Electric Current Changes Research Articles

Effects upon interfacial reactions by electric currents of reversing directions

Sandwich-type reaction couples, Sn/Ni/Sn and Sn/Ag/Sn, were prepared. Two kinds of experiments were conducted: with and without the passage of a direct electric current through the couple. The specimens were placed in a furnace for pre-determined lengths of time at 180 and 200 °C for the Sn/Ni/Sn system and 160 °C for Sn/Ag/Sn. The current density was 500 A cm −2. The direction of the electric current through the couple was reversed during the reaction. Ni 3Sn 4 and Ag 3Sn phases were formed in the Sn/Ni/Sn and Sn/Ag/Sn couples, respectively. The passage of electric current changes the elemental mass fluxes, but not the phases formed in the couples. A mathematical model was proposed to calculate the thickness of the reaction layers. It has been found that the relative magnitudes of the reaction layer thickness at the two interfaces of the couples obtained from the two kinds of experiments are different. A net enhancement in the layer growth was experimentally observed even though the direction of electric current was reversed to neutralize the effect of electromigration. It is concluded that besides producing electromigration effects, the passage of electric currents through the couples affects the diffusion properties.

Modeling of the voltage-controlled friction effect

A phenomenological model of the dependence of friction coefficient on external voltage is proposed based on experimental results of friction and electric current of three different tribopairs, Si 3 N 4 -ball/steel-disc, Si 3 N 4 -ball/brass-disc and SiO 2 -ball/steel-disc, lubricated with zinc strearate suspension. It was found that the variation of friction coefficient correlates with the variation of electric current for all of the three tribopairs. The change in electric current is considered to be caused by the rate of electrochemical reactions occurring on the rubbing surface. By taking the electrochemical reaction into account in the total energy consumption, an expression for describing the relationship between the rates of friction coefficient and electric current is derived, and the constants included in the expression are determined through curve fitting of experimental data.

First thermally responsive supramolecular polymer based on glycosylated amino acid.

In materials science, a dynamic property sensitive to an environmental change (heat, light, electric current, pH, and other chemical or physical changes) is indispensable for intelligent materials. Such organic materials, however, are very limited even in conventional polymers. This paper clearly demonstrates that, regardless of the low molecular weight, a glycosylated amino acid derivative newly screened by a combinatorial method forms a macroscopic supramolecular hydrogel that reversibly swells or shrinks in response to the external temperature. Using the unique thermal response of the present hydrogel, we carried out the controlled release of DNA and the perfect removal of bisphenol A from the polluted water. Recently, advanced supramolecular polymers, in which monomers are noncovalently connected, are expected to be highly advantageous over traditional polymers because of their tunable and recyclable characteristics. The present result newly confers a dynamic feature on the supramolecular polymers, which is desirable for the sophisticated application in many fields.

Theory of `crotchet' impulse component generation

It is known that increasing of the electromagnetic emissions flux during the solar flares is accompanied by sudden disturbance of the geomagnetic field, which manifests itself on the ground magnetograms as a `crotchet'. This disturbance can be understood as a geomagnetic field response to a current intensification in the global ionosphere system due to the conductivity growing. Investigations for the past few years have showed that a temporal structure of the `crotchet' at solar flares, characterized by harder spectra (presence of a gamma rays), is more complicated and, in reality, is the mixture of the two components: a classic or gradual component and an impulse one. It has been suggested that such impulse disturbance be called`crotchet' impulse component (CIC). The possible generation mechanism of CIC is the main concern of this paper. According to themechanism to be discussed, CIC is a geomagnetic field reaction to the changes in the global atmosphere-ionosphere current system related to the stratosphere absorption of solar flare gamma rays (0.1-10 MeV). In this energy band, the most important role the gamma rays absorption plays is the Compton scattering, providing favourable conditions for the vertical transfer of the Compton electrons being produced. The presence of this vertical electric current changes the parameters of the global ionosphere current system and causes the suitable geomagnetic field effect - the CIC event. The theoretical estimates demonstrate good agreement with the characteristics of the CIC event observed on the ground magnetograms.

