WorldWideScience

Sample records for dynamic stress effects

  1. Effect of Magnetohydrodynamic Couple Stresses on Dynamic Characteristics of Exponential Slider Bearing

    Directory of Open Access Journals (Sweden)

    N.B. Naduvinamani

    2017-05-01

    Full Text Available The effect of couple stresses on static and dynamic characteristics of exponential slider bearing in the presence of magnetic field considering squeeze action is theoretically analyzed in this paper. The modified magnetohydrodynamic couple stress Reynolds type equation is derived on the basis of Stokes couple stress model and closed form expressions are obtained for static and dynamic character coefficients. Comparing with bearing lubricated with non-conducting Newtonian lubricants, the magnetohydrodynamic couple stress lubrication provides the higher steady load carrying capacity, dynamic stiffness and damping coefficient. The exponential bearing shows higher efficiency for small film thickness at higher value of couple stress parameter and Hartmann number.

  2. Effects of upper mantle heterogeneities on the lithospheric stress field and dynamic topography

    Science.gov (United States)

    Osei Tutu, Anthony; Steinberger, Bernhard; Sobolev, Stephan V.; Rogozhina, Irina; Popov, Anton A.

    2018-05-01

    The orientation and tectonic regime of the observed crustal/lithospheric stress field contribute to our knowledge of different deformation processes occurring within the Earth's crust and lithosphere. In this study, we analyze the influence of the thermal and density structure of the upper mantle on the lithospheric stress field and topography. We use a 3-D lithosphere-asthenosphere numerical model with power-law rheology, coupled to a spectral mantle flow code at 300 km depth. Our results are validated against the World Stress Map 2016 (WSM2016) and the observation-based residual topography. We derive the upper mantle thermal structure from either a heat flow model combined with a seafloor age model (TM1) or a global S-wave velocity model (TM2). We show that lateral density heterogeneities in the upper 300 km have a limited influence on the modeled horizontal stress field as opposed to the resulting dynamic topography that appears more sensitive to such heterogeneities. The modeled stress field directions, using only the mantle heterogeneities below 300 km, are not perturbed much when the effects of lithosphere and crust above 300 km are added. In contrast, modeled stress magnitudes and dynamic topography are to a greater extent controlled by the upper mantle density structure. After correction for the chemical depletion of continents, the TM2 model leads to a much better fit with the observed residual topography giving a good correlation of 0.51 in continents, but this correction leads to no significant improvement of the fit between the WSM2016 and the resulting lithosphere stresses. In continental regions with abundant heat flow data, TM1 results in relatively small angular misfits. For example, in western Europe the misfit between the modeled and observation-based stress is 18.3°. Our findings emphasize that the relative contributions coming from shallow and deep mantle dynamic forces are quite different for the lithospheric stress field and dynamic

  3. Effects of moving dynamic tyre loads on tyre-pavement contact stresses

    CSIR Research Space (South Africa)

    Steyn, WJvdM

    2002-01-01

    Full Text Available The purpose of this paper is to indicate the effect that moving dynamic tyre loads has on the tyre-pavement contact stresses used in pavement analysis. Traditionally tyre loads (in pavement analysis) are modelled as constant loads applied through...

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

    International Nuclear Information System (INIS)

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

    2005-01-01

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

  5. Strain-rate effect on initial crush stress of irregular honeycomb under dynamic loading and its deformation mechanism

    Science.gov (United States)

    Wang, Peng; Zheng, Zhijun; Liao, Shenfei; Yu, Jilin

    2018-02-01

    The seemingly contradictory understandings of the initial crush stress of cellular materials under dynamic loadings exist in the literature, and a comprehensive analysis of this issue is carried out with using direct information of local stress and strain. Local stress/strain calculation methods are applied to determine the initial crush stresses and the strain rates at initial crush from a cell-based finite element model of irregular honeycomb under dynamic loadings. The initial crush stress under constant-velocity compression is identical to the quasi-static one, but less than the one under direct impact, i.e. the initial crush stresses under different dynamic loadings could be very different even though there is no strain-rate effect of matrix material. A power-law relation between the initial crush stress and the strain rate is explored to describe the strain-rate effect on the initial crush stress of irregular honeycomb when the local strain rate exceeds a critical value, below which there is no strain-rate effect of irregular honeycomb. Deformation mechanisms of the initial crush behavior under dynamic loadings are also explored. The deformation modes of the initial crush region in the front of plastic compaction wave are different under different dynamic loadings.

  6. Effect of dynamic strain aging on cyclic stress response and deformation behavior of Zircaloy-2

    International Nuclear Information System (INIS)

    Sudhakar Rao, G.; Verma, Preeti; Mahobia, G.S.; Santhi Srinivasa, N.C.; Singh, Vakil; Chakravartty, J.K.; Nudurupatic, Saibaba

    2016-01-01

    The effect of strain rate and temperature was studied on cyclic stress response and deformation behavior of annealed Zircaloy-2. Dynamic strain aging was exhibited under some test conditions. The cyclic stress response was found to be dependent on temperature and strain rate. At 300 °C, with decrease in strain rate, there was decrease in the rate as well as the degree of cyclic hardening. However, at 400°C, there was opposite trend and with decrease in strain rate both the rate as well as the degree of hardening increased. The deformation substructure showed dislocation bands, dislocation vein structure, PSB wall structure at both the temperatures. Irrespective of the temperature, there was dislocation loop structure, known as corduroy structure, at both the test temperatures. Based on the dislocation structure, the initial linear hardening is attributed to development of veins and PSB wall structure and the secondary hardening to the Corduroy structure. (author)

  7. Effects of heat stress on dynamic absorption process, tissue distribution and utilization efficiency of vitamin C in broilers

    International Nuclear Information System (INIS)

    Liu Guohua; Chen Guosheng; Cai Huiyi

    1998-01-01

    The experiment was conducted to determine the effects of heat stress on ascorbic acid nutritional physiology of broilers with radioisotope technology. 3 H-Vc was fed to broilers and then the blood, liver, kidney, breast muscle, and excreta were sampled to determine the dynamic absorption process, the tissue distribution and the utilization efficiency of vitamin C. The results indicated that the absorption, metabolism and mobilization of supplemented vitamin C in broilers with heat stress was faster than that in broilers without heat stress. However, the utilization efficiency of supplemented vitamin C in broilers with heat stress was not higher than that of broilers without heat stress

  8. Memory dynamics under stress.

    Science.gov (United States)

    Quaedflieg, Conny W E M; Schwabe, Lars

    2018-03-01

    Stressful events have a major impact on memory. They modulate memory formation in a time-dependent manner, closely linked to the temporal profile of action of major stress mediators, in particular catecholamines and glucocorticoids. Shortly after stressor onset, rapidly acting catecholamines and fast, non-genomic glucocorticoid actions direct cognitive resources to the processing and consolidation of the ongoing threat. In parallel, control of memory is biased towards rather rigid systems, promoting habitual forms of memory allowing efficient processing under stress, at the expense of "cognitive" systems supporting memory flexibility and specificity. In this review, we discuss the implications of this shift in the balance of multiple memory systems for the dynamics of the memory trace. Specifically, stress appears to hinder the incorporation of contextual details into the memory trace, to impede the integration of new information into existing knowledge structures, to impair the flexible generalisation across past experiences, and to hamper the modification of memories in light of new information. Delayed, genomic glucocorticoid actions might reverse the control of memory, thus restoring homeostasis and "cognitive" control of memory again.

  9. Dynamic stress effects in technical superconductors and the ''training'' problem of superconducting magnets

    International Nuclear Information System (INIS)

    Pasztor, G.; Schmidt, C.

    1978-01-01

    The behavior of NbTi superconductors under dynamic mechanical stress was investigated. A training effect was found in short-sample tests when the conductor was strained in a magnetic field and with a transport current applied. Possible mechanisms are discussed which were proposed to explain training in short samples and in magnets. A stress-induced microplastic as well as an incomplete pseudoelastic behavior of NbTi was detected by monitoring acoustic emission. The experiments support the hypothesis that microplastic or shape memory effects in NbTi involving dislocation processes are responsible for training. The minimum energy needed to induce a normal transition in short-sample tests is calculated with a computer program, which gives the exact solution of the heat equation. A prestrain treatment of the conductor at room temperature is shown to be a simple method of reducing training of short samples and of magnets. This is a direct proof that the same mechanisms are involved in both cases

  10. Utilization of the molecular dynamic to study the effect of hydrogen in the stress corrosion

    International Nuclear Information System (INIS)

    Arnoux, P.

    2007-01-01

    Many microscopic and theoretical models of stress corrosion have been proposed, in particularly to explain the grain boundary cracking of stainless steels and nickel base. In this work calculus of molecular dynamic have been used to propose a mechanism of stress corrosion at the atomic scale. The author aims to reproduce, by molecular dynamic, the mechanism of an open crack in irradiated stainless steel in PWR reactor and show that the growth of the oxide at the crack back produce hydrogen. (A.L.B.)

  11. Effects of fiber ellipticity and orientation on dynamic stress concentrations in porous fiber-reinforced composites

    Science.gov (United States)

    Hasheminejad, Seyyed M.; Sanaei, Roozbeh

    2007-11-01

    Interaction of time harmonic fast longitudinal and shear incident plane waves with an elliptical fiber embedded in a porous elastic matrix is studied. The novel features of Biot dynamic theory of poroelasticity along with the classical method of eigen-function expansion and the pertinent boundary conditions are employed to develop a closed form series solution involving Mathieu and modified Mathieu functions of complex arguments. The complications arising due to the non-orthogonality of angular Mathieu functions corresponding to distinct wave numbers in addition to the problems associated with appearance of additional angular dependent terms in the boundary conditions are all avoided by expansion of the angular Mathieu functions in terms of transcendental functions and subsequent integration, leading to a linear set of independent equations in terms of the unknown scattering coefficients. A MATHEMATICA code is developed for computing the Mathieu functions in terms of complex Fourier coefficients which are themselves calculated by numerically solving appropriate sets of eigen-systems. The analytical results are illustrated with numerical examples in which an elastic fiber of elliptic cross section is insonified by a plane fast compressional or shear wave at normal incidence. The effects of fiber cross sectional ellipticity, angle of incidence (fiber two-dimensional orientation), and incident wave polarization (P, SV, SH) on dynamic stress concentrations are studied in a relatively wide frequency range. Limiting cases are considered and fair agreements with well-known solutions are established.

  12. Effects of fluid dynamic stress on fracturing of cell-aggregated tissue during purification for islets of Langerhans transplantation

    Energy Technology Data Exchange (ETDEWEB)

    Shintaku, H; Kawano, S [Department of Mechanical Science and Bioengineering, Graduate School of Engineering Science, Osaka University, Machikaneyama-cho, Toyonaka, Osaka 560-8531 (Japan); Okitsu, T [Transplantation Unit, Kyoto University Hospital, Kawara-cho Shogoin, Sakyo-ku, Kyoto 606-8507 (Japan); Matsumoto, S [Baylor Research Institute Islet Cell Laboratory, 1400 Eight Avenue, Fort Worth, TX 76104 (United States); Suzuki, T; Kanno, I; Kotera, H [Department of Microengineering, Kyoto University, Yoshida-Honmachi, Sakyo-ku, Kyoto 606-8501 (Japan)], E-mail: shintaku@me.es.osaka-u.ac.jp

    2008-06-07

    Among clinical treatments for type 1 diabetes mellitus, the transplantation of islets of Langerhans to the portal vein of the hepar is a commonly used treatment for glucose homeostasis. Islet purification using the density gradient of a solution in a centrifuge separator is required for safety and efficiency. In the purification, the number of tissues to be transplanted is reduced by removing the acinar tissue and gathering the islet from the digest of pancreas. However, the mechanical effects on the fracture of islets in the centrifuge due to fluid dynamic stress are a serious problem in the purification process. In this study, a preliminary experiment using a cylindrical rotating viscometer with a simple geometry is conducted in order to systematically clarify the effect of fluid dynamic stress on the fracture of islets. The effects of fluid dynamic stress on the islet configuration is quantitatively measured for various flow conditions, and a predictive fracture model is developed based on the experimental results. Furthermore, in the practical purification process in the COBE (Gambro BCT), which is widely used in clinical applications, we perform a numerical analysis of the fluid dynamic stress based on Navier-Stokes equations to estimate the stress conditions for islets. Using the fracture model and numerical analysis, the islet fracture characteristics using the COBE are successfully investigated. The results obtained in this study provide crucial information for the purification of islets by centrifuge in practical and clinical applications.

  13. Effects of fluid dynamic stress on fracturing of cell-aggregated tissue during purification for islets of Langerhans transplantation

    International Nuclear Information System (INIS)

    Shintaku, H; Kawano, S; Okitsu, T; Matsumoto, S; Suzuki, T; Kanno, I; Kotera, H

    2008-01-01

    Among clinical treatments for type 1 diabetes mellitus, the transplantation of islets of Langerhans to the portal vein of the hepar is a commonly used treatment for glucose homeostasis. Islet purification using the density gradient of a solution in a centrifuge separator is required for safety and efficiency. In the purification, the number of tissues to be transplanted is reduced by removing the acinar tissue and gathering the islet from the digest of pancreas. However, the mechanical effects on the fracture of islets in the centrifuge due to fluid dynamic stress are a serious problem in the purification process. In this study, a preliminary experiment using a cylindrical rotating viscometer with a simple geometry is conducted in order to systematically clarify the effect of fluid dynamic stress on the fracture of islets. The effects of fluid dynamic stress on the islet configuration is quantitatively measured for various flow conditions, and a predictive fracture model is developed based on the experimental results. Furthermore, in the practical purification process in the COBE (Gambro BCT), which is widely used in clinical applications, we perform a numerical analysis of the fluid dynamic stress based on Navier-Stokes equations to estimate the stress conditions for islets. Using the fracture model and numerical analysis, the islet fracture characteristics using the COBE are successfully investigated. The results obtained in this study provide crucial information for the purification of islets by centrifuge in practical and clinical applications

  14. Stress Analysis of Transcatheter Aortic Valve Leaflets Under Dynamic Loading: Effect of Reduced Tissue Thickness.

    Science.gov (United States)

    Abbasi, Mostafa; Azadani, Ali N

    2017-07-01

    In order to accommodate transcatheter valves to miniaturized catheters, the leaflet thickness must be reduced to a value which is typically less than that of surgical bioprostheses. The study aim was to use finite-element simulations to determine the impact of the thickness reduction on stress and strain distribution. A 23 mm transcatheter aortic valve (TAV) was modelled based on the Edwards SAPIEN XT (Edwards Lifesciences, Irvine, CA, USA). Finite-element (FE) analysis was performed using the ABAQUS/Explicit solver. An ensemble-averaged transvalvular pressure waveform measured from in-vitro tests conducted in a pulse duplicator was applied to the leaflets. Through a parametric study, uniform TAV leaflet thickness was reduced from 0.5 to 0.18 mm. By reducing leaflet thickness, significantly higher stress values were found in the leaflet's fixed edge during systole, and in the commissures during diastole. Through dynamic FE simulations, the highest stress values were found during systole in the leaflet fixed edge. In contrast, at the peak of diastole high-stress regions were mainly observed in the commissures. The peak stress was increased by 178% and 507% within the leaflets after reducing the thickness of 0.5 mm to 0.18 mm at the peak of systole and diastole, respectively. The study results indicated that, the smaller the leaflet thickness, the higher the maximum principal stress. Increased mechanical stress on TAV leaflets may lead to accelerated tissue degeneration. By using a thinner leaflet, TAV durability may not atch with that of surgical bioprostheses.

  15. Finite-size effect on the dynamic and sensing performances of graphene resonators: the role of edge stress.

    Science.gov (United States)

    Kim, Chang-Wan; Dai, Mai Duc; Eom, Kilho

    2016-01-01

    We have studied the finite-size effect on the dynamic behavior of graphene resonators and their applications in atomic mass detection using a continuum elastic model such as modified plate theory. In particular, we developed a model based on von Karman plate theory with including the edge stress, which arises from the imbalance between the coordination numbers of bulk atoms and edge atoms of graphene. It is shown that as the size of a graphene resonator decreases, the edge stress depending on the edge structure of a graphene resonator plays a critical role on both its dynamic and sensing performances. We found that the resonance behavior of graphene can be tuned not only through edge stress but also through nonlinear vibration, and that the detection sensitivity of a graphene resonator can be controlled by using the edge stress. Our study sheds light on the important role of the finite-size effect in the effective design of graphene resonators for their mass sensing applications.

  16. Effects of stress-shielding on the dynamic viscoelasticity and ordering of the collagen fibers in rabbit Achilles tendon.

    Science.gov (United States)

    Ikoma, Kazuya; Kido, Masamitsu; Nagae, Masateru; Ikeda, Takumi; Shirai, Toshiharu; Ueshima, Keiichiro; Arai, Yuji; Oda, Ryo; Fujiwara, Hiroyoshi; Kubo, Toshikazu

    2013-11-01

    We investigated the effects of stress-shielding on both viscoelastic properties and microstructure of collagen fibers in the Achilles tendon by proton double-quantum filtered ((1) H-DQF) NMR spectroscopy. The right hind-limbs of 20 Japanese white rabbits were immobilized for 4 weeks in a cast with the ankle in plantarflexion. Dynamic viscoelasticity of the Achilles tendons was measured using a viscoelastic spectrometer. Proton DQF NMR signals were analyzed to determine the residual dipolar coupling of bound water molecules in the Achilles tendons. Both the dynamic storage modulus (E') and dynamic loss modulus (E″) decreased significantly in the Achilles tendons of the stress-shielding group. The results of the (1) H-DQF NMR examination demonstrated significantly reduced residual dipolar coupling in the Achilles tendons of this same group. The disorientation of collagen fibers by stress-shielding should contribute to degradation of the dynamic storage and loss moduli. The alterations of the collagen fiber orientation that contributed to the function of tendinous tissue can be evaluated by performing an analysis of (1) H DQF NMR spectroscopy. © 2013 Orthopaedic Research Society.

  17. The effect of stress tolerance on dynamics of activity-travel behavior : numerical simulation results

    NARCIS (Netherlands)

    Psarra, I.; Arentze, T.A.; Timmermans, H.J.P.

    2014-01-01

    The primary and secondary effects of various spatial and transportation policies can be evaluated with models of activity–travel behavior. Whereas existing activity-based models of travel demand simulate a typical day, dynamic models simulate behavioral response to endogenous or exogenous change,

  18. THE EFFECTS OF ACUTE AND CHRONIC STRESS ON ERYTHROCYTE DYNAMIC IN COMBINATION WITH ß–ADRENERGIC RECEPTORS BLOCKADE IN RATS

    Directory of Open Access Journals (Sweden)

    Lucian Hritcu

    2005-08-01

    Full Text Available : 3 consecutive days propranolol hydrochloride administration (5 mg/kg b.w., subcutaneous injections under acute and chronic stress conditions causes changes of peripheral erythrocyte distribution in rats. The effects of acute stress and its combination with ȕ-adrenergic receptor blockade on erythrocyte dynamic were more pregnant beside the effects of chronic stress and its combination with ȕ-adrenergic receptor blockade, respectively. ȕ-adrenergic mechanisms were shown to be involved in regulation of erythrocyte dynamic in acute and chronic stress response.

  19. Modeling fish dynamics and effects of stress in a hydrologically pulsed ecosystem

    Science.gov (United States)

    DeAngelis, Donald L.; Loftus, William F.; Trexler, Joel C.; Ulanowicz, Robert E.

    1997-01-01

    Many wetlands undergo seasonal cycles in precipitation and water depth.This environmental seasonality is echoed in patterns of production of fishbiomass, which, in turn, influence the phenology of other components of thefood web, including wading birds. Human activities, such as drainage orother alterations of the hydrology, can exacerbate these natural cycles andresult in detrimental stresses on fish production and the higher trophic levels dependent on this production. In this paper we model theseasonal pattern of fish production in a freshwater marsh, with specialreference to the Everglades/Big Cypress region of southern Florida.The model illustrates the temporal pattern of production through theyear, which can result in very high densities of fish at the end of ahydroperiod (period of flooding), aswell as the importance of ponds and other deep depressions, both as refugia and sinks during dry periods. The model predicts that: (1) there is an effective threshold in the length of the hydroperiod that must beexceeded for high fish-population densities to be produced, (2) large,piscivorous fishes do not appear tohave a major impact on smaller fishes in the marsh habitat, and (3) therecovery of small-fish populations in the marsh following a major droughtmay require up to a year. The last of these results is relevant toassessing anthropogenic impacts on marsh production, as these effectsmay increase the severity and frequency of droughts.

  20. Effects of cross-anisotropy and stress-dependency of pavement layers on pavement responses under dynamic truck loading

    Directory of Open Access Journals (Sweden)

    Rafiqul A. Tarefder

    2016-06-01

    Full Text Available Previous studies by the authors have determined pavement responses under dynamic loading considering cross-anisotropy in one layer only, either the cross-anisotropic viscoelastic asphalt concrete (AC layer or the cross-anisotropic stress-dependent base layer, but not both. This study evaluates pavement stress–strain responses considering cross-anisotropy in all layers, i.e. AC, base and subbase, using finite element modeling (FEM technique. An instrumented pavement section on Interstate I-40 near Albuquerque, New Mexico was used in ABAQUS framework as model geometry. Field asphalt cores were collected and tested in the laboratory to determine the cross-anisotropy (n-values defined by horizontal to vertical modulus ratio, and other viscoelastic parameters as inputs of the model incorporated through user defined material interface (UMAT functionality in ABAQUS. Field base and subbase materials were also collected and tested in the laboratory to determine stress-dependent nonlinear elastic model parameters, as inputs of the model, again incorporated through UMAT. The model validation task was carried out using field-measured deflections and strain values under falling weight deflectometer (FWD loads at the instrumented section. The validated model was then subjected to an actual truck loading for studying cross-anisotropic effects. It was observed that horizontal tensile strain at the bottom of the AC layer and vertical strains in all layers decreased with an increase in n-value of the asphalt layer, from n < 1 (anisotropy to n=1 (isotropy. This indicates that the increase in horizontal modulus caused the decrease in layer strains. It was also observed that if the base and subbase layers were considered stress-dependent instead of linear elastic unbound layers, the horizontal tensile strain at the bottom of the asphalt layer increased and vertical strains on top of the base and subbase also increased.

  1. Nutrients versus emerging contaminants–Or a dynamic match between subsidy and stress effects on stream biofilms

    International Nuclear Information System (INIS)

    Aristi, I.; Casellas, M.; Elosegi, A.; Insa, S.; Petrovic, M.; Sabater, S.; Acuña, V.

    2016-01-01

    Freshwater ecosystems are threatened by multiple anthropogenic stressors, which might be differentiated into two types: those that reduce biological activity at all concentrations (toxic contaminants), and those that subsidize biological activity at low concentrations and reduce it at high concentrations (assimilable contaminants). When occurring in mixtures, these contaminants can have either antagonistic, neutral or synergistic effects; but little is known on their joint effects. We assessed the interaction effects of a mixture of assimilable and toxic contaminants on stream biofilms in a manipulative experiment using artificial streams, and following a factorial design with three nutrient levels (low, medium or high) and either presence or absence of a mixture of emerging contaminants (ciprofloxacin, erythromycin, diclofenac, methylparaben, and sulfamethoxazole). We measured biofilm biomass, basal fluorescence, gross primary production and community respiration. Our initial hypotheses were that biofilm biomass and activity would: increase with medium nutrient concentrations (subsidy effect), but decrease with high nutrient concentrations (stress effect) (i); decrease with emerging contaminants, with the minimum decrease at medium nutrient concentrations (antagonistic interaction between nutrients subsidy and stress by emerging contaminants) and the maximum decrease at high nutrient concentrations (synergistic interaction between nutrients and emerging contaminants stress) (ii). All the measured variables responded linearly to the available nutrients, with no toxic effect at high nutrient concentrations. Emerging contaminants only caused weak toxic effects in some of the measured variables, and only after 3–4 weeks of exposure. Therefore, only antagonistic interactions were observed between nutrients and emerging contaminants, as medium and high nutrient concentrations partly compensated the harmful effects of emerging contaminants during the first weeks of the

  2. Nutrients versus emerging contaminants-Or a dynamic match between subsidy and stress effects on stream biofilms.

    Science.gov (United States)

    Aristi, I; Casellas, M; Elosegi, A; Insa, S; Petrovic, M; Sabater, S; Acuña, V

    2016-05-01

    Freshwater ecosystems are threatened by multiple anthropogenic stressors, which might be differentiated into two types: those that reduce biological activity at all concentrations (toxic contaminants), and those that subsidize biological activity at low concentrations and reduce it at high concentrations (assimilable contaminants). When occurring in mixtures, these contaminants can have either antagonistic, neutral or synergistic effects; but little is known on their joint effects. We assessed the interaction effects of a mixture of assimilable and toxic contaminants on stream biofilms in a manipulative experiment using artificial streams, and following a factorial design with three nutrient levels (low, medium or high) and either presence or absence of a mixture of emerging contaminants (ciprofloxacin, erythromycin, diclofenac, methylparaben, and sulfamethoxazole). We measured biofilm biomass, basal fluorescence, gross primary production and community respiration. Our initial hypotheses were that biofilm biomass and activity would: increase with medium nutrient concentrations (subsidy effect), but decrease with high nutrient concentrations (stress effect) (i); decrease with emerging contaminants, with the minimum decrease at medium nutrient concentrations (antagonistic interaction between nutrients subsidy and stress by emerging contaminants) and the maximum decrease at high nutrient concentrations (synergistic interaction between nutrients and emerging contaminants stress) (ii). All the measured variables responded linearly to the available nutrients, with no toxic effect at high nutrient concentrations. Emerging contaminants only caused weak toxic effects in some of the measured variables, and only after 3-4 weeks of exposure. Therefore, only antagonistic interactions were observed between nutrients and emerging contaminants, as medium and high nutrient concentrations partly compensated the harmful effects of emerging contaminants during the first weeks of the

  3. Dynamics stresses in pipelines and components

    International Nuclear Information System (INIS)

    Prates, C.L.M.; Stukart, R.N.L.; Halbritter, A.L.

