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  • Polymer and Materials Science  (6)
  • 79.40
  • PACS. 77.84.Nh Liquids, emulsions, and suspensions; liquid crystals - 61.30.Cz Theory and models of liquid crystal structure - 61.30.Jf Defects in liquid crystals
  • hydrogen bonding
  • 1995-1999  (7)
  • 1975-1979  (4)
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Keywords
Publisher
Years
Year
  • 1
    ISSN: 1572-8854
    Keywords: Crystal structure ; bicyclononane ; triazene ; bis-triazene ; nitrile substituent ; nitro substituent ; trifluoromethyl substituent ; hydrogen bonding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal and molecular structure of a series of 3,7-bis(arylazo)-1,3,5,7-tetraazabicyclo[3.3.1] nonanes (1a–d) have been determined by single crystal X-ray diffraction analysis. All four compounds have the same feature, that the tetraazabicyclononane unit assumes a cage-like structure with the aryltriazene moieties lying parallel to one another so that the aryl rings are held together by π – π stacking. Crystal data: 1a C17H18N10O4, triclinic, space group P − 1, a = 9.8899(10), b = 13.0845(13), c = 16.458(2) Å, α = 94.095(2)°, β = 107.004(2)°, γ = 111.027(2)°, V = 1863.5(3) Å3 and Z = 4; 1b, C19H18F6N8, orthorhombic, space group Pbca, a = 15.3210(8), b = 10.9512(6), c = 24.5698(13) Å, V = 4122.4(4) Å3 and Z = 8; 1c C19H18N10, monoclinic, space group P21/n a = 6.3742(6), b = 13.7343(13), c = 21.542(2)Å, β = 97.738(2)°, V = 1868.8(3) Å3, and Z = 4; 1d, C19H18N10, monoclinic, space group P21/c, a = 18.205(2), b = 17.398(2), c = 12.784(12) Å, β = 109.480(2)°, V = 3818.0(6) Å3, and Z = 8.
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  • 2
    ISSN: 1572-8854
    Keywords: Thiosemicarbazone ; 2-benzoylpyridine ; N4-substituted ; hydrogen bonding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract 2-Benzoylpyridine N4-methyl-N4-phenylthiosemicarbazone, HBz4MePh, monoclinic,P2(1)/n a=9.141(2),b=18.507(4),c=11.401(2) Å, β=110.58(3)o,V=1805.6(9) Å3,Z=4, μ=1.655 mm−1. HBz4MePh crystallizes in a hydrogen bonded Z isomeric conformation with respect to the C7−N2 bond. The intramolecular hydrogen bond is between N3−H...N1, and the S atom isZ to the azomethine nitrogne, N2.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 10 (1976), S. 265-268 
    ISSN: 1432-0630
    Keywords: 79.40 ; 73
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The field emission current from thin palladium films deposited on insulating tips in UHV was measured as a function of film thickness at relatively low field strengths. The observed periodic oscillations of the field emission current can be interpreted as the quantum size effect.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 10 (1999), S. 311-321 
    ISSN: 1434-6036
    Keywords: PACS. 77.84.Nh Liquids, emulsions, and suspensions; liquid crystals - 61.30.Cz Theory and models of liquid crystal structure - 61.30.Jf Defects in liquid crystals
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: We study the director field around a spherical particle immersed in a uniformly aligned nematic liquid crystal and assume that the molecules prefer a homeotropic orientation at the surface of the particle. Three structures are possible: a dipole, a Saturn-ring, and a surface-ring configuration, which we investigate by numerically minimizing the Frank free energy supplemented by a magnetic-field and a surface term. In the dipole configuration, which is the absolutely stable structure for micron-size particles and sufficiently strong surface anchoring, a twist transition is found and analyzed. We show that a transition from the dipole to the Saturn ring configuration is induced by either decreasing the particle size or by applying a magnetic field. The effect of metastability and the occurrence of hysteresis in connection with a magnetic field are discussed. The surface-ring configuration appears when the surface-anchoring strength W is reduced. It is also favored by a large saddle-splay constant K24. A comparison with recent experiments [#!itapdb:Poulin1997!#,#!itapdb:Poulin1998!#] gives a lower bound for W, i.e., for the interface of water and pentylcyanobiphenyl (5CB) in the presence of the surfactant sodium dodecyl sulfate.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 10 (1999), S. 515-523 
    ISSN: 1434-6036
    Keywords: PACS. 77.84.Nh Liquids, emulsions, and suspensions; liquid crystals - 61.30.Cz Theory and models of liquid crystal structure - 61.30.Jf Defects in liquid crystals
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: Recently, it was observed that water droplets suspended in a nematic liquid crystal form linear chains [Poulin et al., Science 275, 1770 (1997)]. The chaining occurs, e.g., in a large nematic drop with homeotropic boundary conditions at all the surfaces. Between each pair of water droplets a point defect in the liquid crystalline order was found in accordance with topological constraints. This point defect causes a repulsion between the water droplets. In our numerical investigation we limit ourselves to a chain of two droplets. For such a complex geometry we use the method of finite elements to minimize the Frank free energy. We confirm an experimental observation that the distance d of the point defect from the surface of a water droplet scales with the radius r of the droplet like .When the water droplets are moved apart, we find that the point defect does not stay in the middle between the droplets, but rather forms a dipole with one of them. This confirms a theoretical model for the chaining. Analogies to a second order phase transition are drawn. We also find the dipole when one water droplet is suspended in a bipolar nematic drop with two boojums, i.e., surface defects at the outer boundary. Finally, we present a configuration where two droplets repel each other without a defect between them.
