Multigrid solvers for multipoint flux approximations of the Darcy problem on rough quadrilateral grids

In this work, an efficient blackbox-type multigrid method is proposed for solving multipoint flux approximations of the Darcy problem on logically rectangular grids. The approach is based on a cell-centered multigrid algorithm, which combines a piecewise constant interpolation and the restriction operator by Wesseling/Khalil with a line-wise relaxation procedure. A local Fourier analysis is performed for the case of a Cartesian uniform grid. The method shows a robust convergence for different full tensor coefficient problems and several rough quadrilateral grids.Francisco J. Gaspar has received funding from the European Union’s Horizon 2020 Research and Innovation Programme under the Marie Skłodowska–Curie grant agreement no. 705402, POROSOS. The work of Laura Portero is supported by the Spanish project MTM2016-75139-R (AEI/FEDER, UE) and the Young Researchers Programme 2018 from the Public University of Navarre. Andrés Arrarás acknowledges support from the Spanish project PGC2018-099536-A-I00 (MCIU/AEI/FEDER, UE) and the Young Researchers Programme 2018 from the Public University of Navarre. The work of Carmen Rodrigo is supported by the Spanish project PGC2018-099536-A-I00 (MCIU/AEI/FEDER, UE) and the DGA (Grupo de referencia APEDIF, ref. E24_17R)

Mixed-dimensional geometric multigrid methods for single-phase flow in fractured porous media

This paper deals with the efficient numerical solution of single-phase flow problems in fractured porous media. A monolithic multigrid method is proposed for solving two-dimensional arbitrary fracture networks with vertical and/or horizontal possibly intersecting fractures. The key point is to combine two-dimensional multigrid components (smoother and intergrid transfer operators) in the porous matrix with their one-dimensional counterparts within the fractures, giving rise to a mixed-dimensional geometric multigrid method. This combination seems to be optimal since it provides an algorithm whose convergence matches the multigrid convergence factor for solving the Darcy problem. Several numerical experiments are presented to demonstrate the robustness of the monolithic mixed-dimensional multigrid method with respect to the permeability of the fractures, the grid size, and the number of fractures in the network.The work of the first and fourth authors was supported by Spanish project PGC2018-099536-A-I00 (MCIU/AEI/FEDER, UE). The work of the second author was supported by the European Union's Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement 705402, POROSOS. The work of the third author was partially supported by the Spanish project FEDER/MCYT MTM2016-75139-R. The work of the fourth author was supported by the DGA (Grupo de referencia APEDIF, ref. E24 17R)

Effect of a traditional control method (tree removal) on the spread of sharka in an apricot orchard in Southeastern Spain

The spatial spread of sharka disease (Plum pox virus, PPV) was studied from 1990 to 2002 in a traditional apricot (Prunus armeniaca L.) orchard located in Murcia (Southeast of Spain). The occurrence of sharka was determined by the visual observation of symptoms on leaves and fruits during the ripening stage, when symptoms are most visible. To ascertain PPV in doubtful samples, an ELISA-DASI assay was applied to the leaves. All trees infected the previous year were pulled up and were not replanted. Results showed that the virus was introduced to the farm by natural vectors (aphids) from a neighbouring sharka-infected plum orchard. It was then transmitted from these infected trees mainly to nearby trees by the same vectors, although also often to trees standing quite a distance away. The long interval between infection and symptom appearance makes eradication of the disease more difficult. Pulling up infected trees as a control method reduced the percentage of trees ultimately lost, and over the long term could stop the further spread of the disease

Effect of a traditional control method (tree removal) on the spread of sharka in an apricot orchard in Southeastern Spain

The spatial spread of sharka disease (Plum pox virus, PPV) was studied from 1990 to 2002 in a traditional apricot (Prunus armeniaca L.) orchard located in Murcia (Southeast of Spain). The occurrence of sharka was determined by the visual observation of symptoms on leaves and fruits during the ripening stage, when symptoms are most visible. To ascertain PPV in doubtful samples, an ELISA-DASI assay was applied to the leaves. All trees infected the previous year were pulled up and were not replanted. Results showed that the virus was introduced to the farm by natural vectors (aphids) from a neighbouring sharka-infected plum orchard. It was then transmitted from these infected trees mainly to nearby trees by the same vectors, although also often to trees standing quite a distance away. The long interval between infection and symptom appearance makes eradication of the disease more difficult. Pulling up infected trees as a control method reduced the percentage of trees ultimately lost, and over the long term could stop the further spread of the disease

Amphibians in the Region of Murcia (SE Iberian peninsula): conservation status and priority areas

The conservation status of amphibian species was studied in the Region of Murcia, taking into consideration 10 variables concerning their biology and distribution. The results obtained show that the amphibian species exposed to the highest risk of extinction in the study area are those with long larval development and a restricted distribution range. According to this species classification, an index is proposed for assessing areas whose conservation is of the highest priority. In the Region of Murcia, most of these areas are located in the main mountain systems, primarily confined to the northwest. Regional Parks and proposed priority conservation areas overlap by only about 12%. The current isolation of these areas makes it necessary to undertake habitat restoration programmes to ensure their interconnection

Micro and nano smart composite films based on copper-iodine coordination polymer as thermochromic biocompatible sensors

