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  • 1
    Electronic Resource
    Electronic Resource
    High-excitation phenomena in doped III–V semiconductors (1984)
    Springer
    Czechoslovak journal of physics 34 (1984), S. 402-402 
    Details
    ISSN: 1572-9486
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01590080
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  • 2
    Electronic Resource
    Electronic Resource
    The effect of perturbedk-selection and gap shrinkage on the optical transitions in III–V semiconductors (1980)
    Springer
    Czechoslovak journal of physics 30 (1980), S. 381-387 
    Details
    ISSN: 1572-9486
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Optical transitions in direct semiconductors are governed according to simple one-electron treatment by ak-selection rule, which in doped or mixed crystals is but lifted to some extent (Δk) caused by 1) shallow impurities, 2) isoelectronic impurities or 3) alloy scattering. Values of Δk for these mechanisms are given and the implications for line shapes of optical spectra are discussed. Furthermore, as to the position of lines in the optical spectra of highly doped or highly excited crystals, gap shrinkage effects have to be considered, three main mechanisms of which can be distinguished: 1) Quadratic response of the band edges with respect to the fluctuating potential of the (screened) impurities, 2) polaron effects and 3) carrier exchange and correlation effects. Results of theoretical calculation are compared with experimental findings for GaAs and GaP. The practical importance of gap shrinkage effects for gain measurements and for the operation of (Ga, Al) As laser diodes is pointed out. From the Coulomb interaction of the carriers an additional mechanism for the lifting of thek-selection rule (especially valid for pure, but excited semiconductors) can be derived (plasmon coupling): Estimations show that the simplek-selection rule is almost never fulfilled within the energy range of emission spectra and that these spectra can be well explained simply assuming no-k-selection even for pure direct material.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01596092
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  • 3
    Electronic Resource
    Electronic Resource
    Effect of methylprednisolone on experimental noncardiogenic pulmonary edema (1981)
    Springer
    Intensive care medicine 7 (1981), S. 121-124 
    Details
    ISSN: 1432-1238
    Keywords: Glucocorticoid ; Adult respiratory distress syndrome ; Posttraumatic pulmonary insufficiency ; Lung water ; Monocrotaline ; Pulmonary circulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Methylprednisolone, 30 mg/kg body weight, was given to dogs 30 min and 4 h after injection of monocrotaline to produce noncardiogenic pulmonary edema. Control animals received monocrotaline but not corticosteroids. After 6 h the steroid-treated animals demonstrated significantly better gas exchange and significantly less pulmonary edema. A possible mechanism of this beneficial effect of steroids is inhibition of complement-leukocyte interactions which may mediate pulmonary microvascular injury. The results lend some support to the clinical practice of short-term pharmacologic doses of steroids in noncardiogenic pulmonary edema.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01738614
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  • 4
    Electronic Resource
    Electronic Resource
    Separation of unmodified α-amino acid enantiomers by reverse phase HPLC (1980)
    Springer
    Chromatographia 13 (1980), S. 677-685 
    Details
    ISSN: 1612-1112
    Keywords: Ligand-exchange chromatography ; Reversed phase chromatography, amino acids ; Racemates resolution, amino acids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A novel chiral phase system is presented for the resolution of unmodified α-amino acid racemates which is composed of a reverse phase packing coated with N-alkyl-L-hydroxyproline (where alkyl is n-C7H15-, n-C10H21- and n-C16H33-) and a hydro-organic eluent containing copper(II)acetate. The factors controlling retention and enantioselectivity such as concentration of Cu(II)ion and pH of the eluent, addition of NH4Ac to the eluent, type and content of organic solvent of hydro-organic eluent and column temperature were examined. The extremely high enantioselectivity observed (α up to 16) is assumed to be caused by a three site sorbate-sorbent interaction involving bidentate coordination of two amino acids to a Cu(II)ion and hydrophobic attractions between hydrocarbon side chains of amino acids and the n-octadecyl groups of the support. The efficiency and selectivity of the system permits resolution of up to 7 racemic amino acids into enantiomers within 35 minutes on a conventional HPLC apparatus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02303437
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  • 5
    Electronic Resource
    Electronic Resource
    Monomeric vs. polymeric bonded iminodiacetate silica supports in high-performance ligand-exchange chromatography (1983)
    Springer
    Chromatographia 17 (1983), S. 200-204 
    Details
    ISSN: 1612-1112
    Keywords: Liquid chromatography ; Chemically bonded silica ; Metal-complexing ligands
