WorldWideScience

Sample records for operating mechanical stresses

  1. Operation Joint Guard (SFOR) Bosnia. Assessment of Operational Stress and Adaptive Coping Mechanisms of Soldiers

    Science.gov (United States)

    1998-03-01

    Opportunities to contact home acted as a buffer for this stress. ATT phone banks and morale calls home alleviated some of the stress of being away from loved...objectives. Horizontal cohesion (peer group bonding) and vertical cohesion (bonding to unit leadership) were extremely important buffers to stress. Both...4.0 3.0 2.0 7.0 Form Number 7S612-S-88 SURVEY Ivf ^tWoRK1 322 Below are statements about life that people often feel different about. Please

  2. Operator Formulation of Classical Mechanics.

    Science.gov (United States)

    Cohn, Jack

    1980-01-01

    Discusses the construction of an operator formulation of classical mechanics which is directly concerned with wave packets in configuration space and is more similar to that of convential quantum theory than other extant operator formulations of classical mechanics. (Author/HM)

  3. Linear operators for quantum mechanics

    CERN Document Server

    Jordan, Thomas F

    2006-01-01

    This compact treatment highlights the logic and simplicity of the mathematical structure of quantum mechanics. Suitable for advanced undergraduates and graduate students, it treats the language of quantum mechanics as expressed in the mathematics of linear operators.Originally oriented toward atomic physics, quantum mechanics became a basic language for solid-state, nuclear, and particle physics. Its grammar consists of the mathematics of linear operators, and with this text, students will find it easier to understand and use the language of physics. Topics include linear spaces and linear fun

  4. Operator methods in quantum mechanics

    CERN Document Server

    Schechter, Martin

    2003-01-01

    This advanced undergraduate and graduate-level text introduces the power of operator theory as a tool in the study of quantum mechanics, assuming only a working knowledge of advanced calculus and no background in physics. The author presents a few simple postulates describing quantum theory, gradually introducing the mathematical techniques that help answer questions important to the physical theory; in this way, readers see clearly the purpose of the method and understand the accomplishment. The entire book is devoted to the study of a single particle moving along a straight line. By posing q

  5. Influence of tectonic stress on coalification:Stress degradation mechanism and stress polycondensation mechanism

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The function of pressure for coalification is a long-term controversial issue, and the main cause is that the strata pressure and the tectonic stress were confused, which are two different actions of "pres-sure" . The former benefits the physical coalification but retards the chemical coalification, whereas the latter may not only affect the physical structure of coal but also promote its chemical composition changes. In accordance with the organic molecule evolution of coal, there are two kinds of basic mechanisms of the influence of the tectonic stress on the chemical coalification: the tectonic stress degradation and the tectonic stress polycondensation. The stress degradation mechanism is a process of that, when the tectonic stress acted on the large molecule of coal in the form of mechanical force or kinetic energy, some chemical bonds of low decomposed energy, such as aliphatic side-chain and oxygenic functional groups, were broken up and then were degraded into free radicals of less mo-lecular weight, and finally escaped from coal in the form of liquid organic matter (hydrocarbon). The stress polycondensation is considered that, under the control of the anisotropic tectonic stress, the condensed aromatic nucleus trend to be parallel arranged and to be enhanced through rotating or displacing of aromatic rings, the basic structural unit of coal (BSU) increases by directional develop-ment and preferential stack. X-ray diffraction (XRD), Fourier transformation infrared microspectroscopy (FTIR), and rock pyrolysis analysis (Rock-eval) were employed to study the deformed coal series and the non-deformed coal series. The results showed that, compared with the non-deformed coal, the de-formed coal exhibits particular characteristics: weaker aliphatic absorbance peak and stronger aro-matic absorbance peak, lower pyrolysed hydrocarbon yield, and more increscent BSU. The concepts of stress degradation mechanism and stress polycondensation mechanism presented here would

  6. Influence of tectonic stress on coalification: Stress degradation mechanism and stress polycondensation mechanism

    Institute of Scientific and Technical Information of China (English)

    CAO DaiYong; LI XiaoMing; ZHANG ShouRen

    2007-01-01

    The function of pressure for coalification is a long-term controversial issue, and the main cause is that the strata pressure and the tectonic stress were confused, which are two different actions of "pressure". The former benefits the physical coalification but retards the chemical coalification, whereas the latter may not only affect the physical structure of coal but also promote its chemical composition changes. In accordance with the organic molecule evolution of coal, there are two kinds of basic mechanisms of the influence of the tectonic stress on the chemical coalification: the tectonic stress degradation and the tectonic stress polycondensation. The stress degradation mechanism is a process of that, when the tectonic stress acted on the large molecule of coal in the form of mechanical force or kinetic energy, some chemical bonds of low decomposed energy, such as aliphatic side-chain and oxygenic functional groups, were broken up and then were degraded into free radicals of less molecular weight, and finally escaped from coal in the form of liquid organic matter (hydrocarbon). The stress polycondensation is considered that, under the control of the anisotropic tectonic stress, the condensed aromatic nucleus trend to be parallel arranged and to be enhanced through rotating or displacing of aromatic rings, the basic structural unit of coal (BSU) increases by directional development and preferential stack. X-ray diffraction (XRD), Fourier transformation infrared microspectroscopy (FTIR), and rock pyrolysis analysis (Rock-eval) were employed to study the deformed coal series and the non-deformed coal series. The results showed that, compared with the non-deformed coal, the deformed coal exhibits particular characteristics: weaker aliphatic absorbance peak and stronger aromatic absorbance peak, lower pyrolysed hydrocarbon yield, and more increscent BSU. The concepts of stress degradation mechanism and stress polycondensation mechanism presented here would not

  7. The impact of static stress change, dynamic stress change, and the background stress on aftershock focal mechanisms

    Science.gov (United States)

    Hardebeck, Jeanne L.

    2014-01-01

    The focal mechanisms of earthquakes in Southern California before and after four M ≥ 6.7 main shocks provide insight into how fault systems respond to stress and changes in stress. The main shock static stress changes have two observed impacts on the seismicity: changing the focal mechanisms in a given location to favor those aligned with the static stress change and changing the spatial distribution of seismicity to favor locations where the static stress change aligns with the background stress. The aftershock focal mechanisms are significantly aligned with the static stress changes for absolute stress changes of ≥ 0.02 MPa, for up to ~20 years following the main shock. The dynamic stress changes have similar, although smaller, effects on the local focal mechanisms and the spatial seismicity distribution. Dynamic stress effects are best observed at long periods (30–60 s) and for metrics based on repeated stress cycling in the same direction. This implies that dynamic triggering operates, at least in part, through cyclic shear stress loading in the direction of fault slip. The background stress also strongly controls both the preshock and aftershock mechanisms. While most aftershock mechanisms are well oriented in the background stress field, 10% of aftershocks are identified as poorly oriented outliers, which may indicate limited heterogeneity in the postmain shock stress field. The fault plane orientations of the outliers are well oriented in the background stress, while their slip directions are not, implying that the background stress restricts the distribution of available fault planes.

  8. Molecular mechanisms in plant abiotic stress response

    Directory of Open Access Journals (Sweden)

    Poltronieri Palmiro

    2011-01-01

    Full Text Available Improved crop varieties are needed to sustain the food supply, to fight climate changes, water scarcity, temperature increase and a high variability of rainfalls. Variability of drought and increase in soil salinity have negative effects on plant growth and abiotic stresses seriously threaten sustainable agricultural production. To overcome the influence of abiotic stresses, new tolerant plant varieties and breeding techniques using assisted selection are sought. A deep understanding of the mechanisms that respond to stress and sustain stress resistance is required. Here is presented an overview of several mechanisms that interact in the stress response. Localised synthesis of plant hormones, second messengers and local effectors of abiotic stress response and survival, the signaling pathways regulated by plant hormones are today better understood. Metabolic networks in drought stress responses, long distance signaling, cross-talk between plant organs finalised to tissue-specific expression of abiotic stress relieving genes have been at the centre of most recent studies.

  9. Unit Operations for the Food Industry: Equilibrium Processes & Mechanical Operations

    OpenAIRE

    Guiné, Raquel

    2013-01-01

    Unit operations are an area of engineering that is at the same time very fascinating and most essential for the industry in general and the food industry in particular. This book was prepared in a way to achieve simultaneously the academic and practical perspectives. It is organized into two parts: the unit operations based on equilibrium processes and the mechanical operations. Each topic starts with a presentation of the fundamental concepts and principles, followed by a discussion of ...

  10. Mechanisms of cell propulsion by active stresses

    Energy Technology Data Exchange (ETDEWEB)

    Carlsson, A E, E-mail: aec@wustl.edu [Department of Physics, Washington University, Campus Box 1105, One Brookings Drive, St. Louis, MO 63130 (United States)

    2011-07-15

    The mechanisms by which cytoskeletal flows and cell-substrate interactions interact to generate cell motion are explored by using a simplified model of the cytoskeleton as a viscous gel containing active stresses. This model yields explicit general results relating cell speed and traction forces to the distributions of active stress and cell-substrate friction. It is found that (i) the cell velocity is given by a function that quantifies the asymmetry of the active-stress distribution, (ii) gradients in cell-substrate friction can induce motion even when the active stresses are symmetrically distributed, (iii) the traction-force dipole is enhanced by protrusive stresses near the cell edges or contractile stresses near the center of the cell and (iv) the cell velocity depends biphasically on the cell-substrate adhesion strength if active stress is enhanced by adhesion. Specific experimental tests of the calculated dependences are proposed.

  11. Mechanical stress induced mechanism of microtubule catastrophes.

    Science.gov (United States)

    Hunyadi, Viktória; Chrétien, Denis; Jánosi, Imre M

    2005-05-13

    Microtubules assembled in vitro from pure tubulin can switch occasionally from growing to shrinking states or resume assembly, an unusual behavior termed "dynamic instability of microtubule growth". Its origin remains unclear and several models have been proposed, including occasional switching of the microtubules into energetically unfavorable configurations during assembly. In this study, we have asked whether the excess energy accumulated in these configurations would be of sufficient magnitude to destabilize the capping region that must exist at the end of growing microtubules. For this purpose, we have analyzed the frequency distribution of microtubules assembled in vitro from pure tubulin, and modeled the different mechanical constraints accumulated in their wall. We find that the maximal excess energy that the microtubule lattice can store is in the order of 11 kBT per dimer. Configurations that require distortions up to approximately 20 kBT are allowed at the expense of a slight conformational change, and larger distortions are not observed. Modeling of the different elastic deformations suggests that the excess energy is essentially induced by protofilament skewing, microtubule radial curvature change and inter-subunit shearing, distortions that must destabilize further the tubulin subunits interactions. These results are consistent with the hypothesis that unfavorable closure events may trigger the catastrophes observed at low tubulin concentration in vitro. In addition, we propose a novel type of representation that describes the stability of microtubule assembly systems, and which might be of considerable interest to study the effects of stabilizing and destabilizing factors on microtubule structure and dynamics.

  12. Voltage hysteresis of lithium ion batteries caused by mechanical stress.

    Science.gov (United States)

    Lu, Bo; Song, Yicheng; Zhang, Qinglin; Pan, Jie; Cheng, Yang-Tse; Zhang, Junqian

    2016-02-14

    The crucial role of mechanical stress in voltage hysteresis of lithium ion batteries in charge-discharge cycles is investigated theoretically and experimentally. A modified Butler-Volmer equation of electrochemical kinetics is proposed to account for the influence of mechanical stresses on electrochemical reactions in lithium ion battery electrodes. It is found that the compressive stress in the surface layer of active materials impedes lithium intercalation, and therefore, an extra electrical overpotential is needed to overcome the reaction barrier induced by the stress. The theoretical formulation has produced a linear dependence of the height of voltage hysteresis on the hydrostatic stress difference between lithiation and delithiation, under both open-circuit conditions and galvanostatic operation. Predictions of the electrical overpotential from theoretical equations agree well with the experimental data for thin film silicon electrodes.

  13. Mechanisms of oxidative stress and vascular dysfunction

    Science.gov (United States)

    Nedeljkovic, Z; Gokce, N; Loscalzo, J

    2003-01-01

    The endothelium regulates vascular homoeostasis through local elaboration of mediators that modulate vascular tone, platelet adhesion, inflammation, fibrinolysis, and vascular growth. Impaired vascular function contributes to the pathogenesis of atherosclerosis and acute coronary syndromes. There is growing pathophysiological evidence that increased generation of reactive oxygen species and oxidative stress participates in proatherogenic mechanisms of vascular dysfunction and atherothrombosis. In this review, the role of oxidative stress in mechanisms of vascular dysfunction is discussed, and potential antioxidant strategies are reviewed. PMID:12743334

  14. Stress controls the mechanics of collagen networks.

    Science.gov (United States)

    Licup, Albert James; Münster, Stefan; Sharma, Abhinav; Sheinman, Michael; Jawerth, Louise M; Fabry, Ben; Weitz, David A; MacKintosh, Fred C

    2015-08-04

    Collagen is the main structural and load-bearing element of various connective tissues, where it forms the extracellular matrix that supports cells. It has long been known that collagenous tissues exhibit a highly nonlinear stress-strain relationship, although the origins of this nonlinearity remain unknown. Here, we show that the nonlinear stiffening of reconstituted type I collagen networks is controlled by the applied stress and that the network stiffness becomes surprisingly insensitive to network concentration. We demonstrate how a simple model for networks of elastic fibers can quantitatively account for the mechanics of reconstituted collagen networks. Our model points to the important role of normal stresses in determining the nonlinear shear elastic response, which can explain the approximate exponential relationship between stress and strain reported for collagenous tissues. This further suggests principles for the design of synthetic fiber networks with collagen-like properties, as well as a mechanism for the control of the mechanics of such networks.

  15. Mechanical Stresses in Carotid Plaques

    DEFF Research Database (Denmark)

    Samuel, Samuel Alberg

    Aterosklerose er den hyppigste årsag til død og svær invaliditet i verden. Sygdommen danner aterosklerotiske plaques, som består af lipidkerner dækket af en fibrøs kappe. Såfremt kappen brister, dannes overliggende tromber, som kan føres med blodstrømmen og forårsage strokes hvis kappen brister i...... mekaniske kræfter, som påvirker den fibrøse kappe, for at være en medvirkende årsag til plaqueruptur. Endvidere er stress-niveauerne i den fibrøse kappe en risikomarkør, som påvirkes af såvel den fibrøse kappetykkelse som lipid kerne størrelsen, blodtryk og graden af forsnævring. Imidlertid har hidtidige...... for at få fjernet deres plaques (carotis endarterektomi). Dernæst blev skanningerne segmenteret i lipid-kerne, fibrøs kappe, blodbane, karvæg og calcificationer. Endvidere blev blodets hastighed, blodtryk og karvægs deformationer målt. Disse data blev benyttet til longitudinelle fluid-struktur interaktions...

  16. Molecular Mechanisms Underlying Psychological Stress and Cancer.

    Science.gov (United States)

    Shin, Kyeong Jin; Lee, Yu Jin; Yang, Yong Ryoul; Park, Seorim; Suh, Pann-Ghill; Follo, Matilde Yung; Cocco, Lucio; Ryu, Sung Ho

    2016-01-01

    Psychological stress is an emotion experienced when people are under mental pressure or encounter unexpected problems. Extreme or repetitive stress increases the risk of developing human disease, including cardiovascular disease (CVD), immune diseases, mental disorders, and cancer. Several studies have shown an association between psychological stress and cancer growth and metastasis in animal models and case studies of cancer patients. Stress induces the secretion of stress-related mediators, such as catecholamine, cortisol, and oxytocin, via the activation of the hypothalamic-pituitary-adrenocortical (HPA) axis or the sympathetic nervous system (SNS). These stress-related hormones and neurotransmitters adversely affect stress-induced tumor progression and cancer therapy. Catecholamine is the primary factor that influences tumor progression. It can regulate diverse cellular signaling pathways through adrenergic receptors (ADRs), which are expressed by several types of cancer cells. Activated ADRs enhance the proliferation and invasion abilities of cancer cells, alter cell activity in the tumor microenvironment, and regulate the interaction between cancer and its microenvironment to promote tumor progression. Additionally, other stress mediators, such as glucocorticoids and oxytocin, and their cognate receptors are involved in stress-induced cancer growth and metastasis. Here, we will review how each receptor-mediated signal cascade contributes to tumor initiation and progression and discuss how we can use these molecular mechanisms for cancer therapy.

  17. Peripheral and central mechanisms of stress resilience

    Directory of Open Access Journals (Sweden)

    Madeline L. Pfau

    2015-01-01

    Full Text Available Viable new treatments for depression and anxiety have been slow to emerge, likely owing to the complex and incompletely understood etiology of these disorders. A budding area of research with great therapeutic promise involves the study of resilience, the adaptive maintenance of normal physiology and behavior despite exposure to marked psychological stress. This phenomenon, documented in both humans and animal models, involves coordinated biological mechanisms in numerous bodily systems, both peripheral and central. In this review, we provide an overview of resilience mechanisms throughout the body, discussing current research in animal models investigating the roles of the neuroendocrine, immune, and central nervous systems in behavioral resilience to stress.

  18. Interagency mechanical operations group numerical systems group

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1997-09-01

    This report consists of the minutes of the May 20-21, 1971 meeting of the Interagency Mechanical Operations Group (IMOG) Numerical Systems Group. This group looks at issues related to numerical control in the machining industry. Items discussed related to the use of CAD and CAM, EIA standards, data links, and numerical control.

  19. Evaluation of the Operational Stress Control and Readiness (OSCAR) Program

    Science.gov (United States)

    2015-01-01

    that their unit cares about them, and that everyone gets treated fairly and equally. Whether it’s PTS [posttraumatic stress ] or financial issues. When...training on suicide prevention (U.S. Marine Corps, 2012). Recommendation 2.2. Integrate Combat and Operational Stress –Control Training into the...Christine Anne Vaughan, Carrie M. Farmer, Joshua Breslau, Crystal Burnette Evaluation of the Operational Stress Control and Readiness (OSCAR

  20. Composite Overwrap Pressure Vessels: Mechanics and Stress Rupture Lifing Philosophy

    Science.gov (United States)

    Thesken, John C.; Murthy, Pappu L. N.; Phoenix, Leigh

    2007-01-01

    The NASA Engineering and Safety Center (NESC) has been conducting an independent technical assessment to address safety concerns related to the known stress rupture failure mode of filament wound pressure vessels in use on Shuttle and the International Space Station. The Shuttle's Kevlar-49 fiber overwrapped tanks are of particular concern due to their long usage and the poorly understood stress rupture process in Kevlar-49 filaments. Existing long term data show that the rupture process is a function of stress, temperature and time. However due to the presence of load sharing liners and the complex manufacturing procedures, the state of actual fiber stress in flight hardware and test articles is not clearly known. Indeed non-conservative life predictions have been made where stress rupture data and lifing procedures have ignored the contribution of the liner in favor of applied pressure as the controlling load parameter. With the aid of analytical and finite element results, this paper examines the fundamental mechanical response of composite overwrapped pressure vessels including the influence of elastic-plastic liners and degraded/creeping overwrap properties. Graphical methods are presented describing the non-linear relationship of applied pressure to Kevlar-49 fiber stress/strain during manufacturing, operations and burst loadings. These are applied to experimental measurements made on a variety of vessel systems to demonstrate the correct calibration of fiber stress as a function of pressure. Applying this analysis to the actual qualification burst data for Shuttle flight hardware revealed that the nominal fiber stress at burst was in some cases 23% lower than what had previously been used to predict stress rupture life. These results motivate a detailed discussion of the appropriate stress rupture lifing philosophy for COPVs including the correct transference of stress rupture life data between dissimilar vessels and test articles.

  1. Composite Overwrap Pressure Vessels: Mechanics and Stress Rupture Lifting Philosophy

    Science.gov (United States)

    Thesken, John C.; Murthy, Pappu L. N.; Phoenix, S. L.

    2009-01-01

    The NASA Engineering and Safety Center (NESC) has been conducting an independent technical assessment to address safety concerns related to the known stress rupture failure mode of filament wound pressure vessels in use on Shuttle and the International Space Station. The Shuttle s Kevlar-49 (DuPont) fiber overwrapped tanks are of particular concern due to their long usage and the poorly understood stress rupture process in Kevlar-49 filaments. Existing long term data show that the rupture process is a function of stress, temperature and time. However due to the presence of load sharing liners and the complex manufacturing procedures, the state of actual fiber stress in flight hardware and test articles is not clearly known. Indeed nonconservative life predictions have been made where stress rupture data and lifing procedures have ignored the contribution of the liner in favor of applied pressure as the controlling load parameter. With the aid of analytical and finite element results, this paper examines the fundamental mechanical response of composite overwrapped pressure vessels including the influence of elastic plastic liners and degraded/creeping overwrap properties. Graphical methods are presented describing the non-linear relationship of applied pressure to Kevlar-49 fiber stress/strain during manufacturing, operations and burst loadings. These are applied to experimental measurements made on a variety of vessel systems to demonstrate the correct calibration of fiber stress as a function of pressure. Applying this analysis to the actual qualification burst data for Shuttle flight hardware revealed that the nominal fiber stress at burst was in some cases 23 percent lower than what had previously been used to predict stress rupture life. These results motivate a detailed discussion of the appropriate stress rupture lifing philosophy for COPVs including the correct transference of stress rupture life data between dissimilar vessels and test articles.

  2. Mechanical stability of iron under hydrostatic stresses

    Science.gov (United States)

    Mishra, K. L.; Thakur, O. P.; Thakur, K. P.

    1991-09-01

    A comprehensive investigation of the mechanics of iron subjected to arbitrary fluid pressure has been carried out. Apart from the classical elastic moduli ( k, μ, and μ') and conventional elastic moduli (Green and stretch moduli) computations are carried out for a family of generalised moduli of which the conventional moduli are just specific members. With the generalised moduli the mechanical stability of iron is investigated through Born criteria. It is found that classical stability, Green stability and stretch stability are all represented uniquely by the present generalised scheme. The definition of effective classical moduli under stresses enabled the amalgamation of the Born criteria of lattice stability into the single classical criteria of lattice stability of cubic crystal under hydrostatic loading environment. Computations are also carried out to investigate the coordinate and stress dependence of Young's modulus of elasticity, Poisson's ratio, mean velocity of elastic wave, and Debye temperature. Surprisingly, it is found that all these properties of solids play an important role in representing the mechanical stability of the solid. The path of uniaxial loading of iron is also investigated along with its internal energy variation on this path. This indicated the existance of stress-free fcc phase of iron on the path of uniaxial deformation at cell length a=3.6444 Å giving enthalpy of transformation (bcc→fcc) of 1.1 kJ/mol in good agreement with experimental results.

  3. Mechanics of couple-stress fluid coatings

    Science.gov (United States)

    Waxman, A. M.

    1982-01-01

    The formal development of a theory of viscoelastic surface fluids with bending resistance - their kinematics, dynamics, and rheology are discussed. It is relevant to the mechanics of fluid drops and jets coated by a thin layer of immiscible fluid with rather general rheology. This approach unifies the hydrodynamics of two-dimensional fluids with the mechanics of an elastic shell in the spirit of a Cosserat continuum. There are three distinct facets to the formulation of surface continuum mechanics. Outlined are the important ideas and results associated with each: the kinematics of evolving surface geometries, the conservation laws governing the mechanics of surface continua, and the rheological equations of state governing the surface stress and moment tensors.

  4. Mechanically induced residual stresses: Modelling and characterisation

    Science.gov (United States)

    Stranart, Jean-Claude E.

    Accurate characterisation of residual stress represents a major challenge to the engineering community. This is because it is difficult to validate the measurement and the accuracy is doubtful. It is with this in mind that the current research program concerning the characterisation of mechanically induced residual stresses was undertaken. Specifically, the cold expansion of fastener holes and the shot peening treatment of aerospace alloys, aluminium 7075 and titanium Ti-6Al-4V, are considered. The objective of this study is to characterise residual stresses resulting from cold working using three powerful techniques. These are: (i) theoretical using three dimensional non-linear finite element modelling, (ii) semi-destructive using a modified incremental hole drilling technique and (iii) nondestructive using a newly developed guided wave method supplemented by traditional C-scan measurements. The three dimensional finite element results of both simultaneous and sequential cold expansion of two fastener holes revealed the importance of the separation distance, the expansion level and the loading history upon the development and growth of the plastic zone and unloading residual stresses. It further showed that the commonly adopted two dimensional finite element models are inaccurate and incapable of predicting these residual stresses. Similarly, the dynamic elasto-plastic finite element studies of shot peening showed that the depth of the compressed layer, surface and sub-surface residual stresses are significantly influenced by the shot characteristics. Furthermore, the results reveal that the separation distance between two simultaneously impacting shots governs the plastic zone development and its growth. In the semi-destructive incremental hole drilling technique, the accuracy of the newly developed calibration coefficients and measurement techniques were verified with a known stress field and the method was used to measure peening residual stresses. Unlike

  5. Overcoming the effects of stress on reactor operator performance

    Energy Technology Data Exchange (ETDEWEB)

    He Xuhong; Wei Li; Zhao Bingquan [Tsinghua Univ., Nuclear Power Plant Simulation Training Center, Beijing (China)

    2003-03-01

    Reactor operators may be exposed to significant levels of stress during plant emergencies and their performance may be affected by the stress. This paper first identified the potential sources of stress in the nuclear power plant, then discussed the ways in which stress is likely to affect the reactor operators, and finally identified several training approaches for reducing or eliminating stress effects. The challenges for effective stress reducing training may seem daunting, yet the challenges are real and must be addressed. This paper reviewed researches in training design, knowledge and skill acquisition, and training transfer point to a number of strategies that can be used to address these challenges and lead to more effective training and development. (author)

  6. Plant Responses to Salt Stress: Adaptive Mechanisms

    Directory of Open Access Journals (Sweden)

    Jose Ramón Acosta-Motos

    2017-02-01

    Full Text Available This review deals with the adaptive mechanisms that plants can implement to cope with the challenge of salt stress. Plants tolerant to NaCl implement a series of adaptations to acclimate to salinity, including morphological, physiological and biochemical changes. These changes include increases in the root/canopy ratio and in the chlorophyll content in addition to changes in the leaf anatomy that ultimately lead to preventing leaf ion toxicity, thus maintaining the water status in order to limit water loss and protect the photosynthesis process. Furthermore, we deal with the effect of salt stress on photosynthesis and chlorophyll fluorescence and some of the mechanisms thought to protect the photosynthetic machinery, including the xanthophyll cycle, photorespiration pathway, and water-water cycle. Finally, we also provide an updated discussion on salt-induced oxidative stress at the subcellular level and its effect on the antioxidant machinery in both salt-tolerant and salt-sensitive plants. The aim is to extend our understanding of how salinity may affect the physiological characteristics of plants.

  7. Mechanism of store-operated calcium entry

    Indian Academy of Sciences (India)

    Devkanya Dutta

    2000-12-01

    Activation of receptors coupled to the phospholipase C/IP3 signalling pathway results in a rapid release of calcium from its intracellular stores, eventually leading to depletion of these stores. Calcium store depletion triggers an influx of extracellular calcium across the plasma membrane, a mechanism known as the store-operated calcium entry or capacitative calcium entry. Capacitative calcium current plays a key role in replenishing calcium stores and activating various physiological processes. Despite considerable efforts, very little is known about the molecular nature of the capacitative channel and the signalling pathway that activates it. This review summarizes our current knowledge about store operated calcium entry and suggests possible hypotheses for its mode of activation.

  8. Analysis of Mechanical Stresses/Strains in Superconducting Wire

    Science.gov (United States)

    Barry, Matthew; Chen, Jingping; Zhai, Yuhu

    2016-10-01

    The optimization of superconducting magnet performance and development of high-field superconducting magnets will greatly impact the next generation of fusion devices. A successful magnet development, however, relies deeply on the understanding of superconducting materials. Among the numerous factors that impact a superconductor's performance, mechanical stress is the most important because of the extreme operation temperature and large electromagnetic forces. In this study, mechanical theory is used to calculate the stresses/strains in typical superconducting strands, which consist of a stabilizer, a barrier, a matrix and superconducting filaments. Both thermal loads and mechanical loads are included in the analysis to simulate operation conditions. Because this model simulates the typical architecture of major superconducting materials, such as Nb3Sn, MgB2, Bi-2212 etc., it provides a good overall picture for us to understand the behavior of these superconductors in terms of thermal and mechanical loads. This work was supported in part by the U.S. Department of Energy, Office of Science, Office of Workforce Development for Teachers and Scientists (WDTS) under the Science Undergraduate Laboratory Internship (SULI) program.

  9. Resonant breathing biofeedback training for stress reduction among manufacturing operators.

    Science.gov (United States)

    Sutarto, Auditya Purwandini; Wahab, Muhammad Nubli Abdul; Zin, Nora Mat

    2012-01-01

    The aim of this study was to examine the effect of resonant breathing biofeedback training for reducing stress among manufacturing operators. Resonant breathing biofeedback works by teaching people to recognize their involuntary heart rate variability and to control patterns of this physiological response. Thirty-six female operators from an electronic manufacturing factory were randomly assigned as the experimental group (n = 19) and the control group (n = 17). The participants of the intervention received 5 weekly sessions of biofeedback training. Physiological stress profiles and self-perceived depression, anxiety, and stress scale (DASS) were assessed at pre- and post-intervention. Results indicated that depression, anxiety, and stress significantly decreased after the training in the experimental group; they were supported by a significant increase in physiological measures. Overall, these results support the potential application of resonant biofeedback training to reduce negative emotional symptoms among industrial workers.

  10. Continuum mechanics, stresses, currents and electrodynamics.

    Science.gov (United States)

    Segev, Reuven

    2016-04-28

    The Eulerian approach to continuum mechanics does not make use of a body manifold. Rather, all fields considered are defined on the space, or the space-time, manifolds. Sections of some vector bundle represent generalized velocities which need not be associated with the motion of material points. Using the theories of de Rham currents and generalized sections of vector bundles, we formulate a weak theory of forces and stresses represented by vector-valued currents. Considering generalized velocities represented by differential forms and interpreting such a form as a generalized potential field, we present a weak formulation of pre-metric, p-form electrodynamics as a natural example of the foregoing theory. Finally, it is shown that the assumptions leading to p-form electrodynamics may be replaced by the condition that the force functional is continuous with respect to the flat topology of forms.

  11. EFL Foreign Teacher Stress in Korea: Causes and Coping Mechanisms

    Science.gov (United States)

    Brundage, Gregory C.

    2007-01-01

    Survey study of 53 foreign EFL teachers in Jeonju City, South Korea looks at causes of teacher stress and coping mechanisms between the years of 2004 and 2006. Results show foreign EFL teachers report moderate levels of stress and attribute stresses in roughly equal measures to student misbehavior and school director/administrative sources. Survey…

  12. Measurement of residual stresses using fracture mechanics weight functions

    Energy Technology Data Exchange (ETDEWEB)

    Fan, Y. [Bettis Atomic Power Laboratory, West Mifflin, PA (United States)

    2001-07-01

    A residual stress measurement method has been developed to quantify through-the-thickness residual stresses. Accurate measurement of residual stresses is crucial for many engineering structures. Fabrication processes such as welding and machining generate residual stresses that are difficult to predict. Residual stresses affect the integrity of structures through promoting failures due to brittle fracture, fatigue, stress corrosion cracking, and wear. In this work, the weight function theory of fracture mechanics is used to measure residual stresses. The weight function theory is an important development in computational fracture mechanics. Stress intensity factors for arbitrary stress distribution on the crack faces can be accurately and efficiently computed for predicting crack growth. This paper demonstrates that the weight functions are equally useful in measuring residual stresses. In this method, an artificial crack is created by a thin cut in a structure containing residual stresses. The cut relieves the residual stresses normal to the crack-face and allows the relieved residual stresses to deform the structure. Strain gages placed adjacent to the cut measure the relieved strains corresponding to incrementally increasing depths of the cut. The weight functions of the cracked body relate the measured strains to the residual stresses normal to the cut within the structure. The procedure details, such as numerical integration of the singular functions in applying the weight function method, will be discussed. (author)

  13. Plasma membrane mechanical stress activates TRPC5 channels.

    Directory of Open Access Journals (Sweden)

    Bing Shen

    Full Text Available Mechanical forces exerted on cells impose stress on the plasma membrane. Cells sense this stress and elicit a mechanoelectric transduction cascade that initiates compensatory mechanisms. Mechanosensitive ion channels in the plasma membrane are responsible for transducing the mechanical signals to electrical signals. However, the mechanisms underlying channel activation in response to mechanical stress remain incompletely understood. Transient Receptor Potential (TRP channels serve essential functions in several sensory modalities. These channels can also participate in mechanotransduction by either being autonomously sensitive to mechanical perturbation or by coupling to other mechanosensory components of the cell. Here, we investigated the response of a TRP family member, TRPC5, to mechanical stress. Hypoosmolarity triggers Ca2+ influx and cationic conductance through TRPC5. Importantly, for the first time we were able to record the stretch-activated TRPC5 current at single-channel level. The activation threshold for TRPC5 was found to be 240 mOsm for hypoosmotic stress and between -20 and -40 mmHg for pressure applied to membrane patch. In addition, we found that disruption of actin filaments suppresses TRPC5 response to hypoosmotic stress and patch pipette pressure, but does not prevent the activation of TRPC5 by stretch-independent mechanisms, indicating that actin cytoskeleton is an essential transduction component that confers mechanosensitivity to TRPC5. In summary, our findings establish that TRPC5 can be activated at the single-channel level when mechanical stress on the cell reaches a certain threshold.

  14. Measurements of residual stress in fracture mechanics coupons

    Energy Technology Data Exchange (ETDEWEB)

    Prime, Michael B [Los Alamos National Laboratory; Hill, Michael R [U.C. DAVIS; Nav Dalen, John E [HILL ENGINEERING

    2010-01-01

    This paper describes measurements of residual stress in coupons used for fracture mechanics testing. The primary objective of the measurements is to quantify the distribution of residual stress acting to open (and/or close) the crack across the crack plane. The slitting method and the contour method are two destructive residual stress measurement methods particularly capable of addressing that objective, and these were applied to measure residual stress in a set of identically prepared compact tension (C(T)) coupons. Comparison of the results of the two measurement methods provides some useful observations. Results from fracture mechanics tests of residual stress bearing coupons and fracture analysis, based on linear superposition of applied and residual stresses, show consistent behavior of coupons having various levels of residual stress.

  15. Stressors and coping mechanisms associated with perceived stress in Latinos.

    Science.gov (United States)

    Perez, Sasha M; Gavin, Jennifer K; Diaz, Vanessa A

    2015-01-01

    To evaluate the relationship between causes of perceived stress and the coping mechanisms used by Latino adults with perceived stress. This cross-sectional survey was conducted on a convenience sample of 200 Latino adults (aged ≥18 years). They were recruited from clinics, migrant camps, community events, and churches located in Charleston, S.C. This survey included questions regarding causes of perceived stress, perceived stress (Perceived Stress Scale 10), coping mechanisms (Brief COPE), and depression (Perceived Health Questionnaire 9). High perceived stress (PSS ≥15) was the primary outcome measure. Coping mechanisms and stressors were secondary outcomes. Most (92%) of the sample was born outside the United States, and 66% reported high perceived stress. Stressors associated with high perceived stress included discrimination (P=.0010), lack of insurance (P=.0193), health problems (P=.0058), and lack of money (P=.0015). The most frequently utilized coping mechanisms were self-distraction (54.77%), active coping (69.85%), positive reframing (56.78%), planning (63.82%), acceptance (57.87%), and religion (57.79%). Latinos with higher perceived stress were more likely to report discrimination (OR: 3.401; 95%CI 1.285-9.004) and health problems (OR: 2.782; 95%CI 1.088-7.111) as stressors, and to use denial as a coping mechanism (OR: 2.904; 95%CI 1.280-6.589). An increased prevalence of perceived stress among the Latinos evaluated in this study was associated with using denial as a coping mechanism, and encountering discrimination and health problems as sources of perceived stress. Most individuals responded to stressors by utilizing a variety of both adaptive and maladaptive coping mechanisms.

  16. Stress-constrained topology optimization for compliant mechanism design

    DEFF Research Database (Denmark)

    de Leon, Daniel M.; Alexandersen, Joe; Jun, Jun S.;

    2015-01-01

    This article presents an application of stress-constrained topology optimization to compliant mechanism design. An output displacement maximization formulation is used, together with the SIMP approach and a projection method to ensure convergence to nearly discrete designs. The maximum stress...... is approximated using a normalized version of the commonly-used p-norm of the effective von Mises stresses. The usual problems associated with topology optimization for compliant mechanism design: one-node and/or intermediate density hinges are alleviated by the stress constraint. However, it is also shown...

  17. ReMeEx device (External Mechanical Regulator) for female stress urinary incontinence: a critical review of a single-operator, long-term experience on implants and readjustments.

    Science.gov (United States)

    Mantovani, Franco

    2017-04-28

    A single-operator, long-term (15 years) experience on a sling technique that allows a postoperative adjustment of its tension is presented to retrospectively report the objective and subjective outcomes in the treatment of female stress urinary incontinence (SUI). The readjustment option prevents the need of a reoperation in case of relapse with great compliance of the patients. Indications for surgical tratment of SUI by ReMeEx included patients affected with not only true intrinsic sphyncteric deficency (ISD) and fixed urethra but also mild urethral hypermobility, previous incontinence surgery and relapsing conditions such as diabetes and obesity. Fifty-five female patients with severe SUI underwent ReMeEx system positioning between 1998 and 2013. Before surgery, patients were evaluated by physical examination, translabial ultrasonography, urodynamics, pad-test and compilation of a specific incontinence quality of life questionnaire. Out of 55 patients treated, 50 were cured with readjustment in 10; in one case, the device was removed for infection. Complications as one transitory retention, two de novo urgency and one sovrapubic varitensor seroma were easily treated. In our experience, the ReMeEx system produced remerkable long-term results that showed the effective role of this device in obtaining an adequate sling tension, also confirmed in a worse prognosis patient group, as reported in the present study. The limitation of this study, based on a retrospective and not comparative analysis, suggests the need for randomized prospective studies comparing the ReMeEx procedure with other similar anti-incontinence techniques. ReMeEx system offers the possibility to modify the sling support whenever needed during patients' life. By this device, we can improve the outcomes of these patients leaving them completely dry without reoperations. The system produced remarkable 15 years results with a low complication rate. These outcomes have also been confirmed in a worse

  18. Mechanical Stress Promotes Cisplatin-Induced Hepatocellular Carcinoma Cell Death

    Directory of Open Access Journals (Sweden)

    Laila Ziko

    2015-01-01

    Full Text Available Cisplatin (CisPt is a commonly used platinum-based chemotherapeutic agent. Its efficacy is limited due to drug resistance and multiple side effects, thereby warranting a new approach to improving the pharmacological effect of CisPt. A newly developed mathematical hypothesis suggested that mechanical loading, when coupled with a chemotherapeutic drug such as CisPt and immune cells, would boost tumor cell death. The current study investigated the aforementioned mathematical hypothesis by exposing human hepatocellular liver carcinoma (HepG2 cells to CisPt, peripheral blood mononuclear cells, and mechanical stress individually and in combination. HepG2 cells were also treated with a mixture of CisPt and carnosine with and without mechanical stress to examine one possible mechanism employed by mechanical stress to enhance CisPt effects. Carnosine is a dipeptide that reportedly sequesters platinum-based drugs away from their pharmacological target-site. Mechanical stress was achieved using an orbital shaker that produced 300 rpm with a horizontal circular motion. Our results demonstrated that mechanical stress promoted CisPt-induced death of HepG2 cells (~35% more cell death. Moreover, results showed that CisPt-induced death was compromised when CisPt was left to mix with carnosine 24 hours preceding treatment. Mechanical stress, however, ameliorated cell death (20% more cell death.

  19. Mechanism of Oxidative Stress in Neurodegeneration

    Directory of Open Access Journals (Sweden)

    Sonia Gandhi

    2012-01-01

    Full Text Available Biological tissues require oxygen to meet their energetic demands. However, the consumption of oxygen also results in the generation of free radicals that may have damaging effects on cells. The brain is particularly vulnerable to the effects of reactive oxygen species due to its high demand for oxygen, and its abundance of highly peroxidisable substrates. Oxidative stress is caused by an imbalance in the redox state of the cell, either by overproduction of reactive oxygen species, or by dysfunction of the antioxidant systems. Oxidative stress has been detected in a range of neurodegenerative disease, and emerging evidence from in vitro and in vivo disease models suggests that oxidative stress may play a role in disease pathogenesis. However, the promise of antioxidants as novel therapies for neurodegenerative diseases has not been borne out in clinical studies. In this review, we critically assess the hypothesis that oxidative stress is a crucial player in common neurodegenerative disease and discuss the source of free radicals in such diseases. Furthermore, we examine the issues surrounding the failure to translate this hypothesis into an effective clinical treatment.

  20. Endogenous patterns of mechanical stress are required for branching morphogenesis

    Science.gov (United States)

    Gjorevski, Nikolce; Nelson, Celeste M.

    2011-01-01

    Spatial patterning of cell behaviors establishes the regional differences within tissues that collectively develop branched organs into their characteristic treelike shapes. Here we show that the pattern of branching morphogenesis of three-dimensional (3D) engineered epithelial tissues is controlled in part by gradients of endogenous mechanical stress. We used microfabrication to build model mammary epithelial tissues of defined geometry that branched in a stereotyped pattern when induced with growth factors. Branches initiated from sites of high mechanical stress within the tissues, as predicted numerically and measured directly using 3D traction force microscopy. Branch sites were defined by activation of focal adhesion kinase (FAK), inhibition of which disrupted morphogenesis. Stress, FAK activation, and branching were all altered by manipulating cellular contractility, matrix stiffness, intercellular cohesion and tissue geometry. These data suggest that the pattern and magnitude of mechanical stress across epithelial tissues cooperate with biochemical signals to specify branching pattern. Insight, innovation, integration Morphogenesis is ultimately a physical process wherein tissues are sculpted into their final three-dimensional (3D) patterns. Mechanical stresses from the microenvironment can also play regulatory roles, but their influence on pattern is difficult to ascertain in 3D systems in vivo. Here we integrate 3D microscale engineered tissues with insight from biological mechanics to understand the role of endogenous mechanical stresses in patterning tissue development. The innovation lies in the use of numerical modeling to design experiments that can predict the stress distribution and resulting morphogenesis of model tissues. PMID:20717570

  1. Psychological and Physical Stress in Surgeons Operating in a Standard or Modern Operating Room

    DEFF Research Database (Denmark)

    Klein, M.; Andersen, L.P.H.; Gögenür, Ismayil

    2010-01-01

    Purpose: There have been no studies examining the effect of optimized ergonomic and technical environment on the psychological and physiological stress of the surgeon. The aim of this study was to examine whether optimized ergonomics and technical aids within a modern operating room (OR) affect...... psychological and physiological stress in experienced laparoscopic surgeons. Methods: This was a prospective case-controlled study including 10 experienced surgeons. Surgery was performed in 2 different ORs: a standard room and a modern room (OR1-suite, Karl Storz). The surgeons filled out questionnaires...

  2. Oxidant Stress in Renal Inflammation: Mechanisms and Remedies

    NARCIS (Netherlands)

    Ishola, D.A.

    2006-01-01

    Our overall hypothesis was that oxidant stress is a central player in renal inflammation; pharmacological reduction of oxidant stress should therefore relieve renal inflammation. We explored pro- and anti-oxidant mechanisms in three experimental renal injury models. OXIDANT-DEPENDENT RENAL

  3. Stress and Coping Mechanisms Among Breast Cancer Patients and ...

    African Journals Online (AJOL)

    Stress and Coping Mechanisms Among Breast Cancer Patients and Family ... It is also the leading cause of cancer mortality, representing 14.1%. ... to cancer and the last 4 on experiences of family members on care of the terminally ill.

  4. Mechanical stress induces biotic and abiotic stress responses via a novel cis-element.

    Directory of Open Access Journals (Sweden)

    Justin W Walley

    2007-10-01

    Full Text Available Plants are continuously exposed to a myriad of abiotic and biotic stresses. However, the molecular mechanisms by which these stress signals are perceived and transduced are poorly understood. To begin to identify primary stress signal transduction components, we have focused on genes that respond rapidly (within 5 min to stress signals. Because it has been hypothesized that detection of physical stress is a mechanism common to mounting a response against a broad range of environmental stresses, we have utilized mechanical wounding as the stress stimulus and performed whole genome microarray analysis of Arabidopsis thaliana leaf tissue. This led to the identification of a number of rapid wound responsive (RWR genes. Comparison of RWR genes with published abiotic and biotic stress microarray datasets demonstrates a large overlap across a wide range of environmental stresses. Interestingly, RWR genes also exhibit a striking level and pattern of circadian regulation, with induced and repressed genes displaying antiphasic rhythms. Using bioinformatic analysis, we identified a novel motif overrepresented in the promoters of RWR genes, herein designated as the Rapid Stress Response Element (RSRE. We demonstrate in transgenic plants that multimerized RSREs are sufficient to confer a rapid response to both biotic and abiotic stresses in vivo, thereby establishing the functional involvement of this motif in primary transcriptional stress responses. Collectively, our data provide evidence for a novel cis-element that is distributed across the promoters of an array of diverse stress-responsive genes, poised to respond immediately and coordinately to stress signals. This structure suggests that plants may have a transcriptional network resembling the general stress signaling pathway in yeast and that the RSRE element may provide the key to this coordinate regulation.

  5. Stress controls the mechanics of collagen networks

    OpenAIRE

    Licup, Albert James; Münster, Stefan; Sharma, Abhinav; Sheinman, Michael; Jawerth, Louise M.; Fabry, Ben; Weitz, David A.; MacKintosh, Fred C.

    2015-01-01

    Collagen is the main structural and load-bearing element of various connective tissues, where it forms the extracellular matrix that supports cells. It has long been known that collagenous tissues exhibit a highly nonlinear stress-strain relationship (Fung YC, Am J Physiol 213(6),1967; Humphrey JD, Proc R Soc Lond A: Math Phys Eng Sci 459(2029),2003), although the origins of this nonlinearity remain unknown (McMahon TA, Lec Math Life Sci 13,1980). Here, we show that the nonlinear stiffening o...

  6. A thermo-mechanical stress prediction model for contemporary planar sodium sulfur (NaS) cells

    Science.gov (United States)

    Jung, Keeyoung; Colker, Jeffrey P.; Cao, Yuzhe; Kim, Goun; Park, Yoon-Cheol; Kim, Chang-Soo

    2016-08-01

    We introduce a comprehensive finite-element analysis (FEA) computational model to accurately predict the thermo-mechanical stresses at heterogeneous joints and components of large-size sodium sulfur (NaS) cells during thermal cycling. Quantification of the thermo-mechanical stress is important because the accumulation of stress during cell assembly and/or operation is one of the critical issues in developing practical planar NaS cells. The computational model is developed based on relevant experimental assembly and operation conditions to predict the detailed stress field of a state-of-the-art planar NaS cell. Prior to the freeze-and-thaw thermal cycle simulation, residual stresses generated from the actual high temperature cell assembly procedures are calculated and implemented into the subsequent model. The calculation results show that large stresses are developed on the outer surface of the insulating header and the solid electrolyte, where component fracture is frequently observed in the experimental cell fabrication process. The impacts of the coefficients of thermal expansion (CTE) of glass materials and the thicknesses of cell container on the stress accumulation are also evaluated to improve the cell manufacturing procedure and to guide the material choices for enhanced thermo-mechanical stability of large-size NaS cells.

  7. Mechanical behaviour of PEM fuel cell catalyst layers during regular cell operation

    Directory of Open Access Journals (Sweden)

    Maher A.R. Sadiq Al-Baghdadi

    2010-11-01

    Full Text Available Damage mechanisms in a proton exchange membrane fuel cell are accelerated by mechanical stresses arising during fuel cell assembly (bolt assembling, and the stresses arise during fuel cell running, because it consists of the materials with different thermal expansion and swelling coefficients. Therefore, in order to acquire a complete understanding of the mechanical behaviour of the catalyst layers during regular cell operation, mechanical response under steady-state hygro-thermal stresses should be studied under real cell operating conditions and in real cell geometry (three-dimensional. In this work, full three-dimensional, non-isothermal computational fluid dynamics model of a PEM fuel cell has been developed to investigate the behaviour of the cathode and anode catalyst layers during the cell operation. A unique feature of the present model is to incorporate the effect of hygro and thermal stresses into actual three-dimensional fuel cell model. In addition, the temperature and humidity dependent material properties are utilize in the simulation for the membrane. The model is shown to be able to understand the many interacting, complex electrochemical, transport phenomena, and deformation that have limited experimental data.

  8. Transcription factor regulation by mechanical stress.

    Science.gov (United States)

    Mendez, Melissa G; Janmey, Paul A

    2012-05-01

    New technologies and interest in cell mechanics are generating exciting new discoveries about how material properties and forces affect biological structure and function. Mechanical forces are transduced via a variety of mechanisms, recently beginning to be revealed, into signals capable of altering cell function and structure. Responses to physical stimuli occur at multiple levels, from changes in the structures of single proteins to global cascades capable of altering cell proliferation and differentiation. This review describes recent findings in which physical stimuli were shown to modulate transcription factor activity, including that of armadillo/β-catenin, serum response factor (SRF), yes-associated protein (YAP) and nuclear factor κB (NF-κB). Copyright © 2012 Elsevier Ltd. All rights reserved.

  9. Physical activity, stress reduction, and mood: insight into immunological mechanisms.

    Science.gov (United States)

    Hamer, Mark; Endrighi, Romano; Poole, Lydia

    2012-01-01

    Psychosocial factors, such as chronic mental stress and mood, are recognized as an important predictor of longevity and wellbeing. In particular, depression is independently associated with cardiovascular disease and all-cause mortality, and is often comorbid with chronic diseases that can worsen their associated health outcomes. Regular exercise is thought to be associated with stress reduction and better mood, which may partly mediate associations between depression, stress, and health outcomes. The underlying mechanisms for the positive effects of exercise on wellbeing remain poorly understood. In this overview we examine epidemiological evidence for an association between physical activity and mental health. We then describe the exercise withdrawal paradigm as an experimental protocol to study mechanisms linking exercise, mood, and stress. In particular we will discuss the potential role of the inflammatory response as a central mechanism.

  10. Determination of Mechanical Properties of Micromembranes with Compressive Residual Stress

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    A novel model of a load-deflection method to determine the mechanical properties of micromembranes with compressive residual stress is described. Since thin film structures are frequently used in micro devices, characterisation of mechanical properties of thin films is desired by the design and fabrication of micromachines. In this paper, the mechanical properties of thin micromembranes under compressive stress are characterised, which are fabricated by bulk micromachining. The relation between the center deflection and the load pressure on a square membrane is deduced by modelling the membrane as an elastic plate having large deflection with clamped boundaries. According to the model, whether the membrane has initial deflection or not has no effect on the measurement result. The Young's modulus and residual stress are simultaneously determined. The mechanical properties of siliconoxide, silicon nitride membranes and composite membranes of polysilicon with silicon nitride are measured.

  11. Mechanical behavior and stress effects in hard superconductors: a review

    Energy Technology Data Exchange (ETDEWEB)

    Koch, C. C.; Easton, D. S.

    1977-11-01

    The mechanical properties of type II superconducting materials are reviewed as well as the effect of stress on the superconducting properties of these materials. The bcc alloys niobium-titanium and niobium-zirconium exhibit good strength and extensive ductility at room temperature. Mechanical tests on these alloys at 4.2/sup 0/K revealed serrated stress-strain curves, nonlinear elastic effects and reduced ductility. The nonlinear behavior is probably due to twinning and detwinning or a reversible stress-induced martensitic transformation. The brittle A-15 compound superconductors, such as Nb/sub 3/Sn and V/sub 3/Ga, exhibit unusual elastic properties and structural instabilities at cryogenic temperatures. Multifilamentary composites consisting of superconducting filaments in a normal metal matrix are generally used for superconducting devices. The mechanical properties of alloy and compound composites, tapes, as well as composites of niobium carbonitride chemically vapor deposited on high strength carbon fibers are presented. Hysteretic stress-strain behavior in the metal matrix composites produces significant heat generation, an effect which may lead to degradation in the performance of high field magnets. Measurements of the critical current density, J/sub c/, under stress in a magnetic field are reported. Modest stress-reversible degradation in J/sub c/ was observed in niobium-titanium composites, while more serious degradation was found in Nb/sub 3/Sn samples. The importance of mechanical behavior to device performance is discussed.

  12. New fundamental quantum mechanical operator-ordering identities for the coordinate and momentum operators

    Institute of Scientific and Technical Information of China (English)

    FAN HongYi

    2012-01-01

    In quantum mechanics theory one of the basic operator orderings is Q - P and P - Q ordering,where Q and P are the coordinate operator and the momentum operator,respectively.We derive some new fundamental operator identities about their mutual reordering.The technique of integration within Q - P ordering and P - Q ordering is introduced.The Q - P ordered and P - Q ordered formulas of the Wigner operator are also deduced which makes arranging the operators in either Q - P or P - Q ordering much more convenient.

  13. Perinatal programming of neuroendocrine mechanisms connecting feeding behavior and stress

    Directory of Open Access Journals (Sweden)

    Sarah J Spencer

    2013-06-01

    Full Text Available Feeding behavior is closely regulated by neuroendocrine mechanisms that can be influenced by stressful life events. However, the feeding response to stress varies among individuals with some increasing and others decreasing food intake after stress. In addition to the impact of acute lifestyle and genetic backgrounds, the early life environment can have a life-long influence on neuroendocrine mechanisms connecting stress to feeding behavior and may partially explain these opposing feeding responses to stress. In this review I will discuss the perinatal programming of adult hypothalamic stress and feeding circuitry. Specifically I will address how early life (prenatal and postnatal nutrition, early life stress, and the early life hormonal profile can program the hypothalamic-pituitary-adrenal (HPA axis, the endocrine arm of the body’s response to stress long-term and how these changes can, in turn, influence the hypothalamic circuitry responsible for regulating feeding behavior. Thus, over- or under-feeding and / or stressful events during critical windows of early development can alter glucocorticoid (GC regulation of the HPA axis, leading to changes in the GC influence on energy storage and changes in GC negative feedback on HPA axis-derived satiety signals such as corticotropin-releasing-hormone. Furthermore, peripheral hormones controlling satiety, such as leptin and insulin are altered by early life events, and can be influenced, in early life and adulthood, by stress. Importantly, these neuroendocrine signals act as trophic factors during development to stimulate connectivity throughout the hypothalamus. The interplay between these neuroendocrine signals, the perinatal environment, and activation of the stress circuitry in adulthood thus strongly influences feeding behavior and may explain why individuals have unique feeding responses to similar stressors.

  14. Stress and Memory: Behavioral Effects and Neurobiological Mechanisms

    Directory of Open Access Journals (Sweden)

    Carmen Sandi

    2007-01-01

    Full Text Available Stress is a potent modulator of learning and memory processes. Although there have been a few attempts in the literature to explain the diversity of effects (including facilitating, impairing, and lack of effects described for the impact of stress on memory function according to single classification criterion, they have proved insufficient to explain the whole complexity of effects. Here, we review the literature in the field of stress and memory interactions according to five selected classifying factors (source of stress, stressor duration, stressor intensity, stressor timing with regard to memory phase, and learning type in an attempt to develop an integrative model to understand how stress affects memory function. Summarizing on those conditions in which there was enough information, we conclude that high stress levels, whether intrinsic (triggered by the cognitive challenge or extrinsic (induced by conditions completely unrelated to the cognitive task, tend to facilitate Pavlovian conditioning (in a linear-asymptotic manner, while being deleterious for spatial/explicit information processing (which with regard to intrinsic stress levels follows an inverted U-shape effect. Moreover, after reviewing the literature, we conclude that all selected factors are essential to develop an integrative model that defines the outcome of stress effects in memory processes. In parallel, we provide a brief review of the main neurobiological mechanisms proposed to account for the different effects of stress in memory function. Glucocorticoids were found as a common mediating mechanism for both the facilitating and impairing actions of stress in different memory processes and phases. Among the brain regions implicated, the hippocampus, amygdala, and prefrontal cortex were highlighted as critical for the mediation of stress effects.

  15. Sensitivity of stresses and failure mechanisms in SOFCs to the mechanical properties and geometry of the constitutive layers

    Energy Technology Data Exchange (ETDEWEB)

    Nakajo, A.; Van herle, J.; Favrat, D. [Laboratoire d' Energetique Industrielle (LENI), Institut de Genie Mecanique, Ecole Polytechnique Federale de Lausanne, 1015 Lausanne (Switzerland)

    2011-08-15

    A model based on the Euler-Bernoulli theory is used to assess the sensitivity of residual stresses in solid oxide fuel cells to the mechanical properties and geometry of the constituents. It considers different cell configurations, characterised by the presence or not of a compensating layer, and a cathode based on either lanthanum strontium manganite (LSM) or lanthanum strontium cobaltite ferrite (LSCF). The implementation of creep in the model provides insights into the parameters that affect the zero-stress temperature and behaviour during ageing. The amount of irreversible deformation generated in the cell layers after the sintering step depends on the mechanical properties of the layers, type of cell and to some extent, cooling rate. X-ray diffraction measurements from literature are used to verify the prediction. Depending on the mechanical properties, the stress state in the LSM cathode changes from tensile to compressive with respect to temperature. During combined ageing and thermal cycling, tensile stress might arise in the compatibility layer of LSCF-based cells, due to the relief of the initial compressive stress at operating temperature. The Weibull analysis provides the assessment of mechanical failure. A simplified approach is used for buckling-driven delamination, but the propagation of cracks is predicted for unlikely large pre-existing defects. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  16. Oxidative Stress-Mediated Atherosclerosis: Mechanisms and Therapies

    Directory of Open Access Journals (Sweden)

    Xinyu Yang

    2017-08-01

    Full Text Available Atherogenesis, the formation of atherosclerotic plaques, is a complex process that involves several mechanisms, including endothelial dysfunction, neovascularization, vascular proliferation, apoptosis, matrix degradation, inflammation, and thrombosis. The pathogenesis and progression of atherosclerosis are explained differently by different scholars. One of the most common theories is the destruction of well-balanced homeostatic mechanisms, which incurs the oxidative stress. And oxidative stress is widely regarded as the redox status realized when an imbalance exists between antioxidant capability and activity species including reactive oxygen (ROS, nitrogen (RNS and halogen species, non-radical as well as free radical species. This occurrence results in cell injury due to direct oxidation of cellular protein, lipid, and DNA or via cell death signaling pathways responsible for accelerating atherogenesis. This paper discusses inflammation, mitochondria, autophagy, apoptosis, and epigenetics as they induce oxidative stress in atherosclerosis, as well as various treatments for antioxidative stress that may prevent atherosclerosis.

  17. Glucocorticoids and the Brain: Neural Mechanisms Regulating the Stress Response.

    Science.gov (United States)

    Shirazi, Shawn N; Friedman, Aaron R; Kaufer, Daniela; Sakhai, Samuel A

    2015-01-01

    In this chapter, we describe the central role of the brain in the glucocorticoid mediated stress response. We describe the mechanisms by which the brain gauges the severity of stress, mechanisms of hypothalamic-pituitary-adrenal axis (HPA) regulation, and how various sub-systems of the brain respond to glucocorticoid (GC) signaling to regulate stress behavior. In particular, we focus on the hippocampus, pre-frontal cortex, and amygdala, where GCs can induce a series of changes. Finally, we briefly discuss an apparent paradox in GC signaling: while exposure to glucocorticoids promotes the survival of an organism during acute stress, these same hormones in chronic excess can also cause damage and promote illness.

  18. Modeling of Hysteresis Losses in Ferromagnetic Laminations under Mechanical Stress

    OpenAIRE

    Rasilo, Paavo; Singh, Deepak; Aydin, Ugur; Martin, Floran; Kouhia, Reijo; Belahcen, Anouar; Arkkio, Antero

    2015-01-01

    A novel approach for predicting magnetic hysteresis loops and losses in ferromagnetic laminations under mechanical stress is presented. The model is based on combining a Helmholtz free energy -based anhysteretic magnetoelastic constitutive law to a vector Jiles-Atherton hysteresis model. This paper focuses only on unidirectional and parallel magnetic fields and stresses, albeit the model is developed in full 3-D configuration in order to account also for strains perpendicular to the loading d...

  19. Bell operator and Gaussian squeezed states in noncommutative quantum mechanics

    Science.gov (United States)

    Bastos, Catarina; Bernardini, Alex E.; Bertolami, Orfeu; Dias, Nuno Costa; Prata, João Nuno

    2016-05-01

    We examine putative corrections to the Bell operator due to the noncommutativity in the phase space. Starting from a Gaussian squeezed envelope whose time evolution is driven by commutative (standard quantum mechanics) and noncommutative dynamics, respectively, we conclude that although the time-evolving covariance matrix in the noncommutative case is different from the standard case, the squeezing parameter dominates and there are no noticeable noncommutative corrections to the Bell operator. This indicates that, at least for squeezed states, the privileged states to test Bell correlations, noncommutativity versions of quantum mechanics remain as nonlocal as quantum mechanics itself.

  20. Pathway and mechanism of oxidative stress in Alzheimer's disease

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Current hypotheses of pathogenesis of neuronal degeneration in Alzheimer's disease (AD) have been proposed, including formation of free radicals, oxidative stress, mitochondrial dysfunction, inflammatory processes, genetic factors, environmental impact factors, apoptosis, and so on. Especially, oxidative stress plays an essential role in AD pathogenesis by the function of linking agent. Oxidative stress in AD mainly includes lipid peroxidation, protein oxidation and DNA oxidation. Lipid peroxidation plays a key role in the development and progression of AD. Protein oxidation is an important mechanism in AD. Oxidative damage to DNA may plays an important role in aging and AD.

  1. Molecular mechanisms of ROS production and oxidative stress in diabetes.

    Science.gov (United States)

    Newsholme, Philip; Cruzat, Vinicius Fernandes; Keane, Kevin Noel; Carlessi, Rodrigo; de Bittencourt, Paulo Ivo Homem

    2016-12-15

    Oxidative stress and chronic inflammation are known to be associated with the development of metabolic diseases, including diabetes. Oxidative stress, an imbalance between oxidative and antioxidative systems of cells and tissues, is a result of over production of oxidative-free radicals and associated reactive oxygen species (ROS). One outcome of excessive levels of ROS is the modification of the structure and function of cellular proteins and lipids, leading to cellular dysfunction including impaired energy metabolism, altered cell signalling and cell cycle control, impaired cell transport mechanisms and overall dysfunctional biological activity, immune activation and inflammation. Nutritional stress, such as that caused by excess high-fat and/or carbohydrate diets, promotes oxidative stress as evident by increased lipid peroxidation products, protein carbonylation and decreased antioxidant status. In obesity, chronic oxidative stress and associated inflammation are the underlying factors that lead to the development of pathologies such as insulin resistance, dysregulated pathways of metabolism, diabetes and cardiovascular disease through impaired signalling and metabolism resulting in dysfunction to insulin secretion, insulin action and immune responses. However, exercise may counter excessive levels of oxidative stress and thus improve metabolic and inflammatory outcomes. In the present article, we review the cellular and molecular origins and significance of ROS production, the molecular targets and responses describing how oxidative stress affects cell function including mechanisms of insulin secretion and action, from the point of view of possible application of novel diabetic therapies based on redox regulation.

  2. Mechanical modeling of stress generation during cure of encapsulating resins

    Energy Technology Data Exchange (ETDEWEB)

    Lagasse, R.R.; Chambers, R.S.; Guess, T.R. (Sandia National Labs., Albuquerque, NM (USA)); Plazek, D.J.; Bero, C. (Pittsburgh Univ., PA (USA). Dept. of Materials Science and Engineering)

    1991-01-01

    We have developed a numerical model for calculating stresses generated during cure of shrinking encapsulating resins. Mechanical modeling of polymer encapsulated electronic devices usually focuses on stress generated during cooling after cure. The stress developed during cure, due to shrinkage of the encapsulant, is normally neglected. That assumption is valid if both the shear and bulk moduli of the encapsulant at the cure temperature are negligible with respect to the moduli at lower temperatures. Our measurements on a model epoxy encapsulant show that the shear modulus during cure, varying from 0 to 6 MPa, is at least 100 times smaller than that at ambient temperature. In contrast, the bulk modulus at the cure temperature is only 2.5 times smaller. Since the bulk modulus during cure cannot be neglected, significant stress can be produced if volume shrinkage is constrained by a stiff mold or embedded elements. In fact, mechanical failure of encapsulating materials during cure has been evident in some of our experiments. Using measurements of shear and bulk moduli plus volume shrinkage as inputs to a finite element model, we have successfully predicted the shrinkage strains and stresses developed during cure of a model epoxy resin inside a cylindrical tube. Consideration of cure shrinkage stress has led to a process modification that appears to reduce mechanical failures in a real encapsulated device. 6 refs., 6 figs.

  3. Local mechanical stress relaxation of Gunn diodes irradiated by protons

    Science.gov (United States)

    Gradoboev, A. V.; Tesleva, E. P.

    2017-05-01

    The aim of the work is studying the impact of Gunn diodes thermocompression bonding conditions upon their resistance to being radiated with protons of various energies. It was established that the tough conditions of Gunn diodes thermocompression bonding results in local mechanic stresses introduced into the active layer of the device, reduction of electron mobility because of the faults introduction and, subsequently, to reduction of operating current, power of UHF generation, percentage of qualitative units production and general reduction of production efficiency of the devices with required characteristics. Irradiation of Gunn diodes produced under the tough conditions of thermocompression bonding with protons which energy is (40-60) MeV with an absorbed dose of (1-6)·102 Gy does not practically reduce the radiation resistance of Gunn diodes produced with application of the given technique. This technique can be recommended for all semiconductor devices on the base of GaAs, which parameters depend significantly upon the mobility of the electrons, to increase the efficiency of production.

  4. Modeling Chemical Mechanical Polishing with Couple Stress Fluids

    Institute of Scientific and Technical Information of China (English)

    张朝辉; 雒建斌; 温诗铸

    2004-01-01

    Chemical mechanical polishing (CMP) is a manufacturing process used to achieve high levels of global and local planarity.Currently, the slurries used in CMP usually contain nanoscale particles to accelerate the removal ratio and to optimize the planarity, whose rheological properties can no longer be accurately modeled with Newtonian fluids.The Reynolds equation, including the couple stress effects, was derived in this paper.The equation describes the mechanism to solve the CMP lubrication equation with the couple stress effects.The effects on load and moments resulting from the various parameters, such as pivot height, roll angle, and pitch angle, were subsequently simulated.The results show that the couple stress can provide higher load and angular moments.This study sheds some lights into the mechanism of the CMP process.

  5. Intraplate stress field in South America from earthquake focal mechanisms

    Science.gov (United States)

    Assumpção, Marcelo; Dias, Fábio L.; Zevallos, Ivan; Naliboff, John B.

    2016-11-01

    We present an updated compilation of earthquake focal mechanisms in Brazil together with focal mechanisms from the sub-Andean region (mainly from global CMT catalogs). All earthquakes in the sub-Andean region show reverse (majority) or strike-slip faulting mechanisms. Focal mechanisms in Brazil show reverse, strike-slip and normal faulting. Focal mechanisms of nearby earthquakes in the same tectonic environment were grouped and inverted for the stress tensor. In the sub-Andean region, stresses are compressional, as expected, with the principal major compression (S1) roughly E-W, on average. A slight rotation of S1 can be observed and is controlled by the orientation of the Andean plateau. In the sub-Andean region, the intermediate principal stress (S2) is also compressional (i.e., larger than the lithostatic pressure, Sv), a feature that is not always reproduced in numerical models published in the literature. In mid-plate South America stresses seem to vary in nature and orientation. In SE Brazil and the Chaco-Pantanal basins, S1 tends to be oriented roughly E-W with S2 approximately equal to S3. This stress pattern changes to purely compressional (both SHmax and Shmin larger than Sv) in the São Francisco craton. A rotation of SHmax from E-W to SE-NW is suggested towards the Amazon region. Along the Atlantic margin, the regional stresses are very much affected by coastal effects (due to continent/ocean spreading stresses as well as flexural effects from sediment load at the continental margin). This coastal effect tends to make SHmax parallel to the coastline and Shmin (usually S3) perpendicular to the coastline. Few breakout data and in-situ measurements are available in Brazil and are generally consistent with the pattern derived from the earthquake focal mechanisms. Although numerical models of global lithospheric stresses tend to reproduce the main large-scale features in most mid-plate areas, the S1 rotation from ∼E-W in SE Brazil to SE-NW in the Amazon

  6. Mechanical Stress Induces Remodeling of Vascular Networks in Growing Leaves.

    Directory of Open Access Journals (Sweden)

    Yohai Bar-Sinai

    2016-04-01

    Full Text Available Differentiation into well-defined patterns and tissue growth are recognized as key processes in organismal development. However, it is unclear whether patterns are passively, homogeneously dilated by growth or whether they remodel during tissue expansion. Leaf vascular networks are well-fitted to investigate this issue, since leaves are approximately two-dimensional and grow manyfold in size. Here we study experimentally and computationally how vein patterns affect growth. We first model the growing vasculature as a network of viscoelastic rods and consider its response to external mechanical stress. We use the so-called texture tensor to quantify the local network geometry and reveal that growth is heterogeneous, resembling non-affine deformations in composite materials. We then apply mechanical forces to growing leaves after veins have differentiated, which respond by anisotropic growth and reorientation of the network in the direction of external stress. External mechanical stress appears to make growth more homogeneous, in contrast with the model with viscoelastic rods. However, we reconcile the model with experimental data by incorporating randomness in rod thickness and a threshold in the rod growth law, making the rods viscoelastoplastic. Altogether, we show that the higher stiffness of veins leads to their reorientation along external forces, along with a reduction in growth heterogeneity. This process may lead to the reinforcement of leaves against mechanical stress. More generally, our work contributes to a framework whereby growth and patterns are coordinated through the differences in mechanical properties between cell types.

