WorldWideScience

Sample records for stress history simulation

  1. The history of stress hyperglycaemia.

    Science.gov (United States)

    Balasanthiran, A; Shotliff, K

    2015-01-01

    Stress hyperglycaemia, is a common phenomenon, frequently associated with adverse outcomes in a number of prevalent conditions including myocardial infarction and stroke. Knowledge on stress hyperglycaemia evolved in tandem with knowledge relating to homeostasis, stress and disease and involved some of the world's most eminent thinkers. Despite this, it still remains under-recognised. This paper illustrates significant points in the history of stress hyperglycaemia, from antiquity through to the present day, as well as the challenges faced in translating research into clinical benefit for patients. Profiles of significant protagonists including Claude Bernard, Walter Cannon and Hans Seyle are presented, as well their roles in the emergence of modern-day terminology and pathophysiological models. Major themes such as 'fight or flight' and homeostasis are central to this discussion. Closer to the present day, the role of stress hyperglycaemia in a number of common medical conditions is explored in more detail. Contention around evidence for treatment and the future risk of diabetes mellitus are also discussed.

  2. BDNF Val66Met Genotype Interacts With a History of Simulated Stress Exposure to Regulate Sensorimotor Gating and Startle Reactivity.

    Science.gov (United States)

    Notaras, Michael J; Hill, Rachel A; Gogos, Joseph A; van den Buuse, Maarten

    2017-05-01

    Reduced expression of Brain-Derived Neurotrophic Factor (BDNF) has been implicated in the pathophysiology of schizophrenia. The BDNF Val66Met polymorphism, which results in deficient activity-dependent secretion of BDNF, is associated with clinical features of schizophrenia. We investigated the effect of this polymorphism on Prepulse Inhibition (PPI), a translational model of sensorimotor gating which is disrupted in schizophrenia. We utilized humanized BDNFVal66Met (hBDNFVal66Met) mice which have been modified to carry the Val66Met polymorphism, as well as express humanized BDNF in vivo. We also studied the long-term effect of chronic corticosterone (CORT) exposure in these animals as a model of history of stress. PPI was assessed at 30ms and 100ms interstimulus intervals (ISI). Analysis of PPI at the commonly used 100ms ISI identified that, irrespective of CORT treatment, the hBDNFVal/Met genotype was associated with significantly reduced PPI. In contrast, PPI was not different between hBDNFMet/Met and hBDNFVal/Val genotype mice. At the 30ms ISI, CORT treatment selectively disrupted sensorimotor gating of hBDNFVal/Met heterozygote mice but not hBDNFVal/Val or hBDNFMet/Met mice. Analysis of startle reactivity revealed that chronic CORT reduced startle reactivity of hBDNFVal/Val male mice by 51%. However, this was independent of the effect of CORT on PPI. In summary, we provide evidence of a distinct BDNFVal66Met heterozygote-specific phenotype using the sensorimotor gating endophenotype of schizophrenia. These data have important implications for clinical studies where, if possible, the BDNFVal/Met heterozygote genotype should be distinguished from the BDNFMet/Met genotype. © The Author 2016. Published by Oxford University Press on behalf of the Maryland Psychiatric Research Center. All rights reserved. For permissions, please email: journals.permissions@oup.com.

  3. How stressful is doctor-patient communication? Physiological and psychological stress of medical students in simulated history taking and bad-news consultations

    NARCIS (Netherlands)

    Hulsman, Robert L.; Pranger, Susan; Koot, Stephanie; Fabriek, Marcel; Karemaker, John M.; Smets, Ellen M. A.

    2010-01-01

    Introduction: Medical communication can be a stressful experience for both doctors and patients. In particular, inexperienced doctors facing the demanding task of a bad news consultation may experience high levels of distress. The aim of this exploratory study is to test students' differential

  4. An Individual Claims History Simulation Machine

    Directory of Open Access Journals (Sweden)

    Andrea Gabrielli

    2018-03-01

    Full Text Available The aim of this project is to develop a stochastic simulation machine that generates individual claims histories of non-life insurance claims. This simulation machine is based on neural networks to incorporate individual claims feature information. We provide a fully calibrated stochastic scenario generator that is based on real non-life insurance data. This stochastic simulation machine allows everyone to simulate their own synthetic insurance portfolio of individual claims histories and back-test thier preferred claims reserving method.

  5. Stress history of the Tharsis Region, Mars

    Science.gov (United States)

    Francis, Robert A.

    1987-01-01

    The Tharsis topographic rise of Mars is roughly 5000 km wide and 10 km high and is believed to have originated more than 3.5 BY ago. Within its boundaries lie the four largest volcanoes on the planet. It is also the locus of a series of fracture traces which extend over approximately a hemisphere. The events leading to the formation of the Tharsis region continue to generate debate. Three geophysical models of the formation of Tharsis are now in general contention and each of these models has been used to predict a characteristic stress-field. These models are: the volcanic construct model, the isostatic compensation model, and the lithospheric uplift model. Each has been used by its proponents to predict some of the features observed in the Tharsis region but none accurately accounts for all of the fracture features observed. This is due, in part, to the use of fractures too young to be directly related to the origin of Tharsis. To constrain the origin of Tharsis, as opposed to its later history, one should look for the oldest fractures related to Tharsis and compare these to the predictions made by the models. Mapping of old terrains in and around the Tharsis rise has revealed 175 hitherto unknown old fracture features.

  6. Stress history of the Tharsis Region, Mars

    International Nuclear Information System (INIS)

    Francis, R.A.

    1987-01-01

    The Tharsis topographic rise of Mars is roughly 5000 km wide and 10 km high and is believed to have originated more than 3.5 BY ago. Within its boundaries lie the four largest volcanoes on the planet. It is also the locus of a series of fracture traces which extend over approximately a hemisphere. The events leading to the formation of the Tharsis region continue to generate debate. Three geophysical models of the formation of Tharsis are now in general contention and each of these models has been used to predict a characteristic stress-field. These models are: the volcanic construct model, the isostatic compensation model, and the lithospheric uplift model. Each has been used by its proponents to predict some of the features observed in the Tharsis region but none accurately accounts for all of the fracture features observed. This is due, in part, to the use of fractures too young to be directly related to the origin of Tharsis. To constrain the origin of Tharsis, as opposed to its later history, one should look for the oldest fractures related to Tharsis and compare these to the predictions made by the models. Mapping of old terrains in and around the Tharsis rise has revealed 175 hitherto unknown old fracture features

  7. Oxidative stress and life histories: unresolved issues and current needs.

    Science.gov (United States)

    Speakman, John R; Blount, Jonathan D; Bronikowski, Anne M; Buffenstein, Rochelle; Isaksson, Caroline; Kirkwood, Tom B L; Monaghan, Pat; Ozanne, Susan E; Beaulieu, Michaël; Briga, Michael; Carr, Sarah K; Christensen, Louise L; Cochemé, Helena M; Cram, Dominic L; Dantzer, Ben; Harper, Jim M; Jurk, Diana; King, Annette; Noguera, Jose C; Salin, Karine; Sild, Elin; Simons, Mirre J P; Smith, Shona; Stier, Antoine; Tobler, Michael; Vitikainen, Emma; Peaker, Malcolm; Selman, Colin

    2015-12-01

    Life-history theory concerns the trade-offs that mold the patterns of investment by animals between reproduction, growth, and survival. It is widely recognized that physiology plays a role in the mediation of life-history trade-offs, but the details remain obscure. As life-history theory concerns aspects of investment in the soma that influence survival, understanding the physiological basis of life histories is related, but not identical, to understanding the process of aging. One idea from the field of aging that has gained considerable traction in the area of life histories is that life-history trade-offs may be mediated by free radical production and oxidative stress. We outline here developments in this field and summarize a number of important unresolved issues that may guide future research efforts. The issues are as follows. First, different tissues and macromolecular targets of oxidative stress respond differently during reproduction. The functional significance of these changes, however, remains uncertain. Consequently there is a need for studies that link oxidative stress measurements to functional outcomes, such as survival. Second, measurements of oxidative stress are often highly invasive or terminal. Terminal studies of oxidative stress in wild animals, where detailed life-history information is available, cannot generally be performed without compromising the aims of the studies that generated the life-history data. There is a need therefore for novel non-invasive measurements of multi-tissue oxidative stress. Third, laboratory studies provide unrivaled opportunities for experimental manipulation but may fail to expose the physiology underpinning life-history effects, because of the benign laboratory environment. Fourth, the idea that oxidative stress might underlie life-history trade-offs does not make specific enough predictions that are amenable to testing. Moreover, there is a paucity of good alternative theoretical models on which contrasting

  8. Star Formation History of Dwarf Galaxies in Cosmological Hydrodynamic Simulations

    Directory of Open Access Journals (Sweden)

    Kentaro Nagamine

    2010-01-01

    Full Text Available We examine the past and current work on the star formation (SF histories of dwarf galaxies in cosmological hydrodynamic simulations. The results obtained from different numerical methods are still somewhat mixed, but the differences are understandable if we consider the numerical and resolution effects. It remains a challenge to simulate the episodic nature of SF history in dwarf galaxies at late times within the cosmological context of a cold dark matter model. More work is needed to solve the mysteries of SF history of dwarf galaxies employing large-scale hydrodynamic simulations on the next generation of supercomputers.

  9. Posttraumatic stress disorder: a history and a critique.

    Science.gov (United States)

    Andreasen, Nancy C

    2010-10-01

    Although posttraumatic stress disorder (PTSD) is sometimes considered to be a relatively new diagnosis, as the name first appeared in 1980, the concept of the disorder has a very long history. That history has often been linked to the history of war, but the disorder has also been frequently described in civilian settings involving natural disasters, mass catastrophes, and serious accidental injuries. The diagnosis first appeared in the official nomenclature when Diagnostic and Statistical Manual of Mental Disorders (DSM)-I was published in 1952 under the name gross stress reaction. It was omitted, however, in the next edition in 1968, after a long period of relative peace. When DSM-III was developed in the mid-1980s the recent occurrence of the Vietnam War provoked a more thorough examination of the disorder. PTSD was defined as a stress disorder that is a final common pathway occurring as a consequence of many different types of stressors, including both combat and civilian stress. The definition of PTSD has filled an important niche in clinical psychiatry. Its definition continues to raise important questions about the relationship between a stressor, the individual experiencing it, and the characteristic symptoms. © 2010 Association for Research in Nervous and Mental Disease.

  10. Stress and Recovery during Simulated Microgravity

    Science.gov (United States)

    Nicolas, Michel

    The aim of this study was to determine the effects of a 60-day head-down tilt long-term bed rest (HDT) on stress and recovery in sixteen healthy female volunteers during the WISE-2005 study (Women International Space Simulation for Exploration). Participants were randomly assigned to either an exercise group (Exe) that followed a training program combining resistive and aerobic exercises, or to a no-exercise control group (Ctl). Psychological states were assessed using the Rest-Q, a validated questionnaire based on stress-recovery responses. A longitudinal analysis revealed significant changes in the general and specific stress scales for all participants throughout the experiment with a critical stage from supine to standing posture leading to a significant decrease in physical recovery. During HDT, Exe reported higher scores in stress subscales, as well as lower recovery scores compared to the Ctl. During the post HDT ambulatory recovery period, the exercisers still reported higher scores than the non-exercisers on the Lack of energy stress related scale, along with lower scores in general well-being and personal accomplishment. The present findings show that simulated weightlessness such as HDT may induce psychological stress and lead to subsequent alterations in perceived recovery. Exercise did not reduce HDT impaired effects on stress and recovery states. In the perspective of spaceflights of long-duration such as the future missions to Mars, there is a need for additional experiments to further investigate spaceflight-induced changes of stress and recovery parameters and the effects of exercise on these parameters. Further studies might determine and analyze the psychological factors involved, but also how to intervene concerning these factors with efficient psychological preparation which, although not yet fully investigated, may reduce stress, promote recovery and support adaptive responses to such extreme environments.

  11. Effect of power history on the shape and the thermal stress of a large sapphire crystal during the Kyropoulos process

    Science.gov (United States)

    Nguyen, Tran Phu; Chuang, Hsiao-Tsun; Chen, Jyh-Chen; Hu, Chieh

    2018-02-01

    In this study, the effect of the power history on the shape of a sapphire crystal and the thermal stress during the Kyropoulos process are numerically investigated. The simulation results show that the thermal stress is strongly dependent on the power history. The thermal stress distributions in the crystal for all growth stages produced with different power histories are also studied. The results show that high von Mises stress regions are found close to the seed of the crystal, the highly curved crystal surface and the crystal-melt interface. The maximum thermal stress, which occurs at the crystal-melt interface, increases significantly in value as the crystal expands at the crown. After this, there is reduction in the maximum thermal stress as the crystal lengthens. There is a remarkable enhancement in the maximum von Mises stress when the crystal-melt interface is close to the bottom of the crucible. There are two obvious peaks in the maximum Von Mises stress, at the end of the crown stage and in the final stage, when cracking defects can form. To alleviate this problem, different power histories are considered in order to optimize the process to produce the lowest thermal stress in the crystal. The optimal power history is found to produce a significant reduction in the thermal stress in the crown stage.

  12. Effect of loading history on cyclic stress-strain response

    Czech Academy of Sciences Publication Activity Database

    Kunz, Ludvík; Lukáš, Petr; Weiss, B.; Melisova, D.

    2001-01-01

    Roč. 314, 1/2 (2001), s. 1-6 ISSN 0921-5093. [TMS Annual Meeting. Nashville, 12.03.2000-16.03.2000] R&D Projects: GA AV ČR IBS2041001 Institutional research plan: CEZ:AV0Z2041904 Keywords : cyclic plasticity * loading history * mean stress Subject RIV: JL - Materials Fatigue, Friction Mechanics Impact factor: 0.978, year: 2001

  13. Bringing history to life: simulating landmark experiments in psychology.

    Science.gov (United States)

    Boynton, David M; Smith, Laurence D

    2006-05-01

    The course in history of psychology can be challenging for students, many of whom enter it with little background in history and faced with unfamiliar names and concepts. The sheer volume of material can encourage passive memorization unless efforts are made to increase student involvement. As part of a trend toward experiential history, historians of science have begun to supplement their lectures with demonstrations of classic physics experiments as a way to bring the history of science to life. Here, the authors report on computer simulations of five landmark experiments from early experimental psychology in the areas of reaction time, span of attention, and apparent motion. The simulations are designed not only to permit hands-on replication of historically important results but also to reproduce the experimental procedures closely enough that students can gain a feel for the nature of early research and the psychological processes being studied.

  14. Generation of spectra and stress histories for fatigue and damage tolerance analysis of fuselage repairs

    Science.gov (United States)

    1991-10-01

    This report describes a simplified procedure for the development of stress histories : for use in the analysis of aircraft repairs.- Although repairs of all components of : the airframe are of interest, this report concentrates on stress histories fo...

  15. Lack of Social Support Raises Stress Vulnerability in Rats with a History of Ancestral Stress.

    Science.gov (United States)

    Faraji, Jamshid; Soltanpour, Nabiollah; Lotfi, Hamid; Moeeini, Reza; Moharreri, Ali-Reza; Roudaki, Shabnam; Hosseini, S Abedin; Olson, David M; Abdollahi, Ali-Akbar; Soltanpour, Nasrin; Mohajerani, Majid H; Metz, Gerlinde A S

    2017-07-13

    Stress is a primary risk factor for psychiatric disorders. However, it is not fully understood why some stressed individuals are more vulnerable to psychiatric disorders than others. Here, we investigated whether multigenerational ancestral stress produces phenotypes that are sensitive to depression-like symptoms in rats. We also examined whether social isolation reveals potentially latent sensitivity to depression-like behaviours. F4 female rats born to a lineage of stressed mothers (F0-F3) received stress in adulthood while housed in pairs or alone. Social isolation during stress induced cognitive and psychomotor retardation only in rats exposed to ancestral stress. Social isolation also hampered the resilience of the hypothalamic-pituitary-adrenal axis to chronic stress and reduced hippocampal volume and brain-derived neurotrophic factor (BDNF) expression. Thus, synergy between social isolation and stress may unmask a latent history of ancestral stress, and raises vulnerability to mental health conditions. The findings support the notion that social support critically promotes stress coping and resilience.

  16. The major stressful life events and cancer: stress history and cancer.

    Science.gov (United States)

    Tas, Faruk; Karalar, Umran; Aliustaoglu, Mehmet; Keskin, Serkan; Can, Gulbeyaz; Cinar, Fatma Ebru

    2012-06-01

    The objective of this study was to analyze the extent of stressful life events' etiology and to compare socio-demographic and medical characteristics of the presence and absence of stress in Turkish cancer patients. Patients with cancer who attended ambulatory patient care units answered the questionnaires. Medical information was reviewed from chart data. The study population comprised 465 women (60.5%) and 303 men (39.5%), in total 768 cases. The median age was 53 years, ranging between 18 and 94. Three-hundred and twenty patients (41.7%) had at least one type of stress since last year of the time of initial diagnosis. Among patients had stress, the median number of stress modalities presented was 1 (range 1-6). Death, lack of livelihood, quarrel, illness, and debt almost always consisted of stress types. History of stress within last year was found more in women (66.3% vs. 56.5%, P = 0.006) and overweight patients (57.5% vs. 47.2%, P = 0.005). Similarly, among cancer types, only patients with breast cancer (41.9% vs. 31.7%, P = 0.04) had lived more stressful situation. However, the married patients (72.2% vs. 80.6%, P = 0.03) had less stress. Patients with gastric cancer had more frequent debt (29.0%, P history (21.4%, P = 0.001). Additionally, in lung cancer patients, their rate of livelihood difficulty was highly less than average (2.4%, P = 0.003). We found that overweight patients had more illness history (68.9% vs. 51.6%, P = 0.004), patients who were not working had more death history (89.7% vs. 78%, P = 0.01), and female patients had more quarrel history (78.2% vs. 60.5%, P = 0.002). Likewise, history of debt in patients who is a member of large family (56.2% vs. 27.4%, P = 0.01) was more frequent. Additionally, the lack of livelihood was prominent in urban patients (92.8% vs. 78.6%, P = 0.002) and in patients with low income (48.5% vs. 66.7%, P = 0.004). The question of whether or not psychological factors originated from stressful life events have an

  17. Evaluation of stress histories of reactor coolant loop piping for pipe rupture prediction

    International Nuclear Information System (INIS)

    Lu, S.C.; Larder, R.A.; Ma, S.M.

    1981-01-01

    This paper describes the analyses used to evaluate stress histories in the primary coolant loop piping of a selected four-loop PNR power station. In order to make the simulation as realistic as possible, best estimates rather than conservative assumptions were considered throughout. The best estimate solution, however, was aided by a sensitivity study to assess the possible variation of outcomes resulted from uncertainties associated with these assumptions. Sources of stresses considered in the evaluation were pressure, dead weight, thermal expansion, thermal gradients through the pipe wall, residual welding, pump vibrations, and finally seismic excitations. The best estimates of pressure and thermal transient histories arising from plant operations were based on actual plant operation records supplemented by specified plant design conditions. Seismic motions were generated from response spectrum curves developed specifically for the region surrounding the plant site. Stresses due to dead weight and thermal expansion were computed from a three dimensional finite element model which used a combination of pipe, truss, and beam elements to represent the coolant loop piping, the pressure vessel, coolant pumps, steam generators, and the pressurizer. Stresses due to pressure and thermal gradients were obtained by closed form solutions. Seismic stress calculations considered the soil structure interaction, the coupling effect between the containment structure and the reactor coolant system. A time history method was employed for the seismic analysis. Calculations of residual stresses accounted for the actual heat impact, welding speed, weld preparation geometry, and pre- and post-heat treatments. Vibrational stresses due to pump operation were estimated by a dynamic analysis using existing measurements of pump vibrations. (orig./HP)

  18. The acoustical history of Hagia Sophia revived through computer simulations

    DEFF Research Database (Denmark)

    Rindel, Jens Holger; Weitze, C.A.; Christensen, Claus Lynge

    2002-01-01

    The present paper deals with acoustic computer simulations of Hagia Sophia, which is characterized not only by being one of the largest worship buildings in the world, but also by – in its 1500 year history – having served three purposes: as a church, as a mosque and today as a museum. The invest......The present paper deals with acoustic computer simulations of Hagia Sophia, which is characterized not only by being one of the largest worship buildings in the world, but also by – in its 1500 year history – having served three purposes: as a church, as a mosque and today as a museum....... The investigation is done as a part of the EU project - CAHRISMA....

  19. DEM simulation of undrained behaviour with preshearing history for saturated granular media

    International Nuclear Information System (INIS)

    Gong, Guobin; Zha, Xiaoxiong

    2013-01-01

    This paper presents the results of the three-dimensional (3D) discrete element method (DEM) simulations of undrained axisymmetric/triaxial tests on loose assemblies of polydisperse spheres with and without preshearing history using a periodic cell. Undrained tests are modelled by deforming the samples under constant volume conditions. The simulations show that the preshearing process will not induce initial structural anisotropy, and that the presheared and unpresheared samples follow the same initial stress path along a unique limiting boundary in the q–p space, as observed in the published experimental literature, which was not crossed over by any of the stress paths of the presheared samples. It is also shown that the presheared samples are denser compared with the original unpresheared one, and therefore exhibit higher resistance to (temporary) liquefaction. At the grain scale, such higher resistance is found to be attributed to the evolution of a redundancy factor, a microscopic definition of liquefaction (temporary liquefaction). The Lade instability (peak deviator stress) is found to correspond to a unique mechanical coordination number of 4.5, independent of preshearing history. It is also found that the onset of liquefaction (temporary liquefaction) in terms of the redundancy factor lags behind the onset of macroscopic strain softening in terms of the Lade instability for the presheared and unpresheared samples under undrained conditions. (paper)

  20. Parenting Stress Mediates between Maternal Maltreatment History and Maternal Sensitivity in a Community Sample

    Science.gov (United States)

    Pereira, Jessica; Vickers, Kristin; Atkinson, Leslie; Gonzalez, Andrea; Wekerle, Christine; Levitan, Robert

    2012-01-01

    Objective: Maternal maltreatment history and current parenting stress are associated with parenting difficulties. However, researchers have not investigated the mechanism by which these variables are interlinked. We hypothesized that parenting stress mediates the relation between history of maltreatment and parenting behavior. Methods: We assessed…

  1. Design of specimen for weld residual stress simulation

    International Nuclear Information System (INIS)

    Kim, Jin Weon; Park, Jong Sun; Lee, Kyung Soo

    2008-01-01

    The objective of this study is to design a laboratory specimen for simulating residual stress of circumferential butt welding of pipe. Specimen type and method for residual stress generation were proposed based on the review of prior studies and parametric finite element simulation. To prove the proposed specimen type and loading method, the residual stress was generated using the designed specimen by applying proposed method and was measured. The measured residual stress using X-ray diffraction reasonably agreed with the results of finite element simulation considered in the specimen design. Comparison of residual strains measured at several locations of specimen and given by finite element simulation also showed good agreement. Therefore, it is indicated that the designed specimen can reasonably simulate the residual stress of circumferential butt welding of pipe

  2. Endogenous ROS levels in C. elegans under exogenous stress support revision of oxidative stress theory of life-history tradeoffs.

    Science.gov (United States)

    Smith, Samson W; Latta, Leigh C; Denver, Dee R; Estes, Suzanne

    2014-07-24

    The oxidative stress theory of life-history tradeoffs states that oxidative stress caused by damaging free radicals directly underpins tradeoffs between reproduction and longevity by altering the allocation of energetic resources between these tasks. We test this theory by characterizing the effects of exogenous oxidative insult and its interaction with thermal stress and diet quality on a suite of life-history traits and correlations in Caenorhabditis elegans nematodes. We also quantify demographic aging rates and endogenous reactive oxygen species (ROS) levels in live animals. Our findings indicate a tradeoff between investment in reproduction and antioxidant defense (somatic maintenance) consistent with theoretical predictions, but correlations between standard life-history traits yield little evidence that oxidative stress generates strict tradeoffs. Increasing oxidative insult, however, shows a strong tendency to uncouple positive phenotypic correlations and, in particular, to reduce the correlation between reproduction and lifespan. We also found that mild oxidative insult results in lower levels of endogenous ROS accompanied by hormetic changes in lifespan, demographic aging, and reproduction that disappear in combined-stress treatments--consistent with the oxidative stress theory of aging. Our findings demonstrate that oxidative stress is a direct contributor to life-history trait variation and that traditional tradeoffs are not necessary to invoke oxidative stress as a mediator of relationships between life-history traits, supporting previous calls for revisions to theory.

  3. Oxidative stress and life histories: unresolved issues and current needs

    OpenAIRE

    Speakman, John R.; Blount, Jonathan D.; Bronikowski, Anne M.; Buffenstein, Rochelle; Isaksson, Caroline; Kirkwood, Tom B. L.; Monaghan, Pat; Ozanne, Susan E.; Beaulieu, Micha?l; Briga, Michael; Carr, Sarah K.; Christensen, Louise L.; Cochem?, Helena M.; Cram, Dominic L.; Dantzer, Ben

    2015-01-01

    Abstract Life?history theory concerns the trade?offs that mold the patterns of investment by animals between reproduction, growth, and survival. It is widely recognized that physiology plays a role in the mediation of life?history trade?offs, but the details remain obscure. As life?history theory concerns aspects of investment in the soma that influence survival, understanding the physiological basis of life histories is related, but not identical, to understanding the process of aging. One i...

  4. Oxidative stress and life histories : Unresolved issues and current needs

    NARCIS (Netherlands)

    Speakman, John R.; Blount, Jonathan D.; Bronikowski, Anne M.; Buffenstein, Rochelle; Isaksson, Caroline; Kirkwood, Tom B. L.; Monaghan, Pat; Ozanne, Susan E.; Beaulieu, Michael; Briga, Michael; Carr, Sarah K.; Christensen, Louise L.; Cocheme, Helena M.; Cram, Dominic L.; Dantzer, Ben; Harper, Jim M.; Jurk, Diana; King, Annette; Noguera, Jose C.; Salin, Karine; Sild, Elin; Simons, Mirre J. P.; Smith, Shona; Stier, Antoine; Tobler, Michael; Vitikainen, Emma; Peaker, Malcolm; Selman, Colin

    2015-01-01

    Life-history theory concerns the trade-offs that mold the patterns of investment by animals between reproduction, growth, and survival. It is widely recognized that physiology plays a role in the mediation of life-history trade-offs, but the details remain obscure. As life-history theory concerns

  5. Insights into earthquake hazard map performance from shaking history simulations

    Science.gov (United States)

    Stein, S.; Vanneste, K.; Camelbeeck, T.; Vleminckx, B.

    2017-12-01

    Why recent large earthquakes caused shaking stronger than predicted by earthquake hazard maps is under debate. This issue has two parts. Verification involves how well maps implement probabilistic seismic hazard analysis (PSHA) ("have we built the map right?"). Validation asks how well maps forecast shaking ("have we built the right map?"). We explore how well a map can ideally perform by simulating an area's shaking history and comparing "observed" shaking to that predicted by a map generated for the same parameters. The simulations yield shaking distributions whose mean is consistent with the map, but individual shaking histories show large scatter. Infrequent large earthquakes cause shaking much stronger than mapped, as observed. Hence, PSHA seems internally consistent and can be regarded as verified. Validation is harder because an earthquake history can yield shaking higher or lower than that predicted while being consistent with the hazard map. The scatter decreases for longer observation times because the largest earthquakes and resulting shaking are increasingly likely to have occurred. For the same reason, scatter is much less for the more active plate boundary than for a continental interior. For a continental interior, where the mapped hazard is low, even an M4 event produces exceedances at some sites. Larger earthquakes produce exceedances at more sites. Thus many exceedances result from small earthquakes, but infrequent large ones may cause very large exceedances. However, for a plate boundary, an M6 event produces exceedance at only a few sites, and an M7 produces them in a larger, but still relatively small, portion of the study area. As reality gives only one history, and a real map involves assumptions about more complicated source geometries and occurrence rates, which are unlikely to be exactly correct and thus will contribute additional scatter, it is hard to assess whether misfit between actual shaking and a map — notably higher

  6. Determination of Stress Histories in Structures by Natural Input Modal Analysis

    DEFF Research Database (Denmark)

    Hjelm, Henrik P.; Brincker, Rune; Graugaard-Jensen, Jesper

    2005-01-01

    In this paper it is shown that stress histories can be estimated with high accuracy by integrating measured accelerations to obtain displacement and then performing a modal decomposition of the so estimated displacements. The relation between the modal coordinate and the stress in an arbitrary....... It is shown that the so estimated stress histories can replace strain gauge measurements in many cases, and it allows for an accurate estimation of fatigue damage....

  7. Effects of medium renewal and handling stress on life history traits in Daphnia

    NARCIS (Netherlands)

    Rousseaux, S.; Vanoverbeke, J.; Aerts, J.; Declerck, S.A.J.

    2010-01-01

    The zooplankton genus Daphnia is used as a model organism in ecological, ecotoxicological and evolutionary research. It is often used in experimental laboratory setups to examine life history traits under a variety of factors inducing stress. One type of stress, handling stress because of

  8. Scales tell a story on the stress history of fish.

    Science.gov (United States)

    Aerts, Johan; Metz, Juriaan Rogier; Ampe, Bart; Decostere, Annemie; Flik, Gert; De Saeger, Sarah

    2015-01-01

    Fish faced with stressful stimuli launch an endocrine stress response through activation of the hypothalamic-pituitary-interrenal (HPI-) axis to release cortisol into the blood. Scientifically validated biomarkers to capture systemic cortisol exposure over longer periods of time are of utmost importance to assess chronic stress in governmental, wildlife, aquaculture and scientific settings. Here we demonstrate that cortisol in scales of common carp (Cyprinus carpio L.) is the long-sought biomarker for chronic stress. Undisturbed (CTR) and daily stressed (STRESS) carp were compared. Dexamethasone (DEX) or cortisol (CORT) fed fish served as negative and positive controls, respectively. Scale cortisol was quantified with a validated ultra-performance liquid chromatography tandem mass spectrometry method. An increase in scale cortisol content was found in STRESS and CORT but not in CTR and DEX fish. Scale cortisol content reflects its accumulation in a stressor and time dependent manner and validates the scale cortisol content as biomarker for chronic stress. Plasma analyses confirmed that (i) CTR, DEX and CORT treatments were effective, (ii) plasma cortisol of STRESS fish showed no signs of chronic HPI-axis activation, and (iii) plasma cortisol is a poor predictor for chronic stress. The expression of HPI key genes crf, pomc, and star were up-regulated in STRESS fish in the absence of a plasma cortisol response, as was the target gene of cortisol encoding subunit α1 of the Na+/K+-ATPase in gills. When lost, scales of fish regenerate fast. Regenerated scales corroborate our findings, offering (i) unsurpassed time resolution for cortisol incorporation and as such for stressful events, and (ii) the possibility to investigate stress in a well defined and controlled environment and time frame creating novel opportunities for bone physiological research. We conclude that the cortisol content in ontogenetic and regenerated scales is an innovative biomarker for chronic

  9. Stress history increases alcohol intake in relapse: relation to phosphodiesterase 10A.

    Science.gov (United States)

    Logrip, Marian L; Zorrilla, Eric P

    2012-09-01

    Stressful experiences can result in elevated alcohol drinking, as exemplified in many individuals with post-traumatic stress disorder. However, how stress history, rather than acute stressors, influences alcohol intake remains uncertain. To model the protracted effects of past stress, male Wistar rats were subjected to light-cued footshock (stress history) or light cues alone (control) prior to acquisition of alcohol self-administration (1-hour sessions, fixed ratio 1-3, 100 µl of 10% v/v alcohol as reinforcer). Stress history did not alter mean alcohol intake during acquisition of self-administration, but it increased preference for the alcohol-paired lever over the inactive lever. Following an extinction period, rats with a history of stress exposure and low baseline alcohol intake showed a twofold elevation in alcohol self-administration, as compared with low-drinking rats with no stress history. Similar effects were not seen in rats self-administering 0.1% sucrose. Analysis of mRNA levels of phosphodiesterase 10A (PDE10A), a dual-specificity cyclic adenosine monophosphate and cyclic guanosine monophosphate hydrolyzing enzyme, showed that stress history increased Pde10a mRNA levels in the basolateral amygdala and, in low-drinking rats, the prelimbic prefrontal cortex (plPFC). Pde10a mRNA levels in the plPFC correlated directly with greater alcohol self-administration during the relapse-like phase, and greater BLA Pde10a mRNA levels correlated with increased ethanol preference after acquisition. The data demonstrate that stress history sensitizes otherwise low alcohol drinkers to consume more alcohol in a relapse-like situation and identify stress-induced neuroadaptations in amygdala and prefrontal cortical Pde10a expression as changes that may drive heightened alcohol intake and preference in susceptible individuals. © 2012 The Authors. Addiction Biology © 2012 Society for the Study of Addiction.

  10. Variation in adult life history and stress resistance across five ...

    Indian Academy of Sciences (India)

    Unknown

    Life-history evolution in Drosophila has been extensively studied, and .... Overall, if one looks at studies of adult life history and ...... Thus, if the balance of biotic and abiotic selective ... these four species, and indicate that more detailed work on.

  11. Cycle counting procedure for fatigue failure preditions for complicated multi-axial stress histories

    International Nuclear Information System (INIS)

    Jones, D.P.; Friedrich, C.M.; Hoppe, R.G.

    1977-12-01

    A procedure has been developed to determine the cumulative fatigue damage in structures experiencing complicated multi-axial stress histories. The procedure is a generalization of the rainflow method developed by Matsuishi and Endo for one-dimensional situations. It provides a consistent treatment of three-dimensional stress states that is especially suited to computer programming applications for the post-processing of finite element stress data. The procedure includes a unique method to account for the rotation of principal stresses with time during the stress history and for the cumulative fatigue damage resulting from partial stress reversals within a stress cycle. The general procedure and necessary equations for programming are presented. Comparisons are made with life predictions using Section III of the ASME Boiler and Pressure Vessel Code for two hypothetical multi-axial stress histories for which the principal stresses are rotating with time. These comparisons show that the cycle counting method provides a consistent unambiguous interpretation of the fatigue design procedure in the ASME Code for these cases. Finally, the fatigue life of a perforated plate, as analyzed by finite elements, is computed for the combination of several hypothetical stress histories. This example demonstrates the utility of the proposed method when used in conjunction with finite element programs

  12. Examining the mechanical equilibrium of microscopic stresses in molecular simulations

    OpenAIRE

    Torres Sánchez, Alejandro; Vanegas, Juan Manuel; Arroyo Balaguer, Marino

    2015-01-01

    The microscopic stress field provides a unique connection between atomistic simulations and mechanics at the nanoscale. However, its definition remains ambiguous. Rather than a mere theoretical preoccupation, we show that this fact acutely manifests itself in local stress calculations of defective graphene, lipid bilayers, and fibrous proteins. We find that popular definitions of the microscopic stress violate the continuum statements of mechanical equilibrium, and we propose an unambiguous a...

  13. Simulations of embedded lateral stress gauge profiles in shocked targets

    International Nuclear Information System (INIS)

    Winter, R E; Harris, E J

    2008-01-01

    In principle, stress gauges mounted to measure lateral stresses in a shocked matrix allow the shear strength of the material to be determined. However, interpreting the resistance profiles from lateral stress gauges is hindered by the fact that the stress field in the vicinity of the insulating layer in which the gauges are embedded can differ significantly from the stress field that would be generated in the sample if no gauge were present. A series of high resolution Eulerian hydrocode simulations have been run which suggest that the stresses in the insulating layer vary with distance and time in a way that depends on the thickness of the layer, the shock strength and the elastic and plastic properties of both the layer and the matrix. In particular, if the shock velocity in the matrix material is high the stress at a typical gauge position initially rises to a sharp peak then falls with time, but when the shock velocity in the matrix is low the stress rises relatively gradually throughout the time of interest. The shapes of the stress versus time profiles predicted by the hydrocode compare well with the results of lateral gauge experiments on several different materials. It is concluded that lateral gauges can be used to measure the dynamic strength of materials provided high resolution computer simulation is used to take account of the perturbation of the stress field in the shocked sample caused by the gauges

  14. Stress in student teachers during real and simulated, standardized lectures

    NARCIS (Netherlands)

    Houtman, I.L.D.; Bakker, F.C.

    1987-01-01

    This study describes and compares the intensity of stress responses, both psychologically and physiologically, to a real and a simulated stressor. The real stressor involved lecturing to a class of students in a post-secondary institution during a practice teaching course. The simulated stressor was

  15. Dissecting molecular stress networks: identifying nodes of divergence between life-history phenotypes.

    Science.gov (United States)

    Schwartz, Tonia S; Bronikowski, Anne M

    2013-02-01

    The complex molecular network that underlies physiological stress response is comprised of nodes (proteins, metabolites, mRNAs, etc.) whose connections span cells, tissues and organs. Variable nodes are points in the network upon which natural selection may act. Thus, identifying variable nodes will reveal how this molecular stress network may evolve among populations in different habitats and how it might impact life-history evolution. Here, we use physiological and genetic assays to test whether laboratory-born juveniles from natural populations of garter snakes (Thamnophis elegans), which have diverged in their life-history phenotypes, vary concomitantly at candidate nodes of the stress response network, (i) under unstressed conditions and (ii) in response to an induced stress. We found that two common measures of stress (plasma corticosterone and liver gene expression of heat shock proteins) increased under stress in both life-history phenotypes. In contrast, the phenotypes diverged at four nodes both under unstressed conditions and in response to stress: circulating levels of reactive oxygen species (superoxide, H(2)O(2)); liver gene expression of GPX1 and erythrocyte DNA damage. Additionally, allele frequencies for SOD2 diverge from neutral markers, suggesting diversifying selection on SOD2 alleles. This study supports the hypothesis that these life-history phenotypes have diverged at the molecular level in how they respond to stress, particularly in nodes regulating oxidative stress. Furthermore, the differences between the life-history phenotypes were more pronounced in females. We discuss the responses to stress in the context of the associated life-history phenotype and the evolutionary pressures thought to be responsible for divergence between the phenotypes. © 2012 Blackwell Publishing Ltd.

  16. Posttraumatic Stress Disorder, Traumatic Brain Injury, and Suicide Attempt History among Veterans Receiving Mental Health Services

    Science.gov (United States)

    Brenner, Lisa A.; Betthauser, Lisa M.; Homaifar, Beeta Y.; Villarreal, Edgar; Harwood, Jeri E. F.; Staves, Pamela J.; Huggins, Joseph A.

    2011-01-01

    History of posttraumatic stress disorder (PTSD) or traumatic brain injury (TBI) has been found to increase risk of suicidal behavior. The association between suicide attempt history among veterans with PTSD and/or TBI was explored. Cases (N = 81) and 2:1 matched controls (N = 160) were randomly selected from a Veterans Affairs Medical Center…

  17. Differential Reporting of Adolescent Stress as a Function of Maternal Depression History.

    Science.gov (United States)

    Daryanani, Issar; Hamilton, Jessica L; Shapero, Benjamin G; Burke, Taylor A; Abramson, Lyn Y; Alloy, Lauren B

    The depression-distortion hypothesis posits that depressed mothers report child characteristics in a negatively-biased manner, motivating research on discrepant reporting between depressed mothers and their children. However, the literature has predominately focused on report discrepancies of youth psychopathological and behavioral outcomes, with limited focus on youth stress despite the marked increase of stressful events during adolescence. The current study investigated whether the presence versus absence of a maternal history of major depressive disorder differentially influenced reporting of adolescent stress when compared to her child's report, utilizing a community sample of diverse adolescents. As hypothesized, mothers with a history of depression were more likely to report more youth stress than their children reported. Specifically, mothers with a history of depression were more likely than nondepressed mothers to report more familial, social, and youth-dependent stressors relative to their children; nondepressed mothers were more likely to report less independent stressors than their children.

  18. Emotional stress-reactivity and positive affect among college students: the role of depression history.

    Science.gov (United States)

    O'Hara, Ross E; Armeli, Stephen; Boynton, Marcella H; Tennen, Howard

    2014-02-01

    Multiple theories posit that people with a history of depression are at higher risk for a depressive episode than people who have never experienced depression, which may be partly due to differences in stress-reactivity. In addition, both the dynamic model of affect and the broaden-and-build theory suggest that stress and positive affect interact to predict negative affect, but this moderation has never been tested in the context of depression history. The current study used multilevel modeling to examine these issues among 1,549 college students with or without a history of depression. Students completed a 30-day online diary study in which they reported daily their perceived stress, positive affect, and negative affect (including depression, anxiety, and hostility). On days characterized by higher than usual stress, students with a history of depression reported greater decreases in positive affect and greater increases in depressed affect than students with no history. Furthermore, the relations between daily stress and both depressed and anxious affect were moderated by daily positive affect among students with remitted depression. These results indicate that students with a history of depression show greater stress-reactivity even when in remission, which may place them at greater risk for recurrence. These individuals may also benefit more from positive affect on higher stress days despite being less likely to experience positive affect on such days. The current findings have various implications both clinically and for research on stress, mood, and depression. (PsycINFO Database Record (c) 2014 APA, all rights reserved). PsycINFO Database Record (c) 2014 APA, all rights reserved.

  19. Differential reproductive responses to stress reveal the role of life-history strategies within a species.

    Science.gov (United States)

    Schultner, J; Kitaysky, A S; Gabrielsen, G W; Hatch, S A; Bech, C

    2013-11-22

    Life-history strategies describe that 'slow'- in contrast to 'fast'-living species allocate resources cautiously towards reproduction to enhance survival. Recent evidence suggests that variation in strategies exists not only among species but also among populations of the same species. Here, we examined the effect of experimentally induced stress on resource allocation of breeding seabirds in two populations with contrasting life-history strategies: slow-living Pacific and fast-living Atlantic black-legged kittiwakes. We tested the hypothesis that reproductive responses in kittiwakes under stress reflect their life-history strategies. We predicted that in response to stress, Pacific kittiwakes reduce investment in reproduction compared with Atlantic kittiwakes. We exposed chick-rearing kittiwakes to a short-term (3-day) period of increased exogenous corticosterone (CORT), a hormone that is released during food shortages. We examined changes in baseline CORT levels, parental care and effects on offspring. We found that kittiwakes from the two populations invested differently in offspring when facing stress. In response to elevated CORT, Pacific kittiwakes reduced nest attendance and deserted offspring more readily than Atlantic kittiwakes. We observed lower chick growth, a higher stress response in offspring and lower reproductive success in response to CORT implantation in Pacific kittiwakes, whereas the opposite occurred in the Atlantic. Our findings support the hypothesis that life-history strategies predict short-term responses of individuals to stress within a species. We conclude that behaviour and physiology under stress are consistent with trade-off priorities as predicted by life-history theory. We encourage future studies to consider the pivotal role of life-history strategies when interpreting inter-population differences of animal responses to stressful environmental events.

  20. Fatigue crack threshold relevant to stress ratio, crack wake and loading histories

    International Nuclear Information System (INIS)

    Okazaki, Masakazu; Iwasaki, Akira; Kasahara, Naoto

    2013-01-01

    Fatigue crack propagation behavior was investigated in a low alloy steel which experienced several kind of loading histories. Both the effects of stress ratio, test temperature on the fatigue crack threshold, and the change in the threshold depending on the thermo-mechanical loading histories, were experimentally investigated. It was shown that the thermo-mechanical loading history left its effect along the prior fatigue crack wake resulting in the change of fatigue crack threshold. Some discussions are made on how this type of loading history effect should be treated from engineering point of view. (author)

  1. A family history of Type 1 alcoholism differentiates alcohol consumption in high cortisol responders to stress.

    Science.gov (United States)

    Brkic, Sejla; Söderpalm, Bo; Söderpalm Gordh, Anna

    2015-03-01

    The differentiation between high and low cortisol responders to stress is of interest in determining the risk factors which may, along with genetic vulnerability, influence alcohol intake. Thirty-two healthy volunteers, family history positive to alcoholism (FHP, n = 16) and family history negative (FHN, n = 16) attended two laboratory sessions during which alcohol or placebo was offered. There were no differences in consumption of alcohol or placebo between FHP and FHN subjects. STUDY 2: Fifty-eight healthy social drinkers, FHP (n = 27) and FHN (n = 31) attended two laboratory sessions. They were administered either alcohol or placebo in both sessions they attended. All subjects underwent either a stress task (the Trier Social Stress Test, TSST) or a stress-free period, at two separate occasions, before being offered beverage. After the salivary cortisol analysis, subjects in each group were divided into high (HCR) or low (LCR) cortisol responders. After stress, subjects who were FHP-HCR consumed more alcohol than FHN-HCR. There were no differences in the placebo intake between FHP and FHN subjects regardless of their cortisol response. This result indicates that stress promotes alcohol consumption only in subjects with a family history of Type 1 alcoholism who show an increase in cortisol response to stress. This behaviour is similar to that previously observed in alcohol dependent individuals after stress and thus could represent an endophenotype posing a risk for future development of alcohol use disorders. Copyright © 2015. Published by Elsevier Inc.

  2. Elastoplastical Analysis of the Interface between Clay and Concrete Incorporating the Effect of the Normal Stress History

    Directory of Open Access Journals (Sweden)

    Zhao Cheng

    2013-01-01

    Full Text Available The behaviour of the soil-structure interface is crucial to the design of a pile foundation. Radial unloading occurs during the process of hole boring and concrete curing, which will affect the load transfer rule of the pile-soil interface. Through large shear tests on the interface between clay and concrete, it can be concluded that the normal stress history significantly influences the shear behaviour of the interface. The numerical simulation of the bored shaft-soil interaction problem requires proper modelling of the interface. By taking the energy accumulated on the interface as a hardening parameter and viewing the shearing process of the interface as the process of the energy dissipated to do work, considering the influence of the normal stress history on the shearing rigidity, a mechanical model of the interface between clay and concrete is proposed. The methods to define the model parameters are also introduced. The model is based on a legible mathematical theory, and all its parameters have definite physical meaning. The model was validated using data from a direct shear test; the validation results indicated that the model can reproduce and predict the mechanical behaviour of the interface between clay and concrete under an arbitrary stress history.

  3. Social, psychological and psychosomatic disorders in the people with combat stress in their medical histories

    Directory of Open Access Journals (Sweden)

    L. V. Gracheva

    2013-01-01

    Full Text Available The authors examined three groups of patients – military men (40 men in each group with combat stress of different intensity in their medical histories (two main groups and a  control group – without combat stress. The results showed that the military men with a high level combat stress in the past (more than 5 years ago more frequently demonstrated socialmental disadaptation against the background of subclinical chronic posttraumatic stress disorder (PTSD. The conclusion is that this group of people requires dynamic followup and adequate medicopsychological aid.

  4. Compound risk: History of traumatic stress predicts posttraumatic stress disorder symptoms and severity in sudden cardiac arrest survivors.

    Science.gov (United States)

    Rosman, Lindsey; Ford, Jessica; Whited, Amanda; Cahill, John; Lampert, Rachel; Mosesso, Vincent N; Lawless, Christine; Sears, Samuel F

    2016-08-01

    Sudden cardiac arrest (SCA) survivors can develop posttraumatic stress disorder (PTSD) which is associated with worse clinical outcomes. The purpose of this study was to evaluate the prevalence and predictors of PTSD in a large sample of SCA survivors. Prior history of psychological trauma and the effects of repeated trauma exposure on subsequent PTSD and symptom severity after SCA were also explored. A retrospective, cross-sectional study of 188 SCA survivors from the Sudden Cardiac Arrest Association patient registry completed an online questionnaire that included measures of PTSD, trauma history, sociodemographics, general health, and cardiac history. Sixty-three (36.2%) SCA survivors in this sample scored above the clinical cutoff for PTSD. Female gender, worse general health, and younger age predicted PTSD symptoms after SCA. Additionally, 50.2% of SCA survivors (n = 95) reported a history of trauma exposure and 25.4% (n = 48) of the total sample endorsed a traumatic stress response to a historic trauma. Results indicated that a traumatic stress response to a historic trauma was a stronger predictor of PTSD after SCA (odds ratio = 4.77) than all other variables in the model. PTSD symptoms are present in over one-third of SCA survivors. While demographic or health history variables predicted PTSD after SCA, a history of traumatic stress response to a previous trauma emerged as the strongest predictor of these symptoms. Routine assessment and interdisciplinary management are discussed as potential ways to expedite survivors' recovery and return to daily living. © The European Society of Cardiology 2015.

  5. Simulation and experimental comparison of the thermo-mechanical history and 3D microstructure evolution of 304L stainless steel tubes manufactured using LENS

    Science.gov (United States)

    Johnson, Kyle L.; Rodgers, Theron M.; Underwood, Olivia D.; Madison, Jonathan D.; Ford, Kurtis R.; Whetten, Shaun R.; Dagel, Daryl J.; Bishop, Joseph E.

    2017-12-01

    Additive manufacturing enables the production of previously unachievable designs in conjunction with time and cost savings. However, spatially and temporally fluctuating thermal histories can lead to residual stress states and microstructural variations that challenge conventional assumptions used to predict part performance. Numerical simulations offer a viable way to explore the root causes of these characteristics, and can provide insight into methods of controlling them. Here, the thermal history of a 304L stainless steel cylinder produced using the Laser Engineered Net Shape process is simulated using finite element analysis (FEA). The resultant thermal history is coupled to both a solid mechanics FEA simulation to predict residual stress and a kinetic Monte Carlo model to predict the three-dimensional grain structure evolution. Experimental EBSD measurements of grain structure and in-process infrared thermal data are compared to the predictions.

  6. Simulation and experimental comparison of the thermo-mechanical history and 3D microstructure evolution of 304L stainless steel tubes manufactured using LENS

    Science.gov (United States)

    Johnson, Kyle L.; Rodgers, Theron M.; Underwood, Olivia D.; Madison, Jonathan D.; Ford, Kurtis R.; Whetten, Shaun R.; Dagel, Daryl J.; Bishop, Joseph E.

    2018-05-01

    Additive manufacturing enables the production of previously unachievable designs in conjunction with time and cost savings. However, spatially and temporally fluctuating thermal histories can lead to residual stress states and microstructural variations that challenge conventional assumptions used to predict part performance. Numerical simulations offer a viable way to explore the root causes of these characteristics, and can provide insight into methods of controlling them. Here, the thermal history of a 304L stainless steel cylinder produced using the Laser Engineered Net Shape process is simulated using finite element analysis (FEA). The resultant thermal history is coupled to both a solid mechanics FEA simulation to predict residual stress and a kinetic Monte Carlo model to predict the three-dimensional grain structure evolution. Experimental EBSD measurements of grain structure and in-process infrared thermal data are compared to the predictions.

  7. Social identity shapes stress appraisals in people with a history of depression.

    Science.gov (United States)

    Isaksson, Alexandra; Martin, Peter; Kaufmehl, Jan; Heinrichs, Markus; Domes, Gregor; Rüsch, Nicolas

    2017-08-01

    Ingroup perception or the views people with depression have about their group, may influence their vulnerability to social identity threat and lead to enhanced stress reactions and impaired performance. It is unclear how ingroup perception can influence stress appraisals in performance situations among people with a history of depression who are currently in remission. We investigated the impact of ingroup perception on primary stress appraisal, i.e. how threatening a test situation is perceived, as well as on secondary stress appraisal, or perceived coping resources. Sixty people with a history of depression and currently in remission underwent computerized performance tests. Ingroup perception (group identification, group value and entitativity) and stress appraisals were assessed by self-report. In multiple linear regressions higher group identification predicted stronger perception of the situation as stressful if participants perceived people with depression as a coherent group (high entitativity) and held this group in low regard (low group value). In turn, stronger group identification was related to more perceived coping resources especially if participants did not regard people with depression as a coherent group. Our findings highlight the relevance of ingroup perception for stress and coping processes in people with a history of depression. Copyright © 2017 Elsevier Ireland Ltd. All rights reserved.

  8. Stress Wave Propagation in Larch Plantation Trees-Numerical Simulation

    Science.gov (United States)

    Fenglu Liu; Fang Jiang; Xiping Wang; Houjiang Zhang; Wenhua Yu

    2015-01-01

    In this paper, we attempted to simulate stress wave propagation in virtual tree trunks and construct two dimensional (2D) wave-front maps in the longitudinal-radial section of the trunk. A tree trunk was modeled as an orthotropic cylinder in which wood properties along the fiber and in each of the two perpendicular directions were different. We used the COMSOL...

  9. Time, stress, and temperature-dependent deformation in nanostructured copper: Stress relaxation tests and simulations

    International Nuclear Information System (INIS)

    Yang, Xu-Sheng; Wang, Yun-Jiang; Wang, Guo-Yong; Zhai, Hui-Ru; Dai, L.H.; Zhang, Tong-Yi

    2016-01-01

    In the present work, stress relaxation tests, high-resolution transmission electron microscopy (HRTEM), and molecular dynamics (MD) simulations were conducted on coarse-grained (cg), nanograined (ng), and nanotwinned (nt) copper at temperatures of 22 °C (RT), 30 °C, 40 °C, 50 °C, and 75 °C. The comprehensive investigations provide sufficient information for the building-up of a formula to describe the time, stress, and temperature-dependent deformation and clarify the relationship among the strain rate sensitivity parameter, stress exponent, and activation volume. The typically experimental curves of logarithmic plastic strain rate versus stress exhibited a three staged relaxation process from a linear high stress relaxation region to a subsequent nonlinear stress relaxation region and finally to a linear low stress relaxation region, which only showed-up at the test temperatures higher than 22 °C, 22 °C, and 30 °C, respectively, in the tested cg-, ng-, and nt-Cu specimens. The values of stress exponent, stress-independent activation energy, and activation volume were determined from the experimental data in the two linear regions. The determined activation parameters, HRTEM images, and MD simulations consistently suggest that dislocation-mediated plastic deformation is predominant in all tested cg-, ng-, and nt-Cu specimens in the initial linear high stress relaxation region at the five relaxation temperatures, whereas in the linear low stress relaxation region, the grain boundary (GB) diffusion-associated deformation is dominant in the ng- and cg-Cu specimens, while twin boundary (TB) migration, i.e., twinning and detwinning with parallel partial dislocations, governs the time, stress, and temperature-dependent deformation in the nt-Cu specimens.

  10. NUMERICAL SIMULATION OF AN AGRICULTURAL SOIL SHEAR STRESS TEST

    Directory of Open Access Journals (Sweden)

    Andrea Formato

    2007-03-01

    Full Text Available In this work a numerical simulation of agricultural soil shear stress tests was performed through soil shear strength data detected by a soil shearometer. We used a soil shearometer available on the market to measure soil shear stress and constructed special equipment that enabled automated detection of soil shear stress. It was connected to an acquisition data system that displayed and recorded soil shear stress during the full field tests. A soil shearometer unit was used to the in situ measurements of soil shear stress in full field conditions for different types of soils located on the right side of the Sele river, at a distance of about 1 km from each other, along the perpendicular to the Sele river in the direction of the sea. Full field tests using the shearometer unit were performed alongside considered soil characteristic parameter data collection. These parameter values derived from hydrostatic compression and triaxial tests performed on considered soil samples and repeated 4 times and we noticed that the difference between the maximum and minimum values detected for every set of performed tests never exceeded 4%. Full field shear tests were simulated by the Abaqus program code considering three different material models of soils normally used in the literature, the Mohr-Coulomb, Drucker-Prager and Cam-Clay models. We then compared all data outcomes obtained by numerical simulations with those from the experimental tests. We also discussed any further simulation data results obtained with different material models and selected the best material model for each considered soil to be used in tyre/soil contact simulation or in soil compaction studies.

  11. Distinct hip and rearfoot kinematics in female runners with a history of tibial stress fracture.

    Science.gov (United States)

    Milner, Clare E; Hamill, Joseph; Davis, Irene S

    2010-02-01

    Cross-sectional controlled laboratory study. To investigate the kinematics of the hip, knee, and rearfoot in the frontal and transverse planes in female distance runners with a history of tibial stress fracture. Tibial stress fractures are a common overuse injury in runners, accounting for up to half of all stress fractures. Abnormal kinematics of the lower extremity may contribute to abnormal musculoskeletal load distributions, leading to an increased risk of stress fractures. Thirty female runners with a history of tibial stress fracture were compared to 30 age-matched and weekly-running-distance-matched control subjects with no previous lower extremity bony injuries. Kinematic and kinetic data were collected using a motion capture system and a force platform, respectively, as subjects ran in the laboratory. Selected variables of interest were compared between the groups using a multivariate analysis of variance (MANOVA). Peak hip adduction and peak rearfoot eversion angles were greater in the stress fracture group compared to the control group. Peak knee adduction and knee internal rotation angles and all joint angles at impact peak were similar between the groups. Runners with a previous tibial stress fracture exhibited greater peak hip adduction and rearfoot eversion angles during the stance phase of running compared to healthy controls. A consequence of these mechanics may be altered load distribution within the lower extremity, predisposing individuals to stress fracture.

  12. Dispersal timing and drought history influence the response of bacterioplankton to drying-rewetting stress.

    Science.gov (United States)

    Székely, Anna J; Langenheder, Silke

    2017-08-01

    The extent and frequency of drought episodes is expected to increase in the following decades making it a crucial stress factor for smaller water bodies. However, very little is known about how bacterioplankton is affected by increased evaporation and how these communities reassemble after rewetting. Here, we present results from a microcosm experiment that assessed the effect of drying-rewetting stress on bacterioplankton in the light of the stress history and the rate and timing of dispersal after the rewetting. We found that the drying phase resulted mainly in a change of function, whereas the complete desiccation and rewetting processes strongly affected both composition and function, which were, however, influenced by the initial conditions and stress history of the communities. Effects of dispersal were generally stronger when it occurred at an early stage after the rewetting. At this stage, selective establishment of dispersed bacteria coupled with enhanced compositional and functional recovery was found, whereas effects of dispersal were neutral, that is, predictable by dispersal rates, at later stages. Our studies therefore show that both the stress history and the timing of dispersal are important factors that influence the response of bacterial communities to environmental change and stress events.

  13. Remaining life case history studies for high energy piping systems using equivalent stress

    International Nuclear Information System (INIS)

    Cohn, M.J.

    1987-01-01

    As the development of plant life extension for high energy piping systems is progressing, conventional piping system design methodologies are also being reevaluated. Traditional guidelines such as American National Standard Institute/American Society of Mechanical Engineers B31.1 (ANSI/ASME) were developed for plants having design lives in the 25- to 30-year regime based upon relatively short-term base metal creep data. These guidelines use a simplified approach for the piping analysis. Two types of stress criteria must be satisfied. The first type is longitudinal plus torsion stress checks for several types of loading conditions versus the material allowable stresses. The second type is an independent minimum wall thickness check which considers the hoop stress versus the material allowable stress. Seven case histories have been evaluated to estimate the minimum piping system creep life based on the current ANSI/ASME B31.1 finite element type of analysis, which is a traditional approach, versus a multiaxial stress state type of analysis. In nearly every case, the equivalent stress methodology predicted significantly higher stresses. Consequently, the equivalent stress methodology resulted in 11 to 96% lower time to rupture values as compared to the values predicted using ANSI/ASME B31.1 stresses

  14. Simulations of surface stress effects in nanoscale single crystals

    Science.gov (United States)

    Zadin, V.; Veske, M.; Vigonski, S.; Jansson, V.; Muszinsky, J.; Parviainen, S.; Aabloo, A.; Djurabekova, F.

    2018-04-01

    Onset of vacuum arcing near a metal surface is often associated with nanoscale asperities, which may dynamically appear due to different processes ongoing in the surface and subsurface layers in the presence of high electric fields. Thermally activated processes, as well as plastic deformation caused by tensile stress due to an applied electric field, are usually not accessible by atomistic simulations because of the long time needed for these processes to occur. On the other hand, finite element methods, able to describe the process of plastic deformations in materials at realistic stresses, do not include surface properties. The latter are particularly important for the problems where the surface plays crucial role in the studied process, as for instance, in the case of plastic deformations at a nanovoid. In the current study by means of molecular dynamics (MD) and finite element simulations we analyse the stress distribution in single crystal copper containing a nanovoid buried deep under the surface. We have developed a methodology to incorporate the surface effects into the solid mechanics framework by utilizing elastic properties of crystals, pre-calculated using MD simulations. The method leads to computationally efficient stress calculations and can be easily implemented in commercially available finite element software, making it an attractive analysis tool.

  15. Medial tibial stress syndrome can be diagnosed reliably using history and physical examination

    NARCIS (Netherlands)

    Winters, M.; Bakker, E. W. P.; Moen, M. H.; Barten, C. C.; Teeuwen, R.; Weir, A.

    2017-01-01

    The majority of sporting injuries are clinically diagnosed using history and physical examination as the cornerstone. There are no studies supporting the reliability of making a clinical diagnosis of medial tibial stress syndrome (MTSS). Our aim was to assess if MTSS can be diagnosed reliably, using

  16. Local stress calculation in simulations of multicomponent systems

    International Nuclear Information System (INIS)

    Branicio, Paulo S.; Srolovitz, David J.

    2009-01-01

    The virial and Hardy methods provide accurate local stresses for single component materials such as monatomic metals. In contrast to the elemental material case, both methods provide poor estimates of the local stress for multicomponent materials. Using binary materials such as CaO, SiC and AlN and homogeneous strain, we demonstrate that there are several sources for the slow convergence of the virial and Hardy local stresses to the bulk values. Different approaches such as enforced stoichiometry, atomic localization functions and the atomic voronoi volume are used to improve the convergence and increase the spatial resolution of the local stress. The virial method with enforced stoichiometry and atomic voronoi volumes is the most accurate, giving exact stress values by the first atomic shell. In the general case, not assuming stoichiometry, the virial method with localization functions converge to 93% of the bulk value by the third atomic shell. This work may be particularly useful for the real-time description of stresses in simulations of shock waves and deformation dynamics.

  17. A study on the stress history condensation method for a fatigue monitoring system

    International Nuclear Information System (INIS)

    Ko, Hanok; Jhung, Myungjo; Lee, Kihyoung

    2014-01-01

    Fatigue damage is the one of important aging mechanisms. Time-varying thermal, pressure and mechanical loads produce perturbations of stress cycles primarily at the surface of a component. Stress cycles of sufficient magnitude cause fatigue damage, which can ultimately lead to cracking of the component. According to NUREG-1801, fatigue monitoring systems identify acceptable aging management programs, including programs for fatigue and cyclic operation. In a monitoring system, the rainflow counting method is mainly used as the stress cycle counting method. Before determining the stress cycles using rainflow counting method, stress extremum (or peak/valley) must be identified. Because real stress history contains large numbers of very small cycles, which may be a result of digitization noise, these cycles will slow down the analysis and distort the scaling of graphical displays. As a result, it is found that stress cycles smaller than a threshold value are discarded by using the proposed method. In this paper, an engineering methodology which extracts extremum from the real-time transient data, so-called SEE, has been developed. The proposed method is very simple and so fast because it only uses the difference between the input value and local peak/valley. The stress cycles counted by two methods are compared with those counted by only rainflow counting method and it is found that stress cycles smaller than a threshold value were eliminated

  18. Estimating tectonic history through basin simulation-enhanced seismic inversion: Geoinformatics for sedimentary basins

    Science.gov (United States)

    Tandon, K.; Tuncay, K.; Hubbard, K.; Comer, J.; Ortoleva, P.

    2004-01-01

    A data assimilation approach is demonstrated whereby seismic inversion is both automated and enhanced using a comprehensive numerical sedimentary basin simulator to study the physics and chemistry of sedimentary basin processes in response to geothermal gradient in much greater detail than previously attempted. The approach not only reduces costs by integrating the basin analysis and seismic inversion activities to understand the sedimentary basin evolution with respect to geodynamic parameters-but the technique also has the potential for serving as a geoinfomatics platform for understanding various physical and chemical processes operating at different scales within a sedimentary basin. Tectonic history has a first-order effect on the physical and chemical processes that govern the evolution of sedimentary basins. We demonstrate how such tectonic parameters may be estimated by minimizing the difference between observed seismic reflection data and synthetic ones constructed from the output of a reaction, transport, mechanical (RTM) basin model. We demonstrate the method by reconstructing the geothermal gradient. As thermal history strongly affects the rate of RTM processes operating in a sedimentary basin, variations in geothermal gradient history alter the present-day fluid pressure, effective stress, porosity, fracture statistics and hydrocarbon distribution. All these properties, in turn, affect the mechanical wave velocity and sediment density profiles for a sedimentary basin. The present-day state of the sedimentary basin is imaged by reflection seismology data to a high degree of resolution, but it does not give any indication of the processes that contributed to the evolution of the basin or causes for heterogeneities within the basin that are being imaged. Using texture and fluid properties predicted by our Basin RTM simulator, we generate synthetic seismograms. Linear correlation using power spectra as an error measure and an efficient quadratic

  19. Measurement and simulation of deformation and stresses in steel casting

    Science.gov (United States)

    Galles, D.; Monroe, C. A.; Beckermann, C.

    2012-07-01

    Experiments are conducted to measure displacements and forces during casting of a steel bar in a sand mold. In some experiments the bar is allowed to contract freely, while in others the bar is manually strained using embedded rods connected to a frame. Solidification and cooling of the experimental castings are simulated using a commercial code, and good agreement between measured and predicted temperatures is obtained. The deformations and stresses in the experiments are simulated using an elasto-viscoplastic finite-element model. The high temperature mechanical properties are estimated from data available in the literature. The mush is modeled using porous metal plasticity theory, where the coherency and coalescence solid fraction are taken into account. Good agreement is obtained between measured and predicted displacements and forces. The results shed considerable light on the modeling of stresses in steel casting and help in developing more accurate models for predicting hot tears and casting distortions.

  20. Measurement and simulation of deformation and stresses in steel casting

    International Nuclear Information System (INIS)

    Galles, D; Beckermann, C; Monroe, C A

    2012-01-01

    Experiments are conducted to measure displacements and forces during casting of a steel bar in a sand mold. In some experiments the bar is allowed to contract freely, while in others the bar is manually strained using embedded rods connected to a frame. Solidification and cooling of the experimental castings are simulated using a commercial code, and good agreement between measured and predicted temperatures is obtained. The deformations and stresses in the experiments are simulated using an elasto-viscoplastic finite-element model. The high temperature mechanical properties are estimated from data available in the literature. The mush is modeled using porous metal plasticity theory, where the coherency and coalescence solid fraction are taken into account. Good agreement is obtained between measured and predicted displacements and forces. The results shed considerable light on the modeling of stresses in steel casting and help in developing more accurate models for predicting hot tears and casting distortions.

  1. Early parental loss and depression history: associations with recent life stress in major depressive disorder.

    Science.gov (United States)

    Slavich, George M; Monroe, Scott M; Gotlib, Ian H

    2011-09-01

    Although exposure to early adversity and prior experiences with depression have both been associated with lower levels of precipitating life stress in depression, it is unclear whether these stress sensitization effects are similar for all types of stress or whether they are specific to stressors that may be particularly depressogenic, such as those involving interpersonal loss. To investigate this issue, we administered structured, interview-based measures of early adversity, depression history, and recent life stress to one hundred adults who were diagnosed with major depressive disorder. As predicted, individuals who experienced early parental loss or prolonged separation (i.e., lasting one year or longer) and persons with more lifetime episodes of depression became depressed following lower levels of life stress occurring in the etiologically-central time period of three months prior to onset of depression. Importantly, however, additional analyses revealed that these effects were unique to stressors involving interpersonal loss. These data highlight potential stressor-specific effects in stress sensitization and demonstrate for the first time that individuals exposed to early parental loss or separation, and persons with greater histories of MDD, may be selectively sensitized to stressors involving interpersonal loss. Copyright © 2011 Elsevier Ltd. All rights reserved.

  2. Mother's Childrearing History and Current Parenting: Patterns of Association and the Moderating Role of Current Life Stress

    Science.gov (United States)

    Hill, Carri; Stein, Jennifer; Keenan, Kate; Wakschlag, Lauren S.

    2006-01-01

    This study examined the association between positive and negative aspects of childrearing history and current parenting and the moderating effect of current stress. Seventy mother-child dyads participated in this study. Mothers provided retrospective reports of childrearing histories and current reports of life stress. Parenting was assessed via…

  3. Road traffic offending, stress, age, and accident history among male and female drivers.

    Science.gov (United States)

    Simon, F; Corbett, C

    1996-05-01

    This paper draws on data gathered during a larger study of driving behaviour to explore possible connections between stress, offending against the traffic laws, and accident rates, and gives particular attention to comparisons between male and female drivers. Data were gathered from 422 drivers by a postal questionnaire, and further measures of stress were obtained during semi-structured interviews with a specially selected subset of 66 of them. Analyses of variance investigated links between offending rates, accident history, and up to seven measures of stress, taking age and gender into account. In the results accident history, although positively related to offending, played little part in links involving stress variables. The principal findings were that (a) stress, both on and off the road, was positively associated with offending among both male and female drivers, and (b) although females overall offended less than males, females experienced more stress than males whatever their level of offending. One possible interpretation of these results is suggested by the feminist literature, which could account for both the higher levels of stress and lower levels of offending found among women drivers. However, there is unlikely to be a clear-cut gender divide in offending-stress relationships, and some small groups of female drivers in the study behaved like male ones. It is suggested that people's driving reflects their lifestyles, and that women drivers' patterns of offending and stress will resemble those of male drivers to the extent that their lives and concerns are similar to men's. It is concluded that this position warrants further research.

  4. Oxidative stress and lowered total antioxidant status are associated with a history of suicide attempts.

    Science.gov (United States)

    Vargas, Heber Odebrecht; Nunes, Sandra Odebrecht Vargas; Pizzo de Castro, Marcia; Bortolasci, Chiara Cristina; Sabbatini Barbosa, Décio; Kaminami Morimoto, Helena; Venugopal, Kamalesh; Dodd, Seetal; Maes, Michael; Berk, Michael

    2013-09-25

    There is evidence that depression is accompanied by inflammation, oxidative and nitrosative stress (O&NS) and metabolic disorders. However links between oxidative stress and suicide attempts in depressed patients are poorly understood. This study examines whether a history of suicide attempts is associated with inflammation, O&NS and metabolic disorders. Blood specimens were collected from study participants aged 18-60 (N=342) recruited at the State University of Londrina, Brazil, and measured for oxidative stress biomarkers: nitric oxide metabolites (NOx), lipid hydroperoxides, malondialdehyde, advanced oxidation protein products and plasma total antioxidant potential (TRAP); inflammatory biomarkers: fibrinogen, high-sensitivity C-reactive protein, erythrocyte sedimentation rate, interleukin-6 and tumor necrosis factor-α; and metabolic variables. Subjects were divided into those with (n=141) and without (n=201) a history of suicidal attempts. Individuals with a history of suicide attempts had significantly higher levels of NOx and lipid hydroperoxides and lowered TRAP as compared to individuals without suicide attempts. There were no significant associations between a history of suicide attempts and inflammatory and metabolic biomarkers and metabolic syndrome. Logistic regression showed that both unipolar and bipolar disorder, female gender, smoking behavior and lipid hydroperoxides were significantly associated with a history of suicide attempts. The combined effects of oxidative stress, smoking, depression, female gender were independent from classical risk factors, including marital status, years of education and anxiety. O&NS as well as lowered antioxidant levels may play a role in the pathophysiology of suicidal behavior independently from the effects of depression and smoking, both of which are associated with increased O&NS, and classical suicide predictors, such as years of education and marital status. © 2013 Published by Elsevier B.V.

