Numerical analysis of the effect of boundary layer thickness on vortex structures and heat transfer in the wake behind a hill

This study presents a three‐dimensional numerical analysis of the effect of boundary layer thickness on vortex structures and heat transfer behind a hill mounted in a laminar boundary layer. When the thickness of the velocity boundary layer is comparable to the hill height, a hairpin vortex is formed symmetrically to the center of the spanwise direction in the wake. A secondary vortex is formed between the legs, and horn‐shaped secondary vortices appear under the concave parts of the hairpin vortex. When the boundary layer thickness increases, the legs and horn‐shaped secondary vortices move toward the center of the spanwise direction, and thus heat transport and heat transfer increase there. At this time, high‐turbulence areas generated locally move toward the center of the spanwise direction with an increase in the boundary layer thickness. With a further increase in the boundary layer thickness, steady streamwise vortices are formed downstream of the hill, but the heat transfer decreases. © 2009 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20261     

Liquid film dryout in a boiling channel under flow oscillation conditions

A simple theory was developed to elucidate the influence of sinusoidal oscillation of the inlet flow rate on the occurrence of liquid film dryout in an annular two-phase flow regime in a boiling channel. The theory assumes that the critical heat flux (CHF) under an oscillatory condition can be calculated from values in steady states provided that the effect of axial mixing of the liquid film is appropriately considered. The trends of CHFs calculated using a one-dimensional three-fluid model and those experimentally measured under atmospheric pressure were in reasonable agreement with the proposed theory. However, the CHF values measured under oscillatory conditions were usually higher in the experiment than in the numerical simulation, which indicated that axial liquid transport induced by disturbance waves might enhance axial mixing of the liquid film.     

Study of plasma enhanced chemical vapor deposition of ZnO films by non-thermal plasma jet at atmospheric pressure

Plasma enhanced chemical vapor deposition using a non-thermal plasma jet was applied to deposition of ZnO films. Using vaporized bis(octane-2,4-dionato)zinc flow crossed by the plasma jet, the deposition rate was as high as several tens of nm/s. From the results of infrared spectra, the films deposited at the substrate temperature T_sub = 100 °C contained a significant amount of carbon residue, while the films prepared at T_sub = 250 °C showed less carbon fraction. The experimental results confirmed that the plasma jet decomposed bis(octane-2,4-dionato)zinc in the gaseous phase and on the substrate, and that there should be the critical T_sub to form high-quality ZnO films in the range from 100 to 250 °C.     

One-pot sonochemical synthesis of dendron-stabilized gold nanoparticles as promising nano-hybrid with potential impact in biological application

Dihydroxy fatty acid-based (DF) dendron-stabilized gold nanoparticles (AuNps) were synthesized without adding any external reducing or stabilizing agent. Each DHA base dendron (G1, G2, or G3) possesses a single thiol at the focal point and free -OH groups at the other terminal and as a result can be used to reduce AuCl₄⁻ to Au⁰ and stabilize the nascent AuNps by the thiol group. The size and distribution of the AuNp produced can also be correlated with the rate of Au (III) reduction. TEM images vividly demonstrate the specific morphology of gold nanoparticles with different sizes and shapes obtained by using different generations of DF dendrons.     

Moisture Content Measurement for Green Tea Using Phase Shifts at Two Microwave Frequencies

The experimental results for moisture measurement of green tea usingmicrowave free-space technique are presented. The method is based on a ratioof phase shifts at two microwave frequencies after propagating through asample of green tea. It is shown that the method provides the moisturecontent of tea leaves from 6% to 32% on a dry basis without any knowledge onthe thickness and the density of sample. The mean and the maximum errors inthe moisture determination for tea leaves were 1.2% and 3.7%, respectively.     

Oxidation kinetics of low-oxygen silicon carbide fiber

The effect of partial pressure and temperature on the oxidation rate of low-oxygen silicon carbide fiber (Hi-Nicalon) has been investigated. The initial oxidation rate was described by a two-dimensional disc contracting formula for reaction control, and the activation energy was 155 kJ/mol. The rate at the later stage of oxidation obeyed the equation for diffusion control, and the activation energy was 109 kJ/mol. Both the rate constants were proportional to oxygen partial pressure. The diffusion species through the SiO₂ film are considered to be oxygen molecules.     

