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  • 1
    ISSN: 0887-6134
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A kinetic model for chemical events occurring within the high pressure electron capture mass spectrometer (HPECMS) ion source is developed which includes four different pathways by which unconventional negative ions can be produced. These routes to unusual ions include reactions of gas phase free radicals, surface-assisted reactions, ion-electron and ion-ion recombination reactions, and ion-wall neutralization. The model developed here provides a diagnostic tool useful for the elucidation of unusual HPEC spectra. Such spectra for two environmentally important classes of compounds are explained by use of the model. These compound classes include the trifluoroacetic derivatives of polycyclic aromatic amines, which have been shown to be present in materials derived from liquified coal, and the derivatives of hexachlorocyclopentadiene, which are used as pesticides. It is shown in this study that several processes, in addition to electron capture, can be operative in the typical HPECMS ion source, and that these processes can be used advantageously for the generation of informative and sensitive mass spectral signals.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 28 (1982), S. 988-993 
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: A linear form of the mass balance equation is used to determine how turbulent transport of mass to a solid wall is related to the fluctuating velocity field. It is found that at high Schmidt numbers the Reynolds transport is controlled by fluctuations of much lower frequency than the most energetic velocity fluctuations. The characteristic of the velocity field that emerges as being most important is the small frequency limiting value of the spectral function of the velocity fluctuations normal to the wall. However, the linear theory that is explored does not predict the correct dependency of the average and the mean-squared deviation of the mass transfer coefficient on Schmidt number. A nonlinear analysis must be performed to examine fully the mechanism of turbulent mass transfer to a solid surface.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 29 (1983), S. 215-221 
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The relation between the velocity and concentration fields for a fully developed turbulent flow which transfers mass to a pipe wall at large Schmidt numbers has been studied. Measurements of the fluctuations of the concentration gradient and the velocity gradient were obtained simultaneously at multiple locations on the wall. Spatial scales were calculated for the low frequency velocity fluctuations by passing the measured signals through low-pass filters. These scales are the same size as the scales of the concentration fluctuations. This result provides additional support for the notion that mass transfer to a boundary at high Schmidt numbers in controlled by low frequency velocity fluctuations which contain only a small fraction of the total turbulent energy.
    Zusätzliches Material: 13 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 29 (1983), S. 221-229 
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Mass transfer between a turbulent fluid and a solid boundary is considered for the case of large Schmidt numbers. The variation of the mass transfer coefficient with time, K(t), is calculated by solving the mass balance equation using a random velocity input. An interpretation of the mass transfer process which is radically different from that given by classical approaches is obtained.
    Zusätzliches Material: 13 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 19 (1990), S. 520-522 
    ISSN: 1052-9306
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Since the methylation of acids with diazomethane is widely used in trace analysis, it is extremely important for those using this technique to be alert to the analysis of compounds containing other functional groups which might become methylated with high concentrations of diazomethane. We have shown that by adding an excess of diazomethane to dansylated amino acids, not only is the methyl ester formed, but the products can be further methylated. The only remaining acidic hydrogen in the molecule is the hydrogen attached to the sulfonamide nitrogen, and the mass spectrometry results indicate that the methyl ester is formed first, and the N-methylated derivative is formed with excess diazomethane.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 19 (1990), S. 613-618 
    ISSN: 1052-9306
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Several aminophenanthrenes have been examined with electron impact mass spectrometry. The trifluoroacetic anhydride (TFAA) and perfluoropropionic anhydride (PFPA) derivatives of 4-aminophenanthrene have been studied with electron impact as well as both positive and negative ion chemical ionization mass spectrometry utilizing methane as a reagent gas. The resulting mass spectra indicate a loss of water from the derivatives and a mechanism is proposed to account for this loss. The spectra also indicate unique fragmentation patterns associated with the position of the substituent, particularly the four position which is in the region of the molecule termed the bay region. Another interesting aspect is the spectral differences observed for the TFAA and PFPA derivatives of 4-aminophenanthrene. The positive ion chemical ionization mass spectrum of the TFAA derivative indicates an ion [M + H — H2O]+; however, the mass spectrum of the PFPA derivative of 4-aminophenanthrene indicates no water loss from the [M + H]+ ion. The negative ion chemical ionization mass spectra of the two derivatives are also very different. The mass spectrum of the TFAA derivative shows an [M — 18]- ion and the PFPA derivative shows successive losses of HF with no apparent loss of water.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 7
    Digitale Medien
    Digitale Medien
    Chichester [u.a.] : Wiley-Blackwell
    Journal of Raman Spectroscopy 19 (1988), S. 379-382 
    ISSN: 0377-0486
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Raman spectra of single crystals of the layered compounds SbI3 and AsI3 at 15K are reported. Polarization measurements allow the eight principal peaks to be classified according to symmetry species. Results of a group theoretical analysis based on both molecular and ionic descriptions of the crystal structure are discussed, and assignments of the observed spectra are proposed. Some ramifications of the more ionic nature of SbI3 on its spectrum are briefly described.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 8
    Publikationsdatum: 1943-07-01
    Print ISSN: 0021-9606
    Digitale ISSN: 1089-7690
    Thema: Chemie und Pharmazie , Physik
    Standort Signatur Erwartet Verfügbarkeit
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  • 9
    Publikationsdatum: 1943-07-01
    Print ISSN: 0021-9606
    Digitale ISSN: 1089-7690
    Thema: Chemie und Pharmazie , Physik
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 10
    Publikationsdatum: 1971-04-15
    Print ISSN: 0021-9606
    Digitale ISSN: 1089-7690
    Thema: Chemie und Pharmazie , Physik
    Standort Signatur Erwartet Verfügbarkeit
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