On solving constrained optimization problems with neural networks:a penalty method approach

Deals with the use of neural networks to solve linear and nonlinear programming problems. The dynamics of these networks are analyzed. In particular, the dynamics of the canonical nonlinear programming circuit are analyzed. The circuit is shown to be a gradient system that seeks to minimize an unconstrained energy function that can be viewed as a penalty method approximation of the original problem. Next, the implementations that correspond to the dynamical canonical nonlinear programming circuit are examined. It is shown that the energy function that the system seeks to minimize is different than that of the canonical circuit, due to the saturation limits of op-amps in the circuit. It is also noted that this difference can cause the circuit to converge to a different state than the dynamical canonical circuit. To remedy this problem, a new circuit implementation is proposed.     

Methamphetamine Blocks Adenosine A2A Receptor Activation via Sigma 1 and Cannabinoid CB1 Receptors

Methamphetamine is, worldwide, one of the most consumed drugs of abuse. One important side effect is neurodegeneration leading to a decrease in life expectancy. The aim of this paper was to check whether the drug affects one of the receptors involved in neurodegeneration/neuroprotection events, namely the adenosine A_2A receptor (A_2AR). First, we noticed that methamphetamine does not affect A_2A functionality if the receptor is expressed in a heterologous system. However, A_2AR becomes sensitive to the drug upon complexes formation with the cannabinoid CB₁ receptor (CB₁R) and the sigma 1 receptor (σ₁R). Signaling via both adenosine A_2AR and cannabinoid CB₁R was affected by methamphetamine in cells co-expressing the two receptors. In striatal primary cultures, the A_2AR–CB₁R heteromer complex was detected and methamphetamine not only altered its expression but completely blocked the A_2AR- and the CB₁R-mediated activation of the mitogen activated protein kinase (MAPK) pathway. In conclusion, methamphetamine, with the participation of σ₁R, alters the expression and function of two interacting receptors, A_2AR, which is a therapeutic target for neuroprotection, and CB₁R, which is the most abundant G protein-coupled receptor (GPCR) in the brain.     

Spatial constraints and regulatory functions in monkeys' (Cebus apella) search.

By means of an apparatus featuring a set of suspended baited containers, search abilities of 4 capuchin monkeys (Cebus apella) were evaluated. The experiment featured different spatial configurations of the search space. Results showed that monkeys exhaustively searched 9 containers spatially distributed as a 3?×?3 matrix, a cross, a line, or a circle. Search efficiency was higher when the search space featured either a linear or circular arrangement of containers. When faced with a linear arrangement of containers, the subjects developed principled search trajectories from 1 end to the other of the linear array. This behavioral regulation was independent from search efficiency as measured by the amount of visits to containers already explored. The data suggest that monkeys use either the travel distance or the cognitive costs associated with unprincipled travel trajectories as currency for regulation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Response of microglial cells after a cryolesion in the peripheral proliferative retina of tench

We studied the glial response after inducing a lesion in the zone of the peripheral retina of tench, where there is proliferative neuroepithelium. In the retina and optic nerve, the microglial response was analysed with tomato lectin and the macroglial response with antibodies against GFAP and S-100. In lesioned retinas, there was a temporal-spatial distribution pattern of microglia. One day after lesion, primitive ramified cells appeared in the nerve fibre layer. These cells appeared progressively from the vitreal to the scleral layers until day 7 when cells appeared in all layers, with the exception of the outer plexiform layer. From this point, labelling decreased. In the optic nerve, 3 days after lesion, an increase in the number of microglial cells was observed, first in the nerve folds and from day 15 in specific areas of the optic nerve. In the central retina, in the optic nerve head and within the optic nerve itself, the appearance of microglial cells, after the lesion, near the blood vessels, could indicate a vascular origin of microglia, as has been proposed by many authors. However, we cannot discount the idea that some of the reactive microglial cells arise by proliferation of the microglia existing in the normal state. Using GFAP and S-100 antibodies, no important changes in the retina were observed, however in the optic nerve there was response to the lesion. Thus, the macroglial cells appeared to be involved in reorganisation of the optic nerve axons after lesion.     

Net Results: The NetView-Based Problem Resolution and Productivity Tool for the VTAM Environment

This article introduces Net Results, a NetView-based full-screen command processor that facilitates SNA Network management.     

Authors' Reply

The authors accept the corrections, pointed out by E.G. Bakhoum, to their original paper (see ibid., vol.48, no.4, p.632-41, Nov. 2005) an apologise for their mistakes     

Global and local processing of hierarchical visual stimuli in tufted capuchin monkeys (Cebus apella).

Capuchin monkeys' (Cebus apella) relative accuracy in the processing of the global shape or the local features of hierarchical visual stimuli was assessed. Three experiments are presented featuring manipulations of the arrangement and the density of the local elements of the stimuli. The results showed a clear advantage for local level processing in this species, which is robust under manipulations of the density of the local elements of the stimuli. By contrast, the density of the component elements linearly affected accuracy in global processing. These findings, which support those from other studies in which a local superiority emerged in animals, challenge the generality of early claims concerning the adaptive value of global advantage in the processing of hierarchical visual patterns. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The Mahalanobis Distance for Functional Data With Applications to Classification

This article presents a new semidistance for functional observations that generalizes the Mahalanobis distance for multivariate datasets. The main characteristics of the functional Mahalanobis semidistance are shown. To illustrate the applicability of this measure of proximity between functional observations, new versions of several well-known functional classification procedures are developed using the functional Mahalanobis semidistance. A Monte Carlo study and the analysis of two real examples indicate that the classification methods used in conjunction with the functional Mahalanobis semidistance give better results than other well-known functional classification procedures. This article has supplementary material online.     

The organization of exhaustive searches in a patchy space by capuchin monkeys (Cebus apella).

Search is a serial exploration of alternatives. Efficient search involves the ability to minimize costs (i.e., time/energy) and to keep track of alternatives already explored. The search abilities of 4 capuchin monkeys (Cebus apella) were evaluated by means of an apparatus featuring a set of suspended baited containers. The experiment featured conditions with different spatial configurations of the search space. Results show that the monkeys were able to search exhaustively 9 containers spatially distributed either as a 3?×?3 matrix or as 3 "patches" of 3 containers each. Search efficiency was higher in a search space suitable to organization in clusters or spatial chunks. In this condition, evidence for principled organization of search trajectories, as opposed to a random walk through the search space, emerges clearly and parallels search efficiency. This suggests that monkeys impose a structure over the search space and, by doing so, reduce the memory demands of the task. (PsycINFO Database Record (c) 2010 APA, all rights reserved)