A New Method of Evaluating the Average Electro-osmotic Velocity in Microchannels

A new and simple method to evaluate the average electro-osmotic flow velocity in microchannels is presented in this paper. In this method, the average electro-osmotic flow velocity is determined by using the slope of the measured current–time relationship during the electro-osmotic flow of one solution replacing another similar solution. The two solutions have the same electrolyte and a small difference in ionic concentration. Careful experiments were conducted to measure the electrical current change with time during such a displacing process under a constant applied electrical field. KCl and LaCl3 electrolyte solutions and 10-cm-long polyamide-coated silica capillary tubes of 100 and 200 μm in internal diameter were used in this study. The average velocities were determined by using the slope method. A numerical model was also developed to predict the average velocity of such an electro-osmotic flow. An excellent agreement in the average velocities between the slope method and the model predictions was found.

Establishment and Magnetocardiographic Changes of Pressure Overload Left Ventricular Hypertrophy and Its Regression in Rats

Background and Objectives：Regression of left ventricular hypertrophy (LVH is important because development of myocardial ischemia, heart failure or arrhythmias may be reduced. However, an animal model for LVH regression is not well established and there are no useful parameters to predict LVH regression. Magnetocardiogram (MCG, magnetic signal generated from the heart, has recently been investigated for the detection of electrical current changes of the heart. This study was undertaken to establish rat models of LVHregression and to assess MCG changes during LVH induction and regression. Materials and Methods：Rat models of pressure overload LVH were established by transverse aortic constriction (TAC and LVH regression was generated by untying 2 weeks after TAC. Hemodynamic, echocardiographic and biochemical evaluation were performed in order to confirm this model. Magnetic fields were recorded with a SQUID gradiometer before and after TAC, and also recorded at 1, 3, 7, and 14 days after untying, respectively. Results：Rat models of LVH-regression were established successfully by TAC and untying. The pressure gradient across TAC disappeared within 10 minutes after untying. LV weight, LV weight/body weight ratio, LV mass and expression level of atrial natriuretic factor were significantly increased following TAC and decreased to baseline value after pressure unloading. Deeper S waves and strain patterns were observed after LVH induction and gradually returned to basal levels over the 2 weeks after untying. Conclusion：MCG changes in the rat models of LVH-regression indicate that MCG can be a helpful modality for the diagnosis and evaluation of LVH as well as follow-up after treatment of LVH. (Korean Circulation J 2002;32( ( ( (4 :330-338

Magnetic equilibria resulting from a helically symmetric kink instability

This paper explores magnetic equilibria which could result from the kink instability in a cylindrical magnetic flux tube. We examine a variety of cylindrical magnetic equilibria which are susceptible to the kink, and simulate its evolution in a frictional fluid. We assume that the evolution takes place under conditions of helical symmetry, so the problem becomes effectively two-dimensional. The initial cylindrical equilibrium field is specified in terms of its twist function k(r) = B θ/(rBz ) and for a variety of k(r) functions we calculate linear growth rates for the kink instability, assuming that it develops under helical symmetry with pitch τ. We find that the growth rate is sensitive to the value of τ. We simulate nonlinear evolution of the kink using a Lagrangian frictional code which constrains the field to have helical symmetry of a given pitch τ. Ideal MHD is assumed and the plasma pressure is taken to be small in order to mimic conditions in the solar corona. In some cases the flux tube evolves to a new smooth helically symmetric equilibrium which involves a relatively small change in the maximum electric current. In other cases there is evidence of current-sheet formation.

PYROELECTRICITY OF TEMPERATURE-INDUCED PHASE TRANSITION IN TIN-MODIFIED LEAD ZIRCONATE TITANATE

The pyroelectricity of Pb0.99Nb0.02［(Zr1-xSnx)1-yTiy］0.98O3 antiferroelectric and ferroelectric ceramics is investigated. Experimental results show that phase transitions are accompanied with drastic electric current changes and form positive or negative pyroelectric peaks. The transformations from ferroelectric into antiferro- or paraelectric phases make positive pyroelectric peaks, and the transformations from antiferroelectric into ferro- or paraelectric phases make negative pyroelectric peaks. Suppose electrostatic potentials of various phases are different, then the relation between the orientation of pyroelectric peak and the type of phase transition could be explained properly. With the above relation the phase transitions with temperature variations in Pb(Zr,Ti)O3 antiferroelectric-ferroelectric materials can be defined.

