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1
Miller, Luke E., Matthew R. Longo et Ayse P. Saygin. « Tool Use Modulates Somatosensory Cortical Processing in Humans ». Journal of Cognitive Neuroscience 31, no 12 (décembre 2019) : 1782–95. http://dx.doi.org/10.1162/jocn_a_01452.
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Tool use leads to plastic changes in sensorimotor body representations underlying tactile perception. The neural correlates of this tool-induced plasticity in humans have not been adequately characterized. This study used ERPs to investigate the stage of sensory processing modulated by tool use. Somatosensory evoked potentials, elicited by median nerve stimulation, were recorded before and after two forms of object interaction: tool use and hand use. Compared with baseline, tool use—but not use of the hand alone—modulated the amplitude of the P100. The P100 is a mid-latency component that indexes the construction of multisensory models of the body and has generators in secondary somatosensory and posterior parietal cortices. These results mark one of the first demonstrations of the neural correlates of tool-induced plasticity in humans and suggest that tool use modulates relatively late stages of somatosensory processing outside primary somatosensory cortex. This finding is consistent with what has been observed in tool-trained monkeys and suggests that the mechanisms underlying tool-induced plasticity have been preserved across primate evolution.
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Longo, Matthew R., et Andrea Serino. « Tool use induces complex and flexible plasticity of human body representations ». Behavioral and Brain Sciences 35, no 4 (15 juin 2012) : 229–30. http://dx.doi.org/10.1017/s0140525x11001907.
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AbstractPlasticity of body representation fundamentally underpins human tool use. Recent studies have demonstrated remarkably complex plasticity of body representation in humans, showing that such plasticity (1) occurs flexibly across multiple time scales and (2) involves multiple body representations responding differently to tool use. Such findings reveal remarkable sophistication of body plasticity in humans, suggesting that Vaesen may overestimate the similarity of such mechanisms in humans and non-human primates.
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Ferrara, Antonella, Mariachiara Rapuano et Gennaro Ruggiero. « Social Context and Tool Use Can Modulate Interpersonal Comfort Space ». Journal of Clinical Medicine 12, no 4 (18 février 2023) : 1647. http://dx.doi.org/10.3390/jcm12041647.
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Recent research has investigated whether the representation of space around the body, in terms of reach–action (imagining of reaching another person) and comfort–social (tolerance of the other’s proximity) spaces, may reflect a shared sensorimotor basis. Some studies exploiting motor plasticity induced by tool use have not observed sensorimotor identity (i.e., the same mechanisms that underlie, based on sensory information, the representation of proximal space in terms of action possibilities, goal-directed motor actions, and anticipation of the sensorimotor consequences), whereas evidence to the contrary has also emerged. Since the data are not fully convergent, here we wondered whether or not the combination of motor plasticity induced by tool use and the processing of the role of social context might reflect a similar modulation in both spaces. To this end, we conducted a randomized control trial with three groups of participants (N = 62) in which reaching and comfort distances were measured in Pre- and Post-tool-use sessions. The tool-use sessions were conducted under different conditions: (i) in the presence of a social stimulus (determining the social context) (Tool plus Mannequin group); (ii) without any stimulus (Only Tool group); (iii) in the presence of a box (Tool plus Object group) as a control condition. Results showed an extension of comfort distance in the Post-tool session of the Tool plus Mannequin group compared with the other conditions. Conversely, the reaching distance was larger after tool use than at the Pre-tool-use session, independently of the experimental conditions. Our findings suggest that motor plasticity impacts reaching and comfort spaces to different degrees; while reaching space is markedly sensitive to motor plasticity, comfort space needs qualification of social context information.
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Schaefer, Michael, Yvonne Rothemund, Hans-Jochen Heinze et Michael Rotte. « Short-term plasticity of the primary somatosensory cortex during tool use ». NeuroReport 15, no 8 (juin 2004) : 1293–97. http://dx.doi.org/10.1097/01.wnr.0000129573.36301.db.
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Martel, Marie, Lucilla Cardinali, Alice C. Roy et Alessandro Farnè. « Tool-use : An open window into body representation and its plasticity ». Cognitive Neuropsychology 33, no 1-2 (17 février 2016) : 82–101. http://dx.doi.org/10.1080/02643294.2016.1167678.
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Vaesen, Krist. « The cognitive bases of human tool use ». Behavioral and Brain Sciences 35, no 4 (15 juin 2012) : 203–18. http://dx.doi.org/10.1017/s0140525x11001452.
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AbstractThis article has two goals. The first is to assess, in the face of accruing reports on the ingenuity of great ape tool use, whether and in what sense human tool use still evidences unique, higher cognitive ability. To that effect, I offer a systematic comparison between humans and nonhuman primates with respect to nine cognitive capacities deemed crucial to tool use: enhanced hand-eye coordination, body schema plasticity, causal reasoning, function representation, executive control, social learning, teaching, social intelligence, and language. Since striking differences between humans and great apes stand firm in eight out of nine of these domains, I conclude that human tool use still marks a major cognitive discontinuity between us and our closest relatives. As a second goal of the paper, I address the evolution of human technologies. In particular, I show how the cognitive traits reviewed help to explain why technological accumulation evolved so markedly in humans, and so modestly in apes.
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Wang, Liyu, Luzius Brodbeck et Fumiya Iida. « Mechanics and energetics in tool manufacture and use : a synthetic approach ». Journal of The Royal Society Interface 11, no 100 (6 novembre 2014) : 20140827. http://dx.doi.org/10.1098/rsif.2014.0827.
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Tool manufacture and use are observed not only in humans but also in other animals such as mammals, birds and insects. Manufactured tools are used for biomechanical functions such as effective control of fluids and small solid objects and extension of reaching. These tools are passive and used with gravity and the animal users' own energy. From the perspective of evolutionary biology, manufactured tools are extended phenotypes of the genes of the animal and exhibit phenotypic plasticity. This incurs energetic cost of manufacture as compared to the case with a fixed tool. This paper studies mechanics and energetics aspects of tool manufacture and use in non-human beings. Firstly, it investigates possible mechanical mechanisms of the use of passive manufactured tools. Secondly, it formulates the energetic cost of manufacture and analyses when phenotypic plasticity benefits an animal tool maker and user. We take a synthetic approach and use a controlled physical model, i.e. a robot arm. The robot is capable of additively manufacturing scoop and gripper structures from thermoplastic adhesives to pick and place fluid and solid objects, mimicking primates and birds manufacturing tools for a similar function. We evaluate the effectiveness of tool use in pick-and-place and explain the mechanism for gripper tools picking up solid objects with a solid-mechanics model. We propose a way to formulate the energetic cost of tool manufacture that includes modes of addition and reshaping, and use it to analyse the case of scoop tools. Experiment results show that with a single motor trajectory, the robot was able to effectively pick and place water, rice grains, a pebble and a plastic box with a scoop tool or gripper tools that were manufactured by itself. They also show that by changing the dimension of scoop tools, the energetic cost of tool manufacture and use could be reduced. The work should also be interesting for engineers to design adaptive machines.
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Ferroni, Francesca, Vittorio Gallese, Agata Marta Soccini, Nunzio Langiulli, Francesca Rastelli, Donato Ferri, Francesco Bianchi et Martina Ardizzi. « The Remapping of Peripersonal Space in a Real but Not in a Virtual Environment ». Brain Sciences 12, no 9 (24 août 2022) : 1125. http://dx.doi.org/10.3390/brainsci12091125.
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One of the most surprising features of our brain is the fact that it is extremely plastic. Among the various plastic processes supported by our brain, there is the neural representation of the space surrounding our body, the peripersonal space (PPS). The effects of real-world tool use on the PPS are well known in cognitive neuroscience, but little is still known whether similar mechanisms also govern virtual tool use. To this purpose, the present study investigated the plasticity of the PPS before and after a real (Experiment 1) or virtual motor training with a tool (Experiment 2). The results show the expansion of the PPS only following real-world tool use but not virtual use, highlighting how the two types of training potentially rely on different processes. This study enriches the current state of the art on the plasticity of PPS in real and virtual environments. We discuss our data with respect to the relevance for the development of effective immersive environment for trainings, learning and rehabilitation.
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Sposito, Ambra, Nadia Bolognini, Giuseppe Vallar et Angelo Maravita. « Extension of perceived arm length following tool-use : Clues to plasticity of body metrics ». Neuropsychologia 50, no 9 (juillet 2012) : 2187–94. http://dx.doi.org/10.1016/j.neuropsychologia.2012.05.022.
