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PubMed1993

Colored focal visual evoked potentials by cathode ray tube versus scanning laser ophthalmoscope.

We compared the focal visual evoked potentials obtained in 52 young subjects with normal vision, evoked by means of three alternating black/color checkerboards generated by a trichromic cathode ray tube (dominant wavelength, 514 nm; colorimetric purity, 0.45) and by means of a scanning laser ophthalmoscope (argon laser beam, 514 nm; colorimetric purity, approximately 1). These three checkerboards, with an area of 3.5 degrees x 3.5 degrees (stimulating the fovea), then with an area of 3.5 degrees x 3.5 degrees with a central exclusion of 1.5 degrees x 1.5 degrees (stimulating the perifoveola) and finally with an area of 1.5 degrees x 1.5 degrees (stimulating the foveola) were presented within a field (8 degrees x 8 degrees) of homogeneous luminance of 170 cd/m2 and 1500 cd/m2, respectively. Their check sizes were 30', with a reversal temporal frequency of 0.75 Hz. The transient focal visual evoked potentials recorded with these three stimuli generated by the two types of stimulators were clearly detected for at least 85% of subjects. Their characteristics (waveform, amplitude and culmination times of the different waves) were comparable, regardless of the stimulator used (cathode ray tube or scanning laser ophthalmoscope). These results suggest that, under these various conditions of luminance and colorimetric purity, the neurophysiologic circuits tested function in identical ways. The focal visual evoked potential signs, now clearly defined by means of stimuli generated by cathode ray tubes, therefore apparently can be applied to the focal visual evoked potential evoked by stimuli generated by the scanning laser ophthalmoscope.

Adult↗
PubMed1993

Disk-cathode flash X-ray tube driven by a repetitive two-stage Marx pulser.

Fundamental studies of a repetitive flash X-ray generator using a disk-cathode radiation tube are described. The high-voltage pulser employed a modified two-stage surge-Marx circuit. The two condensers in the pulser were charged from 40 to 60 kV, and the electric charges were discharged to the X-ray tube repetitively to generate flash X-rays. The total capacity during the main discharge was 425 pF, and the maximum output voltage from the pulser was about 1.9 times the charged voltage. The flash X-ray tube was of the demountable-diode type and was composed of a rod-shaped anode tip made of tungsten, a disk cathode made of graphite and a tube body made of polymethylmethacrylate. The peak tube voltage was primarily determined by the anode-cathode (A-C) space, and the peak tube current was less than 0.5 kA. Thus the maximum photon energy could be easily controlled by varying the A-C space, and the tube current roughly increased according to increases in the charged voltage. The pulse width ranged from 40 to 100 ns, and the X-ray intensity was less than 1.1 microC kg-1 at 0.5 m per pulse. The repetition rate was less than 50 Hz, and the effective focal spot size was equivalent to the anode diameter.

X-Ray Therapy↗
PubMed1979

Immunichemical determination of cathodal elastase in human duodenal juice.

In human duodenal juice enzymes hydrolysing the elastase substrate succinyl-trialanine-p-nitroanilide have both an anodal and cathodal mobility in agarose gel electrophoresis. The cathodal enzyme, also having an elastinolytic activity, was purified. An application of electroimmunoassay for separate determination of this cathodal elastase is presented. Parallel estimations of esterolytic, elastinolytic and immunochemical activities in duodenal juice from a group of children revealed discrepancies suggesting both variations in the distribution of the two forms of "elastases", and presence of inactive forms.

Adult↗
PubMed1982

The origin of a cathode-migrating creatine kinase found in serum from a cancer patient.

