl and N,O-diacylneuraminic acids, in equal proportions, were present in H. samuelpessoai. However, N-acetylneuraminic acid predominates in DMSO-treated cells.

Regeneration in the mammalian nervous system using applied electric fields: a literature review.

The application of weak electric fields on the damaged peripheral and central nervous systems will promote recovery of function in animal models. The effect of the electric field appears to facilitate the growth and orientation of regenerating neurites towards the cathodal pole in a DC field. Thus, provided the correct parameters are utilized, facilitation of regeneration in the human peripheral and even central nervous system appears possible.

Chapter 15 Cutaneous electroreceptors in the platypus: a new mammalian receptor

This chapter talks about a new mammalian receptor known as Cutaneous electroreceptors in the platypus. Electroreceptors are present in the skin of many species of fish and some amphibians. They are part of the lateral line-eighth nerve system, and comprise two major types, the ampullary variety (e.g., the ampullae of Lorenzini), and tuberous organs. The most effective excitatory conditions for the receptors found in several experiments is to have the cathodal pole of the stimulating dipole at the orifice of the ms gland. The physiological state of the receptor terminal can probably be regarded as an unstable equilibrium because many of the afferent fibres discharge continuously in the absence of an external stimulus. Modulation of ongoing activity in the nerve terminal would presumably facilitate the detection of small changes in the potential field surrounding the animal, and enable the receptor to signal both increases and decreases of field strength.

Perturbation of the direction of neurite growth by pulsed and focal electric fields

We have studied the orientation of neurite growth in the culture of embryonic Xenopus neurons in response to three types of extracellular electric fields: spatially uniform pulsed fields, focally applied steady (DC) fields, and focally applied pulsed fields. Under uniform pulsed fields, neurites showed a preferential orientation toward the cathode pole of the field in a manner similar to that previously found for DC fields. The extent of neurite orientation depended upon the duration, amplitude, and frequency of the pulse but appeared to be similar to that produced by a uniform DC field of an equivalent time-averaged field intensity. For square pulses of 5 msec duration, the minimal amplitude and frequency required to produce a detectable orientation of neurite growth over a period of 24 hr were 2.5 V/cm and 10 Hz, which correspond to a time-averaged field intensity of 125 mV/cm. Steady or pulsed focal fields were applied by passing a current through a micropipette placed near the growth cone of the neurite. Fields of negative polarity (current sink) were found to attract the growth cone, whereas fields of positive polarity (current source) were found to deflect the growth cone away from the pipette. The threshold DC current density needed at the growth cone to perturb its direction of growth within 15 min was 0.2 to 2 pA/micron2 (or 3 to 30 mV/cm); and for focal pulsed currents (pulse duration 5 msec), a typical combination of minimal pulse amplitude and frequency was 4 pA/micron2 and 10 Hz. This threshold focal current is similar to that which occurs at the synaptic cleft during active synaptic activity.

Migration of cell surface concanavalin A receptors in pulsed electric fields

Concanavalin A (con A) receptors on the surface of cultured Xenopus myoblasts redistributed in response to monopolar, pulsed electric fields. The prefield uniform distribution of the receptors became asymmetrical, and was polarized toward the cathodal pole, in the same way as in DC fields. The extent of asymmetry depended on the duration of field exposure, pulse width (or alternatively, interpulse interval), frequency, and intensity. This relationship was most conveniently expressed by using duty cycle, a quantity determined by both pulse width and frequency. Pulses of average intensity 1.5 V/cm induced detectable asymmetry within 5 min. At the lowest average field intensity used, 0.8 V/cm, significant asymmetry was detected at 150 min. For pulses of high duty cycle (greater than 25%), steady state was reached after 30 min exposure and the steady state asymmetry was dependent on average field intensity. For low duty cycle fields, the time required to reach steady state was prolonged (greater than 50 min). Before reaching a steady state, effectiveness of the pulses, as compared with DC fields of equivalent intensity, was a function of duty cycle. A low duty cycle field (fixed number of pulses at low frequency or long interpulse interval) was less effective than high duty cycle fields or DC.