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Galceran, M., A. Albou, K. Renard, M. Coulombier, P. J. Jacques et S. Godet. « Automatic Crystallographic Characterization in a Transmission Electron Microscope : Applications to Twinning Induced Plasticity Steels and Al Thin Films ». Microscopy and Microanalysis 19, no 3 (3 mai 2013) : 693–97. http://dx.doi.org/10.1017/s1431927613000445.
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AbstractA new automated crystallographic orientation mapping tool in a transmission electron microscope technique, which is based on pattern matching between every acquired electron diffraction pattern and precalculated templates, has been used for the microstructural characterization of nondeformed and deformed aluminum thin films and twinning-induced plasticity steels. The increased spatial resolution and the use of electron diffraction patterns rather than Kikuchi lines make this tool very appropriate to characterize fine grained and deformed microstructures.
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Granados, Karol, Juliane Poelchen, Daniel Novak et Jochen Utikal. « Cellular Reprogramming—A Model for Melanoma Cellular Plasticity ». International Journal of Molecular Sciences 21, no 21 (5 novembre 2020) : 8274. http://dx.doi.org/10.3390/ijms21218274.
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Cellular plasticity of cancer cells is often associated with phenotypic heterogeneity and drug resistance and thus remains a major challenge for the treatment of melanoma and other types of cancer. Melanoma cells have the capacity to switch their phenotype during tumor progression, from a proliferative and differentiated phenotype to a more invasive and dedifferentiated phenotype. However, the molecular mechanisms driving this phenotype switch are not yet fully understood. Considering that cellular heterogeneity within the tumor contributes to the high plasticity typically observed in melanoma, it is crucial to generate suitable models to investigate this phenomenon in detail. Here, we discuss the use of complete and partial reprogramming into induced pluripotent cancer (iPC) cells as a tool to obtain new insights into melanoma cellular plasticity. We consider this a relevant topic due to the high plasticity of melanoma cells and its association with a strong resistance to standard anticancer treatments.
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Bao, Min, et Stephen A. Engel. « Augmented Reality as a Tool for Studying Visual Plasticity : 2009 to 2018 ». Current Directions in Psychological Science 28, no 6 (14 août 2019) : 574–80. http://dx.doi.org/10.1177/0963721419862290.
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Augmented reality (AR) has developed rapidly since its conception less than 30 years ago and is now a hot topic for both consumers and scientists. Although much attention has been paid to its application in industry, medicine, education, and entertainment, the use of AR in psychological research has been less noted. In this article, we survey recent progress in basic research that uses AR to explore the plasticity of the adult visual system. We focus on a particular application of AR called altered reality, which has been used to shed new light on mechanisms of long-term contrast adaptation and ocular-dominance plasticity. The results suggest that AR could also be a useful tool for the treatment of visual disorders.
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Magosso, Elisa, Mauro Ursino, Giuseppe di Pellegrino, Elisabetta Làdavas et Andrea Serino. « Neural bases of peri-hand space plasticity through tool-use : Insights from a combined computational–experimental approach ». Neuropsychologia 48, no 3 (février 2010) : 812–30. http://dx.doi.org/10.1016/j.neuropsychologia.2009.09.037.
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Candini, Michela, Virginia Giuberti, Erica Santelli, Giuseppe di Pellegrino et Francesca Frassinetti. « When social and action spaces diverge : A study in children with typical development and autism ». Autism 23, no 7 (20 janvier 2019) : 1687–98. http://dx.doi.org/10.1177/1362361318822504.
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The space around the body has been defined as action space ( peripersonal space) and a social space ( interpersonal space). Within the current debate about the characteristics of these spaces, here we investigated the functional properties and plasticity of action and social space in developmental age. To these aims, children with typical development and autism spectrum disorders were submitted to Reaching- and Comfort-distance tasks, to assess peripersonal and interpersonal space, respectively. Participants approached a person (confederate) or an object and stopped when they thought they could reach the stimulus (Reaching-distance task), or they felt comfortable with stimulus’ proximity (Comfort-distance task). Both tasks were performed before and after a cooperative tool-use training, in which participant and confederate actively cooperated to reach tokens by using either a long (Experiment 1) or a short (Experiment 2) tool. Results showed that in both groups, peripersonal space extended following long-tool-use but not short-tool-use training. Conversely, in typical development, but not in autism spectrum disorders children, interpersonal space toward confederate reduced following the cooperative tool-use training. These findings reveal that action and social spaces are functionally dissociable both in typical and atypical development, and that action but not social space regulation is intact in children with autism.
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Nourani, Sia A., Dirk J. Pons, Digby Symons et Senlin Zhang. « Multiscale Analogue Modelling of Clinching Process to Investigate Thickness Tolerance and Tool Misalignment ». Materials 15, no 10 (20 mai 2022) : 3674. http://dx.doi.org/10.3390/ma15103674.
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NEED—The effect of dimensional variability of sheet thickness (tolerance) and tool misalignment is poorly understood for the clinching process. Finite element analysis (FEA) is valuable but requires a lot of and is difficult to verify in this situation due to the asymmetrical geometry and nonlinear plasticity. OBJECTIVE—The objective of this work was to determine the effect of thickness tolerance, tool misalignment and sheet placement (top vs. bottom) in the clinching process, by use of analogue modelling with plasticine. METHOD—Experiments used a scaled-up punch and die, with plasticine as the analogue. Thickness tolerances were represented by sheet thicknesses of 11 and 7 mm, 12 and 8 mm, 8 and 12 mm and 13 and 9 mm for upper and lower sheets, respectively. Two types of lubricant were tested between sheets: glycerine and silicone oil. Angular variability was also introduced. Measured parameters were interlock (also called undercut) and neck thickness. Analogue results for deformation were compared with microscopy of metal clinching. FINDINGS—The results reveal that the multiscale analogue model is an efficient tool for studying the effect of dimensional deviation on a clinch joint. Thickness tolerance showed a critical relationship with interlock, namely a reduction to about half that of the nominal, for both maximum and least material conditions. Increased angular misalignment also reduced the interlock. Compared with glycerine, silicone oil tests showed reduced interlock, possibly the result of a lower coefficient of friction. ORIGINALITY—This work demonstrates the usefulness of analogue modelling for exploring process variability in clinching. The results also show that significant effects for sheet placement are ductility, lubricant (friction), thickness of samples and tool misalignment.
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Betti, Sonia, Andrea Spoto, Umberto Castiello et Luisa Sartori. « Testing rTMS-Induced Neuroplasticity : A Single Case Study of Focal Hand Dystonia ». Neural Plasticity 2018 (30 mai 2018) : 1–12. http://dx.doi.org/10.1155/2018/6464896.
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Focal hand dystonia in musicians is a neurological motor disorder in which aberrant plasticity is caused by excessive repetitive use. This work’s purposes were to induce plasticity changes in a dystonic musician through five daily thirty-minute sessions of 1 Hz repetitive transcranial magnetic stimulation (rTMS) applied to the left M1 by using neuronavigated stimulation and to reliably measure the effect of these changes. To this aim, the relationship between neuroplasticity changes and motor recovery was investigated using fine-grained kinematic analysis. Our results suggest a statistically significant improvement in motor coordination both in a task resembling the dystonic-inducing symptoms and in a reach-to-grasp task. This single case study supports the safe and effective use of noninvasive brain stimulation in neurologic patients and highlights the importance of evaluating outcomes in measurable ways. This issue is a key aspect to focus on to classify the clinical expression of dystonia. These preliminary results promote the adoption of kinematic analysis as a valuable diagnostic tool.
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Parish, Y., M. Sadek et I. Shahrour. « Review Article : Numerical analysis of the seismic behaviour of earth dam ». Natural Hazards and Earth System Sciences 9, no 2 (23 mars 2009) : 451–58. http://dx.doi.org/10.5194/nhess-9-451-2009.
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Abstract. The present study concerns analysis of the seismic response of earth dams. The behaviour of both the shell and core of the dam is described using the simple and popular non associated Mohr-Coulomb criterion. The use of this constitutive model is justified by the difficulty to obtain constitutive parameters for more advanced constitutive relations including isotropic and kinematic hardening. Analyses with real earthquake records show that the seismic loading induces plasticity in a large part of the shell and in the lower part of the core. Analysis shows that plasticity should be considered in the analysis of the seismic response of the dam, because it leads to a decrease in the natural frequencies of the dam together to energy dissipation, which could significantly affect the seismic response of the dam. Plastic analysis constitutes also a good tool for the verification of the stability of the dam under seismic loading.
