A B S T R A C TProtection of public health against pathogenic viruses transmitted through the airborne route requires effective sampling of airborne viruses for determination of their concentration and distribution. However, sampling viable airborne viruses is challenging as conventional bioaerosol sampling devices operate on inertia-based mechanisms that inherently have low sampling efficiency for virus aerosols in the ultrafine size range (< 100 nm). Herein, a Batch Adiabatic-expansion for Size Intensification by Condensation (BASIC) approach was developed for efficient sampling of virus aerosols. The BASIC utilizes adiabatic expansion in a supersaturated container to activate condensation of water vapor onto virus aerosol particles, thus amplifying the size of the particles by orders of magnitude. Using aerosolized MS2 bacteriophage, the BASIC's performance was evaluated and optimized both from the perspectives of physical size amplification as well as preservation of the viability of the MS2 bacteriophage. Experimental results show that one compression/expansion (C/E) cycle under a compression pressure of 103.5 kPa and water temperature of 25°C was sufficient to increase the particle diameter from < 100 nm to > 1 µm; further increases in the number of C/E cycles neither increased particle number concentration nor diameter. An increase in compression pressure was associated with physical size amplification and a higher concentration of collected viable MS2. Water temperature of 40°C was found to be the optimal for size amplification as well as viability preservation. No significant effect on particle size enlargement was observed by changing the dwell time after expansion. The results illustrate the BASIC's capability as a simple, quick and inexpensive tool for rapid sampling of viable airborne viruses.
A novel particle processor was designed and built for the production of flake-shaped powders. 300 m magnesium and 140 m iron particles processed for 1 and 2 minutes were analyzed for dimensional, ductile, and morphological characteristics. Particle diameter distributions tended to broaden towards higher size ranges after 2 minutes of processing; the mean particle size was in the range of 400 m for magnesium and 300 m for iron. The flake thickness decreased over time, leading to a mean-thickness of 12 m for the magnesium particle sample processed with 2 x 6.0 mm milling ball media after 2 minutes. The effect of particle medium showed that the milling operation had greater influences on the more ductile material. Surface morphology also became smoother as the milling time increased. Larger ball media tended to produce samples with larger particle sizes with wider size distributions, while smaller ball media produced smaller particles with narrower size distributions. Loading weights also tended to have similar trends. The novel process was demonstrated as an effective and efficient method for the production of flake-shaped metal particles which greatly reduced the amount of milling time and energy required for flake particle production.
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