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} $\delta=4$, 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 qq-product

We investigate a generalisation of the logistic map as $x_{n+1}=1-ax_{n}\otimes_{q_{map}} x_{n}$ ($-1 \le x_{n} \le 1$, $0<a\le2$) where $\otimes_q$ stands for a generalisation of the ordinary product, known as $q$-product [Borges, E.P. Physica A {\bf 340}, 95 (2004)]. The usual product, and consequently the usual logistic map, is recovered in the limit $q\to 1$, The tent map is also a particular case for $q_{map}\to\infty$. 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 $q_{map}>1$ at the edge of chaos, particularly at the first critical point $a_c$, that depends on the value of $q_{map}$. Bifurcation diagrams, sensitivity to initial conditions, fractal dimension and rate of entropy growth are evaluated at $a_c(q_{map})$, 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 $(\alpha A)$, 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 características 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 Município 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 características 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 específicas 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 características 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