Alginate hydrogels crosslinked with different strontium-calcium ratios as injectable scaffolds for bone tissue engineering

The easy loss of crosslinking ions in alginate can result in a structural collapse of the physiological environment, thereby losing its characteristics as a bone scaffold. Meanwhile, alginate lacks osteoconductive properties, which are necessary for ideal bone scaffolds. In this study, strontium (Sr) in combination with calcium (Ca) at different ratios were used as a crosslinking agent for the alginate to investigate the effect of Ca–Sr ratio on the physicochemical properties and biological preformation of alginate hydrogel. Here, Ca and Sr in different weight ratios (4:0, 3:1, 2:2, 1:3, and 0:4) were employed as crosslinking agents. The physicochemical properties of hydrogels, including pore size, elastic modulus, degradation rate and swelling ratio, could be effectively tuned by controlling the amount of Sr. The ion release experiment revealed a burst release of Sr²⁺ in the first day after crosslinking. However, after 3 days, the amount of Sr²⁺ release had significantly declined and was proportional to the total strontium initially introduced into the alginate. Meanwhile, the live/dead results exhibited higher cell viability for alginate with 2:2 Ca–Sr weight ratio. The alginate with 2:2 Ca–Sr ratio not only improved osteoblastic attachment, but also up-regulated the alkaline phosphatase activity, the expression of osteogenic marker genes, and relative growth factors. These findings indicate that alginate with 2:2 Ca–Sr ratio might be a promising scaffold for bone tissue engineering.

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Fruit softening correlates with enzymatic activities and compositional changes in fruit cell wall during growing in Lycium barbarum L.

The present study aims to examine fruit cell wall-associated fruit softening in Lycium barbarum L. by the microstructure of the fruit cells and the changes in the contents of cell wall components, molecular weights of cell wall polysaccharides and the activities of related cell wall degrading enzymes at different development stages of L. barbarum L. fruit. Fruit firmness significantly declined during ripening, with the greatest reduction between the 28 and 35 days stages. The decrease in firmness correlated with an extensively deformed microstructure in the parenchyma tissues and positively correlated with reductions in the contents of fruit cell wall materials and molecular weight in cell wall polysaccharide. Cellulase, α-galactosidase, polygalactosidase and pectin methylesterase showed higher activities during 28 days; whereas, the activities of β-galactosidase were higher during 35 days. These results indicate that cell wall-related processes are a key feature of early softening in L. barbarum L.     

土城矿石门跨区段揭煤精准消突技术研究

为有效消除石门揭煤突出危险性,提出石门跨区段施工顺层长钻孔预抽石门揭煤区域瓦斯,充分利用上区段瓦斯治理空间,对石门揭煤区域进行瓦斯超前治理,从而达到精准消突的目的。现场实践表明,该技术钻孔利用率高,揭煤区域瓦斯含量和压力分别下降53%、82%,揭煤期间掘进速率提升61.3%,实现安全、高效、快速揭煤。     

Pressure release characteristics of premixed hydrogen-air mixtures in an explosion venting device with a duct

The technology of explosion venting with a duct can effectively reduce the destructive effect generated from gas accidental explosion in the place of intensive industrial production, while it is not applicable to the production site designed for the technology without ducts. Since it is not clear how to quantitatively evaluate the regularity of energy release in explosion venting especially under high cracking pressure, it is still challenging on the safe application of the technology. This paper aimed to explore the basic characteristics of explosion pressure in a 20 L sphere vessel and venting duct during hydrogen explosion venting for safety design. The effects of the cracking pressure and duct length on explosion pressure at different positions were systematically analyzed according to the test of the hydrogen with different concentrations in an explosion venting device with a duct. Comparing the results of explosion pressure characteristics with experiments conducted in a device without a duct, and quantitatively analyzing the pressure release rule, manifested that the presence of the duct reduced the explosion venting efficiency to a certain extent. In the meantime, by comparing the standard NFPA 68 (P_cra ≤ 0.075 MPa, 0.1 m³ ≤ V ≤ 10,000 m³) for safety design of explosion venting devices, the extended implementation scheme with a venting duct was assessed, implying that the calculation results from NFPA 68 were relatively stable in over-scope (P_cra > 0.075 MPa, V < 0.1 m³) measurement. In future industrial productions, the design of high-pressure hydrogen venting is suggested, leaving sufficient safety margin when referring to the result.     

Super-twisting sliding mode control with defined boundary layer for chattering reduction of permanent magnet linear synchronous motor

Journal of Mechanical Science and Technology - The super-twisting algorithm (STA, a class of second-order sliding mode control (SOSMC)) is widely used in permanent magnet linear synchronous motor...     

Modelling vicious networks with P-graph causality maps

Clean Technologies and Environmental Policy - P-graph causality maps were recently proposed as a methodology for systematic analysis of intertwined causal chains forming network-like structures....     

A fuzzy optimization model for planning integrated terrestrial carbon management networks

Clean Technologies and Environmental Policy - Biochar application and enhanced weathering are negative emission technologies (NETs) with the potential for large-scale deployment for the removal of...     

Scenario analysis on medical treatments of patients with knee osteoarthritis

The Journal of Supercomputing - In developed countries, osteoarthritis (OA) has been among the ten most severe disability diseases in recent years. Approximately, 10% of the world’s...