Pliocene climate and seasonality in North Atlantic shelf seas

This paper reviews North Atlantic shelf seas palaeoclimate during the interval 4-3Ma, prior to and incorporating the 'Mid-Pliocene warm period' (ca 3.29-2.97Ma). Fossil assemblages and stable isotope data demonstrate northwards extension of subtropical faunas along the coast of the Carolinas-Virginia (Yorktown and Duplin Formations) relative to the present day, suggesting a more vigorous Florida Current, with reduced seasonality and warm water extending north of Cape Hatteras (reconstructed annual range for Virginia 12-30 degrees C). This interpretation supports conceptual models of increased meridional heat transport for the Pliocene. Sea temperatures for Florida (Lower Pinecrest Beds) were similar to or slightly cooler than (summers 25-27 degrees C) today, and were probably influenced by seasonal upwelling of cold deep water. Reduced seasonality is also apparent in the Coralline Crag Formation of the southern North Sea, with ostracods suggesting winter sea temperatures of 10 degrees C (modern 4 degrees C). However, estimates from Pliocene bivalves (3.6-16.6 degrees C) are similar to or cooler than the present day. This 'mixed' signal is problematic given warmer seas in the Carolinas-Virginia, and climate model and oceanographic data that show warmer seas in the 'Mid-Pliocene' eastern North Atlantic. This may be because the Coralline Crag Formation was deposited prior to peak Mid-Pliocene warmth.     

Production technology of large-area multicrystalline silicon solar cells

In 1996 a conversion efficiency of 17.1% had been obtained on 15 cm×15 cm mc-Si solar cell. In this paper, large-scale production technology of the high-efficiency processing will be discussed. Enlarging reactive ion etching (RIE) equipment size, technology of passivation, and fine contact grid with low resistance by screenprinted metallization, which is firing through PECVD SiN, have been investigated.     

Oxidation of Low-Oxygen Silicon Carbide Fibers (Hi-Nicalon) in Carbon Dioxide

Polycarbosilane-derived low-oxygen SiC fibers, Hi-Nicalon, were heat-treated for 36 ks at temperatures from 1273 to 1773 K in CO₂ gas. The oxidation of the fibers was investigated through the examination of mass change, crystal phase, resistivity, morphology, and tensile strength. The mass gain, growth of β-SiC crystallites, reduction of resistivity of the fiber core, and formation of protective SiO₂ film were observed for the fibers after heat treatment in CO₂ gas. SiO₂ film crystallized into cristobalite above 1573 K. Despite the low oxygen potential of CO₂ gas ( p _O2= 1.22 Pa at 1273 K − 1.78 × 10² Pa at 1773 K), Hi-Nicalon fibers were passively oxidized at a high rate. There was a large loss of tensile strength in the as-oxidized state at higher temperatures because of imperfections in the SiO₂ film. On the other hand, the fiber cores showed better strength retention even after oxidation at 1773 K.     

Downregulation of miR-122-5p Activates Glycolysis via PKM2 in Kupffer Cells of Rat and Mouse Models of Non-Alcoholic Steatohepatitis

Non-alcoholic steatohepatitis (NASH) has pathological characteristics similar to those of alcoholic hepatitis, despite the absence of a drinking history. The greatest threat associated with NASH is its progression to cirrhosis and hepatocellular carcinoma. The pathophysiology of NASH is not fully understood to date. In this study, we investigated the pathophysiology of NASH from the perspective of glycolysis and the Warburg effect, with a particular focus on microRNA regulation in liver-specific macrophages, also known as Kupffer cells. We established NASH rat and mouse models and evaluated various parameters including the liver-to-body weight ratio, blood indexes, and histopathology. A quantitative phosphoproteomic analysis of the NASH rat model livers revealed the activation of glycolysis. Western blotting and immunohistochemistry results indicated that the expression of pyruvate kinase muscle 2 (PKM2), a rate-limiting enzyme of glycolysis, was upregulated in the liver tissues of both NASH models. Moreover, increases in PKM2 and p-PKM2 were observed in the early phase of NASH. These observations were partially induced by the downregulation of microRNA122-5p (miR-122-5p) and occurred particularly in the Kupffer cells. Our results suggest that the activation of glycolysis in Kupffer cells during NASH was partially induced by the upregulation of PKM2 via miR-122-5p suppression.