Self-Organized Criticality, Plasticity and Sensorimotor Coupling. Explorations with a Neurorobotic Model in a Behavioural Preference Task

During the last two decades, analysis of 1/f noise in cognitive science has led to a considerable progress in the way we understand the organization of our mental life. However, there is still a lack of specific models providing explanations of how 1/f noise is generated in coupled brain-body-environment systems, since existing models and experiments typically target either externally observable behaviour or isolated neuronal systems but do not address the interplay between neuronal mechanisms and sensorimotor dynamics. We present a conceptual model of a minimal neurorobotic agent solving a behavioural task that makes it possible to relate mechanistic (neurodynamic) and behavioural levels of description. The model consists of a simulated robot controlled by a network of Kuramoto oscillators with homeostatic plasticity and the ability to develop behavioural preferences mediated by sensorimotor patterns. With only three oscillators, this simple model displays self-organized criticality in the form of robust 1/f noise and a wide multifractal spectrum. We show that the emergence of self-organized criticality and 1/f noise in our model is the result of three simultaneous conditions: a) non-linear interaction dynamics capable of generating stable collective patterns, b) internal plastic mechanisms modulating the sensorimotor flows, and c) strong sensorimotor coupling with the environment that induces transient metastable neurodynamic regimes. We carry out a number of experiments to show that both synaptic plasticity and strong sensorimotor coupling play a necessary role, as constituents of self-organized criticality, in the generation of 1/f noise. The experiments also shown to be useful to test the robustness of 1/f scaling comparing the results of different techniques. We finally discuss the role of conceptual models as mediators between nomothetic and mechanistic models and how they can inform future experimental research where self-organized critically includes sensorimotor coupling among the essential interaction-dominant process giving rise to 1/f noise.

Ionic Liquids and Cellulose: Dissolution, Chemical Modification and Preparation of New Cellulosic Materials

Due to its abundance and a wide range of beneficial physical and chemical properties, cellulose has become very popular in order to produce materials for various applications. This review summarizes the recent advances in the development of new cellulose materials and technologies using ionic liquids. Dissolution of cellulose in ionic liquids has been used to develop new processing technologies, cellulose functionalization methods and new cellulose materials including blends, composites, fibers and ion gels.

Incidences de la modification de la circulation des eaux sur l'hydrochimie et le degré de contamination bacterienne d'un estuaire eutrophe tropical

In order to control the proliferation of floating aquatic vegetation in Côte d'Ivoire, a coastal inlet, allowing a direct communication between the Comoe river and the ocean, was created in September 1987. The impact of this operation on the hydrochemistry (salinity, nutrients, algal biomass) and the bacterial contamination level was studied in the area close to the Vridi canal.

Nano-modification inside transparent materials by femtosecond laser single beam

Periodic nanostructures along the polarization direction of light are observed inside silica glasses and tellurium dioxide single crystal after irradiation by a focused single femtosecond laser beam. Backscattering electron images of the irradiated spot inside silica glass reveal a periodic structure of stripe-like regions of similar to 20 nm width with a low oxygen concentration. In the case of the tellurium dioxide single crystal, secondary electron images within the focal spot show the formation of a periodic structure of voids with 30 nm width. Oxygen defects in a silica glass and voids in a tellurium dioxide single crystal are aligned perpendicular to the laser polarization direction. These are the smallest nanostructures below the diffraction limit of light, which are formed inside transparent materials. The phenomenon is interpreted in terms of interference between the incident light field and the electric field of electron plasma wave generated in the bulk of material.

Professores especiais para alunos especiais: uma experiência de grupo operativo na capacitação de professores

