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In this study, changes in the molecular mass of alginate were investigated during its enzymatic degradation and the processing parameters for the enzymatic preparation of alginate oligosaccharides were explored. Furthermore, the in vitro immunological activity of degraded products with different molecular mass was evaluated. The results showed that the molecular mass of alginate decreased significantly after degradation by alginate lyase, and three degradation products with different molecular mass were obtained through gradient ethanol fractionation. Their weight-average molecular masses were 13.4, 5.73 and 3.85 kDa, respectively. Using single factor experiments, the optimal processing parameters were determined as pH 7.0, alginate lyase dosage 15 U/g substrate, and hydrolysis time 24 h, giving a yield of 28.05%. All alginate and its degraded products had immunoenhancing activity in mouse macrophages, and among them, the effect of the product with a weight-average molecular mass of 5.73 kDa was most pronounced and more pronounced than that of alginate oligosaccharides. By adding TAK-242, a blocker of macrophage Toll-like receptor 4 (TLR4), it was verified that the degraded products of alginate regulated macrophage immune activity by inducing the secretion of TLR4 and consequently causing cascade reactions to increase the secretion of NO, TNF-α and IL-6. These results can provide a theoretical basis for the high-value utilization of alginate.

As an important content of the modern education system, college English teaching plays an important role in cultivating students to conform to the trend of social development and improving college students’ English application ability. In addition, the transformation of English classroom teaching modes is crucial to the impact on students’ learning effectiveness. Based on this, this paper establishes a semantic comprehension model of oral communication based on the teaching mode of English classroom through the BERT model and then builds a simplified model of 3D images using LOD technology to realize a virtual classroom, which can provide targeted oral exercises and competence enhancement for students with different English levels. Students are expected to have an immersive experience of the communication process in the classroom with the help of VR technology. The results of the study show that the application of VR technology in college English teaching makes 82% of the total number of students in the experimental class score above the good level in the pre-test, while only 64% in the control class. The experimental group accounted for 6% of the total among students with poor oral grades. At the same time, the control group accounted for 22% of the total collective. Obviously, the use of VR technology has an extremely significant effect on students with medium to low oral proficiency. To summarize, VR technology-assisted teaching can improve students’ academic performance and stimulate learners’ interest in learning, which can provide insights into college English classroom teaching.

Four poly(benzoxazine-co-siloxane) oligomers (PBcSs) were successfully synthesized by improving the synthesis step and controlling the ratio of phenol, bisphenol A, 1,3-bis(3-aminopropyl)tetramethyldisiloxane, m-aminophenyl acetylene, and formaldehyde; the resulting compounds all exhibited good processing properties. Siloxane addition can significantly improve the toughness of the polybenzoxazines. Additionally, compared with the PBcSs containing only phenol structure, the introduction of bisphenol A has a decelerating effect on the polymerization process of the benzoxazine oligomer, which leads to an increase in the exothermic peak temperature. Simultaneously, the PBcS containing bisphenol A also exhibits a higher glass transition temperature and increased thermal stability, but reduced flexural strength. Conversely, compared to the benzoxazine oligomers that do not contain alkynyl groups, the introduction of the terminal alkynyl group can accelerate the polymerization process, decrease the exothermic peak temperature, significantly increase the glass transition temperature, and greatly improve the heat resistance; the 5% thermal decomposition temperature of cured product is increased by up to 101[degrees]C. Furthermore, under conditions that ensure high flexural strength, appropriate alkynyl content can also significantly increase the material's flexural modulus. KEYWORDS heat resistance, oligomers, polybenzoxazine, siloxane, terminal alkynyl groups, 1 | INTRODUCTION Polybenzoxazines have attracted considerable attention as important thermosetting resins owing to their outstanding properties, including flexible molecular design, good dielectric properties, a long shelf life, and no [...]

A silicon‐containing arylacetylene resin (PSA)/SiO2 syntactic foam was prepared through a chemical foaming approach, with PSA serving as the matrix, quartz sand (QS) and nanosilica (nSiO2) acting as fillers, and their structures and properties were characterized. The results show that the incorporation of appropriate amounts of QS and nSiO2 can reduce the cell size and apparent density of the syntactic foam, and improve its heat resistance, dielectric properties and wave transmission properties. The addition of QS can increase the compressive strength of the syntactic foam, while the addition of nSiO2 decreases the compressive strength. The apparent densities of the PSA/9QS and PSA/9nSiO2 syntactic foams with 9% filler addition are 0.242 g cm−3 and 0.157 g cm−3, respectively, and the temperatures at 5% weight loss (Td5) under a nitrogen atmosphere were 692 °C and 658 °C, respectively. The dielectric constants were 1.59 and 1.25, respectively. The wave transmittance within the frequency range of 8.2–12.4 GHz was 98.5% and 96.8%, respectively. PSA/SiO2 syntactic foam can be used as a lightweight and high‐temperature‐resistant wave‐transmission material in aerospace and other fields. [ABSTRACT FROM AUTHOR]

