Integrated Multiscale Multilevel Approach to Open Shell Molecular Systems.

We present a novel multiscale approach to study the electronic structure of open shell molecular systems embedded in an external environment. The method is based on the coupling of multilevel Hartree-Fock (MLHF) and Density Functional Theory (MLDFT), suitably extended to the unrestricted formalism, to Molecular Mechanics (MM) force fields (FF). Within the ML region, the system is divided into active and inactive parts, thus describing the most relevant interactions (electrostatic, polarization, and Pauli repulsion) at the quantum level.

Multilevel Density Functional Theory.

Following recent developments in multilevel embedding methods, we introduce a novel density matrix-based multilevel approach within the framework of density functional theory (DFT). In this multilevel DFT, the system is partitioned in an active and an inactive fragment, and all interactions are retained between the two parts. The decomposition of the total system is performed upon the density matrix.

Calculation of Linear and Non-linear Electric Response Properties of Systems in Aqueous Solution: A Polarizable Quantum/Classical Approach with Quantum Repulsion Effects.

We present a computational study of polarizabilities and hyperpolarizabilities of organic molecules in aqueous solutions, focusing on solute-water interactions and the way they affect a molecule's linear and non-linear electric response properties. We employ a polarizable quantum mechanics/molecular mechanics (QM/MM) computational model that treats the solute at the QM level while the solvent is treated classically using a force field that includes polarizable charges and dipoles, which dynamically respond to the solute's quantum-mechanical electron density. Quantum confinement effects are also treated by means of a recently implemented method that endows solvent molecules with a parametric electron density, which exerts Pauli repulsion forces upon the solute.

Interplay between Gold(I)-Ligand Bond Components and Hydrogen Bonding: A Combined Experimental/Computational Study.

The influence of weak interactions on the donation/back-donation bond components in the complex [(NHC)Au()] (NHC = N-heterocyclic carbene; = selenourea) has been studied by coupling experimental and theoretical techniques. In particular, NMR H and pulsed-field gradient spin-echo titrations allowed us to characterize the hydrogen bond (HB) between the -NH moieties of and the anions PF and ClO , whereas Se NMR spectroscopy allowed us to characterize the Au-Se bond. Theoretically, the Au-Se and Au-C orbital interactions have been decomposed using the natural orbital for the chemical valence framework and the bond components quantified through the charge displacement analysis.

Benefits of immunotherapy with a standardized Dermatophagoides pteronyssinus extract in asthmatic children: a three-year prospective study.

Background: Although widely practiced for over 80 years, the role of specific immunotherapy (SIT) in pediatric asthma treatment is still controversial. We assessed the effects of a 3-year period of subcutaneous administration of a standardized preparation of Dermatophagoides pteronyssinus (D pt) on the respiratory health in a group of asthmatic children monosensitized to house dust mite (HDM).

Methods: A randomized clinical trial was performed after 1-year run-in period.