Hot carrier and hot phonon coupling during ultrafast relaxation of photoexcited electrons in graphene

We study, by means of a Monte Carlo simulator, the hot phonon effect on the relaxation dynamics in photoexcited graphene and its quantitative impact as compared to considering an equilibrium phonon distribution. Our multi-particle approach indicates that neglecting the hot phonon effect significantly underestimates the relaxation times in photoexcited graphene. The hot phonon effect is more important for a higher energy of the excitation pulse and photocarrier densities between $1$ and $3\times 10^{12} \mathrm{~cm}^{-2}$. Acoustic intervalley phonons play a non-negligible role, and emitted phonons with wavelengths limited up by a maximum (determined by the carrier concentration) induce a slower carrier cooling rate. Intrinsic phonon heating is damped in graphene on a substrate due to additional cooling pathways, with the hot phonon effect showing a strong inverse dependence with the carrier density.Comment: 12 pages, 5 figure

Drift instability of standing Faraday waves

We consider the weakly nonlinear evolution of the Faraday waves produced in a vertically vibrated two-dimensional liquid layer, at small viscosity. It is seen that the surface wave evolves to a drifting standing wave, namely a wave that is standing in a moving reference frame. This wave is determined up to a spatial phase, whose calculation requires consideration of the associated mean flow. This is just the streaming flow generated in the boundary layer attached to the lower plate supporting the liquid. A system of equations is derived for the coupled slow evolution of the spatial phase and the streaming flow. These equations are numerically integrated to show that the simplest reflection symmetric steady state (the usual array of counter-rotating eddies below the surface wave) becomes unstable for realistic values of the parameters. The new states include limit cycles (the array of eddies oscillating laterally), drifted standing waves (patterns that are standing in a uniformly propagating reference frame) and some more complex attractors

Desigualdad, bienestar y estadísticos ordenados

En este trabajo se definen, a partir de las distribuciones de los estadísticos ordenados, funciones que cumplen las propiedades adecuadas para representar las preferencias sociales en relación a las distribuciones de renta. Ello permite, aplicando el enfoque de Yaari (1987, 1988), construir un conjunto de funciones de bienestar social, de las que se derivan sus correspondientes índices de desigualdad. Las medidas así obtenidas incorporan criterios normativos muy diversos, con diferentes grados de preferencia por la igualdad. Se obtienen, como casos particulares, los índices de Gini generalizados (Kakwani (1980), Donaldson y Weymarck (1980, 1983), Yitzhaki (1983)) y la familia de índices propuesta en Aaberge (2000). El enfoque utilizado demuestra que cada una de estas familias de índices caracteriza la distribución de la renta, salvo un cambio de escal

Variables that predict academic achievement in the spanish compulsory secondary educational system: a longitudinal, multi-level analysis

En el artículo se presenta un estudio cuyo objetivo es identificar determinadas variables personales y de centro asociadas con el rendimiento académico de estudiantes de secundaria españoles y analizar su influencia en el progreso de los alumnos a lo largo de la esta etapa. Para ello, Se realizó un estudio multinivel longitudinal en el que se evaluó a un total de 965 estudiantes de 27 centros distintos en Lengua, Matemáticas y Ciencias Sociales, en tres momentos (inicio, mitad y final de la etapa). Los resultados mostraron progreso en el conjunto de los centros en todas las áreas. Los análisis HLM longitudinales confirmaron en el nivel personal la importancia del sexo y el nivel sociocultural y, a diferencia de otros estudios, también la capacidad predictiva de las habilidades metacognitivas y las estrategias de aprendizaje. En el nivel de escuela, el clima escolar y las expectativas del profesorado hacia los estudiantes fueron las variables más relevantes. El tamaño del centro, el porcentaje de repetidores y el liderazgo del equipo directivo explicaron también una proporción de la varianza en algunas áreas.This article presents a study whose objective was to identify certain personal and institutional variables that are associated with academic achievement among Spanish, secondary school students, and to analyze their influence on the progress of those students over the course of that stage of their education. In order to do this, a longitudinal, multi-level study was conducted in which a total of 965 students and 27 different schools were evaluated in Language, Math and Social Science at three different times (beginning, middle and end of the period). The results show progress in all the schools and in all areas. As for the personal, student variables, the longitudinal, HLM analyses confirmed the importance of sex and sociocultural background and, distinguishing it from other studies, also the predictive capacity of meta-cognitive abilities and learning strategies on success in school. On the institutional level, the school climate and teachers’ expectations of their students were the most relevant of the variables studied. The size of the school, the percentage of students who repeat grades, and the leadership of the administration also explained a portion of the variance in some areas

