A hydrogen-nitrogen gas coulometer

The hydrogen-oxygen gas coulometer yields a negative error at small current densities. A hydrogen-nitrogen gas coulometer, employing a hydrazine sulphate electrolyte, and free from this error, is described. A new form of the gas coulometer, employing the hydrazine sulphate electrolyte and suitable for the accurate integration of small quantities of electricity (5 to 20 coulombs) has been developed.     

EXTRARETINAL PHOTORECEPTION IN ENTRAINMENT OF CRUSTACEAN ORCADIAN RHYTHMS*

Abstract— An attempt was made to determine whether entrainment of the circadian rhythms of locomotor activity and ERG amplitude of the crayfish involved extraretinal photoreception. The results of a variety of experiments involving surgical lesions and localized illumination provided evidence that both rhythms can be entrained via an extraretinal pathway. The data also demonstrate that the caudal photoreceptor is unnecessary for entrainment. Our evidence to date suggests that the extraretinal photoreceptor is located in the supraesophageal ganglion; however, the possibility of photoreceptive input from other regions of the CNS, particularly the optic lobe, has not been eliminated. It is also tentatively concluded that the circadian oscillators for both the locomotor and the ERG amplitude rhythms are located within the supraesophageal ganglion, but more data are needed to confirm this conclusion.     

Photochemical reduction of uranyl ion in nitric acid medium using a XeCl excimer laser

This paper describes the results of photoreduction of uranyl (UO₂ ²⁺) ion to U⁴⁺ in 0.2M HNO₃ and ethanol using a 308 nm XeCl excimer laser. The effects of different concentrations of ethanol and the addition of sulfamic acid on the quantum yield for U⁴⁺ formation are discussed.     

Influence of Alkyl Chain Length and Structure on the Extraction of Copper(II) from Aqueous Acid by 5-Alkyl-2-hydroxybenzaldoximes in Hydrocarbon Solvents: Diffusion Coefficients of Extractants and Their Complexes

Measurement of the kinetics of extraction of copper(II) by 19 different 5-alkyl-2-hydroxybenzaldoximes (alkyl is C7H15 and C9H19) from acidic (hydrogen sulfate buffer) aqueous solution in the range pH 3.4-2.0, into 20% v/v toluene in n-hexane is reported. The lowering of the interfacial tension has been measured in some cases. The solubility of the extractants in water has been measured spectrophotometrically. A modified Taylor-Aris dispersion technique has been used to measure the diffusion coefficients in n-hexane and Orfom SX7 of some of the extractants and of the copper(II) complexes which they form. At low initial bulk concentrations (<10 mol m-3) of the extractants, the rate of extraction is controlled by the rate of diffusion of the extractant from the bulk to the organic-aqueous interface. The diffusion coefficient is related to the steric bulk of the alkyl substituent. At higher initial bulk concentrations (200 mol m-3) of the extractants, when the interface is saturated, the rate of extraction is inversely related to the apparent steric bulk of the alkyl substituent. Copyright 1999 Academic Press.     

Characterisation of organic matter in sediment from Corin Reservoir, Australia

Analytical pyrolysis was performed to characterise the organic matter present in sediments from Corin Reservoir, a major water supply for Canberra, Australia. Pyrolysis of the whole sediment yielded furans, methoxyphenols, aliphatic products and nitrogenous compounds that are indicative of carbohydrates, lignin, lipids and proteins respectively. There was a decrease in the observed relative peak area of polysaccharide and lignin-derived marker compounds with increasing depth of sediment and an increase in nitrogenous marker compounds. In addition, eucalyptol, a molecular marker compound characteristic of eucalyptus—the dominant vegetation of the surrounding catchment—was detected.     

General theory of vibrational mode mixing and frequency shifts in resonance raman scattering

A general formalism is given for treating vibrational mode mixing, frequency shifts, and atomic equilibrium position shifts under electronic excitation in resonance Raman scattering. The theory is exact for first-order scattering at T = 0 K for all linear and quadratic electron-phonon coupling strengths. Numerical results illustrating mode mixing are presented.     

Determination and survey of ochratoxin A in wheat, barley, and coffee--1997

Ochratoxin A (OA) is a nephrotoxic and nephrocarcinogenic mycotoxin produced by Aspergillus and Penicillium species. It has been found mainly in cereal grains and coffee beans. The purpose of this study was to investigate the occurrence of OA in cereal grains and in coffee imported to the United States. A modified liquid chromatographic (LC) method for determining OA in green coffee was applied to wheat, barley, green coffee, and roasted coffee. The test sample was extracted with methanol-1% NaHCO3 (7 + 3), and the extract was filtered. The filtrate was diluted with phosphate-buffered saline (PBS), filtered, and passed through an immunoaffinity column. After the column was washed with PBS and then with water, OA was eluted with methanol. The eluate was evaporated to dryness, and the residue was dissolved in acetonitrile-water (1 + 1). OA was separated on a reversed-phase C18 LC column with acetonitrile-water-acetic acid (55 + 45 + 1) as eluant and quantitated with a fluorescence detector. Recoveries of OA from the 4 commodities spiked over the range 1-4 ng/g were 71-96%. The limit of detection was about 0.03 ng/g. OA contamination at > 0.03 ng/g was found in 56 of 383 wheat samples, 11 of 103 barley samples, 9 of 19 green coffee samples, and 9 of 13 roasted coffee samples. None of the coffee samples contained OA at > 5 ng/g; only 4 samples of wheat and 1 sample of barley were contaminated above this level.     

GAMANAL-PC: A program for gamma-ray spectrum analysis using a microcomputer

The gamma-ray spectrum analysis program, GAMANAL, has been modifed to operate on a microcomputer. The program uses an algorithm involving a Gaussian and a tailing term for fitting and resolving peaks obtained from spectrometers using germanium semiconductor detectors. Gamma-ray energies, intensities and absolute photon emission rates can be determined. A graphical output showing the original and fitted data can also be obtained. The results generated by the program are stored on disk as ASCII files for futher analysis. This allows the use of other computer programs and languages in tasks such as decay curve analysis, radionuclide activity measurements and neutron activation analysis.     

The X-ray fluorescence determination of Cd, Ni, and Zn electrodeposited from aqueous solutions

The concentrations of cadmium, nickel, and zinc in standard solutions were determined by energy-dispersive X-ray fluorescence analysis of deposits prepared by flow electrolysis on graphite cloth electrodes. Reduction of the metal species in solution was complete only if cadmium or zinc was the major constituent (80 or 90 mole%, respectively). Deposits of cadmium and zinc, and cadmium-rich Cd---Ni, Cd---Zn, and Cd---Ni---Zn deposits were analysed. For pure metals the detected X-ray intensity displayed a power-law relationship, Rn^p, for up to 10⁻⁴ moles. The enhancement effect of the cadmium on the nickel and zinc signals, and the absorption and enhancement effects between nickel and zinc, were corrected empirically. The absorption of cadmium X-rays by nickel and zinc was insignificant. Deposits of pure copper on heavier electrodes displayed similar fluorescent intensities.