A crystallographic model for the tensile and fatigue response for Rene N4 at 982 C

NASA Technical Reports Server (NTRS)

Sheh, M. Y.; Stouffer, D. C.

1990-01-01

An anisotropic constitutive model based on crystallographic slip theory was formulated for nickel-base single-crystal superalloys. The current equations include both drag stress and back stress state variables to model the local inelastic flow. Specially designed experiments have been conducted to evaluate the existence of back stress in single crystals. The results showed that the back stress effect of reverse inelastic flow on the unloading stress is orientation-dependent, and a back stress state variable in the inelastic flow equation is necessary for predicting inelastic behavior. Model correlations and predictions of experimental data are presented for the single crystal superalloy Rene N4 at 982 C.

Stress drops of induced and tectonic earthquakes in the central United States are indistinguishable.

PubMed

Huang, Yihe; Ellsworth, William L; Beroza, Gregory C

2017-08-01

Induced earthquakes currently pose a significant hazard in the central United States, but there is considerable uncertainty about the severity of their ground motions. We measure stress drops of 39 moderate-magnitude induced and tectonic earthquakes in the central United States and eastern North America. Induced earthquakes, more than half of which are shallower than 5 km, show a comparable median stress drop to tectonic earthquakes in the central United States that are dominantly strike-slip but a lower median stress drop than that of tectonic earthquakes in the eastern North America that are dominantly reverse-faulting. This suggests that ground motion prediction equations developed for tectonic earthquakes can be applied to induced earthquakes if the effects of depth and faulting style are properly considered. Our observation leads to the notion that, similar to tectonic earthquakes, induced earthquakes are driven by tectonic stresses.

Stress drops of induced and tectonic earthquakes in the central United States are indistinguishable

PubMed Central

Huang, Yihe; Ellsworth, William L.; Beroza, Gregory C.

2017-01-01

Induced earthquakes currently pose a significant hazard in the central United States, but there is considerable uncertainty about the severity of their ground motions. We measure stress drops of 39 moderate-magnitude induced and tectonic earthquakes in the central United States and eastern North America. Induced earthquakes, more than half of which are shallower than 5 km, show a comparable median stress drop to tectonic earthquakes in the central United States that are dominantly strike-slip but a lower median stress drop than that of tectonic earthquakes in the eastern North America that are dominantly reverse-faulting. This suggests that ground motion prediction equations developed for tectonic earthquakes can be applied to induced earthquakes if the effects of depth and faulting style are properly considered. Our observation leads to the notion that, similar to tectonic earthquakes, induced earthquakes are driven by tectonic stresses. PMID:28782040

Anisotropic constitutive modeling for nickel base single crystal superalloys using a crystallographic approach

NASA Technical Reports Server (NTRS)

Stouffer, D. C.; Sheh, M. Y.

1988-01-01

A micromechanical model based on crystallographic slip theory was formulated for nickel-base single crystal superalloys. The current equations include both drag stress and back stress state variables to model the local inelastic flow. Specially designed experiments have been conducted to evaluate the effect of back stress in single crystals. The results showed that (1) the back stress is orientation dependent; and (2) the back stress state variable in the inelastic flow equation is necessary for predicting anelastic behavior of the material. The model also demonstrated improved fatigue predictive capability. Model predictions and experimental data are presented for single crystal superalloy Rene N4 at 982 C.

Sinusoidal current and stress evolutions in lithium-ion batteries

NASA Astrophysics Data System (ADS)

Yang, Xiao-Guang; Bauer, Christoph; Wang, Chao-Yang

2016-09-01

Mechanical breakdown of graphite materials due to diffusion-induced stress (DIS) is a key aging mechanism of lithium-ion batteries. In this work, electrochemical-thermal coupled model along with a DIS model is developed to study the DIS distribution across the anode thickness. Special attention is paid to the evolution behavior of surface tangential stress (STS) in the discharge process for graphite at different locations of the anode. For the first time, we report that the evolution of STS, as well as local current, at all locations of the anode, evolve like sinusoidal waves in the discharge process with several crests and troughs. The staging behavior of graphite active material, in particular the sharp change of open-circuit potential (OCP) of graphite in the region between two plateaus, is found to be the root cause for the sinusoidal patterns of current and stress evolution. Furthermore, the effects of various parameters, such as starting state of charge, discharge C-rate and electrode thickness on the current and stress evolutions are investigated.

Cognitive behavioral therapy for irritable bowel syndrome: the effects on state and trait anxiety and the autonomic nervous system during induced rectal distensions - An uncontrolled trial.

PubMed

Edebol-Carlman, Hanna; Schrooten, Martien; Ljótsson, Brjánn; Boersma, Katja; Linton, Steven; Brummer, Robert Jan

2018-01-26

Irritable bowel syndrome (IBS), is a common multifactorial gastrointestinal disorder linked to disturbances in the microbe gut-brain axis. Cognitive behavioral therapy (CBT), in face-to-face format has showed promising results on IBS and its associated psychological symptoms. The present study explored for the first time if CBT for IBS affects the autonomic nervous system (ANS) during experimentally induced visceral pain and cognitive stress, respectively. The levels of state and trait anxiety, current and perceived stress were also evaluated. In this uncontrolled trial, individual CBT was performed in face-to-face format for 12 weeks in 18 subjects with IBS. Heart rate variability and skin conductance were measured during experimentally induced visceral pain and during a cognitive task (Stroop color-word test), before and after intervention. The levels of state and trait anxiety as well as self-rated current and perceived stress were also measured before and after the intervention. CBT did not affect ANS activity during experimentally induced visceral pain and cognitive stress. The sympathetic activity was high, typical for IBS and triggered during both visceral pain and cognitive stress. The levels of state and trait anxiety significantly decreased after the intervention. No significant changes in self-rated current or perceived stress were found. Results suggest that face-to-face CBT for IBS improved anxiety- a key psychological mechanism for the IBS pathophysiology, rather than the autonomic stress response to experimentally induced visceral pain and cognitive stress, respectively. This study indicates that IBS patients present high levels of stress and difficulties coping with anxiety and ANS activity during visceral pain and a cognitive stress test, respectively. These manifestations of IBS are however not targeted by CBT, and do not seem to be central for the study participants IBS symptoms according to the current and our previous study. Face-to-face CBT for IBS, it does not seem to affect modulation of ANS activity in response to induced visceral pain or cognitive stress. Instead, face-to-face CBT decreased levels of state and trait anxiety. Implications for further studies include that anxiety seems to be important in the IBS pathophysiology, and needs further scientific attention. This is in line with the fear-avoidance model which suggests that anxious responses to pain and discomfort drive hypervigilance to, and (behavioral) avoidance of, symptom provoking stimuli and vice versa. Catastrophic cognitions, hypervigilance and avoidant behavioral responses are proposed to produce vicious circles that withhold and exacerbate pain-related symptoms and disability, and lead to lower quality of life. Larger scale studies of potential autonomic changes are needed in order to elucidate which mechanisms elicit its effects in face-to-face CBT for IBS, and provide new avenues in understanding the pathophysiology of IBS.

High temperature-induced abnormal suppression of sub-threshold swing and on-current degradations under hot-carrier stress in a-InGaZnO thin film transistors

NASA Astrophysics Data System (ADS)

Tsai, Ming-Yen; Chang, Ting-Chang; Chu, Ann-Kuo; Hsieh, Tien-Yu; Chen, Te-Chih; Lin, Kun-Yao; Tsai, Wu-Wei; Chiang, Wen-Jen; Yan, Jing-Yi

2013-07-01

This letter investigates the effect of temperature on hot-carrier stress-induced degradation behavior in InGaZnO thin film transistors. After hot-carrier stress at 25 °C, serious on-current and subthreshold swing degradations are observed due to trap state generation near the drain side. For identical stress performed at elevated temperatures, current degradation in the I-V transfer curve under reverse mode is gradually suppressed and the anomalous hump in the gate-to-drain capacitance-voltage curve becomes more severe. These suppressed degradations and the more severe hump can be both attributed to hole-trapping near the drain side due to high drain bias at high temperature.

Field Study of Stress: Psychophysiological Measures During Project Supex.

DTIC Science & Technology

1978-10-01

recordings proved to be unreliable utilizing the current procedures. The perceived scales evaluated the current state of the individual, but they were not good predictors of performance or heart rate activity. (Author)

The study of the stress - strain state of the tank with bottom water drainage during operation

NASA Astrophysics Data System (ADS)

Shchipkova, Yu V.; Tokarev, V. V.

2018-04-01

Bottom drainage from tank is a current problem in modern tank usage. This article proposes the use of the bottom drainage system from the tank with the shape of the sloped cone to the centre of it. Changing the bottom design alters the stress - strain state to be analyzed in the Ansys. The analysis concluded that the proposed drainage system should be applied.

Anisotropic constitutive modeling for nickel-base single crystal superalloys. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Sheh, Michael Y.

1988-01-01

An anisotropic constitutive model was developed based on crystallographic slip theory for nickel base single crystal superalloys. The constitutive equations developed utilizes drag stress and back stress state variables to model the local inelastic flow. Specially designed experiments were conducted to evaluate the existence of back stress in single crystal superalloy Rene N4 at 982 C. The results suggest that: (1) the back stress is orientation dependent; and (2) the back stress state variable is required for the current model to predict material anelastic recovery behavior. The model was evaluated for its predictive capability on single crystal material behavior including orientation dependent stress-strain response, tension/compression asymmetry, strain rate sensitivity, anelastic recovery behavior, cyclic hardening and softening, stress relaxation, creep and associated crystal lattice rotation. Limitation and future development needs are discussed.

GASICA: generic automated stress induction and control application design of an application for controlling the stress state.

PubMed

van der Vijgh, Benny; Beun, Robbert J; van Rood, Maarten; Werkhoven, Peter

2014-01-01

In a multitude of research and therapy paradigms it is relevant to know, and desirably to control, the stress state of a patient or participant. Examples include research paradigms in which the stress state is the dependent or independent variable, or therapy paradigms where this state indicates the boundaries of the therapy. To our knowledge, no application currently exists that focuses specifically on the automated control of the stress state while at the same time being generic enough to be used in various therapy and research purposes. Therefore, we introduce GASICA, an application aimed at the automated control of the stress state in a multitude of therapy and research paradigms. The application consists of three components: a digital stressor game, a set of measurement devices, and a feedback model. These three components form a closed loop (called a biocybernetic loop by Pope et al. (1995) and Fairclough (2009) that continuously presents an acute psychological stressor, measures several physiological responses to this stressor, and adjusts the stressor intensity based on these measurements by means of the feedback model, hereby aiming to control the stress state. In this manner GASICA presents multidimensional and ecological valid stressors, whilst continuously in control of the form and intensity of the presented stressors, aiming at the automated control of the stress state. Furthermore, the application is designed as a modular open-source application to easily implement different therapy and research tasks using a high-level programming interface and configuration file, and allows for the addition of (existing) measurement equipment, making it usable for various paradigms.

GASICA: generic automated stress induction and control application design of an application for controlling the stress state

PubMed Central

van der Vijgh, Benny; Beun, Robbert J.; van Rood, Maarten; Werkhoven, Peter

2014-01-01

In a multitude of research and therapy paradigms it is relevant to know, and desirably to control, the stress state of a patient or participant. Examples include research paradigms in which the stress state is the dependent or independent variable, or therapy paradigms where this state indicates the boundaries of the therapy. To our knowledge, no application currently exists that focuses specifically on the automated control of the stress state while at the same time being generic enough to be used in various therapy and research purposes. Therefore, we introduce GASICA, an application aimed at the automated control of the stress state in a multitude of therapy and research paradigms. The application consists of three components: a digital stressor game, a set of measurement devices, and a feedback model. These three components form a closed loop (called a biocybernetic loop by Pope et al. (1995) and Fairclough (2009) that continuously presents an acute psychological stressor, measures several physiological responses to this stressor, and adjusts the stressor intensity based on these measurements by means of the feedback model, hereby aiming to control the stress state. In this manner GASICA presents multidimensional and ecological valid stressors, whilst continuously in control of the form and intensity of the presented stressors, aiming at the automated control of the stress state. Furthermore, the application is designed as a modular open-source application to easily implement different therapy and research tasks using a high-level programming interface and configuration file, and allows for the addition of (existing) measurement equipment, making it usable for various paradigms. PMID:25538554

Exploring the Individual Contributory Personality Factors of Stress: A Survey of Washington State Elementary Teachers

ERIC Educational Resources Information Center

Dean, Effie J.

2010-01-01

Prolonged stress is shown to lead to low productivity, which is one of the leading causes of poor performance, and high absenteeism/turnover in occupational fields (Norton, 2002). The field of education is a prime example of low productivity resulting from prolonged stress (Norton, 2002). Currently, there are many existing studies on environmental…

Stress and Anxiety Management in Nursing Students: Biofeedback and Mindfulness Meditation.

PubMed

Ratanasiripong, Paul; Park, Janet F; Ratanasiripong, Nop; Kathalae, Duangrat

2015-09-01

The current study investigated the efficacy of two brief intervention programs-biofeedback and mindfulness meditation-on levels of state anxiety and perceived stress in second-year Thai nursing students as they began clinical training. Eighty-nine participants from a public nursing college in Thailand were randomly assigned to one of three groups: biofeedback group, mindfulness meditation group, or a control group. All participants were given pre- and postintervention surveys, which included demographic information; the State-Trait Anxiety Inventory (State Anxiety Scale); and the Perceived Stress Scale. Findings indicated that biofeedback significantly reduced anxiety and maintained stress levels in nursing students. Mindfulness meditation similarly decreased anxiety levels, while also significantly lowering stress levels. The biofeedback group exhibited significant reduction in anxiety levels among the three groups at postintervention. Despite stressors and demands nursing students experience as they begin clinical practice, study findings support the use of biofeedback and mindfulness meditation interventions to assist nursing students in managing stress and anxiety. Copyright 2015, SLACK Incorporated.

Scenario-neutral Food Security Risk Assessment: A livestock Heat Stress Case Study

NASA Astrophysics Data System (ADS)

Broman, D.; Rajagopalan, B.; Hopson, T. M.

2015-12-01

Food security risk assessments can provide decision-makers with actionable information to identify critical system limitations, and alternatives to mitigate the impacts of future conditions. The majority of current risk assessments have been scenario-led and results are limited by the scenarios - selected future states of the world's climate system and socioeconomic factors. A generic scenario-neutral framework for food security risk assessments is presented here that uses plausible states of the world without initially assigning likelihoods. Measures of system vulnerabilities are identified and system risk is assessed for these states. This framework has benefited greatly by research in the water and natural resource fields to adapt their planning to provide better risk assessments. To illustrate the utility of this framework we develop a case study using livestock heat stress risk within the pastoral system of West Africa. Heat stress can have a major impact not only on livestock owners, but on the greater food production system, decreasing livestock growth, milk production, and reproduction, and in severe cases, death. A heat stress index calculated from daily weather is used as a vulnerability measure and is computed from historic daily weather data at several locations in the study region. To generate plausible states, a stochastic weather generator is developed to generate synthetic weather sequences at each location, consistent with the seasonal climate. A spatial model of monthly and seasonal heat stress provide projections of current and future livestock heat stress measures across the study region, and can incorporate in seasonal climate and other external covariates. These models, when linked with empirical thresholds of heat stress risk for specific breeds offer decision-makers with actionable information for use in near-term warning systems as well as for future planning. Future assessment can indicate under which states livestock are at greatest risk of heat stress; when coupled with assessments of additional measures (e.g. water and fodder availability) can inform on alternatives that provide satisfactory performance under a wide range of states (e.g. optimal cattle breed, supplemental feed, increased water access).

Non-Destructive Quantification of Plastic Deformation in Steel: Employing X-Ray Diffraction Peak Broadening Analysis

DTIC Science & Technology

2013-09-01

pattern of an alloy, such as steel , reveals, among other properties (ex., phase composition, crystal structure), information about the strain state...This, together with elastic strain / residual stress analysis, would enable better evaluation of the current state of health of steel structures and...plastic strain in a component/structure may better evaluate the current state of health of steel structures and components as they near predetermined

Physiological Reactivity to Psychological Stress in Human Pregnancy: Current Knowledge and Future Directions

PubMed Central

Christian, Lisa M.

2012-01-01

Cardiovascular and neuroendocrine reactivity to acute stress are important predictors of health outcomes in non-pregnant populations. Greater magnitude and duration of physiological responses have been associated with increased risk of hypertensive disorders and diabetes, greater susceptibility to infectious illnesses, suppression of cell-mediated immunity as well as risk for depression and anxiety disorders. Stress reactivity during pregnancy has unique implications for maternal health, birth outcomes, and fetal development. However, as compared to the larger literature, our understanding of the predictors and consequences of exaggerated stress reactivity in pregnancy is limited. This paper reviews the current state of this literature with an emphasis on gaps in knowledge and future directions. PMID:22800930

The development and validation of a numerical integration method for non-linear viscoelastic modeling

PubMed Central

Ramo, Nicole L.; Puttlitz, Christian M.

2018-01-01

Compelling evidence that many biological soft tissues display both strain- and time-dependent behavior has led to the development of fully non-linear viscoelastic modeling techniques to represent the tissue’s mechanical response under dynamic conditions. Since the current stress state of a viscoelastic material is dependent on all previous loading events, numerical analyses are complicated by the requirement of computing and storing the stress at each step throughout the load history. This requirement quickly becomes computationally expensive, and in some cases intractable, for finite element models. Therefore, we have developed a strain-dependent numerical integration approach for capturing non-linear viscoelasticity that enables calculation of the current stress from a strain-dependent history state variable stored from the preceding time step only, which improves both fitting efficiency and computational tractability. This methodology was validated based on its ability to recover non-linear viscoelastic coefficients from simulated stress-relaxation (six strain levels) and dynamic cyclic (three frequencies) experimental stress-strain data. The model successfully fit each data set with average errors in recovered coefficients of 0.3% for stress-relaxation fits and 0.1% for cyclic. The results support the use of the presented methodology to develop linear or non-linear viscoelastic models from stress-relaxation or cyclic experimental data of biological soft tissues. PMID:29293558

Application of Non-destructive Methods of Stress-strain State at Hazardous Production Facilities

NASA Astrophysics Data System (ADS)

Shram, V.; Kravtsova, Ye; Selsky, A.; Bezborodov, Yu; Lysyannikova, N.; Lysyannikov, A.

2016-06-01

The paper deals with the sources of accidents in distillation columns, on the basis of which the most dangerous defects are detected. The analysis of the currently existing methods of non-destructive testing of the stress-strain state is performed. It is proposed to apply strain and acoustic emission techniques to continuously monitor dangerous objects, which helps prevent the possibility of accidents, as well as reduce the work.

Deterministic and Probabilistic Creep and Creep Rupture Enhancement to CARES/Creep: Multiaxial Creep Life Prediction of Ceramic Structures Using Continuum Damage Mechanics and the Finite Element Method

NASA Technical Reports Server (NTRS)

Jadaan, Osama M.; Powers, Lynn M.; Gyekenyesi, John P.

1998-01-01

High temperature and long duration applications of monolithic ceramics can place their failure mode in the creep rupture regime. A previous model advanced by the authors described a methodology by which the creep rupture life of a loaded component can be predicted. That model was based on the life fraction damage accumulation rule in association with the modified Monkman-Grant creep ripture criterion However, that model did not take into account the deteriorating state of the material due to creep damage (e.g., cavitation) as time elapsed. In addition, the material creep parameters used in that life prediction methodology, were based on uniaxial creep curves displaying primary and secondary creep behavior, with no tertiary regime. The objective of this paper is to present a creep life prediction methodology based on a modified form of the Kachanov-Rabotnov continuum damage mechanics (CDM) theory. In this theory, the uniaxial creep rate is described in terms of stress, temperature, time, and the current state of material damage. This scalar damage state parameter is basically an abstract measure of the current state of material damage due to creep deformation. The damage rate is assumed to vary with stress, temperature, time, and the current state of damage itself. Multiaxial creep and creep rupture formulations of the CDM approach are presented in this paper. Parameter estimation methodologies based on nonlinear regression analysis are also described for both, isothermal constant stress states and anisothermal variable stress conditions This creep life prediction methodology was preliminarily added to the integrated design code CARES/Creep (Ceramics Analysis and Reliability Evaluation of Structures/Creep), which is a postprocessor program to commercially available finite element analysis (FEA) packages. Two examples, showing comparisons between experimental and predicted creep lives of ceramic specimens, are used to demonstrate the viability of this methodology and the CARES/Creep program.

An in-situ investigation of the acute effects of Bikram yoga on positive- and negative affect, and state-anxiety in context of perceived stress.

PubMed

Szabo, Attila; Nikházy, Letícia; Tihanyi, Benedek; Boros, Szilvia

2017-04-01

Bikram yoga is a relatively new, but an increasingly popular form of exercise. Its health benefits were demonstrated on physical and psychological measures. The current field study tested the acute effects of Bikram yoga on practitioners' positive-/negative-affect and state-anxiety, and their link to the self-perceived stress, in Bikram yoga participants. Field study, within-participants design, testing perceived stress and its relation to changes in positive-/negative-affect and state-anxiety in 53 habitual Bikram yoga participants. Statistically significant positive changes emerged in all three psychological measures after the 90-min Bikram yoga session. The decrease in negative-affect and state-anxiety were significantly and positively related to the perceived stress. Estimated effort was unrelated to the magnitude of the changes recorded in the psychological measures. Heart rates and self-report measures indicated that physically Bikram yoga is only mildly challenging. The findings illustrate that, independently of the physical effort, Bikram yoga is a new mild form of exercise that reduces negative-affect and state-anxiety, and the reduction is directly related to the perceived stress. Therefore, Bikram yoga appears to be beneficial for all practitioners, but even more so for the individuals who experience substantial stress in the daily life.

Physiological reactivity to psychological stress in human pregnancy: current knowledge and future directions.

PubMed

Christian, Lisa M

2012-11-01

Cardiovascular and neuroendocrine reactivity to acute stress are important predictors of health outcomes in non-pregnant populations. Greater magnitude and duration of physiological responses have been associated with increased risk of hypertensive disorders and diabetes, greater susceptibility to infectious illnesses, suppression of cell-mediated immunity as well as risk for depression and anxiety disorders. Stress reactivity during pregnancy has unique implications for maternal health, birth outcomes, and fetal development. However, as compared to the larger literature, our understanding of the predictors and consequences of exaggerated stress reactivity in pregnancy is limited. This paper reviews the current state of this literature with an emphasis on gaps in knowledge and future directions. Copyright © 2012 Elsevier Ltd. All rights reserved.

A Randomized Controlled Dismantling Trial of Post-Workshop Consultation Strategies to Increase Effectiveness and Fidelity to an Evidence-Based Psychotherapy for Posttraumatic Stress Disorder

DTIC Science & Technology

2013-08-01

not eligible for CPT based on the state of research evidence, including those with: current uncontrolled psychotic or bipolar disorder ; substance...among trauma, post-traumatic stress disorder , and health outcomes. Adv Mind Body Med 2004, 20(1):18–29. 10. Kessler RC: Posttraumatic Stress Disorder ...to an evidence-based psychotherapy for Posttraumatic stress disorder Shannon Wiltsey Stirman1, Norman Shields2, Josh Deloriea3, Meredith SH Landy3

Direct Observation of the Biaxial Stress Effect on Efficiency Droop in GaN-based Light-emitting Diode under Electrical Injection.

PubMed

Zheng, Jinjian; Li, Shuiqing; Chou, Chilun; Lin, Wei; Xun, Feilin; Guo, Fei; Zheng, Tongchang; Li, Shuping; Kang, Junyong

2015-12-04

Light-emitting diode (LED) efficiency has attracted considerable interest because of the extended use of solid-state lighting. Owing to lack of direct measurement, identification of the reasons for efficiency droop has been restricted. A direct measurement technique is developed in this work for characterization of biaxial stress in GaN-based blue LEDs under electrical injection. The Raman shift of the GaN E2 mode evidently decreases by 4.4 cm(-1) as the driving current on GaN-based LEDs increases to 700 mA. Biaxial compressive stress is released initially and biaxial tensile stress builds up as the current increases with respect to the value of stress-free GaN. First-principles calculations reveal that electron accumulation is responsible for the stress variation in InxGa1-xN/GaN quantum wells, and then reduces the transition probability among quantum levels. This behavior is consistent with the measured current-dependent external quantum efficiency. The rule of biaxial stress-dependent efficiency is further validated by controlling the biaxial stress of GaN-based LEDs with different sapphire substrate thicknesses. This work provides a method for direct observation of the biaxial stress effect on efficiency droop in LEDs under electrical injection.

Direct Observation of the Biaxial Stress Effect on Efficiency Droop in GaN-based Light-emitting Diode under Electrical Injection

PubMed Central

Zheng, Jinjian; Li, Shuiqing; Chou, Chilun; Lin, Wei; Xun, Feilin; Guo, Fei; Zheng, Tongchang; Li, Shuping; Kang, Junyong

2015-01-01

Light-emitting diode (LED) efficiency has attracted considerable interest because of the extended use of solid-state lighting. Owing to lack of direct measurement, identification of the reasons for efficiency droop has been restricted. A direct measurement technique is developed in this work for characterization of biaxial stress in GaN-based blue LEDs under electrical injection. The Raman shift of the GaN E2 mode evidently decreases by 4.4 cm−1 as the driving current on GaN-based LEDs increases to 700 mA. Biaxial compressive stress is released initially and biaxial tensile stress builds up as the current increases with respect to the value of stress-free GaN. First-principles calculations reveal that electron accumulation is responsible for the stress variation in InxGa1−xN/GaN quantum wells, and then reduces the transition probability among quantum levels. This behavior is consistent with the measured current-dependent external quantum efficiency. The rule of biaxial stress-dependent efficiency is further validated by controlling the biaxial stress of GaN-based LEDs with different sapphire substrate thicknesses. This work provides a method for direct observation of the biaxial stress effect on efficiency droop in LEDs under electrical injection. PMID:26634816

Metabolic products as biomarkers

USGS Publications Warehouse

Melancon, M.J.; Alscher, R.; Benson, W.; Kruzynski, G.; Lee, R.F.; Sikka, H.C.; Spies, R.B.; Huggett, Robert J.; Kimerle, Richard A.; Mehrle, Paul M.=; Bergman, Harold L.

1992-01-01

Ideally, endogenous biomarkers would indicate both exposure and environmental effects of toxic chemicals; however, such comprehensive biochemical and physiological indices are currently being developed and, at the present time, are unavailable for use in environmental monitoring programs. Continued work is required to validate the use of biochemical and physiological stress indices as useful components of monitoring programs. Of the compounds discussed only phytochelatins and porphyrins are currently in biomarkers in a useful state; however, glutathione,metallothioneins, stress ethylene, and polyamines are promising as biomarkers in environmental monitoring.

Static charge outside chamber induces dielectric breakdown of solid-state nanopore membranes

NASA Astrophysics Data System (ADS)

Matsui, Kazuma; Goto, Yusuke; Yanagi, Itaru; Yanagawa, Yoshimitsu; Ishige, Yu; Takeda, Ken-ichi

2018-04-01

Reducing device capacitance is effective for decreasing current noise observed in a solid-state nanopore-based DNA sequencer. On the other hand, we have recently found that voltage stress causes pinhole-like defects in such low-capacitance devices. The origin of voltage stress, however, has not been determined. In this research, we identified that a dominant origin is static charge on the outer surface of a flow cell. Even though the outer surface was not in direct contact with electrolytes in the flow cell, the charge induces high voltage stress on a membrane according to the capacitance coupling ratio of the flow cell to the membrane.

Comprehensive dynamic on-resistance assessments in GaN-on-Si MIS-HEMTs for power switching applications

NASA Astrophysics Data System (ADS)

Chou, Po-Chien; Hsieh, Ting-En; Cheng, Stone; del Alamo, Jesús A.; Chang, Edward Yi

2018-05-01

This study comprehensively analyzed the reliability of trapping and hot-electron effects responsible for the dynamic on-resistance (Ron) of GaN-based metal–insulator–semiconductor high electron mobility transistors. Specifically, this study performed the following analyses. First, we developed the on-the-fly Ron measurement to analyze the effects of traps during stress. With this technique, the faster one (with a pulse period of 20 ms) can characterize the degradation; the transient behavior could be monitored accurately by such short measurement pulse. Then, dynamic Ron transients were investigated under different bias conditions, including combined off state stress conditions, back-gating stress conditions, and semi-on stress conditions, in separate investigations of surface- and buffer-, and hot-electron-related trapping effects. Finally, the experiments showed that the Ron increase in semi-on state is significantly correlated with the high drain voltage and relatively high current levels (compared with the off-state current), involving the injection of greater amount of hot electrons from the channel into the AlGaN/insulator interface and the GaN buffer. These findings provide a path for device engineering to clarify the possible origins for electron traps and to accelerate the development of emerging GaN technologies.

Can meditation slow rate of cellular aging? Cognitive stress, mindfulness, and telomeres

PubMed Central

Epel, Elissa; Daubenmier, Jennifer; Moskowitz, Judith T.; Folkman, Susan; Blackburn, Elizabeth

2010-01-01

Understanding the malleable determinants of cellular aging is critical to understanding human longevity. Telomeres may provide a pathway for exploring this question. Telomeres are the protective caps at the ends of chromosomes. The length of telomeres offers insight into mitotic cell and possibly organismal longevity. Telomere length has now been linked to chronic stress exposure and depression. This raises the question of how might cellular aging be modulated by psychological functioning. We consider two psychological processes or states that are in opposition to one another--threat cognition and mindfulness--and their effects on cellular aging. Psychological stress cognitions, particularly appraisals of threat and ruminative thoughts, can lead to prolonged states of reactivity. In contrast, mindfulness meditation techniques appear to shift cognitive appraisals from threat to challenge, decrease ruminative thought, and reduce stress arousal. Mindfulness may also directly increase positive arousal states. We review data linking telomere length to cognitive stress and stress arousal and present new data linking cognitive appraisal to telomere length. Given the pattern of associations revealed so far, we propose that some forms of meditation may have salutary effects on telomere length by reducing cognitive stress and stress arousal and increasing positive states of mind and hormonal factors that may promote telomere maintenance. Aspects of this model are currently being tested in ongoing trials of mindfulness meditation. PMID:19735238

Life Experiences of Hispanic Adolescents: Developmental and Language Considerations in Acculturation Stress

ERIC Educational Resources Information Center

Cervantes, Richard C.; Cordova, David

2011-01-01

Hispanic youth currently constitute the largest and fastest growing of all ethnic and racial groups in the United States. In addition to normal developmental life stressors, Hispanic youth also face minority status and acculturation-related stress. This study examined the psychosocial and acculturative stressors of Hispanic youth (n=170) residing…

The Potential Explanatory Role of Perceived Stress in Associations Between Subjective Social Status and Health-Related Quality of Life Among Homeless Smokers.

PubMed

Garey, Lorra; Reitzel, Lorraine R; Kendzor, Darla E; Businelle, Michael S

2016-01-01

Homeless individuals smoke at high rates relative to the general population and are at heightened risk of tobacco-related illnesses and poor health-related quality of life (HRQoL). Homeless smokers also report low subjective social status (SSS) or perceived social standing relative to others. SSS may contribute to poor HRQoL, potentially through perceived stress. The current study examined the role of perceived stress in the association of SSS and HRQoL among 227 (70.9% male, Mage = 43.2) homeless smokers. Participants completed self-report measures of SSS, perceived stress, and HRQoL. Perceived stress partially explained the relation between SSS (United States and Community) and HRQoL in covariate-adjusted analyses. Results suggested that perceived stress is a pathway through which SSS contributes to HRQoL among homeless smokers. Findings broaden current understanding of the impact of social disadvantage and perceived stress on HRQoL among homeless smokers. © The Author(s) 2015.

Effect of direct current sputtering power on the behavior of amorphous indium-gallium-zinc-oxide thin-film transistors under negative bias illumination stress: A combination of experimental analyses and device simulation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jang, Jun Tae; Kim, Dong Myong; Choi, Sung-Jin

The effect of direct current sputtering power of indium-gallium-zinc-oxide (IGZO) on the performance and stability of the corresponding thin-film transistor devices was studied. The field effect mobility increases as the IGZO sputter power increases, at the expense of device reliability under negative bias illumination stress (NBIS). Device simulation based on the extracted sub-gap density of states indicates that the field effect mobility is improved as a result of the number of acceptor-like states decreasing. The degradation by NBIS is suggested to be induced by the formation of peroxides in IGZO rather than charge trapping.

Neurophysiologic Methods to Measure Stress During Survival, Evasion, Resistance, and Escape Training

DTIC Science & Technology

2007-05-01

amygdala function as well as perceived stress, trait anxiety , and trait anger. Overview of current research strategy: HRV analysis represents another...expected to relate to perceived stress, trait anxiety , and trait anger. In prospective analyses, HRV is expected to pre- dict cortisol reactivity...studying brain activity linked with fear, anxiety , and other emotional states in humans, is described in this section. The ASER is elicited by an abrupt

A Review and Assessment of Current Airframe Lifing Methodologies and Tools in Air Vehicles Division

DTIC Science & Technology

2006-12-01

effect . The thickness of the part in which the crack is growing affects the stress state in the material...Neuber’s rule and a kinematic hardening constitutive equation of Ziegler-type (Ball 1990), and the stress intensity factor was obtained using the Green’s...sequence effect , and the research efforts over the years have lead to the development of different mean stress equations and damage accumulation

Stress estimation in reservoirs using an integrated inverse method

NASA Astrophysics Data System (ADS)

Mazuyer, Antoine; Cupillard, Paul; Giot, Richard; Conin, Marianne; Leroy, Yves; Thore, Pierre

2018-05-01

Estimating the stress in reservoirs and their surroundings prior to the production is a key issue for reservoir management planning. In this study, we propose an integrated inverse method to estimate such initial stress state. The 3D stress state is constructed with the displacement-based finite element method assuming linear isotropic elasticity and small perturbations in the current geometry of the geological structures. The Neumann boundary conditions are defined as piecewise linear functions of depth. The discontinuous functions are determined with the CMA-ES (Covariance Matrix Adaptation Evolution Strategy) optimization algorithm to fit wellbore stress data deduced from leak-off tests and breakouts. The disregard of the geological history and the simplified rheological assumptions mean that only the stress field, statically admissible and matching the wellbore data should be exploited. The spatial domain of validity of this statement is assessed by comparing the stress estimations for a synthetic folded structure of finite amplitude with a history constructed assuming a viscous response.

Critical review on the mechanisms of maturation stress generation in trees

PubMed Central

Clair, Bruno

2016-01-01

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

[Molecular changes in inbred mice with individual vulnerability vs resilience to stress-induced depressive-like state].

PubMed

Strekalova, T V; Kholod, N S; Bachurin, S O; Koval'zon, V M

2011-08-01

The C57BL/6 mice were subjected to a chronic combined stress which resulted in the induction of a depressive-like state. The occurrence of a depressive-like state was defined by a decrease in sensitivity to the reward determined by the diminished preference of sweetened solutions over regular drinking water. Such decrease is generally considered as a sign of an unhedonic-like state: one of the key features of clinical depression. Applied here, the paradigm in mice allows unhedonia induction in a subpopulation of stressed animals (54% in the current study); remaining mice are regarded as resilient to stress-induced hedonic deficit. The resilient subgroup is taken, therefore, as a "functional control" for those effects of stress that are not accompanied by development of the stress-induced depressive-like state in mice. The analysis of the mRNA extracted from the hippocampi of stress-subjected and home-cage control mice enabled the assessment of gene expression level of over 13 000 genes. This study showed that unhedonic mice are characterized by an up-regulation of 278 and down-regulation of 174 genes related mostly to the CNS development and functions, inter-cellular interactions and signalling, neurological disorders, apoptosis and behavioural regulation. Resilient animals demonstrated up-regulation of 924 and down-regulation of only 29 genes that control formation of cell assemblies, molecular transport, CNS functioning, neurological disorders and various biochemical reactions. Thus, gene expression profiles in the hippocampus of susceptible vs resilient to stress-induced unhedonia inbred subgroups of animals are strictly distinct in both quantity and quality.

A proposal for a new multiaxial model of psychiatric diagnosis. A continuum-based patient model derived from evolutionary developmental gene-environment interaction.

PubMed

Leigh, Hoyle

2009-01-01

To review recent genetic and neuroscientific research on psychiatric syndromes based on the current diagnostic scheme, and develop a better-fitting multiaxial patient-oriented diagnostic model. DSM I, published in 1952, considered psychiatric illnesses as reactions or extremes of adaptations of the patient's personality to stressful environmental demands. Personality itself was determined by constitution and psychodynamic development. In 1980, this continuum model gave way to an atheoretical categorical diagnostic scheme (DSM III), based on research diagnostic criteria for obtaining 'pure cultures' of patients for biological research. Subsequent research using the 'pure cultures' suggests that psychiatric syndromes represent a phenotypic continuum determined by genes, childhood traumas, and recent stress, mitigated by childhood nurturance, education, and current social support. Specific gene x childhood abuse x recent stress interactions have been discovered, which may serve as a model of how interacting vulnerability genes may or may not result in a psychiatric syndrome, depending on the individual's developmental history and current stress. A continuum model is proposed, with genes interacting with early experiences of stress or nurturance resulting in brain states that may evince minor but persistent symptoms (neurosis) or maladaptive patterns of behavior (personality disorder). The addition of recent or current stress may precipitate a major psychiatric syndrome. While a severe genetic predisposition, such as a mutation, may be sufficient to cause a major syndrome, major psychiatric syndromes are best conceptualized as dysregulation of evolutionarily adaptive brain functions, such as anxiety and vigilance. A new multiaxial model of psychiatric diagnosis is proposed based on this model: axis I for phenomenological diagnoses that include major psychiatric syndromes (e.g. depressive syndrome, psychosis), neuroses, personality disorders, and isolated symptoms; axis II for geno-neuroscience diagnoses, some of which may represent biological conditions associated with axis I, i.e. genes, specific brain morphology, and the functional state of specific brain areas based on laboratory and imaging studies; axis III for medical diseases and conditions; axis IV for stress (childhood, recent, and current); axis V for psychosocial assets (intelligence, education, school/work, social support, and global assessment of functioning) over past 5 years and current. (c) 2008 S. Karger AG, Basel.

Light/negative bias stress instabilities in indium gallium zinc oxide thin film transistors explained by creation of a double donor

NASA Astrophysics Data System (ADS)

Migliorato, Piero; Delwar Hossain Chowdhury, Md; Gwang Um, Jae; Seok, Manju; Jang, Jin

2012-09-01

The analysis of current-voltage (I-V) and capacitance-voltage (C-V) characteristics for amorphous indium gallium zinc oxide Thin film transistors as a function of active layer thickness shows that negative bias under illumination stress (NBIS) is quantitatively explained by creation of a bulk double donor, with a shallow singly ionized state ɛ(0/+) > EC-0.073 eV and a deep doubly ionized state ɛ(++/+) < EC-0.3 eV. The gap density of states, extracted from the capacitance-voltage curves, shows a broad peak between EC-E = 0.3 eV and 1.0 eV, which increases in height with NBIS stress time and corresponds to the broadened transition energy between singly and doubly ionized states. We propose that the center responsible is an oxygen vacancy and that the presence of a stable singly ionized state, necessary to explain our experimental results, could be due to the defect environment provided by the amorphous network.

Connecting genes, coexpression modules, and molecular signatures to environmental stress phenotypes in plants

PubMed Central

Weston, David J; Gunter, Lee E; Rogers, Alistair; Wullschleger, Stan D

2008-01-01

Background One of the eminent opportunities afforded by modern genomic technologies is the potential to provide a mechanistic understanding of the processes by which genetic change translates to phenotypic variation and the resultant appearance of distinct physiological traits. Indeed much progress has been made in this area, particularly in biomedicine where functional genomic information can be used to determine the physiological state (e.g., diagnosis) and predict phenotypic outcome (e.g., patient survival). Ecology currently lacks an analogous approach where genomic information can be used to diagnose the presence of a given physiological state (e.g., stress response) and then predict likely phenotypic outcomes (e.g., stress duration and tolerance, fitness). Results Here, we demonstrate that a compendium of genomic signatures can be used to classify the plant abiotic stress phenotype in Arabidopsis according to the architecture of the transcriptome, and then be linked with gene coexpression network analysis to determine the underlying genes governing the phenotypic response. Using this approach, we confirm the existence of known stress responsive pathways and marker genes, report a common abiotic stress responsive transcriptome and relate phenotypic classification to stress duration. Conclusion Linking genomic signatures to gene coexpression analysis provides a unique method of relating an observed plant phenotype to changes in gene expression that underlie that phenotype. Such information is critical to current and future investigations in plant biology and, in particular, to evolutionary ecology, where a mechanistic understanding of adaptive physiological responses to abiotic stress can provide researchers with a tool of great predictive value in understanding species and population level adaptation to climate change. PMID:18248680

Social Support: Main and Moderating Effects on the Relation between Financial Stress and Adjustment among College Students with Disabilities

ERIC Educational Resources Information Center

Murray, Christopher; Lombardi, Allison; Bender, Franklin; Gerdes, Hillary

2013-01-01

Students with disabilities are underrepresented in 4-year colleges and universities in the United States and those that do attend are at an increased risk of performing poorly in these settings. These difficulties for college students with disabilities may be compounded by additional stress related to financial concerns. The current study was…

Development of buoyant currents in yield stress fluids

NASA Astrophysics Data System (ADS)

Rossi, P.; Karimfazli, I.

2017-11-01

Infinitesimal perturbations are known to decay in a motionless yield stress fluid. We present experimental evidence to reveal other mechanisms promoting free advection from a motionless background state. Development of natural convection in a cavity with differentially heated side-walls is investigated as a benchmark. Velocity and temperature fields are measured using particle image velocimetry/thermometry. We examine time evolution of the flow, compare experimental findings with theoretical predictions and comment on the striking features brought about by the yield stress.

Social support in the workplace: nurse leader implications.

PubMed

Shirey, Maria R

2004-01-01

The state of the science as it relates to the stress-mediating role of social support in the health care work environment is explored. The ability to build a nursing leadership workforce is dependent upon a type of social support mechanism that mediates the inherent stress that comes along with managerial positions. Independent of the inevitable work-related stress associated with the nurse manager role, social support provided to current and aspiring nurse leaders is assumed to assist with coping and thriving in the work environment.

Stress and Asthma: Novel Insights on Genetic, Epigenetic and Immunologic Mechanisms

PubMed Central

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

2014-01-01

In the United States, the economically disadvantaged and some ethnic minorities are often exposed to chronic psychosocial stressors and disproportionately affected by asthma. Current evidence suggests a causal association between chronic psychosocial stress and asthma or asthma morbidity. Recent findings suggest potential mechanisms underlying this association, including changes in the methylation and expression of genes that regulate behavioral, autonomic, neuroendocrine, and immunologic responses to stress. There is also evidence suggesting the existence of susceptibility genes that predispose chronically stressed youth to both post-traumatic stress disorder and asthma. In this review, we critically examine published evidence and suggest future directions for research in this field. PMID:25129683

Illness Progression, Recent Stress and Morphometry of Hippocampal Subfields and Medial Prefrontal Cortex in Major Depression

PubMed Central

Treadway, Michael T.; Waskom, Michael L.; Dillon, Daniel G.; Holmes, Avram J.; Park, Min Tae M.; Chakravarty, M. Mallar; Dutra, Sunny J.; Polli, Frida E.; Iosifescu, Dan V.; Fava, Maurizio; Gabrieli, John D.E.; Pizzagalli, Diego A.

2014-01-01

Background Longitudinal studies of illness progression in Major Depressive Disorder (MDD) indicate that the onset of subsequent depressive episodes becomes increasingly decoupled from external stressors. A possible mechanism underlying this phenomenon is that multiple episodes induce long-lasting neurobiological changes that confer increased risk for recurrence. Prior morphometric studies have frequently reported volumetric reductions in MDD—especially in medial prefrontal cortex (mPFC) and the hippocampus— but few studies have investigated whether these changes are exacerbated by prior episodes. Methods We used structural magnetic resonance imaging (sMRI) to examine relationships between number of prior episodes, current stress, and brain volume and cortical thickness in a sample of 103 medication-free depressed patients and never-depressed controls. Volumetric analyses of the hippocampus were performed using a recently-validated subfield segmentation approach, while cortical thickness estimates were obtained using Vertex-Based Cortical Thickness (VBCT). Participants were grouped on the basis of the number of prior depressive episodes as well as current depressive state. Results Number of prior episodes was associated with both lower reported stress levels as well as reduced volume in the dentate gyrus. Cortical thinning of the left medial prefrontal cortex (mPFC) was associated with a greater number of prior depressive episodes, but not current depressive state. Conclusions Collectively, these findings are consistent with preclinical models suggesting that the dentate gyrus and mPFC are especially vulnerable to stress exposure, and provide evidence for morphometric changes that are consistent with stress-sensitization models of recurrence in MDD. PMID:25109665

Effect of Surge Current Testing on Reliability of Solid Tantalum Capacitors

NASA Technical Reports Server (NTRS)

Teverovsky, Alexander

2008-01-01

Tantalum capacitors manufactured per military specifications are established reliability components and have less than 0.001% of failures per 1000 hours for grades D or S, thus positioning these parts among electronic components with the highest reliability characteristics. Still, failures of tantalum capacitors do happen and when it occurs it might have catastrophic consequences for the system. To reduce this risk, further development of a screening and qualification system with special attention to the possible deficiencies in the existing procedures is necessary. The purpose of this work is evaluation of the effect of surge current stress testing on reliability of the parts at both steady-state and multiple surge current stress conditions. In order to reveal possible degradation and precipitate more failures, various part types were tested and stressed in the range of voltage and temperature conditions exceeding the specified limits. A model to estimate the probability of post-surge current testing-screening failures and measures to improve the effectiveness of the screening process has been suggested.

Deposition stress effects on thermal barrier coating burner rig life

NASA Technical Reports Server (NTRS)

Watson, J. W.; Levine, S. R.

1984-01-01

A study of the effect of plasma spray processing parameters on the life of a two layer thermal barrier coating was conducted. The ceramic layer was plasma sprayed at plasma arc currents of 900 and 600 amps onto uncooled tubes, cooled tubes, and solid bars of Waspalloy in a lathe with 1 or 8 passes of the plasma gun. These processing changes affected the residual stress state of the coating. When the specimens were tested in a Mach 0.3 cyclic burner rig at 1130 deg C, a wide range of coating lives resulted. Processing factors which reduced the residual stress state in the coating, such as reduced plasma temperature and increased heat dissipation, significantly increased coating life.

Deposition stress effects on the life of thermal barrier coatings on burner rigs

NASA Technical Reports Server (NTRS)

Watson, J. W.; Levine, S. R.

1984-01-01

A study of the effect of plasma spray processing parameters on the life of a two layer thermal barrier coating was conducted. The ceramic layer was plasma sprayed at plasma arc currents of 900 and 600 amps onto uncooled tubes, cooled tubes, and solid bars of Waspalloy in a lathe with 1 or 8 passes of the plasma gun. These processing changes affected the residual stress state of the coating. When the specimens were tested in a Mach 0.3 cyclic burner rig at 1130 deg C, a wide range of coating lives resulted. Processing factors which reduced the residual stress state in the coating, such as reduced plasma temperature and increased heat dissipation, significantly increased coating life.

The Impact of Environmental Factors in Influencing Epigenetics Related to Oxidative States in the Cardiovascular System.

PubMed

Angelini, Francesco; Pagano, Francesca; Bordin, Antonella; Milan, Marika; Chimenti, Isotta; Peruzzi, Mariangela; Valenti, Valentina; Marullo, Antonino; Schirone, Leonardo; Palmerio, Silvia; Sciarretta, Sebastiano; Murdoch, Colin E; Frati, Giacomo; De Falco, Elena

2017-01-01

Oxidative states exert a significant influence on a wide range of biological and molecular processes and functions. When their balance is shifted towards enhanced amounts of free radicals, pathological phenomena can occur, as the generation of reactive oxygen species (ROS) in tissue microenvironment or in the systemic circulation can be detrimental. Epidemic chronic diseases of western societies, such as cardiovascular disease, obesity, and diabetes correlate with the imbalance of redox homeostasis. Current advances in our understanding of epigenetics have revealed a parallel scenario showing the influence of oxidative stress as a major regulator of epigenetic gene regulation via modification of DNA methylation, histones, and microRNAs. This has provided both the biological link and a potential molecular explanation between oxidative stress and cardiovascular/metabolic phenomena. Accordingly, in this review, we will provide current insights on the physiological and pathological impact of changes in oxidative states on cardiovascular disorders, by specifically focusing on the influence of epigenetic regulation. A special emphasis will highlight the effect on epigenetic regulation of human's current life habits, external and environmental factors, including food intake, tobacco, air pollution, and antioxidant-based approaches. Additionally, the strategy to quantify oxidative states in humans in order to determine which biological marker could best match a subject's profile will be discussed.

The Impact of Environmental Factors in Influencing Epigenetics Related to Oxidative States in the Cardiovascular System

PubMed Central

Angelini, Francesco; Pagano, Francesca; Bordin, Antonella; Milan, Marika; Valenti, Valentina; Marullo, Antonino; Schirone, Leonardo; Palmerio, Silvia; Sciarretta, Sebastiano; Frati, Giacomo

2017-01-01

Oxidative states exert a significant influence on a wide range of biological and molecular processes and functions. When their balance is shifted towards enhanced amounts of free radicals, pathological phenomena can occur, as the generation of reactive oxygen species (ROS) in tissue microenvironment or in the systemic circulation can be detrimental. Epidemic chronic diseases of western societies, such as cardiovascular disease, obesity, and diabetes correlate with the imbalance of redox homeostasis. Current advances in our understanding of epigenetics have revealed a parallel scenario showing the influence of oxidative stress as a major regulator of epigenetic gene regulation via modification of DNA methylation, histones, and microRNAs. This has provided both the biological link and a potential molecular explanation between oxidative stress and cardiovascular/metabolic phenomena. Accordingly, in this review, we will provide current insights on the physiological and pathological impact of changes in oxidative states on cardiovascular disorders, by specifically focusing on the influence of epigenetic regulation. A special emphasis will highlight the effect on epigenetic regulation of human's current life habits, external and environmental factors, including food intake, tobacco, air pollution, and antioxidant-based approaches. Additionally, the strategy to quantify oxidative states in humans in order to determine which biological marker could best match a subject's profile will be discussed. PMID:28607629

Hawking radiation, covariant boundary conditions, and vacuum states

DOE Office of Scientific and Technical Information (OSTI.GOV)

Banerjee, Rabin; Kulkarni, Shailesh

2009-04-15

The basic characteristics of the covariant chiral current and the covariant chiral energy-momentum tensor are obtained from a chiral effective action. These results are used to justify the covariant boundary condition used in recent approaches of computing the Hawking flux from chiral gauge and gravitational anomalies. We also discuss a connection of our results with the conventional calculation of nonchiral currents and stress tensors in different (Unruh, Hartle-Hawking and Boulware) states.

78 FR 19077 - Forwarding of Asylum Applications to the Department of State

Federal Register 2010, 2011, 2012, 2013, 2014

2013-03-29

... Department of State (DOS), Bureau of Democracy, Human Rights, and Labor. Currently, EOIR forwards to DOS all... form of post-traumatic stress or depression that affects long-term memory, making credibility... time of dwindling resources, both human and monetary, the Department has determined that it is best to...

Shear design of wood beams : state of the art

Treesearch

Lawrence A. Soltis; Terry D. Gerhardt

1988-01-01

Current shear design technology in the United States for lumber or glued- laminated beams is confusing. This report summarizes shear stress and strength research including both analytical and experimental approaches. Both checked and unchecked beams are included. The analytical work has been experimentally verified for only limited load conditions and span-to- depth...

Reflecting on Social Emotional Learning: A Critical Perspective on Trends in the United States

ERIC Educational Resources Information Center

Hoffman, Diane M.

2009-01-01

This critical cultural analysis of trends in the field of social emotional learning (SEL) in the United States considers how ideas concerning emotional skills and competencies have informed programmatic discourse. While currently stressing links between SEL and academic achievement, program literature also places emphasis on ideals of caring,…

Naval Law Review. Volume 63, 2014

DTIC Science & Technology

2014-01-01

stating that chaplains may not bear arms.46 Current Marine Corps doctrine states quite succinctly: “Chaplains are noncombatants and will not bear arms...47 Past Marine Corps doctrine , though more verbose, was quite emphatic and clear in stating:   Chaplains must never engage in combat. If they...Bush administration’s executive authority doctrine and stresses rather that it has power to detain individuals under prevailing laws of war

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

PubMed

Alméras, Tancrède; Clair, Bruno

2016-09-01

Trees control their posture by generating asymmetric mechanical stress around the periphery of the trunk or branches. This stress is produced in wood during the maturation of the cell wall. When the need for reaction is high, it is accompanied by strong changes in cell organization and composition called reaction wood, namely compression wood in gymnosperms and tension wood in angiosperms. The process by which stress is generated in the cell wall during its formation is not yet known, and various hypothetical mechanisms have been proposed in the literature. Here we aim at discriminating between these models. First, we summarize current knowledge about reaction wood structure, state and behaviour relevant to the understanding of maturation stress generation. Then, the mechanisms proposed in the literature are listed and discussed in order to identify which can be rejected based on their inconsistency with current knowledge at the frontier between plant science and mechanical engineering. © 2016 The Author(s).

Deterministic Multiaxial Creep and Creep Rupture Enhancements for CARES/Creep Integrated Design Code

NASA Technical Reports Server (NTRS)

Jadaan, Osama M.

1998-01-01

High temperature and long duration applications of monolithic ceramics can place their failure mode in the creep rupture regime. A previous model advanced by the authors described a methodology by which the creep rupture life of a loaded component can be predicted. That model was based on the life fraction damage accumulation rule in association with the modified Monkman-Grant creep rupture criterion. However, that model did not take into account the deteriorating state of the material due to creep damage (e.g., cavitation) as time elapsed. In addition, the material creep parameters used in that life prediction methodology, were based on uniaxial creep curves displaying primary and secondary creep behavior, with no tertiary regime. The objective of this paper is to present a creep life prediction methodology based on a modified form of the Kachanov-Rabotnov continuum damage mechanics (CDM) theory. In this theory, the uniaxial creep rate is described in terms of sum, temperature, time, and the current state of material damage. This scalar damage state parameter is basically an abstract measure of the current state of material damage due to creep deformation. The damage rate is assumed to vary with stress, temperature, time, and the current state of damage itself. Multiaxial creep and creep rupture formulations of the CDM approach are presented in this paper. Parameter estimation methodologies based on nonlinear regression analysis are also described for both, isothermal constant stress states and anisothermal variable stress conditions This creep life prediction methodology was preliminarily added to the integrated design code CARES/Creep (Ceramics Analysis and Reliability Evaluation of Structures/Creep), which is a postprocessor program to commercially available finite element analysis (FEA) packages. Two examples, showing comparisons between experimental and predicted creep lives of ceramic specimens, are used to demonstrate the viability of Ns methodology and the CARES/Creep program.

Psychosocial stressors and cigarette smoking among African American adults in midlife.

PubMed

Slopen, Natalie; Dutra, Lauren M; Williams, David R; Mujahid, Mahasin S; Lewis, Tené T; Bennett, Gary G; Ryff, Carol D; Albert, Michelle A

2012-10-01

Psychosocial stress is a significant risk factor for smoking, and Blacks experience higher levels of psychosocial stress relative to other racial/ethnic groups. Limited research has comprehensively examined psychosocial stressors in relation to smoking among Blacks. We examined psychosocial stressors in relation to smoking status (current, previous, and never) in middle-aged Blacks (34-85 years, n = 592) from Milwaukee, Wisconsin, a subset of the Midlife in the United States Study II (2004-2006). Eleven stressor domains were assessed, including psychological and physical work stress, work-family conflict, perceived inequality, relationship stress, neighborhood stress, discrimination, financial stress, recent problems, stressful events, and childhood adversity. We also calculated a cumulative score. Multinomial models were adjusted for age, gender, education, and income. Seven of the 11 stressors and the cumulative score were associated with higher odds of being a current smoker compared with a never-smoker: neighborhood, financial, relationship, and psychological work stress, perceived inequality, stressful events, childhood adversity (p values <.05; ORs ranged from 1.28 to 1.77). Three stressors and the cumulative score were associated with higher odds of being a previous smoker versus a never-smoker (p < .05). Individuals who scored in the top quartile on 5 or more stressors were 3.74 (95% CI = 2.09-6.71) times as likely to be current smokers, and more than twice as likely to be previous smokers, compared with individuals with no high stressors. These results demonstrate a strong relationship between stress and smoking among urban middle-aged Blacks and suggest that cessation programs should address modifiable individual and community-level stressors.

Antioxidants Mediate Both Iron Homeostasis and Oxidative Stress.

PubMed

Imam, Mustapha Umar; Zhang, Shenshen; Ma, Jifei; Wang, Hao; Wang, Fudi

2017-06-28

Oxidative stress is a common denominator in the pathogenesis of many chronic diseases. Therefore, antioxidants are often used to protect cells and tissues and reverse oxidative damage. It is well known that iron metabolism underlies the dynamic interplay between oxidative stress and antioxidants in many pathophysiological processes. Both iron deficiency and iron overload can affect redox state, and these conditions can be restored to physiological conditions using iron supplementation and iron chelation, respectively. Similarly, the addition of antioxidants to these treatment regimens has been suggested as a viable therapeutic approach for attenuating tissue damage induced by oxidative stress. Notably, many bioactive plant-derived compounds have been shown to regulate both iron metabolism and redox state, possibly through interactive mechanisms. This review summarizes our current understanding of these mechanisms and discusses compelling preclinical evidence that bioactive plant-derived compounds can be both safe and effective for managing both iron deficiency and iron overload conditions.

Antioxidants Mediate Both Iron Homeostasis and Oxidative Stress

PubMed Central

Zhang, Shenshen; Ma, Jifei; Wang, Hao; Wang, Fudi

2017-01-01

Oxidative stress is a common denominator in the pathogenesis of many chronic diseases. Therefore, antioxidants are often used to protect cells and tissues and reverse oxidative damage. It is well known that iron metabolism underlies the dynamic interplay between oxidative stress and antioxidants in many pathophysiological processes. Both iron deficiency and iron overload can affect redox state, and these conditions can be restored to physiological conditions using iron supplementation and iron chelation, respectively. Similarly, the addition of antioxidants to these treatment regimens has been suggested as a viable therapeutic approach for attenuating tissue damage induced by oxidative stress. Notably, many bioactive plant-derived compounds have been shown to regulate both iron metabolism and redox state, possibly through interactive mechanisms. This review summarizes our current understanding of these mechanisms and discusses compelling preclinical evidence that bioactive plant-derived compounds can be both safe and effective for managing both iron deficiency and iron overload conditions. PMID:28657578

Moderate psychosocial stress appears not to impair recall of words learned 4 weeks prior to stress exposure.

PubMed

Wolf, Oliver T; Schommer, Nicole C; Hellhammer, Dirk H; Reischies, Friedel M; Kirschbaum, Clemens

2002-02-01

Recent studies in humans have reported that recall of previously learned material is especially sensitive to the disruptive effects of pharmacologically induced cortisol elevations. Whether similar effects occur after exposure to psychosocial stress remains to be shown. Moreover it is unknown whether stress before or after the initial learning interacts with the later effects of repeated stress on delayed recall (e.g. state-dependent learning). Forty subjects participated in the present experiment. They learned a word list either one hour before or 10 min after exposure to a psychosocial laboratory stressor. Delayed recall was tested 4 weeks later, again either before or after stress. Salivary cortisol levels increased significantly in response to both stress exposures. Stress had no effects on the initial learning and also did not impair delayed recall. Moreover there was no evidence for state-dependent learning. The current data seem to be in conflict with previous studies demonstrating that delayed recall is especially sensitive to elevated cortisol levels. Several reasons for these discrepancies are discussed. Among them is the small sample size, the moderate cortisol increase in response to the second stress exposure but also the long recall delay, which might lead to memory traces less susceptible to stress.

The Interplay between Maternal Nutrition and Stress during Pregnancy: Issues and Considerations.

PubMed

Lindsay, Karen L; Buss, Claudia; Wadhwa, Pathik D; Entringer, Sonja

2017-01-01

Several studies about humans and animals have separately examined the effects of prenatal nutrition and stress on fetal development, pregnancy, and birth outcomes, and subsequent child health and disease risk. Although substantial evidence from non-pregnant literature supports the presence of bidirectional interactions between nutrition and stress at various psychological, behavioral, and physiological levels, such interaction effects have not yet been systematically examined in the context of pregnancy. This paper discusses the multifaceted and multilevel relationship between nutrition and stress. It then reviews the currently available observational and experimental evidence in animals and humans regarding the interplay between maternal psychosocial stress, dietary intake, and nutritional state during pregnancy, and implications for maternal and child health-related outcomes. Key Messages: During pregnancy, maternal psychosocial stress, dietary behavior, and nutritional state likely regulate and counter-regulate one another. Emerging evidence suggests that omega-3 fatty acids may attenuate maternal psychosocial stress, and that high maternal pre-pregnancy body mass index exacerbates unhealthy dietary behaviors under high-stress conditions. Longitudinal studies are warranted in order to understand the interplay between prenatal psychosocial stress, diet, and stress- and nutrition-related biomarkers to obtain further insight and inform the development and design of future, more effective intervention trials for improved maternal and child health outcomes. © 2017 S. Karger AG, Basel.

Characteristics of EMI generated by negative metal-positive dielectric voltage stresses due to spacecraft charging

NASA Technical Reports Server (NTRS)

Chaky, R. C.; Inouye, G. T.

1985-01-01

Charging of spacecraft surfaces by the environmental plasma can result in differential potentials between metallic structure and adjacent dielectric surfaces in which the relative polarity of the voltage stress is either negative dielectric/positive metal or negative metal/positive dielectric. Negative metal/positive dielectric is a stress condition that may arise if relatively large areas of spacecraft surface metals are shadowed from solar UV and/or if the UV intensity is reduced as in the situation in which the spacecraft is entering into or leaving eclipse. The results of experimental studies of negative metal/positive dielectric systems are given. Information is given on: enhanced electron emission I-V curves; e(3) corona noise vs e(3) steady-state current; the localized nature of e(3) and negative metal arc discharge currents; negative metal arc discharges at stress thresholds below 1 kilovolt; negative metal arc discharge characteristics; dependence of blowoff arc discharge current on spacecraft capacitance to space (linear dimension); and damage to second surface mirrors due to negative metal arcs.

Religious and spiritual beliefs, self-esteem, anxiety, and depression among nursing students.

PubMed

Papazisis, Georgios; Nicolaou, Panagiotis; Tsiga, Evangelia; Christoforou, Theodora; Sapountzi-Krepia, Despina

2014-06-01

Research of the role of religious belief and/or spirituality has been conducted on a wide range of health-related topics, across many disciplines, and in many countries. The purpose of this study was to determine the relationship between religious beliefs, self-esteem, anxiety, and depression in nursing students in Cyprus. One hundred and twenty-three nursing students were asked to complete a survey consisting of four self-report questionnaires (Beck Depression Inventory, State-Trait Anxiety Inventory, The Royal Free Interview for Religious and Spiritual Beliefs, and Rosenberg Self-esteem Scale). The lowest levels of depression were observed in the third and fourth study year. Normal self-esteem levels were found in the majority of the students (71.3%) and most of them perceived current stress at mild levels. No significant differences on the basis of sex were observed. The vast majority (98.2%) of the students stated a strong religious and/or a spiritual belief that was strongly positively correlated with increased self-esteem and negatively correlated with depression, current stress, and stress as personality trait. © 2013 Wiley Publishing Asia Pty Ltd.

New developments in satellite oceanography and current measurements

NASA Technical Reports Server (NTRS)

Huang, N. E.

1979-01-01

Principal satellite remote sensing techniques and instruments are described and attention is given to the application of such techniques to ocean current measurement. The use of radiometers, satellite tracking drifters, and altimeters for current measurement is examined. Consideration is also given to other applications of satellite remote sensing in physical oceanography, including measurements of surface wind stress, sea state, tides, ice, sea surface temperature, salinity, ocean color, and oceanic leveling.

Association of occupational stress and social support with health-related behaviors among chinese offshore oil workers.

PubMed

Chen, Wei-Qing; Wong, Tze Wai; Yu, Ignatius Tak-Sun

2008-01-01

To explore the relationship of occupational stress and social support with health-related behaviors of smoking, alcohol usage and physical inactivity, a cross-sectional survey was conducted among 561 offshore oil installation workers of a Chinese state-owned oil company. They were investigated with a self-administered questionnaire about socio-demographic characteristics, occupational stress, social support and health-related behaviors. Logistic regression analysis was used to study the association between occupational stress, social support and health-related behaviors and adjusted for age, educational level, marital status, duration of offshore work and job title. Of 561 workers, 218 (38.9%) were current smokers, 124 (22.1%) current drinkers, and 354 (63.1%) physically inactive in their leisure time. Further multivariate logistic regression analysis indicated that: (1) Current smoking was significantly negatively related with perceived stress from "Safety" (OR=0.74; 95% CI=0.58-0.94) and lack of supervisors' instrumental support (OR=0.34; 95% CI=0.18-0.65); (2) Current drinking was significantly positively related to perceived stress from "Interface between job and family/social life" (OR=1.32; 95% CI=1.02-1.70) and "Organizational structure" (OR=1.35; 95% CI=1.06-1.74), but was significantly negatively related to poor emotional support from friends (OR=0.54; 95% CI=0.62-0.96); (3) Physical inactivity after work was significantly positively associated with perceived stress from "Safety" (OR=1.44; 95% CI=1.16-1.79) and lack of instrumental support from both supervisors (OR=1.74; 95% CI=1.16-2.65) and friends (OR=1.68; 95% CI=1.06-2.42). The findings suggest that psychosocial factors of occupational stress and social support at offshore oil work might affect workers' health-related behaviors in different ways.

Gravitational radiation theory. M.A. Thesis - Rice Univ.; [survey of current research

NASA Technical Reports Server (NTRS)

Wilson, T. L.

1973-01-01

A survey is presented of current research in the theory of gravitational radiation. The mathematical structure of gravitational radiation is stressed. Furthermore, the radiation problem is treated independently from other problems in gravitation. The development proceeds candidly through three points of view - scalar, rector, and tensor radiation theory - and the corresponding results are stated.

In-situ visualization of stress-dependent bulk magnetic domain formation by neutron grating interferometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Betz, B.; École Polytechnique Fédérale de Lausanne, NXMM Laboratory, IMX, CH-1015 Lausanne; Rauscher, P.

The performance and degree of efficiency of industrial transformers are directly influenced by the magnetic properties of high-permeability steel laminations (HPSLs). Industrial transformer cores are built of stacks of single HPSLs. While the insulating coating on each HPSL reduces eddy-current losses in the transformer core, the coating also induces favorable inter-granular tensile stresses that significantly influence the underlying magnetic domain structure. Here, we show that the neutron dark-field image can be used to analyze the influence of the coating on the volume and supplementary surface magnetic domain structures. To visualize the stress effect of the coating on the bulk domainmore » formation, we used an uncoated HPSL and stepwise increased the applied external tensile stress up to 20 MPa. We imaged the domain configuration of the intermediate stress states and were able to reproduce the original domain structure of the coated state. Furthermore, we were able to visualize how the applied stresses lead to a refinement of the volume domain structure and the suppression and reoccurrence of supplementary domains.« less

[Company occupational physician and work related stress: from risk assessment to health surveillance].

PubMed

Buselli, R; Cristaudo, A

2009-01-01

In Italy the recent safety legislation requires a new committment for the company occupational physician. His duty is a balance between legal requirements and the state of art of prevention. There are many tools to tackle stress at work as a general preventive intervention. The hard challenge of the company physician is to keep all the garantees in terms of prevention and social security for the worker at risk of stress. This paper examines some of the difficulties with current approaches and looks at possible solutions.

Computation of turbulent flows-state-of-the-art, 1970

NASA Technical Reports Server (NTRS)

Reynolds, W. C.

1972-01-01

The state-of-the-art of turbulent flow computation is surveyed. The formulations were generalized to increase the range of their applicability, and the excitement of current debate on equation models was brought into the review. Some new ideas on the modeling of the pressure-strain term in the Reynolds stress equations are also suggested.

Examining associations between anxiety and cortisol in high functioning male children with autism

PubMed Central

2013-01-01

Background Autism spectrum disorder (ASD) is characterized by deficits in communication and social ability, as well as restricted interests and repetitive behavior. Anxiety is a persistent anticipation or apprehension about one or more situations to which a person is exposed, and affects many people, including children with ASD. Stress, by contrast, is a response to situations that are threatening, uncontrollable, or unexpected. Indices of anxiety are often measured through informants, with parents and teachers serving as the primary sources of reported anxiety in children. However, self-report measures exist, allowing current (state) and persistent (trait) anxiety to be assessed. The current study was designed to evaluate whether children with autism could identify their own levels of anxiety and the degree to which these levels were associated with symptom profile and physiological arousal. Methods Self-reported state and trait anxiety were collected during exposure to different stress paradigms for 40 children (21 typically developing, 19 with autistic disorder) and compared to parent reported social ability (Social Responsiveness Scale) and stress responsivity (cortisol). Results Significant differences were found between typically developing and children with autism for both state and trait anxiety across all conditions. Associations were identified between severity of parent-reported social impairment and both types of self-report anxiety. No relationship was found between stress (salivary cortisol) and anxiety in children with autism. Conclusions Children with autism are able to consistently report their persistent level of anxiety symptoms in stressful situations of benign character. Therefore, the inclusion of such measures may be useful in identifying and tracking symptoms in children with autism under appropriate circumstances. PMID:24216056

Current stress and poor oral health.

PubMed

Vasiliou, A; Shankardass, K; Nisenbaum, R; Quiñonez, C

2016-09-02

Psychological stress appears to contribute to poor oral health systemically in combination with other chronic diseases. Few studies directly examine this relationship. Data from a cross-sectional study of 2,412 participants between the ages of 25-64 years old living in the City of Toronto between 2009 and 2012 were used to examine the relationship between current stress and two self-rated oral health outcomes (general oral health and oral pain). Dental care utilization and access to dental insurance were examined as effect modifiers. A positive relationship between current stress and poor oral health was observed for both outcomes (oral pain coefficient 0.32, 95 % CI 0.26-0.38; general oral health coefficient 0.28, 95 % CI 0.19-0.36). Effects on oral pain were stronger for the uninsured, while effects on general oral health were stronger with decreasing socioeconomic position. Our findings suggest that individuals with greater perceived stress also report poorer oral health, and that this relationship is modified by dental insurance and socioeconomic position. These findings warrant a greater focus on the role of psychological stress in the development of oral disease, including how perceived stress contributes to health inequities in self-reported oral health status. Patients experiencing stressful lives may differentially require closer monitoring and more vigilant maintenance of their oral health, above and beyond that which is needed to achieve a state of health in the oral environment of less stressed individuals. There may be health promoting effects of addressing psychosocial concerns related to dental care - particularly for the poor and uninsured.

