La información litológica mejora los modelos de distribución de especies de plantas basados en datos de baja resolución espacial

The aim of this study was to assess the improvement of plant species distribution models based on coarse-grained occurrence data when adding lithologic data to climatic models. The distributions of 40 woody plant species from continental Spain were modelled. A logistic regression model with climatic predictors was fitted for each species and compared to a second model with climatic and lithologic predictors. Improvements on model likelihood and prediction accuracy on validation subsamples were assessed, as well as the effect of calcicole–calcifuge habit on model improvemenClimatic models had reasonable mean prediction accuracy, but adding lithologic data improved model likelihood in most cases and increased mean prediction accuracy. Therefore, we recommend utilizing lithologic data for species distribution models based on coarse-grained occurrence data. Our data did not support the hypothesis that calcicole–calcifuge habit may explain model improvement when adding lithologic data to climatic models, but further research is needed.El objetivo de este estudio es evaluar la mejora que supone la incorporación de la litología a modelos climáticos de distribución de especies basados en datos de baja resolución espacial. La zona de estudio es la España peninsular. Se ha ajustado un modelo de regresión logística con variables climáticas para cada una de las 40 especies vegetales consideradas y se ha comparado a un segundo modelo con variables climáticas y litológicas. Se ha evaluado la mejora en la verosimilitud y la capacidad predictiva en submuestras de validación, así como el efecto del grado de preferencia de las especies por suelos calcáreos o silíceos en dicha mejora. Los modelos climáticos ofrecen una capacidad predictiva media razonablemente buena, pero la adición de la litología aumenta la verosimilitud del modelo en la mayoría de los casos y la precisión media de las predicciones aumentan significativamente. Se recomienda utilizar información litológica para los modelos de distribución de especies de plantas basados en datos de baja resolución espacial. Con los datos usados no se puede aceptar la hipótesis de que el grado de preferencia de las especies por suelos calcáreos o silíceos explica las diferencias entre especies en la mejora de los modelos debido a la incorporación de información litológica, pero este aspecto debe ser estudiado con más profundidad en futuras investigaciones

Análisis de las calificaciones compartidas en la modalidad participativa de la evaluación colaborativa entre docente y estudiantes

Current trends in educational assessment in different branches of higher education share the common goal of uniting learning with assessment. Most approaches and theoretical and practical developments in this field revolve around four main factors: feedback, democratization, alignment and relevance. This paper proposes the use of co-assessment as a means of ensuring dialogue-based, democratic and fairer evaluations. With co-assessment, the responsibility is shared by the teacher and the students, who negotiate and agree on the appraisal of student tasks and, in this paper, also on the awarded mark. The aim of this study is to analyse the relationship between a series of jointly agreed marks, following the co-assessment of four tasks, and the marks that the teachers and students would each have individually awarded. Two teachers and 100 students participated in the study, which follows a correlational design and analyses significant statistical differences. The results show a strong correlation between the jointly agreed marks and those assigned individually by the teacher, even though statistically significant differences were found between them. Conversely, no statistically significant differences were identified between the joint marks and the marks assigned individually by the students. These results call for reflection on the real possibility of adapting shared grading methods to students in university frameworks, where the repercussions of awarded marks go far beyond formative goals.Dentro de la variedad existente en las tendencias actuales sobre la evaluación de estudiantes, se encuentra el propósito común de relacionar evaluación y aprendizaje. La retroalimentación, la democratización, la coherencia y la relevancia son cuatro tópicos aglutinadores sobre los que giran la mayoría de los planteamientos y avances teóricos y prácticos en este ámbito. Como forma concreta de cristalizar una evaluación dialógica, democrática y justa, se propone la modalidad participativa de la evaluación colaborativa en la que docentes y estudiantes se reparten la responsabilidad, negociando y consensuando de forma conjunta el valor de las tareas y en nuestro caso, también la calificación final. El propósito de este estudio, que ha involucrado a un total de 100 alumnos y 2 docentes, es precisamente la comprobación del grado de relación existente entre las calificaciones compartidas de 4 tareas universitarias con las que habrían aportado en solitario el docente y el grupo de estudiantes. Se ha seguido un diseño de investigación correlacional y se ha comprobado la existencia de diferencias significativas. Los resultados muestran la estrecha correlación entre las calificaciones compartidas y las calificaciones del docente, aunque se han hallado diferencias estadísticamente significativas entre estas. Por otro lado, no se han encontrado diferencias entre las calificaciones compartidas y las calificaciones de los estudiantes. Las repercusiones de estos resultados, hacen reflexionar, entre otras cuestiones, sobre la posibilidad real de ajustar dichas calificaciones abiertas a la participación de los estudiantes en contextos universitarios donde las repercusiones sobrepasan de largo el ámbito únicamente formativo

