WorldWideScience

Sample records for plasticity mechanisms pulling

  1. Characterization and Effects of Fiber Pull-Outs in Hole Quality of Carbon Fiber Reinforced Plastics Composite

    Directory of Open Access Journals (Sweden)

    Sina Alizadeh Ashrafi

    2016-10-01

    Full Text Available Hole quality plays a crucial role in the production of close-tolerance holes utilized in aircraft assembly. Through drilling experiments of carbon fiber-reinforced plastic composites (CFRP, this study investigates the impact of varying drilling feed and speed conditions on fiber pull-out geometries and resulting hole quality parameters. For this study, hole quality parameters include hole size variance, hole roundness, and surface roughness. Fiber pull-out geometries are quantified by using scanning electron microscope (SEM images of the mechanically-sectioned CFRP-machined holes, to measure pull-out length and depth. Fiber pull-out geometries and the hole quality parameter results are dependent on the drilling feed and spindle speed condition, which determines the forces and undeformed chip thickness during the process. Fiber pull-out geometries influence surface roughness parameters from a surface profilometer, while their effect on other hole quality parameters obtained from a coordinate measuring machine is minimal.

  2. Mechanical plasticity of cells

    Science.gov (United States)

    Bonakdar, Navid; Gerum, Richard; Kuhn, Michael; Spörrer, Marina; Lippert, Anna; Schneider, Werner; Aifantis, Katerina E.; Fabry, Ben

    2016-10-01

    Under mechanical loading, most living cells show a viscoelastic deformation that follows a power law in time. After removal of the mechanical load, the cell shape recovers only incompletely to its original undeformed configuration. Here, we show that incomplete shape recovery is due to an additive plastic deformation that displays the same power-law dynamics as the fully reversible viscoelastic deformation response. Moreover, the plastic deformation is a constant fraction of the total cell deformation and originates from bond ruptures within the cytoskeleton. A simple extension of the prevailing viscoelastic power-law response theory with a plastic element correctly predicts the cell behaviour under cyclic loading. Our findings show that plastic energy dissipation during cell deformation is tightly linked to elastic cytoskeletal stresses, which suggests the existence of an adaptive mechanism that protects the cell against mechanical damage.

  3. Mechanism of oil-pulling therapy -In vitro study

    Directory of Open Access Journals (Sweden)

    Sharath Asokan

    2011-01-01

    Conclusion: The myth that the effect of oil-pulling therapy on oral health was just a placebo effect has been broken and there are clear indications of possible saponification and emulsification process, which enhances its mechanical cleaning action.

  4. Miniature Tractor Pull Helps Teach Mechanical Power Transmission.

    Science.gov (United States)

    Waggoner, Todd C.

    1996-01-01

    A miniature tractor pull was developed as a high school activity, enabling students to assess a tractor's pulling capabilities and determine subsequent horsepower. The activity takes the textbook concept of horsepower and makes it come alive. (JOW)

  5. Deformation mechanisms of plasticized starch materials.

    Science.gov (United States)

    Mikus, P-Y; Alix, S; Soulestin, J; Lacrampe, M F; Krawczak, P; Coqueret, X; Dole, P

    2014-12-19

    The aim of this paper is to understand the influence of plasticizer and plasticizer amount on the mechanical and deformation behaviors of plasticized starch. Glycerol, sorbitol and mannitol have been used as plasticizers. After extrusion of the various samples, dynamic mechanical analyses and video-controlled tensile tests have been performed. It was found that the nature of plasticizer, its amount as well as the aging of the material has an impact on the involved deformation mechanism. The variations of volume deformation could be explained by an antiplasticization effect (low plasticizer amount), a phase-separation phenomenon (excess of plasticizer) and/or by the retrogradation of starch.

  6. Micro/nano-mechanical test system employing tensile test holder with push-to-pull transformer

    Science.gov (United States)

    Oh, Yunje; Cyrankowski, Edward; Shan, Zhiwei; Asif, Syed Amanula Syed

    2013-05-07

    A micromachined or microelectromechanical system (MEMS) based push-to-pull mechanical transformer for tensile testing of micro-to-nanometer scale material samples including a first structure and a second structure. The second structure is coupled to the first structure by at least one flexible element that enables the second structure to be moveable relative to the first structure, wherein the second structure is disposed relative to the first structure so as to form a pulling gap between the first and second structures such that when an external pushing force is applied to and pushes the second structure in a tensile extension direction a width of the pulling gap increases so as to apply a tensile force to a test sample mounted across the pulling gap between a first sample mounting area on the first structure and a second sample mounting area on the second structure.

  7. Micro/nano-mechanical test system employing tensile test holder with push-to-pull transformer

    Energy Technology Data Exchange (ETDEWEB)

    Oh, Yunje; Cyrankowski, Edward; Shan, Zhiwei; Syed Asif, Syed Amanula

    2014-07-29

    A micromachined or microelectromechanical system (MEMS) based push-to-pull mechanical transformer for tensile testing of micro-to-nanometer scale material samples including a first structure and a second structure. The second structure is coupled to the first structure by at least one flexible element that enables the second structure to be moveable relative to the first structure, wherein the second structure is disposed relative to the first structure so as to form a pulling gap between the first and second structures such that when an external pushing force is applied to and pushes the second structure in a tensile extension direction a width of the pulling gap increases so as to apply a tensile force to a test sample mounted across the pulling gap between a first sample mounting area on the first structure and a second sample mounting area on the second structure.

  8. Mechanical heterogeneity and mechanism of plasticity in metallic glasses

    Science.gov (United States)

    Wang, J. G.; Zhao, D. Q.; Pan, M. X.; Shek, C. H.; Wang, W. H.

    2009-01-01

    The mechanical heterogeneity is quantified based on the spatial nanohardness distributions in three bulk metallic glasses with different plasticities. It is found that the metallic glass with high mechanical heterogeneity is more plastic. We propose that the appropriate mechanical heterogeneity makes the metallic glasses meliorate their plasticity by increasing inelastic strained area and promoting energy dissipation.

  9. Regulatory mechanisms link phenotypic plasticity to evolvability.

    Science.gov (United States)

    van Gestel, Jordi; Weissing, Franz J

    2016-04-18

    Organisms have a remarkable capacity to respond to environmental change. They can either respond directly, by means of phenotypic plasticity, or they can slowly adapt through evolution. Yet, how phenotypic plasticity links to evolutionary adaptability is largely unknown. Current studies of plasticity tend to adopt a phenomenological reaction norm (RN) approach, which neglects the mechanisms underlying plasticity. Focusing on a concrete question - the optimal timing of bacterial sporulation - we here also consider a mechanistic approach, the evolution of a gene regulatory network (GRN) underlying plasticity. Using individual-based simulations, we compare the RN and GRN approach and find a number of striking differences. Most importantly, the GRN model results in a much higher diversity of responsive strategies than the RN model. We show that each of the evolved strategies is pre-adapted to a unique set of unseen environmental conditions. The regulatory mechanisms that control plasticity therefore critically link phenotypic plasticity to the adaptive potential of biological populations.

  10. Pulling the trigger: the mechanism of bacterial spore germination.

    Science.gov (United States)

    Foster, S J; Johnstone, K

    1990-01-01

    In spite of displaying the most extreme dormancy and resistance properties known among living systems, bacterial endospores retain an alert environment-sensing mechanism that can respond within seconds to the presence of specific germinants. This germination response is triggered in the absence of both germinant and germinant-stimulated metabolism. Genes coding for components of the sensing mechanism in spores of Bacillus subtilis have been cloned and sequenced. However, the molecular mechanism whereby these receptors interact with germinants to initiate the germination response is unknown. Recent evidence has suggested that in spores of Bacillus megaterium KM, proteolytic activation of an autolytic enzyme constitutes part of the germination trigger reaction.

  11. Mechanisms of GABAergic Homeostatic Plasticity

    Directory of Open Access Journals (Sweden)

    Peter Wenner

    2011-01-01

    Full Text Available Homeostatic plasticity ensures that appropriate levels of activity are maintained through compensatory adjustments in synaptic strength and cellular excitability. For instance, excitatory glutamatergic synapses are strengthened following activity blockade and weakened following increases in spiking activity. This form of plasticity has been described in a wide array of networks at several different stages of development, but most work and reviews have focussed on the excitatory inputs of excitatory neurons. Here we review homeostatic plasticity of GABAergic neurons and their synaptic connections. We propose a simplistic model for homeostatic plasticity of GABAergic components of the circuitry (GABAergic synapses onto excitatory neurons, excitatory connections onto GABAergic neurons, cellular excitability of GABAergic neurons: following chronic activity blockade there is a weakening of GABAergic inhibition, and following chronic increases in network activity there is a strengthening of GABAergic inhibition. Previous work on GABAergic homeostatic plasticity supports certain aspects of the model, but it is clear that the model cannot fully account for some results which do not appear to fit any simplistic rule. We consider potential reasons for these discrepancies.

  12. Mechanical loading of the low back and shoulders during pushing and pulling activities

    NARCIS (Netherlands)

    Hoozemans, Marco J M; Kuijer, P Paul F M; Kingma, Idsart; van Dieën, Jaap H; de Vries, Wiebe H K; van der Woude, Luc H V; Veeger, Dirk Jan H E J; van der Beek, Allard J; Frings-Dresen, Monique H W

    2004-01-01

    The objective of this study was to quantify the mechanical load on the low back and shoulders during pushing and pulling in combination with three task constraints: the use of one or two hands, three cart weights, and two handle heights. The second objective was to explore the relation between the i

  13. Generalized Plastic Mechanics and Its Application

    Institute of Scientific and Technical Information of China (English)

    Zheng Yingren; Kong Liang

    2006-01-01

    The development of geotechnical plasticity is reviewed and some problems of applying the classical plastic mechanics (CPM) to geomaterials are analyzed, and then CPM's three hypotheses not fitted the deformation mechanism of geomaterials are pointed out. By giving up the three hypotheses, a generalized plastic potential theory can be obtained from solid mechanics directly, and then the traditional plastic mechanics can be changed to a more generalized plastic mechanics, namely generalized plastic mechanics (GPM). The GPM adopts the component theory as theoretical base, so it can reflect the influence of transition of stress path. The unreasonable phenomena such as excessive dilatancy caused by adopting the normality-flow law can be avoided, and the error caused by the arbitrary assumption of plastic potential surfaces cannot be produced. The yield surface theory, hardening laws and stress-strain relations of GPM are given, and a GPM including the rotation of principal stress axes is also established. It is pointed out that the yield condition is a state parameter as well as a test parameter, and it can only be given by test. After the practical application, it is shown that the GPM cannot only be applied to the modeling theory of geomaterials but also to other fields of geomechanics such as limit analysis.

  14. Phenotypic plasticity: molecular mechanisms and adaptive significance.

    Science.gov (United States)

    Kelly, Scott A; Panhuis, Tami M; Stoehr, Andrew M

    2012-04-01

    Phenotypic plasticity can be broadly defined as the ability of one genotype to produce more than one phenotype when exposed to different environments, as the modification of developmental events by the environment, or as the ability of an individual organism to alter its phenotype in response to changes in environmental conditions. Not surprisingly, the study of phenotypic plasticity is innately interdisciplinary and encompasses aspects of behavior, development, ecology, evolution, genetics, genomics, and multiple physiological systems at various levels of biological organization. From an ecological and evolutionary perspective, phenotypic plasticity may be a powerful means of adaptation and dramatic examples of phenotypic plasticity include predator avoidance, insect wing polymorphisms, the timing of metamorphosis in amphibians, osmoregulation in fishes, and alternative reproductive tactics in male vertebrates. From a human health perspective, documented examples of plasticity most commonly include the results of exercise, training, and/or dieting on human morphology and physiology. Regardless of the discipline, phenotypic plasticity has increasingly become the target of a plethora of investigations with the methodological approaches utilized ranging from the molecular to whole organsimal. In this article, we provide a brief historical outlook on phenotypic plasticity; examine its potential adaptive significance; emphasize recent molecular approaches that provide novel insight into underlying mechanisms, and highlight examples in fishes and insects. Finally, we highlight examples of phenotypic plasticity from a human health perspective and underscore the use of mouse models as a powerful tool in understanding the genetic architecture of phenotypic plasticity.

  15. Mechanical properties and supporting effect of CRLD bolts under static pull test conditions

    Science.gov (United States)

    Sun, Xiao-ming; Zhang, Yong; Wang, Dong; Yang, Jun; Xu, Hui-chen; He, Man-chao

    2017-01-01

    A device for supporting soft rock masses combined with a constant resistance structure characterized by constant resistance and large deformation at the end of a steel bar, known as the constant resistance and large deformation (CRLD) bolt, has recently been developed to counteract soft rock swelling that often occurs during deep mining. In order to further study the mechanical properties of the CRLD bolt, we investigated its mechanical properties by comparison with the conventional strength bolt (rebar) using static pull tests on many aspects, including supporting capacity, elongation, radial deformation, and energy absorption. The tests verified that the mechanical defects of the rebar, which include the decrease of bolt diameter, reduction of supporting capacity, and emergence and evolution of fracture until failure during the whole pull process, were caused by the Poisson's ratio effect. Due to the special structure set on the CRLD bolt, the bolt presents a seemingly unusual phenomenon of the negative Poisson's ratio effect, i.e., the diameter of the constant resistance structure increases while under-pulling. It is the very effect that ensures the extraordinary mechanical properties, including high resistance, large elongation, and strong energy absorption. According to the comparison and analysis of numerical simulation and field test, we can conclude that the CRLD bolt works better than the rebar bolt.

  16. Neglected infectious diseases: are push and pull incentive mechanisms suitable for promoting drug development research?

    Science.gov (United States)

    Mueller-Langer, Frank

    2013-04-01

    Infectious diseases are among the main causes of death and disability in developing countries, and they are a major reason for the health disparity between rich and poor countries. One of the reasons for this public health tragedy is a lack of lifesaving essential medicines, which either do not exist or badly need improvements. In this article, we analyse which of the push and pull mechanisms proposed in the recent literature may serve to promote research into neglected infectious diseases. A combination of push programmes that subsidise research inputs through direct funding and pull programmes that reward research output rather than research input may be the appropriate strategy to stimulate research into neglected diseases. On the one hand, early-stage (basic) research should be supported through push mechanisms, such as research grants or publicly financed research institutions. On the other hand, pull mechanisms, such as prize funds that link reward payments to the health impacts of effective medicines, have the potential to stimulate research into neglected diseases.

  17. Structural plasticity mechanisms and developmental psychiatric disorders

    Directory of Open Access Journals (Sweden)

    Dominique eMuller

    2014-11-01

    Full Text Available Synaptic plasticity mechanisms are usually discussed in terms of changes in synaptic strength. The capacity of excitatory synapses to rapidly modify the membrane expression of glutamate receptors in an activity-dependent manner plays a critical role in learning and memory processes by re-distributing activity within neuronal networks. Recent work has however also shown that functional plasticity properties are associated with a rewiring of synaptic connections and a selective stabilization of activated synapses. These structural aspects of plasticity have the potential to continuously modify the organization of synaptic networks and thereby introduce specificity in the wiring diagram of cortical circuits. Recent work has started to unravel some of the molecular mechanisms that underlie these properties of structural plasticity, highlighting an important role of signaling pathways that are also major candidates for contributing to developmental psychiatric disorders. We review here some of these recent advances and discuss the hypothesis that alterations of structural plasticity could represent a common mechanism contributing to the cognitive and functional defects observed in diseases such as intellectual disability, autism spectrum disorders and schizophrenia.

  18. Can previous learning alter future plasticity mechanisms?

    Science.gov (United States)

    Crestani, Ana Paula; Quillfeldt, Jorge Alberto

    2016-02-01

    The dynamic processes related to mnemonic plasticity have been extensively researched in the last decades. More recently, studies have attracted attention because they show an unusual plasticity mechanism that is independent of the receptor most usually related to first-time learning--that is, memory acquisition-the NMDA receptor. An interesting feature of this type of learning is that a previous experience may cause modifications in the plasticity mechanism of a subsequent learning, suggesting that prior experience in a very similar task triggers a memory acquisition process that does not depend on NMDARs. The intracellular molecular cascades necessary to assist the learning process seem to depend on the activation of hippocampal CP-AMPARs. Moreover, most of these studies were performed on hippocampus-dependent tasks, even though other brain areas, such as the basolateral amygdala, also display NMDAR-independent learning.

  19. Understanding the mechanism of B(12)-dependent diol dehydratase: a synergistic retro-push--pull proposal.

    Science.gov (United States)

    Smith, D M; Golding, B T; Radom, L

    2001-02-28

    Ab initio molecular orbital theory is used to investigate the coenzyme B(12)-dependent reactions catalyzed by diol dehydratase. The key step in such reactions is believed to be a 1,2-hydroxyl migration, which occurs within free-radical intermediates. The barrier for this migration, if unassisted, is calculated to be too high to be consistent with the observed reaction rate. However, we find that "pushing" the migrating hydroxyl, through interaction with a suitable acid, is able to provide significant catalysis. This is denoted retro-push catalysis, the retro prefix signifying that the motion of the migrating group is in the direction opposite to the electron motion. Similarly, the "pulling" of the migrating group, through interaction of the spectator hydroxyl with an appropriate base, is found to substantially reduce the rearrangement barrier. Importantly, the combination of these two effects results in a barrier reduction that is notably greater than additive. This synergistic interplay of the push and the pull provides an attractive means of catalysis. Our proposed retro-push--pull mechanism leads to results that are consistent with isotope-labeling experiments, with experimental rate data, and with the crystal structure of the enzyme.

  20. Influence of mechanical and metabolic strain on the oxygen consumption slow component during forward pulled running.

    Science.gov (United States)

    Avogadro, Patrick; Kyröläinen, Heikki; Belli, Alain

    2004-10-01

    The possible influence of increased eccentric mechanical work on the increase in oxygen uptake ( V(.)O(2)) after 3 min of running (Delta V(.)O(2)) was investigated through forward pulled running. Ten subjects ran at individually predetermined constant velocity on a treadmill, while being pulled forward. Ground reaction forces, expired gas and EMGs from leg muscles were collected after 3 min and at the end of the run. V(.)O(2) and mechanical work were then calculated. The amplitude of Delta V(.)O(2) was 138 (139) ml x min(-1) [mean (SD)]. Increased ventilation explained only 8% of Delta V(.)O(2). Stride frequency slightly decreased, inducing a similar decrease in internal work and total mechanical work (all P<0.01), while integrated EMG showed no modifications. It was concluded that Delta V(.)O(2) does not come from either an increase in mechanical work production or an increase in muscular activity. Delta V(.)O(2) could come from a lower muscle efficiency that could be due to a modification of fibre type recruitment.

  1. The mechanical and thermodynamical theory of plasticity

    CERN Document Server

    Negahban, Mehrdad

    2012-01-01

    ""an excellent text for a graduate-level course in plasticity…the approach and selection of topics are appropriate for the audience. ... Professor Negahban has done an excellent job in presenting a unified approach to include thermal effects in the theory of finite deformation of plastic solids. The simple thermo-mechanical analog presented at the beginning of the chapter is also very instructive to the reader. {presented figures are] particularly helpful in understanding the mechanisms in a simple (one-dimensional) setting … The learning features included in this chapter are excellent (the fi

  2. Notch Ligand Endocytosis Generates Mechanical Pulling Force Dependent on Dynamin, Epsins and Actin

    Science.gov (United States)

    Meloty-Kapella, Laurence; Shergill, Bhupinder; Kuon, Jane; Botvinick, Elliot; Weinmaster, Gerry

    2012-01-01

    SUMMARY Notch signaling induced by cell surface ligands is critical to development and maintenance of many eukaryotic organisms. Notch and its ligands are integral membrane proteins that facilitate direct cell-cell interactions to activate Notch proteolysis and release the intracellular domain that directs Notch-specific cellular responses. Genetic studies suggest Notch ligands require endocytosis, ubiquitylation and epsin endocytic adaptors to activate signaling, yet the exact role ligand endocytosis serves remains unresolved. Here we characterize a molecularly distinct mode of clathrin-mediated endocytosis requiring ligand ubiquitylation, epsins and actin for ligand cells to activate signaling in Notch cells. Using a cell-bead optical tweezers system, we obtained evidence for cell-mediated mechanical force dependent on this distinct mode of ligand endocytosis. We propose mechanical pulling force produced by endocytosis of Notch-bound ligand drives conformational changes in Notch that permit activating proteolysis. PMID:22658936

  3. The influence of deformation on barbell mechanics during the clean pull.

    Science.gov (United States)

    Chiu, Loren Z F; Schilling, Brian K; Fry, Andrew C; Salem, George J

    2008-05-01

    For simplicity of biomechanical analyses, the weightlifting barbell is typically modelled as a rigid, nondeformable object. Most coaches and weightlifters, however, are aware of the elastic nature of the barbell, and its influence on the successful completion of lifting attempts. Variables such as velocity, work performed, and power output are indicators of the quality of performance during the snatch, clean, and related weightlifting pulling movements. The aim of this study was to establish whether differences exist in determining these biomechanical parameters when the centre of the barbell is analysed compared with each end of the barbell. Nine men performed three maximal-effort repetitions in the clean pull exercise at 85% of their self-reported single repetition maximum (1-RM) clean (90-155 kg) using a barbell instrumented for mechanical analysis. Results indicated that peak barbell speed was 5-30% (P 0.05). Although approximately the same work and power occur for the centre and ends of the barbell, they manifest as different kinematics as a result of the elastic nature of the equipment. The elastic characteristics should be considered when selecting instrumentation and variables for research involving barbells. Coaches should be aware of the elasticity of barbells, including selecting appropriate viewing angles as well as understanding how deformation may affect the ends of the barbell relative to the centre.

  4. Mechanical behaviour of nanoparticles: Elasticity and plastic deformation mechanisms

    Indian Academy of Sciences (India)

    Celine Gerard; Laurent Pizzagalli

    2015-06-01

    Nano-objects often exhibit drastically different properties compared to their bulk counterpart, opening avenues for new applications in many fields, such as in advanced composite materials, nanomanufacturing, nanoelectromechanical systems etc. As such, related research topics have become increasingly prominent in recent years. In this review on the mechanical behaviour of nanoparticles, the main investigation approaches are first briefly presented. The main results in terms of elasticity and plastic deformation mechanisms are then reported and discussed.

  5. Mechanical characterization of commercial biodegradable plastic films

    Science.gov (United States)

    Vanstrom, Joseph R.

    Polylactic acid (PLA) is a biodegradable plastic that is relatively new compared to other plastics in use throughout industry. The material is produced by the polymerization of lactic acid which is produced by the fermentation of starches derived from renewable feedstocks such as corn. Polylactic acid can be manufactured to fit a wide variety of applications. This study details the mechanical and morphological properties of selected commercially available PLA film products. Testing was conducted at Iowa State University and in conjunction with the United States Department of Agriculture (USDA) BioPreferred ProgramRTM. Results acquired by Iowa State were compared to a similar study performed by the Cortec Corporation in 2006. The PLA films tested at Iowa State were acquired in 2009 and 2010. In addition to these two studies at ISU, the films that were acquired in 2009 were aged for a year in a controlled environment and then re-tested to determine effects of time (ageing) on the mechanical properties. All films displayed anisotropic properties which were confirmed by inspection of the films with polarized light. The mechanical testing of the films followed American Society for Testing and Materials (ASTM) standards. Mechanical characteristics included: tensile strength (ASTM D882), elongation of material at failure (ASTM D882), impact resistance (ASTM D1922), and tear resistance (ASTM D4272). The observed values amongst all the films ranged as followed: tensile strength 33.65--8.54 MPa; elongation at failure 1,665.1%--47.2%; tear resistance 3.61--0.46 N; and puncture resistance 2.22--0.28 J. There were significant differences between the observed data for a number of films and the reported data published by the Cortec Corp. In addition, there were significant differences between the newly acquired material from 2009 and 2010, as well as the newly acquired materials in 2009 and the aged 2009 materials, suggesting that ageing and manufacturing date had an effect on

  6. Phenotypic plasticity and selection: nonexclusive mechanisms of adaptation

    OpenAIRE

    Grenier, S.; Barre, P.; Litrico, I.

    2016-01-01

    Selection and plasticity are two mechanisms that allow the adaptation of a population to a changing environment. Interaction between these nonexclusive mechanisms must be considered if we are to understand population survival. This review discusses the ways in which plasticity and selection can interact, based on a review of the literature on selection and phenotypic plasticity in the evolution of populations. The link between selection and phenotypic plasticity is analysed at the level of th...

  7. Drawbar Pull

    Science.gov (United States)

    2017-01-26

    Includes procedures for hard surface, soil, and water tests. Discusses vehicle preparation, instrumentation method of computing results, data reduction...tracked vehicles on hard -surfaced roads, in soft soils, and of amphibious vehicles in water . b. Drawbar pull provides a measure of the reserve power...Drawbar Pull (Common).................................................. 5 4.2 Drawbar Pull on Hard Surface ......................................... 7

  8. Epigenetic Mechanisms Underlying Developmental Plasticity in Horned Beetles

    Directory of Open Access Journals (Sweden)

    Sophie Valena

    2012-01-01

    Full Text Available All developmental plasticity arises through epigenetic mechanisms. In this paper we focus on the nature, origins, and consequences of these mechanisms with a focus on horned beetles, an emerging model system in evolutionary developmental genetics. Specifically, we introduce the biological significance of developmental plasticity and summarize the most important facets of horned beetle biology. We then compare and contrast the epigenetic regulation of plasticity in horned beetles to that of other organisms and discuss how epigenetic mechanisms have facilitated innovation and diversification within and among taxa. We close by highlighting opportunities for future studies on the epigenetic regulation of plastic development in these and other organisms.

  9. Mechanisms of Biliary Plastic Stent Occlusion and Efforts at Prevention

    Science.gov (United States)

    Kwon, Chang-Il; Lehman, Glen A.

    2016-01-01

    Biliary stenting via endoscopic retrograde cholangiopancreatography has greatly improved the quality of patient care over the last 30 years. Plastic stent occlusion limits the life span of such stents. Attempts to improve plastic stent patency duration have mostly failed. Metal stents (self-expandable metal stents [SEMSs]) have therefore replaced plastic stents, especially for malignant biliary strictures. SEMS are at least 10 times more expensive than plastic stents. In this focused review, we will discuss basic mechanisms of plastic stent occlusion, along with a systematic summary of previous efforts and related studies to improve stent patency and potential new techniques to overcome existing limitations. PMID:27000422

  10. Regulatory mechanisms link phenotypic plasticity to evolvability

    NARCIS (Netherlands)

    van Gestel, Jordi; Weissing, Franz J

    2016-01-01

    Organisms have a remarkable capacity to respond to environmental change. They can either respond directly, by means of phenotypic plasticity, or they can slowly adapt through evolution. Yet, how phenotypic plasticity links to evolutionary adaptability is largely unknown. Current studies of plasticit

  11. A Pull-in Based Test Mechanism for Device Diagnostic and Process Characterization

    NARCIS (Netherlands)

    Rocha, L.A.; Mol, L.; Cretu, E.; Wolffenbuttel, R.F.; Machado da Silva, J.

    2008-01-01

    A test technique for capacitive MEMS accelerometers and electrostatic microactuators, based on the measurement of pull-in voltages and resonance frequency, is described. Using this combination of measurements, one can estimate process-induced variations in the device layout dimensions as well as dev

  12. A Pull-in Based Test Mechanism for Device Diagnostic and Process Characterization

    NARCIS (Netherlands)

    Rocha, L.A.; Mol, L.; Cretu, E.; Wolffenbuttel, R.F.; Machado da Silva, J.

    2008-01-01

    A test technique for capacitive MEMS accelerometers and electrostatic microactuators, based on the measurement of pull-in voltages and resonance frequency, is described. Using this combination of measurements, one can estimate process-induced variations in the device layout dimensions as well as

  13. Nicotinic mechanisms influencing synaptic plasticity in the hippocampus

    Institute of Scientific and Technical Information of China (English)

    Andon Nicholas PLACZEK; Tao A ZHANG; John Anthony DANI

    2009-01-01

    Nicotinic acetylcholine receptors (nAChRs) are expressed throughout the hippocampus, and nicotinic signaling plays an important role in neuronal function. In the context of learning and memory related behaviors associated with hippocampal function, a potentially significant feature of nAChR activity is the impact it has on synaptic plasticity. Synaptic plasticity in hippocampal neurons has long been considered a contributing cellular mechanism of learning and memory. These same kinds of cellular mechanisms are a factor in the development of nicotine addiction. Nicotinic signaling has been demonstrated by in vitro studies to affect synaptic plasticity in hippocampal neurons via multiple steps, and the signaling has also been shown to evoke synaptic plasticity in vivo. This review focuses on the nAChRs subtypes that contribute to hippocampal synaptic plasticity at the cellular and circuit level. It also considers nicotinic influences over long-term changes in the hippocampus that may contribute to addiction.

  14. Phenotypic Plasticity and Selection: Nonexclusive Mechanisms of Adaptation.

    Science.gov (United States)

    Grenier, S; Barre, P; Litrico, I

    2016-01-01

    Selection and plasticity are two mechanisms that allow the adaptation of a population to a changing environment. Interaction between these nonexclusive mechanisms must be considered if we are to understand population survival. This review discusses the ways in which plasticity and selection can interact, based on a review of the literature on selection and phenotypic plasticity in the evolution of populations. The link between selection and phenotypic plasticity is analysed at the level of the individual. Plasticity can affect an individual's response to selection and so may modify the end result of genetic diversity evolution at population level. Genetic diversity increases the ability of populations or communities to adapt to new environmental conditions. Adaptive plasticity increases individual fitness. However this effect must be viewed from the perspective of the costs of plasticity, although these are not easy to estimate. It is becoming necessary to engage in new experimental research to demonstrate the combined effects of selection and plasticity for adaptation and their consequences on the evolution of genetic diversity.

  15. A Pull-in Based Test Mechanism for Device Diagnostic and Process Characterization

    Directory of Open Access Journals (Sweden)

    L. A. Rocha

    2008-01-01

    Full Text Available A test technique for capacitive MEMS accelerometers and electrostatic microactuators, based on the measurement of pull-in voltages and resonance frequency, is described. Using this combination of measurements, one can estimate process-induced variations in the device layout dimensions as well as deviations from nominal value in material properties, which can be used either for testing or device diagnostics purposes. Measurements performed on fabricated devices confirm that the 250 nm overetch observed on SEM images can be correctly estimated using the proposed technique.

  16. Plasticity-rigidity cycles: A general adaptation mechanism

    OpenAIRE

    Csermely, Peter

    2015-01-01

    Successful adaptation helped the emergence of complexity. Alternating plastic- and rigid-like states were recurrently considered to play a role in adaptive processes. However, this extensive knowledge remained fragmented. In this paper I describe plasticity-rigidity cycles as a general adaptation mechanism operating in molecular assemblies, assisted protein folding, cellular differentiation, learning, memory formation, creative thinking, as well as the organization of social groups and ecosys...

  17. A coupled elasto-plastic-damage mechanical model for marble

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    A profound understanding of the mechanical behaviors of marble is very important for the design and construction of deep diversion tunnels in Jinping II hydropower station.In this paper,a coupled elasto-plastic-damage mechanical model is presented for Jinping marble.Firstly,the experimental investigations on Jinping marble are summarized.Then,based on the framework of continuum damage and plastic theories,a general mechanical model is proposed to predict the mechanical responses of Jinping marble.The proposed model is used to simulate the triaxial compressive tests,and there is a general good agreement between experimental data and numerical predictions in a qualitative manner.The proposed model is able to capture the main features of Jinping marble observed in experiments,such as progressive yielding process,damage induced by plastic distortion,dilation,elastic degradation and stress sensitivity.

  18. The regulation of myoblast plasticity and its mechanism

    Institute of Scientific and Technical Information of China (English)

    Peng ZHANG; Xiao-ping CHEN

    2012-01-01

    The development of skeletal muscle is a highly regulated,multi-step process in which pluripotent mesodermal cells give rise to myoblasts that subsequently withdraw from the cell cycle and differentiate into myotubes as well as myofibers.The plasticity of myoblasts plays a critical role in maintaining skeletal muscle structure and function by myoblast activation,migration,adhesion,membrane reorganization,nuclear fusion,finally forming myotubes/myofibers.Our studies demonstrate that the local hypoxic microenvironment,a great diversity of regulatory factors such as IL-6 superfamily factors (IL-6,LIF,CNTF) and TGF-β1 could regulate the myoblast plasticity.The aim of this paper is to review the previous studies focused on the regulation of myoblast plasticity and its mechanism in our laboratory.Knowledge about the microenvironment or factors involved in regulating the myoblast plasticity will help develop the prevention and cure measures of skeletal muscle diseases.

  19. Molecular mechanisms of synaptic plasticity and memory.

    Science.gov (United States)

    Elgersma, Y; Silva, A J

    1999-04-01

    To unravel the molecular and cellular bases of learning and memory is one of the most ambitious goals of modern science. The progress of recent years has not only brought us closer to understanding the molecular mechanisms underlying stable, long-lasting changes in synaptic strength, but it has also provided further evidence that these mechanisms are required for memory formation.

  20. Mechanical behavior of plastic materials for automobile cockpit module

    Science.gov (United States)

    Woo, Changsu.; Park, Hyunsung.; Jo, Jinho.

    2013-12-01

    Engineering plastics are used in instrument panels, interior trims, and other vehicle applications, and the thermo-mechanical behaviors of plastic materials are strongly influenced by many environmental factors such as temperature, sunlight, and rain. As the material properties change, the mechanical parts create unexpected noise. In this study, the dynamic mechanical property changes of plastics used in automobiles are measured to investigate the effect of temperature. Visco-elastic properties such as the glass transition temperature and storage modulus and loss factors under temperature and frequency sweeps were measured. The data results were compared with the original ones before aging to analyze the behavioral changes. It was found that as the temperature increased, the storage modulus decreased and the loss factor increased slightly.

  1. Mechanical Characterisation of Interface for Steel/Polymer Composite Using Pull-out Test: Shear-Lag and Frictional Analysis

    Institute of Scientific and Technical Information of China (English)

    Mohamed KHARRAT; Maher DAMMAK; Amine CHARFI

    2006-01-01

    Fibre-matrix interface is known to have contribution to the mechanical performance of fibre-reinforced composite by its potential for load transfer between the fibre and the matrix. Such load transfer is of great importance in dentistry when a post is used for fixing a ceramic crown on the tooth. In this study, a pull-outtest was carried out to analyse the interfacial properties of a steel fibre embedded in a polyester and epoxy matrices.It was found that the fibre-matrix interface is debonded on the whole embedded length when the fibre stress reached the debonding stress. Then, the fibre stress fell down to the initial extraction stress required to pulling out the debonded fibre from the matrix. Both debonding stress and initial extraction stress initiated a linear increase with the implantation length after the debonding stress reached horizontal asymptotes. To analyse the fibre-matrix load transfer before debonding, an analytical shear-lag model was adopted to in this test conditions. Fitting the experimental results with the analytical model provided the interfacial shear strength. By considering the Coulomb friction at the fibre-matrix interface during the fibre extraction process, an analytical model which considers Poisson's effects on both fibre and matrix, was developed. In this model, knowledge of the initial extraction stress of the fibre provides the residual normal stress at the fibre-matrix interface.

  2. Push-pull receptive field organization and synaptic depression: Mechanisms for reliably encoding naturalistic stimuli in V1

    Directory of Open Access Journals (Sweden)

    Jens eKremkow

    2016-05-01

    Full Text Available Neurons in the primary visual cortex are known for responding vigorously but with high variability to classical stimuli such as drifting bars or gratings. By contrast, natural scenes are encoded more efficiently by sparse and temporal precise spiking responses. We used a conductance-based model of the visual system in higher mammals to investigate how two specific features of the thalamo-cortical pathway, namely push-pull receptive field organization and synaptic depression, can contribute to this contextual reshaping of V1 responses. By comparing cortical dynamics evoked respectively by natural vs. artificial stimuli in a comprehensive parametric space analysis, we demonstrate that the reliability and sparseness of the spiking responses during natural vision is not a mere consequence of the increased bandwidth in the sensory input spectrum. Rather, it results from the combined impacts of synaptic depression and push-pull inhibition, the later acting for natural scenes as a form of effective feed-forward inhibition as demonstrated in other sensory systems. Thus, the combination of feedforward-like inhibition with fast thalamo-cortical synaptic depression by simple cells receiving a direct structured input from thalamus composes a generic computational mechanism for generating a sparse and reliable encoding of natural sensory events.

  3. Pulled elbow.

    OpenAIRE

    1999-01-01

    Pulled elbow (distal subluxation of the radial head) is a common, painful condition in young children. Although it has been well documented it is often missed, often mistreated, and generally over-investigated. Treatment is simple and effective. Without treatment the condition can continue for several days.

  4. Nonlinear Fracture Mechanics and Plasticity of the Split Cylinder Test

    DEFF Research Database (Denmark)

    Olesen, John Forbes; Østergaard, Lennart; Stang, Henrik

    2006-01-01

    demonstrates the influence of varying geometry or constitutive properties. For a split cylinder test in load control it is shown how the ultimate load is either plasticity dominated or fracture mechanics dominated. The transition between the two modes is related to changes in geometry or constitutive......The split cylinder testis subjected to an analysis combining nonlinear fracture mechanics and plasticity. The fictitious crack model is applied for the analysis of splitting tensile fracture, and the Mohr-Coulomb yield criterion is adopted for modelling the compressive crushing/sliding failure. Two...

  5. Maladaptive Plasticity for Motor Recovery after Stroke: Mechanisms and Approaches

    Science.gov (United States)

    Takeuchi, Naoyuki; Izumi, Shin-Ichi

    2012-01-01

    Many studies in human and animal models have shown that neural plasticity compensates for the loss of motor function after stroke. However, neural plasticity concerning compensatory movement, activated ipsilateral motor projections and competitive interaction after stroke contributes to maladaptive plasticity, which negatively affects motor recovery. Compensatory movement on the less-affected side helps to perform self-sustaining activity but also creates an inappropriate movement pattern and ultimately limits the normal motor pattern. The activated ipsilateral motor projections after stroke are unable to sufficiently support the disruption of the corticospinal motor projections and induce the abnormal movement linked to poor motor ability. The competitive interaction between both hemispheres induces abnormal interhemispheric inhibition that weakens motor function in stroke patients. Moreover, widespread disinhibition increases the risk of competitive interaction between the hand and the proximal arm, which results in an incomplete motor recovery. To minimize this maladaptive plasticity, rehabilitation programs should be selected according to the motor impairment of stroke patients. Noninvasive brain stimulation might also be useful for correcting maladaptive plasticity after stroke. Here, we review the underlying mechanisms of maladaptive plasticity after stroke and propose rehabilitation approaches for appropriate cortical reorganization. PMID:22792492

  6. The technology and mechanism of removal of plastic mulch and land preparation

    Institute of Scientific and Technical Information of China (English)

    ZHANG Huiyou; HOU Shulin; NA Mingjun; YANG Xiaoli; BAI Shengnan

    2007-01-01

    In this article ,the characteristic of the field plastic mulch, the craft for mechanization removal and land preparation of plastic mulch and the mechanism frequently used in the removal and land preparation of plastic mulch were introduced, which offered references for the design of removal mechanism and land preparation of plastic mulch and structural optimization combination of working components.

  7. Massive weight loss-induced mechanical plasticity in obese gait

    NARCIS (Netherlands)

    Hortobagyi, Tibor; Herring, Cortney; Pories, Walter J.; Rider, Patrick; DeVita, Paul

    2011-01-01

    Hortobagyi T, Herring C, Pories WJ, Rider P, DeVita P. Massive weight loss-induced mechanical plasticity in obese gait. J Appl Physiol 111: 1391-1399, 2011. First published August 18, 2011; doi:10.1152/japplphysiol.00291.2011.-We examined the hypothesis that metabolic surgery-induced massive weight

  8. Massive weight loss-induced mechanical plasticity in obese gait

    NARCIS (Netherlands)

    Hortobagyi, Tibor; Herring, Cortney; Pories, Walter J.; Rider, Patrick; DeVita, Paul

    2011-01-01

    Hortobagyi T, Herring C, Pories WJ, Rider P, DeVita P. Massive weight loss-induced mechanical plasticity in obese gait. J Appl Physiol 111: 1391-1399, 2011. First published August 18, 2011; doi:10.1152/japplphysiol.00291.2011.-We examined the hypothesis that metabolic surgery-induced massive weight

  9. Neural Circuitry and Plasticity Mechanisms Underlying Delay Eyeblink Conditioning

    Science.gov (United States)

    Freeman, John H.; Steinmetz, Adam B.

    2011-01-01

    Pavlovian eyeblink conditioning has been used extensively as a model system for examining the neural mechanisms underlying associative learning. Delay eyeblink conditioning depends on the intermediate cerebellum ipsilateral to the conditioned eye. Evidence favors a two-site plasticity model within the cerebellum with long-term depression of…

  10. A Plastic Damage Mechanics Model for Engineered Cementitious Composites

    DEFF Research Database (Denmark)

    Dick-Nielsen, Lars; Stang, Henrik; Poulsen, Peter Noe

    2007-01-01

    This paper discusses the establishment of a plasticity-based damage mechanics model for Engineered Cementitious Composites (ECC). The present model differs from existing models by combining a matrix and fiber description in order to describe the behavior of the ECC material. The model provides in...

  11. Plastic mechanism of deformation of garnet-- Water weakening

    Institute of Scientific and Technical Information of China (English)

    SU; Wen(苏文); CONG; Bolin(从柏林); YOU; Zhendong(游振东); ZHONG; Zengqiu(钟增球); CHEN; Daizhang(陈代章)

    2002-01-01

    The strongly deformed eclogites are well developed in ultra-high pressure jadeite-quartzite zone of the Dabie Mountains, Eastern China, and garnets had been deformed strongly. Observations by transmission electron microscopy identified not only structure of plastic deformation occurring as free dislocation, dislocation loops and dislocation walls, but also clusters of water molecules present in the deformed garnet. Using infrared spectroscopy, two types of hydrous components are identified as the hydroxyl and free-water in the garnet. Based on analysis of microstructure mechanism of deformation in garnets, and experimental data of petrology, the clusters of water molecules were considered to lead strong plastic deformation of garnet by dislocations because of mechanical weakening.

  12. Differential mechanisms of transmission and plasticity at mossy fiber synapses

    OpenAIRE

    McBain, Chris J.

    2008-01-01

    The last few decades have seen the hippocampal formation at front and center in the field of synaptic transmission. However, much of what we know about hippocampal short- and long-term plasticity has been obtained from research at one particular synapse; the Schaffer collateral input onto principal cells of the CA1 subfield. A number of recent studies, however, have demonstrated that there is much to be learned about target-specific mechanisms of synaptic transmission by study of the lesser k...

  13. Single-Molecule Pull-down FRET (SiMPull-FRET) to dissect the mechanisms of biomolecular machines

    Science.gov (United States)

    Kahlscheuer, Matthew L.; Widom, Julia; Walter, Nils G.

    2016-01-01

    Spliceosomes are multi-megadalton RNA-protein complexes responsible for the faithful removal of non-coding segments (introns) from pre-messenger RNAs (pre-mRNAs), a process critical for the maturation of eukaryotic mRNAs for subsequent translation by the ribosome. Both the spliceosome and ribosome, as well as many other RNA and DNA processing machineries, contain central RNA components that endow biomolecular complexes with precise, sequence-specific nucleic acid recognition and versatile structural dynamics. Single molecule fluorescence (or Förster) resonance energy transfer (smFRET) microscopy is a powerful tool for the study of local and global conformational changes of both simple and complex biomolecular systems involving RNA. The integration of biochemical tools such as immunoprecipitation with advanced methods in smFRET microscopy and data analysis has opened up entirely new avenues towards studying the mechanisms of biomolecular machines isolated directly from complex biological specimens such as cell extracts. Here we detail the general steps for using prism-based total internal reflection fluorescence (TIRF) microscopy in exemplary single molecule pull-down FRET (SiMPull-FRET) studies of the yeast spliceosome and discuss the broad application potential of this technique. PMID:26068753

  14. Mechanical tools for the removal of Ixodes ricinus female ticks--differences of instruments and pulling or twisting?

    Science.gov (United States)

    Duscher, G G; Peschke, R; Tichy, A

    2012-10-01

    The fast and safe removal of ticks is of medical and veterinary importance since many tick-borne pathogens require time to be transmitted. In the past, many tools and applications were used to remove ticks from the skin of humans and pets. Choking the ticks by blocking their respiratory system with chemicals cannot be recommended due to the low respiratory rate of ticks. Mechanical devices to remove ticks are usually recommended; however, they vary with regard to their mechanism of seizing and holding the tick and in the way of extraction (pulling or twisting). In this study, five commercial tick removal devices with different mechanisms were tested on pets according to their practicability, injury of the mouthparts, and the idiosoma of female Ixodes ricinus ticks. Therefore, 22 veterinarians and four pet owners removed 596 ticks from various animals by using the different devices and filled in a questionnaire for each case. The tick species and instars were determined, and for the female I. ricinus ticks (n = 527) the condition of the mouthparts as well as the idiosoma was evaluated. Twisting of the female I. ricinus ticks reduced the force required for extraction, the adverse reaction of the animal and the time needed for removal. The device with a "V"-shaped slot which allows a grabbing of the mouthparts delivered the best results according to the condition of the mouthparts and the intactness of the female I. ricinus tick's body. Therefore, grabbing the mouthparts and twisting can be recommended for removal of I. ricinus females from pets.

  15. Thermo-mechanical coupling strategies in elastic-plastic problems

    Science.gov (United States)

    Vaz, M.; Lange, M. R.

    2017-03-01

    Modeling strategies aimed at thermo-mechanical coupled problems has been developed for a wide range of engineering applications. Staggered-type coupling procedures have been largely used in materials processing operations, especially in commercial codes, owing to their simplicity and flexibility. The present work shows that, in thermo-plastic problems, the classical implementation of the most common coupling procedure may present accuracy issues and time-stepping dependency. Numerical experiments indicate that an iterative coupling scheme constitutes a viable and simple approach to this class of problems.

  16. Elastic, plastic, and fracture mechanisms in graphene materials.

    Science.gov (United States)

    Daniels, Colin; Horning, Andrew; Phillips, Anthony; Massote, Daniel V P; Liang, Liangbo; Bullard, Zachary; Sumpter, Bobby G; Meunier, Vincent

    2015-09-23

    In both research and industry, materials will be exposed to stresses, be it during fabrication, normal use, or mechanical failure. The response to external stress will have an important impact on properties, especially when atomic details govern the functionalities of the materials. This review aims at summarizing current research involving the responses of graphene and graphene materials to applied stress at the nanoscale, and to categorize them by stress-strain behavior. In particular, we consider the reversible functionalization of graphene and graphene materials by way of elastic deformation and strain engineering, the plastic deformation of graphene oxide and the emergence of such in normally brittle graphene, the formation of defects as a response to stress under high temperature annealing or irradiation conditions, and the properties that affect how, and mechanisms by which, pristine, defective, and polycrystalline graphene fail catastrophically during fracture. Overall we find that there is significant potential for the use of existing knowledge, especially that of strain engineering, as well as potential for additional research into the fracture mechanics of polycrystalline graphene and device functionalization by way of controllable plastic deformation of graphene.

  17. SIMULATION OF OPEN MECHANISMS FOR THE ADDITIVE PROCESS WELD PLASTICS

    Directory of Open Access Journals (Sweden)

    N. N. Hurski

    2016-01-01

    Full Text Available This article discusses: model of the two-link mechanism; generalized scheme of mechatronic simulation model of 3D-printer with the positioning units of electric DC; mathematical model of the actuator of the printer unit in the form of a system of differential equations; 3D-printer programming model implemented in the Matlab-Simulink environment using the c standard library blocks and SimMechanics library; virtual (animated 3D printer model on the basis of the library Simulink 3D Animation, supports the visualization of the movements of the designed mechanism of the basic units. We present the initial data and the results of simulation of 3D-printer type Scara as a waveform positioning actuator (extruder in the manufacture of test items by fusing plastic.

  18. Plasticity of intermediate mechanics students’ coordinate system choice

    Directory of Open Access Journals (Sweden)

    Eleanor C. Sayre

    2008-11-01

    Full Text Available We investigate the interplay between mathematics and physics resources in intermediate mechanics students. In the mechanics course, the selection and application of coordinate systems is a consistent thread. At the University of Maine, students often start the course with a strong preference to use Cartesian coordinates, in accordance with their prior physics and mathematics classes. In small-group interviews and in homework help sessions, we ask students to define a coordinate system and set up the equations of motion for a simple pendulum for which polar coordinates are more appropriate. We analyze video data from several encounters using a combination of Process/Object theory and Resource Theory. We find that students sometimes persist in using an inappropriate Cartesian system. Furthermore, students often derive (rather than recall the details of the polar coordinate system, indicating that their knowledge is far from solid. To describe our work more precisely, we define a scale of plasticity and several heuristics for defining resources and their plasticity.

  19. Differential mechanisms of transmission and plasticity at mossy fiber synapses.

    Science.gov (United States)

    McBain, Chris J

    2008-01-01

    The last few decades have seen the hippocampal formation at front and center in the field of synaptic transmission. However, much of what we know about hippocampal short- and long-term plasticity has been obtained from research at one particular synapse; the Schaffer collateral input onto principal cells of the CA1 subfield. A number of recent studies, however, have demonstrated that there is much to be learned about target-specific mechanisms of synaptic transmission by study of the lesser known synapse made between the granule cells of the dentate gyrus; the so-called mossy fiber synapse, and its targets both within the hilar region and the CA3 hippocampus proper. Indeed investigation of this synapse has provided an embarrassment of riches concerning mechanisms of transmission associated with feedforward excitatory and inhibitory control of the CA3 hippocampus. Importantly, work from a number of labs has revealed that mossy fiber synapses possess unique properties at both the level of their anatomy and physiology, and serve as an outstanding example of a synapse designed for target-specific compartmentalization of synaptic transmission. The purpose of the present review is to highlight several aspects of this synapse as they pertain to a novel mechanism of bidirectional control of synaptic plasticity at mossy fiber synapses made onto hippocampal stratum lucidum interneurons. It is not my intention to pour over all that is known regarding the mossy fiber synapse since many have explored this topic exhaustively in the past and interested readers are directed to other fine reviews (Henze et al., 2000; Urban et al., 2001; Lawrence and McBain, 2003; Bischofberger et al., 2006; Nicoll and Schmitz, 2005).

  20. The ultrastructure of fibronectin fibers pulled from a protein monolayer at the air-liquid interface and the mechanism of the sheet-to-fiber transition.

    Science.gov (United States)

    Mitsi, Maria; Handschin, Stephan; Gerber, Isabel; Schwartländer, Ruth; Klotzsch, Enrico; Wepf, Roger; Vogel, Viola

    2015-01-01

    Fibronectin is a globular protein that circulates in the blood and undergoes fibrillogenesis if stretched or under other partially denaturing conditions, even in the absence of cells. Stretch assays made by pulling fibers from droplets of solutions containing high concentrations of fibronectin have previously been introduced in mechanobiology, particularly to ask how bacteria and cells exploit the stretching of fibronectin fibers within extracellular matrix to mechano-regulate its chemical display. Our electron microscopy analysis of their ultrastructure now reveals that the manually pulled fibronectin fibers are composed of densely packed lamellar spirals, whose interlamellar distances are dictated by ion-tunable electrostatic interactions. Our findings suggest that fibrillogenesis proceeds via an irreversible sheet-to-fiber transition as the fibronectin sheet formed at the air-liquid interface of the droplet is pulled off by a sharp tip. This far from equilibrium process is driven by the externally applied force, interfacial surface tension, shear-induced fibronectin self-association, and capillary force-induced buffer drainage. The ultrastructural characterization is then contrasted with previous FRET studies that characterized the molecular strain within these manually pulled fibers. Particularly relevant for stretch-dependent binding studies is the finding that the interior fiber surfaces are accessible to nanoparticles smaller than 10 nm. In summary, our study discovers the underpinning mechanism by which highly hierarchically structured fibers can be generated with unique mechanical and mechano-chemical properties, a concept that might be extended to other bio- or biomimetic polymers. Copyright © 2014 The Authors. Published by Elsevier Ltd.. All rights reserved.

  1. Mechanical and chemical recycling of solid plastic waste.

    Science.gov (United States)

    Ragaert, Kim; Delva, Laurens; Van Geem, Kevin

    2017-08-17

    This review presents a comprehensive description of the current pathways for recycling of polymers, via both mechanical and chemical recycling. The principles of these recycling pathways are framed against current-day industrial reality, by discussing predominant industrial technologies, design strategies and recycling examples of specific waste streams. Starting with an overview on types of solid plastic waste (SPW) and their origins, the manuscript continues with a discussion on the different valorisation options for SPW. The section on mechanical recycling contains an overview of current sorting technologies, specific challenges for mechanical recycling such as thermo-mechanical or lifetime degradation and the immiscibility of polymer blends. It also includes some industrial examples such as polyethylene terephthalate (PET) recycling, and SPW from post-consumer packaging, end-of-life vehicles or electr(on)ic devices. A separate section is dedicated to the relationship between design and recycling, emphasizing the role of concepts such as Design from Recycling. The section on chemical recycling collects a state-of-the-art on techniques such as chemolysis, pyrolysis, fluid catalytic cracking, hydrogen techniques and gasification. Additionally, this review discusses the main challenges (and some potential remedies) to these recycling strategies and ground them in the relevant polymer science, thus providing an academic angle as well as an applied one. Copyright © 2017 Elsevier Ltd. All rights reserved.

  2. Innovative plasticized alginate obtained by thermo-mechanical mixing: Effect of different biobased polyols systems.

    Science.gov (United States)

    Gao, Chengcheng; Pollet, Eric; Avérous, Luc

    2017-02-10

    Plasticized alginate films with different biobased polyols (glycerol and sorbitol) and their mixtures were successfully prepared by thermo-mechanical mixing instead of the usual casting-evaporation procedure. The microstructure and properties of the different plasticized alginate formulations were investigated by SEM, FTIR, XRD, DMTA and uniaxial tensile tests. SEM and XRD results showed that native alginate particles were largely destructured with the plasticizers (polyols and water), under a thermo-mechanical input. With increasing amount of plasticizers, the samples showed enhanced homogeneity while their thermal and mechanical properties decreased. Compared to sorbitol, glycerol resulted in alginate films with a higher flexibility due to its better plasticization efficiency resulting from its smaller size and higher hydrophilic character. Glycerol and sorbitol mixtures seemed to be an optimum to obtain the best properties. This work showed that thermo-mechanical mixing is a promising method to produce, at large scale, plasticized alginate-based films with improved properties.

  3. Hair Pulling (Trichotillomania)

    Science.gov (United States)

    ... Facts for Families Guide Facts for Families - Vietnamese Hair Pulling (Trichotillomania) No. 96; Reviewed July 2013 It ... for children and adolescents to play with their hair. However, frequent or obsessive hair pulling can lead ...

  4. Molecular mechanisms underlying neuronal synaptic plasticity: systems biology meets computational neuroscience in the wilds of synaptic plasticity.

    Science.gov (United States)

    Blackwell, Kim T; Jedrzejewska-Szmek, Joanna

    2013-01-01

    Interactions among signaling pathways that are activated by transmembrane receptors produce complex networks and emergent dynamical behaviors that are implicated in synaptic plasticity. Temporal dynamics and spatial aspects are critical determinants of cell responses such as synaptic plasticity, although the mapping between spatiotemporal activity pattern and direction of synaptic plasticity is not completely understood. Computational modeling of neuronal signaling pathways has significantly contributed to understanding signaling pathways underlying synaptic plasticity. Spatial models of signaling pathways in hippocampal neurons have revealed mechanisms underlying the spatial distribution of extracellular signal-related kinase (ERK) activation in hippocampal neurons. Other spatial models have demonstrated that the major role of anchoring proteins in striatal and hippocampal synaptic plasticity is to place molecules near their activators. Simulations of yet other models have revealed that the spatial distribution of synaptic plasticity may differ for potentiation versus depression. In general, the most significant advances have been made by interactive modeling and experiments; thus, an interdisciplinary approach should be applied to investigate critical issues in neuronal signaling pathways. These issues include identifying which transmembrane receptors are key for activating ERK in neurons, and the crucial targets of kinases that produce long-lasting synaptic plasticity. Although the number of computer programs for computationally efficient simulation of large reaction-diffusion networks is increasing, parameter estimation and sensitivity analysis in these spatial models remain more difficult than in single compartment models. Advances in live cell imaging coupled with further software development will continue to accelerate the development of spatial models of synaptic plasticity. Copyright © 2013 Wiley Periodicals, Inc.

  5. Study on Mechanical Properties of Concrete Using Plastic Waste as an Aggregate

    Science.gov (United States)

    Jaivignesh, B.; Sofi, A.

    2017-07-01

    Disposal of large quantity of plastic causes land, water and air pollution etc.., so a study is conducted to recycle the plastic in concrete. This work investigates about the replacement of natural aggregate with non-biodegradable plastic aggregate made up of mixed plastic waste in concrete. Several tests are conducted such as compressive strength of cube, split tensile strength of cylinder, flexural strength test of prism to identify the properties and behavior of concrete using plastic aggregate. Replacement of fine aggregate weight by 10%, 15%, 20% with Plastic fine (PF) aggregate and for each replacement of fine aggregate 15%, 20%, 25% of coarse aggregate replacement also conducted with Plastic Coarse(PC) aggregate. In literatures reported that the addition of plastic aggregate in concrete causes the reduction of strength in concrete due to poor bonding between concrete and plastic aggregate, so addition of 0.3% of steel fiber by weight of cement in concrete is done to improve the concrete strength. Totally 60 cubes, 60 cylinders and 40 prisms are casted to identify the compressive strength, split tensile strength and flexural strength respectively. Casted specimens are tested at 7 and 28 days. The identified results from concrete using plastic aggregate are compared with conventional concrete. Result shows that reduction in mechanical properties of plastic aggregate added concrete. This reduction in strength is mainly due to poor bond strength between cement and plastic aggregate.

  6. Thermal-mechanical coupled effect on fracture mechanism and plastic characteristics of sandstone

    Institute of Scientific and Technical Information of China (English)

    ZUO; JianPing; XIE; HePing; ZHOU; HongWei; PENG; SuPing

    2007-01-01

    Scanning electronic microscopy (SEM) was employed to investigate fractographs of sandstone in mine roof strata under thermal-mechanical coupled effect. Based on the evolution of sandstone surface morphology in the failure process and fractography, the fracture mechanism was studied and classified under meso and micro scales, respectively. The differences between fractographs under different temperatures were examined in detail. Under high temperature, fatigue fracture and plastic deformation occurred in the fracture surface. Therefore, the temperature was manifested by these phenomena to influence strongly on micro failure mechanism of sandstone. In addition, the failure mechanism would transit from brittle failure mechanism at low temperature to coupled brittle-ductile failure mechanism at high temperature. The variation of sandstone strength under different temperature can be attributed to the occurrence of plastic deformation, fatigue fracture, and microcracking. The fatigue striations in the fracture surfaces under high temperature may be interpreted as micro fold. And the coupled effect of temperature and tensile stress may be another formation mechanism of micro fold in geology.

  7. International conference on Statistical Mechanics of Plasticity and Related Instabilities

    Science.gov (United States)

    2006-11-01

    The papers compiled in this volume are based on talks and posters given at the International Conference on "Statistical Mechanics of Plasticity and Related Instabilities", (SMPRI 2005), held at the Materials Research Center of the Indian Institute of Science, Bangalore, India, from August 29 to September 2, 2005. Our aim in organizing SMPRI 2005 was to promote and enhance interactions between researchers from the statistical physics, materials science and solid mechanics communities. While predicting the (macroscopic) deformation properties of materials is a classical topic of materials science and materials mechanics, statistical physicists have become increasingly interested in the collective processes which control the irreversible deformation of matter on microscopic and mesoscopic scales. The SMPRI 2005 meeting has been a forum for the exchange of concepts, research ideas, and results among these communities. We hope that the contributions contained in this proceedings volume will not only help to continue and deepen this exchange, but also to disseminate the results beyond the, necessarily limited, circle of the actual participants. We want to thank all contributors for the work in preparing their manuscripts. We are grateful to the institutions which have supported this conference, in particular the Asian Office for Aerospace Research and Developement (AOARD/AFOSR), the Jawaharlal Nehru Center for Advanced Scientific Research, the Indian Center for Scientific and Industrial Research, the Indian Defense Research and Developement Organization, The Abdus Salam International Center for Theoretical Physics, Italy, the Indian Institute of Science, in particular the Center for Condensed Matter Theory and Materials Reseach Center, the Department of Science and Technology, India, the Materials Research Society of India, and the Karnatake State Center for Science and Technology. We would also like to thank the staff and students of Materials Research Center, Indian

  8. Sequential push-pull pumping mechanism for washing and evacuation of an immunoassay reaction chamber on a microfluidic CD platform.

    Directory of Open Access Journals (Sweden)

    Tzer Hwai Gilbert Thio

    Full Text Available A centrifugal compact disc (CD microfluidic platform with reservoirs, micro-channels, and valves can be employed for implementing a complete immunoassay. Detection or biosensor chambers are either coated for immuno-interaction or a biosensor chip is inserted in them. On microfluidic CDs featuring such multi-step chemical/biological processes, the biosensor chamber must be repeatedly filled with fluids such as enzymes solutions, buffers, and washing solutions. After each filling step, the biosensor chamber needs to be evacuated by a passive siphoning process to prepare it for the next step in the assay. However, rotational speed dependency and limited space on a CD are two big obstacles to performing such repetitive filling and siphoning steps. In this work, a unique thermo-pneumatic (TP Push-Pull pumping method is employed to provide a superior alternative biosensor chamber filling and evacuation technique. The proposed technique is demonstrated on two CD designs. The first design features a simple two-step microfluidic process to demonstrate the evacuation technique, while the second design shows the filling and evacuation technique with an example sequence for an actual immunoassay. In addition, the performance of the filling and evacuation technique as a washing step is also evaluated quantitatively and compared to the conventional manual bench top washing method. The two designs and the performance evaluation demonstrate that the technique is simple to implement, reliable, easy to control, and allows for repeated push-pulls and thus filling and emptying of the biosensor chamber. Furthermore, by addressing the issue of rotational speed dependency and limited space concerns in implementing repetitive filling and evacuation steps, this newly introduced technique increases the flexibility of the microfluidic CD platform to perform multi-step biological and chemical processes.

  9. Molecular mechanisms of phenotypic plasticity in social insects

    Science.gov (United States)

    Polyphenism in insects, whereby a single genome expresses different phenotypes in response to environmental cues, is a fascinating biological phenomenon. Social insects are especially intriguing examples of phenotypic plasticity because division of labor results in the development of extreme morphol...

