Chemical weathering of the volcanic soils of Isla Santa Cruz (Galápagos Islands, Ecuador)

We present a study on weathering of volcanic soils using 43 profiles (131 horizons) sampled in Santa Cruz Island (Galapagos Islands). Several weathering indices, based on chemical composition, are used. Since the geological material is highly homogeneous the intensity of weathering is mostly related to climatic conditions controlled by topography. There is a gradient of increasing weathering from the arid conditions predominant in the coast to elevations of 400-500 m a.s.l. where much more humid conditions prevail

Approaching steady cavitation: The time scale in hypervelocity cavity expansion in work hardening and transformation hardening solids

The extreme phenomena of dynamic cavitation is studied both theoretically and numerically for two families of strain hardening materials. Though analytical results are limited to the steady, self-similar expansion state, the numerical approach facilitates investigation of the transient response, including evaluation of the time required to approach the steady-state limit. While recent studies show that shock waves may appear in hypervelocity cavity expansion fields, the present study suggests a numerical model which can capture the appearance and evolution of these shock waves. That model is validated by comparison with theoretical results at the steady-state limit, thus facilitating future investigation of the dynamic response for materials with more complicated constitutive behavior, for which theoretical results are limited. The constitutive sensitivities are also examined, showing that the specific hardening response of the material has little effect on the cavitation response.The researchers of the University Carlos III of Madrid are indebted to the Ministerio de Ciencia e Innovación de España (Projects DPI/2011-24068 and DPI/2011-23191) for the financial support received which allowed conducting part of this work.Publicad

Hydroelastic effects during the fast lifting of a disc from a water surface

Here we report the results of an experimental study where we measure the hydrodynamic force acting on a plate which is lifted from a water surface, suddenly starting to move upwards with an acceleration much larger than gravity. Our work focuses on the early stage of the plate motion, when the hydrodynamic suction forces due to the liquid inertia are the most relevant ones. Besides the force, we measure as well the acceleration at the centre of the plate and the time evolution of the wetted area. The results of this study show that, at very early stages, the hydrodynamic force can be estimated by a simple extension of the linear exit theory by Korobkin (J. Fluid Mech., vol. 737, 2013, pp. 368–386), which incorporates an added mass to the body dynamics. However, at longer times, the measured acceleration decays even though the applied external force continues to increase. Moreover, high-speed recordings of the disc displacement and the radius of the wetted area reveal that the latter does not change before the disc acceleration reaches its maximum value. We show in this paper that these phenomena are caused by the elastic deflection of the disc during the initial transient stage of water exit. We present a linearised model of water exit that accounts for the elastic behaviour of the lifted body. The results obtained with this new model agree fairly well with the experimental results

Grapevine European catalogue: towards a comprehensive list

Starting from the 1950’s, different European countries have established official lists of grapevine varieties authorized to be cultivated. The objectives of such lists were to limit ambiguous denomination of varieties and the related trade conflicts, as well as the implementation of viticulture recovery politics through the support of certain varieties and the limitation of others. In the same direction, in 1968 the European Union (EU) decided to create a “common catalogue of varieties”, defined as the sum of current national catalogues (Council Directive of 9 April 1968 “on the marketing of material for the vegetative propagation of the vine”, 68/193/EEC, modified). These catalogues (also called “registers”) include all the wine varieties “classified” by each Member State within the framework of the Common Organisation of the Market in wine (Council Directive No 479/2008), as well as all the non-classified varieties (table grape, rootstocks, etc.). For this work, we took the opportunity of the European research program “GrapeGen06”, focused on the study and the preservation of grapevine genetic resources, to contribute to the establishment and improvement of such an European catalogue. The comprehensive survey aims at two objectives: to support the implementation of European regulations on propagation of grapevine plants within the EU, and to assess priority actions, by technical and research institutes, for the conservation of grapevine genetic resources.Peer reviewe

GRB 051221A and Tests of Lorentz Symmetry

Various approaches to quantum gravity suggest the possibility of violation of Lorentz symmetry at very high energies. In these cases we expect a modification at low energies of the dispersion relation of photons that contains extra powers of the momentum suppressed by a high energy scale. These terms break boost invariance and can be tested even at relatively low energies. We use the light curves of the very bright short Gamma-Ray Burst GRB 051221A and compare the arrival times of photons at different energies with the expected time delay due to a modified dispersion relation. As no time delay was observed, we set a lower bound of 0.0066 E_{pl} \sim 0.66 10^{17} GeV on the scale of Lorentz invariance violation.Comment: 9 pages, 2 figure

