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  • Polymer and Materials Science  (49)
  • C"4-plant  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Multiple cDNAs of phosphoenolpyruvate carboxylase in the C"4 dicot Flaveria trinervia
    Amsterdam : Elsevier
    FEBS Letters 292 (1991), S. 133-136 
    Details
    ISSN: 0014-5793
    Keywords: C"4-plant ; Flaveria ; Gene family ; Phosphoenolpyruvate carboxylase
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/0014-5793(91)80850-3
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  • 2
    Electronic Resource
    Electronic Resource
    Multiple cDNAs of phosphoenolpyruvate carylase in the C"4 dicotFlaveria trinervia
    Amsterdam : Elsevier
    FEBS Letters 292 (1991), S. 133-136 
    Details
    ISSN: 0014-5793
    Keywords: C"4-plant ; Flaveria ; Gene family ; Phosphoenolpyruvate carylase
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/0014-5793(91)80850-3
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  • 3
    Electronic Resource
    Electronic Resource
    Effect of binding on melting transitions in polymer-diluent systems (1967)
    New York : Wiley-Blackwell
    Biopolymers 5 (1967), S. 773-783 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An expression is derived for the melting point of a polymer when in equilibrium with a solution in which binding of low molecular weight compounds to the polymer takes place. Allowance is made for the possibility that the crystalline polymer itself is a complex. The argument is a purely thermodynamic one and is based on a consideration of the change in free energy as a result of a change in binding. Allowance is made also for non-specific polymer-solvent interactions, in which the mixture of low molecular weight solvents is treated as a single solvent. Special attention is paid to “inverted” melting transitions, i.e., cases in which the melting point increases with increasing dilution of the polymer. It is shown that as a rule this is accompanied by a corresponding, inverted effect of the solvent composition on the melting point. It is further shown that-in the absence of binding, “normal” behavior at the critical point (i.e., phase separation is induced by lowering the temperature) is always accompanied by “normal” melting behavior (i.e., a decrease in melting point when the polymer is diluted). Also, “inverted” melting always implies that phase separation at the critical point is induced by heating, but the reverse is not necessarily true.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1967.360050810
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  • 4
    Electronic Resource
    Electronic Resource
    Role of diffusion in gel permeation chromatography (1968)
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 6 (1968), S. 1217-1226 
    Details
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A theory is developed that describes the diffusion of solute into the gel particles during a gel permeation chromatographic experiment. The particles are treated as homogeneous spheres of radius a, into which diffusion takes place with diffusion coefficient Ds. The concentration in the mobile phase at any level at any time is supposed to be uniform throughout the cross-section of the column. It is shown that in the usual columns the effect of diffusion in the mobile phase is unimportant. A determinative quantity in the process is the parameter a2/Dst, where t is the time. For large values of a2/Dst an explicit expression for concentration versus time in the mobile phase at the end of the column is derived [eq. (26) and Fig. 1]. It shows a relatively long tail at large efflux volumes V, where the concentration varies at V-3/2. For arbitrary values of a2/Dst the first three moments of the concentration versus time curve are calculated [eqs. (33)-(37)]. Pronounced skewness of the curve is found unless a2/Dst is small.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1968.160060702
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  • 5
    Electronic Resource
    Electronic Resource
    Study of compositional distribution in a styrene-methyl acrylate copolymer by means of density-gradient centrifugation (1971)
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 9 (1971), S. 1871-1885 
    Details
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Several samples of a copolymer were examined by means of equilibrium centrifugation in a density gradient. The results for the samples without compositional distribution (homogeneous polymers) were used to determine the relation between the chemical composition and the distance from the center of rotation. For one of the homogeneous polymers a quantitative analysis of the schlieren curve was made in order to show the kind of accuracy that can be achieved. For the inhomogeneous polymer it was found that the schlieren curve could, in principle, be described quantitatively by the assumption that fluctuations in composition are independent of fluctuations in molecular weight, but on this basis the average square of the fluctuations in composition is more than four times smaller than the value derived from chromatographic data. A more satisfactory explanation of the experimental results is provided by assuming a linear correlation between average molecular weight and composition, but it is not claimed that this is necessarily the only model that explains the data.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1971.160091009
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  • 6
    Electronic Resource
    Electronic Resource
    Time-dependent elongational viscosity of a solution of elastic dumbbells (1972)
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 10 (1972), S. 1351-1359 
    Details
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The elongational viscosity of dilute polymer solutions must always be measured under nonsteady-state conditions. To predict the time dependence of this viscosity for a polymer solution in which a constant stretching rate is maintained, a simple model is considered in which the polymer molecules are represented by elastic dumbbells. The non-Hookean elastic force in the dumbbell is determined by the conformational entropy of the chain. Use is made of Peterlin's approximation which replaces the elastic force by a function of the root-mean-square end-to-end distance. Application to the transient state is straightforward; it can be extended to include the effect of “internal” chain viscosity by means of approximations that are similar to Peterlin's.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1972.160100713