Earthquake nucleation on faults with rate-and state-dependent strength

USGS Publications Warehouse

Dieterich, J.H.

1992-01-01

Dieterich, J.H., 1992. Earthquake nucleation on faults with rate- and state-dependent strength. In: T. Mikumo, K. Aki, M. Ohnaka, L.J. Ruff and P.K.P. Spudich (Editors), Earthquake Source Physics and Earthquake Precursors. Tectonophysics, 211: 115-134. Faults with rate- and state-dependent constitutive properties reproduce a range of observed fault slip phenomena including spontaneous nucleation of slip instabilities at stresses above some critical stress level and recovery of strength following slip instability. Calculations with a plane-strain fault model with spatially varying properties demonstrate that accelerating slip precedes instability and becomes localized to a fault patch. The dimensions of the fault patch follow scaling relations for the minimum critical length for unstable fault slip. The critical length is a function of normal stress, loading conditions and constitutive parameters which include Dc, the characteristic slip distance. If slip starts on a patch that exceeds the critical size, the length of the rapidly accelerating zone tends to shrink to the characteristic size as the time of instability approaches. Solutions have been obtained for a uniform, fixed-patch model that are in good agreement with results from the plane-strain model. Over a wide range of conditions, above the steady-state stress, the logarithm of the time to instability linearly decreases as the initial stress increases. Because nucleation patch length and premonitory displacement are proportional to Dc, the moment of premonitory slip scales by D3c. The scaling of Dc is currently an open question. Unless Dc for earthquake faults is significantly greater than that observed on laboratory faults, premonitory strain arising from the nucleation process for earthquakes may by too small to detect using current observation methods. Excluding the possibility that Dc in the nucleation zone controls the magnitude of the subsequent earthquake, then the source dimensions of the smallest earthquakes in a region provide an upper limit for the size of the nucleation patch. ?? 1992.

Examining factors involved in stress-related working memory impairments: Independent or conditional effects?

PubMed

Banks, Jonathan B; Tartar, Jaime L; Tamayo, Brittney A

2015-12-01

A large and growing body of research demonstrates the impact of psychological stress on working memory. However, the typical study approach tests the effects of a single biological or psychological factor on changes in working memory. The current study attempted to move beyond the standard single-factor assessment by examining the impact of 2 possible factors in stress-related working memory impairments. To this end, 60 participants completed a working memory task before and after either a psychological stressor writing task or a control writing task and completed measures of both cortisol and mind wandering. We also included a measure of state anxiety to examine the direct and indirect effect on working memory. We found that mind wandering mediated the relationship between state anxiety and working memory at the baseline measurement. This indirect relationship was moderated by cortisol, such that the impact of mind wandering on working memory increased as cortisol levels increased. No overall working memory impairment was observed following the stress manipulation, but increases in state anxiety and mind wandering were observed. State anxiety and mind wandering independently mediated the relationship between change in working memory and threat perception. The indirect paths resulted in opposing effects on working memory. Combined, the findings from this study suggest that cortisol enhances the impact of mind wandering on working memory, that state anxiety may not always result in stress-related working memory impairments, and that high working memory performance can protect against mind wandering. (c) 2015 APA, all rights reserved).

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

NASA Astrophysics Data System (ADS)

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.

Efforts to reform medicaid in a time of fiscal stress: are we merely shuffling chairs on the deck of the titanic?

PubMed

McEldowney, Rene; Jenkins, Carol L

2005-01-01

With states facing their worst financial crisis since World War II, Medicaid programs across the nation are facing a period of significant stress. Medicaid expenditures are a major part of most states' budgets, which make them an important target when policy makers and legislators are faced with budget deficits. This study compares programs across states and identifies major reform trends being used by state officials as they try to balance the needs of their Medicaid recipients with the realities of budget shortfalls. Our research illustrates that the short-term view prevails: many states have relied heavily on one time funding sources, such as tobacco settlement monies in conjunction with traditional cost controlling mechanisms (e.g., freezing provider reimbursement rates, reducing program eligibility levels, requiring prior authorization for services) as their means of addressing the current crisis.

Mindfulness-based stress reduction: an intervention to enhance the effectiveness of nurses' coping with work-related stress.

PubMed

Smith, Sarah A

2014-06-01

This critical literature review explored the current state of the science regarding mindfulness-based stress reduction (MBSR) as a potential intervention to improve the ability of nurses to effectively cope with stress. Literature sources include searches from EBSCOhost, Gale PowerSearch, ProQuest, PubMed Medline, Google Scholar, Online Journal of Issues in Nursing, and reference lists from relevant articles. Empirical evidence regarding utilizing MBSR with nurses and other healthcare professionals suggests several positive benefits including decreased stress, burnout, and anxiety; and increased empathy, focus, and mood. Nurse use of MBSR may be a key intervention to help improve nurses' ability to cope with stress and ultimately improve the quality of patient care provided. © 2014 NANDA International, Inc.

Whole canopy gas exchange among elite loblolly pine families subjected to drought stress

Treesearch

Wilson G. Hood; Michael C. Tyree; Dylan N. Dillaway; Michael A. Blazier; Mary Anne Sword Sayer

2012-01-01

Future climate change simulations predict that the southeastern United States will experience hydrologic patterns similar to that currently found in the Western Gulf Region, meaning, that planted elite loblolly families may be subject to drier, hotter summers (Ruosteenoja et al. 2003, Field et al. 2007). Currently, there is little research on how these fast-growing...

Role of shame and body esteem in cortisol stress responses

PubMed Central

Lupis, Sarah B.; Sabik, Natalie J.

2016-01-01

Studies assessing the role of shame in HPA axis reactivity report mixed findings. Discrepancies may be due to methodological difficulties and inter-individual differences in the propensity to experience shame in a stressful situation. Hence, the current study combined self-report of shame and facial coding of shame expressions and assessed the role of body esteem as a moderator of the shame–stress link. For this, 44 healthy students (24F, age 20.5 ± 2.1 years) were exposed to an acute psychosocial stress paradigm (Trier Social Stress Test: TSST). Salivary cortisol levels were measured throughout the protocol. Trait shame was measured before the stress test, and state shame immediately afterwards. Video recordings of the TSST were coded to determine emotion expressions. State shame was neither associated with cortisol stress responses nor with body esteem (self-report: all ps ≥ .24; expression: all ps ≥ .31). In contrast, higher trait shame was associated with both negative body esteem (p = .049) and stronger cortisol stress responses (p = .013). Lastly, having lower body esteem predicted stronger cortisol stress responses (p = .022); however, it did not significantly moderate the association between shame indices and cortisol stress responses (all ps ≥ .94). These findings suggest that body esteem and trait shame independently contribute to strength of cortisol stress responses. Thus, in addition to trait shame, body esteem emerged as an important predictor of cortisol stress responses and as such, a potential contributor to stress-related negative health outcomes. PMID:26577952

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

PubMed

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

2014-11-01

In the United States the economically disadvantaged and some ethnic minorities are often exposed to chronic psychosocial stressors and disproportionately affected by asthma. Current evidence suggests a causal association between chronic psychosocial stress and asthma or asthma morbidity. Recent findings suggest potential mechanisms underlying this association, including changes in the methylation and expression of genes that regulate behavioral, autonomic, neuroendocrine, and immunologic responses to stress. There is also evidence suggesting the existence of susceptibility genes that predispose chronically stressed youth to both post-traumatic stress disorder and asthma. In this review we critically examine published evidence and suggest future directions for research in this field. Copyright © 2014 American Academy of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.

Aquatic-Aerobic Exercise as a Means of Stress Reduction during Pregnancy

PubMed Central

Parker, Kara Mallory; Smith, Sheila A.

2003-01-01

The goals of this research were to explore the current literature regarding associations between psychological stress and adverse fetal outcome, associations between aerobic exercise and psychological stress reduction, and associations between aerobic exercise and fetal outcome. The published studies that were located provide evidence of the following: 1) Stress reactivity increases physiologically during pregnancy, 2) pregnant women may experience additional stressors that are usually not experienced in a nonpregnant state, 3) psychological stress in pregnancy is associated with adverse fetal outcome, 4) exercise can be a method of stress reduction, 5) exercise in pregnancy is not associated with adverse fetal outcome, and 6) exercise in pregnancy may provide benefit to the fetus. Data were analyzed from an original study and associations were reported between psychological stress-management activities and participation in aquatic aerobic exercise classes. No reports were available investigating an exercise-induced reduction in psychological stress with fetal outcome. PMID:17273326

Using the Elements of Cooperative Learning in School Band Classes in the United States

ERIC Educational Resources Information Center

Whitener, John L.

2016-01-01

The purpose of this article is to answer the question of how we might use the elements of cooperative learning in school band classes in the United States. Current school band programs use age-old traditions that overemphasize group and individual competitiveness, stress large ensemble performance at the expense of all other activities, are…

Thermo-Mechanical and Electrochemistry Modeling of Planar SOFC Stacks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khaleel, Mohammad A.; Recknagle, Kurtis P.; Lin, Zijing

2002-12-01

Modeling activities at PNNL support design and development of modular SOFC systems. The SOFC stack modeling capability at PNNL has developed to a level at which planar stack designs can be compared and optimized for startup performance. Thermal-fluids and stress modeling is being performed to predict the transient temperature distribution and to determine the thermal stresses based on the temperature distribution. Current efforts also include the development of a model for calculating current density, cell voltage, and heat production in SOFC stacks with hydrogen or other fuels. The model includes the heat generation from both Joule heating and chemical reactions.more » It also accounts for species production and destruction via mass balance. The model is being linked to the finite element code MARC to allow for the evaluation of temperatures and stresses during steady state operations.« less

Intimate partner relationship stress and suicidality in a psychiatrically hospitalized military sample.

PubMed

LaCroix, Jessica M; Colborn, Victoria A; Hassen, Helena O; Perera, Kanchana U; Weaver, Jennifer; Soumoff, Alyssa; Novak, Laura A; Ghahramanlou-Holloway, Marjan

2018-07-01

Suicide among United States service members is a significant public health concern. Intimate partner relationship stress may contribute to suicide risk, as a failed or failing relationship is the most commonly documented stressor preceding military suicide attempts and deaths. However, little is known about the manner by which relationship stressors are associated with the experience of military suicidality. A sample of 190 psychiatrically hospitalized military personnel and adult dependents enrolled in an ongoing randomized controlled trial evaluating the efficacy of an inpatient cognitive behavioral treatment for suicidality were included in this study. Analyses examined depression, hopelessness, and suicidality among participants with (n = 105) and without (n = 85) self-reported romantic relationship stress. Over half (55%) of the sample reported current romantic relationship stress. Compared to participants without current romantic relationship stress, results indicated that individuals reporting current romantic relationship stress were more hopeless (AOR = 1.07 (95% CI: 1.01-1.12), p = 0.020), more likely to endorse multiple suicide attempts (AOR = 1.96 (95% CI: 1.01-3.79), p = 0.046), had higher overall suicide risk (AOR = 2.49, (95% CI: 1.03-6.06), p = 0.044), and were more likely to report that the reason for their suicidality was at least in part to get a reaction from others. Findings suggest romantic relationship stress is associated with greater suicide risk, and have clinical implications for suicide prevention and intervention. Future research may examine mechanisms and pathways between romantic relationship stress, suicidality, and prevention and intervention strategies. Published by Elsevier Inc.

Electrical Conductance Tuning and Bistable Switching in Poly(N-vinylcarbazole)-Carbon Nanotube Composite Films.

PubMed

Liu, Gang; Ling, Qi-Dan; Teo, Eric Yeow Hwee; Zhu, Chun-Xiang; Chan, D Siu-Hung; Neoh, Koon-Gee; Kang, En-Tang

2009-07-28

By varying the carbon nanotube (CNT) content in poly(N-vinylcarbazole) (PVK) composite thin films, the electrical conductance behavior of an indium-tin oxide/PVK-CNT/aluminum (ITO/PVK-CNT/Al) sandwich structure can be tuned in a controlled manner. Distinctly different electrical conductance behaviors, such as (i) insulator behavior, (ii) bistable electrical conductance switching effects (write-once read-many-times (WORM) memory effect and rewritable memory effect), and (iii) conductor behavior, are discernible from the current density-voltage characteristics of the composite films. The turn-on voltage of the two bistable conductance switching devices decreases and the ON/OFF state current ratio of the WORM device increases with the increase in CNT content of the composite film. Both the WORM and rewritable devices are stable under a constant voltage stress or a continuous pulse voltage stress, with an ON/OFF state current ratio in excess of 10(3). The conductance switching effects of the composite films have been attributed to electron trapping in the CNTs of the electron-donating/hole-transporting PVK matrix.

Designing skin response meter for psycho galvanic reflex

NASA Astrophysics Data System (ADS)

Dhokalia, Dhruv M.; Atreya, Parul; Kumar, Arun

2011-12-01

Human skin offers some resistance to current and voltage. This resistance changes with the emotional state of the body. The circuit proposed here measures changes in our skin resistance following changes in our mental state. In the relaxed state, the resistance offered by the skin is as high as 2 mega-ohms or more, which reduces to 500 kilo-ohms or less when the emotional stress is too high. The reduction in skin resistance is related to increased blood flow and permeability followed by the physiological changes during high stress. This increases the electrical conductivity of the skin. This circuit is useful to monitor the skin's response to relaxation techniques. It is very sensitive and shows response during a sudden moment of stress. Even a deep sigh will give response in the circuit. The circuit uses a sensitive amplifier to sense variations in the skin resistance. IC CA3140 is designed as a resistance- to-voltage converter that outputs varying voltage based on the skin's conductivity.

Intimate partner violence and anxiety disorders in pregnancy: the importance of vocational training of the nursing staff in facing them1

PubMed Central

Fonseca-Machado, Mariana de Oliveira; Monteiro, Juliana Cristina dos Santos; Haas, Vanderlei José; Abrão, Ana Cristina Freitas de Vilhena; Gomes-Sponholz, Flávia

2015-01-01

Objective: to identify the relationship between posttraumatic stress disorder, trait and state anxiety, and intimate partner violence during pregnancy. Method: observational, cross-sectional study developed with 358 pregnant women. The Posttraumatic Stress Disorder Checklist - Civilian Version was used, as well as the State-Trait Anxiety Inventory and an adapted version of the instrument used in the World Health Organization Multi-country Study on Women's Health and Domestic Violence. Results: after adjusting to the multiple logistic regression model, intimate partner violence, occurred during pregnancy, was associated with the indication of posttraumatic stress disorder. The adjusted multiple linear regression models showed that the victims of violence, in the current pregnancy, had higher symptom scores of trait and state anxiety than non-victims. Conclusion: recognizing the intimate partner violence as a clinically relevant and identifiable risk factor for the occurrence of anxiety disorders during pregnancy can be a first step in the prevention thereof. PMID:26487135

How discrimination and stress affects self-esteem among Dominican immigrant women: an exploratory study.

PubMed

Panchanadeswaran, Subadra; Dawson, Beverly Araujo

2011-01-01

Understanding the factors that contribute to the health disparities among racial and ethnic minorities in the United States is very important given the growing Latina population. Although researchers have investigated the health and mental health status among Latinas, the relationship between mental health and self-esteem has not been given a lot of attention. Given that self-esteem is a proxy for mental health status, investigations exploring the factors that can negatively affect self-esteem are needed. Therefore, the current study examined the influence of discrimination and stress on self-esteem among Dominican immigrant women. A cross-sectional study was undertaken among 235 immigrant Dominican women in New York City. Women (age 18-49 years) and in the United States for fewer than 20 years were more likely to report experiencing discrimination compared to women older than age 50 years and in the United States for more than 20 years. After controlling for age, time in the United States, educational level, and income, high levels of discrimination (-0.09, p < 0.01) and stress (-0.69, p < 0.001) were significantly associated with reduced self-esteem. Interventions with Latino/a populations, especially women, need to acknowledge their individual evaluations of the discriminatory and stressful experiences that negatively influence their self-esteem and subsequently their mental health status.

Anticipatory processes under academic stress: an ERP study.

PubMed

Duan, Hongxia; Yuan, Yiran; Yang, Can; Zhang, Liang; Zhang, Kan; Wu, Jianhui

2015-03-01

It is well known that preparing for and taking high-stakes exams has a significant influence on the emotional and physiological wellbeing of exam-takers, but few studies have investigated the resulting cognitive changes. The current study examined the effect of examination-induced academic stress on anticipation in information processing. Anticipation was indexed using the contingent negative variation (CNV). Electroencephalograms (EEG) were collected from 42 participants using the classic S1-S2 paradigm. These participants were preparing for the Chinese National Postgraduate Entrance Exam (NPEE). EEGs were also collected from 21 age-matched, non-exam comparison participants. The levels of perceived stress and state anxiety were higher and both the initial CNV (iCNV) and the late CNV (lCNV) were more negative in the exam group than in the non-exam group. These results suggest that participants under academic stress experienced greater anticipation of upcoming events. More important, for the non-exam group, state anxiety was positively related to both the iCNV and lCNV amplitude, and this correlation existed when trait anxiety was controlled; however, there was no such relationship in the exam group. These results suggested that the cortical anticipatory activity in the high-stressed exam group reached the maximum ceiling, leaving little room for transient increases in state anxiety. Copyright © 2015 Elsevier Inc. All rights reserved.

Coupled assimilation for an intermediated coupled ENSO prediction model

NASA Astrophysics Data System (ADS)

Zheng, Fei; Zhu, Jiang

2010-10-01

The value of coupled assimilation is discussed using an intermediate coupled model in which the wind stress is the only atmospheric state which is slavery to model sea surface temperature (SST). In the coupled assimilation analysis, based on the coupled wind-ocean state covariance calculated from the coupled state ensemble, the ocean state is adjusted by assimilating wind data using the ensemble Kalman filter. As revealed by a series of assimilation experiments using simulated observations, the coupled assimilation of wind observations yields better results than the assimilation of SST observations. Specifically, the coupled assimilation of wind observations can help to improve the accuracy of the surface and subsurface currents because the correlation between the wind and ocean currents is stronger than that between SST and ocean currents in the equatorial Pacific. Thus, the coupled assimilation of wind data can decrease the initial condition errors in the surface/subsurface currents that can significantly contribute to SST forecast errors. The value of the coupled assimilation of wind observations is further demonstrated by comparing the prediction skills of three 12-year (1997-2008) hindcast experiments initialized by the ocean-only assimilation scheme that assimilates SST observations, the coupled assimilation scheme that assimilates wind observations, and a nudging scheme that nudges the observed wind stress data, respectively. The prediction skills of two assimilation schemes are significantly better than those of the nudging scheme. The prediction skills of assimilating wind observations are better than assimilating SST observations. Assimilating wind observations for the 2007/2008 La Niña event triggers better predictions, while assimilating SST observations fails to provide an early warning for that event.

Soft-type trap-induced degradation of MoS2 field effect transistors.

PubMed

Cho, Young-Hoon; Ryu, Min-Yeul; Lee, Kook Jin; Park, So Jeong; Choi, Jun Hee; Lee, Byung-Chul; Kim, Wungyeon; Kim, Gyu-Tae

2018-06-01

The practical applicability of electronic devices is largely determined by the reliability of field effect transistors (FETs), necessitating constant searches for new and better-performing semiconductors. We investigated the stress-induced degradation of MoS 2 multilayer FETs, revealing a steady decrease of drain current by 56% from the initial value after 30 min. The drain current recovers to the initial state when the transistor is completely turned off, indicating the roles of soft-traps in the apparent degradation. The noise current power spectrum follows the model of carrier number fluctuation-correlated mobility fluctuation (CNF-CMF) regardless of stress time. However, the reduction of the drain current was well fitted to the increase of the trap density based on the CNF-CMF model, attributing the presence of the soft-type traps of dielectric oxides to the degradation of the MoS 2 FETs.

Soft-type trap-induced degradation of MoS2 field effect transistors

NASA Astrophysics Data System (ADS)

Cho, Young-Hoon; Ryu, Min-Yeul; Lee, Kook Jin; Park, So Jeong; Choi, Jun Hee; Lee, Byung-Chul; Kim, Wungyeon; Kim, Gyu-Tae

2018-06-01

The practical applicability of electronic devices is largely determined by the reliability of field effect transistors (FETs), necessitating constant searches for new and better-performing semiconductors. We investigated the stress-induced degradation of MoS2 multilayer FETs, revealing a steady decrease of drain current by 56% from the initial value after 30 min. The drain current recovers to the initial state when the transistor is completely turned off, indicating the roles of soft-traps in the apparent degradation. The noise current power spectrum follows the model of carrier number fluctuation–correlated mobility fluctuation (CNF–CMF) regardless of stress time. However, the reduction of the drain current was well fitted to the increase of the trap density based on the CNF–CMF model, attributing the presence of the soft-type traps of dielectric oxides to the degradation of the MoS2 FETs.

Burnout Syndrome and Demotivation Among Health Care Personnel. Managing Stressful Situations: The Importance of Teamwork.

PubMed

García-Campayo, J; Puebla-Guedea, M; Herrera-Mercadal, P; Daudén, E

2016-06-01

Almost one-third of our lives is spent in the workplace, where much of our interaction with others takes place and where we are exposed to stressful situations. Work-related stress has consequences for the individual's physical and mental health. Stress and professional burnout syndrome are the main consequences of work situations characterized by a constant state of tension. Stress is the second leading cause of absenteeism in the European Union, and around 12% of European workers are currently affected by burnout syndrome. It is therefore vital to identify demotivated and stressed staff in both large organizations (hospitals and clinics) and smaller centers (private practices) so as to facilitate preventive measures and ensure early intervention in situations of stress, with a view to improving the performance of work teams. Copyright © 2015 AEDV. Published by Elsevier España, S.L.U. All rights reserved.

The relationship between skin aging and steady state ultraweak photon emission as an indicator of skin oxidative stress in vivo.

PubMed

Gabe, Y; Osanai, O; Takema, Y

2014-08-01

Ultraweak photon emission (UPE) is one potential method to evaluate the oxidative status of the skin in vivo. However, little is known about how the daily oxidative stress of the skin is related to skin aging-related alterations in vivo. We characterized the steady state UPE and performed a skin survey. We evaluated the skin oxidative status by UPE, skin elasticity, epidermal thickness and skin color on the inner upper arm, the outer forearm, and the buttock of 70 Japanese volunteers. The steady state UPE at the three skin sites increased with age. Correlation analysis revealed that the steady state UPE only from the buttock was related to skin elasticity, which showed age-dependent changes. Moreover, analysis by age group indicated that b* values of the inner upper arm of subjects in their 20s were inversely correlated with UPE as occurred in buttock skin. In contrast, photoaged skin did not show a clear relationship with steady state UPE because the accumulation of sun-exposure might influence the sensitivity to oxidative stress. These results suggest that steady state UPE reflects not only intrinsic skin aging and cutaneous color but also the current oxidative status independent of skin aging. © 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Validity of multiple stress creep recovery (MSCR) test for DOTD asphalt binder specification : final report 564.

DOT National Transportation Integrated Search

2017-09-01

Numerous studies have shown that G*/Sin, the high temperature specification parameter for current Performance Graded (PG) asphalt binder is not adequate to reflect the rutting characteristics of polymer-modified binders. Consequently, many state De...

The self-medication hypothesis: Evidence from terrorism and cigarette accessibility.

PubMed

Pesko, Michael F; Baum, Christopher F

2016-09-01

We use single equation and system instrumental variable models to explore if individuals smoke during times of stress (the motivation effect) and if they are successful in self-medicating short-term stress (the self-medication effect). Short-term stress is a powerful motivator of smoking, and the decision to smoke could trigger biological feedback that immediately reduces short-term stress. We use data on self-reported smoking and stress from 240,388 current and former smokers. We instrument short-term stress with temporal distance from September 11, 2001 (using date of interview). We instrument smoking with cigarette accessibility measures of cigarette price changes and distance to state borders. In the absence of accounting for endogeneity, we find that smoking is associated with increases in short-term stress. However, when we account for endogeneity we find no evidence of smoking affecting short-term stress. We do find a consistent positive effect of short-term stress on smoking. Copyright © 2016 Elsevier B.V. All rights reserved.

[The Role of Resilience Factors in Informal Caregivers of Dementia Patients - A Review on Selected Factors].

PubMed

Kunzler, Angela; Skoluda, Nadine; Nater, Urs

2018-01-01

In the face of demographic change, the informal care of dementia patients is becoming increasingly important. However, due to dementia symptoms as well as persisting care demands, this subgroup of informal caregivers is confronted with a large number of stressors resulting in chronic stress and impaired physical and mental health in many caregivers. Based on the current research on resilience (i. e., maintaining or regaining health despite stress and adversities), there is increasing interest in identifying resilience factors that may serve as resources to cope with informal care and protect caregivers against health problems. The review discusses the role of resilience factors in the association between ongoing caregiving stress and health. In analyzing the current state of research on resilience factors for dementia caregivers, we focus on the factors self-efficacy, relationship quality, and social support. © Georg Thieme Verlag KG Stuttgart · New York.

Psychological problems and psychosocial predictors of cigarette smoking behavior among undergraduate students in Malaysia.

PubMed

Saravanan, Coumaravelou; Heidhy, Imran

2014-01-01

Cigarette smokers have their own motivation and justification to smoke. For example, smoking reduces their stress or enhances their pleasure. This study aimed to identify the (a) prevalence of cigarette smokers among undergraduates in Malaysia, (b) gender differences in nicotine dependence among current smokers, (c) differences in psychological problems (depression, anxiety and stress) based on the status of smoking cigarettes (current, former and non-smokers) and (d) extent to which precipitating factors (tension reduction, addiction, automatism, handling, social interaction, pleasure, and stimulation) predict the smoking behavior among current smokers. In this study 780 undergraduate students participated from a private university in Kuala Lumpur and Selangor state in Malaysia. The Depression, Stress and Anxiety Scale, Modified Reason for Smoking Scale and Fagerstrom Nicotine Dependence Test were used to measure psychological problems, predictors of smoking behavior and nicotine dependency among current smokers. The results showed that 14.7%(n=106) of the students were smokers. Current smokers exhibited more psychological problems (depression, anxiety and stress) compared to former and non-smokers. Addiction, tension reduction, pleasure and automatism were predictors of smoking behavior among the current smoking students. Step wise regression analysis showed that smoking behavior was highly predicted by nicotine dependency or addiction. Smoking students were motivated to smoke cigarettes as they believed that it reduced their tension and enhance pleasure. Hence, there is a need for health promotion and anti-tobacco prevention as cigarette smokers experience more psychological problems. Nicotine dependency or addition was one of the major causes for smoking behavior among the student population in Malaysia.

Boricua de pura cepa: Ethnic identity, cultural stress and self-concept in Puerto Rican youth.

PubMed

Zhen-Duan, Jenny; Jacquez, Farrah; Sáez-Santiago, Emily

2018-05-17

The available literature on ethnic identity among Puerto Ricans has focused on those living in the United States, with little to no attention placed on examining ethnic identity and psychological constructs among youth living in Puerto Rico. Using a colonial mentality framework, the current study examined the associations between ethnic identity, cultural stress, and self-concept among adolescent boys and girls living in Puerto Rico. The current cross-sectional study surveyed participants (N = 187) recruited from several junior high schools in the metropolitan area in Puerto Rico. Relations between ethnic identity, cultural stress, and self-concept differed by gender. First, cultural stress was associated with self-concept for boys, such that higher cultural stress predicted lower self-concept. Second, among girls, cultural stress moderated the relation between ethnic identity and self-concept. Specifically, for girls experiencing high cultural stress, exploration and resolution of their ethnic identity was associated with higher ratings of self-concept. Although cultural stress has been widely understood as a phenomena associated with immigrants, our study indicated that cultural stress is important in understanding self-concept of youth living in Puerto Rico. For boys, cultural stress, but not ethnic identity, is particularly important to their self-concept. Among girls experiencing high cultural stress, exploration and resolution of ethnic identity was associated with higher self-concept. Results suggested that the cultural stress associated with the colonial context of Puerto Rico is salient in ethnic identity and self-concept development, even though Puerto Rican youth are the ethnic majority in the island. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

US forest response to projected climate-related stress: a tolerance perspective.

PubMed

Liénard, Jean; Harrison, John; Strigul, Nikolay

2016-08-01

Although it is widely recognized that climate change will require a major spatial reorganization of forests, our ability to predict exactly how and where forest characteristics and distributions will change has been rather limited. Current efforts to predict future distribution of forested ecosystems as a function of climate include species distribution models (for fine-scale predictions) and potential vegetation climate envelope models (for coarse-grained, large-scale predictions). Here, we develop and apply an intermediate approach wherein we use stand-level tolerances of environmental stressors to understand forest distributions and vulnerabilities to anticipated climate change. In contrast to other existing models, this approach can be applied at a continental scale while maintaining a direct link to ecologically relevant, climate-related stressors. We first demonstrate that shade, drought, and waterlogging tolerances of forest stands are strongly correlated with climate and edaphic conditions in the conterminous United States. This discovery allows the development of a tolerance distribution model (TDM), a novel quantitative tool to assess landscape level impacts of climate change. We then focus on evaluating the implications of the drought TDM. Using an ensemble of 17 climate change models to drive this TDM, we estimate that 18% of US ecosystems are vulnerable to drought-related stress over the coming century. Vulnerable areas include mostly the Midwest United States and Northeast United States, as well as high-elevation areas of the Rocky Mountains. We also infer stress incurred by shifting climate should create an opening for the establishment of forest types not currently seen in the conterminous United States. © 2016 John Wiley & Sons Ltd.

Experiments and FE modeling of stress-strain state in ReBCO tape under tensile, torsional and transverse load

NASA Astrophysics Data System (ADS)

Ilin, K.; Yagotintsev, K. A.; Zhou, C.; Gao, P.; Kosse, J.; Otten, S. J.; Wessel, W. A. J.; Haugan, T. J.; van der Laan, D. C.; Nijhuis, A.

2015-05-01

For high current superconductors in high magnet fields with currents in the order of 50 kA, single ReBCO coated conductors must be assembled in a cable. The geometry of such a cable is mostly such that combined torsion, axial and transverse loading states are anticipated in the tapes and tape joints. The resulting strain distribution, caused by different thermal contraction and electromagnetic forces, will affect the critical current of the tapes. Tape performance when subjected to torsion, tensile and transverse loading is the key to understanding limitations for the composite cable performance. The individual tape material components can be deformed, not only elastically but also plastically under these loads. A set of experimental setups, as well as a convenient and accurate method of stress-strain state modeling based on the finite element method have been developed. Systematic measurements on single ReBCO tapes are carried out combining axial tension and torsion as well as transverse loading. Then the behavior of a single tape subjected to the various applied loads is simulated in the model. This paper presents the results of experimental tests and detailed FE modeling of the 3D stress-strain state in a single ReBCO tape under different loads, taking into account the temperature dependence and the elastic-plastic properties of the tape materials, starting from the initial tape processing conditions during its manufacture up to magnet operating conditions. Furthermore a comparison of the simulations with experiments is presented with special attention for the critical force, the threshold where the tape performance becomes irreversibly degraded. We verified the influence of tape surface profile non-uniformity and copper stabilizer thickness on the critical force. The FE models appear to describe the tape experiments adequately and can thus be used as a solid basis for optimization of various cabling concepts.

Validation of MIL-F-9490D - General Specification for Flight Control System for Piloted Military Aircraft. Volume II. YF-17 Lightweight Fighter Validation

DTIC Science & Technology

1977-04-01

Leakage current shall not exceed 10 milliamps when a dielectric stress voltage of 1,200 volts, 60 liz, is applied for 1 minute between insulated...include requirements which eqtial or exceed requirements of this paragraph. However, lower values for dielectric stress voltage and insulation...resistance were specified for solid state elec- tronic assemblies. Northrop’s requirement for dielectric strenirth specifies a test voltage of 300 volts RMS

Cigarette craving and stressful social interactions: The roles of state and trait social anxiety and smoking to cope.

PubMed

Watson, Noreen L; DeMarree, Kenneth G; Cohen, Lee M

2018-04-01

Previous research indicates that social anxiety (SA) is a risk factor for the maintenance and relapse of smoking behaviors. However, little is known about the mechanisms underlying this relationship. The current study tested the effects of state and trait levels of SA as well as smoking to cope with symptoms of SA on craving during a social stressor task in abstinent conditions. Participants (n = 60) were daily smokers, aged 18-30. Participants attended two sessions: a baseline session and a second session, wherein they engaged in a social stressor task while deprived from nicotine for 24 h. Subjective ratings of cigarette craving and state levels of SA were assessed six times throughout the task. Data were analyzed via multilevel modeling. Both trait SA and some forms of smoking to cope with symptoms of SA were more likely to predict increased craving during times of high, relative to low, social stress. Further, individuals with higher state SA, greater smoking to cope behaviors, and those who experience greater relief of social distress by smoking experienced greater craving throughout the task. These effects remained after controlling for nicotine dependence, withdrawal symptoms, depression, and other symptoms of anxiety and stress. Smoking to cope with symptoms of SA did not moderate the relationship between state SA and craving. Smokers high in SA (state and trait) and smoking to cope with symptoms of SA may be at risk for continued smoking and relapse because of the intensity of cravings they experience during stressful social situations. Copyright © 2018 Elsevier B.V. All rights reserved.

Drain Current Stress-Induced Instability in Amorphous InGaZnO Thin-Film Transistors with Different Active Layer Thicknesses.

PubMed

Wang, Dapeng; Zhao, Wenjing; Li, Hua; Furuta, Mamoru

2018-04-05

In this study, the initial electrical properties, positive gate bias stress (PBS), and drain current stress (DCS)-induced instabilities of amorphous indium gallium zinc oxide (a-IGZO) thin-film transistors (TFTs) with various active layer thicknesses ( T IGZO ) are investigated. As the T IGZO increased, the turn-on voltage ( V on ) decreased, while the subthreshold swing slightly increased. Furthermore, the mobility of over 13 cm²·V −1 ·s −1 and the negligible hysteresis of ~0.5 V are obtained in all of the a-IGZO TFTs, regardless of the T IGZO . The PBS results exhibit that the V on shift is aggravated as the T IGZO decreases. In addition, the DCS-induced instability in the a-IGZO TFTs with various T IGZO values is revealed using current–voltage and capacitance–voltage ( C – V ) measurements. An anomalous hump phenomenon is only observed in the off state of the gate-to-source ( C gs ) curve for all of the a-IGZO TFTs. This is due to the impact ionization that occurs near the drain side of the channel and the generated holes that flow towards the source side along the back-channel interface under the lateral electric field, which cause a lowered potential barrier near the source side. As the T IGZO value increased, the hump in the off state of the C gs curve was gradually weakened.

Enhanced negative emotion and alcohol craving, and altered physiological responses following stress and cue exposure in alcohol dependent individuals.

PubMed

Sinha, Rajita; Fox, Helen C; Hong, Kwangik A; Bergquist, Keri; Bhagwagar, Zubin; Siedlarz, Kristen M

2009-04-01

Chronic alcohol abuse is associated with changes in stress and reward pathways that could alter vulnerability to emotional stress and alcohol craving. This study examines whether chronic alcohol abuse is associated with altered stress and alcohol craving responses. Treatment-engaged, 28-day abstinent alcohol-dependent individuals (ADs; 6F/22M), and social drinkers (SDs; 10F/18M) were exposed to a brief guided imagery of a personalized stressful, alcohol-related and neutral-relaxing situation, one imagery condition per session, presented in random order across 3 days. Alcohol craving, anxiety and emotion ratings, behavioral distress responses, heart rate, blood pressure, and salivary cortisol measures were assessed. Alcohol patients showed significantly elevated basal heart rate and salivary cortisol levels. Stress and alcohol cue exposure each produced a significantly enhanced and persistent craving state in alcohol patients that was marked by increased anxiety, negative emotion, systolic blood pressure responses, and, in the case of alcohol cue, behavioral distress responses, as compared to SDs. Blunted stress-induced cortisol responses were observed in the AD compared to the SD group. These data are the first to document that stress and cue exposure induce a persistent negative emotion-related alcohol craving state in abstinent alcoholics accompanied by dysregulated HPA and physiological arousal responses. As laboratory models of stress and negative mood-induced alcohol craving are predictive of relapse outcomes, one implication of the current data is that treatments targeting decreases in stress and alcohol cue-induced craving and regulation of stress responses could be of benefit in improving alcohol relapse outcomes.

Psychological Stress and Mitochondria: A Systematic Review.

PubMed

Picard, Martin; McEwen, Bruce S

Mitochondria are multifunctional life-sustaining organelles that represent a potential intersection point between psychosocial experiences and biological stress responses. This article provides a systematic review of the effects of psychological stress on mitochondrial structure and function. A systematic review of the literature investigating the effects of psychological stress on mitochondrial function was conducted. The review focused on experimentally controlled studies allowing us to draw causal inference about the effect of induced psychological stress on mitochondria. A total of 23 studies met the inclusion criteria. All studies involved male laboratory animals, and most demonstrated that acute and chronic stressors influenced specific facets of mitochondrial function, particularly within the brain. Nineteen studies showed significant adverse effects of psychological stress on mitochondria and four found increases in function or size after stress. In humans, only six observational studies were available, none with experimental designs, and most only measured biological markers that do not directly reflect mitochondrial function, such as mitochondrial DNA copy number. Overall, evidence supports the notion that acute and chronic stressors influence various aspects of mitochondrial biology, and that chronic stress exposure can lead to molecular and functional recalibrations among mitochondria. Limitations of current animal and human studies are discussed. Maladaptive mitochondrial changes that characterize this subcellular state of stress are termed mitochondrial allostatic load. Prospective studies with sensitive measures of specific mitochondrial outcomes will be needed to establish the link between psychosocial stressors, emotional states, the resulting neuroendocrine and immune processes, and mitochondrial energetics relevant to mind-body research in humans.

The application of minority stress theory to marijuana use among sexual minority adolescents.

PubMed

Goldbach, Jeremy T; Schrager, Sheree M; Dunlap, Shannon L; Holloway, Ian W

2015-02-01

Previous research indicates that lesbian, gay, and bisexual (LGB) adolescents are at increased risk for substance use, including heightened rates of marijuana use. Minority stress theory suggests that difficult social situations create a state of chronic stress that leads to poor health outcomes for LGB adults; however, the applicability of this model has not been well explored in relation to substance use among LGB adolescents. The current study is a secondary analysis of the OutProud survey, conducted in 2000. The original study used purposive sampling to collect data from 1,911 LGB adolescents (age 12-17) across the United States, and represents the largest known study to explore experiences specific to identifying as LGB, such as homophobia and gay-related victimization. We used structural equation modeling (SEM) to explore the feasibility of applying a minority stress framework to understand marijuana use in this population. The final structural model for marijuana use in the LGB adolescent sample displayed excellent fit and modest explanatory power for marijuana use. Two of the five factors, community connectedness and internalized homophobia, were significantly (p < .05) associated with marijuana use. Findings suggest that minority stress theory may be appropriately applied to marijuana use in this population; however, better measurement of minority stress concepts for LGB adolescents is needed.

Prenatal stress effects in a wild, long-lived primate: predictive adaptive responses in an unpredictable environment.

PubMed

Berghänel, Andreas; Heistermann, Michael; Schülke, Oliver; Ostner, Julia

2016-09-28

Prenatal maternal stress affects offspring phenotype in numerous species including humans, but it is debated whether these effects are evolutionarily adaptive. Relating stress to adverse conditions, current explanations invoke either short-term developmental constraints on offspring phenotype resulting in decelerated growth to avoid starvation, or long-term predictive adaptive responses (PARs) resulting in accelerated growth and reproduction in response to reduced life expectancies. Two PAR subtypes were proposed, acting either on predicted internal somatic states or predicted external environmental conditions, but because both affect phenotypes similarly, they are largely indistinguishable. Only external (not internal) PARs rely on high environmental stability particularly in long-lived species. We report on a crucial test case in a wild long-lived mammal, the Assamese macaque (Macaca assamensis), which evolved and lives in an unpredictable environment where external PARs are probably not advantageous. We quantified food availability, growth, motor skills, maternal caretaking style and maternal physiological stress from faecal glucocorticoid measures. Prenatal maternal stress was negatively correlated to prenatal food availability and led to accelerated offspring growth accompanied by decelerated motor skill acquisition and reduced immune function. These results support the 'internal PAR' theory, which stresses the role of stable adverse internal somatic states rather than stable external environments. © 2016 The Author(s).

They did not start the fire: reviewing and resolving the issue of physician stress and burnout.

PubMed

Babyar, Julie Christine

2017-06-19

Purpose Physician stress and burnout is a serious and common concern in healthcare, with over half of physicians in the USA meeting at least one criterion for burnout. The paper aims to discuss these issues. Design/methodology/approach A review on current state of physician stress and burnout research, from 2008 to 2016, was undertaken. A subsequent perspective paper was shaped around these reviews. Findings Findings reveal research strength in prevalence and incidence with opportunities for stronger intervention studies. While descriptive studies on causes and consequences of physician burnout are available, studies on interventions and prevention of physician burnout are lacking. Future research on physician stress and burnout should incorporate intervention studies and take care to avoid limitations found in current research. Accountability and prevention of physician burnout is the responsibility of the healthcare industry as a whole, and organizational strategies must be emphasized in future research. Originality/value The value of this research comes in the original comprehensive review, international inclusion and succinct summary of physician burnout research and strategies.

Mass spectrometry-based plant metabolomics: Metabolite responses to abiotic stress.

PubMed

Jorge, Tiago F; Rodrigues, João A; Caldana, Camila; Schmidt, Romy; van Dongen, Joost T; Thomas-Oates, Jane; António, Carla

2016-09-01

Metabolomics is one omics approach that can be used to acquire comprehensive information on the composition of a metabolite pool to provide a functional screen of the cellular state. Studies of the plant metabolome include analysis of a wide range of chemical species with diverse physical properties, from ionic inorganic compounds to biochemically derived hydrophilic carbohydrates, organic and amino acids, and a range of hydrophobic lipid-related compounds. This complexitiy brings huge challenges to the analytical technologies employed in current plant metabolomics programs, and powerful analytical tools are required for the separation and characterization of this extremely high compound diversity present in biological sample matrices. The use of mass spectrometry (MS)-based analytical platforms to profile stress-responsive metabolites that allow some plants to adapt to adverse environmental conditions is fundamental in current plant biotechnology research programs for the understanding and development of stress-tolerant plants. In this review, we describe recent applications of metabolomics and emphasize its increasing application to study plant responses to environmental (stress-) factors, including drought, salt, low oxygen caused by waterlogging or flooding of the soil, temperature, light and oxidative stress (or a combination of them). Advances in understanding the global changes occurring in plant metabolism under specific abiotic stress conditions are fundamental to enhance plant fitness and increase stress tolerance. © 2015 Wiley Periodicals, Inc. Mass Spec Rev 35:620-649, 2016. © 2015 Wiley Periodicals, Inc.

Assessment of posttraumatic stress disorder in Cambodian refugees using the Clinician-Administered PTSD Scale: psychometric properties and symptom severity.

PubMed

Hinton, Devon E; Chhean, Dara; Pich, Vuth; Pollack, M H; Orr, Scott P; Pitman, Roger K

2006-06-01

Posttraumatic stress disorder (PTSD) symptoms were assessed by using the Clinician-Administered PTSD Scale (CAPS) in a consecutive sample of Cambodian refugees attending a psychiatric clinic in the United States. Psychometric properties of the translated CAPS and severity of PTSD-related symptoms were examined. The CAPS demonstrated adequate psychometric properties, including coefficient alpha (.92) and item-total correlations (.48-.85). Of the sample 56% (101/179) met Diagnostic and Statistical Manual of Mental Disorders, fourth edition, criteria for current PTSD. Those patients who met criteria for current PTSD had significantly higher CAPS total scores (M = 65.3, SD = 18.1) than those who did not meet the criteria (M = 13.9, SD = 16.7).

Unconventional oil and gas development and its stresses on water resources in the context of Water-Energy-Food Nexus: The case of Weld County, Colorado

NASA Astrophysics Data System (ADS)

Oikonomou, P. D.; Waskom, R.; Boone, K.; Ryan, J. N.

2015-12-01

The development of unconventional oil and gas resources in Colorado started to rapidly increase since the early 2000's. The recent oil price plunge resulted in a decline of well starts' rate in the US, but in Weld County, Colorado, it is currently at the 2013-levels. The additional water demand, despite its insignificant percentage in overall state's demand (0.1% in 2012), it competes with traditional ones, since Colorado's water is almost fully appropriated. Presently, the state has 53,597 active producing oil and gas wells. More than 40% of these are located in Weld County, which happens also to be one of top food production U.S. counties. The competition for land and water resources between the energy and agricultural sectors in water stressed areas, like the western U.S., is further intensified if recycle and reuse practices are not preferred to water disposal by the energy industry. Satisfying the multiple objectives of the Water-Energy-Food Nexus in order to achieve sustainable economic development requires balanced management of these resources. Identifying pressures on key areas that food and energy sectors are competing for water, is essential for prudent water management and developing appropriate policies. Weld County, as a water stressed and fossil fuel producing area, was selected for investigating current stresses on local water resources alongside with future climatic and water demand scenarios for exploring probable long-term effects.

Stress management techniques in the prison setting.

PubMed

Kristofersson, Gisli Kort; Kaas, Merrie J

2013-01-01

The percentage of incarcerated individuals in the United States is currently close to an all time high, and more stressful places than prisons are hard to find. Because registered nurses and advance practice nurses are often the only healthcare providers readily available to prison inmates, nurses need a repertoire of effective strategies to minimize prisoners' stress-related symptoms and behaviors. The purpose of this critical literature review was to identify the state of knowledge about using stress management techniques (SMTs) in the prison setting for reducing psychological problems and/or behavioral problems in male and female adult prison populations. A comprehensive, systematic integrated literature search was performed using multiple relevant databases to identify studies using various SMTs for incarcerated adults. Although clinical practice recommendations for the use of SMTs in the prison setting cannot be made with strong certainty, nurses working in the prison setting should continue to incorporate muscle relaxation, Transcendental Meditation, and certain Eastern meditative practices in the care of their clients because of the safety and possible positive impacts and practicality these methods have in this setting.

Mental and Physical Workload, Salivary Stress Biomarkers and Taste Perception: Mars Desert Research Station Expedition

PubMed Central

Rai, Balwant; Kaur, Jasdeep

2012-01-01

Background: Very few studies have been conducted on the effects of simulation of Mars conditions on taste. Aims: This study was planned to find the effects of physical and mental workload on taste sensitivity and salivary stress biomarkers. Materials and Methods: Twelve crew members were selected. Taste reactions and intensity of the taste sensations to quinine sulfate, citric acid, and sucrose were tested before and after mental and physical tasks for one hour. Also, psychological mood states by profile of mood state, salivary, salivary alpha amylase and cortisol, and current stress test scores were measured before and after mental and physical tasks. Results: Average time intensity evaluation showed that after the mental and physical tasks, the perceived duration of bitter, sour, and sweet taste sensations was significantly shortened relative to control group. There were good correlations between average time intensity of sweetness, bitterness, sourness and cortisol levels. Conclusions: Taste alterations due to stress can have an effect on the health and confidence of astronauts in long- term space missions. Thus, this issue remains one of the important issues for future human explorations. PMID:23181230

Periodic and chaotic psychological stress variations as predicted by a social support buffered response model

NASA Astrophysics Data System (ADS)

Field, Richard J.; Gallas, Jason A. C.; Schuldberg, David

2017-08-01

Recent work has introduced social dynamic models of people's stress-related processes, some including amelioration of stress symptoms by support from others. The effects of support may be ;direct;, depending only on the level of support, or ;buffering;, depending on the product of the level of support and level of stress. We focus here on the nonlinear buffering term and use a model involving three variables (and 12 control parameters), including stress as perceived by the individual, physical and psychological symptoms, and currently active social support. This model is quantified by a set of three nonlinear differential equations governing its stationary-state stability, temporal evolution (sometimes oscillatory), and how each variable affects the others. Chaos may appear with periodic forcing of an environmental stress parameter. Here we explore this model carefully as the strength and amplitude of this forcing, and an important psychological parameter relating to self-kindling in the stress response, are varied. Three significant observations are made: 1. There exist many complex but orderly regions of periodicity and chaos, 2. there are nested regions of increasing number of peaks per cycle that may cascade to chaos, and 3. there are areas where more than one state, e.g., a period-2 oscillation and chaos, coexist for the same parameters; which one is reached depends on initial conditions.

Cross-shore variation of wind-driven flows on the inner shelf in Long Bay, South Carolina, United States

NASA Astrophysics Data System (ADS)

Gutierrez, Benjamin T.; Voulgaris, George; Work, Paul A.

2006-03-01

The cross-shore structure of subtidal flows on the inner shelf (7 to 12 m water depth) of Long Bay, South Carolina, a concave-shaped bay, is examined through the analysis of nearly 80 days of near-bed (1.7-2.2 m above bottom) current observations acquired during the spring and fall of 2001. In the spring and under northeastward winds (upwelling favorable) a two-layered flow was observed at depths greater than 10 m, while closer to the shore the currents were aligned with the wind. The two-layered flow is attributed to the presence of stratification, which has been observed under similar conditions in the South Atlantic Bight. When the wind stress was southwestward (downwelling favorable) and exceeded 0.1 N/m2, vertical mixing occurred, the two-layered flow pattern disappeared, and currents were directed alongshore with the wind at all sites and throughout the water column. In the fall, near-bed flows close to the shore (water depth <7 m) were often reduced compared to or opposed those measured farther offshore under southwestward winds. A simplified analysis of the depth-averaged, alongshore momentum balance illustrates that the alongshore pressure gradient approached or exceeded the magnitude of the alongshore wind stress at the same time that the nearshore alongshore current opposed the wind stress and alongshore currents farther offshore. In addition, the analysis suggests that the wind stress is reduced closer to shore so that the alongshore pressure gradient is large enough to drive the flow against the wind.

Consideration of some fundamental erosion processes encountered in hypervelocity electromagnetic propulsion

NASA Astrophysics Data System (ADS)

Buckingham, A. C.; Hawke, R. S.

1982-09-01

Experimental and theoretical research was conducted jointly at the Livermore and Los Alamos National laboratories on dc electromagnetic railgun Lorentz accelerators. Pellets weighing a few grams to tens of grams were launched at velocities up to better than 11 km/s. The research is addressed to attaining repeated launches of samples at hypervelocity in target impact experiments. In these experiments, shock-induced pressure in the tens of megabars range are obtained for high pressure equations of state research. Primary energy sources of the order of several hundred kJ to a MJ and induction currents of the order of 1 or more MA are necessary for these launches. Erosion and deformation of the conductor rails and the accelerated sample material are continuing problems. The beating, stress, and erosion resulting from simultaneous imposition of rail induction current, dense plasma (armature) interaction, current distribution, magnetic field stresses and projectile/rail contact friction are examined.

Review of work-related stress in mainland Chinese nurses.

PubMed

Zeng, Yingchun

2009-03-01

The aim of this review was to identify the specific work-related stressors of mainland Chinese nurses and to present the current state of stress research in order to discuss directions for further research. A literature search from January 2000 to June 2007 was conducted among three electronic databases. The specific stressors among Chinese nurses were effort-reward imbalance, the poor image of nursing in the community, and managerial issues. The studies were limited to either descriptive or correlation designs, a variety of stress scales were used to investigate the nurses' work-related stressors, and there were no published studies reporting stress management interventions for Chinese nurses. This review highlights that further stress research targeted to Chinese nurses needs more prospective and longitudinal studies and has to develop a consistent instrument to measure stressors. The priority issue is the initiation of stress management interventions to improve nurses' coping skills, while the long-term goal is to reduce the level of stress or eliminate the stressors through individual, organizational, and societal interventions.

[Current State of Studies on Job-related Stress among Psychiatric Social Workers and Insights into Future Research].

PubMed

Yada, Hironori; Abe, Hiroshi; Odachi, Ryo; Iwanaga, Yasushi; Yamane, Toshie

2016-01-01

We studied the characteristics of psychiatric social workers (PSWs) and present research on job-related stress among them; we also provide insights into the future of such research. In recent years, studies on job-related stress among PSWs have been gaining interest. In particular, stress associated with the repeated revisions of related laws has increased. Subsequently, it was found that occupational stress in PSWs differs qualitatively and quantitatively depending on educational history, years of experience, and service department. However, no scale captures the specific characteristics of job-related stress among PSWs. Moreover, the development of a mental health care program for PSWs seems difficult. To develop a mental health care program that caters specifically to this group, future research should focus on developing a scale that determines the specific characteristics of job-related stress among PSWs, which should be evaluated on the basis of each PSW's educational history, years of experience, and service department.

The Impact of CO2 Emission Reduction on U.S. Electric Sector Water Use

EPA Science Inventory

The electric power sector is currently one of the largest water withdrawers and fastest growing water consumers in the U.S. Water supply in the United States is becoming increasingly stressed due to growth in population, per capita energy consumption and industrial water use. A...

The Impact of CO2 Emission Reductions on U.S. Electric Sector Water Use

EPA Science Inventory

The electric power sector is currently one of the largest water withdrawers and fastest growing water consumers in the U.S. Water supply in the United States is becoming increasingly stressed due to growth in population, per capita energy consumption and industrial water use. At ...

Elevated CO2 compensates for water stress in northern red oak

Treesearch

Patricia T. Tomlinson; Paul D. Anderson

1996-01-01

Global climate change models predict decreased rainfall in association with elevated CO2 in the western Lakes States region. Currently, the western edge of northern red oak (Quercus rubra L.) distribution coincides with the most xeric conditions of its ecological range. Decreased rainfall and water availability could alter...

Intergovernmental Relations and the Governance of Education.

ERIC Educational Resources Information Center

Campbell, Roald F.

Schools are currently under the many strains and stresses involving change, such as concern with the nature and purpose of schools, the growth of alternative systems, the push for new structures, the demands of new participants, financial worries, and interventions from State and national agencies. Each of these strains creates problems in…

Analysis of rainfall-induced slope instability using a field of local factor of safety

USGS Publications Warehouse

Lu, Ning; Şener-Kaya, Başak; Wayllace, Alexandra; Godt, Jonathan W.

2012-01-01

Slope-stability analyses are mostly conducted by identifying or assuming a potential failure surface and assessing the factor of safety (FS) of that surface. This approach of assigning a single FS to a potentially unstable slope provides little insight on where the failure initiates or the ultimate geometry and location of a landslide rupture surface. We describe a method to quantify a scalar field of FS based on the concept of the Coulomb stress and the shift in the state of stress toward failure that results from rainfall infiltration. The FS at each point within a hillslope is called the local factor of safety (LFS) and is defined as the ratio of the Coulomb stress at the current state of stress to the Coulomb stress of the potential failure state under the Mohr-Coulomb criterion. Comparative assessment with limit-equilibrium and hybrid finite element limit-equilibrium methods show that the proposed LFS is consistent with these approaches and yields additional insight into the geometry and location of the potential failure surface and how instability may initiate and evolve with changes in pore water conditions. Quantitative assessments applying the new LFS field method to slopes under infiltration conditions demonstrate that the LFS has the potential to overcome several major limitations in the classical FS methodologies such as the shape of the failure surface and the inherent underestimation of slope instability. Comparison with infinite-slope methods, including a recent extension to variably saturated conditions, shows further enhancement in assessing shallow landslide occurrence using the LFS methodology. Although we use only a linear elastic solution for the state of stress with no post-failure analysis that require more sophisticated elastoplastic or other theories, the LFS provides a new means to quantify the potential instability zones in hillslopes under variably saturated conditions using stress-field based methods.

Performance enhancement in uniaxially tensile stressed GeSn n-channel fin tunneling field-effect transistor: Impact of stress direction

NASA Astrophysics Data System (ADS)

Wang, Hongjuan; Han, Genquan; Jiang, Xiangwei; Liu, Yan; Zhang, Chunfu; Zhang, Jincheng; Hao, Yue

2017-04-01

In this work, the boosting effect on the performance of GeSn n-channel fin tunneling FET (nFinTFET) enabled by uniaxial tensile stress is investigated theoretically. As the fin rotates within the (001) plane, the uniaxial tensile stress is always along its direction. The electrical characteristics of tensile-stressed GeSn nFinTFETs with point and line tunneling modes are computed utilizing the technology computer aided design (TCAD) simulator in which the dynamic nonlocal band-to-band tunneling (BTBT) algorithm is employed. In comparison with the relaxed devices, tensile-stressed GeSn nFinTFETs achieve a substantial enhancement in band-to-band tunneling generation rate (G BTBT) and on-state current I ON owing to the reduced bandgap E G induced by the tensile stress. Performance improvement of GeSn nFinTFETs induced by tensile stress demonstrates a strong dependence on channel direction and tunneling modes. Under the same magnitude of stress, line-nFinTFETs obtain a more pronounced I ON enhancement over the transistors with point tunneling mode.

Compressive Failure of Fiber Composites under Multi-Axial Loading

NASA Technical Reports Server (NTRS)

Basu, Shiladitya; Waas, Anthony M.; Ambur, Damodar R.

2006-01-01

This paper examines the compressive strength of a fiber reinforced lamina under multi-axial stress states. An equilibrium analysis is carried out in which a kinked band of rotated fibers, described by two angles, is sandwiched between two regions in which the fibers are nominally straight. Proportional multi-axial stress states are examined. The analysis includes the possibility of bifurcation from the current equilibrium state. The compressive strength of the lamina is contingent upon either attaining a load maximum in the equilibrium response or satisfaction of a bifurcation condition, whichever occurs first. The results show that for uniaxial loading a non-zero kink band angle beta produces the minimum limit load. For multi-axial loading, different proportional loading paths show regimes of bifurcation dominated and limit load dominated behavior. The present results are able to capture the beneficial effect of transverse compression in raising the composite compressive strength as observed in experiments.

Cortisol stress reactivity across psychiatric disorders: A systematic review and meta-analysis.

PubMed

Zorn, Jelle V; Schür, Remmelt R; Boks, Marco P; Kahn, René S; Joëls, Marian; Vinkers, Christiaan H

2017-03-01

The hypothalamus-pituitary-adrenal (HPA) axis and its end product cortisol are essential for an adequate response to stress. Considering the role of stress as a risk factor for psychiatric disorders, it is not surprising that cortisol stress reactivity has frequently been investigated in patients versus healthy individuals. However, the large heterogeneity in measures of the cortisol stress response has hampered a systematic evaluation of the evidence. We here report of a systematic literature review and meta-analysis on cortisol reactivity to psychosocial stress across psychiatric disorders. Original data from authors were obtained to construct standardized cortisol outcomes (the areas under the curve with respect to increase (AUCi) and ground (AUCg)) and to examine the influence of sex and symptomatic state on cortisol stress reactivity. Fourteen studies on major depressive disorder (MDD) (n=1129), 9 on anxiety disorders (n=732, including social anxiety disorder (SAD), posttraumatic stress disorder, panic disorder and mixed samples of anxiety disorders) and 4 on schizophrenia (n=180) were included that used the Trier Social Stress Test or an equivalent psychosocial stress task. Sex-dependent changes in stress reactivity were apparent in MDD and anxiety disorders. Specifically, women with current MDD or an anxiety disorder exhibited a blunted cortisol stress response, whereas men with current MDD or SAD showed an increased cortisol response to psychosocial stress. In individuals with remitted MDD, altered cortisol stress reactivity was less pronounced in women and absent in men. For schizophrenia, cortisol stress reactivity was blunted in both men and women, but the number of studies was limited and showed evidence for publication bias. These findings illustrate that sharing individual data to disentangle the effects of sex, symptom levels and other factors is essential for further understanding of the alterations in cortisol stress reactivity across psychiatric disorders. Copyright © 2016 Elsevier Ltd. All rights reserved.

A hypothesis for delayed dynamic earthquake triggering

USGS Publications Warehouse

Parsons, T.

2005-01-01

It's uncertain whether more near-field earthquakes are triggered by static or dynamic stress changes. This ratio matters because static earthquake interactions are increasingly incorporated into probabilistic forecasts. Recent studies were unable to demonstrate all predictions from the static-stress-change hypothesis, particularly seismicity rate reductions. However, current dynamic stress change hypotheses do not explain delayed earthquake triggering and Omori's law. Here I show numerically that if seismic waves can alter some frictional contacts in neighboring fault zones, then dynamic triggering might cause delayed triggering and an Omori-law response. The hypothesis depends on faults following a rate/state friction law, and on seismic waves changing the mean critical slip distance (Dc) at nucleation zones.

Kinetic Simulations of Current-Sheet Formation and Reconnection at a Magnetic X Line

NASA Technical Reports Server (NTRS)

Black, C.; Antiochos, S. K.; Hesse, M.; Karpen, J. T.; DeVore, C. R.; Kuznetsova, M. M.; Zenitani, S.

2011-01-01

The integration of kinetic effects into macroscopic numerical models is currently of great interest to the plasma physics community, particularly in the context of magnetic reconnection. We are examining the formation and reconnection of current sheets in a simple, two-dimensional X-line configuration using high resolution particle-in-cell (PIC) simulations. The initial potential magnetic field is perturbed by thermal pressure introduced into the particle distribution far from the X line. The relaxation of this added stress leads to the development of a current sheet, which reconnects for imposed stress of sufficient strength. We compare the evolution and final state of our PIC simulations with magnetohydrodynamic simulations assuming both uniform and localized resistivities, and with force-free magnetic-field equilibria in which the amount of reconnect ion across the X line can be constrained to be zero (ideal evolution) or optimal (minimum final magnetic energy). We will discuss implications of our results for reconnection onset and cessation at kinetic scales in dynamically formed current sheets, such as those occurring in the terrestrial magnetotail and solar corona.

The role of stress in self-ordered porous anodic oxide formation and corrosion of aluminum

NASA Astrophysics Data System (ADS)

Capraz, Omer Ozgur

The phenomenon of plastic flow induced by electrochemical reactions near room temperature is significant in porous anodic oxide (PAO) films, charging of lithium batteries and stress-corrosion cracking (SCC). As this phenomenon is poorly understood, fundamental insight into flow from our work may provide useful information for these problems. In-situ monitoring of the stress state allows direct correlation between stress and the current or potential, thus providing fundamental insight into technologically important deformation and failure mechanisms induced by electrochemical reactions. A phase-shifting curvature interferometry was designed to investigate the stress generation mechanisms on different systems. Resolution of our curvature interferometry was found to be ten times more powerful than that obtained by state-of-art multiple deflectometry technique and the curvature interferometry helps to resolve the conflicting reports in the literature. During this work, formation of surface patterns during both aqueous corrosion of aluminum and formation of PAO films were investigated. Interestingly, for both cases, stress induced plastic flow controls the formation of surface patterns. Pore formation mechanisms during anodizing of the porous aluminum oxide films was investigated . PAO films are formed by the electrochemical oxidation of metals such as aluminum and titanium in a solution where oxide is moderately soluble. They have been used extensively to design numerous devices for optical, catalytic, and biological and energy related applications, due to their vertically aligned-geometry, high-specific surface area and tunable geometry by adjusting process variables. These structures have developed empirically, in the absence of understanding the process mechanism. Previous experimental studies of anodizing-induced stress have extensively focused on the measurement of average stress, however the measurement of stress evolution during anodizing does not provide sufficient information to understand the potential stress mechanisms. We developed a new method, which enables us to discriminate the potential stress mechanisms during anodizing and characterize the evolution of the stress profile during film growth. Using stress measurement and characterization techniques, we demonstrated the evolution of the stress profile during the film formation and discussed the role of stress on the PAO film formation. Compressive stress builds up linearly during the anodizing, while barrier oxide film gets thicker until the onset of the pore initiation. Both barrier layer thickness and the integrated oxide stress decreased rapidly to the steady-state period when pore initiation began. The morphology change and stress transients points out the transition from elastic to plastic oxide behavior, similar to those observed in other situations such as lithium intercalation into silicon. The stress profile is consistent with the stress gradient needed to drive plastic flow observed experimentally. We also addressed the dependence of overall stress generation on applied current density. Apparently, stress caused by expansion or contraction of oxide and metal interface depends on the volume change due to overall reactions. In the last chapter, the stress generation during alkaline Al corrosion will be discussed. The enhancement of mechanical degradation by corrosion is the basis for the damage process such as stress-corrosion cracking. Understanding the synergistic effect of stress on stress-corrosion cracking mechanism is necessary to design new materials to improve the safety and viability of existing energy conversion systems. the high-resolution in-situ stress measurements during Al corrosion in alkaline solution was presented, supported by characterization techniques and Fast Fourier Transform analysis. Unprecedented curvature resolution of curvature interferometry permits the monitoring of stress during extended periods of corrosion of thick metal samples. Evolution of concaved-shaped surface patterns is in a great harmony with recorded tensile stress. Furthermore, absolute value of tensile stress onset of the plasticity depends on the dissolution rate of metal and yield stress of metal. The measurements reveal corrosion-induced tensile stress generation, leading to surface plasticity. This finding is evidence that corrosion can directly bring about plasticity, and may be relevant to mechanism of corrosion-induced degradation.

The Impact of Organizational Stress and Burnout on Client Engagement

PubMed Central

Landrum, Brittany; Knight, Danica K.; Flynn, Patrick M.

2011-01-01

This paper explores the impact of organizational attributes on client engagement within substance abuse treatment. Previous research has identified organizational features, including small size, accreditation, and workplace practices that impact client engagement (Broome, Flynn, Knight, & Simpson, 2007). The current study sought to explore how aspects of the work environment impact client engagement. The sample included 89 programs located in 9 states across the U.S. Work environment measures included counselor perceptions of stress, burnout, and work satisfaction at each program, while engagement measures included client ratings of participation, counseling rapport, and treatment satisfaction. Using multiple regression, tests of moderation and mediation revealed that staff stress negatively predicted client participation in treatment. Burnout was related to stress, but was not related to participation. Two additional organizational measures – workload and influence – moderated the positive relationship between staff stress and burnout. Implications for drug treatment programs are discussed. PMID:22154029

Impact of Channel, Stress-Relaxed Buffer, and S/D Si1- x Ge x Stressor on the Performance of 7-nm FinFET CMOS Design with the Implementation of Stress Engineering

NASA Astrophysics Data System (ADS)

Othman, Nurul Aida Farhana; Hatta, Sharifah Fatmadiana Wan Muhamad; Soin, Norhayati

2018-04-01

Stress-engineered fin-shaped field effect transistors (FinFET) using germanium (Ge) is a promising performance booster to replace silicon (Si) due to its high holes mobility. This paper presents a three-dimensional simulation by the Sentaurus technology computer-aided design to study the effects of stressors—channel stress, stress-relaxed buffer (SRB), and source/drain (S/D) epitaxial stress—on different bases of FinFET, specifically silicon germanium (SiGe) and Ge-based, whereby the latter is achieved by manipulating the Ge mole fraction inside the three layers; their effects on the devices' figures-of-merits were recorded. The simulation generates an advanced calibration process, by which the drift diffusion simulation was adopted for ballistic transport effects. The results show that current enhancement in p-type FinFET (p-FinFET) with 110% is almost twice that in n-type FinFET (n-FinFET) with 57%, with increasing strain inside the channel suggesting that the use of strain is more effective for holes. In SiGe-based n-FinFET, the use of a high-strained SRB layer can improve the drive current up to 112%, while the high-strain S/D epitaxial for Ge-based p-FinFET can enhance the on-state current to 262%. Further investigations show that the channel and S/D doping are affecting the performances of SiGe-based FinFET with similar importance. It is observed that doping concentrations play an important role in threshold voltage adjustment as well as in drive current and subthreshold leakage improvements.

Current transient spectroscopy for trapping analysis on Au-free AlGaN/GaN Schottky barrier diode

NASA Astrophysics Data System (ADS)

Hu, J.; Stoffels, S.; Lenci, S.; Bakeroot, B.; Venegas, R.; Groeseneken, G.; Decoutere, S.

2015-02-01

This paper presents a combined technique of high voltage off-state stress and current transient measurements to investigate the trapping/de-trapping characteristics of Au-free AlGaN/GaN Schottky barrier diodes. The device features a symmetric three-terminal structure with a central anode contact surrounded by two separate cathodes. Under the diode off-state stress conditions, the two separate cathodes were electrically shorted. The de-trapping dynamics was studied by monitoring the recovery of the two-dimensional electron gas (2DEG) current at different temperatures by applying 0.5 V at cathode 2 while grounding cathode 1. During the recovery, the anode contact acts as a sensor of changes in diode leakage current. This leakage variation was found to be mainly due to the barrier height variation. With this method, the energy level and capture cross section of different traps in the AlGaN/GaN Schottky barrier diode can be extracted. Furthermore, the physical location of different trapping phenomena is indicated by studying the variation of the diode leakage current during the recovery. We have identified two distinct trapping mechanisms: (i) electron trapping at the AlGaN surface in the vicinity of the Schottky contact which results in the leakage reduction (barrier height ϕB increase) together with RON degradation; (ii) the electron trapping in the GaN channel layer which partially depletes the 2DEG. The physical origin of the two different traps is discussed in the text.

Distinguishing and quantifying the torquoselectivity in competitive ring-opening reactions using the stress tensor and QTAIM.

PubMed

Guo, Huan; Morales-Bayuelo, Alejandro; Xu, Tianlv; Momen, Roya; Wang, Lingling; Yang, Ping; Kirk, Steven R; Jenkins, Samantha

2016-12-05

Currently the theories to explain and predict the classification of the electronic reorganization due to the torquoselectivity of a ring-opening reaction cannot accommodate the directional character of the reaction pathway; the torquoselectivity is a type of stereoselectivity and therefore is dependent on the pathway. Therefore, in this investigation we introduced new measures from quantum theory of atoms in molecules and the stress tensor to clearly distinguish and quantify the transition states of the inward (TSIC) and outward (TSOC) conrotations of competitive ring-opening reactions of 3-(trifluoromethyl)cyclobut-1-ene and 1-cyano-1-methylcyclobutene. We find the metallicity ξ(r b ) of the ring-opening bond does not occur exactly at the transition state in agreement with transition state theory. The vector-based stress tensor response β σ was used to distinguish the effect of the CN, CH 3 , and CF 3 groups on the TSIC and TSOC paths that was consistent with the ellipticity ε, the total local energy density H(r b ) and the stress tensor stiffness S σ . We determine the directional properties of the TSIC and TSOC ring-opening reactions by constructing a stress tensor UσTS space with trajectories TσTS (s) with length l in real space, longer l correlated with the lowest density functional theory-evaluated total energy barrier and hence will be more thermodynamically favored. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Does dissociation offer a useful explanation for psychopathology?

