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Sharp Interface (sharp + interface)
Selected AbstractsZnSe,Si Bi-coaxial Nanowire Heterostructures,ADVANCED FUNCTIONAL MATERIALS, Issue 9 2005R. Wang Abstract We report on the fabrication, structural characterization, and luminescence properties of ZnSe/Si bi-coaxial nanowire heterostructures. Uniform ZnSe/Si bi-coaxial nanowire heterostructures are grown on silicon substrates by the simple one-step thermal evaporation of ZnSe powder in the presence of hydrogen. Both ZnSe and silicon are single-crystalline in the bi-coaxial nanowire heterostructures, and there is a sharp interface along the nanowire axial direction. Furthermore, secondary nanostructures of either ZnSe nanobrushes or a SiOx sheath are also grown on the primary bi-coaxial nanowires, depending on the ratio of the source materials. The experimental evidence strongly suggests that bi-coaxial nanowires are formed via a co-growth mechanism, that is, ZnSe terminates specific surfaces of silicon and leads to anisotropic, one-dimensional silicon growth, which simultaneously serves as preferential nucleation sites for ZnSe, resulting in the bi-coaxial nanowire heterostructures. In addition, the optical properties of ZnSe/Si nanowires are investigated using low-temperature photoluminescence spectroscopy. [source] The effect of protein,precipitant interfaces and applied shear on the nucleation and growth of lysozyme crystalsACTA CRYSTALLOGRAPHICA SECTION D, Issue 11 2009Nuno M. Reis This paper is concerned with the effect of protein,precipitant interfaces and externally applied shear on the nucleation and growth kinetics of hen egg-white lysozyme crystals. The early stages of microbatch crystallization of lysozyme were explored using both optical and confocal fluorescence microscopy imaging. Initially, an antisolvent (precipitant) was added to a protein drop and the optical development of the protein,precipitant interface was followed with time. In the presence of the water-soluble polymer poly(ethylene glycol) (PEG) a sharp interface was observed to form immediately within the drop, giving an initial clear separation between the lighter protein solution and the heavier precipitant. This interface subsequently became unstable and quickly developed within a few seconds into several unstable `fingers' that represented regions of high concentration-gradient interfaces. Confocal microscopy demonstrated that the subsequent nucleation of protein crystals occurred preferentially in the region of these interfaces. Additional experiments using an optical shearing system demonstrated that oscillatory shear significantly decreased nucleation rates whilst extending the growth period of the lysozyme crystals. The experimental observations relating to both nucleation and growth have relevance in developing efficient and reliable protocols for general crystallization procedures and the controlled crystallization of single large high-quality protein crystals for use in X-ray crystallography. [source] Importance of Interfacial Adsorption in the Biphasic Hydroformylation of Higher Olefins Promoted by Cyclodextrins: A Molecular Dynamics Study at the Decene/Water InterfaceCHEMISTRY - A EUROPEAN JOURNAL, Issue 7 2007Nicolas Sieffert Abstract We report herein a molecular dynamics study of the main species involved in the hydroformylation of higher olefins promoted by cyclodextrins in 1-decene/water biphasic systems at a temperature of 350,K. The two liquids form a well-defined sharp interface of approximately 7,Å width in the absence of solute; the decene molecules are generally oriented "parallel" to the interface where they display transient contacts with water. We first focused on rhodium complexes bearing water-soluble TPPTS3, ligands (where TPPTS3, represents tris(m -sulfonatophenyl)phosphine) involved in the early steps of the reaction. The most important finding concerned the surface activity of the "active" form of the catalyst [RhH(CO)(TPPTS)2]6,, the [RhH(CO)2(TPPTS)2]6, complex, and the key reaction intermediate [RhH(CO)(TPPTS)2(decene)]6, (with the olefin ,-coordinated to the metal center) which are adsorbed at the water side of the interface in spite of their ,6 charge. The free TPPTS3, ligands themselves are also surface-active, whereas the ,9 charged catalyst precursor [RhH(CO)(TPPTS)3]9, prefers to be solubilized in water. The role of cyclodextrins was then investigated by performing simulations on 2,6-dimethyl-,-cyclodextrin ("CD") and its inclusion complexes with the reactant (1-decene), a reaction product (undecanal), and the corresponding key reaction intermediate [RhH(CO)(TPPTS)2(decene)]6, as guests; they were all shown to be surface-active and prefer the interface over the bulk aqueous phase. These results suggest that the biphasic hydroformylation of higher olefins takes place "right" at the interface and that the CDs promote the "meeting" of the olefin and the catalyst in this peculiar region of the solution by forming inclusion complexes "preorganized" for the reaction. Our results thus point to the importance of adsorption at the liquid/liquid interface in this important phase-transfer-catalyzed reaction. [source] Natural convection of a water-fine particle suspension in a rectangular cell heated and cooled from opposing vertical walls: The effect of distribution of particle sizeHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 8 2001Masashi Okada Abstract A water-fine particle suspension with a uniform initial temperature and concentration in a rectangular cell was heated from a vertical wall and cooled from the opposing vertical wall. The dispersed particles had a distribution in size. In this natural convection, many layers separated by almost-horizontal sharp interfaces were observed. In the beginning many layers appear, and each interface of the layers falls gradually with a constant velocity, and finally all layers vanish. To clarify this phenomenon, concentrations and mean diameters of the particles in each layer and temperature distributions were measured. Moreover, natural convection of the other suspension with particles which had a narrow size distribution was also investigated. © 2001 Scripta Technica, Heat Trans Asian Res, 30(8): 636,647, 2001 [source] "Charge Leakage" at LaMnO3/SrTiO3 InterfacesADVANCED MATERIALS, Issue 5 2010Javier Garcia-Barriocanal Direct evidence for charge leakage at the interface of epitaxial SrTiO3/LaMnO3 superlattices with atomically sharp interfaces is provided. The direction of charge leakage can be reversed by changing the LMO/STO thickness ratio. This result will be important for the understanding of some of the reported limitations of oxide devices involving manganite/titanate interfaces. [source] Hybrid finite element/volume method for shallow water equationsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 13 2010Shahrouz Aliabadi Abstract A hybrid numerical scheme based on finite element and finite volume methods is developed to solve shallow water equations. In the recent past, we introduced a series of hybrid methods to solve incompressible low and high Reynolds number flows for single and two-fluid flow problems. The present work extends the application of hybrid method to shallow water equations. In our hybrid shallow water flow solver, we write the governing equations in non-conservation form and solve the non-linear wave equation using finite element method with linear interpolation functions in space. On the other hand, the momentum equation is solved with highly accurate cell-center finite volume method. Our hybrid numerical scheme is truly a segregated method with primitive variables stored and solved at both node and element centers. To enhance the stability of the hybrid method around discontinuities, we introduce a new shock capturing which will act only around sharp interfaces without sacrificing the accuracy elsewhere. Matrix-free GMRES iterative solvers are used to solve both the wave and momentum equations in finite element and finite volume schemes. Several test problems are presented to demonstrate the robustness and applicability of the numerical method. Copyright © 2010 John Wiley & Sons, Ltd. [source] | ||||||||||||||||