Increase In Current Strength Research Articles

ВЛИЯНИE 4-(ДИФЕНИТИЛФОСФОРИЛ)-3-МЕТИЛПИРИДИНА НА ПРОЦЕСС ЭЛЕКТРОХИМИЧЕСКОГО НИКЕЛИРОВАНИЯ

The effect of the concentration of 4-(diphenitylphosphoryl)-3-methylpyridine on the quality of the nickel coating in the electrolyte was studied. It was found that with an increase in the concentration of the additive from 0.01 g/l to 0.05 g/l, the nickel coating is detached, and with an increase in current strength, nickel hydroxide is formed, which indicates an increase in the pH of the electrolyte in the region of high current densities

An Effect of Electrical Current Strength and DCEN Polarity on SMAW Welding Results in Butt Joint Position 1G

This study aims to understand the effect of current strength variations on the Direct Current Negative Electrode (DCEN) polarity on the results of welding at butt joint joints. In this study, ASTM A36 steel was chosen as the main material, while the E6013 electrode was used as the welding electrode. The method used is an experimental approach with a qualitative approach, which allows researchers to gain a deeper understanding of the effect of current variables on welding results. The results of three experiments conducted at welding current of 60 A, 90 A, and 120 A provide a clear picture of the effect of these variables on the butt joint. In the first specimen with a current strength of 60 A, there was not enough penetration and many defects in the capping. Low current strength does not produce optimal welding results at the joint. However, in the second specimen with a current strength of 90 A, there was an initiation of penetration, although it was still incomplete. There are also fewer defects in the capping compared to the first specimen, and it shows an increase in welding results with an increase in current strength. In the third specimen with a current strength of 120 A, there is better penetration, but still not achieving complete penetration. In addition, the capping has many defects, including the suck back. It shows that using high current strength only sometimes produces optimal welding results and can present challenges, such as joint defects.

ВЛИЯНИЕ ИНДУКТИВНОСТИ НА ПАРАМЕТРЫ ПЛАЗМЕННОГО ФОКУСА В ИМПУЛЬСНОМ КОАКСИАЛЬНОМ УСКОРИТЕЛЕ

Based on the physical analysis of the processes occurring in pulsed plasma accelerators, the pos­sibility of their use for the creation and study of a plasma focus is justified. In particular, the influence of inductance on the parameters of the plasma focus in kilojoule­range «Plasma focus» (PF) installations created on the basis of a pulsed coaxial accelerator is studied. An equivalent installation scheme is proposed and justified, based on the analysis of which the influence of the inductance of the circuit and the capacitance of the capacitor bank on the value of the maximum current and neutron output is analyzed, without taking into account the parameters of the spark gap and the conducting wires. Based on the theoretical estimate of the inductance of the installation, its most probable value is calculated. . It turned out that in the installations of the considered energy range, the inductance is approximately 7.5•10­7 Gn and depends on the capacitance of the capacitor bank. On the contrary, in installations with megajoule energy, the inductance does not depend on the number and capacity of capacitors, so that an increase in the latter does not affect the increase in current strength. Experimental and theoretical dependences of the discharge current on the applied voltage at different capacitances of the capacitor bank are obtained. A comparative analysis of theoretical and experimental current waveforms is pre­sented. The greatest coincidence of theoretical and experimental results was found for the duration of the discharge pulse T = 30 microseconds.

Study of hydrogen concentration in the weld seam during welding of mining equipment

The study of the hydrogen content in the weld during the welding of mining equipment was carried out. It was found that with an increase in current strength, voltage and welding rate, a decrease in the hydrogen concentration in the welded joint of the samples is possible. The obtained welded samples meet the requirements for the hydrogen content – the hydrogen concentration in all samples is less than 2 cm3/100g.