Tumor treatment by direct electric current Tumor perfusion changes

A single-shot electrotherapy with 0.6 mA direct current for 60 minutes delivered via two needle electrodes placed subcutaneously on opposite sides of a tumor induced statistically significant tumor growth delay in SA-1 and LPB murine fibrosarcoma tumor models. A prolonged vascular occlusion is indicated by the results of staining tumors with a Patent Blue dye in the SA-1 tumor model immediately and 24 hours after one hour electrotherapy. The almost complete absence of tumor staining after treatment with electrotherapy in SA-1 tumors suggested that the tumor growth retardation could result from this prolonged vascular occlusion. However, statistically highly significant tumor growth delay in LPB tumors was accompanied by only a slight decrease of a tumor staining with Patent Blue. Thus, the observed effect of electrotherapy on both tumor growth retardation and perfusion in the LPB tumor model raises some doubt about the above hypothesis.

Tolerance of oocyte plasma membrane to electric current changes after fertilisation

The tolerance of the oocyte plasma membrane (oolemma) to electrical pulses (TEP) was investigated for oocytes, zygotes, and embryos at the early and late 2-cell stage. The oocyte survival rate after two electrical pulses (1.4 kV/cm for 640 microns each) was used as an indicator of the TEP of the oolemma. Survival rate of mid-pronuclear zygotes (94.3% +/- 2.3%) was significantly (p < 0.05) higher than that of recently ovulated (2.1% +/- 1.9%) and in vivo aged (25.1% +/- 2.6%) oocytes; survival rate of in vivo aged oocytes was also significantly higher than that of recently ovulated oocytes. Soon after fertilisation, the survival rate of the oocytes markedly increased, up to 94% at the mid-pronuclear stage. Survival rate dropped thereafter. These results suggest that the characteristics of the oocyte plasma membrane (oolemma) change after fertilisation.

Intensity discrimination as a function of stimulus level with electric stimulation

Difference limens (DLs) for changes in electric current were measured from multiple electrodes in each of eight cochlear-implanted subjects. Stimuli were 200-microseconds/phase biphasic pulse trains delivered at 125 Hz in 300-ms bursts. DLs were measured with an adaptive three-alternative forced-choice procedure. Fixed-level psychometric functions were also obtained in four subjects to validate the adaptive DLs. Relative intensity DLs, specified as Weber fractions in decibels [10 log (delta I/I)] for standards above absolute threshold, decreased as a power function of stimulus intensity relative to absolute threshold [delta I/I = beta (I/I0) alpha] in the same manner as Weber fractions for normal acoustic stimulation reported in previous studies. Exponents (alpha) of the power function for electric stimulation ranged from -0.4 to -3.2, on average, an order of magnitude larger than exponents for acoustic stimulation, which range from -0.07 to -0.11. Normalization of stimulus intensity to the dynamic range of hearing resulted in Weber functions with similar negative slopes for electric and acoustic stimulation, corresponding to an 8-dB average improvement in Weber fractions across the dynamic range. Sensitivity to intensity change ¿10 log beta¿ varied from -0.42 to -13.5 dB compared to +0.60 to -3.34 dB for acoustic stimulation, but on average was better with electric stimulation than with acoustic stimulation. Psychometric functions for intensity discrimination yielded Weber fractions consistent with adaptive procedures and d' was a linear function of delta I. Variability among repeated Weber-fraction estimates was constant across dynamic range. Relatively constant Weber fractions across all or part of the dynamic range, observed in some subjects, were traced to the intensity resolution limits of individual implanted receiver/stimulators. DLs could not be accurately described by constant amplitude changes, expressed as a percentage of dynamic range ¿delta A(% DR)¿. Weber fractions from prelingually deafened subjects were no better or worse than those from postlingually deafened subjects. The cumulative number of discriminable intensity steps across the dynamic range of electric hearing ranged from as few as 6.6 to as many as 45.2. Physiologic factors that may determine important features of electric intensity discrimination are discussed in the context of a simple, qualitative, rate-based model. These factors include the lack of compressive cochlear preprocessing, the relative steepness of neural rate-intensity functions, and individual differences in patterns of neural survival.

