Modeling Study on the Entrainment of Ambient Air into Subsonic Laminar and Turbulent Argon Plasma Jets

Modeling study is performed to reveal the special features of the entrainment of ambient air into subsonic laminar and turbulent argon plasma jets. Two different types of jet flows are considered, i.e., the argon plasma jet is impinging normally upon a flat substrate located in atmospheric air surroundings or is freely issuing into the ambient air. It is found that the existence of the substrate not only changes the plasma temperature, velocity and species concentration distributions in the near-substrate region, but also significantly enhances the mass flow rate of the ambient air entrained into the jet due to the additional contribution to the gas entrainment of the wall jet formed along the substrate surface. The fraction of the additional entrainment of the wall jet in the total entrained-air flow rate is especially high for the laminar impinging plasma jet and for the case with shorter substrate standoff distances. Similarly to the case of cold-gas free jets, the maximum mass flow-rate of ambient gas entrained into the turbulent impinging or free plasma jet is approximately directly proportional to the mass flow rate at the jet inlet. The maximum mass flow-rate of ambient gas entrained into the laminar impinging plasma jet slightly increases with increasing jet-inlet velocity but decreases with increasing jet-inlet temperature.

Experimental study on two-phase gas-liquid flow patterns at normal and reduced gravity conditions

Experimental studies have been performed for horizontal two-phase air-water flows at normal and reduced gravity conditions in a square cross-section channel. The experiments at reduced gravity are conducted on board the Russian IL-76 reduced gravity airplane. Four flow patterns, namely bubble, slug, slug-annular transition and annular flows, are observed depending on the liquid and gas superficial velocities at both conditions. Semi-theoretical Weber number model is developed to include the shape influence on the slug-annular transition. It is shown that its prediction is in reasonable agreement with the experimental slug-annular transition under both conditions. For the case of two-phase gas-liquid flow with large value of the Froude number, the drift-flux model can predict well the observed boundary between bubble and slug flows.

Comparative Study Of The Influence Of Natural Convection On Directional Solidification Of Al-3.5 Wt% Ni And Al-7 Wt% Si Alloys

We present numerical simulations of thermosolutal convection for directional solidification of Al-3.5 wt% Ni and Al-7 wt% Si. Numerical results predict that fragmentation of dendrite arms resulting from dissolution could be favored in Al-7 wt% Si, but not in Al-3.5 wt% Ni. Corresponding experiments are in qualitative agreement with the numerical predictions. Distinguishing the two fragmentation mechanisms, namely dissolution and remelting, is critical during experiments on earth, when fluid flow is dominant. (C) 2007 COSPAR. Published by Elsevier Ltd. All rights reserved.

Evolution and propagation of density waves on galactic disk .1. General evolution equation of wavelet and discussion of its solution

This paper presents a general self-consistent theory of evolution and propagation of wavelets on the galactic disk. A simplified model for this theory, i. e. the thin transition-layer approximation is proposed.There are three types of solutions to the basic equation governing the evolution of wavelets on the disk: (ⅰ) normal propagating type; (ⅱ) swing type; (ⅲ) general evolving type. The results show that the first two types are applicable to a certain domain on the galactic disk and a certain region of the wave number of wavelets. The third is needed to join the other two types and to yield a coherent total picture of the wave motion. From the present theory, it can be seen that the well-known "swing theory" of the G-L sheet model holds only for a certain class of basic states of galaxies.

Investigation on upconversion luminescence in Er3+/Yb3+ codoped tellurite glasses and fibers

The upconversion properties of Er3+/Yb3+ codoped tellurite glasses and glass fibers with D-shape cladding under 980 mu excitation were investigated. Intense emission bands centered at 531, 546 and 658 nm corresponding to the transitions Er3+: H-2(11/2) -> I-4(15/2) , S-4(3/2) -> I-4(15/2) and F-4(9/2) -> I-4(15/2), respectively, were observed at room temperature. Compared with that in Er3+/Yb3+ codoped tellurite bulk glass, the upconversion luminescence becomes more efficient in the fiber geometry. The dependence of upconversion intensities on fiber geometry and possible upconversion mechanism are discussed and evaluated. The presented Er3+/Yb3+ codoped tellurite fibers with intense upconversion luminescence can be used as potential host materials for upconversion fiber lasers. (c) 2005 Elsevier B.V. All rights reserved.

