Galvanic Potential Research Articles

Corrosion characteristics of cobalt-silicon nitride electro composites in various corrosive environments

The corrosion characteristics of electro codeposited cobalt-silicon nitride composites in neutral sodium chloride and sulphuric acid solutions are presented. The electro composites showed greatly improved corrosion resistance over pure cobalt in nondeaerated 3.5% sodium chloride solution, but they induced significantly less galvanic corrosion on steel in the same medium. Galvanic current and dissolution current measurements showed a linear variation with the cathode-to-anode area ratio, while the galvanic potential showed a logarithmic variation with the same. Composites of cobalt-silicon nitride also showed improved passivation properties in 1 N sulphuric acid.

Pregnancy Increases Median Nerve Susceptibility to Lidocaine

To determine whether pregnancy renders women more sensitive to local anesthetics, nine nonpregnant and nine pregnant (third trimester) women underwent median nerve block at the wrist using 1% lidocaine HCl. Inhibition of median nerve A alpha sensory and motor fibers was assessed using measurements of sensory nerve action potential (SNAP) amplitude and compound motor action potential (CMAP) amplitude, respectively. Inhibition of median nerve C fibers was assessed by the increase in skin temperature and by the decrease in median (relative to ulnar) galvanic skin potential (GSP) amplitude. Lidocaine inhibited SNAP to a greater extent in pregnant than nonpregnant women at all time points (P = 0.019). CMAP declined differently in the pregnant and nonpregnant groups (P = 0.01): the pregnant subjects achieved steady state inhibition before the nonpregnant subjects. The two groups developed comparable steady state inhibition. Skin temperature was higher in pregnant women at all time points (P less than 0.0001); moreover, the increased skin temperature of pregnant women differed from that of the nonpregnant women (P = 0.037), reflecting a more rapid temperature increase in the pregnant women. GSP amplitude declined to 50% of control more rapidly in pregnant (mean = 4 min) than nonpregnant women (mean = 11.5 min), but these differences did not achieve statistical significance. It is concluded that pregnancy increases median nerve susceptibility to lidocaine.

Pregnancy Increases Median Nerve Susceptibility to Lidocaine

To determine whether pregnancy renders women more sensitive to local anesthetics, nine nonpregnant and nine pregnant (third trimester) women underwent median nerve block at the wrist using 1% lidocaine HCl. Inhibition of median nerve A alpha sensory and motor fibers was assessed using measurements of sensory nerve action potential (SNAP) amplitude and compound motor action potential (CMAP) amplitude, respectively. Inhibition of median nerve C fibers was assessed by the increase in skin temperature and by the decrease in median (relative to ulnar) galvanic skin potential (GSP) amplitude. Lidocaine inhibited SNAP to a greater extent in pregnant than nonpregnant women at all time points (P = 0.019). CMAP declined differently in the pregnant and nonpregnant groups (P = 0.01): the pregnant subjects achieved steady state inhibition before the nonpregnant subjects. The two groups developed comparable steady state inhibition. Skin temperature was higher in pregnant women at all time points (P less than 0.0001); moreover, the increased skin temperature of pregnant women differed from that of the nonpregnant women (P = 0.037), reflecting a more rapid temperature increase in the pregnant women. GSP amplitude declined to 50% of control more rapidly in pregnant (mean = 4 min) than nonpregnant women (mean = 11.5 min), but these differences did not achieve statistical significance. It is concluded that pregnancy increases median nerve susceptibility to lidocaine.

EFFECT OF THERMAL AGING ON MECHANICAL AND ELECTRICAL PROPERTIES OF THE MgO-PARTIALLY STABILIZED ZIRCONIA BODIES

The effects of thermal aging on some properties and thermal-shock behavior of zirconia partially stabilized with 9 mol% MgO (9MZ) were studied. 9MZ specimens were aged over 1300-1400for 12 hours subsequently after sintering at 1 6 5 0 ~ ~ for 4 hours. Fracture strength (both before and after thermal-shock test), linear thermal expansion, monoclinic fraction and phase transition by XRD, density, galvanic potential and microstructure were measured. Quantitative chemical analysis around the grain-boundary of the specimen aged at 1350°C was also conducted by EDX. The aging of 9MZ specimen causes a thermal decomposition of cubic-Zr02 into the formation of metastable tetragonal-Zr02 and MgO. The former increases the residual strength after thermal-shock test and the latter improves the thermal-shock resistance due to thermal conduction through the continuous phase of magnesia. The rate of thermal decomposition of cubic phase and the formation of monoclinic phase in matrix were increased with the decrease of aging temperature from 1400 to 12000C. Galvanic potential of the aged specimen exhibited a proper emf characteristic.