PubMed

Jureidini, Jon

2004-01-01

Dissociation is often conceptualised as an altered state of consciousness, a trance-like state in which normal barriers between conscious and unconscious memories, desires and beliefs break down and other amnestic barriers emerge. This review explores whether it is likely that there is a neurophysiology of pathological dissociative processes that will elucidate management. A critical reading of current research, sourced through Medline and Psychinfo searches from 1990 to 2002, using subject headings: dissociative disorders, hypnosis and stress disorder (post-traumatic), as well as keywords: dissociation, hypnosis and trance. Current knowledge does not support the notion of dissociation as a discrete brain state or process. Psychiatric and neurophysiological research and theory development are better directed towards individual components that contribute to dissociative experience. Copyright (c) 2004 S. Karger AG, Basel.

Assessment of the behavior of reinforced concrete beams retrofitted with pre-stressed CFPR subjected to cyclic loading

NASA Astrophysics Data System (ADS)

Hojatkashani, Ata; Zanjani, Sara

2018-03-01

Rehabilitation of weak and damaged structures has been considered widely during recent years. A relatively modern way of strengthening concrete components is to confine parts under tension and shear by means of carbon fiber reinforce polymer (CFRP). This way of strengthening due to the conditions of composite materials such as light weight, linear elastic behavior until failure point, high tensile strength, high elastic modulus, resistance against corrosion, and high fatigue resistance has become so common. During structural strengthening by means of not pre-stressed FRP materials, usually, it is not possible to benefit from the maximum capacity of FRP materials. In addition, sometimes, the expensive cost of such materials will not make a suitable balance between rates of strengthening and consuming spending. Thus, pre-stressing CFRP materials has an undeniable role in the effective use of materials. In the current research, general procedure of simulation using finite-element method (FEM) by means of the numerical package ABAQUS has been presented. In this article, 12 reinforced concrete (RC) models in two states (strengthened with simple and pre-stressed CFRP) under cycling loading have been considered. A parametric study has been carried out in this research on the effects of parameters such as CFRP surface area, percentage of tensile steel rebar and pre-stressing stress on ultimate load carrying capacity (ULCC), stiffness, and the ability of depreciation energy for the samples. In the current article also, for design parameters, percentages of tensile steel rebars, surface area of CFPR sheets, and the effective pre-stressing stress in RC beams retrofitted with pre-stressed CFPR sheets have investigated. In this paper, it was investigated that using different amount of parameters such as steel rebar percentage, CFRP surface area percentage, and CFRP pre-stressing, the resulted ULCC and energy depreciation of the specimens was observed to be increasing and decreasing. Results from examined specimens with optimum steel rebar percentage, CFRP surface area percentage, and CFRP pre-stressing which had the most enhancement on ULCC and energy depreciation are reported in the current article.

Climate Change Impacts on Water and Energy for Army Installations

DTIC Science & Technology

2015-09-01

TR-15-24 20 Yet the effects of water and water stress go beyond the consumptive uses of the resource. Reductions in a water supply will have...analyses are based on a holistic understand- ing of the effect that water has on the MV of an installation by pairing the current view of consumption ...Clover Creek watershed does not meet State of Washington requirements for dissolved oxygen (DO), fecal coliform (FC), and temperature (WA State

Stress and Displacement Analysis of Microreactors during Thermal and Vacuum Loading

DTIC Science & Technology

2017-09-07

and extend the available energy density well beyond state-of-the-art battery technology (140 W·h/kg for rechargeable lithium [Li]- ion technology).1...time. In the 10–100 W+ power range, battery technology is the best solution currently available, but higher-energy dense technologies are needed to...augment batteries and extend the available energy density well beyond state-of-the-art battery technology. One way to approach this is to take

Low-stress mounting configuration design for large aperture laser transport mirror

NASA Astrophysics Data System (ADS)

Zhang, Zheng; Quan, Xusong; Yao, Chao; Wang, Hui

2016-10-01

TM1-6S1 large aperture laser transport mirror is a crucial optical unit of high power solid-state laser in the Inertial Confinement Fusion (ICF) facility. This article focuses on the low-stress and precise mounting method of large-aperture mirror. Based on the engineering practice of SG-III, the state-of-the-art and key problems of current mounting configuration are clarified firstly. Subsequently, a brand new low-stress mounting configuration with flexure supports is proposed. Opto-mechanical model of the mirror under mounting force is built up with elastic mechanics theory. Further, numerical methods and field tests are employed to verify the favorable load uniform capacity and load adjust capacity of flexure supports. With FEM, the relation between the mounting force from new configuration and the mirror surface distortion (wavefront error) is clarified. The novel mounting method of large aperture optics could be not only used on this laser transport mirror, but also on the other transmission optics and large crystals in ICF facilities.

Associating a prototypical forbidden food item with guilt or celebration: relationships with indicators of (un)healthy eating and the moderating role of stress and depressive symptoms.

PubMed

Kuijer, Roeline G; Boyce, Jessica A; Marshall, Emma M

2015-01-01

The increase in obesity and the many educational messages prompting us to eat a healthy diet have heightened people's concerns about the effects of food choice on health and weight. An unintended side effect may be that such awareness fuels feelings of guilt and worry about food. Although guilt has the potential to motivate behaviour change, it may also lead to feelings of helplessness and loss of control. The current study examined the relationship between a default association of either 'guilt' or 'celebration' with a prototypical forbidden food item (chocolate cake), indicators of healthy eating and choosing food for mood regulation reasons. Following a 'diathesis-stress' perspective, the moderating roles of depressive symptoms and stress were examined. Although a default association of guilt was found to be harmless under some circumstances (i.e. under low stress), those who associated chocolate cake with guilt (vs. celebration) reported unhealthier eating habits and lower levels of perceived behavioural control over healthy eating when under stress, rated mood regulation reasons for food choice as important irrespective of their current affective state, and did not have more positive attitudes towards healthy eating. Implications for public health messages and interventions will be discussed.

Release adiabat measurements on minerals: The effect of viscosity

NASA Technical Reports Server (NTRS)

Jeanloz, R.; Ahrens, T. J.

1979-01-01

The current inversion of pressure-particle velocity data for release from a high pressure shock state to a pressure-density path is analyzed. It is assumed that the release process is isentropic. It was shown that for geological materials below stresses of 150 GPa, the effective viscosity must be 1000 kg/m/s in order that the viscous (irreversible) work carried out on the material in the shock state remains small compared to the mechanical work recovered upon adiabatic rarefaction. The available data pertaining to the offset of the Rayleigh line from the Hugoniot for minerals, the magnitude of the shear stress in the high pressure shock state for minerals, and the direct measurements of the viscosities of several engineering materials shocked to pressures below 150 GPa yield effective viscosities of 1000 kg/m/s or less. An inferance that this indicates that the conditions for isentropic release of minerals from shock states are achieved, and a conclusion that the application of the Riemann integral to obtain pressure-density states along the release adiabats of minerals in shock experiments is valid are made.

Effect of OFF-state stress induced electric field on trapping in AlGaN/GaN high electron mobility transistors on Si (111)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Anand, M. J., E-mail: anand2@e.ntu.edu.sg, E-mail: eging@ntu.edu.sg; Ng, G. I., E-mail: anand2@e.ntu.edu.sg, E-mail: eging@ntu.edu.sg; Syamal, B.

2015-02-23

The influence of electric field (EF) on the dynamic ON-resistance (dyn-R{sub DS[ON]}) and threshold-voltage shift (ΔV{sub th}) of AlGaN/GaN high electron mobility transistors on Si has been investigated using pulsed current-voltage (I{sub DS}-V{sub DS}) and drain current (I{sub D}) transients. Different EF was realized with devices of different gate-drain spacing (L{sub gd}) under the same OFF-state stress. Under high-EF (L{sub gd} = 2 μm), the devices exhibited higher dyn-R{sub DS[ON]} degradation but a small ΔV{sub th} (∼120 mV). However, at low-EF (L{sub gd} = 5 μm), smaller dyn-R{sub DS[ON]} degradation but a larger ΔV{sub th} (∼380 mV) was observed. Our analysis shows that under OFF-state stress, the gatemore » electrons are injected and trapped in the AlGaN barrier by tunnelling-assisted Poole-Frenkel conduction mechanism. Under high-EF, trapping spreads towards the gate-drain access region of the AlGaN barrier causing dyn-R{sub DS[ON]} degradation, whereas under low-EF, trapping is mostly confined under the gate causing ΔV{sub th}. A trap with activation energy 0.33 eV was identified in the AlGaN barrier by I{sub D}-transient measurements. The influence of EF on trapping was also verified by Silvaco TCAD simulations.« less

The effect of pre-enrichment media on the recovery and detection of Salmonella in feed

USDA-ARS?s Scientific Manuscript database

Current methodology for detecting Salmonella in feeds and feed ingredients are adapted from food safety methods. These methods do not take into account the stressed state of Salmonella in feed, presence of competing microorganisms nor the sample matrix. The objective was to evaluate four pre-enrichm...

Stress wave sorting of red maple logs for structural quality

Treesearch

Xiping Wang; Robert J. Ross; David W. Green; Brian Brashaw; Karl Englund; Michael Wolcott

2004-01-01

Existing log grading procedures in the United States make only visual assessments of log quality. These procedures do not incorporate estimates of the modulus of elasticity (MOE) of logs. It is questionable whether the visual grading procedures currently used for logs adequately assess the potential quality of structural products manufactured from them, especially...

The New Independent Higher Education Institutions in China: Dilemmas and Challenges

ERIC Educational Resources Information Center

Zhang, Luxi; Adamson, Bob

2011-01-01

One impact of globalisation has been the expansion of higher education to meet changing current socio-economic and political requirements. This expansion places considerable stress on the public purse and many states have turned to alternative solutions. In China, a new phenomenon has emerged: independent higher education institutions that…

Seasonal dynamics and age of stemwood nonstructural carbohydrates in temperate forest trees

Treesearch

Andrew D. Richardson; Mariah S. Carbone; Trevor F. Keenan; Claudia I. Czimczik; David Y. Hollinger; Paula Murakami; Paul G. Schaberg; Xiaomei Xu

2013-01-01

Nonstructural carbohydrate reserves support tree metabolism and growth when current photosynthates are insufficient, offering resilience in times of stress. We monitored stemwood nonstructural carbohydrate (starch and sugars) concentrations of the dominant tree species at three sites in the northeastern United States. We estimated the mean age of the starch and sugars...

A More Unified View of the Multiple Personality Disorder.

ERIC Educational Resources Information Center

Kelley, Ronald L.; Kodman, Frank

1987-01-01

Offers perspective of Multiple Personality Disorder (MPD) phenomenon based on current clinical experience. Asserts that the Jmind is polypsychic with multitude of psychological systems and processes existing in conjunction with one another, that MPD individuals have fragmented or dissociated ego states due to stress on unity of sense of self, and…

Biological Mechanisms Underlying the Relationship between Stress and Smoking: State of the Science and Directions for Future Work

PubMed Central

Richards, Jessica; Stipelman, Brooke A.; Bornovalova, Marina A.; Daughters, Stacey; Sinha, Rajita; Lejuez, C.W.

2011-01-01

Theories of addiction implicate stress as a crucial mechanism underlying initiation, maintenance, and relapse to cigarette smoking. Examinations of the biological stress systems, including functioning of the hypothalamic-pituitary-adrenal (HPA) axis and the autonomic nervous system (ANS), have provided additional insights into the relationship between stress and smoking. To date, convergent data suggests that chronic cigarette smoking is associated with alterations in HPA and ANS functioning; however, less is known about the role of HPA and ANS functioning in smoking initiation and relapse following cessation. In order to organize existing findings and stimulate future research, the current paper summarizes the available literature on the roles of HPA axis and ANS functioning in the relationship between stress and cigarette smoking, highlights limitations within the existing literature, and suggests directions for future research to address unanswered questions in the extant literature on the biological mechanisms underlying the relationship between stress and smoking. PMID:21741435

The Art of Being Flexible: How to Escape from Shade, Salt, and Drought1

PubMed Central

Pierik, Ronald; Testerink, Christa

2014-01-01

Environmental stresses, such as shading of the shoot, drought, and soil salinity, threaten plant growth, yield, and survival. Plants can alleviate the impact of these stresses through various modes of phenotypic plasticity, such as shade avoidance and halotropism. Here, we review the current state of knowledge regarding the mechanisms that control plant developmental responses to shade, salt, and drought stress. We discuss plant hormones and cellular signaling pathways that control shoot branching and elongation responses to shade and root architecture modulation in response to drought and salinity. Because belowground stresses also result in aboveground changes and vice versa, we then outline how a wider palette of plant phenotypic traits is affected by the individual stresses. Consequently, we argue for a research agenda that integrates multiple plant organs, responses, and stresses. This will generate the scientific understanding needed for future crop improvement programs aiming at crops that can maintain yields under variable and suboptimal conditions. PMID:24972713

Exploring the need for interventions to manage weight and stress during interconception.

PubMed

Huberty, Jennifer; Leiferman, Jenn A; Kruper, Abbey R; Jacobson, Lisette T; Waring, Molly E; Matthews, Jeni L; Wischenka, Danielle M; Braxter, Betty; Kornfield, Sara L

2017-02-01

Interventions to manage weight and stress during the interconception period (i.e., time immediately following childbirth to subsequent pregnancy) are needed to promote optimal maternal and infant health outcomes. To address this gap, we summarize the current state of knowledge, critically evaluate the research focused on weight and stress management during the interconception period, and provide future recommendations for research in this area. Evidence supports the importance of weight and stress management during the reproductive years and the impact of weight on maternal and child health outcomes. However, evidence-based treatment models that address postpartum weight loss and manage maternal stress during the interconception period are lacking. This problem is further compounded by inconsistent definitions and measurements of stress. Recommendations for future research include interventions that address weight and stress tailored for women in the interconception period, interventions that address healthcare providers' understanding of the significance of weight and stress management during interconception, and long-term follow-up studies that focus on the public health implications of weight and stress management during interconception. Addressing obesity and stress during the interconception period via a reproductive lens will be a starting point for women and their families to live long and healthy lives.

Current limit diagrams for dendrite formation in solid-state electrolytes for Li-ion batteries

NASA Astrophysics Data System (ADS)

Raj, R.; Wolfenstine, J.

2017-03-01

We build upon the concept that nucleation of lithium dendrites at the lithium anode-solid state electrolyte interface is instigated by the higher resistance of grain boundaries that raises the local electro-chemical potential of lithium, near the lithium-electrode. This excess electro-chemo-mechanical potential, however, is reduced by the mechanical back stress generated when the dendrite is formed within the electrolyte. These parameters are coalesced into an analytical model that prescribes a specific criterion for dendrite formation. The results are presented in the form of current limit diagrams that show the "safe" and "fail" regimes for battery function. A higher conductivity of the electrolyte can reduce dendrite formation.

Initial Results from the New Stress Map of Texas Project

NASA Astrophysics Data System (ADS)

Lund Snee, J. E.; Zoback, M. D.

2015-12-01

Modern techniques for characterizing tectonic stress orientation and relative magnitude have been successfully used for more than 35 years. Nevertheless, large areas of North America lack high spatial resolution maps of stress orientation, magnitude, and faulting regime. In Texas, for example, <30 A-C-quality stress orientations are currently registered on the World Stress Map and only 7 of these points also describe the stress regime. Stress data are foundational elements of attempts to characterize tectonic driving forces, understand hazards associated with induced seismicity, and optimize production of oil, gas, and geothermal resources. This year, we launched the Texas Stress Map project to characterize tectonic stress patterns at higher spatial resolution across Texas and nearby areas. Following a successful effort just completed in Oklahoma, we will evaluate borehole breakouts, drilling-induced tensile fractures, shear wave anisotropy, and earthquake data. The principal data source will be FMI (fullbore formation microimager), UBI (ultrasonic borehole imager), cross-dipole sonic, density, and caliper logs provided by private industry. Earthquake moment tensor solutions from the U.S. Geological Survey, Saint Louis University and other sources will also be used. Our initial focus is on the Permian Basin and Barnett Shale petroleum plays due to the availability of data, but we will expand our analysis across the state as the project progresses. In addition, we hope to eventually apply the higher spatial resolution data coverage to understanding tectonic and geodynamic characteristics of the southwestern United States and northeastern Mexico. Here we present early results from our work to constrain stress orientations and faulting regime in and near Texas, and we also provide a roadmap for the ongoing research.

A state-of-the-art anisotropic rock deformation model incorporating the development of mobilised shear strength

NASA Astrophysics Data System (ADS)

Noor, M. J. Md; Jobli, A. F.

2018-04-01

Currently rock deformation is estimated using the relationship between the deformation modulus Em and the stress-strain curve. There have been many studies conducted to estimate the value of Em. This Em is basically derived from conducting unconfined compression test, UCS. However, the actual stress condition of the rock in the ground is anisotropic stress condition where the rock mass is subjected to different confining and vertical pressures. In addition, there is still no empirical or semi-empirical framework that has been developed for the prediction of rock stress-strain response under anisotropic stress condition. Arock triaxial machine GCTS Triaxial RTX-3000 has been deployed to obtain the anisotropic stress-strain relationship for weathered granite grade II from Rawang, Selangor sampled at depth of 20 m and subjected to confining pressure of 2 MPa, 7.5 MPa and 14 MPa. The developed mobilised shear strength envelope within the specimen of 50 mm diameter and 100 mm height during the application of the deviator stress is interpreted from the stress-strain curves. These mobilised shear strength envelopes at various axial strains are the intrinsic property and unique for the rock. Once this property has been established then it is being used to predict the stress-strain relationship at any confining pressure. The predicted stress-strain curves are compared against the curves obtained from the tests. A very close prediction is achieved to substantiate the applicability of this rock deformation model. This is a state-of-the art rock deformation theory which characterise the deformation base on the applied load and the developed mobilised shear strength within the rock body.

Obesity-Associated Oxidative Stress: Strategies Finalized to Improve Redox State

PubMed Central

Savini, Isabella; Catani, Maria Valeria; Evangelista, Daniela; Gasperi, Valeria; Avigliano, Luciana

2013-01-01

Obesity represents a major risk factor for a plethora of severe diseases, including diabetes, cardiovascular disease, non-alcoholic fatty liver disease, and cancer. It is often accompanied by an increased risk of mortality and, in the case of non-fatal health problems, the quality of life is impaired because of associated conditions, including sleep apnea, respiratory problems, osteoarthritis, and infertility. Recent evidence suggests that oxidative stress may be the mechanistic link between obesity and related complications. In obese patients, antioxidant defenses are lower than normal weight counterparts and their levels inversely correlate with central adiposity; obesity is also characterized by enhanced levels of reactive oxygen or nitrogen species. Inadequacy of antioxidant defenses probably relies on different factors: obese individuals may have a lower intake of antioxidant- and phytochemical-rich foods, such as fruits, vegetables, and legumes; otherwise, consumption of antioxidant nutrients is normal, but obese individuals may have an increased utilization of these molecules, likewise to that reported in diabetic patients and smokers. Also inadequate physical activity may account for a decreased antioxidant state. In this review, we describe current concepts in the meaning of obesity as a state of chronic oxidative stress and the potential interventions to improve redox balance. PMID:23698776

Cognitive reappraisal attenuates the association between depressive symptoms and emotional response to stress during adolescence.

PubMed

Shapero, Benjamin G; Stange, Jonathan P; McArthur, Brae Anne; Abramson, Lyn Y; Alloy, Lauren B

2018-04-11

Depression is associated with increased emotional response to stress. This is especially the case during the developmental period of adolescence. Cognitive reappraisal is an effective emotion regulation strategy that has been shown to reduce the impact of emotional response on psychopathology. However, less is known about whether cognitive reappraisal impacts the relationship between depressive symptoms and emotional responses, and whether its effects are specific to emotional reactivity or emotional recovery. The current study examined whether cognitive reappraisal moderated the relationship between depressive symptoms and trait or state measures of emotional reactivity and recovery. A community sample of 127 adolescents (M-age = 15.28; 49% female, 47% Caucasian), at an age of risk for depression, completed self-report measures of trait emotional responding and depressive symptoms. In addition, they completed an in vivo social stress task and were assessed on state emotional reactivity and recovery from the stressor. Findings suggested that cognitive reappraisal was associated with an attenuated impact of depressive symptoms on trait and state emotional recovery. These results provide evidence that cognitive reappraisal may be an effective strategy for improving some aspects of emotional responding in relation to depressive symptoms among adolescents.

Improvement of emotional healthcare system with stress detection from ECG signal.

PubMed

Tivatansakul, S; Ohkura, M

2015-01-01

Our emotional healthcare system is designed to cope with users' negative emotions in daily life. To make the system more intelligent, we integrated emotion recognition by facial expression to provide appropriate services based on user's current emotional state. Our emotion recognition by facial expression has confusion issue to recognize some positive, neutral and negative emotions that make the emotional healthcare system provide a relaxation service even though users don't have negative emotions. Therefore, to increase the effectiveness of the system to provide the relaxation service, we integrate stress detection from ECG signal. The stress detection might be able to address the confusion issue of emotion recognition by facial expression to provide the service. Indeed, our results show that integration of stress detection increases the effectiveness and efficiency of the emotional healthcare system to provide services.

Anesthesia and perioperative stress: consequences on neural networks and postoperative behaviors.

PubMed

Borsook, David; George, Edward; Kussman, Barry; Becerra, Lino

2010-12-01

Anesthesia is a state of drug-induced unconsciousness with suppression of sensory perception, and consists of both hypnotic and analgesic components. The anesthesiologist monitors the clinical response to noxious stimuli and adjusts drug dosage(s) to achieve an adequate depth of anesthesia, with the aim of reducing operative stress. Acute stress in the perioperative period has four major contributors: anxiety, pain, the surgical stress response, and the potential neurotoxicity of anesthetic agents. Any or all of these may act deleteriously on multiple systems in the brain and have known significant effects on brain regions such as the hippocampus and the hypothalamic-pituitary-adrenal axis. Perioperative stress on the nervous system and the resultant central nervous system (CNS) changes are likely to be causative for altered behaviors that are seen postoperatively, including chronic pain, posttraumatic stress disorder, and learning difficulties. Improving the ability of the anesthesiologist to control all four components of acute perioperative stress could potentially reduce the negative impact of surgery on the brain. Currently, there is no objective measurement for any of these stressors. The development and application of objective measures for perioperative stressors is the first step towards controlling these risk factors and eliminating or reducing their serious postoperative consequences. In this paper we review known and likely effects of perioperative stressors on brain systems and how they may play a significant role in altered postoperative behaviors. We discuss the role of current (and developing) measures of brain function and their potential for monitoring perioperative stress, with an emphasis on functional neuroimaging. Copyright © 2010 Elsevier Ltd. All rights reserved.

The evaluation of maximum horizontal in-situ stress using the wellbore imagers data

NASA Astrophysics Data System (ADS)

Dubinya, N. V.; Ezhov, K. A.

2016-12-01

Well drilling provides a number of possibilities to improve the knowledge of stress state of the upper layers of the Earth crust. The data obtained from drilling, well logging, core experiments and special tests is used to evaluate the principal stresses' directions and magnitudes. Although the values of vertical stress and minimum horizontal stress may be decently estimated, the maximum horizontal stress remains a major problem. In this study a new method to estimate this value is proposed. The suggested approach is based on the concept of hydraulically conductive and non-conductive fractures near a wellbore (Barton, Zoback and Moos, 1995). It was stated that all the fractures which properties may be acquired from well logging data can be divided into two groups regarding hydraulic conductivity. The fracture properties and the in-situ stress state are put in relationship via the Mohr diagram. This approach was later used by Ito and Zoback (2000) to estimate the magnitude of the maximum horizontal stress from the temperature profiles. In the current study ultrasonic and resistivity borehole imaging are used to estimate the magnitude of maximum horizontal stress in rather precise way. After proper interpretation one is able to obtain orientation and hydraulic conductivity for each fracture appeared at the images. If the proper profiles of vertical and minimum horizontal stresses are known all the fractures may be analyzed at the Mohr diagram. Alteration of maximum horizontal stress profile grants an opportunity to adjust it so the conductive fractures at the Mohr diagram fit the data from imagers' interpretation. The precision of the suggested approach was evaluated for several oil production wells in Siberia with decent wellbore stability models. It appeared that the difference between maximum horizontal stress estimated in a suggested approach and the values obtained from drilling reports did not exceed 0.5 MPa. Thus the proposed approach may be used to evaluate the values of maximum horizontal stress using the wellbore imagers' data. References Barton, C.A., Zoback, M.D., Moos, D. Fluid flow along potentially active faults in crystalline rock - Geology, 1995. T. Ito, M. Zoback, Fracture permeability and in situ stress to 7 km depth in the KTB Scientific Drillhole, Geophysical Research Letters, 2000.

Review of a solution-processed vertical organic transistor as a solid-state vacuum tube

NASA Astrophysics Data System (ADS)

Lin, Hung-Cheng; Zan, Hsiao-Wen; Chao, Yu-Chiang; Chang, Ming-Yu; Meng, Hsin-Fei

2015-05-01

In this paper, we investigate the key issues in raising the on/off current ratio and increasing the output current. A 1 V operated inverter composed of an enhancement-mode space-charge-limited transistor (SCLT) and a depletion-mode SCLT is demonstrated using the self-assembled monolayer modulation process. With a bulk-conduction mechanism, good bias-stress reliability, and good bending durability are obtained. Finally, key scaling-up processes, including nanoimprinting and blade-coated nanospheres, are demonstrated.

Drain Current Stress-Induced Instability in Amorphous InGaZnO Thin-Film Transistors with Different Active Layer Thicknesses

PubMed Central

Zhao, Wenjing; Li, Hua; Furuta, Mamoru

2018-01-01

In this study, the initial electrical properties, positive gate bias stress (PBS), and drain current stress (DCS)-induced instabilities of amorphous indium gallium zinc oxide (a-IGZO) thin-film transistors (TFTs) with various active layer thicknesses (TIGZO) are investigated. As the TIGZO increased, the turn-on voltage (Von) decreased, while the subthreshold swing slightly increased. Furthermore, the mobility of over 13 cm2·V−1·s−1 and the negligible hysteresis of ~0.5 V are obtained in all of the a-IGZO TFTs, regardless of the TIGZO. The PBS results exhibit that the Von shift is aggravated as the TIGZO decreases. In addition, the DCS-induced instability in the a-IGZO TFTs with various TIGZO values is revealed using current–voltage and capacitance–voltage (C–V) measurements. An anomalous hump phenomenon is only observed in the off state of the gate-to-source (Cgs) curve for all of the a-IGZO TFTs. This is due to the impact ionization that occurs near the drain side of the channel and the generated holes that flow towards the source side along the back-channel interface under the lateral electric field, which cause a lowered potential barrier near the source side. As the TIGZO value increased, the hump in the off state of the Cgs curve was gradually weakened. PMID:29621154

Cannabis craving in response to laboratory-induced social stress among racially diverse cannabis users: The impact of social anxiety disorder

PubMed Central

Buckner, Julia D; Zvolensky, Michael J; Ecker, Anthony H; Jeffries, Emily R

2016-01-01

Social anxiety disorder appears to be a risk factor for cannabis-related problems. Although it is presumed that increases in cannabis craving during elevated social anxiety reflect an intent to cope with greater negative affectivity, it is unclear whether increases in physiological arousal during social stress are related to cannabis craving, especially among those with social anxiety disorder. Similarly, no studies have assessed motivational reasons for cannabis use during elevated social stress. Thus, the current study tested whether increases in state social anxiety (measured subjectively and via physiological arousal) were related to greater cannabis craving among 126 current cannabis users (88.9% with cannabis use disorder, 31.7% with social anxiety disorder, 54.0% non-Hispanic Caucasian) randomly assigned to either a social interaction or reading task. As predicted, cannabis users in the social interaction condition reported greater cannabis craving than those in the reading condition. This effect was particularly evident among those with social anxiety disorder. Although physiological arousal did not moderate the relationship between condition and craving, coping motives were the most common reasons cited for wanting to use cannabis and were reported more among those in the social interaction task. These experimental results uniquely add to a growing literature suggesting the importance of elevated state social anxiety (especially among those with social anxiety disorder) in cannabis use vulnerability processes. PMID:26839322

Cannabis craving in response to laboratory-induced social stress among racially diverse cannabis users: The impact of social anxiety disorder.

PubMed

Buckner, Julia D; Zvolensky, Michael J; Ecker, Anthony H; Jeffries, Emily R

2016-04-01

Social anxiety disorder appears to be a risk factor for cannabis-related problems. Although it is presumed that increases in cannabis craving during elevated social anxiety reflect an intent to cope with greater negative affectivity, it is unclear whether increases in physiological arousal during social stress are related to cannabis craving, especially among those with social anxiety disorder. Similarly, no studies have assessed motivational reasons for cannabis use during elevated social stress. Thus, the current study tested whether increases in state social anxiety (measured subjectively and via physiological arousal) were related to greater cannabis craving among 126 current cannabis users (88.9% with cannabis use disorder, 31.7% with social anxiety disorder, 54.0% non-Hispanic Caucasian) randomly assigned to either a social interaction or reading task. As predicted, cannabis users in the social interaction condition reported greater cannabis craving than those in the reading condition. This effect was particularly evident among those with social anxiety disorder. Although physiological arousal did not moderate the relationship between condition and craving, coping motives were the most common reasons cited for wanting to use cannabis and were reported more among those in the social interaction task. These experimental results uniquely add to a growing literature suggesting the importance of elevated state social anxiety (especially among those with social anxiety disorder) in cannabis use vulnerability processes. © The Author(s) 2016.

Review of comparative responses of men and women to heat stress

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kenney, W.L.

Most of their present knowledge regarding human responses to thermal stress is primarily a result of research conducted on male subjects. Recently, as women have moved into the industrial workplace and forefront of athletic activity, attention has turned to comparative responses of men and women. Very limited research on preadolescent children suggests no physiological thermoregulatory sex differences except for a slightly higher sweat rate in lean boys as compared to lean girls of a similar age. Boys also tended to be more tolerant of higher temperatures. Current beliefs regarding men and women are: (1) women, as a population, are lessmore » tolerant to a given imposed heat stress however, if cardiovascular fitness level, body size, and acclimation state are standardized, the differences tend to disappear; (2) women have a lower sweat rate than men of equal fitness, size, and acclimation which is disadvantageous in hot-dry environments, but advantageous in hot-wet environments; and (3) menstrual cycle effects are minimal. It is concluded that aerobic capacity, surface area-to-mass ratio, and state of acclimation are more important than sex in determining physiological responses to heat stress.« less

Positive Holes Flowing through Stressed Igneous Rocks

NASA Astrophysics Data System (ADS)

Takeuchi, Akihiro

Igneous rocks generally involve positive hole pairs (PHPs), a kind of lattice defects also known as peroxy links: O3X-OO-YO3 with X, Y = Si4+, Al3+ etc. When a portion of such a rock block is stressed or heated, PHPs are deformed and positive holes (p-holes) are activated. They are defect electrons corresponding to the O- electronic state in the O2- sublattice and can spread away into unstressed portion. Currents and positive surface electrifications detected in laboratory stressed igneous rocks can be explained by the p-holes. When the p-holes are activated in the Earth's crust accompanied with seismic or volcanic events, they would lead to anomalous electromagnetic phenomena and could affect our electronic communication.

Gender differences in neural correlates of stress-induced anxiety.

PubMed

Seo, Dongju; Ahluwalia, Aneesha; Potenza, Marc N; Sinha, Rajita

2017-01-02

Although gender differences have been identified as a crucial factor for understanding stress-related anxiety and associated clinical disorders, the neural mechanisms underlying these differences remain unclear. To explore gender differences in the neural correlates of stress-induced anxiety, the current study used functional magnetic resonance imaging to examine brain responses in 96 healthy men and women with commensurable levels of trait anxiety as they engaged in a personalized guided imagery paradigm to provoke stress and neutral-relaxing experiences. During the task, a significant gender main effect emerged, with men displaying greater responses in the caudate, cingulate gyrus, midbrain, thalamus, and cerebellum. In contrast, women showed greater responses in the posterior insula, temporal gyrus, and occipital lobe. Additionally, a significant anxiety ratings × gender interaction from whole-brain regression analyses was observed in the dorsomedial prefrontal cortex, left inferior parietal lobe, left temporal gyrus, occipital gyrus, and cerebellum (P < 0.05, whole-brain family-wise error corrected), with positive associations between activity in these regions and stress-induced anxiety in women, but negative associations in men, indicating that men and women differentially use neural resources when experiencing stress-induced anxiety. The findings suggest that in response to stress, there is a greater use of the medial prefrontal-parietal cortices in experiencing subjective anxiety in women, while decreased use of this circuit was associated with increased subjective anxiety states in men. The current study has implications for understanding gender-specific differences in stress-induced anxiety and vulnerability to stress-related clinical disorders, and for developing more effective treatment strategies tailored to each gender. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Work Stress and Altered Biomarkers: A Synthesis of Findings Based on the Effort-Reward Imbalance Model.

PubMed

Siegrist, Johannes; Li, Jian

2017-11-10

While epidemiological studies provide statistical evidence on associations of exposures such as stressful work with elevated risks of stress-related disorders (e.g., coronary heart disease or depression), additional information on biological pathways and biomarkers underlying these associations is required. In this contribution, we summarize the current state of the art on research findings linking stressful work, in terms of an established theoretical model-effort-reward imbalance-with a broad range of biomarkers. Based on structured electronic literature search and recent available systematic reviews, our synthesis of findings indicates that associations of work stress with heart rate variability, altered blood lipids, and risk of metabolic syndrome are rather consistent and robust. Significant relationships with blood pressure, heart rate, altered immune function and inflammation, cortisol release, and haemostatic biomarkers were also observed, but due to conflicting findings additional data will be needed to reach a firm conclusion. This narrative review of empirical evidence supports the argument that the biomarkers under study can act as mediators of epidemiologically established associations of work stress, as measured by effort-reward imbalance, with incident stress-related disorders.

[German translation and validation of the Stress Appraisal Measure (SAM)].

PubMed

Delahaye, M; Stieglitz, R D; Graf, M; Keppler, C; Maes, J; Pflueger, M

2015-05-01

In the present study, the German-language version of the Stress Appraisal Measure (SAM) by Peacock and Wong was validated in a student population. SAM is a relatively short questionnaire (28 items) that evaluates a current, stress-triggering event. The theoretical background is provided by the stress model of Lazarus and Folkman. 85 students (age: 23; 59 female, 26 male) were exposed to two stress scenarios in order to test whether they were suited to provoke stress. A factor analysis was performed and the internal consistency of the seven SAM scales was determined. In addition, the convergent validity of SAM with State and Trait Anxiety Inventory (STAI), Coping Inventory for Stressful Situations (CISS) and specific emotion scales was investigated via Pearson's product-moment correlation. The two stress scenarios were suited to evoke stress. The factor structure and the internal consistency of the individual scales, as well as the convergent validity of SAM were replicated with minor limitations in the present German version. Some items (especially from the fifth factor) were only replicated partially. SAM can also be employed in the German language version. © Georg Thieme Verlag KG Stuttgart · New York.

Role stress amongst nurses at the workplace: concept analysis.

PubMed

Riahi, Sanaz

2011-09-01

The present study explicates the concept of role stress amongst nurses through an analysis adopted from Walker and Avant; Strategies for Theory Construction in Nursing, 4th edn, Prentice Hall, New Jersey, NY. Role stress has become a significant problem amongst nurses and has created much distress leading to burnout among many in the nursing profession. It is significant to analyse the concept of role stress and its relative attributes and consequences, in order to recognize the necessary antecedents needed to create better conditions for nurses at the workplace. A modified method developed by Walker and Avant was used for this concept analysis. A model representing the concept of role stress was developed through careful consideration of the attributes, consequences, antecedents and empirical referents of role stress. The concept analysis of role stress among nurses at the workplace recognized the vulnerability of the nursing discipline towards burnout and distress in general. It is critical to be aware of the current state of health care and note the increased workload created for nurses. Nurses are at a greater vulnerability for role stress, making it imperative for health care organizations to critically evaluate and establish preventative measures for the concept of role stress. 2011 Blackwell Publishing Ltd.

The redox state of endogenous pyridine nucleotides can determine both the degree of mitochondrial oxidative stress and the solute selectivity of the permeability transition pore.

PubMed

Zago, E B; Castilho, R F; Vercesi, A E

2000-07-28

Acetoacetate, an NADH oxidant, stimulated the ruthenium red-insensitive rat liver mitochondrial Ca(2+) efflux without significant release of state-4 respiration, disruption of membrane potential (Deltapsi) or mitochondrial swelling. This process is compatible with the opening of the currently designated low conductance state of the permeability transition pore (PTP) and, under our experimental conditions, was associated with a partial oxidation of the mitochondrial pyridine nucleotides. In contrast, diamide, a thiol oxidant, induced a fast mitochondrial Ca(2+) efflux associated with a release of state-4 respiration, a disruption of Deltapsi and a large amplitude mitochondrial swelling. This is compatible with the opening of the high conductance state of the PTP and was associated with extensive oxidation of pyridine nucleotides. Interestingly, the addition of carbonyl cyanide p-(trifluoromethoxy)phenylhydrazone to the acetoacetate experiment promoted a fast shift from the low to the high conductance state of the PTP. Both acetoacetate and diamide-induced mitochondrial permeabilization were inhibited by exogenous catalase. We propose that the shift from a low to a high conductance state of the PTP can be promoted by the oxidation of NADPH. This impairs the antioxidant function of the glutathione reductase/peroxidase system, strongly strengthening the state of mitochondrial oxidative stress.

Enhanced switching stability in Ta2O5 resistive RAM by fluorine doping

NASA Astrophysics Data System (ADS)

Sedghi, N.; Li, H.; Brunell, I. F.; Dawson, K.; Guo, Y.; Potter, R. J.; Gibbon, J. T.; Dhanak, V. R.; Zhang, W. D.; Zhang, J. F.; Hall, S.; Robertson, J.; Chalker, P. R.

2017-08-01

The effect of fluorine doping on the switching stability of Ta2O5 resistive random access memory devices is investigated. It shows that the dopant serves to increase the memory window and improve the stability of the resistive states due to the neutralization of oxygen vacancies. The ability to alter the current in the low resistance state with set current compliance coupled with large memory window makes multilevel cell switching more favorable. The devices have set and reset voltages of <1 V with improved stability due to the fluorine doping. Density functional modeling shows that the incorporation of fluorine dopant atoms at the two-fold O vacancy site in the oxide network removes the defect state in the mid bandgap, lowering the overall density of defects capable of forming conductive filaments. This reduces the probability of forming alternative conducting paths and hence improves the current stability in the low resistance states. The doped devices exhibit more stable resistive states in both dc and pulsed set and reset cycles. The retention failure time is estimated to be a minimum of 2 years for F-doped devices measured by temperature accelerated and stress voltage accelerated retention failure methods.

Effect of the crown design and interface lute parameters on the stress-state of a machined crown-tooth system: a finite element analysis.

PubMed

Shahrbaf, Shirin; vanNoort, Richard; Mirzakouchaki, Behnam; Ghassemieh, Elaheh; Martin, Nicolas

2013-08-01

The effect of preparation design and the physical properties of the interface lute on the restored machined ceramic crown-tooth complex are poorly understood. The aim of this work was to determine, by means of three-dimensional finite element analysis (3D FEA) the effect of the tooth preparation design and the elastic modulus of the cement on the stress state of the cemented machined ceramic crown-tooth complex. The three-dimensional structure of human premolar teeth, restored with adhesively cemented machined ceramic crowns, was digitized with a micro-CT scanner. An accurate, high resolution, digital replica model of a restored tooth was created. Two preparation designs, with different occlusal morphologies, were modeled with cements of 3 different elastic moduli. Interactive medical image processing software (mimics and professional CAD modeling software) was used to create sophisticated digital models that included the supporting structures; periodontal ligament and alveolar bone. The generated models were imported into an FEA software program (hypermesh version 10.0, Altair Engineering Inc.) with all degrees of freedom constrained at the outer surface of the supporting cortical bone of the crown-tooth complex. Five different elastic moduli values were given to the adhesive cement interface 1.8GPa, 4GPa, 8GPa, 18.3GPa and 40GPa; the four lower values are representative of currently used cementing lutes and 40GPa is set as an extreme high value. The stress distribution under simulated applied loads was determined. The preparation design demonstrated an effect on the stress state of the restored tooth system. The cement elastic modulus affected the stress state in the cement and dentin structures but not in the crown, the pulp, the periodontal ligament or the cancellous and cortical bone. The results of this study suggest that both the choice of the preparation design and the cement elastic modulus can affect the stress state within the restored crown-tooth complex. Copyright © 2013 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Early life social stress and resting state functional connectivity in postpartum rat anterior cingulate circuits.

PubMed

Nephew, Benjamin C; Febo, Marcelo; Huang, Wei; Colon-Perez, Luis M; Payne, Laurellee; Poirier, Guillaume L; Greene, Owen; King, Jean A

2018-03-15

Continued development and refinement of resting state functional connectivity (RSFC) fMRI techniques in both animal and clinical studies has enhanced our comprehension of the adverse effects of stress on psychiatric health. The objective of the current study was to assess both maternal behavior and resting state functional connectivity (RSFC) changes in these animals when they were dams caring for their own young. It was hypothesized that ECSS exposed dams would express depressed maternal care and exhibit similar (same networks), yet different specific changes in RSFC (different individual nuclei) than reported when they were adult females. We have developed an ethologically relevant transgenerational model of the role of chronic social stress (CSS) in the etiology of postpartum depression and anxiety. Initial fMRI investigation of the CSS model indicates that early life exposure to CSS (ECSS) induces long term changes in functional connectivity in adult nulliparous female F1 offspring. ECSS in F1 dams resulted in depressed maternal care specifically during early lactation, consistent with previous CSS studies, and induced changes in functional connectivity in regions associated with sensory processing, maternal and emotional responsiveness, memory, and the reward pathway, with robust changes in anterior cingulate circuits. The sample sizes for the fMRI groups were low, limiting statistical power. This behavioral and functional neuroanatomical foundation can now be used to enhance our understanding of the neural etiology of early life stress associated disorders and test preventative measures and treatments for stress related disorders. Copyright © 2018 Elsevier B.V. All rights reserved.

Structure and Prevalence of PTSD Symptomology in Children Who Have Experienced a Severe Tornado

ERIC Educational Resources Information Center

Evans, Linda Garner; Oehler-Stinnett, Judy

2006-01-01

Children served by school psychologists are frequently impacted by natural disasters. In the United States, tornadoes are a particular threat but have been studied very little. The current investigation developed a scale for assessing posttraumatic stress disorder (PTSD) in children in Kindergarten to Grade 6 impacted by a severe tornado. Six…

Extending breath analysis to the cellular level: current thoughts on the human microbiome and the expression of organic compounds in the human exposome

EPA Science Inventory

Human biomarkers are comprised of compounds from cellular metabolism, oxidative stress, and the microbiome of bacteria in the gut, genitourinary, and pulmonary tracts. When we examine patterns in human biomarkers to discern human health state or diagnose specific diseases, it is...

75 FR 11107 - Revision of Land Management Plan for the George Washington National Forest, Virginia and West...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-03-10

... additional information. Finally, this notice briefly describes the applicable planning rule and how work done..., or recorded at past public meetings, related to the revision of the GW Forest Plan since 2007 will be..., environmental stresses and threats, societal demands and our current state of scientific knowledge. Also since...

Longitudinal Associations between Maternal Work Stress, Negative Work-Family Spillover, and Depressive Symptoms

ERIC Educational Resources Information Center

Goodman, W. Benjamin; Crouter, Ann C.

2009-01-01

The current study examined associations over an 18-month period between maternal work stressors, negative work-family spillover, and depressive symptoms in a sample of 414 employed mothers with young children living in six predominantly nonmetropolitan counties in the Eastern United States. Results from a one-group mediation model showed that a…

Prolonged Exposure Therapy Following Awareness under Anesthesia: A Case Study

ERIC Educational Resources Information Center

Levinson, Cheri A.; Rodebaugh, Thomas L.; Bertelson, Amy D.

2013-01-01

Awareness during surgery is estimated to effect between 40,000 to 140,000 patients per year in the United States, and there is a growing literature suggesting that this event can lead to the development of posttraumatic stress disorder (PTSD). The current article describes treatment implemented from a manualized protocol of a woman diagnosed with…

Faculty Roles: A Primer for Students and Professionals Interested in Careers in Academia

ERIC Educational Resources Information Center

Harris, Bryn; Sullivan, Amanda L.

2012-01-01

Faculty shortage is a major concern for the field of school psychology in the United States. Graduate students are not entering the field at a rate representative of the current need (Clopton & Haselhuhn, 2009). The reasons for this are multifaceted, but some studies have pointed to perceived high levels of job stress, perceived inadequate…

Using Evaluation Research as a Means for Policy Analysis in a "New" Mission-Oriented Policy Context

ERIC Educational Resources Information Center

Amanatidou, Effie; Cunningham, Paul; Gök, Abdullah; Garefi, Ioanna

2014-01-01

Grand challenges stress the importance of multi-disciplinary research, a multi-actor approach in examining the current state of affairs and exploring possible solutions, multi-level governance and policy coordination across geographical boundaries and policy areas, and a policy environment for enabling change both in science and technology and in…

Plant-herbivore interactions in Atriplex: current state of knowledge

Treesearch

Andres F. Cibils; David M. Swift; E. Durant McArthur

1998-01-01

Atriplex is a widespread genus with species dispersed over almost all continents. Many taxa within this genus perform outstandingly under a variety of stress conditions and are often an important source of forage for herbivores. Such attributes have drawn the attention of many researchers who have conducted extensive studies on Atriplex across a wide variety of...

Increasing Women's Influence in Government and Politics: The Inclusion of Women of Color.

ERIC Educational Resources Information Center

Berry, Mary Frances

1986-01-01

Reviews the history, current status, and accomplishments of women in United States politics. Identifies opposing perspectives on such political issues as child care, abortion, and the Equal Rights Amendment, stressing the role of minority women. Concludes with strategies women of color may use to overcome the triple bind of race, sex, and economic…

Encopresis, Soiling and Constipation in Children and Adults with Developmental Disability

ERIC Educational Resources Information Center

Matson, Johnny L.; LoVullo, Santino V.

2009-01-01

Children and adults with developmental disabilities are more likely to evince encopresis, soiling and constipation than the general population. This set of related behaviors can produce a great deal of stress and can be a major restriction in independent living. This paper provides a review of the current state of knowledge on the prevalence,…

Inclusive Curriculum? Challenges to the Role of Civic Education in a Jewish and Democratic State

ERIC Educational Resources Information Center

Pinson, Halleli

2007-01-01

Against the backdrop of growing conflicts in Israeli society and concerns about its democratic character, the current curriculum guidelines and official textbook for civic education in Israel were set to offer a more inclusive civic education that would stress ideas such as pluralistic and democratic citizenship. However, this curriculum does not…

Enhancing the Developmental Appropriateness of Treatment for Depression in Youth: Integrating the Family in Treatment

PubMed Central

Tompson, Martha C.; Boger, Kathryn Dingman; Asarnow, Joan R.

2016-01-01

Youth depression is an impairing and frequently recurrent and persistent disorder that impacts current and later development, resulting in high social and economic costs. Depression and interpersonal stress are frequently transactional, with depression powerfully negatively impacting relationships and relationship stress negatively impacting the course and outcome of depression. In this context, treatment models for youth depression that emphasize interpersonal functioning, particularly family relationships, may be particularly promising. This article has three objectives. It first reviews the current state of knowledge on the efficacy of psychosocial treatments for depression in youth, with an emphasis on the role of family involvement in treatment. Second, it discusses developmental factors that may impact the applicability and structure of family-focused treatment models for preadolescent and adolescent youth. Third, two family-based treatment models that are currently being evaluated in randomized clinical trials are described: one focusing on preadolescent depressed youth and the other on adolescents who have made a recent suicide attempt. PMID:22537731

A new lifetime estimation model for a quicker LED reliability prediction

NASA Astrophysics Data System (ADS)

Hamon, B. H.; Mendizabal, L.; Feuillet, G.; Gasse, A.; Bataillou, B.

2014-09-01

LED reliability and lifetime prediction is a key point for Solid State Lighting adoption. For this purpose, one hundred and fifty LEDs have been aged for a reliability analysis. LEDs have been grouped following nine current-temperature stress conditions. Stress driving current was fixed between 350mA and 1A and ambient temperature between 85C and 120°C. Using integrating sphere and I(V) measurements, a cross study of the evolution of electrical and optical characteristics has been done. Results show two main failure mechanisms regarding lumen maintenance. The first one is the typically observed lumen depreciation and the second one is a much more quicker depreciation related to an increase of the leakage and non radiative currents. Models of the typical lumen depreciation and leakage resistance depreciation have been made using electrical and optical measurements during the aging tests. The combination of those models allows a new method toward a quicker LED lifetime prediction. These two models have been used for lifetime predictions for LEDs.

Multidimensional Profiling of Task Stress States for Human Factors: A Brief Review.

PubMed

Matthews, Gerald

2016-09-01

This article advocates multidimensional assessment of task stress in human factors and reviews the use of the Dundee Stress State Questionnaire (DSSQ) for evaluation of systems and operators. Contemporary stress research has progressed from an exclusive focus on environmental stressors to transactional perspectives on the stress process. Performance impacts of stress reflect the operator's dynamic attempts to understand and cope with task demands. Multidimensional stress assessments are necessary to gauge the different forms of system-operator interaction. This review discusses the theoretical and practical use of the DSSQ in evaluating multidimensional patterns of stress response. It presents psychometric evidence for the multidimensional perspective and illustrative profiles of subjective state response to task stressors and environments. Evidence is also presented on stress state correlations with related variables, including personality, stress process measures, psychophysiological response, and objective task performance. Evidence supports the validity of the DSSQ as a task stress measure. Studies of various simulated environments show that different tasks elicit different profiles of stress state response. Operator characteristics such as resilience predict individual differences in state response to stressors. Structural equation modeling may be used to understand performance impacts of stress states. Multidimensional assessment affords insight into the stress process in a variety of human factors contexts. Integrating subjective and psychophysiological assessment is a priority for future research. Stress state measurement contributes to evaluating system design, countermeasures to stress and fatigue, and performance vulnerabilities. It may also support personnel selection and diagnostic monitoring of operators. © 2016, Human Factors and Ergonomics Society.

Incorporating affective bias in models of human decision making

NASA Technical Reports Server (NTRS)

Nygren, Thomas E.

1991-01-01

Research on human decision making has traditionally focused on how people actually make decisions, how good their decisions are, and how their decisions can be improved. Recent research suggests that this model is inadequate. Affective as well as cognitive components drive the way information about relevant outcomes and events is perceived, integrated, and used in the decision making process. The affective components include how the individual frames outcomes as good or bad, whether the individual anticipates regret in a decision situation, the affective mood state of the individual, and the psychological stress level anticipated or experienced in the decision situation. A focus of the current work has been to propose empirical studies that will attempt to examine in more detail the relationships between the latter two critical affective influences (mood state and stress) on decision making behavior.

New Insights into the Roles of Acidocalcisomes and the Contractile Vacuole Complex in Osmoregulation in Protists

PubMed Central

Docampo, Roberto; Jimenez, Veronica; Lander, Noelia; Li, Zhu-Hong; Niyogi, Sayantanee

2013-01-01

While free-living protists are usually subjected to hyposmotic environments, parasitic protists are also in contact with hyperosmotic habitats. Recent work in one of these parasites, Trypanosoma cruzi, has revealed that its contractile vacuole complex, which usually collects and expels excess water as a mechanism of regulatory volume decrease after hyposmotic stress, has also a role in cell shrinking when the cells are submitted to hyperosmotic stress. Trypanosomes also have an acidic calcium store rich in polyphosphate (polyP), named the acidocalcisome, which is involved in their response to osmotic stress. Here, we review newly emerging insights on the role of acidocalcisomes and the contractile vacuole complex in the cellular response to hyposmotic and hyperosmotic stresses. We also review the current state of knowledge on the composition of these organelles and their other roles in calcium homeostasis and protein trafficking. PMID:23890380

New insights into roles of acidocalcisomes and contractile vacuole complex in osmoregulation in protists.

PubMed

Docampo, Roberto; Jimenez, Veronica; Lander, Noelia; Li, Zhu-Hong; Niyogi, Sayantanee

2013-01-01

While free-living protists are usually subjected to hyposmotic environments, parasitic protists are also in contact with hyperosmotic habitats. Recent work in one of these parasites, Trypanosoma cruzi, has revealed that its contractile vacuole complex, which usually collects and expels excess water as a mechanism of regulatory volume decrease after hyposmotic stress, has also a role in cell shrinking when the cells are submitted to hyperosmotic stress. Trypanosomes also have an acidic calcium store rich in polyphosphate (polyP), named the acidocalcisome, which is involved in their response to osmotic stress. Here, we review newly emerging insights on the role of acidocalcisomes and the contractile vacuole complex in the cellular response to hyposmotic and hyperosmotic stresses. We also review the current state of knowledge on the composition of these organelles and their other roles in calcium homeostasis and protein trafficking. © 2013, Elsevier Inc. All Rights Reserved.

RNA Recognition and Stress Granule Formation by TIA Proteins

PubMed Central

Waris, Saboora; Wilce, Matthew Charles James; Wilce, Jacqueline Anne

2014-01-01

Stress granule (SG) formation is a primary mechanism through which gene expression is rapidly modulated when the eukaryotic cell undergoes cellular stresses (including heat, oxidative, viral infection, starvation). In particular, the sequestration of specifically targeted translationally stalled mRNAs into SGs limits the expression of a subset of genes, but allows the expression of heatshock proteins that have a protective effect in the cell. The importance of SGs is seen in several disease states in which SG function is disrupted. Fundamental to SG formation are the T cell restricted intracellular antigen (TIA) proteins (TIA-1 and TIA-1 related protein (TIAR)), that both directly bind to target RNA and self-associate to seed the formation of SGs. Here a summary is provided of the current understanding of the way in which TIA proteins target specific mRNA, and how TIA self-association is triggered under conditions of cellular stress. PMID:25522169

[Chronic stress and epigenetics. Relation between academic sciences and theology].

PubMed

Simon, Kornél

2012-04-08

The author gives a short account on the principles of Selye's stress theory, and discusses similarities and dissimilarities of acute and chronic stress. Both the external, and the internal environment, as well as the psycho-mental status are involved in the notion of the environment. Basic principles of epigenetics are reviewed: interaction between environment and genes, neuroendocrine and enzymatic mechanisms involved in silencing and activation of genes, notions of phenotypic plasticity, and epigenetic reprogramming are discussed. Epigenetic mechanisms of interrelation between pathological clinical states (diseases) and the characteristic phenotypes, causative role of psycho-mental status in evoking pathological somatic alterations, and the potential therapeutic consequences are briefly discussed. The etiological role of chronic, civilization stress in producing the worldwide increment of cardiovascular morbidity is cited, argumentation and criticism of the current therapeutical practice is discussed. The author concludes that recent advances in epigenetic knowledge seem to solve the controversy between the academic and theological sciences.

Evaluating Options for Improving California's Drought Resilience

NASA Astrophysics Data System (ADS)

Ray, P. A.; Schwarz, A.; Wi, S.; Correa, M.; Brown, C.

2015-12-01

Through a unique collaborative arrangement, the University of Massachusetts (UMass) and the California Department of Water Resources (DWR) have together performed a baseline climate change analysis of the California state (State Water Project) and federal (Central Valley Project) water systems. The first step in the baseline analysis was development of an improved basinwide hydrologic model covering a large area of California including all major tributaries to the state and federal water systems. The CalLite modeling system used by DWR for planning purposes allowed simulation of the system of reservoirs, rivers, control points, and deliveries which are then used to create performance metrics that quantify a wide range of system characteristics including water deliveries, water quality, and environmental/ecological factors. A baseline climate stress test was conducted to identify current vulnerabilities to climate change through the linking of the modeling chain with Decision Scaling concepts through the UMass bottom-up climate stress-testing algorithm. This procedure allowed the first comprehensive climate stress analysis of the California state and federal water systems not constrained by observed historical variability and wet-dry year sequences. A forward-looking drought vulnerability and adaptation assessment of the water systems based on this workflow is ongoing and preliminary results will be presented. Presentation of results will include discussion of the collaborative arrangement between DWR and UMass, which is instrumental to both the success of the research and the education of policy makers.

The Role of Ethnicity and Acculturation in Preoperative Distress in Parents of Children Undergoing Surgery.

PubMed

Stevenson, Robert S; Rosales, Alvina; Fortier, Michelle A; Campos, Belinda; Golianu, Brenda; Zuk, Jeannie; Gold, Jeffrey; Kain, Zeev N

2017-06-01

This study examined the effects of acculturation on anxiety and stress in Latino and non-Latino white parents of children undergoing outpatient surgery. Participants included 686 parent-child dyads from four major children's hospitals in the United States. Latino parents who grew up in the U.S. reported higher levels of anxiety (p = 0.009) and stress (p < 0.001) compared to parents who grew up in a Latin American country. Additionally, English-speaking Latino parents reported higher anxiety and stress compared to both Spanish-speaking Latino and non-Latino white parents (p's < 0.05), whereas Spanish-speaking Latino and non-Latino white parents reported similar levels of stress and anxiety. Results of the current study were consistent with the immigrant health paradox in that more acculturated Latino parents reported higher levels of anxiety and stress than less acculturated Latino and non-Latino white parents, supporting the need for culturally tailored interventions in the perioperative environment.

The Role of Ethnicity and Acculturation in Preoperative Distress in Parents of Children Undergoing Surgery

PubMed Central

Stevenson, Robert S.; Rosales, Alvina; Fortier, Michelle A.; Campos, Belinda; Golianu, Brenda; Zuk, Jeannie; Gold, Jeffrey; Kain, Zeev N.

2017-01-01

Background This study examined the effects of acculturation on anxiety and stress in Latino and non-Latino-White parents of children undergoing outpatient surgery. Methods Participants included 686 parent-child dyads from four major children's hospitals in the United States. Results Latino parents who grew up in the U.S. reported higher levels of anxiety (p = 0.009) and stress (p < 0.001) compared to parents who grew up in a Latin American country. Additionally, English-speaking Latino parents reported higher anxiety and stress compared to both Spanish-speaking Latino and non-Latino White parents (p's < 0.05), whereas Spanish-speaking Latino and non-Latino White parents reported similar levels of stress and anxiety. Discussion Results of the current study were consistent with the immigrant health paradox in that more acculturated Latino parents reported higher levels of anxiety and stress than less acculturated Latino and non-Latino-White parents, supporting the need for culturally tailored interventions in the perioperative environment. PMID:26895152

Disruptions to women's social identity: a comparative study of workplace stress experienced by women in three geographic regions.

PubMed

Shaffer, M A; Joplin, J R; Bell, M P; Lau, T; Oguz, C

2000-10-01

Drawing on social identity theory (P. J. Burke, 1991) and the current status of women and equal opportunity legislation, the authors tested several factors associated with distress in working women in the People's Republic of China (PRC), Hong Kong, and the United States. Women in Hong Kong experienced significantly greater levels of life stress than PRC and U.S. women. Reports of negative attitudes toward women, gender evaluation, and avoidance coping were greater for Hong Kong and PRC women than for U.S. women. Hong Kong women reported more use of positive/confrontational coping mechanisms. Negative attitudes toward women had an important influence on life stress across regions. Moderator tests resulted in 2 significant findings: The effect of negative attitudes toward women on life stress was stronger for PRC and Hong Kong women, and the relationship between nervous/self-destructive coping and life stress was stronger for U.S. women.

Neurobiology of Chronic Stress-Related Psychiatric Disorders: Evidence from Molecular Imaging Studies

PubMed Central

Davis, Margaret T.; Holmes, Sophie E.; Pietrzak, Robert H.; Esterlis, Irina

2018-01-01

Chronic stress accounts for billions of dollars of economic loss annually in the United States alone, and is recognized as a major source of disability and mortality worldwide. Robust evidence suggests that chronic stress plays a significant role in the onset of severe and impairing psychiatric conditions, including major depressive disorder, bipolar disorder, and posttraumatic stress disorder. Application of molecular imaging techniques such as positron emission tomography and single photon emission computed tomography in recent years has begun to provide insight into the molecular mechanisms by which chronic stress confers risk for these disorders. The present paper provides a comprehensive review and synthesis of all positron emission tomography and single photon emission computed tomography imaging publications focused on the examination of molecular targets in individuals with major depressive disorder, posttraumatic stress disorder, or bipolar disorder to date. Critical discussion of discrepant findings and broad strengths and weaknesses of the current body of literature is provided. Recommended future directions for the field of molecular imaging to further elucidate the neurobiological substrates of chronic stress-related disorders are also discussed. This article is part of the inaugural issue for the journal focused on various aspects of chronic stress. PMID:29862379

Occupational stress and suicidality among firefighters: Examining the buffering role of distress tolerance.

PubMed

Stanley, Ian H; Boffa, Joseph W; Smith, Lia J; Tran, Jana K; Schmidt, N Brad; Joiner, Thomas E; Vujanovic, Anka A

2018-05-24

Past research indicates that firefighters are at increased risk for suicide. Firefighter-specific occupational stress may contribute to elevated suicidality. Among a large sample of firefighters, this study examined if occupational stress is associated with multiple indicators of suicide risk, and whether distress tolerance, the perceived and/or actual ability to endure negative emotional or physical states, attenuates these associations. A total of 831 firefighters participated (mean [SD] age = 38.37y[8.53y]; 94.5% male; 75.2% White). The Sources of Occupational Stress-14 (SOOS-14), Distress Tolerance Scale (DTS), and Suicidal Behaviors Questionnaire-Revised (SBQ-R) were utilized to examine firefighter-specific occupational stress, distress tolerance, and suicidality, respectively. Consistent with predictions, occupational stress interacted with distress tolerance, such that the effects of occupational stress on suicide risk, broadly, as well as lifetime suicide threats and current suicidal intent, specifically, were attenuated at high levels of distress tolerance. Distress tolerance may buffer the effects of occupational stress on suicidality among firefighters. Pending replication, findings suggest that distress tolerance may be a viable target for suicide prevention initiatives within the fire service. Copyright © 2018 Elsevier B.V. All rights reserved.

Occupational mental health promotion: a prevention agenda based on education and treatment. The American Psychological Association/National Institute for Occupational Safety and Health, Health Promotion Panel, 1990 Work and Well-Being Conference.

PubMed

1992-01-01

PURPOSE OF THE REVIEW. Psychological disorders are one of the 10 leading work-related diseases and injuries in the United States according to the National Institute for Occupational Safety and Health. This article addresses occupational metal health and preventive stress management in the workplace. The individual and organizational costs are briefly considered with concern for reducing the burden of suffering associated with these problems. SEARCH METHOD. As an American Psychological Association interdisciplinary panel, we searched the psychological, medical, public health, and organizational literature. We selected articles relevant to the problem of psychological disorders in the workplace and to enhancing occupational mental health and preventive stress management. IMPORTANT FINDINGS. The panel proposed a national agenda of education and treatment, combined with a program of evaluation research, for addressing these issues. Target populations are identified, and the need for collaboration among a variety of national constituencies is considered. Advancing occupational mental health and promoting skills in preventive stress management is considered in the context of comprehensive health promotion. MAJOR CONCLUSIONS. The panel concluded that there is a pressing need to: 1) set a 'gold' standard concerning the current state of knowledge in the domains of occupational mental health and stress management; 2) identify Diagnostically Related Groups (DRGs) which are stress-related; 3) establish assessment standards for stress and mental health; 4) set guidelines for reasonable interventions; and 5) establish acceptable post-outcome criteria.

Cardiovascular disease risk factors and the perception of general health among male law enforcement officers: encouraging behavioral change.

PubMed

Ramey, Sandra L

2003-05-01

The relationship among cardiovascular disease (CVD) morbidity, risk factors (including stress), and the perception of health among male law enforcement officers (LEOs) compared to men in the general population were examined in this study. Self reported prevalence of CVD and CVD risk factors among currently employed male LEOs from nine states (n = 2,818) were compared to those of other men in the same states (n = 9,650 for CVD risk factors, n = 3,147 for CVD prevalence). Perceived stress in LEOs was assessed to determine if it affected the relationship between CVD prevalence and CVD risk factors. Cross tabulated simple percentages showed CVD was less prevalent in the LEO group than among the general population. The best predictor variables for CVD were perceived stress, time in the profession, and hypertension. The LEO group had greater prevalence of hypercholesterolemia, overweight, and tobacco use than the general population. However, a greater percentage of LEOs perceived their health as "good to excellent" compared to men in the general population. Using multivariate analysis of variance (MANOVA) it was determined that perceived stress was associated with CVD in the LEO group and three CVD risk factors (i.e., cholesterol, hypertension, physical activity) were significantly affected by perceived stress. Among susceptible officers, stress may contribute to CVD development as well as potentiate several CVD risk factors. However, an apparent lack of association exists between perception of general health and CVD risk in LEOs.

Interpersonal relationship quality mediates the association between military-related posttraumatic stress and academic dysfunction among student veterans.

PubMed

Fredman, Steffany J; Marshall, Amy D; Le, Yunying; Aronson, Keith R; Perkins, Daniel F; Hayes, Jeffrey A

2018-05-03

Large numbers of United States service members and veterans are enrolling in colleges and universities. Many are experiencing posttraumatic stress symptoms secondary to their military service, and these symptoms are associated with academic dysfunction. However, little is known about the mechanism(s) through which posttraumatic stress increases risk for academic difficulties. The goal of the current study was to evaluate perceived interpersonal relationship quality as a mediator of this association. The current study investigated the indirect effect of posttraumatic stress on academic dysfunction through three indices of perceived interpersonal relationship quality (i.e., family distress, family support, and social network support) in a clinical sample of 2,120 student service members and veterans. Participants were further divided into four groups based on relationship status and gender (i.e., partnered women, nonpartnered women, partnered men, and nonpartnered men), and moderation by group was examined. For all four groups, there were significant indirect effects of posttraumatic stress on academic dysfunction through greater family distress and lower social network support. Further, the overall indirect effect of posttraumatic stress on academic dysfunction was stronger for partnered women compared with the three other groups and was attributable to the stronger path from family distress to academic dysfunction for partnered women. Poor perceived relationship quality may be a modifiable risk factor for academic dysfunction among student service members and veterans experiencing military-related posttraumatic stress. Partnered women may be especially well-suited to interventions that enhance the interpersonal context of posttraumatic stress as a way to optimize academic outcomes. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

Stress Coupling Relationship between Mantle Convection and Seismogenic Layer in Southeastern Tibetan Plateau and its Geodynamic Implications

NASA Astrophysics Data System (ADS)

Qiang, H.

2015-12-01

The lithospheric stress states and interlayer coupling interaction is of great significant in studying plate driven mechanism and seismogenic environment. The coupling relationship between mantle convection generated drag stress in the lithospheric base and seismogenic layer stress in the crust represents the lithospheric mechanical coupling intensity level. We calculate the lithospheric bottom mantle convection stress field of the southeastern Tibetan Plateau using 11~36 spherical harmonic coefficients of gravity model EGM2008. Meanwhile we collect and organize the focal mechanism of 1131 earthquakes that occurred from 2000 to now in Sichuan-Yunnan region. The current seismogenic layer stress and stress field before Lushan earthquake are calculated by the damping regional stress tensor inversion. We further analyze the correlation between the two kinds of stress fields, then discuss the relation between mechanics coupling situation and strong earthquakes in different regions. The results show that: (1) Most of Sichuan-Yunnan region is located in the coupling and decoupling intermediate zone. Coupling zones distribute on the basis of block, the eastern South China block has strong coupling, and the coupling phenomenon also exists in parts of the northern Tibet block, Balyanlkalla block in the northwest and southwest Yunnan block. The decoupling mainly occurs in Songpan-Ganzi block, connecting with the strong coupling South China block and Longmenshan fault zone is their boundary. (2) We have analyzed seismogenic mechanism, then proposed the border zone of strong and weak coupling relation between mantle convection stress and seismogenic layer stress exists high seismic risk. The current coupling situation shows that Longmenshan fault zone is still in the large varying gradient area of coupling intensity level, it has conditions to accumulate energy and develop earthquakes. Other dangerous areas are: Mingjiang, Xianshuihe, Anninghe, Zemuhe, the Red River, Nantinghe fault zone and their neighboring areas.

The Role of Sexual Abuse and Dysfunctional Attitudes in Perceived Stress and Negative Mood in Pregnant Adolescents: An Ecological Momentary Assessment Study

PubMed Central

Walsh, Kate; Basu, Archana; Monk, Catherine

2014-01-01

Study Objective Latinas have the highest rates of adolescent pregnancy in the US. Identifying means to improve the well-being among these young women is critical. The current study examined whether a history of child sexual abuse — itself a risk factor for adolescent pregnancy — was associated with more perceived stress and negative mood over the course of pregnancy and whether dysfunctional attitudes explained these associations. Design and Setting This mixed methods study involved lab-based assessments of perceived stress, sexual abuse history, and dysfunctional attitudes as well as Ecological Momentary Assessments (EMA) of mood states every 30 minutes during a 24-hour period once during each trimester of pregnancy. Participants Pregnant adolescents (n = 204, 85% Latina). Main Outcome Measures EMA mood states and lab-based retrospective self–reports of perceived stress. Results One in four pregnant adolescents had a history of sexual abuse. Sexually abused adolescents reported greater perceived stress during the first trimester relative to those without, though the groups did not differ on EMA negative mood ratings. Dysfunctional attitudes explained associations between sexual abuse and perceived stress. Sexual abuse was indirectly associated with the intercept and slope of negative mood through dysfunctional attitudes. Findings were circumscribed to sexual abuse and not other types of child abuse. Conclusions Identifying sexually abused pregnant adolescents and providing support and cognitive therapy to target dysfunctional beliefs may decrease stress during the first trimester as well as negative affect throughout pregnancy. PMID:26130137

Stress, cues, and eating behavior. Using drug addiction paradigms to understand motivation for food.

