Research has shown that cigarette smoke changes chemically and physically after it is released into indoor air, that these changes can increase secondhand smoke (SHS) toxicity, and that acute exposures to even low levels of SHS increase the risk of cardiopulmonary disease. We designed a system to reproduce realistic SHS exposures in the laboratory for use in controlled human exposure studies. We generated cigarette smoke with a smoking machine, diluted it and conducted it through a 6 m 3 stainless steel flow reactor at rates equivalent to the upper ranges of normal residential air exchange rates, to create aged cigarette smoke as a model for secondhand cigarette smoke. We observed that approximately 50% of the particle mass deposited within the system and that particle deposition percentage was higher when absorbent materials were placed within the system. The particle size ranges and deposition percentages, coefficients and velocities observed for this smoke aerosol are in good agreement with published values for SHS observed in residences and vehicles. This apparatus also permits the study of the physical and chemical interactions between SHS and indoor surfaces. The apparatus delivers stable aerosol concentra- Health and Human Services 2006). However, the mechanisms by which SHS exposure causes diseases other than cancer are still unclear. SHS is a complex and dynamic mixture made up of particles and gases that includes smoke from the burning end of the cigarette (sidestream smoke) and exhaled mainstream smoke (U.S. Department of Health and Human Services 1986). Recent evidence, from our laboratory and others, has shown that SHS undergoes numerous chemical and physical changes after it is released into the air. Nicotine and other semivolatile organic compounds in smoke adsorb to surfaces where they can react with oxidant gases present in SHS and ambient air to form new chemical compounds (Singer et al. 2002(Singer et al. , 2003Destaillats et al. 2006;Schick and Glantz 2007;Petrick et al. 2011).Subchronic and chronic exposure studies using laboratory animals have demonstrated that, when quantified on the basis of 1246 AGED CIGARETTE SMOKE FOR HUMAN EXPOSURE STUDIES 1247 particulate material mass, aged cigarette smoke is more toxic to the respiratory epithelium than fresh smoke (Schick and Glantz 2006). Thus, studies that use freshly generated cigarette smoke may not capture the health effects caused by SHS in the real world. We created an aged-cigarette-smoke generation system to reproduce human exposures to secondhand cigarette smoke in the real world as accurately as possible in the laboratory. Controlled exposure studies are an important tool for assessing the acute health effects of exposure to pollutant exposures in humans and the biological mechanisms underlying these health effects. By using human subjects, it is possible to eliminate the doubt and dispute involved when animal exposure data are used to set exposure limits for humans. Previous human exposure studies have used two essential methods to ge...

This paper mathematically studies calendering with a tangent hyperbolic model to simulate non-Newtonian polymers. The constitutive equations based on Lubrication Approximation Theory (LAT) are first non-dimensionalized and then simplified. The simplified equations describing the flow inside the calender are solved (a) analytically using the perturbation method and (b) numerically using MatLab built-in routine “BVP4c” method. The first case, obtains an analytical expression for velocity, pressure gradient, and final sheet thickness with the help of the perturbation method, while “BVP4c and Runge-Kutta methods are used to calculate the velocity, pressure, pressure gradient, and mechanical quantities numerically. The power-law index and Weissenberg number influence on pressure, pressure gradient, and velocity profiles of fluid being calendered are shown with graphs. The pressure inside the calender decreases as the power-law index and Weissenberg number increase. The force function and final sheet thickness decreases as the power-law index and Weissenberg number increases.

No abstract

No abstract