A measurement of galvanic current and electrical potential in extracted human teeth.

When opposing teeth with amalgam and gold restoration are in contact, current flows in the mouth at the instant the dissimilar metals touch. In this study, this condition was simulated by use of resistors and extracted human teeth with amalgam and MOD gold inlay restorations. When both teeth were in contact in a physiological saline solution, we measured current and electrical potential generated in each pulp chamber. Galvanic current generated in the tooth with amalgam was always larger (as much as 18.2 times at the instant of contact) than that in the tooth with gold. Electrical potential generated in the tooth with amalgam was always larger (as much as 9.7 times at the instant of contact) than that in the tooth with gold. It should be emphasized that the larger current generated in the tooth with amalgam was caused mainly by its larger electrical potential. These results correspond well with the clinical phenomenon of galvanic pain, which occurs in the tooth with amalgam rather than in the tooth with gold.

Adsorption behavior of fibronectin on well-characterized silica surfaces

The adsorption behavior of human plasma fibronectin at physiological pH and ionic strength was investigated by in situ ellipsometry on silica substrates of two different surface energies. The silica substrate was characterized by ellipsometry, galvanic potential, and critical surface tension measurements. Adsorption isotherms in the low concentration range for fibronectin were compared with human fibrinogen and found to be qualitatively similar with increased amounts of protein adsorbed at the plateau on a hydrophobic surface as compared to a hydrophilic one. Reversibility for fibronectin upon dilution was found to be small on a hydrophobic surface while a partial desorption was found on a hydrophilic one. Interaction of antibodies with preadsorbed fibronectin suggests that fibronectin adsorbs in different conformations and/or arrangements on the two types of surfaces. The lectin Concanavalin A and its interaction with preadsorbed fibronectin was also investigated.

Measurement of the thermal diffusion coefficient of Ag atoms in α-Ag 2Se

The thermal diffusion coefficient of Ag atoms, D T, has been obtained from thermodynamic and thermoelectric quantities such as ionic conductivity, thermoelectric powers for Ag ions and electrons, and the gradient of galvanic cell potential as a function of temperature. The temperature and concentration dependences of D T were measured from 150–230°C for single-crystal rods of α-Ag 2Se, for which orientations were not specified. The values of D T, which were of the order of 10 15 K −1 s −1 cm −1, were larger for higher temperatures and smaller concentrations of excess Ag in α-Ag 2Se.

Behaviour of galvanic couples of copper alloys in synthetic seawater with benzimidazole-2-thiol

Admiralty brass (Cu Zn 29 Sn 1) has been coupled to Cu, Cu Zn22 Al 2, Cu Al 7, Cu Ni 10 Fe 1/2, Cu Ni 30 Fe 0.4/1, Cu Ni 30 Fe 2 Mn 2 and tubular specimens of the coupled materials have been inserted in an experimental loop. The behaviour of the couples in flowing ASTM seawater at 30°C has been studied, both in uninhibited condition and in the presence of Benzimidazole-2-thiol (BIE) at different concentrations. The efficiency of a surface film, grown in a flowing solution of 10 −3 M BIE in distilled water, in reducing the galvanic effect has been tested, too. Weight loss, galvanic potential and galvanic current measurements have been carried out in ten day tests. As regards to free corrosion condition, the corrosion rate of Cu Zn 29 Sn 1 is more than twice when coupled to Cupronickel alloys; it considerably increases when coupled to Cu Zn 22 Al 2 and to Cu Al 7; it slightly reduces when coupled to Cu. 10 −3M BIE shows a good inhibitor efficiency on all the tested materials, both in free corrosion and in coupling condition. It comes out, too, that the prefilming treatment is an efficacious practice in reducing the corrosive attack on the coupled and uncoupled materials, also when put in seawater containing very small quantities of the inhibitor (10 −5M).

Components of the type A coronary-prone behavior pattern and cardiovascular responses to psychomotor performance challenge.