PubMed

Stojek, Monika Kardacz; Fischer, Sarah; MacKillop, James

2015-09-01

Eating patterns that lead to overconsumption of high fat, high sugar (HFHS) foods share similar features with addictive behaviors. Application of addiction paradigms, such as stress inductions, cue reactivity and behavioral economic assessments, to the study of motivation for HFHS food consumption may be a promising means of understanding food consumption. To date, few studies have investigated the interaction of stress and environmental cues on craving, and no study leveraged the state relative reinforcing value of foods (RRVfood) under varying conditions of affective states, the foci of the current study. This study used a mixed factorial design (Mood Induction: Neutral, Stress; Cues: Neutral, Food) with repeated measures on time (Baseline, Post-Mood Induction, Post-Cue Exposure). Participants (N = 133) were community adults who endorsed liking of HFHS snacks but denied eating pathology. The primary DVs were subjective craving and RRVfood. Negative and positive affect (NA, PA), the amount of food consumed, and latency to first bite were also examined. Participants in the Stress condition reported no change in craving or RRVfood. Exposure to food cues significantly increased participants' craving and RRVfood, but an interaction of stress and cues was not present. Participants did not differ on how many calories they consumed based on exposure to stress or food cues, but participants in the food cues condition had a shorter latency to the first bite of food. This study highlights the importance of environmental cues in food motivation. It also demonstrates the utility of using RRVfood to further characterize food motivation. Copyright © 2015 Elsevier Ltd. All rights reserved.

Innovative materials: the NiTi alloys in orthodontics.

PubMed

Airoldi, G; Riva, G

1996-01-01

Since ten years the NiTi alloys have gained an ever increasing place in orthodontic practice: that is due to their peculiar mechanical properties ascribed to a martensitic thermoelastic transformation which can be thermally or, in a proper temperature range, stress-induced. In the last case, when martensite is stress-induced at body temperature, the stress-strain behaviour is pseudoelastic with large deformations gained or recovered at constant stress, respectively in direct/reverse transformation: this behaviour exploited in orthodontics allowed to overcome the drawbacks intrinsic to the use of conventional alloys as stainless steel or Co-Mo alloys, where small displacements can be achieved at decreasing loads. From the phase state diagram of NiTi alloys it appears that at body temperature they are stable, but out of equilibrium: thermal treatments at intermediate temperatures can therefore modify the equilibrium state and as a consequence the transformation temperatures respect to body temperature. That allows to modify the recovery stress level according to the requirements of practice and thus disclosing new roads: the capability to foresee NiTi archwires pre-programmed in different sections, with a personalized scheme. Attention has not currently been paid to the modifications in the recovery stress induced by a temperature change inside the oral cavity. Recent results have shown that the thermal changes in the oral cavity induced by cold/hot liquid intake can considerably modify the stress level to which the dentition is exposed: though confined to the time extent connected with drinking, similar effects can be expected also for meals intake and should be taken into account for a correct procedure.

Psychosocial support services for family medicine resident physicians.

PubMed

Addison, Richard B; Riesenberg, Lee Ann; Rosenbaum, Paula

2004-02-01

The stress of residency is well documented. Some residency programs recognize the importance of addressing resident stress and provide psychosocial support services. This study assesses the current state of support services offered to family medicine residents and documents historical trends of support. All US family medicine residency programs were surveyed about program characteristics and the presence or absence of 21 psychosocial support services. The prevalence of current services was compared to that of 10 and 20 years ago. The percentage of family medicine programs offering 17 of 19 support services increased over the previous decades. However, percentages of some key services, especially those that address family life, are still quite low. Increases in services may be due to programs' desire to offer more positive and supportive educational experiences. Offering supportive and reflective opportunities may lessen stress, increase flexibility and balance, create enthusiasm for learning, encourage compassion for patients, and promote future well-being. In times of decreasing interest in family medicine, the presence of effective psychosocial support services may be important for attracting and training the best possible family physicians.

A novel method for assessing chronic cortisol concentrations in dogs using the nail as a source.

PubMed

Mack, Z; Fokidis, H B

2017-04-01

Cortisol, a glucocorticoid secreted in response to stress, is used to assess adrenal function and mental health in clinical settings. Current methods assess cortisol sources that reflect short-term secretion that can vary with current stress state. Here, we present a novel method for the extraction and quantification of cortisol from the dog nail using solid phase extraction coupled to enzyme-linked immunosorbent assay. Validation experiments demonstrated accuracy (r = 0.836, P < 0.001) precision (15.1% coefficients of variation), and repeatability (14.4% coefficients of variation) with this method. Furthermore, nail cortisol concentrations were positively correlated to an established hair cortisol method (r = 0.736, P < 0.001). Nail cortisol concentrations did not differ with dog sex, breed, age, or weights; however, sample size limitations may preclude statistical significance. Nail cortisol may provide information on cortisol secretion integrated over the time corresponding to nail growth and may be useful as a tool for diagnosing stress and adrenal disorders in dogs. Copyright © 2016 Elsevier Inc. All rights reserved.

A review of fracture mechanics life technology

NASA Technical Reports Server (NTRS)

Thomas, J. M.; Besuner, P. M.; Harris, D. O.

1985-01-01

Current lifetime prediction technology for structural components subjected to cyclic loads was reviewed. The central objectives of the project were to report the current state of and recommend future development of fracture mechanics-based analytical tools for modeling and forecasting subcritical fatigue crack growth in structures. Of special interest to NASA was the ability to apply these tools to practical engineering problems and the developmental steps necessary to bring vital technologies to this stage. A survey of published literature and numerous discussions with experts in the field of fracture mechanics life technology were conducted. One of the key points made is that fracture mechanics analyses of crack growth often involve consideration of fatigue and fracture under extreme conditions. Therefore, inaccuracies in predicting component lifetime will be dominated by inaccuracies in environment and fatigue crack growth relations, stress intensity factor solutions, and methods used to model given loads and stresses. Suggestions made for reducing these inaccuracies include: development of improved models of subcritical crack growth, research efforts aimed at better characterizing residual and assembly stresses that can be introduced during fabrication, and more widespread and uniform use of the best existing methods.

In-situ stress measurements using core-based methods in the vicinity of Nojima fault.

NASA Astrophysics Data System (ADS)

Yano, S.; Sugimoto, T.; Lin, W.; Lin, A.

2017-12-01

In the cycle of repeatable occurrence of earthquakes, stress accumulates at the source fault and its surroundings in an interseismic period until the next earthquake, and releases abruptly when the earthquake occurs. However, it is almost unknown that the quantitative relationship between stress change and earthquake occurrence. Hence, in order to improve our understanding on the mechanisms of the outbreak of earthquakes, it is important to grasp the stress states in the vicinity of the source fault and to evaluate its change over time. In this study, we carried out in-situ stress measurements by using core samples obtained from a scientific drilling penetrated through the Nojima fault which ruptured and caused the Hyogo-ken Nanbu earthquake, Japan in 1995. Our stress measurements were conducted from 2016 to 2017 when is 22 years after the earthquake. For this purpose, we applied the Anelastic Strain Recovery (ASR) method and Diametrical Core Deformation Analysis (DCDA). First, we measure the ASR change with time of the cores from stress releasing soon and calculate three-dimensional principal in-situ stress orientations and magnitudes from the ASR data. In this study, to ensure the enough amount of ASR, we conducted the measurements using the cores collected within a short time (e.g. 2.5 - 3.5 hours) after stress releasing by drilling at an on-site laboratory in the drilling site in Awaji island, Japan. The site locates at the south-west part of the Nojima fault. In DCDA, we measure the core diameters in all (360°) azimuths, and determine difference of the two horizontal principal stresses and their orientation by using the other cores as those used for ASR. DCDA experiments were conducted indoor and after a long time passed from core collecting. Lithology of all the core samples we used for ASR and DCDA are granite, and 19 and 7 cores were used for ASR and DCDA, respectively. As a result, it was found that the stress state in the depth range of 500 - 560 m and around 822 m were of normal faulting stress regime and that in 711 - 730 m was strike slip faulting type. As mentioned above, we have obtained a data set of the current state of stress around Nojima fault using the two core-based stress measurement methods. In future, we will determine the core orientations and restore the directions of the principal stress axes to the geologic coodinates.

Numerical simulation of solar coronal magnetic fields

NASA Technical Reports Server (NTRS)

Dahlburg, Russell B.; Antiochos, Spiro K.; Zang, T. A.

1990-01-01

Many aspects of solar activity are believed to be due to the stressing of the coronal magnetic field by footpoint motions at the photosphere. The results are presented of a fully spectral numerical simulation which is the first 3-D time dependent simulation of footpoint stressing in a geometry appropriate for the corona. An arcade is considered that is initially current-free and impose a smooth footpoint motion that produces a twist in the field of approx 2 pi. The footprints were fixed and the evolution was followed until the field relaxes to another current-free state. No evidence was seen for any instability, either ideal or resistive and no evidence for current sheet formation. The most striking feature of the evolution is that in response to photospheric motions, the field expands rapidly upward to minimize the stress. The expansion has two important effects. First, it suppresses the development of dips in the field that could support dense, cool material. For the motions assumed, the magnetic field does not develop a geometry suitable for prominence formation. Second, the expansion inhibits ideal instabilities such as kinking. The results indicate that simple stearing of a single arcade is unlikely to lead to solar activity such as flares or prominences. Effects are discussed that might possibly lead to such activity.

Forecasting Induced Seismicity Using Saltwater Disposal Data and a Hydromechanical Earthquake Nucleation Model

NASA Astrophysics Data System (ADS)

Norbeck, J. H.; Rubinstein, J. L.

2017-12-01

The earthquake activity in Oklahoma and Kansas that began in 2008 reflects the most widespread instance of induced seismicity observed to date. In this work, we demonstrate that the basement fault stressing conditions that drive seismicity rate evolution are related directly to the operational history of 958 saltwater disposal wells completed in the Arbuckle aquifer. We developed a fluid pressurization model based on the assumption that pressure changes are dominated by reservoir compressibility effects. Using injection well data, we established a detailed description of the temporal and spatial variability in stressing conditions over the 21.5-year period from January 1995 through June 2017. With this stressing history, we applied a numerical model based on rate-and-state friction theory to generate seismicity rate forecasts across a broad range of spatial scales. The model replicated the onset of seismicity, the timing of the peak seismicity rate, and the reduction in seismicity following decreased disposal activity. The behavior of the induced earthquake sequence was consistent with the prediction from rate-and-state theory that the system evolves toward a steady seismicity rate depending on the ratio between the current and background stressing rates. Seismicity rate transients occurred over characteristic timescales inversely proportional to stressing rate. We found that our hydromechanical earthquake rate model outperformed observational and empirical forecast models for one-year forecast durations over the period 2008 through 2016.

Constitutive relations describing creep deformation for multi-axial time-dependent stress states

NASA Astrophysics Data System (ADS)

McCartney, L. N.

1981-02-01

A THEORY of primary and secondary creep deformation in metals is presented, which is based upon the concept of tensor internal state variables and the principles of continuum mechanics and thermodynamics. The theory is able to account for both multi-axial and time-dependent stress and strain states. The wellknown concepts of elastic, anelastic and plastic strains follow naturally from the theory. Homogeneous stress states are considered in detail and a simplified theory is derived by linearizing with respect to the internal state variables. It is demonstrated that the model can be developed in such a way that multi-axial constant-stress creep data can be presented as a single relationship between an equivalent stress and an equivalent strain. It is shown how the theory may be used to describe the multi-axial deformation of metals which are subjected to constant stress states. The multi-axial strain response to a general cyclic stress state is calculated. For uni-axial stress states, square-wave loading and a thermal fatigue stress cycle are analysed.

On the state of lithospheric stress in the absence of applied tectonic forces

USGS Publications Warehouse

McGarr, A.

1988-01-01

Numerous published analyses of the nontectonic state of stress are based on Hooke's law and the boundary condition of zero horizontal deformation. This approach has been used to determine the gravitational stress state as well as the effects of processes such as erosion and temperature changes on the state of lithospheric stress. The major disadvantage of these analyses involves the assumption of lateral constraint which seems unrealistic in view of the observational fact that the crust can deform horizontally in response to applied loads. If the same problems are addressed by assuming that the remote stress state is constant, instead of the condition of zero horizontal deformation, then the resulting stress states are entirely different and in good accord with observations. The processes of erosion and sedimentation have slight tendencies to increase and decrease, respectively, the state of deviatoric stress. Temperature changes have only minor effects on the stress state, as averaged over the thickness of the lithosphere. -from Author

Reactive Oxygen Species-Mediated Cellular Stress Response and Lipid Accumulation in Oleaginous Microorganisms: The State of the Art and Future Perspectives

PubMed Central

Shi, Kun; Gao, Zhen; Shi, Tian-Qiong; Song, Ping; Ren, Lu-Jing; Huang, He; Ji, Xiao-Jun

2017-01-01

Microbial oils, which are mainly extracted from yeasts, molds, and algae, have been of considerable interest as food additives and biofuel resources due to their high lipid content. While these oleaginous microorganisms generally produce only small amounts of lipids under optimal growth conditions, their lipid accumulation machinery can be induced by environmental stresses, such as nutrient limitation and an inhospitable physical environmental. As common second messengers of many stress factors, reactive oxygen species (ROS) may act as a regulator of cellular responses to extracellular environmental signaling. Furthermore, increasing evidence indicates that ROS may act as a mediator of lipid accumulation, which is associated with dramatic changes in the transcriptome, proteome, and metabolome. However, the specific mechanisms of ROS involvement in the crosstalk between extracellular stress signaling and intracellular lipid synthesis require further investigation. Here, we summarize current knowledge on stress-induced lipid biosynthesis and the putative role of ROS in the control of lipid accumulation in oleaginous microorganisms. Understanding such links may provide guidance for the development of stress-based strategies to enhance microbial lipid production. PMID:28507542

The relationship between exposure to dementia-related aggressive behavior and occupational stress among Japanese care workers.

PubMed

Hirata, Hiromi; Harvath, Theresa A

2015-04-01

Aggressive behaviors (ABs) related to dementia in older adults have been associated with increased occupational stress among care workers (CWs) in the United States and other Western countries, and they may contribute to staff turnover. However, few studies related to this issue have been conducted in Japan. The current cross-sectional study examined (a) the relationship between CW frequency of exposure to dementia-related ABs and CW occupational stress (i.e., job burnout, job satisfaction, and intention to resign), and (b) mediator effects between frequency of exposure to dementia-related ABs and CW occupational stress. A total of 137 CWs in dementia special care units from 10 nursing homes in Japan were recruited as study participants. Major findings indicate that the relationship between exposure to ABs and work outcomes was fully mediated by the appraisal of stress. Findings from this study may be used to develop culturally relevant training and educational interventions targeted at reducing ABs in individuals with dementia and occupational stress from exposure to ABs among CWs. Copyright 2015, SLACK Incorporated.

Redox-induced surface stress of polypyrrole-based actuators.

PubMed

Tabard-Cossa, Vincent; Godin, Michel; Grütter, Peter; Burgess, Ian; Lennox, R B

2005-09-22

We measure the surface stress induced by electrochemical transformations of a thin conducting polymer film. One side of a micromechanical cantilever-based sensor is covered with an electropolymerized dodecyl benzenesulfonate-doped polypyrrole (PPyDBS) film. The microcantilever serves as both the working electrode (in a conventional three-electrode cell configuration) and as the mechanical transducer for simultaneous, in situ, and real-time measurements of the current and interfacial stress changes. A compressive change in surface stress of about -2 N/m is observed when the conducting polymer is electrochemically switched between its oxidized (PPy+) and neutral (PPy0) state by cyclic voltammetry. The surface stress sensor's response during the anomalous first reductive scan is examined. The effect of long-term cycling on the mechanical transformation ability of PPy(DBS) films in both surfactant and halide-based electrolytes is also discussed. We have identified two main competing origins of surface stress acting on the PPy(DBS)/ gold-coated microcantilever: one purely mechanical due to the volume change of the conducting polymer, and a second charge-induced, owing to the interaction of anions of the supporting electrolyte with the gold surface.

Wigner's quantum phase-space current in weakly-anharmonic weakly-excited two-state systems

NASA Astrophysics Data System (ADS)

Kakofengitis, Dimitris; Steuernagel, Ole

2017-09-01

There are no phase-space trajectories for anharmonic quantum systems, but Wigner's phase-space representation of quantum mechanics features Wigner current J . This current reveals fine details of quantum dynamics —finer than is ordinarily thought accessible according to quantum folklore invoking Heisenberg's uncertainty principle. Here, we focus on the simplest, most intuitive, and analytically accessible aspects of J. We investigate features of J for bound states of time-reversible, weakly-anharmonic one-dimensional quantum-mechanical systems which are weakly-excited. We establish that weakly-anharmonic potentials can be grouped into three distinct classes: hard, soft, and odd potentials. We stress connections between each other and the harmonic case. We show that their Wigner current fieldline patterns can be characterised by J's discrete stagnation points, how these arise and how a quantum system's dynamics is constrained by the stagnation points' topological charge conservation. We additionally show that quantum dynamics in phase space, in the case of vanishing Planck constant ℏ or vanishing anharmonicity, does not pointwise converge to classical dynamics.

Effect of Mechanical Stresses on Characteristics of Chip Tantalum Capacitors

NASA Technical Reports Server (NTRS)

Teverovsky, Alexander A.

2007-01-01

The effect of compressive mechanical stresses on chip solid tantalum capacitors is investigated by monitoring characteristics of different part types under axial and hydrostatic stresses. Depending on part types, an exponential increase of leakage currents was observed when stresses exceeded 10 MPa to 40 MPa. For the first time, reversible variations of leakage currents (up to two orders of magnitude) with stress have been demonstrated. Mechanical stresses did not cause significant changes of AC characteristics of the capacitors, whereas breakdown voltages measured during the surge current testing decreased substantially indicating an increased probability of failures of stressed capacitors in low impedance applications. Variations of leakage currents are explained by a combination of two mechanisms: stress-induced scintillations and stress-induced generation of electron traps in the tantalum pentoxide dielectric.

Building a Global Civic Culture. Education for an Interdependent World. The John Dewey Lecture.

ERIC Educational Resources Information Center

Boulding, Elise

Exploring ways in which a successful worldwide civic culture can be achieved, this book stresses the need to stay rooted in local communities and traditions while cooperating with and respecting those whose lives follow other patterns. The first part of the book deals with the current state of worldwide civic culture, setting a context within…

The p53/p21(WAF/CIP) pathway mediates oxidative stress and senescence in dyskeratosis congenita cells with telomerase insufficiency.

PubMed

Westin, Erik R; Aykin-Burns, Nukhet; Buckingham, Erin M; Spitz, Douglas R; Goldman, Frederick D; Klingelhutz, Aloysius J

2011-03-15

Telomere attrition is a natural process that occurs due to inadequate telomere maintenance. Once at a critically short threshold, telomeres signal growth arrest, leading to senescence. Telomeres can be elongated by the enzyme telomerase, which adds de novo telomere repeats to the ends of chromosomes. Mutations in genes for telomere binding proteins or components of telomerase give rise to the premature aging disorder dyskeratosis congenita (DC), which is characterized by extremely short telomeres and an aging phenotype. The current study demonstrates that DC cells signal a DNA damage response through p53 and its downstream mediator, p21(WAF/CIP), which is accompanied by an elevation in steady-state levels of superoxide and percent glutathione disulfide, both indicators of oxidative stress. Poor proliferation of DC cells can be partially overcome by reducing O(2) tension from 21% to 4%. Further, restoring telomerase activity or inhibiting p53 or p21(WAF/CIP) significantly mitigated growth inhibition as well as caused a significant decrease in steady-state levels of superoxide. Our results support a model in which telomerase insufficiency in DC leads to p21(WAF/CIP) signaling, via p53, to cause increased steady-state levels of superoxide, metabolic oxidative stress, and senescence.

Microstructural evaluation of cumulative fatigue damage in a plant component sample

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fukuoka, C.; Nakagawa, Y.G.; Yoshida, K.

1996-12-31

Fatigue damage accumulated in a real plant was evaluated in terms of microstructural conditioning. Microstructural damage induced in laboratory by cyclic deformation near and below the fatigue limit was also examined. A Transmission Electron Microscopy (TEM) technique called the Selected Area Diffraction (SAD) method was employed in this study. In earlier studies, it was found that the SAD value indicating a magnitude of crystallographic misorientation in the substructure (dislocation cells) was increasing with the increase of fatigue damage accumulation. Small samples removed from PWR feed water nozzle welds were examined by the SAD. It was found that the damage statemore » measured by the SAD well agreed with the morphological evidence. Cyclic stresses near or below the fatigue limit were applied to samples taken from a SA508 steel plate at various stresses. The SAD value increased even below the fatigue limit, but there was no sign of microstructural conditioning below the stresses of 50% of the fatigue limit. These results suggested that at stresses below the current design curve (below half the fatigue limit) no microstructural conditioning proceeded. It was concluded that the microstructural method was effective to evaluate damage accumulation in real plant components, and also that the current design curve was adequate in terms of microstructural conditioning state.« less

Differentiating anticipatory from reactive cortisol responses to psychosocial stress.

PubMed

Engert, Veronika; Efanov, Simona I; Duchesne, Annie; Vogel, Susanne; Corbo, Vincent; Pruessner, Jens C

2013-08-01

Most psychosocial stress studies assess the overall cortisol response without further identifying the temporal dynamics within hormone levels. It has been shown, however, that the amplitude of anticipatory cortisol stress levels has a unique predictive value for psychological health. So far, no "best practice" in how to investigate the anticipatory cortisol stress response has emerged. The goal of the current research was to develop a protocol that would allow for a sensitive and easy-to-implement laboratory-based investigation into anticipatory cortisol stress levels. We initially tested 26 healthy men in either an anticipation- or stress-only condition of the Trier Social Stress Test (TSST) to map the distinct timelines of anticipatory and reactive cortisol release profiles (study 1). Subsequently, we administered the TSST to 50 healthy men such that the cortisol responses to anticipatory and reactive stress components could be dissociated (study 2). In both studies we sampled saliva cortisol at high frequency (at baseline, during 10min of anticipation and during and after 10min of acute stress) and the current mood state pre- and post-stress. We found anticipatory responder rates of 20% and 40%, with peak anticipatory cortisol levels between 14 and 20min after onset of anticipation. Visible changes in reactive cortisol levels occurred only after the termination of the acute stressor. We conclude that the best practice to detect a maximum number of anticipatory responders in the TSST would be to extend the anticipation phase to 15min. In doing so, the anticipatory cortisol peak could be captured at a time-point of the actual stressor that is uninfluenced by reactive cortisol levels. Overall, we could reveal several features of anticipatory responders. Most importantly, there was a positive correlation between anticipatory and reactive stress responses. There was no association between anticipatory cortisol and alpha-amylase as well as subjective-psychological stress responses. Future studies will have to determine whether the anticipatory responders differ with respect to various stress-sensitive parameters like sex, personality, psychological wellbeing or chronic stress. Copyright © 2012 Elsevier Ltd. All rights reserved.

Psychosocial treatments for schizophrenia.

PubMed

Mueser, Kim T; Deavers, Frances; Penn, David L; Cassisi, Jeffrey E

2013-01-01

The current state of the literature regarding psychosocial treatments for schizophrenia is reviewed within the frameworks of the recovery model of mental health and the expanded stress-vulnerability model. Interventions targeting specific domains of functioning, age groups, stages of illness, and human service system gaps are classified as evidence-based practices or promising practices according to the extent to which their efficacy is currently supported by meta-analyses and individual randomized controlled trials (RCTs). Evidence-based practices include assertive community treatment (ACT), cognitive behavior therapy (CBT) for psychosis, cognitive remediation, family psychoeducation, illness self-management training, social skills training, and supported employment. Promising practices include cognitive adaptive therapy, CBT for posttraumatic stress disorder, first-episode psychosis intervention, healthy lifestyle interventions, integrated treatment for co-occurring disorders, interventions targeting older individuals, peer support services, physical disease management, prodromal stage intervention, social cognition training, supported education, and supported housing. Implications and future directions are discussed.

The Resistome: A Comprehensive Database of Escherichia coli Resistance Phenotypes.

PubMed

Winkler, James D; Halweg-Edwards, Andrea L; Erickson, Keesha E; Choudhury, Alaksh; Pines, Gur; Gill, Ryan T

2016-12-16

The microbial ability to resist stressful environmental conditions and chemical inhibitors is of great industrial and medical interest. Much of the data related to mutation-based stress resistance, however, is scattered through the academic literature, making it difficult to apply systematic analyses to this wealth of information. To address this issue, we introduce the Resistome database: a literature-curated collection of Escherichia coli genotypes-phenotypes containing over 5,000 mutants that resist hundreds of compounds and environmental conditions. We use the Resistome to understand our current state of knowledge regarding resistance and to detect potential synergy or antagonism between resistance phenotypes. Our data set represents one of the most comprehensive collections of genomic data related to resistance currently available. Future development will focus on the construction of a combined genomic-transcriptomic-proteomic framework for understanding E. coli's resistance biology. The Resistome can be downloaded at https://bitbucket.org/jdwinkler/resistome_release/overview .

Protection for medication-induced hearing loss: the state of the science.

PubMed

Hammill, Tanisha L; Campbell, Kathleen C

2018-04-24

This review will summarise the current state of development of pharmaceutical interventions (prevention or treatment) for medication-induced ototoxicity. Currently published literature was reviewed using PubMed and ClinicalTrials.gov to summarise the current state of the science. Details on the stage of development in the market pipeline are provided, along with evidence for clinical safety and efficacy reported. This review includes reports from 44 articles and clinical trial reports regarding agents in clinical or preclinical trials, having reached approved Investigational New Drug status with the Federal Drug Administration. Vitamins and antioxidants are the most common agents currently evaluated for drug-induced ototoxicity intervention by targeting the oxidative stress pathway that leads to cochlear cell death and hearing loss. However, other strategies, including steroid treatment and reduction of ototoxic properties of the primary drugs, are discussed. Retention of hearing during and after a life threatening illness is a major quality-of-life issue for patients receiving ototoxic drugs and their families. The agents discussed herein, while not mature enough at this point, offer great promise towards that goal. This review will provide a knowledge base for hearing providers to inquiries about such options from patients and interdisciplinary care teams alike.

Evaluation of the Frequencies for Canister Inspections for SCC

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stockman, Christine; Bryan, Charles R.

2016-02-02

This report fulfills the M3 milestone M3FT-15SN0802042, “Evaluate the Frequencies for Canister Inspections for SCC” under Work Package FT-15SN080204, “ST Field Demonstration Support – SNL”. It reviews the current state of knowledge on the potential for stress corrosion cracking (SCC) of dry storage canisters and evaluates the implications of this state of knowledge on the establishment of an SCC inspection frequency. Models for the prediction of SCC by the Japanese Central Research Institute of Electric Power Industry (CRIEPI), the United States (U.S.) Electric Power Research Institute (EPRI), and Sandia National Laboratories (SNL) are summarized, and their limitations discussed.

A Case Study on Engineering Failure Analysis of Link Chain

PubMed Central

Lee, Seong-Beom; Lee, Hong-Chul

2010-01-01

Objectives The objective of this study was to investigate the effect of chain installation condition on stress distribution that could eventually cause disastrous failure from sudden deformation and geometric rupture. Methods Fractographic method used for the failed chain indicates that over-stress was considered as the root cause of failure. 3D modeling and finite element analysis for the chain, used in a crane hook, were performed with a three-dimensional interactive application program, CATIA, commercial finite element analysis and computational fluid dynamic software, ANSYS. Results The results showed that the state of stress was changed depending on the initial position of the chain that was installed in the hook. Especially, the magnitude of the stress was strongly affected by the bending forces, which are 2.5 times greater (under the simulation condition currently investigated) than that from the plain tensile load. Also, it was noted that the change of load state is strongly related to the failure of parts. The chain can hold an ultimate load of about 8 tons with only the tensile load acting on it. Conclusion The conclusions of this research clearly showed that a reduction of the loss from similar incidents can be achieved when an operator properly handles the installation of the chain. PMID:22953162

Sources of Water to Wells for Transient Cyclic Systems

USGS Publications Warehouse

Reilly, T.E.; Pollock, D.W.

1996-01-01

Many state agencies are currently (1995) developing wellhead protection programs. The thrust of some of these programs is to protect water supplies by determining the areas contributing recharge to water-supply wells and by specifying regulations to minimize the opportunity for contamination of the recharge water by activities at the land surface. The area contributing recharge to a discharging well is the surface area at the water table through which the water flowing to the well entered the ground-water system. In the analyses of ground-water flow systems, steady-state average conditions are commonly used to simplify the problem and make a solution tractable. However, recharge is usually cyclic in nature, with seasonal cycles and longer term climatic cycles. The effect of these cyclic stresses on the area contributing recharge to wells is quantitatively analyzed for a hypothetical alluvial valley aquifer system that is representative of a large class of ground-water systems that are extensively developed for water supply. The analysis shows that, in many cases, these cyclic changes in the recharge rates do not significantly affect the location and size of the areas contributing recharge to wells. The ratio of the mean travel time to the length of the cyclic stress period appears to be an indicator of whether the transient effects of the cyclic stress must be explicitly represented in the analysis of contributing areas to wells. For the cases examined, if the ratio of the mean travel time to the period of the cyclic stress was much greater than one, then the transient area contributing recharge to wells was similar to the area calculated using an average steady-state condition. However, cyclic stresses on systems with ratios less than one do have an effect on the location and size of the areas contributing recharge to wells.

The Influence of State Anxiety on Fear Discrimination and Extinction in Females

PubMed Central

Dibbets, Pauline; Evers, Elisabeth A. T.

2017-01-01

Formal theories have linked pathological anxiety to a failure in fear response inhibition. Previously, we showed that aberrant response inhibition is not restricted to anxiety patients, but can also be observed in anxiety-prone adults. However, less is known about the influence of currently experienced levels of anxiety on inhibitory learning. The topic is highly important as state anxiety has a debilitating effect on cognition, emotion, and physiology and is linked to several anxiety disorders. In the present study, healthy female volunteers performed a fear conditioning task, after being informed that they will have to perform the Trier Social Stress Test task (n = 25; experimental group) or a control task (n = 25; control group) upon completion of the conditioning task. The results showed that higher levels of state anxiety corresponded with a reduced discrimination between a stimulus (CS+) typically followed by an aversive event and a stimulus (CS-) that is never followed by an aversive event both during the acquisition and the extinction phase. No effect of state anxiety on the skin conductance response associated with CS+ and CS- was found. Additionally, higher levels of state anxiety coincided with more negative valence ratings of the CSs. The results suggest that increased stress-induced state anxiety might lead to stimulus generalization during fear acquisition, thereby impairing associative learning. PMID:28360869

[Study on the relationship between occupational stress and psychological health state among oil workers].

PubMed

Liu, Jiwen; Wang, Zhiming; Wang, Mianzhen; Lan, Yajia; Zhan, Chenglie; Zhao, Xiaoguo

2002-02-01

To study the relationship between occupational stress and psychological health state among oil workers. 1,230 oil workers in 122 work types of oil industry were selected and written occupational stress questionary(OSQ) and symptom check list (SCL-90). Petroleum workers' psychological health states were poor with increasing occupational stress degree. The scores in physical symptoms(1.87 +/- 0.80, 1.72 +/- 0.70), depression(1.74 +/- 0.76, 1.62 +/- 0.67), horror(1.48 +/- 0.65, 1.39 +/- 0.55) in the high and medium stress group were obviously higher than those in low stress group(1.55 +/- 0.61, 1.43 +/- 0.54, 1.28 +/- 0.46, respectively, P < 0.05). The score of mood state in the high and medium stress group was obviously higher than that in low stress group(P < 0.05). Psychological health states and mood state in the petroleum workers with short service length are significantly poorer than that with long service length(P < 0.01). Occupational stress should affect psychological health state of petroleum workers.

Work Stress and Altered Biomarkers: A Synthesis of Findings Based on the Effort–Reward Imbalance Model

PubMed Central

Siegrist, Johannes; Li, Jian

2017-01-01

While epidemiological studies provide statistical evidence on associations of exposures such as stressful work with elevated risks of stress-related disorders (e.g., coronary heart disease or depression), additional information on biological pathways and biomarkers underlying these associations is required. In this contribution, we summarize the current state of the art on research findings linking stressful work, in terms of an established theoretical model—effort-reward imbalance—with a broad range of biomarkers. Based on structured electronic literature search and recent available systematic reviews, our synthesis of findings indicates that associations of work stress with heart rate variability, altered blood lipids, and risk of metabolic syndrome are rather consistent and robust. Significant relationships with blood pressure, heart rate, altered immune function and inflammation, cortisol release, and haemostatic biomarkers were also observed, but due to conflicting findings additional data will be needed to reach a firm conclusion. This narrative review of empirical evidence supports the argument that the biomarkers under study can act as mediators of epidemiologically established associations of work stress, as measured by effort–reward imbalance, with incident stress-related disorders. PMID:29125555

Etiology and clinical course of pseudoseizures. Relationship to trauma, depression, and dissociation.

PubMed

Bowman, E S

1993-01-01

Twenty-seven outpatients with video-EEG-documented pseudoseizures were interviewed by a psychiatrist to determine the historical course of seizures and diagnose the current presence of these DSM-III-R diagnoses: affective disorders (85%), dissociative disorders (85%), and posttraumatic stress disorder (33%). Their mean (26.7) and median (26.9) Dissociative Experiences Scale scores were elevated. Eighty-eight percent of subjects had sustained significant trauma, including sexual abuse/rape (77%) and physical abuse (70%). Four psychodynamic pathways to pseudoseizures were noted. Most commonly, pseudoseizures originated from dissociated personalities or ego states, were expressions of dissociated memories of child abuse, and were triggered by recent stresses or traumas.

Stress spillover in early marriage: the role of self-regulatory depletion.

PubMed

Buck, April A; Neff, Lisa A

2012-10-01

Stressful experiences external to a marriage (e.g., work stress, finances) are often associated with poor relationship functioning and lowered marital satisfaction, a phenomenon called stress spillover. To date, however, little attention has been devoted to understanding the specific mechanisms through which stress may lead to maladaptive relationship patterns. Drawing from theories of self-regulatory depletion, it was predicted that coping with external stress is an effortful process that consumes spouses' regulatory resources, leaving spouses with less energy to effectively respond to their relationship issues. The current study relied on a sample of newly married couples to examine whether self-regulatory depletion may account for the link between external stress and relationship well-being. Couples were asked to complete a 14-day daily diary that assessed their daily stress, their state of self-regulatory depletion, their marital behaviors, and their daily marital appraisals. Within-person analyses revealed that, on average, couples experienced stress spillover, such that on days when their stress was higher than usual they reported enacting more negative behaviors toward their partner and endorsed less positive appraisals of the relationship. Further analyses confirmed that self-regulatory depletion accounted for a majority of these spillover effects. These findings suggest that even happy couples may find it difficult to engage in adaptive relationship processes under conditions of stress. (PsycINFO Database Record (c) 2012 APA, all rights reserved).

An analysis of fiber-matrix interface failure stresses for a range of ply stress states

NASA Technical Reports Server (NTRS)

Crews, J. H.; Naik, R. A.; Lubowinski, S. J.

1993-01-01

A graphite/bismaleimide laminate was prepared without the usual fiber treatment and was tested over a wide range of stress states to measure its ply cracking strength. These tests were conducted using off-axis flexure specimens and produced fiber-matrix interface failure data over a correspondingly wide range of interface stress states. The absence of fiber treatment, weakened the fiber-matrix interfaces and allowed these tests to be conducted at load levels that did not yield the matrix. An elastic micromechanics computer code was used to calculate the fiber-matrix interface stresses at failure. Two different fiber-array models (square and diamond) were used in these calculations to analyze the effects of fiber arrangement as well as stress state on the critical interface stresses at failure. This study showed that both fiber-array models were needed to analyze interface stresses over the range of stress states. A linear equation provided a close fit to these critical stress combinations and, thereby, provided a fiber-matrix interface failure criterion. These results suggest that prediction procedures for laminate ply cracking can be based on micromechanics stress analyses and appropriate fiber-matrix interface failure criteria. However, typical structural laminates may require elastoplastic stress analysis procedures that account for matrix yielding, especially for shear-dominated ply stress states.

Determination of the lead-acid battery's dynamic response using Butler-Volmer equation for advanced battery management systems in automotive applications

NASA Astrophysics Data System (ADS)

Piłatowicz, Grzegorz; Budde-Meiwes, Heide; Kowal, Julia; Sarfert, Christel; Schoch, Eberhard; Königsmann, Martin; Sauer, Dirk Uwe

2016-11-01

Micro-hybrid vehicles (μH) are currently starting to dominate the European market and seize constantly growing share of other leading markets in the world. On the one hand, the additional functionality of μH reduces the CO2 emissions and improves the fuel economy, but, on the other hand, the additional stress imposed on the lead-acid battery reduces significantly its expected service life in comparison to conventional vehicles. Because of that μH require highly accurate battery state detection solutions. They are necessary to ensure the vehicle reliability requirements, prolong service life and reduce warranty costs. This paper presents an electrical model based on Butler-Volmer equation. The main novelty of the presented approach is its ability to predict accurately dynamic response of a battery considering a wide range of discharge current rates, state-of-charges and temperatures. Presented approach is fully implementable and adaptable in state-of-the-art low-cost platforms. Additionally, shown results indicate that it is applicable as a supporting tool for state-of-charge and state-of-health estimation and scalable for the different battery technologies and sizes. Validation using both static pulses and dynamic driving profile resulted in average absolute error of 124 mV regarding cranking current rate of 800 A respectively.

Effects of Electrical Current and External Stress on the Electromigration of Intermetallic Compounds Between the Flip-Chip Solder and Copper Substrate

NASA Astrophysics Data System (ADS)

Chen, Wei-Jhen; Lee, Yue-Lin; Wu, Ti-Yuan; Chen, Tzu-Ching; Hsu, Chih-Hui; Lin, Ming-Tzer

2018-01-01

This study investigated the effects of electric current and external stress on electromigration of intermetallic compounds (IMC) between solder and copper substrate. Different samples were tested under three different sets of conditions: (1) thermal aging only, (2) thermal aging with electric current ,where resistivity changes were measured using four-point probe measurements, (3) thermal aging with electric current and external stress provided using a four-point bending apparatus. The micro-structural changes in the samples were observed. The results were closely examined; particularly the coupling effect of electric current and external stress to elucidate the electromigration mechanism, as well as the formation of IMC in the samples. For thermal-aging-only samples, the IMC growth mechanism was controlled by grain boundary diffusion. Meanwhile, for thermal aging and applied electric current samples, the IMC growth mechanism was dominated by volume diffusion and interface reaction. Lastly, the IMC growth mechanism in the electric current and external stress group was dominated by grain boundary diffusion with grain growth. The results reveal that the external stress/strain and electric current play a significant role in the electromigration of copper-tin IMC. The samples exposed to tensile stress have reduced electromigration, while those subjected under compressive stress have enhanced electromigration.

Engineering Ethics Education : Its Necessity, Objectives, Methods, Current State, and Challenges

NASA Astrophysics Data System (ADS)

Fudano, Jun

The importance of engineering ethics education has become widely recognized in the industrialized countries including Japan. This paper examines the background against which engineering ethics education is required, and reviews its objectives, methods, and challenges, as well as its current state. In pointing out important issues associated with the apparent acceptance and quantitative development of ethics education, especially after the establishment of the Japan Accreditation Board for Engineering Education in 1999, the author stresses that the most serious problem is the lack of common understanding on the objectives of engineering ethics education. As a strategy to improve the situation, the so-called “Ethics-across-the-Curriculum” approach is introduced. The author also claims that business/organization ethics which is consistent with engineering ethics should be promoted in Japan.

Predictors of parenting stress among Malaysian mothers of children with Down syndrome.

PubMed

Norizan, A; Shamsuddin, K

2010-11-01

Having children with intellectual disability can be stressful for most parents. Currently there are very few studies focusing on parenting stress among mothers of children with Down syndrome (DS) in Asia. The present study examined the level of parenting stress experienced by Malaysian mothers of children with DS and evaluated the child and maternal factors that contributed to parenting stress based on Hill's ABC-X Model (Hill 1949). We conducted a cross-sectional study of mothers of children with DS between the ages of 2-12 years during February-June 2008 in Kedah, a state in Peninsular Malaysia. We used self-administered questionnaires to gather data on parenting stress, child's birth history and current behavioural problems, as well as the maternal sociodemographic characteristics, coping styles and psychological well-being. Parental Stress Scale (PSS) was used to assess parenting stress. Measures of child's behavioural problem using Pediatric Symptom Checklist, mother's coping style using Carver et al. (1989) COPE inventory and their psychological well-being using Lovibond and Lovibond (1995) DASS21, a scale assessing depression, anxiety and stress were also carried out. The 147 mothers who participated in the study had an average age of 43.1 years (SD = 7.6 years), of whom 94.6% were married, 57.1% had secondary level education and 28.6% were working outside their home. Based on PSS, mean parenting stress was 37.6 (SD = 8.1). Parenting stress was significantly higher among mothers who reported having children with behavioural problems. However, parenting stress was modified by positive coping styles and negative maternal psychological well-being. The final model based on hierarchical regression analysis identified maternal depression and lack of acceptance as significant predictors of parenting stress rather than child's behavioural problems. Mean parenting stress among mothers of children with DS significantly differed by behavioural problems in their children. Parenting stress is also significantly correlated with frequent use of acceptance, religious and optimist coping styles, and presence of maternal depressive, anxiety and stress symptoms. However, hierarchical regression analysis identified maternal depression and lack of acceptance of having a child with DS as the most significant predictors of parenting stress in these mothers. © 2010 The Authors. Journal of Intellectual Disability Research © 2010 Blackwell Publishing Ltd.

Some methodological aspects of tectonic stress reconstruction based on geological indicators

NASA Astrophysics Data System (ADS)

Sim, Lidiya A.

2012-03-01

The impact of the initial heterogeneity in rocks on the distribution of slickensides (slip planes), which are used to reconstruct local stress-state, is discussed. The stress-state was reconstructed by a graphic variant of the cinematic method. A new type of stress-state - Variation of Stress-State Type (VSST) - is introduced. The VSST is characterized by dislocation vectors originated both by uniaxial compression and uniaxial tension in the same rock volume, i.e. coefficient μσ = 1-2R varies from +1 to -1. The reasons for differences between slip planes from those predicted by the model are discussed. The distribution of slip planes depends on the stress-state type (μσ coefficient) and on the initial heterogeneity of the rocks. A criterion for the identification of tectonic stress rank is suggested. It is based on the models of tectonic stress distribution in the fracture vicinities. Examples of results of tectonic stress studies are given. Studies of tectonic stresses based on geological indicators are of methodological and practical importance.

Stress-state effects on the stress-induced martensitic transformation of carburized 4320 steels

NASA Astrophysics Data System (ADS)

Karaman, I.; Balzer, M.; Sehitoglu, Huseyin; Maier, H. J.

1998-02-01

The effect of different stress states on the stress-induced martensitic transformation of retained austenite was investigated in carburized 4320 steels with an initial retained austenite content of 15 pct. Experiments were conducted utilizing a specialized pressure rig and comparison between stress-strain behaviors of specimens with different austenitization and tempering histories was performed under these stress states. Experimental results indicated considerable asymmetry between tension and compression, with triaxial stress states resulting in the highest strength levels for the untempered material. Fine carbide precipitates due to low-temperature tempering increased the strength and ductility of the specimens and also changed the austenite-to-martensite transformation behavior. Numerical simulations of stress-strain behaviors under different stress states were obtained, with an existing micromechanical self-consistent framework utilizing the crystallographic theory of austenite/martensite transformation and the minimum complementary free-energy principle. The model was modified for carburized steels upon microstructural investigation and predicted the same trends in effective stress-effective strain behavior as observed experimentally.

A Theoretical Investigation of Composite Overwrapped Pressure Vessel (COPV) Mechanics Applied to NASA Full Scale Tests

NASA Technical Reports Server (NTRS)

Thesken, John C.; Murthy, Pappu L. N.; Phoenix, S. L.; Greene, N.; Palko, Joseph L.; Eldridge, Jeffrey; Sutter, James; Saulsberry, R.; Beeson, H.

2009-01-01

A theoretical investigation of the factors controlling the stress rupture life of the National Aeronautics and Space Administration's (NASA) composite overwrapped pressure vessels (COPVs) continues. Kevlar (DuPont) fiber overwrapped tanks are of particular concern due to their long usage and the poorly understood stress rupture process in Kevlar filaments. Existing long term data show that the rupture process is a function of stress, temperature and time. However due to the presence of a load sharing liner, the manufacturing induced residual stresses and the complex mechanical response, the state of actual fiber stress in flight hardware and test articles is not clearly known. This paper is a companion to a previously reported experimental investigation and develops a theoretical framework necessary to design full-scale pathfinder experiments and accurately interpret the experimentally observed deformation and failure mechanisms leading up to static burst in COPVs. The fundamental mechanical response of COPVs is described using linear elasticity and thin shell theory and discussed in comparison to existing experimental observations. These comparisons reveal discrepancies between physical data and the current analytical results and suggest that the vessel s residual stress state and the spatial stress distribution as a function of pressure may be completely different from predictions based upon existing linear elastic analyses. The 3D elasticity of transversely isotropic spherical shells demonstrates that an overly compliant transverse stiffness relative to membrane stiffness can account for some of this by shifting a thin shell problem well into the realm of thick shell response. The use of calibration procedures are demonstrated as calibrated thin shell model results and finite element results are shown to be in good agreement with the experimental results. The successes reported here have lead to continuing work with full scale testing of larger NASA COPV hardware.

Roles of University Support for International Students in the United States: Analysis of a Systematic Model of University Identification, University Support, and Psychological Well-Being

ERIC Educational Resources Information Center

Cho, Jaehee; Yu, Hongsik

2015-01-01

Unlike previous research on international students' social support, this current study applied the concept of organizational support to university contexts, examining the effects of university support. Mainly based on the social identity/self-categorization stress model, this study developed and tested a path model composed of four key…

Silicon nanowire Esaki diodes.

PubMed

Schmid, Heinz; Bessire, Cedric; Björk, Mikael T; Schenk, Andreas; Riel, Heike

2012-02-08

We report on the fabrication and characterization of silicon nanowire tunnel diodes. The silicon nanowires were grown on p-type Si substrates using Au-catalyzed vapor-liquid-solid growth and in situ n-type doping. Electrical measurements reveal Esaki diode characteristics with peak current densities of 3.6 kA/cm(2), peak-to-valley current ratios of up to 4.3, and reverse current densities of up to 300 kA/cm(2) at 0.5 V reverse bias. Strain-dependent current-voltage (I-V) measurements exhibit a decrease of the peak tunnel current with uniaxial tensile stress and an increase of 48% for 1.3 GPa compressive stress along the <111> growth direction, revealing the strain dependence of the Si band structure and thus the tunnel barrier. The contributions of phonons to the indirect tunneling process were probed by conductance measurements at 4.2 K. These measurements show phonon peaks at energies corresponding to the transverse acoustical and transverse optical phonons. In addition, the low-temperature conductance measurements were extended to higher biases to identify potential impurity states in the band gap. The results demonstrate that the most likely impurity, namely, Au from the catalyst particle, is not detectable, a finding that is also supported by the excellent device properties of the Esaki diodes reported here. © 2012 American Chemical Society

Estimation of stress distribution in ferromagnetic tensile specimens using low cost eddy current stress measurement system and BP neural network.

PubMed

Li, Jianwei; Zhang, Weimin; Zeng, Weiqin; Chen, Guolong; Qiu, Zhongchao; Cao, Xinyuan; Gao, Xuanyi

2017-01-01

Estimation of the stress distribution in ferromagnetic components is very important for evaluating the working status of mechanical equipment and implementing preventive maintenance. Eddy current testing technology is a promising method in this field because of its advantages of safety, no need of coupling agent, etc. In order to reduce the cost of eddy current stress measurement system, and obtain the stress distribution in ferromagnetic materials without scanning, a low cost eddy current stress measurement system based on Archimedes spiral planar coil was established, and a method based on BP neural network to obtain the stress distribution using the stress of several discrete test points was proposed. To verify the performance of the developed test system and the validity of the proposed method, experiment was implemented using structural steel (Q235) specimens. Standard curves of sensors at each test point were achieved, the calibrated data were used to establish the BP neural network model for approximating the stress variation on the specimen surface, and the stress distribution curve of the specimen was obtained by interpolating with the established model. The results show that there is a good linear relationship between the change of signal modulus and the stress in most elastic range of the specimen, and the established system can detect the change in stress with a theoretical average sensitivity of -0.4228 mV/MPa. The obtained stress distribution curve is well consonant with the theoretical analysis result. At last, possible causes and improving methods of problems appeared in the results were discussed. This research has important significance for reducing the cost of eddy current stress measurement system, and advancing the engineering application of eddy current stress testing.

Estimation of stress distribution in ferromagnetic tensile specimens using low cost eddy current stress measurement system and BP neural network

PubMed Central

Li, Jianwei; Zeng, Weiqin; Chen, Guolong; Qiu, Zhongchao; Cao, Xinyuan; Gao, Xuanyi

2017-01-01

Estimation of the stress distribution in ferromagnetic components is very important for evaluating the working status of mechanical equipment and implementing preventive maintenance. Eddy current testing technology is a promising method in this field because of its advantages of safety, no need of coupling agent, etc. In order to reduce the cost of eddy current stress measurement system, and obtain the stress distribution in ferromagnetic materials without scanning, a low cost eddy current stress measurement system based on Archimedes spiral planar coil was established, and a method based on BP neural network to obtain the stress distribution using the stress of several discrete test points was proposed. To verify the performance of the developed test system and the validity of the proposed method, experiment was implemented using structural steel (Q235) specimens. Standard curves of sensors at each test point were achieved, the calibrated data were used to establish the BP neural network model for approximating the stress variation on the specimen surface, and the stress distribution curve of the specimen was obtained by interpolating with the established model. The results show that there is a good linear relationship between the change of signal modulus and the stress in most elastic range of the specimen, and the established system can detect the change in stress with a theoretical average sensitivity of -0.4228 mV/MPa. The obtained stress distribution curve is well consonant with the theoretical analysis result. At last, possible causes and improving methods of problems appeared in the results were discussed. This research has important significance for reducing the cost of eddy current stress measurement system, and advancing the engineering application of eddy current stress testing. PMID:29145500

Distinct Redox Regulation in Sub-Cellular Compartments in Response to Various Stress Conditions in Saccharomyces cerevisiae

PubMed Central

Ayer, Anita; Sanwald, Julia; Pillay, Bethany A.; Meyer, Andreas J.; Perrone, Gabriel G.; Dawes, Ian W.

2013-01-01

Responses to many growth and stress conditions are assumed to act via changes to the cellular redox status. However, direct measurement of pH-adjusted redox state during growth and stress has never been carried out. Organellar redox state (E GSH) was measured using the fluorescent probes roGFP2 and pHluorin in Saccharomyces cerevisiae. In particular, we investigated changes in organellar redox state in response to various growth and stress conditions to better understand the relationship between redox-, oxidative- and environmental stress response systems. E GSH values of the cytosol, mitochondrial matrix and peroxisome were determined in exponential and stationary phase in various media. These values (−340 to −350 mV) were more reducing than previously reported. Interestingly, sub-cellular redox state remained unchanged when cells were challenged with stresses previously reported to affect redox homeostasis. Only hydrogen peroxide and heat stress significantly altered organellar redox state. Hydrogen peroxide stress altered the redox state of the glutathione disulfide/glutathione couple (GSSG, 2H+/2GSH) and pH. Recovery from moderate hydrogen peroxide stress was most rapid in the cytosol, followed by the mitochondrial matrix, with the peroxisome the least able to recover. Conversely, the bulk of the redox shift observed during heat stress resulted from alterations in pH and not the GSSG, 2H+/2GSH couple. This study presents the first direct measurement of pH-adjusted redox state in sub-cellular compartments during growth and stress conditions. Redox state is distinctly regulated in organelles and data presented challenge the notion that perturbation of redox state is central in the response to many stress conditions. PMID:23762325

Markers of Oxidant Stress that are Clinically Relevant in Aging and Age-related Disease

PubMed Central

Jacob, Kimberly D.; Hooten, Nicole Noren; Trzeciak, Andrzej R.; Evans, Michele K.

2013-01-01

Despite the long held hypothesis that oxidant stress results in accumulated oxidative damage to cellular macromolecules and subsequently to aging and age-related chronic disease, it has been difficult to consistently define and specifically identify markers of oxidant stress that are consistently and directly linked to age and disease status. Inflammation because it is also linked to oxidant stress, aging, and chronic disease also plays an important role in understanding the clinical implications of oxidant stress and relevant markers. Much attention has focused on identifying specific markers of oxidative stress and inflammation that could be measured in easily accessible tissues and fluids (lymphocytes, plasma, serum). The purpose of this review is to discuss markers of oxidant stress used in the field as biomarkers of aging and age-related diseases, highlighting differences observed by race when data is available. We highlight DNA, RNA, protein, and lipid oxidation as measures of oxidative stress, as well as other well-characterized markers of oxidative damage and inflammation and discuss their strengths and limitations. We present the current state of the literature reporting use of these markers in studies of human cohorts in relation to age and age-related disease and also with a special emphasis on differences observed by race when relevant. PMID:23428415

Preliminary evidence for a unique role of disgust-based conditioning in posttraumatic stress.

PubMed

Badour, Christal L; Feldner, Matthew T; Blumenthal, Heidemarie; Knapp, Ashley

2013-04-01

Independent lines of evidence have linked posttraumatic stress symptomatology to both peritraumatic disgust (i.e., disgust experienced during a traumatic event) and posttraumatic disgust reactivity in response to traumatic event cues among individuals exposed to traumatic events. Much of this work suggests disgust, defined as a rejection/revulsion response aimed at distancing oneself from a potential source of contamination, may be important in understanding the nature of posttraumatic stress reactions even after accounting for the more frequently studied affective states of fear and anxiety. The current investigation provided a preliminary test of a model of disgust in posttraumatic stress among a sample of 54 community-recruited women with a history sexual victimization. Both peritraumatic disgust (r = .31) and posttraumatic disgust reactivity (r = .42) in response to an idiographic traumatic event script were significantly associated with posttraumatic stress symptom severity. After accounting for variability-associated peritraumatic fear and posttraumatic anxious reactivity, an indirect effect of peritraumatic disgust through posttraumatic disgust reactivity also was found, suggesting that one mechanism through which peritraumatic disgust relates to posttraumatic stress is through its relation with increased posttraumatic disgust reactivity. These findings highlight the importance of further elucidating the nature of disgust in relation to traumatic events and subsequent posttraumatic stress reactions. Copyright © 2013 International Society for Traumatic Stress Studies.

Human-induced seismicity and large-scale hydrocarbon production in the USA and Canada

NASA Astrophysics Data System (ADS)

van der Baan, Mirko; Calixto, Frank J.

2017-07-01

We compare current and historic seismicity rates in six States in the USA and three Provinces in Canada to past and present hydrocarbon production. All States/Provinces are major hydrocarbon producers. Our analyses span three to five decades depending on data availability. Total hydrocarbon production has significantly increased in the past few years in these regions. Increased production in most areas is due to large-scale hydraulic fracturing and thus underground fluid injection. Furthermore, increased hydrocarbon production generally leads to increased water production, which must be treated, recycled, or disposed of underground. Increased fluid injection enhances the likelihood of fault reactivation, which may affect current seismicity rates. We find that increased seismicity in Oklahoma, likely due to salt-water disposal, has an 85% correlation with oil production. Yet, the other areas do not display State/Province-wide correlations between increased seismicity and production, despite 8-16-fold increases in production in some States. However, in various cases, seismicity has locally increased. Multiple factors play an important role in determining the likelihood of anthropogenic activities influencing earthquake rates, including (i) the near-surface tectonic background rate, (ii) the existence of critically stressed and favorably oriented faults, which must be hydraulically connected to injection wells, (iii) the orientation and magnitudes of the in situ stress field, combined with (iv) the injection volumes and implemented depletion strategies. A comparison with the seismic hazard maps for the USA and Canada shows that induced seismicity is less likely in areas with a lower hazard. The opposite, however, is not necessarily true.

NADA Protocol for Behavioral Health. Putting Tools in the Hands of Behavioral Health Providers: The Case for Auricular Detoxification Specialists.

PubMed

Stuyt, Elizabeth B; Voyles, Claudia A; Bursac, Sara

2018-02-07

Background: The National Acupuncture Detoxification Association (NADA) protocol, a simple standardized auricular treatment has the potential to provide vast public health relief on issues currently challenging our world. This includes but is not limited to addiction, such as the opioid epidemic, but also encompasses mental health, trauma, PTSD, chronic stress, and the symptoms associated with these conditions. Simple accessible tools that improve outcomes can make profound differences. We assert that the NADA protocol can have greatest impact when broadly applied by behavioral health professionals, Auricular Detoxification Specialists (ADSes). Methods: The concept of ADS is described and how current laws vary from state to state. Using available national data, a survey of practitioners in three selected states with vastly different laws regarding ADSes, and interviews of publicly funded programs which are successfully incorporating the NADA protocol, we consider possible effects of ADS-friendly conditions. Results: Data presented supports the idea that conditions conducive to ADS practice lead to greater implementation. Program interviews reflect settings in which adding ADSes can in turn lead to improved outcomes. Discussion: The primary purpose of non-acupuncturist ADSes is to expand the access of this simple but effective treatment to all who are suffering from addictions, stress, or trauma and to allow programs to incorporate acupuncture in the form of the NADA protocol at minimal cost, when and where it is needed. States that have changed laws to allow ADS practice for this standardized ear acupuncture protocol have seen increased access to this treatment, benefiting both patients and the programs.

Effect of Compressive Stresses on Leakage Currents in Microchip Tantalum Capacitors

NASA Technical Reports Server (NTRS)

Teverovsky, Alexander

2012-01-01

Microchip tantalum capacitors are manufactured using new technologies that allow for production of small size capacitors (down to EIA case size 0402) with volumetric efficiency much greater than for regular chip capacitors. Due to a small size of the parts and leadless design they might be more sensitive to mechanical stresses that develop after soldering onto printed wiring boards (PWB) compared to standard chip capacitors. In this work, the effect of compressive stresses on leakage currents in capacitors has been investigated in the range of stresses up to 200 MPa. Significant, up to three orders of magnitude, variations of currents were observed after the stress exceeds a certain critical level that varied from 10 MPa to 180 MPa for capacitors used in this study. A stress-induced generation of electron traps in tantalum pentoxide dielectric is suggested to explain reversible variations of leakage currents in tantalum capacitors. Thermo-mechanical characteristics of microchip capacitors have been studied to estimate the level of stresses caused by assembly onto PWB and assess the risk of stress-related degradation and failures. Keywords: tantalum capacitors, leakage current, soldering, reliability, mechanical stress.

Effects of unpredictable chronic stress on behavior and brain-derived neurotrophic factor expression in CA3 subfield and dentate gyrus of the hippocampus in different aged rats.

PubMed

Li, Ying; Ji, Yong-juan; Jiang, Hong; Liu, De-xiang; Zhang, Qian; Fan, Shu-jian; Pan, Fang

2009-07-05

Brain-derived neurotrophic factor (BDNF) is a stress-responsive intercellular messenger modifying hypothalamic-pituitary-adrenal (HPA) axis activity. The interaction between stress and age in BDNF expression is currently not fully understood. This study was conducted to observe unpredictable stress effect on behavior and BDNF expression in CA3 subfield (CA3) and dentate gyrus of hippocampus in different aged rats. Forty-eight Wistar rats of two different ages (2 months and 15 months) were randomly assigned to six groups: two control groups and four stress groups. The rats in the stress group received three weeks of unpredictable mild stress. The depression state and the stress level of the animals were determined by sucrose preference test and observation of exploratory behavior in an open field (OF) test. The expressions of BDNF in CA3 and dentate gyrus of the hippocampus were measured using immunohistochemistry. Age and stress had different effects on the behavior of different aged animals (age: F = 6.173, P < 0.05, stress: F = 6.056, P < 0.05). Stress was the main factor affecting sucrose preference (F = 123.608, P < 0.05). Decreased sucrose preference and suppressed behavior emerged directly following stress, lasting to at least the eighth day after stress in young animals (P < 0.05). The older stress rats showed a lower sucrose preference than young stress rats (P < 0.05). Older control rats behaved differently from the younger control animals in the OF test, spending more time in the central square (P < 0.05), exhibiting fewer vertical movements (P < 0.05) and less grooming (P < 0.05). Following exposure to stress, older-aged rats showed no obvious changes in vertical movement and grooming. This indicates that aged rats were in an unexcited state before the stress period, and responded less to stressful stimuli than younger rats. There was significantly lower BDNF expression in the CA3 and dentate gyrus regions of the hippocampus following stress in both age groups (P < 0.05), a reduction that was still present at the eighth day after stress (P < 0.05). Stress and age were the main factors affecting the expression of BDNF (F = 9.408, P < 0.05; F = 106.303, P < 0.05). The aged stress group showed lower BDNF expression compared to the young stressed group at every testing time point. Stress has age-dependent effects on behavioral responses and hippocampal BDNF expression in rats.

Perceived Race-Based Discrimination, Employment Status, and Job Stress in a National Sample of Black Women: Implications for Health Outcomes

PubMed Central

Mays, Vickie M.; Coleman, Lerita M.; Jackson, James S.

2013-01-01

Previous research has not systematically examined the relationship of perceived race-based discriminations to labor force participation or job related stresses–problems experienced by Black women. The present study investigated the relative contributions of perceived race-based discriminations and sociodemographic characteristics to employment status and job stress in a national probability sample (the National Survey of Black Americans; J. S. Jackson, 1991) of Black women in the United States. Logit and polychotomous logistic regression analyses revealed that Black women’s current employment status was best explained by sociodemographic measures. In contrast, the combination of perceived discrimination and sociodemographics differentially affects patterns of employment status and perceived job stress in the work environment of Black women. Implications of these findings for the health of African American women are discussed. PMID:9547054

Origin of bias-stress induced instability in organic thin-film transistors with semiconducting small-molecule/insulating polymer blend channel.

PubMed

Park, Ji Hoon; Lee, Young Tack; Lee, Hee Sung; Lee, Jun Young; Lee, Kimoon; Lee, Gyu Baek; Han, Jiwon; Kim, Tae Woong; Im, Seongil

2013-03-13

The stabilities of a blending type organic thin-film transistor with phase-separated TIPS-pentacene channel layer were characterized under the conditions of negative-bias-stress (NBS) and positive-bias-stress (PBS). During NBS, threshold voltage (Vth) shifts noticeably. NBS-imposed devices revealed interfacial trap density-of-states (DOS) at 1.56 and 1.66 eV, whereas initial device showed the DOS at only 1.56 eV, as measured by photoexcited charge-collection spectroscopy (PECCS) method. Possible origin of this newly created defect is related to ester group in PMMA, which induces some hole traps at the TIPS-pentacene/i-PMMA interface. PBS-imposed device showed little Vth shift but visible off-current increase as "back-channel" effect, which is attributed to the water molecules trapped on the TFT surface.

Borehole Breakout Derived Constraints on Stress Regimes in the Santa Barbara Channel, Offshore Southern California

NASA Astrophysics Data System (ADS)

Pritchard, E. H.; Persaud, P.; Stock, J. M.

2017-12-01

The Santa Barbara Channel is an E-W trending marine basin that serves as the southern extension of the Western Transverse Ranges block. Several active, E-W trending en echelon fault systems exist beneath the Channel with both N and S dips. These control a series of tight, asymmetric anticlinal folds along the North Channel and Mid-Channel regions. Although controversial, recent models have suggested that these systems are capable of producing large magnitude, tsunamigenic earthquakes. Not controversial, however, is the fact that further knowledge of the stress regime related to these systems would greatly contribute to our understanding of a potential rupture along them. In this study, oriented 4-arm caliper well log data obtained from industry are used to determine the orientations of stress induced shear failures along well bore walls, called borehole breakouts, beneath two offshore drill platforms in the Santa Barbara Channel. Analysis of breakout orientations along 18 differently oriented, highly deviated wells allows for constraint of the current in situ stress regime beneath each of the platforms. The best-fit stress regime can then be used to inform the nature of slip along nearby faults, many of which are blind and display no surface indications of slip. At the Holly platform, located roughly 19 km west of Santa Barbara, and proximate to the Pitas Point, North Channel, and Red Mountain fault systems, lower hemisphere polar projections of breakout orientations in deviated well sections indicate a mainly thrust faulting stress regime, although a strike-slip component is not currently excluded. At the Gail platform, located midway between Ventura and Santa Cruz Island, and proximate to the Western Deep Fault, polar projections of breakouts indicate that a predominantly thrust faulting stress regime also exists beneath this platform. However, a few inconsistencies in the breakout orientations at each platform suggest variability in the stress regime, leading to the hypothesis that the stress field beneath these regions may change with depth, from a shallow degenerate-like thrust faulting stress state, with the horizontal principal stresses roughly equal in magnitude yet greater than the vertical principal stress (SH = Sh > Sv), to a deeper, less degenerate regime.

Stress responses during aerobic exercise in relation to motivational dominance and state.

PubMed

Thatcher, Joanne; Kuroda, Yusuke; Legrand, Fabien D; Thatcher, Rhys

2011-02-01

We examined the hypothesis that congruence between motivational dominance and state results in optimal psychological responses and performance during exercise. Twenty participants (10 telic dominant and 10 paratelic dominant) rated their stress at 5 min intervals as they cycled on an ergometer at gas exchange threshold for 30 min in both telic and paratelic state manipulated conditions. Participants then performed a test to exhaustion at a resistance equivalent to 110% of VO(2max). The hypothesized interaction between condition and dominance was significant for internal tension stress, as paratelic dominants were more stressed than telic dominants when exercising in the telic state and telic dominants were more stressed than paratelic dominants when exercising in the paratelic state. Similarly, the condition × dominance interaction for internal stress discrepancy was significant, as paratelic dominants reported greater internal stress discrepancy exercising in the telic compared with the paratelic state. Findings are discussed in relation to the application of reversal theory for understanding stress responses during aerobic exercise.

Stress State of the Earth's Crust in Azerbaijan

DOE Office of Scientific and Technical Information (OSTI.GOV)

Agayeva, Solmaz T.

2006-03-23

The study of the crustal stress has a practical implication in hazard mitigation. Knowledge on stress-related ground motion may help to improve the stability of public and private buildings. The stress state of the crust in Azerbaijan is studied in this paper by means of focal mechanism analysis and using different methods to determine the principal stress orientations. Two types of stress states were revealed in the studied regions. The territory of Great and Lesser Caucasus and Talysh folded zone are characterized by near-horizontal compression. The territories of Caspian Sea and Kura depression are characterized by near-horizontal tension. For bothmore » types of stress state, the predominant stress axes are oriented perpendicular to the regional geological structures.« less

The cardiovascular perfusionist as a model for the successful technologist in high stress situations.

PubMed

Friday, P J; Mook, W J

1991-01-01

This study investigates the psychological profiles of highly stressed medical technologists. One hundred and four individuals representing a cross-section of the United States who function as operators of heart-lung machines during open heart surgery (perfusionists) were studied using both internal and external models based on the works of Eric Berne and Karen Horney. Daily exposure to life and death responsibilities combined with the constant pressures of maintaining current technical skills can make the profession selected for this study representative of high technology professions that require a great deal of coping. Results of this study indicate that there is a balanced psychological profile in successful technologists functioning in long-term, high-stressed occupations. Female perfusionists appear to be more aggressive and critical than their male counterparts. This is seen as an attempt by female perfusionists to compensate for what has historically been a male dominanted, highly technical and high-stressed occupation. Generalizations for candidate selections to high stressed occupations could be made as well as projections of foundations for possible progressive disillusionment (burn out).

Current Perspectives on Viable but Non-culturable State in Foodborne Pathogens

PubMed Central

Zhao, Xihong; Zhong, Junliang; Wei, Caijiao; Lin, Chii-Wann; Ding, Tian

2017-01-01

The viable but non-culturable (VBNC) state, a unique state in which a number of bacteria respond to adverse circumstances, was first discovered in 1982. Unfortunately, it has been reported that many foodborne pathogens can be induced to enter the VBNC state by the limiting environmental conditions during food processing and preservation, such as extreme temperatures, drying, irradiation, pulsed electric field, and high pressure stress, as well as the addition of preservatives and disinfectants. After entering the VBNC state, foodborne pathogens will introduce a serious crisis to food safety and public health because they cannot be detected using conventional plate counting techniques. This review provides an overview of the various features of the VBNC state, including the biological characteristics, induction and resuscitation factors, formation and resuscitation mechanisms, detection methods, and relationship to food safety. PMID:28421064

Design Optimization of Hybrid FRP/RC Bridge

NASA Astrophysics Data System (ADS)

Papapetrou, Vasileios S.; Tamijani, Ali Y.; Brown, Jeff; Kim, Daewon

2018-04-01

The hybrid bridge consists of a Reinforced Concrete (RC) slab supported by U-shaped Fiber Reinforced Polymer (FRP) girders. Previous studies on similar hybrid bridges constructed in the United States and Europe seem to substantiate these hybrid designs for lightweight, high strength, and durable highway bridge construction. In the current study, computational and optimization analyses were carried out to investigate six composite material systems consisting of E-glass and carbon fibers. Optimization constraints are determined by stress, deflection and manufacturing requirements. Finite Element Analysis (FEA) and optimization software were utilized, and a framework was developed to run the complete analyses in an automated fashion. Prior to that, FEA validation of previous studies on similar U-shaped FRP girders that were constructed in Poland and Texas is presented. A finer optimization analysis is performed for the case of the Texas hybrid bridge. The optimization outcome of the hybrid FRP/RC bridge shows the appropriate composite material selection and cross-section geometry that satisfies all the applicable Limit States (LS) and, at the same time, results in the lightest design. Critical limit states show that shear stress criteria determine the optimum design for bridge spans less than 15.24 m and deflection criteria controls for longer spans. Increased side wall thickness can reduce maximum observed shear stresses, but leads to a high weight penalty. A taller cross-section and a thicker girder base can efficiently lower the observed deflections and normal stresses. Finally, substantial weight savings can be achieved by the optimization framework if base and side-wall thickness are treated as independent variables.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ronold, K.O.; Nielsen, N.J.R.; Tura, F.

