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  • Springer  (92)
  • Oxford University Press  (72)
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  • 1
    Electronic Resource
    Electronic Resource
    The parathiocyanogen electrode (1999)
    Springer
    Journal of solid state electrochemistry 3 (1999), S. 163-171 
    Details
    ISSN: 1433-0768
    Keywords: Key words Parathiocyanogen ; Conductivity ; Photoelectrochemistry ; Raman spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Stable, yellow anodic films of parathiocyanogen (SCN) x were formed on a platinum electrode from 2.8 M KSCN in methanol at 45 °C at a constant current of 20–40 mA cm−2 for 15–30 min. Loosely bound orange crystals of a more amorphous character were removed by rinsing to leave an adherent yellow film with sharp Raman bands under 647.1 nm laser excitation at 627 cm−1 (vCS), 1152 cm−1 and 1236–1261 cm−1 (vNN and vCN). The lack of electroactivity and short-lived photocurrents pointed to an insulating film at potentials up to 1.0 V (SHE). At more positive potentials, longer-lasting photocurrents were obtained, consistent with breakdown of the insulating film. XPS scans confirmed N:C:S ratios close to 1:1:1, with a deficiency of S of some 10% due to S lost as sulfate at the film surface. Oxidation of SeCN− in neutral aqueous solution led to the formation of a less-stable orange paraselenocyanogen film with a Raman band at 1256–1267 cm−1, which decomposed within a day to grey selenium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100080050143
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  • 2
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    The parathiocyanogen electrode (1999)
    Springer
    Details
    Publication Date: 1999-04-07
    Print ISSN: 1432-8488
    Electronic ISSN: 1433-0768
    Topics: Chemistry and Pharmacology
    Published by Springer
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    PAPER CURRENT
  • 3
    Electronic Resource
    Electronic Resource
    A new constitutive model for fibre suspensions: flow past a sphere (1991)
    Springer
    Rheologica acta 30 (1991), S. 44-57 
    Details
    ISSN: 1435-1528
    Keywords: Fibre suspensions ; constitutive equation ; flow past a sphere ; boundary-element method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract A new phenomenological constitutive equation for homogeneous suspensions of macrosized fibres is proposed. In the model, the local averaged orientation of the fibres is represented by a director field, which evolves in time in a manner similar to the rotation of a prolate spheroid. The stress is linear in the strain rate, but the viscosity is a fourth-order tensor that is directly related to the director field. In the limit of low-volume fractions of fibres, the model reduces properly to the leading terms of the constitutive equation for dilute suspensions of spheroids. The model has three parameters: the aspect ratio R of the fibres, the volume fraction Φ, and A, which plays the role of the maximum-volume fraction of the fibres. Experimental shear data are used to estimate the parameter A, and the resulting model is used in a boundary-element program to study the flow past a sphere placed at the centre line of a cylinder for the whole range of volume fractions from 0.01 to near maximum volume fraction. The agreement with experimental data from Milliken et al. [1] is good.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00366793
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  • 4
    Electronic Resource
    Electronic Resource
    Direct measurements of shear-induced particle migration in suspensions of bimodal spheres (1994)
    Springer
    Rheologica acta 33 (1994), S. 185-192 
    Details
    ISSN: 1435-1528
    Keywords: Suspension ; particle migration ; demixing ; bimodal ; anisotropy ; concentration gradient
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract A variety of studies reported in the literature have established that initially well mixed suspensions subjected to non-homogeneous shear flows attain an anisotropic particulate structure. It has also been shown that non-homogeneous shearing causes suspensions of unimodal spheres to demix, i.e., gradients in solids concentration are formed. The objective of this study was to determine the effect of non-homogeneous shear flows on suspensions of bimodal particles, and specifically, to determine if the solids concentration gradients which develop are accompanied by size segregation of the coarse with respect to the fine fraction. We used the simplest and most direct methods to determine the relative solids concentrations: visual observation of tracer particles in transparent suspensions and physical separation of the coarse and fine solid fractions. Three different types of non-homogeneous shear flows were examined, and in each case the data support two main conclusions: 1) suspended particles migrate from regions of high shear rate to regions of low shear rate, and 2) the coarse fraction of particles migrates much faster than the fine fraction, leading to size segregation of initially well-mixed suspensions. While the former conclusion is consistent with other studies reported in the literature, to our knowledge this paper provides the first data supporting and, to a limited extent, quantifying the latter conclusion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00437303
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  • 5
    Electronic Resource
    Electronic Resource
    The squeezing flow of a model suspension fluid (1990)
    Springer
    Rheologica acta 29 (1990), S. 433-441 
    Details
    ISSN: 1435-1528
    Keywords: Squeezingflows ; fibre suspensions ; boundary element method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract The paper is concerned with the squeezing flow of a model suspension fluid. The numerical solution obtained by a time-dependent Boundary Element Method is compared to an asymptotic solution at large radius. It is found that the kinematics are Newtonian in character, and the fibres quickly align themselves radially. Consequently, the squeezing force is only weakly dependent on the initial orientations of the fibres and the device can be used for measuring the effective viscosity of the suspension. The effective viscosity found from the squeezing flow agrees surprisingly well with experimental data and numerical data derived from the falling sphere geometry at low volume fractions (Φ 〈 0.1).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01376794
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  • 6
    Electronic Resource
    Electronic Resource