  7. Hyperglycemia and mechanical stress: targeting the renal podocyte.

    Science.gov (United States)

    Lewko, Barbara; Stepinski, Jan

    2009-11-01

    Hyperglycemia and deriving from glomerular hypertension mechanical stress are the key factors underlying pathogenesis of diabetic nephropathy (DN). Multiple direct and secondary effects of both these factors are mediated by complex signaling pathways with extensive interactions. The common signaling pathways stimulated by high glucose and mechanical insult may act in an additive manner, thereby accelerating the cell damage. Podocytes, the cells covering the outer aspect of glomerular basement membrane (GBM), are subjected not only to the load of filtered glucose but also to diverse mechanical forces. Bulging into the Bowman's space, they have no support from the apical side, which makes them particularly susceptible to the effects of mechanical strain. Both high glucose and mechanical stress may impair the protein systems anchoring the podocyte foot processes in GBM, therefore blunting resistance of these cells to mechanical forces. Modulation by these factors of expression and activity of numerous structural and functional proteins results in the (auto)inflammatory responses, dysfunction, apoptosis or necrosis of the podocytes. Loss of the podocytes is irreversible due to their inability to proliferate and to replenish damaged cells. Podocytes are injured early in the course of DN, which, most likely, underlies further glomerular and renal damage in diabetes. This review summarizes the effects of elevated glucose and mechanical stress that seem to be involved in podocyte impairment in diabetes, with particular focus on the possible interactions between these factors.

  8. Effect of thermal stresses on the mechanism of tooth pain.

    Science.gov (United States)

    Oskui, Iman Z; Ashtiani, Mohammed N; Hashemi, Ata; Jafarzadeh, Hamid

    2014-11-01

    Daily hot and cold thermal loadings on teeth may result in structural deformation, mechanical stress, and pain signaling. The aim of this study was to compare the adverse effects of hot and cold beverages on an intact tooth and, then, to provide physical evidence to support the hydrodynamic theory of tooth pain sensation mechanism. Three-dimensional finite element analysis was performed on a premolar model subjected to hot and cold thermal loadings. Elapsed times for heat diffusion and stress detection at the pulp-dentin junction were calculated as measures of the pain sensation. Extreme tensile stress within the enamel resulted in damage in cold loadings. Also, extreme values of stress at the pulpal wall occurred 21.6 seconds earlier than extreme temperatures in hot and cold loadings. The intact tooth was remarkably vulnerable to cold loading. Earlier changes in mechanical stress rather than temperature at the pulp-dentin junction indicate that the dental pain caused by hot or cold beverages may be based on the hydrodynamic theory. Copyright © 2014 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

  9. Circulatory Responses to Operative Stress in Females with Gestosis

    Directory of Open Access Journals (Sweden)

    I. V. Mikhno

    2007-01-01

    Full Text Available Objective: to study the specific features of hemodynamic responses in females with gestosis in the perioperative period; to evaluate the impact of intensive care on the basis of co-administration of dalargin, dexamethasone, pen-toxifylline, and reamberin.Materials and methods. A Diamant KM-AP-01 rheograph (Saint Petersburg was used to study hemodynamic parameters in 142 patients in whom surgical delivery was made under spinal anesthesia. A control group comprised 30 patients with uncomplicated pregnancy; Group 1 included 26 females with moderate gestosis; Group 2 consisted of 27 females with moderate gestosis who received the developed intensive care regimen; Group 3 comprised 29 females with severe gestosis; Group 4 included 30 females to whom the developed intensive care regimen was applied on the basis of the concurrent use of dalargin, dexamethasone, pentoxifylline, and reamberin.Results: A neurogenic mechanism prevails in females with moderate gestosis. The decreased baseline cardiac index is mostly due to a high postload. Surgical stress does not deteriorate postoperative circulatory parameters, which suggests that females with moderate gestosis have adequate capacities for self-regulation. As gestosis progresses to a severe degree, a role of humoral mechanisms increases in the maintenance of arteriolar spasm. Arteriolar spasm and hypokinetic hemodynamics are retained within 5 postoperative days, which is indicative of the inadequacy of self-regulation and compensatory mechanisms in overcoming two stressors: severe gestosis and surgical aggression.Conclusion: the intensive care regimen developed on the basis of combined use of dalargin, dexamethasone, pentoxifylline, and reamberin favors a more intensive (the promptest normalization of circulatory parameters after surgical delivery in females with moderate and severe gestosis. 

  10. Modification and Performance Evaluation of a Low Cost Electro-Mechanically Operated Creep Testing Machine

    Directory of Open Access Journals (Sweden)

    John J. MOMOH

    2010-12-01

    Full Text Available Existing mechanically operated tensile and creep testing machine was modified to a low cost, electro-mechanically operated creep testing machine capable of determining the creep properties of aluminum, lead and thermoplastic materials as a function of applied stress, time and temperature. The modification of the testing machine was necessitated by having an electro-mechanically operated creep testing machine as a demonstration model ideal for use and laboratory demonstrations, which will provide an economical means of performing standard creep experiments. The experimental result is a more comprehensive understanding of the laboratory experience, as the technology behind the creep testing machine, the test methodology and the response of materials loaded during experiment are explored. The machine provides a low cost solution for Mechanics of Materials laboratories interested in creep testing experiment and demonstration but not capable of funding the acquisition of commercially available creep testing machines. Creep curves of strain versus time on a thermoplastic material were plotted at a stress level of 1.95MPa, 3.25MPa and 4.55MPa and temperature of 20oC, 40oC and 60oC respectively. The machine is satisfactory since it is always ready for operation at any given time.

  11. Damage Mechanics of Ferrite Ductile Iron under Uniaxial Stress

    Institute of Scientific and Technical Information of China (English)

    LIU Jin-hai; LI Guo-lu; FU Han-guang; HAO Xiao-yan; LIU Gen-sheng

    2003-01-01

    According to the principle of damage mechanics, the damage characteristics of ferrite nodular cast iron under uniaxial stress were studied by measuring electric resistance. The results show that the damage in nodular cast iron occurs when the applied stress is more than a certain extent, and the damage variable increases with stress. The evolutional law of damage variable as a function of stress was obtained. The damage threshold of nodular cast iron increases with nodularity, but it is below the yield strength, which provides reference significance to the design of machinery structure and the choice of materials. The critical damage variable is not related to the nodularity, which is about 0.060-0.068.

  12. Pseudo-Hermitian quantum mechanics with unbounded metric operators.

    Science.gov (United States)

    Mostafazadeh, Ali

    2013-04-28

    I extend the formulation of pseudo-Hermitian quantum mechanics to η(+)-pseudo-Hermitian Hamiltonian operators H with an unbounded metric operator η(+). In particular, I give the details of the construction of the physical Hilbert space, observables and equivalent Hermitian Hamiltonian for the case that H has a real and discrete spectrum and its eigenvectors belong to the domain of η(+) and consequently √η(+).

  13. Bell operator and Gaussian squeezed states in noncommutative quantum mechanics

    CERN Document Server

    Bastos, Catarina; Bertolami, Orfeu; Dias, Nuno Costa; Prata, João Nuno

    2015-01-01

    One examines putative corrections to the Bell operator due to the noncommutativity in the phase-space. Starting from a Gaussian squeezed envelop whose time evolution is driven by commutative (standard quantum mechanics) and noncommutative dynamics respectively, one concludes that, although the time evolving covariance matrix in the noncommutative case is different from the standard case, the squeezing parameter dominates and there are no noticeable noncommutative corrections to the Bell operator. This indicates that, at least for squeezed states, the privileged states to test Bell correlations, noncommutativity versions of quantum mechnics remains as non-local as quantum mechanics itself.

  14. Mapping Nondominant Voices into Understanding Stress-Coping Mechanisms

    Science.gov (United States)

    Iwasaki, Yoshitaka; Bartlett, Judith; MacKay, Kelly; Mactavish, Jennifer; Ristock, Janice

    2008-01-01

    This study reports key findings from a research project, which examined the stress and coping mechanisms of several nondominant groups of individuals. The groups were based in Winnipeg, Manitoba, Canada and included (a) Aboriginal individuals with diabetes, (b) individuals with disabilities, and (c) gays and lesbians. Our analyses of personal…

  15. Oxidative stress and diabetic neuropathy : pathophysiotogical mechanisms and treatment perspectives

    NARCIS (Netherlands)

    2002-01-01

    Increased oxidative stress is a mechanism that probably plays a major role in the development of diabetic complications, including peripheral neuropathy. This review summarises recent data from in vitro and in vivo studies that have been performed both to understand this aspect of the pathophysiolog

  16. Biochemical mechanisms of signaling: perspectives in plants under arsenic stress.

    Science.gov (United States)

    Islam, Ejazul; Khan, Muhammad Tahir; Irem, Samra

    2015-04-01

    Plants are the ultimate food source for humans, either directly or indirectly. Being sessile in nature, they are exposed to various biotic and abiotic stresses because of changing climate that adversely effects their growth and development. Contamination of heavy metals is one of the major abiotic stresses because of anthropogenic as well as natural factors which lead to increased toxicity and accumulation in plants. Arsenic is a naturally occurring metalloid toxin present in the earth crust. Due to its presence in terrestrial and aquatic environments, it effects the growth of plants. Plants can tolerate arsenic using several mechanisms like phytochelation, vacuole sequestration and activation of antioxidant defense systems. Several signaling mechanisms have evolved in plants that involve the use of proteins, calcium ions, hormones, reactive oxygen species and nitric oxide as signaling molecules to cope with arsenic toxicity. These mechanisms facilitate plants to survive under metal stress by activating their defense systems. The pathways by which these stress signals are perceived and responded is an unexplored area of research and there are lots of gaps still to be filled. A good understanding of these signaling pathways can help in raising the plants which can perform better in arsenic contaminated soil and water. In order to increase the survival of plants in contaminated areas there is a strong need to identify suitable gene targets that can be modified according to needs of the stakeholders using various biotechnological techniques. This review focuses on the signaling mechanisms of plants grown under arsenic stress and will give an insight of the different sensory systems in plants. Furthermore, it provides the knowledge about several pathways that can be exploited to develop plant cultivars which are resistant to arsenic stress or can reduce its uptake to minimize the risk of arsenic toxicity through food chain thus ensuring food security.

  17. Modal Testing of Mechanical Structures Subject to Operational Excitation Forces

    DEFF Research Database (Denmark)

    Møller, N.; Brincker, Rune; Herlufsen, H.;

    2000-01-01

    Operational Modal Analysis also known as Output Only Modal Analysis has in the recent years been used for extracting modal parameters of civil engineering structures and is now becoming popular for mechanical structures. The advantage of the method is that no artificial excitation need...... to the Operational Modal Analysis. For Operational Modal Analysis two different estimation techniques are used: a non-parametric technique based on Frequency Domain Decomposition (FDD), and a parametric technique working on the raw data in time domain, a data driven Stochastic Subspace Identification (SSI) algorithm....... These are compared to other methods such as traditional Modal Analysis....

  18. Fundamental Entangling Operators in Quantum Mechanics and Their Properties

    Science.gov (United States)

    Dao-Ming, Lu

    2016-07-01

    For the first time, we introduce so-called fundamental entangling operators e^{iQ1 P2} and e^{iP1 Q2 } for composing bipartite entangled states of continuum variables, where Q i and P i ( i = 1, 2) are coordinate and momentum operator, respectively. We then analyze how these entangling operators naturally appear in the quantum image of classical quadratic coordinate transformation ( q 1, q 2) → ( A q 1 + B q 2, C q 1 + D q 2), where A D- B C = 1, which means even the basic coordinate transformation ( Q 1, Q 2) → ( A Q 1 + B Q 2, C Q 1 + D Q 2) involves entangling mechanism. We also analyse their Lie algebraic properties and use the integration technique within an ordered product of operators to show they are also one- and two- mode combinatorial squeezing operators.

  19. Gravitational Mass, Its Mechanics - What It Is; How It Operates

    OpenAIRE

    Ellman, Roger

    1999-01-01

    The earlier paper, Inertial Mass, Its Mechanics - What It Is; How It Operates, developed the mechanics of inertial mass. The present paper is for the purpose of equivalently developing gravitation. The behavior of gravitation is well known, as described by Newton's Law of Gravitation. But just what gravitational mass is, how gravitational behavior comes about, what in material reality produces the effects of gravitational mass, has been little understood. The only extant hypotheses involve th...

  20. Stress tensor and focal mechanisms in the Dead Sea basin

    Science.gov (United States)

    Hofstetter, A.; Dorbath, C.; Dorbath, L.; Braeuer, B.; Weber, M.

    2016-04-01

    We use the recorded seismicity, confined to the Dead Sea basin and its boundaries, by the Dead Sea Integrated Research (DESIRE) portable seismic network and the Israel and Jordan permanent seismic networks for studying the mechanisms of earthquakes in the Dead Sea basin. The observed seismicity in the Dead Sea basin is divided into nine regions according to the spatial distribution of the earthquakes and the known tectonic features. The large number of recording stations and the adequate station distribution allowed the reliable determinations of 494 earthquake focal mechanisms. For each region, based on the inversion of the observed polarities of the earthquakes, we determine the focal mechanisms and the associated stress tensor. For 159 earthquakes, out of the 494 focal mechanisms, we could determine compatible fault planes. On the eastern side, the focal mechanisms are mainly strike-slip mechanism with nodal planes in the N-S and E-W directions. The azimuths of the stress axes are well constrained presenting minimal variability in the inversion of the data, which is in agreement with the Eastern Boundary fault on the east side of the Dead Sea basin and what we had expected from the regional geodynamics. However, larger variabilities of the azimuthal and dip angles are observed on the western side of the basin. Due to the wider range of azimuths of the fault planes, we observe the switching of σ1 and σ2 or the switching of σ2 and σ3 as major horizontal stress directions. This observed switching of stress axes allows having dip-slip and normal mechanisms in a region that is dominated by strike-slip motion.

  1. Stress-induced neuroinflammation: mechanisms and new pharmacological targets

    Directory of Open Access Journals (Sweden)

    C.D. Munhoz

    2008-12-01

    Full Text Available Stress is triggered by numerous unexpected environmental, social or pathological stimuli occurring during the life of animals, including humans, which determine changes in all of their systems. Although acute stress is essential for survival, chronic, long-lasting stress can be detrimental. In this review, we present data supporting the hypothesis that stress-related events are characterized by modifications of oxidative/nitrosative pathways in the brain in response to the activation of inflammatory mediators. Recent findings indicate a key role for nitric oxide (NO and an excess of pro-oxidants in various brain areas as responsible for both neuronal functional impairment and structural damage. Similarly, cyclooxygenase-2 (COX-2, another known source of oxidants, may account for stress-induced brain damage. Interestingly, some of the COX-2-derived mediators, such as the prostaglandin 15d-PGJ2 and its peroxisome proliferator-activated nuclear receptor PPARγ, are activated in the brain in response to stress, constituting a possible endogenous anti-inflammatory mechanism of defense against excessive inflammation. The stress-induced activation of both biochemical pathways depends on the activation of the N-methyl-D-aspartate (NMDA glutamate receptor and on the activation of the transcription factor nuclear factor kappa B (NFκB. In the case of inducible NO synthase (iNOS, release of the cytokine TNF-α also accounts for its expression. Different pharmacological strategies directed towards different sites in iNOS or COX-2 pathways have been shown to be neuroprotective in stress-induced brain damage: NMDA receptor blockers, inhibitors of TNF-α activation and release, inhibitors of NFκB, specific inhibitors of iNOS and COX-2 activities and PPARγ agonists. This article reviews recent contributions to this area addressing possible new pharmacological targets for the treatment of stress-induced neuropsychiatric disorders.

  2. Syringomyelia after operation: diagnosis and its formational mechanism

    Institute of Scientific and Technical Information of China (English)

    Shi Jiangang; Xu Guohua; Jia Lianshun; Yuan Wen; Shi Guodong; Wu Jianfeng; Ye XiaoJian; Ni Bin; Xiao Jianru; Tan Junming

    2008-01-01

    Objective: To describe the MRI findings and discuss the pathogenesis formation mechanism of syringomyelia in the patients after spine surgical operation. Methods: Totally 13 patients were been enrolled in the study. Before operation, none of our patients presented with spinal cord syringomyelia. The mean follow-up duration was 6 years (range 2-10 months) by MRI. Four of the 13 patients after spinal cord tumor removed operation, 3 patients after spinal trauma operation, 2 cases had scoliosis before, 2 cases were cervical spondylotic myelopathy and 2 cases had tethered cord syndrome before operation. MR features of pre- and post-operation on all patients were been studied in contrast with surgical results and clinical symptoms. The radiology diagnostic was made by 3 different radiologists respectively. The characteristics of length, width, signals, shape of cavity and spinal cord position as well as subarachnoid shape were focused on. Results: All the patients had no syringomyelia on MRI before operation. The spinal cord of 7 patients showed persist compression and 2 patients had tethered cord before operation. MRI features of syringomyelia after operation in our cases showed longitudinal cavity with syrinx fluid had T1 and T2 relation characteristics of cerebrospinal fluid (CSF). The mean length was 5.5 spinal segment, 4 cord of 13 patients presented cord compressed from anterior materials, 4 occurred postoperative adhesion to the back of lumbar spinal canal and spinal cord of 1 cases clung to the front wall of cervical spinal canal. Conclusion: The mechanism of syringomyelia in the patients after spinal surgical intervention may be the persisting compression or intention of the spinal cord in the period of pre- or post-operation. The edema, cyst, malacia of spinal cord are the most important lesions and risk factors resulted in the syringomyelia.

  3. Mechanical fatigue of polysilicon: Effects of mean stress and stress amplitude

    Energy Technology Data Exchange (ETDEWEB)

    Kahn, H. [Department of Materials Science and Engineering, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106 7204 (United States)]. E-mail: harold.kahn@case.edu; Chen, L. [Department of Civil Engineering, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106 7201 (United States); Ballarini, R. [Department of Civil Engineering, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106 7201 (United States); Heuer, A.H. [Department of Materials Science and Engineering, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106 7204 (United States)

    2006-02-15

    Polycrystalline silicon (polysilicon) fatigue specimens with micrometer-sized dimensions were fabricated and subjected to cyclic loading using an integrated electrostatic actuator. The fatigue effects were determined by comparing the single edge-notched beam monotonic bend strength measured after cyclic loading to the monotonic strength of 'virgin' specimens that had received no cycling. Both strengthening and weakening were observed, depending on the levels of mean stress and fatigue stress amplitude during the cyclic loading. Monotonic loading with similar sub-critical stress levels had no effect. The physical mechanisms responsible for this behavior are discussed, and a model based on grain boundary plasticity is presented for the strengthening behavior.

  4. The effects of stress on nuclear power plant operational decision making and training approaches to reduce stress effects

    Energy Technology Data Exchange (ETDEWEB)

    Mumaw, R.J.

    1994-08-01

    Operational personnel may be exposed to significant levels of stress during unexpected changes in plant state an plant emergencies. The decision making that identifies operational actions, which is strongly determined by procedures, may be affected by stress, and performance may be impaired. ER report analyzes potential effects of stress in nuclear power plant (NPP) settings, especially in the context of severe accident management (SAM). First, potential sources of stress in the NPP setting are identified. This analysis is followed by a review of the ways in which stress is likely to affect performance, with an emphasis on performance of cognitive skills that are linked to operational decision making. Finally, potential training approaches for reducing or eliminating stress effects are identified. Several training approaches have the potential to eliminate or mitigate stress effects on cognitive skill performance. First, the use of simulated events for training can reduce the novelty and uncertainty that can lead to stress and performance impairments. Second, training to make cognitive processing more efficient and less reliant on attention and memory resources can offset the reductions in these resources that occur under stressful conditions. Third, training that targets crew communications skills can reduce the likelihood that communications will fail under stress.

  5. Neural regulation of the stress response: glucocorticoid feedback mechanisms

    Directory of Open Access Journals (Sweden)

    J.P. Herman

    2012-04-01

    Full Text Available The mammalian stress response is an integrated physiological and psychological reaction to real or perceived adversity. Glucocorticoids are an important component of this response, acting to redistribute energy resources to both optimize survival in the face of challenge and to restore homeostasis after the immediate challenge has subsided. Release of glucocorticoids is mediated by the hypothalamo-pituitary-adrenal (HPA axis, driven by a neural signal originating in the paraventricular nucleus (PVN. Stress levels of glucocorticoids bind to glucocorticoid receptors in multiple body compartments, including the brain, and consequently have wide-reaching actions. For this reason, glucocorticoids serve a vital function in negative feedback inhibition of their own secretion. Negative feedback inhibition is mediated by a diverse collection of mechanisms, including fast, non-genomic feedback at the level of the PVN, stress-shut-off at the level of the limbic system, and attenuation of ascending excitatory input through destabilization of mRNAs encoding neuropeptide drivers of the HPA axis. In addition, there is evidence that glucocorticoids participate in stress activation via feed-forward mechanisms at the level of the amygdala. Feedback deficits are associated with numerous disease states, underscoring the necessity for adequate control of glucocorticoid homeostasis. Thus, rather than having a single, defined feedback ‘switch’, control of the stress response requires a wide-reaching feedback ‘network’ that coordinates HPA activity to suit the overall needs of multiple body systems.

  6. Psychological and Physical Stress in Surgeons Operating in a Standard or Modern Operating Room

    DEFF Research Database (Denmark)

    Klein, M.; Andersen, L.P.H.; Alamili, M.

    2010-01-01

    concerning physical and psychological wellbeing before and after surgery and had their heart rate variability registered during surgery. Results: Preoperative to postoperative physical strain and pain measurements revealed a systematical difference with 14 of 15 parameters favoring the modern OR. Two...... of these parameters reached statistical significance. We did not find any significant differences in the subjective parameters of surgeon satisfaction or the measured heart rate variability parameters. Conclusions: Physical strain on the surgeon was reduced when performing laparoscopic cholecystectomy in a modern......Purpose: There have been no studies examining the effect of optimized ergonomic and technical environment on the psychological and physiological stress of the surgeon. The aim of this study was to examine whether optimized ergonomics and technical aids within a modern operating room (OR) affect...

  7. Mechanical twinning as stress indicator in fault rocks

    Science.gov (United States)

    Wenk, H.

    2011-12-01

    At low stresses and elevated temperatures rocks deform by dislocation movements and diffusion. At very high stresses they undergo brittle failure. For many minerals there is an intermediate regime where mechanical twinning occurs. This has been studied extensively in calcite (Turner, Griggs and Heard, GSA Mem. 1954) and also documented for quartz (Tullis, Science, 1972). In this study we use twinning microstructures to characterize rocks that were subjected to seismic stresses, specifically pseudotachylites and samples from the San Andreas Fault Observatory at Depth. For calcite in SAFOD samples, dislocation densities derived from TEM images as well as twin densities measured by optical microscopy, indicate stresses between 50 and 200 MPa. Similar residual stress magnitudes were obtained from preserved lattice distortion determined by synchrotron X-ray microdiffraction. Also quartz shows characteristic twin microstructures. Orientation maps with SEM-EBSD reveal that quartz associated with pseudotachylite veins is profusely twinned, similar to structures observed in quartz subjected to meteorite impacts. It suggests that local dynamic seismic stresses during earthquakes are responsible for Dauphiné twinning. Thus microstructures in minerals add information to constrain macroscopic conditions during faulting.

  8. Psychosocial stress in pregnancy and preterm birth: associations and mechanisms.

    Science.gov (United States)

    Shapiro, Gabriel D; Fraser, William D; Frasch, Martin G; Séguin, Jean R

    2013-11-01

    Psychosocial stress during pregnancy (PSP) is a risk factor of growing interest in the etiology of preterm birth (PTB). This literature review assesses the published evidence concerning the association between PSP and PTB, highlighting established and hypothesized physiological pathways mediating this association. The PubMed and Web of Science databases were searched using the keywords "psychosocial stress", "pregnancy", "pregnancy stress", "preterm", "preterm birth", "gestational age", "anxiety", and "social support". After applying the exclusion criteria, the search produced 107 articles. The association of PSP with PTB varied according to the dimensions and timing of PSP. Stronger associations were generally found in early pregnancy, and most studies demonstrating positive results found moderate effect sizes, with risk ratios between 1.2 and 2.1. Subjective perception of stress and pregnancy-related anxiety appeared to be the stress measures most closely associated with PTB. Potential physiological pathways identified included behavioral, infectious, neuroinflammatory, and neuroendocrine mechanisms. Future research should examine the biological pathways of these different psychosocial stress dimensions and at multiple time points across pregnancy. Culture-independent characterization of the vaginal microbiome and noninvasive monitoring of cholinergic activity represent two exciting frontiers in this research.

  9. Environmental Stress Response and Adaptation Mechanisms in Rhizobia

    Directory of Open Access Journals (Sweden)

    Sanja Kajić

    2016-11-01

    Full Text Available Rhizobia are bacteria that can fixate atmospheric nitrogen in association within the root or the stem nodules of legume plants and transform atmospheric nitrogen to ammonia. Soil environmental conditions are critical factors for the persistence and survival of rhizobia in the soil. The changes in the rhizosphere environment can affect both growth and saprophytic competence, which will influence competitiveness and persistence. Environmental stress imposes a major threat to symbiotic nitrogen fixation and agriculture that can be limited by soil and climatic factors such as salinity, drought, temperature, acidity/alkalinity and heavy metals. In this review we present several different mechanisms in rhizobia adaptation under stress factors.

  10. STUDIES ON STRESS TRANSFERENCE MECHANISM OF STEEL FIBRE REINFORCED CONCRETE

    Institute of Scientific and Technical Information of China (English)

    杨佑发; 许绍乾; 钟正华

    2001-01-01

    The stress transfer mechanism of steel fibre reinforced concrete is studied. The solutions for the stress and displacement were regarded as the superposition of "the elementary solutions" and "the improved solutions". The elementary solutions were found by using two-dimensional elastic theory and the improved solutions were found by using the Love displacement function method. The calculated results indicate that the solutions possess good convergence. By comparing the three-dimensional solutions with the shear-lag solutions, evident difference may be found.

  11. Correlation between texture and mechanical stress durability of thin aluminum films

    Energy Technology Data Exchange (ETDEWEB)

    Nüssl, R., E-mail: rudolf.nuessl@uct.ac.za [Institut für Physik, Universität der Bundeswehr München, Werner-Heisenberg-Weg 39, 85579 Neubiberg (Germany); Jewula, T.; Ruile, W. [TDK Corporation, Systems, Acoustics, Waves Business Group, Anzingerstraße 13, 81617 Munich (Germany); Sulima, T.; Hansch, W. [Institut für Physik, Universität der Bundeswehr München, Werner-Heisenberg-Weg 39, 85579 Neubiberg (Germany)

    2014-04-01

    In this article, differently textured aluminum (Al) metallizations of surface acoustic wave (SAW) devices have been exposed to cyclic mechanical stress in order to investigate a potential correlation between their texture and their mechanical stress durability. Samples of SAW devices with differently textured Al thin film electrodes have been manufactured, and texture measurements have been carried out on all samples with electron backscatter diffraction. Subsequently, the SAW devices have been operated at heavy electrical load until a defined mechanical fatigue of its Al electrodes occurred. SAW devices with highly textured Al electrodes showed almost 20 times higher power durability than SAW devices with untextured Al electrodes. We show that this increase in electrical power durability has to be fully attributed to the strongly enhanced mechanical stress durability of highly textured Al films. Furthermore, a positive correlation between the Al films' texture and its electrical conductivity has been found. - Highlights: • We show highly textured growth of thin Al films on a clean, monocrystalline LiTaO{sub 3} • Highly textured Al growth gets disturbed by prior photolithographic process steps • Power durability of a SAW device increases with texture of its metallization • Texture and mechanical stress durability of a thin Al film are tightly correlated.

  12. Postdeployment driving stress and related occupational limitations among veterans of Operation Iraqi Freedom and Operation Enduring Freedom.

    Science.gov (United States)

    Hwang, Eric J; Peyton, Claudia G; Kim, David K; Nakama-Sato, Kristine K; Noble, Amy E

    2014-01-01

    Difficulty in driving after deployment has emerged as an impediment for servicemembers returning from Operation Iraqi Freedom and Operation Enduring Freedom (OIF-OEF). This study explored postdeployment driving stress and related occupational limitations using two self-report instruments: the Driver's Stress Profile and the Driving and Occupational Limitations questionnaire. Data gathered from 103 OIF-OEF returnees confirmed that driving and related occupational issues occur postdeployment. Significant low to moderate correlations were found between postdeployment driving stress and limitations in community mobility, leisure, and social participation. The returnees who drove off base more frequently during deployment showed significantly higher levels of postdeployment driving stress than the returnees who drove off base less frequently. Moreover, the returnees who demonstrated higher levels of driving stress and occupational limitations required more time to resume normal driving postdeployment. Findings raise awareness about the need to design effective driver rehabilitation and community reintegration programs for this population.

  13. World Stress Map Release 2005 - Stress orientations from single focal mechanisms at plate boundaries

    Science.gov (United States)

    Heidbach, O.; Barth, A.; Müller, B.; Reinecker, J.; Sperner, B.; Tingay, M.

    2005-12-01

    The World Stress Map (WSM) is a global compilation of data about recent tectonic stresses from a wide range of indicators (e.g. focal mechanisms, borehole breakouts). It is a valuable tool for the solution of numerous of technological and scientific problems. The orientation of the stress field, for instance, is a primary control on subsurface fluid flow and thus WSM data can be used to improve petroleum production or the efficiency of geothermal power stations. In scientific context, information on the stress state is essential for seismic hazard assessment. The WSM database release 2005 contains more than 14,000 data sets all classified according to a unified quality ranking. Thus, the comparability of data from different types of measurement is guaranteed. The database as well as guidelines and software for plotting stress maps are available free of charge from our website www.world-stress-map.org. Users can create their own stress map including their own stress data almost instantly with the CASMO (Create A Stress Map Online) web tool. Alternatively, users can download the software CASMI (Create A Stress Map Interactively) free of charge and produce their own stress maps. In the WSM 2005 release we refined the definition of so-called Possible Plate Boundary Events (PBE) for stress data from single focal mechanisms (FMS) considering that the orientations of these earthquakes might be rather controlled by the geometry of the plate boundary than by the stress field orientation. In general, it is assumed that numerous randomly oriented faults are present in the crust, so that earthquakes occur on faults optimally oriented relative to the regional stress field. In such a setting the principal axes of the moment tensor (P, B, T) provide good approximations for the principal stress orientations (σ_1, σ2, σ3). However, plate boundaries show a different mechanical behavior. They are characterized by faults with preferred orientations and presumably include major

  14. Operation of Control Rod Driving Mechanism controller at HANARO

    Energy Technology Data Exchange (ETDEWEB)

    Gyu, Doo Seung; Woo, Lee Min; San, Choe Yeong; Kyoo, Kim Hyung [KAERI, Daejeon (Korea, Republic of)

    2012-10-15

    HANARO (High flux Advanced Neutron Application Reactor) achieved its first critical operation in 1995. Recently, there has been fast developments in the field of electronics. Many manufacturers of I and C components have disappeared or merged with the other companies. The suppliers of the control systems of the CRDM (Control Rod Driving Mechanism) at HANARO have disappeared. Therefore, we needed to change the control system of the CRDM since we cannot be provided with maintenance any longer. In this paper, we investigated the operation of the control system of the CRDM when the controller and motor driver are changed.

  15. Mechanical Stress Measurement During Thin-Film Fabrication

    Science.gov (United States)

    Broadway, David M. (Inventor)

    2017-01-01

    A method and system are provided for determining mechanical stress experienced by a film during fabrication thereof on a substrate positioned in a vacuum deposition chamber. The substrate's first surface is disposed to have the film deposited thereon and the substrate's opposing second surface is a specular reflective surface. A portion of the substrate is supported. An optical displacement sensor is positioned in the vacuum deposition chamber in a spaced-apart relationship with respect to a portion of the substrate's second surface. During film deposition on the substrate's first surface, displacement of the portion of the substrate's second surface is measured using the optical displacement sensor. The measured displacement is indicative of a radius of curvature of the substrate, and the radius of curvature is indicative of mechanical stress being experienced by the film.

  16. The "footloose" mechanism: Iceberg decay from hydrostatic stresses

    Science.gov (United States)

    Wagner, Till J. W.; Wadhams, Peter; Bates, Richard; Elosegui, Pedro; Stern, Alon; Vella, Dominic; Abrahamsen, E. Povl; Crawford, Anna; Nicholls, Keith W.

    2014-08-01

    We study a mechanism of iceberg breakup that may act together with the recognized melt and wave-induced decay processes. Our proposal is based on observations from a recent field experiment on a large ice island in Baffin Bay, East Canada. We observed that successive collapses of the overburden from above an unsupported wavecut at the iceberg waterline created a submerged foot fringing the berg. The buoyancy stresses induced by such a foot may be sufficient to cause moderate-sized bergs to break off from the main berg. A mathematical model is developed to test the feasibility of this mechanism. The results suggest that once the foot reaches a critical length, the induced stresses are sufficient to cause calving. The theoretically predicted maximum stable foot length compares well to the data collected in situ. Further, the model provides analytical expressions for the previously observed "rampart-moat" iceberg surface profiles.

  17. Main mechanisms of material properties degradation under reactor pressure vessel operating conditions

    Energy Technology Data Exchange (ETDEWEB)

    Karzov, Georgy; Timofeev, Boris [Central Research Inst. of Structural Materials ' prometey' , St. Petersburg (Russian Federation)

    1999-07-01

    In the process of NPP equipment operation materials are subjected to a prolonged influence of loads, associated with the variation of inner pressure and temperature under various conditions. Each equipment element damage is associated with some material fracture mechanism. For NPP equipment the mechanisms of irreversible damage accumulation are related with: irradiation embrittlement, thermal and strain aging, fatigue damages from mechanical and thermal loading, stress corrosion and fatigue corrosion, creep and thermal relaxation stresses, erosion and weak, thermal shock. The basic tasks of specialists working in the sphere of the provision of reliability and service life of nuclear power equipment are not only the determination of the main mechanisms of damages and reasons of their appearance, but also the study of methods which would permit to control these properties completely. By giving some examples of Russian NPP equipment with VVER-440 and VVER-1000 reactors the paper presents most typical degradation mechanisms of equipment material properties, including weldments, in the process of operation and methods to recover by using various technological means. (author)

  18. A Fracture Probability Competition Mechanism of Stress Corrosion Cracking

    Institute of Scientific and Technical Information of China (English)

    Yanliang HUANG

    2001-01-01

    The stress corrosion cracking (SCC) of austenitic stainless steel was studied via polarization,slow strain rate and scanning electron microscope (SEM) techniques. Many SCC mechanisms have been proposed in which hydrogen embrittlement and passive film rupture-repassivation theories are generally accepted, but they can hardly explain the SCC mechanism of austenitic stainless steel in acidic chloride solution adequately, because the steel is in active dissolution state and cathodic polarization can prevent it from occurring. Our experiment shows that the anodic current increases the creep rate and decreases the plastic strength of the material on single smooth specimen as well as at the SCC crack tip. The fractured surface was characterized as brittle cleavage, while the surface crack of smooth specimen was almost vertical to the tensile strength, which can confirm that the cracks were caused by tensile stresses. A fracture probability competition mechanism of SCC was proposed on the basis of the experimental results combined with the viewpoint of ductile-brittle fracture competition. When the anodic dissolution current is increased to a certain degree, the probability of fracture by tensile stress will exceed that by shear stress, and the brittle fracture will occur. The proposed SCC mechanism can not only explain the propagation of SCC cracks but can explain the crack initiation as well. The strain on the surface distributes unevenly when a smooth specimen is deformed, so does the anodic current distribution. The crack will initiate at a point where the anodic current density is large enough to cause the material at a specific point to fracture in brittle manner.

  19. Nematodynamics modelling under extreme mechanical and electric stresses

    Science.gov (United States)

    Amoddeo, Antonino

    2015-01-01

    Nematic liquid crystals confined in asymmetric π-cells and subjected to intense electrical and mechanical stresses undergo strong distortions which can be relaxed by means of the order reconstruction, a fast switching mechanism connecting topologically different textures, assuming bulk and/or surface characteristics depending on both amplitude of the applied electric fields and anchoring angles of the nematic molecules on the confining surfaces. In the frame of the Landau-de Gennes order tensor theory, we provide a numerical model implemented with a moving mesh finite element method appropriate to describe the nematic order dynamics, allowing to map the switching properties of the nematic texture.

  20. Chemical reactions modulated by mechanical stress: extended Bell theory.

    Science.gov (United States)

    Konda, Sai Sriharsha M; Brantley, Johnathan N; Bielawski, Christopher W; Makarov, Dmitrii E

    2011-10-28

    A number of recent studies have shown that mechanical stress can significantly lower or raise the activation barrier of a chemical reaction. Within a common approximation due to Bell [Science 200, 618 (1978)], this barrier is linearly dependent on the applied force. A simple extension of Bell's theory that includes higher order corrections in the force predicts that the force-induced change in the activation energy will be given by -FΔR - ΔχF(2)∕2. Here, ΔR is the change of the distance between the atoms, at which the force F is applied, from the reactant to the transition state, and Δχ is the corresponding change in the mechanical compliance of the molecule. Application of this formula to the electrocyclic ring-opening of cis and trans 1,2-dimethylbenzocyclobutene shows that this extension of Bell's theory essentially recovers the force dependence of the barrier, while the original Bell formula exhibits significant errors. Because the extended Bell theory avoids explicit inclusion of the mechanical stress or strain in electronic structure calculations, it allows a computationally efficient characterization of the effect of mechanical forces on chemical processes. That is, the mechanical susceptibility of any reaction pathway is described in terms of two parameters, ΔR and Δχ, both readily computable at zero force.

  1. Quantum Gravity and a Time Operator in Relativistic Quantum Mechanics

    CERN Document Server

    Bauer, M

    2016-01-01

    The problem of time in the quantization of gravity arises from the fact that time in Schroedinger's equation is a parameter. This sets time apart from the spatial coordinates, represented by operators in quantum mechanics (QM). Thus "time" in QM and "time" in General Relativity (GR) are seen as mutually incompatible notions. The introduction of a dy- namical time operator in relativistic quantum mechanics (RQM), that in the Heisenberg representation is also a function of the parameter t (iden- tifed as the laboratory time), prompts to examine whether it can help to solve the disfunction referred to above. In particular, its application to the conditional interpretation of the canonical quantization approach toquantum gravity is developed. 1

  2. Which computational mechanisms operate in the hippocampus during novelty detection?

    Science.gov (United States)

    Kumaran, Dharshan; Maguire, Eleanor A

    2007-01-01

    A fundamental property of adaptive behavior is the ability to rapidly distinguish what is novel from what is familiar in our environment. Empirical evidence and computational work have provided biologically plausible models of the neural substrate and mechanisms underlying the coding of stimulus novelty in the perirhinal cortex. In this article, we highlight the importance of a different category of novelty, namely associative novelty, which has received relatively little attention, despite its clear ecological importance. While previous studies in both animals and humans have documented hippocampal responses in relation to associative novelty, a key issue concerning the computations underlying these novelty signals has not been previously addressed. We argue that this question has importance not only for our understanding of novelty processing, but also for advancing our knowledge of the fundamental computational operations performed by the hippocampus. We suggest a different approach to this problem, and discuss recent evidence supporting the hypothesis that the hippocampus operates as a comparator during the processing of associative novelty, generating mismatch/novelty signals when prior predictions are violated by sensory reality. We also draw on conceptual similarities between associative novelty and contextual novelty to suggest that empirical findings from these two seemingly distant research fields accord with the operation of a comparator mechanism during novelty detection more generally. We therefore conclude that a comparator mechanism may underlie the role of the hippocampus not only in detecting occurrences that are unexpected given specific associatively retrieved predictions, but also events that violate more abstract properties of the experimental context.

  3. Assessment of nursing students' stress levels and coping strategies in operating room practice.

    Science.gov (United States)

    Yildiz Findik, Ummu; Ozbas, Ayfer; Cavdar, Ikbal; Yildizeli Topcu, Sacide; Onler, Ebru

    2015-05-01

    The aim of this study was to evaluate the stress levels and stress coping strategies of nursing students in their first operating room experience. This descriptive study was done with 126 nursing students who were having an experience in an operating room for the first time. Data were collected by using Personal Information Form, Clinical Stress Questionnaire, and Styles of Coping Inventory. The nursing students mostly had low clinical stress levels (M = 27.56, SD = 10.76) and adopted a self-confident approach in coping with stress (M = 14.3, SD = 3.58). The nursing students generally employed a helpless/self-accusatory approach among passive patterns as their clinical stress levels increased, used a self-confident and optimistic approach among active patterns as their average age increased, and those who had never been to an operating room previously used a submissive approach among passive patterns. The results showed that low levels of stress caused the nursing students to use active patterns in coping with stress, whereas increasing levels of stress resulted in employing passive patterns in stress coping. The nursing students should be ensured to maintain low levels of stress and use active patterns in stress coping.

  4. Acute central cord syndrome: injury mechanisms and stress features.

    Science.gov (United States)

    Li, Xin-Feng; Dai, Li-Yang

    2010-09-01

    Numerical techniques were used to study the mechanisms of acute central cord syndrome. To analyze the features of stress distribution in the cervical cord under different injury conditions using finite element model of the cervical cord and to improve the understanding of the possible pathogenesis of acute central cord syndrome. Acute central cord spinal injury was initially attributed to hemorrhagic damage to the central portion of the spinal cord, but recent histopathologic studies showed that it was predominantly a white matter injury. The precise anatomic location of neuronal injury and the etiology of the clinical manifestation were poorly understood. Cervical cord injury was simulated using a finite element model of the cervical enlargement described previously, with the model loaded under 3 traumatic postures: neutral, flexion, and extension. Five traumatic conditions were simulated and analyzed: hyperextension with the pinch force directed to the anterior (A) or posterior (B); flexion injuries (C), vertical compression with the pinch force directed to the anterior (D) or posterior (E). After simulation, several representative cross-sections of each traumatic pattern were selected. In each cross-section, the average von Mises stress of 9 regions, such as anterior funiculus, lateral part of the lateral funiculus, medial part of the lateral funiculus, lateral part of the posterior funiculus, medial part of the posterior funiculus, anterior horn, the bottom of anterior horn, the cervix cornu posterioris, the caput cornu posterioris, and the apex cornu posterioris was recorded. High localized stress occurred at the portion under compression injury and the level above it. High localized stress tended to occur at the lateral part of the anterior horn motor neurons innervating the hand muscles in traumatic conditions A and D. Under conditions A, D, and E, the average localized stress at the anterior and posterior horn of the gray matter was higher than that at the

  5. Impact of mechanical stress and tension-stress on angiogenesis in wound healing

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Angiogenesis plays a fundamental role in the development of the embryonic vascular tree as well as in several normal and pathologic conditions during postnatal life. Blood supply, established by neovascularization, is imperative for histogenesis during wound healing as well as the limb lengthening applied extensively in the treatment of skeletal trauma sequalae. But little attention has been paid to this area. This review aims to summarize angiogenesis regulation, the process of angiogenesis in wound healing and angiogenesis under mechanical stress, particularly in association with the tension-stress principle.

  6. Bias stress effect and recovery in organic field effect transistors: proton migration mechanism

    Science.gov (United States)

    Sharma, A.; Mathijssen, Simon G. J.; Kemerink, M.; de Leeuw, Dago M.; Bobbert, Peter A.

    2010-08-01

    Organic field-effect transistors exhibit operational instabilities when a gate bias is applied. For a constant gate bias the threshold voltage shifts towards the applied gate bias voltage, an effect known as the bias-stress effect. We have performed a detailed experimental and theoretical study of operational instabilities in p-type transistors with silicon-dioxide gate dielectric. We propose a mechanism in which holes in the semiconductor are converted into protons in the presence of water and a reversible migration of these protons into the gate dielectric to explain the instabilities in organic transistors. We show how redistribution of charge between holes in the semiconductor and protons in the gate dielectric can consistently explain the experimental observations. Furthermore, we explain in detail the recovery of a pres-stressed transistor on applying zero gate bias. We show that recovery dynamics depends strongly on the extent of stressing. Our mechanism is consistent with the known aspects of bias-stress effect like acceleration due to humidity, constant activation energy and reversibility.

  7. Operational Mechanism and Evaluation System for Emergency Logistics Risks

    Directory of Open Access Journals (Sweden)

    Qi Cheng

    2010-12-01

    Full Text Available Lots of risks existed in the operating process of emergency logistics especially when natural disasters happened. Both operating mechanism and evaluation system research on Emergency Logistics Risks (ELR are the basis of effective recognizing, preventing and responding to risks, so it’s of great theoretical and practical significance to study the formation and influence mechanism and to establish an evaluating index system for ELR. Firstly, some foundation research about ELR was carried out, including definition, characteristics and classification of ELR. The formation and influence mechanism of ELR were discussed. The research of questionnaire survey offered an objective support for theoretical mechanism and index system establishment. Then, the evaluating index system for ELR was established. This system was a multi-level index system, and mainly evaluated by the decision-making risk, dispatching and commanding risk, organizing and coordinating risk, executing and controlling risk, resources supporting risk and their sub index. The establishment principles and significance of the index system were discussed. Then, the fuzzy comprehensive evaluation and Delphi method were used to confirm the index weight and value. Finally, a case analysis on ELR of Yushu earthquake was conducted to demonstrate the evaluating index system and to evaluate the actual risk level.

  8. Mechanisms involved in BACE upregulation associated to stress.

    Science.gov (United States)

    Martisova, Eva; Solas, Maite; Gerenu, Gorka; Milagro, Fermin I; Campion, Javier; Ramirez, Maria J

    2012-09-01

    The objective of the present work was to study a purported involvement of stress in amyloid pathology through the modulation of BACE expression. Early-life stressed rats (maternal separation, MS) showed significant increases in corticosterone levels, BACE expression and Aβ levels. The CpG7 site of the BACE promoter was significantly hypomethylated in MS, and corticosterone levels negatively correlated to the methylation status of CpG7. The activation of the stress-activated protein kinase JNK was also increased in MS rats. In SHSY-5Y neuroblastoma cells, corticosterone induced a rapid increase in BACE expression that was abolished by specific inhibiton of JNK activation or by spironolactone, a mineralocorticoid receptor antagonist, but not by mifepristone, a glucocorticoid receptor antagonist. Corticosterone was also able to increase pJNK expression and this effect was fully reverted by spironolactone. Mice chronically treated with corticosterone showed increased BACE and pJNK expression. These increases were reverted by treatment with spironolactone or with a JNK inhibitor. It is suggested that increased corticosterone levels associated to stress lead to increase BACE transcription both through epigenetic mechanisms and activation of JNK.

  9. Research on mechanisms of stress corrosion cracking in Zircaloy

    Energy Technology Data Exchange (ETDEWEB)

    Knorr, D.B.; Pelloux, R.M.

    1981-06-01

    The results of internal gas pressurization tests, primarily at 320/sup 0/C, on cladding tubes from two suppliers, Supplier A and Supplier B, are presented. The two lots show a substantial difference in iodine SCC susceptibility so a test matrix is used to resolve the relative contributions of surface condition, residual stress, and texture. Additional tests with constant deflection split-ring specimens and with unstressed cladding segments are used to understand crack initiation and the early crack growth stages of SCC. The difference in SCC susceptibility is due to crystallographic texture. Other variables such as surface finish, stress relief temperature, and residual stress have little or no effect. Mechanical properties, crack initiation, and crack propagation all depend on texture. Both initiation and propagation features are analyzed by scanning electron microscopy. A mechanism for crack initiation consistent with most observations in this study and with the work of other investigators is proposed. At 320/sup 0/C, lifetime is crack initiation limited while several tests at 390/sup 0/C indicate that lifetime is less initiation limited at higher temperature. 31 figures, 9 tables.

  10. Response mechanisms of Brachiaria brizantha cultivars to water deficit stress

    Directory of Open Access Journals (Sweden)

    Patricia Menezes Santos

    2013-11-01

    Full Text Available Two cultivars of Brachiaria brizantha (Hochst ex. A. Rich Stapf. (Syn. Urochloa were evaluated for their adaptation to water deficit and the stress response mechanisms in a greenhouse experiment. The experimental design was in completely randomized blocks with a 2 × 2 × 4 factorial arrangement. The Marandu and BRS Piatã cultivars were evaluated under two water availability conditions, with or without water restriction. The harvests were carried out 0, 7, 14 and 28 days after the start of water restriction. For both cultivars, the water deficit stress caused a reduction in shoot biomass and leaf area and an increase in the percentage of roots in the deeper soil layers. The B. brizantha cv. Marandu reached critical levels of leaf water potential in a shorter period of water restriction than did the B. brizantha cv. BRS Piatã. The osmoregulation and deepening of the root system are mechanisms of adaptation to water stress observed in both Marandu and BRS Piatã cultivars. Besides that, the Marandu cultivar also increases its leaf senescence and, consequentially, decreases its leaf area, as a response to water deficit.

  11. Operators and representation theory canonical models for algebras of operators arising in quantum mechanics

    CERN Document Server

    Jorgensen, PET

    1987-01-01

    Historically, operator theory and representation theory both originated with the advent of quantum mechanics. The interplay between the subjects has been and still is active in a variety of areas.This volume focuses on representations of the universal enveloping algebra, covariant representations in general, and infinite-dimensional Lie algebras in particular. It also provides new applications of recent results on integrability of finite-dimensional Lie algebras. As a central theme, it is shown that a number of recent developments in operator algebras may be handled in a particularly e

  12. Mechanisms of High Temperature/Low Stress Creep of Ni-Based Superalloy Single Crystals

    Energy Technology Data Exchange (ETDEWEB)

    Michael J. Mills

    2009-03-05

    Cast nickel-based superalloys are used for blades in land-based, energy conversion and powerplant applications, as well as in aircraft gas turbines operating at temperatures up to 1100 C, where creep is one of the life-limiting factors. Creep of superalloy single crystals has been extensively studied over the last several decades. Surprisingly, only recently has work focused specifically on the dislocation mechanisms that govern high temperature and low stress creep. Nevertheless, the perpetual goal of better engine efficiency demands that the creep mechanisms operative in this regime be fully understood in order to develop alloys and microstructures with improved high temperature capability. At present, the micro-mechanisms controlling creep before and after rafting (the microstructure evolution typical of high temperature creep) has occurred have yet to be identified and modeled, particularly for [001] oriented single crystals. This crystal orientation is most interesting technologically since it exhibits the highest creep strength. The major goal of the program entitled ''Mechanisms of High Temperature/Low Stress Creep of Ni-Based Superalloy Single Crystals'' (DOE Grant DE-FG02-04ER46137) has been to elucidate these creep mechanisms in cast nickel-based superalloys. We have utilized a combination of detailed microstructure and dislocation substructure analysis combined with the development of a novel phase-field model for microstructure evolution.

  13. Transcriptome Analysis of Sunflower Genotypes with Contrasting Oxidative Stress Tolerance Reveals Individual- and Combined- Biotic and Abiotic Stress Tolerance Mechanisms.

    Science.gov (United States)

    Ramu, Vemanna S; Paramanantham, Anjugam; Ramegowda, Venkategowda; Mohan-Raju, Basavaiah; Udayakumar, Makarla; Senthil-Kumar, Muthappa

    2016-01-01

    In nature plants are often simultaneously challenged by different biotic and abiotic stresses. Although the mechanisms underlying plant responses against single stress have been studied considerably, plant tolerance mechanisms under combined stress is not understood. Also, the mechanism used to combat independently and sequentially occurring many number of biotic and abiotic stresses has also not systematically studied. From this context, in this study, we attempted to explore the shared response of sunflower plants to many independent stresses by using meta-analysis of publically available transcriptome data and transcript profiling by quantitative PCR. Further, we have also analyzed the possible role of the genes so identified in contributing to combined stress tolerance. Meta-analysis of transcriptomic data from many abiotic and biotic stresses indicated the common representation of oxidative stress responsive genes. Further, menadione-mediated oxidative stress in sunflower seedlings showed similar pattern of changes in the oxidative stress related genes. Based on this a large scale screening of 55 sunflower genotypes was performed under menadione stress and those contrasting in oxidative stress tolerance were identified. Further to confirm the role of genes identified in individual and combined stress tolerance the contrasting genotypes were individually and simultaneously challenged with few abiotic and biotic stresses. The tolerant hybrid showed reduced levels of stress damage both under combined stress and few independent stresses. Transcript profiling of the genes identified from meta-analysis in the tolerant hybrid also indicated that the selected genes were up-regulated under individual and combined stresses. Our results indicate that menadione-based screening can identify genotypes not only tolerant to multiple number of individual biotic and abiotic stresses, but also the combined stresses.

  14. Factors related to teamwork performance and stress of operating room nurses.

    Science.gov (United States)

    Sonoda, Yukio; Onozuka, Daisuke; Hagihara, Akihito

    2017-07-25

    To evaluate operating room nurses' perception of teamwork performance and their level of mental stress and to identify related factors. Little is known about the factors affecting teamwork and the mental stress of surgical nurses, although the performance of the surgical team is essential for patient safety. The questionnaire survey for operation room nurses consisted of simple questions about teamwork performance and mental stress. Multivariate analyses were used to identify factors causing a sense of teamwork performance or mental stress. A large number of surgical nurses had a sense of teamwork performance, but 30-40% of operation room nurses were mentally stressed during surgery. Neither the patient nor the operation factors were related to the sense of teamwork performance in both types of nurses. Among scrub nurses, endoscopic and abdominal surgery, body mass index, blood loss and the American Society of Anesthesiologists physical status class were related to their mental stress. Conversely, circulating nurses were stressed about teamwork performance. The factors related to teamwork performance and mental stress during surgery differed between scrub and circulating nurses. Increased support for operation room nurses is necessary. The increased support leads to safer surgical procedures and better patient outcomes. © 2017 John Wiley & Sons Ltd.

  15. Mechanisms of renewal after the extinction of discriminated operant behavior.

    Science.gov (United States)

    Todd, Travis P; Vurbic, Drina; Bouton, Mark E

    2014-07-01

    Three experiments demonstrated, and examined the mechanisms that underlie, the renewal of extinguished discriminated operant behavior. In Experiment 1, rats were trained to perform 1 response (lever press or chain pull) in the presence of one discriminative stimulus (S; light or tone) in Context A, and to perform the other response in the presence of the other S in Context B. Next, each of the original S/response combinations was extinguished in the alternate context. When the S/response combinations were tested back in the context in which they had been trained, responding in the presence of S returned (an ABA renewal effect was observed). This renewal could not be due to differential context-reinforcer associations, suggesting instead that the extinction context inhibits either the response and/or the effectiveness of the S. Consistent with the latter mechanism, in Experiment 2, ABA renewal was still observed when both the extinction and renewal contexts inhibited the same response. However, in Experiment 3, previous extinction of the response in the renewing context (occasioned by a different S) reduced AAB renewal more than did extinction of the different response. Taken together, the results suggest at least 2 mechanisms of renewal after instrumental extinction. First, extinction performance is at least partly controlled by a direct inhibitory association that is formed between the context and the response. Second, in the discriminated operant procedure, extinction performance can sometimes be partly controlled by a reduction in the effectiveness of the S in the extinction context. Renewal of discriminated operant behavior can be produced by a release from either of these forms of inhibition.

  16. Operational dynamic modeling transcending quantum and classical mechanics.

    Science.gov (United States)

    Bondar, Denys I; Cabrera, Renan; Lompay, Robert R; Ivanov, Misha Yu; Rabitz, Herschel A

    2012-11-09

    We introduce a general and systematic theoretical framework for operational dynamic modeling (ODM) by combining a kinematic description of a model with the evolution of the dynamical average values. The kinematics includes the algebra of the observables and their defined averages. The evolution of the average values is drawn in the form of Ehrenfest-like theorems. We show that ODM is capable of encompassing wide-ranging dynamics from classical non-relativistic mechanics to quantum field theory. The generality of ODM should provide a basis for formulating novel theories.

  17. Crystal structure of peroxide stress regulator from Streptococcus pyogenes provides functional insights into the mechanism of oxidative stress sensing.

    Science.gov (United States)

    Makthal, Nishanth; Rastegari, Sheila; Sanson, Misu; Ma, Zhen; Olsen, Randall J; Helmann, John D; Musser, James M; Kumaraswami, Muthiah

    2013-06-21

    Regulation of oxidative stress responses by the peroxide stress regulator (PerR) is critical for the in vivo fitness and virulence of group A Streptococcus. To elucidate the molecular mechanism of DNA binding, peroxide sensing, and gene regulation by PerR, we performed biochemical and structural characterization of PerR. Sequence-specific DNA binding by PerR does not require regulatory metal occupancy. However, metal binding promotes higher affinity PerR-DNA interactions. PerR metallated with iron directly senses peroxide stress and dissociates from operator sequences. The crystal structure revealed that PerR exists as a homodimer with two metal-binding sites per subunit as follows: a structural zinc site and a regulatory metal site that is occupied in the crystals by nickel. The regulatory metal-binding site in PerR involves a previously unobserved HXH motif located in its unique N-terminal extension. Mutational analysis of the regulatory site showed that the PerR metal ligands are involved in regulatory metal binding, and integrity of this site is critical for group A Streptococcus virulence. Interestingly, the metal-binding HXH motif is not present in the structurally characterized members of ferric uptake regulator (Fur) family but is fully conserved among PerR from the genus Streptococcus. Thus, it is likely that the PerR orthologs from streptococci share a common mechanism of metal binding, peroxide sensing, and gene regulation that is different from that of well characterized PerR from Bacillus subtilis. Together, our findings provide key insights into the peroxide sensing and regulation of the oxidative stress-adaptive responses by the streptococcal subfamily of PerR.

  18. Responses to combined abiotic and biotic stress in tomato are governed by stress intensity and resistance mechanism

    NARCIS (Netherlands)

    Kissoudis, Christos; Sri Sunarti, Sri; De Wiel, Van Clemens; Visser, Richard G.F.; Linden, van der Gerard; Bai, Yuling

    2016-01-01

    Stress conditions in agricultural ecosystems can occur at variable intensities. Different resistance mechanisms against abiotic stress and pathogens are deployed by plants. Thus, it is important to examine plant responses to stress combinations under different scenarios. Here, we evaluated the effec

  19. Supplementary data: Responses to combined abiotic and biotic stress in tomato are governed by stress intensity and mechanism of resistance

    NARCIS (Netherlands)

    Kissoudis, C.; Sri Sunarti, Sri; Wiel, van de C.C.M.; Visser, R.G.F.; Linden, van der C.G.; Bai, Y.

    2016-01-01

    Stress conditions in agricultural ecosystems can occur in variable intensities. Different resistance mechanisms to abiotic stress and pathogens are deployed by plants. Thus, it is important to examine plant responses to stress combinations under different scenarios. Here, we evaluated the effect of

  20. Mechanism-based bioanalysis and biomarkers for hepatic chemical stress.

    Science.gov (United States)

    Antoine, D J; Mercer, A E; Williams, D P; Park, B K

    2009-08-01

    Adverse drug reactions, in particular drug-induced hepatotoxicity, represent a major challenge for clinicians and an impediment to safe drug development. Novel blood or urinary biomarkers of chemically-induced hepatic stress also hold great potential to provide information about pathways leading to cell death within tissues. The earlier pre-clinical identification of potential hepatotoxins and non-invasive diagnosis of susceptible patients, prior to overt liver disease is an important goal. Moreover, the identification, validation and qualification of biomarkers that have in vitro, in vivo and clinical transferability can assist bridging studies and accelerate the pace of drug development. Drug-induced chemical stress is a multi-factorial process, the kinetics of the interaction between the hepatotoxin and the cellular macromolecules are crucially important as different biomarkers will appear over time. The sensitivity of the bioanalytical techniques used to detect biological and chemical biomarkers underpins the usefulness of the marker in question. An integrated analysis of the biochemical, molecular and cellular events provides an understanding of biological (host) factors which ultimately determine the balance between xenobiotic detoxification, adaptation and liver injury. The aim of this review is to summarise the potential of novel mechanism-based biomarkers of hepatic stress which provide information to connect the intracellular events (drug metabolism, organelle, cell and whole organ) ultimately leading to tissue damage (apoptosis, necrosis and inflammation). These biomarkers can provide both the means to inform the pharmacologist and chemist with respect to safe drug design, and provide clinicians with valuable tools for patient monitoring.

  1. Oxidative Stress in Intracerebral Hemorrhage: Sources, Mechanisms, and Therapeutic Targets

    Directory of Open Access Journals (Sweden)

    Xin Hu

    2016-01-01

    Full Text Available Intracerebral hemorrhage (ICH is associated with the highest mortality and morbidity despite only constituting approximately 10–15% of all strokes. Complex underlying mechanisms consisting of cytotoxic, excitotoxic, and inflammatory effects of intraparenchymal blood are responsible for its highly damaging effects. Oxidative stress (OS also plays an important role in brain injury after ICH but attracts less attention than other factors. Increasing evidence has demonstrated that the metabolite axis of hemoglobin-heme-iron is the key contributor to oxidative brain damage after ICH, although other factors, such as neuroinflammation and prooxidases, are involved. This review will discuss the sources, possible molecular mechanisms, and potential therapeutic targets of OS in ICH.

  2. Real-time observations of stressful events in the operating room

    Directory of Open Access Journals (Sweden)

    AlNassar Sami

    2012-01-01

    Full Text Available Aim: To identify and quantify factors causing stress in the operating room (OR and evaluate the relationship between these factors and surgeons′ stress level. Methods: This is a prospective observational study from 32 elective surgical procedures conducted in the OR of King Khalid University Hospital, Riyadh, Saudi Arabia. Before each operation, each surgeon was asked of stressors. Two interns observed 16 surgeries each, separately. The interns watched and took notes during the entire surgical procedure. During each operation, the observer recorded anxiety-inducing activities and events that occurred in real time by means of a checklist of 8 potential stressors: technical, patient problems, teamwork problems, time and management issues, distractions and interruptions, equipment problems, personal problems, and teaching. After each operation, surgeons were asked to answer the validated State-Trait Anxiety Inventory questionnaire and self-report on their stress level from the 8 sources using a scale of 1-8 (1: stress free, 8: extremely stressful. The observer also recorded perceived stress levels experienced by the surgeons during the operation. Results: One hundred ten stressors were identified. Technical problems most frequently caused stress (16.4% and personal issues the least often (6.4%. Frequently encountered stressors (teaching and distractions/interruptions caused less stress to the surgeons. Technical factors, teamwork, and equipment problems occurred frequently and were also a major contributor to OR stress. All patients were discharged in good health and within 1 week of surgery. Conclusion: Certain stressful factors do occur among surgeons in the OR and can increase the potential for errors. Further research is required to determine the impact of stress on performance and the outcome of surgery.

  3. Real-time observations of stressful events in the operating room.

    Science.gov (United States)

    Sami, Alnassar; Waseem, Hajjar; Nourah, Alsubaie; Areej, Alhummaid; Afnan, Almarshedi; Ghadeer, Al-Shaikh; Abdulaziz, Alsaif; Arthur, Isnani

    2012-04-01

    To identify and quantify factors causing stress in the operating room (OR) and evaluate the relationship between these factors and surgeons' stress level. This is a prospective observational study from 32 elective surgical procedures conducted in the OR of King Khalid University Hospital, Riyadh, Saudi Arabia. Before each operation, each surgeon was asked of stressors. Two interns observed 16 surgeries each, separately. The interns watched and took notes during the entire surgical procedure. During each operation, the observer recorded anxiety-inducing activities and events that occurred in real time by means of a checklist of 8 potential stressors: technical, patient problems, teamwork problems, time and management issues, distractions and interruptions, equipment problems, personal problems, and teaching. After each operation, surgeons were asked to answer the validated State-Trait Anxiety Inventory questionnaire and self-report on their stress level from the 8 sources using a scale of 1-8 (1: stress free, 8: extremely stressful). The observer also recorded perceived stress levels experienced by the surgeons during the operation. One hundred ten stressors were identified. Technical problems most frequently caused stress (16.4%) and personal issues the least often (6.4%). Frequently encountered stressors (teaching and distractions/interruptions) caused less stress to the surgeons. Technical factors, teamwork, and equipment problems occurred frequently and were also a major contributor to OR stress. All patients were discharged in good health and within 1 week of surgery. Certain stressful factors do occur among surgeons in the OR and can increase the potential for errors. Further research is required to determine the impact of stress on performance and the outcome of surgery.

  4. Piezo-Operated Shutter Mechanism Moves 1.5 cm

    Science.gov (United States)

    Glaser, Robert; Bamford, Robert

    2005-01-01

    The figure shows parts of a shutter mechanism designed to satisfy a number of requirements specific to its original intended application as a component of an atomic clock to be flown in outer space. The mechanism may also be suitable for use in laboratory and industrial vacuum systems on Earth for which there are similar requirements. The requirements include the following: a) To alternately close, then open, a 1.5-cm-diameter optical aperture twice per second, with a stroke time of no more than 15 ms, during a total operational lifetime of at least a year; b) To attenuate light by a factor of at least 1012 when in the closed position; c) To generate little or no magnetic field; d) To be capable of withstanding bakeout at a temperature of 200 C to minimize outgassing during subsequent operation in an ultrahigh vacuum; and e) To fit within a diameter of 12 in. (=305 mm) a size limit dictated by the size of an associated magnetic shield. The light-attenuation requirement is satisfied by use of overlapping shutter blades. The closure of the aperture involves, among other things, insertion of a single shutter blade between a pair of shutter blades. The requirement to minimize the magnetic field is satisfied by use of piezoelectric actuators. Because piezoelectric actuators cannot withstand bakeout, they must be mounted outside the vacuum chamber, and, hence, motion must be transmitted from the actuators to the shutter levers via a vacuum-chamber-wall diaphragm.

  5. Graphene mechanics: II. Atomic stress distribution during indentation until rupture.

    Science.gov (United States)

    Costescu, Bogdan I; Gräter, Frauke

    2014-06-28

    Previous Atomic Force Microscopy (AFM) experiments found single layers of defect-free graphene to rupture at unexpectedly high loads in the micronewton range. Using molecular dynamics simulations, we modeled an AFM spherical tip pressing on a circular graphene sheet and studied the stress distribution during the indentation process until rupture. We found the graphene rupture force to have no dependency on the sheet size and a very weak dependency on the indenter velocity, allowing a direct comparison to experiment. The deformation showed a non-linear elastic behavior, with a two-dimensional elastic modulus in good agreement with previous experimental and computational studies. In line with theoretical predictions for linearly elastic sheets, rupture forces of non-linearly elastic graphene are proportional to the tip radius. However, as a deviation from the theory, the atomic stress concentrates under the indenter tip more strongly than predicted and causes a high probability of bond breaking only in this area. In turn, stress levels decrease rapidly towards the edge of the sheet, most of which thus only serves the role of mechanical support for the region under the indenter. As a consequence, the high ratio between graphene sheets and sphere radii, hitherto supposed to be necessary for reliable deformation and rupture studies, could be reduced to a factor of only 5-10 without affecting the outcome. Our study suggests time-resolved analysis of forces at the atomic level as a valuable tool to predict and interpret the nano-scale response of stressed materials beyond graphene.

  6. The 'footloose' mechanism: Iceberg decay from hydrostatic stresses

    Science.gov (United States)

    Wagner, T. J. W.; Wadhams, P.; Bates, C. R.; Elosegui, P.; Stern, A. A.; Vella, D.; Abrahamsen, E. P.; Crawford, A. J.; Nicholls, K. W.

