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  • International Union of Crystallography  (37)
  • Wiley-Blackwell  (18)
  • Bremerhaven : Alfred-Wegener-Inst. für Polar- und Meeresforschung  (1)
  • 1
    Series available for loan
    Series available for loan
    Bremerhaven : Alfred-Wegener-Inst. für Polar- und Meeresforschung
    Associated volumes
    Call number: ZSP-189-93
    In: Berichte aus dem Fachgebiet Physik
    Type of Medium: Series available for loan
    Pages: 50 S. : 30 cm
    Series Statement: Berichte aus dem Fachgebiet Physik / Alfred-Wegener-Institut für Polar- und Meeresforschung 93
    Branch Library: AWI Library
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  • 2
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 28 (1990), S. 1001-1014 
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A general expression for the magnetization decay of a multipulse group is derived. This formula is applied to a three-component model of molecular motions in polymer melts. The influence of the several components on the magnetization decay is discussed. The relation of the effective nuclear magnetic relaxation time T2e to the Anderson-Weiss formula is also shown, and an analytical expression for the transverse relaxation in melts is derived. Finally T2e is compared with the relaxation time in the rotating frame T1ρ in the melt. The theoretical results for T2e are tested with measurements of frequency dependence in polyethylene melts.
    Additional Material: 7 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 30 (1992), S. 931-942 
    ISSN: 0887-6266
    Keywords: nuclear magnetic resonance (NMR) relaxation in polymer melts ; relaxation of proton NMR processes in melts (theory) ; chain motions and NMR relaxation in melts ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A theoretical treatment of the nonexponential relaxation behavior of the different proton nuclear magnetic resonance (NMR) relaxation processes in polymer melts is presented. Formulas are derived for a three-component model given by two versions and a homogeneous distribution of correlation times. The theoretical results were tested with measurements of T1, T2e, and T2 as functions of frequency and molecular mass in linear fractionated polyethylene samples. While the T1 relaxation always yields exponential magnetization decays, the T2e and T2 measurements show biexponential relaxation behavior. From the calculations it was found that the correlation time of the local motion is independent of the molecular mass, whereas the correlation time of the slowest motional process increases with M2.8w for the three-component model and with M2.2w for the distribution of correlation times, respectively. © 1992 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 1 (1995), S. 201-206 
    ISSN: 1075-2617
    Keywords: All-aza peptide ; renin inhibitor analogue ; X-ray ; conformation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of the first all-aza-amino acid analogue (2) of a peptidic renin inhibitor is described. The X-ray structural analysis and molecular modelling investigations of this novel compound reveal interesting conformational features which have a significant impact on its biological activity. In addition, insight into conformational features of azapeptides in general in comparison with the corresponding purely peptidic compounds is given.
    Additional Material: 3 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Acta Polymerica 39 (1988), S. 276-281 
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Using a three-component model of molecular motion, the relaxation times T2e and T1 in dependence on frequency and the transversal relaxation time T2 in polymer melts are calculated. The correlation times obtained by this method and the experimentally measured relaxation times are investigated with respect of their dependence on molecular mass.
    Notes: Unter Verwendung eines Dreikomponentenmodells der Molekularbewegung werden Berechnungen zur Frequenzabhängigkeit der kernmagnetischen Relaxationszeiten T2e und T1 sowie zur transversalen Relaxationszeit T2 in der Polymerschmelze durchgeführt. Die daraus gewonnenen Korrelationszeiten sowie die experimentell ermittelten Relaxationszeiten werden hinsichtlich ihrer Molmassenabhängigkeit untersucht.
    Additional Material: 6 Ill.
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  • 6
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthesis, Constitution and Properties of Cage-like Vinyl- and Allylsilylated Silicic AcidsBy silyation of tetramethylammonium silicate [N(CH3)4]8Si8O20 · 69 H2O with vinyldimethylchlorosilane (I) and divinyltetramethyldisiloxane, respectively, or allyldimethylchlorosilane there were synthesized the crystalline silicic esters [CH2=CH(CH3)2Si]8Si8O20 and[CH2=CH—CH2(CH3)2Si]8Si8O20. By means of gas chromatography, mass spectrometry, 1H and 29Si NMR the two compounds were identified to be cage-like double four-ring(D4R)-silicic esters containing eight vinyldimethylsilyl- or allyldimethylsilyl groups, Silylation with a mixture of I and trimethylchlorosilane yields in dependence on the ratio of silanes vinyldimethylsilyltrimethylsilyl D4R silicic esters with average numbers of unsaturated groups 〈 8.