Nivel de cumplimiento del indicador: prevención de infecciones de vías urinarias en pacientes con sonda vesical instalada

Las infecciones de vías urinarias es una de las infecciones nosocomiales más comunes en pacientes hospitalizados y aproximadamente el 80% son ocasionadas por el uso de una sonda vesical. En el año 2009 en el IMSS ocuparon el 5° lugar como causa de infección nosocomial representando el 10.6% de todas las infecciones hospitalarias. Con la finalidad de disminuir esta problemática se implementó el indicador de calidad de los servicios de Enfermería "Prevención de infecciones de vías urinarias en pacientes con sonda vesical instalada

An extended chain and trinuclear complexes based on Pt(II)-M (M = Tl(I), Pb(II)) bonds: Contrasting photophysical behavior

The syntheses and structural characterizations of a Pt–Tl chain [{Pt(bzq)(C6F5)2}Tl(Me2CO)]n 1 and two trinuclear Pt2M clusters (NBu4)[{Pt(bzq)(C6F5)2}2Tl] 2 and [{Pt(bzq)(C6F5)2}2Pb] 3 (bzq = 7,8-benzoquinolinyl), stabilized by donor–acceptor Pt → M bonds, are reported. The one-dimensional heterometallic chain 1 is formed by alternate “Pt(bzq)(C6F5)2” and “Tl(Me2CO)” fragments, with Pt–Tl bond separations in the range of 2.961(1)–3.067(1) Å. The isoelectronic trinuclear complexes 2 (which crystallizes in three forms, namely, 2a, 2b, and 2c) and 3 present a sandwich structure in which the Tl(I) or Pb(II) is located between two “Pt(bzq)(C6F5)2” subunits. NMR studies suggest equilibria in solution implying cleavage and reformation of Pt–M bonds. The lowest-lying absorption band in the UV–vis spectra in CH2Cl2 and tetrahydrofuran (THF) of 1, associated with 1MLCT/1L′LCT 1[5dπ(Pt) → π*(bzq)]/1[(C6F5) → bzq], displays a blue shift in relation to the precursor, suggesting the cleavage of the chain maintaining bimetallic Pt–Tl fragments in solution, also supported by NMR spectroscopy. In 2 and 3, it shows a blue shift in THF and a red shift in CH2Cl2, supporting a more extensive cleavage of the Pt–M bonds in THF solutions than in CH2Cl2, where the trinuclear entities are predominant. The Pt–Tl chain 1 displays in solid state a bright orange-red emission ascribed to 3MM′CT (M′ = Tl). It exhibits remarkable and fast reversible vapochromic and vapoluminescent response to donor vapors (THF and Et2O), related to the coordination/decoordination of the guest molecule to the Tl(I) ion, and mechanochromic behavior, associated with the shortening of the intermetallic Pt–Tl separations in the chain induced by grinding. In frozen solutions (THF, acetone, and CH2Cl2) 1 shows interesting luminescence thermochromism with emissions strongly dependent on the solvent, concentration, and excitation wavelengths. The Pt2Tl complex 2 shows an emission close to 1, ascribed to charge transfer from the platinum fragment to the thallium [3(L+L′)MM′CT]. 2 also shows vapoluminescent behavior in the presence of vapors of Me2CO, THF, and Et2O, although smaller and slower than those of 1. The trinuclear neutral complex Pt2Pb 3 displays a blue-shift emission band, tentatively assigned to admixture of 3MM′CT 3[Pt(d) → Pb(sp)] with some metal-mediated intraligand (3ππ/3ILCT) contribution. In contrast to 1 and 2, 3 does not show vapoluminescent behavior.This work was supported by the Spanish MICINN (DGPTC/FEDER) (Project No. CTQ2008-06669-C02-01-02/BQU) and MINECO/FEDER (Projects Nos. CTQ2012-35251 and CTQ2013-45518-P) and the Gobierno de Aragón (Grupo Consolidado E21: Química Inorgánica y de los Compuestos Organometálicos).Peer Reviewe

