Molecular dynamics simulation of imidazolium CnMIM-BF4 ionic liquids using a coarse grained force-field.

Ionic liquids feature thermophysical properties that are of interest in solvents, energy storage materials and tunable lubrication applications. Here we use new Coarse Grained (CG) models to investigate the structure, dynamics and interfacial properties of the [C2-8MIM][BF4] family of ionic liquids (ILs). The simulated equation of state and diffusion coefficients are in good agreement with experimental data and with all-atom force-fields. We quantify the nano-structure and liquid-vapour interfacial properties of the ILs as a function of the size of the imidazolium cation. The computational efficiency of the CG models enables the simulation of very long time scales (100's of nanoseconds), which are needed to resolve the dynamic and interfacial properties of ILs containing cations with long aliphatic chains. For [C>4MIM] [BF4] the break in symmetry associated to the liquid-vapour interface induces nanostructuring of polar and non-polar domains in the direction perpendicular to the interface plane, with the inhomogeneous regions penetrating deep inside the bulk liquid, typically 5 nm for C8MIM cations.

Influence of flue gas desulfurization (FGD) installations on emission characteristics of PM2.5 from coal-fired power plants equipped with selective catalytic reduction (SCR).

Flue gas desulfurization (FGD) and selective catalytic reduction (SCR) technologies have been widely used to control the emissions of sulphur dioxide (SO2) and nitrogen oxides (NOX) from coal-fired power plants (CFPPs). Field measurements of emission characteristics of four conventional CFPPs indicated a significant increase in particulate ionic species, increasing PM2.5 emission with FGD and SCR installations. The mean concentrations of PM2.5 from all CFPPs tested were 3.79 ± 1.37 mg/m3 and 5.02 ± 1.73 mg/m3 at the FGD inlet and outlet, respectively, and the corresponding contributions of ionic species were 19.1 ± 7.7% and 38.2 ± 7.8%, respectively. The FGD was found to enhance the conversion of NH3 slip from the SCR to NH4+ in the PM2.5, together with the conversion of SO2 to SO42-, and increased the primary NH4+ and SO42- aerosol emissions by approximately 18.9 and 4.2 times, respectively. This adverse effect should be considered when updating the emission inventory of CFPPs and should draw the attention of policy-makers for future air pollution control.

Water in Ionic Liquid Lubricants: Friend and Foe.

To a greater or lesser extent, most room-temperature ionic liquids (RTILs) absorb water from humid air. Penetration of water into the lubricating nanoscale film may affect its equilibrium structure and dynamic properties and thus influence the ability of RTILs as lubricants to reduce friction between solid surfaces. Here we investigate the impact of hydration on lubrication using nonequilibrium molecular dynamics simulations. Water adsorption changes both the ionic liquid molecules' orientation and the slip conditions at the solid-liquid interfaces, resulting in a reduced resistance against squeezing-out of the lubricant by an external load. For the same normal load, the film becomes thinner when water is present. We show that even small amounts of water can screen the electrostatic interactions between the ions, making RTILs more "fluid" and compressible and hence less resistant to external stress. The impact that screening has on friction involves several aspects that are systematically analyzed in this paper.

Electrotunable lubricity with ionic liquids: the influence of nanoscale roughness.

The properties of ionic liquids can be modified by applying an external electrostatic potential, providing a route to control their performance in nanolubrication applications. Most computational studies to date have focused on the investigation of smooth surfaces. Real surfaces are generally inhomogeneous and feature roughness of different length scales. We report here a study of the possible effects that surface roughness may have on electrotunable lubricity with ionic liquids, performed here by means of non-equilibrium molecular dynamics simulations. In order to advance our understanding of the interplay of friction and substrate structure we investigate coarse grained models of ionic liquids confined in model surfaces with nanometer roughness. The friction is shown to depend on the roughness of the substrate and the direction of shear. For the investigated systems, the friction coefficient is found to increase with roughness. These results are in contrast with previous studies, where roughness induced reduction of friction was reported, and they highlight the strong sensitivity of the friction process to the structure of the surfaces. The friction force features a maximum at a specific surface charge density. This behaviour is reminiscent of the one reported in ionic liquids confined by flat surfaces, showing the generality of this physical effect in confined ionic liquids. We find that an increase of the substrate-liquid dispersion interactions shifts the maximum to lower surface charges. This effect opens a route to control electrotunable friction phenomena by tuning both the electrostatic potential and the composition of the confining surfaces.

Status and characteristics of ambient PM2.5 pollution in global megacities.

Ambient PM2.5 pollution is a substantial threat to public health in global megacities. This paper reviews the PM2.5 pollution of 45 global megacities in 2013, based on mass concentration from official monitoring networks and composition data reported in the literature. The results showed that the five most polluted megacities were Delhi, Cairo, Xi'an, Tianjin and Chengdu, all of which had an annual average concentration of PM2.5 greater than 89µg/m(3). The five cleanest megacities were Miami, Toronto, New York, Madrid and Philadelphia, the annual averages of which were less than 10µg/m(3). Spatial distribution indicated that the highly polluted megacities are concentrated in east-central China and the Indo-Gangetic Plain. Organic matter and SNA (sum of sulfate, nitrate and ammonium) contributed 30% and 36%, respectively, of the average PM2.5 mass for all megacities. Notable seasonal variation of PM2.5 polluted days was observed, especially for the polluted megacities of China and India, resulting in frequent heavy pollution episodes occurring during more polluted seasons such as winter. Marked differences in PM2.5 pollution between developing and developed megacities require more effort on local emissions reduction as well as global cooperation to address the PM2.5 pollution of those megacities mainly in Asia.

