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This is an article in the field of ceramics and composites. The mix proportion of limestone powder cement is designed based on the mixture design principle, and the effects of limestone powder content and particle size on the mechanical properties of limestone powder Portland cement system are studied. The hydrate phase and microporous structure of portland cement paste mixed with 0.44 mm and 0.025 mm limestone powder were analyzed by X-ray diffraction (XRD) and low field nuclear magnetic resonance (NMR). The results show that the two limestone powders have a negative effect on the early compressive strength. However, with the progress of hydration, limestone powder within a certain dosage range can enhance the later strength of cement. When the dosage exceeds this range, the compressive strength decreases gradually with the increase of dosage. Although the addition of limestone powder produces hydrated calcium carboaluminate in the hydration products which is conducive to the mechanical properties of cement stone, its coarsening of microporous structure greatly reduces the compressive strength of limestone powder cement specimens when the content of limestone powder exceeds a certain value.

ObjectiveIn response to the problems of high weight and relatively low protective efficiency associated with traditional multicamerate structures (i.e., void compartment-liquid tank-void compartment), this study explores the protective performance of underwater cylindrical protective structures. Methods A numerical model based on an arbitrary Lagrangian-Eulerian (ALE) algorithm is established and verified through a contact explosion case involving a typical structure. On this basis, models of the traditional multicamerate protective structure and cylindrical protective structure are then established. Through numerical simulation, parameters such as maximal stress, strain and energy absorption after underwater contact explosion with the same explosive charge are analyzed, and their respective protective performances obtained.ResultsThe displacement of the defended longitudinal wall of the cylindrical protective structure is smaller than that of the watertight longitudinal wall, which is contrary to the behavior of traditional multicamerate protective structures. Additionally, the energy absorbed by the deck and double bottom is 9.92% less than that of the traditional protective structure, demonstrating a significant advantage in resisting deformation in the vertical direction.ConclusionThe results of this study indicate that the cylindrical protective structure exhibits a lower level of damage under the same charge, providing new insights for the innovative design of underwater protection structures.

The redundancy feature of the parallel mechanism can increase the effective workspace，realize the fault-tolerant motion，which improves the performance of the parallel mechanism. Based on the 3-PRS parallel mechanism structure characteristic，starting from the configuration of a kinematic sub-branches，a redundant kinematic sub-branches is designed，and then a 3-PR（P）S redundant parallel mechanism is proposed. The degree of freedom of 3-PR（P）S redundant parallel mechanism is analyzed by using screw theory，a kinematic model is established，and the kinematic equation is derived. Aiming at the problems of rough boundary and low accuracy in solving the workspace of parallel mechanism by classical Monte Carlo method，a Monte Carlo method based on boundary extremum densification is proposed. The workspace of 3-PR（P）S redundant parallel mechanism is analyzed，and specific solving steps are given. Finally，the workspace of 3-PRS parallel mechanism and redundant parallel mechanism under different parameters are figured by Matlab programming and simulation. The results show that the workspace of the 3-PR（P）S redundant parallel mechanism is greatly improved compared with the 3-PRS parallel mechanism under the same parameters，which provides a theoretical basis for trajectory planning and fault-tolerant control.

In order to diagnose the location and severity of radial friction of centrifugal compressor set in the long-distance gas pipeline accurately, identify causes of radial friction in time, treat the radial friction quickly and properly, and guarantee the safe and stable operation of the long-distance gas pipelines, the mechanism of radial friction was studied. The vibration state of the centrifugal compressor set as a result of fraction faults, such as the local radial friction, local frictional thermal bending and all-round friction was analyzed. Meanwhile, the radial friction of centrifugal compressor set was judged and evaluated according to the abnormal vibration shown by the centrifugal compressor set. Further, it was verified by the fault cases, and the relevant solutions were proposed based on various radial friction types. Conclusively, the research results could provide basis and experience for the identification, analysis, diagnosis, troubleshooting, treatment and overhaul scheme formulation of radial friction fault of centrifugal compressor sets in the long-distance natural gas pipeline, which is helpful to ensure the stable operation of the centrifugal compressor set.