    1982-01-01

    The procedure to generate the dynamic stresses caused by external events, necessary for the structural calculation of pipelines and components in nuclear power plants is presented. A special attention is given to the stress caused by the action of earthquakes and exterior explosions. In the dynamic analysis of pipeline and components is usually to show the stresses procedured by these events under the response spectra form. The methodology to obtain these response spectra is shown and discussed. Some pratical examples of spectra from nuclear power plant building are still shown. (E.G.) [pt

  4. Hot carrier injection degradation under dynamic stress

    International Nuclear Information System (INIS)

    Ma Xiao-Hua; Cao Yan-Rong; Hao Yue; Zhang Yue

    2011-01-01

    In this paper, we have studied hot carrier injection (HCI) under alternant stress. Under different stress modes, different degradations are obtained from the experiment results. The different alternate stresses can reduce or enhance the HC effect, which mainly depends on the latter condition of the stress cycle. In the stress mode A (DC stress with electron injection), the degradation keeps increasing. In the stress modes B (DC stress and then stress with the smallest gate injection) and C (DC stress and then stress with hole injection under V g = 0 V and V d = 1.8 V), recovery appears in the second stress period. And in the stress mode D (DC stress and then stress with hole injection under V g = −1.8 V and V d = 1.8 V), as the traps filled in by holes can be smaller or greater than the generated interface states, the continued degradation or recovery in different stress periods can be obtained. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  5. Dynamic Behavior of Fault Slip Induced by Stress Waves

    Directory of Open Access Journals (Sweden)

    Guang-an Zhu

    2016-01-01

    Full Text Available Fault slip burst is a serious dynamic hazard in coal mining. A static and dynamic analysis for fault slip was performed to assess the risk of rock burst. A numerical model FLAC3D was established to understand the stress state and mechanical responses of fault rock system. The results obtained from the analysis show that the dynamic behavior of fault slip induced by stress waves is significantly affected by mining depth, as well as dynamic disturbance intensity and the distance between the stope and the fault. The isolation effect of the fault is also discussed based on the numerical results with the fault angle appearing to have the strongest influence on peak vertical stress and velocity induced by dynamic disturbance. By taking these risks into account, a stress-relief technology using break-tip blast was used for fault slip burst control. This technique is able to reduce the stress concentration and increase the attenuation of dynamic load by fracturing the structure of coal and rock. The adoption of this stress-relief method leads to an effective reduction of fault slip induced rock burst (FSIRB occurrence.

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

    Science.gov (United States)

    Hardebeck, Jeanne L.

    2014-01-01

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

  7. Point defects dynamics in a stress field

    International Nuclear Information System (INIS)

    Smetniansky de De Grande, Nelida.

    1989-01-01

    The dependence of anisotropic defect diffusion on stress is studied for a hexagonal close packed (hcp) material under irradiation and uniaxially stressed. The diffusion is described as a discrete process of thermally activated jumps. It is shown that the presence of an external stress field enhances the intrinsic anisotropic diffusion, being this variation determined by the defect dipole tensors' symmetry in the equilibrium and saddle point configurations. Also, the point defect diffusion equations to sinks, like edge dislocations and spherical cavities, are solved and the sink strengths are calculated. The conclusion is that the dynamics of the interaction between defects and sinks is controlled by the changes in diffusivity induced by stress fields. (Author) [es

  8. Effects of a father-based in-home intervention on perceived stress and family dynamics in parents of children with autism.

    Science.gov (United States)

    Bendixen, Roxanna M; Elder, Jennifer H; Donaldson, Susan; Kairalla, John A; Valcante, Greg; Ferdig, Richard E

    2011-01-01

    Parents of children with autism report high rates of stress. Parental differences in stress are inconsistent, with most research indicating that mothers report higher levels of stress than fathers. We explored parental differences before and after an in-home training program. Fathers were taught an intervention designed to improve their child's social reciprocity and communication; they then trained mothers. Stress was assessed with the Parenting Stress Index-Short Form, and family dynamics was assessed with the Family Adaptability and Cohesion Evaluation Scales II. Both mothers and fathers reported high preintervention levels of stress. After intervention, fathers' stress was reduced, but not significantly, possibly because of the variability in fathers' scores; mothers' stress scores were significantly reduced. Parenting styles were significantly different before and after intervention. Interdisciplinary teams, including occupational therapists, nurses, and special educators, can work.together to have a positive impact on the lives of families of children with autism.

  9. Effects of edaravone combined with hyperbaric oxygen on cerebral vascular dynamics, oxidative stress products and inflammatory factors in patients with acute cerebral hemorrhage

    Directory of Open Access Journals (Sweden)

    Xia Li

    2017-10-01

    Full Text Available Objective: To investigate the effect of edaravone combined with hyperbaric oxygen therapy on cerebral vasculature, oxidative stress and inflammatory cytokines in patients with acute cerebral hemorrhage (ACH. Methods: A total of 96 patients with ACH were divided into control group (n=48 and observation group (n=48 according to the random number table. Both groups were treated routinely. On this basis, the control group was treated with edaravone injection, and the observation group was treated with edaravone injection combined with hyperbaric oxygen therapy. The change of cerebrovascular dynamics, oxidative stress products and inflammatory factors were examined in all subjects before and after treatment. Results: There were no significant differences in cerebrovascular function between the two groups before treatment. After treatment, the levels of Vmean and Qmean in both groups were significantly higher than those before treatment. The levels of Vmean and Qmean in the observation group were higher than those of the control group after treatment. There was no significant difference in serum oxidative stress between the two groups before treatment. After treatment, the levels of SOD in two groups were significantly higher than those before treatment. The level of SOD in the observation group was higher than that in the control group after treatment. After treatment, the levels of MDA in the two groups were significantly lower than that before treatment. The level of MDA in the observation group was lower than that of the control group after treatment. There were no significant differences in the level of serum inflammatory factors between the two groups before treatment. After treatment, the level of TNF-α and IL-1β in two groups were significantly lower than before treatment. The level of TNF-α and IL-1β in the observation group was lower than those of the control group after treatment. Conclusion: Edaravone combined with hyperbaric oxygen

  10. Motional Effect on Wall Shear Stresses

    DEFF Research Database (Denmark)

    Kock, Samuel Alberg; Torben Fründ, Ernst; Yong Kim, Won

    Atherosclerosis is the leading cause of death and severe disability. Wall Shear Stress (WSS), the stress exerted on vessel walls by the flowing blood is a key factor in the development of atherosclerosis. Computational Fluid Dynamics (CFD) is widely used for WSS estimations. Most CFD simulations...... are based on static models to ease computational burden leading to inaccurate estimations. The aim of this work was to estimate the effect of vessel wall deformations (expansion and bending) on WSS levels....

  11. The effect of academic stress and attachment stress on stress-eaters and stress-undereaters.

    Science.gov (United States)

    Emond, Michael; Ten Eycke, Kayla; Kosmerly, Stacey; Robinson, Adele Lafrance; Stillar, Amanda; Van Blyderveen, Sherry

    2016-05-01

    It is well established that stress is related to changes in eating patterns. Some individuals are more likely to increase their overall food intake under conditions of stress, whereas others are more likely to consume less food when stressed. Attachment style has been linked to disordered eating and eating disorders; however, comparisons of eating behaviors under attachment versus other types of stress have yet to be explored. The present laboratory study examined the eating patterns in self-identified stress-undereaters and stress-eaters under various types of stress. More specifically, the study examined the effects of academic and attachment stress on calorie, carbohydrate and sugar consumption within these two groups. Under the guise of critiquing student films, university students viewed either one of two stress-inducing videos (academic stress or attachment stress, both designed to be emotionally arousing) or a control video (designed to be emotionally neutral), and their food intake was recorded. Results demonstrated that the video manipulations were effective in inducing stress. Differential patterns of eating were noted based on group and stress condition. Specifically, stress-undereaters ate fewer calories, carbohydrates and sugars than stress-eaters in the academic stress condition, but not in the attachment stress or control condition. Findings suggest that specific types of stressors may influence eating behaviors differently. Copyright © 2016 Elsevier Ltd. All rights reserved.

  12. ITER vacuum vessel dynamic stress analysis of a disruption

    International Nuclear Information System (INIS)

    Riemer, B.W.; Conner, D.L.; Strickler, D.J.; Williamson, D.E.

    1994-01-01

    Dynamic stress analysis of the International Thermonuclear Experimental Reactor vacuum vessel loaded by disruption forces was performed. The deformation and stress results showed strong inertial effects when compared to static analyses. Maximum stress predicted dynamically was 300 MPa, but stress shown by static analysis from loads at the same point in time reached only 80 MPa. The analysis also provided a reaction load history in the vessel's supports which is essential in evaluating support design. The disruption forces were estimated by assuming a 25-MA plasma current decaying at 1 MA/ms while moving vertically. In addition to forces developed within the vessel, vertical loadings from the first wall/strong back assemblies and the divertor were applied to the vessel at their attachment points. The first 50 natural modes were also determined. The first mode's frequency was 6.0 Hz, and its shape is characterized by vertical displacement of the vessel inner leg. The predicted deformation of the vessel appeared similar to its first mode shape combined with radial contraction. Kinetic energy history from the analysis also correlated with the first mode frequency

  13. New model for surface fracture induced by dynamical stress

    OpenAIRE

    Andersen, J. V.; Lewis, L. J.

    1997-01-01

    We introduce a model where an isotropic, dynamically-imposed stress induces fracture in a thin film. Using molecular dynamics simulations, we study how the integrated fragment distribution function depends on the rate of change and magnitude of the imposed stress, as well as on temperature. A mean-field argument shows that the system becomes unstable for a critical value of the stress. We find a striking invariance of the distribution of fragments for fixed ratio of temperature and rate of ch...

  14. Microscopic dynamical Casimir effect

    Science.gov (United States)

    Souza, Reinaldo de Melo e.; Impens, François; Neto, Paulo A. Maia

    2018-03-01

    We consider an atom in its ground state undergoing a nonrelativistic oscillation in free space. The interaction with the electromagnetic quantum vacuum leads to two effects to leading order in perturbation theory. When the mechanical frequency is larger than the atomic transition frequency, the dominant effect is the motion-induced transition to an excited state with the emission of a photon carrying the excess energy. We compute the angular distribution of emitted photons and the excitation rate. On the other hand, when the mechanical frequency is smaller than the transition frequency, the leading-order effect is the parametric emission of photon pairs, which constitutes the microscopic counterpart of the dynamical Casimir effect. We discuss the properties of the microscopic dynamical Casimir effect and build a connection with the photon production by an oscillating macroscopic metallic mirror.

  15. Laplace-SGBEM analysis of the dynamic stress intensity factors and the dynamic T-stress for the interaction between a crack and auxetic inclusions

    Science.gov (United States)

    Kwon, Kibum

    A dynamic analysis of the interaction between a crack and an auxetic (negative Poisson ratio)/non-auxetic inclusion is presented. The two most important fracture parameters, namely the stress intensity factors and the T-stress are analyzed by using the symmetric Galerkin boundary element method in the Laplace domain for three different models of crack-inclusion interaction. To investigate the effects of auxetic inclusions on the fracture behavior of composites reinforced by this new type of material, comparisons of the dynamic stress intensity factors and the dynamic T-stress are made between the use of auxetic inclusions as opposed to the use of traditional inclusions. Furthermore, the technique presented in this research can be employed to analyze for the interaction between a crack and a cluster of auxetic/non-auxetic inclusions. Results from the latter models can be employed in crack growth analysis in auxetic-fiber-reinforced composites.

  16. Estimation of flow stress of radiation induced F/M steels using molecular dynamics and discrete dislocation dynamics approach

    International Nuclear Information System (INIS)

    More, Ameya; Dutta, B.K.; Durgaprasad, P.V.; Arya, A.K.

    2012-01-01

    Fe-Cr based Ferritic/Martensitic (F/M) steels are the candidate structural materials for future fusion reactors. In this work, a multi-scale approach comprising atomistic Molecular Dynamics (MD) simulations and Discrete Dislocation Dynamics (DDD) simulations are used to model the effect of irradiation dose on the flow stress of F/M steels. At the atomic scale, molecular dynamics simulations are used to study the dislocation interaction with irradiation induced defects, i.e. voids and He bubbles. Whereas, the DDD simulations are used to estimate the change in flow stress of the material as a result of irradiation hardening. (author)

  17. The temporal dynamics of the stress response

    NARCIS (Netherlands)

    Koolhaas, J.M.; Meerlo, P; de Boer, S.F.; Strubbe, J.H.; Bohus, B.G J

    1997-01-01

    This paper summarises the available evidence that failure of defense mechanisms in (semi)-natural social groups of animals may lead to serious forms of stress pathology. Hence the study of social stress may provide animal models with a high face validity. However, most of the animal models of human

  18. Stress Distribution in Graded Cellular Materials Under Dynamic Compression

    Directory of Open Access Journals (Sweden)

    Peng Wang

    Full Text Available Abstract Dynamic compression behaviors of density-homogeneous and density-graded irregular honeycombs are investigated using cell-based finite element models under a constant-velocity impact scenario. A method based on the cross-sectional engineering stress is developed to obtain the one-dimensional stress distribution along the loading direction in a cellular specimen. The cross-sectional engineering stress is contributed by two parts: the node-transitive stress and the contact-induced stress, which are caused by the nodal force and the contact of cell walls, respectively. It is found that the contact-induced stress is dominant for the significantly enhanced stress behind the shock front. The stress enhancement and the compaction wave propagation can be observed through the stress distributions in honeycombs under high-velocity compression. The single and double compaction wave modes are observed directly from the stress distributions. Theoretical analysis of the compaction wave propagation in the density-graded honeycombs based on the R-PH (rigid-plastic hardening idealization is carried out and verified by the numerical simulations. It is found that stress distribution in cellular materials and the compaction wave propagation characteristics under dynamic compression can be approximately predicted by the R-PH shock model.

  19. Effects of boron nutrition and water stress on nitrogen fixation, seed δ15N and δ13C dynamics, and seed composition in soybean cultivars differing in maturities.

    Science.gov (United States)

    Bellaloui, Nacer; Mengistu, Alemu

    2015-01-01

    Therefore, the objective of the current research was to investigate the effects of foliar B nutrition on seed protein, oil, fatty acids, and sugars under water stress conditions. A repeated greenhouse experiment was conducted using different maturity group (MG) cultivars. Plants were well-watered with no foliar B (W - B), well-watered with foliar B (W + B), water-stressed with no foliar B (WS - B), and water-stressed with foliar B (WS + B). Foliar B was applied at rate of 0.45 kg · ha(-1) and was applied twice at flowering and at seed-fill stages. The results showed that seed protein, sucrose, fructose, and glucose were higher in W + B treatment than in W - B, WS + B, and WS - B. The increase in protein in W + B resulted in lower seed oil, and the increase of oleic in WS - B or WS + B resulted in lower linolenic acid. Foliar B resulted in higher nitrogen fixation and water stress resulted in seed δ (15)N and δ (13)C alteration. Increased stachyose indicated possible physiological and metabolic changes in carbon and nitrogen pathways and their sources under water stress. This research is beneficial to growers for fertilizer management and seed quality and to breeders to use (15)N/(14)N and (13)C/(12)C ratios and stachyose to select for drought tolerance soybean.

  20. Effects of Boron Nutrition and Water Stress on Nitrogen Fixation, Seed δ15N and δ13C Dynamics, and Seed Composition in Soybean Cultivars Differing in Maturities

    Directory of Open Access Journals (Sweden)

    Nacer Bellaloui

    2015-01-01

    Full Text Available Therefore, the objective of the current research was to investigate the effects of foliar B nutrition on seed protein, oil, fatty acids, and sugars under water stress conditions. A repeated greenhouse experiment was conducted using different maturity group (MG cultivars. Plants were well-watered with no foliar B (W − B, well-watered with foliar B (W + B, water-stressed with no foliar B (WS − B, and water-stressed with foliar B (WS + B. Foliar B was applied at rate of 0.45 kg·ha−1 and was applied twice at flowering and at seed-fill stages. The results showed that seed protein, sucrose, fructose, and glucose were higher in W + B treatment than in W − B, WS + B, and WS − B. The increase in protein in W + B resulted in lower seed oil, and the increase of oleic in WS − B or WS + B resulted in lower linolenic acid. Foliar B resulted in higher nitrogen fixation and water stress resulted in seed δ15N and δ13C alteration. Increased stachyose indicated possible physiological and metabolic changes in carbon and nitrogen pathways and their sources under water stress. This research is beneficial to growers for fertilizer management and seed quality and to breeders to use 15N/14N and 13C/12C ratios and stachyose to select for drought tolerance soybean.

  1. Dynamic stress intensity factors for a longitudinal semi-elliptical ...

    African Journals Online (AJOL)

    elliptical crack in a thick-walled cylinder subjected to transient dynamic stresses. First, the problem of dynamic elasticity in a thick-walled cylinder is solved analytically using the finite Hankel transform. Transient pressure is assumed to act on ...

  2. Correlation between electron-irradiation defects and applied stress in graphene: A molecular dynamics study

    Energy Technology Data Exchange (ETDEWEB)

    Kida, Shogo; Yamamoto, Masaya; Kawata, Hiroaki; Hirai, Yoshihiko; Yasuda, Masaaki, E-mail: yasuda@pe.osakafu-u.ac.jp [Department of Physics and Electronics, Osaka Prefecture University, Sakai, Osaka 599-8531 (Japan); Tada, Kazuhiro [Department of Electrical and Control Systems Engineering, National Institute of Technology, Toyama College, Toyama 939-8630 (Japan)

    2015-09-15

    Molecular dynamics (MD) simulations are performed to study the correlation between electron irradiation defects and applied stress in graphene. The electron irradiation effect is introduced by the binary collision model in the MD simulation. By applying a tensile stress to graphene, the number of adatom-vacancy (AV) and Stone–Wales (SW) defects increase under electron irradiation, while the number of single-vacancy defects is not noticeably affected by the applied stress. Both the activation and formation energies of an AV defect and the activation energy of an SW defect decrease when a tensile stress is applied to graphene. Applying tensile stress also relaxes the compression stress associated with SW defect formation. These effects induced by the applied stress cause the increase in AV and SW defect formation under electron irradiation.

  3. Dynamic stresses, coulomb failure, and remote triggering: corrected

    Science.gov (United States)

    Hill, David P.

    2012-01-01

    Dynamic stresses associated with crustal surface waves with 15–30 s periods and peak amplitudes Coulomb failure models based on a frictional strength threshold offer one explanation for instances of rapid‐onset triggered seismicity that develop during the surface‐wave peak dynamic stressing. Evaluation of the triggering potential of surface‐wave dynamic stresses acting on critically stressed faults using a Mohr’s circle representation together with the Coulomb failure criteria indicates that Love waves should have a higher triggering potential than Rayleigh waves for most fault orientations and wave incidence angles. That (1) the onset of triggered seismicity often appears to begin during the Rayleigh wave rather than the earlier arriving Love wave, and (2) Love‐wave amplitudes typically exceed those for Rayleigh waves suggests that the explanation for rapid‐onset dynamic triggering may not reside solely with a simple static‐threshold friction mode. The results also indicate that normal faults should be more susceptible to dynamic triggering by 20‐s Rayleigh‐wave stresses than thrust faults in the shallow seismogenic crust (<10  km) while the advantage tips in favor of reverse faults greater depths. This transition depth scales with wavelength and coincides roughly with the transition from retrograde‐to‐prograde particle motion. Locally elevated pore pressures may have a role in the observed prevalence of dynamic triggering in extensional regimes and geothermal/volcanic systems. The result is consistent with the apparent elevated susceptibility of extensional or transtensional tectonic regimes to remote triggering by Rayleigh‐wave dynamic stresses than compressional or transpressional regimes.

  4. [Dynamics of hormone secretion during chronic emotional stress].

    Science.gov (United States)

    Amiragova, M G; Kovalev, S V; Svirskaia, R I

    1979-05-01

    Study of spontaneous secretion of corticosteroids and thyroid hormones and the direct hormonal response to stress revealed the pathogenic effect of chronic combined emotional stress upon the hormonal function of adrenal glands. The hippocampus takes part in formation of the emotional tension in response to stress stimulus and of the following hormonal secretion.

  5. Effective stress coefficient for uniaxial strain condition

    DEFF Research Database (Denmark)

    Alam, M.M.; Fabricius, I.L.

    2012-01-01

    one dimensional rock mechanical deformation. We further investigated the effect of boundary condition on the stress dependency of effective stress coefficient and discussed its application in reservoir study. As stress field in the reservoirs are most unlikely to be hydrostatic, effective stress...... determined under uniaxial strain condition will be more relevant in reservoir studies. Copyright 2012 ARMA, American Rock Mechanics Association....

  6. Blade dynamic stress analysis of rotating bladed disks

    Directory of Open Access Journals (Sweden)

    Kellner J.

    2007-10-01

    Full Text Available The paper deals with mathematical modelling of steady forced bladed disk vibrations and with dynamic stress calculation of the blades. The blades are considered as 1D kontinuum elastic coupled with three-dimensional elastic disk centrally clamped into rotor rotating with constant angular speed. The steady forced vibrations are generated by the aerodynamic forces acting along the blade length. By using modal synthesis method the mathematical model of the rotating bladed disk is condensed to calculate steady vibrations. Dynamic stress analysis of the blades is based on calculation of the time dependent reduced stress in blade cross-sections by using Hubert-Misses-Hencky stress hypothesis. The presented method is applied to real turbomachinery rotor with blades connected on the top with shroud.

  7. Stresses and elastic constants of crystalline sodium, from molecular dynamics

    International Nuclear Information System (INIS)

    Schiferl, S.K.

    1985-02-01

    The stresses and the elastic constants of bcc sodium are calculated by molecular dynamics (MD) for temperatures to T = 340K. The total adiabatic potential of a system of sodium atoms is represented by pseudopotential model. The resulting expression has two terms: a large, strictly volume-dependent potential, plus a sum over ion pairs of a small, volume-dependent two-body potential. The stresses and the elastic constants are given as strain derivatives of the Helmholtz free energy. The resulting expressions involve canonical ensemble averages (and fluctuation averages) of the position and volume derivatives of the potential. An ensemble correction relates the results to MD equilibrium averages. Evaluation of the potential and its derivatives requires the calculation of integrals with infinite upper limits of integration, and integrand singularities. Methods for calculating these integrals and estimating the effects of integration errors are developed. A method is given for choosing initial conditions that relax quickly to a desired equilibrium state. Statistical methods developed earlier for MD data are extended to evaluate uncertainties in fluctuation averages, and to test for symmetry. 45 refs., 10 figs., 4 tabs

  8. cHRV Uncovering Daily Stress Dynamics Using Bio-Signal from Consumer Wearables.

    Science.gov (United States)

    Hao, Tian; Chang, Henry; Ball, Marion; Lin, Kun; Zhu, Xinxin

    2017-01-01

    Knowing the dynamics of one's daily stress is essential to effective stress management in the context of smart and connected health. However, there lacks a practical and unobtrusive means to obtain real-time and longitudinal stress information. In this paper, we attempt to derive a convenient HRV-based (heart rate variability) biomarker named cHRV, which can be used to reliably reflect stress dynamics. cHRV's key advantage lies in its low maintenance and high practicality. It can be efficiently calculated only using data from photoplethysmography (PPG) sensors, the mainstream heart rate sensor embedded in most of the consumer wearables like Apple Watch. Benefiting from the proliferation of wearables, cHRV is ideal for day-to-day stress monitoring. To evaluate its feasibility and performance, we have conducted 14 in-lab controlled experiments. The result shows that the proposed cHRV has strong correlation with the stress dynamics (r > 0.95), therefore exhibits great potential for continuous stress assessment.

  9. Computational Psychometrics for Modeling System Dynamics during Stressful Disasters

    Directory of Open Access Journals (Sweden)

    Pietro Cipresso

    2017-08-01

    Full Text Available Disasters can be very stressful events. However, computational models of stress require data that might be very difficult to collect during disasters. Moreover, personal experiences are not repeatable, so it is not possible to collect bottom-up information when building a coherent model. To overcome these problems, we propose the use of computational models and virtual reality integration to recreate disaster situations, while examining possible dynamics in order to understand human behavior and relative consequences. By providing realistic parameters associated with disaster situations, computational scientists can work more closely with emergency responders to improve the quality of interventions in the future.

  10. Impact of an intensive dynamic exercise program on oxidative stress and on the outcome in patients with fibromyalgia

    Directory of Open Access Journals (Sweden)

    Amal F Soliman

    2016-01-01

    Conclusion Twelve weeks of intensive dynamic exercise program should be recommended to patients with FM as it was effective in decreasing the oxidative stress parameters, increasing the antioxidant parameters, and improving the clinical outcome of this disease.

