549 research outputs found

    Presence-absence versus presence-only modelling methods for predicting bird habitat suitability

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    Habitat suitability models can be generated using methods requiring information on species presence or species presence and absence. Knowledge of the predictive performance of such methods becomes a critical issue to establish their optimal scope of application for mapping current species distributions under different constraints. Here, we use breeding bird atlas data in Catalonia as a working example and attempt to analyse the relative performance of two methods: the Ecological Niche factor Analysis (ENFA) using presence data only and Generalised Linear Models (GLM) using presence/absence data. Models were run on a set of forest species with similar habitat requirements, but with varying occurrence rates (prevalence) and niche positions (marginality). Our results support the idea that GLM predictions are more accurate than those obtained with ENFA. This was particularly true when species were using available habitats proportionally to their suitability, making absence data reliable and useful to enhance model calibration. Species marginality in niche space was also correlated to predictive accuracy, i.e. species with less restricted ecological requirements were modelled less accurately than species with more restricted requirements. This pattern was irrespective of the method employed. Models for wide-ranging and tolerant species were more sensitive to absence data, suggesting that presence/absence methods may be particularly important for predicting distributions of this type of species. We conclude that modellers should consider that species ecological characteristics are critical in determining the accuracy of models and that it is difficult to predict generalist species distributions accurately and this is independent of the method used. Being based on distinct approaches regarding adjustment to data and data quality, habitat distribution modelling methods cover different application areas, making it difficult to identify one that should be universally applicable. Our results suggest however, that if absence data is available, methods using this information should be preferably used in most situations

    Influencia de factores bióticos a escala local y de paisaje en la distribución del muérdago en pinares mediterráneos

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    The study of the spatial patterns of species allows the examination of hypotheses on the most plausible ecological processes and factors determining their distribution. To investigate the determinants of parasite species on Mediterranean forests at regional scales, occurrence data of the European Misletoe (Viscum album) in Catalonia (NE Iberian Peninsula) were extracted from forest inventory data and combined with different types of explanatory variables by means of generalized linear mixed models. The presence of mistletoes in stands of Pinus halepensis seems to be determined by multiple factors (climatic conditions, and characteristics of the host tree and landscape structure) operating at different spatial scales, with the availability of orchards of Olea europaea in the surroundings playing a relevant role. These results suggest that host quality and landscape structure are important mediators of plant-plant and plant-animal interactions and, therefore, management of mistletoe populations should be conducted at both local (i.e. clearing of infected host trees) and landscape scales (e.g. controlling the availability of nutrient-rich food sources that attract bird dispersers). Research and management at landscape-scales are necessary to anticipate the negative consequence of land-use changes in Mediterranean forests.El estudio de los patrones espaciales de las especies permite examinar hipótesis sobre los procesos ecológicos y factores más plausibles que determinan su distribución. Para investigar los determinantes de una especie parásita en bosques mediterráneos a escala regional, se combinaron datos sobre la presencia de muérdago (Viscum album) en Cataluña (NE de la Península Ibérica) extraídos del inventario forestal con diferentes variables explicativas por medio de modelos mixtos generalizados. La presencia de muérdago en masas de Pinus halepensis parece estar determinada por múltiples factores (condiciones climáticas, características del árbol hospedante, y estructura del paisaje) que operan a diferentes escalas espaciales, jugando los cultivos de Olea europaea un papel relevante. Los resultados sugieren que la calidad de los árboles hospedantes y la estructura del paisaje son importantes mediadores de las interacciones planta-planta y planta- animal y, por tanto, la gestión de las poblaciones de muérdago debería llevarse a cabo tanto a nivel local (es decir, cortando árboles hospedantes infectados) como de paisaje (por ejemplo, controlando la disponibilidad de hábitats ricos en nutrientes que atraen a las aves dispersantes). La investigación y gestión a escala de paisaje son necesarias para prevenir las consecuencias negativas de los cambios de uso del suelo en los bosques mediterráneos

    Le défigement linguistique comme recours stylistique, et les écueils traductologiques induits de l’espagnol vers le français

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    The man\u27s gaze transcends reality to so often cosmetic purposes. Referring to literature, here we will only tackle the part of the narrative creation which are the metaphorical interpretation and its derivatives to linger over this other type of diversion realized by the language de-fossilization in its phraseology and lexical applications, leading to many puns. The translator must accommodate to this sign of discursive freedom of authors, establishing semantic and semiotic relations of collusion between the source language and the target language. This is what we will develop on the basis of about ten illustrations from Hispanic literature. For each case, we will emphasize the intuitive logic of the original find, to propose its transfer in French, pointing that through a translatological "intuitivo-cognitive" posture, the translator can develop his very own creativity, a true wager of literary faithfulness