The origin of an atypical creatine kinase (CK, ATP:creatine N-phosphotransferase, EC 2.7,3.2) migrating cathodic to the MM position found in the serum of a cancer patient was studied. The electrophoretic mobility of the atypical CK is similar to that of the fast-moving cathodal mitochondrial CK. The relative molecular mass was estimated to be approximately 350000, and was similar to that of the fast-moving cathodal mitochondrial CK. The atypical CK reacted with anti-human mitochondrial CK antibody. It is therefore suggested that the atypical CK is of mitochondrial origin. After incubation in 2 mol/l urea, the enzyme was converted into a new form migrating to the MM position. The conversion was observed in liver mitochondrial CK but not heart mitochondrial CK. The residual CK activity after heating at 56 degrees C for 60 s was 77%, and the apparent Km value for creatine phosphate at 30 degrees C was about 0.27 mmol for the atypical CK. These characteristics were very similar to those of the liver mitochondrial CK, because the data from the enzyme determined at the same time were 75% for residual enzyme activity to heat, and 0.24 mmol for apparent Km value. Therefore liver mitochondria are suggested to be the source of the atypical CK.

Adult↗
PubMed2005

Two sites for GTP binding in cathodic haemoglobins from Anguilliformes.

Cathodic haemoglobins of four species of anguilliform fish were characterized from a functional point of view, with special regard to the interaction with their physiological effectors. A series of oxygen-binding experiments at increasing GTP concentrations was carried out in order to compare GTP-binding activities in the absence and presence of saturating amounts of chloride. The results indicated that the cathodic haemoglobin of three species (Anguilla anguilla, Conger conger and Muraena helena) do have two sites for GTP-binding. In the absence of chloride, the two sites cannot be discriminated, whereas in the presence of chloride, a competition between the two anions occurred for the second GTP-binding site. The cathodic haemoglobin of Gymnothorax unicolor, which showed lower GTP sensitivity than the other haemoglobins examined, displayed only one GTP-binding site. The presence of an additional phosphate-binding site is not exceptional, although the way haemoglobin interacts with the two organic phosphate molecules may differ among species. This property may provide an auxiliary means of haemoglobin modulation for species that inhabit environments where oxygen availability is highly variable and haemoglobin-oxygen affinity needs to be modulated to different extents in order to satisfy physiological oxygen requirements.

Animals↗
PubMed2005

Ultrasonic effects on electroorganic processes. Part 25. Stereoselectivity control in cathodic debromination of stilbenedibromides.

Ultrasonic effects on the cathodic debromination of stilbenedibromides on a platinum cathode was examined. Current efficiency and stereoselectivity for trans-stilbene, which was formed along with cis-stilbene in the cathodic debromination of stilbenedibromides, were significantly increased under ultrasonication with an intensity over the ultrasonic cavitation threshold. This ultrasonic effect is rationalized as due to mass transport promotion in the electrode-electrolytic solution interface. A mechanism for the ultrasonic effect is discussed in detail on the basis of the reaction pathway of the debromination of stilbenedibromides.

Bromides↗
PubMed1976

Temporary unipolar pacing using a dual cathode.

Using standard biopolar, temporary pacing catheters, thresholds were measured in four configurations: (1) bipolar (distal electrode negative, proximal electrode positive); (2) distal unipolar (distal electrode negative, right arm electrode positive); (3) proximal unipolar (proximal electrode negative, right arm electrode positive); (4) dual-cathode unipolar (distal and proximal electrodes negative, right arm electrode positive). With one exception, the bipolar threshold was the lower of the distal or proximal unipolar thresholds, suggesting that bipolar temporary pacing is reliable because one of the two electrodes is in good contact with the endocardium. In both the distal and proximal unipolar configurations there were numerous instances of high threshold and failure to pace. However, with one exception, in all cases either the distal or proximal unipolar threshold was normal and thus pacing was possible and effective in the dual-cathode configuration. Dual-cathode unipolar pacing combines the excitation and sensing advantages of unipolar pacing with the reliability of bipolar stimulation.

Arrhythmias, Cardiac↗
PubMed2002

Electrolytic oxygen generation for subsurface delivery: effects of precipitation at the cathode and an assessment of side reactions.

