Reductions in overshoot following intense sound exposures

Overshoot refers to the poorer detectability of brief signals presented soon after the onset of a masking noise compared to those presented after longer delays. In the present experiment, brief tonal signals were presented 2 or 190 ms following the onset of a broadband masker that was 200 ms in duration. These two conditions of signal delay were tested before and after a series of exposures to a tone intense enough to induce temporary threshold shift (TTS). The magnitude of the overshoot was reduced after the exposure when a TTS of at least 10 dB was induced, but not when smaller amounts of TTS were induced. The reduction in overshoot was due to a decrease in the masked thresholds with the 2-ms delay; masked thresholds with the 190-ms delay were not different pre- and post-exposure. The implication is that the mechanisms responsible for the normal overshoot effect are temporarily inactivated by the same stimulus manipulations that produce a mild exposure-induced hearing loss. Thus the result is the paradox that exposure to intense sounds can produce a loss of signal detectability in certain stimulus conditions and a simultaneous improvement in detectability in other stimulus conditions.     

Influence of the counterion size on swelling and collapse of polyelectrolyte gel

A theory that predicts the effect of the counterion size on the swelling and collapse of a weakly charged polyelectrolyte gel was developed. In addition to excluded-volume interactions between monomer units of the gel, the theory involves the counterion-monomer unit and counterion-counterion interactions in terms of the virial approximation. The character of interactions between different units in the system varies from repulsion to attraction depending on the type of solvent, counterion, and dielectric permittivity of the solvent. For solvents with a low permittivity, the effect of condensation of counterions resulting in the formation of ion pairs is taken into account.     

Chemical analysis and distribution investigation of trace elements in indium matrix by spark source mass spectrometry

Summary High-purity indium was analysed by spark source mass spectrometry, using electrical and photoplate detection. For the calibration of the differences in elemental sensitivity, a standard sample was prepared in which 10 impurities were determined by graphite furnace atomic absorption spectrometry. In this way accuracies of less than 40% were obtained for relatively homogeneous elements at ppm and sub-ppm level. About 40 elements could be determined with detection limits of 10 to 30 ppb. Two pattern recognition methods, principal component analysis and clustering analysis, were applied to obtain information on trace element distribution, which indicated that a number of elements were strongly spatially correlated in the analysed sample.

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Chemische Analyse und Verteilungsbestimmung von Spurenelementen in Indium-Matrix durch Funkenquellen-Massenspektrometrie

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On leave from: Department of Chemistry, Nanjing Normal University, Nanjing, People's Republic of China     

Synthesis of New Plant Growth Regulators,Isomeric 1-(Dimethyloctyl)- and 1-Alkylpiperidinium and -morpholinium Halides by Telomerization of Isoprene with Secondary Amines

The known plant growth regulator, Al'den [1-(3,7-dimethyloctyl)-1-allylpiperidinium bromide], and also 1-(3,7-dimethyloctyl)-1-methylpiperidinium iodide were synthesized by treatment with allyl bromide and methyl iodide, respectively, of exhaustively hydrogenated 1-nerylpiperidine which was obtained by anionic telomerization of isoprene with piperidine. Various quaternary ammonium salts having a terpene sub- stituent with unnatural dimethyloctane skeleton, which effectively stimulate florification of Aster Chinensis L., were prepared by the action of alkyl halides on telomerization products derived from isoprene and piperidine or morpholine in the presence of palladium complexes.