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Abstract: We derive an analytic formula for subtracting the spurious self-forces in particle–mesh methods that use the analytical differentiation scheme, such as the Smooth Particle Mesh Ewald (SPME) method and the Particle–Particle Particle–Mesh (P3M) method with analytical differentiation. The impact of the self-forces on the accuracy of the particle–mesh methods is investigated, and it is shown that subtracting them can improve the accuracy of the calculation for some choices of the methodʼs parameters. It is also suggested to subtract exactly the approximate, mesh-computed, self-energy of each particle, replacing them by the exact value. Subtracting in this way the self-energy and self-force of each particle not only improves the accuracy, but also reduces the violation of momentum and energy conservation in particle–mesh methods with analytical differentiation. [Copyright &y& Elsevier]

This study reports the effect of ozone on odor thresholds and the concentration of selected odorous organic compounds in a swine housing facility. This study was conducted in four rooms that each housed 24 pigs. Ozone was injected at different rates into the each of the rooms to give a final concentration of gaseous ozone in the rooms of approximately 0 (control), 0.01, 0.05, or 0.1 ppm. The concentrations of phenolic and indolic compounds and volatile fatty acids (VFAs) were measured in the air in the rooms using solid-phase microextraction (SPME). The results showed that ozonation reduced the levels of indolic compounds in the swine building air significantly (at the 95% confidence level). However, the reduction in the levels of volatile fatty acids and phenolic compounds in the air was small and generally not statistically significant. Sensory measurements showed that there was a small increase (less than 0.5 log units) in the odor detection thresholds for air in the ozonated rooms. At the ozone levels used in this experiment, the reduction in odor levels achieved is small. It is not likely to be practicable to achieve significantly higher reductions in odor levels, as the ozone concentration needed would exceed the OSHA permissible exposure limit for ozone. [ABSTRACT FROM AUTHOR]

Three methods of extracting volatile organic compounds (VOCs) adsorbed on the airborne dust in a swine finishing building were investigated: solvent extraction using dichloromethane, solid--phase microextraction (SPME) using carboxen/ polydimethylsiloxane (CAR/PDMS) and PDMS fibers, and purge and trap. Airborne dust was first collected in pre--baked glass--fiber filters and analyzed using each of the three methods. Solvent extraction with dichloromethane extracted only some high--boiling point carboxylic acids. The SPME CAR/PDMS fiber extracted the low-- to mid--boiling point VOCs such as the carboxylic acids, phenols, and indoles; while the PDMS fiber extracted more of the mid--boiling point compounds, specifically the aliphatic hydrocarbons, indoles, and some aldehydes. The purge and trap method extracted compounds with low-- to mid--boiling points including volatile carboxylic acids, aldehydes, alcohols, ketones, indoles, and esters. Quantitative analysis of five selected VOCs (i.e., acetic acid, propionic acid, butyric acid, hexanal, and nonanal) using the purge and trap method showed acetic acid as generally the most abundant and nonanal as the least abundant. [ABSTRACT FROM AUTHOR]