The present study tested the general hypothesis that behavioral attributes most predictive of the incidence of coronary heart disease (CHD) in epidemiological research would also be most predictive of sympathetic autonomic nervous system (ANS) arousal in response to performance challenges. Subjects (n = 50) were challenged to respond rapidly and accurately on three tasks involving either perceptual-motor or cognitive skills, while the experimenter monitored blood pressure, heart rate, and galvanic skin potential. The hypothesis was generally confirmed in that (1) type A subjects showed significantly greater cardiovascular changes indicative of sympathetic ANS arousal than type B subjects, (2) the Rosenman and Friedman structured interview was a better predictor of this arousal than the Jenkins Activity Survey, as is the case in CHD, and (3) the stylistic and behavioral components of the type A pattern (as defined by the structured interview) which are most predictive of CHD were also found to be the best predictors of challenge-induced sympathetic ANS arousal. The implications of these results for refinements in the definition, assessment, and modification of coronary-prone behavior are discussed.

“False inhibition” of demand pacemaker due to leakage of fluid into the pacemaker lead socket

"False inhibition" of a demand pacemaker usually occurs with a microfracture of the lead system resulting in a galvanic potential at the site of the fracture or with sensing of myopotential with exercise. An increase in the slope of the leading half edge of the pulse contour is generally considered diagnostic of lead fracture. We report the case of a patient in whom "false inhibition" at rest and an increase in the slope of the leading half edge of the pulse contour were caused by leakage of fluid into the pacemaker lead socket.

Physiological response patterns in ulcer patients: phasic and tonic components of the electrogastrogram.

ABSTRACTPhysiological response patterns in duodenal ulcer patients, rheumatoid arthritics, and healthy subjects were investigated by recording electrogastrograms (EGGs) and several other physiological measures during presentations of mildly stressful stimuli. Ulcer patients were physiologically less reactive to the stimuli than the other groups; with the exception of increases in tonic galvanic skin potential (GSP) responses during arithmetic problems, ulcer patients were responsive only while viewing slides taken during autopsies when they evidenced increases in gastric activity and phasic GSP responses. The EGG proved to be a valuable measure for differentiating both the groups and the tasks. Both ulcer patients and healthy subjects demonstrated increases in phasic (frequency and amplitude) EGG activity during affective but not during cognitive stimuli, and ulcer patients and arthritics could be differentiated from healthy subjects on the basis of tonic (basal resting levels and displacement) EGG activity. These results were interpreted to surest the possibility that phasic and tonic components of the EGG may each be associated with different types of gastrointestinal activity.

Influence of polyacrylamides on the quality of copper deposits from acidic copper sulfate solutions

Polyacrylamides have been tested as inhibitors for copper electrowinning from an acidic copper sulfate bath on a copper cathode. The quality of the deposit, the structure, the galvanic potential, the current efficiency, the orientation of the texture and the amount of occluded inhibitor are determined as functions of the anionic or cationic character and of the viscosity of the polyacrylamide solutions. All the results are compared with those obtained with the commonly used guar gum.

Galvanic skin potential as a predictor of mental status, anxiety, depression and denial in acute coronary patients

Galvanic Skin Potential (GSP) responses during an interview were recorded on 25 acute coronary patients in a coronary care unit (CCU). Patients were given rating scale scores for anxiety, depression, mental status and denial. Mean GSP during the interview showed a significant association with impairment of mental status ( r= -0·58). The denial-anxiety ( r= -0·37) and denial-mental status ( r=0·38) relationships showed a trend toward significance. The interview was divided by content into 18 items, with mean GSP output for each item computed separately. Although overall mean GSP showed no relationship to anxiety, depression and denial scores, multiple regression equations predicted these scores from sets of GSP item responses with corrected multiple r's for anxiety, denial and depression respectively. Clinical interpretation of this must be cautious, but the use of the GSP in clinical settings promises further understanding of the interrelation of physiological arousal, affect and the defense of denial.

Physical principles of the zirconia exhaust gas sensor

A brief description of the zirconia exhaust gas sensor is given. The electrochemical principles of the sensor are reviewed. Starting from the Nernst equation, theoretical relations are derived which relate the galvanic potential of the sensor to the composition of the exhaust gas from an internal combustion engine. Theoretical curves of galvanic potential versus the inlet air-fuel ratio are shown and discussed. The utility of the zirconia exhaust gas sensor is defined in applications such as closed-loop engine control systems.

Increase of autonomic arousal by boredom.

Two experiments tested the effect of boredom on galvanic skin potential, skin conductance, and heart rate as autonomic measures of arousal. The results support Berlyne's 1960 hypothesis that boredom increases autonomic arousal. An intelligence measure correlated positively with rated boredom on the experimental task. The subjective state of boredom was seen as resulting from an inadequate rate of information flow. Inadequate information flow may result in increased autonomic arousal because of (a) S-produced arousal increase required to maintain focused attention on the task and/or (6) release of brain stem arousal centers by boredom-reduc ed cortical activation.

