7,615 research outputs found
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
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
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
Recomendação de boro para o maracujazeiro amarelo em solo de Tabuleiro Costeiro.
Nos estados que mais produzem maracujá no Brasil: Bahia, Sergipe, Espírito Santo e Rio de Janeiro, o maracujazeiro é cultivado em solos de Tabuleiros Costeiros. No Estado da Bahia cultiva- se aproximadamente 45% da produção nacional (322.755 toneladas) em 23.227 hectares, cuja produtividade média é inferior à nacional. Em 6.845 hectares de solos de Tabuleiros Costeiros do Estado da Bahia são produzidos 76.355 toneladas de maracujá, o que representa 24% da produção do Estado e 29% da área cultivada (IBGE, 2009). Os solos de Tabuleiros Costeiros são altamente intemperizados, com baixos teores de matéria orgânica, baixa capacidade de armazenamento de água e altos teores de ferro e alumínio, favorecenda deficiência de boro nas plantas de maracujá (BORGES et al., 2010).bitstream/item/55052/1/ComunicadoTecnico-149.pdfPublicação eletrônica
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