5,187 research outputs found
Computational studies on the behaviour of anionic and nonionic surfactants at the SiO (silicon dioxide)/water interface
Molecular dynamics simulations to study the behaviour of anionic (Sodium
Dodecylsulfate, SDS) and nonionic (Monooleate of Sorbitan, SPAN80) surfactants
close to a SiO (silicon dioxide) surface were carried out. Simulations
showed that a water layer was first adsorbed on the surface and then the
surfactants were attached on that layer. Moreover, it was observed that water
behaviour close to the surface influenced the surfactant adsorption since a
semi-spherical micelle was formed on the SiO surface with SDS molecules
whereas a cylindrical micelle was formed with SPAN80 molecules. Adsorption of
the micelles was conducted in terms of structural properties (density profiles
and angular distributions) and dynamical behaviour (diffusion coefficients) of
the systems. Finally, it was also shown that some water molecules moved inside
the solid surface and located at specific sites of the solid surface.Comment: 8 pages, 6 fiigure
Generalized Lyubeznik numbers
Given a local ring containing a field, we define and investigate a family of
invariants that includes the Lyubeznik numbers, but that captures finer
information. These "generalized Lyubeznik numbers" are defined as lengths of
certain iterated local cohomology modules in a category of D-modules, and in
order to define them, we develop the theory of a functor Lyubeznik utilized in
proving that his original invariants are well defined. In particular, this
functor gives an equivalence of categories with a category of D-modules. These
new invariants are indicators of F-regularity and F-rationality in
characteristic p>0, and have close connections with characteristic cycle
multiplicities in characteristic zero. We compute the generalized Lyubeznik
numbers associated to monomial ideals using interpretations as lengths in a
category of straight modules, as well as provide examples of these invariants
associated to certain determinantal ideals.Comment: 25 pages; comments welcom
Josephson Effects in a Bose-Einstein Condensate of Magnons
A phenomenological theory is developed, that accounts for the collective
dynamics of a Bose-Einstein condensate of magnons. In terms of such description
we discuss the nature of spontaneous macroscopic interference between magnon
clouds, highlighting the close relation between such effects and the well known
Josephson effects. Using those ideas we present a detailed calculation of the
Josephson oscillations between two magnon clouds, spatially separated in a
magnonic Josephson junction
Nondiagonal Coset Models and their Poincar\'E Polynomials
coset models of the type with nondiagonal
modular invariants for both and are considered. Poincar\'e
polynomials of the corresponding chiral rings of these algebras are
constructed. They are used to compute the number of chiral generations of the
associated string compactifications. Moddings by discrete symmetries are also
discussed.Comment: 22 pages, (RevTex), preprint GTCRG-92-1 and CNEA-CAB-039/92. % Minor
changes in the result
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