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  • Chemistry  (11)
  • Atomic, Molecular and Optical Physics  (4)
  • Density functional calculations
  • Inorganic Chemistry
  • Molecular dynamics
  • Transition states
  • 1990-1994  (16)
Collection
Keywords
Publisher
Years
Year
  • 1
    Electronic Resource
    Electronic Resource
    Relativistic density-functional studies of naked and ligated gold clusters (1994)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 52 (1994), S. 595-610 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Electronic structure investigations on a broad range of gold compounds, including naked and ligated gold clusters, are reviewed. The calculations have been carried out with a recently introduced relativistic variant of the linear combination of Gaussian-type orbitals density-functional (LCGTO-DF) method which affords all-electron investigations for very large systems. The accuracy of the method will be evaluated for the gold dimer. Then the electronic structure of the naked cluster Au55 is studied, both in Ih and Oh symmetry. Nonrelativistic and relativistic results obtained by the present method are compared to those of the much simpler jellium model. Since triphenylphosphine is among the most common ligands in gold chemistry a series of mononuclear gold phosphine compounds MeAuPR3 with increasingly complex ligands PR3 (R = H, CH3, C5H6) is discussed. The calculations reveal the success and the limitations of simpler phosphines often employed as model ligands in theoretical studies. Some aspects of the phosphine gold interaction in these simpler compounds carry over to the main group element centered gold clusters. Thereby one arrives at a rationalization of the particularly high stability of the carbon-centered octahedral cluster cation [(R3PAu)6C]2+ as compared to the neighboring isoelectronic boron and nitrogen-centered clusters. © 1994 John Wiley & Sons, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560520853
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  • 2
    Electronic Resource
    Electronic Resource
    The structure of ColE1 rop in solution (1991)
    Springer
    Journal of biomolecular NMR 1 (1991), S. 71-82 
    Details
    ISSN: 1573-5001
    Keywords: rop ; Protein conformation ; 2D NMR ; Molecular dynamics ; Repressor proteins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary The structure of the ColE1 repressor of primer (rop) protein in solution was determined from the proton nuclear magnetic resonance data by a combined use of distance geometry and restrained molecular dynamics calculations. A set of structures was determined with low internal energy and virtually no violations of the experimental distance restraints. Rop forms homodimers: Two helical hairpins are arranged as an antiparallel four helix bundle with a left-handed rope-like twist of the helix axes and with left-handed bundle topology. The very compact packing of the side chains in the helix interfaces of the rop coiled-coil structure may well account for its high stability. Overall, the solution structure is highly similar to the recently determined X-ray structure (Banner, D.W., Kokkinidis, M. and Tsernoglou, D. (1987)J. Mol. Biol.,196, 657–675), although there are minor differences in regions where packing forces appear to influence the crystal structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01874570
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  • 3
    Electronic Resource
    Electronic Resource
    Progress in synthesis and application of segmented polymersDedicated to Prof. Dr. H. Sinn on the occasion of his 65th birthday (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 223 (1994), S. 47-60 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Maßgeschneiderte segmentierte Polymere spielen eine Schlüsselrolle bei der Entwicklung von neuen polymeren Materialien. In Abhängigkeit von den molekularen Architekturen der segmentierten Polymeren kann die Ausbildung von Polymermorphologien und von Eigenschaftssynergien gesteuertwerden. An ausgewählten Beispielen werden grundlegende Konzepte und neuere Entwicklungen vorgestellt. Segmentierte Silikon-Flüssigkautschuke, wo unverträgliche Silikonsegmente von zwei mischbaren Oligo(caprolacton)-Segmenten flankiert werden, sind wirkungsvolle Zähmodifikatoren für Epoxidharze. In nanophasenseparierten IPNs auf Basis dieser Silikon-modifizierter Epoxidharze kann die Schlagzähigkeit ohne Verlust der Dimensionsstabilität erhöht werden. Kompatibilisierte Blends aus segmentierten phenolischen Polyurethan- und epoxidfunktionellen Nitril-Flüssigkautschuken bilden diskrete Blend-Mikrophasen, die in Epoxidprepregs dispergiert sind und strukturelles Verkleben von Aluminium in Faser-Metall Laminaten ermöglichen. Reaktive Blendtechnologien werden entwickelt, um während der Polymerverarbeitung, z.B. von Polypropylen/Polyamid 6 Blends, in-situ Phasenvermittler herzustellen. Durch Einbau von definierten Oligo(tetrafluoroethene) Segmenten in Kodensationspolymere werden neben thermischen und mechanischen Eigenschaften auch Oberflächenspannungen und Gasdurchlässigkeiten variiert.