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Loginov, Yuriy, et Yuliya Zamaraeva. « Invariant stress state parameters for forging upsetting of magnesium in the shell ». Metal Working and Material Science 23, no 1 (15 mars 2021) : 79–88. http://dx.doi.org/10.17212/1994-6309-2021-23.1-79-88.
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Introduction. For pressure treatment of low-plastic metals, it is necessary to develop special techniques for increasing plasticity. In the cold state, an increase in plastic properties is possible due to an increase in the level of compressive stresses during deformation. In the processes of forging precipitation, this is achieved by using shells or clips of various types. At the same time, the configuration of the precipitation tool also matters. To create additional compressive stresses and increase the ductility of the metal, the working surface of the tool can be configured differently than with a normal free draft, where it is obviously larger than the contact surface area of the workpiece, so that metal broadening can occur. The stress state has a great influence on the plasticity of the processed material. This state is described by methods of tensor representation, but to assess the situation, it is customary to use invariants of tensors in one form or another, which eliminates the influence of coordinates on the results of the analysis. In the sections of deformable body mechanics dealing with the influence of the stress state on plasticity, the first, but sometimes other invariants of the stress tensor are used, the invariants themselves are transformed into the stress state indicator and the lode coefficient. The aim of the work: mathematical evaluation of invariant parameters of the stress state of the magnesium precipitation process at room temperature, according to the results of which it is possible to obtain a positive result in real experiments. Research methods: finite element simulation using the DEFORM software module. Results and discussion. The theoretical justification of increasing the plasticity of the magnesium billet in the process of precipitation in the cage without its compression is carried out. An increase in the stress state index modulo 2...5 times is revealed, which contributes to an increase in the plasticity of the metal. At the same time, a zone with a lode coefficient close to zero is identified. It is adjacent to the middle of the height of the workpiece at the point of contact with the cage and can be a dangerous cross-section from the position of crack formation.
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Beier, M., M. Baum, H. Rebscher, R. Mauritz, A. Wixmerten, C. F. Stähler, M. Müller et P. F. Stähler. « Exploring Nature's plasticity with a flexible probing tool, and finding new ways for its electronic distribution ». Biochemical Society Transactions 30, no 2 (1 avril 2002) : 78–82. http://dx.doi.org/10.1042/bst0300078.
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Concepts and results are described for the use of a single, but extremely flexible, probing tool to address a wide variety of genomic questions. This is achieved by transforming genomic questions into a software file that is used as the design scheme for potentially any genomic assay in a microarray format. Microarray fabrication takes place in three-dimensional microchannel reaction carriers by in situ synthesis based on spatial light modulation. This set-up allows for maximum flexibility in design and realization of genomic assays. Flexibility is achieved at the molecular, genomic and assay levels. We have applied this technology to expression profiling and genotyping experiments.
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Milman, Yu V., B. M. Mordyuk, K. E. Grinkevych, S. I. Chugunova, I. V. Goncharova, A. I. Lukyanov et D. A. Lesyk. « New Opportunities to Determine the Rate of Wear of Materials at Friction by the Indentation Data ». Uspehi Fiziki Metallov 21, no 4 (décembre 2020) : 554–79. http://dx.doi.org/10.15407/ufm.21.04.554.
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The article is concerned with the determination of physical plasticity δH (the ratio of the plastic strain to the total strain) and yield stress σS by indentation and the application of these characteristics for analysis of the wear rate W during the friction. The experimental part of the work is performed on the AISI O2 and AISI D2 steels, the surface layers of which were hardened by combined thermomechanical treatment consisted of sequential use of laser heat treatment and ultrasonic impact treatment. For the metals, W is shown to be proportional to δH and inversely proportional to σS. The general scheme for the dependence of W on δH is proposed and based on experimental results for tool steels and hard alloys. For the steels, whose wear is caused by the plastic deformation, W increases with increasing δH, and it decreases conversely for hard alloys worn predominantly by the fracture mechanism. The use of physical plasticity δH and yield stress σS, which are calculated using the hardness and Young’s modulus, characterizes both the hardening extent and the wear rate of the surface layers in more full measure and more accurately than the hardness magnitude itself.
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Kochetov, A. N., E. I. Fisunova, T. V. Lavrenova et L. A. Filonenko. « Wear resistance discrete management of formative tool ». Journal of Physics : Conference Series 2131, no 5 (1 décembre 2021) : 052040. http://dx.doi.org/10.1088/1742-6596/2131/5/052040.
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Abstract The article is devoted to the organization of management of the application of wear-resistant materials on the formative tool at set intervals by the method of electro-acoustic spraying. A complex highly concentrated effect of the ultrasonic method in a permanent process, based on the pulse energy, which leads to an increase in the plasticity of the material and is not associated with its heating. The law of electro-plastic deformation for a conducting material, taking into account the high density of the acting amperage in the process of active deformation at a constant rate, considered in this article, establishes a clear dependence of the strengthening of the substrate material. The process of concentration of electromagnetic and thermal fields in a conductive material with defects such as a crack makes it possible to use this technology to slow down the propagation of cracks while reducing the concentration of mechanical stresses.
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Koeberle, Alexander L., Ivan Arismendi, Whitney Crittenden, Cecilia Di Prinzio, Daniel Gomez-Uchida, David L. G. Noakes et Shannon Richardson. « Otolith shape as a classification tool for Chinook salmon (Oncorhynchus tshawytscha) discrimination in native and introduced systems ». Canadian Journal of Fisheries and Aquatic Sciences 77, no 7 (juillet 2020) : 1172–88. http://dx.doi.org/10.1139/cjfas-2019-0280.
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Chinook salmon (Oncorhynchus tshawytscha) are widely distributed across the globe, with native stocks in the North Pacific Ocean and self-sustained populations in both the Northern and Southern hemispheres. In their native range, Chinook salmon face many conservation and management challenges, including depleted stocks, loss of genetic diversity, and hatchery influences, whereas naturalized range expansion poses a threat to novel ecosystems. Therefore, ways to improve stock discrimination would be a useful tool for fishery managers. Here, we evaluated otolith shape variation in Chinook salmon as a potential tool for stock discrimination using wavelet coefficients and Fourier harmonics in three case studies at multiple spatial scales. We adopted a simple Classification Tree model that used otolith shape variation to separate Chinook salmon groups. We found best performance of the model occurring between hemispheres, followed by Oregon basins, within-watershed Elk River, Oregon, and lastly among South American basins. Otolith shape analysis is a promising tool for stock discrimination if used in conjunction with other methods to better understand plasticity of anadromous species that use pan-environmental systems.
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Omelyanov, Oleg, Yurii Polievoda et Mykhailo Zamriі. « PROSPECTS FOR THE USE OF VIBRATION DURING CUTTING MATERIAL ». Vibrations in engineering and technology, no 1(100) (23 mars 2021) : 100–110. http://dx.doi.org/10.37128/2306-8744-2021-1-10.
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Vibration is considered one of the effective ways to sharpen billets from difficult materials. The rational purpose of cutting modes with such a process allows you to increase the resistance of the metal-cutting tool, contributes to the creation of conditions to ensure constant crushing of chips. When cutting materials on the lathes of a turning group with the imposition of oscillations to the cutting tool, processes occur in the cutting zone, which differ from the processes arising from sharpening without oscillations. The article discusses the possibilities of using vibration oscillations when cutting materials. Currently, new materials that have high strength characteristics, viscosity and plasticity are widely used in mechanical engineering, with an increase in the processability: cutting force increases and efficient power spent on cutting; The quality of surface roughness is worsen; the resistance of the cutting tool is reduced; The amount of heat formed in the cutting zone increases and the character of its distribution on the surfaces of the workpiece and the tool changes; the process of forming chips, its shrinkage and type; The intensity of the process of formation of outflow and its form. In this regard, the question arises about the search for rational processing methods, in particular, mechanical processing with cutting on lathes. In this scientific work, the use of low-frequency oscillations is substantiated, which is the complex vibrational effect on the cutting process with the enforcement of solid chips, removal from the top of the cutter and preventing its formation, while ensuring the presence of a given roughness of the treated surface and an increase in the cutter resistance period. Research work in this direction is relevant and requires further research.