Synthesis of tetra-substituted imidazoles and 2-imidazolines by Ni(0)-catalyzed dehydrogenation of benzylic-type imines.

Ni(0)-catalyzed dehydrogenation of benzylic-type imines was performed to yield asymmetrical tetra-substituted imidazoles and 2-imidazolines. This was achieved with a single operational step while maintaining good selectivity and atom economy. The catalytic system shows low to moderate tolerance for fluoro-, trifluoromethyl-, methyl-, and methoxy-substituted benzylic-type imines. In addition, the substitution pattern at the N-heterocyclic products was easily controlled by the appropriate selection of R-groups in the starting organic substrates. Based on experimental observations, we propose a reaction mechanism in which benzylic C(sp(3))-H bond activation and insertion steps play pivotal roles in this nickel-catalyzed organic transformation.

Impacto de la ivermectina sobre las geohelmintiasis en el foco de oncocercosis en Colombia / The effect of ivermectin on geohelminth frequency (i.e. as used in the onchocerciasis control program in Colombia)

Objetivo: Evaluar el efecto de la ivermectina sobre la frecuencia de infección por geohelmintos en una población colombiana incluida en el Programa para la Eliminación de la Oncocercosis en las Américas. Métodos: Estudio de evaluación de impacto con enfoque longitudinal como punto referente inicial, la población de Naicioná (1996) y como control, sujetos de la misma población (2008). Para el enfoque transversal se usó como referente la población de Naicioná en 2008 y como control, sujetos de Dos Quebradas en 2008. El procesamiento de las muestras de materia fecal se hizo por Ritchie-Frick modificado. Resultados: Ascaris lumbricoides fue el parásito más frecuente 49,6 % (60/121; IC 95 %:37,8-63,8) en Naicioná y 47,4 % (36/76; IC 95 %: 33,2-65,6) en Dos Quebradas. El mayor efecto de la ivermectina en mayores de 5 años fue la disminución del riesgo de infección, para Trichiuris trichiura, de 86 % (IC95 %:74-93) en la evaluación longitudinal y 63 % (IC 95 %:24-82) en la evaluación transversal. La disminución en la frecuencia de Strongyloides stercoralis fue 93 % (IC 95 %: 45-99), en la evaluación longitudinal y 85 % (IC95 %:-031 - 99) en la evaluación transversal. Conclusiones: El uso de la ivermectina en el contexto del Programa para la Eliminación de la Oncocercosis en las Américas no es suficiente para el control de la morbilidad de todas las geohelmintiasis, se requiere de programas integrales que incluyan los componentes de educación y saneamiento básico.

Objective: Evaluating the effect of ivermectin on soil-transmitted helminthes (STH) infection frequency in a Colombian population included in the Onchocerciasis Elimination Program for the Americas (OEPA). Methods: This was an impact evaluation study which adopted a longitudinal approach using the population of Naicioná (1996) as baseline for comparison to people from the same population as controls (2008). The cross-sectional approach involved comparing the reference population of Naicioná (2008) to the population of Dos Quebradas (2008) used as controls. Fecal samples were processed by a modified Ritchie-Frick method. Results: Ascaris lumbricoides was the most frequently found parasite in Naicioná (60/121; 49.6 %: 37.8-63.895%CI) and in Dos Quebradas (36/76; 47.4 %: 33.2-65.6 95 % CI). Ivermectin’s main effect on the population aged over 5 years was a decreased risk of Trichiuris trichiura infection in both longitudinal assessment (86 % reduction: 74-93 95 % CI) and cross-sectional assessment (63 %:24-82 95 % CI). A 93 % reduction (45-99 95 % CI) in Strongyloides stercoralis frequency was found in longitudinal assessment, compared to 85 % in cross-sectional assessment (-031-99 95 % CI). Conclusions: Ivermectin use in the OEPA is not sufficient for STH morbidity control. Integrated programs including education and basic sanitation are required.

[The effect of ivermectin on geohelminth frequency (i.e. as used in the onchocerciasis control program in Colombia)]. / Impacto de la ivermectina sobre las geohelmintiasis en el foco de oncocercosis en Colombia.

OBJECTIVE: Evaluating the effect of ivermectin on soil-transmitted helminthes (STH) infection frequency in a Colombian population included in the Onchocerciasis Elimination Program for the Americas (OEPA). METHODS: This was an impact evaluation study which adopted a longitudinal approach using the population of Naicioná (1996) as baseline for comparison to people from the same population as controls (2008). The cross-sectional approach involved comparing the reference population of Naicioná (2008) to the population of Dos Quebradas (2008) used as controls. Fecal samples were processed by a modified Ritchie-Frick method. RESULTS: Ascaris lumbricoides was the most frequently found parasite in Naicioná (60/121; 49.6 %: 37.8-63.895%CI) and in Dos Quebradas (36/76; 47.4 %: 33.2-65.6 95 % CI). Ivermectin's main effect on the population aged over 5 years was a decreased risk of Trichiuris trichiura infection in both longitudinal assessment (86 % reduction: 74-93 95 % CI) and cross-sectional assessment (63 %:24-82 95 % CI). A 93 % reduction (45-99 95 % CI) in Strongyloides stercoralis frequency was found in longitudinal assessment, compared to 85 % in cross-sectional assessment (-031-99 95 % CI). CONCLUSIONS: Ivermectin use in the OEPA is not sufficient for STH morbidity control. Integrated programs including education and basic sanitation are required.