Computational and analytical studies of the Randic index in Erdös-Rényi models

In this work we perform computational and analytical studies of the Randic´ index R(G) in Erdös–Rényi models G(n, p) characterized by n vertices connected independently with probability p ∈ (0, 1). First, from a detailed scaling analysis, we show that R(G) = {R(G)}/(n/2) scales with the product ξ ≈ np, so we can define three regimes: a regime of mostly isolated vertices when ξ 10 (R(G) ≈ n/2). Then, motivated by the scaling of R(G), we analytically (i) obtain new relations connecting R(G) with other topological indices and characterize graphs which are extremal with respect to the relations obtained and (ii) apply these results in order to obtain inequalities on R(G) for graphs in Erdös–Rényi models.J.A.M.-B. acknowledges financial support from FAPESP (Grant No. 2019/06931-2), Brazil, and PRODEP-SEP (Grant No. 511- 6/2019.-11821), Mexico. J.M.R. and J.M.S. were supported in part by two grants from Ministerio de Economía y Competitividad, Agencia Estatal de Investigación (AEI) and Fondo Europeo de Desarrollo Regional (FEDER) (MTM2016-78227-C2-1-P and MTM2017-90584-REDT), Spain

Catalytic reforming of dimethyl ether in microchannels

© . This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/The steam reforming and oxidative steam reforming of dimethyl ether (DME) were tested at 573–773¿K over a CuZn/ZrO2 catalyst in microreactors with three different types of channels: ceramic square channels with side lengths of 900 and 400¿µm, and silicon microchannels of 2¿µm of diameter. The channels were first coated with ZrOCl2 (ceramic channels) or Zr(i-PrO)4 (silicon microchannels) and calcined at 773¿K for 2¿h to obtain a homogeneous and well-adhered ZrO2 layer, as determined by SEM, and then Cu and Zn (Cu:Zn¿=¿1:1¿M, 20¿wt% total metal) were co-impregnated. Operation at highly reduced residence time (10-3¿s) while achieving hydrogen yields similar to those recorded over the ceramic channels was possible for the silicon microchannels due to the three orders of magnitude increased contact area. In addition, the amount of catalyst used for coating the silicon microchannels was two orders of magnitude lower with respect to the conventional ceramic channels. Outstanding specific hydrogen production rates of 0.9 LN of H2 per min and cm3 of reactor volume were achieved as well as stable operation for 80¿h, which demonstrates the feasibility of using on-site, on-demand hydrogen generation from DME for portable fuel cell applications.Peer ReviewedPostprint (published version

Nuevas microbialitas de arqueociatos y trombolitos del Bilbiliense (Cámbrico inferior) de la Formación Láncara (Cordillera Cantábrica, norte de España)

Recent palaeontological and microfacies studies carried out on the Láncara Formation (early Cambrian) provide evidence for an interesting, previously undescribed association of archaeocyaths (Salce locality) and microbialites (Salce and Barrios de Luna localities). The archaeocyathan assemblage consists of Archaeocyathus laqueus (Vologdin, 1932) and Pycnoidocyathus erbiensis (Zhurav leva , 1955), indicating an early Bilbilian age (Stage 4, Series 2, Cambrian) for these materials. The analysis of the upper part of the lower member has allowed differentiation of eleven carbonate facies that have been grouped into: i) non-skeletal grain packstone-grainstone, ii) fenestral mudstone-packstone, iii) heterolithic stylonodular facies, iv) microbialites, v) bioclast-intraclast packstone-grainstone. Archaeocyaths occur reworked in stylonodular facies as well as forming small archaeocyaths-thrombolitic patches (centimetre-scale). The archaeocyath-rich thrombolitic microbialites from Salce were developed in very shallow subtidal conditions surrounded by other microbialites and small lenticular intertidal bars in the inner ramp. Toyonian biostratigraphic and paleobiogeographic analyses have also been carried out. After the comparison with Toyonian archaeocyathan rich facies from Gondwana, it has become evident that the early Cambrian record from the Cantabrian Mountains provides the richest generic assemblage from Gondwana for Toyonian time.Los recientes estudios paleontológicos y de análisis de microfacies de los materiales carbonatados de la Formación Láncara (Cámbrico inferior) han deparado el hallazgo de una inédita asociación de arqueociatos (localidad de Salce) y microbialitas (localidades de Salce y Barrios de Luna). La asociación de arqueociatos está constituida por Archaeocyathus laqueus (Vologdin, 1932) y Pycnoidocyathus erbiensis (Zhurav leva , 1955), lo que indica una edad Bilbiliense (Piso 4, Serie 2, Cámbrico) para estos materiales. En el análisis de los niveles carbonatados, a techo del miembro inferior, se han distinguido once tipos de facies que han sido agrupadas en: i) packstone-grainstone de granos no esqueléticos, ii) mudstone-packstone con fábrica fenestral, iii) facies estilonodulares heterolíticas, iv) microbialitas, v) packstone-grainstone bioclásticos e intraclásticos. Los arqueociatos aparecen resedimentados en las facies estilonodulares y formando pequeños parches trombolíticos (escala centimétrica). Las microbialitas de arqueociatos y trombolitos de Salce se desarrollaron en condiciones submareales muy someras rodeadas de otras microbialitas y pequeñas barras lenticulares en zonas intermareales de la rampa interna. Se han realizado análisis bioestratigráficos y paleobiogeográficos para el Toyoniense. Tras comparar las facies del Toyoniense ricas en arqueociatos de Gondwana, se manifiesta de manera evidente que el registro del Cámbrico inferior de la Cordillera Cantábrica aporta la asociación genérica más rica de Gondwana durante el Toyoniense