  10. Massive weight loss-induced mechanical plasticity in obese gait.

    Science.gov (United States)

    Hortobágyi, Tibor; Herring, Cortney; Pories, Walter J; Rider, Patrick; Devita, Paul

    2011-11-01

    We examined the hypothesis that metabolic surgery-induced massive weight loss causes mass-driven and behavioral adaptations in the kinematics and kinetics of obese gait. Gait analyses were performed at three time points over ∼1 yr in initially morbidly obese (mass: 125.7 kg; body mass index: 43.2 kg/m(2)) but otherwise healthy adults. Ten obese adults lost 27.1% ± 5.1 (34.0 ± 9.4 kg) weight by the first follow-up at 7.0 mo (±0.7) and 6.5 ± 4.2% (8.2 ± 6.0 kg) more by the second follow-up at 12.8 mo (±0.9), with a total weight loss of 33.6 ± 8.1% (42.2 ± 14.1 kg; P = 0.001). Subjects walked at a self-selected and a standard 1.5 m/s speed at the three time points and were also compared with an age- and gender-matched comparison group at the second follow-up. Weight loss increased swing time, stride length, gait speed, hip range of motion, maximal knee flexion, and ankle plantarflexion. Weight loss of 27% led to 3.9% increase in gait speed. An additional 6.5% weight loss led to an additional 7.3% increase in gait speed. Sagittal plane normalized knee torque increased and absolute ankle and frontal plane knee torques decreased after weight loss. We conclude that large weight loss produced mechanical plasticity by modifying ankle and knee torques and gait behavior. There may be a weight loss threshold of 30 kg limiting changes in gait kinematics. Implications for exercise prescription are also discussed.

  11. Dual-functional Memory and Threshold Resistive Switching Based on the Push-Pull Mechanism of Oxygen Ions

    KAUST Repository

    Huang, Yi-Jen

    2016-04-07

    The combination of nonvolatile memory switching and volatile threshold switching functions of transition metal oxides in crossbar memory arrays is of great potential for replacing charge-based flash memory in very-large-scale integration. Here, we show that the resistive switching material structure, (amorphous TiOx)/(Ag nanoparticles)/(polycrystalline TiOx), fabricated on the textured-FTO substrate with ITO as the top electrode exhibits both the memory switching and threshold switching functions. When the device is used for resistive switching, it is forming-free for resistive memory applications with low operation voltage (<±1 V) and self-compliance to current up to 50 μA. When it is used for threshold switching, the low threshold current is beneficial for improving the device selectivity. The variation of oxygen distribution measured by energy dispersive X-ray spectroscopy and scanning transmission electron microscopy indicates the formation or rupture of conducting filaments in the device at different resistance states. It is therefore suggested that the push and pull actions of oxygen ions in the amorphous TiOx and polycrystalline TiOx films during the voltage sweep account for the memory switching and threshold switching properties in the device.

  12. Dual-functional Memory and Threshold Resistive Switching Based on the Push-Pull Mechanism of Oxygen Ions

    Science.gov (United States)

    Huang, Yi-Jen; Chao, Shih-Chun; Lien, Der-Hsien; Wen, Cheng-Yen; He-Hau, Jr.; Lee, Si-Chen

    2016-04-01

    The combination of nonvolatile memory switching and volatile threshold switching functions of transition metal oxides in crossbar memory arrays is of great potential for replacing charge-based flash memory in very-large-scale integration. Here, we show that the resistive switching material structure, (amorphous TiOx)/(Ag nanoparticles)/(polycrystalline TiOx), fabricated on the textured-FTO substrate with ITO as the top electrode exhibits both the memory switching and threshold switching functions. When the device is used for resistive switching, it is forming-free for resistive memory applications with low operation voltage (compliance to current up to 50 μA. When it is used for threshold switching, the low threshold current is beneficial for improving the device selectivity. The variation of oxygen distribution measured by energy dispersive X-ray spectroscopy and scanning transmission electron microscopy indicates the formation or rupture of conducting filaments in the device at different resistance states. It is therefore suggested that the push and pull actions of oxygen ions in the amorphous TiOx and polycrystalline TiOx films during the voltage sweep account for the memory switching and threshold switching properties in the device.

  13. Possible Mechanism of Plasticity Influenced by Magnetic Field

    Institute of Scientific and Technical Information of China (English)

    LIU Zhao-Long; FAN Tian-You; HU Hai-Yun

    2006-01-01

    The strain energy of an edge dislocation in an external static magnetic field is determined by the theory of elasticity and electrodynamics according to the Volterra dislocation model for continuous media. The results show that the strain energy of the edge dislocation in paramagnetic states is increased due to static magnetic field and the increase in the energy of the dislocation is capable of influencing the dislocation depinning which leads to the change of plasticity. This gives an explanation on plasticity induced by magnetic field.

  14. Mechanics Model of Plug Welding

    Science.gov (United States)

    Zuo, Q. K.; Nunes, A. C., Jr.

    2015-01-01

    An analytical model has been developed for the mechanics of friction plug welding. The model accounts for coupling of plastic deformation (material flow) and thermal response (plastic heating). The model predictions of the torque, energy, and pull force on the plug were compared to the data of a recent experiment, and the agreements between predictions and data are encouraging.

  15. Numerical Simulation of the Mechanical Properties and Failure of Heterogeneous Elasto-Plastic Materials

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    A general numerical approach was developed to simulate the mechanical properties and the failure of heterogeneous elasto-plastic materials using statistical distributions of the material properties. An appropriate elastic-plastic constitutive relation is used to describe the material behavior and failure in each element, with a two-parameter Weibull distribution used to produce the initial heterogeneous material property variations. An adaptive incremental load-step is applied so that only one or a few elements (or integration points) change their status (i.e., from elastic to plastic, or from plastic to strain failure) within one load step. A failed element is then assigned a very small modulus to simulate the failure rather than removing it from the model, which keeps the continuity of the geometric mesh. The numerical results show that the model is suitable for simulating the effective mechanical properties and failure of heterogeneous materials with local elasto-plastic constitutive relations.

  16. Design of core-pulling mechanism of injection mould for flaring pipe fitting%扩口类管件注射模抽芯机构设计

    Institute of Scientific and Technical Information of China (English)

    苏伟

    2014-01-01

    分析了扩口类管件结构及成型工艺,以ϕ75 mm扩口管件为例详细介绍了扩口管件注射模的结构,阐述了扩口管件模具抽芯机构、锁模机构以及定位机构等的设计,叙述了模具工作过程,可为扩口类模具设计提供思路。%The structure and forming process of a flaring pipe fitting was analyzed; and the structure and working process of an injection mould for a ϕ75 mm flaring pipe fitting were presented, in particular the flaring, core-pulling, mould clamping and positioning mech-anism.

  17. Mechanisms by Which Phenotypic Plasticity Affects Adaptive Divergence and Ecological Speciation.

    Science.gov (United States)

    Nonaka, Etsuko; Svanbäck, Richard; Thibert-Plante, Xavier; Englund, Göran; Brännström, Åke

    2015-11-01

    Phenotypic plasticity is the ability of one genotype to produce different phenotypes depending on environmental conditions. Several conceptual models emphasize the role of plasticity in promoting reproductive isolation and, ultimately, speciation in populations that forage on two or more resources. These models predict that plasticity plays a critical role in the early stages of speciation, prior to genetic divergence, by facilitating fast phenotypic divergence. The ability to plastically express alternative phenotypes may, however, interfere with the early phase of the formation of reproductive barriers, especially in the absence of geographic barriers. Here, we quantitatively investigate mechanisms under which plasticity can influence progress toward adaptive genetic diversification and ecological speciation. We use a stochastic, individual-based model of a predator-prey system incorporating sexual reproduction and mate choice in the predator. Our results show that evolving plasticity promotes the evolution of reproductive isolation under diversifying environments when individuals are able to correctly select a more profitable habitat with respect to their phenotypes (i.e., adaptive habitat choice) and to assortatively mate with relatively similar phenotypes. On the other hand, plasticity facilitates the evolution of plastic generalists when individuals have a limited capacity for adaptive habitat choice. We conclude that plasticity can accelerate the evolution of a reproductive barrier toward adaptive diversification and ecological speciation through enhanced phenotypic differentiation between diverging phenotypes.

  18. Yarn Pull-Out as a Mechanism for Dissipation of Ballistic Impact Energy in Kevlar KM-2 Fabric, Part 1: Quasi-Static Characterization of Yarn Pull-Out

    Science.gov (United States)

    2004-05-01

    architectures and fiber types, including Kevlar K29, Spectra,* and Zylon .† The study found that the pull-out forces strongly depend on the transverse...during testing. *Spectra is a registered trademark of Honeywell. † Zylon is a registered trademark of...deformations measured by Shockey et al. (2001) for Zylon and Kevlar K29 fabrics. Therefore, yarn stretching does not play an important role in the

  19. MEASURING AND MODELING OF THE MECHANICAL PROPERTIES OF COMPOSITE BEARING PAD MADE OF PLASTIC MATRIX AND FINE BRONZE ELASTIC SPRINGS

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The viscoelastic properties of the normal PTFE plastic and strengthened PTFE plastic for bearing pad are measured. The mechanical properties of the composite material for bearing pad, which is made of the aforementioned plastics as matrix reinforced by fine bronze elastic springs, are modeled and relaxation modulus of the material are presented. The difference between these two kinds of PTFE is studied. The results show that the complex modulus of PTFE plastics for bearing pad is higher than that of normal PTFE plastics.

  20. Technical specifications for mechanical recycling of agricultural plastic waste.

    Science.gov (United States)

    Briassoulis, D; Hiskakis, M; Babou, E

    2013-06-01

    Technical specifications appropriate for the recycling of agricultural plastic wastes (APWs), widely accepted by the recycling industry were developed. The specifications establish quality standards to be met by the agricultural plastics producers, users and the agricultural plastic waste management chain. They constitute the base for the best economical and environmental valorisation of the APW. The analysis of the APW streams conducted across Europe in the framework of the European project "LabelAgriWaste" revealed the inherent characteristics of the APW streams and the inherent constraints (technical or economical) of the APW. The APW stream properties related to its recycling potential and measured during pilot trials are presented and a subsequent universally accepted simplified and expanded list of APW recycling technical specifications is proposed and justified. The list includes two sets of specifications, applied to two different quality categories of recyclable APW: one for pellet production process ("Quality I") and another one for plastic profile production process ("Quality II"). Parameters that are taken into consideration in the specifications include the APW physical characteristics, contamination, composition and degradation. The proposed specifications are focused on polyethylene based APW that represents the vast majority of the APW stream. However, the specifications can be adjusted to cover also APW of different materials (e.g. PP or PVC) that are found in very small quantities in protected cultivations in Europe. The adoption of the proposed specifications could transform this waste stream into a labelled commodity traded freely in the market and will constitute the base for the best economical and environmental valorisation of the APW.

  1. EFFECT OF PLASTICIZERS ON MECHANICAL PROPERTIES OF EDIBLE FILM FROM JANENG STARCH – CHITOSAN

    Directory of Open Access Journals (Sweden)

    Narlis Juandi

    2016-10-01

    Full Text Available The interest in the development of edible and biodegradable films has increased because it is every day more evident that non degradable are doing much damage to the environment. In this research, edible films were based on blends of janeng starch in different proportions, added of palm oil or glycerol, which were used as plasticizers. The objective was to study the effect of two different plasticizers, palm oil and glycerol of edible film from janeng starch–chitosan on the mechanical properties and FTIR spectra. Increasing concentration of glycerol as plasticizer resulted tend to increased tensile strength and elongation at break. The tensile strength and elongation at break values for palm oil is higher than glycerol as plasticizer at the same concentration. FTIR spectra show the process of making edible film from janeng starch–chitosan with palm oil or glycerol as plasticizers are physically mixing in the presence of hydrogen interactions between chains.

  2. From waste plastics to industrial raw materials: A life cycle assessment of mechanical plastic recycling practice based on a real-world case study.

    Science.gov (United States)

    Gu, Fu; Guo, Jianfeng; Zhang, Wujie; Summers, Peter A; Hall, Philip

    2017-12-01

    Mechanical recycling of waste plastics is an environmental solution to the problem of waste plastic disposal, and has already become a common practice in industry. However, limited information can be found on either the industralised plastic recycling or the recycled materials, despite the use of recycled plastics has already extended to automobile production. This study investigates the life cycle environmental impacts of mechanical plastic recycling practice of a plastic recycling company in China. Waste plastics from various sources, such as agricultural wastes, plastic product manufacturers, collected solid plastic wastes and parts dismantled from waste electric and electronic equipments, are processed in three routes with products end up in different markets. The results of life cycle assessments show that the extrusion process has the largest environmental impacts, followed by the use of fillers and additives. Compared to production of virgin plastics and composites, the mechanical recycling is proved to be a superior alternative in most environmental aspects. Substituting virgin plastic composites with recycled plastic composites has achieved the highest environmental benefits, as virgin composite production has an impact almost 4 times higher that of the recycled composite production in each ReCiPe endpoint damage factor. Sensitivity analysis shows that the coverage of collecting network contribute affect little to overall environmental impact, and centralisation plays an important role in reducing overall environmental impacts. Among the fillers and additives, impact modifiers account for the most significant contributions to the environmental impacts of recycled composites. This study provides necessary information about the existing industrialised plastic recycling practice, and recommendations are given. Research implications are presented with the purpose to achieve higher substitution rate and lower environmental impact. Copyright © 2017 Elsevier B

  3. The Effects of Weathering on Mechanical Properties of Glass Fiber Reinforced Plastics (Grp) Materials

    OpenAIRE

    Abdullah, H.; S. Al Araimi and R. A. Siddiqui

    2012-01-01

    Glass fiber reinforced plastics composite is extensively used as a structural material for pools, oil pipes and tanks because it has good corrosion resistance properties.  The effects of weathering on the mechanical properties of glass fiber reinforced plastics (GRP) in the Sultanate of Oman have been studied.  The tensile and three point bend specimens were exposed to outdoor conditions (open atmosphere) in sunlight and tested for various intervals of time.  It was observed th...

  4. Elastic-plastic fracture mechanics of strength-mismatching

    Energy Technology Data Exchange (ETDEWEB)

    Parks, D.M.; Ganti, S.; McClintock, F.A. [Massachusetts Institute of Technology, Cambridge, MA (United States)

    1996-12-31

    Approximate solutions to stress-fields are provided for a strength-mismatched interface crack in small-scale yielding (SSY) for non-hardening and low hardening materials. Variations of local deformation intensities, characterized by a J-type contour integral, are proposed. The softer material experiences a higher deformation intensity level, J{sub S}, while the harder material sees a much lower deformation intensity level, J{sub H}, compared to that obtained from the applied J near the respective homogeneous crack-tips. For a low hardening material, the stress fields are obtained by scaling from an elastic/perfectly-plastic problem, based on an effective mismatch, M{sub eff}, which is a function of mismatch, M, and the hardening exponent, n. Triaxial stress build-up is discussed quantitatively in terms of M. The influence of strength-mismatch on cleavage fracture is discussed using Weibull statistics.

  5. Mechanical properties of orthodontic wires made of super engineering plastic.

    Science.gov (United States)

    Maekawa, Minami; Kanno, Zuisei; Wada, Takahiro; Hongo, Toshio; Doi, Hisashi; Hanawa, Takao; Ono, Takashi; Uo, Motohiro

    2015-01-01

    Most orthodontic equipment is fabricated from alloys such as stainless steel, Co-Cr and Ni-Ti because of their excellent elastic properties. In recent years, increasing esthetic demands, metal allergy and interference of metals with magnetic resonance imaging have driven the development of non-metallic orthodontic materials. In this study, we assessed the feasibility of using three super engineering plastics (PEEK, PES and PVDF) as orthodontic wires. PES and PVDF demonstrated excellent esthetics, although PEEK showed the highest bending strength and creep resistance. PEEK and PVDF showed quite low water absorption. Because of recent developments in coloration of PEEK, we conclude that PEEK has many advantageous properties that make it a suitable candidate for use as an esthetic metal-free orthodontic wire.

  6. Performance Evaluation of Pull Production Control Mechanisms by Mathematical Modeling and Simulation Analysis on EKCS and HEKCS Policies

    Directory of Open Access Journals (Sweden)

    O. Srikanth

    2013-12-01

    Full Text Available Predictive simulation is an advanced analytical technology that is used to support complex decision making within business and organizations. This paper introduces a new mechanism for the co-ordination of machines and other facilities in multi stage manufacturing system. The methodology is mainly to control and optimize the resources in the intelligent manufacturing environment , using discrete event simulation to model, evaluate and compare the performance of Extended Kanban Control System (EKCS, and the projected Hybrid Extended Kanban Control System (HEKCS. Here we are proposing the Hybrid Extended Kanban Control System (HEKCS, hybridization of Conwip sytem to aggravate Hybrid Extended Kanban Control System (HEKCS to develop the combined advantages and also to study their effect in a typical manufacturing environment. A typical multi stage assembly manufacturing system is considered and the system with each hybrid control mechanism is modeled and Simulation studies were performed for 2880 hrs to evaluate the performance parameters like Average Workin-Process, Production rate and Average Waiting Time for all the control mechanisms with exponentially anecdotal demands.

  7. Mechanisms of plastic deformation for powder materials in cold working

    Institute of Scientific and Technical Information of China (English)

    张连洪; 李双义

    2003-01-01

    To deal with the discontinuity of particulate media and subsequent uncertainty of stress, based on the probability theory for mechanics of particulate media, Mohr-Coulomb yield criterion of particulate media, and the theory of crystal deformation, we put forward the statistical mechanisms of deformation of powder materials in cold working and mechanism of texture development of the high temperature superconducting wire/tape. A new yield criterion of powder materials is proposed.

  8. Plasticity of respiratory rhythm-generating mechanisms in adult goats.

    Science.gov (United States)

    Forster, Hubert V; Krause, Katie L; Kiner, Tom; Neumueller, Suzanne E; Bonis, Josh M; Qian, Baogang; Pan, Lawrence G

    2010-01-01

    Abrupt destruction of >70% of the pre-Bötzinger complex (preBötzC) in awake goats results in terminal apnea (Wenninger et al. 2004b). Herein we report data on awake and sleeping goats in which the preBötzC was incrementally destroyed by injection of ibotenic acid (IBO) in increasing volumes at weekly intervals. All injections resulted in an acute tachypnea and dysrhythmia featuring apneas and increased variation in breathing. In studies at night, 10-15 hours after the injections, apneas were nearly all central and occurred during the awake state and variation in breathing was greater while awake than during NREM sleep. However, one week after the final IBO injection, the breathing pattern, breath-to-breath variation, and arterial blood gases were unchanged from baseline, indicating recovery. Histology revealed more than 90% destruction of the preBötzC region, and greater than 80% destruction of the surrounding area. We conclude: (1) the dysrhythmic effects on breathing acutely after the injection are state-dependent, and (2) after incremental, near-complete destruction of the preBötzC region, time-dependent plasticity within the respiratory network provides a normal respiratory rhythm that sustains normal arterial blood gases.

  9. Assessing the quantum mechanical level of theory for prediction of linear and nonlinear optical properties of push-pull organic molecules.

    Science.gov (United States)

    Paschoal, Diego; Santos, Hélio F Dos

    2013-05-01

    In this paper, we assessed the quantum mechanical level of theory for prediction of linear and nonlinear optical (NLO) properties of push-pull organic molecules. The electric dipole moment (μ), mean polarizability ([Symbol: see text]α[Symbol: see text]) and total static first hyperpolarizability (βt) were calculated for a set of benzene, styrene, biphenyl and stilbene derivatives using HF, MP2 and DFT (31 different functionals) levels and over 71 distinct basis sets. In addition, we propose two new basis sets, NLO-V and aNLO-V, for NLO properties calculations. As the main outcomes it is shown that long-range corrected DFT functionals such as M062X, ωB97, cam-B3LYP, LC-BLYP and LC-ωPBE work satisfactorily for NLO properties when appropriate basis sets such as those proposed here (NLO-V or aNLO-V) are used. For most molecules with β ranging from 0 to 190 esu, the average absolute deviation was 13.2 esu for NLO-V basis sets, compared to 27.2 esu for the standard 6-31 G(2d) basis set. Therefore, we conclude that the new basis sets proposed here (NLO-V and aNLO-V), together with the cam-B3LYP functional, make an affordable calculation scheme to predict NLO properties of large organic molecules.

  10. DEVELOPMENT OF PERMANENT MECHANICAL REPAIR SLEEVE FOR PLASTIC PIPE

    Energy Technology Data Exchange (ETDEWEB)

    Hitesh Patadia

    2004-09-30

    The report presents a comprehensive summary of the project status related to the development of a permanent mechanical repair fitting intended to be installed on damaged PE mains under blowing gas conditions. Specifically, the product definition has been developed taking into account relevant codes and standards and industry input. A conceptual design for the mechanical repair sleeve has been developed which meets the product definition.

  11. Inelastic deformation of metal matrix composites: Plasticity and damage mechanisms, part 2

    Science.gov (United States)

    Majumdar, B. S.; Newaz, G. M.

    1992-01-01

    The inelastic deformation mechanisms for the SiC (SCS-6)/Ti-15-3 system were studied at 538 C (1000 F) using a combination of mechanical measurements and detailed microstructural examinations. The objectives were to evaluate the contributions of plasticity and damage to the overall MMC response, and to compare the room temperature and elevated temperature deformation behaviors. Four different laminates were studied: (0)8, (90)8,(+ or -45)2s, and (0/90)2s, with the primary emphasis on the unidirectional (0)8, and (90)8 systems. The elevated temperature responses were similar to those at room temperature, involving a two-stage elastic-plastic type of response for the (0)8 system, and a characteristic three-stage deformation response for the (90)8 and (+ or -45)2s systems. The primary effects of elevated temperatures included: (1) reduction in the 'yield' and failure strengths; (2) plasticity through diffused slip rather than concentrated planar slip (which occurred at room temperature); and (3) time-dependent deformation. The inelastic deformation mechanism for the (0)8 MMC was dominated by plasticity at both temperatures. For the (90)8 and (+ or -45)2s MMCs, a combination of damage and plasticity contributed to the deformation at both temperatures.

  12. Hormones and phenotypic plasticity in an ecological context: linking physiological mechanisms to evolutionary processes.

    Science.gov (United States)

    Lema, Sean C

    2014-11-01

    Hormones are chemical signaling molecules that regulate patterns of cellular physiology and gene expression underlying phenotypic traits. Hormone-signaling pathways respond to an organism's external environment to mediate developmental stage-specific malleability in phenotypes, so that environmental variation experienced at different stages of development has distinct effects on an organism's phenotype. Studies of hormone-signaling are therefore playing a central role in efforts to understand how plastic phenotypic responses to environmental variation are generated during development. But, how do adaptive, hormonally mediated phenotypes evolve if the individual signaling components (hormones, conversion enzymes, membrane transporters, and receptors) that comprise any hormone-signaling pathway show expressional flexibility in response to environmental variation? What relevance do these components hold as molecular targets for selection to couple or decouple correlated hormonally mediated traits? This article explores how studying the endocrine underpinnings of phenotypic plasticity in an ecologically relevant context can provide insights into these, and other, crucial questions into the role of phenotypic plasticity in evolution, including how plasticity itself evolves. These issues are discussed in the light of investigations into how thyroid hormones mediate morphological plasticity in Death Valley's clade of pupfishes (Cyprinodon spp.). Findings from this work with pupfish illustrate that the study of hormone-signaling from an ecological perspective can reveal how phenotypic plasticity contributes to the generation of phenotypic novelty, as well as how physiological mechanisms developmentally link an organism's phenotype to its environmental experiences.

  13. Inelastic Deformation of Metal Matrix Composites. Part 1; Plasticity and Damage Mechanisms

    Science.gov (United States)

    Majumdar, B. S.; Newaz, G. M.

    1992-01-01

    The deformation mechanisms of a Ti 15-3/SCS6 (SiC fiber) metal matrix composite (MMC) were investigated using a combination of mechanical measurements and microstructural analysis. The objectives were to evaluate the contributions of plasticity and damage to the overall inelastic response, and to confirm the mechanisms by rigorous microstructural evaluations. The results of room temperature experiments performed on 0 degree and 90 degree systems primarily are reported in this report. Results of experiments performed on other laminate systems and at high temperatures will be provided in a forthcoming report. Inelastic deformation of the 0 degree MMC (fibers parallel to load direction) was dominated by the plasticity of the matrix. In contrast, inelastic deformations of the 90 degree composite (fibers perpendicular to loading direction) occurred by both damage and plasticity. The predictions of a continuum elastic plastic model were compared with experimental data. The model was adequate for predicting the 0 degree response; however, it was inadequate for predicting the 90 degree response largely because it neglected damage. The importance of validating constitutive models using a combination of mechanical measurements and microstructural analysis is pointed out. The deformation mechanisms, and the likely sequence of events associated with the inelastic deformation of MMCs, are indicated in this paper.

  14. PushPull++

    KAUST Repository

    Lipp, Markus

    2014-07-27

    PushPull tools are implemented in most commercial 3D modeling suites. Their purpose is to intuitively transform a face, edge, or vertex, and then to adapt the polygonal mesh locally. However, previous approaches have limitations: Some allow adjustments only when adjacent faces are orthogonal; others support slanted surfaces but never create new details. Moreover, self-intersections and edge-collapses during editing are either ignored or work only partially for solid geometry. To overcome these limitations, we introduce the PushPull++ tool for rapid polygonal modeling. In our solution, we contribute novel methods for adaptive face insertion, adjacent face updates, edge collapse handling, and an intuitive user interface that automatically proposes useful drag directions. We show that PushPull++ reduces the complexity of common modeling tasks by up to an order of magnitude when compared with existing tools. Copyright © ACM.

  15. Effects of Mixing Temperature and Wood Powder Size on Mechanical Properties of Wood Plastic Recycled Composite

    Science.gov (United States)

    Miki, Tsunehisa; Sugimoto, Hiroyuki; Kojiro, Keisuke; Kanayama, Kozo; Yamamoto, Ken

    In this study, wood (cedar) powder ranging from 53 µm to 1 mm sizes, recycled polypropylene (PP) / polyethylene (PE) and acid-modified PP as a compatibilization agent were used to produce a wood-plastic recycled composite (WPRC). For discussing the effects of the wood powder sizes on the mechanical properties of the WPRC, a mixing process of the wood powder and the plastics in a constant wood content of 50% weight was firstly performed by a mixing machine controlled temperature and rotation of mixing blade. And then, to obtain WPRC panels the wood and plastics mixtures were compressed in a mould under a constant pressure and a temperature for a certain holding time. WPRC specimens for mechanical tests were cut from the WPRC panels, and a tensile strength and a size-stability were acquired. The results show that the successful mixing process runs above 180°C, where the mixing torque required compounding keeps constant or slightly increases. The tensile strength of the WPRC increases when the smaller size of wood powder is used for wood/plastic compound under successful mixing conditions. It is shown from thickness change rate of specimens that mixing temperature of wood/plastic compound affects a size stability of the WPRC.

  16. Physical and Mechanical Properties of Injected Granular Soil with Thick Super Plasticized Grouts

    Directory of Open Access Journals (Sweden)

    Costas A. Anagnostopoulos

    2015-06-01

    Full Text Available The use of super-plasticizers in micro fine or regular cement-based grouts has become of vital importance in advanced professional grouting practices. These super-plasticizers play an important role in the production of more durable grouts with improved rheological characteristics. This report presents a laboratory study of the effect of a new-generation Polycarboxylate Super-plasticizer (PCE on the inject ability of thick cement grouts into a coarse soil, under different grouting pressures, in comparison to that of a polynaphthalene (SNF super-plasticizer. Finally, the physical (dry unit weight, porosity and permeability and mechanical properties (compressive strength, elastic modulus of grouted specimens with various grouts were examined. The experiments were conducted using different additive dosages with grouts proportioned with a water to cement ratio (w/c of 0.33, 0.4 and 0.5, respectively. The results showed that PCE super-plasticizer is more effective than the SNF one for the increase of grout inject ability and the improvement of physical and mechanical properties of grouted soil.

  17. Plastic Mechanisms for Thin-Walled Cold-Formed Steel Members in Eccentric Compression

    Directory of Open Access Journals (Sweden)

    Ungureanu Viorel

    2016-03-01

    Full Text Available The Eurocode 3 concerning thin-walled steel members divides members subjected to compression into four classes, considering their ductility. The representatives of the class C4 are short bars, for which the load-capacity corresponds to the maximum compression stresses less than the yield stress. There are bars prone to local buckling in the elastic range and they do not have a real post-elastic capacity. The failure at ultimate stage of such members, either in compression or bending, always occurs by forming a local plastic mechanism. This fact suggests the possibility to use the local plastic mechanism to characterise the ultimate strength of such members. The present paper is based on previous studies and some latest investigations of the authors, as well as the literature collected data. It represents an attempt to study the plastic mechanisms for members in eccentric compression about minor axis and the evolution of plastic mechanisms, considering several types of lipped channel sections.

  18. Mechanics recycling of plastics in Spain; El reciclado mecanico de materiales plasticos en Espana

    Energy Technology Data Exchange (ETDEWEB)

    Alegre, J. M.

    2002-07-01

    In Spain, the mechanic recycling of plastics has been made from 1960. At the moment, 130 companies compose the industrial sector where the legislation on waste forces to change the policies to companies of free market in order to behave like companies of services for the waste management. A greater growth of this sector requires the development of new markets of applications. (Author)

  19. Fatigue damage mechanism and failure prevention in fiberglass reinforced plastic

    Directory of Open Access Journals (Sweden)

    Raimundo Carlos Silverio Freire Jr.

    2005-03-01

    Full Text Available Damaging of composite laminates was monitored during fatigue tests, revealing the formation and propagation stages for compressive, tensile, or alternate cyclic loading. Two different laminate stacking sequences, with different number of layers, were tested. The laminates consisted of E-glass fibers reinforced orthoftalic polyester resin (FGRP shaped as mats or (bi-direction woven fabric textile. Preliminary density, calcination tests and static compressive and tensile mechanical tests were carried out. Then, tensile (R = 0.1, compressive (R = 10 and alternate axial (R = - 1 fatigue tests were performed at different maximum stresses. Tensile cyclic loading resulted in crack formation and propagation confirming the findings reported in other studies. On the other hand, damage from alternate and compressive fatigue depicted peculiar features. Less extended damage and better fatigue resistance were observed for the laminate with symmetrically distributed layers.

  20. Mechanical Properties of a Unidirectional Basalt-Fiber-Reinforced Plastic Under a Loading Simulating Operation Conditions

    Science.gov (United States)

    Lobanov, D. S.; Slovikov, S. V.

    2017-01-01

    The results of experimental investigations of unidirectional composites based on basalt fibers and different marks of epoxy resins are presented. Uniaxial tensile tests were carried out using a specimen fixation technique simulating the operation conditions of structures. The mechanical properties of the basalt-fiber-reinforced plastics (BFRPs) were determined. The diagrams of loading and deformation of BFRP specimens were obtain. The formulations of the composites with the highest mechanical properties were revealed.

  1. Plasticity theory

    CERN Document Server

    Lubliner, Jacob

    2008-01-01

    The aim of Plasticity Theory is to provide a comprehensive introduction to the contemporary state of knowledge in basic plasticity theory and to its applications. It treats several areas not commonly found between the covers of a single book: the physics of plasticity, constitutive theory, dynamic plasticity, large-deformation plasticity, and numerical methods, in addition to a representative survey of problems treated by classical methods, such as elastic-plastic problems, plane plastic flow, and limit analysis; the problem discussed come from areas of interest to mechanical, structural, and

  2. Effects of Bio-based Plasticizers on Mechanical and Thermal Properties of PVC/Wood Flour Composites

    Directory of Open Access Journals (Sweden)

    Zhenhua Xie

    2014-10-01

    Full Text Available Poly(vinyl chloride/wood flour (WPVC composites with dioctyl phthalate (DOP, dibutyl phthalate (DBP, cardanol acetate (CA, or epoxy fatty acid methyl ester (EFAME were prepared using twin-screw extrusion. The effects of plasticizers on the mechanical, dynamic mechanical, and melt rheological properties of composites and the thermal migration of plasticizers were characterized. The results demonstrated that WPVC/ DBP and WPVC/EFAME composites had better elongation at break; however, composites with bio-based plasticizers exhibited significantly higher impact strength. The morphology indicated that the compatibility between CA and WPVC was poor, while the surface of the composites showed good plasticity with the addition of DBP or EFAME. The PVC matrix with a plasticizer of higher molecular weight exhibited a higher glass transition temperature (Tg. The dynamic rheological test showed that WPVC/EFAME composites had the lowest storage modulus, loss modulus, and complex viscosity, but EFAME migrated more easily from composites than other plasticizers.

  3. The application of plastic compression to modulate fibrin hydrogel mechanical properties.

    Science.gov (United States)

    Haugh, Matthew G; Thorpe, Stephen D; Vinardell, Tatiana; Buckley, Conor T; Kelly, Daniel J

    2012-12-01

    The inherent biocompatibility of fibrin hydrogels makes them an attractive material for use in a wide range of tissue engineering applications. Despite this, their relatively low stiffness and high compliance limits their potential for certain orthopaedic applications. Enhanced mechanical properties are desirable so as to withstand surgical handling and in vivo loading after implantation and additionally, can provide important cues to cells seeded within the hydrogel. Standard methods used to enhance the mechanical properties of biological scaffolds such as chemical or thermal crosslinking cannot be used with fibrin hydrogels as cell seeding and gel formation occurs simultaneously. The objective of this study was to investigate the use of plastic compression as a means to improve the mechanical properties of chondrocyte-seeded fibrin hydrogels and to determine the influence of such compression on cell viability within these constructs. It was found that the application of 80% strain to fibrin hydrogels for 30 min (which resulted in a permanent strain of 47.4%) produced a 2.1-fold increase in the subsequent compressive modulus. Additionally, chondrocyte viability was maintained in the plastically compressed gels with significant cellular proliferation and extracellular matrix accumulation observed over 28 days of culture. In conclusion, plastic compression can be used to modulate the density and mechanical properties of cell-seeded fibrin hydrogels and represents a useful tool for both in theatre and in vitro tissue engineering applications.

  4. The Effects of Weathering on Mechanical Properties of Glass Fiber Reinforced Plastics (Grp Materials

    Directory of Open Access Journals (Sweden)

    H. Abdullah

    2012-08-01

    Full Text Available Glass fiber reinforced plastics composite is extensively used as a structural material for pools, oil pipes and tanks because it has good corrosion resistance properties.  The effects of weathering on the mechanical properties of glass fiber reinforced plastics (GRP in the Sultanate of Oman have been studied.  The tensile and three point bend specimens were exposed to outdoor conditions (open atmosphere in sunlight and tested for various intervals of time.  It was observed that as the exposure time to sunlight, ultraviolet radiation and dust increases the mechanical properties of GRP materials decrease.  The effects of relative humidity (%RH on the mechanical properties were also studied. It was found that as the relative humidity increased in the atmosphere during the exposure time, the tensile strength, flexural strength and modulus of elasticity are lowered. This work has revealed that the decrease in the mechanical properties of GRP under weathering conditions is subjected to atmospheric conditions such as humidity, temperature, ultraviolet radiation and pollutant.Key Words: Weathering, Glass-Fiber Reinforced Plastics, Degradation

  5. Tuning the Mechanical Properties of Tapioca Starch by Plasticizers, Inorganic Fillers and Agrowaste-Based Fillers

    OpenAIRE

    Edwin Azwar; Minna Hakkarainen

    2012-01-01

    Mechanical properties of tapioca starch-based films were tuned by different additives and additive combinations. The additives included plasticizers (glycerol, sorbitol, and citric acid), inorganic fillers (halloysite and kaolin), and agrowaste-based fillers (milled wood flour and rice bran). In addition, new biobased additives were prepared from wood flour and rice bran through liquefaction reaction. Through different additive combinations, starch-based materials with significant differences...

  6. Pulling on adhered vesicles

    Science.gov (United States)

    Smith, Ana-Suncana; Goennenwein, Stefanie; Lorz, Barbara; Seifert, Udo; Sackmann, Erich

    2004-03-01

    A theoretical model describing pulling of vesicles adhered in a contact potential has been developed. Two different regimes have been recognized. For weak to middle-strength adhesive potentials, locally stable shapes are found in a range of applied forces, separated from the free shape by an energy barrier. The phase diagram contains regions with either a unique bound shape or an additional meta-stable shape. Upon pulling, these shapes unbind discontinuously since the vesicle disengage from the surface while still possessing a finite adhesion area (Smith 2003a). In a strong adhesion regime, a competition between adhesion and tether formation is observed. A critical onset force is identified where a tether spontaneously appears as a part of a second order shape transition. Further growth of a tether is followed by a detachment process which terminates at a finite force when a vesicle continuously unbinds from the substrate (Smith 2003b). Both critical forces, as well as all shape parameters, are calculated as a function of the reduced volume and the strength of adhesive potential. Analogous experimental study has been performed where a vertical magnetic tweezers are used in combination with micro-interferometric and confocal techniques to reproduce the same symmetry as in the theoretical investigation. Giant vesicles are bound to the substrate by numerous specific bonds formed between ligands and receptors incorporated into the vesicle and the substrate, respectively. Application of a constant force is inducing a new thermodynamic equilibrium of the system where the vesicle is partially unbound from the substrate (Goennenwein 2003). The shapes of vesicles are compared prior and during application of the force. Very good agreement is obtained, particularly in the middle-strength adhesion regime (Smith 2003c). References: 1. A.-S. Smith, E. Sackmann, U. Seifert: Effects of a pulling force on the shape of a bound vesicle, Europhys. Lett., 64, 2 (2003). 2. A.-S. Smith

  7. Mineralogical Plasticity Acts as a Compensatory Mechanism to the Impacts of Ocean Acidification.

    Science.gov (United States)

    Leung, Jonathan Y S; Russell, Bayden D; Connell, Sean D

    2017-02-15

    Calcifying organisms are considered particularly susceptible to the future impacts of ocean acidification (OA), but recent evidence suggests that they may be able to maintain calcification and overall fitness. The underlying mechanism remains unclear but may be attributed to mineralogical plasticity, which modifies the energetic cost of calcification. To test the hypothesis that mineralogical plasticity enables the maintenance of shell growth and functionality under OA conditions, we assessed the biological performance of a gastropod (respiration rate, feeding rate, somatic growth, and shell growth of Austrocochlea constricta) and analyzed its shell mechanical and geochemical properties (shell hardness, elastic modulus, amorphous calcium carbonate, calcite to aragonite ratio, and magnesium to calcium ratio). Despite minor metabolic depression and no increase in feeding rate, shell growth was faster under OA conditions, probably due to increased precipitation of calcite and trade-offs against inner shell density. In addition, the resulting shell was functionally suitable for increasingly "corrosive" oceans, i.e., harder and less soluble shells. We conclude that mineralogical plasticity may act as a compensatory mechanism to maintain overall performance of calcifying organisms under OA conditions and could be a cornerstone of calcifying organisms to acclimate to and maintain their ecological functions in acidifying oceans.

  8. Reciprocal osmotic challenges reveal mechanisms of divergence in phenotypic plasticity in the killifish Fundulus heteroclitus.

    Science.gov (United States)

    Brennan, Reid S; Galvez, Fernando; Whitehead, Andrew

    2015-04-15

    The killifish Fundulus heteroclitus is an estuarine species with broad physiological plasticity, enabling acclimation to diverse stressors. Previous work suggests that freshwater populations expanded their physiology to accommodate low salinity environments; however, it is unknown whether this compromises their tolerance to high salinity. We used a comparative approach to investigate the mechanisms of a derived freshwater phenotype and the fate of an ancestral euryhaline phenotype after invasion of a freshwater environment. We compared physiological and transcriptomic responses to high- and low-salinity stress in fresh and brackish water populations and found an enhanced plasticity to low salinity in the freshwater population coupled with a reduced ability to acclimate to high salinity. Transcriptomic data identified genes with a conserved common response, a conserved salinity-dependent response and responses associated with population divergence. Conserved common acclimation responses revealed stress responses and alterations in cell-cycle regulation as important mechanisms in the general osmotic response. Salinity-specific responses included the regulation of genes involved in ion transport, intracellular calcium, energetic processes and cellular remodeling. Genes diverged between populations were primarily those showing salinity-specific expression and included those regulating polyamine homeostasis and the cell cycle. Additionally, when populations were matched with their native salinity, expression patterns were consistent with the concept of 'transcriptomic resilience', suggesting local adaptation. These findings provide insight into the fate of a plastic phenotype after a shift in environmental salinity and help to reveal mechanisms allowing for euryhalinity.

  9. A deformation mechanism map for polycrystals modeled using strain gradient plasticity and interfaces that slide and separate

    DEFF Research Database (Denmark)

    Dahlberg, Carl F.O.; Faleskog, Jonas; Niordson, Christian Frithiof

    2013-01-01

    Small scale strain gradient plasticity is coupled with a model of grain boundaries that take into account the energetic state of a plastically strained boundary and the slip and separation between neighboring grains. A microstructure of hexagonal grains is investigated using a plane strain finite...... element model. The results show that three different microstructural deformation mechanisms can be identified. The standard plasticity case in which the material behaves as expected from coarse grained experiments, the nonlocal plasticity region where size of the microstructure compared to some intrinsic...

  10. Effect of elastic and plastic tensile mechanical loading on the magnetic properties of NGO electrical steel

    Science.gov (United States)

    Leuning, N.; Steentjes, S.; Schulte, M.; Bleck, W.; Hameyer, K.

    2016-11-01

    The magnetic properties of non-grain-oriented (NGO) electrical steels are highly susceptible to mechanical stresses, i.e., residual, external or thermal ones. For rotating electrical machines, mechanical stresses are inevitable and originate from different sources, e.g., material processing, machine manufacturing and operating conditions. The efficiency and specific losses are largely altered by different mechanical stress states. In this paper the effect of tensile stresses and plastic deformations on the magnetic properties of a 2.9 wt% Si electrical steel are studied. Particular attention is paid to the effect of magnetic anisotropy, i.e., the influence of the direction of applied mechanical stress with respect to the rolling direction. Due to mechanical stress, the induced anisotropy has to be evaluated as it is related to the stress-dependent magnetostriction constant and the grain alignment.

  11. RIGID-PLASTIC MECHANICAL MODEL FOR THE FORGING METHOD WITH HORIZONTAL V-SHAPED ANVIL

    Institute of Scientific and Technical Information of China (English)

    LIU Zhubai; NI Liyong; LIU Guohui; ZHANG Yongjun; ZHU Wenbo

    2006-01-01

    In order to decrease the anisotropy of mechanical properties, the rigid-plastic mechanical model for the forging method with horizontal V-shaped anvil is presented. The forging method,through the change of anvils shape, is able to control fibrous tissue direction, to improve the anisotropy of mechanical properties of axial forgings, to realize uniform forging. Therefore, the forging method can overcome the defect that conventional forging methods produce. The mechanism of the forging method with horizontal V-shaped anvil and the process of metal deformation are analyzed. The agreement of theoretical analysis with experimental study verifies the fact that the forging method with horizontal V-shaped anvil can control effectively the mechanical properties of axial forgings.

  12. MECHANICAL AND BIOLOGICAL PERFORMANCE OF SODIUM METAPERIODATE-IMPREGNATED PLASTICIZED WOOD (PW

    Directory of Open Access Journals (Sweden)

    Md.Rezaur Rahman

    2010-04-01

    Full Text Available Malaysia, especially the Borneo Island state of Sarawak, has a large variety of tropical wood species. In this study, selected raw tropical wood species namely Artocarpus Elasticus, Artocarpus Rigidus, Xylopia spp., Koompassia Malaccensis, and Eugenia spp. were chemically treated with sodium metaperiodate to convert them into plasticized wood (PW. Manufactured plasticized wood samples were characterized using, Fourier transform infrared spectroscopy, scanning electron microscopy, and mechanical testing (modulus of elasticity (MOE, modulus of rupture (MOR, static Young’s modulus (Es, decay resistance, and water absorption. MOE and MOR were calculated using a three-point bending test. Es and decay resistance were calculated using the compression parallel to grain test and the natural laboratory decay test, respectively. The manufactured PW yielded higher MOE, MOR, and Es. PW had a lower water content compared to the untreated wood and had high resistance to decay exposure, with Eugenia spp. having the highest resistance compared to the others.

  13. Plastic mechanism analysis of T-joints in RHS under concentrated force

    Science.gov (United States)

    Zhao, Xiao-Ling; Hancock, Gregory J.

    1991-11-01

    A new plastic mechanism is developed for T-joints in rectangular hollow sections (RHS) under concentrated loads. This model includes the plastic hinges in the web, the membrane force in the flange and the strain hardening of the material. It can predict the yield load, the post-yield response, and the ultimate load of a T-joint under concentrated force. The model developed is compared with the CIDECT model, the Kato model, and the modified Kato model. The yield load, the post-yield response, and the ultimate load determined from the present model are compared with 6 T-joint tests performed by Zhao and Hancock (1991) and 20 T-joint tests performed by Kato and Nishiyama (1979). The ratio (beta) of the T-joints tested varied from 0.291 to 0.890.

  14. Yarn Pull-Out as a Mechanism for Dissipation of Ballistic Impact Energy in Kevlar KM-2 Fabric, Part 2: Prediction of Ballistic Performance

    Science.gov (United States)

    2004-05-01

    fabrics made from high-strength fibers, such as Kevlar,* Zylon ,† Armos,‡ and Spectra,§ have been widely used in flexible armors such as ballistic vests...pull-out during low velocity (< 300 m/s) impacts of Zylon fabrics, especially when at least two boundaries were unclamped, when impact occurred near the...Kevlar is a registered trademark of DuPont. † Zylon is a registered trademark of Toyobo. ‡ Armos is a registered trademark of Kamenskvolokno JSC

  15. An asymmetry between pushing and pulling for crawling cells

    CERN Document Server

    Recho, Pierre

    2013-01-01

    Eukaryotic cells possess motility mechanisms allowing them not only to self-propel but also to exert forces on obstacles (to push) and to carry cargoes (to pull). To study the inherent asymmetry between active pushing and pulling we model a crawling acto-myosin cell extract as a 1D layer of active gel subjected to external forces. We show that pushing is controlled by protrusion and that the macroscopic signature of the protrusion dominated motility mechanism is concavity of the force velocity relation. Instead, pulling is driven by protrusion only at small values of the pulling force and it is replaced by contraction when the pulling force is sufficiently large. This leads to more complex convex-concave structure of the force velocity relation, in particular, competition between protrusion and contraction can produce negative mobility in a biologically relevant range. The model illustrates active readjustment of the force generating machinery in response to changes in the dipole structure of external forces....

  16. Is phenotypic plasticity a key mechanism for responding to thermal stress in ants?

    Science.gov (United States)

    Oms, Cristela Sánchez; Cerdá, Xim; Boulay, Raphaël

    2017-06-01

    Unlike natural selection, phenotypic plasticity allows organisms to respond quickly to changing environmental conditions. However, plasticity may not always be adaptive. In insects, body size and other morphological measurements have been shown to decrease as temperature increases. This relationship may lead to a physiological conflict in ants, where larger body size and longer legs often confer better thermal resistance. Here, we tested the effect of developmental temperature (20, 24, 28 or 32 °C) on adult thermal resistance in the thermophilic ant species Aphaenogaster senilis. We found that no larval development occurred at 20 °C. However, at higher temperatures, developmental speed increased as expected and smaller adults were produced. In thermal resistance tests, we found that ants reared at 28 and 32 °C had half-lethal temperatures that were 2 °C higher than those of ants reared at 24 °C. Thus, although ants reared at higher temperatures were smaller in size, they were nonetheless more thermoresistant. These results show that A. senilis can exploit phenotypic plasticity to quickly adjust its thermal resistance to local conditions and that this process is independent of morphological adaptations. This mechanism may be particularly relevant given current rapid climate warming.

  17. Reversible adaptive plasticity: A mechanism for neuroblastoma cell heterogeneity and chemo-resistance

    Directory of Open Access Journals (Sweden)

    Lina eChakrabarti

    2012-08-01

    Full Text Available We describe a novel form of tumor cell plasticity characterized by reversible adaptive plasticity in murine and human neuroblastoma. Two cellular phenotypes were defined by their ability to exhibit adhered, anchorage dependent (AD or sphere forming, anchorage independent (AI growth. The tumor cells could transition back and forth between the two phenotypes and the transition was dependent on the culture conditions. Both cell phenotypes exhibited stem-like features such as expression of nestin, self-renewal capacity and mesenchymal differentiation potential. The AI tumorspheres were found to be more resistant to chemotherapy and proliferated slower in vitro compared to the AD cells. Identification of specific molecular markers like MAP2, β-catenin and PDGFRβ enabled us to characterize and observe both phenotypes in established mouse tumors. Irrespective of the phenotype originally implanted in mice, tumors grown in vivo show phenotypic heterogeneity in molecular marker signatures and are indistinguishable in growth or histologic appearance. Similar molecular marker heterogeneity was demonstrated in primary human tumor specimens. Chemotherapy or growth factor receptor inhibition slowed tumor growth in mice and promoted initial loss of AD or AI heterogeneity, respectively. Simultaneous targeting of both phenotypes led to further tumor growth delay with emergence of new unique phenotypes. Our results demonstrate that neuroblastoma cells are plastic, dynamic and may optimize their ability to survive by changing their phenotype. Phenotypic switching appears to be an adaptive mechanism to unfavorable selection pressure and could explain the phenotypic and functional heterogeneity of neuroblastoma.

  18. Short-term plasticity in thalamocortical pathways: cellular mechanisms and functional roles.

    Science.gov (United States)

    Castro-Alamancos, M A

    1997-01-01

    Information reaches the neocortex through different types of thalamocortical pathways. These differ in many morphological and physiological properties. One interesting aspect in which thalamocortical pathways differ is in their temporal dynamics, such as their short-term plasticity. Primary pathways display frequency-dependent depression, while secondary pathways display frequency-dependent enhancement. The cellular mechanisms underlying these dynamic responses involve pre- and post-synaptic and circuit properties. They may serve to synchronize, amplify and/or filter neural activity in neocortex depending on behavioral demands, and thus to adapt each pathway to its specific function.

  19. Determination of mechanical properties of some glass fiber reinforced plastics suitable to Wind Turbine Blade construction

    Science.gov (United States)

    Steigmann, R.; Savin, A.; Goanta, V.; Barsanescu, P. D.; Leitoiu, B.; Iftimie, N.; Stanciu, M. D.; Curtu, I.

    2016-08-01

    The control of wind turbine's components is very rigorous, while the tower and gearbox have more possibility for revision and repairing, the rotor blades, once they are deteriorated, the defects can rapidly propagate, producing failure, and the damages can affect large regions around the wind turbine. This paper presents the test results, performed on glass fiber reinforced plastics (GFRP) suitable to construction of wind turbine blades (WTB). The Young modulus, shear modulus, Poisson's ratio, ultimate stress have been determined using tensile and shear tests. Using Dynamical Mechanical Analysis (DMA), the activation energy for transitions that appear in polyester matrix as well as the complex elastic modulus can be determined, function of temperature.

  20. Mechanical behavior of fiber/matrix interfaces in CFRP sheets subjected to plastic deformation

    Directory of Open Access Journals (Sweden)

    Kamiya Ryuta

    2016-01-01

    Full Text Available The use of Carbon Fiber Reinforced Plastic (CFRP is increasing markedly, partially in the aviation industry, but it has been considered that CFRP sheets cannot be formed by press-forming techniques owing to the low ductility of CFRP. Since the mechanical characteristics of CFRP are dominated by the microscale structure, it is possible to improve its formability by optimizing the material structure. Therefore, to improve the formability, the interaction between the carbon fibers and the matrix must be clarified. In this study, microscale analyses were conducted by a finite-element model with cohesive zone elements.

  1. Mechanisms of plastic deformation in AZ31 magnesium alloy investigated by acoustic emission and transmission electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Janecek, Milos [Charles University, Faculty of Mathematics and Physics, Ke Karlovu 5, CZ-121 16 Prague 2 (Czech Republic)], E-mail: janecek@met.mff.cuni.cz; Kral, Robert [Charles University, Faculty of Mathematics and Physics, Ke Karlovu 5, CZ-121 16 Prague 2 (Czech Republic); Dobron, Patrik [Charles University, Faculty of Mathematics and Physics, Ke Karlovu 5, CZ-121 16 Prague 2 (Czech Republic); Chmelik, Frantisek [Charles University, Faculty of Mathematics and Physics, Ke Karlovu 5, CZ-121 16 Prague 2 (Czech Republic); Supik, Vladimir [Department of Physical Metallurgy and Materials Technology, Technical University of Brandenburg at Cottbus, D-03010 Cottbus (Germany); Hollaender, Frank [Department of Physical Metallurgy and Materials Technology, Technical University of Brandenburg at Cottbus, D-03010 Cottbus (Germany)

    2007-07-25

    The effect of deformation conditions on plastic deformation and acoustic emission (AE) in hot-rolled magnesium alloy AZ31 has been investigated in the temperature range of 20-200 deg. C by constant strain rate tensile tests. Two sets of samples differing in the preheating temperature before individual passes of hot rolling have been studied. Both the yield stress and the tensile strength decrease with increasing temperature of deformation. The ductility was found to increase significantly with increasing temperature of deformation in both specimens. Unstable plastic deformation (Portevin-Le Chatelier effect) has been observed for all used strain rates both at room and elevated temperatures. Plastic instabilities were accompanied by a pronounced AE activity. The AE bursts were correlated with the individual regions of plastic instabilities on the deformation curve. Mechanisms controlling plastic instabilities are suggested respecting the microstructure evolution as observed by optical and transmission electron microscopy.

  2. Studying the mechanical behavior of a plastic, shock-resisting, antitank landmine.

    Science.gov (United States)

    Kirkpatrick Alberts, W C; Waxier, Roger; Sabatier, James M

    2006-12-01

    Modal behavior in landmines has recently become a topic of interest for acoustic landmine detection. It is well known that landmines exhibit mechanical resonance behavior that enhances the soil velocity over a buried landmine. Recent experimental work by Zagrai et al. [A. Zagrai, D. Donskoy, and A. Ekimov, J. Acoust. Soc. Am. 118 (6), 3619-3628 (2005)] demonstrates the existence of structural modes in several landmines. The work reported herein parallels the work of Zagrai et al. in studying the structural modes of the pressure plate of a plastic, cylindrically symmetric, antitank landmine. The pressure plate is considered to act as an elastically supported thin elastic plate. An observed perturbation of the first symmetric mode of the pressure plate is caused by the landmine's shock-resisting mechanism. This is validated by a lumped element model for the first symmetric mode coupled to the shock-resisting mechanism.

  3. Plastic deformation mechanisms in polyimide resins and their semi-interpenetrating networks

    Science.gov (United States)

    Jang, Bor Z.

    1990-01-01

    High-performance thermoset resins and composites are critical to the future growth of space, aircraft, and defense industries in the USA. However, the processing-structure-property relationships in these materials remain poorly understood. In the present ASEE/NASA Summer Research Program, the plastic deformation modes and toughening mechanisms in single-phase and multiphase thermoset resins were investigated. Both thermoplastic and thermoset polyimide resins and their interpenetrating networks (IPNs and semi-IPNs) were included. The fundamental tendency to undergo strain localization (crazing and shear banding) as opposed to a more diffuse (or homogeneous) deformation in these polymers were evaluated. Other possible toughening mechanisms in multiphase thermoset resins were also examined. The topological features of network chain configuration/conformation and the multiplicity of phase morphology in INPs and semi-IPNs provide unprecedented opportunities for studying the toughening mechanisms in multiphase thermoset polymers and their fiber composites.

  4. Plastic deformation mechanism of polycrystalline copper foil shocked with femtosecond laser

    Energy Technology Data Exchange (ETDEWEB)

    Ye, Y.X., E-mail: yeyunxia@mail.ujs.edu.cn [School of Mechanical Engineering, Jiangsu University, Zhenjiang 21203 (China); Jiangsu Provincial Key Laboratory for Science and Technology of Photon Manufacturing, Jiangsu University, Zhenjiang 212013 (China); Feng, Y.Y.; Lian, Z.C.; Hua, Y.Q. [School of Mechanical Engineering, Jiangsu University, Zhenjiang 21203 (China)

    2014-08-01

    Plastic deformation mechanism of polycrystalline copper foil shocked with femtosecond (fs) laser has been characterized through optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Experiments of ns laser shocking copper (Cu) and fs laser shocking aluminum (Al) were also conducted for comparison. Dislocations arranged in multiple forms, profuse twins and stacking faults (SFs) coexist in the fs laser shocked copper. At small strain condition, dislocation slip is the dominant deformation mode and small amount of SFs act as complementary mechanism. With strain increasing, profuse twins and SFs form to accommodate the plastic deformation. Furthermore, new formed SFs incline to locate around the old ones because the dislocation densities there are more higher. So there is a high probability for new SFs overlapping on old ones to form twins, or connecting old ones to lengthen them, which eventually produce the phenomena that twins connect with each other or twins connect with SFs. Strain greatly influences the dislocation density. Twins and SFs are more dependent on strain rate and shock pressure. Medium stacking fault energy (SFE) of copper helps to extend partial dislocations and provides sources for forming SFs and twins.

  5. Sintering boron carbide ceramics without grain growth by plastic deformation as the dominant densification mechanism

    Science.gov (United States)

    Ji, Wei; Rehman, Sahibzada Shakir; Wang, Weimin; Wang, Hao; Wang, Yucheng; Zhang, Jinyong; Zhang, Fan; Fu, Zhengyi

    2015-10-01

    A new ceramic sintering approach employing plastic deformation as the dominant mechanism is proposed, at low temperature close to the onset point of grain growth and under high pressure. Based on this route, fully dense boron carbide without grain growth can be prepared at 1,675-1,700 °C and under pressure of (≥) 80 MPa in 5 minutes. The dense boron carbide shows excellent mechanical properties, including Vickers hardness of 37.8 GPa, flexural strength of 445.3 MPa and fracture toughness of 4.7 MPa•m0.5. Such a process should also facilitate the cost-effective preparation of other advanced ceramics for practical applications.

  6. Sintering boron carbide ceramics without grain growth by plastic deformation as the dominant densification mechanism.

    Science.gov (United States)

    Ji, Wei; Rehman, Sahibzada Shakir; Wang, Weimin; Wang, Hao; Wang, Yucheng; Zhang, Jinyong; Zhang, Fan; Fu, Zhengyi

    2015-10-27

    A new ceramic sintering approach employing plastic deformation as the dominant mechanism is proposed, at low temperature close to the onset point of grain growth and under high pressure. Based on this route, fully dense boron carbide without grain growth can be prepared at 1,675-1,700 °C and under pressure of (≥) 80 MPa in 5 minutes. The dense boron carbide shows excellent mechanical properties, including Vickers hardness of 37.8 GPa, flexural strength of 445.3 MPa and fracture toughness of 4.7 MPa•m(0.5). Such a process should also facilitate the cost-effective preparation of other advanced ceramics for practical applications.

  7. Experimental and Numerical Analyses of the Pull-out Response of a Steel Post/Bovine Bone Cementless Fixation

    Institute of Scientific and Technical Information of China (English)

    Khaled Gammoudi; Mohamed Kharrat; Maher Dammak

    2012-01-01

    Effect of initial interference fit on pull-out strength in cementless fixation between bovine tibia and smooth stainless steel post was investigated in this study.Compressive behavior of bovine spongious bone was studied using mechanical testing in order to evaluate the elastic-plastic properties in different regions of the proximal tibia.Friction tests were carried out in the aim to evaluate the friction behavior of the contact between bovine spongious bone and stainless steel.A cylindrical stainless steel post inserted in a pre-drilled bovine tibia with an initial interference fit was taken as an in vitro model to assess the contribution of post fixation to the initial stability of the Total Knee Arthroplasty (TKA) tibial component.Pull-out experiments were carried out for different initial interference fits.Finite Element Models (FEM) using local elastic-plastic properties of the bovine bone were developed for the analysis of the experimental ultimate pull-out force results.At the post/bone interface,Coulomb friction was considered in the FEM calculations with pressure-dependent friction coefficient.It was found that the FEM results of the ultimate force are in good agreement with the experimental results.The analysis of the FEM interfacial stresses indicates that the micro-slip initiation depends on the local bone properties.

  8. Plasticity of the MAPK signaling network in response to mechanical stress.

    Directory of Open Access Journals (Sweden)

    Andrea M Pereira

    Full Text Available Cells display versatile responses to mechanical inputs and recent studies have identified the mitogen-activated protein kinase (MAPK cascades mediating the biological effects observed upon mechanical stimulation. Although, MAPK pathways can act insulated from each other, several mechanisms facilitate the crosstalk between the components of these cascades. Yet, the combinatorial complexity of potential molecular interactions between these elements have prevented the understanding of their concerted functions. To analyze the plasticity of the MAPK signaling network in response to mechanical stress we performed a non-saturating epistatic screen in resting and stretched conditions employing as readout a JNK responsive dJun-FRET biosensor. By knocking down MAPKs, and JNK pathway regulators, singly or in pairs in Drosophila S2R+ cells, we have uncovered unexpected regulatory links between JNK cascade kinases, Rho GTPases, MAPKs and the JNK phosphatase Puc. These relationships have been integrated in a system network model at equilibrium accounting for all experimentally validated interactions. This model allows predicting the global reaction of the network to its modulation in response to mechanical stress. It also highlights its context-dependent sensitivity.

  9. Mechanisms of Neuroplasticity and Ethanol's Effects on Plasticity in the Striatum and Bed Nucleus of the Stria Terminalis.

    Science.gov (United States)

    Lovinger, David M; Kash, Thomas L

    2015-01-01

    Long-lasting changes in synaptic function (i.e., synaptic plasticity) have long been thought to contribute to information storage in the nervous system. Although synaptic plasticity mainly has adaptive functions that allow the organism to function in complex environments, it is now clear that certain events or exposure to various substances can produce plasticity that has negative consequences for organisms. Exposure to drugs of abuse, in particular ethanol, is a life experience that can activate or alter synaptic plasticity, often resulting in increased drug seeking and taking and in many cases addiction.Two brain regions subject to alcohol's effects on synaptic plasticity are the striatum and bed nucleus of the stria terminalis (BNST), both of which have key roles in alcohol's actions and control of intake. The specific effects depend on both the brain region analyzed (e.g., specific subregions of the striatum and BNST) and the duration of ethanol exposure (i.e., acute vs. chronic). Plastic changes in synaptic transmission in these two brain regions following prolonged ethanol exposure are thought to contribute to excessive alcohol drinking and relapse to drinking. Understanding the mechanisms underlying this plasticity may lead to new therapies for treatment of these and other aspects of alcohol use disorder.

  10. [Multiaxial evaluation of the pathophysiology of mood disorder and therapeutic mechanisms of clinical drugs by neuronal plasticity and neuronal load].

