In this study, a bespoke small-scale brake dynamometer was developed to simulate the braking conditions of a railway disc brake system. Braking squeal experiments were performed with this brake dynamometer at different braking pressures and disc rotation speeds, and the influence of these braking parameters on the generation and characterization of the squeal noise was evaluated and discussed. The obtained results show that both the braking pressure and the disc rotation speed have a significant influence on the generation and evolution of the squeal noise. Higher rotation speeds are found to result in higher sound pressures and more complicated squeal noise spectra, except at a particular braking pressure, for which the highest sound pressure level is found at various disc rotation speeds. This phenomenon indicates that a combination of specific braking parameters may lead to a strong instability of the brake system and consequently to squeal noise. Additionally, a possible correlation of the squeal noise characteristics with the pressure distribution at the braking interface was found and discussed.

The Na+-taurocholate cotransporting polypeptide (NTCP) acts as the major hepatic basolateral uptake system, and plays a key role in balancing bile flow. The anti-tuberculosis drugs rifampin (RFP) can affect bile flow causing liver injury, while tanshinone IIA (TAN IIA) has the effect of protecting liver. This study aimed to investigate the effects of RFP and TAN IIA on the NTCP expression and activity, and explore the potential connections. Herein, we established sandwich-cultured primary rat hepatocytes, and quantified mRNA and protein levels of NRF2 and NTCP after treatment with RFP (10, 25, or 50 μM) or co-treatment with TAN IIA (5, 10, or 20 μM) for 12, 24, 48 h (n = 3). NTCP activity was assessed by measuring the initial uptake rates of known substrates taurocholate (TCA) (n = 3) after treatment with different concentrations of RFP, TAN ⅡA for 12, 24 and 48 h. We found that RFP had inhibition effects on NRF2, NTCP mRNA and protein expression, and co-administration of TAN IIA could reverse RFP inhibition. TCA cellular accumulation was significantly decreased by RFP (39.1%), and TAN IIA could significantly induce TCA uptake of NTCP (2.9-fold at 48 h). The TCA uptake activity was correlated with the NTCP mRNA expression, confirming the role of RFP or TAN IIA on NTCP expression and activity is synchronous, and we can predict NTCP activity by detecting its mRNA expression. In conclusion, our work will enrich the significance of NTCP in the liver protection, and provide theoretical basis for TAN IIA to prevent RFP induced cholestatic liver injury.

The effects of asymmetric magnetic perturbation on the triggering and evolution of double tearing modes (DTMs) are investigated using nonlinear magnetohydrodynamics simulations in a slab geometry. We find that for reversed magnetic shear plasmas the resistive reconnection process induced by the initial perturbation at one rational surface can drive a new island at the other rational surface with the same mode number. The four typical states of the mode for the time evolution are found, and include: (i) a linear growth stage; (ii) a linear/nonlinear stable stage; (iii) an interactively driving stage; and (iv) a symmetric DTM stage. These differ from previous simulation results. Moreover, nonlinear DTM growth is found to strongly depend on the asymmetric magnetic perturbation, particularly in the early nonlinear phase. The initial perturbation strength scale of island width suggests that the left island enters into a Sweet–Parker growth process when the right island is sufficiently large to effectively drive the other. These results predict that although externally applied magnetic perturbations can suppress the neoclassical tearing mode they can also trigger new instabilities such as asymmetric DTMs.