Herein is presented the preparation and characterization of a composite material obtained by the combination of nanosheets of a coordination polymer (CP) based on the copper(I)-I double chain with response to temperature and pressure with polylactic acid (PLA) as biodegradable organic matrix. The new films of composite materials are generated using a simple and low-cost method and can be created with long lateral dimensions and thicknesses ranging from a few microns to a few nanometers. Studies show that the new material maintains the optical response versus the temperature, while the elasticity and flexibility of the PLA totally quenches the response to pressure previously observed for the CP. This new material can act as a reversible sensor at low temperatures, thanks to the flexibility of the copper(I)-iodine chain that conforms the CP. The addition of CP to the PLA matrix reduces the elastic modulus and ultimate elongation of the organic matrix, although it does not reduce its tensile strength

Serendipitous discovery of a dusty disc around WDJ181417.84-735459.83

This is a pre-copyedited, author-produced PDF of an article accepted for publication in Monthly Notices of the Royal Astronomical Society following peer review. The version of record is available online at: https://doi.org/10.1093/mnras/staa3836Spectroscopic observations of white dwarfs reveal that many of them are polluted by exoplanetary material, whose bulk composition can be uniquely probed this way. We present a spectroscopic and photometric analysis of the DA white dwarf WDJ181417.84$-$735459.83, an object originally identified to have a strong infrared excess in the 2MASS and WISE catalogues that we confirmed to be intrinsic to the white dwarf, and likely corresponding to the emission of a dusty disc around the star. The finding of Ca, Fe and Mg absorption lines in two X-SHOOTER spectra of the white dwarf, taken 8 years apart, is further evidence of accretion from a dusty disc. We do not report variability in the absorption lines between these two spectra. Fitting a blackbody model to the infrared excess gives a temperature of 910$\pm50$ K. We have estimated a total accretion flux from the spectroscopic metal lines of $|\dot{\rm M}| = 1.784 \times 10^{9}\,$g s$^{-1}$.Peer reviewedFinal Accepted Versio

Limitations and usefulness of maximum daily shrinkage (MDS) and trunk growth rate (TGR) indicators in the irrigation scheduling of table olive trees

8 páginas.-- 7 figuras.-- 2 tablas.-- 32 referenciasMaximum daily trunk shrinkage (MDS) is the most popular indicator derived from trunk diameter fluctuations in most fruit trees and has been reported to be one of the earliest signs in the detection of water stress. However, in some species such as olive trees (. Olea europaea L.), MDS does not usually change in water stress conditions and trunk growth rate (TGR) has been suggested as better indicator. Most of this lack of sensitivity to drought conditions has been related to the relationship between the MDS and the water potential. This curvilinear relationship produces an uncertain zone were great variations of water potential do not imply any changes of MDS. The MDS signal, the ratio between measured MDS and estimated MDS with full irrigation, has been thought to be a better indicator than MDS, as it reduces the effect of the environment. On the other hand, though literature results suggest an effect of environment in TGR values, there are not clear relationship between this indicator and meteorological data. The aims of this work are, on one hand, to study the improvements of the baseline approach in the MDS signal and, on the other, study the influence of several meteorological variables in TGR. Three years' data from an irrigation experiment were used in to carry out the MDS analysis and six years' data for full irrigated trees during pit hardening period were used for TGR study. The comparison between MDS vs. water potential and MDS signal vs. water potential presented a great scattering in both relationships. Values of MDS signal between 1.1 and 1.4 were always identified with moderate water stress conditions (-1.4 to -2. MPa of water potential). However, since this MDS signal values are around the maximum in the curvilineal relationship with water potential, greater values of MDS signal (in the range of 1.1-1.4) were not necessary lower values of water potential. In addition, during low fruit load seasons MDS signal was not an accurate indicator. On the other hand, absolute values of several climatological measurements were not significantly related with TGR. Only daily increments explain part of the variations of TGR in full irrigated trees. In all the data analysed, the daily increment of average vapour pressure deficit was the best indicator related with TGR. The increase of this indicator decreased TGR values. In addition, the agreement between this indicator and TGR was affected for fruit load. Great yield seasons decrease the influence of VPD increment in TGR.This research was supported by the Spanish Ministerio de Ciencia e Innovación (MICINN), (AGL2010-19201-CO4-03). Thanks are due to J. Rodriguez and A. Montero for help with field measurements.Peer reviewe

The effect of refeeding after starvation on the growth of sharpsnout seabream Diplodus puntazzo (Cetti, 1777)

Compensatory growth is rapid growth induced by hyperphagic behaviour after starvation. The present paper studies this phenomenon in sharpsnout seabream Diplodus puntazzo (Cetti, 1777). We used control groups (LC) feeding ad libitum and starvation-refeeding ad libitum groups (AR). AR growth was double that of LC after the refeeding period, and food intake was also higher. Although AR did not reach LC final weight, condition index K was achieved. These results suggest the need to test this hypothesis over longer starvation and refeeding periods which could lead to hyperphagic behavior.El crecimiento compensatorio se define como un crecimiento rápido provocado por un comportamiento hiperfágico después de un periodo de ayuno. El objetivo del trabajo es poner de manifiesto la existencia de estos fenómenos en Diplodus puntazzo (Cetti, 1777). Para ello se mantuvieron lotes de control alimentados a saciedad (LC) y lotes en ayuno y realimentados posteriormente a saciedad (AR). Se comprobó que la tasa de crecimiento se duplicó en el periodo de realimentación para los lotes AR con respecto a los lotes LC, siendo mayor, también, la tasa de alimentación de los lotes AR; sin embargo, estos lotes no alcanzan el peso de los lotes control, aunque sí recuperaron el factor de condición (K). Estos resultados sugieren la necesidad de comprobar este comportamiento para periodos de ayuno más prolongados que pudieran provocar una mayor respuesta hiperfágica.Instituto Español de Oceanografí