A new, simple, and reproducible method is described for the determination of selenium(IV) based on differential pulse cathodic stripping voltammetry. The optimized experimental conditions are as follows:  selenium(IV) ions in an acidic medium (0.06 M HCl-0.07 M HNO(3)) are electrodeposited on a rotating silver disk electrode as silver selenide at -0.4 V vs SCE for 30 min; the deposit is then cathodically stripped in another solution (2 M NaOH) at a scan rate of 50 mV s(-1) to -1.2 V vs SCE. The cathodic stripping results in only a single well-defined peak at about -0.95 V vs SCE. The calibration (peak height vs selenium concentration) graph is linear up to at least 40 ng mL(-1) of selenium(IV) and passes through the origin, with a relative standard deviation of 2.7% for 20 ng mL(-1) (n = 5). The detection limit (3σ) is 0.20 ng mL(-1). The possible interferences have been evaluated. Dissolved oxygen does not affect the peak height of selenium. The electrode can be used repeatedly at least 20 times with excellent reproducibility without further polishing. The proposed method is an improvement over the existing cathodic stripping techniques.

Twenty-four micro-solar cells connected in series have been fabricated on semi-insulating (SI) GaAs substrates for application in the fields of micro-electromechanical systems. The array was formed in an area of 0.8 × 1.0 mm 2 , and exhibited an open-circuit voltage of 22.5 V under illumination of 5 mW at the wavelength of 815 nm. Calculation and experiment has demonstrated that, unlike conventional solar cells, the shunt resistance deteriorates the output characteristics far more seriously than the series resistance in the case of micro-solar cells. Leakage currents in both the unit diode and the substrate were evaluated separately. A quantitative estimate based on the measurements revealed that photocurrents generated in the surface of the SI substrate could function as a vital shunt resistance. Light-blocking metal films were successfully employed to obtain high output voltage.

Donepezil may be a useful medicine for some patients with Down syndrome with severe cognitive impairment or mental retardation if the adverse effects are manageable.

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The precipitation titration of sodium chloride with electrogenerated silver ion was studied. The production of a precipitate of silver chloride had a significant effect on the titration results because the precipitate involved unreacted chloride or unreacted silver ion. The accuracy of the method was investigated by changing the introduction time of a sodium chloride solution to the coulometric cell during the process of electrolysis, and examining the dependency on the sample size. The accuracy of the measurement of the precipitation titration is discussed.