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  • Chemistry  (6)
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  • 1
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Electroanalysis 3 (1991), S. 325-329 
    ISSN: 1040-0397
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The concentrations of the heavy metals (Cd, Pb, Cu, and Zn) have been determined in oak growth rings from the polluted region of Königstein, Germany, by differential pulse anodic stripping voltammetry and compared to those in soil. The radial distribution was found to be the same for all four metals studied and features a distinct increase in the recent growth rings and a marginal increase in the transition zone between sapwood and heartwood. The toxic metals cadmium and lead are preferentially bound to lower parts of the tree, whereas for essential metals copper and zinc, monotonous axial distribution has been found in the range 0-5 m. This points to different degrees of mobility of heavy metal complexes in wood material.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 60 (1998), S. 156-168 
    ISSN: 0006-3592
    Keywords: fed-batch ; Candida rugosa lipase production ; control ; feeding strategy ; on-line monitoring and estimation ; lipase purification ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Simulation studies have predicted that maximum lipase activity is reached with fed-batch operation strategies. In this work, two different fed-batch operational strategies have been studied: constant substrate feeding rate and specific growth rate control. A constant substrate feeding rate strategy showed that maximum aqueous lipolytic activity (55 U/mL) was reached at low substrate feeding rates, whereas lipase tends to accumulate inside the cell at higher rates of substrate addition. In the second fed-batch strategy studied, a feedback control strategy has been developed based on the estimation of state variables (X and μ) from the measurement of indirect variables such as CER by means of mass spectrometry techniques. An on-off controller was then used to maintain the specific growth rate at the desired value by adjusting the substrate feeding rate. A constant specific growth rate strategy gave higher final levels of aqueous lipolytic activity (117 U/mL) at low specific growth rates. At higher specific growth rates the enzyme remained accumulated inside the cell, as was observed with a constant feeding fed-batch strategy. With a constant specific growth rate strategy, lipase production by Candida rugosa was enhanced 10-fold compared to a batch operation. Purification studies have demonstrated that lipolytic and esterasic specific activity ratios of Candida rugosa isoenzymes can be modified by using different operational conditions. These studies have also showed that the isoenzymes obtained in a controlled growth rate strategy are around three- to four-fold more active than those obtained in a constant feeding rate strategy. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 60: 156-168, 1998.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 50 (1993), S. 1565-1573 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The thermal degradation of a poly(vinyl chloride) (PVC) resin was studied using a non-isothermal thermogravimetric technique. Kinetic parameters such as activation energies, reaction orders, and preexponential factors are calculated using integral and differential methods reported in the literature. Advantages and disadvantages of these methods are discussed in order to characterize PVC. © 1993 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Advanced Materials for Optics and Electronics 1 (1992), S. 117-121 
    ISSN: 1057-9257
