Search results for "hill"

Didáctica de las ciencias experimentales y sociales

2005

RESUMEN: Este artículo presenta un estudio sobre la influencia del uso didáctico y científico de las representaciones gráficas cartesianas en la ejecución que hacen los estudiantes de las tareas propias de tres niveles de comprensión gráfica. Los resultados muestran que el uso didáctico instrumental influye negativamente en la ejecución de las tareas de los niveles de comprensión explícita y conceptual de los estudiantes con formación en ciencias y en el nivel de comprensión implícita de los estudiantes sin esta formación. También, muestran que el uso científico experimental influye positivamente en el nivel de comprensión implícita de los estudiantes con formación científica. ABSTARCT: Thi…

Composition and antimicrobial activity of the essential oil of Achillea falcata L. (Asteraceae).

2005

The composition of the essential oil from aerial parts of Achillea falcata L. (Asteraceae) growing wild in Lebanon was analysed by GC and GC–MS; 58 compounds, representing 94.4% of the oil, were identified. Isomers of the cyclobutane ethanol, 1-methyl-2-(1-methylethenyl), grandisol (21.4%) and fragranol (16.8%) were the main components of the oil. Also abundant were artemisia ketone (5.2%), terpinen-4-ol (4.5%) and 1,8-cineole (4.0%). The essential oil shows inhibitory activity mainly against Gram-positive bacteria.

Enseñanza de la astronomía en el Bachillerato

2011

La observación de los astros y la búsqueda de regularidades en los cielos, puede considerarse una de las primeras manifestaciones científicas del ser humano. Desde entonces, astronomía y humanidad han ido de la mano hasta llegar a nuestros tiempos. El estudio de esta evolución compartida ofrece al estudiante una oportunidad de acercarse a la forma de proceder en ciencia. Estudiar las dificultades en la enseñanza aprendizaje de la astronomía en el bachillerato, debe conducir a una mejora en la correcta comprensión de los conceptos astronómicos, básicos y avanzados, por parte de los estudiantes y profesorado. Con este fin hemos comenzado un estudio en el que nos planteamos • ¿Qué dificultades…

Growth and biomass partitioning of Arbutus unedo, Laurus nobilis, Phillyrea angustifolia and Rhamnus alaternus seedlings under water deficit

2013

Water scarcity in the Mediterranean areas is very common and the selection of drought tolerant species is a priority for landscaping purposes in the Mediterranean areas. The objective of this study was to evaluate the effect of water deficit on growth and biomass partitioning of Arbutus unedo, Laurus nobilis, Phillyrea angustifolia and Rhamnus alaternus. Seventy-two seedlings per species were grown in the greenhouse in 4-liter pots and three water regimes were imposed starting on 6 April and until 9 June, 2010. One-third of the plants was well irrigated to maintain soil water content in the 25-35% range (CTR); a second group of plants was deficit-irrigated to maintain soil water content in …

Overland flow generation on hillslopes of complex topography: analytical Solutions

2007

The analytical solution of the overland flow equations developed by Agnese et al. (2001; Hydrological Processes15: 3225–3238) for rectangular straight hillslopes was extended to convergent and divergent surfaces and to concave and convex profiles. Towards this aim, the conical convergent and divergent surfaces are approximated by a trapezoidal shape, and the overland flow is assumed to be always one-dimensional. A simple ‘shape factor’ accounting for both planform geometry and profile shape was introduced: for each planform geometry, a brachistochrone profile was obtained by minimizing a functional containing a slope function of the profile. Minima shape factors are associated with brachist…

Antike. Romantik. Rousseau. Interferenz in der Parkanlage Achilleion auf Korfu und in der privaten Lyrik der österreichischen Kaiserin Elisabeth

2015

Polystyrene-supported proline as recyclable catalyst in the Baylis–Hillman reaction of arylaldehydes and methyl or ethyl vinyl ketone

2008

Abstract Polystyrene-supported proline has been used as co-organocatalyst (10 mol%) with imidazole (10 mol%) in the Baylis–Hillman reaction between methyl or ethyl vinyl ketone and arylaldehydes. Recycling studies showed that the proline resin can be used up to five cycles with high isolated yields. This study represents the first example of supported proline as heterogeneous catalyst in the above reaction and broaden the scope of this catalytic material.

First Evidence of Proline Acting as a Bifunctional Catalyst in the Baylis–Hillman Reaction Between Alkyl Vinyl Ketones and Aryl Aldehydes

2008

Proline in the presence of sodium hydrogen carbonate has been found to be an effective catalyst for the Baylis–Hillman reaction between methyl or ethyl vinyl ketone and aryl aldehydes. Screening of several amine catalysts showed that an ionizable carboxylic function directly linked to the secondary amine catalyst plays an important role in the synthesis of the desired product in good yield. The data obtained has allowed us to suggest, for the first time, that proline, sarcosine, pipecolinic acid and homoproline may act as bifunctional catalysts via a bicyclic enaminolactone species as intermediate. Quantum-mechanical calculations (PM3/COSMO and ab initio 3-21G/COSMO) support this mechanism …

Supramolecular isomerism in spin crossover networks with aurophilic interactions

2004

Assembly of FeII, 3-cyanopyridine and [Au(CN)2]– affords, in one-pot reaction, three coordination polymers that represent a genuine example of supramolecular isomerism with strong influence in the spin crossover regime of the FeII ions. Real Cabezos, Jose Antonio, Jose.A.Real@uv.es

ChemInform Abstract: First Evidence of Proline Acting as a Bifunctional Catalyst in the Baylis-Hillman Reaction Between Alkyl Vinyl Ketones and Aryl …

2008

Proline in the presence of sodium hydrogen carbonate has been found to be an effective catalyst for the Baylis–Hillman reaction between methyl or ethyl vinyl ketone and aryl aldehydes. Screening of several amine catalysts showed that an ionizable carboxylic function directly linked to the secondary amine catalyst plays an important role in the synthesis of the desired product in good yield. The data obtained has allowed us to suggest, for the first time, that proline, sarcosine, pipecolinic acid and homoproline may act as bifunctional catalysts via a bicyclic enaminolactone species as intermediate. Quantum-mechanical calculations (PM3/COSMO and ab initio 3-21G/COSMO) support this mechanism …