In this study, carbon foam derived from silicon‐containing arylacetylene resin (CFPSA) was prepared by using silicon‐containing arylacetylene (PSA) resin as the carbon precursor and polyurethane (PU) foam as the organic sacrificial template. CFPSAs with diverse apparent densities were prepared through the simple impregnation of PU foam with PSA resin solutions of varying concentrations. Their structures, such as the pore morphology; chemical composition; thermal stability; compression properties, and electromagnetic interference (EMI) shielding effectiveness (SE), were characterized. The results indicate that with an increase in the PSA resin concentration, the skeleton of CFPSA becomes thicker, the pore size slightly increases, the apparent density increases, the compressive strength increases, and the EMI SE slightly reduces. CFPSA‐10's apparent density is 0.032 g/cm3, its 5% thermal weight loss temperature (Td5) in an air atmosphere is 642°C, its thermal conductivity is 38.1 mW/m K, its specific compression strength is 2.45 MPa/g cm3, and its specific EMI SE divided by thickness (SSE/t) is 2367 dB cm2/g. CFPSA exhibits lightweight and antioxidant properties, as well as excellent electromagnetic interference shielding performance, presenting great potential for application in aerospace and other fields. [ABSTRACT FROM AUTHOR]

Efficient hydrogen evolution reaction (HER) electrocatalysts are crucial for renewable energy storage and conversion. Pt remains the most efficient HER catalyst, but its widespread application is hindered by cost and resource constraints. In this study, we investigate the HER electrocatalytic activities of free-metal SiC monolayers through doping and strain engineering. Through density functional theory (DFT) calculations, we explore the effects of B, N, S, and P doping on the HER performance of SiC. Our results reveal that B and P doping enhance the catalytic activity, with P doping showing the most promising activity due to its smaller ΔGH* values. Furthermore, we apply tensile strain to modulate the HER activity of P-doped SiC, achieving further improvements. We also construct composite structures of P-doped SiC with graphene, enhancing conductivity and catalytic performance. Our findings provide valuable insights into tailoring the HER catalytic properties of SiC monolayers, offering a pathway towards sustainable hydrogen production. [ABSTRACT FROM AUTHOR]

Silicon‐containing arylacetylene resin (PSA)‐matrix composites hold great potential for aerospace applications due to their excellent heat resistance. In recent years, many PSAs with specific functions have been designed via materials genome approach (MGA), and appropriate resin transfer molding (RTM) curing processes need to be screened to strike a balance between low cost and high quality. In this study, a novel tool based on finite element curing simulation and multiobjective genetic algorithm was developed to optimize the RTM curing process for novel PSA‐matrix composites. The silicon‐containing fluorenylacetylene resin (PSA‐VBF) was selected as the object to systematically characterize its apparent curing kinetics. To address the problem of explosive polymerization of the resin at the injection port during the RTM process, a multiobjective optimization of the curing process using a genetic algorithm was performed to obtain the Pareto front with the maximum temperature gradient at the injection port of the resin, the maximum degree of cure gradient of the composites, and the process time as the objectives. A global sensitivity analysis was also conducted to identify the key parameters. The results demonstrate that the optimized curing process can significantly reduce the temperature gradient and the curing degree gradient with improved curing efficiency. [ABSTRACT FROM AUTHOR]

Seaweed polysaccharides (SPs) obtained from seaweeds are a class of functional prebiotics. SPs can regulate glucose and lipid anomalies, affect appetite, reduce inflammation and oxidative stress, and therefore have great potential for managing metabolic syndrome (MetS). SPs are poorly digested by the human gastrointestinal tract but are available to the gut microbiota to produce metabolites and exert a series of positive effects, which may be the mechanism by which SPs render their anti-MetS effects. This article reviews the potential of SPs as prebiotics in the management of MetS-related metabolic disturbances. The structure of SPs and studies related to the process of their degradation by gut bacteria and their therapeutic effects on MetS are highlighted. In summary, this review provides new perspectives on SPs as prebiotics to prevent and treat MetS. [ABSTRACT FROM AUTHOR]

Working conditions exert an important influence on the tribological properties of protective coatings, thus affecting the wear resistance of workpieces. In this work, a TiAlSiN hardness-modulated multilayer coating with a good match of strength and toughness was deposited on WC-Co substrates. The adhesive wear played a predominant role under the condition of a larger normal load and lower velocity, leading to the formation of a third body layer composed of compressed and lubricating oxides. As a result, the wear rate of the coating tested at 20 N reduced by 23% of that tested at 5 N. Instead, abrasive wear was more manifest, leading to the formation of big-size abrasives, and thus the wear rate increased by 2.8 times while the velocity elevated from 4 mm/s to 16 mm/s. A full factorial analysis of the wear behaviors, including the nanohardness and roughness of the wear track, and the friction coefficient and wear rate of the coating, offered good guidance for the comprehension of the wear form of the TiAlSiN multilayer coating. The results demonstrated the optimization of multilayer structures for TiAlSiN coatings to attain better wear resistance under coupling conditions of normal load and velocity: harder or more lubricated sublayers. [ABSTRACT FROM AUTHOR]