  11. Dynamic energy release rate in couple-stress elasticity

    International Nuclear Information System (INIS)

    Morini, L; Piccolroaz, A; Mishuris, G

    2013-01-01

    This paper is concerned with energy release rate for dynamic steady state crack problems in elastic materials with microstructures. A Mode III semi-infinite crack subject to loading applied on the crack surfaces is considered. The micropolar behaviour of the material is described by the theory of couple-stress elasticity developed by Koiter. A general expression for the dynamic J-integral including both traslational and micro-rotational inertial contributions is derived, and the conservation of this integral on a path surrounding the crack tip is demonstrated

  12. Stress Effects on Multiple Memory System Interactions

    OpenAIRE

    Ness, Deborah; Calabrese, Pasquale

    2016-01-01

    Extensive behavioural, pharmacological, and neurological research reports stress effects on mammalian memory processes. While stress effects on memory quantity have been known for decades, the influence of stress on multiple memory systems and their distinct contributions to the learning process have only recently been described. In this paper, after summarizing the fundamental biological aspects of stress/emotional arousal and recapitulating functionally and anatomically distinct memory syst...

  13. Emotional effects of dynamic textures

    NARCIS (Netherlands)

    Toet, A.; Henselmans, M.; Lucassen, M.P.; Gevers, T.

    2011-01-01

    This study explores the effects of various spatiotemporal dynamic texture characteristics on human emotions. The emotional experience of auditory (eg, music) and haptic repetitive patterns has been studied extensively. In contrast, the emotional experience of visual dynamic textures is still largely

  14. Toxic Stress: Effects, Prevention and Treatment

    Directory of Open Access Journals (Sweden)

    Hillary A. Franke

    2014-11-01

    Full Text Available Children who experience early life toxic stress are at risk of long-term adverse health effects that may not manifest until adulthood. This article briefly summarizes the findings in recent studies on toxic stress and childhood adversity following the publication of the American Academy of Pediatrics (AAP Policy Report on the effects of toxic stress. A review of toxic stress and its effects is described, including factors of vulnerability, resilience, and the relaxation response. An integrative approach to the prevention and treatment of toxic stress necessitates individual, community and national focus.

  15. Velocity and stress autocorrelation decay in isothermal dissipative particle dynamics

    Science.gov (United States)

    Chaudhri, Anuj; Lukes, Jennifer R.

    2010-02-01

    The velocity and stress autocorrelation decay in a dissipative particle dynamics ideal fluid model is analyzed in this paper. The autocorrelation functions are calculated at three different friction parameters and three different time steps using the well-known Groot/Warren algorithm and newer algorithms including self-consistent leap-frog, self-consistent velocity Verlet and Shardlow first and second order integrators. At low friction values, the velocity autocorrelation function decays exponentially at short times, shows slower-than exponential decay at intermediate times, and approaches zero at long times for all five integrators. As friction value increases, the deviation from exponential behavior occurs earlier and is more pronounced. At small time steps, all the integrators give identical decay profiles. As time step increases, there are qualitative and quantitative differences between the integrators. The stress correlation behavior is markedly different for the algorithms. The self-consistent velocity Verlet and the Shardlow algorithms show very similar stress autocorrelation decay with change in friction parameter, whereas the Groot/Warren and leap-frog schemes show variations at higher friction factors. Diffusion coefficients and shear viscosities are calculated using Green-Kubo integration of the velocity and stress autocorrelation functions. The diffusion coefficients match well-known theoretical results at low friction limits. Although the stress autocorrelation function is different for each integrator, fluctuates rapidly, and gives poor statistics for most of the cases, the calculated shear viscosities still fall within range of theoretical predictions and nonequilibrium studies.

  16. Stress Effects on Multiple Memory System Interactions

    Science.gov (United States)

    Ness, Deborah; Calabrese, Pasquale

    2016-01-01

    Extensive behavioural, pharmacological, and neurological research reports stress effects on mammalian memory processes. While stress effects on memory quantity have been known for decades, the influence of stress on multiple memory systems and their distinct contributions to the learning process have only recently been described. In this paper, after summarizing the fundamental biological aspects of stress/emotional arousal and recapitulating functionally and anatomically distinct memory systems, we review recent animal and human studies exploring the effects of stress on multiple memory systems. Apart from discussing the interaction between distinct memory systems in stressful situations, we will also outline the fundamental role of the amygdala in mediating such stress effects. Additionally, based on the methods applied in the herein discussed studies, we will discuss how memory translates into behaviour. PMID:27034845

  17. Stress Effects on Multiple Memory System Interactions

    Directory of Open Access Journals (Sweden)

    Deborah Ness

    2016-01-01

    Full Text Available Extensive behavioural, pharmacological, and neurological research reports stress effects on mammalian memory processes. While stress effects on memory quantity have been known for decades, the influence of stress on multiple memory systems and their distinct contributions to the learning process have only recently been described. In this paper, after summarizing the fundamental biological aspects of stress/emotional arousal and recapitulating functionally and anatomically distinct memory systems, we review recent animal and human studies exploring the effects of stress on multiple memory systems. Apart from discussing the interaction between distinct memory systems in stressful situations, we will also outline the fundamental role of the amygdala in mediating such stress effects. Additionally, based on the methods applied in the herein discussed studies, we will discuss how memory translates into behaviour.

  18. Stress Effects on Multiple Memory System Interactions.

    Science.gov (United States)

    Ness, Deborah; Calabrese, Pasquale

    2016-01-01

    Extensive behavioural, pharmacological, and neurological research reports stress effects on mammalian memory processes. While stress effects on memory quantity have been known for decades, the influence of stress on multiple memory systems and their distinct contributions to the learning process have only recently been described. In this paper, after summarizing the fundamental biological aspects of stress/emotional arousal and recapitulating functionally and anatomically distinct memory systems, we review recent animal and human studies exploring the effects of stress on multiple memory systems. Apart from discussing the interaction between distinct memory systems in stressful situations, we will also outline the fundamental role of the amygdala in mediating such stress effects. Additionally, based on the methods applied in the herein discussed studies, we will discuss how memory translates into behaviour.

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

    Directory of Open Access Journals (Sweden)

    Daisuke Ohshima

    2015-06-01

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

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

    International Nuclear Information System (INIS)

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

    2010-01-01

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

  1. Stress wave velocity and dynamic modulus of elasticity of yellow-poplar ranging from 100 to 10 percent moisture content

    Science.gov (United States)

    Jody D. Gray; Shawn T. Grushecky; James P. Armstrong

    2008-01-01

    Moisture content has a significant impact on mechanical properties of wood. In recent years, stress wave velocity has been used as an in situ and non-destructive method for determining the stiffness of wooden elements. The objective of this study was to determine what effect moisture content has on stress wave velocity and dynamic modulus of elasticity. Results...

  2. Comparing of Normal Stress Distribution in Static and Dynamic Soil-Structure Interaction Analyses

    International Nuclear Information System (INIS)

    Kholdebarin, Alireza; Massumi, Ali; Davoodi, Mohammad; Tabatabaiefar, Hamid Reza

    2008-01-01

    It is important to consider the vertical component of earthquake loading and inertia force in soil-structure interaction analyses. In most circumstances, design engineers are primarily concerned about the analysis of behavior of foundations subjected to earthquake-induced forces transmitted from the bedrock. In this research, a single rigid foundation with designated geometrical parameters located on sandy-clay soil has been modeled in FLAC software with Finite Different Method and subjected to three different vertical components of earthquake records. In these cases, it is important to evaluate effect of footing on underlying soil and to consider normal stress in soil with and without footing. The distribution of normal stress under the footing in static and dynamic states has been studied and compared. This Comparison indicated that, increasing in normal stress under the footing caused by vertical component of ground excitations, has decreased dynamic vertical settlement in comparison with static state

  3. Death and population dynamics affect mutation rate estimates and evolvability under stress in bacteria.

    Science.gov (United States)

    Frenoy, Antoine; Bonhoeffer, Sebastian

    2018-05-01

    The stress-induced mutagenesis hypothesis postulates that in response to stress, bacteria increase their genome-wide mutation rate, in turn increasing the chances that a descendant is able to better withstand the stress. This has implications for antibiotic treatment: exposure to subinhibitory doses of antibiotics has been reported to increase bacterial mutation rates and thus probably the rate at which resistance mutations appear and lead to treatment failure. More generally, the hypothesis posits that stress increases evolvability (the ability of a population to generate adaptive genetic diversity) and thus accelerates evolution. Measuring mutation rates under stress, however, is problematic, because existing methods assume there is no death. Yet subinhibitory stress levels may induce a substantial death rate. Death events need to be compensated by extra replication to reach a given population size, thus providing more opportunities to acquire mutations. We show that ignoring death leads to a systematic overestimation of mutation rates under stress. We developed a system based on plasmid segregation that allows us to measure death and division rates simultaneously in bacterial populations. Using this system, we found that a substantial death rate occurs at the tested subinhibitory concentrations previously reported to increase mutation rate. Taking this death rate into account lowers and sometimes removes the signal for stress-induced mutagenesis. Moreover, even when antibiotics increase mutation rate, we show that subinhibitory treatments do not increase genetic diversity and evolvability, again because of effects of the antibiotics on population dynamics. We conclude that antibiotic-induced mutagenesis is overestimated because of death and that understanding evolvability under stress requires accounting for the effects of stress on population dynamics as much as on mutation rate. Our goal here is dual: we show that population dynamics and, in particular, the

  4. Gene Expression Dynamics Accompanying the Sponge Thermal Stress Response.

    Science.gov (United States)

    Guzman, Christine; Conaco, Cecilia

    2016-01-01

    Marine sponges are important members of coral reef ecosystems. Thus, their responses to changes in ocean chemistry and environmental conditions, particularly to higher seawater temperatures, will have potential impacts on the future of these reefs. To better understand the sponge thermal stress response, we investigated gene expression dynamics in the shallow water sponge, Haliclona tubifera (order Haplosclerida, class Demospongiae), subjected to elevated temperature. Using high-throughput transcriptome sequencing, we show that these conditions result in the activation of various processes that interact to maintain cellular homeostasis. Short-term thermal stress resulted in the induction of heat shock proteins, antioxidants, and genes involved in signal transduction and innate immunity pathways. Prolonged exposure to thermal stress affected the expression of genes involved in cellular damage repair, apoptosis, signaling and transcription. Interestingly, exposure to sublethal temperatures may improve the ability of the sponge to mitigate cellular damage under more extreme stress conditions. These insights into the potential mechanisms of adaptation and resilience of sponges contribute to a better understanding of sponge conservation status and the prediction of ecosystem trajectories under future climate conditions.

  5. Thermal stress effects in intermetallic matrix composites

    Science.gov (United States)

    Wright, P. K.; Sensmeier, M. D.; Kupperman, D. S.; Wadley, H. N. G.

    1993-01-01

    Intermetallic matrix composites develop residual stresses from the large thermal expansion mismatch (delta-alpha) between the fibers and matrix. This work was undertaken to: establish improved techniques to measure these thermal stresses in IMC's; determine residual stresses in a variety of IMC systems by experiments and modeling; and, determine the effect of residual stresses on selected mechanical properties of an IMC. X ray diffraction (XRD), neutron diffraction (ND), synchrotron XRD (SXRD), and ultrasonics (US) techniques for measuring thermal stresses in IMC were examined and ND was selected as the most promising technique. ND was demonstrated on a variety of IMC systems encompassing Ti- and Ni-base matrices, SiC, W, and Al2O3 fibers, and different fiber fractions (Vf). Experimental results on these systems agreed with predictions of a concentric cylinder model. In SiC/Ti-base systems, little yielding was found and stresses were controlled primarily by delta-alpha and Vf. In Ni-base matrix systems, yield strength of the matrix and Vf controlled stress levels. The longitudinal residual stresses in SCS-6/Ti-24Al-llNb composite were modified by thermomechanical processing. Increasing residual stress decreased ultimate tensile strength in agreement with model predictions. Fiber pushout strength showed an unexpected inverse correlation with residual stress. In-plane shear yield strength showed no dependence on residual stress. Higher levels of residual tension led to higher fatigue crack growth rates, as suggested by matrix mean stress effects.

  6. Effects of external stress on biodegradable orthopedic materials: A review

    Directory of Open Access Journals (Sweden)

    Xuan Li

    2016-09-01

    Full Text Available Biodegradable orthopedic materials (BOMs are used in rehabilitation and reconstruction of fractured tissues. The response of BOMs to the combined action of physiological stress and corrosion is an important issue in vivo since stress-assisted degradation and cracking are common. Although the degradation behavior and kinetics of BOMs have been investigated under static conditions, stress effects can be very serious and even fatal in the dynamic physiological environment. Since stress is unavoidable in biomedical applications of BOMs, recent work has focused on the evaluation and prediction of the properties of BOMs under stress in corrosive media. This article reviews recent progress in this important area focusing on biodegradable metals, polymers, and ceramics.

  7. Stress and Systemic Inflammation: Yin-Yang Dynamics in Health and Diseases.

    Science.gov (United States)

    Yan, Qing

    2018-01-01

    Studies in psychoneuroimmunology (PNI) would provide better insights into the "whole mind-body system." Systems biology models of the complex adaptive systems (CASs), such as a conceptual framework of "Yin-Yang dynamics," may be helpful for identifying systems-based biomarkers and targets for more effective prevention and treatment. The disturbances in the Yin-Yang dynamical balance may result in stress, inflammation, and various disorders including insomnia, Alzheimer's disease, obesity, diabetes, cardiovascular diseases, skin disorders, and cancer. At the molecular and cellular levels, the imbalances in the cytokine pathways, mitochondria networks, redox systems, and various signaling pathways may contribute to systemic inflammation. In the nervous system, Yin and Yang may represent the dynamical associations between the progressive and regressive processes in aging and neurodegenerative diseases. In response to the damages to the heart, the Yin-Yang dynamical balance between proinflammatory and anti-inflammatory cytokine networks is crucial. The studies of cancer have revealed the importance of the Yin-Yang dynamics in the tumoricidal and tumorigenic activities of the immune system. Stress-induced neuroimmune imbalances are also essential in chronic skin disorders including atopic dermatitis and psoriasis. With the integrative framework, the restoration of the Yin-Yang dynamics can become the objective of dynamical systems medicine.

  8. Distribution of Side Abutment Stress in Roadway Subjected to Dynamic Pressure and Its Engineering Application

    Directory of Open Access Journals (Sweden)

    Yao Qiangling

    2015-01-01

    Full Text Available The borehole stress-meter was employed in this study to investigate the distribution of the side abutment stress in roadway subjected to dynamic pressure. The results demonstrate that the side abutment stress of the mining roadway reaches a peak value when the distance to the gob is 8 m and the distribution curve of the side abutment stress can be divided into three zones: stress rising zone, stress stabilizing zone, and stress decreasing zone. Further numerical investigation was carried out to study the effect of the coal mass strength, coal seam depth, immediate roof strength, and thickness on the distribution of the side abutment stress. Based on the research results, we determined the reasonable position of the mining roadway and the optimal width of the barrier pillar. The engineering application demonstrates that the retention of the barrier pillar with a width of 5 m along the gob as the haulage roadway for the next panel is feasible, which delivers favorable technological and economic benefits.

  9. Calculation of dynamic stresses in viscoelastic sandwich beams using oma

    DEFF Research Database (Denmark)

    Pelayo, F.; Aenlle, M. L.; Ismael, G.

    2017-01-01

    The mechanical response of sandwich elements with viscoelastic core is time and temperature dependent. Laminated glass is a sandwich element where the mechanical behavior of the glass layers is usually considered linear-elastic material whereas the core is made of an amorphous thermoplastic which...... data. In simple structures, analytical mode shapes can be used alternatively to the numerical ones. In this paper, the dynamic stresses on the glass layers of a laminated glass beam have estimated using the experimental acceleration responses measured at 7 points of the beam, and the experimental mode...

  10. Dynamic Stress Concentration at the Boundary of an Incision at the Plate Under the Action of Weak Shock Waves

    Directory of Open Access Journals (Sweden)

    Mikulich Olena

    2017-09-01

    Full Text Available This paper proposes the novel technique for analysis of dynamic stress state of multi-connected infinite plates under the action of weak shock waves. For solution of the problem it uses the integral and discrete Fourier transforms. Calculation of transformed dynamic stresses at the incisions of plates is held using the boundary-integral equation method and the theory of complex variable functions. The numerical implementation of the developed algorithm is based on the method of mechanical quadratures and collocation technique. For calculation of originals of the dynamic stresses it uses modified discrete Fourier transform. The algorithm is effective in the analysis of the dynamic stress state of defective plates.

  11. Dynamic stress of impeller blade of shaft extension tubular pump device based on bidirectional fluid-structure interaction

    Energy Technology Data Exchange (ETDEWEB)

    Kan, Kan; Liu, Huiwen; Yang, Chunxia [Hohai University, Nanjing (China); Zheng, Yuan [National Engineering Research Center of Water Resources Efficient Utilization and Engineering Safety, Nanjing (China); Fu, Shifeng; Zhang, Xin [Power China Huadong Engineering Corporation, Hangzhou (China)

    2017-04-15

    Current research on the stability of tubular pumps is mainly concerned with the transient hydrodynamic characteristics. However, the structural response under the influence of fluid-structure interaction hasn't been taken fully into consideration. The instability of the structure can cause vibration and cracks, which may threaten the safety of the unit. We used bidirectional fluid-structure interaction to comprehensively analyze the dynamic stress characteristics of the impeller blades of the shaft extension tubular pump device. Furthermore, dynamic stress of impeller blade of shaft extension tubular pump device was solved under different lift conditions of 0° blade angle. Based on Reynolds-average N-S equation and SST k-ω turbulence model, numerical simulation was carried out for three-dimensional unsteady incompressible turbulent flow field of the pump device whole flow passage. Meanwhile, the finite element method was used to calculate dynamic characteristics of the blade structure. The blade dynamic stress distribution was obtained on the basis of fourth strength theory. The research results indicate that the maximum blade dynamic stress appears at the joint between root of inlet side of the blade suction surface and the axis. Considering the influence of gravity, the fluctuation of the blade dynamic stress increases initially and decreases afterwards within a rotation period. In the meantime, the dynamic stress in the middle part of inlet edge presents larger relative fluctuation amplitude. Finally, a prediction method for dynamic stress distribution of tubular pump considering fluid-structure interaction and gravity effect was proposed. This method can be used in the design stage of tubular pump to predict dynamic stress distribution of the structure under different operating conditions, improve the reliability of pump impeller and analyze the impeller fatigue life.

  12. Effective stress law for anisotropic elastic deformation

    International Nuclear Information System (INIS)

    Carroll, M.M.

    1979-01-01

    An effective stress law is derived analytically to describe the effect of pore fluid pressure on the linearly elastic response of saturated porous rocks which exhibit anisotropy. For general anisotropy the difference between the effective stress and the applied stress is not hydrostatic. The effective stress law involves two constants for transversely isotropic response and three constants for orthotropic response; these constants can be expressed in terms of the moduli of the porous material and of the solid material. These expressions simplify considerably when the anisotropy is structural rather than intrinsic, i.e., in the case of an isotropic solid material with an anisotropic pore structure. In this case the effective stress law involves the solid or grain bulk modulus and two or three moduli of the porous material, for transverse isotropy and orthotropy, respectively. The law reduces, in the case of isotropic response, to that suggested by Geertsma (1957) and by Skempton (1961) and derived analytically by Nur and Byerlee

  13. Unsteady exergy destruction of the neuron under dynamic stress conditions

    International Nuclear Information System (INIS)

    Genc, S.; Sorguven, E.; Ozilgen, M.; Aksan Kurnaz, I.

    2013-01-01

    Just like all physical systems, biological systems also obey laws of thermodynamics, and as such the useful work potential of a biological system is its exergy. In some studies, exergy of living systems is considered with respect to work performance of humans in offices or buildings; however the exergy analysis of biochemical reactions in a cell as a closed system goes largely untouched. In this study, exergy analysis was applied to glucose metabolism of a model neuron, and dynamic exergy destructions were calculated for four different conditions, namely normoxia, hypoxia, glucose starvation and excess glucose. Our results showed that neuronal metabolism achieved a new steady state under each condition within 5 min. This dynamic model predicts that, both exergy destruction and work potential rates increase with increasing blood glucose concentration. The ratio of exergy destruction rate to work potential rate increases logarithmically with increasing blood glucose concentration. The neuronal metabolism is thus found to function in an efficient way and switches to lower exergy destruction under stress conditions such as glucose starvation. This behavior seen in this exergy analysis study confirms the assumption of minimum entropy production in living systems. - Highlights: • Unsteady exergy analysis of glucose metabolism of a model neuron is performed. • Dynamic exergy losses were calculated for four different conditions: normoxia, hypoxia, glucose starvation and excess glucose. • Neuronal metabolism achieved a new steady state under each condition within 5 min. • Both exergy loss and work potential rates increase with increasing blood glucose concentration. • Neuronal metabolism functions in an efficient way and switches to lower exergy loss under stress conditions

  14. Dynamic Response in Transient Stress-Field Behavior Induced by Hydraulic Fracturing

    Science.gov (United States)

    Jenkins, Andrew

    Hydraulic fracturing is a technique which is used to exploit geologic features and subsurface properties in an effort to increase production in low-permeability formations. The process of hydraulic fracturing provides a greater surface contact area between the producing formation and the wellbore and thus increases the amount of recoverable hydrocarbons from within the reservoir. The use of this stimulation technique has brought on massive applause from the industry due to its widespread success and effectiveness, however the dynamic processes that take part in the development of hydraulic fractures is a relatively new area of research with respect to the massive scale operations that are seen today. The process of hydraulic fracturing relies upon understanding and exploiting the in-situ stress distribution throughout the area of study. These in-situ stress conditions are responsible for directing fracture orientation and propagation paths throughout the period of injection. The relative magnitude of these principle stresses is key in developing a successful stimulation plan. In horizontal well plan development the interpretation of stress within the reservoir is required for determining the azimuth of the horizontal well path. These horizontal laterals are typically oriented in a manner such that the well path lies parallel to the minimum horizontal stress. This allows for vertical fractures to develop transversely to the wellbore, or normal to the least principle stress without the theoretical possibility of fractures overlapping, creating the most efficient use of the fluid energy during injection. The orientation and magnitude of these in-situ stress fields however can be dynamic, controlled by the subsequent fracture propagation and redistribution of the surrounding stresses. That is, that as the fracture propagates throughout the reservoir, the relative stress fields surrounding the fractures may see a shift and deviate from their original direction or

  15. Effects of stress on nursing integrity.

    Science.gov (United States)

    McIntosh, Bryan; Sheppy, Bruce

    This article looks at the relationship between stress, nursing integrity and patient care. It has been argued that the professional integrity of nurses has been eroded and consequently they have become more susceptible to anxiety, stress and exhaustion, potentially affecting care delivery. The authors suggest that the goal of providing high professional standards is threatened by increased service demands, and there is therefore a need for nurses to develop effective coping strategies to manage stress resulting from competing tensions in the workplace.

  16. Dynamic regulation of NMDAR function in the adult brain by the stress hormone corticosterone

    Directory of Open Access Journals (Sweden)

    Yiu Chung eTse

    2012-03-01

    Full Text Available Stress and corticosteroids dynamically modulate the expression of synaptic plasticity at glutamatergic synapses in the developed brain. Together with alpha-amino-3-hydroxy-methyl-4-isoxazole propionic acid receptors (AMPAR, N-methyl-D-aspartate receptors (NMDAR are critical mediators of synaptic function and are essential for the induction of many forms of synaptic plasticity. Regulation of NMDAR function by cortisol/corticosterone (CORT may be fundamental to the effects of stress on synaptic plasticity. Recent reports of the efficacy of NMDAR antagonists in treating certain stress-associated psychopathologies further highlight the importance of understanding the regulation of NMDAR function by CORT. Knowledge of how corticosteroids regulate NMDAR function within the adult brain is relatively sparse, perhaps due to a common belief that NMDAR function is relatively stable in the adult brain. We review recent results from our laboratory and others demonstrating dynamic regulation of NMDAR function by CORT in the adult brain. In addition, we consider the issue of how differences in the early life environment may program differential sensitivity to modulation of NMDAR function by CORT and how this may influence synaptic function during stress. Findings from these studies demonstrate that NMDAR function in the adult hippocampus remains sensitive to even brief exposures to CORT and that the capacity for modulation of NMDAR may be programmed, in part, by the early life environment. Modulation of NMDAR function may contribute to dynamic regulation of synaptic plasticity and adaptation in the face of stress, however enhanced NMDAR function may be implicated in mechanisms of stress related psychopathologies including depression.

  17. Adverse effects of stress on microbiota

    Science.gov (United States)

    The complex communities of microorganisms that colonize the gastrointestinal tract impact the health status of an animal. The health of an animal as well as production traits are also affected by exposure to stress. The aim of present study was to evaluate the effects of dehorning stress on the gut ...

  18. Transcriptome Dynamics of Pseudomonas putida KT2440 under Water Stress

    DEFF Research Database (Denmark)

    Gülez, Gamze; Dechesne, Arnaud; Workman, Christopher

    2012-01-01

    Water deprivation can be a major stressor to microbial life in surface and subsurface soil. In unsaturated soils, the matric potential (Ψm) is often the main component of the water potential, which measures the thermodynamic availability of water. A low matric potential usually translates...... into water forming thin liquid films in the soil pores. Little is known of how bacteria respond to such conditions, where, in addition to facing water deprivation that might impair their metabolism, they have to adapt their dispersal strategy as swimming motility may be compromised. Using the pressurized...... porous surface model (PPSM), which allows creation of thin liquid films by controlling Ψm, we examined the transcriptome dynamics of Pseudomonas putida KT2440. We identified the differentially expressed genes in cells exposed to a mild matric stress (–0.4 MPa) for 4, 24, or 72 h. The major response...

