Flexural Properties and Failure Mechanisms of Short-Carbon-Fiber-Reinforced Polylactic Acid Composite Modified with MXene and GO.

Recently, short-fiber-reinforced thermoplastic composites (SFRTPCs) have been playing a more and more crucial role in the application of automotive interior materials due to their advantages of low density and environmental resistance properties. However, their relevant mechanical properties need to be optimized. Previous investigations revealed that the surface modification of fibers is useful to improve their mechanical properties. In this work, carbon fiber (CF)-reinforced polylactic acid (PLA) composites modified with MXene and graphene oxide (GO) were prepared by twin-screw extrusion and injection molding methods. Short CF was firstly modified with polyetherimide (PEI), then different weight ratios of MXene-GO (1:1) were subsequently modified on PEI-CF. Finally, the flexural properties and failure mechanisms were analyzed. The results showed that MXene-GO was successfully coated on CF surface, and the flexural strength and modulus of CF-PEI-MXene-GO-reinforced PLA (CF-PEI-MG/PLA) composite were improved compared to that of CF/PLA composite. In addition, the fracture sections of the composites were flat and white, and the fibers bonded well with PLA for CF-PEI-0.1MG/PLA composite compared to CF/PLA composite. The present study could provide a reference for further improving the mechanical performance of PLA-related composites.

Effect and mechanisms of Polygonatum kingianum (polygonati rhizome) on wound healing in diabetic rats.

ETHNOPHARMACOLOGICAL RELEVANCE: Diabetic dermatopathy is one of the most serious and common complications of diabetes. It has been found that high glucose can lead to abnormal glycometabolism. The skin microenvironment pollution caused by the increase in glucose and the oxidative stress mediated by the deposition of advanced glycation end products can lead to invisible skin injury, and the interaction between them is the key factor that makes the skin wounds of diabetic rats difficult to heal. Therefore, the main task of promoting healing is to reduce blood glucose levels and relieve the deposition of advanced glycation end products. Polygonatum kingianum Collett & Hemsl (PK) of Asparagaceae is planted in Yunnan, China, and is used by the Bai, Hani and Wa nationalities as a traditional medicine for preventing and treating diabetes. AIM OF THE STUDY: To study the effects of PK extract on skin wound healing in diabetic rats and to explore the regulatory mechanism of PK on wound microenvironment pollution, the antioxidative stress signaling pathway and latent injury of wound skin tissue. METHODS: First, wounds were prepared after diabetic rats were given PK extract by gavage for 4 weeks, and then gavage was continued for 2 weeks to observe and calculate the wound healing rate. A scanning electron microscope was used to observe the pathomorphological changes in the skin tissue at the edge of the wound. Western blotting was used to detect protein expression. Immunohistochemistry was used to detect the expression of CD34, AGEs, bFGF and VEGF. The Nrf2/HO-1 signaling pathway in skin tissue was detected by fluorescence quantitative PCR. Serum biochemical indicators and inflammatory cytokine levels were detected by a kit. RESULTS: After PK treatment, the wound healing rate increased significantly (P < 0.001), the infiltration of inflammatory cells in skin tissue of DM lesion rats decreased, the number of new blood vessels increased, and the epidermis and dermis thickened. The content of glucose, AGEs, RAGE protein and RAGE mRNA in skin decreased significantly (P < 0.05, P < 0.01, P < 0.001), while the expression of Nrf2 mRNA, HO-1 mRNA, CD34, bFGF and VEGF increased significantly (P < 0.05, P < 0.01, P < 0.001). The levels of SOD, GSH, MMP-9 and MMP-2 in skin decreased (P < 0.05, P < 0.01, P < 0.001), but the level of TIMP-2 increased (P < 0.001). GSP, GHb and ICAM-1 in plasma decreased (P < 0.05, P < 0.01, P < 0.001), while T-AOC, SOD and FINS increased (P < 0.05, P < 0.01). The levels of MDA, TNF-, IL-6, IL-2 and IFN-γ in plasma and wound skin tissue decreased (P < 0.05, P < 0.01, P < 0.001). CONCLUSION: PK can reduce the infiltration of inflammatory cells and glucose content in the skin tissue at the edge of the wound, reduce inflammatory factors in skin and plasma, and increase angiogenesis, thus improving the wound healing rate. PK can alleviate the microenvironment pollution caused by AGEs and glucose metabolism disorder in diabetic rats and induce antioxidant activity through the Nrf 2/HO-1 signaling pathway, thus reducing oxidative damage and offsetting endogenous skin damage and hidden damage.

