292 research outputs found

    Exergy assessment of topsoil fertility

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    Soil degradation, affecting around 38% of the world''s cropland, threatens the global food supply. Due to the soil''s complexity, the measure of soil degradation that involves the loss of soil fertility due to crop system management processes represents an unsolved problem. Exergy is a property with the potential to be used in soil fertility and/or degradation analysis. A methodology to determine the exergy value fenced in a fertile soil due to its inorganic and organic components is established in this study and will be applied to evaluate soil fertility, degradation, and quality. As a first step, the exergy of perfect topsoil with optimum characteristics called "OptSOIL" is determined. The "OptSOIL" is established by agronomic expertise and will allow establishing a general theoretical reference suitable to execute exergy assessments of soils and compare the degradation grade of any soil concerning the best possible. Consequently, we introduce a perfect fertile planetary crust made of “OptNUT” and “OptSOM” invariant and independent of the different local textures, but not independent of their water content and aeration. We call this imaginary crust -copiously fertile- Pristinia as opposed to Thanatia, a dead state referring to abiotic resources. Thus, any real agricultural soil will be an intermediate soil between Pristinia and Thanatia. This idea might serve to quantitatively diagnose an assessment of all the concepts by which soil is degraded. The methodology has been validated through laboratory agronomic tests for different soils, concluding that exergy is a rigorous indicator to measure topsoil fertility. © 2021 The Author

    Galaxy clusters with the square kilometer array

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    We review some science cases for galaxy clusters and the impact that the future SKA data will have in those analyses. We first describe how the search for galaxy clusters through radio-sources will be significantly improved through the detection of much fainter radiosources in a big volume. Secondly, we bring out the benefits of using very sensitive radio data to study the thermal and non-thermal component of clusters and disentangle the main processes happening in the physics of their plasma. Moreover, we discuss the possibility of using the high frequencies of the SKA to separate the thermal Sunyaev-Zeldovich (SZ) effect from the radio halo emission and use the former as a mass proxy for galaxy clusters. Finally, we investigate how the very high sensitivity and spatial resolution of SKA will result into a great improvement in the lensing treatment, underlining the lensing distribution of the 21-cm intensity from the reionization period. As a whole, SKA will become an impressive window covering a significant wider range in redshift to look at an unknown radio universe and set constraints on different mechanisms happening in clusters.This work has been supported by a grant funded by the “Consorzio per la Fisica di Trieste”. SP also acknowledges support by the PRIN-INAF09 project “Towards an Italian Network for Computational Cosmology”, by the PRIN-MIUR09 “Tracing the growth of structures in the Universe”, and by the PD51 INFN grant. Partial support is also provided by Spanish Ministerio de Ciencia e Innovación (AYA2010-21322-C03-02). JD acknowledges support from the Spanish Ministry of Economy and Competitiveness (MINECO) through grants AYA2010-21766-C03-02, AYA2012-30789, and the Consolider-Ingenio project CSD2010-00064 (EPI: Exploring the Physics of Inflation). YA is financially supported by the Spanish Ramón y Cajal programme (RyC-2011-09461) and grant AYA2013-47742-C4-3-P (MINECO), as well as the ‘Study of Emission-Line Galaxies with Integral-Field Spectroscopy’ (SELGIFS) exchange programme, funded by the EU through the IRSES scheme (FP7-PEOPLE-2013-IRSES-612701). BA acknowledges financial support for a postdoctoral fellowship from the Observatory of Paris.Peer reviewe

    Apples to apples A^2 – II. Cluster selection functions for next-generation surveys

