RESUMO
Abstract: In the last years, a considerable number of patients with hand mobility problems has been reported; in most of these cases, the patients must spend time in a specialized center to carry out a therapy to rehabilitate damaged parts. This paper presents the design of an orthosis for finger rehabilitation. The novelty of this proposal is that the design is formed by rigid links and three semicircular sliders with a center of rotation coincident with the finger joints; moreover, the synthesis of these sliders is realized in a new and simple way. The mechanism is designed to be compact enough to be used by a person during a whole day; it is formed by twelve links and allows the three finger phalanxes to be flexed simultaneously. The mechanism is coupled only to the dorsal side of the hand and has no interference when grasping objects, in such a way that the orthosis presented in this paper enables the patient to perform the Activities of Daily Living. The synthesis of the mechanism presented in this paper focuses on the middle finger, nevertheless, it is possible to use the same configuration for the others fingers only by scaling.
Resumen: En los últimos años un considerable número de pacientes con problemas de movilidad en las manos ha sido reportado; en la mayoría de los casos, los pacientes deben pasar un tiempo determinado en un centro especializado para llevar a cabo una terapia para rehabilitar las partes afectadas. En este artículo se presenta el diseño de una ortesis para rehabilitación de un dedo. La novedad de esta propuesta es que el diseño está formado por eslabones rígidos y tres correderas semicirculares, cuyo centro de rotación coincide con el centro de rotación de los dedos; además, la síntesis de estas correderas se realizó de una manera sencilla y nueva. El mecanismo diseñado es suficientemente compacto para ser utilizado por una persona durante un día entero; está formado por doce eslabones y permite que las tres falanges se muevan simultáneamente. El mecanismo es acoplado al dorso de la mano para no interferir con la sujeción de objetos, y por tanto permitir el desarrollo de las actividades de la vida diaria. La síntesis del mecanismo presentada en este artículo se enfoca en el dedo medio, sin embargo es posible usar la misma configuración para los otros dedos, solo escalando el mecanismo.
RESUMO
The dynamic organization of chromatin plays an essential role in the regulation of gene expression and in other fundamental cellular processes. The underlying physical basis of these activities lies in the sequential positioning, chemical composition, and intermolecular interactions of the nucleosomes-the familiar assemblies of â¼150 DNA base pairs and eight histone proteins-found on chromatin fibers. Here we introduce a mesoscale model of short nucleosomal arrays and a computational framework that make it possible to incorporate detailed structural features of DNA and histones in simulations of short chromatin constructs. We explore the effects of nucleosome positioning and the presence or absence of cationic N-terminal histone tails on the 'local' inter-nucleosomal interactions and the global deformations of the simulated chains. The correspondence between the predicted and observed effects of nucleosome composition and numbers on the long-range communication between the ends of designed nucleosome arrays lends credence to the model and to the molecular insights gleaned from the simulated structures. We also extract effective nucleosome-nucleosome potentials from the simulations and implement the potentials in a larger-scale computational treatment of regularly repeating chromatin fibers. Our results reveal a remarkable effect of nucleosome spacing on chromatin flexibility, with small changes in DNA linker length significantly altering the interactions of nucleosomes and the dimensions of the fiber as a whole. In addition, we find that these changes in nucleosome positioning influence the statistical properties of long chromatin constructs. That is, simulated chromatin fibers with the same number of nucleosomes exhibit polymeric behaviors ranging from Gaussian to worm-like, depending upon nucleosome spacing. These findings suggest that the physical and mechanical properties of chromatin can span a wide range of behaviors, depending on nucleosome positioning, and that care must be taken in the choice of models used to interpret the experimental properties of long chromatin fibers.