    2014-12-01

    We study a mechanism of iceberg breakup that may act together with the recognized melt and wave-induced decay processes. Our proposal is based on observations from a recent field experiment on a large ice island in Baffin Bay, East Canada. We observed that successive collapses of the overburden from above an unsupported wavecut at the iceberg waterline created a submerged foot fringing the berg. The buoyancy stresses induced by such a foot may be sufficient to cause moderate-sized bergs to break off from the main berg. A mathematical model is developed to test the feasibility of this mechanism. The results suggest that once the foot reaches a critical length, the induced stresses are sufficient to cause calving. The theoretically predicted maximum stable foot length compares well to the data collected in situ. Further, the model provides analytical expressions for the previously observed 'rampart-moat' iceberg surface profiles. Finally, we comment on the implications for the calving of icebergs from shelf fronts, where similar underwater 'feet' have been observed.

  7. Muscle mitochondrial stress adaptation operates independently of endogenous FGF21 action

    Directory of Open Access Journals (Sweden)

    Mario Ost

    2016-02-01

    Conclusions: Here we demonstrate that although FGF21 drives WAT remodeling, the adaptive pseudo-starvation response under elevated muscle mitochondrial stress conditions operates independently of both WAT browning and FGF21 action. Thus, our findings challenge FGF21 as key metabolic mediator of the mitochondrial stress adaptation and powerful therapeutic target during muscle mitochondrial disease.

  8. Stress state of thin – walled member of the structure with operation damages under nonuniform loading

    Directory of Open Access Journals (Sweden)

    В.В. Астанін

    2004-01-01

    Full Text Available  The publication is dedicated to determining of stress state in particular the stress concentration factors for thin – walled members of the structures subject to nonuniform tension. A structure member has obtained the operation damage generation by corrosion and other causes.

  9. The Determination of Stresses in Wire-Drawing Operation Using the ...

    African Journals Online (AJOL)

    The Determination of Stresses in Wire-Drawing Operation Using the Finite ... distribution of stresses and pressures set up at various cross-sections of a ... die angle, length and blank radius and compared with the exact solution on a table.

  10. Post-operative stress fractures complicating surgery for painful forefoot conditions.

    Science.gov (United States)

    Edwards, Max R; Jack, Christopher; Jones, Gareth G; Singh, Samrendu K

    2010-01-01

    A stress fracture is caused by repetitive or unusual loading of a bone leading to mechanical failure. Fatigue type stress fractures occur in normal bone exposed to abnormally high repetitive loads, whereas insufficiency type stress fractures occur in abnormal bone exposed to normal loads. We describe three cases of insufficiency stress fractures that have complicated surgery for painful forefoot conditions. The diagnosis and management of these cases are discussed. Stress fractures should be included in the differential diagnosis of any patient who continues or develops pain after surgery to the forefoot.

  11. Control of Mechanical Stresses of High Pressure Container Walls by Magnetoelastic Method

    Science.gov (United States)

    Kulak, S. M.; Novikov, V. F.; Baranov, A. V.

    2016-10-01

    Deformations of the walls of pressure vessels arising in the process of testing and operation, as well as reduce their thickness due to corrosion, to create the prerequisites for the growth of mechanical stresses which accelerating the processes of strain aging, embrittlement of the material and reducing its fatigue properties. This article is devoted to researches of the magnetoelastic demagnetization in the wall of steel vessel of loading by internal pressure. It is established that the increasing pressure on the vessel wall is accompanied by a monotonic decrease in the intensity of the magnetic stray field of local magnetization of steel. It is shown that a magnetic stray field of local magnetization of the wall of steel vessel is non-uniform due to differences in structure and stresses. It is proposed to use the obtained results to control the stress state of vessels, experiencing multi-axial loads generated by internal pressure (pipelines, oil tanks, etc.) The method of magnetoelastic of the demagnetization of the steel has a high sensitivity to mechanical stress, the simplicity of implementation and expressiveness compared to the strain gauge and method of coercive force.

  12. [Relationship between occupational stress and blood glucose, blood lipid, blood pressure of video display terminal operators].

    Science.gov (United States)

    Zhang, Xing; Song, Hui; Chen, Nan; Liu, He-rong; Zhu, Ling-qin; Zhang, Zhen-xiang; Wang, Ling

    2007-03-01

    To explore the relationship between occupational stress and blood glucose, Blood lipid and blood pressure. 108 video display terminals(VDT) operators who had the working experience were recruited to the study. The occupational stress indicator (OSI), the lever of blood glucose, cholesterol, triglyceride, lipoprotein of high density and lipoprotein of low density in serum were measured by using GOD-PAP, CHOD-PAP, GPO-PAP and PVS. The subjects were classified into three groups according to the score of occupational stress. The contents of blood glucose of low, middle and high level of stress groups were (3.39 +/- 1.24), (3.59 +/- 1.26), (2.54 +/- 0.94) mmol/L respectively (F = 7.324, P stress, the content of blood glucose decreased significantly (r = -0.376, P occupational stress, among video display terminals and it can be used as the index for estimating occupational stress.

  13. Comments on the Stress-Energy Tensor Operator in Curved Spacetime

    CERN Document Server

    Moretti, V

    2003-01-01

    The technique based on the *-algebra of local Wick products of (formal) field operators in curved spacetime proposed by Hollands and Wald, is implemented and developed in order to define the stress-energy tensor operator in terms of local Wick products of (derived) field operators only. It shows that, within the proposed formalism, there may be room to accomplish all of physical requirements provided the known problems concerning the conservation property are assumed to be related to the interface between quantum and classical formalisms. Indeed, a stress-energy tensor operator is proposed which, written using local Wick products of fields only, is conserved and it reduces to the classical form when operators are replaced by classical fields satisfying the equation of the motion. The definition is based on the existence of convenient local Wick products of derived fields. These terms are independent from the arbitrary length scale and the quantum state and they classically vanish. Considering averaged stress-...

  14. Antiplatelet Drugs: Mechanisms and Risks of Bleeding Following Cardiac Operations

    Science.gov (United States)

    Ferraris, Victor A.; Ferraris, Suellen P.; Saha, Sibu P.

    2011-01-01

    Preoperative antiplatelet drug use is common in patients undergoing coronary artery bypass grafting (CABG). The impact of these drugs on bleeding and blood transfusion varies. We hypothesize that review of available evidence regarding drug-related bleeding risk, underlying mechanisms of platelet dysfunction, and variations in patient response to antiplatelet drugs will aid surgeons as they assess preoperative risk and attempt to limit perioperative bleeding. The purpose of this review is to (1) examine the role that antiplatelet drugs play in excessive postoperative blood transfusion, (2) identify possible mechanisms to explain patient response to antiplatelet drugs, and (3) formulate a strategy to limit excessive blood product usage in these patients. We reviewed available published evidence regarding bleeding risk in patients taking preoperative antiplatelet drugs. In addition, we summarized our previous research into mechanisms of antiplatelet drug-related platelet dysfunction. Aspirin users have a slight but significant increase in blood product usage after CABG (0.5 U of nonautologous blood per treated patient). Platelet adenosine diphosphate (ADP) receptor inhibitors are more potent antiplatelet drugs than aspirin but have a half-life similar to aspirin, around 5 to 10 days. The American Heart Association/American College of Cardiology and the Society of Thoracic Surgeons guidelines recommend discontinuation, if possible, of ADP inhibitors 5 to 7 days before operation because of excessive bleeding risk, whereas aspirin should be continued during the entire perioperative period in most patients. Individual variability in response to aspirin and other antiplatelet drugs is common with both hyper- and hyporesponsiveness seen in 5 to 25% of patients. Use of preoperative antiplatelet drugs is a risk factor for increased perioperative bleeding and blood transfusion. Point-of-care tests can identify patients at high risk for perioperative bleeding and blood

  15. A Novel Stress-Diathesis Model to Predict Risk of Post-operative Delirium: Implications for Intra-operative Management

    Directory of Open Access Journals (Sweden)

    Renée El-Gabalawy

    2017-08-01

    Full Text Available Introduction: Risk assessment for post-operative delirium (POD is poorly developed. Improved metrics could greatly facilitate peri-operative care as costs associated with POD are staggering. In this preliminary study, we develop a novel stress-diathesis model based on comprehensive pre-operative psychiatric and neuropsychological testing, a blood oxygenation level-dependent (BOLD magnetic resonance imaging (MRI carbon dioxide (CO2 stress test, and high fidelity measures of intra-operative parameters that may interact facilitating POD.Methods: The study was approved by the ethics board at the University of Manitoba and registered at clinicaltrials.gov as NCT02126215. Twelve patients were studied. Pre-operative psychiatric symptom measures and neuropsychological testing preceded MRI featuring a BOLD MRI CO2 stress test whereby BOLD scans were conducted while exposing participants to a rigorously controlled CO2 stimulus. During surgery the patient had hemodynamics and end-tidal gases downloaded at 0.5 hz. Post-operatively, the presence of POD and POD severity was comprehensively assessed using the Confusion Assessment Measure –Severity (CAM-S scoring instrument on days 0 (surgery through post-operative day 5, and patients were followed up at least 1 month post-operatively.Results: Six of 12 patients had no evidence of POD (non-POD. Three patients had POD and 3 had clinically significant confusional states (referred as subthreshold POD; ST-POD (score ≥ 5/19 on the CAM-S. Average severity for delirium was 1.3 in the non-POD group, 3.2 in ST-POD, and 6.1 in POD (F-statistic = 15.4, p < 0.001. Depressive symptoms, and cognitive measures of semantic fluency and executive functioning/processing speed were significantly associated with POD. Second level analysis revealed an increased inverse BOLD responsiveness to CO2 pre-operatively in ST-POD and marked increase in the POD groups when compared to the non-POD group. An association was also noted for

  16. Analysis of stress effects on the cognitive operating work

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Cheol Jung; Park, Jae Hee; Lee, Nahm Sik; Yu, Young Kwan [Korea Research Institute of Standards and Science, Taejon (Korea, Republic of)

    1994-07-01

    This study is carried out to develop the performance evaluation model which explains the relationship between PSFs(performance shaping factors) and performance. The model can improve the safety efficiency of the nuclear power plants by removing the wrong PSFs. The work scope and contents of the project have the following items, such as, survey of the performance evaluation/prediction models, selecting the PSFs and performance measures, task analysis on the EOP(emergency operating procedures) for LOCA(loss of coolant accident) and modeling the relationships between PSFs and performance measures, and knowledge representation using the IF...THEN... rules. The results, knowledge base, can be used to develop the performance evaluation model for nuclear power plant operators. 46 refs.

  17. Effects of mechanical-bending and process-induced stresses on metal effective work function

    Science.gov (United States)

    Yang, Xiaodong; Chu, Min; Huang, Anping; Thompson, Scott

    2013-01-01

    Effective work function (EWF) change is investigated under both externally-applied mechanical stresses and process-induced stresses. Four-point wafer bending and ring bending techniques are used to generate uniaxial and biaxial mechanical stresses, respectively. For the process-induced stresses, bowing technique and charge pumping method are used for stress characterization and interface state measurement. It was found that higher stress presents in devices with thinner metal gate, regardless the thermal treatment cycle. EWF decreases under both tensile and compressive stress was observed due to the increase of defect activation energy lowering induced donor-like interface states.

  18. THEORETICAL CONSIDERATIONS REGARDING THE AUTOMATIC FISCAL STABILIZERS OPERATING MECHANISM

    Directory of Open Access Journals (Sweden)

    Gondor Mihaela

    2012-07-01

    Full Text Available This paper examines the role of Automatic Fiscal Stabilizers (AFS for stabilizing the cyclical fluctuations of macroeconomic output as an alternative to discretionary fiscal policy, admitting its huge potential of being an anti crisis solution. The objectives of the study are the identification of the general features of the concept of automatic fiscal stabilizers and the logical assessment of them from economic perspectives. Based on the literature in the field, this paper points out the disadvantages of fiscal discretionary policy and argue the need of using Automatic Fiscal Stabilizers in order to provide a faster decision making process, shielded from political interference, and reduced uncertainty for households and business environment. The paper conclude about the need of using fiscal policy for smoothing the economic cycle, but in a way which includes among its features transparency, responsibility and clear operating mechanisms. Based on the research results the present paper assumes that pro-cyclicality reduces de effectiveness of the Automatic Fiscal Stabilizer and as a result concludes that it is very important to avoid the pro-cyclicality in fiscal rule design. Moreover, by committing in advance to specific fiscal policy action contingent on economic developments, uncertainty about the fiscal policy framework during a recession should be reduced. Being based on logical analysis and not focused on empirical, contextualized one, the paper presents some features of AFS operating mechanism and also identifies and systematizes the factors which provide its importance and national individuality. Reaching common understanding on the Automatic Fiscal Stabilizer concept as a institutional device for smoothing the gap of the economic cycles across different countries, particularly for the European Union Member States, will facilitate efforts to coordinate fiscal policy responses during a crisis, especially in the context of the fiscal

  19. Spatio-temporal Dynamics and Mechanisms of Stress Granule Assembly.

    Directory of Open Access Journals (Sweden)

    Daisuke Ohshima

    2015-06-01

    Full Text Available Stress granules (SGs are non-membranous cytoplasmic aggregates of mRNAs and related proteins, assembled in response to environmental stresses such as heat shock, hypoxia, endoplasmic reticulum (ER stress, chemicals (e.g. arsenite, and viral infections. SGs are hypothesized as a loci of mRNA triage and/or maintenance of proper translation capacity ratio to the pool of mRNAs. In brain ischemia, hippocampal CA3 neurons, which are resilient to ischemia, assemble SGs. In contrast, CA1 neurons, which are vulnerable to ischemia, do not assemble SGs. These results suggest a critical role SG plays in regards to cell fate decisions. Thus SG assembly along with its dynamics should determine the cell fate. However, the process that exactly determines the SG assembly dynamics is largely unknown. In this paper, analyses of experimental data and computer simulations were used to approach this problem. SGs were assembled as a result of applying arsenite to HeLa cells. The number of SGs increased after a short latent period, reached a maximum, then decreased during the application of arsenite. At the same time, the size of SGs grew larger and became localized at the perinuclear region. A minimal mathematical model was constructed, and stochastic simulations were run to test the modeling. Since SGs are discrete entities as there are only several tens of them in a cell, commonly used deterministic simulations could not be employed. The stochastic simulations replicated observed dynamics of SG assembly. In addition, these stochastic simulations predicted a gamma distribution relative to the size of SGs. This same distribution was also found in our experimental data suggesting the existence of multiple fusion steps in the SG assembly. Furthermore, we found that the initial steps in the SG assembly process and microtubules were critical to the dynamics. Thus our experiments and stochastic simulations presented a possible mechanism regulating SG assembly.

  20. Mechanisms of Extending Operation Regionin the HL-1M Tokamak

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Stable operating region in the HL-1M tokamak has been extended by means ofwall conditioning, core fuelling and current control techniques. The mechanisms of the extensionare analyzed in this paper. Lithiumization diminishes the impurities and hydrogen recycling tothe lowest level. After lithiumization a high density up to 7×1019 m-3 was obtained easily bystrong gas puffing with ordinary ohmic discharge alone. More attractively we found that metalLi-coating exhibited the effects of wall stabilization. The low qa limit with higher density wasextended by a factor of 1.5~2 in comparison with that for boronization, and 1.2 for siliconization.Siliconization not only extended stable operating region significantly by itself, but also provideda good target plasma for other experiments of raising density limit. Core fuelling schemes arefavourable especially for siliconized wall with a higher level of medium-Z impurity (Z=14).After siliconization the maximum density near to 1020 m-3 was achieved by a combination ofsupersonic molecule beam injection and multipellet injection. The new defined slope of Hugilllimit illustrating more clearly the situation under low qa and high ne discharges was created toindicate the new region extended by combining Ip ramp-up with core fuelling. The slope with alarge Murakami coefficient increased by a factor of 50~60 %.

  1. About the velocity operator for spinning particles in quantum mechanics

    Energy Technology Data Exchange (ETDEWEB)

    Salesi, Giovanni [Universita Statale di Catania (Italy). Dipt. di Fisica]|[Istituto Nazionale di Fisica Nucleare, Catania (Italy); Recami, Erasmo; Rodrigues Junior, Waldyr A. [Universidade Estadual de Campinas, SP (Brazil). Dept. de Matematica Aplicada

    1995-12-01

    Starting from the formal expressions of the hydrodynamical (or local) quantities employed in the applications of Clifford Algebras to quantum mechanics, we introduce - in terms of the ordinary tensorial framework - a new definition for the field of a generic quantity. By translating from Clifford into sensor algebra, we also propose a new (non-relativistic) velocity operator for a spin 1/2 particle. This operator is the sum of the ordinary part p/m describing the mean motion (the motion of the center-of-mass), and of a second part associated with the so-called Zitterbewegung, which is the spin internal motion observed in the center-of-mass frame. This spin component of the velocity operator is non-zero not only in the Pauli theoretical framework in presence of external magnetic fields and spin precession, but also in the Schroedinger case, when the wave-function is a spin eigenstate. In the latter case, one gets a decomposition of the velocity field for the Madelueng fluid into two distinct parts: which constitutes the non-relativistic analogue of the Gordon decomposition for the Dirac current. We find furthermore that the Zitterbewegung motion involves a velocity field which is solenoidal, and that the local angular velocity is parallel to the spin vector. In presence of a non-constant spin vector (Pauli case) we have, besides the component normal to spin present even in the Schroedinger theory, also a component of the local velocity which is parallel to the rotor of the spin vector. (author). 19 refs.

  2. Acid Stress Response Mechanisms of Group B Streptococci

    Directory of Open Access Journals (Sweden)

    Sarah Shabayek

    2017-09-01

    Full Text Available Group B streptococcus (GBS is a leading cause of neonatal mortality and morbidity in the United States and Europe. It is part of the vaginal microbiota in up to 30% of pregnant women and can be passed on to the newborn through perinatal transmission. GBS has the ability to survive in multiple different host niches. The pathophysiology of this bacterium reveals an outstanding ability to withstand varying pH fluctuations of the surrounding environments inside the human host. GBS host pathogen interations include colonization of the acidic vaginal mucosa, invasion of the neutral human blood or amniotic fluid, breaching of the blood brain barrier as well as survival within the acidic phagolysosomal compartment of macrophages. However, investigations on GBS responses to acid stress are limited. Technologies, such as whole genome sequencing, genome-wide transcription and proteome mapping facilitate large scale identification of genes and proteins. Mechanisms enabling GBS to cope with acid stress have mainly been studied through these techniques and are summarized in the current review

  3. Stress Wave Isolation by Purely Mechanical Topological Phononic Crystals

    Science.gov (United States)

    Chaunsali, Rajesh; Li, Feng; Yang, Jinkyu

    2016-08-01

    We present an active, purely mechanical stress wave isolator that consists of short cylindrical particles arranged in a helical architecture. This phononic structure allows us to change inter-particle stiffness dynamically by controlling the contact angles of the cylinders. We use torsional travelling waves to control the contact angles, thereby imposing a desired spatio-temporal stiffness variation to the phononic crystal along the longitudinal direction. Such torsional excitation is a form of parametric pumping in the system, which results in the breakage of the time-reversal symmetry. We report that, in quasi-static sense, the system shows topologically non-trivial band-gaps. However, in a dynamic regime where the pumping effect is significant, these band-gaps become asymmetric with respect to the frequency and wavenumber domains in the dispersion relationship. By using numerical simulations, we show that such asymmetry has a direct correspondence to the topological invariant, i.e., Chern number, of the system. We propose that this asymmetry, accompanied by selective inter-band transition, can be utilized for directional isolation of the stress wave propagating along the phononic crystal.

  4. Optimization of release locations for small self-stress large stiffness flexure mechanisms

    NARCIS (Netherlands)

    Brouwer, D.M.; Boer, S.E.; Meijaard, J.P.; Aarts, R.G.K.M.

    2013-01-01

    In overconstrained mechanisms inherent alignment errors cause self-stress. The level of stress can be reduced by inserting flexure releases making the mechanism exactly constrained. The location and orientation of releases can be optimized for a combination of minimum self-stress and maximum stiffne

  5. Stress relaxation insensitive designs for metal compliant mechanism threshold accelerometers

    Directory of Open Access Journals (Sweden)

    Carlos Vilorio

    2015-12-01

    Full Text Available We present two designs for metal compliant mechanisms for use as threshold accelerometers which require zero external power. Both designs rely on long, thin flexures positioned orthogonally to a flat body. The first design involves cutting or stamping a thin spring-steel sheet and then bending elements to form the necessary thin flexors. The second design uses precut spring-steel flexure elements mounted into a mold which is then filled with molten tin to form a bimetallic device. Accelerations necessary to switch the devices between bistable states were measured using a centrifuge. Both designs showed very little variation in threshold acceleration due to stress relaxation over a period of several weeks. Relatively large variations in threshold acceleration were observed for devices of the same design, most likely due to variations in the angle of the flexor elements relative to the main body of the devices.

  6. Embryonic oxidative stress as a mechanism of teratogenesis with special emphasis on diabetic embryopathy.

    Science.gov (United States)

    Ornoy, Asher

    2007-07-01

    Reactive oxygen species (ROS) are involved in the etiology of numerous diseases including cardio-vascular diseases and diabetes mellitus. There is evidence that several teratogens affect the developing embryo by increasing its oxidative stress and, because of its relatively weak antioxidant defense, especially at the early stages of organogenesis, result in severe embryonic damage. This mechanism seems to operate in diabetes-induced embryonic damage as well as in the mechanism of teratogenicity caused by ionizing radiation, hypoxia, alcohol and cocaine use and cigarette smoking. We studied the role of oxidative stress in diabetic induced embryopathy, both in vivo and in vitro. Under diabetic condition there was a significant decrease in the activity of endogenous antioxidant enzymes and of vitamins C and E in the embryos and their yolk sacs. The lowest activity was observed in the malformed experimental embryos when compared to experimental embryos without anomalies. Similar results were obtained in the Cohen diabetic rats, where the diabetic prone (CDs) rats were unable to increase their antioxidant enzyme activity in spite of the diabetes. Studies performed by other investigators show similar results. Human and animal studies show that the main mechanism of fetal damage induced by high levels of ionizing irradiation, cocaine and alcohol abuse, hypoxia and cigarette smoking is also by increased embryonic oxidative stress. Similarly, several drugs exert their teratogenic activity via embryonic oxidative stress. Abnormal placentation may also cause enhanced placental oxidative stress, resulting in embryonic death, preeclampsia or congenital anomalies. Inability of the developing embryo to cope with that stress may result in embryonic death and/or congenital anomalies. Animal studies also show that a variety of antioxidants are effective in decreasing the damaging effects of heightened oxidative stress induced by teratogens. Effective antioxidants, which might also

  7. Ergonomics applications of a mechanical model of the human operator in power hand tool operation.

    Science.gov (United States)

    Lin, Jia-Hua; Radwin, Robert; Nembhard, David

    2005-02-01

    Applications of a new model for predicting power threaded-fastener-driving tool operator response and capacity to react against impulsive torque reaction forces are explored for use in tool selection and ergonomic workplace design. The model is based on a mechanical analog of the human operator, with parameters dependent on work location (horizontal and vertical distances); work orientation (horizontal and vertical); and tool shape (in-line, pistol grip, and right angle); and is stratified by gender. This model enables prediction of group means and variances of handle displacement and force for a given tool configuration. Response percentiles can be ascertained for specific tool operations. For example, a sample pistol grip nutrunner used on a horizontal surface at 30 cm in front of the ankles and 140 cm above the floor results in a predicted mean handle reaction displacement of 39.0 (SD=28.1) mm for males. Consequently 63%of the male users exceed a 30 mm handle displacement limit. When a right angle tool of similar torque output is used instead, the model predicted that only 4.6%of the male tool users exceed a 30 mm handle displacement. A method is described for interpolating individual subject model parameters at any given work location using linear combinations in relation to the range of modeled factors. Additional examples pertinent to ergonomic workstation design and tool selection are provided to demonstrate how the model can be used to aid tool selection and workstation design.

  8. Experimental research of mechanical behavior of porcine brain tissue under rotational shear stress.

    Science.gov (United States)

    Li, Gang; Zhang, Jianhua; Wang, Kan; Wang, Mingyu; Gao, Changqing; Ma, Chao

    2016-04-01

    The objective of this paper is to investigate mechanical behavior of porcine brain tissue with a series of rotational shear stress control experiments. To this end, several experiments including stress sweep tests, frequency sweep tests and quasi-static creep tests were designed and conducted with a standard rheometer (HAAKE RheoStress6000). The effects of the loading stress rates to mechanical properties of brain tissue were also studied in stress sweep tests. The results of stress sweep tests performed on the same brain showed that brain tissue had an obvious regional inhomogeneity and the mechanical damage occurred at the rotational shear stress of 10-15Pa. The experimental data from three different loading stress rates demonstrated that the mechanical behavior of porcine brain tissue was loading stress rate dependent. With the decrease of loading stress rate, a stiffer mechanical characteristic of brain tissue was observed and the occurrence of mechanical damage can be delayed to a higher stress. From the results of frequency sweep tests we found that brain tissue had almost completely elastic properties at high frequency area. The nonlinear creep response under the rotational shear stress of 1, 3, 5, 7 and 9Pa was shown in results of creep tests. A new nonlinear viscoelastic solid model was proposed for creep tests and matched well with the test data. Considering the regional differences, loading stress rates and test conditions effects, loss tangent tan δ in porcine brain tissue showed a high uniformity of 0.25-0.45.

  9. The perturbed magnetic fields caused by mechanical stress

    Institute of Scientific and Technical Information of China (English)

    QIN Fei; YAN Dong-mei

    2006-01-01

    In the framework of the linearized magnetoelastic theory,the perturbed magnetic fields caused by mechanical stress and deformation were investigated theoretically.Governing equations and boundary conditions to determine the perturbed fields were derived.The effect of mechanical deformation on the magnetic fields was taken into account by coupling structural displacement into the perturbed magnetic field continuous conditions on the boundary of the structure.As an example,the perturbed field of a half-plane magnetized structure caused by a point force was calculated by the Fourier transform method.The results show that the calculated magnetic intensity component normal to the boundary of the structure reaches its maximum at the point force acted while the component tangent to the boundary inverses its direction sharply.The magnetic induction of the perturbed field is proportional to the applied force.Magnitude analysis proved that since the applied magnetic field has a relative weak intensity such as the Earth's magnetic field, influence of the magnetic field on deformation of the structure can be neglected.

  10. Thermal stability of nafion membranes under mechanical stress

    Energy Technology Data Exchange (ETDEWEB)

    Quintilii, M.; Struis, R. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1997-06-01

    The feasibility of adequately modified fluoro-ionomer membranes (NAFION{sup R}) is demonstrated for the selective separation of methanol synthesis products from the raw reactor gas at temperatures around 200{sup o}C. For an economically relevant application of this concept on a technical scale the Nafion membranes should be thin ({approx_equal}10 {mu}m) and thermally stable over a long period of time (1-2 years). In cooperation with industry (Methanol Casale SA, Lugano (CH)), we test the thermal stability of Nafion hollow fibers and supported Nafion thin sheet membranes at temperatures between 160 and 200{sup o}C under mechanical stress by applying a gas pressure difference over the membrane surface ({Delta}P{<=} 40 bar). Tests with the hollow fibers revealed that Nafion has visco-elastic properties. Tests with 50 {mu}m thin Nafion sheets supported by a porous metal carrier at 200{sup o}C and {Delta}P=39 bar showed no mechanical defects over a period of 92 days. (author) 5 figs., 4 refs.

  11. Measuring mechanical stresses on inserts during injection molding

    Directory of Open Access Journals (Sweden)

    Martina Heinle

    2015-05-01

    Full Text Available Assembly molding presents an interesting approach to innovative product solutions. Here, individual components can be simultaneously positioned, affixed, and provided with a casing. However, while overmolding elements in the mold cavity with hot polymer melt, high mechanical loads occur on, in some cases, very sensitive components such as electronic devices. For the design of such systems, it is important to know these stresses, the influences on their quantities, and mathematical options for their prediction. In this article, a new measurement method for determining the forces acting on a small element in the cavity during the injection molding process in three dimensions is presented. Therefore, a new installation method for a force sensor was developed. The results in this article concentrate on force changes during one molding cycle. Our research shows that there are different mechanical load spectra in the different phases of the molding process. For example, the force component in flow direction on an element in the cavity is positive in the direction of the flow during filling. However, after the filling step, the force becomes negative due to the contraction of the injected material and results in a continuously increasing permanent force.

  12. Mechanical vulnerability of lower second premolar utilising visco-elastic dynamic stress analysis.

    Science.gov (United States)

    Khani, M M; Tafazzoli-Shadpour, M; Aghajani, F; Naderi, P

    2009-10-01

    Stress analysis determines vulnerability of dental tissues to external loads. Stress values depend on loading conditions, mechanical properties and constrains of structural components. The critical stress levels lead to tissue damage. The aim of this study is to analyse dynamic stress distribution of lower second premolar due to physiological cyclic loading, and dependency of pulsatile stress characteristics to visco-elastic property of dental components by finite element modelling. Results show that visco-elastic property markedly influences stress determinants in major anatomical sites including dentin, cementum-enamel and dentin-enamel junctions. Reduction of visco-elastic parameter leads to mechanical vulnerability through elevation of stress pulse amplitude, maximum stress value; and reduction of stress phase shift as a determinant of stress wave propagation. The results may be applied in situations in which visco-elasticity is reduced such as root canal therapy and post and core restoration in which teeth are more vulnerable to fracture.

  13. Measurement and Modeling of Job Stress of Electric Overhead Traveling Crane Operators

    Science.gov (United States)

    Krishna, Obilisetty B.; Maiti, Jhareswar; Ray, Pradip K.; Samanta, Biswajit; Mandal, Saptarshi; Sarkar, Sobhan

    2015-01-01

    Background In this study, the measurement of job stress of electric overhead traveling crane operators and quantification of the effects of operator and workplace characteristics on job stress were assessed. Methods Job stress was measured on five subscales: employee empowerment, role overload, role ambiguity, rule violation, and job hazard. The characteristics of the operators that were studied were age, experience, body weight, and body height. The workplace characteristics considered were hours of exposure, cabin type, cabin feature, and crane height. The proposed methodology included administration of a questionnaire survey to 76 electric overhead traveling crane operators followed by analysis using analysis of variance and a classification and regression tree. Results The key findings were: (1) the five subscales can be used to measure job stress; (2) employee empowerment was the most significant factor followed by the role overload; (3) workplace characteristics contributed more towards job stress than operator's characteristics; and (4) of the workplace characteristics, crane height was the major contributor. Conclusion The issues related to crane height and cabin feature can be fixed by providing engineering or foolproof solutions than relying on interventions related to the demographic factors. PMID:26929839

  14. Mechanical grading in PGI Tropea red onion post harvest operations

    Directory of Open Access Journals (Sweden)

    Bruno Bernardi

    2013-09-01

    Full Text Available The growing interest expressed by consumers toward food products quality as well as toward their linkage to the territory, has led producers to fit to the continuous rising demand for “typical products”, and to look for new and more efficient production and marketing strategies. An emblematic case is represented by Tropea red onion that, as a typical product, plays an important role in economical and rural development of the territory to which it is linked. The organoleptic features offered by “Tropea Red Onion”, PGI certified (Calabria, have to be associated as well to the quality of services that accompanies its processing. Technology application in post-harvest operations, has certainly contributed to make faster and less tiring all processing tasks. The main problem related to the mechanization of Tropea red onion post-harvest operations lies in the removal of the various layers of the external tunic, making it impossible for optical or electronic grader to achieve this task in a satisfactory way since the sensors are not able yet to separate the “bulb” from its involucre. In this context, the current study aims to assess the productivity of three different machines used for round Tropea red onion grading, and determine their work efficiency. The carried out analysis highlighted the ability of the studied machines to ensure a high work capacity, while maintaining a high level of precision during calibration process. Such precision allows to decrease laborer employment and increase processing chain speed, rising as well the annual use of the machines, allowing consequently processing cost savings. For a more profitable employment of such graders, it is, however, necessary from one hand, to properly form the technicians responsible of processing plants management, and from the other hand, to be able to take advantage of a technical assistance network, able to serve users in a short time.

  15. Mechanisms involved in regulation of osteoclastic differentiation by mechanical stress-loaded osteoblasts

    Energy Technology Data Exchange (ETDEWEB)

    Kaneuji, Takeshi [Division of Oral and Maxillofacial Reconstructive Surgery, Department of Oral and Maxillofacial Surgery, Kyushu Dental College, 2-6-1 Manazuru, Kokurakita-ku, Kitakyushu 803-8580 (Japan); Division of Infections and Molecular Biology, Department of Health Promotion, Kyushu Dental College, 2-6-1 Manazuru, Kokurakita-ku, Kitakyushu 803-8580 (Japan); Ariyoshi, Wataru; Okinaga, Toshinori; Toshinaga, Akihiro [Division of Infections and Molecular Biology, Department of Health Promotion, Kyushu Dental College, 2-6-1 Manazuru, Kokurakita-ku, Kitakyushu 803-8580 (Japan); Takahashi, Tetsu [Division of Oral and Maxillofacial Reconstructive Surgery, Department of Oral and Maxillofacial Surgery, Kyushu Dental College, 2-6-1 Manazuru, Kokurakita-ku, Kitakyushu 803-8580 (Japan); Oral Bioresearch Center, Kyushu Dental College, 2-6-1 Manazuru, Kokurakita-ku, Kitakyushu 803-8580 (Japan); Nishihara, Tatsuji, E-mail: tatsujin@kyu-dent.ac.jp [Division of Infections and Molecular Biology, Department of Health Promotion, Kyushu Dental College, 2-6-1 Manazuru, Kokurakita-ku, Kitakyushu 803-8580 (Japan); Oral Bioresearch Center, Kyushu Dental College, 2-6-1 Manazuru, Kokurakita-ku, Kitakyushu 803-8580 (Japan)

    2011-04-29

    Highlights: {yields} Effect of compressive force on osteoblasts were examined. {yields} Compressive force induced OPG expression and suppressed osteoclastogenesis. {yields} This enhancement of OPG is dependent on Wnt/Ca2+ signal pathway. -- Abstract: Mechanical stress is known to be important for regulation of bone turnover, though the detailed mechanisms are not fully understood. In the present study, we examined the effect of mechanical stress on osteoblasts using a novel compression model. Mouse osteoblastic MC3T3-E1 cells were embedded in three-dimensional (3D) gels and cultured with continuous compressive force (0-10.0 g/cm{sup 2}) for 48 h, and the conditioned medium were collected. RAW264.7 cells were then incubated with the conditioned medium for various times in the presence of receptor activator of nuclear factor-{kappa}B ligand (RANKL). Conditioned medium was found to inhibit the differentiation of RAW264.7 cells into osteoclasts induced by RANKL via down-regulation of the expression of tumor necrosis factor receptor-associated factor 6 (TRAF6), phosphorylation of I{kappa}B{alpha}, and nuclear translocation of p50 and p65. Interestingly, the conditioned medium also had a high level of binding activity to RANKL and blocked the binding of RANK to RANKL. Furthermore, the binding activity of conditioned medium to RANKL was reduced when the 3D gel was supplemented with KN-93, an inhibitor of non-canonical Wnt/Ca{sup 2+} pathway. In addition, expression level of osteoprotegerin (OPG) mRNA was increased in time- and force-dependent manners, and remarkably suppressed by KN-93. These results indicate that osteoblastic cells subjected to mechanical stress produce OPG, which binds to RANKL. Furthermore, this binding activity strongly inhibited osteoclastogenesis through suppression of TRAF6 and the nuclear factor-kappa B (NF-{kappa}B) signaling pathway, suggesting that enhancement of OPG expression induced by mechanical stress is dependent on non-canonical Wnt

  16. Cell wall pectic arabinans influence the mechanical properties of Arabidopsis thaliana inflorescence stems and their response to mechanical stress.

    Science.gov (United States)

    Verhertbruggen, Yves; Marcus, Susan E; Chen, Jianshe; Knox, J Paul

    2013-08-01

    Little is known of the dynamics of plant cell wall matrix polysaccharides in response to the impact of mechanical stress on plant organs. The capacity of the imposition of a mechanical stress (periodic brushing) to reduce the height of the inflorescence stem of Arabidopsis thaliana seedlings has been used to study the role of pectic arabinans in the mechanical properties and stress responsiveness of a plant organ. The arabinan-deficient-1 (arad1) mutation that affects arabinan structures in epidermal cell walls of inflorescence stems is demonstrated to reduce the impact on inflorescence stem heights caused by mechanical stress. The arabinan-deficient-2 (arad2) mutation, that does not have detectable impact on arabinan structures, is also shown to reduce the impact on stem heights caused by mechanical stress. The LM13 linear arabinan epitope is specifically detected in epidermal cell walls of the younger, flexible regions of inflorescence stems and increases in abundance at the base of inflorescence stems in response to an imposed mechanical stress. The strain (percentage deformation) of stem epidermal cells in the double mutant arad1 × arad2 is lower in unbrushed plants than in wild-type plants, but rises to wild-type levels in response to brushing. The study demonstrates the complexity of arabinan structures within plant cell walls and also that their contribution to cell wall mechanical properties is a factor influencing responsiveness to mechanical stress.

  17. Influence of effective stress coefficient on mechanical failure of chalk

    DEFF Research Database (Denmark)

    Alam, Mohammad Monzurul; Fabricius, Ida Lykke; Hjuler, M.L.

    2012-01-01

    and vice versa. However, as the effective stress working on the rock decreases with increased effective stress coefficient, the reduction of elastic region will have less effect on pore collapse strength if we consider the change in the effective stress coefficient. This finding will help estimate a more...

  18. Proton migration mechanism for operational instabilities in organic field-effect transistors

    Science.gov (United States)

    Sharma, A.; Mathijssen, S. G. J.; Smits, E. C. P.; Kemerink, M.; de Leeuw, D. M.; Bobbert, P. A.

    2010-08-01

    Organic field-effect transistors exhibit operational instabilities involving a shift of the threshold gate voltage when a gate bias is applied. For a constant gate bias the threshold voltage shifts toward the applied gate bias voltage, an effect known as the bias-stress effect. Here, we report on a detailed experimental and theoretical study of operational instabilities in p -type transistors with silicon-dioxide gate dielectric both for a constant as well as for a dynamic gate bias. We associate the instabilities with a reversible reaction in the organic semiconductor in which holes are converted into protons in the presence of water and a reversible migration of these protons into the gate dielectric. We show how redistribution of charge between holes in the semiconductor and protons in the gate dielectric can consistently explain the experimental observations. Furthermore, we show how a shorter period of application of a gate bias leads to a faster backward shift of the threshold voltage when the gate bias is removed. The proposed mechanism is consistent with the observed acceleration of the bias-stress effect with increasing humidity, increasing temperature, and increasing energy of the highest molecular orbital of the organic semiconductor.

  19. Involvement of lignin and hormones in the response of woody poplar taproots to mechanical stress.

    Science.gov (United States)

    Trupiano, Dalila; Di Iorio, Antonino; Montagnoli, Antonio; Lasserre, Bruno; Rocco, Mariapina; Grosso, Alessandro; Scaloni, Andrea; Marra, Mauro; Chiatante, Donato; Scippa, Gabriella S

    2012-09-01

    Mechanical stress is a widespread condition caused by numerous environmental factors that severely affect plant stability. In response to mechanical stress, plants have evolved complex response pathways able to detect mechanical perturbations and inducing a suite of modifications in order to improve anchorage. The response of woody roots to mechanical stresses has been studied mainly at the morphological and biomechanical level, whereas investigations on the factors triggering these important alterations are still at the initial stage. Populus has been widely used to study the response of stem to different mechanical stresses and, since it has the first forest tree genome to be decoded, represents a model woody plant for addressing questions on the mechanisms controlling adaptation of woody roots to changing environments. In this study, a morphological and physiological analysis was used to investigate factors controlling modifications in Populus nigra woody taproots subjected to mechanical stress. An experimental model analyzing spatial and temporal mechanical force distribution along the woody taproot axis enabled us to compare the events occurring in its above-, central- and below-bending sectors. Different morphogenetic responses and local variations of lignin and plant hormones content have been observed, and a relation with the distribution of the mechanical forces along the stressed woody taproots is hypothesized. We investigated the differences of the response to mechanical stress induction during the time; in this regard, we present data referring to the effect of mechanical stress on plant transition from its condition of winter dormancy to that of full vegetative activity.

  20. Thermo-Mechanical Stress in High-Frequency Vacuum Electron Devices

    Science.gov (United States)

    Gamzina, Diana; Luhmann, Neville C.; Ravani, Bahram

    2017-01-01

    Analysis of the thermo-mechanical performance of high-frequency vacuum electron devices is essential to the advancement of RF sources towards high-power generation. Operation in an ultra-high vacuum environment, space restricting magnetic focusing, and limited material options are just some of the constraints that complicate thermal management in a high-power VED. An analytical method for evaluating temperature, stress, and deformation distribution in thin vacuum-to-cooling walls is presented, accounting for anisotropic material properties. Thin plate geometry is used and analytical expressions are developed for thermo-mechanical analysis that includes the microstructure effects of grain orientations. The method presented evaluates the maximum allowable heat flux that can be used to establish the power-handling limitation of high-frequency VEDs prior to full-scale design, accelerating time-to-manufacture.

  1. Thermo-Mechanical Stress in High-Frequency Vacuum Electron Devices

    Science.gov (United States)

    Gamzina, Diana; Luhmann, Neville C.; Ravani, Bahram

    2016-09-01

    Analysis of the thermo-mechanical performance of high-frequency vacuum electron devices is essential to the advancement of RF sources towards high-power generation. Operation in an ultra-high vacuum environment, space restricting magnetic focusing, and limited material options are just some of the constraints that complicate thermal management in a high-power VED. An analytical method for evaluating temperature, stress, and deformation distribution in thin vacuum-to-cooling walls is presented, accounting for anisotropic material properties. Thin plate geometry is used and analytical expressions are developed for thermo-mechanical analysis that includes the microstructure effects of grain orientations. The method presented evaluates the maximum allowable heat flux that can be used to establish the power-handling limitation of high-frequency VEDs prior to full-scale design, accelerating time-to-manufacture.

  2. Stress optimization of leaf-spring crossed flexure pivots for an active Gurney flap mechanism

    Science.gov (United States)

    Freire Gómez, Jon; Booker, Julian D.; Mellor, Phil H.

    2015-04-01

    The EU's Green Rotorcraft programme is pursuing the development of a functional and airworthy Active Gurney Flap (AGF) for a full-scale helicopter rotor blade. Interest in the development of this `smart adaptive rotor blade' technology lies in its potential to provide a number of aerodynamic benefits, which would in turn translate into a reduction in fuel consumption and noise levels. The AGF mechanism selected employs leaf-spring crossed flexure pivots. These provide important advantages over bearings as they are not susceptible to seizing and do not require maintenance (i.e. lubrication or cleaning). A baseline design of this mechanism was successfully tested both in a fatigue rig and in a 2D wind tunnel environment at flight-representative deployment schedules. For full validation, a flight test would also be required. However, the severity of the in-flight loading conditions would likely compromise the mechanical integrity of the pivots' leaf-springs in their current form. This paper investigates the scope for stress reduction through three-dimensional shape optimization of the leaf-springs of a generic crossed flexure pivot. To this end, a procedure combining a linear strain energy formulation, a parametric leaf-spring profile definition and a series of optimization algorithms is employed. The resulting optimized leaf-springs are proven to be not only independent of the angular rotation at which the pivot operates, but also linearly scalable to leaf-springs of any length, minimum thickness and width. Validated using non-linear finite element analysis, the results show very significant stress reductions relative to pivots with constant cross section leaf-springs, of up to as much as 30% for the specific pivot configuration employed in the AGF mechanism. It is concluded that shape optimization offers great potential for reducing stress in crossed flexure pivots and, consequently, for extending their fatigue life and/or rotational range.

  3. Estimation of Lifetime Duration for a Lever Pin of Runner Blade Operating Mechanism using a Graphic – analytic Method

    Directory of Open Access Journals (Sweden)

    Ana-Maria Budai

    2015-09-01

    Full Text Available In this paper are presented a graphic - analytic method that can be used to estimate the fatigue lifetime duration for an operating mechanism lever pin to a Kaplan turbine. The presented calculus algorithm is adapted from the one used by Fuji Electric to made strength calculus in order to refurbish a Romanian hydropower plant, equipped with a Kaplan turbine. The graphic part includes a 3D fatigue diagram for rotating bending stress designed by Fuji Electric specialists.

  4. Oxidative Stress in Neurodegenerative Diseases: Mechanisms and Therapeutic Perspectives

    Directory of Open Access Journals (Sweden)

    Ailton Melo

    2011-01-01

    Full Text Available The incidence and prevalence of neurodegenerative diseases (ND increase with life expectancy. This paper reviews the role of oxidative stress (OS in ND and pharmacological attempts to fight against reactive oxygen species (ROS-induced neurodegeneration. Several mechanisms involved in ROS generation in neurodegeneration have been proposed. Recent articles about molecular pathways involved in ROS generation were reviewed. The progress in the development of neuroprotective therapies has been hampered because it is difficult to define targets for treatment and determine what should be considered as neuroprotective. Therefore, the attention was focused on researches about pharmacological targets that could protect neurons against OS. Since it is necessary to look for genes as the ultimate controllers of all biological processes, this paper also tried to identify gerontogenes involved in OS and neurodegeneration. Since neurons depend on glial cells to survive, recent articles about the functioning of these cells in aging and ND were also reviewed. Finally, clinical trials testing potential neuroprotective agents were critically reviewed. Although several potential drugs have been screened in in vitro and in vivo models of ND, these results were not translated in benefit of patients, and disappointing results were obtained in the majority of clinical trials.

  5. A CFD study of hygro-thermal stresses distribution in tubular-shaped ambient air-breathing PEM micro fuel cell during regular cell operation

    Directory of Open Access Journals (Sweden)

    Maher A.R. Sadiq Al-Baghdadi

    2010-03-01

    Full Text Available The need for improved lifetime of air-breathing proton exchange membrane (PEM fuel cells for portable applications necessitates that the failure mechanisms be clearly understood and life prediction models be developed, so that new designs can be introduced to improve long-term performance. An operating air-breathing PEM fuel cell has varying local conditions of temperature, humidity. As a result of in the changes in temperature and moisture, the membrane, GDL and bipolar plates will all experience expansion and contraction. Because of the different thermal expansion and swelling coefficients between these materials, hygro-thermal stresses are introduced into the unit cell during operation. In addition, the non-uniform current and reactant flow distributions in the cell result in non-uniform temperature and moisture content of the cell which could in turn, potentially causing localized increases in the stress magnitudes, and this leads to mechanical damage, which can appear as through-the-thickness flaws or pinholes in the membrane, or delaminating between the polymer membrane and gas diffusion layers. Therefore, in order to acquire a complete understanding of these damage mechanisms in the membranes and gas diffusion layers, mechanical response under steady-state hygro-thermal stresses should be studied under real cell operation conditions. A three-dimensional, multi–phase, non-isothermal computational fluid dynamics model of a novel, tubular, ambient air-breathing, proton exchange membrane micro fuel cell has been developed and used to investigate the displacement, deformation, and stresses inside the whole cell, which developed during the cell operation due to the changes of temperature and relative humidity. The behaviour of the fuel cell during operation has been studied and investigated under real cell operating conditions. In addition to the new and complex geometry, a unique feature of the present model is to incorporate the effect of

  6. Evidence for particle mobilization as a mechanism for permeability enhancement via dynamic stressing

    Science.gov (United States)

    Candela, T.; Brodsky, E. E.; Marone, C.; Elsworth, D.

    2013-12-01

    Dynamic permeability change by seismic waves is a well-established natural phenomenon yet the mechanism remains poorly understood. We investigate the mechanism by generating well-controlled repeatable permeability enhancement in a laboratory experiment. Each experiment proceeded as: (1) pore pressure oscillations, simulating dynamic stresses, were applied at one end of intact Berea sandstone samples under triaxial stresses of tens of megapascals, (2) samples were fractured within the apparatus, and (3) pore pressure oscillations resumed post-fracturing. In this way, both the fracture and porous media response to the dynamic stresses were investigated. In addition, we controled the mobility of fine particles by adjusting the pore fluid chemistry (deionized water, and brines of: NaCl 5%, NaCl 35%, CaCl2 5%). Our results are consistent with natural observations. Dynamic stressing produces an immediate permeability enhancement ranging from 1-60%, which scales with the amplitude of the dynamic strain, 7*10^-7 to 7*10^-6, followed by a progressive permeability recovery. In our experiments a flow-dependent mechanism associated with mobilization of fines appears to control both the magnitude of the permeability enhancement and the recovery rate. Both processes operate at two time scales, i.e., fast flushing/unclogging of the fines during the pore pressure oscillations and progressive clogging of the pore throats by particle migration, and were influenced by the fluid chemistry. The dynamic permeability changes were not associated with permanent deformation. We show that: 1) injection of unequilibrated fluids favors particle mobilization, and 2) transient permeability change results from the migration of fines which in turn results from dynamic stressing. Our results suggest that areas where pore fluids are in disequilibrium should be more sensitive to dynamic stressing. Interestingly, early observations of dynamic earthquake-triggering revealed preferential triggering in

  7. ADDITIONAL STRESS AND FRACTURE MECHANICS ANALYSES OF PRESSURIZED WATER REACTOR PRESSURE VESSEL NOZZLES

    Energy Technology Data Exchange (ETDEWEB)

    Walter, Matthew [Structural Integrity Associates, Inc.; Yin, Shengjun [ORNL; Stevens, Gary [U.S. Nuclear Regulatory Commission; Sommerville, Daniel [Structural Integrity Associates, Inc.; Palm, Nathan [Westinghouse Electric Company, Cranberry Township, PA; Heinecke, Carol [Westinghouse Electric Company, Cranberry Township, PA

    2012-01-01

    In past years, the authors have undertaken various studies of nozzles in both boiling water reactors (BWRs) and pressurized water reactors (PWRs) located in the reactor pressure vessel (RPV) adjacent to the core beltline region. Those studies described stress and fracture mechanics analyses performed to assess various RPV nozzle geometries, which were selected based on their proximity to the core beltline region, i.e., those nozzle configurations that are located close enough to the core region such that they may receive sufficient fluence prior to end-of-life (EOL) to require evaluation of embrittlement as part of the RPV analyses associated with pressure-temperature (P-T) limits. In this paper, additional stress and fracture analyses are summarized that were performed for additional PWR nozzles with the following objectives: To expand the population of PWR nozzle configurations evaluated, which was limited in the previous work to just two nozzles (one inlet and one outlet nozzle). To model and understand differences in stress results obtained for an internal pressure load case using a two-dimensional (2-D) axi-symmetric finite element model (FEM) vs. a three-dimensional (3-D) FEM for these PWR nozzles. In particular, the ovalization (stress concentration) effect of two intersecting cylinders, which is typical of RPV nozzle configurations, was investigated. To investigate the applicability of previously recommended linear elastic fracture mechanics (LEFM) hand solutions for calculating the Mode I stress intensity factor for a postulated nozzle corner crack for pressure loading for these PWR nozzles. These analyses were performed to further expand earlier work completed to support potential revision and refinement of Title 10 to the U.S. Code of Federal Regulations (CFR), Part 50, Appendix G, Fracture Toughness Requirements, and are intended to supplement similar evaluation of nozzles presented at the 2008, 2009, and 2011 Pressure Vessels and Piping (PVP

  8. The conduction mechanism of stress induced leakage current through ultra-thin gate oxide under constant voltage stresses

    Institute of Scientific and Technical Information of China (English)

    Wang Yan-Gang; Xu Ming-Zhen; Tan Chang-Hua; Zhang Zhang J.F; Duan Xiao-Rong

    2005-01-01

    The conduction mechanism of stress induced leakage current (SILC) through 2nm gate oxide is studied over a gate voltage range between 1.7V and stress voltage under constant voltage stress (CVS). The simulation results show that the SILC is formed by trap-assisted tunnelling (TAT) process which is dominated by oxide traps induced by high field stresses. Their energy levels obtained by this work are approximately 1.9eV from the oxide conduction band, and the traps are believed to be the oxygen-related donor-like defects induced by high field stresses. The dependence of the trap density on stress time and oxide electric field is also investigated.

  9. Yielding to stress: Recent developments in viscoplastic fluid mechanics

    OpenAIRE

    Balmforth, Neil; Frigaard, Ian A.; Ovarlez, Guillaume

    2014-01-01

    The archetypal feature of a viscoplastic fluid is its yield stress: If the material is not sufficiently stressed, it behaves like a solid, but once the yield stress is exceeded, the material flows like a fluid. Such behavior characterizes materials common in industries such as petroleum and chemical processing, cosmetics, and food processing and in geophysical fluid dynamics. The most common idealization of a viscoplastic fluid is the Bingham model, which has been widely used to rationalize e...

  10. Relative Damage Stress: Dominant Mechanical Factor for the Failure of Soldered Joints under Temperature Cycling

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    By temperature normalization of the concept of equivalent damage stress proposed by Lemaitre,a new concept of relative damage stress has been put forward as the dominant mechanical factor for the failure of soldered joints under temperature cycling. Finite element numerical simulation results showed that the highest value of relative damage stress occurred at the high temperaturehold time during temperature cycling history.

  11. Are geometrical and structural variations along the length of the aorta governed by a principle of "optimal mechanical operation"?

    Science.gov (United States)

    Rachev, Alexander; Greenwald, Stephen; Shazly, Tarek

    2013-08-01

    It is well-documented that the geometrical dimensions, the longitudinal stretch ratio in situ, certain structural mechanical descriptors such as compliance and pressure-diameter moduli, as well as the mass fractions of structural constituents, vary along the length of the descending aorta. The origins of and possible interrelations among these observed variations remain open questions. The central premise of this study is that having considered the variation of the deformed inner diameter, axial stretch ratio, and area compliance along the aorta to be governed by the systemic requirements for flow distribution and reduction of cardiac preload, the zero-stress state geometry and mass fractions of the basic structural constituents of aortic tissue meet a principle of optimal mechanical operation. The principle manifests as a uniform distribution of the circumferential stress in the aortic wall that ensures effective bearing of the physiological load and a favorable mechanical environment for mechanosensitive vascular smooth muscle cells. A mathematical model is proposed and inverse boundary value problems are solved for the equations that follow from finite elasticity, structure-based constitutive modeling within constrained mixture theory, and stress-induced control of aortic homeostasis, mediated by the synthetic activity of vascular smooth muscle cells. Published experimental data are used to illustrate the predictive power of the proposed model. The results obtained are in agreement with published experimental data and support the proposed principle of optimal mechanical operation for the descending aorta.

  12. A Comparison between Deep and Shallow Stress Fields in Korea Using Earthquake Focal Mechanism Inversions and Hydraulic Fracturing Stress Measurements

    Science.gov (United States)

    Lee, Rayeon; Chang, Chandong; Hong, Tae-kyung; Lee, Junhyung; Bae, Seong-Ho; Park, Eui-Seob; Park, Chan

    2016-04-01

    We are characterizing stress fields in Korea using two types of stress data: earthquake focal mechanism inversions (FMF) and hydraulic fracturing stress measurements (HF). The earthquake focal mechanism inversion data represent stress conditions at 2-20 km depths, whereas the hydraulic fracturing stress measurements, mostly conducted for geotechnical purposes, have been carried out at depths shallower than 1 km. We classified individual stress data based on the World Stress Map quality ranking scheme. A total of 20 FMF data were classified into A-B quality, possibly representing tectonic stress fields. A total of 83 HF data out of compiled 226 data were classified into B-C quality, which we use for shallow stress field characterization. The tectonic stress, revealed from the FMF data, is characterized by a remarkable consistency in its maximum stress (σ1) directions in and around Korea (N79±2° E), indicating a quite uniform deep stress field throughout. On the other hand, the shallow stress field, represented by HF data, exhibits local variations in σ1 directions, possibly due to effects of topography and geologic structures such as faults. Nonetheless, there is a general similarity in σ1 directions between deep and shallow stress fields. To investigate the shallow stress field statistically, we follow 'the mean orientation and wavelength analysis' suggested by Reiter et al. (2014). After the stress pattern analysis, the resulting stress points distribute sporadically over the country, not covering the entire region evenly. In the western part of Korea, the shallow σ1directions are generally uniform with their search radius reaching 100 km, where the average stress direction agrees well with those of the deep tectonic stress. We note two noticeable differences between shallow and deep stresses in the eastern part of Korea. First, the shallow σ1 orientations are markedly non-uniform in the southeastern part of Korea with their search radius less than 25 km

  13. Effect of internal stresses on the mechanical parameters of silicon wafers

    Energy Technology Data Exchange (ETDEWEB)

    Oksanich, A.P.; Cherner, V.M.; Tuzovskii, K.A.

    1988-12-01

    The authors examined how the mechanical parameters of silicon wafers vary with the stress area. The polished (100) wafers were cut from a billet grown by Czochralski's method. The internal stresses were produced by moving the wafers in and out of an oven having a working zone at 1420 K. Then the oxide film was removed. The area of the stressed parts was determined by photoelasticity. The mechanical parameters were measured with contactless pneumatic loading and continuous central deflection measurement. The internal stresses affect the properties; at a given load the central deflection in an unstressed wafer is larger than in a stressed one.

  14. Impact of bacterial priming on some stress tolerance mechanisms and growth of cold stressed wheat seedlings

    Directory of Open Access Journals (Sweden)

    Mohammed E.H. Osman

    2014-01-01

    Full Text Available The potential to enhance growth of cold stressed wheat by seed treatment (priming with the beneficial bacteria Bacillus amyloliquefaciens 5113 and Azospirillum brasilense NO40 were tested. Results showed an improved ability of bacteria-treated seedlings to survive at −5°C up to 12 h. Cold stress increased transcript levels of three stress marker genes and increased activity for the ascorbate-glutathione redox enzymes. However, primed and stressed seedlings generally showed smaller effects on the stress markers correlating with better growth and improved stress tolerance. Bacterial priming to improve crop plant performance at low temperature seems a useful strategy to explore further.

  15. Soldiers Working Internationally: Impacts of Masculinity, Military Culture, and Operational Stress on Cross-Cultural Adaptation

    Science.gov (United States)

    Keats, Patrice A.

    2010-01-01

    This paper explores the ramifications of masculinized military culture and operational stress on cross-cultural adaptation. The author examines how characteristics of military culture may obstruct effective cross-cultural adaptation by promoting a hypermasculinity that tends to oppose effective management of trauma, and thereby suppresses skills…

  16. Molecular mechanisms of the yeast adaptive response and tolerance to stresses encountered during ethanol fermentation.

    Science.gov (United States)

    Auesukaree, Choowong

    2017-08-01

    During ethanol fermentation, yeast cells encounter various stresses including sugar substrates-induced high osmolarity, increased ethanol concentration, oxygen metabolism-derived reactive oxygen species (ROS), and elevated temperature. To cope with these fermentation-associated stresses, appropriate adaptive responses are required to prevent stress-induced cellular dysfunctions and to acquire stress tolerances. This review will focus on the cellular effects of these stresses, molecular basis of the adaptive response to each stress, and the cellular mechanisms contributing to stress tolerance. Since a single stress can cause diverse effects, including specific and non-specific effects, both specific and general stress responses are needed for achieving comprehensive protection. For instance, the high-osmolarity glycerol (HOG) pathway and the Yap1/Skn7-mediated pathways are specifically involved in responses to osmotic and oxidative stresses, respectively. On the other hand, due to the common effect of these stresses on disturbing protein structures, the upregulation of heat shock proteins (HSPs) and trehalose is induced upon exposures to all of these stresses. A better understanding of molecular mechanisms underlying yeast tolerance to these fermentation-associated stresses is essential for improvement of yeast stress tolerance by genetic engineering approaches. Copyright © 2017 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

  17. Modal Testing of Mechanical Structures subject to Operational Excitation Forces

    DEFF Research Database (Denmark)

    Møller, N.; Brincker, Rune; Herlufsen, H.;

    2001-01-01

    to the Operational Modal Analysis. For Operational Modal Analysis two different estimation techniques are used: a non-parametric technique based on Frequency Domain Decomposition (FDD), and a parametric technique working on the raw data in time domain, a data driven Stochastic Subspace Identification (SSI) algorithm...

  18. Modal Testing of Mechanical Structures Subject to Operational Excitation Forces

    DEFF Research Database (Denmark)

    Møller, N.; Brincker, Rune; Herlufsen, H.;

    2000-01-01

    to the Operational Modal Analysis. For Operational Modal Analysis two different estimation techniques are used: a non-parametric technique based on Frequency Domain Decomposition (FDD), and a parametric technique working on the raw data in time domain, a data driven Stochastic Subspace Identification (SSI) algorithm...

  19. Influence of effective stress coefficient on mechanical failure of chalk

    DEFF Research Database (Denmark)

    Alam, Mohammad Monzurul; Fabricius, Ida Lykke; Hjuler, M.L.

    2012-01-01

    The Effective stress coefficient is a measure of how chalk grains are connected with each other. The stiffness of chalk may decrease if the amount of contact cements between the grains decreases, which may lead to an increase of the effective stress coefficient. We performed CO2 injection in chal...

  20. Mechanical stress activates neurites and somata of myenteric neurons

    Directory of Open Access Journals (Sweden)

    Eva Maria Kugler

    2015-09-01

    Full Text Available The particular location of myenteric neurons, sandwiched between the 2 muscle layers of the gut, implies that their somata and neurites undergo mechanical stress during gastrointestinal motility. Existence of mechanosensitive enteric neurons (MEN is undoubted but many of their basic features remain to be studied. In this study, we used ultra-fast neuroimaging to record activity of primary cultured myenteric neurons of guinea pig and human intestine after von Frey hair evoked deformation of neurites and somata. Independent component analysis was applied to reconstruct neuronal morphology and follow neuronal signals. Of the cultured neurons 45% (114 out of 256, 30 guinea pigs responded to neurite probing with a burst spike frequency of 13.4 Hz. Action potentials generated at the stimulation site invaded the soma and other neurites. Mechanosensitive sites were expressed across large areas of neurites. Many mechanosensitive neurites appeared to have afferent and efferent functions as those that responded to deformation also conducted spikes coming from the soma. Mechanosensitive neurites were also activated by nicotine application. This supported the concept of multifunctional MEN. 14% of the neurons (13 out of 96, 18 guinea pigs responded to soma deformation with burst spike discharge of 17.9 Hz. Firing of MEN adapted rapidly (RAMEN, slowly (SAMEN or ultra-slowly (USAMEN. The majority of MEN showed SAMEN behavior although significantly more RAMEN occurred after neurite probing. Cultured myenteric neurons from human intestine had similar properties. Compared to MEN, dorsal root ganglion neurons were activated by neurite but not by soma deformation with slow adaptation of firing. We demonstrated that MEN exhibit specific features very likely reflecting adaptation to their specialized functions in the gut.

  1. Protective mechanisms of Cucumis sativus in diabetes-related models of oxidative stress and carbonyl stress

    Directory of Open Access Journals (Sweden)

    Himan Heidari

    2016-03-01

    Conclusion: It can be concluded that C. sativus has protective effects in diabetes complications and can be considered a safe and suitable candidate for decreasing the oxidative stress and carbonyl stress that is typically observed in diabetes mellitus.

  2. Epigenetic and chromatin-based mechanisms in environmental stress adaptation and stress memory in plants

    National Research Council Canada - National Science Library

    Jorn Lamke; Isabel Baurle

    2017-01-01

    .... Given their potential epigenetic nature, such modifications may provide a mechanistic basis for a stress memory, enabling plants to respond more efficiently to recurring stress or even to prepare...

  3. Determining the stress field in active volcanoes using focal mechanisms

    Directory of Open Access Journals (Sweden)

    Bruno Massa

    2016-11-01

    Full Text Available Stress inversion of seismological datasets became an essential tool to retrieve the stress field of active tectonics and volcanic areas. In particular, in volcanic areas, it is able to put constrains on volcano-tectonics and in general in a better understanding of the volcano dynamics. During the last decades, a wide range of stress inversion techniques has been proposed, some of them specifically conceived to manage seismological datasets. A modern technique of stress inversion, the BRTM, has been applied to seismological datasets available at three different regions of active volcanism: Mt. Somma-Vesuvius (197 Fault Plane Solutions, FPSs, Campi Flegrei (217 FPSs and Long Valley Caldera (38,000 FPSs. The key role of stress inversion techniques in the analysis of the volcano dynamics has been critically discussed. A particular emphasis was devoted to performances of the BRTM applied to volcanic areas.

  4. Determining the stress field in active volcanoes using focal mechanisms

    Science.gov (United States)

    Massa, Bruno; D'Auria, Luca; Cristiano, Elena; De Matteo, Ada

    2016-11-01

    Stress inversion of seismological datasets became an essential tool to retrieve the stress field of active tectonics and volcanic areas. In particular, in volcanic areas, it is able to put constrains on volcano-tectonics and in general in a better understanding of the volcano dynamics. During the last decades, a wide range of stress inversion techniques has been proposed, some of them specifically conceived to manage seismological datasets. A modern technique of stress inversion, the BRTM, has been applied to seismological datasets available at three different regions of active volcanism: Mt. Somma-Vesuvius (197 Fault Plane Solutions, FPSs), Campi Flegrei (217 FPSs) and Long Valley Caldera (38,000 FPSs). The key role of stress inversion techniques in the analysis of the volcano dynamics has been critically discussed. A particular emphasis was devoted to performances of the BRTM applied to volcanic areas.

  5. A Review & Assessment of Current Operating Conditions Allowable Stresses in ASME Section III Subsection NH

    Energy Technology Data Exchange (ETDEWEB)

    R. W. Swindeman

    2009-12-14

    The current operating condition allowable stresses provided in ASME Section III, Subsection NH were reviewed for consistency with the criteria used to establish the stress allowables and with the allowable stresses provided in ASME Section II, Part D. It was found that the S{sub o} values in ASME III-NH were consistent with the S values in ASME IID for the five materials of interest. However, it was found that 0.80 S{sub r} was less than S{sub o} for some temperatures for four of the materials. Only values for alloy 800H appeared to be consistent with the criteria on which S{sub o} values are established. With the intent of undertaking a more detailed evaluation of issues related to the allowable stresses in ASME III-NH, the availabilities of databases for the five materials were reviewed and augmented databases were assembled.

  6. Mechanical Stress Changes the Complex Interplay Between HO-1, Inflammation and Fibrosis, During Excisional Wound Repair

    NARCIS (Netherlands)

    Cremers, N.A.J.; Suttorp, M.; Gerritsen, M.M.; Wong, R.J.; Run-van Breda, C. van; Dam, G.M. van; Brouwer, K.M.; Kuijpers-Jagtman, A.M.; Carels, C.E.L.; Lundvig, D.M.; Wagener, F.A.D.T.G.

    2015-01-01

    Mechanical stress following surgery or injury can promote pathological wound healing and fibrosis, and lead to functional loss and esthetic problems. Splinted excisional wounds can be used as a model for inducing mechanical stress. The cytoprotective enzyme heme oxygenase-1 (HO-1) is thought to orch

  7. 2D Modelling of Mechanical Stress Evolution and Electromigration in Confined Aluminium Interconnects

    NARCIS (Netherlands)

    Petrescu, V.; Mouthaan, A.J.

    1997-01-01

    A complete description for mechanical stress evolution and electromigration in confined Al interconnects, taking into account the microstructure features, is presented in this paper. In the last years there were proposed several 1D models for the time-dependent evolution of the mechanical stress in

  8. 46 CFR 113.35-13 - Mechanical engine order telegraph systems; operation.

    Science.gov (United States)

    2010-10-01

    ... 46 Shipping 4 2010-10-01 2010-10-01 false Mechanical engine order telegraph systems; operation...) ELECTRICAL ENGINEERING COMMUNICATION AND ALARM SYSTEMS AND EQUIPMENT Engine Order Telegraph Systems § 113.35-13 Mechanical engine order telegraph systems; operation. If more than one transmitter operates...

  9. Calcium-mediated oxidative stress: a common mechanism in tight junction disruption by different types of cellular stress.

    Science.gov (United States)

    Gangwar, Ruchika; Meena, Avtar S; Shukla, Pradeep K; Nagaraja, Archana S; Dorniak, Piotr L; Pallikuth, Sandeep; Waters, Christopher M; Sood, Anil; Rao, RadhaKrishna

    2017-02-20

    The role of reactive oxygen species (ROS) in osmotic stress, dextran sulfate sodium (DSS) and cyclic stretch-induced tight junction (TJ) disruption was investigated in Caco-2 cell monolayers in vitro and restraint stress-induced barrier dysfunction in mouse colon in vivo Live cell imaging showed that osmotic stress, cyclic stretch and DSS triggered rapid production of ROS in Caco-2 cell monolayers, which was blocked by depletion of intracellular Ca(2+) by 1,2-bis-(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid. Knockdown of CaV1.3 or TRPV6 channels blocked osmotic stress and DSS-induced ROS production and attenuated TJ disruption and barrier dysfunction. N-Acetyl l-cysteine (NAC) and l-N(G)-Nitroarginine methyl ester (l-NAME) blocked stress-induced TJ disruption and barrier dysfunction. NAC and l-NAME also blocked stress-induced activation of c-Jun N-terminal kinase (JNK) and c-Src. ROS was colocalized with the mitochondrial marker in stressed cells. Cyclosporin A blocked osmotic stress and DSS-induced ROS production, barrier dysfunction, TJ disruption and JNK activation. Mitochondria-targeted Mito-TEMPO blocked osmotic stress and DSS-induced barrier dysfunction and TJ disruption. Chronic restraint stress in mice resulted in the elevation of intracellular Ca(2+), activation of JNK and c-Src, and disruption of TJ in the colonic epithelium. Furthermore, corticosterone administration induced JNK and c-Src activation, TJ disruption and protein thiol oxidation in colonic mucosa. The present study demonstrates that oxidative stress is a common signal in the mechanism of TJ disruption in the intestinal epithelium by different types of cellular stress in vitro and bio behavioral stress in vivo.

