Cooler and bigger than thought? Planetary host stellar parameters from the InfraRed Flux Method

Effective temperatures and radii for 92 planet-hosting stars as determined from the InfraRed Flux Method (IRFM) are presented and compared with those given by other authors using different approaches. The IRFM temperatures we have derived are systematically lower than those determined from the spectroscopic condition of excitation equilibrium, the mean difference being as large as 110 K. They are, however, consistent with previous IRFM studies and with the colors derived from Kurucz and MARCS model atmospheres. Comparison with direct measurements of stellar diameters for 7 dwarf stars, which approximately cover the range of temperatures of the planet-hosting stars, suggest that the IRFM radii and temperatures are reliable in an absolute scale. A better understanding of the fundamental properties of the stars with planets will be achieved once this discrepancy between the IRFM and the spectroscopic temperature scales is resolved.Comment: 15 pages, 4 figures. Accepted for publication in Ap

The mechanism of silver(I) oxide formation on polycrystalline silver in alkaline solution. Determination of nucleation and growth rates

The nucleation and growth of Ag(I) oxide layers on polycrystalline Ag electrodes is studied by potentiodynamic and potentiostatic current transients in 0.1 M NaOH. A model involving the diffusion controlled growth of a basal layer followed by the nucleation and growth of a secondary layer is proposed. Various nucleation parameters are estimated by comparing experimental data with simulated transients, and the results are discussed in terms of the atomistic theory of electrochemical phase formation. The influence of the nucleation parameters on the shape of the current transients is analysed and some controversial results in the literature are explained.Instituto de Investigaciones Fisicoquímicas Teóricas y AplicadasFacultad de Ciencias Exacta

The surface diffusion of gold atoms on gold electrodes in acid solution and its dependence on the presence of foreign adsorbates

The surface diffusion coefficient (Ds) of Au atoms in 0.5 M H2SO4 at 298 K has been determined from the time dependence of the surface roughness factor of electrodispersed Au electrodes in 0.5 M H2SO4. The value of Ds for 0.5 M H2SO4 is 5 × 10−14 cm2 s−1, a figure which depends considerably on the presence of adsorbable species in solution. Thus, the adsorption of pyridine produces a remarkable decrease of Ds, whereas the adsorption of Cl− ion results in the opposite effect. The corresponding values of Ds are 1.2 × 10−14 cm2 s−1 for 0.5 M H2SO4 + 0.1 M pyridine, and 2.5 × 10−13 cm2 s−1 for 0.5 M H2SO4 + 5 × 10−4 M KCl. These results are interpreted through the influence of the adsorbate on the Au surface atom diffusion mechanism.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA)Facultad de Ciencias Exacta

The surface diffusion of gold atoms on gold electrodes in acid solution and its dependence on the presence of foreign adsorbates

The surface diffusion coefficient (Ds) of Au atoms in 0.5 M H2SO4 at 298 K has been determined from the time dependence of the surface roughness factor of electrodispersed Au electrodes in 0.5 M H2SO4. The value of Ds for 0.5 M H2SO4 is 5 × 10−14 cm2 s−1, a figure which depends considerably on the presence of adsorbable species in solution. Thus, the adsorption of pyridine produces a remarkable decrease of Ds, whereas the adsorption of Cl− ion results in the opposite effect. The corresponding values of Ds are 1.2 × 10−14 cm2 s−1 for 0.5 M H2SO4 + 0.1 M pyridine, and 2.5 × 10−13 cm2 s−1 for 0.5 M H2SO4 + 5 × 10−4 M KCl. These results are interpreted through the influence of the adsorbate on the Au surface atom diffusion mechanism.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA)Facultad de Ciencias Exacta

The mechanism of silver(I) oxide formation on polycrystalline silver in alkaline solution. Determination of nucleation and growth rates