  5. The competition between thermal contraction and differentiation in the stress history of the moon

    Science.gov (United States)

    Kirk, Randolph L.; Stevenson, David J.

    1989-01-01

    The stress history of the moon is discussed, taking into consideration the effects of thermal contraction and differentiation. The amount of expansion caused by extracting basalt from undifferentiated lunar material is estimated taking account of the uncertainty in the knowledge of the appropriate compositions, and the resulting estimate of the expansion is used to compare the relative importance of the thermal and differentiation effects in the moon's volumetric history. The results of calculations show that differentiation is likely to be of major importance and, thus, thermal expansion is not the sole possible contributor to evolutionary changes in the lunar radius.

  6. Effects of prior stress history on the irradiation creep of 20% cold-worked AISI 316 stainless steel

    International Nuclear Information System (INIS)

    Chin, B.A.; Straalsund, J.L.; Wire, G.L.

    1979-01-01

    The following conclusions resulted from this study: An in-reactor transient component of creep is found to occur whenever the stress level is increased. The transient is principally a thermal process, short in duration, and only weakly dependent on flux. The observed irradiation component of in-reactor creep is independent of prior stress history. Microstructural development during irradiation is influenced predominantly by the irradiation flux and temperature variables, and only to a minor extent by the irradiation stress history. (Auth.)

  7. History of chronic stress modifies acute stress-evoked fear memory and acoustic startle in male rats.

    Science.gov (United States)

    Schmeltzer, Sarah N; Vollmer, Lauren L; Rush, Jennifer E; Weinert, Mychal; Dolgas, Charles M; Sah, Renu

    2015-01-01

    Chronicity of trauma exposure plays an important role in the pathophysiology of posttraumatic stress disorder (PTSD). Thus, exposure to multiple traumas on a chronic scale leads to worse outcomes than acute events. The rationale for the current study was to investigate the effects of a single adverse event versus the same event on a background of chronic stress. We hypothesized that a history of chronic stress would lead to worse behavioral outcomes than a single event alone. Male rats (n = 14/group) were exposed to either a single traumatic event in the form of electric foot shocks (acute shock, AS), or to footshocks on a background of chronic stress (chronic variable stress-shock, CVS-S). PTSD-relevant behaviors (fear memory and acoustic startle responses) were measured following 7 d recovery. In line with our hypothesis, CVS-S elicited significant increases in fear acquisition and conditioning versus the AS group. Unexpectedly, CVS-S elicited reduced startle reactivity to an acoustic stimulus in comparison with the AS group. Significant increase in FosB/ΔFosB-like immunostaining was observed in the dentate gyrus, basolateral amygdala and medial prefrontal cortex of CVS-S rats. Assessments of neuropeptide Y (NPY), a stress-regulatory transmitter associated with chronic PTSD, revealed selective reduction in the hippocampus of CVS-S rats. Collectively, our data show that cumulative stress potentiates delayed fear memory and impacts defensive responding. Altered neuronal activation in forebrain limbic regions and reduced NPY may contribute to these phenomena. Our preclinical studies support clinical findings reporting worse PTSD outcomes stemming from cumulative traumatization in contrast to acute trauma.

  8. Toxic stress history and hypothalamic-pituitary-adrenal axis function in a social stress task: Genetic and epigenetic factors.

    Science.gov (United States)

    Lapp, Hannah E; Ahmed, Sarah; Moore, Celia L; Hunter, Richard G

    2018-02-21

    Histories of early life stress (ELS) or social discrimination can reach levels of severity characterized as toxic to mental and physical health. Such toxic social stress during development has been linked to altered acute hypothalamic-pituitary-adrenal (HPA) response to social stress in adulthood. However, there are important individual differences in the size and direction of these effects. We explored developmental, genetic, epigenetic, and contextual sources of individual differences in the relationship between ELS, discrimination, and adult responses to acute social stress in a standard laboratory test. Additional measures included perceived status, social support, background activity of HPA axis, and genetic variants in aspects of the stress response system. Participants (n = 90) answered questions about historical and ongoing stress, provided a DNA sample to examine genetic polymorphisms and epigenetic marks, and underwent the Trier Social Stress Test (TSST) during which three saliva samples were collected to assess HPA function. Individuals who reported high levels of childhood adversity had a blunted salivary cortisol response to the TSST. Childhood adversity, discrimination experiences, and FKBP5 genotype were found to predict pretest cortisol levels. Following up on recent observations that the glucocorticoid receptor directly interacts with the mitochondrial genome, particularly the NADH dehydrogenase 6 (MT-ND6) gene, individuals who reported high childhood adversity were also found to have higher percent methylation across six CpG sites upstream of MT-ND6. These findings suggest multiple contributions across psychological, genetic, epigenetic, and social domains to vulnerability and resilience in hypothalamic-pituitary-adrenal axis regulation. Further study to examine how these multiple contributors affect developmental endpoints through integrated or independent pathways will be of use. Copyright © 2018 Elsevier Inc. All rights reserved.

  9. Muscle stiffness of posterior lower leg in runners with a history of medial tibial stress syndrome.

    Science.gov (United States)

    Saeki, J; Nakamura, M; Nakao, S; Fujita, K; Yanase, K; Ichihashi, N

    2018-01-01

    Previous history of medial tibial stress syndrome (MTSS) is a risk factor for MTSS relapse, which suggests that there might be some physical factors that are related to MTSS development in runners with a history of MTSS. The relationship between MTSS and muscle stiffness can be assessed in a cross-sectional study that measures muscle stiffness in subjects with a history of MTSS, who do not have pain at the time of measurement, and in those without a history of MTSS. The purpose of this study was to compare the shear elastic modulus, which is an index of muscle stiffness, of all posterior lower leg muscles of subjects with a history of MTSS and those with no history and investigate which muscles could be related to MTSS. Twenty-four male collegiate runners (age, 20.0±1.7 years; height, 172.7±4.8 cm; weight, 57.3±3.7 kg) participated in this study; 14 had a history of MTSS, and 10 did not. The shear elastic moduli of the lateral gastrocnemius, medial gastrocnemius, soleus, peroneus longus, peroneus brevis, flexor hallucis longus, flexor digitorum longus, and tibialis posterior were measured using shear wave elastography. The shear elastic moduli of the flexor digitorum longus and tibialis posterior were significantly higher in subjects with a history of MTSS than in those with no history. However, there was no significant difference in the shear elastic moduli of other muscles. The results of this study suggest that flexor digitorum longus and tibialis posterior stiffness could be related to MTSS. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  10. Numerical simulation of stress wave propagation from underground nuclear explosions

    Energy Technology Data Exchange (ETDEWEB)

    Cherry, J T; Petersen, F L [Lawrence Radiation Laboratory, University of California, Livermore, CA (United States)

    1970-05-01

    This paper presents a numerical model of stress wave propagation (SOC) which uses material properties data from a preshot testing program to predict the stress-induced effects on the rock mass involved in a Plowshare application. SOC calculates stress and particle velocity history, cavity radius, extent of brittle failure, and the rock's efficiency for transmitting stress. The calculations are based on an equation of state for the rock, which is developed from preshot field and laboratory measurements of the rock properties. The field measurements, made by hole logging, determine in situ values of the rock's density, water content, and propagation velocity for elastic waves. These logs also are useful in judging the layering of the rock and in choosing which core samples to test in the laboratory. The laboratory analysis of rock cores includes determination of hydrostatic compressibility to 40 kb, triaxial strength data, tensile strength, Hugoniot elastic limit, and, for the rock near the point of detonation, high-pressure Hugoniot data. Equation-of-state data are presented for rock from three sites subjected to high explosive or underground nuclear shots, including the Hardhat and Gasbuggy sites. SOC calculations of the effects of these two shots on the surrounding rock are compared with the observed effects. In both cases SOC predicts the size of the cavity quite closely. Results of the Gasbuggy calculations indicate that useful predictions of cavity size and chimney height can be made when an adequate preshot testing program is run to determine the rock's equation of state. Seismic coupling is very sensitive to the low-pressure part of the equation of state, and its successful prediction depends on agreement between the logging data and the static compressibility data. In general, it appears that enough progress has been made in calculating stress wave propagation to begin looking at derived numbers, such as number of cracks per zone, for some insight into the

  11. Numerical simulation of stress wave propagation from underground nuclear explosions

    International Nuclear Information System (INIS)

    Cherry, J.T.; Petersen, F.L.

    1970-01-01

    This paper presents a numerical model of stress wave propagation (SOC) which uses material properties data from a preshot testing program to predict the stress-induced effects on the rock mass involved in a Plowshare application. SOC calculates stress and particle velocity history, cavity radius, extent of brittle failure, and the rock's efficiency for transmitting stress. The calculations are based on an equation of state for the rock, which is developed from preshot field and laboratory measurements of the rock properties. The field measurements, made by hole logging, determine in situ values of the rock's density, water content, and propagation velocity for elastic waves. These logs also are useful in judging the layering of the rock and in choosing which core samples to test in the laboratory. The laboratory analysis of rock cores includes determination of hydrostatic compressibility to 40 kb, triaxial strength data, tensile strength, Hugoniot elastic limit, and, for the rock near the point of detonation, high-pressure Hugoniot data. Equation-of-state data are presented for rock from three sites subjected to high explosive or underground nuclear shots, including the Hardhat and Gasbuggy sites. SOC calculations of the effects of these two shots on the surrounding rock are compared with the observed effects. In both cases SOC predicts the size of the cavity quite closely. Results of the Gasbuggy calculations indicate that useful predictions of cavity size and chimney height can be made when an adequate preshot testing program is run to determine the rock's equation of state. Seismic coupling is very sensitive to the low-pressure part of the equation of state, and its successful prediction depends on agreement between the logging data and the static compressibility data. In general, it appears that enough progress has been made in calculating stress wave propagation to begin looking at derived numbers, such as number of cracks per zone, for some insight into the

  12. Simulating the Thermal History of the Unsaturated Zone at Yucca Mountain, Nevada

    International Nuclear Information System (INIS)

    B.D. Marshal; J.F. Whelan

    2001-01-01

    Heat transfer within Earth's upper crust is primarily by conduction, and conductive thermal models adequately explain the cooling history of deep, batholith-scale intrusions and surrounding wall rocks, as confirmed by numerous thermochronometric studies. However, caldera magmatic systems require consideration of the small and localized component of hydrothermal convection and numerical models to simulate additional boundary conditions, irregular magma chamber shapes, and complex intrusive histories. At Yucca Mountain, Nevada, the site of a potential high-level nuclear waste repository, simulating the detailed thermal history at any location in the unsaturated zone requires knowledge of the shape of the magma chamber and its proximity to Yucca Mountain (the southern margin of the Timber Mountain caldera complex is approximately 8 km north of the potential repository site), the temporal and spatial extent of hydrothermal convection, the erosional history of the area, and past levels of the water table

  13. Simulations of stress-induced twinning and de-twinning: A phase field model

    International Nuclear Information System (INIS)

    Hu Shenyang; Henager, Chuck H.; Chen Longqing

    2010-01-01

    Twinning in certain metals or under certain conditions is a major plastic deformation mode. Here we present a phase field model to describe twin formation and evolution in a polycrystalline fcc metal under loading and unloading. The model assumes that twin nucleation, growth and de-twinning is a process of partial dislocation nucleation and slip on successive habit planes. Stacking fault energies, energy pathways (γ surfaces), critical shear stresses for the formation of stacking faults and dislocation core energies are used to construct the thermodynamic model. The simulation results demonstrate that the model is able to predict the nucleation of twins and partial dislocations, as well as the morphology of the twin nuclei, and to reasonably describe twin growth and interaction. The twin microstructures at grain boundaries are in agreement with experimental observation. It was found that de-twinning occurs during unloading in the simulations, however, a strong dependence of twin structure evolution on loading history was observed.

  14. A primary simulation for residual stress neutron diffractometer

    International Nuclear Information System (INIS)

    Wang Shuying; Liu Lijuan; Sun Liangwei

    2012-01-01

    At present, neutron diffraction method is the unique and nondestructive method that can directly measure the residual stress distribution in deep materials and engineering components. It has an important application in engineering. A simulation of the flux at the position of the sample table was reported, and the resolution of the residual stress instrument was computed at the same time. The effect of the parameters of the second collimator on the flux at the sample position and the resolution of the instrument have been analyzed. The result indicated that the second collimator empress much on the neutron flux and the instrument resolution is well when the sample's diffraction angle is less than 120°. (authors)

  15. Quantitative genetic analysis of life-history traits of Caenorhabditis elegans in stressful environments

    Directory of Open Access Journals (Sweden)

    Shorto Alison

    2008-01-01

    Full Text Available Abstract Background Organisms live in environments that vary. For life-history traits that vary across environments, fitness will be maximised when the phenotype is appropriately matched to the environmental conditions. For the free-living nematode Caenorhabditis elegans, we have investigated how two major life-history traits, (i the development of environmentally resistant dauer larvae and (ii reproduction, respond to environmental stress (high population density and low food availability, and how these traits vary between lines and the genetic basis of this variation. Results We found that lines of C. elegans vary in their phenotypic plasticity of dauer larva development, i.e. there is variation in the likelihood of developing into a dauer larva for the same environmental change. There was also variation in how lifetime fecundity and the rate of reproduction changed under conditions of environmental stress. These traits were related, such that lines that are highly plastic for dauer larva development also maintain a high population growth rate when stressed. We identified quantitative trait loci (QTL on two chromosomes that control the dauer larva development and population size phenotypes. The QTLs affecting the dauer larva development and population size phenotypes on chromosome II are closely linked, but are genetically separable. This chromosome II QTL controlling dauer larva development does not encompass any loci previously identified to control dauer larva development. This chromosome II region contains many predicted 7-transmembrane receptors. Such proteins are often involved in information transduction, which is clearly relevant to the control of dauer larva development. Conclusion C. elegans alters both its larval development and adult reproductive strategy in response to environmental stress. Together the phenotypic and genotypic data suggest that these two major life-history traits are co-ordinated responses to environmental stress

  16. Maternal history of child abuse moderates the association between daily stress and diurnal cortisol in pregnancy: a pilot study.

    Science.gov (United States)

    Bublitz, Margaret H; Stroud, Laura R

    2013-11-01

    Previous research on the association between maternal daily stress and cortisol in pregnancy has yielded inconsistent findings. However, past studies have not considered whether stressful experiences in childhood impact maternal cortisol regulation in pregnancy. In this pilot study, we aimed to examine whether the association between maternal daily stress and cortisol differed according to maternal history of child abuse. Forty-one women provided salivary cortisol samples at wake-up, 30 min after wake-up, and bedtime for 3 days at three times over second and third trimesters of pregnancy. On each day of cortisol collection women reported their daily stress. Women reported child abuse experiences prior to age 18 years by completing 15 items from the Adverse Childhood Experiences Scale. Twenty-one percent (N = 9) of women reported a history of child sexual abuse (CSA), 44% (N = 18) reported a history of non-sexual child abuse and 34% (N = 14) reported no history of child abuse. Hierarchical Linear Modeling (HLM) analyses revealed that stress in the day prior was associated with increases in morning cortisol in women with CSA histories compared to women with non-sexual abuse histories or no history of child abuse. Increases in evening cortisol were associated with increases in daily stress in women with CSA histories compared to women with non-sexual abuse histories or no history of child abuse. Results reveal a dynamic association between daily stress and cortisol in pregnancy and suggest that patterns differ according to maternal child abuse history.

  17. Bone geometry, strength, and muscle size in runners with a history of stress fracture.

    Science.gov (United States)

    Popp, Kristin L; Hughes, Julie M; Smock, Amanda J; Novotny, Susan A; Stovitz, Steven D; Koehler, Scott M; Petit, Moira A

    2009-12-01

    Our primary aim was to explore differences in estimates of tibial bone strength, in female runners with and without a history of stress fractures. Our secondary aim was to explore differences in bone geometry, volumetric density, and muscle size that may explain bone strength outcomes. A total of 39 competitive distance runners aged 18-35 yr, with (SFX, n = 19) or without (NSFX, n = 20) a history of stress fracture were recruited for this cross-sectional study. Peripheral quantitative computed tomography (XCT 3000; Orthometrix, White Plains, NY) was used to assess volumetric bone mineral density (vBMD, mg x mm(-3)), bone area (ToA, mm(2)), and estimated compressive bone strength (bone strength index (BSI) = ToA x total volumetric density (ToD(2))) at the distal tibia (4%). Total (ToA, mm(2)) and cortical (CoA, mm(2)) bone area, cortical vBMD, and estimated bending strength (strength-strain index (SSIp), mm(3)) were measured at the 15%, 25%, 33%, 45%, 50%, and 66% sites. Muscle cross-sectional area (MCSA) was measured at the 50% and 66% sites. Participants in the SFX group had significantly smaller (7%-8%) CoA at the 45%, 50%, and 66% sites (P stress fracture. However, the lower strength was appropriate for the smaller muscle size, suggesting that interventions to reduce stress fracture risk might be aimed at improving muscle size and strength.

  18. The study of fkbp and ubiquitin reveals interesting aspects of Artemia stress history.

    Science.gov (United States)

    Maniatsi, Stefania; Farmaki, Theodora; Abatzopoulos, Theodore J

    2015-08-01

    Research on stress responses in animals has increased greatly during the last decades. Though most studies focus on the cellular and molecular bases of the stress response mechanisms, the ecological and evolutionary aspects of stress responses gain more and more interest. Here, we use species and parthenogenetic strains of the genus Artemia, an extremophile model organism, to study, for the first time, a protein well known for its chaperone activity and its involvement in stress responses. More specifically, transcription and protein accumulation of an FK506-Binding Protein (FKBP) homologue were investigated under heat and salt stresses. Additionally, the mRNA levels of ubiquitin, a heat-inducible protein related to the proteasomal pathway, were quantitated under these conditions. Biochemical and phylogenetic analyses showed that the studied FKBP orthologue is a typical representative of the family that clusters with other crustacean sequences. The expression was increased in both fkbp and ubiquitin genes after salt and heat stresses. However, our results in combination with the fact that Artemia species and parthenogenetic strains, selected for this study, exhibit different heat or salt tolerance provide useful hints about the evolutionary significance of FKBP and ubiquitin. Regarding FKBP, mRNA expression and protein accumulation seem to depend on the environmental conditions and the evolutionary history of each Artemia population while ubiquitin has a clear and more conserved role under heat shock. Copyright © 2015 Elsevier Inc. All rights reserved.

  19. Distribution and natural history of stress fractures in U.S. Marine recruits

    International Nuclear Information System (INIS)

    Greaney, R.B.; Gerber, F.H.; Laughlin, R.L.; Kmet, J.P.; Metz, C.D.; Kilcheski, T.S.; Rao, B.R.; Silverman, E.D.

    1983-01-01

    In a prospective study of stress injuries of the lower extremities of U.S. Marine recruits, researchers derived a frequency distribution of stress fractures. The most frequently fractured bone was the tibia (73%), while the single most common site was the posterior calcaneal tuberosity (21%). The natural history of stress fractures by scintigraphy and radiography has been outlined, showing the evolutionary changes on either study as a universal progression independent of injury site or type of stress. An identical spectrum of changes should be present within any group undergoing intense new exercise. The frequency distribution of stress fractures should be a function of differing forms and intensities of exercise, therefore, our figures should not be applied to other groups. Researchers used the presence of a scintigraphic abnormality at a symptomatic site as the criterion for diagnosis of stress fracture. Since the distribution of skeletal radiotracer uptake is directly dependent on local metabolic activity, it is expected that a focal alteration in bone metabolism will result in a scintigram approaching 100% sensitivity for the abnormality (9). In the proper clinical setting, the specificity should approximate this figure; however, a focal, nonstress-related bone abnormality which has not manifested any radiographic change, such as early osteomyelitis, could result in a false-positive examination. Specificity cannot, therefore, be accurately determined without an actual determination of the pathologic changes within the bone, necessarily involving biopsy

  20. A re-examination of two-step lateral stress history in silicon carbide

    International Nuclear Information System (INIS)

    Dandekar, Dattatraya P.

    2004-01-01

    The observed two-step lateral stress history in silicon carbide, SiC-B under plane shock wave propagation [N. K. Bourne, J. Millett, and I. Pickup, J. Appl. Phys. 81, 6019 (1997)] is attributed to a delayed failure in SiC-B due to propagation of a slow moving front traveling behind the main shock wave. According to this attribution, the first lower magnitude, step corresponds to the lateral stress in intact shock compressed silicon carbide as a result of the fast moving plane shock wave. The second step of higher magnitude, observed after a few hundred nanoseconds, corresponds to the lateral stress in failed silicon carbide due to propagation of the slower moving front. The current analysis, takes into account additional relevant existing results dealing with shock response of SiC-B, and shows that the suggested explanation for the observed phenomenon remains in doubt

  1. Simulation of the collimator of the residual stress instrument

    International Nuclear Information System (INIS)

    Li, Jian; Wang, Xiaoying; Xie, Chaomei

    2009-04-01

    In order to understand the detailed influence from the collimator system to the main index of the Residual Stress Nertron Diffractometer (RSND) such as the flux at sample position, and the resolution of the spectrometer, the MCStas simulation software is used to build the proper Model of the Collimator system to complete the calculation and simulation. During the simulation, the authors setup the divergence and length of each collimator to check if it had big effect to the whole system. Based on the simulation, the authors obtained an optimized result: When the α 1 =α 2 =30', the horizontal flux at the sample position can be 2.3 x 10 6 n·cm -2 ·s -1 , the vertical flux can be 3.5 x 10 6 n·cm -2 ·s -1 , and when the α 1 =α 2 =10' the best resolution of the spectrometer can be 0.2 degree. This is a valuable result for the RDND. (authors)

  2. Evidence for altered brain reactivity to norepinephrine in Veterans with a history of traumatic stress

    Directory of Open Access Journals (Sweden)

    Rebecca C. Hendrickson

    2018-02-01

    Full Text Available Background: Increases in the quantity or impact of noradrenergic signaling have been implicated in the pathophysiology of posttraumatic stress disorder (PTSD. This increased signaling may result from increased norepinephrine (NE release, from altered brain responses to NE, or from a combination of both factors. Here, we tested the hypothesis that Veterans reporting a history of trauma exposure would show an increased association between brain NE and mental health symptoms commonly observed after trauma, as compared to Veterans who did not report a history of trauma exposure, consistent with the possibility of increased brain reactivity to NE after traumatic stress. Methods: Using a convenience sample of 69 male Veterans with a history of combat-theater deployment, we examined the relationship between trauma-related mental health symptoms and the concentration of NE in cerebrospinal fluid (CSF. CSF NE levels were measured by HPLC in CSF from morning lumbar puncture. Behavioral symptoms associated with diagnoses of PTSD, depression, insomnia, or post-concussive syndrome (PCS, which together cover a wide variety of symptoms associated with alterations in arousal systems, such as sleep, mood, concentration, and anxiety, were assessed via self-report (PTSD Checklist [PCL] for PTSD, Patient Health Questionnaire 9 [PHQ9] for depression, Pittsburgh Sleep Quality Index [PSQI] for sleep problems including insomnia, and Neurobehavioral Symptom Inventory [NSI] for PCS and structured clinical interview (Clinician-Administered PSTD Scale [CAPS]. Individuals meeting criterion A of the DSM-IV diagnostic criteria for PTSD were considered trauma-exposed. Linear regression models were used to quantify the association between CSF NE and symptom intensity in participants with and without a history of trauma exposure, as well as in participants with a history of trauma exposure who were currently taking the noradrenergic receptor antagonist prazosin. Results: Fifty

  3. Validity of a Simulation Game as a Method for History Teaching

    Science.gov (United States)

    Corbeil, Pierre; Laveault, Dany

    2011-01-01

    The aim of this research is, first, to determine the validity of a simulation game as a method of teaching and an instrument for the development of reasoning and, second, to study the relationship between learning and students' behavior toward games. The participants were college students in a History of International Relations course, with two…

  4. Quadratic genetic modifications: a streamlined route to cosmological simulations with controlled merger history

    Science.gov (United States)

    Rey, Martin P.; Pontzen, Andrew

    2018-02-01

    Recent work has studied the interplay between a galaxy's history and its observable properties using `genetically modified' cosmological zoom simulations. The approach systematically generates alternative histories for a halo, while keeping its cosmological environment fixed. Applications to date altered linear properties of the initial conditions, such as the mean overdensity of specified regions; we extend the formulation to include quadratic features, such as local variance, that determines the overall importance of smooth accretion relative to mergers in a galaxy's history. We introduce an efficient algorithm for this new class of modification and demonstrate its ability to control the variance of a region in a one-dimensional toy model. Outcomes of this work are twofold: (i) a clarification of the formulation of genetic modifications and (ii) a proof of concept for quadratic modifications leading the way to a forthcoming implementation in cosmological simulations.

  5. Chronic Stress and Adolescents' Mental Health : Modifying Effects of Basal Cortisol and Parental Psychiatric History. The TRAILS Study

    NARCIS (Netherlands)

    Zandstra, Anna Roos E.; Hartman, Catharina A.; Nederhof, Esther; van den Heuvel, Edwin R.; Dietrich, Andrea; Hoekstra, Pieter J.; Ormel, Johan

    Large individual differences in adolescent mental health following chronic psychosocial stress suggest moderating factors. We examined two established moderators, basal cortisol and parental psychiatric history, simultaneously. We hypothesized that individuals with high basal cortisol, assumed to

  6. The Inclusion of Arbitrary Load Histories in the Strength Decay Model for Stress Rupture

    Science.gov (United States)

    Reeder, James R.

    2014-01-01

    Stress rupture is a failure mechanism where failures can occur after a period of time, even though the material has seen no increase in load. Carbon/epoxy composite materials have demonstrated the stress rupture failure mechanism. In a previous work, a model was proposed for stress rupture of composite overwrap pressure vessels (COPVs) and similar composite structures based on strength degradation. However, the original model was limited to constant load periods (holds) at constant load. The model was expanded in this paper to address arbitrary loading histories and specifically the inclusions of ramp loadings up to holds and back down. The broadening of the model allows for failures on loading to be treated as any other failure that may occur during testing instead of having to be treated as a special case. The inclusion of ramps can also influence the length of the "safe period" following proof loading that was previously predicted by the model. No stress rupture failures are predicted in a safe period because time is required for strength to decay from above the proof level to the lower level of loading. Although the model can predict failures during the ramp periods, no closed-form solution for the failure times could be derived. Therefore, two suggested solution techniques were proposed. Finally, the model was used to design an experiment that could detect the difference between the strength decay model and a commonly used model for stress rupture. Although these types of models are necessary to help guide experiments for stress rupture, only experimental evidence will determine how well the model may predict actual material response. If the model can be shown to be accurate, current proof loading requirements may result in predicted safe periods as long as 10(13) years. COPVs design requirements for stress rupture may then be relaxed, allowing more efficient designs, while still maintaining an acceptable level of safety.

  7. MUSIDH, multiple use of simulated demographic histories, a novel method to reduce computation time in microsimulation models of infectious diseases.

    Science.gov (United States)

    Fischer, E A J; De Vlas, S J; Richardus, J H; Habbema, J D F

    2008-09-01

    Microsimulation of infectious diseases requires simulation of many life histories of interacting individuals. In particular, relatively rare infections such as leprosy need to be studied in very large populations. Computation time increases disproportionally with the size of the simulated population. We present a novel method, MUSIDH, an acronym for multiple use of simulated demographic histories, to reduce computation time. Demographic history refers to the processes of birth, death and all other demographic events that should be unrelated to the natural course of an infection, thus non-fatal infections. MUSIDH attaches a fixed number of infection histories to each demographic history, and these infection histories interact as if being the infection history of separate individuals. With two examples, mumps and leprosy, we show that the method can give a factor 50 reduction in computation time at the cost of a small loss in precision. The largest reductions are obtained for rare infections with complex demographic histories.

  8. Simulating fission product transients via the history-based local-parameter methodology

    International Nuclear Information System (INIS)

    Jenkins, D.A.; Rouben, B.; Salvatore, M.

    1993-01-01

    This paper describes the fission-product-calculation capacity of the history-based local-parameter methodology for evaluating lattice properties for use in core-tracking calculations in CANDU reactors. In addition to taking into account the individual past history of each bundles flux/power level, fuel temperature, and coolant density and temperature that the bundle has seen during its stay in the core, the latest refinement of the history-based method provides the capability of fission-product-drivers. It allows the bundle-specific concentrations of the three basic groups of saturating fission products to be calculated in steady state or following a power transient, including long shutdowns. The new capability is illustrated by simulating the startup period following a typical long-shutdown, starting from a snapshot in the Point Lepreau operating history. 9 refs., 7 tabs

  9. Prediction of thermal and mechanical stress-strain responses of TMC's subjected to complex TMF histories

    Science.gov (United States)

    Johnson, W. S.; Mirdamadi, M.

    1994-01-01

    This paper presents an experimental and analytical evaluation of cross-plied laminates of Ti-15V-3Cr-3Al-3Sn (Ti-15-3) matrix reinforced with continuous silicon-carbide fibers (SCS-6) subjected to a complex TMF loading profile. Thermomechanical fatigue test techniques were developed to conduct a simulation of a generic hypersonic flight profile. A micromechanical analysis was used. The analysis predicts the stress-strain response of the laminate and of the constituents in each ply during thermal and mechanical cycling by using only constituent properties as input. The fiber was modeled as elastic with transverse orthotropic and temperature-dependent properties. The matrix was modeled using a thermoviscoplastic constitutive relation. The fiber transverse modulus was reduced in the analysis to simulate the fiber-matrix interface failures. Excellent correlation was found between measured and predicted laminate stress-strain response due to generic hypersonic flight profile when fiber debonding was modeled.

  10. Manganese-enhanced magnetic resonance imaging (MEMRI) reveals brain circuitry involved in responding to an acute novel stress in rats with a history of repeated social stress.

    Science.gov (United States)

    Bangasser, Debra A; Lee, Catherine S; Cook, Philip A; Gee, James C; Bhatnagar, Seema; Valentino, Rita J

    2013-10-02

    Responses to acute stressors are determined in part by stress history. For example, a history of chronic stress results in facilitated responses to a novel stressor and this facilitation is considered to be adaptive. We previously demonstrated that repeated exposure of rats to the resident-intruder model of social stress results in the emergence of two subpopulations that are characterized by different coping responses to stress. The submissive subpopulation failed to show facilitation to a novel stressor and developed a passive strategy in the Porsolt forced swim test. Because a passive stress coping response has been implicated in the propensity to develop certain psychiatric disorders, understanding the unique circuitry engaged by exposure to a novel stressor in these subpopulations would advance our understanding of the etiology of stress-related pathology. An ex vivo functional imaging technique, manganese-enhanced magnetic resonance imaging (MEMRI), was used to identify and distinguish brain regions that are differentially activated by an acute swim stress (15 min) in rats with a history of social stress compared to controls. Specifically, Mn(2+) was administered intracerebroventricularly prior to swim stress and brains were later imaged ex vivo to reveal activated structures. When compared to controls, all rats with a history of social stress showed greater activation in specific striatal, hippocampal, hypothalamic, and midbrain regions. The submissive subpopulation of rats was further distinguished by significantly greater activation in amygdala, bed nucleus of the stria terminalis, and septum, suggesting that these regions may form a circuit mediating responses to novel stress in individuals that adopt passive coping strategies. The finding that different circuits are engaged by a novel stressor in the two subpopulations of rats exposed to social stress implicates a role for these circuits in determining individual strategies for responding to stressors

  11. Maternal Sadness and Adolescents' Responses to Stress in Offspring of Mothers with and without a History of Depression

    Science.gov (United States)

    Jaser, Sarah S.; Fear, Jessica M.; Reeslund, Kristen L.; Champion, Jennifer E.; Reising, Michelle M.; Compas, Bruce E.

    2008-01-01

    This study examined maternal sadness and adolescents' responses to stress in the offspring (n = 72) of mothers with and without a history of depression. Mothers with a history of depression reported higher levels of current depressive symptoms and exhibited greater sadness during interactions with their adolescent children (ages 11-14) than…

  12. The mediating effect of daily stress on the sexual arousal function of women with a history of childhood sexual abuse.

    Science.gov (United States)

    Zollman, Gena; Rellini, Alessandra; Desrocher, Danielle

    2013-01-01

    Psychopathologies such as posttraumatic stress disorder are often proposed as mediators of the sexual arousal dysfunction experienced by women with a history of childhood maltreatment. However, posttraumatic stress disorder symptoms are only part of the difficulties experienced by these women. Other factors to consider include negative affectivity and perceived daily stress. To assess the mediating role of posttraumatic stress disorder symptoms, negative affectivity, and perceived daily stress, we collected data from 62 women with and without a history of childhood maltreatment (sexual, physical and emotional abuse). A comprehensive assessment of sexual arousal functioning and sexual responses was obtained using self-reported measures and psychophysiological measures of vaginal engorgement and subjective sexual arousal during exposure to sexual visual stimuli. The model assessed the simultaneous mediating effect of posttraumatic stress disorder symptoms, negative affectivity and perceived daily stress on the relation between childhood maltreatment and sexual variables. Daily stress, showed a significant and stronger mediation effect on sexual arousal functioning as compared to posttraumatic stress disorder and negative affectivity. These findings suggest that daily stress may be an important mechanism to consider when treating sexual arousal functioning in women who have a history of childhood maltreatment.

  13. Exploring the Experience of Life Stress Among Black Women with a History of Fetal or Infant Death: a Phenomenological Study.

    Science.gov (United States)

    Brown, Kyrah K; Lewis, Rhonda K; Baumgartner, Elizabeth; Schunn, Christy; Maryman, J'Vonnah; LoCurto, Jamie

    2017-06-01

    Disparate birth outcomes among Black women continue to be a major public health problem. Whereas prior research has investigated the influence of stress on Black women's birth outcomes, few studies have explored how stress is experienced among Black women across the life course. The objectives of this study were to describe the experience of stress across the life course among Black women who reported a history of fetal or infant death and to identify stressful life events (SLE) that may not be represented in the widely used SLE inventory. Using phenomenological, qualitative research design, in-depth interviews were conducted with six Black women in Kansas who experienced a fetal or infant death. Analyses revealed that participants experienced multiple, co-occurring stressors over the course of their lives and experienced a proliferation of stress emerging in early life and persisting into adulthood. Among the types of stressors cited by participants, history of sexual assault (trauma-related stressor) was a key stressful life event that is not currently reflected in the SLE inventory. Our findings highlight the importance of using a life-course perspective to gain a contextual understanding of the experiences of stress among Black women, particularly those with a history of adverse birth outcomes. Further research investigating Black women's experiences of stress and the mechanisms by which stress impacts their health could inform efforts to reduce disparities in birth outcomes. An additional focus on the experience and impact of trauma-related stress on Black women's birth outcomes may also be warranted.

  14. Early life thermal stress: Impact on future thermotolerance, stress response, behavior, and intestinal morphology in piglets exposed to a heat stress challenge during simulated transport

    Science.gov (United States)

    Study objectives were to evaluate the impact of early life thermal stress (ELTS) on thermoregulation, stress, and intestinal health of piglets subjected to a future heat stress (HS) challenge during simulated transport. Approximately 7 d after farrowing, 12 first parity gilts and their litters were ...

  15. Bone strength estimates relative to vertical ground reaction force discriminates women runners with stress fracture history.

    Science.gov (United States)

    Popp, Kristin L; McDermott, William; Hughes, Julie M; Baxter, Stephanie A; Stovitz, Steven D; Petit, Moira A

    2017-01-01

    To determine differences in bone geometry, estimates of bone strength, muscle size and bone strength relative to load, in women runners with and without a history of stress fracture. We recruited 32 competitive distance runners aged 18-35, with (SFX, n=16) or without (NSFX, n=16) a history of stress fracture for this case-control study. Peripheral quantitative computed tomography (pQCT) was used to assess volumetric bone mineral density (vBMD, mg/mm 3 ), total (ToA) and cortical (CtA) bone areas (mm 2 ), and estimated compressive bone strength (bone strength index; BSI, mg/mm 4 ) at the distal tibia. ToA, CtA, cortical vBMD, and estimated strength (section modulus; Zp, mm 3 and strength strain index; SSIp, mm 3 ) were measured at six cortical sites along the tibia. Mean active peak vertical (pkZ) ground reaction forces (GRFs), assessed from a fatigue run on an instrumented treadmill, were used in conjunction with pQCT measurements to estimate bone strength relative to load (mm 2 /N∗kg -1 ) at all cortical sites. SSIp and Zp were 9-11% lower in the SFX group at mid-shaft of the tibia, while ToA and vBMD did not differ between groups at any measurement site. The SFX group had 11-17% lower bone strength relative to mean pkZ GRFs (phistory of stress fracture. Bone strength relative to load is also lower in this same region suggesting that strength deficits in the middle 1/3 of the tibia and altered gait biomechanics may predispose an individual to stress fracture. Copyright © 2016. Published by Elsevier Inc.

  16. A tool for assessing case history and feedback skills in audiology students working with simulated patients.

    Science.gov (United States)

    Hughes, Jane; Wilson, Wayne J; MacBean, Naomi; Hill, Anne E

    2016-12-01

    To develop a tool for assessing audiology students taking a case history and giving feedback with simulated patients (SP). Single observation, single group design. Twenty-four first-year audiology students, five simulated patients, two clinical educators, and three evaluators. The Audiology Simulated Patient Interview Rating Scale (ASPIRS) was developed consisting of six items assessing specific clinical skills, non-verbal communication, verbal communication, interpersonal skills, interviewing skills, and professional practice skills. These items are applied once for taking a case history and again for giving feedback. The ASPIRS showed very high internal consistency (α = 0.91-0.97; mean inter-item r = 0.64-0.85) and fair-to-moderate agreement between evaluators (29.2-54.2% exact and 79.2-100% near agreement; κ weighted up to 0.60). It also showed fair-to-moderate absolute agreement amongst evaluators for single evaluator scores (intraclass correlation coefficient [ICC] r = 0.35-0.59) and substantial consistency of agreement amongst evaluators for three-evaluator averaged scores (ICC r = 0.62-0.81). Factor analysis showed the ASPIRS' 12 items fell into two components, one containing all feedback items and one containing all case history items. The ASPIRS shows promise as the first published tool for assessing audiology students taking a case history and giving feedback with an SP.

  17. Differential Gene Expression of Longan Under Simulated Acid Rain Stress.

    Science.gov (United States)

    Zheng, Shan; Pan, Tengfei; Ma, Cuilan; Qiu, Dongliang

    2017-05-01

    Differential gene expression profile was studied in Dimocarpus longan Lour. in response to treatments of simulated acid rain with pH 2.5, 3.5, and a control (pH 5.6) using differential display reverse transcription polymerase chain reaction (DDRT-PCR). Results showed that mRNA differential display conditions were optimized to find an expressed sequence tag (EST) related with acid rain stress. The potential encoding products had 80% similarity with a transcription initiation factor IIF of Gossypium raimondii and 81% similarity with a protein product of Theobroma cacao. This fragment is the transcription factor activated by second messenger substances in longan leaves after signal perception of acid rain.

  18. Gene and stress history interplay in emergence of PTSD-like features.

    Science.gov (United States)

    Chakraborty, Nabarun; Meyerhoff, James; Gautam, Aarti; Muhie, Seid; Jibitu, Meskerem; De Lima, Thereza C M; Hammamieh, Rasha; Jett, Marti

    2015-10-01

    Systematically distinguishing genetic liability from other contributing factors is critical for designing a preventive strategy for post-traumatic stress disorder (PTSD). To address this issue, we investigated a murine model exposing C57BL/6j, DBA/2j and BALB/cj mice to repeated stress via exposure to conspecific aggressors (Agg-E). Naïve mice from each strain were subjected to the proximity of aggressor (Agg) mice for 6h using a 'cage-within-a-cage' paradigm, which was repeated for 5 or 10 days with intermittent and unpredictable direct contact with Agg mice. During the Agg-E stress, DBA/2j developed a different strategy to evade Agg mice, which potentially contributed to its phenotypic resilience to Agg-E stress. Although Agg mice inflicted C57BL/6j and BALB/cj with equivalent numbers of strikes, BALB/cj displayed a distinct behavioral phenotype with delayed exhibition of a number of PTSD-like features. By contrast, C57BL/6j mice displayed unique vulnerability to Agg-E stress induced myocardopathy, possibly attributable to their particular susceptibility to hypoxia. A group of genes (Bdnf, Ngf, Zwint, Cckbr, Slc6a4, Fkbp5) linked to PTSD and synaptic plasticity were significantly altered in C57BL/6j and BALB/cj Agg-E mice. Contributions of Agg-E stress history and genotypic heterogeneity emerged as the key mediators of PTSD-like features. Linking genetic components to specific phenotypic and pathological features could have potential clinical implications. Copyright © 2015 Elsevier B.V. All rights reserved.

  19. Evolutionary history and stress regulation of the lectin superfamily in higher plants

    Directory of Open Access Journals (Sweden)

    Ramachandran Srinivasan

    2010-03-01

    Full Text Available Abstract Background Lectins are a class of carbohydrate-binding proteins. They play roles in various biological processes. However, little is known about their evolutionary history and their functions in plant stress regulation. The availability of full genome sequences from various plant species makes it possible to perform a whole-genome exploration for further understanding their biological functions. Results Higher plant genomes encode large numbers of lectin proteins. Based on their domain structures and phylogenetic analyses, a new classification system has been proposed. In this system, 12 different families have been classified and four of them consist of recently identified plant lectin members. Further analyses show that some of lectin families exhibit species-specific expansion and rapid birth-and-death evolution. Tandem and segmental duplications have been regarded as the major mechanisms to drive lectin expansion although retrogenes also significantly contributed to the birth of new lectin genes in soybean and rice. Evidence shows that lectin genes have been involved in biotic/abiotic stress regulations and tandem/segmental duplications may be regarded as drivers for plants to adapt various environmental stresses through duplication followed by expression divergence. Each member of this gene superfamily may play specialized roles in a specific stress condition and function as a regulator of various environmental factors such as cold, drought and high salinity as well as biotic stresses. Conclusions Our studies provide a new outline of the plant lectin gene superfamily and advance the understanding of plant lectin genes in lineage-specific expansion and their functions in biotic/abiotic stress-related developmental processes.

  20. Sex and family history of cardiovascular disease influence heart rate variability during stress among healthy adults.

    Science.gov (United States)

    Emery, Charles F; Stoney, Catherine M; Thayer, Julian F; Williams, DeWayne; Bodine, Andrew

    2018-07-01

    Studies of sex differences in heart rate variability (HRV) typically have not accounted for the influence of family history (FH) of cardiovascular disease (CVD). This study evaluated sex differences in HRV response to speech stress among men and women (age range 30-49 years) with and without a documented FH of CVD. Participants were 77 adults (mean age = 39.8 ± 6.2 years; range: 30-49 years; 52% female) with positive FH (FH+, n = 32) and negative FH (FH-, n = 45) of CVD, verified with relatives of participants. Cardiac activity for all participants was recorded via electrocardiogram during a standardized speech stress task with three phases: 5-minute rest, 5-minute speech, and 5-minute recovery. Outcomes included time domain and frequency domain indicators of HRV and heart rate (HR) at rest and during stress. Data were analyzed with repeated measures analysis of variance, with sex and FH as between subject variables and time/phase as a within subject variable. Women exhibited higher HR than did men and greater HR reactivity in response to the speech stress. However, women also exhibited greater HRV in both the time and frequency domains. FH+ women generally exhibited elevated HRV, despite the elevated risk of CVD associated with FH+. Although women participants exhibited higher HR at rest and during stress, women (both FH+ and FH-) also exhibited elevated HRV reactivity, reflecting greater autonomic control. Thus, enhanced autonomic function observed in prior studies of HRV among women is also evident among FH+ women during a standardized stress task. Copyright © 2018 Elsevier Inc. All rights reserved.

  1. Stratigraphy and Stress History Recorded by a Complex Volcano-Tectonic Feature in the Nemesis Tessera Quadrangle, Venus

    Science.gov (United States)

    Doggett, T. C.; Grosfils, E. B.

    2002-01-01

    The stress history of a feature, identified as a previously uncataloged dike swarm, at 45N 191E is mapped as clockwise rotation of maximum horizontal compressive stress. It is intermediate between areas associated with compression, mantle upwelling and convection. Additional information is contained in the original extended abstract.

  2. Stress analysis and deformation prediction of sheet metal workpieces based on finite element simulation

    OpenAIRE

    Ren Penghao; Wang Aimin; Wang Xiaolong; Zhang Yanlin

    2017-01-01

    After aluminum alloy sheet metal parts machining, the residual stress release will cause a large deformation. To solve this problem, this paper takes a aluminum alloy sheet aerospace workpiece as an example, establishes the theoretical model of elastic deformation and the finite element model, and places quantitative initial stress in each element of machining area, analyses stress release simulation and deformation. Through different initial stress release simulative analysis of deformation ...

  3. Stress analysis and deformation prediction of sheet metal workpieces based on finite element simulation

    Directory of Open Access Journals (Sweden)

    Ren Penghao

    2017-01-01

    Full Text Available After aluminum alloy sheet metal parts machining, the residual stress release will cause a large deformation. To solve this problem, this paper takes a aluminum alloy sheet aerospace workpiece as an example, establishes the theoretical model of elastic deformation and the finite element model, and places quantitative initial stress in each element of machining area, analyses stress release simulation and deformation. Through different initial stress release simulative analysis of deformation of the workpiece, a linear relationship between initial stress and deformation is found; Through simulative analysis of coupling direction-stress release, the superposing relationship between the deformation caused by coupling direction-stress and the deformation caused by single direction stress is found. The research results provide important theoretical support for the stress threshold setting and deformation controlling of the workpieces in the production practice.

  4. Structure simulation of a pre-stressed concrete containment model

    International Nuclear Information System (INIS)

    Grebner, H.; Sievers, J.

    2004-01-01

    An axisymmetric Finite-Element-Model of the 1:4 pre-stressed containment model tested at SANDIA was developed. The model is loaded by the pre-stressing of the tendons and by increasing internal pressure (up to 1.3 MPa). The analyses results in terms of displacements and strains in the liner, the rebars, the tendons and the concrete of the cylindrical part agree well with measured data up to about 0.6 MPa internal pressure (i.e. 1.5 times design pressure). First circumferential micro-cracks in the concrete are found at about 0.75 MPa. With increasing pressure micro-cracks are present through the whole wall. Above about 0.9 MPa the formation of micro-cracks in radial and meridional direction is calculated. At the maximum load (1.3 MPa) almost all concrete parts of the model have micro-cracks which may cause leaks. Nevertheless the failure of the containment model is not expected for loads up to 1.3 MPa without consideration of geometric inhomogeneities due to penetrations in the wall. Although the calculated strains in liner, rebars and tendons show some plastification, the maximum values are below the critical ones. The safety margin against failure is smallest in some hoop tendons. At present parametric studies are performed to investigate the differences between calculations and measured data. Furthermore three-dimensional models are developed for a better simulation of the meridional tendons in the dome region. (orig.)

  5. Ankle and toe muscle strength characteristics in runners with a history of medial tibial stress syndrome.

    Science.gov (United States)

    Saeki, Junya; Nakamura, Masatoshi; Nakao, Sayaka; Fujita, Kosuke; Yanase, Ko; Morishita, Katsuyuki; Ichihashi, Noriaki

    2017-01-01

    A high proportion of flexor digitorum longus attachment is found at the posteromedial border of the tibia, which is the most common location of medial tibial stress syndrome (MTSS). Therefore, plantar flexion strength of the lesser toes could be related to MTSS; however, the relationship between MTSS and muscle strength of the hallux and lesser toes is not yet evaluated due to the lack of quantitative methods. This study investigated the muscle strength characteristics in runners with a history of MTSS by using a newly developed device to measure the muscle strength of the hallux, lesser toes, and ankle. This study comprised 27 collegiate male runner participants (20.0 ± 1.6 years, 172.1 ± 5.1 cm, 57.5 ± 4.0 kg). Maximal voluntary isometric contraction (MVIC) torque of the plantar flexion, dorsiflexion, inversion, and eversion of the ankle were measured by using an electric dynamometer. MVIC torque of the 1st metatarsophalangeal joint (MTPJ) and 2nd-5th MTPJ were measured by using a custom-made torque-measuring device. MVIC torques were compared between runners with and without a history of MTSS. MVIC torque of the 1st MTPJ plantar flexion was significantly higher in runners with a history of MTSS than in those without it. In contrast, there were no significant differences in the MVIC torque values of the 2nd-5th MTPJ plantar flexion and each MVIC torque of the ankle between runners with and without a history of MTSS. A history of MTSS increased the isometric FHL strength.

  6. CFD simulation of estimating critical shear stress for cleaning flat ...

    Indian Academy of Sciences (India)

    Sumit Kawale

    2017-11-22

    Nov 22, 2017 ... Jet impingement; wall shear stress; cleaning of flat plate; turbulence model; critical shear stress; ... On comparing the theoretical predictions with wall shear ... distance and Reynolds number on peak value of local shear stress ...

  7. Chronic Stress and Adolescents' Mental Health: Modifying Effects of Basal Cortisol and Parental Psychiatric History. The TRAILS Study.

    Science.gov (United States)

    Zandstra, Anna Roos E; Hartman, Catharina A; Nederhof, Esther; van den Heuvel, Edwin R; Dietrich, Andrea; Hoekstra, Pieter J; Ormel, Johan

    2015-08-01

    Large individual differences in adolescent mental health following chronic psychosocial stress suggest moderating factors. We examined two established moderators, basal cortisol and parental psychiatric history, simultaneously. We hypothesized that individuals with high basal cortisol, assumed to indicate high context sensitivity, would show relatively high problem levels following chronic stress, especially in the presence of parental psychiatric history. With Linear Mixed Models, we investigated the hypotheses in 1917 Dutch adolescents (53.2% boys), assessed at ages 11, 13.5, and 16. Low basal cortisol combined with the absence of a parental psychiatric history increased the risk of externalizing but not internalizing problems following chronic stress. Conversely, low basal cortisol combined with a substantial parental psychiatric history increased the risk of internalizing but not externalizing problems following chronic stress. Thus, parental psychiatric history moderated stress- cortisol interactions in predicting psychopathology, but in a different direction than hypothesized. We conclude that the premise that basal cortisol indicates context sensitivity may be too crude. Context sensitivity may not be a general trait but may depend on the nature of the context (e.g., type or duration of stress exposure) and on the outcome of interest (e.g., internalizing vs. externalizing problems). Although consistent across informants, our findings need replication.

  8. High performance thermal stress analysis on the earth simulator

    International Nuclear Information System (INIS)

    Noriyuki, Kushida; Hiroshi, Okuda; Genki, Yagawa

    2003-01-01

    In this study, the thermal stress finite element analysis code optimized for the earth simulator was developed. A processor node of which of the earth simulator is the 8-way vector processor, and each processor can communicate using the message passing interface. Thus, there are two ways to parallelize the finite element method on the earth simulator. The first method is to assign one processor for one sub-domain, and the second method is to assign one node (=8 processors) for one sub-domain considering the shared memory type parallelization. Considering that the preconditioned conjugate gradient (PCG) method, which is one of the suitable linear equation solvers for the large-scale parallel finite element methods, shows the better convergence behavior if the number of domains is the smaller, we have determined to employ PCG and the hybrid parallelization, which is based on the shared and distributed memory type parallelization. It has been said that it is hard to obtain the good parallel or vector performance, since the finite element method is based on unstructured grids. In such situation, the reordering is inevitable to improve the computational performance [2]. In this study, we used three reordering methods, i.e. Reverse Cuthil-McKee (RCM), cyclic multicolor (CM) and diagonal jagged descending storage (DJDS)[3]. RCM provides the good convergence of the incomplete lower-upper (ILU) PCG, but causes the load imbalance. On the other hand, CM provides the good load balance, but worsens the convergence of ILU PCG if the vector length is so long. Therefore, we used the combined-method of RCM and CM. DJDS is the method to store the sparse matrices such that longer vector length can be obtained. For attaining the efficient inter-node parallelization, such partitioning methods as the recursive coordinate bisection (RCM) or MeTIS have been used. Computational performance of the practical large-scale engineering problems will be shown at the meeting. (author)

  9. A method of taking control rod history into account in core simulation calculations for BWR'S

    International Nuclear Information System (INIS)

    Hojerup, C.F.; Nonbol, E.

    1990-01-01

    The problem of taking control rod history into account in core simulator codes using precalculated cross sections has been examined, and two methods have been devised and tested. The very demanding first method, using the accumulated control rod in burn-up as a parameter, turned out to be even more inaccurate than the much less demanding second method, which only requires two full burn-up histories, one with the control rod in all the time, and another with the control rod out all the time. From the analysis it can be seen that the proper treatment of the control rod history is quite important, both for the cross sections, as several per cent on the reactivity are at stake, as for the pin powers, which for some pins are very much affected

  10. The BWR core simulator COSIMA with 2 group nodal flux expansion and control rod history

    International Nuclear Information System (INIS)

    Hoejerup, C.F.

    1989-08-01

    The boiling water simulator NOTAM has been modified and improved in several aspects: - The ''1 1/2'' energy group TRILUX nodal flux solution method has been exchanged with a 2 group modal expansion method. - Control rod ''history'' has been introduced. - Precalculated instrument factors have been introduced. The paper describes these improvements, which were considered sufficiently large to justify a new name to the programme: COSIMA. (author)

  11. Characterization of Flame Cut Heavy Steel: Modeling of Temperature History and Residual Stress Formation

    Science.gov (United States)

    Jokiaho, T.; Laitinen, A.; Santa-aho, S.; Isakov, M.; Peura, P.; Saarinen, T.; Lehtovaara, A.; Vippola, M.

    2017-12-01

    Heavy steel plates are used in demanding applications that require both high strength and hardness. An important step in the production of such components is cutting the plates with a cost-effective thermal cutting method such as flame cutting. Flame cutting is performed with a controlled flame and oxygen jet, which burns the steel and forms a cutting edge. However, the thermal cutting of heavy steel plates causes several problems. A heat-affected zone (HAZ) is generated at the cut edge due to the steep temperature gradient. Consequently, volume changes, hardness variations, and microstructural changes occur in the HAZ. In addition, residual stresses are formed at the cut edge during the process. In the worst case, unsuitable flame cutting practices generate cracks at the cut edge. The flame cutting of thick steel plate was modeled using the commercial finite element software ABAQUS. The results of modeling were verified by X-ray diffraction-based residual stress measurements and microstructural analysis. The model provides several outcomes, such as obtaining more information related to the formation of residual stresses and the temperature history during the flame cutting process. In addition, an extensive series of flame cut samples was designed with the assistance of the model.

  12. Attachment as a mediator between community violence and posttraumatic stress symptoms among adolescents with a history of maltreatment.

    Science.gov (United States)

    London, Melissa J; Lilly, Michelle M; Pittman, Laura

    2015-04-01

    Experiences that are detrimental to the attachment relationship, such as childhood maltreatment, may reduce feelings of safety among survivors and exacerbate the effects of exposure to subsequent violence, such as witnessing community violence. Though attachment style has been examined in regard to posttraumatic stress in adults who have a history of exposure to violence in childhood, less is known about the influence of attachment on the relationship between exposure to violence and posttraumatic stress symptoms in children and adolescents. The current study aimed to explore the role of attachment in the link between exposure to community violence and posttraumatic stress symptoms in adolescents with a history of childhood abuse. Participants included adolescents (aged 15-18 years) who had a history of maltreatment (N=75) and a matched sample without a childhood abuse history (N=78) from the National Data Archive on Child Abuse and Neglect (Salzinger, Feldman, & Ng-Mak, 2008). A conditional process model using bootstrapping to estimate indirect effects showed a significant indirect effect of insecure attachment on the relationship between exposure to community violence and posttraumatic stress symptoms for adolescents with a history of childhood physical abuse, but not for adolescents without this history. Implications for a cumulative risk model for post-trauma pathology starting in adolescence are discussed. Copyright © 2014 Elsevier Ltd. All rights reserved.

  13. [Relationship between simulated acid rain stress and leaf reflectance].

    Science.gov (United States)

    Song, Xiao-dong; Jiang, Hong; Yu, Shu-quan; Zhou, Guo-mo; Jiang, Zi-shan

    2010-01-01

    Acid rain is a worldwide environmental problem. Serious acid rain pollution in subtropical China has constituted a potential threat to the health of the local forest. In the present paper, the changing properties of the chlorophyll concentration and spectral reflectance at the visible wavelengths for the six subtropical broad-leaved tree species leaves under simulated acid rain (SAR) treatment with different pH levels were studied. With the increasing strength of the SAR, the chlorophyll concentrations of the experimental species under pH 2.5 and pH 4.0 treatment were higher than that under pH 5.6; the spectral reflectance at the visible wavelengths for pH 2.5 and pH 4.0 were lower than that for pH 5.6 in general; while there weren't significant differences between pH 2.5 and pH 4.0. After the treatment with different levels of SAR, the differences in spectral reflectance at the visible wavelengths mainly focused around the green peak and red edge on the reflectance curve. The subtropical broad-leaved tree species studied were relatively not sensitive to acid rain stresses; some stronger acid rain may accelerate the growth of the tree species used here to some extent.

  14. Efficient simulation of voxelized phantom in GATE with embedded SimSET multiple photon history generator

    Science.gov (United States)

    Lin, Hsin-Hon; Chuang, Keh-Shih; Lin, Yi-Hsing; Ni, Yu-Ching; Wu, Jay; Jan, Meei-Ling

    2014-10-01

    GEANT4 Application for Tomographic Emission (GATE) is a powerful Monte Carlo simulator that combines the advantages of the general-purpose GEANT4 simulation code and the specific software tool implementations dedicated to emission tomography. However, the detailed physical modelling of GEANT4 is highly computationally demanding, especially when tracking particles through voxelized phantoms. To circumvent the relatively slow simulation of voxelized phantoms in GATE, another efficient Monte Carlo code can be used to simulate photon interactions and transport inside a voxelized phantom. The simulation system for emission tomography (SimSET), a dedicated Monte Carlo code for PET/SPECT systems, is well-known for its efficiency in simulation of voxel-based objects. An efficient Monte Carlo workflow integrating GATE and SimSET for simulating pinhole SPECT has been proposed to improve voxelized phantom simulation. Although the workflow achieves a desirable increase in speed, it sacrifices the ability to simulate decaying radioactive sources such as non-pure positron emitters or multiple emission isotopes with complex decay schemes and lacks the modelling of time-dependent processes due to the inherent limitations of the SimSET photon history generator (PHG). Moreover, a large volume of disk storage is needed to store the huge temporal photon history file produced by SimSET that must be transported to GATE. In this work, we developed a multiple photon emission history generator (MPHG) based on SimSET/PHG to support a majority of the medically important positron emitters. We incorporated the new generator codes inside GATE to improve the simulation efficiency of voxelized phantoms in GATE, while eliminating the need for the temporal photon history file. The validation of this new code based on a MicroPET R4 system was conducted for 124I and 18F with mouse-like and rat-like phantoms. Comparison of GATE/MPHG with GATE/GEANT4 indicated there is a slight difference in energy

  15. Psychological adjustment and psychosocial stress among Japanese couples with a history of recurrent pregnancy loss

    DEFF Research Database (Denmark)

    Kagami, M; Maruyama, T; Koizumi, T

    2012-01-01

    BACKGROUND Little is known about the effects of recurrent pregnancy loss (RPL) on the psychological adjustment of couples. The aim of this study was to elucidate psychological adjustment and RPL-associated psychosocial stress affecting Japanese couples with a history of RPL, focusing on gender....... CONCLUSIONS Women were significantly more distressed than men. Poor quality of the marital relationship was significantly associated with impaired psychological adjustment among women, but not among men. These gender discrepancies may foster a mutual worsening of psychological adjustment and marital...... relationships in RPL couples. The need to seek help not only in women but also in a substantial portion of men suggests the importance of couple-based psychological care in the management of RPL....

  16. An experimental study of the influence of stress history on fault slip during injection of supercritical CO2

    Science.gov (United States)

    Cuss, Robert J.; Wiseall, Andrew C.; Tamayo-Mas, Elena; Harrington, Jon F.

    2018-04-01

    The injection of super-critical CO2 into a depleted reservoir will alter the pore pressure of the basin, which if sufficiently perturbed could result in fault slip. Therefore, knowledge of the acceptable pressure limits is required in order to maintain fault stability. A two-part laboratory study was conducted on fully saturated kaolinite fault gouge to investigate this issue. Previously, we showed that fault slip occurred once pore-pressure within the gouge was sufficient to overcome the normal stress acting on the fault. For kaolinite, this behaviour occurred at a pressure similar to the yield stress. The current study shows that following a slow-reduction in the maximum principal stress, as would be expected through changes in effective stress, the reactivation pressure shows a stress memory. Consequently, the pressure necessary to initiate fault slip is similar to that required at the maximum stress encountered. Therefore, fault slip is at least partially controlled by the previous maximum stress and not the current stress state. During the slow reduction in normal stress, the flow characteristics of the fault remain unchanged until pore-pressure exceeds shear stress and does not increase significantly until it exceeds normal stress. This results in fault slip, which slows the rate of flow increase as shear is an effective self-sealing mechanism. These observations lead to the conclusion that stress history is a vital parameter when considering fault stability.

  17. Analysis and modeling of simulated residual stress of mold injected plastic parts by using robust correlations

    OpenAIRE

    Vargas, Carlos; Sierra, Juan; Posada, Juan; Botero-Cadavid, Juan F.

    2017-01-01

    ABSTRACT The injection molding process is the most widely used processing technique for polymers. The analysis of residual stresses generated during this process is crucial for the part quality assessment. The present study evaluates the residual stresses in a tensile strength specimen using the simulation software Moldex3D for two polymers, polypropylene and polycarbonate. The residual stresses obtained under a simulated design of experiment were modeled using a robust multivariable regressi...

  18. Trauma histories among justice-involved youth: findings from the National Child Traumatic Stress Network

    Directory of Open Access Journals (Sweden)

    Carly B. Dierkhising

    2013-07-01

    Full Text Available Background: Up to 90% of justice-involved youth report exposure to some type of traumatic event. On average, 70% of youth meet criteria for a mental health disorder with approximately 30% of youth meeting criteria for post-traumatic stress disorder (PTSD. Justice-involved youth are also at risk for substance use and academic problems, and child welfare involvement. Yet, less is known about the details of their trauma histories, and associations among trauma details, mental health problems, and associated risk factors. Objective: This study describes detailed trauma histories, mental health problems, and associated risk factors (i.e., academic problems, substance/alcohol use, and concurrent child welfare involvement among adolescents with recent involvement in the juvenile justice system. Method: The National Child Traumatic Stress Network Core Data Set (NCTSN-CDS is used to address these aims, among which 658 adolescents report recent involvement in the juvenile justice system as indexed by being detained or under community supervision by the juvenile court. Results: Age of onset of trauma exposure was within the first 5 years of life for 62% of youth and approximately one-third of youth report exposure to multiple or co-occurring trauma types each year into adolescence. Mental health problems are prevalent with 23.6% of youth meeting criteria for PTSD, 66.1% in the clinical range for externalizing problems, and 45.5% in the clinical range for internalizing problems. Early age of onset of trauma exposure was differentially associated with mental health problems and related risk factors among males and females. Conclusions: The results indicate that justice-involved youth report high rates of trauma exposure and that this trauma typically begins early in life, is often in multiple contexts, and persists over time. Findings provide support for establishing trauma-informed juvenile justice systems that can respond to the needs of traumatized youth.

  19. Simulating population recovery of an aquatic isopod: Effects of timing of stress and landscape structure

    NARCIS (Netherlands)

    Galic, N.; Baveco, H.; Hengeveld, G.M.; Thorbeck, P.; Bruns, E.; Brink, P.

    2012-01-01

    In agroecosystems, organisms may regularly be exposed to anthropogenic stressors, e.g. pesticides. Species' sensitivity to stress depends on toxicity, life-history, and landscape structure. We developed an individual-based model of an isopod, Asellus aquaticus, to explore how timing of stress events

  20. Medial tibial stress syndrome can be diagnosed reliably using history and physical examination.

    Science.gov (United States)

    Winters, M; Bakker, E W P; Moen, M H; Barten, C C; Teeuwen, R; Weir, A

    2017-02-08

    The majority of sporting injuries are clinically diagnosed using history and physical examination as the cornerstone. There are no studies supporting the reliability of making a clinical diagnosis of medial tibial stress syndrome (MTSS). Our aim was to assess if MTSS can be diagnosed reliably, using history and physical examination. We also investigated if clinicians were able to reliably identify concurrent lower leg injuries. A clinical reliability study was performed at multiple sports medicine sites in The Netherlands. Athletes with non-traumatic lower leg pain were assessed for having MTSS by two clinicians, who were blinded to each others' diagnoses. We calculated the prevalence, percentage of agreement, observed percentage of positive agreement (Ppos), observed percentage of negative agreement (Pneg) and Kappa-statistic with 95%CI. Forty-nine athletes participated in this study, of whom 46 completed both assessments. The prevalence of MTSS was 74%. The percentage of agreement was 96%, with Ppos and Pneg of 97% and 92%, respectively. The inter-rater reliability was almost perfect; k=0.89 (95% CI 0.74 to 1.00), phistory and physical examination, in clinical practice and research settings. We also found that concurrent lower leg injuries are common in athletes with MTSS. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2017. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

  1. Survival of juvenile fishes receiving thermal and mechanical stresses in a simulated power plant condenser

    International Nuclear Information System (INIS)

    Kedl, R.J.; Coutant, C.C.

    Experiments were conducted in a water-recirculating loop to determine the effects of fluid-induced stresses (e.g., turbulence, pressure, and vacuum) on six species of larval fish and one species each of frog tadpoles and zooplankton. These stresses simulate the insults developed in the condenser portion, but not including the pump, of a steam power plant. Some experiments were conducted with thermal stresses superimposed on fluid-induced stresses. Fluid-induced stresses of the magnitude developed in these experiments were generally not fatal to the larval fish within the precision of the experiments, although some sublethal effects were noted. When thermal stress was superimposed on the fluid-induced stresses, the mortalities were equivalent to those resulting from thermal stress alone. Fluid-induced stresses of low magnitude were not fatal to Daphnia magna, but fluid-induced stresses of higher magnitude were responsible for significant mortalities. (U.S.)

  2. Prediction of residual stress distributions due to surface machining and welding and crack growth simulation under residual stress distribution

    International Nuclear Information System (INIS)

    Ihara, Ryohei; Katsuyama, JInya; Onizawa, Kunio; Hashimoto, Tadafumi; Mikami, Yoshiki; Mochizuki, Masahito

    2011-01-01

    Research highlights: → Residual stress distributions due to welding and machining are evaluated by XRD and FEM. → Residual stress due to machining shows higher tensile stress than welding near the surface. → Crack growth analysis is performed using calculated residual stress. → Crack growth result is affected machining rather than welding. → Machining is an important factor for crack growth. - Abstract: In nuclear power plants, stress corrosion cracking (SCC) has been observed near the weld zone of the core shroud and primary loop recirculation (PLR) pipes made of low-carbon austenitic stainless steel Type 316L. The joining process of pipes usually includes surface machining and welding. Both processes induce residual stresses, and residual stresses are thus important factors in the occurrence and propagation of SCC. In this study, the finite element method (FEM) was used to estimate residual stress distributions generated by butt welding and surface machining. The thermoelastic-plastic analysis was performed for the welding simulation, and the thermo-mechanical coupled analysis based on the Johnson-Cook material model was performed for the surface machining simulation. In addition, a crack growth analysis based on the stress intensity factor (SIF) calculation was performed using the calculated residual stress distributions that are generated by welding and surface machining. The surface machining analysis showed that tensile residual stress due to surface machining only exists approximately 0.2 mm from the machined surface, and the surface residual stress increases with cutting speed. The crack growth analysis showed that the crack depth is affected by both surface machining and welding, and the crack length is more affected by surface machining than by welding.

  3. Effects of nutritional history on stress response in gibel carp (Carassius auratus gibelio) and largemouth bass (Micropterus salmoides).

    Science.gov (United States)

    Jiang, Danli; Wu, Yubo; Huang, Di; Ren, Xing; Wang, Yan

    2017-08-01

    The stress response of omnivorous gibel carp (Carassius auratus gibelio) and carnivorous largemouth bass (Micropterus salmoides) with different nutritional history were evaluated. A 2×2 layout, including two fish species (gibel carp or largemouth bass) and two nutritional history (fasted or fed to satiation for four weeks), was used. After feeding or fasting, the fishes were subjected to an acute handling. Fasting resulted in decrease of plasma glucose level and liver glycogen content of gibel carp and largemouth bass. After handling stress, plasma levels of cortisol, glucose and lactate of gibel carp and largemouth bass increased, regardless the fasted fish or fed fish. During the period from 0h to 24h post-stress, the fasted gibel carp exhibited lower plasma cortisol and glucose levels, brain and liver glycogen contents, and liver phosphoenolpyruvate carboxykinase (PEPCK) activity compared with the fed counterpart. The plasma glucose level, brain glucose level, brain and liver glycogen contents were lower, while the liver PEPCK and hexokinase (HK) activities were higher, in the faster largemouth bass than the fed counterpart. This study indicates that nutritional history can influence stress response of gibel carp and largemouth bass, and the stress response is less severe in the fasted fish relative to the fed counterpart. This study also reveals that gibel carp and largemouth bass may have different strategies in response to fasting and acute handling stress. Copyright © 2017 Elsevier Inc. All rights reserved.

  4. Simulations of isolated dwarf galaxies formed in dark matter halos with different mass assembly histories

    International Nuclear Information System (INIS)

    González-Samaniego, A.; Avila-Reese, V.; Rodríguez-Puebla, A.; Valenzuela, O.; Colín, P.

    2014-01-01

    We present zoom-in N-body/hydrodynamics resimulations of dwarf galaxies formed in isolated cold dark matter (CDM) halos with the same virial mass (M v ≈ 2.5 × 10 10 M ☉ ) at redshift z = 0. Our goals are to (1) study the mass assembly histories (MAHs) of the halo, stellar, and gaseous components; and (2) explore the effects of the halo MAHs on the stellar/baryonic assembly of simulated dwarfs. Overall, the dwarfs are roughly consistent with observations. More specific results include: (1) the stellar-to-halo mass ratio remains roughly constant since z ∼ 1, i.e., the stellar MAHs closely follow halo MAHs. (2) The evolution of the galaxy gas fractions, f g , are episodic, showing that the supernova-driven outflows play an important role in regulating f g —and hence, the star formation rate (SFR)—however, in most cases, a large fraction of the gas is ejected from the halo. (3) The star formation histories are episodic with changes in the SFRs, measured every 100 Myr, of factors of 2-10 on average. (4) Although the dwarfs formed in late assembled halos show more extended SF histories, their z = 0 specific SFRs are still below observations. (5) The inclusion of baryons most of the time reduces the virial mass by 10%-20% with respect to pure N-body simulations. Our results suggest that rather than increasing the strength of the supernova-driven outflows, processes that reduce the star formation efficiency could help to solve the potential issues faced by CDM-based simulations of dwarfs, such as low values of the specific SFR and high stellar masses.

