Modelling of Behavior for Inhibition Corrosion of Bronze Using Artificial Neural Network (ANN).

In this work, three models based on Artificial Neural Network (ANN) were developed to describe the behavior for the inhibition corrosion of bronze in 3.5% NaCl + 0.1 M Na2SO4, using the experimental data of Electrochemical Impedance Spectroscopy (EIS). The database was divided into training, validation, and test sets randomly. The parameters process used as the inputs of the ANN models were frequency, temperature, and inhibitor concentration. The outputs for each ANN model and the components in the EIS spectrum (Zre, Zim, and Zmod) were predicted. The transfer functions used for the learning process were the hyperbolic tangent sigmoid in the hidden layer and linear in the output layer, while the Levenberg-Marquardt algorithm was applied to determine the optimum values of the weights and biases. The statistical analysis of the results revealed that ANN models for Zre, Zim, and Zmod can successfully predict the inhibition corrosion behavior of bronze in different conditions, where what was considered included variability in temperature, frequency, and inhibitor concentration. In addition, these three input parameters were keys to describe the behavior according to a sensitivity analysis.

Septal serotonin depletion in rats facilitates working memory in the radial arm maze and increases hippocampal high-frequency theta activity.

Hippocampal theta activity, which is strongly modulated by the septal medial/Broca׳s diagonal band neurons, has been linked to information processing of the hippocampus. Serotonin from the medial raphe nuclei desynchronises hippocampal theta activity, whereas inactivation or a lesion of this nucleus induces continuous and persistent theta activity in the hippocampus. Hippocampal serotonin depletion produces an increased expression of high-frequency theta activity concurrent with the facilitation of place learning in the Morris maze. The medial septum-diagonal band of Broca complex (MS/DBB) has been proposed as a key structure in the serotonin modulation of theta activity. We addressed whether serotonin depletion of the MS/DBB induces changes in the characteristics of hippocampal theta activity and whether the depletion is associated with learning in a working memory spatial task in the radial arm maze. Sprague Dawley rats were depleted of 5HT with the infusion of 5,7-dihydroxytriptamine (5,7-DHT) in MS/DBB and were subsequently trained in the standard test (win-shift) in the radial arm, while the CA1 EEG activity was simultaneously recorded through telemetry. The MS/DBB serotonin depletion induced a low level of expression of low-frequency (4.5-6.5Hz) and a higher expression of high-frequency (6.5-9.5Hz) theta activity concomitant to a minor number of errors committed by rats on the working memory test. Thus, the depletion of serotonin in the MS/DBB caused a facilitator effect on working memory and a predominance of high-frequency theta activity.

Differential learning-related changes in theta activity during place learning in young and old rats.

The participation key role of the hippocampus in place learning ability as well as the decline of cognitive functions associated with aging, have been established in experimental and clinical studies. On the other hand, hippocampal theta activity has been proposed as a part of the cerebral phenomena underlying hippocampal-dependent learning processes. In the present study, the relative power of low, high, and maximal frequency components of hippocampal CA1 theta activity during a 6-day training period (four daily trials; basal, searching, and platform stages) and the probe trial of a place learning paradigm (Morris water maze) were analyzed in young and aged rats. An increase in high frequency, and a decrease in low frequency relative power of theta activity during the searching stage, which were correlated with shorter swimming path lengths and predominant hippocampal-dependent allocentric strategies, were observed in young rats as became trained in place learning and memory tasks, in the Morris water maze; while, under these conditions, no changes in theta activity and predominant non hippocampal-dependent egocentric strategies occurred in the old rats. Besides, an overall (theta activity recorded during the three behavioral stages) increase of low frequency and an overall decrease of high frequency theta bands in the old group as compared to the young group were observed. These electrophysiological data suggest that old rats process information relevant for cognitive functions in a different manner, possibly leading to the use of different learning strategies, than young rats.

Schistosomiasis vesical. Lesiones endoscopicas. / Vesical schistosomiasis.Endoscopic lesions

Se realizaron 1.127 endoscopias en el periodo comprendido desde marzo de 1977 hasta octubre de 1979 en el Hospital Universitario "Americo Boavida" de Luanda.Se selecciona para el estudio 690 (61.1%) endoscopias con diagnostico de schistosomiasis vesical. Se encuentran como lesiones mas frecuentes los huevos calcificados del parasito y la mucosa vesical deslustrada, signos de cronicidad que alertan sobre lo tardiamente que acuden a las consultas de urologia los pacientes portadores de esta enfermedad en el medio estudiado