Synergistic Effect of Chemical Enhancer And Iontophoresis For Transdermal Delivery Of Nebivolol Hydrochloride

The aim of the present study was to develop and investigate the feasibility of delivering Nebivolol as a transdermal patch by iontophoresis. The passive and electrically assisted transdermal delivery of Nebivolol hydrochloride by iontophoresis will improve the therapeutic efficacy and overcome the difficulties raised in oral drug delivery. Because of its extensive hepatic metabolism and low dose, Nebivolol hydrochloride become a suitable candidate for transdermal administration. The matrix transdermal patches of Nebivolol hydrochloride were prepared and tested for in-vitro drug release and ex-vivo permeation. The study was conducted with the help of silver-silver chloride electrodes by iontophoresis across hairless rat skin. Drug release was evaluated in the presence of iontophoresis field using a current density of 0.5 mA/cm2 or without electric field i.e passive diffusion by the process of electro-migration and electro-osmosis. Drug was measured spectrophotometrically and flux was determined. The flux of Nebivolol significantly increased (P<0.05) with increase in current strength from 0.5 – 1.0 mA/cm2. The findings show that Nebivolol hydrochloride matrix transdermal therapeutic systems could be prepared with the required flux having suitable mechanical properties. It can be concluded from the results that the appliance of iontophoresis with penetration enhancer enhances the flux compared to the passive diffusion.

Simulation of electric-field and spin-transfer-torque induced magnetization switching in perpendicular magnetic tunnel junctions

Macrospin simulations are performed to model the magnetization switching driven by the combined action of electric-field and spin-polarized electric current (spin-transfer torque; STT) in MgO/CoFeB based magnetic tunnel junctions with interfacial perpendicular magnetic anisotropy. The results indicate that at low current case, the free layer magnetization shows a fast toggle-like switching, the final parallel or antiparallel magnetization state is determined by the electric-field effect, and the STT just helps or resists it to reach the final state depending on the current direction. However, with the increase of current strength, the contribution of STT effect gradually increases, which eventually achieves a deterministic magnetization switching state. Simulations further demonstrate that by appropriately tuning the parameters of applied electric-field and current the power consumption can be easily reduced by two orders of magnitude.

Structure-Skin Permeability Relationship of Dendrimers

To investigate skin penetration of poly (amidoamine) (PAMAM) dendrimers as a function of surface charge and molecular weight in presence and absence of iontophoresis. Dendrimers were labeled with fluoroisothiocynate (FITC); skin penetration of dendrimers was studied using excised porcine skin in-vitro. Skin penetration of FITC-labeled dendrimers was quantified using confocal laser scanning microscope (CLSM). G2-G6 NH(2), G3.5-COOH and G4-OH dendrimers were used. Cationic dendrimers showed higher skin penetration than neutral and anionic dendrimers. Skin penetration of cationic dendrimer increased linearly with increase in treatment time. Iontophoresis enhanced skin penetration of cationic and neutral dendrimers. Increase in current strength and current duration increased skin transport of dendrimers. Passive and iontophoretic skin penetration of cationic dendrimers was inversely related to their molecular weight. Dendrimer penetrated the skin through intercellular lipids and hair follicles. With iontophoresis, dendrimer was also found in localized skin regions. The study demonstrates that the physicochemical properties of dendrimers influence their skin transport. Findings can be used to design dendrimer-based nanocarriers for drug delivery to skin.

Characteristics of F‐region dynamo currents deduced from CHAMP magnetic field measurements

Using magnetic field observations of the CHAMP satellite we provide the first comprehensive study of F‐region dynamo currents as a function of season, local time, geographic longitude, and solar activity. From bipolar variations of the zonal magnetic field component the density of vertical current driven by the F‐region dynamo is deduced. The current strength is smallest around June solstice, which is attributed to a reduced F‐region Pedersen conductance caused by a lower electron density and neutral density at that season. During the hours around noon highest current densities are observed. They are flowing downward over the dip equator. A secondary peak of upward currents appears at dusk. The polarity switch occurs between15 and 16 (local time) independent of season. The noontime F‐region dynamo current peaks at longitudes connected to the South Atlantic Anomaly, which can be explained by the enhanced conductivity in the region of reduced B field. The F‐region current at dusk exhibits no peak in the longitude sector of the South Atlantic Anomaly. At noon, the F‐region dynamo currents exhibit a wave 4 longitudinal structure during equinoxes and June solstice. The wave 4 signature becomes weak during December solstice. At dusk the wave 4 signature of F‐region dynamo currents is much reduced in all seasons. This behavior can be explained by the DE3 tidal signature in the zonal wind at CHAMP altitude. F‐region dynamo currents increase linearly with the solar flux index, F10.7, during both noon and dusk time sectors. The increase in current strength with increasing F10.7 is slightly higher at dusk than at noon.