    Science.gov (United States)

    Omata, Naoto; Mizuno, Tomoyuki; Mitsuya, Hironori; Wada, Yuji

    2013-11-01

    Impairment of neuronal plasticity is important in the pathophysiology of mood disorder. Both zinc deficiency and social isolation impair neuronal plasticity. Both cause a depressive state. However, in experiments using animals, their combined loading induced manic-like behavior. Therefore, it was inferred that moderate impairment of neuronal plasticity induces a depressive state, and that further impairment of neuronal plasticity induces a manic state. However, some kind of load toward neuronal function through neural transmission can influence mood disorder symptoms without direct effects on neuronal plasticity. Our hypothesis is that mania is an aggravation of depression from the perspective of neuronal plasticity, and that multiaxial evaluation by neuronal plasticity and neuronal load through neural transmission is useful for understanding the pathophysiology of mood disorder. There are many clinical aspects that have been difficult to interpret in mood disorder: Why is a mood stabilizer or electric convulsive therapy useful for both mania and depression? What is the pathophysiology of the mixed state? Why does manic switching by an antidepressant occur or not? Our hypothesis is useful to understand these aspects, and using this hypothesis, it is expected that the pathophysiology of mood disorder and clinical mechanism of mood stabilizers and antidepressants can now be understood as an integrated story.

  11. Localization of Presynaptic Plasticity Mechanisms Enables Functional Independence of Synaptic and Ectopic Transmission in the Cerebellum

    Directory of Open Access Journals (Sweden)

    Katharine L. Dobson

    2015-01-01

    Full Text Available In the cerebellar molecular layer parallel fibre terminals release glutamate from both the active zone and from extrasynaptic “ectopic” sites. Ectopic release mediates transmission to the Bergmann glia that ensheathe the synapse, activating Ca2+-permeable AMPA receptors and glutamate transporters. Parallel fibre terminals exhibit several forms of presynaptic plasticity, including cAMP-dependent long-term potentiation and endocannabinoid-dependent long-term depression, but it is not known whether these presynaptic forms of long-term plasticity also influence ectopic transmission to Bergmann glia. Stimulation of parallel fibre inputs at 16 Hz evoked LTP of synaptic transmission, but LTD of ectopic transmission. Pharmacological activation of adenylyl cyclase by forskolin caused LTP at Purkinje neurons, but only transient potentiation at Bergmann glia, reinforcing the concept that ectopic sites lack the capacity to express sustained cAMP-dependent potentiation. Activation of mGluR1 caused depression of synaptic transmission via retrograde endocannabinoid signalling but had no significant effect at ectopic sites. In contrast, activation of NMDA receptors suppressed both synaptic and ectopic transmission. The results suggest that the signalling mechanisms for presynaptic LTP and retrograde depression by endocannabinoids are restricted to the active zone at parallel fibre synapses, allowing independent modulation of synaptic transmission to Purkinje neurons and ectopic transmission to Bergmann glia.

  12. Adaptive transgenerational plasticity in plants: case studies, mechanisms, and implications for natural populations

    Directory of Open Access Journals (Sweden)

    Jacob J. Herman

    2011-12-01

    Full Text Available Plants respond to environmental conditions not only by plastic changes to their own development and physiology, but also by altering the phenotypes expressed by their offspring. This transgenerational plasticity was initially considered to entail only negative effects of stressful parental environments, such as production of smaller seeds by resource- or temperature-stressed parent plants, and was therefore viewed as environmental noise. Recent evolutionary ecology studies have shown that in some cases, these inherited environmental effects can include specific growth adjustments that are functionally adaptive to the parental conditions that induced them, which can range from contrasting states of controlled laboratory environments to the complex habitat variation encountered by natural plant populations. Preliminary findings suggest that adaptive transgenerational effects can be transmitted by means of diverse mechanisms including changes to seed provisioning and biochemistry, and epigenetic modifications such as DNA methylation that can persist across multiple generations. These non-genetically inherited adaptations can influence the ecological breadth and evolutionary dynamics of plant taxa and promote the spread of invasive plants. Interdisciplinary studies that join mechanistic and evolutionary ecology approaches will be an important source of future insights.

  13. Localization of Presynaptic Plasticity Mechanisms Enables Functional Independence of Synaptic and Ectopic Transmission in the Cerebellum

    Science.gov (United States)

    Dobson, Katharine L.; Bellamy, Tomas C.

    2015-01-01

    In the cerebellar molecular layer parallel fibre terminals release glutamate from both the active zone and from extrasynaptic “ectopic” sites. Ectopic release mediates transmission to the Bergmann glia that ensheathe the synapse, activating Ca2+-permeable AMPA receptors and glutamate transporters. Parallel fibre terminals exhibit several forms of presynaptic plasticity, including cAMP-dependent long-term potentiation and endocannabinoid-dependent long-term depression, but it is not known whether these presynaptic forms of long-term plasticity also influence ectopic transmission to Bergmann glia. Stimulation of parallel fibre inputs at 16 Hz evoked LTP of synaptic transmission, but LTD of ectopic transmission. Pharmacological activation of adenylyl cyclase by forskolin caused LTP at Purkinje neurons, but only transient potentiation at Bergmann glia, reinforcing the concept that ectopic sites lack the capacity to express sustained cAMP-dependent potentiation. Activation of mGluR1 caused depression of synaptic transmission via retrograde endocannabinoid signalling but had no significant effect at ectopic sites. In contrast, activation of NMDA receptors suppressed both synaptic and ectopic transmission. The results suggest that the signalling mechanisms for presynaptic LTP and retrograde depression by endocannabinoids are restricted to the active zone at parallel fibre synapses, allowing independent modulation of synaptic transmission to Purkinje neurons and ectopic transmission to Bergmann glia. PMID:26171253

  14. Geometrical foundations of continuum mechanics an application to first- and second-order elasticity and elasto-plasticity

    CERN Document Server

    Steinmann, Paul

    2015-01-01

    This book illustrates the deep roots of the geometrically nonlinear kinematics of generalized continuum mechanics in differential geometry. Besides applications to first- order elasticity and elasto-plasticity an appreciation thereof is particularly illuminating for generalized models of continuum mechanics such as second-order (gradient-type) elasticity and elasto-plasticity.   After a motivation that arises from considering geometrically linear first- and second- order crystal plasticity in Part I several concepts from differential geometry, relevant for what follows, such as connection, parallel transport, torsion, curvature, and metric for holonomic and anholonomic coordinate transformations are reiterated in Part II. Then, in Part III, the kinematics of geometrically nonlinear continuum mechanics are considered. There various concepts of differential geometry, in particular aspects related to compatibility, are generically applied to the kinematics of first- and second- order geometrically nonlinear con...

  15. Strategies to improve the mechanical properties of starch-based materials: plasticization and natural fibers reinforcement

    Directory of Open Access Journals (Sweden)

    A. Lopez-Gil

    2014-01-01

    Full Text Available Biodegradable polymers are starting to be introduced as raw materials in the food-packaging market. Nevertheless, their price is very high. Starch, a fully biodegradable and bioderived polymer is a very interesting alternative due to its very low price. However, the use of starch as the polymer matrix for the production of rigid food packaging, such as trays, is limited due to its poor mechanical properties, high hidrophilicity and high density. This work presents two strategies to overcome the poor mechanical properties of starch. First, the plasticization of starch with several amounts of glycerol to produce thermoplastic starch (TPS and second, the production of biocomposites by reinforcing TPS with promising fibers, such as barley straw and grape waste. The mechanical properties obtained are compared with the values predicted by models used in the field of composites; law of mixtures, Kerner-Nielsen and Halpin-Tsai. To evaluate if the materials developed are suitable for the production of food-packaging trays, the TPS-based materials with better mechanical properties were compared with commercial grades of oil-based polymers, polypropylene (PP and polyethylene-terphthalate (PET, and a biodegradable polymer, polylactic acid (PLA.

  16. Transformation from slip to plastic flow deformation mechanism during tensile deformation of zirconium nanocontacts

    Science.gov (United States)

    Yamada, Kohei; Kizuka, Tokushi

    2017-01-01

    Various types of nanometer-sized structures have been applied to advanced functional and structural devices. Inherent structures, thermal stability, and properties of such nanostructures are emphasized when their size is decreased to several nanometers, especially, to several atoms. In this study, we observed the atomistic tensile deformation process of zirconium nanocontacts, which are typical nanostructures used in connection of nanometer-sized wires, transistors, and diodes, memory devices, and sensors, by in situ transmission electron microscopy. It was found that the contact was deformed via a plastic flow mechanism, which differs from the slip on lattice planes frequently observed in metals, and that the crystallinity became disordered. The various irregular relaxed structures formed during the deformation process affected the conductance. PMID:28218244

  17. Grain Refinement and Deformation Mechanisms in Room Temperature Severe Plastic Deformed Mg-AZ31

    Directory of Open Access Journals (Sweden)

    Ludwig Schultz

    2013-07-01

    Full Text Available A Ti-AZ31 composite was severely plastically deformed by rotary swaging at room temperature up to a logarithmic deformation strain of 2.98. A value far beyond the forming limit of pure AZ31 when being equivalently deformed. It is observed, that the microstructure evolution in Mg-AZ31 is strongly influenced by twinning. At low strains the {̅1011} (10̅12 and the {̅1012} (10̅11 twin systems lead to fragmentation of the initial grains. Inside the primary twins, grain refinement takes place by dynamic recrystallization, dynamic recovery and twinning. These mechanisms lead to a final grain size of ≈1 μm, while a strong centered ring fibre texture is evolved.

  18. Transformation from slip to plastic flow deformation mechanism during tensile deformation of zirconium nanocontacts

    Science.gov (United States)

    Yamada, Kohei; Kizuka, Tokushi

    2017-02-01

    Various types of nanometer-sized structures have been applied to advanced functional and structural devices. Inherent structures, thermal stability, and properties of such nanostructures are emphasized when their size is decreased to several nanometers, especially, to several atoms. In this study, we observed the atomistic tensile deformation process of zirconium nanocontacts, which are typical nanostructures used in connection of nanometer-sized wires, transistors, and diodes, memory devices, and sensors, by in situ transmission electron microscopy. It was found that the contact was deformed via a plastic flow mechanism, which differs from the slip on lattice planes frequently observed in metals, and that the crystallinity became disordered. The various irregular relaxed structures formed during the deformation process affected the conductance.

  19. Effect of plastic media blasting method on mechanical properties of Al 2024-T6 alloy

    Energy Technology Data Exchange (ETDEWEB)

    Uner, Umit [1st Air Supply and Maintenance Centre, Eskisehir (Turkmenistan); Orak, Sezan; Sofuoglu, Mehmet Alper [Dept. of Mechanical Engineering, Eskisehir Osmangazi University, Eskisehir (Turkmenistan)

    2016-11-15

    We investigated the effect of Plastic media blasting (PMB) method on mechanical properties of Al 2024-T6 alloy for aircraft body coatings. Painting-stripping process with three cycles was performed using PMB for three different thicknesses. The relationship between surface morphology-deformation and defects was characterized. PMB affects the fatigue life and surface morphology of specimens. The fatigue life decreases when the specimen thickness decreases. In contrast, this method does not significantly affect the fatigue life of thick specimens. The surface roughness was between 0.30-0.65 Ra for processed specimens. The study will determine proper sheet metal thickness which is not affected seriously because of the method for Al 2024-T6 alloy.

  20. Dynamic regulation of midbrain dopamine neuron activity: intrinsic, synaptic, and plasticity mechanisms.

    Science.gov (United States)

    Morikawa, H; Paladini, C A

    2011-12-15

    Although the roles of dopaminergic signaling in learning and behavior are well established, it is not fully understood how the activity of dopaminergic neurons is dynamically regulated under different conditions in a constantly changing environment. Dopamine neurons must integrate sensory, motor, and cognitive information online to inform the organism to pursue outcomes with the highest reward probability. In this article, we provide an overview of recent advances on the intrinsic, extrinsic (i.e., synaptic), and plasticity mechanisms controlling dopamine neuron activity, mostly focusing on mechanistic studies conducted using ex vivo brain slice preparations. We also hope to highlight some unresolved questions regarding information processing that takes place at dopamine neurons, thereby stimulating further investigations at different levels of analysis.

  1. Influence of Ionizing Radiation on the Mechanical Properties of a Wood-Plastic Composite

    Science.gov (United States)

    Palm, Andrew; Smith, Jennifer; Driscoll, Mark; Smith, Leonard; Larsen, L. Scott

    The focus of this study was to examine the potential benefits of irradiating polyethylene (PE)-based wood-plastic composites (WPCs) in order to enhance the mechanical properties of the WPC. The PE-based WPCs were irradiated, post extrusion, at dose levels of 0, 50, 100, 150, 200, and 250 kGy with an electron beam (EB). The irradiated WPCs were then evaluated using a third point bending test (ASTM D4761) along with scanning electron microscopy (SEM). It was found that ultimate strength and modulus of elasticity (MOE) increased with increasing dose level. Examination of the fracture surfaces of polyethylene revealed a distinct difference in failure between irradiated and non-irradiated surfaces.

  2. Crack formation mechanisms during micro and macro indentation of diamond-like carbon coatings on elastic-plastic substrates

    DEFF Research Database (Denmark)

    Thomsen, N.B.; Fischer-Cripps, A.C.; Swain, M.V.

    1998-01-01

    In the present study crack formation is investigated on both micro and macro scale using spherical indenter tips. in particular, systems consisting of elastic coatings that are well adhered to elastic-plastic substrates are studied. Depth sensing indentation is used on the micro scale and Rockwell...... indentation on the macro scale. The predominant driving force for coating failure and crack formation during indentation is plastic deformation of the underlying substrate. The aim is to relate the mechanisms creating both delamination and cohesive cracking on both scales with fracture mechanical models...

  3. Import-push or Export-pull?

    DEFF Research Database (Denmark)

    Jäkel, Ina Charlotte

    2014-01-01

    Does the selection effect of trade work solely through competition from imports, or does the export market further contribute to firm selection? This paper provides a re-interpretation of the different mechanisms in terms of selection on profitability - rather than productivity - and derives novel...... predictions regarding the export market and the role of product differentiation. Empirical results for a sample of Danish manufacturing industries confirm the import- "push" hypothesis as well as the export- "pull" hypothesis, but also reveal differences across industries. The selection effect of trade...... is mainly driven by the "import-push" if product differentiation is high, whereas it is driven by the "export-pull" if goods are homogeneous....

  4. Import-push or Export-pull?

    DEFF Research Database (Denmark)

    Jäkel, Ina Charlotte

    Does the selection effect of trade work solely through competition from imports, or does the export market further contribute to firm selection? This paper provides a re-interpretation of the different mechanisms in terms of selection on profitability - rather than productivity - and derives novel...... predictions regarding the export market and the role of product differentiation. Empirical results for a sample of Danish manufacturing industries confirm the import-"push" hypothesis as well as the export-"pull" hypothesis, but also reveal differences across industries. The selection effect of trade...... is mainly driven by the "import-push" if product differentiation is high, whereas it is driven by the "export-pull" if goods are homogeneous....

  5. Plasticity of hatching in amphibians: evolution, trade-offs, cues and mechanisms.

    Science.gov (United States)

    Warkentin, Karen M

    2011-07-01

    Many species of frogs and salamanders, in at least 12 families, alter their timing of hatching in response to conditions affecting mortality of eggs or larvae. Some terrestrially laid or stranded embryos wait to hatch until they are submerged in water. Some embryos laid above water accelerate hatching if the eggs are dehydrating; others hatch early if flooded. Embryos can hatch early in response to predators and pathogens of eggs or delay hatching in response to predators of larvae; some species do both. The phylogenetic pattern of environmentally cued hatching suggests that similar responses have evolved convergently in multiple amphibian lineages. The use of similar cues, including hypoxia and physical disturbance, in multiple contexts suggests potential shared mechanisms underlying the capacity of embryos to respond to environmental conditions. Shifts in the timing of hatching often have clear benefits, but we know less about the trade-offs that favor plasticity, the mechanisms that enable it, and its evolutionary history. Some potentially important types of cued hatching, such as those involving embryo-parent interactions, are relatively unexplored. I discuss promising directions for research and the opportunities that the hatching of amphibians offers for integrative studies of the mechanisms, ecology and evolution of a critical transition between life-history stages.

  6. Progressive DVE Prefetching Mechanism Using Social Recommendation and Pull-Push Strategy%结合社交推荐和推拉策略的渐进式DVE预下载机制

    Institute of Scientific and Technical Information of China (English)

    王明飞; 范辰; 贾金原

    2015-01-01

    为了提高基于对等网络的分布式虚拟环境(DVE)场景预下载的预测精度并降低场景数据传输延迟,将社交推荐和推拉混合策略应用到DVE场景预下载中。首先描述和量化节点化身在虚拟环境中的兴趣,并对化身间相似度进行计算,生成预推荐场景集;然后将化身的视野区域划分为预拉取和预推送区域,提出针对不同区域预下载的推拉策略。基于开源 DVE 平台 FLoD 进行的实验结果表明,该机制能提高场景的预测精度并减少信息交互次数,进而提升DVE场景传输效率和化身漫游流畅度。%In order to improve prediction precision of the scene prefetching and reduce the scene transmis-sion latency in the distributed virtual environment (DVE) based peer to peer network, we propose an effi-cient progressive prefetching mechanism, which combines the social recommendation with different Pull-Push strategies. First, we describe and quantify the avatar interests in the virtual environment to obtain the interest similarity between avatars and generate pre-recommend scene set. Then, we divide the avatar viewing area into the pull area and the push area, and provide different Pull-Push strategies for prefetching the scene in different area. Finally, we demonstrate the proposed prefetching mechanism using an open-source DVE platform called FLoD. Experiment results show that our approach improves the scene prediction precision, reduces the information exchange, and promotes the scene transmission efficiency and avatar roaming fluency.

  7. Increasing ionic conductivity and mechanical strength of a plastic electrolyte by inclusion of a polymer

    Energy Technology Data Exchange (ETDEWEB)

    Patel, Monalisa; Chandrappa, Kodihalli G. [Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore 560012 (India); Bhattacharyya, Aninda J. [Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore 560012 (India)], E-mail: aninda_jb@sscu.iisc.ernet.in

    2008-12-30

    In this contribution we present a soft matter solid electrolyte which was obtained by inclusion of a polymer (polyacrylonitrile, PAN) in LiClO{sub 4}/LiTFSI-succinonitrile (SN), a semi-solid organic plastic electrolyte. Addition of the polymer resulted in considerable enhancement in ionic conductivity as well as mechanical strength of LiX-SN (X = ClO{sub 4}, TFSI) plastic electrolyte. Ionic conductivity of 92.5%-[1 M LiClO{sub 4}-SN]:7.5%-PAN (PAN amount as per SN weight) composite at 25 deg. C recorded a remarkably high value of 7 x 10{sup -3} {omega}{sup -1} cm{sup -1}, higher by few tens of order in magnitude compared to 1 M LiClO{sub 4}-SN. Composite conductivity at sub-ambient temperature is also quite high. At -20 deg. C, the ionic conductivity of (100 - x)%-[1 M LiClO{sub 4}-SN]:x%-PAN composites are in the range 3 x 10{sup -5}-4.5 x 10{sup -4} {omega}{sup -1} cm{sup -1}, approximately one to two orders of magnitude higher with respect to 1 M LiClO{sub 4}-SN electrolyte conductivity. Addition of PAN resulted in an increase of the Young's modulus (Y) from Y {yields} 0 for LiClO{sub 4}-SN to a maximum of 0.4 MPa for the composites. Microstructural studies based on X-ray diffraction, differential scanning calorimetry and Fourier transform infrared spectroscopy suggest that enhancement in composite ionic conductivity is a combined effect of decrease in crystallinity and enhanced trans conformer concentration.

  8. A phenomenological model for mechanically mediated growth, remodeling, damage, and plasticity of gel-derived tissue engineered blood vessels.

    Science.gov (United States)

    Raykin, Julia; Rachev, Alexander I; Gleason, Rudolph L

    2009-10-01

    Mechanical stimulation has been shown to dramatically improve mechanical and functional properties of gel-derived tissue engineered blood vessels (TEBVs). Adjusting factors such as cell source, type of extracellular matrix, cross-linking, magnitude, frequency, and time course of mechanical stimuli (among many other factors) make interpretation of experimental results challenging. Interpretation of data from such multifactor experiments requires modeling. We present a modeling framework and simulations for mechanically mediated growth, remodeling, plasticity, and damage of gel-derived TEBVs that merge ideas from classical plasticity, volumetric growth, and continuum damage mechanics. Our results are compared with published data and suggest that this model framework can predict the evolution of geometry and material behavior under common experimental loading scenarios.

  9. Effect of initial plastic strain on mechanical training of non-modulated Ni–Mn–Ga martensite structure

    Energy Technology Data Exchange (ETDEWEB)

    Szczerba, M.J., E-mail: m.szczerba@imim.pl [Institute of Metallurgy and Materials Science, Polish Academy of Sciences, 25 Reymonta Street, 30-059 Kraków (Poland); Chulist, R. [Institute of Metallurgy and Materials Science, Polish Academy of Sciences, 25 Reymonta Street, 30-059 Kraków (Poland); Kopacz, S.; Szczerba, M.S. [Department of Materials Science and Non-Ferrous Metals Engineering, AGH University of Science and Technology, 30 Mickiewicza Ave., 30-059 Kraków (Poland)

    2014-08-12

    The influence of plastic pre-straining on the mechanical training process of Ni–Mn–Ga single crystals with a non-modulated martensite structure was examined using uniaxial quasi static compression tests and electron backscatter diffraction technique. Firstly, the optimal pre-straining temperature, for which a large plastic strain can be imposed to as-grown crystals with low flow stress and low rate of strain hardening, was established. Then, the maximum value of plastic pre-straining which allows performing successful room temperature mechanical training was found to be of about 20% of total sample thickness reduction. Below this value, training process leads to single variant state, which is able to accommodate true plastic strain of about 0.14 in each step of further training. Above 20% of deformation a multiple martensite variant state of characteristic triangular arrangements is generated. The latter structure cannot practically afford any plastic accommodation during further training; thus the training process fails to operate.

  10. Continuum mechanics through the ages from the renaissance to the twentieth century : from hydraulics to plasticity

    CERN Document Server

    Maugin, Gérard A

    2016-01-01

    Mixing scientific, historic and socio-economic vision, this unique book complements two previously published volumes on the history of continuum mechanics from this distinguished author. In this volume, Gérard A. Maugin looks at the period from the renaissance to the twentieth century and he includes an appraisal of the ever enduring competition between molecular and continuum modelling views. Chapters trace early works in hydraulics and fluid mechanics not covered in the other volumes and the author investigates experimental approaches, essentially before the introduction of a true concept of stress tensor. The treatment of such topics as the viscoelasticity of solids and plasticity, fracture theory, and the role of geometry as a cornerstone of the field, are all explored. Readers will find a kind of socio-historical appraisal of the seminal contributions by our direct masters in the second half of the twentieth century. The analysis of the teaching and research texts by Duhem, Poincaré and Hilbert on cont...

  11. Drying Mechanisms in Plasticized Latex Films: Role of Horizontal Drying Fronts.

    Science.gov (United States)

    Divry, V; Gromer, A; Nassar, M; Lambour, C; Collin, D; Holl, Y

    2016-07-14

    This article presents studies on the drying kinetics of latexes with particles made progressively softer by adding increasing amounts of a plasticizer, in relation to speeds of horizontal drying fronts and particle deformation mechanisms. Global drying rates were measured by gravimetry, and speeds of the horizontal fronts were recorded using a video camera and image processing. Particle deformation mechanisms were inferred using the deformation map established by Routh and Russel (RR). This required precise measurements of the rheological properties of the polymers using a piezorheometer. The results show that latexes with softer particles dry slowly, but in our systems, this is not due to skin formation. A correlation between global drying rates and speeds of horizontal fronts could be established and interpreted in terms of the evolution of mass transfer coefficients of water in different areas of the drying system. The speeds of the horizontal drying fronts were compared with the RR model. A remarkable qualitative agreement of the curve shapes was observed; however, the fit could not be considered good. These results call for further research efforts in modeling and simulation.

  12. EFFECTS OF ETHYLENE VINYL ACETATE CONTENT ON PHYSICAL AND MECHANICAL PROPERTIES OF WOOD-PLASTIC COMPOSITES

    Directory of Open Access Journals (Sweden)

    Dongfang Li,

    2012-05-01

    Full Text Available To investigate the effects of different ethylene vinyl acetate (EVA contents on the performance of wood plastic composites (WPCs made from poplar wood flour (PWF and high density polyethylene (HDPE, physical properties tests, mechanical properties tests, and scanning electron microscope (SEM tests were employed. The thermal stability and functional groups of PWF treated by EVA were evaluated by thermogravimetric analysis (TGA, differential thermal analysis (DTA, and Fourier transform infrared spectroscopy (FTIR, respectively. The results showed that the hardness, water uptake, and thickness swelling of the WPCs was reduced with increasing content of EVA. The MOR and tensile strength of the WPC treated by 15% EVA content were enhanced by 17.48% and 9.97%, respectively, compared with those of the WPC without EVA. TGA results showed that the thermal stability of PWF treated by EVA was improved. FTIR analysis indicated that PWF was reacted and coated with EVA. SEM results showed that gaps and voids hardly existed in the sections of the WPCs treated by EVA. This research suggests that the flexibility and mechanical properties of WPCs could be improved by adding EVA. The best condition of EVA content could be 15%.

  13. Microstructure Evolution and Mechanical Behavior of a Hot-Rolled High-Manganese Dual-Phase Transformation-Induced Plasticity/Twinning-Induced Plasticity Steel

    Science.gov (United States)

    Fu, Liming; Shan, Mokun; Zhang, Daoda; Wang, Huanrong; Wang, Wei; Shan, Aidang

    2017-05-01

    The microstructures and deformation behavior were studied in a high-temperature annealed high-manganese dual-phase (28 vol pct δ-ferrite and 72 vol pct γ-austenite) transformation-induced plasticity/twinning-induced plasticity (TRIP/TWIP) steel. The results showed that the steel exhibits a special Lüders-like yielding phenomenon at room temperature (RT) and 348 K (75 °C), while it shows continuous yielding at 423 K, 573 K and 673 K (150 °C, 300 °C and 400 °C) deformation. A significant TRIP effect takes place during Lüders-like deformation at RT and 348 K (75 °C) temperatures. Semiquantitative analysis of the TRIP effect on the Lüders-like yield phenomenon proves that a softening effect of the strain energy consumption of strain-induced transformation is mainly responsible for this Lüders-like phenomenon. The TWIP mechanism dominates the 423 K (150 °C) deformation process, while the dislocation glide controls the plasticity at 573 K (300 °C) deformation. The delta-ferrite, as a hard phase in annealed dual-phase steel, greatly affects the mechanical stability of austenite due to the heterogeneous strain distribution between the two phases during deformation. A delta-ferrite-aided TRIP effect, i.e., martensite transformation induced by localized strain concentration of the hard delta-ferrite, is proposed to explain this kind of Lüders-like phenomenon. Moreover, the tensile curve at RT exhibits an upward curved behavior in the middle deformation stage, which is principally attributed to the deformation twinning of austenite retained after Lüders-like deformation. The combination of the TRIP effect during Lüders-like deformation and the subsequent TWIP effect greatly enhances the ductility in this annealed high-manganese dual-phase TRIP/TWIP steel.

  14. Microstructure Evolution and Mechanical Behavior of a Hot-Rolled High-Manganese Dual-Phase Transformation-Induced Plasticity/Twinning-Induced Plasticity Steel

    Science.gov (United States)

    Fu, Liming; Shan, Mokun; Zhang, Daoda; Wang, Huanrong; Wang, Wei; Shan, Aidang

    2017-02-01

    The microstructures and deformation behavior were studied in a high-temperature annealed high-manganese dual-phase (28 vol pct δ-ferrite and 72 vol pct γ-austenite) transformation-induced plasticity/twinning-induced plasticity (TRIP/TWIP) steel. The results showed that the steel exhibits a special Lüders-like yielding phenomenon at room temperature (RT) and 348 K (75 °C), while it shows continuous yielding at 423 K, 573 K and 673 K (150 °C, 300 °C and 400 °C) deformation. A significant TRIP effect takes place during Lüders-like deformation at RT and 348 K (75 °C) temperatures. Semiquantitative analysis of the TRIP effect on the Lüders-like yield phenomenon proves that a softening effect of the strain energy consumption of strain-induced transformation is mainly responsible for this Lüders-like phenomenon. The TWIP mechanism dominates the 423 K (150 °C) deformation process, while the dislocation glide controls the plasticity at 573 K (300 °C) deformation. The delta-ferrite, as a hard phase in annealed dual-phase steel, greatly affects the mechanical stability of austenite due to the heterogeneous strain distribution between the two phases during deformation. A delta-ferrite-aided TRIP effect, i.e., martensite transformation induced by localized strain concentration of the hard delta-ferrite, is proposed to explain this kind of Lüders-like phenomenon. Moreover, the tensile curve at RT exhibits an upward curved behavior in the middle deformation stage, which is principally attributed to the deformation twinning of austenite retained after Lüders-like deformation. The combination of the TRIP effect during Lüders-like deformation and the subsequent TWIP effect greatly enhances the ductility in this annealed high-manganese dual-phase TRIP/TWIP steel.

  15. Repeatability of arm pull patterns in front crawl swimming

    Science.gov (United States)

    Su, Lester K.; Kegelman, John C.

    2009-11-01

    The arm pull in human swimming has seen extensive study, particularly involving the front crawl stroke. This work has primarily been aimed either at clarifying the mechanisms of thrust generation by the arm and hand, or at comparing the relative performance of different canonical pulling patterns. In this work we investigate the degree to which swimmers adjust their arm and hand trajectories in response to instantaneous ambient conditions. Video imaging data from competitive swimmers indicates that there may be wide stroke-to-stroke variations in pull trajectories. This suggests that optimal stroking form may be less about a swimmer's ability to repeat idealized pull patterns, than about the swimmer's ability to respond to local flow conditions, or what is referred to in the swimming vernacular as the ``feel'' for the water.

  16. Behavioural analysis of the pull-in dynamic transition

    Science.gov (United States)

    Rocha, L. A.; Cretu, E.; Wolffenbuttel, R. F.

    2004-09-01

    A careful analysis of the dynamics of the pull-in displacement reveals a metastable transient interval for devices with a Q factor lower than 1.2. The duration of this metastable regime could be up to 20 ms for the structure used in this work, depending on the damping. For typical device dimensions this regime dominates pull-in dynamics. This paper explicitly focuses on the metastable regime. The results of numerical simulations are confirmed with measurement results with the purpose of providing a better understanding of the underlying mechanisms. This may contribute to both improved actuator design and enhanced sensitivity of pressure sensors and accelerometers operating on pull-in time interval measurement. The sensitivity of the pull-in time to external accelerations is 6 × 10-2 s/ms-2 (~0.6 ms mg-1) for current devices and can be increased by design.

  17. A critical review of fracture mechanics as a tool for multiaxial fatigue life prediction of plastics1

    Directory of Open Access Journals (Sweden)

    Anders Winkler

    2015-07-01

    Full Text Available Plastics belong to the most complex and probably least understood engineering materials of today. Combining the best aspects of design, mechanical properties and manufacturing, the structural integrity of plastics is on par with aluminium and can in some cases even rival those of steels. One of the most important aspects of plastics is the ability to tailor-drive their material properties for a specific purpose or towards a specific strength value. The morphology of plastics is directly dependent on the manufacturing process, e.g. injection moulding, extruding and casting. Plastics contain multiple phases (crystalline, amorphous, oriented, and are in no sense at all isotropic, although integrally deduced mechanical properties may appear to claim the opposite. As such, it becomes obvious that attempting to analyse such materials using conventional material models and explanations of mechanics is an inherently complex task. The static situation alone requires concepts such as creep, relaxation and rate effects to be incorporated on a numerical level. If the load situation changes, such that cyclic loading is acting on the continuum, with the morphology taken into account (without considering the actual geometrical shape, then the result is that of a complex multiaxial fatigue case. Classical theories used for treating fatigue such as SN or eN analysis have proven much less successful for plastics than they have for metals. Fatigue crack propagation using fracture mechanics has seen some success in application, although appropriate crack initiation criteria still need to be established. The physical facts are more than intriguing. For injection moulded parts (being the most common manufacturing process in place, fracture is in most cases seen to initiate from inside the material, unless the surface has been mechanically compromised. This appears to hold true regardless of the load case. In this review, we have scrutinised physically useful methods

  18. Push-pull farming systems.

    Science.gov (United States)

    Pickett, John A; Woodcock, Christine M; Midega, Charles A O; Khan, Zeyaur R

    2014-04-01

    Farming systems for pest control, based on the stimulo-deterrent diversionary strategy or push-pull system, have become an important target for sustainable intensification of food production. A prominent example is push-pull developed in sub-Saharan Africa using a combination of companion plants delivering semiochemicals, as plant secondary metabolites, for smallholder farming cereal production, initially against lepidopterous stem borers. Opportunities are being developed for other regions and farming ecosystems. New semiochemical tools and delivery systems, including GM, are being incorporated to exploit further opportunities for mainstream arable farming systems. By delivering the push and pull effects as secondary metabolites, for example, (E)-4,8-dimethyl-1,3,7-nonatriene repelling pests and attracting beneficial insects, problems of high volatility and instability are overcome and compounds are produced when and where required.

  19. Shaping development through mechanical strain: the transcriptional basis of diet-induced phenotypic plasticity in a cichlid fish.

    Science.gov (United States)

    Gunter, Helen M; Fan, Shaohua; Xiong, Fan; Franchini, Paolo; Fruciano, Carmelo; Meyer, Axel

    2013-09-01

    Adaptive phenotypic plasticity, the ability of an organism to change its phenotype to match local environments, is increasingly recognized for its contribution to evolution. However, few empirical studies have explored the molecular basis of plastic traits. The East African cichlid fish Astatoreochromis alluaudi displays adaptive phenotypic plasticity in its pharyngeal jaw apparatus, a structure that is widely seen as an evolutionary key innovation that has contributed to the remarkable diversity of cichlid fishes. It has previously been shown that in response to different diets, the pharyngeal jaws change their size, shape and dentition: hard diets induce an adaptive robust molariform tooth phenotype with short jaws and strong internal bone structures, while soft diets induce a gracile papilliform tooth phenotype with elongated jaws and slender internal bone structures. To gain insight into the molecular underpinnings of these adaptations and enable future investigations of the role that phenotypic plasticity plays during the formation of adaptive radiations, the transcriptomes of the two divergent jaw phenotypes were examined. Our study identified a total of 187 genes whose expression differs in response to hard and soft diets, including immediate early genes, extracellular matrix genes and inflammatory factors. Transcriptome results are interpreted in light of expression of candidate genes-markers for tooth size and shape, bone cells and mechanically sensitive pathways. This study opens up new avenues of research at new levels of biological organization into the roles of phenotypic plasticity during speciation and radiation of cichlid fishes.

  20. Microstructure and Mechanical Properties of Warm-Sprayed Titanium Coating on Carbon Fiber-Reinforced Plastic

    Science.gov (United States)

    Ganesan, Amirthan; Takuma, Okada; Yamada, Motohiro; Fukumoto, Masahiro

    2016-04-01

    Polymer materials are increasingly dominating various engineering fields. Recently, polymer-based composite materials' surface performances—in particular, surface in relative motion—have been improved markedly by thermal spray coating. Despite this recent progress, the deposition of high-strength materials—producing a coating thickness of the order of more than 500 μm—remains highly challenging. In the present work, a highly dense and thick titanium coating was successfully deposited onto the carbon fiber-reinforced plastic (CFRP) substrate using a newly developed high-pressure warm spray (WS) system. The coating properties, such as hardness (300 ± 20 HV) and adhesion strength (8.1 ± 0.5 MPa), were evaluated and correlated with the microstructures of the coating. In addition, a wipe-test and in situ particle velocity and temperature measurement were performed to validate the particle deposition behavior as a function of the nitrogen flow rate in the WS system. It was found that the microstructures, deposition efficiency, and mechanical properties of the coatings were highly sensitive to nitrogen flow rates. The coating porosity increased with increasing nitrogen flow rates; however, the highest density was observed for nitrogen flow rate of 1000 standard liters per minute (SLM) samples due to the high fraction of semi-molten particles in the spray stream.

  1. High purity ultrafine-grained nickel processed by dynamic plastic deformation: microstructure and mechanical properties

    Energy Technology Data Exchange (ETDEWEB)

    Farbaniec, Lukasz; Dirras, Guy [Universite Paris 13, Sorbonne Paris Cite LSPM-CNRS, 99, Avenue J. B. Clement, 93430 Villetaneuse (France); Abdul-Latif, Akrum [Laboratoire d' Ingenierie des Systemes Mecaniques et des Materiaux 3, Rue Fernand Hainaut, 93407 St. Ouen Cedex (France); Gubicza, Jeno [Department of Materials Physics, Eoetvoes Lorand University Budapest, P.O. Box 32, H-1518 (Hungary)

    2012-11-15

    Bulk ultrafine-grained samples are processed by dynamic plastic deformation at an average strain rate of 3.3 x 10{sup 2} s{sup -1} from bulk coarse-grained nickel with purity higher than 98.4 wt.%. The obtained microstructure is investigated by electron backscattering diffraction, transmission electron microscopy and X-ray line profile analysis. After dynamic deformation the microstructure evolves into submicron-size lamellar and subgrain structures. Evaluation of average grain size shows a heterogeneous microstructure along both the diameter and the thickness of the sample. X-ray line profile analysis reveals high dislocation density of about 13 {+-} 2 x 10{sup 14} m{sup -2} in the impacted material. The mechanical properties are investigated by means of uniaxial quasi-static compression tests conducted at room temperature. The stress-strain behavior of the impacted Ni depends on the location in the impacted disk and on the orientation of the compression axis relative to the impact direction. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  2. Mechanical Properties and Atomic Explanation of Plastic Deformation for Diamond-Like BC2

    Directory of Open Access Journals (Sweden)

    Baobing Zheng

    2016-06-01

    Full Text Available Motivated by a recently predicted structure of diamond-like BC2 with a high claimed hardness of 56 GPa (J. Phys. Chem. C 2010, 114, 22688–22690, we focus on whether this tetragonal BC2 (t-BC2 is superhard or not in spite of such an ultrahigh theoretical hardness. The mechanical properties of t-BC2 were thus further extended by using the first principles in the framework of density functional theory. Our results suggest that the Young’s and shear moduli of t-BC2 exhibit a high degree of anisotropy. For the weakest shear direction, t-BC2 undergoes an electronic instability and structural collapse upon a shear strain of about 0.11, with its theoretically ideal strength of only 36.2 GPa. Specifically, the plastic deformation under shear strain along the (110[001] direction can be attributed to the breaking of d1 B–C bonds.

  3. Evaluation of the Mechanical Properties of AA 6063 Processed by Severe Plastic Deformation

    Science.gov (United States)

    Jafarlou, Davoud Mashhadi; Zalnezhad, Erfan; Hamouda, Abdelmagid Salem; Faraji, Ghader; Mardi, Noor Azizi Bin; Hassan Mohamed, Mohsen Abdelnaeim

    2015-05-01

    In this study, the mechanical properties, including surface hardness, tensile strength, fatigue, and fretting fatigue behavior of AA 6063 processed by equal channel angular pressing as the most efficient severe shear plastic deformation (SPD) technique, were investigated. Following the SPD process, samples were subjected to heat treatment (HT), hard anodizing (HA), and a combination of HT and HA. Rotating-bending fretting fatigue tests were performed to explore the samples' response to the fretting condition. From the experimental fatigue and fretting fatigue tests, it was apparent that the SPD treatment had a positive effect on enhancing the fatigue and fretting fatigue lives of the samples at low and high-cyclic loads compared with the HT technique by 78 and 67 pct, and 131 and 154 pct respectively. The results also indicate that the SPD + HT technique significantly increased the fatigue and fretting fatigue lives of the samples at high and low cycles by 15.56 and 8.33 pct, and 14.4 and 5.1 pct respectively, compared with the SPD method. HA of AA6063 increased the fatigue and fretting fatigue lives of SPD + HT-processed samples at low cycle by 15.5 and 18.4 pct respectively; however, at high cycle, HA had reverse effects, whereby the fatigue and fretting fatigue lives of SPD + HT-processed samples decreased by 16.7 and 30 pct, respectively.

  4. The wiring of developing sensory circuits - from patterned spontaneous activity to mechanisms of synaptic plasticity

    Directory of Open Access Journals (Sweden)

    Alexandra Helen Leighton

    2016-09-01

    Full Text Available In order to accurately process incoming sensory stimuli, neurons must be organized into functional networks, with both genetic and environmental factors influencing the precise arrangement of connections between cells. Teasing apart the relative contributions of molecular guidance cues, spontaneous activity and visual experience during this maturation is on-going. During development of the sensory system, the first, rough organization of connections is created by molecular factors. These connections are then modulated by the intrinsically generated activity of neurons, even before the senses have become operational. Spontaneous waves of depolarisations sweep across the nervous system, placing them in a prime position to strengthen correct connections and weaken others, shaping synapses into a useful network. A large body of work now supports the idea that, rather than being a mere side-effect of the system, spontaneous activity actually contains information which readies the nervous system so that, as soon as the senses become active, sensory information can be utilized by the animal. An example is the neonatal mouse. As soon as the eyelids first open, neurons in the cortex respond to visual information without the animal having previously encountered structured sensory input (Cang et al., 2005a; Ko et al., 2013; Rochefort et al., 2011; Zhang et al., 2012. In vivo imaging techniques have advanced considerably, allowing observation of the natural activity in the brain of living animals down to the level of the individual synapse. New (optogenetic methods make it possible to subtly modulate the spatio-temporal properties of activity, aiding our understanding of how these characteristics relate to the function of spontaneous activity. Such experiments have had a huge impact on our knowledge by permitting direct testing of ideas about the plasticity mechanisms at play in the intact system, opening up a provocative range of fresh questions. Here, we

  5. Epoxidized Vegetable Oils Plasticized Poly(lactic acid Biocomposites: Mechanical, Thermal and Morphology Properties

    Directory of Open Access Journals (Sweden)

    Buong Woei Chieng

    2014-10-01

    Full Text Available Plasticized poly(lactic acid PLA with epoxidized vegetable oils (EVO were prepared using a melt blending method to improve the ductility of PLA. The plasticization of the PLA with EVO lowers the Tg as well as cold-crystallization temperature. The tensile properties demonstrated that the addition of EVO to PLA led to an increase of elongation at break, but a decrease of tensile modulus. Plasticized PLA showed improvement in the elongation at break by 2058% and 4060% with the addition of 5 wt % epoxidized palm oil (EPO and mixture of epoxidized palm oil and soybean oil (EPSO, respectively. An increase in the tensile strength was also observed in the plasticized PLA with 1 wt % EPO and EPSO. The use of EVO increases the mobility of the polymeric chains, thereby improving the flexibility and plastic deformation of PLA. The SEM micrograph of the plasticized PLA showed good compatible morphologies without voids resulting from good interfacial adhesion between PLA and EVO. Based on the results of this study, EVO may be used as an environmentally friendly plasticizer that can improve the overall properties of PLA.

  6. Motion planning with pull moves

    CERN Document Server

    Ritt, Marcus

    2010-01-01

    It is well known that Sokoban is PSPACE-complete (Culberson 1998) and several of its variants are NP-hard (Demaine et al. 2003). In this paper we prove the NP-hardness of some variants of Sokoban where the warehouse keeper can only pull boxes.

  7. Import-push or Export-pull?

    DEFF Research Database (Denmark)

    Jäkel, Ina Charlotte

    2014-01-01

    Does the selection effect of trade work solely through competition from imports, or does the export market further contribute to firm selection? This paper provides a re-interpretation of the different mechanisms in terms of selection on profitability - rather than productivity - and derives novel...... predictions regarding the export market and the role of product differentiation. Empirical results for a sample of Danish manufacturing industries confirm the import- "push" hypothesis as well as the export- "pull" hypothesis, but also reveal differences across industries. The selection effect of trade...

  8. Crystal Plasticity Modeling of Microstructure Evolution and Mechanical Fields During Processing of Metals Using Spectral Databases

    Science.gov (United States)

    Knezevic, Marko; Kalidindi, Surya R.

    2017-05-01

    This article reviews the advances made in the development and implementation of a novel approach to speeding up crystal plasticity simulations of metal processing by one to three orders of magnitude when compared with the conventional approaches, depending on the specific details of implementation. This is mainly accomplished through the use of spectral crystal plasticity (SCP) databases grounded in the compact representation of the functions central to crystal plasticity computations. A key benefit of the databases is that they allow for a noniterative retrieval of constitutive solutions for any arbitrary plastic stretching tensor (i.e., deformation mode) imposed on a crystal of arbitrary orientation. The article emphasizes the latest developments in terms of embedding SCP databases within implicit finite elements. To illustrate the potential of these novel implementations, the results from several process modeling applications including equichannel angular extrusion and rolling are presented and compared with experimental measurements and predictions from other models.

  9. Strain gradient crystal plasticity: A continuum mechanics approach to modeling micro-structural evolution

    DEFF Research Database (Denmark)

    El-Naaman, Salim Abdallah; Nielsen, Kim Lau; Niordson, Christian Frithiof

    2015-01-01

    In agreement with dislocation theory, recent experiments show, both quantitatively and qualitatively, how geometrically necessary dislocations (GNDs) distribute in dislocation wall and cell structures. Hence, GND density fields are highly localized with large gradients and discontinuities occurring...... between the cells. This behavior is not typical for strain gradient crystal plasticity models. The present study employs a higher order extension of conventional crystal plasticity theory in which the viscous slip rate is influenced by the gradients of GND densities through a back stress...

  10. Strain gradient crystal plasticity: A continuum mechanics approach to modeling micro-structural evolution

    DEFF Research Database (Denmark)

    El-Naaman, Salim Abdallah; Nielsen, Kim Lau; Niordson, Christian Frithiof

    2015-01-01

    In agreement with dislocation theory, recent experiments show, both quantitatively and qualitatively, how geometrically necessary dislocations (GNDs) distribute in dislocation wall and cell structures. Hence, GND density fields are highly localized with large gradients and discontinuities occurring...... between the cells. This behavior is not typical for strain gradient crystal plasticity models. The present study employs a higher order extension of conventional crystal plasticity theory in which the viscous slip rate is influenced by the gradients of GND densities through a back stress...

  11. Structure versus solvent effects on nonlinear optical properties of push-pull systems: a quantum-mechanical study based on a polarizable continuum model.

    Science.gov (United States)

    Corozzi, Alessandro; Mennucci, Benedetta; Cammi, Roberto; Tomasi, Jacopo

    2009-12-31

    A quantum mechanical investigation on the effects of the solvent and the structure on nonlinear optical activity of a class of merocyanine compounds has been conducted. The interplay of the two effects on the first hyperpolarizability, computed at density functional theory and second-order Møller-Plesset level, has been analyzed in combination with ground state properties and geometries and excited state energies and dipoles. A critical analysis of the simplified two-level model has also been presented.

  12. Elastic-Plastic Nonlinear Response of a Space Shuttle External Tank Stringer. Part 2; Thermal and Mechanical Loadings

    Science.gov (United States)

    Knight, Norman F., Jr.; Warren, Jerry E.; Elliott, Kenny B.; Song, Kyongchan; Raju, Ivatury S.

    2012-01-01

    Elastic-plastic, large-deflection nonlinear thermo-mechanical stress analyses are performed for the Space Shuttle external tank s intertank stringers. Detailed threedimensional finite element models are developed and used to investigate the stringer s elastic-plastic response for different thermal and mechanical loading events from assembly through flight. Assembly strains caused by initial installation on an intertank panel are accounted for in the analyses. Thermal loading due to tanking was determined to be the bounding loading event. The cryogenic shrinkage caused by tanking resulted in a rotation of the intertank chord flange towards the center of the intertank, which in turn loaded the intertank stringer feet. The analyses suggest that the strain levels near the first three fasteners remain sufficiently high that a failure may occur. The analyses also confirmed that the installation of radius blocks on the stringer feet ends results in an increase in the stringer capability.

  13. The effects of fiber length and fiber loading on the mechanical properties of wood-plastic (polypropylene) composites

    OpenAIRE

    BASIJI, Farshid; SAFDARI, Vahidreza; NOURBAKHSH, Amir; Pilla, Srikanth

    2014-01-01

    This study examined the effects of wood pulp fiber length (short, medium, and long), and fiber loading (27%, 37%, 47%, and 0% [non-reinforced PP]) with 3% maleic anhydride-grafted polypropylene on the mechanical properties of wood-plastic composites (WPCs). Polypropylene and fibers were compounded into pellets using a counter-rotating twin-screw extruder and test specimens were prepared by injection molding. The results show that increases in fiber length and fiber loading significantly incre...

  14. Influence of the Repetitive Corrugation on the Mechanism Occuring During Plastic Deformation of CuSn6 Alloy

    OpenAIRE

    Nuckowski P. M.; Kwaśny W.; Rdzawski Z.; Głuchowski W.; Pawlyta M.

    2016-01-01

    This paper presents the research results of CuSn6 alloy strip at semi-hard state, plastically deformed in the process of repetitive corrugation. The influence of process parameters on the mechanical properties and structure of examined alloy were investigated. Examination in high-resolution transmission electron microscopy (HRTEM) confirmed the impact of the repetitive corrugation to obtain the nano-scale structures. It has been found, that the application of repetitive corrugation increases ...

  15. Variation of mechanical properties of the metallic sheath in composite Ag/BSCCO tapes during plastic conformation

    Science.gov (United States)

    Hassan, Mohamed K.; Navarro, Rafael

    2002-08-01

    The evolution of the mechanical properties of Ag/BSCCO monocore composites, during powder in tube conformation by wire drawing and free ends tape rolling is analysed. Results on composite wires and tapes with different thickness of the cladding sheaths and on a reference empty tube are reported. The properties of the metallic sheaths and of the compact powder cores are characterised. A correlation of the variations induced in the sheaths by the overall plastic work per unit volume is outlined.

  16. Mechanical characteristics of plastic base Ports and impact on flushing efficacy

    Science.gov (United States)

    Guiffant, Gérard; Flaud, Patrice; Royon, Laurent; Burnet, Espérie; Merckx, Jacques

    2017-01-01

    Background Three types of totally implantable venous access devices, Ports, are currently in use: titanium, plastic (polyoxymethylene, POM), and mixed (titanium base with a POM shell). Physics theory suggests that the interaction between a non-coring needle (NCN, made of stainless steel) and a plastic base would lead to the stronger material (steel) altering the more malleable material (plastic). Objectives To investigate whether needle impacts can alter a plastic base’s surface, thus potentially reducing flushing efficacy. Study design and methods A Port made of POM was punctured 200 times with a 19-gauge NCN. Following the existing guidelines, the needle tip pricked the base with each puncture. The Port’s base was then examined using a two-dimensional optical instrument, and a bi-dimensional numerical simulation using COMSOL® was performed to investigate potential surface irregularities and their impact on fluid flow. Results Each needle impact created a hole (mean depth, 0.12 mm) with a small bump beside it (mean height, 0.02 mm) the Reynolds number Rek≈10. A numerical simulation of the one hole/bump set showed that the flushing efficacy was 60% that of flushing along a flat surface. Discussion In clinical practice, the number of times a Port is punctured depends on patient and treatment characteristics, but each needle impact on the plastic base may increase the risk of decreased flushing effectiveness. Therefore, the more a plastic Port is accessed, the greater the risk of microorganisms, blood products, and medication accumulation. Conclusions Multiple needle impacts created an irregular surface on the Port’s base, which decreased flushing efficacy. Clinical investigation is needed to determine whether plastic base Ports are associated with an increased risk of Port infection and occlusion compared to titanium base Ports. PMID:28176897

  17. Pull factors of Finland and voluntary work

    OpenAIRE

    Jurvakainen, Janika

    2016-01-01

    This thesis studies pull factors of Finland and voluntary work. The aim of this study is to understand the pull factors of Finland from the perspective of young travelers. Which pull factors attract to choose Finland as their destination? In addition, which pull factors attract young travelers to participate in international voluntary work? The commissioner of this thesis is Allianssi Youth Exchange. The thesis is research-based and includes a quantitative Webropol survey and some qualit...

  18. Numerical Simulation and Experimental Investigation of the Viscoelastic Heating Mechanism in Ultrasonic Plasticizing of Amorphous Polymers for Micro Injection Molding

    Directory of Open Access Journals (Sweden)

    Bingyan Jiang

    2016-05-01

    Full Text Available Ultrasonic plasticizing of polymers for micro-injection molding has been proposed and studied for its unique potential in materials and energy-saving. In our previous work, we have demonstrated the characteristics of the interfacial friction heating mechanism in ultrasonic plasticizing of polymer granulates. In this paper, the other important heating mechanism in ultrasonic plasticizing, i.e., viscoelastic heating for amorphous polymer, was studied by both theoretical modeling and experimentation. The influence mechanism of several parameters, such as the initial temperature of the polymer, the ultrasonic frequency, and the ultrasonic amplitude, was investigated. The results from both numerical simulation and experimentation indicate that the heat generation rate of viscoelastic heating can be significantly influenced by the initial temperature of polymer. The glass transition temperature was found to be a significant shifting point in viscoelastic heating. The heat generation rate is relatively low at the beginning and can have a steep increase after reaching glass transition temperature. In comparison with the ultrasonic frequency, the ultrasonic amplitude has much greater influence on the heat generation rate. In light of the quantitative difference in the viscoelastic heating rate, the limitation of the numerical simulation was discussed in the aspect of the assumptions and the applied mathematical models.

  19. 挠性电路板焊盘拉脱失效原因分析及控制%The study of failure mechanism of Flexible Printed Circuit Board pad pull-off and its control

    Institute of Scientific and Technical Information of China (English)

    易小龙; 莫欣满; 陈蓓

    2016-01-01

    As an important media of electronic components mounting, pads are vitally important to the life and reliability of the final products. In this paper, a universal tensile testing machine was employed to comprehensively survey the impact of the type of material, copper thickness, pad size, welding temperature and welding times on the pads’ pull-off strength from three suppliers’ lfexible substrates; a metallurgical microscope and TGA were further used to discuss the pads’ pull-off failure mechanism; orthogonal analysis method was then employed to obtain that the main factors during the welding process are welding temperature and welding times, and on the basis of above, the range of parameters were ifnally given to optimize the process design.%焊盘作为线路板与电子元器件焊接装联的必要媒介,其焊接的可靠性是影响最终产品的寿命和可靠性的重要因素。本文以三家供应商的无胶挠性板材为例,运用万能实验拉力机在不同条件下对焊盘进行拉脱,从材料种类、铜厚、焊盘尺寸、焊接温度、焊接次数五个方面考察了其对焊盘拉脱强度的影响;通过金相显微镜和热重分析讨论了挠性板材在焊接过程中焊盘脱落的机制;最后运用正交分析法得出了焊接过程中的主要影响因素是焊接温度及焊接次数,在此基础上给出了参数范围,优化了工艺设计。

  20. MicroRNAs regulate neuronal plasticity and are involved in pain mechanisms.

    Directory of Open Access Journals (Sweden)

    Sara eElramah

    2014-02-01

    Full Text Available MicroRNAs(miRNAs are emerging as master regulators of gene expression in the nervous system where they contribute not only to brain development but also to neuronal network homeostasis and plasticity. Their function is the result of a cascade of events including miRNA biogenesis, target recognition and translation inhibition. It has been suggested that miRNAs are major switches of the genome owing to their ability to regulate multiple genes at the same time. This regulation is essential for normal neuronal activity and, when affected, can lead to drastic pathological conditions. As an example, we illustrate how deregulation of miRNAs can affect neuronal plasticity leading to chronic pain.The origin of pain and its dual role as a key physiological function and a debilitating disease has been highly debated until now. The incidence of chronic pain is estimated to be 20-25% worldwide, thus making it a public health problem. Chronic pain can be considered as a form of maladaptive plasticity. Long-lasting modifications develop as a result of global changes in gene expression, and are thus likely to be controlled by miRNAs. Here, we review the literature on miRNAs and their targets responsible for maladaptive plasticity in chronic pain conditions. In addition, we conduct a retrospective analysis of miRNA expression data published for different pain models, taking into account recent progress in our understanding of the role of miRNAs in neuronal plasticity.

  1. MicroRNAs regulate neuronal plasticity and are involved in pain mechanisms.

    Science.gov (United States)

    Elramah, Sara; Landry, Marc; Favereaux, Alexandre

    2014-01-01

    MicroRNAs (miRNAs) are emerging as master regulators of gene expression in the nervous system where they contribute not only to brain development but also to neuronal network homeostasis and plasticity. Their function is the result of a cascade of events including miRNA biogenesis, target recognition, and translation inhibition. It has been suggested that miRNAs are major switches of the genome owing to their ability to regulate multiple genes at the same time. This regulation is essential for normal neuronal activity and, when affected, can lead to drastic pathological conditions. As an example, we illustrate how deregulation of miRNAs can affect neuronal plasticity leading to chronic pain. The origin of pain and its dual role as a key physiological function and a debilitating disease has been highly debated until now. The incidence of chronic pain is estimated to be 20-25% worldwide, thus making it a public health problem. Chronic pain can be considered as a form of maladaptive plasticity. Long-lasting modifications develop as a result of global changes in gene expression, and are thus likely to be controlled by miRNAs. Here, we review the literature on miRNAs and their targets responsible for maladaptive plasticity in chronic pain conditions. In addition, we conduct a retrospective analysis of miRNA expression data published for different pain models, taking into account recent progress in our understanding of the role of miRNAs in neuronal plasticity.

  2. Mechanisms of short-term plasticity at neuromuscular active zones of Drosophila

    Science.gov (United States)

    Hallermann, Stefan; Heckmann, Manfred; Kittel, Robert J.

    2010-01-01

    During short bursts of neuronal activity, changes in the efficacy of neurotransmitter release are governed primarily by two counteracting processes: (1) Ca2+-dependent elevations of vesicle release probability and (2) depletion of synaptic vesicles. The dynamic interplay of both processes contributes to the expression of activity-dependent synaptic plasticity. Here, we exploited various facets of short-term plasticity at the Drosophila neuromuscular junction to dissect these two processes. This enabled us to rigorously analyze different models of synaptic vesicle pools in terms of their size and mobilization properties. Independent of the specific model, we estimate ∼300 readily releasable vesicles with an average release probability of ∼50% in 1 mM extracellular calcium (∼5% in 0.4 mM extracellular calcium) under resting conditions. The models also helped interpreting the altered short-term plasticity of the previously reported mutant of the active zone component Bruchpilot (BRP). Finally, our results were independently confirmed through fluctuation analysis. Our data reveal that the altered short-term plasticity observed in BRP mutants cannot be accounted for by delocalized Ca2+ channels alone and thus suggest an additional role of BRP in short-term plasticity. PMID:20811513

  3. Trypanosoma cruzi mitochondrial tryparedoxin peroxidase is located throughout the cell and its pull down provides one step towards the understanding of its mechanism of action.

    Science.gov (United States)

    Peloso, E F; Dias, L; Queiroz, R M L; Leme, A F P Paes; Pereira, C N; Carnielli, C M; Werneck, C C; Sousa, M V; Ricart, C A O; Gadelha, F R

    2016-01-01

    Trypanosoma cruzi depends on the effectiveness of redox metabolism to survive and ensure infection in the host. Homeostasis of redox metabolism in T. cruzi is achieved by the actions of several proteins that differ in many aspects from host proteins. Although extensive research has been performed examining hydroperoxide cytosolic antioxidant defense centered on trypanothione, the mechanisms of mitochondrial antioxidant defense are not yet known. The aim of this study was to elucidate the partners of TcMPx antioxidant pathway and to determine the influence of the cellular context (physiological versus oxidative stress). Through co-precipitation coupled with a mass spectrometry approach, a variety of proteins were detected under physiological and oxidative stress conditions. Interestingly, functional category analysis of the proteins identified under physiological conditions showed that they were involved in the stress response, oxidoreduction, thiol transfer, and metabolic processes; this profile is distinct under oxidative stress conditions likely due to structural alterations. Our findings help to elucidate the reactions involving TcMPx and most importantly also reveal that this protein is present throughout the cell and that its interaction partners change following oxidative stress exposure. The involvement and significance of the proteins found to interact with TcMPx and other possible functions for this protein are discussed widening our knowledge regarding T. cruzi mitochondrial antioxidant defenses.

  4. Influence of Cellulose on the Mechanical and Thermal Stability of ABS Plastic Composites

    Directory of Open Access Journals (Sweden)

    K. Crews

    2016-01-01

    Full Text Available Microcrystalline cellulose was explored as possible biodegradable fillers in the fabrication of ABS plastic composites. TGA indicates that upon inclusion of cellulose microcrystals the thermal stability of the ABS plastics was improved significantly when compared to the neat ABS plastic counterparts. Furthermore, inclusion of extracted cellulose from plant biomass showed a higher thermal stability with maximum decomposition temperatures around 131.95°C and 124.19°C for cellulose from cotton and Hibiscus sabdariffa, respectively, when compared to that of the purchased cellulose. In addition, TMA revealed that the average CTE value for the neat ABS and 1 : 1 ratio of cellulose to ABS fabricated in this study was significantly lower than the reported CTE (ca. 73.8 μm/m°C.

  5. Mechanical Properties and Fracture Behavior of Cu-Co-Be Alloy after Plastic Deformation and Heat Treatment

    Institute of Scientific and Technical Information of China (English)

    Yan-jun ZHOU; Ke-xing SONG; Jian-dong XING; Zhou LI; Xiu-hua GUO

    2016-01-01

    Mechanical properties and fracture behavior of Cu-0.84Co-0.23Be alloy after plastic deformation and heat treatment were comparatively investigated.Severe plastic deformation by hot extrusion and cold drawing was adopted to induce large plastic strain of Cu-0.84Co-0.23Be alloy.The tensile strength and elongation are up to 476.6 MPa and 1 8%,respectively.The fractured surface consists of deep dimples and micro-voids.Due to the formation of su-persaturated solid solution on the Cu matrix by solution treatment at 950 ℃ for 1 h,the tensile strength decreased to 271.9 MPa,while the elongation increased to 42%.The fracture morphology is parabolic dimple.Furthermore,the tensile strength increased significantly to 580.2 MPa after aging at 480 ℃ for 4 h.During the aging process,a large number of precipitates formed and distributed on the Cu matrix.The fracture feature of aged specimens with low elongation (4.6%)exhibits an obvious brittle intergranular fracture.It is confirmed that the mechanical properties and fracture behavior are dominated by the microstructure characteristics of Cu-0.84Co-0.23Be alloy after plastic de-formation and heat treatment.In addition,the fracture behavior at 450 ℃ of aged Cu-0.84Co-0.23Be alloy was also studied.The tensile strength and elongation are 383.6 MPa and 11.2%,respectively.The fractured morphologies are mainly candy-shaped with partial parabolic dimples and equiaxed dimples.The fracture mode is multi-mixed mechanism that brittle intergranular fracture plays a dominant role and ductile fracture is secondary.

