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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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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim [u.a.] : Wiley-Blackwell
    Materials and Corrosion/Werkstoffe und Korrosion 33 (1982), S. 416-420 
    ISSN: 0947-5117
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Untersuchung der auf Blei in Meerwasser und in neutralen Salzlösungen entstehenden Korrosionsprodukte.Zur Identifizierung und quantitativen Bestimmung der in Meerwasser und neutralen Salzlösungen auf Blei entstehenden Korrosionsprodukte wurde eine Methode entwickelt. Sie beruht auf der selektiven Auflösung verschiedener Verbindungen in geeigneten Reagenzien (Methanol, Glycin, Kaliumnitrat u. a.) und der anschließenden chemischen Analyse der in Lösung befindlichen Elemente. Die Ergebnisse werden dann mittels Röntgenbeugung verifiziert.Diese Methode wurde benutzt zur Untersuchung der Korrosionsprodukte auf einer Bleiplatte von einem vor etwa 2000 Jahren im Golf von Toulon gesunkenen römischen Schiff.Dabei wurden die folgenden Punkte gefunden: \documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm PbCl}_{{\rm 2}^{\rm - } } {\rm Pb}_2 {\rm Cl}_3 {\rm OH} - 3{\rm PbCO}_3 \cdot 2{\rm Pb(OH)}_2 \cdot {\rm H}_2 {\rm O} - {\rm Pb}_2 {\rm O}_{3^ - \,} \,{\rm Pb}_4 {\rm O}_3 {\rm SO}_4 \cdot {\rm n}\,{\rm H}_2 {\rm O} - {\rm Pb}_{\rm x} {\rm S}_{{\rm y}\,} {\rm or}\,{\rm PbS}. $$\end{document}Bei Vergleichsversuchen mit Blei in Meerwasser wurden die folgenden Verbindungen festgestellt: \documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm PbCl}_{2^ - } {\rm PbCO}_3 \cdot {\rm PbCl}_{2^ - } {\rm Pb}_3 ({\rm CO}_3)_2 ({\rm OH})_{2^ - } {\rm PbO} - {\rm Pb}_{\rm 2} {\rm O}_3 . $$\end{document}Der Unterschied zwischen beiden Ergebnissen dürfte darauf zurückzuführen sei, daß in Meeresablagerungen durch sulfatreduzierende Bakterien Schwefelwasserstoff entsteht, der den pH-Wert verändert und damit das Gleichgewicht des Systems CO3---HCO3--CO2-SO4--HSO4- verschiebt, wodurch wieder die Art der Korrosionsprodukte verändert wird.Blei ist trotz seiner guten Korrosionsbeständigkeit in verschiedenen Medien wegen seiner schlechten mechanischen Eigenschaften in seiner praktischen Anwendung begrenzt und wird deshalb nur für Rohrleitungen, Bedeckungen u. ä. benutzt. Das gilt auch für die Antike: die Römer plattierten die Schiffsrumpfe mit Blei, da hierdurch lange Lebensdauer gesichert war.
