The differential diffusion effect of the intermediate species on the stability of premixed flames propagating in microchannels

The propagation of premixed flames in adiabatic and non-catalytic planar microchannels subject to an assisted or opposed Poiseuille flow is considered. The diffusive-thermal model and the well-known two-step chain-branching kinetics are used in order to investigate the role of the differential diffusion of the intermediate species on the spatial and temporal flame stability. This numerical study successfully compares steady-state and time-dependent computations to the linear stability analysis of the problem. Results show that for fuel Lewis numbers less than unity, LeF 1, flames propagating in adiabatic channels suffer from oscillatory instabilities. The Poiseuille flow stabilises the flame and the effect of LeZ is opposite to that found for LeF < 1. Small values of LeZ further destabilise the flame to oscillating or pulsating instabilities.This research was supported by the Spanish Ministerio de Ciencia e Innovación (MICINN) [Projects #ENE2011-27686-C02-01, #ENE2012-33213]; the Comunidad de Madrid [Project #S2009/ENE-1597, CONSOLIDER CSD2010-00011].Publicad

Diamond forms during low pressure serpentinisation of oceanic lithosphere

Diamond is commonly regarded as an indicator of ultra-high pressure conditions in Earth System Science. This canonical view is challenged by recent data and interpretations that suggest metastable growth of diamond in low pressure environments. One such environment is serpentinisation of oceanic lithosphere, which produces highly reduced CH4-bearing fluids after olivine alteration by reaction with infiltrating fluids. Here we report the first ever observed in situ diamond within olivine-hosted, CH4-rich fluid inclusions from low pressure oceanic gabbro and chromitite samples from the Moa-Baracoa ophiolitic massif, eastern Cuba. Diamond is encapsulated in voids below the polished mineral surface forming a typical serpentinisation array, with methane, serpentine and magnetite, providing definitive evidence for its metastable growth upon low temperature and low pressure alteration of oceanic lithosphere and super-reduction of infiltrated fluids. Thermodynamic modelling of the observed solid and fluid assemblage at a reference P-T point appropriate for serpentinisation (350 °C and 100 MPa) is consistent with extreme reduction of the fluid to logfO2 (MPa) = −45.3 (ΔlogfO2[Iron-Magnetite] = −6.5). These findings imply that the formation of metastable diamond at low pressure in serpentinised olivine is a widespread process in modern and ancient oceanic lithosphere, questioning a generalised ultra-high pressure origin for ophiolitic diamond.European Union (EU)Spanish Projects CGL2015-65824 RTI2018-099157-A-I00 PID2019-105625RB-C21 A.RNM.186.UGR18Spanish Government RYC-2015-17596Mexican research program CONACYT-Ciencia Basica A1-S-14574Mexican research program UNAM-PAPIIT IA-10141

La primera de abono : sainete lírico en un acto y cuatro cuadros

Representado con extraordinario éxito en el Teatro de Recoletos la noche del 20 de Junio de 1887.Copia digital. Valladolid : Junta de Castilla y León. Consejería de Cultura y Turismo, 201

A forced thermal ratchet in a memory heat bath

The present work studies a non-Markovian forced thermal ratchet model on an asymmetric periodic potential. The Brownian dynamics is described by a generalized Langevin equation with an Ornstein-Uhlenbeck-type friction memory kernel. We show that for the case of a time-dependent driving force, also in the form of an Ornstein-Uhlenbeck-like process, an exact expression of the probability current can be derived. We also obtain the behavior of the particle's average rate of flow as a function of the external amplitude force and of the bath temperature when the driving force behaves as a square wave modulation. All our results are compared with those obtained in the Markovian case and we find, fairly remarkably, that in some cases a friction memory kernel results in an enhancement of the curren

Carnot, Stirling, Ericsson stochastic heat engines: Efficiency at maximum power

This work obtains the efficiency at maximum power for a stochastic heat engine performing Carnot-like, Stirling-like and Ericsson-like cycles. For the mesoscopic engine a Brownian particle trapped by an optical tweezers is considered. The dynamics of this stochastic engine is described as an overdamped Langevin equation with a harmonic potential, whereas is in contact with two thermal baths at different temperatures, namely, hot ($T_h$) and cold ($T_c$). The harmonic oscillator Langevin equation is transformed into a macroscopic equation associated with the mean value $\langle x^2(t)\rangle$ using the original Langevin approach. At equilibrium stationary state this quantity satisfies a state-like equation from which the thermodynamic properties are calculated. To obtained the efficiency at maximum power it is considered the finite-time cycle processes under the framework of low dissipation approach.Comment: 2 3pages, 5 figure

Characterization of Susceptible Landslide Zones by an Accumulated Index

In order to characterize the landslide susceptibility in the central zone of Guerrero State in Mexico, a spatial model has been designed and implemented, which automatically generates cartography. Conditioning factors as geomorphological, geological, and anthropic variables were considered, and as a detonating factor, the effect of the accumulated rain. The use of an inventory map of landslides that occurred in the past (IL) was also necessary, which was produced by an unsupervised detection method. Before the design of the model, an analysis of the contribution of each factor, related to the landslide inventory map, was performed by the Jackknife test. The designed model consists of a susceptibility index (SI) calculated pixel by pixel by the accumulation of the individual contribution of each factor, and the final index allows the susceptibility cartography to slide in the study area. The evaluation of the obtained map was performed by applying an analysis of the frequency ratio (FR) graphic, and an analysis of the receiver operating characteristic (ROC) curve was developed. Studies like this can help different safeguarding institutions, locating the areas where there is a greater vulnerability according to the considered factors, and integrating disaster attention management or prevention plans

