Recent Thermodynamic Data on Vicinal Water and a Model for Their Interpretation

Results of recent measurements on vicinal (i.e. surface modified) water are reported, particularly data for the density, thermal expansion coefficient, and viscosity. The results are discussed and related to previous studies, suggesting that vicinal water extends over large distances, probably in the range of 30 to 100 molecular diameters. It is proposed also that vicinal water is induced not only by proximity to a »solid« interface but may also occur as vicinal hydration of macromolecules larger than a certain minimum size, likely in the range of 1000 to 5000 Daltons. The temperatures (Tk) at which the thermal anomalies in the properties of vicinal water occur have been confirmed by an extensive DSC study. The critical temperatures are found to be independent of the chemical nature of the solid substrate, based on DSC measurements with porous quartz, polystyrene suspensions and diamond powder, thus lending credence to the reality of the »Paradoxical Effect«. Finally, a percolation model of vicinal water, based on the work by Stanley and Teixeira, is discussed. The model leads to a predicted value for the density of vicinal water of 0.97 g/cm3 in good agreement with the observed value. However the model does not predict the occurence of the thermal anomalies

An algorithm for estimating contact angle

"February 1995.""Submitted to Langmuir.

Symbol Nomenclature for Graphical Representations of Glycans

ISSN:0959-665

Prediction of inter-particle adhesion force from surface energy and surface roughness

Fine powder flow is a topic of great interest to industry, in particular for the pharmaceutical industry; a major concern being their poor flow behavior due to high cohesion. In this study, cohesion reduction, produced via surface modification, at the particle scale as well as bulk scale is addressed. The adhesion force model of Derjaguin-Muller-Toporov (DMT) was utilized to quantify the inter-particle adhesion force of both pure and surface modified fine aluminum powders (∼8 μm in size). Inverse Gas Chromatography was utilized for the determination of surface energy of the samples, and Atomic Force Microscopy was utilized to evaluate surface roughness of the powders. Surface modification of the original aluminum powders was done for the purpose of reduction in cohesiveness and improvement in flowability, employing either silane surface treatment or dry mechanical coating of nano-particles on the surface of original powders. For selected samples, the AFM was utilized for direct evaluation of the particle pull-off force. The results indicated that surface modification reduced the surface energy and altered the surface nano-roughness, resulting in drastic reduction of the inter-particle adhesion force. The particle bond number values were computed based on either the inter-particle adhesion force from the DMT model or the inter-particle pull-off force obtained from direct AFM measurements. Surface modification resulted in two to three fold reductions in the Bond number. In order to examine the influence of the particle scale property such as the Bond number on the bulk-scale flow characterization, Angle of Repose measurements were done and showed good qualitative agreements with the Bond number and acid/base surface characteristics of the powders. The results indicate a promising method that may be used to predict flow behavior of original (cohesive) and surface modified (previously cohesive) powders utilizing very small samples

Fig. 14 in A Revision of the Genus Hemicrepidius Germar, 1839 (Coleoptera: Elateridae) of the New World, with Comments on Global Classification

Fig. 14. Distribution maps of examined Hemicrepidius specimens (blue/gray dots). a) H. brooksi, new species, b) H. californicus

A comparison of the properties of vicinal water in silica, clay, wood, cellulose and other polymeric materials

"February 1996.

Fig. 34. Hemicrepidius palpalis. a in A Revision of the Genus Hemicrepidius Germar, 1839 (Coleoptera: Elateridae) of the New World, with Comments on Global Classification

Fig. 34. Hemicrepidius palpalis. a) Dorsal habitus, male, b) Pronotum, lateral view. Male genitalia: c) Dorsal view, d) Ventral view. Scale bars: 5 mm (a), 1 mm (b–d)

Fig. 31 in A Revision of the Genus Hemicrepidius Germar, 1839 (Coleoptera: Elateridae) of the New World, with Comments on Global Classification

Fig. 31. Hemicrepidius obscurus. Dorsal habitus: a) Male, b) Female. c) Pronotum, lateral view. Male genitalia