Molecular dynamics simulations incorporating explicit gold atoms in the simulations have been carried out for alkanethiol self-assembled monolayers chemisorbed on the Au(111) surface. The structural properties of the monolayer are evaluated for two force fields:  one in which the Au−S−C bond is fixed (FF I), and the other in which it is flexible (FF II). The influence of these force fields on the structural properties of HS(CH2)14CH3 on the structured Au surface is compared at different temperatures. FF I yields greater tilt angles and a smaller film thickness when compared with FF II. Both of the force fields predict that the tilt angles do not follow a monotonic decrease with temperature but show minima around 200 K. Simulations carried out at different chain lengths at 300 K reveal that FF II predicts a greater film thickness than FF I; however, the difference is within 1 Å.

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Point-of-use (POU) gravity-driven household water purifiers have been proven to be a simple, low-cost and effective intervention for reducing the impact of waterborne diseases in developing countries. The goal of this study was to compare commonly used water disinfectants for their feasibility of adoption in low-cost POU water purifiers. The potency of each candidate disinfectant was evaluated by conducting a batch disinfection study for estimating the concentration of disinfectant needed to inactivate a given concentration of the bacterial strain Escherichia coli ATCC 11229. Based on the concentration of disinfectant required, the size, weight and cost of a model purifier employing that disinfectant were estimated. Model purifiers based on different disinfectants were compared and disinfectants which resulted in the most safe, compact and inexpensive purifiers were identified. Purifiers based on bromine, tincture iodine, calcium hypochlorite and sodium dichloroisocyanurate were found to be most efficient, cost effective and compact with replacement parts costing US$3.60-6.00 for every 3,000 L of water purified and are thus expected to present the most attractive value proposition to end users.

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