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Affected by climatic factors (e.g., low temperature and intense ultraviolet radiation), high-altitude regions experience numerous pavement diseases, which compromise driving safety and negatively impact user travel experience. Timely planning and execution of pavement maintenance are particularly critical. In this paper, considering the characteristics of pavement maintenance in high-altitude regions (e.g., volatility of traffic volume, seasonality of maintenance timing, and fragility of the ecological environment), we aim to derive optimal monthly maintenance plans. We develop a multi-objective nonlinear optimization model that comprehensively accounts for minimizing maintenance costs, affected traffic volume and carbon emissions, and maximizing pavement maintenance effectiveness. Utilizing linearization methods, the model is reconstructed into a typical mixed-integer linear programming (MILP) model, enabling it to be solved directly using conventional solvers. We consider five types of decision strategies to reflect the preferences of different decision-makers. Given the uncertainty of maintenance costs, we also utilize the robust optimization method based on the acceptable objective variation range (AOVR) to construct a robust optimization model and discuss the characteristics of optimistic, robust, and pessimistic solutions. The results suggest that different decision strategies show differences in the indicators of maintenance costs, affected traffic volume, carbon emissions, and pavement performance. When multiple decision objectives are comprehensively considered, the indicators are between the maximum and minimum values, which can effectively balance the decision needs of maintenance effectiveness, maintenance timing, and environmental protection. The number of maintenance workers, the requirement of the minimum pavement condition index (PCI), and the annual budget influence the maintenance planning. The obtained robust solution can somewhat overcome the conservative nature of the pessimistic solution. The method proposed in this paper helps address the complexities of pavement maintenance decisions in high-altitude regions and provides guidance for pavement maintenance decisions in such areas. [ABSTRACT FROM AUTHOR]

L -3,4-Dihydroxyphenylalanine (L -DOPA) is widely used in Parkinson's disease treatment and is therefore in high demand. Development of an efficient method for the production of L -DOPA is urgently required. Nanozymes emulating tyrosine hydroxylase have attracted enormous attention for biomimetic synthesis of L -DOPA, but suffered from heterogeneity. Herein, a spherical porous iron–nitrogen–carbon nanozyme was developed for production of L -DOPA. Tannic acid chelated with ferrous ions to form a tannin-iron coordination framework as a carbon precursor. Iron and nitrogen co-doped carbon nanospheres were assembled via an evaporation-induced self-assembly process using urea as a nitrogen source, F127 as a soft template, and formaldehyde as a crosslinker. The nanozyme was obtained after carbonization and acid etching. The nanozyme possessed a dispersive iron atom anchored in the Fe–N coordination structure as an active site to mimic the active center of tyrosine hydroxylase. The material showed spherical morphology, uniform size, high specific surface area, a mesoporous structure and easy magnetic separation. The structural properties could promote the density and accessibility of active sites and facilitate mass transport and electron transfer. The nanozyme exhibited high activity to catalyze the hydroxylation of tyrosine to L -DOPA as tyrosine hydroxylase in the presence of ascorbic acid and hydrogen peroxide. The titer of DOPA reached 1.2 mM. The nanozyme showed good reusability and comparable enzyme kinetics to tyrosine hydroxylase with a Michaelis–Menten constant of 2.3 mM. The major active species was the hydroxyl radical. Biomimetic simulation of tyrosine hydroxylase using a nanozyme with a fine structure provided a new route for the efficient production of L -DOPA. [ABSTRACT FROM AUTHOR]

Here, we report the detailed mechanisms of benzophenone (BZP) photosensitized thymine damage and repair by Paternò–Büchi (PB) cycloaddition. It was found that the head-to-head and head-to-tail PB cycloadditions lead to the formation of the C–O bonds in the 3(nπ*) state and the 3(ππ*) state, respectively. The conical intersection occurs before the head-to-tail C–O bonding. Then, the C–C bonds are formed via intersystem crossing (ISC). The C–O bonding is the rate-determining step of PB cycloaddition. For the cycloreversion reactions, the ring-opening processes completely occur in the singlet excited states of oxetanes. The head-to-head oxetane goes through a conical intersection before cycloreversion with a little energy barrier of 1.8 kcal mol−1. The head-to-tail oxetane splits without a barrier. Then, the ISC processes take place to restore thymine. Throughout the ring-closing and ring-opening processes, ISC plays an important role. These findings are in good agreement with the available experimental findings. We hope that this comprehensive work can provide a deeper understanding of photosensitive DNA damage and repair. [ABSTRACT FROM AUTHOR]