933 resultados para shape memory alloy,shape memory polymers,effetto memoria di forma


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The polymer backbone of a side-chain liquid crystal polymer exhibits an anisotropic shape due to the coupling of the liquid crystal orientational order of the mesogenic side-chains to the backbone. The magnitude and sign of this coupling may be controlled by chemical design. The introduction of chemical cross-links in to such a system provides both a memory of the anisotropic organisation and a mechanism by which the microscopic anisotropy can be realised at a macroscopic level. We show how this anisotropic network structure yields new phenomena when electric or mechanical fields are applied.

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Recalling information involves the process of discriminating between relevant and irrelevant information stored in memory. Not infrequently, the relevant information needs to be selected from amongst a series of related possibilities. This is likely to be particularly problematic when the irrelevant possibilities are not only temporally or contextually appropriate but also overlap semantically with the target or targets. Here, we investigate the extent to which purely perceptual features which discriminate between irrelevant and target material can be used to overcome the negative impact of contextual and semantic relatedness. Adopting a distraction paradigm, it is demonstrated that when distracters are interleaved with targets presented either visually (Experiment 1) or auditorily (Experiment 2), a within-modality semantic distraction effect occurs; semantically-related distracters impact upon recall more than unrelated distracters. In the semantically-related condition, the number of intrusions in recall is reduced whilst the number of correctly recalled targets is simultaneously increased by the presence of perceptual cues to relevance (color features in Experiment 1 or speaker’s gender in Experiment 2). However, as demonstrated in Experiment 3, even presenting semantically-related distracters in a language and a sensory modality (spoken Welsh) distinct from that of the targets (visual English) is insufficient to eliminate false recalls completely, or to restore correct recall to levels seen with unrelated distracters . Together, the study shows how semantic and non-semantic discriminability shape patterns of both erroneous and correct recall.

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Thermal analysis and compression tests at room temperature have been carried out for Cu-10 wt.% Al and Cu-10 wt.% Al-10 wt.% Ag alloys samples. The results indicate that the decomposition reaction of the (beta(1)) parent phase is decreased suppressed and a martensite stabilization effect can be induced by Ag addition. The Cu-Al-Ag alloy shows some degree of shape memory capacity. (C) 2007 Elsevier B.V. All rights reserved.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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For those of us who shared many years of friendship and professional collaboration with Pedro Vuskovic, the news of his recent death in Mexico has been the cause of great sorrow, not only because of the circumstances of his death, following a cruel disease that gradually sapped his physical -but not intellectual- strength, but also because it signifies the loss of a great Latin American, of a teacher who helped shape so many generations of young people in our region, and of a companion during so many days of intellectual strivings and political struggle. Pedro joined the Commission in 1950, shortly after its birth as an institution. For nearly 20 years he served it brilliantly in a professional capacity, with his career in ECLAC culminating in the position of Director of the Development Division. He played a crucial role in structuring and disseminating the thinking of ECLAC during a time when the very air teemed with the ideas and concerns of a pleiad of gifted economists and social scientists. These were the post-war years, the 1950s and 1960s, when we all had to "construct" Latin America. Pedro Vuskovic laid many of the bricks in that collective theoretical and political edifice which has been of such importance to the countries of the region. Concurrently, he served as a professor in ECLAC and ILPES training programmes while at the same time teaching classes at the schools of economics and sociology at the University of Chile and the School of Economics at the University of Concepción. When he left ECLAC, Pedro plunged wholeheartedly into the academic world, serving as the Director of the Institute of Economics of the University of Chile, and then went on to claim a position at the forefront of Chilean politics. In November 1970 he was named Minister of Economic Affairs by President Salvador Allende and in June 1972, took over the cabinet-level position of Executive Vice President of the Production Development Corporation (CORFO);, where he served until September 1973. When political events carried him into exile in Mexico, which generously welcomed him as it did so many other Latin Americans who faced similar problems, Pedro carried on his valuable academic work, first at the Economic Research and Teaching Centre (CIDE);, where he directed the Institute of Economic Studies of Latin America, and later at the Centre for Interdisciplinary Research in the Humanities at the National University of Mexico (UNAM);, where he was named to the position of Coordinator for a programme on poverty and development options in various countries of Latin America. Although he will be remembered for his important political role, Pedro's work as a scholar and as an economist deserve special mention. He was a brilliant speaker, at the same time both methodical and incisive, who mastered his subjects with great wisdom and intellectual breadth, and he derived a special joy from being with young people, from providing them with intellectual stimulation and receiving it from them in turn. The many generations of Latin American students who were fortunate enough to have him as a teacher can attest to this. Pedro Vuskovic brought to his work as a researcher and teacher a deep sense of political and social responsibility which moved him to espouse the cause of Latin America 's poor and dispossessed, whose position he had come to understand very early on in his life through the many studies he carried out in this area while at ECLAC. He was tenacious in upholding his ideas and principles, he lived in accordance with them, and he championed them in all the forums open to him, in both the political and academic worlds, to the end of his days. His friends and colleagues also remember his geniality, his sense of humour and great personal warmth -traits which were coupled with an unshakable loyalty to his principles and values. Our farewell is deeply felt; Pedro Vuskovic has left us a legacy of memories and lessons that we will always hold close to our hearts. On behalf of his friends and colleagues, Jacobo Schatan, former Director of the Joint ECLAC/FAO, Agriculture Division

