4,168 research outputs found
Diferenciación geográfica de poblaciones españolas silvestres de castaño en caracteres adaptativos (Castanea sativa Miller)
Flushing, spring frost damages and height were recorded in a provenance test including nineteen populations covering most Spanish chestnut distribution and were analysed to study the differentiation among wild populations. There was remarkable differentiation among populations in flushing time and height growth and Qst was higher for flushing and frost damage, and lower for height. The coefficients of quantitative differentiation among populations were similar to the values obtained for other autochthonous species. Spanish chestnut wild populations were classified in three groups: early flushing xeric populations from the Mediterranean, late flushing populations from northern mountains and intermediate flushing populations from Galician coast and Canary Islands. The observation of variability patterns indicated the importance of natural selection and a restricted gene flow as factors shaping the structure of wild populations in Spain. The use of local sources in plantations was recommended.Se analizaron datos de brotación, daños por heladas y crecimiento en altura de un ensayo de procedencias, con 19 poblaciones de gran parte del área de distribución española de Castanea sativa, con la finalidad de estudiar la diferenciación entre poblaciones. Se encontró una diferenciación importante en fechas de brotación y crecimiento. Los coeficientes de diferenciación cuantitativa entre poblaciones fueron similares a los valores obtenidos en otras especies autóctonas. Las poblaciones españolas de castaño silvestre se clasificaron en tres grupos: poblaciones xéricas mediterráneas de brotación temprana, poblaciones de brotación tardía de las montañas del Norte, poblaciones de carácter oceánico de brotación intermedia de la costa gallega e islas Canarias. Las pautas de variación geográfica encontradas indican que la selección natural junto con un flujo genético muy restringido fueron los factores determinantes de la estructura de las poblaciones. Se recomienda el uso de semillas de poblaciones locales en las plantaciones
An Overview of the Rotational Behavior of Metal--Poor Stars
The present paper describes the behavior of the rotational velocity in
metal--poor stars ([Fe/H]<-0.5 dex) in different evolutionary stages, based on
Vsini values from the literature. Our sample is comprised of stars in the field
and some Galactic globular clusters, including stars on the main sequence, the
red giant branch (RGB), and the horizontal branch (HB). The metal--poor stars
are, mainly, slow rotators, and their Vsini distribution along the HR diagram
is quite homogeneous. Nevertheless, a few moderate to high values of Vsini are
found in stars located on the main sequence and on the HB. We show that the
overall distribution of Vsini values is basically independent of metallicity
for the stars in our sample. In particular, the fast-rotating main sequence
stars in our sample present similar rotation rates as their metal-rich
counterparts, suggesting that some of them may actually be fairly young, in
spite of their low metallicity, or else that at least some of them would be
better classified as blue straggler stars. We do not find significant evidence
of evolution in Vsini values as a function of position on the RGB; in
particular, we do not confirm previous suggestions that stars close to the RGB
tip rotate faster than their less evolved counterparts. While the presence of
fast rotators among moderately cool blue HB stars has been suggested to be due
to angular momentum transport from a stellar core that has retained significant
angular momentum during its prior evolution, we find that any such transport
mechanisms must likely operate very fast as the star arrives on the zero-age HB
(ZAHB), since we do not find a link between evolution off the ZAHB and Vsini
values.
We present an extensive tabulation of all quantities discussed in this paper,
including rotation velocities, temperatures, gravitieComment: 22 pages, 10 figure
VINHOS QUE PENSAM - parte I/III GESTÃO DO VIGOR VEGETATIVO DA VINHA A PARTIR DE SENSORES ATIVOS MUTIESPECTRAIS PRÓXIMOS
Costumo dizer que o projeto “Vinhos
que pensam” nasceu de um aperto
de mão entre a equipa de Agricultura
de Precisão da Universidade
de Évora e a Fundação Eugénio de
Almeida, nasceu sem financiamento
próprio mas com uma visão muito
clara de criar valor social na área da
vitivinicultura Alentejana. Passados 6
anos, julgamos que o conhecimento
produzido é relevante para a atividade
e gestão vitivinícola Alentejana,
no entanto, novas perguntas surgem
todos os anos e dessa forma somos
alimentados na motivação de prosseguir
com este projeto, ao qual, outras
entidades e vontades se vão agora
também associando.
