Modeling, control and experimental validation of a novel actuator based on shape memory alloys

The paper presents the development of a mechanical actuator using a shape memory alloy with a cooling system based on the thermoelectric effect (Seebeck-Peltier effect). Such a method has the advantage of reduced weight and requires a simpler control strategy as compared to other forced cooling systems. A complete mathematical model of the actuator was derived, and an experimental prototype was implemented. Several experiments are used to validate the model and to identify all parameters. A robust and nonlinear controller, based on sliding-mode theory, was derived and implemented. Experiments were used to evaluate the actuator closed-loop performance, stability, and robustness properties. The results showed that the proposed cooling system and controller are able to improve the dynamic response of the actuator. (C) 2009 Elsevier Ltd. All rights reserved.

On Building a Memory Evolutive System for Application to Learning and Cognition Modeling

We address here aspects of the implementation of a memory evolutive system (MES), based on the model proposed by A. Ehresmann and J. Vanbremeersch (2007), by means of a simulated network of spiking neurons with time dependent plasticity. We point out the advantages and challenges of applying category theory for the representation of cognition, by using the MES architecture. Then we discuss the issues concerning the minimum requirements that an artificial neural network (ANN) should fulfill in order that it would be capable of expressing the categories and mappings between them, underlying the MES. We conclude that a pulsed ANN based on Izhikevich`s formal neuron with STDP (spike time-dependent plasticity) has sufficient dynamical properties to achieve these requirements, provided it can cope with the topological requirements. Finally, we present some perspectives of future research concerning the proposed ANN topology.

Synaptic compensation on Hopfield network: implications for memory rehabilitation

The discrete-time neural network proposed by Hopfield can be used for storing and recognizing binary patterns. Here, we investigate how the performance of this network on pattern recognition task is altered when neurons are removed and the weights of the synapses corresponding to these deleted neurons are divided among the remaining synapses. Five distinct ways of distributing such weights are evaluated. We speculate how this numerical work about synaptic compensation may help to guide experimental studies on memory rehabilitation interventions.

Memory with emotional content, brain amygdala and Alzheimer`s disease

Objectives - A highly adaptive aspect of human memory is the enhancement of explicit, consciously accessible memory by emotional stimuli. We studied the performance of Alzheimer`s disease (AD) patients and elderly controls using a memory battery with emotional content, and we correlated these results with the amygdala and hippocampus volume. Methods - Twenty controls and 20 early AD patients were subjected to the International Affective Picture System (IAPS) and to magnetic resonance imaging-based volumetric measurements of the medial temporal lobe structures. Results - The results show that excluding control group subjects with 5 or more years of schooling, both groups showed improvement with pleasant or unpleasant figures for the IAPS in an immediate free recall test. Likewise, in a delayed free recall test, both the controls and the AD group showed improvement for pleasant pictures, when education factor was not controlled. The AD group showed improvement in the immediate and delayed free recall test proportional to the medial temporal lobe structures, with no significant clinical correlation between affective valence and amygdala volume. Conclusion - AD patients can correctly identify emotions, at least at this early stage, but this does not improve their memory performance.

Pre and post-natal exposure to ambient level of air pollution impairs memory of rats: the role of oxidative stress

The aims of this study were to evaluate whether air pollution during pre-natal and post-natal phases change habituation and short-term discriminative memories and if oxidants are involved in this process. As secondary objectives, it was to evaluate if the change of filtered to nonfiltered environment could protect the cortex of rats against oxidative stress as well as to modify the behavior of these animals. Wistar, male rats were divided into four groups (n = 12/group): pre and post-natal exposure until adulthood to filtered air (FA); pre-natal period to nonfiltered air (NFA-FA); until (21st post-natal day) and post-natal to filtered air until adulthood (PND21); prenatal to filtered air until PND21 and post-natal to nonfiltered air until adulthood (FA-NFA); pre and post-natal to nonfiltered air (NFA). After 150 days of air pollution exposure, animals were tested in the spontaneous object recognition test to evaluate short-term discriminative and habituation memories. Rats were euthanized; blood was collected for metal determination; cortex dissected for oxidative stress evaluation. There was a significant increase in malondialdehyde (MDA) levels in the NFA group when compared to other groups (FA: 1.730 +/- 0.217; NFA-FA: 1.101 +/- 0.217; FA-NFA: 1.014 +/- 0.300; NFA: 5.978 +/- 1.920 nmol MDA/mg total proteins; p = 0.007). NFA group presented a significant decrease in short-term discriminative (FA: 0.603 +/- 0.106; NFA-FA: 0.669 +/- 0.0666; FA-NFA: 0.374 +/- 0.178; NFA: -0.00631 +/- 0.106 sec; p = 0.006) and an improvement in habituation memories when compared to other groups. Therefore, exposure to air pollution during both those periods impairs short-term discriminative memory and cortical oxidative stress may mediate this process.