    Notes: A method was developed to characterize and quality lead corrosion products in sea water and in saline neutral solutions.This method is based on selective dissolution of various compounds, using suitable reagents (methanol, glycine, potassium nitrate etc.) and on subsequent chemical analysis of the various dissolved elements.The findings are then verified by X-ray diffractometer analysis.This method was used for an examination of the corrosion products adhering to a lead plate of a Roman ship wrecked in the Gulf of Toulon about two thousand years ago. The following corrosion products were determined: \documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm PbCl}_{{\rm 2}^{\rm - } } {\rm Pb}_2 {\rm Cl}_3 {\rm OH} - 3{\rm PbCO}_3 \cdot 2{\rm Pb(OH)}_2 \cdot {\rm H}_2 {\rm O} - {\rm Pb}_2 {\rm O}_{3^ - \,} \,{\rm Pb}_4 {\rm O}_3 {\rm SO}_4 \cdot {\rm n}\,{\rm H}_2 {\rm O} - {\rm Pb}_{\rm x} {\rm S}_{{\rm y}\,} {\rm or}\,{\rm PbS}. $$\end{document}These products were compared with those obtained on sea water immersed lead specimen.In the latter case, the products were the following: \documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm PbCl}_{2^ - } {\rm PbCO}_3 \cdot {\rm PbCl}_{2^ - } {\rm Pb}_3 ({\rm CO}_3)_2 ({\rm OH})_{2^ - } {\rm PbO} - {\rm Pb}_{\rm 2} {\rm O}_3 . $$\end{document}The difference between the two test specimen is deemed to be due to the known formation caused by bacterial fouling processes (desulfovibrio desulfuricans) of hydrogen sulphide in marine sediments which, by altering the pH value, also alter the equilibrium of the CO3---HCO3--CO2-SO4--—HSO4- systems thus affecting the differentiated formation of the corrosion products.Lead, despite its improved corrosion resistance in various environments as compared with other normally used metals (e.g. iron), is not so commonly employed because of its poor mechanical properties (deformation, grain coarsening, brittleness [1], etc.) so that it is only used for certain structures like pipings or coverings (roofs, chemical vats etc.) not exposed to strong mechanical stresses.These applications were common even in ancient times, when the Romans already covered their hulls with lead plates because they did not corrode easily and thus had a long life.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim [u.a.] : Wiley-Blackwell
    Materials and Corrosion/Werkstoffe und Korrosion 34 (1983), S. 78-83 
    ISSN: 0947-5117
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Bestimmung der Korrosionsprodukte auf Eisen in reinem und in mit Sulfiden verunreinigtem MeerwasserZum Nachweis und zur quantitativen Bestimmung der Korrosionsprodukte von Eisen in reinem und in mit Schwefelwasserstoff verunreinigtem Meerwasser wurde eine Methode entwickelt. Diese beruht auf der selektiven Auflösung der verschiedenen Verbindungen mit geeigneten Reagenzien (Methanol, Glycin, Brom-Methanol, Salzsäure usw.); anschließend werden die verschiedenen gelösten Elemente bestimmt. Die so erhaltenen Informationen werden mit Hilfe einer Röntgenbeugungsanalyse integriert. Die folgenden Korrosionsprodukte wurden gefunden:Fe(OH)2 = Fe3O4FeO(OH)/Fe2O3 + einer nicht identifizierten Verbindung (wahrscheinlich Oxychlorid) in Meerwasser bei pH 8,1 und 7 ppm SauerstoffFeOC1/Fe(OH)2/Fe3O4/FeOOH in teilweise entlüftetem Meerwasser (3 ppm Sauerstoff bei pH 8,1)Fe0.95S/Fe(OH)2 in Meerwasser bei pH 7 und 10 ppm Sulfid.Fe0.95S/FeS/Fe3.6 · Fe0.9 (O · OH · CI) und FeOCI/Fe3O4/FeO(OH)/Fe2O3 · H2O in Meerwasser bei pH 7 und anfänglich 10 ppm oxidierbaren Sulfids.Da die hier entwickelte chemische Analysenmethode quantitative Informationen über die Verteilung des Eisens auf die verschiedenen Anionen und die verschiedenen Oxidationsstufen liefert, ist sie als ein nützliches Hilfsmittel zur Untersuchung von Korrosionskinetik und -mechanismus anzusehen.