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Kaljuzhnyj, V. L., et V. V. Pimanov. « Cold extrusion with differentiated counter-pressure of die cavities ». Izvestiya MGTU MAMI 7, no 2-2 (20 mars 2013) : 32–37. http://dx.doi.org/10.17816/2074-0530-67982.
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The article describes the engineering method to obtain the correlation for the determination of stresses on the contact surfaces of the workpiece and the tool, the efforts of the extrusion of cavities by spherical die. It shows numerical simulations made on computer simulation by the finite element method on examples of extrusion by spherical die of billets made of R6M5 (Р6М5) steel under the action of counter-pressure on the free surface of the workpiece. The paper contains the definition of the maximum counter-pressure through simulation that provides extrusion without destruction and the efforts of the processes, the distribution of stresses in the deforming tool and the stress-strain state, the degree of resource use of metal plasticity, as well as the final product dimensions. The article contains a description of the experiment on the extrusion billets of steel R6M5 (Р6М5) spherical die.
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Sebastiani, Giorgia, Laura Almeida-Toledano, Mariona Serra-Delgado, Elisabet Navarro-Tapia, Sebastian Sailer, Olga Valverde, Oscar Garcia-Algar et Vicente Andreu-Fernández. « Therapeutic Effects of Catechins in Less Common Neurological and Neurodegenerative Disorders ». Nutrients 13, no 7 (29 juin 2021) : 2232. http://dx.doi.org/10.3390/nu13072232.
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In recent years, neurological and neurodegenerative disorders research has focused on altered molecular mechanisms in search of potential pharmacological targets, e.g., imbalances in mechanisms of response to oxidative stress, inflammation, apoptosis, autophagy, proliferation, differentiation, migration, and neuronal plasticity, which occur in less common neurological and neurodegenerative pathologies (Huntington disease, multiple sclerosis, fetal alcohol spectrum disorders, and Down syndrome). Here, we assess the effects of different catechins (particularly of epigalocatechin-3-gallate, EGCG) on these disorders, as well as their use in attenuating age-related cognitive decline in healthy individuals. Antioxidant and free radical scavenging properties of EGCG -due to their phenolic hydroxyl groups-, as well as its immunomodulatory, neuritogenic, and autophagic characteristics, makes this catechin a promising tool against neuroinflammation and microglia activation, common in these pathologies. Although EGCG promotes the inhibition of protein aggregation in experimental Huntington disease studies and improves the clinical severity in multiple sclerosis in animal models, its efficacy in humans remains controversial. EGCG may normalize DYRK1A (involved in neural plasticity) overproduction in Down syndrome, improving behavioral and neural phenotypes. In neurological pathologies caused by environmental agents, such as FASD, EGCG enhances antioxidant defense and regulates placental angiogenesis and neurodevelopmental processes. As demonstrated in animal models, catechins attenuate age-related cognitive decline, which results in improvements in long-term outcomes and working memory, reduction of hippocampal neuroinflammation, and enhancement of neuronal plasticity; however, further studies are needed. Catechins are valuable compounds for treating and preventing certain neurodegenerative and neurological diseases of genetic and environmental origin. However, the use of different doses of green tea extracts and EGCG makes it difficult to reach consistent conclusions for different populations.
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Black, Bryan J., Aswini Kanneganti, Alexandra Joshi-Imre, Rashed Rihani, Bitan Chakraborty, Justin Abbott, Joseph J. Pancrazio et Stuart F. Cogan. « Chronic recording and electrochemical performance of Utah microelectrode arrays implanted in rat motor cortex ». Journal of Neurophysiology 120, no 4 (1 octobre 2018) : 2083–90. http://dx.doi.org/10.1152/jn.00181.2018.
Texte intégralRésumé :
Multisite implantable electrode arrays serve as a tool to understand cortical network connectivity and plasticity. Furthermore, they enable electrical stimulation to drive plasticity, study motor/sensory mapping, or provide network input for controlling brain-computer interfaces. Neurobehavioral rodent models are prevalent in studies of motor cortex injury and recovery as well as restoration of auditory/visual cues due to their relatively low cost and ease of training. Therefore, it is important to understand the chronic performance of relevant electrode arrays in rodent models. In this report, we evaluate the chronic recording and electrochemical performance of 16-channel Utah electrode arrays, the current state-of-the-art in pre-/clinical cortical recording and stimulation, in rat motor cortex over a period of 6 mo. The single-unit active electrode yield decreased from 52.8 ± 10.0 ( week 1) to 13.4 ± 5.1% ( week 24). Similarly, the total number of single units recorded on all electrodes across all arrays decreased from 106 to 15 over the same time period. Parallel measurements of electrochemical impedance spectra and cathodic charge storage capacity exhibited significant changes in electrochemical characteristics consistent with development of electrolyte leakage pathways over time. Additionally, measurements of maximum cathodal potential excursion indicated that only a relatively small fraction of electrodes (10–35% at 1 and 24 wk postimplantation) were capable of delivering relevant currents (20 µA at 4 nC/ph) without exceeding negative or positive electrochemical potential limits. In total, our findings suggest mainly abiotic failure modes, including mechanical wire breakage as well as degradation of conducting and insulating substrates. NEW & NOTEWORTHY Multisite implantable electrode arrays serve as a tool to record cortical network activity and enable electrical stimulation to drive plasticity or provide network feedback. The use of rodent models in these fields is prevalent. We evaluated chronic recording and electrochemical performance of 16-channel Utah electrode arrays in rat motor cortex over a period of 6 mo. We primarily observed abiotic failure modes suggestive of mechanical wire breakage and/or degradation of insulation.
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Del Guerra, Alberto, Salleh Ahmad, Mihai Avram, Nicola Belcari, Arne Berneking, Laura Biagi, Maria Giuseppina Bisogni et al. « TRIMAGE : A dedicated trimodality (PET/MR/EEG) imaging tool for schizophrenia ». European Psychiatry 50 (avril 2018) : 7–20. http://dx.doi.org/10.1016/j.eurpsy.2017.11.007.
Texte intégralRésumé :
AbstractSimultaneous PET/MR/EEG (Positron Emission Tomography – Magnetic Resonance – Electroencephalography), a new tool for the investigation of neuronal networks in the human brain, is presented here within the framework of the European Union Project TRIMAGE. The trimodal, cost-effective PET/MR/EEG imaging tool makes use of cutting edge technology both in PET and in MR fields. A novel type of magnet (1.5T, non-cryogenic) has been built together with a PET scanner that makes use of the most advanced photodetectors (i.e., SiPM matrices), scintillators matrices (LYSO) and digital electronics. The combined PET/MR/EEG system is dedicated to brain imaging and has an inner diameter of 260 mm and an axial Field-of-View of 160 mm.It enables the acquisition and assessment of molecular metabolic information with high spatial and temporal resolution in a given brain simultaneously. The dopaminergic system and the glutamatergic system in schizophrenic patients are investigated via PET, the same physiological/pathophysiological conditions with regard to functional connectivity, via fMRI, and its electrophysiological signature via EEG. In addition to basic neuroscience questions addressing neurovascular-metabolic coupling, this new methodology lays the foundation for individual physiological and pathological fingerprints for a wide research field addressing healthy aging, gender effects, plasticity and different psychiatric and neurological diseases.The preliminary performances of two components of the imaging tool (PET and MR) are discussed. Initial results of the search of possible candidates for suitable schizophrenia biomarkers are also presented as obtained with PET/MR systems available to the collaboration.
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Scriabin, Vladimir. « FEATURES OF MACHINING PARTS MADE OF POLYMER MATERIALS WITH EDGE TOOLS ». Transport engineering 2022, no 5 (5 mai 2022) : 13–21. http://dx.doi.org/10.30987/2782-5957-2022-5-13-21.
Texte intégralRésumé :
The study objective is to select the tool cutting part materials and to assign the operating parameters taking into account the properties of polymer materials that characterize their machinability. The problems to which the paper is devoted are experimental studies of ways to expand the technological capabilities of cutting polymer materials. Research methods: experimental studies are conducted on the basis of the main provisions of the engineering technology, the theory of elasticity and plasticity. Experimental studies are carried out according to standard methods in production and laboratory conditions with the use of certified control and measuring equipment. The obtained data are processed using computational techniques and presented in the form of empirical dependencies convenient for practical application. The novelty of the work consists in conducting experimental studies of choosing materials for the tool cutting parts and their design features and geometric parameters, as well as in obtaining the operating parameters of machining parts made of polymer materials.
