Relevance of Dispersion and the Electronic Spin in the DFT + U Approach for the Description of Pristine and Defective TiO2 Anatase.

A density functional theory + U systematic theoretical study was performed on the geometry, electronic structure, and energies of properties relevant for the chemical reactivity of TiO2 anatase. The effects of D3(BJ) dispersion correction and the Hubbard U value over the energies corresponding to the TiO2/Ti2O3 reduction reaction, the oxygen vacancy formation, and transition-metal doping were analyzed to attain an accurate and well-balanced description of these properties. It is suggested to fit the Hubbard correction for the metal dopant atom by taking as reference the observed low spin-high spin (HS) energy difference for the metal atom. PBEsol-D3 calculations revealed a distinct electronic ground state for the yttrium-doped TiO2 anatase surface depending upon the type of doping and interstitial or substitutional defects. Based on the calculations, it was found that a HS state explains the observed ferromagnetism in cobalt-substituted TiO2 anatase. The results presented herein might be relevant for further catalytic studies on TiO2 anatase using a large surface model that would be worthwhile for heterogeneous catalysis simulations.

Role of the base Cs2CO3 on the palladium-catalyzed intramolecular cyclization of two bromoindole derivatives to yield paullone-type products.

Reactions for the palladium-catalyzed intramolecular cyclization of the o-bromoindole and the o-bromo-N-methyl-indole derivatives in the presence and absence of base (Cs2CO3) were explored through DFT calculations. For the base-free reactions, the palladium atom firstly interacts with the aromatic rings of the indole molecule to yield a stable adduct. Once this adduct has been formed, reaction proceeds readily to the oxidative addition intermediate that arises from the insertion of the metal atom into the C-Br bond of the organic fragment. Further steps leading to the paullone (or dimethyl paullone) product, mainly those involving the metalation and deprotonation of the inserted intermediate, are not energetically viable for these reactions. When the effect of the base on the metalation-deprotonation steps is modeled by replacing the bromide ion with CO32- in the metal-inserted structure, a feasible pathway connecting the oxidative addition intermediate with the paullone-type product was located for each of the investigated reactions. The results emerging from this study suggest that palladium can insert into the C-Br bond of the indole derivatives to yield the oxidative addition intermediate (without participation of the base). However, the metalation and deprotonation steps that evolve to the paullone-type product take place via a concerted action involving both the metal and the base. Metalation and deprotonation steps that evolve to the paullone-type product take place via a concerted action involving both the metal and the base.

Halogen-Doping Effect on the Delithiation and Charge Transfer of (Li2S)10 Cluster.

Previous studies have suggested beneficial effects in lithium-sulfur batteries containing iodide in a sulfur-based cathode or as an electrolyte additive. These effects include preventing electrolyte degradation and improving the cycle stability of Li-S cells. However, little is known regarding the underlying reasons of such performance improvements. In this work, we present a theoretical study of the halogen-doping effect on the delithiation (charge) process on a (Li2S)10 model structure representing a potential final discharge product. It is revealed that the electron polaron is the dominant charge carrier during the charge process, and iodine is a facilitating agent for lithium detachment from the lithium sulfide cluster. However, the graphene support was found as potentially slowing down the ionic transport during the delithiation process due to charge transfer exerted by the support to the doped cluster that may retain the positive ions in the particle.

Explaining the singlet complexes detected for the reaction Zr(3F) + CH3CH3 through a non-spin flip scheme.

Energy profiles for the lowest lying triplet and singlet electronic pathways that link the reactants Zr + CH3CH3 with the products observed under matrix-isolation conditions were obtained from DFT and CASSCF-MRMP2 calculations. The insertion of the metal into the C-H bond of the organic molecule to yield the oxidative addition product is not favorable for any of the investigated channels. However, the inserted structure H-Zr-CH2CH3 can be obtained from two sequential reactions involving the radical species ZrH and CH2CH3. According to this scheme, a first reaction produces the radical fragments from the ground state of the reactants. Then, the radicals can recombine themselves in a second reaction to form the inserted species H-Zr-CH2CH3. As the triplet and singlet radical asymptotes ZrH + CH2CH3 that vary only in spin of the non-metallic fragment are degenerate, the rebounding of the radicals can occur through both multiplicity channels. It is shown that the low spin channel leads to the most stable structures of the dihydride ZrH2-(CH2)2 and the vinyl metal trihydride complexes ZrH3-CH=CH2 experimentally determined for this reaction under matrix-isolation conditions. The description attained for this interaction does not invoke interactions between the triplet and singlet electronic states emerging from the reactants, as proposed by other authors.

Multiconfigurational character of the ground states of polycyclic aromatic hydrocarbons. A systematic study.

