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  • 1
    ISSN: 1399-0047
    Quelle: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Thema: Chemie und Pharmazie , Geologie und Paläontologie , Physik
    Notizen: Peptide methionine sulfoxide reductase mediates the reduction of protein sulfoxide methionyl residues back to methionines and could thus be implicated in the antioxidant defence of organisms. Hexagonal crystals of the Escherichia coli enzyme (MsrA) were obtained by the hanging-drop vapour-diffusion technique. They belong to space group P6522, with unit-cell parameters a = b = 102.5, c = 292.3 Å, γ = 120°. A native data set was collected at 1.9 Å resolution. Crystals of selenomethionine-substituted MsrA were also grown under the same crystallization conditions. A three-wavelength MAD experiment has led to the elucidation of the positions of the Se atoms and should result in a full structure determination.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Oxford [u.a.] : International Union of Crystallography (IUCr)
    Acta crystallographica 56 (2000), S. e165-e166 
    ISSN: 1600-5759
    Quelle: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Thema: Chemie und Pharmazie , Geologie und Paläontologie , Physik
    Notizen: The title compound, C14H16N2O2, contains a diazepine ring, which appears in a boat conformation. An intramolecular hydrogen bond is formed between the NH group of the diazepine ring and a carbonyl O atom of one of the side chains.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    ISSN: 1572-8935
    Schlagwort(e): Functional monomers ; Polymerization ; Copolymerization ; Kinetic studies ; Reactivity ratios
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Abstract 1-Cyanoethanoyl-4-acryloylthiosemicarbazide (CEATS) was synthesized for the first time as a new chelating monomer. Its structure was confirmed by both elemental and spectral analyses. Radical polymerization and copolymerization of CEATS was been carried out in dimethylformamide (DMF) in the presence of azobisisobutyronitrile (AIBN) as an initiator. Kinetic studies for the polymerization behavior of CEATS were performed. The complex formation of the CEATS monomer and polymer (PCEATS) with Cu II cation was investigated and its stability constant determined. The rate of copolymerization of CEATS with some conventional monomers, namely vinyl acetate, methyl methacrylate and acrylonitrile, was measured as a function of the mole fraction of the monomers. The reactivity ratios (r1, r2) for the various copolymer systems investigated together with the Q and e values of the CEATS monomer were determined. Moreover, the thermal gravimetric analysis of the prepared polymers and their copolymers with acrylonitrile were also studied.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    Springer
    Monatshefte für Chemie 131 (2000), S. 1031-1038 
    ISSN: 1434-4475
    Schlagwort(e): Keywords. Potentiometry; Glycine; Cephalosporins; Complexes.
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary.  The interaction of Ca(II), Cu(II), Zn(II), Pb(II), and La(III) ions with the antibiotics cephalexin, cefadroxil, cephaloridine, and cefoperazone as secondary ligands was investigated potentiometrically. The formation constants were determined for a ligand-to-metal ratio of 1:1 at 25°C and KNO3. The protonation constants of the complexes were evaluated for the system . The order of stability of the binary and ternary complexes were examined. It was found that glycine adds preferably [M(II)-cephalosporin] rather than to the aqueous complexes of M(II). In all cases 1:1:1 complexes were formed.
    Materialart: Digitale Medien
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  • 5
    ISSN: 1434-4475
    Schlagwort(e): Keywords. Sea water; Brine; Crystallization sequence; Simulation.
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung.  Die Kristallisationsabfolge beim Abdampfen von Salzsolen wurde bei 25°C aufder Basis der entsprechenden Phasendiagramme computerunterstützt berechnet. Dabei wurden sowohl die auskristallisierenden festen Phasen bestimmt als auch deren Massenbilanzen ermittelt. Um quantitative Information über das Abdampfverhalten von Salzsolen zu erhalten, wurden diesen Berechnungen zwei Grenzannahmen zugrunde gelegt: i) das Fest-flüssig-Gleichgewicht stellt sich laufend ein, sodaß sich feste Phasen während des Verdampfungsprozesses teilweise oder vollständig wieder auflösen können, bzw. ii) die festen Phasen sedimentieren und trennen sich von der flüssigen Phase, sodaß keine Wiederauflösung möglich ist. Tages- bzw. jahreszeitliche Temperaturschwankungen sowie metastabile Gleichgewichte wurden nicht berücksichtigt.
