Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto

About: Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto is a based out in . It is known for research contribution in the topics: Population & Genus. The organization has 2143 authors who have published 3674 publications receiving 71071 citations. The organization is also known as: FFCLRP & FFCLRP-USP.

Intensity Coding in Two-Dimensional Excitable Neural Networks

Abstract: In the light of recent experimental findings that gap junctions are essential for low level intensity detection in the sensory periphery, the Greenberg–Hastings cellular automaton is employed to model the response of a two-dimensional sensory network to external stimuli. We show that excitable elements (sensory neurons) that have a small dynamical range are shown to give rise to a collective large dynamical range. Therefore the network transfer (gain) function (which is Hill or Stevens law-like) is an emergent property generated from a pool of small dynamical range cells, providing a basis for a “neural psychophysics”. The growth of the dynamical range with the system size is approximately logarithmic, suggesting a functional role for electrical coupling. For a fixed number of neurons, the dynamical range displays a maximum as a function of the refractory period, which suggests experimental tests for the model. A biological application to ephaptic interactions in olfactory nerve fascicles is proposed.

Texture descriptor based on partially self-avoiding deterministic walker on networks

Abstract: Texture image analysis is an important field of investigation that has attracted the attention from computer vision community in the last decades. In this paper, a novel approach for texture image analysis is proposed by using a combination of graph theory and partially self-avoiding deterministic walks. From the image, we build a regular graph where each vertex represents a pixel and it is connected to neighboring pixels (pixels whose spatial distance is less than a given radius). Transformations on the regular graph are applied to emphasize different image features. To characterize the transformed graphs, partially self-avoiding deterministic walks are performed to compose the feature vector. Experimental results on three databases indicate that the proposed method significantly improves correct classification rate compared to the state-of-the-art, e.g. from 89.37% (original tourist walk) to 94.32% on the Brodatz database, from 84.86% (Gabor filter) to 85.07% on the Vistex database and from 92.60% (original tourist walk) to 98.00% on the plant leaves database. In view of these results, it is expected that this method could provide good results in other applications such as texture synthesis and texture segmentation.

Simulation study of the role and structure of monatomic ions multiple hydration shells

Abstract: The hydration structures of five monatomic cations and two monatomic anions are studied by Monte Carlo NpT simulations conducted on infinite dilute aqueous electrolyte solutions. The complete first and second hydration shells are defined by the successive minima of the radial distribution functions’ ion–water oxygen atoms. The first shell structure is determined essentially by the electrostatic charge of the ion and by the short-range ion–water molecule interactions so that it is always constituted by six molecules located at the vertices of regular octahedra unless if the distance between the charge of the ion and the opposite charge in the water molecule is large enough to allow the presence of more than six water molecules. This is the case of the K+ which presents eight molecules in its first shell. The pairs of hydrogen atoms are, in the first shell, preferentially perpendicular. The structure of the second shell is defined by the bulk tetrahedral structure induced by the water molecules so that they are similar for cations and anions. The resulting second shell densities are very close to the pure water density. Both complete hydration shells are maintained stable by means of a compromise between the strong attraction that the ion carry out on the water molecules and by the resulting repulsion between these molecules which are forced to get too close to one another.

The development of an immobilized enzyme reactor containing glyceraldehyde-3-phosphate dehydrogenase from Trypanosoma cruzi: the effect of species' specific differences on the immobilization

Abstract: Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) plays an important role in the life cycle of the Trypanosoma cruzi, and an immobilized enzyme reactor (IMER) has been developed for use in the on-line screening for GAPDH inhibitors. An IMER containing human GAPDH has been previously reported; however, these conditions produced a T. cruzi GAPDH-IMER with poor activity and stability. The factors affecting the stability of the human and T. cruzi GAPDHs in the immobilization process and the influence of pH and buffer type on the stability and activity of the IMERs have been investigated. The resulting T. cruzi GAPDH-IMER was coupled to an analytical octyl column, which was used to achieve chromatographic separation of NAD+ from NADH. The production of NADH stimulated by D-glyceraldehyde-3-phosphate was used to investigate the activity and kinetic parameters of the immobilized T. cruzi GAPDH. The Michaelis–Menten constant (Km) values determined for D-glyceraldehyde-3-phosphate and NAD+ were Km = 0.5 ± 0.05 mM and 0.648 ± 0.08 mM, respectively, which were consistent with the values obtained using the non-immobilized enzyme.