A Agrobótica, muito recentemente,
desafiou-nos a apresentar os resultados
mais relevantes do projeto
“Vinhos que pensam” e com o maior
prazer lhe dissemos que sim, no entanto,
colocou-se-nos um problema,
os resultados mais relevantes, muito
dificilmente caberiam num único artigo,
como tal, decidimos dividir tais resultados em três artigos, este primeiro
mais virado para os aspetos da gestão
do vigor da vegetação da vinha; o segundo
mais virado para os sensores
geoelétricos do solo e sua aplicação na gestão e estudo do solo; e por fim,
um terceiro mais virado para aspetos
da nutrição das plantas considerando
a interação solo/planta e a utilização
dos sensores multiespectrais
Vinhos que pensam - parte ii|iii: utilização da condutividade elétrica aparente do solo na instalação e gestão das culturas: exemplificação na vinha
Vinhos que pensam - parte ii|iii: utilização da condutividade elétrica aparente do solo na instalação e gestão das culturas: exemplificação na vinh
Vinhos que pensam - parte i|iii: gestão do vigor vegetativo da vinha a partir de sensores ativos multiespectrais próximos
Vinhos que pensam - parte i|iii: gestão do vigor vegetativo da vinha a partir de sensores ativos multiespectrais próximo
On non-zero space average density perturbation effects in tokamak plasma reflectometer signals
12th International Congress on Plasma Physics, 25-29 October 2004, Nice (France)The effects of the non-zero average density perturbation on phase and amplitude measured by reflectometry are presented. The non-zero average density perturbation on the phase variation can be seen as an index effect as soon as the shape of the density perturbation does not introduce spectral effects. Amplitude modulation in time follows generally the properties of the cut-off layer seen as a mirror but some specific situations produce a time modulation two times higher than the input time variation of the density perturbation as observed in Tore Supra. The introduction of secondary cut-off can exhibit this effect as shown in 2D simulations
Kullback-Leibler and Renormalized Entropy: Applications to EEGs of Epilepsy Patients
Recently, renormalized entropy was proposed as a novel measure of relative
entropy (P. Saparin et al., Chaos, Solitons & Fractals 4, 1907 (1994)) and
applied to several physiological time sequences, including EEGs of patients
with epilepsy. We show here that this measure is just a modified
Kullback-Leibler (K-L) relative entropy, and it gives similar numerical results
to the standard K-L entropy. The latter better distinguishes frequency contents
of e.g. seizure and background EEGs than renormalized entropy. We thus propose
that renormalized entropy might not be as useful as claimed by its proponents.
In passing we also make some critical remarks about the implementation of these
methods.Comment: 15 pages, 4 Postscript figures. Submitted to Phys. Rev. E, 199
Social cognitive predictors of well-being in African college students
Lent and Brown's (2006, 2008) social cognitive model of work well-being was tested in two samples of African college students, one from Angola (N = 241) and one from Mozambique (N = 425). Participants completed domain-specific measures of academic self-efficacy, environmental support, goal progress, and satisfaction, along with measures of global positive affect and life satisfaction. Path analyses indicated that the model fit the data well overall, both in the full sample and in separate sub-samples by country and gender. Contrary to expectations, however, self-efficacy predicted academic satisfaction only indirectly, via goal progress; and goal progress predicted life satisfaction only indirectly, via academic satisfaction. The predictors accounted for substantial portions of the variance in both academic domain satisfaction and life satisfaction. Implications for research and practice involving the social cognitive model are considered.info:eu-repo/semantics/publishedVersio
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