Plasticity

In conseguenza di gravi traumi, talvolta per un nonnulla, la storia di ognuno di noi può subire un radicale cambiamento: la vita che avevamo progettato per anni è costretta a una deviazione improvvisa e irreversibile. Dal trauma sorge una personalità nuova, senza precedenti. Una personalità nata da un incidente, nata per accidente. Il fortuito diviene così sostanziale e l’inaspettato s’inscrive nel nucleo più profondo del nostro essere. Affrontando con delicatezza il tema dell’impatto che i traumi psicofisici possono avere sulla nostra vita, Catherine Malabou intraprende un’avventura filosofica e letteraria in cui Spinoza, Deleuze e Freud incrociano Ovidio, Kafka, Proust e Duras, disegnando un’inedita ontologia fondata sul potere plastico della distruzione, sulla tendenza esplosiva che minaccia segretamente ognuno di noi.

Catherine Malabou insegna Filosofia all’Université Paris-Ouest Nanterre ed è docente presso il Centre for Research in Modern European Philosophy della Kingston University di Londra. È autrice di numerosi saggi, fra i quali, tradotti in italiano, ricordiamo: Cosa fare del nostro cervello (2007) e, con Judith Butler, Che tu sia il mio corpo. Una lettura contemporanea della signoria e della servitù in Hegel (2017).

Autistics often exhibit enhanced perceptual abilities when engaged in visual search, visual discrimination, and embedded figure detection. In similar fashion, while performing a range of perceptual or cognitive tasks, autistics display stronger physiological engagement of the visual system than do non-autistics. To account for these findings, the Enhanced Perceptual Functioning Model proposes that enhanced autistic performance in basic perceptual tasks results from stronger engagement of sensory processing mechanisms, a situation that may facilitate an atypically prominent role for perceptual mechanisms in supporting cognition. Using quantitative meta-analysis of published functional imaging studies from which Activation Likelihood Estimation maps were computed, we asked whether autism is associated with enhanced task-related activity for a broad range of visual tasks. To determine whether atypical engagement of visual processing is a general or domain-specific phenomenon, we examined three different visual processing domains: faces, objects, and words. Overall, we observed more activity in autistics compared to non-autistics in temporal, occipital, and parietal regions. In contrast, autistics exhibited less activity in frontal cortex. The spatial distribution of the observed differential between-group patterns varied across processing domains. Autism may be characterized by enhanced functional resource allocation in regions associated with visual processing and expertise. Atypical adult organizational patterns may reflect underlying differences in developmental neural plasticity that can result in aspects of the autistic phenotype, including enhanced visual skills, atypical face processing, and hyperlexia. Hum Brain Mapp, 2011 © 2011 Wiley-Liss, Inc.

Metal matrix composites with high interface density are produced via severe plastic co-deformation of multiphase alloys. 1–15 Corresponding compounds are first prepared by liquid or powder metallurgy3–12 or through restacking solids of different composition. 2 Subsequent extreme straining, to promote intense microstructure refinement, proceeds by wire drawing, ball milling, accumulative roll bonding, damascene forging, equal channel angular extrusion, friction, or highpressure torsion. 7

Climate change is taking place more rapidly and severely in the Arctic than anywhere on the globe, exposing Arctic vertebrates to a host of impacts. Changes in the cryosphere dominate the physical changes that already affect these animals, but increasing air temperatures, changes in precipitation, and ocean acidification will also affect Arctic ecosystems in the future. Adaptation via natural selection is problematic in such a rapidly changing environment. Adjustment via phenotypic plasticity is therefore likely to dominate Arctic vertebrate responses in the short term, and many such adjustments have already been documented. Changes in phenology and range will occur for most species but will only partly mitigate climate change impacts, which are particularly difficult to forecast due to the many interactions within and between trophic levels. Even though Arctic species richness is increasing via immigration from the South, many Arctic vertebrates are expected to become increasingly ...