A systematic study of the electronic structure of polycyclic hydrocarbons from naphthalene to a system containing 80 fused benzene has been carried out. Geometries were optimized for closed shell singlet, open shell singlet, triplet and multiplet states at B3LYP/cc-pVDZ level of theory, D1 (second order Møller-Plesset) and D1 (second-order approximate coupled-cluster) diagnostics have been calculated for studied molecules. Complete active space self-consistent field (10,10)/6-31G(d) single point energy calculations have been carried out for all optimized structures. Multireference character of the ground state becomes important when the number of atoms in the polycyclic hydrocarbon exceeds 40-50. At this point, D1 diagnostics reaches 0.04-0.05 and the squared configuration interaction expansion coefficient for dominant configuration drops to about 0.6. However, only for the three largest systems predominantly polyradicalic ground states have been detected. All other polycyclic hydrocarbons showing significant multiconfigurational character of singlet ground state have only two dominant configurations which are closed shell singlet and doubly excited singlet, respectively. Thus, small polycyclic hydrocarbons have mostly single reference singlet ground state, the medium size systems have notably multireference ground state (singlet or triplet) with only moderate polyradicalic character. The ground state of largest systems is singlet polyradical.

Ventilación mecánica en el recién nacido: experiencia de 2 años de trabajo / Mechanical ventilation in the newborn: a two year experince

Se estudiaron 100 recién nacidos sometidos a tratamiento con ventilación mecánica durante los años 1986 y 1987, en la Unidad de Cuidados Intensivos del Hospital Pediátrico Provincial de Villa Clara. El 57 % del total estuvo comprendido en el grupo de más de 2 500 g de peso al nacimiento y el 41 % de ellos tuvo un Aggar menor de 7. De los recién nacidos con edad entre 0 a 6 días al inicio de la ventilación fallecieron 17, los que representaron el 65,4 % de este grupo. Se pudo demostrar que en el 36 y el 17 %, respectivamente, del total de pacientes, la hipoxia perinatal y la enfermedad de la membrana hialina fueron las entidades que más motivaron la ventilación. Se comprobó la sobrevida en el 36 % del total de niños ventilados. Las complicaciones más comúnmente halladas fueron la sepsis y el borotrauma (AU)

Ventilación mecánica en el recién nacido: experiencia de 2 años de trabajo / Mechanical ventilation in the newborn: a two year experince

Se estudiaron 100 recién nacidos sometidos a tratamiento con ventilación mecánica durante los años 1986 y 1987, en la Unidad de Cuidados Intensivos del Hospital Pediátrico Provincial de Villa Clara. El 57 % del total estuvo comprendido en el grupo de más de 2 500 g de peso al nacimiento y el 41 % de ellos tuvo un Aggar menor de 7. De los recién nacidos con edad entre 0 a 6 días al inicio de la ventilación fallecieron 17, los que representaron el 65,4 % de este grupo. Se pudo demostrar que en el 36 y el 17 %, respectivamente, del total de pacientes, la hipoxia perinatal y la enfermedad de la membrana hialina fueron las entidades que más motivaron la ventilación. Se comprobó la sobrevida en el 36 % del total de niños ventilados. Las complicaciones más comúnmente halladas fueron la sepsis y el borotrauma

Fracaso multiorgánico en la unidad de cuidados intensivos

Se estudiaron 104 pacientes que presentaron manifestaciones de fracaso multiorgánico (FMO) a su ingreso o en algún momento de su evolución en la unidad de cuidados intensivos (UCI) del Hospital Pediátrico de Santa Clara durante 1988. De ellos egresaron vivos 60 y fallecieron 44, con predominio de los menores de un año. La malnutrición por defecto fue un índice de mal pronóstico. El fracaso monofásico fue el de diagnóstico más frecuente. Las lesiones respiratorias y cardiovasculares constituyeron las causas iniciales de fracaso en un alto porcentaje de pacientes. Se observó una relación directa entre el número de sistemas en fallo y la mortalidad (AU)

Morbimortalidad en cuidados intensivos: año 1986 / Morbid death rate in Intensive care units: year 1986

Se realizó un estudio sobre morbimortalidad en la UTI del ÿ Hospital Pediátrico Provincial Docente "José Luis Miranda" de ÿ Santa Clara durante el año 1986. Fueron sometidos a estudio, el ÿ total de pacientes que ingresaron en la misma durante dicho ÿ periodo, para lo que se agruparon por edades, sexo, provincia ÿ de origen, servicio de procedencia, estadía, diagnóstico al ÿ egreso y causa de fallecimiento. El total de ingresos durante el ÿ año fue de 774. Los menores de 1 año constituyeron el 51.9 porciento del ÿ total. La mayoría de los pacientes procedieron del Departamento de ÿ Urgencias. La enfermedad meningocócica continuó siendo la causa ÿ más frecuente de ingresos en la Unidad

Morbimortalidad en cuidados intensivos. Año 1986 / Morbid death rate in Intensive Care Units. Year 1986

Se realizó un estudio sobre morbimortalidad en la UTI del ÿ Hospital Pediátrico Provincial Docente "José Luis Miranda" de ÿ Santa Clara durante el año 1986. Fueron sometidos a estudio, el ÿ total de pacientes que ingresaron en la misma durante dicho ÿ periodo, para lo que se agruparon por edades, sexo, provincia ÿ de origen, servicio de procedencia, estadía, diagnóstico al ÿ egreso y causa de fallecimiento. El total de ingresos durante el ÿ año fue de 774. Los menores de 1 año constituyeron el 51.9 porciento del ÿ total. La mayoría de los pacientes procedieron del Departamento de ÿ Urgencias. La enfermedad meningocócica continuó siendo la causa ÿ más frecuente de ingresos en la Unidad(AU)