Conclusions: On the basis of experimental studies, the ways of expanding the technological capabilities of cutting polymer materials are chosen.
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Bengoetxea, Harkaitz, Naiara Ortuzar, Susana Bulnes, Irantzu Rico-Barrio, José Vicente Lafuente et Enrike G. Argandoña. « Enriched and Deprived Sensory Experience Induces Structural Changes and Rewires Connectivity during the Postnatal Development of the Brain ». Neural Plasticity 2012 (2012) : 1–10. http://dx.doi.org/10.1155/2012/305693.
Texte intégralRésumé :
During postnatal development, sensory experience modulates cortical development, inducing numerous changes in all of the components of the cortex. Most of the cortical changes thus induced occur during the critical period, when the functional and structural properties of cortical neurons are particularly susceptible to alterations. Although the time course for experience-mediated sensory development is specific for each system, postnatal development acts as a whole, and if one cortical area is deprived of its normal sensory inputs during early stages, it will be reorganized by the nondeprived senses in a process of cross-modal plasticity that not only increases performance in the remaining senses when one is deprived, but also rewires the brain allowing the deprived cortex to process inputs from other senses and cortices, maintaining the modular configuration. This paper summarizes our current understanding of sensory systems development, focused specially in the visual system. It delineates sensory enhancement and sensory deprivation effects at both physiological and anatomical levels and describes the use of enriched environment as a tool to rewire loss of brain areas to enhance other active senses. Finally, strategies to apply restorative features in human-deprived senses are studied, discussing the beneficial and detrimental effects of cross-modal plasticity in prostheses and sensory substitution devices implantation.
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Franz, C., G. Besserdich, V. Schulze, H. Müller et D. Löhe. « Influence of transformation plasticity on residual stresses and distortions due to the heat treatment of steels with different carbon contents ». Journal de Physique IV 120 (décembre 2004) : 481–88. http://dx.doi.org/10.1051/jp4:2004120055.
Texte intégralRésumé :
The simulation of manufacturing processes is more and more becoming an important tool in simultaneous engineering. The aim is to cut the time necessary for development and to optimise processes by simulation of the complete manufacturing chain. The field of heat treatment offers a large variety of applications for the use of simulation tools. Heat treatment of steels always includes the development of residual stresses and distortions. The geometry of the part, the composition of the material, the heat treatment process as well as the initial state of the part interact with each other in complex ways and have an influence on the distortion of the part. Using simulation the temporal development of temperature, phases, stresses and distortions while quenching as well as the residual stress distribution and distortion after quenching can be calculated. Transformation plasticity has been proved to be very important for heat treatment simulation. Three steels with identical contents of alloying elements but different carbon contents of 0.2, 0.5 and 0.8 wt.-% were analysed. The transformation plasticity constants for the martensitic transformation under tensile as well as compressive stresses were determined by quenching hollow specimen with nitrogen. Distortions and residual stresses were examined experimentally with cylinders made out of the three steels. Additionally, simulations of the quenching process of the cylinders were taken into account in the analysis of the experimental findings.
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Rondini, Elizabeth A., et James G. Granneman. « Single cell approaches to address adipose tissue stromal cell heterogeneity ». Biochemical Journal 477, no 3 (6 février 2020) : 583–600. http://dx.doi.org/10.1042/bcj20190467.
Texte intégralRésumé :
A central function of adipose tissue is in the management of systemic energy homeostasis that is achieved through the co-ordinated regulation of energy storage and mobilization, adipokine release, and immune functions. With the dramatic increase in the prevalence of obesity and obesity-related metabolic disease over the past 30 years, there has been extensive interest in targeting adipose tissue for therapeutic benefit. However, in order for this goal to be achieved it is essential to establish a comprehensive atlas of adipose tissue cellular composition and define mechanisms of intercellular communication that mediate pathologic and therapeutic responses. While traditional methods, such as fluorescence-activated cell sorting (FACS) and genetic lineage tracing, have greatly advanced the field, these approaches are inherently limited by the choice of markers and the ability to comprehensively identify and characterize dynamic interactions among stromal cells within the tissue microenvironment. Single cell RNA sequencing (scRNAseq) has emerged as a powerful tool for deconvolving cellular heterogeneity and holds promise for understanding the development and plasticity of adipose tissue under normal and pathological conditions. scRNAseq has recently been used to characterize adipose stem cell (ASC) populations and has provided new insights into subpopulations of macrophages that arise during anabolic and catabolic remodeling in white adipose tissue. The current review summarizes recent findings that use this technology to explore adipose tissue heterogeneity and plasticity.
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Matviychuk, Viktor, et Oleg Gaidamak. « INCREASING OF THE DURABILITY OF DETAILS WORKING UNDER REPEATABLE- LOADS ». Vibrations in engineering and technology, no 1(96) (27 août 2020) : 5–14. http://dx.doi.org/10.37128/2306-8744-2020-1-1.
Texte intégralRésumé :
The article develops processes of increase the durability of parts operating under repeated loads, by justifying the parameters of surface plastic deformation (SPD) and cold gas-dynamic coating. The influence on the depth of the reinforced surface layer, the nature of the distribution of the stress-strain state of the material and residual compressive stresses, as well as the value of the used plasticity of the metal, the parameters of the SPD process. The hypothesis is substantiated that the main factor in the formation of residual compressive stresses during SPD is the decrease in metal density, which is associated with the use of the plasticity resource. The model of definition of the used resource of plasticity of metals at SPD is developed, that allows to provide qualitative characteristics of a surface layer of details. Methods for shifting the layer with maximum hardening and residual compressive stresses to the surface of the part by using a deformable tool of smaller dimensions in subsequent passes and gas-dynamic coating before SPD. The vast majority of traditional gas-thermal coating methods occur at significant temperature effects on the surface of the part, which is unacceptable for the surface treated by SPD methods. Cold gas-dynamic spraying provides an allowable temperature regime for the creation of special auxiliary coatings while maintaining the properties of the surface treated by SPD methods. The technology of gas-dynamic coating includes heating the compressed gas (air), feeding it into the nozzle and forming a supersonic air stream in this nozzle, introducing a powder material into this stream, accelerating this material in the nozzle by a supersonic air flow and directing it to the surface of the workpiece. As a result, a special auxiliary coating is formed on the surface of the product, which provides optimal parameters of the SPD process.
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Beretta, Carlo Antonio, Sheng Liu, Alina Stegemann, Zheng Gan, Lirong Wang, Linette Liqi Tan et Rohini Kuner. « Quanty-cFOS, a Novel ImageJ/Fiji Algorithm for Automated Counting of Immunoreactive Cells in Tissue Sections ». Cells 12, no 5 (23 février 2023) : 704. http://dx.doi.org/10.3390/cells12050704.
Texte intégralRésumé :
Analysis of neural encoding and plasticity processes frequently relies on studying spatial patterns of activity-induced immediate early genes’ expression, such as c-fos. Quantitatively analyzing the numbers of cells expressing the Fos protein or c-fos mRNA is a major challenge owing to large human bias, subjectivity and variability in baseline and activity-induced expression. Here, we describe a novel open-source ImageJ/Fiji tool, called ‘Quanty-cFOS’, with an easy-to-use, streamlined pipeline for the automated or semi-automated counting of cells positive for the Fos protein and/or c-fos mRNA on images derived from tissue sections. The algorithms compute the intensity cutoff for positive cells on a user-specified number of images and apply this on all the images to process. This allows for the overcoming of variations in the data and the deriving of cell counts registered to specific brain areas in a highly time-efficient and reliable manner. We validated the tool using data from brain sections in response to somatosensory stimuli in a user-interactive manner. Here, we demonstrate the application of the tool in a step-by-step manner, with video tutorials, making it easy for novice users to implement. Quanty-cFOS facilitates a rapid, accurate and unbiased spatial mapping of neural activity and can also be easily extended to count other types of labelled cells.
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Lopez-Crespo, Pablo, A. Shterenlikht, Eann A. Patterson, J. R. Yates et Philip J. Withers. « Fatigue Crack Monitoring Using Image Correlation ». Key Engineering Materials 385-387 (juillet 2008) : 341–44. http://dx.doi.org/10.4028/www.scientific.net/kem.385-387.341.