Surface Anionic Groups in Symbiote‐Bearing and Symbiote‐Free Strains ofCrithidia deanei1

ABSTRACTThe surface anionic groups of symbiote‐bearing and symbiote‐free strains ofCrithidia deaneiwere compared by determining cellular electrophoretic mobility, by ultrastructural cytochemistry, and by identification of sialic acids by thin‐layer and gasliquid chromatography. Symbiote‐freeCrithidia deaneihas a highly negative surface charge (‐0.9984 μmċs‐1ċ V‐1ċ cm), which is slightly reduced (‐0.8527 μmċs‐1ċ V‐1ċ cm) by the presence of the endosymbiote. Treatment of both strains ofC. deaneiwith neuraminidase decreased significantly the electrophoretic mobility of cells toward the cathodic pole, indicating the existence of exposed sialic acid residues responsible for the negative charge on the protozoan cell surface. Thin‐layer and gas‐liquid chromatography showed thatN‐glycolyl‐ andN‐acetylneuraminic acids were present in both strains ofC. deanei.

Electrophoresis and diffusion in the plane of the cell membrane

Electrophoretic and diffusional movements of concanavalin A (Con A) receptors and acetylcholine (ACh) receptors in the plane of the plasma membrane of mononucleate, spherical Xenopus myoblasts were studied by microfluorimetry and iontophoresis. We found that (a) a uniform electric field of 10 V/cm applied along the cell surface produces a partial accumulation of both types of receptors toward the cathodal pole of the cell within 30 min: (b) post-field relaxation of the culture results in the complete recovery of the uniform distribution of the Con A receptors within 10 min; and (c) in contrast to the Con A receptor in general, accumulation of ACh receptors by the electric field results in the formation of stable, localized receptor aggregates. Theoretical analyses were carried out for the distribution of charged membrane receptors at equilibrium between electrophoresis and diffusion, and for the rate of back diffusion after the removal of the field. These analyses indicated that, at 22 degrees C, the average electrophoretic mobility of the electrophoretically mobile population of the Con A receptors is about 1.9 X 10(-3) micron/s per V/cm, while their average diffusion coefficient is 5.1 X 10(-9) cm2/s.

Pole reversals and hypothalamic self-stimulation: Ascending spread of rewarding excitation

Direction of the spread of rewarding impulses has been studied by analysis the changes in the efficiency of monophasic square wave pulses established by reversing the position of cathode (which is the active pole for self-stimulation) and anode (under which blockade of neural conduction may occur) for the same two wires of such bipolar electrodes whose two poles were aligned sagittally in lateral hypothalamus of rats. Lower bipolar self-stimulation thresholds were observed to belong to the anterior cathodal and posterior anodal pole positions and the same current level was found to maintain higher rate of bar pressing in this case than when stimulations with reversed cathodal-anodal pole positions were applied. This finding suggests that rewarding excitation starts to spread in anterior direction from the active pole of lateral hypothalamic self-stimulation electrodes.

A submillipound mercury electron bombardment thruster

Submillipound mercury electron bombardment ion thrustor efficiency, noting cathode pole piece, baffle position and geometry influence on ion chamber performance

COLOUR SENSITIVITY, CONTRAST AND POLARITY OF THE RETINAL ELEMENTS

SINCE the time of Purkinje and Ritter, it has been known and often confirmed that a galvanic current passed through the eye elicits a sensation of bluishviolet when the electrode on the bulb is an anode, of greenish-yellow when it is a cathode. Kravkov and Galochkina1 have recently shown that the anodal pole (on the eye) enhances the sensitivity to short wavelengths and depresses that to long wavelengths, whereas the cathodal pole has opposite effects. In view of the results on different polarity in retinal elements isolated by the micro-electrode technique, reported above2, it was thought to be of interest to combine polarization of the retina with measurements of the colour sensitivity of such elements. The micro-electrode technique and the cat's eye were used, as above2. The strength of the current was 1.0 mA.

Colour Sensitivity, Contrast and Polarity of the Retinal Elements

SINCE the time of Purkinje and Ritter, it has been known and often confirmed that a galvanic current passed through the eye elicits a sensation of bluishviolet when the electrode on the bulb is an anode, of greenish-yellow when it is a cathode. Kravkov and Galochkina1 have recently shown that the anodal pole (on the eye) enhances the sensitivity to short wavelengths and depresses that to long wavelengths, whereas the cathodal pole has opposite effects. In view of the results on different polarity in retinal elements isolated by the micro-electrode technique, reported above2, it was thought to be of interest to combine polarization of the retina with measurements of the colour sensitivity of such elements. The micro-electrode technique and the cat's eye were used, as above2. The strength of the current was 1.0 mA.