Potential measurements in drill holes for identifying ores

Laboratory studies showed characteristic potentials to occur on some ores (e. g., fahlore, copper pyrite, pyrite, and gersdorffite) with respect to any reference electrode. Using these galvanic potentials it has become possible to separate ores. This method shall now be applied for identifying ores in drill holes. In nature, the galvanic potential belonging to the respective ore and to the reference electrode is superimposed by the so-called natural potential which is caused by geological stratification, water flows and differences in the pore water concentration. A method is described of how to separate the galvanic potential from the natural potential. The device required for these examinations has been developed in the Montanwerke Brixlegg/Tyrol, Austria. The described method has been applied for geoelectric examinations of some drill holes in the barite fahlore deposits of Grosskogl/Reith near Brixlegg, Tyrol, and in the copper deposits of Mitterberg near Salzburg, Austria. Ore was thus identified clearly also when it occurred only in traces.

Area Relationships in Galvanic Corrosion

Abstract The effect of variations of the area of two metals in a galvanic couple is discussed for three common cases. In Case 1, it is assumed that the only significant process on the more active metal (A) at the galvanic potential (ϕg) is metal oxidation (dissolution), while the only significant process on the more noble metal (C) is reduction of the oxidizer (H+, H2O, O2) and Tafel behavior is observed. Various possibilities to present the galvanic current as a function of electrode areas, which might have lead to some confusion in the literature, are discussed. In Case 2, it is assumed that metal (A), the anode in the galvanic couple, is polarized only slightly from its corrosion potential. It is shown that in this case the galvanic current density (igA) is not equal to the dissolution rate (idA) of the anode. A correlation between these two values is given. In Case 3, it is assumed that the cathodic process on both metals is entirely diffusion controlled. In this case, the dissolution rate of the anod...

Performance and acceptance of respirator facial seals.

Three respirator full face masks with different paripheral seal designs (flat, inner flap, and pneumatic) were modified to permit study of the facial seal component. Twelve subjects participated in the study. Each subject completed a three-hour test session on each mask. The first half of each session was devoted to a study of leakage at five seating forces; the second half of the session was devoted to a comfort study of the same mask under the same five seating forces. To test for the differences in' leakage for a given seating force a uranine aerosol test was used to challenge the integrity of the facial seal and permit quantitative measurement of percent leakage. Differences in apparent seating force (and therefore comfort) between the three facial seal designs were studied utilizing a psycho-physical technique. A suggested physiological correlate of comfort, galvanic skin potential, was also measured during the second half of the session. Significant differences were noted in the performance of one o...

Heart rate conditioning in the cat and its relationship to other physiological responses.

ABSTRACTTwenty cats were classically conditioned using electric shock as the unconditional stimulus (US). A 1000 cps tone served as the reinforced conditional stimulus (CS+) and a 500 cps tone as the non‐reinforced conditional stimulus (CS–). The CS–US interval was 10 seconds. Data collected show a heart rate deceleration to the CS+ which is accompanied by a drop in blood pressure, respiratory apnea, a negative baseline shift of the galvanic skin potential (GSP), pupillary dilatation, a decrease of the electromyographic (EMG) activity of the muscles of the shocked foreleg, and a low voltage fast pattern of the electroencephalographic (EEG) activity of the sigmoid gyrus of the cerebral cortex and olfactory bulb. The heart rate deceleration is present after muscle paralysis with succinyl choline and it is blocked by atropine. It is presumed to be of vagal origin. Difference in CS+ and US responsivity is discussed.

Skin Potential Correlates and Rating Assessments of Self-Evaluation under Different Degrees of Awareness

Self-evaluation was investigated by having adolescent female Ss rate photographs stereoscopically fused of two strangers (St-Sr), stranger and self (St-Sf), and two of self (Sf-Sf). Attractiveness and semantic differential ratings were obtained for each stereoscopic composite, and Galvanic Skin Potential (GSP) was monitored during viewing. With self-recognition, GSP was significantly greater for Sf-Sf than for St-St, but without self-recognition of Sf-Sf, GSP showed significantly less change. A tendency for greater GSP was found for St-Sf without self-recognition. Number of Ss rating St-Sf more (1) attractive, (2) highly valued, and (3) active was of borderline significance. Ss not recognizing self under St-Sf condition were high on a measure of self-esteem. Stereoscopically fused faces were rated as more attractive than same two faces normally viewed.