Transdermal Iontophoresis of Hydromorphone across Hairless Rat Skin In Vitro

The feasibility of delivering hydromorphone by transdermal iontophoresis to obtain therapeutically effective analgesic concentrations for the management of cancer-related pain was evaluated. Anodal iontophoresis was performed, and the effect of current strength, current duration, solution pH, presence of buffer ions, and drug concentration on the transdermal permeation of hydromorphone was investigated in vitro. Freshly excised full‐thickness hairless rat skin and side-by-side permeation cells connected to the Phoresor IITM with Ag/AgCl electrodes was used. The flux of hydromorphone was observed to significantly increase (P < 0.05) from 72.04–280.30 μg/cm2/h with increase in current strength from 0.10–0.50 mA. A linear relationship was obtained between hydromorphone flux and current strength. Furthermore, the flux of hydromorphone was influenced by solution pH and presence of buffer ions. Also, the in vitro permeation flux of hydromorphone was observed to significantly increase (P < 0.05) with a 10-fold increase in hydromorphone hydrochloride concentration from 0.01–0.10 M. However, with further increase to 0.50 M, there was no significant difference in flux. These results show that by manipulating electronic and formulation variables, the transdermal iontophoretic delivery of hydromorphone can be controlled, and therapeutically effective concentrations of hydromorphone for the management of cancer-related pain can be obtained.

Electrically-evoked release of taurine in the rat vas deferens: evidence for a purinoceptor-mediated effect.

Release of taurine evoked by electrical stimulation (2700 pulses; 5 Hz; 10 mA unless stated otherwise) and its dependence on noradrenaline and ATP was studied in isolated, perifused rat vas deferens. Outflow of noradrenaline was also measured in some experiments. The basal outflow of taurine averaged 3.90 +/- 0.32 nmol/g tissue per min. Electrical stimulation increased the outflow to about 4 times basal values. The electrically-evoked overflow averaged 128.0 +/- 11.7 nmol/g. An increase in current strength to 40 mA increased the evoked overflow by about 50%. At either current strength, the evoked overflow of taurine (and noradrenaline) was abolished by tetrodotoxin. Ca(2+)-deprivation blocked the overflow of taurine elicited by 10 mA and increased the overflow elicited by 40 mA pulses (but abolished noradrenaline overflow under either condition). Neither prazosin nor pretreatment of the rats with reserpine reduced electrically-evoked overflow of taurine (although reserpine pretreatment abolished evoked noradrenaline overflow). Tyramine (100 mumols/l; 9 min) caused an overflow of taurine 36% of that caused by electrical stimulation (but an overflow of noradrenaline 3 times higher than that evoked by electrical stimulation). Exogenous noradrenaline (9 min) caused a concentration-dependent overflow of taurine with a maximal effect at 162 mumol/l, amounting to 33% of the electrically-evoked overflow. alpha,beta-Methylene ATP (19 mumols/l) elicited an overflow of taurine that faded despite continued exposure to the drug and amounted to 62% of the response to electrical stimulation. Thirty minutes after the start of application of alpha,beta-methylene ATP, electrically-evoked overflow of taurine was greatly reduced. Suramin (100 mumols/l) also reduced taurine overflow in response to electrical stimulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Strength-interval relation for ventricular functional refractoriness