  6. Severe plastic deformation using friction stir processing, and the characterization of microstructure and mechanical behavior using neutron diffraction

    Science.gov (United States)

    Woo, Wanchuck

    Friction-stir welding (FSW) is a solid-state joining process, which utilizes a cylindrical rotating tool consisting of a concentric threaded tool pin and tool shoulder. The strong metallurgical bonding during the FSW is accomplished through: (1) the severe plastic deformation caused by the rotation of the tool pin that plunges into the material and travels along the joining line; and (2) the frictional heat generated mainly from the pressing tool shoulder. Recently, a number of variations of the FSW have been applied to modify the microstructure, for example, grain refinements and homogenization of precipitate particles, namely friction-stir processing (FSP). Applications of the FSP/FSW are widespread for the transportation industries. The microstructure and mechanical behavior of light-weight materials subjected to the FSW/FSP are being studied extensively. However, separating the effect of the frictional heat and severe plastic deformation on the residual stress and texture has been a standing problem for the fundamental understanding of FSW/FSP. The fundamental issues are: (i) the heat- and plastic-deformation-induced internal stresses that may be detrimental to the integrity and performance of components; (ii) the frictional heating that causes a microstructural softening due to the dissolution or growth of the precipitates in precipitation-hardenable Al alloys during the process; and (iii) the crystallographic texture can be significantly altered from the original texture, which could affect the physical and mechanical properties. The understanding of the influences of the de-convoluted sources (e.g. frictional heat, severe plastic deformation, or their combination) on the residual stress, microstructural softening, and texture variations during FSW can be used for a physicsvi based optimization of the processing parameters and new tool designs. Furthermore, the analyses and characterization of the natural aging behavior and the aging kinetics can be

  7. Microdroplet oscillations during optical pulling

    CERN Document Server

    Ellingsen, Simen Å

    2011-01-01

    It was recently shown theoretically that it is possible to pull a spherical dielectric body towards the source of a laser beam [Nature Photonics {\\bf 5}, 531 (2011)], a result with immediate consequences to optical manipulation of small droplets. Optical pulling can be realised e.g.\\ using a diffraction free Bessel beam, and is expected to be of great importance in manipulation of microscopic droplets in micro- and nanofluidics. Compared to conventional optical pushing, however, the radio of optical net force to stress acting on a droplet is much smaller, increasing the importance of oscillations. We describe the time-dependent surface deformations of a water microdroplet under optical pulling to linear order in the deformation. Shape oscillations have a lifetime in the order of microseconds for droplet radii of a few micrometers. The force density acting on the initially spherical droplet is strongly peaked near the poles on the beam axis, causing the deformations to take the form of jet-like protrusions.

  8. In situ atomic scale mechanical microscopy discovering the atomistic mechanisms of plasticity in nano-single crystals and grain rotation in polycrystalline metals

    Energy Technology Data Exchange (ETDEWEB)

    Han, Xiaodong, E-mail: xdhan@bjut.edu.cn [Institute of Microstructure and Property of Advanced Materials, Beijing University of Technology (China); Wang, Lihua; Yue, Yonghai [Institute of Microstructure and Property of Advanced Materials, Beijing University of Technology (China); Zhang, Ze, E-mail: zezhang@zju.edu.cn [Institute of Microstructure and Property of Advanced Materials, Beijing University of Technology (China); Department of Materials Science, National Key Lab of Silicon Materials, Zhejiang University (China)

    2015-04-15

    In this review, we briefly introduce our in situ atomic-scale mechanical experimental technique (ASMET) for transmission electron microscopy (TEM), which can observe the atomic-scale deformation dynamics of materials. This in situ mechanical testing technique allows the deformation of TEM samples through a simultaneous double-tilt function, making atomic-scale mechanical microscopy feasible. This methodology is generally applicable to thin films, nanowires (NWs), tubes and regular TEM samples to allow investigation of the dynamics of mechanically stressed samples at the atomic scale. We show several examples of this technique applied to Pt and Cu single/polycrystalline specimens. The in situ atomic-scale observation revealed that when the feature size of these materials approaches the nano-scale, they often exhibit “unusual” deformation behaviours compared to their bulk counterparts. For example, in Cu single-crystalline NWs, the elastic–plastic transition is size-dependent. An ultra-large elastic strain of 7.2%, which approaches the theoretical elasticity limit, can be achieved as the diameter of the NWs decreases to ∼6 nm. The crossover plasticity transition from full dislocations to partial dislocations and twins was also discovered as the diameter of the single-crystalline Cu NWs decreased. For Pt nanocrystals (NC), the long-standing uncertainties of atomic-scale plastic deformation mechanisms in NC materials (grain size G less than 15 nm) were clarified. For larger grains with G<∼10 nm, we frequently observed movements and interactions of cross-grain full dislocations. For G between 6 and 10 nm, stacking faults resulting from partial dislocations become more frequent. For G<∼6 nm, the plasticity mechanism transforms from a mode of cross-grain dislocation to a collective grain rotation mechanism. This grain rotation process is mediated by grain boundary (GB) dislocations with the assistance of GB diffusion and shuffling. These in situ atomic

  9. Mechanical characteristics of plastic base Ports and impact on flushing efficacy

    Directory of Open Access Journals (Sweden)

    Guiffant G

    2017-01-01

    Full Text Available Gérard Guiffant,1 Patrice Flaud,1 Laurent Royon,1 Espérie Burnet,2 Jacques Merckx1–3 1University Paris Diderot, Biofluidic Group, UMR CNRS, 2Pulmonary Department and Adult Cystic Fibrosis Centre, Cochin Hospital, 3University Teaching Hospital, Necker-Enfants Malades, Paris, France Background: Three types of totally implantable venous access devices, Ports, are currently in use: titanium, plastic (polyoxymethylene, POM, and mixed (titanium base with a POM shell. Physics theory suggests that the interaction between a non-coring needle (NCN, made of stainless steel and a plastic base would lead to the stronger material (steel altering the more malleable material (plastic. Objectives: To investigate whether needle impacts can alter a plastic base’s surface, thus potentially reducing flushing efficacy. Study design and methods: A Port made of POM was punctured 200 times with a 19-gauge NCN. Following the existing guidelines, the needle tip pricked the base with each puncture. The Port’s base was then examined using a two-dimensional optical instrument, and a bi-dimensional numerical simulation using COMSOL® was performed to investigate potential surface irregularities and their impact on fluid flow. Results: Each needle impact created a hole (mean depth, 0.12 mm with a small bump beside it (mean height, 0.02 mm the Reynolds number Rek≈10. A numerical simulation of the one hole/bump set showed that the flushing efficacy was 60% that of flushing along a flat surface. Discussion: In clinical practice, the number of times a Port is punctured depends on patient and treatment characteristics, but each needle impact on the plastic base may increase the risk of decreased flushing effectiveness. Therefore, the more a plastic Port is accessed, the greater the risk of microorganisms, blood products, and medication accumulation. Conclusions: Multiple needle impacts created an irregular surface on the Port’s base, which decreased flushing efficacy

  10. Mechanism of Notch Pathway Activation and Its Role in the Regulation of Olfactory Plasticity in Drosophila melanogaster.

    Science.gov (United States)

    Kidd, Simon; Lieber, Toby

    2016-01-01

    The neural plasticity of sensory systems is being increasingly recognized as playing a role in learning and memory. We have previously shown that Notch, part of an evolutionarily conserved intercellular signaling pathway, is required in adult Drosophila melanogaster olfactory receptor neurons (ORNs) for the structural and functional plasticity of olfactory glomeruli that is induced by chronic odor exposure. In this paper we address how long-term exposure to odor activates Notch and how Notch in conjunction with chronic odor mediates olfactory plasticity. We show that upon chronic odor exposure a non-canonical Notch pathway mediates an increase in the volume of glomeruli by a mechanism that is autonomous to ORNs. In addition to activating a pathway that is autonomous to ORNs, chronic odor exposure also activates the Notch ligand Delta in second order projection neurons (PNs), but this does not appear to require acetylcholine receptor activation in PNs. Delta on PNs then feeds back to activate canonical Notch signaling in ORNs, which restricts the extent of the odor induced increase in glomerular volume. Surprisingly, even though the pathway that mediates the increase in glomerular volume is autonomous to ORNs, nonproductive transsynaptic Delta/Notch interactions that do not activate the canonical pathway can block the increase in volume. In conjunction with chronic odor, the canonical Notch pathway also enhances cholinergic activation of PNs. We present evidence suggesting that this is due to increased acetylcholine release from ORNs. In regulating physiological plasticity, Notch functions solely by the canonical pathway, suggesting that there is no direct connection between morphological and physiological plasticity.

  11. Mechanism of Notch Pathway Activation and Its Role in the Regulation of Olfactory Plasticity in Drosophila melanogaster.

    Directory of Open Access Journals (Sweden)

    Simon Kidd

    Full Text Available The neural plasticity of sensory systems is being increasingly recognized as playing a role in learning and memory. We have previously shown that Notch, part of an evolutionarily conserved intercellular signaling pathway, is required in adult Drosophila melanogaster olfactory receptor neurons (ORNs for the structural and functional plasticity of olfactory glomeruli that is induced by chronic odor exposure. In this paper we address how long-term exposure to odor activates Notch and how Notch in conjunction with chronic odor mediates olfactory plasticity. We show that upon chronic odor exposure a non-canonical Notch pathway mediates an increase in the volume of glomeruli by a mechanism that is autonomous to ORNs. In addition to activating a pathway that is autonomous to ORNs, chronic odor exposure also activates the Notch ligand Delta in second order projection neurons (PNs, but this does not appear to require acetylcholine receptor activation in PNs. Delta on PNs then feeds back to activate canonical Notch signaling in ORNs, which restricts the extent of the odor induced increase in glomerular volume. Surprisingly, even though the pathway that mediates the increase in glomerular volume is autonomous to ORNs, nonproductive transsynaptic Delta/Notch interactions that do not activate the canonical pathway can block the increase in volume. In conjunction with chronic odor, the canonical Notch pathway also enhances cholinergic activation of PNs. We present evidence suggesting that this is due to increased acetylcholine release from ORNs. In regulating physiological plasticity, Notch functions solely by the canonical pathway, suggesting that there is no direct connection between morphological and physiological plasticity.

  12. Dislocation-based plasticity and strengthening mechanisms in sub-20 nm lamellar structures in pearlitic steel wire

    DEFF Research Database (Denmark)

    Zhang, Xiaodan; Hansen, Niels; Godfrey, Andrew

    2016-01-01

    at a strain of 5.4; the dislocations are stored as threading dislocations, as dislocation tangles and as cell boundaries with low to medium misorientation angles. An analysis of the evolution of microstructure and strength with increasing strain suggests that dislocation-based plasticity is a dominating...... mechanism in the wire and three strengthening mechanisms are applied: boundary strengthening, dislocation strengthening and solid solution hardening with their relative contributions to the total flow stress which change as the strain is increased. Based on linear additivity good correspondence between...

  13. Effect of Palm Oil Bio-Based Plasticizer on the Morphological, Thermal and Mechanical Properties of Poly(Vinyl Chloride)

    OpenAIRE

    Kar Min Lim; Yern Chee Ching; Seng Neon Gan

    2015-01-01

    Flexible poly(vinyl chloride) (PVC) was fabricated using a palm oil-based alkyd as a co-plasticizer to di-octyl phthalate (DOP) and di-isononyl phthalate (DiNP). The effects of the incorporation of the palm oil-based alkyd on morphological, thermal and mechanical properties of PVC compounds were studied. Results showed the incorporation of the alkyd enhanced the mechanical and thermal properties of the PVC compounds. Fourier transform infrared spectroscopy (FTIR) results showed that the polar...

  14. Microstructure and mechanical properties of an Al–Mg–Si tube processed by severe plastic deformation and subsequent annealing

    Energy Technology Data Exchange (ETDEWEB)

    Farshidi, M.H., E-mail: farshidi@um.ac.ir [Department of Materials Science and Metallurgical Engineering, Ferdowsi University of Mashhad, Azadi Square, Mashhad (Iran, Islamic Republic of); Kazeminezhad, M. [Department of Materials Science and Engineering, Sharif University of Technology, Azadi Avenue, Tehran (Iran, Islamic Republic of); Miyamoto, H. [Department of Mechanical Engineering, Doshisha University, Kyotanabe City, Kyoto (Japan)

    2015-07-29

    This study is aimed to realize evolution of microstructure and mechanical properties of aluminum 6061 alloy tube subjected to Severe Plastic Deformation (SPD) and subsequent annealing. For this purpose, the tube is initially processed by different passes of an SPD process called Tube Channel Pressing (TCP) and then subjected to a subsequent annealing at 473 °K for 2 h. Afterwards, tension test is used for the evaluation of mechanical properties while Electron Back-Scattered Diffraction (EBSD) equipped Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) are utilized for the microstructural characterizations. Results show that the Continuous Static Recrystallization (CSRX) is the main restoration phenomenon during annealing of aluminum 6061 alloy, even after imposing a moderate plastic strain. For instance, CSRX has been observed during annealing treatment after imposing an equivalent plastic strain as low as 1. However, the used annealing treatment causes different microstructural variations in specimens depending on the pass number of TCP. As an illustration, while the average grain size impressively decreases due to annealing of 1 pass TCPed specimen, it moderately increases after annealing of 5 passes TCPed specimen. This is due to development of a bimodal microstructure after 5 pass of TCP which leads to a different evolution of microstructure during successive annealing. It is also notable that TCPed and annealed specimens show higher strength and ductility compared with as TCPed specimens which is attributed to the occurrence of precipitation hardening besides restoration phenomenon during the annealing treatment.

  15. Studies on Physico-Mechanical and Explosive Characteristics of RDX/HMX-Based Castable Plastic-Bonded Explosives

    Directory of Open Access Journals (Sweden)

    J. S. Gharia

    1998-01-01

    Full Text Available Conventional cast explosives (RDX/TNT have major drawbacks of poor mechanical properties,shrinkages and higher sensitivity .These properties can be improved by applying plastic bindersystems. The plastic-bonded explosive (PBX is a composite material in which solid explosive particles are dispersed in a polymer matrix. The present paper describes the development of anitramine/hydroxy-terminated polybutadiene (HTPB-based castable PBX. The PBXs were processed as per standard procedures. Bimodal/trimodal particle size system was selected to reach asolid loading of 88 wt per cent. High solid loading was made possible through proper combination ofcoarse/fine ratio of solid ingredients, which was based on a number of tap density experiments.Processability of the binder system was studied by using various wetting agents as well as by selectingbinder/plasticizer ratios. Mechanical properties of the PBXs were enhanced by different crosslinkingagents. The explosive properties ofPBXs including detonation velocity , processability and sensitivityto different types of stimuli, were studied. The results show that PBXs can be manufactured withdetonation properties better than those of composition B/octol with the added advantages of superiorthermal and sensitivity characteristics.

  16. Mechanisms operating during plastic deformation of metals under concurrent production of cascades and dislocations

    DEFF Research Database (Denmark)

    Trinkaus, H.; Singh, Bachu Narain

    Recent in-reactor tensile tests (IRTs) on pure copper have revealed a deformation behaviour which is significantly different from that observed in post-irradiation tensile tests (PITs). In IRTs, the material deforms uniformly and homogeneously without yield drop and plastic instability as commonly...

  17. Stability and photodegradation mechanisms of conjugated polymer/fullerene plastic solar cells

    NARCIS (Netherlands)

    Neugebauer, H.; Brabec, C.; Hummelen, J.C.; Sariciftci, N.S.

    2000-01-01

    Degradation studies of poly(2-methoxy-5-(3',7'-dimethyloctyloxy)-1,4-phenylene-vinylene) (MDMO-PPV), fullerenes ((6,6)-phenyl C-61-butyric acid methyl ester (PCBM) and C-60), and mixtures, which are the photoactive components in plastic solar cells, are shown. The degradation processes of the indivi

  18. Mechanical and time-dependent behavior of wood-plastic composites subjected to tension and compression

    Science.gov (United States)

    Scott E. Hamel; John C. Hermanson; Steven M. Cramer

    2012-01-01

    The thermoplastics within wood—plastic composites (WPCs) are known to experience significant time-dependent deformation or creep. In some formulations, creep deformation can be twice as much as the initial quasi-static strain in as little as 4 days. While extensive work has been done on the creep behavior of pure polymers, little information is available on the...

  19. Tailoring dislocation structures and mechanical properties of nanostructured metals produced by plastic deformation

    DEFF Research Database (Denmark)

    Huang, Xiaoxu

    2009-01-01

    The presence of a dislocation structure associated with low-angle dislocation boundaries and interior dislocations is a common and characteristic feature in nanostructured metals produced by plastic deformation, and plays an important role in determining both the strength and ductility of the nan...

  20. Elastic-Plastic Fracture Mechanics Analysis of Critical Flaw Size in ARES I-X Flange-to-Skin Welds

    Science.gov (United States)

    Chell, G. Graham; Hudak, Stephen J., Jr.

    2008-01-01

    NASA's Ares 1 Upper Stage Simulator (USS) is being fabricated from welded A516 steel. In order to insure the structural integrity of these welds it is of interest to calculate the critical initial flaw size (CIFS) to establish rational inspection requirements. The CIFS is in turn dependent on the critical final flaw size (CFS), as well as fatigue flaw growth resulting from transportation, handling and service-induced loading. These calculations were made using linear elastic fracture mechanics (LEFM), which are thought to be conservative because they are based on a lower bound, so called elastic, fracture toughness determined from tests that displayed significant plasticity. Nevertheless, there was still concern that the yield magnitude stresses generated in the flange-to-skin weld by the combination of axial stresses due to axial forces, fit-up stresses, and weld residual stresses, could give rise to significant flaw-tip plasticity, which might render the LEFM results to be non-conservative. The objective of the present study was to employ Elastic Plastic Fracture Mechanics (EPFM) to determine CFS values, and then compare these values to CFS values evaluated using LEFM. CFS values were calculated for twelve cases involving surface and embedded flaws, EPFM analyses with and without plastic shakedown of the stresses, LEFM analyses, and various welding residual stress distributions. For the cases examined, the computed CFS values based on elastic analyses were the smallest in all instances where the failures were predicted to be controlled by the fracture toughness. However, in certain cases, the CFS values predicted by the elastic-plastic analyses were smaller than those predicted by the elastic analyses; in these cases the failure criteria were determined by a breakdown in stress intensity factor validity limits for deep flaws (a greater than 0.90t), rather than by the fracture toughness. Plastic relaxation of stresses accompanying shakedown always increases the

  1. Mechanism of a plastic phenotypic response: predator-induced shell thickening in the intertidal gastropod Littorina obtusata.

    Science.gov (United States)

    Brookes, J I; Rochette, Rémy

    2007-05-01

    Phenotypic plasticity has been the object of considerable interest over the past several decades, but in few cases are mechanisms underlying plastic responses well understood. For example, it is unclear whether predator-induced changes in gastropod shell morphology represent an active physiological response or a by-product of reduced feeding. We address this question by manipulating feeding and growth of intertidal snails, Littorina obtusata, using two approaches: (i) exposure to predation cues from green crabs Carcinus maenas and (ii) reduced food availability, and quantifying growth in shell length, shell mass, and body mass, as well as production of faecal material and shell micro-structural characteristics (mineralogy and organic fraction) after 96 days. We demonstrate that L. obtusata actively increases calcification rate in response to predation threat, and that this response entails energetic and developmental costs. That this induced response is not strictly tied to the animal's behaviour should enhance its evolutionary potential.

  2. Mechanisms of Plastic and Fracture Instabilities for Alloy Development of Fusion Materials. Final Project Report for period July 15, 1998 - July 14, 2003

    Energy Technology Data Exchange (ETDEWEB)

    Ghoniem, N. M.

    2003-07-14

    The main objective of this research was to develop new computational tools for the simulation and analysis of plasticity and fracture mechanisms of fusion materials, and to assist in planning and assessment of corresponding radiation experiments.

  3. Mechanism of plasticity Development for Ceramic Dough (Part 2). Investigation on Plasticity by Particle Packing Structure; Seramiku nendo no kasakusei hatsugen mekanizumu 2. Nendo juten kozo to kasakusei

    Energy Technology Data Exchange (ETDEWEB)

    Kawai, Shuji. [Wet Forming of Ceramics Technology Research Association, Aichi (Japan); Ichikawa, Yukari.; Ishida, Hideki. [INAX Corporation, Aichi (Japan); Shibasaki, Yasuo.; Oda, Kiichi. [National Industrial Research Institute of Nagoya, Aichi (Japan)

    1999-01-01

    Plasticity and packing structure of clay and alumina dough, and of alumina mixed with water-soluble and non-water-soluble plasticizers were investigated. It was found that both plastic clay dough and alumina dough with plasticizers showed a two-peak pore population. When the larger-sized pores increased in volume, the fluidity of the dough was improved. On the otherhand, when the smaller-sized pores decreased in volume, a high rigidity was showed. An aggregate structure was observed in the clay and the dough mixed with water-soluble plasticizer like methyl cellulose. Plasticity was generated when the aggregates were deformed by using the larger-sized pores among each aggregate. The non-water-soluble curdlan did not dissolve in the dough and remained in gel. The larger-sized pores were formed by the gel, whose deformation produced plasticity. It was understood that plasticity is fenerated when either the aggregates or the gel act as a buffer in the dough and enhance deformation of the dough. (author)

  4. AGGLOMERATION AND RADIATION EFFECT OF THE PULL OF URBANIZATION

    Institute of Scientific and Technical Information of China (English)

    QI Jin-li

    2003-01-01

    In order to explore the train of thought for China's urbanizing development and coordinated rural eco-nomic development, and to find good ways of solving rural problems through urbanization, this paper absorbs the push-and-pull forces theory and the systematic dynamic theory in the traditional population migration theories, views urbanization as a dynamic system, makes research on the push-and-pull mechanism of urbanization. The pull ingpower of urbanization is analyzed according to two aspects, the agglomeration effect and the radiation effect of cities. The agglomeration effect provides continuous propelling force for urbanization, and the radiation effect furtheraccelerates the urbanization process by pushing forward the development of rural economy. Of course, the slow de-velopment of urbanization can result in the hindrance to rural economic development.

  5. Stochastic Finite Element Method for analyzing static and dynamic pull-in of microsystems

    NARCIS (Netherlands)

    Hannot, S.D.A.; Verhoosel, C.V.; Rixen, D.J.

    2010-01-01

    Electro–mechanical sensors and actuators are a specific type of microsystems. The electrostatic pull-in value is one of the defining characteristics for these devices. Because the material and geometrical properties of micro fabricated systems are often very uncertain, this pull-in value can be

  6. Characterization of a pull-in based μg-resolution accelerometer

    NARCIS (Netherlands)

    Dias, R.A.; Cretu, E.; Wolffenbuttel, R.F.; Rocha, L.A.

    2012-01-01

    The pull-in time of electrostatically actuated parallel-plate microstructures enables the realization of a high-sensitivity accelerometer that uses time measurement as the transduction mechanism. The key feature is the existence of a metastable region that dominates pull-in behavior, thus making

  7. Characterization of a pull-in based μg-resolution accelerometer

    NARCIS (Netherlands)

    Dias, R.A.; Cretu, E.; Wolffenbuttel, R.F.; Rocha, L.A.

    2012-01-01

    The pull-in time of electrostatically actuated parallel-plate microstructures enables the realization of a high-sensitivity accelerometer that uses time measurement as the transduction mechanism. The key feature is the existence of a metastable region that dominates pull-in behavior, thus making pul

  8. Atomic mechanisms governing the elastic limit and the incipient plasticity of bending Si nanowires.

    Science.gov (United States)

    Zheng, Kun; Han, Xiaodong; Wang, Lihua; Zhang, Yuefei; Yue, Yonghai; Qin, Yan; Zhang, Xiaona; Zhang, Ze

    2009-06-01

    Individual single-crystalline Si nanowires (NWs) were bent by forming loops or arcs with different radius. Positional-resolved atomic level strain distribution (PRALSD) along both of the radial and axial directions were calculated and mapped directly from the atomic-resolution strained high-resolution electron microscopy (HREM) images of the bent Si NWs. For the first time, the neutral-strain axis shifted from the compressive zone to the tensile region was directly demonstrated from the PRALSD along the radial direction. Bending-induced ripple-buckling of the bent Si NW was observed and a significant strain variation along the bending axial direction in the compressive region was revealed. The tensile surface atomic steps and the compressive buckling are the physical origin of the asymmetric tensile-compressive properties of postelastic instabilities and the incipient plasticity. Both of the tensile surface atomic-steps and the compressive buckling initiated versatile ductile plastic dislocation events.

  9. Plasticity and Ductility in Graphene Oxide Through a Mechanochemically Induced Damage Tolerance Mechanism

    Science.gov (United States)

    2015-08-20

    Research Office P.O. Box 12211 Research Triangle Park , NC 27709-2211 plasticity, graphene oxide REPORT DOCUMENTATION PAGE 11. SPONSOR/MONITOR’S REPORT...c,d) AFM topology images of ruptured monolayer GO (c) and A-GO (d) membranes after membrane deflection tests, respectively. (e,f) AFM topology ...discussed earlier (cf. Fig. 1i,g). Furthermore, the typical rupture topology of a suspended monolayer A-GO membrane that exhibited brittle failure (Fig. 1d

  10. Mechanics of granular-frictional-visco-plastic fluids in civil and mining engineering

    Science.gov (United States)

    Alehossein, H.; Qin, Z.

    2013-10-01

    The shear stress generated in mine backfill slurries and fresh concrete contains both velocity gradient dependent and frictional terms, categorised as frictional viscous plastic fluids. This paper discusses application of the developed analytical solution for flow rate as a function of pressure and pressure gradient in discs, pipes and cones for such frictional Bingham-Herschel-Bulkley fluids. This paper discusses application of this continuum fluid model to industrial materials like mine and mineral slurries, backfills and fresh concrete tests.

  11. Coupled Simulations of Mechanical Deformation and Microstructural Evolution Using Polycrystal Plasticity and Monte Carlo Potts Models

    Energy Technology Data Exchange (ETDEWEB)

    Battaile, C.C.; Buchheit, T.E.; Holm, E.A.; Neilsen, M.K.; Wellman, G.W.

    1999-01-12

    The microstructural evolution of heavily deformed polycrystalline Cu is simulated by coupling a constitutive model for polycrystal plasticity with the Monte Carlo Potts model for grain growth. The effects of deformation on boundary topology and grain growth kinetics are presented. Heavy deformation leads to dramatic strain-induced boundary migration and subsequent grain fragmentation. Grain growth is accelerated in heavily deformed microstructures. The implications of these results for the thermomechanical fatigue failure of eutectic solder joints are discussed.

  12. Mechanisms of translation control underlying long-lasting synaptic plasticity and the consolidation of long-term memory.

    Science.gov (United States)

    Santini, Emanuela; Huynh, Thu N; Klann, Eric

    2014-01-01

    The complexity of memory formation and its persistence is a phenomenon that has been studied intensely for centuries. Memory exists in many forms and is stored in various brain regions. Generally speaking, memories are reorganized into broadly distributed cortical networks over time through systems level consolidation. At the cellular level, storage of information is believed to initially occur via altered synaptic strength by processes such as long-term potentiation. New protein synthesis is required for long-lasting synaptic plasticity as well as for the formation of long-term memory. The mammalian target of rapamycin complex 1 (mTORC1) is a critical regulator of cap-dependent protein synthesis and is required for numerous forms of long-lasting synaptic plasticity and long-term memory. As such, the study of mTORC1 and protein factors that control translation initiation and elongation has enhanced our understanding of how the process of protein synthesis is regulated during memory formation. Herein we discuss the molecular mechanisms that regulate protein synthesis as well as pharmacological and genetic manipulations that demonstrate the requirement for proper translational control in long-lasting synaptic plasticity and long-term memory formation. © 2014 Elsevier Inc. All rights reserved.

  13. Molecular and Neuronal Plasticity Mechanisms in the Amygdala-Prefrontal Cortical Circuit: Implications for Opiate Addiction Memory Formation

    Directory of Open Access Journals (Sweden)

    Laura G Rosen

    2015-11-01

    Full Text Available The persistence of associative memories linked to the rewarding properties of drugs of abuse is a core underlying feature of the addiction process. Opiate class drugs in particular, possess potent euphorigenic effects which, when linked to environmental cues, can produce drug-related ‘trigger’ memories that may persist for lengthy periods of time, even during abstinence, in both humans and other animals. Furthermore, the transitional switch from the drug-naïve, non-dependent state to states of dependence and withdrawal, represents a critical boundary between distinct neuronal and molecular substrates associated with opiate-reward memory formation. Identifying the functional molecular and neuronal mechanisms related to the acquisition, consolidation, recall and extinction phases of opiate-related reward memories is critical for understanding, and potentially reversing, addiction-related memory plasticity characteristic of compulsive drug-seeking behaviors. The mammalian prefrontal cortex (PFC and basolateral nucleus of the amygdala (BLA share important functional and anatomical connections that are involved importantly in the processing of associative memories linked to drug reward. In addition, both regions share interconnections with the mesolimbic pathway’s ventral tegmental area (VTA and nucleus accumbens (NAc and can modulate dopamine (DA transmission and neuronal activity associated with drug-related DAergic signaling dynamics. In this review, we will summarize research from both human and animal modelling studies highlighting the importance of neuronal and molecular plasticity mechanisms within this circuitry during critical phases of opiate addiction-related learning and memory processing. Specifically, we will focus on two molecular signaling pathways known to be involved in both drug-related neuroadaptations and in memory-related plasticity mechanisms; the extracellular-signal-regulated kinase system (ERK and the Ca2+/calmodulin

  14. Molecular and neuronal plasticity mechanisms in the amygdala-prefrontal cortical circuit: implications for opiate addiction memory formation.

    Science.gov (United States)

    Rosen, Laura G; Sun, Ninglei; Rushlow, Walter; Laviolette, Steven R

    2015-01-01

    The persistence of associative memories linked to the rewarding properties of drugs of abuse is a core underlying feature of the addiction process. Opiate class drugs in particular, possess potent euphorigenic effects which, when linked to environmental cues, can produce drug-related "trigger" memories that may persist for lengthy periods of time, even during abstinence, in both humans, and other animals. Furthermore, the transitional switch from the drug-naïve, non-dependent state to states of dependence and withdrawal, represents a critical boundary between distinct neuronal and molecular substrates associated with opiate-reward memory formation. Identifying the functional molecular and neuronal mechanisms related to the acquisition, consolidation, recall, and extinction phases of opiate-related reward memories is critical for understanding, and potentially reversing, addiction-related memory plasticity characteristic of compulsive drug-seeking behaviors. The mammalian prefrontal cortex (PFC) and basolateral nucleus of the amygdala (BLA) share important functional and anatomical connections that are involved importantly in the processing of associative memories linked to drug reward. In addition, both regions share interconnections with the mesolimbic pathway's ventral tegmental area (VTA) and nucleus accumbens (NAc) and can modulate dopamine (DA) transmission and neuronal activity associated with drug-related DAergic signaling dynamics. In this review, we will summarize research from both human and animal modeling studies highlighting the importance of neuronal and molecular plasticity mechanisms within this circuitry during critical phases of opiate addiction-related learning and memory processing. Specifically, we will focus on two molecular signaling pathways known to be involved in both drug-related neuroadaptations and in memory-related plasticity mechanisms; the extracellular-signal-regulated kinase system (ERK) and the Ca(2+)/calmodulin-dependent protein

  15. Mechanical energy losses in plastically deformed and electron plus neutron irradiated high purity single crystalline molybdenum at elevated temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Zelada, Griselda I. [Laboratorio de Materiales, Escuela de Ingenieria Electrica, Facultad de Ciencias Exactas, Ingenieria y Agrimensura, Universidad Nacional de Rosario, Avda. Pellegrini 250, 2000 Rosario (Argentina); Lambri, Osvaldo Agustin [Laboratorio de Materiales, Escuela de Ingenieria Electrica, Facultad de Ciencias Exactas, Ingenieria y Agrimensura, Universidad Nacional de Rosario, Avda. Pellegrini 250, 2000 Rosario (Argentina); Instituto de Fisica Rosario - CONICET, Member of the CONICET& #x27; s Research Staff, Avda. Pellegrini 250, 2000 Rosario (Argentina); Bozzano, Patricia B. [Laboratorio de Microscopia Electronica, Unidad de Actividad Materiales, Centro Atomico Constituyentes, Comision Nacional de Energia Atomica, Avda. Gral. Paz 1499, 1650 San Martin (Argentina); Garcia, Jose Angel [Departamento de Fisica Aplicada II, Facultad de Ciencias y Tecnologia, Universidad del Pais Vasco, Apdo. 644, 48080 Bilbao, Pais Vasco (Spain)

    2012-10-15

    Mechanical spectroscopy (MS) and transmission electron microscopy (TEM) studies have been performed in plastically deformed and electron plus neutron irradiated high purity single crystalline molybdenum, oriented for single slip, in order to study the dislocation dynamics in the temperature range within one third of the melting temperature. A damping peak related to the interaction of dislocation lines with both prismatic loops and tangles of dislocations was found. The peak temperature ranges between 900 and 1050 K, for an oscillating frequency of about 1 Hz. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  16. Multiaxial mechanical properties and constitutive modeling of human adipose tissue: a basis for preoperative simulations in plastic and reconstructive surgery.

    Science.gov (United States)

    Sommer, Gerhard; Eder, Maximilian; Kovacs, Laszlo; Pathak, Heramb; Bonitz, Lars; Mueller, Christoph; Regitnig, Peter; Holzapfel, Gerhard A

    2013-11-01

    A preoperative simulation of soft tissue deformations during plastic and reconstructive surgery is desirable to support the surgeon's planning and to improve surgical outcomes. The current development of constitutive adipose tissue models, for the implementation in multilayer computational frameworks for the simulation of human soft tissue deformations, has proved difficult because knowledge of the required mechanical parameters of fat tissue is limited. Therefore, for the first time, human abdominal adipose tissues were mechanically investigated by biaxial tensile and triaxial shear tests. The results of this study suggest that human abdominal adipose tissues under quasi-static and dynamic multiaxial loadings can be characterized as a nonlinear, anisotropic and viscoelastic soft biological material. The nonlinear and anisotropic features are consequences of the material's collagenous microstructure. The aligned collagenous septa observed in histological investigations causes the anisotropy of the tissue. A hyperelastic model used in this study was appropriate to represent the quasi-static multiaxial mechanical behavior of fat tissue. The constitutive parameters are intended to serve as a basis for soft tissue simulations using the finite element method, which is an apparent method for obtaining promising results in the field of plastic and reconstructive surgery.

  17. RACE pulls for shared control

    Science.gov (United States)

    Leahy, M. B., Jr.; Cassiday, B. K.

    1993-02-01

    Maintaining and supporting an aircraft fleet, in a climate of reduced manpower and financial resources, dictates effective utilization of robotics and automation technologies. To help develop a winning robotics and automation program the Air Force Logistics Command created the Robotics and Automation Center of Excellence (RACE). RACE is a command wide focal point. Race is an organic source of expertise to assist the Air Logistic Center (ALC) product directorates in improving process productivity through the judicious insertion of robotics and automation technologies. RACE is a champion for pulling emerging technologies into the aircraft logistic centers. One of those technology pulls is shared control. Small batch sizes, feature uncertainty, and varying work load conspire to make classic industrial robotic solutions impractical. One can view ALC process problems in the context of space robotics without the time delay. The ALC's will benefit greatly from the implementation of a common architecture that supports a range of control actions from fully autonomous to teleoperated. Working with national laboratories and private industry, we hope to transition shared control technology to the depot floor. This paper provides an overview of the RACE internal initiatives and customer support, with particular emphasis on production processes that will benefit from shared control technology.

  18. Station Program Note Pull Automation

    Science.gov (United States)

    Delgado, Ivan

    2016-01-01

    Upon commencement of my internship, I was in charge of maintaining the CoFR (Certificate of Flight Readiness) Tool. The tool acquires data from existing Excel workbooks on NASA's and Boeing's databases to create a new spreadsheet listing out all the potential safety concerns for upcoming flights and software transitions. Since the application was written in Visual Basic, I had to learn a new programming language and prepare to handle any malfunctions within the program. Shortly afterwards, I was given the assignment to automate the Station Program Note (SPN) Pull process. I developed an application, in Python, that generated a GUI (Graphical User Interface) that will be used by the International Space Station Safety & Mission Assurance team here at Johnson Space Center. The application will allow its users to download online files with the click of a button, import SPN's based on three different pulls, instantly manipulate and filter spreadsheets, and compare the three sources to determine which active SPN's (Station Program Notes) must be reviewed for any upcoming flights, missions, and/or software transitions. Initially, to perform the NASA SPN pull (one of three), I had created the program to allow the user to login to a secure webpage that stores data, input specific parameters, and retrieve the desired SPN's based on their inputs. However, to avoid any conflicts with sustainment, I altered it so that the user may login and download the NASA file independently. After the user has downloaded the file with the click of a button, I defined the program to check for any outdated or pre-existing files, for successful downloads, to acquire the spreadsheet, convert it from a text file to a comma separated file and finally into an Excel spreadsheet to be filtered and later scrutinized for specific SPN numbers. Once this file has been automatically manipulated to provide only the SPN numbers that are desired, they are stored in a global variable, shown on the GUI, and

  19. RNA unwinding from reweighted pulling simulations

    CERN Document Server

    Colizzi, Francesco; 10.1021/ja210531q

    2012-01-01

    The forming and melting of complementary base pairs in RNA duplexes are conformational transitions required to accomplish a plethora of biological functions. Yet the dynamic steps of these transitions have not been quantitatively characterized at the molecular level. In this work, the base opening process was first enforced by atomistic pulling simulations and then analyzed with a novel reweighting scheme which allowed the free-energy profile along any suitable reaction coordinate, e.g. solvation, to be reconstructed. The systematic application of such approach to different base-pair combinations provides a molecular motion picture of helix opening which is validated by comparison with an extensive set of experimental observations and links them to the enzyme-dependent unwinding mechanism. The RNA intrinsic dynamics disclosed in this work could rationalize the directionality observed in RNA-processing molecular machineries.

  20. Molecular junctions: can pulling influence optical controllability?

    Science.gov (United States)

    Parker, Shane M; Smeu, Manuel; Franco, Ignacio; Ratner, Mark A; Seideman, Tamar

    2014-08-13

    We suggest the combination of single molecule pulling and optical control as a way to enhance control over the electron transport characteristics of a molecular junction. We demonstrate using a model junction consisting of biphenyl-dithiol coupled to gold contacts. The junction is pulled while optically manipulating the dihedral angle between the two rings. Quantum dynamics simulations show that molecular pulling enhances the degree of control over the dihedral angle and hence over the transport properties.

  1. The Baldwin effect and genetic assimilation: revisiting two mechanisms of evolutionary change mediated by phenotypic plasticity.

    Science.gov (United States)

    Crispo, Erika

    2007-11-01

    Two different, but related, evolutionary theories pertaining to phenotypic plasticity were proposed by James Mark Baldwin and Conrad Hal Waddington. Unfortunately, these theories are often confused with one another. Baldwin's notion of organic selection posits that plasticity influences whether an individual will survive in a new environment, thus dictating the course of future evolution. Heritable variations can then be selected upon to direct phenotypic evolution (i.e., "orthoplasy"). The combination of these two processes (organic selection and orthoplasy) is now commonly referred to as the "Baldwin effect." Alternately, Waddington's genetic assimilation is a process whereby an environmentally induced phenotype, or "acquired character," becomes canalized through selection acting upon the developmental system. Genetic accommodation is a modern term used to describe the process of heritable changes that occur in response to a novel induction. Genetic accommodation is a key component of the Baldwin effect, and genetic assimilation is a type of genetic accommodation. I here define both the Baldwin effect and genetic assimilation in terms of genetic accommodation, describe cases in which either should occur in nature, and propose that each could play a role in evolutionary diversification.

  2. Homer 1a gates the induction mechanism for endocannabinoid-mediated synaptic plasticity.

    Science.gov (United States)

    Roloff, Alan M; Anderson, Garret R; Martemyanov, Kirill A; Thayer, Stanley A

    2010-02-24

    At hippocampal excitatory synapses, endocannabinoids (eCBs) mediate two forms of retrograde synaptic inhibition that are induced by postsynaptic depolarization or activation of metabotropic glutamate receptors (mGluRs). The homer family of molecular scaffolds provides spatial organization to regulate postsynaptic signaling cascades, including those activated by mGluRs. Expression of the homer 1a (H1a) immediate-early gene produces a short homer protein that lacks the domain required for homer oligomerization, enabling it to uncouple homer assemblies. Here, we report that H1a differentially modulates two forms of eCB-mediated synaptic plasticity, depolarization-induced suppression of excitation (DSE) and metabotropic suppression of excitation (MSE). EPSCs were recorded from cultured hippocampal neurons and DSE evoked by a 15 s depolarization to 0 mV and MSE evoked by a type I mGluR agonist. Expression of H1a enhanced DSE and inhibited MSE at the same synapse. Many physiologically important stimuli initiate H1a expression including brain-derived neurotrophic factor (BDNF). Treating hippocampal cultures with BDNF increased transcription of H1a and uncoupled homer 1c-GFP (green fluorescent protein) clusters. BDNF treatment blocked MSE and enhanced DSE. Thus, physiological changes in H1a expression gate the induction pathway for eCB-mediated synaptic plasticity by uncoupling mGluR from eCB production.

  3. Effect of Palm Oil Bio-Based Plasticizer on the Morphological, Thermal and Mechanical Properties of Poly(Vinyl Chloride

    Directory of Open Access Journals (Sweden)

    Kar Min Lim

    2015-10-01

    Full Text Available Flexible poly(vinyl chloride (PVC was fabricated using a palm oil-based alkyd as a co-plasticizer to di-octyl phthalate (DOP and di-isononyl phthalate (DiNP. The effects of the incorporation of the palm oil-based alkyd on morphological, thermal and mechanical properties of PVC compounds were studied. Results showed the incorporation of the alkyd enhanced the mechanical and thermal properties of the PVC compounds. Fourier transform infrared spectroscopy (FTIR results showed that the polar –OH and –C=O groups of alkyd have good interaction with the –C–Cl group in PVC via polar interaction. The morphological results showed good incorporation of the plasticizers with PVC. Improved tensile strength, elastic modulus, and elongation at break were observed with increasing amount of the alkyd, presumably due to chain entanglement of the alkyd with the PVC molecules. Thermogravimetric analysis results confirmed that the alkyd has improved the thermostability of the PVC compounds.

  4. Influence of the Repetitive Corrugation on the Mechanism Occuring During Plastic Deformation of CuSn6 Alloy

    Directory of Open Access Journals (Sweden)

    Nuckowski P.M.

    2016-09-01

    Full Text Available This paper presents the research results of CuSn6 alloy strip at semi-hard state, plastically deformed in the process of repetitive corrugation. The influence of process parameters on the mechanical properties and structure of examined alloy were investigated. Examination in high-resolution transmission electron microscopy (HRTEM confirmed the impact of the repetitive corrugation to obtain the nano-scale structures. It has been found, that the application of repetitive corrugation increases the tensile strength (Rm, yield strength (Rp0.2 and elastic limit (Rp0,05 of CuSn6 alloy strips. In the present work it has been confirmed that the repetitive corrugation process is a more efficient method for structure and mechanical properties modification of commercial CuSn6 alloy strip (semi-hard as compared with the classic rolling process.

  5. Observation of the TWIP + TRIP Plasticity-Enhancement Mechanism in Al-Added 6 Wt Pct Medium Mn Steel

    Science.gov (United States)

    Lee, Seawoong; Lee, Kyooyoung; De Cooman, Bruno C.

    2015-06-01

    The intercritically annealed Fe-0.15 pctC-6.0 pctMn-1.5 pctSi-3.0 pctAl and Fe-0.30 pctC-6.0 pctMn-1.5 pctSi-3.0 pctAl medium Mn steels were found to have improved mechanical properties due to the TWIP and TRIP plasticity-enhancing mechanisms being activated in succession during tensile deformation. The increase of the C content from 0.15 to 0.30 pct resulted in ultra-high strength properties and a strength-ductility balance of approximately 65,000 MPa-pct, i.e., equivalent to the strength-ductility balance of high Mn TWIP steel with a fully austenitic microstructure.

  6. Design on Injection Mold for Wine Bottle Cover with Outer Side Core-pulling Mechanism of Slanted Slide Block%利用斜滑块实现外侧抽芯的酒瓶下盖注塑模具设计

    Institute of Scientific and Technical Information of China (English)

    熊毅; 于玲

    2012-01-01

    The structure characteristics of wine bottle cover was analyzed, and outer side core-pulling was realized by adding a parting surface, controlling mold open order, and using the plastic product to make slanted slide block move.After verification of production, the mold is proved to be reasonable in structure, and reliable in movement.%分析了酒瓶下盖的结构特点,通过增加一个分型面、控制开模顺序,以及利用塑件带动斜滑块的移动实现了该注塑模具的外侧抽芯.经过生产验证,该模具结构合理、动作可靠.

  7. PLASTIC LIMIT ANALYSIS OF DUCTILE COMPOSITE STRUCTURES FROM MICRO-TO MACRO-MECHANICAL ANALYSIS

    Institute of Scientific and Technical Information of China (English)

    Hongtao Zhang; Yinghua Liu; Bingye Xu

    2009-01-01

    The load-bearing capacity of ductile composite structures comprised of periodic composites is studied by a combined micro/macromechanical approach. Firstly, on the microscopic level, a representative volume element (RVE) is selected to reflect the microstructures of the composite materials and the constituents are assumed to be elastic perfectly-plastic. Based on the homogenization theory and the static limit theorem, an optimization formulation to directly calculate the macroscopic strength domain of the RVE is obtained. The finite element modeling of the static limit analysis is formulated as a nonlinear mathematical programming and solved by the sequential quadratic programming method, where the temperature parameter method is used to construct the self-stress field. Secondly, Hill's yield criterion is adopted to connect the micromechanical and macromechanical analyses. And the limit loads of composite structures are worked out on the macroscopic scale. Finally, some examples and comparisons are shown.

  8. Prediction of plastic instabilities under thermo-mechanical loadings in tension and simple shear

    Science.gov (United States)

    Manach, P. Y.; Mansouri, L. F.; Thuillier, S.

    2016-08-01

    Plastic instabilities like Portevin-Le Châtelier were quite thoroughly investigated experimentally in tension, under a large range of strain rates and temperatures. Such instabilities are characterized both by a jerky flow and a localization of the strain in bands. Similar phenomena were also recorded for example in simple shear [1]. Modelling of this phenomenon is mainly performed at room temperature, taking into account the strain rate sensitivity, though an extension of the classical Estrin-Kubin-McCormick was proposed in the literature, by making some of the material parameters dependent on temperature. A similar approach is considered in this study, furthermore extended for anisotropic plasticity with Hill's 1948 yield criterion. Material parameters are identified at 4 different temperatures, ranging from room temperature up to 250°C. The identification procedure is split in 3 steps, related to the elasticity, the average stress level and the magnitude of the stress drops. The anisotropy is considered constant in this temperature range, as evidenced by experimental results [2]. The model is then used to investigate the temperature dependence of the critical strain, as well as its capability to represent the propagation of the bands. Numerical predictions of the instabilities in tension and simple shear at room temperature and up to 250°C are compared with experimental results [3]. In the case of simple shear, a monotonic loading followed by unloading and reloading in the reverse direction (“Bauschinger-type” test) is also considered, showing that (i) kinematic hardening should be taken into account to fully describe the transition at re-yielding (ii) the modelling of the critical strain has to be improved.

  9. Plastic Surgery

    Science.gov (United States)

    ... Surgery? A Week of Healthy Breakfasts Shyness Plastic Surgery KidsHealth > For Teens > Plastic Surgery Print A A ... forehead lightened with a laser? What Is Plastic Surgery? Just because the name includes the word "plastic" ...

  10. Mechanics of a contracting reservoir in an elastic half-space with an intervening visco-elasto-plastic layer

    Science.gov (United States)

    Mossop, A.; Fredrich, J. T.

    2004-12-01

    The extraction of fluids from porous rocks within the Earth's crust leads to localised volume strains. These in turn induce stress changes and displacements in the surrounding rock mass. The relationships between these processes are governed by the constitutive properties of the rocks. For the case of a poroelastic fluid reservoir in a linear-elastic matrix the mechanics are relatively well known and understood. In this study we extend these models by investigating the case of a contracting rock body (caused by declining pore pressure) embedded within a linear-elastic half space, but with the addition of a visco-elasto-plastic layer between the contracting reservoir and the free surface. The problem is of growing importance as the exploitation of hydrocarbon reservoirs beneath salt bodies occurs at ever greater depths in the deepwater Gulf of Mexico. This is because the creep properties of salt are strongly temperature dependent, so that as depths increase, and hence ambient temperatures, creep can occur at a rate that is impossible to ignore over the reservoir lifecycle. The models are explored using a finite element approach and make use of sophisticated salt constitutive models and large-deformation three-dimensional geomechanical simulation codes; the reservoir deformations are governed by either poro-elastic or cap plasticity constitutive laws. However, a general behaviour pattern can be observed: the visco-elasto-plastic salt layer tends to decouple the deformation fields from the free surface with stress and displacements accentuated below the salt. The magnitude of the increased horizontal displacements below the salt layer are relatively independent of the layer thickness. The accentuated vertical displacements though are more strongly dependent on the thickness of the salt layer. This work was performed at Sandia National Laboratories funded by the US DOE under Contract DE-AC04-94AL85000. Sandia is a multiprogam laboratory operated by Sandia Corporation

  11. Oil pulling: A traditional method on the edge of evidence

    Directory of Open Access Journals (Sweden)

    H Mythri

    2017-01-01

    Full Text Available Introduction: Oil pulling is an ancient, traditional folk remedy that has been practiced for centuries in India and southern Asia as a holistic Ayurvedic technique. The practice of oil pulling involves placing a tablespoon of an edible oil (e.g. sesame, olive, sunflower, coconut inside the mouth, and swishing or “pulling” the oil through the teeth and oral cavity for anywhere from 1–5 minutes to up to 20 minutes or longer. Materials and Methods: Articles related to oil pulling were collected by using oil pulling as Keyword in Google and Medline. Out of the 21 related articles published till 2016, 6 articles with the proper study designs were used for analysis. Results: The studies were unreliable for many reasons, including the misinterpretation of results due to small sample size and improper study design. Conclusion: Though the promoters claim it as one of the best method to be as adjuvant to mechanical control methods, scientific evidences are lacking.

  12. Social Plasticity Relies on Different Neuroplasticity Mechanisms across the Brain Social Decision-Making Network in Zebrafish

    Science.gov (United States)

    Teles, Magda C.; Cardoso, Sara D.; Oliveira, Rui F.

    2016-01-01

    indicate that social plasticity relies on multiple neuroplasticity mechanisms across the SDMN, and that there is not a single neuromolecular module underlying this type of behavioral flexibility. PMID:26909029

  13. Long-term follow-up of redo pull-through procedures for Hirschsprung's disease: efficacy of the endorectal pull-through.

    Science.gov (United States)

    van Leeuwen, K; Teitelbaum, D H; Elhalaby, E A; Coran, A G

    2000-06-01

    The purpose of this study was to review the authors' 25-year experience with redo pull-through procedures for Hirschsprung's disease including surgical technique and long-term outcome. From 1974 to now, over 325 patients with Hirschsprung's disease have been treated at C.S. Mott Children's Hospital. This includes 30 patients referred after an unsuccessful pull-through at another hospital and 2 patients with an unsuccessful pull-through from C.S. Mott. All redo pull-throughs (n = 19) were performed in these patients, and their clinical courses are reviewed. Twelve patients required reoperation secondary to a mechanical problem with their first pull-through. The other 7 patients had evidence of residual segments of dilated colon leading to functional failure of their initial operation including 5 patients with documented aganglionic bowel present at the second pull-through. Ten of the patients requiring reoperation initially had an endorectal pull-through (ERPT), 5 had a Duhamel procedure, 3 had a Swenson procedure, and 1 had a Rehbein procedure. Choice of revision was an ERPT in 8 patients in whom an adequate rectal cuff could be developed. Additional redo procedures included a Duhamel in 8 patients and a Swenson in 3 patients. Follow-up ranges from 3 months to 23 years (mean, 13.8 years). There were no deaths in the series, and 1 patient required a third pull-through. All patients who are not neurologically impaired and are over age 3 are continent except one (94%). Stools per day range from 1 to 10 (mean, 3.2). Redo pull-through operations for Hirschsprung's disease appear to be as effective as primary procedures in terms of continence and stooling frequency. Distinct from other series, we found an ERPT to be the procedure of choice if an adequate rectal cuff was present.

  14. Plastic condoms.

    Science.gov (United States)

    1968-01-01

    Only simple equipment, simple technology and low initial capital investment are needed in their manufacture. The condoms can be made by people who were previously unskilled or only semi-skilled workers. Plastic condoms differ from those made of latex rubber in that the nature of the plastic film allows unlimited shelf-life. Also, the plastic has a higher degree of lubricity than latex rubber; if there is a demand for extra lubrication in a particular market, this can be provided. Because the plastic is inert, these condoms need not be packaged in hermetically sealed containers. All these attributes make it possible to put these condoms on the distributors' shelves in developing countries competitively with rubber condoms. The shape of the plastic condom is based on that of the lamb caecum, which has long been used as luxury-type condom. The plastic condom is made from plastic film (ethylene ethyl acrilate) of 0.001 inch (0.0254 mm.) thickness. In addition, a rubber ring is provided and sealed into the base of the condom for retention during coitus. The advantage of the plastic condom design and the equipment on which it is made is that production can be carried out either in labour-intensive economy or with varying degrees of mechanization and automation. The uniform, finished condom if made using previously untrained workers. Training of workers can be done in a matter of hours on the two machines which are needed to produce and test the condoms. The plastic film is provided on a double wound roll, and condom blanks are prepared by means of a heat-sealing die on the stamping machine. The rubber rings are united to the condom blanks on an assembly machine, which consists of a mandrel and heat-sealing equipment to seal the rubber ring to the base of the condom. Built into the assembly machine is a simple air-testing apparatus that can detect the smallest pinhole flaw in a condom. The manufacturing process is completed by unravelling the condom from the assembly

  15. Mechanical and service properties of low carbon steels processed by severe plastic deformation

    Directory of Open Access Journals (Sweden)

    J. Zrnik

    2009-07-01

    Full Text Available The structure and properties of the 0,09% C-Mn-Si-Nb-V-Ti, 0,1% C-Mn-V-Ti and 0,09% C-Mo-V-Nb low-carbon steels were studied after cold equal-channel angular pressing (ECAP. ECAP leads to the formation of partially submicrocrystalline structure with a grain size of 150 – 300 nm. The submicrocrystalline 0,09% C-Mn-Si-Nb-V-Ti steel compared with the normalized steel is characterized by Re higher more than by a factor of 2 and by the impact toughness higher by a factor of 3,5 at a test temperature of -40°C. The plasticity in this case is somewhat lower. The high-strength state of the submicrocrystalline 0,1% C-Mn-V-Ti and 0,09% C-Mo-V-Nb steels after ECAP is retained up to a test temperature of 500°C. The strength properties at 600°C (i.e. the fire resistance of these steels are higher by 20-25% as compared to those of the undeformed steels. The strength of the 0,09% C-Mo-V-Nb steel at 600°C is substantially higher than that of the 0,1% C-Mn-V-Ti steel.

  16. Mechanisms of nanoclay-enhanced plastic foaming processes: effects of nanoclay intercalation and exfoliation

    Energy Technology Data Exchange (ETDEWEB)

    Wong, Anson; Wijnands, Stephan F. L.; Kuboki, Takashi; Park, Chul B., E-mail: park@mie.utoronto.ca [University of Toronto, Microcellular Plastics Manufacturing Laboratory, Department of Mechanical and Industrial Engineering (Canada)

    2013-08-15

    The foaming behaviors of high-density polypropylene-nanoclay composites with intercalated and exfoliated nanoclay particles blown with carbon dioxide were examined via in situ observation of the foaming processes in a high-temperature/high-pressure view-cell. The intercalated nanoclay particles were 300-600 nm in length and 50-200 nm in thickness, while the exfoliated nanoclay particles were 100-200 nm in length and 1 nm in thickness. Contrary to common belief, it was discovered that intercalated nanoclay yielded higher cell density than exfoliated nanoclay despite its lower particle density. This was attributed to the higher tensile stresses generated around the larger and stiffer intercalated nanoclay particles, which led to increase in supersaturation level for cell nucleation. Also, the coupling agent used to exfoliate nanoclay would increase the affinity between polymer and surface of nanoclay particles. Consequently, the critical work needed for cell nucleation would be increased; pre-existing microvoids, which could act as seeds for cell nucleation, were also less likely to exist. Meanwhile, exfoliated nanoclay had better cell stabilization ability to prevent cell coalescence and cell coarsening. This investigation clarifies the roles of nanoclay in plastic foaming processes and provides guidance for the advancement of polymer nanocomposite foaming technology.

  17. Application of elastic and elastic-plastic fracture mechanics methods to surface flaws

    Science.gov (United States)

    McCabe, Donald E.; Ernst, Hugo A.; Newman, James C., Jr.

    Fuel tanks that are a part of the External Tank assembly for the Space Shuttle are made of relatively thin 2219-T87 aluminum plate. These tanks contain about 917 m of fusion weld seam, all of which is nondestructively inspected for flaws and all those found are repaired. The tanks are subsequently proof-tested to a pressure that is sufficiently severe to cause weld metal yielding in a few local regions of the weld seam. The work undertaken in the present project was to develop a capability to predict flaw growth from undetected surface flaws that are assumed to be located in the highly stressed regions. The technical challenge was to develop R-curve prediction capability for surface cracks in specimens that contain the flaws of unusual sizes and shapes deemed to be of interest. The test techniques developed and the elastic-plastic analysis concepts adopted are presented. The flaws of interest were quite small surface cracks that were narrow-deep ellipses that served to exacerbate the technical difficulties involved.

  18. Effects of Stress Concentration on the Mechanical Properties of Carbon Fiber Reinforced Plastic

    Directory of Open Access Journals (Sweden)

    Ryo Naito

    2017-03-01

    Full Text Available Mechanical properties of conventional CFRP plates with small holes were investigated systematically. Those artificial holes are considered to be rivet connection between CFRP and other materials. The machining holes were employed with different number (n=0-5 and different mode, e.g., parallel (Sample A, 45 degree (Sample B and perpendicular (Sample C against the loading direction. To understand the mechanical properties of the CFRP plates clearly, tensile tests and failure analysis were conducted experimentally. Excellent mechanical properties were obtained for Sample A, compared to the other ones. This is due to the different size of the cross-section area in the specimen. With increasing the number of rivet hole, the mechanical properties were lineally decreasing. Such mechanical properties were analyzed by direct observation using a high speed camera, i.e., in-situ measurement of deformation during the tensile loading was carried

  19. Effects of mechanical tensile properties of plastic film on plastic recycling method%农田地膜拉伸性能变化对缠绕式回收的影响

    Institute of Scientific and Technical Information of China (English)

    张佳喜; 王学农; 张丽; 喻晨; 蒋永新; 张海春; 刘旋峰; 乔园园; 王祥金

    2015-01-01

    农田长期覆膜种植产生的大量地膜对农田土壤质量、作物生长及环境造成严重的影响,为解决这一问题,于 2014年3月至2014年10月在新疆库尔勒尉犁县达西村开展大田试验,对比不同厚度、不同时间及不同位置地膜拉伸性能的变化规律,并针对0.01 mm地膜进行缠绕式回收试验.结果表明:地膜铺放后的30~60 d期间,由于受到风和紫外线照射等因素,拉伸强度有明显的下降,下降幅度较大;当地膜回收的时候,0.01 mm地膜最大拉伸力在近株端和远株端分别为1.52 N和1.305 N,是0.008 mm地膜的1.4倍和1.22倍.显然0.01 mm地膜的拉伸性能较0.008 mm拉伸性能有了一定的提升,这对地膜回收有一定的积极作用,但是经过理论计算及田间试验0.01 mm地膜的拉伸性能还是不足以采用简单缠绕的方式进行回收.本研究揭示了地膜拉伸性能在不同时间、不同厚度及不同位置受到紫外线等影响的变化规律,为地膜回收机的研制提供了理论依据.%Plastic mulching technology has brought huge economic benefits, while the residual plastic film produced series of serious problems such as pollution on land. A large number of plastic recycling is becoming urgent and important task in our country. A large amount and long term of used plastic film on soil has caused great serious influence on the high quality of farmland planting, crop growth, the rural ecological environment and new rural construction, which has attracted more and more attention. Now, the research on the recovery mechanism is limited to equipment of plastic film enwinding recycling, and there are few studies on the variation rule of the tensile properties of used plastic film and the impact. During our practical research work, performance such as unstable recycling capability, low film recovery rate and work parts deformation often appears in the used plastic film recycling. To address these problems, we carried out some

  20. Fuzzy PID Adaptive Control Algorithm of Pulling-up Mechanism on the Cassava Harvester%木薯收获机块根拔起机构自适应控制算法研究

    Institute of Scientific and Technical Information of China (English)

    郑贤; 陈科余; 杨望; 杨坚; 李杨

    2017-01-01

    The pulling-up cassava harvester can ’ t pulling up the cassava root accurately according to the variation of cassava growth condition and soil condition,and its root pulling off loss rate is very high when the cassava growth condi-tion and soil condition have a big change. To solve the problem,this paper adopts the co_simulation technology and uses fuzzy PID adaptive control algorithm which based on the optimal velocity to control the cassava root lifting velocity accord-ing to the pulling force change,and regards reducing root pulling off loss rate as a goal,it shows that the optimizational fuzzy PID adaptive control algorithm can make the speed of gear rack swing hydraulic cylinder track the given speed curve very well,and the whole machine is very well in the self-adaption and it can adapt to different working load.%针对挖拔式木薯收获机无法根据木薯块根生长情况和土质情况的变化实现精确控制木薯块根拔起,且在木薯块根生长情况和土质情况变化大时其块根拔断损失率高的情况,采用联合仿真技术,以较优块根拔起速度模型为基础,根据拔起力变化,控制木薯收获机拔起速度使其达到减少块根拔断损失率的目标,对木薯块根拔起过程进行模糊PID 自适应控制,且对模糊PID 自适应控制算法进行了优化和物理试验验征。结果表明:在木薯块根拔起过程中,优化的模糊 PID 控制算法能使齿轮齿条摆动液压缸转速很好地跟踪给定转速曲线,且整机的自适应控制效果好,能适应不同的工作载荷。

  1. Determination of structural and mechanical properties, diffractometry, and thermal analysis of chitosan and hydroxypropylmethylcellulose (HPMC films plasticized with sorbitol

    Directory of Open Access Journals (Sweden)

    Jefferson Rotta

    2011-06-01

    Full Text Available In this work, the structural, mechanical, diffractometric, and thermal parameters of chitosan-hydroxypropylmethylcellulose (HPMC films plasticized with sorbitol were studied. Solutions of HPMC (2% w/v in water and chitosan (2% w/v in 2% acetic acid solution were prepared. The concentration of sorbitol used was 10% (w/w to both polymers. This solutions were mixed at different proportions (100/0; 70/30; 50/50; 30/70, and 0/100 of chitosan and HPMC, respectively, and 20 mL was cast in Petri dishes for further analysis of dried films. The miscibility of polymers was assessed by X-ray diffraction, scanning electronic microscopy (SEM, differential scanning calorimetry (DSC, and thermal gravimetric analysis (TGA. The results obtained indicate that the films are not fully miscible at a dry state despite the weak hydrogen bonding between the polymer functional groups.