Significant progress has been made in the application of low plasticity burnishing (LPB) technology to military engine components, leading to orders of magnitude improvement in damage tolerance. Improved damage tolerance can facilitate inspection, reduce inspection frequency, and improve engine operating margins, all leading to improved military readiness at significantly reduced total costs. Basic understanding of the effects of the different LPB process parameters has evolved, and finite element based compressive residual stress distribution design methodologies have been developed. By incorporating accurate measurement of residual stresses to verify and validate processing, this combined technology leads to a total solutions approach to solve damage problems in engine components. An example of the total solution approach

Musician's brains constitute an interesting model for neuroplasticity. Imaging studies demonstrated that sensorimotor cortical representations are altered in musicians, which was assumed to arise from the development of skilled performance. However, the perceptual consequences of ...

The objective of this review article is to provide a concise discussion of atomistic modeling efforts aimed at understanding the nanoscale behavior and the role of grain boundaries in plasticity of metallic polycrystalline materials. Atomistic simulations of grain boundary behavior during plastic deformation have focused mainly on three distinct configurations: (i) bicrystal models, (ii) columnar nanocrystalline models, and (iii) 3D nanocrystalline models. Bicrystal models facilitate the isolation of specific mechanisms that occur at the grain boundary during plastic deformation, whereas columnar and 3D nanocrystalline models allow for an evaluation of triple junctions and complex stress states characteristic of polycrystalline microstructures. Ultimately, both sets of calculations have merits and are necessary to determine the role of grain boundary structure on material properties. Future directions in grain boundary modeling are discussed, including studies focused on the role of...

The creep of a dislocation on its glide plane is essentially controlled by three different stress fields: the external applied stress, the internal stress field due to a multi-scale hierarchy of different obstacles (the structural defects acting on the dislocation by short-or long-range interactions) and the thermal stress field due to thermal fluctuations. The dislocation glide dynamics involves solution of a string equation, which can be written as a Langevin equation. In this paper, it is shown that general analytical solutions of this equation can be found, allowing calculation of the plastic strain rate and the amplitude-dependent internal friction (ADIF), by using simple assumptions concerning the multi-scale hierarchy of obstacles and the mechanisms of Brownian dislocation creep through the different kinds of interacting obstacles. It is also shown that several experimental observations are well explained by this approach.

Aubin and her coworkers conducted a unique set of experiments demonstrating the influence of loading non-proportionality on ratcheting responses of duplex stainless steel. In order to further explore their new observation, a set of experiments was conducted on stainless steel (SS) 304L under various biaxial stress-controlled non-proportional histories. This new set of data reiterated Aubin and her coworkers’ observation and illustrated many new responses critical to model development and validation. Two recent and different classes of cyclic plasticity models, the modified Chaboche model proposed by Bari and Hassan and the version of the multi-mechanism model proposed by Taleb and Cailletaud, are evaluated in terms of their simulations of the SS304L non-proportional ratcheting responses. A modeling scheme for non-proportional ratcheting responses using the kinematic hardening rule parameters in addition to the conventionally used isotropic hardening rule parameter (yield surface size change) in the modified Chaboche model is evaluated. Strengths and weaknesses of the models in simulating the non-proportional ratcheting responses are identified. Further improvements of these models needed for improving the non-proportional ratcheting simulations are suggested in the paper.

Concrete is considered as a 3-phase composite material; mortar matrix, aggregates, and interfacial transmission zone (ITZ). In order to investigate the contribution of each phase to the strength and damage response of concrete, 2-D and 3-D meso-scale simulations based on a coupled plasticity-damage model are carried out. The aggregates are modeled as a linear-elastic material, whereas the mortar matrix and ITZ are modeled using a coupled plasticity-damage model with different tensile and compressive mechanical behavior. Aggregate shape, distribution, and volume fraction are considered as simulated variables. The effect of the ITZ thickness and the strength of the ITZ and mortar matrix are also evaluated. It is shown that the behavior of concrete is merely dependent on the aggregate distribution and the strength of the mortar matrix, but dependent on aggregate shape, size, and volume fraction, and the thickness and strength of the ITZ.