    Potential of UAV images as ground-truth data for burn severity classification of Landsat imagery: approaches to an useful product for post-fire management

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    Revista oficial de la Asociación Española de Teledetección[EN] Mapping fire severity is determinant to understand landscape evolution after a wildfire and provides useful information for decision making during post fire management. Quantitative fire severity mapping from relative changes in Normalized Burn Ratio index (RdNBR) is not actually being incorporated into decision making processes, being more useful the categorization in severity levels (high, moderate and low). However, the most common mapping severity methodologies based on the definition of RdNBR thresholds from field information are not always possible due to lack of field data or because the published thresholds are unsatisfactory in new regions. The boom in the use of UAVs (Unmanned Aerial Vehicle) has raised these platforms as potential tools for validation of remote sensing data. This paper presents the potential of UAVs as ground truth information in forest fires. From the photointerpretation of high resolution RGB images, the Aerial Severity Proportion Index (ASPI) has been created. Non-linear regression models between RdNBR and ASPI allows to delimitate of thresholds for the classification of Landsat images and to obtain qualitative severity maps. Validation with random points presents a kappa index of 0,5 and a relative accuracy of 70,8%. Therefore, UAV images become a very useful tool for wildfire severity mapping and for fill the gap between remote sensing information and expensive field ground campaigns.[ES] La cuantificación de la severidad de los incendios forestales es determinante para conocer la evolución del paisaje después de un incendio forestal y provee información de gran utilidad frente a la toma de decisiones en la gestión post incendio. La cartografía cuantitativa de severidad de incendios a partir de cambios relativos del índice Normalized Burn Ratio (RdNBR) no está siendo realmente incorporada en los procesos de toma de decisiones, siendo más utilizada la categorización en niveles de severidad (alta, mediana y baja). Sin embargo, las clasificaciones de severidad más comunes, basadas en la definición de umbrales de corte de RdNBR a partir de información de campo, no son siempre posibles por falta de datos de campo o bien porque los umbrales publicados resultan poco satisfactorios en localizaciones distintas a las de su calibración. El auge del uso de UAVs (Unmaned Aerial Vehicle) ha planteado estas plataformas como posible herramienta para la validación de información de satélite. En el presente trabajo se presenta la potencialidad de los UAV como información de verdad terreno en incendios forestales. A partir de la fotointerpretación de imágenes RGB de alta resolución se ha creado el índice ASPI (Aerial Severity Proportion Index), el cual, a partir de modelos de regresión no lineales con el índice RdNBR, permite delimitar umbrales para la clasificación de las imágenes Landsat y obtener un mapa cualitativo de severidad. La validación de los modelos de regresión entre RdNDR y ASPI a partir de puntos al azar muestra un índice kappa de 0,5 con un acierto relativo del 70,8%. Por lo tanto, las imágenes UAV son una herramienta muy útil para la clasificación de la severidad de incendios forestales y para rellenar la brecha existente entre la información proveniente de imágenes de satélite y las costosas campañas de campo.Pla, M.; Duane, A.; Brotons, L. (2017). Potencial de las imágenes UAV como datos de verdad terreno para la clasificación de la severidad de quema de imágenes Landsat: aproximaciones a un producto útil para la gestión post incendio. Revista de Teledetección. (49):91-102. doi:10.4995/raet.2017.7140SWORD911024

    Meltable, Glass-Forming, Iron Zeolitic Imidazolate Frameworks

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    We describe the first meltable iron-based zeolitic imidazolate framework (ZIF), denoted MUV-24. This material, elusive from direct synthesis, is obtained from the thermal treatment of [Fe3(im)6(Him)2], which yields Fe(im)2 upon loss of the neutral imidazole molecules. Different crystalline phase transformations are observed upon further heating, until the material melts at 482 °C. Vitrification upon cooling of the liquid phase gives rise to the first Fe-metal-organic framework glass. X-ray total scattering experiments show that the tetrahedral environment of the crystalline solids is maintained in the glass, whereas nanoindentation measurements reveal an increase in Young's modulus, in agreement with stiffening upon vitrification

    Prescripción de antibióticos en la infección del tracto urinario: adecuación a criterios de calidad en atención primaria

