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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Il nuovo cimento della Società Italiana di Fisica 2 (1983), S. 1-14 
    ISSN: 0392-6737
    Keywords: Fluorescence, phosphorescence, radiationless transitions (intersystem crossing, internal conversion)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto È stata esaminata la possibilità di applicare la cosiddetta «approssimazione armonica locale» al calcolo delle funzioni generatrici usate nella teoria delle transizioni non radiative. La suddetta approssimazione tenta di «adattare» punto per punto la funzione generatrice alla curvatura del potenziale, variando in modo opportuno la frequenza dell’oscillatore. Nel caso semplice di due oscillatori di Morse identici separati da un dislivello costante di energia ΔE, la probabilità di transizione non radiativa è stata calcolata per un vasto intervallo di valori di ΔE. I risultati sono stati paragonati con quelli ottenuti eseguendo la somma sulle autofunzioni esatte degli stati legati dell’oscillatore di Morse. Si è riscontrato che la forma di linea è qualitativamente corretta, anche se l’approssimazione introduce dei picchi negativi spurii.
    Notes: Summary The possibility of applying the «local harmonic approximation» to the calculation of the generating functions used in the theory of radiationless transitions has been investigated. The approximation attempts to «adapt» point by point the generating function to the curvature of the potential, varying the oscillator frequency in a suitable manner. In the simple case of two identical Morse oscillators separated by a constant energy gap ΔE, the radiationless transition probability has been computed for a wide range of ΔE values. The results are compared with those obtained by summing over the exact bound states of a Morse oscillator. It is found that the line shape is qualitatively correct although some spurious negative contribution is introduced by the approximation.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1246
    Keywords: Toluene ; Xylene ; Styrene ; Hippuric acid ; m-Methylhippuric acid ; Phenylglyoxylic acid ; Mandelic acid ; Urinary metabolites
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A new high-pressure liquid chromatography (HPLC) method for simultaneous quantitative determination of the urinary metabolites of toluene, m-xylene, and styrene (hippuric acid, m-methylhippuric acid, phenylglyoxylic acid, mandelic acid) is described. The extraction procedure was performed on acidified urines, after addition of 4-hydroxybenzoic acid as internal standard, using a butylchloride/isopropanol mixture and drying 0.5 ml of the organic layer under nitrogen flow. The residue obtained was dissolved in 0.1 ml water/acetonitrile and 5 μl were injected into an HPLC apparatus equipped with a 0.26 × 25 cm HC ODS SIL X column. Absorbance measures were performed at 225 nm throughout the investigation. All metabolites were clearly separated in a short time (12 min) and the amounts of other urinary compounds affecting the analysis were so small that the measurement of low concentrations of the urinary metabolites could be easily performed. Linear calibration curves were obtained from 0.1 to 3 mg/ml and a correlation coefficient greater than 0.99 was found between concentrations of the standards and areas of the peaks. Statistical analysis confirms that this method, which has a high reproducibility, is simple, reliable, and useful for the biologic monitoring of industrial exposure to aromatic compounds.
    Type of Medium: Electronic Resource
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