  10. Earthquakes focal mechanism and stress field pattern in the northeastern part of Egypt

    Directory of Open Access Journals (Sweden)

    Emad K. Mohamed

    2015-12-01

    The inversion technique scheme is used also in the present study for determining the regional stress field parameters for earthquake focal mechanism solutions based on the grid search method of Gephart and Forsyth (1984. The Results of the stress tensor using focal mechanisms of recent earthquakes show a prevailed tension stress field in N52°E, N41°E and N52°E for the northern Red Sea, Gulf of Suez and Gulf of Aqaba zone respectively.

  11. Mechanical Pre Stressing a Transducer through a Negative DC Biasing Field

    Science.gov (United States)

    2017-04-21

    interesting concept but would not work under high-drive conditions. 17 (18 blank) BIBLIOGRAPHY Butler, S.C., “MLTRT Element FEA Dynamic Stress ...NUWC-NPT Technical Report 12,224 21 April 2017 Mechanical Pre- Stressing a Transducer through a Negative DC Biasing Field Stephen C...TITLE AND SUBTITLE Mechanical Pre- Stressing a Transducer through a Negative DC Biasing Field 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c

  12. Stress and Fatigue in Operators Under Radiofrequency Electromagnetic Radiation and Shift Work

    Directory of Open Access Journals (Sweden)

    Vangelova K.

    2014-12-01

    Full Text Available The aim was to study the effect of radiofrequency electromagnetic radiation (EMR on stress indices, health complaints and fatigue of operators working fast-rotating extended shifts. Working conditions, job content, job control, social support, health complaints and fatigue were followed in 220 operators, 110 exposed to EMR and 110 control operators, matched by age and sex. The EMR was measured and time-weighted average (TWA was calculated. The excretion rates of stress hormones cortisol, adrenaline and noradrenaline were followed during the extended shifts in 36 operators, working at different levels of exposure and 24-hour exposure was calculated. The exposed group pointed more problems with the working conditions, including EMR, noise, currents and risk of accidents, more health complaints and higher level of fatigue. The most common health complaints were mental and physical exhaustion after work, pains in the chest, musculoskeletal complaints, headache, and apathy. High level EMR exposure (TWAmean = 3.10 μW/cm2, TWAmax = 137.00 μW/cm2 significantly increased the 24-hour excretion of cortisol and noradrenaline, whereas the increase of adrenaline excretion did not reach significance, as well as hormone excretion rates under low level exposure (TWAmean = 1.89 μW/cm2, TWAmax = 5.24 μW/cm2. In conclusion, higher number of health complaints, higher stress hormone excretion rates and fatigue were found in operators under EMR.

  13. Is the microscopic stress computed from molecular simulations in mechanical equilibrium?

    Science.gov (United States)

    Torres-Sánchez, Alejandro; Vanegas, Juan M.; Arroyo, Marino

    The microscopic stress field connects atomistic simulations with the mechanics of materials at the nano-scale through statistical mechanics. However, its definition remains ambiguous. In a recent work we showed that this is not only a theoretical problem, but rather that it greatly affects local stress calculations from molecular simulations. We find that popular definitions of the local stress, which are continuously being employed to understand the mechanics of various systems at the nanoscale, violate the continuum statements of mechanical equilibrium. We exemplify these facts in local stress calculations of defective graphene, lipid bilayers, and fibrous proteins. Furthermore, we propose a new physical and sound definition of the microscopic stress that satisfies the continuum equations of balance, irrespective of the many-body nature of the inter-atomic potential. Thus, our proposal provides an unambiguous link between discrete-particle models and continuum mechanics at the nanoscale.

  14. Maximum-power-point tracking with reduced mechanical stress applied to wind-energy-conversion-systems

    Energy Technology Data Exchange (ETDEWEB)

    Gonzalez, L.G. [Departamento de Electronica y Comunicaciones, Universidad de los Andes, nucleo la Hechicera, 5101 Merida (Venezuela); Figueres, E.; Garcera, G. [Grupo de Sistemas Electronicos Industriales, Universidad Politecnica de Valencia, Camino de vera s/n, 46022 Valencia (Spain); Carranza, O. [Escuela Superior de Computo, Instituto Politecnico Nacional, Av. Juan de Dios Batiz s/n, 07738 DF (Mexico)

    2010-07-15

    This paper presents an improved maximum-power-point tracking algorithm for wind-energy-conversion-systems. The proposed method significantly reduces the turbine mechanical stress with regard to conventional techniques, so that both the maintenance needs and the medium time between failures are expected to be improved. To achieve these objectives, a sensorless speed control loop receives its reference signal from a modified Perturb and Observe algorithm, in which the typical steps on the reference speed have been substituted by a fixed and well-defined slope ramp signal. As a result, it is achieved a soft dynamic response of both the torque and the speed of the wind turbine, so that the whole system suffers from a lower mechanical stress than with conventional P and O techniques. The proposed method has been applied to a wind turbine based on a permanent magnet synchronous generator operating at variable speed, which is connected to the distribution grid by means of a back to back converter. (author)

  15. Mechanisms of ER Stress-Mediated Mitochondrial Membrane Permeabilization.

    LENUS (Irish Health Repository)

    Gupta, Sanjeev

    2010-01-01

    During apoptosis, the process of mitochondrial outer membrane permeabilization (MOMP) represents a point-of-no-return as it commits the cell to death. Here we have assessed the role of caspases, Bcl-2 family members and the mitochondrial permeability transition pore on ER stress-induced MOMP and subsequent cell death. Induction of ER stress leads to upregulation of several genes such as Grp78, Edem1, Erp72, Atf4, Wars, Herp, p58ipk, and ERdj4 and leads to caspase activation, release of mitochondrial intermembrane proteins and dissipation of mitochondrial transmembrane potential (DeltaPsim). Mouse embryonic fibroblasts (MEFs) from caspase-9, -2 and, -3 knock-out mice were resistant to ER stress-induced apoptosis which correlated with decreased processing of pro-caspase-3 and -9. Furthermore, pretreatment of cells with caspase inhibitors (Boc-D.fmk and DEVD.fmk) attenuated ER stress-induced loss of DeltaPsim. However, only deficiency of caspase-9 and -2 could prevent ER stress-mediated loss of DeltaPsim. Bcl-2 overexpression or pretreatment of cells with the cell permeable BH4 domain (BH4-Tat) or the mitochondrial permeability transition pore inhibitors, bongkrekic acid or cyclosporine A, attenuated the ER stress-induced loss of DeltaPsim. These data suggest a role for caspase-9 and -2, Bcl-2 family members and the mitochondrial permeability transition pore in loss of mitochondrial membrane potential during ER stress-induced apoptosis.

  16. Moderate stress enhances memory persistence: are adrenergic mechanisms involved?

    Science.gov (United States)

    Parfitt, Gustavo Morrone; Barbosa, Ândrea Kraemer; Campos, Renan Costa; Koth, André Peres; Barros, Daniela Martí

    2012-10-01

    Memory persistence in the inhibitory avoidance (IA) task has been recently shown to require a new event of consolidation 12 hr after acquisition. The immobilization stress (IS) model is largely used to study the effects of stress on memory. In this study we investigated the interactions between stress by immobilization and its effect on the persistence of memory, and also a possible effect mediated by β-adrenergic modulation of stress on memory persistence. An enhancement of long-term memory (LTM) persistence caused by stress through immobilization applied 12 hr after IA training was observed when the animals were submitted to 15 min or 1 hr of IS, but not to 3 hr. The reversal of this memory enhancement caused by IS was observed when the β-adrenergic antagonist propranolol was infused intraperitoneally prior to stress, which implies that β-adrenergic receptors are involved in stress enhancement of LTM persistence. PsycINFO Database Record (c) 2012 APA, all rights reserved.

  17. Achieving reversibility of ultra-high mechanical stress by hydrogen loading of thin films

    Science.gov (United States)

    Hamm, M.; Burlaka, V.; Wagner, S.; Pundt, A.

    2015-06-01

    Nano-materials are commonly stabilized by supports to maintain their desired shape and size. When these nano-materials take up interstitial atoms, this attachment to the support induces mechanical stresses. These stresses can be high when the support is rigid. High stress in the nano-material is typically released by delamination from the support or by the generation of defects, e.g., dislocations. As high mechanical stress can be beneficial for tuning the nano-materials properties, it is of general interest to deduce how real high mechanical stress can be gained. Here, we show that below a threshold nano-material size, dislocation formation can be completely suppressed and, when delamination is inhibited, even the ultrahigh stress values of the linear elastic limit can be reached. Specifically, for hydrogen solved in epitaxial niobium films on sapphire substrate supports a threshold film thickness of 6 nm was found and mechanical stress of up to (-10 ± 1) GPa was reached. This finding is of basic interest for hydrogen energy applications, as the hydride stability in metals itself is affected by mechanical stress. Thus, tuning of the mechanical stress-state in nano-materials may lead to improved storage properties of nano-sized materials.

  18. Root elongation, water stress, and mechanical impedance: a review of limiting stresses and beneficial root tip traits.

    Science.gov (United States)

    Bengough, A Glyn; McKenzie, B M; Hallett, P D; Valentine, T A

    2011-01-01

    Root elongation in drying soil is generally limited by a combination of mechanical impedance and water stress. Relationships between root elongation rate, water stress (matric potential), and mechanical impedance (penetration resistance) are reviewed, detailing the interactions between these closely related stresses. Root elongation is typically halved in repacked soils with penetrometer resistances >0.8-2 MPa, in the absence of water stress. Root elongation is halved by matric potentials drier than about -0.5 MPa in the absence of mechanical impedance. The likelihood of each stress limiting root elongation is discussed in relation to the soil strength characteristics of arable soils. A survey of 19 soils, with textures ranging from loamy sand to silty clay loam, found that ∼10% of penetration resistances were >2 MPa at a matric potential of -10 kPa, rising to nearly 50% >2 MPa at - 200 kPa. This suggests that mechanical impedance is often a major limitation to root elongation in these soils even under moderately wet conditions, and is important to consider in breeding programmes for drought-resistant crops. Root tip traits that may improve root penetration are considered with respect to overcoming the external (soil) and internal (cell wall) pressures resisting elongation. The potential role of root hairs in mechanically anchoring root tips is considered theoretically, and is judged particularly relevant to roots growing in biopores or from a loose seed bed into a compacted layer of soil.

  19. Responses to combined abiotic and biotic stress in tomato are governed by stress intensity and resistance mechanism.

    Science.gov (United States)

    Kissoudis, Christos; Sunarti, Sri; van de Wiel, Clemens; Visser, Richard G F; van der Linden, C Gerard; Bai, Yuling

    2016-09-01

    Stress conditions in agricultural ecosystems can occur at variable intensities. Different resistance mechanisms against abiotic stress and pathogens are deployed by plants. Thus, it is important to examine plant responses to stress combinations under different scenarios. Here, we evaluated the effect of different levels of salt stress ranging from mild to severe (50, 100, and 150mM NaCl) on powdery mildew resistance and overall performance of tomato introgression lines with contrasting levels of partial resistance, as well as near-isogenic lines (NILs) carrying the resistance gene Ol-1 (associated with a slow hypersensitivity response; HR), ol-2 (an mlo mutant associated with papilla formation), and Ol-4 (an R gene associated with a fast HR). Powdery mildew resistance was affected by salt stress in a genotype- and stress intensity-dependent manner. In susceptible and partial resistant lines, increased susceptibility was observed under mild salt stress (50mM) which was accompanied by accelerated cell death-like senescence. In contrast, severe salt stress (150mM) reduced disease symptoms. Na(+) and Cl(-) accumulation in the leaves was linearly related to the decreased pathogen symptoms under severe stress. In contrast, complete resistance mediated by ol-2 and Ol-4 was unaffected under all treatment combinations, and was associated with a decreased growth penalty. Increased susceptibility and senescence under combined stress in NIL-Ol-1 was associated with the induction of ethylene and jasmonic acid pathway genes and the cell wall invertase gene LIN6. These results highlight the significance of stress severity and resistance type on the plant's performance under the combination of abiotic and biotic stress.

  20. induction of oxidative stress and antioxidative mechanisms in ...

    African Journals Online (AJOL)

    Prof. Adipala Ekwamu

    malondialdehyde, ascorbate, proline, soluble sugars, putrescine and spermidine were elevated in both tissues, ... indicates a dynamic action similar to other stress factors. ... leakage of electrons onto molecular oxygen from ... Model No. 128).

  1. [Molecular mechanism of accelerating ageing by oxidative stress].

    Science.gov (United States)

    Yoshikawa, Toshikazu; Naito, Yuji

    2009-07-01

    Reactive oxygen species are important for many life sustaining processes of cells and tissues, but they can also induce cell damage and death. If their production and levels within cells are not effectively controlled, then the detrimental effects of oxidative stress can accumulate. Oxidative stress is widely thought to underpin many ageing processes, and the oxidative stress theory of ageing is one of the most widely acknowledged theories of ageing. As well as being the major source of reactive oxygen species, mitochondria are also a major site of oxidative damage. The purpose of this review is a concise and current review of the role of oxidative stress in ageing process. Emphasis is placed upon the roles of mitochondrial proton leak, the uncoupling proteins, and the anti-ageing effects of caloric restriction.

  2. Operation analysis of a Chebyshev-Pantograph leg mechanism for a single DOF biped robot

    Science.gov (United States)

    Liang, Conghui; Ceccarelli, Marco; Takeda, Yukio

    2012-12-01

    In this paper, operation analysis of a Chebyshev-Pantograph leg mechanism is presented for a single degree of freedom (DOF) biped robot. The proposed leg mechanism is composed of a Chebyshev four-bar linkage and a pantograph mechanism. In contrast to general fully actuated anthropomorphic leg mechanisms, the proposed leg mechanism has peculiar features like compactness, low-cost, and easy-operation. Kinematic equations of the proposed leg mechanism are formulated for a computer oriented simulation. Simulation results show the operation performance of the proposed leg mechanism with suitable characteristics. A parametric study has been carried out to evaluate the operation performance as function of design parameters. A prototype of a single DOF biped robot equipped with two proposed leg mechanisms has been built at LARM (Laboratory of Robotics and Mechatronics). Experimental test shows practical feasible walking ability of the prototype, as well as drawbacks are discussed for the mechanical design.

  3. Measuring Propellant Stress Relaxation Modulus Using Dynamic Mechanical Analyzer

    Science.gov (United States)

    2017-03-29

    P. N., Singh, P. P., and Bhattacharya, B., “Determination of Activation Energy of Relaxation Events in Composite Solid Propellants by Dynamic...Article 3. DATES COVERED (From - To) 04 August 2016 – 29 March 2017 4. TITLE AND SUBTITLE Measuring Propellant Stress Relaxation Modulus Using Dynamic...ERC 14. ABSTRACT A method for determining the stress relaxation master curve of solid rocket propellants was developed. The propellant was tested in

  4. Mechanism of Residual Stress Reduction in Low Alloy Steel by a Low Frequency Alternating Magnetic Treatment

    Institute of Scientific and Technical Information of China (English)

    Yanli Song; Lin Hua

    2012-01-01

    Residual stress reduction in low alloy steel by a low frequency alternating magnetic treatment and its mechanism were investigated. Experimental results revealed that average stress reductions of 20%-24% were obtained in the welded samples. Moreover, compared with the zones with lower initial stress levels, more remarkable stress reductions were obtained in the stress concentration zones. The microstructures and magnetic domains were observed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Based on the analysis of the microstructure and magnetic domain changes, the mechanism of stress reduction by the magnetic treatment has been concluded: (1) the magneto-plastic deformations mainly due to the more uniform redistribution of dislocations are the fundamental cause of stress relaxation; and (2) surface topography is also proved to affect the magnetic treatment results to some degree by influencing magnetic domains.

  5. Effect of longwall length on mechanical characteristics of surrounding rock stress shell in mining face

    Energy Technology Data Exchange (ETDEWEB)

    Guang-Xiang Xie; Lei Wang [Anhui University of Science and Technology, Huainan (China)

    2008-12-15

    The mechanical characteristics of surrounding rock stress shell in longwall mining face were studied, based on the results of in-situ measurement combined with numerical simulation, and the effect of longwall length on mechanical characteristics of surrounding rock stress shell was discovered. The results show that the mechanical characteristics of surrounding rock stress shell are influenced by the length of the face. With an increase of mining face length, the level of concentration of shell stress located in the front face and surrounding rock of roadway is amplified and the three- dimensional stress is focused in the working face. The damage lies in the head entry corner of face and the vertical displacement is reduced but horizontal displacement is enlarged. The dynamic balance of surrounding rock stress shell is improved with rational adjustment of face length. It is effective in protecting the working face and controlling strata behavior. 5 refs., 7 figs.

  6. Potentiality of Soybean Proteomics in Untying the Mechanism of Flood and Drought Stress Tolerance

    Directory of Open Access Journals (Sweden)

    Zahed Hossain

    2014-03-01

    Full Text Available Dissecting molecular pathways at protein level is essential for comprehensive understanding of plant stress response mechanism. Like other legume crops, soybean, the world’s most widely grown seed legume and an inexpensive source of protein and vegetable oil, is also extremely sensitive to abiotic stressors including flood and drought. Irrespective of the kind and severity of the water stress, soybean exhibits a tight control over the carbon metabolism to meet the cells required energy demand for alleviating stress effects. The present review summarizes the major proteomic findings related to changes in soybean proteomes in response to flood and drought stresses to get a clear insight into the complex mechanisms of stress tolerance. Furthermore, advantages and disadvantages of different protein extraction protocols and challenges and future prospects of soybean proteome study are discussed in detail to comprehend the underlying mechanism of water stress acclimation.

  7. Potentiality of Soybean Proteomics in Untying the Mechanism of Flood and Drought Stress Tolerance.

    Science.gov (United States)

    Hossain, Zahed; Komatsu, Setsuko

    2014-03-07

    Dissecting molecular pathways at protein level is essential for comprehensive understanding of plant stress response mechanism. Like other legume crops, soybean, the world's most widely grown seed legume and an inexpensive source of protein and vegetable oil, is also extremely sensitive to abiotic stressors including flood and drought. Irrespective of the kind and severity of the water stress, soybean exhibits a tight control over the carbon metabolism to meet the cells required energy demand for alleviating stress effects. The present review summarizes the major proteomic findings related to changes in soybean proteomes in response to flood and drought stresses to get a clear insight into the complex mechanisms of stress tolerance. Furthermore, advantages and disadvantages of different protein extraction protocols and challenges and future prospects of soybean proteome study are discussed in detail to comprehend the underlying mechanism of water stress acclimation.

  8. Thermo-mechanical and damage analyses of EAST carbon divertor under type-I ELMy H-mode operation

    Energy Technology Data Exchange (ETDEWEB)

    Li, W.X. [School of Nuclear Science and Technology, University of Science and Technology of China, Hefei 230026 (China); Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China); Song, Y.T. [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China); School of Nuclear Science and Technology, University of Science and Technology of China, Hefei 230026 (China); Ye, M.Y. [School of Nuclear Science and Technology, University of Science and Technology of China, Hefei 230026 (China); Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China); Peng, X.B., E-mail: pengxb@ipp.ac.cn [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China); Wu, S.T. [School of Nuclear Science and Technology, University of Science and Technology of China, Hefei 230026 (China); Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China); Qian, X.Y.; Zhu, C.C. [School of Nuclear Science and Technology, University of Science and Technology of China, Hefei 230026 (China)

    2016-04-15

    Highlights: • Type-I ELMy H-mode is one of the most severe operating environment in tokamak. • An actual time-history heat load has been used in thermo-mechanical analysis. • The analysis results are time-dependent during the whole discharge process. • The analysis could be very useful in evaluating the operational capability of the divertor. - Abstract: The lower carbon divertor has been used since 2008 in EAST, and many significant physical results, like the 410 s long pulse discharge and the 32 s H-mode operation, have been achieved. As the carbon divertor will still be used in the next few years while the injected auxiliary heating power would be increased gradually, it’s necessary to evaluate the operational capability of the carbon divertor under the heat loads during future operation. In this paper, an actual time-history heat load during type-I ELMy H-mode from EAST experiment, as one of the most severe operating environment in tokamak, has been used in the calculation and analysis. The finite element (FE) thermal and mechanical calculations have been carried out to analysis the stress and deformation of the carbon divertor during the heat loads. According to the results, the main impact on the overall temperature comes from the relative stable phase before and after the type-I ELMs and local peak load, and the transient thermal load such as type-I ELMy only has a significant effect on the surface temperature of the graphite tiles. The carbon divertor would work with high stress near the screw bolts in the current operational conditions, because of high preload and conservative frictional coefficient between the bolts and heatsink. For the future operation, new plasma facing materials (PFM) and divertor technology should be developed.

  9. Generalized space and linear momentum operators in quantum mechanics

    Energy Technology Data Exchange (ETDEWEB)

    Costa, Bruno G. da, E-mail: bruno.costa@ifsertao-pe.edu.br [Instituto Federal de Educação, Ciência e Tecnologia do Sertão Pernambucano, Campus Petrolina, BR 407, km 08, 56314-520 Petrolina, Pernambuco (Brazil); Instituto de Física, Universidade Federal da Bahia, R. Barão de Jeremoabo s/n, 40170-115 Salvador, Bahia (Brazil); Borges, Ernesto P., E-mail: ernesto@ufba.br [Instituto de Física, Universidade Federal da Bahia, R. Barão de Jeremoabo s/n, 40170-115 Salvador, Bahia (Brazil)

    2014-06-15

    We propose a modification of a recently introduced generalized translation operator, by including a q-exponential factor, which implies in the definition of a Hermitian deformed linear momentum operator p{sup ^}{sub q}, and its canonically conjugate deformed position operator x{sup ^}{sub q}. A canonical transformation leads the Hamiltonian of a position-dependent mass particle to another Hamiltonian of a particle with constant mass in a conservative force field of a deformed phase space. The equation of motion for the classical phase space may be expressed in terms of the generalized dual q-derivative. A position-dependent mass confined in an infinite square potential well is shown as an instance. Uncertainty and correspondence principles are analyzed.

  10. Heat stress management program improving worker health and operational effectiveness: a case study.

    Science.gov (United States)

    Huss, Rosalyn G; Skelton, Scott B; Alvis, Kimberly L; Shane, Leigh A

    2013-03-01

    Heat stress monitoring is a vital component of an effective health and safety program when employees work in exceptionally warm environments. Workers at hazardous waste sites often wear personal protective equipment (PPE), which increases the body heat stress load. No specific Occupational Safety and Health Administration (OSHA) regulations address heat stress; however, OSHA does provide several guidance documents to assist employers in addressing this serious workplace health hazard. This article describes a heat stress and surveillance plan implemented at a hazardous waste site as part of the overall health and safety program. The PPE requirement for work at this site, coupled with extreme environmental temperatures, made heat stress a significant concern. Occupational health nurses and industrial hygienists developed a monitoring program for heat stress designed to prevent the occurrence of significant heat-related illness in site workers. The program included worker education on the signs of heat-related illness and continuous physiologic monitoring to detect early signs of heat-related health problems. Biological monitoring data were collected before workers entered the exclusion zone and on exiting the zone following decontamination. Sixty-six site workers were monitored throughout site remediation. More than 1,700 biological monitoring data points were recorded. Outcomes included improved worker health and safety, and increased operational effectiveness.

  11. Mechanism of biaxial pre-stress method on welding residual stress and hot cracks controlling

    Institute of Scientific and Technical Information of China (English)

    LIU Xuesong; ZHOU Guangtao; WANG Ping; LIU Haoyuan; FANG Hongyuan

    2009-01-01

    Based on the conventional uniaxial pre-tensile stress method during welding, this study presents a new method of welding with biaxial pre-stress. With the help of numerical simulation, experiments were carried out on the self-designed device. Except for the control on residual stress and distortion as-welded, the experimental results also show its effect on the prevention of hot cracks, thus this method can make up for the disadvantage of the conventional pre-stress method. Hot cracks

  12. 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

  13. Renormalizing the Kinetic Energy Operator in Elementary Quantum Mechanics

    Science.gov (United States)

    Coutinho, F. A. B.; Amaku, M.

    2009-01-01

    In this paper, we consider solutions to the three-dimensional Schrodinger equation of the form [psi](r) = u(r)/r, where u(0) [is not equal to] 0. The expectation value of the kinetic energy operator for such wavefunctions diverges. We show that it is possible to introduce a potential energy with an expectation value that also diverges, exactly…

  14. Renormalizing the Kinetic Energy Operator in Elementary Quantum Mechanics

    Science.gov (United States)

    Coutinho, F. A. B.; Amaku, M.

    2009-01-01

    In this paper, we consider solutions to the three-dimensional Schrodinger equation of the form [psi](r) = u(r)/r, where u(0) [is not equal to] 0. The expectation value of the kinetic energy operator for such wavefunctions diverges. We show that it is possible to introduce a potential energy with an expectation value that also diverges, exactly…

  15. Stress coping mechanisms in patients with chronic dermatoses

    Directory of Open Access Journals (Sweden)

    Korabel, Hanna

    2013-09-01

    Full Text Available Objective. The results of numerous studies of today confirm that persons suffering from psychosomatic disorders are not able to effectively cope with stress. The experience of stress is also frequently combined with the occurrence or aggravation of various skin diseases. The goal of our study was to identify the predominantways of coping with stress in the group of patients with chronic dermatoses.Methods. The group under study included patients receiving treatment in the Dermatology Clinic of Collegium Medicum, Jagiellonian University. They were either hospitalized patients or those who came for control examinations at the Outpatient Clinic. Evaluation of the forms of coping with stress was conducted with the help of the Endler and Parker Questionnaire – CISS.Results. They significantly more often apply the style of coping focused on avoiding (p-value= 0.0056. It also turned out that the patients in the dermatological groups manifested a constant tendency to get involved in vicarious activities (p-value=0.0247.Discussion. The results of the presented study indicate that there is a statistically significant difference between the patients with dermatological disorders and those in the control group as regards their ways of coping with stress.Conclusion. The results obtained in the discussed study may be a starting point for designing a complex support for the patients with skin diseases. The therapeutic technique that may prove helpful for this group of patients is the cognitive-behavioral therapy (CTB.

  16. Mechanical factors in primary water stress corrosion cracking of cold-worked stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Hammadi, Rashid Al, E-mail: rashid.alhammadi@fanr.gov.ae [Nuclear Security Division, Federal Authority for Nuclear Regulation, Abu Dhabi (United Arab Emirates); Yi, Yongsun, E-mail: yongsun.yi@kustar.ac.ae [Department of Nuclear Engineering, Khalifa University, Abu Dhabi (United Arab Emirates); Zaki, Wael, E-mail: wael.zaki@kustar.ac.ae [Department of Mechanical Engineering, Khalifa University, Abu Dhabi (United Arab Emirates); Cho, Pyungyeon, E-mail: pyungyeon.cho@kustar.ac.ae [Department of Nuclear Engineering, Khalifa University, Abu Dhabi (United Arab Emirates); Jang, Changheui, E-mail: chjang@kaist.ac.kr [Nuclear and Quantum Engineering Department, Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of)

    2016-05-15

    Highlights: • PWSCC of cold-worked austenitic stainless steel was studied. • Finite element analysis was performed on a compact tension specimen. • Mechanical fields near a crack tip were evaluated using FEA. • The dependence of mechanical factors on K{sub I} and yield stress was investigated. • The crack tip normal stress was identified as a main factor controlling PWSCC. - Abstract: Finite element analysis was performed on a compact tension specimen to determine the stress and strain distributions near a crack tip. Based on the results, the crack tip stain rates by crack advance and creep rates near crack tip were estimated. By comparing the dependence of the mechanical factors on the stress intensity factor and yield stress with that of the SCC crack growth rates, it was tried to identify the main mechanical factor for the primary water stress corrosion cracking (PWSCC) of cold-worked austenitic stainless steels. The analysis results showed that the crack tip normal stress could be the main mechanical factor controlling the PWSCC, suggesting that the internal oxidation mechanism might be the most probable PWSCC mechanism of cold-worked austenitic stainless steels.

  17. Arbitrary multimode Gaussian operations on mechanical cluster states

    Science.gov (United States)

    Moore, Darren W.; Houhou, Oussama; Ferraro, Alessandro

    2017-08-01

    We consider opto- and electromechanical quantum systems composed of a driven cavity mode interacting with a set of mechanical resonators. It has been proposed that the latter can be initialized in arbitrary cluster states, including universal resource states for measurement-based quantum computation (MBQC). We show that, despite the unavailability in this setup of direct measurements over the mechanical resonators, computation can still be performed to a high degree of accuracy. In particular, it is possible to indirectly implement the measurements necessary for arbitrary Gaussian MBQC by properly coupling the mechanical resonators to the cavity field and continuously monitoring the leakage of the latter. We provide a thorough theoretical analysis of the performances obtained via indirect measurements, comparing them with what is achievable when direct measurements are instead available. We show that high levels of fidelity are attainable in parameter regimes within reach of present experimental capabilities.

  18. Arcsecond grating drive mechanism for operation at 4 K

    Science.gov (United States)

    Downey, C. H.; Kubitschek, M. J.; Tarde, R. W.; Houck, J. R.

    1991-12-01

    A grating drive mechanism that achieves arcsecond positional control at both room temperature and 4 K is described. The mechanism accommodates eight equally spaced facets on a 360-deg drum, with each facet having arcsecond control over an angular range of +/-3 deg. The cryogenic portion consists of dry lubricated angular contact bearings, a dc brushless torque motor, and a compact magnetic position sensor capable of less than 1 arcsec rms resolution. Test results demonstrate angular repeatability of less than 2 arcsec rms at 4 K and static power dissipation to the helium bath of less than 100 microW.

  19. Relaxation phenomena of electrical signal emissions from rock following application of abrupt mechanical stress

    Directory of Open Access Journals (Sweden)

    George Hloupis

    2012-04-01

    Full Text Available

    The emission of electrical signals during application of mechanical stress to brittle geo-materials (the so-called pressure-stimulated current; PSC can provide significant information regarding the mechanical status of a studied rock sample. PSCs originate as a result of the opening of cracks and microfractures in rock. In this study, such electrical signal emissions are detected and studied when rock samples are subjected to step-wise mechanical stress, increased from low stress levels vL up to higher stress levels vH. This increase is performed at high stress rates and consequently the stress is maintained practically constant for a long period. During this time, the applied stress reaches its maximum value, and the emitted PSC decays gradually and relaxes back to a minimum value. The conducted experiments suggest that the characteristics of the relaxation processes of the PSC depend directly on the high level of the applied stress that is maintained constant after the application of each stress step. Analysis of the macroscopic parameters that characterize the relaxation phenomenon of the PSC provides clear information regarding the proximity of the applied stress to the fracture limit of the rock sample.

  20. Simulation of Mechanical Stress on Stainless Steel for Pb-Bi Corrosion Test by Using ABAQUS

    Science.gov (United States)

    Irwanto, D.; Mustari, A. P. A.; Budiman, B. A.

    2017-03-01

    Pb-Bi eutectic with its advantageous is proposed to be utilized as a coolant in the GEN IV type of rSeactor. However, high temperature corrosion when contact with stainless steels is one of the issues of Pb-Bi eutectic utilization. It is known that in the environment of high temperature Pb-Bi, mechanical strength of stainless steel may decrease. Thus, simulation of mechanical stress working on stainless steel during in-situ bending test by using ABAQUS was conducted. Several bending degrees were simulated at high temperature to obtain the mechanical stress information. Temperature condition was strongly affect the stress vs. displacement profile. The reported mechanical strength reduction percentage was used to draw predicted mechanical stress under high temperature Pb-Bi environment.

  1. Skeletal muscle adaptation in response to mechanical stress in p130cas-/- mice.

    Science.gov (United States)

    Akimoto, Takayuki; Okuhira, Kanako; Aizawa, Katsuji; Wada, Shogo; Honda, Hiroaki; Fukubayashi, Toru; Ushida, Takashi

    2013-03-01

    Mammalian skeletal muscles undergo adaptation in response to changes in the functional demands upon them, involving mechanical-stress-induced cellular signaling called "mechanotransduction." We hypothesized that p130Cas, which is reported to act as a mechanosensor that transduces mechanical extension into cellular signaling, plays an important role in maintaining and promoting skeletal muscle adaptation in response to mechanical stress via the p38 MAPK signaling pathway. We demonstrate that muscle-specific p130Cas-/- mice express the contractile proteins normally in skeletal muscle. Furthermore, muscle-specific p130Cas-/- mice show normal mechanical-stress-induced muscle adaptation, including exercise-induced IIb-to-IIa muscle fiber type transformation and hypertrophy. Finally, we provide evidence that exercise-induced p38 MAPK signaling is not impaired by the muscle-specific deletion of p130Cas. We conclude that p130Cas plays a limited role in mechanical-stress-induced skeletal muscle adaptation.

  2. Mechanical Transformation of Task Heuristics into Operational Procedures

    Science.gov (United States)

    1981-04-14

    specified form. Given a mechanism for performing such a search, the ability to solve a particula kind of problem can be dramatically improved just by...oIStRIBUTE by RULE1A2) ---> (OR f, IDE OS) DECK] (. (tOC QS) POT] (, (LOC OS) HOLE] E’ (LOC QS) ( NANO ME)]) (OR (OR (I (LOC OS) DECE] Et (LOC QS

  3. 16 CFR 703.5 - Operation of the Mechanism.

    Science.gov (United States)

    2010-01-01

    ... consumer that: (i) The dispute has been settled to the consumer's satisfaction; and (ii) The settlement... of a dispute, the Mechanism shall immediately inform both the warrantor and the consumer of receipt..., and to what extent, warrantor will abide by its decision; and (4) Disclose to the consumer...

  4. The operational mechanism of ferroelectric-driven organic resistive switches

    NARCIS (Netherlands)

    Kemerink, M.; Asadi, K.; Blom, P.W.M.; Leeuw, D.M. de

    2012-01-01

    The availability of a reliable memory element is crucial for the fabrication of 'plastic' logic circuits. We use numerical simulations to show that the switching mechanism of ferroelectric-driven organic resistive switches is the stray field of the polarized ferroelectric phase. The stray field modu

  5. Yielding to Stress: Recent Developments in Viscoplastic Fluid Mechanics

    Science.gov (United States)

    Balmforth, Neil J.; Frigaard, Ian A.; Ovarlez, Guillaume

    2014-01-01

    The archetypal feature of a viscoplastic fluid is its yield stress: If the material is not sufficiently stressed, it behaves like a solid, but once the yield stress is exceeded, the material flows like a fluid. Such behavior characterizes materials common in industries such as petroleum and chemical processing, cosmetics, and food processing and in geophysical fluid dynamics. The most common idealization of a viscoplastic fluid is the Bingham model, which has been widely used to rationalize experimental data, even though it is a crude oversimplification of true rheological behavior. The popularity of the model is in its apparent simplicity. Despite this, the sudden transition between solid-like behavior and flow introduces significant complications into the dynamics, which, as a result, has resisted much analysis. Over recent decades, theoretical developments, both analytical and computational, have provided a better understanding of the effect of the yield stress. Simultaneously, greater insight into the material behavior of real fluids has been afforded by advances in rheometry. These developments have primed us for a better understanding of the various applications in the natural and engineering sciences.

  6. The mechanisms behind stress: from populations to genes in nematodes

    NARCIS (Netherlands)

    Alda Alvarez, O.

    2006-01-01

    The increasing presence of abiotic stress factors in ecosystems over the past few decades has become an issue of major concern. The growing awareness of the detrimental effects that processes such as climatic change or chemical contamination can have on ecosystems and the species that inhabit them

  7. The mechanisms behind stress: from populations to genes in nematodes

    NARCIS (Netherlands)

    Alda Alvarez, O.

    2006-01-01

    The increasing presence of abiotic stress factors in ecosystems over the past few decades has become an issue of major concern. The growing awareness of the detrimental effects that processes such as climatic change or chemical contamination can have on ecosystems and the species that inhabit them h

  8. Mechanisms of Nanoparticle-Induced Oxidative Stress and Toxicity

    Directory of Open Access Journals (Sweden)

    Amruta Manke

    2013-01-01

    Full Text Available The rapidly emerging field of nanotechnology has offered innovative discoveries in the medical, industrial, and consumer sectors. The unique physicochemical and electrical properties of engineered nanoparticles (NP make them highly desirable in a variety of applications. However, these novel properties of NP are fraught with concerns for environmental and occupational exposure. Changes in structural and physicochemical properties of NP can lead to changes in biological activities including ROS generation, one of the most frequently reported NP-associated toxicities. Oxidative stress induced by engineered NP is due to acellular factors such as particle surface, size, composition, and presence of metals, while cellular responses such as mitochondrial respiration, NP-cell interaction, and immune cell activation are responsible for ROS-mediated damage. NP-induced oxidative stress responses are torch bearers for further pathophysiological effects including genotoxicity, inflammation, and fibrosis as demonstrated by activation of associated cell signaling pathways. Since oxidative stress is a key determinant of NP-induced injury, it is necessary to characterize the ROS response resulting from NP. Through physicochemical characterization and understanding of the multiple signaling cascades activated by NP-induced ROS, a systemic toxicity screen with oxidative stress as a predictive model for NP-induced injury can be developed.

  9. Contact mechanical analysis of O-ring stresses

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Hyung Kyu

    2007-02-15

    The purpose of this project is to develop the approximate solutions of contact traction and internal stress of an O-ring by using a two dimensional elasticity for enhancing the design and failure prediction technology. Investigated were the applicability of Lindley's formulae of contact force prediction and the Hertz theory. Three cases of O-ring installation were considered. The approximate solution of contact tractions and internal stresses of each case were derived. The key results are summarized as follows: 1. It is verified that Lindley's formulae predicts the relationship between the fractional compression and contact force. 2. In the case of Case I, II and III without internal pressure, it is found that a function form of the contact traction is the Hertzian. So it is possible to express the traction with a Hertzian form and correction factors. 3. The internal stresses are derived in the case of the Hertzian traction profile. The stresses at the center of O-ring show a satisfactory result when compared with the finite element result.

  10. Mechanically induced martensitic transformation as a stress driven process

    NARCIS (Netherlands)

    Geijselaers, Hubertus J.M.; Perdahcioglu, Emin Semih

    2009-01-01

    Combined shear-tension tests at room temperature performed on a 12Cr9Ni4Mo low carbon austenitic stainless steel have been reviewed and evaluated under the assumption that the martensitic transformation is exclusively stress driven. It is shown that the start of the transformation is very well

  11. Stress predictions in a Francis turbine at no-load operating regime

    Science.gov (United States)

    Morissette, JF; Chamberland-Lauzon, J.; Nennemann, B.; Monette, C.; Giroux, AM; Coutu, A.; Nicolle, J.

    2016-11-01

    In the operation of hydraulic turbines, no-load and very low load conditions are among the most damaging. Even though there is no power generation, there is still a significant amount of energy which has to be entirely dissipated, mainly in the runner, where the flow is quite complex, with large scale unsteady and chaotic vortices resulting from partial pumping. This paper presents different approaches to perform stress analyses at low load conditions on a Francis turbine, taking into account the pressure fluctuations on the runner blades due to the large stochastic flow structures inherent in no-load operating regimes. With appropriate mesh density and time step, unsteady computational fluid dynamics (CFD) simulations using the SAS-SST turbulence model can be used on a Francis runner to predict the pressure fluctuations with reasonable accuracy when compared to measurements. These calculated pressure loads can then be used to predict the dynamic stresses with finite-element analyses (FEA). Different approaches are discussed ranging from quasi-static single-blade models to full runner time- dependent one-way fluid-structure interaction (FSI). Pros and cons of the different modelling strategies will be discussed in a detailed analysis of the structural results with comparisons to experimental data. Once the time signal of the stochastic stress at no-load conditions is obtained, the runner fatigue damage related to this operating condition can be estimated using different tools such as time signal extrapolation and rainflow counting.

  12. Tissue-specific defense and thermo-adaptive mechanisms of soybean seedlings under heat stress revealed by proteomic approach.

    Science.gov (United States)

    Ahsan, Nagib; Donnart, Tifenn; Nouri, Mohammad-Zaman; Komatsu, Setsuko

    2010-08-06

    A comparative proteomic approach was employed to explore tissue-specific protein expression patterns in soybean seedlings under heat stress. The changes in the protein expression profiles of soybean seedling leaves, stems, and roots were analyzed after exposure to high temperatures. A total of 54, 35, and 61 differentially expressed proteins were identified from heat-treated leaves, stems, and roots, respectively. Differentially expressed heat shock proteins (HSPs) and proteins involved in antioxidant defense were mostly up-regulated, whereas proteins associated with photosynthesis, secondary metabolism, and amino acid and protein biosynthesis were down-regulated in response to heat stress. A group of proteins, specifically low molecular weight HSPs and HSP70, were up-regulated and expressed in a similar manner in all tissues. Proteomic analysis indicated that the responses of HSP70, CPN-60 beta, and ChsHSP were tissue specific, and this observation was validated by immunoblot analysis. The heat-responsive sHSPs were not induced by other stresses such as cold and hydrogen peroxide. Taken together, these results suggest that to cope with heat stress soybean seedlings operate tissue-specific defenses and adaptive mechanisms, whereas a common defense mechanism associated with the induction of several HSPs was employed in all three tissues. In addition, tissue-specific proteins may play a crucial role in defending each type of tissues against thermal stress.

  13. Understanding Abiotic Stress Tolerance Mechanisms: Recent Studies on Stress Response in Rice

    Institute of Scientific and Technical Information of China (English)

    Ji-Ping Gao; Dai-Yin Chao; Hong-Xuan Lin

    2007-01-01

    Abiotic stress is the main factor negatively affecting crop growth and productivity worldwide. The advances in physiology, genetics, and molecular biology have greatly improved our understanding of plant responses to stresses. Rice plants are sensitive to various abiotic stresses. In this short review, we present recent progresses in adaptation of rice to salinity, water deficit and submergence. Many studies show that salt tolerance is tightly associated with the ability to maintain ion homeostasis under salinity. Na+ transporter SKC1 unloads NaMrom xylem, plasma membrane NaVHTantiporter SOS1 excludes sodium out of cytosol and tonoplast Na+/H+antiporter NHX1 sequesters Na+ into the vacuole. Silicon deposition in exodermis and endodermis of rice root reduces sodium transport through the apoplastic pathway. A number of transcription factors regulate stress-inducible gene expression that leads to initiating stress responses and establishing plant stress tolerance. Overexpression of some transcription factors, including DREB/CBF and MAC, enhances salt, drought, and cold tolerance in rice. A variant of one of ERF family genes, Sub1A-1, confers immersion tolerance to lowland rice. These findings and their exploitation will hold promise for engineering breeding to protect crop plants from certain abiotic stresses.

  14. Intelligent Control Mechanism of Part Picking Operations of Automated Warehouse

    Institute of Scientific and Technical Information of China (English)

    Chwen-Tzeng; Su

    2002-01-01

    This paper studies the part picking operations of a ut omated warehouse. It assumed the demand of picking orders of automated warehouse are dynamic generated. Once the picking orders of certain period of time are kn own, it is necessary to decide an efficient order picking sequence and routing t o minimize the total travel distance to complete those orders. Assumed there are n i items to be picked in order O i. Each item in the picking ord er is located in different locations in the warehouse. Since i...

  15. Renormalizing the kinetic energy operator in elementary quantum mechanics

    Energy Technology Data Exchange (ETDEWEB)

    Coutinho, F A B [Faculdade de Medicina, Universidade de Sao Paulo e LIM 01-HCFMUSP, 05405-000 Sao Paulo (Brazil); Amaku, M [Faculdade de Medicina Veterinaria e Zootecnia, Universidade de Sao Paulo, 05508-970 Sao Paulo (Brazil)], E-mail: coutinho@dim.fm.usp.br

    2009-09-15

    In this paper, we consider solutions to the three-dimensional Schroedinger equation of the form {psi}(r) = u(r)/r, where u(0) {ne} 0. The expectation value of the kinetic energy operator for such wavefunctions diverges. We show that it is possible to introduce a potential energy with an expectation value that also diverges, exactly cancelling the kinetic energy divergence. This renormalization procedure produces a self-adjoint Hamiltonian. We solve some problems with this new Hamiltonian to illustrate its usefulness.

  16. Electronics: Mott Transistor: Fundamental Studies and Device Operation Mechanisms

    Science.gov (United States)

    2016-03-21

    hopping transport . It is well known that localized states exist in the forbidden gap of doped semiconductors /disordered insulators. For a semiconductor , σ... semiconductors and their response to electric fields. This is relevant to their eventual use as advanced semiconductors in microwave devices or high speed...transistors where collective effects are exploited to design switches.The report presents our progress in studying electron transport mechanisms in

  17. Research on Mechanism of Rock Burst Generation and Development for High Stress Rock Tunnels

    Institute of Scientific and Technical Information of China (English)

    高全臣; 赫建明; 王代华

    2001-01-01

    Through the investigation and analysis of high stress distribution in surrounding rock during the excavation of rock tunnels,the key factors to cause rock burst and the mechanism of rock burst generation and development are researched. The result shows that the scale and range of rock burst are related with elastic deformation energy storied in rock mass and the characteristics of unloading stress waves. The measures of preventing from rock burst for high stress rock tunnels are put forward.

  18. Multiscale stress field inversion in the crust from focal mechanism datasets

    Science.gov (United States)

    Massa, Bruno; D'Auria, Luca; Cristiano, Elena; De Matteo, Ada

    2016-04-01

    Earthquake focal mechanisms are an important tool to study spatial and temporal patterns of the stress field within the lithosphere. Nowadays various techniques are able to exploit focal mechanisms dataset to retrieve the orientation of the principal stress tensor axes and a ratio of their respective magnitudes (Bishop's ratio). However these techniques rely on the assumption of a homogeneous stress field responsible for the earthquakes. Within the Earth's lithosphere the stress field is highly variable depending on the geodynamic context, heterogeneities of the mechanical properties and time-varying perturbations (earthquakes, volcanic processes). Various methods have been devised to effectively capture the complexity of the stress field. An important category relies on a clustering approach to identify different contributions to the heterogeneous dataset. However these techniques are effective only when the different stress field components are not so many and are well separated. Other techniques are more appropriated when dealing with smooth varying stress fields. They rely on a damped linearized inversion on a grid and allow imaging the spatial variations in the stress field. We propose a novel approach based on a space-time 4D Discrete Wavelet representation of the stress field. The usage of Discrete Wavelets provides a natural framework to capture the multiscale nature of the stress field. We parameterize the spatial and temporal distribution of the stress field parameters using 4D wavelets, selecting only those constrained by a sufficient numbers of focal mechanisms. This allows reducing the computational efforts of the inverse methods, keeping a greater level of details in regions/intervals more constrained by the data. Using a linearized damped inverse method we are able retrieve the spatial and temporal pattern of the stress field simultaneously at different scales. We show the performances of the method using both synthetic tests as well as example

  19. Impaired Functional Connectivity in the Prefrontal Cortex: A Mechanism for Chronic Stress-Induced Neuropsychiatric Disorders

    Science.gov (United States)

    Negrón-Oyarzo, Ignacio; Aboitiz, Francisco; Fuentealba, Pablo

    2016-01-01

    Chronic stress-related psychiatric diseases, such as major depression, posttraumatic stress disorder, and schizophrenia, are characterized by a maladaptive organization of behavioral responses that strongly affect the well-being of patients. Current evidence suggests that a functional impairment of the prefrontal cortex (PFC) is implicated in the pathophysiology of these diseases. Therefore, chronic stress may impair PFC functions required for the adaptive orchestration of behavioral responses. In the present review, we integrate evidence obtained from cognitive neuroscience with neurophysiological research with animal models, to put forward a hypothesis that addresses stress-induced behavioral dysfunctions observed in stress-related neuropsychiatric disorders. We propose that chronic stress impairs mechanisms involved in neuronal functional connectivity in the PFC that are required for the formation of adaptive representations for the execution of adaptive behavioral responses. These considerations could be particularly relevant for understanding the pathophysiology of chronic stress-related neuropsychiatric disorders. PMID:26904302

  20. Impaired Functional Connectivity in the Prefrontal Cortex: A Mechanism for Chronic Stress-Induced Neuropsychiatric Disorders

    Directory of Open Access Journals (Sweden)

    Ignacio Negrón-Oyarzo

    2016-01-01

    Full Text Available Chronic stress-related psychiatric diseases, such as major depression, posttraumatic stress disorder, and schizophrenia, are characterized by a maladaptive organization of behavioral responses that strongly affect the well-being of patients. Current evidence suggests that a functional impairment of the prefrontal cortex (PFC is implicated in the pathophysiology of these diseases. Therefore, chronic stress may impair PFC functions required for the adaptive orchestration of behavioral responses. In the present review, we integrate evidence obtained from cognitive neuroscience with neurophysiological research with animal models, to put forward a hypothesis that addresses stress-induced behavioral dysfunctions observed in stress-related neuropsychiatric disorders. We propose that chronic stress impairs mechanisms involved in neuronal functional connectivity in the PFC that are required for the formation of adaptive representations for the execution of adaptive behavioral responses. These considerations could be particularly relevant for understanding the pathophysiology of chronic stress-related neuropsychiatric disorders.

  1. Thermal mechanical stress modeling of GCtM seals

    Energy Technology Data Exchange (ETDEWEB)

    Dai, Steve Xunhu [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States); Chambers, Robert [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States)

    2015-09-01

    Finite-element thermal stress modeling at the glass-ceramic to metal (GCtM) interface was conducted assuming heterogeneous glass-ceramic microstructure. The glass-ceramics were treated as composites consisting of high expansion silica crystalline phases dispersed in a uniform residual glass. Interfacial stresses were examined for two types of glass-ceramics. One was designated as SL16 glass -ceramic, owing to its step-like thermal strain curve with an overall coefficient of thermal expansion (CTE) at 16 ppm/ºC. Clustered Cristobalite is the dominant silica phase in SL16 glass-ceramic. The other, designated as NL16 glass-ceramic, exhibited clusters of mixed Cristobalite and Quartz and showed a near-linear thermal strain curve with a same CTE value.

  2. Surface stress relaxation of oxide glasses: The effects on mechanical strength

    Science.gov (United States)

    Lezzi, Peter Joseph

    A new glass strengthening mechanism based upon surface compressive stress formation by surface stress relaxation of glasses that were held under a tensile stress, at a temperature lower than the glass transition temperature, in low water vapor pressure, has been demonstrated. Although glass fibers are traditionally known to become mechanically weaker when heat-treated at a temperature lower than the glass transition temperature in the presence of water vapor, the strength was found to become greater than the as-received fiber strength when fibers were subjected to a sub-critical tensile stress during heat-treatment. The observed strengthening was attributed to surface compressive residual stress formation through surface stress relaxation during the sub-critical tensile stress application in the atmosphere containing water vapor. Surface stress relaxation of the same glass fibers was shown to take place under conditions identical to those experienced by the strengthened mechanical test specimens by observing permanent bending of the fiber. Furthermore, the magnitude and presence of the residual stresses formed during bending or tensile heat-treatments were confirmed by FTIR, fiber etching, and fiber slicing methods. The method can in principle be used to strengthen any oxide glass and is not subjected to the constraints of traditional strengthening methods such as a minimum thickness for tempering, or a glass containing alkali ions for ion-exchange. Thus far, the method has been successful in strengthening silica glass, E-glass, and soda-lime silicate glass by approximately 20-30%.

  3. Mechanisms of Aerobic Performance Impairment With Heat Stress and Dehydration

    Science.gov (United States)

    2010-08-01

    uptake ( VO2max ), which leads to higher relative exercise intensity and an exponential decline in aerobic performance at any given exercise workload...reductions, which combine to accentuate cardiovascular strain and reduce VO2max . Importantly, the negative performance consequences of dehydration...environmental heat stress on aerobic exercise “performance” has been evaluated using time to exhaustion (TTE) tests (incremental or constant work rate) and

  4. Adaptive translation as a mechanism of stress response and adaptation

    OpenAIRE

    Pan, Tao

    2013-01-01

    The composition of the cellular proteome is commonly thought to strictly adhere to the genetic code. However, accumulating evidence indicates that cells also regulate the synthesis of mutant protein molecules that deviate from the genetic code. Production of mutant proteins varies in amounts and specificity and generally occurs when cells are stressed or undergo environmental adaptation. The deliberate synthesis of protein mutants suggests that some of these proteins can be useful in cellular...

  5. Emotion Dysregulation as a Mechanism Linking Stress Exposure to Adolescent Aggressive Behavior

    Science.gov (United States)

    Herts, Kate L.; McLaughlin, Katie A.; Hatzenbuehler, Mark L.

    2012-01-01

    Exposure to stress is associated with a wide range of internalizing and externalizing problems in adolescents, including aggressive behavior. Extant research examining mechanisms underlying the associations between stress and youth aggression has consistently identified social information processing pathways that are disrupted by exposure to…

  6. SPENCER OPERATOR AND APPLICATIONS: From Continuum Mechanics to Mathematical physics

    OpenAIRE

    Pommaret, J.F.

    2011-01-01

    Though a few of the results presented are proved in the recent references provided, the way they are combined with others and patched together around the three books quoted is new. In view of the importance of the full paper, the present version is only a summary of the definitive version to appear later on. Finally, the reader must not forget that "each formula" appearing in this new general framework has been used explicitly or implicitly in (C), (M) and (W) for a mechanical, mathematical o...

  7. Critical review on the mechanisms of maturation stress generation in trees

    Science.gov (United States)

    Clair, Bruno

    2016-01-01

    Trees control their posture by generating asymmetric mechanical stress around the periphery of the trunk or branches. This stress is produced in wood during the maturation of the cell wall. When the need for reaction is high, it is accompanied by strong changes in cell organization and composition called reaction wood, namely compression wood in gymnosperms and tension wood in angiosperms. The process by which stress is generated in the cell wall during its formation is not yet known, and various hypothetical mechanisms have been proposed in the literature. Here we aim at discriminating between these models. First, we summarize current knowledge about reaction wood structure, state and behaviour relevant to the understanding of maturation stress generation. Then, the mechanisms proposed in the literature are listed and discussed in order to identify which can be rejected based on their inconsistency with current knowledge at the frontier between plant science and mechanical engineering. PMID:27605169

  8. Mechanisms underlying the effects of prenatal psychosocial stress on child outcomes: beyond the HPA axis

    NARCIS (Netherlands)

    Beijers, R.; Buitelaar, J.K.; Weerth, C. de

    2014-01-01

    Accumulating evidence from preclinical and clinical studies indicates that maternal psychosocial stress and anxiety during pregnancy adversely affect child outcomes. However, knowledge on the possible mechanisms underlying these relations is limited. In the present paper, we review the most often

  9. Critical review on the mechanisms of maturation stress generation in trees.

    Science.gov (United States)

    Alméras, Tancrède; Clair, Bruno

    2016-09-01

    Trees control their posture by generating asymmetric mechanical stress around the periphery of the trunk or branches. This stress is produced in wood during the maturation of the cell wall. When the need for reaction is high, it is accompanied by strong changes in cell organization and composition called reaction wood, namely compression wood in gymnosperms and tension wood in angiosperms. The process by which stress is generated in the cell wall during its formation is not yet known, and various hypothetical mechanisms have been proposed in the literature. Here we aim at discriminating between these models. First, we summarize current knowledge about reaction wood structure, state and behaviour relevant to the understanding of maturation stress generation. Then, the mechanisms proposed in the literature are listed and discussed in order to identify which can be rejected based on their inconsistency with current knowledge at the frontier between plant science and mechanical engineering.

  10. Mechanical Stress Results in Immediate Accumulation of Glucosinolates in Fresh-Cut Cabbage

    National Research Council Canada - National Science Library

    Požrl, Tomaž; Cigić, Blaž; Demšar, Lea; Hribar, Janez; Polak, Tomaž

    2015-01-01

    The intensity of mechanical stress and the temperature significantly affect the levels of individual and total glucosinolates in shredded white cabbage (cv. Galaxy). Mild processing (shredding to 2 mm thickness) at 8...

  11. Study on the control mechanism of China aerospace enterprises' binary multinational operation

    Institute of Scientific and Technical Information of China (English)

    Wang Jian; Li Hanling; Wu Weiwei

    2008-01-01

    China's aerospace enterprises carry on the multinational operation and participate in the international competition and the international division of labor and cooperation positively.This article first analyzs China aerospace enterprises' binary multinational business control objective and constructes its model.Then the article analyzes the tangible and intangible control mechanism of China aerospace enterprises' binary multinational operation respectively.Finally,the article constructs the model of China aerospace enterprises' binary multinational operation mechanisms.

  12. The Effect of Mechanical Combined Contact Stress with Buckling Load on the Stress Distribution in the Ball and SocketJoint Mechanism

    Directory of Open Access Journals (Sweden)

    Fatima Salman

    2010-01-01

    Full Text Available The design of components subjected to contact stress as local compressive stress is important in engineering application especially in ball and socket Joining. Two kinds of contact stress are introduced in the ball and socket joint, the first is from normal contact while the other is from sliding contact. Although joining two long links (drive shaft in steering cars will cause the effect of flexural and tensional buckling stress in hollow columns through the ball and socket ends on the failure condition of the joining mechanism. In this paper the consideration of the combined effect of buckling Load and contact stress on the ball and socket joints have been taken, epically on the stress distribution in the contact area. Different parameters have been taken in the design of joint. This is done by changing the angles for applied loads with the principle axis, the angle of contact between ball and socket and using different applied loads. The problem has been solved using analytical solution for computing the critical loads and using these loads for calculating the stress distribution with finite element method using ANSYS 10. The numerical results have been compared with the experimental method using photo elasticity pattern which shows good agreement between experimental and simulation results.

  13. Source mechanism of small-moderate earthquakes and tectonic stress field in Yunnan Province

    Institute of Scientific and Technical Information of China (English)

    吴建平; 明跃红; 王椿镛

    2004-01-01

    In the paper, source mechanisms of 33 small-moderate earthquakes occurred in Yunnan are determined by modeling of regional waveforms from Yunnan digital seismic network. The result shows that most earthquakes occurred within or near the Chuandian rhombic block have strike-slip mechanism. The orientations of maximum compressive stresses obtained from source mechanism are changed from NNW-SSN to NS in the areas from north to south of the block, and tensile stresses are mainly in ENE-WSW or NE-SE. In the eastern Tibetan Plateau, the orientations of maximum compressive stress radiate toward outside from the plateau, and the tensile stress orientations mostly parallel to arc structures. Near 28°N the orientations of both maximum compressive stress and tensile stress changed greatly, and the boundary seems to correspond to the southwestern extended line of Longmenshan fault. Outside of the Chuandian rhombic block, the orientations of P and T axes are some different from those within the block. The comparison shows that the source mechanism of small-moderate events presented in the paper is consistence with that of moderate-strong earthquakes determined by Harvard University, which means the source mechanism of small-moderate events can be used to study the tectonic stress field in this region.

  14. Statistical learning: a powerful mechanism that operates by mere exposure.

    Science.gov (United States)

    Aslin, Richard N

    2017-01-01

    How do infants learn so rapidly and with little apparent effort? In 1996, Saffran, Aslin, and Newport reported that 8-month-old human infants could learn the underlying temporal structure of a stream of speech syllables after only 2 min of passive listening. This demonstration of what was called statistical learning, involving no instruction, reinforcement, or feedback, led to dozens of confirmations of this powerful mechanism of implicit learning in a variety of modalities, domains, and species. These findings reveal that infants are not nearly as dependent on explicit forms of instruction as we might have assumed from studies of learning in which children or adults are taught facts such as math or problem solving skills. Instead, at least in some domains, infants soak up the information around them by mere exposure. Learning and development in these domains thus appear to occur automatically and with little active involvement by an instructor (parent or teacher). The details of this statistical learning mechanism are discussed, including how exposure to specific types of information can, under some circumstances, generalize to never-before-observed information, thereby enabling transfer of learning. WIREs Cogn Sci 2017, 8:e1373. doi: 10.1002/wcs.1373 For further resources related to this article, please visit the WIREs website.

  15. Newton Leibniz integration for ket bra operators in quantum mechanics and derivation of entangled state representations

    Science.gov (United States)

    Fan, Hong-yi; Lu, Hai-liang; Fan, Yue

    2006-02-01

    Newton-Leibniz integration rule only applies to commuting functions of continuum variables, while operators made of Dirac's symbols (ket versus bra, e.g., | q>mechanics are usually not commutative. Therefore, integrations over the operators of type |>mathematical gap between classical mechanics and quantum mechanics, and further reveals the beauty and elegance of Dirac's symbolic method and transformation theory. Various applications of the IWOP technique, including constructing the entangled state representations and their applications, are presented.

  16. Work related stress and coping mechanisms among bankers in Lagos, Nigeria.

    Science.gov (United States)

    Olatona, F A; Ezeobika, E N; Okafor, I P; Owoeye, O B A

    2014-03-01

    This study assessed knowledge, prevalence, associated factors and mechanisms of coping with stress among bankers in Lagos State. It was a descriptive cross sectional study. A two stage sampling technique was used to select two hundred and twenty seven (227) respondents. Data was collected using a structured self administered questionnaire. The analysis was done using Epi-info version 2002 software and Chi Square was used to determine association between variables at p value 0.05. Fischer's Exact test was used where Chi-square was not valid. The age range of respondents was between 20 and 49 years while the mean age was 31.3 +/- 5.0 years. Only 3.6% had good level of knowledge about stress, 42.2% had fair level while more than half of the respondents had poor level of knowledge about stress (54.3%). Majority (67.0%) of the respondents were moderately stressed while one quarter (24.7%) were highly stressed. Majority (92.4%) of the respondents used good coping mechanisms though 69.5% of the respondents also used bad coping mechanisms. A greater proportion of those who had poor knowledge about stress were stressed or highly stressed (p = 0.002). A statistically significant association was also found between the departments in the bank and level of stress of the respondents (p = 0.002). The prevalence of stress was high among the bank workers studied. It is recommended that effective stress management programmes are implemented to address the problem of stress among bank workers.

  17. Operative stress response and energy metabolism after laparoscopic cholecystectomy compared to open surgery

    Institute of Scientific and Technical Information of China (English)

    Kai Luo; Jie-Shou Li; Ling-Tang Li; Kei-Hui Wang; Jing-Mei Shun

    2003-01-01

    AIM: To determine the least invasive surgical procedure by comparing the levels of operative stress hormones, responsereactive protein (CRP) and rest energy expenditure (REE)after laparoscopic (LC) and open cholecystectomy (OC).METHODS: Twenty-six consecutive patients with noncomplicated gallstones were randomized for LC (14) and OC (12). Plasma concentrations of somatotropin, insulin, cortisol and CRP were measured. The levels of REE were determined.RESULTS: In the third postoperative day, the insulin levels were lower compared to that before operation (P<0.05).Tn the first postoperative day, the levels of somatotropin and cortisol were higher in OC than those in LC. After operation the parameters of somatotropin, CRP and cortisol increased, compared to those in the preoperative period in the all patients (P<0.05). In the all-postoperative days,the CRP level was higher in OC than that in LC (7.46±0.02;7.38±0.01, P<0.05). After operation the REE level all increased in OC and LC (P<0.05). In the all-postoperative days, the REE level was higher in OC than that in LC (1438.5±A18.5;1222.3±L80.8, P<0.05).CONCLUSION: LC results in less prominent stress response and smaller metabolic interference compared to open surgery. These advantages are beneficial to the restoration of stress hormones, the nitrogen balance, and the energy metabolism. However, LC can also induce acidemia and pulmonary hypoperfusion because of the penumoperitonium it uses during surgery.

  18. Operational Review of the First Wireline In Situ Stress Test in Scientific Ocean Drilling

    Directory of Open Access Journals (Sweden)

    Casey Moore

    2012-04-01

    Full Text Available Scientific ocean drilling’s first in situ stress measurement was made at Site C0009A during Integrated Ocean Drilling Program (IODP Expedition 319 as part of Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE Stage 2. The Modular Formation Dynamics Tester (MDT, Schlumbergerwireline logging tool was deployed in riser Hole C0009A to measure in situ formation pore pressure, formation permeability (often reported as mobility=permeability/viscosity, and the least principal stress (S3 at several isolated depths (Saffer et al., 2009; Expedition 319 Scientists, 2010. The importance of in situ stress measurements is not only for scientific interests in active tectonic drilling, but also for geomechanical and well bore stability analyses. Certain in situ tools were not previously available for scientific ocean drilling due to the borehole diameter and open hole limits of riserless drilling. The riser-capable drillship, D/V Chikyu,now in service for IODP expeditions, allows all of the techniques available to estimate the magnitudes and orientations of 3-D stresses to be used. These techniques include downhole density logging for vertical stress, breakout and caliper log analyses for maximum horizontal stress, core-based anelastic strain recovery (ASR, used in the NanTroSEIZE expeditions in 2007–2008, and leak-off test (Lin et al., 2008 and minifrac/hydraulic fracturing (NanTroSEIZE Expedition319 in 2009. In this report, the whole operational planning process related to in situ measurements is reviewed, and lessons learned from Expedition 319 are summarized for efficient planning and testing in the future.

  19. Description of combat and operational stress control in Regional Command East, Afghanistan.

    Science.gov (United States)

    Ogle, Alan D; Bradley, Devvon; Santiago, Patcho; Reynolds, David

    2012-11-01

    Combat and Operational Stress Control (COSC) continues to be a vital component of medical operations in support of military forces serving in Afghanistan in Operation Enduring Freedom and elsewhere. Although numerous studies cover postdeployment mental health, and several cover in-theater conditions, data on behavioral health clinical service provision are presented here to elucidate from COSC provider "boots on the ground" how operations have been executed in one part of the Operation Enduring Freedom theater between 2007 and 2010. The most common types of stressors that led to care included combat, mission demands, home front concerns, and relationships with leaders and peers within units. Classes and consultation for sleep difficulties and anger management were of high interest. Frequent behavioral health diagnoses were depressive and anxiety disorders as well as exacerbation of a previously diagnosed condition. Management of suicidality and other psychiatric emergencies are discussed, as well as care outcomes. The authors present lessons learned regarding the importance of Operational Relationships/Tactical Politics, reducing stigma and barriers to care, collaboration with chaplains, and other strategies seen as supporting COSC success.

  20. Stress and asthma: novel insights on genetic, epigenetic, and immunologic mechanisms.

    Science.gov (United States)

    Rosenberg, Stacy L; Miller, Gregory E; Brehm, John M; Celedón, Juan C

    2014-11-01

    In the United States the economically disadvantaged and some ethnic minorities are often exposed to chronic psychosocial stressors and disproportionately affected by asthma. Current evidence suggests a causal association between chronic psychosocial stress and asthma or asthma morbidity. Recent findings suggest potential mechanisms underlying this association, including changes in the methylation and expression of genes that regulate behavioral, autonomic, neuroendocrine, and immunologic responses to stress. There is also evidence suggesting the existence of susceptibility genes that predispose chronically stressed youth to both post-traumatic stress disorder and asthma. In this review we critically examine published evidence and suggest future directions for research in this field.

  1. Residual stresses in coating-based systems, part Ⅰ:Mechanisms and analytical modeling

    Institute of Scientific and Technical Information of China (English)

    ZHANG Xiancheng; WU Yixiong; XU Binshi; WANG Haidou

    2007-01-01

    Thin films and multi-layered coatings comprised of different classes of materials are often used for various fimctional devices. The thermo-mechanical integrity of these systems is becoming a major concern and is strongly related to the residual stresses because of the fabrication processes. In this paper, the sources of the residual stresses in the coating-based systems and the concept of"misfit strain" were briefly reviewed. Analytical models were developed to predict the residual stresses in multi-layered film structures or coating-based systems using the force and moment balances. In addition, the residual stress distributions in the functionally and compositionally graded coatings were also analyzed.

  2. [Advances in studies on growth metabolism and response mechanisms of medicinal plants under drought stress].

    Science.gov (United States)

    Si, Can; Zhang, Jun-Yi; Xu, Hu-Chao

    2014-07-01

    Drought stress exerts a considerable effect on growth, physiology and secondary metabolisms of the medicinal plants. It could inhabit the growth of the medicinal plants but promote secretion of secondary metabolites. Other researches indicated that the medicinal plants could depend on the ABA signaling pathway and secreting osmotic substances to resist the drought stress and reduce the damage by it. The article concludes the changes in growth, physiology, secondary metabolisms and response mechanisms of medicinal plants to drought stress that provides a theoretical basis for exploring the relationship between medicinal plants and drought stress.