  5. Simulations of isolated dwarf galaxies formed in dark matter halos with different mass assembly histories

    Energy Technology Data Exchange (ETDEWEB)

    González-Samaniego, A.; Avila-Reese, V.; Rodríguez-Puebla, A.; Valenzuela, O. [Instituto de Astronomía, Universidad Nacional Autónoma de México, A.P. 70-264, 04510 México D. F. (Mexico); Colín, P. [Centro de Radioastronomía y Astrofísica, Universidad Nacional Autónoma de México, A.P. 72-3 (Xangari), Morelia, Michoacán 58089 (Mexico)

    2014-04-10

    We present zoom-in N-body/hydrodynamics resimulations of dwarf galaxies formed in isolated cold dark matter (CDM) halos with the same virial mass (M{sub v} ≈ 2.5 × 10{sup 10} M {sub ☉}) at redshift z = 0. Our goals are to (1) study the mass assembly histories (MAHs) of the halo, stellar, and gaseous components; and (2) explore the effects of the halo MAHs on the stellar/baryonic assembly of simulated dwarfs. Overall, the dwarfs are roughly consistent with observations. More specific results include: (1) the stellar-to-halo mass ratio remains roughly constant since z ∼ 1, i.e., the stellar MAHs closely follow halo MAHs. (2) The evolution of the galaxy gas fractions, f{sub g} , are episodic, showing that the supernova-driven outflows play an important role in regulating f{sub g} —and hence, the star formation rate (SFR)—however, in most cases, a large fraction of the gas is ejected from the halo. (3) The star formation histories are episodic with changes in the SFRs, measured every 100 Myr, of factors of 2-10 on average. (4) Although the dwarfs formed in late assembled halos show more extended SF histories, their z = 0 specific SFRs are still below observations. (5) The inclusion of baryons most of the time reduces the virial mass by 10%-20% with respect to pure N-body simulations. Our results suggest that rather than increasing the strength of the supernova-driven outflows, processes that reduce the star formation efficiency could help to solve the potential issues faced by CDM-based simulations of dwarfs, such as low values of the specific SFR and high stellar masses.

  6. History of cervical insufficiency increases the risk of pelvic organ prolapse and stress urinary incontinence in parous women.

    Science.gov (United States)

    Sheyn, David; Addae-Konaedu, Kateena L; Bauer, Alison M; Dawodu, Konyinsola I; Hackney, David N; El-Nashar, Sherif A

    2018-01-01

    A likely contributor to pelvic floor disorders is injury and degradation of connective tissue components such as collagen and elastin, leading to weakening of the pelvic floor. Prior studies have found similar connective tissue component changes in women with cervical insufficiency (CI). However, the connection between pelvic floor disorders and cervical insufficiency has not previously been evaluated. Our objective was to determine whether a history of cervical insufficiency is associated with an increased risk of pelvic organ prolapse and stress urinary incontinence after controlling for confounders. The study used de-identified clinical data from a large multi-institution electronic health records HIPAA-compliant data web application, Explorys Inc. (Cleveland, Ohio, USA). Women with a history of at least one prior delivery after at least 20 weeks' gestation between the years 1999 and 2016 were identified. Logistic regression models were used to identify risk factors and adjust for confounders. The primary outcome was subsequent development of either stress incontinence or pelvic organ prolapse. A total of 1,182,650 women were identified, of whom 30,890 (2.6%) had a history of cervical cerclage or insufficiency. A history of cervical insufficiency was associated with an increased risk of either pelvic organ prolapse or stress urinary incontinence (aOR=1.93, 95%CI: 1.84-2.02). A history of cervical insufficiency was more strongly associated with an increased risk of pelvic organ prolapse (aOR=2.06, 95%CI: 1.91-2.21) than with stress urinary incontinence (aOR=1.91, 95%CI: 1.80-2.02). A history of cervical insufficiency is associated with an increased risk of development of pelvic organ prolapse and stress urinary incontinence. Copyright © 2017 Elsevier B.V. All rights reserved.

  7. Simulation of the Point Lepreau core-follow history with SORO

    International Nuclear Information System (INIS)

    Shanes, F.C.; Olive, C.G.; Cheng, I.; Banica, C.; Newman, C.; Nainer, O.

    2006-01-01

    The core tracking SORO program calculates the flux, burn-ups, bundle and channel powers, and is used for Ontario Power Generation and Bruce Power reactors. This paper presents the results of a comparison of the SORO cell fluxes against the Point Lepreau CANDU-6 measured flux data. A SORO model was created for the Point Lepreau reactor, and simulations were carried out to compare the SORO fluxes to the Travelling Flux Detector (TFD) scans and one year of operating history. Considering the good agreement between measured and computed fluxes, the results provide confidence that SORO accurately calculates the cell fluxes and bundle powers. (author)

  8. Simulation of the Point Lepreau core-follow history with SORO

    Energy Technology Data Exchange (ETDEWEB)

    Shanes, F.C.; Olive, C.G.; Cheng, I. [Nuclear Safety Solutions Limited, Toronto, Ontario (Canada); Banica, C. [Ontario Power Generation, Ajax, Ontario (Canada); Newman, C. [NB Power Nuclear, Point Lepreau Generating Station, Lepreau, New Brunswick (Canada); Nainer, O. [Bruce Power, Toronto, Ontario (Canada)

    2006-07-01

    The core tracking SORO program calculates the flux, burn-ups, bundle and channel powers, and is used for Ontario Power Generation and Bruce Power reactors. This paper presents the results of a comparison of the SORO cell fluxes against the Point Lepreau CANDU-6 measured flux data. A SORO model was created for the Point Lepreau reactor, and simulations were carried out to compare the SORO fluxes to the Travelling Flux Detector (TFD) scans and one year of operating history. Considering the good agreement between measured and computed fluxes, the results provide confidence that SORO accurately calculates the cell fluxes and bundle powers. (author)

  9. A computer program for estimating the power-density spectrum of advanced continuous simulation language generated time histories

    Science.gov (United States)

    Dunn, H. J.

    1981-01-01

    A computer program for performing frequency analysis of time history data is presented. The program uses circular convolution and the fast Fourier transform to calculate power density spectrum (PDS) of time history data. The program interfaces with the advanced continuous simulation language (ACSL) so that a frequency analysis may be performed on ACSL generated simulation variables. An example of the calculation of the PDS of a Van de Pol oscillator is presented.

  10. Stress, deformation and diffusion interactions in solids - A simulation study

    Czech Academy of Sciences Publication Activity Database

    Fischer, F. D.; Svoboda, Jiří

    2015-01-01

    Roč. 78, MAY (2015), s. 427-442 ISSN 0022-5096 R&D Projects: GA ČR(CZ) GA14-24252S Institutional support: RVO:68081723 Keywords : Diffusion * Bulk * Microstructure * Viscoelastic material * Stress relaxation * Residual stress Subject RIV: BJ - Thermodynamics Impact factor: 3.875, year: 2015

  11. Transient water stress in a vegetation canopy - Simulations and measurements

    Science.gov (United States)

    Carlson, Toby N.; Belles, James E.; Gillies, Robert R.

    1991-01-01

    Consideration is given to observational and modeling evidence of transient water stress, the effects of the transpiration plateau on the canopy radiometric temperature, and the factors responsible for the onset of the transpiration plateau, such as soil moisture. Attention is also given to the point at which the transient stress can be detected by remote measurement of surface temperature.

  12. Simulation of Residual Stresses at Holes in Tempered Glass

    DEFF Research Database (Denmark)

    Nielsen, Jens Henrik; Olesen, John Forbes; Poulsen, Peter Noe

    2010-01-01

    This work presents a full 3D numerical study of the residual stresses in tempered (toughened) glass near holes using Narayanaswamy’s model for the tempering process. It is the objective of the paper to elucidate the influence on the minimal residual compressive stresses at holes from variations in...

  13. Comparing measured with simulated vertical soil stress under vehicle load

    DEFF Research Database (Denmark)

    Keller, Thomas; Lamandé, Mathieu; Arvidsson, Johan

    The load transfer within agricultural soil is typically modelled on the basis of the theory of stress transmission in elastic media, usually in the semi-empirical form that includes the “concentration factor” (v). Measurements of stress in soil are needed to evaluate model calculations, but may...

  14. Cylinder-averaged histories of nitrogen oxide in a DI diesel with simulated turbocharging

    Science.gov (United States)

    Donahue, Ronald J.; Borman, Gary L.; Bower, Glenn R.

    1994-10-01

    An experimental study was conducted using the dumping technique (total cylinder sampling) to produce cylinder mass-averaged nitric oxide histories. Data were taken using a four stroke diesel research engine employing a quiescent chamber, high pressure direct injection fuel system, and simulated turbocharging. Two fuels were used to determine fuel cetane number effects. Two loads were run, one at an equivalence ratio of 0.5 and the other at a ratio of 0.3. The engine speed was held constant at 1500 rpm. Under the turbocharged and retarded timing conditions of this study, nitric oxide was produced up to the point of about 85% mass burned. Two different models were used to simulate the engine mn conditions: the phenomenological Hiroyasu spray-combustion model, and the three dimensional, U.W.-ERO modified KIVA-2 computational fluid dynamic code. Both of the models predicted the correct nitric oxide trend. Although the modified KIVA-2 combustion model using Zeldovich kinetics correctly predicted the shapes of the nitric oxide histories, it did not predict the exhaust concentrations without arbitrary adjustment based on experimental values.

  15. Context-dependent effects of cold stress on behavioral, physiological, and life-history traits of the red flour beetle.

    Science.gov (United States)

    Scharf, Inon; Wertheimer, Keren-Or; Xin, Joy Lim; Gilad, Tomer; Goldenberg, Inna; Subach, Aziz

    2017-06-20

    Animals are exposed in nature to a variety of stressors. While stress is generally harmful, mild stress can also be beneficial and contribute to reproduction and survival. We studied the effect of five cold shock events versus a single cold shock and a control group, representing three levels of stress (harsh, mild, and no stress), on behavioral, physiological, and life-history traits of the red flour beetle (Tribolium castaneum, Herbst 1797). Beetles exposed to harsh cold stress were less active than a control group: they moved less and failed more frequently to detect a food patch. Their probability to mate was also lower. Beetle pairs exposed to harsh cold stress frequently failed to reproduce at all, and if reproducing, females laid fewer eggs, which were, as larvae in mid-development, smaller than those in the control group. However, harsh cold stress led to improved female starvation tolerance, probably due to enhanced lipid accumulation. Harsh cold shock also improved tolerance to an additional cold shock compared to the control. Finally, a single cold shock event negatively affected fewer measured response variables than the harsh cold stress, but also enhanced neither starvation tolerance nor tolerance to an additional cold shock. The consequences of a harsher cold stress are thus not solely detrimental but might even enhance survival under stressful conditions. Under benign conditions, nevertheless, harsh stress impedes beetle performance. The harsh stress probably shifted the balance point of the survival-reproduction trade-off, a shift that did not take place following exposure to mild stress. © 2017 Institute of Zoology, Chinese Academy of Sciences.

  16. Nutritional history does not modulate hepatic oxidative status of European sea bass (Dicentrarchus labrax) submitted to handling stress.

    Science.gov (United States)

    Castro, Carolina; Peréz-Jiménez, Amalia; Coutinho, Filipe; Corraze, Geneviève; Panserat, Stéphane; Peres, Helena; Teles, Aires Oliva; Enes, Paula

    2018-02-19

    The aim of the present study was to assess the impact of an acute handling stress on hepatic oxidative status of European sea bass (Dicentrarchus labrax) juveniles fed diets differing in lipid so urce and carbohydrate content. For that purpose, four diets were formulated with fish oil (FO) and vegetable oils (VO) as lipid source and with 20 or 0% gelatinized starch as carbohydrate source. Triplicate groups of fish with 74 g were fed each diet during 13 weeks and then subjected to an acute handling stress. Stress exposure decreased hematocrit (Ht) and hemoglobin (Hb) levels. Independent of dietary treatment, stress exposure increased hepatic lipid peroxidation (LPO). Stressed fish exhibited lower glucose 6-phosphate dehydrogenase (G6PD), catalase (CAT), and superoxide dismutase (SOD) activities, independent of previous nutritional history. In the VO groups, stress exposure increased glutathione peroxidase (GPX) activity. Diet composition had no effect on Ht and Hb levels. In contrast, dietary carbohydrate decreased hepatic LPO and CAT activity and increased glutathione reductase (GR) and G6PD activities. Dietary lipids had no effect on LPO. Fish fed the VO diets exhibited higher G6PD activity than fish fed the FO diets. In conclusion, dietary carbohydrates contributed to the reduction of oxidative stress in fish. However, under the imposed handling stress conditions, liver enzymatic antioxidant mechanisms were not enhanced, which may explain the overall increased oxidative stress.

  17. Stress history influence on sedimentary rock porosity estimates: Implications for geological CO2 storage in Northern Taiwan

    Directory of Open Access Journals (Sweden)

    Wen-Jie Wu

    2017-01-01

    Full Text Available We established a stress-history-dependent porosity model of potential target rocks for CO2 geosequestration based on rock sample porosity measurements under various effective stresses (5 - 120 MPa. The measured samples were collected from shallow boreholes (< 300 m depth drilled at the frontal fold in northern Taiwan. The lithology, density, and the stress-history-dependent porosity derived from shallow boreholes enabled us to predict the porosity-depth relationship of given rock formations at (burial depths of approximately 3170 - 3470 m potential sites for CO2 geosequestration located near the Taoyuan Tableland coastline. Our results indicate that the porosity of samples derived from laboratory tests under atmospheric pressure is significantly greater than the porosity measured under stress caused by sediment burial. It is therefore strongly recommended that CO2 storage capacity assessment not be estimated from the porosity measured under atmospheric pressure. Neglecting the stress history effect on the porosity of compacted and uplifted rocks may induce a percentage error of 7.7% at a depth of approximately 1000 m, where the thickness of the eroded, formerly overlying formation is 2.5 km in a synthetic case. The CO2 injection pressure effect on the porosity was also evaluated using the stress-history-dependent porosity model. As expected, the pore pressure buildup during CO2 injection will induce an increase in the rock porosity. For example, a large injection pressure of 13 MPa at a depth of approximately 1000 m will increase the rock porosity by a percentage error of 6.7%. Our results have implications for CO2 storage capacity injection pressure estimates.

  18. Discrete element simulation of internal stress in SiCp/aluminum ...

    African Journals Online (AJOL)

    2002-07-22

    Jul 22, 2002 ... microcosmic two-dimensional numerical model of SiCp / Al matrix composites was established and the simulation of the size ... In the metal matrix composite ... stress and strain distribution, strengthen mechanisms and overall ...

  19. Fatigue Crack Propagation Simulation in Plane Stress Constraint

    DEFF Research Database (Denmark)

    Ricardo, Luiz Carlos Hernandes; Spinelli, Dirceu

    2010-01-01

    Nowadays, structural and materials engineers develop structures and materials properties using finite element method. This work presents a numerical determination of fatigue crack opening and closure stress intensity factors of a C(T) specimen. Two different standard variable spectrum loadings...... are utilized, Mini-Falstaff and Wisper. The effects in two-dimensional (2D) small scale yielding models of fatigue crack growth were studied considering plane stress constraint....

  20. Physiological responses of genotypes soybean to simulated drought stress

    Directory of Open Access Journals (Sweden)

    Eleonóra Krivosudská

    2016-12-01

    Full Text Available The objective of this research was to investigate possible genetic variation in the sensitivity of soybean cultivars for nitrogen fixation rates in response to soil drying. The work confirmed that the selected physiological characteristics (RWC, osmotic potential, stress index and created nodules on roots are good evaluating parameters for the determination of water stress in plant. In the floricultural year 2014 an experiment with four genetic resources of soybean was launched. Sowing of Maverick (USA, Drina (HRV, Nigra (SVK and Polanka (CZK genotypes was carried out in the containers of 15 l capacity. This stress had a negative impact on the physiological parameters. By comparing the RWC values, the decrease was more significant at the end of dehydration, which was monitored in Maverick and Drina genotypes using the Nitrazon inoculants and water stress effect. Inoculated stressed Nigra and Polanka genotypes have kept higher water content till the end of dehydration period. Also the proline accumulation was monitored during the water stress, whilst higher content of free proline reached of Maverick. More remarkable decrease of osmotic potential was again registered in a foreign Drina and Maverick genotypes in the inoculated variations. Nigra and Polanka genotypes responses not so significant in the given conditions.

  1. Stress influences decisions to break a safety rule in a complex simulation task in females.

    Science.gov (United States)

    Starcke, Katrin; Brand, Matthias; Kluge, Annette

    2016-07-01

    The current study examines the effects of acutely induced laboratory stress on a complex decision-making task, the Waste Water Treatment Simulation. Participants are instructed to follow a certain decision rule according to safety guidelines. Violations of this rule are associated with potential high rewards (working faster and earning more money) but also with the risk of a catastrophe (an explosion). Stress was induced with the Trier Social Stress Test while control participants underwent a non-stress condition. In the simulation task, stressed females broke the safety rule more often than unstressed females: χ(2) (1, N=24)=10.36, pbreak the safety rule because stressed female participants focused on the potential high gains while they neglected the risk of potential negative consequences. Copyright © 2016 Elsevier B.V. All rights reserved.

  2. Role of trait shame in the association between posttraumatic stress and aggression among men with a history of interpersonal trauma.

    Science.gov (United States)

    Schoenleber, Michelle; Sippel, Lauren M; Jakupcak, Matthew; Tull, Matthew T

    2015-01-01

    Given the theoretical and empirical associations among posttraumatic stress, shame, and interpersonal aggression, this study examined whether trait shame accounts for the associations between posttraumatic stress and aggressive behavior in a sample of 103 men with a history of interpersonal trauma. Results indicated that trait shame accounted for the associations of posttraumatic stress with the variety of both physically and psychologically aggressive behavior, as well as with the frequency of physical aggression. This study also examined trait guilt, given its conceptual relationship to both shame and posttraumatic stress; unlike trait shame, trait guilt did not account for the association between posttraumatic stress and the variety of physically aggressive acts. Additionally, although trait guilt reduced the association between posttraumatic stress and the frequency of physical aggression, the indirect path including guilt was nonsignificant. Taken together, the present study supports existing theories suggesting that shame, but not guilt, may contribute to aggressive behavior, especially among individuals with histories of traumatic exposure. (c) 2015 APA, all rights reserved).

  3. Cardiovascular reactions to psychological stress and abuse history: the role of occurrence, frequency, and type of abuse.

    Science.gov (United States)

    Ginty, Annie T; Masters, Nicole A; Nelson, Eliza B; Kaye, Karen T; Conklin, Sarah M

    2017-03-01

    Extreme cardiovascular reactions to psychological stress have been associated with traumatic life experiences. Previous studies have focused on the occurrence or frequency of abuse rather than type of abuse. We examined how occurrence, frequency, and the type of abuse history are related to cardiovascular reactivity (CVR) to acute psychological stress. The study consisted of between group and continuous analyses to examine the association between occurrence, type, and frequency of abuse with cardiovascular reactions to acute psychological stress. Data from 64 participants were collected. Heart rate, systolic blood pressure, and diastolic blood pressure were measured at baseline and during a standard mental arithmetic stress task. Individuals who experienced abuse showed diminished CVR to acute psychological stress; this was driven specifically by the history of sexual abuse. Frequency of abuse did not relate to stress reactions. These findings accord with previous work suggesting a relationship between traumatic life experience and hypoarousal in physiological reactivity and extend previous findings by suggesting the relationship may be driven by sexual abuse.

  4. History of stress-related health changes: a cue to pursue a diagnosis of latent primary adrenal insufficiency.

    Science.gov (United States)

    Yamamoto, Toshihide

    2014-01-01

    Routine delays in the diagnosis of primary adrenal insufficiency (PAI) are well known and conceivably attributable to the absence of cues, other than anti-adrenal autoantibodies, to pursue subclinical PAI. Subclinical PAI is latent unless the afflicted patient encounters stress such as an acute illness, surgery, psychosocial burden, etc. It remains to be demonstrated whether a history of stress-related health changes is a useful cue to pursue a diagnosis of latent PAI. The patients were selected for a history of recurrent symptoms, i.e., gastrointestinal symptoms, fatigue, or lassitude, aggravated by stress and alleviated by the removal of stress, and signs, i.e., weight loss, hypotension, and hyperpigmentation. As the early morning cortisol levels were low or low-normal and the adrenocorticotropic hormone (ACTH) levels were within the reference ranges, provocation tests, i.e., insulin-induced hypoglycemia tests and low-dose (1 μg) corticotropin tests (LDTs), were used to estimate the hypothalamus-pituitary-adrenal (HPA) axis status. Patients with the HPA axis dysfunction on two provocation tests were supplemented with physiologic doses of glucocorticoids (GCs). The effects of GC supplementation on stress-related health changes were observed. The ACTH levels after insulin-induced hypoglycemia were higher and the cortisol levels were lower in the patients than in the control subjects. The cortisol levels in the patients were increased less significantly by LDT than those observed in the control subjects. Stress-related health changes ceased to recur and signs, i.e., a low body weight, hypotension, and hyperpigmentation, were ameliorated following GC supplementation. A history of stress-related health changes is useful as a cue to pursue latent PAI in patients with low or low-normal early morning cortisol levels.

  5. Simulation of Stress-Strain State of Shovel Rotary Support Kingpin

    Science.gov (United States)

    Khoreshok, A. A.; Buyankin, P. V.; Vorobiev, A. V.; Dronov, A. A.

    2016-04-01

    The article presents the sequence of computational simulation of stress-strain state of shovel’s rotary support. Computation results are analyzed, the kingpin is specified as the most loaded element, maximum stress zones are identified. Kingpin design modification such as enhancement of fillet curvature radius to 25 mm and displacement of eyebolt holes on the diameter of 165 mm are proposed, thus diminishing impact of stress concentrators and improving reliability of the rotary support.

  6. Epidemiology of mixed, stress, and urgency urinary incontinence in middle-aged/older women: the importance of incontinence history.

    Science.gov (United States)

    Komesu, Yuko M; Schrader, Ronald M; Ketai, Loren H; Rogers, Rebecca G; Dunivan, Gena C

    2016-05-01

    Urinary incontinence (UI) is common and the relationship among its subtypes complex. Our objective was to describe the natural history and predictors of the incontinence subtypes stress, urgency, and mixed, in middle-aged and older US women. We tested our hypothesis that UI subtype history predicted future occurrence, evaluating subtype incidence/remission over multiple time points in a stable cohort of women. We analyzed longitudinal urinary incontinence data in 10,572 community-dwelling women aged ≥50 in the 2004-2010 Health and Retirement Study. Mixed, stress, and urgency incontinence prevalence (2004, 2006, 2008, 2010) and 2-year cumulative incidence and remissions (2004-2006, 2006-2008, 2008-2010) were estimated. Patient characteristics and incontinence subtype status 2004-2008 were entered into a multivariable, transition model to determine predictors for incontinence subtype occurrence in 2010. The prevalence of each subtype in this population (median age 63-66) was 2.6-8.9 %. Subtype incidence equaled 2.1-3.5 % and remissions for each varied between 22.3 and 48.7 %. Incontinence subtype incidence predictors included ethnicity/race, age, body mass index, and functional limitations. Compared with white women, black women had decreased odds of incident stress incontinence and Hispanic women had increased odds of stress incontinence remission. The age range 80-90 and severe obesity predicted incident mixed incontinence. Functional limitations predicted mixed and urgency incontinence. The strongest predictor of incontinence subtype was subtype history. The presence of the respective incontinence subtypes in 2004 and 2006 strongly predicted 2010 recurrence (odds ratio [OR] stress incontinence = 30.7, urgency OR = 47.4, mixed OR = 42.1). Although the number of remissions was high, a previous history of incontinence subtypes predicted recurrence. Incontinence status is dynamic, but tends to recur over the longer term.

  7. Electrical stress and strain in lunar regolith simulants

    Science.gov (United States)

    Marshall, J.; Richard, D.; Davis, S.

    2011-11-01

    Experiments to entrain dust with electrostatic and fluid-dynamic forces result in particulate clouds of aggregates rather than individual dust grains. This is explained within the framework of Griffith-flaw theory regarding the comminution/breakage of weak solids. Physical and electrical inhomogeneities in powders are equivalent to microcracks in solids insofar as they facilitate failure at stress risers. Electrical charging of powders induces bulk sample stresses similar to mechanical stresses experienced by strong solids, depending on the nature of the charging. A powder mass therefore "breaks" into clumps rather than separating into individual dust particles. This contrasts with the expectation that electrical forces on the Moon will eject a submicron population of dust from the regolith into the exosphere. A lunar regolith will contain physical and electrostatic inhomogeneities similar to those in most charged powders.

  8. On computing stress in polymer systems involving multi-body potentials from molecular dynamics simulation

    Science.gov (United States)

    Fu, Yao; Song, Jeong-Hoon

    2014-08-01

    Hardy stress definition has been restricted to pair potentials and embedded-atom method potentials due to the basic assumptions in the derivation of a symmetric microscopic stress tensor. Force decomposition required in the Hardy stress expression becomes obscure for multi-body potentials. In this work, we demonstrate the invariance of the Hardy stress expression for a polymer system modeled with multi-body interatomic potentials including up to four atoms interaction, by applying central force decomposition of the atomic force. The balance of momentum has been demonstrated to be valid theoretically and tested under various numerical simulation conditions. The validity of momentum conservation justifies the extension of Hardy stress expression to multi-body potential systems. Computed Hardy stress has been observed to converge to the virial stress of the system with increasing spatial averaging volume. This work provides a feasible and reliable linkage between the atomistic and continuum scales for multi-body potential systems.

  9. Numerical simulation of random stresses on an annular turbulent flow

    International Nuclear Information System (INIS)

    Marti-Moreno, Marta

    2000-01-01

    The flow along a circular cylinder may induce structural vibrations. For the predictive analysis of such vibrations, the turbulent forcing spectrum needs to be characterized. The aim of this work is to study the turbulent fluid forces acting on a single tube in axial flow. More precisely we have performed numerical simulations of an annular flow. These simulations were carried out on a cylindrical staggered mesh by a finite difference method. We consider turbulent flow with Reynolds number up to 10 6 . The Large Eddy Simulation Method has been used. A survey of existent experiments showed that hydraulic diameter acts as an important parameter. We first showed the accuracy of the numerical code by reproducing the experiments of Mulcahy. The agreement between pressure spectra from computations and from experiments is good. Then, we applied this code to simulate new numerical experiments varying the hydraulic diameter and the flow velocity. (author) [fr

  10. One stimulus-Two responses: Host and parasite life-history variation in response to environmental stress.

    Science.gov (United States)

    Gleichsner, Alyssa M; Cleveland, Jessica A; Minchella, Dennis J

    2016-11-01

    Climate change stressors will place different selective pressures on both parasites and their hosts, forcing individuals to modify their life-history strategies and altering the distribution and prevalence of disease. Few studies have investigated whether parasites are able to respond to host stress and respond by varying their reproductive schedules. Additionally, multiple environmental stressors can limit the ability of a host to respond adaptively to parasite infection. This study compared both host and parasite life-history parameters in unstressed and drought-stressed environments using the human parasite, Schistosoma mansoni, in its freshwater snail intermediate host. Snail hosts infected with the parasite demonstrated a significant reproductive burst during the prepatent period (fecundity compensation), but that response was absent in a drought-stressed environment. This is the first report of the elimination of host fecundity compensation to parasitism when exposed to additional environmental stress. More surprisingly, we found that infections in drought-stressed snails had significantly higher parasite reproductive outputs than infections in unstressed snails. The finding suggests that climate change may alter the infection dynamics of this human parasite. © 2016 The Author(s). Evolution © 2016 The Society for the Study of Evolution.

  11. Photosynthetic efficiency of Pedunculate oak seedlings under simulated water stress

    Directory of Open Access Journals (Sweden)

    Popović Zorica

    2010-01-01

    Full Text Available Photosynthetic performance of seedlings of Quercus robur exposed to short-term water stress in the laboratory conditions was assessed through the method of induced fluorometry. The substrate for seedlings was clayey loam, with the dominant texture fraction made of silt, followed by clay and fine sand, with total porosity 68.2%. Seedlings were separated in two groups: control (C (soil water regime in pots was maintained at the level of field water capacity and treated (water-stressed, WS (soil water regime was maintained in the range of wilting point and lentocapillary capacity. The photosynthetic efficiency was 0.642±0.25 and 0.522±0.024 (WS and C, respectively, which was mostly due to transplantation disturbances and sporadic leaf chlorosis. During the experiment Fv/Fm decreased in both groups (0.551±0.0100 and 0.427±0.018 in C and WS, respectively. Our results showed significant differences between stressed and control group, in regard to both observed parameters (Fv/Fm and T½. Photosynthetic efficiency of pedunculate oak seedlings was significantly affected by short-term water stress, but to a lesser extent than by sufficient watering.

  12. Calculation of residual stresses by means of a 3D numerical weld simulation

    International Nuclear Information System (INIS)

    Nicak, Tomas; Huemmer, Matthias

    2008-01-01

    The numerical weld simulation has developed very fast in recent years. The problem complexity has increased from simple 2D models to full 3D models, which can describe the entire welding process more realistically. As recent research projects indicate, a quantitative assessment of the residual stresses by means of a 3D analysis is possible. The structure integrity can be assessed based on the weld simulation results superimposed with the operating load. Moreover, to support the qualification of welded components parametric studies for optimization of the residual stress distribution in the weld region can be performed. In this paper a full 3D numerical weld simulation for a man-hole drainage nozzle in a steam generator will be presented. The residual stresses are calculated by means of an uncoupled transient thermal and mechanical FE analysis. The paper will present a robust procedure allowing reasonable predictions of the residual stresses for complex structures in industrial practice. (authors)

  13. Numerical simulation of transformation-induced microscopic residual stress in ferrite-martensite lamellar steel

    International Nuclear Information System (INIS)

    Mikami, Y; Inao, A; Mochizuki, M; Toyoda, M

    2009-01-01

    The effect of transformation-induced microscopic residual stress on fatigue crack propagation behavior of ferrite-martensite lamellar steel was discussed. Fatigue tests of prestrained and non-prestrained specimens were performed. Inflections and branches at ferrite-martensite boundaries were observed in the non-prestrained specimens. On the other hand, less inflections and branches were found in the prestrained specimens. The experimental results showed that the transformation induced microscopic residual stress has influence on the fatigue crack propagation behavior. To estimate the microscopic residual, a numerical simulation method for the calculation of microscopic residual stress stress induced by martensitic transformation was performed. The simulation showed that compressive residual stress was generated in martensite layer, and the result agree with the experimental result that inflections and branches were observed at ferrite-martensite boundaries.

  14. An accelerated life test model for harmonic drives under a segmental stress history and its parameter optimization

    Directory of Open Access Journals (Sweden)

    Zhang Chao

    2015-12-01

    Full Text Available Harmonic drives have various distinctive advantages and are widely used in space drive mechanisms. Accelerated life test (ALT is commonly conducted to shorten test time and reduce associated costs. An appropriate ALT model is needed to predict the lifetime of harmonic drives with ALT data. However, harmonic drives which are used in space usually work under a segmental stress history, and traditional ALT models can hardly be used in this situation. This paper proposes a dedicated ALT model for harmonic drives applied in space systems. A comprehensive ALT model is established and genetic algorithm (GA is adopted to obtain optimal parameters in the model using the Manson fatigue damage rule to describe the fatigue failure process and a cumulative damage method to calculate and accumulate the damage caused by each segment in the stress history. An ALT of harmonic drives was carried out and experimental results show that this model is acceptable and effective.

  15. Paternal history of mental illness associated with posttraumatic stress disorder among veterans.

    Science.gov (United States)

    Shepherd-Banigan, Megan; Kelley, Michelle L; Katon, Jodie G; Curry, John F; Goldstein, Karen M; Brancu, Mira; Wagner, H Ryan; Fecteau, Teresa E; Van Houtven, Courtney H

    2017-10-01

    This study examined the association between parent and family reported history of non-PTSD mental illness (MI), PTSD specifically, and substance use problems, and participant clinical diagnosis of PTSD. Participants were drawn from the US Department of Veterans Affairs Mid-Atlantic Mental Illness Research, Education and Clinical Center (MIRECC) Post-Deployment Mental Health (PDMH) study (n = 3191), an ongoing multi-site cohort study of US Afghanistan and Iraq conflict era veterans. Participants who recalled a father history of PTSD had a 26-percentage point higher likelihood of meeting criteria for PTSD; while participants reporting any family history of PTSD had a 15-percentage point higher probability of endorsing symptoms consistent with PTSD. Mother history of substance use problems was associated with Veteran current PTSD, but results were sensitive to model specification. Current PTSD was not associated with family/parent history of non-PTSD mental illness, mother history of PTSD, or family/father history of substance use problems. Family history of PTSD may increase PTSD risk among veterans exposed to trauma, particularly when a father history is reported. Knowledge of family history could improve clinical decision-making for trauma-exposed individuals and allow for more effective targeting of programs and clinical services. Published by Elsevier B.V.

  16. Frictional response of simulated faults to normal stresses perturbations probed with ultrasonic waves

    Science.gov (United States)

    Shreedharan, S.; Riviere, J.; Marone, C.

    2017-12-01

    We report on a suite of laboratory friction experiments conducted on saw-cut Westerly Granite surfaces to probe frictional response to step changes in normal stress and loading rate. The experiments are conducted to illuminate the fundamental processes that yield friction rate and state dependence. We quantify the microphysical frictional response of the simulated fault surfaces to normal stress steps, in the range of 1% - 600% step increases and decreases from a nominal baseline normal stress. We measure directly the fault slip rate and account for changes in slip rate with changes in normal stress and complement mechanical data acquisition by continuously probing the faults with ultrasonic pulses. We conduct the experiments at room temperature and humidity conditions in a servo controlled biaxial testing apparatus in the double direct shear configuration. The samples are sheared over a range of velocities, from 0.02 - 100 μm/s. We report observations of a transient shear stress and friction evolution with step increases and decreases in normal stress. Specifically, we show that, at low shear velocities and small increases in normal stress ( 5% increases), the shear stress evolves immediately with normal stress. We show that the excursions in slip rate resulting from the changes in normal stress must be accounted for in order to predict fault strength evolution. Ultrasonic wave amplitudes which first increase immediately in response to normal stress steps, then decrease approximately linearly to a new steady state value, in part due to changes in fault slip rate. Previous descriptions of frictional state evolution during normal stress perturbations have not adequately accounted for the effect of large slip velocity excursions. Here, we attempt to do so by using the measured ultrasonic amplitudes as a proxy for frictional state during transient shear stress evolution. Our work aims to improve understanding of induced and triggered seismicity with focus on

  17. Hierarchical Petascale Simulation Framework for Stress Corrosion Cracking

    Energy Technology Data Exchange (ETDEWEB)

    Vashishta, Priya

    2014-12-01

    Reaction Dynamics in Energetic Materials: Detonation is a prototype of mechanochemistry, in which mechanically and thermally induced chemical reactions far from equilibrium exhibit vastly different behaviors. It is also one of the hardest multiscale physics problems, in which diverse length and time scales play important roles. The CACS group has performed multimillion-atom reactive MD simulations to reveal a novel two-stage reaction mechanism during the detonation of cyclotrimethylenetrinitramine (RDX) crystal. Rapid production of N2 and H2O within ~10 ps is followed by delayed production of CO molecules within ~ 1 ns. They found that further decomposition towards the final products is inhibited by the formation of large metastable C- and O-rich clusters with fractal geometry. The CACS group has also simulated the oxidation dynamics of close-packed aggregates of aluminum nanoparticles passivated by oxide shells. Their simulation results suggest an unexpectedly active role of the oxide shell as a nanoreactor.

  18. A Virtual Rat for Simulating Environmental and Exertional Heat Stress

    Science.gov (United States)

    2014-10-02

    unsuitable for accurately determin- ing the spatiotemporal temperature distribution in the animal due to heat stress and for performing mechanistic analysis ...possible in the original experiments. Finally, we performed additional simu- lations using the virtual rat to facilitate comparative analysis of the...capability of the virtual rat to account for the circadian rhythmicity in core temperatures during an in- crease in the external temperature from 22

  19. Induced Stress, Artificial Environment, Simulated Tactical Operations Center Model

    Science.gov (United States)

    1973-06-01

    hiebman, Stress Situations (Philadelphia: J. Is. IJ iui ott CO., .lqý1.), pp. ’ - 6. ’ | ;* .- -~~~~~~~~. , ’ • :• ",. . .... . , • . 33 provides one or...April 1964, pp. 545-556. ~ .~:.;a-d K. " -Iu: izodoiog;ical Ls;suL5- in Experiuienting, withi Sil-.ISiilatý’ionS of Lusincss Pim ~"paper presentecd at

  20. Surgeons' and surgical trainees' acute stress in real operations or simulation: A systematic review.

    Science.gov (United States)

    Georgiou, Konstantinos; Larentzakis, Andreas; Papavassiliou, Athanasios G

    2017-12-01

    Acute stress in surgery is ubiquitous and has an immediate impact on surgical performance and patient safety. Surgeons react with several coping strategies; however, they recognise the necessity of formal stress management training. Thus, stress assessment is a direct need. Surgical simulation is a validated standardised training milieu designed to replicate real-life situations. It replicates stress, prevents biases, and provides objective metrics. The complexity of stress mechanisms makes stress measurement difficult to quantify and interpret. This systematic review aims to identify studies that have used acute stress estimation measurements in surgeons or surgical trainees during real operations or surgical simulation, and to collectively present the rationale of these tools, with special emphasis in salivary markers. A search strategy was implemented to retrieve relevant articles from MEDLINE and SCOPUS databases. The 738 articles retrieved were reviewed for further evaluation according to the predetermined inclusion/exclusion criteria. Thirty-three studies were included in this systematic review. The methods for acute stress assessment varied greatly among studies with the non-invasive techniques being the most commonly used. Subjective and objective tests for surgeons' acute stress assessment are being presented. There is a broad spectrum of acute mental stress assessment tools in the surgical field and simulation and salivary biomarkers have recently gained popularity. There is a need to maintain a consistent methodology in future research, towards a deeper understanding of acute stress in the surgical field. Copyright © 2017 Royal College of Surgeons of Edinburgh (Scottish charity number SC005317) and Royal College of Surgeons in Ireland. Published by Elsevier Ltd. All rights reserved.

  1. Simulation of stress-modulated magnetization precession frequency in Heusler-based spin torque oscillator

    International Nuclear Information System (INIS)

    Huang, Houbing; Zhao, Congpeng; Ma, Xingqiao

    2017-01-01

    We investigated stress-modulated magnetization precession frequency in Heusler-based spin transfer torque oscillator by combining micromagnetic simulations with phase field microelasticity theory, by encapsulating the magnetic tunnel junction into multilayers structures. We proposed a novel method of using an external stress to control the magnetization precession in spin torque oscillator instead of an external magnetic field. The stress-modulated magnetization precession frequency can be linearly modulated by externally applied uniaxial in-plane stress, with a tunable range 4.4–7.0 GHz under the stress of 10 MPa. By comparison, the out-of-plane stress imposes negligible influence on the precession frequency due to the large out-of-plane demagnetization field. The results offer new inspiration to the design of spin torque oscillator devices that simultaneously process high frequency, narrow output band, and tunable over a wide range of frequencies via external stress. - Highlights: • We proposed stress-modulated magnetization precession in spin torque oscillator. • The magnetization precession frequency can be linearly modulated by in-plane stress. • The stress also can widen the magnetization frequency range 4.4–7.0 GHz. • The stress-modulated oscillation frequency can simplify STO devices.

  2. Simulation of stress-modulated magnetization precession frequency in Heusler-based spin torque oscillator

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Houbing, E-mail: hbhuang@ustb.edu.cn; Zhao, Congpeng; Ma, Xingqiao, E-mail: xqma@sas.ustb.edu.cn

    2017-03-15

    We investigated stress-modulated magnetization precession frequency in Heusler-based spin transfer torque oscillator by combining micromagnetic simulations with phase field microelasticity theory, by encapsulating the magnetic tunnel junction into multilayers structures. We proposed a novel method of using an external stress to control the magnetization precession in spin torque oscillator instead of an external magnetic field. The stress-modulated magnetization precession frequency can be linearly modulated by externally applied uniaxial in-plane stress, with a tunable range 4.4–7.0 GHz under the stress of 10 MPa. By comparison, the out-of-plane stress imposes negligible influence on the precession frequency due to the large out-of-plane demagnetization field. The results offer new inspiration to the design of spin torque oscillator devices that simultaneously process high frequency, narrow output band, and tunable over a wide range of frequencies via external stress. - Highlights: • We proposed stress-modulated magnetization precession in spin torque oscillator. • The magnetization precession frequency can be linearly modulated by in-plane stress. • The stress also can widen the magnetization frequency range 4.4–7.0 GHz. • The stress-modulated oscillation frequency can simplify STO devices.

  3. Stress sensitivity interacts with depression history to predict depressive symptoms among youth: prospective changes following first depression onset.

    Science.gov (United States)

    Technow, Jessica R; Hazel, Nicholas A; Abela, John R Z; Hankin, Benjamin L

    2015-04-01

    Predictors of depressive symptoms may differ before and after the first onset of major depression due to stress sensitization. Dependent stressors, or those to which characteristics of individuals contribute, have been shown to predict depressive symptoms in youth. The current study sought to clarify how stressors' roles may differ before and after the first depressive episode. Adolescents (N = 382, aged 11 to 15 at baseline) were assessed at baseline and every 3 months over the course of 2 years with measures of stressors and depressive symptoms. Semi-structured interviews were conducted every 6 months to assess for clinically significant depressive episodes. Hierarchical linear modeling showed a significant interaction between history of depression and idiographic fluctuations in dependent stressors to predict prospective elevations of symptoms, such that dependent stressors were more predictive of depressive symptoms after onset of disorder. Independent stressors predicted symptoms, but the strength of the association did not vary by depression history. These results suggest a synthesis of dependent stress and stress sensitization processes that might maintain inter-episode depressive symptoms among youth with a history of clinical depression.

  4. Pace bowlers in cricket with history of lumbar stress fracture have increased risk of lower limb muscle strains, particularly calf strains.

    Science.gov (United States)

    Orchard, John; Farhart, Patrick; Kountouris, Alex; James, Trefor; Portus, Marc

    2010-01-01

    To assess whether a history of lumbar stress fracture in pace bowlers in cricket is a risk factor for lower limb muscle strains. This was a prospective cohort risk factor study, conducted using injury data from contracted first class pace bowlers in Australia during seasons 1998-1999 to 2008-2009 inclusive. There were 205 pace bowlers, 33 of whom suffered a lumbar stress fracture when playing first class cricket. Risk ratios ([RR] with 95% confidence intervals[CI]) were calculated to compare the seasonal incidence of various injuries between bowlers with a prior history of lumbar stress fracture and those with no history of lumbar stress fracture. Risk of calf strain was strongly associated with prior lumbar stress fracture injury history (RR = 4.1; 95% CI: 2.4-7.1). Risks of both hamstring strain (RR = 1.5; 95% CI: 1.03-2.1) and quadriceps strain (RR = 2.0; 95% CI: 1.1-3.5) were somewhat associated with history of lumbar stress fracture. Risk of groin strain was not associated with history of lumbar stress fracture (RR = 0.7; 95% CI: 0.4-1.1). Other injuries showed little association with prior lumbar stress fracture, although knee cartilage injuries were more likely in the non-stress fracture group. Bony hypertrophy associated with lumbar stress fracture healing may lead to subsequent lumbar nerve root impingement, making lower limb muscle strains more likely to occur. Confounders may be responsible for some of the findings. In particular, bowling speed is likely to be independently correlated with risk of lumbar stress fracture and risk of muscle strain. However, as the relationship between lumbar stress fracture history and calf strain was very strong, and that there is a strong theoretical basis for the connection, it is likely that this is a true association.

  5. Simulation of stresses, residual stresses, and distortion in stepped cylinders of AISI 4140 due to martensitical hardening by immersion cooling

    Energy Technology Data Exchange (ETDEWEB)

    Ehlers, M.; Mueller, H.; Loehe, D. [Karlsruhe Univ. (Germany). Inst. for Materials Science and Engineering I

    1999-09-01

    Heat treatment improves mechanical properties of steel parts, but also causes residual stresses and distortion. Stresses and deformation occurring during heat treatment can not be measured in-situ with appropriate temporal and spatial resolution. In order to evaluate the processes occurring in the workpiece during quenching as well as the residual stresses and distortions, numerical methods have to be used. Heat conduction, phase transformations, and mechanical behaviour of the material as well as the couplings between the processes such as transformation plasticity have to be modeled for the simulation of steel hardening. Temperature and phase dependent properties (including TTT-data) have to incorporated into calculations. One of the major factors determining the evolution of stress and deformation is the heat-transfer coefficient between component and quenching medium. For vapourizing liquids, heat transfer depends on temperature and location. But heat transfer is not only influenced by the quenchant but also by part geometry and size. Stepped cylinders of AISI 4140 steel were quenched in water and oil. Both experimental measurements and numerical calculations were carried out. The variation of dive-in direction strongly influences the rewetting of the specimen surface and therefore the cooling behaviour, stress and deformation evolution, and resultant residual stresses and distortion. Excellent agreement is obtained between calculated and experimental results. (orig.)

  6. Activity of earthworm in Latosol under simulated acid rain stress

    Science.gov (United States)

    Jia-En Zhang; Jiayu Yu; Ying Ouyang

    2015-01-01

    Acid rain is still an issue of environmental concerns. This study investigated the impacts of simulated acid rain (SAR) upon earthworm activity from the Latosol (acidic red soil). Laboratory experiment was performed by leaching the soil columns grown with earthworms (Eisenia fetida) at the SAR pH levels ranged from 2.0 to 6.5 over a 34-day period....

  7. Simulated drought influences oxidative stress in Zea mays seedlings ...

    African Journals Online (AJOL)

    Drought is an abiotic factor that limits the productivity of crop plants survival and productivity. This study was conducted to evaluate the effects of simulated drought on the malondialdehyde (MDA) and antioxidant enzymes activity in Zea mays. Seedlings were grown for 8 weeks in nursery bags filled with sandy-loam soil in ...

  8. Stress-Induced Impairment of a Working Memory Task: Role of Spiking Rate and Spiking History Predicted Discharge

    Science.gov (United States)

    Devilbiss, David M.; Jenison, Rick L.; Berridge, Craig W.

    2012-01-01

    Stress, pervasive in society, contributes to over half of all work place accidents a year and over time can contribute to a variety of psychiatric disorders including depression, schizophrenia, and post-traumatic stress disorder. Stress impairs higher cognitive processes, dependent on the prefrontal cortex (PFC) and that involve maintenance and integration of information over extended periods, including working memory and attention. Substantial evidence has demonstrated a relationship between patterns of PFC neuron spiking activity (action-potential discharge) and components of delayed-response tasks used to probe PFC-dependent cognitive function in rats and monkeys. During delay periods of these tasks, persistent spiking activity is posited to be essential for the maintenance of information for working memory and attention. However, the degree to which stress-induced impairment in PFC-dependent cognition involves changes in task-related spiking rates or the ability for PFC neurons to retain information over time remains unknown. In the current study, spiking activity was recorded from the medial PFC of rats performing a delayed-response task of working memory during acute noise stress (93 db). Spike history-predicted discharge (SHPD) for PFC neurons was quantified as a measure of the degree to which ongoing neuronal discharge can be predicted by past spiking activity and reflects the degree to which past information is retained by these neurons over time. We found that PFC neuron discharge is predicted by their past spiking patterns for nearly one second. Acute stress impaired SHPD, selectively during delay intervals of the task, and simultaneously impaired task performance. Despite the reduction in delay-related SHPD, stress increased delay-related spiking rates. These findings suggest that neural codes utilizing SHPD within PFC networks likely reflects an additional important neurophysiological mechanism for maintenance of past information over time. Stress

  9. Doctors' stress responses and poor communication performance in simulated bad-news consultations.

    Science.gov (United States)

    Brown, Rhonda; Dunn, Stewart; Byrnes, Karen; Morris, Richard; Heinrich, Paul; Shaw, Joanne

    2009-11-01

    No studies have previously evaluated factors associated with high stress levels and poor communication performance in breaking bad news (BBN) consultations. This study determined factors that were most strongly related to doctors' stress responses and poor communication performance during a simulated BBN task. In 2007, the authors recruited 24 doctors comprising 12 novices (i.e., interns/residents with 1-3 years' experience) and 12 experts (i.e., registrars, medical/radiation oncologists, or cancer surgeons, with more than 4 years' experience). Doctors participated in simulated BBN consultations and a number of control tasks. Five-minute-epoch heart rate (HR), HR variability, and communication performance were assessed in all participants. Subjects also completed a short questionnaire asking about their prior experience BBN, perceived stress, psychological distress (i.e., anxiety, depression), fatigue, and burnout. High stress responses were related to inexperience with BBN, fatigue, and giving bad versus good news. Poor communication performance in the consultation was related to high burnout and fatigue scores. These results suggest that BBN was a stressful experience for doctors even in a simulated encounter, especially for those who were inexperienced and/or fatigued. Poor communication performance was related to burnout and fatigue, but not inexperience with BBN. These results likely indicate that burnout and fatigue contributed to stress and poor work performance in some doctors during the simulated BBN task.

  10. Temperature-induced physiological stress and reproductive characteristics of the migratory seahorse Hippocampus erectus during a thermal stress simulation.

    Science.gov (United States)

    Qin, Geng; Johnson, Cara; Zhang, Yuan; Zhang, Huixian; Yin, Jianping; Miller, Glen; Turingan, Ralph G; Guisbert, Eric; Lin, Qiang

    2018-05-15

    Inshore-offshore migration occurs frequently in seahorse species either because of prey opportunities or because it is driven by reproduction, and variations in water temperature may dramatically change migratory seahorse behavior and physiology. The present study investigated the behavioral and physiological responses of the lined seahorse Hippocampus erectus under thermal stress and evaluated the potential effects of different temperatures on its reproduction. The results showed that the thermal tolerance of the seahorses was time dependent. Acute thermal stress (30°C, 2-10 hours) increased the basal metabolic rate (breathing rate) and the expression of stress response genes ( Hsp genes) significantly and further stimulated seahorse appetite. Chronic thermal treatment (30°C, 4 weeks) led to a persistently higher basal metabolic rate, higher stress response gene expression, and higher mortality, indicating that the seahorses could not acclimate to chronic thermal stress and might experience massive mortality due to excessive basal metabolic rates and stress damage. Additionally, no significant negative effects on gonad development or reproductive endocrine regulation genes were observed in response to chronic thermal stress, suggesting that seahorse reproductive behavior could adapt to higher-temperature conditions during migration and within seahorse breeding grounds. In conclusion, this simulation experiment indicated that temperature variations during inshore-offshore migration have no effect on reproduction but promote basal metabolic rates and stress responses significantly. Therefore, we suggest that the high observed tolerance of seahorse reproduction was in line with the inshore-offshore reproductive migration pattern of lined seahorse. © 2018. Published by The Company of Biologists Ltd.

  11. Evaluation of cladding residual stresses in clad blocks by measurements and numerical simulations

    International Nuclear Information System (INIS)

    Dupas, P.; Moinereau, D.

    1996-01-01

    Reactor pressure vessels are internally clad with austenitic stainless steel. This welding operation generates residual stresses which can have an important role in integrity assessments. In order to evaluate these stresses, an experimental and numerical programme has been conducted. The experiments includes cladding operations, macrographic analyses, temperature and residual stresses measurements with different methods. According to these measurements, transversal stresses (perpendicular to the welding direction) and longitudinal stresses (parallel to the welding direction) are highly tensile in stainless steel and they are compressive in the HAZ. Finite element calculations were used to simulate both welding operations and post weld heat treatment. These calculations coupled the thermal, metallurgical and mechanical aspects in a 2D representation. Different models were studied including effect of generalised plane strain, transformation plasticity, creep and tempering. The transversal stresses calculated are similar to the measured ones, but the longitudinal stresses showed to be very sensitive to the model used. As expected because of the two-dimension model, the longitudinal stresses can't be well estimated. More work is needed to improve measurements of stresses in depth (important differences appeared between the different methods). A predictive model would be also very useful to determine the thermal loading which is at present dependant on measurements. A 3D calculation appears to be necessary to evaluate longitudinal stresses. (orig.)

  12. Psychobiological stress response to a simulated school shooting in police officers.

    Science.gov (United States)

    Strahler, Jana; Ziegert, Thomas

    2015-01-01

    Police work is one of the most demanding professions with various sources of high occupational stress. Among the most demanding tasks are amok situations, such as school shootings. Hardly anything is known about endocrine and cardiovascular markers in safety professionals during emergency situations in real life and how this relates to stress perception and management. This study will therefore explore police officers' stress responses to a reality-based school shooting simulation assessing neuroendocrine, cardiovascular, and psychological stress markers. A convenience sample of 50 police officers (39.5 ± 8.7 yrs, 9 women) participating in a basic or refresher amok training session for the German uniformed and criminal police were recruited. Saliva samples were collected shortly before the simulation task (school shooting), immediately after, 20 and 45 min after finishing the task for the assessment of cortisol and alpha-amylase (sAA), as markers of the hypothalamic-pituitary-adrenal axis and the autonomic nervous system, respectively. Heart rate (variability) was assessed continuously. Officers rated their actual mood right before and 10 min after the simulation. Subjective experience of task stressfulness was assessed minutes after finishing the simulation. Overall, the simulated school shooting did not result in changes of mood, tiredness, or calmness but higher restlessness was experienced during the basic training, which was also experienced as more controllable. Female officers reported to experience more strain and anxiety. Cortisol showed highest levels at the beginning of the training and steadily decreasing values thereafter. In contrast, sAA increased substantially right after the simulation with officers on the front position showing most pronounced changes. Cardiovascular reactivity was highest in officers acting on the side positions while advancing to find the suspect. Furthermore higher self-efficacy as well as, by trend, controllability and

  13. FEM simulation study on relationship of interfacial morphology and residual stress in TBCs

    Energy Technology Data Exchange (ETDEWEB)

    Liqiang Chen; Shengkai Gong; Huibin Xu [School of Materials Science and Engineering, Beihang Univ., Beijing, BJ (China)

    2005-07-01

    It is generally believed that the failure of TBCs is attributed to the spallation occurred in the ceramic coat. The spallation is closed linked with sinuate morphology factors, including its amplitude and period, at the TGO/bond coat interface. In this work, dependence of the residual stress distribution on the sinuate morphology in the TBCs has been studied by means of finite element method (FEM) simulation for isothermally annealed specimens. The simulation results indicated that the maximum value of residual stress existed inside the TGO layer. It was also found that the maximum residual stress occurred at different points, near the TGO/bond coat interface at the peak of the sinuate interface, while near the TGO/ceramic coat interface at the valley, respectively. And the maximum residual stress increased with increasing the ratio of the amplitude to period in the sine morphology, which has been proved by the thermal cycle experimental results. (orig.)

  14. Altered Stress-Induced Regulation of Genes in Monocytes in Adults with a History of Childhood Adversity.

    Science.gov (United States)

    Schwaiger, Marion; Grinberg, Marianna; Moser, Dirk; Zang, Johannes C S; Heinrichs, Markus; Hengstler, Jan G; Rahnenführer, Jörg; Cole, Steve; Kumsta, Robert

    2016-09-01

    Exposure to serious or traumatic events early in life can lead to persistent alterations in physiological stress response systems, including enhanced cross talk between the neuroendocrine and immune system. These programming effects may be mechanistically involved in mediating the effects of adverse childhood experience on disease risk in adulthood. We investigated hormonal and genome-wide mRNA expression responses in monocytes to acute stress exposure, in a sample of healthy adults (n=30) with a history of early childhood adversity, and a control group (n=30) without trauma experience. The early adversity group showed altered hypothalamus-pituitary-adrenal axis responses to stress, evidenced by lower ACTH and cortisol responses. Analyses of gene expression patterns showed that stress-responsive transcripts were enriched for genes involved in cytokine activity, cytokine-cytokine receptor interaction, chemokine activity, and G-protein coupled receptor binding. Differences between groups in stress-induced regulation of gene transcription were observed for genes involved in steroid binding, hormone activity, and G-protein coupled receptor binding. Transcription factor binding motif analysis showed an increased activity of pro-inflammatory upstream signaling in the early adversity group. We also identified transcripts that were differentially correlated with stress-induced cortisol increases between the groups, enriched for genes involved in cytokine-cytokine receptor interaction and glutamate receptor signaling. We suggest that childhood adversity leads to persistent alterations in transcriptional control of stress-responsive pathways, which-when chronically or repeatedly activated-might predispose individuals to stress-related psychopathology.

  15. Trans-generational effects of mild heat stress on the life history traits of an aphid parasitoid.

    Science.gov (United States)

    Ismaeil, Ibrahim; Doury, Géraldine; Desouhant, Emmanuel; Dubois, Françoise; Prevost, Geneviève; Couty, Aude

    2013-01-01

    Temperature changes are common in nature and insects are particularly exposed and sensitive to such variations which can be potential stresses, ultimately affecting life history traits and overall fitness. Braconids have been widely used to study the effects of temperature on host-parasitoid interactions and the present work focused on the solitary endoparasitoid Aphidius ervi Haliday (Hymenoptera: Braconidae Aphidiidae), an efficient biological control agent commercially used against aphids such as the potato aphid Macrosiphum euphorbiae Thomas (Sternorrhyncha: Aphididae). Contrary to previous studies using heat shocks at extreme temperatures, we evaluated the effects of mild heat stresses by transferring young parasitoid adults from the constant temperature of 20°C to either a warm (25°C) or hot (28°C) temperature, for either 1 h or 48 h. Such treatments are consistent with situations commonly experienced by parasitoids when moved from their rearing conditions to greenhouses or field conditions. The effects were evaluated both on the heat stressed A. ervi adults (G0) (immediate effects) and on their first generation (G1) progeny (trans-generational effects). G0 wasps' mortality was significantly affected by the temperature in interaction with the duration of the stress. Longevity of G0 wasps surviving the heat stress was negatively affected by the temperature and females lived longer than males. Heat stress applied to A. ervi parents also had consequences on their G1 progeny whose developmental time, rates of mummification and percentage of parasitoid completing total development were negatively affected. Surprisingly, the egg load at emergence of the G1 female progeny was increased when their mothers had been submitted to a mild heat stress of 25°C or 28°C. These results clearly demonstrate trans-generational phenotypic plasticity, showing that adaptation to thermal stresses may be achieved via maternal effects. This study also sheds light on the complexity

  16. Trans-generational effects of mild heat stress on the life history traits of an aphid parasitoid.

    Directory of Open Access Journals (Sweden)

    Ibrahim Ismaeil

    Full Text Available Temperature changes are common in nature and insects are particularly exposed and sensitive to such variations which can be potential stresses, ultimately affecting life history traits and overall fitness. Braconids have been widely used to study the effects of temperature on host-parasitoid interactions and the present work focused on the solitary endoparasitoid Aphidius ervi Haliday (Hymenoptera: Braconidae Aphidiidae, an efficient biological control agent commercially used against aphids such as the potato aphid Macrosiphum euphorbiae Thomas (Sternorrhyncha: Aphididae. Contrary to previous studies using heat shocks at extreme temperatures, we evaluated the effects of mild heat stresses by transferring young parasitoid adults from the constant temperature of 20°C to either a warm (25°C or hot (28°C temperature, for either 1 h or 48 h. Such treatments are consistent with situations commonly experienced by parasitoids when moved from their rearing conditions to greenhouses or field conditions. The effects were evaluated both on the heat stressed A. ervi adults (G0 (immediate effects and on their first generation (G1 progeny (trans-generational effects. G0 wasps' mortality was significantly affected by the temperature in interaction with the duration of the stress. Longevity of G0 wasps surviving the heat stress was negatively affected by the temperature and females lived longer than males. Heat stress applied to A. ervi parents also had consequences on their G1 progeny whose developmental time, rates of mummification and percentage of parasitoid completing total development were negatively affected. Surprisingly, the egg load at emergence of the G1 female progeny was increased when their mothers had been submitted to a mild heat stress of 25°C or 28°C. These results clearly demonstrate trans-generational phenotypic plasticity, showing that adaptation to thermal stresses may be achieved via maternal effects. This study also sheds light on

  17. ATF4 is involved in the regulation of simulated microgravity induced integrated stress response

    Science.gov (United States)

    Li, Yingxian; Li, Qi; Wang, Xiaogang; Sun, Qiao; Wan, Yumin; Li, Yinghui; Bai, Yanqiang

    Objective: Many important metabolic and signaling pathways have been identified as being affected by microgravity, thereby altering cellular functions such as proliferation, differentiation, maturation and cell survival. It has been demonstrated that microgravity could induce all kinds of stress response such as endoplasmic reticulum stress and oxidative stress et al. ATF4 belongs to the ATF/CREB family of basic region leucine zipper transcription factors. ATF4 is induced by stress signals including anoxia/hypoxia, ER stress, amino acid deprivation and oxidative stress. ATF4 regulates the expression of genes involved in oxidative stress, amino acid synthesis, differentiation, metastasis and angiogenesis. The aim of this study was to examine the changes of ATF4 under microgravity, and to investigate the role of ATF4 in microgravity induced stress. MethodsMEF cells were cultured in clinostat to simulate microgravity. Reverse transcription polymerase chain reaction (RT-PCR) and western blotting were used to examine mRNA and protein levels of ATF4 expression under simulated microgravity in MEF cells. ROS levels were measured with the use of the fluorescent signal H2DCF-DA. GFP-XBP1 stably transfected cell lines was used to detect the extent of ER stress under microgravity by the intensity of GFP. Dual luciferase reporter assay was used to detect the activity of ATF4. Co-immunoprecipitation was performed to analyze protein interaction. Results: ATF4 protein levels in MEF cells increased under simulated microgravity. However, ATF4 mRNA levels were consistent. XBP1 splicing can be induced due to ER stress caused by simulated microgravity. At the same time, ROS levels were also increased. Increased ATF4 could promote the expression of CHOP, which is responsible for cell apoptosis. ATF4 also play an important role in cellular anti-oxidant stress. In ATF4 -/-MEF cells, the ROS levels after H2O2 treatment were obviously higher than that of wild type cells. HDAC4 was

  18. Life-history responses of insects to water-deficit stress: a case study with the aphid Sitobion avenae.

    Science.gov (United States)

    Liu, Deguang; Dai, Peng; Li, Shirong; Ahmed, Syed Suhail; Shang, Zheming; Shi, Xiaoqin

    2018-05-29

    Drought may become one of the greatest challenges for cereal production under future warming scenarios, and its impact on insect pest outbreaks is still controversial. To address this issue, life-history responses of the English grain aphid, Sitobion avenae (Fabricius), from three areas of different drought levels were compared under three water treatments. Significant differences were identified in developmental time, fecundity and adult weight among S. avenae clones from moist, semiarid and arid areas under all the three water treatments. Semiarid and arid area clones tended to have higher heritability for test life-history traits than moist area clones. We identified significant selection of water-deficit on the developmental time of 1st instar nymphs and adult weight for both semiarid and arid area clones. The impact of intermediate and severe water-stress on S. avenae's fitness was neutral and negative (e.g., decreased fecundity and weight), respectively. Compared with arid-area clones, moist- and semiarid-area clones showed higher extents of adaptation to the water-deficit level of their respective source environment. Adult weight was identified as a good indicator for S. avenae's adaptation potential under different water-stress conditions. After their exposure to intermediate water-deficit stress for only five generations, adult weight and fecundity tended to decrease for moist- and semiarid-area clones, but increase for arid-area clones. It is evident from our study that S. avenae clones from moist, semiarid and arid areas have diverged under different water-deficit stress, and such divergence could have a genetic basis. The impact of drought on S. avenae's fitness showed a water-level dependent pattern. Clones of S. avenae were more likely to become adapted to intermediate water-deficit stress than severe water-deficit stress. After continuous water-deficit stress of only five generations, the adaptation potential of S. avenae tended to decrease for moist

  19. Numerical simulation of residual stress in piping components at Framatome-ANP

    International Nuclear Information System (INIS)

    Gilies, P.; Franco, C.; Cipiere, M.-F.; Ould, P.

    2005-01-01

    Numerous manufacturing processes induce residual stresses and distortions in piping components and associated welds: quenching of cast pipings, machining and welding. In Pressurized Water Reactors, most of the components have a large thickness for sustaining pressure and distortions are a minor source of concern. This is not the case for residual stresses which may have a strong influence on several type of damage such as fatigue, corrosion, brittle fracture. In low toughness components, residual stress fields may contribute to ductile tearing initiation. These potential damages are mitigated after welding by stress relief heat treatment, which is applied in a systematic manner to ferritic components of the primary system in nuclear reactors. This treatment is not applied on austenitic piping for which the heat treatment temperature is limited due to the risk of sensitization and residual stresses are difficult to eliminate completely. Since on site measurements are costly and difficult to perform, numerical simulation appears to be an attractive tool for estimating residual stress distributions. Framatome-ANP is working on modelling manufacturing processes with that purpose in mind. This paper presents three kinds of applications illustrating efforts on welding, quenching and machining simulation. First a comparison is shown between computations and measurements of residual stress induced by welding of a dissimilar weld metal junction. Then numerical simulations of quenching of a cast stainless steel nozzle are presented. Finally quenching followed by machining and grinding of this cast component are considered in a full simulation of the manufacturing process. Computed distortions and residual stresses are compared with experimental measurements at different stages of the manufacturing process. (authors)

  20. Life stress and family history for depression: the moderating role of past depressive episodes.

    Science.gov (United States)

    Monroe, Scott M; Slavich, George M; Gotlib, Ian H

    2014-02-01

    Three of the most consistently reported and powerful predictors of depression are a recent major life event, a positive family history for depression, and a personal history of past depressive episodes. Little research, however, has evaluated the inter-relations among these predictors in depressed samples. Such information is descriptively valuable and potentially etiologically informative. In the present article we summarize the existing literature and test four predictions in a sample of 62 clinically depressed individuals: (1) participants who experienced a major life event prior to onset would be less likely than participants who did not experience a major life event to have a positive family history for depression; (2) participants with a recent major life event would have fewer lifetime episodes of depression than would participants without; (3) participants with a positive family history for depression would have more lifetime episodes of depression than would participants with a negative family history for depression; and (4) we would obtain a 3-way interaction in which participants with a positive family history and without a major life event would have the most lifetime episodes, whereas participants with a negative family history and a major life event would have the fewest lifetime episodes. The first three predictions were confirmed, and the fourth prediction partially confirmed. These novel findings begin to elucidate the complex relations among these three prominent risk factors for depression, and point to avenues of research that may help illuminate the origins of depressive episodes. Copyright © 2013 Elsevier Ltd. All rights reserved.

  1. Jewish History Engagement in an Online Simulation: Golda and Coco, Leah and Lou at the Jewish Court of All Time

    Science.gov (United States)

    Katz, Meredith L.; Kress, Jeffrey S.

    2018-01-01

    This study investigates the Jewish history engagement for middle school students "playing" in the Jewish Court of All Time (JCAT), an online simulation of a current events court case with historical roots (http://jcat.icsmich.org). Through an online platform across several schools, students research and play historical and current…

  2. Equivalent Young's modulus of composite resin for simulation of stress during dental restoration.

    Science.gov (United States)

    Park, Jung-Hoon; Choi, Nak-Sam

    2017-02-01

    For shrinkage stress simulation in dental restoration, the elastic properties of composite resins should be acquired beforehand. This study proposes a formula to measure the equivalent Young's modulus of a composite resin through a calculation scheme of the shrinkage stress in dental restoration. Two types of composite resins remarkably different in the polymerization shrinkage strain were used for experimental verification: the methacrylate-type (Clearfil AP-X) and the silorane-type (Filtek P90). The linear shrinkage strains of the composite resins were gained through the bonded disk method. A formula to calculate the equivalent Young's moduli of composite resin was derived on the basis of the restored ring substrate. Equivalent Young's moduli were measured for the two types of composite resins through the formula. Those values were applied as input to a finite element analysis (FEA) for validation of the calculated shrinkage stress. Both of the measured moduli through the formula were appropriate for stress simulation of dental restoration in that the shrinkage stresses calculated by the FEA were in good agreement within 3.5% with the experimental values. The concept of equivalent Young's modulus so measured could be applied for stress simulation of 2D and 3D dental restoration. Copyright © 2016 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  3. Infrared thermometry and the crop water stress index. I. History, theory, and baselines

    International Nuclear Information System (INIS)

    Gardner, B.R.; Nielsen, D.C.; Shock, C.C.

    1992-01-01

    Development of portable infrared thermometers and the definition of the Crop Water Stress Index (CWSI) have led to widespread interest in infrared thermometry to monitor water stress and schedule irrigations. But the CWSI concept is still new and poorly understood by many. The purpose of this paper is to review the definition of CWSI, and the determination and interpretation of the non-water-stressed baselines used to compute CWSI. The non-water-stressed baseline equation normalizes the canopy minus air temperature differential for variations in vapor pressure deficit. Non-water-stressed baselines can be determined empirically from measurements of canopy and air temperatures and vapor pressure deficit, made diurnally on a single day, or at a single time of day over many days, on well-watered plants. The value of the maximum canopy minus air temperature differential under maximum water stress should also be determined empirically. Causes for CWSI values falling outside of the defined 0 to 10 unit range are reviewed. Non-water-stressed baselines may shift with plant growth stage. Effective use of CWSI is dependent on understanding the definition of CWSI, and the proper determination and use of non-water-stressed baselines. (author)

  4. Impact of trace metal concentrations on coccolithophore growth and morphology: laboratory simulations of Cretaceous stress

    Science.gov (United States)

    Faucher, Giulia; Hoffmann, Linn; Bach, Lennart T.; Bottini, Cinzia; Erba, Elisabetta; Riebesell, Ulf

    2017-07-01

    The Cretaceous ocean witnessed intervals of profound perturbations such as volcanic input of large amounts of CO2, anoxia, eutrophication and introduction of biologically relevant metals. Some of these extreme events were characterized by size reduction and/or morphological changes of a few calcareous nannofossil species. The correspondence between intervals of high trace metal concentrations and coccolith dwarfism suggests a negative effect of these elements on nannoplankton biocalcification processes in past oceans. In order to test this hypothesis, we explored the potential effect of a mixture of trace metals on growth and morphology of four living coccolithophore species, namely Emiliania huxleyi, Gephyrocapsa oceanica, Pleurochrysis carterae and Coccolithus pelagicus. The phylogenetic history of coccolithophores shows that the selected living species are linked to Mesozoic species showing dwarfism under excess metal concentrations. The trace metals tested were chosen to simulate the environmental stress identified in the geological record and upon known trace metal interactions with living coccolithophore algae.Our laboratory experiments demonstrated that elevated trace metal concentrations, similarly to the fossil record, affect coccolithophore algae size and/or weight. Smaller coccoliths were detected in E. huxleyi and C. pelagicus, while coccoliths of G. oceanica showed a decrease in size only at the highest trace metal concentrations. P. carterae coccolith size was unresponsive to changing trace metal concentrations. These differences among species allow discriminating the most- (P. carterae), intermediate- (E. huxleyi and G. oceanica) and least-tolerant (C. pelagicus) taxa. The fossil record and the experimental results converge on a selective response of coccolithophores to metal availability.These species-specific differences must be considered before morphological features of coccoliths are used to reconstruct paleo-chemical conditions.