    Notes: Durch Umsatz des Tetramethylammoniumsilicats [N(CH3)4]8Si8O20 · 69 H2O mit Vinyldimethylchlorsilan (I) bzw. Divinyltetramethyldisiloxan oder Allydimethylchlorsilan wurden der Vinyldimethylsilylkieselsäureester [CH2=CH—CH2(CH3)2Si]8Si8O20 und Allyldimethylsilyl-kieselsäureester [CH2=CH—CH2(CH3)2Si]8Si8O20 erhalten. Mit Hilfe der Gaschromatographie, Massenspektroskopie sowie 1H-und 29Si-NMR wurden die Verbindungen charakterisiert und eine käfigartig aufgebaute Doppelvierring (D4R)-Struktur des Kieselsäuregerüsts nachgewiesen, an deren 8 terminalen O-Atomen des Kieselsäuregerüsts nachgewiesen, an deren 8 terminalen O-Atomen des Kieselsäuregerüsts Vinyldimethylsiyl- bzw. Allydimethylsilylgruppen gebunden sind. Durch Silylierung mit I und Trimethylchlorsilan sind in Abhängigkeit vom Mischungsverhältnis Vinyldimethylsilytrimethysily1-D4R-Kieselsäureester mit einer mittleren Anzahl ungesättigter Gruppen 〈 8 herzustellen.
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  • 7
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 589 (1990), S. 175-186 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Bis[dichloro-bis(trimethylsilyl)methylalane] - Synthesis and Molecular StructureBis[dichloro-bis(trimethylsilyl)methylalane] 1 is synthesized via a distribution reaction melting AlCl3 and tris[bis(trimethylsilyl)methyl]alane in the stoichiometric ratio of 2:1 at 110°C. A similar reaction for preparing the monochloro analogue 2 gives not the desired compound. 1 dimerizes through Al—Cl bridges; the crystal structure shows a large difference between terminal (206.8 pm) and bridging (228.6 pm Al—Cl distances. Treatment of 1 with potassium in hexane yields only disproportionation products: elemental aluminium), chloro-bis[bis(trimethylsilyl)methyl]alane 2, and tris[bis(trimethylsilyl)methyl]alane. From the reaction of thereby formed KCl with the educt 1 we isolate potassium-[trichloro-bis(trimethylsilyl)methylalanate] 3 as a by-product.
    Notes: Bis[dichlor-bis(trimethylsilyl)methylalan] 1 wird über eine Austauschreaktion in der Schmelze aus Aluminiumtrichlorid und Tris[bis(trimethylsilyl)methyl]alan im Molverhältnis 2:1 bei 110°C dargestellt. Das analoge Chlor-bis[bis(trimethylsilyl)methyl]alan 2 ist auf diesem Weg nicht zugänglich. 1 liegt im gelösten und kristallinen Zustand über Aluminium-Chlor-Brücken dimerisiert vor; die terminale (206,8 pm) ist gegenüber der verbrückenden Al—Cl-Bindung um 21 pm verkürzt. Bei der Reaktion von 1 mit Kalium beobachteten wir ausschließlich Disproportionierung zu elementarem Aluminium, Tris[bis(trimethylsilyl)methyl]alan und Chlor-bis[bis(trimethylsilyl)methyl]alan; dabei gebildetes Kaliumchlorid ergibt mit der Ausgangsverbindung 1 als Nebenprodukt Kalium[trichlor-bis(trimethylsilyl)methylalanat] 3.
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 596 (1991), S. 63-72 
    ISSN: 0044-2313
    Keywords: Organic silicic acid derivatives ; cage-like structures ; hydrosilylation ; n.m.r. spectroscopy ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Reaction of the Cage-like Silicic Acid Derivative [(CH3)2HSi]8Si8O20 with Unsaturated Organic CompoundsBy 29Si, 1H, and 13C NMR investigations were shown that the eight HSi≡groups of the double four-ring silicic acid derivative [(CH3)2HSi]8Si8O20 react with the following unsaturated compounds: vinylcyclohexene, allyl glycidyl ether, methyl methacrylate, octadecene-1, and styrene. The resulting oily products are soluble in organic solvents. The compounds were characterized by the chemical shifts of the 29Si, 1H, and 13C NMR signals. Their formulae are [C6H9(CH2)2Si(CH3)2]8Si8O20, [CH3OOCCH(CH3)CH2Si(CH3)2]8Si8O20, [CH3(CH2)17Si(CH3)2]8Si8O20 and [C6H5(CH2)2Si(CH3)2]8Si8O20, and [C6H5CH(CH3)Si(CH3)2]8 Si8O20, respectively. Mainly the addition reactions do not follow the Markovnikov rule.
