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Shape memory blends of polycaprolactone/thermoplastic polyurethane (PCL/TPU) were prepared by in situ ring-opening polymerization (ROP) of [epsilon]-caprolactone (CL) and thermoplastic polyurethane (TPU). Fourier infrared spectrometer and [sup.1]H-NMR were used to characterize the chemical structure of PCL/TPU copolymers. The results show that TPU has been involved in the ROP of CL, leading to the formation of copolymers with homogeneous morphologies. Besides, pure PCL and all the blends exhibit an excellent shape fixation ratio of 100%, due to their high crystallinity. When a small amount of TPU is introduced, the crystallinity of PCL decreases, and as a result, the shape recovery ratio of the copolymer is enhanced compared with pure PCL. However, with the increased loading of TPU, the content of PCL as the reversible phase decreases and the storage modulus of the PCL/TPU blend declines, so the driving force for the blends to return from the temporary shape to the initial shape becomes smaller, leading to a decrease in the shape recovery ratio. Notably, when the amount of TPU is only 5%, the shape recovery ratio of the blend could reach 83.3%, which is 26% higher than that of pure PCL, and meanwhile, the tensile strength of the blend decreases slightly. This study provides a new strategy for the design of shape-memory materials with high shape-memory properties. KEYWORDS copolymer, polycaprolactone, shape memory material, thermoplastic polyurethane, orcid.org/0000-0003-3259-8361 orcid.org/0000-0002-6161-8993 1 | INTRODUCTION Shape memory polymers (SMPs) are a class of stimulus-response materials, and the stimulus signal can be thermal, [1-6] electrical, [7,8] optical, [9] or magnetic. [10] [...]

In order to study the mechanical properties of the ballastless track structure under the load of the train, this paper simplified the ballastless track structure to an infinite double-layer elastic beam. The double-layer elastic beam model and its theoretical expression formula was established using the elastic foundation beam concept. When the train was at a certain position on the rail, the differential balance equation between the rail and the concrete slab was established under the action of the vehicle load. Combined with the generalized “initial parameter method” and its boundary conditions, the analytical solution of the double-layer beam displacement and stress were obtained under the vehicle load. Through calculation examples, the displacement and stress of the rail and concrete slab were analyzed, and the analytical results were compared with the results of ANSYS, which proved the reliability of the analytical solution. Therefore, simplifying the slab ballastless track into infinite double-layer elastic beam is closer to the actual working conditions. The results can provide a reliable basis for the theoretical study of the ballastless track of high-speed railways and design reference for related projects.

In recent decades, hypoxic areas have rapidly expanded worldwide in estuaries and coastal zones. The Pearl River Estuary (PRE), one of China's largest estuaries, experiences frequent seasonal hypoxia due to intense human activities and eutrophication. However, the ecological effects of hypoxia in the PRE, particularly on fish communities, remain unclear. To explore these effects, we collected fish community and environmental data in July 2021 during the summer hypoxia development period. The results revealed that bottom‐layer dissolved oxygen (DO) in the PRE ranged from 0.08 to 5.71 mg/L, with extensive hypoxic zones (DO ≤ 2 mg/L) observed. Hypoxia has varied effects on fish community composition, distribution, species, and functional diversity in the PRE. A total of 104 fish species were collected in this study, with approximately 30 species (28.6%) exclusively found in hypoxic areas. Species responses to hypoxia varied: species such as Sardinella zunasi, Coilia mystus, and Nuchequula nuchalis were sensitive, while Decapterus maruadsi, Siganus fuscescens, and Lagocephalus spadiceus showed higher tolerance. Within the hypoxia area, dissolved oxygen was the main limiting factor for fish community diversity. Functional diversity (FDiv) decreased with higher dissolved oxygen levels, indicating a potential shift in the functional traits and ecological roles of fish species in response to changing oxygen conditions. Further analysis demonstrated that dissolved oxygen had a significantly stronger effect on fish community structure at hypoxic sites than in the whole PRE. Moreover, other environmental variables also had significant effects on the fish community structure and interacted with dissolved oxygen in the hypoxia area. These findings suggest that maintaining sufficient dissolved oxygen levels is essential for sustaining fish communities and ecosystem health in the PRE. This study provides novel insights into the effects of hypoxia on fish communities in estuarine ecosystems and has significant implications for the ecological health and management of the PRE. [ABSTRACT FROM AUTHOR]

Fresh‐cut potato browning is a severe problem in the potato processing industry. Ascorbic acid, L‐cysteine, hydrogen sulfide (H2S), and nitric oxide (NO) have been reported to reduce the browning in fresh‐cut vegetables and fruits. We compared the effect of each food additive at its commonly used concentration on fresh‐cut potato browning in order to choose a highly efficient treatment and explore its mechanism. Fresh‐cut potato slices were immersed in 0.3 mmol L−1 ascorbic acid, 0.7 mmol L−1 L‐cysteine, 0.7 mmol L−1 H2S, or 2.0 mmol L−1 NO for 10 min and stored at 4°C until the measurements finished. Results showed that the ascorbic acid and L‐cysteine treatments showed less browning than the control treatment, while the H2S and NO treatments did not. Ascorbic acid increased total phenolic content, polyphenol oxidase (PPO) and peroxidase (POD) activities, while L‐cysteine decreased PPO and POD activities with no change in total phenolic content. In addition, these two treatments did not influence respiration rate, weight loss, or rot index. In conclusion, ascorbic acid (0.3 mmol L−1) and L‐cysteine (0.7 mmol L−1) can be valuable means to control fresh‐cut potato browning. Ascorbic acid inhibits the browning mainly by reducing quinones back to phenolic compounds, but L‐cysteine inhibits the browning mainly by decreasing PPO and POD activities. [ABSTRACT FROM AUTHOR]