Search results for "Surfaces"
showing 10 items of 2837 documents
Thermal Diffusion and Partial Molar Enthalpy Variations of n-Butane in Silicalite-1
2008
International audience; We report for the first time the heat of transfer and the Soret coefficient for n-butane in silicalite-1. The heat of transfer was typically 10 kJ/mol. The Soret coefficient was typically 0.006 K−1 at 360 K. Both varied with the temperature and the concentration. The thermal conductivity of the crystal with butane adsorbed was 1.46 ±0.07 W/Km. Literature values of the isosteric enthalpy of adsorption, the concentration at saturation, and the diffusion coefficients were reproduced. Non-equilibrium molecular dynamics simulations were used to find these results, and a modified heat exchange algorithm, Soft-HEX, was developed for the purpose. Enthalpies of butane were al…
Density Functional Theory Investigation on the Nucleation of Homo- and Heteronuclear Metal Clusters on Defective Graphene
2016
Nucleation of homo- (Ni, Pd, Re, Pt) and heterometallic (Ni–Pd, Re–Pt) clusters on monovacancy sites of a graphene sheet has been investigated by means of periodic density functional theory calculations. It is shown that a vacant site in graphene is an effective nucleation center for both the monometallic and bimetallic clusters, whose characteristics are described in terms of structural distortions, nucleation energetics, affinities between different metal atoms, metal–carbon interactions, and ease of diffusion of metal atoms on graphene.
Numerical analysis of masonry structures via interface models
2001
The present paper is devoted to the theoretical formulation and numerical implementation of an interface model suitable to simulate the behavior of mortar joints in masonry structures. The interface laws are formulated in the framework of elasto-plasticity for non-standard materials in order to simulate the softening response which occurs along the decohesion process in presence of shear and tension tractions. A variable material dilatancy parameter is introduced together with a further geometrical dilatancy related to the roughness of contact surfaces after joint fracture. An asperity model is adopted with the aim to describe the evolution of the contact surface shape during the loss of co…
Aggregation Behavior of Halogenated Squaraine Dyes in Buffer, Electrolytes, Organized Media, and DNA
2002
Aggregation properties of bis(3,5-dibromo-2,4,6-trihydroxyphenyl)squaraine (1) and bis(3,5-diiodo-2,4,6-trihydroxyphenyl)squaraine (2) have been examined in buffer and in the presence of electrolytes, β-cyclodextrin, micelles and DNA. These dyes were found to form aggregates in buffer and methanol−water solutions that have absorption bands blue-shifted to those of the monomeric forms. The iodo derivative 2 forms aggregates at much lower concentrations (1.7 × 10-6 M) compared to the bromo derivative 1 (2.35 × 10-6 M) in 20% (vol/vol) methanol−buffer solution. Increase in methanol concentration in methanol−water solutions resulted in the disruption of the aggregates. The intermediate dimer in…
Acyl-Chain Mismatch Driven Superlattice Arrangements in DPPC/DLPC/Cholesterol Bilayers
2010
Fluorescence and infrared spectroscopy and cholesterol oxidase activity were employed to investigate the effect of phosphatidylcholine (PC) acyl chain length mismatch on the lateral organizations of lipids in liquid-ordered dipalmitoyl-PC/dilauroyl-PC/cholesterol (DPPC/DLPC/CHOL) bilayers. Plots of steady-state fluorescence emission anisotropy of diphenylhexatriene (DPH) labeled PC (DPH-PC) embedded in the DPPC/DLPC/CHOL bilayers revealed significant peaks at several DPPC mole fractions (Y(DPPC)) when the cholesterol mole fraction (X(CHOL)) was fixed to particular values. Analogously, the DPH-PC anisotropy peaked at several critical X(CHOL)'s when Y(DPPC) was fixed. Acyl chain C-H and C hor…
On a linear diophantine problem of Frobenius
1993
Abstract In this paper, linear diophantine problem of Frobenius is discussed. A theorem concerning the largest integer g m (a1,a2) and the smallest integer G m (a1,a2) with m different representations with a1,a2 as basis is proved.
An exact and efficient approach for computing a cell in an arrangement of quadrics
2006
AbstractWe present an approach for the exact and efficient computation of a cell in an arrangement of quadric surfaces. All calculations are based on exact rational algebraic methods and provide the correct mathematical results in all, even degenerate, cases. By projection, the spatial problem is reduced to the one of computing planar arrangements of algebraic curves. We succeed in locating all event points in these arrangements, including tangential intersections and singular points. By introducing an additional curve, which we call the Jacobi curve, we are able to find non-singular tangential intersections. We show that the coordinates of the singular points in our special projected plana…
Symplectic automorphisms of prime order on K3 surfaces
2006
The aim of this paper is to study algebraic K3 surfaces (defined over the complex number field) with a symplectic automorphism of prime order. In particular we consider the action of the automorphism on the second cohomology with integer coefficients. We determine the invariant sublattice and its perpendicular complement, and show that the latter coincides with the Coxeter-Todd lattice in the case of automorphism of order three. We also compute many explicit examples, with particular attention to elliptic fibrations.
Triple planes with $p_g=q=0$
2019
We show that general triple planes with p_g=q=0 belong to at most 12 families, that we call surfaces of type I,..., XII, and we prove that the corresponding Tschirnhausen bundle is direct sum of two line bundles in cases I, II, III, whereas is a rank 2 Steiner bundle in the remaining cases. We also provide existence results and explicit constructions for surfaces of type I,..., VII, recovering all classical examples and discovering several new ones. In particular, triple planes of type VII provide counterexamples to a wrong claim made in 1942 by Bronowski.
Synthesis and Spectroscopic Properties of Silica−Dye−Semiconductor Nanocrystal Hybrid Particles
2010
We prepared silica-dye-nanocrystal hybrid particles and studied the energy transfer from semiconductor nanocrystals (= donor) to organic dye molecules (= acceptor). Multishell CdSe/CdS/ZnS semiconductor nanocrystals were adsorbed onto monodisperse Stöber silica particles with an outer silica shell of thickness 2-23 nm containing organic dye molecules (Texas Red). The thickness of this dye layer has a strong effect on the energy transfer efficiency, which is explained by the increase in the number of dye molecules homogeneously distributed within the silica shell, in combination with an enhanced surface adsorption of nanocrystals with increasing dye amount. Our conclusions were underlined by…