Tuning the dimensionality of ZnO nanowires through thermal treatment: an investigation of growth mechanism

ABSTRACT: In this study we synthesized various dimensionalities of ZnO nanowires using the Ti-grid assisted chemical vapor deposition process. Energy dispersive x-ray spectroscopic mapping technique accompanied with a lattice diffusion model was used to characterize the growth mechanism. A diffusion ratio was obtained to describe the mechanism based on short-circuit- and lattice- diffusion of Zn ions from the Zn base film is then proposed for the growth of ZnO nanowires. The tunable dimensionalities of ZnO nanowires allow us to modify the morphology of ZnO nanocrystals by developing well controlled potential applications.     

Design and mixing efficiency of rhombic micromixer with flat angles

In this paper, we used CFD-ACE software to investigate fluid mixing of the rhombic micromixer with flat angles. According to the results of the numerical simulations, this rhombic microchannel with flat angles showed high mixing efficiency compared to cross-shape straight microchannel. Over 95% mixing efficiency had been achieved at Re > 180 due to enhancement of vortices. In processing, CO₂ laser machining is used to fabricate the master mold easily instead of conventional photolithography process. From results of the mixing experiment, high Reynolds number resulted in better fluid mixing because of stronger Dean vortices and recirculation effect.     

A performance-based parallel loop scheduling on grid environments

The effectiveness of loop self-scheduling schemes has been shown on traditional multiprocessors in the past and computing clusters in the recent years. However, parallel loop scheduling has not been widely applied to computing grids, which are characterized by heterogeneous resources and dynamic environments. In this paper, a performance-based approach, taking the two characteristics above into consideration, is proposed to schedule parallel loop iterations on grid environments. Furthermore, we use a parameter, SWR, to estimate the proportion of the workload which can be scheduled statically, thus alleviating the effect of irregular workloads. Experimental results on a grid testbed show that the proposed approach can reduce the completion time for applications with regular or irregular workloads. Consequently, we claim that parallel loop scheduling can benefit applications on grid environments.     

The effect of liquid gallium on the strengths of stainless steel and thermoplastics

We have investigated the effect of liquid gallium on type 316L stainless steel (as a candidate for the P–V–T pressure vessel), and four thermoplastics: two semicrystalline (high-density polyethylene and polypropylene) and two amorphous (polystyrene and poly(methyl methacrylate)). Specimens were coated with gallium and held at elevated temperatures and reduced pressure for extended periods. Measurements conducted on the plastics include weight change analyses, tensile tests and particle diffusion analysis using dispersion X-ray spectroscopy. For the stainless steel specimens, tensile and corrosion tests were conducted. Scanning electron microscopy was used to determine the level of corrosion. The results are compared with specimens heat treated identically but without gallium contact. After 3 months, the gallium corroded the surface of the steel to a depth of only 12 m. No penetration path of the gallium into the steel has been observed. The gallium was also found to cause no change in the mechanical properties of the polymers tested, nor was it found to have caused any weight change in the specimens.     

Theoretical investigation of the SAW properties of ferroelectric film composite structures

The characteristics of surface acoustic waves (SAW) propagating on a three-layered structure consisting of a perovskite-type ferroelectric film, a buffer layer and a semiconductor substrate have been studied theoretically. Large coupling coefficients (K(2)) can be obtained when the interdigital transducer (IDT) is on top of the perovskite-type ferroelectric film, with (type 4) and without (type 3) the floating-plane electrode at the perovskite-type ferroelectric film-buffer layer interface. In the above cases, the peak values of K (2) Of the Pb(Zr,Ti)O(3) (PZT) films (3.2%-3.8%) are higher than those of the BaTiO(3) (BT) and PbTiO(3) (PT) films. In the IDT configuration of type 4, there exists a minor peak of the coupling coefficients for the PZT and BT films, but not for the PT films when the normalized thickness (hK) of the perovskite-type ferroelectric film is about 0.3. The minor peak values of the coupling coefficients (0.62%-0.93%) for different layered structures (PZT/STO/Si, PZT/MgO/Si, and PZT/MgO/GaAs) all decrease when we increase hK value from 0 to 0.25. The results could be useful in the integration of ferroelectric devices, semiconductor devices, and SAW devices on the same substrate.     