  19. No effect of stress on false recognition.

    Science.gov (United States)

    Beato, María Soledad; Cadavid, Sara; Pulido, Ramón F; Pinho, María Salomé

    2013-02-01

    The present study aimed to analyze the effect of acute stress on false recognition in the Deese/Roediger-McDermott (DRM) paradigm. In this paradigm, lists of words associated with a non-presented critical lure are studied and, in a subsequent memory test, critical lures are often falsely remembered. In two experiments, participants were randomly assigned to either the stress group (Trier Social Stress Test) or the no-stress control group. Because we sought to control the level-of-processing at encoding, in Experiment 1, participants created a visual mental image for each presented word (deep encoding). In Experiment 2, participants performed a shallow encoding (to respond whether each word contained the letter "o"). The results indicated that, in both experiments, as predicted, heart rate and STAI-S scores increased only in the stress group. However, false recognition did not differ across stress and no-stress groups. Results suggest that, although psychosocial stress was successfully induced, it does not enhance the vulnerability of individuals with acute stress to DRM false recognition, regardless of the level of processing.

  20. Dynamical Franz-Keldysh Effect

    DEFF Research Database (Denmark)

    Jauho, Antti-Pekka; Johnsen, Kristinn

    1996-01-01

    We introduce and analyze the properties of dynamical Franz-Keldysh effect, i.e., the change of density of states, or absorption spectra, of semiconductors under the influence of time-dependent electric fields. In the case of a harmonic time dependence, we predict the occurrence of significant fin...... structure, both below and above the zero-field band gap, which should be experimentally observable.......We introduce and analyze the properties of dynamical Franz-Keldysh effect, i.e., the change of density of states, or absorption spectra, of semiconductors under the influence of time-dependent electric fields. In the case of a harmonic time dependence, we predict the occurrence of significant fine...

  1. Hydrodynamic view of electrodynamics: energy rays and electromagnetic effective stress

    International Nuclear Information System (INIS)

    Chou, Chia-Chun; Wyatt, Robert E

    2011-01-01

    Energy rays ('photon trajectories') based upon the hydrodynamic formulation of electrodynamics are presented for time-dependent electromagnetic wave propagation. We derive Cauchy's equation of motion for the electromagnetic effective force governing the dynamics of energy rays. The effective force generated by the electromagnetic effective stress provides a surface force acting on the energy fluid element. For the head-on collision of two electromagnetic Gaussian pulses, the electromagnetic effective force, analogous to the role played by the quantum force in Bohmian mechanics, guides these non-crossing energy rays. For an electromagnetic pulse traveling from free space to a dielectric medium, the energy rays guided by the electromagnetic effective stress display reflection and refraction at the interface.

  2. Communicating Intrapersonally about Stress: The Dynamics on Self.

    Science.gov (United States)

    Edson, Belle A.

    When designing a workshop about communication and stress, it is important to consider the medical definition--that stress is a physiological reaction to an external force that is interpreted by the individual--and the psychological definition--which suggests that through communication with self one can change the stress in one's life. Stress can…

  3. Stress concentration effects in high pressure components

    International Nuclear Information System (INIS)

    Aller, J.E.

    1990-01-01

    This paper examines the stress concentration effects of sideholes in thick walled, high pressure cylinders. It has been shown that the theoretical stress concentration factor at the intersection of a small crossbore in a closed end, thick walled cylinder varies between 3.0 and 4.0. Tests have shown that this effect can be greatly reduced in practice by carefully radiusing the bore intersection and autofrettaging the cylinder. It has also been shown that the minimum stress concentration factor occurs when the main bore and sidehole or crossbore have the same diameter, and the radius of the intersection is approximately equal to the sidehole radius. When the bore and sidehole intersection angle decreases from 90 degrees, the stress concentration factor increases significantly. Knowledge of these fundamental relationships can be used in maintaining, as well ad designing, high pressure equipment

  4. Conceptualizing the dynamics of workplace stress: a systems-based study of nursing aides

    OpenAIRE

    Jetha, Arif; Kernan, Laura; Kurowski, Alicia

    2017-01-01

    Background Workplace stress is a complex phenomenon that may often be dynamic and?evolving over time. Traditional linear modeling does not allow representation of recursive feedback loops among the implicated factors. The objective of this study was to develop a multidimensional system dynamics model (SDM) of workplace stress among nursing aides and conduct simulations to illustrate how changes in psychosocial perceptions and workplace factors might influence workplace stress over time. Metho...

  5. Field Measurement of Dynamic Compressive Stress Response of Pavement-Subgrade Induced by Moving Heavy-Duty Trucks

    Directory of Open Access Journals (Sweden)

    Lingshi An

    2018-01-01

    Full Text Available This paper presents the dynamic compressive stress response of pavement-subgrade induced by moving heavy-duty trucks. In order to study the distribution characteristic of dynamic pressure of pavement-subgrade in more detail, truck loadings, truck speeds, and dynamic pressure distributions at different depths were monitored under twenty-five working conditions on the section of Qiqihar-Nenjiang Highway in Heilongjiang Province, China. The effects of truck loading, truck speed, and depth on dynamic compressive stress response can be concluded as follows: (1 increasing truck loading will increase the dynamic pressure amplitude of subgrade-pavement and dominant frequencies are close to the characteristic frequencies caused by heavy-duty trucks at the speed of 70 km/h; (2 as truck speed increases, the dynamic pressure amplitudes of measuring points have an increasing tendency; the dynamic pressure spectrums are also significantly influenced by truck speed: the higher the truck speed, the wider the spectrum and the higher the dominant frequencies; (3 as depth increases, the dynamic pressure amplitudes of measuring points decrease rapidly. The influence of the front axle decreases gradually until disappearing and the compressive stress superposition phenomenon caused by rear double axles can be found with increasing depth.

  6. Dynamical effects in electron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Jianqiang Sky, E-mail: jianqiang.zhou@polytechnique.edu; Reshetnyak, Igor; Giorgetti, Christine; Sottile, Francesco; Reining, Lucia [Laboratoire des Solides Irradiés, École Polytechnique, CNRS, CEA-DSM-IRAMIS, Université Paris-Saclay, F-91128 Palaiseau (France); Kas, J. J.; Rehr, J. J. [Department of Physics, University of Washington, Seattle, Washington 98195-1560 (United States); Sponza, Lorenzo [Department of Physics, King’s College London, London WC2R 2LS (United Kingdom); Guzzo, Matteo [Institut für Physik und IRIS Adlershof, Humboldt-Universität zu Berlin, D-12489 Berlin (Germany); Gatti, Matteo [Laboratoire des Solides Irradiés, École Polytechnique, CNRS, CEA-DSM-IRAMIS, Université Paris-Saclay, F-91128 Palaiseau (France); Synchrotron SOLEIL, L’Orme des Merisiers, Saint-Aubin, BP 48, F-91192 Gif-sur-Yvette (France)

    2015-11-14

    One of the big challenges of theoretical condensed-matter physics is the description, understanding, and prediction of the effects of the Coulomb interaction on materials properties. In electronic spectra, the Coulomb interaction causes a renormalization of energies and change of spectral weight. Most importantly, it can lead to new structures, often called satellites. These can be linked to the coupling of excitations, also termed dynamical effects. State-of-the-art methods in the framework of many-body perturbation theory, in particular, the widely used GW approximation, often fail to describe satellite spectra. Instead, approaches based on a picture of electron-boson coupling such as the cumulant expansion are promising for the description of plasmon satellites. In this work, we give a unified derivation of the GW approximation and the cumulant expansion for the one-body Green’s function. Using the example of bulk sodium, we compare the resulting spectral functions both in the valence and in the core region, and we discuss the dispersion of quasi-particles and satellites. We show that self-consistency is crucial to obtain meaningful results, in particular, at large binding energies. Very good agreement with experiment is obtained when the intrinsic spectral function is corrected for extrinsic and interference effects. Finally, we sketch how one can approach the problem in the case of the two-body Green’s function, and we discuss the cancellation of various dynamical effects that occur in that case.

  7. Dynamical effects in electron spectroscopy

    International Nuclear Information System (INIS)

    Zhou, Jianqiang Sky; Reshetnyak, Igor; Giorgetti, Christine; Sottile, Francesco; Reining, Lucia; Kas, J. J.; Rehr, J. J.; Sponza, Lorenzo; Guzzo, Matteo; Gatti, Matteo

    2015-01-01

    One of the big challenges of theoretical condensed-matter physics is the description, understanding, and prediction of the effects of the Coulomb interaction on materials properties. In electronic spectra, the Coulomb interaction causes a renormalization of energies and change of spectral weight. Most importantly, it can lead to new structures, often called satellites. These can be linked to the coupling of excitations, also termed dynamical effects. State-of-the-art methods in the framework of many-body perturbation theory, in particular, the widely used GW approximation, often fail to describe satellite spectra. Instead, approaches based on a picture of electron-boson coupling such as the cumulant expansion are promising for the description of plasmon satellites. In this work, we give a unified derivation of the GW approximation and the cumulant expansion for the one-body Green’s function. Using the example of bulk sodium, we compare the resulting spectral functions both in the valence and in the core region, and we discuss the dispersion of quasi-particles and satellites. We show that self-consistency is crucial to obtain meaningful results, in particular, at large binding energies. Very good agreement with experiment is obtained when the intrinsic spectral function is corrected for extrinsic and interference effects. Finally, we sketch how one can approach the problem in the case of the two-body Green’s function, and we discuss the cancellation of various dynamical effects that occur in that case

  8. Reconstructing a Network of Stress-Response Regulators via Dynamic System Modeling of Gene Regulation

    Directory of Open Access Journals (Sweden)

    Wei-Sheng Wu

    2008-01-01

    Full Text Available Unicellular organisms such as yeasts have evolved mechanisms to respond to environmental stresses by rapidly reorganizing the gene expression program. Although many stress-response genes in yeast have been discovered by DNA microarrays, the stress-response transcription factors (TFs that regulate these stress-response genes remain to be investigated. In this study, we use a dynamic system model of gene regulation to describe the mechanism of how TFs may control a gene’s expression. Then, based on the dynamic system model, we develop the Stress Regulator Identification Algorithm (SRIA to identify stress-response TFs for six kinds of stresses. We identified some general stress-response TFs that respond to various stresses and some specific stress-response TFs that respond to one specifi c stress. The biological significance of our findings is validated by the literature. We found that a small number of TFs is probably suffi cient to control a wide variety of expression patterns in yeast under different stresses. Two implications can be inferred from this observation. First, the response mechanisms to different stresses may have a bow-tie structure. Second, there may be regulatory cross-talks among different stress responses. In conclusion, this study proposes a network of stress-response regulators and the details of their actions.

  9. Altered oscillatory brain dynamics after repeated traumatic stress

    Directory of Open Access Journals (Sweden)

    Ruf Martina

    2007-10-01

    Full Text Available Abstract Background Repeated traumatic experiences, e.g. torture and war, lead to functional and structural cerebral changes, which should be detectable in cortical dynamics. Abnormal slow waves produced within circumscribed brain regions during a resting state have been associated with lesioned neural circuitry in neurological disorders and more recently also in mental illness. Methods Using magnetoencephalographic (MEG-based source imaging, we mapped abnormal distributions of generators of slow waves in 97 survivors of torture and war with posttraumatic stress disorder (PTSD in comparison to 97 controls. Results PTSD patients showed elevated production of focally generated slow waves (1–4 Hz, particularly in left temporal brain regions, with peak activities in the region of the insula. Furthermore, differential slow wave activity in right frontal areas was found in PTSD patients compared to controls. Conclusion The insula, as a site of multimodal convergence, could play a key role in understanding the pathophysiology of PTSD, possibly accounting for what has been called posttraumatic alexithymia, i.e., reduced ability to identify, express and regulate emotional responses to reminders of traumatic events. Differences in activity in right frontal areas may indicate a dysfunctional PFC, which may lead to diminished extinction of conditioned fear and reduced inhibition of the amygdala.

  10. Three dimensional viscoelastic simulation on dynamic evolution of stress field in North China induced by the 1966 Xingtai earthquake

    Science.gov (United States)

    Chen, Lian-Wang; Lu, Yuan-Zhong; Liu, Jie; Guo, Ruo-Mei

    2001-09-01

    Using three dimensional (3D) viscoelastic finite element method (FEM) we study the dynamic evolution pattern of the coseismic change of Coulomb failure stress and postseismic change, on time scale of hundreds years, of rheological effect induced by the M S=7.2 Xingtai earthquake on March 22, 1966. Then, we simulate the coseismic disturbance in stress field in North China and dynamic change rate on one-year scale caused by the Xingtai earthquake and Tangshan earthquake during 15 years from 1966 to 1980. Finally, we discuss the triggering of a strong earthquake to another future strong earthquake.

  11. Dynamic effects in fragmentation reactions

    International Nuclear Information System (INIS)

    Bertsch, G. F.; Esbensen, H.

    2002-01-01

    Fragmentation reactions offer a useful tool to study the spectroscopy of halo nuclei, but the large extent of the halo wave function makes the reaction theory more difficult. The simple reaction models based on the eikonal approximation for the nuclear interaction or first-order perturbation theory for the Coulomb interaction have systematic errors that they investigate here, comparing to the predictions of complete dynamical calculations. They find that stripping probabilities are underpredicted by the eikonal model, leading to extracted spectroscopy strengths that are two large. In contrast, the Coulomb excitation is overpredicted by the simple theory. They attribute this to a screening effect, as is well known in the Barkas effect on stopping powers. The errors decrease with beam energy as E(sub beam)(sup -1), and are not significant at beam energies above 50 MeV/u. At lower beam energies, the effects should be taken into account when extracting quantitative spectroscopic strengths

  12. Noise and stress effects on preschool personnel

    Directory of Open Access Journals (Sweden)

    Fredrik Sjödin

    2012-01-01

    Full Text Available The aim of the study was to analyze the presence of stress-related health problems among preschool employees and the way in which these reactions are related to noise and other work parameters. The investigation included 101 employees at 17 preschools in Umeå County, located in northern Sweden. Individual noise recordings and recordings in dining rooms and play halls were made at two departments from each preschool. The adverse effects on the employees were analyzed by use of different validated questionnaires and by saliva cortisol samples. Stress and energy output were pronounced among the employees, and about 30% of the staff experienced strong burnout syndromes. Mental recovery after work was low, indicated by remaining high levels of stress after work. The burnout symptoms were associated with reduced sleep quality and morning sleepiness. Cortisol levels supported the conclusion about pronounced daily stress levels of the preschool employees.

  13. Strain rate effects in stress corrosion cracking

    Energy Technology Data Exchange (ETDEWEB)

    Parkins, R.N. (Newcastle upon Tyne Univ. (UK). Dept. of Metallurgy and Engineering Materials)

    1990-03-01

    Slow strain rate testing (SSRT) was initially developed as a rapid, ad hoc laboratory method for assessing the propensity for metals an environments to promote stress corrosion cracking. It is now clear, however, that there are good theoretical reasons why strain rate, as opposed to stress per se, will often be the controlling parameter in determining whether or not cracks are nucleated and, if so, are propagated. The synergistic effects of the time dependence of corrosion-related reactions and microplastic strain provide the basis for mechanistic understanding of stress corrosion cracking in high-pressure pipelines and other structures. However, while this may be readily comprehended in the context of laboratory slow strain tests, its extension to service situations may be less apparent. Laboratory work involving realistic stressing conditions, including low-frequency cyclic loading, shows that strain or creep rates give good correlation with thresholds for cracking and with crack growth kinetics.

  14. Conceptualizing the dynamics of workplace stress: a systems-based study of nursing aides.

    Science.gov (United States)

    Jetha, Arif; Kernan, Laura; Kurowski, Alicia

    2017-01-05

    Workplace stress is a complex phenomenon that may often be dynamic and evolving over time. Traditional linear modeling does not allow representation of recursive feedback loops among the implicated factors. The objective of this study was to develop a multidimensional system dynamics model (SDM) of workplace stress among nursing aides and conduct simulations to illustrate how changes in psychosocial perceptions and workplace factors might influence workplace stress over time. Eight key informants with prior experience in a large study of US nursing home workers participated in model building. Participants brainstormed the range of components related to workplace stress. Components were grouped together based on common themes and translated into feedback loops. The SDM was parameterized through key informant insight on the shape and magnitude of the relationship between model components. Model construction was also supported utilizing survey data collected as part of the larger study. All data was entered into the software program, Vensim. Simulations were conducted to examine how adaptations to model components would influence workplace stress. The SDM included perceptions of organizational conditions (e.g., job demands and job control), workplace social support (i.e., managerial and coworker social support), workplace safety, and demands outside of work (i.e. work-family conflict). Each component was part of a reinforcing feedback loop. Simulations exhibited that scenarios with increasing job control and decreasing job demands led to a decline in workplace stress. Within the context of the system, the effects of workplace social support, workplace safety, and work-family conflict were relatively minor. SDM methodology offers a unique perspective for researchers and practitioners to view workplace stress as a dynamic process. The portrayal of multiple recursive feedback loops can guide the development of policies and programs within complex organizational contexts

  15. Dynamic characteristics of rotating pretwisted clamped-clamped beam under thermal stress

    International Nuclear Information System (INIS)

    Zhang, Bo; Li, Yueming; Lu, Wei Zhen

    2016-01-01

    Effects of thermal stress on the vibration characteristics, buckling limit and critical speed of a rotating pretwisted beam clamped to rigid hub at a stagger angle were investigated. By considering the work done by thermal stress, the thermal influence on stiffness matrix was introduced in the dynamic model. The motion equations were derived based on Lagrange equation by employing three pure Cartesian deformation variables combined with nonlinear von Karman strain formula. Numerical investigations studied the modal characteristics of the beam. Numerical results calculated from a commercial finite element code and obtained with the present modeling method were in good agreement with the previous results reported in the literature. The combined softening effects due to the thermal stress and the rotation motion were observed. Furthermore, it is shown that the inclusion of thermal stress is necessary for blades operating under a high temperature field. Buckling thermal loads and the critical rotating speed were calculated through solving the corresponding nonlinear equations numerically, and some pertinent conclusions are outlined. It is also found that the peak value position of the first mode shape approaches to the tip of blade with the increment of rotating speed and hub radius. However, the variation in the environment temperature causes only a slight alteration in the mode shape

  16. Dynamic characteristics of rotating pretwisted clamped-clamped beam under thermal stress

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Bo; Li, Yueming [State Key Laboratory for Strength and Vibration of Mechanical Structures, Shaanxi Key Laboratory of Environment and Control for Flight Vehicle, School of Aerospace, Xi' an Jiaotong UniversityXi' an (China); Lu, Wei Zhen [Dept. of Civil and Architectural Engineering, City University of Hong Kong, Hong Kong (China)

    2016-09-15

    Effects of thermal stress on the vibration characteristics, buckling limit and critical speed of a rotating pretwisted beam clamped to rigid hub at a stagger angle were investigated. By considering the work done by thermal stress, the thermal influence on stiffness matrix was introduced in the dynamic model. The motion equations were derived based on Lagrange equation by employing three pure Cartesian deformation variables combined with nonlinear von Karman strain formula. Numerical investigations studied the modal characteristics of the beam. Numerical results calculated from a commercial finite element code and obtained with the present modeling method were in good agreement with the previous results reported in the literature. The combined softening effects due to the thermal stress and the rotation motion were observed. Furthermore, it is shown that the inclusion of thermal stress is necessary for blades operating under a high temperature field. Buckling thermal loads and the critical rotating speed were calculated through solving the corresponding nonlinear equations numerically, and some pertinent conclusions are outlined. It is also found that the peak value position of the first mode shape approaches to the tip of blade with the increment of rotating speed and hub radius. However, the variation in the environment temperature causes only a slight alteration in the mode shape.

  17. Dietary intake and the dynamics of stress, hypertension and obesity ...

    African Journals Online (AJOL)

    Hypertension increased with mean age whiles stress decreased with mean age. Hypertensive subjects recorded a significantly higher BMI and sodium intake whiles high stress individuals recorded a lower animal protein but a higher cereal protein intake (p<.05). Chronic stress was associated with intake of low animal ...

  18. Dietary intake and the dynamics of stress, hypertension and obesity ...

    African Journals Online (AJOL)

    2016-03-01

    Mar 1, 2016 ... with high stress (32.89%) especially in females (57.14%, p=.036). Hypertension increased with mean age whiles stress decreased with mean age. Hypertensive subjects recorded a significantly higher BMI and sodium intake whiles high stress individuals recorded a lower animal protein but a higher cereal ...

  19. Simulations of surface stress effects in nanoscale single crystals

    Science.gov (United States)

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

    2018-04-01

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

  20. Effect of normal stress under an excitation in poroelastic flat slabs

    African Journals Online (AJOL)

    user

    Biot's poroelastic theory is employed to investigate stresses under an ... Keywords: Flat slab, radial normal stress, pervious surface, impervious ... warranted, because of above mentioned applications. ...... M.Tajuddin, and G. Narayan Reddy, Effect of boundaries on the dynamic interaction of a liquid filled porous layer and a.

  1. Opposite Effects of Stress on Pain Modulation Depend on the Magnitude of Individual Stress Response.

    Science.gov (United States)

    Geva, Nirit; Defrin, Ruth

    2018-04-01

    The effect of acute stress on pain threshold and intolerance threshold are reported as producing either hypoalgesia or hyperalgesia. Yet, the contribution of individual stress reactivity in this respect has not been established. The aim was to test 2 pain modulation paradigms under acute stress manipulation, to our knowledge, for the first time, to study whether stress differentially affects pain modulation, and whether the effect is related to individual stress response. Participants were 31 healthy subjects. Conditioned pain modulation (CPM) and pain adaptation were measured before and after inducing an acute stress response using the Montreal Imaging Stress Task. Subjects' stress response was evaluated according to salivary cortisol, autonomic function, and perceived stress and anxiety. The Montreal Imaging Stress Task induced a validated stress response. On a group level, stress induced reduction in CPM magnitude and increase in pain adaptation compared with baseline. These responses correlated with stress reactivity. When the group was subdivided according to stress reactivity, only high stress responders exhibited reduced CPM whereas only low stress responders exhibited increased pain adaptation. The results suggest that acute stress may induce opposite effects on pain modulation, depending on individual stress reactivity magnitude, with an advantage to low stress responders. This study evaluated the effect of acute stress on pain modulation. Pain modulation under stress is affected by individual stress responsiveness; decreased CPM occurs in high stress responders whereas increased pain adaptation occurs in low stress responders. Identification of high stress responders may promote better pain management. Copyright © 2017 The American Pain Society. Published by Elsevier Inc. All rights reserved.

  2. Dynamic response of plant genome to ultraviolet radiation and other genotoxic stresses

    International Nuclear Information System (INIS)

    Molinier, Jean; Oakeley, Edward J.; Niederhauser, Olivier; Kovalchuk, Igor; Hohn, Barbara

    2005-01-01

    Oligonucleotide microarray technology was used to identify genes, which are responding after exposure to UV-C radiation and to other agents causing genotoxic stress. The effect of these conditions on recombinational DNA repair was monitored in parallel. Global changes in gene expression were investigated in Arabidopsis wild-type plants challenged with UV-C, bleomycin, another abiotic agent and xylanase, a biotic factor, all leading to elevated homologous recombination frequencies. The comparison of the expression profile of each treatment allowed defining genes specifically involved in the dynamic response to UV. In the future, the potential roles of such genes in the different forms of stress recognition, signal transduction, and their roles in DNA repair processes will be assessed by using reverse genetic tools available for Arabidopsis thaliana

  3. Telomere dynamics in human mesenchymal stem cells after exposure to acute oxidative stress

    DEFF Research Database (Denmark)

    Harbo, M.; Koelvraa, S.; Serakinci, N.

    2012-01-01

    mesenchymal stem cells, either primary or hTERT immortalized, were exposed to sub-lethal doses of hydrogen peroxide, and the short term effect on telomere dynamics was monitored by Universal STELA and TRF measurements. Both telomere measures were then correlated with the percentage of senescent cells......A gradual shortening of telomeres due to replication can be measured using the standard telomere restriction fragments (TRF) assay and other methods by measuring the mean length of all the telomeres in a cell. In contrast, stress-induced telomere shortening, which is believed to be just...... estimated by senescence-associated beta-galactosidase staining. The exposure to acute oxidative stress resulted in an increased number of ultra-short telomeres, which correlated strongly with the percentage of senescent cells, whereas a correlation between mean telomere length and the percentage...

  4. Flow stress and dynamic strain-ageing of β-transformed Zircaloy-4

    International Nuclear Information System (INIS)

    Woo, O.T.; Tseng, D.; Tangri, K.; MacEwen, S.R.

    1979-01-01

    The 0.2% yield stress of β-transformed Zircaloy-4 was found to be independent of prior-β grain size but varied as the inverse of the transformed β plate width. A dislocation loop expansion model originally proposed by Langford and Cohen (1969) for cold-drawn iron wires is used to explain the inverse plate width dependence. Both air-cooled and water-quenched samples exhibited dynamic strain-ageing effects in approximately the same temperature range of 573 to 673 K: (a) a local minimum in strain-rate sensitivity is associated with a peak or an inflection point in the temperature dependence of the 0.2% yield stress for water-quenched or air-cooled samples respectively, and (b) yield drops were observed in strain rate change tests. (Auth.)

  5. ANSYS Modeling of Hydrostatic Stress Effects

    Science.gov (United States)

    Allen, Phillip A.