  5. Impact of trace metal concentrations on coccolithophore growth and morphology: laboratory simulations of Cretaceous stress

    Directory of Open Access Journals (Sweden)

    G. Faucher

    2017-07-01

    Full Text Available The Cretaceous ocean witnessed intervals of profound perturbations such as volcanic input of large amounts of CO2, anoxia, eutrophication and introduction of biologically relevant metals. Some of these extreme events were characterized by size reduction and/or morphological changes of a few calcareous nannofossil species. The correspondence between intervals of high trace metal concentrations and coccolith dwarfism suggests a negative effect of these elements on nannoplankton biocalcification processes in past oceans. In order to test this hypothesis, we explored the potential effect of a mixture of trace metals on growth and morphology of four living coccolithophore species, namely Emiliania huxleyi, Gephyrocapsa oceanica, Pleurochrysis carterae and Coccolithus pelagicus. The phylogenetic history of coccolithophores shows that the selected living species are linked to Mesozoic species showing dwarfism under excess metal concentrations. The trace metals tested were chosen to simulate the environmental stress identified in the geological record and upon known trace metal interactions with living coccolithophore algae.Our laboratory experiments demonstrated that elevated trace metal concentrations, similarly to the fossil record, affect coccolithophore algae size and/or weight. Smaller coccoliths were detected in E. huxleyi and C. pelagicus, while coccoliths of G. oceanica showed a decrease in size only at the highest trace metal concentrations. P. carterae coccolith size was unresponsive to changing trace metal concentrations. These differences among species allow discriminating the most- (P. carterae, intermediate- (E. huxleyi and G. oceanica and least-tolerant (C. pelagicus taxa. The fossil record and the experimental results converge on a selective response of coccolithophores to metal availability.These species-specific differences must be considered before morphological features of coccoliths are used to reconstruct paleo-chemical conditions.

  6. Finite Element Simulation and Experimental Verification of Internal Stress of Quenched AISI 4140 Cylinders

    Science.gov (United States)

    Liu, Yu; Qin, Shengwei; Hao, Qingguo; Chen, Nailu; Zuo, Xunwei; Rong, Yonghua

    2017-03-01

    The study of internal stress in quenched AISI 4140 medium carbon steel is of importance in engineering. In this work, the finite element simulation (FES) was employed to predict the distribution of internal stress in quenched AISI 4140 cylinders with two sizes of diameter based on exponent-modified (Ex-Modified) normalized function. The results indicate that the FES based on Ex-Modified normalized function proposed is better consistent with X-ray diffraction measurements of the stress distribution than FES based on normalized function proposed by Abrassart, Desalos and Leblond, respectively, which is attributed that Ex-Modified normalized function better describes transformation plasticity. Effect of temperature distribution on the phase formation, the origin of residual stress distribution and effect of transformation plasticity function on the residual stress distribution were further discussed.

  7. Stress sensitivity interacts with depression history to predict depressive symptoms among youth: Prospective changes following first depression onset

    Science.gov (United States)

    Technow, Jessica R.; Hazel, Nicholas A.; Abela, John R. Z.; Hankin, Benjamin L.

    2015-01-01

    Predictors of depressive symptoms may differ before and after the first onset of major depression due to stress sensitization. Dependent stressors, or those to which characteristics of individuals contribute, have been shown to predict depressive symptoms in youth. The current study sought to clarify how stressors’ roles may differ before and after the first depressive episode. Adolescents (N = 382, aged 11 to 15 at baseline) were assessed at baseline and every three months over the course of two years with measures of stressors and depressive symptoms. Semi-structured interviews were conducted every 6 months to assess for clinically significant depressive episodes. Hierarchical linear modeling showed a significant interaction between history of depression and idiographic fluctuations in dependent stressors to predict prospective elevations of symptoms, such that dependent stressors were more predictive of depressive symptoms after onset of disorder. Independent stressors predicted symptoms, but the strength of the association did not vary by depression history. These results suggest a synthesis of stress sensitization and generation processes that might maintain inter-episode depressive symptoms among youth with a history of clinical depression. PMID:25123081

  8. Effect of deformation history on the stress relaxation behaviour of Colombian Caribbean coastal cheese from goat milk.

    Science.gov (United States)

    Tirado, Diego F; Acevedo, Diofanor; Torres-Gallo, Ramiro

    2018-01-01

    Textural attributes are a manifestation of the rheological properties and physical structure of foods, cheeses among these. In order to describe these physical properties, the objective of this work was to analyse the effect of deformation history on the stress relaxation behaviour of Colombian Caribbean coastal cheese made from goat milk with 3.75% (F1), 4.00% (F2) and 4.25% (F3) fat content, through prediction made by a four-term Prony series based on Chen's model. For this, stress relaxation data and stress relaxation spectra were analysed. Moreover, textural attributes by texture profile analysis were measured. Physicochemical results were similar to those published by other authors, and all samples meet national and international standards. Results from this work showed that Chen's model could be successfully used to describe the effect of deformation history on the stress relaxation behaviour of Colombian Caribbean coastal cheese made from goat milk. F1 had the highest elastic response, with the most significant residual modules ( P 0 ) and relaxation times (τ 1 , τ 2 and τ 3 ). On the other hand, residual modules and relaxation times (τ 1 , τ 2 and τ 3 ) for cheeses F2 and F3 did not present statistically significant differences (p > 0.05). Besides, by interpretation of the stress relaxation spectra, F1 presented the firmest structure (greatest distribution function and relaxation time) which was characterised by the highest elastic behaviour. Finally, according to texture profile analysis test, F1 had the highest hardness, cohesiveness and chewiness, whereas F2 and F3 did not present statistically significant differences (p > 0.05) between them.

  9. Stress Analysis of Non-Ferrous Metals Welds by Numerical Simulation

    Directory of Open Access Journals (Sweden)

    Kravarikova Helena

    2017-01-01

    Full Text Available Thermal energy welded material unevenly heated and thus supports the creation of tension. During the fusing process welding transient tensions generated in the welded material. Generation of the transient tensions depends on the thermal expansion and fixed permanently welded parts. Tensions are the result of the interaction of material particles. For welded parts and constructions it is necessary to know the size and direction of application of tensions. The emerging tensions can cause local change or a total deformation of welded materials. Deformations and residual stresses impair the performance of a welded construction, reduces the stability of the parts. To reduce or eliminate of action or a screening direction stresses and strains it is necessary to know the mechanism of their emergence. It is now possible to examine the emergence of tensions numerical experiments on any model using numerical simulation using FEM. Results of numerical experiment is the analysis of stress and deformation course. In the plane the tension it divided into normal σ and τ tangential folders. Decomposition stress on components simplifies the stress analysis. The results obtained from numerical analysis are correct to predict the stress distribution and size. The paper presents the results of numerical experiments stress analysis solutions fillet welds using FEM numerical simulation of welding of non-ferrous metals.

  10. Simulation of Stress Distribution in a Thick- Walled Bushing Produced by Die-Casting

    Directory of Open Access Journals (Sweden)

    Pisarek B.P.

    2017-12-01

    Full Text Available Metallographic investigations and a computer simulation of stresses in a gravity die-casting bushing were performed. Simulation of the casting process, solidification of the thick-walled bushing and calculations of the stress was performed using MAGMA5.3 software. The size variability of phases κII affecting the formation of phase stresses σf, depending on the location of the metallographic test area, was identified. The distribution of thermal σt and shrinkage stresses σs, depending on the location of the control point SC in the bushing's volume, was estimated. Probably the nature of these stresses will change slightly even after machining. This can cause variations in operating characteristics (friction coefficient, wear. Due to the strong inhomogeneity of the stress distribution in the bushing's casting, it is necessary to perform further tests of the possibility to conduct thermal treatment guaranteeing homogenization of the internal stresses in the casting, as well as to introduce changes in the bushing' s construction and the casting technology. The paper presents the continuation of the results of research aimed at identifying the causes of defects in the thick-walled bushing, die-casting made of CuAl10Fe5Ni5Cr aluminium bronze.

  11. Multibody Dynamic Stress Simulation of Rigid-Flexible Shovel Crawler Shoes

    Directory of Open Access Journals (Sweden)

    Samuel Frimpong

    2016-06-01

    Full Text Available Electric shovels are used in surface mining operations to achieve economic production capacities. The capital investments and operating costs associated with the shovels deployed in the Athabasca oil sands formation are high due to the abrasive conditions. The shovel crawler shoes interact with sharp and abrasive sand particles, and, thus, are subjected to high transient dynamic stresses. These high stresses cause wear and tear leading to crack initiation, propagation and premature fatigue failure. The objective of this paper is to develop a model to characterize the crawler stresses and deformation for the P&H 4100C BOSS during propel and loading using rigid-flexible multi-body dynamic theory. A 3-D virtual prototype model of the rigid-flexible crawler track assembly and its interactions with oil sand formation is simulated to capture the model dynamics within multibody dynamics software MSC ADAMS. The modal and stress shapes and modal loads due to machine weight for each flexible crawler shoes are generated from finite element analysis (FEA. The modal coordinates from the simulation are combined with mode and stress shapes using modal superposition method to calculate real-time stresses and deformation of flexible crawler shoes. The results show a maximum von Mises stress value of 170 MPa occurring in the driving crawler shoe during the propel motion. This study provides a foundation for the subsequent fatigue life analysis of crawler shoes for extending crawler service life.

  12. Barefoot-simulating footwear associated with metatarsal stress injury in 2 runners.

    Science.gov (United States)

    Giuliani, Jeffrey; Masini, Brendan; Alitz, Curtis; Owens, Brett D

    2011-07-07

    Stress-related changes and fractures in the foot are frequent in runners. However, the causative factors, including anatomic and kinematic variables, are not well defined. Footwear choice has also been implicated in contributing to injury patterns with changes in force transmission and gait analyses reported in the biomechanical literature. Despite the benefits of footwear, there has been increased interest among the running community in barefoot running with proposed benefits including a decreased rate of injury. We report 2 cases of metatarsal stress fracture in experienced runners whose only regimen change was the adoption of barefoot-simulating footwear. One was a 19-year-old runner who developed a second metatarsal stress reaction along the entire diaphysis. The second case was a 35-year-old ultra-marathon runner who developed a fracture in the second metatarsal diaphysis after 6 weeks of use of the same footwear. While both stress injuries healed without long-term effects, these injuries are alarming in that they occurred in experienced male runners without any other risk factors for stress injury to bone. The suspected cause for stress injury in these 2 patients is the change to barefoot-simulating footwear. Runners using these shoes should be cautioned on the potential need for gait alterations from a heel-strike to a midfoot-striking pattern, as well as cautioned on the symptoms of stress injury. Copyright 2011, SLACK Incorporated.

  13. Activity of earthworm in Latosol under simulated acid rain stress.

    Science.gov (United States)

    Zhang, Jia-En; Yu, Jiayu; Ouyang, Ying

    2015-01-01

    Acid rain is still an issue of environmental concerns. This study investigated the impacts of simulated acid rain (SAR) upon earthworm activity from the Latosol (acidic red soil). Laboratory experiment was performed by leaching the soil columns grown with earthworms (Eisenia fetida) at the SAR pH levels ranged from 2.0 to 6.5 over a 34-day period. Results showed that earthworms tended to escape from the soil and eventually died for the SAR at pH = 2.0 as a result of acid toxicity. The catalase activity in the earthworms decreased with the SAR pH levels, whereas the superoxide dismutases activity in the earthworms showed a fluctuate pattern: decreasing from pH 6.5 to 5.0 and increasing from pH 5.0 to 4.0. Results implied that the growth of earthworms was retarded at the SAR pH ≤ 3.0.

  14. Response of single bacterial cells to stress gives rise to complex history dependence at the population level

    Science.gov (United States)

    Mathis, Roland; Ackermann, Martin

    2016-01-01

    Most bacteria live in ever-changing environments where periods of stress are common. One fundamental question is whether individual bacterial cells have an increased tolerance to stress if they recently have been exposed to lower levels of the same stressor. To address this question, we worked with the bacterium Caulobacter crescentus and asked whether exposure to a moderate concentration of sodium chloride would affect survival during later exposure to a higher concentration. We found that the effects measured at the population level depended in a surprising and complex way on the time interval between the two exposure events: The effect of the first exposure on survival of the second exposure was positive for some time intervals but negative for others. We hypothesized that the complex pattern of history dependence at the population level was a consequence of the responses of individual cells to sodium chloride that we observed: (i) exposure to moderate concentrations of sodium chloride caused delays in cell division and led to cell-cycle synchronization, and (ii) whether a bacterium would survive subsequent exposure to higher concentrations was dependent on the cell-cycle state. Using computational modeling, we demonstrated that indeed the combination of these two effects could explain the complex patterns of history dependence observed at the population level. Our insight into how the behavior of single cells scales up to processes at the population level provides a perspective on how organisms operate in dynamic environments with fluctuating stress exposure. PMID:26960998

  15. Spectral entropy as a mean to quantify water stress history for natural vegetation and irrigated agriculture in a water-stressed tropical environment

    Science.gov (United States)

    Kim, Y.; Johnson, M. S.

    2017-12-01

    Spectral entropy (Hs) is an index which can be used to measure the structural complexity of time series data. When a time series is made up of one periodic function, the Hs value becomes smaller, while Hs becomes larger when a time series is composed of several periodic functions. We hypothesized that this characteristic of the Hs could be used to quantify the water stress history of vegetation. For the ideal condition for which sufficient water is supplied to an agricultural crop or natural vegetation, there should be a single distinct phenological cycle represented in a vegetation index time series (e.g., NDVI and EVI). However, time series data for a vegetation area that repeatedly experiences water stress may include several fluctuations that can be observed in addition to the predominant phenological cycle. This is because the process of experiencing water stress and recovering from it generates small fluctuations in phenological characteristics. Consequently, the value of Hs increases when vegetation experiences several water shortages. Therefore, the Hs could be used as an indicator for water stress history. To test this hypothesis, we analyzed Moderate Resolution Imaging Spectroradiometer (MODIS) Normalized Difference Vegetation Index (NDVI) data for a natural area in comparison to a nearby sugarcane area in seasonally-dry western Costa Rica. In this presentation we will illustrate the use of spectral entropy to evaluate the vegetative responses of natural vegetation (dry tropical forest) and sugarcane under three different irrigation techniques (center pivot irrigation, drip irrigation and flood irrigation). Through this comparative analysis, the utility of Hs as an indicator will be tested. Furthermore, crop response to the different irrigation methods will be discussed in terms of Hs, NDVI and yield.

  16. Physical robustness of canopy temperature models for crop heat stress simulation across environments and production conditions

    DEFF Research Database (Denmark)

    Webber, Heidi; White, Jeffrey W; Kimball, Bruce

    2018-01-01

    to simulate Tc. Model performance in predicting Tc was evaluated for two experiments in continental North America with various water, nitrogen and CO2 treatments. An empirical model fit to one dataset had the best performance, followed by the EBSC models. Stability conditions explained much of the differences...... between modeling approaches. More accurate simulation of heat stress will likely require use of energy balance approaches that consider atmospheric stability conditions....

  17. Time-history simulation of civil architecture earthquake disaster relief- based on the three-dimensional dynamic finite element method

    Directory of Open Access Journals (Sweden)

    Liu Bing

    2014-10-01

    Full Text Available Earthquake action is the main external factor which influences long-term safe operation of civil construction, especially of the high-rise building. Applying time-history method to simulate earthquake response process of civil construction foundation surrounding rock is an effective method for the anti-knock study of civil buildings. Therefore, this paper develops a civil building earthquake disaster three-dimensional dynamic finite element numerical simulation system. The system adopts the explicit central difference method. Strengthening characteristics of materials under high strain rate and damage characteristics of surrounding rock under the action of cyclic loading are considered. Then, dynamic constitutive model of rock mass suitable for civil building aseismic analysis is put forward. At the same time, through the earthquake disaster of time-history simulation of Shenzhen Children’s Palace, reliability and practicability of system program is verified in the analysis of practical engineering problems.

  18. Are adult life history traits in oriental fruit moth affected by a mild pupal heat stress?

    Science.gov (United States)

    Zheng, Jincheng; Cheng, Xiongbin; Hoffmann, Ary A; Zhang, Bo; Ma, Chun-Sen

    2017-10-01

    Thermal stress at one life stage can affect fitness at a later stage in ectotherms with complex life cycles. Most relevant studies have focused on extreme stress levels, but here we also show substantial fitness effects in a moth when pupae are exposed to a relatively mild and sublethal heat stress. We consider the impact of a 35°C heat stress of 2h in three geographically separate populations of the oriental fruit moth (OFM, Grapholita molesta) from northern, middle and southern China. Heat stress negatively affected fecundity but increased adult heat resistance and adult longevity. Fitness effects were mostly consistent across populations but there were also some population differences. In the Shenyang population from northern China, there was a hormetic effect of heat on female longevity not evident in the other populations. Adults from all populations had higher LT 50 s due to heat stress after pupal exposure to the sublethal stress. These results highlight that the pupal stage is a particularly sensitive window for development and they have implications for seasonal adaptation in uncertain environments as well as changes in pest dynamics under climate warming. Copyright © 2017 Elsevier Ltd. All rights reserved.

  19. Integration of Heat Transfer, Stress, and Particle Trajectory Simulation

    Energy Technology Data Exchange (ETDEWEB)

    Thuc Bui; Michael Read; Lawrence ives

    2012-05-17

    Calabazas Creek Research, Inc. developed and currently markets Beam Optics Analyzer (BOA) in the United States and abroad. BOA is a 3D, charged particle optics code that solves the electric and magnetic fields with and without the presence of particles. It includes automatic and adaptive meshing to resolve spatial scales ranging from a few millimeters to meters. It is fully integrated with CAD packages, such as SolidWorks, allowing seamless geometry updates. The code includes iterative procedures for optimization, including a fully functional, graphical user interface. Recently, time dependent, particle in cell capability was added, pushing particles synchronically under quasistatic electromagnetic fields to obtain particle bunching under RF conditions. A heat transfer solver was added during this Phase I program. Completed tasks include: (1) Added a 3D finite element heat transfer solver with adaptivity; (2) Determined the accuracy of the linear heat transfer field solver to provide the basis for development of higher order solvers in Phase II; (3) Provided more accurate and smoother power density fields; and (4) Defined the geometry using the same CAD model, while maintaining different meshes, and interfacing the power density field between the particle simulator and heat transfer solvers. These objectives were achieved using modern programming techniques and algorithms. All programming was in C++ and parallelization in OpenMP, utilizing state-of-the-art multi-core technology. Both x86 and x64 versions are supported. The GUI design and implementation used Microsoft Foundation Class.

  20. Alcohol Use Disorder History Moderates the Relationship Between Avoidance Coping and Posttraumatic Stress Symptoms

    OpenAIRE

    Hruska, Bryce; Fallon, William; Spoonster, Eileen; Sledjeski, Eve M.; Delahanty, Douglas L.

    2011-01-01

    Avoidance coping (AVC) is common in individuals with posttraumatic stress disorder (PTSD) and in individuals with alcohol use disorder (AUD). Given that PTSD and AUD commonly co-occur, AVC may represent a risk factor for the development of comorbid post-traumatic stress and alcohol use. In this study, the relationship between AVC and PTSD symptoms (PTSS) was examined in individuals with versus without AUDs. Motor vehicle accident (MVA) victims were assessed 6-weeks post accident for AUD histo...

  1. Analysis of performance and stress caused by a simulation of a mass casualty incident.

    Science.gov (United States)

    Nieto Fernández-Pacheco, Antonio; Castro Delgado, Rafael; Arcos González, Pedro; Navarro Fernández, José Luis; Cerón Madrigal, José Joaquín; Juguera Rodriguez, Laura; Perez Alonso, Nuria; Armero-Barranco, David; Lidon López Iborra, María; Damian, Escribano Tortosa; Pardo Rios, Manuel

    2018-03-01

    To determine the stress that is potentially produced in professional health workers due to a mass casualty incident (MCI) simulated exercise, and its relation to prior academic training and the role played in the simulation. Observational study of stress in a MCI. For this work, two MCI drills comprised of 40 victims each were conducted. Two randomized groups of 36 students each were created: Master's Students Group (MSG) and Undergraduate Student Group (USG). The role performed by each student (triage or sectorization) was assessed. The stress level was determined by prior and subsequent measurements of alpha-amylase (αA), HR, SBP and DBP. The percentage of victims that were correctly triaged was 88.6%, 91.84% for MSG and 83.76% for the USG (p=0.004). The basal αA was 97,107.50±72,182.67IU/L and the subsequent αA was 136,195.55±90,176.46±IU/L (pperformed the triage and those who performed sectorization but there were no differences between undergraduate and Masters' students. Conducting a simulated exercise caused stress in personnel involved in the MCI, with a greater impact on participants who performed triage, although it was not influenced by their prior academic level. The stress level in our case did not affect or determine the performance of acquired skills. Copyright © 2017 Elsevier Ltd. All rights reserved.

  2. Internal stress evolution in Fe laths deformed at low temperature analysed by dislocation dynamics simulations

    International Nuclear Information System (INIS)

    Chaussidon, Julien; Fivel, Marc; Robertson, Christian; Marini, Bernard

    2010-01-01

    Stress evolution in Fe laths undergoing plastic deformation is investigated using three-dimensional dislocation dynamics simulations adapted to body centred cubic crystals, in the ductile to brittle transition temperature range. The selected boundary conditions, applied stress tensor and initial dislocation structures account for the realistic microstructure observed in bainitic steels. The effective stress field projected in the three different {1 0 0}cleavage planes is calculated for two different temperatures (50 and 200 K) and presented quantitatively, in the form of stress/frequency diagrams. It is shown that plastic activity tends to relax the stress acting in certain cleavage planes (the (0 1 0) and (0 0 1) planes) while, at the same time, amplifying the stress acting in other cleavage planes (the (1 0 0) planes). The selective stress amplification in the latter planes depends on the applied load direction, in combination with the limited set of available slip systems and the lath geometry. In the examined configuration, this selection effect is more pronounced with decreasing temperature, emphasizing the role of thermally activated plasticity on deformation-induced stress concentrations

  3. Realizability conditions for the turbulent stress tensor in large-eddy simulation

    NARCIS (Netherlands)

    Vreman, A.W.; Geurts, Bernardus J.; Kuerten, Johannes G.M.

    1994-01-01

    The turbulent stress tensor in large-eddy simulation is examined from a theoretical point of view. Realizability conditions for the components of this tensor are derived, which hold if and only if the filter function is positive. The spectral cut-off, one of the filters frequently used in large-eddy

  4. The impact of assessing simulated bad news consultations on medical students' stress response and communication performance.

    NARCIS (Netherlands)

    Dulmen, S. van; Tromp, F.; Grosfeld, F.; Cate, O. ten; Bensing, J.M.

    2007-01-01

    Seventy second-year medical students volunteered to participate in a study with the aim of evaluating the impact of the assessment of simulated bad news consultations on their physiological and psychological stress and communication performance. Measurements were taken of salivary cortisol, systolic

  5. The stress generated by non-Brownian fibers in turbulent channel flow simulations

    NARCIS (Netherlands)

    Gillissen, J.J.J.; Boersma, B.J.; Mortensen, P.H.; Andersson, H.I.

    2007-01-01

    Turbulent fiber suspension channel flow is studied using direct numerical simulation. The effect of the fibers on the fluid mechanics is governed by a stress tensor, involving the distribution of fiber position and orientation. Properties of this function in channel flow are studied by computing the

  6. Simulating Stresses Associated with the Bending of Wood Using a Finite Element Method

    Directory of Open Access Journals (Sweden)

    Milan Gaff

    2015-02-01

    Full Text Available This article examines the stress-strain curves of various thicknesses of soft and hard wood when bent during three-point loading. The finite element method was used to simulate the course of stresses that occurred during the bending of these materials. Reference curves obtained by bending real specimens offered a basis for simulation. The results showed that with increasing material thickness, deflection values decreased and the proportionality limit increased; eventually, the bendability coefficient value decreased and the loading force necessary for bending increased. Moreover, it was apparent when bending hard materials that higher loading forces were necessary for different materials of the same thickness. It is possible to determine the stress-strain curves without having to perform experiments (except for indispensable reference ones under real conditions.

  7. Large eddy simulation in a rotary blood pump: Viscous shear stress computation and comparison with unsteady Reynolds-averaged Navier-Stokes simulation.

    Science.gov (United States)

    Torner, Benjamin; Konnigk, Lucas; Hallier, Sebastian; Kumar, Jitendra; Witte, Matthias; Wurm, Frank-Hendrik

    2018-06-01

    Numerical flow analysis (computational fluid dynamics) in combination with the prediction of blood damage is an important procedure to investigate the hemocompatibility of a blood pump, since blood trauma due to shear stresses remains a problem in these devices. Today, the numerical damage prediction is conducted using unsteady Reynolds-averaged Navier-Stokes simulations. Investigations with large eddy simulations are rarely being performed for blood pumps. Hence, the aim of the study is to examine the viscous shear stresses of a large eddy simulation in a blood pump and compare the results with an unsteady Reynolds-averaged Navier-Stokes simulation. The simulations were carried out at two operation points of a blood pump. The flow was simulated on a 100M element mesh for the large eddy simulation and a 20M element mesh for the unsteady Reynolds-averaged Navier-Stokes simulation. As a first step, the large eddy simulation was verified by analyzing internal dissipative losses within the pump. Then, the pump characteristics and mean and turbulent viscous shear stresses were compared between the two simulation methods. The verification showed that the large eddy simulation is able to reproduce the significant portion of dissipative losses, which is a global indication that the equivalent viscous shear stresses are adequately resolved. The comparison with the unsteady Reynolds-averaged Navier-Stokes simulation revealed that the hydraulic parameters were in agreement, but differences for the shear stresses were found. The results show the potential of the large eddy simulation as a high-quality comparative case to check the suitability of a chosen Reynolds-averaged Navier-Stokes setup and turbulence model. Furthermore, the results lead to suggest that large eddy simulations are superior to unsteady Reynolds-averaged Navier-Stokes simulations when instantaneous stresses are applied for the blood damage prediction.

  8. Mindfulness-Based Stress Reduction for Low-Income, Predominantly African American Women with PTSD and a History of Intimate Partner Violence

    Science.gov (United States)

    Dutton, Mary Ann; Bermudez, Diana; Matas, Armely; Majid, Haseeb; Myers, Neely L.

    2013-01-01

    In this article, we consider the use of Mindfulness-Based Stress Reduction (MBSR; Kabat-Zinn, 1991) as a community-based intervention for posttraumatic stress disorder (PTSD) among low-income, predominantly African American women with a history of intimate partner violence (IPV). The results of a pilot randomized clinical trial (RCT) of MBSR as an…

  9. Numerical Simulation of Stress evolution and earthquake sequence of the Tibetan Plateau

    Science.gov (United States)

    Dong, Peiyu; Hu, Caibo; Shi, Yaolin

    2015-04-01

    The India-Eurasia's collision produces N-S compression and results in large thrust fault in the southern edge of the Tibetan Plateau. Differential eastern flow of the lower crust of the plateau leads to large strike-slip faults and normal faults within the plateau. From 1904 to 2014, more than 30 earthquakes of Mw > 6.5 occurred sequentially in this distinctive tectonic environment. How did the stresses evolve during the last 110 years, how did the earthquakes interact with each other? Can this knowledge help us to forecast the future seismic hazards? In this essay, we tried to simulate the evolution of the stress field and the earthquake sequence in the Tibetan plateau within the last 110 years with a 2-D finite element model. Given an initial state of stress, the boundary condition was constrained by the present-day GPS observation, which was assumed as a constant rate during the 110 years. We calculated stress evolution year by year, and earthquake would occur if stress exceed the crustal strength. Stress changes due to each large earthquake in the sequence was calculated and contributed to the stress evolution. A key issue is the choice of initial stress state of the modeling, which is actually unknown. Usually, in the study of earthquake triggering, people assume the initial stress is zero, and only calculate the stress changes by large earthquakes - the Coulomb failure stress changes (Δ CFS). To some extent, this simplified method is a powerful tool because it can reveal which fault or which part of a fault becomes more risky or safer relatively. Nonetheless, it has not utilized all information available to us. The earthquake sequence reveals, though far from complete, some information about the stress state in the region. If the entire region is close to a self-organized critical or subcritical state, earthquake stress drop provides an estimate of lower limit of initial state. For locations no earthquakes occurred during the period, initial stress has to be

  10. STRESS LOADING SIMULATION OF HYDRO-MECHANICAL TRANSMISSION OF DUMP TRUCK

    Directory of Open Access Journals (Sweden)

    S. A. Sidorov

    2006-01-01

    Full Text Available The Transmission model and software package to investigate stress loading of a hydromechanical transmission of a dump truck have been developed. The given software package allows to model stress loading of transmission gears in taking-off and acceleration modes at various road resistance, positions of an engine control pedal and initial revolutions of an engine crankshaft, various laws of friction clutch switching and some other parameters that permit to reveal a rate of various operational mode influence on stress loading of a dump truck transmission. An equivalence of the developed software is proved by the comparison of the experimentally obtained stress loading process of the hydro-mechanical transmission of a BelAZ- 7555 dump truck with the results of the simulation 

  11. Residual stresses in surface induction hardening of steels: Comparison between experiment and simulation

    International Nuclear Information System (INIS)

    Coupard, Dominique; Palin-luc, Thierry; Bristiel, Philippe; Ji, Vincent; Dumas, Christian

    2008-01-01

    Deep induction hardening has been performed on two batches of smooth cylindrical specimens with a hardening depth respectively around 2 mm and 3 mm. The distributions of axial and circumferential residual stresses are analysed for the two specimen batches by X-ray diffraction technique. The radial normal stress field is estimated through the use of the well known Moore and Evans correction. Finally, the experimental residual stresses are compared with those obtained from a multiphysic finite element modelling of the whole induction treatment process, including electromagnetic, thermal, metallurgical and mechanical phenomena. The simulated residual stress field is in good agreement with X-ray analysis especially at depths lower than one-tenth the specimen diameter. At deeper depths, a correction of the experimental X-ray analysis has been done to obtain realistic values

  12. Evaluation of Package Stress during Temperature Cycling using Metal Deformation Measurement and FEM Simulation

    International Nuclear Information System (INIS)

    Hoeglauer, J.; Bohm, C.; Otremba, R.; Maerz, J.; Nelle, P.; Stecher, M.; Alpern, P.

    2006-01-01

    Plastic encapsulated devices that are exposed to Temperature Cycling (TC) tests undergo an excessive mechanical stress due to different Coefficients of Thermal Expansion (CTE) of the various materials used in the system. Especially in the corners of the die, passivation cracks and shifted metal lines can be observed, which demonstrates an increasing mechanical stress from chip center to the corners of the die. This effect has been known for a long time. This paper presents a simple measurement technique to quantify the mechanical shear stress at the chip-Mold Compound (MC) interface by measuring the deformation of a periodical metal structure. Based on this deformation measurement, we evaluated the stress distribution within the package, and the influence of different parameters such as number of cycles and chip size. Furthermore, these experimental results were compared with FEM simulation, and showed good agreement but could not account in all cases for the total amount of observed shift

  13. History of Maltreatment in Childhood and Subsequent Parenting Stress in At-Risk, First-Time Mothers: Identifying Points of Intervention During Home Visiting.

    Science.gov (United States)

    Shenk, Chad E; Ammerman, Robert T; Teeters, Angelique R; Bensman, Heather E; Allen, Elizabeth K; Putnam, Frank W; Van Ginkel, Judith B

    2017-04-01

    Home visiting is an effective preventive intervention that can improve parenting outcomes for at-risk, new mothers, thereby optimizing subsequent child development. A history of maltreatment in childhood is common in mothers participating in home visiting, yet the extent to which such a history is related to parenting outcomes during home visiting is unknown. The current study evaluated whether mothers with a history of maltreatment in childhood respond less favorably to home visiting by examining the direct and indirect pathways to subsequent parenting stress, a key parenting outcome affecting child development. First-time mothers (N = 220; age range = 16-42) participating in one of two home visiting programs, Healthy Families America or Nurse Family Partnership, were evaluated at enrollment and again at 9-and 18-month post-enrollment assessments. Researchers administered measures of maternal history of maltreatment in childhood, depressive symptoms, social support, and parenting stress. Maternal history of maltreatment in childhood predicted worsening parenting stress at the 18-month assessment. Mediation modeling identified two indirect pathways, one involving social support at enrollment and one involving persistent depressive symptoms during home visiting, that explained the relation between a history of maltreatment in childhood and parenting stress at the 18-month assessment. Ways to improve the preventive effects of home visiting for mothers with a history of maltreatment in childhood through the identification of relevant intervention targets and their ideal time of administration are discussed.

  14. Dislocation-induced stress in polycrystalline materials: mesoscopic simulations in the dislocation density formalism

    Science.gov (United States)

    Berkov, D. V.; Gorn, N. L.

    2018-06-01

    In this paper we present a simple and effective numerical method which allows a fast Fourier transformation-based evaluation of stress generated by dislocations with arbitrary directions and Burgers vectors if the (site-dependent) dislocation density is known. Our method allows the evaluation of the dislocation stress using a rectangular grid with shape-anisotropic discretization cells without employing higher multipole moments of the dislocation interaction coefficients. Using the proposed method, we first simulate the stress created by relatively simple non-homogeneous distributions of vertical edge and so-called ‘mixed’ dislocations in a disk-shaped sample, which is necessary to understand the dislocation behavior in more complicated systems. The main part of our research is devoted to the stress distribution in polycrystalline layers with the dislocation density rapidly varying with the distance to the layer bottom. Considering GaN as a typical example of such systems, we investigate dislocation-induced stress for edge and mixed dislocations, having random orientations of Burgers vectors among crystal grains. We show that the rapid decay of the dislocation density leads to many highly non-trivial features of the stress distributions in such layers and study in detail the dependence of these features on the average grain size. Finally we develop an analytical approach which allows us to predict the evolution of the stress variance with the grain size and compare analytical predictions with numerical results.

  15. Numerical simulation of the double pits stress concentration in a curved casing inner surface

    Directory of Open Access Journals (Sweden)

    Wei Yan

    2016-12-01

    Full Text Available Sour or sweet oil fields development is common in recent years. Casing and tubing are usually subjected to pitting corrosion because of exposure to the strong corrosion species, such as CO2, H2S, and saline water. When the corrosion pits formed in the casing inner surface, localized stress concentration will occur and the casing strength will be degraded. Thus, it is essential to evaluate the degree of stress concentration factor accurately. This article performed a numerical simulation on double pits stress concentration factor in a curved inner surface using the finite element software ABAQUS. The results show that the stress concentration factor of double pits mainly depends on the ratio of two pits distance to the pit radius (L/R. It should not be only assessed by the absolute distance between the two pits. When the two pits are close and tangent, the maximum stress concentration factor will appear on the inner tangential edges. Stress concentration increased by double pits in a curved casing inner surface is more serious than that in a flat surface. A correction factor of 1.9 was recommended in the curved inner surface double pits stress concentration factor predict model.

  16. Pace bowlers in cricket with history of lumbar stress fracture have increased risk of lower limb muscle strains, particularly calf strains

    Directory of Open Access Journals (Sweden)

    John Orchard

    2010-09-01

    Full Text Available John Orchard1, Patrick Farhart2, Alex Kountouris3, Trefor James3, Marc Portus31School of Public Health, University of Sydney, Australia; 2Punjab Kings XI team, Indian Premier League, India; 3Cricket Australia, Melbourne, AustraliaObjective: To assess whether a history of lumbar stress fracture in pace bowlers in cricket is a risk factor for lower limb muscle strains.Methods: This was a prospective cohort risk factor study, conducted using injury data from contracted first class pace bowlers in Australia during seasons 1998–1999 to 2008–2009 inclusive. There were 205 pace bowlers, 33 of whom suffered a lumbar stress fracture when playing first class cricket. Risk ratios ([RR] with 95% confidence intervals[CI] were calculated to compare the seasonal incidence of various injuries between bowlers with a prior history of lumbar stress fracture and those with no history of lumbar stress fracture.Results: Risk of calf strain was strongly associated with prior lumbar stress fracture injury history (RR = 4.1; 95% CI: 2.4–7.1. Risks of both hamstring strain (RR = 1.5; 95% CI: 1.03–2.1 and quadriceps strain (RR = 2.0; 95% CI: 1.1–3.5 were somewhat associated with history of lumbar stress fracture. Risk of groin strain was not associated with history of lumbar stress fracture (RR = 0.7; 95% CI: 0.4–1.1. Other injuries showed little association with prior lumbar stress fracture, although knee cartilage injuries were more likely in the non-stress fracture group.Conclusion: Bony hypertrophy associated with lumbar stress fracture healing may lead to subsequent lumbar nerve root impingement, making lower limb muscle strains more likely to occur. Confounders may be responsible for some of the findings. In particular, bowling speed is likely to be independently correlated with risk of lumbar stress fracture and risk of muscle strain. However, as the relationship between lumbar stress fracture history and calf strain was very strong, and that there is a

  17. White ash (Fraxinus americana) decline and mortality: the role of site nutrition and stress history

    Science.gov (United States)

    Alejandro A. Royo; Kathleen S. Knight

    2012-01-01

    Over the past century, white ash (Fraxinus americana) populations throughout its range have deteriorated as a result of declining tree health and increased mortality rates. Although co-occurring factors including site nutritional deficiencies and punctuated stress events (e.g., defoliations, drought) are hypothesized to trigger white ash decline,...

  18. Personality Disorders, Coping Strategies, and Posttraumatic Stress Disorder in Women with Histories of Childhood Sexual Abuse

    Science.gov (United States)

    Johnson, Dawn M.; Sheahan, Timothy C.; Chard, Kathleen M.

    2003-01-01

    Using a treatment-seeking sample of adult female survivors of childhood sexual abuse, the relationships between coping strategies, personality disorders (PD) and Posttraumatic Stress Disorder (PTSD) were explored. A variety of PDs were found to exist in this population, with avoidant, antisocial, dependent PDs having higher frequencies than…

  19. Tectonic stress history and the relationship with uranium mineralization in Shenchong mining area

    International Nuclear Information System (INIS)

    Zhu Mingqiang; Lin Yinshan; Kang Zili

    1996-01-01

    The rejection method of maximum statistical for principal stress axis is applied to complex granite body, this paper divide mining area tectonic process into six epochs. The relationship between the tectonic process and uranium mineralization is also discussed, and the later 3 times fracture process of Diwa epoch control the removing and gathering of Uranium in this area

  20. History of Solitary Confinement Is Associated with Post-Traumatic Stress Disorder Symptoms among Individuals Recently Released from Prison.

    Science.gov (United States)

    Hagan, Brian O; Wang, Emily A; Aminawung, Jenerius A; Albizu-Garcia, Carmen E; Zaller, Nickolas; Nyamu, Sylviah; Shavit, Shira; Deluca, Joseph; Fox, Aaron D

    2018-04-01

    This study assessed the relationship between solitary confinement and post-traumatic stress disorder (PTSD) symptoms in a cohort of recently released former prisoners. The cross-sectional design utilized baseline data from the Transitions Clinic Network, a multi-site prospective longitudinal cohort study of post-incarceration medical care. Our main independent variable was self-reported solitary confinement during the participants' most recent incarceration; the dependent variable was the presence of PTSD symptoms determined by primary care (PC)-PTSD screening when participants initiated primary care in the community. We used multivariable logistic regression to adjust for potential confounders, such as prior mental health conditions, age, and gender. Among 119 participants, 43% had a history of solitary confinement and 28% screened positive for PTSD symptoms. Those who reported a history of solitary confinement were more likely to report PTSD symptoms than those without solitary confinement (43 vs. 16%, p history of solitary confinement (OR = 3.93, 95% CI 1.57-9.83) and chronic mental health conditions (OR = 4.04, 95% CI 1.52-10.68) were significantly associated with a positive PTSD screen after adjustment for the potential confounders. Experiencing solitary confinement was significantly associated with PTSD symptoms among individuals accessing primary care following release from prison. Larger studies should confirm these findings.

  1. Two-dimensional simulation of the thermal stress effect on static and dynamic VDMOS characteristics

    International Nuclear Information System (INIS)

    Alwan, M.; Beydoun, B.; Ketata, K.; Zoaeter, M.

    2005-01-01

    Using a two-dimensional simulator, the effect of the thermal stress on static and dynamic vertical double-diffusion metal oxide semiconductor (VDMOS) characteristics have been investigated. The use of the device under certain thermal stress conditions can produce modifications of its physical and electrical properties. Based on physics and 2D simulations, this paper proposes an analysis of this stress effect observed on the electrical characteristics of the device. Parameters responsible of these modifications are determined. Approximate expressions of the ionization coefficients and breakdown voltage in terms of temperature are proposed. Non-punch-through junction theory is used to express the breakdown voltage and the space charge extension with respect to the impurity concentration and the temperature. The capacitances of the device have been also studied. The effect of the stress on C-V characteristics is observed and analyzed. We notice that the drain-gate, drain-source and gate-source capacitances are shifted due to the degradation of device physical properties versus thermal stress

  2. Physiological Response of Wheat to Chemical Desiccants Used to Simulate Post-Anthesis Drought Stress

    Directory of Open Access Journals (Sweden)

    Nasrein Mohamed Kamal

    2018-04-01

    Full Text Available Post-anthesis drought stress is one of the main constraints on the production of wheat (Triticum aestivum L.. Because field screening for post-anthesis drought tolerance is difficult, effective and validated methods to simulate drought in order to identify sources of tolerance can facilitate screening of breeding materials. Chemical desiccants are widely used to simulate post-anthesis drought stress. We aimed to identify physiological traits that respond to desiccants as they do to drought. We examined the responses of ‘Norin 61’ to six treatments in a greenhouse: irrigated control, drought after anthesis, and 2% or 4% potassium chlorate (KClO3 at anthesis (A or grain filling (GF. We measured δ13C in leaves, aboveground fresh biomass, stomatal conductance, chlorophyll content, harvest index, and grain yield. Both 2% and 4% KClO3 at both A and GF simulated the effect of drought stress. Selection of drought-tolerant genotypes can be aided by chlorophyll content and δ13C measurement of leaves when 2% or 4% KClO3 is used to simulate drought.

  3. [The history of the Science of Stress: From Hans Selye to the discovery of anti-inflammatory medication].

    Science.gov (United States)

    Lupien, Sonia

    2015-01-01

    To make an important scientific discovery that will make history takes a lot of determination, creativity, perseverance and luck! The story behind the discovery of stress and its biological basis is a fascinating one that places Dr. Hans Selye in the forefront. Dr. Selye was a great scientist that taught at the Université de Montréal from 1945 to his death in 1982. Dr. Selye was curious and hard working. He was determined to understand how various disorders can lead to similar physical manifestations, and this interest led him to discover the role of the adrenal glands involved in the stress response and to better understand the effects of glucocorticoids on the body. Today, the science of stress is based on the foundations established by Dr. Selye. In celebration of the 50th anniversary of the Département de psychiatrie de l'Université de Montréal, and the special issue of the Revue Santé Mentale au Québec, this historical review summarizes the discoveries of this great scientist who worked in Quebec.

  4. Etiopathogenesis, diagnostics and history of surgical treatment of stress urinary incontinence.

    Science.gov (United States)

    Jovan, Hadži-Djokić; Uroš, Babić; Aleksandar, Argirović; Miodrag, Aćimović; Milan, Radovanović; Bogomir, Milojević; Tomisla, Pejčić; Zoran, Džamić

    2014-01-01

    Urinary incontinence represents involuntary urine leakage into the urethra. This pathological condition represents a major medical, social and hygienic problem. The paper presents risk factors for development of the disorder, as well as diagnostic methods applied in evaluation of the female patients. Chronological review of diverse surgical techniques used in treatment of stress urinary incontinence reported in the published scientific papers is also presented. Review of the literature data was also performed. Sling procedures with application of suburethral loops have been used since the beginning of the last century in treatment of this disorder. Surgical treatment of stress urinary incontinence is applied when conservative treatment fails to give any effects according to strictly defined indications. During the last 100 years, surgical techniques have undergone different improvements and the results have also been significantly improved.

  5. The chronic mild stress (CMS) model of depression: History, evaluation and usage.

    Science.gov (United States)

    Willner, Paul

    2017-02-01

    Now 30 years old, the chronic mild stress (CMS) model of depression has been used in >1300 published studies, with a year-on-year increase rising to >200 papers in 2015. Data from a survey of users show that while a variety of names are in use (chronic mild/unpredictable/varied stress), these describe essentially the same procedure. This paper provides an update on the validity and reliability of the CMS model, and reviews recent data on the neurobiological basis of CMS effects and the mechanisms of antidepressant action: the volume of this research may be unique in providing a comprehensive account of antidepressant action within a single model. Also discussed is the use of CMS in drug discovery, with particular reference to hippocampal and extra-hippocampal targets. The high translational potential of the CMS model means that the neurobiological mechanisms described may be of particular relevance to human depression and mechanisms of clinical antidepressant action.

  6. History matching of transient pressure build-up in a simulation model using adjoint method

    Energy Technology Data Exchange (ETDEWEB)

    Ajala, I.; Haekal, Rachmat; Ganzer, L. [Technische Univ. Clausthal, Clausthal-Zellerfeld (Germany); Almuallim, H. [Firmsoft Technologies, Inc., Calgary, AB (Canada); Schulze-Riegert, R. [SPT Group GmbH, Hamburg (Germany)

    2013-08-01

    The aim of this work is the efficient and computer-assisted history-matching of pressure build-up and pressure derivatives by small modification to reservoir rock properties on a grid by grid level. (orig.)

  7. A Survey of Coping Strategies With Stress in Patients With Acute Myocardial Infarction and Individuals Without a History of Fixed Myocardial Infarction.

    Science.gov (United States)

    Sadr Bafghi, Seyed Mahmood; Ahmadi, Nastaran; Yassini Ardekani, Seyyed Mojtaba; Jafari, Lida; Bitaraf Ardekani, Bahareh; Heydari, Roya; Maroufi, Fahame; Faraji, Reza

    2018-02-01

    This study aimed at investigating the coping strategies with stress in patients with acute myocardial infarction (MI) and individuals without a history of fixed MI and cardiovascular disorders. This case-control crossover study was conducted from March 2015 to February 2016 on 220 patients with acute MI (MI patients) as case group and 220 patients without any history of MI and cardiovascular diseases as the control group using availability sampling method. To collect the required data, demographic information questionnaire, Holms-Raheh life stress inventory, perceived stress questionnaire, and coping inventory for stressful situations (CISS) were applied. On the basis of our findings, 118 patients (53.6%) with MI used emotion-focused coping strategy. Ninety-seven patients (82.2%) with MI who used emotion-focused coping strategy had negative perceived stress. Additionally, 71 patients (60.2%) with MI who had used emotion-focused coping strategy suffered from very high level of stress. The most MI patients had very high level of stress while most people in control group had high level of stress. Most MI patients that had very high level of stress cope with it in emotion-focused coping strategy and it proves that people with higher levels of stress are more likely to use inefficient coping strategies.

  8. Numerical simulation of residual stress in laser based additive manufacturing process

    Science.gov (United States)

    Kalyan Panda, Bibhu; Sahoo, Seshadev

    2018-03-01

    Minimizing the residual stress build-up in metal-based additive manufacturing plays a pivotal role in selecting a particular material and technique for making an industrial part. In beam-based additive manufacturing, although a great deal of effort has been made to minimize the residual stresses, it is still elusive how to do so by simply optimizing the processing parameters, such as beam size, beam power, and scan speed. Amid different types of additive manufacturing processes, Direct Metal Laser Sintering (DMLS) process uses a high-power laser to melt and sinter layers of metal powder. The rapid solidification and heat transfer on powder bed endows a high cooling rate which leads to the build-up of residual stresses, that will affect the mechanical properties of the build parts. In the present work, the authors develop a numerical thermo-mechanical model for the measurement of residual stress in the AlSi10Mg build samples by using finite element method. Transient temperature distribution in the powder bed was assessed using the coupled thermal to structural model. Subsequently, the residual stresses were estimated with varying laser power. From the simulation result, it found that the melt pool dimensions increase with increasing the laser power and the magnitude of residual stresses in the built part increases.

  9. Effect of surface stress state on dissolution property of Alloy 690 in simulated primary water condition

    International Nuclear Information System (INIS)

    Kim, Kyung Mo; Shim, Hee-Sang; Lee, Eun Hee; Seo, Myung Ji; Han, Jung Ho; Hur, Do Haeng

    2014-01-01

    The dissolution control of nickel is important to reduce the radioactive dose rate and deterioration of fuel performance in the operation of nuclear power plants (PWR). The corrosion properties are affected by the metal surface residual stress introduced in manufacture process such as work hardening. This work studied the effect of surface modification on the release rate of Alloy 690, nickel-base alloy for a steam generator tube, in the test condition of simulated primary water chemistry in PWRs. The surface stress modification was applied by the electro-polishing and shot peening method. Shot peening process was applied using ceramic beads with different intensities through the variation of air pressure. The corrosion release tests performed at 330degC with LiOH 2 ppm and H 3 BO 4 1200 ppm, DH(dissolved hydrogen) 35 cc/kg (STP) and about 20 ppb of DO(dissolved oxygen) condition. The corrosion release rate was evaluated by a gravimetric analysis method and the surface analysed by SEM and optical microscope. The surface residual stress was measured by an X-ray diffractometer, and the distribution of stress state was evaluated by a micro-hardness tester. The metal ion release rate of alloy 690 was evaluated from the influence of the stress state on the metal surface. The oxide property and structure was affected by the residual stress in the oxide layer. (author)

  10. Thermal expansion and thermal stress in the moon and terrestrial planets - Clues to early thermal history

    Science.gov (United States)

    Solomon, S. C.; Chaiken, J.

    1976-01-01

    The paper discusses how features of the surface geology of the moon and also Mars and Mercury impose constraints on the volumetric expansion or contraction of a planet and consequently provide a test of thermal history models. The moon has changed very little in volume over the last 3.8 b.y. Thermal models satisfying this constraint involve early heating and perhaps melting of the outer 200 km of the moon and an initially cold interior. Mercury has contracted by about 2 km in radius since emplacement of its present surface, so core formation must predate that surface. A hot initial temperature distribution is implied.

  11. On history dependence of stress-strain diagrams and creep curves under variable repeated loading

    International Nuclear Information System (INIS)

    Gokhfeld, D.A.; Sadakov, O.S.; Martynenko, M.E.

    1979-01-01

    The ability of structural alloys to 'keep in memory' the loading prehistory becomes of special importance when inelastic variable repeated loading is considered. There are two main approaches to the development of the mathematical description of this phenomenon: the inclusion of hidden state variables in the incremental theory constitutive equations (a) and construction of proper hereditary functionals (b). In this respect the assumption that the 'memory' regarding the previous deformation history is due to structural nonhomogeneity of actual materials proves to be fruitful. (orig.)

  12. Simulation of diffusion-induced stress using reconstructed electrodes particle structures generated by micro/nano-CT

    International Nuclear Information System (INIS)

    Lim, Cheolwoong; Yan Bo; Yin Leilei; Zhu Likun

    2012-01-01

    Highlights: ► The microstructure of LIB electrodes was obtained by X-ray micro/nano-CT. ► We studied diffusion-induced stresses based on realistic 3D microstructures. ► Stresses depend on geometric characteristics of electrode particle. ► Stresses in a real particle are much higher than those in a spherical particle. - Abstract: Lithium ion batteries experience diffusion-induced stresses during charge and discharge processes which can cause electrode failure in the form of fracture. Previous diffusion-induced stress models and simulations are mainly based on simple active material particle structures, such as spheres and ellipsoids. However, the simple structure model cannot reveal the stress development in a real complex lithium ion battery electrode. In this paper, we studied the diffusion-induced stresses numerically based on a realistic morphology of reconstructed particles during the lithium ion intercalation process. The morphology of negative and positive active materials of a lithium ion battery was determined using X-ray micro/nano computed tomography technology. Diffusion-induced stresses were simulated at different C rates under galvonostatic conditions and compared with spherical particles. The simulation results show that the intercalation stresses of particles depend on their geometric characteristics. The highest von Mises stress and Tresca stress in a real particle are several times higher than the stresses in a spherical particle with the same volume.

  13. Stress induced conditioning and thermal relaxation in the simulation of quasi-static compression experiments

    International Nuclear Information System (INIS)

    Scalerandi, M; Delsanto, P P; Johnson, P A

    2003-01-01

    Local interaction simulation approach simulations of the ultrasonic wave propagation in multi-grained materials have succeeded in reproducing most of the recently observed nonclassical nonlinear effects, such as stress-strain hysteresis and discrete memory in quasi-static experiments and a downwards shift of the resonance frequency and the generation of odd harmonics at specific amplitude rates in dynamics experiments. By including a simple mechanism of thermally activated random transitions, we can predict the occurrence of experimentally observed effects, such as the conditioning and relaxation of the specimen. Experiments are also suggested for a quantitative assessment of the validity of the model

  14. Stress induced conditioning and thermal relaxation in the simulation of quasi-static compression experiments

    CERN Document Server

    Scalerandi, M; Johnson, P A

    2003-01-01

    Local interaction simulation approach simulations of the ultrasonic wave propagation in multi-grained materials have succeeded in reproducing most of the recently observed nonclassical nonlinear effects, such as stress-strain hysteresis and discrete memory in quasi-static experiments and a downwards shift of the resonance frequency and the generation of odd harmonics at specific amplitude rates in dynamics experiments. By including a simple mechanism of thermally activated random transitions, we can predict the occurrence of experimentally observed effects, such as the conditioning and relaxation of the specimen. Experiments are also suggested for a quantitative assessment of the validity of the model.

  15. Analysis of stresses on buried pipeline subjected to landslide based on numerical simulation and regression analysis

    Energy Technology Data Exchange (ETDEWEB)

    Han, Bing; Jing, Hongyuan; Liu, Jianping; Wu, Zhangzhong [PetroChina Pipeline RandD Center, Langfang, Hebei (China); Hao, Jianbin [School of Petroleum Engineering, Southwest Petroleum University, Chengdu, Sichuan (China)

    2010-07-01

    Landslides have a serious impact on the integrity of oil and gas pipelines in the tough terrain of Western China. This paper introduces a solving method of axial stress, which uses numerical simulation and regression analysis for the pipelines subjected to landslides. Numerical simulation is performed to analyze the change regularity of pipe stresses for the five vulnerability assessment indexes, which are: the distance between pipeline and landslide tail; the thickness of landslide; the inclination angle of landslide; the pipeline length passing through landslide; and the buried depth of pipeline. A pipeline passing through a certain landslide in southwest China was selected as an example to verify the feasibility and effectiveness of this method. This method has practical applicability, but it would need large numbers of examples to better verify its reliability and should be modified accordingly. Also, it only considers the case where the direction of the pipeline is perpendicular to the primary slip direction of the landslide.

  16. Early Stress History Alters Serum Insulin-Like Growth Factor-1 and Impairs Muscle Mitochondrial Function in Adult Male Rats.

    Science.gov (United States)

    Ghosh, S; Banerjee, K K; Vaidya, V A; Kolthur-Seetharam, U

    2016-09-01

    Early-life adversity is associated with an enhanced risk for adult psychopathology. Psychiatric disorders such as depression exhibit comorbidity for metabolic dysfunction, including obesity and diabetes. However, it is poorly understood whether, besides altering anxiety and depression-like behaviour, early stress also evokes dysregulation of metabolic pathways and enhances vulnerability for metabolic disorders. We used the rodent model of the early stress of maternal separation (ES) to examine the effects of early stress on serum metabolites, insulin-like growth factor (IGF)-1 signalling, and muscle mitochondrial content. Adult ES animals exhibited dyslipidaemia, decreased serum IGF1 levels, increased expression of liver IGF binding proteins, and a decline in the expression of specific metabolic genes in the liver and muscle, including Pck1, Lpl, Pdk4 and Hmox1. These changes occurred in the absence of alterations in body weight, food intake, glucose tolerance, insulin tolerance or insulin levels. ES animals also exhibited a decline in markers of muscle mitochondrial content, such as mitochondrial DNA levels and expression of TFAM (transcription factor A, mitochondrial). Furthermore, the expression of several genes involved in mitochondrial function, such as Ppargc1a, Nrf1, Tfam, Cat, Sesn3 and Ucp3, was reduced in skeletal muscle. Adult-onset chronic unpredictable stress resulted in overlapping and distinct consequences from ES, including increased circulating triglyceride levels, and a decline in the expression of specific metabolic genes in the liver and muscle, with no change in the expression of genes involved in muscle mitochondrial function. Taken together, our results indicate that a history of early adversity can evoke persistent changes in circulating IGF-1 and muscle mitochondrial function and content, which could serve to enhance predisposition for metabolic dysfunction in adulthood. © 2016 British Society for Neuroendocrinology.

  17. Inflammation in adult women with a history of child maltreatment: The involvement of mitochondrial alterations and oxidative stress.

    Science.gov (United States)

    Boeck, Christina; Koenig, Alexandra Maria; Schury, Katharina; Geiger, Martha Leonie; Karabatsiakis, Alexander; Wilker, Sarah; Waller, Christiane; Gündel, Harald; Fegert, Jörg Michael; Calzia, Enrico; Kolassa, Iris-Tatjana

    2016-09-01

    The experience of maltreatment during childhood is associated with chronic low-grade inflammation in adulthood. However, the molecular mechanisms underlying this pro-inflammatory phenotype remain unclear. Mitochondria were recently found to principally coordinate inflammatory processes via both inflammasome activation and inflammasome-independent pathways. To this end, we hypothesized that alterations in immune cell mitochondrial functioning and oxidative stress might be at the interface between the association of maltreatment experiences during childhood and inflammation. We analyzed pro-inflammatory biomarkers (levels of C-reactive protein, cytokine secretion by peripheral blood mononuclear cells (PBMC) in vitro, PBMC composition, lysophosphatidylcholine levels), serum oxidative stress levels (arginine:citrulline ratio, l-carnitine and acetylcarnitine levels) and mitochondrial functioning (respiratory activity and density of mitochondria in PBMC) in peripheral blood samples collected from 30 women (aged 22-44years) with varying degrees of maltreatment experiences in form of abuse and neglect during childhood. Exposure to maltreatment during childhood was associated with an increased ROS production, higher levels of oxidative stress and an increased mitochondrial activity in a dose-response relationship. Moreover, the increase in mitochondrial activity and ROS production were positively associated with the release of pro-inflammatory cytokines by PBMC. Decreased serum levels of lysophosphatidylcholines suggested higher inflammasome activation with increasing severity of child maltreatment experiences. Together these findings offer preliminary evidence for the association of alterations in immune cell mitochondrial functioning, oxidative stress and the pro-inflammatory phenotype observed in individuals with a history of maltreatment during childhood. The results emphasize that the early prevention of child abuse and neglect warrants more attention, as the

  18. Brief Report: Parent's Assessments of Their Care-Related Stress and Child's ASD Symptoms in Relation to Their child's Intervention History.

    Science.gov (United States)

    Shepherd, Daniel; Csako, Rita; Landon, Jason; Goedeke, Sonja; Ty, Kelly

    2018-03-20

    Parenting a child with autism spectrum disorder (ASD) can be stressful. Understanding parent's perceptions of their stress and their child's ASD-related symptoms is important for both the well-being of parent and child and for other reasons, such as intervention adherence and diagnostic accuracy. We report parent (N = 570) ratings of both their ASD Care-Related Stress scores and their child's symptoms in relation to the child's exposure to five mainstream ASD interventions. Differences across intervention history in the way parents perceive their child's symptoms and rate the stressfulness of performing ASD-related parenting duties were found.

  19. 150 Years of Coulomb Stress History Along the California-Nevada Border, USA.

    Science.gov (United States)

    Carena, S.; Verdecchia, A.

    2014-12-01

    The temporal and spatial correlation among earthquakes in diffuse plate boundary zones is not well understood yet. The region north of the Garlock fault between the Sierra Nevada and Death Valley is part of a diffuse plate boundary zone, which absorbs a significant fraction of the plate motion between Pacific and North America. This area has experienced at least eight Mw ≥ 6 earthquakes in historical times, beginning with the 1872 Mw 7.5 Owens Valley earthquake. Furthermore, since 1978 Long Valley caldera has been undergoing periods of unrest, with earthquake swarms and resurgence. Our goal is to determine whether the 1872 Owens Valley earthquake has influenced the seismicity and volcanic activity in the area. We model the evolution of coseismic, interseismic and postseismic Coulomb stress (ΔCFS) in the region due to both earthquakes and caldera activity in the last 150 years. Our results show that the 1872 Owens Valley earthquake strongly encourages faulting in northern Owens Valley. In addition, there is a correlation among smaller events, in the form of a west-to-east migration of earthquakes from Long Valley caldera toward the White Mountains immediately following the 1978 caldera inflation event. The last event in this sequence, the 1986 Mw 6.3 Chalfant Valley earthquake, controls the location of over 80% of its own aftershocks, which occur in areas of positive ΔCFS and reach Mw 5.7. We also calculate the cumulative ΔCFS on several major active faults in the region. Stresses up to 30 bars and 10 bars respectively have accumulated on the White Mountains (Central section) and Deep Springs faults, comparable to the expected stress drop in an average earthquake. Because no surface ruptures more recent than 1.8 ka have been identified on these faults [dePolo, 1989; Lee et al., 2001], we consider them as likely candidates for the next major earthquake in the region.

  20. Reconciliation of stress and structural histories of the Tharsis region of Mars

    Science.gov (United States)

    Tanaka, Kenneth L.; Golombek, Matthew P.; Banerdt, W. B.

    1991-01-01

    New information is presented on the structural and stratigraphic evolution of the Tharsis region of Mars, along with a lithospheric deformation model that can account for the observations. According to this model, the lithosphere beneath Tharsis consists of a thin elastic crustal cap on the rise, which is mechanically detached from the strong upper mantle by a volcanically thickened, hot, weak lower crust; these layers merge into a single cooler strong lithospheric layer around the edges of the rise. It is suggested that the nonuniform distribution of tectonic features and strain around Tharsis is due to the concentration of regional stresses near weaker volcanotectonic centers.

  1. Rheology, strain localization and stress history in the limestones of Bure (Meuse, France)

    International Nuclear Information System (INIS)

    Rolland, A.

    2013-01-01

    In order to demonstrate the feasibility of a radioactive waste repository (HLW) in clay-stone formation, the french national radioactive waste management agency (Andra) started in 2000 to build an underground research laboratory (URL) at Bure in the south of the Meuse district. The target horizon for the laboratory is a 135 m thick layer of argillaceous rock (Callovo-Oxfordian clay-stone) that lies between about 420 and 555 meters below the surface at the URL site. The argillite layer (COX) is surrounded by limestones from the Dogger and the Oxfordian ages (respectively 164,7 to 175,6 Ma and 161,2 to 164,7 Ma). Numerous stylolites were found in these limestones. The aim of this work is to study the rheology of these stylolites-rich horizons and the stylolites as stress gauges in the Dogger and Oxfordian formations. In this work, a wide range of samples with and without stylolites were sampled in the Dogger and Oxfordian formations. Petrophysical measurements and microstructural studies showed that all these limestones have a microporous structure. We showed that the stylolites induced significant variations in some physical properties and in the rock strength. Based on an analytical model, presented here in details, linking a characteristic length associated to the stylolites morphology and the stress associated to the development of that stylolites, a method for the morphology analysis of stylolites is developed, using a Fourier power spectrum technique, by taking into account all the difficulties linked to the use of cores from deep boreholes. We apply this method on stylolites at various depths, starting from the Oxfordian formation at a depth of 158 meters to the Dogger formation at a depth of 800 meters. No stylolites are found in the intermediate Callovo-Oxfordian clay-stone formation. We analyze 1D profiles taken on the outer part of the cores. In agreement with theoretical predictions, we always observe two regimes for small and large scales separated by a

  2. Stress corrosion cracking resistance of 22% Cr duplex stainless steel in simulated sour environments

    International Nuclear Information System (INIS)

    Kudo, T.; Tsuge, H.; Moroishi, T.

    1989-01-01

    This paper reports the effect of nickel and nitrogen contents on stress corrosion cracking (SCC) of 22%Cr - 3%Mo-base duplex stainless steel investigated in simulated sour environments with respect to both the base metal and the heat-affected zone (HAZ) of welding. The threshold stress and the critical chloride concentration for SCC were evaluated as a function of the ferrite content (α-content) in the alloy. The threshold stress is highest at the α-content of 40 to 45%, and is lowered with decreasing and increasing the α-content from its value. The alloy whose α-content exceeds 80% at the HAZ has also high susceptibilities to pitting corrosion and intergranular corrosion (ICG). The critical chloride concentration for cracking increases with the decrease in the α-content. Moreover, the contents of chromium, nickel and molybdenum in the α-phase are considered to be an important factor for determining the critical chloride concentration

  3. Real-time simulation of thermal stresses and creep in plates subjected to transient heat input

    DEFF Research Database (Denmark)

    Hattel, Jesper Henri; Jacobsen, Torben Krogsdal; Hansen, P.N.

    1997-01-01

    -difference approach. It applies a general formulation which takes into account nonconstant material properties (e.g. temperature, material, or time dependency), heat-transfer coefficients, and creep. The temperature calculation applies a one-dimensional numerical model, whereas the stress analysis is semi......This paper presents a novel numerical technique for solving the temperature and stress fields in a plate subjected to arbitrarily varying transient boundary conditions (transient temperature and heat-flux variations) on a surface. The numerical method is based on the control-volume finite......-two-dimensional. Both plane stress and plane strain conditions are considered as extreme cases. It is shown that, by using the developed numerical technique, very fast real-time simulations can be performed. The method has proved its applicability in e.g. high-pressure die-casting, and applications to this industrial...

  4. Severe Trauma Stress Inoculation Training for Combat Medics using High Fidelity Simulation

    Science.gov (United States)

    2013-12-01

    expressions; and improved sensors and communication systems for current medical training simulators. He has prior experience in software development for DoD...the "look and feel" of such injuries by providing the highly realistic visual, auditory, and haptic (touch) stimuli necessary to elicit stress...addressed during development included the following: • Microcontroller-based control system for monitoring sensors and automating the actions of the

  5. Evaluation of the Effectiveness of LTR Training versus Simulation Training and Stress Inoculation

    Science.gov (United States)

    2016-10-01

    noncash compensation including health care, 16 retirement pay, child care and free or subsidized food, housing and education . Those supplements...the impact of a stressful environment on acquisition and retention of clinical skills is critically important . The Combat Casualty Training...translation of the Department of Defense’s medical education training objectives. The integration of simulation technology has augmented but not replaced the

  6. Simulation of multi-photon emission isotopes using time-resolved SimSET multiple photon history generator

    Energy Technology Data Exchange (ETDEWEB)

    Chiang, Chih-Chieh; Lin, Hsin-Hon; Lin, Chang-Shiun; Chuang, Keh-Shih [Department of Biomedical Engineering and Environmental Sciences, National Tsing-HuaUniversity, Hsinchu, Taiwan (China); Jan, Meei-Ling [Health Physics Division, Institute of Nuclear Energy Research, Atomic Energy Council, Taoyuan, Taiwan (China)

    2015-07-01

    Abstract-Multiple-photon emitters, such as In-111 or Se-75, have enormous potential in the field of nuclear medicine imaging. For example, Se-75 can be used to investigate the bile acid malabsorption and measure the bile acid pool loss. The simulation system for emission tomography (SimSET) is a well-known Monte Carlo simulation (MCS) code in nuclear medicine for its high computational efficiency. However, current SimSET cannot simulate these isotopes due to the lack of modeling of complex decay scheme and the time-dependent decay process. To extend the versatility of SimSET for simulation of those multi-photon emission isotopes, a time-resolved multiple photon history generator based on SimSET codes is developed in present study. For developing the time-resolved SimSET (trSimSET) with radionuclide decay process, the new MCS model introduce new features, including decay time information and photon time-of-flight information, into this new code. The half-life of energy states were tabulated from the Evaluated Nuclear Structure Data File (ENSDF) database. The MCS results indicate that the overall percent difference is less than 8.5% for all simulation trials as compared to GATE. To sum up, we demonstrated that time-resolved SimSET multiple photon history generator can have comparable accuracy with GATE and keeping better computational efficiency. The new MCS code is very useful to study the multi-photon imaging of novel isotopes that needs the simulation of lifetime and the time-of-fight measurements. (authors)

  7. Simulated Service and Stress Corrosion Cracking Testing for Friction Stir Welded Spun Formed Domes

    Science.gov (United States)

    Stewart, Thomas J.; Torres, Pablo D.; Caratus, Andrei A.; Curreri, Peter A.

    2010-01-01

    Simulated service testing (SST) development was required to help qualify a new 2195 aluminum lithium (Al-Li) alloy spin forming dome fabrication process for the National Aeronautics and Space Administration (NASA) Exploration Development Technology Program. The application for the technology is to produce high strength low weight tank components for NASA s next generation launch vehicles. Since plate material is not currently manufactured large enough to fabricate these domes, two plates are joined by means of friction stir welding. The plates are then pre-contour machined to near final thicknesses allowing for a thicker weld land and anticipating the level of stretch induced by the spin forming process. The welded plates are then placed in a spin forming tool and hot stretched using a trace method producing incremental contours. Finally the dome receives a room temperature contour stretch to final dimensions, heat treatment, quenching, and artificial aging to emulate a T-8 condition of temper. Stress corrosion cracking (SCC) tests were also performed by alternate immersion in a sodium chloride (NaCl) solution using the typical double beam assembly and with 4-point loaded specimens and use of bent-beam stress-corrosion test specimens under alternate immersion conditions. In addition, experiments were conducted to determine the threshold stress intensity factor for SCC (K(sub ISCC)) which to our knowledge has not been determined previously for Al-Li 2195 alloy. The successful simulated service and stress corrosion testing helped to provide confidence to continue to Ares 1 scale dome fabrication

  8. The impact of delivery style on doctors' experience of stress during simulated bad news consultations.

    Science.gov (United States)

    Shaw, Joanne; Brown, Rhonda; Dunn, Stewart

    2015-10-01

    The purpose of this study was to investigate the relationship between doctors' bad news delivery style and their experience of physiological stress during simulated bad news consultations. 31 doctors participated in two simulated breaking bad news (BBN) consultations. Delivery style was categorized as either blunt, forecasting or stalling (i.e. avoidant), based on the time to deliver the bad news and qualitative analysis of the interaction content and doctor's language style. Doctors' heart rate (HR) and skin conductance (SC) were recorded in consecutive 30s epochs. Doctors experienced a significant decrease in HR (F(1,36)=44.9, p.05) or SC (F(2,48)=.66, p>.05). Doctors experience heightened stress in the pre-news delivery phase of breaking bad news interactions. Delaying the delivery of bad news exposes doctors to a longer period of increased stress.This suggests that medical students and doctors should be taught to deliver bad news without delay, to help mitigate their response to this stressful encounter. Copyright © 2015. Published by Elsevier Ireland Ltd.

  9. One hundred and fifty years of Coulomb stress history along the California-Nevada border, USA

    Science.gov (United States)

    Verdecchia, Alessandro; Carena, Sara

    2015-02-01

    The region north of the Garlock Fault between the Sierra Nevada and Death Valley has experienced at least eight Mw ≥ 6 earthquakes in historical times, beginning with the 1872, Mw 7.5, Owens Valley earthquake. Furthermore, since 1978, the Long Valley Caldera has been undergoing periods of unrest, with earthquake swarms and resurgence. Our goal is to determine whether the 1872 Owens Valley earthquake and the caldera unrest have influenced the evolution of seismicity in the area. We model the evolution of coseismic, postseismic, and interseismic Coulomb stress change (Coulomb failure stress (ΔCFS)) in the region due to both Mw ≥ 6 earthquakes and caldera inflation in the last 150 years. Our results show that the 1872 Owens Valley earthquake has an important influence on subsequent events, strongly encouraging faulting in northern Owens Valley while inhibiting it elsewhere. There is also a correlation between caldera inflation and seismicity in northern Owens Valley, evidenced by the west-to-east migration of earthquakes from the Long Valley Caldera toward the White Mountains immediately following the 1978 caldera inflation event. Finally, we show that a total ΔCFS increase of up to 30 bars in the last 150 years has occurred on part of the White Mountains fault, making it a possible candidate for the next major earthquake in this region.

