First-Principles Study of Optical Absorption Energies, Ligand Field and Spin-Hamiltonian Parameters of Cr³⁺ Ions in Emeralds

Herein, we study the electronic structure, energies, and vibronic structure of optical d-d transitions of Cr3+ ions doped in beryl (Be3Si6Al2O18:Cr3+, emerald). A computational protocol is developed that combines periodic density functional theory (for modeling of the bulk crystalline lattice of emerald) and the multireference configuration interaction complete active space self-consistent field method supplemented with n-electron valence second-order perturbation theory (for the calculation of the energy levels, wave functions, and spin-Hamiltonian and ligand-field parameters of the trigonal Cr3+ centers in the [CrO6]9– clusters embedded in an extended point charge field). Ligand-field parameters were extracted from mapping the effective ligand-field Hamiltonian onto the full many-particle Hamiltonian from one side and from a direct fit to energies of computed d-d transitions on the other side. These have been analyzed using ab initio ligand-field theory. The quality of the theoretical predictions is critically assessed through a detailed comparison with the available experimental data

Influencia de la revibración sobre las propiedades de la pasta de cemento endurecida y de los hormigones

Not availableEste trabajo forma parte de una serie de estudios e investigaciones experimentales efectuadas desde 1962 en los laboratorios de la cátedra de Hormigón Armado del Instituto Politécnico de Timisoara y de la Sección de Materiales de Construcción de la Academia Rumana. El trabajo se centra, desde el punto de vista teórico, en la aclaración de ciertos aspectos nuevos de la formación de la estructura de la pasta de cemento endurecida bajo la acción de la vibración repetida (revibración) durante el fraguado del cemento y, desde el punto de vista práctico, en la obtención de hormigones de gran resistencia y gran durabilidad junto con la reducción de las deformaciones bajo cargas de corta y larga duración

The Beginning of the End of the Anthropic Principle

We argue that if string theory as an approach to the fundamental laws of physics is correct, then there is almost no room for anthropic arguments in cosmology. The quark and lepton masses and interaction strengths are determined.Comment: 12 page

Poluarea mediului riveran pe cursul superior al râului Tazlăul Sărat

The paper presents an analysis of the pollution phenomenon in the Tazlăul Sărat River basin. The studies and researches were carried out on the upper course of the river, in the area of Zemeş locality, where there are a series of wells for oil extraction. The floods have morphologically altered the minor river bed, which has influenced the stability of the banks and river basins. Crude oil pipelines are located in the river bank. Field research has analyzed the river sector between "Toderaş" and "Canton of Maxim", which administratively belongs to the commune of Zemeş, Bacău County. The flood of June 2016 had an excessive impact on the stability of oil pipelines, a situation that caused the scrapping and suspension of the pipeline