  3. Mechanical stress-induced switching kinetics of ferroelectric thin films at the nanoscale

    Science.gov (United States)

    Alsubaie, A.; Sharma, P.; Liu, G.; Nagarajan, V.; Seidel, J.

    2017-02-01

    We investigate ferroelectric domain structure and piezoelectric response under variable mechanical compressive stress in Pb(Zr0.2TiO0.8)O3 (PZT) thin films using high-resolution piezoresponse force microscopy (PFM) and an in situ sample bending stage. Measurements reveal a drastic change in the ferroelectric domain structure which is presented along with details of the mediating switching process involving domain wall motion, nucleation, and domain wall roughening under an applied external mechanical stimulus. Furthermore, local PFM hysteresis loops reveal significant changes in the observed coercive biases under applied stress. The PFM hysteresis loops become strongly imprinted under increasing applied compressive stress.

  4. Under Stress: Social Coping Mechanisms for Survival among the Working Professionals

    Directory of Open Access Journals (Sweden)

    Ms. Coral Barboza

    2016-10-01

    Full Text Available The nature of work of professionals and their family life may very often expose them to high level of stress which has the potential of affecting their productive and earning capacity. Coping strategies have been the subject of many studies and various suggestions have been made regarding the most appropriate way to categorise them in terms of function and efficacy (Amble, 2006; Buys et al., 2010. The goal of the current study was to examine how social coping mechanisms are helpful to employees in reducing stress and the stressful situations for their behavioural and emotional well-being. In achieving this goal, the researcher collected the data from the field through a structured questionnaire consisting of three phases- the demographic details, the stressors at workplace, social coping mechanisms adopted by them. Findings from the study show the existence of high level of stress among the working professionals. The sources of stress among the working professionals range from their nature of their work to work-family imbalance. In terms of coping strategies of stress, it was revealed that the respondents indulge in setting their goals, relaxing, exercising, diet, using sedatives and various others strategies suiting their needs. The need for appropriate mechanisms to be put in place by the managements of these organisations to address the stress needs of employees is essential to help reduce their stress levels

  5. Mechanical Properties of Gas Shale During Drilling Operations

    Science.gov (United States)

    Yan, Chuanliang; Deng, Jingen; Cheng, Yuanfang; Li, Menglai; Feng, Yongcun; Li, Xiaorong

    2017-07-01

    The mechanical properties of gas shale significantly affect the designs of drilling, completion, and hydraulic fracturing treatments. In this paper, the microstructure characteristics of gas shale from southern China containing up to 45.1% clay were analyzed using a scanning electron microscope. The gas shale samples feature strongly anisotropic characteristics and well-developed bedding planes. Their strength is controlled by the strength of both the matrix and the bedding planes. Conventional triaxial tests and direct shear tests are further used to study the chemical effects of drilling fluids on the strength of shale matrix and bedding planes, respectively. The results show that the drilling fluid has a much larger impact on the strength of the bedding plane than that of the shale matrix. The impact of water-based mud (WBM) is much larger compared with oil-based mud. Furthermore, the borehole collapse pressure of shale gas wells considering the effects of drilling fluids are analyzed. The results show that the collapse pressure increases gradually with the increase of drilling time, especially for WBM.

  6. Occupation Stress and Coping Mechanism to Increase Job Satisfaction Amount Supervisors at Karachi Pharmaceuticals

    Directory of Open Access Journals (Sweden)

    Mohammad Ahmed Khan

    2007-01-01

    Full Text Available This research explores the extent of stress and coping mechanism, in pharmaceuticals based in Korangi and other industrial areas in Karachi. The research is based on a previous study conducted by MA Khan (2006. The findings substantiate the view that coping mechanism increases job satisfaction of supervisors in the sampled firms. The design of the research is based on the measurement of the Organizational Stress Index. The data collected and analyzed is both from national and multinational pharmaceutical companies.Major causes of job stress have been identified as task demand, role demand and organizational structure. In Korangi area there is no significant difference in overall stress and job satisfaction levels between national and multinational pharmas. In the non Korangi sample job satisfaction is higher and job stress level in the multinationals is lower than in national pharmas.

  7. Cell biological mechanism for triggering of ABA accumulation under water stress in Vicia faba leaves.

    Science.gov (United States)

    Zhang, D; He, F; Jia, W

    2001-08-01

    Water stress-induced ABA accumulation is a cellular signaling process from water stress perception to activation of genes encoding key enzymes of ABA biosynthesis, of which the water stress-signal perception by cells or triggering mechanism of the ABA accumulation is the center in the whole process of ABA related-stress signaling in plants. The cell biological mechanism for triggering of ABA accumulation under water stress was studied in leaves of Vicia faba. Mannitol at 890 mmol * kg(-1) osmotic concentration induced an increase of more than 5 times in ABA concentration in detached leaf tissues, but the same concentration of mannitol only induced an increase of less than 40 % in ABA concentration in protoplasts. Like in detached leaf tissues, ABA concentration in isolated cells increased more than 10 times under the treatment of mannitol at 890 mmol * kg(-1) concentration, suggesting that the interaction between plasmalemma and cell wall was essential to triggering of the water stress-induced ABA accumulation. Neither Ca(2+)-chelating agent EGTA nor Ca(2+)channel activator A23187 nor the two cytoskeleton inhibitors, colchicine and cytochalasin B, had any effect on water stress-induced ABA accumulation. Interestingly water stress-induced ABA accumulation was effectively inhibited by a non-plasmalemma-permeable sulfhydryl-modifier PCMBS (p-chloromercuriphenyl-sulfonic acid), suggesting that plasmalemma protein(s) may be involved in the triggering of water stress-induced ABA accumulation, and the protein may contain sulfhydryl group at its function domain.

  8. Detection of Operator Performance Breakdown as an Automation Triggering Mechanism

    Science.gov (United States)

    Yoo, Hyo-Sang; Lee, Paul U.; Landry, Steven J.

    2015-01-01

    Performance breakdown (PB) has been anecdotally described as a state where the human operator "loses control of context" and "cannot maintain required task performance." Preventing such a decline in performance is critical to assure the safety and reliability of human-integrated systems, and therefore PB could be useful as a point at which automation can be applied to support human performance. However, PB has never been scientifically defined or empirically demonstrated. Moreover, there is no validated objective way of detecting such a state or the transition to that state. The purpose of this work is: 1) to empirically demonstrate a PB state, and 2) to develop an objective way of detecting such a state. This paper defines PB and proposes an objective method for its detection. A human-in-the-loop study was conducted: 1) to demonstrate PB by increasing workload until the subject reported being in a state of PB, and 2) to identify possible parameters of a detection method for objectively identifying the subjectively-reported PB point, and 3) to determine if the parameters are idiosyncratic to an individual/context or are more generally applicable. In the experiment, fifteen participants were asked to manage three concurrent tasks (one primary and two secondary) for 18 minutes. The difficulty of the primary task was manipulated over time to induce PB while the difficulty of the secondary tasks remained static. The participants' task performance data was collected. Three hypotheses were constructed: 1) increasing workload will induce subjectively-identified PB, 2) there exists criteria that identifies the threshold parameters that best matches the subjectively-identified PB point, and 3) the criteria for choosing the threshold parameters is consistent across individuals. The results show that increasing workload can induce subjectively-identified PB, although it might not be generalizable-only 12 out of 15 participants declared PB. The PB detection method based on

  9. A vertex-based model relating cell shape and mechanical stress in an epithelium

    CERN Document Server

    Nestor-Bergmann, Alexander; Woolner, Sarah; Jensen, Oliver

    2016-01-01

    Using a popular vertex-based model to describe a spatially disordered planar epithelial monolayer, we examine the relationship between cell shape and mechanical stress at the cell and tissue level. Deriving expressions for stress tensors starting from an energetic formulation of the model, we show that the principal axes of stress for an individual cell align with the principal axes of shape, and we determine the bulk effective tissue pressure when the monolayer is isotropic at the tissue level. Using simulations for a monolayer that is not under peripheral stress, we fit parameters of the model to experimental data for Xenopus embryonic tissue. The model predicts that mechanical interactions can generate mesoscopic patterns within the monolayer that exhibit long-range correlations in cell shape. The model also suggests that the orientation of mechanical and geometric cues for processes such as cell division are likely to be strongly correlated in real epithelia.

  10. Stress: perceptions, manifestations, and coping mechanisms of student registered nurse anesthetists.

    Science.gov (United States)

    Chipas, Anthony; Cordrey, Dan; Floyd, David; Grubbs, Lindsey; Miller, Sarah; Tyre, Brooks

    2012-08-01

    Stress is a response to change from the norm. Stress affects all individuals to varying degrees and can be positive, such as eustress, or negative, such as distress. The purpose of this qualitative, cross-sectional study was to investigate the stressors of the typical student registered nurse anesthetist (SRNA), with the objective of identifying trends in the perceptions, manifestations, and coping mechanisms of stress. An online (SurveyMonkey) questionnaire composed of 54 study-specific questions was developed to assess stress in the SRNA population. The questionnaire was sent to members of the American Association of Nurse Anesthetists via email invitation. The study yielded a sample of 1,282 SRNA participants. Analysis revealed statistically significant relationships between self-reported stress and negative outcomes, such as increased sick days, decreased health and wellness, and depression. The study demonstrated that SRNAs perceive their stress as above average, and it remains a central concern for them.

  11. Calcium ion involvement in growth inhibition of mechanically stressed soybean (Glycine max) seedlings

    Science.gov (United States)

    Jones, R. S.; Mitchell, C. A.

    1989-01-01

    A 40-50% reduction in soybean [Glycine max (L.) Merr. cv. Century 84] hypocotyl elongation occurred 24 h after application of mechanical stress. Exogenous Ca2+ at 10 mM inhibited growth by 28% if applied with the Ca2+ ionophore A23187 to the zone of maximum hypocotyl elongation. La3+ was even more inhibitory than Ca2+, especially above 5 mM. Treatment with ethyleneglycol-bis-(beta-aminoethylether)-N, N, N', N'-tetraacetic acid (EGTA) alone had no effect on growth of non-stressed seedlings at the concentrations used but negated stress-induced growth reduction by 36% at 4 mM when compared to non-treated, stressed controls. Treatment with EDTA was ineffective in negating stress-induced growth inhibition. Calmodulin antagonists calmidazolium, chlorpromazine, and 48/80 also negated stress-induced growth reduction by 23, 50, and 35%, respectively.

  12. Mechanisms of Alcohol-Induced Endoplasmic Reticulum Stress and Organ Injuries

    Directory of Open Access Journals (Sweden)

    Cheng Ji

    2012-01-01

    Full Text Available Alcohol is readily distributed throughout the body in the blood stream and crosses biological membranes, which affect virtually all biological processes inside the cell. Excessive alcohol consumption induces numerous pathological stress responses, part of which is endoplasmic reticulum (ER stress response. ER stress, a condition under which unfolded/misfolded protein accumulates in the ER, contributes to alcoholic disorders of major organs such as liver, pancreas, heart, and brain. Potential mechanisms that trigger the alcoholic ER stress response are directly or indirectly related to alcohol metabolism, which includes toxic acetaldehyde and homocysteine, oxidative stress, perturbations of calcium or iron homeostasis, alterations of S-adenosylmethionine to S-adenosylhomocysteine ratio, and abnormal epigenetic modifications. Interruption of the ER stress triggers is anticipated to have therapeutic benefits for alcoholic disorders.

  13. The sex differences in nature of vascular endothelial stress: nitrergic mechanisms

    Science.gov (United States)

    Sindeev, Sergey; Gekaluyk, Artem; Ulanova, Maria; Agranovich, Ilana; Sharref, Ali Esmat; Semyachkina-Glushkovskaya, Oxana

    2016-04-01

    Here we studied the role of nitric oxide in cardiovascular regulation in male and female hypertensive rats under normal and stress conditions. We found that the severity of hypertension in females was lower than in males. Hypertensive females demonstrated more favorable pattern of cardiovascular responses to stress. Nitric oxide blockade by NG-nitro-L-arginine methyl ester (L-NAME) increased the mean arterial pressure and decreased the heart rate more effectively in females than in males. During stress, L-NAME modified the stress-induced cardiovascular responses more significantly in female compared with male groups. Our data show that hypertensive females demonstrated the more effective nitric oxide control of cardiovascular activity under normal and especially stress conditions than male groups. This sex differences may be important mechanism underlying greater in females vs. males stress-resistance of cardiovascular system and hypertension formation.

  14. Endoplasmic reticulum stress as a primary pathogenic mechanism leading to age-related macular degeneration.

    Science.gov (United States)

    Libby, Richard T; Gould, Douglas B

    2010-01-01

    Age-related macular degeneration (AMD) is a multi-factorial disease and a leading cause of blindness. Proteomic and genetic data suggest that activation or de-repression of the alternate complement cascade of innate immunity is involved in end-stage disease. Several lines of evidence suggest that production of reactive oxygen species and chronic oxidative stress lead to protein and lipid modifications that initiate the complement cascade. Understanding the triggers of these pathogenic pathways and the site of the primary insult will be important for development of targeted therapeutics. Endoplasmic reticulum (ER) stress from misfolded mutant proteins and other sources are an important potential tributary mechanism. We propose that misfolded-protein-induced ER stress in the retinal-pigmented epithelium and/or choroid could lead to chronic oxidative stress, complement deregulation and AMD. Small molecules targeted to ER stress and oxidative stress could allow for a shift from disease treatment to disease prevention.

  15. LBNF Hadron Absorber: Mechanical Design and Analysis for 2.4MW Operation

    Energy Technology Data Exchange (ETDEWEB)

    Hartsell, B. [Fermilab; Anderson, K. [Fermilab; Hylen, J. [Fermilab; Sidorov, V. [Fermilab; Tariq, S. [Fermilab

    2015-06-01

    Fermilab’s Long-Baseline Neutrino Facility (LBNF) requires an absorber, essentially a large beam dump consisting of actively cooled aluminum and steel blocks, at the end of the decay pipe to stop leftover beam particles and provide radiation protection to people and groundwater. At LBNF’s final beam power of 2.4 MW and assuming the worst case condition of a 204 m long helium filled decay pipe, the absorber is required to handle a heat load of about 750 kW. This results in significant thermal management challenges which have been mitigated by the addition of an aluminum ‘spoiler’ and ‘sculpting’ the central portion of the aluminum core blocks. These thermal effects induce structural stresses which can lead to fatigue and creep considerations. Various accident conditions are considered and safety systems are planned to monitor operation and any accident pulses. Results from these thermal and structural analyses will be presented as well as the mechanical design of the absorber. The design allows each of the core blocks to be remotely removed and replaced if necessary. A shielded remote handling structure is incorporated to hold the hadron monitor when it is removed from the beam.

  16. A Preliminary Study on Mechanisms of Well Water Temperature Responses Based on the Modes of Stress Loading

    Institute of Scientific and Technical Information of China (English)

    Chen Daqing; Wan Yongfang

    2011-01-01

    Based on the studies of the predecessors, and contrasting the modes of stress loading with water level and water temperature response characteristics of a well-aquifer system, this paper draws a preliminary conclusion on the mechanisms of water temperature responses in a well caused by three modes of stress loading, i.e. gas escape, heat dispersion and cold water penetration mechanisms for elastic seismic wave stress loading; the fracture seepage mechanism for seismic wave stress loading and the hydrodynamic mechanism for earth tide stress loading and stress-dissipative heat mechanism for long period slow stress loading in the earthquake preparation stage. This paper illustrates the typical observation examples for each mode of stress loading and makes a preliminary study on their mechanisms.

  17. Ascending mechanisms of stress integration: Implications for brainstem regulation of neuroendocrine and behavioral stress responses.

    Science.gov (United States)

    Myers, Brent; Scheimann, Jessie R; Franco-Villanueva, Ana; Herman, James P

    2017-03-01

    In response to stress, defined as a real or perceived threat to homeostasis or well-being, brain systems initiate divergent physiological and behavioral processes that mobilize energy and promote adaptation. The brainstem contains multiple nuclei that engage in autonomic control and reflexive responses to systemic stressors. However, brainstem nuclei also play an important role in neuroendocrine responses to psychogenic stressors mediated by the hypothalamic-pituitary-adrenocortical axis. Further, these nuclei integrate neuroendocrine responses with stress-related behaviors, significantly impacting mood and anxiety. The current review focuses on the prominent brainstem monosynaptic inputs to the endocrine paraventricular hypothalamic nucleus (PVN), including the periaqueductal gray, raphe nuclei, parabrachial nuclei, locus coeruleus, and nucleus of the solitary tract (NTS). The NTS is a particularly intriguing area, as the region contains multiple cell groups that provide neurochemically-distinct inputs to the PVN. Furthermore, the NTS, under regulatory control by glucocorticoid-mediated feedback, integrates affective processes with physiological status to regulate stress responding. Collectively, these brainstem circuits represent an important avenue for delineating interactions between stress and health.

  18. Mechanisms of aerobic performance impairment with heat stress and dehydration.

    Science.gov (United States)

    Cheuvront, Samuel N; Kenefick, Robert W; Montain, Scott J; Sawka, Michael N

    2010-12-01

    Environmental heat stress can challenge the limits of human cardiovascular and temperature regulation, body fluid balance, and thus aerobic performance. This minireview proposes that the cardiovascular adjustments accompanying high skin temperatures (T(sk)), alone or in combination with high core body temperatures (T(c)), provide a primary explanation for impaired aerobic exercise performance in warm-hot environments. The independent (T(sk)) and combined (T(sk) + T(c)) effects of hyperthermia reduce maximal oxygen uptake (Vo(2max)), which leads to higher relative exercise intensity and an exponential decline in aerobic performance at any given exercise workload. Greater relative exercise intensity increases cardiovascular strain, which is a prominent mediator of rated perceived exertion. As a consequence, incremental or constant-rate exercise is more difficult to sustain (earlier fatigue) or requires a slowing of self-paced exercise to achieve a similar sensation of effort. It is proposed that high T(sk) and T(c) impair aerobic performance in tandem primarily through elevated cardiovascular strain, rather than a deterioration in central nervous system (CNS) function or skeletal muscle metabolism. Evaporative sweating is the principal means of heat loss in warm-hot environments where sweat losses frequently exceed fluid intakes. When dehydration exceeds 3% of total body water (2% of body mass) then aerobic performance is consistently impaired independent and additive to heat stress. Dehydration augments hyperthermia and plasma volume reductions, which combine to accentuate cardiovascular strain and reduce Vo(2max). Importantly, the negative performance consequences of dehydration worsen as T(sk) increases.

  19. Understanding the fluid mechanics behind transverse wall shear stress.

    Science.gov (United States)

    Mohamied, Yumnah; Sherwin, Spencer J; Weinberg, Peter D

    2017-01-04

    The patchy distribution of atherosclerosis within arteries is widely attributed to local variation in haemodynamic wall shear stress (WSS). A recently-introduced metric, the transverse wall shear stress (transWSS), which is the average over the cardiac cycle of WSS components perpendicular to the temporal mean WSS vector, correlates particularly well with the pattern of lesions around aortic branch ostia. Here we use numerical methods to investigate the nature of the arterial flows captured by transWSS and the sensitivity of transWSS to inflow waveform and aortic geometry. TransWSS developed chiefly in the acceleration, peak systolic and deceleration phases of the cardiac cycle; the reverse flow phase was too short, and WSS in diastole was too low, for these periods to have a significant influence. Most of the spatial variation in transWSS arose from variation in the angle by which instantaneous WSS vectors deviated from the mean WSS vector rather than from variation in the magnitude of the vectors. The pattern of transWSS was insensitive to inflow waveform; only unphysiologically high Womersley numbers produced substantial changes. However, transWSS was sensitive to changes in geometry. The curvature of the arch and proximal descending aorta were responsible for the principal features, the non-planar nature of the aorta produced asymmetries in the location and position of streaks of high transWSS, and taper determined the persistence of the streaks down the aorta. These results reflect the importance of the fluctuating strength of Dean vortices in generating transWSS.

  20. Is mechanical stress an important pathogenic factor in hidradenitis suppurativa?

    NARCIS (Netherlands)

    K. de Winter (K.); H.H. van der Zee (Hessel); E.P. Prens (Errol)

    2012-01-01

    textabstractHidradenitis suppurativa (HS) is a chronic of recurrent, inflammatory, follicular disease that usually presents after puberty with painful deep-seated, inflamed lesions in the inverse skin areas of the body. It has been hypothesized that mechanical pressure or friction is a risk factor f

  1. Whole-body vibration and postural stress among operators of construction equipment: a literature review.

    Science.gov (United States)

    Kittusamy, N Kumar; Buchholz, Bryan

    2004-01-01

    Operators of construction equipment perform various duties at work that expose them to a variety of risk factors that may lead to health problems. A few of the health hazards among operators of construction equipment are: (a) whole-body vibration, (b) awkward postural requirements (including static sitting), (c) dust, (d) noise, (e) temperature extremes, and (f) shift work. It has been suggested that operating engineers (OEs) are exposed to two important risk factors for the development of musculoskeletal disorders: whole-body vibration and non-neutral body postures. This review evaluates selected papers that have studied exposure to whole-body vibration and awkward posture among operators of mobile equipment. There have been only few studies that have specifically examined exposure of these risk factors among operators of construction equipment. Thus other studies from related industry and equipment were reviewed as applicable. In order to better understand whole-body vibration and postural stress among OEs, it is recommended that future studies are needed in evaluating these risk factors among OEs.

  2. Effects of Mechanical Stress and Plant Density on Mechanical Characteristics, Growth, and Lifetime Reproduction of Tobacco Plants

    NARCIS (Netherlands)

    Anten, N.P.R.; Casado-Garcia, R.; Nagashima, H.

    2005-01-01

    Plastic increases in stem elongation in dense vegetation are generally believed to be induced by canopy shading, but because plants protect each other from wind, shielding (reduced mechanical stress) could also play a role. To address this issue, tobacco Nicotiana tabacum plants were subjected to

  3. Mechanical stress activates Smad pathway through PKCδ to enhance interleukin-11 gene transcription in osteoblasts.

    Directory of Open Access Journals (Sweden)

    Shinsuke Kido

    Full Text Available BACKGROUND: Mechanical stress rapidly induces ΔFosB expression in osteoblasts, which binds to interleukin (IL-11 gene promoter to enhance IL-11 expression, and IL-11 enhances osteoblast differentiation. Because bone morphogenetic proteins (BMPs also stimulate IL-11 expression in osteoblasts, there is a possibility that BMP-Smad signaling is involved in the enhancement of osteoblast differentiation by mechanical stress. The present study was undertaken to clarify whether mechanical stress affects BMP-Smad signaling, and if so, to elucidate the role of Smad signaling in mechanical stress-induced enhancement of IL-11 gene transcription. METHODOLOGY/PRINCIPAL FINDINGS: Mechanical loading by fluid shear stress (FSS induced phosphorylation of BMP-specific receptor-regulated Smads (BR-Smads, Smad1/5, in murine primary osteoblasts (mPOBs. FSS rapidly phosphorylated Y311 of protein kinase C (PKCδ, and phosphorylated PKCδ interacted with BR-Smads to phosphorylate BR-Smads. Transfection of PKCδ siRNA or Y311F mutant PKCδ abrogated BR-Smads phosphorylation and suppressed IL-11 gene transcription enhanced by FSS. Activated BR-Smads bound to the Smad-binding element (SBE of IL-11 gene promoter and formed complex with ΔFosB/JunD heterodimer via binding to the C-terminal region of JunD. Site-directed mutagenesis in the SBE and the AP-1 site revealed that both SBE and AP-1 sites were required for full activation of IL-11 gene promoter by FSS. CONCLUSIONS/SIGNIFICANCE: These results demonstrate that PKCδ-BR-Smads pathway plays an important role in the intracellular signaling in response to mechanical stress, and that a cross-talk between PKCδ-BR-Smads and ΔFosB/JunD pathways synergistically stimulates IL-11 gene transcription in response to mechanical stress.

  4. Cellular and Molecular Mechanisms of Arrhythmia by Oxidative Stress

    Directory of Open Access Journals (Sweden)

    Ali A. Sovari

    2016-01-01

    Full Text Available Current therapies for arrhythmia using ion channel blockade, catheter ablation, or an implantable cardioverter defibrillator have limitations, and it is important to search for new antiarrhythmic therapeutic targets. Both atrial fibrillation and heart failure, a condition with increased arrhythmic risk, are associated with excess amount of reactive oxygen species (ROS. There are several possible ways for ROS to induce arrhythmia. ROS can cause focal activity and reentry. ROS alter multiple cardiac ionic currents. ROS promote cardiac fibrosis and impair gap junction function, resulting in reduced myocyte coupling and facilitation of reentry. In order to design effective antioxidant drugs for treatment of arrhythmia, it is essential to explore the molecular mechanisms by which ROS exert these arrhythmic effects. Activation of Ca2+/CaM-dependent kinase II, c-Src tyrosine kinase, protein kinase C, and abnormal splicing of cardiac sodium channels are among the recently discovered molecular mechanisms of ROS-induced arrhythmia.

  5. Job Stress and Coping Mechanisms among Nursing Staff in Public Health Services

    Directory of Open Access Journals (Sweden)

    Loo-See Beh

    2012-07-01

    Full Text Available The main purpose of this study is to investigate the prominent causes and effects of job stress and coping mechanism among nurses in public health services. The research methodology included qualitative and quantitative survey. The results indicated that the major contributor of job stress among nurses is the job itself. Heavy workload, repetitive work, and poor working environment were among the stressors identified in the category of job itself. Respondents identified that inconsiderate and inequitable superior/matron, lack of recognition, and conflict within and between groups were the stressors. Respondents also view social support as a buffer against the dysfunctional consequences of stress emanating from the workplace and established network of friends, family, superior, peers, and colleagues to seek emotional support when faced with job-related stress in the workplace. Further, respondents adopt more than one coping mechanisms to combat job stress based on scenarios, situations, and level of job stress. This study is limited only to the investigation of job stress and coping mechanism among nurses in a public hospital. Other non-medical and medical staffs such as administrators and doctors were not included in this study. Suggestions for future research are also mentioned.

  6. Molecular Mechanisms of Stress-Induced Increases in Fear Memory Consolidation within the Amygdala.

    Science.gov (United States)

    Aubry, Antonio V; Serrano, Peter A; Burghardt, Nesha S

    2016-01-01

    Stress can significantly impact brain function and increase the risk for developing various psychiatric disorders. Many of the brain regions that are implicated in psychiatric disorders and are vulnerable to the effects of stress are also involved in mediating emotional learning. Emotional learning has been a subject of intense investigation for the past 30 years, with the vast majority of studies focusing on the amygdala and its role in associative fear learning. However, the mechanisms by which stress affects the amygdala and amygdala-dependent fear memories remain unclear. Here we review the literature on the enhancing effects of acute and chronic stress on the acquisition and/or consolidation of a fear memory, as measured by auditory Pavlovian fear conditioning, and discuss potential mechanisms by which these changes occur in the amygdala. We hypothesize that stress-mediated activation of glucocorticoid receptors (GR) and norepinephrine release within the amygdala leads to the mobilization of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors to the synapse, which underlies stress-induced increases in fear memory. We discuss the implications of this hypothesis for evaluating the effects of stress on extinction and for developing treatments for anxiety disorders. Understanding how stress-induced changes in glucocorticoid and norepinephrine signaling might converge to affect emotional learning by increasing the trafficking of AMPA receptors and enhancing amygdala excitability is a promising area for future research.

  7. Molecular Mechanisms of Stress-Induced Increases in Fear Memory Consolidation Within the Amygdala

    Directory of Open Access Journals (Sweden)

    Antonio Aubry

    2016-10-01

    Full Text Available Stress can significantly impact brain function and increase the risk for developing various psychiatric disorders. Many of the brain regions that are implicated in psychiatric disorders and are vulnerable to the effects of stress are also involved in mediating emotional learning. Emotional learning has been a subject of intense investigation for the past 30 years, with the vast majority of studies focusing on the amygdala and its role in associative fear learning. However, the mechanisms by which stress affects the amygdala and amygdala-dependent fear memories remain unclear. Here we review the literature on the enhancing effects of acute and chronic stress on the acquisition and/or consolidation of a fear memory, as measured by auditory Pavlovian fear conditioning, and discuss potential mechanisms by which these changes occur in the amygdala. We hypothesize that stress-mediated activation of glucocorticoid receptors (GR and norepinephrine release within the amygdala leads to the mobilization of AMPA receptors to the synapse, which underlies stress-induced increases in fear memory. We discuss the implications of this hypothesis for evaluating the effects of stress on extinction and for developing treatments for anxiety disorders. Understanding how stress-induced changes in glucocorticoid and norepinephrine signaling might converge to affect emotional learning by increasing the trafficking of AMPA receptors and enhancing amygdala excitability is a promising area for future research.

  8. Transcutaneous mechanical nerve stimulation using perineal vibration: a novel method for the treatment of female stress urinary incontinence

    DEFF Research Database (Denmark)

    Sønksen, Jens; Ohl, Dana A; Bonde, Birthe;

    2007-01-01

    We defined basic guidelines for transcutaneous mechanical nerve stimulation in modifying pelvic floor responses in women and determined the efficacy of transcutaneous mechanical nerve stimulation in treating stress urinary incontinence.......We defined basic guidelines for transcutaneous mechanical nerve stimulation in modifying pelvic floor responses in women and determined the efficacy of transcutaneous mechanical nerve stimulation in treating stress urinary incontinence....

  9. Neural mechanisms of impaired fear inhibition in posttraumatic stress disorder

    Directory of Open Access Journals (Sweden)

    Tanja eJovanovic

    2011-07-01

    Full Text Available Posttraumatic stress disorder (PTSD can develop in some individuals who are exposed to an event that causes extreme fear, horror, or helplessness (APA, 1994. PTSD is a complex and heterogeneous disorder, which is often co-morbid with depression, substance abuse, and anxiety disorders such as panic or social phobia. Given this complexity, progress in the field can be greatly enhanced by focusing on phenotypes that are more proximal to the neurobiology of the disorder. Such neurobiological intermediate phenotypes can provide investigative tools to increase our understanding of the roots of the disorder and develop better prevention or intervention programs. In the present paper, we argue that the inhibition of fear responses is an intermediate phenotype that is related to both the neurocircuitry associated with the disorder, and is linked to its clinical symptoms. An advantage of focusing on fear inhibition is that the neurobiology of fear has been well investigated in animal models providing the necessary groundwork in understanding alterations. Furthermore, because many paradigms can be tested across species, fear inhibition is an ideal translational tool. Here we review both the behavioral tests and measures of fear inhibition and the related neurocircuitry in neuroimaging studies with both healthy and clinical samples.

  10. Investigating feedback mechanisms between stress and grain-size: preliminary findings from finite-element modelling

    Science.gov (United States)

    Cross, A. J.; Prior, D. J.; Ellis, S. M.

    2012-12-01

    It is widely accepted that changes in stress and grain size can induce a switch between grain-size insensitive (GSI) and sensitive (GSS) creep mechanisms. Under steady-state conditions, grains evolve to an equilibrium size in the boundary region between GSS and GSI, described by the paleopiezometer for a given material. Under these conditions, significant rheological weakening is not expected, as grain size reduction processes are balanced by grain growth processes. However, it has been shown that the stress field surrounding faults varies through the seismic cycle, with both rapid loading and unloading of stress possible in the co- and post-seismic stages. We propose that these changes in stress in the region of the brittle-ductile transition zone may be sufficient to force a deviation from the GSI-GSS boundary and thereby cause a change in grain size and creep mechanism prior to system re-equilibration. Here we present preliminary findings from numerical modelling of stress and grain size changes in response to loading of mechanical inhomogeneities. Our results are attained using a grain-size evolution (GSE) subroutine incorporated into the SULEC finite-element code developed by Susan Ellis and Susanne Buiter, which utilises an iterative approach of solving for spatial and temporal changes in differential stress, grain size and active creep mechanism. Preliminary models demonstrate that stress changes in response to the opening of a fracture in a flowing medium can be significant enough to cause a switch from GSI to GSS creep. These results are significant in the context of understanding spatial variations and feedback between stress, grain size and deformation mechanisms through the seismic cycle.

  11. Mechanical stress and glucose concentration modulate glucose transport in cultured rat podocytes.

    Science.gov (United States)

    Lewko, Barbara; Bryl, Ewa; Witkowski, Jacek M; Latawiec, Elzbieta; Angielski, Stefan; Stepinski, Jan

    2005-02-01

    Recent studies show that mechanical stress modifies both morphology and protein expression in podocytes. Ambient glucose is another factor modulating protein synthesis in these cells. In diabetes, podocytes experience elevated glucose concentrations as well as mechanical strain generated by high intracapillary pressures. Both these factors are responsible for podocyte injury, leading to impairment of kidney glomerular function. In the present study, we examined the effects of glucose concentration and mechanical stress on glucose uptake in podocytes. Following a 24 h pre-incubation in low (2.5 mM, LG), normal (5.6 mM, NG) or high (30 mM, HG) glucose media, cultured rat podocytes were exposed to 4 h mechanical stress. We used the labelled glucose analogue, [3H]2-deoxy-D-glucose, to measure glucose uptake. The distribution of facilitative glucose transporters GLUT2 and GLUT4 was assessed by flow cytometry. In the control (static) cells, glucose uptake was similar in the three glucose groups. In mechanically stressed podocytes, glucose uptake increased 2-fold in the LG and NG groups but increased 3-fold in the HG group. In the NG cells, mechanical load increased the membrane expression of GLUT2 and reduced the membrane-bound GLUT4. In stretched HG cells, the membrane expression of both GLUT2 and GLUT4 was decreased. High glucose decreased the plasma membrane GLUT2 content in the stretched cells, whereas both static and stretched podocytes showed an elevation in GLUT4. Mechanical stress potentiated glucose uptake in podocytes and this effect was enhanced by high ambient glucose. The decreased expression of GLUT2 and GLUT4 on the surface of stretched cells suggests that the activity of other glucose transporters may be regulated by mechanical stress in podocytes.

  12. NF-κB and epigenetic mechanisms as integrative regulators of brain resilience to anoxic stress.

    Science.gov (United States)

    Sarnico, Ilenia; Branca, Caterina; Lanzillotta, Annamaria; Porrini, Vanessa; Benarese, Marina; Spano, Pier Franco; Pizzi, Marina

    2012-10-02

    Brain cells display an amazing ability to respond to several different types of environmental stimuli and integrate this response physiologically. Some of these responses can outlive the original stimulus by days, weeks or even longer. Long-lasting changes in both physiological and pathological conditions occurring in response to external stimuli are almost always mediated by changes in gene expression. To effect these changes, cells have developed an impressive repertoire of signaling systems designed to modulate the activity of numerous transcription factors and epigenetic mechanisms affecting the chromatin structure. Since its initial characterization in the nervous system, NF-κB has shown to respond to multiple signals and elicit pleiotropic activities suggesting that it may play a pivotal role in integration of different types of information within the brain. Ample evidence demonstrates that NF-κB factors are engaged in and necessary for neuronal development and synaptic plasticity, but they also regulate brain response to environmental noxae. By focusing on the complexity of NF-κB transcriptional activity in neuronal cell death, it emerged that the composition of NF-κB active dimers finely tunes the neuronal vulnerability to brain ischemia. Even though we are only beginning to understand the contribution of distinct NF-κB family members to the regulation of gene transcription in the brain, an additional level of regulation of NF-κB activity has emerged as operated by the epigenetic mechanisms modulating histone acetylation. We will discuss NF-κB and epigenetic mechanisms as integrative regulators of brain resilience to anoxic stress and useful drug targets for restoration of brain function. This article is part of a Special Issue entitled: Brain Integration.

  13. Unified Theory of Annihilation-Creation Operators for Solvable (`Discrete') Quantum Mechanics

    OpenAIRE

    Odake, Satoru; Sasaki, Ryu

    2006-01-01

    The annihilation-creation operators $a^{(\\pm)}$ are defined as the positive/negative frequency parts of the exact Heisenberg operator solution for the `sinusoidal coordinate'. Thus $a^{(\\pm)}$ are hermitian conjugate to each other and the relative weights of various terms in them are solely determined by the energy spectrum. This unified method applies to most of the solvable quantum mechanics of single degree of freedom including those belonging to the `discrete' quantum mechanics.

  14. Analysis of stress and natural frequencies of high-speed spatial parallel mechanism

    Institute of Scientific and Technical Information of China (English)

    陈修龙; 李文彬; 邓昱; 李云峰

    2013-01-01

    In order to grasp the dynamic behaviors of 4-UPS-UPU high-speed spatial parallel mechanism, the stress of driving limbs and natural frequencies of parallel mechanism were investigated. Based on flexible multi-body dynamics theory, the dynamics model of 4-UPS-UPU high-speed spatial parallel mechanism without considering geometric nonlinearity was derived. The stress of driving limbs and natural frequencies of 4-UPS-UPU parallel mechanism with specific parameters were analyzed. The relationship between the basic parameters of parallel mechanism and its dynamic behaviors, such as stress of driving limbs and natural frequencies of parallel mechanism, were discussed. The numerical simulation results show that the stress and natural frequencies are relatively sensitive to the section parameters of driving limbs, the characteristic parameters of material on driving limbs, and the mass of moving platform. The researches can provide important theoretical base of the analysis of dynamic behaviors and optimal design for high-speed spatial parallel mechanism.

  15. Mapping of Mechanical Strains and Stresses around Quiescent Engineered Three-Dimensional Epithelial Tissues

    Science.gov (United States)

    Gjorevski, Nikolce; Nelson, Celeste M.

    2012-01-01

    Understanding how physical signals guide biological processes requires qualitative and quantitative knowledge of the mechanical forces generated and sensed by cells in a physiologically realistic three-dimensional (3D) context. Here, we used computational modeling and engineered epithelial tissues of precise geometry to define the experimental parameters that are required to measure directly the mechanical stress profile of 3D tissues embedded within native type I collagen. We found that to calculate the stresses accurately in these settings, we had to account for mechanical heterogeneities within the matrix, which we visualized and quantified using confocal reflectance and atomic force microscopy. Using this technique, we were able to obtain traction forces at the epithelium-matrix interface, and to resolve and quantify patterns of mechanical stress throughout the surrounding matrix. We discovered that whereas single cells generate tension by contracting and pulling on the matrix, the contraction of multicellular tissues can also push against the matrix, causing emergent compression. Furthermore, tissue geometry defines the spatial distribution of mechanical stress across the epithelium, which communicates mechanically over distances spanning hundreds of micrometers. Spatially resolved mechanical maps can provide insight into the types and magnitudes of physical parameters that are sensed and interpreted by multicellular tissues during normal and pathological processes. PMID:22828342

  16. Action Mechanism of Relation Skills of Villager Autonomy Organizations on Operation Performance of Farmer Households

    Institute of Scientific and Technical Information of China (English)

    Jianhui; WU; Jintao; HE; Huazhong; LI

    2015-01-01

    Through building " relation skills- knowledge acquisition- operation performance",this paper discussed action mechanism of relation skills of villager autonomy organizations on operation performance of farmer households. On the basis of questionnaire survey of 208 farmer households in Guangdong,it studied influence of relation skills of villager autonomy organizations on operation performance of farmer households from hierarchical relation skills and market relation skills,and introduced knowledge acquisition as mediator variables to discuss the influence mechanism. Results indicate that relation skills and knowledge acquisition have positive influence on operation performance of farmer households,knowledge acquisition takes intermediate action on market relation skills and operation performance,while hierarchical relation skills promote improvement of operation performance only through acquisition of explicit knowledge.

  17. An analytical model of the mechanical properties of bulk coal under confined stress

    Science.gov (United States)

    Wang, G.X.; Wang, Z.T.; Rudolph, V.; Massarotto, P.; Finley, R.J.

    2007-01-01

    This paper presents the development of an analytical model which can be used to relate the structural parameters of coal to its mechanical properties such as elastic modulus and Poisson's ratio under a confined stress condition. This model is developed primarily to support process modeling of coalbed methane (CBM) or CO2-enhanced CBM (ECBM) recovery from coal seam. It applied an innovative approach by which stresses acting on and strains occurring in coal are successively combined in rectangular coordinates, leading to the aggregated mechanical constants. These mechanical properties represent important information for improving CBM/ECBM simulations and incorporating within these considerations of directional permeability. The model, consisting of constitutive equations which implement a mechanically consistent stress-strains correlation, can be used as a generalized tool to study the mechanical and fluid behaviors of coal composites. An example using the model to predict the stress-strain correlation of coal under triaxial confined stress by accounting for the elastic and brittle (non-elastic) deformations is discussed. The result shows a good agreement between the prediction and the experimental measurement. ?? 2007 Elsevier Ltd. All rights reserved.

  18. Seismogenic response to fluid injection operations in Oklahoma and California: Implications for crustal stresses

    Science.gov (United States)

    Goebel, T.; Aminzadeh, F.

    2015-12-01

    The seismogenic response to induced pressure changes provides insight into the proximity to failure of faults close to injection sites. Here, we examine possible seismicity rate changes in response to wastewater disposal and enhanced oil recovery operations in hydrocarbon basins in California and Oklahoma. We test whether a statistically significant rate increase exists within these areas and determine the corresponding timing and location based on nonparametric modeling of background seismicity rates. Annual injection volumes increased monotonically since ~2001 in California and ~1998 in Oklahoma. While OK experienced a recent surge in seismic activity which exceeded the 95% confidence limit of a stationary Poisson process in ~2010, seismicity in CA showed no increase in background rates between 1980 and 2014. A systematic analysis of frequency-magnitude-distributions (FMDs) of likely induced earthquakes in OK indicates that FMDs are depleted in large-magnitude events. Seismicity in CA hydrocarbon basins, on the other hand, shows Gutenberg-Richter type FMDs and b~1. Moreover, the earthquakes and injection operations occur preferably in distinct areas in CA whereas in OK earthquakes occur closer to injection wells than expected from a random uniform process. To test whether injection operations may be responsible for the strongly different seismicity characteristics in CA and OK, we compare overall well density, wellhead pressures, peak and cumulative rates as well as injection depths. We find that average injection rates, pressures and volumes are comparable between CA and OK and that injection occurs on average 0.5 km deeper in CA than in OK. Thus, the here tested operational parameters can not easily explain the vastly different seismogenic response to injection operations in CA and OK, and may only be of secondary importance for the resulting earthquake activity. The potential to induce earthquakes by fluid injection operations is likely controlled by the

  19. The human operator transfer function: Identification of the limb mechanics subsystem

    Science.gov (United States)

    Jones, Lynette A.; Hunter, Ian W.

    1991-01-01

    The objective of our research is to decompose the performance of the human operator in terms of the subsystems that determine the operator's responses in order to establish how the dynamics of these component subsystems influence the operator's performance. In the present experiment, the dynamic stiffness of the human elbow joint was measured at rest and under different levels of biceps muscle activation; this work forms part of the analysis of the limb mechanics subsystem.

  20. Residual stress in a M3:2 PM high speed steel; effect of mechanical loading

    DEFF Research Database (Denmark)

    Højerslev, Christian; Odén, Magnus; Carstensen, Jesper V.

    2001-01-01

    X-ray lattice strains were investigated in an AISI M3:2 PM high-speed steel in the as heat treated condition and after exposure to alternating mechanical load. The volume changes during heat treatment were monitored with dilatometry. Hardened and tempered AISI M3:2 steel consists of tempered lath...... martensite and the carbides M6C,V8C7 and M23C6. In the as heat treated condition the stress state is triaxial. The primary carbides M6C and V8C7 experience a compressive state of stress. Exposure to an alternating mechanical load, changes the states of stress of V8C7 and tempered martensite, but does...... not appear to change the state of stress in M6C....

  1. Interdependence of the volume and stress ensembles and equipartition in statistical mechanics of granular systems.

    Science.gov (United States)

    Blumenfeld, Raphael; Jordan, Joe F; Edwards, Sam F

    2012-12-07

    We discuss the statistical mechanics of granular matter and derive several significant results. First, we show that, contrary to common belief, the volume and stress ensembles are interdependent, necessitating the use of both. We use the combined ensemble to calculate explicitly expectation values of structural and stress-related quantities for two-dimensional systems. We thence demonstrate that structural properties may depend on the angoricity tensor and that stress-based quantities may depend on the compactivity. This calls into question previous statistical mechanical analyses of static granular systems and related derivations of expectation values. Second, we establish the existence of an intriguing equipartition principle-the total volume is shared equally amongst both structural and stress-related degrees of freedom. Third, we derive an expression for the compactivity that makes it possible to quantify it from macroscopic measurements.

  2. Mechanical Alterations Associated with Repeated Treadmill Sprinting under Heat Stress

    Science.gov (United States)

    Brocherie, Franck; Morin, Jean-Benoit; Racinais, Sébastien; Millet, Grégoire P.; Périard, Julien D.

    2017-01-01

    Purpose Examine the mechanical alterations associated with repeated treadmill sprinting performed in HOT (38°C) and CON (25°C) conditions. Methods Eleven recreationally active males performed a 30-min warm-up followed by three sets of five 5-s sprints with 25-s recovery and 3-min between sets in each environment. Constant-velocity running for 1-min at 10 and 20 km.h-1 was also performed prior to and following sprinting. Results Mean skin (37.2±0.7 vs. 32.7±0.8°C; P<0.001) and core (38.9±0.2 vs. 38.8±0.3°C; P<0.05) temperatures, together with thermal comfort (P<0.001) were higher following repeated sprinting in HOT vs. CON. Step frequency and vertical stiffness were lower (-2.6±1.6% and -5.5±5.5%; both P<0.001) and contact time (+3.2±2.4%; P<0.01) higher in HOT for the mean of sets 1–3 compared to CON. Running distance per sprint decreased from set 1 to 3 (-7.0±6.4%; P<0.001), with a tendency for shorter distance covered in HOT vs. CON (-2.7±3.4%; P = 0.06). Mean vertical (-2.6±5.5%; P<0.01), horizontal (-9.1±4.4%; P<0.001) and resultant ground reaction forces (-3.0±2.8%; P<0.01) along with vertical stiffness (-12.9±2.3%; P<0.001) and leg stiffness (-8.4±2.7%; P<0.01) decreased from set 1 to 3, independently of conditions. Propulsive power decreased from set 1 to 3 (-16.9±2.4%; P<0.001), with lower propulsive power values in set 2 (-6.6%; P<0.05) in HOT vs. CON. No changes in constant-velocity running patterns occurred between conditions, or from pre-to-post repeated-sprint exercise. Conclusions Thermal strain alters step frequency and vertical stiffness during repeated sprinting; however without exacerbating mechanical alterations. The absence of changes in constant-velocity running patterns suggests a strong link between fatigue-induced velocity decrements during sprinting and mechanical alterations. PMID:28146582

  3. Mechanical and thermal stresses analysis in diesel engine exhaust valve with and without thermal coating layer on valve face

    Directory of Open Access Journals (Sweden)

    Maher A.R. Sadiq Al-Baghdadi,Sahib Shihab Ahmed, Nabeel Abdulhadi Ghayadh

    2016-01-01

    Full Text Available This paper investigates mechanical and thermal stresses that arise in the exhaust valve due to its operating with and without thermal coating layer (ceramic on face exhaust valve. Three dimensional models of an exhaust valve four cylinders, four stroke, and direct injection diesel engine have been presented. The governing equations were discretized using a finite-volume method (FVM and solved using multi-physics COMSOL package Version 5. The engine’s exhaust valve crown is coated with various materials in different thermal conductivity such as (Gd2Zr2O7, over a 150μm thickness of bond coat. The maximum thickness of coating is about 300 μm. Results indicate that after creating a coating layer exhaust valve the temperature distribution, temperature gradients distribution, von-Mises stress distribution and displacement distribution are decreased.

  4. Oxidative stress mechanisms and potential therapeutics in Alzheimer disease.

    Science.gov (United States)

    Moreira, P I; Siedlak, S L; Aliev, G; Zhu, X; Cash, A D; Smith, M A; Perry, G

    2005-07-01

    Oxidative damage of biological macromolecules is a hallmark of most neurodegenerative disorders such as Alzheimer, Parkinson and diffuse Lewy body diseases. Another important phenomenon involved in these disorders is the alteration of iron and copper homeostasis. Data from the literature support the involvement of metal homeostasis in mitochondrial dysfunction, protein alterations and nucleic acid damage which are relevant in brain function and consequently, in the development of neurodegenerative disorders. Although alterations in transition metal homeostasis, redox activity, and localization are well documented, it must be determined how alterations of specific copper- and iron-containing metalloenzymes are also involved in Alzheimer disease. The clarification of these phenomena can open a new window for understanding the mechanisms underlying neurodegeneration and, consequently, for the development of new therapeutic strategies such as gene therapy and new pharmaceutical formulations with antioxidant and chelating properties.

  5. Thermal stresses in hexagonal materials - heat treatment influence on their mechanical behaviour

    Energy Technology Data Exchange (ETDEWEB)

    Gloaguen, D.; Freour, S.; Guillen, R.; Royer, J. [Nantes Univ., GeM, Institut de Recherche en Genie Civil et Mecanique, Ecole Centrale de Nantes, UMR CNRS 6183, 44 (France); Francois, M. [Universite de Technologie de Troyes, Lab. des Systemes Mecaniques et d' Ingenierie Simultanee (LASMIS), 10 - Troyes (France)

    2004-12-01

    Internal stresses due to anisotropic thermal and plastic properties were investigated in rolled zirconium and titanium. The thermal stresses induced by a cooling process were predicted using a self-consistent model and compared with experimental results obtained by X-ray diffraction. The study of the elastoplastic response during uniaxial loading was performed along the rolling and the transverse direction of the sheet, considering the influence of the texture and the thermal stresses on the mechanical behaviour. An approach in order to determine the thermal behaviour of phases embedded in two-phase materials is also presented. For zirconium, the residual stresses due to thermal anisotropy are rather important (equivalent to 35% of the yield stress) and consequently they play an important role on the elastoplastic transition contrary to titanium. The study of two-phase material shows the influence and the interaction of the second phase on the thermal behaviour in the studied phase.

  6. Long-term effects of early life stress exposure: Role of epigenetic mechanisms.

    Science.gov (United States)

    Silberman, Dafne M; Acosta, Gabriela B; Zorrilla Zubilete, María A

    2016-07-01

    Stress is an adaptive response to demands of the environment and thus essential for survival. Exposure to stress during the first years of life has been shown to have profound effects on the growth and development of an adult individual. There are evidences demonstrating that stressful experiences during gestation or in early life can lead to enhanced susceptibility to mental disorders. Early-life stress triggers hypothalamic-pituitary-adrenocortical (HPA) axis activation and the associated neurochemical reactions following glucocorticoid release are accompanied by a rapid physiological response. An excessive response may affect the developing brain resulting in neurobehavioral and neurochemical changes later in life. This article reviews the data from experimental studies aimed to investigate hormonal, functional, molecular and epigenetic mechanisms involved in the stress response during early-life programming. We think these studies might prove useful for the identification of novel pharmacological targets for more effective treatments of mental disorders.

  7. Effects of prenatal stress on pregnancy and human development: mechanisms and pathways

    Science.gov (United States)

    Coussons-Read, Mary E

    2013-01-01

    A growing body of research shows that prenatal stress can have significant effects on pregnancy, maternal health and human development across the lifespan. These effects may occur directly through the influence of prenatal stress-related physiological changes on the developing fetus, or indirectly through the effects of prenatal stress on maternal health and pregnancy outcome which, in turn, affect infant health and development. Animal and human studies suggest that activation of the maternal stress response and resulting changes in endocrine and inflammatory activity play a role in the aetiology of these effects. Ongoing research is focusing on clarifying these mechanisms, understanding the role of racial and cultural factors in these effects, and examining the epigenetic and transgenerational influences of prenatal stress. PMID:27757157

  8. Molecular Mechanism of Salinity Stress and Biotechnological Strategies for Engineering Salt Tolerance in Plants

    Institute of Scientific and Technical Information of China (English)

    Wei Tang; Latoya Harris; Ronald J. Newton

    2003-01-01

    Molecular mechanisms of plant responses to salinity stress and the physiological consequences of altered gene expression are reviewed. Extensive use of comparisons with halophytic plants and glycophytos provide a paradigm for many responses to salinity exhibited by stress sensitive plants. Osmolyte biosynthesis, water flux control, and membrane transport of ions are important for maintenance and re-establishment of homeostasis. Transgenic plant and mutant analyses in Arabidopsis improve the understanding of stress responses and elements of stress signal transduction pathways. The genomic DNA sequences and cell-specific transcript expression data, combined with determinant identification based on molecular genetics, will provide the infrastructure for functional physiological dissection of salt tolerance determinants in plants. Protein interaction analysis, genetic activation and suppression screens will lead inevitably to an understanding of the interrelationships of the multiple signaling systems that control stress-adaptive responses and provide more opportunity to engineer salt tolerance in plants.

  9. Potentiality of Soybean Proteomics in Untying the Mechanism of Flood and Drought Stress Tolerance

    OpenAIRE

    Zahed Hossain; Setsuko Komatsu

    2014-01-01

    Dissecting molecular pathways at protein level is essential for comprehensive understanding of plant stress response mechanism. Like other legume crops, soybean, the world’s most widely grown seed legume and an inexpensive source of protein and vegetable oil, is also extremely sensitive to abiotic stressors including flood and drought. Irrespective of the kind and severity of the water stress, soybean exhibits a tight control over the carbon metabolism to meet the cells required energy demand...

  10. Laboratory evidence for particle mobilization as a mechanism for permeability enhancement via dynamic stressing

    Science.gov (United States)

    Candela, Thibault; Brodsky, Emily E.; Marone, Chris; Elsworth, Derek

    2014-04-01

    It is well-established that seismic waves can increase the permeability in natural systems, yet the mechanism remains poorly understood. We investigate the underlying mechanics by generating well-controlled, repeatable permeability enhancement in laboratory experiments. Pore pressure oscillations, simulating dynamic stresses, were applied to intact and fractured Berea sandstone samples under confining stresses of tens of MPa. Dynamic stressing produces an immediate permeability enhancement ranging from 1 to 60%, which scales with the amplitude of the dynamic strain (7×10-7 to 7×10-6) followed by a gradual permeability recovery. We investigated the mechanism by: (1) recording deformation of samples both before and after fracturing during the experiment, (2) varying the chemistry of the water and therefore particle mobility, (3) evaluating the dependence of permeability enhancement and recovery on dynamic stress amplitude, and (4) examining micro-scale pore textures of the rock samples before and after experiments. We find that dynamic stressing does not produce permanent deformation in our samples. Water chemistry has a pronounced effect on the sensitivity to dynamic stressing, with the magnitude of permeability enhancement and the rate of permeability recovery varying with ionic strength of the pore fluid. Permeability recovery rates generally correlate with the permeability enhancement sensitivity. Microstructural observations of our samples show clearing of clay particulates from fracture surfaces during the experiment. From these four lines of evidence, we conclude that a flow-dependent mechanism associated with mobilization of fines controls both the magnitude of the permeability enhancement and the recovery rate in our experiments. We also find that permeability sensitivity to dynamic stressing increases after fracturing, which is a process that generates abundant particulate matter in situ. Our results suggest that fluid permeability in many areas of the

  11. On the influence of residual stress on nano-mechanical characterization of thin coatings.

    Science.gov (United States)

    Sebastiani, M; Bemporad, E; Carassiti, F

    2011-10-01

    In the present paper, the effect of residual stress on the mechanical behavior of thin hard coatings has been investigated by a new methodology based on the combined use of focused ion beam (FIB) micro-machining techniques and nanoindentation testing. Surface elastic residual stress were determined by nanoindentation testing on Focused Ion Beam (FIB) milled micro-pillars. The average residual stress present in a 3.8 microm CAE-PVD TiN coating on WC-Co substrate was calculated by the comparison of two different sets of load-depth curves, the first one obtained at centre of stress relieved pillars, the second one on the undisturbed (residually stressed) surface. Results for stress measurement were in good agreement with the estimate obtained by XRD (sin2 psi method) analysis on the same sample, adopting the same elastic constants. In addition, nanoindentation on stress relieved pillars also allowed to perform a more accurate evaluation of elastic modulus and hardness of the coating. The effect of residual stress on crack propagation modes was quantitatively analyzed by high-load nanoindentation and application of energy methods for fracture toughness evaluation. It is found that compressive residual stress plays a relevant role in determining the fracture behavior and failure modes of the coating. Finally, Microstructural observations of the deformation mechanisms of the TiN coating were performed by TEM analysis on the cross section of the indentation, obtained by FIB lamella thinning. Results showed that plastic deformation at the nanoscale essentially occurs by formation of shear bands inside the columnar grains, independently of residual stress. A transition between intra-granular shear deformation and columnar grain sliding is also observed as a function of the applied load.

  12. Study on mechanism and practice of surrounding rock control of high stress coal roadway

    Institute of Scientific and Technical Information of China (English)

    WANG Wei-jun; YANG Lei; OUYANG Guang-bin

    2006-01-01

    The mechanical principle and surrounding rock deformation feature of high stress coal roadway was analyzed. The condition of stress balance of the kind of the roadway was put forward. The surrounding rock control principle and supporting technique of high stress coal roadway were discussed. It was very important to control early days deformation of coal sides. The supporting strength is should increased, so the strength loss of coal sides is decreased. The range of plastic fluid zone is reduced. The above mention-ned principle is applied in industrial test, and the new supporting technique is applied successfully.

  13. AFM research on the mechanism of Fe-based alloy stress annealed inducing magnetic anisotropy

    Institute of Scientific and Technical Information of China (English)

    FANG YunZhang; ZHENG JinJu; SHI FangYe; WU FengMin; SUN HuaiJun; LIN GenJin; YANG XiaoHong; MAN QiKui; YE FangMin

    2008-01-01

    The cross-section of the Fe-based alloy (Fe73.5Cu1Nb3Si13.5B9) ribbon annealed at 540℃ under various tensile stress was investigated with atomic force microscope (AFM). The stress effect mechanism in Fe-based alloy ribbon tensile stress an- nealed inducing transverse magnetic anisotropy field was studied using the X-ray diffraction spectra and longitudinal drive giant magneto-impedance effect curves, and the model of direction dominant in encapsulated grain agglomeration was es- tablished. The relationship between the direction dominant in encapsulated grain agglomeration and magnetic anisotropy field was disclosed.

  14. AFM research on the mechanism of Fe-based alloy stress annealed inducing magnetic anisotropy

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The cross-section of the Fe-based alloy (Fe73.5Cu1Nb3Si13.5B9) ribbon annealed at 540℃ under various tensile stress was investigated with atomic force microscope (AFM). The stress effect mechanism in Fe-based alloy ribbon tensile stress an-nealed inducing transverse magnetic anisotropy field was studied using the X-ray diffraction spectra and longitudinal drive giant magneto-impedance effect curves, and the model of direction dominant in encapsulated grain agglomeration was es-tablished. The relationship between the direction dominant in encapsulated grain agglomeration and magnetic anisotropy field was disclosed.

  15. Effects of Geometry of Reactor Pressure Vessel Upper Head Control Rod Drive Mechanism Penetration Nozzles on J-Groove Weld Residual Stress

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Ju Hee; Kim, Yun Jae; Bae, Hong Yeol [Korea University, Seoul (Korea, Republic of); and others

    2011-10-15

    In pressurized water reactors (PWRs), the reactor pressure vessel (RPV) upper head contains numerous control rod drive mechanism (CRDM) nozzles. In the last 10 years, the incidences of cracking in alloy 600 CRDM nozzles and their associated welds has increased significantly. Several axial and circumferential cracks have been found in CRDM nozzles in European PWRs and U.S. nuclear power plants. These cracks are caused by primary water stress corrosion cracking (PWSCC) and have been shown to be driven by welding residual stresses and operational stresses in the weld region. Therefore, detailed finite-element (FE) simulations for the Korea Nuclear Reactor Pressure Vessel have been conducted in order to predict the magnitudes of the weld residual stresses in the tube materials. In particular, the weld residual stress results are compared in terms for nozzle location, geometry factor ro/t, geometry of fillet, and adjacent nozzle.

  16. Assessment of Clinical Stressful Factors Among Academic Students of Nursing and Operating Room of Dezful University of Medical Sciences (2015

    Directory of Open Access Journals (Sweden)

    Mojtaba Raji

    2016-07-01

    Full Text Available Background and Objective: Nursing students are exposed to clinical environmental stresses in addition to educational environmental stresses. The aim of this study was to assessment of clinical stressful factors among Academic Students of Nursing and Operating Room of Dezful University of Medical Sciences in 2015.Materials and Methods: This study was a description-analytical study with 234 students of nursing and operation room up to two semesters for enrolled. Data was using a self-made researcher Questionnaire consisted of demographic information and clinical stressful factors. Data analysis was performed by descriptive and inferential statistics using SPSS-PC (v.20.Results: The findings showed that the main stressors in students of nursing and operation room were unpleasant emotions and least stressful areas were interpersonal communication in a clinical environment. The results showed that the average score of the field of education and humiliating experiences using Spearman correlation test (P=0/045 (r=0/16.Conclusion: Study showed, the mean stress is the moderate level. Stressful areas obtained in the four areas of personal communication, clinical practice stressful, unpleasant feelings and humiliating experience that fortunately, in many cases reform and change.

  17. Thermo-mechanical stress analysis of cryopreservation in cryobags and the potential benefit of nanowarming.

    Science.gov (United States)

    Solanki, Prem K; Bischof, John C; Rabin, Yoed

    2017-02-10

    Cryopreservation by vitrification is the only promising solution for long-term organ preservation which can save tens of thousands of lives across the world every year. One of the challenges in cryopreservation of large-size tissues and organs is to prevent fracture formation due to the tendency of the material to contract with temperature. The current study focuses on a pillow-like shape of a cryobag, while exploring various strategies to reduce thermo-mechanical stress during the rewarming phase of the cryopreservation protocol, where maximum stresses are typically found. It is demonstrated in this study that while the level of stress may generally increase with the increasing amount of CPA filled in the cryobag, the ratio between width and length of the cryobag play a significant role. Counterintuitively, the overall maximum stress is not found when the bag is filled to its maximum capacity (when the filled cryobag resembles a sphere). Parametric investigation suggests that reducing the initial rewarming rate between the storage temperature and the glass transition temperature may dramatically decrease the thermo-mechanical stress. Adding a temperature hold during rewarming at the glass transition temperature may reduce the thermo-mechanical stress in some cases, but may have an adverse effect in other cases. Finally, it is demonstrated that careful incorporation of volumetric heating by means on nanoparticles in an alternating magnetic field, or nanowarming, can dramatically reduce the resulting thermo-mechanical stress. These observations display the potential benefit of a thermo-mechanical design of the cryopreservation protocols in order to prevent structural damage.

  18. Mechanical and chemical behavior of intergranular fluids in nonhydrostatically stressed rocks at low temperature

    Institute of Scientific and Technical Information of China (English)

    刘亮明; 彭省临

    2001-01-01

    Intergranular fluids within the nonhydrostatically stressed solids are a sort of important fluids in the crust. Research on the mechanical and chemical behavior of the intergranular fluids in nonhydrostatically stressed rocks at low temperature is a key for understanding deformation and syntectonic geochemical processes in mid to shallow crust. Theoretically, it is suggested that the fluid film sandwiched between solid grains is one of the main states of intergranular fluids in the nonhydrostatically stressed solids. Their superthin thickness makes the fluid films have the mechanical and chemical behavior very different from the common fluids. Because of hydration force, double-layer repulsive force or osmotic pressure due to double-layer, the fluid films can transmit nonhydrostatic stress. The solid minerals-intergranular fluids interaction and mass transfer by intergranular fluids is stress-related, because the stress in solid minerals can enhance the free energy of solid matter on the interfaces. The thermodynamic and kinetic equations for the simple case of stress induced processes are derived.

  19. Increased Dicarbonyl Stress as a Novel Mechanism of Multi-Organ Failure in Critical Illness

    Science.gov (United States)

    van Bussel, Bas C. T.; van de Poll, Marcel C. G.; Schalkwijk, Casper G.; Bergmans, Dennis C. J. J.

    2017-01-01

    Molecular pathological pathways leading to multi-organ failure in critical illness are progressively being unravelled. However, attempts to modulate these pathways have not yet improved the clinical outcome. Therefore, new targetable mechanisms should be investigated. We hypothesize that increased dicarbonyl stress is such a mechanism. Dicarbonyl stress is the accumulation of dicarbonyl metabolites (i.e., methylglyoxal, glyoxal, and 3-deoxyglucosone) that damages intracellular proteins, modifies extracellular matrix proteins, and alters plasma proteins. Increased dicarbonyl stress has been shown to impair the renal, cardiovascular, and central nervous system function, and possibly also the hepatic and respiratory function. In addition to hyperglycaemia, hypoxia and inflammation can cause increased dicarbonyl stress, and these conditions are prevalent in critical illness. Hypoxia and inflammation have been shown to drive the rapid intracellular accumulation of reactive dicarbonyls, i.e., through reduced glyoxalase-1 activity, which is the key enzyme in the dicarbonyl detoxification enzyme system. In critical illness, hypoxia and inflammation, with or without hyperglycaemia, could thus increase dicarbonyl stress in a way that might contribute to multi-organ failure. Thus, we hypothesize that increased dicarbonyl stress in critical illness, such as sepsis and major trauma, contributes to the development of multi-organ failure. This mechanism has the potential for new therapeutic intervention in critical care. PMID:28178202

  20. Increased Dicarbonyl Stress as a Novel Mechanism of Multi-Organ Failure in Critical Illness.

    Science.gov (United States)

    van Bussel, Bas C T; van de Poll, Marcel C G; Schalkwijk, Casper G; Bergmans, Dennis C J J

    2017-02-07

    Molecular pathological pathways leading to multi-organ failure in critical illness are progressively being unravelled. However, attempts to modulate these pathways have not yet improved the clinical outcome. Therefore, new targetable mechanisms should be investigated. We hypothesize that increased dicarbonyl stress is such a mechanism. Dicarbonyl stress is the accumulation of dicarbonyl metabolites (i.e., methylglyoxal, glyoxal, and 3-deoxyglucosone) that damages intracellular proteins, modifies extracellular matrix proteins, and alters plasma proteins. Increased dicarbonyl stress has been shown to impair the renal, cardiovascular, and central nervous system function, and possibly also the hepatic and respiratory function. In addition to hyperglycaemia, hypoxia and inflammation can cause increased dicarbonyl stress, and these conditions are prevalent in critical illness. Hypoxia and inflammation have been shown to drive the rapid intracellular accumulation of reactive dicarbonyls, i.e., through reduced glyoxalase-1 activity, which is the key enzyme in the dicarbonyl detoxification enzyme system. In critical illness, hypoxia and inflammation, with or without hyperglycaemia, could thus increase dicarbonyl stress in a way that might contribute to multi-organ failure. Thus, we hypothesize that increased dicarbonyl stress in critical illness, such as sepsis and major trauma, contributes to the development of multi-organ failure. This mechanism has the potential for new therapeutic intervention in critical care.

  1. Tuning the tunneling probability by mechanical stress in Schottky barrier based reconfigurable nanowire transistors

    Science.gov (United States)

    Baldauf, Tim; Heinzig, André; Trommer, Jens; Mikolajick, Thomas; Weber, Walter Michael

    2017-02-01

    Mechanical stress is an established and important tool of the semiconductor industry to improve the performance of modern transistors. It is well understood for the enhancement of carrier mobility but rather unexplored for the control of the tunneling probability for injection dominated research devices based on tunneling phenomena, such as tunnel FETs, resonant tunnel FETs and reconfigurable Schottky FETs. In this work, the effect of stress on the tunneling probability and overall transistor characteristics is studied by three-dimensional device simulations in the example of reconfigurable silicon nanowire Schottky barrier transistors using two independently gated Schottky junctions. To this end, four different stress sources are investigated. The effects of mechanical stress on the average effective tunneling mass and on the multi-valley band structure applying the deformation potential theory are being considered. The transfer characteristics of strained transistors in n- and p-configuration and corresponding charge carrier tunneling are analyzed with respect to the current ratio between electron and hole conduction. For the implementation of these devices into complementary circuits, the mandatory current ratio of unity can be achieved by appropriate mechanical stress either by nanowire oxidation or the application of a stressed top layer.

