3D Simulations of Surface Harmonic Generation with few-cycle laser pulses

The mechanism of harmonic generation in the interaction of short laser pulses with solid targets holds the promise for the production of intense attosecond pulses. Using the three dimensional code ILLUMINATION we have performed simulations pertaining to an experimentally realizable parameter range by high power laser systems to become available in the near future. The emphasis of the investigation is on the coherent nature of the emission. We studied the influence of the plasma scale length on the harmonic efficiency, angular distribution and the focusability using a post processing scheme in which the far-field of the emission is calculated. It is found that the presence of an extended density profile reduces significantly the transverse coherence length of the emitted XUV light. The different stages of the interaction for two particular cases can be followed with the help of movies.

La evolución de destinos turísticos litorales consolidados. Análisis comparado de Balneario Camnoriú (Brasil) y Benidorm (España)

El objetivo de este trabajo consiste en estudiar la evolución de los destinos turísticos litorales consolidados a partir del análisis comparado entre Balneario Camboriú y Benidorm. Se trata de dos destinos localizados en contextos territoriales y turísticos diferentes, en los que se contrastan de manera empírica los indicadores de evolución de los destinos y se vinculan las dinámicas evolutivas con el modelo territorial-turístico resultante en cada destino. El análisis realizado permite contrastar los postulados de los modelos evolutivos clásicos (Butler, 1980) e incorporar los nuevos planteamientos de la geografía económica evolutiva. La investigación delimita cronológicamente los periodos de desarrollo de ambos destinos para identificar los factores con mayor incidencia en la evolución de los mismos. Una evolución marcada, fundamentalmente, por la ubicación geográfica, la planificación y gestión urbanoturística a diferentes escalas, la dependencia de determinados mercados emisores y la influencia de factores macroeconómicos. Un conjunto de factores interrelacionados que dibujan trayectorias dispares para los destinos analizados.

Ca(2+) signals coordinate zygotic polarization and cell cycle progression in the brown alga Fucus serratus

Zygotes of the fucoid brown algae provide excellent models for addressing fundamental questions about zygotic symmetry breaking. Although the acquisition of polarity is tightly coordinated with the timing and orientation of the first asymmetric division-with zygotes having to pass through a G1/S-phase checkpoint before the polarization axis can be fixed -the mechanisms behind the interdependence of polarization and cell cycle progression remain unclear. In this study, we combine in vivo Ca(2+) imaging, single cell monitoring of S-phase progression and multivariate analysis of high-throughput intracellular Ca(2+) buffer loading to demonstrate that Ca(2+) signals coordinate polarization and cell cycle progression in the Fucus serratus zygote. Consistent with earlier studies on this organism, and in contrast to animal models, we observe no fast Ca(2+) wave following fertilization. Rather, we show distinct slow localized Ca(2+) elevations associated with both fertilization and S-phase progression, and we show that both S-phase and zygotic polarization are dependent on pre-S-phase Ca(2+) increases. Surprisingly, this Ca(2+) requirement cannot be explained by co-dependence on a single G1/ S-phase checkpoint, as S phase and zygotic polarization are differentially sensitive to pre-S-phase Ca(2+) elevations and can be uncoupled. Furthermore, subsequent cell cycle progression through M phase is independent of localized actin polymerization and zygotic polarization. This absence of a morphogenesis checkpoint, together with the observed Ca(2+)dependences of S phase and polarization, show that the regulation of zygotic division in the brown algae differs from that in other eukaryotic model systems, such as yeast and Drosophila.

Cell polarity: Scaffold proteins par excellence

Par proteins are involved in determining cellular asymmetry. Recent studies have identified one of these proteins, Par6, as a key regulator of cell polarity and transformation via its interactions with small GTPases and atypical forms of protein kinase C.