This paper demonstrates how a structural reliability method can be applied as a rational means to analyze free spans of submarine pipelines with respect to failure in ultimate loading, and to establish partial safety factors for design of such free spans against this failure mode. It is important to note that the described procedure shall be considered as an illustration of a structural reliability methodology, and that the results do not represent a set of final design recommendations. A scope of design cases, consisting of a number of available site-specific pipeline spans, is established and is assumed representative for themore » future occurrence of submarine pipeline spans. Probabilistic models for the wave and current loading and its transfer to stresses in the pipe wall of a pipeline span is established together with a stochastic representation of the material resistance. The event of failure in ultimate loading is considered as based on a limit state which is reached when the maximum stress over the design life of the pipeline exceeds the yield strength of the pipe material. The yielding limit state is considered an ultimate limit state (ULS).« less

Consequences of child exposure to war and terrorism.

PubMed

Joshi, Paramjit T; O'Donnell, Deborah A

2003-12-01

Acts of war and terrorism are increasingly prevalent in contemporary society. Throughout history, weaponry has become more efficient, accurate, and powerful, resulting in more devastation and loss of human life. Children are often overlooked as victims of such violence. Around the world, children are exposed to violence in multiple forms, frequently developing traumatic stress reactions. Such reactions are best understood within the context of social-emotional and cognitive development, as children respond differently to the stress of violence depending on their developmental level. Furthermore, the violence of war and terrorism often results in a multitiered cascade of negative life events including loss of loved ones, displacement, lack of educational structure, and drastic changes in daily routine and community values. These numerous losses, challenges, and stresses affect children's brains, minds, and bodies in an orchestrated whole-organism response. This paper describes these effects, synthesizing the current state of research on childhood traumatic stress reactions from the fields of neuroscience, clinical psychology, and pediatric diagnostic epidemiology.

Impact of oxygen precursor flow on the forward bias behavior of MOCVD-Al2O3 dielectrics grown on GaN

NASA Astrophysics Data System (ADS)

Chan, Silvia H.; Bisi, Davide; Liu, Xiang; Yeluri, Ramya; Tahhan, Maher; Keller, Stacia; DenBaars, Steven P.; Meneghini, Matteo; Mishra, Umesh K.

2017-11-01

This paper investigates the effects of the oxygen precursor flow supplied during metalorganic chemical vapor deposition (MOCVD) of Al2O3 films on the forward bias behavior of Al2O3/GaN metal-oxide-semiconductor capacitors. The low oxygen flow (100 sccm) delivered during the in situ growth of Al2O3 on GaN resulted in films that exhibited a stable capacitance under forward stress, a lower density of stress-generated negative fixed charges, and a higher dielectric breakdown strength compared to Al2O3 films grown under high oxygen flow (480 sccm). The low oxygen grown Al2O3 dielectrics exhibited lower gate current transients in stress/recovery measurements, providing evidence of a reduced density of trap states near the GaN conduction band and an enhanced robustness under accumulated gate stress. This work reveals oxygen flow variance in MOCVD to be a strategy for controlling the dielectric properties and performance.

Effect of Initial State of Lithium on the Propensity for Dendrite Formation: A Theoretical Study

DOE PAGES

Barai, Pallab; Higa, Kenneth; Srinivasan, Venkat

2016-12-17

Mechanical constraints have been widely used experimentally to prevent the growth of dendrites within lithium metal. The only article known to the authors that tries to theoretically understand how mechanical forces prevent dendrite growth was published by Monroe and Newman [J. Electrochem. Soc., 150 (10) A1377 (2005)]. Based on the assumption that surface tension prevents the growth of interfacial roughness, Monroe and Newman considered pre-stressed conditions of the lithium electrodes. This scenario indicates that prevention of dendrite growth by mechanical means is only possible by using electrolytes with shear modulus at least two times larger than that of lithium metal.more » Here, a different scenario of relaxed lithium metal (without any pre-existing surface stresses) has been considered in the present analysis. Deposition of lithium due to electrochemical reaction at the lithium/electrolyte interface induces compressive stress at the electrode, the electrolyte, and the newly deposited lithium metal. Present simulations indicate that during operation at low current densities, the scenario of relaxed lithium leads to no dendrites. Rather, the present study points to the importance of including the effect of current distribution to accurately capture the mechanical forces needed to prevent dendrite growth.« less

Effect of Initial State of Lithium on the Propensity for Dendrite Formation: A Theoretical Study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barai, Pallab; Higa, Kenneth; Srinivasan, Venkat

Mechanical constraints have been widely used experimentally to prevent the growth of dendrites within lithium metal. The only article known to the authors that tries to theoretically understand how mechanical forces prevent dendrite growth was published by Monroe and Newman [J. Electrochem. Soc., 150 (10) A1377 (2005)]. Based on the assumption that surface tension prevents the growth of interfacial roughness, Monroe and Newman considered pre-stressed conditions of the lithium electrodes. This scenario indicates that prevention of dendrite growth by mechanical means is only possible by using electrolytes with shear modulus at least two times larger than that of lithium metal.more » Here, a different scenario of relaxed lithium metal (without any pre-existing surface stresses) has been considered in the present analysis. Deposition of lithium due to electrochemical reaction at the lithium/electrolyte interface induces compressive stress at the electrode, the electrolyte, and the newly deposited lithium metal. Present simulations indicate that during operation at low current densities, the scenario of relaxed lithium leads to no dendrites. Rather, the present study points to the importance of including the effect of current distribution to accurately capture the mechanical forces needed to prevent dendrite growth.« less

Guidelines and Suggestions for Balloon Gondola Design

NASA Technical Reports Server (NTRS)

Franco, Hugo

2017-01-01

This paper discusses the current gondola design requirements for the Columbia Scientific Balloon Facility (CSBF). The CSBF is responsible for launching and supporting balloon borne scientific instruments and has some current updated guidelines that will be discussed in this presentation. As the sophistication of Payload systems have increased in size and complexity new guidelines have been implemented in order to make these instruments stay within the acceptable launch risks. Additionally, there is a requirement to submit a proper stress analysis report that states the flight design requirements have been met. Suggestions are discussed in this presentation that establish the proper guidelines to submit these.

A 7-year follow-up study on the mental health of North Korean defectors in South Korea.

PubMed

Jeon, Woo-Taek; Eom, Jin-Sup; Min, Sung Kil

2013-02-01

This study was conducted to describe the relationship of past trauma and current stress on the mental health of North Korean (NK) defectors living in South Korea 7 years after a baseline assessment. Of the 200 who participated in the initial study, 106 participated in follow-up. Previous data regarding past traumatic events experienced in North Korea and during defection, past posttraumatic stress disorder (PTSD), and their current stress levels were correlated with the participants' current mental health status including depression, anxiety, and PTSD. The rate of PTSD in the sample and the scores on the PTSD symptom scale decreased significantly from the baseline. The participants' current mental health was negatively related to previous traumatic experiences in North Korea and past symptoms of PTSD, but unrelated to previous trauma experienced during defection. In addition, although current mental health was negatively related to only current culture-related stress, it was unrelated to the level of current ordinary life stress. The results of this study suggest that PTSD symptoms decreased during the 7 years between assessments, and that current culture-related stress is the most important variable related to the mental health of NK defectors living in South Korea. Copyright © 2013 International Society for Traumatic Stress Studies.

Disruption of crystalline structure of Sn3.5Ag induced by electric current

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Han-Chie; Lin, Kwang-Lung, E-mail: matkllin@mail.ncku.edu.tw; Wu, Albert T.

2016-03-21

This study presented the disruption of the Sn and Ag{sub 3}Sn lattice structures of Sn3.5Ag solder induced by electric current at 5–7 × 10{sup 3} A/cm{sup 2} with a high resolution transmission electron microscope investigation and electron diffraction analysis. The electric current stressing induced a high degree of strain on the alloy, as estimated from the X-ray diffraction (XRD) peak shift of the current stressed specimen. The XRD peak intensity of the Sn matrix and the Ag{sub 3}Sn intermetallic compound diminished to nearly undetectable after 2 h of current stressing. The electric current stressing gave rise to a high dislocation density ofmore » up to 10{sup 17}/m{sup 2}. The grain morphology of the Sn matrix became invisible after prolonged current stressing as a result of the coalescence of dislocations.« less

Early developmental and temporal characteristics of stress-induced secretion of pituitary-adrenal hormones in prenatally stressed rat pups.

PubMed

Takahashi, L K; Kalin, N H

1991-08-30

Previous experiments revealed that 14-day-old prenatally stressed rats have significantly elevated concentrations of plasma adrenocorticotrophic hormone (ACTH) and corticosterone suggesting these animals have an overactive hypothalamic-pituitary-adrenal (HPA) system. In these studies, however, stress-induced hormone levels were determined only immediately after exposure to an acute stressor. Therefore, in the current study, we examined in postnatal days 7, 14 and 21 prenatally stressed rats the stress-induced time course of this pituitary-adrenal hormone elevation. Plasma ACTH and corticosterone were measured in the basal state and at 0.0, 0.5, 1.0, 2.0 and 4.0 h after a 10-min exposure period to foot shocks administered in the context of social isolation. Results indicated that at all 3 ages, plasma ACTH in prenatally stressed rats was significantly elevated. Corticosterone concentrations were also significantly higher in prenatally stressed than in control rats, especially in day 14 rats. Analysis of stress-induced hormone fluctuations over time indicated that by 14 days of age, both prenatally stressed than in control and control rats had significant increases in plasma ACTH and corticosterone after exposure to stress. Furthermore, although prenatally stressed rats had significantly higher pituitary-adrenal hormone concentrations than control animals, the post-stress temporal patterns of decline in ACTH and corticosterone levels were similar between groups. Results suggest that throughout the preweaning period, prenatal stress produces an HPA system that functions in a manner similar to that of controls but at an increased level.

Chemosignals of stress influence social judgments.

PubMed

Dalton, Pamela; Mauté, Christopher; Jaén, Cristina; Wilson, Tamika

2013-01-01

Human body odors have important communicative functions regarding genetic identity, immune fitness and general health, but an expanding body of research suggests they can also communicate information about an individual's emotional state. In the current study, we tested whether axillary odors obtained from women experiencing psychosocial stress could negatively influence personality judgments of warmth and competence made about other women depicted in video scenarios. 44 female donors provided three types of sweat samples: untreated exercise sweat, untreated stress sweat and treated stress sweat. After a 'washout' period, a commercial unscented anti-perspirant product was applied to the left axilla only to evaluate whether 'blocking' the stress signal would improve the social evaluations. A separate group of male and female evaluators (n = 120) rated the women in the videos while smelling one of the three types of sweat samples. Women in the video scenes were rated as being more stressed by both men and women when smelling the untreated vs. treated stress sweat. For men only, the women in the videos were rated as less confident, trustworthy and competent when smelling both the untreated stress and exercise sweat in contrast to the treated stress sweat. Women's social judgments were unaffected by sniffing the pads. The results have implications for influencing multiple types of professional and personal social interactions and impression management and extend our understanding of the social communicative function of body odors.

Chronic Pain and Chronic Stress: Two Sides of the Same Coin?

PubMed

Abdallah, Chadi G; Geha, Paul

2017-02-01

Pain and stress share significant conceptual and physiological overlaps. Both phenomena challenge the body's homeostasis and necessitate decision-making to help animals adapt to their environment. In addition, chronic stress and chronic pain share a common behavioral model of failure to extinguish negative memories. Yet, they also have discrepancies such that the final brain endophenotype of posttraumatic stress disorder, depression, and chronic pain appears to be different among the three conditions, and the role of the hypothalamic-pituitary-adrenal axis remains unclear in the physiology of pain. Persistence of either stress or pain is maladaptive and could lead to compromised well-being. In this brief review, we highlight the commonalities and differences between chronic stress and chronic pain, while focusing particularly on the central role of the limbic brain. We assess the current attempts in the field to conceptualize and understand chronic pain, within the context of knowledge gained from the stress literature. The limbic brain-including hippocampus, amygdala, and ventromedial pre-frontal cortex-plays a critical role in learning. These brain areas integrate incoming nociceptive or stress signals with internal state, and generate learning signals necessary for decision-making. Therefore, the physiological and structural remodeling of this learning circuitry is observed in conditions such as chronic pain, depression, and posttraumatic stress disorder, and is also linked to the risk of onset of these conditions.

Evaluating the sensitivity of an ice sheet model to changes in bed elevation and inclusion of membrane stresses

NASA Astrophysics Data System (ADS)

Aschwanden, Andy; Bueler, Ed; Khroulev, Constantine

2010-05-01

To predict Greenland's contribution to global sea level rise in the next few centuries with some confidence, an accurate representation of its current state is crucial. Simulations of the present state of Greenland using the "Parallel Ice Sheet Model" (PISM) capture the essential flow features but overestimate the current volume by about 30%. Possible sources of error include (1) limited understanding of physical processes involved, (2) the choice of approximations made by the numerical model, (3) values of tunable parameters, and (4) uncertainties in boundary conditions. The response of an ice sheet model to given forcing contains the above mentioned error sources, with unknown weights. In this work we focus on a small subset, namely errors arising from uncertainties in bed elevation and whether or not membrane stresses are included in the stress balance. CReSIS provides recently updated bedrock maps for Greenland include high-resolution data for Jacobshavn Isbræ and Petermann Glacier. We present a four-way comparison between the original BEDMAP, the new CReSIS bedrock data, a non-sliding shallow ice model, and hybrid model which includes the shallow shelf approximation as a sliding law. Large gradients possibly found in high-resolution bedrock elevation are expected to make a hybrid model the more appropriate choice. To elucidate this question, runs are performed on a unprecedented high spatial resolution of 2km for the whole ice sheet. Finally, model predictions are evaluated against observed quantities such as surface velocities, ice thickness, and temperature profiles in bore holes using different metrics.

Simulation fails to replicate stress in trainees performing a technical procedure in the clinical environment.

PubMed

Baker, B G; Bhalla, A; Doleman, B; Yarnold, E; Simons, S; Lund, J N; Williams, J P

2017-01-01

Simulation-based training (SBT) has become an increasingly important method by which doctors learn. Stress has an impact upon learning, performance, technical, and non-technical skills. However, there are currently no studies that compare stress in the clinical and simulated environment. We aimed to compare objective (heart rate variability, HRV) and subjective (state trait anxiety inventory, STAI) measures of stress theatre with a simulated environment. HRV recordings were obtained from eight anesthetic trainees performing an uncomplicated rapid sequence induction at pre-determined procedural steps using a wireless Polar RS800CX monitor © in an emergency theatre setting. This was repeated in the simulated environment. Participants completed an STAI before and after the procedure. Eight trainees completed the study. The theatre environment caused an increase in objective stress vs baseline (p = .004). There was no significant difference between average objective stress levels across all time points (p = .20) between environments. However, there was a significant interaction between the variables of objective stress and environment (p = .045). There was no significant difference in subjective stress (p = .27) between environments. Simulation was unable to accurately replicate the stress of the technical procedure. This is the first study that compares the stress during SBT with the theatre environment and has implications for the assessment of simulated environments for use in examinations, rating of technical and non-technical skills, and stress management training.

Behavior data of battery and battery pack SOC estimation under different working conditions.

PubMed

Zhang, Xu; Wang, Yujie; Yang, Duo; Chen, Zonghai

2016-12-01

This article provides the dataset of operating conditions of battery behavior. The constant current condition and the dynamic stress test (DST) condition were carried out to analyze the battery discharging and charging features. The datasets were achieved at room temperature, in April, 2016. The shared data contributes to clarify the battery pack state-of-charge (SOC) and the battery inconsistency, which is also shown in the article of "An on-line estimation of battery pack parameters and state-of-charge using dual filters based on pack model" (X. Zhang, Y. Wang, D. Yang, et al., 2016) [1].

Prevalence and predictors of posttraumatic stress disorder among victims of violence applying for state compensation.

PubMed

Kunst, Maarten; Winkel, Frans Willem; Bogaerts, Stefan

2010-09-01

Many studies have focused on the predictive value of victims' emotions experienced shortly after violence exposure to identify those vulnerable for development of posttraumatic stress disorder (PTSD). However, many victims remain unidentified during the initial recovery phase, yet may still be highly in need of psychological help after substantial time since victimization has passed. Professionals involved in the settlement of civil damage claims filed by victims of violence may play an important role in referring victims with current psychological problems to appropriate treatment services, as they are likely to maintain relations with victims until all compensation possibilities have been exhausted. As an exploratory examination of this topic, the current study investigates the potential utility of file characteristics as predictors of chronic PTSD among 686 victims of violence who had applied for state compensation with the Dutch Victim Compensation Fund (DVCF) in 2006. Identification of significant predictors is preceded by estimating prevalence rates of PTSD. Results indicate that approximately 1 of 2 victims applying for state compensation in the Netherlands still have PTSD many years after victimization and claim settlement. Age, female sex, time since victimization, acquaintance with the perpetrator, violence-related hospitalization, and compensation for immaterial damage prove to be predictive of PTSD, although female sex and immaterial damage compensation fail to reach significance after adjusting for recalled peritraumatic distress severity. Implications for policy practice as well as strengths and limitations of the study are discussed.

Structural evolution of nanoporous ultra-low k dielectrics under voltage stress

NASA Astrophysics Data System (ADS)

Raja, Archana; Shaw, Thomas; Grill, Alfred; Laibowitz, Robert; Heinz, Tony

2013-03-01

High speed interconnects in advanced integrated circuits require ultra-low-k dielectrics. Reduction of the dielectric constant is achieved via incorporation of nanopores in structures containing silicon, carbon, oxygen and hydrogen (SiCOH). We study nanoporous SiCOH films of k=2.5 and thicknesses of 40 - 400 nm. Leakage currents develop in the films under long-term voltage stress, eventually leading to breakdown and chip failure. Previous work* has shown the build-up of trap states as dielectric breakdown progresses. Using FTIR spectroscopy we have tracked the reorganization of the bonds in the SiCOH networks induced by voltage stress. Our results indicate that the cleavage of the Si-C and SiC-O bonds contribute toward increase in the density of bulk trapping states as breakdown is approached. AC conductance and capacitance measurements have also been carried out to describe interfacial and bulk traps and mechanisms. Comparison of breakdown properties of films with differing carbon content will also be presented to further delineate the role of carbon. *Atkin, J.M.; Shaw, T.M.; Liniger, E.; Laibowitz, R.B.; Heinz, T.F. Reliability Physics Symposium (IRPS), 2012 IEEE International Supported by the Semiconductor Research Corporation

Relaxor-ferroelectric crossover in (B i1 /2K1 /2)Ti O3 : Origin of the spontaneous phase transition and the effect of an applied external field

NASA Astrophysics Data System (ADS)

Hagiwara, Manabu; Ehara, Yoshitaka; Novak, Nikola; Khansur, Neamul H.; Ayrikyan, Azatuhi; Webber, Kyle G.; Fujihara, Shinobu

2017-07-01

The temperature evolution of polar order in an A -site complex perovskite (B i1 /2K1 /2)Ti O3 (BKT) has been investigated by measurements of dielectric permittivity, depolarization current, and stress-stain curves at elevated temperatures. Upon cooling from high temperatures, BKT first enters a relaxor state and then spontaneously transforms into a ferroelectric state. The analyses of temperature and frequency dependence of permittivity have revealed that polar nanoregions of the relaxor phase appear at temperatures higher than 560°C, and also that their freezing at 296°C triggers the spontaneous relaxor-ferroelectric transition. We discuss the key factors determining the development of long-range polar order in A -site complex perovskites through a comparison with the relaxor (B i1 /2N a1 /2)Ti O3 . We also show that application of biasing electric fields and compressive stresses to BKT favors its ferroelectric phase, resulting in a significant shift of the relaxor-ferroelectric transition temperature towards higher temperatures. Based on the obtained results, electric field-temperature and stress-temperature phase diagrams are firstly determined for BKT.

High field superconductors for superconducting machines

NASA Astrophysics Data System (ADS)

Rupp, G.; Wilhelm, M.; Wohlleben, K.; Ziegler, G.; Springer, E.

1980-11-01

High current capacity Nb3Sn multifilament conductors were fabricated. A solid state diffusion process was used. The number of conductor filaments approaches 70,000 with filament diameters being approximately 1.5 microns. Effective current densities reach 86,000 A/sq cm at a magnetic flux density of 10 T and operating temperature of 4.2 K. Calibrated flattened cables of twisted strands were fabricated for higher currents (up to 1000 A at 10 T). Generally, quantitative relations can be given for the rise in the critical current of Nb3Sn multifilament conductors, observed under the influence of mechanical stresses. Long lengths (km) of these conductors were used to manufacture superconducting solenoids two different ways. These rise to the short sample current, usually without conditioning, and deliver magnetic flux densities up to 14 T with an 8.5 T NbTi background field.

Sectoral Vulnerabilities to Changing Water Resources: Current and Future Tradeoffs between Supply and Demand in the Conterminous U.S

NASA Astrophysics Data System (ADS)

Meldrum, J.; Averyt, K.; Caldwell, P.; Sun, G.; Huber-lee, A. T.; McNulty, S.

2012-12-01

Assessing the sustainability of human activities depends, in part, on the availability of water supplies to meet the demands of those activities. Thermoelectric cooling, agriculture, and municipal uses all compete for water supplies, but each sector differs in its characteristic ratio of water consumption versus withdrawals. This creates different implications for contributing to water supply stress and, conversely, vulnerabilities within each sector to changing water supplies. In this study, we use two measures of water stress, relating to water withdrawals and to water consumption, and calculate the role of each of these three sectors in contributing to the two different measures. We estimate water stress with an enhanced version of the Water Supply Stress Index (WaSSI), calculating the ratio of water demand to water supply at the 8-digit Hydrologic Unit Code (HUC) scale (Sun et al. 2008, 2011; Caldwell et al. 2011). Current water supplies are based on an integrated water balance and flow routing model of the conterminous United States, which accounts for surface water supply, groundwater supply, and major return flows. Future supplies are based on simulated regional changes in streamflow in 2050 from an ensemble of 12 climate models (Milly et al. 2005). We estimate water demands separately for agriculture, municipal uses, and thermoelectric cooling, with the first two based on Kenny et al. (2005) and the last on the approach of Averyt et al. (2011). We find substantial regional variation not only in the overall WaSSI for withdrawals and consumption but also in contribution of the three water use sectors to that total. Results suggest that the relative vulnerabilities of different sectors of human activity to water supply stress vary spatially and that policies for alleviating that stress must consider the specific, regional context of the tradeoffs between competing water demands. Ref's: Averyt, K., Fisher, J., Huber-Lee, A., Lewis, A., Macknick, J., Madden, N., Rogers, J., and Tellinghuisen, S. 2011. Freshwater use by US power plants: electricity's thirst for a precious resource. A report of the Energy and Water in a Warming World initiative, Cambridge, MA: Union of Concerned Scientists, 52 pp. Caldwell, P., Sun, G., McNulty, S., Cohen, E., and Moore Myers, J. 2011. Modeling Impacts of Environmental Change on Ecosystem Services across the Conterminous United States, in: Proceedings of the Fourth Interagency Conference on Research in the Watersheds, Fairbanks, AK, 26-30 Sept 2011, 63-69. Kenny, J., Barber, N., Hutson, S., Linsey, K., Lovelace, J., and Maupin, M. 2009. Estimated use of water in the United States in 2005. US Geological Survey Circular 1344, 52 pp. Milly, P. C. D., Dunne, K. A., and Vecchia, A. V. 2005. Global pattern of trends in streamflow and water availability in a changing climate. Nature 438(7066):347-350. Sun, G., McNulty, S., Moore Myers, J., and Cohen, E. 2008. Impacts of multiple stresses on water demand and supply across the Southeastern United States. Journal of American Water Resources Association 44(6):1441-1457. Sun, G., Caldwell, P., Noormets, A., Cohen, E., McNulty, S., Treasure, E., Domec, J., Mu, Q., Xiao, J., John, R., and Chen, J. 2011. Upscaling key ecosystem functions across the Conterminous United States by a water-centric ecosystem model, J. Geophys. Res., 116.

Biohydrogen from Microalgae

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dubini, Alexandra; Gonzalez-Ballester, David

2016-03-01

This chapter provides an overview of the current state of knowledge of the mechanisms involved in biohydrogen production from microalgae. The known limitations linked to photohydrogen productivity are addressed. Particular attention is given to physiological and molecular strategies to sustain and improve hydrogen production. The impact of different nutrient stresses and the effect of carbon supply on hydrogen production are discussed. The genetic and metabolic engineering approaches for increasing hydrogen production are outlined.

Detection of stress/anxiety state from EEG features during video watching.

PubMed

Giannakakis, Giorgos; Grigoriadis, Dimitris; Tsiknakis, Manolis

2015-01-01

This paper studies the effect of stress/anxiety states on EEG signals during video sessions. The levels of arousal and valence that are induced to each subject while watching each video are self rated. These levels are mapped in stress and relaxed states and subjects that fufill criteria of adequate anxiety/stress scale were chosen leading to a subset of 18 subjects. Then, temporal, spectral and non linear EEG features are evaluated for being able to represent accurately states under investigation. Feature selection schemes choose the most significant of them in order to provide increased discrimination ability between relaxed and anxiety/stress states.

Visualising Three Dimensional Damage and Failure Envelopes: Implications for True Triaxial Deformation

NASA Astrophysics Data System (ADS)

Harland, S. R.; Browning, J.; Healy, D.; Meredith, P. G.; Mitchell, T. M.

2017-12-01

Ultimate failure in brittle rocks is commonly accepted to occur as a coalescence of micro-crack damage into a single failure plane. The geometry and evolution with stress of the cracks (damage) within the medium will play a role in dictating the geometry of the ultimate failure plane. Currently, the majority of experimental studies investigating damage evolution and rock failure use conventional triaxial stress states (σ1 > σ2 = σ3). Results from these tests can easily be represented on a Mohr-Coulomb plot (σn - τ), conveniently allowing the user to determine the geometry of the resultant failure plane. In reality however, stress in the subsurface is generally truly triaxial (σ1 > σ2 > σ3) and in this case, the Mohr-Coulomb failure criterion is inadequate as it incorporates no dependence on the intermediate stress (σ2), which has been shown to play an important role in controlling failure. It has recently been shown that differential stress is the key driver in initiating crack growth, regardless of the mean stress. Polyaxial failure criteria that incorporate the effect of the intermediate stress do exist and include the Modified Lade, Modified Wiebols and Cook, and the Drucker-Prager criteria. However, unlike the Mohr-Coulomb failure criterion, these polyaxial criteria do not offer any prediction of, or insight into, the geometry of the resultant failure plane. An additional downfall of all of the common conventional and polyaxial failure criteria is that they fail to describe the geometry of the damage (i.e. pre-failure microcracking) envelope with progressive stress; it is commonly assumed that the damage envelope is parallel to the ultimate brittle failure envelope. Here we use previously published polyaxial failure data for the Shirahama sandstone and Westerley granite to illustrate that the commonly used Mohr-Coulomb and polyaxial failure criteria do not sufficiently describe or capture failure or damage envelopes under true triaxial stress states. We investigate if and how Mohr-Coulomb type constructions can provide geometrical solutions to truly-triaxial problems. We look to incorporate both the intermediate stress and the differential stress as the controlling parameters in failure and examine the geometry of damage envelopes using damage onset data.

Sediment movement along the U.S. east coast continental shelf-I. Estimates of bottom stress using the Grant-Madsen model and near-bottom wave and current measurements

USGS Publications Warehouse

Lyne, V.D.; Butman, B.; Grant, W.D.

1990-01-01

Bottom stress is calculated for several long-term time-series observations, made on the U.S. east coast continental shelf during winter, using the wave-current interaction and moveable bed models of Grant and Madsen (1979, Journal of Geophysical Research, 84, 1797-1808; 1982, Journal of Geophysical Research, 87, 469-482). The wave and current measurements were obtained by means of a bottom tripod system which measured current using a Savonius rotor and vane and waves by means of a pressure sensor. The variables were burst sampled about 10% of the time. Wave energy was reasonably resolved, although aliased by wave groupiness, and wave period was accurate to 1-2 s during large storms. Errors in current speed and direction depend on the speed of the mean current relative to the wave current. In general, errors in bottom stress caused by uncertainties in measured current speed and wave characteristics were 10-20%. During storms, the bottom stress calculated using the Grant-Madsen models exceeded stress computed from conventional drag laws by a factor of about 1.5 on average and 3 or more during storm peaks. Thus, even in water as deep as 80 m, oscillatory near-bottom currents associated with surface gravity waves of period 12 s or longer will contribute substantially to bottom stress. Given that the Grant-Madsen model is correct, parameterizations of bottom stress that do not incorporate wave effects will substantially underestimate stress and sediment transport in this region of the continental shelf.

Heart rate, startle response, and intrusive trauma memories

PubMed Central

Chou, Chia-Ying; Marca, Roberto La; Steptoe, Andrew; Brewin, Chris R

2014-01-01

The current study adopted the trauma film paradigm to examine potential moderators affecting heart rate (HR) as an indicator of peritraumatic psychological states and as a predictor of intrusive memories. We replicated previous findings that perifilm HR decreases predicted the development of intrusive images and further showed this effect to be specific to images rather than thoughts, and to detail rather than gist recognition memory. Moreover, a group of individuals showing both an atypical sudden reduction in HR after a startle stimulus and higher trait dissociation was identified. Only among these individuals was lower perifilm HR found to indicate higher state dissociation, fear, and anxiety, along with reduced vividness of intrusions. The current findings emphasize how peritraumatic physiological responses relate to emotional reactions and intrusive memory. The moderating role of individual difference in stress defense style was highlighted. PMID:24397333

Stress-induced alterations in estradiol sensitivity increase risk for obesity in women.

PubMed

Michopoulos, Vasiliki

2016-11-01

The prevalence of obesity in the United States continues to rise, increasing individual vulnerability to an array of adverse health outcomes. One factor that has been implicated causally in the increased accumulation of fat and excess food intake is the activity of the limbic-hypothalamic-pituitary-adrenal (LHPA) axis in the face of relentless stressor exposure. However, translational and clinical research continues to understudy the effects sex and gonadal hormones and LHPA axis dysfunction in the etiology of obesity even though women continue to be at greater risk than men for stress-induced disorders, including depression, emotional feeding and obesity. The current review will emphasize the need for sex-specific evaluation of the relationship between stress exposure and LHPA axis activity on individual risk for obesity by summarizing data generated by animal models currently being leveraged to determine the etiology of stress-induced alterations in feeding behavior and metabolism. There exists a clear lack of translational models that have been used to study female-specific risk. One translational model of psychosocial stress exposure that has proven fruitful in elucidating potential mechanisms by which females are at increased risk for stress-induced adverse health outcomes is that of social subordination in socially housed female macaque monkeys. Data from subordinate female monkeys suggest that increased risk for emotional eating and the development of obesity in females may be due to LHPA axis-induced changes in the behavioral and physiological sensitivity of estradiol. The lack in understanding of the mechanisms underlying these alterations necessitate the need to account for the effects of sex and gonadal hormones in the rationale, design, implementation, analysis and interpretation of results in our studies of stress axis function in obesity. Doing so may lead to the identification of novel therapeutic targets with which to combat stress-induced obesity exclusively in females. Copyright © 2016 Elsevier Inc. All rights reserved.

Stress-Induced Alterations in Estradiol Sensitivity Increase Risk for Obesity in Women

PubMed Central

Michopoulos, Vasiliki

2016-01-01

The prevalence of obesity in the United States continues to rise, increasing individual vulnerability to an array of adverse health outcomes. One factor that has been implicated causally in the increased accumulation of fat and excess food intake is the activity of the limbic-hypothalamic-pituitary-adrenal (LHPA) axis in the face of relentless stressor exposure. However, translational and clinical research continues to understudy the effects sex and gonadal hormones and LHPA axis dysfunction in the etiology of obesity even though women continue to be at greater risk than men for stress-induced disorders, including depression, emotional feeding and obesity. The current review will emphasize the need for sex-specific evaluation of the relationship between stress exposure and LHPA axis activity on individual risk for obesity by summarizing data generated by animal models currently being leveraged to determine the etiology of stress-induced alterations in feeding behavior and metabolism. There exists a clear lack of translational models that have been used to study female-specific risk. One translational model of psychosocial stress exposure that has proven fruitful in elucidating potential mechanisms by which females are at increased risk for stress-induced adverse health outcomes is that of social subordination in socially housed female macaque monkeys. Data from subordinate female monkeys suggest that increased risk for emotional eating and the development of obesity in females may be due to LHPA axis-induced changes in the behavioral and physiological sensitivity of estradiol. The lack in understanding of the mechanisms underlying these alterations necessitate the need to account for the effects of sex and gonadal hormones in the rationale, design, implementation, analysis and interpretation of results in our studies of stress axis function in obesity. Doing so may lead to the identification of novel therapeutic targets with which to combat stress-induced obesity exclusively in females. PMID:27182047

Environmental History Modulates Arabidopsis Pattern-Triggered Immunity in a HISTONE ACETYLTRANSFERASE1-Dependent Manner.

PubMed

Singh, Prashant; Yekondi, Shweta; Chen, Po-Wen; Tsai, Chia-Hong; Yu, Chun-Wei; Wu, Keqiang; Zimmerli, Laurent

2014-06-01

In nature, plants are exposed to a fluctuating environment, and individuals exposed to contrasting environmental factors develop different environmental histories. Whether different environmental histories alter plant responses to a current stress remains elusive. Here, we show that environmental history modulates the plant response to microbial pathogens. Arabidopsis thaliana plants exposed to repetitive heat, cold, or salt stress were more resistant to virulent bacteria than Arabidopsis grown in a more stable environment. By contrast, long-term exposure to heat, cold, or exposure to high concentrations of NaCl did not provide enhanced protection against bacteria. Enhanced resistance occurred with priming of Arabidopsis pattern-triggered immunity (PTI)-responsive genes and the potentiation of PTI-mediated callose deposition. In repetitively stress-challenged Arabidopsis, PTI-responsive genes showed enrichment for epigenetic marks associated with transcriptional activation. Upon bacterial infection, enrichment of RNA polymerase II at primed PTI marker genes was observed in environmentally challenged Arabidopsis. Finally, repetitively stress-challenged histone acetyltransferase1-1 (hac1-1) mutants failed to demonstrate enhanced resistance to bacteria, priming of PTI, and increased open chromatin states. These findings reveal that environmental history shapes the plant response to bacteria through the development of a HAC1-dependent epigenetic mark characteristic of a primed PTI response, demonstrating a mechanistic link between the primed state in plants and epigenetics. © 2014 American Society of Plant Biologists. All rights reserved.

Heat stress responses modulate calcium regulations and electrophysiological characteristics in atrial myocytes.

PubMed

Chen, Yao-Chang; Kao, Yu-Hsun; Huang, Chun-Feng; Cheng, Chen-Chuan; Chen, Yi-Jen; Chen, Shih-Ann

2010-04-01

Heat stress-induced responses change the ionic currents and calcium homeostasis. However, the molecular insights into the heat stress responses on calcium homeostasis remain unclear. The purposes of this study were to examine the mechanisms of heat stress responses on calcium handling and electrophysiological characteristics in atrial myocytes. We used indo-1 fluorimetric ratio technique and whole-cell patch clamp to investigate the intracellular calcium, action potentials, and ionic currents in isolated rabbit single atrial cardiomyocytes with or without (control) exposure to heat stress (43 degrees C, 15 min) 5+/-1 h before experiments. The expressions of sarcoplasmic reticulum ATPase (SERCA2a), and Na(+)-Ca(2+) exchanger (NCX) in the control and heat stress-treated atrial myocytes were evaluated by Western blot and real-time PCR. As compared with control myocytes, the heat stress-treated myocytes had larger sarcoplasmic reticulum calcium content and larger intracellular calcium transient with a shorter decay portion. Heat stress-treated myocytes also had larger L-type calcium currents, transient outward potassium currents, but smaller NCX currents. Heat stress responses increased the protein expressions, SERCA2a, NCX, and heat shock protein. However, heat stress responses did not change the RNA expression of SERCA2a and NCX. In conclusion, heat stress responses change calcium handling through protein but not RNA regulation. Copyright (c) 2009 Elsevier Ltd. All rights reserved.

Stress among Secondary School Teachers in Ebonyi State, Nigeria: Suggested Interventions in the Worksite Milieu

ERIC Educational Resources Information Center

Nwimo, Ignatius O.; Onwunaka, Chinagorom

2015-01-01

The aim of the study was to determine the level of stress experienced by secondary school teachers in Ebonyi State. The dimensions of stress studied included physical stress, mental stress, emotional stress and social stress. The study adopted the cross-sectional survey design using a sample of 660 (male 259, female 401) teachers randomly drawn…

Chronic and Acute Stress Promote Overexploitation in Serial Decision Making

PubMed Central

Lenow, Jennifer K.; Constantino, Sara M.

2017-01-01

Many decisions that humans make resemble foraging problems in which a currently available, known option must be weighed against an unknown alternative option. In such foraging decisions, the quality of the overall environment can be used as a proxy for estimating the value of future unknown options against which current prospects are compared. We hypothesized that such foraging-like decisions would be characteristically sensitive to stress, a physiological response that tracks biologically relevant changes in environmental context. Specifically, we hypothesized that stress would lead to more exploitative foraging behavior. To test this, we investigated how acute and chronic stress, as measured by changes in cortisol in response to an acute stress manipulation and subjective scores on a questionnaire assessing recent chronic stress, relate to performance in a virtual sequential foraging task. We found that both types of stress bias human decision makers toward overexploiting current options relative to an optimal policy. These findings suggest a possible computational role of stress in decision making in which stress biases judgments of environmental quality. SIGNIFICANCE STATEMENT Many of the most biologically relevant decisions that we make are foraging-like decisions about whether to stay with a current option or search the environment for a potentially better one. In the current study, we found that both acute physiological and chronic subjective stress are associated with greater overexploitation or staying at current options for longer than is optimal. These results suggest a domain-general way in which stress might bias foraging decisions through changing one's appraisal of the overall quality of the environment. These novel findings not only have implications for understanding how this important class of foraging decisions might be biologically implemented, but also for understanding the computational role of stress in behavior and cognition more broadly. PMID:28483979

Understanding the impact of prior depression on stress generation: examining the roles of current depressive symptoms and interpersonal behaviours.

PubMed

Shih, Josephine H; Eberhart, Nicole K

2008-08-01

Stress generation is a process in which individuals contribute to stressful life events. While research has supported an association between current depression and stress generation, it has been noted that individuals with prior depression tend to contribute to stressors even when they are no longer experiencing a depressive episode. The aim of the study is to elucidate the pathways through which prior major depression predicts interpersonal stress generation in women. Specifically, we examined current subsyndromal depressive symptoms and problematic interpersonal behaviours as potential mediators. Fifty-one college women were followed prospectively for 6 weeks. Participants were interviewed to assess current and past depression as well as stressful life events they experienced over the 6-week period. The findings suggest that prior major depression continues to have an impact even after the episode has ended, as the disorder continues to contribute to stress generation through residual depressive symptoms.

The stress shadow induced by the 1975-1984 Krafla rifting episode

NASA Astrophysics Data System (ADS)

Maccaferri, F.; Rivalta, E.; Passarelli, L.; Jónsson, S.

2013-03-01

It has been posited that the 1975-1984 Krafla rifting episode in northern Iceland was responsible for a significant drop in the rate of earthquakes along the Húsavík-Flatey Fault (HFF), a transform fault that had previously been the source of several magnitude 6-7 earthquakes. This compelling case of the existence of a stress shadow has never been studied in detail, and the implications of such a stress shadow remain an open question. According to rate-state models, intense stress shadows cause tens of years of low seismicity rate followed by a faster recovery phase of rate increase. Here, we compare the long-term predictions from a Coulomb stress model of the rifting episode with seismological observations from the SIL catalog (1995-2011) in northern Iceland. In the analyzed time frame, we find that the rift-induced stress shadow coincides with the eastern half of the fault where the observed seismicity rates are found to be significantly lower than expected, given the historical earthquake activity there. We also find that the seismicity rates on the central part of the HFF increased significantly in the last 17 years, with the seismicity progressively recovering from west to east. Our observations confirm that rate-state theory successfully describes the long-term seismic rate variation during the reloading phase of a fault invested by a negative Coulomb stress. Coincident with this recovery, we find that the b-value of the frequency-magnitude distribution changed significantly over time. We conclude that the rift-induced stress shadow not only decreased the seismic rate on the eastern part of the HFF but also temporarily modified how the system releases seismic energy, with more large magnitude events in proportion to small ones. This behavior is currently being overturned, as rift-induced locking is now being compensated by tectonic forcing.

Understanding the atomic-level Green-Kubo stress correlation function for a liquid through phonons in a model crystal

NASA Astrophysics Data System (ADS)

Levashov, V. A.

2014-11-01

In order to gain insight into the connection between the vibrational dynamics and the atomic-level Green-Kubo stress correlation function in liquids, we consider this connection in a model crystal instead. Of course, vibrational dynamics in liquids and crystals are quite different and it is not expected that the results obtained on a model crystal should be valid for liquids. However, these considerations provide a benchmark to which the results of the previous molecular dynamics simulations can be compared. Thus, assuming that vibrations are plane waves, we derive analytical expressions for the atomic-level stress correlation functions in the classical limit and analyze them. These results provide, in particular, a recipe for analysis of the atomic-level stress correlation functions in Fourier space and extraction of the wave-vector and frequency-dependent information. We also evaluate the energies of the atomic-level stresses. The energies obtained are significantly smaller than the energies previously determined in molecular dynamics simulations of several model liquids. This result suggests that the average energies of the atomic-level stresses in liquids and glasses are largely determined by the structural disorder. We discuss this result in the context of equipartition of the atomic-level stress energies. Analysis of the previously published data suggests that it is possible to speak about configurational and vibrational contributions to the average energies of the atomic-level stresses in a glass state. However, this separation in a liquid state is problematic. We also introduce and briefly consider the atomic-level transverse current correlation function. Finally, we address the broadening of the peaks in the pair distribution function with increase of distance. We find that the peaks' broadening (by ≈40 % ) occurs due to the transverse vibrational modes, while contribution from the longitudinal modes does not change with distance.

A critical role for prefrontocortical endocannabinoid signaling in the regulation of stress and emotional behavior.

PubMed

McLaughlin, Ryan J; Hill, Matthew N; Gorzalka, Boris B

2014-05-01

The prefrontal cortex (PFC) provides executive control of the brain in humans and rodents, coordinating cognitive, emotional, and behavioral responses to threatening stimuli and subsequent feedback inhibition of the hypothalamic-pituitary-adrenal (HPA) axis. The endocannabinoid system has emerged as a fundamental regulator of HPA axis feedback inhibition and an important modulator of emotional behavior. However, the precise role of endocannabinoid signaling within the PFC with respect to stress coping and emotionality has only recently been investigated. This review discusses the current state of knowledge regarding the localization and function of the endocannabinoid system in the PFC, its sensitivity to stress and its role in modulating the neuroendocrine and behavioral responses to aversive stimuli. We propose a model whereby steady-state endocannabinoid signaling in the medial PFC indirectly regulates the outflow of pyramidal neurons by fine-tuning GABAergic inhibition. Local activation of this population of CB1 receptors increases the downstream targets of medial PFC activation, which include inhibitory interneurons in the basolateral amygdala, inhibitory relay neurons in the bed nucleus of the stria terminalis and monoamine cell bodies such as the dorsal raphe nucleus. This ultimately produces beneficial effects on emotionality (active coping responses to stress and reduced anxiety) and assists in constraining activation of the HPA axis. Under conditions of chronic stress, or in individuals suffering from mood disorders, this system may be uniquely recruited to help maintain appropriate function in the face of adversity, while breakdown of the endocannabinoid system in the medial PFC may be, in and of itself, sufficient to produce neuropsychiatric illness. Thus, we suggest that endocannabinoid signaling in the medial PFC may represent an attractive target for the treatment of stress-related disorders. Copyright © 2014 Elsevier Ltd. All rights reserved.

Alongshore Momentum Balance Over Shoreface-Connected Ridges, Fire Island, NY

NASA Astrophysics Data System (ADS)

Ofsthun, C.; Wu, X.; Voulgaris, G.; Warner, J. C.

2016-12-01

he momentum balance of alongshore flows over straight, uniform shelfs has been analyzed extensively over the last few decades. More recently, the effect of coastline curvature and how this might alter the relative significance of the momentum terms has received additional attention. In this contribution, the alongshore momentum over shelves with straight coastline, but non-uniform bathymetry is examined. Hydrodynamic and hydrographic data collected by the US Geological Survey (Fire Island Coastal Change project) on the inner shelf of Fire Island, NY over a region of shore-face connected ridges (SFCRs) are used to describe wind-induced circulation and the terms of the alongshore momentum balance equation. Analysis of the data revealed a predominantly alongshore circulation, under westward wind forcing, with localized offshore (onshore) current veering over the ridge crests (troughs). Momentum balance analysis hinted that local acceleration, advective acceleration, and bottom stress are balanced by wind stress and regional (>100 km) pressure gradient force. In addition, a numerical model using an idealized SFCR bathymetry, forced by our observed winds, was employed to compare the momentum balance relationships identified by the data and those under steady-state conditions published earlier (Warner et al., 2014). A synthesis of the numerical and experimental data revealed that the true pressure gradient force results from the sum of local pressure gradient force, which maintains a Bernoulli-like relationship with alongshore advective acceleration, and regional pressure gradient force, which maintains a strong, negative relationship with wind stress. The differences between steady-state and realistic conditions is mainly on the contributions of regional scale pressure gradients that develop under realistic conditions, and the reduced contribution of local scale pressure gradients which develop best under steady-state conditions. Our analysis indicates that current veering over ridge crests, a consistent occurrence, is a combination of a cross-shore gradient in the inconsistent relationship between local advective acceleration and pressure gradient and frictional-torque with the latter being the dominant mechanism under realistic forcing.

FEAR OF PAST ABUSIVE PARTNER(S) IMPACTS CURRENT POSTTRAUMATIC STRESS AMONG WOMEN EXPERIENCING PARTNER VIOLENCE

PubMed Central

Jaquier, Véronique; Sullivan, Tami P.

2014-01-01

This study examines the impact of fear of past abusive partner(s) on posttraumatic stress among 212 community-recruited women currently exposed to intimate partner violence (IPV). The path analysis model tested explained 60% of the variation in IPV-related posttraumatic stress. Findings revealed that fear of past abusive partner(s) was uniquely associated with the severity of current posttraumatic stress symptoms over and above the impact of current IPV or childhood abuse and neglect. Future research should continue examining women's subjective emotional experience of past and current victimization so as to further inform both clinical practice and intervention planning. PMID:24590514

Cytokine involvement in stress may depend on corticotrophin releasing factor to sensitize ethanol withdrawal anxiety

PubMed Central

Knapp, Darin J.; Whitman, Buddy A.; Wills, Tiffany A.; Angel, Robert A.; Overstreet, David H.; Criswell, Hugh E.; Ming, Zhen; Breese, George R.

2011-01-01

Stress has been shown to facilitate ethanol withdrawal-induced anxiety. Defining neurobiological mechanisms through which stress has such actions is important given the associated risk of relapse. While CRF has long been implicated in the action of stress, current results show that stress elevates the cytokine TNFα in the rat brain and thereby implicates cytokines in stress effects. In support of this view, prior TNFα microinjection into the central amygdala (CeA) of rats facilitated ethanol withdrawal-induced anxiety—a response that could not be attributed to an increase in plasma corticosterone. To test for a possible interaction between cytokines and CRF, a CRF1-receptor antagonist (SSR125543) administered prior to the repeated administration of TNFα or MCP-1/CCL2 reduced the magnitude of the withdrawal-induced anxiety. This finding provided evidence for cytokine action being dependent upon CRF. Additionally, the sensitizing effect of stress on withdrawal-induced anxiety was reduced by treating the repeated stress exposure prior to ethanol with the MEK inhibitor SL327. Consistent with cytokines having a neuromediator function distinct from a neuroimmune action, TNFα increased firing rate and GABA release from CeA neurons. Thus, an interaction of glial and neuronal function is proposed to contribute to the interaction of stress and chronic ethanol. Interrupting this potential glial-neuronal interaction could provide a novel means by which to alter the development of emotional states induced by stress that predict relapse in the alcoholic. PMID:21377524

Age, cumulative trauma and stressful life events, and post-traumatic stress symptoms among older adults in prison: do subjective impressions matter?

PubMed

Maschi, Tina; Morgen, Keith; Zgoba, Kristen; Courtney, Deborah; Ristow, Jennifer

2011-10-01

The aging prison population in the United States presents a significant public health challenge with high rates of trauma and mental health issues that the correctional system alone is ill-prepared to address. The purpose of this study was to examine the relationship of age, objective, and subjective measures of trauma and stressful life events and post-traumatic stress symptoms among older adults in prison. Data were gathered from 334 prisoners (aged 55+) housed in the New Jersey Department of Corrections, as of September 2010. An anonymous self-report, self-administered survey was mailed to the total population of 1,000 prisoners aged 55 years and older. Objective and subjective trauma was measured using the Life Stressors Checklist-Revised (LSC-R), and post-traumatic stress symptoms were measured using the Civilian Version of the Post-traumatic Stress Scale. Results of a path analysis revealed that past year subjective impressions of traumatic and stressful life events had a positive and significant relationship to current post-traumatic stress symptoms. Age was found to have a significant and inverse relationship to subjective traumatic and stressful life events. That is, younger participants reported higher levels of cumulative traumatic and stressful life events and past year subjective ratings of being bothered by these past events. These findings have significance for interdisciplinary/interprofessional practice and appropriate institutional and community care, including reentry planning of older adults in the criminal justice system.

A nonmolecular derivation of Maxwell's thermal-creep boundary condition in gases and liquids via application of the LeChatelier-Braun principle to Maxwell's thermal stress

NASA Astrophysics Data System (ADS)

Brenner, Howard

2009-05-01

According to the LeChatelier-Braun principle, when a closed quiescent system initially in an equilibrium or unstressed steady state is subjected to an externally imposed "stress" it responds in a manner tending to alleviate that stress. Use of this entropically based qualitative rule, in combination with the notion of Maxwell thermal stresses existing in nonisothermal gases and liquids, enables one to (i) derive Maxwell's thermal-creep boundary condition prevailing at the boundary between a solid and a fluid (either gas or liquid) and (ii) rationalize the phenomenon of thermophoresis in liquids, for which, in contrast with the case of gases, an elementary explanation is currently lacking. These two objectives are achieved by quantitatively interpreting the heretofore qualitative LeChatelier-Braun notion of stress in the present context as being the fluid's stress tensor, the latter including Maxwell's thermal stress. In effect, thermophoretic particle motion is interpreted as the manifestation of the fluid's attempt to expel the particle from its interior so as to alleviate the thermal stress that would otherwise ensue were the particle to remain at rest (thus obeying the traditional no slip rather than thermal-creep boundary condition) following its introduction into the previously stress-free quiescent fluid. With Kn the Knudsen number in the case of rarefied gases, Maxwell's thermal stress constitutes a noncontinuum phenomenon of O(Kn2), whereas his thermal-creep phenomenon constitutes a continuum phenomenon of O(Kn). That these two phenomena can, nevertheless, be proved to be synonymous (in the sense, so to speak, of being two sides of the same coin), as is done in the present paper, supports the "ghost effect" findings of Sone [Y. Sone, "Flows induced by temperature fields in a rarefied gas and their ghost effect on the behavior of a gas in the continuum limit," Annu. Rev. Fluid Mech 32, 779 (2000)], which, philosophically, imply the artificiality of the distinction currently existing between continuum- and noncontinuum-level phenomena.

Strain control of composite superconductors to prevent degradation of superconducting magnets due to a quench: I. Ag/Bi 2Sr 2CaCu 2O x multifilament round wires

DOE PAGES

Ye, Liyang; Li, Pei; Jaroszynski, Jan; ...

2016-12-01

The critical current of many practical superconductors is sensitive to strain, and this sensitivity is exacerbated during a quench that induces a peak local strain which can be fatal to superconducting magnets. Here, a new method is introduced to quantify the influence of the conductor stress and strain state during normal operation on the margin to degradation during a quench, as measured by the maximum allowable hot spot temperature T allowable, for composite wires within superconducting magnets. The first conductor examined is Ag-sheathed Bi 2Sr 2CaCu 2O x round wire carrying high engineering critical current density, J E, of 550more » A mm -2 at 4.2 K and 15 T. The critical axial tensile stress of this conductor is determined to be 150 MPa and, in the absence of Lorentz forces, T allowable is greater than 450 K. With increasing axial tensile stress, σ a, however, T allowable decreases nonlinearly, dropping to 280 K for σ a = 120 MPa and to 160 K for σ a = 145 MPa. T allowable(σ a) is shown to be nonlinear and independent of magnetic field from 15 to 30 T. T allowable(σ a) dictates the balance between magnetic field generation, which increases with the magnet operating current and stress, and the safety margin, which decreases with decreasing T allowable, and therefore has important engineering value. Lastly, it is also shown that T allowable(σ a) can be predicted accurately by a general strain model, showing that strain control is the key to preventing degradation of superconductors during a quench.« less

Hot-carrier degradation in deep-submicrometer nMOSFETs: lightly doped drain vs. large angle tilt implanted drain

NASA Astrophysics Data System (ADS)

Rafí, J. M.; Campabadal, F.

2001-08-01

The hot-carrier degradation of lightly doped drain (LDD) and large angle tilt implanted drain (LATID) nMOSFETs of a 0.35 μm CMOS technology is analysed and compared by means of I-V characterisation and charge pumping current measurements. LATID nMOSFETs are found to exhibit a significant improvement in terms of both, current drivability and hot-carrier immunity at maximum substrate current condition. The different factors which can be responsible for this improved hot-carrier resistance are investigated. It is shown that this must be attributed to a reduction of the maximum lateral electric field along the channel, but not to a minor generation of physical damage for a given electric field or to a reduced I-V susceptibility to a given amount of generated damage. Further to this analysis, the hot-carrier degradation comparison between LDD and LATID devices is extended to the whole range of gate-stress regimes and the effects of short electron injection (SEI) and short hole injection (SHI) phases on hot-carrier-stressed devices are analysed. Apart from a significant improved resistance to hot-carrier effects registered for LATID devices, a similar behaviour is observed for the two types of architectures. In this way, SEI phases are found to be an efficient tool for revealing part of the damage generated in stresses at low gate voltages, whereas the performance of a first SHI phase after stress at high gate bias is found to result in a significant additional degradation of the devices. This enhanced degradation is attributed to a sudden interface states build-up occurring in both, LDD and LATID devices, near the Si/spacer interface only under the first hot-hole injection condition.

Strain control of composite superconductors to prevent degradation of superconducting magnets due to a quench: I. Ag/Bi 2Sr 2CaCu 2O x multifilament round wires

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ye, Liyang; Li, Pei; Jaroszynski, Jan

The critical current of many practical superconductors is sensitive to strain, and this sensitivity is exacerbated during a quench that induces a peak local strain which can be fatal to superconducting magnets. Here, a new method is introduced to quantify the influence of the conductor stress and strain state during normal operation on the margin to degradation during a quench, as measured by the maximum allowable hot spot temperature T allowable, for composite wires within superconducting magnets. The first conductor examined is Ag-sheathed Bi 2Sr 2CaCu 2O x round wire carrying high engineering critical current density, J E, of 550more » A mm -2 at 4.2 K and 15 T. The critical axial tensile stress of this conductor is determined to be 150 MPa and, in the absence of Lorentz forces, T allowable is greater than 450 K. With increasing axial tensile stress, σ a, however, T allowable decreases nonlinearly, dropping to 280 K for σ a = 120 MPa and to 160 K for σ a = 145 MPa. T allowable(σ a) is shown to be nonlinear and independent of magnetic field from 15 to 30 T. T allowable(σ a) dictates the balance between magnetic field generation, which increases with the magnet operating current and stress, and the safety margin, which decreases with decreasing T allowable, and therefore has important engineering value. Lastly, it is also shown that T allowable(σ a) can be predicted accurately by a general strain model, showing that strain control is the key to preventing degradation of superconductors during a quench.« less

Neuroticism, social network, stressful life events: association with mood disorders, depressive symptoms and suicidal ideation in a community sample of women.

PubMed

Mandelli, Laura; Nearchou, Finiki A; Vaiopoulos, Chrysostomos; Stefanis, Costas N; Vitoratou, Silia; Serretti, Alessandro; Stefanis, Nicholas C

2015-03-30

According to the stress-diathesis hypothesis, depression and suicidal behavior may be precipitated by psychosocial stressors in vulnerable individuals. However, risk factors for mental health are often gender-specific. In the present study, we evaluated common risk factors for female depression in association with depressive symptoms and suicidal ideation in a community sample of women. The sample was composed by 415 women evaluated for mood disorders (MDs), depressive symptoms and suicidal ideation by structured interviews and the Beck depression inventory II (BDI II). All women also filled in the Eysenck personality questionnaire to evaluate neuroticism and were interviewed for social contact frequency and stressful life events (SLEs). In the whole sample, 19% of the women satisfied criteria for MD and suicidal ideation was reported by 12% of the women. Though stressful life events, especially personal and interpersonal problems, and poor social network were associated with all the outcome variables (mood disorder, depressive symptomatology and suicidal ideation), neuroticism survived to all multivariate analyses. Social network, together with neuroticism, also showed strong association with depressive severity, independently from current depressive state. Though we were unable to compare women and men, data obtained from the present study suggest that in women neurotic traits are strongly related to depression and suicidal ideation, and potentially mediate reporting of stressful life events and impaired social network. Independently from a current diagnosis of depression, impaired social network increases depressive symptoms in the women. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

Daily Stress Magnifies the Association between Cognitive Decline and Everyday Memory Problems: An Integration of Longitudinal and Diary Methods

PubMed Central

Rickenbach, Elizabeth H.; Almeida, David M.; Seeman, Teresa E.; Lachman, Margie E.

2014-01-01

We examined whether long-term fluid cognitive decline was associated with memory problems in everyday life, and whether stress plays a moderating role. We expected that the association between cognitive decline and everyday memory problems would be magnified in the context of self-reported and physiological stress. Data are from the Boston Longitudinal Study, a subsample of the Midlife in the United States study. Participants in the current study (n=112) completed a battery of tests measuring fluid cognitive functioning at Time 1 (T1) and 2 (T2) over ten years. At T2, participants completed weekly diaries of self-reported daily stressors and everyday memory problems for twelve consecutive weeks. Also at T2, participants provided four saliva samples over the course of one day to assess physiological stress using diurnal cortisol profiles [cortisol awakening response (CAR) and diurnal cortisol slope (DCS)]. Self-reported daily stressors and a less healthy DCS were associated with more everyday memory problems, and participants with greater cognitive decline reported more memory problems compared to those with less or no decline. Self-reported daily stressors and CAR moderated the relationship of cognitive decline and memory problems. As expected, more cognitive decline was associated with greater increases in memory problems on weeks when individuals reported more daily stressors and for individuals with a less healthy CAR. The current findings can inform interventions aimed to identify factors, such as daily stress, that contribute to daily functioning in the context of cognitive decline. PMID:25365691

A study of RSI under combined stresses

NASA Technical Reports Server (NTRS)

Kibler, J. J.; Rosen, B. W.

1974-01-01

The behavior of typical rigidized surface insulation material (RSI) under combined loading states was investigated. In particular, the thermal stress states induced during reentry of the space shuttle were of prime concern. A typical RSI tile was analyzed for reentry thermal stresses under computed thermal gradients for a model of the RSI material. The results of the thermal stress analyses were then used to aid in defining typical combined stress states for the failure analysis of RSI.

Bounds on internal state variables in viscoplasticity

NASA Technical Reports Server (NTRS)

Freed, Alan D.

1993-01-01

A typical viscoplastic model will introduce up to three types of internal state variables in order to properly describe transient material behavior; they are as follows: the back stress, the yield stress, and the drag strength. Different models employ different combinations of these internal variables--their selection and description of evolution being largely dependent on application and material selection. Under steady-state conditions, the internal variables cease to evolve and therefore become related to the external variables (stress and temperature) through simple functional relationships. A physically motivated hypothesis is presented that links the kinetic equation of viscoplasticity with that of creep under steady-state conditions. From this hypothesis one determines how the internal variables relate to one another at steady state, but most importantly, one obtains bounds on the magnitudes of stress and back stress, and on the yield stress and drag strength.

Current-Sheet Formation and Reconnection at a Magnetic X Line in Particle-in-Cell Simulations

NASA Technical Reports Server (NTRS)

Black, C.; Antiochos, S. K.; Hesse, M.; Karpen, J. T.; Kuznetsova, M. M.; Zenitani, S.

2011-01-01

The integration of kinetic effects into macroscopic numerical models is currently of great interest to the heliophysics community, particularly in the context of magnetic reconnection. Reconnection governs the large-scale energy release and topological rearrangement of magnetic fields in a wide variety of laboratory, heliophysical, and astrophysical systems. We are examining the formation and reconnection of current sheets in a simple, two-dimensional X-line configuration using high-resolution particle-in-cell (PIC) simulations. The initial minimum-energy, potential magnetic field is perturbed by excess thermal pressure introduced into the particle distribution function far from the X line. Subsequently, the relaxation of this added stress leads self-consistently to the development of a current sheet that reconnects for imposed stress of sufficient strength. We compare the time-dependent evolution and final state of our PIC simulations with macroscopic magnetohydrodynamic simulations assuming both uniform and localized electrical resistivities (C. R. DeVore et al., this meeting), as well as with force-free magnetic-field equilibria in which the amount of reconnection across the X line can be constrained to be zero (ideal evolution) or optimal (minimum final magnetic energy). We will discuss implications of our results for understanding magnetic-reconnection onset and cessation at kinetic scales in dynamically formed current sheets, such as those occurring in the solar corona and terrestrial magnetotail.

Stress transferred by the 1995 Mw = 6.9 Kobe, Japan, shock: Effect on aftershocks and future earthquake probabilities

USGS Publications Warehouse

Toda, S.; Stein, R.S.; Reasenberg, P.A.; Dieterich, J.H.; Yoshida, A.

1998-01-01

The Kobe earthquake struck at the edge of the densely populated Osaka-Kyoto corridor in southwest Japan. We investigate how the earthquake transferred stress to nearby faults, altering their proximity to failure and thus changing earthquake probabilities. We find that relative to the pre-Kobe seismicity, Kobe aftershocks were concentrated in regions of calculated Coulomb stress increase and less common in regions of stress decrease. We quantify this relationship by forming the spatial correlation between the seismicity rate change and the Coulomb stress change. The correlation is significant for stress changes greater than 0.2-1.0 bars (0.02-0.1 MPa), and the nonlinear dependence of seismicity rate change on stress change is compatible with a state- and rate-dependent formulation for earthquake occurrence. We extend this analysis to future mainshocks by resolving the stress changes on major faults within 100 km of Kobe and calculating the change in probability caused by these stress changes. Transient effects of the stress changes are incorporated by the state-dependent constitutive relation, which amplifies the permanent stress changes during the aftershock period. Earthquake probability framed in this manner is highly time-dependent, much more so than is assumed in current practice. Because the probabilities depend on several poorly known parameters of the major faults, we estimate uncertainties of the probabilities by Monte Carlo simulation. This enables us to include uncertainties on the elapsed time since the last earthquake, the repeat time and its variability, and the period of aftershock decay. We estimate that a calculated 3-bar (0.3-MPa) stress increase on the eastern section of the Arima-Takatsuki Tectonic Line (ATTL) near Kyoto causes fivefold increase in the 30-year probability of a subsequent large earthquake near Kyoto; a 2-bar (0.2-MPa) stress decrease on the western section of the ATTL results in a reduction in probability by a factor of 140 to 2000. The probability of a Mw = 6.9 earthquake within 50 km of Osaka during 1997-2007 is estimated to have risen from 5-6% before the Kobe earthquake to 7-11% afterward; during 1997-2027, it is estimated to have risen from 14-16% before Kobe to 16-22%.

Non-equilibrium steady states in the Klein-Gordon theory

NASA Astrophysics Data System (ADS)

Doyon, Benjamin; Lucas, Andrew; Schalm, Koenraad; Bhaseen, M. J.

2015-03-01

We construct non-equilibrium steady states in the Klein-Gordon theory in arbitrary space dimension d following a local quench. We consider the approach where two independently thermalized semi-infinite systems, with temperatures {{T}L} and {{T}R}, are connected along a d-1-dimensional hypersurface. A current-carrying steady state, described by thermally distributed modes with temperatures {{T}L} and {{T}R} for left and right-moving modes, respectively, emerges at late times. The non-equilibrium density matrix is the exponential of a non-local conserved charge. We obtain exact results for the average energy current and the complete distribution of energy current fluctuations. The latter shows that the long-time energy transfer can be described by a continuum of independent Poisson processes, for which we provide the exact weights. We further describe the full time evolution of local observables following the quench. Averages of generic local observables, including the stress-energy tensor, approach the steady state with a power-law in time, where the exponent depends on the initial conditions at the connection hypersurface. We describe boundary conditions and special operators for which the steady state is reached instantaneously on the connection hypersurface. A semiclassical analysis of freely propagating modes yields the average energy current at large distances and late times. We conclude by comparing and contrasting our findings with results for interacting theories and provide an estimate for the timescale governing the crossover to hydrodynamics. As a modification of our Klein-Gordon analysis we also include exact results for free Dirac fermions.

Normal-faulting stress state associated with low differential stress in an overriding plate in northeast Japan prior to the 2011 Mw 9.0 Tohoku earthquake

NASA Astrophysics Data System (ADS)

Otsubo, Makoto; Miyakawa, Ayumu; Imanishi, Kazutoshi

2018-03-01

Spatial and temporal variations in inland crustal stress prior to the 2011 Mw 9.0 Tohoku earthquake are investigated using focal mechanism solutions for shallow seismicity in Iwaki City, Japan. The multiple inverse method of stress tensor inversion detected two normal-faulting stress states that dominate in different regions. The stress field around Iwaki City changed from a NNW-SSE-trending triaxial extensional stress (stress regime A) to a NW-SE-trending axial tension (stress regime B) between 2005 and 2008. These stress changes may be the result of accumulated extensional stress associated with co- and post-seismic deformation due to the M7 class earthquakes. In this study we suggest that the stress state around Iwaki City prior to the 2011 Tohoku earthquake may have been extensional with a low differential stress. High pore pressure is required to cause earthquakes under such small differential stresses.

Test of nonhost angiosperm volatiles and verbenone to protect trap trees for Sirex noctilio (Hymenoptera: Siricidae) from attacks by bark beetles (Coleoptera: Scolytidae) in the Northeastern United States

Treesearch

Kevin Dodds; Daniel Miller

2010-01-01

Sirex noctilio F. (Hymenoptera: Siricidae) is an invasive woodwasp, currently established in northeastern North America. In other regions of the world, stressed trap trees are used to monitor populations of S. noctilio and to provide inoculation points for the biological control nematode Deladenus siricidicola Bedding. However, the operational use of trap trees for S....

Epidemiological Study of Mild Traumatic Brain Injury Sequelae Caused by Blast Exposure During Operations Iraqi Freedom and Enduring Freedom

DTIC Science & Technology

2013-10-01

1991), pain using both the McGill Pain Questionnaire short form (MPQ-SF) (Melzak, 1987) and the 11 point Numerical Scale (Jensen MP et al, 1989...subject above, complete standardized current state questionnaires for qualitative and quantitative measurement of: Post-concussion syndrome (PCS) using...consciousness, stress, pain , helmet wearing, shrapnel injury, tympanic membrane rupture, hearing loss, type of blast, immediate blast effects, number of

Theory of thin-walled rods

NASA Technical Reports Server (NTRS)

Goldenveizer, A L

1951-01-01

Starting with the Love equations for bending of extensible shells, "principal stress states" are sought for a thin-walled rod of arbitrary but open cross section. Principal stress states exclude those local states arising from end conditions which damp out with distance from the ends. It is found that for rods of intermediate length, long enough to avoid local bending at a support, and short enough that elementary torsion and bending are not the most significant stress states, four principal states exist. Three of these states are associated with the planar distribution of axial stress and are equivalent to the engineering theory of extension and bending of solid sections. The fourth state resembles that which has been called in the literature "bending stress due to torsional", except that cross sections are permitted to bend and the shear along the center line of the cross section is permitted to differ from zero.

Development of the NASA/FLAGRO computer program for analysis of airframe structures

NASA Technical Reports Server (NTRS)

Forman, R. G.; Shivakumar, V.; Newman, J. C., Jr.

1994-01-01

The NASA/FLAGRO (NASGRO) computer program was developed for fracture control analysis of space hardware and is currently the standard computer code in NASA, the U.S. Air Force, and the European Agency (ESA) for this purpose. The significant attributes of the NASGRO program are the numerous crack case solutions, the large materials file, the improved growth rate equation based on crack closure theory, and the user-friendly promptive input features. In support of the National Aging Aircraft Research Program (NAARP); NASGRO is being further developed to provide advanced state-of-the-art capability for damage tolerance and crack growth analysis of aircraft structural problems, including mechanical systems and engines. The project currently involves a cooperative development effort by NASA, FAA, and ESA. The primary tasks underway are the incorporation of advanced methodology for crack growth rate retardation resulting from spectrum loading and improved analysis for determining crack instability. Also, the current weight function solutions in NASGRO or nonlinear stress gradient problems are being extended to more crack cases, and the 2-d boundary integral routine for stress analysis and stress-intensity factor solutions is being extended to 3-d problems. Lastly, effort is underway to enhance the program to operate on personal computers and work stations in a Windows environment. Because of the increasing and already wide usage of NASGRO, the code offers an excellent mechanism for technology transfer for new fatigue and fracture mechanics capabilities developed within NAARP.

Temperature is a potent driver of regional forest drought stress, disturbance, and tree mortality (Invited)

NASA Astrophysics Data System (ADS)

Williams, P.; Allen, C. D.; Macalady, A.; Griffin, D.; Woodhouse, C. A.; Meko, D. M.; Swetnam, T. W.; Rauscher, S.; Seager, R.; Grissino-Mayer, H.; Dean, J.; Cook, E. R.; Gangodagamage, C.; Cai, M.; McDowell, N. G.

