h i g h l i g h t sLaminar burning velocities of ammonia/air flames at high pressures are evaluated. Maximum value of laminar burning velocity of ammonia/air flame is about 7 cm/s. Laminar burning velocity decreases with the increase in the pressure. Markstein length increases with the increase in equivalence ratio. Markstein lengths at high pressure are lower than those at 0.1 MPa. a b s t r a c tAmmonia is expected to be useful not only as a hydrogen-energy carrier but also as a carbon-free fuel. In order to design an ammonia fueled combustor, fundamental flame characteristics of ammonia must be understood. However, knowledge of the characteristics of ammonia/air flames, especially at the high pressures, has been insufficient. In this study, the unstretched laminar burning velocity and the Markstein length of ammonia/air premixed flames at various pressures up to 0.5 MPa were experimentally clarified for the first time. Spherically propagating premixed flames, which propagate in a constant volume combustion chamber, were observed using high-speed schlieren photography. Results indicate that the maximum value of unstretched laminar burning velocities is less than 7 cm/s within the examined conditions and is lower than those of hydrocarbon flames. The unstretched laminar burning velocity decreases with the increase in the initial mixture pressure, tendency being the same as that of hydrocarbon flames. The burned gas Markstein length increases with the increase in the equivalence ratio, the tendency being the same as that of hydrogen/air flames and methane/air flames. The burned gas Markstein lengths at 0.1 MPa are higher than those at 0.3 MPa and 0.5 MPa. However, the values of burned gas Markstein length at 0.3 MPa and 0.5 MPa are almost the same. In addition, numerical simulations using CHEMKIN-PRO with five detailed reaction mechanisms which are presently applicable for the ammonia/air combustion were also conducted. However, qualitative predictions of unstretched laminar burning velocity using those reaction mechanisms are inaccurate. Thus, further improvements of reaction mechanisms are essential for application of ammonia/air premixed flames.

DEC1 (also known as Stra13/Bhlhb2/Sharp2) and DEC2 (also known as Bhlhb3/Sharp1) are two paralogous basic helix-loop-helix (bHLH) transcriptional regulators which exhibit a robust circadian gene expression pattern in the suprachiasmatic nucleus (SCN) and in peripheral organs. DEC1 has been suggested to play key roles in mammalian cell differentiation, the cell cycle and circadian regulation, hypoxia response, and carcinogenesis. Here we show that DEC1 overexpression exhibits delayed wound healing and reduces cell proliferation, migration, and invasion. DEC1 strongly repressed the promoter activity of cyclin D1. We further identify a possible DEC-response element in the cyclin D1 promoter region, and confirmed the direct binding of DEC1 to that element. Forced expression of DEC1 efficiently repressed the cyclin D1 promoter and expression. Our clinical data provide the first evidence that there is a strong inverse correlation between DEC1 and cyclin D1 expression in oral cancer, and DEC1 expression significantly correlated with clinicopathological parameters. We suggest that radiation-induced DEC1 overexpression and Akt phosphorylation in cancer cells are mediated via PI-3K signalling. Overexpression of DEC1 activates the PI-3K/Akt signalling pathway through reactive oxygen species (ROS).

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