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The synthesis of monomeric and polymeric bonded iminodiacetate-groups on silica supports is described. The polymeric support offers advantages over the monomeric, such as (i) preparation is much simpler, (ii) higher surface concentration of functional groups can be achieved without loss of efficiency and (iii) hydrolytic stability. Cu2+ loaded supports were examined for their kinetic performance, in particular for the C-parameter of the Knox equation, and for their hydrolytic stability. Calculation of the surface coverage shows that only a rather thin polymeric layer is formed; this is in agreement with the results of the kinetic performance. The retention of α-amino acids on the Cu2+ loaded polymeric support demonstrates its use in HPLEC.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02290557
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  • 6
    Electronic Resource
    Electronic Resource
    Thinlayer-chromatography — Column liquid chromatography: Partners or competitors? (1984)
    Springer
    Chromatographia 18 (1984), S. 46-46 
    Details
    ISSN: 1612-1112
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02279466
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  • 7
    Electronic Resource
    Electronic Resource
    Comments on the use of alumina in HPLC (1984)
    Springer
    Chromatographia 18 (1984), S. 47-48 
    Details
    ISSN: 1612-1112
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02279467
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  • 8
    Electronic Resource
    Electronic Resource
    Anwendungsmöglichkeiten der HPLC bei der Trennung, Isolierung, Identifizierung und quantitativen Bestimmung von Substanzen aus komplexen Stoffgemischen—am Beispiel von Carbonsäuren in Natriumaluminatlaugen aus dem Bayerprozeß der Aluminiumoxidgewinnung (1982)
    Springer
    Chromatographia 15 (1982), S. 107-116 
    Details
    ISSN: 1612-1112
    Keywords: HPLC ; Carboxylic acids ; Bayer process ; Aluminate liquors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Es wird die Anwendung der Hochdruckflüssigchromatographie (HPLC) in Bezug auf die Identifizierung und quantitative Bestimmung von Carbonsäuren in Aluminatlaugen aus dem Bayerprozeß beschrieben. Die Vorgehensweise besteht in folgenden Teilschritten: Optimierung von HPLC Phasensystemen zur Trennung von synthetischen Gemischen von Carbonsäuren, Aufarbeitung der Aluminatlauge, semi-präparative Isolierung von Substanzen, Identifizierung auf flüssigchromatographischem Wege und durch Massenspektrometrie, quantitative Bestimmung durch Peakhöhenauswertung mit Hilfe externer Standards.
    Notes: Summary The paper describes the application of high performance liquid chromatography (HPLC) to the identification and quantitation of carboxylic acids in aluminate liquors from the Bayer process. The procedure comprises the following consecutive steps: optimization of HPLC phase systems employing synthetic mixtures of carboxylic acids, clean-up of the liquor, semi-preparative isolation of substances, identification by means of HPLC and mass spectrometry and estimation based on peak height measurement using external standards.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02290443
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  • 9
    Electronic Resource
    Electronic Resource
    Hydrolytically stable chemically bonded silica supports with metal complexating ligands: Synthesis, characterization and use in high-performance ligand-exchange chromatography (HPLEC) (1982)
    Springer
    Chromatographia 16 (1982), S. 117-125 
    Details
    ISSN: 1612-1112
    Keywords: Liquid chromatography ; Chemically bonded silica ; Hydrolytically stable ; Metal complexing ligands ; Amino acid separation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A silica of 14 nm pore size was reacted according to two procedures with the following silanes: γ-aminopropyltriethoxysilane (1), N-aminoethyl-N′-aminopropyltrimethoxysilane (2), N-aminoethyl-N′-aminoethyl-N″-aminopropyltrimethoxysilane (3), N-(3-triethoxysilanepropyl)-N, N-diacetic dimethylester (4), N-(3-trisodiumsilanolatepropyl)-N, N-diacetic acid disodium salt (5) and N-(3-trisodiumsilanolatepropyl)-ethylenediamine-N, N′, N′-triacetic acid trisodium salt (6). The reaction of silanes 1–4 with the silica was carried out under anhydrous conditions (procedure A). Silanes 1–6 were subjected to surface modification under essentially hydrous conditions applying a two-step procedure (procedure B). Procedure B is much simpler to perform and allows binding of high and definite amounts of silane onto the surface. Complexation of all bonded phases with Cu2+ was examined by measuring the sorption isotherms at constant pH. The pH-dependence of Cu2+ uptake at constant Cu2+ concentration was evaluated. Tests on the chemical and chromatographic stability of the packings showed that only the silicas with bonded iminodiacetate and ethylenediaminetriacetate groups remain hydrolytically stable. Retention of aliphatic and α-amino acids on these two packings was found to be mainly controlled by the pH and the ionic strength of the eluent.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02258881
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  • 10
    Electronic Resource
    Electronic Resource
    Direkte Kopplung der Hochdruckextraktion mit verflüssigten und überkritischen Gasen mit der Hochdruckflüssig-Chromatographie (1984)
    Springer
    Fresenius' Zeitschrift für analytische Chemie 318 (1984), S. 305-306 
    Details
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00528621
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