  2. Mechanisms of food processing and storage-related stress tolerance in Clostridium botulinum.

    Science.gov (United States)

    Dahlsten, Elias; Lindström, Miia; Korkeala, Hannu

    2015-05-01

    Vegetative cultures of Clostridium botulinum produce the extremely potent botulinum neurotoxin, and may jeopardize the safety of foods unless sufficient measures to prevent growth are applied. Minimal food processing relies on combinations of mild treatments, primarily to avoid deterioration of the sensory qualities of the food. Tolerance of C. botulinum to minimal food processing is well characterized. However, data on effects of successive treatments on robustness towards further processing is lacking. Developments in genetic manipulation tools and the availability of annotated genomes have allowed identification of genetic mechanisms involved in stress tolerance of C. botulinum. Most studies focused on low temperature, and the importance of various regulatory mechanisms in cold tolerance of C. botulinum has been demonstrated. Furthermore, novel roles in cold tolerance were shown for metabolic pathways under the control of these regulators. A role for secondary oxidative stress in tolerance to extreme temperatures has been proposed. Additionally, genetic mechanisms related to tolerance to heat, low pH, and high salinity have been characterized. Data on genetic stress-related mechanisms of psychrotrophic Group II C. botulinum strains are scarce; these mechanisms are of interest for food safety research and should thus be investigated. This minireview encompasses the importance of C. botulinum as a food safety hazard and its central physiological characteristics related to food-processing and storage-related stress. Special attention is given to recent findings considering genetic mechanisms C. botulinum utilizes in detecting and countering these adverse conditions.

  3. 42 CFR 433.116 - FFP for operation of mechanized claims processing and information retrieval systems.

    Science.gov (United States)

    2010-10-01

    ... FISCAL ADMINISTRATION Mechanized Claims Processing and Information Retrieval Systems § 433.116 FFP for operation of mechanized claims processing and information retrieval systems. (a) Subject to 42 CFR 433.113(c... and information retrieval systems. 433.116 Section 433.116 Public Health CENTERS FOR...

  4. The role of mechanization and integration of manufacturing processes in achieving operational performance

    DEFF Research Database (Denmark)

    Naqvi, Syed Turab Haider; Farooq, Sami; Johansen, John

    2014-01-01

    Small manufacturing firms are the dominant organization type for most of the developed countries. However, these firms have not been the focus of research and their strategic and operational needs are not extensively addressed by the academic community. Therefore, this research aims at empirically...... finding the impact of mechanization and integration of manufacturing processes and systems on operational performance in small Danish manufacturing firms. We use data of 357 small Danish manufacturing firms and empirically found distinct impact of mechanization and integration of systems on operational...... performance in context of production to order (PTO) and production to stock (PTS) strategies....

  5. The role of mechanization and integration of manufacturing processes in achieving operational performance

    DEFF Research Database (Denmark)

    Naqvi, Syed Turab Haider; Farooq, Sami; Johansen, John

    2014-01-01

    finding the impact of mechanization and integration of manufacturing processes and systems on operational performance in small Danish manufacturing firms. We use data of 357 small Danish manufacturing firms and empirically found distinct impact of mechanization and integration of systems on operational......Small manufacturing firms are the dominant organization type for most of the developed countries. However, these firms have not been the focus of research and their strategic and operational needs are not extensively addressed by the academic community. Therefore, this research aims at empirically...

  6. Effect of STI-induced mechanical stress on leakage current in deep submicron CMOS devices

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The shallow trench isolation (STI) induced mechanical stress significantly affects the CMOS device off-state leakage behaviour. In this paper, we designed two types of devices to investigate this effect, and all leakage components,including sub-threshold leakage (Isub), gate-induced-drain-leakage (IGIDL), gate edge-direct-tunnelling leakage (IEDT) and band-to-band-tunnelling leakage (IBTBT) were analysed. For NMOS, Isub can be reduced due to the mechanical stress induced higher boron concentration in well region. However, the GIDL component increases simultaneously as a result of the high well concentration induced drain-to-well depletion layer narrowing as well as the shrinkage of the energy gap. For PMOS, the only mechanical stress effect on leakage current is the energy gap narrowing induced GIDL increase.

  7. Mechanical-Stress Analytical Modeling for the Design of Coils in Power Applications

    Directory of Open Access Journals (Sweden)

    Bellan D.

    2014-12-01

    Full Text Available Modern electrical-power systems are often exploited for transmitting high-frequency carrier signals for communications purposes. Series-connected air-core coils represent the fundamental component allowing such applications by providing a proper filtering in the frequency domain. They must be designed, however, to withstand also the line short-circuit current. When a high-magnitude current flows through a coil, strong mechanical stresses are produced within the conductor, leading to possible damage of the coil. In this paper, an approximate analytical model is derived for the relationship between the maximum mechanical stress and the electrical/geometrical parameters of the coil. Such a model provides the guidelines for a fast and safe coil design, whereas numerical simulations are only needed for the design refinement. The presented approach can be extended to other applications such as, for example, the mechanical stress resulting from the inrush currents in the coils of power transformers.

  8. Thermo-Mechanical Behaviour of Turbine Disc Assembly in the Presence of Residual Stresses

    Science.gov (United States)

    Maricic, Luke Anthony

    A comprehensive three dimensional coupled thermo-mechanical finite element study is performed on turbine blade attachments in gas turbine engines. The effects of the self-generated centrifugal forces of the disc and the associated blades, thermal loads, and shot peening residual are all considered in this thesis. Three aspects of the work were accordingly examined. The first was concerned with the coupled thermo-mechanical stress analysis and load sharing between the teeth of the fir-tree root. The second was devoted to the development of a complete model incorporating the effect of shot peening residual stresses upon the developed stress state. The effectiveness of shot peening treatment in response to cyclic thermo-mechanical loadings at the contact interface has also been studied. The third was concerned with the validation of some aspects of the developed models analytically using closed form solutions and experimentally using photoelasticity.

  9. Aneuploidy as a mechanism for stress-induced liver adaptation.

    Science.gov (United States)

    Duncan, Andrew W; Hanlon Newell, Amy E; Bi, Weimin; Finegold, Milton J; Olson, Susan B; Beaudet, Arthur L; Grompe, Markus

    2012-09-01

    Over half of the mature hepatocytes in mice and humans are aneuploid and yet retain full ability to undergo mitosis. This observation has raised the question of whether this unusual somatic genetic variation evolved as an adaptive mechanism in response to hepatic injury. According to this model, hepatotoxic insults select for hepatocytes with specific numerical chromosome abnormalities, rendering them differentially resistant to injury. To test this hypothesis, we utilized a strain of mice heterozygous for a mutation in the homogentisic acid dioxygenase (Hgd) gene located on chromosome 16. Loss of the remaining Hgd allele protects from fumarylacetoacetate hydrolase (Fah) deficiency, a genetic liver disease model. When adult mice heterozygous for Hgd and lacking Fah were exposed to chronic liver damage, injury-resistant nodules consisting of Hgd-null hepatocytes rapidly emerged. To determine whether aneuploidy played a role in this phenomenon, array comparative genomic hybridization (aCGH) and metaphase karyotyping were performed. Strikingly, loss of chromosome 16 was dramatically enriched in all mice that became completely resistant to tyrosinemia-induced hepatic injury. The frequency of chromosome 16-specific aneuploidy was approximately 50%. This result indicates that selection of a specific aneuploid karyotype can result in the adaptation of hepatocytes to chronic liver injury. The extent to which aneuploidy promotes hepatic adaptation in humans remains under investigation.

  10. Heavy Metal Stress and Some Mechanisms of Plant Defense Response

    Directory of Open Access Journals (Sweden)

    Abolghassem Emamverdian

    2015-01-01

    Full Text Available Unprecedented bioaccumulation and biomagnification of heavy metals (HMs in the environment have become a dilemma for all living organisms including plants. HMs at toxic levels have the capability to interact with several vital cellular biomolecules such as nuclear proteins and DNA, leading to excessive augmentation of reactive oxygen species (ROS. This would inflict serious morphological, metabolic, and physiological anomalies in plants ranging from chlorosis of shoot to lipid peroxidation and protein degradation. In response, plants are equipped with a repertoire of mechanisms to counteract heavy metal (HM toxicity. The key elements of these are chelating metals by forming phytochelatins (PCs or metallothioneins (MTs metal complex at the intra- and intercellular level, which is followed by the removal of HM ions from sensitive sites or vacuolar sequestration of ligand-metal complex. Nonenzymatically synthesized compounds such as proline (Pro are able to strengthen metal-detoxification capacity of intracellular antioxidant enzymes. Another important additive component of plant defense system is symbiotic association with arbuscular mycorrhizal (AM fungi. AM can effectively immobilize HMs and reduce their uptake by host plants via binding metal ions to hyphal cell wall and excreting several extracellular biomolecules. Additionally, AM fungi can enhance activities of antioxidant defense machinery of plants.

  11. Preliminary research to determine stress districts from focal mechanism solutions in Southwest China and its adjacent area

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    The method of sliding direction fitting is used to determine stress districts, taking the shear stress directions and ratios of shear stress to stress on fault planes given by focal mechanism solutions as the criteria to select focal mechanism solutions of one region and sorting out the earthquakes controlled by different tectonic stress fields, and then determining the stress districts from epicenter distribution of earthquakes. We call this method as step by step convergence method. By inversion analyzing of 297 focal mechanism solutions, we consider that Southwest China and its adjacent area can be divided into 5 stress districts, and we worked out directions of the three principal stresses and values of shape factor φin 5 stress districts.

  12. Mechanical Weakening during Fluid Injection in Critically Stressed Sandstones with Acoustic Monitoring

    Science.gov (United States)

    David, C.; Dautriat, J. D.; Sarout, J.; Macault, R.; Bertauld, D.

    2014-12-01

    Water weakening is a well-known phenomenon which can lead to subsidence during the production of hydrocarbon reservoirs. The example of the Ekofisk oil field in the North Sea has been well documented for years. In order to assess water weakening effects in reservoir rocks, previous studies have focused on changes in the failure envelopes derived from mechanical tests conducted on rocks saturated either with water or with inert fluids. However, little attention has been paid so far on the mechanical behaviour during the fluid injection stage, like in enhanced oil recovery operations. We studied the effect of fluid injection on the mechanical behaviour of Sherwood sandstone, a weakly-consolidated sandstone sampled at Ladram Bay in UK. In order to highlight possible weakening effects, water and inert oil have been injected into critically-loaded samples to assess their effect on strength and elastic properties and to derive the acoustic signature of the saturation front for each fluid. The specimens were instrumented with 16 ultrasonic P-wave transducers for both passive and active acoustic monitoring during fluid injection and loading. After conducting standard triaxial tests on three samples saturated with air, water and oil respectively, mechanical creep tests were conducted on dry samples loaded at 80% of the compressive strength of the dry rock. While these conditions are kept constant, a fluid is injected at the bottom end of the sample with a low back pressure (0.5 MPa) to minimize effective stress variations during injection. Both water and oil were used as the injected pore fluid in two experiments. As soon as the fluids start to flow into the samples, creep is taking place with a much higher strain rate for water injection compared to oil injection. A transition from secondary creep to tertiary creep is observed in the water injection test whereas in the oil injection test no significant creep acceleration is observed after one pore volume of oil was

  13. NEW METHODS FOR TUNING OF MECHANICAL SYSTEMS DURING OPERATION IN STEADY STATE

    Directory of Open Access Journals (Sweden)

    Jaroslav HOMIŠIN

    2014-12-01

    Full Text Available The main purpose of this paper is to inform the technical community about new tuning methods of torsional oscillating mechanical systems (TOMS during operation in a steady state by means of application of pneumatic flexible shaft couplings. It is possible to change the torsional stiffness of pneumatic couplings by means of a change of gaseous medium pressure either out of operation or during operation. There are two possibilities how to tune the torsional oscillating mechanical systems: - tuning of torsion oscillating mechanical systems out of operation, what fulfils condition of given system tuning, - tuning of torsion oscillating mechanical systems during operation in a steady state, what fulfils condition of given system continual tuning. The basic principle of TOMS tuning during operation in the steady state consists in an adjustment of basic dynamical properties of pneumatic coupling according to the system dynamics. This adjustment can be made by means of a regulation system working in regulation circuit arrangement with a feedback. In this way it is possible to change dynamical properties of pneumatic coupling continuously with regard to dynamic of mechanical system, so that it can be eliminated dangerous torsional oscillation of given system in the working mode.

  14. Trophic mechanisms for exercise-induced stress resilience: Potential role of interactions between BDNF and galanin

    Directory of Open Access Journals (Sweden)

    Philip V Holmes

    2014-07-01

    Full Text Available Current concepts of the neurobiology of stress-related disorders such as anxiety and depression emphasize disruptions in neural plasticity and neurotrophins. The potent trophic actions of exercise therefore represent not only an effective means for prevention and treatment of these disorders, they also afford the opportunity to employ exercise paradigms as a basic research tool to uncover the neurobiological mechanisms underlying these disorders. Novel approaches to studying stress-related disorders focus increasingly on trophic factor signaling in corticolimbic circuits that both mediate and regulate cognitive, behavioral, and physiological responses to deleterious stress. Recent evidence demonstrates that the neural plasticity supported by these trophic mechanisms is vital for establishing and maintaining resilience to stress. Therapeutic interventions that promote these mechanisms, be they pharmacological, behavioral, or environmental, may therefore prevent or reverse stress-related mental illness by enhancing resilience. The present paper will provide an overview of trophic mechanisms responsible for the enhancement of resilience by voluntary exercise with an emphasis on BDNF, galanin, and interactions between these two trophic factors.

  15. Three-dimensional Finite Element Analysis of the Mechanical Stress on Root from Orthodontic Tooth Movement by Sliding Mechanics

    Institute of Scientific and Technical Information of China (English)

    LI Ping; MAO Jing; PENG Zhou; XIE Hui

    2007-01-01

    In order to study mechanical stress on root from orthodontic tooth movement by sliding mechanics, a 3-dimensional finite element model incorporating all layers of a human mandibular dental arch with orthodontic appliance has been developed to simulate mechanical stress on root from the orthodontic tooth movement. Simulated orthodontic force of 2 N at 0, 30 and 45 degree from the horizontal axis was applied to the crown of the teeth. The finite element analysis showed when or- thodontic forces were applied to the tooth, the stress was mainly concentrated at the neck of the tooth decreasing uniformly to the apex and crown. The highest stress on the root was 0.621 N/ram2 for cer- vical margin of the canine, and 0.114 N/mm2 for apical region of the canine. The top of canine crown showed the largest amount of displacement (2.417 μm), while the lowest amount of displacement was located at the apical region of canine (0.043 μm). In conclusion, this model might enable one to simulate orthodontic tooth movements clinically. Sliding force at 2 N is ideal to ensure the bodily or- thodontic tooth movement. The highest stress concentration in the roots was always localized at the cervical margin when orthodontic force of 2 N at 0, 30 and 45 degree from the horizontal axis, so there may be the same risk of root resorption when orthodontic force of 2 N at 0, 30 and 45 degree was used in clinic cases.

  16. Stress Analysis and Failure Mechanisms of Plasma-Sprayed Thermal Barrier Coatings

    Science.gov (United States)

    Yang, Jiasheng; Wang, Liang; Li, Dachuan; Zhong, Xinghua; Zhao, Huayu; Tao, Shunyan

    2017-06-01

    Yttria-stabilized zirconia coatings were deposited by plasma spraying and heat-treated at 1100 °C for 50, 100, 150, and 200 h in air, respectively. Mechanical properties including microhardness and Young's modulus were evaluated using the nanoindentation test. Residual stresses in the ceramic topcoat and the thermally grown oxide (TGO) layer were measured using Raman spectroscopy and photoluminescence piezo-spectroscopy (PLPS) techniques, respectively. The results showed that both the modulus and hardness increased with the thermal exposure time up to 100 h and then gradually decreased. The accumulated tensile stress in the as-sprayed topcoat changed to compressive stress after thermal exposure, and the compressive stress in the topcoat increased with an increase of thermal exposure time up to 150 h. The average compressive stresses in the TGO layer were higher than that of the cross-sectional topcoat, and the measured in-plane compressive stress increased firstly and then gradually decreased with increasing exposure time. The local interface geometry strongly affect the nature and evolution of hydrostatic stresses in the TGO. Finally, the crack initiation and propagation at the topcoat/TGO/bondcoat interface has been discussed with respect to the residual stresses in the plasma-sprayed TBC system.

  17. Periodic variation of stress field in the Koyna-Warna reservoir triggered seismic zone inferred from focal mechanism studies

    Science.gov (United States)

    Rao, N. Purnachandra; Shashidhar, D.

    2016-06-01

    The Koyna-Warna region in western India is globally recognized as the premier site of reservoir triggered seismicity (RTS) associated with the Koyna and Warna reservoirs. The region is characterized by continuous seismic activity observed since several decades, including the world's largest triggered earthquake of M6.3 which occurred in Koyna in 1967. While the role of reservoirs in triggering earthquakes has been widely discussed, the actual tectonic mechanism controlling earthquake genesis in this region is hardly understood. The Koyna-Warna region is exclusively governed by earthquakes of strike-slip and normal fault mechanism distinct from the thrust faulting seen in other active zones in the Indian region. In the present study, a comprehensive catalog of 50 focal mechanism solutions of earthquakes that occurred during the last 45 years in the Koyna-Warna region is developed, both from previous literature and from moment tensor inversion studies by the authors using broadband data from a local seismic network operating since 2005. The seismicity and fault plane data have enabled precise delineation of trends of the major causative faults, which are further accentuated using the double-difference technique. Stress inversion of the focal mechanism data has provided the best fitting principal compressive and tensile stress field of the region, which in conjunction with the deciphered fault zones provides a feasible model of seismogenesis in this region. Based on the observed temporal variation of faulting mechanism a model of alternating cycles of predominantly strike-slip and normal faulting is proposed, which is attributed to a periodic peaking and relaxation respectively of the horizontal compressive stress field in this region due to the Indian plate collision with Eurasia.

  18. Stress, deformation, conservation, and rheology: a survey of key concepts in continuum mechanics

    Science.gov (United States)

    Major, J.J.

    2013-01-01

    This chapter provides a brief survey of key concepts in continuum mechanics. It focuses on the fundamental physical concepts that underlie derivations of the mathematical formulations of stress, strain, hydraulic head, pore-fluid pressure, and conservation equations. It then shows how stresses are linked to strain and rates of distortion through some special cases of idealized material behaviors. The goal is to equip the reader with a physical understanding of key mathematical formulations that anchor continuum mechanics in order to better understand theoretical studies published in geomorphology.

  19. p75 neurotrophin receptor signaling: mechanisms for neurotrophic modulation of cell stress?

    Science.gov (United States)

    Dobrowsky, R T; Carter, B D

    2000-08-01

    The recent recognition that the p75 neurotrophin receptor, p75((NTR)), can induce apoptotic signals has contributed to the perception that it acts primarily as a death receptor. Although the molecular mechanisms of p75(NTR) signaling remain to be fully characterized, many of the currently identified pathways activated by p75(NTR) may be generally characterized as stress response signals. This review describes recent advances in identifying the molecular components involved in p75(NTR) signal transduction and suggests that p75(NTR) signaling may more aptly serve as a general mechanism for the transduction and modulation of stress signals.

  20. Beller Lectureship Talk: Active response of biological cells to mechanical stress

    Science.gov (United States)

    Safran, Samuel

    2009-03-01

    Forces exerted by and on adherent cells are important for many physiological processes such as wound healing and tissue formation. In addition, recent experiments have shown that stem cell differentiation is controlled, at least in part, by the elasticity of the surrounding matrix. We present a simple and generic theoretical model for the active response of biological cells to mechanical stress. The theory includes cell activity and mechanical forces as well as random forces as factors that determine the polarizability that relates cell orientation to stress. This allows us to explain the puzzling observation of parallel (or sometimes random) alignment of cells for static and quasi-static stresses and of nearly perpendicular alignment for dynamically varying stresses. In addition, we predict the response of the cellular orientation to a sinusoidally varying applied stress as a function of frequency and compare the theory with recent experiments. The dependence of the cell orientation angle on the Poisson ratio of the surrounding material distinguishes cells whose activity is controlled by stress from those controlled by strain. We have extended the theory to generalize the treatment of elastic inclusions in solids to ''living'' inclusions (cells) whose active polarizability, analogous to the polarizability of non-living matter, results in the feedback of cellular forces that develop in response to matrix stresses. We use this to explain recent observations of the non-monotonic dependence of stress-fiber polarization in stem cells on matrix rigidity. These findings provide a mechanical correlate for the existence of an optimal substrate elasticity for cell differentiation and function. [3pt] *In collaboration with R. De (Brown University), Y. Biton (Weizmann Institute), and A. Zemel (Hebrew University) and the experimental groups: Max Planck Institute, Stuttgart: S. Jungbauer, R. Kemkemer, J. Spatz; University of Pennsylvania: A. Brown, D. Discher, F. Rehfeldt.

  1. Stress field estimation based on focal mechanisms and back projected imaging in the Eastern Llanos Basin (Colombia)

    Science.gov (United States)

    Gómez-Alba, Sebastián; Fajardo-Zarate, Carlos Eduardo; Vargas, Carlos Alberto

    2016-11-01

    At least 156 earthquakes (Mw 2.8-4.4) were detected in Puerto Gaitán, Colombia (Eastern Llanos Basin) between April 2013 and December 2014. Out of context, this figure is not surprising. However, from its inception in 1993, the Colombian National Seismological Network (CNSN) found no evidence of significant seismic events in this region. In this study, we used CNSN data to model the rupture front and orientation of the highest-energy events. For these earthquakes, we relied on a joint inversion method to estimate focal mechanisms and, in turn, determine the area's fault trends and stress tensor. While the stress tensor defines maximum stress with normal tendency, focal mechanisms generally represent normal faults with NW orientation, an orientation which lines up with the tracking rupture achieved via Back Projection Imaging for the study area. We ought to bear in mind that this anomalous earthquake activity has taken place within oil fields. In short, the present paper argues that, based on the spatiotemporal distribution of seismic events, hydrocarbon operations may induce the study area's seismicity.

  2. Explicit expressions of quantum mechanical rotation operators for spins 1 to 2

    Science.gov (United States)

    Kocakoç, Mehpeyker; Tapramaz, Recep

    2016-03-01

    Quantum mechanical rotation operators are the subject of quantum mechanics, mathematics and pulsed magnetic resonance spectroscopies, namely NMR, EPR and ENDOR. They are also necessary for spin based quantum information systems. The rotation operators of spin 1/2 are well known and can be found in related textbooks. But rotation operators of other spins greater than 1/2 can be found numerically by evaluating the series expansions of exponential operator obtained from Schrödinger equation, or by evaluating Wigner-d formula or by evaluating recently established expressions in polynomial forms discussed in the text. In this work, explicit symbolic expressions of x, y and z components of rotation operators for spins 1 to 2 are worked out by evaluating series expansion of exponential operator for each element of operators and utilizing linear curve fitting process. The procedures gave out exact expressions of each element of the rotation operators. The operators of spins greater than 2 are under study and will be published in a separate paper.

  3. Investigation of abrupt degradation of drain current caused by under-gate crack in AlGaN/GaN high electron mobility transistors during high temperature operation stress

    Energy Technology Data Exchange (ETDEWEB)

    Zeng, Chang; Liao, XueYang; Li, RuGuan; Wang, YuanSheng; Chen, Yiqiang, E-mail: yiqiang-chen@hotmail.com; Su, Wei; Liu, Yuan; Wang, Li Wei; Lai, Ping; Huang, Yun; En, YunFei [Science and Technology on Reliability Physics and Application of Electronic Component Laboratory, The 5th Electronics Research Institute of the Ministry of Industry and Information Technology, 510610 Guangzhou (China)

    2015-09-28

    In this paper, we investigate the degradation mode and mechanism of AlGaN/GaN based high electron mobility transistors (HEMTs) during high temperature operation (HTO) stress. It demonstrates that there was abrupt degradation mode of drain current during HTO stress. The abrupt degradation is ascribed to the formation of crack under the gate which was the result of the brittle fracture of epilayer based on failure analysis. The origin of the mechanical damage under the gate is further investigated and discussed based on top-down scanning electron microscope, cross section transmission electron microscope and energy dispersive x-ray spectroscopy analysis, and stress simulation. Based on the coupled analysis of the failure physical feature and stress simulation considering the coefficient of thermal expansion (CTE) mismatch in different materials in gate metals/semiconductor system, the mechanical damage under the gate is related to mechanical stress induced by CTE mismatch in Au/Ti/Mo/GaN system and stress concentration caused by the localized structural damage at the drain side of the gate edge. These results indicate that mechanical stress induced by CTE mismatch of materials inside the device plays great important role on the reliability of AlGaN/GaN HEMTs during HTO stress.

  4. Increased skin autofluorescence after colorectal operation reflects surgical stress and postoperative outcome

    NARCIS (Netherlands)

    Pol, Henk Willem D.; Sibma, Els; Zeebregts, Clark J.; Pierik, Erik G. J. M.; Meerwaldt, Robbert

    2011-01-01

    BACKGROUND: Abdominal surgery is a major oxidative stress effector. The increase in oxidative stress has been related to postoperative complications. Oxidative stress leads to the formation and accumulation of oxidation protein end products, which exhibit autofluorescence (AF) and induce inflammator

  5. Physiological, biochemical, and molecular mechanisms of heat stress tolerance in plants.

    Science.gov (United States)

    Hasanuzzaman, Mirza; Nahar, Kamrun; Alam, Md Mahabub; Roychowdhury, Rajib; Fujita, Masayuki

    2013-05-03

    High temperature (HT) stress is a major environmental stress that limits plant growth, metabolism, and productivity worldwide. Plant growth and development involve numerous biochemical reactions that are sensitive to temperature. Plant responses to HT vary with the degree and duration of HT and the plant type. HT is now a major concern for crop production and approaches for sustaining high yields of crop plants under HT stress are important agricultural goals. Plants possess a number of adaptive, avoidance, or acclimation mechanisms to cope with HT situations. In addition, major tolerance mechanisms that employ ion transporters, proteins, osmoprotectants, antioxidants, and other factors involved in signaling cascades and transcriptional control are activated to offset stress-induced biochemical and physiological alterations. Plant survival under HT stress depends on the ability to perceive the HT stimulus, generate and transmit the signal, and initiate appropriate physiological and biochemical changes. HT-induced gene expression and metabolite synthesis also substantially improve tolerance. The physiological and biochemical responses to heat stress are active research areas, and the molecular approaches are being adopted for developing HT tolerance in plants. This article reviews the recent findings on responses, adaptation, and tolerance to HT at the cellular, organellar, and whole plant levels and describes various approaches being taken to enhance thermotolerance in plants.

  6. Emotion dysregulation as a mechanism linking stress exposure to adolescent aggressive behavior.

    Science.gov (United States)

    Herts, Kate L; McLaughlin, Katie A; Hatzenbuehler, Mark L

    2012-10-01

    Exposure to stress is associated with a wide range of internalizing and externalizing problems in adolescents, including aggressive behavior. Extant research examining mechanisms underlying the associations between stress and youth aggression has consistently identified social information processing pathways that are disrupted by exposure to violence and increase risk of aggressive behavior. In the current study, we use longitudinal data to examine emotion dysregulation as a potential mechanism linking a broader range of stressful experiences to aggressive behavior in a diverse sample of early adolescents (N = 1065). Specifically, we examined the longitudinal associations of peer victimization and stressful life events with emotion dysregulation and aggressive behavior. Structural equation modeling was used to create latent constructs of emotion dysregulation and aggression. Both stressful life events and peer victimization predicted subsequent increases in emotion dysregulation over a 4-month period. These increases in emotion dysregulation, in turn, were associated with increases in aggression over the subsequent 3 months. Longitudinal mediation models showed that emotion dysregulation mediated the relationship of both peer victimization (z = 2.35, p = 0.019) and stressful life events (z = 2.32, p = 0.020) with aggressive behavior. Increasing the use of adaptive emotion regulation strategies is an important target for interventions aimed at preventing the onset of adolescent aggressive behavior.

  7. Leaf Proteome Analysis Reveals Prospective Drought and Heat Stress Response Mechanisms in Soybean

    Directory of Open Access Journals (Sweden)

    Aayudh Das

    2016-01-01

    Full Text Available Drought and heat are among the major abiotic stresses that affect soybean crops worldwide. During the current investigation, the effect of drought, heat, and drought plus heat stresses was compared in the leaves of two soybean varieties, Surge and Davison, combining 2D-DIGE proteomic data with physiology and biochemical analyses. We demonstrated how 25 differentially expressed photosynthesis-related proteins affect RuBisCO regulation, electron transport, Calvin cycle, and carbon fixation during drought and heat stress. We also observed higher abundance of heat stress-induced EF-Tu protein in Surge. It is possible that EF-Tu might have activated heat tolerance mechanisms in the soybean. Higher level expressions of heat shock-related protein seem to be regulating the heat tolerance mechanisms. This study identifies the differential expression of various abiotic stress-responsive proteins that regulate various molecular processes and signaling cascades. One inevitable outcome from the biochemical and proteomics assays of this study is that increase of ROS levels during drought stress does not show significant changes at the phenotypic level in Davison and this seems to be due to a higher amount of carbonic anhydrase accumulation in the cell which aids the cell to become more resistant to cytotoxic concentrations of H2O2.

  8. Stress, burnout and depression: A systematic review on DNA methylation mechanisms.

    Science.gov (United States)

    Bakusic, Jelena; Schaufeli, Wilmar; Claes, Stephan; Godderis, Lode

    2017-01-01

    Despite that burnout presents a serious burden for modern society, there are no diagnostic criteria. Additional difficulty is the differential diagnosis with depression. Consequently, there is a need to dispose of a burnout biomarker. Epigenetic studies suggest that DNA methylation is a possible mediator linking individual response to stress and psychopathology and could be considered as a potential biomarker of stress-related mental disorders. Thus, the aim of this review is to provide an overview of DNA methylation mechanisms in stress, burnout and depression. In addition to state-of-the-art overview, the goal of this review is to provide a scientific base for burnout biomarker research. We performed a systematic literature search and identified 25 pertinent articles. Among these, 15 focused on depression, 7 on chronic stress and only 3 on work stress/burnout. Three epigenome-wide studies were identified and the majority of studies used the candidate-gene approach, assessing 12 different genes. The glucocorticoid receptor gene (NR3C1) displayed different methylation patterns in chronic stress and depression. The serotonin transporter gene (SLC6A4) methylation was similarly affected in stress, depression and burnout. Work-related stress and depressive symptoms were associated with different methylation patterns of the brain derived neurotrophic factor gene (BDNF) in the same human sample. The tyrosine hydroxylase (TH) methylation was correlated with work stress in a single study. Additional, thoroughly designed longitudinal studies are necessary for revealing the cause-effect relationship of work stress, epigenetics and burnout, including its overlap with depression.

  9. An effective stress approach for hydro-mechanical coupling of unsaturated soils

    Directory of Open Access Journals (Sweden)

    Arroyo Hiram

    2016-01-01

    Full Text Available The simulation of the mechanical and hydraulic behaviour of soils is one of the most important tasks in soil mechanics. It is inaccurate to consider that the behaviour of saturated and unsaturated soils as if their governing laws were utterly different, this last condition is not sufficient to do so. However, unlike the laws governing the behaviour of saturated soils, those used to describe the behaviour of unsaturated soils lack the simplicity and predictability associated to the complexity of the phenomena that occur within these porous media. This is why it is important to establish a unified soil mechanics theory to reconcile saturated and unsaturated soil mechanics. In the present work, we describe a simple analytical equation to obtain effective stresses for any type of soil. The equation is coupled to an elastoplastic constitutive model which is capable to reproduce the stress-strain relationship of soil taking into account the hydro-dynamic coupling.

  10. Mechanism of preventing coal and gas compression disseminated values outburst with stress pre-released hydraulically

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Zhong-fei; Yu, Qi-xiang [Jiangsu University, Zhenjiang (China). Center of Safety Engineering

    2007-01-15

    Based on the conditions of coal and gas outburst, the action mechanism for preventing coal and gas compression disseminated values outburst with stress pre-released hydraulically was analyzed. The accuracy of this mechanism was validated by measuring the gas emission before and after pre-releasing stress hydraulically, measuring the rupture failure by the electromagnetic radiation technique and the correlative practical datum. The results show that the electromagnetic radiation intensity and pulse count are increscent when taking the measure of stress pre-released hydraulically, which is propitious to prevent the coal and gas outburst. The action mechanism consists of three aspects: 1) Pre-releasing gas and increasing tangential stress and disseminated values friction resistance; 2) Pre-releaseing the radial effective geostress on high-tension side and reducing the radial stress difference of disseminated values chop motion for enhancing coal displacement; 3) Making the disseminated values and adjacent coal and rock felting by flooding water and increasing the disseminated values' friction resistance coefficients. 9 refs., 2 figs.

  11. Oxidative stress-driven parvalbumin interneuron impairment as a common mechanism in models of schizophrenia

    Science.gov (United States)

    Steullet, P; Cabungcal, J-H; Coyle, J; Didriksen, M; Gill, K; Grace, A A; Hensch, T K; LaMantia, A-S; Lindemann, L; Maynard, T M; Meyer, U; Morishita, H; O'Donnell, P; Puhl, M; Cuenod, M; Do, K Q

    2017-01-01

    Parvalbumin inhibitory interneurons (PVIs) are crucial for maintaining proper excitatory/inhibitory balance and high-frequency neuronal synchronization. Their activity supports critical developmental trajectories, sensory and cognitive processing, and social behavior. Despite heterogeneity in the etiology across schizophrenia and autism spectrum disorder, PVI circuits are altered in these psychiatric disorders. Identifying mechanism(s) underlying PVI deficits is essential to establish treatments targeting in particular cognition. On the basis of published and new data, we propose oxidative stress as a common pathological mechanism leading to PVI impairment in schizophrenia and some forms of autism. A series of animal models carrying genetic and/or environmental risks relevant to diverse etiological aspects of these disorders show PVI deficits to be all accompanied by oxidative stress in the anterior cingulate cortex. Specifically, oxidative stress is negatively correlated with the integrity of PVIs and the extracellular perineuronal net enwrapping these interneurons. Oxidative stress may result from dysregulation of systems typically affected in schizophrenia, including glutamatergic, dopaminergic, immune and antioxidant signaling. As convergent end point, redox dysregulation has successfully been targeted to protect PVIs with antioxidants/redox regulators across several animal models. This opens up new perspectives for the use of antioxidant treatments to be applied to at-risk individuals, in close temporal proximity to environmental impacts known to induce oxidative stress. PMID:28322275

  12. Effects of the three-dimensional residual stresses on the mechanical properties of arterial walls.

    Science.gov (United States)

    Zheng, Xianbing; Ren, Jiusheng

    2016-03-21

    Effects of the three-dimensional residual stresses on the mechanical properties of arterial walls are analyzed in this paper, based on the model which considered the bending and stretching both in the circumferential and axial directions of the three distinct arterial layers. Moreover, different constitutive models are proposed to quantify the nonlinear mechanics of the three distinct layers and the important constituents, i.e. elastin, collagen fibers and smooth muscle cells (SMCs), are all taken into account. The stress distributions and pressure-radius curves of the arterial wall are given in details. Results demonstrate that the maximum values of the circumferential stress and the corresponding stress gradient in the media under the mean arterial pressure are reduced significantly as a consequence of the SMCs. The bending in the axial direction of the media and the opening angle of the intima have an obvious impact on the mechanical behaviors of arterial walls. This study may not only develop the understanding of effects of the three-dimensional residual stresses on the arterial wall response, but also can increase the accuracy of the analyses for patient-specific studies used for the treatments of arterial diseases. Copyright © 2016 Elsevier Ltd. All rights reserved.

  13. Physical discomfort and psychosocial job stress among male and female operators at telecommunication call centers in Taiwan.

    Science.gov (United States)

    Lin, Yen-Hui; Chen, Chih-Yong; Lu, Shih-Yi

    2009-07-01

    The prevalence of job stress, distributions of major job stressors, and associations between perceived job stress levels and multiple physical discomforts are assessed via a cross-sectional study of 1023 male and female operators at telecommunication call centers in Taiwan. Cases of discomfort are identified via questionnaire surveys requiring respondents to self-reported symptoms of discomfort. Information is obtained on demographics, health status, perceived job stress levels, major job stressors and psychosocial job characteristics. Multivariate logistic regression models are developed to predict physical discomfort in nine body areas. 'Eye strain', 'hoarse or painful throat' and 'musculoskeletal discomfort' are the most pronounced and prevalent complaints after prolonged work time at call centers. Female operators had higher prevalence of physical discomfort than male operators for all body areas. 'Encountering difficult customers' ranked as the most important job stress factor among both male and female operators. Working in a call center for more than 4 years is strongly associated with discomfort in all body areas (odds ratio ranges from 1.65 to 2.15). Analysis of risk factors vs. physical discomfort reveals that operators who perceive higher job stress have significantly increased risk of several health complaints, including eye strain, tinnitus, hoarse or painful throat, chronic cough with phlegm, chest tightness, irritable stomach or peptic ulcers, frequent urination and musculoskeletal discomfort.

  14. The Dislocation Mechanism of Stress Corrosion Embrittlement in Ti-6Al-2Sn-4Zr-6Mo

    Science.gov (United States)

    Chapman, Tamara P.; Vorontsov, Vassili A.; Sankaran, Ananthi; Rugg, David; Lindley, Trevor C.; Dye, David

    2016-01-01

    An observation of the dislocation mechanisms operating below a naturally initiated hot-salt stress corrosion crack is presented, suggesting how hydrogen may contribute to embrittlement. The observations are consistent with the hydrogen-enhanced localized plasticity mechanism. Dislocation activity has been investigated through post-mortem examination of thin foils prepared by focused ion beam milling, lifted directly from the fracture surface. The results are in agreement with the existing studies, suggesting that hydrogen enhances dislocation motion. It is found that the presence of hydrogen in (solid) solution results in dislocation motion on slip systems that would not normally be expected to be active. A rationale is presented regarding the interplay of dislocation density and the hydrogen diffusion length.

  15. Thermal Stresses in a Cylinder Block Casting Due to Coupled Thermal and Mechanical Effects

    Institute of Scientific and Technical Information of China (English)

    XU Yan; KANG Jinwu; HUANG Tianyou; HU Yongyi

    2008-01-01

    Thermal stress in castings results from nonuniform cooling. The thermal stress and the deforma-tion can change the casting and mold contact conditions which then alter the heat transfer between the cast-ing and the mold. The contact element method was used to study the interaction between a sand mold and a casting. The contact status was then fed back to the heat transfer analysis between the sand mold and the casting to re-evaluate the heat transfer coefficient based on the gap size or pressure between surfaces. The thermal and mechanical phenomena are then coupled in two directions. The method was applied to analyze stress in a stress frame specimen casting and a cylinder block. The results are more accurate than without consideration of the contact effects on the heat transfer.

  16. Simulation of mechanical properties and residual stress of nanostructural coatings based on transition metals nitrides

    Science.gov (United States)

    Danilyuk, Alexander L.; Shaposhnikov, Victor L.; Filonov, Andrew B.; Anischik, Victor M.; Uglov, Vladimir V.; Kuleshov, Andrew K.; Danilyuk, Maxim A.

    2008-07-01

    Physical properties of novel nanostructural coatings, formed by ion-plasmous flux from solid solutions of transition and refractory metals (Ti, Zr, Cr) have been intensively studied to enhance characteristics of tool materials. We have developed the modeling technique for effective predictions of internal stresses and calculation of elastic properties of nanostructural coatings composed of metal nitrides. Quantum-mechanical modeling of microstructure, elastic constants, bulk modulus and residual stress for binary and ternary metal nitride clusters have been performed. The dependences of these characteristics on the crystal structure deformations have been investigated. The essential modification of elastic constants and bulk moduli with changes in lattice constants and stoichiometric composition has been observed. The influence of elastically stressed state of sample on X-ray diffraction intensity has been examined by using the exponential model. The model of residual stress distribution identifying in depth of wear-resistant nanostructural coating from the data of diffraction experiments has been developed.

  17. Mechanisms of Selenium Mitigating Stress and Accumulation of Heavy Metals in Plants

    Directory of Open Access Journals (Sweden)

    YUAN Si-li

    2014-12-01

    Full Text Available Selenium (Se plays an important role in improving plant stress resistance, mitigating heavy metal stress and reducing heavy metal uptake. This paper reviewed mechanisms involved with Se for mitigation of heavy metal stress and accumulation. Se could alleviate heavy metals stress because of the combined physiological and biochemical effects of the relevant products, including GSH-Px which could change toxic peroxides to non-toxic substances and remove free radicals induced by heavy metals. Se could activate phytochelatins synthase and increase the amount of precursors to phytochelatin (PC, and make plant produce more PC, and form more heavy metal-PC complexes. The formation of Se-heavy metal complexes reduced the biotoxicity of heavy metals. Se could produce antagonistic effect with a variety of heavy metals, and reduce the uptake of heavy metals.

  18. Influence of microstructure and mechanical stress on behavior of hydrogen in 500 nm Pd films

    Energy Technology Data Exchange (ETDEWEB)

    Vlček, Marián, E-mail: Marian.Vlcek@gmail.com [Faculty of Mathematics and Physics, Charles University in Prague, V Holešovičkách 2, CZ-18000 Praha 8 (Czech Republic); Lukáč, František; Vlach, Martin [Faculty of Mathematics and Physics, Charles University in Prague, V Holešovičkách 2, CZ-18000 Praha 8 (Czech Republic); Wagner, Stefan; Uchida, Helmut [Institute of Materials Physics, University of Göttingen, Friedrich-Hund-Platz 1, D-37077 Göttingen (Germany); Baehtz, Carsten; Shalimov, Artem [Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, D-01314 Dresden (Germany); Pundt, Astrid [Institute of Materials Physics, University of Göttingen, Friedrich-Hund-Platz 1, D-37077 Göttingen (Germany); Čížek, Jakub [Faculty of Mathematics and Physics, Charles University in Prague, V Holešovičkách 2, CZ-18000 Praha 8 (Czech Republic)

    2015-10-05

    Highlights: • Influence of nano-structure and stresses on hydrogenation of Pd films was studied. • Nanocrystalline Pd films deposited on hard and soft substrates were compared. • It was found that nanocrystalline structure leads to narrowing of the miscibility gap. • Compressive in-plane stress suppresses the hydride formation. • The lattice constants for α-phase and the hydride phase are closer than in bulk Pd. - Abstract: Pd films can be used as a model system to examine the influence of microstructure and stress on the hydrogen absorption. In this work we study 500 nm Pd films deposited on different substrates with different binding strengths. The films were electrochemically loaded with hydrogen up to hydride concentration. Development of lattice constant during hydrogen loading of Pd films was investigated by in situ X-ray diffraction using synchrotron radiation. The influence of microstructure and mechanical stress in the films on the phase transition from Pd to Pd hydride was examined.

  19. Estimation of viscous dissipative stresses induced by a mechanical heart valve using PIV data.

    Science.gov (United States)

    Li, Chi-Pei; Lo, Chi-Wen; Lu, Po-Chien

    2010-03-01

    Among the clinical complications of mechanical heart valves (MHVs), hemolysis was previously thought to result from Reynolds stresses in turbulent flows. A more recent hypothesis suggests viscous dissipative stresses at spatial scales similar in size to red blood cells may be related to hemolysis in MHVs, but the resolution of current instrumentation is insufficient to measure the smallest eddy sizes. We studied the St. Jude Medical (SJM) 27 mm valve in the aortic position of a pulsatile circulatory mock loop under physiologic conditions with particle image velocimetry (PIV). Assuming a dynamic equilibrium assumption between the resolved and sub-grid-scale (SGS) energy flux, the SGS energy flux was calculated from the strain rate tensor computed from the resolved velocity fields and the SGS stress was determined by the Smagorinsky model, from which the turbulence dissipation rate and then the viscous dissipative stresses were estimated. Our results showed Reynolds stresses up to 80 N/m2 throughout the cardiac cycle, and viscous dissipative stresses below 12 N/m2. The viscous dissipative stresses remain far below the threshold of red blood cell hemolysis, but could potentially damage platelets, implying the need for further study in the phenomenon of MHV hemolytic complications.

  20. Exploratory study of mechanical kinematic innovation design based on gene recombination operation

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Yixiong; Gao, Yicong; Tan, Jianrong [Zhejiang University, Hangzhou (China); Hagiwara, Ichiro [Tokyo Institute of Technology, Tokyo (Korea, Republic of)

    2013-03-15

    This paper analyzes the influencing factor of motion output of the inspired mechanism under the premise that the motion input is invariant. These factors are respectively expressed as kinematic pair chromosome number, kinematic pair feature gene and distance relationship vector gene by virtue of several concepts and principles in genetics, and then they are encoded. Mechanism chromosome model is established, which is constituted by mechanism chromosome relationship graph and mechanism chromosome matrix. Three kinematic pair chromosome gene recombination operations on mechanism chromosome model (dominance, translocation and metastasis), are proposed by using meiosis and chromosome variance in genetics for reference. Finally the paper takes shaper as the original mechanism and acquires its inspired mechanism, which proves the convenience and practicality of the methods.

  1. [Oxidative stress in mechanism of psychosomatic disorders realization in duodenal ulcer in students].

    Science.gov (United States)

    Oparin, A G; Oparin, A A

    2005-01-01

    To study the role of oxidative stress in mechanism of psychosomatic disorders involvement in pathogenesis of ulcerogenesis. Psychosomatic disorders (PSD) and oxidative stress (OS) were assessed in 120 students with duodenal ulcer (DU) who had no concomitant pathology. Examination for PSD included interviewing by questionnaires. OS was judged by the level of lipid peroxidation products (malonic dialdehyde and dienic conjugates) and antioxidant activity--by glutathion peroxidase and superoxidedismutase. Melatonin was measured by enzyme immunoassay. A close correlation was discovered between the severity and features of PSD, lowering of melatonin, severity of OS and clinical features of the disease. DU students develop PSD which become leading factors of ulcerogenesis. One of the mechanisms of their participation in ulcerogenesis may be related with lowering of melatonin which is a potent stress regulator and corrector of lipid peroxidation and antioxidant activity.

  2. Oxidative Stress-Mediated Skeletal Muscle Degeneration: Molecules, Mechanisms, and Therapies

    Directory of Open Access Journals (Sweden)

    Min Hee Choi

    2016-01-01

    Full Text Available Oxidative stress is a loss of balance between the production of reactive oxygen species during cellular metabolism and the mechanisms that clear these species to maintain cellular redox homeostasis. Increased oxidative stress has been associated with muscular dystrophy, and many studies have proposed mechanisms that bridge these two pathological conditions at the molecular level. In this review, the evidence indicating a causal role of oxidative stress in the pathogenesis of various muscular dystrophies is revisited. In particular, the mediation of cellular redox status in dystrophic muscle by NF-κB pathway, autophagy, telomere shortening, and epigenetic regulation are discussed. Lastly, the current stance of targeting these pathways using antioxidant therapies in preclinical and clinical trials is examined.

  3. Engineering the residual stress state and microstructure of stainless steel with mechanical surface treatments

    Energy Technology Data Exchange (ETDEWEB)

    Turski, M.; Clitheroe, S.; Withers, P.J. [Manchester University, School of Materials, Manchester (United Kingdom); Evans, A.D. [Paul Scherrer Institut, Villigen-PSI (Switzerland); Rodopoulos, C. [University of Patras, Patras (Greece); Hughes, D.J. [Institut Laue Langevin, Grenoble (France)

    2010-06-15

    Four mechanical surface treatments have been considered for the application to austenitic stainless steel structures. Shot peening (SP), laser shock peening (LSP), ultrasonic impact treatment (UIT) and water jet cavitation peening (WJCP), also known as cavitation shotless peening (CSP), have been applied to 8 mm thick Type 304 austenitic stainless steel coupons. This study considers the merits of each of these mechanical surface treatments in terms of their effect on the surface roughness, microstructure, level of plastic work and through thickness residual stress distribution. Microstructural studies have revealed the formation of martensite close to the treated surface for each process. Residual stress measurements in the samples show compressive stresses to a significantly greater depth for the LSP, UIT and WJCP samples compared to the more conventional SP treated sample. (orig.)

  4. Computational modeling of the mechanism of hydrogen embrittlement (HE) and stress corrosion cracking (SCC) in metals

    Science.gov (United States)

    Cendales, E. D.; Orjuela, F. A.; Chamarraví, O.

    2016-02-01

    In this article theoretical models and some existing data sets were examined in order to model the two main causes (hydrogen embrittlement and corrosion-cracking under stress) of the called environmentally assisted cracking phenomenon (EAC). Additionally, a computer simulation of flat metal plate subject to mechanical stress and cracking due both to hydrogen embrittlement and corrosion was developed. The computational simulation was oriented to evaluate the effect on the stress-strain behavior, elongation percent and the crack growth rate of AISI SAE 1040 steel due to three corrosive enviroments (H2 @ 0.06MPa; HCl, pH=1.0; HCl, pH=2.5). From the computer simulation we conclude that cracking due to internal corrosion of the material near to the crack tip limits affects more the residual strength of the flat plate than hydrogen embrittlement and generates a failure condition almost imminent of the mechanical structural element.

  5. The stress response to surgery: release mechanisms and the modifying effect of pain relief

    DEFF Research Database (Denmark)

    Kehlet, H

    1989-01-01

    This short review updates information on the release mechanisms of the systemic response to surgical injury and the modifying effect of pain relief. Initiation of the response is primarily due to afferent nerve impulses combined with release of humoral substances (such as prostaglandins, kinins...... in releasing the classical endocrine catabolic response, while humoral factors are important for the hyperthermic response, changes in coagulation and fibrinolysis immunofunction, and capillary permeability. The modifying effect of pain relief on the surgical stress response is dependent upon the technique...... on the stress response. In summary, pain alleviation itself may not necessarily lead to an important modification of the stress response, and a combined approach with inhibition of the neural and humoral release mechanisms is necessary for a pronounced inhibition or prevention of the response to surgical injury....

  6. Earthquake focal mechanisms and stress orientations in the eastern Swiss Alps

    Energy Technology Data Exchange (ETDEWEB)

    Marschall, I.; Deichmann, N. [Swiss Seismological Service, ETH Zuerich, Zuerich (Switzerland); Marone, F. [Paul Scherrer Institute PSI, Villigen (Switzerland)

    2013-04-15

    This study presents an updated set of earthquake focal mechanisms in the Helvetic and Penninic/Austroalpine domains of the eastern Swiss Alps. In eight cases, based on high-precision relative hypocentre locations of events within individual earthquake sequences, it was possible to identify the active fault plane. Whereas the focal mechanisms in the Helvetic domain are mostly strike-slip, the Penninic/Austroalpine domain is dominated by normal-faulting mechanisms. Given this systematic difference in faulting style, an inversion for the stress field was performed separately for the two regions. The stress field in the Penninic/Austroalpine domain is characterized by extension oriented obliquely to the E-W strike of the orogen. Hence, the Penninic nappes, which were emplaced as large-scale compressional structures during the Alpine orogenesis, are now deforming in an extensional mode. This contrasts with the more compressional strike-slip regime in the Helvetic domain towards the northern Alpine front. Relative to the regional stress field seen in the northern Alpine foreland with a NNW-SSE compression and an ENE-WSW extension, the orientation of the least compressive stress in the Penninic/Austroalpine domain is rotated counter-clockwise by about 40 °C. Following earlier studies, the observed rotation of the orientation of the least compressive stress in the Penninic/Austroalpine region can be explained as the superposition of the regional stress field of the northern foreland and a uniaxial extensional stress perpendicular to the local trend of the Alpine mountain belt. (authors)

  7. Mechanisms underlying the effects of prenatal psychosocial stress on child outcomes: beyond the HPA axis

    NARCIS (Netherlands)

    Beijers, R.; Buitelaar, J.K.; Weerth, C. de

    2014-01-01

    Accumulating evidence from preclinical and clinical studies indicates that maternal psychosocial stress and anxiety during pregnancy adversely affect child outcomes. However, knowledge on the possible mechanisms underlying these relations is limited. In the present paper, we review the most often pr

  8. The influence of initial defects on mechanical stress and deformation distribution in oxidized silicon

    Directory of Open Access Journals (Sweden)

    Kulinich O. A.

    2008-10-01

    Full Text Available The near-surface silicon layers in silicon – dioxide silicon systems with modern methods of research are investigated. It is shown that these layers have compound structure and their parameters depend on oxidation and initial silicon parameters. It is shown the influence of initial defects on mechanical stress and deformation distribution in oxidized silicon.

  9. Focal mechanisms and variations in tectonic stress fields in eastern Canada (western Quebec and southern Ontario)

    Science.gov (United States)

    Asgharzadeh Sadegh, Parisa

    Earthquakes in western Quebec and southern Ontario present a major contribution to the natural hazards in south eastern Canada due to their proximity to major population centres. However, the seismic characteristics of the events in these regions have not been well documented. Improved knowledge of earthquake distribution and seismic controlling mechanisms provides a great benefit for earthquake hazard analysis in eastern Canada. The available information about the tectonic stress indicators, including focal mechanisms, was compiled for Canada prior to 1994. The present research is concentrated mainly on determination of the focal mechanisms and hypocentre locations of the earthquakes after 1993 with M > 3.5 to characterize the present-day regional and local stress fields in southern Ontario and western Quebec. An attempt was also made to differentiate local zones with comparatively homogeneous tectonic stresses orientation and seismic regimes, thus providing information for future re-assessment of the seismic hazard in each region. Considering seismic parameters such as the trend of the epicentres, focal depths and the state of stress of the events along with their tectonic settings, ten distinct clusters have been proposed for western Quebec and two clusters of events were determined for southern Ontario with comparatively consistent focal mechanisms. The locations and characteristics of seismicity clusters appear to be consistent with the hypothesis that they are near the locations of large historic and prehistoric events, and represent exceptionally persistent aftershocks of past large earthquakes.

  10. Interpersonal Stress Generation as a Mechanism Linking Rumination to Internalizing Symptoms in Early Adolescents

    Science.gov (United States)

    McLaughlin, Katie A.; Nolen-Hoeksema, Susan

    2012-01-01

    Rumination is a risk factor for depressive and anxiety symptoms in adolescents. Previous investigations of the mechanisms linking rumination to internalizing problems have focused primarily on cognitive factors. We investigated whether interpersonal stress generation plays a role in the longitudinal relationship between rumination and…

  11. Synergistic defensive mechanism of phytochelatins and antioxidative enzymes in Brassica chinensis L. against Cd stress

    Institute of Scientific and Technical Information of China (English)

    CHEN LiQin; GUO YiFei; YANG LiMin; WANG QiuQuan

    2008-01-01

    Brassica chinensis L. was chosen and exposed to different concentrations of Cd exposure to evaluate its Cd-accumulating capacity and its potential cellular defensive mechanisms. Cd accumulation in the shoots and roots of B. chinensis was up to 1348.3±461.8 and 3761.0±795.0 mg per killogram of dry weight, respectively, under 200 μmol/L of Cd exposure. Increasing Cd accumulation in the plant was accompanied by rapid accumulation of phytochelatins (PCs), and the sequestration of Cd by PCs pro-vided a primary cellular mechanism for Cd detoxification and tolerance of B. chinensis. Furthermore, malondialdehyde formation, hydrogen peroxide content and antioxidative enzyme activities such as superoxide dismutase, catalase, guaiacol peroxidase and ascorbate peroxidase were observed in the shoots of Cd-stressed B. chinensis. Increasing enzyme activities in response to concentrations of 5 to 50 μmol/L Cd showed an efficient defense against oxidative stress, suggesting that the antioxidative system was a secondary defensive mechanism. These resulted in reduced free Cd damage and en-hanced Cd accumulation and tolerance. Glutathione plays a pivotal role in these two detoxification pathways. In general, these results suggested that PCs and the antioxidative system are synergistic in combatting Cd-induced oxidative stress and that they play important roles in Cd detoxification of B. chinensis, and also give a deep understanding of the natural defensive mechanisms in plants under heavy metal stress.

  12. Vulnerability of the retinal microvasculature to oxidative stress: ion channel-dependent mechanisms.

    Science.gov (United States)

    Fukumoto, Masanori; Nakaizumi, Atsuko; Zhang, Ting; Lentz, Stephen I; Shibata, Maho; Puro, Donald G

    2012-05-01

    Although oxidative stress is a hallmark of important vascular disorders such as diabetic retinopathy, it remains unclear why the retinal microvasculature is particularly vulnerable to this pathophysiological condition. We postulated that redox-sensitive ion channels may play a role. Using H(2)O(2) to cause oxidative stress in microvascular complexes freshly isolated from the adult rat retina, we assessed ionic currents, cell viability, intracellular oxidants, and cell calcium by using perforated-patch recordings, trypan blue dye exclusion, and fura-2 fluorescence, respectively. Supporting a role for the oxidant-sensitive ATP-sensitive K (K(ATP)) channels, we found that these channels are activated during exposure of retinal microvessels to H(2)O(2). Furthermore, their inhibition by glibenclamide significantly lessened H(2)O(2)-induced microvascular cell death. Additional experiments established that by increasing the influx of calcium into microvascular cells, the K(ATP) channel-mediated hyperpolarization boosted the vulnerability of these cells to oxidative stress. In addition to the K(ATP) channel-dependent mechanism for increasing the lethality of oxidative stress, we also found that the vulnerability of cells in the capillaries, but not in the arterioles, was further boosted by a K(ATP) channel-independent mechanism, which our experiments indicated involves the oxidant-induced activation of calcium-permeable nonspecific cation channels. Taken together, our findings support a working model in which both K(ATP) channel-independent and K(ATP) channel-dependent mechanisms render the capillaries of the retina particularly vulnerable to oxidative stress. Identification of these previously unappreciated mechanisms for boosting the lethality of oxidants may provide new targets for pharmacologically limiting damage to the retinal microvasculature during periods of oxidative stress.

  13. The visual stress model—A psycho-physiological method for the evaluation of operational reliability of pilots and cosmonauts

    Science.gov (United States)

    Kammel, H.; Haase, H.

    An experimental psycho-physiological method is presented for the evaluation of visual-cognitive performance preconditions and operational reliability of pilots and cosmonauts. As visual-cognitive stress are used tachistoscopically presented instrument symbols under conditions of individual speed of work and time pressure. The results of the compared extreme groups consisting of pilots with good and insufficient flight performance showed that the pilots with impairments to the quality of flight activity differ already before the test in their individual habitual characteristics and actual motivation, during the stress in their operational parameters, in the dimensions of their cardiorespiratory activation as well as in their efficiency and after the stress in their subjective experience of the stress. Conclusions are drawn for the evaluation of the aptitude of pilots and cosmonauts.

  14. Study of a self-adjoint operator indicating the direction of time within standard quantum mechanics

    CERN Document Server

    Strauss, Y; Machnes, S; Horwitz, L P

    2011-01-01

    In [J. Math. Phys. 51 (2010) 022104] a self-adjoint operator was introduced that has the property that it indicates the direction of time within the framework of standard quantum mechanics, in the sense that as a function of time its expectation value decreases monotonically for any initial state. In this paper we study some of this operator's properties. In particular, we derive its spectrum and generalized eigenstates, and treat the example of the free particle.

  15. Damage and fracture mechanism of 6063 aluminum alloy under three kinds of stress states

    Institute of Scientific and Technical Information of China (English)

    ZHU Hao; ZHU Liang; CHEN Jianhong

    2008-01-01

    To study the damage and fracture mechanism of 6063 aluminum alloy under different stress states,three kinds of representative triaxial stress states have been adopted,namely smooth tensile,notch tensile,and pure shear.The results of the study indicate the following.During the notch tensile test,a relatively higher stress triaxiality appears in the root of the notch.With the applied loading increasing,the volume fraction of microvoids in the root of the notch increases continuously.When it reaches the critical volume fraction of microvoids,the specimen fractures.During the pure shear test,the stress triaxiality almost equals to zero,and there is almost no microvoids but a shear band at the center of the butterfly specimen.The shear band results from nonuniform deformation constantly under the shear stress.With stress concentration,cracks are produced within the shear band and are later coalesced.When the equivalent plastic strain reaches the critical value (equivalent plastic fracture strain),the butterfly specimen fractures.During the smooth tensile test,the stress triaxiality in the gauge of the specimen remains constant at 0.33.Thus,the volume of microvoids of the smooth tensile test is less than that of the notch tensile test and the smooth specimen fractures due to shearing between microvoids.The G-T-N damage model and Johnson-Cook model are used to simulate the notch tensile and shear test,respectively.The simulated engineering stress-strain curves fit the measured engineering stress-strain curves very well.In addition,the empirical damage evolution equation for the notch specimen is obtained from the experimental data and FEM simulations.

  16. Expression of HSPs: an adaptive mechanism during long-term heat stress in goats ( Capra hircus)

    Science.gov (United States)

    Dangi, Satyaveer Singh; Gupta, Mahesh; Dangi, Saroj K.; Chouhan, Vikrant Singh; Maurya, V. P.; Kumar, Puneet; Singh, Gyanendra; Sarkar, Mihir

    2015-08-01

    Menacing global rise in surface temperature compelled more focus of research over understanding heat stress response mechanism of animals and mitigation of heat stress. Twenty-four goats divided into four groups ( n = 6) such as NHS (non-heat-stressed), HS (heat-stressed), HS + VC (heat-stressed administered with vitamin C), and HS + VE + Se (heat-stressed administered with vitamin E and selenium). Except NHS group, other groups were exposed to repeated heat stress (42 °C) for 6 h on 16 consecutive days. Blood samples were collected at the end of heat exposure on days 1, 6, 11, and 16. When groups compared between days, expression of all heat shock proteins (HSPs) showed a similar pattern as first peak on day 1, reached to basal level on the sixth day, and followed by second peak on day 16. The relative messenger RNA (mRNA) and protein expression of HSP 60, HSP70, and HSP90 was observed highest ( P < 0.05) in HS group, followed by antioxidant-administered group on days 1 and 16, which signifies that antioxidants have dampening effect on HSP expression. HSP105/110 expression was highest ( P < 0.05) on day 16. We conclude that HSP expression pattern is at least two-peak phenomenon, i.e., primary window of HSP protection on the first day followed by second window of protection on day 16. HSP60, HSP70, and HSP90 play an important role during the initial phase of heat stress acclimation whereas HSP105/110 joins this cascade at later phase. Antioxidants may possibly attenuate the HSP expression by reducing the oxidative stress.

  17. Perspectives on deciphering mechanisms underlying plant heat stress response and thermotolerance

    Directory of Open Access Journals (Sweden)

    Kamila Lucia Bokszczanin

    2013-08-01

    Full Text Available Global warming is a major threat for agriculture and food safety and in many cases the negative effects are already apparent. The current challenge of basic and applied plant science is to decipher the molecular mechanisms of heat stress response and thermotolerance in detail and use this information to identify genotypes that will withstand unfavorable environmental conditions. Nowadays X-omics approaches complement the findings of previous targeted studies and highlight the complexity of heat stress response mechanisms giving information for so far unrecognized genes, proteins and metabolites as potential key players of thermotolerance. Even more, roles of epigenetic mechanisms and the involvement of small RNAs in thermotolerance are currently emerging and thus open new directions of yet unexplored areas of plant heat stress response. In parallel it is emerging that although the whole plant is vulnerable to heat, specific organs are particularly sensitive to elevated temperatures. This has redirected research from the vegetative to generative tissues. The sexual reproduction phase is considered as the most sensitive to heat and specifically pollen exhibits the highest sensitivity and frequently an elevation of the temperature just a few degrees above the optimum during pollen development can have detrimental effects for crop production. Compared to our knowledge on heat stress response of vegetative tissues, the information on pollen is still scarce. Nowadays, several techniques for high-throughput X-omics approaches provide major tools to explore the principles of pollen heat stress response and thermotolerance mechanisms in specific genotypes. The collection of such information will provide an excellent support for improvement of breeding programs to facilitate the development of tolerant cultivars. The review aims at describing the current knowledge of thermotolerance mechanisms and the technical advances which will foster new insights into

  18. Quantum Mechanical Version of z-Transform Related to Eigenkets of Boson Creation Operator

    Institute of Scientific and Technical Information of China (English)

    FANHong-Yi; FULiang; A.Wiinsche

    2004-01-01

    Using the completeness relation composed of the coherent state and of the eigenket of bosonic creation operator, we establish a one-to-one correspondence between the z-transform and the quantum-mechanical transform from the representation by number states |n) to the representation by coherent states |(z)) (Bargmann representation).In this way, the quantum-mechanical version of the various properties of z-transform are obtained and the operators for embodying these properties in the Fock space are derived, which may find applications in quantum states engineering.

  19. Importance of epigenetic mechanisms in visceral pain induced by chronic water avoidance stress.

    Science.gov (United States)

    Tran, L; Chaloner, A; Sawalha, A H; Greenwood Van-Meerveld, B

    2013-06-01

    Epigenetic molecular mechanisms, which include DNA methylation and histone deacetylation, are implicated in the dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis. Previously, we demonstrated that repeated water avoidance stress (WAS), a validated model of chronic psychological stress, induces heightened visceral pain behaviors in rodents that resemble irritable bowel syndrome (IBS) sequelae. However, the involvement of epigenetic molecular mechanisms in the pathophysiology of stress-induced visceral pain has not been explored. Our hypothesis is that epigenetic mechanisms within the central nervous system (CNS) are important to chronic stress-induced visceral hypersensitivity. Adult male F-344 rats with intracerebroventricular (i.c.v.) cannulae were exposed to 7 days of repeated WAS. Controls received a SHAM stress. Following the daily 1h stressor, trichostatin A (TSA; 100 ng/ml), a potent histone deacetylase inhibitor, or vehicle (VEH; 0.1% DMSO/saline,) as control was administered via the i.c.v. cannula. Visceral sensitivity was assessed 24h after the final WAS and quantified the visceromotor response (VMR) by recording the number of abdominal contractions in response to graded pressures (20-60 mmHg) of colorectal distensions (CRD). From a separate group of rats that were exposed to repeated WAS or SHAM stress, the amygdala was isolated to assess the methylation status of glucocorticoid receptor (GR) and corticotropin releasing-factor (CRF) genes via bisulfite sequencing and verified by pyrosequencing. GR and CRF gene expression was quantified via qRT-PCR. Stressed rats exhibited visceral hypersensitivity that was significantly attenuated by TSA. Compared to SHAM controls, methylation of the GR gene was increased following WAS while expression of the GR gene was decreased. Methylation of the CRF promoter was decreased with WAS with a concomitant increase in CRF expression. This study demonstrates the involvement of central epigenetic mechanisms in

  20. 3-D finite element stress analysis for fatigue design and evaluation: a parametric study of MOV(Motor Operated Valve)

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Hyeong Keun; Lee, Sang Min; Chang, Yoon Suk; Choi, Jae Boong; Kim, Young Jin [Sungkyunkwan Univ., Suwon (Korea, Republic of); Kim, Yun Jae [Korea Univ., Seoul (Korea, Republic of)

    2004-07-01

    In this paper, a new procedure is proposed to accomplish the primary plus secondary stress(P+Q) at the 'structural element' instead of 'transition element'. For the P+Q evaluation, the calculated stresses by FEA are linearized along a stress classification line to extract the stress category, then the stress intensity is calculated to compare with the 3Sm limit. Also, in this paper, the 'design by analysis' criteria, adopted fundamental concepts and a new approach to calculate Ke factors are explained. The new procedure combined with 3-D FEA has been applied to motor operated valve in order to the over conservatism and the rack of margin. The evaluation results show a good applicability and can be utilized for fatigue life evaluation by using P+Q.

  1. Elastic stress transmission and transformation (ESTT) by confined liquid: A new mechanics for fracture in elastic lithosphere of the earth

    Science.gov (United States)

    Xu, Xing-Wang; Peters, Stephen; Liang, Guang-He; Zhang, Bao-Lin

    2016-01-01

    We report on a new mechanical principle, which suggests that a confined liquid in the elastic lithosphere has the potential to transmit a maximum applied compressive stress. This stress can be transmitted to the internal contacts between rock and liquid and would then be transformed into a normal compressive stress with tangential tensile stress components. During this process, both effective compressive normal stress and tensile tangential stresses arise along the liquid–rock contact. The minimum effective tensile tangential stress causes the surrounding rock to rupture. Liquid-driven fracture initiates at the point along the rock–liquid boundary where the maximum compressive stress is applied and propagates along a plane that is perpendicular to the minimum effective tensile tangential stress and also is perpendicular to the minimum principal stress.

  2. 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.

  3. Dissolution Condensation Mechanism of Stress Corrosion Cracking in Liquid Metals: Driving Force and Crack Kinetics

    Science.gov (United States)

    Glickman, Evgeny E.

    2011-02-01

    Stress corrosion cracking (SCC) in aqueous solution is driven by exothermic reactions of metal oxidation. This stimulus, as well as classical mechanisms of SCC, does not apply to SCC in liquid metals (LMs). In the framework of the dissolution-condensation mechanism (DCM), we analyzed the driving force and crack kinetics for this nonelectrochemical mode of SCC that is loosely called "liquid metal embrittlement" (LME). According to DCM, a stress-induced increase in chemical potential at the crack tip acts as the driving force for out-of-the-tip diffusion mass transfer that is fast because diffusion in LMs is very fast and surface energy at the solid-liquid interface is small. In this article, we review two versions of DCM mechanism, discuss the major physics behind them, and develop DCM further. The refined mechanism is applied then to the experimental data on crack velocity V vs stress intensity factor, the activation energy of LME, and alloying effects. It is concluded that DCM provides a good conceptual framework for analysis of a unified kinetic mechanism of LME and may also contribute to SCC in aqueous solutions.

