Background: Surgical mortality data are collected routinely in high-income countries, yet virtually no low-or middle-income countries have outcome surveillance in place. The aim was prospectively to collect worldwide mortality data following emergency abdominal surgery, comparing findings across countries with a low, middle or high Human Development Index (HDI).Methods: This was a prospective, multicentre, cohort study. Self-selected hospitals performing emergency surgery submitted prespecified data for consecutive patients from at least one 2-week interval during July to December 2014. Postoperative mortality was analysed by hierarchical multivariable logistic regression.

Quartz and corundum surfaces in water are capable of adsorbing and releasing protons, a behavior attributed to the amphoteric character of their silanol and ab initio calculations are used to obtain different charge densities on crystalline (101) quartz and (001) corundum surfaces and the corresponding charge delocalization after deprotonation of the silanol and aluminol groups, respectively. Then, classical molecular dynamics simulations are used to study the interaction of water with the charged quartz and corundum surfaces in the presence of aqueous solutions of monovalent alkali and alkalineearth metal chlorides. Results include density profiles of adsorbed cations, and the effect of cations on the orientation profiles of water molecules close to the mineral surfaces and the distance at which such surfaces become neutral or reverse their charges. In all cases where there are experimental or simulation data, the results here compare very well. The adsorption density of cations on quartz increases with the size of the cations, either monovalent or divalent. The density of adsorbed monovalent cations on corundum decreases for larger cation sizes, while this behavior on quartz is the opposite. In both cases the adsorption of cations is enhanced by the increase of the surface charge. Adsorption on corundum is much more extensive compared to that on quartz for all surface charges and cations. The sequence of simulations of cation adsorption on silica and alumina provide support to the idea that high isoelectric point materials preferentially adsorb well-hydrated cations and low isoelectric point materials preferentially adsorb poorly hydrated cations. The results of this work are expected to contribute to improving current knowledge on the interaction of mineral oxides with macromolecules, such as polyelectrolytes in solid−liquid separation processes and biomolecules in lung inflammatory processes.

Molecular dynamics simulations are used to study adsorption of cations on the (010) kaolinite edge surface at and above the pH of zero charge. The cation solutions are highly concentrated and include alkali and alkaline-earth metals. It is known that the pH-dependent edge surface of kaolinite is more reactive than the basal surfaces and more eager to adsorb metal ions; however, knowledge of the atomic scale is scarce regarding the structure of the surface edge, charge distribution, solvation, and structure of layers of adsorbed cations. First, ab initio calculations are used to determine the energetically most favorable surface terminations and the distribution of partial atomic charges on both neutral (protonated) and negatively charged (deprotonated) edge surfaces of kaolinite. Then, molecular dynamics simulations are used to study the solvation of kaolinite and the adsorption of cations. Results include density profiles of adsorbed cations, orientation profiles of water molecules close to the mineral surface for different cations, and the distance at which such surfaces become neutral or reverse their charges. Results compare well with available experimental and simulation data. Findings are expected to contribute to the selection or design of organic compounds that effectively adhere to kaolinite in aqueous electrolyte solutions in water recovery processes.

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