Estudio palinológico del género Rosmarinus L. (Labiatae)

Se ha llevado a cabo un estudio de l as característi cas de l os gra nos de polen del género Rosmarinus L. en microscopía ópt ica y M. E. B. . Estos s e presentan, en cuant o a su forma, como suboblados , e xacol pados , de exina sem itectada y r eticulada . Se han estud i ado 12 poblaciones de las especies R. of fici nalis L., R. eriocalyx Jordan & Four r. y R. t ome ntosus Huber-Morath & Mai re . Este género como l a mayoría de l a fam ilia Labiatae e s estenopal ino , por ello , las difer enci as que se observan , no son l o s uficien teme nte significativas como para consi derarlas como un buen carácter taxonómicoA study has been made of the poll en grai ns of the genus Rosmarinus L. •11ith light microsc.opy and S. E.M. They are with rega r d to thei r fo nn, suboblate , exacolpate, wi t h semitectate and ret i cul a t e exi ne . A t otal of 12 populations of t he speci es R. officinalis L. R. eriocalyx Jordan & Fourr . and R. tomentosus Huber-Mor ath & Maire were stud ied . This genus , l ike most of the family I..abiatae, is s t enopalynous, and consequently the d i fferences observed were not suffi ciently discrete to be cons i derated as a good taxonomic charac ter s

Estudios taxonómicos en el género Salvia L., secciones Salvia y Aethiopis Bentham: palinología

Utilizando microscopía óptica y microscopio electrónico de barrido se han estudiado los caracteres polinices de 31 poblaciones de 6 especies, 8 subespecies y 3 variedades de la Península Ibér ic ~ y Norte de Africa pertenecientes a Salvia L. sect . Salvia y sect. Aethiopis Bentham. Se ha observado que este género , como l a mayoría de la fami l ia Lamiaceae es estenopal ino, no obstante, los caracteres de la exina permiten diferenciar parcialmente ambas seccionesThe pollen characters of 6 species , 8 subspecies and 3 varieties from 31 populat ions belonging to Salvia L. sect. Sal via and sect. Aethiopis Bentharn from t he Iberian Peninsula and N Africa, were examined both wi th light and scanni ng electron micrqscopy . The resul ts show that t he genus, like the most of the family Larniaceae, is stenopalynous . However , sexine characters can be used to dis t inguish each section

Variation in the intensity of selection on codon bias over time causes contrasting patterns of base composition evolution in Drosophila

Four-fold degenerate coding sites form a major component of the genome, and are often used to make inferences about selection and demography, so that understanding their evolution is important. Despite previous efforts, many questions regarding the causes of base composition changes at these sites in Drosophila remain unanswered. To shed further light on this issue, we obtained a new whole-genome polymorphism dataset from D. simulans. We analysed samples from the putatively ancestral range of D. simulans, as well as an existing polymorphism dataset from an African population of D. melanogaster. By using D. yakuba as an outgroup, we found clear evidence for selection on 4-fold sites along both lineages over a substantial period, with the intensity of selection increasing with GC content. Based on an explicit model of base composition evolution, we suggest that the observed AT-biased substitution pattern in both lineages is probably due to an ancestral reduction in selection intensity, and is unlikely to be the result of an increase in mutational bias towards AT alone. By using two polymorphism-based methods for estimating selection coefficients over different timescales, we show that the selection intensity on codon usage has been rather stable in D. simulans in the recent past, but the long-term estimates in D. melanogaster are much higher than the short-term ones, indicating a continuing decline in selection intensity, to such an extent that the short-term estimates suggest that selection is only active in the most GC-rich parts of the genome. Finally, we provide evidence for complex evolutionary patterns in the putatively neutral short introns, which cannot be explained by the standard GC-biased gene conversion model. These results reveal a dynamic picture of base composition evolution

Antiferromagnetism in four dimensions: search for non-triviality

We present antiferromagnetism as a mechanism capable of modifying substantially the phase diagram and the critical behaviour of statistical mechanical models. This is particularly relevant in four dimensions, due to the connection between second order transition points and the continuum limit as a quantum field theory. We study three models with an antiferromagnetic interaction: the Ising and the O(4) Models with a second neighbour negative coupling, and the \RP{2} Model. Different conclusions are obtained depending on the model.Comment: 4 pages LateX. Contribution to Lat9

