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  • Analytical Chemistry and Spectroscopy  (3)
  • 65N35  (2)
Materialart
Erscheinungszeitraum
Schlagwörter
  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Advances in computational mathematics 1 (1993), S. 259-335 
    ISSN: 1572-9044
    Schlagwort(e): Periodic pseudodifferential equations ; pre-wavelets ; biorthogonal wavelets ; generalized Petrov-Galerkin schemes ; wavelet representation ; atomic decomposition ; Calderón-Zygmund operators ; matrix compression ; error analysis ; 65F35 ; 65J10 ; 65N30 ; 65N35 ; 65R20 ; 47A20 ; 47G30 ; 45P05 ; 41A25
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Abstract This is the second part of two papers which are concerned with generalized Petrov-Galerkin schemes for elliptic periodic pseudodifferential equations in ℝ n . This setting covers classical Galerkin methods, collocation, and quasi-interpolation. The numerical methods are based on a general framework of multiresolution analysis, i.e. of sequences of nested spaces which are generated by refinable functions. In this part, we analyse compression techniques for the resulting stiffness matrices relative to wavelet-type bases. We will show that, although these stiffness matrices are generally not sparse, the order of the overall computational work which is needed to realize a certain accuracy is of the formO(N(logN) b ), whereN is the number of unknowns andb ≥ 0 is some real number.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Integral equations and operator theory 15 (1992), S. 626-672 
    ISSN: 1420-8989
    Schlagwort(e): Primary, 65R20 ; Secondary, 35S05 ; 45E05 ; 45L10 ; 47G30 ; 65J10 ; 65N30 ; 65N35
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Abstract We investigate several numerical methods for solving the pseudodifferential equationAu=f on the n-dimensional torusT n . We examine collocation methods as well as Galerkin-Petrov methods using various periodical spline functions. The considered spline spaces are subordinated to a uniform rectangular or triangular grid. For given approximation method and invertible pseudodifferential operatorA we compute a numerical symbolα C , resp.α G , depending onA and on the approximation method. It turns out that the stability of the numerical method is equivalent to the ellipticity of the corresponding numerical symbol. The case of variable symbols is tackled by a local principle. Optimal error estimates are established.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    ISSN: 0935-6304
    Schlagwort(e): Solvents and GC detectors ; Coupled HPLC-GC ; Column effluent splitter ; Di-(2-ethylhexyl) phthalate ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Introduction of solutions of up to several milliliters by on-column injection of large volumes or by coupled HPLC-GC may cause problems with GC detectors (FID, AFID, MS). For instance, dichloromethane forms large amounts of hydrochloric acid and carbon black in FIDs.A column effluent splitter was developed for keeping the major portion of the solvent vapors away from the detector; approximately 99% of the vapor is vented while the remaining 1% of vapor is used for detecting the widths of the solvent peaks. During analysis, the split ratio is reversed by a strong increase of the resistance to the gas flow through the split exit line.The system was used for the determination of di-(2-ethylhexyl)-phthalate (DEHP) in triglyceride matrices of various foods. Direct determination by HPLC is not sufficiently sensitive, whereas direct analysis by GC is hindered by the triglycerides. Solutions of fats or oils were pre-separated on a silica column using dichloro-methanelcyclohexane 1:l with addition of 0.05 % acetonitrile as eluent. The HPLC fraction containing the DEHP was transferred to GC through a loop-type interface using concurrent solvent evaporation. Detection limits were around 0.1 ppm.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 4
    ISSN: 1052-9306
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A specific assay is described for the confirmatory identification of danofloxacin residues in edible tissues of cattle and chicken. The assay utilizes on-line microbore high-performance liquid chromatography and pneumatically assisted electrospray tandem mass spectrometry (MS/MS). Collision-induced dissociation of the danofloxacin protonated molecule results in two significant daughter ions. Monitoring both ions provides the specificity required for this confirmatory assay. Optimum electrospray and MS/MS operating conditions permitted the specific monitoring of danofloxacin and the confirmation of its residues in chicken and cattle liver extracts down to 50 ppb. The analysis of control liver or the commercially available antibacterial quinolones enrofloxacin and its metabolite ciprofloxacin gave no response under the assay conditions. The ratios of the two daughter ions were similar for danofloxacin standard solutions, fortified tissues and incurred tissues.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 4 (1990), S. 24-29 
    ISSN: 0951-4198
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Notizen: A simple method for off-line coupling of desorption mass spectrometry and capillary-zone electrophoresis (CZE) is described. Use of a “porous glass joint”, near the cathodic end of the CZE column, facilitates fraction collection in a manner similar to that used with liquid chromatography. This method allows independent optimization of both the CZE and mass spectrometry parts of the experiment. It is directly applicable to a number of desorption mass spectrometry methods (including plasma desorption (PD) and UV laser desorption (LD)). In the present study, PD mass spectrometry was used for eluant characterization. The fraction collection procedure is described, as is mass transfer through the porous glass joint. Detection limits are discussed and the approach is illustrated by analysis of a simple mixture of bradykinin derivatives. Finally, a brief comparison to current on-line CZE/mass spectrometric methods is presented.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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