    Keywords: Tin(II) sulphide ; Tin(IV) oxide ; Photoconductor ; Air annealing ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: The thermal decomposition of chemically deposited SnS thin films to SnO2 films by air annealing at temperatures up to 400°C is discussed. The conversion of a 0.7 μm thick SnS thin film to an SnO2 film involves the creation of non-stoichiometric SnS, SnS + SnS2 mixed phase and non-stoichiometric SnO2 (i.e. SnO2 — x), as concluded from X-ray diffraction patterns, optical transmission spectra and electrical characteristics. The SnO2 thin films obtained in this manner are photoconductive, with a lowest sheet resistance (in the dark) of about 105 Ω/□ and an activation energy (Ea) of 0.1 eV for the electrical conductivity observed for the SnS films annealed at 325°C. This was found as the onset temperature for conversion of the SnS + SnS2 phase to the non-stoichiometric SnO2 - x film. Elevation of the annealing temperature to 400°C results in an elevation of the sheet resistance to about 109 Ω/□ with the value of Ea at 1.3 eV, indicating an improvement in the degree of stoichiometry.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Advanced Materials for Optics and Electronics 2 (1993), S. 133-141 
    ISSN: 1057-9257
    Keywords: CdS ; Chemical deposition ; Photodetector ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Very interesting behaviour is shown by chemically deposited CdS thin films for optoelectronic applications after air and vacuum (10-5 Torr) annealing. Vacuum annealing of samples at about 100°C caused the dark conductivity to improve by five orders of magnitude. The dark and photoconductivity of air-annealed (at around 200°C) samples increased by seven and two orders of magnitude respectively. Air-annealed (at 350°C for about 2 min) samples exhibited a very quick photoresponse (〈2 s for two decades of photocurrent decay) with σp/σd ≈ 105 for a bias of 10 V, which may be exploited for photodetector applications. Air or vacuum annealing of samples for a minimum of 10-15 min caused the optical transmittance above the band edge to increase by 10%-15% and annealing the sample at 200°C caused the absorption edge to shift towards the longer-wavelength region compared with the as-prepared and 100 and 350°C annealed films.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 0044-2313
    Keywords: Cadmium Complexes ; Thiosemicarbazone Complexes ; Crystal Structure ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Cadmium(II)-Komplexe von 2,6-Diacetylpyridin-bis- und -monothiosemicarbazon. Die Kristallstruktur von Aquodichlor(2,6-diacetylpyridin-monothiosemicarbazon-N,N′,O,S)cadmium(II)-MonohydratDie Reaktionen von Cadmiumacetat bzw,-chlorid mit 2,6-Diacetylpyridin bis(thiosemicarbazon) (H2L1) ergaben die Komplexe [CdL1] bzw. [CdCl2(H2L1)]. Aus der Mutterlösung der Reaktion mit CdCl2 kristallisierte noch [CdCl2(HL2)(H2O)] · H2O, mit HL2 = 2,6-Diacetylpyridin-monothiosemicarbazon. [CdC]2(HL2)(H2O) · H2O ist orthorhombisch, Raumgruppe P212121 mit a = 7,257(1), b = 14,559(2), c = 15,214(2) Å, Z = 4 und R = 0,0455. Der Ligand ist hier vierzähnig, koordiniert über S und N(3) des Thiosemicarbazons, das O-Atom der CH3O-Gruppe und den Pyridinstickstoff in der äquatorialen Ebene einer verzerrten pentagonalen Pyramide. Die fünfte äquatoriale Position wird von einem der Chlorid-Ionen besetzt und die apicalen Positionen durch das andere Chlorid und ein Wassermolekül. Die IR-Spektren deuten auf eine dimere Festkörperstruktur mit sechsfach koordiniertem Cd im (CdL1) und auf eine monomere Form beim siebenfach koordiniertem Cd im [CdCl2(H2L1)]. Alle Komplexe wurden in Lösung mit 1H-, 13C- und 113Cd-NMR untersucht.
    Notes: The reactions of cadmium(II) acetate and cadmium(II) chloride with 2,6-diaceiylpyndinebis(thiosemicar bazone) (H2L1) afforded the complexes [CdL1] and [CdCl2(H2L1)] respectively. The mother liquor of the chloride reaction also afforded [CdCl2(HL2)(H2O)] · H2O, where HL2 is 2,6-diacetylpyridine monothiosemicarbazone. [CdCl2(HL2)(H2O)] · H2O is orthorhombic (space group P212121) with a = 7.257(1), b = 14.559(2), c = 15.214(2) Å, Z = 4 and R = 0.0455. The ligand in this latter is tetradentate, coordinating through the S and N(3) atoms of the thiosemi carbazone moiety, the oxygen atom of the CH3CO group and the pyridine nitrogen in the equatorial plane of a distorted pentagonal bipyramid whose fifth equatorial position is occupied by one of the chloride ions and whose apical po sitions are occupied by the other chloride and the water molecule. The IR spectra suggest a dimeric solid state structure with hexacoordinated Cd atoms for [CdL1] and monomeric with heptacoordinated Cd atoms for [CdCl2(H2L1)]. All the complexes were also studied in solution by 1H, 13C, and 113Cd NMR spectroscopy.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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