    1999-01-01

    Classical metal plasticity theory assumes that hydrostatic pressure has no effect on the yield and postyield behavior of metals. Plasticity textbooks, from the earliest to the most modem, infer that there is no hydrostatic effect on the yielding of metals, and even modem finite element programs direct the user to assume the same. The object of this study is to use the von Mises and Drucker-Prager failure theory constitutive models in the finite element program ANSYS to see how well they model conditions of varying hydrostatic pressure. Data is presented for notched round bar (NRB) and "L" shaped tensile specimens. Similar results from finite element models in ABAQUS are shown for comparison. It is shown that when dealing with geometries having a high hydrostatic stress influence, constitutive models that have a functional dependence on hydrostatic stress are more accurate in predicting material behavior than those that are independent of hydrostatic stress.

  6. Dynamics of neuroendocrine stress response: bistability, timing, and control of hypocortisolism

    Science.gov (United States)

    D'Orsogna, Maria; Chou, Tom; Kim, Lae

    The hypothalamic-pituitary-adrenal (HPA) axis is a neuroendocrine system that regulates numerous physiological processes. Disruptions in its activity are correlated with stress-related diseases such as post-traumatic stress disorder (PTSD) and major depressive disorder. We characterize ``normal'' and ``diseased'' states of the HPA axis as basins of attraction of a dynamical system describing the inhibition of peptide hormones, corticotropin-releasing hormone (CRH) and adrenocorticotropic hormone (ACTH), by circulating glucocorticoids such as cortisol (CORT). Our model includes ultradian oscillations, CRH self-upregulation of CRH release, and distinguishes two components of negative feedback by cortisol on circulating CRH levels: a slow direct suppression of CRH synthesis and a fast indirect effect on CRH release. The slow regulation mechanism mediates external stress-driven transitions between the stable states in novel, intensity, duration, and timing-dependent ways. We find that the timing of traumatic events may be an important factor in determining if and how the hallmarks of depressive disorders will manifest. Our model also suggests a mechanism whereby exposure therapy of stress disorders may act to normalize downstream dysregulation of the HPA axis.

  7. Effect of insulin pump infusion on comprehensive stress state of ...

    African Journals Online (AJOL)

    Effect of insulin pump infusion on comprehensive stress state of patients with diabetic ketoacidosis. ... Relevant diabetes-associated serum indices, oxidative stress and stress hormone levels were compared between the ... from 32 Countries:.

  8. Stress, strain, and structural dynamics an interactive handbook of formulas, solutions, and Matlab toolboxes

    CERN Document Server

    Yang, Bingen

    2005-01-01

    Stress, Strain, and Structural Dynamics is a comprehensive and definitive reference to statics and dynamics of solids and structures, including mechanics of materials, structural mechanics, elasticity, rigid-body dynamics, vibrations, structural dynamics, and structural controls. This text integrates the development of fundamental theories, formulas and mathematical models with user-friendly interactive computer programs, written in the powerful and popular MATLAB. This unique merger of technical referencing and interactive computing allows instant solution of a variety of engineering problems

  9. Investigating degradation behavior of hole-trapping effect under static and dynamic gate-bias stress in a dual gate a-InGaZnO thin film transistor with etch stop layer

    International Nuclear Information System (INIS)

    Liao, Po-Yung; Chang, Ting-Chang; Hsieh, Tien-Yu; Tsai, Ming-Yen; Chen, Bo-Wei; Chu, Ann-Kuo; Chou, Cheng-Hsu; Chang, Jung-Fang

    2016-01-01

    The degree of degradation between the amorphous-indium–gallium–zinc oxide (a-IGZO) thin film transistor (TFT) using the top-gate only or bottom-gate only is compared. Under negative gate bias illumination stress (NBIS), the threshold voltage (V T ) after bottom-gate NBIS monotonically shifts in the negative direction, whereas top-gate NBIS operation exhibits on-state current increases without V T shift. Such anomalous degradation behavior of NBIS under top-gate operation is due to hole-trapping in the etch stop layer above the central portion of the channel. These phenomena can be ascribed to the screening of the electric field by redundant source/drain electrodes. In addition, the device degradation of dual gate a-IGZO TFT stressed with different top gate pulse waveforms is investigated. It is observed that the degradation is dependent on the frequency of the top gate pulses. The V T shift increases with decreasing frequency, indicating the hole mobility of IGZO is low. - Highlights: • Static and dynamic gate bias stresses are imposed on dual gate InGaZnO TFTs. • Top-gate NBIS operation exhibits on-state current increases without VT shift. • The degradation behavior of top-gate NBIS is due to hole-trapping in the ESL. • The degradation is dependent on the frequency of the top gate pulses. • The V T shift increases with decreasing frequency of the top gate pulses.

  10. Effective stress, friction and deep crustal faulting

    Science.gov (United States)

    Beeler, N.M.; Hirth, Greg; Thomas, Amanda M.; Burgmann, Roland

    2016-01-01

    Studies of crustal faulting and rock friction invariably assume the effective normal stress that determines fault shear resistance during frictional sliding is the applied normal stress minus the pore pressure. Here we propose an expression for the effective stress coefficient αf at temperatures and stresses near the brittle-ductile transition (BDT) that depends on the percentage of solid-solid contact area across the fault. αf varies with depth and is only near 1 when the yield strength of asperity contacts greatly exceeds the applied normal stress. For a vertical strike-slip quartz fault zone at hydrostatic pore pressure and assuming 1 mm and 1 km shear zone widths for friction and ductile shear, respectively, the BDT is at ~13 km. αf near 1 is restricted to depths where the shear zone is narrow. Below the BDT αf = 0 is due to a dramatically decreased strain rate. Under these circumstances friction cannot be reactivated below the BDT by increasing the pore pressure alone and requires localization. If pore pressure increases and the fault localizes back to 1 mm, then brittle behavior can occur to a depth of around 35 km. The interdependencies among effective stress, contact-scale strain rate, and pore pressure allow estimates of the conditions necessary for deep low-frequency seismicity seen on the San Andreas near Parkfield and in some subduction zones. Among the implications are that shear in the region separating shallow earthquakes and deep low-frequency seismicity is distributed and that the deeper zone involves both elevated pore fluid pressure and localization.

  11. Prediction of flow- induced dynamic stress in an axial pump impeller using FEM

    International Nuclear Information System (INIS)

    Gao, J Y; Hou, Y S; Xi, S Z; Cai, Z H; Yao, P P; Shi, H L

    2013-01-01

    Axial pumps play an important role in water supply and flood control projects. Along with growing requirements for high reliability and large capacity, the dynamic stress of axial pumps has become a key problem. Unsteady flow is a significant reason which results structural dynamic stress of a pump. This paper reports on a flow-induced dynamic stress simulation in an axial pump impeller at three flow conditions by using FEM code. The pressure pulsation obtained from flow simulation using CFD code was set as the force boundary condition. The results show that the maximum stress of impeller appeared at joint between blade and root flange near trailing edge or joint between blade and root flange near leading edge. The dynamic stress of the two zones was investigated under three flow conditions (0.8Q d , 1.0Q d , 1.1Q d ) in time domain and frequency domain. The frequencies of stress at zones of maximum stress are 22.9Hz and 37.5Hz as the fundamental frequency and its harmonics. The fundamental frequencies are nearly equal to vane passing frequency (22.9 Hz) and 3 times blade passing frequency (37.5Hz). The first dominant frequency at zones of maximum stress is equal to the vane passing frequency due to rotor-stator interaction between the vane and the blade. This study would be helpful for axial pumps in reducing stress, improving structure design and fatigue life

  12. Dynamic changes in saliva after acute mental stress

    Science.gov (United States)

    Naumova, Ella A.; Sandulescu, Tudor; Bochnig, Clemens; Khatib, Philipp Al; Lee, Wing-Kee; Zimmer, Stefan; Arnold, Wolfgang H.

    2014-01-01

    Stress-related variations of fluoride concentration in supernatant saliva and salivary sediment, salivary cortisol, total protein and pH after acute mental stress were assessed. The hypothesis was that stress reactions have no influence on these parameters. Thirty-four male students were distributed into two groups: first received the stress exposure followed by the same protocol two weeks later but without stress exposure, second underwent the protocol without stress exposure followed by the stress exposure two weeks later. The stressor was a public speech followed by tooth brushing. Saliva was collected before, immediately after stress induction and immediately, at 10, 30 and 120 min. after tooth brushing. Cortisol concentrations, total protein, intraoral pH, and fluoride content in saliva were measured. The data were analyzed statistically. Salivary sediment was ca 4.33% by weight of whole unstimulated saliva. Fluoride bioavailability was higher in salivary sediment than in supernatant saliva. The weight and fluoride concentration was not altered during 2 hours after stress exposure. After a public speech, the salivary cortisol concentration significantly increased after 20 minutes compared to the baseline. The salivary protein concentration and pH also increased. Public speaking influences protein concentration and salivary pH but does not alter the fluoride concentration of saliva. PMID:24811301

  13. Dynamic regulation of cerebral DNA repair genes by psychological stress

    DEFF Research Database (Denmark)

    Forsberg, Kristin; Aalling, Nadia; Wörtwein, Gitta

    2015-01-01

    Neuronal genotoxic insults from oxidative stress constitute a putative molecular link between stress and depression on the one hand, and cognitive dysfunction and dementia risk on the other. Oxidative modifications to DNA are repaired by specific enzymes; a process that plays a critical role...... restraint stress (6h/day) or daily handling (controls), and sacrificed after 1, 7 or 21 stress sessions. The mRNA expression of seven genes (Ogg1, Ape1, Ung1, Neil1, Xrcc1, Ercc1, Nudt1) involved in the repair of oxidatively damaged DNA was determined by quantitative real time polymerase chain reaction...

  14. Dynamic release and clearance of circulating microparticles during cardiac stress.

    Science.gov (United States)

    Augustine, Daniel; Ayers, Lisa V; Lima, Eduardo; Newton, Laura; Lewandowski, Adam J; Davis, Esther F; Ferry, Berne; Leeson, Paul

    2014-01-03

    Microparticles are cell-derived membrane vesicles, relevant to a range of biological responses and known to be elevated in cardiovascular disease. To investigate microparticle release during cardiac stress and how this response differs in those with vascular disease. We measured a comprehensive panel of circulating cell-derived microparticles by a standardized flow cytometric protocol in 119 patients referred for stress echocardiography. Procoagulant, platelet, erythrocyte, and endothelial but not leukocyte, granulocyte, or monocyte-derived microparticles were elevated immediately after a standardized dobutamine stress echocardiogram and decreased after 1 hour. Twenty-five patients developed stress-induced wall motion abnormalities suggestive of myocardial ischemia. They had similar baseline microparticle levels to those who did not develop ischemia, but, interestingly, their microparticle levels did not change during stress. Furthermore, no stress-induced increase was observed in those without inducible ischemia but with a history of vascular disease. Fourteen patients subsequently underwent coronary angiography. A microparticle rise during stress echocardiography had occurred only in those with normal coronary arteries. Procoagulant, platelet, erythrocyte, and endothelial microparticles are released during cardiac stress and then clear from the circulation during the next hour. This stress-induced rise seems to be a normal physiological response that is diminished in those with vascular disease.

  15. Greater physiological and behavioral effects of interrupted stress pattern compared to daily restraint stress in rats.

    Directory of Open Access Journals (Sweden)

    Wei Zhang

    Full Text Available Repeated stress can trigger a range of psychiatric disorders, including anxiety. The propensity to develop abnormal behaviors after repeated stress is related to the severity, frequency and number of stressors. However, the pattern of stress exposure may contribute to the impact of stress. In addition, the anxiogenic nature of repeated stress exposure can be moderated by the degree of coping that occurs, and can be reflected in homotypic habituation to the repeated stress. However, expectations are not clear when a pattern of stress presentation is utilized that diminishes habituation. The purpose of these experiments is to test whether interrupted stress exposure decreases homotypic habituation and leads to greater effects on anxiety-like behavior in adult male rats. We found that repeated interrupted restraint stress resulted in less overall homotypic habituation compared to repeated daily restraint stress. This was demonstrated by greater production of fecal boli and greater corticosterone response to restraint. Furthermore, interrupted restraint stress resulted in a lower body weight and greater adrenal gland weight than daily restraint stress, and greater anxiety-like behavior in the elevated plus maze. Control experiments demonstrated that these effects of the interrupted pattern could not be explained by differences in the total number of stress exposures, differences in the total number of days that the stress periods encompased, nor could it be explained as a result of only the stress exposures after an interruption from stress. These experiments demonstrate that the pattern of stress exposure is a significant determinant of the effects of repeated stress, and that interrupted stress exposure that decreases habituation can have larger effects than a greater number of daily stress exposures. Differences in the pattern of stress exposure are therefore an important factor to consider when predicting the severity of the effects of repeated

  16. Effective stress principle for partially saturated media

    International Nuclear Information System (INIS)

    McTigue, D.F.; Wilson, R.K.; Nunziato, J.W.

    1984-04-01

    In support of the Nevada Nuclear Waste Storage Investigation (NNWSI) Project, we have undertaken a fundamental study of water migration in partially saturated media. One aspect of that study, on which we report here, has been to use the continuum theory of mixtures to extend the classical notion of effective stress to partially saturated media. Our analysis recovers previously proposed phenomenological representations for the effective stress in terms of the capillary pressure. The theory is illustrated by specializing to the case of linear poroelasticity, for which we calculate the deformation due to the fluid pressure in a static capillary fringe. We then examine the transient consolidation associated with liquid flow induced by an applied surface load. Settlement accompanies this flow as the liquid is redistributed by a nonlinear diffusion process. For material properties characteristic of tuff from the Nevada Test Site, these effects are found to be vanishingly small. 14 references, 7 figures, 1 table

  17. Effects of dynamical quarks in UKQCD simulations

    International Nuclear Information System (INIS)

    Allton, Chris

    2002-01-01

    Recent results from the UKQCD Collaboration's dynamical simulations are presented. The main feature of these ensembles is that they have a fixed lattice spacing and volume, but varying sea quark mass from infinite (corresponding to the quenched simulation) down to roughly that of the strange quark mass. The main aim of this work is to uncover dynamical quark effects from these 'matched' ensembles. We obtain some evidence of dynamical quark effects in the static quark potential with less effects in the hadronic spectrum

  18. Development of crankshaft dynamic stress prediction; Jitsudoji crankshaft oryoku yosoku shuho no kaihatsu

    Energy Technology Data Exchange (ETDEWEB)

    Takahashi, S; Iwamoto, A; Miyazawa, H; Sato, K; Ozaki, H [Honda R and D Co. Ltd., Tokyo (Japan)

    1997-10-01

    In this paper, the development of the simulation model which predicts the stress of the crankshaft under running condition precisely is described. This simulation model considers about the nonlinearity of the oil film stiffness in the main bearing, the dynamic characteristic of the crankshaft system including resonance and the cylinder block stiffness. By the development of this stress analysis simulation, the stress m each part of the crankshaft during durability testing could be precisely predicted. 1 ref., 10 figs.

  19. Cardiorespiratory Dynamic Response to Mental Stress: A Multivariate Time-Frequency Analysis

    Directory of Open Access Journals (Sweden)

    Devy Widjaja

    2013-01-01

    out continuously in time to evaluate the dynamic response to mental stress and attention. The results show an increased heart and respiratory rate during stress and attention, compared to a resting condition. Also a fast reduction in vagal activity is noted. The partial TF analysis reveals a faster reduction of RRV power related to (3 s than unrelated to (30 s respiration, demonstrating that the autonomic response to mental stress is driven by mechanisms characterized by different temporal scales.

  20. Coupling effects of chemical stresses and external mechanical stresses on diffusion

    International Nuclear Information System (INIS)

    Xuan Fuzhen; Shao Shanshan; Wang Zhengdong; Tu Shantung

    2009-01-01

    Interaction between diffusion and stress fields has been investigated extensively in the past. However, most of the previous investigations were focused on the effect of chemical stress on diffusion due to the unbalanced mass transport. In this work, the coupling effects of external mechanical stress and chemical stress on diffusion are studied. A self-consistent diffusion equation including the chemical stress and external mechanical stress gradient is developed under the framework of the thermodynamic theory and Fick's law. For a thin plate subjected to unidirectional tensile stress fields, the external stress coupled diffusion equation is solved numerically with the help of the finite difference method for one-side and both-side charging processes. Results show that, for such two types of charging processes, the external stress gradient will accelerate the diffusion process and thus increase the value of concentration while reducing the magnitude of chemical stress when the direction of diffusion is identical to that of the stress gradient. In contrast, when the direction of diffusion is opposite to that of the stress gradient, the external stress gradient will obstruct the process of solute penetration by decreasing the value of concentration and increasing the magnitude of chemical stress. For both-side charging process, compared with that without the coupling effect of external stress, an asymmetric distribution of concentration is produced due to the asymmetric mechanical stress field feedback to diffusion.

  1. Allee effects on population dynamics with delay

    International Nuclear Information System (INIS)

    Celik, C.; Merdan, H.; Duman, O.; Akin, O.

    2008-01-01

    In this paper, we study the stability analysis of equilibrium points of population dynamics with delay when the Allee effect occurs at low population density. Mainly, our mathematical results and numerical simulations point to the stabilizing effect of the Allee effects on population dynamics with delay

  2. The effect of couple-stresses on the stress concentration around a moving crack

    Directory of Open Access Journals (Sweden)

    S. Itou

    1981-01-01

    Full Text Available The problem of a uniformly propagating finite crack in an infinite medium is solved within the linearized couple-stress theory. The self-equilibrated system of pressure is applied to the crack surfaces. The problem is reduced to dual integral equations and solved by a series-expansion method. The dynamic stress-intensity factor is computed numerically.

  3. Wall Shear Stress Estimation of Thoracic Aortic Aneurysm Using Computational Fluid Dynamics

    Directory of Open Access Journals (Sweden)

    J. Febina

    2018-01-01

    Full Text Available An attempt has been made to evaluate the effects of wall shear stress (WSS on thoracic aortic aneurysm (TAA using Computational Fluid Dynamics (CFD. Aneurysm is an excessive localized swelling of the arterial wall due to many physiological factors and it may rupture causing shock or sudden death. The existing imaging modalities such as MRI and CT assist in the visualization of anomalies in internal organs. However, the expected dynamic behaviour of arterial bulge under stressed condition can only be effectively evaluated through mathematical modelling. In this work, a 3D aneurysm model is reconstructed from the CT scan slices and eventually the model is imported to Star CCM+ (Siemens, USA for intensive CFD analysis. The domain is discretized using polyhedral mesh with prism layers to capture the weakening boundary more accurately. When there is flow reversal in TAA as seen in the velocity vector plot, there is a chance of cell damage causing clots. This is because of the shear created in the system due to the flow pattern. It is observed from the proposed mathematical modelling that the deteriorating WSS is an indicator for possible rupture and its value oscillates over a cardiac cycle as well as over different stress conditions. In this model, the vortex formation pattern and flow reversals are also captured. The non-Newtonian model, including a pulsatile flow instead of a steady average flow, does not overpredict the WSS (15.29 Pa compared to 16 Pa for the Newtonian model. Although in a cycle the flow behaviour is laminar-turbulent-laminar (LTL, utilizing the non-Newtonian model along with LTL model also overpredicted the WSS with a value of 20.1 Pa. The numerical study presented here provides good insight of TAA using a systematic approach to numerical modelling and analysis.

  4. Growing up with stress - carbon sequestration and allocation dynamics of a broadleaf evergreen forest

    Science.gov (United States)

    Griebel, Anne; Bennett, Lauren T.; Arndt, Stefan K.

    2016-04-01

    recorded in the years with highest NEE, but NEE was not a strong seasonal driver of stem increment. Recently developed terrestrial lidar scanners (VEGNET) monitored the daily changes in canopy dynamics with a comparable temporal resolution to dendrometer and eddy covariance measurements. Growth of each canopy stratum was distinctly seasonal, and we detected contrasting responses to climatic stress along the canopy height gradient. Leaf turnover was predominantly in summer and was initiated by prolonged heat stress and isolated storm events. Leaf shedding and replacement happened concurrently, with leaves being mainly discarded from the middle stratum and replaced in the top stratum. Due to our novel multi-instrument approach and the high temporal resolution of tree to ecosystem-scale growth dynamics we were able to demonstrate that above ground carbon allocation to stem and crown pools followed separate seasonal dynamics that did not necessarily follow the same seasonality as ecosystem scale carbon sequestration. Our findings will ultimately improve our understanding of the effects of short- and long-term variability in temperature and moisture stress on carbon allocation dynamics to the above ground biomass pools for broadleaf evergreen ecosystems.

  5. Effect of applied stress on the compressive residual stress introduced by laser peening

    International Nuclear Information System (INIS)

    Sumiya, Rie; Tazawa, Toshiyuki; Narazaki, Chihiro; Saito, Toshiyuki; Kishimoto, Kikuo

    2016-01-01

    Peening is the process which is able to be generated compressive residual stress and is known to be effective for preventing SCC initiation and improvement of fatigue strength. Laser peening is used for the nuclear power plant components in order to prevent SCC initiation. Although it is reported that the compressive residual stress decreases due to applied stresses under general operating condition, the change of residual stress might be large under excessive loading such as an earthquake. The objectives of this study are to evaluate the relaxation behavior of the compressive residual stress due to laser peening and to confirm the surface residual stress after loading. Therefore laser peened round bar test specimens of SUS316L which is used for the reactor internals of nuclear power plant were loaded at room temperature and elevated temperature and then surface residual stresses were measured by X-ray diffraction method. In the results of this test, it was confirmed that the compressive residual stress remained after applying uniform stress larger than 0.2% proof stress, and the effect of cyclic loading on the residual stress was small. The effect of applying compressive stress on the residual stress relaxation was confirmed to be less than that of applying tensile stress. Plastic deformation through a whole cross section causes the change in the residual stress distribution. As a result, the surface compressive residual stress is released. It was shown that the effect of specimen size on residual stress relaxation and the residual stress relaxation behavior in the stress concentration region can be explained by assumed stress relaxation mechanism. (author)

  6. Manipulating the magnetic anisotropy and magnetization dynamics by stress: Numerical calculation and experiment

    Science.gov (United States)

    Correa, M. A.; Bohn, F.

    2018-05-01

    We perform a theoretical and experimental investigation of the magnetic properties and magnetization dynamics of a ferromagnetic magnetostrictive multilayer grown onto a flexible substrate and submitted to external stress. We calculate the magnetic behavior and magnetoimpedance effect for a trilayered system from an approach that considers a magnetic permeability model for planar geometry and a magnetic free energy density which takes into account induced uniaxial and magnetoelastic anisotropy contributions. We verify remarkable modifications of the magnetic anisotropy with external stress, as well as we show that the dynamic magnetic response is strongly affected by these changes. We discuss the magnetic features that lead to modifications of the frequency limits where distinct mechanisms are responsible by the magnetoimpedance variations, enabling us to manipulate the resonance fields. To test the robustness of the approach, we directly compare theoretical results with experimental data. Thus, we provide experimental evidence to confirm the validity of the theoretical approach, as well as to manipulate the resonance fields to tune the MI response according to real applications in devices.

  7. Investigating degradation behavior of hole-trapping effect under static and dynamic gate-bias stress in a dual gate a-InGaZnO thin film transistor with etch stop layer

    Energy Technology Data Exchange (ETDEWEB)

    Liao, Po-Yung [Department of Physics, National Sun Yat-sen University, 70 Lien-hai Road, Kaohsiung 80424, Taiwan (China); Chang, Ting-Chang, E-mail: tcchang3708@gmail.com [Department of Physics, National Sun Yat-sen University, 70 Lien-hai Road, Kaohsiung 80424, Taiwan (China); Advanced Optoelectronics Technology Center, National Cheng Kung University, Taiwan (China); Hsieh, Tien-Yu [Department of Physics, National Sun Yat-sen University, 70 Lien-hai Road, Kaohsiung 80424, Taiwan (China); Tsai, Ming-Yen; Chen, Bo-Wei; Chu, Ann-Kuo [Department of Photonics, National Sun Yat-Sen University, 70 Lien-hai Road, Kaohsiung 80424, Taiwan (China); Chou, Cheng-Hsu; Chang, Jung-Fang [Product Technology Center, Chimei Innolux Corp., Tainan 741, Taiwan (China)

    2016-03-31

    The degree of degradation between the amorphous-indium–gallium–zinc oxide (a-IGZO) thin film transistor (TFT) using the top-gate only or bottom-gate only is compared. Under negative gate bias illumination stress (NBIS), the threshold voltage (V{sub T}) after bottom-gate NBIS monotonically shifts in the negative direction, whereas top-gate NBIS operation exhibits on-state current increases without V{sub T} shift. Such anomalous degradation behavior of NBIS under top-gate operation is due to hole-trapping in the etch stop layer above the central portion of the channel. These phenomena can be ascribed to the screening of the electric field by redundant source/drain electrodes. In addition, the device degradation of dual gate a-IGZO TFT stressed with different top gate pulse waveforms is investigated. It is observed that the degradation is dependent on the frequency of the top gate pulses. The V{sub T} shift increases with decreasing frequency, indicating the hole mobility of IGZO is low. - Highlights: • Static and dynamic gate bias stresses are imposed on dual gate InGaZnO TFTs. • Top-gate NBIS operation exhibits on-state current increases without VT shift. • The degradation behavior of top-gate NBIS is due to hole-trapping in the ESL. • The degradation is dependent on the frequency of the top gate pulses. • The V{sub T} shift increases with decreasing frequency of the top gate pulses.

