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  • Chemistry  (12)
  • Polymer and Materials Science  (7)
  • 1995-1999  (7)
  • 1975-1979  (5)
  • 1
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A theoretical and experimental investigation of a water jet impinging on a melting solid surface has been carried out. Ice, octane, p-xylene, and olive oil served as the meltable solid materials, comprising a Prandtl number range of 5 to 2 800. An available laminar stagnation flow model was utilized to describe melting heat transfer in the jet impingement region. Melting rate measurements were found to agree quite well with the values predicted with this model.
    Additional Material: 9 Ill.
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  • 2
    ISSN: 0947-6539
    Keywords: electron transfer ; magnetic properties ; metalloporphryins ; polymers ; spin density ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: [MnIIITtBuPP]+[C4(CN)6].- · 5PhMe [MnIIITtBuPP = meso-tetrakis-(4′-tert-butylphenyl)porphinatomanganese(III)] has been prepared and structurally and magnetically characterized. The uniform, linear-chain (1-D) coordination polymer comprises alternating cations and anions. The bond lengths in planar ion [C4(CN)6].-]'- are 1.377(10) (CC-CC), 1.418(7) (C-CCC), 1.414 (C-CN), 1.457 (C-CNMn), 1.150 (C≡N), and 1.134 Å (C = NMn). The Mn-N-C angle is 172.3(4)°, and the intrachain Mn  -  Mn separation is 10.685 Å. Each [C4(CN)6].-]' unit is bonded to two MnIII atoms through the interior nitrogen atoms in a trans-μ2-N-σ manner with N-Mn bond lengths of 2.353 Å. The ṽCN absorptions are at 2217 (w, br) and 2190 (m) cm-1. Above 50 K the magnetic susceptibility of [MnIIITtBuPP]+[C4(CN)6].- can be fitted to the Curie-Weiss expression, χ∝1(T - θ), with an effective θ of -13 K. This is consistent with weak antiferromagnetic coupling, which is in contrast to the effective θ of +67 K for the uniform chain [MnIIIOEP]+[C4(CN)6].- [OEP = octaethylporphinato]. Here, the [C4(CN)6].-'- units are bonded to the MnIII centers through endo CN nitrogen atoms in a similar trans-μ2 manner. Density functional theory MO calculations reveal that the spin density of the CN nitrogen atom bound to [MnIIITtBuPP]+ (0.019 μBÅ-3) is significantly lower than that of the N atom bound to [MnIIIOEP]+ (0.102 μBÅ-3). This is consistent with the reduced spin coupling observed for [MnIIITtBuPP]+[C4(CN)6].-with respect to [MnIIITtBuPP]+[C4(CN)6].-, as evidenced by the lower θ value. The different orientations of the [C4(CN)6].- units - almost perpendicular (84.72°) for [MnIIITtBuPP]+[C4(CN)6].- and substantially tilted (32.1°) for [MnIIIOEP]+ [C4(CN)6].- may also contribute to the poorer overlap and weaker spin coupling. Hence, binding between sites with large spin densities is needed to stabilize strong ferromagnetic coupling.
    Additional Material: 4 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 33 (1995), S. 1227-1234 
    ISSN: 0887-624X
    Keywords: polyanilines ; derivatives ; chemical synthesis ; oxidation state ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Syntheses of parent polyaniline and methyl, methoxy, and ethoxy ortho-substituted polyanilines were performed using the conventional chemical methodology and monitored using the new open-circuit-potential (Voc) profile technique. The intermediate pernigraniline oxidation state was identified and isolated at the Voc maximum (A) during the conventional chemical synthesis of poly(o-methoxyaniline) in the emeraldine oxidation state. The introduction of the substituent on the aniline ring leads to longer polymerization times and lower Voc values. Syntheses in the presence of two different monomers in solution were also investigated and showed preferential polymerization of the monomer with the lowest Voc potential. All polymers produced were characterized by elemental analysis, gel permeation chromatography, UV-VIS spectroscopy, and cyclic voltammetry. The influence of the substituent on the Voc profile and on the polymer characteristics are rationalized in terms of steric and electronic effects. © 1995 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
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  • 4
    ISSN: 0935-9648
    Keywords: 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 , Physics
    Additional Material: 3 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 2037-2050 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Many ligands, including basic polypeptides, histones, and other proteins bind nonspecifically to DNA in such a way as to render unavailable for further binding several contiguous sites (generally bases or base pairs). An accurate description of the kinetics of such large ligand binding requires a more complex theoretical analysis than does the study of the binding of small ligands to DNA. An exact analytical solution of the problem does not appear feasible. Instead, a Monte Carlo approach is developed which provides an essentially exact numerical solution by simulating the binding experiment using a model one-dimensional lattice to represent the DNA molecule. For the limiting cases of totally irreversible binding and of instantaneous redistribution of bound ligands along the lattice, relatively simple equations can be written and solved for the binding kinetics. These solutions and their realms of applicability are discussed in some detail.