  10. Simulation as a Teaching Technology: A Brief History of Its Use in Nursing Education

    Science.gov (United States)

    Sanko, Jill S.

    2017-01-01

    Simulation can be used for teaching or practicing both technical skills (insertion of intravenous catheters, or suturing for example) and non-technical skills (communication and teamwork). A combination of full body, high and low technology simulators (mannequins designed to depict humans), body part or body system-specific task trainers (models…

  11. NUMERICAL SIMULATION OF RESIDUAL STRESSES GENERATED IN THE WIRE DRAWING PROCESS FOR DIFFERENT PROCESS PARAMETERS

    Directory of Open Access Journals (Sweden)

    Juliana Zottis

    2014-03-01

    Full Text Available The drawing process of steel bars is usually used to check better dimensional accuracy and mechanical properties to the material. In the other hand, the major concern found in manufacturing axes through this process is the appearance of distortion of shape. Such distortions are directly linked to the accumulation of residual stresses generated during the processes. As a result, this paper aims to study the influence of process parameters such as shape of puller, speed and lubrication used in wire drawing analyzing the accumulation of residual stress after the process. The stress analysis was performed by FEM being used two simulation software: Simufact.formingGP and DeformTM. Through these analyzes, it was found that the shape of how the bar is pulled causes a reduction of up to 100 MPa in residual stresses in the center of the bar, which represents an important factor in the study of the possible causes of the distortion. As well as factors speed and homogeneity of lubrication significantly altered the profile of residual stresses in the bar.

  12. Smaller amygdala volume and reduced anterior cingulate gray matter density associated with history of post-traumatic stress disorder.

    Science.gov (United States)

    Rogers, Mark A; Yamasue, Hidenori; Abe, Osamu; Yamada, Haruyasu; Ohtani, Toshiyuki; Iwanami, Akira; Aoki, Shigeki; Kato, Nobumasa; Kasai, Kiyoto

    2009-12-30

    Although post-traumatic stress disorder (PTSD) may be seen to represent a failure to extinguish learned fear, significant aspects of the pathophysiology relevant to this hypothesis remain unknown. Both the amygdala and hippocampus are necessary for fear extinction occur, and thus both regions may be abnormal in PTSD. Twenty-five people who experienced the Tokyo subway sarin attack in 1995, nine who later developed PTSD and 16 who did not, underwent magnetic resonance imaging (MRI) with manual tracing to determine bilateral amygdala and hippocampus volumes. At the time of scanning, one had PTSD and eight had a history of PTSD. Results indicated that the group with a history of PTSD had significantly smaller mean bilateral amygdala volume than did the group that did not develop PTSD. Furthermore, left amygdala volume showed a significant negative correlation with severity of PTSD symptomatology as well as reduced gray matter density in the left anterior cingulate cortex. To our knowledge, this is the first observation of an association between PTSD and amygdala volume. Furthermore the apparent interplay between amygdala and anterior cingulate cortex represents support at the level of gross brain morphology for the theory of PTSD as a failure of fear extinction.

  13. A Simulated Learning Environment of History Games for Enhancing Players' Cultural Awareness

    Science.gov (United States)

    Shih, Ju-Ling; Jheng, Shun-Cian; Tseng, Jia-Jiun

    2015-01-01

    This research attempted to create the historical context of Southern Taiwan in the late nineteenth century based on the martial art novel "Xiao-Mao" (Pussy) by designing a role-play digital game "Taiwan Epic Game" about the war time; in which, Taiwanese history, geography, and culture are presented in an innovative way with…

  14. Evaluation of the Aqua‎Crop Model to Simulate Maize Yiled Response under Salinity Stress

    Directory of Open Access Journals (Sweden)

    Aida Mehrazar

    2017-01-01

    Full Text Available Introduction: Limited water resources and its salinity uptrend has caused reducing water and soil quality and consequently reducing the crop production. Thus, use of saline water is the management strategies to decrease drought and water crisis. Furthermore, simulation models are valuable tools for improving on-farm water management and study about the effects of water quality and quantity on crop yield.. The AquaCrop model has recently been developed by the FAO which has the ability to check the production process under different propositions. The initial version of the model was introduced for simulation of crop yield and soil water movement in 2007, that the effect of salinity on crop yield was not considered. Version 4 of the model was released in 2012 in which also considered the effects of salinity on crop yield and simulation of solute Transmission in soil profile. Material and methods: In this project, evaluation of the AquaCrop model and its accuracy was studied in the simulating yield of maize under salt stress. This experiment was conducted in Karaj, on maize hybrid (Zea ma ys L in a sandy soil for investigation of salinity stress on maize yield in 2011-2012. This experiment was conducted in form of randomized complete block design in four replications and five levels of salinity treatments including 0, 4.53, 9.06, 13.59 and 18.13 dS/m at the two times sampling. To evaluate the effect of different levels of salinity on the yield of maize was used Version 4 AquaCrop model and SAS ver 9.1 software .The model calibration was performed by comparing the results of the field studies and the results of simulations in the model. In calculating the yield under different scenarios of salt stress by using AquaCrop, the model needs climate data, soil data, vegetation data and information related to farm management. The effects of salinity on yield and some agronomic and physiological traits of hybrid maize (Shoot length, root length, dry weight

  15. Analysis of the coherent and turbulent stresses of a numerically simulated rough wall pipe

    Science.gov (United States)

    Chan, L.; MacDonald, M.; Chung, D.; Hutchins, N.; Ooi, A.

    2017-04-01

    A turbulent rough wall flow in a pipe is simulated using direct numerical simulation (DNS) where the roughness elements consist of explicitly gridded three-dimensional sinusoids. Two groups of simulations were conducted where the roughness semi-amplitude h+ and the roughness wavelength λ+ are systematically varied. The triple decomposition is applied to the velocity to separate the coherent and turbulent components. The coherent or dispersive component arises due to the roughness and depends on the topological features of the surface. The turbulent stress on the other hand, scales with the friction Reynolds number. For the case with the largest roughness wavelength, large secondary flows are observed which are similar to that of duct flows. The occurrence of these large secondary flows is due to the spanwise heterogeneity of the roughness which has a spacing approximately equal to the boundary layer thickness δ.

  16. Stress

    Science.gov (United States)

    ... can be life-saving. But chronic stress can cause both physical and mental harm. There are at least three different types of stress: Routine stress related to the pressures of work, family, and other daily responsibilities Stress brought about ...

  17. A brief history of the introduction of generalized ensembles to Markov chain Monte Carlo simulations

    Science.gov (United States)

    Berg, Bernd A.

    2017-03-01

    The most efficient weights for Markov chain Monte Carlo calculations of physical observables are not necessarily those of the canonical ensemble. Generalized ensembles, which do not exist in nature but can be simulated on computers, lead often to a much faster convergence. In particular, they have been used for simulations of first order phase transitions and for simulations of complex systems in which conflicting constraints lead to a rugged free energy landscape. Starting off with the Metropolis algorithm and Hastings' extension, I present a minireview which focuses on the explosive use of generalized ensembles in the early 1990s. Illustrations are given, which range from spin models to peptides.

  18. North American water availability under stress and duress: building understanding from simulations, observations and data products

    Science.gov (United States)

    Maxwell, R. M.; Condon, L. E.; Atchley, A. L.; Hector, B.

    2017-12-01

    Quantifying the available freshwater for human use and ecological function depends on fluxes and stores that are hard to observe. Evapotranspiration (ET) is the largest terrestrial flux of water behind precipitation but is observed with low spatial density. Likewise, groundwater is the largest freshwater store, yet is equally uncertain. The ability to upscale observations of these variables is an additional complication; point measurements are made at scales orders of magnitude smaller than remote sensing data products. Integrated hydrologic models that simulate continental extents at fine spatial resolution are now becoming an additional tool to constrain fluxes and address interconnections. For example, recent work has shown connections between water table depth and transpiration partitioning, and demonstrated the ability to reconcile point observations and large-scale inferences. Here we explore the dynamics of large hydrologic systems experiencing change and stress across continental North America using integrated model simulations, observations and data products. Simulations of aquifer depletion due to pervasive groundwater pumping diagnose both stream depletion and changes in ET. Simulations of systematic increases in temperature are used to understand the relationship between snowpack dynamics, surface and groundwater flow, ET and a changing climate. Remotely sensed products including the GRACE estimates of total storage change are downscaled using model simulations to better understand human impacts to the hydrologic cycle. These example applications motivate a path forward to better use simulations to understand water availability.

  19. Complex interactions between the subject factors of biological sex and prior histories of binge-drinking and unpredictable stress influence behavioral sensitivity to alcohol and alcohol intake.

    Science.gov (United States)

    Quadir, Sema G; Guzelian, Eugenie; Palmer, Mason A; Martin, Douglas L; Kim, Jennifer; Szumlinski, Karen K

    2017-08-10

    Alcohol use disorders, affective disorders and their comorbidity are sexually dimorphic in humans. However, it is difficult to disentangle the interactions between subject factors influencing alcohol sensitivity in studies of humans. Herein, we combined murine models of unpredictable, chronic, mild stress (UCMS) and voluntary binge-drinking to examine for sex differences in the interactions between prior histories of excessive ethanol-drinking and stress upon ethanol-induced changes in motor behavior and subsequent drinking. In Experiment 1, female mice were insensitive to the UCMS-induced increase in ethanol-induced locomotion and ethanol intake under continuous alcohol-access. Experiment 2 revealed interactions between ethanol dose and sex (females>males), binge-drinking history (water>ethanol), and UCMS history (UCMS>controls), with no additive effect of a sequential prior history of both binge drinking and UCMS observed. We also observed an interaction between UCMS history and sex for righting recovery. UCMS history potentiated subsequent binge-drinking in water controls of both sexes and in male binge-drinking mice. Conversely, a prior binge-drinking history increased subsequent ethanol intake in females only, irrespective of prior UCMS history. In Experiment 3, a concurrent history of binge-drinking and UCMS did not alter ethanol intake, nor did it influence the ethanol dose-locomotor response function, but it did augment alcohol-induced sedation and reduced subsequent alcohol intake over that produced by binge-drinking alone. Thus, the subject factors of biological sex, prior stressor history and prior binge-drinking history interact in complex ways in mice to impact sensitivity to alcohol's motor-stimulating, -incoordinating and intoxicating effects, as well as to influence subsequent heavy drinking. Copyright © 2017 Elsevier Inc. All rights reserved.

  20. Coral reefs in an urban embayment in Hawaii: a complex case history controlled by natural and anthropogenic stress

    Science.gov (United States)

    Grigg, R. W.

    1995-11-01

    The effects of natural and anthropogenic stress need to be separated before coral reef ecosystems can be effectively managed. In this paper, a 25 year case history of coral reefs in an urban embayment (Mamala Bay) off Honolulu, Hawaii is described and differences between natural and man-induced stress are distinguished. Mamala Bay is a 30 km long shallow coastal bay bordering the southern (leeward) shore of Oahu and the city of Honolulu in the Hawaiian Islands. During the last 25 years, this area has been hit by two magnitude 5 hurricane events (winds > 240 km/h) generating waves in excess of 7.5 m. Also during this period, two large sewer outfalls have discharged up to 90 million gallons per day (mgd) or (360 × 106 L/day) of point source pollution into the bay. Initially the discharge was raw sewage, but since 1977 it has received advanced primary treatment. Non-point source run-off from the Honolulu watershed also enters the bay on a daily basis. The results of the study show that discharge of raw sewage had a serious but highly localized impact on shallow (˜10 m) reef corals in the bay prior to 1977. After 1977, when treatment was upgraded to the advanced primary level and outfalls were extended to deep water (> 65 m), impacts to reef corals were no longer significant. No measurable effects of either point or non-point source pollution on coral calcification, growth, species composition, diversity or community structure related to pollution can now be detected. Conversely the effects of hurricane waves in 1982 and 1992 together caused major physical destruction to the reefs. In 1982, average coral cover of well-developed offshore reefs dropped from 60-75% to 5-15%. Only massive species in high relief areas survived. Today, recovery is occurring, and notwithstanding major future disturbance events, long-term biological processes should eventually return the coral ecosystems to a more mature successional stage. This case history illustrates the complex nature of

  1. Finite element simulation of stress evolution in thermal barrier coating systems

    Energy Technology Data Exchange (ETDEWEB)

    Bednarz, P.

    2007-07-01

    Gas turbine materials exposed to extreme high temperature require protective coatings. To design reliable components, a better understanding of the coating failure mechanisms is required. Damage in Thermal Barrier Coating Systems (TBCs) is related to oxidation of the Bond Coat, sintering of the ceramic, thermal mismatch of the material constituents, complex shape of the BC/TGO/TBC interface, redistribution of stresses via creep and plastic deformation and crack resistance. In this work, experimental data of thermo-mechanical properties of CMSX-4, MCrAlY (Bond Coat) and APS-TBC (partially stabilized zirconia), were implemented into an FE-model in order to simulate the stress development at the metal/ceramic interface. The FE model reproduced the specimen geometry used in corresponding experiments. It comprises a periodic unit cell representing a slice of the cylindrical specimen, whereas the periodic length of the unit cell equals an idealized wavelength of the rough metal/ceramic interface. Experimental loading conditions in form of thermal cycling with a dwelltime at high temperature and consideration of continuous oxidation were simulated. By a stepwise consideration of various material properties and processes, a reference model was achieved which most realistically simulated the materials behavior. The influences of systematic parameter variations on the stress development and critical sites with respect to possible crack paths were shown. Additionally, crack initiation and propagation at the peak of asperity at BC/TGO interface was calculated. It can be concluded that a realistic modeling of stress development in TBCs requires at least reliable data of i) BC and TGO plasticity, ii) BC and TBC creep, iii) continuous oxidation including in particular lateral oxidation, and iv) critical energy release rate for interfaces (BC/TGO, TGO/TBC) and for each layer. The main results from the performed parametric studies of material property variations suggest that

  2. Rapid corticosteroid actions on synaptic plasticity in the mouse basolateral amygdala: relevance of recent stress history and β-adrenergic signaling.

    Science.gov (United States)

    Sarabdjitsingh, R A; Joëls, M

    2014-07-01

    The rodent stress hormone corticosterone rapidly enhances long-term potentiation in the CA1 hippocampal area, but leads to a suppression when acting in a more delayed fashion. Both actions are thought to contribute to stress effects on emotional memory. Emotional memory formation also involves the basolateral amygdala, an important target area for corticosteroid actions. We here (1) investigated the rapid effects of corticosterone on amygdalar synaptic potentiation, (2) determined to what extent these effects depend on the mouse's recent stress history or (3) on prior β-adrenoceptor activation; earlier studies at the single cell level showed that especially a recent history of stress changes the responsiveness of basolateral amygdala neurons to corticosterone. We report that, unlike the hippocampus, stress enhances amygdalar synaptic potentiation in a slow manner. In vitro exposure to 100 nM corticosterone quickly decreases synaptic potentiation, and causes only transient potentiation in tissue from stressed mice. This transient type of potentiation is also seen when β-adrenoceptors are blocked during stress and this is further exacerbated by subsequent in vitro administered corticosterone. We conclude that stress and corticosterone change synaptic potentiation in the basolateral amygdala in a manner opposite to that seen in the hippocampus and that renewed exposure to corticosterone only allows induction of non-persistent forms of synaptic potentiation. Copyright © 2013 Elsevier Inc. All rights reserved.

  3. Bipolar affective disorder and borderline personality disorder: Differentiation based on the history of early life stress and psychoneuroendocrine measures.

    Science.gov (United States)

    Mazer, Angela Kaline; Cleare, Anthony J; Young, Allan H; Juruena, Mario F

    2018-04-24

    Borderline Personality Disorder (BPD) and Bipolar Affective Disorder (BD) have clinical characteristics in common which often make their differential diagnosis difficult. The history of early life stress (ELS) may be a differentiating factor between BPD and BD, as well as its association with clinical manifestations and specific neuroendocrine responses in each of these diagnoses. Assessing and comparing patients with BD and BPD for factors related to symptomatology, etiopathogenesis and neuroendocrine markers. The study sample consisted of 51 women, divided into 3 groups: patients with a clinical diagnosis of BPD (n = 20) and BD (n = 16) and healthy controls (HC, n = 15). Standardized instruments were used for the clinical evaluation, while the history of ELS was quantified with the Childhood Trauma Questionnaire (CTQ), and classified according to the subtypes: emotional abuse, physical abuse, sexual abuse, emotional neglect and physical neglect. The functioning of the hypothalamic-pituitary-adrenal (HPA) axis was evaluated by measuring a single plasma cortisol sample. Patients with BPD presented with more severe psychiatric symptoms of: anxiety, impulsivity, depression, hopelessness and suicidal ideation than those with BD. The history of ELS was identified as significantly more prevalent and more severe in patients (BPD and BP) than in HC. Emotional abuse, emotional neglect and physical neglect also showed differences and were higher in BPD than BD patients. BPD patients had greater severity of ELS overall and in the subtypes of emotional abuse, emotional neglect and physical neglect than BD patients. The presence of ELS in patients with BPD and BP showed significant difference with lower cortisol levels when compared to HC. The endocrine evaluation showed no significant differences between the diagnoses of BPD and BD. Cortisol measured in patients with BPD was significantly lower compared to HC in the presence of emotional neglect and physical

  4. Determination of the optimum temperature history of inlet water for minimizing thermal stresses in a pipe by the multiphysics inverse analysis

    International Nuclear Information System (INIS)

    Kubo, S; Uchida, K; Ishizaka, T; Ioka, S

    2008-01-01

    It is important to reduce the thermal stresses for managing and extending the lives of pipes in plants. In this problem, heat conduction, elastic deformation, heat transfer, liquid flow should be considered, and therefore the problem is of a multidisciplinary nature. An inverse method was proposed by the present authors for determining the optimum thermal load history which reduced transient thermal stress considering the multidisciplinary physics. But the obtained solution had a problem that the temperature increasing rate of inner surface of the pipe was discontinuous at the end time of heat up. In this study we introduce temperature history functions that ensure the continuity of the temperature increasing rate. The multidisciplinary complex problem is decomposed into a heat conduction problem, a heat transfer problem, and a thermal stress problem. An analytical solution of the temperature distribution of radial thickness and thermal hoop stress distribution is obtained. The maximum tensile and compressive hoop stresses are minimized for the case where inner surface temperature T s (t) is expressed in terms of the 4th order polynomial function of time t. Finally, from the temperature distributions, the optimum fluid temperature history is obtained for reducing the thermal stresses.

  5. Simulation of distortion and residual stress in high pressure die casting – modelling and experiments

    International Nuclear Information System (INIS)

    Hofer, P; Kaschnitz, E; Schumacher, P

    2012-01-01

    Two individual high-pressure die-casting geometries were developed in order to study the influence of process parameters and different alloys on the distortion behaviour of castings. These geometries were a stress lattice and a V-shaped sample tending to form residual stress due to different wall thickness respectively by a deliberate massive gating system. In the experimental castings the influence of the most important process parameters such as die temperature and die opening time and the cooling regime was examined. The time evolution of process temperatures was measured using thermal imaging. The heat transfer coefficients were adapted to the observed temperature distributions. Castings were produced from the two alloys AlSi12 and AlSi10MnMg. The distortion of the castings was measured by means of a tactile measuring device. For the alloy AlSi10MnMg thermo-physical and thermo-mechanical data were obtained using differential scanning calorimetry, laser flash technique, dilatometry and tensile testing at elevated temperatures. These data were used for modelling the material behaviour of the AlSi10MnMg alloy in the numerical model while for the alloy AlSi12(Fe) literature data were used. Process and stress simulation were conducted using the commercial FEM software ANSYS Workbench. A survey on the results of the comparison between simulation and experiment is given for both alloys.

  6. An Agent-Based Modeling Framework for Simulating Human Exposure to Environmental Stresses in Urban Areas

    Directory of Open Access Journals (Sweden)

    Liang Emlyn Yang

    2018-04-01

    Full Text Available Several approaches have been used to assess potential human exposure to environmental stresses and achieve optimal results under various conditions, such as for example, for different scales, groups of people, or points in time. A thorough literature review in this paper identifies the research gap regarding modeling approaches for assessing human exposure to environment stressors, and it indicates that microsimulation tools are becoming increasingly important in human exposure assessments of urban environments, in which each person is simulated individually and continuously. The paper further describes an agent-based model (ABM framework that can dynamically simulate human exposure levels, along with their daily activities, in urban areas that are characterized by environmental stresses such as air pollution and heat stress. Within the framework, decision-making processes can be included for each individual based on rule-based behavior in order to achieve goals under changing environmental conditions. The ideas described in this paper are implemented in a free and open source NetLogo platform. A basic modeling scenario of the ABM framework in Hamburg, Germany, demonstrates its utility in various urban environments and individual activity patterns, as well as its portability to other models, programs, and frameworks. The prototype model can potentially be extended to support environmental incidence management through exploring the daily routines of different groups of citizens, and comparing the effectiveness of different strategies. Further research is needed to fully develop an operational version of the model.

  7. Force and Stress along Simulated Dissociation Pathways of Cucurbituril-Guest Systems.

    Science.gov (United States)

    Velez-Vega, Camilo; Gilson, Michael K

    2012-03-13

    The field of host-guest chemistry provides computationally tractable yet informative model systems for biomolecular recognition. We applied molecular dynamics simulations to study the forces and mechanical stresses associated with forced dissociation of aqueous cucurbituril-guest complexes with high binding affinities. First, the unbinding transitions were modeled with constant velocity pulling (steered dynamics) and a soft spring constant, to model atomic force microscopy (AFM) experiments. The computed length-force profiles yield rupture forces in good agreement with available measurements. We also used steered dynamics with high spring constants to generate paths characterized by a tight control over the specified pulling distance; these paths were then equilibrated via umbrella sampling simulations and used to compute time-averaged mechanical stresses along the dissociation pathways. The stress calculations proved to be informative regarding the key interactions determining the length-force profiles and rupture forces. In particular, the unbinding transition of one complex is found to be a stepwise process, which is initially dominated by electrostatic interactions between the guest's ammoniums and the host's carbonyl groups, and subsequently limited by the extraction of the guest's bulky bicyclooctane moiety; the latter step requires some bond stretching at the cucurbituril's extraction portal. Conversely, the dissociation of a second complex with a more slender guest is mainly driven by successive electrostatic interactions between the different guest's ammoniums and the host's carbonyl groups. The calculations also provide information on the origins of thermodynamic irreversibilities in these forced dissociation processes.

  8. History of sexual trauma moderates psychotherapy outcome for posttraumatic stress disorder.

    Science.gov (United States)

    Markowitz, John C; Neria, Yuval; Lovell, Karina; Van Meter, Page E; Petkova, Eva

    2017-08-01

    Moderators of differential psychotherapy outcome for posttraumatic stress disorder (PTSD) are rare, yet have crucial clinical importance. We tested the moderating effects of trauma type for three psychotherapies in 110 unmedicated patients with chronic DSM-IV PTSD. Patients were randomized to 14 weeks of prolonged exposure (PE, N = 38), interpersonal psychotherapy (IPT, N = 40), or relaxation therapy (RT, N = 32). The Clinician-Administered PTSD Scale (CAPS) was the primary outcome measure. Moderator candidates were trauma type: interpersonal, sexual, physical. We fit a regression model for week 14 CAPS as a function of treatment (a three-level factor), an indicator of trauma type presence/absence, and their interactions, controlling for baseline CAPS, and evaluated potential confounds. Thirty-nine (35%) patients reported sexual, 68 (62%) physical, and 102 (93%) interpersonal trauma. Baseline CAPS scores did not differ by presence/absence of trauma types. Sexual trauma as PTSD criterion A significantly moderated treatment effect: whereas all therapies had similar efficacy among nonsexually-traumatized patients, IPT had greater efficacy among sexually traumatized patients (efficacy difference with and without sexual trauma: IPT vs. PE and IPT vs. RT P's < .05), specifically in PTSD symptom clusters B and D (P's < .05). Few studies have assessed effects of varying trauma types on effects of differing psychotherapies. In this exploratory study, sexual trauma moderated PTSD outcomes of three therapies: IPT showed greater benefit for sexually traumatized patients than PE or RT. The IPT focuses on affect to help patients determine trust in their current environments may particularly benefit patients who have suffered sexual assault. © 2017 Wiley Periodicals, Inc.

  9. Use of observation followed by outpatient stress testing in chest pain patients with prior coronary artery disease history: An evaluation of prognostic utility.

    Science.gov (United States)

    Khalil, Yasser; Schwartz, Melvin H; Pandey, Prasant S; Abdul Latif, Maida S; Matsumura, Martin E

    2015-06-01

    To determine the outcomes of patients with chest pain (CP) and prior history of coronary artery disease (CAD) managed with observation followed by outpatient stress myocardial perfusion imaging (MPI). Retrospective analysis of patients with CP managed with observation followed by outpatient stress MPI, comparing cardiovascular (CV) event rates stratified by CAD history. 375 patients were included: 111 with and 264 without a CAD history. All patients underwent outpatient stress MPI within 72 h of observation. MPI identified patients at risk for CV events. However, while patients with negative MPI and without a CAD history had very low rates of short- and long-term CAD events (0.8%, 0.8%, and 1.3% at 30 days, 1 year, and 3 years, respectively), event rates of those with a negative test but a CAD history were significantly higher (2.6%, 5.3%, and 6.6% at 30 days, 1 year and 3 years, respectively; p = 0.044 and p = 0.034 compared to CAD- patients at 1 year and 3 years, respectively). In a multivariable logistic regression model, a positive MPI proved to be an independent predictor of long-term CV events in patients with CP and prior CAD. Observation followed by stress MPI can effectively risk stratify CP patients with prior CAD for CV risk. These patients are at increased risk of CV events even after a low-risk stress MPI study. Patients presenting with CP and managed with a strategy of observation followed by a negative stress MPI warrant close short- and long-term monitoring for recurrent events.

  10. Simulation of Weld Mechanical Behavior to Include Welding-Induced Residual Stress and Distortion: Coupling of SYSWELD and Abaqus Codes

    Science.gov (United States)

    2015-11-01

    Memorandum Simulation of Weld Mechanical Behavior to Include Welding-Induced Residual Stress and Distortion: Coupling of SYSWELD and Abaqus Codes...Weld Mechanical Behavior to Include Welding-Induced Residual Stress and Distortion: Coupling of SYSWELD and Abaqus Codes by Charles R. Fisher...Welding- Induced Residual Stress and Distortion: Coupling of SYSWELD and Abaqus Codes 5a. CONTRACT NUMBER N/A 5b. GRANT NUMBER N/A 5c

  11. Assessment of shear stress related parameters in the carotid bifurcation using mouse-specific FSI simulations.

    Science.gov (United States)

    De Wilde, David; Trachet, Bram; Debusschere, Nic; Iannaccone, Francesco; Swillens, Abigail; Degroote, Joris; Vierendeels, Jan; De Meyer, Guido R Y; Segers, Patrick

    2016-07-26

    The ApoE(-)(/)(-) mouse is a common small animal model to study atherosclerosis, an inflammatory disease of the large and medium sized arteries such as the carotid artery. It is generally accepted that the wall shear stress, induced by the blood flow, plays a key role in the onset of this disease. Wall shear stress, however, is difficult to derive from direct in vivo measurements, particularly in mice. In this study, we integrated in vivo imaging (micro-Computed Tomography-µCT and ultrasound) and fluid-structure interaction (FSI) modeling for the mouse-specific assessment of carotid hemodynamics and wall shear stress. Results were provided for 8 carotid bifurcations of 4 ApoE(-)(/)(-) mice. We demonstrated that accounting for the carotid elasticity leads to more realistic flow waveforms over the complete domain of the model due to volume buffering capacity in systole. The 8 simulated cases showed fairly consistent spatial distribution maps of time-averaged wall shear stress (TAWSS) and relative residence time (RRT). Zones with reduced TAWSS and elevated RRT, potential indicators of atherosclerosis-prone regions, were located mainly at the outer sinus of the external carotid artery. In contrast to human carotid hemodynamics, no flow recirculation could be observed in the carotid bifurcation region. Copyright © 2015 Elsevier Ltd. All rights reserved.

  12. Wound-healing ability is conserved during periods of chronic stress and costly life history events in a wild-caught bird.

    Science.gov (United States)

    DuRant, S E; de Bruijn, R; Tran, M N; Romero, L M

    2016-04-01

    Chronic stress, potentially through the actions of corticosterone, is thought to directly impair the function of immune cells. However, chronic stress may also have an indirect effect by influencing allocation of energy, ultimately shifting resources away from the immune system. If so, the effects of chronic stress on immune responses may be greater during energetically-costly life history events. To test whether the effects of chronic stress on immune responses differ during expensive life history events we measured wound healing rate in molting and non-molting European starlings (Sturnus vulgaris) exposed to control or chronic stress conditions. To determine whether corticosterone correlated with wound healing rates before starting chronic stress, we measured baseline and stress-induced corticosterone and two estimates of corticosterone release and regulation, negative feedback (using dexamethasone injection), and maximal capacity of the adrenals to secrete corticosterone (using adrenocorticotropin hormone [ACTH] injection). After 8days of exposure to chronic stress, we wounded both control and chronically stressed birds and monitored healing daily. We monitored nighttime heart rate, which strongly correlates with energy expenditure, and body mass throughout the study. Measures of corticosterone did not differ with molt status. Contrary to work on lizards and small mammals, all birds, regardless of stress or molt status, fully-healed wounds at similar rates. Although chronic stress did not influence healing rates, individuals with low baseline corticosterone or strong negative feedback had faster healing rates than individuals with high baseline corticosterone or weak negative feedback. In addition, wound healing does appear to be linked to energy expenditure and body mass. Non-molting, chronically stressed birds decreased nighttime heart rate during healing, but this pattern did not exist in molting birds. Additionally, birds of heavier body mass at the start of

  13. Effect of heat stress on cardiac output and systemic vascular conductance during simulated hemorrhage to presyncope in young men

    DEFF Research Database (Denmark)

    Ganio, Matthew S; Overgaard, Morten; Seifert, Thomas

    2012-01-01

    During moderate actual or simulated hemorrhage, as cardiac output decreases, reductions in systemic vascular conductance (SVC) maintain mean arterial pressure (MAP). Heat stress, however, compromises the control of MAP during simulated hemorrhage, and it remains unknown whether this response is due...... to a persistently high SVC and/or a low cardiac output. This study tested the hypothesis that an inadequate decrease in SVC is the primary contributing mechanism by which heat stress compromises blood pressure control during simulated hemorrhage. Simulated hemorrhage was imposed via lower body negative pressure...... normothermic is no longer adequate during a heat-stressed-simulated hemorrhage. The absence of a decrease in SVC at a time of profound reductions in MAP suggests that inadequate control of vascular conductance is a primary mechanism compromising blood pressure control during these conditions....

  14. Depression, Anxiety, and Stress Among People With Chronic Hepatitis C Virus Infection and a History of Injecting Drug Use in New South Wales, Australia.

    Science.gov (United States)

    Fortier, Emmanuel; Alavi, Maryam; Bruneau, Julie; Micallef, Michelle; Perram, Jacinta; Sockalingam, Sanjeev; Dunlop, Adrian J; Balcomb, Annie C; Day, Carolyn A; Treloar, Carla; Bath, Nicky; Haber, Paul S; Dore, Gregory J; Grebely, Jason

    The aims of this study were to assess symptoms of depression, anxiety, and stress and associated sociodemographic factors among people living with chronic hepatitis C virus (HCV) infection with a history of injecting drug use and to assess the association between symptoms of depression, anxiety, or stress and HCV treatment intent, specialist assessment, or treatment uptake. The Enhancing Treatment for Hepatitis C in Opioid Substitution Settings was an observational cohort study evaluating the provision of HCV assessment and treatment among people with chronic HCV and a history of injecting drug use, recruited from 9 community health centers and opioid substitution therapy (OST) clinics (New South Wales, Australia). Symptoms were assessed using the Depression Anxiety Stress Scales (DASS-21). Analyses were performed using logistic regression. Among 415 participants (mean age 41 years, 71% male), 47%, 52%, and 36% demonstrated moderate to extremely severe symptoms of depression, anxiety, and stress, respectively. In adjusted analyses, depression symptoms were associated with recent injecting drug use [adjusted odds ratio (aOR) 1.63, 95% confidence interval (CI) 1.07-2.49), whereas stress symptoms were associated with unemployment (aOR 2.99, 95% CI 1.09-8.15) and not living with a spouse or other relatives/friends (aOR 1.55, 95% CI 1.01-2.39). Symptoms of depression, anxiety, or stress or having a history of treated mental illness were not independently associated with HCV treatment intent, specialist assessment, or treatment uptake. Findings suggest a need for improved interventions and care regarding mental health among people living with chronic HCV with a history of injecting drug use, but suggest that symptoms of depression, anxiety, and stress should not be immediate contraindications to HCV assessment and treatment.

  15. Fabrication of simulated plate fuel elements: Defining role of out-of-plane residual shear stress

    Energy Technology Data Exchange (ETDEWEB)

    Rakesh, R., E-mail: rakesh.rad87@gmail.com [DAE Graduate Fellows, IIT Bombay, Powai, Mumbai 400076 (India); Metallic Fuels Division, BARC, Trombay, Mumbai 400085 (India); Kohli, D. [DAE Graduate Fellows, IIT Bombay, Powai, Mumbai 400076 (India); Metallic Fuels Division, BARC, Trombay, Mumbai 400085 (India); Sinha, V.P.; Prasad, G.J. [Metallic Fuels Division, BARC, Trombay, Mumbai 400085 (India); Samajdar, I. [Department of Metallurgical Engineering and Materials Science, IIT Bombay, Powai, Mumbai 400076 (India)

    2014-02-01

    Bond strength and microstructural developments were investigated during fabrication of simulated plate fuel elements. The study involved roll bonding of aluminum–aluminum (case A) and aluminum–aluminum + yttria (Y{sub 2}O{sub 3}) dispersion (case B). Case B approximated aluminum–uranium silicide (U{sub 3}Si{sub 2}) ‘fuel-meat’ in an actual plate fuel. Samples after different stages of fabrication, hot and cold rolling, were investigated through peel and pull tests, micro-hardness, residual stresses, electron and micro-focus X-ray diffraction. Measurements revealed a clear drop in bond strength during cold rolling: an observation unique to case B. This was related to significant increase in ‘out-of-plane’ residual shear stresses near the clad/dispersion interface, and not from visible signatures of microstructural heterogeneities.

  16. MD simulation of plastic deformation nucleation in stressed crystallites under irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Korchuganov, A. V., E-mail: avkor@ispms.tsc.ru; Zolnikov, K. P., E-mail: kost@ispms.tsc.ru; Kryzhevich, D. S., E-mail: kryzhev@ispms.tsc.ru [Russian Academy of Sciences, Institute of Strength Physics and Materials Science, Siberian Branch (Russian Federation); Chernov, V. M., E-mail: VMChernov@bochvar.ru [National Research Tomsk State University (Russian Federation); Psakhie, S. G., E-mail: sp@ispms.tsc.ru [Russian Academy of Sciences, Institute of Strength Physics and Materials Science, Siberian Branch (Russian Federation)

    2016-12-15

    The investigation of plastic deformation nucleation in metals and alloys under irradiation and mechanical loading is one of the topical issues of materials science. Specific features of nucleation and evolution of the defect system in stressed and irradiated iron, vanadium, and copper crystallites were studied by molecular dynamics simulation. Mechanical loading was performed in such a way that the modeled crystallite volume remained unchanged. The energy of the primary knock-on atom initiating a cascade of atomic displacements in a stressed crystallite was varied from 0.05 to 50 keV. It was found that atomic displacement cascades might cause global structural transformations in a region far larger than the radiation-damaged area. These changes are similar to the ones occurring in the process of mechanical loading of samples. They are implemented by twinning (in iron and vanadium) or through the formation of partial dislocation loops (in copper).

  17. Numerical Simulation of Temperature Field and Residual Stress Distribution for Laser Cladding Remanufacturing

    Directory of Open Access Journals (Sweden)

    Liang Hua

    2014-05-01

    Full Text Available A three-dimensional finite element model was employed to simulate the cladding process of Ni-Cr-B-Si coatings on 16MnR steel under different parameters of laser power, scanning speed, and spot diameter. The temperature and residual stress distribution, the depth of the heat affected zone (HAZ, and the optimized parameters for laser cladding remanufacturing technology were obtained. The orthogonal experiment and intuitive analysis on the depth of the HAZ were performed to study the influence of different cladding parameters. A new criterion based on the ratio of the maximum tensile residual stress and fracture strength of the substrate was proposed for optimization of the remanufacturing parameters. The result showed well agreement with that of the HAZ analysis.

  18. Stress corrosion cracking tests on high-level-waste container materials in simulated tuff repository environments

    International Nuclear Information System (INIS)

    Abraham, T.; Jain, H.; Soo, P.

    1986-06-01

    Types 304L, 316L, and 321 austenitic stainless steel and Incoloy 825 are being considered as candidate container materials for emplacing high-level waste in a tuff repository. The stress corrosion cracking susceptibility of these materials under simulated tuff repository conditions was evaluated by using the notched C-ring method. The tests were conducted in boiling synthetic groundwater as well as in the steam/air phase above the boiling solutions. All specimens were in contact with crushed Topopah Spring tuff. The investigation showed that microcracks are frequently observed after testing as a result of stress corrosion cracking or intergranular attack. Results showing changes in water chemistry during test are also presented

  19. Finite element simulations of internal stresses generated during the ferroelastic deformation of NiTi bodies

    International Nuclear Information System (INIS)

    Manach, P.Y.; Favier, D.; Rio, G.

    1996-01-01

    The aim of this paper is to analyse the generation of internal stresses during the predeformation of NiTi shape memory alloys in the martensitic state. This allows to determine the initial stress state in which the material will transform during the shape memory effect due to heating consecutively to this prestrain. In that way a three-dimensional finite element model of the deformation of shape memory alloys has been developed, the constitutive law being defined using an elastohysteresis tensor model. The influence of behavioural and geometrical factors are illustrated considering the numerical simulation of different cases of practical importance for industrial applications : the study of the bending behaviour of a NiTi cantilever beam as well as the study of the swelling of a pipe connection under both uniform and non uniform internal displacement fields. (orig.)

  20. Constraining Thermal Histories by Monte Carlo Simulation of Mg-Fe Isotopic Profiles in Olivine

    Science.gov (United States)

    Sio, C. K. I.; Dauphas, N.

    2016-12-01

    In thermochronology, random time-temperature (t-T) paths are generated and used as inputs to model fission track data. This random search method is used to identify a range of acceptable thermal histories that can describe the data. We have extended this modeling approach to magmatic systems. This approach utilizes both the chemical and stable isotope profiles measured in crystals as model constraints. Specifically, the isotopic profiles are used to determine the relative contribution of crystal growth vs. diffusion in generating chemical profiles, and to detect changes in melt composition. With this information, tighter constraints can be placed on the thermal evolution of magmatic bodies. We use an olivine phenocryst from the Kilauea Iki lava lake, HI, to demonstrate proof of concept. We treat this sample as one with little geologic context, then compare our modeling results to the known thermal history experienced by that sample. To complete forward modeling, we use MELTS to estimate the boundary condition, initial and quench temperatures. We also assume a simple relationship between crystal growth and cooling rate. Another important parameter is the isotopic effect for diffusion (i.e., the relative diffusivity of the light vs. heavy isotope of an element). The isotopic effects for Mg and Fe diffusion in olivine have been estimated based on natural samples; experiments to better constrain these parameters are underway. We find that 40% of the random t-T paths can be used to fit the Mg-Fe chemical profiles. However, only a few can be used to simultaneously fit the Mg-Fe isotopic profiles. These few t-T paths are close to the independently determined t-T history of the sample. This modeling approach can be further extended other igneous and metamorphic systems where data exist for diffusion rates, crystal growth rates, and isotopic effects for diffusion.

  1. Infinite fuel element simulation of pin power distributions and control blade history in a BWR fuel assembly

    Energy Technology Data Exchange (ETDEWEB)

    Li, J.; Nuenighoff, K.; Allelein, H.J. [Forschungszentrum Juelich GmbH (DE). Inst. fuer Energie- und Klimaforschung (IEK), Sicherheitsforschung und Reaktortechnik (IEK-6)

    2011-07-01

    Pellet-Cladding Interaction (PCI) is a well known effect in fuel pins. One possible reason for PCI-effects could be local power excursions in the fuel pins, which can led to a rupture of the fuel cladding tube. From a reactor safety point of view this has to be considered as a violence of the barrier principal in order to retain fission products in the fuel pins. This paper focuses on the pin power distributions in a 2D infinite lattice of a BWR fuel element. Lots of studies related PCI effect can be found in the literature. In this compact, coupled neutronic depletion calculations taking the control history effect into account are described. Depletion calculations of an infinite fuel element of a BWR were carried out with controlled, uncontrolled and temporarily controlled scenarios. Later ones are needed to describe the control blade history (CBH) effect. A Monte-Carlo approach is mandatory to simulate the neutron physics. The VESTA code was applied to couple the Monte-Carlo-Code MCNP(X) with the burnup code ORIGEN. Additionally, CASMO-4 is also employed to verify the method of simulation results from VESTA. The cross sections for Monte Carlo and burn-up calculations are derived from ENDF/B-VII.0. (orig.)

  2. Capstone Teaching Models: Combining Simulation, Analytical Intuitive Learning Processes, History and Effectiveness

    Science.gov (United States)

    Reid, Maurice; Brown, Steve; Tabibzadeh, Kambiz

    2012-01-01

    For the past decade teaching models have been changing, reflecting the dynamics, complexities, and uncertainties of today's organizations. The traditional and the more current active models of learning have disadvantages. Simulation provides a platform to combine the best aspects of both types of teaching practices. This research explores the…

  3. Navigating the Problem Space: The Medium of Simulation Games in the Teaching of History

    Science.gov (United States)

    McCall, Jeremiah

    2012-01-01

    Simulation games can play a critical role in enabling students to navigate the problem spaces of the past while simultaneously critiquing the models designers offer to represent those problem spaces. There is much to be gained through their use. This includes rich opportunities for students to engage the past as independent historians; to consider…

  4. Oxidative stress physiology in relation to life history traits of a free-living vertebrate : the spotted snow skink, Niveoscincus ocellatus

    NARCIS (Netherlands)

    Isaksson, Caroline; While, Geoffrey M.; Olsson, Mats; Komdeur, Jan; Wapstra, Erik

    Recent research suggests that oxidative stress, via its links to metabolism and senescence, is a key mechanism linking life history traits such as fecundity and growth with survival; however, this has rarely been put under empirical scrutiny within free-living populations. Using a wild population of

  5. The Impact of Stress on the Life History Strategies of African American Adolescents: Cognitions, Genetic Moderation, and the Role of Discrimination

    Science.gov (United States)

    Gibbons, Frederick X.; Roberts, Megan E.; Gerrard, Meg; Li, Zhigang; Beach, Steven R. H.; Simons, Ronald L.; Weng, Chih-Yuan; Philibert, Robert A.

    2012-01-01

    The impact of 3 different sources of stress--environmental, familial (e.g., low parental investment), and interpersonal (i.e., racial discrimination)--on the life history strategies (LHS) and associated cognitions of African American adolescents were examined over an 11-year period (5 waves, from age 10.5 to 21.5). Analyses indicated that each one…

  6. A Growth Curve Analysis of the Course of Dysthymic Disorder: The Effects of Chronic Stress and Moderation by Adverse Parent-Child Relationships and Family History

    Science.gov (United States)

    Dougherty, Lea R.; Klein, Daniel N.; Davila, Joanne

    2004-01-01

    Using mixed effects models, the authors examined the effects of chronic stress, adverse parent-child relationships, and family history on the 7.5-year course of dysthymic disorder. Participants included 97 outpatients with early-onset dysthymia who were assessed with semistructured interviews at baseline and 3 additional times at 30-month…

  7. Calcium affecting protein expression in longan under simulated acid rain stress.

    Science.gov (United States)

    Pan, Tengfei; Li, Yongyu; Ma, Cuilan; Qiu, Dongliang

    2015-08-01

    Longan (Dimocarpus longana Lour. cv. Wulongling) of uniform one-aged seedlings grown in pots were selected to study specific proteins expressed in leaves under simulated acid rain (SiAR) stress and exogenous Ca(2+) regulation. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) results showed that there was a protein band specifically expressed under SiAR of pH 2.5 stress for 15 days with its molecular weight of about 23 kD. A 17 kD protein band specifically expressed after SiAR stress 5 days. Compared with pH 2.5, the pH 3.5 of SiAR made a less influence to protein expression. Two-dimensional electrophoresis (2-DE) results showed that six new specific proteins including C4 (20.2 kD pI 6.0), F (24 kD pI 6.35), B3 (22.3 kD pI 6.35), B4 (23.5 kD pI 6.5), C5 (21.8 kD pI 5.6), and C6 (20.2 kD pI 5.6) specifically expressed. C4 always expressed during SiAR stress. F expressed under the stress of pH 2.5 for 15 days and expressed in all pH SiAR stress for 20 days. The expression of proteins including B3, C5, and C6 was related to pH value and stress intensity of SiAR. The expression of B4 resulted from synergistic effects of SiAR and Ca. The expression of G1 (Mr 19.3 kD, pI 4.5), G2 (Mr 17.8 kD, pI 4.65), G3 (Mr 16.6 kD, pI 4.6), and G4 (Mr 14.7 kD, pI 4.4) enhanced under the treatment of 5 mM ethylene glycol tetraacetic acid (EGTA) and 2 mM chlorpromazine (CPZ). These proteins showed antagonistic effects and might be relative to the Ca-calmodulin (Ca-CaM) system of longan in response to SiAR stress.

  8. Tough Adults, Frail Babies: An Analysis of Stress Sensitivity across Early Life-History Stages of Widely Introduced Marine Invertebrates

    Science.gov (United States)

    Pineda, M. Carmen; McQuaid, Christopher D.; Turon, Xavier; López-Legentil, Susanna; Ordóñez, Víctor; Rius, Marc

    2012-01-01

    All ontogenetic stages of a life cycle are exposed to environmental conditions so that population persistence depends on the performance of both adults and offspring. Most studies analysing the influence of abiotic conditions on species performance have focussed on adults, while studies covering early life-history stages remain rare. We investigated the responses of early stages of two widely introduced ascidians, Styela plicata and Microcosmus squamiger, to different abiotic conditions. Stressors mimicked conditions in the habitats where both species can be found in their distributional ranges and responses were related to the selection potential of their populations by analysing their genetic diversity. Four developmental stages (egg fertilisation, larval development, settlement, metamorphosis) were studied after exposure to high temperature (30°C), low salinities (26 and 22‰) and high copper concentrations (25, 50 and 100 µg/L). Although most stressors effectively led to failure of complete development (fertilisation through metamorphosis), fertilisation and larval development were the most sensitive stages. All the studied stressors affected the development of both species, though responses differed with stage and stressor. S. plicata was overall more resistant to copper, and some stages of M. squamiger to low salinities. No relationship was found between parental genetic composition and responses to stressors. We conclude that successful development can be prevented at several life-history stages, and therefore, it is essential to consider multiple stages when assessing species' abilities to tolerate stress. Moreover, we found that early development of these species cannot be completed under conditions prevailing where adults live. These populations must therefore recruit from elsewhere or reproduce during temporal windows of more benign conditions. Alternatively, novel strategies or behaviours that increase overall reproductive success might be

  9. Tough adults, frail babies: an analysis of stress sensitivity across early life-history stages of widely introduced marine invertebrates.

    Directory of Open Access Journals (Sweden)

    M Carmen Pineda

    Full Text Available All ontogenetic stages of a life cycle are exposed to environmental conditions so that population persistence depends on the performance of both adults and offspring. Most studies analysing the influence of abiotic conditions on species performance have focussed on adults, while studies covering early life-history stages remain rare. We investigated the responses of early stages of two widely introduced ascidians, Styela plicata and Microcosmus squamiger, to different abiotic conditions. Stressors mimicked conditions in the habitats where both species can be found in their distributional ranges and responses were related to the selection potential of their populations by analysing their genetic diversity. Four developmental stages (egg fertilisation, larval development, settlement, metamorphosis were studied after exposure to high temperature (30°C, low salinities (26 and 22‰ and high copper concentrations (25, 50 and 100 µg/L. Although most stressors effectively led to failure of complete development (fertilisation through metamorphosis, fertilisation and larval development were the most sensitive stages. All the studied stressors affected the development of both species, though responses differed with stage and stressor. S. plicata was overall more resistant to copper, and some stages of M. squamiger to low salinities. No relationship was found between parental genetic composition and responses to stressors. We conclude that successful development can be prevented at several life-history stages, and therefore, it is essential to consider multiple stages when assessing species' abilities to tolerate stress. Moreover, we found that early development of these species cannot be completed under conditions prevailing where adults live. These populations must therefore recruit from elsewhere or reproduce during temporal windows of more benign conditions. Alternatively, novel strategies or behaviours that increase overall reproductive success

  10. Acute stress in residents playing different roles during emergency simulations: a preliminary study.

    Science.gov (United States)

    Dias, Roger Daglius; Scalabrini-Neto, Augusto

    2017-06-19

    To investigate acute stress response in residents playing nurse and physician roles during emergency simulations. Sixteen second-year internal medicine residents participated in teams of four (two playing physician roles and two playing nurse roles). Stress markers were assessed in 24 simulations at baseline (T1) and immediately after the scenario (T2), using heart rate, systolic and diastolic blood pressure, salivary α-amylase, salivary cortisol and salivary interleukin-1β. The State-Trait Anxiety Inventory was applied at T2. Continuous data were summarized for the median (1st-3rd interquartile ranges), and the Mann-Whitney U Test was used to compare the groups. The percent variations of the stress markers in the physician and nurse roles, respectively, were the following: heart rate: 70.5% (46.0-136.5) versus 53.0% (29.5-117.0), U=89.00, p=0.35; systolic blood pressure: 3.0% (0.0-10.0) versus 2.0% (-2.0-9.0), U=59.50, p=0.46; diastolic blood pressure: 5.5% (0.0-13.5) versus 0.0% (0.0-11.5), U=91.50, p=0.27; α-amylase: -5.35% (-62.70-73.90) versus 42.3% (12.4-133.8), U=23.00, p=0.08; cortisol: 35.3% (22.2-83.5) versus 42.3% (12.4-133.8), U=64.00, p=0.08); and interleukin-1β: 54.4% (21.9-109.3) versus 112.55% (29.7-263.3), U= 24.00, p=0.277. For the physician and nurse roles, respectively, the average heart rate was 101.5 (92.0-104.0) versus 91.0 (83.0-99.5) beats per minute, U=96.50, p=0.160; and the state anxiety inventory score was 44.0 (40.0-50.0) versus 42.0 (37.50-48.0) points, U= 89.50, p=0.319. Different roles during emergency simulations evoked similar participants' engagement, as indicated by acute stress levels. Role-play strategies can provide high psychological fidelity for simulation-based training, and these results reinforce the potential of role-play methodologies in medical education.

  11. SCARF-4, Nonlinear Stresses in Pressure Vessel Liner with Plastic Behaviour Simulation

    International Nuclear Information System (INIS)

    Chadwick, A.

    1976-01-01

    1 - Nature of physical problem solved: Calculates non-linear stresses in a pressure vessel liner, simulating plastic behaviour on both panels and shear connectors. 2 - Method of solution: Iterations on the relevant formulae to obtain values of forces and deflections, adding a displacement factor when yielding has occurred. 3 - Restrictions on the complexity of the problem: It is assumed that the left-hand end-load will stay constant throughout each loading cycle. Number of panels must be less than or equal to 62

  12. Experimental and CFD Simulation Studies of Wall Shear Stress for Different Impeller Configurations and MBR Activated Sludge

    DEFF Research Database (Denmark)

    Ratkovich, Nicolas Rios; Chan, C.C.V.; Bentzen, Thomas Ruby

    2012-01-01

    in an MBR. Nevertheless, proper experimental validation is required to validate CFD simulation. In this work experimental measurements of shear stress induced by impellers at a membrane surface were made with an electrochemical approach and the results were used to validate CFD simulations. As good results...... appealing for full-scale applications. It has been widely demonstrated that the filtration performances in MBRs can be improved by understanding the shear stress over the membrane surface. Modern tools such as Computational Fluid Dynamics (CFD) can be used to diagnose and understand the shear stress...

  13. Randomized controlled trial of multidisciplinary team stress and performance in immersive simulation for management of infant in shock: study protocol.

    Science.gov (United States)

    Ghazali, Daniel Aiham; Ragot, Stéphanie; Breque, Cyril; Guechi, Youcef; Boureau-Voultoury, Amélie; Petitpas, Franck; Oriot, Denis

    2016-03-25

    Human error and system failures continue to play a substantial role in adverse outcomes in healthcare. Simulation improves management of patients in critical condition, especially if it is undertaken by a multidisciplinary team. It covers technical skills (technical and therapeutic procedures) and non-technical skills, known as Crisis Resource Management. The relationship between stress and performance is theoretically described by the Yerkes-Dodson law as an inverted U-shaped curve. Performance is very low for a low level of stress and increases with an increased level of stress, up to a point, after which performance decreases and becomes severely impaired. The objectives of this randomized trial are to study the effect of stress on performance and the effect of repeated simulation sessions on performance and stress. This study is a single-center, investigator-initiated randomized controlled trial including 48 participants distributed in 12 multidisciplinary teams. Each team is made up of 4 persons: an emergency physician, a resident, a nurse, and an ambulance driver who usually constitute a French Emergency Medical Service team. Six multidisciplinary teams are planning to undergo 9 simulation sessions over 1 year (experimental group), and 6 multidisciplinary teams are planning to undergo 3 simulation sessions over 1 year (control group). Evidence of the existence of stress will be assessed according to 3 criteria: biological, electrophysiological, and psychological stress. The impact of stress on overall team performance, technical procedure and teamwork will be evaluated. Participant self-assessment of the perceived impact of simulations on clinical practice will be collected. Detection of post-traumatic stress disorder will be performed by self-assessment questionnaire on the 7(th) day and after 1 month. We will concomitantly evaluate technical and non-technical performance, and the impact of stress on both. This is the first randomized trial studying

  14. Casting and stress-strain simulations of a cast ductile iron component using microstructure based mechanical behavior

    International Nuclear Information System (INIS)

    Olofsson, Jakob; Svensson, Ingvar L

    2012-01-01

    The industrial demand for increased component performance with concurrent reductions in component weight, development times and verifications using physical prototypes drives the need to use the full potential of casting and Finite Element Method (FEM) simulations to correctly predict the mechanical behavior of cast components in service. The mechanical behavior of the component is determined by the casting process, and factors as component geometry and casting process parameters are known to affect solidification and microstructure formation throughout the component and cause local variations in mechanical behavior as well as residual stresses. Though residual stresses are known to be an important factor in the mechanical behavior of the component, the importance of local mechanical behavior is not well established and the material is typically considered homogeneous throughout the component. This paper deals with the influence of solidification and solid state transformation on microstructure formation and the effect of local microstructure variations on the mechanical behavior of the cast component in service. The current work aims to investigate the coupling between simulation of solidification, microstructure and local variations in mechanical behavior and stress-strain simulation. This is done by performing several simulations of a ductile iron component using a recently developed simulation strategy, a closed chain of simulations for cast components, able to predict and describe the local variations in not only elastic but also plastic behavior throughout the component by using microstructural parameters determined by simulations of microstructural evolution in the component during the casting process. In addition the residual stresses are considered. The results show that the FEM simulation results are significantly affected by including microstructure based mechanical behavior. When the applied load is low and the component is subjected to stress levels

  15. RHAPSODY. I. STRUCTURAL PROPERTIES AND FORMATION HISTORY FROM A STATISTICAL SAMPLE OF RE-SIMULATED CLUSTER-SIZE HALOS

    International Nuclear Information System (INIS)

    Wu, Hao-Yi; Hahn, Oliver; Wechsler, Risa H.; Mao, Yao-Yuan; Behroozi, Peter S.

    2013-01-01

    We present the first results from the RHAPSODY cluster re-simulation project: a sample of 96 'zoom-in' simulations of dark matter halos of 10 14.8±0.05 h –1 M ☉ , selected from a 1 h –3 Gpc 3 volume. This simulation suite is the first to resolve this many halos with ∼5 × 10 6 particles per halo in the cluster mass regime, allowing us to statistically characterize the distribution of and correlation between halo properties at fixed mass. We focus on the properties of the main halos and how they are affected by formation history, which we track back to z = 12, over five decades in mass. We give particular attention to the impact of the formation history on the density profiles of the halos. We find that the deviations from the Navarro-Frenk-White (NFW) model and the Einasto model depend on formation time. Late-forming halos tend to have considerable deviations from both models, partly due to the presence of massive subhalos, while early-forming halos deviate less but still significantly from the NFW model and are better described by the Einasto model. We find that the halo shapes depend only moderately on formation time. Departure from spherical symmetry impacts the density profiles through the anisotropic distribution of massive subhalos. Further evidence of the impact of subhalos is provided by analyzing the phase-space structure. A detailed analysis of the properties of the subhalo population in RHAPSODY is presented in a companion paper.

  16. First-Principles and Thermodynamic Simulation of Elastic Stress Effect on Energy of Hydrogen Dissolution in Alpha Iron

    Science.gov (United States)

    Rakitin, M. S.; Mirzoev, A. A.; Mirzaev, D. A.

    2018-04-01

    Mobile hydrogen, when dissolving in metals, redistributes due to the density gradients and elastic stresses, and enables destruction processes or phase transformations in local volumes of a solvent metal. It is rather important in solid state physics to investigate these interactions. The first-principle calculations performed in terms of the density functional theory, are used for thermodynamic simulation of the elastic stress effect on the energy of hydrogen dissolution in α-Fe crystal lattice. The paper presents investigations of the total energy of Fe-H system depending on the lattice parameter. As a result, the relation is obtained between the hydrogen dissolution energy and stress. A good agreement is shown between the existing data and simulation results. The extended equation is suggested for the chemical potential of hydrogen atom in iron within the local stress field. Two parameters affecting the hydrogen distribution are compared, namely local stress and phase transformations.

  17. Simulation of Distortion and Residual Stress Development During Heat Treatment of Steel Castings

    Energy Technology Data Exchange (ETDEWEB)

    Beckermann, Christoph; Carlson, Kent

    2011-07-22

    of the Navy-C ring (a classical test shape for heat treatment experiments) for several carbon and low alloy steels in order to generate data necessary to validate the code. The predicted distortions were in reasonable agreement with the experimentally measured values. However, the final distortions in the castings were small, making it difficult to determine how accurate the predictions truly are. It is recommended that further validation of the software be performed with the aid of additional experiments with large production steel castings that experience significant heat treatment distortions. It is apparent from this research that the mechanical properties of the bonded sand used for cores and sand molds are key in producing accurate stress simulation results. Because of this, experiments were performed to determine the temperature-dependent elastic modulus of a resin-bonded sand commonly utilized in the steel casting industry. The elastic modulus was seen to vary significantly with heating and cooling rates. Also, the retained room temperature elastic modulus after heating was seen to degrade significantly when the sand was heated above 125°C. The elastic modulus curves developed in this work can readily be utilized in casting simulation software. Additional experiments with higher heating rates are recommended to determine the behavior of the elastic modulus in the sand close to the mold-metal interface. The commercial heat treatment residual stress and distortion code, once fully validated, is expected to result in an estimated energy savings of 2.15 trillion BTU's/year. Along with these energy savings, reduction of scrap and improvement in casting yield will result in a reduction of the environmental emissions associated with the melting and pouring of the metal which will be saved as a result of this technology.

  18. Simulating extreme environments: Ergonomic evaluation of Chinese pilot performance and heat stress tolerance.

    Science.gov (United States)

    Li, Jing; Tian, Yinsheng; Ding, Li; Zou, Huijuan; Ren, Zhaosheng; Shi, Liyong; Feathers, David; Wang, Ning

    2015-06-05

    High-temperatures in the cockpit environment can adversely influence pilot behavior and performance. To investigate the impact of high thermal environments on Chinese pilot performance in a simulated cockpit environment. Ten subjects volunteered to participate in the tests under 40°C and 45°C high-temperature simulations in an environmentally controlled chamber. Measures such as grip strength, perception, dexterity, somatic sense reaction, and analytical reasoning were taken. The results were compared to the Combined Index of Heat Stress (CIHS). CIHS exceeded the heat stress safety limit after 45 min under 40°C, grip strength decreased by 12% and somatic perception became 2.89 times larger than the initial value. In the case of 45°C, CIHS exceeded the safety limit after only 20 min, while the grip strength decreased just by 3.2% and somatic perception increased to 4.36 times larger than the initial value. Reaction and finger dexterity were not statistically different from baseline measurements, but the error rate of analytical reasoning test rose remarkably. Somatic perception was the most sensitive index to high-temperature, followed by grip strength. Results of this paper may help to improve environmental control design of new fighter cockpit and for pilot physiology and cockpit environment ergonomics research for Chinese pilots.

  19. The Ecology of Stress: linking life-history traits with physiological control mechanisms in free-living guanacos.

    Science.gov (United States)

    Ovejero Aguilar, Ramiro J A; Jahn, Graciela A; Soto-Gamboa, Mauricio; Novaro, Andrés J; Carmanchahi, Pablo

    2016-01-01

    Providing the context for the evolution of life-history traits, habitat features constrain successful ecological and physiological strategies. In vertebrates, a key response to life's challenges is the activation of the Stress (HPA) and Gonadal (HPG) axes. Much of the interest in stress ecology is motivated by the desire to understand the physiological mechanisms in which the environment affects fitness. As reported in the literature, several intrinsic and extrinsic factors affect variability in hormone levels. In both social and non-social animals, the frequency and type of interaction with conspecifics, as well as the status in social species, can affect HPA axis activity, resulting in changes in the reproductive success of animals. We predicted that a social environment can affect both guanaco axes by increasing the secretion of testosterone (T) and Glucocorticoid (GCs) in response to individual social interactions and the energetic demands of breeding. Assuming that prolonged elevated levels of GCs over time can be harmful to individuals, it is predicted that the HPA axis suppresses the HPG axis and causes T levels to decrease, as GCs increase. All of the data for individuals were collected by non-invasive methods (fecal samples) to address hormonal activities. This is a novel approach in physiological ecology because feces are easily obtained through non-invasive sampling in animal populations. As expected, there was a marked adrenal ( p -value = .3.4e-12) and gonadal ( p -value = 0.002656) response due to seasonal variation in Lama guanicoe . No significant differences were found in fecal GCs metabolites between males/females*season for the entire study period ( p -value = 0.2839). Despite the seasonal activity variation in the hormonal profiles, our results show a positive correlation ( p -value = 1.952e-11, COR = 0.50) between the adrenal and gonadal system. The marked endocrine ( r 2  = 0.806) and gonad ( r 2  = 0.7231) response due to seasonal

  20. The Ecology of Stress: linking life-history traits with physiological control mechanisms in free-living guanacos

    Directory of Open Access Journals (Sweden)

    Ramiro J.A. Ovejero Aguilar

    2016-11-01

    Full Text Available Background Providing the context for the evolution of life-history traits, habitat features constrain successful ecological and physiological strategies. In vertebrates, a key response to life’s challenges is the activation of the Stress (HPA and Gonadal (HPG axes. Much of the interest in stress ecology is motivated by the desire to understand the physiological mechanisms in which the environment affects fitness. As reported in the literature, several intrinsic and extrinsic factors affect variability in hormone levels. In both social and non-social animals, the frequency and type of interaction with conspecifics, as well as the status in social species, can affect HPA axis activity, resulting in changes in the reproductive success of animals. We predicted that a social environment can affect both guanaco axes by increasing the secretion of testosterone (T and Glucocorticoid (GCs in response to individual social interactions and the energetic demands of breeding. Assuming that prolonged elevated levels of GCs over time can be harmful to individuals, it is predicted that the HPA axis suppresses the HPG axis and causes T levels to decrease, as GCs increase. Methods All of the data for individuals were collected by non-invasive methods (fecal samples to address hormonal activities. This is a novel approach in physiological ecology because feces are easily obtained through non-invasive sampling in animal populations. Results As expected, there was a marked adrenal (p-value = .3.4e−12 and gonadal (p-value = 0.002656 response due to seasonal variation in Lama guanicoe. No significant differences were found in fecal GCs metabolites between males/females*season for the entire study period (p-value = 0.2839. Despite the seasonal activity variation in the hormonal profiles, our results show a positive correlation (p-value = 1.952e−11, COR = 0.50 between the adrenal and gonadal system. The marked endocrine (r2 = 0.806 and gonad (r2 = 0

  1. Characteristics of the Foot Static Alignment and the Plantar Pressure Associated with Fifth Metatarsal Stress Fracture History in Male Soccer Players: a Case-Control Study.

    Science.gov (United States)

    Matsuda, Sho; Fukubayashi, Toru; Hirose, Norikazu

    2017-12-01

    There is a large amount of information regarding risk factors for fifth metatarsal stress fractures; however, there are few studies involving large numbers of subjects. This study aimed to compare the static foot alignment and distribution of foot pressure of athletes with and without a history of fifth metatarsal stress fractures. The study participants comprised 335 collegiate male soccer players. Twenty-nine with a history of fifth metatarsal stress fractures were in the fracture group and 306 were in the control group (with subgroups as follows: 30 in the fracture foot group and 28 in the non-fracture group). We measured the foot length, arch height, weight-bearing leg-heel alignment, non-weight-bearing leg-heel alignment, forefoot angle relative to the rearfoot, forefoot angle relative to the horizontal axis, and foot pressure. The non-weight-bearing leg-heel alignment was significantly smaller and the forefoot angle relative to the rearfoot was significantly greater in the fracture foot group than in the control foot group (P = 0.049 and P = 0.038, respectively). With regard to plantar pressure, there were no significant differences among the groups. Midfield players had significantly higher rates of fifth metatarsal stress fracture in their histories, whereas defenders had significantly lower rates (chi-square = 13.2, P stress fractures according to the type of foot (kicking foot vs. pivoting foot) or the severity of ankle sprain. Playing the midfield position and having an everted rearfoot and inverted forefoot alignment were associated with fifth metatarsal stress fractures. This information may be helpful for preventing fifth metatarsal stress fracture recurrence. More detailed load evaluations and a prospective study are needed in the future.

  2. Effects of cold plasma treatment on alfalfa seed growth under simulated drought stress

    Science.gov (United States)

    Jinkui, FENG; Decheng, WANG; Changyong, SHAO; Lili, ZHANG; Xin, TANG

    2018-03-01

    The effect of different cold plasma treatments on the germination and seedling growth of alfalfa (Medicago sativa L.) seeds under simulated drought stress conditions was investigated. Polyethyleneglycol-6000 (PEG 6000)with the mass fraction of 0% (purified water), 5%, 10%, and 15% were applied to simulate the drought environment. The alfalfa seeds were treated with 15 different power levels ranged between 0-280 W for 15 s. The germination potential, germination rate, germination index, seedling root length, seedling height, and vigor index were investigated. Results indicated significant differences between treated with proper power and untreated alfalfa seeds. With the increase of treatment power, these indexes mentioned above almost presented bimodal curves. Under the different mass fractions of PEG 6000, results showed that the lower power led to increased germination, and the seedlings presented good adaptability to different drought conditions. Meanwhile, higher power levels resulted in a decreased germination rate. Seeds treated with 40 W resulted in higher germination potential, germination rate, seedling height, root length, and vigor index. Vigor indexes of the treated seeds under different PEG 6000 stresses increased by 38.68%, 43.91%, 74.34%, and 39.20% respectively compared to CK0-0, CK5-0, CK10-0, and CK15-0 (the control sample under 0%, 5%, 10%, and 15% PEG 6000). Therefore, 40 W was regarded as the best treatment in this research. Although the trend indexes of alfalfa seeds treated with the same power were statistically the same under different PEG 6000 stresses, the cold plasma treatment had a significant effect on the adaptability of alfalfa seeds in different drought environments. Thus, this kind of treatment is worth implementing to promote seed growth under drought situations.

  3. Experimental and numerical simulation of the behaviour of building components under alternating thermal stresses

    International Nuclear Information System (INIS)

    Stegmeyer, R.

    1985-01-01

    This publication is intended to clear up to what extent the results from laboratory experiments on components thermally stressed on several axes can be transferred. The turbine shaft was used for this purpose and was geometrically simulated on a reduced scale by means of a test body (model). The deviations of shape due to the design, such as shaft shoulders, grooves etc. were simulated by notches and the position of the expected crack was defined in this way. A 1% Cr steel was selected as the material, for which many results of experiments on laboratory samples were available. The turbine shaft steel 28 CrMoNiV 4 9 was used. With a specially designed experimental rig, it was possible to expose the model to a changing temperature stress, as it occurs during starting and shutdown of turbines. Different notch radii made it possible to vary the strains at the bottom of the notches due to temperature gradients. After developing special travel transducers, the strain behaviour of the sample could be determined relative to the temperature. The crack characteristics obtained were compared with the characteristics of single axis experiments at constant temperature. Fractographic examination of fatigue cracks made it possible to determine the growth of cracks per load change from the existing vibration strip (da/dN). The stress intensity factor was derived from a modified theoretical expression and the characteristic designed from it was compared with crack growth measurements on CT samples. Accompanying numerical and empirical processes (according to Neuber) were examined by direct comparison of the measured strains with the calculated or estimated strains. Finally, regulations such as the ASME code and TRD 301 were applied to the model experiments and evaluated. (orig.) [de

  4. Numerical simulation of CTE mismatch and thermal-structural stresses in the design of interconnects

    Science.gov (United States)

    Peter, Geoffrey John M.

    With the ever-increasing chip complexity, interconnects have to be designed to meet the new challenges. Advances in optical lithography have made chip feature sizes available today at 70 nm dimensions. With advances in Extreme Ultraviolet Lithography, X-ray Lithography, and Ion Projection Lithography it is expected that the line width will further decrease to 20 nm or less. With the decrease in feature size, the number of active devices on the chip increases. With higher levels of circuit integration, the challenge is to dissipate the increased heat flux from the chip surface area. Thermal management considerations include coefficient of thermal expansion (CTE) matching to prevent failure between the chip and the board. This in turn calls for improved system performance and reliability of the electronic structural systems. Experience has shown that in most electronic systems, failures are mostly due to CTE mismatch between the chip, board, and the solder joint (solder interconnect). The resulting high thermal-structural stress and strain due to CTE mismatch produces cracks in the solder joints with eventual failure of the electronic component. In order to reduce the thermal stress between the chip, board, and the solder joint, this dissertation examines the effect of inserting wire bundle (wire interconnect) between the chip and the board. The flexibility of the wires or fibers would reduce the stress at the rigid joints. Numerical simulations of two, and three-dimensional models of the solder and wire interconnects are examined. The numerical simulation is linear in nature and is based on linear isotropic material properties. The effect of different wire material properties is examined. The effect of varying the wire diameter is studied by changing the wire diameter. A major cause of electronic equipment failure is due to fatigue failure caused by thermal cycling, and vibrations. A two-dimensional modal and harmonic analysis was simulated for the wire interconnect

  5. Neuroendocrine and cardiovascular parameters during simulation of stress-induced rise in circulating oxytocin in the rat.