Texte intégralRésumé :
A novel methodology based on a combination of experimental and analytical methods is used for monitoring the stress intensity factor in fatigue cracks subjected to constant amplitude loads. Full-field displacement information is fitted, following a multi-point over-deterministic approach, to an analytical model. This is developed from Muskhelishvili’s complex formulation. The methodology allowed accurate monitoring of the stress intensity factor during three fatigue cycles when small-scale yielding conditions were achieved. Moreover for larger loads where important plastic deformation occurs around the crack tip, Dugdale’s correction accounted for the differences between theoretical and calculated stress intensity factors. Accordingly the tool provides an indirect approach for measuring crack tip plasticity. Due to the fact that image correlation is relatively simple to use and is a non-contacting technique, the approach pioneered in this work seems ideal for monitoring fatigue cracks in industrial applications.
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Rohit, Nikisha, et Hitesh Solanki. « A REVIEW METHOD FOR IDENTIFICATION OF RARE AND ENDANGERED PLANTS THROUGH DNA BARCODING ». International Association of Biologicals and Computational Digest 1, no 2 (5 octobre 2022) : 31–35. http://dx.doi.org/10.56588/iabcd.v1i2.39.
Texte intégralRésumé :
DNA barcoding is a new concept. It has been developed for providing fast, precise and automatable species identification which uses standardized DNA sequences as tags. DNA barcoding can provide the taxonomists; conservationists. The early goal of the DNA barcoding process is to build online libraries of barcode sequences for all known species that can serve as a standard to which DNA barcodes of any identified or unidentified specimens can be matched. This can improve several inherent problems related with traditional taxonomic identification, based on morphological characters, such as incorrect identification of species due to phenotypic plasticity and genotypic variability of the characters, such as incorrect identification of species due to phenotypic plasticity and genotypic variability of the characters, overlooking cryptic taxa, difficulty in finding reliable characters due to long maturity periods (CBOL Plant Working Group, 2009). It is particularly of much use in areas where species identification with morphological characters is not practicable due to widespread damage or delayed expression. It should be enduring in mind that DNA barcoding is not an alternative to taxonomy, and it cannot replace taxonomy as such, but is a useful tool that creates information on unknown taxa. In this paper, methods of the process of selecting and redefining barcodes for plants evaluation of the factors which manipulate the discriminatory power of the advance with some early applications of DNA barcoding are discussed and then added the authors’ for their views and recommendations.
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MacDonald, Monica A., Hawazin Khan, Sarah N. Kraeutner, Francesco Usai, Emily A. Rogers, Derek S. Kimmerly, Gail Dechman et Shaun G. Boe. « Intensity of acute aerobic exercise but not aerobic fitness impacts on corticospinal excitability ». Applied Physiology, Nutrition, and Metabolism 44, no 8 (août 2019) : 869–78. http://dx.doi.org/10.1139/apnm-2018-0643.
Texte intégralRésumé :
Aerobic exercise (AE) modulates cortical excitability. It can alter both corticospinal excitability and intra-cortical networks, which has implications for its use as a tool to facilitate processes such as motor learning, where increased levels of excitability are conducive to the induction of neural plasticity. Little is known about how different intensities of AE modulate cortical excitability or how individual-level characteristics impact on it. Therefore, we investigated whether AE intensities, lower than those previously employed, would be effective in increasing cortical excitability. We also examined whether the aerobic fitness of individual participants was related to the magnitude of change in AE-induced cortical excitability. In both experiments we employed transcranial magnetic stimulation to probe corticospinal excitability before and after AE. We show that 20 min of continuous moderate- (40% and 50% of heart rate reserve, HRR), but not low- (30% HRR) intensity AE was effective at increasing corticospinal excitability. We also found that while we observed increased corticospinal excitability following 20 min of continuous moderate-intensity (50% HRR) AE, aerobic fitness was not related to the magnitude of change. Our results suggest that there is a lower bound intensity of AE that is effective at driving changes in cortical excitability, and that while individual-level characteristics are important predictors of response to AE, aerobic fitness is not. Overall these findings have implication for the way that AE is used to facilitate processes such as motor learning, where increased levels of cortical excitability and plasticity are favourable.
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Olsen, Christopher M., Yong Huang, Shirlean Goodwin, Daniel C. Ciobanu, Lu Lu, Thomas R. Sutter et Danny G. Winder. « Microarray analysis reveals distinctive signaling between the bed nucleus of the stria terminalis, nucleus accumbens, and dorsal striatum ». Physiological Genomics 32, no 3 (février 2008) : 283–98. http://dx.doi.org/10.1152/physiolgenomics.00224.2006.
Texte intégralRésumé :
To identify distinct transcriptional patterns between the major subcortical dopamine targets commonly studied in addiction we studied differences in gene expression between the bed nucleus of the stria terminalis (BNST), nucleus accumbens (NAc), and dorsal striatum (dStr) using microarray analysis. We first tested for differences in expression of genes encoding transcripts for common neurotransmitter systems as well as calcium binding proteins routinely used in neuroanatomical delineation of brain regions. This a priori method revealed differential expression of corticotropin releasing hormone ( Crh), the GABA transporter ( Slc6a1), and prodynorphin ( Pdyn) mRNAs as well as several others. Using a gene ontology tool, functional scoring analysis, and Ingenuity Pathway Analysis, we further identified several physiological pathways that were distinct among these brain regions. These two different analyses both identified calcium signaling, G-coupled protein receptor signaling, and adenylate cyclase-related signaling as significantly different among the BNST, NAc, and dStr. These types of signaling pathways play important roles in, amongst other things, synaptic plasticity. Investigation of differential gene expression revealed several instances that may provide insight into reported differences in synaptic plasticity between these brain regions. The results support other studies suggesting that crucial pathways involved in neurotransmission are distinct among the BNST, NAc, and dStr and provide insight into the potential use of pharmacological agents that may target region-specific signaling pathways. Furthermore, these studies provide a framework for future mouse-mouse comparisons of transcriptional profiles after behavioral/pharmacological manipulation.
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Brevini, T. A. L., G. Pennarossa, S. Maffei et F. Gandolfi. « Phenotype switching through epigenetic conversion ». Reproduction, Fertility and Development 27, no 5 (2015) : 776. http://dx.doi.org/10.1071/rd14246.
Texte intégralRésumé :
Different cell types have been suggested as candidates for use in regenerative medicine. Embryonic pluripotent stem cells can give rise to all cells of the body and possess unlimited self-renewal potential. However, they are unstable, difficult to control and have a risk of neoplastic transformation. Adult stem cells are safe but have limited proliferation and differentiation abilities and are usually not within easy access. In recent years, induced pluripotent stem (iPS) cells have become a new promising tool in regenerative medicine. However, the use of transgene vectors, commonly required for the induction of iPS cells, seriously limits their use in therapy. The same problem arising from the use of retroviruses is associated with the use of cells obtained through transdifferentiation. Developing knowledge of the mechanisms controlling epigenetic regulation of cell fate has boosted the use of epigenetic modifiers that drive cells into a ‘highly permissive’ state. We recently set up a new strategy for the conversion of an adult mature cell into another cell type. We increased cell plasticity using 5-aza-cytidine and took advantage of a brief window of epigenetic instability to redirect cells to a different lineage. This approach is termed ‘epigenetic conversion’. It is a simple, direct and safe way to obtain both cells for therapy avoiding gene transfection and a stable pluripotent state.
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Korsakova, S. P., et A. K. Sharmagiy. « Phenotypic plasticity of the Cydalima perspectalis Walker life cycle stages development in the Crimea ». Plant Biology and Horticulture : theory, innovation, no 160 (9 novembre 2021) : 63–75. http://dx.doi.org/10.36305/2712-7788-2021-3-160-63-75.
Texte intégralRésumé :
The box tree moth ( Cydalima perspectalis Walker) is an invasive insect that has rapidly colonized the vast area of the European continent, damaging tonatural and ornamental box trees. In order to develop effective phytophagous control measures there are features of the local populations seasonal development that have been studied in the Crimea. It is determined that during the growing season in the green spaces of the Crimean parks there is a temporary overlapping of both development stages and generations of the C. perspectalis populations. An important seasonal adaptation of C. perspectalis to the habitat’s conditions is thermal sensitivity reduction and development acceleration of all life cycle stages in the second summer generation under the influence of photoperiod. This flexibility of ontogenetic requirements for the transition to diapause provides higher phenological variability in populations. There is identified the temperature and photoperiod impact to development rate of larvae and the influence of relative humidity to development rate of pupae. With identical thermal reaction norms for development of the overwintered larvae, for complete of life cycle of the one generation life cycle in the Southern coast of the Crimea conditions needed the sum of growing degrees-days are 80 °С higher than in the Foothill Crimea. It is identified relative constancy of growing degrees-days needed for complete of the second summer generation of C. perspectalis . It allows considering them as a tool for determining the timing of effective treatment of third-generation larvae before they cause severe damage. For the comparability of the research results with the available publications, it was proposed to use the temperature threshold of 9.5 °С when calculating the growing degrees-days.
