A monolithic and flexible fluoropolymer film microreactor for organic synthesis applications

A photocurable and viscous fluoropolymer with chemical stability is a highly desirable material for fabrication of microchemical devices. Lack of a reliable fabrication method, however, limits actual applications for organic reactions. Herein, we report fabrication of a monolithic and flexible fluoropolymer film microreactor and its use as a new microfluidic platform. The fabrication involves facile soft lithography techniques that enable partial curing of thin laminates, which can be readily bonded by conformal contact without any external forces. We demonstrate fabrication of various functional channels (similar to 300 mu m thick) such as those embedded with either a herringbone micromixer pattern or a droplet generator. Organic reactions under strongly acidic and basic conditions can be carried out in this film microreactor even at elevated temperature with excellent reproducibility. In particular, the transparent film microreactor with good deformability could be wrapped around a light-emitting lamp for close contact with the light source for efficient photochemical reactions with visible light, which demonstrates easy integration with optical components for functional miniaturized systems.open1112Ysciescopu

Velocity blow-up in C1∩H2C^1\cap H^2 for the 2D Euler equations

We give a vorticity-dynamical proof of $C^1\cap H^2$-illposedness of the 2D Euler equations. Our construction shows that the unique Yudovich solution escapes both $C^1$ and $H^2$ instantaneously

Congruence Matters: Volunteer Motivation, Value Internalization, and Retention

Volunteer research suggests that both altruistic and non-altruistic motivations may improve retention. We challenge the assumption that this is true for all volunteer work. Drawing on congruity theory of attitude change, we argue that volunteer motivation may lead to high (or low) retention when the volunteer experience is perceived as congruent (or incongruent) with their motivation. Specifically, altruistic motivation can lead to a low retention during a non-altruistic event, while non-altruistic motivation can increase the retention. Using data from a mega sports event, our findings demonstrate a negative effect of altruistic motivation on retention in a non-altruistic event. We discuss implications of the role of motivation-experience congruence in volunteer retention

The quasi-geostrophic approximation for the rotating stratified Boussinesq equations

We prove that the solution of the 3D inviscid Boussinesq equations converges to the solution of the quasi-geostrophic (QG) equations in an asymptotic regime where the intensities of rotation and stratification increase to infinity while the rotation-stratification ratio tends to any positive number other than one. Despite the non-uniformity of the generic convergence rates near the region where the ratio is one, we further show that such quasi-geostrophic approximation continues to be valid even when the ratio goes to one as long as both intensities increase to infinity fast enough. In contrast, we prove non-convergence when such intensities grow sufficiently slow to infinity with the ratio tending to one. Our proof of the non-convergence result contains the first mathematical proof of the Devil's staircase paradox that was originally cast in Theoret. Comput. Fluid Dynamics 9, 223-251 (1997). Combining both results for convergence and non-convergence, we give a lower bound for the growth of the convergence rates when the ratio tends to one. Independently of the aforementioned results proved with respect to the mixed norm for $L^q(0,T;W^{1,\infty})$ which is spatially a type of $L^\infty$, we investigate as well whether spatially $L^2$ type spaces are appropriate for analyzing the quasi-geostrophic approximation or not. We verify that non-convergence actually takes place for any fixed positive rotation-stratification ratio with respect to the $H^s$ norm with any integer $s\geq 3$. Nevertheless, in view of the projections onto the eigenspaces of the linear propagator, we specify a particular class of initial data which ensures convergence even in such $H^s$ regardless of the ratio

Dimerization-Induced Fermi-Surface Reconstruction in IrTe2

We report a de Haas-van Alphen (dHvA) oscillation study on IrTe2 single crystals showing complex dimer formations. By comparing the angle dependence of dHvA oscillations with band structure calculations, we show distinct Fermi surface reconstruction induced by a 1/5-type and a 1/8-type dimerizations. This verifies that an intriguing quasi-two-dimensional conducting plane across the layers is induced by dimerization in both cases. A phase transition to the 1/8 phase with higher dimer density reveals that local instabilities associated with intra-and interdimer couplings are the main driving force for complex dimer formations in IrTe2.X11149sciescopu

EFFECTS OF TEMPERING AND PWHT ON MICROSTRUCTURES AND MECHANICAL PROPERTIES OF SA508 GR.4N STEEL

Presented in this study are the variations of microstructures and mechanical properties with tempering and Post-Weld Heat Treatment (PWHT) conditions for SA508 Gr.4N steel used as Reactor Pressure Vessel (RPV) material. The blocks of model alloy were austenitized at the conventional temperature of 880 °C, then tempered and post-weld heat treated at four different conditions. The hardness and yield strength decrease with increased tempering and PWHT temperatures, but impact toughness is significantly improved, especially in the specimens tempered at 630 °C. The sample tempered at 630 °C with PWHT at 610 °C shows optimum mechanical properties in hardness, strength, and toughness, excluding only the transition property in the low temperature region. The microstructural observation and quantitative analysis of carbide size distribution show that the variations of mechanical properties are caused by the under-tempering and carbide coarsening which occurred during the heat treatment process. The introduction of PWHT results in the deterioration of the ductile-brittle transition property by an increase of coarse carbides controlling cleavage initiation, especially in the tempered state at 630 °C