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  • Analytical Chemistry and Spectroscopy  (4)
  • Self organization  (2)
  • Collective Choice
  • C72
  • 1
    Electronic Resource
    Electronic Resource
    Morphological instabilities in pattern formation by precipitation and crystallization processes (1996)
    Springer
    Geologische Rundschau 85 (1996), S. 19-28 
    Details
    ISSN: 0016-7835
    Keywords: Key words Anastomoses ; Crystal zoning ; Snow bands ; Liesegang rings ; Ostwald ripening ; Self organization ; Siderite ; Supersaturation theory ; Zebra rock
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  Morphological instabilities in periodic patterns occurring both in precipitation and crystallization processes (Liesegang rings and crystal zoning) are investigated and compared with similar patterns in geological samples (zebra rocks and mud bands in snow sediments). In classical Liesegang systems, undisturbed parallel or concentric precipitation bands are emanated from even or concentric diffusion sources in homogeneous diffusion matrices of gelatine or other gels. In the case of superposing diffusion sources, sources with undulatory curvatures or local diffusion barriers there may occur several types of instabilities within the sequence of regular patterns: (a) gaps within the bands forming radial alleys free of precipitate, (b) transition from broken bands to speckled patterns and (c) apparent branching of bands linked together by so-called anastomoses. Calculations with a competitive particle growth (CPG) model show that lateral instabilities in Liesegang bands (gaps and radial alleys of gaps) are the result of Ostwald ripening effects taking place after precipitation. Apparent branching of bands or formation of anastomoses can be simulated with a prenucleation model according to Ostwald's supersaturation theory. Similar irregularities can be observed in zebra rocks (e.g. banded siderite) whose bandings are commonly explained by sequential sedimentation processes. A very different mechanism is assumed to be responsible for the origin of mud bands in snow sediments. An initially homogeneous distribution of intrinsic mud in snow sediments can be arranged into parallel bands according to a crystal zoning mechanism which is based on repeated thawing and freezing of the snow sediment due to the daily alternation of sun and darkness.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00192056
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  • 2
    Electronic Resource
    Electronic Resource
    Morphological instabilities in pattern formation by precipitation and crystallization processes (1996)
    Springer
    International journal of earth sciences 85 (1996), S. 19-28 
    Details
    ISSN: 1437-3262
    Keywords: Anastomoses ; Crystal zoning ; Snow bands ; Liesegang rings ; Ostwald ripening ; Self organization ; Siderite ; Supersaturation theory ; Zebra rock
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Morphological instabilities in periodic patterns occurring both in precipitation and crystallization processes (Liesegang rings and crystal zoning) are investigated and compared with similar patterns in geological samples (zebra rocks and mud bands in snow sediments). In classical Liesegang systems, undisturbed parallel or concentric precipitation bands are emanated from even or concentric diffusion sources in homogeneous diffusion matrices of gelatine or other gels. In the case of superposing diffusion sources, sources with undulatory curvatures or local diffusion barriers there may occur several types of instabilities within the sequence of regular patterns: (a) gaps within the bands forming radial alleys free of precipitate, (b) transition from broken bands to speckled patterns and (c) apparent branching of bands linked together by so-called anastomoses. Calculations with a competitive particle growth (CPG) model show that lateral instabilities in Liesegang bands (gaps and radial alleys of gaps) are the result of Ostwald ripening effects taking place after precipitation. Apparent branching of bands or formation of anastomoses can be simulated with a prenucleation model according to Ostwald's supersaturation theory. Similar irregularities can be observed in zebra rocks (e.g. banded siderite) whose bandings are commonly explained by sequential sedimentation processes. A very different mechanism is assumed to be responsible for the origin of mud bands in snow sediments. An initially homogeneous distribution of intrinsic mud in snow sediments can be arranged into parallel bands according to a crystal zoning mechanism which is based on repeated thawing and freezing of the snow sediment due to the daily alternation of sun and darkness.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00192056
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  • 3
    Electronic Resource