    Notizen: Summary.  A computer assisted calculation of the crystallization sequence of a brine is performed on the basis of the respective phase diagrams at 25°C. The nature of the solids and the mass balance are determined. The calculation gives immediate quantitative information of the brine behavior during evaporation. The calculation is performed assuming that i) the solids are always in equilibrium with the liquid, i.e. that some solid phases can be partially or completely redissolved during evaporation, or ii) the solids are separated from liquid by sedimentation and no redissolution is possible. The seasonal or day-night fluctuations of temperature and metastable equilibria have not been taken into account.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
    ISSN: 1432-1211
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 7
    Digitale Medien
    Digitale Medien
    Springer
    Communications in mathematical physics 208 (2000), S. 761-770 
    ISSN: 1432-0916
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik , Physik
    Notizen: Abstract: Let $M$ be a compact immersed submanifold of the Euclidean space, the hyperbolic space or the standard sphere. For any continuous potential q on M, we give a sharp upper bound for the second eigenvalue of the operator −Δ+q in terms of the total mean curvature of M and the mean value of q. Moreover, we analyze the case where this bound is achieved. As a consequence of this result we obtain an alternative proof for the Alikakos–Fusco conjecture concerning the stability of the interface in the Allen–Cahn reaction diffusion model.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 8
    Digitale Medien
    Digitale Medien
    Springer
    Journal of thermal analysis and calorimetry 63 (2000), S. 525-532 
    ISSN: 1572-8943
    Schlagwort(e): bitumen ; portland cement ; safety considerations ; solidification ; thermal stability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The thermal stability of solidified NaNO3 salts in bitumen and cement has been investigated for safety considerations in the field of solidification of radioactive waste. The thermal decomposition of bitumen and cement in presence of NaNO3 in a temperature range 22–650°C has been studied. The fraction decomposed of the pure samples and mixtures showed slow linear reactions followed by acceleratory and decay stages. Data are analyzed according to both Freeman-Carroll and Coats-Redfern kinetics to evaluate the activation energy and the order of reactions of all mixtures. It is found that the activation energies of bitumen and cement were 594 and 203 kJ mol-1, respectively. The order of reactions of bitumen and cement was 2 and 4, respectively. The addition of NaNO3 shortens the duration of the induction period in all mixtures. It was concluded that solidification of radioactive waste containing NaNO3 in bitumen and cement should be applied in the temperature range 22–300°C. At temperature higher than300°C solidification should be in cement.
    Materialart: Digitale Medien
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  • 9
    ISSN: 1573-1472
    Schlagwort(e): Coherent structures ; Numerical modelling ; Turbulence
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract In two preceding papers, coherent structures of theatmospheric boundary layer (ABL), such as rollvortices or cells, were investigated through radar andaircraft observations collected during the TRAC-93(Turbulence Radar Aircraft Cells) experiment held inFrance in June 1993. The analysis of this experimentaldata set provided information on the spatialcharacteristics of these organisations (length scale,orientation, type ... ), their temporal and verticalevolution, and their relation with the dynamic andthermodynamic conditions of the ABL. For the thirdpaper in this series, a large eddy simulation model is used to examine the impact of thecoherent structures on the ABL vertical fluxes. Theanalysis of the simulated horizontal fields is madewith two-dimensional auto and cross-correlationsapplied on different pertinent ABL variables. Theresults emphasise a directional anisotropy of theseorganised fields throughout the ABL, much morepronounced in the heat flux fields, not only at thelength scale of organisations but also at theturbulence scales. This finding has an importantconsequence for traditional ABL flux measurementsbased on the hypothesis of isotropic and homogeneousturbulence. It can explain part of the underestimationof the surface fluxes often mentioned in theliterature. This approach makes it possible tomodify the concept of diffusion time (in chemicalmodelling) and could also lead to revised ABLparameterisations in Range Scale models.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 10
    Digitale Medien
    Digitale Medien
    Springer
    Journal of intelligent information systems 14 (2000), S. 131-154 
    ISSN: 1573-7675
    Schlagwort(e): content-based access of images ; image representation ; intelligent information retrieval ; knowledge representation ; image databases ; query containment ; description logics ; intentional reasoning
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik
    Notizen: Abstract The problem of content management of multimedia data types (e.g., image, video, graphics) is becoming increasingly important with the development of advanced multimedia applications. Traditional database management systems are inadequate for the handling of such data types. They require new techniques for query formulation, retrieval, evaluation, and navigation. In this paper we develop a knowledge-based framework for modeling and retrieving image data by content. To represent the various aspects of an image object's characteristics, we propose a model which consists of three layers: (1) Feature & Content Layer, intended to contain image visual features such as contours, shapes, etc.; (2) Object Layer, which provides the (conceptual) content dimension of images; and (3) Schema Layer, which contains the structured abstractions of images, i.e., a general schema about the classes of objects represented in the object layer. We propose two abstract languages on the basis of description logics: one for describing knowledge of the object and schema layers, and the other, more expressive, for making queries. Queries can refer to the form dimension (i.e., information of the Feature & Content Layer) or to the content dimension (i.e., information of the Object Layer). These languages employ a variable free notation. As the amount of information contained in the previous layers may be huge and operations performed at the Feature & Content Layer are time-consuming, resorting to the use of materialized views to process and optimize queries may be extremely useful. For that, we propose a formal framework for testing containment of a query in a view expressed in our query language.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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