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  • Analytical Chemistry and Spectroscopy  (5)
  • Chemical Engineering  (3)
  • Physics  (3)
  • 71.70.-d  (1)
  • 1980-1984  (7)
  • 1970-1974  (5)
Collection
Keywords
Publisher
Years
Year
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 33 (1984), S. 97-105 
    ISSN: 1432-0630
    Keywords: 78.65.-s ; 71.70.-d ; 68.55.+b
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Low-temperature photoluminescence measurements on nominally undoped AlxGa1−xAs/GaAs quantum well heterostructures (QWHs) grown by molecular beam epitaxy (MBE) exemplified the exclusivelyintrinsic free-exciton nature of the luminescence under moderate excitation conditions. Neither any spectroscopic evidence for alloy clustering in the AlxGa1−xAs barriers nor any extrinsic luminescence due to recombination with residual acceptors has been detected in single and double QWHs when grown at 670 °C under optimized MBE growth conditions. Carrier confinement in AlxGa1−xAs/GaAs QWHs starts at a well width ofL z≌30 nm when x≌0.25. The minor average well thickness fluctuation ofΔL z=4×10−2nm as determined from the excitonic halfwidth allowed the realization of well widths as low asL z=1 nm and thus a shift of the free-exciton line as high as 2.01 eV which is close to the conduction band edge of the employed Al0.43Ga0.57As confinement layer. The measurements further revealed a strongly enhanced luminescence efficiency of the quantum wells as compared to bulk material which is caused by the modified exciton transition probabilities due to carrier localization.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 17 (1971), S. 732-740 
    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 method is described for obtaining the exact solution to the problem of thermal entry region heat transfer which takes into account both transverse non-uniformity in the velocity field and axial conduction. To allow for the effect of upstream conduction, the fluid temperature was taken to be uniform at × = - ∞, and the first 20 eigenvalues and the corresponding eigenfunctions were determined separately for the heated and adiabatic regions. Both the temperatures and temperature gradients were then matched at × = 0 by constructing a pair of orthonormal functions from the nonorthogonal eigenfunctions.Nusselt numbers calculated for pipe flow subject to the boundary condition of uniform wall heat flux show virtually perfect agreement with those reported recently by Hennecke, who solved the governing partial differential equation numerically. To illustrate its general applicability, the present method was further employed to analyze the corresponding problem in parallel-plate channel flow, for which no solution has hitherto been reported.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 29 (1983), S. 903-909 
    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 unified approach is proposed for the prediction of heat transfer coefficients in turbulent falling films undergoing heating, evaporation or condensation for both of the cases with or without interfacial shear. A modified van Driest eddy viscosity model, which incorporated a damping factor f and takes into account the effect of variable shear stress, is used to predict the hydrodynamics of turbulent falling films. The calculated film thicknesses are in good agreement with the Nusselt-Brauer correlations for the non-sheared film and the Dukler prediction for highly sheared film. Also, by including a van Driest type turbulent Prandtl number model, the asymptotic heat transfer coefficients are accurately predicted and show better agreement with the extensive literature data and correlations than do most of the existing turbulence models proposed to date.
    Additional Material: 10 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 16 (1970), S. 493-496 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 1 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 1 (1974), S. 1-4 
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The two major metabolites of [14C]niflumic acid, 2-(3′-[14C] trifluoromethylanilino)nicotinic acid have been isolated from human urine. Low and high resolution mass spectrometry indicate that both metabolites (M2a and M2b) are monohydroxylated derivatives of niflumic acid. The 100 MHz proton magnetic resonance spectrum of M2b demonstrates it to be 5-hydroxyniflumic acid, whereas M2a is either the 4′- or 6′-hydroxy derivative. The synthesis of 6′-methoxyniflumic acid methyl ester and comparison of its spectral data and melting point with that of the corresponding derivative of M2a reveal their non-identity. The structure of M2a is, therefore, 4′-hydroxyniflumic acid.
    Additional Material: 4 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 11 (1973), S. 217-221 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Nylon 6 in the form of bundles of fibers or rods was treated to contain traces of chloranil of other quinones. When stressed within an EPR cavity, the radicals produced were trapped in a relatively stable form containing the quinone. This method offers a quantitative measurement of the integrated number of free radicals produced during a stress history.
    Additional Material: 3 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 22 (1984), S. 567-576 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: It has been shown, using the significant structure theory of liquids, that a lower critical solution temperature behavior as well as a upper critical solution temperature behavior can be expected for polymer-polymer systems and that a phase diagram of closed-loop-type in a polymer-polymer-solvent system can be possible. In this article the sublimation energy of a mixture was expressed as a quadratic form of segment surface fractions on pure components rather than that of mole fractions, and the effect of the segment surface fractions on critical compositions was explained. The calculated partial miscibilities were in good agreement with the experiment.
    Additional Material: 5 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 17 (1981), S. 303-305 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The two possible conformations of 13-R-substituted oxyprotoberberines are enantiomeric. The racemization barriers are determined for three of these compounds (R=OMe, OCOMe, OCOPh) using variable temperature 1H NMR. It was found that ΔG203
    Additional Material: 1 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 2 (1970), S. 251-257 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A useful method for the assignment of hydroxyl groups in steroids is described in which hydroxy-steroids are reacted with trifluoroacetic anhydride. The δ-values of the CF3 signals from the resulting trifluoroacetates characterize the positions of the trifluoroacetylated hydroxyl groups.
    Additional Material: 1 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 21 (1983), S. 465-466 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The dependence of three-bond 13C-13C couplings of cis-butane and cis-butene on the valence angle, the torsional angle of the methyl groups and methyl and methylene substituents is discussed on the basis of INDO-SCPT calculations. The results support the interpretation of the experimental couplings between the bridgehead carbons of bicyclic hydrocarbons based on a multiple-path mechanism.
    Additional Material: 1 Ill.
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