Comparison of antinociceptive, cardiovascular, and respiratory effects, head ptosis, and position of pelvic limbs in mares after caudal epidural administration of xylazine and detomidine hydrochloride solution

Abstract Objective To examine and compare effects of 2α2- adrenergic receptor agonists, xylazine and detomidine, administered into the sacrococcygeal epidural space to induce safe and effective perineal analgesia on cardio-vascular and respiratory functions, head ptosis, and po-sition of pelvic limbs in healthy mares. Animals 8 healthy mares. Procedure Blood samples were drawn and systemic hemodynamics were determined, including cardiac output and pulmonary arterial, systemic arterial, and right atrial pressures. Two-way ANOVA with repeated measures was used to detect significant (P &lt; 0.05) differences between mean scores of perineal analgesia, cardiorespiratory variables, head ptosis, and position of pelvic limbs in mares before and during a 3-hour testing period. Analgesia was determined by lack of sensory perception to electrical stimulation at the perineal dermatome and no response to needle prick stimulation in dermatomes extending from the coccyx to T15. Avoidance responses to electrical current and needle prick stimulation and behavioral changes (head ptosis, position of pelvic limbs) were quantitatively assessed by use of a scoring system. Results Epidurally administered xylazine induced perineal analgesia and variable bilateral caudal analgesia extending from the coccyx to S3 dermatome, with minimal cardiovascular and respiratory depression, head ptosis, changes in position of pelvic limbs, and no urination in standing mares. Epidurally administered detomidine in-duced perineal analgesia, variable bilateral analgesia with dermatomal spread ranging from coccyx to S3 and coccyx to T15, with cardiovascular depression, marked head ptosis, changes in position of pelvic limbs, and diuresis in standing mares. Onset of perineal analgesia after xylazine and detomidine administrations was 13.1 ± 3.7 and 12.5 ± 2.7 minutes (mean ± SD), respectively. The period of perineal analgesia was significantly (P &lt; 0.05) longer in mares after epidural xylazine administration than after epidural detomidine administration (165 to &gt; 180 minutes vs 160 ± 8 minutes). Conclusions Caudal epidurally administered xylazine (0.25 mg/kg of body weight in 8 ml of 0.9% NaCI) offers the most desirable conditions in mares: long-term perineal analgesia (&gt; 2.5 hours), with minimal cardiopulmonary depression, head ptosis, changes in pelvic limb position, and no urination in standing mares during a 3- hour test period. (Am J Vet Res 1996;57:1338-1345)

チタン含有プラズマ重合薄膜の有機ガス応答特性に及ぼす可視光照射の効果

A titanium-containing organic thin film was prepared from titanium tetraisopropoxide (TIPP) by plasma polymerization. The effects of photoirradiation (visible light) on the electric conductivity of the film in the presence of organic vapors such as ethanol, acetaldehyde, formaldehyde, and benzaldehyde were investigated at various temperatures. The film showed electric current changes as large as 6-20 μA when exposed to ethanol and acetaldehyde under visible light irradiation. These results indicated the possibility of an organic gas sensor operable below 100°C.

Possibilities of the reopulmonography method

Geography, or impedance plethysmography, is a method of studying the blood supply of organs and tissues by recording changes in their electrical resistance. A special case of this method is reopulmonography (RPG)-a method of assessing pulmonary circulation and ventilation. Electrical current resistance changes under conditions of pulsatile blood flow and breathing can be recorded graphically in the form of a characteristic periodic curve, the form of which depends on the functional and morphological state of the studied lung area. The configuration of the rheogram is close to the plethysmogram, but not identical to it, as it is determined not only by blood flow, but also by the blood flow rate in the studied area. This fact is clearly illustrated by RPE recordings from different parts of the lung.

Degradation of Cu-Sn/Pb Surface Layers on Aluminum Conductors by the Action of an Electric Current

The effect of an electric current on the morphology of the coating layers on an aluminum conductor has been investigated. The results show that an electric current causes profound changes in the coating layers, resulting in substantial degradation of the conductor contact properties.