2013-12-01

I present a forest drought-stress index (FDSI) for the Southwestern United States using a comprehensive set of regional tree-ring records for AD 1000-2007. Comparing the last century of FDSI data to observed climate records, regional FDSI appears approximately equally influenced by warm-season atmospheric moisture demand (mostly controlled by temperature) and cold-season precipitation, together explaining an astounding 82% of southwestern FDSI variability. When atmospheric moisture demand intensifies, so does forest drought stress. Importantly, intensified moisture demand is not only associated with decreased tree growth; it is also associated with increased mortality. In particular, among a suite of drought-related climate variables, warm-season moisture demand has been the best predictor of annual forest area burned by stand-replacing wildfires since at least 1984. Further, the relationship between moisture demand and burned area is exponential, where incremental increases in moisture demand correspond to increasingly large influences on area burned. Using climate observations to update FDSI through 2013, I show that the current Southwestern drought-stress event, which began in 2000, is the most severe in over 400 years, but not as severe as those that occurred during the infamous 'Megadroughts' of AD 1000-1600. Like the Megadroughts of the past, the current drought will come to an end, but unlike the Megadroughts of the past, the current drought and those that will follow will be superimposed upon a warming-induced trend toward increased moisture demand and intensified forest drought stress, disturbance, and mortality. If atmospheric moisture demand continues increasing as projected by climate models, then mean annual Southwestern US climate by the 2050s will be less suitable for forest growth and survival than it was during the worst years of last millennium's Megadroughts. An intense La-Niña driven drought anomaly superimposed upon mean conditions in the 2050s would lead to forest drought stress, mortality, and wildfire conditions that are far more disastrous than those observed thusfar. These results foreshadow 21st-century transitions of Southwestern forests, and probably forests elsewhere, toward distributions unfamiliar to modern civilization.

Chronic Stress is Prospectively Associated with Sleep in Midlife Women: The SWAN Sleep Study.

PubMed

Hall, Martica H; Casement, Melynda D; Troxel, Wendy M; Matthews, Karen A; Bromberger, Joyce T; Kravitz, Howard M; Krafty, Robert T; Buysse, Daniel J

2015-10-01

Evaluate whether levels of upsetting life events measured over a 9-y period prospectively predict subjective and objective sleep outcomes in midlife women. Prospective cohort study. Four sites across the United States. 330 women (46-57 y of age) enrolled in the Study of Women's Health Across the Nation (SWAN) Sleep Study. N/A. Upsetting life events were assessed annually for up to 9 y. Trajectory analysis applied to life events data quantitatively identified three distinct chronic stress groups: low stress, moderate stress, and high stress. Sleep was assessed by self-report and in-home polysomnography (PSG) during the ninth year of the study. Multivariate analyses tested the prospective association between chronic stress group and sleep, adjusting for race, baseline sleep complaints, marital status, body mass index, symptoms of depression, and acute life events at the time of the Sleep Study. Women characterized by high chronic stress had lower subjective sleep quality, were more likely to report insomnia, and exhibited increased PSG-assessed wake after sleep onset (WASO) relative to women with low to moderate chronic stress profiles. The effect of chronic stress group on WASO persisted in the subsample of participants without baseline sleep complaints. Chronic stress is prospectively associated with sleep disturbance in midlife women, even after adjusting for acute stressors at the time of the sleep study and other factors known to disrupt sleep. These results are consistent with current models of stress that emphasize the cumulative effect of stressors on health over time. © 2015 Associated Professional Sleep Societies, LLC.

Perceived Stress and Coping Styles among Malay Caregivers of Children with Learning Disabilities in Kelantan

PubMed Central

Isa, Siti Nor Ismalina; Ishak, Ismarulyusda; Rahman, Azriani Ab; Saat, Nur Zakiah Mohd; Din, Normah Che; Lubis, Syarif Husin; Ismail, Muhammad Faiz Mohd

2017-01-01

Background Caregivers of children with learning disabilities have been shown to experience increased stress and greater negative caregiving consequences than those with typically developing children. There remains a lack of studies focusing on stress and coping mechanisms among caregivers of a wider age group and diagnosis of individuals with disabilities in Asian countries. The current study examines levels of perceived stress and associated child and caregiver factors among caregivers of children with learning disabilities in the Malaysian context. An additional aim was to determine whether caregiver coping styles may be predictors of perceived stress. Methods The Malay version of the Perceived Stress Scale with 10 items and the Brief COPE Scale were administered to a sample of 190 Malay caregivers of children with learning disabilities registered with community-based rehabilitation centres in Kelantan, a state in Peninsular Malaysia. Multiple linear regression analysis was applied to determine the predictors of perceived stress. Results The mean total perceived stress score of caregivers was 16.96 (SD = 4.66). The most frequently used coping styles found among caregivers included religion, acceptance and positive reframing, while substance use and behavioural disengagement were least frequently used. Higher perceived stress was significantly predicted among caregivers with fewer children, frequent use of instrumental support and behavioural disengagement coping, and lack of emotional support and religious coping. Conclusion Findings indicate that the perceived stress levels among caregivers were significantly predicted by different coping styles. It is vital to help the caregivers improve their good coping styles in order to reduce their stress levels. PMID:28381931

Music listening as a means of stress reduction in daily life.

PubMed

Linnemann, Alexandra; Ditzen, Beate; Strahler, Jana; Doerr, Johanna M; Nater, Urs M

2015-10-01

The relation between music listening and stress is inconsistently reported across studies, with the major part of studies being set in experimental settings. Furthermore, the psychobiological mechanisms for a potential stress-reducing effect remain unclear. We examined the potential stress-reducing effect of music listening in everyday life using both subjective and objective indicators of stress. Fifty-five healthy university students were examined in an ambulatory assessment study, both during a regular term week (five days) and during an examination week (five days). Participants rated their current music-listening behavior and perceived stress levels four times per day, and a sub-sample (n = 25) additionally provided saliva samples for the later analysis of cortisol and alpha-amylase on two consecutive days during both weeks. Results revealed that mere music listening was effective in reducing subjective stress levels (p = 0.010). The most profound effects were found when 'relaxation' was stated as the reason for music listening, with subsequent decreases in subjective stress levels (p ≤ 0.001) and lower cortisol concentrations (p ≤ 0.001). Alpha-amylase varied as a function of the arousal of the selected music, with energizing music increasing and relaxing music decreasing alpha-amylase activity (p = 0.025). These findings suggest that music listening can be considered a means of stress reduction in daily life, especially if it is listened to for the reason of relaxation. Furthermore, these results shed light on the physiological mechanisms underlying the stress-reducing effect of music, with music listening differentially affecting the physiological stress systems. Copyright © 2015 Elsevier Ltd. All rights reserved.

Perceived Stress and Coping Styles among Malay Caregivers of Children with Learning Disabilities in Kelantan.

PubMed

Isa, Siti Nor Ismalina; Ishak, Ismarulyusda; Rahman, Azriani Ab; Saat, Nur Zakiah Mohd; Din, Normah Che; Lubis, Syarif Husin; Ismail, Muhammad Faiz Mohd

2017-03-01

Caregivers of children with learning disabilities have been shown to experience increased stress and greater negative caregiving consequences than those with typically developing children. There remains a lack of studies focusing on stress and coping mechanisms among caregivers of a wider age group and diagnosis of individuals with disabilities in Asian countries. The current study examines levels of perceived stress and associated child and caregiver factors among caregivers of children with learning disabilities in the Malaysian context. An additional aim was to determine whether caregiver coping styles may be predictors of perceived stress. The Malay version of the Perceived Stress Scale with 10 items and the Brief COPE Scale were administered to a sample of 190 Malay caregivers of children with learning disabilities registered with community-based rehabilitation centres in Kelantan, a state in Peninsular Malaysia. Multiple linear regression analysis was applied to determine the predictors of perceived stress. The mean total perceived stress score of caregivers was 16.96 (SD = 4.66). The most frequently used coping styles found among caregivers included religion, acceptance and positive reframing, while substance use and behavioural disengagement were least frequently used. Higher perceived stress was significantly predicted among caregivers with fewer children, frequent use of instrumental support and behavioural disengagement coping, and lack of emotional support and religious coping. Findings indicate that the perceived stress levels among caregivers were significantly predicted by different coping styles. It is vital to help the caregivers improve their good coping styles in order to reduce their stress levels.

Initial Results of Accelerated Stress Testing on Single-Channel and Multichannel Drivers: Solid-State Lighting Technology Area

DOE Office of Scientific and Technical Information (OSTI.GOV)

None

This report is the first in a series of studies on accelerated stress testing (AST) of drivers used for SSL luminaires, such as downlights, troffers, and streetlights. A representative group of two-stage commercial driver products was exposed to an AST environment consisting of 75°C and 75% relative humidity (7575). These drivers were a mix of single-channel drivers (i.e., a single output current for one LED primary) and multichannel drivers (i.e., separate output currents for multiple LED primaries). This AST environment was chosen because previous testing on downlights with integrated drivers demonstrated that 38% of the sample population failed in lessmore » than 2,500 hours of testing using this method. In addition to AST test results, the performance of an SSL downlight product incorporating an integrated, multichannel driver during extended room temperature operational life (RTOL) testing is also reported. A battery of measurements was used to evaluate these products during accelerated testing, including full electrical characterization (i.e., power consumption, PF, total harmonic distortion [THD], and inrush current) and photometric characterization of external LED loads attached to the drivers (i.e., flicker performance and lumen maintenance).« less

Organelle redox autonomy during environmental stress.

PubMed

Bratt, Avishay; Rosenwasser, Shilo; Meyer, Andreas; Fluhr, Robert

2016-09-01

Oxidative stress is generated in plants because of inequalities in the rate of reactive oxygen species (ROS) generation and scavenging. The subcellular redox state under various stress conditions was assessed using the redox reporter roGFP2 targeted to chloroplastic, mitochondrial, peroxisomal and cytosolic compartments. In parallel, the vitality of the plant was measured by ion leakage. Our results revealed that during certain physiological stress conditions the changes in roGFP2 oxidation are comparable to application of high concentrations of exogenous H2 O2 . Under each stress, particular organelles were affected. Conditions of extended dark stress, or application of elicitor, impacted chiefly on the status of peroxisomal redox state. In contrast, conditions of drought or high light altered the status of mitochondrial or chloroplast redox state, respectively. Amalgamation of the results from diverse environmental stresses shows cases of organelle autonomy as well as multi-organelle oxidative change. Importantly, organelle-specific oxidation under several stresses proceeded cell death as measured by ion leakage, suggesting early roGFP oxidation as predictive of cell death. The measurement of redox state in multiple compartments enables one to look at redox state connectivity between organelles in relation to oxidative stress as well as assign a redox fingerprint to various types of stress conditions. © 2016 John Wiley & Sons Ltd.

Stressed Ge:Ga photoconductors for space-based astronomy. (Is there life beyond 120 micron)

NASA Technical Reports Server (NTRS)

Beeman, J. W.; Haller, E. E.; Hansen, W. L.; Luke, P. N.; Richards, P. L.

1989-01-01

Information is given in viewgraph form. Information is given on the characteristics of stressed Ge:Ga, a spring type stress cavity, mounting hardware, materials parameters affecting dark current, and the behavior of low dark current stressed Ge:Ga. It is concluded that detectors exist today for background-limited detection at 200 microns, that researchers are narrowing in on the significant parameters that effect dark current in stressed photoconductors, that these findings may be applied to other photoconductor materials, and that some creative problem solving for an ionizing effect reset mechanism is needed.

Long Term Analysis of Deformations in Salt Mines: Kłodawa Salt Mine Case Study, Central Poland

NASA Astrophysics Data System (ADS)

Cała, Marek; Tajduś, Antoni; Andrusikiewicz, Wacław; Kowalski, Michał; Kolano, Malwina; Stopkowicz, Agnieszka; Cyran, Katarzyna; Jakóbczyk, Joanna

2017-09-01

Located in central Poland, the Kłodawa salt dome is 26 km long and about 2 km wide. Exploitation of the dome started in 1956, currently rock salt extraction is carried out in 7 mining fields and the 12 mining levels at the depth from 322 to 625 meters below sea level (m.b.s.l.). It is planned to maintain the mining activity till 2052 and extend rock salt extraction to deeper levels. The dome is characterised by complex geological structure resulted from halokinetic and tectonic processes. Projection of the 3D numerical analysis took into account the following factors: mine working distribution within the Kłodawa mine (about 1000 rooms, 350 km of galleries), complex geological structure of the salt dome, complicated structure and geometry of mine workings and distinction in rocks mechanical properties e.g. rock salt and anhydrite. Analysis of past mine workings deformation and prediction of future rock mass behaviour was divided into four stages: building of the 3D model (state of mine workings in year 2014), model extension of the future mine workings planned for extraction in years 2015-2052, the 3D model calibration and stability analysis of all mine workings. The 3D numerical model of Kłodawa salt mine included extracted and planned mine workings in 7 mining fields and 14 mining levels (about 2000 mine workings). The dimensions of the model were 4200 m × 4700 m × 1200 m what was simulated by 33 million elements. The 3D model was calibrated on the grounds of convergence measurements and laboratory tests. Stability assessment of mine workings was based on analysis of the strength/stress ratio and vertical stress. The strength/stress ratio analysis enabled to indicate endangered area in mine workings and can be defined as the factor of safety. Mine workings in state close to collapse are indicated by the strength/stress ratio equals 1. Analysis of the vertical stress in mine workings produced the estimation of current state of stress in comparison to initial (pre-mining) conditions. The long-term deformation analysis of the Kłodawa salt mine for year 2014 revealed that stability conditions were fulfilled. Local disturbances indicated in the numerical analysis were connected with high chambers included in the mining field no 1 and complex geological structure in the vicinity of mine workings located in the mining fields no 2 and 3. Moreover, numerical simulations that projected the future extraction progress (till year 2052) showed positive performance. Local weakness zones in the mining field no 7 are associated with occurrence of carnallite layers and intensive mining which are planned in the mining field no 6 at the end of rock salt extraction.

Stress and the HPA Axis

PubMed Central

Stephens, Mary Ann C.; Wand, Gary

2012-01-01

Stress has long been suggested to be an important correlate of uncontrolled drinking and relapse. An important hormonal response system to stress—the hypothalamic–pituitary–adrenal (HPA) axis—may be involved in this process, particularly stress hormones known as glucocorticoids and primarily cortisol. The actions of this hormone system normally are tightly regulated to ensure that the body can respond quickly to stressful events and return to a normal state just as rapidly. The main determinants of HPA axis activity are genetic background, early-life environment, and current life stress. Alterations in HPA axis regulation are associated with problematic alcohol use and dependence; however, the nature of this dysregulation appears to vary with respect to stage of alcohol dependence. Much of this research has focused specifically on the role of cortisol in the risk for, development of, and relapse to chronic alcohol use. These studies found that cortisol can interact with the brain’s reward system, which may contribute to alcohol’s reinforcing effects. Cortisol also can influence a person’s cognitive processes, promoting habit-based learning, which may contribute to habit formation and risk of relapse. Finally, cortisol levels during abstinence may be useful clinical indicators of relapse vulnerability in alcohol-dependent people. PMID:23584113

Perceptions of stress, burnout, and support systems in pediatric bone marrow transplantation nursing.

PubMed

Gallagher, Regan; Gormley, Denise K

2009-12-01

Bone marrow transplantation (BMT) is used to treat various conditions, ranging from immune disorders to many types of cancer. The critical complexity of patients and the environment in which BMT nurses work can lead to stress, burnout, and, ultimately, poor retention. This study aimed to investigate nurses' perceptions of work-related stress and burnout as well as current support systems for nurses. The study included 30 BMT staff nurses from a large pediatric medical center in the midwestern United States. Critical illness or acuity of patients was reported as the most stressful factor; long work hours was the least stressful factor. Most nurses perceived moderate to high levels of emotional exhaustion, and 33% reported moderate levels of depersonalization. Fifty percent perceived high levels of personal accomplishment, despite the critical illness or acuity of their patients, demanding patient families, rotating shifts, short staffing, and caring for dying patients. Most nurses felt that support systems were in place and that staff was accessible, but most respondents were undecided about the helpfulness of the support systems. Results suggest that support systems may significantly affect work satisfaction and feelings of accomplishment for BMT nurses.

Effect of Cutting Tool Properties and Depth of Cut in Rock Cutting: An Experimental Study

NASA Astrophysics Data System (ADS)

Rostamsowlat, Iman

2018-06-01

The current paper is designed to investigate the effect of worn (blunt) polycrystalline diamond compact cutter properties on both the contact stress (σ) and friction coefficient ( μ) mobilized at the wear flat-rock interface at different inclination angles of the wear flat surface and at a wide range of depths of cut. An extensive and comprehensive set of cutting experiments is carried out on two sedimentary rocks (one limestone and one sandstone) using a state-of-the-art rock cutting equipment (Wombat) and various blunt cutters. Experiments with blunt cutters are characterized by different wear flat inclination angles (β), different wear flat surface roughness (Ra), different wear flat material, and different cutting tool velocities ({\\varvec{v}}) were conducted. The experimental results show that both the contact stress and friction coefficient are predominantly affected by the wear flat roughness at all inclination angles of the wear flat; however, the cutting tool velocity has a negligible influence on both the contact stress and friction coefficient. Further investigations suggest that the contact stress is greatly affected by the depth of cut within the plastic regime of frictional contact while the contact stress is insensitive to the depth of cut within the elastic regime.

Accidents at work in the health care - legal aspects in Poland.

PubMed

Szereda, Kamil; Szymańska, Jolanta

2016-01-01

An accident at work is a sudden event caused by external circumstances that occurred in relation to work. Referring to the current legislation, the Supreme Court judgments and the opinions contained in publications, the authors discuss the legal aspects of selected accidents: needle stick injuries, cuts with other sharp tools, heart attacks and strokes among health professionals and social workers in Poland. It has been stressed that defining rigid criteria that allow for stating unequivocal work - accidents relationships would be difficult or even impossible. Especially in the case of medical personnel the long-term and negative impact of stress on health is significant, and thus the occurrence of work accidents - heart attack or stroke. © 2016 MEDPRESS.

Biological Studies of Posttraumatic Stress Disorder

PubMed Central

Pitman, Roger K.; Rasmusson, Ann M.; Koenen, Karestan C.; Shin, Lisa M.; Orr, Scott P.; Gilbertson, Mark W.; Milad, Mohammed R.; Liberzon, Israel

2016-01-01

Preface Posttraumatic stress disorder (PTSD) is the only major mental disorder for which a cause is considered to be known, viz., an event that involves threat to the physical integrity of oneself or others and induces a response of intense fear, helplessness, or horror. Although PTSD is still largely regarded as a psychological phenomenon, over the past three decades the growth of the biological PTSD literature has been explosive, and thousands of references now exist. Ultimately, the impact of an environmental event, such as a psychological trauma, must be understood at organic, cellular, and molecular levels. The present review attempts to present the current state of this understanding, based upon psychophysiological, structural and functional neuroimaging, endocrinological, genetic, and molecular biological studies in humans and in animal models. PMID:23047775

Thermal and Electrical Effects of Partial Shade in Monolithic Thin-Film Photovoltaic Modules: Preprint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Silverman, Timothy J.; Deceglie, Michael G.; Sun, Xingshu

2015-09-02

Photovoltaic cells can be damaged by reverse bias stress, which arises during service when a monolithically integrated thin-film module is partially shaded. We introduce a model for describing a module's internal thermal and electrical state, which cannot normally be measured. Using this model and experimental measurements, we present several results with relevance for reliability testing and module engineering: Modules with a small breakdown voltage experience less stress than those with a large breakdown voltage, with some exceptions for modules having light-enhanced reverse breakdown. Masks leaving a small part of the masked cells illuminated can lead to very high temperature andmore » current density compared to masks covering entire cells.« less

Thermal and Electrical Effects of Partial Shade in Monolithic Thin-Film Photovoltaic Modules

DOE Office of Scientific and Technical Information (OSTI.GOV)

Silverman, Timothy J.; Deceglie, Michael G.; Sun, Xingshu

2015-06-14

Photovoltaic cells can be damaged by reverse bias stress, which arises during service when a monolithically integrated thin-film module is partially shaded. We introduce a model for describing a module's internal thermal and electrical state, which cannot normally be measured. Using this model and experimental measurements, we present several results with relevance for reliability testing and module engineering: Modules with a small breakdown voltage experience less stress than those with a large breakdown voltage, with some exceptions for modules having light-enhanced reverse breakdown. Masks leaving a small part of the masked cells illuminated can lead to very high temperature andmore » current density compared to masks covering entire cells.« less

Comparing crack damage evolution in rocks deformed under conventional and true triaxial loading

NASA Astrophysics Data System (ADS)

Browning, J.; Meredith, P. G.; Stuart, C.; Healy, D.; Harland, S. R.; Mitchell, T. M.

2017-12-01

The vast majority of experimental studies investigate damage evolution using conventional triaxial stress states (σ1 > σ2 = σ3, CTA), whereas in nature the stress state is generally truly triaxial (σ1 > σ2 > σ3, TTA). We present a comparative study of crack damage evolution during CTA vs. TTA stress conditions using results from measurements made on cubic samples of sandstone deformed in three orthogonal directions with independently controlled stress paths. We have measured, simultaneously with stress and strain, changes in wave velocities in the three principal directions, together with acoustic emission (AE) output. Changes in wave velocities are associated with both elastic closure and opening of pre-existing cracks, and the inelastic formation of new cracks. By contrast, AE is associated only with the inelastic growth of new crack damage. The onset of new damage is shown to be a function of differential stress regardless of the magnitude of mean stress. Hence, we show that damage can form due to a decrease in the minimum principal stress, which reduces mean stress but increases the differential stress. We find an approximately fivefold decrease in the number of AE events in the TTA case in comparison to the CTA case. In essence, we create two end-member crack distributions; one displaying cylindrical transverse isotropy and the other planar transverse isotropy. Taken together, the AE data, the velocities and the crack densities indicate that the intermediate principal stress plays a key role in suppressing the total amount of crack growth and concentrating it in planes sub-parallel to the minimum stress. However, the size of individual cracks remains constant. Hence, the differential stress at which rocks fail (i.e. strength) will be significantly higher under TTA stress (where σ2 > σ3) than under CTA stress (where σ2 = σ3). Cyclic loading tests show that while individual stress states are important, the stress path by which these stress states are reached is equally important. Whether the stress state has been `visited' before is key to determining and understanding damage states. Further damage commences only when the previous maximum differential stress is exceeded, regardless of whether this is achieved by increasing the maximum principal stress or by decreasing the minimum principal stress.

Processing of lexical stress cues by young children.

PubMed

Quam, Carolyn; Swingley, Daniel

2014-07-01

Although infants learn an impressive amount about their native-language phonological system by the end of the first year of life, after the first year children still have much to learn about how acoustic dimensions cue linguistic categories in fluent speech. The current study investigated what children have learned about how the acoustic dimension of pitch indicates the location of the stressed syllable in familiar words. Preschoolers (2.5- to 5-year-olds) and adults were tested on their ability to use lexical-stress cues to identify familiar words. Both age groups saw pictures of a bunny and a banana and heard versions of "bunny" and "banana" in which stress either was indicated normally with convergent cues (pitch, duration, amplitude, and vowel quality) or was manipulated such that only pitch differentiated the words' initial syllables. Adults (n=48) used both the convergent cues and the isolated pitch cue to identify the target words as they unfolded. Children (n=206) used the convergent stress cues but not pitch alone in identifying words. We discuss potential reasons for children's difficulty in exploiting isolated pitch cues to stress despite children's early sensitivity to pitch in language. These findings contribute to a view in which phonological development progresses toward the adult state well past infancy. Copyright © 2014 Elsevier Inc. All rights reserved.

Stress and deformation characteristics of sea ice in a high resolution numerical sea ice model.

NASA Astrophysics Data System (ADS)

Heorton, Harry; Feltham, Daniel; Tsamados, Michel

2017-04-01

The drift and deformation of sea ice floating on the polar oceans is due to the applied wind and ocean currents. The deformations of sea ice over ocean basin length scales have observable patterns; cracks and leads in satellite images and within the velocity fields generated from floe tracking. In a climate sea ice model the deformation of sea ice over ocean basin length scales is modelled using a rheology that represents the relationship between stresses and deformation within the sea ice cover. Here we investigate the link between observable deformation characteristics and the underlying internal sea ice stresses and force balance using the Los Alamos numerical sea ice climate model. In order to mimic laboratory experiments on the deformation of small cubes of sea ice we have developed an idealised square domain that tests the model response at spatial resolutions of up to 500m. We use the Elastic Anisotropic Plastic and Elastic Viscous Plastic rheologies, comparing their stability over varying resolutions and time scales. Sea ice within the domain is forced by idealised winds in order to compare the confinement of wind stresses and internal sea ice stresses. We document the characteristic deformation patterns of convergent, divergent and rotating stress states.

The Human BNST: Functional Role in Anxiety and Addiction

PubMed Central

Avery, S N; Clauss, J A; Blackford, J U

2016-01-01

The consequences of chronic stress on brain structure and function are far reaching. Whereas stress can produce short-term adaptive changes in the brain, chronic stress leads to long-term maladaptive changes that increase vulnerability to psychiatric disorders, such as anxiety and addiction. These two disorders are the most prevalent psychiatric disorders in the United States, and are typically chronic, disabling, and highly comorbid. Emerging evidence implicates a tiny brain region—the bed nucleus of the stria terminalis (BNST)—in the body's stress response and in anxiety and addiction. Rodent studies provide compelling evidence that the BNST plays a central role in sustained threat monitoring, a form of adaptive anxiety, and in the withdrawal and relapse stages of addiction; however, little is known about the role of BNST in humans. Here, we review current evidence for BNST function in humans, including evidence for a role in the production of both adaptive and maladaptive anxiety. We also review preliminary evidence of the role of BNST in addiction in humans. Together, these studies provide a foundation of knowledge about the role of BNST in adaptive anxiety and stress-related disorders. Although the field is in its infancy, future investigations of human BNST function have tremendous potential to illuminate mechanisms underlying stress-related disorders and identify novel neural targets for treatment. PMID:26105138

The Human BNST: Functional Role in Anxiety and Addiction.

PubMed

Avery, S N; Clauss, J A; Blackford, J U

2016-01-01

The consequences of chronic stress on brain structure and function are far reaching. Whereas stress can produce short-term adaptive changes in the brain, chronic stress leads to long-term maladaptive changes that increase vulnerability to psychiatric disorders, such as anxiety and addiction. These two disorders are the most prevalent psychiatric disorders in the United States, and are typically chronic, disabling, and highly comorbid. Emerging evidence implicates a tiny brain region-the bed nucleus of the stria terminalis (BNST)-in the body's stress response and in anxiety and addiction. Rodent studies provide compelling evidence that the BNST plays a central role in sustained threat monitoring, a form of adaptive anxiety, and in the withdrawal and relapse stages of addiction; however, little is known about the role of BNST in humans. Here, we review current evidence for BNST function in humans, including evidence for a role in the production of both adaptive and maladaptive anxiety. We also review preliminary evidence of the role of BNST in addiction in humans. Together, these studies provide a foundation of knowledge about the role of BNST in adaptive anxiety and stress-related disorders. Although the field is in its infancy, future investigations of human BNST function have tremendous potential to illuminate mechanisms underlying stress-related disorders and identify novel neural targets for treatment.

Stress enhances reconsolidation of declarative memory.

PubMed

Bos, Marieke G N; Schuijer, Jantien; Lodestijn, Fleur; Beckers, Tom; Kindt, Merel

2014-08-01

Retrieval of negative emotional memories is often accompanied by the experience of stress. Upon retrieval, a memory trace can temporarily return into a labile state, where it is vulnerable to change. An unresolved question is whether post-retrieval stress may affect the strength of declarative memory in humans by modulating the reconsolidation process. Here, we tested in two experiments whether post-reactivation stress may affect the strength of declarative memory in humans. In both experiments, participants were instructed to learn neutral, positive and negative words. Approximately 24h later, participants received a reminder of the word list followed by exposure to the social evaluative cold pressor task (reactivation/stress group, nexp1=20; nexp2=18) or control task (reactivation/no-stress group, nexp1=23; nexp2=18). An additional control group was solely exposed to the stress task, without memory reactivation (no-reactivation/stress group, nexp1=23; nexp2=21). The next day, memory performance was tested using a free recall and a recognition task. In the first experiment we showed that participants in the reactivation/stress group recalled more words than participants in the reactivation/no-stress and no-reactivation/stress group, irrespective of valence of the word stimuli. Furthermore, participants in the reactivation/stress group made more false recognition errors. In the second experiment we replicated our observations on the free recall task for a new set of word stimuli, but we did not find any differences in false recognition. The current findings indicate that post-reactivation stress can improve declarative memory performance by modulating the process of reconsolidation. This finding contributes to our understanding why some memories are more persistent than others. Copyright © 2014. Published by Elsevier Ltd.

Evaluation of Data Retention and Imprint Characteristics of FRAMs Under Environmental Stresses for NASA Applications

NASA Technical Reports Server (NTRS)

Sharma, Ashok K.; Teverovsky, Alexander; Dowdy, Terry W.; Hamilton, Brett

2000-01-01

A major reliability issue for all advanced nonvolatile memory (NVM) technology devices including FRAMs (Ferroelectric random access memories) is the data retention characteristics over extended period of time, under environmental stresses and exposure to total ionizing dose (TID) radiation effects. For this testing, 256 Kb FRAMs in 28-pin plastic DIPS, rated for industrial grade temperature range of -40 C to +85 C, were procured. These are two-transistor, two-capacitor (2T-2C) design FRAMs. In addition to data retention characteristics, the parts were also evaluated for imprint failures, which are defined as the failure of cells to change from a "preferred" state, where it has been for a significant period of time to an opposite state (e.g., from 1 to 0, or 0 to 1). These 256 K FRAMs were subjected to scanning acoustic microscopy (C-SAM); 1,000 temperature cycles from -65 C to +150 C; high temperature aging at 150 C, 175 C, and 200 C for 1,000 hours; highly accelerated stress test (HAST) for 500 hours; 1,000 hours of operational life test at 125 C; and total ionizing dose radiation testing. As a preconditioning, 10 K read/write cycles were performed on all devices. Interim electrical measurements were performed throughout this characterization, including special imprint testing and final electrical testing. Some failures were observed during high temperature aging test at 200 C, during HAST testing, and during 1,000 hours of operational life at 125 C. The parts passed 10 Krad exposure, but began showing power supply current increases during the dose increment from 10 Krad to 30 Krad, and at 40 Krad severe data retention and parametric failures were observed. Failures from various environmental group testing are currently being analyzed.

Evaluation of Data Retention and Imprint Characteristics of FRAMs Under Environmental Stresses for NASA Applications

NASA Technical Reports Server (NTRS)

Sharma, Asbok K.; Teverovsky, Alexander; Dowdy, Terry W.; Hamilton, Brett

2002-01-01

A major reliability issue for all advanced nonvolatile memory (NVM) technology devices including FRAMs is the data retention characteristics over extended period of time, under environmental stresses and exposure to total ionizing dose (TID) radiation effects. For this testing, 256 Kb FRAMs in 28-pin plastic DIPS, rated for industrial grade temperature range of -40 C to +85 C, were procured. These are two-transistor, two-capacitor (2T-2C) design FRAMs. In addition to data retention characteristics, the parts were also evaluated for imprint failures, which are defined as the failure of cells to change from a "preferred" state, where it has been for a significant period of time to an opposite state (e.g., from 1 to 0, or 0 to 1). These 256 K FRAMs were subjected to scanning acoustic microscopy (C-SAM); 1,000 temperature cycles from -65 C to +150 C; high temperature aging at 150 C, 175 C, and 200 C for 1,000 hours; highly accelerated stress test (HAST) for 500 hours; 1,000 hours of operational life test at 125 C; and total ionizing dose radiation testing. As a preconditioning, 10 K read/write cycles were performed on all devices. Interim electrical measurements were performed throughout this characterization, including special imprint testing and final electrical testing. Some failures were observed during high temperature aging test at 200 C, during HAST testing, and during 1,000 hours of operational life at 125 C. The parts passed 10 Krad exposure, but began showing power supply current increases during the dose increment from 10 Krad to 30 Krad, and at 40 Krad severe data retention and parametric failures were observed. Failures from various environmental group testing are currently being analyzed.

Multi-year strongest California drought from 500 m SNPP/VIIRS

NASA Astrophysics Data System (ADS)

Guo, W.; Kogan, F.

2016-12-01

Starting in 2006, the western United States was affected by a 10-year long mega-drought. Among 17 western states, California was the most severely drought-affected, especially in 2012-2015, when the area of stronger than moderate vegetation stress reached 70%. This drought had considerable impacts on California's environmental, economy and society. Currently, drought in the USA is monitored by the US Drought Monitor (USDM), which estimates drought area and intensity on an area with an effective resolution of around 30-by-30 km. California produces more than 90% of US fruits, vegetables, berries and nuts, which are grown on relatively small areas (200-500 acres, or 0.5 to 2 km²). Since most of these crops are irrigated, it is important to estimate crop conditions on the area comparable to the size of the planted crop. This paper demonstrates how the new 0.5-by-0.5 km Vegetation health (VH) technology (VH-500) developed from the data collected by the Visible Infrared Imaging Radiometer Suite (VIIRS) on the Suomi National Polar-orbiting Partnership (SNPP) satellite launched in 2011, monitors the current mega-drought in California, distinguishing drought-affected area with and without irrigation and estimating drought start/end, intensity, duration and impacts. The VH-500 method and data showed that California's vegetation was under medium-to-exceptional stress, especially in 2013 and 2014. However, in the middle of such intensive stress, in some of the 500-m areas of the Central Valley where principal crops are growing, vegetation experienced favorable conditions because some of these crops were irrigated. The VH-500 drought estimates showed general similarities with the assessed economic drought impacts (crop fallowing, employment loss and crop revenue change) in California.

The Use of Medicinal Marijuana for Posttraumatic Stress Disorder: A Review of the Current Literature.

PubMed

Yarnell, Stephanie

2015-01-01

Medicinal marijuana has already been legalized in over 23 states with more considering legalization. Despite the trend toward legalization, to date, there has been no systematic review of the existing literature for the efficacy of medicinal marijuana for many of the conditions for which it is proposed to treat. This study seeks to understand the current literature regarding the use of medicinal marijuana in the treatment of posttraumatic stress disorder (PTSD). PubMed and PsycINFO databases were searched until April 2014 for articles outlining outcomes of case files, control studies, and observational studies regarding the efficacy of medicinal marijuana in treating PTSD. Various combinations of the following search terms were used: marijuana, medicinal marijuana, cannabis, cannabinoid, PTSD, efficacy, trial, and neurobiology. Full text of each article was reviewed, and those directly addressing the question of efficacy of medicinal marijuana on PTSD symptomatology were included. Data were extracted from a total of 46 articles. Analysis revealed that most reports are correlational and observational in basis with a notable lack of randomized, controlled studies. Many of the published studies suggest a decrease in PTSD symptoms with marijuana use. Though the directionality of cannabis use and PTSD could not be fully differentiated at this time, there appears to also be a correlation between PTSD and problematic cannabis use. Despite this finding, there is a growing amount of neurobiological evidence and animal studies suggesting potential neurologically based reasons for the reported efficacy. Posttraumatic stress disorder is 1 of the approved conditions for medicinal marijuana in some states. While the literature to date is suggestive of a potential decrease in PTSD symptomatology with the use of medicinal marijuana, there is a notable lack of large-scale trials, making any final conclusions difficult to confirm at this time.

Thermography detection on the fatigue damage

NASA Astrophysics Data System (ADS)

Yang, Bing

It has always been a great temptation in finding new methods to in-situ "watch" the material fatigue-damage processes so that in-time reparations will be possible, and failures or losses can be minimized to the maximum extent. Realizing that temperature patterns may serve as fingerprints for stress-strain behaviors of materials, a state-of-art infrared (IR) thermography camera has been used to "watch" the temperature evolutions of both crystalline and amorphous materials "cycle by cycle" during fatigue experiments in the current research. The two-dimensional (2D) thermography technique records the surface-temperature evolutions of materials. Since all plastic deformations are related to heat dissipations, thermography provides an innovative method to in-situ monitor the heat-evolution processes, including plastic-deformation, mechanical-damage, and phase-transformation characteristics. With the understanding of the temperature evolutions during fatigue, thermography could provide the direct information and evidence of the stress-strain distribution, crack initiation and propagation, shear-band growth, and plastic-zone evolution, which will open up wide applications in studying the structural integrity of engineering components in service. In the current research, theoretical models combining thermodynamics and heat-conduction theory have been developed. Key issues in fatigue, such as in-situ stress-strain states, cyclic softening and hardening observations, and fatigue-life predictions, have been resolved by simply monitoring the specimen-temperature variation during fatigue. Furthermore, in-situ visulizations as well as qualitative and quantitative analyses of fatigue-damage processes, such as Luders-band evolutions, crack propagation, plastic zones, and final fracture, have been performed by thermography. As a method requiring no special sample preparation or surface contact by sensors, thermography provides an innovative and convenient method to in-situ monitor and analyze the mechanical-damage processes of materials and components.

Predictors of sports motivation among gay and bisexual men.

PubMed

Zamboni, Brian D; Crawford, Isiaah; Carrico, Adam W

2008-01-01

Athletic activities are associated with reduced levels of stress and negative mood states among heterosexuals; thus, examining this association among gay/bisexual men is warranted. The current study examined the relationship between sports motivation and mood states, self-esteem, body esteem, life satisfaction, perceptions of masculinity/femininity, and parental encouragement for athletic endeavors among 195 gay/bisexual men. The results were mixed, but suggest that sports participation among gay/bisexual men may relate to a desire to express their masculinity and maintain a positive body image. Gay/bisexual men may be more likely to participate in sports if they receive positive reinforcement from others.

A critical state model for mudrock behavior at high stress levels

NASA Astrophysics Data System (ADS)

Heidari, M.; Nikolinakou, M. A.; Flemings, P. B.

2016-12-01

Recent experimental work has documented that the compression behavior, friction angle, and lateral stress ratio (k0) of mudrocks vary over the stress range of 1 to 100 MPa. We integrate these observations into a critical state model. The internal friction angle and the slope of the compression curve are key parameters in a mudrock critical state model. Published models assume that these parameters do not depend on the stress level, and hence predict lateral stress and normalized strength ratios that do not change with the stress level. However, recent experimental data on resedimented mudrock samples from Eugene Island, Gulf of Mexico, demonstrate that all these parameters vary considerably with the stress level (Casey and Germaine, 2013; Casey et al., 2015). To represent these variations, we develop an enhanced critical state model that uses a stress-level-dependent friction angle and a curvilinear compression curve. We show that this enhanced model predicts the observed variations of the lateral stress and strength ratios. The successful performance of our model indicates that the critical state theory developed for soil can predict mudrock nonlinear behavior at high stress levels and thus can be used in modeling geologic systems. Casey, B., Germaine, J., 2013. Stress Dependence of Shear Strength in Fine-Grained Soils and Correlations with Liquid Limit. J. Geotech. Geoenviron. Eng. 139, 1709-1717. Casey, B., Germaine, J., Flemings, P.B., Fahy, B.P., 2015. Estimating horizontal stresses for mudrocks under one-dimensional compression. Mar. Pet. Geol. 65, 178-186.

Use of E-Cigarettes Among Current Smokers: Associations Among Reasons for Use, Quit Intentions, and Current Tobacco Use

PubMed Central

Blake, Kelly D.; Agunwamba, Amenah A.; Grana, Rachel A.; Wilson, Patrick M.; Ebbert, Jon O.; Okamoto, Janet; Leischow, Scott J.

2015-01-01

Introduction: Research has documented growing availability and use of e-cigarettes in the United States over the last decade. Methods: We conducted a national panel survey of current adult cigarette smokers to assess attitudes, beliefs, and behaviors relating to e-cigarette use in the United States (N = 2,254). Results: Among current cigarette smokers, 20.4% reported current use of e-cigarettes on some days and 3.7% reported daily use. Reported reasons for e-cigarette use included: quit smoking (58.4%), reduce smoking (57.9%), and reduce health risks (51.9%). No significant differences in sociodemographic characteristics between e-cigarette users and nonusers were observed. Prior quit attempts were reported more frequently among e-cigarette users (82.8%) than nonusers (74.0%). Intention to quit was reported more frequently among e-cigarette users (64.7%) than nonusers (46.8%). Smokers intending to quit were more likely to be e-cigarette users than those not intending to quit (odds ratio [OR] = 1.90, CI =1.36–2.65). Those who used e-cigarettes to try to quit smoking (OR = 2.25, CI = 1.25–4.05), reduce stress (OR = 3.66, CI = 1.11–12.09), or because they cost less (OR = 3.42, CI = 1.64–7.13) were more likely to report decreases in cigarette smoking than those who did not indicate these reasons. Smokers who reported using e-cigarettes to quit smoking (OR = 16.25, CI = 8.32–31.74) or reduce stress (OR = 4.30, CI = 1.32–14.09) were significantly more likely to report an intention to quit than those who did not indicate those reasons for using e-cigarettes. Conclusions: Nearly a quarter of smokers in our study reported e-cigarettes use, primarily motivated by intentions to quit or reduce smoking. These findings identify a clinical and public health opportunity to re-engage smokers in cessation efforts. PMID:25589678

Chronic and Acute Stress Promote Overexploitation in Serial Decision Making.

PubMed

Lenow, Jennifer K; Constantino, Sara M; Daw, Nathaniel D; Phelps, Elizabeth A

2017-06-07

Many decisions that humans make resemble foraging problems in which a currently available, known option must be weighed against an unknown alternative option. In such foraging decisions, the quality of the overall environment can be used as a proxy for estimating the value of future unknown options against which current prospects are compared. We hypothesized that such foraging-like decisions would be characteristically sensitive to stress, a physiological response that tracks biologically relevant changes in environmental context. Specifically, we hypothesized that stress would lead to more exploitative foraging behavior. To test this, we investigated how acute and chronic stress, as measured by changes in cortisol in response to an acute stress manipulation and subjective scores on a questionnaire assessing recent chronic stress, relate to performance in a virtual sequential foraging task. We found that both types of stress bias human decision makers toward overexploiting current options relative to an optimal policy. These findings suggest a possible computational role of stress in decision making in which stress biases judgments of environmental quality. SIGNIFICANCE STATEMENT Many of the most biologically relevant decisions that we make are foraging-like decisions about whether to stay with a current option or search the environment for a potentially better one. In the current study, we found that both acute physiological and chronic subjective stress are associated with greater overexploitation or staying at current options for longer than is optimal. These results suggest a domain-general way in which stress might bias foraging decisions through changing one's appraisal of the overall quality of the environment. These novel findings not only have implications for understanding how this important class of foraging decisions might be biologically implemented, but also for understanding the computational role of stress in behavior and cognition more broadly. Copyright © 2017 the authors 0270-6474/17/375681-09$15.00/0.

Endocannabinoid Signaling, Glucocorticoid-Mediated Negative Feedback and Regulation of the HPA Axis

PubMed Central

Hill, M. N.; Tasker, J. G.

2012-01-01

The hypothalamic-pituitary-adrenal (HPA) axis regulates the outflow of glucocorticoid hormones under basal conditions and in response to stress. Within the last decade, a large body of evidence has mounted indicating that the endocannabinoid system is involved in the central regulation of the stress response; however, the specific role endocannabinoid signalling plays in phases of HPA axis regulation, or the neural sites of action mediating this regulation, was not mapped out until recently. This review aims to collapse the current state of knowledge regarding the role of the endocannabinoid system in the regulation of the HPA axis to put together a working model of how and where endocannabinoids act within the brain to regulate outflow of the HPA axis. Specifically, we discuss the role of the endocannabinoid system in the regulation of the HPA axis under basal conditions, activation in response to acute stress and glucocorticoid-mediated negative feedback. Interestingly, there appears to be some anatomical specificity to the role of the endocannabinoid system in each phase of HPA axis regulation, as well as distinct roles of both anandamide and 2-arachidonoylglycerol in these phases. Ultimately, the current level of information indicates that endocannabinoid signalling acts to suppress HPA axis activity through concerted actions within the prefrontal cortex, amygdala and hypothalamus. PMID:22214537

Distribution of Reynolds stress carried by mesoscale variability in the Antarctic Circumpolar Current

NASA Technical Reports Server (NTRS)

Johnson, Thomas J.; Stewart, Robert H.; Shum, C. K.; Tapley, Byron D.

1992-01-01

Satellite altimeter data collected by the Geosat Exact Repeat Mission were used to investigate turbulent stress resulting from the variability of surface geostrophic currents in the Antarctic Circumpolar Current. The altimeter measured sea level along the subsatellite track. The variability of the along-track slope of sea level is directly proportional to the variability of surface geostrophic currents in the cross-track direction. Because the grid of crossover points is dense at high latitudes, the satellite data could be used for mapping the temporal and spatial variability of the current. Two and a half years of data were used to compute the statistical structure of the variability. The statistics included the probability distribution functions for each component of the current, the time-lagged autocorrelation functions of the variability, and the Reynolds stress produced by the variability. The results demonstrate that stress is correlated with bathymetry. In some areas the distribution of negative stress indicate that eddies contribute to an acceleration of the mean flow, strengthening the hypothesis that baroclinic instability makes important contributions to strong oceanic currents.

Analysis of residual stress state in sheet metal parts processed by single point incremental forming

NASA Astrophysics Data System (ADS)

Maaß, F.; Gies, S.; Dobecki, M.; Brömmelhoff, K.; Tekkaya, A. E.; Reimers, W.

2018-05-01

The mechanical properties of formed metal components are highly affected by the prevailing residual stress state. A selective induction of residual compressive stresses in the component, can improve the product properties such as the fatigue strength. By means of single point incremental forming (SPIF), the residual stress state can be influenced by adjusting the process parameters during the manufacturing process. To achieve a fundamental understanding of the residual stress formation caused by the SPIF process, a valid numerical process model is essential. Within the scope of this paper the significance of kinematic hardening effects on the determined residual stress state is presented based on numerical simulations. The effect of the unclamping step after the manufacturing process is also analyzed. An average deviation of the residual stress amplitudes in the clamped and unclamped condition of 18 % reveals, that the unclamping step needs to be considered to reach a high numerical prediction quality.

[Test of thermal deformation for electronic devices of high thermal reliability].

PubMed

Li, Hai-yuan; Li, Bao-ming

2002-06-01

Thermal deformation can be caused by high partial heat flux and greatly reduce thermal reliability of electronic devices. In this paper, an attempt is made to measure the thermal deformation of high power electronic devices under working condition using laser holographic interferometry with double exposure. Laser holographic interferometry is an untouched measurement with measurement precision up to micron dimension. The electronic device chosen for measurement is a type of solid state relay which is used for ignition of rockets. The output circuit of the solid state relay is made up of a MOSFET chip and the power density of the chip can reach high value. In particular situations thermal deformation and stress may significantly influence working performance of the solid state relay. The bulk deformation of the chip and its mount is estimated by number of interferential stripes on chip surface. While thermal stress and deformation can be estimated by curvature of interferential stripes on chip surface. Experimental results indicate that there are more interferential stripes on chip surface and greater flexural degree of stripes under high power. Therefore, these results reflect large out-of-plain displacement and deformed size of the chip with the increase of load current.

[Study on the current situation and influential factors of anxiety sensitivity among middle school students in Chongqing].

PubMed

Li, Qian-Qian; Zhang, Da-Jun; Guo, Lan-Ting; Feng, Zheng-Zhi; Wu, Ming-Xia

2007-09-01

To explore the status and influencing factors on anxiety sensitivity among middle school students in Chongqing. 58 classes from 12 schools were randomly selected in four administrative districts of Chongqing city. A total number of 2700 students was included for final analysis including 48.5% from junior high school and 51.5% from senior high school students with 49.2% boys and 50.8% girls. The Chinese version of the Anxiety Sensitivity Index-Revision, Adolescent Self-Rating Life Events Check List (ASLEC) and State-Trait Anxiety Inventory (STAI) were used. (1) There was no significant difference between grade groups (P = 0.49). (2) The level of girl's anxiety sensitivity was always higher than boy's (P < 0.001). (3) Data from multiple linear regression showed that the influential factors to the degree of anxiety sensitivity were: state of anxiety, trait anxiety, life events, sex, stress from learning, etc (standard coefficients of regression were 0.258, 0.163, 0.112, 0.093, 0.124, -0.096, 0.096). The major influential factors of anxiety sensitivity would include: sex, stress from learning, life events, interpersonal relationship, state of anxiety and trait anxiety.

Hydrostatic Stress Effects Incorporated Into the Analysis of the High-Strain-Rate Deformation of Polymer Matrix Composites

NASA Technical Reports Server (NTRS)

Goldberg, Robert K.; Roberts, Gary D.

2003-01-01

Procedures for modeling the effect of high strain rate on composite materials are needed for designing reliable composite engine cases that are lighter than the metal cases in current use. The types of polymer matrix composites that are likely to be used in such an application have a deformation response that is nonlinear and that varies with strain rate. The nonlinearity and strain rate dependence of the composite response is primarily due to the matrix constituent. Therefore, in developing material models to be used in the design of impact-resistant composite engine cases, the deformation of the polymer matrix must be correctly analyzed. However, unlike in metals, the nonlinear response of polymers depends on the hydrostatic stresses, which must be accounted for within an analytical model. An experimental program has been carried out through a university grant with the Ohio State University to obtain tensile and shear deformation data for a representative polymer for strain rates ranging from quasi-static to high rates of several hundred per second. This information has been used at the NASA Glenn Research Center to develop, characterize, and correlate a material model in which the strain rate dependence and nonlinearity (including hydrostatic stress effects) of the polymer are correctly analyzed. To obtain the material data, Glenn s researchers designed and fabricated test specimens of a representative toughened epoxy resin. Quasi-static tests at low strain rates and split Hopkinson bar tests at high strain rates were then conducted at the Ohio State University. The experimental data confirmed the strong effects of strain rate on both the tensile and shear deformation of the polymer. For the analytical model, Glenn researchers modified state variable constitutive equations previously used for the viscoplastic analysis of metals to allow for the analysis of the nonlinear, strain-rate-dependent polymer deformation. Specifically, we accounted for the effects of hydrostatic stresses. An important discovery in the course of this work was that the hydrostatic stress effects varied during the loading process, which needed to be accounted for within the constitutive equations. The model is characterized primarily by shear data, with tensile data used to characterize the hydrostatic stress effects.

Shinrin-Yoku (Forest Bathing) and Nature Therapy: A State-of-the-Art Review.

PubMed

Hansen, Margaret M; Jones, Reo; Tocchini, Kirsten

2017-07-28

Current literature supports the comprehensive health benefits of exposure to nature and green environments on human systems. The aim of this state-of-the-art review is to elucidate empirical research conducted on the physiological and psychological effects of Shinrin-Yoku (or Forest Bathing) in transcontinental Japan and China. Furthermore, we aim to encourage healthcare professionals to conduct longitudinal research in Western cultures regarding the clinically therapeutic effects of Shinrin-Yoku and, for healthcare providers/students to consider practicing Shinrin-Yoku to decrease undue stress and potential burnout. A thorough review was conducted to identify research published with an initial open date range and then narrowing the collection to include papers published from 2007 to 2017. Electronic databases (PubMed, PubMed Central, CINAHL, PsycINFO and Scopus) and snowball references were used to cull papers that evaluated the use of Shinrin-Yoku for various populations in diverse settings. From the 127 papers initially culled using the Boolean phrases: "Shinrin-yoku" AND/OR "forest bathing" AND/OR "nature therapy", 64 studies met the inclusion criteria and were included in this summary review and then divided into "physiological," "psychological," "sensory metrics" and "frameworks" sub-groups. Human health benefits associated with the immersion in nature continue to be currently researched. Longitudinal research, conducted worldwide, is needed to produce new evidence of the relationships associated with Shinrin-Yoku and clinical therapeutic effects. Nature therapy as a health-promotion method and potential universal health model is implicated for the reduction of reported modern-day "stress-state" and "technostress.".

State-of-technology for joining TD-NiCr sheet

NASA Technical Reports Server (NTRS)

Holko, K. H.; Moore, T. J.; Gyorgak, C. A.

1972-01-01

At the current state-of-technology there are many joining processes that can be used to make sound welds in TD-NiCr sheet. Some of these that are described in this report are electron beam welding, gas-tungsten arc welding, diffusion welding, resistance spot welding, resistance seam welding, and brazing. The strengths of the welds made by the various processes show considerable variation, especially at elevated temperatures. Most of the fusion welding processes tend to give weak welds at elevated temperatures (with the exception of fusion-type resistance spotwelds). However, solid-state welds have been made with parent metal properties. The process used for a specific application will be dictated by the specific joint requirements. In highly stressed joints at elevated temperatures, one of the solid-state processes, such as DFW, RSW (solid-state or fusion), and RSEW, offer the most promise.

Sleep Deprivation and Oxidative Stress in Animal Models: A Systematic Review

PubMed Central

Villafuerte, Gabriel; Miguel-Puga, Adán; Murillo Rodríguez, Eric; Machado, Sergio; Manjarrez, Elias; Arias-Carrión, Oscar

2015-01-01

Because the function and mechanisms of sleep are partially clear, here we applied a meta-analysis to address the issue whether sleep function includes antioxidative properties in mice and rats. Given the expansion of the knowledge in the sleep field, it is indeed ambitious to describe all mammals, or other animals, in which sleep shows an antioxidant function. However, in this paper we reviewed the current understanding from basic studies in two species to drive the hypothesis that sleep is a dynamic-resting state with antioxidative properties. We performed a systematic review of articles cited in Medline, Scopus, and Web of Science until March 2015 using the following search terms: Sleep or sleep deprivation and oxidative stress, lipid peroxidation, glutathione, nitric oxide, catalase or superoxide dismutase. We found a total of 266 studies. After inclusion and exclusion criteria, 44 articles were included, which are presented and discussed in this study. The complex relationship between sleep duration and oxidative stress is discussed. Further studies should consider molecular and genetic approaches to determine whether disrupted sleep promotes oxidative stress. PMID:25945148

[The application of ecological momentary assessment to the study of compulsive buying].

PubMed

Silbermann, Andrea; Henkel, Andreas; Müller, Astrid; de Zwaan, Martina

2008-12-01

Although compulsive buying is a disorder that has begun to receive attention from researchers in recent years, relatively little is known about the relationship between compulsive buying, mood, and daily stressful events. In our pilot study ecological momentary assessment (EMA) was used to examine the described relationships for the first time. 26 patients, who met criteria for compulsive buying, self-monitored their pathological behaviour, their momentary mood and the occurrence of stressful events four times a day on a handheld computer for a period of two weeks. On days with excessive buying behaviour patients reported significantly more daily stressful events compared to days without pathological buying. Before the buying episode patients recorded significantly more positive emotions. The most common consequence of compulsive buying was a significant decrease of positive affects. Thus the results of the current study suggest that mood states and daily stressful events are associated with compulsive buying behaviour. Although mood got worse immediately after excessive buying, this negative consequence did not reduce the frequency of pathological behaviour. This could implicate a high presence-orientation and impulsivity of the patients.

Decomposing associations between acculturation and drinking in Mexican Americans

PubMed Central

Mills, Britain A.; Caetano, Raul

2011-01-01

Background Acculturation to life in the United States is a known predictor of Hispanic drinking behavior. We compare the ability of 2 theoretical models of this effect – sociocultural theory and general stress theory – to account for associations between acculturation and drinking in a sample of Mexican Americans. Limitations of previous evaluations of these theoretical models are addressed by using a broader range of hypothesized cognitive mediators and a more direct measure of acculturative stress. In addition, we explore nonlinearities as possible underpinnings of attenuated acculturation effects among males. Methods Respondents (N = 2,595, current drinker N = 1,351) were interviewed as part of 2 recent multistage probability samples in a study of drinking behavior among Mexican Americans in the United States. The ability of norms, drinking motives, alcohol expectancies, and acculturation stress to account for relations between acculturation and drinking outcomes (volume and heavy drinking days) were assessed with a hierarchical linear regression strategy. Nonlinear trends were assessed by modeling quadratic effects of acculturation and acculturation stress on cognitive mediators and drinking outcomes. Results Consistent with previous findings, acculturation effects on drinking outcomes were stronger for females than males. Among females, only drinking motives explained acculturation associations with volume or heavy drinking days. Among males, acculturation was linked to increases in norms, and norms were positive predictors of drinking outcomes. However, adjusted effects of acculturation were non-existent or trending in a negative direction, which counter-acted this indirect normative influence. Acculturation stress did not explain positive associations between acculturation and drinking. Conclusions Stress and alcohol outcome expectancies play little role in the positive linear association between acculturation and drinking outcomes, but drinking motives appears to at least partially account for this effect. Consistent with recent reports, these results challenge stress models of linear acculturation effects on drinking outcomes and provide (partial) support for sociocultural models. Inconsistent mediation patterns – rather than nonlinearities – represented a more plausible statistical description of why acculturation-drinking associations are weakened among males. PMID:22316139

Decomposing associations between acculturation and drinking in Mexican Americans.

PubMed

Mills, Britain A; Caetano, Raul

2012-07-01

Acculturation to life in the United States is a known predictor of Hispanic drinking behavior. We compare the ability of 2 theoretical models of this effect-sociocultural theory and general stress theory-to account for associations between acculturation and drinking in a sample of Mexican Americans. Limitations of previous evaluations of these theoretical models are addressed using a broader range of hypothesized cognitive mediators and a more direct measure of acculturative stress. In addition, we explore nonlinearities as possible underpinnings of attenuated acculturation effects among men. Respondents (N = 2,595, current drinker N = 1,351) were interviewed as part of 2 recent multistage probability samples in a study of drinking behavior among Mexican Americans in the United States. The ability of norms, drinking motives, alcohol expectancies, and acculturation stress to account for relations between acculturation and drinking outcomes (volume and heavy drinking days) were assessed with a hierarchical linear regression strategy. Nonlinear trends were assessed by modeling quadratic effects of acculturation and acculturation stress on cognitive mediators and drinking outcomes. Consistent with previous findings, acculturation effects on drinking outcomes were stronger for women than men. Among women, only drinking motives explained acculturation associations with volume or heavy drinking days. Among men, acculturation was linked to increases in norms, and norms were positive predictors of drinking outcomes. However, adjusted effects of acculturation were nonexistent or trending in a negative direction, which counteracted this indirect normative influence. Acculturation stress did not explain the positive associations between acculturation and drinking. Stress and alcohol outcome expectancies play little role in the positive linear association between acculturation and drinking outcomes, but drinking motives appear to at least partially account for this effect. Consistent with recent reports, these results challenge stress models of linear acculturation effects on drinking outcomes and provide (partial) support for sociocultural models. Inconsistent mediation patterns-rather than nonlinearities-represented a more plausible statistical description of why acculturation-drinking associations are weakened among men. Copyright © 2012 by the Research Society on Alcoholism.

A Theoretical Investigation of Composite Overwrapped Pressure Vessel (COPV) Mechanics Applied to NASA Full Scale Tests

NASA Technical Reports Server (NTRS)

Greene, N.; Thesken, J. C.; Murthy, P. L. N.; Phoenix, S. L.; Palko, J.; Eldridge, J.; Sutter, J.; Saulsberry, R.; Beeson, H.

2006-01-01

A theoretical investigation of the factors controlling the stress rupture life of the National Aeronautics and Space Agency's (NASA) composite overwrapped pressure vessels (COPVs) continues. Kevlar(TradeMark) fiber overwrapped tanks are of particular concern due to their long usage and the poorly understood stress rupture process in Kevlar(TradeMark) filaments. Existing long term data show that the rupture process is a function of stress, temperature and time. However, due to the presence of a load sharing liner, the manufacturing induced residual stresses and the complex mechanical response, the state of actual fiber stress in flight hardware and test articles is not clearly known. This paper is a companion to the experimental investigation reported in [1] and develops a theoretical framework necessary to design full-scale pathfinder experiments and accurately interpret the experimentally observed deformation and failure mechanisms leading up to static burst in COPVs. The fundamental mechanical response of COPVs is described using linear elasticity and thin shell theory and discussed in comparison to existing experimental observations. These comparisons reveal discrepancies between physical data and the current analytical results and suggest that the vessel's residual stress state and the spatial stress distribution as a function of pressure may be completely different from predictions based upon existing linear elastic analyses. The 3D elasticity of transversely isotropic spherical shells demonstrates that an overly compliant transverse stiffness relative to membrane stiffness can account for some of this by shifting a thin shell problem well into the realm of thick shell response. The use of calibration procedures are demonstrated as calibrated thin shell model results and finite element results are shown to be in good agreement with the experimental results. The successes reported here have lead to continuing work with full scale testing of larger NASA COPV hardware.

The Effects of Stress State on the Strain Hardening Behaviors of TWIP Steel

NASA Astrophysics Data System (ADS)

Liu, F.; Dan, W. J.; Zhang, W. G.

2017-05-01

Twinning-Induced Plasticity (TWIP) steels have received great attention due to their excellent mechanical properties as a result of austenite twinning during straining. In this paper, the effects of stress state on the strain hardening behaviors of Fe-20Mn-1.2C TWIP steel were studied. A twinning model considering stress state was presented based on the shear-band framework, and a strain hardening model was proposed by taking dislocation mixture evolution into account. The models were verified by the experimental results of uniaxial tension, simple shear and rolling processes. The strain hardening behaviors of TWIP steel under different stress states were predicted. The results show that the stress state can improve the austenite twining and benefit the strain hardening of TWIP steel.

Tremor frequency characteristics in Parkinson's disease under resting-state and stress-state conditions.

PubMed

Lee, Hong Ji; Lee, Woong Woo; Kim, Sang Kyong; Park, Hyeyoung; Jeon, Hyo Seon; Kim, Han Byul; Jeon, Beom S; Park, Kwang Suk

2016-03-15

Tremor characteristics-amplitude and frequency components-are primary quantitative clinical factors for diagnosis and monitoring of tremors. Few studies have investigated how different patient's conditions affect tremor frequency characteristics in Parkinson's disease (PD). Here, we analyzed tremor characteristics under resting-state and stress-state conditions. Tremor was recorded using an accelerometer on the finger, under resting-state and stress-state (calculation task) conditions, during rest tremor and postural tremor. The changes of peak power, peak frequency, mean frequency, and distribution of power spectral density (PSD) of tremor were evaluated across conditions. Patients whose tremors were considered more than "mild" were selected, for both rest (n=67) and postural (n=25) tremor. Stress resulted in both greater peak powers and higher peak frequencies for rest tremor (p<0.001), but not for postural tremor. Notably, peak frequencies were concentrated around 5 Hz under stress-state condition. The distributions of PSD of tremor were symmetrical, regardless of conditions. Tremor is more evident and typical tremor characteristics, namely a lower frequency as amplitude increases, are different in stressful condition. Patient's conditions directly affect neural oscillations related to tremor frequencies. Therefore, tremor characteristics in PD should be systematically standardized across patient's conditions such as attention and stress levels. Copyright © 2016. Published by Elsevier B.V.

Stressful life events and depression symptoms: the effect of childhood emotional abuse on stress reactivity.

PubMed

Shapero, Benjamin G; Black, Shimrit K; Liu, Richard T; Klugman, Joshua; Bender, Rachel E; Abramson, Lyn Y; Alloy, Lauren B

2014-03-01

Stressful life events are associated with an increase in depressive symptoms and the onset of major depression. Importantly, research has shown that the role of stress changes over the course of depression. The present study extends the current literature by examining the effects of early life stress on emotional reactivity to current stressors. In a multiwave study (N = 281, mean age = 18.76; 68% female), we investigated the proximal changes that occur in depressive symptoms when individuals are faced with life stress and whether a history of childhood emotional abuse moderates this relationship. Results support the stress sensitivity hypothesis for early emotional abuse history. Individuals with greater childhood emotional abuse severity experienced greater increases in depressive symptoms when confronted with current dependent stressors, controlling for childhood physical and sexual abuse. This study highlights the importance of emotional abuse as an indicator for reactivity to stressful life events. © 2013 Wiley Periodicals, Inc.

Electroformed silicon nitride based light emitting memory device

NASA Astrophysics Data System (ADS)

Anutgan, Tamila; Anutgan, Mustafa; Atilgan, Ismail; Katircioglu, Bayram

2017-07-01

The resistive memory switching effect of an electroformed nanocrystal silicon nitride thin film light emitting diode (LED) is demonstrated. For this purpose, current-voltage (I-V) characteristics of the diode were systematically scanned, paying particular attention to the sequence of the measurements. It was found that when the voltage polarity was changed from reverse to forward, the previously measured reverse I-V behavior was remembered until some critical forward bias voltage. Beyond this critical voltage, the I-V curve returns to its original state instantaneously, and light emission switches from the OFF state to the ON state. The kinetics of this switching mechanism was studied for different forward bias stresses by measuring the corresponding time at which the switching occurs. Finally, the switching of resistance and light emission states was discussed via energy band structure of the electroformed LED.

Identifying psychological responses of stigmatized groups to referendums.

PubMed

Flores, Andrew R; Hatzenbuehler, Mark L; Gates, Gary J

2018-04-10

Public votes and referendums on the rights of marginalized communities are utilized in 27 states and occur with some regularity. However, research has only recently begun to examine the psychological consequences of these voter referendums for members of stigmatized groups, and a number of important questions remain regarding the internal validity and generalizability of the existing evidence. The current study advances this literature by combining survey data from a large probability-based sample conducted in 2012 [lesbian, gay, bisexual, and/or transgender (LGBT) n = 939; non-LGBT n = 31,067] with media market ad-buy data in states where marriage equality was on the ballot. Television media markets cross state boundaries, ensuring that there was an unintended group of people in 12 states who were exposed to the same-sex marriage discourse but who did not live in states with the voter referendum ("media market spillovers"). We take advantage of this unique data structure by comparing LGBT people in the media market spillovers to those residing in the same state but in nonspillover markets with no ad exposure. LGBT people are emotionally affected by these campaigns, and non-LGBT people are unaffected. LGBT people in markets with a cumulative total of 400 ads have a 34.0% greater probability of reporting stress than LGBT people not exposed to ads. Additionally, while the negative ads evoked sadness, positive ads evoked enjoyment and happiness. Thus, public votes on minority rights represent both a source of minority stress and resilience.

The off-shore Transport of China Coastal Current over Taiwan Bank in Winter

NASA Astrophysics Data System (ADS)

Liao, E.; Yan, X. H.; Oey, L. Y.; Jiang, Y.

2016-12-01

In winter, an off-shore flow of China Coastal Current can be inferred from satellite and in-situ data over the Taiwan Bank. The dynamics related to this off-shore flow have not been previously explained and are examined here using observations and model. Influenced by southward wind stress and opposing pressure gradient, currents over the Taiwan Bank can be classified into three regimes. The southward China Coastal Current flows pass the Taiwan Bank when the wind stress is stronger than a critical value which depends on the opposite pressure gradient force. The coastal current turns northward under a weak wind stress. Two opposite currents converge over the bank and a branch of the coastal current then turns into the northward warm current when these two forces are in balance. Analysis of the vorticity balance shows that the cross-isobath movement is related to a negative bottom stress curl over the Taiwan Bank. Both bottom Ekman transport and shear and curvature vorticity related to the weak bottom slope over the Taiwan Bank contribute to the bottom stress curl. Composite analyses using observations tend to support the model results.

Impact of Unconventional Energy Development using Hydraulic Fracturing on Louisiana Water Resources Availability.

NASA Astrophysics Data System (ADS)

Unruh, H. G., Sr.; Habib, E. H.; Borrok, D. M.

2017-12-01

Unconventional oil and gas extraction around United States has been deployed significantly in the recent years. The current study focuses on the impact of Hydraulic fracturing (HF) on the sustainability of water resources in Louisiana. This impact is measured by quantifying the stress for current and future scenarios of HF water use in the two-main shale plays in Louisiana, the Haynesville and Tuscaloosa. The assessment is conducted at the HUC-12 fine catchment spatial scale. Initially, sectored stress metrics were calculated for surface and groundwater, respectively, without including HF water use. Demand sectors involved in this first stress estimation are power generation, public supply, industrial, etc. Once both stress metrics were estimated with the reported water sources and uses in Louisiana corresponding to the 2010 year, several scenarios for both sources were evaluated. In the first scenario, a peak year (2011) of HF water use was added as a water demand new category into the stress calculation matrices. The results indicate that a significant variability in the calculated stress metric with and without HF is reflected only for the groundwater sector. On the other hand, surface water sector doesn't seem to be affected for the HF water use. However, this apparent abundant surface water in the catchment, the location of the wells is not always adjacent to the body of water, and then trucking or piping of water may be required. For this reason, availability of groundwater in situ is a relevant factor in terms of production cost. Additional tested scenarios consist of increasing the number of wells in both shale play locations. Existing wells scenario calculates the stress including the water use of the total number of wells that currently exist in both shale plays in a short period (one year). The other additional tested scenario consists of increase of 100% of the required number of wells to extract the expected total shale play capacity. Results of the additional scenarios follow the same pattern as the first scenario. This analysis can be useful for water management authorities to consider recycled flow-back as an alternative resource for HF water use. Additionally, a cost analysis can be developed in a future study analyzing the economic feasibility of treating and reusing the wastewater as a source in the HF process.

Illness severity, trait anxiety, cognitive impairment and heart rate variability in bipolar disorder.

PubMed

Levy, Boaz

2014-12-30

Numerous studies have documented a significant association between symptom severity and cognitive functioning in bipolar disorder (BD). These findings advanced speculations about a potential link between the physiological stress associated with illness severity and cognitive dysfunction. To explore this hypothesis, the current study employed heart rate variability (HRV) as a physiological measure that is sensitive to the effects of chronic stress, and a scale of trait anxiety for assessing a psychological condition that is correlated with hyper sympathetic arousal. Analyses indicated that BD patients with High Illness Severity reported more symptoms of trait-anxiety (i.e., State Trait Anxiety Inventory), performed more poorly on a computerized neuropsychological battery (i.e., CNS Vital Signs), and exhibited a more constricted HRV profile (i.e., lower SDNN with elevated LF/HF ratio) than patients with Low Illness Severity. Illness severity was determined by a history of psychosis, illness duration, and number of mood episodes. A third group of healthy controls (n=22) performed better on the neuropsychological battery and exhibited a healthier HRV profile than the BD groups. This study provides preliminary evidence that illness severity and cognitive impairment in BD may be associated with state anxiety and neuro-cardiac alterations that are sensitive to physiological stress. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

Metabolic Profiling in Association with Vascular Endothelial Cell Dysfunction Following Non-Toxic Cadmium Exposure

PubMed Central

Li, Xiaofei; Nong, Qingjiao; Mao, Baoyu; Pan, Xue

2017-01-01

This study aimed to determine the metabolic profile of non-toxic cadmium (Cd)-induced dysfunctional endothelial cells using human umbilical vein endothelial cells (HUVECs). HUVECs (n = 6 per group) were treated with 0, 1, 5, or 10 μM cadmium chloride (CdCl2) for 48 h. Cell phenotypes, including nitric oxide (NO) production, the inflammatory response, and oxidative stress, were evaluated in Cd-exposed and control HUVECs. Cd-exposed and control HUVECs were analysed using gas chromatography time-of-flight/mass spectrometry. Compared to control HUVECs, Cd-exposed HUVECs were dysfunctional, exhibiting decreased NO production, a proinflammatory state, and non-significant oxidative stress. Further metabolic profiling revealed 24 significantly-altered metabolites in the dysfunctional endothelial cells. The significantly-altered metabolites were involved in the impaired tricarboxylic acid (TCA) cycle, activated pyruvate metabolism, up-regulated glucogenic amino acid metabolism, and increased pyrimidine metabolism. The current metabolic findings further suggest that the metabolic changes linked to TCA cycle dysfunction, glycosylation of the hexosamine biosynthesis pathway (HBP), and compensatory responses to genomic instability and energy deficiency may be generally associated with dysfunctional phenotypes, characterized by decreased NO production, a proinflammatory state, and non-significant oxidative stress, in endothelial cells following non-toxic Cd exposure. PMID:28872622

Delineation of tectonic provinces of New York state as a component of seismic-hazard evaluation

USGS Publications Warehouse

Fakundiny, R.H.