Successful initiation and termination of presumed reentrant ventricular tachycardia frequently depends on the ability to deliver closely coupled impulses to the region of the tachycardia origin. To evaluate systematically the relative influence of local latency and large-scale conduction delay in limiting the delivery of closely coupled impulses, the strength-interval relation of the effective refractory period (RP), and the local and remote functional RP in 35 patients at paced cycle length of 500 ms were measured. The pacing threshold was ≤0.25 mA in all patients. The drive-train (S 1 and the extrastimulus (S 2) were applied from the same site, the right ventricular (RV) apex, in 25 patients, and from separate sites (RV apex and RV outflow tract) in 10 patients. The effect of procalnamide (plasma concentration 10.1 ± 2.3 μg/ml) on the strength-interval relations in 10 patients was also assessed. Although effective RP decreased significantly with each successive increase in current strength (p < 0.001), local functional RP decreased only up to current strength of 4 mA, and remote functional RP decreased only up to 2 mA. Procainamide shifted the effective RP and local and remote functional RP strength-interval curves uniformly to the right without altering their relation. These data indicate that large-scale conduction delay provides the principal limitation for using increasing current strengths of a single extrastimulus to initiate or terminate ventricular tachycardia.

A low-voltage activated, transient calcium current is responsible for the time-dependent depolarizing inward rectification of rat neocortical neurons in vitro.

Intracellular recordings were obtained from rat neocortical neurons in vitro. The current-voltage-relationship of the neuronal membrane was investigated using current- and single-electrode-voltage-clamp techniques. Within the potential range up to 25 mV positive to the resting membrane potential (RMP: -75 to -80 mV) the steady state slope resistance increased with depolarization (i.e. steady state inward rectification in depolarizing direction). Replacement of extracellular NaCl with an equimolar amount of choline chloride resulted in the conversion of the steady state inward rectification to an outward rectification, suggesting the presence of a voltage-dependent, persistent sodium current which generated the steady state inward rectification of these neurons. Intracellularly injected outward current pulses with just subthreshold intensities elicited a transient depolarizing potential which invariably triggered the first action potential upon an increase in current strength. Single-electrode-voltage-clamp measurements revealed that this depolarizing potential was produced by a transient calcium current activated at membrane potentials 15-20 mV positive to the RMP and that this current was responsible for the time-dependent increase in the magnitude of the inward rectification in depolarizing direction in rat neocortical neurons. It may be that, together with the persistent sodium current, this calcium current regulates the excitability of these neurons via the adjustment of the action potential threshold.

Influence of current strength on excitability and conduction of human atrium and atrioventricular node.

The influence of current strength on excitability and conduction of atrium and atrioventricular node was assessed in 25 patients using different current strengths (2, 3, 4, 5, 7, 10, 15 mA) and introducing extrastimuli (parasinusal zone) after the eighth paced complex of a basic drive (100 beats X min-1). Bipolar stimulation with the distal pole as cathode was performed so that effective and functional refractoriness of atrium and atrioventricular node, and the maximum value of atrial latency (interval between the extrastimulus and the beginning of atrial activity), intra-atrial conduction time, and AH interval could be determined at each current strength. In some patients atrioventricular nodal effective refractoriness could or could not be determined at each current strength, whereas in others the determination was possible only at the highest or the lowest current strengths. Moreover, the increase in current strength induced a progressive parallel reduction in both atrial effective and functional refractoriness; induced a progressive lengthening of intra-atrial conduction time (this was seen only in patients with a history of atrial arrhythmias); allowed the maximum possible lengthening of AH interval; and did not visibly influence atrioventricular nodal refractoriness and atrial latency. By altering atrial refractoriness and intra-atrial conduction time current strength affects the prematurity of the atrial impulse and the time at which it reaches the atrioventricular node. These findings should be taken into account when diagnostic and therapeutic electrophysiological procedures are performed.