    Notes: Tailor-made segmented polymers play a key role in the development of novel polymeric materials exhibiting unsual bulk and surface properties. As a function of molecular architectures of segmented polymers, it is possible to control polymer morphologies and to achieve property synergisms. Selected examples are presented to illustrate basic concepts and recent developments. Segmented reactive liquid rubbers, containing an immiscible silicone segment flanked by two miscible oligo(caprolactone) segments, are efficient epoxy toughening agents. In such nano-phase-separated silicone-modified IPNs impact strength is improved without sacrificing dimensional stability. Compatibilized blends of segmented phenolic polyurethane and nitrile liquid rubbers produce rubber blend microphases dispersed in epoxy prepregs which are used to bond aluminum sheets in structural laminates. Reactive blending technologies are developed to produce segmented polymers as blend compatibilizers during melt processing, e.g., of polypropylene/polyamide 6 blends. Incorporation of oligo(tetrafluoroethene) segments into various condensation polymers modifies thermal and mechanical properties as well as surface tension and gas permeabilities.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1994.052230104
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  • 4
    Electronic Resource
    Electronic Resource
    An INDO/S-CI treatment including spin-orbit interaction based on Rumer spin functions. Application to the hydrated cerium ion (1991)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 40 (1991), S. 545-555 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We examine the inclusion of spin-orbit effects within the Rumer configuration interaction technique and discuss its implementation in the spectroscopic version of the intermediate neglect of differential overlap model (INDO/S-CI). An efficient strategy for calculating excitation energies, transition moments, and Mulliken populations for Rumer-adapted functions is described. As an example, results are presented for the ground and excited states of the hydrated trivalent cerium ion [Ce(H2O)9]3+, which confirm the low energy assignments to 4ƒ → 5 d transitions split by some 10000 cm-1 through spin-orbit coupling and ligand field interaction. Comparisons are made between this technique and one that we have used previously that utilizes configuration interaction over double-group adapted linear combinations of determinants.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560400848
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  • 5
    Electronic Resource
    Electronic Resource
    Electronic and magnetic properties of organometallic clusters: From the molecular to the metallic state (1992)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 44 (1992), S. 605-619 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We have performed a linear combination of Gaussian-type orbitals, LCGTO, local density functional, LDF, calculations on a series of low- and high-nuclearity carbonylated Ni clusters and on their naked counterparts. We have found that while the bare Ni clusters do exhibit several features in common with the bulk metal, the low-nuclearity carbonylated clusters do not show any metallic behavior. Signs of a developing metallic character are found for high-nuclearity Ni cluster carbonyls where it is possible to distinguish between “surface” atoms, which are directly interacting with the ligand sphere, and “bulk” atoms, which are only interacting with other metal atoms. Through the analysis of the magnetic properties of these systems it is possible to formulate a general model which rationalizes both the metallic behavior of the free Ni clusters and the nonmetallic behavior in certain carbonylated Ni clusters. This model is based on the perturbations induced by the ligands on the electronic structure of the metal atoms in the cluster. © 1992 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560440854
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  • 6
    Electronic Resource
    Electronic Resource
    The role of compatibilizers and elastomeric interlayers in glass-bead-reinforced poly(propylene) (1994)
    Weinheim : Wiley-Blackwell
    Macromolecular Rapid Communications 15 (1994), S. 691-696 
    Details
    ISSN: 1022-1336
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/marc.1994.030150905
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  • 7
    Electronic Resource
