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  • 1995-1999  (3)
  • 1955-1959
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  • 1
    Electronic Resource
    Electronic Resource
    Rotational analysis and tunnel splittings of the intermolecular vibrations of the phenol–water complex by high resolution UV spectroscopy (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 108 (1998), S. 4496-4504 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Highly resolved (Δν〈100 MHz) UV-REMPI (ultraviolet-resonantly enhanced multiphoton ionization) spectra of different vibronic bands in the phenol–water complex are presented. The torsional splitting caused by the hindered rotation of the water moiety in the hydrogen-bonded system is investigated. An autocorrelation procedure reveals torsional subbands, a correlation automated rotational fitting (CARF) of the spectra yields the rotational constants: The analyzed vibrations are classified by the rotational constants of the corresponding vibronic band and the symmetry of the torsional state. The transition to the stretching vibration at 156 cm−1 excess energy is shown to consist of two different torsional transitions similar to the electronic origin. The torsional splitting in the origin band is 0.8491(2) cm−1 and that of the stretching vibration is 0.8915(3) cm−1, demonstrating a very small coupling between the stretching and the torsional motion. We assign the 121 cm−1 band as the negative parity component of the transition to the wagging vibration β2 while the band at 125 cm−1 is tentatively assigned as the positive parity component of the same band. The resulting large torsional splitting of −4.596(3) cm−1 points to a strong coupling to the torsional motion. The band at 95 cm−1 has only one torsional parity component within its rotational envelope. The observed large change of its rotational constants does not fit to the pattern of the other vibrations and the band is tentatively assigned as an overtone of the torsional vibration τ with positive parity. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.475861
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  • 2
    Electronic Resource
    Electronic Resource
    A new approach for determining effective soil hydraulic functions (1998)
    Oxford, UK : Blackwell Science Ltd
    European journal of soil science 49 (1998), S. 0 
    Details
    ISSN: 1365-2389
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: We investigated the possibility of inferring effective hydraulic properties of soil from the structure of the pore space. The aim was to identify structural properties, which are essential for water flow, so that physical experiments may be replaced by direct morphological measurements. The pore structure was investigated in three dimensions by serial sections through impregnated samples. The complex geometry of pore space was quantified in terms of two characteristics: pore-size distribution and pore connectivity. Only pores larger than 0.04 mm were considered. The results were used as input parameters for a pore-scale network model. The main desorption branch of the soil-water characteristic and the corresponding hydraulic conductivity function of the network model were calculated by numerical simulation. The simulation results, which are exclusively based on morphological investigations, were compared with independently measured results from a multi-step outflow experiment. This approach was demonstrated for two centrasting soil materials: the A and B horizons of a silty agricultural soil. The simulations were close to the experimental data, except for the absolute values of the hydraulic conductivity. The pore-size distribution and pore connectivity govern the shape of hydraulic functions and the applied morphometric methods are suitable for predicting essential characteristics of hydraulic soil properties.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2389.1998.4940547.x
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  • 3
    Electronic Resource
    Electronic Resource
    Morphological determination of pore connectivity as a function of pore size using serial sections (1997)
    Oxford, UK : Blackwell Publishing Ltd
    European journal of soil science 48 (1997), S. 0 
    Details
    ISSN: 1365-2389
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The geometry of pore space in soil is considered to be the key in understanding transport of water, gas and solute. However, a quantitative and explicit characterization, by means of a physical interpretation, is difficult because of the geometric complexity of soil structure.Pores larger than 40 μm within two soil horizons have been analysed morphologically on 3-dimensional digital representations of the pore space obtained by serial sections through impregnated specimens. The Euler-Poincaré characteristic has been determined as an index of connectivity in three dimensions. The pore connectivity is quantified as a function of the minimum pore diameter considered leading to a connectivity function of the pore space. Different pore size classes were distinguished using 3-dimensional erosion and dilation. The connectivity function turned out to differentiate between two soil materials. The pore space in an upper Ah horizon is intensely connected through pores between 40 and 100 μm, in contrast to the pore space in the AhBv beneath it. The morphological pore-size distributions were compared to the pore-size distribution obtained by water retention measurements. The discrepancy between these different methods corresponds to the expectation due to pore connectivity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2389.1997.tb00203.x
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