Leukotrienes Are Potent Adjuvant during Fungal Infection: Effects on Memory T Cells

Leukotrienes (LTs) are potent lipid mediators involved in the control of host defense. LTB(4) induces leukocyte accumulation, enhances phagocytosis and bacterial clearance, and increases NO synthesis. LTB(4) is also important in early effector T cell recruitment that is mediated by LTB(4) receptor 1, the high-affinity receptor for LTB(4). The aims of this study were to evaluate whether LTs are involved in the secondary immune response to vaccination in a murine model of Histoplasma capsulatum infection. Our results demonstrate that protection of wild-type mice immunized with cell-free Ags from H. capsulatum against histoplasmosis was associated with increased LTB(4) and IFN-gamma production as well as recruitment of memory T cells into the lungs. In contrast, cell-free Ag-immunized mice lacking 5-lipoxygenase(-/-), a critical enzyme involved in LT synthesis, displayed a marked decrease on recruitment of memory T cells to the lungs associated with increased synthesis of TGF-beta as well as IL-10. Strikingly, these effects were associated with increased mortality to 5-lipoxygenase(-/-)-infected mice. These data establish an important immunomodulatory role of LTs, in both the primary and secondary immune responses to histoplasmosis. The Journal of Immunology, 2008,181: 8544-8551.

High-level and phonological awareness abilities of children following management for supratentorial tumour: Part II

Background. Limited information is available regarding the impact of childhood tumour on the cerebral hemispheres and supratentorial cranial fossa. However, a recent study found that children managed for a tumour located in this region may demonstrate reduced general language abilities. However, the indirect or direct impact of a tumour in this region on higher-level language abilities in childhood is at present largely unknown. Materials and methods. The present study examined the higher language and phonological awareness abilities of five children treated for supratentorial tumour ranging in age from seven to fourteen years in age. Assessments included measures of receptive and expressive semantic abilities, inferencing, figurative language, and problem solving, as well as a comprehensive pre-literacy test. Results. As a group, reductions were evident in problem solving, and in the ability to receive and decode content of high-level language when compared to a group of age- and gender-matched peers. At an individual level, only two of five children managed for supratentorial tumour demonstrated language deficits. These two cases were noted to be the same children previously identified as also having general language deficits. More widespread findings were noted in phonological awareness, with four of the five children previously managed for supratentorial tumour demonstrating weaknesses in one or more areas. Conclusions. Findings demonstrated that weaknesses in general language ability in children managed for supratentorial tumour may indicate higher-level language difficulties. Language abilities beyond general measures of language should be monitored, as well as long-term consideration of phonological awareness abilities in this population.

Effects of temporal association on recognition memory

The influence of temporal association on the representation and recognition of objects was investigated. Observers were shown sequences of novel faces in which the identity of the face changed as the head rotated. As a result, observers showed a tendency to treat the views as if they were of the same person. Additional experiments revealed that this was only true if the training sequences depicted head rotations rather than jumbled views; in other words, the sequence had to be spatially as well as temporally smooth. Results suggest that we are continuously associating views of objects to support later recognition, and that we do so not only on the basis of the physical similarity, but also the correlated appearance in time of the objects.