  4. Oxidative Stress-Related Mechanisms and Antioxidant Therapy in Diabetic Retinopathy

    Directory of Open Access Journals (Sweden)

    Cheng Li

    2017-01-01

    Full Text Available Diabetic retinopathy (DR is one of the most common microvascular complications of diabetes and is the leading cause of blindness in young adults. Oxidative stress has been implicated as a critical cause of DR. Metabolic abnormalities induced by high-glucose levels are involved in the development of DR and appear to be influenced by oxidative stress. The imbalance between reactive oxygen species (ROS production and the antioxidant defense system activates several oxidative stress-related mechanisms that promote the pathogenesis of DR. The damage caused by oxidative stress persists for a considerable time, even after the blood glucose concentration has returned to a normal level. Animal experiments have proved that the use of antioxidants is a beneficial therapeutic strategy for the treatment of DR, but more data are required from clinical trials. The aims of this review are to highlight the improvements to our understanding of the oxidative stress-related mechanisms underlying the development of DR and provide a summary of the main antioxidant therapy strategies used to treat the disease.

  5. Oxidative Stress-Related Mechanisms and Antioxidant Therapy in Diabetic Retinopathy

    Science.gov (United States)

    Miao, Xiao

    2017-01-01

    Diabetic retinopathy (DR) is one of the most common microvascular complications of diabetes and is the leading cause of blindness in young adults. Oxidative stress has been implicated as a critical cause of DR. Metabolic abnormalities induced by high-glucose levels are involved in the development of DR and appear to be influenced by oxidative stress. The imbalance between reactive oxygen species (ROS) production and the antioxidant defense system activates several oxidative stress-related mechanisms that promote the pathogenesis of DR. The damage caused by oxidative stress persists for a considerable time, even after the blood glucose concentration has returned to a normal level. Animal experiments have proved that the use of antioxidants is a beneficial therapeutic strategy for the treatment of DR, but more data are required from clinical trials. The aims of this review are to highlight the improvements to our understanding of the oxidative stress-related mechanisms underlying the development of DR and provide a summary of the main antioxidant therapy strategies used to treat the disease.

  6. Mechanical Behavior of Methane Infiltrated Coal: the Roles of Gas Desorption, Stress Level and Loading Rate

    Science.gov (United States)

    Wang, Shugang; Elsworth, Derek; Liu, Jishan

    2013-09-01

    We report laboratory experiments to investigate the role of gas desorption, stress level and loading rate on the mechanical behavior of methane infiltrated coal. Two suites of experiments are carried out. The first suite of experiments is conducted on coal (Lower Kittanning seam, West Virginia) at a confining stress of 2 MPa and methane pore pressures in the fracture of 1 MPa to examine the role of gas desorption. These include three undrained (hydraulically closed) experiments with different pore pressure distributions in the coal, namely, overpressured, normally pressured and underpressured, and one specimen under drained condition. Based on the experimental results, we find quantitative evidence that gas desorption weakens coal through two mechanisms: (1) reducing effective stress controlled by the ratio of gas desorption rate over the drainage rate, and (2) crushing coal due to the internal gas energy release controlled by gas composition, pressure and content. The second suite of experiments is conducted on coal (Upper B seam, Colorado) at confining stresses of 2 and 4 MPa, with pore pressures of 1 and 3 MPa, under underpressured and drained condition with three different loading rates to study the role of stress level and loading rate. We find that the Biot coefficient of coal specimens is coal. This study has important implications for the stability of underground coal seams.

  7. Hyperosmotic stress inhibits insulin receptor substrate-1 function by distinct mechanisms in 3T3-L1 adipocytes

    DEFF Research Database (Denmark)

    Gual, Philippe; Gonzalez, Teresa; Grémeaux, Thierry

    2003-01-01

    . In addition, prolonged osmotic stress enhanced the degradation of IRS proteins through a rapamycin-insensitive pathway and a proteasome-independent process. These data support evidence of new mechanisms involved in osmotic stress-induced cellular insulin resistance. Short-term osmotic stress induces......-regulation of insulin action....

  8. Mechanical Stress Downregulates MHC Class I Expression on Human Cancer Cell Membrane

    DEFF Research Database (Denmark)

    La Rocca, Rosanna; Tallerico, Rossana; Hassan, Almosawy Talib

    2014-01-01

    treated either with mechanical stress delivered by a micropump (fabricated by deep X-ray nanolithography) or by ultrasound wave stimuli. A specific down-regulation of Major Histocompatibility Complex (MHC) class I molecules expression on cancer cell membrane compared to different kinds of healthy cells......In our body, cells are continuously exposed to physical forces that can regulate different cell functions such as cell proliferation, differentiation and death. In this work, we employed two different strategies to mechanically stress cancer cells. The cancer and healthy cell populations were...... (fibroblasts, macrophages, dendritic and lymphocyte cells) was observed, stimulating the cells with forces in the range of nano-newton, and pressures between 1 and 10 bar (1 bar5100.000 Pascal), depending on the devices used. Moreover, Raman spectroscopy analysis, after mechanical treatment, in the range...

  9. Transcutaneous mechanical nerve stimulation using perineal vibration: a novel method for the treatment of female stress urinary incontinence

    DEFF Research Database (Denmark)

    Sønksen, Jens; Ohl, Dana A; Bonde, Birthe

    2007-01-01

    We defined basic guidelines for transcutaneous mechanical nerve stimulation in modifying pelvic floor responses in women and determined the efficacy of transcutaneous mechanical nerve stimulation in treating stress urinary incontinence....

  10. The State of Stress in the Afar Region From Inversion of Earthquake Focal Mechanisms

    Science.gov (United States)

    Hagos, L.; Lund, B.; Roberts, R.

    2006-12-01

    The state of stress in the Afar region, where the Arabian, Nubian, and Somalian plates meet, is investigated by inversion of earthquake focal mechanisms. Based on earlier studies in the region, we compiled a catalogue of 93 earthquakes, M > 4, with focal mechanisms, spanning the time period from 1969 to present. From this data set we select three clusters suitable for inversion: one along the EW trending Gulf of Aden and Tadjoura rift, one in central Afar, and one on the western margin of the Afar depression. Using the grid-search based inversion of Lund and Slunga (1999), we assess how the choice of fault plane from the nodal planes affect the results and include known fault data where possible. The resulting stress states show an overall normal faulting stress regime. This especially pronounced in the cluster on the western margin of the Afar depression, whereas the southern two clusters have more oblique stress states with significant strike-slip components. The estimated directions of the minimum principal stress vary from NE on the Danakil -Somalia plate boundary to an approximate EW direction at the western margin of the Afar depression. Although the data is scarce, we discuss the temporal consistency of the stress field through the studied time period. The broad zone of active extensional deformation at the Afar Depression, a triple junction where the Red Sea, the Gulf of Aden and the Main Ethiopian rift systems meet, constitutes a complicated tectonic region and we discuss our results in this context. We also compare the stress estimates to available deformation data in the region.

  11. Mechanism of oxidative stress involved in the toxicity of ZnO nanoparticles against eukaryotic cells

    Directory of Open Access Journals (Sweden)

    M. Saliani

    2016-01-01

    Full Text Available ZnO NPs (zinc oxide nanoparticles has generated significant scientific interest as a novel antibacterial and anticancer agent. Since oxidative stress is a critical determinant of ZnO NPs-induced damage, it is necessary to characterize their underlying mode of action. Different structural and physicochemical properties of ZnO NPs such as particle surface, size, shape, crystal structure, chemical position, and presence of metals can lead to changes in biological activities including ROS (reactive oxygen species production. However, there are some inconsistencies in the literature on the relation between the physicochemical features of ZnO NPs and their plausible oxidative stress mechanism. Herein, the possible oxidative stress mechanism of ZnO NPs was reviewed. This is worthy of further detailed evaluations in order to improve our understanding of vital NPs characteristics governing their toxicity. Therefore, this study focuses on the different reported oxidative stress paradigms induced by ZnO NPs including ROS generated by NPs, oxidative stress due to the NPs-cell interaction, and role of the particle dissolution in the oxidative damage. Also, this study tries to characterize and understand the multiple pathways involved in oxidative stress induced by ZnO NPs. Knowledge about different cellular signaling cascades stimulated by ZnO NPs lead to the better interpretation of the toxic influences induced by the cellular and acellular parameters. Regarding the potential benefits of toxic effects of ZnO NPs, in-depth evaluation of their toxicity mechanism and various effects of these nanoparticles would facilitate their implementation for biomedical applications.

  12. Theoretical Investigation of Influence of Mechanical Stress on Magnetic Properties of Ferromagnetic/Antiferromagnetic Bilayers Deposited on Flexible Substrates

    Institute of Scientific and Technical Information of China (English)

    Yu-Hao Bai; Xia Wang; Lin-Ping Mu; Xiao-Hong Xu

    2016-01-01

    Effect of mechanical stress on magnetic properties of an exchange-biased ferromagnetic/antiferromagnetic bilayer deposited on a flexible substrate is investigated.The hysteresis loops with different magnitudes and orientations of the stress can be classified into three types.The corresponding physical conditions for each type of the loop are deduced based on the principle of minimal energy.The equation of the critical stress is derived,which can judge whether the loops show hysteresis or not.Numerical calculations suggest that except for the magnitude of the mechanical stress,the relative orientation of the stress is also an important factor to tune the exchange bias effect.

  13. Asymmetric effect of mechanical stress on the forward and reverse reaction catalyzed by an enzyme.

    Directory of Open Access Journals (Sweden)

    Collin Joseph

    Full Text Available The concept of modulating enzymatic activity by exerting a mechanical stress on the enzyme has been established in previous work. Mechanical perturbation is also a tool for probing conformational motion accompanying the enzymatic cycle. Here we report measurements of the forward and reverse kinetics of the enzyme Guanylate Kinase from yeast (Saccharomyces cerevisiae. The enzyme is held in a state of stress using the DNA spring method. The observation that mechanical stress has different effects on the forward and reverse reaction kinetics suggests that forward and reverse reactions follow different paths, on average, in the enzyme's conformational space. Comparing the kinetics of the stressed and unstressed enzyme we also show that the maximum speed of the enzyme is comparable to the predictions of the relaxation model of enzyme action, where we use the independently determined dissipation coefficient [Formula: see text] for the enzyme's conformational motion. The present experiments provide a mean to explore enzyme kinetics beyond the static energy landscape picture of transition state theory.

  14. Dynamic Reliability Analysis Method of Degraded Mechanical Components Based on Process Probability Density Function of Stress

    Directory of Open Access Journals (Sweden)

    Peng Gao

    2014-01-01

    Full Text Available It is necessary to develop dynamic reliability models when considering strength degradation of mechanical components. Instant probability density function (IPDF of stress and process probability density function (PPDF of stress, which are obtained via different statistical methods, are defined, respectively. In practical engineering, the probability density function (PDF for the usage of mechanical components is mostly PPDF, such as the PDF acquired via the rain flow counting method. For the convenience of application, IPDF is always approximated by PPDF when using the existing dynamic reliability models. However, it may cause errors in the reliability calculation due to the approximation of IPDF by PPDF. Therefore, dynamic reliability models directly based on PPDF of stress are developed in this paper. Furthermore, the proposed models can be used for reliability assessment in the case of small amount of stress process samples by employing the fuzzy set theory. In addition, the mechanical components in solar array of satellites are chosen as representative examples to illustrate the proposed models. The results show that errors are caused because of the approximation of IPDF by PPDF and the proposed models are accurate in the reliability computation.

  15. Mechanical stress in silicon nanosized architectures: Defects of SOD processed silica filler

    Energy Technology Data Exchange (ETDEWEB)

    Ricci, Pier Carlo, E-mail: carlo.ricci@dsf.unica.it [Dipartimento di Fisica, Università di Cagliari, s.p. n 8 Km 0.700, 09042 Monserrato, Cagliari (Italy); Casula, Riccardo [Dipartimento di Fisica, Università di Cagliari, s.p. n 8 Km 0.700, 09042 Monserrato, Cagliari (Italy); Gulleri, Gianluca; Fumagalli, Francesco [Micron Semiconductor Italia, s.r.l. via Camillo Olivetti, 2 20864 Agrate Brianza, MB (Italy); Carbonaro, Carlo Maria; Corpino, Riccardo [Dipartimento di Fisica, Università di Cagliari, s.p. n 8 Km 0.700, 09042 Monserrato, Cagliari (Italy)

    2014-07-25

    Highlights: • Structural and optical properties of silica filled STI architectures. • The silica filler induces a compressive stress. • PL spectra show a large distribution of emitting defects in the UV–blue. • The defects were identified and located at the silica–liner interface. - Abstract: The mechanical stress in nanosized silicon architectures is studied in shallow trench isolation systems with different liners and spin on dielectrics processed silica filler by means of Raman spectroscopy. The nanopatterning of silicon wafers causes a tensile stress of the system whereas the presence of the filler induces a compressive stress which depends on the interaction between silica filler and liner: by changing the liner from silicon dioxide to silicon nitride one can induce a larger compressive stress. The analysis of the ultraviolet excited emission properties in the visible range (nanosecond lasting bands at 2.5, 3.0 and 3.3 eV) allowed us to individuate and locate silica related defects and to correlate their presence to the induced compressive stress.

  16. Analysis of differentially expressed genes and adaptive mechanisms of Prunus triloba Lindl. under alkaline stress.

    Science.gov (United States)

    Liu, Jia; Wang, Yongqing; Li, Qingtian

    2017-01-01

    Prunus triloba Lindl. is a naturally salt-alkaline-tolerant plant with several unique characteristics, and it can be used as the rootstock of Chinese plum (Prunus salicina Lindl.) in saline-alkaline soils. To comprehensively investigate the alkaline acclimation mechanisms in P. triloba, a series of analyses were conducted under alkaline stress, including analyses of the kinetics of molecular and physiological changes, and leaf microstructure. To understand the kinetics of molecular changes under short-term alkaline stress, we used Illumina HiSeq 2500 platform to identify alkaline stress-related differentially expressed genes (DEGs) in P. triloba. Approximately 53.0 million high-quality clean reads were generated from 59.6 million raw reads, and a total of 124,786 unigenes were obtained after de novo assembly of P. triloba transcriptome data. After alkaline stress treatment, a total of 8948 unigenes were identified as DEGs. Based on these DEGs, a Gene Ontology (GO) enrichment analysis was conducted, suggesting that 28 genes may play an important role in the early alkaline stress response. In addition, analysis of DEGs with the Kyoto Encyclopedia of Genes and Genomes (KEGG) revealed that pathways were significant at different treatment time points. A significant positive correlation was found between the quantitative real-time PCR (qRT-PCR) results and the RNA-Seq data for seven alkaline-related genes, confirming the reliability of the RNA-Seq results. Based on physiological analysis of P. triloba in response to long-term alkaline stress, we found that the internal microstructures of the leaves of P. triloba changed to adapt to long-term alkaline stress. Various physiological indexes indicated that the degree of membrane injury increased with increasing duration of alkaline stress, affecting photosynthesis in P. triloba seedlings. This represents the first investigation into the physiology and transcriptome of P. triloba in response to alkaline stress. The results of

  17. Analysis of Mechanical Stresses Due to Voltage Dips in Fixed-Speed Wind Turbines

    DEFF Research Database (Denmark)

    Veluri, Badrinath; Santos-Martin, David; Jensen, Henrik Myhre

    2011-01-01

    drivetrain components. An electro-mechanical model is built to simulate the grid disturbances that easily excite the asynchronous generator poorly damped stator flux oscillations, which cause high transients of the generator electromagnetic torque. This article focuses in estimating the resulting significant...... stresses transients that may have a detrimental effect on the fatigue life of drivetrain system due to voltage dips. A rainflow cycle counting method for the stress history during the voltage dip event, analyses mean and amplitudes of the counted cycles, their occurrence moment and time of duration....

  18. Focus ion beam-induced mechanical stress switching in an ultra-fast resistive switching device

    Science.gov (United States)

    Yang, Xiang

    2016-06-01

    The Mo/Si3N4:Pt/Pt nanometallic resistive switching devices with ultra-fast write/erase speed (meta-stable state, while LRS (detrapping state) is a stable state. Strong mechanical stress facilitates local bond distortion in dielectric films and thus lowers the energy barrier between HRS and LRS, eventually leading to a barrier-less state transition. A quantitative model based on stress-mediated parallel conduction paths were established to provide a more accurate description of the resistive switching devices.

  19. Assessment of Initial Test Conditions for Experiments to Assess Irradiation Assisted Stress Corrosion Cracking Mechanisms

    Energy Technology Data Exchange (ETDEWEB)

    Busby, Jeremy T [ORNL; Gussev, Maxim N [ORNL

    2011-04-01

    Irradiation-assisted stress corrosion cracking is a key materials degradation issue in today s nuclear power reactor fleet and affects critical structural components within the reactor core. The effects of increased exposure to irradiation, stress, and/or coolant can substantially increase susceptibility to stress-corrosion cracking of austenitic steels in high-temperature water environments. . Despite 30 years of experience, the underlying mechanisms of IASCC are unknown. Extended service conditions will increase the exposure to irradiation, stress, and corrosive environment for all core internal components. The objective of this effort within the Light Water Reactor Sustainability program is to evaluate the response and mechanisms of IASCC in austenitic stainless steels with single variable experiments. A series of high-value irradiated specimens has been acquired from the past international research programs, providing a valuable opportunity to examine the mechanisms of IASCC. This batch of irradiated specimens has been received and inventoried. In addition, visual examination and sample cleaning has been completed. Microhardness testing has been performed on these specimens. All samples show evidence of hardening, as expected, although the degree of hardening has saturated and no trend with dose is observed. Further, the change in hardening can be converted to changes in mechanical properties. The calculated yield stress is consistent with previous data from light water reactor conditions. In addition, some evidence of changes in deformation mode was identified via examination of the microhardness indents. This analysis may provide further insights into the deformation mode under larger scale tests. Finally, swelling analysis was performed using immersion density methods. Most alloys showed some evidence of swelling, consistent with the expected trends for this class of alloy. The Hf-doped alloy showed densification rather than swelling. This observation may be

  20. Understanding lithospheric stresses: systematic analysis of controlling mechanisms with applications to the African Plate

    Science.gov (United States)

    Medvedev, Sergei

    2016-06-01

    Many mechanisms control the state of stress within Earth plates. First-order well-known mechanisms include stresses induced by lateral variations of lithospheric density structure, sublithospheric tractions, ridge push, and subduction pull. In this study, we attempt to quantify the influence of these mechanisms to understand the origin of stresses in the lithosphere, choosing the African plate (TAP) as an example. A finite-element based suite, Proshell, was developed to combine several data sets, to estimate the gravitational potential energy (GPE) of the lithosphere, and to calculate stresses acting on the real (non-planar) geometry of TAP. We introduce several quantitative parameters to measure the degree of fit between the model and observations. Our modelling strategy involves nine series of numerical experiments. We start with the simplest possible model and then, step by step, build it up to be a more physically realistic model, all the while discussing the influence of each additional component. The starting (oversimplified) model series (1) is based on the CRUST2 data set for the crust, and a half-space-cooling approximation of the lithospheric mantle. We then describe models (series 2-5) that account for lithospheric mantle density heterogeneities to build a more reliable GPE model. The consecutive series involve basal traction from the convective mantle (series A, C), and the rheological heterogeneity of the TAP via variations in its effective elastic thickness (series B, C). The model quality reflects the increase in complexity between series with an improving match toobserved stress regimes and directions. The most complex model (series D) also accounts for the bending stresses in the elastic lithosphere and achieves a remarkably good fit to observations. All of our experiments were based on the iteration of controlling parameters in order to achieve the best fit between modelled and observed stresses, always considering physically feasible values. This

  1. The contribution of personal and seniority variables to the presence of stress symptoms among Israeli UAV operators.

    Science.gov (United States)

    Gal, Shiri; Shelef, Leah; Oz, Idit; Yavnai, Nirit; Carmon, Erez; Gordon, Shirley

    2016-01-01

    The exposure to war scenes via screens, despite offering a degree of detachment, can be stressful for the operator. The aim of the current study is to examine the existence of anxiety, depression, and post traumatic stress disorder (PTSD) symptoms among unmanned aerial vehicle (UAV) Israeli operators. Participants comprised 41 UAV operators (87.2% male), aged 22-38 (Mage = 26.05, SD = 3.54). Most (78.0%) reported having viewed battlefield scenes. All participants completed a total of five questionnaires: Beck Depression Inventory, State-Trait Anxiety Inventory, and three questionnaires of PTSD: Post Trauma Questionnaire (CAPS), the Post-Traumatic Cognition Inventory (CTPI), and the Post-Traumatic Symptom Scale (PSS). Mean scores of depression and anxiety were found significantly lower than diagnosis cut-off points (p UAV operators are highly beneficial for preventing psychopathology.

  2. The Stress and Vascular Catastrophes in Newborn Rats: Mechanisms Preceding and Accompanying the Brain Hemorrhages

    Science.gov (United States)

    Semyachkina-Glushkovskaya, Oxana; Borisova, Ekaterina; Abakumov, Maxim; Gorin, Dmitry; Avramov, Latchezar; Fedosov, Ivan; Namykin, Anton; Abdurashitov, Arkady; Serov, Alexander; Pavlov, Alexey; Zinchenko, Ekaterina; Lychagov, Vlad; Navolokin, Nikita; Shirokov, Alexander; Maslyakova, Galina; Zhu, Dan; Luo, Qingming; Chekhonin, Vladimir; Tuchin, Valery; Kurths, Jürgen

    2016-01-01

    In this study, we analyzed the time-depended scenario of stress response cascade preceding and accompanying brain hemorrhages in newborn rats using an interdisciplinary approach based on: a morphological analysis of brain tissues, coherent-domain optical technologies for visualization of the cerebral blood flow, monitoring of the cerebral oxygenation and the deformability of red blood cells (RBCs). Using a model of stress-induced brain hemorrhages (sound stress, 120 dB, 370 Hz), we studied changes in neonatal brain 2, 4, 6, 8 h after stress (the pre-hemorrhage, latent period) and 24 h after stress (the post-hemorrhage period). We found that latent period of brain hemorrhages is accompanied by gradual pathological changes in systemic, metabolic, and cellular levels of stress. The incidence of brain hemorrhages is characterized by a progression of these changes and the irreversible cell death in the brain areas involved in higher mental functions. These processes are realized via a time-depended reduction of cerebral venous blood flow and oxygenation that was accompanied by an increase in RBCs deformability. The significant depletion of the molecular layer of the prefrontal cortex and the pyramidal neurons, which are crucial for associative learning and attention, is developed as a consequence of homeostasis imbalance. Thus, stress-induced processes preceding and accompanying brain hemorrhages in neonatal period contribute to serious injuries of the brain blood circulation, cerebral metabolic activity and structural elements of cognitive function. These results are an informative platform for further studies of mechanisms underlying stress-induced brain hemorrhages during the first days of life that will improve the future generation's health. PMID:27378933

  3. ON THE PRO-METASTATIC STRESS RESPONSE TO CANCER THERAPIES: EVIDENCE FOR A POSITIVE CO-OPERATION BETWEEN TIMP-1, HIF-1α, AND miR-210

    Directory of Open Access Journals (Sweden)

    Haissi eCui

    2012-07-01

    Full Text Available In contrast to expectations in the past that tumor starvation or unselective inhibition of proteolytic activity would cure cancer, there is accumulating evidence that microenvironmental stress, such as hypoxia or broad spectrum inhibition of metalloproteinases can promote metastasis. In fact, malignant tumor cells, due to their genetic and epigenetic instability, are predisposed to react to stress by adaptation and, if the stress persists, by escape and formation of metastasis. Recent recognition of the concepts of dynamic evolution as well as population and systems biology is extremely helpful to understand the disappointments of clinical trials with new drugs and may lead to paradigm-shifts in therapy strategies. This must be complemented by an increased understanding of molecular mechanism involved in stress response. Here, we review new roles of Hypoxia-inducible factor-1 (HIF-1, one transcription factor regulating stress response-related gene expression: HIF-1 is crucial for invasion and metastasis, independent from its pro-survival function. In addition, HIF-1 mediates pro-metastatic microenvironmental changes of the proteolytic balance as triggered by high systemic levels of tissue inhibitor of metalloproteinases-1 (TIMP-1, typical for many aggressive cancers, and regulates the metabolic switch to glycolysis, notably via activation of the microRNA miR-210. There is preliminary evidence that TIMP-1 also induces miR-210. Such positive-regulatory co-operation of HIF-1α, miR-210, and TIMP-1, all described to correlate with bad prognosis of cancer patients, opens new perspectives of gaining insight into molecular mechanisms of metastasis-inducing evasion of tumor cells from stress.

  4. Evaluation of stress and geomechanical characteristics of rocks at Penn West's Pembina CO{sub 2}-enhanced oil recovery pilot operation

    Energy Technology Data Exchange (ETDEWEB)

    Haug, K.M.; Bachu, S. [Alberta Energy and Utilities Board, Calgary, AB (Canada); Hawkes, C.D. [Saskatchewan Univ., Regina, SK (Canada)

    2007-07-01

    The geologic capture and storage of carbon dioxide (CO{sub 2}) is gaining interest as a viable option to reduce emissions of greenhouse gases into the atmosphere. This paper presented a multidisciplinary research pilot study on CO{sub 2} enhanced oil recovery (EOR) operations in Alberta. Minimizing the potential for CO{sub 2} leakage through faults or fractures has become one of the primary safety issues affecting the successful capture and geological storage of CO{sub 2}. The potential CO{sub 2} leakage paths are controlled by geomechanical parameters, such as the in-situ stress regime, rock stiffness and rock strength, and the integrity of the wellbore seal. Rock mechanical properties control the behaviour of rock when it is subjected to stresses. As such, the pilot study examined the stress and geomechanical properties of the rocks, which are important elements in evaluating the safety of CO{sub 2} injection and storage. The mechanical properties control hydraulic fracturing, induced shear failure, stresses and strains induced in reservoirs due to fluid pressure and temperature changes, and borehole stability, all of which impact CO{sub 2} storage. The pilot study involved the injection of CO{sub 2} into the Upper Cretaceous Cardium Formation sandstone at a depth of about 1650 m. Thick Colorado Group shale overlies and underlies the Cardium sandstone and conglomerate. This paper included an assessment of the stress regime of the Pembina oil field and a review of the relevant rock properties. The minimum horizontal stress in the reservoir was found to be significantly lower than the caprock. Hydraulic fractures induced in the study area would propagate in a vertical plane in a southwest-northeast direction. Available rock elastic properties suggest that conditions in the study area are favourable for fracture containment. Available data indicates that the caprock is strong, which favours the maintenance of caprock integrity as reservoir pressure and temperature

  5. Feeding Behavior of Aplysia: A Model System for Comparing Cellular Mechanisms of Classical and Operant Conditioning

    Science.gov (United States)

    Baxter, Douglas A.; Byrne, John H.

    2006-01-01

    Feeding behavior of Aplysia provides an excellent model system for analyzing and comparing mechanisms underlying appetitive classical conditioning and reward operant conditioning. Behavioral protocols have been developed for both forms of associative learning, both of which increase the occurrence of biting following training. Because the neural…

  6. On the mechanism of gene amplification induced under stress in Escherichia coli.

    Directory of Open Access Journals (Sweden)

    2006-04-01

    Full Text Available Gene amplification is a collection of processes whereby a DNA segment is reiterated to multiple copies per genome. It is important in carcinogenesis and resistance to chemotherapeutic agents, and can underlie adaptive evolution via increased expression of an amplified gene, evolution of new gene functions, and genome evolution. Though first described in the model organism Escherichia coli in the early 1960s, only scant information on the mechanism(s of amplification in this system has been obtained, and many models for mechanism(s were possible. More recently, some gene amplifications in E. coli were shown to be stress-inducible and to confer a selective advantage to cells under stress (adaptive amplifications, potentially accelerating evolution specifically when cells are poorly adapted to their environment. We focus on stress-induced amplification in E. coli and report several findings that indicate a novel molecular mechanism, and we suggest that most amplifications might be stress-induced, not spontaneous. First, as often hypothesized, but not shown previously, certain proteins used for DNA double-strand-break repair and homologous recombination are required for amplification. Second, in contrast with previous models in which homologous recombination between repeated sequences caused duplications that lead to amplification, the amplified DNAs are present in situ as tandem, direct repeats of 7-32 kilobases bordered by only 4 to 15 base pairs of G-rich homology, indicating an initial non-homologous recombination event. Sequences at the rearrangement junctions suggest nonhomologous recombination mechanisms that occur via template switching during DNA replication, but unlike previously described template switching events, these must occur over long distances. Third, we provide evidence that 3'-single-strand DNA ends are intermediates in the process, supporting a template-switching mechanism. Fourth, we provide evidence that lagging

  7. Mechanical loading by fluid shear stress of myotube glycocalyx stimulates growth factor expression and nitric oxide production

    NARCIS (Netherlands)

    Juffer, P.; Bakker, A.D.; Klein-Nulend, J.; Jaspers, R.T.

    2014-01-01

    Skeletal muscle fibers have the ability to increase their size in response to a mechanical overload. Finite element modeling data suggest that mechanically loaded muscles in vivo may experience not only tensile strain but also shear stress. However, whether shear stress affects biological pathways i

  8. Mechanical stress downregulates MHC class I expression on human cancer cell membrane.

    Directory of Open Access Journals (Sweden)

    Rosanna La Rocca

    Full Text Available In our body, cells are continuously exposed to physical forces that can regulate different cell functions such as cell proliferation, differentiation and death. In this work, we employed two different strategies to mechanically stress cancer cells. The cancer and healthy cell populations were treated either with mechanical stress delivered by a micropump (fabricated by deep X-ray nanolithography or by ultrasound wave stimuli. A specific down-regulation of Major Histocompatibility Complex (MHC class I molecules expression on cancer cell membrane compared to different kinds of healthy cells (fibroblasts, macrophages, dendritic and lymphocyte cells was observed, stimulating the cells with forces in the range of nano-newton, and pressures between 1 and 10 bar (1 bar = 100.000 Pascal, depending on the devices used. Moreover, Raman spectroscopy analysis, after mechanical treatment, in the range between 700-1800 cm(-1, indicated a relative concentration variation of MHC class I. PCA analysis was also performed to distinguish control and stressed cells within different cell lines. These mechanical induced phenotypic changes increase the tumor immunogenicity, as revealed by the related increased susceptibility to Natural Killer (NK cells cytotoxic recognition.

  9. Mechanical Stress Downregulates MHC Class I Expression on Human Cancer Cell Membrane

    KAUST Repository

    La Rocca, Rosanna

    2014-12-26

    In our body, cells are continuously exposed to physical forces that can regulate different cell functions such as cell proliferation, differentiation and death. In this work, we employed two different strategies to mechanically stress cancer cells. The cancer and healthy cell populations were treated either with mechanical stress delivered by a micropump (fabricated by deep X-ray nanolithography) or by ultrasound wave stimuli. A specific down-regulation of Major Histocompatibility Complex (MHC) class I molecules expression on cancer cell membrane compared to different kinds of healthy cells (fibroblasts, macrophages, dendritic and lymphocyte cells) was observed, stimulating the cells with forces in the range of nano-newton, and pressures between 1 and 10 bar (1 bar = 100.000 Pascal), depending on the devices used. Moreover, Raman spectroscopy analysis, after mechanical treatment, in the range between 700–1800 cm−1, indicated a relative concentration variation of MHC class I. PCA analysis was also performed to distinguish control and stressed cells within different cell lines. These mechanical induced phenotypic changes increase the tumor immunogenicity, as revealed by the related increased susceptibility to Natural Killer (NK) cells cytotoxic recognition.

  10. Investigation of the dynamic mechanical behavior of polyetheretherketone (PEEK) in the high stress tensile regime

    Science.gov (United States)

    Berer, M.; Major, Z.; Pinter, G.; Constantinescu, D. M.; Marsavina, L.

    2014-11-01

    Due to its outstanding mechanical performance both in static and dynamic loading and its resistance up to very high temperatures, Polyetheretherketone (PEEK) has attracted many practical applications. The loaded contact state for the application of PEEK rolls as bearing elements was recently analyzed by the corresponding author. High irreversible deformations on the mantle side were caused by the rolling contact and thus the rolling performance is supposed to be strongly affected by the dynamic mechanical properties of this irreversibly deformed material. Tensile fatigue tests at various stress levels up to the thermally dominated fatigue regime were conducted in order to get information regarding the dynamic mechanical material behavior at high stress regimes. Two types of PEEK (annealed and untreated) were investigated and two load ratios, R, were used (0.1 and 0.5). During the fatigue tests extensometer strain, load and surface temperature were recorded and a quantitative hysteresis loop analysis with calculated secant modulus and dynamic modulus was performed. Furthermore, the concept of isocyclic stress-strain diagrams was applied to enlarge and confirm the results obtained from the hysteresis loop analysis. A sharp transition between thermally dominated and mechanically dominated fatigue regimes was found for both PEEK types (annealed and untreated) and for both load ratios. Moreover, the annealed PEEK was stiffer in the tensile fatigue tests than the untreated material. Both examined PEEK types showed distinct hardening throughout the fatigue tests which made them "more elastic" (higher stiffness and less damping).

  11. Mechanical stress downregulates MHC class I expression on human cancer cell membrane.

    Science.gov (United States)

    La Rocca, Rosanna; Tallerico, Rossana; Talib Hassan, Almosawy; Das, Gobind; Lakshmikanth, Tadepally; Tadepally, Lakshmikanth; Matteucci, Marco; Liberale, Carlo; Mesuraca, Maria; Scumaci, Domenica; Gentile, Francesco; Cojoc, Gheorghe; Perozziello, Gerardo; Ammendolia, Antonio; Gallo, Adriana; Kärre, Klas; Cuda, Giovanni; Candeloro, Patrizio; Di Fabrizio, Enzo; Carbone, Ennio

    2014-01-01

    In our body, cells are continuously exposed to physical forces that can regulate different cell functions such as cell proliferation, differentiation and death. In this work, we employed two different strategies to mechanically stress cancer cells. The cancer and healthy cell populations were treated either with mechanical stress delivered by a micropump (fabricated by deep X-ray nanolithography) or by ultrasound wave stimuli. A specific down-regulation of Major Histocompatibility Complex (MHC) class I molecules expression on cancer cell membrane compared to different kinds of healthy cells (fibroblasts, macrophages, dendritic and lymphocyte cells) was observed, stimulating the cells with forces in the range of nano-newton, and pressures between 1 and 10 bar (1 bar = 100.000 Pascal), depending on the devices used. Moreover, Raman spectroscopy analysis, after mechanical treatment, in the range between 700-1800 cm(-1), indicated a relative concentration variation of MHC class I. PCA analysis was also performed to distinguish control and stressed cells within different cell lines. These mechanical induced phenotypic changes increase the tumor immunogenicity, as revealed by the related increased susceptibility to Natural Killer (NK) cells cytotoxic recognition.

  12. Time resolved impedance spectroscopy analysis of lithium phosphorous oxynitride - LiPON layers under mechanical stress

    Science.gov (United States)

    Glenneberg, Jens; Bardenhagen, Ingo; Langer, Frederieke; Busse, Matthias; Kun, Robert

    2017-08-01

    In this paper we present investigations on the morphological and electrochemical changes of lithium phosphorous oxynitride (LiPON) under mechanically bent conditions. Therefore, two types of electrochemical cells with LiPON thin films were prepared by physical vapor deposition. First, symmetrical cells with two blocking electrodes (Cu/LiPON/Cu) were fabricated. Second, to simulate a more application-related scenario cells with one blocking and one non-blocking electrode (Cu/LiPON/Li/Cu) were analyzed. In order to investigate mechanical distortion induced transport property changes in LiPON layers the cells were deposited on a flexible polyimide substrate. Morphology of the as-prepared samples and deviations from the initial state after applying external stress by bending the cells over different radii were investigated by Focused Ion Beam- Scanning Electron Microscopy (FIB-SEM) cross-section and surface images. Mechanical stress induced changes in the impedance were evaluated by time-resolved electrochemical impedance spectroscopy (EIS). Due to the formation of a stable, ion-conducting solid electrolyte interphase (SEI), cells with lithium show decreased impedance values. Furthermore, applying mechanical stress to the cells results in a further reduction of the electrolyte resistance. These results are supported by finite element analysis (FEA) simulations.

  13. Periodic Mechanical Stress INDUCES Chondrocyte Proliferation and Matrix Synthesis via CaMKII-Mediated Pyk2 Signaling.

    Science.gov (United States)

    Liang, Wenwei; Li, Zeng; Wang, Zhen; Zhou, Jinchun; Song, Huanghe; Xu, Shun; Cui, Weiding; Wang, Qing; Chen, Zhefeng; Liu, Feng; Fan, Weimin

    2017-01-01

    Periodic mechanical stress can promote chondrocyte proliferation and matrix synthesis to improve the quality of tissue-engineered cartilage. Although the integrin β1-ERK1/2 signal cascade has been implicated in periodic mechanical stress-induced mitogenic effects in chondrocytes, the precise mechanisms have not been fully established. The current study was designed to probe the roles of CaMKII and Pyk2 signaling in periodic mechanical stress-mediated chondrocyte proliferation and matrix synthesis. Chondrocytes were subjected to periodic mechanical stress, proliferation was assessed by direct cell counting and CCK-8 assay; gene expressions were analyzed using quantitative real-time PCR, protein abundance by Western blotting. Mechanical stress, markedly enhanced the phosphorylation levels of Pyk2 at Tyr402 and CaMKII at Thr286. Both suppression of Pyk2 with Pyk2 inhibitor PF431396 or Pyk2 shRNA and suppression of CaMKII with CaMKII inhibitor KN-93 or CaMKII shRNA blocked periodic mechanical stress-induced chondrocyte proliferation and matrix synthesis. Additionally, either pretreatment with KN-93 or shRNA targeted to CaMKII prevented the activation of ERK1/2 and Pyk2 under conditions of periodic mechanical stress. Interestingly, in relation to periodic mechanical stress, in the context of Pyk2 inhibition with PF431396 or its targeted shRNA, only the phosphorylation levels of ERK1/2 were abrogated, while CaMKII signal activation was not affected. Moreover, the phosphorylation levels of CaMKII- Thr286 and Pyk2- Tyr402 were abolished after pretreatment with blocking antibody against integrinβ1 exposed to periodic mechanical stress. Our results collectively indicate that periodic mechanical stress promotes chondrocyte proliferation and matrix synthesis through the integrinβ1-CaMKII-Pyk2-ERK1/2 signaling cascade. © 2017 The Author(s). Published by S. Karger AG, Basel.

  14. Reversible and rapid transfer-RNA deactivation as a mechanism of translational repression in stress.

    Science.gov (United States)

    Czech, Andreas; Wende, Sandra; Mörl, Mario; Pan, Tao; Ignatova, Zoya

    2013-08-01

    Stress-induced changes of gene expression are crucial for survival of eukaryotic cells. Regulation at the level of translation provides the necessary plasticity for immediate changes of cellular activities and protein levels. In this study, we demonstrate that exposure to oxidative stress results in a quick repression of translation by deactivation of the aminoacyl-ends of all transfer-RNA (tRNA). An oxidative-stress activated nuclease, angiogenin, cleaves first within the conserved single-stranded 3'-CCA termini of all tRNAs, thereby blocking their use in translation. This CCA deactivation is reversible and quickly repairable by the CCA-adding enzyme [ATP(CTP):tRNA nucleotidyltransferase]. Through this mechanism the eukaryotic cell dynamically represses and reactivates translation at low metabolic costs.

  15. Reversible and rapid transfer-RNA deactivation as a mechanism of translational repression in stress.

    Directory of Open Access Journals (Sweden)

    Andreas Czech

    2013-08-01

    Full Text Available Stress-induced changes of gene expression are crucial for survival of eukaryotic cells. Regulation at the level of translation provides the necessary plasticity for immediate changes of cellular activities and protein levels. In this study, we demonstrate that exposure to oxidative stress results in a quick repression of translation by deactivation of the aminoacyl-ends of all transfer-RNA (tRNA. An oxidative-stress activated nuclease, angiogenin, cleaves first within the conserved single-stranded 3'-CCA termini of all tRNAs, thereby blocking their use in translation. This CCA deactivation is reversible and quickly repairable by the CCA-adding enzyme [ATP(CTP:tRNA nucleotidyltransferase]. Through this mechanism the eukaryotic cell dynamically represses and reactivates translation at low metabolic costs.

  16. The influence of thermal-mechanical processing on residual stresses in titanium matrix composites

    Energy Technology Data Exchange (ETDEWEB)

    Rangaswamy, P. [Los Alamos National Lab., NM (United States); Bourke, M.A.M. [Los Alamos National Lab., NM (United States); Wright, P.K. [General Electric Aircraft Engines, Evendale, Cincinnati, OH (United States); Jayaraman, N. [Cincinnati Univ., OH (United States). Dept. of Materials Science and Engineering; Kartzmark, E. [Los Alamos National Lab., NM (United States); Roberts, J.A. [Los Alamos National Lab., NM (United States)

    1997-03-31

    The effects of three distinct thermo-mechanical processes on the residual stress state in a uni-directionally reinforced SCS-6/Ti-6-2-4-2 [0]{sub 6} titanium-alloy matrix composite were predicted using a finite element model. For comparison the residual stresses were measured using X-ray and neutron diffraction. Reductions in stress were predicted by the models and both experimental techniques recorded a reduction compared to the as-fabricated material. While the numerically predicted trends qualitatively agreed with the neutron measurements quantitative agreement was not achieved. In the longitudinal direction the neutron results showed closer agreement to the calculation whereas in the transverse direction the X-ray results did. Nevertheless the changes did correlate with improvement in fatigue lifetimes. (orig.)

  17. Formulation of Deformation Stress Fields and Constitutive Equations in Rational Mechanics

    CERN Document Server

    Jianhua, Xiao

    2010-01-01

    In continuum mechanics, stress concept plays an essential role. For complicated materials, different stress concepts are used with ambiguity or different understanding. Geometrically, a material element is expressed by a closed region with arbitral shape. The internal region is acted by distance dependent force (internal body force), while the surface is acted by surface force. Further more, the element as a whole is in a physical background (exterior region) which is determined by the continuum where the element is embedded (external body force). Physically, the total energy can be additively decomposed as three parts: internal region energy, surface energy, and the background energy. However, as forces, they cannot be added directly. After formulating the general forms of physical fields, the deformation tensor is introduced to formulate the force variations caused by deformation. As the force variation is expressed by the deformation tensor, the deformation stress concept is well formulated. Furthermore, a...

  18. Gaze angle: a possible mechanism of visual stress in virtual reality headsets.

    Science.gov (United States)

    Mon-Williams, M; Plooy, A; Burgess-Limerick, R; Wann, J

    1998-03-01

    It is known that some Virtual Reality (VR) head-mounted displays (HMDs) can cause temporary deficits in binocular vision. On the other hand, the precise mechanism by which visual stress occurs is unclear. This paper is concerned with a potential source of visual stress that has not been previously considered with regard to VR systems: inappropriate vertical gaze angle. As vertical gaze angle is raised or lowered the 'effort' required of the binocular system also changes. The extent to which changes in vertical gaze angle alter the demands placed upon the vergence eye movement system was explored. The results suggested that visual stress may depend, in part, on vertical gaze angle. The proximity of the display screens within an HMD means that a VR headset should be in the correct vertical location for any individual user. This factor may explain some previous empirical results and has important implications for headset design. Fortuitously, a reasonably simple solution exists.

  19. Family support, family stress, and suicidal ideation in a combat-exposed sample of Operation Enduring Freedom/Operation Iraqi Freedom veterans.

    Science.gov (United States)

    Gradus, Jaimie L; Smith, Brian N; Vogt, Dawne

    2015-01-01

    Deployment-related risk factors for suicidal ideation among Operation Enduring Freedom (OEF) and Operation Iraqi Freedom (OIF) veterans have received a great deal of attention. Studies show that mental health symptoms mediate the association between most deployment stressors and suicidal ideation; however, family-related factors during deployment are largely unexplored. We examined posttraumatic stress disorder (PTSD) and depression symptoms as mediators of the associations between deployment family support and stress and post-deployment suicidal ideation in combat-exposed OEF/OIF veterans. National cross-sectional mail survey. 1046 veterans responded to the survey. The sample for this study was 978 veterans who experienced combat. Regression-based path analyses were conducted. Family support and stress had direct associations with suicidal ideation. When PTSD and depression symptoms were examined as mediators of these associations, results revealed significant indirect paths through these symptoms. This study contributes to the literature on suicidal ideation risk factors among OEF/OIF veterans. Deployment family support and family stress are associated with suicidal ideation; however these associations occur primarily through mental health symptomatology, consistent with findings observed for other deployment factors. This research supports ongoing efforts to treat mental health symptomatology as a means of suicide prevention.

  20. Difference of operation mechanisms in SWNTs network FETs studied via scanning gate microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Wei, Xiaojun; Matsunaga, Masahiro; Yahagi, Tatsurou; Maeda, Kenji; Ochiai, Yuichi; Aoki, Nobuyuki [Graduate School of Advanced Integration Science, Chiba University, Chiba 263-8522 (Japan); Bird, Jonathan P. [Department of Electrical Engineering, University at Buffalo, the State University of New York, Buffalo, NY 14260-1920 (United States); Ishibashi, Koji [Advanced Device Laboratory, RIKEN, Wako, Saitama 351-0198 (Japan)

    2013-12-04

    Field effect transistors (FETs) whose channel is composed of a network of single wall carbon nanotubes (SWNTs) have been studied to investigate the mechanism of the device operation via scanning gate microscopy (SGM) at room temperature. We observed different SGM response in networks of SWNTs either synthesized by CoMoCAT process or semiconducting enriched by density gradient ultracentrifuge process. In the former case, SGM response was observed at specific inter-tube junctions suggesting a Schottky junction formed with semiconducting and metallic SWNTs in the network. In contrast, multiple concentric rings in the SGM response are observed within the tubes in a network of the latter SWNTs suggesting a possibility of quantum mechanical transport at room-temperature. Different type of SGM responses are confirmed in the two kinds of SWNTs networks, nevertheless such active positions would likely have an important role in the FET operation mechanism in each network.

  1. How stress and temperature conditions affect rock-fluid chemistry and mechanical deformation

    Directory of Open Access Journals (Sweden)

    Anders eNermoen

    2016-02-01

    Full Text Available We report the results from a series of chalk flow-through-compaction experiments performed at three effective stresses (0.5 MPa, 3.5 MPa and 12.3 MPa and two temperatures (92℃ and and 130℃. The results show that both stress and temperature are important to both chemical alteration and mechanical deformation. The experiments were conducted on cores drilled from the same block of outcrop chalks from the Obourg quarry within the Saint Vast formation (Mons, Belgium. The pore pressure was kept at 0.7 MPa for all experiments with a continuous flow of 0.219 M MgCl2 brine at a constant flow rate; 1 original pore volume (PV per day. The experiments have been performed in tri-axial cells with independent control of the external stress (hydraulic pressure in the confining oil, pore pressure, temperature, and the injected flow rate. Each experiment consists of two phases; a loading phase where stress-strain dependencies are investigated (approx. 2 days, and a creep phase that lasts for more than 150-160 days. During creep, the axial deformation was logged, and the effluent samples were collected for ion chromatography analyses. Any difference between the injected and produced water chemistry gives insight into the rock-fluid interactions that occur during flow through of the core. The observed effluent concentration shows a reduction in Mg2+, while the Ca2+ concentration is increased. This, together with SEM-EDS analysis, indicates that magnesium-bearing mineral phases are precipitated leading to dissolution of calcite, an observation . This is in-line with other flow-through experiments reported earlier. The observed dissolution and precipitation are sensitive to the effective stress and test temperature. Typically. H, higher stress and temperature lead to increased concentration differences of Mg2+ and Ca2+ concentration changes.. The observed strain can be partitioned additively into a mechanical and chemical driven component.

  2. How stress and temperature conditions affect rock-fluid chemistry and mechanical deformation

    Science.gov (United States)

    Nermoen, Anders; Korsnes, Reidar; Aursjø, Olav; Madland, Merete; Kjørslevik, Trygve Alexander; Østensen, Geir

    2016-02-01

    We report the results from a series of chalk flow-through-compaction experiments performed at three effective stresses (0.5 MPa, 3.5 MPa and 12.3 MPa) and two temperatures (92° and and 130°). The results show that both stress and temperature are important to both chemical alteration and mechanical deformation. The experiments were conducted on cores drilled from the same block of outcrop chalks from the Obourg quarry within the Saint Vast formation (Mons, Belgium). The pore pressure was kept at 0.7 MPa for all experiments with a continuous flow of 0.219 M MgCl2 brine at a constant flow rate; 1 original pore volume (PV) per day. The experiments have been performed in tri-axial cells with independent control of the external stress (hydraulic pressure in the confining oil), pore pressure, temperature, and the injected flow rate. Each experiment consists of two phases; a loading phase where stress-strain dependencies are investigated (approx. 2 days), and a creep phase that lasts for more than 150-160 days. During creep, the axial deformation was logged, and the effluent samples were collected for ion chromatography analyses. Any difference between the injected and produced water chemistry gives insight into the rock-fluid interactions that occur during flow through of the core. The observed effluent concentration shows a reduction in Mg2+, while the Ca2+ concentration is increased. This, together with SEM-EDS analysis, indicates that magnesium-bearing mineral phases are precipitated leading to dissolution of calcite, an observation . This is in-line with other flow-through experiments reported earlier. The observed dissolution and precipitation are sensitive to the effective stress and test temperature. Typically. H, higher stress and temperature lead to increased concentration differences of Mg2+ and Ca2+ concentration changes.. The observed strain can be partitioned additively into a mechanical and chemical driven component.

  3. Effects of 60 Hz electric fields on operant and social stress behaviors of nonhuman primates

    Energy Technology Data Exchange (ETDEWEB)

    Rogers, W.R.; Coelho, A.M. Jr.; Easley, S.P.; Lucas, J.H.; Moore, G.T.; Orr, J.L.; Smith, H.D.; Taylor, L.L.; Tuttle, M.L.

    1987-10-24

    The objective of this program is to investigate, using the baboon as a nonhuman primate surrogate for the human, possible behavioral effects associated with exposure to high intensity 60 Hz electric fields. Results from this program, along with information from experiments conducted elsewhere, will be used by the Department of Energy (DOE) to estimate and evaluate the likelihood of deleterious consequences resulting from exposure of humans to the electric fields associated with power transmission over high voltage lines. This research program consists of four major research projects, all of which have been successfully completed. The first project evaluated the potentially aversive character of exposure to 60 Hz electric fields by determining the threshold intensity that produces escape or avoidance responses. The second project estimated the threshold intensity for detection threshold was 12 kV/m; the range of means was 6 to 16 kV/m. The third project assessed, in separate experiments conducted at 30 and 60 kV/m, effects of chronic exposure to electric fields on the performance of two operant conditioning tasks, fixed ratio (FR), and differential reinforcement of low rate (DRL). In the same two experiments, the fourth project investigated, using the systematic quantitative observational sampling methods of primatology, the possible stress-inducing effects of chronic exposure to 60 Hz electric fields on the behavior of baboons living in small social groups. 131 refs., 87 figs., 123 tabs.

  4. Connection Between Internal Structural Stresses of the Ist and the IInd kind and Operational Reliability of the Boiler Heating Surface

    Directory of Open Access Journals (Sweden)

    Lyubimova Lyudmila

    2016-01-01

    Full Text Available This paper presents new approaches to solving problems of forecasting the life of heating surface of boilers, based on an analysis of internal structural stresses of the first and second kind that could affect the intragranular and intergranular strength and reliability of the pipeline in continuous operation by making it work without damage by preventing the disclosure of zone cracks.

  5. Static and dynamic mechanics of the temporomandibular joint: plowing forces, joint load and tissue stress.

    Science.gov (United States)

    Nickel, J; Spilker, R; Iwasaki, L; Gonzalez, Y; McCall, W D; Ohrbach, R; Beatty, M W; Marx, D

    2009-08-01

    OBJECTIVES - To determine the combined effects 1) of stress-field aspect ratio and velocity and compressive strain and 2) joint load, on temporomandibular joint (TMJ) disc mechanics. SETTING AND SAMPLE POPULATION - Fifty-two subjects (30 female; 22 male) participated in the TMJ load experiments. MATERIAL AND METHODS - In the absence of human tissue, pig TMJ discs were used to determine the effects of variables 1) on surface plowing forces, and to build a biphasic finite element model (bFEM) to test the effect of human joint loads and 2) on tissue stresses. In the laboratory, discs received a 7.6 N static load via an acrylic indenter before cyclic movement. Data were recorded and analysed using anova. To determine human joint loads, Research Diagnostic Criteria calibrated investigators classified subjects based on signs of disc displacement (DD) and pain (+DD/+pain, n = 18; +DD/-pain, n = 17; -DD/-pain, n = 17). Three-dimensional geometries were produced for each subject and used in a computer model to calculate joint loads. RESULTS - The combined effects of compressive strain, and aspect ratio and velocity of stress-field translation correlated with plowing forces (R(2) = 0.85). +DD/-pain subjects produced 60% higher joint loads (ANOVA, p dynamic variables of the stress-field and subject-dependent joint load significantly affect disc mechanics.

  6. Molecular mechanism of dehydrin in response to environmental stress in plant

    Institute of Scientific and Technical Information of China (English)

    ZHANG Yuxiu; WANG Zi; XU Jin

    2007-01-01

    Dehydrins, known as the D-11 subgroup of late embryogenesis abundant (LEA) protein, are an immunologically distinct family of proteins, which typically accumulate in desiccation-tolerant seed embryo or in vegetative tissues in response to various environmental stresses such as drought, salinity and freezing. The existence of conservative sequences designated as K, S, and Y segments is a structural feature of dehydrins, and the K segment found in all dehydrins represents a highly conserved 15 amino acid motif (EKKGIMDKIKEKLPG) and forms an amphiphilic a-helix. According to the arrangement of these domains and clustering analysis, dehydrins are subdivided into 5 subtypes: YnSK, Kn, KnS, SKn and YnK. Different types of dehydrins are induced by different environmental stress in plants. Study results showed that dehydrins might play important protective roles under abiotic stress via a number of different mechanisms, including improving or protecting enzyme activities by the cryoprotective activity in responding to freeze/thaw or dehydration; stabilizing vesicles or other endomembrane structures by function as the membrane stabilizer during freeze induced dehydration,and preventing the membrane system from the oxidative damage induced by reactive oxygen radicals as the radical scavenger. Here, the gene expression and molecular mechanisms of dehydrin in response to stress in plants are discussed.

  7. Mechanical evaluation and fem analysis of stress in fixed partial dentures zirconium-ceramic.

    Science.gov (United States)

    Cardelli, P L; Vertucci, V; Balestra, F; Montani, M; Arcuri, C

    2013-03-01

    Over the last several years, the Finite Element Analysis (FEM) has been widely recognized as a reference method in different fields of study, to simulate the distribution of mechanical stress, in order to evaluate the relative distribution of loads of different nature. The aim of this study is to investigate through the FEM analysis the stress distribution in fixed prostheses that have a core in Zirconia and a ceramic veneer supported by implants. In this work we investigated the mechanical flexural strength of a ceramic material (Noritake(®)) and a of zirconium framework (Zircodent(®)) and the effects of the manufacturing processes of the material commonly performed during the production of fixed prostheses with CAD/CAM technology. Specifically three point bending mechanical tests were performed (three-point-bending) (1-3), using a machine from Test Equipment Instron 5566(®), on two structures in zirconium framework-ceramic (structures supported by two implant abutments with pontic elements 1 and 2). A further in-depth analysis on the mechanical behavior in flexure of the specimens was conducted carrying out FEM studies in order to compare analog and digital data. The analysis of the data obtained showed that the stresses are distributed in a different way according to the intrinsic elasticity of the structure. The analysis of FPD with four elements, the stresses are mainly concentrated on the surface of the load, while, in the FPD of three elements, much more rigid, the stresses are concentrated near the inner margins of the abutments. The concentration of many stresses in this point could be correlated to chipping (4) that is found in the outer edges of the structure, as a direct result of the ceramic brittleness which opposes the resilience of the structure subjected to bending. The analysis of the UY linear displacement confirms previous data, showing, in a numerical way, that the presence of the ceramic is related to the lowering of the structure. So, the

  8. Molecular mechanisms of Saccharomyces cerevisiae stress adaptation and programmed cell death in response to acetic acid

    Directory of Open Access Journals (Sweden)

    Sergio eGiannattasio

    2013-02-01

    Full Text Available Beyond its classical biotechnological applications such as food and beverage production or as a cell factory, the yeast Saccharomyces cerevisiae is a valuable model organism to study fundamental mechanisms of cell response to stressful environmental changes. Acetic acid is a physiological product of yeast fermentation and it is a well-known food preservative due to its antimicrobial action. Acetic acid has recently been shown to cause yeast cell death and aging. Here we shall focus on the molecular mechanisms of S. cerevisiae stress adaptation and programmed cell death in response to acetic acid. We shall elaborate on the intracellular signaling pathways involved in the cross-talk of pro-survival and pro-death pathways underlying the importance of understanding fundamental aspects of yeast cell homeostasis to improve the performance of a given yeast strain in biotechnological applications.

  9. Computer simulation study of nanoparticle interaction with a lipid membrane under mechanical stress.

    Science.gov (United States)

    Lai, Kan; Wang, Biao; Zhang, Yong; Zheng, Yue

    2013-01-07

    Pore formation of lipid bilayers under mechanical stress is critical to biological processes. A series of coarse grained molecular dynamics simulations of lipid bilayers with carbon nanoparticles different in size have been performed. Surface tension was applied to study the disruption of lipid bilayers by nanoparticles and the formation of pores inside the bilayers. The presence of small nanoparticles enhances the probability of water penetration thus decreasing the membrane rupture tension, while big nanoparticles have the opposite effect. Nanoparticle volume affects bilayer strength indirectly, and particle surface density can complicate the interaction. The structural, dynamic, elastic properties and lateral densities of lipid bilayers with nanoparticles under mechanical stress were analyzed. The results demonstrate the ability of nanoparticles to adjust the structural and dynamic properties of a lipid membrane, and to efficiently regulate the pore formation behavior and hydrophobicity of membranes.

  10. Changes in permeability caused by transient stresses: field observations, experiments, and mechanisms

    Science.gov (United States)

    Manga, Michael; Beresnev, Igor; Brodsky, Emily E.; Elkhoury, Jean E.; Elsworth, Derek; Ingebritsen, Steve E.; Mays, David C.; Wang, Chi-yuen

    2012-01-01

    Oscillations in stress, such as those created by earthquakes, can increase permeability and fluid mobility in geologic media. In natural systems, strain amplitudes as small as 10–6 can increase discharge in streams and springs, change the water level in wells, and enhance production from petroleum reservoirs. Enhanced permeability typically recovers to prestimulated values over a period of months to years. Mechanisms that can change permeability at such small stresses include unblocking pores, either by breaking up permeability-limiting colloidal deposits or by mobilizing droplets and bubbles trapped in pores by capillary forces. The recovery time over which permeability returns to the prestimulated value is governed by the time to reblock pores, or for geochemical processes to seal pores. Monitoring permeability in geothermal systems where there is abundant seismicity, and the response of flow to local and regional earthquakes, would help test some of the proposed mechanisms and identify controls on permeability and its evolution.

  11. Tectonic stress pattern in the Chinese Mainland from the inversion of focal mechanism data

    Indian Academy of Sciences (India)

    Ju Wei; Sun Weifeng; Ma Xiaojing

    2017-04-01

    The tectonic stress pattern in the Chinese Mainland and kinematic models have been subjected to much debate. In the past several decades, several tectonic stress maps have been figured out; however, they generally suffer a poor time control. In the present study, 421 focal mechanism data up to January 2010 were compiled from the Global/Harvard CMT catalogue, and 396 of them were grouped into 23 distinct regions in function of geographic proximity. Reduced stress tensors were obtained from formal stress inversion for each region. The results indicated that, in the Chinese Mainland, the directions of maximum principal stress were ∼NE–SW-trending in the northeastern region, ∼NEE–SWW-trending in the North China region, ∼N–S-trending in western Xinjiang, southern Tibet and the southern Yunnan region, ∼NNE–SSW-trending in the northern Tibet and Qinghai region, ∼NW–SE-trending in Gansu region, and ∼E–W-trending in the western Sichuan region. The average tectonic stress regime was strikeslip faulting (SS) in the eastern Chinese Mainland and northern Tibet region, normal faulting (NF) in the southern Tibet, western Xinjiang and Yunnan region, and thrust faulting (TF) in most regions of Xinjiang, Qinghai and Gansu. The results of the present study combined with GPS velocities in the Chinese Mainland supported and could provide new insights into previous tectonic models (e.g., the extrusion model). From the perspective of tectonics, the mutual actions among the Eurasian plate, Pacific plate and Indian plate caused the present-day tectonic stress field in the Chinese Mainland.

  12. The influence of acute stress on attention mechanisms and its electrophysiological correlates

    Directory of Open Access Journals (Sweden)

    Jessica eSänger

    2014-10-01

    Full Text Available For the selection of relevant information out of a continuous stream of information, which is a common definition of attention, two core mechanisms are assumed: a competition-based comparison of the neuronal activity in sensory areas and the top-down modulation of this competition by frontal executive control functions. Those control functions are thought to bias the processing of information towards the intended goals. Acute stress is thought to impair these frontal functions through the release of cortisol.In the present study, subjects had to detect a luminance change of a stimulus and ignore more salient but task irrelevant orientation changes. Before the execution of this task, subjects underwent a socially evaluated cold pressor test (SECPT or a non-stressful control situation. The SECPT revealed reliable stress response with a significant increase of cortisol and alpha-amylase. Stressed subjects showed higher error rates than controls, particularly in conditions which require top-down control processing to bias the less salient target feature against the more salient and spatially separated distracter.By means of the EEG, subjects who got stressed showed a reduced allocation to the relevant luminance change apparent in a modulation of the N1pc. The following N2pc, which reflects a re-allocation of attentional resources, supports the error pattern. There was only an N2pc in conditions, which required to bias the less salient luminance change. Moreover, this N2pc was decreased as a consequence of the induced stress. These results allow the conclusion that acute stress impairs the intention-based attentional allocation and enhances the stimulus-driven selection, leading to a strong distractibility during attentional information selection.

  13. The influence of acute stress on attention mechanisms and its electrophysiological correlates.

    Science.gov (United States)

    Sänger, Jessica; Bechtold, Laura; Schoofs, Daniela; Blaszkewicz, Meinolf; Wascher, Edmund

    2014-01-01

    FOR THE SELECTION OF RELEVANT INFORMATION OUT OF A CONTINUOUS STREAM OF INFORMATION, WHICH IS A COMMON DEFINITION OF ATTENTION, TWO CORE MECHANISMS ARE ASSUMED: a competition-based comparison of the neuronal activity in sensory areas and the top-down modulation of this competition by frontal executive control functions. Those control functions are thought to bias the processing of information toward the intended goals. Acute stress is thought to impair these frontal functions through the release of cortisol. In the present study, subjects had to detect a luminance change of a stimulus and ignore more salient but task irrelevant orientation changes. Before the execution of this task, subjects underwent a socially evaluated cold pressor test (SECPT) or a non-stressful control situation. The SECPT revealed reliable stress response with a significant increase of cortisol and alpha-amylase. Stressed subjects showed higher error rates than controls, particularly in conditions which require top-down control processing to bias the less salient target feature against the more salient and spatially separated distracter. By means of the EEG, subjects who got stressed showed a reduced allocation to the relevant luminance change apparent in a modulation of the N1pc. The following N2pc, which reflects a re-allocation of attentional resources, supports the error pattern. There was only an N2pc in conditions, which required to bias the less salient luminance change. Moreover, this N2pc was decreased as a consequence of the induced stress. These results allow the conclusion that acute stress impairs the intention-based attentional allocation and enhances the stimulus-driven selection, leading to a strong distractibility during attentional information selection.

  14. Physiological and transcriptomic analyses reveal a response mechanism to cold stress in Santalum album L. leaves

    Science.gov (United States)

    Zhang, Xinhua; Teixeira da Silva, Jaime A.; Niu, Meiyun; Li, Mingzhi; He, Chunmei; Zhao, Jinhui; Zeng, Songjun; Duan, Jun; Ma, Guohua

    2017-01-01

    Santalum album L. (Indian sandalwood) is an economically important plant species because of its ability to produce highly valued perfume oils. Little is known about the mechanisms by which S. album adapts to low temperatures. In this study, we obtained 100,445,724 raw reads by paired-end sequencing from S. album leaves. Physiological and transcriptomic changes in sandalwood seedlings exposed to 4 °C for 0–48 h were characterized. Cold stress induced the accumulation of malondialdehyde, proline and soluble carbohydrates, and increased the levels of antioxidants. A total of 4,424 differentially expressed genes were responsive to cold, including 3,075 cold-induced and 1,349 cold-repressed genes. When cold stress was prolonged, there was an increase in the expression of cold-responsive genes coding for transporters, responses to stimuli and stress, regulation of defense response, as well as genes related to signal transduction of all phytohormones. Candidate genes in the terpenoid biosynthetic pathway were identified, eight of which were significantly involved in the cold stress response. Gene expression analyses using qRT-PCR showed a peak in the accumulation of SaCBF2 to 4, 50-fold more than control leaves and roots following 12 h and 24 h of cold stress, respectively. The CBF-dependent pathway may play a crucial role in increasing cold tolerance. PMID:28169358

  15. Stress, sex and neural adaptation to a changing environment: mechanisms of neuronal remodeling

    Science.gov (United States)

    McEwen, Bruce S.

    2010-01-01

    The adult brain is much more resilient and adaptable than previously believed, and adaptive structural plasticity involves growth and shrinkage of dendritic trees, turnover of synapses and limited amounts of neurogenesis in the forebrain, especially the dentate gyrus of the hippocampal formation. Stress and sex hormones help to mediate adaptive structural plasticity, which has been extensively investigated in hippocampus and to a lesser extent in prefrontal cortex and amygdala, all brain regions that are involved in cognitive and emotional functions. Stress and sex hormones exert their effects on brain structural remodeling through both classical genomic as well as non-genomic mechanisms, and they do so in collaboration with neurotransmitters and other intra- and extracellular mediators. This review will illustrate the actions of estrogen on synapse formation in the hippocampus and the process of stress-induced remodelling of dendrites and synapses in the hippocampus, amygdala and prefrontal cortex. The influence of early developmental epigenetic events, such as early life stress and brain sexual differentiation, is noted along with the interactions between sex hormones and the effects of stress on the brain. Because hormones influence brain structure and function and because hormone secretion is governed by the brain, applied molecular neuroscience techniques can begin to reveal the role of hormones in brain-related disorders and the treatment of these diseases. A better understanding of hormone-brain interactions should promote more flexible approaches to the treatment of psychiatric disorders, as well as their prevention through both behavioral and pharmaceutical interventions. PMID:20840167

  16. Introduction of Enhanced Compressive Residual Stress Profiles in Aerospace Components Using Combined Mechanical Surface Treatments

    Science.gov (United States)

    Gopinath, Abhay; Lim, Andre; Nagarajan, Balasubramanian; Cher Wong, Chow; Maiti, Rajarshi; Castagne, Sylvie

    2016-11-01

    Mechanical surface treatments such as Shot Peening (SP) and Deep Cold Rolling (DCR) are being used to introduce Compressive Residual Stress (CRS) at the surface and subsurface layers of aerospace components, respectively. This paper investigates the feasibility of a combined introduction of both the surface and sub-surface compressive residual stress on Ti6Al4V material through a successive application of the two aforementioned processes, one after the other. CRS profiles between individual processes were compared to that of combination of processes to validate the feasibility. It was found out that shot peening introduces surface compressive residual stress into the already deep cold rolled sample, resulting in both surface and sub-surface compressive residual stresses in the material. However the drawback of such a combination would be the increased surface roughness after shot peening a deep cold rolled sample which can be critical especially in compressor components. Hence, a new technology, Vibro-Peening (VP) may be used as an alternative to SP to introduce surface stress at reduced roughness.