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Srivastava, MV Padma. « Restorative Therapies after Stroke : Drugs, Devices and Robotics ». Annals of the National Academy of Medical Sciences (India) 53, no 01 (janvier 2017) : 051–65. http://dx.doi.org/10.1055/s-0040-1712745.
Texte intégralRésumé :
ABSTRACTRestorative therapies aim to improve outcome and function by promoting plasticity within a therapeutic time window between days to weeks to years. In this article, the mechanisms by which cell-based, pharmacological and robotic treatments stimulate endogenous brain remodelling after stroke, particularly neurogenesis, axonal plasticity and white-matter integrity are described with a brief outline of the potential of neuroimaging (fMRI) techniques. Stem cells aid stroke recovery via mechanisms depending on the type of cells used. Transplanted embryonic stem cells (ESCs), induced pluripotent stem cells (iPSCs), and neural stem cells (NSCs) can replace the missing brain cells in the Infarcted area, while adult stem cells, such as mesenchymal stem cells or multipotent stromal cells (MSCs) and MNCs, provide trophic support to enhance self-repair systems such as endogenous neurogenesis. Most preclinical studies of stem cell therapy for stroke have emphasized the need to enhance self-repair systems rather than to replace lost cells, regardless of the type of cells used. Noninvasive brain stimulation (NIBS) provides a valuable tool for interventional neurophysiology by modulating brain activity in a specific distributed, cortico-subcortical network. The two most commonly used techniques for noninvasive brain stimulation are transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS). The article also discusses the potential role and current evidence for the use of pharmacological therapy, robotics and specific forms of physiotherapy regimes in optimizing stroke recovery. Neurorestoration is a concept that has been proven emphatically in several experimental models and clinical studies of stroke. Elucidating the underlying mechanisms of cell-based, pharmacological and rehabilitative therapies is of primary interest and crucial for translation of treatments to clinical use. The knowledge must provide an impetus for the development of superior, advanced and cost effective neuro restorative interventions that will enhance stroke recovery.
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Kosma, Madison M., Alexander J. Werth, Andrew R. Szabo et Janice M. Straley. « Pectoral herding : an innovative tactic for humpback whale foraging ». Royal Society Open Science 6, no 10 (octobre 2019) : 191104. http://dx.doi.org/10.1098/rsos.191104.
Texte intégralRésumé :
Humpback whales ( Megaptera novaeangliae ) have exceptionally long pectorals (i.e. flippers) that aid in shallow water navigation, rapid acceleration and increased manoeuvrability. The use of pectorals to herd or manipulate prey has been hypothesized since the 1930s. We combined new technology and a unique viewing platform to document the additional use of pectorals to aggregate prey during foraging events. Here, we provide a description of ‘pectoral herding’ and explore the conditions that may promote this innovative foraging behaviour. Specifically, we analysed aerial videos and photographic sequences to assess the function of pectorals during feeding events near salmon hatchery release sites in Southeast Alaska (2016–2018). We observed the use of solo bubble-nets to initially corral prey, followed by calculated movements to establish a secondary boundary with the pectorals—further condensing prey and increasing foraging efficiency. We found three ways in which humpback whales use pectorals to herd prey: (i) create a physical barrier to prevent evasion, (ii) cause water motion to guide prey towards the mouth, and (iii) position the ventral side to reflect light and alter prey movement. Our findings suggest that behavioural plasticity may aid foraging in changing environments and shifts in prey availability. Further study would clarify if ‘pectoral herding’ is used as a principal foraging tool by the broader humpback whale population and the conditions that promote its use.
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Moscatelli, Fiorenzo, Antonietta Messina, Anna Valenzano, Vincenzo Monda, Monica Salerno, Francesco Sessa, Ester La Torre et al. « Transcranial Magnetic Stimulation as a Tool to Investigate Motor Cortex Excitability in Sport ». Brain Sciences 11, no 4 (28 mars 2021) : 432. http://dx.doi.org/10.3390/brainsci11040432.
Texte intégralRésumé :
Transcranial magnetic stimulation, since its introduction in 1985, has brought important innovations to the study of cortical excitability as it is a non-invasive method and, therefore, can be used both in healthy and sick subjects. Since the introduction of this cortical stimulation technique, it has been possible to deepen the neurophysiological aspects of motor activation and control. In this narrative review, we want to provide a brief overview regarding TMS as a tool to investigate changes in cortex excitability in athletes and highlight how this tool can be used to investigate the acute and chronic responses of the motor cortex in sport science. The parameters that could be used for the evaluation of cortical excitability and the relative relationship with motor coordination and muscle fatigue, will be also analyzed. Repetitive physical training is generally considered as a principal strategy for acquiring a motor skill, and this process can elicit cortical motor representational changes referred to as use-dependent plasticity. In training settings, physical practice combined with the observation of target movements can enhance cortical excitability and facilitate the process of learning. The data to date suggest that TMS is a valid technique to investigate the changes in motor cortex excitability in trained and untrained subjects. Recently, interest in the possible ergogenic effect of non-invasive brain stimulation in sport is growing and therefore in the future it could be useful to conduct new experiments to evaluate the impact on learning and motor performance of these techniques.
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Bonarski, Jan T., Igor V. Alexandrov, Vil D. Sitdikov, Leszek Tarkowski, J. Grzonka et M. Bieda-Niemiec. « Texture/Stress Characteristics of Microstructure Used in Interpreting Deformation Effects of Ti Subjected to ECAP Process ». Solid State Phenomena 160 (février 2010) : 103–8. http://dx.doi.org/10.4028/www.scientific.net/ssp.160.103.
Texte intégralRésumé :
The common feature of the technologies, such as the equal channel angular pressing (ECAP) is the use of a changeable deformation path, which changes the configuration (value and direction) of the acting forces that impose various directions of plastic flow. The changes destabilize a temporary dislocation structure as well as the spatial distribution of the areas with elevated elastic energy cumulated in deformed lattice. The application of that technique results in a potentially large deformation (up to several hundred percent) and plasticity of materials considered to be brittle at ambient temperature. The microstructure effects accompanied with intensive and large deformation are reflected in the space orientation of grains (crystallographic texture) as well as in the configuration of the residual stresses existing in deformed material. The presented results based on experimental data registered by X-ray diffraction and TEM techniques are helpful in interpreting deformation mechanisms operating in the bend-zone of the ECAP tool during processing Ti-ingot by the mentioned method of severe plastic deformation.
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Li, Mingshen, Chaoqun Zhang, Dayong Wang, Li Zhou, Daniel Wellmann et Yingtao Tian. « Friction Stir Spot Welding of Aluminum and Copper : A Review ». Materials 13, no 1 (31 décembre 2019) : 156. http://dx.doi.org/10.3390/ma13010156.
Texte intégralRésumé :
Aluminum (Al) and copper (Cu) have been widely used in many industrial fields thanks to their good plasticity, high thermal conductivity and excellent electrical conductivity. An effective joining of dissimilar Al and Cu materials can make full use of the special characteristics of these two metals. Friction stir spot welding (FSSW), as an efficient solid-state welding method suitable for joining of dissimilar metal materials, has great prospects in future industrial applications. In this paper, the FSSW studies on Al-Cu dissimilar materials are reviewed. The research progress and current status of Al-Cu FSSW are reviewed with respect to tool features, macroscopic characteristics of welded joints, microstructures, defects in welds and mechanical properties of joints. In addition, some suggestions on further study are put forward in order to promote the development and progress of Al-Cu FSSW studies in several respects: material flow, thermal history, addition of intermediate layer, auxiliary methods and functionalization of Al-Cu FSSW joint.
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Matviychuk, Viktor, et Oleg Gaidamak. « INCREASING THE DURABILITY OF DETAILS TO WORK UNDER REPEATABLE LOADS ». Vibrations in engineering and technology, no 3(98) (30 octobre 2020) : 15–24. http://dx.doi.org/10.37128/2306-8744-2020-3-2.