On the origin and evolution of new genes-a genomic and experimental perspective

The inherent interest on the origin of genetic novelties can be traced back to Darwin. But it was not until recently that we were allowed to investigate the fundamental process of origin of new genes by the studies on newly evolved Young genes. Two indisp

STUDIES ON THE PURIFYING SPACE IN ARTIFICIAL WETLANDS WITH CATTAIL AND RUSH

调查了人工湿地水生植物根区理化特性，根系扩展的深度和位置，微生物和酶的分布状况；比较了不同深度人工湿地污水净化效果；探讨了人工湿地污水处理系统最佳净化空间位点。通过对香蒲、灯心草人工湿地的研究，发现植物的根系主要分布在基质上层２５ｃｍ区域内，在５到１０ｃｍ区域内，微生物数量最多，２５ｃｍ区域次之，３５ｃｍ以下较少。系统表层磷酸酶，葡聚糖脱水酶和蛋白酶的活性较２０ｃｍ区域内各酶活性强。对于废水的净化而言，系统２０ｃｍ和６０ｃｍ处的净化效果差别很小。结果表明，人工湿地废水处理系统上部区域为较佳净化空间。

Effects of adrenergic agonists on the extrahepatic expression of vitellogenin Ao1 in heart and brain of the Chinese rare minnow (Gobiocypris rarus)

Teleost vitellogenins (VTGs) are large multidomain apolipoproteins and traditionally considered as the estrogen responsive precursors of the major egg yolk proteins. We identified five clones encoding VTGs, about 16% of the random EST clones from our constructed cDNA library from Chinese rare minnow liver tissue treated with 17 beta-estradiol (E2). Full-length vtgAo1 has been obtained based on the sequence information of four partial cDNA inserts by RACE. The inducibility of the vtgAo1 expression in liver by E2 was confirmed by RT-PCR. The presence of vtgAo1 transcripts have been observed primarily in liver. However. a significant level of the vtgAo1 was found in an unexpected location, heart, particularly in atrial cells by RT-PCR and whole mount in situ hybridization analyses. The vtgAo1 mRNA expression in heart and liver tissue could be suppressed by both alpha-adrenergic agonist, phenylephrine (PE) and beta-adrenergic agonist, isoproterenol (ISO). The expression of VTG in the heart observed in the present studies suggested it may provide protection from surplus intracellular lipids in fish cardiomyocytes as triglyceride transport proteins do in mammals. The results also indicated that the production of teleost vtg in vivo can be regulated by riot only estrogenic agents, but adrenergic signals as well. (c) 2008 Elsevier B.V. All rights reserved.

Allelopathic effects on Scenedesmus obliquus by two submerged macrophytes Najas minor and Potamogeton malaianus

The allelopathic effects of two submerged macrophytes, Najas minor and Potamogeton malaianus, on growth, photosynthesis and antioxidant systems of Scenedesmus obliquus were assessed in coexistence experiments. The growth of S. obliquus was significantly suppressed by the two macrophytes. Moreover, P. malaianus showed the stronger growth inhibition effect on S. obliquus than N. minor. P. malaianus obviously inhibited the photosynthetic rate of S. obliquus, while N. minor had no inhibitory effect. Lipid peroxidation and three antioxidant enzymes activities (superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD)) of S. obliquus were investigated at the end of the co-cultures. The two macrophytes significantly enhanced the malondialdehyde (MDA) content, a product of lipid peroxidation, in S. obliquus. Activities of the three antioxidant enzymes of S. obliquus were simultaneously stimulated in P. malaianus treatment, while no significant variation of POD activity was observed in N. minor treatment. The results indicated that the two macrophytes N. minor and P. malaianus had significant allelopathic effects on S. obliquus. However, the two macrophytes influenced S. obliquus in different ways.

Comparative study on in vitro inhibition of grass carp (Ctenopharyngodon idellus) and mouse protein phosphatases by microcystins

Microcystins isolated from toxic cyanobacteria are potent inhibitors of protein phosphatases 1 and 2A (PP1 and PP2A). The inhibitory effects of three structural variants of microcystins (microcystin-LR, -YR, and -RR) on protein phosphatases isolated and purified from the liver and kidney of grass carp (Ctenopharyngodon idellus) were investigated using the P-32 radiometric assay. The relationships between percentage inhibition of protein phosphatase activity and microcystin levels followed a typical dose-dependent sigmoid curve. These results were compared to those obtained from mouse PP2A. The degree and pattern of inhibition of both fish and mouse protein phosphatases by microcystins were similar. Protein phosphatases in crude fish tissue homogenates showed similar inhibition patterns as purified fish PP2A toward microcystins. (C) 2000 by John Wiley & Sons, Inc.