  2. About the mechanisms governing the hydrogen effect on visco plasticity of unirradiated fully annealed zircaloy-4 sheet

    Energy Technology Data Exchange (ETDEWEB)

    Rupa, N [Electricite de France (EDF), Nuclear Power Div., Lab. Group, 93 - Saint-Denis (France); Clavel, M. [Universite de Technologie de Compiegne, Centre de Recherches de Royalliu, 60 (France); Bouffioux, P.; Domain, C. [Electricite de France, Research engineer, RD Div., Material Study Branch, 77 - Moret sur Loing (France); Legris, A. [Lille-1 Univ., UMR 8517, 59 - Villeneuve-d' Ascq (France)

    2002-07-01

    It has been observed that hydrogen either in solid solution or precipitated under the form of hydrides has an impact on the visco-plasticity of CWSR Zircaloy-4 cladding tubes, increasing significantly the creep resistance. The use of TEM on the structurally complex CWSR material being unlikely to identify the deformation mechanisms, it has been decided to complete this R and D program on recrystallized material. A study has been carried out on fully annealed unirradiated Zircaloy-4 sheet used for the manufacturing of the fuel subassembly grids. Mechanical tests were performed for large ranges of temperatures (300 to 400 deg C), stresses (120 to 250 MPa), and strain rates (2 x 10{sup -7} to 2 x 10{sup -3} s{sup -1}) on as-received and hydrided specimen. The results emphasize: - Hydrogen in solid solution induces a softening of the material. The TEM observations have revealed identical structure of dislocations for both as-received and hydrided specimens. The softening has been particularly observed when dynamic strain aging is activated. It is assumed that atomic hydrogen decreases the dislocation pinning caused by interstitial and/or enhances the intrinsic mobility of the dislocations. With respect to ab initio calculation, atomic hydrogen might be trapped easily by the core of the dislocation, this phenomenon contributing to decrease the lattice friction and to enhance planar glide. - Precipitated hydrides induce a hardening of the material as observed for CWSR Zircaloy 4. The magnitude of the phenomenon depends upon temperature and stress. An analysis of the unload sequences for tension tests and of the secondary strain rates for creep tests leads to the conclusion that hydrides change the kinematics hardening by increasing the internal stress with respect to the as-received material. TEM observation combined with this visco-plasticity approach has revealed that: first, as long as the internal stress is increasing versus plastic strain, hydride are obstacles to

  3. Large Deformation Mechanisms, Plasticity, and Failure of an Individual Collagen Fibril With Different Mineral Content.

    Science.gov (United States)

    Depalle, Baptiste; Qin, Zhao; Shefelbine, Sandra J; Buehler, Markus J

    2016-02-01

    Mineralized collagen fibrils are composed of tropocollagen molecules and mineral crystals derived from hydroxyapatite to form a composite material that combines optimal properties of both constituents and exhibits incredible strength and toughness. Their complex hierarchical structure allows collagen fibrils to sustain large deformation without breaking. In this study, we report a mesoscale model of a single mineralized collagen fibril using a bottom-up approach. By conserving the three-dimensional structure and the entanglement of the molecules, we were able to construct finite-size fibril models that allowed us to explore the deformation mechanisms which govern their mechanical behavior under large deformation. We investigated the tensile behavior of a single collagen fibril with various intrafibrillar mineral content and found that a mineralized collagen fibril can present up to five different deformation mechanisms to dissipate energy. These mechanisms include molecular uncoiling, molecular stretching, mineral/collagen sliding, molecular slippage, and crystal dissociation. By multiplying its sources of energy dissipation and deformation mechanisms, a collagen fibril can reach impressive strength and toughness. Adding mineral into the collagen fibril can increase its strength up to 10 times and its toughness up to 35 times. Combining crosslinks with mineral makes the fibril stiffer but more brittle. We also found that a mineralized fibril reaches its maximum toughness to density and strength to density ratios for a mineral density of around 30%. This result, in good agreement with experimental observations, attests that bone tissue is optimized mechanically to remain lightweight but maintain strength and toughness.

  4. Cross-Split of Dislocations: An Athermal and Rapid Plasticity Mechanism

    Science.gov (United States)

    Kositski, Roman; Kovalenko, Oleg; Lee, Seok-Woo; Greer, Julia R.; Rabkin, Eugen; Mordehai, Dan

    2016-05-01

    The pathways by which dislocations, line defects within the lattice structure, overcome microstructural obstacles represent a key aspect in understanding the main mechanisms that control mechanical properties of ductile crystalline materials. While edge dislocations were believed to change their glide plane only by a slow, non-conservative, thermally activated motion, we suggest the existence of a rapid conservative athermal mechanism, by which the arrested edge dislocations split into two other edge dislocations that glide on two different crystallographic planes. This discovered mechanism, for which we coined a term “cross-split of edge dislocations”, is a unique and collective phenomenon, which is triggered by an interaction with another same-sign pre-existing edge dislocation. This mechanism is demonstrated for faceted α-Fe nanoparticles under compression, in which we propose that cross-split of arrested edge dislocations is resulting in a strain burst. The cross-split mechanism provides an efficient pathway for edge dislocations to overcome planar obstacles.

  5. Insulin signaling as a mechanism underlying developmental plasticity: the role of FOXO in a nutritional polyphenism.

    Directory of Open Access Journals (Sweden)

    Emilie C Snell-Rood

    Full Text Available We investigated whether insulin signaling, known to mediate physiological plasticity in response to changes in nutrition, also facilitates discrete phenotypic responses such as polyphenisms. We test the hypothesis that the gene FOXO--which regulates growth arrest under nutrient stress--mediates a nutritional polyphenism in the horned beetle, Onthophagus nigriventris. Male beetles in the genus Onthophagus vary their mating strategy with body size: large males express horns and fight for access to females while small males invest heavily in genitalia and sneak copulations with females. Given that body size and larval nutrition are linked, we predicted that 1 FOXO expression would differentially scale with body size (nutritional status between males and females, and 2 manipulation of FOXO expression would affect the nutritional polyphenism in horns and genitalia. First, we found that FOXO expression varied with body size in a tissue- and sex-specific manner, being more highly expressed in the abdominal tissue of large (horned males, in particular in regions associated with genitalia development. Second, we found that knockdown of FOXO through RNA-interference resulted in the growth of relatively larger copulatory organs compared to control-injected individuals and significant, albeit modest, increases in relative horn length. Our results support the hypothesis that FOXO expression in the abdominal tissue limits genitalia growth, and provides limited support for the hypothesis that FOXO regulates relative horn length through direct suppression of horn growth. Both results support the idea that tissue-specific FOXO expression may play a general role in regulating scaling relationships in nutritional polyphenisms by signaling traits to be relatively smaller.

  6. A possible mechanism for the initiation of the Yinggehai Basin: A visco-elasto-plastic model

    Science.gov (United States)

    Wang, Xinguo; He, Jiankun; Ding, Lin; Gao, Risheng

    2013-09-01

    The Yinggehai Basin, lying along the trace of the Red River fault zone in the South China Sea, has been related to the movements of the Red River fault zone and the rotation of the Indochina block. However, the tectonic origin of the Yinggehai Basin remains unclear. This paper explores the initiation of the Yinggehai Basin using a visco-elasto-plastic model. This model concentrates on two main aspects: lateral viscosity variations (mainly controlled by temperature) in the lithosphere and internal friction angles of the pre-existing fault zone. Modeling results show that: (1) for a layered viscosity, en echelon faults would likely form when there is no pre-existing strike-slip fault; whereas, the basin would be narrow and deep, if any, when there is a pre-existing fault; (2) for moderate lateral viscosity variations, a large basin forms, even without a pre-existing fault zone; and (3) for strong lateral viscosity variations, a major rift could form over geologic time. Our results indicate that the initiation of the Yinggehai Basin requires moderate lateral viscosity variations (i.e., a pre-existing gentle upwelling of the Mohorovicic discontinuity) but no pre-existing fault. In addition, the initial extension predicted is NE-SW and is generated by the rotation of the Indochina block. This differs from the NW-SE extension that resulted from the movements of the Red River fault zone. This indicates that the left-lateral displacements of the Red River fault zone and the spreading of the South China Sea only influence the basin evolution after its initiation.

  7. Effect of addition of butyl benzyl phthalate plasticizer and zinc oxide nanoparticles on mechanical properties of cellulose acetate butyrate/organoclay biocomposite

    Science.gov (United States)

    Putra, B. A. P.; Juwono, A. L.; Rochman, N. T.

    2017-07-01

    Plastics as packaging materials and coatings undergo increasing demands globally each year. This pose a serious problem to the environment due to its difficulty to degrade. One solution to addressing the problem of plastic wastes is the use of bioplastics. According to the European Organization Bioplastic, one of the biodegradable plastics is derivative of cellulose. To improve mechanical properties of bioplastic, biocomposites are made with the addition of certain additives and fillers. The aim of this study is to investigate the effect of butyl benzyl phthalate plasticizer (BBP) and ZnO nanoparticles addition on mechanical properties of cellulose acetate butyrate (CAB) / organoclay biocomposite. ZnO nanoparticles synthesized from commercial ZnO precursor by using sol-gel size reduction method. ZnO was dissolved in a solution of citric acid in the ratio 1:1 to 1:5 to form zinc citrate. Zinc citrate then decomposed by calcination at temperature of 600oC. ZnO nanoparticles with an average size of 44.4 nm is obtained at a ratio of 1: 2. The addition of ZnO nanoparticles and BBP plasticizer was varied to determine the effect on the mechanical properties of biocomposite. The addition of 10 - 15 %wt ZnO nanoparticles and 30 - 40 %wt BBP plasticizer was studied to determine the effect on the tensile strength, elongation, and modulus elasticity of the biocomposites. Biocomposite films were made by using solution casting method with acetone as solvent. The addition of plasticizer BBP and ZnO nanoparticles by 30% and 10% made biocomposite has a tensile strength of 2.223 MPa.

  8. Effect of reduction of area on microstructure and mechanical properties of twinning-induced plasticity steel during wire drawing

    Science.gov (United States)

    Hwang, Joong-Ki; Son, Il-Heon; Yoo, Jang-Yong; Zargaran, A.; Kim, Nack J.

    2015-09-01

    The effect of reduction of area (RA), 10%, 20%, and 30%, during wire drawing on the inhomogeneities in microstructure and mechanical properties along the radial direction of Fe-Mn-Al-C twinning-induced plasticity steel has been investigated. After wire drawing, the deformation texture developed into the major and minor duplex fiber texture. However, the texture became more pronounced in both center and surface areas as the RA per pass increased. It also shows that a larger RA per pass resulted in a higher yield strength and smaller elongation than a smaller RA per pass at all strain levels. Although inhomogeneities in microstructure and mechanical properties along the radial direction decreased with increasing RA per pass, there existed an optimum RA per pass for maximum drawing limit. Insufficient penetration of strain from surface to center at small RA per pass (e.g., 10%) and high friction and unsound metal flow at large RA per pass (e.g., 30%) all resulted in heterogeneous microstructure and mechanical properties along the radial direction of drawn wire. On the other hand, 20% RA per pass improved the drawing limit by about 30% as compared to the 10% and 30% RAs per pass.

  9. Effect of hot plastic deformation on microstructure and mechanical property of Mg-Mn-Ce magnesium alloy

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Hot plastic deformation was conducted using a new solid die on a Mg-Mn-Ce magnesium alloy. The results of microstructural examination through OM and TEM show that the grain size is greatly refined from 45 μm to 1.1 μm with uniform distribution due to the occurrence of dynamic recrystallization. The grain refinement and high angle grain boundary formation improve the mechanical properties through tensile testing with the strain rate of 1.0× 10-4 s-1 at room temperature and Vickers microhardness testing. The maximum values of tensile strength, elongation and Vickers microhardness are increased to 256.37 MPa,17.69% and HV57.60, which are 21.36%, 133.80% and 20.50% more than those of the as-received Mg-Mn-Ce magnesium alloy,respectively. The SEM morphologies of tensile fractured surface indicate that the density and size of ductile dimples rise with accumulative strain increasing. The mechanism of microstructural evolution and the relationship between microstructure and mechanical property of Mg-Mn-Ce magnesium alloy processed by this solid die were also analyzed.

  10. Mechanical and degradation properties of biodegradable Mg strengthened poly-lactic acid composite through plastic injection molding.

    Science.gov (United States)

    Butt, Muhammad Shoaib; Bai, Jing; Wan, Xiaofeng; Chu, Chenglin; Xue, Feng; Ding, Hongyan; Zhou, Guanghong

    2017-01-01

    Full biodegradable magnesium alloy (AZ31) strengthened poly-lactic acid (PLA) composite rods for potential application for bone fracture fixation were prepared by plastic injection process in this work. Their surface/interfacial morphologies, mechanical properties and vitro degradation were studied. In comparison with untreated Mg rod, porous MgO ceramic coating on Mg surface formed by Anodizing (AO) and micro-arc-oxidation (MAO)treatment can significantly improve the interfacial binding between outer PLA cladding and inner Mg rod due to the micro-anchoring action, leading to better mechanical properties and degradation performance of the composite rods.With prolonging immersion time in simulated body fluid (SBF) solution until 8weeks, the MgO porous coating were corroded gradually, along with the disappearance of original pores and the formation of a relatively smooth surface. This resulted in a rapidly reduction in mechanical properties for corresponding composite rods owing to the weakening of interfacial binding capacity. The present results indicated that this new PLA-clad Mg composite rods show good potential biomedical applications for implants and instruments of orthopedic inner fixation. Copyright © 2016 Elsevier B.V. All rights reserved.

  11. Physical and Mechanical Properties of Plasticized HMX under Effect of Mechanical Loadings, Temperature Drops and Shock Waves

    Institute of Scientific and Technical Information of China (English)

    E.N. Kostyukov; L.V. Fomicheva; Yu. A. Vlasov; E.A.Pazhina

    2004-01-01

    @@ During their life cycles, energetic materials (EM) can be subjected to various external effects, including non-authorized effects. Due to these effects, irreversible changes can occur in EM structures that, in turn, can be the reason for change of their physical and mechanical properties.

  12. Mechanisms operating during plastic deformation of metals under concurrent production of cascades and dislocations

    Energy Technology Data Exchange (ETDEWEB)

    Trinkaus, H. [Institut fuer Festkoerperforschung, Forschungszentrum Juelich (Germany); Singh, B.N. [Technical Univ. of Denmark, Risoe National Laboratory for Sustainable Energy, Materials Research Dept., Roskilde (Denmark)

    2008-04-15

    Recent in-reactor tensile tests (IRTs) on pure copper have revealed a deformation behaviour which is significantly different from that observed in post-irradiation tensile tests (PITs). In IRTs, the material deforms uniformly and homogeneously without yield drop and plastic instability as commonly observed in PITs. An increase in the pre-yield dose results in an increase in the level of hardening over the whole test periods and a decrease in the uniform elongation suggesting that the materials 'remember' the impact of the pre-yield damage level. These features are modelled in terms of the decoration of dislocations with glissile dislocation loops. During pre-yield irradiation, dislocation decoration is due to the one-dimensional (1D) diffusion of cascade induced self-interstitial (SIA) clusters and their trapping in the stress field of the static grown-in dislocations. During post-yield irradiation and deformation, moving dislocations are decorated by the sweeping of matrix loops. The interaction of dislocations with loops and between loops is discussed as a function of the relevant parameters. On this basis, the kinetics of decoration is treated in terms of fluxes of loops to and reactions with each other in a conceived 2D space of decoration. In this space, loop coalescence, alignment and mutual blocking reactions are characterised by appropriate reaction cross sections. In the kinetic equations for 'dynamic decoration' under deformation, the evolution of the dislocation density is taken into account. Simple solutions of the kinetic equations are discussed. The apparent memory of the system for the pre-yield dose is identified as the result of simultaneous and closely parallel transient evolutions of the cascade damage and the dislocations up to the end of the IRTs. The contributions of dislocation decoration to yield and flow stresses are attributed to the interaction of dislocations with aligned loops temporarily or permanently immobilized

  13. Testing Plastic Deformations of Materials in the Introductory Undergraduate Mechanics Laboratory

    Science.gov (United States)

    Romo-Kroger, C. M.

    2012-01-01

    Normally, a mechanics laboratory at the undergraduate level includes an experiment to verify compliance with Hooke's law in materials, such as a steel spring and an elastic rubber band. Stress-strain curves are found for these elements. Compression in elastic bands is practically impossible to achieve due to flaccidity. A typical experiment for…

  14. Water vapor permeability, mechanical, optical and sensorial properties of plasticized guar gumedible films

    Science.gov (United States)

    Edible films were prepared by casting method using guar gum and glycerol in different ratios. The concentration of guar gum was 1.0, 1.5 and 2.0% whereas glycerol concentration was 20, 30 and 40% (w/v). The water vapor permeability (WVP), mechanical properties (tensile strength and elongation), thic...

  15. Mechanical Sensors and Plastic Syringes to Verify the Gas Laws without Neglecting Friction

    Science.gov (United States)

    Onorato, P.; Mascheretti, P.; De Ambrosis, A.

    2010-01-01

    Two experiments are proposed to study Boyle's law and the pressure law in a school laboratory. The peculiar feature of the experiments is that the value of the pressure and of the volume are obtained respectively by means of a force and a position sensor, thus allowing students to connect, in an experimental context, mechanics variables, such as…

  16. Methylphenidate Amplifies Long-Term Plasticity in the Hippocampus via Noradrenergic Mechanisms

    Science.gov (United States)

    Dommett, Eleanor J.; Henderson, Emma L.; Westwell, Martin S.; Greenfield, Susan A.

    2008-01-01

    Methylphenidate treatment is used for Attention Deficit Hyperactivity Disorder and can improve learning and memory. Previously, improvements were considered a by-product of increased attention; however, we hypothesize that methylphenidate directly alters mechanisms underlying learning and memory, and therefore examined its effects on hippocampal…

  17. Wood plastic composites from agro-waste materials: Analysis of mechanical properties.

    Science.gov (United States)

    Nourbakhsh, Amir; Ashori, Alireza

    2010-04-01

    This article presents the application of agro-waste materials (i.e., corn stalk, reed stalk, and oilseed stalk) in order to evaluate and compare their suitability as reinforcement for thermoplastics as an alternative to wood fibers. The effects of fiber loading and CaCO(3) content on the mechanical properties were also studied. Overall trend shows that with addition of agro-waste materials, tensile and flexural properties of the composites are significantly enhanced. Oilseed fibers showed superior mechanical properties due to their high aspect ratio and chemical characteristics. The order of increment in the mechanical properties of the composites is oilseed stalk >corn stalk>reed stalk at all fiber loadings. The tensile and flexural properties of the composite significantly decreased with increasing CaCO(3) content, due to the reduction of interface bond between the fiber and matrix. It can be concluded from this study that the used agro-waste materials are attractive reinforcements from the standpoint of their mechanical properties.

  18. Mechanisms of plastic deformation in highly cross-linked UHMWPE for total hip components--the molecular physics viewpoint.

    Science.gov (United States)

    Takahashi, Yasuhito; Shishido, Takaaki; Yamamoto, Kengo; Masaoka, Toshinori; Kubo, Kosuke; Tateiwa, Toshiyuki; Pezzotti, Giuseppe

    2015-02-01

    Plastic deformation is an unavoidable event in biomedical polymeric implants for load-bearing application during long-term in-vivo service life, which involves a mass transfer process, irreversible chain motion, and molecular reorganization. Deformation-induced microstructural alterations greatly affect mechanical properties and durability of implant devices. The present research focused on evaluating, from a molecular physics viewpoint, the impact of externally applied strain (or stress) in ultra-high molecular weight polyethylene (UHMWPE) prostheses, subjected to radiation cross-linking and subsequent remelting for application in total hip arthroplasty (THA). Two different types of commercial acetabular liners, which belong to the first-generation highly cross-linked UHMWPE (HXLPE), were investigated by means of confocal/polarized Raman microprobe spectroscopy. The amount of crystalline region and the spatial distribution of molecular chain orientation were quantitatively analyzed according to a combined theory including Raman selection rules for the polyethylene orthorhombic structure and the orientation distribution function (ODF) statistical approach. The structurally important finding was that pronounced recrystallization and molecular reorientation increasingly appeared in the near-surface regions of HXLPE liners with increasing the amount of plastic (compressive) deformation stored in the microstructure. Such molecular rearrangements, occurred in response to external strains, locally increase surface cross-shear (CS) stresses, which in turn trigger microscopic wear processes in HXLPE acetabular liners. Thus, on the basis of the results obtained at the molecular scale, we emphasize here the importance of minimizing the development of irrecoverable deformation strain in order to retain the pristine and intrinsically high wear performance of HXLPE components.

  19. MeCP2 post-translational modifications: a mechanism to control its involvement in synaptic plasticity and homeostasis?

    Directory of Open Access Journals (Sweden)

    Elisa eBellini

    2014-08-01

    Full Text Available Although Rett syndrome (RTT represents one of the most frequent forms of severe intellectual disability in females worldwide, we still have an inadequate knowledge of the many roles played by MeCP2 (whose mutations are responsible for most cases of RTT and their relevance for RTT pathobiology. Several studies support a role of MeCP2 in the regulation of synaptic plasticity and homeostasis. At the molecular level, MeCP2 is described as a repressor capable of inhibiting gene transcription through chromatin compaction. Indeed, it interacts with several chromatin remodeling factors, such as HDAC-containing complexes and ATRX. Other studies have inferred that MeCP2 functions also as an activator; a role in regulating mRNA splicing and in modulating protein synthesis has also been proposed. Further, MeCP2 avidly binds both 5-methyl- and 5-hydroxymethyl-cytosine. Recent evidence suggests that it is the highly disorganized structure of MeCP2, together with its post-translational modifications (PTMs that generate and regulate this functional versatility. Indeed, several reports have demonstrated that differential phosphorylation of MeCP2 is a key mechanism by which the methyl binding protein modulates its affinity for its partners, gene expression and cellular adaptations to stimuli and neuronal plasticity. As logic consequence, generation of phospho-defective Mecp2 knock-in mice has permitted associating alterations in neuronal morphology, circuit formation, and mouse behavioral phenotypes with specific phosphorylation events. MeCP2 undergoes various other PTMs, including acetylation, ubiquitination and sumoylation, whose functional roles remain largely unexplored. These results, together with the genome-wide distribution of MeCP2 and its capability to substitute histone H1, recall the complex regulation of histones and suggest the relevance of quickly gaining a deeper comprehension of MeCP2 PTMs, the respective writers and readers and the consequent

  20. MODIFICATION OF RESIN EDT-69N FOR THE PURPOSE OF MECHANICAL PROPERTIES OF PLASTICS

    Directory of Open Access Journals (Sweden)

    В. Краля

    2012-04-01

    Full Text Available The epoxy matrix EDT-69N it is one of license matrix which applies by aviation industry in theCommonwealth of Independent States. This matrix created according to the standards NLGS-3 with a glanceto requirements of a self-damping. A self-damping achieved by a mixing of resin UP-631 in a recipe of amatrix EDT-69N. It led to a increasing of matrix cost and a decreasing of the physical-mechanical properties.According to current standards AP-25 the matrix EDT-69N does not ensure the compliances by requirementsof combustibility, fume evolution and toxicity of combustion products. That is why a pressing problem ofmodification of matrix EDT-69N appears for the purpose of increasing of the physical-mechanical andtechnologic properties in the prejudice of requirement of combustibility.

  1. Mechanical and morphological characterization of novel vinyl plastisols with epoxidized linseed oil as natural-based plasticizer

    Science.gov (United States)

    Fenollar, O.; Balart, R.; Sánchez-Nácher, L.; García-Sanoguera, D.; Boronat, T.

    2010-06-01

    Poly(vinyl chloride) (PVC) is one of the most commonly used plastics in the current market due to its low cost and versatility in processing, combined with its satisfactory physical and chemical properties. However, there is an important problem associated to the use of plasticized PVC. This problem is regarding to the toxicity of the most common plasticized used like DOP, DEHP, DINP, due to its possible migration. This problem limits the use of the plasticized PVC in the industry. In this work we have used epoxidized linseed oil (ELO) as a non toxic plasticizer for PVC. This type of natural oil is characterized by acting as both plasticizer and stabilizer of PVC. With this purpose, ELO have been added to PVC. The processing conditions (temperature and time of curing) are vital to determine the final properties of the material. A study of the processing conditions shows the adequate temperature and time to achieve the optimum properties.

  2. Glassy metallic plastics

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    This paper reports a class of bulk metallic glass including Ce-, LaCe-, CaLi-, Yb-, and Sr-based metallic glasses, which are regarded as glassy metallic plastics because they combine some unique properties of both plastics and metallic alloys. These glassy metallic plastics have very low glass transition temperature (Tg~25oC to 150oC) and low Young’s modulus (~20 GPa to 35 GPa). Similar to glassy plastics, these metallic plastics show excellent plastic-like deformability on macro-, micro- and even nano-scale in their supercooled liquid range and can be processed, such as elongated, compressed, bent, and imprinted at low temperatures, in hot water for instance. Under ambient conditions, they display such metallic properties as high thermal and electric conductivities and excellent mechanical properties and other unique properties. The metallic plastics have potential applications and are also a model system for studying issues in glass physics.

  3. Investigation of Deformation Mechanisms in Deep-Drawn and Tensile-Strained Austenitic Mn-Based Twinning Induced Plasticity (TWIP) Steel

    NARCIS (Netherlands)

    Van Tol, R.T.; Zhao, L.; Schut, H.; Sietsma, J.

    2012-01-01

    The effect of strain on the deformation mechanisms in an austenitic Mn-based twinning induced plasticity (TWIP) steel is investigated using magnetic measurements, XRD, positron beam Doppler spectroscopy, and finite element method simulations. The experimental observations reveal the formation of a0-

  4. Cortical plasticity as a mechanism for storing Bayesian priors in sensory perception.

    Directory of Open Access Journals (Sweden)

    Hania Köver

    Full Text Available Human perception of ambiguous sensory signals is biased by prior experiences. It is not known how such prior information is encoded, retrieved and combined with sensory information by neurons. Previous authors have suggested dynamic encoding mechanisms for prior information, whereby top-down modulation of firing patterns on a trial-by-trial basis creates short-term representations of priors. Although such a mechanism may well account for perceptual bias arising in the short-term, it does not account for the often irreversible and robust changes in perception that result from long-term, developmental experience. Based on the finding that more frequently experienced stimuli gain greater representations in sensory cortices during development, we reasoned that prior information could be stored in the size of cortical sensory representations. For the case of auditory perception, we use a computational model to show that prior information about sound frequency distributions may be stored in the size of primary auditory cortex frequency representations, read-out by elevated baseline activity in all neurons and combined with sensory-evoked activity to generate a perception that conforms to Bayesian integration theory. Our results suggest an alternative neural mechanism for experience-induced long-term perceptual bias in the context of auditory perception. They make the testable prediction that the extent of such perceptual prior bias is modulated by both the degree of cortical reorganization and the magnitude of spontaneous activity in primary auditory cortex. Given that cortical over-representation of frequently experienced stimuli, as well as perceptual bias towards such stimuli is a common phenomenon across sensory modalities, our model may generalize to sensory perception, rather than being specific to auditory perception.

  5. Damage Tolerance Assessment of Friction Pull Plug Welds

    Science.gov (United States)

    McGill, Preston; Burkholder, Jonathan

    2012-01-01

    Friction stir welding is a solid state welding process developed and patented by The Welding Institute in Cambridge, England. Friction stir welding has been implemented in the aerospace industry in the fabrication of longitudinal welds in pressurized cryogenic propellant tanks. As the industry looks to implement friction stir welding in circumferential welds in pressurized cryogenic propellant tanks, techniques to close out the termination hole associated with retracting the pin tool are being evaluated. Friction pull plug welding is under development as a one means of closing out the termination hole. A friction pull plug weld placed in a friction stir weld results in a non-homogenous weld joint where the initial weld, plug weld, their respective heat affected zones and the base metal all interact. The welded joint is a composite, plastically deformed material system with a complex residual stress field. In order to address damage tolerance concerns associated with friction plug welds in safety critical structures, such as propellant tanks, nondestructive inspection and proof testing may be required to screen hardware for mission critical defects. The efficacy of the nondestructive evaluation or the proof test is based on an assessment of the critical flaw size in the test or service environments. Test data relating residual strength capability to flaw size in two aluminum alloy friction plug weld configurations is presented.

  6. Mechanical Properties and Microstructures of Ni20Cr Micro-wires with Abnormal Plastic Deformation

    Science.gov (United States)

    Zhou, Xiuwen; Liu, Xudong; Qi, Yidong; Wu, Weidong

    2017-05-01

    Ni80Cr20 (Ni20Cr, wt%) micro-wires were fabricated by the cold-drawing method with single die. Abnormal engineering strains were approximately 17.3-46.6 % for each pass. The relationship between mechanical properties and microstructures of Ni20Cr micro-wires were investigated under different engineering strains and annealing conditions. Experiment results indicate that the as-drawn NiCr micro-wires present obviously brittle fractures. The ultimate tensile strength (UTS) significantly increases from 781 to 1,147 MPa and the elongation decreases from 17.2 % to 1 % with engineering strains increasing. The deformed microstructures of Ni20Cr micro-wire were analyzed in detail including two-phase (solid solution/amorphous phase), edge dislocations and twins. With the annealing temperature increasing, specimens had experienced three stages and their mechanical properties were improved. After annealing at 890 °C (with 6.5 g stress) for 7.3 s in N2, the Ni20Cr micro-wires benefited for the second drawing pass. The results are very importance in fabricating Ni20Cr micro-wire with the diameter from 25 to 10 μm.

  7. Mechanisms of Long Non-coding RNAs in Mammalian Nervous System Development, Plasticity, Disease, and Evolution.

    Science.gov (United States)

    Briggs, James A; Wolvetang, Ernst J; Mattick, John S; Rinn, John L; Barry, Guy

    2015-12-02

    Only relatively recently has it become clear that mammalian genomes encode tens of thousands of long non-coding RNAs (lncRNAs). A striking 40% of these are expressed specifically in the brain, where they show precisely regulated temporal and spatial expression patterns. This begs the question, what is the functional role of these many lncRNA transcripts in the brain? Here we canvass a growing number of mechanistic studies that have elucidated central roles for lncRNAs in the regulation of nervous system development and function. We also survey studies indicating that neurological and psychiatric disorders may ensue when these mechanisms break down. Finally, we synthesize these insights with evidence from comparative genomics to argue that lncRNAs may have played important roles in brain evolution, by virtue of their abundant sequence innovation in mammals and plausible mechanistic connections to the adaptive processes that occurred recently in the primate and human lineages.

  8. Plasticity and Interfacial Dislocation Mechanisms in Epitaxial and Polycrystalline Al Films Constrained by Substrates

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Stresses in epitaxial and textured Al films were determined by substrate-curvature measurements. It was found that in both cases the flow stresses increase with decreasing film thickness. The flow stresses in the epitaxial Al films are in agreement with a dislocation-based model, while the same model strongly underestimates the flow stresses of textured Al films. In-situ transmission electron microscopy studies indicate that dislocations channeling through epitaxial Al films on single-crystalline (0001) α-AI2O3 substrates frequently deposit dislocation segments adjacent to the interface. Furthermore, the AI/α-AI2O3 interface acted as a dislocation source. In this case, the interface is between two crystalline lattices. In contrast, the interface of textured Al films on oxidized silicon substrates is between the crystalline Al and the amorphous SiOx interlayer. It is speculated that the different nature of the interfaces changes dislocation mechanisms and thus influences the flow stresses.

  9. Intermittent Hypoxia-Induced Spinal Inflammation Impairs Respiratory Motor Plasticity by a Spinal p38 MAP Kinase-Dependent Mechanism.

    Science.gov (United States)

    Huxtable, Adrianne G; Smith, Stephanie M C; Peterson, Timothy J; Watters, Jyoti J; Mitchell, Gordon S

    2015-04-29

    Inflammation is characteristic of most clinical disorders that challenge the neural control of breathing. Since inflammation modulates neuroplasticity, we studied the impact of inflammation caused by prolonged intermittent hypoxia on an important form of respiratory plasticity, acute intermittent hypoxia (three, 5 min hypoxic episodes, 5 min normoxic intervals) induced phrenic long-term facilitation (pLTF). Because chronic intermittent hypoxia elicits neuroinflammation and pLTF is undermined by lipopolysaccharide-induced systemic inflammation, we hypothesized that one night of intermittent hypoxia (IH-1) elicits spinal inflammation, thereby impairing pLTF by a p38 MAP kinase-dependent mechanism. pLTF and spinal inflammation were assessed in anesthetized rats pretreated with IH-1 (2 min hypoxia, 2 min normoxia; 8 h) or sham normoxia and allowed 16 h for recovery. IH-1 (1) transiently increased IL-6 (1.5 ± 0.2-fold; p = 0.02) and inducible nitric oxide synthase (iNOS) (2.4 ± 0.4-fold; p = 0.01) mRNA in cervical spinal homogenates, (2) elicited a sustained increase in IL-1β mRNA (2.4 ± 0.2-fold; p < 0.001) in isolated cervical spinal microglia, and (3) abolished pLTF (-1 ± 5% vs 56 ± 10% in controls; p < 0.001). pLTF was restored after IH-1 by systemic NSAID administration (ketoprofen; 55 ± 9%; p < 0.001) or spinal p38 MAP kinase inhibition (58 ± 2%; p < 0.001). IH-1 increased phosphorylated (activated) p38 MAP kinase immunofluorescence in identified phrenic motoneurons and adjacent microglia. In conclusion, IH-1 elicits spinal inflammation and impairs pLTF by a spinal p38 MAP kinase-dependent mechanism. By targeting inflammation, we may develop strategies to manipulate respiratory motor plasticity for therapeutic advantage when the respiratory control system is compromised (e.g., sleep apnea, apnea of prematurity, spinal injury, or motor neuron disease).

  10. Mechanisms regulating nutrition-dependent developmental plasticity through organ-specific effects in insects

    Directory of Open Access Journals (Sweden)

    Takashi eKoyama

    2013-09-01

    Full Text Available Nutrition, via the insulin/insulin-like growth factor (IIS/Target of Rapamycin (TOR signaling pathway, can provide a strong molding force for determining animal size and shape. For instance, nutrition induces a disproportionate increase in the size of male horns in dung and rhinoceros beetles, or mandibles in staghorn or horned flour beetles, relative to body size. In these species, well-fed male larvae produce adults with greatly enlarged horns or mandibles, whereas males that are starved or poorly fed as larvae bear much more modest appendages. Changes in IIS/TOR signaling plays a key role in appendage development by regulating growth in the horn and mandible primordia. In contrast, changes the IIS/TOR pathway produces minimal effects on the size of other adult structures, such as the male genitalia in fruit flies and dung beetles. The horn, mandible and genitalia illustrate that although all tissues are exposed to the same hormonal environment within the larval body, the extent to which insulin can induce growth is organ specific. In addition, the IIS/TOR pathway affects body size and shape by controlling production of metamorphic hormones important for regulating developmental timing, like the steroid molting hormone ecdysone and sesquiterpenoid hormone juvenile hormone. In this review, we discuss recent results from Drosophila and other insects that highlight mechanisms allowing tissues to differ in their sensitivity to IIS/TOR and the potential consequences of these differences on body size and shape.

  11. Flat-pressed wood plastic composites from sawdust and recycled polyethylene terephthalate (PET): physical and mechanical properties.

    Science.gov (United States)

    Rahman, Khandkar-Siddikur; Islam, Md Nazrul; Rahman, Md Mushfiqur; Hannan, Md Obaidullah; Dungani, Rudi; Khalil, Hps Abdul

    2013-01-01

    This study deals with the fabrication of composite matrix from saw dust (SD) and recycled polyethylene terephthalate (PET) at different ratio (w/w) by flat-pressed method. The wood plastic composites (WPCs) were made with a thickness of 6 mm after mixing the saw dust and PET in a rotary type blender followed by flat press process. Physical i.e., density, moisture content (MC), water absorption (WA) and thickness swelling (TS), and mechanical properties i.e., Modulus of Elasticity (MOE) and Modulus of Rupture (MOR) were assessed as a function of mixing ratios according to the ASTM D-1037 standard. WA and TS were measured after 24 hours of immersion in water at 25, 50 and 75°C temperature. It was found that density decreased 18.3% when SD content increased from 40% to 70% into the matix. WA and TS increased when the PET content decreased in the matrix and the testing water temperature increased. MOE and MOR were reached to maximum for the fabricated composites (2008.34 and 27.08 N/mm(2), respectively) when the SD content were only 40%. The results indicated that the fabrication of WPCs from sawdust and PET would technically feasible; however, the use of additives like coupling agents could further enhance the properties of WPCs.

  12. Mechanisms involved in systemic nicotine-induced glutamatergic synaptic plasticity on dopamine neurons in the ventral tegmental area.

    Science.gov (United States)

    Gao, Ming; Jin, Yu; Yang, Kechun; Zhang, Die; Lukas, Ronald J; Wu, Jie

    2010-10-13

    Systemic exposure to nicotine induces glutamatergic synaptic plasticity on dopamine (DA) neurons in the ventral tegmental area (VTA), but mechanisms are largely unknown. Here, we report that single, systemic exposure in rats to nicotine (0.17 mg/kg free base) increases the ratio of DA neuronal currents mediated by AMPA relative to NMDA receptors (AMPA/NMDA ratio) assessed 24 h later, based on slice-patch recording. The AMPA/NMDA ratio increase is evident within 1 h and lasts for at least 72 h after nicotine exposure (and up to 8 d after repeated nicotine administration). This effect cannot be prevented by systemic injection of either α7-nAChR (nicotinic ACh receptor)-selective [methyllycaconitine (MLA)] or β2*-nAChR-selective [mecamylamine (MEC)] antagonists but is prevented by coinjection of MLA and MEC. In either nAChR α7 or β2 subunit knock-out mice, systemic exposure to nicotine still increases the AMPA/NMDA ratio. Preinjection in rats of a NMDA receptor antagonist MK-801((+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine maleate), but neither DA receptor antagonists [SCH-23390 (R-(+)-7-chloro-8-hydroxy-3-methyl-1-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine) plus haloperidol] nor a calcineurin inhibitor (cyclosporine), prevents the nicotine-induced increase in AMPA/NMDA ratio. After systemic exposure to nicotine, glutamatergic (but not GABAergic) transmission onto rat VTA DA neuronal inputs is enhanced. Correspondingly, DA neuronal firing measured 24 h after nicotine exposure using extracellular single-unit recording in vivo is significantly faster, and there is conversion of silent to active DA neurons. Collectively, these findings demonstrate that systemic nicotine acting via either α7- or β2*-nAChRs increases presynaptic and postsynaptic glutamatergic function, and consequently initiates glutamatergic synaptic plasticity, which may be an important, early neuronal adaptation in nicotine reward and reinforcement.

  13. Maximization of Growth Rates During Czochralski Pulling

    Science.gov (United States)

    Wargo, M. J.

    1984-01-01

    It was suggested from theory(1-4) that silicon can be grown from the melt at rates far exceeding the current state of the art. Previous theoretical and experimental investigations which predict maximum rates of pulling during Czochralski growth are reviewed. Several experimental methods are proposed to modify the temperature distribution in a growing crystal to achieve higher rates of pulling. A physical model of a Czochralski crystal of germanium in contact with its melt was used to quantitatively determine, by direct measurement of the axial temperature distribution in the solid, the increase in axial temperature gradients effected by an inverted conical heat reflector located above the melt and coaxially about the physical model. Preliminary results indicate that this is an effective method of increasing the thermal resistance between the hot melt and crucible wall and a growing crystal. Under these conditions the enhancement of the interfacial temperature gradients permit a commensurate increase in the rate of crystal pulling.

  14. The effect of di-(-2-ethyl hexyl phthalate (Dehp as plasticizer on the thermal and mechanical properties of pvc/pmma blends

    Directory of Open Access Journals (Sweden)

    Kamira Aouachria

    2014-08-01

    Full Text Available Plasticizers play a key role in the formulation of polymers and in determining their physical properties and processability. This study examines the effect of di(2-ethyl hexylphthalate (DEHP as plasticizer on the thermal and mechanical properties of PVC/PMMA blends. For that purpose, blends of variable composition, from 0 to 100 wt%, were prepared in the presence (15, 30 and 50 wt % and in the absence of di(2-ethyl hexylphthalate. The thermal degradation of the blends was investigated by thermogravimetric analysis (TGA in an atmosphere of synthetic air in the temperature range of 50-550°C. The variation of the mechanical properties, such as tensile behavior, hardness and impact resistance, were investigated for all blend compositions. The effect of the plasticizer on the same properties was considered. The results obtained show that a range of properties can be generated according to the blend compositions. Therefore, the addition of PMMA to the blends stabilized PVC, for the initial thermal degradation, and the addition of the plasticizer caused a decrease of stress at break and Young modulus.

  15. Research on Mechanization Technology of Plastic Film Mulching%地膜覆盖机械化技术研究

    Institute of Scientific and Technical Information of China (English)

    孙杰

    2016-01-01

    介绍地膜覆盖机的分类、结构组成及性能,分别论述各类地膜覆盖机械的工作原理及特点,阐述地膜覆盖机的使用、调试、维护要点,为地膜覆盖机械的选用及维护提供技术借鉴。%In this paper, it introduced the classification, structural composition and performance of plastic mulching machine, dis-cussed separately the working principle of every kind of plastic mulching machine, expounded the main points of application, debugging and maintaining of plastic mulching machine, providing technical references for the selection and maintaining of plastic mulching ma-chine.

  16. Highly plastic behavior and fluidization of gouge; implications for fault and landslide mechanics and for the generation of mud volcanoes

    Science.gov (United States)

    Shimamoto, Toshihiko; Aoki, Kazuhiro; Seshimo, Kazuyoshi; Hu, Wei; Ma, Shengli; Yao, Lu; Xiong, Ran; Xiao, Yinke

    2016-04-01

    We address an issue on "how low gouge friction can be with an increasing amount of pore fluid" (an unexplored problem in fault mechanics), as studied with a rotary-shear low to high-velocity friction apparatus in Beijing using host specimens of Ti-Al-V alloy with a Teflon sleeve. A friction experiment was conducted on about 1 mm-thick, smectite-rich gouge from Shionohira fault zone, Fukushima, Japan, with 80 wt% of initial pore water, at a normal stress of 1 MPa, and with velocity steps of 17 times ranging in 0.21 microns/s to 2.1 m/s. Friction coefficients at slow rates were initially 0.003 to 0.005 with abundant water, but the coefficients increased to about 0.2 owing to the loss of water during the drained tests. Gouge was squeezed out slowly from host-specimen/Teflon interface as very thin paper-like flakes during a part of the run, indicating highly plastic behavior of gouge. The initial friction was by far the lowest ever reported! A dry high-velocity friction experiment on the same gouge (normal stress 2 MPa, velocity 2.1 m/s) revealed fluidization of gouge due to vaporized water released during decomposition of clay minerals. Friction coefficient increased to its peak (~ 0.8), followed by nearly exponential decay to a steady-state value of ~ 0.2. Then the friction coefficient began to decrease almost linearly with displacement down to ca. 0.07, deviating from an exponential decay. The gouge was lost almost instantly in less than one second, terminating the run. Temperature, measured at the sliding surface, began to decrease at the onset of the nearly linear weakening, strongly suggesting dehydration of clays (endothermic reactions). We interpret the results that steam pressure increased in gouge till a limit to cause a small explosion of gouge. Gouge can fluidize! A series of low to intermediate-velocity experiments on slip-zone materials from Kualiangzi landslide, Sichuan, China, demonstrated that the initial friction coefficient was less than 0.1 with a

  17. Presence of two emissive minima in the lowest excited state of a push-pull cationic dye unequivocally proved by femtosecond up-conversion spectroscopy and vibronic quantum-mechanical computations.

    Science.gov (United States)

    Benassi, Enrico; Carlotti, Benedetta; Segado, Mireia; Cesaretti, Alessio; Spalletti, Anna; Elisei, Fausto; Barone, Vincenzo

    2015-05-14

    The long-standing controversy about the presence of two different emissive minima in the lowest excited state of the cationic push-pull dye o-(p-dimethylamino-styryl)-methylpyridinium (DASPMI) was definitively proved through the observation of dual emission, evidenced by both experimental (femtosecond up-conversion measurements) and theoretical (density functional theory calculations) approaches. From the fluorescence up-conversion data of DASPMI in water, the time resolved area normalized spectra (TRANES) were calculated, showing one isoemissive point and therefore revealing the presence of two distinct emissive minima of the excited state potential energy hypersurface with lifetimes of 0.51 and 4.8 ps. These spectroscopic techniques combined with proper data analysis allowed us to discriminate the sub-picosecond emitting state from the occurrence of ultrafast solvation dynamics and to disentangle the overlapping fluorescence (very close in energy) of the two components. Vibronic computations based on TD-DFT potential energy surfaces fully confirm those results and provide deeper insights about the key factors playing a role in determining the overall result. The two emissive minima have different structural and electronic characteristics: on one hand, the locally excited (LE) minimum has a flat geometry and an electric dipole moment smaller than the ground state; on the other hand, the twisted-intramolecular-charge-transfer (TICT) minimum shows a rotation of the methylpyridinium moiety with respect to the rest of the structure, and has an electric dipole moment significantly larger than the ground state.

  18. UK pulls out of plans for ILC

    CERN Multimedia

    Durrani, Matin

    2007-01-01

    "A funding crisis at one of the UK's leading research councils has forced the country to pull out of plans for the International Linear Collider (ILC). The science and Technology Facilities Council (STFC) says in a report published today that it does not see "a practicable path towards the realization of this facility as currently conceived on a reasonable timescale". (1 page)

  19. Intermode beat stabilized laser with frequency pulling.

    Science.gov (United States)

    Yokoyama, S; Araki, T; Suzuki, N

    1994-01-20

    A frequency-stabilized two-mode He-Ne laser has been developed. The intermode beat frequency of the experimental laser was approximately 600 MHz for a 25-cm cavity. The laser frequency in which the mode stands is pulled to the center of the gain curve (frequency pulling). The degree of pulling depends on where the longitudinal modes stand in the broadened gain curve. Beat frequency is thereby changed periodically of the order of hundreds of kilohertz with respect to cavity expansion. The frequency pulling was effectively used for frequency stabilization of the laser. The standing position of the longitudinal mode lights was locked in the gain curve by controlling the change of intermode beat frequency. A microwave mixer was applied to extract the frequency change of the intermode beat. Excellent frequency stability (10(10) for the laser oscillation and 10(6) for the beat frequency) was attained. The polarization orthogonality of the proposed laser was superior to that of Zeeman lasers.

  20. Targeting tumour Cell Plasticity

    Institute of Scientific and Technical Information of China (English)

    Elizabeth D. WILLIAMS

    2009-01-01

    @@ Her research is focused on understanding the mechanisms of tumour progression and metastasis, particularly in uro-logical carcinomas (bladder and prostate). Tumour cell plasticity, including epithelial-mesenchymal transition, is a cen-tral theme in Dr Williams' work.

  1. Plastic Jellyfish.

    Science.gov (United States)

    Moseley, Christine

    2000-01-01

    Presents an environmental science activity designed to enhance students' awareness of the hazards of plastic waste for wildlife in aquatic environments. Discusses how students can take steps to reduce the effects of plastic waste. (WRM)

  2. The push-pull theory of migration and its application.

    Science.gov (United States)

    Zhang, Z; Zhang, T; Zhang, Q

    1997-01-01

    Since the start of the 1980s, a migration project involving 550,000 people in Gansu and Ningxia provinces has been underway as part of a program to explore the natural resources, eliminate poverty, and improve the environment. A similar project has been carried out in Xinjiang, involving hundreds of thousands of people, and 400,000 people in the karst areas of Guangxi have moved to open up and cultivate barren hills. Millions of people will eventually be moved out of the impoverished areas of western China. The success of these migration projects over the past decade, however, has also brought some social and ecological problems. In order for the projects to have scientific footing and to follow a standard procedure, a theoretical model must be established which fits the conditions in China concerning the mechanism, magnitude, settlement planning, impact evaluation, and management system of migration. To that end, the authors conducted this study based upon empirical research. Sections cover a review of the push-pull mechanism theory in western demographics and the push-pull mechanism theory in China as part of the Help-the-Poor program and its application.

  3. Filament depolymerization can pull a chromosome during bacterial mitosis

    Science.gov (United States)

    Banigan, Edward; Gelbart, Michael; Gitai, Zemer; Liu, Andrea; Wingreen, Ned

    2011-03-01

    Chromosome segregation is fundamental to all cells, but the force-generating mechanisms underlying chromosome translocation in bacteria remain mysterious. Caulobacter crescentus utilizes a depolymerization-driven process in which a ParA protein structure elongates from the new cell pole and binds to a ParB-decorated chromosome, and then retracts via disassembly, thus pulling the chromosome across the cell. This poses the question of how a depolymerizing structure can robustly pull the chromosome that is disassembling it. We perform Brownian dynamics simulations with a simple and physically consistent model of the ParABS system. The simulations suggest that the mechanism of translocation is ``self-diffusiophoretic'': by disassembling ParA, ParB generates a ParA concentration gradient so that the concentration of ParA is higher in front of the chromosome than behind it. Since the chromosome is attracted to ParA via ParB, it moves up the ParA gradient and across the cell. We find that translocation is controlled by the product of an effective relaxation time for the chromosome and the rate of ParA disassembly. Our results provide a physical explanation of the mechanism of depolymerization-driven translocation and suggest physical explanations for recent experimental observations.

  4. Filament depolymerization can explain chromosome pulling during bacterial mitosis.

    Science.gov (United States)

    Banigan, Edward J; Gelbart, Michael A; Gitai, Zemer; Wingreen, Ned S; Liu, Andrea J

    2011-09-01

    Chromosome segregation is fundamental to all cells, but the force-generating mechanisms underlying chromosome translocation in bacteria remain mysterious. Caulobacter crescentus utilizes a depolymerization-driven process in which a ParA protein structure elongates from the new cell pole, binds to a ParB-decorated chromosome, and then retracts via disassembly, pulling the chromosome across the cell. This poses the question of how a depolymerizing structure can robustly pull the chromosome that disassembles it. We perform Brownian dynamics simulations with a simple, physically consistent model of the ParABS system. The simulations suggest that the mechanism of translocation is "self-diffusiophoretic": by disassembling ParA, ParB generates a ParA concentration gradient so that the ParA concentration is higher in front of the chromosome than behind it. Since the chromosome is attracted to ParA via ParB, it moves up the ParA gradient and across the cell. We find that translocation is most robust when ParB binds side-on to ParA filaments. In this case, robust translocation occurs over a wide parameter range and is controlled by a single dimensionless quantity: the product of the rate of ParA disassembly and a characteristic relaxation time of the chromosome. This time scale measures the time it takes for the chromosome to recover its average shape after it is has been pulled. Our results suggest explanations for observed phenomena such as segregation failure, filament-length-dependent translocation velocity, and chromosomal compaction.

  5. Filament depolymerization can explain chromosome pulling during bacterial mitosis.

    Directory of Open Access Journals (Sweden)

    Edward J Banigan

    2011-09-01

    Full Text Available Chromosome segregation is fundamental to all cells, but the force-generating mechanisms underlying chromosome translocation in bacteria remain mysterious. Caulobacter crescentus utilizes a depolymerization-driven process in which a ParA protein structure elongates from the new cell pole, binds to a ParB-decorated chromosome, and then retracts via disassembly, pulling the chromosome across the cell. This poses the question of how a depolymerizing structure can robustly pull the chromosome that disassembles it. We perform Brownian dynamics simulations with a simple, physically consistent model of the ParABS system. The simulations suggest that the mechanism of translocation is "self-diffusiophoretic": by disassembling ParA, ParB generates a ParA concentration gradient so that the ParA concentration is higher in front of the chromosome than behind it. Since the chromosome is attracted to ParA via ParB, it moves up the ParA gradient and across the cell. We find that translocation is most robust when ParB binds side-on to ParA filaments. In this case, robust translocation occurs over a wide parameter range and is controlled by a single dimensionless quantity: the product of the rate of ParA disassembly and a characteristic relaxation time of the chromosome. This time scale measures the time it takes for the chromosome to recover its average shape after it is has been pulled. Our results suggest explanations for observed phenomena such as segregation failure, filament-length-dependent translocation velocity, and chromosomal compaction.

  6. Evolution of plastic deformation and its effect on mechanical properties of laser additive repaired Ti64ELI titanium alloy

    Science.gov (United States)

    Zhao, Zhuang; Chen, Jing; Tan, Hua; Lin, Xin; Huang, Weidong

    2017-07-01

    In this paper, laser additive manufacturing (LAM) technology with powder feeding has been employed to fabricate 50%LAMed specimens (i.e. the volume fraction of the laser deposited zone was set to 50%). With aid of the 3D-DIC technique, the tensile deformation behavior of 50%LAMed Ti64ELI titanium alloy was investigated. The 50%LAMed specimen exhibits a significant characteristic of strength mismatch due to the heterogeneous microstructure. The tensile fracture of 50%LAMed specimen occurs in WSZ (wrought substrate zone), but the tensile strength is slightly higher and the plastic elongation is significantly lower than that of the wrought specimen. The 3D-DIC results shows that the 50%LAMed specimen exhibits a characteristic of dramatic plastic strain heterogeneity and the maximal strain is invariably concentrated in WSZ. The ABAQUS simulation indicates that, the LDZ (laser deposited zone) can constrain the plastic deformation of the WSZ and biaxial stresses develop at the interface after yielding.

  7. Process Design of a Ball Joint, Considering Caulking and Pull-Out Strength

    Directory of Open Access Journals (Sweden)

    Bong-Su Sin

    2014-01-01

    Full Text Available A ball joint for an automobile steering system is a pivot component which is connected to knuckle and lower control arm. The manufacturing process for its caulking comprises spinning and deforming. In this study, the process was simulated by flexible multibody dynamics. The caulking was evaluated qualitatively through numerical analysis and inspecting a plastically deformed shape. The structural responses of a ball joint, namely, pull-out strength and stiffness, are commonly investigated in the development process. Thus, following the caulking analysis, the structural responses were considered. In addition, three design variables related to the manufacturing process were defined, and the effects of design variables with respect to pull-out strength, caulking depth, and maximum stress were obtained by introducing the DOE using an L9 orthogonal array. Finally, the optimum design maximizing the pull-out strength was suggested. For the final design, the caulking quality and the pull-out strength were investigated by making six samples and their tests.

  8. Push-me-pull-you: how microtubules organize the cell interior.

    Science.gov (United States)

    Tolić-Nørrelykke, Iva M

    2008-09-01

    Dynamic organization of the cell interior, which is crucial for cell function, largely depends on the microtubule cytoskeleton. Microtubules move and position organelles by pushing, pulling, or sliding. Pushing forces can be generated by microtubule polymerization, whereas pulling typically involves microtubule depolymerization or molecular motors, or both. Sliding between a microtubule and another microtubule, an organelle, or the cell cortex is also powered by molecular motors. Although numerous examples of microtubule-based pushing and pulling in living cells have been observed, it is not clear why different cell types and processes employ different mechanisms. This review introduces a classification of microtubule-based positioning strategies and discusses the efficacy of pushing and pulling. The positioning mechanisms based on microtubule pushing are efficient for movements over small distances, and for centering of organelles in symmetric geometries. Mechanisms based on pulling, on the other hand, are typically more elaborate, but are necessary when the distances to be covered by the organelles are large, and when the geometry is asymmetric and complex. Thus, taking into account cell geometry and the length scale of the movements helps to identify general principles of the intracellular layout based on microtubule forces.

  9. Push-me-pull-you: how microtubules organize the cell interior

    Science.gov (United States)

    2008-01-01

    Dynamic organization of the cell interior, which is crucial for cell function, largely depends on the microtubule cytoskeleton. Microtubules move and position organelles by pushing, pulling, or sliding. Pushing forces can be generated by microtubule polymerization, whereas pulling typically involves microtubule depolymerization or molecular motors, or both. Sliding between a microtubule and another microtubule, an organelle, or the cell cortex is also powered by molecular motors. Although numerous examples of microtubule-based pushing and pulling in living cells have been observed, it is not clear why different cell types and processes employ different mechanisms. This review introduces a classification of microtubule-based positioning strategies and discusses the efficacy of pushing and pulling. The positioning mechanisms based on microtubule pushing are efficient for movements over small distances, and for centering of organelles in symmetric geometries. Mechanisms based on pulling, on the other hand, are typically more elaborate, but are necessary when the distances to be covered by the organelles are large, and when the geometry is asymmetric and complex. Thus, taking into account cell geometry and the length scale of the movements helps to identify general principles of the intracellular layout based on microtubule forces. PMID:18404264

  10. 突触可塑性分子机制的相关研究%Molecular Mechanisms of Synaptic Plasticity Related Research

    Institute of Scientific and Technical Information of China (English)

    张永杰

    2012-01-01

    In recent years,researchers have paid close attention to the role of synaptic plasticity in learning and memory. Synaptic is a key part of neural information transmission, and synaptic plasticity is considered as synaptic changes, the new synaptic formation and the establishment of transmission performance. Synaptic plasticity is the molecular basis of learning and memory, which mediates the transmission of nerve excitability, and has a major influence on synaptic plasticity of neurons establishment, therefore is closely related to learning and memory. Here is to make a review on the molecular mechanisms of synaptic plasticity in learning and memory.%近年来,突触可塑性在学习记忆中所产生的作用一直是人们关注的焦点.突触是神经信息传递的关键部位,突触可塑性被认为是突触形态的改变、新的突触的形成及传递性能的建立,突触可塑性是学习与记忆的细胞分子学基础,其介导了神经兴奋性的传导,对神经元突触可塑性和神经构筑产生了重要影响,因而与学习记忆关系密切.现就突触可塑性分子机制对学习记忆的影响进行综述.

  11. Affective and sensory correlates of hair pulling in pediatric trichotillomania.

    Science.gov (United States)

    Meunier, Suzanne A; Tolin, David F; Franklin, Martin

    2009-05-01

    Hair pulling in pediatric populations has not received adequate empirical study. Investigations of the affective and sensory states contributing to the etiology and maintenance of hair pulling may help to elucidate the classification of trichotillomania (TTM) as an impulse control disorder or obsessive-compulsive spectrum disorder. The current study aimed to examine children's self-reported affective and sensory states associated with hair pulling. Fifteen participants completed a questionnaire assessing children's experiences during first and recent hair pulling episodes. Results revealed that pulling hair for the first time was associated with pleasure and pain whereas recent hair pulling was associated with pleasure only, suggesting that the punishing quality of hair pulling may diminish over time. The findings also support the notion that hair pulling may be maintained primarily through positive reinforcement, which is consistent with its classification as an impulse control disorder.

  12. 机械自紧厚壁圆筒塑性半径的计算%Calculation of Plastic Radius for Thick-Walled Cylinders of Mechanical Autofrettage

    Institute of Scientific and Technical Information of China (English)

    常列珍; 潘玉田; 马新谋; 潘丹阳

    2011-01-01

    机械自紧是依靠冲头同身管内径的过盈量使身管内壁产生塑性变形,提高承载能力,达到自紧的目的.准确建立冲头过盈量与塑性半径之间的关系,才能准确地预测自紧度.为此,利用合理的简化假设,通过对冲头进行弹性分析和对厚壁圆筒进行塑性分析,利用机械自紧在加载过程中冲头圆柱段和厚壁圆筒接触处径向应力相等这一边界条件,推导出了过盈量与塑性半径之间的计算公式,从该公式可直接由过盈量求出塑性半径,由塑性半径便可预测出机械自紧厚壁圆筒的自紧度.为了验证公式的正确性,对10种不同过盈量的机械自紧过程进行了数值模拟,理论计算与数值模拟的结果进行比较,发现理论计算结果与数值模拟的结果比较吻合.%The swage autofrettage barrel is formed depending on the depth of plastic deformation since the diameter of the tool is slightly larger than the barrel inner diameter. The barrel forged in this way can withstand large internal pressures. In order to calculate the degree of autofrettage, the relation between the interference and the plastic radius must be accurately investigated. In loading process, the radial stress of cylindrical section of swage and thick-walled cylinder contact section is equal. By using this boundary condition, an elastic analysis for swage and a plastic analysis for thick-walled cylinder were conducted, and formulas were obtained for calculating excess and plastic radius. Knowing interference, the plastic radius could be calculated directly and the tight tolerance could be pre-estimated by using the plastic radius. To verify the accuracy of the formula, the process of mechanical autofrettage with ten kind different interferences were simulated. Calculated plastic radius agreed well with the results of numerical simulation.

  13. Weightlifting pulling derivatives: rationale for implementation and application.

    Science.gov (United States)

    Suchomel, Timothy J; Comfort, Paul; Stone, Michael H

    2015-06-01

    This review article examines previous weightlifting literature and provides a rationale for the use of weightlifting pulling derivatives that eliminate the catch phase for athletes who are not competitive weightlifters. Practitioners should emphasize the completion of the triple extension movement during the second pull phase that is characteristic of weightlifting movements as this is likely to have the greatest transference to athletic performance that is dependent on hip, knee, and ankle extension. The clean pull, snatch pull, hang high pull, jump shrug, and mid-thigh pull are weightlifting pulling derivatives that can be used in the teaching progression of the full weightlifting movements and are thus less complex with regard to exercise technique. Previous literature suggests that the clean pull, snatch pull, hang high pull, jump shrug, and mid-thigh pull may provide a training stimulus that is as good as, if not better than, weightlifting movements that include the catch phase. Weightlifting pulling derivatives can be implemented throughout the training year, but an emphasis and de-emphasis should be used in order to meet the goals of particular training phases. When implementing weightlifting pulling derivatives, athletes must make a maximum effort, understand that pulling derivatives can be used for both technique work and building strength-power characteristics, and be coached with proper exercise technique. Future research should consider examining the effect of various loads on kinetic and kinematic characteristics of weightlifting pulling derivatives, training with full weightlifting movements as compared to training with weightlifting pulling derivatives, and how kinetic and kinematic variables vary between derivatives of the snatch.