  17. Mechanisms of Stress-Induced Visceral Pain: Implications in Irritable Bowel Syndrome.

    Science.gov (United States)

    Greenwood-Van Meerveld, B; Moloney, R D; Johnson, A C; Vicario, M

    2016-08-01

    Visceral pain is a term describing pain originating from the internal organs of the body and is a common feature of many disorders, including irritable bowel syndrome (IBS). Stress is implicated in the development and exacerbation of many visceral pain disorders. Recent evidence suggests that stress and the gut microbiota can interact through complementary or opposing factors to influence visceral nociceptive behaviours. The Young Investigator Forum at the International Society of Psychoneuroendocrinology (ISPNE) annual meeting reported experimental evidence suggesting the gut microbiota can affect the stress response to affect visceral pain. Building upon human imaging data showing abnormalities in the central processing of visceral stimuli in patients with IBS and knowledge that the amygdala plays a pivotal role in facilitating the stress axis, the latest experimental evidence supporting amygdala-mediated mechanisms in stress-induced visceral pain was reviewed. The final part of the session at ISPNE reviewed experimental evidence suggesting that visceral pain in IBS may be a result, at least in part, of afferent nerve sensitisation following increases in epithelial permeability and mucosal immune activation. © 2016 British Society for Neuroendocrinology.

  18. Mechanism of dynamic reorientation of cortical microtubules due to mechanical stress

    CERN Document Server

    Muratov, Alexander

    2015-01-01

    Directional growth caused by gravitropism and corresponding bending of plant cells has been explored since 19th century, however, many aspects of mechanisms underlying the perception of gravity at the molecular level are still not well known. Perception of gravity in root and shoot gravitropisms is usually attributed to gravisensitive cells, called statocytes, which exploit sedimentation of macroscopic and heavy organelles, amyloplasts, to sense the direction of gravity. Gravity stimulus is then transduced into distal elongation zone, which is several mm far from statocytes, where it causes stretching. It is suggested that gravity stimulus is conveyed by gradients in auxin flux. We propose a theoretical model that may explain how concentration gradients and/or stretching may indirectly affect the global orientation of cortical microtubules, attached to the cell membrane and induce their dynamic reorientation perpendicular to the gradients. In turn, oriented microtubules arrays direct the growth and orientatio...

  19. Use of the RoboFlag synthetic task environment to investigate workload and stress responses in UAV operation.

    Science.gov (United States)

    Guznov, Svyatoslav; Matthews, Gerald; Funke, Gregory; Dukes, Allen

    2011-09-01

    Use of unmanned aerial vehicles (UAVs) is an increasingly important element of military missions. However, controlling UAVs may impose high stress and workload on the operator. This study evaluated the use of the RoboFlag simulated environment as a means for profiling multiple dimensions of stress and workload response to a task requiring control of multiple vehicles (robots). It tested the effects of two workload manipulations, environmental uncertainty (i.e., UAV's visual view area) and maneuverability, in 64 participants. The findings confirmed that the task produced substantial workload and elevated distress. Dissociations between the stress and performance effects of the manipulations confirmed the utility of a multivariate approach to assessment. Contrary to expectations, distress and some aspects of workload were highest in the low-uncertainty condition, suggesting that overload of information may be an issue for UAV interface designers. The strengths and limitations of RoboFlag as a methodology for investigating stress and workload responses are discussed.

  20. Thermo-mechanical Modeling for Residual Stresses of Friction Stir Welding of Dissimilar Alloys

    OpenAIRE

    ABDUL ARIF; ABHISHEK; K. N. Pandey

    2013-01-01

    Friction stir welding is an advanced joining process that has been used for high production since 1996. FSW produces a weld that is strong than the base material because melting does not occur and joining takes place below the melting temperature of the material. FSW produces no fumes and can join aluminum alloys, magnesium, steels, copper and titanium. In this study, a thermo-mechanical model with improved potential is developed to study the formation of residual stress field in dissimilar ...

  1. Involvement of epigenetic mechanisms in the development of posttraumatic stress disorder

    Directory of Open Access Journals (Sweden)

    Tomaž Zupanc

    2012-03-01

    victims with no childhood abuse were found. It was suggested that changes in glucocorticoid system are mediated by tissue-specific changes in gene expression. Recent studies suggest that epigenetic mechanisms may play an important role in the interplay between stress exposure and genetic vulnerability. Conclusions: Integrating epigenetics into a model that permits prior experience to have a central role in determining individual differences is also consistent with a developmental perspective of PTSD vulnerability.

  2. New Drugs for Anemia Treatment Based on a New Understanding of the Mechanisms of Stress Erythropoiesis

    Science.gov (United States)

    2015-11-01

    Award Number: W81XWH-12-1-0449 TITLE: New Drugs for Anemia Treatment Based on a New Understanding of the Mechanisms of Stress Erythropoiesis...COVERED 1Sep2012 - 31Aug2015 4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER New Drugs for Anemia Treatment Based on a New Understanding of the...cell formation in "Nan" (neonatal anemia ) mice, raising the level of red cells to almost normal. It also causes an increase in the numbers of splenic

  3. [The operative cystoscope with joystick control mechanism of flexible tools inserted into the urinary bladder and the ureter].

    Science.gov (United States)

    Komiakov, B K; Topuzov, M É; Zubarev, V A; Stetsik, O V

    2014-01-01

    The authors developed an operative cystoscope with joystick control mechanism of ureter catheters and other flexible tools. This construction allowed control of flexible tools inserted into the bladder and the ureter in various directions, thus providing a necessary observation of the operative field at endoscopic operations on the bladder and ureter. This was one of the factors, which determined the operation success.

  4. A comparison of material removal mechanism under low stress abrasive condition of steel and hardfacing alloys

    Science.gov (United States)

    Dasgupta, R.; Prasad, B. K.; Modi, O. P.; Jha, A. K.

    1999-08-01

    The low stress abrasive wear behavior of two types of steels commonly used for making a number of commonly used engineering components has been compared with the composition of a few hardfacing alloys that can be overlayed on the steels to impart a wear-resistant surface. The mechanism of material removal as studied by the scanning electron micrographs of the worn and transverse sections is different for the steels and hardfacing alloys. An attempt has been made to explain the mechanism of material removal for the steels and hardfacing alloys.

  5. Mechanical strain downregulates C/EBPβ in MSC and decreases endoplasmic reticulum stress.

    Directory of Open Access Journals (Sweden)

    Maya Styner

    Full Text Available Exercise prevents marrow mesenchymal stem cell (MSC adipogenesis, reversing trends that accompany aging and osteoporosis. Mechanical input, the in-vitro analogue to exercise, limits PPARγ expression and adipogenesis in MSC. We considered whether C/EBPβ might be mechanoresponsive as it is upstream to PPARγ, and also is known to upregulate endoplasmic reticulum (ER stress. MSC (C3H10T1/2 pluripotent cells as well as mouse marrow-derived MSC were cultured in adipogenic media and a daily mechanical strain regimen was applied. We demonstrate herein that mechanical strain represses C/EBPβ mRNA (0.6-fold ±0.07, p<0.05 and protein (0.4-fold ±0.1, p<0.01 in MSC. SiRNA silencing of β-catenin prevented mechanical repression of C/EBPβ. C/EBPβ overexpression did not override strain's inhibition of adipogenesis, which suggests that mechanical control of C/EBPβ is not the primary site at which adipogenesis is regulated. Mechanical inhibition of C/EBPβ, however, might be critical for further processes that regulate MSC health. Indeed, overexpression of C/EBPβ in MSC induced ER stress evidenced by a dose-dependent increase in the pro-apoptotic CHOP (protein 4-fold ±0.5, p<0.05 and a threshold reduction in the chaperone BiP (protein 0.6-fold ±0.1, p = 0.2; mRNA 0.3-fold ±0.1, p<0.01. ChIP-seq demonstrated a significant association between C/EBPβ and both CHOP and BiP genes. The strain regimen, in addition to decreasing C/EBPβ mRNA (0.5-fold ±0.09, p<0.05, expanded ER capacity as measured by an increase in BiP mRNA (2-fold ±0.2, p<0.05 and protein. Finally, ER stress induced by tunicamycin was ameliorated by mechanical strain as demonstrated by decreased C/EBPβ, increased BiP and decreased CHOP protein expression. Thus, C/EBPβ is a mechanically responsive transcription factor and its repression should counter increases in marrow fat as well as improve skeletal resistance to ER stress.

  6. Optimal mechanical harvester route planning for sugarcane f ield operations using particle swarm optimization

    Directory of Open Access Journals (Sweden)

    Woraya Neungmatcha

    2015-06-01

    Full Text Available Since current agricultural production systems such as the sugarcane supply system in the sugar industry are developing towards larger and more complicated systems, there is consequently increasing use of agricultural machinery. Even though mechanization can help to increase the sugarcane yield, if the mechanical operation efficiency is low, then higher harvest costs and machinery shortages will occur. Global route planning for mechanical harvesters is one of the most important problems in the field of sugarcane harvesting and transporting operations. Improved efficiency and realistic implementation can be achieved by applying advanced planning methods for the execution of field operations, especially considering the field accessibility aspect. To address this issue, participative research was undertaken with a sugar milling company to produce and implement a mixed integer programming model that represents the mechanical harvester route plan. Particle swarm optimization was applied to find a solution to the model, leading to potential cost savings versus schedules produced manually by the mill officer. The model was also applied to explore regional planning options for a more integrated harvesting and transport system.

  7. Micro-environmental mechanical stress controls tumor spheroid size and morphology by suppressing proliferation and inducing apoptosis in cancer cells.

    Directory of Open Access Journals (Sweden)

    Gang Cheng

    Full Text Available Compressive mechanical stress produced during growth in a confining matrix limits the size of tumor spheroids, but little is known about the dynamics of stress accumulation, how the stress affects cancer cell phenotype, or the molecular pathways involved.We co-embedded single cancer cells with fluorescent micro-beads in agarose gels and, using confocal microscopy, recorded the 3D distribution of micro-beads surrounding growing spheroids. The change in micro-bead density was then converted to strain in the gel, from which we estimated the spatial distribution of compressive stress around the spheroids. We found a strong correlation between the peri-spheroid solid stress distribution and spheroid shape, a result of the suppression of cell proliferation and induction of apoptotic cell death in regions of high mechanical stress. By compressing spheroids consisting of cancer cells overexpressing anti-apoptotic genes, we demonstrate that mechanical stress-induced apoptosis occurs via the mitochondrial pathway.Our results provide detailed, quantitative insight into the role of micro-environmental mechanical stress in tumor spheroid growth dynamics, and suggest how tumors grow in confined locations where the level of solid stress becomes high. An important implication is that apoptosis via the mitochondrial pathway, induced by compressive stress, may be involved in tumor dormancy, in which tumor growth is held in check by a balance of apoptosis and proliferation.

  8. Effects of mechanical stress on the volume phase transition of poly(N-isopropylacrylamide) based polymer gels

    Science.gov (United States)

    Takigawa, T.; Araki, H.; Takahashi, K.; Masuda, T.

    2000-11-01

    The effects of mechanical stress on the volume phase transition of a poly(N-isopropylacrylamide) (PNIPA) gel as well as a copolymer gel composed of N-isopropylacrylamide (NIPA) and sodium acrylate (SA) were investigated in the relatively low stress region. The PNIPA gel without elongational stress showed the behavior close to the second order phase transition. The character of the first order transition became clear under tension, and the transition temperature increased with increasing applied stress. Similar behavior was observed for the NIPA-SA copolymer gel, but the copolymer gel showed the first order transition in the whole stress range investigated. The thermodynamical linear region, where the transition temperature varies linearly with applied stress, was narrower than the mechanical linear region determined by the stress-strain relation of the gels. The change in the transition behavior by the application of the mechanical stress originated chiefly from the volume change in the gels by the applied mechanical stress. It was found that the curve of the transition temperature against applied stress corresponds to the phase boundary between the swollen and collapsed phases for the gels. On the basis of the experimental data, a phenomenological model describing the volume phase transition of the polymer gels is proposed in the frame of the Landau-type free energy expression.

  9. Effects of mechanical stress and vitreous samples in retinal pigment epithelial cells

    Energy Technology Data Exchange (ETDEWEB)

    Takahashi, Eri, E-mail: eritakahashi@fc.kuh.kumamoto-u.ac.jp; Fukushima, Ayako; Haga, Akira; Inomata, Yasuya; Ito, Yasuhiro; Fukushima, Mikiko; Tanihara, Hidenobu

    2016-02-12

    In rhegmatogenous retinal detachment (RRD), scattered RPE cells from the basement membrane into the vitreous cavity undergo an epithelial mesenchymal transition (EMT) and form the intraocular fibrous membrane in response to vitreous fluid. We investigated whether exposure to vitreous samples was associated with EMT-associated signals and mesenchymal characters. Human vitreous samples were collected from patients with RRD, epiretinal membrane (ERM), or macular hole (MH). We evaluated the effects of vitreous on ARPE-19 cells in suspension cultures using poly 2-hydroxyethyl methacrylate-coated dishes and three-dimensional (3D) Matrigel cultures. We found that exposure to vitreous samples did not induce morphological changes or accelerate wound closure in monolayers. Several samples showed increased phosphorylation of Smad2 and nuclear translocation of nuclear factor-κB. Mechanical stress triggered an elevation of phosphorylation levels in Smad2. In addition, exposure to vitreous fluid increased the phosphorylation of p38 mitogen-activated protein kinase in cell suspension cultures after mechanical stress. Moreover, ARPE-19 cells showed a stellate invasive phenotype in 3D Matrigel cultures with vitreous samples. In this study, we demonstrated that mechanical stress and vitreous were associated with EMT-associated signals and invasive phenotypes in 3D cultures but not in monolayers. These results have important implications for the role of vitreous humor in the induction of EMT and intraocular fibrosis.

  10. Mechanical Stress Results in Immediate Accumulation of Glucosinolates in Fresh-Cut Cabbage

    Directory of Open Access Journals (Sweden)

    Tomaž Požrl

    2015-01-01

    Full Text Available The intensity of mechanical stress and the temperature significantly affect the levels of individual and total glucosinolates in shredded white cabbage (cv. Galaxy. Mild processing (shredding to 2 mm thickness at 8°C resulted in the accumulation of glucosinolates (40% increase in comparison with unshredded cabbage, which was already seen 5 min after the mechanical stress. Severe processing (shredding to 0.5 mm thickness at 20°C, however, resulted in an initial 50% decrease in glucosinolates. The glucosinolates accumulated in all of the cabbage samples 30 min from processing, resulting in higher levels than in unshredded cabbage, except for the severe processing at 20°C where the increase was not sufficient to compensate for the initial loss. Glucobrassicin and neoglucobrassicin were the major glucosinolates identified in the cabbage samples. Mechanical stress resulted in an increase in the relative proportion of glucobrassicin and in a decrease in neoglucobrassicin.

  11. Stationary-Phase Mutagenesis in Stressed Bacillus subtilis Cells Operates by Mfd-Dependent Mutagenic Pathways.

    Science.gov (United States)

    Gómez-Marroquín, Martha; Martin, Holly A; Pepper, Amber; Girard, Mary E; Kidman, Amanda A; Vallin, Carmen; Yasbin, Ronald E; Pedraza-Reyes, Mario; Robleto, Eduardo A

    2016-07-05

    In replication-limited cells of Bacillus subtilis, Mfd is mutagenic at highly transcribed regions, even in the absence of bulky DNA lesions. However, the mechanism leading to increased mutagenesis through Mfd remains currently unknown. Here, we report that Mfd may promote mutagenesis in nutritionally stressed B. subtilis cells by coordinating error-prone repair events mediated by UvrA, MutY and PolI. Using a point-mutated gene conferring leucine auxotrophy as a genetic marker, it was found that the absence of UvrA reduced the Leu⁺ revertants and that a second mutation in mfd reduced mutagenesis further. Moreover, the mfd and polA mutants presented low but similar reversion frequencies compared to the parental strain. These results suggest that Mfd promotes mutagenic events that required the participation of NER pathway and PolI. Remarkably, this Mfd-dependent mutagenic pathway was found to be epistatic onto MutY; however, whereas the MutY-dependent Leu⁺ reversions required Mfd, a direct interaction between these proteins was not apparent. In summary, our results support the concept that Mfd promotes mutagenesis in starved B. subtilis cells by coordinating both known and previously unknown Mfd-associated repair pathways. These mutagenic processes bias the production of genetic diversity towards highly transcribed regions in the genome.

  12. Role of Mechanical Stress in Regulating Airway Surface Hydration and Mucus Clearance Rates

    Science.gov (United States)

    Button, Brian; Boucher, Richard C.

    2008-01-01

    Effective clearance of mucus is a critical innate airway defense mechanism, and under appropriate conditions, can be stimulated to enhance clearance of inhaled pathogens. It has become increasingly clear that extracellular nucleotides (ATP and UTP) and nucleosides (adenosine) are important regulators of mucus clearance in the airways as a result of their ability to stimulate fluid secretion, mucus hydration, and cilia beat frequency (CBF). One ubiquitous mechanism to stimulate ATP release is through external mechanical stress. This article addresses the role of physiologically-relevant mechanical forces in the lung and their effects on regulating mucociliary clearance (MCC). The effects of mechanical forces on the stimulating ATP release, fluid secretion, CBF, and MCC are discussed. Also discussed is evidence suggesting that airway hydration and stimulation of MCC by stress-mediated ATP release may play a role in several therapeutic strategies directed at improving mucus clearance in patients with obstructive lung diseases, including cystic fibrosis (CF) and chronic obstructive pulmonary disease (COPD). PMID:18585484

  13. 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.

  14. Mechanical spectroscopy of thermal stress relaxation in aluminium alloys reinforced with short alumina fibres

    Energy Technology Data Exchange (ETDEWEB)

    Carreno-Morelli, E.; Schaller, R. [Ecole Polytechnique Federale, Lausanne (Switzerland). Inst. de Genie Atomique; Urreta, S.E.

    1998-05-01

    The mechanical behaviour under low temperature thermal cycling of aluminium-based composites reinforced with short Al{sub 2}O{sub 3} SAFFIL fibres has been investigated by mechanical spectroscopy (mechanical loss and elastic shear modulus measurements). A mechanical loss maximum has been observed during cooling which originates in the relaxation of thermal stresses at the interfaces due to the differential thermal expansion between matrix and reinforcement. The maximum height increases with the volumetric fibre content. In addition, if the matrix strength is increased by the appropriated choice of alloy and thermal treatment, the maximum diminishes and shifts to lower temperatures. No damage accumulation at the interfaces has been detected during long period thermal cycling in the range 100 to 500 K. A description of the damping behaviour is made in terms of the development of microplastic zones which surround the fibres. (orig.) 9 refs.

  15. Coral bleaching under thermal stress: putative involvement of host/symbiont recognition mechanisms

    Directory of Open Access Journals (Sweden)

    Tambutte Sylvie

    2009-08-01

    Full Text Available Abstract Background Coral bleaching can be defined as the loss of symbiotic zooxanthellae and/or their photosynthetic pigments from their cnidarian host. This major disturbance of reef ecosystems is principally induced by increases in water temperature. Since the beginning of the 1980s and the onset of global climate change, this phenomenon has been occurring at increasing rates and scales, and with increasing severity. Several studies have been undertaken in the last few years to better understand the cellular and molecular mechanisms of coral bleaching but the jigsaw puzzle is far from being complete, especially concerning the early events leading to symbiosis breakdown. The aim of the present study was to find molecular actors involved early in the mechanism leading to symbiosis collapse. Results In our experimental procedure, one set of Pocillopora damicornis nubbins was subjected to a gradual increase of water temperature from 28°C to 32°C over 15 days. A second control set kept at constant temperature (28°C. The differentially expressed mRNA between the stressed states (sampled just before the onset of bleaching and the non stressed states (control were isolated by Suppression Subtractive Hybridization. Transcription rates of the most interesting genes (considering their putative function were quantified by Q-RT-PCR, which revealed a significant decrease in transcription of two candidates six days before bleaching. RACE-PCR experiments showed that one of them (PdC-Lectin contained a C-Type-Lectin domain specific for mannose. Immunolocalisation demonstrated that this host gene mediates molecular interactions between the host and the symbionts suggesting a putative role in zooxanthellae acquisition and/or sequestration. The second gene corresponds to a gene putatively involved in calcification processes (Pdcyst-rich. Its down-regulation could reflect a trade-off mechanism leading to the arrest of the mineralization process under stress

  16. RNAseq revealed the important gene pathways controlling adaptive mechanisms under waterlogged stress in maize.

    Science.gov (United States)

    Arora, Kanika; Panda, Kusuma Kumari; Mittal, Shikha; Mallikarjuna, Mallana Gowdra; Rao, Atmakuri Ramakrishna; Dash, Prasanta Kumar; Thirunavukkarasu, Nepolean

    2017-09-08

    Waterlogging causes yield penalty in maize-growing countries of subtropical regions. Transcriptome analysis of the roots of a tolerant inbred HKI1105 using RNA sequencing revealed 21,364 differentially expressed genes (DEGs) under waterlogged stress condition. These 21,364 DEGs are known to regulate important pathways including energy-production, programmed cell death (PCD), aerenchyma formation, and ethylene responsiveness. High up-regulation of invertase (49-fold) and hexokinase (36-fold) in roots explained the ATP requirement in waterlogging condition. Also, high up-regulation of expansins (42-fold), plant aspartic protease A3 (19-fold), polygalacturonases (16-fold), respiratory burst oxidase homolog (12-fold), and hydrolases (11-fold) explained the PCD of root cortical cells followed by the formation of aerenchyma tissue during waterlogging stress. We hypothesized that the oxygen transfer in waterlogged roots is promoted by a cross-talk of fermentative, metabolic, and glycolytic pathways that generate ATPs for PCD and aerenchyma formation in root cortical cells. SNPs were mapped to the DEGs regulating aerenchyma formation (12), ethylene-responsive factors (11), and glycolysis (4) under stress. RNAseq derived SNPs can be used in selection approaches to breed tolerant hybrids. Overall, this investigation provided significant evidence of genes operating in the adaptive traits such as ethylene production and aerenchyma formation to cope-up the waterlogging stress.

  17. Orientation effect on the giant stress field induced in a single Ni nanowire by mechanical strain

    Science.gov (United States)

    Melilli, G.; Madon, B.; Clochard, M.-C.; Wegrowe, J.-E.

    2015-09-01

    The change of magnetization (i.e. using the inverse magnetostriction effect) allows to investigate at the nanoscale the effects of thermoelastic and piezoelectric strain of an active track-etched β-PVDF polymer matrix on an electrodeposited single-contacted Ni nanowire (NW). The magnetization state is measured locally by anisotropic magnetoresitance (AMR). The ferromagnetic NW plays thus the role of a mechanical probe that allows the effects of mechanical strain to be characterized and described qualitatively and quantitatively. Due to the inverse magnetostriction, a quasi-disappearance of the AMR signal for a variation of the order of ΔT ≍ 10 K has been evidenced. The coplanarity of the vectors between the magnetization and the magnetic field is broken. A way of studying the effect of the geometry on such a system, is to fabricate oriented polymer templates. Track-etched polymer membranes were thus irradiated at various angles (αirrad) leading, after electrodeposition, to embedded Ni NWs of different orientations. With cylindrical Ni NW oriented normally to the template surface, the induced stress field in a single Ni NW was found 1000 time higher than the bulk stress field (due to thermal expansion measured on the PVDF). This amplification results in three nanoscopic effects: (1) a stress mismatch between the Ni NW and the membrane, (2) a non-negligible role of the surface tension on Ni NW Young modulus, and (3) the possibility of non-linear stress-strain law. When the Ni NWs are tilted from the polymer template surface normality, the induced stress field is reduced and the amplification phenomenon is less important.

  18. Stress distribution and mechanical properties of free and assembled Ni3Al nanoclusters

    Science.gov (United States)

    Zhurkin, E. E.; Hautier, G.; Hou, M.

    2006-03-01

    Classical molecular dynamics with a semiempirical N -body potential is used to study the distribution of local stress in bimetallic Ni3Al nanoparticles and in cluster-assembled materials. The materials considered are synthesized with these particles by low-energy deposition at 0.5eV per atom and by compaction with an external pressure of 2GPa , thus featuring different nanostructures. Both are nanoporous, the lowest density being obtained by deposition. Their mechanical response to a uniaxial external load is then studied and deformation mechanisms are identified and are found to be similar in both nanostructures. In the core of isolated clusters, the partial pressures on the nickel and aluminium subsystems are found to differ by several GPa and, as a balance to surface tension, the hydrostatic core pressure is positive and depends on the cluster size. The surface stress is tensile and, because of structural disorder, the partial pressures distributions on Ni and Al at the surface are scattered. When nanostructured systems are formed, strong and highly inhomogeneous shear stress appears, the cluster cores may become tensile, and the interfacial areas remain mainly tensile as well. The partial pressure difference between Ni and Al is somewhat reduced. It is shown that the effect of temperature is to reduce this difference still further and to homogenize the spatial stress distribution. When subjected to a uniaxial stress, both materials display an elastic and a plastic regime. The elastic limit is the lowest for the most porous material and decreases with increasing temperature. Plastic deformation is dominated by both grain boundary sliding and by the enlargement of the open volumes, without evidence for the nucleation of cracks. These open volumes are found to facilitate dislocation activity which is evidenced in grains with sizes as small as two nanometers. This dislocation activity is found to result in the production of stacking faults as well as to the

  19. Overlapping mechanisms of stress-induced relapse to opioid use disorder and chronic pain: Clinical implications

    Directory of Open Access Journals (Sweden)

    Udi E Ghitza

    2016-05-01

    Full Text Available Over the past two decades, a steeply growing number of persons with chronic non-cancer pain have been using opioid analgesics chronically to treat it, accompanied by a markedly increased prevalence of individuals with opioid-related misuse, opioid use disorders, emergency department visits, hospitalizations, admissions to drug treatment programs, and drug overdose deaths. This opioid misuse and overdose epidemic calls for well-designed randomized-controlled clinical trials into more skillful and appropriate pain management and for developing effective analgesics which have lower abuse liability and are protective against stress induced by chronic non-cancer pain. However, incomplete knowledge regarding effective approaches to treat various types of pain has been worsened by an under-appreciation of overlapping neurobiological mechanisms of stress, stress-induced relapse to opioid use, and chronic non-cancer pain in patients presenting for care for these conditions. This insufficient knowledge base has unfortunately encouraged common prescription of conveniently-available opioid pain-relieving drugs with abuse liability, as opposed to treating underlying problems using team-based multidisciplinary, patient-centered, collaborative-care approaches for addressing pain and co-occurring stress and risk for opioid use disorder. This paper reviews recent neurobiological findings regarding overlapping mechanisms of stress-induced relapse to opioid misuse and chronic non-cancer pain, and then discusses these in the context of key outstanding evidence gaps and clinical-treatment research directions which may be pursued to fill these gaps. Such research directions, if conducted through well-designed randomized controlled trials, may substantively inform clinical practice in general medical settings on how to effectively care for patients presenting with pain-related distress and these common co-occurring conditions.

  20. Oxidative stress protection and stomatal patterning as components of salinity tolerance mechanism in quinoa (Chenopodium quinoa).

    Science.gov (United States)

    Shabala, Lana; Mackay, Alex; Tian, Yu; Jacobsen, Sven-Erik; Zhou, Daowei; Shabala, Sergey

    2012-09-01

    Two components of salinity stress are a reduction in water availability to plants and the formation of reactive oxygen species. In this work, we have used quinoa (Chenopodium quinoa), a dicotyledonous C3 halophyte species displaying optimal growth at approximately 150 mM NaCl, to study mechanisms by which halophytes cope with the afore-mentioned components of salt stress. The relative contribution of organic and inorganic osmolytes in leaves of different physiological ages (e.g. positions on the stem) was quantified and linked with the osmoprotective function of organic osmolytes. We show that the extent of the oxidative stress (UV-B irradiation) damage to photosynthetic machinery in young leaves is much less when compared with old leaves, and attribute this difference to the difference in the size of the organic osmolyte pool (1.5-fold difference under control conditions; sixfold difference in plants grown at 400 mM NaCl). Consistent with this, salt-grown plants showed higher Fv/Fm values compared with control plants after UV-B exposure. Exogenous application of physiologically relevant concentrations of glycine betaine substantially mitigated oxidative stress damage to PSII, in a dose-dependent manner. We also show that salt-grown plants showed a significant (approximately 30%) reduction in stomatal density observed in all leaves. It is concluded that accumulation of organic osmolytes plays a dual role providing, in addition to osmotic adjustment, protection of photosynthetic machinery against oxidative stress in developing leaves. It is also suggested that salinity-induced reduction in stomatal density represents a fundamental mechanism by which plants optimize water use efficiency under saline conditions.

  1. Digital monitoring and health diagnosis for mechanical equipment operation safety based on fiber Bragg grating sensor

    Institute of Scientific and Technical Information of China (English)

    Zude ZHOU; Desheng JIANG; Quan LIU

    2009-01-01

    This paper introduces fiber Bragg grating (FBG) based on a fiber optic grating sensor developed to be embedded on mechanical equipment for digital monitoring and health diagnosis. The theoretical and experimental researches on the new-style FBG sensor (FBGS) technology, high-speed demodulation, and data transmission are discussed. The transmission characteristics between the FBG and the detection interface, modeling and compensation method for online distributed multi-parameter digital monitoring and methods for data processing, synchronous sampling, and long-term dynamic digital monitoring using embedded technology are also presented. The acquired information by an FBGS can be used for the optimization of maintenance schedules and refinement of mechanical equipment design. It is a chal-lenge to gather real-time data from components working at high speed and in a severe environment of high temperature, high pressure, and high rotation speed. Currently, there are no sensors or technologies available for digital monitoring and health diagnosis under this rigorous situation for use in mechanical engineering operation safety. As a result, this paper introduces an online distributed and integrated digital monitoring system and health diagnosis. The new principle and new method will contribute to modem measurements in science and technology, mechanical engineering, and large mechanical equipment operation safety.

  2. Focal mechanism and stress inversion in the Mendocino Triple Junction from OBS data

    Science.gov (United States)

    Li, D.; McGuire, J. J.; Liu, Y.

    2016-12-01

    The Mendocino Triple Junction (MTJ) is at the south end of the Cascadia subduction zone, where the North American, Gorda and Pacific Plates intersect. This region contains many active faults and experiences strong internal deformation, resulting in many small-to-intermediate size earthquakes. In 1992, A Mw7.2 thrust earthquake occurred on a shallow dipping fault parallel to the subduction interface, suggesting a relatively weak thrust fault that ruptures under the inferred trench-parallel compressive stress. This contrasts to the high strength of the subducting Gorda plate [Choy and McGarr, 2002] where most of the seismicity occurs. A Mw 5.7 rupture of the Mendocino Transform Fault that occurred just offshore on January 28, 2015 (See Gong and McGuirethis section). However, we did not identify any thrust mechanism aftershock during the following two weeks, using data acquired during the Cascadia Initiative ocean-bottom seismometers (OBS) Expedition 2012-2013, 2014-2015 as well as from the PBO and NCSN onshore networks, We obtain focal mechanisms for earthquakes near the MTJ with a cutoff magnitude of Ml 2.0. The OBS data improve both the number and resolution of the focal mechanisms compared to the onshore only catalogs. The associated azimuth distribution of selected earthquakes is suitable for resolving the focal mechanisms with the first P-arrival polarity [Hardebeck and Shear, 2002]. We also invert the principle stress orientations with the NCSN focal mechanisms from 1977 to 2016, using the method introduced by Hardebeck and Micheal, [2006]. To distinguish the spatial variation, we divide the earthquakes into three groups in depth, overlying continent, oceanic crust and oceanic mantle. We further divide each group into four subareas, based on the distance to Mendocino transform fault. Our preliminary results show that there are both vertical and lateral rotations of the principle compressive stress axes. Similar to previous studies, the orientation of

  3. Operation Mechanism of Farmers’ Professional Cooperatives from the Point of Low-Carbon Agricultural Products

    Institute of Scientific and Technical Information of China (English)

    2012-01-01

    We firstly take a look at internal logic of cluster development of low-carbon agricultural products.In combination with operation features of farmers’ professional cooperatives and actual requirements for cluster development of low-carbon agricultural products;we elaborate establishing benefit allocation mechanism,bearing education and training functions,forming low-carbon value,building low-carbon identification system,as well as realizing low-carbon value.According to these situations,we systematically analyze operation mechanism of farmers’ professional cooperatives suitable for cluster development of low-carbon agricultural products.To promote cluster development of low-carbon agricultural products,we put forward following suggestions,including government guidance and encouragement,social acceptance and active cooperation,and integration into global low-carbon development system to share benefit of low-carbon development.

  4. Focal mechanisms and stress variations in the Caucasus and Northeast Turkey from constraints of regional waveforms

    Science.gov (United States)

    Tseng, Tai-Lin; Hsu, Hsin-Chih; Jian, Pei-Ru; Huang, Bor-Shouh; Hu, Jyr-Ching; Chung, Sun-Lin

    2016-11-01

    The continental collision between Arabia and Eurasia created large strike-slip faults in Turkey as well as mountains in the Caucasus and the volcanic plateau between them. In this study, we use regional waveforms of a new seismic array deployed between 2008 and 2012 to constrain the focal mechanisms and depths of small to moderate sized earthquakes occurring in the western part of the Central Caucasus and northeast Turkey. The distribution of aftershocks and the twelve focal mechanisms involved in the sequence of the 2009 earthquake in Racha are clearly a reactivation of a deeper segment of the 1991 M7 Racha rupture zone. The deeper segment is not well connected to the shallower décollement separating the basement and sedimentary basin. The earthquakes we determined in northeastern Turkey and southern Georgia are related to the strike-slip fault system. We further combined all of the reliably determined focal mechanisms over the last 30 years to investigate the current stress status of the crust in three areas: Racha in the western Greater Caucasus, Javakheti near the Lesser Caucasus and in Northeast Turkey. Our results show that the directions of maximum compressional stress consistently fall within - 2 to 14°N throughout the entire study region. This appears to be controlled by the continental collision. Nonetheless, the minimum compression switches from vertical (in the Greater Caucasus) to the east-west direction (in northeastern Turkey), due to the westward extrusion of the Anatolia block, which is driven partly by the Hellenic subduction. The transition of the stress field is close to the Javakheti volcanic plateau in the Lesser Caucasus, where the relative magnitude between the principal stresses appears to be strongly variable.

  5. Oxidant mechanisms in childhood obesity: the link between inflammation and oxidative stress.

    Science.gov (United States)

    Codoñer-Franch, Pilar; Valls-Bellés, Victoria; Arilla-Codoñer, Angela; Alonso-Iglesias, Eulalia

    2011-12-01

    Evidence of obesity-induced oxidative stress in adults has emerged in the past several years, and similar evidence has been demonstrated in children more recently. The reactive species of oxygen or nitrogen can chemically alter all major classes of biomolecules by modifying their structure and function. Organisms have developed mechanisms to protect biomolecules from the deleterious effects of free radicals. These include the enzymes superoxide dismutase, catalase, and glutathione peroxidase, as well as water and lipid-soluble antioxidants, such as glutathione, ascorbate (vitamin C), α-tocopherol (vitamin E), and β-carotene. Obesity creates oxidant conditions that favor the development of comorbid diseases. Energy imbalances lead to the storage of excess energy in adipocytes, resulting in both hypertrophy and hyperplasia. These processes are associated with abnormalities of adipocyte function, particularly mitochondrial stress and disrupted endoplasmic reticulum function. In this sense, oxidative stress can also be induced by adipocyte associated inflammatory macrophages. There is a close link among obesity, a state of chronic low-level inflammation, and oxidative stress. In addition, the dysregulation of adipocytokines, which are secreted by adipose tissue and promoted by oxidative stress, act synergistically in obesity-related metabolic abnormalities. Adipocytokines link the local and systemic inflammation responses in the context of obesity. It is thought that the evaluation of oxidative status may allow for the identification of patients at an increased risk of complications. Decreasing the levels of chronic inflammation and oxidative stress in childhood may decrease cardiovascular morbidity and mortality in adulthood. Copyright © 2011 Mosby, Inc. All rights reserved.

  6. Endoplasmic reticulum stress-sensing mechanism is activated in Entamoeba histolytica upon treatment with nitric oxide.

    Directory of Open Access Journals (Sweden)

    Julien Santi-Rocca

    Full Text Available The Endoplasmic Reticulum stores calcium and is a site of protein synthesis and modification. Changes in ER homeostasis lead to stress responses with an activation of the unfolded protein response (UPR. The Entamoeba histolytica endomembrane system is simple compared to those of higher eukaryotes, as a canonical ER is not observed. During amoebiasis, an infection of the human intestine and liver by E. histolytica, nitric oxide (NO triggers an apoptotic-like event preceded by an impairment of energy production and a loss of important parasite pathogenic features. We address the question of how this ancient eukaryote responds to stress induced by immune components (i.e. NO and whether stress leads to ER changes and subsequently to an UPR. Gene expression analysis suggested that NO triggers stress responses marked by (i dramatic up-regulation of hsp genes although a bona fide UPR is absent; (ii induction of DNA repair and redox gene expression and iii up-regulation of glycolysis-related gene expression. Enzymology approaches demonstrate that NO directly inhibits glycolysis and enhance cysteine synthase activity. Using live imaging and confocal microscopy we found that NO dramatically provokes extensive ER fragmentation. ER fission in E. histolytica appears as a protective response against stress, as it has been recently proposed for neuron self-defense during neurologic disorders. Chronic ER stress is also involved in metabolic diseases including diabetes, where NO production reduces ER calcium levels and activates cell death. Our data highlighted unique cellular responses of interest to understand the mechanisms of parasite death during amoebiasis.

  7. Optimal Manoeuvres of Underactuated Linear Mechanical Systems: The Case of Controlling Gantry Crane Operations

    Directory of Open Access Journals (Sweden)

    S. Woods

    2014-01-01

    Full Text Available A method of solving optimal manoeuvre control of linear underactuated mechanical systems is presented. The nonintegrable constraints present in such systems are handled by adding dummy actuators and then by applying Lagrange multipliers to reduce their action to zero. The open- and closed-loop control schemes can be analyzed. The method, referred to as the constrained modal space optimal control (CMSOC, is illustrated in the examples of gantry crane operations.

  8. Optimal Manoeuvres of Underactuated Linear Mechanical Systems: The Case of Controlling Gantry Crane Operations

    OpenAIRE

    Woods, S; Szyszkowski, W.

    2014-01-01

    A method of solving optimal manoeuvre control of linear underactuated mechanical systems is presented. The nonintegrable constraints present in such systems are handled by adding dummy actuators and then by applying Lagrange multipliers to reduce their action to zero. The open- and closed-loop control schemes can be analyzed. The method, referred to as the constrained modal space optimal control (CMSOC), is illustrated in the examples of gantry crane operations.

  9. Microwave power transmission system studies. Volume 3, section 8: Mechanical systems and flight operations

    Science.gov (United States)

    Maynard, O. E.; Brown, W. C.; Edwards, A.; Haley, J. T.; Meltz, G.; Howell, J. M.; Nathan, A.

    1975-01-01

    The efforts and recommendations associated with preliminary design and concept definition for mechanical systems and flight operations are presented. Technical discussion in the areas of mission analysis, antenna structural concept, configuration analysis, assembly and packaging with associated costs are presented. Technology issues for the control system, structural system, thermal system and assembly including cost and man's role in assembly and maintenance are identified. Background and desired outputs for future efforts are discussed.

  10. Mechanical stress as the common denominator between chronic inflammation, cancer and Alzheimer’s disease

    Directory of Open Access Journals (Sweden)

    Marcel eLevy Nogueira

    2015-09-01

    Full Text Available The pathogenesis of common diseases such as Alzheimer’s disease (AD and cancer are currently poorly understood. Inflammation is a common risk factor for cancer and AD. Recent data, provided by our group and from others, demonstrate that increased pressure and inflammation are synonymous. There is a continuous increase in pressure from inflammation to fibrosis and then cancer. This in line with the numerous papers reporting high interstitial pressure in cancer. But most authors focus on the role of pressure in the lack of delivery of chemotherapy in the center of the tumor. Pressure may also be a key factor in carcinogenesis. Increased pressure is responsible for oncogene activation and cytokine secretion. Accumulation of mechanical stress plays a key role in the development of diseases of old age such as cardiomyopathy, atherosclerosis and osteoarthritis. Growing evidence suggest also a possible link between mechanical stress in the pathogenesis of AD. The aim of this review is to describe environmental and endogenous mechanical factors possibly playing a pivotal role in the mechanism of chronic inflammation, AD and cancer.

  11. Mechanical stress contributes to the expression of the STM homeobox gene in Arabidopsis shoot meristems

    Science.gov (United States)

    Landrein, Benoît; Kiss, Annamaria; Sassi, Massimiliano; Chauvet, Aurélie; Das, Pradeep; Cortizo, Millan; Laufs, Patrick; Takeda, Seiji; Aida, Mitsuhiro; Traas, Jan; Vernoux, Teva; Boudaoud, Arezki; Hamant, Olivier

    2015-01-01

    The role of mechanical signals in cell identity determination remains poorly explored in tissues. Furthermore, because mechanical stress is widespread, mechanical signals are difficult to uncouple from biochemical-based transduction pathways. Here we focus on the homeobox gene SHOOT MERISTEMLESS (STM), a master regulator and marker of meristematic identity in Arabidopsis. We found that STM expression is quantitatively correlated to curvature in the saddle-shaped boundary domain of the shoot apical meristem. As tissue folding reflects the presence of mechanical stress, we test and demonstrate that STM expression is induced after micromechanical perturbations. We also show that STM expression in the boundary domain is required for organ separation. While STM expression correlates with auxin depletion in this domain, auxin distribution and STM expression can also be uncoupled. STM expression and boundary identity are thus strengthened through a synergy between auxin depletion and an auxin-independent mechanotransduction pathway at the shoot apical meristem. DOI: http://dx.doi.org/10.7554/eLife.07811.001 PMID:26623515

  12. [Regulatory role of mechanical stress response in cellular function: development of new drugs and tissue engineering].

    Science.gov (United States)

    Momose, Kazutaka; Matsuda, Takehisa; Oike, Masahiro; Obara, Kazuo; Laher, Ismail; Sugiura, Seiryo; Ohata, Hisayuki; Nakayama, Koichi

    2003-02-01

    The investigation of mechanotransduction in the cardiovascular system is essentially important for elucidating the cellular and molecular mechanisms involved in not only the maintenance of hemodynamic homeostasis but also etiology of cardiovascular diseases including arteriosclerosis. The present review summarizes the latest research performed by six academic groups, and presented at the 75th Annual Meeting of the Japanese Pharmacological Society. Technology of cellular biomechanics is also required for research and clinical application of a vascular hybrid tissue responding to pulsatile stress. 1) Vascular tissue engineering: Design of pulsatile stress-responsive scaffold and in vivo vascular wall reconstruction (T. Matsuda); 2) Cellular mechanisms of mechanosensitive calcium transients in vascular endothelium (M. Oike et al.); 3) Cross-talk of stimulation with fluid flow and lysophosphatidic acid in vascular endothelial cells (K. Momose et al.); 4) Mechanotransduction of vascular smooth muscles: Rate-dependent stretch-induced protein phosphorylations and contractile activation (K. Obara et al.); 5) Lipid mediators in vascular myogenic tone (I. Laher et al.); and 6) Caldiomyocyte regulates its mechanical output in response to mechanical load (S. Sugiura et al.).

  13. Immunohistochemical expression of heat shock proteins in the mouse periodontal tissues due to orthodontic mechanical stress*

    Directory of Open Access Journals (Sweden)

    Muraoka R

    2010-11-01

    Full Text Available Abstract The histopathology of periodontal ligament of the mouse subjected to mechanical stress was studied. Immunohistochemical expressions of HSP27 and pHSP27 were examined. Experimental animals using the maxillary molars of ddY mouse by Waldo method were used in the study. A separator was inserted to induce mechanical stress. After 10 minutes, 20 minutes, 1 hour, 3 hours, 9 hours and 24 hours, the regional tissues were extracted, fixed in 4% paraformaldehyde and 0.05 M phosphate-buffered fixative solution. Paraffin sections were made for immunohistochemistry using HSP27 and p-HSP27. In the control group, the periodontal ligament fibroblasts expressed low HSP27 and p-HSP27. However, in the experimental group, periodontal ligament fibroblasts expressed HSP27 10 minutes after mechanical load application in the tension side. The strongest expression was detected 9 hours after inducing mechanical load. p-HSP27 was also expressed in a time-dependent manner though weaker than HSP27. The findings suggest that HSP27 and p-HSP27 were expressed for the maintenance of homeostasis of periodontal ligament by the activation of periodontal ligament fibroblasts on the tension side. It also suggests that these proteins act as molecular chaperones for osteoblast activation and maintenance of homeostasis.

  14. Focal mechanism and stress analyses for main tectonic zones in Albania

    Science.gov (United States)

    Dushi, Edmond; Koçi, Rexhep; Begu, Enkela; Bozo, Rrezart

    2017-04-01

    In this study, a number of 33 moderate earthquakes for the period 2013-2015, ranging in magnitude within 2.2 ≤ MW ≤ 4.9 and located within the Albanian territory, have been analyzed. As an earthquake prone country, situated at the frontal collision boundary between Adria microplate and Eurasian tectonic plate, Albania is characterized frequently by micro earthquakes, many moderate and seldom by strong ones. It is evidenced that the whole territory is divided in two different tectonic domains, correspondingly the outer and the inner domain, showing different stress regime as clearly evidenced based on earthquake focal mechanism and geodetic studies. Although strong earthquakes are clearly related to faults in tectonically active areas, moderate events are more frequent revealing valuable information on this purpose. All the studied events are selected to be well-recorded by a maximum possible number of the local broadband (BB) seismological stations of Albanian Seismological Network (ASN), although regional stations have been used as well to constrain the solution. Earthquakes are grouped according to their location, within three well-defined tectonic zones, namely: Adriatic-Ionian (AI), Lushnja-Elbasani-Dibra (LED) and Ohrid-Korça (OK). For each event, the seismic moment M0is determined, through spectral analyses. Moment values vary ranging 1012 - 1015 Nm, for the Adriatic-Ionian (AI) outer zone; 1013 - 1016 Nm, for the Lushnja-Elbasani-Dibra (LED) transversal zone, which cuts through both the outer and the inner domains and 1012 - 1014 Nm, for the Ohrid-Korça (OK), north-south trending inner zone. Focal mechanism solutions (FMS) have been determined for each earthquake, based on the robust first motion polarities method, as applied in the FOCMEC (Seisan 10.1) routine. Using the Michael's linear bootstrap invertion on FMS, a stress analysis is applied. Results show the minimum compressional stress directions variation: σ1 370/270, σ23030/80 and σ31980

  15. Mechanisms of Action Involved in Ozone Therapy: Is healing induced via a mild oxidative stress?

    Science.gov (United States)

    Sagai, Masaru; Bocci, Velio

    2011-12-20

    The potential mechanisms of action of ozone therapy are reviewed in this paper. The therapeutic efficacy of ozone therapy may be partly due the controlled and moderate oxidative stress produced by the reactions of ozone with several biological components. The line between effectiveness and toxicity of ozone may be dependent on the strength of the oxidative stress. As with exercise, it is well known that moderate exercise is good for health, whereas excessive exercise is not.Severe oxidative stress activates nuclear transcriptional factor kappa B (NFκB), resulting in an inflammatory response and tissue injury via the production of COX2, PGE2, and cytokines. However, moderate oxidative stress activates another nuclear transcriptional factor, nuclear factor-erythroid 2-related factor 2 (Nrf2). Nrf2 then induces the transcription of antioxidant response elements (ARE). Transcription of ARE results in the production of numerous antioxidant enzymes, such as SOD, GPx, glutathione-s-transferase(GSTr), catalase (CAT), heme-oxygenase-1 (HO-1), NADPH-quinone-oxidoreductase (NQO-1), phase II enzymes of drug metabolism and heat shock proteins (HSP). Both free antioxidants and anti-oxidative enzymes not only protect cells from oxidation and inflammation but they may be able to reverse the chronic oxidative stress. Based on these observations, ozone therapy may also activate Nrf2 via moderate oxidative stress, and suppress NFκB and inflammatory responses. Furthermore, activation of Nrf2 results in protection against neurodegenerative diseases, such as Alzheimer's and Parkinson's diseases. Mild immune responses are induced via other nuclear transcriptional factors, such as nuclear factor of activated T-cells (NFAT) and activated protein-1 (AP-1).Additionally, the effectiveness of ozone therapy in vascular diseases may also be explained by the activation of another nuclear transcriptional factor, hypoxia inducible factor-1α (HIF-1a), which is also induced via moderate oxidative

  16. Faulting mechanisms and stress regime at the European HDR site of Soultz-sous-Forets, France

    Energy Technology Data Exchange (ETDEWEB)

    Cuenot, Nicolas; Charlety, Jean; Haessler, Henri [Institut de Physique du Globe de Strasbourg, Ecole et Observatoire des Sciences de la Terre (IPGS-EOST), 5 rue Rene Descartes, 67084 Strasbourg Cedex (France); Dorbath, Louis [Institut de Physique du Globe de Strasbourg, Ecole et Observatoire des Sciences de la Terre (IPGS-EOST), 5 rue Rene Descartes, 67084 Strasbourg Cedex (France); Institut de Recherche pour le Developpement, Laboratoire des Mecanismes et Transferts en Geologie (IRD, LMTG), 14 Avenue Edouard Belin, 31400 Toulouse (France)

    2006-10-15

    The state of stress and its implications for shear on fault planes during fluid injection are crucial issues for the HDR (Hot Dry Rock) or EGS (Enhanced or Engineered Geothermal System) concept. This is especially true for hydraulic stimulation experiments, aimed at enhancing the connectivity of a borehole to the natural fracture network, since they tend to induce the shearing of fractures, which is controlled by the local stress regime. During the 2000 and 2003 stimulation tests at Soultz-sous-Forets, France, about 10,000 microearthquakes were located with a surface seismological network. Hundreds of double-couple (DC) focal mechanisms were automatically determined from first-motion polarities using the FPFIT program [Reasenberg, P.A., Oppenheimer, D., 1985. FPFIT, FPPLOT and FPPAGE: Fortran computer programs for calculating and displaying earthquake fault-plane solutions. US Geological Survey Open-File Report 85-739, 25 pp.]. The majority of these mechanisms indicate normal-faulting movement with a more or less pronounced strike-slip component. Some quasi-pure strike-slip events also occurred, especially in the deeper part of the stimulated rock volume, at more than 5 km depth. Although we found a double-couple solution for all events, we tried to observe and quantify the proportion of the non-double-couple (NDC) component in the seismic moment tensor for several microseisms from the 2003 data. The study shows that the NDC is higher for the events in the vicinity of the injection well than for the events far from the well. We used the method of Rivera and Cisternas [Rivera, L., Cisternas, A., 1990. Stress tensor and fault-plane solutions for a population of earthquakes. Bull. Seismol. Soc. Am. 80, 600-614.] to perform the inversion of the deviatoric part of the stress tensor from P-wave polarities. This method was applied to different datasets from the 2000 test, taken from the shallower and deeper parts of the stimulated region. The results show a stable

  17. Mechanisms of Action Involved in Ozone Therapy: Is healing induced via a mild oxidative stress?

    Directory of Open Access Journals (Sweden)

    Sagai Masaru

    2011-12-01

    Full Text Available Abstract The potential mechanisms of action of ozone therapy are reviewed in this paper. The therapeutic efficacy of ozone therapy may be partly due the controlled and moderate oxidative stress produced by the reactions of ozone with several biological components. The line between effectiveness and toxicity of ozone may be dependent on the strength of the oxidative stress. As with exercise, it is well known that moderate exercise is good for health, whereas excessive exercise is not. Severe oxidative stress activates nuclear transcriptional factor kappa B (NFκB, resulting in an inflammatory response and tissue injury via the production of COX2, PGE2, and cytokines. However, moderate oxidative stress activates another nuclear transcriptional factor, nuclear factor-erythroid 2-related factor 2 (Nrf2. Nrf2 then induces the transcription of antioxidant response elements (ARE. Transcription of ARE results in the production of numerous antioxidant enzymes, such as SOD, GPx, glutathione-s-transferase(GSTr, catalase (CAT, heme-oxygenase-1 (HO-1, NADPH-quinone-oxidoreductase (NQO-1, phase II enzymes of drug metabolism and heat shock proteins (HSP. Both free antioxidants and anti-oxidative enzymes not only protect cells from oxidation and inflammation but they may be able to reverse the chronic oxidative stress. Based on these observations, ozone therapy may also activate Nrf2 via moderate oxidative stress, and suppress NFκB and inflammatory responses. Furthermore, activation of Nrf2 results in protection against neurodegenerative diseases, such as Alzheimer's and Parkinson's diseases. Mild immune responses are induced via other nuclear transcriptional factors, such as nuclear factor of activated T-cells (NFAT and activated protein-1 (AP-1. Additionally, the effectiveness of ozone therapy in vascular diseases may also be explained by the activation of another nuclear transcriptional factor, hypoxia inducible factor-1α (HIF-1a, which is also induced via

  18. Jamming Transition of Point-To Traffic Through Co-Operative Mechanisms

    Science.gov (United States)

    Fang, Jun; Qin, Zheng; Chen, Xiqun; Xu, Zhaohui

    2012-11-01

    We study the jamming transition of two-dimensional point-to-point traffic through co-operative mechanisms (DCM) using computer simulation. We propose two decentralized co-operative mechanisms CM which are incorporated into the point-to-point traffic models: stepping aside (CM-SA) and choosing alternative routes (CM-CAR). Incorporating CM-SA is to prevent a type of ping-pong jumps from happening when two objects standing face-to-face want to move in opposite directions. Incorporating CM-CAR is to handle the conflict when more than one object competes for the same point in parallel update. We investigate and compare four models mainly from fundamental diagrams, jam patterns and the distribution of co-operation probability. It is found that although it decreases the average velocity a little, the CM-SA increases the critical density and the average flow. Despite increasing the average velocity, the CM-CAR decreases the average flow by creating substantially vacant areas inside jam clusters. We investigate the jam patterns of four models carefully and explain this result qualitatively. In addition, we discuss the advantage and applicability of decentralized co-operation modeling.

  19. Stress Field in Brazil with Focal Mechanism: Regional and Local Patterns

    Science.gov (United States)

    Dias, F.; Assumpcao, M.

    2013-05-01

    The knowledge of stress field is fundamental not only to understand driving forces and plate deformation but also in the study of intraplate seismicity. The stress field in Brazil has been determined mainly using focal mechanisms and a few breakout data and in-situ measurements. However the stress field still is poorly known in Brazil. The focal mechanisms of recent earthquakes (magnitude lower than 5 mb) were studied using waveform modeling. We stacked the record of several teleseismic stations ( delta > 30°) stacked groups of stations separated according to distance and azimuth. Every record was visually inspected and those with a good signal/noise ratio (SNR) were grouped in windows of ten degrees distance and stacked. The teleseismic P-wave of the stacked signals was modeled using the hudson96 program of Herrmann seismology package (Herrmann, 2002) and the consistency of focal mechanism with the first-motion was checked. Some events in central Brazil were recorded by closer stations (~ 1000 km) and the moment tensor was determined with the ISOLA code (Sokos & Zahradnik, 2008). With the focal mechanisms available in literature and those obtained in this work, we were able to identify some patterns: the central region shows a purely compressional pattern (E-W SHmax), which is predicted by regional theoretical models (Richardson & Coblentz, 1996 and the TD0 model of Lithgow & Bertelloni, 2004). Meanwhile in the Amazon we find an indication of SHmax oriented in the SE-NW direction, probably caused by the Caribbean plate interaction (Meijer, 1995). In northern coastal region, the compression rotates following the coastline, which indicates an important local component related to spreading effects at the continental/oceanic transition (Assumpção, 1998) and flexural stresses caused by sedimentary load in Amazon Fan. We determine the focal mechanism of several events in Brazil using different techniques according to the available data. The major difficulty is to

  20. Stress

    Science.gov (United States)

    ... diabetes. Shopdiabetes.org: Your Stress-Free System for Family Dinners! - 2017-03-book-oclock-scramble.html Shopdiabetes.org Your Stress-Free System for Family Dinners! A year of delicious meals to help prevent ...

  1. Stress

    Science.gov (United States)

    ... sudden negative change, such as losing a job, divorce, or illness Traumatic stress, which happens when you ... stress, so you can avoid more serious health effects. NIH: National Institute of Mental Health

  2. Adaptation of grapevine flowers to cold involves different mechanisms depending on stress intensity.

    Directory of Open Access Journals (Sweden)

    Mélodie Sawicki

    Full Text Available Grapevine flower development and fruit set are influenced by cold nights in the vineyard. To investigate the impact of cold stress on carbon metabolism in the inflorescence, we exposed the inflorescences of fruiting cuttings to chilling and freezing temperatures overnight and measured fluctuations in photosynthesis and sugar content. Whatever the temperature, after the stress treatment photosynthesis was modified in the inflorescence, but the nature of the alteration depended on the intensity of the cold stress. At 4°C, photosynthesis in the inflorescence was impaired through non-stomatal limitations, whereas at 0°C it was affected through stomatal limitations. A freezing night (-3°C severely deregulated photosynthesis in the inflorescence, acting primarily on photosystem II. Cold nights also induced accumulation of sugars. Soluble carbohydrates increased in inflorescences exposed to -3°C, 0°C and 4°C, but starch accumulated only in inflorescences of plants treated at 0 and -3°C. These results suggest that inflorescences are able to cope with cold temperatures by adapting their carbohydrate metabolism using mechanisms that are differentially induced according to stress intensity.

  3. Advances in functional genomics for investigating salinity stress tolerance mechanisms in cereals

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    Megan C Shelden

    2013-05-01

    Full Text Available Abiotic stresses such as low water availability and high salinity are major causes of cereal crop yield losses and significantly impact on sustainability. Wheat and barley are two of the most important cereal crops (after maize and rice and are grown in increasingly hostile environments with soil salinity and drought both expected to increase this century, reducing the availability of arable land. Barley and wheat are classified as glycophytes (salt-sensitive, yet they are more salt-tolerant than other cereal crops such as rice and so are good models for studying salt-tolerance in cereals. The exploitation of genetic variation of phenotypic traits through plant breeding could significantly improve growth of cereals in salinity-affected regions, thus leading to improved crop yields. Genetic variation in phenotypic traits for abiotic stress tolerance have been identified in land races and wild germplasm but the molecular basis of these differences is often difficult to determine due to the complex genetic nature of these species. High-throughput functional genomics technologies, such as transcriptomics, metabolomics, proteomics and ionomics are powerful tools for investigating the molecular responses of plants to abiotic stress. The advancement of these technologies has allowed for the identification and quantification of transcript /metabolites in specific cell types and/or tissues. Using these new technologies on plants will provide a powerful tool to uncovering genetic traits in more complex species such as wheat and barley and provide novel insights into the molecular mechanisms of salinity stress tolerance.

  4. Deformation and Failure Mechanism of Roadway Sensitive to Stress Disturbance and Its Zonal Support Technology

    Directory of Open Access Journals (Sweden)

    Qiangling Yao

    2016-01-01

    Full Text Available The 6163 haulage roadway in the Qidong coal mine passes through a fault zone, which causes severe deformation in the surrounding rock, requiring repeated roadway repairs. Based on geological features in the fault area, we analyze the factors affecting roadway deformation and failure and propose the concept of roadway sensitive to stress disturbance (RSSD. We investigate the deformation and failure mechanism of the surrounding rocks of RSSD using field monitoring, theoretical analysis, and numerical simulation. The deformation of the surrounding rocks involves dilatation of shallow rocks and separation of deep rocks. Horizontal and longitudinal fissures evolve to bed separation and fracture zones; alternatively, fissures can evolve into fracture zones with new fissures extending to deeper rock. The fault affects the stress field of the surrounding rock to ~27 m radius. Its maximum impact is on the vertical stress of the rib rock mass and its minimum impact is on the vertical stress of the floor rock mass. Based on our results, we propose a zonal support system for a roadway passing through a fault. Engineering practice shows that the deformation of the surrounding rocks of the roadway can be effectively controlled to ensure normal and safe production in the mine.

  5. Mechanisms of carbon nanotube-induced toxicity: Focus on oxidative stress

    Energy Technology Data Exchange (ETDEWEB)

    Shvedova, Anna A., E-mail: ats1@cdc.gov [Pathology and Physiology Research Branch, Health Effects Laboratory Division, National Institute for Occupational Safety and Health, University of Rome “Tor Vergata”, Rome (Italy); Department of Physiology and Pharmacology, West Virginia University, Morgantown, WV, University of Rome “Tor Vergata”, Rome (Italy); Pietroiusti, Antonio [Department of Biopathology, University of Rome “Tor Vergata”, Rome (Italy); Fadeel, Bengt [Division of Molecular Toxicology, Institute of Environmental Medicine, Karolinska Institutet, Stockholm (Sweden); Department of Environmental and Occupational Health, University of Pittsburgh, Pittsburgh, PA (United States); Kagan, Valerian E. [Department of Environmental and Occupational Health, University of Pittsburgh, Pittsburgh, PA (United States)

    2012-06-01

    Nanotechnologies are emerging as highly promising technologies in many sectors in the society. However, the increasing use of engineered nanomaterials also raises concerns about inadvertent exposure to these materials and the potential for adverse effects on human health and the environment. Despite several years of intensive investigations, a common paradigm for the understanding of nanoparticle-induced toxicity remains to be firmly established. Here, the so-called oxidative stress paradigm is scrutinized. Does oxidative stress represent a secondary event resulting inevitably from disruption of biochemical processes and the demise of the cell, or a specific, non-random event that plays a role in the induction of cellular damage e.g. apoptosis? The answer to this question will have important ramifications for the development of strategies for mitigation of adverse effects of nanoparticles. Recent examples of global lipidomics studies of nanoparticle-induced tissue damage are discussed along with proteomics and transcriptomics approaches to achieve a comprehensive understanding of the complex and interrelated molecular changes in cells and tissues exposed to nanoparticles. We also discuss instances of non-oxidative stress-mediated cellular damage resulting from direct physical interference of nanomaterials with cellular structures. -- Highlights: ► CNT induced non-random oxidative stress associated with apoptosis. ► Non-oxidative mechanisms for cellular toxicity of carbon nanotubes. ► Biodegradation of CNT by cells of innate immune system. ► “Omics”-based biomarkers of CNT exposures.

  6. Glucocorticoid Mechanisms of Functional Connectivity Changes in Stress-Related Neuropsychiatric Disorders.

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    Hall, Baila S; Moda, Rachel N; Liston, Conor

    2015-01-01

    Stress-especially chronic, uncontrollable stress-is an important risk factor for many neuropsychiatric disorders. The underlying mechanisms are complex and multifactorial, but they involve correlated changes in structural and functional measures of neuronal connectivity within cortical microcircuits and across neuroanatomically distributed brain networks. Here, we review evidence from animal models and human neuroimaging studies implicating stress-associated changes in functional connectivity in the pathogenesis of PTSD, depression, and other neuropsychiatric conditions. Changes in fMRI measures of corticocortical connectivity across distributed networks may be caused by specific structural alterations that have been observed in the prefrontal cortex, hippocampus, and other vulnerable brain regions. These effects are mediated in part by glucocorticoids, which are released from the adrenal gland in response to a stressor and also oscillate in synchrony with diurnal rhythms. Recent work indicates that circadian glucocorticoid oscillations act to balance synapse formation and pruning after learning and during development, and chronic stress disrupts this balance. We conclude by considering how disrupted glucocorticoid oscillations may contribute to the pathophysiology of depression and PTSD in vulnerable individuals, and how circadian rhythm disturbances may affect non-psychiatric populations, including frequent travelers, shift workers, and patients undergoing treatment for autoimmune disorders.

  7. An experimental study on the mechanical properties of rat brain tissue using different stress-strain definitions.

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    Karimi, Alireza; Navidbakhsh, Mahdi

    2014-07-01

    There are different stress-strain definitions to measure the mechanical properties of the brain tissue. However, there is no agreement as to which stress-strain definition should be employed to measure the mechanical properties of the brain tissue at both the longitudinal and circumferential directions. It is worth knowing that an optimize stress-strain definition of the brain tissue at different loading directions may have implications for neuronavigation and surgery simulation through haptic devices. This study is aimed to conduct a comparative study on different results are given by the various definitions of stress-strain and to recommend a specific definition when testing brain tissues. Prepared cylindrical samples are excised from the parietal lobes of rats' brains and experimentally tested by applying load on both the longitudinal and circumferential directions. Three stress definitions (second Piola-Kichhoff stress, engineering stress, and true stress) and four strain definitions (Almansi-Hamel strain, Green-St. Venant strain, engineering strain, and true strain) are used to determine the elastic modulus, maximum stress and strain. The highest non-linear stress-strain relation is observed for the Almansi-Hamel strain definition and it may overestimate the elastic modulus at different stress definitions at both the longitudinal and circumferential directions. The Green-St. Venant strain definition fails to address the non-linear stress-strain relation using different definitions of stress and triggers an underestimation of the elastic modulus. The results suggest the application of the true stress-true strain definition for characterization of the brain tissues mechanics since it gives more accurate measurements of the tissue's response using the instantaneous values.

  8. [Systemic control of the molecular, cell, and epigenetic mechanisms of long-lasting consequences of stress].

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    Baĭdo, A I; Diuzhikova, N A; Shiriaeva, N V; Sokolova, N E; Vshivtseva, V V; Savenko, Iu N

    2009-03-01

    Based on M.E. Lobashev's views of the systemic control of genetic and cytogeneitc processes and a substantial effect of excitability on plastic changes in the central nervous system (CNS), the effect of prolonged emotional and pain stress (PEPS) on the molecular, cell, and epigenetic mechanisms of injury memory was studied in rat strains bred for a certain excitability of the nervous system. PEPS was for the first time found to cause long-lasting (2 months) morphological alterations of the CA3 region of the hippocampus and to modify the genome activity of its pyramidal neurons. The two phenomena were potentiated by a genetically determined low functional state of the CNS. The post-stress regulation of the genome function in hippocampal neurons was mediated by changes in heterochromatin conformation, activation of methyl-CpG-binding protein (MeCP2) synthesis, and subsequent changes in acetylation of histone H4. Genetically determined high excitability of the nervous system proved to be a risk factor that affects the specifics and time course of the observed molecular, cell, and genetic transformations of neurons. The results provide for a better understanding of the epigenetic mechanisms of injury memory, which forms a pathogenetic basis for posttraumatic stress disorder and other human psychogenic conditions characterized by a prolonged duration.

  9. Numerical simulation of mechanisms of deformation,failure and energy dissipation in porous rock media subjected to wave stresses

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The pore characteristics,mineral compositions,physical and mechanical properties of the subarkose sandstones were acquired by means of CT scan,X-ray diffraction and physical tests.A few physical models possessing the same pore characteristics and matrix properties but different porosities compared to the natural sandstones were developed.The 3D finite element models of the rock media with varied porosities were established based on the CT image processing of the physical models and the MIMICS software platform.The failure processes of the porous rock media loaded by the split Hopkinson pressure bar(SHPB) were simulated by satisfying the elastic wave propagation theory.The dynamic responses,stress transition,deformation and failure mechanisms of the porous rock media subjected to the wave stresses were analyzed.It is shown that an explicit and quantitative analysis of the stress,strain and deformation and failure mechanisms of porous rocks under the wave stresses can be achieved by using the developed 3D finite element models.With applied wave stresses of certain amplitude and velocity,no evident pore deformation was observed for the rock media with a porosity less than 15%.The deformation is dominantly the combination of microplasticity(shear strain),cracking(tensile strain) of matrix and coalescence of the cracked regions around pores.Shear stresses lead to microplasticity,while tensile stresses result in cracking of the matrix.Cracking and coalescence of the matrix elements in the neighborhood of pores resulted from the high transverse tensile stress or tensile strain which exceeded the threshold values.The simulation results of stress wave propagation,deformation and failure mechanisms and energy dissipation in porous rock media were in good agreement with the physical tests.The present study provides a reference for analyzing the intrinsic mechanisms of the complex dynamic response,stress transit mode,deformation and failure mechanisms and the disaster

  10. Combat Stress: A Collateral Effect in the Operational Effectiveness Loss Multiplier (OELM) Methodology

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    2015-02-01

    the American Civil War (1861–1865), physicians referred to the negative reactions of service members to combat stress as nostalgia, an accurate...experience mental health symptoms.43 The prevalence of PTSD is approximately 19 to 30 percent in Vietnam veterans44, 10 percent in Gulf War veterans45, 6...9 3. Posttraumatic Stress Disorder ( PTSD

  11. Combat and Operational Stress: Minimizing Its Adverse Effects on Service Members

    Science.gov (United States)

    2008-04-18

    effects of stress. It named and described coping techniques such as relaxation techniques, self-suggestion, meditation , and inoculation as ways to minimize...This includes training service members on how to use biofeedback techniques and implementing these methods to reduce stress. Second, DoD should

  12. Mechanism of organophosphates (nerve gases and pesticides) and antidotes: electron transfer and oxidative stress.

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    Kovacic, Peter

    2003-12-01

    Evidence indicates that nerve gas toxins operate in ways in addition to inhibition of acetylcholine esterase. Alternative bioactivities are discussed with focus on electron transfer. The main class, including pralidoxime (2-PAM), incorporates conjugated iminium and oxi