  8. Extraversion and cardiovascular responses to recurrent social stress: Effect of stress intensity.

    Science.gov (United States)

    Lü, Wei; Xing, Wanying; Hughes, Brian M; Wang, Zhenhong

    2017-10-28

    The present study sought to establish whether the effects of extraversion on cardiovascular responses to recurrent social stress are contingent on stress intensity. A 2×5×1 mixed-factorial experiment was conducted, with social stress intensity as a between-subject variable, study phase as a within-subject variable, extraversion as a continuous independent variable, and cardiovascular parameter (HR, SBP, DBP, or RSA) as a dependent variable. Extraversion (NEO-FFI), subjective stress, and physiological stress were measured in 166 undergraduate students randomly assigned to undergo moderate (n=82) or high-intensity (n=84) social stress (a public speaking task with different levels of social evaluation). All participants underwent continuous physiological monitoring while facing two consecutive stress exposures distributed across five laboratory phases: baseline, stress exposure 1, post-stress 1, stress exposure 2, post-stress 2. Results indicated that under moderate-intensity social stress, participants higher on extraversion exhibited lesser HR reactivity to stress than participants lower on extraversion, while under high-intensity social stress, they exhibited greater HR, SBP, DBP and RSA reactivity. Under both moderate- and high-intensity social stress, participants higher on extraversion exhibited pronounced SBP and DBP response adaptation to repeated stress, and showed either better degree of HR recovery or greater amount of SBP and DBP recovery after stress. These findings suggest that individuals higher on extraversion exhibit physiological flexibility to cope with social challenges and benefit from adaptive cardiovascular responses. Copyright © 2017 Elsevier B.V. All rights reserved.

  9. Effect of step width manipulation on tibial stress during running.

    Science.gov (United States)

    Meardon, Stacey A; Derrick, Timothy R

    2014-08-22

    Narrow step width has been linked to variables associated with tibial stress fracture. The purpose of this study was to evaluate the effect of step width on bone stresses using a standardized model of the tibia. 15 runners ran at their preferred 5k running velocity in three running conditions, preferred step width (PSW) and PSW±5% of leg length. 10 successful trials of force and 3-D motion data were collected. A combination of inverse dynamics, musculoskeletal modeling and beam theory was used to estimate stresses applied to the tibia using subject-specific anthropometrics and motion data. The tibia was modeled as a hollow ellipse. Multivariate analysis revealed that tibial stresses at the distal 1/3 of the tibia differed with step width manipulation (p=0.002). Compression on the posterior and medial aspect of the tibia was inversely related to step width such that as step width increased, compression on the surface of tibia decreased (linear trend p=0.036 and 0.003). Similarly, tension on the anterior surface of the tibia decreased as step width increased (linear trend p=0.029). Widening step width linearly reduced shear stress at all 4 sites (pstresses experienced by the tibia during running were influenced by step width when using a standardized model of the tibia. Wider step widths were generally associated with reduced loading of the tibia and may benefit runners at risk of or experiencing stress injury at the tibia, especially if they present with a crossover running style. Copyright © 2014 Elsevier Ltd. All rights reserved.

  10. Long-range correlations and fractal dynamics in C. elegans: Changes with aging and stress

    Science.gov (United States)

    Alves, Luiz G. A.; Winter, Peter B.; Ferreira, Leonardo N.; Brielmann, Renée M.; Morimoto, Richard I.; Amaral, Luís A. N.

    2017-08-01

    Reduced motor control is one of the most frequent features associated with aging and disease. Nonlinear and fractal analyses have proved to be useful in investigating human physiological alterations with age and disease. Similar findings have not been established for any of the model organisms typically studied by biologists, though. If the physiology of a simpler model organism displays the same characteristics, this fact would open a new research window on the control mechanisms that organisms use to regulate physiological processes during aging and stress. Here, we use a recently introduced animal-tracking technology to simultaneously follow tens of Caenorhabdits elegans for several hours and use tools from fractal physiology to quantitatively evaluate the effects of aging and temperature stress on nematode motility. Similar to human physiological signals, scaling analysis reveals long-range correlations in numerous motility variables, fractal properties in behavioral shifts, and fluctuation dynamics over a wide range of timescales. These properties change as a result of a superposition of age and stress-related adaptive mechanisms that regulate motility.

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

    Directory of Open Access Journals (Sweden)

    Samuel Frimpong

    2016-06-01

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

  12. Role of Reynolds stress and toroidal momentum transport in the dynamics of internal transport barriers

    International Nuclear Information System (INIS)

    Kim, S. S.; Jhang, Hogun; Diamond, P. H.

    2012-01-01

    We study the interplay between intrinsic rotation and internal transport barrier (ITB) dynamics through the dynamic change of the parallel Reynolds stress. Global flux-driven gyrofluid simulations are used for this study. In particular, we investigate the role of parallel velocity gradient instability (PVGI) in the ITB formation and the back transition. It is found that the excitation of PVGI is followed by a change in the Reynolds stress which drives a momentum redistribution. This significantly influences E×B shear evolution and subsequent ITB dynamics. Nonlocal interactions among fluctuations are also observed during the PVGI excitation, resulting in turbulence suppression at the ITB.

  13. The effect of stress on men's food selection.

    Science.gov (United States)

    Zellner, Debra A; Saito, Shin; Gonzalez, Johanie

    2007-11-01

    This study investigates the effect of stress on food choice among men. Two groups of men were given either solvable (no-stress) or unsolvable (stress) anagrams to solve. Four bowls of snack foods-two healthy (peanuts and grapes) and two unhealthy (potato chips and M&M chocolate candies)-were available and subjects were invited to snack on them. Men in the no-stress group ate significantly more of the unhealthy foods than did men in the stress group. This finding is quite different from that found with women [Zellner et al. (2006). Food selection changes under stress. Physiology & Behavior, 87, 789-793]. Women tended to eat more grapes when not stressed than when stressed and more M&Ms when stressed than when not stressed. Thus, the effect of stress level on food choice is different for men and women.

  14. When does stress help or harm? The effects of stress controllability and subjective stress response on Stroop performance.

    OpenAIRE

    Roselinde Kaiser Henderson; Hannah R. Snyder; Tina eGupta; Marie T. Banich; Marie T. Banich

    2012-01-01

    The ability to engage in goal-directed behavior despite exposure to stress is critical to resilience. Questions of how stress can impair or improve behavioral functioning are important in diverse settings, from athletic competitions to academic testing to clinical therapy. Previous research suggests that controllability is a key factor in the impact of stress on behavior: learning how to control stressors buffers people from the negative effects of stress on subsequent cognitively demanding ...

  15. When Does Stress Help or Harm? The Effects of Stress Controllability and Subjective Stress Response on Stroop Performance

    OpenAIRE

    Henderson, Roselinde K.; Snyder, Hannah R.; Gupta, Tina; Banich, Marie T.

    2012-01-01

    The ability to engage in goal-directed behavior despite exposure to stress is critical to resilience. Questions of how stress can impair or improve behavioral functioning are important in diverse settings, from athletic competitions to academic testing. Previous research suggests that controllability is a key factor in the impact of stress on behavior: learning how to control stressors buffers people from the negative effects of stress on subsequent cognitively demanding tasks. In addition, r...

  16. Stress Symptoms: Effects on Your Body and Behavior

    Science.gov (United States)

    ... heart disease, obesity and diabetes. Common effects of stress on your body Headache Muscle tension or pain ... drive Stomach upset Sleep problems Common effects of stress on your mood Anxiety Restlessness Lack of motivation ...

  17. Protective effects of flavonoids from corn silk on oxidative stress ...

    African Journals Online (AJOL)

    Protective effects of flavonoids from corn silk on oxidative stress induced by ... The present study aims at exploring the effects of flavonoids from corn silk (FCS) on oxidative stress induced by exhaustive exercise in mice. ... from 32 Countries:.

  18. Osmotic and Heat Stress Effects on Segmentation.

    Directory of Open Access Journals (Sweden)

    Julian Weiss

    Full Text Available During vertebrate embryonic development, early skin, muscle, and bone progenitor populations organize into segments known as somites. Defects in this conserved process of segmentation lead to skeletal and muscular deformities, such as congenital scoliosis, a curvature of the spine caused by vertebral defects. Environmental stresses such as hypoxia or heat shock produce segmentation defects, and significantly increase the penetrance and severity of vertebral defects in genetically susceptible individuals. Here we show that a brief exposure to a high osmolarity solution causes reproducible segmentation defects in developing zebrafish (Danio rerio embryos. Both osmotic shock and heat shock produce border defects in a dose-dependent manner, with an increase in both frequency and severity of defects. We also show that osmotic treatment has a delayed effect on somite development, similar to that observed in heat shocked embryos. Our results establish osmotic shock as an alternate experimental model for stress, affecting segmentation in a manner comparable to other known environmental stressors. The similar effects of these two distinct environmental stressors support a model in which a variety of cellular stresses act through a related response pathway that leads to disturbances in the segmentation process.

  19. Municipal solid waste effective stress analysis

    International Nuclear Information System (INIS)

    Shariatmadari, Nader; Machado, Sandro Lemos; Noorzad, Ali; Karimpour-Fard, Mehran

    2009-01-01

    The mechanical behavior of municipal solid waste (MSW) has attracted the attention of many researchers in the field of geo-environmental engineering in recent years and several aspects of waste mechanical response under loading have been elucidated. However, the mechanical response of MSW materials under undrained conditions has not been described in detail to date. The knowledge of this aspect of the MSW mechanical response is very important in cases involving MSW with high water contents, seismic ground motion and in regions where landfills are built with poor operation conditions. This paper presents the results obtained from 26 large triaxial tests performed both in drained and undrained conditions. The results were analyzed taking into account the waste particles compressibility and the deformation anisotropy of the waste samples. The waste particles compressibility was used to modify the Terzaghi effective stress equation, using the Skempton (1961) proposition. It is shown that the use of the modified effective stress equation led to much more compatible shear strength values when comparing Consolidated-Drained (CD) and Consolidated-Undrained (CU), results, explaining the high shear strength values obtained in CU triaxial tests, even when the pore pressure is almost equal to the confining stress.

  20. Effect of material parameters on stress wave propagation during fast upsetting

    Institute of Scientific and Technical Information of China (English)

    WANG Zhong-jin; CHENG Li-dong

    2008-01-01

    Based'on a dynamic analysis method and an explicit algorithm, a dynamic explicit finite element code was developed for modeling the fast upsetting process of block under drop hammer impact, in which the hammer velocity during the deformation was calculated by energy conservation law according to the operating principle of hammer equipment. The stress wave propagation and its effect on the deformation were analyzed by the stress and strain distributions. Industrial pure lead, oxygen-free high-conductivity (OFHC) copper and 7039 aluminum alloy were chosen to investigate the effect of material parameters on the stress wave propagation. The results show that the stress wave propagates from top to bottom of block, and then reflects back when it reaches the bottom surface. After that, stress wave propagates and reflects repeatedly between the upper surface and bottom surface. The stress wave propagation has a significant effect on the deformation at the initial stage, and then becomes weak at the middle-final stage. When the ratio of elastic modulus or the slope of stress-strain curve to mass density becomes larger, the velocity of stress wave propagation increases, and the influence of stress wave on the deformation becomes small.

  1. The Effect of Overskilling Dynamics on Wages

    Science.gov (United States)

    Mavromaras, Kostas; Mahuteau, Stephane; Sloane, Peter; Wei, Zhang

    2013-01-01

    We use a random-effects dynamic probit model to estimate the effect of overskilling dynamics on wages. We find that overskilling mismatch is common and more likely among those who have been overskilled in the past. It is also highly persistent, in a manner that is inversely related to educational level. Yet, the wages of university graduates are…

  2. Effect of stress management interventions on job stress among nurses working in critical care units.

    Science.gov (United States)

    Light Irin, C; Bincy, R

    2012-01-01

    Stress in nurses affects their health and increases absenteeism, attrition rate, injury claims, infection rates and errors in treating patients. This in turn significantly increases the cost of employment in healthcare units. Proper management of stress ensures greater efficiency at work place and improved wellbeing of the employee. Therefore, a pre-experimental study was conducted among 30 Critical Care Unit nurses working inMedical College Hospital, Thiruvananthapuram, (Kerala) to assess the effect of stress management interventions such as Job Stress Awareness, Assertiveness Training, Time Management, andProgressive Muscle Relaxation on job stress. The results showed that caring for patients, general job requirements and workload were the major sources of stress for the nurses. The level of severe stress was reduced from 60 percent to 20 percent during post-test. The Stress Management Interventions were statistically effective in reducing the stress of nurses at p<0.001 level.

  3. Friction stress effects on mode I crack growth predictions

    NARCIS (Netherlands)

    Chen, Q.; Deshpande, V.S.; Giessen, E. van der; Needleman, A.

    2003-01-01

    The effect of a lattice friction stress on the monotonic growth of a plane strain mode I crack under small-scale yielding conditions is analyzed using discrete dislocation plasticity. When the friction stress is increased from zero to half the dislocation nucleation stress, the crack tip stress

  4. Effect of Thickness Stress in Stretch-Bending

    NARCIS (Netherlands)

    van den Boogaard, Antonius H.; Emmens, W.C.; Huetink, Han; Barlat, F; Moon, Y.H.; Lee, M.G.

    2010-01-01

    In any situation where a strip is pulled over a curved tool, locally a contact stress acts on the strip in thickness direction. This contact stress changes the stress state in the material, which will influence the deformation. One effect is that the yield stress in the plane of the strip is

  5. Stress vulnerability and the effects of moderate daily stress on sleep polysomnography and subjective sleepiness.

    Science.gov (United States)

    Petersen, Helena; Kecklund, Göran; D'Onofrio, Paolo; Nilsson, Jens; Åkerstedt, Torbjörn

    2013-02-01

    The purpose of this study was to investigate if and how sleep physiology is affected by naturally occurring high work stress and identify individual differences in the response of sleep to stress. Probable upcoming stress levels were estimated through weekly web questionnaire ratings. Based on the modified FIRST-scale (Ford insomnia response to stress) participants were grouped into high (n = 9) or low (n = 19) sensitivity to stress related sleep disturbances (Drake et al., 2004). Sleep was recorded in 28 teachers with polysomnography, sleep diaries and actigraphs during one high stress and one low stress condition in the participants home. EEG showed a decrease in sleep efficiency during the high stress condition. Significant interactions between group and condition were seen for REM sleep, arousals and stage transitions. The sensitive group had an increase in arousals and stage transitions during the high stress condition and a decrease in REM, whereas the opposite was seen in the resilient group. Diary ratings during the high stress condition showed higher bedtime stress and lower ratings on the awakening index (insufficient sleep and difficulties awakening). Ratings also showed lower cognitive function and preoccupation with work thoughts in the evening. KSS ratings of sleepiness increased during stress for the sensitive group. Saliva samples of cortisol showed no effect of stress. It was concluded that moderate daily stress is associated with a moderate negative effect on sleep sleep efficiency and fragmentation. A slightly stronger effect was seen in the sensitive group. © 2012 European Sleep Research Society.

  6. Stress effects on memory: an update and integration

    NARCIS (Netherlands)

    Schwabe, L.; Joëls, M.; Roozendaal, B.; Wolf, O.T.; Oitzl, M.S.

    2012-01-01

    It is well known that stressful experiences may affect learning and memory processes. Less clear is the exact nature of these stress effects on memory: both enhancing and impairing effects have been reported. These opposite effects may be explained if the different time courses of stress hormone, in

  7. Stress effects on memory : An update and integration

    NARCIS (Netherlands)

    Schwabe, Lars; Joëls, Marian; Roozendaal, Benno; Wolf, Oliver T.; Oitzl, Melly S.

    It is well known that stressful experiences may affect learning and memory processes. Less clear is the exact nature of these stress effects on memory: both enhancing and impairing effects have been reported. These opposite effects may be explained if the different time courses of stress hormone, in

  8. Family stress dynamics, domestic violence and their combined ...

    African Journals Online (AJOL)

    This study utilized the classical ABCX family crisis model in identifying how families perceive, interpret and react to various sources of stress confronting them and their perceived impact on their health. The study is timely because of the recent upsurge in domestic violence cases in Ghana, which are mainly attributable to ...

  9. Hydrostatic Stress Effects in Metal Plasticity

    Science.gov (United States)

    Wilson, Christopher D.

    1999-01-01

    Since the 1940s, the theory of plasticity has assumed that hydrostatic stress does not affect the yield or postyield behavior of metals. This assumption is based on the early work of Bridgman. Bridgman found that hydrostatic pressure (compressive stress) does not affect yield behavior until a substantial amount of pressure (greater than 100 ksi) is present. The objective of this study was to determine the effect of hydrostatic tension on yield behavior. Two different specimen geometries were examined: an equal-arm bend specimen and a double edge notch specimen. The presence of a notch is sufficient to develop high enough hydrostatic tensile stresses to affect yield. The von Mises yield function, which does not have a hydrostatic component, and the Drucker-Prager yield function, which includes a hydrostatic component, were used in finite element analyses of the two specimen geometries. The analyses were compared to test data from IN 100 specimens. For both geometries, the analyses using the Drucker-Prager yield function more closely simulated the test data. The von Mises yield function lead to 5-10% overprediction of the force-displacement or force-strain response of the test specimens.

  10. Acute stress does not affect the impairing effect of chronic stress on memory retrieval

    Science.gov (United States)

    Ozbaki, Jamile; Goudarzi, Iran; Salmani, Mahmoud Elahdadi; Rashidy-Pour, Ali

    2016-01-01

    Objective(s): Due to the prevalence and pervasiveness of stress in modern life and exposure to both chronic and acute stresses, it is not clear whether prior exposure to chronic stress can influence the impairing effects of acute stress on memory retrieval. This issue was tested in this study. Materials and Methods: Adult male Wistar rats were randomly assigned to the following groups: control, acute, chronic, and chronic + acute stress groups. The rats were trained with six trials per day for 6 consecutive days in the water maze. Following training, the rats were either kept in control conditions or exposed to chronic stress in a restrainer 6 hr/day for 21 days. On day 22, a probe test was done to measure memory retention. Time spent in target and opposite areas, platform location latency, and proximity were used as indices of memory retention. To induce acute stress, 30 min before the probe test, animals received a mild footshock. Results: Stressed animals spent significantly less time in the target quadrant and more time in the opposite quadrant than control animals. Moreover, the stressed animals showed significantly increased platform location latency and proximity as compared with control animals. No significant differences were found in these measures among stress exposure groups. Finally, both chronic and acute stress significantly increased corticosterone levels. Conclusion: Our results indicate that both chronic and acute stress impair memory retrieval similarly. Additionally, the impairing effects of chronic stress on memory retrieval were not influenced by acute stress. PMID:27635201

  11. Carbon and Nitrogen dynamics in deciduous and broad leaf trees under drought stress

    Science.gov (United States)

    Joseph, Jobin; Schaub, Marcus; Arend, Matthias; Saurer, Matthias; siegwolf, Rolf; Weiler, Markus; Gessler, Arthur

    2017-04-01

    Climate change is projected to lead to an increased frequency and duration of severe drought events in future. Already within the last twenty years, however, drought stress related forest mortality has been increasing across the globe. Tree and forest die off events have multiple adverse effects on ecosystem functioning and might convert previous carbon sinks to act as carbon sources instead and can thus intensify the effect of climate change and global warming. Current predictions of forest's functioning under drought and thus forest mortality under future climatic conditions are constrained by a still incomplete picture of the trees' physiological reactions that allows some trees to survive drought periods while others succumb. Concerning the effects of drought on the carbon balance and on tree hydraulics our picture is getting more complete, but still interactions between abiotic factors and pest and diseases as well as the interaction between carbon and nutrient balances as factors affecting drought induced mortality are not well understood. Reduced carbon allocation from shoots to roots might cause a lack of energy for root nutrient uptake and to a shortage of carbon skeletons for nitrogen assimilation and thus to an impaired nutrient status of trees. To tackle these points, we have performed a drought stress experiment with six different plant species, 3 broad leaf (maple, beech and oak) and 3 deciduous (pine, fir and spruce). Potted two-year-old seedlings were kept inside a greenhouse for 5 months and 3 levels of drought stress (no stress (control), intermediate and intensive drought stress) were applied by controlling water supply. Gas exchange measurements were performed periodically to monitor photosynthesis, transpiration, stomatal conductance. At the pinnacle of drought stress, we applied isotopic pulse labelling: On the one hand we exposed trees to 13CO2 to investigate on carbon dynamics and the allocation of new assimilates within the plant. Moreover

  12. Effects of stress on alcohol drinking: a review of animal studies

    Science.gov (United States)

    Lopez, Marcelo F.; Doremus-Fitzwater, Tamara L.

    2011-01-01

    Rationale While stress is often proposed to play a significant role in influencing alcohol consumption, the relationship between stress and alcohol is complex and poorly understood. Over several decades, stress effects on alcohol drinking have been studied using a variety of animal models and experimental procedures, yet this large body of literature has generally produced equivocal results. Objectives This paper reviews results from animal studies in which alcohol consumption is evaluated under conditions of acute/sub-chronic stress exposure or models of chronic stress exposure. Evidence also is presented indicating that chronic intermittent alcohol exposure serves as a stressor that consequently influences drinking. Results The effects of various acute/sub-chronic stress procedures on alcohol consumption have generally been mixed, but most study outcomes suggest either no effect or decreased alcohol consumption. In contrast, most studies indicate that chronic stress, especially when administered early in development, results in elevated drinking later in adulthood. Chronic alcohol exposure constitutes a potent stressor itself, and models of chronic intermittent alcohol exposure reliably produce escalation of voluntary alcohol consumption. Conclusions A complex and dynamic interplay among a wide array of genetic, biological, and environmental factors govern stress responses, regulation of alcohol drinking, and the circumstances in which stress modulates alcohol consumption. Suggestions for future directions and new approaches are presented that may aid in developing more sensitive and valid animal models that not only better mimic the clinical situation, but also provide greater understanding of mechanisms that underlie the complexity of stress effects on alcohol drinking. PMID:21850445

  13. The dichotomous effect of chronic stress on obesity

    OpenAIRE

    Razzoli, Maria; Bartolomucci, Alessandro

    2016-01-01

    Obesity and metabolic diseases are linked to chronic stress and low socio-economic status. The mechanistic link between stress and obesity has not been clarified, partly due to the inherent complexity exemplified by the bidirectional effect of stress on eating and body weight. Recent studies focusing on adaptive-thermogenesis and brown adipose tissue (BAT) function support a dichotomous relationship to explain the impact of stress on obesity: stress promotes obesity in the presence of hyperph...

  14. Chernobyl health effects: radiation or stress?

    International Nuclear Information System (INIS)

    Grinkhal', G.

    1996-01-01

    Consideration is given to results of wide-scale examination of human population, subjected to the effect of radiation in result of Chernobyl accident. The examined contingents consisted of liquidators, evacuated from 30-km zone, people still living in contamination territories, children of irradiated parents and children, who received large radiation doses. High levels of respiratory system diseases, digestive system diseases, cardiovascular diseases and nervous system diseases were revealed for these people. It was revealed that stress, socio-economic and chemical factors played sufficient role in disease incidence. It is shown that fair of radiation may damage more, than radiation itself

  15. Non-linear hydrotectonic phenomena: Part I - fluid flow in open fractures under dynamical stress loading

    International Nuclear Information System (INIS)

    Archambeau, C.B.

    1994-01-01

    A fractured solid under stress loading (or unloading) can be viewed as behaving macroscopically as a medium with internal, hidden, degrees of freedom, wherein changes in fracture geometry (i.e. opening, closing and extension) and flow of fluid and gas within fractures will produce major changes in stresses and strains within the solid. Likewise, the flow process within fractures will be strongly coupled to deformation within the solid through boundary conditions on the fracture surfaces. The effects in the solid can, in part, be phenomenologically represented as inelastic or plastic processes in the macroscopic view. However, there are clearly phenomena associated with fracture growth and open fracture fluid flows that produce effects that can not be described using ordinary inelastic phenomenology. This is evident from the fact that a variety of energy release phenomena can occur, including seismic emissions of previously stored strain energy due to fracture growth, release of disolved gas from fluids in the fractures resulting in enhanced buoyancy and subsequent energetic flows of gas and fluids through the fracture system which can produce raid extension of old fractures and the creation of new ones. Additionally, the flows will be modulated by the opening and closing of fractures due to deformation in the solid, so that the flow process is strongly coupled to dynamical processes in the surrounding solid matrix, some of which are induced by the flow itself

  16. Dynamical System Analysis of Reynolds Stress Closure Equations

    Science.gov (United States)

    Girimaji, Sharath S.

    1997-01-01

    In this paper, we establish the causality between the model coefficients in the standard pressure-strain correlation model and the predicted equilibrium states for homogeneous turbulence. We accomplish this by performing a comprehensive fixed point analysis of the modeled Reynolds stress and dissipation rate equations. The results from this analysis will be very useful for developing improved pressure-strain correlation models to yield observed equilibrium behavior.

  17. On the Stress Transfer of Nanoscale Interlayer with Surface Effects

    Directory of Open Access Journals (Sweden)

    Quan Yuan

    2018-01-01

    Full Text Available An improved shear-lag model is proposed to investigate the mechanism through which the surface effect influences the stress transfer of multilayered structures. The surface effect of the interlayer is characterized in terms of interfacial stress and surface elasticity by using Gurtin–Murdoch elasticity theory. Our calculation result shows that the surface effect influences the efficiency of stress transfer. The surface effect is enhanced with decreasing interlayer thickness and elastic modulus. Nonuniform and large residual surface stress distribution amplifies the influence of the surface effect on stress concentration.