  14. Methods for an investigation of the effect of material components on the mechanical characteristics of glass-fiber-reinforced plastics

    Science.gov (United States)

    Willax, H. O.

    1980-01-01

    The materials used in the production of glass reinforced plastics are discussed. Specific emphasis is given to matrix polyester materials, the reinforcing glass materials, and aspects of specimen preparation. Various methods of investigation are described, giving attention to optical impregnation and wetting measurements and the gravimetric determination of the angle of contact. Deformation measurements and approaches utilizing a piezoelectric device are also considered.

  15. J-integral elastic plastic fracture mechanics evaluation of the stability of cracks in nuclear reactor pressure vessels

    Energy Technology Data Exchange (ETDEWEB)

    Gomez, M. P.; McMeeking, R. M.; Parks, D. M.

    1980-06-01

    Contributions were made toward developing a new methodology to assess the stability of cracks in pressure vessels made from materials that exhibit a significant increase in toughness during the early increments of crack growth. It has a wide range of validity from linear elastic to fully plastic behavior.

  16. Application of microdynamics and lattice mechanics to problems in plastic flow and fracture. Final report, 1 April 1973--31 March 1978

    Energy Technology Data Exchange (ETDEWEB)

    Bilello, J C; Liu, J M

    1978-06-21

    Progress in an investigation of the application of microdynamics and lattice mechanics to the problems in plastic flow and fracture is described. The research program consisted of both theoretical formulations and experimental measurements of a number of intrinsic material parameters in bcc metals and alloys including surface energy, phonon-dispersion curves for dislocated solids, dislocation-point defect interaction energy, slip initiation and microplastic flow behavior. The study has resulted in an improved understanding in the relationship among the experimentally determined fracture surface energy, the intrinsic cohesive energy between atomic planes, and the plastic deformation associated with the initial stages of crack propagation. The values of intrinsic surface energy of tungsten, molybdenum, niobium and niobium-molybdenum alloys, deduced from the measurements, serve as a starting point from which fracture toughness of these materials in engineering service may be intelligently discussed.

  17. Customized Pull Systems for Single-Product Flow Lines

    NARCIS (Netherlands)

    Gaury, E.G.A.; Kleijnen, J.P.C.; Pierreval, H.

    1998-01-01

    Traditionally pull production systems are managed through classic control systems such as Kanban, Conwip, or Base stock, but this paper proposes ‘customized’ pull control. Customization means that a given production line is managed through a pull control system that in principle connects each stage

  18. 30 CFR 75.828 - Trailing cable pulling.

    Science.gov (United States)

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Trailing cable pulling. 75.828 Section 75.828... Longwalls § 75.828 Trailing cable pulling. The trailing cable must be de-energized prior to being pulled by any equipment other than the continuous mining machine. The cable manufacturer's recommended...

  19. Customized Pull Systems for Single-Product Flow Lines

    NARCIS (Netherlands)

    Gaury, E.G.A.; Kleijnen, J.P.C.; Pierreval, H.

    1998-01-01

    Traditionally pull production systems are managed through classic control systems such as Kanban, Conwip, or Base stock, but this paper proposes ‘customized’ pull control. Customization means that a given production line is managed through a pull control system that in principle connects each stage

  20. A review of higher order strain gradient theories of plasticity: Origins, thermodynamics and connections with dislocation mechanics

    Indian Academy of Sciences (India)

    Suman Guha; Sandeep Sangal; Sumit Basu

    2015-06-01

    In this paper we review developments in higher order strain gradient theories. Several variants of these theories have been proposed in order to explain the effects of size on plastic properties that are manifest in several experiments with micron sized metallic structures. It is generally appreciated that the size effect arises from the storage of geometrically necessary dislocations (GNDs) over and above the statistically stored dislocations (SSDs) required for homogeneous deformations. We review developments that show that the GNDs result from the non-homogeneous nature of the deformation field. Though the connection between GNDs and strain gradients are established in the framework of single crystal plasticity, generalisations to polycrystal plasticity has been made. Strain gradient plasticity inherently involves an intrinsic length scale. In our review, we show, through a few illustrative problems, that conventional plasticity solutions can always be reduced to a scale independent form. The same problems are solved with a simple higher order strain gradient formulation to capture the experimentally observed size effects. However, higher order theories need to be thermodynamically consistent. It has recently been shown that only a few of the existing theories pass this test. We review a few that do. Higher order theories require higher order boundary conditions that enable us to model effects of dislocation storage at impermeable boundaries. But these additional boundary conditions also lead to unique conceptual issues that are not encountered in conventional theories. We review attempts at resolving these issues pertaining to higher order boundary conditions. Finally, we review the future of such theories, their relevance and experimental validation.

  1. Surface plasmon polariton assisted optical pulling force

    CERN Document Server

    Petrov, M I; Bogdanov, A A; Shalin, A S; Dogariu, A

    2016-01-01

    We demonstrate both analytically and numerically the existence of optical pulling forces acting on particles located near plasmonic interfaces. Two main factors contribute to the appearance of this negative reaction force. The interference between the incident and reflected waves induces a rotating dipole with an asymmetric scattering pattern while the directional excitation of surface plasmon polaritons (SPP) enhances the linear momentum of scattered light. The strongly asymmetric SPP excitation is determined by spin-orbit coupling of the rotating dipole and surface plasmon polariton. As a result of the total momentum conservation, the force acting on the particle points in a direction opposite to the incident wave propagation. We derive analytical expressions for the force acting on a dipolar particles placed in the proximity of plasmonic surfaces. Analytical expressions for this pulling force are derived within the dipole approximation and are in excellent agreement with results of electromagnetic numerica...

  2. RF Bead Pull Measurements of the DQW

    CERN Document Server

    Jaume, Guillaume

    2015-01-01

    This report was written within the framework of the CERN Summer Student Program. It is focused on the Radio Frequency study of the Double Quarter Wave Crab Cavity [1] considered for the crab-crossing scheme of the LHC Luminosity upgrade [2]. HFSS simulation [3] and Bead-Pull Measurements technique were used for the characterization of the higher-order terms of the main deflecting mode.

  3. Laparoscopic assisted anorectal pull through: Reformed techniques

    OpenAIRE

    2009-01-01

    Aim: To assess the modifications in the technique of laparoscopic assisted anorectal pull through (LAARP) practiced at our institute and analyze the post operative outcome and associated complications. Materials and Methods: A retrospective study from January 2001 to May 2009 analyzing LAARP for high anorectal malformations. Results: A total of 40 patients - 34 males and six females, in the age group of two months to six years were studied. Staged procedure was done in 39 patients; one c...

  4. Pulling rigid bodies through granular material

    Science.gov (United States)

    Kubik, Ryan; Dressaire, Emilie

    2016-11-01

    The need for anchoring systems in granular materials such as sand is present in the marine transportation industry, e.g. to layout moorings, keep vessels and docks fixed in bodies of water, build oil rigs, etc. The holding power of an anchor is associated with the force exerted by the granular media. Empirical evidence indicates that the holding power depends on the size and shape of the anchoring structure. In this model study, we use a two-dimensional geometry in which a rigid body is pulled through a granular media at constant velocity to determine the drag and lift forces exerted by a granular medium on a moving object. The method allows measuring the drag force and recording the trajectory of the rigid object through the sand. We systematically vary the size and geometry of the rigid body, the properties of the granular medium and the extraction speed. For different initial positions of a cylindrical object pulled horizontally through the medium, we record large variations in magnitude of the drag and a significant lift force that pulls the object out of the sand.

  5. Optical Pulling Force and Tractor Beams

    Science.gov (United States)

    Paul, Nayan Kumar

    Light-matter interaction has been an interesting subject of intense analytical and experimental research since the formulation of Maxwell's electromagnetic wave theory. Optical forces exerted on particles excited by incident light waves have been studied for the last few decades. The interaction of light with materials gives rise to light scattering from the particle in the form of energy. The divergence of the Maxwell stress tensor provides a good approximation of the total optical forces on a particle. The divergence of the stress tensor is mathematically equal to the time average Lorentz force since [special characters omitted]. Others have claimed that the stress tensor is "fraught with danger," but it is a matter of application. The stress tensor approach is computationally simpler since application of the divergence theorem allows for a reduction of dimension in the integration. For example, you can either integrate the force density over the volume of an object (3-D), or integrate the divergence of the stress tensor on a surface (2-D) enclosing the volume. It gives a straightforward prediction of the total optical forces on a particle, but may be challenging in the case of multiple particles or for larger particles. The Rayleigh approximation estimates the radiation pressure on small particles in the propagation direction of light, but may be inappropriate for larger particles in comparison to the wavelength of the incident light waves. Light waves exert radiation pressure on a particle and pushes it away from the light source toward the direction of propagation. It is shown that plane waves propagating in a rectangular waveguide not only push a passive particle toward the propagation direction, but also pull it toward the light source. The particle remains trapped in the transverse direction of the rectangular waveguide. The Lorentz force and the Rayleigh approximation are applied to calculate the total force on the particle. The push-pull phenomenon

  6. Mechanism of plasticity development for ceramic dough (5). Influence of the deformability of buffer domain on plasticity; Seramikku nendo no kasakusei hatsugen mekanizumu (5). Kanshoryoiki no henkeino no kasakusei eno eikyo

    Energy Technology Data Exchange (ETDEWEB)

    Kawai, S. [Wet Forming of Ceramics Technology Research Association, Aichi (Japan); Ishida, H. [INAX Corporation, Aichi (Japan). Space Design Research Center; Shibasaki, Y; Oda, K. [National Industrial Research Institute of Nagoya, Aichi (Japan)

    1999-11-01

    Plasticity of ceramic dough is determined by the deformation of the buffer domain that consists of aggregate or gel. Effect of the deformability of each buffer domain on the plasticity of alumina dough, in presence of various additives, was investigated. Those additives were konjak, agar, curdlan and super-absorbent polymer. Moderately deformable additives such as konjak and agar worked as buffer domains, and plasticity was generated. However, soft and brittle additives such as curdlan and super-absorbent polymer could not improve plasticity because of their lower ability in generating the buffer domains. It was clarified that the deformability of buffer domain directly influences plasticity. (author)

  7. The crystallography of carbide-free bainites in thermo-mechanically processed low Si transformation-induced plasticity steels

    Energy Technology Data Exchange (ETDEWEB)

    Pereloma, Elena V. [School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong, New South Wales 2522 (Australia); Electron Microscopy Centre, University of Wollongong, New South Wales 2500 (Australia); Al-Harbi, Fayez [School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong, New South Wales 2522 (Australia); Gazder, Azdiar A., E-mail: azdiar@uow.edu.au [Electron Microscopy Centre, University of Wollongong, New South Wales 2500 (Australia)

    2014-12-05

    Highlights: • First EBSD study comparing ferrite in granular bainite and bainitic laths in two TRIP steels. • Both TRIP steels (base and with Nb–Ti additions) subjected to the same TMP schedule. • Crystallography of the ferrite in the 2 bainites studied using the K–S orientation relationship. • Variants in GB associated with self-accommodation. • BF variant selection linked to RA plastic accommodation and limited volume. - Abstract: Carbide-free bainites are important microstructural constituents in bainitic, nanobainitic and transformation-induced plasticity (TRIP) steels. A comparison of the crystallography of ferrite in granular bainite and bainitic ferrite lath morphologies, both of which were simultaneously present in a base and a Nb–Ti containing TRIP steel, has been carried out using electron back-scattering diffraction. Ferrite in granular bainite was characterised by the realisation of nearly all 24 variants of the Kurdjumov–Sachs orientation relationship; which in turn was associated with the self-accommodation of the transformation strain. On the other hand, bainitic ferrite comprised a mostly parallel lath structure between thick interlayers of retained austenite and exhibited variant selection such that one or more crystallographic packets are not realised and sometimes only 1–2 variants formed in a crystallographic packet. The variant selection in bainitic ferrite laths was associated with: (i) the plastic accommodation of transformation strain by retained austenite and, (ii) the limited available volume for its formation.

  8. Selectively Encrypted Pull-Up Based Watermarking of Biometric data

    Science.gov (United States)

    Shinde, S. A.; Patel, Kushal S.

    2012-10-01

    Biometric authentication systems are becoming increasingly popular due to their potential usage in information security. However, digital biometric data (e.g. thumb impression) are themselves vulnerable to security attacks. There are various methods are available to secure biometric data. In biometric watermarking the data are embedded in an image container and are only retrieved if the secrete key is available. This container image is encrypted to have more security against the attack. As wireless devices are equipped with battery as their power supply, they have limited computational capabilities; therefore to reduce energy consumption we use the method of selective encryption of container image. The bit pull-up-based biometric watermarking scheme is based on amplitude modulation and bit priority which reduces the retrieval error rate to great extent. By using selective Encryption mechanism we expect more efficiency in time at the time of encryption as well as decryption. Significant reduction in error rate is expected to be achieved by the bit pull-up method.

  9. Pull-pull position control of dual motor wire rope transmission

    Science.gov (United States)

    Guo, Quan; Jiao, Zongxia; Yan, Liang; Yu, Qian; Shang, Yaoxing

    2016-08-01

    Wire rope transmission is very efficient because of the small total moving object mass. The wire rope could only transmit pulling force. Therefore it has to be kept in a tightened state during transmission; in high speed applications the dynamic performance depends on the rope's stiffness, which can be adjusted by the wire rope tension. To improve the system dynamic performance output, this paper proposes a novel pull-pull method based on dual motors connected by wire ropes, for precise, high speed position control applications. The method can regulate target position and wire rope tension simultaneously. Wire ropes remain in a pre-tightening state at all times, which prevents the influence of elasticity and reduces the position tracking error in the changing direction process. Simulations and experiments were conducted; the results indicate that both position precision and superior dynamic performance can be synchronously achieved. The research is relevant to space craft precision pointing instruments.

  10. Investigation of Mechanical Properties and Plastic Deformation Behavior of (Ti45Cu40Zr10Ni5100−xAlx Metallic Glasses by Nanoindentation

    Directory of Open Access Journals (Sweden)

    Lanping Huang

    2014-01-01

    Full Text Available The effect of Al addition on mechanical properties and plastic deformation behavior of (Ti45Cu40Zr10Ni5100−xAlx (x = 0, 2, 4, 6 and 8 amorphous alloy ribbons have been investigated by nanoindentation. The hardness and elastic modulus do not simply increase with the increase of Al content. The alloy with 8 at.% Al exhibits the highest hardness and elastic modulus. The serrations or pop-in events are strongly dependent on the loading rate and alloy composition.

  11. From the atom to the cell: Is the cat alive? Quantum mechanics and stem cell plasticity as déjà vu.

    Science.gov (United States)

    Askenasy, Nadir; Nadir, Askenasy

    2006-08-01

    The concepts submitted by quantum mechanics fascinated the scientific community during the first half of the 20(th) century. The second half was dominated by biology, culminating in the sequencing of the human genome and the study of stem cells. Although the anticipated revolution of cellular therapies in medicine is in its infancy, the conceptual debate over stem cell plasticity shares similarities with evolution of the quantum theory. Are there notions and modes of thinking that stem cell biologists should adopt from the evolution in the interpretation of the laws of physics?

  12. Mechanism of functional recovery after repetitive transcranial magnetic stimulation (rTMS) in the subacute cerebral ischemic rat model: neural plasticity or anti-apoptosis?

    Science.gov (United States)

    Yoon, Kyung Jae; Lee, Yong-Taek; Han, Tai Ryoon

    2011-10-01

    Repetitive transcranial magnetic stimulation (rTMS) has been studied increasingly in recent years to determine whether it has a therapeutic benefit on recovery after stroke. However, the underlying mechanisms of rTMS in stroke recovery remain unclear. Here, we evaluated the effect of rTMS on functional recovery and its underlying mechanism by assessing proteins associated with neural plasticity and anti-apoptosis in the peri-lesional area using a subacute cerebral ischemic rat model. Twenty cerebral ischemic rats were randomly assigned to the rTMS or the sham group at post-op day 4. A total of 3,500 impulses with 10 Hz frequency were applied to ipsilesional cortex over a 2-week period. Functional outcome was measured before (post-op day 4) and after rTMS (post-op day 18). The rTMS group showed more functional improvement on the beam balance test and had stronger Bcl-2 and weaker Bax expression on immunohistochemistry compared with the sham group. The expression of NMDA and MAP-2 showed no significant difference between the two groups. These results suggest that rTMS in subacute cerebral ischemia has a therapeutic effect on functional recovery and is associated with an anti-apoptotic mechanism in the peri-ischemic area rather than with neural plasticity.

  13. Positioning of microtubule organizing centers by cortical pushing and pulling forces

    Science.gov (United States)

    Pavin, Nenad; Laan, Liedewij; Ma, Rui; Dogterom, Marileen; Jülicher, Frank

    2012-10-01

    Positioning of microtubule (MT) organizing centers with respect to the confining geometry of cells depends on pushing and/or pulling forces generated by MTs that interact with the cell cortex (Dogterom et al 2005 Curr. Opin. Cell Biol. 17 67-74). How, in living cells, these forces lead to proper positioning is still largely an open question. Recently, it was shown by in vitro experiments using artificial microchambers that in a square geometry, MT asters center more reliably by a combination of pulling and pushing forces than by pushing forces alone (Laan et al 2012a Cell 148 502-14). These findings were explained by a physical description of aster mechanics that includes slipping of pushing MT ends along chamber boundaries. In this paper, we extend that theoretical work by studying the influence of the shape of the confining geometry on the positioning process. We find that pushing and pulling forces can have centering or off-centering behavior in different geometries. Pushing forces center in a one-dimensional and a square geometry, but lead to off-centering in a circle if slipping is sufficiently pronounced. Pulling forces, however, do not center in a one-dimensional geometry, but improve centering in a circle and a square. In an elongated stadium geometry, positioning along the short axis depends mainly on pulling forces, while positioning along the long axis depends mainly on pushing forces. Our theoretical results suggest that different positioning strategies could be used by different cell types.

  14. Auto-calibration of capacitive MEMS accelerometers based on pull-in voltage

    NARCIS (Netherlands)

    Rocha, L.A.; Dias, R.A.; Cretu, E.; Mol, L.; Wolffenbuttel, R.F.

    2011-01-01

    This paper describes an electro-mechanical auto-calibration technique for use in capacitive MEMS accelerometers. Auto-calibration is achieved using the combined information derived from an initial measurement of the resonance frequency and the measurement of the pull-in voltages during device

  15. Auto-calibration of capacitive MEMS accelerometers based on pull-in voltage

    NARCIS (Netherlands)

    Rocha, L.A.; Dias, R.A.; Cretu, E.; Mol, L.; Wolffenbuttel, R.F.

    2011-01-01

    This paper describes an electro-mechanical auto-calibration technique for use in capacitive MEMS accelerometers. Auto-calibration is achieved using the combined information derived from an initial measurement of the resonance frequency and the measurement of the pull-in voltages during device operat

  16. Forming technology for fine-ceramics in application of traditional ceramic forming. Mechanism of the plasticity of ceramic doughs; Tojiki no seikeiho wo riyoshita fineceramics no seikei gijutsu. Ceramics rendo no kasosei hatsugen kiko

    Energy Technology Data Exchange (ETDEWEB)

    Oda, K.; Shibasaki, Y.; Sano, S.; Banno, T.; Hotta, Y. [National Industrial Research Institute of Nagoya,Nagoya (Japan); Kawai, H.; Ichikawa, Y.; ishida, H. [Inax Corp., Aichi (Japan)

    2000-05-30

    The relationships between plasticity and packing structure of doughs such as Hara-Gairome clay, Georgia kaolin, platy- and spherical alumina were investigated. The plasticity and packing structure were evaluated from measurements by the uni-axial testing method and porosimetry, respectively. The doughs showing good plasticity contained a large number of L-pore (large-sized pore) with the diameter of about several {mu}m. On the contrary, the doughs showing poor plasticity contained a large number of S-pore (small-sized pore) with the diameter of about 0.1 {mu}m, which is approximately equal to the distance between primary particles. Forming additives (methylcellulose, curdlan) much improved the plasticity, which is attributed to the increase in the number of L-pore. The results of the injection test supported the relation between the plasticity and the packing structure. The SEM observation revealed that the alumina-methylcellulose doughs consisted of agglomerates with the size of several tens {mu} m in diameter in a similar manner as the clay doughs, in which the size of L-pore roughly corresponds to that of the space among agglomerates. It is considered that the plasticity originates mainly from the deformation of the agglomerates and/or forming additive gels. When the buffer (agglomerates, gels, L-pore) size ranges from about ten to thousand {mu} m in diameter, the buffer works effectively. While, the buffer is not effective when the size is smaller or they are fractured into small pieces, resulting in a poor plasticity. In conclusion, the proposed mechanism of the plasticity is applicable not only to clay but also to fine-ceramic doughs, and useful to design a new-type of plasticizer and to control the plasticity of ceramic doughs in the forming process. (author)

  17. Plastic Logic quits e-reader market

    Science.gov (United States)

    Perks, Simon

    2012-07-01

    A UK firm spun out from the University of Cambridge that sought to be a world leader in flexible organic electronic circuits and displays has pulled out of the competitive e-reader market as it struggles to find a commercial outlet for its technology. Plastic Logic announced in May that it is to close its development facility in Mountain View, California, with the loss of around 40 jobs.

  18. Plastics Technology.

    Science.gov (United States)

    Barker, Tommy G.

    This curriculum guide is designed to assist junior high schools industrial arts teachers in planning new courses and revising existing courses in plastics technology. Addressed in the individual units of the guide are the following topics: introduction to production technology; history and development of plastics; safety; youth leadership,…

  19. Cortical plasticity and rehabilitation.

    Science.gov (United States)

    Moucha, Raluca; Kilgard, Michael P

    2006-01-01

    The brain is constantly adapting to environmental and endogenous changes (including injury) that occur at every stage of life. The mechanisms that regulate neural plasticity have been refined over millions of years. Motivation and sensory experience directly shape the rewiring that makes learning and neurological recovery possible. Guiding neural reorganization in a manner that facilitates recovery of function is a primary goal of neurological rehabilitation. As the rules that govern neural plasticity become better understood, it will be possible to manipulate the sensory and motor experience of patients to induce specific forms of plasticity. This review summarizes our current knowledge regarding factors that regulate cortical plasticity, illustrates specific forms of reorganization induced by control of each factor, and suggests how to exploit these factors for clinical benefit.

  20. A QSPR for the plasticization efficiency of polyvinylchloride plasticizers.

    Science.gov (United States)

    Chandola, Mridula; Marathe, Sujata

    2008-01-01

    A simple quantitative structure property relationship (QSPR) for correlating the plasticization efficiency of 25 polyvinylchloride (PVC) plasticizers was obtained using molecular modeling. The plasticizers studied were-aromatic esters (phthalate, terephthalate, benzoate, trimellitate), aliphatic esters (adipate, sebacate, azelate), citrates and a phosphate. The low temperature flex point, Tf, of plasticized polyvinylchloride resins was considered as an indicator of plasticization efficiency. Initially, we attempted to predict plasticization efficiency of PVC plasticizers from physical and structural descriptors derived from the plasticizer molecule alone. However, the correlation of these descriptors with Tf was not very good with R=0.78 and r2=0.613. This implied that the selected descriptors were unable to predict all the interactions between PVC and plasticizer. Hence, to account for these interactions, a model containing two polyvinylchloride (PVC) chain segments along with a plasticizer molecule in a simulation box was constructed, using molecular mechanics. A good QSPR equation correlating physical and structural descriptors derived from the model to Tf of the plasticized resins was obtained with R=0.954 and r2=0.909.

  1. Interfacial interactions between plastic particles in plastics flotation.

    Science.gov (United States)

    Wang, Chong-qing; Wang, Hui; Gu, Guo-hua; Fu, Jian-gang; Lin, Qing-quan; Liu, You-nian

    2015-12-01

    Plastics flotation used for recycling of plastic wastes receives increasing attention for its industrial application. In order to study the mechanism of plastics flotation, the interfacial interactions between plastic particles in flotation system were investigated through calculation of Lifshitz-van der Waals (LW) function, Lewis acid-base (AB) Gibbs function, and the extended Derjaguin-Landau-Verwey-Overbeek potential energy profiles. The results showed that van der Waals force between plastic particles is attraction force in flotation system. The large hydrophobic attraction, caused by the AB Gibbs function, is the dominant interparticle force. Wetting agents present significant effects on the interfacial interactions between plastic particles. It is found that adsorption of wetting agents promotes dispersion of plastic particles and decreases the floatability. Pneumatic flotation may improve the recovery and purity of separated plastics through selective adsorption of wetting agents on plastic surface. The relationships between hydrophobic attraction and surface properties were also examined. It is revealed that there exists a three-order polynomial relationship between the AB Gibbs function and Lewis base component. Our finding provides some insights into mechanism of plastics flotation.

  2. 残膜回收机械化技术在和静县的示范推广应用%Demonstration and application of plastic film recovery mechanization technology in Hejing County

    Institute of Scientific and Technical Information of China (English)

    冉亚平

    2013-01-01

      残膜对农业生产和生态环境造成了严重的污染,实施机械化回收残膜技术,减少“白色污染”,提出了残膜回收机在作业中存在的问题及措施建议。%  Plastic film for agricultural production and ecological environment caused serious pollution, the implemen-tation of mechanized recycling plastic film technology to reduce "white pollution", plastic film recycling machine existing problems in the job and measures recommended.

  3. Use of recycled plastics in wood plastic composites - a review.

    Science.gov (United States)

    Kazemi Najafi, Saeed

    2013-09-01

    The use of recycled and waste thermoplastics has been recently considered for producing wood plastic composites (WPCs). They have great potential for WPCs manufacturing according to results of some limited researches. This paper presents a detailed review about some essential properties of waste and recycled plastics, important for WPCs production, and of research published on the effect of recycled plastics on the physical and mechanical properties of WPCs.

  4. Laparoscopic assisted anorectal pull through: Reformed techniques

    Directory of Open Access Journals (Sweden)

    Bhandary Karthik

    2009-01-01

    Full Text Available Aim: To assess the modifications in the technique of laparoscopic assisted anorectal pull through (LAARP practiced at our institute and analyze the post operative outcome and associated complications. Materials and Methods: A retrospective study from January 2001 to May 2009 analyzing LAARP for high anorectal malformations. Results: A total of 40 patients - 34 males and six females, in the age group of two months to six years were studied. Staged procedure was done in 39 patients; one child with recto vestibular fistula underwent single stage procedure. All the patients withstood surgery well. One patient required conversion due to problems in gaining enough length for the distal rectum in a patient with rectovesical fistula so colostomy was closed and re-located at a proximal splenic flexure. The complications were mucosal prolapse (six cases, anal stenosis (three, adhesive obstruction (two, distal rectal necrosis (one, and urethral diverticulum (one. The patients were followed up with clinical evaluation and continence scoring. The progress has been satisfactory and weight-gain is adequate. Conclusions: The advantages of the reformed techniques are as follows: Transcutaneous bladder stitch provides excellent visualization; traction over the fistula helps in dissection of the puborectalis, dividing the fistula without ligation is safe, railroading of Hegar′s dilators over the suction canula creates adequate pull through channel, saves time and makes procedure simpler with reproducible comparable reports.

  5. Static Pull Testing of a New Type of Large Deformation Cable with Constant Resistance

    Directory of Open Access Journals (Sweden)

    Zhigang Tao

    2017-01-01

    Full Text Available A new type of energy-absorbing cable, Constant-Resistance Large Deformation cable (CRLD cable with three different specifications, has been recently developed and tested. An effective cable should occupy the ability of absorbing deformation energy from these geodisaster loads and additionally must be able to yield with the sliding mass movements and plastic deformation over large distances at high displacement rates. The new cable mainly consists of constant-resistance casing tube and frictional cone unit that transfers the load from the slope. When experiencing a static or dynamic load and especially the load exceeding the constant resistance force (CR-F, a static friction force derived from the movement of frictional cone unit in casing tube of CRLD cable, the frictional cone unit will move in the casing tube along the axis and absorb deformation energy, accordingly. In order to assess the performance of three different specified cables in situ, a series of field static pull tests have been performed. The results showed that the first type of CRLD cable can yield 2000 mm displacement while acting 850 kN static pull load, which is superior to that of other two types, analyzing based on the length of the displacement and the level of static pull load.

  6. Perspectives of oil pulling therapy in dental practice

    Directory of Open Access Journals (Sweden)

    T Lakshmi

    2013-01-01

    Full Text Available Oil pulling has its origin in Ayurvedic medicine, is a natural remedy to improve oral health. Its antibacterial properties help to eradicate the bacteria and other debris from adhering to the oral cavity. It reduces the accumulation of plaque, prevents halitosis, cavities, gingivitis. It is used to heal the bleeding gums and mouth ulcers. Oil pulling with sesame oil improves overall health. Other than oral health, oil pulling also helps in reducing asthma, allergies, chronic fatigue, diabetes, migraine headaches and chronic skin problems. It works by detoxifying or cleansing the body. The aim of this article is to highlight the benefits of oil pulling in management of oral health.

  7. 机械产品设计中的造型学研究%Plasticism study in design of mechanical products

    Institute of Scientific and Technical Information of China (English)

    孙文涛

    2011-01-01

    This paper analyzes the application of plasticism in the design of mechanical product designs. By taking the aesthetics rules of product modeling as the starting point, and with mechanical products as the main design object, the study is emphasized on the mechanical product design modeling element characteristics and design method in the mechanical product designs according to its category. Based on the analysis and designs of geometric modeling, technology modeling and bionic modeling, the purpose of the study is how to unify industrial technology and art design to make excellent mechanical product design.%文中分析了机械产品设计中的造型学运用,以产品造型的美学法则为切入点,再以机械产品为主要设计对象,重点分类研究机械产品设计的造型元素特征和设计方法.针对几何造型、工艺造型和仿生造型进行设计分析,研究如何将工业技术和设计艺术结合统一,造就优良的机械产品.

  8. Plastic bronchitis

    National Research Council Canada - National Science Library

    Singhi, Anil Kumar; Vinoth, Bharathi; Kuruvilla, Sarah; Sivakumar, Kothandam

    2015-01-01

    Plastic bronchitis, a rare but serious clinical condition, commonly seen after Fontan surgeries in children, may be a manifestation of suboptimal adaptation to the cavopulmonary circulation with unfavorable hemodynamics...

  9. Using metaheuristic and fuzzy system for the optimization of material pull in a push-pull flow logistics network

    OpenAIRE

    Afshin Mehrsai; Hamid-Reza Karimi; Klaus-Dieter Thoben; Bernd Scholz-Reiter

    2013-01-01

    Alternative material flow strategies in logistics networks have crucial influences on the overall performance of the networks. Material flows can follow push, pull, or hybrid systems. To get the advantages of both push and pull flows in networks, the decoupling-point strategy is used as coordination mean. At this point, material pull has to get optimized concerning customer orders against pushed replenishment-rates. To compensate the ambiguity and uncertainty of both dynamic flows, fuzzy set ...

  10. Using Metaheuristic and Fuzzy System for the Optimization of Material Pull in a Push-Pull Flow Logistics Network

    OpenAIRE

    Afshin Mehrsai; Hamid-Reza Karimi; Klaus-Dieter Thoben; Bernd Scholz-Reiter

    2013-01-01

    Alternative material flow strategies in logistics networks have crucial influences on the overall performance of the networks. Material flows can follow push, pull, or hybrid systems. To get the advantages of both push and pull flows in networks, the decoupling-point strategy is used as coordination mean. At this point, material pull has to get optimized concerning customer orders against pushed replenishment-rates. To compensate the ambiguity and uncertainty of both dynamic flows, fuzzy set ...

  11. Plastic Fishes

    CERN Multimedia

    Trettnak, Wolfgang

    2015-01-01

    In terms of weight, the plastic pollution in the world’s oceans is estimated to be around 300,000 tonnes. This plastic comes from both land-based and ocean-based sources. A lecture at CERN by chemist Wolfgang Trettnak addressed this issue and highlighted the role of art in raising people’s awareness. The slideshow below gives you a taste of the artworks by Wolfgang Trettnak and Margarita Cimadevila.

  12. Plastic Bridge

    Institute of Scientific and Technical Information of China (English)

    履之

    1994-01-01

    Already ubiquitous in homes and cars, plastic is now appearing inbridges. An academic-industrial consortium based at the University ofCalifornia in San Diego is launching a three-year research program aimed atdeveloping the world’s first plastic highway bridge, a 450-foot span madeentirely from glass-,carbon,and polymer-fiber-reinforced composite mate-rials, the stuff of military aircraft. It will cross Interstate 5 to connect thetwo sides of the school’s campus.

  13. Erythropoietin Restores Long-Term Neurocognitive Function Involving Mechanisms of Neuronal Plasticity in a Model of Hyperoxia-Induced Preterm Brain Injury

    Directory of Open Access Journals (Sweden)

    Daniela Hoeber

    2016-01-01

    Full Text Available Cerebral white and grey matter injury is the leading cause of an adverse neurodevelopmental outcome in prematurely born infants. High oxygen concentrations have been shown to contribute to the pathogenesis of neonatal brain damage. Here, we focused on motor-cognitive outcome up to the adolescent and adult age in an experimental model of preterm brain injury. In search of the putative mechanisms of action we evaluated oligodendrocyte degeneration, myelination, and modulation of synaptic plasticity-related molecules. A single dose of erythropoietin (20,000 IU/kg at the onset of hyperoxia (24 hours, 80% oxygen in 6-day-old Wistar rats improved long-lasting neurocognitive development up to the adolescent and adult stage. Analysis of white matter structures revealed a reduction of acute oligodendrocyte degeneration. However, erythropoietin did not influence hypomyelination occurring a few days after injury or long-term microstructural white matter abnormalities detected in adult animals. Erythropoietin administration reverted hyperoxia-induced reduction of neuronal plasticity-related mRNA expression up to four months after injury. Thus, our findings highlight the importance of erythropoietin as a neuroregenerative treatment option in neonatal brain injury, leading to improved memory function in adolescent and adult rats which may be linked to increased neuronal network connectivity.

  14. Erythropoietin Restores Long-Term Neurocognitive Function Involving Mechanisms of Neuronal Plasticity in a Model of Hyperoxia-Induced Preterm Brain Injury.

    Science.gov (United States)

    Hoeber, Daniela; Sifringer, Marco; van de Looij, Yohan; Herz, Josephine; Sizonenko, Stéphane V; Kempe, Karina; Serdar, Meray; Palasz, Joanna; Hadamitzky, Martin; Endesfelder, Stefanie; Fandrey, Joachim; Felderhoff-Müser, Ursula; Bendix, Ivo

    2016-01-01

    Cerebral white and grey matter injury is the leading cause of an adverse neurodevelopmental outcome in prematurely born infants. High oxygen concentrations have been shown to contribute to the pathogenesis of neonatal brain damage. Here, we focused on motor-cognitive outcome up to the adolescent and adult age in an experimental model of preterm brain injury. In search of the putative mechanisms of action we evaluated oligodendrocyte degeneration, myelination, and modulation of synaptic plasticity-related molecules. A single dose of erythropoietin (20,000 IU/kg) at the onset of hyperoxia (24 hours, 80% oxygen) in 6-day-old Wistar rats improved long-lasting neurocognitive development up to the adolescent and adult stage. Analysis of white matter structures revealed a reduction of acute oligodendrocyte degeneration. However, erythropoietin did not influence hypomyelination occurring a few days after injury or long-term microstructural white matter abnormalities detected in adult animals. Erythropoietin administration reverted hyperoxia-induced reduction of neuronal plasticity-related mRNA expression up to four months after injury. Thus, our findings highlight the importance of erythropoietin as a neuroregenerative treatment option in neonatal brain injury, leading to improved memory function in adolescent and adult rats which may be linked to increased neuronal network connectivity.

  15. Optical Micro- and Nanofiber Pulling Rig

    CERN Document Server

    Ward, J M; Le, Vu H; Chormaic, S Nic

    2014-01-01

    We review the method of producing adiabatic optical micro- and nanofibers using a hydrogen/oxygen flame brushing technique. The flame is scanned along the fiber, which is being simultaneously stretched by two translation stages. The tapered fiber fabrication is reproducible and yields highly adiabatic tapers with either exponential or linear profiles. Details regarding the setup of the flame brushing rig and the various parameters used are presented. Information available from the literature is compiled and further details that are necessary to have a functioning pulling rig are included. This should enable the reader to fabricate various taper profiles, while achieving adiabatic transmission of ~ 99% for fundamental mode propagation. Using this rig, transmissions greater than 90% for higher order modes in an optical nanofiber have been obtained.

  16. GREEN PLASTIC: A NEW PLASTIC FOR PACKAGING

    OpenAIRE

    Mr. Pankaj Kumar*, Sonia

    2016-01-01

    This paper gives a brief idea about a new type of plastic called as bio-plastic or green plastic. Plastic is used as a packaging material for various products, but this plastic is made up of non renewable raw materials. There are various disadvantages of using conventional plastic like littering, CO2 production, non-degradable in nature etc. To overcome these problems a new type of plastic is discovered called bio-plastic or green plastic. Bio-plastic is made from renewable resources and also...

  17. Ion conduction mechanism in non-aqueous polymer electrolytes based on oxalic acid: Effect of plasticizer and polymer

    Energy Technology Data Exchange (ETDEWEB)

    Missan, Harinder Pal Singh; Chu, P.P. [Department of Chemistry, National Central University, Chungli 32001 (Taiwan); Sekhon, S.S. [Department of Applied Physics, Guru Nanak Dev University, Amritsar, Punjab 143005 (India)

    2006-08-25

    Non-aqueous proton-conducting polymer electrolytes in the film form are synthesized through the complexation of oxalic acid (OA) and polyvinylidenefluoride-co-hexafluoro propylene (PVdF-HFP). Interestingly, the addition of a small amount of the basic component dimethylacetamide (DMA) gives rise to a three-order increase in conductivity. The value is found to depend on the concentrations of the weak acid and DMA in the electrolytes. A maximum conductivity of 0.12x10{sup -3}Scm{sup -1} has been achieved at ambient temperature for electrolytes containing 40wt.% OA with DMA. The observed increase in conductivity is considered to be due to interactions taking place between the high dielectric polymer media, the acid and the basic plasticizer. These interactions are confirmed from fourier transform infra red (FTIR) studies and supported by differential scanning calorimetry (DSC) measurements. Apart from providing acid-base interaction, the base DMA also improves the surface morphology and reduces the pore volume, both of which help to retain the acid-base complex within the membrane. (author)

  18. Migration kinetics and mechanisms of plasticizers, stabilizers at interfaces of NEPE propellant/HTPB liner/EDPM insulation.

    Science.gov (United States)

    Huang, Zhi-ping; Nie, Hai-ying; Zhang, Yuan-yuan; Tan, Li-min; Yin, Hua-li; Ma, Xin-gang

    2012-08-30

    Migration appeared in the interfaces of nitrate ester plasticized polyether (NEPE) based propellant/hydroxyl-terminated polybutadiene (HTPB) based liner/ethylene propylene terpolymer (EPDM) based insulation was studied by aging at different temperatures. The migration components were extracted with solvent and determined by high performance liquid chromatography (HPLC). The migration occurred within 1mm to the interfaces, and the apparent migration activation energy (Ea) of nitroglycerin (NG), 1,2,4-butanetriol trinitrate (BTTN) and a kind of aniline stabilizer AD in propellant, liner and insulation was calculated respectively on the basis of HPLC data. The Ea values were among 15 and 50 kJ/mol, which were much less than chemical energy, and almost the same as hydrogen bond energy. The average diffusion coefficients were in the range of 10(-19)m(2)s(-1) to 10(-16)m(2)s(-1). It seemed the faster the migration rates, the smaller the apparent migration activation energy, the larger the diffusion coefficient and the less the amount of migration. It could be explained that the migration rate and energy were affected by the molecular volume of a mobile component and its diffusion property, and the amount of migration was resulted from the molecular polarity comparability of a mobile component to the based material.

  19. Coupled hydro-mechanical analysis of slope under rainfall using modified elasto-plastic model for unsaturated soils

    Institute of Scientific and Technical Information of China (English)

    WANG Liu-jiang; LIU Si-hong; FU Zhong-zhi; LI Zhuo

    2015-01-01

    Two modifications for the basic Barcelona model (BBM) are present. One is the replacement of the net stress by the average skeleton stress in unsaturated soil modeling, and the other is the adoption of an expression for the load-collapse (LC) yield surface that can match flexibly the normal compression lines at different suctions. The predictions of the modified BBM for the controlled-suction triaxial test on the unsaturated compacted clay are presented and compared with the experimental results. A good agreement between the predicted and experimental results demonstrates the reasonability of the modified BBM. On this basis, the coupled processes of groundwater flow and soil deformation in a homogeneous soil slope under a long heavy rainfall are simulated with the proposed elasto-plastic model. The numerical results reveal that the failure of a slope under rainfall infiltration is due to both the reduction of soil suction and the significant rise in groundwater table. The evolution of the displacements is greatly related to the change of suction. The maximum collapse deformation happens near the surface of slope where infiltrated rainwater can quickly reach. The results may provide a helpful reference for hazard assessment and control of rainfall-induced landslides.

  20. Meristem maintenance, auxin, jasmonic and abscisic acid pathways as a mechanism for phenotypic plasticity in Antirrhinum majus

    Science.gov (United States)

    Weiss, Julia; Alcantud-Rodriguez, Raquel; Toksöz, Tugba; Egea-Cortines, Marcos

    2016-01-01

    Plants grow under climatic changing conditions that cause modifications in vegetative and reproductive development. The degree of changes in organ development i.e. its phenotypic plasticity seems to be determined by the organ identity and the type of environmental cue. We used intraspecific competition and found that Antirrhinum majus behaves as a decoupled species for lateral organ size and number. Crowding causes decreases in leaf size and increased leaf number whereas floral size is robust and floral number is reduced. Genes involved in shoot apical meristem maintenance like ROA and HIRZ, cell cycle (CYCD3a; CYCD3b, HISTONE H4) or organ polarity (GRAM) were not significantly downregulated under crowding conditions. A transcriptomic analysis of inflorescence meristems showed Gene Ontology enriched pathways upregulated including Jasmonic and Abscisic acid synthesis and or signalling. Genes involved in auxin synthesis such as AmTAR2 and signalling AmANT were not affected by crowding. In contrast, AmJAZ1, AmMYB21, AmOPCL1 and AmABA2 were significantly upregulated. Our work provides a mechanistic working hypothesis where a robust SAM and stable auxin signalling enables a homogeneous floral size while changes in JA and ABA signalling maybe responsible for the decreased leaf size and floral number.

  1. Modification of carbon fabrics by radio-frequency capacitive discharge at low pressure to regulate mechanical properties of carbon fiber reinforced plastics based on it

    Science.gov (United States)

    Garifullin, A. R.; Krasina, I. V.; Skidchenko, E. A.; Shaekhov, M. F.; Tikhonova, N. V.

    2017-01-01

    To increase the values of mechanical properties of carbon fiber (CF) composite materials used in sports equipment production the method of radio-frequency capacitive (RFC) low-pressure plasma treatment in air was proposed. Previously it was found that this type of modification allows to effectively regulate the surface properties of fibers of different nature. This treatment method differs from the traditional ones by efficiency and environmental friendliness as it does not require the use of aggressive, environmentally hazardous chemicals. In this paper it was established that RFC low-pressure air plasma treatment of carbon fabrics enhances the interlaminar shear strength (ILSS) of carbon fiber reinforced plastic (CFRP). As a result of experimental studies of CF by Fourier Transform Infrared (FTIR) spectroscopy method it was proved that after radio-frequency capacitive plasma treatment at low pressure in air the oxygen-containing functional groups is grafted on the surface. These groups improve adhesion at the interface “matrix-fiber”.

  2. Mechanisms of plastic instability and fracture of compressed and tensile tested Mg-Li alloys investigated using the acoustic emission method

    Directory of Open Access Journals (Sweden)

    A. Pawełek

    2016-01-01

    Full Text Available The results of the investigation of both mechanical and acoustic emission (AE behaviors of Mg4Li5Al alloy subjected to compression and tensile tests at room temperature are compared with the test results obtained using the same alloy and loading scheme but at elevated temperatures. The main aim of the paper is to investigate, to determine and to explain the possible influence of factors related with enhanced internal stresses such as: segregation of precipitates along grain boundaries or solute atoms along dislocations (Cottrell atmospheres or dislocation pile-ups at grain boundaries which create very high stress concentration leading to fracture. The results show that the plastic instabilities are related to the Portevin–Le Châtelier phenomenon (PL effect and they are correlated with the generation of AE peaks. The fractography of breaking samples was analyzed on the basis of light (optical, TEM and SEM images.

  3. THE EFFECT OF PLASTICIZER CONTENT AND DISACCHARIDE TYPE ON THE MECHANICAL, BARRIER AND PHYSICAL PROPERTIES OF BOVINE GELATIN-BASED FILMS

    Directory of Open Access Journals (Sweden)

    PEDRO GUERRERO1

    2014-06-01

    Full Text Available Gelatins are regarded as alternative raw materials to prepare films for food packaging. However, the improvement of their mechanical and water barrier properties is necessary in order to obtain useful materials in service conditions. To improve these functional properties, two strategies have been carried out in this work. First, glycerol was added as plasticizer to increase the flexibility of the films. Second, lactose or sucrose was added to react with gelatin and increase water resistance of gelatin-based films. Commercial gelatin, glycerol and lactose or sucrose were employed in this work and processing of the films was carried out by solution casting. All gelatin films obtained were transparent and flexible. Moreover, the hydrophobic character of the films was increased and the film solubility was decreased by the addition of glycerol and disaccharides. As was observed via FTIR, the changes were due to the interactions between gelatin and glycerol and Maillard reaction between gelatin and disaccharides.

  4. Analytical Model for Hook Anchor Pull-Out

    DEFF Research Database (Denmark)

    Brincker, Rune; Ulfkjær, J. P.; Adamsen, P.

    1995-01-01

    A simple analytical model for the pull-out of a hook anchor is presented. The model is based on a simplified version of the fictitious crack model. It is assume that the fracture process is the pull-off of a cone shaped concrete part, simplifying the problem by assuming pure rigid body motions...

  5. Analytical Model for Hook Anchor Pull-out

    DEFF Research Database (Denmark)

    Brincker, Rune; Ulfkjær, J. P.; Adamsen, P.

    A simple analytical model for the pull-out of a hook anchor is presented. The model is based on a simplified version of the fictitious crack model. It is assumed that the fracture process is the pull-off of a cone shaped concrete part, simplifying the problem by assuming pure rigid body motions...

  6. Workload balancing capability of pull systems in MTO production

    NARCIS (Netherlands)

    Germs, R.; Riezebos, J.

    2010-01-01

    Pull systems focusing on throughput time control and applicable in situations with high variety and customisation are scarce. This paper compares three unit-based pull systems that can cope with such situations: POLCA, CONWIP and m-CONWIP. These systems control the shop floor throughput time of orde

  7. Heat-and-pull rig for fiber taper fabrication

    NARCIS (Netherlands)

    Ward, Jonathan M.; O'Shea, Danny G.; Shortt, Brian J.; Morrissey, Michael J.; Deasy, Kieran; Chormaic, Sile G. Nic

    2006-01-01

    We describe a reproducible method of fabricating adiabatic tapers with 3-4 mu m diameter. The method is based on a heat-and-pull rig, whereby a CO(2) laser is continuously scanned across a length of fiber that is being pulled synchronously. Our system relies on a CO(2) mirror mounted on a geared ste

  8. Designing pull production control systems : Customization and robustness

    NARCIS (Netherlands)

    Gaury, E.G.A.

    2000-01-01

    In this dissertation we address the issues of selecting and configuring pull production control systems for single-product flowlines. We start with a review of pull systems in the literature, yielding a new classification. Then we propose a novel selection procedure based on a generic system that we

  9. Workload balancing capability of pull systems in MTO production

    NARCIS (Netherlands)

    Germs, R.; Riezebos, J.

    2010-01-01

    Pull systems focusing on throughput time control and applicable in situations with high variety and customisation are scarce. This paper compares three unit-based pull systems that can cope with such situations: POLCA, CONWIP and m-CONWIP. These systems control the shop floor throughput time of

  10. On the Push-Pull Mobile Learning of Electric Welding

    Science.gov (United States)

    Chung, Chih-Chao; Dzan, Wei-Yuan; Cheng, Yuh-Ming; Lou, Shi-Jer

    2017-01-01

    This study aims to explore the learning effects and attitudes of students in the course electric welding practice in a university of science and technology to which the push-pull technology-based mobile learning system is applied. In this study, the push-pull technology is adopted to establish a mobile learning system and develop the Push-pull…

  11. Discrete dislocation plasticity

    NARCIS (Netherlands)

    van der Giessen, E.; Finel, A; Maziere, D; Veron, M

    2003-01-01

    Conventional continuum mechanics models of inelastic deformation processes axe size scale independent. In contrast, there is considerable experimental evidence that plastic flow in crystalline materials is size dependent over length scales of the order of tens of microns and smaller. At present ther

  12. Casing pull tests for directionally drilled environmental wells

    Energy Technology Data Exchange (ETDEWEB)

    Staller, G.E.; Wemple, R.P. [Sandia National Labs., Albuquerque, NM (United States); Layne, R.R. [Charles Machine Works, Inc., Perry, OK (United States)

    1994-11-01

    A series of tests to evaluate several types of environmental well casings have been conducted by Sandia National Laboratories (SNL) and it`s industrial partner, The Charles Machine Works, Inc. (CMW). A test bed was constructed at the CMW test range to model a typical shallow, horizontal, directionally drilled wellbore. Four different types of casings were pulled through this test bed. The loads required to pull the casings through the test bed and the condition of the casing material were documented during the pulling operations. An additional test was conducted to make a comparison of test bed vs actual wellbore casing pull loads. A directionally drilled well was emplaced by CMW to closely match the test bed. An instrumented casing was installed in the well and the pull loads recorded. The completed tests are reviewed and the results reported.

  13. Thermoplastic Starch Prepared with Different Plasticizers:Relation between Degree of Plasticization and Properties

    Institute of Scientific and Technical Information of China (English)

    ZUO Yingfeng; GU Jiyou; TAN Haiyan; ZHANG Yanhua

    2015-01-01

    Ethylene glycol, glycerol, sorbitol, formamide, and urea were used as plasticizers for the preparation of thermoplastic starch (TPS) from corn starch. The properties of TPS were tested by analysis method. The results showed that TPSs were more highly plasticized with amines than alcohols. For the same type of plasticizer, the degree of plasticization decreased as the molecular weight of plasticizer increased. The relationship between plasticization degree and TPS properties was characterized and described by mechanical properties and water absorption. The experimental results showed that when the degree of plasticization increased, the tensile strength decreased and the elongation at breakage and water absorption increased.

  14. Elastic-brittle-plastic mechanical model for rock with confining pressure%考虑围压影响的岩石弹脆塑力学模型

    Institute of Scientific and Technical Information of China (English)

    张春会; 徐晓攀; 王锡朝; 赵全胜

    2015-01-01

    To model effects of confining pressure on the post-peak mechanical properties for rock such as the degradation of strength and modulus, and dilatancy, the deformation process is simplified into three phases including linear-elastic, brittle degradation and perfect plasticity. Degradation index and dilatancy index are employed to reflect the effects of confining pressure on the peak-post mechanical properties for rock in this paper, and an elastic-brittle-plastic model with confining pressure is presented. Based on the transformation relationship between Hoek-Brown failure criterion and Mohr-Column fail-ure criterion, how to obtain the calculation parameters of the peak-post mechanical model in this paper is presented. The Fish function method within FLAC is adopted to realize the elastic-brittle-plastic me-chanical model model in this paper. In numerical case study the peak-post mechanical properties of rock under varied confining pressure including the degradation of strength and modulus, and dilatancy are modelled. The results show that the model can perfectly describe the deformation process and the effects of confining pressure on peak-post mechanical properties of rock.%为模拟围压对岩石峰后强度、模量退化和剪胀的影响,将岩石的变形过程简化为线弹性变形、脆性跌落和理想塑性3个阶段,利用退化指数和扩容指数描述围压对岩石峰后强度、模量退化和剪胀的影响,建立了考虑围压影响的岩石弹脆塑力学模型。通过Hoek-Brown和Mohr-Column准则之间参数的转换关系,给出了模型峰后力学参数的确定方法。在 FLAC 软件下,利用 Fish函数方法实现了建立的弹脆塑性力学模型。在数值算例中,利用本文模型分析了不同围压下岩石的峰后力学特性劣化和剪胀扩容特征,结果表明本文模型不仅能较好地模拟岩石峰前、峰后全程变形发展过程,而且能较好地考虑围压对岩石峰后力学特性的影响。

  15. Effectiveness of organoclays as compatibilizers for multiphase polymer blends - A sustainable route for the mechanical recycling of co-mingled plastics

    Science.gov (United States)

    Causa, Andrea; Mistretta, Maria Chiara; Acierno, Domenico; Filippone, Giovanni

    2014-05-01

    We prepare and characterize multiphase systems in which small amounts of recycled polymer, namely polyethylene terephtalate (PET) ground from waste bottles, are dispersed in a co-continuous blend of high-density polyethylene (HDPE) and polypropylene (PP). Some of such ternary systems are also filled with plate-like clay nanoparticles with different polarities, in order to assess their influence on the morphology and mechanical behaviour of the blends. On the basis of preliminary wettability considerations and inspections by means of scanning electron microscopy (SEM), the PET is found to preferentially locate within the PP phase. Such a positioning is desirable in order to minimize the presence of multiple interfaces, which is one of the major issues in the recycling process of co-mingles plastics. By means of SEM, dynamic-mechanical analysis and tensile tests we show that the addition of a filler with low polarity, which locates at the PET-matrix interface, has relevant implications on the structure and properties of the ternary systems, refining their morphology at the micro-scale and enhancing their high-temperature mechanical behaviour.

  16. Effectiveness of organoclays as compatibilizers for multiphase polymer blends – A sustainable route for the mechanical recycling of co-mingled plastics

    Energy Technology Data Exchange (ETDEWEB)

    Causa, Andrea; Acierno, Domenico; Filippone, Giovanni [Dipartimento di Ingegneria Chimica, dei Materiali e della Produzione Industriale, Università di Napoli Federico II, Piazzale V. Tecchio, 80, 80125 Napoli (Italy); Mistretta, Maria Chiara [Dipartimento di Ingegneria Civile, Ambientale, Aerospaziale, dei Materiali, Università di Palermo, Viale delle Scienze, ed. 6, 90128 Palermo (Italy)

    2014-05-15

    We prepare and characterize multiphase systems in which small amounts of recycled polymer, namely polyethylene terephtalate (PET) ground from waste bottles, are dispersed in a co-continuous blend of high-density polyethylene (HDPE) and polypropylene (PP). Some of such ternary systems are also filled with plate-like clay nanoparticles with different polarities, in order to assess their influence on the morphology and mechanical behaviour of the blends. On the basis of preliminary wettability considerations and inspections by means of scanning electron microscopy (SEM), the PET is found to preferentially locate within the PP phase. Such a positioning is desirable in order to minimize the presence of multiple interfaces, which is one of the major issues in the recycling process of co-mingles plastics. By means of SEM, dynamic-mechanical analysis and tensile tests we show that the addition of a filler with low polarity, which locates at the PET-matrix interface, has relevant implications on the structure and properties of the ternary systems, refining their morphology at the micro-scale and enhancing their high-temperature mechanical behaviour.

  17. Application of a Microstructure-Based ISV Plasticity Damage Model to Study Penetration Mechanics of Metals and Validation through Penetration Study of Aluminum

    Directory of Open Access Journals (Sweden)

    Yangqing Dou

    2017-01-01

    Full Text Available A developed microstructure-based internal state variable (ISV plasticity damage model is for the first time used for simulating penetration mechanics of aluminum to find out its penetration properties. The ISV damage model tries to explain the interplay between physics at different length scales that governs the failure and damage mechanisms of materials by linking the macroscopic failure and damage behavior of the materials with their micromechanical performance, such as void nucleation, growth, and coalescence. Within the continuum modeling framework, microstructural features of materials are represented using a set of ISVs, and rate equations are employed to depict damage history and evolution of the materials. For experimental calibration of this damage model, compression, tension, and torsion straining conditions are considered to distinguish damage evolutions under different stress states. To demonstrate the reliability of the presented ISV model, that model is applied for studying penetration mechanics of aluminum and the numerical results are validated by comparing with simulation results yielded from the Johnson-Cook model as well as analytical results calculated from an existing theoretical model.

  18. Enhancement of the Mechanical Properties of Basalt Fiber-Wood-Plastic Composites via Maleic Anhydride Grafted High-Density Polyethylene (MAPE Addition

    Directory of Open Access Journals (Sweden)

    Yun Lu

    2013-06-01

    Full Text Available This study investigated the mechanisms, using microscopy and strength testing approaches, by which the addition of maleic anhydride grafted high-density polyethylene (MAPE enhances the mechanical properties of basalt fiber-wood-plastic composites (BF-WPCs. The maximum values of the specific tensile and flexural strengths are achieved at a MAPE content of 5%–8%. The elongation increases rapidly at first and then continues slowly. The nearly complete integration of the wood fiber with the high-density polyethylene upon MAPE addition to WPC is examined, and two models of interfacial behavior are proposed. We examined the physical significance of both interfacial models and their ability to accurately describe the effects of MAPE addition. The mechanism of formation of the Model I interface and the integrated matrix is outlined based on the chemical reactions that may occur between the various components as a result of hydrogen bond formation or based on the principle of compatibility, resulting from similar polarity. The Model I fracture occurred on the outer surface of the interfacial layer, visually demonstrating the compatibilization effect of MAPE addition.

  19. Low temperature creep plasticity

    Directory of Open Access Journals (Sweden)

    Michael E. Kassner

    2014-07-01

    Full Text Available The creep behavior of crystalline materials at low temperatures (T < 0.3Tm is discussed. In particular, the phenomenological relationships that describe primary creep are reviewed and analyzed. A discussion of the activation energy for creep at T < 0.3Tm is discussed in terms of the context of higher temperature activation energy. The basic mechanism(s of low temperature creep plasticity are discussed, as well.

  20. Plastic Bronchitis.

    Science.gov (United States)

    Rubin, Bruce K

    2016-09-01

    Plastic bronchitis is an uncommon and probably underrecognized disorder, diagnosed by the expectoration or bronchoscopic removal of firm, cohesive, branching casts. It should not be confused with purulent mucous plugging of the airway as seen in patients with cystic fibrosis or bronchiectasis. Few medications have been shown to be effective and some are now recognized as potentially harmful. Current research directions in plastic bronchitis research include understanding the genetics of lymphatic development and maldevelopment, determining how abnormal lymphatic malformations contribute to cast formation, and developing new treatments. Copyright © 2016 Elsevier Inc. All rights reserved.

  1. The dependence on pressure of the plastic flow of rocksalt in the temperature range 25-250° C: implications for the rate controlling mechanism

    Science.gov (United States)

    Muhammad, Nawaz; Spiers, Chris; De Bresser, Hans; Peach, Colin

    2014-05-01

    Despite the large body of data that already exists, the question what microphysical mechanisms govern plastic flow of natural rocksalt at in situ conditions has not yet been answered to full satisfaction. In particular, the exact mechanism controlling dislocation motion at relatively low temperature is still insufficiently understood. As a result, uncertainties exist regarding the appropriate mechanism-based flow-law for low temperature, hampering reliable extrapolation of lab creep data to in situ strain rates. Such extrapolation is required for the modelling of the long term behaviour of salt for geomechanical purposes (e.g. subsidence prognosis). Several dislocation models have been proposed to control plastic flow of rocksalt, such as dislocation climb, cross-slip and (impurity-controlled) glide, but none of these have been rigorously verified. One way to test which model is appropriate is by investigating the pressure dependence of flow of rocksalt. Dislocation glide is expected to be hardly affected by pressure, cross slip (controlled by constriction of partial dislocations) will become easier with increasing pressure, and dislocation climb will become more difficult. We performed conventional axi-symmetric compression tests on synthetic polycrystalline salt samples with an average grain size of 300 μm. The samples were dry, in order to eliminate the possible influence of pressure solution creep. The experiments were carried out at temperatures in the range 25-250° C, i.e. 0.28-0.48Tm, and at pressure ranging 50-600 MPa, which is a range not previously covered for polycrystalline rocksalt. Argon gas was used as the pressure medium. With confining pressure increasing from 50 to 600 MPa, the rocksalt remained of the same strength at RT, but became about 60% stronger at 125oC and about 80% stronger at 250oC at strain rate 10-6 s-1 (at 15% strain). Using a conventional (Dorn-type) power law to describe the mechanical behaviour, stress exponents (n) were found

  2. Adult myelination:wrapping up neuronal plasticity

    Institute of Scientific and Technical Information of China (English)

    Megan ORourke; Robert Gasperini; Kaylene M.Young

    2014-01-01

    In this review, we outline the major neural plasticity mechanisms that have been identiifed in the adult central nervous system (CNS), and offer a perspective on how they regulate CNS function. In particular we examine how myelin plasticity can operate alongside neurogenesis and synaptic plasticity to inlfuence information processing and transfer in the mature CNS.

  3. Mixed plastics recycling technology

    CERN Document Server

    Hegberg, Bruce

    1995-01-01

    Presents an overview of mixed plastics recycling technology. In addition, it characterizes mixed plastics wastes and describes collection methods, costs, and markets for reprocessed plastics products.

  4. An engineering approach to dry friction behaviour of numerous engineering plastics with respect to the mechanical properties

    Directory of Open Access Journals (Sweden)

    G. Kalacska

    2013-02-01

    Full Text Available Twenty-one different commercial-grade engineering polymers, including virgin and composite types, were selected for testing, based on mechanical engineering practices. Three groups were formed according to typical applications: 1 Sliding machine element materials; 2 Mechanically load-carrying machine element materials that are often subjected to friction and wear effects; and 3 Additional two amorphous materials used as chemically resistant materials that have rare sliding load properties. The friction running-in state was tested using a dynamic pin-on-plate test rig. During steady-state friction tests, two pv regimes (0.8 and 2 MPa"ms–1 were analysed by a pin-on-disc test system. Based on the measured forces on ground structural steel, surface friction coefficients were calculated and analysed with respect to the mechanical effects of friction. The friction results were evaluated by the measured mechanical properties: yield stress, Shore D hardness, Young’s modulus and elongation at the break. The three material groups exhibited different trends in friction with respect to changing mechanical properties. Linear (with varying positive and negative slopes, logarithmic and exponential relationships were observed, and occasionally there were no effects observed. At steady-state friction, the elongation at the break had less effect on the friction coefficients. The dynamic sliding model, which correlates better to real machine element applications, showed that increasing hardness and yield stress decreases friction. During steady-state friction, an increase in pv regime often changed the sign of the linear relationship between the material property and the friction, which agrees with the frictional theory of polymer/steel sliding pairs.

