RESUMO
We have performed extensive numerical simulations of the autonomous evolution of memristive neuromorphic networks (CrossNets) with the recurrent InBar topology. The synaptic connections were assumed to have the quasi-Hebbian plasticity that may be naturally implemented using a stochastic multiplication technique. When somatic gain g exceeds its critical value g(t), the trivial fixed point of the system becomes unstable, and it enters a self-excitory transient process that eventually leads to a stable static state with equal magnitudes of all the action potentials x(j) and synaptic weights w(jk). However, even in the static state, the spatial distribution of the action potential signs and their correlation with the distribution of initial values x(j)(0) may be rather complicated because of the activation function's nonlinearity. We have quantified such correlation as a function of g, cell connectivity M, and plasticity rate η, for a random distribution of initial values of x(j) and w(jk), by numerical simulation of network dynamics, using a high-performance graphical processing unit system. Most interestingly, the autocorrelation function of action potentials is a nonmonotonic function of g because of a specific competition between self-excitation of the potentials and self-adaptation of synaptic weights.
RESUMO
Here we report on a novel fluorescent analog of phenytoin as a potential inhibitor of neuropathic pain with potential use as an imaging agent. Compound 2 incorporated a heptyl side chain and dansyl moiety onto the parent compound phenytoin and produced greater displacement of BTX from sodium channels and greater functional blockade with greatly reduced toxicity. Compound 2 reduced mechano-allodynia in a rat model of neuropathic pain and was visualized ex vivo in sensory neuron axons with two-photon microscopy. These results suggest a promising strategy for developing novel sodium channel inhibitors with imaging capabilities.
Assuntos
Fluorescência , Corantes Fluorescentes/farmacologia , Neuralgia/tratamento farmacológico , Fenitoína/farmacologia , Bloqueadores dos Canais de Sódio/farmacologia , Animais , Modelos Animais de Doenças , Desenho de Fármacos , Feminino , Corantes Fluorescentes/síntese química , Corantes Fluorescentes/química , Modelos Moleculares , Estrutura Molecular , Fenitoína/síntese química , Fenitoína/química , Ratos , Ratos Sprague-Dawley , Bloqueadores dos Canais de Sódio/síntese química , Bloqueadores dos Canais de Sódio/química , Relação Estrutura-AtividadeRESUMO
Brain abscess is not a common diagnosis as there are only approximately 2000 cases reported each year in the United States. There are three main routes of access to the brain including contiguous infection from the oropharynx, direct implantation and hematogenously. We present a case of brain abscess in a child who had multiple visits for ear pain to various physicians including pediatricians and to emergency departments. Additionally, the microbiology of brain abscesses is briefly discussed, as is treatment.
RESUMO
We have developed a method for calculation of quantum fluctuation effects, in particular, of the uncertainty zone developing at the potential curvature sign inversion, for a damped harmonic oscillator with arbitrary time dependence of frequency and for arbitrary temperature, within the Caldeira-Leggett model. The method has been applied to the calculation of the gray zone width Delta Ix of Josephson-junction balanced comparators. The calculated temperature dependence of Delta Ix in the range 1.5 to 4.2 K is in virtually perfect agreement with experimental data for Nb-trilayer comparators with critical current densities of 1.0 and 5.5 kA/cm2, without any fitting parameters.