Parámetros relevantes en el estudio de la no-linealidad de fotodiodos

OPTOEL 2015, Salamanca 13 a 15 de julio de 2015; http://optoel2015.usal.es/El comportamiento lineal en la respuesta de un fotodiodo es una condición fundamental en medidas radiométricas, espectrofotométricas y de radiación pulsada o continua. Por tanto, se requiere que la respuesta eléctrica del fotodiodo sea proporcional al flujo radiante incidente y que se mantenga estable en el tiempo y en un rango de irradiancia. Sin embargo, diversas medidas publicadas evidencian una falta de linealidad dependiente de la estructura interna del fotodiodo, de la potencia y del tamaño del haz incidente. Este trabajo, para caracterizar la no-linealidad en la respuesta de fotodiodos como función de estos mismos factores, adopta el modelo de eficiencia cuántica interna desarrollado por Ferrero et al. en el Instituto de Óptica (CSIC). Además, mediante simulaciones para distintos supuestos, evalúa la influencia de cada parámetro en la no-linealidad de respuesta comparando resultados de las simulaciones con datos experimentales seleccionados en una recopilación bibliográfica.Los autores agradecen al EMRP la subvención del proyecto NEWSTAR. El programa EMRP está financiado conjuntamente por los países de EURAMET participantes y la Unión Europea.Peer Reviewe

The antiferromagnetic phi4 Model, II. The one-loop renormalization

It is shown that the four dimensional antiferromagnetic lattice phi4 model has the usual non-asymptotically free scaling law in the UV regime around the chiral symmetrical critical point. The theory describes a scalar and a pseudoscalar particle. A continuum effective theory is derived for low energies. A possibility of constructing a model with a single chiral boson is mentioned.Comment: To appear in Phys. Rev.

The U(1)-Higgs Model: Critical Behaviour in the Confinig-Higgs region

We study numerically the critical properties of the U(1)-Higgs lattice model, with fixed Higgs modulus, in the region of small gauge coupling where the Higgs and Confining phases merge. We find evidence of a first order transition line that ends in a second order point. By means of a rotation in parameter space we introduce thermodynamic magnitudes and critical exponents in close resemblance with simple models that show analogous critical behaviour. The measured data allow us to fit the critical exponents finding values in agreement with the mean field prediction. The location of the critical point and the slope of the first order line are accurately given.Comment: 21 text pages. 12 postscript figures available on reques

Medida de goniofluorescencia en materiales fotoluminiscentes

1 pág.; 1 fig.; XI Reunión Nacional de Óptica, Salamanca, 1-4 Septiembre de 2015; http://rno11.usal.es/Se ha medido la función de distribución de la luminiscencia bidireccional (BLDF) para seis patrones de fluorescencia bajo diferentes geometrías de observación y detección. Estas medidas se realizaron con el gonioespectrofotómetro GEFE, usando iluminación monocromática y un espectrorradiómetro como detector. Se encontró que, en general, que la forma en que variaba la fluorescencia era la misma para todo patrón y dirección de irradiación: variación simétrica con el ángulo de detección (¿d) respecto a ¿d=0º.Peer Reviewe

Impact of Climate, Agriculture and Vegetation in the Sahel in the recent past : the CAVIARS Projet. [P-3330-53]

The semi-arid regions of the Earth are particularly vulnerable to wind erosion. The Sahelian region experienced contrasted climatic conditions during the last decades, with severe drought in the 70's and 80's and a relative re-greening in the recent years. Over the same period, changes in land use have occurred with an increase of the cultivated surfaces leading to a decrease of fallows and rangelands. As a result, a significant proportion of the land is bare or sparsely vegetated, and thus is not efficiently protected from the erosive action of wind. In this region, wind erosion tends to decrease the productive capacity of the soils whose fertility is already very low. In addition, the impact of wind erosion is expected to increase significantly in the near future (1) in relation with the expected changes in climate (in particular the modifications of precipitation and surface wind) and (2) in response to the increasing land use due to population increase and the related food needs. The aims of the CAVIARS project (Climate, Agriculture and Vegetation: Impacts on Aeolian ERosion in the Sahel) are to develop an integrated modeling tool to describe the evolution of wind erosion in the Sahel in connection with climatic and land use changes, to validate this tool in the current period by making the best possible use of the numerous data sets acquired in recent years over West Africa, and to test its ability to reproduce specific events (such as the drought in the Sahel) of the recent past (about the last 50 years). This project is based on a modeling approach of this recent past (hindcasts) that is justified by the need to ensure the robustness of the simulations with different forcings prior to any simulation of future scenarios. The proposed strategy is (1) to develop or optimize reliable modeling tools for quantifying the various terms (land use, changes in aridity...) responsible for changes in the intensity of wind erosion (2) to synthesize quality checked observations, that can be used as direct or indirect indicators of wind erosion (precipitation time series, changes in vegetation cover, atmospheric dust load,...) (3) to implement a validation strategy based on the quantification of wind erosion both locally, measured on grazed and cultivated plots, and at the regional and continental scales. (Texte intégral