Ab initio calculations of structures and stabilities of (NaI)_nNa+ and (CsI)_nCs+ cluster ions

Ab initio calculations using the Perturbed Ion model, with correlation contributions included, are presented for nonstoichiometric (NaI)_nNa+ and (CsI)_nCs+ (n=1-14) cluster ions. The ground state and several low-lying isomers are identified and described. Rocksalt ground states are common and appear at cluster sizes lower than in the corresponding neutral systems. The most salient features of the measured mobilities seem to be explained by arguments related to the changes of the compactness of the clusters as a function of size. The stability of the cluster ions against evaporation of a single alkali halide molecule shows variations that explain the enhanced stabilities found experimentally for cluster sizes n=4, 6, 9, and 13. Finally, the ionization energies and the orbital eigenvalue spectrum of two (NaI)_13Na+ isomers are calculated and shown to be a fingerprint of the structure.Comment: 8 pages plus 13 postscript figures, LaTeX. Accepted for publication in Phys, Rev. B; minor changes including a more complete comparison to pair potential result

f(R)f(R) quantum cosmology: avoiding the Big Rip

Extended theories of gravity have gathered a lot of attention over the last years, for they not only provide an excellent framework to describe the inflationary era but also yields an alternative to the elusive and mysterious dark energy. Among the different extended theories of gravity, on this work we focus on metric $f(R)$ theories. In addition, it is well known that if the late-time acceleration of the universe is stronger than the one induced by a cosmological constant then some future cosmic singularities might arise, being the Big Rip the most virulent one. Following this reasoning, on this work, we analyse the Big Rip singularity in the framework of $f(R)$ quantum geometrodynamics. Invoking the DeWitt criterium, i. e. that the wave function vanishes at the classical singularity, we proof that a class of solutions to the Wheeler-DeWitt equation fulfilling this condition can be found. Therefore, this result hints towards the avoidance of the Big Rip in metric $f(R)$ theories of gravity.Comment: V1:13 pages. Dedicated to the memory of Prof. Pedro F. Gonzalez-Diaz (our former PhD supervisor). V2: 9 pages (new style), minor clarifications included, no physics changes, 6 references added. Version accepted for publication in Physical Review

Evaluacion de la union adhesiva en la fabricacion de tableros contrachapados de grado exterior ignifugados

100 p.En este estudio se confeccionaron tableros contrachapados con chapas tratadas con un producto retardarte de llama (Stop-fire), unidas con un adhesivo fenolico, (Oxilite 2200), con el objetivo de obtener una unión satisfactoria en la conformación de un tablero contra chapado; debido a que existen probadas sustancias ignifugas de origen chileno en el mercado, que interfieren en el fraguado de los adhesivos fenolicos. Para la obtención de una unión adhesiva de calidad, se modifico el pH del retardante de llama. Una vez incorporado este a la madera, se aplico un tratamiento superficial a la chapa para mejorar la calidad de la unión. Fabricados los tableros, se extrajeron las probetas para realizar los ensayos de resistencia de la unión adhesiva, resistencia mecánica en flexión y de reacción al fuego. Estas propiedades fueron medidas de acuerdo a las normas PS 1-95, ASTM D 3043 - 87 y ISO 5660-1. El análisis de resultados indica que el tratamiento superficial aplicado a las chapas no mejoró la calidad de la unión adhesiva. El tratamiento ignifugo que se preparo con un pH de 9,6 logro aprobar el ensayo de unión adhesiva en la conformación de un tablero contrachapado, sin alterar las propiedades ignifugas del producto retardante de llama, solo mostrando una leve disminución en la resistencia mecánica en flexión de los tableros

Orbital-Free Molecular Dynamics Simulations of Melting in Na8 and Na20: Melting in Steps

