This research aims to investigate the aging resistance of asphalts from different crude oils based on molecular structure and rheological properties. The average molecular structure of five types of asphalt from different crude oils were analyzed with the element analyzer, nuclear magnetic resonance, gel permeation chromatograph, and the improved Brown–Ladner method. The rheological properties of the asphalts were tested by the dynamic shear rheometer before and after laboratory aging. The antiaging properties of the asphalts were evaluated by the rheological aging index (RAI). The findings indicate that there were significant differences in the molecular structures among the five types of asphalt. The asphalt with the least hydrogen–carbon ratio (H/C), the largest aromatic carbon ratio (f_A), and the largest condensation index (CI) had the lowest rate of decline in rheological properties and therefore, the best antiaging performance. The H/C, f_A, and CI had good correlations with RAI, which indicated that it was feasible to use these molecular structure parameters to evaluate the differences in the aging resistance of various asphalts.

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This research aimed to explore the impact of aging on the molecular structure of asphalts from different crude oils. The elemental composition of five types of original asphalts was measured. The structure changes of the asphalts were analyzed with Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (1H-NMR) before and after thin-film oven test, ultraviolet light (UV), and pressure aging vessel (PAV). The result of the elemental analysis showed that the hydrogen-carbon ratio (H/C) of asphalts ranges from 1.347 to 1.602 with different contents of sulfur, nitrogen, and oxygen. The FTIR indicated that asphalts with a low H/C had a low rate of change of carbonyl index after aging. Asphalts were more likely to produce an aromatic ring structure and sulfoxide group during the PAV aging process. The aliphatic structure was easier to reduce during the UV aging process. The 1H-NMR analysis showed that the content of aromatic hydrogen (Har) of asphalts is between 0.022 and 0.056, the content of Har decreased after aging, and the asphalt with a low Har content had a smaller change rate of hydrogen atom content. The outlined research results revealed that the asphalt with lower H/C and Har content was prone to have better aging resistance.@en

Engineered genetic circuits with tailored functions that mimic how cells process information in changing environments (e.g. cell fate decision, chemotaxis, immune response) have great applications in biomedicine and synthetic biology. Although there is a lot of progress toward the design of gene circuits yielding desired steady states (e.g. logic-based networks), building synthetic circuits for dynamic signal processing (e.g. filters, frequency modulation, and controllers) is still challenging. Here, we provide a model-based approach to build gene networks that can operate as band-pass filters by taking advantage of molecular sequestration. By suitably approximating the dynamics of molecular sequestration, we analyze an Incoherent Feed-Forward Loop (IFFL) and a Negative Feedback (NF) circuit and illustrate how they can achieve band-pass filter behavior. Computational analysis shows that a circuit that incorporates both IFFL and NF motifs improves the filter performance. Our approach facilitates the design of sequestration-based filters, and may support the synthesis of molecular controllers with desired specifications.

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