Cyanoethylation of Hydroxyethyl Cellulose: Preparation and Characterization

Commercial hydroxyethyl cellulose (HEC) was cyanoethylated with acrylonitrile in nonaqueous medium in the presence of sodium hydroxide under a variety of conditions. Variables studied included the amount of acrylonitrile and the reaction temperature. The reaction was proved by NMR and its extent was measured by determining the nitrogen content. The physical properties of the obtained derivatives—i.e., the electric properties and the apparent viscosity at various rates of shear—were investigated. It was found that the extent of reaction was increased by increasing the amount of acrylonitrile as well as the reaction temperature. The products were water soluble and their apparent viscosity increased with increasing nitrogen content. The same holds true for the dielectric constant and dielectric loss.     

KINETICS OF WATER SORPTION IN OKARA AND ITS RELATIONSHIP TO THE GLASS TRANSITION TEMPERATURE

ABSTRACT

The water adsorption and desorption kinetics of okara were determined at different relative humidities (51·4- 83·6 %) at 30 °C. Initial rates of water sorption and the specific rate constants showed different responses to increased RH. Both the adsorption and desorption rate constants dropped significantly at RH 51-55 %; this behaviour is related to occurrence of glass transition phenomenon.     

An Idealized Child Throat that Mimics Average Pediatric Oropharyngeal Deposition

Copyright 2012 American Association for Aerosol Research     

Factors Affecting the Collision of Aerosol Particles with Small Water Drops

The factors influencing the collision of aerosol particles with small water drops at low collision efficiencies are examined. The gravitational force and velocity slip of air on the drop surface are found to affect the collision efficiency in the range of values of 10^?4–^?2. The efficacies of the different computational models are compared for ratios of particle radius to drop radius of less than 0.1. The accuracy of the numerical scheme in the trajectory model can be verified by comparing the efficiencies obtained for submicrometer particles with the convective-diffusion model.     

Dispersion of a Plume of Volatile Aerosol

A theoretical basis and numerical schemes are presented for simulating the dispersion of a plume of volatile aerosol. For special cases where analytical solutions are possible, excellent agreement is shown between analytical and numerical solutions. It is demonstrated that the error in the numerical simulation can be reduced to any desired level. Simulation results for volatile plume dispersion under realistic atmospheric conditions are also presented.     

Detection Efficiency of a Water-Based TSI Condensation Particle Counter 3785

In this article we present observations on the detection efficiency of a recently developed TSI 3785 Water Condensation Particle Counter (WCPC). The instrument relies on activation of sampled particles by water condensation. The supersaturation is generated by directing a saturated airflow into a “growth tube,” in which the mass transfer of water vapor is faster than heat transfer. This results in supersaturated conditions with respect to water vapor in the centerline of a “growth tube.” In this study, the cut-off diameter, that is, the size, where 50% of the sampled particles are successfully activated, varied from 4 to 14 nm for silver particles as a function of temperature difference between the saturator and the growth tube. The solubility of the sampled particles to water played an important role in the detection efficiency. Cut-off diameters for ammonium sulphate and sodium chloride particles were 5.1 and 3.6–3.8 nm, respectively at nominal operation conditions. Corresponding cut-off diameter for hydrophobic silver particles was 5.8 nm.     

Observations of Twelve USEPA Priority Polycyclic Aromatic Hydrocarbons in the Aitken Size Range (10–32 nm D p )

Particle size distribution measurements of twelve USEPA priority pollutant polycyclic aromatic hydrocarbons (PAHs)—collected in Riverside, California, down to 10 nm aerodynamic diameter (D_p)—observed on integrated nocturnal samples (7:00 p.m.-6:30 a.m.) revealed that between 46 and 100% of the mass of particles in the Aitken size range was found in the 10–18 nm size bin. Particles in this size range have high alveolar deposition efficiency.     

Black Snow Episodes in Austria

Two “black” snow episodes in the Salzburg region of Austria were studied. The melted snow samples were fractionated into soluble and solid portions. The solid fraction was analyzed for C, S, N, and trace metals; the solution was analyzed for ions, pH, and conductivity. The solid fraction of the black snow contained > 30% C, ～1% S, and 2% N. The carbon content of the black snow was 1000 times higher than that of the “white snow.” The NO₃ ^? and SO₄ ⁼ content of the black snow was, respectively, 20 and 80 times higher than in the white snow. Trajectory analyses indicate that the black snow originated 200 to 300 km to the northeast of the sampling sites.     

A Cough Aerosol Simulator for the Study of Disease Transmission by Human Cough-Generated Aerosols

Aerosol particles expelled during human coughs are a potential pathway for infectious disease transmission. However, the importance of airborne transmission is unclear for many diseases. To better understand the role of cough aerosol particles in the spread of disease and the efficacy of different types of protective measures, we constructed a cough aerosol simulator that produces a human-like cough in a controlled environment. The simulated cough has a 4.2 l volume and is based on coughs recorded from influenza patients. In one configuration, the simulator produces a cough aerosol containing particles from 0.1 to 100 μm in diameter with a volume median diameter (VMD) of 8.5 μm and a geometric standard deviation (GSD) of 2.9. In a second configuration, the cough aerosol has a size range of 0.1–30 μm, a VMD of 3.4 μm, and a GSD of 2.3. The total aerosol volume expelled during each cough is 68 μl. By generating a controlled and reproducible artificial cough, the simulator allows us to test different ventilation, disinfection, and personal protection scenarios. The system can be used with live pathogens, including influenza virus, which allows isolation precautions used in the healthcare field to be tested without risk of exposure for workers or patients. The information gained from tests with the simulator will help to better understand the transmission of infectious diseases, develop improved techniques for infection control, and improve safety for healthcare workers and patients.

Copyright 2013 American Association for Aerosol Research