121 research outputs found

    Fermi resonance in Ne, Ar and Kr-matrix infrared spectra of 5-bromouracil

    No full text
    Low-temperature matrix isolation Fourier-transform infrared spectroscopy and quantum-chemical calcula-tions with DFT/B3LYP and MP2 methods were used for investigation of isolated 5-bromouracil (BrU) mole-cules. Only one tautomeric form of BrU was dominated in the low-temperature Ne, Ar, and Kr matrices. It was revealed that population of minor hydroxy-tautomers did not exceed 0.2%. Appearance of additional absorption bands in the region of stretching vibrations CO (about 1710 cm⁻¹) as well as of deformation ones (1297, 1093, 901 cm⁻¹) was explained by Fermi resonance. In Ne matrices the peak intensities of absorption bands assigned to the out-of-plane vibrations of the ring and exocyclic atoms were decreased sharply. For the first time, least square method with the using of polynomial was proposed for the corrective scaling of calculated frequencies of vibrations. It is shown that the correction of calculated frequencies with the polynomial of degree two permits to decrease the root-mean-square discrepancy between the calculated and experimental ones to 4–5 cm⁻¹ in the re-gion of 1500–500 cm⁻¹. The same polynomial may be applied for the correction of spectra of molecules with a similar structure

    Stability of Negative Image Equilibria in Spike-Timing Dependent Plasticity

    Full text link
    We investigate the stability of negative image equilibria in mean synaptic weight dynamics governed by spike-timing dependent plasticity (STDP). The neural architecture of the model is based on the electrosensory lateral line lobe (ELL) of mormyrid electric fish, which forms a negative image of the reafferent signal from the fish's own electric discharge to optimize detection of external electric fields. We derive a necessary and sufficient condition for stability, for arbitrary postsynaptic potential functions and arbitrary learning rules. We then apply the general result to several examples of biological interest.Comment: 13 pages, revtex4; uses packages: graphicx, subfigure; 9 figures, 16 subfigure

    Linear stability analysis of retrieval state in associative memory neural networks of spiking neurons

    Full text link
    We study associative memory neural networks of the Hodgkin-Huxley type of spiking neurons in which multiple periodic spatio-temporal patterns of spike timing are memorized as limit-cycle-type attractors. In encoding the spatio-temporal patterns, we assume the spike-timing-dependent synaptic plasticity with the asymmetric time window. Analysis for periodic solution of retrieval state reveals that if the area of the negative part of the time window is equivalent to the positive part, then crosstalk among encoded patterns vanishes. Phase transition due to the loss of the stability of periodic solution is observed when we assume fast alpha-function for direct interaction among neurons. In order to evaluate the critical point of this phase transition, we employ Floquet theory in which the stability problem of the infinite number of spiking neurons interacting with alpha-function is reduced into the eigenvalue problem with the finite size of matrix. Numerical integration of the single-body dynamics yields the explicit value of the matrix, which enables us to determine the critical point of the phase transition with a high degree of precision.Comment: Accepted for publication in Phys. Rev.

    One health, une seule santé

    Get PDF
    One Health, « Une seule santé », est une stratégie mondiale visant à développer les collaborations interdisciplinaires pour la santé humaine, animale et environnementale. Elle promeut une approche intégrée, systémique et unifiée de la santé aux échelles locale, nationale et mondiale, afin de mieux affronter les maladies émergentes à risque pandémique, mais aussi s'adapter aux impacts environnementaux présents et futurs. Bien que ce mouvement s’étende, la littérature en français reste rare. Traduit de l’anglais, coordonné par d’éminents épidémiologistes et s'appuyant sur un large panel d' approches scientifiques rarement réunies autour de la santé, cet ouvrage retrace les origines du concept et présente un contenu pratique sur les outils méthodologiques, la collecte de données, les techniques de surveillance et les plans d’étude. Il combine recherche et pratique en un seul volume et constitue un ouvrage de référence unique pour la santé mondiale

    Genetic heterogeneity of day blindness in Alaskan Malamutes

    No full text
    Day blindness is a progressive and specific degeneration of cone photoreceptors in the retina of young dogs. This disorder has been associated with a breed-specific non-synonymous substitution in exon 6 of the cyclic nucleotide gated channel beta 3 (CNGB3) gene in German Shorthaired Pointer dogs and a genomic deletion removing the entire gene in Alaskan Malamute dogs from the USA. To further investigate this disorder, we characterized CNGB3 in a three-generation pedigree of Alaskan Malamute dogs from Australia segregating for day blindness. Fifteen of the dogs showed clinical signs of day blindness. Four of these were definitively diagnosed by standardized electroretinography. Polymerase chain reaction amplification of exon 6 of CNGB3 was attempted, and as expected, amplification was successful in the 18 unaffected or carrier dogs. However, a non-mutated exon 6 was also amplified and sequenced in six of the 15 affected dogs. On sequencing each exon and exon/intron boundary in two such affected individuals and two unaffected individuals, three exonic substitutions and 12 intronic changes were noted. These sequence variations in affected individuals were also present in one or both unaffected dogs and so appear to have no obvious effect on the protein's function. Hence, day blindness shows genetic heterogeneity within the Alaskan Malamute population of Australia, a result that is somewhat unexpected given the relatively small effective population size of this breed
    corecore