The nucleation and growth of Ag(I) oxide layers on polycrystalline Ag electrodes is studied by potentiodynamic and potentiostatic current transients in 0.1 M NaOH. A model involving the diffusion controlled growth of a basal layer followed by the nucleation and growth of a secondary layer is proposed. Various nucleation parameters are estimated by comparing experimental data with simulated transients, and the results are discussed in terms of the atomistic theory of electrochemical phase formation. The influence of the nucleation parameters on the shape of the current transients is analysed and some controversial results in the literature are explained.Instituto de Investigaciones Fisicoquímicas Teóricas y AplicadasFacultad de Ciencias Exacta

Perverse coherent t-structures through torsion theories

Bezrukavnikov (later together with Arinkin) recovered the work of Deligne defining perverse $t$-structures for the derived category of coherent sheaves on a projective variety. In this text we prove that these $t$-structures can be obtained through tilting torsion theories as in the work of Happel, Reiten and Smal\o. This approach proves to be slightly more general as it allows us to define, in the quasi-coherent setting, similar perverse $t$-structures for certain noncommutative projective planes.Comment: New revised version with important correction

Cultura política y elecciones

Compilación de cuatro ensayos que iluminan sobre los cambios en la cultura política en Jalisco, Aguascalientes, Guanajuato y Chihuahua, según lo muestran las transformaciones políticas, económicas y sociales del país.ITESO, A.C

Self-control of a lively footbridge under pedestrian flow

Congreso celebrado en la Escuela de Arquitectura de la Universidad de Sevilla desde el 24 hasta el 26 de junio de 2015.In this paper, a case study about a lively footbridge is developed; the vibration levels caused by the pedestrian action are controlled by the change of the modal parameters of the structure due to the pedestrian-structure interaction. A detailed finite element model of the structure has been updated from an operational modal analysis. The updated model has been used to obtain the numerical acceleration at the mid-span of the footbridge under different pedestrian flows. A relation between the maximum acceleration and the pedestrian density on the deck has been obtained numerically, pointing out an improvement in the comfort level of the structure when the number of pedestrians increases. This result validates a design rule for cable-stayed footbridges in order to avoid vibratory problems, since the first vertical natural frequency of the structure remains below the range that characterizes the pedestrian walking action

Motor and cognitive deficits in the heterozygous leaner mouse, a Cav2.1 voltage-gated Ca2+ channel mutant

Supplementary data associated with this article can be found, in the online version, at doi:10.1016/j.neurobiolaging.The leaner mutation in mice affects the Ca(v)2.1 voltage-gated calcium channel alpha(1A)-subunit gene (Cacna1a), causing a reduction in calcium currents predominantly in Purkinje cells. This reduction in calcium currents causes severe progressive cerebellar ataxia, beginning around postnatal day 10, in homozygous leaner mice (tg(la)/tg(la)), while their heterozygous littermates (tg(la)/+) present no obvious behavioral deficits. In humans, heterozygous mutations in the Cacna1a orthologous gene produce a broad range of neurological manifestations. To evaluate the phenotypic status of the tg(la)/+ animals, we assessed motor performance and cognition, at different ages, in these mutant mice. We were able to observe age-dependent impairment in motor and cognitive tasks; balance and motor learning deficits were found in demanding tasks on the rotarod and on the hanging wire test, while spatial learning and memory impairment was observed in the Morris water maze. Progressive dysfunction in escape reflexes, indicative of neurological impairment, was also present in tg(la)/+ animals. Although not presenting major motor alterations, tg(la)/+ mice show age-dependent motor and cognitive deficits.We would like to thank Carolina Lemos for her help with statistical analysis and Victor Mendes for image technical assistance. This work was supported by research grants POCTI/MGI/34517/00, POCTI/NSE/45352/2002 and POCI/SAU-MMO/56387/2004, FCT (Fundação para a Ciência e Tecnologia) and co-funded by FEDER. I.A. is recipient of a scholarship from FCT, Portugal