Quantifying the role of bedrock lithology in water movement at different scales

The wide variety of geological materials on Earth and the irregularity of its distribution patterns are some evidences of the heterogeneity and complexity of our planet. Bedrock lithology plays an important role inside this heterogeneity

Using synchronization to improve earthquake forecasting in a cellular automaton model

A new forecasting strategy for stochastic systems is introduced. It is inspired by the concept of anticipated synchronization between pairs of chaotic oscillators, recently developed in the area of Dynamical Systems, and by the earthquake forecasting algorithms in which different pattern recognition functions are used for identifying seismic premonitory phenomena. In the new strategy, copies (clones) of the original system (the master) are defined, and they are driven using rules that tend to synchronize them with the master dynamics. The observation of definite patterns in the state of the clones is the signal for connecting an alarm in the original system that efficiently marks the impending occurrence of a catastrophic event. The power of this method is quantitatively illustrated by forecasting the occurrence of characteristic earthquakes in the so-called Minimalist Model.Comment: 4 pages, 3 figure

Stereoselective synthesis and reactivity of cis- and trans- dimolybdenum nitrosyl derivatives with the bridging bis(dimethylsilanediyl)di(η5-cyclopentadienyl) ligand. X-ray molecular structures of cis-[{Mo(CO)2(NO)}2(μ-(η5-C5H3)2(SiMe2)2}], trans-[(Mo(CO)(NO)(CNtBu)}2(μ-(η5-C5H3)2(SiMe2)2}], cis-[{Mo2(CO)3(NO)2(PMe3)}{μ-(η5-C 5H3)2(SiMe2)2}] and trans-[{Mo(NO)(CNtBu)2}2(μ-(η5-C5H3)2(SiMe2)2}]