Human ventricular refractoriness: Effects of increasing current

The ventricular effective refractory period is commonly employed as a measurement of ventricular excitability. Because the current strength used to make this determination varies among laboratories, the relation of refractoriness and current was examined over a range of current strengths from 0.1 to 10 mA. Sixty determinations of refractoriness at variable current strengths were made in 40 patients using the extrastimulus technique with a rectangular pulse of 1 ms duration. These data were obtained by measuring the effective refractory period at threshold current and at 0.25 to 0.50 mA increments from threshold up to 10 mA. In these studies the drive stimulus (S 1) and extrastimulus (S 2) were kept at the same amplitude. In all patients the ventricular effective refractory period decreased as the current increased. The total decrease ranged from 8 to 100 ms (mean ± standard deyiation 36.9 ± 17.1). The current strength at which the ventricular effective refractory period became fixed (that is, less than 2 ms change in ventricular effective refractory period with further increase in current strength) varied among the patients, but in all instances equaled or exceeded 1.8 mA, which in all but three patients was greater than three times threshold. The curves relating current strength and refractoriness were shifted to the left at shorter cycle lengths with no change in threshold. These data suggest that (1) current strength-effective refractory period curves more completely characterize ventricular excitability than does a ventricular effective refractory period at single current strength; and (2) studies of drug effects, alterations of autonomic tone, or reentrant arrhythmias, which may affect or are affected by ventricular refractoriness, may be enhanced by more complete measurements of refractoriness afforded by the current strength-effective refractoriness curves.

Respiratory Response to Electrical Stimulation of the Brain Stem of Fetal and Neonatal Sheep

Extract: Focal electrical stimulation of the medulla was undertaken in exteriorized fetal sheep and neonatal lambs, anesthetized with pentobarbital. The area from which respiratory responses were obtained was mapped using stereotaxic coordinates. Focal stimulation of the fetal medulla caused one or two inspiratory gasps. In only a few instances was the response expiratory and this appeared to be nonspecific. The area in the fetal brain stem from which respiratory responses were elicited was diffuse and extended from obex to lower pons. This region occupied a volume of about 130 mm3.In one exteriorized fetus with spontaneous, rhythmic ventilation, focal stimulation caused an apneic pause. Later when respiration ceased spontaneously, focal stimulation at the same current strength induced inspiratory gasps. In the spontaneously breathing neonatal lamb, focal stimulation of the medulla was associated with a diminution in tidal volume and an apneic pause could be produced with an increase in current strength. The apneic pause occurred at about the same current strength as that required to initiate respiration in the fetus.In the neonatal lamb the brain stem area from which a respiratory response could be obtained was less diffuse than that of the fetus and occupied a volume of about 65 mm3. This region was similar to the inspiratory center of adult sheep reported by others.Speculation: The respiratory center of the fetus appears to be just as sensitive to focal electrical stimulation as that of the neonatal animal. However, differing ventilatory response to stimulation depending on the presence or absence of respiration suggests a different functional organization of the fetal respiratory center. This is further supported by the characteristic inspiratory response of the fetus and the diffuse area from which such a response was obtained.

Polarization effects of sinusoidal 50-cycle alternating current on membrane potential of mammalian cardiac fibres.

Using a sucrose gap, sinusoidal 50-cycle alternating current was passed through isolated papillary muscles of the rhesus monkey. Responses of the membrane potential accompanying AC polarization were recorded with intracellular microelektrodes. The following results were obtained: Upon AC polarization with just threshold intensity, several subthreshold oscillations of the membrane potential preceded the initiation of an all-or-none response (Gildemeister effect). Without any change in the effective strength of the polarizing current, the amplitudes of the local oscillations increased in the depolarizing direction up to threshold. Alternating current of 1.5 x rheobasic intensity gave rise to a rhythmic selective series of action potentials depending on refractory conditions. With a further increase of current strength, the rhythmic firing of action potentials ceased and the oscillation band of the membrane potential dislocated more and more to positive values, either forming a constant plateau of fluctuating rhythmically similar to electrical pacemaker activity. With isotonic replacement of all Na+-compounds of the Tyrode's solution by sucrose the membrane behaved like a rectifier with inward going rectification. Hence, under these conditions, AC polarization caused the membrane potential to oscillate asymmetrically about the resting potential, preferring the depolarizing half-periods. Time-dependent changes of the membrane conductance disappeared. In normal Thyrode's solution an increased mechanical tension was maintained throughout AC polarization if the average potential level of the oscillation band became more positive than about−30 mV. Possible ionic current mechanisms concerning the movement of Na+-or K+-ions, respectively, which may account for some of the observed effects were analysed by means of an electronic computer model of the cardiac fibre membrane.