This research investigated the oxygen-generating characteristics and side reactions of an electrolytic cell assembly that could be used to remediate sites with contaminants that are amenable to aerobic biodegradation. The oxygen-generating capabilities of new electrolytic cells and cells with light and heavy calcium carbonate precipitates on the cathode were evaluated in the laboratory under current densities ranging from 0.5 to 5.0 mA/cm2. Higher current densities resulted in higher mass transfer coefficients (K(L)a) and greater saturation oxygen concentrations (Csat). As the cathodic deposits increased, the K(L)a tended to decrease and the Csat tended to increase. The oxygen transfer efficiency (OTE) did not vary as a function of current density or cathode coating, while the average OTE for all the tests was 67%. Laboratory column tests showed that chlorine production increased with current density and depended on chloride levels in the water. Hydrogen peroxide was generated at low concentrations (< 1 mg/L) and at higher levels when chloride was absent in the feed solution. Calcium removal from solution increased with current density and resulted in a decrease in solution pH. Tests at a field monitoring well showed average Csat levels of 16.9 mg/L after 14 days of operation, no chlorine production because of low chloride levels in the well, artificially elevated hydrogen peroxide levels because of background interferences, and a pH decrease of 2.4 units. With passive venting, the average hydrogen gas levels at the headspace of the well were less than 1%.

Biodegradation, Environmental↗
PubMed2002

Coupling of anodic and cathodic reactions for phenol electro-oxidation using three-dimensional electrodes.

We studied the electrochemical oxidation of phenol by the coupling of anodic and cathodic reactions. The experiments were done in an electrochemical filter press cell equipped with an Sb-doped SnO2-coated titanium foam and a RVC cathode. The oxidation occurs by a direct oxidation on the anodic side, while on the cathodic side oxidation occurs via an electro-Fenton mechanism. We studied the influence of the working parameters. The electrical yield increases when pH decreases and is strongly dependent on an optimum between current density, iron and dissolved oxygen concentration. This method may be applicable to refractory compounds.

Electrochemistry↗
PubMed2001

Mathematical modelling of physicochemical reactions and transport processes occurring around a platinum cathode during the electrochemical treatment of tumours.

The electrochemical treatment (EChT) of tumours is an anti-tumour therapy in which a continuous direct current is applied to electrodes, placed in or near a tumour. Promising results have been reported from clinical trials in China, where more than 10,000 patients have been treated with EChT during the past 10 years. Before clinical trials can be conducted outside of China, a reliable dose-planning strategy has to be developed. One approach in achieving this is the use of physicochemical simulation models. A simplified mathematical model of the physicochemical processes, occurring around a spherical platinum cathode during EChT, is developed and visualized in three steps in this paper. In the final step, tissue is treated as an aqueous solution of sodium chloride, containing a bicarbonate buffer system and organic constituents susceptible to reactions with hydroxyl ions. This model is shown to give a good description of the pH profile obtained around the cathode after EChT. The simulation results reveal a strong correlation between the pH profiles and size of experimentally measured lesions, thus indicating that it is the spreading of hydroxyl ions that determines the extent of tissue destruction around the cathode. In addition, the simulations indicate that the model could be of use in predicting the size of a lesion produced by EChT.

Animals↗
PubMed1992

Axial evolution of the negative glow in a hollow cathode discharge.

The purpose of these studies was to examine the axial evolution of the negative glow in a hollow cathode discharge. The time-average negative glow profiles along the central axis of a hollow cathode were recorded for 81 pulse widths over the range of 5-25 microseconds in increments of 0.25 microseconds at a constant interpulse delay of 206.4 microseconds. Subsequent numerical processing yielded the instantaneous negative glow profile. The negative glow was viewed through a mesh-covered slot along the length of the hollow cathode. The negative flow profiles were imaged using a vidicon video camera. A PC-based frame grabber digitized the video images and stored them for subsequent processing.

