RESUMO
We question the global universe isotropy by probing the alignment of local structures in the cosmic microwave background (CMB) radiation. The original method proposed relies on a steerable wavelet decomposition of the CMB signal on the sphere. The analysis of the first-year Wilkinson Microwave Anisotropy Probe data identifies a mean preferred plane with a normal direction close to the CMB dipole axis, and a mean preferred direction in this plane, very close to the ecliptic poles axis. Previous statistical anisotropy results are thereby synthesized, but further analyses are still required to establish their origin.
RESUMO
Several approaches have been used to trace axonal trajectories from diffusion MRI data. If such techniques were first developed in a deterministic framework reducing the diffusion information to one single main direction, more recent approaches emerged that were statistical in nature and that took into account the whole diffusion information. Based on diffusion tensor MRI data coming from normal brains, this paper presents how brain connectivity could be modelled globally by means of a random walk algorithm. The mass of connections thus generated was then virtually dissected to uncover different tracts. Corticospinal, corticobulbar, and corticothalamic tracts, the corpus callosum, the limbic system, several cortical association bundles, the cerebellar peduncles, and the medial lemniscus were all investigated. The results were then displayed in the form of an in vivo brain connectivity atlas. The connectivity pattern and the individual fibre tracts were then compared to known anatomical data; a good matching was found.
Assuntos
Mapeamento Encefálico , Encéfalo/anatomia & histologia , Fibras Nervosas/fisiologia , Vias Neurais/anatomia & histologia , Algoritmos , Axônios/fisiologia , Cerebelo/anatomia & histologia , Cerebelo/fisiologia , Córtex Cerebral/anatomia & histologia , Córtex Cerebral/fisiologia , Gráficos por Computador , Humanos , Processamento de Imagem Assistida por Computador , Imageamento por Ressonância Magnética , Modelos Neurológicos , Tratos Piramidais/anatomia & histologia , Tratos Piramidais/fisiologia , Tálamo/anatomia & histologia , Tálamo/fisiologiaRESUMO
A correlation function that compares each base in a DNA sequence to its various neighbours and which is subsequently processed by Fourier and wavelet transforms has been developed. The procedure has been applied to sequences from the human chromosome 22, to nef genes from various HIV clones and to myosin heavy chain DNA. It permits to readily visualize regular features in DNA which are related to the stability of heteroduplexes formed upon strand slippage.