Remembering sport history: Narrative, social memory and the origins of the rugby league in Australia

This study examines the historiography of the origins of rugby league in Australia. By accepting the inclusive nature of representation of the past as found in social memory theory, a wide range of sources ranging from histories written by academics to annuals, yearbooks and newspaper books are consulted. These sources reveal that there are several competing and conflicting accounts of the emergence of rugby league in Australia. These divergent accounts are used to facilitate a discussion of the role of narrative in sport history This article argues that narrative is an integral, not optional, feature of the production of history and that the historography of the origins of rugby league highlight the problematic nature of objectivity in history and the unavoidable, impositionalist role of the historian.

Emotional awareness and emotional intelligence in leadership teaching

Recent research has highlighted the importance of emotional awareness and emotional intelligence in organizations, and these topics are attracting increasing attention. In this article, the authors present the results of a preliminary classroom study in which emotion concepts were incorporated into an undergraduate leadership course. In the study, students completed self report and ability tests of emotional intelligence. The test results were compared with students' interest in emotions and their performance in the course assessment. Results showed that interest in and knowledge of emotional intelligence predicted team performance, whereas individual performance was related to emotional intelligence.

Emotional Intelligence, emotional Self-Awareness, and Team Effectiveness

An issue at the forefront of recent emotional intelligence debates revolves around whether emotional intelligence can be linked to work performance. Although many authors continue to develop new and improved measures of emotional intelligence (e.g. Mayer, Caruso, & Salovey, 2001) to give us a better understanding of emotional intelligence, the links to performance in work settings, especially in the context of group effectiveness, have received much less attention. In this chapter, we present the results of a study in which we examined the role of emotional self-awareness and emotional intelligence as a predictor of group effectiveness. The study also addresses the utility of self- and peer assessment in measureing emotional self-awareness and emotional intelligence.

An everyday nostalgia: Memory and the fictions of belonging

In 1984, George Orwell presented the future as a dystopian vision, where everyday existence was governed and redefined by an oppressive regime. Winston Smith's daily duties at the Ministry of Truth involved the invention, rewriting and erasing of fragments of history as a means of perpetuating contentment, uniformity and control. History, as Orwell described it in the novel 'was a palimpsest, scraped clean and reinscribed exactly as often as was necessary.' More that a quarter of a century after the publication of 1984, Michel Foucault discussed the cinematic representation and misrepresentation of French history and identity in terms of what he called the manipulation of 'popular memory'. In what was tantamount to a diluted version of Orwell's palimpsestic histories, Foucault stated that 'people are not shown what they were, but what they must remember having been.' This paper will investigate notions of memory, identity and the everyday through a discussion of the community of Celebration in Florida. Conceived in the 1990s, Celebration was designed around a fictionalised representation of pre 1940s small town America, using nostalgia for a mythologised past to create a sense of comfort, community and conformity among its residents. Adapting issues raised by Orwell, Foucault and Baudrillard, this paper will discuss the way in which architecture, like film and literature, can participate in what Foucault discussed as the manipulation of popular memory, inducing and exploiting a nostalgia for an everyday past that that never really existed.

Effects of memory load and distraction on performance and event-related slow potentials in a visuospatial working memory task

Brain electrical activity related to working memory was recorded at 15 scalp electrodes during a visuospatial delayed response task. Participants (N = 18) touched the remembered position of a target on a computer screen after either a 1 or 8 sec delay. These memory trials were compared to sensory trials in which the target remained present throughout the delay and response periods. Distracter stimuli identical to the target were briefly presented during the delay on 30% of trials. Responses were less accurate in memory than sensory trials, especially after the long delay. During the delay slow potentials developed that were significantly more negative in memory than sensory trials. The difference between memory and sensory trials was greater at anterior than posterior electrodes. On trials with distracters, the slow potentials generated by memory trials showed further enhancement of negativity whereas there were minimal effects on accuracy of performance. The results provide evidence that engagement of visuospatial working memory generates slow wave negativity with a timing and distribution consistent with frontal activation. Enhanced brain activity associated with working memory is required to maintain performance in the presence of distraction. © 1997 by the Massachusetts Institute of Technology