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    We present the cluster selection function for three of the largest next-generation stage-IV surveys in the optical and infrared: Euclid-Optimistic, Euclid-Pessimistic and the Large Synoptic Survey Telescope (LSST). To simulate these surveys, we use the realistic mock catalogues introduced in the first paper of this series. We detected galaxy clusters using the Bayesian Cluster Finder in the mock catalogues. We then modelled and calibrated the total cluster stellar mass observable–theoretical mass (M^∗_(CL)—M_h) relation using a power-law model, including a possible redshift evolution term. We find a moderate scatter of σM^∗_(CL)|M_h) of 0.124, 0.135 and 0.136 dex for Euclid-Optimistic, Euclid-Pessimistic and LSST, respectively, comparable to other work over more limited ranges of redshift. Moreover, the three data sets are consistent with negligible evolution with redshift, in agreement with observational and simulation results in the literature. We find that Euclid-Optimistic will be able to detect clusters with >80 per cent completeness and purity down to 8 × 10^(13) h^(−1) M_⊙ up to z < 1. At higher redshifts, the same completeness and purity are obtained with the larger mass threshold of 2 × 10^(14) h^(−1) M_⊙ up to z = 2. The Euclid-Pessimistic selection function has a similar shape with ∼10 per cent higher mass limit. LSST shows ∼5 per cent higher mass limit than Euclid-Optimistic up to z < 0.7 and increases afterwards, reaching a value of 2 × 10^(14) h^(−1) M_⊙ at z = 1.4. Similar selection functions with only 80 per cent completeness threshold have also been computed. The complementarity of these results with selection functions for surveys in other bands is discussed

    Next Generation Cosmology: Constraints from the Euclid Galaxy Cluster Survey

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    We study the characteristics of the galaxy cluster samples expected from the European Space Agency's Euclid satellite and forecast constraints on cosmological parameters describing a variety of cosmological models. The method used in this paper, based on the Fisher Matrix approach, is the same one used to provide the constraints presented in the Euclid Red Book (Laureijs et al.2011). We describe the analytical approach to compute the selection function of the photometric and spectroscopic cluster surveys. Based on the photometric selection function, we forecast the constraints on a number of cosmological parameter sets corresponding to different extensions of the standard LambdaCDM model. The dynamical evolution of dark energy will be constrained to Delta w_0=0.03 and Delta w_a=0.2 with free curvature Omega_k, resulting in a (w_0,w_a) Figure of Merit (FoM) of 291. Including the Planck CMB covariance matrix improves the constraints to Delta w_0=0.02, Delta w_a=0.07 and a FoM=802. The amplitude of primordial non-Gaussianity, parametrised by f_NL, will be constrained to \Delta f_NL ~ 6.6 for the local shape scenario, from Euclid clusters alone. Using only Euclid clusters, the growth factor parameter \gamma, which signals deviations from GR, will be constrained to Delta \gamma=0.02, and the neutrino density parameter to Delta Omega_\nu=0.0013 (or Delta \sum m_\nu=0.01). We emphasise that knowledge of the observable--mass scaling relation will be crucial to constrain cosmological parameters from a cluster catalogue. The Euclid mission will have a clear advantage in this respect, thanks to its imaging and spectroscopic capabilities that will enable internal mass calibration from weak lensing and the dynamics of cluster galaxies. This information will be further complemented by wide-area multi-wavelength external cluster surveys that will already be available when Euclid flies. [Abridged]Comment: submitted to MNRA

    Auditing the accessibility of MOOCs: a four-component approach

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    This paper reports the design of a four-component audit to evaluate the accessibility of Massive Open Online Courses (MOOCs). The MOOC accessibility audit was designed as part of a research programme at The Open University (UK) that aimed to assess the current state of accessibility of MOOC platforms and resources, to uncover accessibility barriers, and to derive recommendations on how the barriers could be addressed. The audit is composed of four evaluation components: technical accessibility, user experience (UX), quality and learning design. The audit consists of four processes supported by checklists corresponding to each of the four components implemented via a heuristic evaluation approach, an evaluation technique from Human-Computer Interaction literatur

    Optical coherence tomography in patients with chronic migraine: Literature review and update

