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  • Articles  (44)
  • Wiley-Blackwell  (44)
  • 1990-1994  (44)
  • Physics  (40)
  • Mathematics  (4)
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  • Articles  (44)
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  • 11
    Electronic Resource
    Electronic Resource
    Adiabatic anionic polymerization of caprolactam in the presence of N-acylated caprolactam macroactivator: Kinetic study (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 50 (1993), S. 1671-1681 
    Details
    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: In this study, bis ∊-caprolactam bis-diphenyl methane diisocyanate polypropylene glycol 1000 used as the macroactivator was prepared and well characterized prior to use. The anionic polymerization of ∊-caprolactam with the macroactivator as a function of the macroactivator concentration was adiabatically carried out. The adiabatic temperature rise method as well as the macrokinetics were used for elucidation of the kinetics of the polymerization. A nonlinear regression technique was used for determining the parameters of the macrokinetic equation. The equilibrium conversion and equilibrium time obtained were 94-96% and 2-9 min depending on the macroactivator concentration. The effects of the concentrations of macroactivator and ∊-caprolactam on the initial rate, apparent overall reaction rate, and the empirical parameters were studied. A side reaction induced by the transfer of the proton in the isocyanurate group of the macroactivator to caprolactam anion was found. According to this finding, a new reaction kinetic model was proposed by properly modifying the macrokinetic equation. © 1993 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1993.070501001
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  • 12
    Electronic Resource
    Electronic Resource
    A thermally stimulated current/relaxation map analysis of the relaxation processes in aromatic polyester, liquid crystal polymer film (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 53 (1994), S. 587-608 
    Details
    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: Thermally stimulated current (TSC) and relaxation map analysis (RMA) have been applied to the examination of dynamics of thermally induced relaxation processes in highly oriented, wholly aromatic, polyester liquid crystalline polymer films. Films of two compositions were examined. A primary distinction in composition was the difference in level of 6-hydroxy-2-napthoic acid. Following an analysis protocol developed by Sauer et al., it was found that values of activation enthalpy were well above the zero entropy value at temperatures well below the Sauer “Tg.” This indicates a high level of cooperativity in rotational relaxation processes even at low temperatures. Cooperative rotational relaxation domains were postulated to account for this behavior. The persistence of cooperativity above the Sauer “Tg.” is evidence that these materials did not undergo a conventional glass transition at any temperature in the range-80 to 200°C. The behavior of these materials as a model system of “loosely bundled rods” was examined using a modified Barker-Crine analysis. This type of model behavior seemed to fall off at relatively low temperatures. The occurrence of rotational processes at high temperatures with little or no loss in orientation suggests that polymer chains are physically constrained to maintain their relative positions. © 1994 John Wiley & Sons, Inc.
    Additional Material: 24 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1994.070530511
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  • 13
    Electronic Resource
    Electronic Resource
    Acetals as nucleating agents for polypropylene (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 52 (1994), S. 591-596 
    Details
    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: Nucleating agents increase the impact strength, tensile strength, and tensile elasticity modulus of semicrystalline polymers. Nucleating agents also decrease product cycle times, resulting in a cost savings per product unit. We have synthesized and tested 15 compounds as nucleactors for polypropylene. Of these, trinapthylidene sorbitol, tri-(4-methyl-1-naphthylidene)sorbitol, tri-(4-methoxy-1-naphthylidene) sorbitol, and dibenzylidene xylitol are efficient nucleators of polypropylene. Trinaphthylidene sorbitol (tns) has two major diastereomers: The “S” diastereomer yields a faster crystallization rate for polypropylene than does the commercial nucleator dibenzylidene sorbitol (Millad 3905). Crystallization rates are 208 and 88, respectively (t-1.05 min-1 × 1000). The “R” diastereomer, however, is a poor nucleator and interferes with the nucleating activity of the “S” diastereomer. A 52/48 mixture of diastereomers does not nucleate polypropylene, even at twice the concentration. This is first time that the importance of stereochemistry has been demonstrated in the nucleating action. © 1994 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1994.070520502
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  • 14
    Electronic Resource
    Electronic Resource
    Tensile drawing behaviour of polyethylene terephthalate (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 42 (1991), S. 1911-1920 
    Details
    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: A wide range of polyethylene terephthalate fibres was prepared by melt spinning to different degrees of molecular orientation. The tensile drawing behaviour of these fibers was then studied, either by drawing over a heated cylinder at 85°C or by drawing over both a heated cylinder and a plate at 180°C. The mechanical properties and structure of the subsequent drawn fibres are discussed in terms of the network draw ratio, determined by matching true stress-strain curves for the drawn and initial melt spun fibres. It is shown that this procedure provides valuable insight into subtle differences in properties and structure that can arise from differences in processing routes.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1991.070420714
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  • 15
    Electronic Resource
    Electronic Resource
    Reactive ion etching of selected polymers in O2 and in CF4/O2 (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 47 (1993), S. 2135-2142 
    Details