    Science.gov (United States)

    Ondrejcakova, M; Bakos, J; Garafova, A; Kovacs, L; Kvetnansky, R; Jezova, D

    2010-07-01

    Physiological functions of oxytocin released during stress are not well understood. We have (1) investigated the release of oxytocin during chronic stress using two long-term stress models and (2) simulated stress-induced oxytocin secretion by chronic treatment with oxytocin via osmotic minipumps. Plasma oxytocin levels were significantly elevated in rats subjected to acute immobilization stress for 120 min, to repeated immobilization for 7 days and to combined chronic cold stress exposure for 28 days with 7 days immobilization. To simulate elevation of oxytocin during chronic stress, rats were implanted with osmotic minipumps subcutaneously and treated with oxytocin (3.6 microg/100 g body weight/day) or vehicle for 2 weeks. Chronic subcutaneous oxytocin infusion led to an increase in plasma oxytocin, adrenocorticotropic hormone, corticosterone, adrenal weights and heart/body weight ratio. Oxytocin treatment had no effect on the incorporation of 5-bromo-2-deoxyuridine into DNA in the heart ventricle. Mean arterial pressure response to intravenous phenylephrine was reduced in oxytocin-treated animals. Decrease in adrenal tyrosin hydroxylase mRNA following oxytocin treatment was not statistically significant. Oxytocin treatment failed to modify food intake and slightly increased water consumption. These data provide evidence on increased concentrations of oxytocin during chronic stress. It is possible that the role of oxytocin released during stress is in modulating hypothalamic-pituitary-adrenocortical axis and selected sympathetic functions.

  6. Predicting Attitudes toward Press- and Speech Freedom across the U.S.A.: A Test of Climato-Economic, Parasite Stress, and Life History Theories.

    Science.gov (United States)

    Zhang, Jinguang; Reid, Scott A; Xu, Jing

    2015-01-01

    National surveys reveal notable individual differences in U.S. citizens' attitudes toward freedom of expression, including freedom of the press and speech. Recent theoretical developments and empirical findings suggest that ecological factors impact censorship attitudes in addition to individual difference variables (e.g., education, conservatism), but no research has compared the explanatory power of prominent ecological theories. This study tested climato-economic, parasite stress, and life history theories using four measures of attitudes toward censoring the press and offensive speech obtained from two national surveys in the U.S.A. Neither climate demands nor its interaction with state wealth--two key variables for climato-economic theory--predicted any of the four outcome measures. Interstate parasite stress significantly predicted two, with a marginally significant effect on the third, but the effects became non-significant when the analyses were stratified for race (as a control for extrinsic risks). Teenage birth rates (a proxy of human life history) significantly predicted attitudes toward press freedom during wartime, but the effect was the opposite of what life history theory predicted. While none of the three theories provided a fully successful explanation of individual differences in attitudes toward freedom of expression, parasite stress and life history theories do show potentials. Future research should continue examining the impact of these ecological factors on human psychology by further specifying the mechanisms and developing better measures for those theories.

  7. Predicting Attitudes toward Press- and Speech Freedom across the U.S.A.: A Test of Climato-Economic, Parasite Stress, and Life History Theories.

    Directory of Open Access Journals (Sweden)

    Jinguang Zhang

    Full Text Available National surveys reveal notable individual differences in U.S. citizens' attitudes toward freedom of expression, including freedom of the press and speech. Recent theoretical developments and empirical findings suggest that ecological factors impact censorship attitudes in addition to individual difference variables (e.g., education, conservatism, but no research has compared the explanatory power of prominent ecological theories. This study tested climato-economic, parasite stress, and life history theories using four measures of attitudes toward censoring the press and offensive speech obtained from two national surveys in the U.S.A. Neither climate demands nor its interaction with state wealth--two key variables for climato-economic theory--predicted any of the four outcome measures. Interstate parasite stress significantly predicted two, with a marginally significant effect on the third, but the effects became non-significant when the analyses were stratified for race (as a control for extrinsic risks. Teenage birth rates (a proxy of human life history significantly predicted attitudes toward press freedom during wartime, but the effect was the opposite of what life history theory predicted. While none of the three theories provided a fully successful explanation of individual differences in attitudes toward freedom of expression, parasite stress and life history theories do show potentials. Future research should continue examining the impact of these ecological factors on human psychology by further specifying the mechanisms and developing better measures for those theories.

  8. Predicting Attitudes toward Press- and Speech Freedom across the U.S.A.: A Test of Climato-Economic, Parasite Stress, and Life History Theories

    Science.gov (United States)

    Zhang, Jinguang; Reid, Scott A.; Xu, Jing

    2015-01-01

    National surveys reveal notable individual differences in U.S. citizens’ attitudes toward freedom of expression, including freedom of the press and speech. Recent theoretical developments and empirical findings suggest that ecological factors impact censorship attitudes in addition to individual difference variables (e.g., education, conservatism), but no research has compared the explanatory power of prominent ecological theories. This study tested climato-economic, parasite stress, and life history theories using four measures of attitudes toward censoring the press and offensive speech obtained from two national surveys in the U.S.A. Neither climate demands nor its interaction with state wealth—two key variables for climato-economic theory—predicted any of the four outcome measures. Interstate parasite stress significantly predicted two, with a marginally significant effect on the third, but the effects became non-significant when the analyses were stratified for race (as a control for extrinsic risks). Teenage birth rates (a proxy of human life history) significantly predicted attitudes toward press freedom during wartime, but the effect was the opposite of what life history theory predicted. While none of the three theories provided a fully successful explanation of individual differences in attitudes toward freedom of expression, parasite stress and life history theories do show potentials. Future research should continue examining the impact of these ecological factors on human psychology by further specifying the mechanisms and developing better measures for those theories. PMID:26030736

  9. Toxicity assessment of simulated urban runoff containing polycyclic musks and cadmium in Carassius auratus using oxidative stress biomarkers

    International Nuclear Information System (INIS)

    Chen Fang; Gao Jie; Zhou Qixing

    2012-01-01

    The objective of this study was to assess potential toxic effects of simulated urban runoff on Carassius auratus using oxidative stress biomarkers. The activity of antioxidant enzymes including superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT), and the content of malondialdehyde (MDA) in the liver of C. auratus were analyzed after a 7-, 14- and 21-day exposure to simulated urban runoff containing galaxolide (HHCB) and cadmium (Cd). The results showed that the activity of antioxidant enzymes and the content of MDA increased significantly exposed to the simulated urban runoff containing HHCB alone or mixture of HHCB and Cd. The activity of the investigated enzymes and the content of MDA then returned to the blank level over a longer period of exposure. The oxidative stress could be obviously caused in the liver of C. auratus under the experimental conditions. This could provide useful information for toxic risk assessment of urban runoff. - Highlights: ► We assessed potential toxicity of urban runoff containing HHCB and Cd. ► Exposure of simulated urban runoff can caused oxidative stress in C. auratus liver. ► SOD and CAT are more sensitive than POD and more suitable for indicating the toxicity of urban runoff. ► The present study using oxidative stress biomarkers could provide useful information for toxic risk assessment of urban runoff. - Simulated urban runoff containing HHCB and Cd could cause oxidative stress on the liver of Carassius auratus, which could provide useful information for toxic risk assessment of urban runoff.

  10. Stress-related salivary alpha-amylase (sAA) activity in alcohol dependent patients with and without a history of childhood maltreatment.

    Science.gov (United States)

    Muehlhan, Markus; Höcker, Anja; Höfler, Michael; Wiedemann, Klaus; Barnow, Sven; Schäfer, Ingo

    2017-06-01

    Alcohol-dependent (AD) patients with a history of childhood maltreatment (CM) have shown a more severe clinical profile and a higher risk of relapse than those without CM. It was hypothesized that stress responsivity plays an important role in moderating the relationship between CM and AD. Surprisingly, systematic investigations about the stress responsivity in AD patients with CM are rare. This study compared physiological and subjective stress responses in AD patients with and without CM as well as in healthy controls with and without CM. A total of 130 participants performed the Trier Social Stress Test (TSST). Physiological stress reactivity related to the noradrenergic system was assessed by salivary alpha-amylase (sAA) activity. Subjective ratings of anxiety, nervousness, distress, and mood were rated on visual analogue scales. AD patients showed significantly lower stress-related sAA activity than healthy controls (p ≤ 0.024; z ≥ 1.97). A different pattern was found in the subjective ratings. In particular, anticipatory anxiety revealed a clear effect of CM (p ≤ 0.005; z ≥ 2.43) but no difference between AD patients and healthy controls (p > 0.05). After the TSST, distress ratings differed between AD patients with CM and AD patients without CM (p ≤ 0.009; z ≥ 2.61). The discrepancy between physiological responsivity and subjective stress experiences may account for an increased inability to cope with stressful situations, which in turn might explain the enhanced risk of relapse in AD patients with a history of CM during early abstinence.

  11. Tectono-Thermal History Modeling and Reservoir Simulation Study of the Nenana Basin, Central Alaska: Implications for Regional Tectonics and Geologic Carbon Sequestration

    Science.gov (United States)

    Dixit, Nilesh C.

    basin. Coals have significant capacity for sequestering anthropogenic CO 2 emissions and offer the benefit of enhanced coal bed methane production that can offset the costs associated with the sequestration processes. In order to do a preliminary assessment of the CO2 sequestration and coal bed methane production potential of the Nenana basin, I used available surface and subsurface data to build and simulate a reservoir model of subbituminous Healy Creek Formation coals. The petroleum exploration data were also used to estimate the state of subsurface stresses that are critical in modeling the orientation, distribution and flow behavior of natural coal fractures in the basin. The effect of uncertainties within major coal parameters on the total CO2 sequestration and coal bed methane capacity estimates were evaluated through a series of sensitivity analyses, experimental design methods and fluid flow simulations. Results suggest that the mature, unmineable Healy Creek Formation coals of the Nenana basin can sequester up to 0.41 TCF of CO2 while producing up to 0.36 TCF of CH4 at the end of 44-year forecast. However, these volumes are estimates and they are also sensitive to the well type, pattern and cap rock lithology. I used a similar workflow to evaluate the state of in situ stress in the northeastern North Slope province of Alaska. The results show two distinct stress regimes across the northeastern North Slope. The eastern Barrow Arch exhibits both strike-slip and normal stress regimes. Along the northeastern Brooks Range thrust front, an active thrust-fault regime is present at depths up to 6000 ft but changes to a strike-slip stress regime at depths greater than 6000 ft.

  12. Numerical investigation of thermal and residual stress of sapphire during c-axis vertical Bridgman growth process considering the solidification history effect

    Science.gov (United States)

    Hwang, Ji Hoon; Lee, Young Cheol; Lee, Wook Jin

    2018-01-01

    Sapphire single crystals have been highlighted for epitaxial of gallium nitride films in high-power laser and light emitting diode industries. In this study, the evolution of thermally induced stress in sapphire during the vertical Bridgman crystal growth process was investigated using a finite element model that simplified the real Bridgman process. A vertical Bridgman process of cylindrical sapphire crystal with a diameter of 50 mm was considered for the model. The solidification history effect during the growth was modeled by the quite element technique. The effects of temperature gradient, seeding interface shape and seeding position on the thermal stress during the process were discussed based on the finite element analysis results.

  13. Corticotropin Releasing Factor in the Bed Nucleus of the Stria Terminalis in Socially Defeated and Non-stressed Mice with a History of Chronic Alcohol Intake.

    Science.gov (United States)

    Albrechet-Souza, Lucas; Viola, Thiago W; Grassi-Oliveira, Rodrigo; Miczek, Klaus A; de Almeida, Rosa M M

    2017-01-01

    consumption in both socially defeated and non-stressed mice with a history of chronic intake.

  14. Corticotropin Releasing Factor in the Bed Nucleus of the Stria Terminalis in Socially Defeated and Non-stressed Mice with a History of Chronic Alcohol Intake

    Directory of Open Access Journals (Sweden)

    Lucas Albrechet-Souza

    2017-10-01

    alcohol consumption in both socially defeated and non-stressed mice with a history of chronic intake.

  15. Neoclassical viscous stress tensor for non-linear MHD simulations with XTOR-2F

    International Nuclear Information System (INIS)

    Mellet, N.; Maget, P.; Meshcheriakov, D.; Lütjens, H.

    2013-01-01

    The neoclassical viscous stress tensor is implemented in the non-linear MHD code XTOR-2F (Lütjens and Luciani 2010 J. Comput. Phys. 229 8130–43), allowing consistent bi-fluid simulations of MHD modes, including the metastable branch of neoclassical tearing modes (NTMs) (Carrera et al 1986 Phys. Fluids 29 899–902). Equilibrium flows and bootstrap current from the neoclassical theory are formally recovered in this Chew–Goldberger–Low formulation. The non-linear behaviour of the new model is verified on a test case coming from a Tore Supra non-inductive discharge. A NTM threshold that is larger than with the previous model is obtained. This is due to the fact that the velocity is now part of the bootstrap current and that it differs from the theoretical neoclassical value. (paper)

  16. Stress

    Science.gov (United States)

    ... taking care of an aging parent. With mental stress, the body pumps out hormones to no avail. Neither fighting ... with type 1 diabetes. This difference makes sense. Stress blocks the body from releasing insulin in people with type 2 ...

  17. A meta-analytic review of overgeneral memory: The role of trauma history, mood, and the presence of posttraumatic stress disorder.

    Science.gov (United States)

    Ono, Miyuki; Devilly, Grant J; Shum, David H K

    2016-03-01

    A number of studies suggest that a history of trauma, depression, and posttraumatic stress disorder (PTSD) are associated with autobiographical memory deficits, notably overgeneral memory (OGM). However, whether there are any group differences in the nature and magnitude of OGM has not been evaluated. Thus, a meta-analysis was conducted to quantify group differences in OGM. The effect sizes were pooled from studies examining the effect on OGM from a history of trauma (e.g., childhood sexual abuse), and the presence of PTSD or current depression (e.g., major depressive disorder). Using multiple search engines, 13 trauma studies and 12 depression studies were included in this review. A depression effect was observed on OGM with a large effect size, and was more evident by the lack of specific memories, especially to positive cues. An effect of trauma history on OGM was observed with a medium effect size, and this was most evident by the presence of overgeneral responses to negative cues. The results also suggested an amplified memory deficit in the presence of PTSD. That is, the effect sizes of OGM among individuals with PTSD were very large and relatively equal across different types of OGM. Future studies that directly compare the differences of OGM among 4 samples (i.e., controls, current depression without trauma history, trauma history without depression, and trauma history and depression) would be warranted to verify the current findings. (c) 2016 APA, all rights reserved).

  18. Strength evolution of simulated carbonate-bearing faults: The role of normal stress and slip velocity

    Science.gov (United States)

    Mercuri, Marco; Scuderi, Marco Maria; Tesei, Telemaco; Carminati, Eugenio; Collettini, Cristiano

    2018-04-01

    A great number of earthquakes occur within thick carbonate sequences in the shallow crust. At the same time, carbonate fault rocks exhumed from a depth plasticity). We performed friction experiments on water-saturated simulated carbonate-bearing faults for a wide range of normal stresses (from 5 to 120 MPa) and slip velocities (from 0.3 to 100 μm/s). At high normal stresses (σn > 20 MPa) fault gouges undergo strain-weakening, that is more pronounced at slow slip velocities, and causes a significant reduction of frictional strength, from μ = 0.7 to μ = 0.47. Microstructural analysis show that fault gouge weakening is driven by deformation accommodated by cataclasis and pressure-insensitive deformation processes (pressure solution and granular plasticity) that become more efficient at slow slip velocity. The reduction in frictional strength caused by strain weakening behaviour promoted by the activation of pressure-insensitive deformation might play a significant role in carbonate-bearing faults mechanics.

  19. Projections of rising heat stress over the western Maritime Continent from dynamically downscaled climate simulations

    Science.gov (United States)

    Im, Eun-Soon; Kang, Suchul; Eltahir, Elfatih A. B.

    2018-06-01

    This study assesses the future changes in heat stress in response to different emission scenarios over the western Maritime Continent. To better resolve the region-specific changes and to enhance the performance in simulating extreme events, the MIT Regional Climate Model with a 12-km horizontal resolution is used for the dynamical downscaling of three carefully selected CMIP5 global projections forced by two Representative Concentration Pathway (RCP4.5 and RCP8.5) scenarios. Daily maximum wet-bulb temperature (TWmax), which includes the effect of humidity, is examined to describe heat stress as regulated by future changes in temperature and humidity. An ensemble of projections reveals robust pattern in which a large increase in temperature is accompanied by a reduction in relative humidity but a significant increase in wet-bulb temperature. This increase in TWmax is relatively smaller over flat and coastal regions than that over mountainous region. However, the flat and coastal regions characterized by warm and humid present-day climate will be at risk even under modest increase in TWmax. The regional extent exposed to higher TWmax and the number of days on which TWmax exceeds its threshold value are projected to be much higher in RCP8.5 scenario than those in RCP4.5 scenario, thus highlighting the importance of controlling greenhouse gas emissions to reduce the adverse impacts on human health and heat-related mortality.

  20. Flexural Capability of Patterned Transparent Conductive Substrate by Performing Electrical Measurements and Stress Simulations

    Directory of Open Access Journals (Sweden)

    Chang-Chun Lee

    2016-10-01

    Full Text Available The suitability of stacked thin films for next-generation display technology was analyzed based on their properties and geometrical designs to evaluate the mechanical reliability of transparent conducting thin films utilized in flexural displays. In general, the high bending stress induced by various operation conditions is a major concern regarding the mechanical reliability of indium–tin–oxide (ITO films deposited on polyethylene terephthalate (PET substrates; mechanical reliability is commonly used to estimate the flexibility of displays. However, the pattern effect is rarely investigated to estimate the mechanical reliability of ITO/PET films. Thus, this study examined the flexible content of patterned ITO/PET films with two different line widths by conducting bending tests and sheet resistance measurements. Moreover, a stress–strain simulation enabled by finite element analysis was performed on the patterned ITO/PET to explore the stress impact of stacked film structures under various levels of flexural load. Results show that the design of the ITO/PET film can be applied in developing mechanically reliable flexible electronics.

  1. Life prediction of steam generator tubing due to stress corrosion crack using Monte Carlo Simulation

    International Nuclear Information System (INIS)

    Hu Jun; Liu Fei; Cheng Guangxu; Zhang Zaoxiao

    2011-01-01

    Highlights: → A life prediction model for SG tubing was proposed. → The initial crack length for SCC was determined. → Two failure modes called rupture mode and leak mode were considered. → A probabilistic life prediction code based on Monte Carlo method was developed. - Abstract: The failure of steam generator tubing is one of the main accidents that seriously affects the availability and safety of a nuclear power plant. In order to estimate the probability of the failure, a probabilistic model was established to predict the whole life-span and residual life of steam generator (SG) tubing. The failure investigated was stress corrosion cracking (SCC) after the generation of one through-wall axial crack. Two failure modes called rupture mode and leak mode based on probabilistic fracture mechanics were considered in this proposed model. It took into account the variance in tube geometry and material properties, and the variance in residual stresses and operating conditions, all of which govern the propagations of cracks. The proposed model was numerically calculated by using Monte Carlo Simulation (MCS). The plugging criteria were first verified and then the whole life-span and residual life of the SG tubing were obtained. Finally, important sensitivity analysis was also carried out to identify the most important parameters affecting the life of SG tubing. The results will be useful in developing optimum strategies for life-cycle management of the feedwater system in nuclear power plants.

  2. Flow through internal elastic lamina affects shear stress on smooth muscle cells (3D simulations).

    Science.gov (United States)

    Tada, Shigeru; Tarbell, John M

    2002-02-01

    We describe a three-dimensional numerical simulation of interstitial flow through the medial layer of an artery accounting for the complex entrance condition associated with fenestral pores in the internal elastic lamina (IEL) to investigate the fluid mechanical environment around the smooth muscle cells (SMCs) right beneath the IEL. The IEL was modeled as an impermeable barrier to water flow except for the fenestral pores, which were assumed to be uniformly distributed over the IEL. The medial layer was modeled as a heterogeneous medium composed of a periodic array of cylindrical SMCs embedded in a continuous porous medium representing the interstitial proteoglycan and collagen matrix. Depending on the distance between the IEL bottom surface and the upstream end of the proximal layer of SMCs, the local shear stress on SMCs right beneath the fenestral pore could be more than 10 times higher than that on the cells far removed from the IEL under the conditions that the fenestral pore diameter and area fraction of pores were kept constant at 1.4 microm and 0.05, respectively. Thus these proximal SMCs may experience shear stress levels that are even higher than endothelial cells exposed to normal blood flow (order of 10 dyn/cm(2)). Furthermore, entrance flow through fenestral pores alters considerably the interstitial flow field in the medial layer over a spatial length scale of the order of the fenestral pore diameter. Thus the spatial gradient of shear stress on the most superficial SMC is noticeably higher than computed for endothelial cell surfaces.

  3. Thermal simulation of drift emplacement (TSS): In-situ instrumentation and numerical modeling of stress measurement methods

    International Nuclear Information System (INIS)

    Heusermann, S.

    1988-01-01

    In the course of the planned demonstration test Thermal Simulation of Drift Emplacement (TSS) BGR is carrying out in-situ-measurements of rock stresses, rock deformability and permeability of salt rock and backfill material. The following techniques developed and proved by BGR during the last years are planned to be used in the TSS project: overcoring technique, dilatometer technique, hard inclusion technique, slot-cutting techniques, large-flatjack technique, compensation tests in laboratory, vacuum tests, injection tests, and tracer tests. The purpose of measurements is to determine: the initial stress state; stress gradients around test drifts; stress change caused by mining activities, by creep and stress relaxation and by temperature; the in-situ load-deformation behavior of rock salt; the permeability of rock salt around test drifts; the compaction behavior of backfill material; and the load-deformation behavior of rock salt and borehole grout in laboratory tests

  4. Post-Traumatic Cognition Mediates the Relationship between a History of Sexual Abuse and the Post-Traumatic Stress Symptoms in Sexual Assault Victims.

    Science.gov (United States)

    Shin, Kyoung Min; Chung, Young Ki; Shin, Yee Jin; Kim, Miran; Kim, Nam Hee; Kim, Kyoung Ah; Lee, Hanbyul; Chang, Hyoung Yoon

    2017-10-01

    More than half of all sexual assault victims report experiencing sexual victimization more than once. The aim of this paper was to determine the role post-traumatic cognition plays in the relationship between a history of sexual abuse and post-traumatic stress symptoms in sexual assault victims. The relationship between a history of sexual assault and the severity of post-traumatic stress symptoms was investigated retrospectively using data from a sexual assault crisis center in Korea. Data on psychological symptoms were collected in person at the initial assessment and by telephone 1 month later using the Post-traumatic Cognitions Inventory and the Post-traumatic Stress Disorder Symptoms Scale: Self-report Version. Of 105 women included in the analysis, 10 (9.5%) reported prior sexual abuse and were classified as sexually revictimized. Revictimized women had more post-traumatic negative cognition at initial assessment (t = -2.98; P = 0.004) and more post-traumatic symptoms at 1 month follow-up (t = -2.39; P = 0.019) than singly victimized women. At 1 month follow-up, the severity of post-traumatic stress symptoms had increased in revictimized women but had decreased slightly in singly victimized women. Negative post-traumatic cognition fully mediated the association between a history of sexual abuse and the severity of post-traumatic stress symptoms. Early detection of sexually revictimized women and tailored service and treatment intervention is needed to better serve this group of victims. Interventions targeted at preventing revictimization or post crime victimization may also help victims recover from the trauma and prevent future abuse. © 2017 The Korean Academy of Medical Sciences.

  5. Post-Traumatic Cognition Mediates the Relationship between a History of Sexual Abuse and the Post-Traumatic Stress Symptoms in Sexual Assault Victims

    Science.gov (United States)

    2017-01-01

    More than half of all sexual assault victims report experiencing sexual victimization more than once. The aim of this paper was to determine the role post-traumatic cognition plays in the relationship between a history of sexual abuse and post-traumatic stress symptoms in sexual assault victims. The relationship between a history of sexual assault and the severity of post-traumatic stress symptoms was investigated retrospectively using data from a sexual assault crisis center in Korea. Data on psychological symptoms were collected in person at the initial assessment and by telephone 1 month later using the Post-traumatic Cognitions Inventory and the Post-traumatic Stress Disorder Symptoms Scale: Self-report Version. Of 105 women included in the analysis, 10 (9.5%) reported prior sexual abuse and were classified as sexually revictimized. Revictimized women had more post-traumatic negative cognition at initial assessment (t = −2.98; P = 0.004) and more post-traumatic symptoms at 1 month follow-up (t = −2.39; P = 0.019) than singly victimized women. At 1 month follow-up, the severity of post-traumatic stress symptoms had increased in revictimized women but had decreased slightly in singly victimized women. Negative post-traumatic cognition fully mediated the association between a history of sexual abuse and the severity of post-traumatic stress symptoms. Early detection of sexually revictimized women and tailored service and treatment intervention is needed to better serve this group of victims. Interventions targeted at preventing revictimization or post crime victimization may also help victims recover from the trauma and prevent future abuse. PMID:28875614

  6. 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

  7. Olivine on Vesta as exogenous contaminants brought by impacts: Constraints from modeling Vesta's collisional history and from impact simulations

    Science.gov (United States)

    Turrini, D.; Svetsov, V.; Consolmagno, G.; Sirono, S.; Pirani, S.

    2016-12-01

    The survival of asteroid Vesta during the violent early history of the Solar System is a pivotal constraint on theories of planetary formation. Particularly important from this perspective is the amount of olivine excavated from the vestan mantle by impacts, as this constrains both the interior structure of Vesta and the number of major impacts the asteroid suffered during its life. The NASA Dawn mission revealed that olivine is present on Vesta's surface in limited quantities, concentrated in small patches at a handful of sites not associated with the two large impact basins Rheasilvia and Veneneia. The first detections were interpreted as the result of the excavation of endogenous olivine, even if the depth at which the detected olivine originated was a matter of debate. Later works raised instead the possibility that the olivine had an exogenous origin, based on the geologic and spectral features of the deposits. In this work, we quantitatively explore the proposed scenario of a exogenous origin for the detected vestan olivine to investigate whether its presence on Vesta can be explained as a natural outcome of the collisional history of the asteroid over the last one or more billion years. To perform this study we took advantage of the impact contamination model previously developed to study the origin and amount of dark and hydrated materials observed by Dawn on Vesta, a model we updated by performing dedicated hydrocode impact simulations. We show that the exogenous delivery of olivine by the same impacts that shaped the vestan surface can offer a viable explanation for the currently identified olivine-rich sites without violating the constraint posed by the lack of global olivine signatures on Vesta. Our results indicate that no mantle excavation is in principle required to explain the observations of the Dawn mission and support the idea that the vestan crust could be thicker than indicated by simple geochemical models based on the Howardite

  8. Effects of silicon on Oryza sativa L. seedling roots under simulated acid rain stress.

    Science.gov (United States)

    Ju, Shuming; Yin, Ningning; Wang, Liping; Zhang, Cuiying; Wang, Yukun

    2017-01-01

    Silicon (Si) has an important function in reducing the damage of environmental stress on plants. Acid rain is a serious abiotic stress factor, and Si can alleviate the stress induced by acid rain on plants. Based on these assumptions, we investigated the effects of silicon on the growth, root phenotype, mineral element contents, hydrogen peroxide (H2O2) and antioxidative enzymes of rice (Oryza sativa L.) seedling roots under simulated acid rain (SAR) stress. The results showed that the combined or single effects of Si and/or SAR on rice roots depend on the concentration of Si and the pH of the SAR. The combined or single effects of a low or moderate concentration of Si (1.0 or 2.0 mM) and light SAR (pH 4.0) enhanced the growth of rice roots, and the combined effects were stronger than those of the single treatment. A high concentration of Si (4.0 mM) or severe SAR (pH 2.0) exerted deleterious effects. The incorporation of Si (1.0, 2.0 or 4.0 mM) into SAR with pH 3.0 or 2.0 promoted the rice root growth, decreased the H2O2 content, increased the Si concentration and the superoxide dismutase (SOD), catalase (CAT), peroxidase (POD) and ascorbate peroxidase (APX) activities, maintained the balance of mineral element (K, Ca, Mg, Fe, Zn, and Cu) concentrations in the roots of rice seedlings compared with SAR alone. The alleviatory effects observed with a moderate concentration of Si (2.0 mM) were better than the effects obtained with a low or high concentration of Si (1.0 or 4.0 mM). The observed effects were due to disruptions in the absorption and utilization of mineral nutrients and impacts on the activity of antioxidant enzymes in roots, and this conclusion suggests that the degree of rice root damage caused by acid rain might be attributed to not only acid rain but also the level of Si in the soil.

  9. Effects of silicon on Oryza sativa L. seedling roots under simulated acid rain stress

    Science.gov (United States)

    Wang, Liping; Zhang, Cuiying; Wang, Yukun

    2017-01-01

    Silicon (Si) has an important function in reducing the damage of environmental stress on plants. Acid rain is a serious abiotic stress factor, and Si can alleviate the stress induced by acid rain on plants. Based on these assumptions, we investigated the effects of silicon on the growth, root phenotype, mineral element contents, hydrogen peroxide (H2O2) and antioxidative enzymes of rice (Oryza sativa L.) seedling roots under simulated acid rain (SAR) stress. The results showed that the combined or single effects of Si and/or SAR on rice roots depend on the concentration of Si and the pH of the SAR. The combined or single effects of a low or moderate concentration of Si (1.0 or 2.0 mM) and light SAR (pH 4.0) enhanced the growth of rice roots, and the combined effects were stronger than those of the single treatment. A high concentration of Si (4.0 mM) or severe SAR (pH 2.0) exerted deleterious effects. The incorporation of Si (1.0, 2.0 or 4.0 mM) into SAR with pH 3.0 or 2.0 promoted the rice root growth, decreased the H2O2 content, increased the Si concentration and the superoxide dismutase (SOD), catalase (CAT), peroxidase (POD) and ascorbate peroxidase (APX) activities, maintained the balance of mineral element (K, Ca, Mg, Fe, Zn, and Cu) concentrations in the roots of rice seedlings compared with SAR alone. The alleviatory effects observed with a moderate concentration of Si (2.0 mM) were better than the effects obtained with a low or high concentration of Si (1.0 or 4.0 mM). The observed effects were due to disruptions in the absorption and utilization of mineral nutrients and impacts on the activity of antioxidant enzymes in roots, and this conclusion suggests that the degree of rice root damage caused by acid rain might be attributed to not only acid rain but also the level of Si in the soil. PMID:28291806

  10. Effect of Simulated Heat Stress on Digestibility, Methane Emission and Metabolic Adaptability in Crossbred Cattle

    Directory of Open Access Journals (Sweden)

    Brijesh Yadav

    2016-11-01

    Full Text Available The present experiment was conducted to evaluate the effect of simulated heat stress on digestibility and methane (CH4 emission. Four non-lactating crossbred cattle were exposed to 25°C, 30°C, 35°C, and 40°C temperature with a relative humidity of 40% to 50% in a climatic chamber from 10:00 hours to 15:00 hours every day for 27 days. The physiological responses were recorded at 15:00 hours every day. The blood samples were collected at 15:00 hours on 1st, 6th, 11th, 16th, and 21st days and serum was collected for biochemical analysis. After 21 days, fecal and feed samples were collected continuously for six days for the estimation of digestibility. In the last 48 hours gas samples were collected continuously to estimate CH4 emission. Heat stress in experimental animals at 35°C and 40°C was evident from an alteration (p<0.05 in rectal temperature, respiratory rate, pulse rate, water intake and serum thyroxin levels. The serum lactate dehydrogenase, aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase activity and protein, urea, creatinine and triglyceride concentration changed (p<0.05, and body weight of the animals decreased (p<0.05 after temperature exposure at 40°C. The dry matter intake (DMI was lower (p<0.05 at 40°C exposure. The dry matter and neutral detergent fibre digestibilities were higher (p<0.05 at 35°C compared to 25°C and 30°C exposure whereas, organic matter (OM and acid detergent fibre digestibilities were higher (p<0.05 at 35°C than 40°C thermal exposure. The CH4 emission/kg DMI and organic matter intake (OMI declined (p<0.05 with increase in exposure temperature and reached its lowest levels at 40°C. It can be concluded from the present study that the digestibility and CH4 emission were affected by intensity of heat stress. Further studies are necessary with respect to ruminal microbial changes to justify the variation in the digestibility and CH4 emission during differential heat stress.

  11. Laser treatment of female stress urinary incontinence: optical, thermal, and tissue damage simulations

    Science.gov (United States)

    Hardy, Luke A.; Chang, Chun-Hung; Myers, Erinn M.; Kennelly, Michael J.; Fried, Nathaniel M.

    2016-02-01

    Treatment of female stress urinary incontinence (SUI) by laser thermal remodeling of subsurface tissues is studied. Light transport, heat transfer, and thermal damage simulations were performed for transvaginal and transurethral methods. Monte Carlo (MC) provided absorbed photon distributions in tissue layers (vaginal wall, endopelvic fascia, urethral wall). Optical properties (n,μa,μs,g) were assigned to each tissue at λ=1064 nm. A 5-mm-diameter laser beam and power of 5 W for 15 s was used, based on previous experiments. MC output was converted into absorbed energy, serving as input for ANSYS finite element heat transfer simulations of tissue temperatures over time. Convective heat transfer was simulated with contact cooling probe set at 0 °C. Thermal properties (κ,c,ρ) were assigned to each tissue layer. MATLAB code was used for Arrhenius integral thermal damage calculations. A temperature matrix was constructed from ANSYS output, and finite sum was incorporated to approximate Arrhenius integral calculations. Tissue damage properties (Ea,A) were used to compute Arrhenius sums. For the transvaginal approach, 37% of energy was absorbed in endopelvic fascia layer with 0.8% deposited beyond it. Peak temperature was 71°C, treatment zone was 0.8-mm-diameter, and almost all of 2.7-mm-thick vaginal wall was preserved. For transurethral approach, 18% energy was absorbed in endopelvic fascia with 0.3% deposited beyond it. Peak temperature was 80°C, treatment zone was 2.0-mm-diameter, and only 0.6 mm of 2.4-mm-thick urethral wall was preserved. A transvaginal approach is more feasible than transurethral approach for laser treatment of SUI.

  12. Perceived stress, external locus of control, and social support as predictors of psychological adjustment among female inmates with or without a history of sexual abuse.

    Science.gov (United States)

    Asberg, Kia; Renk, Kimberly

    2014-01-01

    Given the growing number of women who are incarcerated across the United States, the current study investigated the relationships among female inmates' perceptions of their own stress, external locus of control (LOC), social support adequacy, and various aspects of psychological functioning. Generally, female inmates with a self-reported history of childhood sexual abuse did not differ from their nonabused counterparts on the variables of interest. Results suggested that female inmates' perceptions of higher stress, a higher degree of external LOC, and inadequate social support correlated with greater symptoms of depression and hopelessness as well as lower self-esteem. In regression analyses, stress and social support were significant predictors for depression and anxiety. In contrast, stress was the only significant predictor of hopelessness and self-esteem. Finally, none of the predictors examined here was significant in the prediction of traumatic stress. Overall, findings suggested the importance of stress and social support in the prediction of female inmates' adjustment, specifically their symptoms of depression and anxiety.

  13. Effects of cocaine history on postsynaptic GABA receptors on dorsal raphe serotonin neurons in a stress-induced relapse model in rats.

    Science.gov (United States)

    Li, Chen; Kirby, Lynn G

    2016-01-01

    The serotonin (5-hydroxytryptamine, 5-HT) system plays an important role in stress-related psychiatric disorders and substance abuse. Stressors and stress hormones can inhibit the dorsal raphe nucleus (DRN)-5-HT system, which composes the majority of forebrain-projecting 5-HT. This inhibition is mediated via stimulation of GABA synaptic activity at DRN-5-HT neurons. Using swim stress-induced reinstatement of morphine conditioned place-preference, recent data from our laboratory indicate that morphine history sensitizes DRN-5-HT neurons to GABAergic inhibitory effects of stress. Moreover, GABAA receptor-mediated inhibition of the serotonergic DRN is required for this reinstatement. In our current experiment, we tested the hypothesis that GABAergic sensitization of DRN-5-HT neurons is a neuroadaptation elicited by multiple classes of abused drugs across multiple models of stress-induced relapse by applying a chemical stressor (yohimbine) to induce reinstatement of previously extinguished cocaine self-administration in Sprague-Dawley rats. Whole-cell patch-clamp recordings of GABA synaptic activity in DRN-5-HT neurons were conducted after the reinstatement. Behavioral data indicate that yohimbine triggered reinstatement of cocaine self-administration. Electrophysiology data indicate that 5-HT neurons in the cocaine group exposed to yohimbine had increased amplitude of inhibitory postsynaptic currents compared to yoked-saline controls exposed to yohimbine or unstressed animals in both drug groups. These data, together with previous findings, indicate that interaction between psychostimulant or opioid history and chemical or physical stressors may increase postsynaptic GABA receptor density and/or sensitivity in DRN-5-HT neurons. Such mechanisms may result in serotonergic hypofunction and consequent dysphoric mood states which confer vulnerability to stress-induced drug reinstatement. Copyright © 2015 Elsevier B.V. and ECNP. All rights reserved.

  14. Finite Element Simulation of Mechanical and Moisture-Related Stresses in Laterally Loaded Multi-Dowel Timber Connections

    DEFF Research Database (Denmark)

    Ormarsson, Sigurdur; Dahlblom, O.; Nygaard, M. J.

    2010-01-01

    Numerical simulations of stress distribution within a moment stiff timber frame corner have been performed. The frame corner is a multi-dowel connection with two slotted-in steel plates. The interaction between the fasteners and the wood material is modelled as a full contact interaction based...

  15. Study on Real-Time Simulation Analysis and Inverse Analysis System for Temperature and Stress of Concrete Dam

    Directory of Open Access Journals (Sweden)

    Lei Zhang

    2015-01-01

    Full Text Available In the concrete dam construction, it is very necessary to strengthen the real-time monitoring and scientific management of concrete temperature control. This paper constructs the analysis and inverse analysis system of temperature stress simulation, which is based on various useful data collected in real time in the process of concrete construction. The system can produce automatically data file of temperature and stress calculation and then achieve the remote real-time simulation calculation of temperature stress by using high performance computing techniques, so the inverse analysis can be carried out based on a basis of monitoring data in the database; it fulfills the automatic feedback calculation according to the error requirement and generates the corresponding curve and chart after the automatic processing and analysis of corresponding results. The system realizes the automation and intellectualization of complex data analysis and preparation work in simulation process and complex data adjustment in the inverse analysis process, which can facilitate the real-time tracking simulation and feedback analysis of concrete temperature stress in construction process and enable you to discover problems timely, take measures timely, and adjust construction scheme and can well instruct you how to ensure project quality.

  16. Corticotropin-releasing Factor in the Rat Dorsal Raphe Nucleus Promotes Different Forms of Behavioral Flexibility Depending on Social Stress History.

    Science.gov (United States)

    Snyder, Kevin P; Hill-Smith, Tiffany E; Lucki, Irwin; Valentino, Rita J

    2015-10-01

    The stress-related neuropeptide, corticotropin-releasing factor (CRF) regulates the dorsal raphe nucleus-serotonin (DRN-5-HT) system during stress and this may underlie affective and cognitive dysfunctions that characterize stress-related psychiatric disorders. CRF acts on both CRF1 and CRF2 receptor subtypes in the DRN that exert opposing inhibitory and excitatory effects on DRN-5-HT neuronal activity and 5-HT forebrain release, respectively. The current study first assessed the cognitive effects of intra-DRN microinfusion of CRF or the selective CRF2 agonist, urocortin II in stress-naive rats on performance of an operant strategy set-shifting task that is mediated by the medial prefrontal cortex (mPFC). CRF (30 ng) facilitated strategy set-shifting performance, whereas higher doses of CRF and urocortin II that would interact with CRF2 were without effect, consistent with a CRF1-mediated action. This dose decreased 5-HT extracellular levels in the mPFC, further supporting a role for CRF1. The effects of CRF were then assessed in rats exposed to repeated social stress using the resident-intruder model. Repeated social stress shifted the CRF effect from facilitation of strategy set shifting to facilitation of reversal learning and this was most prominent in a subpopulation of rats that resist defeat. Notably, in this subpopulation of rats 5-HT neuronal responses to CRF have been demonstrated to shift from CRF1-mediated inhibition to CRF2-mediated excitation. Because 5-HT facilitates reversal learning, the present results suggest that stress-induced changes in the cellular effects of CRF in the DRN translate to changes in cognitive effects of CRF. Together, the results underscore the potential for stress history to shift cognitive processing through changes in CRF neurotransmission in the DRN and the association of this effect with coping strategy.

  17. Simulation of thermal stress and buckling instability in Si/Ge and Ge/Si core/shell nanowires.

    Science.gov (United States)

    Das, Suvankar; Moitra, Amitava; Bhattacharya, Mishreyee; Dutta, Amlan

    2015-01-01

    The present study employs the method of atomistic simulation to estimate the thermal stress experienced by Si/Ge and Ge/Si, ultrathin, core/shell nanowires with fixed ends. The underlying technique involves the computation of Young's modulus and the linear coefficient of thermal expansion through separate simulations. These two material parameters are combined to obtain the thermal stress on the nanowires. In addition, the thermally induced stress is perceived in the context of buckling instability. The analysis provides a trade-off between the geometrical and operational parameters of the nanostructures. The proposed methodology can be extended to other materials and structures and helps with the prediction of the conditions under which a nanowire-based device might possibly fail due to elastic instability.

  18. 3D-simulation of residual stresses in TBC plasma sprayed coating

    International Nuclear Information System (INIS)

    Kundas, S.; Kashko, T.; Hurevich, V.E.; Lugscheider, E.; Hayn, G. von; Ilyuschenko, A.

    2001-01-01

    Thermal barrier coatings (TBC) are used in gas turbine technology in order to protect against overheating of the nickel alloy turbine blades. This coatings allows to increase turbine inlet temperatures and improve their efficiency. Plasma spraying processes are widely used since several years in thermal barrier coating technology. Although the plasma spraying process of TBC's is largely successful, a fundamental understanding of the process parameters influencing the TBC microstructure and mechanical properties is necessary. But this investigation has received much less attention so they could lead to considerable advances in performance of plasma sprayed thermal barrier coatings. The main reason of this mate is difficulties in experimental investigation of high temperature and high velocity process. One of the most effective ways to accelerate the process optimization is the application of computer simulation for the modeling of plasma spraying. This enables the achievement of a maximum of information about the investigated process by carrying out a minimum number of experiments. The main problem of plasma spray TBC coatings is crack information during the deposition process and coating cooling. The reasons for this are quenched and residual stresses in the coating-substrate system, and peculiarities of TBC coating properties. The problem of deposition and solidification of plasma sprayed coatings have received little attention to date and remains one of the unintelligible parts of process. A fundamental understanding of heat transfer in the coating-substrate system and particles deformation processes are, however, critical for the prediction of the microstructural characteristics of the deposited coatings, the understanding of the mechanisms involved in formation of thermal stresses and defects (cracks, debonding etc.). (author)

  19. Effects of platooning on signal-detection performance, workload, and stress: A driving simulator study.

    Science.gov (United States)

    Heikoop, Daniël D; de Winter, Joost C F; van Arem, Bart; Stanton, Neville A

    2017-04-01

    Platooning, whereby automated vehicles travel closely together in a group, is attractive in terms of safety and efficiency. However, concerns exist about the psychological state of the platooning driver, who is exempted from direct control, yet remains responsible for monitoring the outside environment to detect potential threats. By means of a driving simulator experiment, we investigated the effects on recorded and self-reported measures of workload and stress for three task-instruction conditions: (1) No Task, in which participants had to monitor the road, (2) Voluntary Task, in which participants could do whatever they wanted, and (3) Detection Task, in which participants had to detect red cars. Twenty-two participants performed three 40-min runs in a constant-speed platoon, one condition per run in counterbalanced order. Contrary to some classic literature suggesting that humans are poor monitors, in the Detection Task condition participants attained a high mean detection rate (94.7%) and a low mean false alarm rate (0.8%). Results of the Dundee Stress State Questionnaire indicated that automated platooning was less distressing in the Voluntary Task than in the Detection Task and No Task conditions. In terms of heart rate variability, the Voluntary Task condition yielded a lower power in the low-frequency range relative to the high-frequency range (LF/HF ratio) than the Detection Task condition. Moreover, a strong time-on-task effect was found, whereby the mean heart rate dropped from the first to the third run. In conclusion, participants are able to remain attentive for a prolonged platooning drive, and the type of monitoring task has effects on the driver's psychological state. Copyright © 2016 Elsevier Ltd. All rights reserved.

  20. Microsecond molecular dynamics simulations of intrinsically disordered proteins involved in the oxidative stress response.

    Directory of Open Access Journals (Sweden)

    Elio A Cino

    Full Text Available Intrinsically disordered proteins (IDPs are abundant in cells and have central roles in protein-protein interaction networks. Interactions between the IDP Prothymosin alpha (ProTα and the Neh2 domain of Nuclear factor erythroid 2-related factor 2 (Nrf2, with a common binding partner, Kelch-like ECH-associated protein 1(Keap1, are essential for regulating cellular response to oxidative stress. Misregulation of this pathway can lead to neurodegenerative diseases, premature aging and cancer. In order to understand the mechanisms these two disordered proteins employ to bind to Keap1, we performed extensive 0.5-1.0 microsecond atomistic molecular dynamics (MD simulations and isothermal titration calorimetry experiments to investigate the structure/dynamics of free-state ProTα and Neh2 and their thermodynamics of bindings. The results show that in their free states, both ProTα and Neh2 have propensities to form bound-state-like β-turn structures but to different extents. We also found that, for both proteins, residues outside the Keap1-binding motifs may play important roles in stabilizing the bound-state-like structures. Based on our findings, we propose that the binding of disordered ProTα and Neh2 to Keap1 occurs synergistically via preformed structural elements (PSEs and coupled folding and binding, with a heavy bias towards PSEs, particularly for Neh2. Our results provide insights into the molecular mechanisms Neh2 and ProTα bind to Keap1, information that is useful for developing therapeutics to enhance the oxidative stress response.

  1. HPC in Basin Modeling: Simulating Mechanical Compaction through Vertical Effective Stress using Level Sets

    Science.gov (United States)

    McGovern, S.; Kollet, S. J.; Buerger, C. M.; Schwede, R. L.; Podlaha, O. G.

    2017-12-01

    In the context of sedimentary basins, we present a model for the simulation of the movement of ageological formation (layers) during the evolution of the basin through sedimentation and compactionprocesses. Assuming a single phase saturated porous medium for the sedimentary layers, the modelfocuses on the tracking of the layer interfaces, through the use of the level set method, as sedimentationdrives fluid-flow and reduction of pore space by compaction. On the assumption of Terzaghi's effectivestress concept, the coupling of the pore fluid pressure to the motion of interfaces in 1-D is presented inMcGovern, et.al (2017) [1] .The current work extends the spatial domain to 3-D, though we maintain the assumption ofvertical effective stress to drive the compaction. The idealized geological evolution is conceptualized asthe motion of interfaces between rock layers, whose paths are determined by the magnitude of a speedfunction in the direction normal to the evolving layer interface. The speeds normal to the interface aredependent on the change in porosity, determined through an effective stress-based compaction law,such as the exponential Athy's law. Provided with the speeds normal to the interface, the level setmethod uses an advection equation to evolve a potential function, whose zero level set defines theinterface. Thus, the moving layer geometry influences the pore pressure distribution which couplesback to the interface speeds. The flexible construction of the speed function allows extension, in thefuture, to other terms to represent different physical processes, analogous to how the compaction rulerepresents material deformation.The 3-D model is implemented using the generic finite element method framework Deal II,which provides tools, building on p4est and interfacing to PETSc, for the massively parallel distributedsolution to the model equations [2]. Experiments are being run on the Juelich Supercomputing Center'sJureca cluster. [1] McGovern, et.al. (2017

  2. Monte Carlo simulation taking account of surface crack effect for stress corrosion cracking in a stainless steel SUS 304

    International Nuclear Information System (INIS)

    Tohgo, Keiichiro; Suzuki, Hiromitsu; Shimamura, Yoshinobu; Nakayama, Guen; Hirano, Takashi

    2008-01-01

    Stress corrosion cracking (SCC) in structural metal materials occurs by initiation and coalescence of micro cracks, subcritical crack propagation and multiple large crack formation or final failure under the combination of materials, stress and corrosive environment. In this paper, a Monte Carlo simulation for the process of SCC has been proposed based on the stochastic properties of micro crack initiation and fracture mechanics concept for crack coalescence and propagation. The emphasis in the model is put on the influence of semi-elliptical surface cracks. Numerical simulations are carried out based on CBB (creviced bent beam) test results of a sensitized stainless steel SUS 304 and the influence of micro crack initiation rate and coalescence condition on the simulation results is discussed. The numerical examples indicate the applicability of the present model to a prediction of the SCC behavior in real structures. (author)

  3. Effect of single-cat versus multi-cat home history on perceived behavioral stress in domestic cats (Felis silvestrus catus) in an animal shelter.

    Science.gov (United States)

    Broadley, Heidi M; McCobb, Emily C; Slater, Margaret R

    2014-02-01

    This study investigates the effect of living with other cats in a prior home on stress levels of cats recently surrendered to an animal shelter. A total of 63 cats was evaluated using a Cat-Stress-Score and an approach test. Cats were categorized in terms of previous home history with or without other cats. No significant difference was found in stress scores between cats from single-cat households and those from multiple-cat households, although single cats that had been in the shelter less than 4 days demonstrated higher stress levels. No significant difference was found between the two groups in terms of approach results. Results of this study suggest that, in traditional individual cage settings, cats that are not accustomed to living with other cats may experience more stress in the initial few days of attempting to adjust to shelter existence. Through the use of such assessments, shelter personnel may develop an increased awareness to the needs of these cats and attempt to provide measures to improve their well-being within the shelter environment.

  4. Stress-induced change in serum BDNF is related to quantitative family history of alcohol use disorder and age at first alcohol use.

    Science.gov (United States)

    Sharma, Shobhit; Graham, Reiko; Rohde, Rodney; Ceballos, Natalie A

    2017-02-01

    Previous research in animal models suggests that brain-derived neurotrophic factor (BDNF) is involved in stress-modulated alcohol consumption. However, relatively few studies have investigated this issue in humans, and results of existing studies have been heterogeneous. The primary aim of the current study was to examine the within-subjects effect of acute stress (timed math plus cold pressor) on serum BDNF levels (ΔBDNF: post- minus pre-stress) in healthy social drinkers (N=68, 20 male). A secondary aim was to explore which heritable and environmental factors in our limited sample might exert the greatest influences on ΔBDNF. Importantly, presence versus absence of the BDNF Val 66 Met polymorphism (rs6265), which has often been discounted in studies of human serum BDNF, was included as a between-subjects control variable in all statistical analyses. Our results indicated that acute stress decreased serum BDNF. Further, multiple regression analyses revealed that quantitative family history of alcohol use disorder (qFH) and age at first alcohol use together accounted for 15% of the variance in ΔBDNF. Thus, the influences of qFH and age at first alcohol use may explain some of the heterogeneity that exists in previous studies of human serum BDNF. These results parallel findings in animal models and suggest that stress-related changes in serum BDNF are influenced by both heritable (qFH) and environmental (early alcohol consumption) factors. Copyright © 2016 Elsevier Inc. All rights reserved.

  5. Numerical simulation of residual stresses at holes near edges and corners in tempered glass: A parametric study

    DEFF Research Database (Denmark)

    Pourmoghaddam, Navid; Nielsen, Jens Henrik; Schneider, Jens

    2016-01-01

    This work presents 3D results of the thermal tempering simulation by the Finite Element Method in order to calculate the residual stresses in the area of the holes near edges and corners of a tem-pered glass plate. A viscoelastic material behavior of the glass is considered for the tempering...... process. The structural relaxation is taken into account using Narayanaswamy’s model. The motiva-tion for this work is to study the effect of the reduction of the hole and edge minimum distances, which are defined according to EN 12150-1. It is the objective of the paper to demonstrate and elucidate...... the influence of the hole and edge distances on the minimal residual compressive stress-es at holes after the tempering process. The residual stresses in the area of the holes are calculat-ed varying the following parameters: the hole diameter, the plate thickness and the interaction between holes and edges...

  6. Stress concentration during pellet cladding interaction: Comparison of closed-form solutions with 2D(r,θ) finite element simulations

    International Nuclear Information System (INIS)

    Sercombe, Jérôme; Masson, Renaud; Helfer, Thomas

    2013-01-01

    Highlights: • This paper presents closed-formed solutions concerning pellet cladding interaction. • First, the opening of a radial crack in a pellet fragment is estimated. • Second, the stresses in the cladding in front of the pellet crack are calculated. • The closed-formed solutions are found in good agreement with 2D FE simulations. • They are then used in the fuel code ALCYONE to model PCI during power ramps. -- Abstract: This paper presents two closed-form solutions that can be used to enrich the mechanical description of fuel pellets and cladding behavior in standard one-dimensional based fuel performance codes. The first one is concerned with the estimation of the opening of a radial crack in a pellet fragment induced by the radial thermal gradient in the pellet and limited by the pellet-clad contact pressure. The second one describes the stress distribution in a cladding bore in front of an opening pellet crack. A linear angular variation of the pellet-clad contact pressure and a constant prescribed radial displacement are considered. The closed-form solutions are checked by comparison to independent finite element models of the pellet fragment and of the cladding. Their ability to describe non-axisymmetric displacement and stress fields during loading histories representative of base irradiation and power ramps is then demonstrated by cross-comparison with the 2D pellet fragment-cladding model of the multi-dimensional fuel performance code ALCYONE. The calculated radial crack opening profiles at different times and the hoop stress concentration in the cladding at the top of the ramp are found in good agreement with ALCYONE

  7. Stress-Induced Enhancement of Ethanol Intake in C57BL/6J Mice with a History of Chronic Ethanol Exposure: Involvement of Kappa Opioid Receptors.

    Science.gov (United States)

    Anderson, Rachel I; Lopez, Marcelo F; Becker, Howard C

    2016-01-01

    Our laboratory has previously demonstrated that daily forced swim stress (FSS) prior to ethanol drinking sessions facilitates enhanced ethanol consumption in mice with a history of chronic intermittent ethanol (CIE) vapor exposure without altering ethanol intake in air-exposed controls. Because both stress and chronic ethanol exposure have been shown to activate the dynorphin/kappa opioid receptor (KOR) system, the present study was designed to explore a potential role for KORs in modulating stress effects on ethanol consumption in the CIE model of dependence and relapse drinking. After stable baseline ethanol intake was established in adult male C57BL/6J mice, subjects received chronic intermittent exposure (16 h/day × 4 days/week) to ethanol vapor (CIE group) or air (CTL group). Weekly cycles of inhalation exposure were alternated with 5-day limited access drinking tests (1 h access to 15% ethanol). Experiment 1 compared effects of daily FSS and KOR activation on ethanol consumption. CIE and CTL mice were either exposed to FSS (10 min), the KOR agonist U50,488 (5 mg/kg), or a vehicle injection (non-stressed condition) prior to each daily drinking session during test weeks. FSS selectively increased drinking in CIE mice. U50,488 mimicked this effect in CIE mice, but also increased drinking in CTL mice. Experiment 2 assessed effects of KOR blockade on stress-induced drinking in CIE and CTL mice. Stressed and non-stressed mice were administered the short-acting KOR antagonist LY2444296 (0 or 5 mg/kg) 30 min prior to each drinking session during test weeks. FSS selectively increased ethanol consumption in CIE mice, an effect that was abolished by LY2444296 pretreatment. In Experiment 3, CIE and CTL mice were administered one of four doses of U50,488 (0, 1.25, 2.5, 5.0 mg/kg) 1 h prior to each daily drinking test (in lieu of FSS). All doses of U50,488 increased ethanol consumption in both CIE and CTL mice. The U50,488-induced increase in drinking was blocked by LY

  8. Stress-induced enhancement of ethanol intake in C57BL/6J mice with a history of chronic ethanol exposure: Involvement of kappa opioid receptors

    Directory of Open Access Journals (Sweden)

    Rachel Ivy Anderson

    2016-02-01

    Full Text Available Our laboratory has previously demonstrated that daily forced swim stress (FSS prior to ethanol drinking sessions facilitates enhanced ethanol consumption in mice with a history of chronic intermittent ethanol (CIE vapor exposure without altering ethanol intake in air-exposed controls. Because both stress and chronic ethanol exposure have been shown to activate the dynorphin/kappa opioid receptor (KOR system, the present study was designed to explore a potential role for KORs in modulating stress effects on ethanol consumption in the CIE model of dependence and relapse drinking. After stable baseline ethanol intake was established in adult male C57BL/6J mice, subjects received chronic intermittent exposure (16 hr/day x 4 days/week to ethanol vapor (CIE group or air (CTL group. Weekly cycles of inhalation exposure were alternated with 5-day limited access drinking tests (1 hour access to 15% ethanol. Experiment 1 compared effects of daily FSS and KOR activation on ethanol consumption. CIE and CTL mice were either exposed to FSS (10 min, the KOR agonist U50,488 (5 mg/kg, or a vehicle injection (non-stressed condition prior to each daily drinking session during test weeks. FSS selectively increased drinking in CIE mice. U50,488 mimicked this effect in CIE mice, but also increased drinking in CTL mice. Experiment 2 assessed effects of KOR blockade on stress-induced drinking in CIE and CTL mice. Stressed and non-stressed mice were administered the short-acting KOR antagonist LY2444296 (0 or 5 mg/kg 30 min prior to each drinking session during test weeks. FSS selectively increased ethanol consumption in CIE mice, an effect that was abolished by LY2444296 pretreatment. In Experiment 3, CIE and CTL mice were administered one of four doses of U50,488 (0,1.25, 2.5, 5.0 mg/kg one hour prior to each daily drinking test (in lieu of FSS. All doses of U50,488 increased ethanol consumption in both CIE and CTL mice. The U50,488-induced increase in drinking was

  9. Comparison of plantar flexor musculotendinous stiffness, geometry, and architecture in male runners with and without a history of tibial stress fracture.

    Science.gov (United States)

    Pamukoff, Derek N; Blackburn, J Troy

    2015-02-01

    Greater lower extremity joint stiffness may be related to the development of tibial stress fractures in runners. Musculotendinous stiffness is the largest contributor to joint stiffness, but it is unclear what factors contribute to musculotendinous stiffness. The purpose of this study was to compare plantar flexor musculotendinous stiffness, architecture, geometry, and Achilles tendon stiffness between male runners with and without a history of tibial stress fracture. Nineteen healthy runners (age = 21 ± 2.7 years; mass = 68.2 ± 9.3 kg; height = 177.3 ± 6.0 cm) and 19 runners with a history of tibial stress fracture (age = 21 ± 2.9 years; mass = 65.3 ± 6.0 kg; height = 177.2 ± 5.2 cm) were recruited from community running groups and the university's varsity and club cross-country teams. Plantar flexor musculotendinous stiffness was estimated from the damped frequency of oscillatory motion about the ankle follow perturbation. Ultrasound imaging was used to measure architecture and geometry of the medial gastrocnemius. Dependent variables were compared between groups via one-way ANOVAs. Previously injured runners had greater plantar flexor musculotendinous stiffness (P < .001), greater Achilles tendon stiffness (P = .004), and lesser Achilles tendon elongation (P = .003) during maximal isometric contraction compared with healthy runners. No differences were found in muscle thickness, pennation angle, or fascicle length.

  10. Aprendizaje de la Historia y Simulación Educativa / The Learning of History and Educational Simulation

    Directory of Open Access Journals (Sweden)

    Jesús Valverde Berrocoso

    2010-09-01

    Full Text Available Resumen. El aprendizaje de la Historia tiene como finalidad fundamental que los alumnos adquieran los conocimientos y actitudes necesarios para comprender la realidad del mundo en que viven, las experiencias colectivas pasadas y presentes, así como el espacio en que se desarrolla la vida en sociedad. El conocimiento histórico se fundamenta en relatos, pero también en la interpretación explicativa de los fenómenos históricos, de sus causas y sus relaciones con acontecimientos posteriores. Esto explica las dificultades que los alumnos encuentran para comprender conceptos históricos de carácter multicausal que, además, tienen que ser contextualizados en un tiempo y en un espacio. La simulación educativa basada en el juego, en objetos o en procesos dinámicos, es una herramienta didáctica que puede contribuir a mejorar la comprensión de la Historia porque favorece la comprensión de ideas y conceptos abstractos, es idónea para manipular y modificar, según las necesidades educativas del momento, las variables espacio-temporales y, por último, es útil para situarnos en un lugar o en un tiempo donde sería imposible tener una experiencia directa. Summary. The fundamental purpose of learning History is that students acquire the knowledge and attitudes necessary to understand the reality of the world they live in, the collective experiences past and present, as well as the space in which life develops in society. Historical knowledge is based on stories, but also in the explanatory interpretation of historical phenomena, its causes and its relationship to subsequent events. This explains the difficulties that students encounter in understanding multicausal historical concepts that also have to be contextualized in time and space. The simulation-based educational game, objects or dynamic processes, is an educational tool that can help improve understanding of History because it promotes understanding of abstract ideas and concepts, is

  11. Detection of endogenous cortisol in equine tears and blood at rest and after simulated stress.

    Science.gov (United States)

    Monk, Caroline S; Hart, Kelsey A; Berghaus, Roy D; Norton, Natalie A; Moore, Phillip A; Myrna, Kathern E

    2014-07-01

    To determine whether cortisol is present in equine tears at rest and during simulated stress and compare tear cortisol to serum free and total cortisol. Fourteen healthy adult horses were included. Paired tear total cortisol and serum total and free cortisol concentrations were measured with ELISA, chemiluminescent immunoassay, and ultrafiltration methodology, respectively, in 10 horses at rest once daily for five consecutive days. In an additional four horses, paired tear and serum samples were collected for cortisol measurement before and after adrenocorticotropic hormone (ACTH) stimulation (cosyntropin, 1 μg/kg IV). Cortisol was detectable in equine tears at rest. Following ACTH stimulation, tear cortisol increased significantly from baseline at 60-120 min (P ≤ 0.001). Serum total and free cortisol also increased significantly at 30-180 min after ACTH stimulation (P ≤ 0.001). Both serum and tear cortisol returned to baseline concentrations by 360 min. Changes in tear cortisol were similarly associated with changes in serum total and free cortisol, although high tear cortisol concentrations suggest a portion of tear cortisol may be protein-bound. Cortisol is present in equine tears and increases in concert with serum cortisol following ACTH stimulation. Further study is needed to determine whether endogenous cortisol in tears contributes to ocular pathology. © 2013 American College of Veterinary Ophthalmologists.

  12. Comparative assessment of wheat landraces against polyethylene glycol simulated drought stress

    International Nuclear Information System (INIS)

    Jatoi, S.A.; Latif, M.M.; Arif, M.; Ahson, M.; Siddiqui, S.U.

    2014-01-01

    Current investigation reports a comparative assessment and relative performance of 10 wheat accessions including check variety Inqilab-91 against polyethylene glycol (PEG) simulated drought stress at seedling. Wheat genotypes were tested against 0, 19, 21, 23 and 25% solutions of PEG 6000. The young seedlings were observed for germination (%) and root length (cm). In general, a decrease in germination percentage was observed with the increase in PEG concentration. All the investigated wheat genotypes performed better than the check variety Inqilab-91. The wheat accession 18699 that had more than 30% surviving seedlings at the highest concentration of used PEG was rated as the tolerant genotype. On the other hand, 18671 and 18698 appeared to be less tolerant having less than 5% germination at 25% PEG. Similarly, the root length decreased with the increase in PEG concentrations. The mean root length of all the wheat accessions, which were studied, was comparatively less affected than the control (Inqilab-91). The wheat genotypes 18670 and 18671 were the better performers than the rest of genotypes investigated and belonged to rainfed area of the Pothowar region. A detailed investigation of these genotypes in the field conditions is suggested. (author)

  13. Changes in emotion regulation in adults with and without a history of childhood abuse following posttraumatic stress disorder treatment.

    Science.gov (United States)

    Jerud, Alissa B; Zoellner, Lori A; Pruitt, Larry D; Feeny, Norah C

    2014-08-01

    This study compared changes in emotion regulation and trait affect over the course of PTSD treatment with either prolonged exposure (PE) therapy or sertraline in adults with and without a history of childhood abuse (CA). Two hundred adults with PTSD received 10 weeks of PE or sertraline. Emotion regulation and trait affect were assessed pre- and posttreatment and at 6-month follow-up with the Emotion Regulation Questionnaire (Gross & John, 2003), the Negative Mood Regulation Scale (Catanzaro & Mearns, 1990), and the Positive and Negative Affect Schedule (Watson, Clark, & Tellegen, 1988). Individuals with and without a history of CA did not differ from one another at pretreatment on PTSD severity, emotion regulation, or positive/negative affect. In addition, treatment was effective at improving emotion regulation and trait affect in those with and without a history of CA, and no significant differences in emotion regulation or trait affect emerged posttreatment or at 6-month follow-up between adults with and without a history of CA. Furthermore, noninferiority analyses indicated that the emotion regulation and trait affect outcomes of individuals with a history of CA were no worse than those of individuals without a history of CA. These findings cast doubt on the assumption that CA is associated with worse emotion regulation following PTSD treatment, arguing against assertions that a history of CA itself is a contraindication for traditional PTSD treatment, and that there is a clear necessity for additional interventions designed to target assumed emotion regulation deficits. [Corrected] PsycINFO Database Record (c) 2014 APA, all rights reserved.

  14. Numerical simulation of elasto-plastic deformation of composites: evolution of stress microfields and implications for homogenization models

    Science.gov (United States)

    González, C.; Segurado, J.; LLorca, J.

    2004-07-01

    The deformation of a composite made up of a random and homogeneous dispersion of elastic spheres in an elasto-plastic matrix was simulated by the finite element analysis of three-dimensional multiparticle cubic cells with periodic boundary conditions. "Exact" results (to a few percent) in tension and shear were determined by averaging 12 stress-strain curves obtained from cells containing 30 spheres, and they were compared with the predictions of secant homogenization models. In addition, the numerical simulations supplied detailed information of the stress microfields, which was used to ascertain the accuracy and the limitations of the homogenization models to include the nonlinear deformation of the matrix. It was found that secant approximations based on the volume-averaged second-order moment of the matrix stress tensor, combined with a highly accurate linear homogenization model, provided excellent predictions of the composite response when the matrix strain hardening rate was high. This was not the case, however, in composites which exhibited marked plastic strain localization in the matrix. The analysis of the evolution of the matrix stresses revealed that better predictions of the composite behavior can be obtained with new homogenization models which capture the essential differences in the stress carried by the elastic and plastic regions in the matrix at the onset of plastic deformation.

  15. How does stress affect human being—a molecular dynamic simulation study on cortisol and its glucocorticoid receptor

    Directory of Open Access Journals (Sweden)

    Dan Zhang

    2017-03-01

    Full Text Available Stress can be either positive or negative to human beings. Under stressful conditions, the mental and physical conditions of human can be affected. There exists certain relation between stress and illness. The cortisol and other glucocorticoids bind to the same receptor, which is called glucocorticoid receptor. Some evidences indicated that cortisol molecule binding to its glucocorticoid receptor was necessary for the stress response. Up to now, the structure–function relationships between cortisol molecule and its glucocorticoid receptor have not been deliberated from the atomic-level. In order to get a detailed understanding of the structure–function relationships between the cortisol molecule and glucocorticoids receptor, we have carried out molecular dynamic (MD simulations on glucocorticoid receptor (Apo system and cortisol with its glucocorticoid receptor complex (HCY system. On the basis of molecular dynamic simulations, a couple of key residues were identified, which were crucial for the binding of cortisol molecule. The results of binding free energy calculations are in good agreement with the experiment data. Our research gives clear insights from atomic-level into the structural–functional aspects of cortisol molecule and its glucocorticoid receptor, and also provides valuable information for the design of drug which can treat stress related illnesses.

  16. Stress

    DEFF Research Database (Denmark)

    Keller, Hanne Dauer

    2015-01-01

    Kapitlet handler om stress som følelse, og det trækker primært på de få kvalitative undersøgelser, der er lavet af stressforløb.......Kapitlet handler om stress som følelse, og det trækker primært på de få kvalitative undersøgelser, der er lavet af stressforløb....

  17. Stress !!!

    OpenAIRE

    Fledderus, M.

    2012-01-01

    Twee op de vijf UT-studenten hebben last van ernstige studiestress, zo erg zelfs dat het ze in hun privéleven belemmert. Die cijfers komen overeen met het landelijk beeld van stress onder studenten. Samen met 14 andere universiteits- en hogeschoolbladen enquêteerde UT Nieuws bijna 5500 studenten. Opvallend is dat mannelijke studenten uit Twente zich veel minder druk lijken te maken over hun studie. Onder vrouwen ligt de stress juist erg hoog ten opzichte van het landelijk gemiddelde.

  18. Is the Level of Nitric Oxide in the Dental Follicular Tissues of Impacted Third Molars With a History of Recurrent Pericoronitis a True Marker of Oxidative Stress?

    Science.gov (United States)

    Hendek, Meltem Karsiyaka; Şenses, Fatma; Kisa, Üçler; Aksoy, Nurkan; Tekin, Umut

    2017-10-01

    Nitric oxide (NO) is an indicator of oxidative stress in several tissues. Its role in dental follicular (DF) tissues of impacted third molars with a history of recurrent pericoronitis is not well elucidated. The present study compared NO levels between inflamed and noninflamed DF tissues of impacted third molars with a history of recurrent pericoronitis. A cross-sectional study was designed. The study sample included inflamed DF tissues (test group) with certain local inflammatory symptoms, such as pain, tenderness, swelling, and erythema and noninflamed DF tissues (control group) without local inflammatory symptoms of impacted mandibular third molars. Each patient contributed only 1 specimen to the samples. All tissues samples were biochemically investigated for NO levels as an indicator of oxidative stress. The primary predictor variable was inflammatory status; secondary predictor variables were age and gender. The primary outcome variable was NO level. Descriptive and comparative analyses were conducted. The test group consisted of 57 patients (28 men, 29 women; mean age, 23.28 ± 5.16 yr) and the control group consisted of 57 patients (30 men, 27 women; mean age, 23.02 ± 5.42 yr). No relevant intergroup differences were noted for demographic findings such as age and gender. NO levels were significantly higher in inflamed DF tissues of impacted third molars than in noninflamed DF tissues (P stress and the necessity to remove impacted mandibular third molars with a history of recurrent pericoronitis. Copyright © 2017 American Association of Oral and Maxillofacial Surgeons. Published by Elsevier Inc. All rights reserved.

  19. Simulated Seasonal Photoperiods and Fluctuating Temperatures Have Limited Effects on Blood Feeding and Life History in Aedes triseriatus (Diptera: Culicidae).