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    Migraine is a chronic disease characterized by unilateral, pulsating, and often moderate-to-severe recurrent episodes of headache with nausea and vomiting. It affects approximately 15% of the general population, yet the underlying pathophysiological mechanisms are not fully understood. Optical coherence tomography (OCT) is a safe and reproducible diagnostic technique that utilizes infrared wavelengths and has a sensitivity of 8-10 µm. It can be used to measure thinning of the retinal nerve fiber layer (RNFL) in some neurological disorders. Although ophthalmologists are often the first specialists to examine patients with migraine, few studies have addressed the involvement of the optic nerve and retino-choroidal structures in this group. We reviewed the literature on the etiological and pathological mechanisms of migraine and the relationship between recurrent constriction of cerebral and retrobulbar vessels and ischemic damage to the optic nerve, retina, and choroid. We also assessed the role of OCT for measuring peripapillary RNFL thickness and macular and choroidal changes in migraine patients. There is considerable evidence of cerebral and retrobulbar vascular involvement in the etiology of migraine. Transitory and recurrent constriction of the retinal and ciliary arteries may cause ischemic damage to the optic nerve, retina, and choroid in patients with migraine. OCT to assess the thickness of the peripapillary RNFL, macula, and choroid might increase our understanding of the pathophysiology of migraine and facilitate diagnosis of retino-choroidal compromise and follow-up of therapy in migraine patients. Future studies should determine the usefulness of OCT findings as a biomarker of migraine

    The response to iron supplementation of pregnant women with the haemoglobin genotype AA or AS

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    The influence of haemoglobin genotype on the response to iron supplementation was studied in a randomized, double blind, placebo-controlled trial involving 497 multigravid pregnant women from a rural area of The Gambia. Women were randomly allocated to receive either oral iron (60mg elemental iron per day) or placebo. At 36 weeks of pregnancy, women who had received oral iron during pregnancy had higher mean haemoglobin, packed cell volume, plasma iron and ferritin levels than did women who received placebo. Iron supplementation of pregnant women with the AA haemoglobin genotype also resulted in increases in the packed cell volume (PCV) and haemoglobin level measured after delivery, and in the birth weight of the infant. However, in AS women PCV and haemoglobin level at delivery were lower in the supplemented group and supplementation was also associated with reduced birth weights. In malaria endemic areas, pregnant women with the haemoglobin genotype AS may not benefit from iron supplementation during pregnanc

    The evolution of Balmer jump selected galaxies in the ALHAMBRA survey

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    We present a new color-selection technique, based on the Bruzual & Charlot models convolved with the bands of the ALHAMBRA survey, and the redshifted position of the Balmer jump to select star-forming galaxies in the redshift range 0.5 < z < 1.5. These galaxies are dubbed Balmer jump Galaxies BJGs. We apply the iSEDfit Bayesian approach to fit each detailed SED and determine star-formation rate (SFR), stellar mass, age and absolute magnitudes. The mass of the haloes where these samples reside are found via a clustering analysis. Five volume-limited BJG sub-samples with different mean redshifts are found to reside in haloes of median masses 1012.5±0.2M\sim 10^{12.5 \pm 0.2} M_\odot slightly increasing toward z=0.5. This increment is similar to numerical simulations results which suggests that we are tracing the evolution of an evolving population of haloes as they grow to reach a mass of 1012.7±0.1M\sim 10^{12.7 \pm 0.1} M_\odot at z=0.5. The likely progenitors of our samples at z\sim3 are Lyman Break Galaxies, which at z\sim2 would evolve into star-forming BzK galaxies, and their descendants in the local Universe are elliptical galaxies.Hence, this allows us to follow the putative evolution of the SFR, stellar mass and age of these galaxies. From z\sim1.0 to z\sim0.5, the stellar mass of the volume limited BJG samples nearly does not change with redshift, suggesting that major mergers play a minor role on the evolution of these galaxies. The SFR evolution accounts for the small variations of stellar mass, suggesting that star formation and possible minor mergers are the main channels of mass assembly.Comment: 14 pages, 10 figures. Submitted to A&A. It includes first referee's comments. Abstract abridged due to arXiv requirement

    Efecto de la inclusión de aceite de murta en la dieta de cabritos sobre la calidad sensorial de la carne

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    Los autores agradecen a Zina Taghouti, técnica en el laboratorio de Producción Animal del INRAT por la asistencia técnicaPublishe
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