Multicolor phase-correlation interferometer for shock wave refractive index measurements.

Refractive index measurements are critical for characterizing the properties of hypersonic flows, but moderate- to high-pressure experiments require alternative methods to traditional interferometric fringe counting. In this work, we introduce a novel, to the best of our knowledge, multi-wavelength phase-correlation interferometric technique to estimate the refractive index changes across nearly discrete shock wave boundaries and also simultaneously capture optical dispersion and vibrational relaxation times. By comparing the interference pattern of three or more wavelengths against each other, the refractive index can be accurately determined. To demonstrate this technique, laser diodes in two wavelength combinations are tested producing refractive index resolutions on the order of 2.65 × 10-7. Results in air across a range of initial pressure conditions (P1 = 2.66 to 5.33 kPa) and incident wave speeds (Mach 2 to 5) show density changes that agree with theoretical estimates within 2%. Single-shot dispersion and vibrational relaxation measurements with this method also illustrate good agreement with other techniques.

Shock Tube Measurement of the C2H4 + H ⇔ C2H3 + H2 Rate Constant.

The rate constant for the reaction C2H4 + H ⇔ C2H3 + H2 was studied behind reflected shock waves at temperatures between 1619 and 1948 K and pressures near 10 atm in a mixture of C2H4, CH4, H2, and argon. C2H4 time histories were measured using laser absorption of a CO2 gas laser near 10.53 µm. Experimental mixtures were designed to optimize sensitivity to the title reaction with only weak sensitivity to secondary reactions. Two mechanisms, FFCM1 and ARAMCO v2, are used for data analysis. The well-selected operating conditions and Monte Carlo sampling data analysis procedure resulted in mechanism-independent reaction rate constant measurements with a 2σ uncertainty of ±35%. The current data disagree with a broadly used theoretical calculation (Knyazev et al. (1996)), but they are in good consensus with one of the review studies (Baulch et al. (2005)), k = (3.9 × 1022) T3.62 exp(-5670/ T) cm3 molecule-1 s-1. To the best of our knowledge, this work provides the first high-temperature study of the C2H4 + H ⇔ C2H3 + H2 reaction rate constant with well-defined uncertainty.

C2-ceramide enhances sorafenib-induced caspase-dependent apoptosis via PI3K/AKT/mTOR and Erk signaling pathways in HCC cells.

Sorafenib as an effective multikinase inhibitor has been approved for the clinical treatment against advanced hepatocellular carcinoma (HCC). HCC treatment requires usually combined therapy because of its complex pathogenesis. Ceramide has been confirmed to induce remarkable apoptosis in human tumor cells and has attracted increasing attention in investigations on combination therapy. In this paper, the anti-HCC effect of sorafenib combined with C2-ceramide was investigated on cell vitality, apoptosis, and migration, and the underlying mechanism was examined using flow cytometry and western blot. Bel7402 cells coincubated with sorafenib and C2-ceramide exhibited lower cell vitality and more irregular cellular morphology and cell cycle arrest. Sorafenib plus C2-ceramide stimulated significantly the production of reactive oxygen species (ROS) and mitochondrial depolarization, which promoted caspases-dependent cell apoptosis as illustrated by related protein expression including caspase 3, caspase 9, Bax, Bcl-2, and cytochrome c. Combination treatment of sorafenib and C2-ceramide inhibited obviously cell growth and proliferation via PI3K/AKT/mTOR and Erk signaling pathways. Furthermore, the combination treatment was proved to inhibit cell migration and epithelial-mesenchymal transition (EMT). These findings indicated that the combination of C2-ceramide and sorafenib provided synergistic inhibitory effects on HCC cells.