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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Geologische Rundschau 85 (1996), S. 19-28 
    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.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Geologische Rundschau 85 (1996), S. 29-37 
    ISSN: 0016-7835
    Keywords: Key words Banded mineralization ; Harz mountains ; Self-organization ; Iron ; manganese ; ferrihydrite ; birnessite ; Time-series analysis ; Aquatic systems ; Iron bacteria ; Ostwald ripening
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  A recent early diagenetic banded iron–manganese mud has been forming underground in a closed lead–zinc mine for approximately 40 years. The processes leading to the banded structure of the precipitate were studied during a period of 2 years. Therefore, 19 physical and chemical parameters were measured regularly in short intervals. The resulting time series were analysed with respect to the data sets of the monthly chemical analyses of the descendent mine water, the daily rainfall and the mineral content. The results reveal that the precipitated material undergoes internal self-organization due to interaction of redox, colloid-chemical, microbial, electrical and ripening processes, and not exclusively produced by seasonal fluctuations of material input. Thus, the primary banding of the material, caused by externally forced fluctuations of the redox conditions within the mine water, is reorganized after a short time. The finally observed bands are controlled by non-linear coupling of reaction and transport processes within the mud. A genetic model for the banded mineralization was developed and verified by numerical simulation.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    International journal of earth sciences 85 (1996), S. 19-28 
    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.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    International journal of earth sciences 85 (1996), S. 29-37 
    ISSN: 1437-3262
    Keywords: Banded mineralization ; Harz mountains ; Self-organization ; Iron, manganese, ferrihydrite, birnessite ; Time-series analysis ; Aquatic systems ; Iron bacteria ; Ostwald ripening
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract A recent early diagenetic banded iron-manganese mud has been forming underground in a closed lead-zinc mine for approximately 40 years. The processes leading to the banded structure of the precipitate were studied during a period of 2 years. Therefore, 19 physical and chemical parameters were measured regularly in short intervals. The resulting time series were analysed with respect to the data sets of the monthly chemical analyses of the descendent mine water, the daily rainfall and the mineral content. The results reveal that the precipitated material undergoes internal self-organization due to interaction of redox, colloid-chemical, microbial, electrical and ripening processes, and not exclusively produced by seasonal fluctuations of material input. Thus, the primary banding of the material, caused by externally forced fluctuations of the redox conditions within the mine water, is reorganized after a short time. The finally observed bands are controlled by non-linear coupling of reaction and transport processes within the mud. A genetic model for the banded mineralization was developed and verified by numerical simulation.
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  • 5
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 33 (1987), S. 1698-1706 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Particulate expansion and minimum bubbling parameters (n, u′t, umB, εmB) are measured for fine carbon powders (dp = 44 and 112 μm) fluidized with synthesis gas (H2/CO = 0.8) at pressures within the range 2,070 〈 P 〈 12,420 kPa in an industrial, pilot-scale fluidized bed. Deviations between minimum bubbling (umB and εmB) and minimum fluidization (umf and εmf) conditions increase with increasing pressure, P. The expansion index, n, decreases with increasing P and always exceeds values recommended by Richardson and Zaki for solid/liquid systems. Particulate bed expansion for the fine powders is well characterized by the equations of Foscolo et al. and Abrahamsen and Geldart. The theory of Foscolo and Gibilaro adequately estimates the onset of bubbling for both powders at all P, provided that experimentally determined values of n and u′t, are applied. For the dp = 112 μm powder, the theory of Foscolo and Gibilaro is applicable with calculated values of ut and experimental values of n.
    Additional Material: 10 Ill.
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  • 6
    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.
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  • 7
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 5 (1978), S. 302-311 
    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.
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 425 (1976), S. 151-154 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Contributions to the Chemistry of Transition Metal Alkyl Compounds. XX. On the Reaction of NiCl2 · 2 PR3 and CoCl2 · 2 PR3 with LiSn(CH2C6H5)3LiSn(CH2C6H5)3 reacts with NiCl2 · 2 P(n-C4H9)3 in tetrahydrofuran forming benzyl nickel chloride, which could be isolated in form of the bipyridyl complex C6H5CH2-NiCl · dipy. NiCl2 · 2 P(C6H5)3 and CoCl2 · 2 P(C6H5)3 are reduced to complexes of the formula MCl · 2 P(C6H5)3 · 3 THF (M = Ni, Co).
