Alternating current, use

When this solution was electrolyzed for thirty hours with alternating currents, using platinum electrodes, then the following products were obtained ... 

Hydroxocobalamin (vitamin another antidote, is a potential alternative to sodium nitrite treatment. It works by binding with cyanide to form nontoxic cyano-cobalamin (vitamin Bj ). Although effective and relatively safe in experimental models, the concentration available in the United States requires large infusion volumes and has a short shelf life due to light instability, and reports of anaphylactoid reactions have limited its use (8,13,21). Further studies using higher concentrations available in European formulations may eventually lead to its use as an outpatient alterative to sodium nitrite treatment in the United States (7,32). Other alternatives currently used or undergoing clinical trials in Europe include cobalt salts, limited by their toxicity, aldehydes, and aminophenol derivatives. These alternative treatments are not currently available in the United States (7). 

Why is alternating current used in the measurement of conductivities of ions in solution ... 

The flow of ionic molecules is estimated by measuring the resistance of the cell monolayer subjected to an alternating current using a pair of electrodes designed to convey the current and measure the voltage deflection. Although the procedure is simple, particular precautions must be taken to minimize variability. We calibrate the instrument (EVOM, World Precision Instruments, Sarasota, FL) by bathing the electrodes for 2 h at 37° in the TER medium, which is our cell culture medium (MEM) without serum and buffered with an Hepes solution to a 10 mM final... 

In view of the success of the 3-element model for the quantitative description of the variation of the low-frequency conductivity of resin-solution columns with the solution concentration, it is logical to inquire whether the same model can explain the electrical behavior of these or similar systems at high frequencies, at which the admittance of the system as a whole and/or of the model elements is appreciable. In other words, the question is asked Can the 3-element model describe the change of the complex impedance of these systems with the frequency of the alternating current used to measure the impedance ... 

This method relies on the simple principle that the flow of ions into an electrolyte-filled micropipette as it nears a surface is dependent on the distance between the sample and the mouth of the pipette [211] (figure B 1.19.40). The probe height can then be used to maintain a constant current flow (of ions) into the micropipette, and the technique fiinctions as a non-contact imaging method. Alternatively, the height can be held constant and the measured ion current used to generate the image. This latter approach has, for example, been used to probe ion flows tlirough chaimels in membranes. The lateral resolution obtainable by this method depends on the diameter of the micropipette. Values of 200 nm have been reported. 

Selectivity of propylene oxide from propylene has been reported as high as 97% (222). Use of a gas cathode where oxygen is the gas, reduces required voltage and eliminates the formation of hydrogen (223). Addition of carbonate and bicarbonate salts to the electrolyte enhances ceU performance and product selectivity (224). Reference 225 shows that use of alternating current results in reduced current efficiencies, especiaHy as the frequency is increased. Electrochemical epoxidation of propylene is also accompHshed by using anolyte-containing silver—pyridine complexes (226) or thallium acetate complexes (227,228). 

Inverters make it possible to control a variable-speed fan by changing the frequency modulation. Standard alternating-current fan motors may be speed-regulated between 0 and 60 Hz. In using inverters for this apphcation, it is important to avoid frequencies that would result in fan critical speeds. 

Application The theoretical considerations that have been expounded should be used only for order-of-magnitude estimates, since a number of extraneous factors may enter into actual performance. In actual instaUations rectified alternating current is em-... 

An alternating-current electrode svstern referred to in the indiisti v as a wiper is often installed in the nonconductor product-collection section behind each drum. The function of the wiper is to use an ac corona to neutralize the charge on the nonconductor particles pinned... 

TABLE 29-1 Useful Formulas for Alternating-Current Motors... 

In single-phase bridge circuits for ac connections and for very low ac output voltages below 5 V, single-phase center tap circuits are used as rectifier circuits for CP transformer-rectifiers. They have an efficiency of 60 to 15% and a residual ripple of 48% with a frequency of 100 Hz. A three-phase bridge circuit for three-phase alternating current is more economical for outputs of about 2 kW. It has an efficiency of about 80 to 90% and a residual ripple of 4% with a frequency of 300 Hz. The residual ripple is not significant in the electrochemical effect of the protection current so that both circuits are equally valid. 

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