The effect of linguistic entropy on speech perception in noise in young and elderly listeners.

The rationale for a method to quantify the information content of linguistic stimuli, i.e., the linguistic entropy, is developed. The method is an adapted version of the letter-guessing procedure originally devised by Shannon [Bell Syst. Tech. J. 30, 50-64 (1951)]. It is applied to sentences included in a widely used test to measure speech-reception thresholds and originally selected to be approximately equally redundant. Results of a first experiment reveal that this method enables one to detect subtle differences between sentences and sentence lists with respect to linguistic entropy. Results of a second experiment show that (1) in young listeners and with the sentences employed, manipulating linguistic entropy can result in an effect on SRT of approximately 4 dB in terms of signal-to-noise ratio; (2) the range of this effect is approximately the same in elderly listeners.     

FT-EPR and HPLC study of the mechanism of 4-chlorophenol photolysis

The mechanism of 4-chlorophenol (4CP) photolysis was investigated with the aid of Fourier Transform Electron Paramagnetic Resonance (FT-EPR) and pulsed-laser photolysis combined with High Performance Liquid Chromatography (HPLC) detection-of stable (diamagnetic) products. With FT-EPR transient free radicals produced by pulsed-laser excitation of solutions of 4CP in alcohols could be identified. Time profiles of the FT-EPR spectra provided information on reaction kinetics and Chemically Induced Dynamic, Electron Polarization (CIDEP) effects. It was found that 4CP photolysis in alcohols leads to the simultaneous formation of the phenoxyl radical and radicals produced by hydrogen abstraction from the solvent. CIDEP patterns establish that these radicals are formed in a reaction sequence involving a triplet state precursor and radical pair intermediate. Results of earlier transient optical absorption measurements indicate that the triplet precursor must be the carbene 4-oxocyclohexa-2,5-dienylidene. This assignment is supported by the finding that photolysis of quinone diazide in a hydrogen-donating solvent gives the same free radical products as those obtained from 4CP. The formation of the phenoxyl radical intermediate accounts for the finding that photolysis of deoxygenated solutions of 4CP in alcohols gives phenol as stable diamagnetic product. By contrast, photolysis of aerated and deoxygenated aqueous solutions of 4CP produces benzoquinone and hydroquinone as primary products, respectively.     

Trace pollutants analysis in soil by a time-resolved laser-induced breakdown spectroscopy technique

The results of a joint experiment of IFAM-Pisa and ENEA-Frascati for the detection of traces of pollutants in soil by a time-resolved laser-induced spectroscopy technique are reported. Using samples of soil with known pollutants' concentration [Geochemical Exploration Reference (GXR) silicate from US Geological Survey], we were able to estimate the sensitivity of this Laser-Induced Breakdown Spectroscopy (LIBS) technique to be of the order of some parts per million for a vast class of metallic pollutants, including extremely dangerous soil pollutants such as copper, lead and chromium.ENEA guest with HC&M fellowship     

Mössbauer spectroscopic study of core and mantle of rattle stones

Mössbauer spectroscopy has been applied to two rattle stones found in the Netherlands, which have been formed under different pedoenvironment conditions in the past. Ultrafine particles of goethite are dominantly present in both core and mantle of these stones. The latter differs in both composition and mean particle size; this is related to the distinct manner of their formation.