New dimolybdenum nitrosyl [Mo(CO)2(NO)2μ-(η5-C5H3)2(SiMe2)2] cis-3 and trans-3 complexes have been isolated from the reaction of the previously reported cis-[Mo(CO)3H2μ-(η5-C5H3)2(SiMe2)2] cis-1 and trans-K2[Mo(CO)32μ-(η5-C5H3)2(SiMe2)2] trans-2 respectively, with p-CH3C6H4SO2N(NO)(CH3) (diazald). The reaction of [Mo(CO)2(NO)2μ-(η5-C5H3)2(SiMe2)2] cis-3 and trans-3 with Lewis bases L (L = tert-butylisocyanide and trimethylphosphine) under appropriate conditions gave monosubstituted [Mo2(CO)3(NO)2Lμ-(η5-C5H3)2(SiMe2)2] complexes (L = CNtBu cis-4; PMe3cis-5 and trans-5), disubstituted [Mo(CO)(NO)L2μ-(η5-C5H3)2(SiMe2)2] (L = CNtBu, cis-6, trans-6; PMe3cis-7 and trans-7) and tetrasubstituted [Mo(NO)L22μ-(η5-C5H3)2(SiMe2)2] complexes (L = CNtBu, cis-8 and trans-8), which were isolated in moderate yields and fully characterized by conventional analytical and spectroscopic methods. Addition of PCl5 under appropriate conditions to a diethyl ether solution of cis-3 or trans-3 afforded the dichloronitrosyl derivatives cis- and trans-[MoCl2(NO)2μ-(η5-C5H3)2(SiMe2)2] cis-9 and trans-9. The 13C and variable temperature 1H NMR spectra of complex cis-9 are consistent with the formation of 18 electron metal centres bridged by two chlorine atoms, providing two cis- and trans-nitrosyl isomers, which interchange rapidly in solution at room temperature through a postulated 16 electron intermediate. Treatment of cis-8 and trans-8 with stoichiometric amounts of PCl5 gave the tetrahalo derivatives [Mo(NO)(CNtBu)Cl22μ-(η5-C5H3)2(SiMe2)2] cis-10 and trans-10 respectively, whereas the oxidation of trans-6 with PCl5 under similar conditions gave a mixture of trans-10 and trans-[Mo2(CO)(NO)2(CNtBu)Cl4μ-(η5-C5H3)2(SiMe2)2] (trans-11). In addition, single crystal X-ray crystallographic analyses were performed for cis-3, cis-5, trans-6 and trans-8. All the complexes show two metal fragments bridged by the μ-(η5-C5H3)2(SiMe2)2 ligand, with different dispositions of the metal fragments. Stereoselective synthesis and reactivity of cis- and trans- dimolybdenum nitrosyl derivatives with the bridging bis(dimethylsilanediyl)di(η5-cyclopentadienyl) ligand. X-ray molecular structures of cis-[Mo(CO)2(NO)2μ-(η5-C5H3)2(SiMe2)2], trans-[Mo(CO)(NO)(CNtBu)2μ-(η5-C5H3)2(SiMe2)2], cis-[Mo2(CO)3(NO)2(PMe3)μ-(η5-C5H3)2(SiMe2)2] and trans-[Mo(NO)(CNtBu)22μ-(η5-C5H3)2(SiMe2)2]. Available from: http://www.researchgate.net/publication/256790936_Stereoselective_synthesis_and_reactivity_of_cis-_and_trans-_dimolybdenum_nitrosyl_derivatives_with_the_bridging_bis(dimethylsilanediyl)di(5-cyclopentadienyl)_ligand._X-ray_molecular_structures_of_cis-Mo(CO)2(NO)2-(5-C5H3)2(SiMe2)2_trans-Mo(CO)(NO)(CNtBu)2-(5-C5H3)2(SiMe2)2_cis-Mo2(CO)3(NO)2(PMe3)-(5-C5H3)2(SiMe2)2_and_trans-Mo(NO)(CNtBu)22-(5-C5H3)2(SiMe2)2 [accessed Nov 23, 2015].We acknowledge financial support from DGICYT (Project 92-0178-C). R.G-G acknowledges CAM for a fellowship

Reuse of Zeolite By-Products Derived from Petroleum Refining for Sustainable Roads

The reduction in consumption of natural resources (fuel, gas, etc.) and contaminant emissions (CO2, CO, NOx, etc.) during the production of asphalt mixtures has become one of the main challenges in road engineering. Warm mix asphalts (WMAs) have been developed in order to achieve this objective while ensuring the mechanical performance and durability of traditional hot mix asphalts (HMAs). However, these materials are commonly manufactured using additives or products whose production could reduce both their environmental benefits and cost effectiveness. /is paper presents a research study that aims to analyse the reuse of zeolite wastes derived from petroleum refining in the production of warm mix asphalts. For this purpose, two different types of zeolite wastes were analysed as additives for the manufacture of two warm mix asphalts, whose mechanical performance was compared with conventional WMA and hot mix asphalt. /e results indicate that zeolite wastes with a lower particles size presented higher capacity to absorb water, while its dosage at 0.3% allows for producing warm mix asphalts at temperatures around 145°C, with comparable workability and densification to conventional HMA at 165°C without reducing its bearing capacity, fatigue life, and resistance to water action and plastic deformation.“Soluciones de Pavimentación Ecológicamente Sostenibles: Ecoasfaltos” funded by the Ministry of Economy and Knowledge of Andalusia and the Ministry of Economy and Competitiveness of Spain in the framework of CTA (Corporación Tecnológica de Andalucía)

Preprocessing approaches in machine-learning-based groundwater potential mapping: an application to the Koulikoro and Bamako regions, Mali

