6,195 research outputs found
Neighbour transitivity on codes in Hamming graphs
We consider a \emph{code} to be a subset of the vertex set of a \emph{Hamming
graph}. In this setting a \emph{neighbour} of the code is a vertex which
differs in exactly one entry from some codeword. This paper examines codes with
the property that some group of automorphisms acts transitively on the
\emph{set of neighbours} of the code. We call these codes \emph{neighbour
transitive}. We obtain sufficient conditions for a neighbour transitive group
to fix the code setwise. Moreover, we construct an infinite family of neighbour
transitive codes, with \emph{minimum distance} , where this is not
the case. That is to say, knowledge of even the complete set of code neighbours
does not determine the code
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
Generalising the logistic map through the -product
We investigate a generalisation of the logistic map as (, )
where stands for a generalisation of the ordinary product, known as
-product [Borges, E.P. Physica A {\bf 340}, 95 (2004)]. The usual product,
and consequently the usual logistic map, is recovered in the limit ,
The tent map is also a particular case for . The
generalisation of this (and others) algebraic operator has been widely used
within nonextensive statistical mechanics context (see C. Tsallis, {\em
Introduction to Nonextensive Statistical Mechanics}, Springer, NY, 2009). We
focus the analysis for at the edge of chaos, particularly at the
first critical point , that depends on the value of . Bifurcation
diagrams, sensitivity to initial conditions, fractal dimension and rate of
entropy growth are evaluated at , and connections with
nonextensive statistical mechanics are explored.Comment: 12 pages, 23 figures, Dynamics Days South America. To be published in
Journal of Physics: Conference Series (JPCS - IOP
The Collins-Roscoe mechanism and D-spaces
We prove that if a space X is well ordered , or linearly
semi-stratifiable, or elastic then X is a D-space
Melhoramento genético da videira.
Classificação botânica; citogenética; biologia flora e reprodução; recursos genéticos; melhoramento genético da videira; biotecnologia aplicada ao melhoramento da videira.bitstream/item/17927/1/SDC224.pd
Utilização de porta-enxertos em cultivares de uvas sem sementes no Vale do São Francisco.
O objetivo do presente trabalho foi avaliar a influência de diferentes porta-enxertos sobre a produção e caracterÃsticas do fruto nas cultivares Thompson Seedless, Sugraone, Catalunha, Crimson Seedless, Marroo Seedless e Fantasy Seedless nas condições do Submédio do Vale do São Francisco. Foram realizados três experimentos, sendo um no Campo Experimental de Bebedouro, da Embrapa Semiárido, em Petrolina, PE e os demais em um vinhedo comercial no MunicÃpio de Sento Sé, BA. No experimento 1, foram avaliadas três cultivares copa Thompson Seedless, Catalunha e Sugraone sobre cinco portaenxertos e uma testemunha não enxertada (pé-franco). Os portaenxertos foram Harmony, 420 A, IAC 766, Couderc 1613 e Paulsen 1103. No experimento 2, as cultivares copa foram Crimson Seedless e Marroo Seedless enxertadas sobre os mesmos porta-enxertos. No experimento 3 foram utilizadas as cultivares copa Sugraone, Crimson Seedless e Fantasy Seedless avaliadas sobre os porta-enxertos Paulsen 1103, Harmony, 420 A e SO4. Em todos os experimentos, utilizou se delineamento experimental em blocos com parcelas subdivididas e três repetições, considerando-se como parcela principal as cultivares copa, e como parcelas secundárias, os porta-enxertos. No momento da colheita avaliaram-se as caracterÃsticas relacionadas à produção e qualidade dos frutos: produção; massa média de cachos; massa, comprimento e diâmetro médio de bagas; teor de sólidos solúveis totais (SST) (oBrix); acidez total titulável (ATT) (% ácido tartárico) e relação SST/ATT. O vigor das plantas foi mensurado pela massa da parte aérea determinada após a poda. O efeito dos porta-enxertos variou em função das cultivares copa e das condições ambientais e de manejo especÃficas de cada experimento. De modo geral, as melhores respostas nas cultivares Thompson Seedless e Sugraone foram observadas sobre os porta-enxertos Harmony e Paulsen 1103, enquanto em Marroo Seedless e Crimson Seedless, destacou-se o porta-enxerto IAC 766 para a maioria das caracterÃsticas avaliadas. As cultivares Catalunha e Fantasy Seedless foram menos influenciadas pelos porta-enxertos.bitstream/item/56485/1/BPD90.pd
Mapping dynamical systems onto complex networks
A procedure to characterize chaotic dynamical systems with concepts of
complex networks is pursued, in which a dynamical system is mapped onto a
network. The nodes represent the regions of space visited by the system, while
edges represent the transitions between these regions. Parameters used to
quantify the properties of complex networks, including those related to higher
order neighborhoods, are used in the analysis. The methodology is tested for
the logistic map, focusing the onset of chaos and chaotic regimes. It is found
that the corresponding networks show distinct features, which are associated to
the particular type of dynamics that have generated them.Comment: 13 pages, 8 eps files in 5 figure
- …