Articular cartilage has a poor ability to regenerate itself, therefore it is important to establish the treatment methodologies for cartilage diseases such as osteoarthritis (OA) or rheumatoid arthritis (RA). In these cartilage diseases, RA is known as an autoimmune disease that causes an unexplained persistent inflammation in synovial tissue. TNF-α (tumor necrosis factor-alpha) is one of inflammatory cytokine released by synoviocytes which causes cartilage destruction by producing the matrix metalloproteinase. To understand pathology of RA, various studies were performed in vivo and in vitro. One of the approaches is based on co-culture of cartilage explants and synoviocytes extracted from RA tissue. This co-culture system is superior for evaluating the effect of synoviocytes on cartilage degeneration in vitro. However, the studies using co-culture system focused on only biochemical properties. The purpose of this study is to establish the co-culture system to enable the evaluation of biomechanical as well as biochemical properties. The bovine cartilage explants were co-cultured with human synoviocytes from RA patients in the medium containing TNF-α and the mechanical properties of cartilage were evaluated. As the results, it was suggested that the synoviocytes from RA caused the decrease in compressive modulus as well as sGAG content of the cartilage explants.

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In the process plant, random vibration excited by the turbulence generated at tee connection might cause problem such as piping damage. In general, the beam mode piping vibration is known to be excited when the internal flow of the piping is the severe turbulent conditions. However, the shell mode piping vibration could occur when the piping stiffness of the circumferential direction is relatively low. In this study, an experiment was executed in order to obtain the basic characteristics of flow induced vibration at tee connection downstream. The experiment results showed the dominated vibration is circumferential direction and the dominated vibration source is the turbulence generated at tee connection. In order to evaluate the integrity of the piping system for the tee connection downstream against flow induced vibration, a new evaluation index is investigated based on the experimental results and random vibration theory. As a result, it was confirmed that the new evaluation index tends to be proportional to the shell mode stress of the random vibration.

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