Effect of grafting on phenology, susceptibility to Phytophthora cinnamomi and hormone profile of chestnut

Ink disease caused by the root-rot pathogen P. cinnamomi (Pc) threatens European sweet chestnut (Castanea sativa Mill.) orchards, and growers increasingly graft susceptible C. sativa traditional varieties on Pc-resistant hybrid commercial rootstocks. The influence of the scion, the rootstock, and grafting per se on the vegetative budburst, growth, susceptibility to Pc and defence-related hormone profile of Castanea spp. are unknown. In a greenhouse experiment, these effects were evaluated by reciprocally grafting two Pc resistant C. crenata x C. sativa clones and two Pc susceptible C. sativa clones. Resistance to Pc and the hormone content of leaves and roots were rootstock-dependent, and survival rates of susceptible chestnuts strongly increased when grafted on resistant rootstocks. The scion had no effect on the resistance to Pc and the hormone profile of leaves and roots of grafted trees, but influenced vegetative budburst and primary growth. Grafting per se increased susceptibility to Pc and altered the defence-related phytohormone content of trees, especially in resistant rootstocks, but did not influence budburst and growth of trees. Grafting-induced alteration of the constitutive defense-related hormone profile could explain the increased susceptibility of resistant rootstocks to Pc. Nine days after infection, a dynamic hormonal response consisting of decreased jasmonates (JA and JA-Ile) in leaves and increased ABA and JA-Ile in roots was observed in resistant chestnuts. This is the first study addressing the role of grafting in modulating resistance to the soil-borne pathogen Pc in chestnut trees

Population structure of Asconema setubalense Kent, 1870 at Concepción Seamount, Canary Islands (Spain). Methodological approach using non-invasive techniques

The hexactinellid sponge Asconema setubalense Kent, 1870is a large bathyal species of the North Atlantic Ocean with a funnel-like body and very large osculum. Populations of A. setubalense have a three-dimensional structure and increase the complexity and biodiversity in their habitat, and are therefore considered to be a habitat-forming species. Nevertheless, at present the information on the extension, biomass, density, population structure, and ecology of this species is scarce, and it could be susceptible to the longline fishing practices that take place in the Canary Islands. The main objectives of this study are to define a functional and accurate methodology to measure specimens of A. setubalense by comparing differences in users, techniques, and morphometric measurements; to describe the height-size relationship; to present the population size structure of the species, and to establish a relationship between the size of A. setubalense and the environmental variables that can be found at the “Banco de La Concepción” seamount (BC). The obtained results suggest that surface area is the most reliable measurement to define the size of this species, whilst also showing a clear correlation with the height of the species. The selected methodology has made it possible to measure the surface area of 1035 specimens and thus obtain the size structure of the population of A. setubalense in BC. The GAM model that was used to analyse the relationship between the size of A. setubalense and the geomorphologic variables of BC, shows areas where there is a high probability of finding large specimens of the species. The results of this study greatly enhance the knowledge of this species and its habitat, and should be considered in future conservation directives, or in the development of indicators to show the good environmental state of habitats. Additionally, the study improves analysis methodology that, with the appropriate morphometric measurements, can favour the development of future studies of this species, and indeed others with a similar morphology or growth pattern.En prensa2,42