10,771 research outputs found
Efeito de diferentes solventes orgânicos sobre a viabilidade do pólen de jerivá (Syagrus romanzoffiana S. CHAM).
EVINCI. Resumo
An evaluation of the reliability of the pictorial scale of perceived water competence and its relationship with actual water competence
In its recent development, the Pictorial Scale of Perceived Water Competence (PSPWC) showed good face and construct validity. However, additional reliability and validity research is needed, including test-retest reliability and a demonstration of the relationship between PSPWEC test scores and actual water competence. Toward that aim, we administered the PSPWC to 124 children, aged 5–8 years. We repeated this test administration after one week for a subset of 55 children to determine its test-retest reliability, and the remaining 69 children also performed the fully aligned Actual Aquatic Skills Test (AAST) in an indoor swimming pool to provide data for our investigation of the relationship between PSPWC scores and actual water competence. We found good test-retest reliability, both at the global level (ICC = 0.81, n = 55) and at the level of individual skills (Weighted kappa coefficients from 0.58 to 0.90), with no significant differences between these two test scores. We also found a moderate positive relationship between PSPWC and AAST total scores (r = .64, n = 69), with no significant difference between total scores of actual and perceived water competencies. Children overestimated their competence in three specific skills: the back star, swimming on the front, and diving in deep water. While these results underline specific situations in which children’s higher self-perceptions of their water competence are a risk factor for their water safety, these data confirm that the PSPWC is reliable for measuring children’s perceived competencies in aquatic education and drowning prevention, and there is further support for its validity through a moderate correlation with actual water competencies
Electrical activation and electron spin coherence of ultra low dose antimony implants in silicon
We implanted ultra low doses (2x10^11 cm-2) of 121Sb ions into isotopically
enriched 28Si and find high degrees of electrical activation and low levels of
dopant diffusion after rapid thermal annealing. Pulsed Electron Spin Resonance
shows that spin echo decay is sensitive to the dopant depths, and the interface
quality. At 5.2 K, a spin decoherence time, T2, of 0.3 ms is found for profiles
peaking 50 nm below a Si/SiO2 interface, increasing to 0.75 ms when the surface
is passivated with hydrogen. These measurements provide benchmark data for the
development of devices in which quantum information is encoded in donor
electron spins
Detecção de Piper yellow mottle virus em espécimes de Cochonilhas de pimenteira-do-reino por meio de PCR.
A pimenteira-do-reino (Piper nigrum L.) pode ser infectada pelos vírus Cucumber mosaic virus (CMV) e Piper yellow mottle virus (PYMoV) que podem causar grandes perdas na produção. Os sintomas causados por estes vírus são clorose, mosqueado, clareamento de nervuras, deformação foliar, nanismo e redução da produção de frutos. O CMV é transmitido por pulgões enquanto que o PYMoV é transmitido por cochonilhas. Nos plantios de pimenta-do-reino é comum a presença de cochonilhas, e no Brasil já foram relatadas como vetoras do PYMoV as espécies Ferrisia virgata e Planococcus minor. Segundo a literatura na Índia há outras espécies transmissoras. O objetivo deste trabalho foi o de verificar a adequação do teste de PCR para detecção do PYMoV em espécimes de cochonilhas. Foram colocadas vinte cochonilhas F. virgata e vinte P. minor para se alimentar em folhas infectadas pelo PYMoV, destacadas, por um período de 24hs. Dez de cada espécie tiveram seu ácido nucléico extraído separadamente para proceder o teste de PCR com primers específicos para PYMoV. Este trabalho dará subsídios para os estudos da interação cochonilha x PYMoV, além da elaboração de estratégia de inspeção da vetora no campo e mudas de pimenta-do-reino.PIBIC-2011
Chaos and Synchronized Chaos in an Earthquake Model
We show that chaos is present in the symmetric two-block Burridge-Knopoff
model for earthquakes. This is in contrast with previous numerical studies, but
in agreement with experimental results. In this system, we have found a rich
dynamical behavior with an unusual route to chaos. In the three-block system,
we see the appearance of synchronized chaos, showing that this concept can have
potential applications in the field of seismology.Comment: To appear in Physical Review Letters (13 pages, 6 figures
Transmissão de Piper yellow mottle virus por meio de podas em plantas de pimenteira-do-reino.
A pimenteira-do-reino (Piper nigrum L.) pode ser infectada pelo vírus Piper yellow mottle virus (PYMoV) que pode causar grandes perdas na produção. Os sintomas causados por este vírus são clorose, mosqueado, clareamento de nervuras, deformação foliar, nanismo e redução da produção de frutos. O PYMoV é transmitido por cochonilhas, mas é disseminado principalmente por meio de mudas infectadas, geradas por propagação vegetativa (estacas). Estas estacas geralmente são obtidas da própria lavoura do produtor rural por meio de tesoura de poda ou facões. Muitas espécies virais podem ser transmitidas via tratos culturais, como a poda. Entretanto, até o momento não há relato sobre este tipo de transmissão para o PYMoV nesta cultura. Assim, o objetivo deste trabalho foi avaliar a transmissão do PYMoV por meio de podas de plantas infectadas pelo PYMoV. Foi feita a contaminação de tesoura de poda cortando estacas de plantas infectadas pelo PYMoV e em seguida poda de 19 mudas de pimenta-do-reino. Estas foram mantidas por um período de cerca de 3 meses em estufa e em seguida teve o ácido nucléico (DNA e RNA) extraído a partir de folhas novas. Posteriormente, foi realizado o teste de PCR com primers específicos para PYMoV. Das 19 mudas podadas, 15 tiveram resultados positivos para o PYMoV. Este resultado permitirá a elaboração de estratégia de manejo para a cultura.PIBIC-2011
Simulations of a mortality plateau in the sexual Penna model for biological ageing
The Penna model is a strategy to simulate the genetic dynamics of
age-structured populations, in which the individuals genomes are represented by
bit-strings. It provides a simple metaphor for the evolutionary process in
terms of the mutation accumulation theory. In its original version, an
individual dies due to inherited diseases when its current number of
accumulated mutations, n, reaches a threshold value, T. Since the number of
accumulated diseases increases with age, the probability to die is zero for
very young ages (n = T). Here, instead
of using a step function to determine the genetic death age, we test several
other functions that may or may not slightly increase the death probability at
young ages (n < T), but that decreases this probability at old ones. Our
purpose is to study the oldest old effect, that is, a plateau in the mortality
curves at advanced ages. Imposing certain conditions, it has been possible to
obtain a clear plateau using the Penna model. However, a more realistic one
appears when a modified version, that keeps the population size fixed without
fluctuations, is used. We also find a relation between the birth rate, the
age-structure of the population and the death probability.Comment: submitted to Phys. Rev.
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