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  • Chemistry  (34)
  • General Chemistry  (6)
  • 78.20.Dj
  • AMS(MOS)
  • 1990-1994  (19)
  • 1985-1989  (17)
  • 1
    Electronic Resource
    Electronic Resource
    An algorithm to compute a sparse basis of the null space (1985)
    Springer
    Numerische Mathematik 47 (1985), S. 483-504 
    Details
    ISSN: 0945-3245
    Keywords: AMS(MOS) ; 65F30 ; CR: G1.3
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Summary LetA be a realm×n matrix with full row rankm. In many algorithms in engineering and science, such as the force method in structural analysis, the dual variable method for the Navier-Stokes equations or more generally null space methods in quadratic programming, it is necessary to compute a basis matrixB for the null space ofA. HereB isn×r, r=n−m, of rankr, withAB=0. In many instancesA is large and sparse and often banded. The purpose of this paper is to describe and test a variation of a method originally suggested by Topcu and called the turnback algorithm for computing a banded basis matrixB. Two implementations of the algorithm are given, one using Gaussian elimination and the other using orthogonal factorization by Givens rotations. The FORTRAN software was executed on an IBM 3081 computer with an FPS-164 attached array processor at the Triangle Universities Computing Center and on a CYBER 205 vector computer. Test results on a variety of structural analysis problems including two- and three-dimensional frames, plane stress, plate bending and mixed finite element problems are discussed. These results indicate that both implementations of the algorithm yielded a well-conditioned, banded, basis matrixB whenA is well-conditioned. However, the orthogonal implementation yielded a better conditionedB for large, illconditioned problems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01389453
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  • 2
    Electronic Resource
    Electronic Resource
    Reduction of optical absorption at a wavelength of around 0.8 μm in LPE garnet (TmBiCa)3(FeGaPt)5O12 (1985)
    Springer
    Applied physics 38 (1985), S. 281-284 
    Details
    ISSN: 1432-0630
    Keywords: 78.20.Dj ; 68.55.+b ; 78.20.Ls
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Liquid-phase epitaxy (LPE) garnet films (TmBiCa)3(FeGaPt)5O12 have been grown using only Bi2O3 as the flux so that the film containing Bi gives high specific Faraday rotation. The film does not contain Pb, which may affect optical absorption. The optical absorption coefficientα at 810 nm has been effectively reduced by doping Ca in the melt. Our data show that a minimum level ofα and of the anisotropy constantK u and also the maximum of the electrical resistivityϱ are achieved when Ca2+ replaces Fe2+. Fe2+ results from Pt4+ incorporation in the film due to a Bi2O3 flux attack on a Pt crucible. Using a compensated film,α of 58 cm−1 and a figure of merit of 9deg/dB were obtained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00616064
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  • 3
    Electronic Resource
    Electronic Resource
    Incorporation of a well-defined polyether side-chain into segmented poly(ether-urethane urea) and examination for blood-compatibility (1989)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 172 (1989), S. 177-183 
    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: Es wird eine neue Methode zur Einführung von hydrophilen Polyetherseitenketten in segmentierte Polyurethane unter Verwendung eines Polypropylenoxid-Macromeren mit 1,3-Diol-Gruppen an einem Kettenende, die als Kettenverlängerer fungieren, beschrieben. In diesem Prozeß wird eine Seitenkette quantitativ und direkt in medizinische Polyurethanelastomere eingebaut. Diese Entwicklung ist auch für Biowerkstoffe in künstlichen Organen von Interesse.