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 50 (1976), S. 9-14 
    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: Verbindungen der Strukturformeln [π-C5H5M(CO)nX] (M = Fe, n = 2; M = Mo, n = 3; X = CH3, CH2C6H5, CH2Si(CH3)3, CH2OCH3, Sn(C6H5)3, SnCl3, HgCl, I), [Mn(CO)5CH3], und [(π-CH3C5H4)Mn(CO)3] wurden als Katalysatoren für die Härtung von Epoxidharzen unter verschiedenen Bedingungen geprüft. Es wurde gefunden, daß die Verbindungen [π-C5H5Fe(CO)2R] (R = CH3, CH2C6H5) und [π-C5H5Mo(CO)3CH3] wirksame lichtempfindliche Beschleuniger für die Anhydridhärtung von Expoxidharzen sind. Der Aktivierungsmechanismus wird diskutiert.
    Notes: Compounds of the types [π-C5H5M(CO)nX] (M = Fe, n = 2; M = Mo, n = 3; X = CH3, CH2C6H5, CH2Si(CH3)3, CH2OCH3, Sn(C6H5)3, SnCl3, HgCl, I), [Mn(CO)5CH3], and [(π-CH3C5H4)Mn(CO)3] have been examined as catalysts for the cure of epoxy resins under various conditions. It was found that the compounds [π-C5H5Fe(CO)2R] (R = CH3, CH2C6H5) and [π-C5H5Mo(CO)3CH3] are active photosensitizing agents for the anhydride cure of certain epoxy resins. The mechanism of the process is discussed.
    Additional Material: 1 Tab.
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  • 7
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 56 (1976), S. 157-162 
    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: 13C-und 1H-NMR-Untersuchungen haben überzeugend gezeigt, daß die Hauptkomponente des Epoxidharzes aus Phenolphthalein und Epichlorhydrin ein aromatischer Diglycidyläther mit einem Lactonring ist und nicht eine chinoide Verbindung mit Glycidylätherund Glycidylesterstruktur.
    Notes: 13C- and 1H-NMR studies have shown conclusively that the main component of the epoxy resin derived from phenolphthalein and epichlorohydrin is an aromatic diglycidyl ether containing a lactone ring, rather than a glycidyl ether-glycidyl ester compound containing a quinoid ring.
    Additional Material: 1 Tab.
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  • 8
    ISSN: 1057-9257
    Keywords: gallium nitride ; nanocrystallites ; detonation ; gallium azide ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: High quality nanoscale, phase-pure hexagonal gallium nitride (GaN) crystallites have been synthesized by the thermal induced detonation of molecular precursors of the type (R3N)Ga(N3)3 (R=CH3, C2H5, etc.). The method allows the control of the particle size regime from 2 to about 1000 nm. X-ray diffraction and Rietveld simulations revealed an anisotropic platelet-like shape of the particles. The obtained GaN material was as well characterized by transmission electron microscopy and electron diffraction, photoluminescence spectroscopy, SEM, IR, RAMAN, thermal gas effusion/mass spectrometry, thermal analysis, elemental analysis. Gas absorption measurements (BET method) showed a specific surface area of about 90 m2 · g-1. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 10 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 13 (1979), S. 339-342 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Additional Material: 3 Tab.
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  • 10
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 29 (1995), S. 619-626 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The mechanisms of wear in ultra-high-molecular-weight polyethylene (UHMWPE) acetabular cups were investigated on both laboratory simulator-tested cups and a clinically retrieved component. Two different levels of wear process were identified: one characterized by the formation and detachment of platelet-like flakes from initial machining marks, and the other by the formation of fine ripples and fibrils by repeated passes of microscopic asperities on the femoral head. Both wear processes could be described by a criterion of critical plastic strain. A theoretical model was developed to account for the generation of the microscopic wear particles based on such a critical strain criterion. Its predictions of the dependence of the UHMWPE wear rate on surface roughness and applied load were in excellent agreement with previously published experimental correlations. © 1995 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
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