New observations on high‐pressure phases in a shock melt vein in the Villalbeto de la Peña meteorite: Insights into the shock behavior of diopside     

Marina Martinez  Adrian J. Brearley  Josep M. Trigo‐Rodríguez  Jordi Llorca 《Meteoritics & planetary science》2019,54(11):2845-2863

The petrology and mineralogy of shock melt veins in the L6 ordinary chondrite host of Villalbeto de la Peña, a highly shocked, L chondrite polymict breccia, have been investigated in detail using scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and electron probe microanalysis. Entrained olivine, enstatite, diopside, and plagioclase are transformed into ringwoodite, low‐Ca majorite, high‐Ca majorite, and an assemblage of jadeite‐lingunite, respectively, in several shock melt veins and pockets. We have focused on the shock behavior of diopside in a particularly large shock melt vein (10 mm long and up to 4 mm wide) in order to provide additional insights into its high‐pressure polymorphic phase transformation mechanisms. We report the first evidence of diopside undergoing shock‐induced melting, and the occurrence of natural Ca‐majorite formed by solid‐state transformation from diopside. Magnesiowüstite has also been found as veins injected into diopside in the form of nanocrystalline grains that crystallized from a melt and also occurs interstitially between majorite‐pyrope grains in the melt‐vein matrix. In addition, we have observed compositional zoning in majorite‐pyrope grains in the matrix of the shock‐melt vein, which has not been described previously in any shocked meteorite. Collectively, all these different lines of evidence are suggestive of a major shock event with high cooling rates. The minimum peak shock conditions are difficult to constrain, because of the uncertainties in applying experimentally determined high‐pressure phase equilibria to complex natural systems. However, our results suggest that conditions between 16 and 28 GPa and 2000–2200 °C were reached.  相似文献   

Evaluating functional connectivity in a small agricultural catchment under contrasting flood events by using UAV     

Aleix Calsamiglia  Jorge Gago  Julián Garcia-Comendador  Josep Fortesa Bernat  Adolfo Calvo-Cases  Joan Estrany 《地球表面变化过程与地形》2020,45(4):800-815

Concentrated erosion, a major feature of land degradation, represents a serious problem for soil and water resources management and a threat to ecosystems. Understanding the internal mechanisms (de-)coupling sediment pathways can improve the management and resilience of catchments. In this study, concentrated erosion and deposition forms were mapped accurately through field and aerial unmanned aerial vehicle (UAV) campaigns, in order to assess the evolution of connectivity pathways over a series of three contrasted and consecutive flood events occurring between October 2016 and January 2017 (return period ranging from 0.5 to 25 years) in a small Mediterranean agricultural catchment (Can Revull, Mallorca, Spain; 1.4 km²). In addition, a morphometric index of connectivity (IC) was used to identify the potential trajectories of different concentrated erosion forms and deposition areas. IC predictions were calibrated by identifying the optimal critical thresholds, i.e. those most consistent with field observations after each of the events studied. The results found that the index performed well in predicting the occurrence and the length/area of the different type of landforms, giving kappa (κ) coefficients of variation ranging between 0.21 and 0.92 and linear correlations R² between 0.33 and 0.72. The type of landform affected the correspondence of IC predictions and field observations, with lower thresholds the greater the magnitude of their associated geomorphic processes. Rainfall magnitude proved to be a very important factor controlling the development of erosion and deposition landforms, with large differences in length/area between the contrasted events. The evolution of the observed trajectories revealed feedback dynamics between the structural and functional connectivity of the catchment, in which morphological changes determined the spatial distribution of the processes’ activity in the successive events and vice versa. © 2020 John Wiley & Sons, Ltd.  相似文献   

Short-term residence and movement patterns of the annular seabream Diplodus annularis in a temperate marine reserve     

David March  Josep Als  Amlia Grau  Miquel Palmer 《Estuarine, Coastal and Shelf Science》2011,92(4):251-587

The short-term movements of a small temperate fish, the annular seabream Diplodus annularis (Linnaeus 1758), were examined using standard tag-recapture and passive acoustic telemetry in Palma Bay (NW Mediterranean), a marine protected area (MPA). The study aimed to provide valuable information for assessing the recreational fishery and its results suggest that MPAs can be used to protect the adult stock of D. annularis. All the fish tagged with standard tags were recaptured near the release locations, with a maximum distance of ∼300 m. The maximum time between release and recapture was 185 d. Two different arrays of acoustic receivers were deployed, one in 2008 and another in 2009, within the MPA. Twenty adults were surgically tagged with acoustic transmitters. Fish monitored in 2008 (n = 12) were translocated from the point of capture to analyse the movement behaviour after artificial displacement. Upon release at displaced locations, 67% of the fish moved towards the original capture location using a time of return that ranged from 0.75 to 15.25 h. Fish monitored in 2009 (n = 8) were released at the point of capture. They showed high site fidelity with a maximum period of 27 d between the first time and the last time they were detected.  相似文献   