  5. Plastic fish

    CERN Multimedia

    Antonella Del Rosso

    2015-01-01

    In terms of weight, the plastic pollution in the world’s oceans is estimated to be around 300,000 tonnes. This plastic comes from both land-based and ocean-based sources. A lecture at CERN by chemist Wolfgang Trettnak addressed this issue and highlighted the role of art in raising people’s awareness.   Artwork by Wolfgang Trettnak. Packaging materials, consumer goods (shoes, kids’ toys, etc.), leftovers from fishing and aquaculture activities… our oceans and beaches are full of plastic litter. Most of the debris from beaches is plastic bottles. “PET bottles have high durability and stability,” explains Wolfgang Trettnak, a chemist by education and artist from Austria, who gave a lecture on this topic organised by the Staff Association at CERN on 26 May. “PET degrades very slowly and the estimated lifetime of a bottle is 450 years.” In addition to the beach litter accumulated from human use, rivers bring several ki...

  6. Plastic zonnecellen

    NARCIS (Netherlands)

    Roggen, Marjolein

    1998-01-01

    De zonnecel van de toekomst is in de maak. Onderzoekers van uiteenlopend pluimage werken eendrachtig aan een plastic zonnecel. De basis is technisch gelegd met een optimale, door invallend licht veroorzaakte, vorming van ladingdragers binnen een composiet van polymeren en buckyballs. Nu is het zaak

  7. WE(EE) Demand - Recycled Plastic

    OpenAIRE

    Førby, Marie; Pedersen, Jakob; Borgen, Nanna; Hansen, Rasmus Nør

    2015-01-01

    Plastic management – from production to waste – has massive negative effects on the environment of which one of the main problems are the CO2 released from the fossil fuels. The focus of this paper lies on the possibilities of increasing demand for recycled plastics from electric and electronic equipment (WEEE-plastic) through modifications in the Danish waste systems. Due to the chemical build of plastic, it is not possible to reprocess it with mechanical recycle technologies while keeping t...

  8. Biomechanical study of the final push-pull in archery.

    Science.gov (United States)

    Leroyer, P; Van Hoecke, J; Helal, J N

    1993-02-01

    The purpose of this study was to analyse archery performance among eight archers of different abilities by means of displacement pull-hand measurements during the final push-pull phase of the shoot. The archers showed an irregular displacement negatively related to their technical level. Displacement signal analysis showed high power levels in both the 0-5 Hz and 8-12 Hz ranges. The latter peak corresponds to electromyographic tremor observed during a prolonged push-pull effort. The results are discussed in relation to some potentially helpful training procedures such as biofeedback and strength conditioning.

  9. 波形齿夹具张拉CFRP带的力学性能试验研究及夹具体系设计%EXPERIMENTAL RESEARCH ON MECHANICAL PROPERTY OF PULLING CFRP BELT WITH WAVE-SHAPED-GEAR CLAMP AND DESIGN OF CLAMP SYSTEM

    Institute of Scientific and Technical Information of China (English)

    陈小英; 李唐宁; 黄音; 陈明政

    2012-01-01

    Based on the analyses of the stress of a pulling CFRP belt with a wave-shaped-gear (WSG) clamping, this paper theoretically proposes the modification in the theoretical elongation of the CFRP belt and the computation of the axial and shear forces in the screw bolt of the WSG clamping. Aimed at those three problems, two types of experiments are designed to study the WSG clamping for a pulling CFRP belt. One type test is only pulling a CFRP belt on a steel beam dado; another type test is a reinforced concrete T-beams strengthened with a pulling CFRP belt. The results of tests indicate that the reduction factor can be used to evaluate the modification of theoretical elongation in a CFRP belt under pulling with a WSG clamping; when the CFRP belt is pulled with a WSG clamping, the ratio of the axial force of the screw bolt to the pulling force of the CFRP belt is fixed, which can be used to monitor the pulling force of the CFRP belt in existing strengthening methods. The design shear force and design axial force of the single screw bolt are proposed in this paper as well.%对波形齿夹具在张拉CFRP带时的受力状态的分析,理论上提出了CFRP带理论伸长值的修正以及波形齿夹具配套螺杆的轴力、剪力验算。针对这3个方面的问题,共设计了两大类试验来研究张拉CFRP带时的波形齿夹具:一类是钢梁台座上仅张拉CFRP带的试验;另一类是张拉CFRP带加固钢筋混凝土T形梁的试验。试验表明:以折减率来考虑波形齿夹具张拉CFRP带的理论伸长值的修正;在张拉时螺杆轴力与CFRP带的预拉力值呈定值比例,在工程实际中可以通过螺杆轴力值对CFRP带预拉力值的监控。并提出了单个螺杆的轴力值与剪力值的计算公式。

  10. Plastic deformation to enhance plasma-assisted nitriding: On surface contamination induced by Surface Mechanical Attrition Treatment

    Science.gov (United States)

    Samih, Youssef; Novelli, Marc; Thiriet, Tony; Bolle, Bernard; Allain, Nathalie; Fundenberger, Jean-Jacques; Marcos, Grégory; Czerwiec, Thierry; Grosdidier, Thierry

    2014-08-01

    The Surface Mechanical Attrition Treatment is a recent technique leading to the formation of nanostructured layers by the repeated action of impacting balls. While several communications have revealed possible contamination of the SMATed surfaces, the nature of this surface contamination was analyzed in the present contribution for the treatment of an AISI 316L stainless steel. It is shown, by a combination of Transmission Electron Microscopy and Glow Discharge - Optical Emission Spectrometry, that the surface was alloyed with Ti, Al and V coming from the sonotrode that is used to move the balls as well as Zr coming from the zirshot® balls themselves.

  11. Progress in neural plasticity

    Institute of Scientific and Technical Information of China (English)

    POO; Mu-Ming

    2010-01-01

    One of the properties of the nervous system is the use-dependent plasticity of neural circuits.The structure and function of neural circuits are susceptible to changes induced by prior neuronal activity,as reflected by short-and long-term modifications of synaptic efficacy and neuronal excitability.Regarded as the most attractive cellular mechanism underlying higher cognitive functions such as learning and memory,activity-dependent synaptic plasticity has been in the spotlight of modern neuroscience since 1973 when activity-induced long-term potentiation(LTP) of hippocampal synapses was first discovered.Over the last 10 years,Chinese neuroscientists have made notable contributions to the study of the cellular and molecular mechanisms of synaptic plasticity,as well as of the plasticity beyond synapses,including activity-dependent changes in intrinsic neuronal excitability,dendritic integration functions,neuron-glia signaling,and neural network activity.This work highlight some of these significant findings.

  12. Plastic Surgery Statistics

    Science.gov (United States)

    ... PSN PSEN GRAFT Contact Us News Plastic Surgery Statistics Plastic surgery procedural statistics from the American Society of Plastic Surgeons. Statistics by Year Print 2016 Plastic Surgery Statistics 2015 ...

  13. Brain mechanisms for reading in children with and without dyslexia: a review of studies of normal development and plasticity.

    Science.gov (United States)

    Papanicolaou, Andrew C; Simos, Panagiotis G; Breier, Joshua I; Fletcher, Jack M; Foorman, Barbara R; Francis, David; Castillo, Eduardo M; Davis, Robert N

    2003-01-01

    In this article we review our experience with the application of magnetic source imaging (MSI), the newest of the functional imaging methods, to the study of brain mechanisms for reading among children who read normally and among those with dyslexia. After giving a general description of MSI, we present evidence for reliable and valid maps of the brain mechanism for aural language comprehension as well as for reading. Next, we present data from 39 normal readers, 40 children with dyslexia, and 30 younger children at risk for developing a reading disability. These data show different brain activation maps for individual children with dyslexia and children at risk for dyslexia than for those of normal readers. Such differences most likely reflect aberrant brain organization underlying phonological decoding, rather than variables such as degree of effort. Finally, we present preliminary data demonstrating that the aberrant activation profiles of children with dyslexia may return to normative patterns as a result of a successful reading intervention that enables children to improve phonological decoding skills.

  14. Effects of drying temperature and relative humidity on the mechanical properties of amaranth flour films plasticized with glycerol

    Directory of Open Access Journals (Sweden)

    D. Tapia-Blácido

    2005-06-01

    Full Text Available Biofilms are made of biopolymers. In the casting technique, biofilms are obtained by the drying of a polymer suspension in the final stage of processing. The aim of the present paper was to analyze the effect of this drying process on the mechanical properties of films produced with amaranth flour. Variables considered include glycerol content (30, 35 and 40%, g/g dry flour and air-drying conditions (air temperatures of 30, 40 and 50ºC and relative humidities of 40, 55 and 70%. As amaranth flour films constitute a complex mixture of amylopectin and amylose as well as native protein and lipid, certain unexpected results were obtained. The toughest films were obtained at the lowest temperature and the lowest relative humidity (30ºC, 40%.

  15. Universal features of amorphous plasticity

    Science.gov (United States)

    Budrikis, Zoe; Castellanos, David Fernandez; Sandfeld, Stefan; Zaiser, Michael; Zapperi, Stefano

    2017-07-01

    Plastic yielding of amorphous solids occurs by power-law distributed deformation avalanches whose universality is still debated. Experiments and molecular dynamics simulations are hampered by limited statistical samples, and although existing stochastic models give precise exponents, they require strong assumptions about fixed deformation directions, at odds with the statistical isotropy of amorphous materials. Here, we introduce a fully tensorial, stochastic mesoscale model for amorphous plasticity that links the statistical physics of plastic yielding to engineering mechanics. It captures the complex shear patterning observed for a wide variety of deformation modes, as well as the avalanche dynamics of plastic flow. Avalanches are described by universal size exponents and scaling functions, avalanche shapes, and local stability distributions, independent of system dimensionality, boundary and loading conditions, and stress state. Our predictions consistently differ from those of mean-field depinning models, providing evidence that plastic yielding is a distinct type of critical phenomenon.

  16. A Parallel-pulling Protocol for Free Energy Evaluation

    CERN Document Server

    Ngo, Van

    2011-01-01

    Jarzynski's equality (JE) allows us to compute free energy differences (FEDs) from distributions of work performed on a system. We show that it is possible to generate the work distributions in single step-wise pulling simulations in order to compute FEDs by JE without generating many trajectories using virtual optical traps. We suggest an alternative method for directly computing FEDs in both sequential- and parallel-pulling protocols based on measurements of averaged reaction coordinates along pathways. In comparison with the commonly used Potential of Mean Force method applied to stretching a Deca-Alanine molecule, we show that the parallel-pulling protocol is at least 20 times faster than slow sequential-pulling protocols for producing the same free energy barrier with the uncertainty less than 2.0 kcal/mol.

  17. Plastic bronchitis

    Directory of Open Access Journals (Sweden)

    Anil Kumar Singhi

    2015-01-01

    Full Text Available Plastic bronchitis, a rare but serious clinical condition, commonly seen after Fontan surgeries in children, may be a manifestation of suboptimal adaptation to the cavopulmonary circulation with unfavorable hemodynamics. They are ominous with poor prognosis. Sometimes, infection or airway reactivity may provoke cast bronchitis as a two-step insult on a vulnerable vascular bed. In such instances, aggressive management leads to longer survival. This report of cast bronchitis discusses its current understanding.

  18. Study on Mechanical Properties of PVC Wood-plastic Composite%PVC基木塑复合材料力学性能的研究

    Institute of Scientific and Technical Information of China (English)

    沈凡成; 贾润礼; 魏伟

    2011-01-01

    利用胺类改性剂M处理木粉,研究了改性剂M和力学性能改性剂丙烯腈-苯乙烯共聚物(AS)的用量对聚氯乙烯(PVC)基复合材料力学性能的影响.结果表明:随着改性剂M用量的增加,复合材料的拉伸强度、无缺口冲击强度、弯曲强度以及弯曲模量都呈先上升后下降的趋势,且当M用量略大于2%时达到最大值;随着AS用量的增加,复合材料的拉伸强度、弯曲强度及弯曲模量都呈逐渐上升的趋势,无缺口冲击强度呈逐渐下降的趋势,到8%时越于平缓.%The wood flour was treated by amine reagent (modifier M).The effects of content of modifier M and mechanical properties modifier (AS) on the mechanical properties of PVC wood-plastic composites were studied.The results show that with the increase of modifier M content, the tensile strength, non-notched impact strength, flexural strength and flexural modulus of the composites increase at first and then decrease; when the modifier M content is slightly more than 2%, the mechanical properties of the composites are up to the maximum values; with the increase of AS content, the tensile strength, flexural strength and flexural modulus of the composites increase gradually, while the non-notched impact strength decreases gradually, and there is no obvious change when AS content is 8%.

  19. Using a metal detector to locate a swallowed ring pull.

    Science.gov (United States)

    Ryan, J; Perez-Avila, C A; Cherukuri, A; Tidey, B

    1995-03-01

    A 48-year-old man accidently swallowed the ring pull from a soft drink can. He complained of pain in his chest. Chest radiographs were normal. A metal detector emitted a strong response when passed across the front of his chest. Oesophagoscopy was carried out and the ring pull was successfully removed. We recommend the wider use of metal detectors by accident and emergency (A&E) department staff particularly when dealing with patients who have ingested metals of low radiodensity.

  20. Pull-Through Capacity in Plywood and OSB

    DEFF Research Database (Denmark)

    Munch-Andersen, Jørgen; Sørensen, John Dalsgaard

    The characteristic pull-through capacity of heads of nails and screws is needed to determine the rope effect for laterally loaded fasteners used to fix sheathing to timberframes. There is no values given in EN 1995 (Eurocode 5) but data for the pull through capacity of nail and screw heads has be...... found in four different references. All fasteners and panels are North American. A fairly general and accurate model is found and the characteristic values according to EN 1990 are determined....

  1. Push and pull strategies: applications for health care marketing.

    Science.gov (United States)

    Kingsley, B R

    1987-08-01

    As health care markets mature and expand, strategies available in other industries become useful. This article examines how traditional push-pull strategies apply to health care. Marketers using a push strategy recognize that the sale of their services or goods is dependent upon the endorsement of a middleman and promote their product through the middleman. Those using a pull strategy market directly to the consumer. In this article, the author outlines the advantages and disadvantages of using each strategy.

  2. Chronic stress and brain plasticity: mechanisms underlying adaptive and maladaptive changes and implications for stress-related CNS disorders

    Science.gov (United States)

    Radley, Jason; Morilak, David; Viau, Victor; Campeau, Serge

    2015-01-01

    Stress responses entail neuroendocrine, autonomic, and behavioral changes to promote effective coping with real or perceived threats to one’s safety. While these responses are critical for the survival of the individual, adverse effects of repeated exposure to stress are widely known to have deleterious effects on health. Thus, a considerable effort in the search for treatments to stress-related CNS disorders necessitates unraveling the brain mechanisms responsible for adaptation under acute conditions and their perturbations following chronic stress exposure. This paper is based upon a symposium from the 2014 International Behavioral Neuroscience Meeting, summarizing some recent advances in understanding the effects of stress on adaptive and maladaptive responses subserved by limbic forebrain networks. An important theme highlighted in this review is that the same networks mediating neuroendocrine, autonomic, and behavioral processes during adaptive coping also comprise targets of the effects of repeated stress exposure in the development of maladaptive states. Where possible, reference is made to the similarity of neurobiological substrates and effects observed following repeated exposure to stress in laboratory animals and the clinical features of stress-related disorders in humans. PMID:26116544

  3. Sensory deprivation unmasks a PKA-dependent synaptic plasticity mechanism that operates in parallel with CaMKII.

    Science.gov (United States)

    Hardingham, Neil; Wright, Nick; Dachtler, James; Fox, Kevin

    2008-12-10

    Calcium/calmodulin kinase II (CaMKII) is required for LTP and experience-dependent potentiation in the barrel cortex. Here, we find that whisker deprivation increases LTP in the layer IV to II/III pathway and that PKA antagonists block the additional LTP. No LTP was seen in undeprived CaMKII-T286A mice, but whisker deprivation again unmasked PKA-sensitive LTP. Infusion of a PKA agonist potentiated EPSPs in deprived wild-types and deprived CaMKII-T286A point mutants but not in undeprived animals of either genotype. The PKA-dependent potentiation mechanism was not present in GluR1 knockouts. Infusion of a PKA antagonist caused depression of EPSPs in undeprived but not deprived cortex. LTD was occluded by whisker deprivation and blocked by PKA manipulation, but not blocked by cannabinoid antagonists. NMDA receptor currents were unaffected by sensory deprivation. These results suggest that sensory deprivation causes synaptic depression by reversing a PKA-dependent process that may act via GluR1.

  4. Effects of pedal type and pull-up action during cycling.

    Science.gov (United States)

    Mornieux, G; Stapelfeldt, B; Gollhofer, A; Belli, A

    2008-10-01

    The aim of this study was to determine the influence of different shoe-pedal interfaces and of an active pulling-up action during the upstroke phase on the pedalling technique. Eight elite cyclists (C) and seven non-cyclists (NC) performed three different bouts at 90 rev . min (-1) and 60 % of their maximal aerobic power. They pedalled with single pedals (PED), with clipless pedals (CLIP) and with a pedal force feedback (CLIPFBACK) where subjects were asked to pull up on the pedal during the upstroke. There was no significant difference for pedalling effectiveness, net mechanical efficiency (NE) and muscular activity between PED and CLIP. When compared to CLIP, CLIPFBACK resulted in a significant increase in pedalling effectiveness during upstroke (86 % for C and 57 % NC, respectively), as well as higher biceps femoris and tibialis anterior muscle activity (p shoe-pedal interface (PED vs. CLIP) did not significantly influence cycling technique during submaximal exercise. However, an active pulling-up action on the pedal during upstroke increased the pedalling effectiveness, while reducing net mechanical efficiency.

  5. Demonstration of Jarzynski's Equality in Open Quantum Systems Using a Step-Wise Pulling Protocol

    CERN Document Server

    Ngo, Van A

    2012-01-01

    We present a generalization of Jarzynski's Equality, applicable to quantum systems, relating discretized mechanical work and free-energy changes. The theory is based on a step-wise pulling protocol. We find that work distribution functions can be constructed from fluctuations of a reaction coordinate along a reaction pathway in the step-wise pulling protocol. We also propose two sets of equations to determine the two possible optimal pathways that provide the most significant contributions to free-energy changes. We find that the transitions along these most optimal pathways, satisfying both sets of equations, follow the principle of detailed balance. We then test the theory by explicitly computing the free-energy changes for a one-dimensional quantum harmonic oscillator. This approach suggests a feasible way of measuring the fluctuations to experimentally test Jarzynski's Equality in many-body systems, such as Bose-Einstein condensates.

  6. "Pulling out" as a procedural resource when solving partial differential equations

    CERN Document Server

    Modir, Bahar

    2016-01-01

    We investigate how students solve partial differential equations and partial derivatives in the context of quantum mechanics. We use the resources framework to investigate students' discussion in a group problem-solving environment to investigate the fine-grain elements of their problem solving. We analyze an example of students' use of separation of variables to solve a partial differential equation for a free particle problem. We identify a mathematical action called "pulling out" as a procedural resource to help students with separating the time part from the space part of the wave function in the course of solving the time-dependent Schrodinger equation. We discuss how students use "pulling out" as a procedural step in solving partial differential equations and sense-making.

  7. Protein co-translocational unfolding depends on the direction of pulling

    Science.gov (United States)

    Rodriguez-Larrea, David; Bayley, Hagan

    2014-09-01

    Protein unfolding and translocation through pores occurs during trafficking between organelles, protein degradation and bacterial toxin delivery. In vivo, co-translocational unfolding can be affected by the end of the polypeptide that is threaded into the pore first. Recently, we have shown that co-translocational unfolding can be followed in a model system at the single-molecule level, thereby unravelling molecular steps and their kinetics. Here, we show that the unfolding kinetics of the model substrate thioredoxin, when pulled through an α-haemolysin pore, differ markedly depending on whether the process is initiated from the C terminus or the N terminus. Further, when thioredoxin is pulled from the N terminus, the unfolding pathway bifurcates: some molecules finish unfolding quickly, while others finish ~100 times slower. Our findings have important implications for the understanding of biological unfolding mechanisms and in the application of nanopore technology for the detection of proteins and their modifications.

  8. Study of electrical breakdown and secondary pull-in failure modes for NEM relays

    Science.gov (United States)

    Ramezani, M.; Severi, S.; Tilmans, H. A. C.; De Meyer, K.

    2017-01-01

    In this work, two common failure modes of nano-electro-mechanical (NEM) relays: (1) electrical breakdown and (2) stiction due to secondary pull-in were analyzed. These effects are dominant when dimensions of the device are scaled to the sub-micrometer scale. Like MEMS devices, design adjustments, such as introduction of dimples, cannot provide a solution. The geometrical parameters and working environment drive directly the occurrence of these failure modes. The beam length is the key parameter in driving the electrical breakdown while the distance of the gate to the drain, the beam thickness, and the actuation gap set the limits for secondary pull-in voltage. The analysis shows that these failure modes could be mitigated and a physical parameters design space could be identified to achieve NEM devices for high speed operation.

  9. Effects of Rice Hull Particle Size and Content on the Mechanical Properties and Visual Appearance of Wood Plastic Composites Prepared from Poly(vinyl chloride)

    Institute of Scientific and Technical Information of China (English)

    Nawadon Petchwattana; Sirijutaratana Covavisaruch

    2013-01-01

    This research aims to develop Wood Plastic Composites (WPCs) from rice hull and poly(vinyl chloride) (PVC).The influences of the rice hull particle size and content on the mechanical properties and the visual appearance of the WPC decking board were investigated.The experimental results revealed that the impact strength tended to decrease with increasing rice hull content.The composites with larger particle sizes exhibited higher impact strength.Under tensile and flexure load,higher rice hull content induced greater modulus and ultimate strength when the rice hull was applied at less than 60 phr.Beyond this concentration,the modulus and the strength dropped due to the formation of rice hull agglomerates.The smaller particles of the milled rice hull,the greater tendency there was for them to act as a pigment to form a darker shade close that of the rice hull on the composite decking board.The larger particle sizes were 106 μm and beyond simply embedded in the white PVC matrix.

  10. Effect of Heat Treatment on Microstructures and Mechanical Properties of Severe Plastically Deformed Hypo- and Hyper-Eutectoid Steels by Caliber Rolling Process.

    Science.gov (United States)

    Yun, Shin-Cheon; Kim, Hyun-Jin; Bae, Chul-Min; Lee, Kee-Ahn

    2016-02-01

    This study investigated the effect of post-heat treatment on the microstructures and mechanical properties of severe plastically deformed hypo- and hyper-eutectoid steels that underwent a caliber rolling process. First, 28 passes of caliber rolling were performed on both the hypo-eutectoid steel with Fe-0.47% C (wt%) composition and the hyper-eutectoid steel with Fe-1.02%C (wt%) composition. Then, the caliber rolled materials underwent heat treatment at 500 degrees C for 1, 3, 5, 10, 30 and 60 minutes. The caliber rolled steel possessed a 300-400 nm-sized oval cementite structure created through elongating and segmentation regardless of the C composition. The observation of heat-treated microstructures showed that cementite structure became globular and ferrite size increased as heat treatment temperature increased. In the hardness measurement, the initial caliber rolled samples showed 372.8 Hv (hypoeutectoid) and 480.1 Hv (hyper-eutectoid). However, hardness dramatically decreased up to 10 min. heat treatments, and then showed a constant or small reduction with time. The yield strengths (compression) of caliber rolled hypo- and hypereutectoid steels obtained were 1097 MPa and 1426 MPa, respectively, and the yield strengths of the same steels after heat treatment (500 degrees C, 60 min.) were identified to be 868 MPa and 1316 MPa, respectively.

  11. Cambrian origin of the CYP27C1-mediated vitamin A1-to-A2 switch, a key mechanism of vertebrate sensory plasticity

    Science.gov (United States)

    Morshedian, Ala; Toomery, Matthew B.; Pollock, Gabriel E.; Frederiksen, Rikard; Enright, Jennifer; McCormick, Stephen; Cornwall, M. Carter; Fain, Gordon L.; Corbo, Joseph C.

    2017-01-01

    The spectral composition of ambient light varies across both space and time. Many species of jawed vertebrates adapt to this variation by tuning the sensitivity of their photoreceptors via the expression of CYP27C1, an enzyme that converts vitamin A1 into vitamin A2, thereby shifting the ratio of vitamin A1-based rhodopsin to red-shifted vitamin A2-based porphyropsin in the eye. Here, we show that the sea lamprey (Petromyzon marinus), a jawless vertebrate that diverged from jawed vertebrates during the Cambrian period (approx. 500 Ma), dynamically shifts its photoreceptor spectral sensitivity via vitamin A1-to-A2 chromophore exchange as it transitions between photically divergent aquatic habitats. We further show that this shift correlates with high-level expression of the lamprey orthologue of CYP27C1, specifically in the retinal pigment epithelium as in jawed vertebrates. Our results suggest that the CYP27C1-mediated vitamin A1-to-A2 switch is an evolutionarily ancient mechanism of sensory plasticity that appeared not long after the origin of vertebrates.

  12. 橡胶增韧塑料机理研究进展%Advance in research on mechanisms for rubber-toughening of plastics

    Institute of Scientific and Technical Information of China (English)

    王荣伟

    2012-01-01

    The mechanisms for deformation behaviors of rubber-toughened plastics are summarized in terms of their evolution, limitations and relationship with the failure behaviors of glassy polymer matrices. The difference between craze and crack is explained in detail using many experimental evidences in literature. In particular, Souheng Wu's quantitative method is systematically explained, which is derived from this yielding-crazing competition theory and reveals the quantitative relationship between molecular chain parameters of the matrices and morphological parameters of the dispersed rubber phase. In addition, Wu's view is emphasized that chain parameters of the matrices control the intrinsic brittleness and toughness of both matrix and its blend with rubber, and determine the favorable morphology of rubber phase as well.%介绍了橡胶增韧塑料机理演进及其与不同链结构基体树脂断裂行为的关系,描述了银纹和裂缝区别,详细地介绍了不同基体树脂的分子链参数与橡胶分散相形态参数的定量关系,同时强调基体树脂的链参数既控制聚合物/橡胶共混物的本征韧性,又决定了橡胶分散相的适宜形态.

  13. Two-Dimensional Large Deformation Finite Element Analysis for the Pulling-up of Plate Anchor

    Institute of Scientific and Technical Information of China (English)

    WANG Dong; HU Yu-xia; JIN Xia

    2006-01-01

    Based on mesh regeneration and stress interpolation from an old mesh to a new one, a large deformation finite element model is developed for the study of the behaviour of circular plate anchors subjected to uplift loading. For the determination of the distributions of stress components across a clay foundation, the Recovery by Equilibrium in Patches is extended to plastic analyses. ABAQUS, a commercial finite element package, is customized and linked into our program so as to keep automatic and efficient running of large deformation calculation. The quality of stress interpolation is testified by evaluations of Tresca stress and nodal reaction forces. The complete pulling-up processes of plate anchors buried in homogeneous clay are simulated, and typical pulling force-displacement responses of a deep anchor and a shallow anchor are compared. Different from the results of previous studies, large deformation analysis is of the capability of estimating the breakaway between the anchor bottom and soils. For deep anchors, the variation of mobilized uplift resistance with anchor settlement is composed of three stages, and the initial buried depths of anchors affect the separation embedment slightly. The uplift bearing capacity of deep anchors is usually higher than that of shallow anchors.

  14. Disturbed state model for sand-geosynthetic interfaces and application to pull-out tests

    Science.gov (United States)

    Pal, Surajit; Wije Wathugala, G.

    1999-12-01

    Successful numerical simulation of geosynthetic-reinforced earth structures depends on selecting proper constitutive models for soils, geosynthetics and soil-geosynthetic interfaces. Many constitutive models are available for modelling soils and geosynthetics. However, constitutive models for soil-geosynthetic interfaces which can capture most of the important characteristics of interface response are not readily available. In this paper, an elasto-plastic constitutive model based on the disturbed state concept (DSC) for geosynthetic-soil interfaces has been presented. The proposed model is capable of capturing most of the important characteristics of interface response, such as dilation, hardening and softening. The behaviour of interfaces under the direct shear test has been predicted by the model. The present model has been implemented in the finite element procedure in association with the thin-layer element. Five pull-out tests with two different geogrids have been simulated numerically using FEM. For the calibration of the constitutive models used in FEM, the standard laboratory tests used are: (1) triaxial tests for the sand, (2) direct shear tests for the interfaces and (3) axial tension tests for the geogrids. The results of the finite element simulations of pull-out tests agree well with the test data. The proposed model can be used for the stress-deformation study of geosynthetic-reinforced embankments through numerical simulation.

  15. Studies of elastic-plastic instabilities

    DEFF Research Database (Denmark)

    Tvergaard, Viggo

    1999-01-01

    Analyses of plastic instabilities are reviewed, with focus on results in structural mechanics as well as continuum mechanics. First the basic theories for bifurcation and post-bifurcation behavior are briefly presented. Then, localization of plastic flow is discussed, including shear band formation...... in solids, localized necking in biaxially stretched metal sheets, and the analogous phenomenon of buckling localization in structures. Also some recent results for cavitation instabilities in elastic-plastic solids are reviewed....

  16. Using Metaheuristic and Fuzzy System for the Optimization of Material Pull in a Push-Pull Flow Logistics Network

    Directory of Open Access Journals (Sweden)

    Afshin Mehrsai

    2013-01-01

    Full Text Available Alternative material flow strategies in logistics networks have crucial influences on the overall performance of the networks. Material flows can follow push, pull, or hybrid systems. To get the advantages of both push and pull flows in networks, the decoupling-point strategy is used as coordination mean. At this point, material pull has to get optimized concerning customer orders against pushed replenishment-rates. To compensate the ambiguity and uncertainty of both dynamic flows, fuzzy set theory can practically be applied. This paper has conceptual and mathematical parts to explain the performance of the push-pull flow strategy in a supply network and to give a novel solution for optimizing the pull side employing Conwip system. Alternative numbers of pallets and their lot-sizes circulating in the assembly system are getting optimized in accordance with a multi-objective problem; employing a hybrid approach out of meta-heuristics (genetic algorithm and simulated annealing and fuzzy system. Two main fuzzy sets as triangular and trapezoidal are applied in this technique for estimating ill-defined waiting times. The configured technique leads to smoother flows between push and pull sides in complex networks. A discrete-event simulation model is developed to analyze this thesis in an exemplary logistics network with dynamics.

  17. New Class of Plastic Bulk Metallic Glass

    Science.gov (United States)

    Chen, L. Y.; Fu, Z. D.; Zhang, G. Q.; Hao, X. P.; Jiang, Q. K.; Wang, X. D.; Cao, Q. P.; Franz, H.; Liu, Y. G.; Xie, H. S.; Zhang, S. L.; Wang, B. Y.; Zeng, Y. W.; Jiang, J. Z.

    2008-02-01

    An intrinsic plastic Cu45Zr46Al7Ti2 bulk metallic glass (BMG) with high strength and superior compressive plastic strain of up to 32.5% was successfully fabricated by copper mold casting. The superior compressive plastic strain was attributed to a large amount of randomly distributed free volume induced by Ti minor alloying, which results in extensive shear band formation, branching, interaction and self-healing of minor cracks. The mechanism of plasticity presented here suggests that the creation of a large amount of free volume in BMGs by minor alloying or other methods might be a promising new way to enhance the plasticity of BMGs.

  18. Fast photo-processes in triazole-based push-pull systems

    NARCIS (Netherlands)

    Zoon, P.D.; van Stokkum, I.H.M.; Parent, M.; Mongin, O.; Blanchard-Desce, M.; Brouwer, A.M.

    2010-01-01

    Electron donor-acceptor compounds 1 (asymmetrical push-pull derivative) and 2 (symmetrical push-pull-push derivative) were studied in which one (push-pull) or two aniline units (push-pull-push) are connected to a biphenyl group via triazole linkers, made by "click" chemistry. Steady-state and time-r

  19. Sorting Techniques for Plastics Recycling

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    This paper presents the basic principles of three different types of separating methods and a general guideline for choosing the most effective method for sorting plastic mixtures. It also presents the results of the tests carried out for separation of PVC, ABS and PET from different kinds of plastic mixtures in order to improve the grade of the raw input used in mechanical or feedstock recycling.

  20. Step-wise pulling protocols for non-equilibrium dynamics

    Science.gov (United States)

    Ngo, Van Anh

    The fundamental laws of thermodynamics and statistical mechanics, and the deeper understandings of quantum mechanics have been rebuilt in recent years. It is partly because of the increasing power of computing resources nowadays, that allow shedding direct insights into the connections among the thermodynamics laws, statistical nature of our world, and the concepts of quantum mechanics, which have not yet been understood. But mostly, the most important reason, also the ultimate goal, is to understand the mechanisms, statistics and dynamics of biological systems, whose prevailing non-equilibrium processes violate the fundamental laws of thermodynamics, deviate from statistical mechanics, and finally complicate quantum effects. I believe that investigations of the fundamental laws of non-equilibrium dynamics will be a frontier research for at least several more decades. One of the fundamental laws was first discovered in 1997 by Jarzynski, so-called Jarzynski's Equality. Since then, different proofs, alternative descriptions of Jarzynski's Equality, and its further developments and applications have been quickly accumulated. My understandings, developments and applications of an alternative theory on Jarzynski's Equality form the bulk of this dissertation. The core of my theory is based on stepwise pulling protocols, which provide deeper insight into how fluctuations of reaction coordinates contribute to free-energy changes along a reaction pathway. We find that the most optimal pathways, having the largest contribution to free-energy changes, follow the principle of detailed balance. This is a glimpse of why the principle of detailed balance appears so powerful for sampling the most probable statistics of events. In a further development on Jarzynski's Equality, I have been trying to use it in the formalism of diagonal entropy to propose a way to extract useful thermodynamic quantities such temperature, work and free-energy profiles from far

  1. Forearm posture and grip effects during push and pull tasks.

    Science.gov (United States)

    Di Domizio, Jennifer; Keir, Peter J

    2010-03-01

    Direction of loading and performance of multiple tasks have been shown to elevate muscle activity in the upper extremity. The purpose of this study was to evaluate the effects of gripping on muscle activity and applied force during pushing and pulling tasks with three forearm postures. Twelve volunteers performed five hand-based tasks in supinated, neutral and pronated forearm postures with the elbow at 90 degrees and upper arm vertical. All tasks were performed with the right (dominant) hand and included hand grip alone, push and pull with and without hand grip. Surface EMG from eight upper extremity muscles, hand grip force, tri-axial push and pull forces and wrist angles were recorded during the 10 s trials. The addition of a pull force to hand grip elevated activity in all forearm muscles (all p push with grip tasks, forearm extensor muscle activity tended to increase when compared with grip only while flexor activity tended to decrease. Forearm extensor muscle activity was higher with the forearm pronated compared with neutral and supinated postures during most isolated grip tasks and push or pull with grip tasks (all p push and pull forces could act to assist in creating grip force, forearm muscle activity generally decreased. These results provide strategies for reducing forearm muscle loading in the workplace. STATEMENT OF RELEVANCE: Tools and tasks designed to take advantage of coupling grip with push or pull actions may be beneficial in reducing stress and injury in the muscles of the forearm. These factors should be considered in assessing the workplace in terms of acute and cumulative loading.

  2. KOMPARASI SISTEM MANUFAKTUR PUSH DAN PULL MELALUI PENDEKATAN SIMULASI

    Directory of Open Access Journals (Sweden)

    Eric Wibisono

    2004-01-01

    Full Text Available Manufacturing systems that are often classified as push and pull often invite question: "How far do the differences between those two systems exist?" Many researches have been carried out but succinct answer to the above question is always difficult to reach. The difficulty roots from the variety of definition of the push and pull systems itself and also from the variety of complexity of a manufacturing system. This paper attempts to study the differences in performance between push and pull systems in a relatively simple model that consists of 4 serial processors with buffers located between these processors. Variations being modelled is on the setting of the system's load (high and low and the buffer size with performance being measured include machine utilization, number of outputs and mean flow time of jobs. The approach used is simulation using ProModel software as the tool. From the experiments it can be derived that buffer size turns out to be a very critical factor in system performance. Moreover, it is also proved that when the buffer size is large, push and pull systems do not differ significantly. Abstract in Bahasa Indonesia : Sistem manufaktur yang umumnya dikategorikan menjadi sistem push dan pull sering mengundang pertanyaan: "Seberapa jauh perbedaan dari kedua sistem tersebut ada?" Banyak penelitian telah dilakukan namun jawaban yang lugas atas pertanyaan tersebut sulit diperoleh. Kesulitan ini umumnya berakar dari beragamnya definisi sistem push dan pull itu sendiri serta variasi dari kompleksitas suatu sistem manufaktur. Makalah ini mencoba melihat perbedaan antara kinerja sistem push dan pull dalam suatu model sederhana yang terdiri dari 4 prosesor serial dengan buffer yang diletakkan di antara masing-masing prosesor tersebut. Variasi yang dilakukan adalah pada setting beban kerja sistem (padat dan ringan dan ukuran buffer dengan kinerja yang diukur adalah utilisasi mesin, jumlah output dan rata-rata waktu tinggal job

  3. Investigation on 2331 cases of pulled elbow over the last 10 years

    Directory of Open Access Journals (Sweden)

    Takashi Irie

    2014-05-01

    Full Text Available Pulled elbow is a common upper extremity injury in children. We present a retrospective study of 2331 pulled elbow cases examined in our hospital over the last ten years. All pediatric patients with a diagnosis of pulled elbow from January 2002 to December 2011 were retrospectively reviewed according to sex, age, affected arm, recurrence rate, mechanism of injury and treatment outcomes. There is no significant sex difference. The frequency of injury peaked for both boys and girls at 6 months and 2 years of age. The left arm was more affected than the right. The recurrence rate was 14%. In about 50% of cases, the cause of injury was forcible traction to the forearm. Almost all of the splinted patients, caused by severe pain or lack of mobility of the affected limb following reduction, recovered within 2 weeks, but 2 were later diagnosed with a fracture. For infants less than 1 year old, injury can often occur when rolling over. For children 1 year old or older the left arm is more commoly affected, and the frequency of injuries to the left arm increases with age, possibly because the left hand is commonly held by the guardian’s dominant right hand and faster development of muscle strength in the child’s dominant right arm works toward preventing injury to that arm with age.

  4. Making sense of plastics recycling

    NARCIS (Netherlands)

    Van Bruggen, E.; Koster, R.P.; Rageart, K.; Cardon, L.; Moerman, M.; Blessing, E.

    2012-01-01

    Major benefits of plastics recycling are reduced depletion of non-renewable resources and reduction of world-wide waste. Traditional thermo-mechanical recycling causes reduction of mechanical properties for most thermoplastics. Down-cycled materials may nevertheless be suited for certain useful appl

  5. Overcoming maladaptive plasticity through plastic compensation

    Directory of Open Access Journals (Sweden)

    Matthew R.J. MORRIS, Sean M. ROGERS

    2013-08-01

    Full Text Available Most species evolve within fluctuating environments, and have developed adaptations to meet the challenges posed by environmental heterogeneity. One such adaptation is phenotypic plasticity, or the ability of a single genotype to produce multiple environmentally-induced phenotypes. Yet, not all plasticity is adaptive. Despite the renewed interest in adaptive phenotypic plasticity and its consequences for evolution, much less is known about maladaptive plasticity. However, maladaptive plasticity is likely an important driver of phenotypic similarity among populations living in different environments. This paper traces four strategies for overcoming maladaptive plasticity that result in phenotypic similarity, two of which involve genetic changes (standing genetic variation, genetic compensation and two of which do not (standing epigenetic variation, plastic compensation. Plastic compensation is defined as adaptive plasticity overcoming maladaptive plasticity. In particular, plastic compensation may increase the likelihood of genetic compensation by facilitating population persistence. We provide key terms to disentangle these aspects of phenotypic plasticity and introduce examples to reinforce the potential importance of plastic compensation for understanding evolutionary change [Current Zoology 59 (4: 526–536, 2013].

  6. Overcoming maladaptive plasticity through plastic compensation

    Institute of Scientific and Technical Information of China (English)

    Matthew R.J.MORRIS; Sean M.ROGERS

    2013-01-01

    Most species evolve within fluctuating environments,and have developed adaptations to meet the challenges posed by environmental heterogeneity.One such adaptation is phenotypic plasticity,or the ability of a single genotype to produce multiple environmentally-induced phenotypes.Yet,not all plasticity is adaptive.Despite the renewed interest in adaptive phenotypic plasticity and its consequences for evolution,much less is known about maladaptive plasticity.However,maladaptive plasticity is likely an important driver of phenotypic similarity among populations living in different environments.This paper traces four strategies for overcoming maladaptive plasticity that result in phenotypic similarity,two of which involve genetic changes (standing genetic variation,genetic compensation) and two of which do not (standing epigenetic variation,plastic compensation).Plastic compensation is defined as adaptive plasticity overcoming maladaptive plasticity.In particular,plastic compensation may increase the likelihood of genetic compensation by facilitating population persistence.We provide key terms to disentangle these aspects of phenotypic plasticity and introduce examples to reinforce the potential importance of plastic compensation for understanding evolutionary change.

  7. Push-pull membrane mirrors for adaptive optics.

    Science.gov (United States)

    Bonora, Stefano; Poletto, Luca

    2006-12-11

    We propose an improvement to the electrostatic membrane deformable mirror technique introducing push-pull capability that increases the performance in the correction of optical aberrations. The push-pull effect is achieved by the addition of some transparent electrodes on the top of the device. The transparent electrode is an indium-tin-oxide coated glass. The improvement of the mirror in generating surfaces is demonstrated by the comparison with a pull membrane mirror. The control is carried out in open loop by the knowledge of the response of each single electrode. An effective iterative strategy for the clipping management is presented. The performances are evaluated both in terms of Zernike polynomials generation and in terms of aberrations compensation based on the statistics of human eyes.

  8. Push-pull membrane mirrors for adaptive optics

    Science.gov (United States)

    Bonora, Stefano; Poletto, Luca

    2006-12-01

    We propose an improvement to the electrostatic membrane deformable mirror technique introducing push-pull capability that increases the performance in the correction of optical aberrations. The push-pull effect is achieved by the addition of some transparent electrodes on the top of the device. The transparent electrode is an indium-tin-oxide coated glass. The improvement of the mirror in generating surfaces is demonstrated by the comparison with a pull membrane mirror. The control is carried out in open loop by the knowledge of the response of each single electrode. An effective iterative strategy for the clipping management is presented. The performances are evaluated both in terms of Zernike polynomials generation and in terms of aberrations compensation based on the statistics of human eyes.

  9. The push-pull strategy for citrus psyllid control.

    Science.gov (United States)

    Yan, Huaxue; Zeng, Jiwu; Zhong, Guangyan

    2015-07-01

    The Asian citrus psyllid (ACP), Diaphorina citri Kuwayama (Hemiptera: Psyllidae), is the only natural vector of Candidatus Liberibacter asiaticus that causes citrus huanglongbing (HLB), a most destructive disease of citrus. Currently, no remedial therapy exists for the disease, and so effective control of ACP is very important in curbing the transmission of the disease. The push-pull strategy should be thoroughly explored as an approach to ACP management. This mini-review summarises the current progress towards more effective repellent and attractant chemicals through investigating known repellent and attractive plants. Interactions between ACP and its host plants are also addressed, with emphasis on the possible involvement of the host biochemicals in attracting the insect. Potential ways to increase the effectiveness of the pull-push strategy are briefly discussed. It is expected that the pull-push strategy will be gradually developed following more extensive research.

  10. Frobenius Pull Backs of Vector Bundles in Higher Dimensions

    Indian Academy of Sciences (India)

    V Trivedi

    2012-11-01

    We prove that for a smooth projective variety of arbitrary dimension and for a vector bundle over , the Harder–Narasimhan filtration of a Frobenius pull back of is a refinement of the Frobenius pull back of the Harder–Narasimhan filtration of , provided there is a lower bound on the characteristic (in terms of rank of and the slope of the destabilizing sheaf of the cotangent bundle of ). We also recall some examples, due to Raynaud and Monsky, to show that some lower bound on is necessary. We also give a bound on the instability degree of the Frobenius pull back of in terms of the instability degree of and well defined invariants of .

  11. EFFECT OF DRIVING WHEEL TYPE ON DRAWBAR PULL OF TRACTOR

    Directory of Open Access Journals (Sweden)

    Rudolf Abrahám

    2013-12-01

    Full Text Available This paper is focused on the possibility of increasing the drawbar pull of agricultural tractor on the soil and grass-covered surface. From our perspective, we have chosen one available and the cheapest way, i.e. steel boots for tyres of small tractors, and this was compared with a newly developed system of auto-extensible blades next to the wheel. The tractor with steel boots and auto-extensible blades reached a higher drawbar pull on average by 70 % in comparison with tyres.

  12. A pulled sutures technique for bony Bankart lesion.

    Science.gov (United States)

    Lee, Byung Ill; Choi, Hyung Suk; Min, Kyung Dae; Kwon, Sai Won; Kim, Jun Bum; Kim, Yong-Beom; Chun, Dong-Il

    2014-05-01

    In an attempt to present a new surgical technique for arthroscopic bony Bankart fixation, the authors developed the pulled sutures technique. In executing the new method, the authors first passed several non-absorbable sutures through labroligamentous tissue with displaced articular fragment by mimicking transglenoid suture technique. Aimed at achieving a safe and stable fixation, using a knotless anchor rather than transglenoid suture, was deployed. Overall, this pulled sutures technique was shown to be effective with the result of direct reduction, stable, and safe fixation for bony Bankart's lesion.

  13. Constraints on the evolution of phenotypic plasticity: limits and costs of phenotype and plasticity.

    Science.gov (United States)

    Murren, C J; Auld, J R; Callahan, H; Ghalambor, C K; Handelsman, C A; Heskel, M A; Kingsolver, J G; Maclean, H J; Masel, J; Maughan, H; Pfennig, D W; Relyea, R A; Seiter, S; Snell-Rood, E; Steiner, U K; Schlichting, C D

    2015-10-01

    Phenotypic plasticity is ubiquitous and generally regarded as a key mechanism for enabling organisms to survive in the face of environmental change. Because no organism is infinitely or ideally plastic, theory suggests that there must be limits (for example, the lack of ability to produce an optimal trait) to the evolution of phenotypic plasticity, or that plasticity may have inherent significant costs. Yet numerous experimental studies have not detected widespread costs. Explicitly differentiating plasticity costs from phenotype costs, we re-evaluate fundamental questions of the limits to the evolution of plasticity and of generalists vs specialists. We advocate for the view that relaxed selection and variable selection intensities are likely more important constraints to the evolution of plasticity than the costs of plasticity. Some forms of plasticity, such as learning, may be inherently costly. In addition, we examine opportunities to offset costs of phenotypes through ontogeny, amelioration of phenotypic costs across environments, and the condition-dependent hypothesis. We propose avenues of further inquiry in the limits of plasticity using new and classic methods of ecological parameterization, phylogenetics and omics in the context of answering questions on the constraints of plasticity. Given plasticity's key role in coping with environmental change, approaches spanning the spectrum from applied to basic will greatly enrich our understanding of the evolution of plasticity and resolve our understanding of limits.

  14. Recycling of Plastic

    DEFF Research Database (Denmark)

    Christensen, Thomas Højlund; Fruergaard, Thilde

    2011-01-01

    Plastic is produced from fossil oil. Plastic is used for many different products. Some plastic products like, for example, wrapping foil, bags and disposable containers for food and beverage have very short lifetimes and thus constitute a major fraction of most waste. Other plastic products like......, good strength and long durability. Recycling of plastic waste from production is well-established, while recycling of postconsumer plastic waste still is in its infancy. This chapter describes briefly how plastic is produced and how waste plastic is recycled in the industry. Quality requirements...

  15. Energetics and Compatibility of Plasticizers in Composite Solid Propellants

    National Research Council Canada - National Science Library

    Rm. Muthiah; U. I. Somasundaran; T. L. Verghese; V. A. Thornas

    1989-01-01

    ...) ter polymer andhydroxyl terminated polybutadiene (HTPB) have been reported. The compatibility of all the plasticizers on HTPB binder was also studied at different concentration levels and temperatures using Brookfield viscometer and reported. The mechanism of plasticization is also reviewed.

  16. Percutaneous Endoscopic Gastrostomy (pull method and Jejunal Extension Tube Placement

    Directory of Open Access Journals (Sweden)

    Shou-jiang Tang

    2014-04-01

    Conclusions: PEG-pull method is the most widely used PEG technique. Appropriate patient selection, timing of the procedure, informed consent, antibiotic prophylaxis, adequate endoscopic air insufflation during PEG site selection, and optimal PEG site localization are the keys in this procedure.

  17. An Original Testing Apparatus for Rapid Pull-Out Test

    Directory of Open Access Journals (Sweden)

    Aprialdi, D.

    2014-01-01

    Full Text Available Pull-out test is commonly used to investigate the pull-out behavior of geotextile reinforcement embedded in soil. It is also used by different authors to propose interface friction angles values. Unfortunately these works mainly deal with cyclic loadings with reference to seismic action, which are believed to be different to the load exposed to reinforced earthworks due to lateral impacts. Therefore an original rapid pull-out test apparatus is proposed in this study. This article assess the proposed test method in addressing the rapid pull-out response of a geotextile embedded in soil. The testing apparatus allows investigating shear velocities within the range of 0.1 to 1.2 m/s. This test method seems promising in addressing the response of soil-geotextile interfaces under dynamic loadings. Nevertheless, improvements concerning the testing apparatus are still required. The loading system could be modified to avoid oscillations and specific equipment should be added to increase the normal stress.

  18. Pulling cylindrical particles using a soft-nonparaxial tractor beam

    DEFF Research Database (Denmark)

    Novitsky, Andrey; Ding, Weiqiang; Wang, Maoyan

    2017-01-01

    the nonparaxiality requirements, reducing the incidence angle of the partial plane waves of the light beam down to 45 degrees and even to 30 degrees for respectively dipole and dipole-quadrupole objects. The optical pulling force attributed to the interaction of magnetic dipole and magnetic quadrupole moments...

  19. Ultrabroadband pulse shaping with a push-pull deformable mirror.

    Science.gov (United States)

    Bonora, Stefano; Brida, Daniele; Villoresi, Paolo; Cerullo, Giulio

    2010-10-25

    We report the programmable pulse shaping of ultrabroadband pulses by the use of a novel design of electrostatic deformable mirror based on push pull technology. We shape few-optical pulses from near-IR and visible optical parametric amplifiers, and demonstrate strong-field control of excited state population transfer in a dye molecule.

  20. Effectiveness of Push and Pull Learning Strategies in Construction Management.

    Science.gov (United States)

    Santos, Aguinaldo; Powell, James Alfred

    2001-01-01

    Study of a construction contractor modernizing production showed that creation of an effective learning mood was more likely in a supportive environment in which people explore their actions as they work ("pull learning"). However, an external change agent ("push learning") was useful in provoking the reflection that triggered workplace learning.…

  1. Active Harmonic Load–Pull With Realistic Wideband Communications Signals

    NARCIS (Netherlands)

    Marchetti, M.; Pelk, M.J.; Buisman, K.; Neo, W.C.E.; Spirito, M.; De Vreede, L.C.N.

    2008-01-01

    A new wideband open-loop active harmonic load–pull measurement approach is presented. The proposed method is based on wideband data-acquisition and wideband signal-injection of the incident and device generated power waves at the frequencies of interest. The system provides full, user defined, in-ba

  2. Non-paraxial beam to push and pull microparticles

    DEFF Research Database (Denmark)

    Novitsky, Andrey; Qiu, C.-W.

    2011-01-01

    We discuss a feasibility of the pulling (backward) force acting on a spherical microparticle in a non-paraxial Bessel beam. The effect can be explained by the strong interaction of particle's multipoles or by the conservation of momentum in the system “photons-particle.” It is remarkable that the...

  3. Effectiveness of Push and Pull Learning Strategies in Construction Management.

    Science.gov (United States)

    Santos, Aguinaldo; Powell, James Alfred

    2001-01-01

    Study of a construction contractor modernizing production showed that creation of an effective learning mood was more likely in a supportive environment in which people explore their actions as they work ("pull learning"). However, an external change agent ("push learning") was useful in provoking the reflection that triggered workplace learning.…

  4. Research on Mechanical Properties, Microstructure and Rheological Properties of Wood-plastic Composites%木塑复合材料的力学性能、微观结构与流变性能的研究

    Institute of Scientific and Technical Information of China (English)

    朱明源; 易红玲; 林珩; 郑柏存

    2013-01-01

    Wood-plastic composites were prepared with HDPE and wood flour as raw material. The effects of wood content and compatibilizer content on mechanical properties, rheological properties and microstructure of wood-plastic composites were investigated. The results indicated that rigidity, melt viscosity and shear sensitivity of the composites were increased with increasing wood content, but toughness of the composites was decreased. The compatibilizer enhanced interface microstructure, mechanical properties and processing flowability of wood-plastic composites.%以高密度聚乙烯(HDPE)和木粉为原料制备了木塑复合材料.研究了木粉、相容剂含量对木塑复合材料力学性能、流变性能及微观结构的影响.结果表明:木粉含量的增加,可提高复合材料的刚性、熔体黏度以及剪切敏感性,但韧性有所降低;而添加适量的相容剂改善了复合材料的界面微观结构,从而改善了木塑复合材料的力学性能,而且还在一定程度上改善了复合材料的加工流动性.

  5. 双滑块弯销内抽芯机构设计%Design of Double Sliders Forniciform Dowel Inside Core-pulling Structure

    Institute of Scientific and Technical Information of China (English)

    陈怀民

    2013-01-01

    在带有90°弯管的移位器底座注塑模具设计中,提出一种适用于弯管抽芯的双滑块弯销内抽芯机构。通过从弯管弯曲段主型芯中分割出滑块型芯先进行内抽芯,避免了脱模时带倒扣的弯管与主型芯发生摩擦。通过在滑块型芯的弯销内抽芯机构中引进辅助滑块,替代传统的注塑模具辅助分型面结构,可实现滑块型芯任意角度的内抽芯,从而简化了注塑模具的结构,提高了模具抽芯机构的工作稳定性。%In the injection mold design process of the shifter pedestal with 90° bending pipe,a double sliders forniciform dowel inside core-pulling mechanism suitable for the bending pipe core-pulling was put forward. Through separating slider core from main bending core of the bending pipe for doing inside core-pulling firstly,the interference of the main core and the bending pipe with undercut is avoided when demolding. Through adding auxiliary slider into the forniciform dowel inside core-pulling mechanism of the slider core for replacing traditional auxiliary parting surface of injection mold,the inside core-pulling at any angle of the slider core can be realized. The inside core-pulling mechanism can reduce the complexity of the mold structure and enhance the core-pulling work stability.

  6. The Prism Plastic Calorimeter (PPC)

    CERN Multimedia

    2002-01-01

    This proposal supports two goals: \\\\ \\\\ First goal:~~Demonstrate that current, widely used plastic technologies allow to design Prism Plastic Calorimeter~(PPC) towers with a new ``liquid crystal'' type plastic called Vectra. It will be shown that this technique meets the requirements for a LHC calorimeter with warm liquids: safety, hermeticity, hadronic compensation, resolution and time response. \\\\ \\\\ Second goal:~~Describe how one can design a warm liquid calorimeter integrated into a LHC detector and to list the advantages of the PPC: low price, minimum of mechanical structures, minimum of dead space, easiness of mechanical assembly, accessibility to the electronics, possibility to recirculate the liquid. The absorber and the electronic being outside of the liquid and easily accessible, one has maximum flexibility to define them. \\\\ \\\\ The R&D program, we define here aims at showing the feasibility of these new ideas by building nine towers of twenty gaps and exposing them to electron and hadron beams.

  7. Plastic bronchitis: a management challenge.

    Science.gov (United States)

    Eberlein, Michael H; Drummond, Michael B; Haponik, Edward F

    2008-02-01

    Plastic bronchitis is an uncommon and underdiagnosed entity, characterized by recurrent expectoration of large, branching bronchial casts. We describe a 39-year-woman with no prior lung disease who had episodic wheezing, severe dyspnea with expectoration of large and thick secretions, branching in appearance, which she described as resembling squid. A comprehensive evaluation revealed no specific cause and a diagnosis of idiopathic plastic bronchitis was made. In plastic bronchitis the bronchial casts may vary in size from small segmental casts of a bronchus to casts filling the airways of an entire lung. Plastic bronchitis can therefore present as an acute life-threatening emergency if mechanical obstruction of major airways occurs. The casts are differentiated into type I, inflammatory casts, or type II, acellular casts. The type I inflammatory casts are often associated with bronchial disease and often have an acute presentation. The acellular type of cast production is often chronic or recurrent. Numerous systemic illnesses are associated with plastic bronchitis, but often, as in our patient, no underlying cause can be identified. The treatment of plastic bronchitis includes acute therapy to aid the removal and expectoration of casts, and specific short- or long-term treatments attempting to address the underlying hypersecretory process. The therapeutic options are supported only by anecdotal evidence based on case reports as the rarity and heterogeneity of plastic bronchitis confounds systematic investigations of its treatment. Improved understanding of the regulation of mucus production may allow for new treatment options in plastic bronchitis and other chronic lung diseases characterized by hypersecretion of mucus.

  8. Injection Mold Design with Thread Rotating Demoulding Mechanism of Plastic Part with Internal Thread%螺纹旋转脱模内螺纹塑件注塑模设计

    Institute of Scientific and Technical Information of China (English)

    王成

    2013-01-01

    The injection mold with thread rotating demoulding mechanism was designed by taking acrylonitrile-butadiene -styrene plastic bottle cap as example. Without external unscrewing power plant attached to the mold, the plastic part can be automatically rotating demoulded by using opening force of the injection molding machine, so the problems of time-consuming being long and plastic part thread being scuffed when thread was demoulded were solved and the quality of the plastic part was ensured. The gating system, small rod limitting structure and thread rotating demoulding mechanism were designed and analyzed, the overall structure, working process of the mold and demoulding step exploded view were introduced also. The mold has the advantages of simple, compact structure and small size, is suitable for large-scale production.%以ABS塑料瓶盖为例,设计了螺纹旋转脱模内螺纹塑件注塑模.该模具无需外接脱螺纹动力装置,利用注塑机的开模力实现塑件自动旋转脱模顶出,保证了内螺纹塑件的质量,解决了现有技术中螺纹脱模耗时、易拉伤塑件螺纹的问题.对浇注系统、小拉杆限位结构、螺纹旋转脱模结构等进行了设计分析,介绍了模具的整体结构和开、合模工作过程及脱模步骤分解图.该模具结构简单、紧凑、体积小,适用于大批量生产.

  9. Cyclic Plastic Deformation and Welding Simulation

    NARCIS (Netherlands)

    Ten Horn, C.H.L.J.

    2003-01-01

    One of the concerns of a fitness for purpose analysis is the quantification of the relevant material properties. It is known from experiments that the mechanical properties of a material can change due to a monotonic plastic deformation or a cyclic plastic deformation. For a fitness for purpose anal

  10. Constraints on the evolution of phenotypic plasticity

    DEFF Research Database (Denmark)

    Murren, Courtney J; Auld, Josh R.; Callahan, Hilary S

    2015-01-01

    Phenotypic plasticity is ubiquitous and generally regarded as a key mechanism for enabling organisms to survive in the face of environmental change. Because no organism is infinitely or ideally plastic, theory suggests that there must be limits (for example, the lack of ability to produce an opti...

  11. A review of plastic waste biodegradation.

    Science.gov (United States)

    Zheng, Ying; Yanful, Ernest K; Bassi, Amarjeet S

    2005-01-01

    With more and more plastics being employed in human lives and increasing pressure being placed on capacities available for plastic waste disposal, the need for biodegradable plastics and biodegradation of plastic wastes has assumed increasing importance in the last few years. This review looks at the technological advancement made in the development of more easily biodegradable plastics and the biodegradation of conventional plastics by microorganisms. Additives, such as pro-oxidants and starch, are applied in synthetic materials to modify and make plastics biodegradable. Recent research has shown that thermoplastics derived from polyolefins, traditionally considered resistant to biodegradation in ambient environment, are biodegraded following photo-degradation and chemical degradation. Thermoset plastics, such as aliphatic polyester and polyester polyurethane, are easily attacked by microorganisms directly because of the potential hydrolytic cleavage of ester or urethane bonds in their structures. Some microorganisms have been isolated to utilize polyurethane as a sole source of carbon and nitrogen source. Aliphatic-aromatic copolyesters have active commercial applications because of their good mechanical properties and biodegradability. Reviewing published and ongoing studies on plastic biodegradation, this paper attempts to make conclusions on potentially viable methods to reduce impacts of plastic waste on the environment.

  12. Patching It Up, Pulling It Forward

    Directory of Open Access Journals (Sweden)

    Marlon E. Pierce

    2015-11-01

    Full Text Available An important reason for making any software open source is to encourage code and other community contributions, resulting in more diverse developer communities coalescing around valuable software efforts. We believe the full picture of open developer communities is underappreciated by scientific and cyberinfrastructure open source software efforts. Free and open source licensing is popular in scientific and cyberinfrastructure software, and Web-based tools for source code management (such as GitHub and Bitbucket are in common use, but community building efforts and associated governance models that foster these communities need improvement. We propose here a simple mechanism to address this problem: developers should be given incentives to submit patches and to make other measurable contributions to code bases that they use but are not otherwise connected to, and projects should be given incentives to accept these outside contributions. As an example implementation, we outline a contest system with small monetary rewards for individuals and recognition for both individuals and projects. The goal is to change the mindset of scientific and cyberinfrastructure developers, converting them from passive downstream users to active contributors. We hypothesize that this easily measurable concrete action will contribute to the sustainability of many projects and also create a more flexible scientific workforce. Building this effort on currently available, federally funded software will establish a foundation of public data that can be used to verify our hypothesis. More broadly, the effort will demonstrate the benefits for scientific and cyberinfrastructure projects that adopt workable governance models that are already well established in the broader open source software ecosystem.

  13. Tunable plasticity in amorphous silicon carbide films.

    Science.gov (United States)

    Matsuda, Yusuke; Kim, Namjun; King, Sean W; Bielefeld, Jeff; Stebbins, Jonathan F; Dauskardt, Reinhold H

    2013-08-28

    Plasticity plays a crucial role in the mechanical behavior of engineering materials. For instance, energy dissipation during plastic deformation is vital to the sufficient fracture resistance of engineering materials. Thus, the lack of plasticity in brittle hybrid organic-inorganic glasses (hybrid glasses) often results in a low fracture resistance and has been a significant challenge for their integration and applications. Here, we demonstrate that hydrogenated amorphous silicon carbide films, a class of hybrid glasses, can exhibit a plasticity that is even tunable by controlling their molecular structure and thereby leads to an increased and adjustable fracture resistance in the films. We decouple the plasticity contribution from the fracture resistance of the films by estimating the "work-of-fracture" using a mean-field approach, which provides some insight into a potential connection between the onset of plasticity in the films and the well-known rigidity percolation threshold.