Effects of powder processing on the characterization of magnesia derived from alkoxide precursors

Compaction and sintering behaviour of three magnesia powders derived from three different processes were compared. Powder preparation and properties have been reported in Part I. It was found in this study that the starting powder morphologies, especially the state of hard agglomeration, strongly affect the uniformity and microstructural evolution during forming and densification. However, a uniform, high-strength, dense (98–99%) and translucent magnesia can be achieved by sintering the modified powder compacts at temperatures much lower than those required for conventional magnesia powders.     

A new variant of esophageal atresia with tracheoesophageal fistula and duodenal atresia: a diagnostic dilemma

A new variant of esophageal atresia (EA) with tracheoesophageal fistula (TEF) associated with duodenal atresia is reported. The TEF was between the lower pouch and the trachea, with a cystic dilatation in the midportion. The tracheal end of the fistula was obstructed by a membranous septum at both ends of a cystic dilatation, leading to a diagnosis of pure EA (gasless abdomen). After the lower pouch was opened beyond the cystic dilatation, 100 ml nonbilious fluid was obtained. A laparotomy revealed a type III atresia of the first part of the duodenum.     

NCAM140 interacts with the focal adhesion kinase p125(fak) and the SRC-related tyrosine kinase p59(fyn)

Axonal growth cones respond to adhesion molecules and extracellular matrix components by rapid morphological changes and growth rate modification. Neurite outgrowth mediated by the neural cell adhesion molecule (NCAM) requires the src family tyrosine kinase p59(fyn) in nerve growth cones, but the molecular basis for this interaction has not been defined. The NCAM140 isoform, which is found in migrating growth cones, selectively co-immunoprecipitated with p59(fyn) from nonionic detergent (Brij 96) extracts of early postnatal mouse cerebellum and transfected rat B35 neuroblastoma and COS-7 cells. p59(fyn) did not associate significantly with the NCAM180 isoform, which is found at sites of stable neural cell contacts, or with the glycophosphatidylinositol-linked NCAM120 isoform. pp60(c-)src, a tyrosine kinase that promotes neurite growth on the neuronal cell adhesion molecule L1, did not interact with any NCAM isoform. Whereas p59(fyn) was constitutively associated with NCAM140, the focal adhesion kinase p125(fak), a nonreceptor tyrosine kinase known to mediate integrin-dependent signaling, became recruited to the NCAM140-p59(fyn) complex when cells were reacted with antibodies against the extracellular region of NCAM. Treatment of cells with a soluble NCAM fusion protein or with NCAM antibodies caused a rapid and transient increase in tyrosine phosphorylation of p125(fak) and p59(fyn). These results suggest that NCAM140 binding interactions at the cell surface induce the assembly of a molecular complex of NCAM140, p125(fak), and p59(fyn) and activate the catalytic function of these tyrosine kinases, initiating a signaling cascade that may modulate growth cone migration.     

Differential concentrations of monocyte chemotactic protein-1 and interleukin-8 within the fluid compartments present during the first trimester of pregnancy

Monocyte chemotactic protein-1 (MCP-1) and interleukin-8 (IL-8) are important chemokines which effect the chemotaxis of monocytes and neutrophils, respectively. There is increasing evidence that such chemokines play an integral role in the control and maintenance of a normal pregnancy from implantation to parturition. However, little is known about the sites of secretion and function of MCP-1 and IL-8 in particular with respect to establishment of the placenta and membranes during first trimester. The aim of this study was therefore to investigate the concentrations and localization of MCP-1 and IL-8 in amniotic fluid and extra-embryonic coelomic fluid (EECF) collected by ultrasound-guided needle aspiration and maternal serum during the first trimester of pregnancy. Using specific enzyme-linked immunosorbent assays, MCP-1 was present at high concentrations in the EECF, significantly higher than those in amniotic fluid and maternal serum. IL-8 was also present predominantly in the EECF with concentrations being significantly higher than the low values detected in maternal serum and the very low amounts found in amniotic fluid. This strict compartmentalization of these cytokines in the fluid compartments of early pregnancy may be important for establishment and development of a viable pregnancy.