Growth and grazing rate dynamics of major phytoplankton groups in an oligotrophic coastal site   总被引：1，自引：0，他引：1  

Andrés Gutiérrez-Rodríguez  Mikel Latasa  Renate Scharek  Ramon Massana  Gemma Vila  Josep M. Gasol 《Estuarine, Coastal and Shelf Science》2011

There has been more attention to phytoplankton dynamics in nutrient-rich waters than in oligotrophic ones thus requiring the need to study the dynamics and responses in oligotrophic waters. Accordingly, phytoplankton community in Blanes Bay was overall dominated by Prymnesiophyceae, remarkably constant throughout the year (31 ± 13% Total chlorophyll a, Tchl a) and Bacillariophyta with a more episodic appearance (20 ± 23% Tchl a). Prasinophyceae and Synechococcus contribution became substantial in winter (Prasinophyceae = 30% Tchl a) and summer (Synechococcus = 35% Tchl a). Phytoplankton growth and grazing mortality rates for major groups were estimated by dilution experiments in combination with high pressure liquid chromatography and flow cytometry carried out monthly over two years. Growth rates of total phytoplankton (range = 0.30–1.91 d⁻¹) were significantly higher in spring and summer (μ > 1.3 d⁻¹) than in autumn and winter (μ ∼ 0.65 d⁻¹) and showed a weak dependence on temperature but a significant positive correlation with day length. Microzooplankton grazing (range = 0.03–1.4 d⁻¹) was closely coupled to phytoplankton growth. Grazing represented the main process for loss of phytoplankton, removing 60 ± 34% (±SD) of daily primary production and 70 ± 48% of Tchl a stock. Chla synthesis was highest during the Bacillarophyceae-dominated spring bloom (Chl a_synt = 2.3 ± 1.6 μg Chl a L⁻¹ d⁻¹) and lowest during the following post-bloom conditions dominated by Prymnesiophyceae (Chl a_synt = 0.23 ± 0.08 μg Chl a L⁻¹ d⁻¹). This variability was smoothed when expressed in carbon equivalents mainly due to the opposite dynamics of C:chl a (range = 11–135) and chl a concentration (range = 0.07–2.0 μg chl a L⁻¹). Bacillariophyta and Synechococcus contribution to C fluxes was higher than to biomass because of their fast-growth rate. The opposite was true for Prymnesiophyceae.  相似文献   

A comparative study of the modelling of cement hydration and cement-rock laboratory experiments     

David Savage  Josep M. SolerKohei Yamaguchi  Colin WalkerAkira Honda  Manabu InagakiClaire Watson  James WilsonSteven Benbow  Irina GausJoerg Rueedi 《Applied Geochemistry》2011,26(7):1138-1152

The use of cement and concrete as fracture grouting or as tunnel seals in a geological disposal facility for radioactive wastes creates potential issues concerning chemical reactivity. From a long-term safety perspective, it is desirable to be able model these interactions and changes quantitatively. The ‘Long-term Cement Studies’ (LCS) project was formulated with an emphasis on in situ field experiments with more realistic boundary conditions and longer time scales compared with former experiments. As part of the project programme, a modelling inter-comparison has been conducted, involving the modelling of two experiments describing cement hydration on one hand and cement-rock reaction on the other, with teams representing the NDA (UK), Posiva (Finland), and JAEA (Japan).This modelling exercise showed that the dominant reaction pathways in the two experiments are fairly well understood and are consistent between the different modelling teams, although significant differences existed amongst the precise parameterisation (e.g. reactive surface areas, dependences of rate upon pH, types of secondary minerals), and in some instances, processes (e.g. partition of alkali elements between solids and liquid during cement hydration; kinetic models of cement hydration). It was not conclusive if certain processes such as surface complexation (preferred by some modellers, but not by others) played a role in the cement-rock experiment or not. These processes appear to be more relevant at early times in the experiment and the evolution at longer timescales was not affected. The observed permeability profile with time could not be matched. The fact that no secondary minerals could be observed and that the precipitated mass calculated during the simulations is minor might suggest that the permeability reduction does not have a chemical origin, although a small amount of precipitates at pore throats could have a large impact on permeability.The modelling exercises showed that there is an interest in keeping the numerical models as simple as possible and trying to obtain a reasonable fit with a minimum of processes, minerals and parameters. However, up-scaling processes and model parameterisation to the timescales appropriate to repository safety assessment are of considerable concern. Future modelling exercises of this type should focus on a suitable natural or industrial analogue that might aid assessing mineral-fluid reactions at these longer timescales.  相似文献   

Population dynamics and tolerance to desiccation in a crustacean ostracod adapted to life in small ephemeral water bodies   总被引：1，自引：0，他引：1  