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  • 7
    Electronic Resource
    Electronic Resource
    Grafting onto cellulose and cellulose derivatives using ultraviolet irradiationPresented at the Second Cellulose Conference, Syracuse, N. Y. May 1959. A fuller account of the earlier part of this work may be found in Makromol. Chem., 36, 52 (1959). (1960)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 3 (1960), S. 54-60 
    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: The cellulose-tendering properties of anthraquinone-2,7-disulfonic acid disodium salt have been successfully applied to graft various vinyl monomers onto cellulosic materials. A cellophane (or cellulose derivative) film is suspended in a solution containing monomer, solvent, dye, and water and irradiated with a 100-w. AH-4 mercury-vapor lamp. The photoexcited dye molecule abstracts a hydrogen atom from the substrate. The radical formed on the cellulose backbone initiates vinyl polymerization and a graft polymer is formed. The grafted film may be up to three and one-half times as heavy as the original substrate and has entirely different solubility characteristics. The degree of grafting is dependent on the monomer concentration in the solution and on the irradiation time. Maximum grafting is usually obtained employing a 24 hour irradiation period. The grafting is always accompanied by homopolymerization, which is not inhibited by atmospheric oxygen, but bubbling air through the solution will completely inhibit both the homopolymerization and the grafting. Substantial grafting can be obtained employing the following monomer-solvent systems: acrylonitrile-N,N-dimethylformamide; acrylamide-water; styrene-acrylonitrile-N,N-dimethylformamide. Good evidence for grafting has been obtained by comparing the solubility characteristics of the graft with those of a physical mixture of the cellulose and the homopolymer.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1960.070030707
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  • 8
    Electronic Resource
    Electronic Resource
    Plasma-enhanced MOVPE and nitrogen doping of ZnSe (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Advanced Materials for Optics and Electronics 3 (1994), S. 203-208 
    Details
    ISSN: 1057-9257
    Keywords: ZnSe ; Diallylselende ; Plasma ; MOVPE ; Nitrogen doping ; Raman spectroscopy ; Photoluminescence ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: In order to obtain high quality Znse epilayers on GaAs which can be intentionally P- and n-type doped growth at a reduced temperature is highly desirable. Therefore in this work the suitability of diallylselenide and the influrnce of plasma precracking have ben investigated. Photoluminesscence, Raman spectroscopy, scanning electron microscopy, X-ray, SIMS and Hall measurements were used to anaylse the samples. The selenium precursor was fully decomposed at temperatures above 360°C if it was precracked by a plasma. Bound excitions could be resolved with negligible donor-acceptor pair (DAP) and copper green emission in the PL spectra form films which were grown with a plasma at temperatures beyond 530°C. Clearly the hpe for reduction in the deposition temperature was not achieved. Raman spectra also revealed strong crystalline quality variations. For the doping experiments nitrogen was used as the carrier gasa instead of hydrogen. Plasma cracking of the selenium precursor was still necessary. Thye substitution of the H2 carrier gas by nitrogen reduced the growth rate by a factor of 2.6 but enhanced the crystalline properties of the samples as shown by the Raman measurements. Strong DAP emission at 2.7eV in the (PL) spectra was observed. SIMS measurements showed a nitrogend concertration of about 3 × 1017 cm-3. An additional nirtogen plasama (0-7W) had a begligible effect on the nitrogen concentration in the sample. The samples were semi-insulating, whichmight be a conswquence of the crystalline quality of ZnSe grown with DASe as selenium precursor.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/amo.860030129
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  • 9
    Electronic Resource
    Electronic Resource
    Far-infrared and Raman spectroscopy of Zn(Se,S) layers (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Advanced Materials for Optics and Electronics 3 (1994), S. 275-282 
    Details
    ISSN: 1057-9257
    Keywords: Far-infrared spectroscopy ; Raman spectroscopy ; MOVPE ; ZnSe ; Implantation ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: We discuss the optical analysis of Zn(Se,S) layers by the application of far-infrared (FIR) and Raman spectroscopy. First a summary is presented of the principles of FIR and Raman Spectroscopy with regard to the relevant epilayer properties which can be investigated by these methods. Subsequently we treat some selected results of FIR and Raman analysis of epilayers grown on GaAs(100) by metal organic vapour phase epitaxy (MOVPE). The main points of interest are crystalline quality, free carrier concentration and interface sharpness. It is shown that n-type conductivty is achieved by Ga implantation in ZnSe but the annealing process (870°C, 30 s) leads to a p-type interface layer in the GaAs due to Zn diffusion. Furthermore, the beneficial effect of growth interruptions to the sharpness of ZnS/ZnSe multiquantum-well interfaces is demonstrated.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/amo.860030139
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  • 10
    Electronic Resource
    Electronic Resource
    Hydrodynamic interaction for time-dependent motions: Steady rotation of a rigid dumbbell (1973)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 11 (1973), S. 1941-1948 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: An expression for the flow field resulting from a time-dependent force with time-dependent point of action is derived from the linearized Navier-Stokes equations. The result is written as a sum of terms, the first of which is the “slow-change limit” corresponding to a stationary force acting at a stationary position. The application to the steady rotation of a dumbbell shows that this sum corresponds to a series expansion in powers of (L2|Ω|/v)1/2 where 2L is the length of the dumbbell, Ω is its angular velocity, and v is the kinematic viscosity of the liquid. It is pointed out that the results obtained are relevant to the problem of rotatory Brownian motion and to that of non-Newtonian viscosity.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1973.180111005
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