Zone of excitation when electrically stimulating human teeth

When an electrical impulse is passed through a human tooth to determine the pain perception threshold, the effective stimulus is the current density (current per unit area) at the place where excitation occurs. It was therefore suggested that passing the current through a larger area at the pulpo-dentinal junction would necessitate an increase in current strength to maintain the current density at a level sufficient to excite receptors. This was found to be true up to a limiting value at which level it is speculated that the current density might be sufficiently great to cause excitation of nerve fibres in the pulp canal.

Self-stimulation in the goat.

AbstractA method is described to obtain intracerebral self‐stimulation in the goat. Permanent platinum iridium electrodes were implanted into the hypothalamus. The animal could elicit the electrical stimuli by pressing a switch connected to a stimulator that delivered trains of damped square pulses to the electrodes. High rates of self‐stimulation were obtained in the premamillary region of the hypothalamus between columna fornices descendens and tractus mamillothalamicus. The behaviour of the goats during self‐stimulation was observed, as well as the different rates and frequencies of self‐stimulation that they developed at various electrode sites. The influence of different strengths of current on the rate of self‐stimulation was also observed. In some parts where high rates of self‐stimulation were obtained, an increase in current strength up to 1.0 mA did not decrease the rate of self‐stimulation. A sudden change to stimuli in “rewarding areas” that never before had been tested with electric current immediately developed high rates of self‐stimulation. Amphetamine was tested on self‐stimulating animals. The drug increased the animals' urge for self‐stimulation.

Effect of an Electric Current on the Efficiency of Homogenization of Ultrasonically Irradiated Milk

Summary This study was concerned principally with determining the influence of a dissolved gas phase and/or an electric current on the efficiency of homogenization. There is evidence of a positive relation between homogenization efficiency and current strength through the sample. Theoretically, there should be an optimum electric current strength, and the homogenization efficiency should be expected to increase with an increase in current strength, reach maximum, then decrease, with a further increase in current. Such an experimental relationship was observed. During radiation in a metallic tube, the efficiency factor was not affected conclusively by reversing the polarity of the container and the platinum probe. But, when the milk was radiated directly in the transducer bowl, the homogenization efficiency factor improved when the central electrode was negatively charged.

Some Inhibitory Phenomena in the Dorsal Root Reflex.

Summary.The efferent “reflex” output in the dorsal root L 6 in response to afferent discharges from L 7 (the so‐called dorsal root reflex) has been studied in decerebrate cats with the aid of electrical stimuli of variable form. Special attention has been paid to the effect of temperature.Prolonged afferent discharges, set up by constant currents, cause prolonged dorsal root reflexes. Increased duration of the afferent discharge is accompanied by an inhibitory block, far more pronounced at normal temperature than at low temperature of the spinal cord.Intermittent afferent stimuli, set up by brief iterated shocks, elicit intermittent dorsal root “reflex” discharges which successively diminish in size. This depression increases with stimulus frequency and for any frequency is far more pronounced at normal temperature than at low temperature of the spinal cord.Afferent discharges set up by linearly rising currents of steep gradient, elicit well marked “reflex” discharges. But slowly rising currents, which still give well marked impulses in the input root, fail to cause the reflex response. For this to occur the linearly rising stimuli must be increased in strength so as to cause prolonged repetitive discharges. The necessary increase in current strength is greater at high than at low temperature of the spinal cord.