RESUMEN
Resting state functional magnetic resonance imaging (fMRI) is a neuroimaging technique based on analyzing spontaneous, low frequency fluctuations in the activity of brain areas by measuring by their MRI signal to investigate the functional architecture of the brain during rest. The use of resting state fMRI opens up possibilities for assessing brain functional relationships in both normal conditions and in different CNS pathologies in order to clarify the disturbed mechanisms of brain functioning and develop approaches for therapeutic non-invasive neuromodulation. Understanding the acquisition of data, the features of their preprocessing and analysis is very important for clinicians who use resting state fMRI in their studies, since it is neurologists, psychiatrists, and neurosurgeons who set research tasks and are the final consumers of the results. The article details the methodological features of obtaining and analyzing resting state fMRI data, the advantages and disadvantages of the method. The article is intended for a wide range of specialists using this method in their work or planning to include it in their research.
Asunto(s)
Neurología , Psiquiatría , Encéfalo/diagnóstico por imagen , Humanos , Imagen por Resonancia Magnética/métodos , DescansoRESUMEN
Evolution of the theoretical spectrum during the course of spectrum analysis and comparison of the result with the experimental spectrum.
RESUMEN
The novel algorithm for a total lineshape analysis of high-resolution NMR spectra has been developed. A global optimization by simulated annealing has been applied that has allowed to overcome the main trouble of common approaches which had frequently returned solutions for local minima rather than for global ones. The algorithm has been verified for the four-spin test systems ABCD, and has been successfully used for analysis of experimental NMR spectra of proline. The approach has allowed to avoid a sophisticated manual setup of initial parameters and to conduct the analysis of complicated high-resolution NMR spectra nearly automatically.
RESUMEN
Textures (i.e., smooth space nonuniform distributions of the order parameter) in biaxial nematics turned out to be much more complex and interesting than expected. Scanning the literature we find only a very few publications on this topic. Thus, the immediate motivation of the present paper is to develop a systematic procedure to study, classify, and visualize possible textures in biaxial nematics. Based on the elastic energy of a biaxial nematic (written in the most simple form that involves the least number of phenomenological parameters) we derive and solve numerically the Lagrange equations of the first kind. It allows one to visualize the solutions and offers a deep insight into their geometrical and topological features. Performing Fourier analysis we find some particular textures possessing two or more characteristic space periods (we term such solutions quasiperiodic ones because the periods are not necessarily commensurate). The problem is not only of intellectual interest but also of relevance to optical characteristics of the liquid-crystalline textures.