    Notes: 29Si-, 1H- und 13C-NMR-Untersuchungen zeigen, daß das Doppelvierring-kieselsäurederivat [(CH3)2HSi]8Si8O20 mit seinen acht HSi≡Gruppen pro Molekül Additionsreaktionen mit den einfach ungesättigten Verbindungen Vinylcyclohexen, Allylglycidylether, Methacrylsäuremethylester, Octadecen-1 und Styren eingeht. Die Addition erfolgt überwiegend entgegen der Markovnikov-Regel.Als Reaktionsprodukte werden meist ölartige, in organischen Lösungsmitteln lösliche Verbindungen der Formeln [C6H9(CH2)2Si(CH3)2]8Si8O20, [CH3OOCCH(CH3)CH2Si(CH3)2]8Si8O20, CH3(CH2)17Si([CH3)2]8Si8O20 und [C6H5(CH2)2Si(CH3)2]8Si8O20 bzw. [C6H5CH(CH3)Si(CH3)2]8Si8O20 erhalten, die durch die chemischen Verschiebungen der 29Si-, 1H- und 13C-NMR-Signale charakterisiert werden.
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  • 9
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthesis, Properties, and Structure of [2-(1′-methyl-4-imidazolyl)phenyl-1-C,3′-N]-palladium(II) AcetylacetonateThe reaction of Di-μ-chloro-bis[2-(1′-methyl-4-imidazolyl)phenyl-1-C,3′-N]palladium(II) with Thallium(I) acetylacetonate yields [2-(1′-methyl-4-imidazolyl)phenyl-1-C,3′-N]palladium(II) acetylacetonate. The complex crystallizes monoclinic in the space group P21/n with the lattice constants a = 1302.4(3), b = 836.0(2), c = 1341.3(3) pm, β = 93.69(3)°. Pd has a squareplanar coordination by two O atoms of acetylacetonate, the N atom of the imidazole ring, and the C atom of the phenyl group. I.r., n.m.r., and mass spectra are reported.
    Notes: Die Umsetzung von Di-μ-chloro-bis(2-(1′-methyl-4-imidazolyl)phenyl-1-C,3′-N]palladium(II) mit Thallium(I)-acetylacetonat ergibt [2-(1′-methyl-4-imidazolyl)phenyl-1-C,3′-N]palladium(II)-acetylacetonat. Der Komplex kristallisiert monoklin in der Raumgruppe P21/n mit den Gitterkonstanten a = 1302,4(3), b = 836,0(2), c = 1341,3(3) pm, β = 93,69(3)°. Im Molekül ist Pd quadratisch planar von den beiden O-Atomen des Acetylacetonat-Liganden, einem N-Atom des Imidazol-Rings und einem C-Atom der Phenylgruppe umgeben. IR-, NMR- und Massenspektrum werden diskutiert.
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  • 10
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 571 (1989), S. 69-74 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthesis and Crystal Structure of Tris[1,3-bis(phenyltriazenido)benzene]-di-Thallium(III)Tris[1,3-bis(phenyltriazenido)benzene]-di-thallium(III) is formed by the reaction of di-sodium-1,3-bis(phenyltriazenido)benzene with thallium(I)-sulfate in a THF/H2O mixture in the presence of oxygen. The compound crystallizes in the triclinic space group P11 with the lattice parameters a = 1368.8(2), b = 1539.3(2), c = 1676.0(3) pm, α = 106.04(3)°, β = 90.50(3)°, γ = 109.94(3)° and two formula units in the unit cell. The complex consists of two Tl atoms and three ligands, of which each N3-unit acts as bidentate chelating group. The coordination sphere of Tl is trigonal prismatic with a coordination number of 6. The distances Tl—N range from 228 to 244 pm.
    Notes: Tris[1,3-bis(phenyltriazenido)benzol]-di-thallium(III) entsteht durch Umsetzung von Di-Natrium-1,3-bis(phenyltriazenido)benzol mit Thallium(I)-sulfat unter Luftoxidation in einem THF/H2O-Gemisch. Die Verbindung kristallisiert triklin in der Raumgruppe P11 mit den Gitterkonstanten a = 1368,8(2), b = 1539,3(2), c = 1676,0(3) pm, α = 106,04(3)°, β = 90,50(3)°, γ = 109,94(3)° mit 2 Formeleinheiten pro Elementarzelle. Im Komplex sind die drei Liganden mit jeweils beiden N3-Einheiten chelatförmig an die zwei Tl-Atome gebunden, woraus für die Zentralatome eine trigonal-prismatische Umgebung mit der Koordinationszahl 6 resultiert. Die Thallium-Ligand Abstände Tl—N variieren von 228 bis 244 pm.
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