Chemistry Techniques, Analytical↗
PubMed2006

An upflow microbial fuel cell with an interior cathode: assessment of the internal resistance by impedance spectroscopy.

An upflow microbial fuel cell (UMFC) system with a U-shaped cathode inside the anode chamber was developed and produced a maximum volumetric power of 29.2 W/m3 at a volumetric loading rate of 3.40 kg COD/(m3 day) and an operating temperature of 35 degrees C while feeding sucrose continuously. The Coulombic efficiency decreased from 51.0% to 10.6% with the increase in the volumetric loading rate from 0.57 to 4.29 kg COD/(m3 day). In addition, the lab-scale UMFC maintained soluble chemical oxygen demand (COD) removal efficiencies exceeding 90% and volatile fatty acid concentrations of approximately 40 mg/L, indicating efficient wastewater treatment. The analysis of impedance spectroscopy, generated by fitting experimental data into an equivalent circuit, revealed that at a volumetric loading rate of 3.40 kg COD/(m3 day) the overall internal resistance was 17.13 omega. This internal resistance was composed of electrolyte resistance (8.62 omega), charge-transfer resistance (7.05 omega), and diffusion resistance (1.46 omega). Electrolyte resistance dominated throughout the entire range of loading rates. In addition, impedance spectroscopy demonstrated that both the anodic and the cathodic charge-transfer resistances were important limiting factors. To further improve the power output of the UMFC, we must reduce the electrolyte resistance by optimizing reactor configuration, reduce the anode charge-transfer resistances by selecting superior anodic microbiota, and reduce the cathodic charge-transfer resistance by exploring sustainable and efficient catalysts.

Bacteria↗
PubMed2006

Stainless steels can be cathodically protected using energy stored at the marine sediment/seawater interface.

Laboratory-scale experiments were performed in which the corrosion protection of stainless steels in seawater was afforded by cathodic protection. The method was implemented for the first time using the potential difference at the marine sediment/seawater interface as the only source of electric power. Graphite electrodes buried in marine sediment, developing a potential of -0.45 V versus a saturated calomel electrode (SCE), were used as anodes to cathodically polarize UNS S30403 stainless steel coupons that were exposed to seawater. The cathodic protection system was operated with low polarization of stainless steel, typically to -0.2 V (vs SCE) and was found to properly prevent material failure even in the presence of a well-developed biofilm. With voltammetry, the protection current was found to be related to the oxidation of reduced sulfur compounds in the sediments. Results demonstrate that this inexpensive and environmentally friendly method can, so far, extend the service life of stainless steels in seawater.

Biofilms↗
PubMed2005

Cathodic modifications of platinum surfaces in organic solvent: reversibility and cation type effects.

Cathodic modification of platinum surfaces leads to the formation of iono-platinic phases ([Pt(n-), M+, MX]), which involves the insertion of cations and salts into the platinum electrode. This process was investigated at the local scale by in situ observation of surface electrochemical processes by atomic force microscopy (EC-AFM) techniques as a function of the salt and the injected charge, with special attention about the process reversibility. AFM images recorded in solution after the cathodic modifications of well-defined platinum surfaces [epitaxial platinum deposit on (100) MgO substrate] show drastic modification on the morphology of the surface, confirming previous ex situ studies. The amplitude of the modifications directly depends on both the nature of supporting electrolyte and the quantity of charge injected into the platinum. As long as the injected charge remains small enough to maintain the adhesion of the Pt deposit onto the MgO substrate, the process was found to be fully reversible. Indeed, impressive morphology changes occur under the cathodic treatment (formation of [Pt(n-), M+, MX]) but the initial geometry is totally recovered after reoxidation of the iono-platinic phase. This cycle of reduction-reoxidation can be performed several times without any significant alteration of the recovered surface and of its structural characteristics. It is suggested that the modification starts at the interface solution platinum surface and then its insertion into the platinum surface.

