815 research outputs found
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
A new strategy to design SIW-fed arrays
In this work, a new full-wave strategy, with very low
iteration times, is proposed for the optimization and design of
antenna arrays fed by substrate integrated waveguides. The
device is decomposed into fixed and modifiable (to be optimized)
sections, whose generalized scattering matrices are precomputed.
The response of the array is calculated by considering firstly only
the interactions between the fixed sections, which are then
coupled to the modifiable ones in each iteration of an
optimization process. To validate the proposed strategy, a
transversal 16-slot antenna array, placed on the top plate of a
substrate integrated waveguide, has been designed. A speed-up
factor of over 2000 times, compared to general purpose
commercial software, has been obtained in this optimization
process. The final design presents a 1.05 GHz bandwidth under -
10 dB in terms of |S11|, a maximum realized gain of 17.5 dBi at 17
GHz, and a 99.95% maximum efficiency (without dielectric and
conductor losses).
Index Terms—Addition theorems, cylindrical modes, spherical
modes, optimization process, antenna array, substrate integrated
waveguide (SIW)
Model for illuminance produced by LEDs as a function of distance
CIE 2015, Manchester/UK, June 28 - July 4, 2015; http://session2015.cie.co.at/The lighting industry has experienced a revolution with the arrival of novel lighting
technologies in particular Light Emitting Diodes. LEDs have clear advantages in energy
efficiency over conventional lighting technologies, and since 19 % of electricity worldwide is
used for lighting, this can contribute significantly to saving energy problems worldwide and
contributing to Europe¿s 2020 strategy. In order to validate performance claims and stimulate
user confidence, as well as facilitate efficient development of this kind of products, dedicated
metrology is needed. The objective of this work was to study goniometrical aspects of LEDs,
and their dependence with distance to find a model to predict the illuminance at any distance.
A modified inverse-square law model, considering only the offset of the LED virtual source
with respect to their front tip is proposed. The applicability of the method was tested for 18
LED¿s types, with different angular and spectral distributions.This work was accomplished within the EMRP ENG05 Project “Metrology for Solid State Lighting”. The EMRP is jointly funded by the EMRP participating countries within EURAMET and the European Union. The authors are also grateful to Comunidad de Madrid for funding
the project SINFOTON-CM: S2013/MIT-2790Peer Reviewe
The impact on the marine recreational fisheries of longliner operations in the Caribbean
Campos, J.L.; Muñoz-Roure, O
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
Performance Evaluation of Distributed Mobility Management Protocols: Limitations and Solutions for Future Mobile Networks
Mobile Internet data traffic has experienced an exponential growth over the last few years due to the rise of demanding multimedia content and the increasing number of mobile devices. Seamless mobility support at the IP level is envisioned as a key architectural requirement in order to deal with the ever-increasing demand for data and to efficiently utilize a plethora of different wireless access networks. Current efforts from both industry and academia aim to evolve the mobility management protocols towards a more distributed operation to tackle shortcomings of fully centralized approaches. However, distributed solutions face several challenges that can result in lower performance which might affect real-time and multimedia applications. In this paper, we conduct an analytical and simulated evaluation of the main centralized and proposed Distributed Mobility Management (DMM) solutions. Our results show that, in some scenarios, when users move at high speed and/or when the mobile node is running long-lasting applications, the DMM approaches incur high signaling cost and long handover latency.This work was supported by the Government of Extremadura
under Grant no. GR15099 and by the European Regional
Development Fund Programme (2014–2020) and the Regional
Fund, through Computing and Advanced Technologies
Foundation of Extremadura (COMPUTAEX)
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
Adaptation and validation to Portuguese of the Reasons for Higher Education Dropout Scale
Enquadramento: O abandono escolar é um problema com que os sistemas educacionais se debatem, colocando em causa a qualidade da instituição escolar e do próprio sistema de ensino. Objetivos: Adaptar e avaliar as qualidades psicométricas da Escala de Motivos de Intenção de Abandono do Ensino Superior para os estudantes do ensino superior português. Metodologia: Estudo quantitativo, transversal, descritivo e correlacional. Foi aplicado um questionário de caracterização sociodemográfica e a Escala de Motivos de Intenção de Abandono do Ensino Superior a uma amostra de 891
estudantes, maioritariamente feminina (68,2%), com uma idade média de 19,68 anos. Recorreu-se à análise fatorial exploratória e confirmatória. Resultados: A escala composta por 30 itens, organizados em 4 dimensões: Organizacional; Gestão de vida; Profissional e Relacional. Apresenta uma variância explicada de 46,5%, e um alfa de Cronbach de 0,959. Conclusão: Os resultados apoiam a adequação psicométrica da escala para a população portuguesa, indicando que poderá ser utilizada em ensaios futuros neste âmbito e permitir a implementação de medidas que o contrariem.info:eu-repo/semantics/publishedVersio
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