Phase transitions in simple models of rod-like and disc-like micelles

The interplay of interactions between micelles, and the aggregation of these micelles into large, highly anisotropic micelles, is studied. Simple, hard-body, models of rod-like and disc-like micelles are used, which allows us to apply fundamental measure theory to determine the free energy. Then we study the phase transition from the fluid phase to a liquid crystalline phase. We find that aggregation induces a strongly first order transition from a fluid phase of small micelles to a close packed liquid crystalline phase of infinitely large micelles. Received: 3 December 1997     

CCSD‐CTOCD static dipole shielding polarizability for quantification of the chiral NMR effects in oxaziridine derivatives

Chiral discrimination by nuclear magnetic resonance (NMR) spectroscopy might be achieved through the pseudo‐scalar derived from the dipole shielding polarizability tensor. Coupled Cluster Singles and Doubles‐Quadratic Response (CCSD‐QR) calculations inside the continuous translation of the origin of the current density formalism have been carried out to determine the effects of basis set, electron correlation, and gauge translation on the determination of this magnitude in oxaziridine derivatives. Inclusion of electronic correlation is needed for adequately describing the pseudo‐scalar for the heavier nuclei, making CCSD a rigorous and affordable method to compute these high order properties in medium‐sized molecules. The observable magnitudes for chiral discrimination (produced RF voltage and required electric field) are calculated. Half of the considered molecules show values of the observable magnitudes near the lower limit for experimental detection. Nuclei ¹⁹F, ³¹P, and ⁷⁹Br produce the largest values of RF voltage (50–80 nV). Moreover, ³¹P and ⁷⁹Br are the nuclei requiring smallest electric fields (3 MVm^?1) to separate the NMR signals, being then suitable for both the techniques. © 2014 Wiley Periodicals, Inc.     

A numerical comparison of two different approximations of the error in a meshless method

Meshless methods still require considerable improvement before they equal the prominence of finite elements in computer science and engineering. In the Element Free Galerkin (EFG) method, it is obviously important that the error of approximation should be estimated, as it is in the Finite Element Method (FEM).In this paper we compare two different procedures to approximate the a posteriori error for the EFG method, both procedures are recovery based errors. The performance of the two different approximations of the error is illustrated by analysing different examples for 2-D potential and elasticity problems with known analytical solutions, using regular and irregular clouds of points. For irregular clouds of points, it is recommended to use smooth transition of nodes, thus creating areas of decreasing nodal densities.     

A posteriori error estimates and maximal regularity for approximations of fully nonlinear parabolic problems in Banach spaces

A posteriori error estimates are provided for discretizations in time of abstract nonlinear parabolic problems u′ = F(u), by the backward Euler method in the maximal regularity framework of Banach spaces. The estimates are of conditional type, i.e., are valid under assumptions on the approximate solution, and the proofs are based on appropriate fixed point arguments. Work partially supported by Grant HPMD-CT-200100121, Institute of Applied and Computational Mathematics, FORTH, 71110 Heraklion-Crete, Greece, by a Spain–Greece Research Collaboration grant jointly funded by the Ministry of Education and Science, Spain, and the General Secretariat of Research and Technology, Greece and a Pytrhagoras–EPEAEK II grant.     

Adsorption of designed pyrimidine derivative ligands on an activated carbon for the removal of Cu(II) ions from aqueous solution

The adsorption of five Nalpha-substituted amino acids with a 5-nitroso-6-oxo pyrimidine as substituent on a commercial activated carbon (AC) has been studied in aqueous solution at several pH values. The adsorption processes of these organic compounds have been analyzed on the basis of the electrolytic behavior of the adsorbates. In all cases, the adsorption process is highly irreversible due to strong pi-pi interactions between the arene centers of the AC and the pyrimidine residue of the adsorbates. This interaction is consistent with XPS data and HOMO-LUMO theoretical calculations. The adsorption of these organic compounds provides a new route for the functionalization of the AC surface with carboxyl groups. In addition, the adsorption capacity of the AC/organic compound systems for Cu(II) ions in aqueous solution has been studied at different pH values. These systems show an increase of the adsorption capacity for Cu(II) compared to the AC, which is related to the AC functionalization with carboxyl groups due to the adsorbed organic compounds.