    Science.gov (United States)

    Westby, K M; Juliano, S A

    2015-09-01

    Biotic and abiotic factors change seasonally and impact life history in temperate-zone ectotherms. Temperature and photoperiod are factors that change in predictable ways. Most studies testing for effects of temperature on vectors use constant temperatures and ignore potential correlated effects of photoperiod. In two experiments, we tested for effects of larval rearing environments creating ecologically relevant temperatures and photoperiods simulating early and late season conditions (June and August), or constant temperatures (cool and warm) with the June or August photoperiods, respectively. We determined effects on survivorship, development, size, and a composite performance index in a temperate-zone population of Aedes triseriatus (Say). We followed cohorts of resulting females, all held under the same environmental conditions, to assess carry-over effects of rearing conditions for larvae on longevity, blood feeding, and egg production. Larval survivorship was affected by treatment in one experiment. Development time was greater in the June and cool treatments, but the constant and fluctuating temperatures did not differ. Significantly larger mosquitoes were produced in fluctuating versus constant temperature treatments. There were no significant treatment effects on the composite performance index. Adult female longevity was lower after rearing at constant versus fluctuating temperature, but there was no difference between June and August, nor did size affect longevity. There was no effect of treatments on blood feeding and a limited effect on egg production. We conclude that seasonal temperatures and photoperiods during development have limited effects on this population of A. triseriatus and find little evidence of strong effects of fluctuating versus constant temperatures. © The Authors 2015. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  20. Quantifying the Physiological Stress Response to Simulated Maritime Pilotage Tasks: The Influence of Task Complexity and Pilot Experience.

    Science.gov (United States)

    Main, Luana C; Wolkow, Alexander; Chambers, Timothy P

    2017-11-01

    The aim of this study was to quantify the stress associated with performing maritime pilotage tasks in a high-fidelity simulator. Eight trainee and 13 maritime pilots completed two simulated pilotage tasks of varying complexity. Salivary cortisol samples were collected pre- and post-simulation for both trials. Heart rate was measured continuously throughout the study. Significant changes in salivary cortisol (P = 0.000, η = 0.139), average (P = 0.006, η = 0.087), and peak heart rate (P = 0.013, η = 0.077) from pre- to postsimulation were found. Varying task complexity did partially influence stress response; average (P = 0.016, η = 0.026) and peak heart rate (P = 0.034, η = 0.020) were higher in the experimental condition. Trainees also recorded higher average (P = 0.000, η = 0.054) and peak heart rates (P = 0.027, η = 0.022). Performing simulated pilotage tasks evoked a measurable stress response in both trainee and expert maritime pilots.

  1. On the Effects of Thermal History on the Development and Relaxation of Thermo-Mechanical Stress in Cryopreservation.

    Science.gov (United States)

    Eisenberg, David P; Steif, Paul S; Rabin, Yoed

    2014-01-01

    This study investigates the effects of the thermal protocol on the development and relaxation of thermo-mechanical stress in cryopreservation by means of glass formation, also known as vitrification. The cryopreserved medium is modeled as a homogeneous viscoelastic domain, constrained within either a stiff cylindrical container or a highly compliant bag. Annealing effects during the cooling phase of the cryopreservation protocol are analyzed. Results demonstrate that an intermediate temperature-hold period can significantly reduce the maximum tensile stress, thereby decreasing the potential for structural damage. It is also demonstrated that annealing at temperatures close to glass transition significantly weakens the dependency of thermo-mechanical stress on the cooling rate. Furthermore, a slower initial rewarming rate after cryogenic storage may drastically reduce the maximum tensile stress in the material, which supports previous experimental observations on the likelihood of fracture at this stage. This study discusses the dependency of the various stress components on the storage temperature. Finally, it is demonstrated that the stiffness of the container wall can affect the location of maximum stress, with implications on the development of cryopreservation protocols.

  2. Three dimensional viscoelastic simulation on dynamic evolution of stress field in North China induced by the 1966 Xingtai earthquake

    Science.gov (United States)

    Chen, Lian-Wang; Lu, Yuan-Zhong; Liu, Jie; Guo, Ruo-Mei

    2001-09-01

    Using three dimensional (3D) viscoelastic finite element method (FEM) we study the dynamic evolution pattern of the coseismic change of Coulomb failure stress and postseismic change, on time scale of hundreds years, of rheological effect induced by the M S=7.2 Xingtai earthquake on March 22, 1966. Then, we simulate the coseismic disturbance in stress field in North China and dynamic change rate on one-year scale caused by the Xingtai earthquake and Tangshan earthquake during 15 years from 1966 to 1980. Finally, we discuss the triggering of a strong earthquake to another future strong earthquake.

  3. Lessons denied: a history of therapeutic response to combat stress reaction during Israel's War of Independence (1948), the Sinai Campaign (1956) and the Six Day War (1967)

    Science.gov (United States)

    Witztum, E; Levy, A; Solomon, Z

    1996-01-01

    The current article examines the history of therapeutic response in the Israel Defense Forces toward combat stress reaction during two decades, and in the course of three wars: the 1948 War of Independence, the 1956 Sinai Campaign, and the 1967 Six Day War. Three independent sources were used: recorded debriefing materials; interviews conducted with therapists, commanders and military historians; and professional literature on the wars in Hebrew and other languages. The collected material is described and issues of attitudes, treatment approaches and preparedness are discussed.

  4. The Impact of Stress on the Life History Strategies of African American Adolescents: Cognitions, Genetic Moderation, and the Role of Discrimination

    OpenAIRE

    Gibbons, Frederick X.; Roberts, Megan E.; Gerrard, Meg; Li, Zhigang; Beach, Steven R. H.; Simons, Ronald L.; Weng, Chih-Yuan; Philibert, Robert A.

    2012-01-01

    The impact of three different sources of stress—environmental, familial (e.g., low parental investment), and interpersonal (i.e., racial discrimination)—on the life history strategies (LHS) and associated cognitions of African American adolescents were examined over an 11-year period (five waves, from age 10.5 to 21.5). Analyses indicated that each one of the sources of stress was associated with faster LHS cognitions (e.g., tolerance of deviance, willingness to engage in risky sex), which, i...

  5. Investigation programme and procedure for creep and long-term rupture strength in materials with accounting for stress deviator and loading history

    International Nuclear Information System (INIS)

    Mozharovskaya, T.N.

    1984-01-01

    A programme and procedure are given to study 08Kh18N9 steel at 600 deg C and 15Kh2MFA steel at 550 deg C for creep and long-term strength at different parameters of proportional loading as well as at different parameters under loading in two-link irregular trajectories. This makes it possible to estimate the effect of the kind of a stress deviator, history and prehistory of loading on plastic deformation in creep and on failure under long-term loading

  6. Investigation programme and procedure for creep and long-term rupture strength in materials with accounting for stress deviator and loading history

    Energy Technology Data Exchange (ETDEWEB)

    Mozharovskaya, T N [AN Ukrainskoj SSR, Kiev. Inst. Problem Prochnosti

    1984-11-01

    A programme and procedure are given to study 08Kh18N9 steel at 600 deg C and 15Kh2MFA steel at 550 deg C for creep and long-term strength at different parameters of proportional loading as well as at different parameters under loading in two-link irregular trajectories. This makes it possible to estimate the effect of the kind of a stress deviator, history and prehistory of loading on plastic deformation in creep and on failure under long-term loading.

  7. Shock-induced transformations in crystalline RDX: a uniaxial constant-stress Hugoniostat molecular dynamics simulation study.

    Science.gov (United States)

    Bedrov, Dmitry; Hooper, Justin B; Smith, Grant D; Sewell, Thomas D

    2009-07-21

    Molecular dynamics (MD) simulations of uniaxial shock compression along the [100] and [001] directions in the alpha polymorph of hexahydro-1,3,5-trinitro-1,3,5-triazine (alpha-RDX) have been conducted over a wide range of shock pressures using the uniaxial constant stress Hugoniostat method [Ravelo et al., Phys. Rev. B 70, 014103 (2004)]. We demonstrate that the Hugoniostat method is suitable for studying shock compression in atomic-scale models of energetic materials without the necessity to consider the extremely large simulation cells required for an explicit shock wave simulation. Specifically, direct comparison of results obtained using the Hugoniostat approach to those reported by Thompson and co-workers [Phys. Rev. B 78, 014107 (2008)] based on large-scale MD simulations of shocks using the shock front absorbing boundary condition (SFABC) approach indicates that Hugoniostat simulations of systems containing several thousand molecules reproduced the salient features observed in the SFABC simulations involving roughly a quarter-million molecules, namely, nucleation and growth of nanoscale shear bands for shocks propagating along the [100] direction and the polymorphic alpha-gamma phase transition for shocks directed along the [001] direction. The Hugoniostat simulations yielded predictions of the Hugoniot elastic limit for the [100] shock direction consistent with SFABC simulation results.

  8. Heat indicators of oxidative stress, inflammation and metal transport show dependence of cadmium pollution history in the liver of female zebrafish.

    Science.gov (United States)

    Zhu, Qing-Ling; Guo, Sai-Nan; Yuan, Shuang-Shuang; Lv, Zhen-Ming; Zheng, Jia-Lang; Xia, Hu

    2017-10-01

    Environmental stressors such as high temperature and metal exposure may occur sequentially, simultaneously, previously in aquatic ecosystems. However, information about whether responses to high temperature depend on Cd exposure history is still unknown in fish. Zebrafish were exposed to 0 (group 1), 2.5 (group 2) and 5μg/L (group 3) cadmium (Cd) for 10 weeks, and then each group was subjected to Cd-free water maintained at 26°C and 32°C for 7days respectively. 26 indicators were used to compare differences between 26°C and 32°C in the liver of female zebrafish, including 5 biochemical indicators (activity of Cu/Zn-SOD, CAT and iNOS; LPO; MT protein), 8 molecular indicators of oxidative stress (mRNA levels of Nrf2, Cu/Zn-SOD, CAT, HSF1, HSF2, HSP70, MTF-1 and MT), 5 molecular indicators of inflammation (mRNA levels of IL-6, IL-1β, TNF-α, iNOS and NF-κB), 8 molecular indicators of metal transport (mRNA levels of, ZnT1, ZnT5, ZIP8, ZIP10, ATP7A, ATP7B and CTR1). All biochemical indicators were unchanged in group 1 and changed in group 2 and 3. Contrarily, differences were observed in almost all of molecular indicators of inflammation and metal transport in group 1, about half in group 2, and few in group 3. We also found that all molecular indicators of oxidative stress in group 2 and fewer in group 1 and 3 were significantly affected by heat. Our data indicated that heat indicators of oxidative stress, inflammation and metal transport showed dependence of previous cadmium exposure in the liver of zebrafish, emphasizing metal pollution history should be carefully considered when evaluating heat stress in fish. Copyright © 2017. Published by Elsevier B.V.

  9. Residual stresses analysis of friction stir welding using one-way FSI simulation

    International Nuclear Information System (INIS)

    Kang, Sung Wook; Jang, Beom Seon; Song, Ha Cheol

    2015-01-01

    When certain mechanisms, such as plastic deformations and temperature gradients, occur and are released in a structure, stresses remain because of the shape of the structure and external constraints. These stresses are referred to as residual stresses. The base material locally expands during heating in the welding process. When the welding is completed and cooled to room temperature, the residual stresses are left at nearly the yield strength level. In the case of friction stir welding, the maximum temperature is 80% to 90% of the melting point of the materials. Thus, the residual stresses in the welding process are smaller than those in other fusion welding processes; these stresses have not been considered previously. However, friction stir welding residual stresses are sometimes measured at approximately 70% or above. These residual stresses significantly affect fatigue behavior and lifetime. The present study investigates the residual stress distributions in various welding conditions and shapes of friction stir welding. In addition, the asymmetric feature is considered in temperature and residual stress distribution. Heat transfer analysis is conducted using the commercial computational fluid dynamics program Fluent, and results are used in the finite element structural analysis with the ANSYS Multiphysics software. The calculated residual stresses are compared with experimental values using the X-ray diffraction method.

  10. Stress history and fracture pattern in fault-related folds based on limit analysis: application to the Sub-Andean thrust belt of Bolivia

    Science.gov (United States)

    Barbe, Charlotte; Leroy, Yves; Ben Miloud, Camille

    2017-04-01

    A methodology is proposed to construct the stress history of a complex fault-related fold in which the deformation mechanisms are essentially frictional. To illustrate the approach, fours steps of the deformation of an initially horizontally layered sand/silicone laboratory experiment (Driehaus et al., J. of Struc. Geol., 65, 2014) are analysed with the kinematic approach of limit analysis (LA). The stress, conjugate to the virtual velocity gradient in the sense of mechanicam power, is a proxy for the true statically admmissible stress field which prevailed over the structure. The material properties, friction angles and cohesion, including their time evolution are selected such that the deformation pattern predicted by the LA is consistent with the two main thrusting events, the first forward and the second backward once the layers have sufficiently rotated. The fractures associated to the stress field determined at each step are convected on today configuration to define the complete pattern which should be observed. The end results are presented along virtual vertical wells and could be used within the oil industry at an early phase of exploration to prepare drealing operations.

  11. The Impact of Sleep Restriction and Simulated Physical Firefighting Work on Acute Inflammatory Stress Responses.

    Science.gov (United States)

    Wolkow, Alexander; Ferguson, Sally A; Vincent, Grace E; Larsen, Brianna; Aisbett, Brad; Main, Luana C

    2015-01-01

    This study investigated the effect restricted sleep has on wildland firefighters' acute cytokine levels during 3 days and 2 nights of simulated physical wildfire suppression work. Firefighters completed multiple days of physical firefighting work separated by either an 8-h (Control condition; n = 18) or 4-h (Sleep restriction condition; n = 17) sleep opportunity each night. Blood samples were collected 4 times a day (i.e., 06:15, 11:30, 18:15, 21:30) from which plasma cytokine levels (IL-6, IL-8, IL-1β, TNF-α, IL-4, IL-10) were measured. The primary findings for cytokine levels revealed a fixed effect for condition that showed higher IL-8 levels among firefighters who received an 8-h sleep each night. An interaction effect demonstrated differing increases in IL-6 over successive days of work for the SR and CON conditions. Fixed effects for time indicated that IL-6 and IL-4 levels increased, while IL-1β, TNF-α and IL-8 levels decreased. There were no significant effects for IL-10 observed. Findings demonstrate increased IL-8 levels among firefighters who received an 8-h sleep when compared to those who had a restricted 4-h sleep. Firefighters' IL-6 levels increased in both conditions which may indicate that a 4-h sleep restriction duration and/or period (i.e., 2 nights) was not a significant enough stressor to affect this cytokine. Considering the immunomodulatory properties of IL-6 and IL-4 that inhibit pro-inflammatory cytokines, the rise in IL-6 and IL-4, independent of increases in IL-1β and TNF-α, could indicate a non-damaging response to the stress of simulated physical firefighting work. However, given the link between chronically elevated cytokine levels and several diseases, further research is needed to determine if firefighters' IL-8 and IL-6 levels are elevated following repeated firefighting deployments across a fire season and over multiple fire seasons.

  12. Automated correction of spin-history related motion artefacts in fMRI : Simulated and phantom data

    NARCIS (Netherlands)

    Muresan, L; Renken, R.; Roerdink, J.B.T.M.; Duifhuis, H.

    This paper concerns the problem of correcting spin-history artefacts in fMRI data. We focus on the influence of through-plane motion on the history of magnetization. A change in object position will disrupt the tissue’s steady-state magnetization. The disruption will propagate to the next few

  13. Changes in stress hormones and metabolism during a 105-day simulated Mars mission.

    Science.gov (United States)

    Strollo, Felice; Vassilieva, Galina; Ruscica, Massimiliano; Masini, Mariangela; Santucci, Daniela; Borgia, Luisa; Magni, Paolo; Celotti, Fabio; Nikiporuc, Igor

    2014-08-01

    The Mars-105 project was aimed at simulating crew's activities, workload, and communication during a mission to Mars, evaluating the homeostatic adaptations to prolonged confinement and cohabitation. Fasting plasma glucose (FPG) and insulin, C-peptide, leptin, cortisol, and NGF and BDNF plasma levels were monitored in six healthy nonsmoking male subjects taking part in a 105-d Mars mission simulation. Samples were collected from each subject before (0 wk), during (2.5 wk; 5 wk; 10 wk; 15 wk), and after confinement (+1 wk). Confinement resulted in impaired glucometabolic parameters, since FPG increased during the first 5 wk (baseline: 85.2 ± 10.8 mg · dl⁻¹; 2.5 wk: 98.4 ± 4.7 mg · dl⁻¹; 5 wk: 92.5 ± 6.0 mg · dl⁻¹) and insulin dropped at 2.5 wk (baseline: 14.4 ± 4.8 mU · L⁻¹; 2.5 wk: 7.7 ± 2.1 mU · L⁻¹), subsequently returning to baseline values. HOMA-IR paralleled plasma insulin, dropping to 1.8 ± 0.5 at 2.5 wk (baseline: 3.0 ± 1.2). At all time-points tested, plasma leptin levels were decreased (baseline: 4.4 ± 3.3 ng · dl⁻¹; 2.5 wk: 1.6 ± 1.2 ng · dl⁻¹; 5 wk: 1.3 ± 0.8 ng · dl⁻¹; 10 wk: 1.5 ± 1.1 ng · dl⁻¹; 15 wk:1.7 ± 0.8 ng · dl⁻¹), whereas cortisol levels were increased (baseline: 10.8 ± 4.9 ng · dl⁻¹; 2.5 wk: 16.8 ± 3.5 ng · dl⁻¹; 5 wk: 18.1 ± 7.6 ng · dl⁻¹; 10 wk: 18.1 ± 8.3 ng · dl⁻¹; 15 wk:14.2 ± 4.4 ng · dl⁻¹), resulting in a negative correlation between these hormones. BDNF levels increased only at 5 and 10 wk (baseline: 67.1 ± 36.0 pg · ml⁻¹; 5 wk: 164 ± 54 pg · ml⁻¹; and 10 wk: 110.2 ± 28.9 pg · ml⁻¹). The data obtained with the Mars-105 experiment suggest that environmental stress has a strong impact upon metabolic and stress response, indicating the need for further studies and the implementation of specific countermeasures.

  14. The influence of die geometry on stress distribution by experimental and FEM simulation on electrolytic copper wiredrawing

    Directory of Open Access Journals (Sweden)

    Leonardo Kyo Kabayama

    2009-09-01

    Full Text Available The study of die geometry is vital in determining the surface and mechanical properties of drawn wires, and consequently, their application. In this work, annealed electrolytic copper wire (ETP, with 0.5 mm original diameter was reduced by 19% in dies with 2β = 10º and 18º and Hc = 35 and 50%. The best experimental results were then studied by the Finite Element Method to simulate residual stress distribution. The experimental results show that the friction coefficient decreases as the wire drawing speed increases, and that low 2β and Hc values bring about the most favorable wiredrawing conditions. The simulation shows a variation in the axial and radial tensions, both for the compression and traction stresses on all regions during the wire drawing process. In conclusion, the influence of the internal die geometry on the drawn wire is clarified.

  15. The feeling of discomfort during vaginal examination, history of abuse and sexual abuse and post-traumatic stress disorder in women.

    Science.gov (United States)

    Güneş, Gizem; Karaçam, Zekiye

    2017-08-01

    To examine the feeling of discomfort during vaginal examinations, history of abuse and sexual abuse and post-traumatic stress disorder in women to determine the correlation between these variables. Women who have experienced abuse or sexual abuse may feel more discomfort during vaginal examinations and may perceive a sensation similar to what they experienced during sexual abuse. Cross-sectional. This study included 320 women receiving a vaginal examination. The data were collected using a questionnaire composed of items related to descriptive characteristics, vaginal examinations and violence, a visual analogue scale of discomfort, and the Post-Traumatic Stress Disorder Scale-civilian version. The mean score for the feeling of discomfort during vaginal examinations was 3·92 ± 3·34; 26·3% of the women described discomfort. Thirty-eight (12%) of the 320 women had experienced emotional violence, 25 (8%) had experienced physical violence, and 25 (8%) had been forced into sexual intercourse by their spouses. Of the women, 64·7% suffered from post-traumatic stress disorder, and physical, emotional and sexual violence were found to increase the possibility of this disorder. Exposure to emotional violence increased the possibility of discomfort during vaginal examinations by 4·5 (OR = 4·482; 95% CI = 1·421-14·134). Post-traumatic stress disorder (OR = 1·038; 95% CI = 1·009-1·066) was found to increase the possibility of discomfort during vaginal examinations; however, as the number of live births increases, women reported a reduction in their discomfort with vaginal examinations. This study revealed a positive correlation between discomfort during vaginal examinations and emotional violence and post-traumatic stress disorder but a negative correlation between discomfort during vaginal examinations and the number of live births. In addition, having a history of abuse and sexual abuse was found to increase post-traumatic stress disorder. Considering

  16. Fish Individual-based Numerical Simulator (FINS): A particle-based model of juvenile salmonid movement and dissolved gas exposure history in the Columbia River Basin

    International Nuclear Information System (INIS)

    Scheibe, Timothy D.; Richmond, Marshall C.

    2002-01-01

    This paper describes a numerical model of juvenile salmonid migration in the Columbia and Snake Rivers. The model, called the Fish Individual-based Numerical Simulator or FINS, employs a discrete, particle-based approach to simulate the migration and history of exposure to dissolved gases of individual fish. FINS is linked to a two-dimensional (vertically-averaged) hydrodynamic simulator that quantifies local water velocity, temperature, and dissolved gas levels as a function of river flow rates and dam operations. Simulated gas exposure histories can be input to biological mortality models to predict the effects of various river configurations on fish injury and mortality due to dissolved gas supersaturation. Therefore, FINS serves as a critical linkage between hydrodynamic models of the river system and models of biological impacts. FINS was parameterized and validated based on observations of individual fish movements collected using radiotelemetry methods during 1997 and 1998 . A quasi-inverse approach was used to decouple fish swimming movements from advection with the local water velocity, allowing inference of time series of non-advective displacements of individual fish from the radiotelemetry data. Statistical analyses of these displacements are presented, and confirm that strong temporal correlation of fish swimming behavior persists in some cases over several hours. A correlated random-walk model was employed to simulate the observed migration behavior, and parameters of the model were estimated that lead to close correspondence between predictions and observations

  17. Simulation investigation of thermal phase transformation and residual stress in single pulse EDM of Ti-6Al-4V

    Science.gov (United States)

    Tang, Jiajing; Yang, Xiaodong

    2018-04-01

    The thermal phase transformation and residual stress are ineluctable in the electrical discharge machining (EDM) process, and they will greatly affect the working performances of the machined surface. This paper presents a simulation study on the thermal phase transformation and residual stress in single-pulse EDM of Ti-6Al-4V, which is the most popular titanium alloy in fields such as aircraft engine and some other leading industries. A multi-physics model including thermal, hydraulic, metallography and structural mechanics was developed. Based on the proposed model, the thickness and metallographic structure of the recast layer and heat affected layer (HAZ) were investigated. The distribution and characteristics of residual stress around the discharge crater were obtained. The recast layer and HAZ at the center of crater are found to be the thinnest, and their thicknesses gradually increase approaching the periphery of the crater. The recast layer undergoes a complete α‧ (martensitic) transformation, while the HAZ is mainly composed by the α  +  β  +  α‧ three-phase microstructure. Along the depth direction of crater, the Von Mises stress increases first and then decreases, reaching its maximal value near the interface of recast layer and HAZ. In the recast layer, both compressive stress component and tensile stress component are observed. ANOVA results showed that the influence of discharge current on maximal tensile stress is more significant than that of pulse duration, while the pulse duration has more significant influence on average thickness of the recast layer and the depth location of the maximal tensile stress. The works conducted in this study will help to evaluate the quality and integrity of EDMed surface, especially when the non-destructive testing is difficult to achieve.

  18. The interplay between Reynolds stress and zonal flows: direct numerical simulation as a bridge between theory and experiment

    International Nuclear Information System (INIS)

    Vergote, M; Schoor, M Van; Xu, Y; Jachmich, S; Weynants, R

    2006-01-01

    We describe the results of a measurement campaign on the CASTOR tokamak where the drive of flows and zonal flows by Reynolds stress was investigated by means of a dual probe head system allowing us to measure the properties of the electrostatic turbulence and the rotation velocities at the same location and at the same moment. We compare these experimental results with a turbulence model linked to a one dimensional fluid model describing the electrostatic turbulence and its influence on the background flow. The turbulence is simulated locally on the basis of the Hasegawa-Wakatani equations, completed with magnetic inhomogeneity terms. In the fluid model the toroidal geometry is correctly taken into account, while various sources and sinks like viscosity, interaction with neutrals, Reynolds stress and electric current induced by biasing are included. The good agreement of the predicted flow with the measured one demonstrates that in a pure cylindrical geometry the modelled strength of Reynolds stress acceleration of flow is overestimated

  19. Colloid volume loading does not mitigate decreases in central blood volume during simulated hemorrhage while heat stressed

    DEFF Research Database (Denmark)

    Crandall, Craig G; Wilson, Thad E; Marving, Jens

    2012-01-01

    attenuates the reduction in regional blood volumes during a simulated hemorrhagic challenge imposed via lower-body negative pressure (LBNP). Seven subjects underwent 30 mmHg LBNP while normothermic, during passive heat stress (increased internal temperature ~1°C), and while continuing to be heated after...... intravenous colloid volume loading (11 ml/kg). Relative changes in torso and regional blood volumes were determined by gamma camera imaging with technetium-99m labeled erythrocytes. Heat stress reduced blood volume in all regions (ranging from 7 to 16%), while subsequent volume loading returned those values...... to normothermic levels. While normothermic, LBNP reduced blood volume in all regions (torso: 22±8%; heart: 18±6%; spleen: 15±8%). During LBNP while heat stressed, the reductions in blood volume in each region were markedly greater when compared to LBNP while normothermic (torso: 73±2%; heart: 72±3%; spleen: 72...

  20. Calcium and Calmodulin Are Involved in Nitric Oxide-Induced Adventitious Rooting of Cucumber under Simulated Osmotic Stress.

    Science.gov (United States)

    Niu, Lijuan; Yu, Jian; Liao, Weibiao; Yu, Jihua; Zhang, Meiling; Dawuda, Mohammed M

    2017-01-01

    Osmotic stress is a major form of abiotic stress that adversely affects growth and development of plants and subsequently reduces yield and quality of crops. In this study, the effect of nitric oxide (NO) and calcium (Ca 2+ ) on the process of adventitious rooting in cucumber ( Cucumis sativus L.) under simulated osmotic stress was investigated. The results revealed that the effect of exogenous NO and Ca 2+ in promoting the development of adventitious roots in cucumber seedlings under simulated osmotic stress was dose-dependent, with a maximal biological response at 10 μM NO donor nitroprusside (SNP) or 200 μM Ca 2+ . The application of Ca 2+ chelators or channel inhibitors and calmodulin (CaM) antagonists significantly reversed NO-induced adventitious rooting, implying that endogenous Ca 2+ /CaM might be involved in NO-induced adventitious rooting under osmotic stress. Moreover, intracellular Ca amount was also increased by NO in cucumber hypocotyls during the development of adventitious roots under osmotic stress. This increase of endogenous Ca 2+ was inhibited by NO specific scavenger 2-(4-carboxyphenyl) -4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide potassium salt (cPTIO), nitrate reductase inhibitors tungstate (Na 2 WO 4 ) and sodium azide (NaN 3 ) . This gives an indication that Ca 2+ might be a downstream signaling molecule in the adventitious root development by NO under osmotic condition. The results also show that NO or Ca 2+ play a positive role in improving plant water status and photosynthetic system by increasing chlorophyll content and photochemical activity in leaves. Furthermore, NO and Ca 2+ treatment might alleviate the negative effects of osmotic stress by decreasing membrane damage and reactive oxygen species (ROS) production by enhancing the activities of superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX). Therefore, Ca 2+ /CaM may act as a downstream signaling molecule in NO-induced development of adventitious root

  1. Variation in the oxytocin receptor gene is associated with increased risk for anxiety, stress and depression in individuals with a history of exposure to early life stress.

    Science.gov (United States)

    Myers, Amanda J; Williams, Leanne; Gatt, Justine M; McAuley-Clark, Erica Z; Dobson-Stone, Carol; Schofield, Peter R; Nemeroff, Charles B

    2014-12-01

    Oxytocin is a neuropeptide that is involved in the regulation of mood, anxiety and social biology. Genetic variation in the oxytocin receptor gene (OXTR) has been implicated in anxiety, depression and related stress phenotypes. It is not yet known whether OXTR interacts with other risk factors such as early life trauma to heighten the severity of experienced anxiety and depression. In this study, we examined genotypes in 653 individuals and tested whether SNP variation in OXTR correlates with severity of features of self-reported experience on the Depression Anxiety and Stress Scale (DASS), and whether this correlation is enhanced when early life trauma is taken into account. We also assessed the effects of OXTR SNPs on RNA expression levels in two separate brain tissue cohorts totaling 365 samples. A significant effect of OXTR genotype on DASS anxiety, stress and depression scores was found and ELS events, in combination with several different OXTR SNPs, were significantly associated with differences in DASS scores with one SNP (rs139832701) showing significant association or a trend towards association for all three measures. Several OXTR SNPs were correlated with alterations in OXTR RNA expression and rs3831817 replicated across both sets of tissues. These results support the hypothesis that the oxytocin system plays a role in the pathophysiology of mood and anxiety disorders. Copyright © 2014 Elsevier Ltd. All rights reserved.

  2. Weld residual stress according to the ways of heat input in the simulation of weld process using finite element analysis

    International Nuclear Information System (INIS)

    Yang, Jun Seog; Lee, Kyoung Soo; Park, Chi Yong

    2008-01-01

    This paper is to discuss distribution of welding residual stresses of a ferritic low alloy steel nozzle with dissimilar metal weld using Alloy 82/182. Two Dimensional (2D) thermo-mechanical finite element analyses are carried out to simulate multi-pass welding process on the basis of the detailed and fabrication data. On performing the welding analysis generally, the characteristics on the heat input and heat transfer of weld are affected on the weld residual stress analyses. Thermal analyses in the welding heat cycle process is very important process in weld residual stress analyses. Therefore, heat is rapidly input to the weld pass material, using internal volumetric heat generation, at a rate which raises the peak weld metal temperature to 2200 .deg. C and the base metal adjacent to the weld to about 1400 .deg. C. These are approximately the temperature that the weld metal and surrounding base materials reach during welding. Also, According to the various ways of applying the weld heat source, the predicted residual stress results are compared with measured axial, hoop and radial through-wall profiles in the heat affected zone of test component. Also, those results are compared with those of full 3-dimensional simulation

  3. In vitro simulator with numerical stress analysis for evaluation of stent-assisted coiling embolization in cerebral aneurysm treatments.

    Science.gov (United States)

    Shi, Chaoyang; Kojima, Masahiro; Tercero, Carlos; Najdovski, Zoran; Ikeda, Seiichi; Fukuda, Toshio; Arai, Fumihito; Negoro, Makoto

    2014-12-01

    There are several complications associated with Stent-assisted Coil Embolization (SACE) in cerebral aneurysm treatments, due to damaging operations by surgeons and undesirable mechanical properties of stents. Therefore, it is necessary to develop an in vitro simulator that provides both training and research for evaluating the mechanical properties of stents. A new in vitro simulator for three-dimensional digital subtraction angiography was constructed, followed by aneurysm models fabricated with new materials. Next, this platform was used to provide training and to conduct photoelastic stress analysis to evaluate the SACE technique. The average interaction stress increasingly varied for the two different stents. Improvements for the Maximum-Likelihood Expectation-Maximization method were developed to reconstruct cross-sections with both thickness and stress information. The technique presented can improve a surgeon's skills and quantify the performance of stents to improve mechanical design and classification. This method can contribute to three-dimensional stress and volume variation evaluation and assess a surgeon's skills. Copyright © 2013 John Wiley & Sons, Ltd.

  4. Importance of Force Decomposition for Local Stress Calculations in Biomembrane Molecular Simulations.

    Science.gov (United States)

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

    2014-02-11

    Local stress fields are routinely computed from molecular dynamics trajectories to understand the structure and mechanical properties of lipid bilayers. These calculations can be systematically understood with the Irving-Kirkwood-Noll theory. In identifying the stress tensor, a crucial step is the decomposition of the forces on the particles into pairwise contributions. However, such a decomposition is not unique in general, leading to an ambiguity in the definition of the stress tensor, particularly for multibody potentials. Furthermore, a theoretical treatment of constraints in local stress calculations has been lacking. Here, we present a new implementation of local stress calculations that systematically treats constraints and considers a privileged decomposition, the central force decomposition, that leads to a symmetric stress tensor by construction. We focus on biomembranes, although the methodology presented here is widely applicable. Our results show that some unphysical behavior obtained with previous implementations (e.g. nonconstant normal stress profiles along an isotropic bilayer in equilibrium) is a consequence of an improper treatment of constraints. Furthermore, other valid force decompositions produce significantly different stress profiles, particularly in the presence of dihedral potentials. Our methodology reveals the striking effect of unsaturations on the bilayer mechanics, missed by previous stress calculation implementations.

  5. Stress !!!

    NARCIS (Netherlands)

    Fledderus, M.

    2012-01-01

    Twee op de vijf UT-studenten hebben last van ernstige studiestress, zo erg zelfs dat het ze in hun privéleven belemmert. Die cijfers komen overeen met het landelijk beeld van stress onder studenten. Samen met 14 andere universiteits- en hogeschoolbladen enquêteerde UT Nieuws bijna 5500 studenten.

  6. Effects of experimentally elevated traffic noise on nestling white-crowned sparrow stress physiology, immune function and life history.

    Science.gov (United States)

    Crino, Ondi L; Johnson, Erin E; Blickley, Jessica L; Patricelli, Gail L; Breuner, Creagh W

    2013-06-01

    Roads have been associated with behavioral and physiological changes in wildlife. In birds, roads decrease reproductive success and biodiversity and increase physiological stress. Although the consequences of roads on individuals and communities have been well described, the mechanisms through which roads affect birds remain largely unexplored. Here, we examine one mechanism through which roads could affect birds: traffic noise. We exposed nestling mountain white-crowned sparrows (Zonotrichia leucophrys oriantha) to experimentally elevated traffic noise for 5 days during the nestling period. Following exposure to traffic noise we measured nestling stress physiology, immune function, body size, condition and survival. Based on prior studies, we expected the traffic noise treatment to result in elevated stress hormones (glucocorticoids), and declines in immune function, body size, condition and survival. Surprisingly, nestlings exposed to traffic noise had lower glucocorticoid levels and improved condition relative to control nests. These results indicate that traffic noise does affect physiology and development in white-crowned sparrows, but not at all as predicted. Therefore, when evaluating the mechanisms through which roads affect avian populations, other factors (e.g. edge effects, pollution and mechanical vibration) may be more important than traffic noise in explaining elevated nestling stress responses in this species.

  7. Early stress, parental motivation, and reproductive decision-making: applications of life history theory to parental behavior.

    Science.gov (United States)

    Cabeza de Baca, Tomás; Ellis, Bruce J

    2017-06-01

    This review focuses on the impact of parental behavior on child development, as interpreted from an evolutionary-developmental perspective. We employ psychosocial acceleration theory to reinterpret the effects of variation in parental investment and involvement on child development, arguing that these effects have been structured by natural selection to match the developing child to current and expected future environments. Over time, an individual's development, physiology, and behavior are organized in a coordinated manner (as instantiated in 'life history strategies') that facilitates survival and reproductive success under different conditions. We review evidence to suggest that parental behavior (1) is strategic and contingent on environmental opportunities and constraints and (2) influences child life history strategies across behavioral, cognitive, and physiological domains. Copyright © 2017 Elsevier Ltd. All rights reserved.

  8. Teaching Women's History.

    Science.gov (United States)

    Fain, George

    1995-01-01

    Argues that women's history should stress the broad sociological view of women's roles not only in politics but in mundane, day-to-day life throughout all of history, rather that reducing women's history to a few token figures. Notes that many college and secondary texts and testing materials have recognized the trend toward the inclusion of…

  9. Measurement and Interpretation of Flow Stress Data for the Simulation of Metal-Forming Processes

    Science.gov (United States)

    2010-01-01

    fitting constants that differ in each equation): Ludwik Equation: c)εb(aσ += , (29) Voce Equation: )]εcexp([1*a][baσ −−−+= (30) Swift...stress at low strains (ɘ.2) and to overestimate the stress for high strains. For heavily prestrained materials, c ~ 1. The Voce and Swift equations tend

  10. Cue-responding in a simulated bad news situation: exploring a stress hypothesis.

    NARCIS (Netherlands)

    Valck, C. de; Bruynooghe, R.; Bensing, J.; Kerssens, J.J.; Hulsman, R.L.

    2001-01-01

    The stress-coping paradigm of Folkman and Lazarus (1984) was applied to investigate if the communicative reactions of the physician in a bad news transaction are related to the stressfulness of the situation. A standardized video bad news consultation was presented to 88 medical students. To examine

  11. Cue-responding in a Simulated Bad News Situation: Exploring a Stress Hypothesis

    NARCIS (Netherlands)

    de Valck, C.; Bruynooghe, R.; Bensing, J. M.; Kerssens, J. J.; Hulsman, R. L.

    2001-01-01

    The stress-coping paradigm of Folkman and Lazarus (1984) was applied to investigate if the communicative reactions of the physician in a bad news transaction are related to the stressfulness of the situation. A standardized video bad news consultation was presented to 88 medical students. To examine

  12. A Comparison of Objective and Subjective Stress in Homogeneous Male and Female Teams in a Mars Simulation

    Science.gov (United States)

    Bishop, S.; Sundaresan, A.

    Introduction The role of stress and its impact on coping performance motivation behavior cognitive functioning and psychological well-being has become a key focus for long duration missions Since all extreme environments are characterized by significant physical demands e g skiing climbing EVAs as well as inescapable environmental characteristics e g imminent danger noise isolation confinement loss of normal sensory stimuli an examination of the impact of prolong stress in analogue environments should provide insight into developing effective support and countermeasures for long duration space crews The presence of even low levels of chronic stressors if not met with functional adaptation and or countermeasures has been shown to produce subjective symptoms of stress persistent performance incompetence accelerated fatiguability altered mood states increased rate of infections and decrements in attention and cognitive Gender has been shown to cut across both individual factors and group factors including response to stress and ways of coping Generally men and women differ in many arenas such as interaction and communication styles need for affiliation responses to crowding privacy and confined spaces Men and women in homogeneous groups interact in significantly different ways than those in mixed groups Therefore differences between genders on subjective and objective responses to stress are of interest The Mars Society Utah Desert Simulation MDRS facility provides a unique opportunity to examine the interaction of

  13. Mesenchymal Stromal Cells Cultured in Serum from Heart Failure Patients Are More Resistant to Simulated Chronic and Acute Stress

    Directory of Open Access Journals (Sweden)

    Timo Z. Nazari-Shafti

    2018-01-01

    Full Text Available Despite regulatory issues surrounding the use of animal-derived cell culture supplements, most clinical cardiac cell therapy trials using mesenchymal stromal cells (MSCs still rely on fetal bovine serum (FBS for cell expansion before transplantation. We sought to investigate the effect of human serum from heart failure patients (HFS on cord blood MSCs (CB-MSCs during short-term culture under regular conditions and during simulated acute and chronic stress. Cell survival, proliferation, metabolic activity, and apoptosis were quantified, and gene expression profiles of selected apoptosis and cell cycle regulators were determined. Compared to FBS, HFS and serum from healthy donors (CS showed similar effects by substantially increasing cell survival during chronic and acute stress and by increasing cell yields 5 days after acute stress. Shortly after the termination of acute stress, both HFS and CS resulted in a marked decrease in apoptotic cells. Transcriptome analysis suggested a decrease in TNF-mediated induction of caspases and decreased activation of mitochondrial apoptosis. Our data confirm that human serum from both healthy donors and heart failure patients results in increased cell yields and increased resistance to cellular stress signals. Therefore, we consider autologous serum a valid alternative to FBS in cell-based therapies addressing severe heart disease.

  14. Numerical Simulation on Open Wellbore Shrinkage and Casing Equivalent Stress in Bedded Salt Rock Stratum

    Directory of Open Access Journals (Sweden)

    Jianjun Liu

    2013-01-01

    Full Text Available Most salt rock has interbed of mudstone in China. Owing to the enormous difference of mechanical properties between the mudstone interbed and salt rock, the stress-strain and creep behaviors of salt rock are significantly influenced by neighboring mudstone interbed. In order to identify the rules of wellbore shrinkage and casings equivalent stress in bedded salt rock stratum, three-dimensional finite difference models were established. The effects of thickness and elasticity modulus of mudstone interbed on the open wellbore shrinkage and equivalent stress of casing after cementing operation were studied, respectively. The results indicate that the shrinkage of open wellbore and equivalent stress of casings decreases with the increase of mudstone interbed thickness. The increasing of elasticity modulus will reduce the shrinkage of open wellbore and casing equivalent stress. Research results can provide the scientific basis for the design of mud density and casing strength.

  15. Simulation of thermal stresses in anode-supported solid oxide fuel cell stacks. Part II: Loss of gas-tightness, electrical contact and thermal buckling

    Science.gov (United States)

    Nakajo, Arata; Wuillemin, Zacharie; Van herle, Jan; Favrat, Daniel

    Structural stability issues in planar solid oxide fuel cells arise from the mismatch between the coefficients of thermal expansion of the components. The stress state at operating temperature is the superposition of several contributions, which differ depending on the component. First, the cells accumulate residual stresses due to the sintering phase during the manufacturing process. Further, the load applied during assembly of the stack to ensure electric contact and flatten the cells prevents a completely stress-free expansion of each component during the heat-up. Finally, thermal gradients cause additional stresses in operation. The temperature profile generated by a thermo-electrochemical model implemented in an equation-oriented process modelling tool (gPROMS) was imported into finite-element software (ABAQUS) to calculate the distribution of stress and contact pressure on all components of a standard solid oxide fuel cell repeat unit. The different layers of the cell in exception of the cathode, i.e. anode, electrolyte and compensating layer were considered in the analysis to account for the cell curvature. Both steady-state and dynamic simulations were performed, with an emphasis on the cycling of the electrical load. The study includes two different types of cell, operation under both thermal partial oxidation and internal steam-methane reforming and two different initial thicknesses of the air and fuel compressive sealing gaskets. The results generated by the models are presented in two papers: Part I focuses on cell cracking. In the present paper, Part II, the occurrences of loss of gas-tightness in the compressive gaskets and/or electrical contact in the gas diffusion layer were identified. In addition, the dependence on temperature of both coefficients of thermal expansion and Young's modulus of the metallic interconnect (MIC) were implemented in the finite-element model to compute the plastic deformation, while the possibilities of thermal buckling

  16. Comparative study on the stress corrosion cracking of X70 pipeline steel in simulated shallow and deep sea environments

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Feilong [Corrosion and Protection Center, University of Science and Technology Beijing, Beijing 100083 (China); Key Laboratory of Corrosion and Protection of Ministry of Education, Beijing 100083 (China); China Building Material Test & Certification Group Co. Ltd., Beijing 100024 (China); Ren, Shuai [Corrosion and Protection Center, University of Science and Technology Beijing, Beijing 100083 (China); Key Laboratory of Corrosion and Protection of Ministry of Education, Beijing 100083 (China); Li, Zhong [Department of Chemical and Materials Engineering, University of Alberta, Edmonton, AB, Canada T6G 2G6 (Canada); Liu, Zhiyong, E-mail: liuzhiyong7804@ustb.edu.cn [Corrosion and Protection Center, University of Science and Technology Beijing, Beijing 100083 (China); Key Laboratory of Corrosion and Protection of Ministry of Education, Beijing 100083 (China); Li, Xiaogang; Du, Cuiwei [Corrosion and Protection Center, University of Science and Technology Beijing, Beijing 100083 (China); Key Laboratory of Corrosion and Protection of Ministry of Education, Beijing 100083 (China)

    2017-02-08

    The stress corrosion cracking (SCC) behavior of X70 steel in simulated shallow and deep sea environments was studied using potentiodynamic polarization measurement, a slow strain rate tensile (SSRT) test and scanning electron microscopy (SEM). The results indicate that the predominant cathodic reaction changes from an oxygen reduction reaction to the hydrogen evolution reaction as the dissolved oxygen (DO) content decreases. In the simulated deep sea environment, the SCC susceptibility of X70 steel decreased first, reached its lowest point at 15 MPa and then increased as the simulated sea hydrostatic pressure (HP) further increased. This is consistent with the regularity for the change of the cathodic hydrogen evolution reaction current density i{sub H} at E{sub corr}, which indicates that the HP may influence the SCC susceptibility of X70 steel by changing the permeated hydrogen concentration.

  17. Simulation of residual stresses and deformations in electron beam-welded copper canisters

    International Nuclear Information System (INIS)

    Aronen, A.; Leikko, J.; Taskinen, P.; Karvinen, R.

    2013-07-01

    This report presents the modelling of residual stresses and deformations of an EB-welded copper canister. Two different mock-up lengths are modelled with the Abaqus FEA program, and the similarity of those results is studied. Canister mock-ups of 450 mm and 915 mm were chosen for the test cases. The heat treatment results presented in Taskinen 2009 are used as input data for the mechanical model. For the mechanical analysis some simplifications were made to the model. The contact surface between pipe and lid is assumed to be tied and support from the bottom surface is provided with four support points. Results show that, due to the similarity of 450 mm and 915 mm canisters, the short mock-up can be used to predict the stresses and deformation on a full-length canister (5000 mm). The similarity of the temperature fields has already been shown in the previous reports (Taskinen 2009). The main result in the deformation is the shape of the canister in the residual state. The top of the canister tries to shrink, resulting in the lid buckling inwards. The deformation of the lid of the canister is about 2.2 mm at the centre of the lid. The main results in the stresses are the stress level on the surface, the deviation of stresses over the circle and the stresses near the welding. On the surface there are areas where the circumferential stress is at tension. However, radial and axial stresses are usually in compression on the surface. The deviation of the stress level over the circle is quite small, except in the overlap area and near it. The residual stresses from 0 deg C to 45 deg C change remarkably, but over the rest of the area the stresses are more constant. Near the welding the stresses on the top surface are in compression, but in the centre of the welding the stresses are in tension. In the modelling, the possibility of calculating a mechanical model with the contact surface between pipe and lid, so that they could be separated during the welding, was also tested

  18. Simulation of residual stresses and deformations in electron beam-welded copper canisters

    Energy Technology Data Exchange (ETDEWEB)

    Aronen, A.; Leikko, J.; Taskinen, P.; Karvinen, R. [Tampere Univ. of Technology (Finland)

    2013-07-15

    This report presents the modelling of residual stresses and deformations of an EB-welded copper canister. Two different mock-up lengths are modelled with the Abaqus FEA program, and the similarity of those results is studied. Canister mock-ups of 450 mm and 915 mm were chosen for the test cases. The heat treatment results presented in Taskinen 2009 are used as input data for the mechanical model. For the mechanical analysis some simplifications were made to the model. The contact surface between pipe and lid is assumed to be tied and support from the bottom surface is provided with four support points. Results show that, due to the similarity of 450 mm and 915 mm canisters, the short mock-up can be used to predict the stresses and deformation on a full-length canister (5000 mm). The similarity of the temperature fields has already been shown in the previous reports (Taskinen 2009). The main result in the deformation is the shape of the canister in the residual state. The top of the canister tries to shrink, resulting in the lid buckling inwards. The deformation of the lid of the canister is about 2.2 mm at the centre of the lid. The main results in the stresses are the stress level on the surface, the deviation of stresses over the circle and the stresses near the welding. On the surface there are areas where the circumferential stress is at tension. However, radial and axial stresses are usually in compression on the surface. The deviation of the stress level over the circle is quite small, except in the overlap area and near it. The residual stresses from 0 deg C to 45 deg C change remarkably, but over the rest of the area the stresses are more constant. Near the welding the stresses on the top surface are in compression, but in the centre of the welding the stresses are in tension. In the modelling, the possibility of calculating a mechanical model with the contact surface between pipe and lid, so that they could be separated during the welding, was also tested

  19. Contributions to Executive Dysfunction in Operation Enduring Freedom/Operation Iraqi Freedom Veterans With Posttraumatic Stress Disorder and History of Mild Traumatic Brain Injury.

    Science.gov (United States)

    Jurick, Sarah M; Crocker, Laura D; Sanderson-Cimino, Mark; Keller, Amber V; Trenova, Liljana S; Boyd, Briana L; Twamley, Elizabeth W; Rodgers, Carie S; Schiehser, Dawn M; Aupperle, Robin L; Jak, Amy J

    Posttraumatic stress disorder (PTSD), history of mild traumatic brain injury (mTBI), and executive function (EF) difficulties are prevalent in Operation Enduring Freedom/Operation Iraqi Freedom (OEF/OIF) Veterans. We evaluated the contributions of injury variables, lower-order cognitive component processes (processing speed/attention), and psychological symptoms to EF. OEF/OIF Veterans (N = 65) with PTSD and history of mTBI were administered neuropsychological tests of EF and self-report assessments of PTSD and depression. Those impaired on one or more EF measures had higher PTSD and depression symptoms and lower processing speed/attention performance than those with intact performance on all EF measures. Across participants, poorer attention/processing speed performance and higher psychological symptoms were associated with worse performance on specific aspects of EF (eg, inhibition and switching) even after accounting for injury variables. Although direct relationships between EF and injury variables were equivocal, there was an interaction between measures of injury burden and processing speed/attention such that those with greater injury burden exhibited significant and positive relationships between processing speed/attention and inhibition/switching, whereas those with lower injury burden did not. Psychological symptoms as well as lower-order component processes of EF (attention and processing speed) contribute significantly to executive dysfunction in OEF/OIF Veterans with PTSD and history of mTBI. However, there may be equivocal relationships between injury variables and EF that warrant further study. Results provide groundwork for more fully understanding cognitive symptoms in OEF/OIF Veterans with PTSD and history of mTBI that can inform psychological and cognitive interventions in this population.

  20. Log-layer mismatch and modeling of the fluctuating wall stress in wall-modeled large-eddy simulations

    Science.gov (United States)

    Yang, Xiang I. A.; Park, George Ilhwan; Moin, Parviz

    2017-10-01

    Log-layer mismatch refers to a chronic problem found in wall-modeled large-eddy simulation (WMLES) or detached-eddy simulation, where the modeled wall-shear stress deviates from the true one by approximately 15 % . Many efforts have been made to resolve this mismatch. The often-used fixes, which are generally ad hoc, include modifying subgrid-scale stress models, adding a stochastic forcing, and moving the LES-wall-model matching location away from the wall. An analysis motivated by the integral wall-model formalism suggests that log-layer mismatch is resolved by the built-in physics-based temporal filtering. In this work we investigate in detail the effects of local filtering on log-layer mismatch. We show that both local temporal filtering and local wall-parallel filtering resolve log-layer mismatch without moving the LES-wall-model matching location away from the wall. Additionally, we look into the momentum balance in the near-wall region to provide an alternative explanation of how LLM occurs, which does not necessarily rely on the numerical-error argument. While filtering resolves log-layer mismatch, the quality of the wall-shear stress fluctuations predicted by WMLES does not improve with our remedy. The wall-shear stress fluctuations are highly underpredicted due to the implied use of LES filtering. However, good agreement can be found when the WMLES data are compared to the direct numerical simulation data filtered at the corresponding WMLES resolutions.

  1. Simulations

    CERN Document Server

    Ngada, Narcisse

    2015-06-15

    The complexity and cost of building and running high-power electrical systems make the use of simulations unavoidable. The simulations available today provide great understanding about how systems really operate. This paper helps the reader to gain an insight into simulation in the field of power converters for particle accelerators. Starting with the definition and basic principles of simulation, two simulation types, as well as their leading tools, are presented: analog and numerical simulations. Some practical applications of each simulation type are also considered. The final conclusion then summarizes the main important items to keep in mind before opting for a simulation tool or before performing a simulation.

  2. Numerical simulations on the temperature gradient and thermal stress of a thermoelectric power generator

    International Nuclear Information System (INIS)

    Wu, Yongjia; Ming, Tingzhen; Li, Xiaohua; Pan, Tao; Peng, Keyuan; Luo, Xiaobing

    2014-01-01

    Highlights: • An appropriate ceramic plate thickness is effective in alleviating the thermal stress. • A smaller distance between thermo-pins can help prolong lifecycle of the TE module. • Either a thicker or a thinner copper conducting strip effectively reduces thermal stress. • A suitable tin soldering thickness will alleviate thermal stress intensity and increase thermal efficiency. - Abstract: Thermoelectric generator is a device taking advantage of the temperature difference in thermoelectric material to generate electric power, where the higher the temperature difference of the hot-cold ends, the higher the efficiency will be. However, higher temperature or higher heat flux upon the hot end will cause strong thermal stress which will negatively influence the lifecycle of the thermoelectric module. This phenomenon is very common in industrial applications but seldom has research work been reported. In this paper, numerical analysis on the thermodynamics and thermal stress performance of the thermoelectric module has been performed, considering the variation on the thickness of materials; the influence of high heat flux on thermal efficiency, power output, and thermal stress has been examined. It is found that under high heat flux imposing upon the hot end, the thermal stress is so strong that it has a decisive effect on the life expectation of the device. To improve the module’s working condition, different geometrical configurations are tested and the optimum sizes are achieved. Besides, the side effects on the efficiency, power output, and open circuit voltage output of the thermoelectric module are taken into consideration

  3. Effects of simulated microgravity on surfactant and water balance of lung in animals with different resistance to stress

    Science.gov (United States)

    Bryndina, Irina; Vasilieva, Natalia

    Weightlessness is accompanied by redistribution of blood flow in lung, changes of lung volumes and gas exchange (Prisk et al., 2002; Grigoriev, Baranov, 2003). On the other hand, it is known that microgravity is considered as a kind of moderate stress (Grigoriev et al., 2004). Stress response may differ in animals resistant or vulnerable to stress (Sudakov, 2007). To study the effects of simulated microgravity upon lung, we used 20 male albino rats tested for behavior in the "open field" and than divided into active (stress resistant - SR ) and passive (stress vulnerable - CV) groups. Two mouse lines were used with similar goal - C57Bl/6 and BALB/c mice (n=16). According to data obtained earlier, BALB/c mice referred as more stress vulnerable, in contrast to C57BL/6 mice, which are considered to be relatively stress resistant (Flint et al., 2007). We have previously shown that changes in lung surfactant system after psychosocial stress or long-term immobilization are less pronounced in stress resistant rats (Vasilieva, Bryndina, 2012). The aim of this work is to study the properties and biochemical composition of pulmonary surfactant and lung water balance in rats and mice with different stress resistance in antiorthostatic suspension (AOS) of short and long duration. Simulated microgravity was reproduced according to procedure of Ilyin-Novikov in modification of Morey-Holton. The duration of exposure was 10 days for rats and 30 days for mice. The properties of pulmonary surfactant were assessed by the evaluation of surface activity (surface tension - ST), the content of total phospholipids (PL) and their fractions. Simultaneously we calculated the gravimetric water balance indices: lung coefficient, "dry residue" and wet-to-dry ratio. Total and extravascular lung fluid and pulmonary blood supply were estimated as well. The experiments demonstrated that there was a decrease of surface tension of surfactant films after 10-day AOS in both groups of rats (to a greater

  4. Simulation of Stress Concentration Problems in Laminated Plates by Quasi-Trefftz Finite Element Models

    Directory of Open Access Journals (Sweden)

    Flávio Luiz de Silva Bussamra

    Full Text Available Abstract Hybrid quasi-Trefftz finite elements have been applied with success to the analysis of laminated plates. Two independent fields are approximated by linearly independent, hierarchical polynomials: the stress basis in the domain, adapted from Papkovitch-Neuber solution of Navier equations, and the displacement basis, defined on element surface. The stress field that satisfies the Trefftz constraint a priori for isotropic material is adapted for orthotropic materials, which leads to the term "quasi". In this work, the hexahedral hybrid quasi-Trefftz stress element is applied to the modeling of nonsymmetric laminates and laminated composite plates with geometric discontinuities. The hierarchical p-refinement is exploited.

  5. Psychological and support interventions to reduce levels of stress, anxiety or depression on women's subsequent pregnancy with a history of miscarriage: an empty systematic review.

    Science.gov (United States)

    San Lazaro Campillo, Indra; Meaney, Sarah; McNamara, Karen; O'Donoghue, Keelin

    2017-09-07

    The aim of this systematic review was to assess the effect of interventions to reduce stress in pregnant women with a history of miscarriage. A systematic review of randomised controlled trials (RCTs). A total of 13 medical, psychological and social electronic databases were searched from January 1995 to April 2016 including PUBMED, CENTRAL, Web of Science and EMBASE. This review focused on women in their subsequent pregnancy following miscarriage. All published RCTs which assessed the effect of non-medical interventions such as counselling or support interventions on psychological and mental health outcomes such as stress, anxiety or depression when compared with a control group were included. Stress, anxiety or depression had to be measured at least preintervention and postintervention. This systematic review found no RCT which met our initial inclusion criteria. Of the 4140 titles screened, 17 RCTs were identified. All of them were excluded. One RCT, which implemented a caring-based intervention, included pregnant women in their subsequent pregnancy; however, miscarriage was analysed as a composite variable among other pregnancy losses such as stillbirth and neonatal death. Levels of perceived stress were measured by four RCTs. Different types of non-medical interventions, time of follow-up and small sample sizes were found. Cohort studies and RCTs in non-pregnant women suggest that support and psychological interventions may improve pregnant women's psychological well-being after miscarriage. This improvement may reduce adverse pregnancy-related outcomes in subsequent pregnancies. However, this review found no RCTs which met our criteria. There is a need for targeted RCTs that can provide reliable and conclusive results to determine effective interventions for this vulnerable group. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2017. All rights reserved. No commercial use is permitted unless otherwise expressly

  6. Infant sleep and feeding patterns are associated with maternal sleep, stress, and depressed mood in women with a history of major depressive disorder (MDD).

    Science.gov (United States)

    Sharkey, Katherine M; Iko, Ijeoma N; Machan, Jason T; Thompson-Westra, Johanna; Pearlstein, Teri B

    2016-04-01

    Our goal was to examine associations of infant sleep and feeding patterns with maternal sleep and mood among women at risk for postpartum depression. Participants were 30 women (age ± SD = 28.3 ± 5.1 years) with a history of MDD (but not in a mood episode at enrollment) who completed daily sleep diaries, wore wrist actigraphs to estimate sleep, and had their mood assessed with the Hamilton Depression Rating Scale (HAM-D-17) during four separate weeks of the perinatal period (33 weeks pregnancy and weeks 2, 6, and 16 postpartum). They logged their infants' sleep and feeding behaviors daily and reported postnatal stress on the Childcare Stress Inventory (CSI) at week 16. Mothers' actigraphically estimated sleep showed associations with infant sleep and feeding patterns only at postpartum week 2. Shorter duration of the longest infant-sleep bout was associated with shorter maternal sleep duration (p = .02) and lower sleep efficiency (p = .04), and maternal sleep efficiency was negatively associated with the number of infant-sleep bouts (p = .008) and duration of infant feeding (p = .008). Neither infant sleep nor feeding was associated with maternal sleep at 6 or 16 weeks, but more disturbed infant sleep and more frequent feeding at 6 weeks were associated with higher HAM-D scores at 6 and 16 weeks and higher CSI scores. Sleep in the mother-infant dyad is most tightly linked in the early postpartum weeks, but mothers continue to experience disturbed sleep and infant sleep and feeding behaviors continue to be associated with mothers' depressive symptoms and stress ratings as long as 16 weeks postpartum. These data imply that interventions designed to improve maternal sleep and postpartum mood should include both mothers and infants because improving infant sleep alone is not likely to improve maternal sleep, and poor infant sleep is linked to postpartum depression and stress.

  7. Infant Sleep and Feeding Patterns are Associated with Maternal Sleep, Stress, and Depressed Mood in Women with a History of Major Depressive Disorder

    Science.gov (United States)

    Sharkey, Katherine M.; Iko, Ijeoma N.; Machan, Jason T.; Thompson-Westra, Johanna; Pearlstein, Teri B.

    2015-01-01

    Purpose Our goal was to examine associations of infant sleep and feeding patterns with maternal sleep and mood among women at risk for postpartum depression. Methods Participants were 30 women (age±SD = 28.3±5.1 years) with a history of MDD (but not in a mood episode at enrollment) who completed daily sleep diaries, wore wrist actigraphs to estimate sleep, and had mood assessed with the Hamilton Depression Rating Scale (HAM-D-17) during 4 separate weeks of the perinatal period (33 weeks pregnancy and weeks 2, 6, and 16 postpartum). They logged their infants’ sleep and feeding behaviors daily and reported postnatal stress on the Childcare Stress Inventory (CSI) at week 16. Results Mothers’ actigraphically-estimated sleep showed associations with infant sleep and feeding patterns only at postpartum week 2. Shorter duration of the longest infant sleep bout was associated with shorter maternal sleep duration (p=.02) and lower sleep efficiency (p=.04), and maternal sleep efficiency was negatively associated with number of infant sleep bouts (p =.008) and duration of infant feeding (p =.008). Neither infant sleep nor feeding was associated with maternal sleep at 6 or 16 weeks, but more disturbed infant sleep and more frequent feeding at 6 weeks were associated with higher HAM-D scores at 6 and 16 weeks and higher CSI scores. Conclusions Sleep in the mother-infant dyad is most tightly linked in the early postpartum weeks, but mothers continue to experience disturbed sleep and infant sleep and feeding behaviors continue to be associated with mothers’ depressive symptoms and stress ratings as long as 16 weeks postpartum. These data imply that interventions designed to improve maternal sleep and postpartum mood should include both mothers and infants, because improving infant sleep alone is not likely to improve maternal sleep and poor infant sleep is linked to postpartum depression and stress. PMID:26228760

  8. Crash simulation of hybrid structures considering the stress and strain rate dependent material behavior of thermoplastic materials

    Science.gov (United States)

    Hopmann, Ch.; Schöngart, M.; Weber, M.; Klein, J.

    2015-05-01

    Thermoplastic materials are more and more used as a light weight replacement for metal, especially in the automotive industry. Since these materials do not provide the mechanical properties, which are required to manufacture supporting elements like an auto body or a cross bearer, plastics are combined with metals in so called hybrid structures. Normally, the plastics components are joined to the metal structures using different technologies like welding or screwing. Very often, the hybrid structures are made of flat metal parts, which are stiffened by a reinforcement structure made of thermoplastic materials. The loads on these structures are very often impulsive, for example in the crash situation of an automobile. Due to the large stiffness variation of metal and thermoplastic materials, complex states of stress and very high local strain rates occur in the contact zone under impact conditions. Since the mechanical behavior of thermoplastic materials is highly dependent on these types of load, the crash failure of metal plastic hybrid parts is very complex. The problem is that the normally used strain rate dependent elastic/plastic material models are not capable to simulate the mechanical behavior of thermoplastic materials depended on the state of stress. As part of a research project, a method to simulate the mechanical behavior of hybrid structures under impact conditions is developed at the IKV. For this purpose, a specimen for the measurement of mechanical properties dependet on the state of stress and a method for the strain rate depended characterization of thermoplastic materials were developed. In the second step impact testing is performed. A hybrid structure made from a metal sheet and a reinforcement structure of a Polybutylenterephthalat Polycarbonate blend is tested under impact conditions. The measured stress and strain rate depended material data are used to simulate the mechanical behavior of the hybrid structure under highly dynamic load with

  9. SIMULATION OF THE stress-strain state of excavation BOUNDARIES in fractured massifs

    Directory of Open Access Journals (Sweden)

    Nizomov Dzhahongir Nizomovich

    2012-07-01

    Any limiting process, namely, if or and any results are in line with the isotropic medium. The proposed algorithm and calculation pattern may be used to research the concentrated stresses alongside the boundaries of hydrotechnical engineering facilities.

  10. Finite Element Simulation of Shot Peening: Prediction of Residual Stresses and Surface Roughness

    Science.gov (United States)

    Gariépy, Alexandre; Perron, Claude; Bocher, Philippe; Lévesque, Martin

    Shot peening is a surface treatment that consists of bombarding a ductile surface with numerous small and hard particles. Each impact creates localized plastic strains that permanently stretch the surface. Since the underlying material constrains this stretching, compressive residual stresses are generated near the surface. This process is commonly used in the automotive and aerospace industries to improve fatigue life. Finite element analyses can be used to predict residual stress profiles and surface roughness created by shot peening. This study investigates further the parameters and capabilities of a random impact model by evaluating the representative volume element and the calculated stress distribution. Using an isotropic-kinematic hardening constitutive law to describe the behaviour of AA2024-T351 aluminium alloy, promising results were achieved in terms of residual stresses.

  11. Design and simulation of thermal residual stresses of coatings on WC-Co cemented carbide cutting tool substrate

    International Nuclear Information System (INIS)

    Li, Anhai; Zhao, Jun; Zang, Jian; Zheng, Wei

    2016-01-01

    Large thermal residual stresses in coatings during the coating deposition process may easily lead to coating delamination of coated carbide tools in machining. In order to reduce the possibility of coating delamination during the tool failure process, a theoretical method was proposed and a numerical method was constructed for the coating design of WC-Co cemented carbide cutting tools. The thermal residual stresses of multi-layered coatings were analytically modeled based on equivalent parameters of coating properties, and the stress distribution of coatings are simulated by Finite element method (FEM). The theoretically calculated results and the FEM simulated results were verified and in good agreement with the experimental test results. The effects of coating thickness, tool substrate, coating type and interlayer were investigated by the proposed geometric and FEM model. Based on the evaluations of matchability of tool substrate and tool coatings, the basic principles of tool coating design were proposed. This provides theoretical basis for the selection and design of coatings of cutting tools in high-speed machining

  12. STRESS LOADING SIMULATION OF HYDRO-MECHANICAL TRANSMISSION OF DUMP TRUCK

    OpenAIRE

    S. A. Sidorov

    2006-01-01

    The Transmission model and software package to investigate stress loading of a hydromechanical transmission of a dump truck have been developed. The given software package allows to model stress loading of transmission gears in taking-off and acceleration modes at various road resistance, positions of an engine control pedal and initial revolutions of an engine crankshaft, various laws of friction clutch switching and some other parameters that permit to reveal a rate of various operational m...

  13. Face, Content, and Construct Validations of Endoscopic Needle Injection Simulator for Transurethral Bulking Agent in Treatment of Stress Urinary Incontinence.

    Science.gov (United States)

    Farhan, Bilal; Soltani, Tandis; Do, Rebecca; Perez, Claudia; Choi, Hanul; Ghoniem, Gamal

    2018-05-02

    Endoscopic injection of urethral bulking agents is an office procedure that is used to treat stress urinary incontinence secondary to internal sphincteric deficiency. Validation studies important part of simulator evaluation and is considered important step to establish the effectiveness of simulation-based training. The endoscopic needle injection (ENI) simulator has not been formally validated, although it has been used widely at University of California, Irvine. We aimed to assess the face, content, and construct validity of the UC, Irvine ENI simulator. Dissected female porcine bladders were mounted in a modified Hysteroscopy Diagnostic Trainer. Using routine endoscopic equipment for this procedure with video monitoring, 6 urologists (experts group) and 6 urology trainee (novice group) completed urethral bulking agents injections on a total of 12 bladders using ENI simulator. Face and content validities were assessed by using structured quantitative survey which rating the realism. Construct validity was assessed by comparing the performance, time of the procedure, and the occlusive (anatomical and functional) evaluations between the experts and novices. Trainees also completed a postprocedure feedback survey. Effective injections were evaluated by measuring the retrograde urethral opening pressure, visual cystoscopic coaptation, and postprocedure gross anatomic examination. All 12 participants felt the simulator was a good training tool and should be used as essential part of urology training (face validity). ENI simulator showed good face and content validity with average score varies between the experts and the novices was 3.9/5 and 3.8/5, respectively. Content validity evaluation showed that most aspects of the simulator were adequately realistic (mean Likert scores 3.9-3.8/5). However, the bladder does not bleed, and sometimes thin. Experts significantly outperformed novices (p ENI simulator shows face, content and construct validities, although few

  14. Design and Simulation of an RF-MEMS Switch and analysis of its Electromagnetic aspect in realtion to stress

    Directory of Open Access Journals (Sweden)

    Amna Riaz

    2018-01-01

    Full Text Available Microelectromechanical Systems (MEMS are devices made up of several electrical and mechanical components. They consist of mechanical functions (sensing, thermal, inertial and electrical functions (switching, decision making on a single chip made by microfabrication methods. These chips exhibit combined properties of the two functions. The size of system has characteristic dimensions less than 1mm but more than 1μm. The configuration of these components determine the final deliverables of the switch. MEMS can be designed to meet user requirements on any level from microbiological application such as biomedical transducers or tissue engineering, to mechanical systems such as microfluidic diagnoses or chemical fuel cells. The low cost, small mass and minimal power consumption of the MEMS makes it possible to readily integrate to any kind of system in any environment. MEMS are faster, better and cheaper. They offer excellent electrical performances. MEMS working at Radio frequencies are RF MEMS. RF-MEMS switches find huge market in the modern telecommunication networks, biological, automobiles, satellites and defense systems because of their lower power consumptions at relatively higher frequencies and better electrical performances. But the reliability is the major hurdle in the fate of RF MEMS switches. Reliability mainly arises due to the presence of residual stresses, charging current, fatigue and creep and contact degradation. The presence of residual stresses in switches the S-Parameters of the switches are affected badly and the residual stress affects the final planarity of the fabricated structure. Design and simulation of an RF-MEMS switch is proposed considering the residual stresses in both on and off state. The operating frequency band is being optimized and the best possible feasible fabrication technique for the proposed switch design is being analyzed. S-Parameters are calculated and a comparison for the switches with stress and

  15. Stress.

    Science.gov (United States)

    Chambers, David W

    2008-01-01

    We all experience stress as a regular, and sometimes damaging and sometimes useful, part of our daily lives. In our normal ups and downs, we have our share of exhaustion, despondency, and outrage--matched with their corresponding positive moods. But burnout and workaholism are different. They are chronic, dysfunctional, self-reinforcing, life-shortening habits. Dentists, nurses, teachers, ministers, social workers, and entertainers are especially susceptible to burnout; not because they are hard-working professionals (they tend to be), but because they are caring perfectionists who share control for the success of what they do with others and perform under the scrutiny of their colleagues (they tend to). Workaholics are also trapped in self-sealing cycles, but the elements are ever-receding visions of control and using constant activity as a barrier against facing reality. This essay explores the symptoms, mechanisms, causes, and successful coping strategies for burnout and workaholism. It also takes a look at the general stress response on the physiological level and at some of the damage American society inflicts on itself.

  16. FE-simulation of hot forging with an integrated heat treatment with the objective of residual stress prediction

    Science.gov (United States)

    Behrens, Bernd-Arno; Chugreeva, Anna; Chugreev, Alexander

    2018-05-01

    Hot forming as a coupled thermo-mechanical process comprises numerous material phenomena with a corresponding impact on the material behavior during and after the forming process as well as on the final component performance. In this context, a realistic FE-simulation requires reliable mathematical models as well as detailed thermo-mechanical material data. This paper presents experimental and numerical results focused on the FE-based simulation of a hot forging process with a subsequent heat treatment step aiming at the prediction of the final mechanical properties and residual stress state in the forged component made of low alloy CrMo-steel DIN 42CrMo4. For this purpose, hot forging experiments of connecting rod geometry with a corresponding metallographic analysis and x-ray residual stress measurements have been carried out. For the coupled thermo-mechanical-metallurgical FE-simulations, a special user-defined material model based on the additive strain decomposition method and implemented in Simufact Forming via MSC.Marc solver features has been used.

  17. Simulations of stress evolution and the current density scaling of electromigration-induced failure times in pure and alloyed interconnects

    Science.gov (United States)

    Park, Young-Joon; Andleigh, Vaibhav K.; Thompson, Carl V.

