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The zirconium alloy cladding of PWR fuel rods which undergo high neutron irradiation during service, will cause significant changes in its microstructure, thereby affecting its macroscopic performance. Therefore, the study of neutron irradiation behavior of zirconium alloy cladding is a focus of nuclear field. However, due to the strong radioactivity of materials after neutron irradiation, relevant experiments must be conducted in a hot cell. Therefore, research on the microstructure of irradiated fuel cladding is a difficult task. In this study, the microstructure of M5TM zirconium alloy cladding material after neutron irradiation was studied by means of transmission electron microscope in the hot cell facility of China Institute of Atomic Energy. The samples were from commercial pressurized water reactor AFA3G type spent fuel rods with burnup of 14 GW·d/tU and 41 GW·d/tU, respectively. A cladding sample with a length of about 10 mm from the fuel rod was cut, and the defueling and chemical cleaning in the hot cell were carried out to obtain a clean cladding sample. Then, mechanical sampling methods was used to prepare a thin slice sample of the cladding with 3 mm diameter. Finally, the electrolytic twin-jet thinning method was used to prepare the cladding transmission electron microscopy observation and analysis sample. In addition, to compare the structural changes of zirconium alloy cladding before and after irradiation, the same method was used to prepare un-irradiated observation and analysis samples of the same material. The observation and analysis results of the un-irradiated and irradiated samples reveal that there are native second phase particles (SPPs) inside the matrix structure of the un-irradiated zirconium alloy cladding, and the overall interior of the matrix is with few nano precipitates and no obvious dislocation structure observed. After irradiation, there is no significant difference in the size and distribution of the native SPPs in the matrix compared to the un-irradiated sample, but significant nano precipitates and high-density dislocation structures appear. As the fuel burnup increases, the size of nano precipitates increases. The similarity of dislocation structures between low and high burnup samples indicates that under the burnup of 14 GW·d/tU, the dislocation structures generated by irradiation in the zirconium alloy cladding basically reach saturation state. The results of selected area electron diffraction (SAED) indicate that although there are some amorphous structures in the native SPPs in the matrix after irradiation, the bcc crystal structure is still the main structure, indicating that the SPPs maintain certain irradiation stability at the burnup of 41 GW·d/tU. In addition, the EDS results of the SPPs indicate that with the increase of fuel burnup, the content of Nb element tends to be depleted. Analysis suggests that after neutron irradiation, the Nb atoms in the SPPs of zirconium alloy expand into the Zr matrix, promoting the precipitation of Nb elements in the form of nano Nb rich phases in the Zr matrix.

Micro-addition of alloying elements is not only an effective method to improve the overall performance of aluminum matrix composites but also a proven workable low-cost technology in improving the reinforced phase/matrix interface structure and regulating the mechanical property of strength-toughness other than the physical processes such as electromagnetic stirring and ultrasonic vibration, as well as preparation technologies like bimodal structure and biomimetic layered materials, etc. In recent years, the research of alloying elements in TiB2 particles reinforced aluminum matrix composites has attracted much attention and achieved remarkable results which lay a good foundation for better understanding of its mechanism on the nano-level or even the atomic level. A series of latest developments on the properties of TiB2/Al composites by adding alloying elements at home and abroad were summarized, i.e. TiB2 particle morphology, microstructure and mechanical properties.The mechanism of micro-alloying and its prospect on regulating crack initiation and propagation, exerting intrinsic mechanical properties of micro and nano scale, along with coordinating the dilemma of strength-ductility trade-off were also forecasted, aimed at providing reference for the preparation of high-performance aluminum matrix composites.

Dual-specificity phosphatase 2 (DUSP2) regulates the activation of members of the mitogen-activated protein kinase (MAPK) family, which is involved in a variety of cellular processes including cell proliferation, differentiation, apoptosis, and migration. DUSP2 also regulates the expression of inflammatory mediators in macrophages; however, it remains unknown whether DUSP2 participates in macrophage migration. Here, using the tail fin injury model in zebrafish larvae, we found that the deletion of DUSP2 inhibited the expression of pro-inflammatory cytokines and macrophage chemokines. Moreover, live imaging results showed that the migration of macrophages to the injury site was inhibited after DUSP2 deletion. This inhibitory effect was mediated through the reduced activation of extracellular regulated protein kinases (ERK) in DUSP2 knockout zebrafish. [ABSTRACT FROM AUTHOR]

Hypertension is a significant risk factor of cardiovascular diseases (CVDs) with high prevalence worldwide, the current treatment has multiple adverse effects and requires continuous administration. The glucagon‐like peptide‐1 receptor (GLP‐1R) agonists have shown great potential in treating diabetes mellitus, neurodegenerative diseases, obesity and hypertension. Butyric acid is a potential target in treating hypertension. Yet, the application of GLP‐1 analogue and butyric acid in reducing blood pressure and reversing ventricular hypertrophy remains untapped. In this study, we combined the therapeutic capability of GLP‐1 and butyric acid by transforming Clostridium butyricum (CB) with recombinant plasmid pMTL007 encoded with hGLP gene to construct the engineered probiotics Clostridium butyricum‐pMTL007‐GLP‐1 (CB‐GLP‐1). We used spontaneous hypertensive rat (SHR) models to evaluate the positive effect of this strain in treating hypertension. The results revealed that the intragastric administration of CB‐GLP‐1 had markedly reduced blood pressure and improved cardiac marker ACE2, AT2R, AT1R, ANP, BNP, β‐MHC, α‐SMA and activating AMPK/mTOR/p70S6K/4EBP1 signalling pathway. The high‐throughput sequencing further demonstrated that CB‐GLP‐1 treatments significantly improved the dysbiosis in the SHR rats via downregulating the relative abundance of Porphyromonadaceae at the family level and upregulating Lactobacillus at the genus level. Hence, we concluded that the CB‐GLP‐1 greatly improves blood pressure and cardiomegaly by restoring the gut microbiome and reducing ventricular hypertrophy in rat models. This is the first time using engineered CB in treating hypertension, which provides a new idea for the clinical treatment of hypertension. [ABSTRACT FROM AUTHOR]