Turing instabilities in a mathematical model for signaling networks

GTPase molecules are important regulators in cells that continuously run through an activation/deactivation and membrane-attachment/membrane-detachment cycle. Activated GTPase is able to localize in parts of the membranes and to induce cell polarity. As feedback loops contribute to the GTPase cycle and as the coupling between membrane-bound and cytoplasmic processes introduces different diffusion coefficients a Turing mechanism is a natural candidate for this symmetry breaking. We formulate a mathematical model that couples a reaction-diffusion system in the inner volume to a reaction-diffusion system on the membrane via a flux condition and an attachment/detachment law at the membrane. We present a reduction to a simpler non-local reaction-diffusion model and perform a stability analysis and numerical simulations for this reduction. Our model in principle does support Turing instabilities but only if the lateral diffusion of inactivated GTPase is much faster than the diffusion of activated GTPase.Comment: 23 pages, 5 figures; The final publication is available at http://www.springerlink.com http://dx.doi.org/10.1007/s00285-011-0495-

Objektivierung der Einstellung der Verstärkungsfunktion von CI - Sprachprozessoren

Der Hörerfolg von Patienten mit Cochlea - Implantaten hängt neben einem guten Implantationsergebnis nicht allein von der korrekten Ermittlung der Schwellen und der C - Werte (MCL - Werte) ab. Auch die Einstellung der Verstärkungskurve kann eine wichtige Rolle spielen. Die Verstärkungskurve sollte an die Wachstumsfunktion der elektrisch evozierten Potenziale des Hörnervs angepasst werden. Gründe hierfür sind die Forderung nach einer möglichst guten Wahrnehmung akustischer Signale zwischen den beiden Grenzwerten Schwelle und C - level sowie eine ungenügende Kenntnis über die dem CI - Träger täglich applizierte Schalldosis (insbesondere von Hintergrundgeräuschen, die ständig präsent sind). Diese Schalldosis kann minimiert werden, wenn die Verstärkungskurve optimal angepasst wird. Bisher war eine kategoriale Lautheitsskalierung das Mittel der Wahl bei der Festlegung der Verstärkungskurve. Deren Ergebnis ist aber sehr stark von der Kooperationsbereitschaft und -fähigkeit der Patienten abhängig und dauert sehr lange. Es wird gezeigt, ob mit Hilfe der NRT - Methode (neural response telemetry) die aufwendige kategoriale Lautheitsskalierung umgangen werden kann

Análise da estrutura e organização esportiva da natação no Estado de São Paulo

Resumo O objetivo deste artigo é analisar a estrutura de organização para o desenvolvimento da natação de alto rendimento no Estado de São Paulo. Para isso foi realizada uma entrevista semiestruturada com 11 técnicos de natação de alto rendimento do Estado de São Paulo, e dois funcionários da Federação Aquática Paulista. Na análise dos dados foi utilizado o método do Discurso do Sujeito Coletivo. Verificou-se que os clubes e as Entidades Municipais de Práticas Desportivas são responsáveis tanto pela formação esportiva, quanto pelo treinamento a longo prazo para a natação de alto rendimento. A administração das ações e políticas esportivas para o desenvolvimento da natação no Estado de São Paulo não acontece de modo centralizado, não segue orientação de entidades nacionais como o COB ou o Ministério do Esporte, ou de alguma entidade de administração da modalidade, como CBDA ou FAP. A elaboração e administração de ações e políticas esportivas para o desenvolvimento da natação de alto rendimento ocorre nos clubes e Entidades Municipais de Práticas Desportivas, de maneira autônoma e individualizada. Deste modo, cada entidade de prática é responsável pela definição de suas diretrizes, aplicação de recursos financeiros, prestação de contas, auditorias e relacionamento com patrocinadores

Uniform exciton fluorescence from individual molecular nanotubes immobilized on solid substrates

Self-assembled quasi one-dimensional nanostructures of π-conjugated molecules may find a use in devices owing to their intriguing optoelectronic properties, which include sharp exciton transitions, strong circular dichroism, high exciton mobilities and photoconductivity. However, many applications require immobilization of these nanostructures on a solid substrate, which is a challenge to achieve without destroying their delicate supramolecular structure. Here, we use a drop-flow technique to immobilize double-walled tubular J-aggregates of amphiphilic cyanine dyes without affecting their morphological or optical properties. High-resolution images of the topography and exciton fluorescence of individual J-aggregates are obtained simultaneously with polarization-resolved near-field scanning optical microscopy. These images show remarkably uniform supramolecular structure, both along individual nanotubes and between nanotubes in an ensemble, demonstrating their potential for light harvesting and energy transport.

Existence of solutions for two types of generalized versions of the Cahn-Hilliard equation

summary:We show existence of solutions to two types of generalized anisotropic Cahn-Hilliard problems: In the first case, we assume the mobility to be dependent on the concentration and its gradient, where the system is supplied with dynamic boundary conditions. In the second case, we deal with classical no-flux boundary conditions where the mobility depends on concentration $u$, gradient of concentration $\nabla u$ and the chemical potential $\Delta u-s'(u)$. The existence is shown using a newly developed generalization of gradient flows by the author and the theory of Young measures