Temporal and spatial variability in population traits of an intertidal fucoid reveals local-scale climatic refugia

Global change is imposing significant losses in the functional traits of marine organisms. Although areas of climatic refugia ameliorate local conditions and help them to persist, the extent to which mesoscale effects contribute for intraregional variability on population traits and conservation is uncertain. Here we assess patterns of conservation status of Fucus guiryi, the main intertidal habitat-forming seaweed in the Strait of Gibraltar (southern Spain and northern Morocco). We investigated the demography, reproductive phenology, and morphology at northern and southern side populations. Population traits were compared seasonally within populations from each side, and at spatial scale in early summer 2019. In the last decade three populations became extinct; two marginal populations had dispersed individuals with a narrower fertility season and miniaturized individuals below 3 cm; and five populations showed variable density and cover with more than 20% of reproductive individuals over the seasons. Highest density, cover, morphology, and reproductive potential was detected at one population from each side, suggesting local-scale climatic refugia in upwelling areas located inside marine protected areas. Southern recruits were more warm-tolerant but grew less at colder conditions than northern ones, revealing a mesoscale heterogeneity in thermal affinities. This study evidenced functional losses and distinct reproductive strategies experienced by F. guiryi at peripheral locations and urges to prioritize its conservation and restoration at contemporary climatic refugia.We thank the Plant Culture unit of SCAI-UMA for providing culture chambers, particularly Dr Lara Jim ́enez for her technical assistance. The authors thank the anonymous reviewer that helped us improve the first version of manuscript. Funding for open access charge: Universidad de Málaga / CBU

Cap al desenvolupament de circuits multifuncionals utilitzant dispositius emergents basats en carboni

Durant els últims anys la demanda de sistemes de comunicació robustos ha anat en augment com a resposta a les necessitats de la població per més i millors opcions de connectivitat. Les tecnologies de semiconductors emergents, com per exemple dispositius a base de carboni, han sorgit com a alternativa a curt termini per incrementar els límits d'acompliment de circuits integrats. En particular, els nanotubs de carboni (CNTs) apareixen com a una opció per a ser utilitzats en el canal de transistors d'efecte de camp (FETs) de nova generació, tot obrint la porta per ser utilitzats en el disseny de circuits de radiofreqüència, explotant les característiques intrínseques dels CNTs, com la ambipolaritat, per dissenyar circuits multifuncionals d'alt acompliment.Durante los últimos años la demanda de sistemas de comunicación robustos ha ido en aumento como respuesta a las necesidades de la población por más y mejores opciones de conectividad. Las tecnologías de semiconductores emergentes, como por ejemplo dispositivos a base de carbono, han surgido como una alternativa en el corto plazo para incrementar los límites de desempeño de circuitos integrados. En particular, los nanotubos de carbono (CNTs) aparecen como una opción para ser utilizados en el canal de transistores de efecto de campo (FETs) de nueva generación, abriendo la puerta para ser utilizados en el diseño de circuitos de radiofrecuencia, explotando las características intrínsecas de los CNTs, como la ambipolaridad, para diseñar circuitos multifuncionales de alto desempeño.During the last years, the claim of high-performance communication systems has increased as a result of the requirements of the population for more and better connectivity options. Emerging semiconductor technologies, e.g., carbon-based devices, have emerged as a short-term alternative to increase the performance limits of the integrated circuits. In particular, carbon nanotubes (CNTs) appeared as an option to use on the channel of new-generation field-effect transistors (FETs). Opening the door to being used during the design of radiofrequency circuits, using the intrinsic characteristics of the CNTs, such as ambipolarity, in order to design high-performance multifunctional circuits

Los objetivos de la empresa familiar, una cuestión previa en la definición de un modelo de gobierno

La teoría de la agencia es un marco de referencia adecuado para explicar los conflictos que surgen en el seno de la empresa familiar entre directivos y propietarios. Sin embargo, en este tipo de organizaciones dicho conflicto adquiere matices especiales, derivados de la confluencia de dos instituciones muy arraigadas: la empresa y la familia, pero con orígenes, objetivos y relaciones de naturaleza distinta. Por tanto, en las empresas familiares, debido a esta confluencia de instituciones, no se puede hablar del objetivo típico de la empresa no familiar, la maximización del valor, sino que se analizará cuáles son los objetivos desde el punto de vista de los diferentes grupos de interés y, en definitiva, qué es valioso para los propietarios de la empresa familiar.La resolución de conflictos pasa por establecer un sistema de gobierno efectivo, que alinee los intereses de los diversos grupos hacia la consecución de los objetivos comunes.Agency theory constitutes an adequate framework for explaining the family business’ conflict between the executives and the owners. However, in these organizations, this conflict has special features, due to the confluence of two rooted institutions, such as: the family and the enterprise, but with diverse origins, objectives and relations. So, in family business, because of this confluence of institutions, it is not possible to think in only one objective as in a non-family business, the maximization of value creation. It is required to analyze which are the objectives from the point of view of the different interests’ groups and, obviously, what is worth for owners in family business. Conflict solution needs to establish an effective corporate governance system that let to align the diverse interests towards the achievement of common goals