    Electronic Resource
    Reactive blending of polypropylene/polyamide-6 in the presence of tailor-made succinic anhydride-terminated oligopropene compatibilizersDedicated to honor the 70th birthday of Professor Dr. Dr. h.c. H.-J. Cantow. (1993)
    New York, NY : Wiley-Blackwell
    Polymers for Advanced Technologies 4 (1993), S. 465-474 
    Details
    ISSN: 1042-7147
    Keywords: Polypropylene ; Polyamide ; Blend ; Compatibilizer ; Ziegler-Natta catalysts ; Metallocene ; Maleic anhydride ; Graft copolymer ; Block copolymer ; 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
    Notes: Various anhydride-terminated isotactic and atactic oligopropenes of number average molecular weights ranging between 1,000 and 10,000 g/mole, prepared by maleinating vinylidene-terminated propene oligomers obtained with isospecific and nonstereospecific metallocene-based Ziegler-Natta catalysts, have been evaluated as blend compatibilizers of polypropylene/polyamide-6 (70 vol%/30 vol%) blends to study the role of blend compatibilizer molecular architecture. When added during processing, as shown by IR spectroscopic analysis, the anhydride-terminated oligopropenes react with the amine-terminated polyamide-6 to yield polypropylene-block-polyamide-6 in situ. Such block copolymers are efficient dispersing agents. While the polyamide dispersion in the polypropylene continuous phase is not affected by blend compatibilizer stereoregularities, both stiffness and yield stress as well as notched Charpy impact strength increase with increasing stereoregularities and molecular weights. With oligopropene molecular weights exceeding 1,150 g/mole, the average size of the dispersed polyamide microphases correlates with the volume fraction of the oligopropene-block-polyamide-6 blend compatibilizer and the dicarboxylic acid anhydride/amine molar ratio.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pat.1993.220040710
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  • 8
    Electronic Resource
    Electronic Resource
    Anisotropic dispersion polymerization of N-(4-aminobenzoyl)-caprolactam in polymer melts (1994)
    New York, NY : Wiley-Blackwell
    Polymers for Advanced Technologies 5 (1994), S. 282-286 
    Details
    ISSN: 1042-7147
    Keywords: Dispersion ; Microcomposite ; Polyamide ; Polyaramide ; Molecular composite ; 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
    Notes: When N-(4-aminobenzoyl)-caprolactam (PAC) is injected into polymer melts, dispersions of anisotropic polyaramide particles with average diameters of 100-400 nm and aspect ratios of 5-10 are formed within few minutes. At 200°C PAC dispersion polymerization yields caprolactam and predominantly poly(p-phenylenebenzamide), whereas with increasing polymerization temperatures PAC ring-opening polymerization accounts for the incorporation of 6-aminocaproic acid units into the polyaramide backbone. Covalent bond formation between microparticle surfaces and functional groups of the matrix polymer provides excellent interfacial adhesion and stabilizes the anisotropic polyaramide microparticle dispersions. This in situ PAC dispersion polymerization during melt processing, producing polyaramide-whisker reinforced thermoplastics, represents a versatile route to organic microcomposites exhibiting improved stiffness and strength.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pat.1994.220050507
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  • 9
    Electronic Resource
    Electronic Resource
    Das Konzessions-Handbuch der Hoechst AGVortrag von W. Bender auf dem Jahrestreffen der Verfahrens-Ingenieure, 25. bis 27. Sept. 1991 in Köln. (1992)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 64 (1992), S. 204-205 
    Details
    ISSN: 0009-286X
    Keywords: Behörden-Engineering ; BImSchG ; Genehmigungsantrag ; Konzession ; Projektmanagement ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.330640230
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  • 10
    Electronic Resource
    Electronic Resource
    Comparison of maleic anhydride-grafted poly(propylene) with maleic anhydride-grafted polystyrene-block-poly(ethene-co-but-1-ene)-block-polystyrene as blend compatibilizers of poly(propylene)/polyamide-6 blends (1993)
    Basel : Wiley-Blackwell
    Die Makromolekulare Chemie, Rapid Communications 14 (1993), S. 503-509 
    Details
    ISSN: 0173-2803
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/marc.1993.030140808
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