New family of potentials with analytical twiston-like solutions

In this letter we present a new approach to find analytical twiston models. The effective two-field model was constructed by a non-trivial combination of two one field systems. In such an approach we successfully build analytical models which are satisfied by a combination of two defect-like solutions, where one is responsible to twist the molecular chain by $180^{\,0}$, while the other implies in a longitudinal movement. Such a longitudinal movement can be fitted to have the size of the distance between adjacent molecular groups. The procedure works nicely and can be used to describe the dynamics of several other molecular chains.Comment: 7 pages, 3 figure

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

Optimized Multimode Interference Fiber Based Refractometer in A Reflective Interrogation Scheme

A fiber based refractometer in a reflective interrogation scheme is investigated and optimized. A thin gold film was deposited on the tip of a coreless fiber section, which is spliced with a single mode fiber. The coreless fiber is a multimode waveguide, and the observed effects are due to multimode interference. To investigate and optimize the structure, the multimode part of the sensor is built with 3 different lengths: 58 mm, 29 mm and 17 mm. We use a broadband light source ranging from 1475 nm to 1650 nm and we test the sensors with liquids of varying refractive indices, from 1.333 to 1.438. Our results show that for a fixed wavelength, the sensor sensitivity is independent of the multimode fiber length, but we observed a sensitivity increase of approximately 0.7 nm/RIU for a one-nanometer increase in wavelength

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

Diffraction and an infrared finite gluon propagator

We discuss some phenomenological applications of an infrared finite gluon propagator characterized by a dynamically generated gluon mass. In particular we compute the effect of the dynamical gluon mass on $pp$ and ${\bar{p}}p$ diffractive scattering. We also show how the data on $\gamma p$ photoproduction and hadronic $\gamma \gamma$ reactions can be derived from the $pp$ and $\bar{p}p$ forward scattering amplitudes by assuming vector meson dominance and the additive quark model.Comment: 4 pages, 7 figures, added references and figures, changed structure. Contribution to Proceedings of XVIIIth Reuniao de Trabalho sobre Interacoes Hadronicas, Sao Paulo, Brazil, 22-24 May, 200

Produção de grãos e aporte de carbono e nitrogênio de feijão-caupi em sistema de corte-e-trituração da vegetação secundária.

O feijão-caupi Vigna unguiculata (L.) Walp é uma das fontes alimentares mais importantes e estratégicas para as regiões tropicais e subtropicais do mundo. O objetivo deste estudo foi avaliar a produtividade e o aporte de carbono e nitrogênio por meio de resíduos do cultivo de feijão-caupi em sistema de corte-e-trituração da vegetação secundária. A produção de grãos e a biomassa da parte aérea do feijão foram avaliadas em 4 parcelas de 2,0 m x 2,0 m em 9 áreas de agricultores. A produtividade média (553,3 kg ha-1) foi menor que a média da região norte (858 kg ha-1). Houve um retorno de 211,7 kg ha-1 de carbono e 6,1 kg ha-1 de nitrogênio para o solo por meio dos resíduos do material vegetativo da parte aérea. Do ponto de vista de produção de grãos de feijão-caupi no sistema de corte-e-trituração no primeiro ano, a produção foi baixa quando comparada com a média da região norte.PIBIC-2011

Complementary action of chemical and electrical synapses to perception

Acknowledgements This study was possible by partial financial support from the following agencies: Fundação Araucária, EPSRC-EP/I032606/1, CNPq No. 441553/2014-1, CAPES No. 17656-12-5 and Science Without Borders Program— Process Nos. 17656125, 99999.010583/2013-00 and 245377/2012-3.Peer reviewedPostprin