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Background: Low back pain (LBP) is regarded as a frequent disease that causes disability. We aimed to explore the effect of naringin on intervertebral disc degeneration (IDD) in IL-1b-induced human nucleus pulposus (NP) cells and its corresponding molecular mechanisms. Material/Methods: Human NP cells were identified by toluidine blue and Safranin O staining. Cell viability was determined by MTT assay. The expression levels of matrix metalloproteinases (MMP-3, MMP-13, ADAMTS-4, ADAMTS-5, collagen II, aggrecan), inflammatory genes (tumor necrosis factor [TNF]-a, interleukin [IL]-6), kappa B kinase a (IkBa), p65 and p53 were determined by quantitative real-time polymerase chain reaction (qPCR) and western blotting. Immunofluorescence study was performed to detect the position and expression of p65 protein in IL-1b-induced human NP cells. Results: Human NP cells were successfully separated from intervertebral disc tissue. We found that naringin could significantly reduce the expressions of matrix metalloproteinases (MMP-3, MMP-13, ADAMTS-4, and ADAMTS-5) and inflammatory genes in IL-1b-stimulated human NP cells, while collagen II and aggrecan were increased at mRNA and protein level. Immunofluorescence showed that naringin pretreatment decreased the p65 protein expression in the nucleus and suppressed the phosphorylation of IkBa and p65. Conclusions: These results demonstrated that naringin could attenuate matrix metalloproteinase catabolism and inflammation in IL-1b-treated human nucleus pulposus cells via downregulating NF-kB pathway and p53 expression, suggesting that naringin has the potential to prevent and treat IDD.

Abstract:To reuse waste concrete in a more straightforward and simplified way, a new kind of structural member containing fresh concrete (FC) and demolished concrete lumps (DCLs) distinctly larger than conventional recycled aggregates has been proposed. Previous research has shown that, at room temperature, the mechanical performance of the U-shaped steel beams filled with DCLs and FC is similar to that of the U-shaped steel beams filled with FC alone. This research explores the fire behavior of the U-shaped steel beams filled with DCLs and FC. Five specimens including three beams filled with DCLs and FC and two reference beams filled with FC alone were tested in fire. The experimental parameters included the replacement ratio of DCLs, the longitudinal reinforcement ratio, the load ratio, and the thickness of fire insulation. Based on the test results, numerical models in which the thermal resistance at the interface between the U-shaped steel and the in-filled concrete is considered are developed using SAFIR to determine the thermal and structural responses of the specimens. Lastly, parametric studies are carried out preliminarily to investigate the effects of some parameters on the fire resistance of such beams. It is found that the replacement ratio of DCLs within a range of 0% to 33% has a very limited effect on the temperature distribution, structural response, and fire resistance of the specimens, that embedding longitudinal reinforcements can significantly increase the fire resistance of such beams, that the interface thermal resistance can generate a temperature drop of up to 280 • C at the interface between the U-shaped steel and the in-filled concrete, and that the numerical models are capable of predicting the thermal and structural responses of such beams.

This paper considers the observer design problem for a class of discrete-time system whose nonlinear time-varying terms satisfy incremental quadratic constraints. We first construct a circle criterion based full-order observer by injecting output estimation error into the observer nonlinear terms. We also construct a reduced-order observer to estimate the unmeasured system state. The proposed observers guarantee exponential convergence of the state estimation error to zero. The design of the proposed observers is reduced to solving a set of linear matrix inequalities. It is proved that the conditions under which a full-order observer exists also guarantee the existence of a reduced-order observer. Compared to some previous results in the literature, this work considers a larger class of nonlinearities and unifies some related observer designs for discrete-time nonlinear systems. Finally, a numerical example is included to illustrate the effectiveness of the proposed design.

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