2004-01-01

Seismic-hazard evaluations in the eastern United States must be based on interpretations of the composition and form of Proterozoic basement-rock terranes and overlying Paleozoic strata, and on factors that can cause relative movements among their units, rather than Phanerozoic orogenic structures, which may be independent of modern tectonics. The tectonic-province concept is a major part of both probabilistic and deterministic seismic-hazard evaluations, yet those that have been proposed to date have not attempted to geographically correlate modern earthquakes with regional basement structure. Comparison of basement terrane (megablock) boundaries with the spatial pattern of modern seismicity may lead to the mechanically sound definition of tectonic provinces, and thus, better seismic-hazard evaluation capability than is currently available. Delineation of megablock boundaries will require research on the many factors that affect their structure and movement. This paper discusses and groups these factors into two broad categories-megablock tectonics in relation to seismicity and regional horizontal-compressive stresses, with megablock tectonics divided into subcategories of basement, overlying strata, regional lineaments, basement tectonic terranes, earthquake epicenter distribution, and epeirogeny, and compressive stresses divided into pop-ups and the contemporary maximum horizontal-compressive stress field. A list presenting four to nine proposed research topics for each of these categories is given at the end.

A cell-centered Lagrangian finite volume approach for computing elasto-plastic response of solids in cylindrical axisymmetric geometries

NASA Astrophysics Data System (ADS)

Sambasivan, Shiv Kumar; Shashkov, Mikhail J.; Burton, Donald E.

2013-03-01

A finite volume cell-centered Lagrangian formulation is presented for solving large deformation problems in cylindrical axisymmetric geometries. Since solid materials can sustain significant shear deformation, evolution equations for stress and strain fields are solved in addition to mass, momentum and energy conservation laws. The total strain-rate realized in the material is split into an elastic and plastic response. The elastic and plastic components in turn are modeled using hypo-elastic theory. In accordance with the hypo-elastic model, a predictor-corrector algorithm is employed for evolving the deviatoric component of the stress tensor. A trial elastic deviatoric stress state is obtained by integrating a rate equation, cast in the form of an objective (Jaumann) derivative, based on Hooke's law. The dilatational response of the material is modeled using an equation of state of the Mie-Grüneisen form. The plastic deformation is accounted for via an iterative radial return algorithm constructed from the J2 von Mises yield condition. Several benchmark example problems with non-linear strain hardening and thermal softening yield models are presented. Extensive comparisons with representative Eulerian and Lagrangian hydrocodes in addition to analytical and experimental results are made to validate the current approach.

Few Like it Hot: Coral Reef Reponses to Elevated Temperatures and CO2

NASA Astrophysics Data System (ADS)

Eakin, C. M.; Gledhill, D. K.; Heron, S. F.; Skirving, W.; Christensen, T.; Morgan, J.; Liu, G.; Strong, A. E.

2007-12-01

Coral reefs live within a fairly narrow envelope of environmental conditions constrained by water temperatures, light, salinity, nutrients, bathymetry and the aragonite saturation state of seawater. As documented in numerous studies, the world's coral reefs are "in crisis" as a result of human impacts on their environment. While local stresses currently dominate, coral reefs are increasingly confronted with global-scale changes due to rising greenhouse gas concentrations. These changes are rapidly modifying the environmental envelope of coral reefs through both increased thermal stress and ocean acidification. In the former case, there is a well-documented relationship between thermal stress and the response of corals that include coral bleaching, disease, and mortality. Clear tolerance thresholds exist beyond which high temperature and accumulated thermal stress have deleterious effects. However, the synergistic effects of increasing temperature and ocean acidification are not yet fully understood. At this time, there is mounting concern that decreasing pH and aragonite saturation state will cause net reef accretion to cease or become negative. The threshold at which this could occur is likely to be reached much sooner than the pH drop necessary to induce carbonate dissolution. Both the thermal and chemical limits that control coral survival and reef growth will likely be passed before 2100 assuming even conservative projections reported in the 4th Assessment Report of the Intergovernmental Panel on Climate Change. This talk will discuss these thresholds and their ramifications for ecosystems and resource management.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chauhan, Aditya; Patel, Satyanarayan; Vaish, Rahul, E-mail: rahul@iitmandi.ac.in

With the advent of modern power electronics, embedded circuits and non-conventional energy harvesting, the need for high performance capacitors is bound to become indispensible. The current state-of-art employs ferroelectric ceramics and linear dielectrics for solid state capacitance. However, lead-free ferroelectric ceramics propose to offer significant improvement in the field of electrical energy storage owing to their high discharge efficiency and energy storage density. In this regards, the authors have investigated the effects of compressive stress as a means of improving the energy storage density of lead-free ferroelectric ceramics. The energy storage density of 0.91(Bi{sub 0.5}Na{sub 0.5})TiO{sub 3}-0.07BaTiO{sub 3}-0.02(K{sub 0.5}Na{sub 0.5})NbO{submore » 3} ferroelectric bulk ceramic was analyzed as a function of varying levels of compressive stress and operational temperature .It was observed that a peak energy density of 387 mJ.cm{sup -3} was obtained at 100 MPa applied stress (25{sup o}C). While a maximum energy density of 568 mJ.cm{sup -3} was obtained for the same stress at 80{sup o}C. These values are indicative of a significant, 25% and 84%, improvement in the value of stored energy compared to an unloaded material. Additionally, material's discharge efficiency has also been discussed as a function of operational parameters. The observed phenomenon has been explained on the basis of field induced structural transition and competitive domain switching theory.« less

Plio-Quaternary stress states in NE Iran: Kopeh Dagh and Allah Dagh-Binalud mountain ranges

NASA Astrophysics Data System (ADS)

Shabanian, Esmaeil; Bellier, Olivier; Abbassi, Mohammad R.; Siame, Lionel; Farbod, Yassaman

2010-01-01

NE Iran, including the Kopeh Dagh and Allah Dagh-Binalud deformation domains, comprises the northeastern boundary of the Arabia-Eurasia collision zone. This study focuses on the evolution of the Plio-Quaternary tectonic regimes of northeast Iran. We present evidence for drastic temporal changes in the stress state by inversion of both geologically and seismically determined fault slip vectors. The inversions of fault kinematics data reveal distinct temporal changes in states of stress during the Plio-Quaternary (since ˜ 5 Ma). The paleostress state is characterized by a regional transpressional tectonic regime with a mean N140 ± 10°E trending horizontal maximum stress axis ( σ1). The youngest (modern) state of stress shows two distinct strike-slip and compressional tectonic regimes with a regional mean of N030 ± 15°E trending horizontal σ1. The change from the paleostress to modern stress states has occurred through an intermediate stress field characterized by a mean regional N trending σ1. The inversion analysis of earthquake focal mechanisms reveals a homogeneous, transpressional tectonic regime with a regional N023 ± 5°E trending σ1. The modern stress state, deduced from the youngest fault kinematics data, is in close agreement with the present-day stress state given by the inversions of earthquake focal mechanisms. According to our data and the deduced results, in northeast Iran, the Arabia-Eurasia convergence is taken up by strike-slip faulting along NE trending left-lateral and NNW trending right-lateral faults, as well as reverse to oblique-slip reverse faulting along NW trending faults. Such a structural assemblage is involved in a mechanically compatible and homogeneous modern stress field. This implies that no strain and/or stress partitioning or systematic block rotations have occurred in the Kopeh Dagh and Allah Dagh-Binalud deformation domains. The Plio-Quaternary stress changes documented in this paper call into question the extrapolation of the present-day seismic and GPS-derived deformation rates over geological time intervals encompassing tens of millions of years.

On stress-state optimization in steel-concrete composite structures

NASA Astrophysics Data System (ADS)

Brauns, J.; Skadins, U.

2017-10-01

The plastic resistance of a concrete-filled column commonly is given as a sum of the components and taking into account the effect of confinement. The stress state in a composite column is determined by taking into account the non-linear relationship of modulus of elasticity and Poisson’s ratio on the stress level in the concrete core. The effect of confinement occurs at a high stress level when structural steel acts in tension and concrete in lateral compression. The stress state of a composite beam is determined taking into account non-linear dependence on the position of neutral axis. In order to improve the stress state of a composite element and increase the safety of the construction the appropriate strength of steel and concrete has to be applied. The safety of high-stressed composite structures can be achieved by using high-performance concrete (HPC). In this study stress analysis of the composite column and beam is performed with the purpose of obtaining the maximum load-bearing capacity and enhance the safety of the structure by using components with the appropriate strength and by taking into account the composite action. The effect of HPC on the stress state and load carrying capacity of composite elements is analysed.

Disruption of Fatty Acid Amide Hydrolase Activity Prevents the Effects of Chronic Stress on Anxiety and Amygdalar Microstructure

PubMed Central

Hill, Matthew N.; Kumar, Shobha Anil; Filipski, Sarah B.; Iverson, Moriah; Stuhr, Kara L.; Keith, John M.; Cravatt, Benjamin F.; Hillard, Cecilia J.; Chattarji, Sumantra; McEwen, Bruce S.

2014-01-01

Hyperactivation of the amygdala following chronic stress is believed to be one of the primary mechanisms underlying the increased propensity for anxiety-like behaviors and pathological states; however, the mechanisms by which chronic stress modulates amygdalar function are not well characterized. The aim of the current study was to determine the extent to which the endocannabinoid system, which is known to regulate emotional behavior and neuroplasticity, contributes to changes in amygdalar structure and function following chronic stress. To examine the hypothesis, we have exposed C57/Bl6 mice to chronic restraint stress which results in an increase in fatty acid amide hydrolase (FAAH) activity and a reduction in the concentration of the endocannabinoid N-arachidonylethanolamine (AEA) within the amygdala. Chronic restraint stress also increased dendritic arborization, complexity and spine density of pyramidal neurons in the basolateral nucleus of the amygdala (BLA) and increased anxiety-like behavior in wild-type mice. All of the stress-induced changes in amygdalar structure and function were absent in mice deficient in FAAH. Further, the anti-anxiety effect of FAAH deletion was recapitulated in rats treated orally with a novel pharmacological inhibitor of FAAH, JNJ5003 (50 mg/kg/day), during exposure to chronic stress. These studies suggest that FAAH is required for chronic stress to induce hyperactivity and structural remodeling of the amygdala. Collectively, these studies indicate that FAAH-mediated decreases in AEA occur following chronic stress and that this loss of AEA signaling is functionally relevant to the effects of chronic stress. These data support the hypothesis that inhibition of FAAH has therapeutic potential in the treatment of anxiety disorders, possibly by maintaining normal amygdalar function in the face of chronic stress. PMID:22776900

Development of novel ash hybrids to introgress resistance to emerald ash borer into north American ash species

Treesearch

Jennifer L. Koch; David W. Carey; Mary E. Mason

2008-01-01

Currently, there is no evidence that any of the native North American ash species have any resistance to the emerald ash borer (EAB). This means that the entire ash resource of the eastern United States and Canada is at risk of loss due to EAB. In contrast, outbreaks of EAB in Asian ash species are rare and appear to be isolated responses to stress (Bauer et al. 2005,...

Efficiency degradation behaviors of current/thermal co-stressed GaN-based blue light emitting diodes with vertical-structure

NASA Astrophysics Data System (ADS)

Liu, Lilin; Ling, Minjie; Yang, Jianfu; Xiong, Wang; Jia, Weiqing; Wang, Gang

2012-05-01

With this work, we demonstrate a three-stage degradation behavior of GaN based LED chips under current/thermal co-stressing. The three stages in sequence are the initial improvement stage, the platform stage, and the rapid degradation stage, indicating that current/thermal co-stressing activates positive effects and negative ones simultaneously, and the dominant degradation mechanisms evolve with aging time. Degradation mechanisms are discussed. Electric current stress has dual characters: damaging the active layers by generating defects and at the same time improving the p-type conductivity by activating the Mg-dopant. High temperature stresses will promote the effects from electric current stresses. The activation of the Mg-dopant will saturate, whereas the generation of defects is carried on in a progressive way. Other mechanisms, such as deterioration of ohmic contacts, also operate. These mechanisms compete/cooperate with each other and evolve with aging time, resulting in the observed three-stage degradation behavior. There exist risks to predict the lifetime of LEDs by a model with a constant accelerated factor.

Long-term strength of metals in complex stress state (a survey)

NASA Astrophysics Data System (ADS)

Lokoshchenko, A. M.

2012-05-01

An analytic survey of experimental data and theoretical approaches characterizing the long-term strength of metals in complex stress state is given. In Sections 2 and 3, the results of plane stress tests (with opposite and equal signs of the nonzero principal stresses, respectively) are analyzed. In Section 4, the results of inhomogeneous stress tests (thick-walled tubes under the action of internal pressures and tensile forces) are considered. All known experimental data (35 test series) are analyzed by a criterion approach. An equivalent stress σ e is introduced as a characteristic of the stress state. Attention is mainly paid to the dependence of σ e on the principal stresses. Statistical methods are used to obtain an expression for σ e, which can be used to study various types of the complex stress state. It is shown that for the long-term strength criterion one can use the power or power-fractional dependence of the time to rupture on the equivalent stress. The methods proposed to describe the test results give a good correspondence between the experimental and theoretical values of the time to rupture. In Section 5, the possibilities of complicating the expressions for σ e by using additional material constants are considered.

Gum chewing modulates heart rate variability under noise stress.

PubMed

Ekuni, Daisuke; Tomofuji, Takaaki; Takeuchi, Noriko; Morita, Manabu

2012-12-01

Gum chewing may relieve stress, although this hypothesis has not been proven. Heart-rate variability (HRV) is commonly used to measure stress levels. However, it is not known if gum chewing modulates HRV under acute stress. The aim of this study was to investigate the effects of gum chewing on HRV under acute stress. A cross-over study involving 47 non-smoking healthy subjects, aged 22-27 years, was carried out. The subjects received a stress procedure with gum chewing (GS group) and without gum chewing (S group). Additionally, the other 20 subjects were allocated to the gum chewing without stress group (G group). The GS and S groups were exposed to noise for 5 min (75 dBA) as stress. Before and after stress exposure/gum chewing, participants completed the state portion of the State-Trait Anxiety Inventory (STAI-s) and a single Stress Visual Analogue Scale (VAS) measurement. HRV measurement was performed before and during stress/gum chewing for 5 min. After the stress procedure, VAS score significantly increased in the GS and S groups. During the stress procedure, the GS group showed a significantly lower level of high frequency (HF) and higher levels of low frequency (LF) and LF/HF than the S group. However, there were no significant differences in the scores of the state portion of the State-Trait Anxiety Inventory (STAI-s) and VAS between the two stress groups. These findings suggest that gum chewing modulates HRV, but may not relieve acute stress caused by noise.

An approach to an acute emotional stress reference scale.

PubMed

Garzon-Rey, J M; Arza, A; de-la-Camara, C; Lobo, A; Armario, A; Aguilo, J

2017-06-16

The clinical diagnosis aims to identify the degree of affectation of the psycho-physical state of the patient as a guide to therapeutic intervention. In stress, the lack of a measurement tool based on a reference makes it difficult to quantitatively assess this degree of affectation. To define and perform a primary assessment of a standard reference in order to measure acute emotional stress from the markers identified as indicators of the degree. Psychometric tests and biochemical variables are, in general, the most accepted stress measurements by the scientific community. Each one of them probably responds to different and complementary processes related to the reaction to a stress stimulus. The reference that is proposed is a weighted mean of these indicators by assigning them relative weights in accordance with a principal components analysis. An experimental study was conducted on 40 healthy young people subjected to the psychosocial stress stimulus of the Trier Social Stress Test in order to perform a primary assessment and consistency check of the proposed reference. The proposed scale clearly differentiates between the induced relax and stress states. Accepting the subjectivity of the definition and the lack of a subsequent validation with new experimental data, the proposed standard differentiates between a relax state and an emotional stress state triggered by a moderate stress stimulus, as it is the Trier Social Stress Test. The scale is robust. Although the variations in the percentage composition slightly affect the score, but they do not affect the valid differentiation between states.

Subgenual anterior cingulate-insula resting-state connectivity as a neural correlate to trait and state stress resilience.

PubMed

Shao, Robin; Lau, Way K W; Leung, Mei-Kei; Lee, Tatia M C

2018-07-01

Accumulating evidence indicates important roles of the subgenual anterior cingulate cortex and rostral limbic regions such as the anterior insula, in regulating stress-related affective responses and negative affect states in general. However, research is lacking in simultaneously assessing the inter-relations between trait and state affective responses to stress, and the functional connectivity between the subgenual anterior cingulate and anterior insula. This preliminary research involved matched healthy participants with high (N = 10) and low (N = 10) self-reported trait stress resilience, and assessed their affective and subgenual anterior cingulate-anterior insula resting-state functional connectivity patterns before and after a psychosocial stress task. We found that while the low-resilience group displayed higher trait negative affect and perceived greater task-related stress, only the high-resilience group showed increase of negative affect, along with greater decrease of left subgenual anterior cingulate-right anterior insula connectivity, following stress induction. Moreover, the functional connectivity change mediated group difference in affect change following stress task. We speculate that the contingent increase of negative affect, and the associated temporary decoupling of subgenual anterior cingulate-insula circuitry, may represent a normative and adaptive stress response underpinned by adaptive and dynamic interplay between the default mode and salience networks. Such findings, if consolidated, have important implications for promoting stress resilience and reducing risk for stress-related affective disorders. Copyright © 2018. Published by Elsevier Inc.

Electromechanical Apparatus Measures Residual Stress

NASA Technical Reports Server (NTRS)

Chern, Engmin J.; Flom, Yury

1993-01-01

Nondestructive test exploits relationship between stress and eddy-current-probe resistance. Yields data on residual stress or strain in metal tension/compression specimen (stress or strain remaining in specimen when no stress applied from without). Apparatus is assembly of commercial equipment: tension-or-compression testing machine, eddy-current probe, impedance gain-and-phase analyzer measuring impedance of probe coil, and desktop computer, which controls other equipment and processes data received from impedance gain-and-phase analyzer.

Prenatal Stress, Prematurity, and Asthma.

PubMed

Medsker, Brock; Forno, Erick; Simhan, Hyagriv; Celedón, Juan C

2015-12-01

Asthma is the most common chronic disease of childhood, affecting millions of children in the United States and worldwide. Prematurity is a risk factor for asthma, and certain ethnic or racial minorities such as Puerto Ricans and non-Hispanic blacks are disproportionately affected by both prematurity and asthma. In this review, we examine current evidence to support maternal psychosocial stress as a putative link between prematurity and asthma, while also focusing on disruption of the hypothalamic-pituitary-adrenal (HPA) axis and immune responses as potential underlying mechanisms for stress-induced "premature asthma." Prenatal stress may cause not only abnormalities in the HPA axis but also epigenetic changes in the fetal glucocorticoid receptor gene (NR3C1), leading to impaired glucocorticoid metabolism. Moreover, maternal stress can alter fetal cytokine balance, favoring TH2 (allergic) immune responses characteristic of atopic asthma: interleukin 6 (IL-6), which has been associated with premature labor, can promote TH2 responses by stimulating production of IL-4 and IL-13. Given a link among stress, prematurity, and asthma, future research should include birth cohorts aimed at confirming and better characterizing "premature asthma." If confirmed, clinical trials of prenatal maternal stress reduction would be warranted to reduce the burden of these common comorbidities. While awaiting the results of such studies, sound policies to prevent domestic and community violence (eg, from firearms) are justified, not only by public safety but also by growing evidence of detrimental effects of violence-induced stress on psychiatric and somatic health.

Cumulative Adversity Sensitizes Neural Response to Acute Stress: Association with Health Symptoms

PubMed Central

Seo, Dongju; Tsou, Kristen A; Ansell, Emily B; Potenza, Marc N; Sinha, Rajita

2014-01-01

Cumulative adversity (CA) increases stress sensitivity and risk of adverse health outcomes. However, neural mechanisms underlying these associations in humans remain unclear. To understand neural responses underlying the link between CA and adverse health symptoms, the current study assessed brain activity during stress and neutral-relaxing states in 75 demographically matched, healthy individuals with high, mid, and low CA (25 in each group), and their health symptoms using the Cornell Medical Index. CA was significantly associated with greater adverse health symptoms (P=0.01) in all participants. Functional magnetic resonance imaging results indicated significant associations between CA scores and increased stress-induced activity in the lateral prefrontal cortex, insula, striatum, right amygdala, hippocampus, and temporal regions in all 75 participants (p<0.05, whole-brain corrected). In addition to these regions, the high vs low CA group comparison revealed decreased stress-induced activity in the medial orbitofrontal cortex (OFC) in the high CA group (p<0.01, whole-brain corrected). Specifically, hypoactive medial OFC and hyperactive right hippocampus responses to stress were each significantly associated with greater adverse health symptoms (p<0.01). Furthermore, an inverse correlation was found between activity in the medial OFC and right hippocampus (p=0.01). These results indicate that high CA sensitizes limbic–striatal responses to acute stress and also identifies an important role for stress-related medial OFC and hippocampus responses in the effects of CA on increasing vulnerability to adverse health consequences. PMID:24051900

Cumulative adversity sensitizes neural response to acute stress: association with health symptoms.

PubMed

Seo, Dongju; Tsou, Kristen A; Ansell, Emily B; Potenza, Marc N; Sinha, Rajita

2014-02-01

Cumulative adversity (CA) increases stress sensitivity and risk of adverse health outcomes. However, neural mechanisms underlying these associations in humans remain unclear. To understand neural responses underlying the link between CA and adverse health symptoms, the current study assessed brain activity during stress and neutral-relaxing states in 75 demographically matched, healthy individuals with high, mid, and low CA (25 in each group), and their health symptoms using the Cornell Medical Index. CA was significantly associated with greater adverse health symptoms (P=0.01) in all participants. Functional magnetic resonance imaging results indicated significant associations between CA scores and increased stress-induced activity in the lateral prefrontal cortex, insula, striatum, right amygdala, hippocampus, and temporal regions in all 75 participants (p<0.05, whole-brain corrected). In addition to these regions, the high vs low CA group comparison revealed decreased stress-induced activity in the medial orbitofrontal cortex (OFC) in the high CA group (p<0.01, whole-brain corrected). Specifically, hypoactive medial OFC and hyperactive right hippocampus responses to stress were each significantly associated with greater adverse health symptoms (p<0.01). Furthermore, an inverse correlation was found between activity in the medial OFC and right hippocampus (p=0.01). These results indicate that high CA sensitizes limbic-striatal responses to acute stress and also identifies an important role for stress-related medial OFC and hippocampus responses in the effects of CA on increasing vulnerability to adverse health consequences.

Role of back stress in the creep behavior of particle strengthened alloys

NASA Technical Reports Server (NTRS)

Purushothaman, S.; Tien, J. K.

1978-01-01

Recent developments in the interpolation of high-temperature steady-state creep results have introduced the concept that the stress dependence of the creep rate should be in terms of the effective stress referred to as the applied stress minus a back stress. This paper reports on back stresses taken from data on a gamma-prime-strengthened wrought nickel-base superalloy, an oxide dispersion-strengthened ODS nickel-base solid solution alloy, and an ODS nickel-base superalloy. The effect of air versus vacuum environments and the effect of dynamic changes in the strengthening microstructures on the magnitude of the back stress are assessed. The role of modulus normalization and the back stress correction in determining the true creep activation energy are examined. It is shown that the high values of the apparent stress exponent 'n' of the steady-state creep equation can be easily explained through a relationship between n, the true stress exponent of steady-state creep, and the stress which when subtracted from the applied stress results in the effective driving stress acting on the mobile dislocations during creep.

Survey of career satisfaction, lifestyle, and stress levels among pharmacy school faculty.

PubMed

Lindfelt, Tristan A; Ip, Eric J; Barnett, Mitchell J

2015-09-15

U.S. pharmacy school faculty were surveyed to assess their career satisfaction, lifestyle, and stress levels. A 48-item survey, administered through Qualtrics (Provo, UT), was sent to current members of the American Association of Colleges of Pharmacy and included questions regarding respondents' academic institution and appointment status; lifestyle traits; career satisfaction; work-life balance; neurologic and psychiatric diagnoses; use of illicit drugs, alcohol, and tobacco; and stress levels. of the 4787 faculty invited to participate in the survey, 811 usable surveys were collected (16.9% response rate). Nearly all respondents (95.0%) reported working 40 or more hours per week. The majority had an average daily one-way commute of less than 30 minutes (64.2%), slept 5.5-7.5 hours per night (74.8%), and exercised for no more than 120 minutes per week (61.8%). A majority of respondents (63.7%) reported being very or extremely satisfied with their current position in academia. Only 36.9% reported being very or extremely satisfied with their work-life balance. Mean perceived stress scores were near those found in the general adult population. Although most respondents reported seeing a primary care provider and dentist annually, other findings regarding preventive health measures were not as encouraging. A survey of pharmacy faculty in the United States revealed high levels of job satisfaction among respondents, but lower levels of satisfaction with work-life balance and comparable levels of stress to the general population were found. Administrators and stakeholders should explore options to improve lifestyle factors to decrease potential burnout among faculty. Copyright © 2015 by the American Society of Health-System Pharmacists, Inc. All rights reserved.

Study of the inhomogeneity of critical current under in-situ tensile stress for YBCO tape

NASA Astrophysics Data System (ADS)

Zhu, Y. P.; Chen, W.; Zhang, H. Y.; Liu, L. Y.; Pan, X. F.; Yang, X. S.; Zhao, Y.

2018-07-01

A Hall sensor system was used to measure the local critical current of YBCO tape with high spatial resolution under in-situ tensile stress. The hot spot generation and minimum quench energy of YBCO tape, which depended on the local critical current, was calculated through the thermoelectric coupling model. With the increase in tensile stress, the cracks which have different dimensions and critical current degradation arose more frequently and lowered the thermal stability of the YBCO tape.

'Bright side' and 'dark side' hypomania are associated with differences in psychological functioning, sleep and physical activity in a non-clinical sample of young adults.

PubMed

Brand, Serge; Gerber, Markus; Pühse, Uwe; Holsboer-Trachsler, Edith

2011-06-01

No research has yet focused on hypomanic states in non-clinical early adult populations. The aim of the present study was therefore to assess hypomania in a large non-clinical sample of young adults. A total of 862 participants (639 females and 223 males; mean age: M=24.67; SD=5.91) took part in the study. They completed a series of validated self-report questionnaires assessing hypomania (HCL-32) and other aspects of psychological functioning, sleep, stress, quality of life, cognitive-emotional elaboration of pain, self-efficacy, and physical activity. Based on the HCL-32, 19% of the participants (n=169) were categorized as currently being in a hypomanic state. Of those, 57.6% were classified as "active/elated" ('bright side'), whereas 42.4% were classified as "irritable/risk-taking" ('dark side'). Compared to non-hypomanic participants and the 'bright side' group, 'dark side' hypomanic participants reported more depressive symptoms, sleep disturbances, somatic complaints, perceived stress, negative coping strategies, and lower self-efficacy. By contrast, 'bright side' hypomanic participants had lower stress scores, more positive self-instructions, and higher levels of exploration, self-efficacy, and physical activity. A cross-sectional design was adopted, assessing university students, who may not be representative of the stage of early adulthood. The present results underscore the notion of a continuity between a mood state and both favorable ('bright side') and unfavorable ('dark side') hypomanic states. In early adulthood, 'bright' and 'dark side' hypomania differs with respect to physical activity, psychological functioning and sleep. Copyright © 2010 Elsevier B.V. All rights reserved.

Host Coenzyme Q Redox State Is an Early Biomarker of Thermal Stress in the Coral Acropora millepora

PubMed Central

Motti, Cherie A.; Miller, David J.; van Oppen, Madeleine J. H.

2015-01-01

Bleaching episodes caused by increasing seawater temperatures may induce mass coral mortality and are regarded as one of the biggest threats to coral reef ecosystems worldwide. The current consensus is that this phenomenon results from enhanced production of harmful reactive oxygen species (ROS) that disrupt the symbiosis between corals and their endosymbiotic dinoflagellates, Symbiodinium. Here, the responses of two important antioxidant defence components, the host coenzyme Q (CoQ) and symbiont plastoquinone (PQ) pools, are investigated for the first time in colonies of the scleractinian coral, Acropora millepora, during experimentally-induced bleaching under ecologically relevant conditions. Liquid chromatography-mass spectrometry (LC-MS) was used to quantify the states of these two pools, together with physiological parameters assessing the general state of the symbiosis (including photosystem II photochemical efficiency, chlorophyll concentration and Symbiodinium cell densities). The results show that the responses of the two antioxidant systems occur on different timescales: (i) the redox state of the Symbiodinium PQ pool remained stable until twelve days into the experiment, after which there was an abrupt oxidative shift; (ii) by contrast, an oxidative shift of approximately 10% had occurred in the host CoQ pool after 6 days of thermal stress, prior to significant changes in any other physiological parameter measured. Host CoQ pool oxidation is thus an early biomarker of thermal stress in corals, and this antioxidant pool is likely to play a key role in quenching thermally-induced ROS in the coral-algal symbiosis. This study adds to a growing body of work that indicates host cellular responses may precede the bleaching process and symbiont dysfunction. PMID:26426118

Stress and Traumatic Stress: How Do Past Events Influence Current Traumatic Stress among Mothers Experiencing Homelessness?

ERIC Educational Resources Information Center

Williams, Julie K.; Hall, James A.

2009-01-01

The purpose of this research was to evaluate the relationship between past traumatic events and the level of current traumatic stress among mothers experiencing homelessness. The data for this study were gathered from 75 homeless mothers between May 2006 and October 2006 using a cross-sectional survey design with purposive sampling. All mothers…

Reintegration of National Guard Soldiers with Post-Traumatic Stress Disorder

DTIC Science & Technology

2010-03-01

Post - Traumatic Stress Disorder ( PTSD ). An alarming number of soldiers returning from our current wars in Iraq...veterans have been diagnosed with the invisible wounds of Post - Traumatic Stress Disorder ( PTSD ). An alarming number of soldiers returning from our current...returning veterans have been diagnosed with the invisible wounds of Post - Traumatic Stress Disorder ( PTSD ). These veterans’ coping skills have

Computationally driven drug discovery meeting-3 - Verona (Italy): 4 - 6th of March 2014.

PubMed

Costantino, Gabriele

2014-12-01

The following article reports on the results and the outcome of a meeting organised at the Aptuit Auditorium in Verona (Italy), which highlighted the current applications of state-of-the-art computational science to drug design in Italy. The meeting, which had > 100 people in attendance, consisted of over 40 presentations and included keynote lectures given by world-renowned speakers. The topics included in the meeting are areas related to ligand and structure-based ligand design and library design and screening; it also provided discussion pertaining to chemometrics. The meeting also stressed the importance of public-private collaboration and reviewed the different approaches to computationally driven drug discovery taken within academia and industry. The meeting helped define the current position of state-of-the-art computational drug discovery in Italy, pointing out criticalities and assets. This kind of focused meeting is important in the sense that it lends the opportunity of a restricted yet representative community of fellow professionals to deeply discuss the current methodological approaches and provide future perspectives for computationally driven drug discovery.

Corrosion and Potentiostatic Polarization of an Al-Cu-Li Alloy under Tensile Stress

NASA Astrophysics Data System (ADS)

Li, Jin-feng; Zheng, Zi-qiao

The stress corrosion cracking (SCC) of an Al-3.8Cu-1.5Li-0.5Zn-0.5Mg-0.3Mn alloy in 3.5% NaCl solution was studied through using slow strain rate tension(SSRT). The potentiodynamic polarization and anodic potentiostastic polarization of the stressed and stress free alloy with T6 temper were investigated. The tensile stress decreased the break down potential. The alloy was sensitive to intergranular SCC (IGSCC), due to the continuous distribution of anodic phase of T2(Al6CuLi3) along the grain boundary. During the potentiostastic polarization, the current-time curve of the stressed alloy displayed a repeated transient feature that the current increased suddenly followed by a slower recovery, and corrosion crack appeared along the grain boundary. While the stress free alloy did not show this current feature and corrosion crack along the grain boundary. The repeated current transient was associated with the crack tip propagation and crack wall passivation. This feature may be used to analyze the SCC process.

Redox biology of tuberculosis pathogenesis.

PubMed

Trivedi, Abhishek; Singh, Nisha; Bhat, Shabir Ahmed; Gupta, Pawan; Kumar, Ashwani

2012-01-01

Mycobacterium tuberculosis (Mtb) is one of the most successful human pathogens. Mtb is persistently exposed to numerous oxidoreductive stresses during its pathogenic cycle of infection and transmission. The distinctive ability of Mtb, not only to survive the redox stress manifested by the host but also to use it for synchronizing the metabolic pathways and expression of virulence factors, is central to its success as a pathogen. This review describes the paradigmatic redox and hypoxia sensors employed by Mtb to continuously monitor variations in the intracellular redox state and the surrounding microenvironment. Two component proteins, namely, DosS and DosT, are employed by Mtb to sense changes in oxygen, nitric oxide, and carbon monoxide levels, while WhiB3 and anti-sigma factor RsrA are used to monitor changes in intracellular redox state. Using these and other unidentified redox sensors, Mtb orchestrates its metabolic pathways to survive in nutrient-deficient, acidic, oxidative, nitrosative, and hypoxic environments inside granulomas or infectious lesions. A number of these metabolic pathways are unique to mycobacteria and thus represent potential drug targets. In addition, Mtb employs versatile machinery of the mycothiol and thioredoxin systems to ensure a reductive intracellular environment for optimal functioning of its proteins even upon exposure to oxidative stress. Mtb also utilizes a battery of protective enzymes, such as superoxide dismutase (SOD), catalase (KatG), alkyl hydroperoxidase (AhpC), and peroxiredoxins, to neutralize the redox stress generated by the host immune system. This chapter reviews the current understanding of mechanisms employed by Mtb to sense and neutralize redox stress and their importance in TB pathogenesis and drug development. Copyright © 2012 Elsevier Ltd. All rights reserved.

High-Performance All-Solid-State Na-S Battery Enabled by Casting-Annealing Technology.

PubMed

Fan, Xiulin; Yue, Jie; Han, Fudong; Chen, Ji; Deng, Tao; Zhou, Xiuquan; Hou, Singyuk; Wang, Chunsheng

2018-04-24

Room-temperature all-solid-state Na-S batteries (ASNSBs) using sulfide solid electrolytes are a promising next-generation battery technology due to the high energy, enhanced safety, and earth abundant resources of both sodium and sulfur. Currently, the sulfide electrolyte ASNSBs are fabricated by a simple cold-pressing process leaving with high residential stress. Even worse, the large volume change of S/Na 2 S during charge/discharge cycles induces additional stress, seriously weakening the less-contacted interfaces among the solid electrolyte, active materials, and the electron conductive agent that are formed in the cold-pressing process. The high and continuous increase of the interface resistance hindered its practical application. Herein, we significantly reduce the interface resistance and eliminate the residential stress in Na 2 S cathodes by fabricating Na 2 S-Na 3 PS 4 -CMK-3 nanocomposites using melting-casting followed by stress-release annealing-precipitation process. The casting-annealing process guarantees the close contact between the Na 3 PS 4 solid electrolyte and the CMK-3 mesoporous carbon in mixed ionic/electronic conductive matrix, while the in situ precipitated Na 2 S active species from the solid electrolyte during the annealing process guarantees the interfacial contact among these three subcomponents without residential stress, which greatly reduces the interfacial resistance and enhances the electrochemical performance. The in situ synthesized Na 2 S-Na 3 PS 4 -CMK-3 composite cathode delivers a stable and highly reversible capacity of 810 mAh/g at 50 mA/g for 50 cycles at 60 °C. The present casting-annealing strategy should provide opportunities for the advancement of mechanically robust and high-performance next-generation ASNSBs.

Parenting stress as a mediator of parents' negative mood state and behavior problems in children with newly diagnosed cancer.

PubMed

van der Geest, Ivana M; van den Heuvel-Eibrink, Marry M; Passchier, Jan; van den Hoed-Heerschop, Corry; Pieters, Rob; Darlington, Anne-Sophie E

2014-07-01

The aim was to investigate the influence of parents' negative mood state and parenting stress on behavior in children with newly diagnosed cancer. A total of 123 parents (n=58 fathers, n=65 mothers) of 67 children with newly diagnosed cancer completed three questionnaires separately at the same time measuring parents' negative mood state, parenting stress, and child behavior problems. Parents' negative mood state was weakly correlated to more child behavior problems (r=0.31, p<0.01), and higher levels of parenting stress were strongly correlated to more child behavior problems (r=0.61, p<0.01). Mediation analyses indicated that the relationship between parents' negative mood state and child behavior problems (c=0.29, p=0.02 (fathers); c=0.25, p=0.04 (mothers)) became non-significant after mediating for parenting stress (c'=0.003, p=0.98 (fathers); c'=0.10, p=0.42 (mothers)). The indirect effect of parents' negative mood state and child behavior problems was only significant for fathers (95% CI [0.12; 0.51]), indicating that parenting stress mediates the effect between fathers' negative mood state and child behavior problems. This is the first study to demonstrate the mediational role of parenting stress in fathers of a child with newly diagnosed cancer. Copyright © 2014 John Wiley & Sons, Ltd.

Early life trauma exposure and stress sensitivity in young children.

PubMed

Grasso, Damion J; Ford, Julian D; Briggs-Gowan, Margaret J

2013-01-01

The current study replicates and extends work with adults that highlights the relationship between trauma exposure and distress in response to subsequent, nontraumatic life stressors. The sample included 213 2-4-year-old children in which 64.3% had a history of potential trauma exposure. Children were categorized into 4 groups based on trauma history and current life stress. In a multivariate analysis of variance, trauma-exposed children with current life stressors had elevated internalizing and externalizing problems compared with trauma-exposed children without current stress and nontrauma-exposed children with and without current stressors. The trauma-exposed groups with or without current stressors did not differ on posttraumatic stress disorder symptom severity. Accounting for number of traumatic events did not change these results. These findings suggest that early life trauma exposure may sensitize young children and place them at risk for internalizing or externalizing problems when exposed to subsequent, nontraumatic life stressors.

Trauma and Aggression: Investigating the Mediating Role of Mentalizing in Female and Male Inpatient Adolescents.

PubMed

Abate, Anna; Marshall, Kaisa; Sharp, Carla; Venta, Amanda

2017-12-01

High rates of posttraumatic stress disorder (PTSD) symptoms and elevated levels of aggression are common among youth in inpatient psychiatric settings. Several models link trauma exposure to aggression through anomalous mental state reasoning. Some theoretical frameworks linking trauma to aggression specify that the over-attribution of hostile mental states contributes to the development of aggressive behavior whereas other theories suggest that an inhibition of mental state reasoning leads to aggressive behavior. Using a sample of inpatient adolescents, the current study examined relations between PTSD symptoms and four forms of aggression, exploring the role of both over- and under-mentalizing (i.e., hypo- and hypermentalizing) as mediators and gender as a moderator. The results suggest that hypermentalizing, but not hypomentalizing, mediates the relation between trauma and aggression, extending prior research related to inpatient adolescents for the first time. Evidence of moderated mediation was noted, such that this mediational relation was evident for females but not males. The current study offers support for differential underlying causes of aggression among males and females with PTSD symptoms.

Using Real-Time Social Media Technologies to Monitor Levels of Perceived Stress and Emotional State in College Students: A Web-Based Questionnaire Study.

PubMed

Liu, Sam; Zhu, Miaoqi; Yu, Dong Jin; Rasin, Alexander; Young, Sean D

2017-01-10

College can be stressful for many freshmen as they cope with a variety of stressors. Excess stress can negatively affect both psychological and physical health. Thus, there is a need to find innovative and cost-effective strategies to help identify students experiencing high levels of stress to receive appropriate treatment. Social media use has been rapidly growing, and recent studies have reported that data from these technologies can be used for public health surveillance. Currently, no studies have examined whether Twitter data can be used to monitor stress level and emotional state among college students. The primary objective of our study was to investigate whether students' perceived levels of stress were associated with the sentiment and emotions of their tweets. The secondary objective was to explore whether students' emotional state was associated with the sentiment and emotions of their tweets. We recruited 181 first-year freshman students aged 18-20 years at University of California, Los Angeles. All participants were asked to complete a questionnaire that assessed their demographic characteristics, levels of stress, and emotional state for the last 7 days. All questionnaires were completed within a 48-hour period. All tweets posted by the participants from that week (November 2 to 8, 2015) were mined and manually categorized based on their sentiment (positive, negative, neutral) and emotion (anger, fear, love, happiness) expressed. Ordinal regressions were used to assess whether weekly levels of stress and emotional states were associated with the percentage of positive, neutral, negative, anger, fear, love, or happiness tweets. A total of 121 participants completed the survey and were included in our analysis. A total of 1879 tweets were analyzed. A higher level of weekly stress was significantly associated with a greater percentage of negative sentiment tweets (beta=1.7, SE 0.7; P=.02) and tweets containing emotions of fear (beta=2.4, SE 0.9; P=.01) and love (beta=3.6, SE 1.4; P=.01). A greater level of anger was negatively associated with the percentage of positive sentiment (beta=-1.6, SE 0.8; P=.05) and tweets related to the emotions of happiness (beta=-2.2, SE 0.9; P=.02). A greater level of fear was positively associated with the percentage of negative sentiment (beta=1.67, SE 0.7; P=.01), particularly a greater proportion of tweets related to the emotion of fear (beta=2.4, SE 0.8; P=.01). Participants who reported a greater level of love showed a smaller percentage of negative sentiment tweets (beta=-1.3, SE 0.7; P=0.05). Emotions of happiness were positively associated with the percentage of tweets related to the emotion of happiness (beta=-1.8, SE 0.8; P=.02) and negatively associated with percentage of negative sentiment tweets (beta=-1.7, SE 0.7; P=.02) and tweets related to the emotion of fear (beta=-2.8, SE 0.8; P=.01). Sentiment and emotions expressed in the tweets have the potential to provide real-time monitoring of stress level and emotional well-being in college students. ©Sam Liu, Miaoqi Zhu, Dong Jin Yu, Alexander Rasin, Sean D Young. Originally published in JMIR Mental Health (http://mental.jmir.org), 10.01.2017.

The State of Stress Beyond the Borehole

NASA Astrophysics Data System (ADS)

Johnson, P. A.; Coblentz, D. D.; Maceira, M.; Delorey, A. A.; Guyer, R. A.

2015-12-01

The state of stress controls all in-situ reservoir activities and yet we lack the quantitative means to measure it. This problem is important in light of the fact that the subsurface provides more than 80 percent of the energy used in the United States and serves as a reservoir for geological carbon sequestration, used fuel disposition, and nuclear waste storage. Adaptive control of subsurface fractures and fluid flow is a crosscutting challenge being addressed by the new Department of Energy SubTER Initiative that has the potential to transform subsurface energy production and waste storage strategies. Our methodology to address the above mentioned matter is based on a novel Advance Multi-Physics Tomographic (AMT) approach for determining the state of stress, thereby facilitating our ability to monitor and control subsurface geomechanical processes. We developed the AMT algorithm for deriving state-of-stress from integrated density and seismic velocity models and demonstrate the feasibility by applying the AMT approach to synthetic data sets to assess accuracy and resolution of the method as a function of the quality and type of geophysical data. With this method we can produce regional- to basin-scale maps of the background state of stress and identify regions where stresses are changing. Our approach is based on our major advances in the joint inversion of gravity and seismic data to obtain the elastic properties for the subsurface; and coupling afterwards the output from this joint-inversion with theoretical model such that strain (and subsequently) stress can be computed. Ultimately we will obtain the differential state of stress over time to identify and monitor critically stressed faults and evolving regions within the reservoir, and relate them to anthropogenic activities such as fluid/gas injection.

Mother-Infant Emotion Regulation at Three Months: The Role of Maternal Anxiety, Depression and Parenting Stress.

PubMed

Riva Crugnola, Cristina; Ierardi, Elena; Ferro, Valentino; Gallucci, Marcello; Parodi, Cinzia; Astengo, Marina

While the association between anxiety and postpartum depression is well known, few studies have investigated the relationship between these two states and parenting stress. Furthermore, a number of studies have found that postpartum depression affects mother-infant emotion regulation, but there has been only one study on anxiety and emotion regulation and no studies at all on parenting stress and emotion regulation. Therefore, the primary aim of our study is to identify, in a community sample of 71 mothers, the relationship between maternal depression, anxiety, and parenting stress. The second aim is to examine the relationship between anxiety, postpartum depression, and parenting stress and mother-infant emotion regulation assessed at 3 months. Mother-infant interaction was coded with a modified version of the Infant Caregiver and Engagement Phases (ICEP) using a microanalytic approach. The Edinburgh Postnatal Depression Scale (EPDS), State-Trait Anxiety Inventory (STAI), and Parenting Stress Index-Short Form (PSI-SF) were administered to the mothers to assess depression, anxiety, and parenting stress, respectively. Analysis revealed correlations between anxiety and depression, showing that parenting stress is associated with both states. In a laboratory observation, depression was correlated with both negative maternal states and negative dyadic matches as well as infant positive/mother negative mismatches; anxiety was correlated with both negative maternal states and infant negative states as well as mismatches involving one of the partners having a negative state. Multiple regression analysis showed that anxiety is a greater predictor than depression of less adequate styles of mother-infant emotion regulation. Parenting stress was not shown to predict such regulation. © 2016 S. Karger AG, Basel.

Effect of substrate thinning on the electronic transport characteristics of AlGaN/GaN HEMTs

NASA Astrophysics Data System (ADS)

Zhu, Hui; Meng, Xiao; Zheng, Xiang; Yang, Ying; Feng, Shiwei; Zhang, Yamin; Guo, Chunsheng

2018-07-01

We studied how substrate thinning affected the electronic transport characteristics of AlGaN/GaN HEMTs. By thinning their sapphire substrate from 460 μm to 80 μm, we varied the residual stress in these HEMTs. The thinned sample showed decreased drain-source current and occurrence of kink effect. Furthermore, shown by current transient measurements and time constant analysis, the detrapping behaviors of trap states shifted toward a larger time constant, and the detrapping behavior under the gate and in the gate-drain access region showed increased amplitude. By using pulsed current-voltage measurements, the thinned sample showed a positive shift of the threshold voltage, a decrease in peak transconductance, and an aggravation in current collapse, as compared with the thick one. The degradation of electrical behavior were associated with the structural degradation, as confirmed by the increase of pit density on the thinned sample surface.

State of the art in protection of erosion-corrosion on vertical axis tidal current turbine

NASA Astrophysics Data System (ADS)

Musabikha, Siti; Utama, I. Ketut Aria Pria; Mukhtasor

2018-05-01

Vertical axis tidal current turbine is main part of ocean energy devices which converts the tidal current energy into electricity. Its development is arising too due to increased interest research topic concerning climate change mitigation. Due to its rotating movement, it will be induced mechanical forces, such as shear stress and/or particle impact. Because of its natural operations, vertical axis turbine is also being exposed to harsh and corroding marine environment itself. In order to secure the vertical tidal turbine devices from mechanical wear and corrosion effects which is lead to a material loss, an appropriate erosion-corrosion protection needs to be defined. Its protection actionscan be derived such as design factors, material selections, inhibitors usage, cathodic protections, and coatings. This paper aims to analyze protection method which is necessary to control erosion-corrosion phenomenon that appears to the vertical axis tidal current turbine.

Plant xylem hydraulics: What we understand, current research, and future challenges.

PubMed

Venturas, Martin D; Sperry, John S; Hacke, Uwe G

2017-06-01

Herein we review the current state-of-the-art of plant hydraulics in the context of plant physiology, ecology, and evolution, focusing on current and future research opportunities. We explain the physics of water transport in plants and the limits of this transport system, highlighting the relationships between xylem structure and function. We describe the great variety of techniques existing for evaluating xylem resistance to cavitation. We address several methodological issues and their connection with current debates on conduit refilling and exponentially shaped vulnerability curves. We analyze the trade-offs existing between water transport safety and efficiency. We also stress how little information is available on molecular biology of cavitation and the potential role of aquaporins in conduit refilling. Finally, we draw attention to how plant hydraulic traits can be used for modeling stomatal responses to environmental variables and climate change, including drought mortality. © 2017 Institute of Botany, Chinese Academy of Sciences.

Be Cool with Academic Stress: The Association between Emotional States and Regulatory Strategies among Chinese Adolescents

ERIC Educational Resources Information Center

Sang, Biao; Pan, Tingting; Deng, Xinmei; Zhao, Xu

2018-01-01

Numerous studies have suggested that academic stress has negative impact on adolescents' psychological function, few of those studies, however, considered whether and how the impact of stress on adolescents' emotional states is moderated by corresponding regulation. This study aimed to examine the fluctuation of emotional states before and after…

Relationship between Organizational Climate, Job Stress and Job Performance Officer at State Education Department

ERIC Educational Resources Information Center

Suandi, Turiman; Ismail, Ismi Arif; Othman, Zulfadli

2014-01-01

This research aims at finding out the relationship between Organizational Climate, job stress and job performance among State Education Department (JPN) officers . The focus of the research is to determine the job performance of state education department officers, level of job stress among the officers, level of connection between organizational…

Spontaneous and deliberate dissociative states in military personnel: are such states helpful?

PubMed

Morgan, Charles A; Taylor, Marcus K

2013-08-01

This study explored distinctions between spontaneous and deliberate dissociative states in 335 military personnel exposed to stressful survival training. Participants completed the Clinician-Administered Dissociative States Scale (CADSS) after a stressful mock-captivity event. They were also asked to indicate whether the dissociative experiences just happened (i.e., spontaneous), or whether they chose to have them happen (i.e., deliberate); and whether they appraised the dissociative experience as helpful (i.e., facilitative) or hurtful (i.e., debilitative) to their ability to cope with the stressful event. A majority (95.4%) endorsed dissociative states during stress. More than half (57.4%) described dissociative experiences as spontaneous, 13.0% as deliberate, and 29.5% endorsed neither. In Special Forces soldiers only, those who endorsed facilitative dissociation exhibited higher total CADSS scores than those who endorsed debilitative dissociation. Seventy-three percent of spontaneous dissociators described the experience as debilitative to coping with stress; conversely, 76% of deliberate dissociators said these experiences facilitated coping with stress. Individuals with prior trauma exposure tended to appraise dissociative states as more debilitative to coping. This research may enhance the fidelity of studies of dissociation constructs and may offer pivot points for prevention and treatment of stress-related disorders. Published 2013. This article is a US Government work and is in the public domain in the USA.

Faulting of Rocks in a Three-Dimensional Stress Field by Micro-Anticracks

PubMed Central

Ghaffari, H. O.; Nasseri, M. H. B.; Young, R. Paul

2014-01-01

Nucleation and propagation of a shear fault is known to be the result of interaction and coalescence of many microcracks. Yet the character and rate of the microcracks' interactions, and their dependence on the three-dimensional stress state are poorly understood. Here we investigate formation of microcracks during sandstone faulting under 3D-polyaxial stress fields by analyzing multi-stationary acoustic waveforms. We show that in a true three-dimensional stress state (a) faulting forms in a orthorhombic pattern, and (b) the emitted acoustic waveforms from microcracking carry a shorter rapid slip phase. The later is associated with microcracking that dominantly develops parallel to the minimum stress direction. Our results imply that due to inducing the micro-anticracks, the three-dimensional (3D) stress state can quicken dynamic weakening and rupture propagation by a factor of two relatively to simpler stress states. The results suggest a new nucleation mechanism of 3D-faulting with implications for earthquakes' instabilities, as well as the understanding of avalanches associated with dislocations. PMID:24862447

Chinese International Students' Academic Stressors in the United States

ERIC Educational Resources Information Center

Yan, Kun; Berliner, David C.

2009-01-01

No empirical research has focused on understanding the academic stress of Chinese international students in the United States. This qualitative inquiry examines the most stressful aspects of their academic lives in the U.S., how they characterize their academic stress, and what conditions they believe tend to account for their academic stress.…

Experimental research data on stress state of salt rock mass around an underground excavation

NASA Astrophysics Data System (ADS)

Baryshnikov, VD; Baryshnikov, DV

2018-03-01

The paper presents the experimental stress state data obtained in surrounding salt rock mass around an excavation in Mir Mine, ALROSA. The deformation characteristics and the values of stresses in the adjacent rock mass are determined. Using the method of drilling a pair of parallel holes in a stressed area, the authors construct linear relationship for the radial displacements of the stress measurement hole boundaries under the short-term loading of the perturbing hole. The resultant elasticity moduli of rocks are comparable with the laboratory core test data. Pre-estimates of actual stresses point at the presence of a plasticity zone in the vicinity of the underground excavation. The stress state behavior at a distance from the excavation boundary disagrees with the Dinnik–Geim hypothesis.

Variability of the internal tide on the southern Monterey Bay continental shelf and associated bottom boundary layer sediment transport

USGS Publications Warehouse

Rosenberger, Kurt; Storlazzi, Curt; Cheriton, Olivia

2016-01-01

A 6-month deployment of instrumentation from April to October 2012 in 90 m water depth near the outer edge of the mid-shelf mud belt in southern Monterey Bay, California, reveals the importance regional upwelling on water column density structure, potentially accounting for the majority of the variability in internal tidal energy flux across the shelf. Observations consisted of time-series measurements of water-column currents, temperature and salinity, and near-bed currents and suspended matter. The internal tide accounted for 15–25% of the water-column current variance and the barotropic tide accounted for up to 35%. The subtidal flow showed remarkably little shear and was dominated by the 7–14 day band, which is associated with relaxations in the dominant equatorward winds typical of coastal California in the spring and summer. Upwelling and relaxation events resulted in strong near-bed flows and accounted for almost half of the current stress on the seafloor (not accounting for wave orbital velocities), and may have driven along-shelf geostrophic flow during steady state conditions. Several elevated suspended particulate matter (SPM) events occurred within 3 m of the bed and were generally associated with higher, long-period surface waves. However, these peaks in SPM did not coincide with the predicted resuspension events from the modeled combined wave–current shear stress, indicating that the observed SPM at our site was most likely resuspended elsewhere and advected along-isobath. Sediment flux was almost equal in magnitude in the alongshore and cross-shore directions. Instances of wave–current shear stress that exceeded the threshold of resuspension for the silty-clays common at these water depths only occurred when near-bed orbital velocities due to long-period surface waves coincided with vigorous near-bed currents associated with the internal tide or upwelling/relaxation events. Thus upwelling/relaxation dynamics are primarily responsible for variability in the internal tide, as well as transport of near-bottom sediment in the mid-self mud belt during the relatively quiescent summer months.

Telomere Length, Current Perceived Stress, and Urinary Stress Hormones in Women

PubMed Central

Parks, Christine G.; Miller, Diane B.; McCanlies, Erin C.; Cawthon, Richard M.; Andrew, Michael E.; DeRoo, Lisa A.; Sandler, Dale P.

2009-01-01

Telomeres are repetitive DNA sequences that cap and protect the ends of chromosomes; critically short telomeres may lead to cellular senescence or carcinogenic transformation. Previous findings suggest a link between psychosocial stress, shorter telomeres, and chronic disease risk. This cross-sectional study examined relative telomere length in relation to perceived stress and urinary stress hormones in a sample of participants (n = 647) in the National Institute of Environmental Health Sciences Sister Study, a cohort of women ages 35 to 74 years who have a sister with breast cancer. Average leukocyte telomere length was determined by quantitative PCR. Current stress was assessed using the Perceived Stress Scale and creatinine-adjusted neuroendocrine hormones in first morning urines. Linear regression models estimated differences in telomere length base pairs (bp) associated with stress measures adjusted for age, race, smoking, and obesity. Women with higher perceived stress had somewhat shorter telomeres [adjusted difference of −129bp for being at or above moderate stress levels; 95% confidence interval (CI), −292 to 33], but telomere length did not decrease monotonically with higher stress levels. Shorter telomeres were independently associated with increasing age (−27bp/year), obesity, and current smoking. Significant stress-related differences in telomere length were seen in women ages 55 years and older (−289bp; 95% CI, −519 to −59), those with recent major losses (−420bp; 95% CI, −814 to −27), and those with above-average urinary catecholamines (e.g., epinephrine: −484bp; 95% CI, −709 to −259). Although current perceived stress was only modestly associated with shorter telomeres in this broad sample of women, our findings suggest the effect of stress on telomere length may vary depending on neuroendocrine responsiveness, external stressors, and age. PMID:19190150

Electromigration failures under bidirectional current stress

NASA Astrophysics Data System (ADS)

Tao, Jiang; Cheung, Nathan W.; Hu, Chenming

1998-01-01

Electromigration failure under DC stress has been studied for more than 30 years, and the methodologies for accelerated DC testing and design rules have been well established in the IC industry. However, the electromigration behavior and design rules under time-varying current stress are still unclear. In CMOS circuits, as many interconnects carry pulsed-DC (local VCC and VSS lines) and bidirectional AC current (clock and signal lines), it is essential to assess the reliability of metallization systems under these conditions. Failure mechanisms of different metallization systems (Al-Si, Al-Cu, Cu, TiN/Al-alloy/TiN, etc.) and different metallization structures (via, plug and interconnect) under AC current stress in a wide frequency range (from mHz to 500 MHz) has been study in this paper. Based on these experimental results, a damage healing model is developed, and electromigration design rules are proposed. It shows that in the circuit operating frequency range, the "design-rule current" is the time-average current. The pure AC component of the current only contributes to self-heating, while the average (DC component) current contributes to electromigration. To ensure longer thermal-migration lifetime under high frequency AC stress, an additional design rule is proposed to limit the temperature rise due to self-joule heating.

Unique and related predictors of major depressive disorder, posttraumatic stress disorder, and their comorbidity after Hurricane Katrina.

PubMed

Nillni, Yael I; Nosen, Elizabeth; Williams, Patrick A; Tracy, Melissa; Coffey, Scott F; Galea, Sandro

2013-10-01

The current study examined demographic and psychosocial factors that predict major depressive disorder (MDD) and comorbid MDD/posttraumatic stress disorder (MDD/PTSD) diagnostic status after Hurricane Katrina, one of the deadliest and costliest hurricanes in the history of the United States. This study expanded on the findings published in the article by Galea, Tracy, Norris, and Coffey (J Trauma Stress 21:357-368, 2008), which examined the same predictors for PTSD, to better understand related and unique predictors of MDD, PTSD, and MDD/PTSD comorbidity. A total of 810 individuals representative of adult residents living in the 23 southernmost counties of Mississippi before Hurricane Katrina were interviewed. Ongoing hurricane-related stressors, low social support, and hurricane-related financial loss were common predictors of MDD, PTSD, and MDD/PTSD, whereas educational and marital status emerged as unique predictors of MDD. Implications for postdisaster relief efforts that address the risk for both MDD and PTSD are discussed.

Institutions, Parasites and the Persistence of In-group Preferences

PubMed Central

Hruschka, Daniel J.; Henrich, Joseph

2013-01-01

Much research has established reliable cross-population differences in motivations to invest in one’s in-group. We compare two current historical-evolutionary hypotheses for this variation based on (1) effective large-scale institutions and (2) pathogen threats by analyzing cross-national differences (N = 122) in in-group preferences measured in three ways. We find that the effectiveness of government institutions correlates with favoring in-group members, even when controlling for pathogen stress and world region, assessing reverse causality, and providing a check on endogeneity with an instrumental variable analysis. Conversely, pathogen stress shows inconsistent associations with in-group favoritism when controlling for government effectiveness. Moreover, pathogen stress shows little to no association with in-group favoritism within major world regions whereas government effectiveness does. These results suggest that variation in in-group preferences across contemporary nation-states is more consistent with a generalized response to institutions that meet basic needs rather than an evolved response dedicated to pathogens. PMID:23704926

Physics Based Electrolytic Capacitor Degradation Models for Prognostic Studies under Thermal Overstress

NASA Technical Reports Server (NTRS)

Kulkarni, Chetan S.; Celaya, Jose R.; Goebel, Kai; Biswas, Gautam

2012-01-01

Electrolytic capacitors are used in several applications ranging from power supplies on safety critical avionics equipment to power drivers for electro-mechanical actuators. This makes them good candidates for prognostics and health management research. Prognostics provides a way to assess remaining useful life of components or systems based on their current state of health and their anticipated future use and operational conditions. Past experiences show that capacitors tend to degrade and fail faster under high electrical and thermal stress conditions that they are often subjected to during operations. In this work, we study the effects of accelerated aging due to thermal stress on different sets of capacitors under different conditions. Our focus is on deriving first principles degradation models for thermal stress conditions. Data collected from simultaneous experiments are used to validate the desired models. Our overall goal is to derive accurate models of capacitor degradation, and use them to predict performance changes in DC-DC converters.

Acid Stress Response Mechanisms of Group B Streptococci

PubMed Central

Shabayek, Sarah; Spellerberg, Barbara

2017-01-01

Group B streptococcus (GBS) is a leading cause of neonatal mortality and morbidity in the United States and Europe. It is part of the vaginal microbiota in up to 30% of pregnant women and can be passed on to the newborn through perinatal transmission. GBS has the ability to survive in multiple different host niches. The pathophysiology of this bacterium reveals an outstanding ability to withstand varying pH fluctuations of the surrounding environments inside the human host. GBS host pathogen interations include colonization of the acidic vaginal mucosa, invasion of the neutral human blood or amniotic fluid, breaching of the blood brain barrier as well as survival within the acidic phagolysosomal compartment of macrophages. However, investigations on GBS responses to acid stress are limited. Technologies, such as whole genome sequencing, genome-wide transcription and proteome mapping facilitate large scale identification of genes and proteins. Mechanisms enabling GBS to cope with acid stress have mainly been studied through these techniques and are summarized in the current review PMID:28936424

Stressful Life Events and Depression Symptoms: The Effect of Childhood Emotional Abuse on Stress Reactivity

PubMed Central

Shapero, Benjamin G.; Black, Shimrit K.; Liu, Richard T.; Klugman, Joshua; Bender, Rachel E.; Abramson, Lyn Y.; Alloy, Lauren B.

2013-01-01

Objective Stressful life events are associated with an increase in depressive symptoms and the onset of major depression. Importantly, research has shown that the role of stress changes over the course of depression. The present study extends the current literature by examining the effects of early life stress on emotional reactivity to current stressors. Method In a multiwave study (N = 281, mean age = 18.76; 68% female), we investigated the proximal changes that occur in depressive symptoms when individuals are faced with life stress and whether a history of childhood emotional abuse moderates this relationship. Results Results support the stress sensitivity hypothesis for early emotional abuse history. Individuals with greater childhood emotional abuse severity experienced greater increases in depressive symptoms when confronted with current dependent stressors, controlling for childhood physical and sexual abuse. Conclusions This study highlights the importance of emotional abuse as an indicator for reactivity to stressful life events. PMID:23800893

Encopresis, soiling and constipation in children and adults with developmental disability.

PubMed

Matson, Johnny L; LoVullo, Santino V

2009-01-01

Children and adults with developmental disabilities are more likely to evince encopresis, soiling and constipation than the general population. This set of related behaviors can produce a great deal of stress and can be a major restriction in independent living. This paper provides a review of the current state of knowledge on the prevalence, etiology, assessment and treatment of this co-occurring set of disorders. These problems are more common in persons with developmental disabilities then the general population. Furthermore, classical and operant treatment methods appear to be the best supported interventions for most cases. Strengths and weaknesses of the current research base are discussed along with potential avenues for future research.

Magnetic factor in solar-terrestrial relations and its impact on the human body: physical problems and prospects for research

NASA Astrophysics Data System (ADS)

Breus, T. K.; Binhi, V. N.; Petrukovich, A. A.

2016-05-01

The body of current heliobiological evidence suggests that very weak variable magnetic fields due to solar- and geomagnetic-activities do have a biological effect. Geomagnetic disturbances can cause a nonspecific reaction in the human body - a kind of general adaptation syndrome which occurs due to any external stress factor. Also, specific reactions can develop. One of the reasons discussed for the similarity between biological and heliogeophysical rhythms is that geomagnetic variations have a direct influence on organisms, although exact magnetoreception mechanisms are not yet clear. The paper briefly reviews the current state of empirical and theoretical work on this fundamental multidisciplinary problem.

Displacement behaviour regulates the experience of stress in men.

PubMed

Mohiyeddini, Changiz; Semple, Stuart

2013-03-01

Behavioural coping strategies represent a key means by which people regulate their stress levels. Attention has recently focused on the potential role in coping of 'displacement behaviour' - activities such as scratching, lip biting and face touching. Increased levels of displacement behaviour are associated with feelings of anxiety and stress; however, the extent to which displacement behaviour, as a short-term behavioural response to emotionally challenging stimuli, influences the subsequent experience of stress remains poorly understood. The aim of this study was to investigate the potential role of displacement behaviour in coping with stress. In a study population of 42 healthy adult men (mean age = 28.09 years, SD = 7.98), we quantified displacement behaviour during a Trier Social Stress Test (TSST), and used self-report questionnaires to assess trait and state anxiety before the TSST, and the experience of stress afterwards. We predicted displacement behaviour would diminish the negative impact of the stressful situation, and hence be associated with lower post-TSST stress levels. Furthermore, we predicted displacement behaviour would mediate the link between state and trait anxiety on the one hand and the experience of stress on the other. Results showed the rate of displacement behaviour was positively correlated with state anxiety but unrelated to trait anxiety, and negatively correlated with the self-reported experience of stress, in agreement with the idea that displacement behaviour has a crucial impact on regulation of stress. Moreover, serial mediation analyses using a bias-corrected bootstrapping approach indicated displacement behaviour mediated the relationship between state anxiety and the experience of stress, and that state anxiety and displacement behaviour - in combination, respectively - mediated the link between trait anxiety and experience of stress. These results shed important new light on the function of displacement behaviour, and highlight promising new avenues for research into emotional expression and stress regulation.

Baseline and post-stress seasonal changes in immunocompetence and redox state maintenance in the fishing bat Myotis vivesi.

PubMed

Hernández-Arciga, Ulalume; Herrera M, L Gerardo; Ibáñez-Contreras, Alejandra; Miranda-Labra, Roxana U; Flores-Martínez, José Juan; Königsberg, Mina

2018-01-01

Little is known of how the stress response varies when animals confront seasonal life-history processes. Antioxidant defenses and damage caused by oxidative stress and their link with immunocompetence are powerful biomarkers to assess animal´s physiological stress response. The aim of this study was A) to determine redox state and variation in basal (pre-acute stress) immune function during summer, autumn and winter (spring was not assessed due to restrictions in collecting permit) in the fish-eating Myotis (Myotis vivesi; Chiroptera), and B) to determine the effect of acute stress on immunocompetence and redox state during each season. Acute stress was stimulated by restricting animal movement for 6 and 12 h. The magnitude of the cellular immune response was higher during winter whilst that of the humoral response was at its highest during summer. Humoral response increased after 6 h of movement restriction stress and returned to baseline levels after 12 h. Basal redox state was maintained throughout the year, with no significant changes in protein damage, and antioxidant activity was modulated mainly in relation to variation to environment cues, increasing during high temperatures and decreasing during windy nights. Antioxidant activity increased after the 6 h of stressful stimuli especially during summer and autumn, and to a lesser extent in early winter, but redox state did not vary. However, protein damage increased after 12 h of stress during summer. Prolonged stress when the bat is engaged in activities of high energy demand overcame its capacity to maintain homeostasis resulting in oxidative damage.

Baseline and post-stress seasonal changes in immunocompetence and redox state maintenance in the fishing bat Myotis vivesi

PubMed Central

Ibáñez-Contreras, Alejandra; Miranda-Labra, Roxana U.; Flores-Martínez, José Juan

2018-01-01

Little is known of how the stress response varies when animals confront seasonal life-history processes. Antioxidant defenses and damage caused by oxidative stress and their link with immunocompetence are powerful biomarkers to assess animal´s physiological stress response. The aim of this study was A) to determine redox state and variation in basal (pre-acute stress) immune function during summer, autumn and winter (spring was not assessed due to restrictions in collecting permit) in the fish-eating Myotis (Myotis vivesi; Chiroptera), and B) to determine the effect of acute stress on immunocompetence and redox state during each season. Acute stress was stimulated by restricting animal movement for 6 and 12 h. The magnitude of the cellular immune response was higher during winter whilst that of the humoral response was at its highest during summer. Humoral response increased after 6 h of movement restriction stress and returned to baseline levels after 12 h. Basal redox state was maintained throughout the year, with no significant changes in protein damage, and antioxidant activity was modulated mainly in relation to variation to environment cues, increasing during high temperatures and decreasing during windy nights. Antioxidant activity increased after the 6 h of stressful stimuli especially during summer and autumn, and to a lesser extent in early winter, but redox state did not vary. However, protein damage increased after 12 h of stress during summer. Prolonged stress when the bat is engaged in activities of high energy demand overcame its capacity to maintain homeostasis resulting in oxidative damage. PMID:29293551

Ab initio-aided CALPHAD thermodynamic modeling of the Sn-Pb binary system under current stressing

PubMed Central

Lin, Shih-kang; Yeh, Chao-kuei; Xie, Wei; Liu, Yu-chen; Yoshimura, Masahiro

2013-01-01

Soldering is an ancient process, having been developed 5000 years ago. It remains a crucial process with many modern applications. In electronic devices, electric currents pass through solder joints. A new physical phenomenon – the supersaturation of solders under high electric currents – has recently been observed. It involves (1) un-expected supersaturation of the solder matrix phase, and (2) the formation of unusual “ring-shaped” grains. However, the origin of these phenomena is not yet understood. Here we provide a plausible explanation of these phenomena based on the changes in the phase stability of Pb-Sn solders. Ab initio-aided CALPHAD modeling is utilized to translate the electric current-induced effect into the excess Gibbs free energies of the phases. Hence, the phase equilibrium can be shifted by current stressing. The Pb-Sn phase diagrams with and without current stressing clearly demonstrate the change in the phase stabilities of Pb-Sn solders under current stressing. PMID:24060995

Fracture mechanics concepts in reliability analysis of monolithic ceramics

NASA Technical Reports Server (NTRS)

Manderscheid, Jane M.; Gyekenyesi, John P.