  14. Environmental evaluation of plastic waste management scenarios

    DEFF Research Database (Denmark)

    Rigamonti, L.; Grosso, M.; Møller, Jacob

    2014-01-01

    The management of the plastic fraction is one of the most debated issues in the discussion on integrated municipal solid waste systems. Both material and energy recovery can be performed on such a waste stream, and different separate collection schemes can be implemented. The aim of the paper...... is to contribute to the debate, based on the analysis of different plastic waste recovery routes. Five scenarios were defined and modelled with a life cycle assessment approach using the EASEWASTE model. In the baseline scenario (P0) the plastic is treated as residual waste and routed partly to incineration...... with energy recovery and partly to mechanical biological treatment. A range of potential improvements in plastic management is introduced in the other four scenarios (P1–P4). P1 includes a source separation of clean plastic fractions for material recycling, whereas P2 a source separation of mixed plastic...

  15. Plastics disassembly versus bulk recycling: engineering design for end-of-life electronics resource recovery.

    Science.gov (United States)

    Rios, Pedro; Stuart, Julie Ann; Grant, Ed

    2003-12-01

    Annual plastic flows through the business and consumer electronics manufacturing supply chain include nearly 3 billion lb of high-value engineering plastics derived from petroleum. The recovery of resource value from this stream presents critical challenges in areas of materials identification and recycling process design that demand new green engineering technologies applied together with life cycle assessment and ecological supply chain analysis to create viable plastics-to-plastics supply cycles. The sustainable recovery of potentially high-value engineering plastics streams requires that recyclers either avoid mixing plastic parts or purify later by separating smaller plastic pieces created in volume reduction (shredding) steps. Identification and separation constitute significant barriers in the plastics-to-plastics recycling value proposition. In the present work, we develop a model that accepts randomly arriving electronic products to study scenarios by which a recycler might identify and separate high-value engineering plastics as well as metals. Using discrete eventsimulation,we compare current mixed plastics recovery with spectrochemical plastic resin identification and subsequent sorting. Our results show that limited disassembly with whole-part identification can produce substantial yields in separated streams of recovered engineering thermoplastics. We find that disassembly with identification does not constitute a bottleneck, but rather, with relatively few workers, can be configured to pull the process and thus decrease maximum staging space requirements.

  16. Transverse isotropic modeling of the ballistic response of glass reinforced plastic composites

    Energy Technology Data Exchange (ETDEWEB)

    Taylor, P.A. [Sandia National Labs., Albuquerque, NM (United States)

    1997-12-31

    The use of glass reinforced plastic (GRP) composites is gaining significant attention in the DoD community for use in armor applications. These materials typically possess a laminate structure consisting of up to 100 plies, each of which is constructed of a glass woven roving fabric that reinforces a plastic matrix material. Current DoD attention is focused on a high strength, S-2 glass cross-weave (0/90) fabric reinforcing a polyester matrix material that forms each ply of laminate structure consisting anywhere from 20 to 70 plies. The resulting structure displays a material anisotropy that is, to a reasonable approximation, transversely isotropic. When subjected to impact and penetration from a metal fragment projectile, the GRP displays damage and failure in an anisotropic manner due to various mechanisms such as matrix cracking, fiber fracture and pull-out, and fiber-matrix debonding. In this presentation, the author will describe the modeling effort to simulate the ballistic response of the GRP material described above using the transversely isotropic (TI) constitutive model which has been implemented in the shock physics code, CTH. The results of this effort suggest that the model is able to describe the delamination behavior of the material but has some difficulty capturing the in-plane (i.e., transverse) response of the laminate due to its cross-weave fabric reinforcement pattern which causes a departure from transverse isotropy.

  17. Oxytocin and Maternal Brain Plasticity

    Science.gov (United States)

    Kim, Sohye; Strathearn, Lane

    2016-01-01

    Although dramatic postnatal changes in maternal behavior have long been noted, we are only now beginning to understand the neurobiological mechanisms that support this transition. The present paper synthesizes growing insights from both animal and human research to provide an overview of the plasticity of the mother's brain, with a particular…

  18. Research on the Mechanic Performance of Honeycomb Plastic Tire%蜂巢式塑料轮胎力学性能研究

    Institute of Scientific and Technical Information of China (English)

    王若云; 贺建芸; 丁玉梅; 刘肖英; 杨卫民; 焦志伟

    2014-01-01

    基于聚氨酯弹性体优异的性能,建立了3种不同密度的蜂巢式塑料轮胎模型,并以ABAQUS软件为工具,以同型号的传统橡胶轮胎为参照,对比分析了稳态滚动工况下轮胎的接地性能和应力分布。分析结果表明,与传统橡胶轮胎相比,蜂巢式塑料轮胎的等效应力分布更加均匀。因此,蜂巢式塑料轮胎局部发生过度磨损的可能性降低。此外,蜂巢式塑料轮胎支撑板的受力情况与蜂巢密度密切相关。%Based on superior performance of polyurethane elastomer,three different density of honeycomb plastic tires models were established,the same model of the traditional rubber tires were taken as reference,and ABAQUS software was used as analysis tool to compare and analyze the grounding performance and stress distribution of the plastic tires under the steady rolling conditions. The results show that the equivalent stresses of honeycomb plastic tires distribute more uniformly than that of the traditional rubber tires. Therefore, the possibility of excessive wear of honeycomb plastic tires gets smaller. In addition, the stress conditions of support plates of the tires are closely related to honeycomb density.

  19. Energy Harvesting from Upper-Limb Pulling Motions for Miniaturized Human-Powered Generators

    Directory of Open Access Journals (Sweden)

    Jeongjin Yeo

    2015-07-01

    Full Text Available The human-powered self-generator provides the best solution for individuals who need an instantaneous power supply for travel, outdoor, and emergency use, since it is less dependent on weather conditions and occupies less space than other renewable power supplies. However, many commercial portable self-generators that employ hand-cranking are not used as much as expected in daily lives although they have enough output capacity due to their intensive workload. This study proposes a portable human-powered generator which is designed to obtain mechanical energy from an upper limb pulling motion for improved human motion economy as well as efficient human-mechanical power transfer. A coreless axial-flux permanent magnet machine (APMM and a flywheel magnet rotor were used in conjunction with a one-way clutched power transmission system in order to obtain effective power from the pulling motion. The developed prototype showed an average energy conversion efficiency of 30.98% and an average output power of 0.32 W with a maximum of 1.89 W. Its small form factor (50 mm × 32 mm × 43.5 mm, 0.05 kg and the substantial electricity produced verify the effectiveness of the proposed method in the utilization of human power. It is expected that the developed generator could provide a mobile power supply.

  20. Energy Harvesting from Upper-Limb Pulling Motions for Miniaturized Human-Powered Generators.

    Science.gov (United States)

    Yeo, Jeongjin; Ryu, Mun-ho; Yang, Yoonseok

    2015-07-03

    The human-powered self-generator provides the best solution for individuals who need an instantaneous power supply for travel, outdoor, and emergency use, since it is less dependent on weather conditions and occupies less space than other renewable power supplies. However, many commercial portable self-generators that employ hand-cranking are not used as much as expected in daily lives although they have enough output capacity due to their intensive workload. This study proposes a portable human-powered generator which is designed to obtain mechanical energy from an upper limb pulling motion for improved human motion economy as well as efficient human-mechanical power transfer. A coreless axial-flux permanent magnet machine (APMM) and a flywheel magnet rotor were used in conjunction with a one-way clutched power transmission system in order to obtain effective power from the pulling motion. The developed prototype showed an average energy conversion efficiency of 30.98% and an average output power of 0.32 W with a maximum of 1.89 W. Its small form factor (50 mm × 32 mm × 43.5 mm, 0.05 kg) and the substantial electricity produced verify the effectiveness of the proposed method in the utilization of human power. It is expected that the developed generator could provide a mobile power supply.

  1. Recycling of Plastic

    DEFF Research Database (Denmark)

    Christensen, Thomas Højlund; Fruergaard, Thilde

    2011-01-01

    Plastic is produced from fossil oil. Plastic is used for many different products. Some plastic products like, for example, wrapping foil, bags and disposable containers for food and beverage have very short lifetimes and thus constitute a major fraction of most waste. Other plastic products like......, for example, gutters, window frames, car parts and transportation boxes have long lifetimes and thus appear as waste only many years after they have been introduced on the market. Plastic is constantly being used for new products because of its attractive material properties: relatively cheap, easy to form......, good strength and long durability. Recycling of plastic waste from production is well-established, while recycling of postconsumer plastic waste still is in its infancy. This chapter describes briefly how plastic is produced and how waste plastic is recycled in the industry. Quality requirements...

  2. Effect of Plasticizers on Physical and Mechanical Properties of Potato Starch- based Composite Films%增塑剂对马铃薯淀粉基复合膜物理机械性能的影响

    Institute of Scientific and Technical Information of China (English)

    贾超; 王利强; 卢立新; 赵艺程

    2012-01-01

    Potato starch based composite films were prepared by casting using potato starch, pullulan, gelatin as film forming material, calcium chloride as cross-linking agent, and glycerol, sorbitol, and polyethylene glycol as plasticizer. The effects of three kinds of plasticizers on physical and mechanical properties of composite films were studied. The results showed that tensile strength and Young's modulus of the composite films decrease significantly with plasticizer contents; elongation increases significantly with glycerol and sorbitol contents; effect of polyethylene glycol on elongation is not obvious; water vapor permeability and water solubility of composite films increase with plasticizer contents; polyethylene glycol can reduce the light transmission rate of the composite films significantly.%以马铃薯淀粉、普鲁兰多糖、明胶为成膜物质,氯化钙为交联剂,甘油、山梨醇、聚乙二醇为增塑剂,采用流延法制备了马铃薯淀粉基复合膜,研究了3种增塑剂对复合膜物理机械性能的影响。结果表明:复合膜的抗拉强度和弹性模量均随增塑剂含量的增加而显著减小,断裂伸长率随甘油和山梨醇含量的增加而显著增加,聚乙二醇对其影响不显著;复合膜的水蒸气透过率和水溶性均随增塑剂含量的增加而增加;聚乙二醇能够显著降低复合膜的透光率。

  3. Push and pull factors of national parks in South Africa

    OpenAIRE

    Slabbert, E.; Viviers, P.

    2012-01-01

    South Africa's national parks are one of South Africa's major attractions. Since visitors are among the most important role players in the sustainability of these parks, and in-depth research is needed to understand them, this article analyses the push and pull factors that bring them to the parks. The study used a structured questionnaire to collect data on these factors and the socio-demographic profile of the visitors. Surveys conducted at nine National Parks produced 1300 questionnaires. ...

  4. Mucosal proctectomy and ileoanal pull-through technique and functional results in 23 consecutive patients.

    Science.gov (United States)

    Bodzin, J H; Kestenberg, W; Kaufmann, R; Dean, K

    1987-07-01

    Mucosal proctectomy with ileoanal pull-through in the treatment of ulcerative colitis and familial polyposis provides a technique for the preservation of the anal sphincters and relatively normal mechanisms of continence. Five patients had straight ileoanal anastomosis while 18 had the construction of a J-pouch. A two-team approach was used for simultaneous abdominal and perineal procedures to facilitate a shortened operating time. A loop ileostomy was routinely used in the postoperative period and was closed an average of 4.5 months (range: 2-16 months) later without complication. Prolonged preoperative hospitalization was rarely necessary and outpatient steroid enema preparation was routinely used. There were no deaths. Nineteen patients with functioning pull-through procedures have been followed an average of 23 months (range: 3-42 months). Two other patients have not had ileostomy closure because of complications. The two remaining patients had intractable diarrhea and have since undergone conversion to a permanent ileostomy. The 19 patients are continent, having three to nine bowel movements each day. Nearly all wear a perineal sanitary pad because of rare, unpredictable leakage of small amounts of fluid, especially at night. Complications were significant in this group of patients. Intestinal obstruction was a frequent problem, occurring in 52 per cent of the entire series and necessitating reoperation in 22 per cent. Anal stricture was a problem in another five patients. A variety of other minor problems occurred and most were treated nonoperatively. In spite of moderate diarrhea and occasional leakage of stool, all patients with functioning pull-through procedures prefer their current status to life with an ileostomy.(ABSTRACT TRUNCATED AT 250 WORDS)

  5. Intracellular organelles mediate cytoplasmic pulling force for centrosome centration in the Caenorhabditis elegans early embryo

    Science.gov (United States)

    Kimura, Akatsuki

    2010-01-01

    The centrosome is generally maintained at the center of the cell. In animal cells, centrosome centration is powered by the pulling force of microtubules, which is dependent on cytoplasmic dynein. However, it is unclear how dynein brings the centrosome to the cell center, i.e., which structure inside the cell functions as a substrate to anchor dynein. Here, we provide evidence that a population of dynein, which is located on intracellular organelles and is responsible for organelle transport toward the centrosome, generates the force required for centrosome centration in Caenorhabditis elegans embryos. By using the database of full-genome RNAi in C. elegans, we identified dyrb-1, a dynein light chain subunit, as a potential subunit involved in dynein anchoring for centrosome centration. DYRB-1 is required for organelle movement toward the minus end of the microtubules. The temporal correlation between centrosome centration and the net movement of organelle transport was found to be significant. Centrosome centration was impaired when Rab7 and RILP, which mediate the association between organelles and dynein in mammalian cells, were knocked down. These results indicate that minus end-directed transport of intracellular organelles along the microtubules is required for centrosome centration in C. elegans embryos. On the basis of this finding, we propose a model in which the reaction forces of organelle transport generated along microtubules act as a driving force that pulls the centrosomes toward the cell center. This is the first model, to our knowledge, providing a mechanical basis for cytoplasmic pulling force for centrosome centration. PMID:21173218

  6. Lattice pulling effect and strain relaxation in axial (In,Ga)N/GaN nanowire heterostructures grown on GaN-buffered Si(111) substrate

    Energy Technology Data Exchange (ETDEWEB)

    Kong, X.; Trampert, A. [Paul-Drude-Institut fuer Festkoerperelektronik, Hausvogteiplatz 5-7, 10117, Berlin (Germany); Albert, S.; Bengoechea-Encabo, A.; Sanchez-Garcia, M.A.; Calleja, E. [Dpto. Ingenieria Electronica, ETSI Telecomunicacion, Universidad Politecnica, Ciudad Universitaria, 28040, Madrid (Spain)

    2015-04-01

    Transmission electron microscopy and spatially resolved electron energy-loss spectroscopy have been applied to investigate the indium distribution and the interface morphology in axial (In,Ga)N/GaN nanowire heterostructures. The ordered axial (In,Ga)N/GaN nanowire heterostructures with an indium concentration up to 80% are grown by molecular beam epitaxy on GaN-buffered Si(111) substrates. We observed a pronounced lattice pulling effect in all the nanowire samples given in a broad transition region at the interface. The lattice pulling effect becomes smaller and the (In,Ga)N/GaN interface width is reduced as the indium concentration is increased in the (In,Ga)N section. The result can be interpreted in terms of the increased plastic strain relaxation via the generation of the misfit dislocations at the interface. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  7. 综采面支承压力及塑性区变化规律数值模拟研究%Numerical simulation on the variation of support pressure and plastic deformation zone in fully mechanized mining face

    Institute of Scientific and Technical Information of China (English)

    乔军伟

    2011-01-01

    以白坪矿二,煤层为具体原始条件,利用三维数值模拟软件FLAC^3D,分析了随采高不同,综采工作面前方支承压力及煤壁塑性区分布特征和变化规律。%Using three-dimensional numerical simulation software FLAC^3D, the paper analyzed the variation of support pressure and plastic deformation zone in the different mining height in fully mechanized mining face.

  8. β-Functionalized Push-Pull opp-Dibenzoporphyrins.

    Science.gov (United States)

    Jinadasa, R G Waruna; Fang, Yuanyuan; Kumar, Siddhartha; Osinski, Allen J; Jiang, Xiaoqin; Ziegler, Christopher J; Kadish, Karl M; Wang, Hong

    2015-12-18

    The synthesis of a series of β-functionalized push-pull dibenzoporphyrins was realized. These porphyrins display subtle push-pull effects, demonstrating the exceptional tunability of their electronic and electrochemical properties. The UV-vis spectra of these porphyrins show unique absorption patterns with shouldered Soret bands and extra absorptions in the Q-band region. Stronger electron-withdrawing groups display more significant bathochromic shifts of the Soret bands. The fluorescence spectra of these porphyrins show strong near-IR emission bands (600-850 nm). In particular, fluorescence quenching effect was observed for pyridyl carrying push-pull porphyrin 4c in the presence of an acid. TFA titration study of 4c using UV-vis and fluorescence spectroscopy reveals that the fluorescence quenching can be mainly attributed to the protonation of the pyridyl groups of 4c. The versatile synthetic methods developed in this work may open a door to access a large number of functionalized organic materials that are currently unavailable. The structure-property studies provided in this work may provide useful guidelines for the design of new generations of materials in dye-sensitized solar cells, in nonlinear optical applications, as fluorescence probes, as well as sensitizers for photodynamic therapy.

  9. The string-pulling paradigm in comparative psychology.

    Science.gov (United States)

    Jacobs, Ivo F; Osvath, Mathias

    2015-05-01

    String pulling is one of the most widely used paradigms in comparative psychology. First documented 2 millennia ago, it has been a well-established scientific paradigm for a century. More than 160 bird and mammal species have been tested in over 200 studies with countless methodological variations. The paradigm can be used to address a wide variety of issues on animal cognition; for example, what animals understand about contact and connection as well as whether they rely on perceptual feedback, grasp the functionality of strings, generalize across conditions, apply their knowledge flexibly, and possess insight. Mammals are typically tested on a horizontal configuration, birds on a vertical one, making the studies difficult to compare; in particular, pulling a string vertically requires better coordination and attention. A species' performance on the paradigm is often influenced by its ecology, especially concerning whether limbs are used for foraging. Many other factors can be of importance and should be considered. The string-pulling paradigm is easy to administer, vary, and apply to investigate a wide array of cognitive abilities. Although it can be and has been used to compare species, divergent methods and unclear reporting have limited its comparative utility. With increasing research standards, the paradigm is expected to become an even more fundamental tool in comparative psychology. (c) 2015 APA, all rights reserved).

  10. Plasticity in glutamatergic NTS neurotransmission.

    Science.gov (United States)

    Kline, David D

    2008-12-10

    Changes in the physiological state of an animal or human can result in alterations in the cardiovascular and respiratory system in order to maintain homeostasis. Accordingly, the cardiovascular and respiratory systems are not static but readily adapt under a variety of circumstances. The same can be said for the brainstem circuits that control these systems. The nucleus tractus solitarius (NTS) is the central integration site of baroreceptor and chemoreceptor sensory afferent fibers. This central nucleus, and in particular the synapse between the sensory afferent and second-order NTS cell, possesses a remarkable degree of plasticity in response to a variety of stimuli, both acute and chronic. This brief review is intended to describe the plasticity observed in the NTS as well as the locus and mechanisms as they are currently understood. The functional consequence of NTS plasticity is also discussed.

  11. VISCO-ELASTIC (PLASTIC) EFFECTS AND FAILURE BEHAVIOR OF PUR FOAMED PLASTICS

    Institute of Scientific and Technical Information of China (English)

    1998-01-01

    The viscous effects and failure behavior of PUR foamed plastics are investigated by the cycling loading and preloading experiments. On the basis of static and dynamic compressive experiments, the SEM analysis is given for the PUR foamed plastics specimens which have been tested and the deformation as well as failure mechanisms are determined at the same time. In addition, the relaxation characteristics and the failure criterion of foamed plastics are discussed adequately.

  12. Mitochondria, synaptic plasticity, and schizophrenia.

    Science.gov (United States)

    Ben-Shachar, Dorit; Laifenfeld, Daphna

    2004-01-01

    The conceptualization of schizophrenia as a disorder of connectivity, i.e., of neuronal?synaptic plasticity, suggests abnormal synaptic modeling and neuronal signaling, possibly as a consequence of flawed interactions with the environment, as at least a secondary mechanism underlying the pathophysiology of this disorder. Indeed, deficits in episodic memory and malfunction of hippocampal circuitry, as well as anomalies of axonal sprouting and synapse formation, are all suggestive of diminished neuronal plasticity in schizophrenia. Evidence supports a dysfunction of mitochondria in schizophrenia, including mitochondrial hypoplasia, and a dysfunction of the oxidative phosphorylation system, as well as altered mitochondrial-related gene expression. Mitochondrial dysfunction leads to alterations in ATP production and cytoplasmatic calcium concentrations, as well as reactive oxygen species and nitric oxide production. All of the latter processes have been well established as leading to altered synaptic strength or plasticity. Moreover, mitochondria have been shown to play a role in plasticity of neuronal polarity, and studies in the visual cortex show an association between mitochondria and synaptogenesis. Finally, mitochondrial gene upregulation has been observed following synaptic and neuronal activity. This review proposes that mitochondrial dysfunction in schizophrenia could cause, or arise from, anomalies in processes of plasticity in this disorder.

  13. 77 FR 54930 - Carlyle Plastics and Resins, Formerly Known as Fortis Plastics, A Subsidiary of Plastics...

    Science.gov (United States)

    2012-09-06

    ... Employment and Training Administration Carlyle Plastics and Resins, Formerly Known as Fortis Plastics, A... plastic parts. New information shows that Fortis Plastics is now called Carlyle Plastics and Resins. In... of Carlyle Plastics and Resins, formerly known as Fortis Plastics, a subsidiary of...

  14. Biobased additive plasticizing Polylactic acid (PLA

    Directory of Open Access Journals (Sweden)

    Mounira Maiza

    2015-12-01

    Full Text Available Polylactic acid (PLA is an attractive candidate for replacing petrochemical polymers because it is from renewable resources. In this study, a specific PLA 2002D was melt-mixed with two plasticizers: triethyl citrate (TEC and acetyl tributyl citrate (ATBC. The plasticized PLA with various concentrations were analyzed by differential scanning calorimetry (DSC, dynamic mechanical analysis (DMA, melt flow index (MFI, thermogravimetric analysis (TGA, X-ray diffraction (XRD, UV-Visible spectroscopy and plasticizer migration test. Differential scanning calorimetry demonstrated that the addition of TEC and ATBC resulted in a decrease in glass transition temperature (Tg, and the reduction was the largest with the plasticizer having the lowest molecular weight (TEC. Plasticizing effect was also shown by decrease in the dynamic storage modulus and viscosity of plasticized mixtures compared to the treated PLA. The TGA results indicated that ATBC and TEC promoted a decrease in thermal stability of the PLA. The X-ray diffraction showed that the PLA have not polymorphic crystalline transition. Analysis by UV-Visible spectroscopy showed that the two plasticizers: ATBC and TEC have no effect on the color change of the films. The weight loss plasticizer with heating time and at 100°C is lesser than at 135 °C. Migration of TEC and ATBC results in cracks and changed color of material. We have concluded that the higher molecular weight of citrate in the studied exhibited a greater plasticizing effect to the PLA.

  15. Characterization and evaluation physical properties biodegradable plastic composite from seaweed (Eucheuma cottonii)

    Science.gov (United States)

    Deni, Glar Donia; Dhaningtyas, Shalihat Afifah; Fajar, Ibnu; Sudarno

    2015-12-01

    The characterization and evaluation of biodegradable plastic composed of a mixture PVA - carrageenan - chitosan was conducted in this study. Obtained data were then compared to commercial biodegradable plastic. Characteristic of plastic was mechanical tested such as tensile - strength and elongation. Plastic degradation was studied using composting method for 7 days and 14 days. The results showed that the increase carrageenan will decrease tensile-strength and elongation plastic composite. In addition, increase carrageenan would increase the degraded plastics composite.

  16. Disorientations and work-hardening behaviour during severe plastic deformation

    DEFF Research Database (Denmark)

    Pantleon, Wolfgang

    2012-01-01

    Orientation differences develop during plastic deformation even in grains of originally uniform orientation. The evolution of these disorientations is modelled by dislocation dynamics taking into account different storage mechanisms. The predicted average disorientation angles across different...... types of boundaries are in agreement with experimental data for small and moderate plastic strains. At large plastic strains after severe plastic deformation, saturation of the measured average disorientation angle is observed. This saturation is explained as an immediate consequence of the restriction...

  17. Plastic equation of state determined by nano indentation

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    In order to characterize the plastic state of a deformed material, an indentation method to determine the plastic equation of state (PES) was developed. The work-hardening coefficient and the strain rate sensitivity coefficient of the plastic mechanic equation of state were determined by two kinds of indentation tests respectively. Therefore, the PES of materials under deformation can be obtained, and the plastic state of materials can be determined.

  18. Our plastic age

    National Research Council Canada - National Science Library

    Richard C. Thompson; Shanna H. Swan; Charles J. Moore; Frederick S. vom Saal

    2009-01-01

    Within the last few decades, plastics have revolutionized our daily lives. Globally we use in excess of 260 million tonnes of plastic per annum, accounting for approximately 8 per cent of world oil production...

  19. Weinig plastic in vissenmaag

    NARCIS (Netherlands)

    Foekema, E.M.

    2012-01-01

    Waar de magen van sommige zeevogels vol plastic zitten, lijken vissen in de Noordzee nauwelijks last te hebben van kunststofafval. Onderzoekers die plastic resten zochten in vissenmagen vonden ze in elk geval nauwelijks.

  20. Ear Plastic Surgery

    Science.gov (United States)

    ... ENTCareers Marketplace Find an ENT Doctor Near You Ear Plastic Surgery Ear Plastic Surgery Patient Health Information ... they may improve appearance and self-confidence. Can Ear Deformities Be Corrected? Formation of the ear during ...

  1. Psychophysical basis for maximum pushing and pulling forces: A review and recommendations.

    Science.gov (United States)

    Garg, Arun; Waters, Thomas; Kapellusch, Jay; Karwowski, Waldemar

    2014-03-01

    The objective of this paper was to perform a comprehensive review of psychophysically determined maximum acceptable pushing and pulling forces. Factors affecting pushing and pulling forces are identified and discussed. Recent studies show a significant decrease (compared to previous studies) in maximum acceptable forces for males but not for females when pushing and pulling on a treadmill. A comparison of pushing and pulling forces measured using a high inertia cart with those measured on a treadmill shows that the pushing and pulling forces using high inertia cart are higher for males but are about the same for females. It is concluded that the recommendations of Snook and Ciriello (1991) for pushing and pulling forces are still valid and provide reasonable recommendations for ergonomics practitioners. Regression equations as a function of handle height, frequency of exertion and pushing/pulling distance are provided to estimate maximum initial and sustained forces for pushing and pulling acceptable to 75% male and female workers. At present it is not clear whether pushing or pulling should be favored. Similarly, it is not clear what handle heights would be optimal for pushing and pulling. Epidemiological studies are needed to determine relationships between psychophysically determined maximum acceptable pushing and pulling forces and risk of musculoskeletal injuries, in particular to low back and shoulders.

  2. Biodegradability of Plastics

    OpenAIRE

    Yutaka Tokiwa; Calabia, Buenaventurada P.; Charles U. Ugwu; Seiichi Aiba

    2009-01-01

    Plastic is a broad name given to different polymers with high molecular weight, which can be degraded by various processes. However, considering their abundance in the environment and their specificity in attacking plastics, biodegradation of plastics by microorganisms and enzymes seems to be the most effective process. When plastics are used as substrates for microorganisms, evaluation of their biodegradability should not only be based on their chemical structure, but also on their physical ...

  3. Mechanism analysis of shear deformation of joint bolt based on elastic-plastic theory%基于弹塑性理论的节理处锚杆剪切变形机理分析

    Institute of Scientific and Technical Information of China (English)

    马超甫; 冯涛; 姚琦; 王平; 廖泽

    2016-01-01

    为了研究节理面处锚杆的剪切变形机制,建立了节理岩体中锚杆的受力模型,对锚杆在节理面处的剪切变形进行了理论分析,利用单位载荷法推导了节理面处锚杆竖向位移与载荷、节理宽度、材料性质间的关系。理论分析表明,节理岩体中锚杆的剪切变形过程为:小挠度变形阶段、弹塑性剪切变形阶段、塑性铰阶段;剪切变形至塑性铰阶段时,节理面处杆体将出现两个塑性铰;节理面处锚杆具有一段结构对称、载荷反对称部分;节理宽度对节理处杆体的弹性区、弹塑性区的分界面位置存在线性影响。%The stressing model of anchor bolt in jointed rock mass is established to study the shear deformation mechanism of jointed rock bolts,and the shear deformation at the joints is analyzed theoretically. Relationships between vertical displacement and load,and joint width and material properties of anchor bolt in the vicinity of the joint plane are deducted.The theoretical analysis shows that the shear deformation process of anchor bolt in jointed rock has the following stages,i.e.small deflection deformation stage,elastic -plastic shear deformation stage,and plastic hinge stage.In plastic hinge stage,two plastic hinges will appear on the anchor bolt near the joint plane.The anchor bolt has a section of body of symmetrical structure and anti -symmetrical load near the joint plane.The joint width has linear effect on Interface position between elastic region and elastic-plastic region near the joint.

  4. Chemical Recycle of Plastics

    Directory of Open Access Journals (Sweden)

    Sara Fatima

    2014-11-01

    Full Text Available Various chemical processes currently prevalent in the chemical industry for plastics recycling have been discussed. Possible future scenarios in chemical recycling have also been discussed. Also analyzed are the effects on the environment, the risks, costs and benefits of PVC recycling. Also listed are the various types of plastics and which plastics are safe to use and which not after rcycle

  5. Plastic value chains

    DEFF Research Database (Denmark)

    Baxter, John; Wahlstrom, Margareta; Zu Castell-Rüdenhausen, Malin

    2014-01-01

    Optimizing plastic value chains is regarded as an important measure in order to increase recycling of plastics in an efficient way. This can also lead to improved awareness of the hazardous substances contained in plastic waste, and how to avoid that these substances are recycled. As an example...

  6. Mechanical Properties of Composite Materials

    Directory of Open Access Journals (Sweden)

    Mitsuhiro Okayasu

    2014-10-01

    Full Text Available An examination has been made of the mechanical and failure properties of several composite materials, such as a short and a long carbon fiber reinforced plastic (short- and long-CFRP and metal based composite material. The short CFRP materials were used for a recycled CFRP which fabricated by the following process: the CFRP, consisting of epoxy resin with carbon fiber, is injected to a rectangular plate cavity after mixing with acrylonitrile butadiene styrene resin with different weight fractions of CFRP. The fatigue and ultimate tensile strength (UTS increased with increasing CFRP content. These correlations, however, break down, especially for tensile strength, as the CFPR content becomes more than 70%. Influence of sample temperature on the bending strength of the long-CFRP was investigated, and it appears that the strength slightly decreases with increasing the temperature, due to the weakness in the matrix. Broken fiber and pull-out or debonding between the fiber and matrix were related to the main failure of the short- and long-CFRP samples. Mechanical properties of metal based composite materials have been also investigated, where fiber-like high hardness CuAl2 structure is formed in aluminum matrix. Excellent mechanical properties were obtained in this alloy, e.g., the higher strength and the higher ductility, compared tothe same alloy without the fiber-like structure. There are strong anisotropic effects on the mechanical properties due to the fiber-like metal composite in a soft Al based matrix.

  7. Thermal, size and surface effects on the nonlinear pull-in of small-scale piezoelectric actuators

    Science.gov (United States)

    SoltanRezaee, Masoud; Ghazavi, Mohammad-Reza

    2017-09-01

    Electrostatically actuated miniature wires/tubes have many operational applications in the high-tech industries. In this research, the nonlinear pull-in instability of piezoelectric thermal small-scale switches subjected to Coulomb and dissipative forces is analyzed using strain gradient and modified couple stress theories. The discretized governing equation is solved numerically by means of the step-by-step linearization method. The correctness of the formulated model and solution procedure is validated through comparison with experimental and several theoretical results. Herein, the length-scale, surface energy, van der Waals attraction and nonlinear curvature are considered in the present comprehensive model and the thermo-electro-mechanical behavior of cantilever piezo-beams are discussed in detail. It is found that the piezoelectric actuation can be used as a design parameter to control the pull-in phenomenon. The obtained results are applicable in stability analysis, practical design and control of actuated miniature intelligent devices.

  8. In-straw cryoprotectant dilution of IVP bovine blastocysts vitrified in hand-pulled glass micropipettes.

    Science.gov (United States)

    Vieira, A D; Forell, F; Feltrin, C; Rodrigues, J L

    2007-06-01

    The aim of this study was to determine the influence of two ethylene glycol-based vitrification solutions on in vitro and in vivo survival after in-straw cryoprotectant dilution of vitrified in vitro-produced bovine embryos. Day-7 expanded blastocysts were selected according to diameter (> or = 180 microm) and osmotic characteristics and randomly assigned to one of three groups (i) VSa: vitrification in 40% EG+17.1% SUC+0.1% PVA; (ii) VSb: vitrification in 20% EG+20% DMSO; (iii) control: non-vitrified embryos. Vitrification was performed in hand-pulled glass micropipettes (GMP) and cryoprotectant dilution in 0.25 ml straws after warming in a plastic tube. Embryo viability was assessed by re-expansion and hatching rates after 72 h of IVC and by pregnancy rates after direct transfer of vitrified embryos. No differences in re-expansion rates were observed between vitrified groups after 24 h in culture (VSa=84.5%; VSb=94.8%). However, fewer VSa embryos (55.2%, Pstraw cryoprotectant dilution and direct embryo transfer.

  9. Damage Tolerance Assessment of Friction Pull Plug Welds in an Aluminum Alloy

    Science.gov (United States)

    McGill, Preston; Burkholder, Jonathan

    2012-01-01

    Friction stir welding is a solid state welding process used in the fabrication of cryogenic propellant tanks. Self-reacting friction stir welding is one variation of the friction stir weld process being developed for manufacturing tanks. Friction pull plug welding is used to seal the exit hole that remains in a circumferential self-reacting friction stir weld. A friction plug weld placed in a self-reacting friction stir weld results in a non-homogenous weld joint where the initial weld, plug weld, their respective heat affected zones and the base metal all interact. The welded joint is a composite plastically deformed material system with a complex residual stress field. In order to address damage tolerance concerns associated with friction plug welds in safety critical structures, such as propellant tanks, nondestructive inspection and proof testing may be required to screen hardware for mission critical defects. The efficacy of the nondestructive evaluation or the proof test is based on an assessment of the critical flaw size. Test data relating residual strength capability to flaw size in an aluminum alloy friction plug weld will be presented.

  10. Mechanical Properties of Different Fillers and Different Plastic-Based Wood Plastic Composite%不同填料及不同塑料基木塑复合材料的力学性能

    Institute of Scientific and Technical Information of China (English)

    朱栋君; 何春霞

    2011-01-01

    以稻秸秆粉、稻壳粉、衫木粉、竹粉,PP、PE-HD、PE-LD膜为原材料,采用模压成型工艺制备不同填料及不同塑料基体的木塑复合材料,并对复合材料力学性能进行分析.结果表明:无油墨PP基复合材料的综合力学性能较好,而含油墨PE-LD基复合材料的冲击韧性较好.稻秸秆粉作为填料增强无油墨PP复合材料效果最佳,制得稻秸秆粉/PP综合力学性能较好,而稻壳粉/PP复合材料冲击韧性较好.%Rice straw powder、 rice husk powder、 wood powder、 bamboo powder, PP、 PE-HD、 PE-LD were mainly materials,molding technics had been taken to make several different composite, its mechanical properties was analyzed.The results showed that using PP film which contained no ink to make composite could be better on the mechanical properties, besides,using PE-LD film which contained ink to make composites could be better on the impact toughness.As a kind of filling material,rice straw powder was much better than other materials to make composites.Rice straw powder/PP composite'mechanical properties was best,besides,rice husk powder/PP composites' impact toughness was best.

  11. Plastics for corrosion inhibition

    CERN Document Server

    Goldade, Victor A; Makarevich, Anna V; Kestelman, Vladimir N

    2005-01-01

    The development of polymer composites containing inhibitors of metal corrosion is an important endeavour in modern materials science and technology. Corrosion inhibitors can be located in a polymer matrix in the solid, liquid or gaseous phase. This book details the thermodynamic principles for selecting these components, their compatibility and their effectiveness. The various mechanisms of metal protection – barrier, inhibiting and electromechanical – are considered, as are the conflicting requirements placed on the structure of the combined material. Two main classes of inhibited materials (structural and films/coatings) are described in detail. Examples are given of structural plastics used in friction units subjected to mechano-chemical wear and of polymer films/coatings for protecting metal objects against corrosion.

  12. 不同配方木塑复合材料的力学性能比较与分析%Comparison and Analysis on the Mechanical Properties of Wood-plastic Composite with Different Formulations

    Institute of Scientific and Technical Information of China (English)

    简伟程; 潘惠; 徐长妍

    2012-01-01

    The mechanical properties of four wood-plastic composite materials, including elastic modu lus, bending strength, compression strength were tested, and the results were briefly analyzed. The results showed that the productions of four kinds of formulations had excellent mechanical properties which can meet the demand of outdoor use.%测试了四种配方木塑复合材料的力学性能,包括弹性模量、弯曲强度和抗压强度,并对其结果进行了简要的分析.实验结果表明,四种配方生产的材料力学性能都较为优异,都能符合户外装饰板材的要求.

  13. Design of a haptic device with grasp and push-pull force feedback for a master-slave surgical robot.

    Science.gov (United States)

    Hu, Zhenkai; Yoon, Chae-Hyun; Park, Samuel Byeongjun; Jo, Yung-Ho

    2016-07-01

    We propose a portable haptic device providing grasp (kinesthetic) and push-pull (cutaneous) sensations for optical-motion-capture master interfaces. Although optical-motion-capture master interfaces for surgical robot systems can overcome the stiffness, friction, and coupling problems of mechanical master interfaces, it is difficult to add haptic feedback to an optical-motion-capture master interface without constraining the free motion of the operator's hands. Therefore, we utilized a Bowden cable-driven mechanism to provide the grasp and push-pull sensation while retaining the free hand motion of the optical-motion capture master interface. To evaluate the haptic device, we construct a 2-DOF force sensing/force feedback system. We compare the sensed force and the reproduced force of the haptic device. Finally, a needle insertion test was done to evaluate the performance of the haptic interface in the master-slave system. The results demonstrate that both the grasp force feedback and the push-pull force feedback provided by the haptic interface closely matched with the sensed forces of the slave robot. We successfully apply our haptic interface in the optical-motion-capture master-slave system. The results of the needle insertion test showed that our haptic feedback can provide more safety than merely visual observation. We develop a suitable haptic device to produce both kinesthetic grasp force feedback and cutaneous push-pull force feedback. Our future research will include further objective performance evaluations of the optical-motion-capture master-slave robot system with our haptic interface in surgical scenarios.

  14. Biodegradability of plastics.

    Science.gov (United States)

    Tokiwa, Yutaka; Calabia, Buenaventurada P; Ugwu, Charles U; Aiba, Seiichi

    2009-08-26

    Plastic is a broad name given to different polymers with high molecular weight, which can be degraded by various processes. However, considering their abundance in the environment and their specificity in attacking plastics, biodegradation of plastics by microorganisms and enzymes seems to be the most effective process. When plastics are used as substrates for microorganisms, evaluation of their biodegradability should not only be based on their chemical structure, but also on their physical properties (melting point, glass transition temperature, crystallinity, storage modulus etc.). In this review, microbial and enzymatic biodegradation of plastics and some factors that affect their biodegradability are discussed.

  15. Plastic value chains

    DEFF Research Database (Denmark)

    Baxter, John; Wahlstrom, Margareta; Zu Castell-Rüdenhausen, Malin

    2014-01-01

    Optimizing plastic value chains is regarded as an important measure in order to increase recycling of plastics in an efficient way. This can also lead to improved awareness of the hazardous substances contained in plastic waste, and how to avoid that these substances are recycled. As an example......, plastics from WEEE is chosen as a Nordic case study. The project aims to propose a number of improvements for this value chain together with representatives from Nordic stakeholders. Based on the experiences made, a guide for other plastic value chains shall be developed....

  16. Biodegradability of Plastics

    Directory of Open Access Journals (Sweden)

    Yutaka Tokiwa

    2009-08-01

    Full Text Available Plastic is a broad name given to different polymers with high molecular weight, which can be degraded by various processes. However, considering their abundance in the environment and their specificity in attacking plastics, biodegradation of plastics by microorganisms and enzymes seems to be the most effective process. When plastics are used as substrates for microorganisms, evaluation of their biodegradability should not only be based on their chemical structure, but also on their physical properties (melting point, glass transition temperature, crystallinity, storage modulus etc.. In this review, microbial and enzymatic biodegradation of plastics and some factors that affect their biodegradability are discussed.

  17. Journal of CHINA PLASTICS

    Institute of Scientific and Technical Information of China (English)

    2012-01-01

    Journal of CHINA PLASTICS was authorized and approved by The State Committee of Science and Technology of China and The Bureau of News Press of China, and published by The China Plastics Processing Industry Association,Beijing Technology and Business University and The Institute of Plastics Processing and Application of Light Industry, distributed worldwide. Since its birth in 1987, CHINA PLASTICS has become a leading magazine in plastics industry in China, a national Chinese core journal and journal of Chinese scientific and technological article statistics. It is covered by CA.

  18. Strain rate dependence in plasticized and un-plasticized PVC

    Directory of Open Access Journals (Sweden)

    Siviour C.R.

    2012-08-01

    Full Text Available An experimental and analytical investigation has been made into the mechanical behaviour of two poly (vinyl chloride (PVC polymers – an un-plasticized PVC and a diisononyl phthalate (DINP-plasticized PVC. Measurements of the compressive stress-strain behaviour of the PVCs at strain rates ranging from 10−3 to 103s−1 and temperatures from − 60 to 100∘C are presented. Dynamic Mechanical Analysis was also performed in order to understand the material transitions observed in compression testing as the strain rate is increased. This investigation develops a better understanding of the interplay between the temperature dependence and rate dependence of polymers, with a focus on locating the temperature and rate-dependent material transitions that occur during high rate testing.

  19. Strain rate dependence in plasticized and un-plasticized PVC

    Science.gov (United States)

    Kendall, M. J.; Siviour, C. R.

    2012-08-01

    An experimental and analytical investigation has been made into the mechanical behaviour of two poly (vinyl chloride) (PVC) polymers - an un-plasticized PVC and a diisononyl phthalate (DINP)-plasticized PVC. Measurements of the compressive stress-strain behaviour of the PVCs at strain rates ranging from 10-3 to 103s-1 and temperatures from - 60 to 100∘C are presented. Dynamic Mechanical Analysis was also performed in order to understand the material transitions observed in compression testing as the strain rate is increased. This investigation develops a better understanding of the interplay between the temperature dependence and rate dependence of polymers, with a focus on locating the temperature and rate-dependent material transitions that occur during high rate testing.

  20. Challenges in plastics recycling

    DEFF Research Database (Denmark)

    Pivnenko, Kostyantyn; Jakobsen, L. G.; Eriksen, Marie Kampmann

    2015-01-01

    Recycling of waste plastics still remains a challenging area in the waste management sector. The current and potential goals proposed on EU or regional levels are difficult to achieve, and even to partially fullfil them the improvements in collection and sorting should be considerable. A study...... was undertaken to investigate the factors affecting quality in plastics recycling. The preliminary results showed factors primarily influencing quality of plastics recycling to be polymer cross contamination, presence of additives, non-polymer impurities, and polymer degradation. Deprivation of plastics quality......, with respect to recycling, has been shown to happen throughout the plastics value chain, but steps where improvements may happen have been preliminary identified. Example of Cr in plastic samples analysed showed potential spreading and accumulation of chemicals ending up in the waste plastics. In order...

  1. A high-sensitivity push-pull magnetometer

    Science.gov (United States)

    Breschi, E.; Grujić, Z. D.; Knowles, P.; Weis, A.

    2014-01-01

    We describe our approach to atomic magnetometry based on the push-pull optical pumping technique. Cesium vapor is pumped and probed by a resonant laser beam whose circular polarization is modulated synchronously with the spin evolution dynamics induced by a static magnetic field. The magnetometer is operated in a phase-locked loop, and it has an intrinsic sensitivity below 20fT/√Hz , using a room temperature paraffin-coated cell. We use the magnetometer to monitor magnetic field fluctuations with a sensitivity of 300fT/√Hz .

  2. A high-sensitivity push-pull magnetometer

    CERN Document Server

    Breschi, E; Knowles, P; Weis, A

    2013-01-01

    We describe our approach to atomic magnetometry based on the push-pull optical pumping technique. Cesium vapor is pumped and probed by a resonant laser beam whose circular polarization is modulated synchronously with the spin evolution dynamics induced by a static magnetic field. The magnetometer is operated in a phase-locked loop, and it has an intrinsic sensitivity below 20fT/\\sqrt(Hz) using a room temperature paraffin-coated cell. We use the magnetometer to monitor magnetic field fluctuations with a sensitivity of 300fT/\\sqrt(Hz).

  3. Friction pull plug welding: dual chamfered plate hole

    Science.gov (United States)

    Coletta, Edmond R. (Inventor); Cantrell, Mark A. (Inventor)

    2001-01-01

    Friction Pull Plug Welding (FPPW) is a solid state repair process for defects up to one inch in length, only requiring single sided tooling (OSL) for usage on flight hardware. Early attempts with FPPW followed the matching plug/plate geometry precedence of the successful Friction Push Plug Welding program, however no defect free welds were achieved due to substantial plug necking and plug rotational stalling. The dual chamfered hole has eliminated plug rotational stalling, both upon initial plug/plate contact and during welding. Also, the necking of the heated plug metal under a tensile heating/forging load has been eliminated through the usage of the dual chamfered plate hole.

  4. Nonlinear Finite Element Analysis of Pull-Out Test

    DEFF Research Database (Denmark)

    Saabye Ottesen, N

    1981-01-01

    A specific pull-out test used to determine in-situ concrete compressive strength is analyzed. This test consists of a steel disc that is extracted from the structure. The finite element analysis considers cracking as well as strain hardening and softening in the pre- and post-failure region......, respectively. The aim is to attain a clear insight into structural behavior. Special attention is given to the failure mode. Severe cracking occurs and the stress distribution is very inhomogeneous. However, large compressive forces run from the disc in a rather narrow band towards the support...

  5. N -annulated perylene-based push-pull-type sensitizers

    KAUST Repository

    Qi, Qingbiao

    2015-02-06

    Alkoxy-wrapped N-annulated perylene (NP) was synthesized and used as a rigid and coplanar π-linker for three push-pull type metal-free sensitizers QB1-QB3. Their optical and electrochemical properties were tuned by varying the structure of acceptor. These new dyes were applied in Co(II)/(III) based dye-sensitized solar cells, and power conversion efficiency up to 6.95% was achieved, indicating that NP could be used as a new building block for the design of high-performance sensitizers in the future.

  6. THE DISCUSSION ON BEAM-ARCH ACTION MECHANISM OF DEEP PILE CAPS WITH PULL PILE UNDER UNBALANCED BENDING MOMENT%不平衡弯矩作用下有受拉桩的厚承台梁拱作用机理探讨

    Institute of Scientific and Technical Information of China (English)

    郭宏磊

    2012-01-01

    进行了不平衡弯矩作用下有受拉桩的厚承台实验与有限元研究,表明该种承台可以因有梁作用而发生弯曲破坏,而受弯曲作用的同时,又因有拱作用而使得空间桁架的传力体系依然存在.梁拱作用并存在厚承台中具有一定的普遍性.%The study of the deep pile cap with a pull pile under an unbalanced bending moment is processed, based on the test and finite element method. The research indicates that this kind of pile cap may induce bending failure due to the beam action, and at the same time, it still acts as a load transfer system of the spatial strut-and-tie due to the arch action. It is definitely universal that both the beam action and the arch action exist in the deep pile cap.

  7. Degradation studies on plasticized PVC films submited to gamma radiation

    Directory of Open Access Journals (Sweden)

    Vinhas Glória Maria

    2003-01-01

    Full Text Available Poly (vinyl chloride, PVC, is a rigid polymer and for several of its applications must be compounded with plasticizing agents. The plasticizers minimize the dipolar interactions, which exist between the polymer's chains, promoting their mobility. In this work we studied the properties of PVC/plasticizer systems submitted to different doses of gamma radiation. We have used four commercial plasticizers amongt them di(2-ethylhexyl phthalate, DEHP, which is present in a great number of commercial applications. The PVC/plasticizer systems have been studied as films made by the solvent evaporation technique. Irradiated and non-irradiated films have been characterized by viscosimetric analysis, mechanical essays and infrared spectroscopy. The results have shown that the rigid, non plasticized, PVC film presented the greatest degradation index, while among the plasticized films the one which presented the larger degradation index due to chain scission was the DEHP plasticized PVC.

  8. Biological degradation of plastics: a comprehensive review.

    Science.gov (United States)

    Shah, Aamer Ali; Hasan, Fariha; Hameed, Abdul; Ahmed, Safia

    2008-01-01

    Lack of degradability and the closing of landfill sites as well as growing water and land pollution problems have led to concern about plastics. With the excessive use of plastics and increasing pressure being placed on capacities available for plastic waste disposal, the need for biodegradable plastics and biodegradation of plastic wastes has assumed increasing importance in the last few years. Awareness of the waste problem and its impact on the environment has awakened new interest in the area of degradable polymers. The interest in environmental issues is growing and there are increasing demands to develop material which do not burden the environment significantly. Biodegradation is necessary for water-soluble or water-immiscible polymers because they eventually enter streams which can neither be recycled nor incinerated. It is important to consider the microbial degradation of natural and synthetic polymers in order to understand what is necessary for biodegradation and the mechanisms involved. This requires understanding of the interactions between materials and microorganisms and the biochemical changes involved. Widespread studies on the biodegradation of plastics have been carried out in order to overcome the environmental problems associated with synthetic plastic waste. This paper reviews the current research on the biodegradation of biodegradable and also the conventional synthetic plastics and also use of various techniques for the analysis of degradation in vitro.

  9. Integrating Hebbian and homeostatic plasticity: introduction.

    Science.gov (United States)

    Fox, Kevin; Stryker, Michael

    2017-03-05

    Hebbian plasticity is widely considered to be the mechanism by which information can be coded and retained in neurons in the brain. Homeostatic plasticity moves the neuron back towards its original state following a perturbation, including perturbations produced by Hebbian plasticity. How then does homeostatic plasticity avoid erasing the Hebbian coded information? To understand how plasticity works in the brain, and therefore to understand learning, memory, sensory adaptation, development and recovery from injury, requires development of a theory of plasticity that integrates both forms of plasticity into a whole. In April 2016, a group of computational and experimental neuroscientists met in London at a discussion meeting hosted by the Royal Society to identify the critical questions in the field and to frame the research agenda for the next steps. Here, we provide a brief introduction to the papers arising from the meeting and highlight some of the themes to have emerged from the discussions.This article is part of the themed issue 'Integrating Hebbian and homeostatic plasticity'. © 2017 The Author(s).

  10. Exercise and plasticize the brain

    DEFF Research Database (Denmark)

    Mala, Hana; Wilms, Inge

    Neuroscientific studies continue to shed light on brain’s plasticity and its innate mechanisms to recover. The recovery process includes re-wiring of the existing circuitry, establishment of new connections, and recruitment of peri-lesional and homologous areas in the opposite hemisphere. The pla......Neuroscientific studies continue to shed light on brain’s plasticity and its innate mechanisms to recover. The recovery process includes re-wiring of the existing circuitry, establishment of new connections, and recruitment of peri-lesional and homologous areas in the opposite hemisphere...... potential through available training methods. Furthermore, research into neurorehabilitation is dependent on input from a number of fields (such as neuropsychology, neurology, physiotherapy, speech and language therapy, special education, and social work) and requires a close collaboration between...

  11. Brain plasticity and aerobic fitness

    OpenAIRE

    2014-01-01

    Regular aerobic exercise has a wide range of positive effects on health and cognition. Exercise has been demonstrated to provide a particularly powerful and replicable method of triggering a wide range of structural changes within both human and animal brains. However, the details and mechanisms of these changes remain poorly understood. This thesis undertakes a comprehensive examination of the relationship between brain plasticity and aerobic exercise. A large, longitudinal experiment ...

  12. The rise of plastic bioelectronics

    Science.gov (United States)

    Someya, Takao; Bao, Zhenan; Malliaras, George G.

    2016-12-01

    Plastic bioelectronics is a research field that takes advantage of the inherent properties of polymers and soft organic electronics for applications at the interface of biology and electronics. The resulting electronic materials and devices are soft, stretchable and mechanically conformable, which are important qualities for interacting with biological systems in both wearable and implantable devices. Work is currently aimed at improving these devices with a view to making the electronic-biological interface as seamless as possible.

  13. HOM identification by bead pulling in the Brookhaven ERL cavity

    CERN Document Server

    Hahn, H; Jain, Puneet; Johnson, Elliott C; Xu, Wencan

    2014-01-01

    Exploratory measurements of the Brookhaven Energy Recovery Linac (ERL) cavity at superconducting temperature produced a long list of high order modes (HOMs). The niobium 5-cell cavity is terminated at each end with HOM ferrite dampers that successfully reduce the Q-factors to levels required to avoid beam break up (BBU) instabilities. However, a number of un-damped resonances with Q≥106 were found at 4 K and their mode identification forms the focus of this paper. The approach taken here consists of bead pulling on a copper (Cu) replica of the ERL cavity with dampers involving various network analyzer measurements. Several different S21 transmission measurements are used, including those taken from the fundamental input coupler to the pick-up probe across the cavity, others between beam-position monitor probes in the beam tubes, and also between probes placed into the cells. The bead pull technique suitable for HOM identification with a metallic needle or dielectric bead is detailed. This paper presents the...

  14. Biomechanical and physiological analyses of a luggage-pulling task.

    Science.gov (United States)

    Jung, Myung-Chul; Haight, Joel M; Hallbeck, M Susan

    2007-12-01

    The purpose of this study was to identify the degree of physical stresses on two-wheeled carry-on luggage users in terms of biomechanics and work physiology. Based on 3D kinematics, a 3D inverse dynamic biomechanical model having fifteen segments was developed to evaluate a one-hand pulling task. Joint reaction forces, joint moments and physiological variables (energy expenditure and heart rate) were measured from four subjects who performed 32 luggage-pulling tasks on a doublewide treadmill in the configurations of handle height (100 cm and 110 cm), handle rotation (0 degrees and 90 degrees ), pole angle (0 degrees and 10 degrees ), wheel diameter (8 cm and 15 cm), load weight (15 kg or 23 kg), center of mass (low and middle), carpeting (no and yes), trial day (first and second) and subject height (short and tall). ANOVA revealed that wheel diameter, center of mass and subject height were highly associated with the physical stresses of luggage users, especially their right arm. Although the task seems light work, users should place heavy belongings at the bottom of luggage when packing and manufacturers should give a priority to large wheels for ergonomic design.

  15. Lessons learned from tubes pulled from French steam generators

    Energy Technology Data Exchange (ETDEWEB)

    Berge, Ph.; Boursier, J.M.; Dallery, D.; De Keroulas, F.; Rouillon, Y. [Electricite de France, Generating and Transmission Div. (France)

    1998-07-01

    Since 1981, the Chinon Hot Laboratory has completed more than 380 metallurgical examinations of pulled French steam generator tubes. Electricite de France decided to perform such investigations from the very outset of the French nuclear program, in order to contribute to nuclear power plant safety. The main reasons for withdrawing tubes are to evaluate the degradation, to validate non destructive examination (NDE) techniques, to gain a better understanding of cracking phenomena, and to ensure that the criteria on which plugging operations are based remain conservative. Considerable experience has been accumulated in the field of primary water stress corrosion cracking (PWSCC), OD (secondary) side corrosion, leak and burst tests, and various tube plugging techniques. This paper focuses on the PWSCC phenomenon and on the secondary side corrosion process, and in particular, attempts to correlate French data from pulled tubes with the results of fundamental R and D studies. Finally, within the framework of the Nuclear Power Plant Safety and Maintenance Policy, all these results are discussed in terms of optimization of the field inspection of tube bundles and plugging criteria. (author)

  16. Heat-and-pull rig for fiber taper fabrication

    Science.gov (United States)

    Ward, Jonathan M.; O'Shea, Danny G.; Shortt, Brian J.; Morrissey, Michael J.; Deasy, Kieran; Nic Chormaic, Síle G.

    2006-08-01

    We describe a reproducible method of fabricating adiabatic tapers with 3-4μm diameter. The method is based on a heat-and-pull rig, whereby a CO2 laser is continuously scanned across a length of fiber that is being pulled synchronously. Our system relies on a CO2 mirror mounted on a geared stepper motor in order to scan the laser beam across the taper region. We show that this system offers a reliable alternative to more traditional rigs incorporating galvanometer scanners. We have routinely obtained transmission losses between 0.1 and 0.3dB indicating the satisfactory production of adiabatic tapers. The operation of the rig is described in detail and an analysis on the produced tapers is provided. The flexibility of the rig is demonstrated by fabricating prolate dielectric microresonators using a microtapering technique. Such a rig is of interest to a range of fields that require tapered fiber fabrication such as microcavity-taper coupling, atom guiding along a tapered fiber, optical fiber sensing, and the fabrication of fused biconical tapered couplers.

  17. Neural plasticity on depression and its drug interference mechanisms%抑郁症海马神经可塑性改变及药物干预机制研究

    Institute of Scientific and Technical Information of China (English)

    张齐; 张曼; 戴建业; 司琳

    2015-01-01

    抑郁症作为常见的情感障碍疾病,其发病率呈现逐年增加的趋势。研究显示慢性、低强度、长期的应激性生活事件是引发抑郁的主要原因,抑郁症患者及慢性应激抑郁模型动物边缘系统部分脑区尤其是海马部位,均存在神经可塑性改变,抑郁症发病的神经可塑性机制研究成为新亮点。近年来,中、西医学界对此进行了一些有益的探索,并取得了一定的进展。%Depressionisa common disease of emotional disorder;its incidence has an increasing tendency. Research showed that the main reason of depression was chronic, low intensity and long-term stressful life event. Neural plasticity exists in some partial brain areas of the limbic system especially in hippocampus of the depressed patients and model animals of depression induced by chronic stresses. Neural plasticity on depression is becoming the new highlight of the mechanism of depression. For the past few years, TCM medicine and western medicine have made a beneficial research and progress on it.

  18. 压缩载荷作用下岩石的细观损伤和塑性研究%Crack-mechanics damage and plasticity for rock-like materials under compressive loading

    Institute of Scientific and Technical Information of China (English)

    袁小平; 刘红岩; 王志乔

    2013-01-01

    建立岩石微裂纹扩展的细观力学模型,研究了岩石的细观损伤和塑性性质.压缩载荷下微裂纹尖端翼裂纹稳定扩展表征岩石的细观损伤,采用应变能密度准则求解复合型断裂的翼裂纹扩展长度,微裂隙统计的二参数Weibull函数模型反映绝对体积应变对微裂纹分布数目影响,进而用翼裂纹扩展所表征的应力释放体积和微裂纹数目来表示含有微裂隙的岩石损伤演化变量;宏观塑性屈服函数采用Voyiadjis等的等效塑性应变的硬化函数,反映了塑性内变量对硬化函数的影响;建立岩石模型的本构关系及其数值算法,并用回映隐式积分算法编制了模型的本构程序.分析弹塑性损伤模型的围压对岩石损伤的影响,并从围压和短微裂隙长度等因素分析模型的岩石的损伤和宏观塑性特性.%A crack-mechanics based model of rock together with plasticity under compressive loading is presented in this work. The propagation of wing crack in the micro-crack tip is characterized for rock damage,and the wing crack length is obtained based on the strain energy density for mixed-mode fracture. The distribution of micro-cracks is presented by the absolute volume strain with the two-parameter Weibull statistical model. The damage evolution variable of rock is employed by the distribution of micro-cracks and stress release volume. Voyiadjis's strain hardening function is employed as the plastic yield function and plastic potential function. The elastoplastic damage model with its numerical algorithm is proposed and the code of elastoplastic damage model is implemented by using return mapping method. The plastic properties of the rock are analyzed from the respects of short micro-crack lengths, confining pressures.

  19. Traumatic rupture of gastric pull-up after apparent mild thoracic trauma: a case report and literature review.

    Science.gov (United States)

    Valle, Joaquin; Srinivasrao, Hanumantha; Snow, David; Asbitt, Mike

    2016-05-01

    While elderly patients account for only 10-12% of all trauma victims, they consume 25% of trauma-related health care resources, with higher rates of mortality and complication. Presently described is the case of an elderly patient who presented to the emergency department (ED) following mild thoracic trauma, with previous history of gastric pull-up surgery. The patient had consulted another facility 48 hours earlier and was prescribed analgesia and x-ray follow-up for a mechanical fall and pain in the lower rib cage. At arrival, the patient complained of increasing dyspnea and pain at the right hemithorax. X-ray showed right hemithorax effusion, and contrast computed tomography (CT) demonstrated a large amount of contrast filling the pleural space and a relatively small point of gastric pull-up rupture in the stomach. The patient was referred to the cardiothoracic unit, but was unresponsive upon arrival and died. The aim of the present report was to raise the index of clinical suspicion of traumatic rupture of the gastric pull-up following traumatic chest injury, and to affirm that contrast CT should be the gold standard for diagnosis.

  20. Stress distribution in maxillary first molar periodontium using straight pull headgear with vertical and horizontal tubes: A finite element analysis.

    Science.gov (United States)

    Feizbakhsh, Masood; Kadkhodaei, Mahmoud; Zandian, Dana; Hosseinpour, Zahra

    2017-01-01

    One of the most effective ways for distal movement of molars to treat Class II malocclusion is using extraoral force through a headgear device. The purpose of this study was the comparison of stress distribution in maxillary first molar periodontium using straight pull headgear in vertical and horizontal tubes through finite element method. Based on the real geometry model, a basic model of the first molar and maxillary bone was obtained using three-dimensional imaging of the skull. After the geometric modeling of periodontium components through CATIA software and the definition of mechanical properties and element classification, a force of 150 g for each headgear was defined in ABAQUS software. Consequently, Von Mises and Principal stresses were evaluated. The statistical analysis was performed using T-paired and Wilcoxon nonparametric tests. Extension of areas with Von Mises and Principal stresses utilizing straight pull headgear with a vertical tube was not different from that of using a horizontal tube, but the numerical value of the Von Mises stress in the vertical tube was significantly reduced (P 0/05). Based on the results, when force applied to the straight pull headgear with a vertical tube, Von Mises stress was reduced significantly in comparison with the horizontal tube. Therefore, to correct the mesiolingual movement of the maxillary first molar, vertical headgear tube is recommended.