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  • 1
    Electronic Resource
    Electronic Resource
    The solute size effect in rotational diffusion experiments: A test of microscopic friction theories (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 1019-1029 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The experimentally measured rotational diffusion times of various neutral solute molecules are compared with hydrodynamic and molecular models for microscopic friction. New viscosity and temperature dependent results for the rotational time of a large neutral solute (26 A(ring) long) indicate nearly perfect agreement with stick hydrodynamic predictions in both alkane and alcohol solvents. For smaller solute molecules, the results of previous studies show an increasingly large deviation from hydrodynamic predictions as the solute size decreases. This solute size dependent effect is compared with the theoretical predictions of Zwanzig's hydrodynamic "bumpy cylinder'' model, Dote–Kivelson-Schwartz's molecular free volume model, and a new generalized hydrodynamic model for the effects of frequency dependent viscosity on molecular rotational diffusion. Although hydrodynamic predictions agree with experiment in some respects, it is found that molecular aspects of the solvation process must be introduced in order to get quantitative agreement with the observed solute size dependence.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455253
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  • 2
    Electronic Resource
    Electronic Resource
    Critical evaluation of the application of direct energy transfer in probing the morphology of porous solids (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 5224-5236 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The decay of an initially excited donor due to the presence of acceptor molecules embedded in porous silica gels has been studied. The time evolution of the decay process has been related to the geometrical restrictions imposed on the participating molecules by the porous structure of the silicas. Fractal and regular geometrical shape models have been confronted with experimental findings. We conclude that for silica gels simple pore geometries, i.e., spheres and cylinders, account well for the relaxation behavior. The decay patterns exhibit temporal crossovers typical of dynamics in restricted geometries.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455613
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  • 3
    Electronic Resource
    Electronic Resource
    Main Drainage Design for the New Kuala Lumpur International Airport (1998)
    Oxford, UK : Blackwell Publishing Ltd
    Water and environment journal 12 (1998), S. 0 
    Details
    ISSN: 1747-6593
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: The new Kuala Lumpur International Airport in Malaysia requires substantial works for the management and attenuation of surface-water runoff from a large platform constructed on both high ground and low-lying swamp. This paper describes the key features of the main drainage system and reviews (a) the hydrological context of the scheme, (b) the design principles, and (c) the methodologies which were adopted. The platform drainage works comprise concrete-lined open channels discharging through large balancing ponds into the local rivers. Other components of the scheme include numerous culverts, a river diversion, and an interim system to drain the earthworks’platform prior to completion of the permanent airport drainage. Measures to mitigate the impact of the development, and the application of hydrodynamic modelling in optimizing the system design, are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1747-6593.1998.tb00144.x
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  • 4
    Electronic Resource
    Electronic Resource
    A photoluminescence study of poly(phenylene vinylene) derivatives: The effect of intrinsic persistence length (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 1673-1678 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We report the results of light scattering, absorption, excitation, and emission spectroscopy of three polyphenylene vinylene (PPV) derivatives; poly[2-methoxy, 5-(2'-ethyl-hexyloxy-p-phenylene- vinylene] (MEH-PPV), poly[2-butoxy, 5-(2'-ethyl-hexyloxy-p-phenylene-vinylene] (BEH-PPV), and poly[2-dicholestanoxy-p-phenylene-vinylene] (BCHA-PPV) in solution with p-xylene. We find that increasing the size of the solubilizing side chains increases the intrinsic persistence length of the polyphenylene vinylene backbone and that this change in stiffness has dramatic effects on the photoluminescence of polyphenylene vinylene. We have determined the luminescence quantum efficiencies of the polyphenylene vinylene derivatives relative to a known standard, Rhodamine 6G, and find that the photoluminescence can be greatly enhanced by increasing the intrinsic stiffness of the polymer backbone. The stiffest polymer, poly[2-dicholestanoxy-p-phenylene-vinylene] (BCHA-PPV), has a quantum efficiency of 0.66±0.05. The quantum efficiency decreases to 0.22±0.05 for poly[2-butoxy, 5-(2'-ethyl-hexyloxy-p-phenylene-vinylene] (BEH-PPV) and 0.20±0.05 for poly[2-methoxy, 5-(2'-ethyl-hexyloxy-p-phenylene-vinylene] (MEH-PPV), the most coiled derivative. Excitation profiles of the three derivatives also show an increase in nonradiative decay at high energies when the polymer assumes a more coiled comformation. Thus, the quantum yields are dependent on pump energy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.468438
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  • 5
    Electronic Resource
    Electronic Resource
    Photophysics of coumarin inclusion complexes with cyclodextrin. Evidence for normal and inverted complex formation (1985)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 89 (1985), S. 2432-2435 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100257a056
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  • 6
    Electronic Resource
    Electronic Resource
    Nitrogen Adsorption on Porous Silica: Model-Dependent Analysis (1994)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 98 (1994), S. 380-382 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100053a002
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  • 7
    Electronic Resource
    Electronic Resource
    Dipole-dipole coupling between excited aromatic probe molecules and defect sites in silica gel (1992)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 96 (1992), S. 8498-8502 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100200a054
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  • 8
    Electronic Resource
    Electronic Resource
    Porous vycor glass: The microstructure as probed by electron microscopy, direct energy transfer, small-angle scattering, and molecular adsorption (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 6151-6161 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We provide a comprehensive analysis of the microstructure of the porous glass, vycor. Using transmission electron microscopy, small-angle x-ray scattering, molecular adsorption, and the dynamic process of direct energy transfer, a consistent picture of the mass, pore, and interfacial features of this material is presented. From a transmission-electron-microscopy image of an ultrathin section of vycor the material appears to have a homogeneous distribution of mass with no hierarchical organization. The pore interface exhibits a roughness which is probed by both small-angle x-ray scattering and molecular adsorption. The roughness has an upper cutoff of 〈20 A(ring) which is not resolved in the transmission-electron-microscopy image and is shown to be unimportant to the dynamics of the direct energy transfer process. The dimensionality probed by direct energy transfer is shown to be related to interfacial geometrical crossover from two dimensional to three dimensional, which is characterized by a persistent length of the interface of 45 A(ring).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461583
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  • 9
    Electronic Resource
    Electronic Resource
    Direct energy transfer from excited organic adsorbates to intrinsic defect sites in silicalite (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 97 (1992), S. 3736-3743 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The decay of the excited singlet state of an aromatic molecule such as naphthalene adsorbed to the surface of silica is nonexponential. This nonexponential decay is shown to result from a multipolar interaction between the excited adsorbate and the intrinsic defects of silica. We present experimental evidence for direct energy transfer between the donor molecules, naphthalene and 2-methoxynaphthalene, and acceptor defects sites of a crystalline silica zeloite (silicalite). The principal condition for direct energy transfer, spectral overlap between the optical absorption of the defects and the fluorescence emission of the adsorbate is demonstrated for this system, and the nonexponential relaxation of the donor is shown to be described by a Forster-type stretched exponential. Based on the spectral overlap and energy transfer rate determined, the intrinsic defect density of silicalite is calculated to be 3±2×1020 cm−3.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.463955
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  • 10
    Electronic Resource
    Electronic Resource
    Benzophenone triplet quenching by oxygen at the gas/solid interface: a target annihilation reaction in the restricted pore geometry of silica (1988)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 92 (1988), S. 4680-4684 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100327a025
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