Contact line pinning by microfabricated patterns: effects of microscale topography

We study how the microscale topography of a solid surface affects the apparent advancing and receding angles at the contact line of a liquid drop pinned to this surface. Photolithographic methods are used to produce continuous circular polymer rings of varying cross-sectional size and shape on hydrophilic silicon wafer surfaces. Drops of water and glycerol are dispensed into the areas bounded by these rings, and critical apparent advancing and receding angles are measured and correlated with the parameters that characterize the ring cross section. For much of the examined parameter space, the apparent critical angles are independent of ring height and width and are determined primarily by the slope of the ring's sidewalls, consistent with a model by Gibbs. For ring heights below a few micrometers, the critical angles decrease below the values predicted by the sidewall slopes alone. These results provide data for calculation of hysteresis on naturally rough surfaces and demonstrate a simple method for controlling and enhancing contact line pinning on solid surfaces.

Effect of Characteristics of Compounds on Maintenance of an Amorphous State in Solid Dispersion with Crospovidone

Solid dispersion (SD) of indomethacin with crospovidone (CrosPVP) shows useful characteristics for preparation of dosage forms. This study aimed to determine the types of drugs that could adopt a stable amorphous form in SD. Twenty compounds with various melting points (70-218 degrees C), molecular weights (135-504) and functional groups (amide, amino, carbonyl, hydroxyl, ketone etc.) were prepared in SD with CrosPVP. The CrosPVP SDs were prepared using a mechanical mixing and heating method. Melting point and molecular weight were found to have no influence on the ability of a compound to maintain an amorphous state in SD. All compounds containing hydrogen-bond-donor functional groups existed in an amorphous state in SD for at least 6 months. Infrared spectra suggested an interaction between the functional groups of these compounds and amide carbonyl group of CrosPVP. Compounds without hydrogen-bond-donor groups could not maintain an amorphous state and underwent recrystallization within 1 month. It was suggested that the presence of a hydrogen-bond-donor functional group in a compound is an important factor affecting the stable formation of SD with CrosPVP, which contains a hydrogen-bond acceptor.

Zinc, cadmium, and mercury complexes of 5,7-dimethyl-[1,2,4]triazolo[1,5-a]pyrimidine (dmtp). Preparation, spectroscopic characterization, and biological activity. X-ray crystal structures of [Zn(dmtp)2Br2], [Hg(dmtp)2Cl2], and [Hdmtp]2[CdBr4]. 2H2O

The preparation and spectroscopic characterization of a series of dmtp complexes of Zn, Cd, and Hg, where dmtp is 5,7-dimethyl[1,2,4]triazolo[1,5-a]pyrimidine, is reported. Crystal structure analyses of [Zn(dmtp)2Br2] and [Hg(dmtp)2Cl2] reveal distorted tetrahedral geometries about the central atoms and the dmtp ligands to coordinate via the N(3) atom exclusively. In the X-ray structure of [Hdmtp]2[CdBr4].2H2O, the [Hdmtp]+ cation is protonated at the N(3) atom, there being no significant interaction between Hdmtp and cadmium. A study of the antimicrobial activity of the complexes shows that the [Cd(dmtp)X2(OH2)] (X = Cl, Br) compounds display activity against two strains.