    Notes: A new method of introducing a hydrophilic polyether side chain into segmented polyurethane using a polypropylene oxide macromer with 1,3-diol at one chain-end, which behaves as chain extender, is described. In this procedure, a molecular-designed side-chain is incorporated quantitatively and directly into polyurethane biomedical elastomer. The design is also of interest to biomaterials in artificial organs.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1989.051720115
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  • 4
    Electronic Resource
    Electronic Resource
    Synthesis of polysiloxanes with pendant viologen groups and their characteristic behavior of aggregation and deposition observed on electron transfer (1990)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 191 (1990), S. 2871-2880 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: In order to prepare polysiloxanes with the ability of electron transport, pendant viologen groups were introduced. Chloromethylated poly(methyl-β-phenethylsiloxane) (2) was reacted with monoalkylbipyridinium chlorides (3a, 3b) to give polysiloxanes (4a, 4b) containing pendant viologen groups. These polymers show reversible redox behavior. They are deposited on ITO electrodes when the pendant viologen dication groups are electrochemically reduced to cation radicals. The polymer deposited shows an absorption maximum (λmax) at 500 nm, which is due to a highly aggregated structure of cation radicals. On the contrary, when the electrode was coated by the polymer before the measurement (pre-cast membrane), the cation radicals formed electrochemically show λmax at 530 nm, indicating that the degree of aggregation is lower than that in the membrane formed reductively from solution.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1990.021911203
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  • 5
    Electronic Resource
    Electronic Resource
    Luminescent characteristics of tris(2,2′-bipyridine)-ruthenium(II) adsorbed in a silk fibroin membrane (1991)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 192 (1991), S. 1649-1654 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The emission characteristics of the excited state of tris(2,2′-bipyridine)ruthenium(II), Ru(bpy)32+, adsorbed on a silk fibroin membrane is studied. The life time of the excited state of the adsorbed Ru(bpy)32+ is unusually longer (1 000 ns) than that of Ru(bpy)32+ in aqueous solution (598 ns). The excited state of the adsorbed Ru(bpy)32+ is quenched by oxygen when dipped in methanol, but not in water. The quenching by oxygen in methanol follows the Stern-Volmer equation. The luminescent characteristics of the adsorbed Ru complex is discussed in terms of binding in hydrophobic domains composed of tyrosine residues of the protein.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1991.021920717
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  • 6
    Electronic Resource
    Electronic Resource
    Dioxygen sensitivity of a photoexcited thin film of phthalocyanine dispersed in poly(N-vinylcarbazole) (1988)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 189 (1988), S. 2419-2423 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Thin films (thickness 0,3 μm) of a mixture of phthalocyaninatozinc(II) (1) and poly(1-vinylcarbazole) (2) are prepared by coating from a solution on ITO glass. The blue coloured films are investigated in an electrochemical cell under irradiation with visible light. In the presence of dioxygen from air the films exhibit an intensive cathodic photocurrent. The action spectrum of the photocurrent corresponds to the absorption spectrum of the phthalocyanine. The results show a device which can be switched by air and visible light.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1988.021891019
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  • 7
    Electronic Resource
    Electronic Resource
    Quenching of the excited state of membranes having polymerpendant tris(2,2′-bypyridine)ruthenium(II) groups by methylviologen and dioxygen (1987)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 188 (1987), S. 2011-2017 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Quenching of the excited state of copolymer-pendant Ru(bpy)2+3 membranes by methylviologen (MV2+) and dioxygen was studied and its application proposed. The copolymers used were the copolymer of styrene (St) and 4-methyl-4′-vinyl-2,2′-bipyridine (Vbpy) and that of methyl methacrylate (MMA) and Vbpy. The copolymer-pendant complexes were prepared by reaction of the St- and MMA-copolymers with cis-Ru(bpy)2Cl2. The excited state of the St-copolymer complex membrane was not quenched by MV2+ solution in aqueous medium, but quenched in methanol. The excited state of the MMA-copolymer complex membrane was not quenched by MV2+ neither in water nor in water/methanol mixture. The excited state of St-copolymer complex membrane was not quenched by dioxygen in water, but in methanol. The excited state of MMA-copolymer complex membrane was quenched by dioxygen both in water and water/methanol mixture. The quenching by dioxygen can be used to measure the oxygen concentration in solutions.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1987.021880823
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  • 8
    Electronic Resource
    Electronic Resource
    Quenching of photo-excited state of copolymer pendant Ru(bpy)32+ complexes with methylviologen (1986)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 24 (1986), S. 2749-2756 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Copolymer pendant tris(2,2′-bipyridine)ruthenium(II) complexes were prepared from the copolymers of 4-methyl-4′-vinyl-2,2′-bipyridine with styrene, acrylic acid, methyl methacrylate, hydroxyethyl methacrylate, acrylonitrile, N-vinylpyrrolidone, 4-vinylpyridine, and quaternized 4-vinylpyridine. The quenching of the photo-excited state of the polymer complexes by methylviologen was studied. Pendant anionic groups such as acrylate enhanced remarkably the quenching of the cationic sensitizer by the cationic substrate, however, pendant cationic groups such as quaternized pyridine did not affect the reaction. The polymer chain showed generally retarding effect on the quenching reaction.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1986.080241104
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  • 9
    Electronic Resource
    Electronic Resource
    Why are random copolymers of styrene and acrylic acid effective as stabilizers for nonaqueous dispersion polymerization of styrene? (1994)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 32 (1994), S. 571-574 
    Details
    ISSN: 0887-624X
    Keywords: styrene-acrylic acid random copolymers ; copolymer composition distribution ; nonaqueous dispersion polymerization ; HPLC ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1994.080320318
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  • 10
    Electronic Resource
    Electronic Resource
    Polynuclear-metal-complex batteryDedicated to Professor Georg Manecke in the Free University of Berlin for his 70th birthday. (1986)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Letters Edition 24 (1986), S. 435-437 
    Details
    ISSN: 0887-6258
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1986.140240901
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