    1999-04-01

    An electromigration model is developed to simulate the reliability of Al and Al-Cu interconnects. A polynomial expression for the free energy of solution by Murray [Int. Met. Rev. 30, 211 (1985)] was used to calculate the chemical potential for Al and Cu while the diffusivities were defined based on a Cu-trapping model by Rosenberg [J. Vac. Sci. Technol. 9, 263 (1972)]. The effects of Cu on stress evolution and lifetime were investigated in all-bamboo and near-bamboo stud-to-stud structures. In addition, the significance of the effect of mechanical stress on the diffusivity of both Al and Cu was determined in all-bamboo and near-bamboo lines. The void nucleation and growth process was simulated in 200 μm, stud-to-stud lines. Current density scaling behavior for void-nucleation-limited failure and void-growth-limited failure modes was simulated in long, stud-to-stud lines. Current density exponents of both n=2 for void nucleation and n=1 for void growth failure modes were found in both pure Al and Al-Cu lines. Limitations of the most widely used current density scaling law (Black's equation) in the analysis of the reliability of stud-to-stud lines are discussed. By modifying the input materials properties used in this model (when they are known), this model can be adapted to predict the reliability of other interconnect materials such as pure Cu and Cu alloys.

  18. Simulation of tensile stress-strain properties of irradiated type 316 SS by heavily cold-worked material

    International Nuclear Information System (INIS)

    Muto, Yasushi; Jitsukawa, Shiro; Hishinuma, Akimichi

    1995-07-01

    Type 316 stainless steel is one of the most promising candidate materials to be used for the structural parts of plasma facing components in the nuclear fusion reactor. The neutron irradiation make the material brittle and reduces its uniform elongation to almost zero at heavy doses. In order to apply such a material of reduced ductility to structural components, the structural integrity should be examined and assured by the fracture mechanics. The procedure requires a formulated stress-strain relationship. However, the available irradiated tensile test data are very limited at present, so that the cold-worked material was used as a simulated material in this study. Property changes of 316 SS, that is, a reduction of uniform elongation and an enhancement of yield stress are seemingly very similar for both the irradiated 316 SS and the cold-worked one. The specimens made of annealed 316 SS, 20% (or 15%) cold worked one and 40% cold worked one were prepared. After the formulation of stress strain behavior, the equation for the cold-worked 316 SS was fitted to the data on irradiated material under the assumption that the yield stress is the same for both materials. In addition, the upper limit for the plastic strain was introduced using the data on the irradiated material. (author)

  19. Precursor Evolution and Stress Corrosion Cracking Initiation of Cold-Worked Alloy 690 in Simulated Pressurized Water Reactor Primary Water

    Energy Technology Data Exchange (ETDEWEB)

    Zhai, Ziqing [Pacific Northwest National Laboratory, 622 Horn Rapids Road, P.O. Box 999, Richland, Washington 99352.; Toloczko, Mychailo [Pacific Northwest National Laboratory, 622 Horn Rapids Road, P.O. Box 999, Richland, Washington 99352.; Kruska, Karen [Pacific Northwest National Laboratory, 622 Horn Rapids Road, P.O. Box 999, Richland, Washington 99352.; Bruemmer, Stephen [Pacific Northwest National Laboratory, 622 Horn Rapids Road, P.O. Box 999, Richland, Washington 99352.

    2017-05-22

    Stress corrosion crack initiation of two thermally-treated, cold-worked (CW) alloy 690 (UNS N06690) materials was investigated in 360oC simulated PWR primary water using constant load tensile (CLT) tests and blunt notch compact tension (BNCT) tests equipped with direct current potential drop (DCPD) for in-situ detection of cracking. SCC initiation was not detected by DCPD for either the 21% or 31%CW CLT specimens loaded at their yield stress after ~9,220 hours, however intergranular (IG) precursor damage and isolated surface cracks were observed on the specimens. The two 31%CW BNCT specimens loaded at moderate stress intensity after several cyclic loading ramps showed DCPD-indicated crack initiation after 10,400 hours of exposure at constant stress intensity, which was resulted from significant growth of IG cracks. The 21%CW BNCT specimens only exhibited isolated small IG surface cracks and showed no apparent DCPD change throughout the test. Post-test cross-section examinations revealed many grain boundary (GB) nano-cavities in the bulk of all the CLT and BNCT specimens particularly for the 31%CW materials. Cavities were also found along GBs extending to the surface suggesting an important role in crack nucleation. This paper provides an overview of the evolution of GB cavities and discusses their effects on crack initiation in CW alloy 690.

  20. Pitfalls in training simulated patients to respond appropriately to questions from medical students in family history-taking activities: the current situation surrounding the training of simulated patients for learning activities at Nippon Medical School.

    Science.gov (United States)

    Aso, Ryoko; Inoue, Chikako; Yoshimura, Akinobu; Shimura, Toshiro

    2013-01-01

    Our goal was to train simulated patients (SPs) to respond appropriately to questions about family history from medical students in simulated medical interviews. To this end, we carried out a survey of 91 SPs and 76 4th-year medical students to investigate their notions of what constitutes a family. All of the SPs and students surveyed deemed parents and children living together to be members of a family. In a situation where one spouse's parents live together with the basic family unit, 93% of the SPs considered them to be members of the family, whereas only 79% of the students did. Married children living apart from their parents were considered members of the family by 18% of the SPs and 39% of the students. These results indicate clear differences between the SPs and students in their notions of the family. To verify the level of understanding of the definitions of family and blood relatives in particular scenarios used in simulated medical interviews, we administered a written test to 14 SPs who were training to assist in the nationwide common achievement test in medicine, the Objective Structured Clinical Examination (OSCE). The overall score of the SPs was 93.5%; the incorrect answers were "a sibling is not a blood relative" and "a spouse is a blood relative." We analyzed the performance of these 14 SPs in medical interviews carried out after training for the OSCE, in which they were asked questions that required them to reveal their understanding of blood relatives, cohabiting relatives, and the family. All of the SPs responded appropriately to the students' questions about family history. After the OSCE, we asked the SPs to assess themselves on how well they had given their family histories and to evaluate the usefulness of the SP training they had received. Their mean self-assessment score on providing a family history was 3.6 (scale: 1-4); on the usefulness of training, it was 3.4 (scale: 1-4). In conclusion, training SPs to respond appropriately to

  1. The effect of stress tolerance on dynamics of activity-travel behavior : numerical simulation results

    NARCIS (Netherlands)

    Psarra, I.; Arentze, T.A.; Timmermans, H.J.P.

    2014-01-01

    The primary and secondary effects of various spatial and transportation policies can be evaluated with models of activity–travel behavior. Whereas existing activity-based models of travel demand simulate a typical day, dynamic models simulate behavioral response to endogenous or exogenous change,

  2. A Systematic Review of Longitudinal Risk and Protective Factors and Correlates for Posttraumatic Stress and Its Natural History in Forcibly Displaced Children.

    Science.gov (United States)

    Tam, Stephanie Y; Houlihan, Shea; Melendez-Torres, G J

    2015-12-30

    Posttraumatic stress (PTS) results in significant distress or functional impairment. Prevalence studies report higher rates of PTS in forcibly displaced children (FDC). Current evidence deriving mainly from cross-sectional studies is unable to make causal attributions. Given rising rates of forcible displacement reported by the United Nations High Commissioner for Refugees (UNHCR) in 2014, there is increasing need to determine the best policies and practice for engaging mental health needs of FDC. This systematic review identifies (1) longitudinal risk and protective factors and correlates for PTS and (2) its natural history in FDC, contributing to research identifying vulnerable subgroups and malleable factors for PTS and understanding its natural history. No meta-analysis was conducted due to heterogeneity; results were analyzed through narrative synthesis. Eleven longitudinal studies were identified. All but one were prospective cohort designs. They identified prevalence rates between 20% and 48.7% at baseline, 10% and 48.3% at 1 year (k = 7), 18% and 48% at 2-3 years (k = 2), 8% and 38% at 6 years (k = 2), and 35% at 12 years using nine measurement methods in seven independent samples. Evidence from multiple associations supported the following risk factors: exposure to traumatic stressors or other stress, older age, and prior psychopathology. Evidence predominantly supported the stability of PTS with some decline. While results should be interpreted with caution given small or unrepresentative samples, they suggest regular mental health screenings should be conducted for FDC, who are a vulnerable subgroup with variable onset and remission. Risk associations with prior psychopathology also suggest that screening upon arrival may be advisable for early intervention and prevention. © The Author(s) 2015.

  3. Biomarkers of nutrition and stress in pregnant women with a history of eating disorders in relation to head circumference and neurocognitive function of the offspring.

    Science.gov (United States)

    Koubaa, Saloua; Hällström, Tore; Brismar, Kerstin; Hellström, Per M; Hirschberg, Angelica Lindén

    2015-11-27

    Eating disorders during pregnancy can affect fetal growth and the child's early development, but the underlying mechanisms have not been elucidated. The aim of the present study was to investigate serum biomarkers of nutrition and stress in pregnant women with previous eating disorders compared to controls and in relation to head circumference and early neurocognitive development of the offspring. In a longitudinal cohort study, pregnant nulliparous non-smoking women with a history of anorexia nervosa (n = 20), bulimia nervosa (n = 17) and controls (n = 59) were followed during pregnancy and their children's growth and neurocognitive development were followed up to five years of age. We investigated maternal serum biomarkers of nutrition and stress (ferritin, cortisol, thyroid-stimulating hormone, free thyroxine, insulin, insulin-like growth factor I (IGF-I) and IGF binding protein 1) in blood samples collected during early pregnancy and compared between groups (ANOVA, LSD post-hoc test). The results were related to previous data on head circumference at birth and neurocognitive development at five years of age of the offspring (Spearman rank correlation or Pearson correlation test). Serum levels of ferritin in the women with previous anorexia nervosa, but not in those with a history of bulimia nervosa, were significantly lower than in the controls (p children (rs = -0.70, p children in the bulimia nervosa group (r = 0.48, p anorexia nervosa group (r = 0.42, p = 0.07), but not in the controls (r = 0.006). There were no significant differences in cortisol or the other biomarkers between groups. Low maternal serum ferritin in women with previous anorexia nervosa may be of importance for impaired memory capacity in the offspring at five years of age. Our results also indicate that thyroxin levels in pregnant women with previous eating disorders are positively associated with fetal head growth.

  4. Stress Response of Veterinary Students to Gynaecological Examination of Horse Mares - Effects of Simulator-Based and Animal-Based Training.

    Science.gov (United States)

    Nagel, C; Ille, N; Erber, R; Aurich, C; Aurich, J

    2015-10-01

    Invasive procedures in animals are challenging for veterinary students who may perceive a gynaecological examination of mares as stressful. Simulator-based training may reduce stress. In this study, students received equine gynaecology training 4 times either on horses (group H; n = 14) or a teaching simulator (group SIM; n = 13). One day and 14 days thereafter, their diagnostic skills were tested on horses (skills tests 1 and 2). During the skills tests, the students' stress response was analysed by heart rate, heart rate variability (HRV) parameters SDRR (standard deviation of beat-to-beat [RR] interval) and RMSSD (root-mean-square of successive RR differences), and salivary cortisol. In addition, students answered a questionnaire on their perceived stress. Sympathetic activation with increased heart rate (p stress response. Subjective stress perception of students was higher in skills test 1 vs 2 (p stressed than SIM students (p stress parameters. In conclusion, gynaecological examination of mares evoked a moderate stress response in veterinary students, which was more evident after simulator-based than animal-based training. © 2015 Blackwell Verlag GmbH.

  5. Neuropsychological Performance and Subjective Symptom Reporting in Military Service Members With a History of Multiple Concussions: Comparison With a Single Concussion, Posttraumatic Stress Disorder, and Orthopedic Trauma.

    Science.gov (United States)

    Cooper, Douglas B; Curtiss, Glenn; Armistead-Jehle, Patrick; Belanger, Heather G; Tate, David F; Reid, Matthew; Bowles, Amy O; Velez, Carmen S; Kennedy, Jan E; Vanderploeg, Rodney D

    To examine differences in objective neurocognitive performance and subjective cognitive symptoms in individuals with a history of a single concussion, multiple concussions, orthopedic injuries, and posttraumatic stress disorder (PTSD). Participants included 116 military service members who sustained a mild traumatic brain injury (mTBI) during combat deployment. Subjects were subdivided into groups based on concussion frequency: a single concussion (n = 42), 2 concussions (n = 21), and 3 or more concussions (n = 53). Eighty-one subjects sustained an orthopedic injury (n = 60) during deployment or were diagnosed with PTSD (n = 21), but had no history of mTBI. Subjects completed a battery of neuropsychological tests and self-report measures of postconcussive symptoms, PTSD symptoms, and psychopathology. No differences were found among the concussion groups on a composite neuropsychological measure. The PTSD group had the highest number of symptom complaints, with the 2-concussion and 3-plus-concussion groups being most similar to the PTSD group. The concussion groups showed a nonsignificant pattern of increasing distress with increasing number of concussions. The current findings are consistent with meta-analytic results showing no differential effect on neuropsychological functioning due to multiple concussions. Results also support the burden of adversity hypothesis suggesting increasing symptom levels with increasing psychological or physically traumatic exposures.

  6. Survival of Listeria monocytogenes in simulated gastrointestinal system and transcriptional profiling of stress- and adhesion-related genes

    DEFF Research Database (Denmark)

    Jiang, Lingli; Olesen, Inger; Andersen, Thomas

    2010-01-01

    -related genes after exposure to the conditions similar to those encountered in the mouth, stomach, and small intestine. None of the L. monocytogenes strains investigated could survive in the gastric juice at pH 2.5 or 3.0. Their survival increased at higher pH (3.5 and 4.0) in the gastric stress. Relative...... afterpassing through the simulated gastrointestinal tract, whereas that of the adhesion-related gene ami was downregulated. Taken together, this study revealed that L. monocytogenes strains enhanced the expression of stressrelated genes and decreased the transcription of adhesion-related gene in order...

  7. The impact of stress on the life history strategies of African American adolescents: cognitions, genetic moderation, and the role of discrimination.

    Science.gov (United States)

    Gibbons, Frederick X; Roberts, Megan E; Gerrard, Meg; Li, Zhigang; Beach, Steven R H; Simons, Ronald L; Weng, Chih-Yuan; Philibert, Robert A

    2012-05-01

    The impact of 3 different sources of stress--environmental, familial (e.g., low parental investment), and interpersonal (i.e., racial discrimination)--on the life history strategies (LHS) and associated cognitions of African American adolescents were examined over an 11-year period (5 waves, from age 10.5 to 21.5). Analyses indicated that each one of the sources of stress was associated with faster LHS cognitions (e.g., tolerance of deviance, willingness to engage in risky sex), which, in turn, predicted faster LHS behaviors (e.g., frequent sexual behavior). LHS, then, negatively predicted outcome (resilience) at age 21.5 (i.e., faster LHS → less resilience). In addition, presence of the risk ("sensitivity") alleles of 2 monoamine-regulating genes, the serotonin transporter gene (5HTTLPR) and the dopamine D4 receptor gene (DRD4), moderated the impact of perceived racial discrimination on LHS cognitions: Participants with more risk alleles (higher "sensitivity") reported faster LHS cognitions at age 18 and less resilience at age 21 if they had experienced higher amounts of discrimination and slower LHS and more resilience if they had experienced smaller amounts of discrimination. Implications for LHS theories are discussed.

  8. Mathematical simulation of stressed-deformed state in rod cylindrical fuel elemnts KONDOR program

    International Nuclear Information System (INIS)

    Khmelevskij, M.Ya.; Malakhova, E.I.; Dolmatov, P.S.

    1987-01-01

    A mathematical model for numerical computation of stressed-deformed stae in a rod cylindrical fuel element is developed. The model is based on preliminary discretization of the design scheme and linearization of radial parameters as radius functions. The formulation generality enables to calculate strength parameter kinetics in any circular cylindrical fuel element (e.g. annular fuel element; solid or tubular core; ceramic, metallic or dispersion fuel) for arbitrary transient operating conditions and taking into account all possible loading factors. The method is realized in the KONDOR programm (FORTRAN, ES-1061 computer). An example illustrating computation of stress kinetics in a fast reactor fuel element during transient operation is given

  9. One Basin, One Stress Regime, One Orientation of Seismogenic Basement Faults, Variable Spatio-Temporal Slip Histories: Lessons from Fort Worth Basin Induced Earthquake Sequences

    Science.gov (United States)

    DeShon, H. R.; Brudzinski, M.; Frohlich, C.; Hayward, C.; Jeong, S.; Hornbach, M. J.; Magnani, M. B.; Ogwari, P.; Quinones, L.; Scales, M. M.; Stump, B. W.; Sufri, O.; Walter, J. I.

    2017-12-01

    Since October 2008, the Fort Worth basin in north Texas has experienced over 30 magnitude (M) 3.0+ earthquakes, including one M4.0. Five named earthquake sequences have been recorded by local seismic networks: DFW Airport, Cleburne-Johnson County, Azle, Irving-Dallas, and Venus-Johnson County. Earthquakes have occurred on northeast (NE)-southwest (SW) trending Precambrian basement faults and within the overlying Ellenburger limestone unit used for wastewater disposal. Focal mechanisms indicate primarily normal faulting, and stress inversions indicate maximum regional horizontal stress strikes 20-30° NE. The seismogenic sections of the faults in either the basement or within the Ellenburger appear optimally oriented for failure within the modern stress regime. Stress drop estimates range from 10 to 75 bars, with little variability between and within the named sequences, and the values are consistent with intraplate earthquake stress drops in natural tectonic settings. However, the spatio-temporal history of each sequence relative to wastewater injection data varies. The May 2015 M4.0 Venus earthquake, for example, is only the largest of what is nearly 10 years of earthquake activity on a single fault structure. Here, maximum earthquake size has increased with time and exhibits a log-linear relationship to cumulative injected volume from 5 nearby wells. At the DFW airport, where the causative well was shut-in within a few months of the initial earthquakes and soon after the well began operation, we document migration away from the injector on the same fault for nearly 6 km sporadically over 5 years. The Irving-Dallas and Azle sequences, like DFW airport, appear to have started rather abruptly with just a few small magnitude earthquakes in the weeks or months preceding the significant set of magnitude 3.5+ earthquakes associated with each sequence. There are no nearby (<10 km) injection operations to the Irving-Dallas sequence and the Azle linked wells operated for

  10. Simulation of Stress-Strain behavior for one-dimensional aluminum samples subjected to high temperature

    DEFF Research Database (Denmark)

    Bellini, Anna; Thorborg, Jesper; Hattel, Jesper

    2004-01-01

    , financed by the EU in frame work 6 and born in collaboration with the automobile and foundry industries, to fill the mentioned gap. Through a systematic analysis of experimental tests, this study aims to develop a powerful predicting tool capable of capturing stress relaxation effects through an adequate...

  11. Stream mesocosm response sensitivities to simulated ion stress in produced waters from resource extraction activities

    Science.gov (United States)

    To increase the ecological relevance of laboratory exposures intent on determining species sensitivity to ion stress from resource extraction activities we have conducted several stream mesocosm dosing studies that pair single-species and community-level responses in-situ and all...

  12. Nuclear power plant accident simulations of gasket materials under simultaneous radiation plus thermal plus mechanical stress conditions

    International Nuclear Information System (INIS)

    Gillen, K.T.; Malone, G.M.

    1997-07-01

    In order to probe the response of silicone door gasket materials to a postulated severe accident in an Italian nuclear power plant, compression stress relaxation (CSR) and compression set (CS) measurements were conducted under combined radiation (approximately 6 kGy/h) and temperature (up to 230 degrees C) conditions. By making some reasonable initial assumptions, simplified constant temperature and dose rates were derived that should do a reasonable job of simulating the complex environments for worst-case severe events that combine overall aging plus accidents. Further simplification coupled with thermal-only experiments allowed us to derive thermal-only conditions that can be used to achieve CSR and CS responses similar to those expected from the combined environments that are more difficult to simulate. Although the thermal-only simulations should lead to sealing forces similar to those expected during a severe accident, modulus and density results indicate that significant differences in underlying chemistry are expected for the thermal-only and the combined environment simulations. 15 refs., 31 figs., 15 tabs

  13. Development of a model for unsteady deterministic stresses adapted to the multi-stages turbomachines simulation; Developpement d'un modele de tensions deterministes instationnaires adapte a la simulation de turbomachines multi-etagees

    Energy Technology Data Exchange (ETDEWEB)

    Charbonnier, D.

    2004-12-15

    The physical phenomena observed in turbomachines are generally three-dimensional and unsteady. A recent study revealed that a three-dimensional steady simulation can reproduce the time-averaged unsteady phenomena, since the steady flow field equations integrate deterministic stresses. The objective of this work is thus to develop an unsteady deterministic stresses model. The analogy with turbulence makes it possible to write transport equations for these stresses. The equations are implemented in steady flow solver and e model for the energy deterministic fluxes is also developed and implemented. Finally, this work shows that a three-dimensional steady simulation, by taking into account unsteady effects with transport equations of deterministic stresses, increases the computing time by only approximately 30 %, which remains very interesting compared to an unsteady simulation. (author)

  14. Evaluation between residual stresses obtained by neutron diffraction and simulation for dual phase steel welded by laser process

    Science.gov (United States)

    Kouadri-Henni, Afia; Malard, Benoit

    2018-05-01

    This study aimed at characterizing the residual stresses (RS) distribution of a Dual Phase Steel (DP600) undergoing a Laser Beam Welding (LBW) with two different laser parameters. The RS in the ferritic phase have been experimentally determined by the use of the neutrons diffraction technique. The results confirmed a gradient of RS among different zones both on the top and below surfaces but also through the thickness of the fusion zone. Low compressive stresses were observed in the Base Metal (BM) close to the Heat Affected Zone (HAZ) whereas high tensile stresses were observed in the Fusion Zone (FZ). Numerical results showed a difference in the RS distribution depending on the model used. In the end, it appears that the high temperature gradient, specific to the laser beam, is the main factor governing the RS. Our results suggest as well that the approach regarding the RS should consider not only the temperature but also process parameters. When comparing simulation results with experimental data, the values converge well in some zones, in particular the FZ and the others less.

  15. Physical Forces Modulate Oxidative Status and Stress Defense Meditated Metabolic Adaptation of Yeast Colonies: Spaceflight and Microgravity Simulations

    Science.gov (United States)

    Hammond, Timothy G.; Allen, Patricia L.; Gunter, Margaret A.; Chiang, Jennifer; Giaever, Guri; Nislow, Corey; Birdsall, Holly H.

    2018-05-01

    Baker's yeast ( Saccharomyces cerevisiae) has broad genetic homology to human cells. Although typically grown as 1-2mm diameter colonies under certain conditions yeast can form very large (10 + mm in diameter) or `giant' colonies on agar. Giant yeast colonies have been used to study diverse biomedical processes such as cell survival, aging, and the response to cancer pharmacogenomics. Such colonies evolve dynamically into complex stratified structures that respond differentially to environmental cues. Ammonia production, gravity driven ammonia convection, and shear defense responses are key differentiation signals for cell death and reactive oxygen system pathways in these colonies. The response to these signals can be modulated by experimental interventions such as agar composition, gene deletion and application of pharmaceuticals. In this study we used physical factors including colony rotation and microgravity to modify ammonia convection and shear stress as environmental cues and observed differences in the responses of both ammonia dependent and stress response dependent pathways We found that the effects of random positioning are distinct from rotation. Furthermore, both true and simulated microgravity exacerbated both cellular redox responses and apoptosis. These changes were largely shear-response dependent but each model had a unique response signature as measured by shear stress genes and the promoter set which regulates them These physical techniques permitted a graded manipulation of both convection and ammonia signaling and are primed to substantially contribute to our understanding of the mechanisms of drug action, cell aging, and colony differentiation.

  16. Silicon alleviates simulated acid rain stress of Oryza sativa L. seedlings by adjusting physiology activity and mineral nutrients.

    Science.gov (United States)

    Ju, Shuming; Wang, Liping; Yin, Ningning; Li, Dan; Wang, Yukun; Zhang, Cuiying

    2017-11-01

    Silicon (Si) has been a modulator in plants under abiotic stresses, such as acid rain. To understand how silicon made an effect on rice (Oryza sativa L.) exposed to simulated acid rain (SAR) stress, the growth, physiologic activity, and mineral nutrient content in leaves of rice were investigated. The results showed that combined treatments with Si (1.0, 2.0, or 4.0 mM) and SAR (pH 4.0, 3.0, or 2.0) obviously improved the rice growth compared with the single treatment with SAR. Incorporation of Si into SAR treatment decreased malondialdehyde (MDA) content; increased soluble protein and proline contents; promoted CAT, POD, SOD, and APX activity; and maintained the K, Ca, Mg, Fe, Zn, Cu content balance in leaves of rice seedlings under SAR stress. The moderate concentration of Si (2.0 mM) was better than the low and high concentration of Si (1.0 and 4.0 mM). Therefore, application of Si could be a better strategy for maintaining the crop productivity in acid rain regions.

  17. Physical Forces Modulate Oxidative Status and Stress Defense Meditated Metabolic Adaptation of Yeast Colonies: Spaceflight and Microgravity Simulations

    Science.gov (United States)

    Hammond, Timothy G.; Allen, Patricia L.; Gunter, Margaret A.; Chiang, Jennifer; Giaever, Guri; Nislow, Corey; Birdsall, Holly H.

    2017-12-01

    Baker's yeast (Saccharomyces cerevisiae) has broad genetic homology to human cells. Although typically grown as 1-2mm diameter colonies under certain conditions yeast can form very large (10 + mm in diameter) or `giant' colonies on agar. Giant yeast colonies have been used to study diverse biomedical processes such as cell survival, aging, and the response to cancer pharmacogenomics. Such colonies evolve dynamically into complex stratified structures that respond differentially to environmental cues. Ammonia production, gravity driven ammonia convection, and shear defense responses are key differentiation signals for cell death and reactive oxygen system pathways in these colonies. The response to these signals can be modulated by experimental interventions such as agar composition, gene deletion and application of pharmaceuticals. In this study we used physical factors including colony rotation and microgravity to modify ammonia convection and shear stress as environmental cues and observed differences in the responses of both ammonia dependent and stress response dependent pathways We found that the effects of random positioning are distinct from rotation. Furthermore, both true and simulated microgravity exacerbated both cellular redox responses and apoptosis. These changes were largely shear-response dependent but each model had a unique response signature as measured by shear stress genes and the promoter set which regulates them These physical techniques permitted a graded manipulation of both convection and ammonia signaling and are primed to substantially contribute to our understanding of the mechanisms of drug action, cell aging, and colony differentiation.

  18. NASA Trapezoidal Wing Simulation Using Stress-w and One- and Two-Equation Turbulence Models

    Science.gov (United States)

    Rodio, J. J.; Xiao, X; Hassan, H. A.; Rumsey, C. L.

    2014-01-01

    The Wilcox 2006 stress-omega model (also referred to as WilcoxRSM-w2006) has been implemented in the NASA Langley code CFL3D and used to study a variety of 2-D and 3-D configurations. It predicted a variety of basic cases reasonably well, including secondary flow in a supersonic rectangular duct. One- and two-equation turbulence models that employ the Boussinesq constitutive relation were unable to predict this secondary flow accurately because it is driven by normal turbulent stress differences. For the NASA trapezoidal wing at high angles of attack, the WilcoxRSM-w2006 model predicted lower maximum lift than experiment, similar to results of a two-equation model.

  19. Constant load and constant displacement stress corrosion in simulated water reactor environments

    International Nuclear Information System (INIS)

    Lloyd, G.J.

    1987-02-01

    The stress corrosion behaviour of selected water reactor constructional materials, as determined by constant load or constant displacement test techniques, is reviewed. Experimental results obtained using a very wide range of conditions have been collected in a form for easy reference. A discussion is given of some apparent trends in these data. The possible reasons for these trends are considered together with a discussion of how the observed discrepancies may be resolved. (author)

  20. Simulation of cyclic stress-strain relation under non proportional loading

    International Nuclear Information System (INIS)

    Chen, X.; Zhu, Q.X.; Abel, A.

    1995-01-01

    A series of cyclic constitutive experiments have been conducted on 42 Cr Mo steel on MTS809 machine under tension-torsional loading. Thin-walled tube specimen were used. Two kinds of cruciform strain path have been investigated. The paper suggests a simple method for the calculation of stable cyclic stress and strain values based on a modified endochronic constitutive theory by redefined intrinsic time scale. (author). 6 refs., 3 figs

  1. Role of bed nucleus of the stria terminalis corticotrophin-releasing factor receptors in frustration stress-induced binge-like palatable food consumption in female rats with a history of food restriction.

    Science.gov (United States)

    Micioni Di Bonaventura, Maria Vittoria; Ciccocioppo, Roberto; Romano, Adele; Bossert, Jennifer M; Rice, Kenner C; Ubaldi, Massimo; St Laurent, Robyn; Gaetani, Silvana; Massi, Maurizio; Shaham, Yavin; Cifani, Carlo

    2014-08-20

    We developed recently a binge-eating model in which female rats with a history of intermittent food restriction show binge-like palatable food consumption after 15 min exposure to the sight of the palatable food. This "frustration stress" manipulation also activates the hypothalamic-pituitary-adrenal stress axis. Here, we determined the role of the stress neurohormone corticotropin-releasing factor (CRF) in stress-induced binge eating in our model. We also assessed the role of CRF receptors in the bed nucleus of the stria terminalis (BNST), a brain region implicated in stress responses and stress-induced drug seeking, in stress-induced binge eating. We used four groups that were first exposed or not exposed to repeated intermittent cycles of regular chow food restriction during which they were also given intermittent access to high-caloric palatable food. On the test day, we either exposed or did not expose the rats to the sight of the palatable food for 15 min (frustration stress) before assessing food consumption for 2 h. We found that systemic injections of the CRF1 receptor antagonist R121919 (2,5-dimethyl-3-(6-dimethyl-4-methylpyridin-3-yl)-7 dipropylamino pyrazolo[1,5-a]pyrimidine) (10-20 mg/kg) and BNST (25-50 ng/side) or ventricular (1000 ng) injections of the nonselective CRF receptor antagonist D-Phe-CRF(12-41) decreased frustration stress-induced binge eating in rats with a history of food restriction. Frustration stress also increased Fos (a neuronal activity marker) expression in ventral and dorsal BNST. Results demonstrate a critical role of CRF receptors in BNST in stress-induced binge eating in our rat model. CRF1 receptor antagonists may represent a novel pharmacological treatment for bingeing-related eating disorders. Copyright © 2014 the authors 0270-6474/14/3411316-09$15.00/0.

  2. The effect of residual thermal stresses on the fatigue crack growth of laser-surface-annealed AISI 304 stainless steel Part I: computer simulation

    International Nuclear Information System (INIS)

    Shiue, R.K.; Chang, C.T.; Young, M.C.; Tsay, L.W.

    2004-01-01

    The effect of residual thermal stresses on the fatigue crack growth of the laser-surface-annealed AISI 304 stainless steel, especially the effect of stress redistribution ahead of the crack tip was extensively evaluated in the study. Based on the finite element simulation, the longitudinal residual tensile stress field has a width of roughly 20 mm on the laser-irradiated surface and was symmetric with respect to the centerline of the laser-annealed zone (LAZ). Meanwhile, residual compressive stresses distributed over a wide region away from the LAZ. After introducing a notch perpendicular to the LAZ, the distribution of longitudinal residual stresses became unsymmetrical about the centerline of LAZ. High residual compressive stresses exist within a narrow range ahead of notch tip. The improved crack growth resistance of the laser-annealed specimen might be attributed to those induced compressive stresses. As the notch tip passed through the centerline of the LAZ, the residual stress ahead of the notch tip was completely reverted into residual tensile stresses. The existence of unanimous residual tensile stresses ahead of the notch tip was maintained, even if the notch tip extended deeply into the LAZ. Additionally, the presence of the residual tensile stress ahead of the notch tip did not accelerate the fatigue crack growth rate in the compact tension specimen

  3. Patterns of stress responses shift during seasonal life-history transitions: An analysis comparing baseline, maximal and integrated corticosterone in female red-sided garter snakes (Thamnophis sirtalis parietalis).

    Science.gov (United States)

    Dayger, Catherine A; Lutterschmidt, Deborah I

    2017-05-15

    Glucocorticoids often rise and fall with a variety of external and internal cues and frequently vary among life-history stages. This suggests that changing glucocorticoids may coordinate life-history transitions. To explore this hypothesis, we asked if the time-course of stress-induced glucocorticoid levels differ between two life-history transitions (i.e., spring and fall migration) in female red-sided garter snakes (Thamnophis sirtalis parietalis). We collected non-migratory females from a communal den and migratory females from a road along the migration route and treated them with 4h of capture stress; plasma corticosterone was measured before, during and after capture stress. During the spring, den-collected females exhibited a stress-induced peak in corticosterone at an earlier sampling time than migrating, road-collected females. Because the pattern of corticosterone responses varied with migratory state, negative feedback on and/or sensitivity of the hypothalamus-pituitaryadrenal (HPA) axis may be linked to spring migration. During the fall, capture stress elicited an increase in corticosterone in den-collected females but not in migrating, road-collected females. Baseline corticosterone was higher and both maximal and integrated corticosterone responses were lower during the fall compared to spring, indicating that stress responses are smaller when baseline corticosterone is elevated, perhaps due to a "ceiling effect". These data suggest that HPA axis regulation changes during seasonal migration, possibly via altering negative feedback, HPA axis sensitivity, or some other mechanism. This study supports the hypothesis that glucocorticoids coordinate life-history events and suggests that examining a suite of stress response characteristics is most informative for understanding the function of HPA modulation. Copyright © 2017 Elsevier Inc. All rights reserved.

  4. Numerical Simulations of the Effects of a Tidal Turbine Array on Near-Bed Velocity and Local Bed Shear Stress

    Directory of Open Access Journals (Sweden)

    Philip A. Gillibrand

    2016-10-01

    Full Text Available We apply a three-dimensional hydrodynamic model to consider the potential effects of energy extraction by an array of tidal turbines on the ambient near-bed velocity field and local bed shear stress in a coastal channel with strong tidal currents. Local bed shear stress plays a key role in local sediment dynamics. The model solves the Reynold-averaged Navier-Stokes (RANS equations on an unstructured mesh using mixed finite element and finite volume techniques. Tidal turbines are represented through an additional form drag in the momentum balance equation, with the thrust imparted and power generated by the turbines being velocity dependent with appropriate cut-in and cut-out velocities. Arrays of 1, 4 and 57 tidal turbines, each of 1.5 MW capacity, were simulated. Effects due to a single turbine and an array of four turbines were negligible. The main effect of the array of 57 turbines was to cause a shift in position of the jet through the tidal channel, as the flow was diverted around the tidal array. The net effect of this shift was to increase near-bed velocities and bed shear stress along the northern perimeter of the array by up to 0.8 m·s−1 and 5 Pa respectively. Within the array and directly downstream, near-bed velocities and bed shear stress were reduced by similar amounts. Changes of this magnitude have the potential to modify the known sand and shell banks in the region. Continued monitoring of the sediment distributions in the region will provide a valuable dataset on the impacts of tidal energy extraction on local sediment dynamics. Finally, the mean power generated per turbine is shown to decrease as the turbine array increased in size.

  5. Simulation of root water uptake. II. Non-uniform transient water stress using different reduction functions

    NARCIS (Netherlands)

    Homaee, M.; Feddes, R.A.; Dirksen, C.

    2002-01-01

    The macroscopic root water uptake approach was used in the numerical simulation model HYSWASOR to test four different pressure head-dependent reduction functions. The input parameter values were obtained from the literature and derived from extensive measurements under controlled conditions in the

  6. Discrete element simulation of internal stress in SiCp/aluminum ...

    African Journals Online (AJOL)

    SiCp / Al-Mg-Si matrix composite was prepared by pressureless Infiltration Process. By discrete element method, microcosmic two-dimensional numerical model of SiCp / Al matrix composites was established and the simulation of the size and distribution of micro-contact pressure and tension was performed from small load ...

  7. Simulation of Co-Seismic Off-Fault Stress Effects: Influence of Fault Roughness and Pore Pressure Coupling

    Science.gov (United States)

    Fälth, B.; Lund, B.; Hökmark, H.

    2017-12-01

    Aiming at improved safety assessment of geological nuclear waste repositories, we use dynamic 3D earthquake simulations to estimate the potential for co-seismic off-fault distributed fracture slip. Our model comprises a 12.5 x 8.5 km strike-slip fault embedded in a full space continuum where we apply a homogeneous initial stress field. In the reference case (Case 1) the fault is planar and oriented optimally for slip, given the assumed stress field. To examine the potential impact of fault roughness, we also study cases where the fault surface has undulations with self-similar fractal properties. In both the planar and the undulated cases the fault has homogeneous frictional properties. In a set of ten rough fault models (Case 2), the fault friction is equal to that of Case 1, meaning that these models generate lower seismic moments than Case 1. In another set of ten rough fault models (Case 3), the fault dynamic friction is adjusted such that seismic moments on par with that of Case 1 are generated. For the propagation of the earthquake rupture we adopt the linear slip-weakening law and obtain Mw 6.4 in Case 1 and Case 3, and Mw 6.3 in Case 2 (35 % lower moment than Case 1). During rupture we monitor the off-fault stress evolution along the fault plane at 250 m distance and calculate the corresponding evolution of the Coulomb Failure Stress (CFS) on optimally oriented hypothetical fracture planes. For the stress-pore pressure coupling, we assume Skempton's coefficient B = 0.5 as a base case value, but also examine the sensitivity to variations of B. We observe the following: (I) The CFS values, and thus the potential for fracture slip, tend to increase with the distance from the hypocenter. This is in accordance with results by other authors. (II) The highest CFS values are generated by quasi-static stress concentrations around fault edges and around large scale fault bends, where we obtain values of the order of 10 MPa. (III) Locally, fault roughness may have a

  8. Effects of trimethoprim on life history parameters, oxidative stress, and the expression of cytochrome P450 genes in the copepod Tigriopus japonicus.

    Science.gov (United States)

    Han, Jeonghoon; Lee, Min-Chul; Kim, Duck-Hyun; Lee, Young Hwan; Park, Jun Chul; Lee, Jae-Seong

    2016-09-01

    Trimethoprim (TMP) is an antibiotic that has been detected in various environments including marine habitats; however, the toxic effects of TMP are poorly understood in non-target marine organisms. In this study, the effects of TMP on mortality, development, reproduction, intracellular reactive oxygen species (ROS) levels, and transcription levels of antioxidant and xenobiotic detoxification-related enzyme genes were investigated in the copepod Tigriopus japonicus. The TMP half lethal dose at 48 h (LC50-48 h) in nauplius and TMP LC50-96 h in adult T. japonicus copepods was determined as 156 mg/L and 200 mg/L, respectively. In TMP-exposed T. japonicus, delayed developmental time and impaired reproduction were observed as harmful effects on the life history parameters. Increased ROS levels were also shown in response to TMP exposure at the highest concentration (100 mg/L TMP) and the expression of antioxidant- (e.g. GST-kappa, GST-sigma) and xenobiotic detoxification (e.g. CYPs)-related genes were upregulated in a time and/or dose-dependent manner in response to TMP. Particularly, significant upregulation of three CYP genes (Tj-CYP3024A2, Tj-CYP3024A3 and Tj-CYP3027C2) were examined, suggesting that these CYP genes are likely playing an important role in the TMP detoxification metabolism in T. japonicus. In summary, we found that TMP induced oxidative stress via the transcriptional regulation of antioxidant- and xenobiotic detoxification-related genes, leading to changes in life history parameters such as developmental delay and reproduction impairment. Three Tj-CYP genes (Tj-CYP3024A2, Tj-CYP3024A3 and Tj-CYP3027C2) could be useful as potential T. japonicus biomarkers in response to antibiotics. Copyright © 2016 Elsevier Ltd. All rights reserved.

  9. Simulation of inter- and transgranular crack propagation in polycrystalline aggregates due to stress corrosion cracking

    International Nuclear Information System (INIS)

    Musienko, Andrey; Cailletaud, Georges

    2009-01-01

    The motivation of the study is the development of a coupled approach able to account for the interaction between environment and plasticity in a polycrystalline material. The paper recalls first the constitutive equations used to describe the behavior of the grain core and of the grain boundary (GB). The procedure that is applied to generate synthetic polycrystalline aggregates with an explicit representation of the grain boundary area by 2D or 3D finite elements is then described. The approach is applied to the modeling of iodine-assisted stress corrosion cracking (IASCC) in Zircaloy tubes used in nuclear power plants.

  10. United States History Simulations: 1787-1868: Constitution Convention, Missouri Compromise, Treaty of Guadalupe Hidalgo, The Compromise of 1850, The Kansas/Nebraska Act, Southern Secession from the Union, and the Impeachment and Trial of Andrew Johnson. ETC Simulations Number Two.

    Science.gov (United States)

    Hostrop, Richard W.

    This book presents simulation activities for significant events in U.S. history from 1787-1868. Intended for student involvement, the simulations require student research and practice in order to carry out the designated roles. The simulation and role play serve to involve the students actively in their learning, using both the affective and…

  11. Association of DSM-IV Posttraumatic Stress Disorder With Traumatic Experience Type and History in the World Health Organization World Mental Health Surveys.

    Science.gov (United States)

    Liu, Howard; Petukhova, Maria V; Sampson, Nancy A; Aguilar-Gaxiola, Sergio; Alonso, Jordi; Andrade, Laura Helena; Bromet, Evelyn J; de Girolamo, Giovanni; Haro, Josep Maria; Hinkov, Hristo; Kawakami, Norito; Koenen, Karestan C; Kovess-Masfety, Viviane; Lee, Sing; Medina-Mora, Maria Elena; Navarro-Mateu, Fernando; O'Neill, Siobhan; Piazza, Marina; Posada-Villa, José; Scott, Kate M; Shahly, Victoria; Stein, Dan J; Ten Have, Margreet; Torres, Yolanda; Gureje, Oye; Zaslavsky, Alan M; Kessler, Ronald C

    2017-03-01

    Previous research has documented significant variation in the prevalence of posttraumatic stress disorder (PTSD) depending on the type of traumatic experience (TE) and history of TE exposure, but the relatively small sample sizes in these studies resulted in a number of unresolved basic questions. To examine disaggregated associations of type of TE history with PTSD in a large cross-national community epidemiologic data set. The World Health Organization World Mental Health surveys assessed 29 TE types (lifetime exposure, age at first exposure) with DSM-IV PTSD that was associated with 1 randomly selected TE exposure (the random TE) for each respondent. Surveys were administered in 20 countries (n = 34 676 respondents) from 2001 to 2012. Data were analyzed from October 1, 2015, to September 1, 2016. Prevalence of PTSD assessed with the Composite International Diagnostic Interview. Among the 34 676 respondents (55.4% [SE, 0.6%] men and 44.6% [SE, 0.6%] women; mean [SE] age, 43.7 [0.2] years), lifetime TE exposure was reported by a weighted 70.3% of respondents (mean [SE] number of exposures, 4.5 [0.04] among respondents with any TE). Weighted (by TE frequency) prevalence of PTSD associated with random TEs was 4.0%. Odds ratios (ORs) of PTSD were elevated for TEs involving sexual violence (2.7; 95% CI, 2.0-3.8) and witnessing atrocities (4.2; 95% CI, 1.0-17.8). Prior exposure to some, but not all, same-type TEs was associated with increased vulnerability (eg, physical assault; OR, 3.2; 95% CI, 1.3-7.9) or resilience (eg, participation in sectarian violence; OR, 0.3; 95% CI, 0.1-0.9) to PTSD after the random TE. The finding of earlier studies that more general history of TE exposure was associated with increased vulnerability to PTSD across the full range of random TE types was replicated, but this generalized vulnerability was limited to prior TEs involving violence, including participation in organized violence (OR, 1.3; 95% CI, 1.0-1.6), experience of

  12. Autologous nerve graft repair of different degrees of sciatic nerve defect:stress and displacement at the anastomosis in a three-dimensional finite element simulation model

    Institute of Scientific and Technical Information of China (English)

    Cheng-dong Piao; Kun Yang; Peng Li; Min Luo

    2015-01-01

    In the repair of peripheral nerve injury using autologous or synthetic nerve grafting, the mag-nitude of tensile forces at the anastomosis affects its response to physiological stress and the ultimate success of the treatment. One-dimensional stretching is commonly used to measure changes in tensile stress and strain; however, the accuracy of this simple method is limited. There-fore, in the present study, we established three-dimensional ifnite element models of sciatic nerve defects repaired by autologous nerve grafts. Using PRO E 5.0 ifnite element simulation software, we calculated the maximum stress and displacement of an anastomosis under a 5 N load in 10-, 20-, 30-, 40-mm long autologous nerve grafts. We found that maximum displacement increased with graft length, consistent with specimen force. These ifndings indicate that three-dimensional ifnite element simulation is a feasible method for analyzing stress and displacement at the anas-tomosis after autologous nerve grafting.

  13. Autologous nerve graft repair of different degrees of sciatic nerve defect: stress and displacement at the anastomosis in a three-dimensional fnite element simulation model

    Directory of Open Access Journals (Sweden)

    Cheng-dong Piao

    2015-01-01

    Full Text Available In the repair of peripheral nerve injury using autologous or synthetic nerve grafting, the magnitude of tensile forces at the anastomosis affects its response to physiological stress and the ultimate success of the treatment. One-dimensional stretching is commonly used to measure changes in tensile stress and strain however, the accuracy of this simple method is limited. Therefore, in the present study, we established three-dimensional finite element models of sciatic nerve defects repaired by autologous nerve grafts. Using PRO E 5.0 finite element simulation software, we calculated the maximum stress and displacement of an anastomosis under a 5 N load in 10-, 20-, 30-, 40-mm long autologous nerve grafts. We found that maximum displacement increased with graft length, consistent with specimen force. These findings indicate that three-dimensional finite element simulation is a feasible method for analyzing stress and displacement at the anastomosis after autologous nerve grafting.

  14. Development of a coping intervention to improve traumatic stress and HIV care engagement among South African women with sexual trauma histories.

    Science.gov (United States)

    Sikkema, Kathleen J; Choi, Karmel W; Robertson, Corne; Knettel, Brandon A; Ciya, Nonceba; Knippler, Elizabeth T; Watt, Melissa H; Joska, John A

    2018-06-01

    This paper describes the development and preliminary trial run of ImpACT (Improving AIDS Care after Trauma), a brief coping intervention to address traumatic stress and HIV care engagement among South African women with sexual trauma histories. We engaged in an iterative process to culturally adapt a cognitive-behavioral intervention for delivery within a South African primary care clinic. This process involved three phases: (a) preliminary intervention development, drawing on content from a prior evidence-based intervention; (b) contextual adaptation of the curriculum through formative data collection using a multi-method qualitative approach; and (c) pre-testing of trauma screening procedures and a subsequent trial run of the intervention. Feedback from key informant interviews and patient in-depth interviews guided the refinement of session content and adaptation of key intervention elements, including culturally relevant visuals, metaphors, and interactive exercises. The trial run curriculum consisted of four individual sessions and two group sessions. Strong session attendance during the trial run supported the feasibility of ImpACT. Participants responded positively to the logistics of the intervention delivery and the majority of session content. Trial run feedback helped to further refine intervention content and delivery towards a pilot randomized clinical trial to assess the feasibility and potential efficacy of this intervention. Copyright © 2018 Elsevier Ltd. All rights reserved.

  15. Reconstructing and analyzing China's fifty-nine year (1951–2009 drought history using hydrological model simulation

    Directory of Open Access Journals (Sweden)

    Z. Y. Wu

    2011-09-01

    Full Text Available The 1951–2009 drought history of China is reconstructed using daily soil moisture values generated by the Variable Infiltration Capacity (VIC land surface macroscale hydrology model. VIC is applied over a grid of 10 458 points with a spatial resolution of 30 km × 30 km, and is driven by observed daily maximum and minimum air temperature and precipitation from 624 long-term meteorological stations. The VIC soil moisture is used to calculate the Soil Moisture Anomaly Percentage Index (SMAPI, which can be used as a measure of the severity of agricultural drought on a global basis. We have developed a SMAPI-based drought identification procedure for practical uses in the identification of both grid point and regional drought events. As a result, a total of 325 regional drought events varying in time and strength are identified from China's nine drought study regions. These drought events can thus be assessed quantitatively at different spatial and temporal scales. The result shows that the severe drought events of 1978, 2000 and 2006 are well reconstructed, which indicates that the SMAPI is capable of identifying the onset of a drought event, its progression, as well as its termination. Spatial and temporal variations of droughts in China's nine drought study regions are studied. Our result shows that on average, up to 30% of the total area of China is prone to drought. Regionally, an upward trend in drought-affected areas has been detected in three regions (Inner Mongolia, Northeast and North from 1951–2009. However, the decadal variability of droughts has been weak in the rest of the five regions (South, Southwest, East, Northwest, and Tibet. Xinjiang has even been showing steadily wetter since the 1950s. Two regional dry centres are discovered in China as the result of a combined analysis on the occurrence of drought events from both grid points and drought study regions. The first centre is located in the area partially covered by the North

  16. Research on Impact Stress and Fatigue Simulation of a New Down-to-the-Hole Impactor Based on ANSYS

    Science.gov (United States)

    Wu, Tao; Wang, Wei; Yao, Aiguo; Li, Yongbo; He, Wangyong; Fei, Dongdong

    2018-06-01

    In the present work, a down-to-the-hole electric hammer driven by linear motor is reported for drilling engineering. It differs from the common hydraulic or pneumatic hammers in that it can be applied to some special occasions without circulating medium due to its independence of the drilling fluid. The impact stress caused by the reciprocating motion between stator and rotor and the fatigue damage in key components of linear motor are analyzed by the ANSYS Workbench software and 3D model. Based on simulation results, the hammer's structure is optimized by using special sliding bearing, increasing the wall thickness of key and multilayer buffer gasket. Fatigue life and coefficient issues of the new structure are dramatically improved. However buffer gasket reduces the impactor's energy, different bumper structure effect on life improving and energy loss have also been elaborated.

  17. Simulation and analysis of the residual stresses in functionally graded Al2O3 coatings on CLAM steel

    International Nuclear Information System (INIS)

    Yan Zilin; Huang Qunying; Song Yong; Guo Zhihui; Wu Yican

    2008-01-01

    Alumina coatings on CLAM steel substrate are proposed to serve as tritium, corrosion and electric insulation barriers in the design of Dual Functional Lithium Lead Test Blanket Module (DFLL-TBM) in China in the frame of ITER. In order to avoid the crack failure due to thermal expansion mismatch of the coating and the substrate, the functionally graded materials (FGM) concept was adopted. In this paper, the residual thermal stresses in the coatings were calculated with the commercial software ANSYS. It is recommended that the compositional factor, numbers of the gradient interlayers and the thickness of the FGM zone are p=0.8, N=8, H=0.6 mm, respectively, according to the simulation results. These results could be helpful and theoretical guidance to the preparation and optimization of the coatings in the future. (authors)

  18. Field measurements, simulation modeling and development of analysis for moisture stressed corn and soybeans, 1982 studies

    Science.gov (United States)

    Blad, B. L.; Norman, J. M.; Gardner, B. R.

    1983-01-01

    The experimental design, data acquisition and analysis procedures for agronomic and reflectance data acquired over corn and soybeans at the Sandhills Agricultural Laboratory of the University of Nebraska are described. The following conclusions were reached: (1) predictive leaf area estimation models can be defined which appear valid over a wide range of soils; (2) relative grain yield estimates over moisture stressed corn were improved by combining reflectance and thermal data; (3) corn phenology estimates using the model of Badhwar and Henderson (1981) exhibited systematic bias but were reasonably accurate; (4) canopy reflectance can be modelled to within approximately 10% of measured values; and (5) soybean pubescence significantly affects canopy reflectance, energy balance and water use relationships.

  19. Methodology to evaluate the crack growth rate by stress corrosion cracking in dissimilar metals weld in simulated environment of PWR nuclear reactor

    International Nuclear Information System (INIS)

    Paula, Raphael G.; Figueiredo, Celia A.; Rabelo, Emerson G.

    2013-01-01

    Inconel alloys weld metal is widely used to join dissimilar metals in nuclear reactors applications. It was recently observed failures of weld components in plants, which have triggered an international effort to determine reliable data on the stress corrosion cracking behavior of this material in reactor environment. The objective of this work is to develop a methodology to determine the crack growth rate caused by stress corrosion in Inconel alloy 182, using the specimen (Compact Tensile) in simulated PWR environment. (author)

  20. Effects of Rayleigh damping, friction and rate-dependency on 3D residual stress simulation of angled shot peening

    International Nuclear Information System (INIS)

    Kim, Taehyung; Lee, Hyungyil; Hyun, Hong Chul; Jung, Sunghwan

    2013-01-01

    Highlights: ► We propose a 3D FE model to study peening residual stress involving angled shots. ► The FE model set with plastic shot are found to best match the X-ray diffraction data. ► The model provides 3D multi-shot impact FE solution with various incidence angles. - Abstract: In this study, we propose a 3D finite element (FE) model to study shot peening involving angled shots. Using the FE model for angled shot peening, we examine relationships with the residual stress introduced by shot peening of the factors such as the Rayleigh damping in the material, dynamic friction, and the rate dependency of the material and systematically integrate them with the FE model. The FE model is set with rigid shot, elastic shot, and plastic shot respectively. Plastic deformation of the shot is also explored with the FE model. The FE model is applied to study angled multi-shots. The FE results are verified with experimental data using X-ray diffraction (XRD). The FE model set with plastic shot are found to best match the XRD results validating accuracy of the 3D FE model properly integrated with the factors and plastically deformable shot ball. The proposed model will serve to simulate actual shot peening cases, which generally involve multi-shots with various incidence angles

  1. Numerical simulation of stress distribution in Inconel 718 components realized by metal injection molding during supercritical debinding

    Science.gov (United States)

    Agne, Aboubakry; Barrière, Thierry

    2018-05-01

    Metal injection molding (MIM) is a process combining advantages of thermoplastic injection molding and powder metallurgy process in order to manufacture components with complex and near net-shape geometries. The debinding of a green component can be performed in two steps, first by using solvent debinding in order to extract the organic part of the binder and then by thermal degradation of the rest of the binder. A shorter and innovative method for extracting an organic binder involves the use of supercritical fluid instead of a regular solvent. The debinding via a supercritical fluid was recently investigated to extract organic binders contained in components obtained by Metal Injection Molding. It consists to put the component in an enclosure subjected to high pressure and temperature. The supercritical fluid has various properties depending on these two conditions, e.g., density and viscosity. The high-pressure combined with the high temperature during the process affect the component structure. Three mechanisms contributing to the deformation of the component can been differentiated: thermal expansion, binder extraction and supercritical fluid effect on the outer surfaces of the component. If one supposes that, the deformation due to binder extraction is negligible, thermal expansion and the fluid effect are probably the main mechanisms that can produce several stress. A finite-element model, which couples fluid-structures interaction and structural mechanics, has been developed and performed on the Comsol Multiphysics® finite-element software platform allowed to estimate the stress distribution during the supercritical debinding of MIM component composed of Inconel 718 powders, polypropylene, polyethylene glycol and stearic acid as binder. The proposed numerical simulations allow the estimation of the stress distribution with respect to the processing parameters for MIM components during the supercritical debinding process using a stationary solver.

  2. Satellite alignment. I. Distribution of substructures and their dependence on assembly history from n-body simulations

    International Nuclear Information System (INIS)

    Wang, Yang Ocean; Lin, W. P.; Yu, Yu; Kang, X.; Dutton, Aaron; Macciò, Andrea V.

    2014-01-01

    Observations have shown that the spatial distribution of satellite galaxies is not random, but aligned with the major axes of central galaxies. This alignment is dependent on galaxy properties, such that red satellites are more strongly aligned than blue satellites. Theoretical work conducted to interpret this phenomenon has found that it is due to the non-spherical nature of dark matter halos. However, most studies overpredict the alignment signal under the assumption that the central galaxy shape follows the shape of the host halo. It is also not clear whether the color dependence of alignment is due to an assembly bias or an evolution effect. In this paper we study these problems using a cosmological N-body simulation. Subhalos are used to trace the positions of satellite galaxies. It is found that the shapes of dark matter halos are mis-aligned at different radii. If the central galaxy shares the same shape as the inner host halo, then the alignment effect is weaker and agrees with observational data. However, it predicts almost no dependence of alignment on the color of satellite galaxies, though the late accreted subhalos show stronger alignment with the outer layer of the host halo than their early accreted counterparts. We find that this is due to the limitation of pure N-body simulations where satellite galaxies without associated subhalos ('orphan galaxies') are not resolved. These orphan (mostly red) satellites often reside in the inner region of host halos and should follow the shape of the host halo in the inner region.

  3. The relationship between driving simulation performance and obstructive sleep apnoea risk, daytime sleepiness, obesity and road traffic accident history of commercial drivers in Turkey.

    Science.gov (United States)

    Demirdöğen Çetinoğlu, Ezgi; Görek Dilektaşlı, Aslı; Demir, Nefise Ateş; Özkaya, Güven; Acet, Nilüfer Aylin; Durmuş, Eda; Ursavaş, Ahmet; Karadağ, Mehmet; Ege, Ercüment

    2015-09-01

    Driving performance is known to be very sensitive to cognitive-psychomotor impairment. The aim of the study was to determine the relationship between obesity, risk of obstructive sleep apnoea (OSA), daytime sleepiness, history of road traffic accident (RTA) and performance on a driving simulator, among commercial drivers. We examined commercial vehicle drivers admitted to Psycho-Technical Assessment System (PTAS), which is a computer-aided system that includes a driving simulator test and tests assessing psychomotor-cognitive skills required for driving. Risk of OSA and daytime sleepiness were assessed by the Berlin Questionnaire and the Epworth Sleepiness Scale (ESS), respectively. A total of 282 commercial vehicle drivers were consecutively enrolled. The age range was 29-76 years. Thirty drivers were at high risk of OSA. Median ESS of the group was 2 (0-20). Forty-seven percent of the subjects at high risk of OSA failed in early reaction time test, while 28% of the drivers with low risk of OSA failed (p = 0.03). The obese drivers failed the peripheral vision test when compared with non-obese drivers (p = 0.02). ESS was higher for drivers with a history of RTA when compared to those without RTA (p = 0.02). Cognitive-psychomotor functions can be impaired in obese and high risk of OSA patients. In our opinion, requiring obese and/or high risk of OSA drivers to take PTAS tests that assess driving skills and psychomotor-cognitive functions crucial to those skills would significantly improve road traffic safety, which is of considerable importance to public health.

  4. Determining the explosion effects on the Gasbuggy reservoir from computer simulation of the postshot gas production history

    Energy Technology Data Exchange (ETDEWEB)

    Rogers, Leo A [El Paso Natural Gas Company (United States)

    1970-05-01

    Analysis of the gas production data from Gasbuggy to deduce reservoir properties outside the chimney is complicated by the large gas storage volume in the chimney because the gas flow from the surrounding reservoir into the chimney cannot be directly measured. This problem was overcome by developing a chimney volume factor F (M{sup 2}CF/PSI) based upon analysis of rapid drawdowns during the production tests. The chimney volume factor was in turn used to construct the time history of the required influx of gas into the chimney from the surrounding reservoir. The most probable value of F to describe the chimney is found to be 0.150 M{sup 2}CF/PSI. Postulated models of the reservoir properties outside the chimney are examined by calculating the pressure distribution and flow of gas through the reservoir with the experimentally observed chimney pressure history applied to the cavity wall. The calculated influx from the reservoir into the chimney is then compared to the required influx and the calculated pressure at a radius of 300 feet is compared to the observed pressures in a shut-in satellite well (GB-2RS) which intersects the gas-bearing formation 300 feet from the center of the chimney. A description of the mathematics in the computer program used to perform the calculations is given. Gas flow for a radial model wherein permeability and porosity are uniform through the gas producing sand outside the chimney was calculated for several values of permeability. These calculations indicated that for the first drawdown test (July 1968) the permeability-producing height product (kh) was in the region of 15 to 30 millidarcy-feet (md-ft) and that after several months of testing, the effective kh had dropped to less than 8 md-ft. Calculations wherein (1) the permeability decreases from the chimney out to the 'fracture' radius, and (2) an increased production height is used near the chimney, match the data better than the simple radial model. Reasonable fits to the data for

  5. Determining the explosion effects on the Gasbuggy reservoir from computer simulation of the postshot gas production history

    International Nuclear Information System (INIS)

    Rogers, Leo A.

    1970-01-01

    Analysis of the gas production data from Gasbuggy to deduce reservoir properties outside the chimney is complicated by the large gas storage volume in the chimney because the gas flow from the surrounding reservoir into the chimney cannot be directly measured. This problem was overcome by developing a chimney volume factor F (M 2 CF/PSI) based upon analysis of rapid drawdowns during the production tests. The chimney volume factor was in turn used to construct the time history of the required influx of gas into the chimney from the surrounding reservoir. The most probable value of F to describe the chimney is found to be 0.150 M 2 CF/PSI. Postulated models of the reservoir properties outside the chimney are examined by calculating the pressure distribution and flow of gas through the reservoir with the experimentally observed chimney pressure history applied to the cavity wall. The calculated influx from the reservoir into the chimney is then compared to the required influx and the calculated pressure at a radius of 300 feet is compared to the observed pressures in a shut-in satellite well (GB-2RS) which intersects the gas-bearing formation 300 feet from the center of the chimney. A description of the mathematics in the computer program used to perform the calculations is given. Gas flow for a radial model wherein permeability and porosity are uniform through the gas producing sand outside the chimney was calculated for several values of permeability. These calculations indicated that for the first drawdown test (July 1968) the permeability-producing height product (kh) was in the region of 15 to 30 millidarcy-feet (md-ft) and that after several months of testing, the effective kh had dropped to less than 8 md-ft. Calculations wherein (1) the permeability decreases from the chimney out to the 'fracture' radius, and (2) an increased production height is used near the chimney, match the data better than the simple radial model. Reasonable fits to the data for the

  6. Canopy temperature for simulation of heat stress in irrigated wheat in a semi-arid environment: A multi-model comparison

    DEFF Research Database (Denmark)

    Webber, Heidi; Martre, Pierre; Asseng, Senthold

    2017-01-01

    Even brief periods of high temperatures occurring around flowering and during grain filling can severely reduce grain yield in cereals. Recently, ecophysiological and crop models have begun to represent such phenomena. Most models use air temperature (Tair) in their heat stress responses despite...... evidence that crop canopy temperature (Tc) better explains grain yield losses. Tc can deviate significantly from Tair based on climatic factors and the crop water status. The broad objective of this study was to evaluate whether simulation of Tc improves the ability of crop models to simulate heat stress...... impacts on wheat under irrigated conditions. Nine process-based models, each using one of three broad approaches (empirical, EMP; energy balance assuming neutral atmospheric stability, EBN; and energy balance correcting for the atmospheric stability conditions, EBSC) to simulate Tc, simulated grain yield...

  7. Is it Trauma- or Fantasy-based? Comparing dissociative identity disorder, post-traumatic stress disorder, simulators, and controls.

    Science.gov (United States)

    Vissia, E M; Giesen, M E; Chalavi, S; Nijenhuis, E R S; Draijer, N; Brand, B L; Reinders, A A T S

    2016-08-01

    The Trauma Model of dissociative identity disorder (DID) posits that DID is etiologically related to chronic neglect and physical and/or sexual abuse in childhood. In contrast, the Fantasy Model posits that DID can be simulated and is mediated by high suggestibility, fantasy proneness, and sociocultural influences. To date, these two models have not been jointly tested in individuals with DID in an empirical manner. This study included matched groups [patients (n = 33) and controls (n = 32)] that were compared on psychological Trauma and Fantasy measures: diagnosed genuine DID (DID-G, n = 17), DID-simulating healthy controls (DID-S, n = 16), individuals with post-traumatic stress disorder (PTSD, n = 16), and healthy controls (HC, n = 16). Additionally, personality-state-dependent measures were obtained for DID-G and DID-S; both neutral personality states (NPS) and trauma-related personality states (TPS) were tested. For Trauma measures, the DID-G group had the highest scores, with TPS higher than NPS, followed by the PTSD, DID-S, and HC groups. The DID-G group was not more fantasy-prone or suggestible and did not generate more false memories. Malingering measures were inconclusive. Evidence consistently supported the Trauma Model of DID and challenges the core hypothesis of the Fantasy Model. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  8. Possible origin of the discrepancy in Peierls stresses of fcc metals: First-principles simulations of dislocation mobility in aluminum

    Science.gov (United States)

    Shin, Ilgyou; Carter, Emily A.

    2013-08-01

    Dislocation motion governs the strength and ductility of metals, and the Peierls stress (σp) quantifies dislocation mobility. σp measurements carry substantial uncertainty in face-centered cubic (fcc) metals, and σp values can differ by up to two orders of magnitude. We perform first-principles simulations based on orbital-free density functional theory (OFDFT) to calculate the most accurate currently possible σp for the motion of (1)/(2)111 dislocations in fcc Al. We predict the σps of screw and edge dislocations (dissociated in their equilibrium state) to be 1.9×10-4G and 4.9×10-5G, respectively (G is the shear modulus). These values fall within the range of measurements from mechanical deformation tests (10-4-10-5G). OFDFT also finds a new metastable structure for a screw dislocation not seen in earlier simulations, in which a dislocation core on the glide plane does not dissociate into partials. The corresponding σp for this undissociated dislocation is predicted to be 1.1×10-2G, which agrees with typical Bordoni peak measurements (10-2-10-3G). The calculated σps for dissociated and undissociated screw dislocations differ by two orders of magnitude. The presence of undissociated, as well as dissociated, screw dislocations may resolve the decades-long mystery in fcc metals regarding the two orders of magnitude discrepancy in σp measurements.

  9. Stochastic stresses in granular matter simulated by dripping identical ellipses into plane silo

    DEFF Research Database (Denmark)

    Berntsen, Kasper Nikolaj; Ditlevsen, Ove Dalager

    2000-01-01

    A two-dimensional silo pressure model-problem is investigated by molecular dynamics simulations. A plane silo container is filled by a granular matter consisting of congruent elliptic particles dropped one by one into the silo. A suitable energy absorbing contact force mechanism is activatedduring...... the granular matter in the silo are compared to thesolution of a stochastic equilibrium differential equation. In this equation the stochasticity source is a homogeneouswhite noise gamma-distributed side pressure factor field along the walls. This is a generalization of the deterministic side pressure factor...... proposed by Janssen in 1895. The stochastic Janssen factor model is shown to be fairly consistentwith the observations from which the mean and the intensity of the white noise is estimated by the method of maximumlikelihood using the properties of the gamma-distribution. Two wall friction coefficients...

  10. Simulation

    DEFF Research Database (Denmark)

    Gould, Derek A; Chalmers, Nicholas; Johnson, Sheena J

    2012-01-01

    Recognition of the many limitations of traditional apprenticeship training is driving new approaches to learning medical procedural skills. Among simulation technologies and methods available today, computer-based systems are topical and bring the benefits of automated, repeatable, and reliable p...... performance assessments. Human factors research is central to simulator model development that is relevant to real-world imaging-guided interventional tasks and to the credentialing programs in which it would be used....

  11. A simulation of atomic force microscope microcantilever in the tapping mode utilizing couple stress theory.

    Science.gov (United States)

    Abbasi, Mohammad

    2018-04-01

    The nonlinear vibration behavior of a Tapping mode atomic force microscopy (TM-AFM) microcantilever under acoustic excitation force has been modeled and investigated. In dynamic AFM, the tip-surface interactions are strongly nonlinear, rapidly changing and hysteretic. First, the governing differential equation of motion and boundary conditions for dynamic analysis are obtained using the modified couple stress theory. Afterwards, closed-form expressions for nonlinear frequency and effective nonlinear damping ratio are derived utilizing perturbation method. The effect of tip connection position on the vibration behavior of the microcantilever are also analyzed. The results show that nonlinear frequency is size dependent. According to the results, an increase in the equilibrium separation between the tip and the sample surface reduces the overall effect of van der Waals forces on the nonlinear frequency, but its effect on the effective nonlinear damping ratio is negligible. The results also indicate that both the change in the distance between tip and cantilever free end and the reduction of tip radius have significant effects on the accuracy and sensitivity of the TM-AFM in the measurement of surface forces. The hysteretic behavior has been observed in the near resonance frequency response due to softening and hardening of the forced vibration response. Copyright © 2018 Elsevier Ltd. All rights reserved.

  12. Numerical simulation of stress-strain state of electrophoretic shell molds

    Science.gov (United States)

    Sviridov, A. V.; Odinokov, V. I.; Dmitriev, E. A.; Evstigneev, A. I.; Bashkov, O. V.

    2017-10-01

    In the foundry engineering, castings obtained in one-piece non-gas-generating high-refractory electrophoretic shell molds (ShM) by investment patterns (IP) have an increased rejects percentage associated with low deformation resistance and crack resistance of the SM at different stages of their formation and manufacturing. Crack resistance of the ShM based on IP depends mainly on their stress-strain state (SSS) at various stages of mold forming. SSS decrease significantly improves their crack resistance and decreases their rejects percentage of castings occurring due to clogging and surface defects. In addition, the known methods of decreasing the SSS are still poorly understood. Thus, current research trends are to determine SSS at each stage of ShM forming and develop the ways to decrease it. Theoretical predicting of crack formation in multiple-layer axisymmetric shell molds is given in the work [1], and SSS of multiple-layer axisymmetric shell molds is given in the work [2]. Monolayer electrophoretic ShM had a lack of concern in this field, thus it became an argument for the present workMathematical Model of ShM SSS

  13. Assessment of susceptibility of Type 304 stainless steel to intergranular stress corrosion cracking in simulated Savannah River Reactor environments

    International Nuclear Information System (INIS)

    Ondrejcin, R.S.; Caskey, C.R. Jr.

    1989-01-01

    Intergranular stress corrosion cracking (IGSCC) of Type 304 stainless steel rate tests (CERT) of specimens machined was evaluated by constant extension from Savannah River Plant (SRP) decontaminated process water piping. Results from 12 preliminary CERT tests verified that IGSCC occurred over a wide range of simulated SRP envirorments. 73 specimens were tested in two statistical experimental designs of the central composite class. In one design, testing was done in environments containing hydrogen peroxide; in the other design, hydrogen peroxide was omitted but oxygen was added to the environment. Prediction equations relating IGSCC to temperature and environmental variables were formulated. Temperature was the most important independent variable. IGSCC was severe at 100 to 120C and a threshold temperature between 40C and 55C was identified below which IGSCC did not occur. In environments containing hydrogen peroxide, as in SRP operation, a reduction in chloride concentration from 30 to 2 ppB also significantly reduced IGSCC. Reduction in sulfate concentration from 50 to 7 ppB was effective in reducing IGSCC provided the chloride concentration was 30 ppB or less and temperature was 95C or higher. Presence of hydrogen peroxide in the environment increased IGSCC except when chloride concentration was 11 ppB or less. Actual concentrations of hydrogen peroxide, oxygen and carbon dioxide did not affect IGSCC. Large positive ECP values (+450 to +750 mV Standard Hydrogen Electrode (SHE)) in simulated SRP environments containing hydrogen peroxide and were good agreement with ECP measurements made in SRP reactors, indicating that the simulated environments are representative of SRP reactor environments. Overall CERT results suggest that the most effective method to reduce IGSCC