Journal Article↗
PubMed2006

High-efficiency polymer light-emitting diodes using neutral surfactant modified aluminum cathode.

High-efficiency polymer light-emitting diodes were fabricated by inserting a layer of nonionic neutral surfactant between the electroluminescent (EL) layer and the high-work-function aluminum cathode via spin coating. It was found that both the poly(ethylene glycol)- and poly(propylene glycol)-based surfactants as well as their copolymers can all demonstrate similar performance enhancement. Device performances comparable to or even better than those of the control devices using calcium as the cathode have been achieved for both poly(p-phenylene)-based and polyfluorene-based conjugated polymers with orange-red, green, and blue emission colors. It is possible that when both surfactant and aluminum are used as the cathode, the abundant hole injection through a hole-transporting layer and hole pile-up at the inner side of the EL/surfactant interface might cause an effective electric field to induce the realignment of the dipole moment of those polar surfactant molecules, thus lowering the barrier for electron injection. In addition, the coordination between the aluminum and oxygen atoms on the surfactant might cause n-type doping in the areas near surfactant in the EL polymer layer that causes the enhancement of electron injection.

Journal Article↗
PubMed1997

Molecular evolution in bacteria: surfaces, cathodes and anodes.

Molecular evolution is examined in bacteria with an emphasis on mineral surfaces, membranes, cathodes and anodes. In early molecular evolution, cathode-anode system may have been naturally occurring on a nm to micron scale. Secondly, the cathode-anode system could have been separated by a primitive, permeable lipid or microsphere on a mineral surface, that was a precursor of a more advanced membrane with a charge differential on either side of the membrane. These aspects will be considered from a theoretical evolutionary perspective.

Bacteria↗
PubMed2004

Rechargeable Fe(III/VI) super-iron cathodes.

This study addresses a fundamental challenge posed by hexavalent iron electrochemical irreversibility, which had slowed practical development of reversible Fe(VI) cathodes; nanolayers circumvent fundamental passivation challenges, and are electrodeposited from solution phase FeO(4)(2-), forming 601 mAh g(-1) Li, and 485 mAh g(-1) Na, Fe(III/VI) alkaline cathodes, the latter exhibiting 100-200 storage cycles at 80% depth of discharge, providing pathways towards metal hydride batteries with twice the cathode capacity.

Journal Article↗
PubMed1995

The cathodic hemoglobin of Anguilla anguilla. Amino acid sequence and oxygen equilibria of a reverse Bohr effect hemoglobin with high oxygen affinity and high phosphate sensitivity.

As in other fish, the cathodic hemoglobin of the eel Anguilla anguilla is considered to play an important role in oxygen transport under hypoxic and acidotic conditions. In the absence of phosphates this hemoglobin shows a reverse Bohr effect and high oxygen affinity, which is strongly modulated over a side pH range by GTP (whose concentration in the red blood cells varies with ambient oxygen availability). GTP obliterates the reverse Bohr effects in the cathodic hemoglobin. The molecular basis for the reverse Bohr effect in fish hemoglobins has remained obscure due to the lack of structural data. We have determined the complete amino acid sequence of the alpha and beta chains of the cathodic hemoglobins of A. anguilla and relate it to the oxygen equilibrium characteristics. Several substitutions in crucial positions are observed compared with other hemoglobins, such as the replacement of the C-terminal His of the beta chain of Phe (that suppresses the alkaline Bohr effect) and of residues at the switch region between alpha and beta subunits (that may alter the allosteric equilibrium, thus causing the high intrinsic oxygen affinity and low cooperativity). The residues binding organic phosphate in the beta cleft of fish hemoglobins are conserved, which explains the strong effect of GTP on oxygen affinity and suggests that these residues contribute to the reverse Bohr effect in the absence of alkaline Bohr groups. Moreover, His beta 143 that is considered to be responsible for the reverse Bohr effect in human and tadpole Hbs is replaced by Lys.

Amino Acid Sequence↗