Dissipative-Hamiltonian decomposition of smooth vector fields based on symmetries

We propose a method to decompose a smooth vector field into conservative and dissipative components. The procedure is based on the identification of the kernel of a linear operator associated with a given Hamiltonian combined with the use of Lie transformations for vector fields. Moreover, under certain conditions the nonconservative part of the splitting can be dropped at a given order of the transformation, obtaining after truncation, a Hamilton vector field. The technique is illustrated through the application to the motion of a particle subject to the potential of a champagne bottle plus a small friction.     

Short-time dynamics in quasi-two-dimensional colloidal suspensions

The short-time dynamic properties of colloidal particles in quasi-two-dimensional geometries are studied by digital video microscopy. We demonstrate experimentally that the effective-two-dimensional physical quantities such as the dynamic structure factor, the hydrodynamic function, and the hydrodynamic diffusion coefficients are related in exactly the same manner as their three-dimensional counterparts.     

From labdanes to drimanes. Degradation of the side chain of dihydrozamoranic acid

A new route for the degradation of the saturated side chain of dihydrozamoranic acid has been devised, giving an advanced intermediate, compound 14, useful for the synthesis of insect antifeedants such as warburganal and polygodial.     

Formation of trinuclear palladium orthometalated complexes with unprecedented asymmetrical (mu 3-S)(mu 3-X) bridges (X = OH, SR, O2CR) from mu 2-hydroxo dimeric complexes and CS2

Complexes [Pd(3)(mu(3)-S)(mu(3)-X)(L)(3)] (L = orthometalated imine), obtained by an unusual reaction of mu(2)-OH dimeric complexes and CS(2), are an unprecedented type of asymmetrical bridges between metallatriangles, which force an all-cis arrangement of the three orthometalated ligands relative to the metallatriangle.     

A molecular dynamics description of the conformational flexibility of the L-iduronate ring in glycosaminoglycans

For a synthetic hexasaccharide model it is shown that the conformational flexibility of the L-iduronate ring in glycosaminoglycans can be adequately described by using the PME methodology together with simulation protocols suitable for highly charged systems.     

Adhesion Forces between LewisX Determinant Antigens as Measured by Atomic Force Microscopy

No Abstract     

Transfer Matrices and Partition-Function Zeros for Antiferromagnetic Potts Models. II. Extended Results for Square-Lattice Chromatic Polynomial

We study the chromatic polynomials for m×n square-lattice strips, of width 9m13 (with periodic boundary conditions) and arbitrary length n (with free boundary conditions). We have used a transfer matrix approach that allowed us also to extract the limiting curves when n. In this limit we have also obtained the isolated limiting points for these square-lattice strips and checked some conjectures related to the Beraha numbers.     

Computational study on the characteristics of the interaction in naphthalene...(H2X)n=1,2 (X = O,S) clusters

The characteristics of the interaction between the pi cloud of naphthalene and up to two H2O or H2S molecules were studied. Calculations show that clusters formed by naphthalene and one H2O or H2S molecule have similar geometric features, and also present similar interaction energies. Our best estimates for the interaction energy amount to -2.95 and -2.92 kcal/mol for H2O and H2S, respectively, as obtained with the CCSD(T) method. Calculations at the MP2 level employing large basis sets should be avoided because they produce highly overestimated interaction energies, especially for hydrogen sulfide complexes. The MPWB1K functional, however, provides values pretty similar to those obtained with the CCSD(T) method. Although the magnitude of the interaction is similar with both H2X molecules, its nature is somewhat different: the H2O complex presents electrostatic and dispersion contributions of similar magnitude, whereas for H2S the interaction is dominated by dispersion. In clusters containing two H2X molecules several minima were characterized. In water clusters, the total interaction energy is dominated by the presence of a O-H...O hydrogen bond and, as a consequence, structures where this contact is present are the most stable. However, clusters containing H2S show structures with no interaction between H2S moieties which are as stable as the hydrogen bonded ones, because they allow an optimal H2S...naphthalene interaction, which is stronger than the S-H...S contact. Therefore it is possible that in larger polycycles hydrogen sulfide molecules will be spread onto the surface maximizing S-H...pi interactions rather than aggregated, forming H2S clusters.