    Electronic Resource
    Selected ion monitoring determination of mono- and bifunctional amines by using phosphorus-containing derivativesPresented in parts at the 17th International Symposium on ‘Advances in Chromatography’, Las Vegas, Nevada, USA (1982). (1983)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 10 (1983), S. 175-182 
    Details
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Numerous monofunctional amines have been reacted with dimethylthiophosphinic chloride to form stable derivatives. Their good gas chromatographic properties and abundant molecular ions afforded highly sensitive and specific detection by selected ion monitoring (SIM) down to the picogram level. Based upon this derivatization procedure, new methods for the determination of aniline in serum and urine by SIM were developed. The minimum detectable concentration of aniline was 500 pg ml-1. Linear response curves were obtained from 1.5 to 150 ng ml-1 using (2H5)aniline as the internal standard. Specific derivatization of a series of bifunctional amines was achieved with methyldichlorophosphine and sulfur resulting in the formation of stable phospholidine-thiones. These derivatives chromatograph well on nonpolar stationary phases, and their mass spectra exhibit abundant molecular ions. This derivatization reaction was applied to the quantification of ephedrine from urine and serum by SIM with (2H2)ephedrine as the internal standard. The detection limit of the method was 1 ng ml-1. The linearity was established in the range from 10 to 160 ng ml-1.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200100312
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  • 4
    Electronic Resource
    Electronic Resource
    Mass spectrometry of dimethylthiophosphinates of aromatic hydroxy compounds (1978)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 5 (1978), S. 302-311 
    Details
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The mass spectra of 20 differently substituted dimethylthiophosphinic esters of aromatic hydroxy compounds are presented. Fragmentation routes were investigated using high resolution mass measurements, decoupled metastable determinations and deuterium labelling. All compounds exhibited abundant molecular ions and typical phosphorus-containing ions. Characteristic elimination processes strongly dependent upon the respective type of substitution were observed. Due to their high stability, their great ease of formation and their good gas chromatographic properties these new types of derivatives are of special interest for establishing gas chromatography mass spectrometry profiles of acidic catecholamine metabolites.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200050406
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  • 5
    Electronic Resource
    Electronic Resource
    Steroid phosphorus compounds. V - mass spectrometry of phosphinic esters of monohydroxy steroidsAbbreviations: E1 = estrone; A = androsterone; 3αEt = 3α-etiocholanolone; 3βEt = 3β-etiocholanolone; DHEA = dehydroepiandrosterone; DHT = 5α-dihydrotestosterone: T = testosterone: PO, PS and P = the dimethylphosphinic, dimethylthiophosphinic and dimethylphosphinous ester groups of the corresponding hydroxy steroid, respectively. (1976)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 3 (1976), S. 64-70 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The mass spectra of the dimethylphosphinic, dimethylthiophosphinic and dimethylphosphinous ester derivatives of several monohydroxy steroids are reported. The fragmentations of the derivatized steroids largely depend on the nature of the the phosphorus-containing ester group. Phenolic ester derivatives exhibit the base peak at the molecular ion, whereas the spectra of the secondary phosphinic esters are dominated by very intense protonated phosphinic acid ions [Me2 P(XH)(OH)]+ at m/e 95 (X = O) or at m/e 111 (X = S). The present results also indicate the low ionization potential for the phosphinic ester group. Due to their good gas chromatographic properties, these steroid derivatives appear to be particularly suitable for gas chromatographic mass spectrometric analysis of biochemical materials.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200030205
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  • 6
    Electronic Resource
    Electronic Resource
    Rapid and simple direct determination of porphyrins in urine by ion-pair reversed-phase high performance liquid chromatography (1980)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 3 (1980), S. 85-86 
    Details
    ISSN: 0935-6304
    Keywords: Liquid chromatography, HPLC ; Ion-pair reversed-phase ; Free porphyrin carboxylic acids in urine, complete separation ; Quantitation within 4.4-5.4% precision ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240030206
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