Josep A. Aguilar-Alberola  Francesc Mesquita-Joanes 《Limnologica》2011,41(4):348-355

Given their small size, isolation and unpredictability, temporary rockpools present high environmental stress and impoverished communities of species that have adapted to such stressful conditions. Special adaptations of the invertebrates living in these habitats include tolerance to desiccation and fast ontogenetic development in order to maintain stable populations and face high risk of extinction. Dozens of small rockpools (mostly with Ø < 1 m) can be found in east Spain on limestone substrate, where the only known Iberian populations of Heterocypris bosniacaPetkovski et al. (2000), an ostracod species with geographic parthenogenesis, have been recently found. In this survey, two of these rockpools have been monitored during the main hydroperiod between the fall of 2005 and summer 2006 to test the ability of H. bosniaca parthenogenetic populations to face unpredictable hydroperiod dynamics. Pools were visited weekly, and limnological data and ostracod samples were obtained from either water or substrate in dry periods. Ostracod individuals were counted and assigned to growth instars to monitor population changes. In the laboratory, experimental cultures allowed the estimation of survival dependence on the substrate desiccation rate. Throughout the hydrological cycle studied, several hatching periods were observed, usually preceded by desiccation, followed by substrate hydration and water dilution by rain. The demographic changes observed indicate that H. bosniaca populations are able to persist in intermittently inundated environments and produce several generations per annual hydrological cycle. In addition, adult individuals were able to survive in the wet mud of dry pools for longer than five weeks. The experimental data suggest a lower average survival time when exposed to desiccation processes, and that the velocity of substrate water loss is a determining factor for the survival rate of ostracods resisting dry events in temporary ponds. As shown by ostracods’ life histories in temporary aquatic environments undergoing unpredictable desiccation events, a combined strategy of adult tolerance to short periods of water scarcity and rapid hatching from resting egg banks can be advantageous for the monopolization of small-sized ephemeral habitats.  相似文献   

The 23 April 1909 Benavente earthquake (Portugal): macroseismic field revision   总被引：1，自引：0，他引：1  

Paula Teves-Costa  Josep Batlló 《Journal of Seismology》2011,15(1):59-70

The 23 April 1909 earthquake, with epicentre near Benavente (Portugal), was the largest crustal earthquake in the Iberian Peninsula during the twentieth century (M _w = 6.0). Due to its importance, several studies were developed soon after its occurrence, in Portugal and in Spain. A perusal of the different studies on the macroseismic field of this earthquake showed some discrepancies, in particular on the abnormal patterns of the isoseismal curves in Spain. Besides, a complete list of intensity data points for the event is unavailable at present. Seismic moment, focal mechanism and other earthquake parameters obtained from the instrumental records have been recently reviewed and recalculated. Revision of the macroseismic field of this earthquake poses a unique opportunity to study macroseismic propagation and local effects in central Iberian Peninsula. For this reasons, a search to collect new macroseismic data for this earthquake has been carried out, and a re-evaluation of the whole set has been performed and it is presented here. Special attention is paid to the observed low attenuation of the macroseismic effects, heterogeneous propagation and the distortion introduced by local amplifications. Results of this study indicate, in general, an overestimation of the intensity degrees previously assigned to this earthquake in Spain; also it illustrates how difficult it is to assign an intensity degree to a large town, where local effects play an important role, and confirms the low attenuation of seismic propagation inside the Iberian Peninsula from west and southwest to east and northeast.  相似文献   

Historical torrential flood events in the Kolubara river basin   总被引：1，自引：0，他引：1  

Ana M. Petrović  Slavoljub S. Dragićević  Boris P. Radić  Ana Z. Milanović Pešić 《Natural Hazards》2015,79(1):537-547

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Low-order stabilized finite element for the full Biot formulation in soil mechanics at finite strain     

Lluís Monforte  Pedro Navas  Josep Maria Carbonell  Marcos Arroyo  Antonio Gens 《国际地质力学数值与分析法杂志》2019,43(7):1488-1515

This article presents a novel finite element formulation for the Biot equation using low-order elements. Additionally, an extra degree of freedom is introduced to treat the volumetric locking steaming from the effective response of the medium; its balance equation is also stabilized. The accuracy of the proposed formulation is demonstrated by means of numerical analyses.  相似文献   

Interacting Ricci-like holographic dark energy     

F. Arévalo  P. Cifuentes  Samuel Lepe  Francisco Peña 《Astrophysics and Space Science》2014,352(2):899-907

In a flat Friedmann–Lemaitre–Robertson–Walker background, a scheme of dark matter–dark energy interaction is studied considering a holographic Ricci-like model for the dark energy. Without giving a priori some specific model for the interaction function, we show that this function can experience a change of sign during the cosmic evolution. The parameters involved in the holographic model are adjusted with Supernova data and we obtained results compatible with the observable universe.  相似文献