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    ObjetivoDeterminar la prevalencia de insuficiencia renal crónica (IRC) sin tratamiento sustitutivo (TSR), describir el tipo de enfermedades renales primarias y los factores de riesgo asociados que pueden favorecer su evolución hacia la insuficiencia renal terminal.DiseñoEstudio descriptivo, transversal.EmplazamientoPoblación atendida por un centro de atención primaria.ParticipantesMayores de 14 años con historia clínica abierta en el CAP Bon Pastor.ResultadosDurante el período 1-I-1997 hasta 1-XII-1997 se revisaron 12.241 historias clínicas. Se identificaron 64 pacientes que cumplían criterios de IRC sin TSR; prevalencia, 5.228 pacientes por millón de habitantes (pmp) (IC del 95%, 3.950–6.510 pmp). Un 71,9% era varón, la edad media era de 72 años (DE, 13,5). La media de la última creatinina plasmática fue de 2 mg/dl (DE, 0,66). La frecuencia según tipo de nefropatía fue: glomerular, 3 (4,7%); diabética, 5 (7,8%); intersticial, 3 (4,7%); vascular (HTA), 41 (64,1%); indeterminada, 2 (3,1%), e inclasificable, 10 (15,6%). Los factores de riesgo asociados en estos pacientes fueron: hipertensos, 47 (73,4%); diabéticos, 16 (25%); hipercolesterémicos, 26 (40,6%); consumidores crónicos de analgésicos, 20 (31,3%), y 10 (15,6%), fumadores. Un 51,6% de los pacientes presentaba otras enfermedades cardiovasculares.ConclusionesLa prevalencia estimada de IRC sin TRS en la población es de 5.228 pmp, y la hipertensión es el factor de riesgo más frecuente asociado a esta patología.ObjectiveTo determine the prevalence of chronic renal failure (CRF) without replacement treatment (RT), and to describe the primary renal diseases and associated risk factors that might favour its evolution to terminal renal failure.DesignCross-sectional, descriptive study.SettingPopulation attended at a primary care centre (PCC).ParticipantsOver-14s with a clinical history opened at the Bon Pastor PCC.ResultsBetween the 1st of January 1997 and the 1st of December 1997, 12241 clinical histories were reviewed. 64 patients were identified who satisfied criteria of CRF without RT, a prevalence of 5228 patients per million inhabitants (95% CI, 3,950–6,510). 71.9% were men, and mean age was 72 (SD, 13.5). The most recent plasma creatinine averaged 2 mg/dl (SD, 0.66). Frequency according to kind of nephropathy was: 3 (4.7%) glomerular, 5 (7.8%) diabetic, 3 (4.7%) interstitial, 41 (64.1%) vascular (hypertension), 2 (3.1%) indeterminate and 10 (15.6%) unclassifiable. Associated risk factors in these patients were: 47 (73.4%) with hypertension, 16 (25%) diabetic, 26 (40.6%) with hypercholesterolaemia, 20 (31.3%) chronic consumers of analgesics, and 10 (15.6%) smokers. 51.6% of the patients suffered other cardiovascular illnesses.ConclusionsThe estimated prevalence in the population of CRF without RT is 5,228 per million inhabitants. Hypertension is the risk factor most closely associated with this pathology

    Fluorescent Self-Assembled Mono layers of Umbelliferone: A Relationship between Contact Angle and Fluorescence

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    Self-assembled monolayers (SAMs) that contain fluorophore units are nowadays widely used to tune surface properties and design new chemical sensor chips. It is well-known that the nature of the substrate may strongly interfere with the emission properties of the grafted molecules, but the organization of the monolayer may also have an important role. To study the influence of the SAM organization on the luminescence properties, we prepared different coumarin-based derivatives endowed with tethered chains of different lengths and elaborated the corresponding SAMs on glass slides. Besides SAM structural characterizations by atomic force microscopy and X-ray reflectivity, we carried out contact angle measurements and applied the Van Oss-Chaudhury-Good theory, which was rarely used previously for self-assembled monolayers. As expected, by increasing the tethered chain length, a higher surface coverage, a higher degree of organization, and a stronger molecular packing were observed. However, it appears to facilitate the self-quenching process, and thus, this strongly affects the fluorescent properties of the SAMs

    Pipelines and Systems for Threshold-Avoiding Quantification of LC-MS/MS Data

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    The accurate processing of complex liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) data from biological samples is a major challenge for metabolomics, proteomics, and related approaches. Here, we present the pipelines and systems for threshold-avoiding quantification (PASTAQ) LC-MS/MS preprocessing toolset, which allows highly accurate quantification of data-dependent acquisition LC-MS/MS datasets. PASTAQ performs compound quantification using single-stage (MS1) data and implements novel algorithms for high-performance and accurate quantification, retention time alignment, feature detection, and linking annotations from multiple identification engines. PASTAQ offers straightforward parameterization and automatic generation of quality control plots for data and preprocessing assessment. This design results in smaller variance when analyzing replicates of proteomes mixed with known ratios and allows the detection of peptides over a larger dynamic concentration range compared to widely used proteomics preprocessing tools. The performance of the pipeline is also demonstrated in a biological human serum dataset for the identification of gender-related proteins.</p
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