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[ES] El estudio de las inscripciones que se conservan en los tres cementerios ingleses de Canarias, así como de los propios monumentos funerarios en los que estas se inscriben, permite un acercamiento al ars moriendi, pero también a los mecanismos de autorrepresentación de los miembros de la comunidad británica radicada en Canarias cuyos restos reposan en estas necrópolis. El presente estudio pretende analizar estas escrituras últimas en el contexto de una historia social de la cultura escrita en Canarias que cuenta, como elemento de diferenciación con respecto a otras regiones españolas, con una importante presencia británica, evidenciada en la mayor concentración de cementerios protestantes de todo el país.

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Intestinal immunoglobulin A (IgA) ensures host defense and symbiosis with our commensal microbiota. Yet previous studies hint at a surprisingly low diversity of intestinal IgA, and it is unknown to what extent the diverse Ig arsenal generated by somatic recombination and diversification is actually used. In this study, we analyze more than one million mouse IgA sequences to describe the shaping of the intestinal IgA repertoire, its determinants, and stability over time. We show that expanded and infrequent clones combine to form highly diverse polyclonal IgA repertoires with very little overlap between individual mice. Selective homing allows expanded clones to evenly seed the small but not large intestine. Repertoire diversity increases during aging in a dual process. On the one hand, microbiota-, T cell-, and transcription factor RORγt-dependent but Peyer's patch-independent somatic mutations drive the diversification of expanded clones, and on the other hand, new clones are introduced into the repertoire of aged mice. An individual's IgA repertoire is stable and recalled after plasma cell depletion, which is indicative of functional memory. These data provide a conceptual framework to understand the dynamic changes in the IgA repertoires to match environmental and intrinsic stimuli.

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The goal of this study was to investigate recognition memory performance across the lifespan and to determine how estimates of recollection and familiarity contribute to performance. In each of three experiments, participants from five groups from 14 up to 85 years of age (children, young adults, middle-aged adults, young-old adults, and old-old adults) were presented with high- and low-frequency words in a study phase and were tested immediately afterwards and/or after a one day retention interval. The results showed that word frequency and retention interval affected recognition memory performance as well as estimates of recollection and familiarity. Across the lifespan, the trajectory of recognition memory followed an inverse u-shape function that was neither affected by word frequency nor by retention interval. The trajectory of estimates of recollection also followed an inverse u-shape function, and was especially pronounced for low-frequency words. In contrast, estimates of familiarity did not differ across the lifespan. The results indicate that age differences in recognition memory are mainly due to differences in processes related to recollection while the contribution of familiarity-based processes seems to be age-invariant.

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Multiple interlinked positive feedback loops shape the stimulus responses of various biochemical systems, such as the cell cycle or intracellular Ca2+ release. Recent studies with simplified models have identified two advantages of coupling fast and slow feedback loops. This dual-time structure enables a fast response while enhancing resistances of responses and bistability to stimulus noise. We now find that (1) the dual-time structure similarly confers resistance to internal noise due to molecule number fluctuations, and (2) model variants with altered coupling, which better represent some specific biochemical systems, share all the above advantages. We also develop a similar bistable model with coupling of a fast autoactivation loop to a slow loop. This model's topology was suggested by positive feedback proposed to play a role in long-term synaptic potentiation (LTP). The advantages of fast response and noise resistance are also present in this autoactivation model. Empirically, LTP develops resistance to reversal over approximately 1h . The model suggests this resistance may result from increased amounts of synaptic kinases involved in positive feedback.

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Memory is an indispensable tool for all architects. An architect without memory is worthless or less than worthless.

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El nuevo edificio del Museo de la Memoria de Andalucía constituye una metáfora de las actividades que Caja Granada desarrolla en esa ciudad y, por ello, se ha propuesto un edificio dialogante con la vecina Sede Central de Caja Granada, obra de los mismos arquitectos.

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Museo Memoria de Andalucía, Granada = Andalucía Museum of Memory, Granada. Texto en español e inglés