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Numerical models for the evaluation of the contact angle from axisymmetric drop profiles: A statistical comparison
No full textAxisymmetric drop shape analysis (ADSA) is a well-established methodology for estimating the contact angle value and the surface tension of liquids starting from sessile drops images. It consists of an iterative procedure in which a best fit between a theoretical axisymmetric Laplacian curve and an experimental drop profile is performed. When only an evaluation of the geometric contact angle value is needed, a similar numerical approach can be adopted by using simpler algebraic models in place of a Laplace profile, thus allowing more straightforward implementations and shorter computation times.
In this work the relative merits of the different methodologies are compared. Beside the standard ADSA procedure, four different mathematical models are examined, namely the circular and elliptical models, the first-order perturbative solution of the Laplace equation, and a cubic spline model. Their relative statistical performances are tested on both calculated and experimental drop profiles. For simulated drops, the actual capability of the models to predict the correct contact angle is also investigated
Diffusion and double diffusive convection in the isothermal barium chloride-potassium chloride-water system at 25°C
No full textThe four diffusion coeffs. describing the isothermal interdiffusion transport in the three-component system BaCl2(1)-KCl(2)-H2O(3) at one concn. were measured. The conditions for the growth of convection inside the diffusion boundary (double diffusive convection) were computed according to the theory proposed by McDougall and compared with the exptl. results. Good agreement was found between theory and exptl. results. In this system, convection at the borders of the boundary grows even if the heavier components BaCl2 and KCl are more concd. at the bottom of the diffusion boundary
Diffusion and double diffusive convection in the isothermal barium chloride-potassium chloride-water system at 25°C. [Erratum to document cited in CA117(18):178798p]
No full textNuclear magnetic resonance studies of aqueous solutions of alkylureas: Proton and carbon-13 chemical shifts
No full textAqueous solutions of methylated and ethylated derivatives of urea have been investigated by proton and carbon-13 magnetic resonance technique. The chemical shifts of water protons in solution of alkylureas, relative to that of pure water, are as a measure of the hydrogen-bonding reinforcing or weakening ability of these substances. The dependence of this effect on the concentration and on the temperature has also been studied. The results obtained indicate that different contrasting effects act in these solutions, among then the water structuring effect of the nonpolar surface of the alkylureas and the effect of the volume of the solute.13C chemical shifts of the carbonyl groups of the alkylureas give useful information about the interactions between water and the polar part of the ureas. Carbonyl-water interactions exist but are partially destroyed by increasing concentrations of the solute. © 1977 Plenum Publishing Corporation
Molecular connectivity methods for the characterization of surface energetics of liquids and polymers
No full textIn the topological approach to structure–property relationships, the molecular structure is described in terms of appropriate weighted graphs to which suitable topological parameters, usually known as molecular connectivity indices, can be associated. Molecular connectivity indices are here applied to the prediction of surface free energy and Good–van Oss–Chaudhury acid–base components of organic compounds. To this aim, some quantitative structure–property relationships (QSPRs) are determined, involving both topological indices and group indicator variables of the customary functional group theory. The semiempirical models obtained to appear satisfactory and show significant advantages with respect to the models based on the purely functional group approach
The combined effect of roughness and heterogeneity on contact angles: the case of polymer coating for stone protection
No full textCorrect use of the contact angle in the evaluation of the protective action induced from polymer coating on the stone
No full textMolecular connectivity methods for the characterization of surface energetics of polymers
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Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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