The measurement of a small transient signal superposed on a large electric current

Two methods, manual back-off and capacitor coupling (by cutting off the d.c. component) are usually used to measure a small transient signal superposed on a large electric current. The shortcomings of them are analysed and an automatic current back-off circuit with high accuracy is described in this paper. The response time of this circuit needed for compensating a sudden change in the large electric current is less than 50 microseconds. The described circuit can be used for the time scale from 1 microsecond per division upward on an oscilloscope. Mathematical analysis of the response time of the circuit is presented and a practical circuit is also given in detail.

The Transient Response and Impedance Locus of a Mobile Site Membrane

The kinetic properties of a mobile site membrane are analyzed theoretically and the results are compared with experimental data obtained from a simple model system. In the model system the measured response to a step change in electric current is a single relaxation process, in excellent agreement with the theoretically predicted behavior. To this relaxation process corresponds an anomalous capacitance whose properties are obtained by performing a frequency analysis of the system. By plotting the impedance locus of this mobile site membrane, the locus is shown to exhibit a 45 degrees phase angle at high frequencies, a phenomenon which is generally associated with depletion layers.

Studies on the Relations between Olfactometry and Psychological Effect of Odoriferous Substances

A physical model equipped with two heat-sensitive thermistors, of which only one is coated with polymer film for adsorbing odoriferous material in ordor to measure the odor, was established.Each thermistor is connected with Wheaston bridge, by which the change of adsorption heat generated by adsorption of gaseous odoriferous substance on the coating film of the thermistor is transformed into the change of resistance, thence into the change of electric current that is recorded through DC-amplifier.This apparatus employed “Two Path System”. Each response of twenty one species of odoriferous substances was measured by the apparatus and corresponding human olfactory response measurable by the same as an appropriate sensory scale.In examination of the relationship between the ammetric response by the apparatus and human olfaction, it was discussed whether there be possible that this apparatus would serve for estimating odor intensity and characteristics as substution for human olfaction.

Inadequacy of "rheoencephalography". A clinical study of impedance cephalography for evaluation of cerebrovascular disorders.

A RELIABLE and sensitive technique for the simple and safe measurement, through the intact skull, of changes in the flow or circulation of blood in the human brain would be extremely useful for the diagnosis and management of cerebrovascular disorders. Rheoencephalography, which we prefer to call cephalography, has been proposed as a method for the study of the cerebral circulation. Basically, impedance cephalography is the technique of impedance plethysmography, applied to the head. The impedance recorded from the head during the passage of an electric current changes with the cardiac cycle; the cyclic changes of impedance presumably are related in some way to the entrance of blood into the head. Certain earlier reports1,2on the use of impedance cephalography for the diagnosis of cerebrovascular disease indicated that the technique is of little value. These earlier studies have been criticized by proponents3(R. Sano and R. Namon, personal

Activation of the contractile mechanism in striated muscle.

Summary. When a frog's striated muscle (m. sartorius) is immersed in Ringer solution containing 2.5–10 × 10–4 w/v of the free base caffeine tension develops and the muscle contracts. The contracture is graded according to dose and reverses rapidly upon removal of the drug. Higher concentrations of caffeine produce an irreversible contracture. In a muscle immersed in isotonic K2SO4 or KCl solution caffeine produces exactly the same kind of muscle contracture as in a muscle kept in Ringer's fluid. Prolonged soaking (96 hours) of a muscle in isotonic K2SO4 solution does not reduce its responsiveness to caffeine. Local application of caffeine from a micropipette to a muscle fibre produces a localized contracture when the tip of the pipette is at the outer surface of the cell membrane. When the tip is inserted into the fibre no contracture is observed indicating that the caffeine action is confined to the muscle membrane. In concentrations helow 10‐3 w/v caffeine does not alter the resting meinhrane potential of iituscle fibres. Neither does the drug markedly reduce the transverse niuscle iiienibraiie resistance. It is suggested that caffeine at the niuscle membrane starts a process which activates the contractile mechanism in the interior of the fibre. This process is believed to be the same as that activated by the propagated action potential. The nature of the process (or processes) linking the membrane to the contractile elements is unknown hut the present results makes it unlikely that it is an electric current or potential change.