  18. Determination of the Critical Stress Associated with Dynamic Phase Transformation in Steels by Means of Free Energy Method

    Directory of Open Access Journals (Sweden)

    Clodualdo Aranas

    2018-05-01

    Full Text Available The double differentiation method overestimates the critical stress associated with the initiation of dynamic transformation (DT because significant amounts of the dynamic phase must be present in order for its effect on the work hardening rate to be detectable. In this work, an alternative method (referred to here as the free energy method is presented based on the thermodynamic condition that the driving force is equal to the total energy obstacle during the exact moment of transformation. The driving force is defined as the difference between the DT critical stress (measured in the single-phase austenite region and the yield stress of the fresh ferrite that takes its place. On the other hand, the energy obstacle consists of the free energy difference between austenite and ferrite, and the work of shear accommodation and dilatation associated with the phase transformation. Here, the DT critical stresses in a C-Mn steel were calculated using the free energy method at temperatures ranging from 870 °C to 1070 °C. The results show that the calculated critical stress using the present approach appears to be more accurate than the values measured by the double differentiation method.

  19. Fatigue life estimation of welded components considering welding residual stress relaxation and its mean stress effect

    International Nuclear Information System (INIS)

    Han, Seung Ho; Han, Jeong Woo; Shin, Byung Chun; Kim, Jae Hoon

    2003-01-01

    The fatigue life of welded joints is sensitive to welding residual stress and complexity of their geometric shapes. To predict the fatigue life more reasonably, the effects of welding residual stress and its relaxation on their fatigue strengths should be considered quantitatively, which are often regarded to be equivalent to the effects of mean stresses by external loads. The hot-spot stress concept should be also adopted which can reduce the dependence of fatigue strengths for various welding details. Considering the factors mentioned above, a fatigue life prediction model using the modified Goodman's diagram was proposed. In this model, an equivalent stress was introduced which is composed of the mean stress based on the hot-spot stress concept and the relaxed welding residual stress. From the verification of the proposed model to real welding details, it is proved that this model can be applied to predict reasonably their fatigue lives

  20. Noise effects on the health status in a dynamic failure model for living organisms

    Science.gov (United States)

    Kang, H.; Jo, J.; Choi, M. Y.; Choi, J.; Yoon, B.-G.

    2007-03-01

    We study internal and external noise effects on the healthy-unhealthy transition and related phenomena in a dynamic failure model for living organisms. It is found that internal noise makes the system weaker, leading to breakdown under smaller stress. The discontinuous healthy-unhealthy transition in a system with global load sharing below a critical point is naturally explained in terms of the bistability for the health status. External noise present in constant stress gives similar results; further, it induces resonance in response to periodic stress, regardless of load transfer. In the case of local load sharing, such periodic stress is revealed more hazardous than the constant stress.

  1. Experimental investigation of transient thermoelastic effects in dynamic fracture

    International Nuclear Information System (INIS)

    Rittel, D.

    1997-01-01

    Thermoelastic effects in fracture are generally considered to be negligible at the benefit of the conversion of plastic work into heat. For the case of dynamic crack initiation, the experimental and theoretical emphasis has been put on the temperature rise associated with crack-tip plasticity. Nevertheless, earlier experimental work with polymers has shown that thermoelastic cooling precedes the temperature rise at the tip of a propagating crack (Fuller et al., 1975). Transient thermoelastic effects at the tip of a dynamically loaded crack have been theoretically assessed and shown to be significant when thermal conductivity is initially neglected. However, the fundamental question of the relation between crack initiation and thermal fields, both of transient nature, is still open. In this paper, we present an experimental investigation of the thermoelastic effect at the tip of fatigue cracks subjected to mixed-mode (dominant mode 1) dynamic loading. The material is commercial polymethylmethacrylate as an example of 'brittle' material. The applied loads, crack-tip temperatures and fracture time are simultaneously monitored to provide a more complete image of dynamic crack initiation. The corresponding evolution of the stress intensity factors is calculated by a hybrid-experimental numerical model. The results show that substantial crack-tip cooling develops initially to an extent which corroborates theoretical estimates. This effect is followed by a temperature rise. Fracture is shown to initiate during the early cooling phase, thus emphasizing the relevance of the phenomenon to dynamic crack initiation in this material as probably in other materials. (author)

  2. Modeling the Effects of Stress: An Approach to Training

    Science.gov (United States)

    Cuper, Taryn

    2010-01-01

    Stress is an integral element of the operational conditions experienced by combat medics. The effects of stress can compromise the performance of combat medics who must reach and treat their comrades under often threatening circumstances. Examples of these effects include tunnel vision, loss of motor control, and diminished hearing, which can result in an inability to perceive further danger, satisfactorily treat the casualty, and communicate with others. While many training programs strive to recreate this stress to aid in the experiential learning process, stress inducement may not always be feasible or desired. In addition, live simulations are not always a practical, convenient, and repeatable method of training. Instead, presenting situational training on a personal computer is proposed as an effective training platform in which the effects of stress can be addressed in a different way. We explore the cognitive and motor effects of stress, as well as the benefits of training for mitigating these effects in real life. While many training applications focus on inducing stress in order to "condition" the stress response, the author explores the possibilities of modeling stress to produce a similar effect. Can presenting modeled effects of stress help prepare or inoculate soldiers for stressful situations in which they must perform at a high level? This paper investigates feasibility of modeling stress and describes the preliminary design considerations of a combat medic training system that utilizes this method of battlefield preparation.

  3. Characterizing the intra-urban spatiotemporal dynamics of High Heat Stress Zones (Hotspots)

    Science.gov (United States)

    Shreevastava, A.; Rao, P. S.; McGrath, G. S.

    2017-12-01

    In this study, we present an innovative framework to characterize the spatio-temporal dynamics of High Heat Stress Zones (Hot spots) created within an Urban area in the event of a Heat Wave. Heat waves are one of the leading causes of weather-related human mortality in many countries, and cities receive its worst brunt. The extreme heat stress within urban areas is often a synergistic combination of large-scale meteorological events, and the locally exacerbated impacts due to Urban Heat Islands (UHI). UHI is typically characterized as the difference between mean temperature of the urban and rural area. As a result, it fails to capture the significant variability that exists within the city itself. This variability arises from the diverse and complex spatial geometries of cities. Previous studies that have attempted to quantify the heat stress at an intra-urban scale are labor intensive, expensive, and difficult to emulate globally as they rely on availability of extensive data and their assimilation. The proposed study takes advantage of the well-established notion of fractal properties of cities to make the methods scalable to other cities where in-situ observational data might not be available. As an input, land surface temperatures are estimated using Landsat data. Using clustering analysis, we probe the emergence of thermal hotspots. The probability distributions (PD) of these hotspots are found to follow a power-law distribution in agreement with fractal characteristics of the city. PDs of several archetypical cities are then investigated to compare the effect of different spatial structures (e.g. monocentric v/s polycentric, sprawl v/s compact). Further, the temporal variability of the distributions on a diurnal as well as a seasonal scale is discussed. Finally, the spatiotemporal dynamics of the urban hotspots under a heat-wave (E.g. Delhi Heat wave, 2015) are compared against the non-heat wave scenarios. In summary, a technique that is globally adaptive and

  4. Using Mouse and Keyboard Dynamics to Detect Cognitive Stress During Mental Arithmetic

    OpenAIRE

    Ayesh, Aladdin, 1972-; Stacey, Martin; Lim, Yee Mei

    2015-01-01

    To build a personalized e-learning system that can deliver adaptive learning content based on student’s cognitive effort and efficiency, it is important to develop a construct that can help measuring perceived mental state, such as stress and cognitive load. The construct must be able to be quantified, computerized and automated. Our research investigates how mouse and keyboard dynamics analyses could be used to detect cognitive stress, which is induced by high mental arithmetic demand with t...

  5. impact of workload induced stress on the professional effectiveness

    African Journals Online (AJOL)

    PROF EKWUEME

    aids, evaluation of students, learning motivation, classroom management, supervision of co-curricular activities and ... of workload. KEYWORDS; Stress, Workload, Professional effectiveness, Teachers, Cross River State .... determining the relationship between workload ..... adapted to cope with the stress that could have.

  6. Investigating the effects of different physical and chemical stress ...

    African Journals Online (AJOL)

    2018-04-09

    Apr 9, 2018 ... bacteria from extreme physical and chemical stress conditions. Additionally .... by inducing stress response genes, become more tolerant phenotypes ..... biofilm, monochloramine is more effective than free chlorine over long ...

  7. Effects of copper stress on antioxidative enzymes, chlorophyll and ...

    African Journals Online (AJOL)

    Effects of copper stress on antioxidative enzymes, chlorophyll and protein content in Atriplex ... Journal Home > Vol 10, No 50 (2011) > ... The aim of this work was to investigate some enzymatic systems response of this plant to copper stress.

  8. Local Segmental Dynamics and Stresses in Polystyrene - C$_{60}$ Mixtures

    OpenAIRE

    Vogiatzis, Georgios G.; Theodorou, Doros N.

    2014-01-01

    The polymer dynamics of homogeneous C$_{60}$-polystyrene mixtures in the molten state are studied via molecular simulations using two interconnected levels of representation for polystyrene nanocomposites: (a) A coarse-grained representation, in which each polystyrene repeat unit is mapped into a single "superatom" and each fullerene is viewed as a spherical shell. Equilibration of coarse-grained polymer-nanoparticle systems at all length scales is achieved via connectivity-altering Monte Car...

  9. Effects of stress on health and aging: Two paradoxes

    OpenAIRE

    Aldwin, Carolyn M; Yancura, Loriena A.

    2010-01-01

    Although older adults are thought to experience more stress and to be more vulnerable to its adverse effects, they often report less stress than younger adults and sometimes show more resilience. Paradoxically, while stress sometimes has long-term positive effects on well-being, studies differ as to whether this increases or decreases with age. We conclude that older individuals have learned to appraise and cope differently with stress. This protects them in spite of their increased physiolog...

  10. Dynamic, large-deflection, inelastic and thermal stress analysis by the finite element method

    International Nuclear Information System (INIS)

    Haisler, W.E.; Stricklin, J.A.

    1975-01-01

    A finite element theory and computer program have been developed for predicting the dynamic, large displacement, inelastic and thermal response of stiffened and layered structures. The dependence of material properties on temperature is explicitly accounted for and any arbitrary, transient mechanical or thermal load history is allowed. The shell may have internal or external stiffeners and be constructed with up to three layers. The equations of motion are developed by using the pseudo force approach to represent all nonlinearities and are then solved by using either the Houbolt method or central differences. Moderately large rotations are allowed. The program is based on an incremental theory of plasticity using the Von Mises yield condition and associated flow rule. The post yield or work-hardening behavior is idealized with either the isotropic hardening or mechanical sublayer models. Two models are utilized since it has been found through comparison with experimental results that isotropic hardening is best for simple loading conditions while the mechanical sublayer model is better for reverse and cyclic loading. Strain-rate effects are also accounted for in the program by using a power-law type model based on the strain rate. The dependence of material properties on temperature is taken into account in the pseudo forces. Young's modulus, Poisson's ratio, thermal coefficient of expansion, the yield stress, and the entire stress strain curve are treated as functions of the applied temperature. Containment vessels subjected to transient and shock-type mechanical and thermal loads have been analyzed

  11. Projections of rising heat stress over the western Maritime Continent from dynamically downscaled climate simulations

    Science.gov (United States)

    Im, Eun-Soon; Kang, Suchul; Eltahir, Elfatih A. B.

    2018-06-01

    This study assesses the future changes in heat stress in response to different emission scenarios over the western Maritime Continent. To better resolve the region-specific changes and to enhance the performance in simulating extreme events, the MIT Regional Climate Model with a 12-km horizontal resolution is used for the dynamical downscaling of three carefully selected CMIP5 global projections forced by two Representative Concentration Pathway (RCP4.5 and RCP8.5) scenarios. Daily maximum wet-bulb temperature (TWmax), which includes the effect of humidity, is examined to describe heat stress as regulated by future changes in temperature and humidity. An ensemble of projections reveals robust pattern in which a large increase in temperature is accompanied by a reduction in relative humidity but a significant increase in wet-bulb temperature. This increase in TWmax is relatively smaller over flat and coastal regions than that over mountainous region. However, the flat and coastal regions characterized by warm and humid present-day climate will be at risk even under modest increase in TWmax. The regional extent exposed to higher TWmax and the number of days on which TWmax exceeds its threshold value are projected to be much higher in RCP8.5 scenario than those in RCP4.5 scenario, thus highlighting the importance of controlling greenhouse gas emissions to reduce the adverse impacts on human health and heat-related mortality.

  12. Mean-Field Scenario for the Athermal Creep Dynamics of Yield-Stress Fluids

    Science.gov (United States)

    Liu, Chen; Martens, Kirsten; Barrat, Jean-Louis

    2018-01-01

    We develop a theoretical description based on an existent mean-field model for the transient dynamics prior to the steady flow of yielding materials. The mean-field model not only reproduces the experimentally observed nonlinear time dependence of the shear-rate response to an external stress, but also allows for the determination of the different physical processes involved in the onset of the reacceleration phase after the initial slowing down and a distinct fluidization phase. The fluidization time displays a power-law dependence on the distance of the applied stress to an age-dependent yield stress, which is not universal but strongly dependent on initial conditions.

  13. Effects of work stress and home stress on autonomic nervous function in Japanese male workers.

    Science.gov (United States)

    Maeda, Eri; Iwata, Toyoto; Murata, Katsuyuki

    2015-01-01

    Autonomic imbalance is one of the important pathways through which psychological stress contributes to cardiovascular diseases/sudden death. Although previous studies have focused mainly on stress at work (work stress), the association between autonomic function and stress at home (home stress) is still poorly understood. The purpose was to clarify the effect of work/home stress on autonomic function in 1,809 Japanese male workers. We measured corrected QT (QTc) interval and QT index on the electrocardiogram along with blood pressure and heart rate. Participants provided self-reported information about the presence/absence of work/home stress and the possible confounders affecting QT indicators. Home stress was related positively to QT index (p=0.040) after adjusting for the possible confounders, though work stress did not show a significant relation to QTc interval or QT index. The odds ratio of home stress to elevated QT index (≥105) was 2.677 (95% CI, 1.050 to 6.822). Work/home stress showed no significant relation to blood pressure or heart rate. These findings suggest that autonomic imbalance, readily assessed by QT indicators, can be induced by home stress in Japanese workers. Additional research is needed to identify different types of home stress that are strongly associated with autonomic imbalance.

  14. Nonlinear cosmological consistency relations and effective matter stresses

    International Nuclear Information System (INIS)

    Ballesteros, Guillermo; Hollenstein, Lukas; Jain, Rajeev Kumar; Kunz, Martin

    2012-01-01

    We propose a fully nonlinear framework to construct consistency relations for testing generic cosmological scenarios using the evolution of large scale structure. It is based on the covariant approach in combination with a frame that is purely given by the metric, the normal frame. As an example, we apply this framework to the ΛCDM model, by extending the usual first order conditions on the metric potentials to second order, where the two potentials start to differ from each other. We argue that working in the normal frame is not only a practical choice but also helps with the physical interpretation of nonlinear dynamics. In this frame, effective pressures and anisotropic stresses appear at second order in perturbation theory, even for ''pressureless'' dust. We quantify their effect and compare them, for illustration, to the pressure of a generic clustering dark energy fluid and the anisotropic stress in the DGP model. Besides, we also discuss the effect of a mismatch of the potentials on the determination of galaxy bias

  15. Dynamics effects on a wooden footbridge

    Directory of Open Access Journals (Sweden)

    Vašková Veronika

    2017-01-01

    Full Text Available The timber is the current trend for the construction of many footbridges because of many reasons as price, aesthetics and ecology. Most of these structures are designed using simple static models and massive elements. However, there are implemented more complicated constructions including suspended footbridge in Příbor in Czech Republic. This construction with efficient use of material is more susceptible to dynamic effect. The article describes monitoring of dynamics effects at the construction with result of installation dynamics dampers.

  16. Shearographic System for Dynamic Analysis of Materials under Heat Stress

    Directory of Open Access Journals (Sweden)

    Nelson A. Correa-Rojas

    2013-11-01

    Full Text Available Shearography is a tool for monitoring and inspecting of structural flaws and imperfections in different types of industrial, automotive and aeronautics applications. It is based on digital correlation of two speckle patterns in two states of interest: with and without load. The technique has the special quality of being very robust against environmental disturbances. We present a shearographic system to analyze the dynamic behavior of the strain that suffers a material in response to changes in temperature throughout the thermal load process.

  17. Loneliness and sleep quality: dyadic effects and stress effects.

    Science.gov (United States)

    Segrin, Chris; Burke, Tricia J

    2015-01-01

    The aims of this investigation are to determine whether loneliness is associated with a person's own sleep quality and sleep quality of their partner, and to test stress as a potential mediator. Participants were 255 couples in married (75%) or cohabiting relationships who completed self-report measures of loneliness, sleep quality, stress, and depression. Results of Actor-Partner Interdependence analyses replicated findings in the literature showing an association between loneliness and poor sleep quality. The more lonely a male participant was, the lower his partner's sleep quality. In addition, the more lonely participants were, the higher they rated their partner's sleep disturbance. There were significant indirect effects of loneliness on poor sleep quality through increased stress, even after controlling for depression.

  18. Oxidative stress and nitrite dynamics under maximal load in elite athletes: relation to sport type.

    Science.gov (United States)

    Cubrilo, Dejan; Djordjevic, Dusica; Zivkovic, Vladimir; Djuric, Dragan; Blagojevic, Dusko; Spasic, Mihajlo; Jakovljevic, Vladimir

    2011-09-01

    Maximal workload in elite athletes induces increased generation of reactive oxygen/nitrogen species (RONS) and oxidative stress, but the dynamics of RONS production are not fully explored. The aim of our study was to examine the effects of long-term engagement in sports with different energy requirements (aerobic, anaerobic, and aerobic/anaerobic) on oxidative stress parameters during progressive exercise test. Concentrations of lactates, nitric oxide (NO) measured through stabile end product-nitrites (NO(2) (-)), superoxide anion radical (O(2) (•-)), and thiobarbituric reactive substances (TBARS) as index of lipid peroxidation were determined in rest, after maximal workload, and at 4 and 10th min of recovery in blood plasma of top level competitors in rowing, cycling, and taekwondo. Results showed that sportmen had similar concentrations of lactates and O(2) (•-) in rest. Nitrite concentrations in rest were the lowest in taekwondo fighters, while rowers had the highest levels among examined groups. The order of magnitude for TBARS level in the rest was bicycling > taekwondo > rowing. During exercise at maximal intensity, the concentration of lactate significantly elevated to similar levels in all tested sportsmen and they were persistently elevated during recovery period of 4 and 10 min. There were no significant changes in O(2) (•-), nitrite, and TBARS levels neither at the maximum intensity of exercise nor during the recovery period comparing to the rest period in examined individuals. Our results showed that long term different training strategies establish different basal nitrites and lipid peroxidation levels in sportmen. However, progressive exercise does not influence basal nitrite and oxidative stress parameters level neither at maximal load nor during the first 10 min of recovery in sportmen studied.

  19. THE DYNAMIC INTERCONNECTION BETWEEN MAN AND ENVIRONMENT, A FACTOR OF STRESS AND ECO STRESS

    Directory of Open Access Journals (Sweden)

    SIMIONESCU (BARBU IRINA

    2014-05-01

    Full Text Available The reason for writing this paper is the omnipresence but also the impact of stress in our times. In order to explain why stress has gained an important place in modern history, we need to understand the evolution of medical science and technology, which over the last decades, have taken important steps towards establishing the biological links between stress and human behaviour but also the political and cultural contexts that have endowed with meaning and authority the scientific knowledge. In the same time, we must concentrate on the interaction between the individual and his social and physical environment from a holistic perspective, surpassing the interdisciplinary limits. The term ‘stress’ is used as a metaphor for disasters at a macroeconomic level, when national economies are destabilized and recently it has been associated with the idea of environmental damage. All natural disasters are environmental events, and their impact on human beings (from a psychological, physical, economic and social point of view can be seen as a major eco-stress. It’s essential to understand man`s influence on the environment in order to review the attitude of communities that, under the pretext of modernity, continue to exert destructive actions

  20. Comparison of erythrocyte dynamics in shear flow under different stress-free configurations

    Science.gov (United States)

    Cordasco, Daniel; Yazdani, Alireza; Bagchi, Prosenjit

    2014-04-01

    An open question that has persisted for decades is whether the cytoskeleton of a red blood cell is stress-free or under a stress. This question is important in the context of theoretical modeling of cellular motion under a flowing condition where it is necessary to make an assumption about the stress-free state. Here, we present a 3D numerical study to compare the cell dynamics in a simple shear flow under two different stress-free states, a biconcave discocyte representing the resting shape of the cell, and a nearly spherical oblate shape. We find that whether the stress-free states make a significant difference or not depends on the viscosity of the suspending medium. If the viscosity is close to that of blood plasma, the two stress-free states do not show any significant difference in cell dynamics. However, when the suspending medium viscosity is well above that of the physiological range, as in many in vitro studies, the shear rate separating the tank-treading and tumbling dynamics is observed to be higher for the biconcave stress-free state than the spheroidal state. The former shows a strong shape oscillation with repeated departures from the biconcave shape, while the latter shows a nearly stable biconcave shape. It is found that the cell membrane in the biconcave stress-free state is under a compressive stress and a weaker bending force density, leading to a periodic compression of the cell. The shape oscillation then leads to a higher energy barrier against membrane tank-tread leading to an early transition to tumbling. However, if the cells are released with a large off-shear plane angle, the oscillations can be suppressed due to an azimuthal motion of the membrane along the vorticity direction leading to a redistribution of the membrane points and lowering of the energy barrier, which again results in a nearly similar behavior of the cells under the two different stress-free states. A variety of off-shear plane dynamics is observed, namely, rolling

  1. Dynamic airway pressure-time curve profile (Stress Index): a systematic review.

    Science.gov (United States)

    Terragni, Pierpaolo; Bussone, Guido; Mascia, Luciana

    2016-01-01

    The assessment of respiratory mechanics at the bedside is necessary in order to identify the most protective ventilatory strategy. Indeed in the last 20 years, adverse effects of positive ventilation to the lung structures have led to a reappraisal of the objectives of mechanical ventilation. The ventilator setting requires repeated readjustment over the period of mechanical ventilation dependency and careful respiratory monitoring to minimize the risks, preventing further injury and permitting the lung and airways healing. Among the different methods that have been proposed and validated, the analysis of dynamic P-t curve (named Stress Index, SI) represents an adequate tool available at the bedside, repeatable and, therefore, able to identify the amount of overdistension occurring in the daily clinical practice, when modifying positive end-expiratory pressure. In this review we will analyze the evidence that supports respiratory mechanics assessment at the bedside and the application of the dynamic P/t curve profile (SI) to optimize protective ventilation in patients with acute respiratory failure.

  2. Structural damping values as a function of dynamic response stress and deformation levels

    International Nuclear Information System (INIS)

    Stevenson, J.D.

    1980-01-01

    Damping as it is normally defined is the means by which the response motion of a structural system is reduced as the result of energy losses. However, as used in the context of nuclear plant design, the effects of changes in structural stiffness, geometry, support configuration, and modulus of elasticity are also usually lumped under the general heading of damping in current design methods. For convenience in structural design, damping in usually assumed as viscous in nature and in recognition of its use in modal response spectrum dynamic analysis is normally expressed as a percent of critical. In general, it should be understood that damping as used in design or analysis of nuclear plants is an experimentally determined factor which is used to make the results of linear elasticity analysis of dynamic systems agree reasonably well with observed experimental results. In this paper, damping data existing in the open literature applicable to nuclear power plant structures and equipment is summarized and statistically analyzed. Results of this analysis are used to develop damping trend curves which predict applicable damping values to be used in design at various levels of stress or deformation. (orig.)

  3. Expectancy of Stress-Reducing Aromatherapy Effect and Performance on a Stress-Sensitive Cognitive Task

    Directory of Open Access Journals (Sweden)

    Irina Chamine

    2015-01-01

    Full Text Available Objective. Stress-reducing therapies help maintain cognitive performance during stress. Aromatherapy is popular for stress reduction, but its effectiveness and mechanism are unclear. This study examined stress-reducing effects of aromatherapy on cognitive function using the go/no-go (GNG task performance and event related potentials (ERP components sensitive to stress. The study also assessed the importance of expectancy in aromatherapy actions. Methods. 81 adults were randomized to 3 aroma groups (active experimental, detectable, and undetectable placebo and 2 prime subgroups (prime suggesting stress-reducing aroma effects or no-prime. GNG performance, ERPs, subjective expected aroma effects, and stress ratings were assessed at baseline and poststress. Results. No specific aroma effects on stress or cognition were observed. However, regardless of experienced aroma, people receiving a prime displayed faster poststress median reaction times than those receiving no prime. A significant interaction for N200 amplitude indicated divergent ERP patterns between baseline and poststress for go and no-go stimuli depending on the prime subgroup. Furthermore, trends for beneficial prime effects were shown on poststress no-go N200/P300 latencies and N200 amplitude. Conclusion. While there were no aroma-specific effects on stress or cognition, these results highlight the role of expectancy for poststress response inhibition and attention.

  4. Expectancy of Stress-Reducing Aromatherapy Effect and Performance on a Stress-Sensitive Cognitive Task

    Science.gov (United States)

    Chamine, Irina; Oken, Barry S.