    Notes: A method was developed to characterize and quantify iron corrosion products in clean and sulphide polluted sea water. This method is based upon a selective dissolution with suitable reagents (methanol, glycine, bromine-methanol, hydrochloric acid etc.) of the various compounds and the subsequent chemical analysis of the various dissolved elements. The information thus obtained is integrated by a diffractometric X-ray analysis.The following corrosion products were found:Fe(OH)2 = Fe3O4 - FeO(OH) - Fe2O3 + unidentified compound Cr (probably oxychloride) in sea water with pH = 8.1 having a 7 ppm D.O. content.FeOC1 - Fe(OH)2 - Fe3O4 - FeO.OH in partially deoxygenated sea water (D.O. = 3 ppm) at pH 8.1;Fe0.95S - Fe(OH)2 in sea water at pH = 7 with 10 ppm of sulphides;Fe0.95S - FeS - Fe3.6 · Fe0.9(O · OH · C1) and FeOC1 - iron oxisulphide - Fe3O4 - FeO(OH) - Fe2O3 · H2O in sea water at pH = 7 and 10 ppm initial sulphides left to oxidate.Since the method of chemical analysis thus developed supplies quantitative information in iron distribution among the various anions and on the various oxidation forms, it is deemed a useful tool for investigation of the corrosion kinetics and mechanism.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim [u.a.] : Wiley-Blackwell
    Materials and Corrosion/Werkstoffe und Korrosion 34 (1983), S. 236-240 
    ISSN: 0947-5117
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Untersuchung der Korrosionsprodukte von Aluminum in Meeresatmosphäre oder industriell-maritimer AtmosphäreZur Analyse der auf Aluminium in verschmutzter oder nicht verschmutzter Meeresatmosphäre entstandenen Passivierungsschichten wird eine Methode entwickelt. Diese beruht auf der selektiven Auflösung der verschiedenen Verbindungen mit geeigneten Reagenzien (Wasser, Salpetersäure, Salpetersäure/Flußsäure) und der anschließenden Bestimmung der in Lösung gegangenen Stoffe. Die so erhaltenen. Informationen werden mittels Röntgenbeugungsanalyse integriert. In Meeresatmosphäre wurden Al2O3 · 3 H2O, Aluminiumoxychlorid und Aluminiumhydroxid gefunden (die beiden letzten wurden bei der Röntgenanalyse nicht wieder identifiziert). Die in der verschmutzten Atmosphäre gefundenen Korrosionsprodukte waren AlF3; Al2(SO4)3 · H2SO4; Al11(OH)30Cl3; AlF1.96(OH)1.4; 16Al(OH,F)3 · 6H2O; AlF1.65(OH)1.35 · H2O.Da die neue Methode quantitative Informationen zur Verteilung des Aluminiums auf die verschiedenen Anionen enthält, dürfte sie bei der Untersuchung der Korrosionskinetik und der Korrosionsmechanismen von Nutzen sein.
    Notes: A method has been developed to characterize the passivation film formed on aluminum in marine atmosphere, whether polluted or not by sulphur oxides and fluoridesThe information thus obtained was integrated by X-ray diffractometric analyses.The following corrosion products were found in the marine atmosphere:Al2O3· 3H2O + Al (oxychoride) + Al (hydroxide)(The latter two compounds had not been revealed by X-ray analysis).The corrosion products found in the polluted atmosphere were:AlF3; Al2(SO4)3 · H2SO4; Al11(OH)30Cl3; AlF1.96(OH)1.4; 16Al(OH,F)3 · 6H2O; AlF1.65(OH)1.35 · H2O.Since the developed method provides useful quantitative information on the aluminum distribution between the various anions, it is deemed to be a useful tool to study the corrosion kineties and mechanism.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 4 (1983), S. 260-266 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Molecular orbital computations on the sign and magnitude of the Cotton effect of (-)-α-phellandrene (a conjugated diene) and the separate twisted butadiene chromophore were performed using configuration interaction (CI) and the random phase approximation (RPA) methods with a standard minimal basis set of STO/3G orbitals. The relative contributions to the rotatory strength of (-)-α-phellandrene which arise from a twist in the diene unit, the allylic axial bond, and nonplanarity of either one or both of the C=C double bonds were determined by examining various molecular geometries. This theoretical study confirms that the allylic axial substituent/bond provides the largest contribution to the longwavelength Cotton effect. It is found that the rotatory strength arising from distortion of the planar geometry of the double bonds tends to cancel the rotatory strength arising from the sense of twist of the diene unit. The computed energies suggest that molecular geometries where the trisubstituted bond is kept planar, and where twisting is allowed about the cis double bond, may be favored over geometries where torsion is allowed about both double bonds.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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