Effect of Temperature and Process on Quantity and Composition of Laboratory-generated Bitumen Emissions

<div><p>In this study we investigated the impact of temperature on emissions as related to various bitumen applications and processes used in commercial products. Bitumen emissions are very complex and can be influenced in quantity and composition by differences in crude source, refining processes, application temperature, and work practices. This study provided a controlled laboratory environment to study five bitumen test materials from three European refineries; three paving grade, one used for primarily roofing and some paving applications, and one oxidized industrial specialty bitumen. Emissions were generated at temperatures between 140°C and 230°C based on typical application temperatures of each product. Emissions were characterized by aerodynamic particle size, total organic matter (TOM), simulated distillation, 40 individual PACs, and fluorescence (FL-PACs) spectroscopy.</p><p>Results showed that composition of bitumen emissions is influenced by temperature under studied experimental conditions. A distinction between the oxidized bitumen with flux oil (industrial specialty bitumen) and the remaining bitumens was observed. Under typical temperatures used for paving (150°C–170°C), the TOM and PAC concentrations in the emissions were low. However, bitumen with flux oil produced significantly higher emissions at 230°C, laden with high levels of PACs. Flux oil in this bitumen mixture enhanced release of higher boiling-ranged compounds during application conditions.</p><p>At 200°C and below, concentrations of 4–6 ring PACs were ≤6.51 μg/m³ for all test materials, even when flux oil was used. Trends learned about emission temperature-process relationships from this study can be used to guide industry decisions to reduce worker exposure during processing and application of hot bitumen.</p></div

Vesicle Budding Induced by a Pore-Forming Peptide

We describe, in a system whose uniqueness is that the presence of pores allows the volume to vary as budding proceeds, how phase separation on the surface of spheres extrudes material in the process called &quot;budding&quot;. The system is giant phospholipid vesicles (GUVs) containing phase-separated regions of DOPC (soft, liquid) and DPPC (stiff, gel), with cholesterol and without it. Budding is triggered by adding the cationic pore-forming peptide, melittin. Without cholesterol, fluorescence experiments show that melittin selectively binds to the liquid domains, inducing them to form mainly exocytotic monodisperse smaller vesicle buds of this same material, causing the parent GUV to shrink. The effect of cholesterol is to produce just a few large buds following domain coalescence, rather than numerous smaller monodisperse ones. Line tension is experimentally shown to be essential for budding in this multicomponent membrane.close282