    Molecular Dynamics of the Ha-ras Protein: Nucleotide Atom-Centred Charges within the AMBER Force Field (1995)
    Springer
    Journal of molecular modeling 1 (1995), S. 123-142 
    Details
    ISSN: 0948-5023
    Keywords: Keywords: Atom-centred charges, Molecular electrostatic potential, Ha-ras protein, guanosine nucleotides, molecular dynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Molecular dynamics simulations have become an essential tool for the study of biological systems. The Ha-ras protein, is a system suitable for such studies. Despite much recent progress, it is still not known exactly how the protein functions in the cell growth cycle. In this work atom-centred point charges for the guanosine nucleotide ligands are calculated and tested. To be compatible with the other AMBER force field parameters these are fitted to a molecular electrostatic potential derived from an ab initio wavefunction. The smallest basis set able to produce a stable wavefunction for the negatively charged GDP and GTP molecule ions was 3-21G* with diffuse functions added on the phosphate groups. To maintain force field integrity these charges were scaled to be equivalent to STO-3G derived values. This procedure is seen to produce a good magnesium-phosphate interaction potential when compared to 6-31++G* ab initio calculations. With the nucleotides fixed in the binding site conformation, it was found essential to include the electrostatics of the binding site in the calculation of the charges. It was also found to be inappropriate to divide the nucleotide into constituent parts for the calculations. From the calculated charges and experimental data, the nucleotide protonation states in the protein are deduced. It is unlikely that GDP is protonated, GTP probably binds one proton. The charges were tested in MD simulations of a protein modelled on the crystal structure of Tong et al., during which the dynamics of the nucleotide and binding site residues were in good agreement with the crystal structure data. The model is seen to be sensitive, not only to the inclusion of explicit solvent, but to the number of waters ligating the magnesium ion and the conformation of the loop between residues 60 and 66; both pieces of information are lacking in the crystal structure data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s008940050010
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  • 7
    Electronic Resource
    Electronic Resource
    A sufficient condition for a finite group to be solvable (1970)
    Springer
    Mathematische Zeitschrift 116 (1970), S. 65-68 
    Details
    ISSN: 1432-1823
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01110186
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  • 8
    Electronic Resource
    Electronic Resource
    A model for nurturing and assessing multidigit number sense among first grade children (1994)
    Springer
    Educational studies in mathematics 27 (1994), S. 117-143 
    Details
    ISSN: 1573-0816
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract Based on a synthesis of the literature and on the results of a two-year teaching program working with young primary children, a framework was developed, refined and validated for nurturing and assessing multidigit number sense. The major constructs incorporated in this framework were counting, partitioning, grouping, and number relationships. For each of these constructs, four different levels of thinking were established which, in essence, reflected a “learning apprenticeship“ for multidigit number sense. At each level, and across all four constructs, learning indicators were developed and matched to distinctive problem tasks that went beyond the four basic operations. The framework was validated through data obtained from six case studies of grade 1 children. The thinking of these children was assessed and analyzed on the problem tasks for the four constructs and four levels. While the students were at different levels, all but one showed striking consistencies across the four constructs. Moreover, no student was able to solve a problem at a higher level when they had not solved a lower-level problem in the same category. The present framework for multidigit number sense covers only the lower primary grades, but research and instruction would benefit from an extended framework across the elementary grades.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01278918
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  • 9
    Electronic Resource
    Electronic Resource
    A television programme on finite differences (1971)
    Springer
    Educational studies in mathematics 3 (1971), S. 206-219 
    Details
    ISSN: 1573-0816
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00305449
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  • 10
    Electronic Resource
    Electronic Resource
    A framework for assessing and nurturing young children‘s thinking in probability (1997)
    Springer
    Educational studies in mathematics 32 (1997), S. 101-125 
    Details
    ISSN: 1573-0816
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract Based on a synthesis of the literature and observations of young children over two years, a framework for assessing probabilistic thinking was formulated, refined and validated. The major constructs incorporated in this framework were sample space, probability of an event, probability comparisons, and conditional probability. For each of these constructs, four levels of thinking, which reflected a continuum from subjective to numerical reasoning, were established. At each level, and across all four constructs, learning descriptors were developed and used to generate probability tasks. The framework was validated through data obtained from eight grade three children who served as case studies. The thinking of these children was assessed at three points over a school year and analyzed using the problem tasks in interview settings. The results suggest that although the framework produced a coherent picture of children‘s thinking in probability, there was ‘static’ in the system which generated inconsistencies within levels of thinking. These inconsistencies were more pronounced following instruction. The levels of thinking in the framework appear to be in agreement with levels of cognitive functioning postulated by Neo-Piagetian theorists and provide a theoretical foundation for designers of curriculum and assessment programs in elementary school probability. Further studies are needed to investigate whether the framework is appropriate for children from other cultural and linguistic backgrounds.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1002981520728
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