A numerical model for cloud cavitation based on bubble cluster

The cavitation cloud of different internal structures results in different collapse pressures owing to the interaction among bubbles. The internal structure of cloud cavitation is required to accurately predict collapse pressure. A cavitation model was developed through dimensional analysis and direct numerical simulation of collapse of bubble cluster. Bubble number density was included in proposed model to characterize the internal structure of bubble cloud. Implemented on flows over a projectile, the proposed model predicts a higher collapse pressure compared with Singhal model. Results indicate that the collapse pressure of detached cavitation cloud is affected by bubble number density.

Comprehensive modeling of ignition and combustion of multiscale aluminum particles under various pressure conditions

The ignition and combustion of aluminum particles are crucial to achieve optimal energy release in propulsion and power systems within a limited residence time.This study seeks to develop theoretical ignition and combustion models for aluminum particles ranging from 10 nm to 1000μm under wide pressure ranges of normal to beyond 10 MPa.Firstly,a parametric analysis illustrates that the convective heat transfer and heterogeneous surface reaction are strongly influenced by pressure,which directly affects the ignition process.Accordingly,the ignition delay time can be correlated with pressure through the p^(b)relationship,with b increasing from-1 to-0.1 as the system transitions from the free molecular regime to the continuum regime.Then,the circuit comparison analysis method was used to interpret an empirical formula capable of predicting the ignition delay time of aluminum particles over a wide range of pressures in N_(2),O_(2),H_(2)O,and CO_(2)atmospheres.Secondly,an analysis of experimental data indicates that the exponents of pressure dependence in the combustion time of large micron-sized particles and nanoparticles are-0.15 and-0.65,respectively.Further,the dominant combustion mechanism of multiscale aluminum particles was quantitatively demonstrated through the Damköhler number(Da)concept.Results have shown that aluminum combustion is mainly controlled by diffusion as Da>10,by chemical kinetics when Da≤0.1,and codetermined by both diffusion and chemical kinetics when 0.1<Da≤10.Finally,an empirical formula was proposed to predict the combustion time of multiscale aluminum particles under high pressure,which showed good agreement with available experimental data.

The epigallocatechin gallate derivative Y_6 reverses drug resistance mediated by the ABCB1 transporter both in vitro and in vivo

Previously, we reported that Y_6, a new epigallocatechin gallate derivative, is efficacious in reversing doxorubicin(DOX)–mediated resistance in hepatocellular carcinoma BEL-7404/DOX cells. In this study, we evaluated the efficacy of Y_6 in reversing drug resistance both in vitro and in vivo by determining its effect on the adenosine triphosphate-binding cassette protein B1 transporter(ABCB1 or P-glycoprotein, P-gp). Our results showed that Y_6 significantly sensitized cells overexpressing the ABCB1 transporter to anticancer drugs that are ABCB1 substrates. Y_6 significantly stimulated the adenosine triphosphatase activity of ABCB1. Furthermore, Y_6 exhibited a higher docking score as compared with epigallocatechin gallate inside the transmembrane domain of ABCB1. In addition, in the nude mousetumor xenograft model, Y_6(110 mg/kg, intragastric administration), in combination with doxorubicin(2 mg/kg, intraperitoneal injection), significantly inhibited the growth of BEL-7404/DOX cell xenograft tumors, compared to equivalent epigallocatechin gallate. In conclusion, Y_6 significantly reversed ABCB1-mediated multidrug resistance and its mechanisms of action may result from its competitive inhibition of the ABCB1 drug efflux function.