    Notes: LiSn(CH2C6H5)3 reagiert mit NiCl2 · 2 P(n-C4H9)3 in Tetrahydrofuran zu Benzylnickelchlorid, das als Dipyridylkomplex isoliert werden konnte. Bei Einsatz von NiCl2 · 2 P(C6H5)3 und CoCl2 · 2 P(C6H5)3 erfolgt dagegen eine Reduktion zu Komplexen der Zusammensetzung MCl · 2 P(C6H5)3 · 3 THF (M = Ni, Co).
    Additional Material: 1 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 455 (1979), S. 3-12 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Contributions to the Chemistry of Transition Metal Alkyl Compounds. XXIX. Dibenzyl Manganese - Preparation and ReactionsManganese(II) acetylacetonate reacts with tribenzyl aluminium and dibenzyl magnesium forming the yellow complexes 3(C6H5CH2)2Mn · Al(acac)3 and (C6H5CH2)2Mn · Mg(acac)2 Dibenzyl manganese is also formed at the reaction of dibenzyl magnesium or benzyl magnesium chloride with MnCl2 · 1.5 THF and was separated as the dioxan complex (C6H5CH2)2Mn · 2C4H8O2, the ligands of which can be removed to a great extent in vacuum.Dibenzyl manganese reacts with CO2, CS2 and SO2 with insertion into the Mn-C-bonds. The corresponding manganese compounds were isolated and furtherly characterized.
    Notes: Mangan(II)-acetylacetonat reagiert mit Tribenzylaluminium bzw. Dibenzylmagnesium zu den gelben Komplexen 3(C6H5CH2)2Mn · Al(acac)3 bzw. (C6H5CH2)2Mn Mg(acac)2. Dibenzylmangan entsteht auch bei Einwirkung von Dibenzylmagnesium oder Benzyl magnesiumchlorid auf MnCl2 · 1,5 THF; eine Abtrennung von den Magnesiumsalzen gelingt in Form des 1,4-Dioxankomplexes (C6H5CH2)2Mn · 2C4H8O2, dessen Ligandenmoleküle im Vakuum weit gehend entfernt werden können.Dibenzylmangan reagiert mit CO2, CS2 und SO2 unter Insertion in die Mn-C-Bindungen. Die entsprechenden Mangansalze wurden isoliert und näher charakterisiert.
    Additional Material: 3 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 508 (1984), S. 50-54 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Contributions to the Chemistry of Transition Metal Alkyl Compounds. XXXVII. About the Existence of 1-Norbornyl Compounds of Tungsten and MolybdenumReactions of WCl6, WCl4, WO2Cl2, WOCl4, MoCl5, and MoO2(acac)2 with 1-Norbornyl lithium (1-NorLi1)) are described. From WCl6 and WCl4 [(1-Nor)2W]n is formed, whereas in dependence of the solvent WO2Cl2 and WOCl4 are transformed into the complexes Li2[1-NorWOCl4] · THF, Li[WOCl4], Li[WO2Cl2], and Li2[WO2Cl2]. MoCl5 and MoO2(acac)2 are reduced with formation of Li[MoCl5], Li[MoO2(acac)2] and Li2[MoO2(acac)2].  -  Stable (1-Nor)4M-derivatives of molybdenum and tungsten, comparable those of 3d-metals (M = Ti—Co) seem not to exist.
    Notes: Es wird über Reaktionen von WCl6, WCl4, WO2Cl2, WOCl4, MoCl5 und MoO2(acac)2) mit 1-Norbornyllithium (1-NorLi1)) berichtet. Ausgehend von WCl6 und WCl4 wird [(1-Nor)2W]n gebildet, während WO2Cl2 und WOCl4 je nach Lösungsmittel Komplexe der Formeln Li2[1-NorWOCl4] · THF, Li[WOCl4], Li[WO2Cl2] und Li2[WO2Cl2] ergeben. MoCl5 und MoO2(acac)2 werden zu Li[MoCl5], Li[MoO2(acac)2] und Li2[MoO2(acac)2] reduziert. - Den stabilen (1-Nor)4M-Derivaten der 3d-Metalle (M = Ti—Co) vergleichbare Verbindungen des Molybdäns und Wolframs scheinen nicht zu existieren.
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