357 resultados para Cacho


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[95] hojas : ilustraciones.

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18 hojas : ilustraciones, fotografías a color, mapas.

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Studies on the flora and fauna of the Canary Islands show that this Archipelago is one of the planet’s diversity hot spots. However, an analysis of the differences in the phytogeographic characteristics of each of the islands that make up this Archipelago is lacking. This article focuses on the phytogeographic characterization of the island of Gran Canaria. This island exhibits geological and climatic characteristics resulting in a rich vascular flora, including endemic species and genera that are significantly different from the other islands of the Archipelago. These differences are verified through statistical analysis of the existing similarity between the floras of the members of the Canary Islands. This study also analyses the subdivision of Gran Canaria Island, indicating that there are three well-differentiated areas on the island itself. Finally, this study argues that these areas, themselves, should be considered biogeographic sectors.

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Las siguientes páginas versan sobre el pensamiento político de José Ortega y Gasset, mostrando –entre otras cosas– su evolución desde lo que sería el neokantismo de mocedad de Ortega hasta su madurez. Para cumplir con nuestro objetivo se ha recurrido a los escritos de Ortega, así como a autores especializados en su pensamiento. La historia del pensamiento político contemporáneo tiene una deuda contraída con Ortega que desde sus primeros escritos manifestó un claro interés por la política concebida ésta como pedagogía social y cuyo fin debía ser, en primer lugar, solventar los problemas de la vida pública nacional. El pensamiento político de Ortega se define asimismo por la defensa de los valores liberales (liberalismo) compatibles con los principios socialistas (socialismo), que en una primera época de juventud idealista neokantiana adquieren un significado eminentemente cultural aunque también moral, que no se perderá completamente en su madurez o época de plenitud vital, aunque bien es verdad que aquellos dos conceptos (liberalismo y socialismo), así como también su idea de democracia, irán respondiendo a la evolución de su pensamiento.

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Laser induced acoustic desorption (LIAD) has been used for the first time to study the parent ion production and fragmentation mechanisms of a biological molecule in an intense femtosecond (fs) laser field. The photoacoustic shock wave generated in the analyte substrate (thin Ta foil) has been simulated using the hydrodynamic HYADES code, and the full LIAD process has been experimentally characterised as a function of the desorption UV-laser pulse parameters. Observed neutral plumes of densities > 10(9) cm(-3) which are free from solvent or matrix contamination demonstrate the suitability and potential of the source for studying ultrafast dynamics in the gas phase using fs laser pulses. Results obtained with phenylalanine show that through manipulation of fundamental femtosecond laser parameters (such as pulse length, intensity and wavelength), energy deposition within the molecule can be controlled to allow enhancement of parent ion production or generation of characteristic fragmentation patterns. In particular by reducing the pulse length to a timescale equivalent to the fastest vibrational periods in the molecule, we demonstrate how fragmentation of the molecule can be minimised whilst maintaining a high ionisation efficiency.

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High power femtosecond laser pulses have unique properties that could lead to their application as ionization or activation sources in mass spectrometry. By concentrating many photons into pulse lengths approaching the timescales associated with atomic motion, very strong electric field strengths are generated, which can efficiently ionize and fragment molecules without the need for resonant absorption. However, the complex interaction between these pulses and biomolecular species is not well understood. To address this issue, we have studied the interaction of intense, femtosecond pulses with a number of amino acids and small peptides. Unlike previous studies, we have used neutral forms of these molecular targets, which allowed us to investigate dissociation of radical cations without the spectra being complicated by the action of mobile protons. We found fragmentation was dominated by fast, radical-initiated dissociation close to the charge site generated by the initial ionization or from subsequent ultrafast migration of this charge. Fragments with lower yields, which are useful for structural determinations, were also observed and attributed to radical migration caused by hydrogen atom transfer within the molecule.

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Se examina la posibilidad de que la versión castellana del Palmerín de Inglaterra sea la anterior a la edición portuguesa. Se proporciona una serie de datos que pueden corroborar esta afirmación.

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Seleccionado en la convocatoria: Ayudas a proyectos de innovación e investigación educativa en el campo de la educación permanente, Gobierno de Aragón 2008-09

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Seleccionado en la convocatoria: Ayudas a la innovación e investigación educativa en centros docentes de niveles no universitarios, Gobierno de Aragón 2009-10