ABSTRACT
A binary mixture of droplets and patchy colloids, where patches are arranged in tetrahedral symmetry, is studied with Metropolis Monte Carlo simulations. The colloidal patches attract droplets, while both the colloid-colloid and the droplet-droplet interactions are hard sphere like. We find stable crystal structures with atomic analogs ZnS, CaF_{2}, and fcc or hcp (face centered cubic or hexagonal close packed) of the droplets coexisting with a dispersed fluid of the colloids. The simulated crystal structures agree well with those predicted by close-packing calculations for an intermediate range of droplet-colloid size ratios. A discrepancy between the simulations and theoretical predictions occurs at low and high size ratios. The results of the simulations for mixtures with anisotropic colloid-droplet interactions reveal a richer phase diagram, with ZnS-gas and ZnS-fluid coexistence, as compared to the isotropic case. For the example of a square planar patch arrangement, we find a particular crystal structure, consisting of two interpenetrating fcc or hcp lattices with right bond angles. Such a structure has no known atomic analog. Our study of generic models of anisotropic colloid-droplet mixtures could provide a promising way towards the fabrication of novel and complex colloidal structures.
ABSTRACT
We study the cluster structures of one-patch colloidal particles generated by droplet evaporation using Monte Carlo simulations. The addition of anisotropic patch-patch interaction between the colloids produces different cluster configurations. We find a well-defined category of sphere packing structures that minimize the second moment of mass distribution when the attractive surface coverage of the colloids χ is larger than 0 . 3 . For χ < 0 . 3 , the uniqueness of the packing structures is lost, and several different isomers are found. A further decrease of χ below 0 . 2 leads to formation of many isomeric structures with less dense packings. Our results could provide an explanation of the occurrence of uncommon cluster configurations in the literature observed experimentally through evaporation-driven assembly.
ABSTRACT
This paper describes progress on formulating a national asbestos profile for the country of Vietnam. The Center of Asbestos Resource, Vietnam, formulated a National Profile on Asbestos-related Occupational Health, with due reference to the International Labor Organization/World Health Organization National Asbestos Profile. The Center of Asbestos Resource was established by the Vietnamese Health Environment Management Agency and the National Institute of Labor Protection, with the support of the Australian Agency for International Development, as a coordinating point for asbestos-related issues in Vietnam. Under the National Profile on Asbestos-related Occupational Health framework, the Center of Asbestos Resource succeeded in compiling relevant information for 15 of the 18 designated items outlined in the International Labor Organization/World Health Organization National Asbestos Profile, some overlaps of the information items notwithstanding. Today, Vietnam continues to import and use an average of more than 60,000 metric tons of raw asbestos per year. Information on asbestos-related diseases is limited, but the country has begun to diagnose mesothelioma cases, with the technical cooperation of Japan. As it stands, the National Profile on Asbestos-related Occupational Health needs further work and updating. However, we envisage that the National Profile on Asbestos-related Occupational Health will ultimately facilitate the smooth transition to an asbestos-free Vietnam.