1987-01-01

Basic design concepts for high-performance, monolithic ceramic structural components are addressed. The design of brittle ceramics differs from that of ductile metals because of the inability of ceramic materials to redistribute high local stresses caused by inherent flaws. Random flaw size and orientation requires that a probabilistic analysis be performed in order to determine component reliability. The current trend in probabilistic analysis is to combine linear elastic fracture mechanics concepts with the two parameter Weibull distribution function to predict component reliability under multiaxial stress states. Nondestructive evaluation supports this analytical effort by supplying data during verification testing. It can also help to determine statistical parameters which describe the material strength variation, in particular the material threshold strength (the third Weibull parameter), which in the past was often taken as zero for simplicity.

Longitudinal Associations between Maternal Work Stress, Negative Work-Family Spillover, and Depressive Symptoms

PubMed Central

Goodman, W. Benjamin; Crouter, Ann C.

2009-01-01

The current study examined associations over an 18-month period between maternal work stressors, negative work-family spillover, and depressive symptoms in a sample of 414 employed mothers with young children living in six predominantly nonmetropolitan counties in the Eastern United States. Results from a one-group mediation model revealed that a less flexible work environment and greater work pressure predicted higher levels of depressive symptoms, and further, that these associations were mediated by perceptions of negative work-family spillover. Additionally, results from a two-group mediation model suggested that work pressure predicted greater perceptions of spillover only for mothers employed full-time. Findings suggest the need for policies that reduce levels of work stress and help mothers manage their work and family responsibilities. PMID:20161088

Longitudinal Associations between Maternal Work Stress, Negative Work-Family Spillover, and Depressive Symptoms.

PubMed

Goodman, W Benjamin; Crouter, Ann C

2009-07-01

The current study examined associations over an 18-month period between maternal work stressors, negative work-family spillover, and depressive symptoms in a sample of 414 employed mothers with young children living in six predominantly nonmetropolitan counties in the Eastern United States. Results from a one-group mediation model revealed that a less flexible work environment and greater work pressure predicted higher levels of depressive symptoms, and further, that these associations were mediated by perceptions of negative work-family spillover. Additionally, results from a two-group mediation model suggested that work pressure predicted greater perceptions of spillover only for mothers employed full-time. Findings suggest the need for policies that reduce levels of work stress and help mothers manage their work and family responsibilities.

Physical activity and negative affective reactivity in daily life.

PubMed

Puterman, Eli; Weiss, Jordan; Beauchamp, Mark R; Mogle, Jacqueline; Almeida, David M

2017-12-01

The results from experimental studies indicate that physically active individuals remain calmer and report less anxiety after the induction of a standardized stressor. The current study extends this research to real life, and examines whether daily physical activity attenuates negative affect that occurs in response to naturally occurring daily stressors. The current study used data from the second wave of the National Study of Daily Experiences, a sub-study of the second wave of the Midlife in the United States Study (MIDUS-II) of 2,022 individuals aged 33-84 questioned nightly for eight consecutive days about their general affect and affective responses to stressful events and their engagement in physical activity. Results indicated that while negative affect is significantly elevated on days with stressful events compared to days free of events in all individuals, these effects are attenuated in those who remain physically active when compared to those who were underactive. This was also true for any day participants were physically active. Importantly, negative affect in response to any specific stressor was reduced the closer in time that the stressor occurred to the bout of exercise in underactive participants, while, in active participants, negative affect in response to any stressor remained low throughout the entire day that participants reported that they were active. Given the significant mental and physical health implications of elevated affective reactivity observed in previous studies, the current study sheds further light on the importance of remaining physically active in times of stress. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

Self-regulation and recovery: approaching an understanding of the process of recovery from stress.

PubMed

Beckmann, Jürgen; Kellmann, Michael

2004-12-01

Stress has been studied extensively in psychology. Only recently, however, has research started to address the question of how individuals manage to recover from stress. Recovery from stress is analyzed as a process of self-regulation. Several individual difference variables which affect the efficiency of self-regulation have been integrated into a structured model of the recovery process. Such variables are action versus state orientation (a tendency to ruminate, e.g., about a past experience) and volitional components, such as self-determination, self-motivation, emotion control, rumination, and self-discipline. Some of these components are assumed to promote recovery from stress, whereas others are assumed to further the perseverance of stress. The model was supported by the empirical findings of three independent studies (Study 1, N=58; Study 2, N=221; Study 3, N= 105). Kuhl's Action Control Scale measured action versus state orientation. Volitional components were assessed with Kuhl and Fuhrmann's Volitional Components Questionnaire. The amounts of experienced stress and recovery from stress was assessed with Kellmann and Kallus's Recovery-Stress Questionnaire. As hypothesized in the model, the disposition towards action versus state orientation was a more distant determinant of the recovery from stress and perseverance of stress. The volitional components are more proximal determinants in the recovery process. Action orientation promotes recovery from stress via adequate volitional skills, e.g., self-determination, self-motivation, emotion control, whereas state orientation furthers a perseverance of stress through rumination and self-discipline.

Stress evaluation of metallic material under steady state based on nonlinear critically refracted longitudinal wave

NASA Astrophysics Data System (ADS)

Mao, Hanling; Zhang, Yuhua; Mao, Hanying; Li, Xinxin; Huang, Zhenfeng

2018-06-01

This paper presents the study of applying the nonlinear ultrasonic wave to evaluate the stress state of metallic materials under steady state. The pre-stress loading method is applied to guarantee components with steady stress. Three kinds of nonlinear ultrasonic experiments based on critically refracted longitudinal wave are conducted on components which the critically refracted longitudinal wave propagates along x, x1 and x2 direction. Experimental results indicate the second and third order relative nonlinear coefficients monotonically increase with stress, and the normalized relationship is consistent with simplified dislocation models, which indicates the experimental result is logical. The combined ultrasonic nonlinear parameter is proposed, and three stress evaluation models at x direction are established based on three ultrasonic nonlinear parameters, which the estimation error is below 5%. Then two stress detection models at x1 and x2 direction are built based on combined ultrasonic nonlinear parameter, the stress synthesis method is applied to calculate the magnitude and direction of principal stress. The results show the prediction error is within 5% and the angle deviation is within 1.5°. Therefore the nonlinear ultrasonic technique based on LCR wave could be applied to nondestructively evaluate the stress of metallic materials under steady state which the magnitude and direction are included.

Automated Quantitative Nuclear Cardiology Methods

PubMed Central

Motwani, Manish; Berman, Daniel S.; Germano, Guido; Slomka, Piotr J.

2016-01-01

Quantitative analysis of SPECT and PET has become a major part of nuclear cardiology practice. Current software tools can automatically segment the left ventricle, quantify function, establish myocardial perfusion maps and estimate global and local measures of stress/rest perfusion – all with minimal user input. State-of-the-art automated techniques have been shown to offer high diagnostic accuracy for detecting coronary artery disease, as well as predict prognostic outcomes. This chapter briefly reviews these techniques, highlights several challenges and discusses the latest developments. PMID:26590779

Standards, Regulation and Registration of Dental Laboratories. An Industry Update.

PubMed

Giovannone, Paul L

2015-01-01

State dental associations are showing increased interest in maintaining current standards and regulations affecting the dental laboratory industry as mandated by the Food and Drug Administration. The domestic dental laboratory industry is being significantly stressed by foreign competition, rapid technology development and unprecedented consolidation, which are changing the way that prosthetic devices and restorations are manufactured and delivered to dentists. Of paramount importance to the prescribing dentist is the accurate documentation of the source and materials being used in prostheses being delivered to patients.

Impacts of the Mesoscale Ocean-Atmosphere Coupling on the Peru-Chile Ocean Dynamics: The Current-Induced Wind Stress Modulation

NASA Astrophysics Data System (ADS)

Oerder, V.; Colas, F.; Echevin, V.; Masson, S.; Lemarié, F.

2018-02-01

The ocean dynamical responses to the surface current-wind stress interaction at the oceanic mesoscale are investigated in the South-East Pacific using a high-resolution regional ocean-atmosphere coupled model. Two simulations are compared: one includes the surface current in the wind stress computation while the other does not. In the coastal region, absolute wind velocities are different between the two simulations but the wind stress remains very similar. As a consequence, the mean regional oceanic circulation is almost unchanged. On the contrary, the mesoscale activity is strongly reduced when taking into account the effect of the surface current on the wind stress. This is caused by a weakening of the eddy kinetic energy generation near the coast by the wind work and to intensified offshore eddy damping. We show that, above coherent eddies, the current-stress interaction generates eddy damping through Ekman pumping and eddy kinetic energy dissipation through wind work. This alters significantly the coherent eddy vertical structures compared with the control simulation, weakening the temperature and vorticity anomalies and increasing strongly the vertical velocity anomalies associated to eddies.

Current development in selected stress and thermal analysis software interfaces with PRO-ENGINEER

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schulze, J.

1993-06-01

Ever since PRO-ENGINEER has become a dominating CAD package available to the public, some of us have been saying, ``Gee, if only I could export my geometry to a stress analysis program without having to recreate any of the details already created, wouldn`t that be spectacular?`` Well, much to the credit of the major stress and thermal analysis software vendors, some of them have been listening to design engineers like me badger them to furnish a seamless interface between PRO and their stress analysis programs. The down side of this problem is the fact that a lot of problems stillmore » exist with most of the vendors and their interfaces. I want to discuss the interfaces that I feel are currently ``State of the Art``, and how they are developing and the future for finally arriving at a transparent procedure that an engineer at a workstation can utilize in his or her design process. In years past, engineers would develop a design and changes would evolve based on intuition, or somebody else`s critical evaluation. Then the design would be forwarded to the production group, or the stress analysis group for further evaluation and analysis. Maybe data from a preliminary prototype would be collected and an evaluation report made. All of this took time and increased the cost of the item to be manufactured. Today, the engineer must assume responsibility for design and functional capability early on in the design process, if for no other reason than costs associated with diverse channels of critiquing. For that reason, one place to enhance the design process is to have the ability to do preliminary stress and thermal analysis during the initial design phase. This is both cost and time effective. But, as I am sure you are aware, this has been easier said than done.« less

Passive smoking reduces and vitamin C increases exercise-induced oxidative stress: does this make passive smoking an anti-oxidant and vitamin C a pro-oxidant stimulus?

PubMed

Theodorou, Anastasios A; Paschalis, Vassilis; Kyparos, Antonios; Panayiotou, George; Nikolaidis, Michalis G

2014-11-07

The current interpretative framework states that, for a certain experimental treatment (usually a chemical substance) to be classified as "anti-oxidant", it must possess the property of reducing (or even nullifying) exercise-induced oxidative stress. The aim of the study was to compare side by side, in the same experimental setup, redox biomarkers responses to an identical acute eccentric exercise session, before and after chronic passive smoking (considered a pro-oxidant stimulus) or vitamin C supplementation (considered an anti-oxidant stimulus). Twenty men were randomly assigned into either passive smoking or vitamin C group. All participants performed two acute eccentric exercise sessions, one before and one after either exposure to passive smoking or vitamin C supplementation for 12 days. Vitamin C, oxidant biomarkers (F2-isoprostanes and protein carbonyls) and the non-enzymatic antioxidant (glutathione) were measured, before and after passive smoking, vitamin C supplementation or exercise. It was found that chronic exposure to passive smoking increased the level of F2-isoprostanes and decreased the level of glutathione at rest, resulting in minimal increase or absence of oxidative stress after exercise. Conversely, chronic supplementation with vitamin C decreased the level of F2-isoprostanes and increased the level of glutathione at rest, resulting in marked exercise-induced oxidative stress. Contrary to the current scientific consensus, our results show that, when a pro-oxidant stimulus is chronically delivered, it is more likely that oxidative stress induced by subsequent exercise is decreased and not increased. Reversely, it is more likely to find greater exercise-induced oxidative stress after previous exposure to an anti-oxidant stimulus. We believe that the proposed framework will be a useful tool to reach more pragmatic explanations of redox biology phenomena. Copyright © 2014 Elsevier Inc. All rights reserved.

Determination of in situ state of stress at the Spent Fuel Test-Climax site, Climax Stock, Nevada Test Site

USGS Publications Warehouse

Ellis, W.L.; Magner, J.E.

1982-01-01

Determination of the in situ state of stress at the site of the Spent Fuel Test--Climax, using the U.S. Bureau of Mines overcore method, indicates principal stress magnitudes of 11.6 MPa, 7.1 MPa, and 2.8 MPa. The bearing and plunge of the maximum and minimum principal stress components are, respectively: N. 56? E., 29? NE; and N. 42? W., 14? NW. The vertical stress magnitude of 7.9 MPa calculated from the overcore data is significantly less than expected from overburden pressure, suggesting the stress field is influenced by local or areal geologic factors. Results from this investigation indicate (1) the stress state at the Spent Fuel Test--Climax site deviates significantly from a gravitational stress field, both in relative stress magnitudes and in orientation; (2) numerical modeling will not realistically simulate the near-field response of the Spent Fuel Test--Climax site if gravitational and (or) horizontal and vertical applied stress boundary conditions are assumed; and (3) substantial stress variations may occur spatially within the stock.

Environmental study of ERTS-1 imagery: Lake Champlain and Vermont

NASA Technical Reports Server (NTRS)

Lind, A. O.; Henson, E. B.; Pelton, J. O.

1973-01-01

Environmental concerns of the State of Vermont currently being stressed include water quality in Lake Champlain and a state-wide land use and capability plan. Significant results obtained from ERTS-1 relate directly to the above concerns. Industrial water pollution and turbidity in Lake Champlain have been identified and mapped and the ERTS pollution data will be used in the developing court suit which Vermont has initiated against the polluters. ERTS imagery has also provided a foundation for updating and revising land use inventories. Major classes of land use have been identified and mapped, and substantial progress has been made toward the mapping of such land use divisions as crop and forest type, and wetlands.

Cycle of charge carrier states with formation and extinction of a floating gate in an ambipolar tetracyanoquaterthienoquinoid-based field-effect transistor

NASA Astrophysics Data System (ADS)

Itoh, Takuro; Toyota, Taro; Higuchi, Hiroyuki; Matsushita, Michio M.; Suzuki, Kentaro; Sugawara, Tadashi

2017-03-01

A tetracyanoquaterthienoquinoid (TCT4Q)-based field effect transistor is characterized by the ambipolar transfer characteristics and the facile shift of the threshold voltage induced by the bias stress. The trapping and detrapping kinetics of charge carriers was investigated in detail by the temperature dependence of the decay of source-drain current (ISD). We found a repeatable formation of a molecular floating gate is derived from a 'charge carrier-and-gate' cycle comprising four stages, trapping of mobile carriers, formation of a floating gate, induction of oppositely charged mobile carriers, and recombination between mobile and trapped carriers to restore the initial state.

Caregiver stress: does states' expenditure on home- and community-based services matter?

PubMed

Hong, Michin; Casado, Banghwa Lee

2015-01-01

This study examined how state expenditure on home- and community-based services (HCBS) and individual factors are associated with caregiver stress. A total of 1,849 cases from the 2004 National Long-Term Care Survey were included. Gender, education, perceived physical strain, and economic hardship, as well as the number of limitations in instrumental activities of daily living (IADL) for the care recipient, were associated with caregiver stress. The cross-level interaction between service utilization and state expenditure on HCBS was significant, suggesting that living in states with a higher expenditure on HCBS is associated with reduced stress regardless of service utilization.

Stress state in turbopump bearing induced by shrink fitting

NASA Technical Reports Server (NTRS)

Sims, P.; Zee, R.

1991-01-01

The stress generated by shrink fitting in bearing-like geometries is studied. The feasibility of using strain gages to determine the strain induced by shrink fitting process is demonstrated. Results from a ring with a uniform cross section reveal the validity of simple stress mechanics calculations for determining the stress state induced in this geometry by shrink fitting.

Probing Earth's State of Stress

NASA Astrophysics Data System (ADS)

Delorey, A. A.; Maceira, M.; Johnson, P. A.; Coblentz, D. D.

2016-12-01

The state of stress in the Earth's crust is a fundamental physical property that controls both engineered and natural systems. Engineered environments including those for hydrocarbon, geothermal energy, and mineral extraction, as well those for storage of wastewater, carbon dioxide, and nuclear fuel are as important as ever to our economy and environment. Yet, it is at spatial scales relevant to these activities where stress is least understood. Additionally, in engineered environments the rate of change in the stress field can be much higher than that of natural systems. In order to use subsurface resources more safely and effectively, we need to understand stress at the relevant temporal and spatial scales. We will present our latest results characterizing the state of stress in the Earth at scales relevant to engineered environments. Two important components of the state of stress are the orientation and magnitude of the stress tensor, and a measure of how close faults are to failure. The stress tensor at any point in a reservoir or repository has contributions from both far-field tectonic stress and local density heterogeneity. We jointly invert seismic (body and surface waves) and gravity data for a self-consistent model of elastic moduli and density and use the model to calculate the contribution of local heterogeneity to the total stress field. We then combine local and plate-scale contributions, using local indicators for calibration and ground-truth. In addition, we will present results from an analysis of the quantity and pattern of microseismicity as an indicator of critically stressed faults. Faults are triggered by transient stresses only when critically stressed (near failure). We show that tidal stresses can trigger earthquakes in both tectonic and reservoir environments and can reveal both stress and poroelastic conditions.

Stress free configuration of the human eye.

PubMed

Elsheikh, Ahmed; Whitford, Charles; Hamarashid, Rosti; Kassem, Wael; Joda, Akram; Büchler, Philippe

2013-02-01

Numerical simulations of eye globes often rely on topographies that have been measured in vivo using devices such as the Pentacam or OCT. The topographies, which represent the form of the already stressed eye under the existing intraocular pressure, introduce approximations in the analysis. The accuracy of the simulations could be improved if either the stress state of the eye under the effect of intraocular pressure is determined, or the stress-free form of the eye estimated prior to conducting the analysis. This study reviews earlier attempts to address this problem and assesses the performance of an iterative technique proposed by Pandolfi and Holzapfel [1], which is both simple to implement and promises high accuracy in estimating the eye's stress-free form. A parametric study has been conducted and demonstrated reliance of the error level on the level of flexibility of the eye model, especially in the cornea region. However, in all cases considered 3-4 analysis iterations were sufficient to produce a stress-free form with average errors in node location <10(-6)mm and a maximal error <10(-4)mm. This error level, which is similar to what has been achieved with other methods and orders of magnitude lower than the accuracy of current clinical topography systems, justifies the use of the technique as a pre-processing step in ocular numerical simulations. Crown Copyright © 2012. Published by Elsevier Ltd. All rights reserved.

A discrete dislocation dynamics model of creeping single crystals

NASA Astrophysics Data System (ADS)

Rajaguru, M.; Keralavarma, S. M.

2018-04-01

Failure by creep is a design limiting issue for metallic materials used in several high temperature applications. Current theoretical models of creep are phenomenological with little connection to the underlying microscopic mechanisms. In this paper, a bottom-up simulation framework based on the discrete dislocation dynamics method is presented for dislocation creep aided by the diffusion of vacancies, known to be the rate controlling mechanism at high temperature and stress levels. The time evolution of the creep strain and the dislocation microstructure in a periodic unit cell of a nominally infinite single crystal is simulated using the kinetic Monte Carlo method, together with approximate constitutive laws formulated for the rates of thermal activation of dislocations over local pinning obstacles. The deformation of the crystal due to dislocation glide between individual thermal activation events is simulated using a standard dislocation dynamics algorithm, extended to account for constant stress periodic boundary conditions. Steady state creep conditions are obtained in the simulations with the predicted creep rates as a function of stress and temperature in good agreement with experimentally reported values. Arrhenius scaling of the creep rates as a function of temperature and power-law scaling with the applied stress are also reproduced, with the values of the power-law exponents in the high stress regime in good agreement with experiments.

The impact of shift work on nurses' job stress, sleep quality and self-perceived health status.

PubMed

Lin, Shu-Hui; Liao, Wen-Chun; Chen, Mei-Yen; Fan, Jun-Yu

2014-07-01

The aim of this study was to describe the current state of nurses' shift work in Taiwan and how it affects nurses' stress, sleep quality and self-perceived health status. To enable the provision of 24-hour patient care, nurses need to work various shifts. Long-term shift work significantly affects nurses' overall physical and mental health. Nurses from four Chiayi County district hospitals in Taiwan (n = 266) participated in this cross-sectional study from August to September 2010. Demographics, work schedule forms, a stress checklist, a sleep-quality measure and a health-status measure were used to collect data. Independent t-test, one-way anova, Pearson's r, and hierarchical regression were applied for analysis. The results showed that regardless of the amount of shift work they performed, nurses reported moderate job stress, poor sleep quality and moderate self-perceived health. The following significant relationships were observed: job stress was inversely related to sleep quality, which was directly related to self-perceived health status. Hospital managers need to ensure more healthy shift work scheduling in order to improve nurses' clinical performance and personal health status, thereby also improving the quality of patient care. © 2012 John Wiley & Sons Ltd.

Increased Small-World Network Topology Following Deployment-Acquired Traumatic Brain Injury Associated with the Development of Post-Traumatic Stress Disorder.

PubMed

Rowland, Jared A; Stapleton-Kotloski, Jennifer R; Dobbins, Dorothy L; Rogers, Emily; Godwin, Dwayne W; Taber, Katherine H

2018-05-01

Cross-sectional and longitudinal studies in active duty and veteran cohorts have both demonstrated that deployment-acquired traumatic brain injury (TBI) is an independent risk factor for developing post-traumatic stress disorder (PTSD), beyond confounds such as combat exposure, physical injury, predeployment TBI, and pre-deployment psychiatric symptoms. This study investigated how resting-state brain networks differ between individuals who developed PTSD and those who did not following deployment-acquired TBI. Participants included postdeployment veterans with deployment-acquired TBI history both with and without current PTSD diagnosis. Graph metrics, including small-worldness, clustering coefficient, and modularity, were calculated from individually constructed whole-brain networks based on 5-min eyes-open resting-state magnetoencephalography (MEG) recordings. Analyses were adjusted for age and premorbid IQ. Results demonstrated that participants with current PTSD displayed higher levels of small-worldness, F(1,12) = 5.364, p < 0.039, partial eta squared = 0.309, and Cohen's d = 0.972, and clustering coefficient, F(1, 12) = 12.204, p < 0.004, partial eta squared = 0.504, and Cohen's d = 0.905, than participants without current PTSD. There were no between-group differences in modularity or the number of modules present. These findings are consistent with a hyperconnectivity hypothesis of the effect of TBI history on functional networks rather than a disconnection hypothesis, demonstrating increased levels of clustering coefficient rather than a decrease as might be expected; however, these results do not account for potential changes in brain structure. These results demonstrate the potential pathological sequelae of changes in functional brain networks following deployment-acquired TBI and represent potential neurobiological changes associated with deployment-acquired TBI that may increase the risk of subsequently developing PTSD.

Kinetic model for dependence of thin film stress on growth rate, temperature, and microstructure

NASA Astrophysics Data System (ADS)

Chason, E.; Shin, J. W.; Hearne, S. J.; Freund, L. B.

2012-04-01

During deposition, many thin films go through a range of stress states, changing from compressive to tensile and back again. In addition, the stress depends strongly on the processing and material parameters. We have developed a simple analytical model to describe the stress evolution in terms of a kinetic competition between different mechanisms of stress generation and relaxation at the triple junction where the surface and grain boundary intersect. The model describes how the steady state stress scales with the dimensionless parameter D/LR where D is the diffusivity, R is the growth rate, and L is the grain size. It also explains the transition from tensile to compressive stress as the microstructure evolves from isolated islands to a continuous film. We compare calculations from the model with measurements of the stress dependence on grain size and growth rate in the steady state regime and of the evolution of stress with thickness for different temperatures.

Experimental residual stress evaluation of hydraulic expansion transitions in Alloy 690 steam generator tubing

DOE Office of Scientific and Technical Information (OSTI.GOV)

McGregor, R.; Doherty, P.; Hornbach, D.

1995-12-31

Nuclear Steam Generator (SG) service reliability and longevity have been seriously affected worldwide by corrosion at the tube-to-tubesheet joint expansion. Current SG designs for new facilities and replacement projects enhance corrosion resistance through the use of advanced tubing materials and improved joint design and fabrication techniques. Here, transition zones of hydraulic expansions have undergone detailed experimental evaluation to define residual stress and cold-work distribution on and below the secondary-side surface. Using X-ray diffraction techniques, with supporting finite element analysis, variations are compared in tubing metallurgical condition, tube/pitch geometry, expansion pressure, and tube-to-hole clearance. Initial measurements to characterize the unexpanded tubemore » reveal compressive stresses associated with a thin work-hardened layer on the outer surface of the tube. The gradient of cold-work was measured as 3% to 0% within .001 inch of the surface. The levels and character of residual stresses following hydraulic expansion are primarily dependent on this work-hardened surface layer and initial stress state that is unique to each tube fabrication process. Tensile stresses following expansion are less than 25% of the local yield stress and are found on the transition in a narrow circumferential band at the immediate tube surface (< .0002 inch/0.005 mm depth). The measurements otherwise indicate a predominance of compressive stresses on and below the secondary-side surface of the transition zone. Excellent resistance to SWSCC initiation is offered by the low levels of tensile stress and cold-work. Propagation of any possible cracking would be deterred by the compressive stress field that surrounds this small volume of tensile material.« less

Stress induced neural reorganization: A conceptual framework linking depression and Alzheimer's disease.

PubMed

Ross, Jennifer A; Gliebus, Gediminas; Van Bockstaele, Elisabeth J

2018-07-13

Chronic stress is a risk factor for a number of physiological disorders including cardiovascular disease, obesity and gastrointestinal disorders, as well as psychiatric and neurodegenerative disorders. There are a number of underlying molecular and cellular mechanisms altered in the course of chronic stress, which may increase the vulnerability of individuals to develop psychiatric disorders such as depression, and neurodegenerative disorders such as Alzheimer's Disease (AD). This is evident in the influence of stress on large-scale brain networks, including the resting state Default Mode Network (DMN), the effects of stress on neuronal circuitry and architecture, and the cellular and molecular adaptations to stress, which may render individuals with stress related psychiatric disorders more vulnerable to neurodegenerative disease later in life. These alterations include decreased negative feedback inhibition of the hypothalamic pituitary axis (HPA) axis, decreased dendritic arborization and spine density in the prefrontal cortex (PFC) and hippocampus, and the release of proinflammatory cytokines, which may suppress neurogenesis and promote neuronal cell death. Each of these factors are thought to play a role in stress-related psychiatric disease as well as AD, and have been observed in clinical and post-mortem studies of individuals with depression and AD. The goal of the current review is to summarize clinical and preclinical evidence supporting a role for chronic stress as a putative link between neuropsychiatric and neurodegenerative disease. Moreover, we provide a rationale for the importance of taking a medical history of stress-related psychiatric diseases into consideration during clinical trial design, as they may play an important role in the etiology of AD in stratified patient populations. Copyright © 2017 Elsevier Inc. All rights reserved.

The dual blocker of FAAH/TRPV1 N-arachidonoylserotonin reverses the behavioral despair induced by stress in rats and modulates the HPA-axis.

PubMed

Navarria, Andrea; Tamburella, Alessandra; Iannotti, Fabio A; Micale, Vincenzo; Camillieri, Giovanni; Gozzo, Lucia; Verde, Roberta; Imperatore, Roberta; Leggio, Gian Marco; Drago, Filippo; Di Marzo, Vincenzo

2014-09-01

In recent years, several studies have explored the involvement of the deregulation of the hypothalamus-pituitary-adrenal (HPA) axis in the pathophysiology of stress-related disorders. HPA hyper-activation as a consequence of acute/chronic stress has been found to play a major role in the neurobiological changes that are responsible for the onset of such states. Currently available medications for depression, one of the most relevant stress-related disorders, present several limitations, including a time lag for treatment response and low rates of efficacy. N-Arachidonoylserotonin (AA-5-HT), a dual blocker at fatty acid amide hydrolase (FAAH, the enzyme responsible for the inactivation of the endocannabinoid anandamide) and transient receptor potential vanilloid type-1 channel (TRPV1), produces anxiolytic-like effects in mice. The present study was designed to assess the capability of AA-5-HT to reverse the behavioral despair following exposure to stress in rats and the role of the HPA-axis. Behavioral tasks were performed, and corticosterone and endocannabinoid (anandamide and 2-arachidonoylglycerol) levels were measured in selected brain areas critically involved in the pathophysiology of stress-related disorders (medial PFC and hippocampus) under basal and stress conditions, and in response to treatment with AA-5-HT. Our data show that AA-5-HT reverses the rat behavioral despair in the forced swim test under stress conditions, and this effect is associated with the normalization of the HPA-axis deregulation that follows stress application and only in part with elevation of anandamide levels. Blockade of FAAH and TRPV1 may thus represent a novel target to design novel therapeutic strategies for the treatment of stress-related disorders. Copyright © 2014 Elsevier Ltd. All rights reserved.

The effect of music-reinforced nonnutritive sucking on state of preterm, low birthweight infants experiencing heelstick.

PubMed

Whipple, Jennifer

2008-01-01

This study examined the physiologic and behavioral effects of music-reinforced nonnutritive sucking (NNS) for preterm, low birthweight (LBW) infants experiencing heelstick. Subjects were 60 infants, age 32 to 37 weeks post conceptional age in a neonatal intensive care unit. Infants were randomly assigned to one of three treatment groups: pacifier-activated lullaby (PAL), pacifier-only, and no-contact. Experimental infants were provided the Sondrex PAL System, which plays music contingent on infant sucking. Pacifier-only infants did not receive music reinforcement for sucking, and no-contact infants were not provided a pacifier or music at any point during the procedure. Stress level and behavior state were assessed continuously and heart, respiratory, and oxygen saturation rates were recorded at 15-second intervals for all infants. Most physiologic data results were inconclusive. However, analysis of behavior state and stress level revealed the following significant differences for the PAL and pacifier-only groups compared to the no-contact group, all of which were greatest between the PAL and no-contact groups: lower during-heelstick behavior state means, less time in undesirable behavior states, lower during- and post-heelstick stress level means, and smaller behavior state and stress level differences between intervals. In addition, the PAL group had a significantly lower pre-heelstick stress level mean than the no-contact group. Behavior state and stress level were also more stable across time for the PAL group than the other groups, and patterns of changes in oxygen saturation, behavior state, and stress level indicate that music-reinforced NNS may facilitate return to homeostasis.

Metabolic Stress and Disorders Related to Alterations in Mitochondrial Fission or Fusion

PubMed Central

Babbar, Mansi; Sheikh, M. Saeed

2014-01-01

Mitochondrial morphology and metabolism play an important role in cellular homeostasis. Recent studies have shown that the fidelity of mitochondrial morphology is important in maintaining mitochondrial shape, number, size, membrane potential, ATP synthesis, mtDNA, motility, signaling, quality control, response to cellular stress, mitophagy and apoptosis. This article provides an overview of the current state of knowledge of the fission and fusion machinery with a focus on the mechanisms underlying the regulation of the mitochondrial morphology and cellular energy state. Several lines of evidence indicate that dysregulation of mitochondrial fission or fusion is associated with mitochondrial dysfunction, which in turn impacts mitophagy and apoptosis. Metabolic disorders are also associated with dysregulation of fission or fusion and the available lines of evidence point to a bidirectional interplay between the mitochondrial fission or fusion reactions and bioenergetics. Clearly, more in-depth studies are needed to fully elucidate the mechanisms that control mitochondrial fission and fusion. It is envisioned that the outcome of such studies will improve the understanding of the molecular basis of related metabolic disorders and also facilitate the development of better therapeutics. PMID:24533171

Numerical simulation of stress-strain state of electrophoretic shell molds

NASA Astrophysics Data System (ADS)

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

Thick thermal barrier coatings for diesel engines

NASA Technical Reports Server (NTRS)

Beardsley, M. Brad

1995-01-01

Caterpillar's approach to applying thick thermal barrier coatings (TTBC's) to diesel engine combustion chambers has been to use advanced modeling techniques to predict engine conditions and combine this information with fundamental property evaluation of TTBC systems to predict engine performance and TTBC stress states. Engine testing has been used to verify the predicted performance of the TTBC systems and provide information on failure mechanisms. The objective Caterpillar's program to date has been to advance the fundamental understanding of thick thermal barrier coating systems. Previous reviews of thermal barrier coating technology concluded that the current level of understanding of coating system behavior is inadequate and the lack of fundamental understanding may impeded the application of TTBC's to diesel engines. Areas of TTBC technology being examined in this program include powder characteristics and chemistry; bond coat composition; coating design, microstructure, and thickness as they affect properties, durability, and reliability; and TTBC 'aging' effects (microstructural and property changes) under diesel engine operating conditions. Methods to evaluate the reliability and durability of TTBC's have been developed that attempt to understand the fundamental strength of TTBC's for particular stress states.

Thick thermal barrier coatings for diesel engines

NASA Technical Reports Server (NTRS)

Beardsley, M. B.

1995-01-01

Caterpillar's approach to applying Thick Thermal Barrier Coatings (TTBC's) to diesel engine combustion chambers has been to use advanced modeling techniques to predict engine conditions and combine this information with fundamental property evaluation of TTBC systems to predict engine performance and TTBC stress states. Engine testing has been used to verify the predicted performance of the TTBC systems and provide information on failure mechanisms. The objective of Caterpillar's subcontract with ORNL is to advance the fundamental understanding of thick thermal barrier coating systems. Previous reviews of thermal barrier coating technology concluded that the current level of understanding of coating system behavior is inadequate and the lack of fundamental understanding may impede the application of TTBC's to diesel engines. Areas of TTBC technology being examined in this program include powder characteristics and chemistry; bond coat composition; coating design, microstructure, and thickness as they affect properties, durability, and reliability; and TTBC 'aging' effects (microstructural and property changes) under diesel engine operating conditions. Methods to evaluate the reliability and durability of TTBC's have been developed that attempt to understand the fundamental strength of TTBC's for particular stress states.

Uric Acid Induces Hepatic Steatosis by Generation of Mitochondrial Oxidative Stress

PubMed Central

Lanaspa, Miguel A.; Sanchez-Lozada, Laura G.; Choi, Yea-Jin; Cicerchi, Christina; Kanbay, Mehmet; Roncal-Jimenez, Carlos A.; Ishimoto, Takuji; Li, Nanxing; Marek, George; Duranay, Murat; Schreiner, George; Rodriguez-Iturbe, Bernardo; Nakagawa, Takahiko; Kang, Duk-Hee; Sautin, Yuri Y.; Johnson, Richard J.

2012-01-01

Metabolic syndrome represents a collection of abnormalities that includes fatty liver, and it currently affects one-third of the United States population and has become a major health concern worldwide. Fructose intake, primarily from added sugars in soft drinks, can induce fatty liver in animals and is epidemiologically associated with nonalcoholic fatty liver disease in humans. Fructose is considered lipogenic due to its ability to generate triglycerides as a direct consequence of the metabolism of the fructose molecule. Here, we show that fructose also stimulates triglyceride synthesis via a purine-degrading pathway that is triggered from the rapid phosphorylation of fructose by fructokinase. Generated AMP enters into the purine degradation pathway through the activation of AMP deaminase resulting in uric acid production and the generation of mitochondrial oxidants. Mitochondrial oxidative stress results in the inhibition of aconitase in the Krebs cycle, resulting in the accumulation of citrate and the stimulation of ATP citrate lyase and fatty-acid synthase leading to de novo lipogeneis. These studies provide new insights into the pathogenesis of hepatic fat accumulation under normal and diseased states. PMID:23035112

Mechanism-based modeling of solute strengthening: application to thermal creep in Zr alloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tome, Carlos; Wen, Wei; Capolungo, Laurent

2017-08-01

This report focuses on the development of a physics-based thermal creep model aiming to predict the behavior of Zr alloy under reactor accident condition. The current models used for this kind of simulations are mostly empirical in nature, based generally on fits to the experimental steady-state creep rates under different temperature and stress conditions, which has the following limitations. First, reactor accident conditions, such as RIA and LOCA, usually take place in short times and involve only the primary, not the steady-state creep behavior stage. Moreover, the empirical models cannot cover the conditions from normal operation to accident environments. Formore » example, Kombaiah and Murty [1,2] recently reported a transition between the low (n~4) and high (n~9) power law creep regimes in Zr alloys depending on the applied stress. Capturing such a behavior requires an accurate description of the mechanisms involved in the process. Therefore, a mechanism-based model that accounts for the evolution with time of microstructure is more appropriate and reliable for this kind of simulation.« less

Abiotic Stress Signaling in Wheat – An Inclusive Overview of Hormonal Interactions During Abiotic Stress Responses in Wheat

PubMed Central

Abhinandan, Kumar; Skori, Logan; Stanic, Matija; Hickerson, Neil M. N.; Jamshed, Muhammad; Samuel, Marcus A.

2018-01-01

Rapid global warming directly impacts agricultural productivity and poses a major challenge to the present-day agriculture. Recent climate change models predict severe losses in crop production worldwide due to the changing environment, and in wheat, this can be as large as 42 Mt/°C rise in temperature. Although wheat occupies the largest total harvested area (38.8%) among the cereals including rice and maize, its total productivity remains the lowest. The major production losses in wheat are caused more by abiotic stresses such as drought, salinity, and high temperature than by biotic insults. Thus, understanding the effects of these stresses becomes indispensable for wheat improvement programs which have depended mainly on the genetic variations present in the wheat genome through conventional breeding. Notably, recent biotechnological breakthroughs in the understanding of gene functions and access to whole genome sequences have opened new avenues for crop improvement. Despite the availability of such resources in wheat, progress is still limited to the understanding of the stress signaling mechanisms using model plants such as Arabidopsis, rice and Brachypodium and not directly using wheat as the model organism. This review presents an inclusive overview of the phenotypic and physiological changes in wheat due to various abiotic stresses followed by the current state of knowledge on the identified mechanisms of perception and signal transduction in wheat. Specifically, this review provides an in-depth analysis of different hormonal interactions and signaling observed during abiotic stress signaling in wheat. PMID:29942321

Weibull crack density coefficient for polydimensional stress states

NASA Technical Reports Server (NTRS)

Gross, Bernard; Gyekenyesi, John P.

1989-01-01

A structural ceramic analysis and reliability evaluation code has recently been developed encompassing volume and surface flaw induced fracture, modeled by the two-parameter Weibull probability density function. A segment of the software involves computing the Weibull polydimensional stress state crack density coefficient from uniaxial stress experimental fracture data. The relationship of the polydimensional stress coefficient to the uniaxial stress coefficient is derived for a shear-insensitive material with a random surface flaw population.

Shared and unique responses of plants to multiple individual stresses and stress combinations: physiological and molecular mechanisms

PubMed Central

Pandey, Prachi; Ramegowda, Venkategowda; Senthil-Kumar, Muthappa

2015-01-01

In field conditions, plants are often simultaneously exposed to multiple biotic and abiotic stresses resulting in substantial yield loss. Plants have evolved various physiological and molecular adaptations to protect themselves under stress combinations. Emerging evidences suggest that plant responses to a combination of stresses are unique from individual stress responses. In addition, plants exhibit shared responses which are common to individual stresses and stress combination. In this review, we provide an update on the current understanding of both unique and shared responses. Specific focus of this review is on heat–drought stress as a major abiotic stress combination and, drought–pathogen and heat–pathogen as examples of abiotic–biotic stress combinations. We also comprehend the current understanding of molecular mechanisms of cross talk in relation to shared and unique molecular responses for plant survival under stress combinations. Thus, the knowledge of shared responses of plants from individual stress studies and stress combinations can be utilized to develop varieties with broad spectrum stress tolerance. PMID:26442037

On the energetics of tensile and shear void coalescences

NASA Astrophysics Data System (ADS)

Wong, W. H.; Guo, T. F.

2015-09-01

This paper investigates the mechanisms of tensile and shear void coalescences in ductile materials from energetics perspective. By examining and comparing the elastic and plastic energies of a voided cell throughout its deformation history, the onset of and final coalescence can be distinctly established. This energy-based approach offers a single unified method and criterion for determining the occurrences of both mechanisms. This paper also reports a novel micromechanics model that considers general stress states described by three macroscopic normal stresses and one macroscopic shear stress. Detailed formulation of the model is presented that includes the homogenization-based derivation and implementation of a 4×4 orthogonal transformation matrix, which relates the macroscopic deformation rate of the cell to displacement rates of non-physical degrees-of-freedom (DOFs), and the polar decomposition of the macroscopic deformation gradient tensor which admits the explicit determination of the logarithmic strain measures and rotation angle. In terms of stress ratios, ρ1 (=Σ11 /Σ22) ,ρ2 (=Σ12 /Σ22) ,ρ3 (=Σ33 /Σ22), it is analytically shown that multiple macroscopic stress states {ρ1 ,ρ2 ,ρ3 } can exist that result in the same stress triaxiality T and Lode parameter L. Specifically, it is shown that for a prescribed pair of T and L and in the absence of shear stress, at most six stress states {ρ1 , 0 ,ρ3 } are possible. On the other extreme in the presence of shear stress, an infinite number of stress states is possible, due to the existence of Mohr's circle for this stress state. This model, together with the proposed energy-based criteria, is used to examine void coalescence under multiple stress-state conditions for any given T and L. Numerical results have shown that the presence of shear stress has a significant effect of reducing the effective strains for the onset of and final void coalescences. In addition, a relationship has also been established between shear angle and effective strain at the onset of shear void coalescence.

Stress state reconstruction and tectonic evolution of the northern slope of the Baikit anteclise, Siberian Craton, based on 3D seismic data

NASA Astrophysics Data System (ADS)

Moskalenko, A. N.; Khudoley, A. K.; Khusnitdinov, R. R.

2017-05-01

In this work, we consider application of an original method for determining the indicators of the tectonic stress fields in the northern Baikit anteclise based on 3D seismic data for further reconstruction of the stress state parameters when analyzing structural maps of seismic horizons and corresponded faults. The stress state parameters are determined by the orientations of the main stress axes and shape of the stress ellipsoid. To calculate the stress state parameters from data on the spatial orientations of faults and slip vectors, we used the algorithms from quasiprimary stress computation methods and cataclastic analysis, implemented in the software products FaultKinWin and StressGeol, respectively. The results of this work show that kinematic characteristics of faults regularly change toward the top of succession and that the stress state parameters are characterized by different values of the Lode-Nadai coefficient. Faults are presented as strike-slip faults with normal or reverse component of displacement. Three stages of formation of the faults are revealed: (1) partial inversion of ancient normal faults, (2) the most intense stage with the predominance of thrust and strike-slip faults at north-northeast orientation of an axis of the main compression, and (3) strike-slip faults at the west-northwest orientation of an axis of the main compression. The second and third stages are pre-Vendian in age and correlate to tectonic events that took place during the evolution of the active southwestern margin of the Siberian Craton.

Plantar pressure and daily cumulative stress in persons affected by leprosy with current, previous and no previous foot ulceration.

PubMed

van Schie, Carine H M; Slim, Frederik J; Keukenkamp, Renske; Faber, William R; Nollet, Frans

2013-03-01

Not only plantar pressure but also weight-bearing activity affects accumulated mechanical stress to the foot and may be related to foot ulceration. To date, activity has not been accounted for in leprosy. The purpose was to compare barefoot pressure, in-shoe pressure and daily cumulative stress between persons affected by leprosy with and without previous or current foot ulceration. Nine persons with current plantar ulceration were compared to 15 with previous and 15 without previous ulceration. Barefoot peak pressure (EMED-X), in-shoe peak pressure (Pedar-X) and daily cumulative stress (in-shoe forefoot pressure time integral×mean daily strides (Stepwatch™ Activity Monitor)) were measured. Barefoot peak pressure was increased in persons with current and previous compared to no previous foot ulceration (mean±SD=888±222 and 763±335 vs 465±262kPa, p<0.05). In-shoe peak pressure was only increased in persons with current compared to without previous ulceration (mean±SD=412±145 vs 269±70kPa, p<0.05). Daily cumulative stress was not different between groups, although persons with current and previous foot ulceration were less active. Although barefoot peak pressure was increased in people with current and previous plantar ulceration, it did not discriminate between these groups. While in-shoe peak pressure was increased in persons with current ulceration, they were less active, resulting in no difference in daily cumulative stress. Increased in-shoe peak pressure suggests insufficient pressure reducing footwear in persons with current ulceration, highlighting the importance of pressure reducing qualities of footwear. Copyright © 2012 Elsevier B.V. All rights reserved.

Analysis of the stress state in an Iosipescu sheartest specimen

NASA Technical Reports Server (NTRS)

Walrath, D. E.; Adams, D. F.

1983-01-01

The state of stress in an Iosipescu shear test specimen is analyzed, utilizing a finite element computer program. The influence of test fixture configuration on this stress state is included. Variations of the standard specimen configuration, including notch depth, notch angle, and notch root radius are modeled. The purpose is to establish guidelines for a specimen geometry which will accommodate highly orthotropic materials while minimizing stress distribution nonuniformities. Materials ranging from isotropic to highly orthotropic are considered. An optimum specimen configuration is suggested, along with changes in the test fixture.

The vertical structure of the circulation and dynamics in Hudson Shelf Valley

USGS Publications Warehouse

Lentz, Steven J.; Butman, Bradford; Harris, Courtney K.

2014-01-01

Hudson Shelf Valley is a 20–30 m deep, 5–10 km wide v-shaped submarine valley that extends across the Middle Atlantic Bight continental shelf. The valley provides a conduit for cross-shelf exchange via along-valley currents of 0.5 m s−1 or more. Current profile, pressure, and density observations collected during the winter of 1999–2000 are used to examine the vertical structure and dynamics of the flow. Near-bottom along-valley currents having times scales of a few days are driven by cross-shelf pressure gradients setup by wind stresses, with eastward (westward) winds driving onshore (offshore) flow within the valley. The along-valley momentum balance in the bottom boundary layer is predominantly between the pressure gradient and bottom stress because the valley bathymetry limits current veering. Above the bottom boundary layer, the flow veers toward an along-shelf (cross-valley) orientation and a geostrophic balance with some contribution from the wind stress (surface Ekman layer). The vertical structure and strength of the along-valley current depends on the magnitude and direction of the wind stress. During offshore flows driven by westward winds, the near-bottom stratification within the valley increases resulting in a thinner bottom boundary layer and weaker offshore currents. Conversely, during onshore flows driven by eastward winds the near-bottom stratification decreases resulting in a thicker bottom boundary layer and stronger onshore currents. Consequently, for wind stress magnitudes exceeding 0.1 N m−2, onshore along-valley transport associated with eastward wind stress exceeds the offshore transport associated with westward wind stress of the same magnitude.

The Effects of Mild Traumatic Brain Injury, Post-Traumatic Stress Disorder, and Combined Mild Traumatic Brain Injury/Post-Traumatic Stress Disorder on Returning Veterans.

PubMed

Combs, Hannah L; Berry, David T R; Pape, Theresa; Babcock-Parziale, Judith; Smith, Bridget; Schleenbaker, Randal; Shandera-Ochsner, Anne; Harp, Jordan P; High, Walter M

2015-07-01

United States veterans of the Iraqi (Operation Iraqi Freedom [OIF]) and Afghanistan (Operation Enduring Freedom [OEF]) conflicts have frequently returned from deployment after sustaining mild traumatic brain injury (mTBI) and enduring stressful events resulting in post-traumatic stress disorder (PTSD). A large number of returning service members have been diagnosed with both a history of mTBI and current PTSD. Substantial literature exists on the neuropsychological factors associated with mTBI and PTSD occurring separately; far less research has explored the combined effects of PTSD and mTBI. The current study employed neuropsychological and psychological measures in a sample of 251 OIF/OEF veterans to determine whether participants with a history of mTBI and current PTSD (mTBI+PTSD) have poorer cognitive and psychological outcomes than participants with mTBI only (mTBI-o), PTSD only (PTSD-o), or veteran controls (VC), when groups are comparable on intelligence quotient, education, and age. The mTBI+PTSD group performed more poorly than VC, mTBI-o, and PTSD-o groups on several neuropsychological measures. Effect size comparisons suggest small deleterious effects for mTBI-o on measures of processing speed and visual attention and small effects for PTSD-o on measures of verbal memory, with moderate effects for mTBI+PTSD on the same variables. Additionally, the mTBI+PTSD group was significantly more psychologically distressed than the PTSD-o group, and PTSD-o group was more distressed than VC and mTBI-o groups. These findings suggest that veterans with mTBI+PTSD perform significantly lower on neuropsychological and psychiatric measures than veterans with mTBI-o or PTSD-o. The results also raise the possibility of mild but persisting cognitive changes following mTBI sustained during deployment.

The Effects of Mild Traumatic Brain Injury, Post-Traumatic Stress Disorder, and Combined Mild Traumatic Brain Injury/Post-Traumatic Stress Disorder on Returning Veterans

PubMed Central

Combs, Hannah L.; Berry, David T. R.; Pape, Theresa; Babcock-Parziale, Judith; Smith, Bridget; Schleenbaker, Randal; Shandera-Ochsner, Anne; Harp, Jordan P.

2015-01-01

Abstract United States veterans of the Iraqi (Operation Iraqi Freedom [OIF]) and Afghanistan (Operation Enduring Freedom [OEF]) conflicts have frequently returned from deployment after sustaining mild traumatic brain injury (mTBI) and enduring stressful events resulting in post-traumatic stress disorder (PTSD). A large number of returning service members have been diagnosed with both a history of mTBI and current PTSD. Substantial literature exists on the neuropsychological factors associated with mTBI and PTSD occurring separately; far less research has explored the combined effects of PTSD and mTBI. The current study employed neuropsychological and psychological measures in a sample of 251 OIF/OEF veterans to determine whether participants with a history of mTBI and current PTSD (mTBI+PTSD) have poorer cognitive and psychological outcomes than participants with mTBI only (mTBI-o), PTSD only (PTSD-o), or veteran controls (VC), when groups are comparable on intelligence quotient, education, and age. The mTBI+PTSD group performed more poorly than VC, mTBI-o, and PTSD-o groups on several neuropsychological measures. Effect size comparisons suggest small deleterious effects for mTBI-o on measures of processing speed and visual attention and small effects for PTSD-o on measures of verbal memory, with moderate effects for mTBI+PTSD on the same variables. Additionally, the mTBI+PTSD group was significantly more psychologically distressed than the PTSD-o group, and PTSD-o group was more distressed than VC and mTBI-o groups. These findings suggest that veterans with mTBI+PTSD perform significantly lower on neuropsychological and psychiatric measures than veterans with mTBI-o or PTSD-o. The results also raise the possibility of mild but persisting cognitive changes following mTBI sustained during deployment. PMID:25350012

An Examination of Individual Level Factors in Stress and Coping Processes: Perspectives of Chinese International Students in the United States

ERIC Educational Resources Information Center

Yan, Kun; Berliner, David C.

2011-01-01

No empirical research has focused solely upon understanding the stress and coping processes of Chinese international students in the United States. This qualitative inquiry examines the individual-level variables that affect the stress-coping process of Chinese international students and how they conceptualize and adapt to their stress at an…

Sequential Data Assimilation for Seismicity: a Proof of Concept

NASA Astrophysics Data System (ADS)

van Dinther, Ylona; Fichtner, Andreas; Kuensch, Hansruedi

2016-04-01

Our probabilistic forecasting ability and physical understanding of earthquakes is significantly hampered by limited indications on the current and evolving state of stress and strength on faults. This information is typically thought to be beyond our resolution capabilities based on surface data. We show that the state of stress and strength are actually obtainable for settings with one dominant fault. State variables and their uncertainties are obtained using Ensemble Kalman Filtering, a sequential data assimilation technique extensively developed for weather forecasting purposes. Through the least-squares solution of Bayes theorem erroneous data is for the first time assimilated to update a Partial Differential Equation-driven seismic cycle model. This visco-elasto-plastic continuum forward model solves Navier-Stokes equations with a rate-dependent friction coefficient (van Dinther et al., JGR, 2013). To prove the concept of this weather - earthquake forecasting bridge we perform a perfect model test. Synthetic numerical data from a single analogue borehole is assimilated into 20 ensemble models over 14 cycles of analogue earthquakes. Since we know the true state of the numerical data model, a quantitative and qualitative evaluation shows that meaningful information on the stress and strength of the unobserved fault is typically already available, once data from a single, shallow borehole is assimilated over part of a seismic cycle. This is possible, since the sampled error covariance matrix contains prior information on the physics that relates velocities, stresses, and pressures at the surface to those at the fault. During the analysis step stress and strength distributions are thus reconstructed in such a way that fault coupling can be updated to either inhibit or trigger events. In the subsequent forward propagation step the physical equations are solved to propagate the updated states forward in time and thus provide probabilistic information on the occurrence of the next analogue earthquake. At the next constant assimilation step, the systems forecasting ability turns out to be beyond expectations; 5 analogue events are forecasted approximately accurately, 5 had indications slightly earlier, 3 were identified only during propagation, and 1 was missed. Else predominantly quite interseismic times were forecasted, but for 3 occasions where smaller events triggered prolonged probabilities until the larger event that came slightly latter. Besides temporal forecasting, we also observe some magnitude forecasting skill for 59% of the events, while the other event sizes were underestimated. This new framework thus provides potential to in the long-term assist with improving our probabilistic hazard assessment.

Changes in the performance characteristics of a GaAs near infrared light emitting diode when exposed to various current and thermal stresses

NASA Technical Reports Server (NTRS)

Thomas, E. F., Jr.

1974-01-01

The changes that occurred in the optical and electrical characteristics of a near infrared, GaAs light emitting diode, when operated under various levels and combinations of current and thermal stresses are discussed. A total of forty parts were operated for two thousand hours under eight different sets of dc current and ambient temperature conditions. Degradation in the radiant optical power of these devices was thirty-four percent when operated at their rated current and an ambient temperature of 298K (25 C). Derating the current and/or the thermal stress reduced the degradation of this parameter in approximately a linear manner. All degraded devices behaved similarly, exhibiting rapid nonlinear degradation followed by a gradual linear degradation and finally a period of stable operation. An attempt was made to correlate initial device condition to degradation during stress testing, but met with little success.

Zero-stress states of human pulmonary arteries and veins.

PubMed

Huang, W; Yen, R T

1998-09-01

The zero-stress states of the pulmonary arteries and veins from order 3 to order 9 were determined in six normal human lungs within 15 h postmortem. The zero-stress state of each vessel was obtained by cutting the vessel transversely into a series of short rings, then cutting each ring radially, which caused the ring to spring open into a sector. Each sector was characterized by its opening angle. The mean opening angle varied between 92 and 163 degrees in the arterial tree and between 89 and 128 degrees in the venous tree. There was a tendency for opening angles to increase as the sizes of the arteries and veins increased. We computed the residual strains based on the experimental measurements and estimated the residual stresses according to Hooke's law. We found that the inner wall of a vessel at the state in which the internal pressure, external pressure, and longitudinal stress are all zero was under compression and the outer wall was in tension, and that the magnitude of compressive stress was greater than the magnitude of tensile stress.

Mindfulness-Based Cognitive Therapy Improves Emotional Reactivity to Social Stress: Results from A Randomized Controlled Trial

PubMed Central

Britton, Willoughby B.; Shahar, Ben; Szepsenwol, Ohad; Jacobs, W. Jake

2012-01-01

Objectives The high likelihood of recurrences in depression is linked to progressive increase in emotional reactivity to stress (stress sensitization). Mindfulness-based therapies teach mindfulness skills designed to decrease emotional reactivity in the face of negative-affect producing stressors. The primary aim of the current study was to assess whether Mindfulness-Based Cognitive Therapy (MBCT) is efficacious in reducing emotional reactivity to social evaluative threat in a clinical sample with recurrent depression. A secondary aim was to assess whether improvement in emotional reactivity mediates improvements in depressive symptoms. Methods Fifty-two individuals with partially-remitted depression were randomized into an 8-week MBCT course or a waitlist control condition. All participants underwent the Trier Social Stress Test (TSST) before and after the 8-week trial period. Emotional reactivity to stress was assessed with the Spielberger State Anxiety Inventory at several time points before, during and after the stressor. Results MBCT was associated with decreased emotional reactivity to social stress, specifically during the recovery (post-stressor) phase of the TSST. Waitlist controls showed an increase in anticipatory (pre-stressor) anxiety, which was absent in the MBCT group. Improvements in emotional reactivity partially mediated improvements in depressive symptoms. Limitations Limitations include small sample size, lack of objective or treatment adherence measures, and non-generalizability to more severely depressed populations. Conclusions Given that emotional reactivity to stress is an important psychopathological process underlying the chronic and recurrent nature of depression, these findings suggest that mindfulness skills are important in adaptive emotion regulation when coping with stress. PMID:22440072

Mental State Assessment and Validation Using Personalized Physiological Biometrics

PubMed Central

Patel, Aashish N.; Howard, Michael D.; Roach, Shane M.; Jones, Aaron P.; Bryant, Natalie B.; Robinson, Charles S. H.; Clark, Vincent P.; Pilly, Praveen K.

2018-01-01

Mental state monitoring is a critical component of current and future human-machine interfaces, including semi-autonomous driving and flying, air traffic control, decision aids, training systems, and will soon be integrated into ubiquitous products like cell phones and laptops. Current mental state assessment approaches supply quantitative measures, but their only frame of reference is generic population-level ranges. What is needed are physiological biometrics that are validated in the context of task performance of individuals. Using curated intake experiments, we are able to generate personalized models of three key biometrics as useful indicators of mental state; namely, mental fatigue, stress, and attention. We demonstrate improvements to existing approaches through the introduction of new features. Furthermore, addressing the current limitations in assessing the efficacy of biometrics for individual subjects, we propose and employ a multi-level validation scheme for the biometric models by means of k-fold cross-validation for discrete classification and regression testing for continuous prediction. The paper not only provides a unified pipeline for extracting a comprehensive mental state evaluation from a parsimonious set of sensors (only EEG and ECG), but also demonstrates the use of validation techniques in the absence of empirical data. Furthermore, as an example of the application of these models to novel situations, we evaluate the significance of correlations of personalized biometrics to the dynamic fluctuations of accuracy and reaction time on an unrelated threat detection task using a permutation test. Our results provide a path toward integrating biometrics into augmented human-machine interfaces in a judicious way that can help to maximize task performance.

Mental State Assessment and Validation Using Personalized Physiological Biometrics.

PubMed

Patel, Aashish N; Howard, Michael D; Roach, Shane M; Jones, Aaron P; Bryant, Natalie B; Robinson, Charles S H; Clark, Vincent P; Pilly, Praveen K

2018-01-01

Mental state monitoring is a critical component of current and future human-machine interfaces, including semi-autonomous driving and flying, air traffic control, decision aids, training systems, and will soon be integrated into ubiquitous products like cell phones and laptops. Current mental state assessment approaches supply quantitative measures, but their only frame of reference is generic population-level ranges. What is needed are physiological biometrics that are validated in the context of task performance of individuals. Using curated intake experiments, we are able to generate personalized models of three key biometrics as useful indicators of mental state; namely, mental fatigue, stress, and attention. We demonstrate improvements to existing approaches through the introduction of new features. Furthermore, addressing the current limitations in assessing the efficacy of biometrics for individual subjects, we propose and employ a multi-level validation scheme for the biometric models by means of k -fold cross-validation for discrete classification and regression testing for continuous prediction. The paper not only provides a unified pipeline for extracting a comprehensive mental state evaluation from a parsimonious set of sensors (only EEG and ECG), but also demonstrates the use of validation techniques in the absence of empirical data. Furthermore, as an example of the application of these models to novel situations, we evaluate the significance of correlations of personalized biometrics to the dynamic fluctuations of accuracy and reaction time on an unrelated threat detection task using a permutation test. Our results provide a path toward integrating biometrics into augmented human-machine interfaces in a judicious way that can help to maximize task performance.

Influence of basal-plane dislocation structures on expansion of single Shockley-type stacking faults in forward-current degradation of 4H-SiC p-i-n diodes

NASA Astrophysics Data System (ADS)

Hayashi, Shohei; Yamashita, Tamotsu; Senzaki, Junji; Miyazato, Masaki; Ryo, Mina; Miyajima, Masaaki; Kato, Tomohisa; Yonezawa, Yoshiyuki; Kojima, Kazutoshi; Okumura, Hajime

2018-04-01

The origin of expanded single Shockley-type stacking faults in forward-current degradation of 4H-SiC p-i-n diodes was investigated by the stress-current test. At a stress-current density lower than 25 A cm-2, triangular stacking faults were formed from basal-plane dislocations in the epitaxial layer. At a stress-current density higher than 350 A cm-2, both triangular and long-zone-shaped stacking faults were formed from basal-plane dislocations that converted into threading edge dislocations near the interface between the epitaxial layer and the substrate. In addition, the conversion depth of basal-plane dislocations that expanded into the stacking fault was inside the substrate deeper than the interface. These results indicate that the conversion depth of basal-plane dislocations strongly affects the threshold stress-current density at which the expansion of stacking faults occurs.

100 years of the physics of diodes

NASA Astrophysics Data System (ADS)

Zhang, Peng; Valfells, Ágúst; Ang, L. K.; Luginsland, J. W.; Lau, Y. Y.

2017-03-01

The Child-Langmuir Law (CL), discovered a century ago, gives the maximum current that can be transported across a planar diode in the steady state. As a quintessential example of the impact of space charge shielding near a charged surface, it is central to the studies of high current diodes, such as high power microwave sources, vacuum microelectronics, electron and ion sources, and high current drivers used in high energy density physics experiments. CL remains a touchstone of fundamental sheath physics, including contemporary studies of nanoscale quantum diodes and nano gap based plasmonic devices. Its solid state analog is the Mott-Gurney law, governing the maximum charge injection in solids, such as organic materials and other dielectrics, which is important to energy devices, such as solar cells and light emitting diodes. This paper reviews the important advances in the physics of diodes since the discovery of CL, including virtual cathode formation and extension of CL to multiple dimensions, to the quantum regime, and to ultrafast processes. We review the influence of magnetic fields, multiple species in bipolar flow, electromagnetic and time dependent effects in both short pulse and high frequency THz limits, and single electron regimes. Transitions from various emission mechanisms (thermionic-, field-, and photoemission) to the space charge limited state (CL) will be addressed, especially highlighting the important simulation and experimental developments in selected contemporary areas of study. We stress the fundamental physical links between the physics of beams to limiting currents in other areas, such as low temperature plasmas, laser plasmas, and space propulsion.

The effect of executive function on stress, depression, anxiety, and quality of life in multiple sclerosis.

PubMed

Grech, Lisa B; Kiropoulos, Litza A; Kirby, Katherine M; Butler, Ernest; Paine, Mark; Hester, Robert

2015-01-01

The experience of cognitive deficits and emotional dysfunction are prevalent in people with multiple sclerosis (PwMS), although research examining their interaction has provided inconsistent findings. The current study examined the ability of executive function to predict psychosocial adjustment in PwMS. One hundred and seven PwMS underwent cognitive assessment and completed measures of stress, depression, anxiety, and quality of life (QoL). There was limited support for a relationship. There was no relationship between objective cognitive tasks and state or trait anxiety, mental health QoL, overall QoL, or stress frequency. The only relationship with depression was found when the Beck Depression Inventory Fast-Screen was used, with a task of planning when the timing element was removed. A measure of error rates on a task of cognitive flexibility predicted physical health QoL, and severity, but not frequency, of stress was predicted by a task of working memory. The results of this study highlight the need for further research into the relationship between cognitive deficits and psychosocial adjustment because of the conflicting findings between studies and call for a common measurement framework for future investigation.

Effects of various gate materials on electrical degradation of a-Si:H TFT in industrial display application

NASA Astrophysics Data System (ADS)

Ho, Ching-Yuan; Chang, Yaw-Jen

2016-02-01

Both aluminum (Al) and copper (Cu), acting as transmission lines in the hydrogenated amorphous silicon of a thin film transistor (a-Si:H TFT), were studied to investigate electrical degradation including electron-migration (EM) and threshold voltage (Vt) stability and recovery performance. Under long-term current stress, the Cu material exhibited excellent resistance to EM properties, but a passivated SiNx crack was observed due to fast heat conductivity. By applying electrical stress on the gate and drain for 5 × 104 s, the power-law time dependency of the threshold voltage shift (ΔVt) indicated that the defective state creation dominated the TFT device's instability. The presence of drain stress increased the overall ΔVt because the high longitudinal field induced impact ionization and then, enhanced hot-carrier-induced electron trapping within the gate SiNx dielectric. An annealing effect prompted a stressed a-Si:H TFT back to virgin status. This study proposes better ΔVt stability and excellent resistance against electron-migration in a Cu gate device which can be considered as a candidate for a transmission line on prolonged TFT applications.

Fluid Mechanical Forces and Endothelial Mitochondria: A Bioengineering Perspective.

PubMed

Scheitlin, Christopher G; Nair, Devi M; Crestanello, Juan A; Zweier, Jay L; Alevriadou, B Rita

2014-12-01

Endothelial cell dysfunction is the hallmark of every cardiovascular disease/condition, including atherosclerosis and ischemia/reperfusion injury. Fluid shear stress acting on the vascular endothelium is known to regulate cell homeostasis. Altered hemodynamics is thought to play a causative role in endothelial dysfunction. The dysfunction is associated with/preceded by mitochondrial oxidative stress. Studies by our group and others have shown that the form and/or function of the mitochondrial network are affected when endothelial cells are exposed to shear stress in the absence or presence of additional physicochemical stimuli. The present review will summarize the current knowledge on the interconnections among intracellular Ca 2+ - nitric oxide - mitochondrial reactive oxygen species, mitochondrial fusion/fission, autophagy/mitophagy, and cell apoptosis vs. survival. More specifically, it will list the evidence on potential regulation of the above intracellular species and processes by the fluid shear stress acting on the endothelium under either physiological flow conditions or during reperfusion (following a period of ischemia). Understanding how the local hemodynamics affects mitochondrial physiology and the cell redox state may lead to development of novel therapeutic strategies for prevention or treatment of the endothelial dysfunction and, hence, of cardiovascular disease.

The contribution of personal and seniority variables to the presence of stress symptoms among Israeli UAV operators.

PubMed

Gal, Shiri; Shelef, Leah; Oz, Idit; Yavnai, Nirit; Carmon, Erez; Gordon, Shirley

2016-01-01

The exposure to war scenes via screens, despite offering a degree of detachment, can be stressful for the operator. The aim of the current study is to examine the existence of anxiety, depression, and post traumatic stress disorder (PTSD) symptoms among unmanned aerial vehicle (UAV) Israeli operators. Participants comprised 41 UAV operators (87.2% male), aged 22-38 ( M age  = 26.05, SD  = 3.54). Most (78.0%) reported having viewed battlefield scenes. All participants completed a total of five questionnaires: Beck Depression Inventory, State-Trait Anxiety Inventory, and three questionnaires of PTSD: Post Trauma Questionnaire (CAPS), the Post-Traumatic Cognition Inventory (CTPI), and the Post-Traumatic Symptom Scale (PSS). Mean scores of depression and anxiety were found significantly lower than diagnosis cut-off points ( p  < .001). Senior operators showed higher means for depression (5.69 vs. 2.58, p  = .040), of stress level (PSS; 3.17 vs. 0.25, p  = .020) and for distress intensity (3.79 vs. 0.57, p  = 0.041) than less-experienced operators. Investigating and monitoring the impact of battlefield exposure in UAV operators are highly beneficial for preventing psychopathology.

Testing a Military Family Stress Model.

PubMed

Gewirtz, Abigail H; DeGarmo, David S; Zamir, Osnat

2017-03-15

The current study examines a military family stress model, evaluating associations between deployment-related stressors (i.e., deployment length/number, posttraumatic stress disorder [PTSD] symptoms) and parent, child, parenting, and dyadic adjustment among families in which a parent had previously deployed to Iraq or Afghanistan in the recent conflicts. Married families (N = 293) with at least one child between the ages of 4 and 12 were recruited from a Midwestern state. Service members were from the Reserve Component (National Guard or Reserves); fathers (N = 253) and/or mothers had deployed (N = 45) to the recent conflicts in the Middle East. Multiple-method (observations of parenting and couple interactions; questionnaires) and multiple informant measures were gathered online and in the homes of participants, from parents, children, and teachers. Findings demonstrated associations between mothers' and fathers' PTSD symptoms and a latent variable of child adjustment comprising teacher, parent, and child report. Mothers' but not fathers' PTSD symptoms were also associated with dyadic adjustment and parenting practices; parenting practices were in turn associated with child adjustment. The results are discussed in terms of their implications for military family stress research and interventions to support and strengthen parents and families after deployment. © 2017 Family Process Institute.

Assessment of Creep Deformation, Damage, and Rupture Life of 304HCu Austenitic Stainless Steel Under Multiaxial State of Stress

NASA Astrophysics Data System (ADS)

Sahoo, K. C.; Goyal, Sunil; Parameswaran, P.; Ravi, S.; Laha, K.

2018-03-01

The role of the multiaxial state of stress on creep deformation and rupture behavior of 304HCu austenitic stainless steel was assessed by performing creep rupture tests on both smooth and notched specimens of the steel. The multiaxial state of stress was introduced by incorporating circumferential U-notches of different root radii ranging from 0.25 to 5.00 mm on the smooth specimens of the steel. Creep tests were carried out at 973 K over the stress range of 140 to 220 MPa. In the presence of notch, the creep rupture strength of the steel was found to increase with the associated decrease in rupture ductility. Over the investigated stress range and notch sharpness, the strengthening was found to increase drastically with notch sharpness and tended toward saturation. The fractographic studies revealed the mixed mode of failure consisting of transgranular dimples and intergranular creep cavitation for shallow notches, whereas the failure was predominantly intergranular for relatively sharper notches. Detailed finite element analysis of stress distribution across the notch throat plane on creep exposure was carried out to assess the creep failure of the material in the presence of notch. The reduction in von-Mises stress across the notch throat plane, which was greater for sharper notches, increased the creep rupture strength of the material. The variation in fracture behavior of the material in the presence of notch was elucidated based on the von-Mises, maximum principal, and hydrostatic stresses. Electron backscatter diffraction analysis of creep strain distribution across the notch revealed localized creep straining at the notch root for sharper notches. A master curve for predicting creep rupture life under the multiaxial state of stress was generated considering the representative stress having contributions from both the von-Mises and principal stress components of the stress field in the notch throat plane. Rupture ductility was also predicted based on the multiaxial state of stress.