Objective: To investigate the protective effect of fermented Lycium barbarum polysaccharides (FLBP) on the intestine in an aging mouse model. Methods: The aging model was established by continuous subcutaneous injection of 1 000 mg/(kg mb · d) D-galactose in the back of the neck, followed by gavage of low (150 mg/(kg mb · d)) and high (300 mg/(kg mb · d)) doses of FLBP. After 10 weeks, body mass, organ indexes, serum inflammatory markers and anti-inflammatory indicators including tumor necrosis factor-α (TNF-α), interleukin (IL)-1β, IL-6 and IL-10 levels, intestinal permeability, intestinal barrier damage biomarkers such as lipopolysaccharide (LPS) and lipopolysaccharide binding protein (LBP) contents, the histological structure of the colon, colonic mucin 2 (Muc2) expression, intestinal flora composition and fecal short-chain fatty acid contents were detected and analyzed. Results: High-dose FLBP antagonized D-galactose-induced growth retardation and thymus atrophy, decreased the serum levels of TNF-α, IL-1β and IL-6 and significantly increased serum IL-10 levels in the aging mice (P < 0.05). Furthermore, FLBP significantly ameliorated colonic barrier damage in mice, as evidenced by a significant decrease in intestinal permeability, LPS and LBP contents (P < 0.05), alterations in colonic tissue structure, and a significant increase in MUC2 secretion (P < 0.05). Meanwhile, FLBP regulated the gut microbiota composition by changing the α- and β-diversity, increasing the relative abundance of the beneficial bacteria norank_f_Muribaculaceae and Lactobacillus, and decreasing the relative abundance of the harmful bacteria Atopostipes and Jeotgalicoccus, and increasing the fecal contents of acetic acid, propionic acid, valeric acid and isobutyric acid significantly (P < 0.05). Conclusion: High-dose FLBP reduced circulating pro-inflammatory cytokine levels and enhanced anti-inflammatory function in aging mice, which might be related to improving colonic barrier function, regulating the intestinal flora composition, and increasing the levels of beneficial SCFAs in the intestinal tract of mice. This study provides a theoretical reference for the application of FLBP as a functional food ingredient for intestinal health.

In this study, an ethanol extract from P. chinense Pursh was obtained by ultrasonic-assisted extraction, whose contents of total flavonoids and phenols were (17.43 ± 1.41) mg/g and (14.78 ± 0.95) mg/g, respectively. In total, 43 major chemical compounds were identified in the extract by ultra-high performance liquid chromatography-quadrupole-time of flight-mass spectrometry (UPLC-QTOF-MS). In addition, the effects of 0.05%, 0.1% and 0.3% P. chinense Pursh extract or 0.02% butylated hydroxyanisole (BHA) combined with butylated hydroxytoluene (BHT; 1:1, m/m) on lipid oxidation and protein stability in Chinese sausage were studied. The acid value (AV), peroxide value (POV), thiobarbituric acid reactive substance (TBARS) value, carbonyl content, sulfhydryl content and total volatile basic nitrogen (TVB-N) content of Chinese sausage were determined at different storage times. It was found that the TBARS value of the sausage with 0.3% P. chinense Pursh extract was significantly lower than that of the control group (0.02% BHA + BHT) on the 35th day, and the protein carbonyl and sulfhydryl contents and TVB-N content of the sausage with P. chinense Pursh extract were similar to those of the control group. Although the AV and POV of the P. chinense Pursh extract group were slightly higher than those of the control group, its lipid oxidation resistance was significantly better than that of the control group. Therefore, as a potential candidate to replace synthetic antioxidants, P. chinense Pursh extract has the potential to be used in the production of Chinese sausage for its positive effect on improving the product quality and extending the shelf life.

Some transcriptional regulators contribute to the expression of Streptococcus mutans (S. mutans) cariogenic virulence factors. Although the target sequence transcriptional regulators anchored on the cell wall and the molecular mechanism of the regulation of S. mutans are yet to be clarified, certain global regulators potentially associated with the cariogenicity of S. mutans have been identified. This review is about these related transcriptional regulators, their function, and possible mechanisms.