Texte intégralRésumé :
The article presents the results of the development of processes to improve the performance of parts operating under repeated variable loads, taking into account the reasonable parameters of surface plastic deformation (SPD) and cold gas-dynamic spraying of coatings. The influence on the parameters of the working surface layer, the nature of the distribution of the stress-strain state of the surface layer of material and residual compressive stresses, as well as the values of the used resource of plasticity of the surface layer of the workpiece, the parameters of the SPD process. The article shows that the main factor in the formation of residual compressive stresses during SPD is the decrease in the density of the surface layer of the workpiece, which is associated with the use of the plasticity resource. The model of calculation of the used resource of plasticity of material of preparation at SPD which allows to provide the improved quality of a surface layer of details is offered. A method of moving the workpiece layers with maximum hardening and residual compression stresses to the surface of the part by applying a deforming tool of reduced size in the following passes with coating the surface of the part with gas-dynamic spraying before SPD. Cold gas-dynamic coating by spraying, in contrast to most known gas-thermal coating methods that take place under significant temperature effects on the surface of the part, which is unacceptable for surfaces treated by SPD methods, provides a permissible temperature regime for creating special auxiliary coatings while preserving surface properties SPD. The technology of gas-dynamic coating by spraying includes heating the compressed gas (air), directing it into the nozzle and forming in this nozzle supersonic air-powder flow, sprayed material (copper, aluminum), acceleration of this powder material to supersonic speeds and directing it to the surface of the processed product. As a result, a special auxiliary coating (copper or aluminum) is formed on the surface of the product, which improves the parameters of the SPD process.
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González-Benito, María Elena, Miguel Ángel Ibáñez, Michela Pirredda, Sara Mira et Carmen Martín. « Application of the MSAP Technique to Evaluate Epigenetic Changes in Plant Conservation ». International Journal of Molecular Sciences 21, no 20 (10 octobre 2020) : 7459. http://dx.doi.org/10.3390/ijms21207459.
Texte intégralRésumé :
Epigenetic variation, and particularly DNA methylation, is involved in plasticity and responses to changes in the environment. Conservation biology studies have focused on the measurement of this variation to establish demographic parameters, diversity levels and population structure to design the appropriate conservation strategies. However, in ex situ conservation approaches, the main objective is to guarantee the characteristics of the conserved material (phenotype and epi-genetic). We review the use of the Methylation Sensitive Amplified Polymorphism (MSAP) technique to detect changes in the DNA methylation patterns of plant material conserved by the main ex situ plant conservation methods: seed banks, in vitro slow growth and cryopreservation. Comparison of DNA methylation patterns before and after conservation is a useful tool to check the fidelity of the regenerated plants, and, at the same time, may be related with other genetic variations that might appear during the conservation process (i.e., somaclonal variation). Analyses of MSAP profiles can be useful in the management of ex situ plant conservation but differs in the approach used in the in situ conservation. Likewise, an easy-to-use methodology is necessary for a rapid interpretation of data, in order to be readily implemented by conservation managers.
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Pelegatti, Marco, Alex Lanzutti, Enrico Salvati, Jelena Srnec Novak, Francesco De Bona et Denis Benasciutti. « Cyclic Plasticity and Low Cycle Fatigue of an AISI 316L Stainless Steel : Experimental Evaluation of Material Parameters for Durability Design ». Materials 14, no 13 (27 juin 2021) : 3588. http://dx.doi.org/10.3390/ma14133588.
Texte intégralRésumé :
AISI 316L stainless steels are widely employed in applications where durability is crucial. For this reason, an accurate prediction of its behaviour is of paramount importance. In this work, the spotlight is on the cyclic response and low-cycle fatigue performance of this material, at room temperature. Particularly, the first aim of this work is to experimentally test this material and use the results as input to calibrate the parameters involved in a kinematic and isotropic nonlinear plasticity model (Chaboche and Voce). This procedure is conducted through a newly developed calibration procedure to minimise the parameter estimates errors. Experimental data are eventually used also to estimate the strain–life curve, namely the Manson–Coffin curve representing the 50% failure probability and, afterwards, the design strain–life curves (at 5% failure probability) obtained by four statistical methods (i.e., deterministic, “Equivalent Prediction Interval”, univariate tolerance interval, Owen’s tolerance interval for regression). Besides the characterisation of the AISI 316L stainless steel, the statistical methodology presented in this work appears to be an efficient tool for engineers dealing with durability problems as it allows one to select fatigue strength curves at various failure probabilities depending on the sought safety level.
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Tran, V., Stephane Avril et Fabrice Pierron. « Software Implementation of the Virtual Fields Method ». Applied Mechanics and Materials 7-8 (août 2007) : 57–62. http://dx.doi.org/10.4028/www.scientific.net/amm.7-8.57.
Texte intégralRésumé :
The virtual fields method is a tool dedicated to the identification of the mechanical properties of materials from full-field deformation measurements. It is now validated in elasticity and plasticity but one of the remaining problems is the fact that researchers wanting to use the method must invest significant time in order to programme the routines. To help them, a software called CamFit has been developed. The purpose of this paper is to present this software. It is based on MATLAB® and uses a graphical pre-processing interface to produce the geometry, the conditions on the virtual fields, to choose the type of behaviour etc... Then, series of displacement maps are uploaded and the identification is launched. Since no iterative solution of the direct problem is required, computation times are very small compared to updating techniques. An important step in the procedure is the smoothing of the displacement measurements to produce strains. FE based approximations are presently available in the software. The final purpose is to introduce the software onto the market. This will be done in the very near future.
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Pennarossa, Georgia, Alessio Paffoni, Guido Ragni, Fulvio Gandolfi et Tiziana Brevini. « Parthenogenesis in mammals : pros and cons in pluripotent cell derivation ». Open Life Sciences 6, no 5 (1 octobre 2011) : 770–75. http://dx.doi.org/10.2478/s11535-011-0047-3.
Texte intégralRésumé :
AbstractEmbryonic stem cells (ESCs) represent a useful tool for cell therapy studies, however the use of embryos for their derivation give rise to ethical, religious and legal problems when applied to the human. During the last years parthenogenesis has been proposed as an alternative source to obtain ESCs. Based on the fact that parthenotes avoid many concerns surrounding the “ad hoc” in vitro production and following destruction of viable human embryos. Unfortunately many aspects related to parthenogenetic cell biology are not fully understood and still need to be elucidated. In this review we describe advantages and limits of these cells. We discuss their typical ESC morphology and high telomerase activity, which disappears after differentiation. We examine the pluripotency signature that they share with bi-parental ESCs. We review their high differentiation plasticity that allow for the derivation of several mature cell type populations when we expose these cells to adequate conditions. On the other hand, in-depth analysis demonstrated chromosome mal-segregation and altered mechanisms controlling centriole arrangement and mitotic spindle formation in these cells. We hypothesize their monoparental origin as one of the possible cause of these anomalies and suggest a great caution if a therapeutic use is considered.
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Othman, Houcemeddine, Sherlyn Jemimah et Jorge Emanuel Batista da Rocha. « SWAAT Bioinformatics Workflow for Protein Structure-Based Annotation of ADME Gene Variants ». Journal of Personalized Medicine 12, no 2 (11 février 2022) : 263. http://dx.doi.org/10.3390/jpm12020263.
Texte intégralRésumé :
Recent genomic studies have revealed the critical impact of genetic diversity within small population groups in determining the way individuals respond to drugs. One of the biggest challenges is to accurately predict the effect of single nucleotide variants and to get the relevant information that allows for a better functional interpretation of genetic data. Different conformational scenarios upon the changing in amino acid sequences of pharmacologically important proteins might impact their stability and plasticity, which in turn might alter the interaction with the drug. Current sequence-based annotation methods have limited power to access this type of information. Motivated by these calls, we have developed the Structural Workflow for Annotating ADME Targets (SWAAT) that allows for the prediction of the variant effect based on structural properties. SWAAT annotates a panel of 36 ADME genes including 22 out of the 23 clinically important members identified by the PharmVar consortium. The workflow consists of a set of Python codes of which the execution is managed within Nextflow to annotate coding variants based on 37 criteria. SWAAT also includes an auxiliary workflow allowing a versatile use for genes other than ADME members. Our tool also includes a machine learning random forest binary classifier that showed an accuracy of 73%. Moreover, SWAAT outperformed six commonly used sequence-based variant prediction tools (PROVEAN, SIFT, PolyPhen-2, CADD, MetaSVM, and FATHMM) in terms of sensitivity and has comparable specificity. SWAAT is available as an open-source tool.