    Additional Material: 3 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 14 (1975), S. 2401-2415 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Interaction between polylysine and DNA's of varied G + C contents was studied using thermal denaturation and circular dichroism (CD). For each complex there is one melting band at a lower temperature tm, corresponding to the helix-coil transition of free base pairs, and another band at a higher temperature t′m, corresponding to the transition of polylysine-bound base pairs. For free base pairs, with natural DNA's and poly(dA-dT) a linear relation is observed between the tm and the G + C content of the particular DNA used. This is not true with poly(dG)·poly(dC), which has a tm about 20°C lower than the extrapolated value for DNA of 100% G + C. For polylysine-bound base pairs, a linear relation is also observed between the t′m and the G + C content of natural DNA's but neither poly(dA-dT) nor poly(dG)·poly(dC) complexes follow this relationship. The dependence of melting temperature on composition, expressed as dtm/dXG·C, where XG·C is the fraction of G·C pairs, is 60°C for free base pairs and only 21°C for polylysine-bound base pairs. This reduction in compositional dependence of Tm is similar to that observed for pure DNA in high ionic strength. Although the t′m of polylysine-poly(dA-dT) is 9°C lower than the extrapolated value for 0% G + C in EDTA buffer, it is independent of ionic strength in the medium and is equal to the tm0 extrapolated from the linear plot of tm against log Na+. There is also a noticeable similarity in the CD spectra of polylysine· and polyarginine·DNA complexes, except for complexes with poly(dA-dT). The calculated CD spectrum of polylysine-bound poly(dA-dT) is substantially different from that of polyarginine-bound poly(dA-dT).
    Additional Material: 8 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 765-788 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Exact solutions are obtained for the time dependence of the extent of irreversible binding of ligands that cover more than one lattice site to a homogeneous one-dimensional lattice. The binding may be cooperative or noncooperative and the lattice either finite or infinite. Although the form of the solution is most convenient when the ligand concentration is buffered, exact numerical or approximate analytical solutions, including upper and lower bounds, can be derived for the case of variable ligand concentration as well. The physical reason behind the relative simplicity of the kinetics of irreversible as opposed to reversible binding in such systems is discussed.
    Additional Material: 6 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 18 (1978), S. 908-916 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Hydrostatic extrusion of high density polyethylene at an extrusion ratio of 15:1 was investigated in the temperature range between 100 and 134°C. A thin-walled tube was extruded having a tensile strength of 370 MPa and a tensile modulus of 10 GPa. The extrusion rate was limited by severe extrudate distortion which occurs at a limiting shear stress under stick-slip conditions. Even during steady extrusion wall slip was evident. At a constant extrusion speed, the extrusion pressure was found to be very sensitive to the extrusion temperature. An increase from 120 to 125°C reduced the extrusion pressure by half. Various thermal pretreatments of the starting billets were found to have little effect on the extrusion behavior and physical properties of the extrudate.
    Additional Material: 15 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 57 (1995), S. 751-765 
    ISSN: 0021-8995
    Keywords: 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 , Physics
    Notes: The influence of fiber type and fiber-surface properties on matrix flow behavior was investigated using structural reaction injection-molding (SRIM). The influence of fiber type, fiber-surface properties, and matrix type on strength properties in elastomeric composites reinforced with nonwoven fibrous structures was investigated using tensile tests on elastomer composite samples from SRIM and latex coagulation (LC) fabrication methods and the microbond strength method on individual fibers. The fibers used were PET, LLDPE, and p-aramid. Fibers were treated with epoxy, styrene, and isocyanate derivatives, which make the surface chemically reactive. Treatments were also made with NaOH and a copolymer of polyester and polyol ether, causing a change in the fiber surface energy. The matrix types were polyurethane elastomer and natural rubber. The results show that the surface treatments which produced a change in the surface energy influenced the flow rate of the matrix polymer during the composite fabrication process. The treatments resulted in chemically reactive fiber surfaces which improved the fiber-matrix bond strength without affecting the Young's modulus of the composite material. Good correlation was found between bond strength and surface energy including the dispersive component of surface energy in the case of polyurethane elastomer and surface-modified PET fibers. The age of the polyurethane matrix has a marked influence on the bond strength. The fiber volume fraction in composites has a strong influence on the Young's modulus of the elastomer composite. © 1995 John Wiley & Sons, Inc.
    Additional Material: 16 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 34 (1996), S. 1005-1018 
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The dilute solution properties of copolymers are briefly discussed in relation to those of the parent homopolymers. It is shown that copolymer molecules are usually more expanded in solution than would be expected from the averaged behavior of the pure polymers, because of repulsive interactions between the unlike monomer units. A thermodynamic parameter χAB characterizing these interactions can be derived from measurements of the dilute solution properties of copolymers. In favorable cases this parameter can be independently evaluated from studies of ternary systems composed of the two parent homopolymers and a solvent, thus allowing prediction of the behavior of the copolymer. Light scattering and viscosity measurements on fractions of approximately equimolal copolymers of styrene and methyl methacrylate are presented and analyzed. The values of χAB deduced from the results in two solvents agree satisfactorily with each other, but are somewhat larger than those earlier obtained from measurements on ternary systems.
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