Groundwater is crucial for domestic supplies in the Sahel, where the strategic importance of aquifers will increase in the coming years due to climate change. Groundwater potential mapping is a valuable tool to underpin water management in the region and, hence, to improve drinking water access. This paper presents a machine learning method to map groundwater potential. This is illustrated through its application in two administrative regions of Mali. A set of explanatory variables for the presence of groundwater is developed first. Scaling methods (standardization, normalization, maximum absolute value and max–min scaling) are used to avoid the pitfalls associated with reclassification. Noisy, collinear and counterproductive variables are identified and excluded from the input dataset. A total of 20 machine learning classifiers are then trained and tested on a large borehole database (n=3345) in order to find meaningful correlations between the presence or absence of groundwater and the explanatory variables. Maximum absolute value and standardization proved the most efficient scaling techniques, while tree-based algorithms (accuracy >0.85) consistently outperformed other classifiers. The borehole flow rate data were then used to calibrate the results beyond standard machine learning metrics, thereby adding robustness to the predictions. The southern part of the study area presents the better groundwater prospect, which is consistent with the geological and climatic setting. Outcomes lead to three major conclusions: (1) picking the best performers out of a large number of machine learning classifiers is recommended as a good methodological practice, (2) standard machine learning metrics should be complemented with additional hydrogeological indicators whenever possible and (3) variable scaling contributes to minimize expert bias

Alkyl and alkylidene imido cyclopentadienyl tungsten complexes

This paper reports the alkylation of the cyclopentadienyl imido tungsten complexes [WCp′(NtBu)Cl3] (Cp′=η5-C5H5, η5-C5Me5) with β-hydrogen containing alkyl groups to render halo alkyl and trialkyl complexes [WCp′(NtBu)Cl3−nRn] (R=Et, n-Pr). Thermal decomposition of the trialkyl compounds gives the alkylidene derivatives [WCp′(NtBu)(CHR)(CH2R)] (R=Me, Et) by α-hydrogen elimination. All of the compounds were characterized by NMR spectroscopy and the molecular structure of [W(η5-C5Me5)(NtBu)Et3] was determined by X-ray diffraction methods.The authors acknowledge DGICYT (project PB97-0677) for financial support

Real Space Renormalization Group Methods and Quantum Groups

We apply real-space RG methods to study two quantum group invariant Hamiltonians, that of the XXZ model and the Ising model in a transverse field defined in an open chain with appropiate boundary terms. The quantum group symmetry is preserved under the RG transformation except for the appearence of a quantum group anomalous term which vanishes in the classical case. We obtain correctly the line of critical XXZ models. In the ITF model the RG-flow coincides with the tensor product decomposition of cyclic irreps. of $SU_q(2)$ with $q^4=1$.Comment: 7 pages, LATEX, no figure

Lithologic Control on the Scaling Properties of the First-Order Streams of Drainage Networks: A Monofractal Analysis

The movement of water through the landscape can be investigated at different scales. This study dealt with the interrelation between bedrock lithology and the geometry of the overlying drainage systems. Parameters of fractal analysis, such as fractal dimension and lacunarity, were used to measure and quantify this relationship. The interrelation between bedrock lithology and the geometry of the drainage systems has been widely studied in the last decades. The quantification of this linkage has not yet been clearly established. Several studies have selected river basins or regularly shaped areas as study units, assuming them to be lithologically homogeneous. This study considered irregular distributions of rock types, establishing areas of the soil map (1:25,000) with the same lithologic information as study units. The tectonic stability and the low climatic variability of the study region allowed effective investigation of the lithologic controls on the drainage networks developed on the plutonic rocks, the metamorphic rocks, and the sedimentary materials existing in the study area. To exclude the effect of multiple in- and outflows in the lithologically homogeneous units, we focused this study on the first-order streams of the drainage networks. The geometry of the hydrologic features was quantified through traditional metrics of fluvial geomorphology and scaling parameters of fractal analysis, such as the fractal dimension, the reference density, and the lacunarity. The results demonstrate the scale invariance of both the drainage networks and the set of first-order streams at the study scale and a relationship between scaling in the lithology and the drainage network