Biodiesel, as an alternative fuel, is gradually receiving more popularity for use in internal combustion engines. However questions continue to arise with regard to its compatibility with elastomeric materials. The present work aims to investigate the comparative degradation of physical properties for different elastomers [e.g. ethylene propylene diene monomer (EPDM), silicone rubber (SR), polychloroprene (CR), polytetrafluroethylene (PTFE) and nitrile rubber (NBR)] upon exposure to diesel and palm biodiesel. Static immersion tests in B0(diesel), B10 (10% biodiesel in diesel), B20, B50 and B100(biodiesel) were carried out at room temperature (25 °C) for 1000 h. Different physical properties like, changes in weight and volume, hardness and tensile strength were measured at every 250 h of immersion time. Compositional changes in biodiesel due to exposure of different elastomers were investigated by Gas chromatography mass spectroscopy (GCMS). The overall sequence of compatible elastomers in palm biodiesel is found to be PTFE > SR > NBR > EPDM > CR.

http://www.sciencedirect.com/science/article/pii/S0360544210007139

In urban environments, long-term tree survival and performance requires physiological tolerance or phenotypic plasticity in plant functional traits. Knowledge of these traits can inform the likely persistence of urban forests under future, more severe climates. We assessed the plasticity of morphological and physiological traits of tree species planted along an urban climatic gradient in the Greater Sydney region during a severe, multi-year drought in eastern Australia. We selected four sites along a~55 km east-west transect, ranging from the cool/wet coast to the warm/dry inland. We assessed five tree species (four natives, one exotic) with different predicted climatic vulnerability based on climate-origins, estimating functional traits indicative of drought tolerance: carbon isotope composition (δ 13 C), Huber value (HV), specific leaf area (SLA), wood density (WD), and leaf turgor loss point (π tlp). Broadly, trees planted in warm/dry sites had more negative π tlp , higher WD, δ 13 C and HV, and lower SLA than cool/wet sites, indicating phenotypic plasticity to drought. The leaf-level traits π tlp , δ 13 C and SLA were more strongly correlated with temperature and precipitation, compared to HV and WD. Species differed in the extent of their trait shifts along the transect, with greater plasticity evident in the exotic Celtis australis and the more temperate cool-climate Tristaniopsis laurina, compared to the more tropical, warm-climate Cupaniopsis anacardioides, which showed limited plasticity and lower drought tolerance. Our findings reveal adaptive capacity of urban trees to climate via plasticity in drought tolerance traits, which can direct species selection to improve urban forests resistance to climate change.

In this paper, we consider the mechanical response of granular materials and compare the predictions of a hypoplastic model with that of a recently developed dilatant double shearing model which includes the effects of fabric. We implement the constitutive relations of the dilatant double shearing model and the hypoplastic model in the finite element program ABACUS/Explicit and compare their predictions in the triaxial compression and cyclic shear loading tests. Although the origins and the constitutive relations of the double shearing model and the hypoplastic model are quite different, we find that both models are capable of capturing typical behaviours of granular materials. This is significant because while hypoplasticity is phenomenological in nature, the double shearing model is based on a kinematic hypothesis and microstructural considerations, and can easily be calibrated through standard tests. Copyright © 2006 John Wiley & Sons, Ltd.

This contribution examines the magic-realist metaphor of the Matacão in Karen Tei Yamashita's (1990) debut novel Through the Arc of the Rain Forest as a trope that invites us to imagine, reflect on, and explore plastic's cross-cultural meanings, aesthetic experiences, and materialist implications. I contend that through the Matacão, Yamashita engenders a narrative about, as well as an aesthetic experience of, plastic that is inherently ambivalent and paradoxical. While it provides societies with material wealth and sensual pleasures, it poses at the same time a profound threat to life-human and nonhuman. The main part of the article is divided into two major sections: in the first part, I read Yamashita's story about the Matacão as historiographic metafiction that parodies the socio-cultural history of plastic and its utopian promises and failures. In the second part, I draw on Catherine Malabou's philosophical concept of plasticity to explore the Matacão's material agency, as well as the social mobility and economic connectivity of Yamashita's human protagonists in their plastic environments. The theoretical perspective of Malabou's concept of plasticity shifts the focus to the agentic forces of the waste material and allows us to read Yamashita's Matacão as both a site and material that, notwithstanding its devastating impacts, also holds potentialities for resilience and repair, and even the possibility for an, at least temporary, utopia.

This article discusses simulation as an optimal vehicle for brain plasticity, a primary and distinct area of neuroscience and essential to human enhancement. By specu-lating on second-order enhancement cybernetics, the article links the 3D, virtual world of the ...