The melting-like transitions of Na8 and Na20 are investigated by ab initio constant energy molecular dynamics simulations, using a variant of the Car-Parrinello method which employs an explicit electronic kinetic energy functional of the density, thus avoiding the use of one-particle orbitals. Several melting indicators are evaluated in order to determine the nature of the various transitions, and compared with other simulations. Both Na8 and Na20 melt over a wide temperature range. For Na8, a transition is observed to begin at approx. 110 K, between a rigid phase and a phase involving isomerizations between the different permutational isomers of the ground state structure. The ``liquid'' phase is completely established at approx. 220 K. For Na20, two transitions are observed: the first, at approx. 110 K, is associated with isomerization transitions between those permutational isomers of the ground state structure which are obtained by interchanging the positions of the surface-like atoms; the second, at approx. 160 K, involves a structural transition from the ground state isomer to a new set of isomers with the surface molten. The cluster is completely ``liquid'' at approx. 220 K.Comment: Revised version, accepted for publication in J. Chem. Phys. The changes include longer simulations for the Na20 microcluster, a more complete comparison to previous theoretical results, and the discussion of some technical details of the method applie

Outflow of hot and cold molecular gas from the obscured secondary nucleus of NGC3256: closing in on feedback physics

The nuclei of merging galaxies are often deeply buried in dense layers of gas and dust. In these regions, gas outflows driven by starburst and AGN activity are believed to play a crucial role in the evolution of these galaxies. However, to fully understand this process it is essential to resolve the morphology and kinematics of such outflows. Using near-IR integral-field spectroscopy obtained with VLT/SINFONI, we detect a kpc-scale structure of high-velocity molecular hydrogen (H2) gas associated with the deeply buried secondary nucleus of the IR-luminous merger NGC3256. We show that this structure is likely the hot component of a molecular outflow, which is detected also in the cold molecular gas by Sakamoto et al. This outflow, with a molecular gas mass of M(H2)~2x10^7 Msun, is among the first to be spatially resolved in both the hot H2 gas with VLT/SINFONI and the cold CO-emitting gas with ALMA. The hot and cold components share a similar morphology and kinematics, with a hot-to-cold molecular gas mass ratio of ~6x10^-5. The high (~100 pc) resolution at which we map the geometry and velocity structure of the hot outflow reveals a biconical morphology with opening angle ~40 deg and gas spread across a FWZI~1200 km/s. Because this collimated outflow is oriented close to the plane of the sky, the molecular gas may reach maximum intrinsic outflow velocities of ~1800 km/s, with an average mass outflow rate of at least ~20 Msun/yr. By modeling the line-ratios of various near-IR H2 transitions, we show that the H2 gas in the outflow is heated through shocks or X-rays to a temperature of ~1900K. The energy needed to drive the outflow is likely provided by a hidden Compton-thick AGN or by the nuclear starburst. We show that the global kinematics of the molecular outflow in NGC3256 mimic those of CO-outflows that have been observed at low spatial resolution in starburst- and active galaxies.Comment: Accepted in Astronomy and Astrophysics (accepted 29 Aug 2014 v.3, initial submission v.1 14 March 2014), 13 pages, 8 figure

Intervención farmacéutica en la detección de un trastorno de síndrome de piernas inquietas

Sexo: mujer. Edad: 72 años. Patología: diabetes tipo 2. Tratamiento: insulina glargina e insulina glulisina y también con hipolipemiantes (ezetimiba y atorvastatina 10 mg)

Dental Treatment under General Anesthesia in Healthy and Medically Compromised/Developmentally Disabled Children: A Comparative Study

Aim: To compare the type, number of procedures and working time of dental treatment provided under dental general anesthesia (DGA) in healthy and medically compromised/developmentally disabled children (MCDD children). Design: This cross-sectional prospective study involved 80 children divided into two groups of 40 children each. Group 1 consisted of healthy and Group 2 consisted of MCDD children. Results: Healthy children needed more working time than MCDD children, the means being 161±7.9 and 84±5.7 minutes, respectively (P= 0.0001). Operative dentistry and endodontic treatments showed a significant statistical difference (P= 0.0001). The means of procedures were 17±5.0 for healthy children and 11±4.8 for MCDD children (P= 0.0001). Conclusions: Healthy children needed more extensive dental treatment than MCDD children under DGA. The information from this sample of Mexican children could be used as reference for determining trends both within a facility as well as in comparing facilities in cross-population studies