    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: A series of 17 polymers was etched in the reactive ion-etching (RIE) mode. The etch rates were monitored using a laser interferometer. The gases used were oxygen alone and a mixture of carbon tetrafluoride with oxygen (8% O2). The polymers fell into three groups: the aromatics (polystyrene and derivatives), the aliphatics (methacrylates and vinyl acetate), and the cellulosics (methyl ether and nitrate). In oxygen with a power density of 0.25 W/cm2, the etch rates for the three groups fell in the range of 200-300 nm/min, 350-450 nm/min, and 500-850 nm/min, respectively. The etch rates were also measured at a power density of 0.50 W/cm2. The etch rates at the higher-power density were about 75-80% higher than those at the lower-power density. The etch rate in the fluoride mixture was about half that in the oxygen, all other parameters being the same. Plasticizers that lower the glass transition temperature of polymers based on vinyl chloride, methyl methacrylate, or styrene do not change the etch rate of the polymers very much. There is a slight increase in the rate for polystyrene and a slight decrease in the rate for poly(methyl methacrylate). All the effects of composition on etching rate can be correlated to a first approximation with the molar fractions of carbon and oxygen in the resist. © 1993 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1993.070471207
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  • 16
    Electronic Resource
    Electronic Resource
    Non-linear parabolic problem associated with the penetration of a magnetic field into a substance (1993)
    Chichester, West Sussex : Wiley-Blackwell
    Mathematical Methods in the Applied Sciences 16 (1993), S. 281-295 
    Details
    ISSN: 0170-4214
    Keywords: Mathematics and Statistics ; Applied Mathematics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: We study the following initial and boundary value problem: In section 1, with u0 in L2(Ω), f continuous such that f(u) + ∊ non-decreasing for ∊ positive, we prove the existence of a unique solution on (0,T), for each T 〉 0. In section 2 it is proved that the unique soluition u belongs to L2(0, T; H01 ∩ H2) ∩ L∞(0, T; H01) if we assume u0 in H01 and f in C1(∝,∝). Numerical results are given for these two cases.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mma.1670160404
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  • 17
    Electronic Resource
    Electronic Resource
    Methacrylate-based block ionomers I: Synthesis of block ionomers derived from t-butyl methacrylate and alkyl methacrylatesDedicated to Professor Maurice Morton to commemorate the establishment of the Maurice Morton Institute of Polymer Science at the University of Akron. (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Polymer International 33 (1994), S. 205-216 
    Details
    ISSN: 0959-8103
    Keywords: block ionomer ; anionic polymerization ; methacrylates ; 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: Diblock and triblock copolymers of t-butyl methacrylate (tBMA) with 2-ethylhexyl methacrylate (EHMA) and n-hexyl methacrylate were prepared via alkyl lithium initiation and sequential addition techniques in THF at -78°C. The tBMA blocks were quantiatively and selectively hydrolyzed to afford poly(methacrylic acid) (PMAA) blocks which were then neutralized with alkali metal bases to form block ionomers. The unhydrolyzed copolymers had a phase mixed morphology as evidenced by thermal analysis while the hydrolyzed and neutralized polymers were multiphase materials. The carboxylic acid and ioncontaning triblock copolymers formed gels in nonpolar solvents which could be disrupted by the addition of polar additives. Certain carboxylic acid and ioncontaining EHMA/tBMA diblock copolymers also showed this behavior. The triblock ionomers did not show thermoplastic flow prior to degradation, except at the lowest ionic content studied (2%).
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pi.1994.210330212
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  • 18
    Electronic Resource
    Electronic Resource
    Monolayer formation of chitin derivatives containing PMMA side-chains (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Polymer International 35 (1994), S. 303-307 
    Details
    ISSN: 0959-8103
    Keywords: monolayer formation ; PMMA-grafted chitin derivative ; phase transition ; accessible monolayer to lysozyme ; 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 monolayer behaviour of poly(methyl methacrylate) (PMMA)-grafted chitin derivatives was studied on an air-water interface by measuring surface pressure-area isotherms. The formation of a stable monolayer indicates the well-defined packing and orientation of the chitin derivative, which can be regulated by the main-chain length under appropriate experimental conditions. The isotherms exhibit a transition point from a liquid expanded phase to a condensed phase at a surface pressure of approximately 15mN/m for almost all monolayers examined. The transition pressure decreases with increase of temperature from 10 to 20°C. The properties of the sub-phase affected the formation of a monolayer greatly. The collapse of a surface film takes place at lower pressure on the sub-phase of a 0.1 M NaCI solution. After introducing lysozyme at a concentration at 2.4 × 10-8M to the sub-phase, the monolayer showed an extensively expanded phase with a longer transition region. This indicates that the monolayer was degraded by the lysozyme, resulting in a disordered structure. The results are contrasted with those of an aqueous phase where N-acetylglucosamine residues may be inaccessible to lysozyme so that the degradation of the chitin derivative occurs at a very slow rate.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pi.1994.210350401
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  • 19
    Electronic Resource
    Electronic Resource
    Matrix-assisted laser desorption ionization Fourier-transform mass spectrometry (1994)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 8 (1994), S. 498-500 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290080615
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  • 20
    Electronic Resource
    Electronic Resource
    Photoswitch based on bacteriorhodopsin Langmuir-Blodgett films (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Advanced Materials for Optics and Electronics 4 (1994), S. 219-224 
    Details
    ISSN: 1057-9257
    Keywords: Bacteriorhodopsin ; Langmuir-Blodgett films ; Differential response ; Photoswitch ; Photoalarm ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Langmuir-Blodgett (LB) films of bacteriorhodopsin (bR) without addition of lipids were deposited on indium tin oxide (ITO) conductive electrodes. A sandwich photocell with a juction structure of ITO/bR/electrolyte/ITO has been constructed in which the bR LB film was put into contact directly with an aqueous electrolyte immobilized in an agar gel. Under visible light irradiation a transient photocurrent due to a change in light intensity can be observedl showing the property of vision-imitative material. It can be used as a multiple optical switch, since it gives positive and negative transient photocurrnts during application and removal of light irradiation respectively and has a photoresponse repeatedly in the same direction when the light intensity increases or decreases stepwise. A photoalarm consisting of the bR photocell and an amplifier was set up by utilizing the switching function of the bR LB film.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/amo.860040305
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