t. yu

The efficacy of low-dose rate ionizing radiation (LDRIR) for anti-inflammatory treatment has been confirmed in various clinical studies. However, the radiobiological mechanisms involved in the anti-inflammatory action of LDRIR have not been completely elucidated. This study investigated whether LDRIR at 0.5 or 1 Gy affected the regulation of cytokine messenger RNA expression and protein levels in inflamed synoviocytes and chondrocytes induced by lipopolysaccharide. Intercellular adhesion molecule-1, interleukin-6, interleukin-8, and growth-regulated alpha protein expression were analyzed in synoviocytes and chondrocytes at 24 h after lipopolysaccharide treatment using reverse transcription polymerase chain reaction, immunostaining, Western blotting, and enzyme-linked immunosorbent assays. The messenger RNA expression levels of interleukin-6, interleukin-8, and growth-regulated alpha protein were lower in synoviocytes cotreated with lipopolysaccharide and 0.5 or 1 Gy radiation than in those treated with lipopolysaccharide alone. The immunostaining results showed that all target cytokines were downregulated after 0.5 and 1 Gy of radiation in inflamed synoviocytes and chondrocytes. In chondrocytes, all four cytokines were significantly downregulated at a dose rate of 0.053 Gy/min, and the extent of regulation was similar to that at 4.02 Gy/min. Our findings indicate that LDRIR may regulate pro-inflammatory cytokine expression in both synoviocytes and chondrocytes, regardless of the dose rate. Therefore, LDRIR can alleviate concerns of carcinogenesis and may be useful in clinical settings.

Flow separation in overexpanded single expansion ramp nozzles (SERN) involves complex phenomena, such as shock waves, expansion waves, turbulent boundary layers, and shear layers. Computational fluid dynamics plays a crucial role in studying unsteady flow behaviour in supersonic nozzles, allowing for an investigation into the dynamic flow field characteristics. However, the application of OpenFOAM as a numerical tool for studying SERN in the field of compressible flows, particularly in the overexpansion state where the flow field characteristics are more complex, has received relatively less attention. In this study, the flow field characteristics of an overexpanded SERN under different turbulence models are investigated through a combination of experiments and numerical calculations. The qualitative and quantitative predictive performance of two compressible flow solvers in OpenFOAM, namely, rhoCentralFOAM and sonicFOAM, are compared in terms of flow separation pattern and separation pattern transitions within the overexpanded SERN. The ability of rhoCentralFOAM and sonicFOAM to accurately predict complex flow states is evaluated. Results indicate that the numerical simulations conducted using rhoCentralFOAM and sonicFOAM successfully capture flow separation, separated shock waves, separated bubbles and shear layers for two types of restricted shock separation patterns at the same nozzle pressure ratio (NPR), demonstrating agreement with experimental results. However, sonicFOAM initiates the transition in the separation pattern 0.0773 NPR earlier than rhoCentralFOAM during the whole separation pattern transition process of the SERN. The transition process in sonicFOAM lasts longer and exhibits a greater variation in NPR. SonicFOAM fails to accurately predict certain aspects, such as the pressure rise after the separation bubble, the reattachment shock wave, and tends to overestimat the length of the separation shock length. Consequently, sonicFOAM cannot be recommended as a suitable solver for accurately capturing the separation pattern of an overexpanded nozzle.

As a typical buffer energy absorbing structure, thin-walled tube filled with foam aluminum has good mechanical properties and energy absorption characteristics. Therefore, the axial compression performance of square tube and foam aluminum filled square tube was experimentally studied by quasi-static mechanical loading method. On the basis of the existing experimental research and theoretical analysis, the strain rate is introduced into the dynamic compression theory, and the mathematical model of the average crushing load of foam aluminum filled square tube under the axial quasi-static and impact loads is obtained. By comparing the theoretical results with the simulation results, the relative error of quasi-static and impact state is 2.8% and 8% respectively. This paper not only proves that foam aluminum filling can significantly improve the bearing capacity and energy absorption performance of square tube structure in the axial compression process, but also provides a more specific theoretical basis for the axial compression energy absorption design of square tube filled with foam aluminum.