Field sources in a Lorentz symmetry breaking scenario with a single background vector

This paper is devoted to investigating the interactions between stationary sources of the electromagnetic field, in a model which exhibits explicit Lorentz-symmetry breaking due to the presence of a single background vector. We focus on physical phenomena that emerge from this kind of breaking and which have no counterpart in Maxwell Electrodynamics

Alterations in brain connectivity due to plasticity and synaptic delay

Brain plasticity refers to brain's ability to change neuronal connections, as a result of environmental stimuli, new experiences, or damage. In this work, we study the effects of the synaptic delay on both the coupling strengths and synchronisation in a neuronal network with synaptic plasticity. We build a network of Hodgkin-Huxley neurons, where the plasticity is given by the Hebbian rules. We verify that without time delay the excitatory synapses became stronger from the high frequency to low frequency neurons and the inhibitory synapses increases in the opposite way, when the delay is increased the network presents a non-trivial topology. Regarding the synchronisation, only for small values of the synaptic delay this phenomenon is observed

Sobre la identidad y el estatus de Desmanthus (Leguminosae, clado Mimosoideae) en Macaronesia

In this paper, the identity and degree of naturalization of Desmanthus (Leguminosae, Mimosoid clade) in the Canary Islands (Gran Canaria, Fuerteventura) and Cape Verde (Santo Antão, São Vicente) are critically re-assessed. The study of morphological features of the plant material sampled allowed to conclude that all specimens must be assigned to D. pernambucanus, instead of D. virgatus as previously thought. Previous records for D. virgatus from Macaronesia still require confirmation but are probably all erroneous. D. pernambucanus is well-established and the number of populations is increasing in the studied area. The species can be classified as an environmental weed or even as a transformer species in natural habitats, often barrancos. The results also show that the distinction between D. pernambucanus and D. virgatus is not always clear-cut and that for an accurate identification the study of living material usually is required.En este artículo se reevalúa la identidad y grado de naturalización del género Desmanthus (Leguminosae, clado Mimosoideae) en diversas áreas de las Islas Canarias (Gran Canaria, Fuerteventura) y de Cabo Verde (Santo Antão, São Vicente). El estudio de los caracteres morfológicos del material vegetal permitió concluir que todos los especímenes deben ser asignados a D. pernambucanus, en lugar de a D. virgatus, como se pensaba hasta ahora. Los registros previos de D. virgatus para Macaronesia requieren confirmación, pero posiblemente sean todos erróneos. Desmanthus pernambucanus está bien establecido en la zona estudiada y el número de poblaciones se está incrementando. La especie puede ser clasificada como “mala hierba alóctona” o, incluso, como una especie transformadora en hábitats naturales, especialmente en barrancos. Los resultados también muestran que no siempre está clara la distinción entre D. pernambucanus y D. virgatus y que, generalmente, el estudio de material vivo es necesario para una identificación precisa

Queima das folhas de bananeiras no Nordeste do Brasil

A banqnicultura e uma das principais exploracao agricolas do Nordeste e, entre as fruteiras, assume importancia fundamental por seu valor economico e social, mulhorando a dieta alimentar das populacoes mais carentes e contribuindo para fixar o pequeno proprietario na zona rural. A regiao Nordeste produz cerca de 2,1 milhoes de toneladas de banana/ano, representando 42% da producao brasileira (CUNHA, 1984). A introducao da bananicultura em regiao de baixa precipitacao pulviometrica, feita normalmente com o uso da irrigacao, tem grande potencial de crescimento, nao so por ser uma das prantas de maior consumo na regiao como tambem pela extencao de areas disponiveis ao plantio. A sua exploracao, no entanto, e limitada, principalmente por problemas de salinizacao do solo, onde assume maior relevancia de fitotoxider por sodio. Este elemento, mesmo em niveis nao prejudicais a maioria das plantas cultivadas, causa serios problemas na bananeira, que lhe e extremamante sensivel (IRFA, 1982).bitstream/item/81298/1/queima-das-folhas-Ana-Lucia-Borges-Documentos-35-1991.pd

Fertirrigação em fruteiras tropicais.

Aspectos básicos da fertirrigação; Fertilizantes para fertirrigação; Equipamentos de injeção de fertilizantes; Manejo da fertirrigação; Cálculo e preparo da solução de fertilizantes; Requerimentos de nutrientes para fertirrigação.bitstream/item/138313/1/Fertirrigacao-2009.pdf2. ed. rev. ampl

Treatment of bimodality in proficiency test of pH in bioethanol matrix

The pH value in bioethanol is a quality control parameter related to its acidity and to the corrosiveness of vehicle engines when it is used as fuel. In order to verify the comparability and reliability of the measurement of pH in bioethanol matrix among some experienced chemical laboratories, reference material (RM) of bioethanol developed by Inmetro - the Brazilian National Metrology Institute - was used in a proficiency testing (PT) scheme. There was a difference of more than one unit in the value of the pH measured due to the type of internal filling electrolytic solutions (potassium chloride, KCl or lithium chloride, LiCl) from the commercial pH combination electrodes used by the participant laboratories. Therefore, bimodal distribution has occurred from the data of this PT scheme. This work aims to present the possibilities that a PT scheme provider can use to overcome the bimodality problem. Data from the PT of pH in bioethanol were treated by two different statistical approaches: kernel density model and the mixture of distributions. Application of these statistical treatments improved the initial diagnoses of PT provider, by solving bimodality problem and contributing for a better performance evaluation in measuring pH of bioethanol.Comment: 20 pages, 6 figures, Accepted for publication in Accreditation and Quality Assurance (ACQUAL

Probing the ejecta of evolved massive stars in transition: A VLT/SINFONI K-band survey

Massive evolved stars in transition phases, such as Luminous Blue Variables (LBVs), B[e] Supergiants (B[e]SGs), and Yellow Hypergiants (YHGs), are not well understood, and yet crucial steps in determining accurate stellar and galactic evolution models. The circumstellar environments of these stars reveal their mass-loss history, identifying clues to both their individual evolutionary status and the connection between objects of different phases. Here we present a survey of 25 such evolved massive stars (16 B[e]SGs, 6 LBVs, 2 YHGs, and 1 Peculiar Oe star), observed in the K-band with the Spectrograph for INtegral Field Observation in the Near-Infrared (SINFONI; R = 4500) on the ESO VLT UT4 8 m telescope. The sample can be split into two categories based on spectral morphology: one group includes all of the B[e]SGs, the Peculiar Oe star, and two of the LBVs, while the other includes the YHGs and the rest of the LBVs. The difference in LBV spectral appearance is due to some objects being in a quiescent phase and some objects being in an active or outburst phase. CO emission features are found in 13 of our targets, with first time detections for MWC 137, LHA 120-S 35, and LHA 115-S 65. From model fits to the CO band heads, the emitting regions appear to be detached from the stellar surface. Each star with ^12CO features also shows ^13CO emission, signaling an evolved nature. Based on the level of ^13C enrichment, we conclude that many of the B[e]SGs are likely in a pre-Red Supergiant phase of their evolution. There appears to be a lower luminosity limit of log L/L_solar = 5.0 below which CO is not detected. The lack of CO features in several high luminosity B[e]SGs and variability in others suggests that they may in fact be LBV candidates, strengthening the connection between these two very similar transition phases.Comment: 20 pages, 13 figures, 7 tables. Accepted for publication in A&