Al-Modified CuO/Cu2O for High-Temperature Thermochemical Energy Storage: from Reaction Performance to Modification Mechanism.

Next-generation concentrated solar power plants with high-temperature energy storage requirements stimulate the pursuit of advanced thermochemical energy storage materials. Copper oxide emerges as an attractive option with advantages of high energy density and low cost. But its easy sinterability limits its reversibility and cyclic stability performance. In this work, aluminum-doped copper oxides are synthesized and evaluated via thermogravimetric analysis. The reversibility of Cu-Al oxides reaches 99.5% in the first redox cycle and maintains 81.1% of the initial capacity after 120 cycles. The Al element can modify the CuO particle surface in the form of CuAl2O4, which separates the copper oxide particles from each other during redox cycles to avoid agglomeration and participates in the redox reaction. Through DFT analysis, the introduction of Al is found to increase the formation energy of copper vacancies in copper oxides, which helps avoid the sintering problem and thus improves the oxidation rate. This study provides a generalizable operational mechanism of element doping and can serve as a guideline for the optimization of high-performance materials in thermochemical energy storage.

Self-Assembled Structure Evolution of MnFe Oxides for High Temperature Thermochemical Energy Storage.

Thermochemical energy storage (TCES) materials have emerged as a promising alternative to meet the high-temperature energy storage requirements of concentrated solar power plants. However, most of the energy storage materials are facing challenges in redox kinetics and cyclic stability. Iron-doped manganese oxide attracts raising attention due to its non-toxicity, low cost, and high energy capacity over 800 °C. However, there are few investigations on the reversibility enhancement of the redox reaction from the microstructural-evolution-mechanism point of view. Herein, bixbyite-type (Mn0.8 Fe0.2 )2 O3 is synthesized and extruded into honeycomb units, which can maintain an 85% initial capacity after 100 redox cycles. It is also found that a self-assembled core-shell MnFe2 O4 @Mn2.7 Fe0.3 O4 structure forms during the reduction step, and then transforms into a homogeneous solid solution of (Mn0.8 Fe0.2 )2 O3 in the following oxidation step. During the reduction step, shells are formed spontaneously from the Mn2.7 Fe0.3 O4 with the MnFe2 O4 as cores due to the lower surface energy, which facilitates the oxygen adsorption and dissociation during subsequent oxidation step. Through the density functional theory calculation, it is revealed that the lower formation energy of oxygen vacancies in the shell contributes to the improvement of oxygen diffusion rate. This study can provide a guideline to design prospective materials for high-temperature TCES.

A circular RNA-DNA enzyme obtained by in vitro selection.

A circular RNA-DNA enzyme with higher activity to target RNA cleavage and higher stability than that of the hammerhead ribozyme in the presence of RNase A was obtained by in vitro selection. The molecule is composed of a catalytic domain of 22-mer ribonucleotides derived from the hammerhead ribozyme and a fragment of 55-mer deoxyribonucleotides. The DNA fragment contains two substrate-binding domains (9-mer and 6-mer, respectively) and a "regulation domain" (assistant 40-mer DNA with 20-mer random deoxyribonucleotides sequence), which probably play the role in the regulation of flexibility and rigidity of the circular RNA-DNA enzyme. The above results suggest that the circular RNA-DNA enzyme will have a great prospect in gene-targeting therapies.