For the last four decades, the role of polyynes such as diacetylene (HCCCCH) and triacetylene (HCCCCCCH) in the chemical evolution of the atmosphere of Saturn's moon Titan has been a subject of vigorous research. These polyacetylenes are thought to serve as an UV radiation shield in planetary environments; thus, acting as prebiotic ozone, and are considered as important constituents of the visible haze layers on Titan. However, the underlying chemical processes that initiate the formation and control the growth of polyynes have been the least understood to date. Here, we present a combined experimental, theoretical, and modeling study on the synthesis of the polyyne triacetylene (HCCCCCCH) via the bimolecular gas phase reaction of the ethynyl radical (CCH) with diacetylene (HCCCCH). This elementary reaction is rapid, has no entrance barrier, and yields the triacetylene molecule via indirect scattering dynamics through complex formation in a single collision event. Photochemical models of Titan's atmosphere imply that triacetylene may serve as a building block to synthesize even more complex polyynes such as tetraacetylene (HCCCCCCCCH).electronic structure calculations ͉ planetary chemistry ͉ crossed molecular beams ͉ photochemical model

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Particle-based delivery systems demonstrate a pregnant value in the fields of drug research and development. Efforts to advance this technology focus on the fabrication of functional particles with enhanced efficiency and performance for drug delivery. Here, we present a new type of mesoporous colloidal photonic crystal particle (MCPCP)-based drug-delivery system with distinct features. As the MCPCPs were constructed by self-assembling monodisperse mesoporous nanoparticles in microfluidic droplet templates, they were composed of hierarchical macro- and mesoporous structures and could provide plenty of nanopores and interconnected nanochannels for synergistic loading of both micro- and macromolecule drugs with large quantity and sustained release. In addition, by integrating the stimuli-responsive poly( N-isopropylacrylamide) hydrogel into the MCPCPs and employing it as a "gating" to control the opening of the macro- and mesopores, the MCPCP delivery systems were imparted with the function of controllable release. More attractively, as the average refractive index of the MCPCPs was decreased during the release of the loaded actives, the photonic band gaps of the MCPCPs blue-shifted correspondingly; this provided a novel stratagem for real-time self-reporting of the therapeutic agent release process of the MCPCPs. Hence, the MCPCPs are ideal for intelligent drug delivery because of these dramatical features.

In this paper, microscopic technique tests were carried out to observe and evaluate the degree of blending between reclaimed asphalt pavement (RAP) binder and virgin binder in hot mixed asphalt mixture. To this end, titanium dioxide (TiO2) was selected as a tracer to tag virgin binder. Scanning electron microscope/energy dispersive spectrometer (SEM/EDS) experiments were conducted on compacted recycled asphalt mixtures and virgin asphalt mixtures. The element mass ratio of titanium over sulfur (Ti:S) was proposed as an quantitative indicator of blending ratio to accurately evaluate the degree of partial blending between RAP and virgin binders. The SEM/EDS images visually displayed the partial blending in high RAP mixtures. Different partial blending patterns were observed under different handling processes. The results of EDS tests indicated that with the increase of the RAP content, the blending degree of virgin and aged binder decreased rapidly, and the homogeneity of blended binder became weakened. In addition, aging process and recycling agent could improve the efficiency of RAP binder as it is blended with virgin one, and it should be noted that the inter-diffusion of old and new binders need enough time. This methodology provides a systemic approach to determine the degree of binder blending in RAP mixture.

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