The effect of titanium dioxide nanoparticles on pulmonary surfactant function and ultrastructure

<p>Abstract</p> <p>Background</p> <p>Pulmonary surfactant reduces surface tension and is present at the air-liquid interface in the alveoli where inhaled nanoparticles preferentially deposit. We investigated the effect of titanium dioxide (TiO₂) nanosized particles (NSP) and microsized particles (MSP) on biophysical surfactant function after direct particle contact and after surface area cycling <it>in vitro</it>. In addition, TiO₂effects on surfactant ultrastructure were visualized.</p> <p>Methods</p> <p>A natural porcine surfactant preparation was incubated with increasing concentrations (50-500 μg/ml) of TiO₂NSP or MSP, respectively. Biophysical surfactant function was measured in a pulsating bubble surfactometer before and after surface area cycling. Furthermore, surfactant ultrastructure was evaluated with a transmission electron microscope.</p> <p>Results</p> <p>TiO₂NSP, but not MSP, induced a surfactant dysfunction. For TiO₂NSP, adsorption surface tension (γ_ads) increased in a dose-dependent manner from 28.2 ± 2.3 mN/m to 33.2 ± 2.3 mN/m (p < 0.01), and surface tension at minimum bubble size (γ_min) slightly increased from 4.8 ± 0.5 mN/m up to 8.4 ± 1.3 mN/m (p < 0.01) at high TiO₂NSP concentrations. Presence of NSP during surface area cycling caused large and significant increases in both γ_ads(63.6 ± 0.4 mN/m) and γ_min(21.1 ± 0.4 mN/m). Interestingly, TiO₂NSP induced aberrations in the surfactant ultrastructure. Lamellar body like structures were deformed and decreased in size. In addition, unilamellar vesicles were formed. Particle aggregates were found between single lamellae.</p> <p>Conclusion</p> <p>TiO₂nanosized particles can alter the structure and function of pulmonary surfactant. Particle size and surface area respectively play a critical role for the biophysical surfactant response in the lung.</p

Experimental Verification of Principal Losses in a Regulatory Particulate Matter Emissions Sampling System for Aircraft Turbine Engines

13-C-AJFF-MST-004This is an open access article under the terms of the Creative Commons Attribution-Noncommercial-No Derivatives License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.To cite this article: D. B. Kittelson, J. Swanson, M. Aldridge, R. A. Giannelli, J. S. Kinsey, J. A. Stevens, D. S. Liscinsky, D. Hagen, C. Leggett, K. Stephens, B. Hoffman, R. Howard, R. W. Frazee, W. Silvis, T. McArthur, P. Lobo, S. Achterberg, M. Trueblood, K. Thomson, L. Wolff, K. Cerully, T. Onasch, R. Miake-Lye, A. Freedman, W. Bachalo & G. Payne (2022) Experimental verification of principal losses in a regulatory particulate matter emissions sampling system for aircraft turbine engines, Aerosol Science and Technology, 56:1, 63-74, DOI: 10.1080/02786826.2021.1971152A sampling system for measuring emissions of nonvolatile particulate matter (nvPM) from aircraft gas turbine engines has been developed to replace the use of smoke number and is used for international regulatory purposes. This sampling system can be up to 35m in length. The sampling system length in addition to the volatile particle remover (VPR) and other sampling system components lead to substantial particle losses, which are a function of the particle size distribution, ranging from 50 to 90% for particle number concentrations and 10-50% for particle mass concentrations. The particle size distribution is dependent on engine technology, operating point, and fuel composition. Any nvPM emissions measurement bias caused by the sampling system will lead to unrepresentative emissions measurements which limit the method as a universal metric. Hence, a method to estimate size dependent sampling system losses using the system parameters and the measured mass and number concentrations was also developed (SAE 2017; SAE 2019). An assessment of the particle losses in two principal components used in ARP6481 (SAE 2019) was conducted during the VAriable Response In Aircraft nvPM Testing (VARIAnT) 2 campaign. Measurements were made on the 25-meter sample line portion of the system using multiple, well characterized particle sizing instruments to obtain the penetration efficiencies. An agreement of +/-15% was obtained between the measured and the ARP6481 method penetrations for the 25-meter sample line portion of the system. Measurements of VPR penetration efficiency were also made to verify its performance for aviation nvPM number. The research also demonstrated the difficulty of making system loss measurements and substantiates the E-31 decision to predict rather than measure system losses

EVALUATION OF SHOPPING CENTER TRIP TYPES

The results are described of field studies aimed at identifying the net traffic impact of commercial establishments on the surrounding street system. The study results are believed to be indicative of conditions widely to be found in many types of commercial activities and urban environments. The background to the study, the basic shopping trip types, and study site selection are detailed. The data collection procedure and the cross-check analysis are described. The study led to several conclusions: (1) commercial activities typically generate relatively few new vehicle trips; (2) commercial centers located on major arterials are likely to draw a significant percentage of their total customers from the passing traffic stream; and (3) in any case, the net traffic impacts of commercial activities quickly dissipate as the distance from the commercial activity is increased