O objetivo desta pesquisa foi estudar a contribuição que a interação vivenciada em grupos operativos pode oferecer ao desenvolvimento da capacidade de aprendizagem no amplo processo de capacitação docente, numa perspectiva psicopedagógica. Buscou-se perceber como a técnica dos grupos operativos contribuiria para a modificação da pratica pedagógica desenvolvida por professores de aceleração de aprendizagem no sentido de otimizar os resultados do trabalho por eles desenvolvidos junto aos alunos dessas classes.Foram acompanhados, em dinâmica de grupo operativo, vinte docentes de classes de aceleração incluídos em um projeto de capacitação para professores desenvolvido em Mangaratiba, RJ. A tarefa explicita nesse grupo foi a elaboração de temas sobre a aprendizagem dos alunos e dos professores, considerando a auto-estima acadêmica de ambos.A base teórica adotada foi a Epistemologia Convergente, na qual Jorge Visca propõe um modelo específico de intervenção psicopedagógica. Neste modelo, a perspectiva relacional está fundada nas contribuições da psicologia social, conforme é compreendida por Pichon-Riviére. Aí, a técnica dos grupos operativos é utilizada para favorecer o desenvolvimento relacional do grupo participante, otimizando suas possibilidades de aprender. Realizou-se então, uma intervenção psicopedagógica para a capacitação de docentes de classe de aceleração de aprendizagem e um dos instrumentos dessa intervenção foi a vivencia em grupo operativo. A pesquisa acompanhou o desenvolvimento desse grupo observando e interagindo para que se produzissem os movimentos que contribuíram para mobilizar a resignificação do modelo de aprendizagem dos seus membros.Essa resignificação possibilitou ao professor considerar a capacidade para aprender em grupo fator de grande importância na tarefa docente, aspecto considerado original na capacitação realizada. Os resultados qualitativos observados tornaram-se explícitos ao longo da vivencia grupal na significativa mudança da relação do grupo com a produção de conhecimento e da auto-estima profissional dos participantes. A pesquisa concluiu que os processos de capacitação docente devem continuar buscando alternativas mais coerentes com os aspectos que se deseja formar nos professores e apresenta os grupos operativos como estratégia psicopedagógica de excelentes possibilidades na capacitação dos mesmos.Enfatiza ainda, a possibilidade de reconstrução do sentido e pratica da cidadania na dinâmica desses grupos já que neles, os sujeitos encontram oportunidades de redefinição dos papeis que desempenham, pelo exercício da flexibilização dos mesmos. Confirma a certeza de que o professor que poderá ensinar a construir conhecimento deverá, ele mesmo, ter construído o seu como a condição para que possa ajudar o aluno a superar as inúmeras dificuldades inerentes à aprendizagem presentes nas estruturas sociais, nos sistemas escolares e em sua própria historia pessoal. É nessa superação que alunos e professores já marcados pelas vivências de fracasso escolar poderão retomar no grupo social a construção de sua condição cidadã, justificando o empenho realizado pela educação escolar.

Modification of the biological intercept model to account for ontogenetic effects in laboratory-reared delta smelt (Hypomesus transpacificus)*

We investigated age, growth, and ontogenetic effects on the proportionality of otolith size to fish size in laboratory-reared delta smelt (Hypomesus transpacificus) from the San Francisco Bay estuary. Delta smelt larvae were reared from hatching in laboratory mesocosms for 100 days. Otolith increments from known-age fish were enumerated to validate that growth increments were deposited daily and to validate the age of fish at first ring formation. Delta smelt were found to lay down daily ring increments; however, the first increment did not form until six days after hatching. The relationship between otolith size and fish size was not biased by age or growth-rate effects but did exhibit an interruption in linear growth owing to an ontogenetic shift at the postflexon stage. To back-calculate the size-at-age of individual fish, we modified the biological intercept (BI) model to account for ontogenetic changes in the otolith-size−fish-size relationship and compared the results to the time-varying growth model, as well as the modified Fry model. We found the modified BI model estimated more accurately the size-at-age from hatching to 100 days after hatching. Before back-calculating size-at-age with existing models, we recommend a critical evaluation of the effects that age, growth, and ontogeny can have on the otolith-size−fish-size relations

Food conversion efficiency and the von Bertalanffy growth function 1: a modification of Pauly's model

A simple modification of Pauly's model for relating food conversion efficiency (K sub(1)) and body weight is proposed. The key parameter is an index to how efficiently food can be absorbed; the other parameter is related to the surface-limiting growth, an important component of von Bertalanff's and Pauly's theories of fish growth.

The Fish Funnel: A Trawl Modification to Reduce Fish Escapement

In the Gulf of Mexico there is a need to assess the potential of underutilized fish resource stocks before a commercial fishery develops. Standard sampling trawls used in the Gulf are ineffective for sampling the resource, so larger, high opening, bottom trawls have been introduced. The larger trawls are more effective, but most of the faster swimming fish species are able to escape these nets, especially during haul back. To reduce fish escapement, webbing panels, attached inside the trawls ahead of the cod ends, were tested. Initial tests were conducted with two single panel designs--a fish flap and a "floppa." Neither design reduced fish escapement. The floppa distorted the trawl webbing and actually increased fish escapement. A multi-panel conical funnel design (the fish funnel) was tested and found to increase fish retention by trapping the fish after they passed through it. When used in combination with a technique known as pulsing the trawl, the fish funnel substantially increased trawl catch rates with no indication of fish escapement.