    2015-01-01

    Objective. Stress-reducing therapies help maintain cognitive performance during stress. Aromatherapy is popular for stress reduction, but its effectiveness and mechanism are unclear. This study examined stress-reducing effects of aromatherapy on cognitive function using the go/no-go (GNG) task performance and event related potentials (ERP) components sensitive to stress. The study also assessed the importance of expectancy in aromatherapy actions. Methods. 81 adults were randomized to 3 aroma groups (active experimental, detectable, and undetectable placebo) and 2 prime subgroups (prime suggesting stress-reducing aroma effects or no-prime). GNG performance, ERPs, subjective expected aroma effects, and stress ratings were assessed at baseline and poststress. Results. No specific aroma effects on stress or cognition were observed. However, regardless of experienced aroma, people receiving a prime displayed faster poststress median reaction times than those receiving no prime. A significant interaction for N200 amplitude indicated divergent ERP patterns between baseline and poststress for go and no-go stimuli depending on the prime subgroup. Furthermore, trends for beneficial prime effects were shown on poststress no-go N200/P300 latencies and N200 amplitude. Conclusion. While there were no aroma-specific effects on stress or cognition, these results highlight the role of expectancy for poststress response inhibition and attention. PMID:25802539

  5. Dynamic strain aging of zircaloy-4 PWR fuel cladding in biaxial stress state

    International Nuclear Information System (INIS)

    Park, Ki Seong; Lee, Byong Whi

    1989-01-01

    The expanding copper mandrel test performed at three strain rates (3.2x10E-5/s,2.0x10E-6/s and 1.2x10E-7/s) over 553-873 K temperature range by varying the heating rates (8-10deg C/s,1-2deg C/s and 0.5deg C/s) in air and in vacuum (5x10E-5 torr). The yield stress peak, the strain rate sensitivity minimum and the activation volume peaks could be explained in terms of the dynamic strain aging. The activation energy for dynamic strain aging obtained from the yield stress peak temperature and strain rate was 196 KJ/mol and this value was in good agreement with the activation energy for oxygen diffusion in α-zirconium and Zircaloy-2 (207-220KJ/mol). Therefore, oxygen atoms are responsible for the dynamic strain aging which appeared between 573K and 673K. The yield stress increase due to the oxidation was obtained by comparing the yield stress in air with that in vacuum and represented by the percentage increase of yield stress (σ y a -σ y v /σ y v ). The slower the strain rate, the greater the percentage increase occurs. In order to estimate the yield stress of PWR fuel cladding material under the service environment, the yield stress in water was obtained by comparing the oxidation rate in air that in water assuming the relationship between the oxygen pick-up amount and the yield stress increase. (Author)

  6. Studies of earthquakes stress drops, seismic scattering, and dynamic triggering in North America

    Science.gov (United States)

    Escudero Ayala, Christian Rene

    at 1.5, 3, 5, 7.5, 10.5, and 13.5 Hz. Coda Q present a great correlation with tectonic and geology setting, as well as the crustal thickness. I analyze global and Middle American Subduction Zone (MASZ) seismicity from 1998 to 2008 to quantify the transient stresses effects at teleseismic distances. I use the Bulletin of the International Seismological Centre Catalog (ISCCD) published by the Incorporated Research Institutions for Seismology (IRIS). To identify MASZ seismicity changes due to distant, large (Mw ¿ 7) earthquakes, I first identify local earthquakes that occurred before and after the mainshocks. I then group the local earthquakes within a cluster radius between 75 to 200 km. I obtain statistics based on characteristics of both mainshocks and local earthquakes clusters, such as cluster-mainshock azimuth, mainshock focal mechanism, and local earthquakes clusters within the MASZ. Based on the lateral variations of the dip along the subducted oceanic plate, I divide the Mexican subduction zone into four segments. I then apply the Paired Samples Statistical Test (PSST) to the sorted data to identify increment, decrement or either in the local seismicity associated with distant large earthquakes passage of surface waves. I identify dynamic triggering for all MASZ segments produced by large earthquakes emerging from specific azimuths, as well as, a decrease for some cases. I find no dependence of seismicity changes on mainshock focal mechanism.

  7. Excitonic dynamical Franz-Keldysh effect

    DEFF Research Database (Denmark)

    Nordstrøm, K.B.; Johnsen, Kristinn; Allen, S.J.

    1998-01-01

    The dynamical Franz-Keldysh effect is exposed by exploring near-band-gap absorption in the presence of intense THz electric fields. It bridges the gap between the de Franz-Keldysh effect and multiphoton absorption and competes with the THz ac Stark effect in shifting the energy of the excitonic...... resonance. A theoretical model which includes the strong THz field nonperturbatively via a nonequilibrium Green functions technique is able to describe the dynamical Franz-Keldysh effect in the presence of excitonic absorption....

  8. Strain-energy effects on dynamic fragmentation

    International Nuclear Information System (INIS)

    Glenn, L.A.; Chudnovsky, A.

    1986-01-01

    Grady's model of the dynamic fragmentation process, in which the average fragment size is determined by balancing the local kinetic energy and the surface energy, is modified to include the stored elastic (strain) energy. The revised model predicts that the strain energy should dominate for brittle materials, with low fracture toughness and high fracture-initiation stress. This conclusion is not borne out, however, by limited experimental data on brittle steels, even when the kinetic-energy density is small compared with the strain-energy density

  9. Comparison of dynamic ultrasound and stress radiology for assessment of inferior glenohumeral laxity in asymptomatic shoulders

    International Nuclear Information System (INIS)

    Cheng, S.C.; Wallace, W.A.; Hulse, D.; Fairbairn, K.J.; Clarke, M.

    2008-01-01

    To determine the level of agreement between dynamic ultrasound imaging and stress radiography used for the measurement of inferior glenohumeral laxity in asymptomatic shoulders, and to determine the repeatability of the dynamic ultrasound technique. Using a custom-made stress device to apply an inferior displacement force of 90 N, we assessed 20 asymptomatic male subjects for inferior glenohumeral laxity, using stress radiography and dynamic ultrasound. Paired differences between the two methods were evaluated by the 95% limits of agreement method. At a separate session, 19 subjects had inferior glenohumeral laxity assessed by two observers, using dynamic ultrasound. Inter- and intra-observer repeatability was determined for the ultrasound technique. The mean [± standard deviation (SD)] inferior translation was 4.7 ± 4.1 mm by stress radiography and 4.4 ± 2.3 mm by dynamic ultrasound. The 95% limits of agreement showed good agreement between the two methods. The paired difference between the two measurement methods varied with the magnitude of the measurement (P < 0.001). Intra-observer repeatability of dynamic ultrasound was determined by the use of intra-class correlation coefficients and was 0.94 and 0.89 for the two investigators. Inter-observer repeatability was 0.85. The standard error of the measurement was 0.60 mm and 0.66 mm, for repeated measurements by the two investigators, and 0.85 mm between investigators. Repeatability coefficients demonstrated excellent consistency of measurement between sessions and good consistency between observers. Dynamic ultrasound is a valid and reproducible method for the assessment and quantification of inferior glenohumeral laxity. (orig.)

  10. Effects of Humor on Teacher Stress, Affect, and Job Satisfaction

    Science.gov (United States)

    Shirley, Jacqueline Dena

    2013-01-01

    Teachers are at high risk for stress, negative emotion, and job dissatisfaction, which has been linked with health problems and early attrition. Humor has been found to relieve various forms of stress. However, there is a gap in the literature regarding humor effects on teacher stress and its related consequences. The purpose of this quantitative,…

  11. Propagating stress-pulses and wiggling transition revealed in string dynamics

    Science.gov (United States)

    Yao, Zhenwei

    2018-02-01

    Understanding string dynamics yields insights into the intricate dynamic behaviors of various filamentary thin structures in nature and industry covering multiple length scales. In this work, we investigate the planar dynamics of a flexible string where one end is free and the other end is subject to transverse and longitudinal motions. Under transverse harmonic motion, we reveal the propagating pulse structure in the stress profile over the string, and analyze its role in bringing the system into a chaotic state. For a string where one end is under longitudinal uniform acceleration, we identify the wiggling transition, derive the analytical wiggling solution from the string equations, and present the phase diagram.

  12. Stress tensor and viscosity of water: Molecular dynamics and generalized hydrodynamics results

    Science.gov (United States)

    Bertolini, Davide; Tani, Alessandro

    1995-08-01

    The time correlation functions (CF's) of diagonal and off-diagonal components of the stress tensor of water have been calculated at 245 and 298 K in a molecular dynamics (MD) study on 343 molecules in the microcanonical ensemble. We present results obtained at wave number k=0 and at a few finite values of k, in the atomic and molecular formalism. In all cases, more than 98% of these functions are due to the potential term of the stress tensor. At k=0, their main features are a fast oscillatory initial decay, followed by a long-time tail more apparent in the supercooled region. Bulk and shear viscosities, calculated via Green-Kubo integration of the relevant CF at k=0, are underestimated with respect to experimental data, mainly at low temperature, but their ratio (~=2) is correctly reproduced. Both shear and bulk viscosity decrease as a function of k, the latter more rapidly, so that they become almost equal at ~=1 Å-1. Also, both viscosities drop rapidly from their maximum at ω=0. This behavior has been related to the large narrowing observed in the acoustic band, mainly in the supercooled region. The infinite frequency bulk and shear rigidity moduli have been shown to be in fair agreement with the experimental data, provided the MD value used for comparison is that corresponding to the frequency range relevant to ultrasonic measurements. The MD results of stress-stress CF's compare well with those predicted by Bertolini and Tani [Phys. Rev. E 51, 1091 (1995)] at k=0, by an application of generalized hydrodynamics [de Schepper et al., Phys. Rev. A 38, 271 (1988)] in the molecular formalism, to the same model of water (TIP4P) [Jorgensen et al., J. Chem. Phys. 79, 926 (1983)]. These CF's are essentially equal in the atomic and molecular formalism, the only minor difference being restricted to the high frequency librational region of the shear function. By a comparison of atomic and molecular results, we show here that neglecting libration has no effect on the

  13. COMT Diplotype Amplifies Effect of Stress on Risk of Temporomandibular Pain.

    Science.gov (United States)

    Slade, G D; Sanders, A E; Ohrbach, R; Bair, E; Maixner, W; Greenspan, J D; Fillingim, R B; Smith, S; Diatchenko, L

    2015-09-01

    When measured once, psychological stress predicts development of painful temporomandibular disorder (TMD). However, a single measurement fails to characterize the dynamic nature of stress over time. Moreover, effects of stress on pain likely vary according to biological susceptibility. We hypothesized that temporal escalation in stress exacerbates risk for TMD, and the effect is amplified by allelic variants in a gene, catechol-O-methyltransferase (COMT), regulating catechol neurotransmitter catabolism. We used data from the Orofacial Pain: Prospective Evaluation and Risk Assessment prospective cohort study of 2,707 community-dwelling adults with no lifetime history of TMD on enrollment. At baseline and quarterly periods thereafter, the Perceived Stress Scale (PSS) measured psychological stress. Genotyped DNA from blood samples determined COMT diplotypes. During follow-up of 0.25 to 5.2 y, 248 adults developed examiner-verified incident TMD. PSS scores at baseline were 20% greater (P stress escalation was limited to incident cases with COMT diplotypes coding for low-activity COMT, signifying impaired catabolism of catecholamines. Cox regression models confirmed significant effects on TMD hazard of both baseline PSS (P stress showed that a postbaseline increase of 1.0 standard deviation in PSS more than doubled risk of TMD incidence in subjects with low-activity COMT diplotypes (hazard ratio = 2.35; 95% confidence limits: 1.66, 3.32), an effect not found in subjects with high-activity COMT diplotypes (hazard ratio = 1.42; 95% confidence limits: 0.96, 2.09). Findings provide novel insights into dynamic effects of psychological stress on TMD pain, highlighting that effects are most pronounced in individuals whose genetic susceptibility increases responsiveness to catecholamine neurotransmitters. © International & American Associations for Dental Research 2015.

  14. Effects of Hospital Workers’ Friendship Networks on Job Stress

    Science.gov (United States)

    Shin, Sung Yae; Lee, Sang Gyu

    2016-01-01

    Background This study attempted to identify the sources of job stress according to job position and investigate how friendship networks affect job stress. Methods Questionnaires based on The Health Professions Stress Inventory (HPSI) developed by Wolfgang experienced by healthcare providers were collected from 420 nurses, doctors and radiological technologists in two general hospitals in Korea by a multistage cluster sampling method. Multiple regression analysis was used to examine the effects of friendship networks on job stress after controlling for other factors. Results The severity of job stress differed according to level of job demands (p = .006); radiologic technologists experienced the least stress (45.4), nurses experienced moderate stress (52.4), and doctors experienced the most stress (53.6). Those with long-term friendships characterized by strong connections reported lower levels of stress than did those with weak ties to friends among nurses (1.3, p job stress experienced by nurses (8.2, p job stress (9.2, p job stress. Conclusion The strength and density of such friendship networks were related to job stress. Life information support from their friendship network was the primary positive contributor to control of job stress. PMID:26900945

  15. Computational fluid dynamics (CFD) insights into agitation stress methods in biopharmaceutical development.

    Science.gov (United States)

    Bai, Ge; Bee, Jared S; Biddlecombe, James G; Chen, Quanmin; Leach, W Thomas

    2012-02-28

    Agitation of small amounts of liquid is performed routinely in biopharmaceutical process, formulation, and packaging development. Protein degradation commonly results from agitation, but the specific stress responsible or degradation mechanism is usually not well understood. Characterization of the agitation stress methods is critical to identifying protein degradation mechanisms or specific sensitivities. In this study, computational fluid dynamics (CFD) was used to model agitation of 1 mL of fluid by four types of common laboratory agitation instruments, including a rotator, orbital shaker, magnetic stirrer and vortex mixer. Fluid stresses in the bulk liquid and near interfaces were identified, quantified and compared. The vortex mixer provides the most intense stresses overall, while the stir bar system presented locally intense shear proximal to the hydrophobic stir bar surface. The rotator provides gentler fluid stresses, but the air-water interfacial area and surface stresses are relatively high given its low rotational frequency. The orbital shaker provides intermediate-level stresses but with the advantage of a large stable platform for consistent vial-to-vial homogeneity. Selection of experimental agitation methods with targeted types and intensities of stresses can facilitate better understanding of protein degradation mechanisms and predictability for "real world" applications. Copyright © 2011 Elsevier B.V. All rights reserved.

  16. When does stress help or harm? The effects of stress controllability and subjective stress response on stroop performance.

    Science.gov (United States)

    Henderson, Roselinde K; Snyder, Hannah R; Gupta, Tina; Banich, Marie T

    2012-01-01

    The ability to engage in goal-directed behavior despite exposure to stress is critical to resilience. Questions of how stress can impair or improve behavioral functioning are important in diverse settings, from athletic competitions to academic testing. Previous research suggests that controllability is a key factor in the impact of stress on behavior: learning how to control stressors buffers people from the negative effects of stress on subsequent cognitively demanding tasks. In addition, research suggests that the impact of stress on cognitive functioning depends on an individual's response to stressors: moderate responses to stress can lead to improved performance while extreme (high or low) responses can lead to impaired performance. The present studies tested the hypothesis that (1) learning to behaviorally control stressors leads to improved performance on a test of general executive functioning, the color-word Stroop, and that (2) this improvement emerges specifically for people who report moderate (subjective) responses to stress. Experiment 1: Stroop performance, measured before and after a stress manipulation, was compared across groups of undergraduate participants (n = 109). People who learned to control a noise stressor and received accurate performance feedback demonstrated reduced Stroop interference compared with people exposed to uncontrollable noise stress and feedback indicating an exaggerated rate of failure. In the group who learned behavioral control, those who reported moderate levels of stress showed the greatest reduction in Stroop interference. In contrast, in the group exposed to uncontrollable events, self-reported stress failed to predict performance. Experiment 2: In a second sample (n = 90), we specifically investigated the role of controllability by keeping the rate of failure feedback constant across groups. In the group who learned behavioral control, those who reported moderate levels of stress showed the greatest Stroop

  17. Protective effects of carnosol against oxidative stress induced brain damage by chronic stress in rats.

    Science.gov (United States)

    Samarghandian, Saeed; Azimi-Nezhad, Mohsen; Borji, Abasalt; Samini, Mohammad; Farkhondeh, Tahereh

    2017-05-04

    Oxidative stress through chronic stress destroys the brain function. There are many documents have shown that carnosol may have a therapeutic effect versus free radical induced diseases. The current research focused the protective effect of carnosol against the brain injury induced by the restraint stress. The restraint stress induced by keeping animals in restrainers for 21 consecutive days. Thereafter, the rats were injected carnosol or vehicle for 21 consecutive days. At the end of experiment, all the rats were subjected to his open field test and forced swimming test. Afterwards, the rats were sacrificed for measuring their oxidative stress parameters. To measure the modifications in the biochemical aspects after the experiment, the activities of malondialdehyde (MDA), reduced glutathione (GSH), as well as superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione reductase (GR) and catalase (CAT) were evaluated in the whole brain. Our data showed that the animals received chronic stress had a raised immobility time versus the non-stressed animals (p < 0.01). Furthermore, chronic stress diminished the number of crossing in the animals that were subjected to the chronic stress versus the non-stressed rats (p < 0.01). Carnosol ameliorated this alteration versus the non-treated rats (p < 0.05). In the vehicle treated rats that submitted to the stress, the level of MDA levels was significantly increased (P < 0.001), and the levels of GSH and antioxidant enzymes were significantly decreased versus the non-stressed animals (P < 0.001). Carnosol treatment reduced the modifications in the stressed animals as compared with the control groups (P < 0.001). All of these carnosol effects were nearly similar to those observed with fluoxetine. The current research shows that the protective effects of carnosol may be accompanied with enhanced antioxidant defenses and decreased oxidative injury.

  18. Dynamic effects of diabatization in distillation columns

    DEFF Research Database (Denmark)

    Bisgaard, Thomas; Huusom, Jakob Kjøbsted; Abildskov, Jens

    2013-01-01

    The dynamic effects of diabatization in distillation columns are investigated in simulation emphasizing the heat-integrated distillation column (HIDiC). A generic, dynamic, first-principle model has been formulated, which is flexible enough to describe various diabatic distillation configurations....... Dynamic Relative Gain Array and Singular Value Analysis have been applied in a comparative study of a conventional distillation column and a HIDiC. The study showed increased input-output coupling due to diabatization. Feasible SISO control structures for the HIDiC were also found and control...

  19. Influence of effective stress on swelling pressure of expansive soils

    Directory of Open Access Journals (Sweden)

    Baille Wiebke

    2016-01-01

    Full Text Available The volume change and shear strength behaviour of soils are controlled by the effective stress. Recent advances in unsaturated soil mechanics have shown that the effective stress as applicable to unsaturated soils is equal to the difference between the externally applied stress and the suction stress. The latter can be established based on the soil-water characteristic curve (SWCC of the soil. In the present study, the evolution of swelling pressure in compacted bentonite-sand mixtures was investigated. Comparisons were made between magnitudes of applied suction, suction stress, and swelling pressure.

  20. Dynamic functional connectivity and individual differences in emotions during social stress.

    Science.gov (United States)

    Tobia, Michael J; Hayashi, Koby; Ballard, Grey; Gotlib, Ian H; Waugh, Christian E

    2017-12-01

    Exposure to acute stress induces multiple emotional responses, each with their own unique temporal dynamics. Dynamic functional connectivity (dFC) measures the temporal variability of network synchrony and captures individual differences in network neurodynamics. This study investigated the relationship between dFC and individual differences in emotions induced by an acute psychosocial stressor. Sixteen healthy adult women underwent fMRI scanning during a social evaluative threat (SET) task, and retrospectively completed questionnaires that assessed individual differences in subjectively experienced positive and negative emotions about stress and stress relief during the task. Group dFC was decomposed with parallel factor analysis (PARAFAC) into 10 components, each with a temporal signature, spatial network of functionally connected regions, and vector of participant loadings that captures individual differences in dFC. Participant loadings of two networks were positively correlated with stress-related emotions, indicating the existence of networks for positive and negative emotions. The emotion-related networks involved the ventromedial prefrontal cortex, cingulate cortex, anterior insula, and amygdala, among other distributed brain regions, and time signatures for these emotion-related networks were uncorrelated. These findings demonstrate that individual differences in stress-induced positive and negative emotions are each uniquely associated with large-scale brain networks, and suggest that dFC is a mechanism that generates individual differences in the emotional components of the stress response. Hum Brain Mapp 38:6185-6205, 2017. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

  1. Stress relaxation in vanadium under shock and shockless dynamic compression

    International Nuclear Information System (INIS)

    Kanel, G. I.; Razorenov, S. V.; Garkushin, G. V.; Savinykh, A. S.; Zaretsky, E. B.

    2015-01-01

    Evolutions of elastic-plastic waves have been recorded in three series of plate impact experiments with annealed vanadium samples under conditions of shockless and combined ramp and shock dynamic compression. The shaping of incident wave profiles was realized using intermediate base plates made of different silicate glasses through which the compression waves were entered into the samples. Measurements of the free surface velocity histories revealed an apparent growth of the Hugoniot elastic limit with decreasing average rate of compression. The growth was explained by “freezing” of the elastic precursor decay in the area of interaction of the incident and reflected waves. A set of obtained data show that the current value of the Hugoniot elastic limit and plastic strain rate is rather associated with the rate of the elastic precursor decay than with the local rate of compression. The study has revealed the contributions of dislocation multiplications in elastic waves. It has been shown that independently of the compression history the material arrives at the minimum point between the elastic and plastic waves with the same density of mobile dislocations

  2. Kaolin modulates ABA and IAA dynamics and physiology of grapevine under Mediterranean summer stress.

    Science.gov (United States)

    Dinis, L-T; Bernardo, S; Luzio, A; Pinto, G; Meijón, M; Pintó-Marijuan, M; Cotado, A; Correia, C; Moutinho-Pereira, J

    2018-01-01

    The foliar exogenous application of kaolin, a radiation-reflecting inert mineral, has proven to be an effective short-term climate change mitigation strategy for Mediterranean vineyards. In this work, we address the hypothesis that kaolin could improve both the hormonal dynamics and physiological responses of grapevines growing in Douro Region, northern Portugal. For this purpose, the leaf water potential, gas exchange and chlorophyll a fluorescence parameters were monitored, as well as the abscisic acid (ABA) and indole-3-acetic acid (IAA) quantification and immunolocalization were assessed. The study revealed a slight decrease in ABA and an increase in IAA in the kaolin treatment, which in turn were associated with the improvement of physiological performance. A month after spraying, kaolin improves the water potential respectively, 30% and 17% in the predawn and midday periods. Besides, plants treated with kaolin showed higher values of stomatal conductance, net CO 2 assimilation rate and intrinsic water use efficiency. Kaolin also ameliorates the effective PSII efficiency (67%), as well as the maximum quantum efficiency of photosystem II and the photosynthetic electron transport rate (>73%). These results were consistent with the higher photochemical quenching and the lower non-photochemical quenching observed in treated leaves and with the better performance obtained by the JIP test parameters. Physiological and hormonal analysis confirmed that kaolin effectively enhance grapevine summer stress tolerance. Copyright © 2017 Elsevier GmbH. All rights reserved.

  3. The Role of Molecular Microtubule Motors and the Microtubule Cytoskeleton in Stress Granule Dynamics

    Directory of Open Access Journals (Sweden)

    Kristen M. Bartoli

    2011-01-01

    Full Text Available Stress granules (SGs are cytoplasmic foci that appear in cells exposed to stress-induced translational inhibition. SGs function as a triage center, where mRNAs are sorted for storage, degradation, and translation reinitiation. The underlying mechanisms of SGs dynamics are still being characterized, although many key players have been identified. The main components of SGs are stalled 48S preinitiation complexes. To date, many other proteins have also been found to localize in SGs and are hypothesized to function in SG dynamics. Most recently, the microtubule cytoskeleton and associated motor proteins have been demonstrated to function in SG dynamics. In this paper, we will discuss current literature examining the function of microtubules and the molecular microtubule motors in SG assembly, coalescence, movement, composition, organization, and disassembly.

  4. Non equilibrium effects in nuclear dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Papa, M.; Arena, N.; Cardella, G.; Lanzano, G.; Filippo, E. de; Lanzalone, G.; Pagano, A.; Pirrone, S.; Politi, G. [Catania Univ., INFN Catania and Dipartimento di Fisica e Astronomia (Italy); Amorini, F.; Anzalone, A.; Bonasera, A.; Cavallaro, S.; Di Pietro, A.; Figuera, P.; Giustolisi, F.; Iacono Manno, M.; La Guidara, E.; Maiolino, C.; Porto, F.; Rizzo, F.; Sperduto, M.L. [Catania Univ., INFN-LNS and Dipartimento di Fisica e Astronomia (Italy); Auditore, L.; Trifiro, A.; Trimarchi, M. [Messina Univ., INFN and Dipartimento di Fisica (Italy)

    2003-07-01

    A Constraint Molecular Dynamics (CoMD) approach is used to study dynamical effects related to both the average dynamics and the fluctuations around it. Data obtained in the REVERSE and in TRASMARAD experiments were compared with the theoretical simulations. The concept of temperature, as derived from a fully dynamical description of the GDR (giant dipole resonance) mode, is also discussed. In this contribution we have discussed the comparison between the CoMD model and two classes of phenomena, induced by heavy ion collisions. The first one is related to the IMF (intermediate mass fragment) production in semi-peripheral collisions for the {sup 124}Sn + {sup 64}Ni system at 35 MeV/nucleon. The comparison put in evidence clear preequilibrium effects in the fragment production mechanism which are essentially related to the behavior of the average dynamics. The second one concerns the high {gamma}-ray productions, due to dipolar resonant mechanisms, in the {sup 40}Ca + {sup 48}Ca system at 25 MeV/nucleon. In this case the comparisons with the model allows to put in evidence preequilibrium effects related both to the average dynamics and to the fluctuating one.

  5. Stress effects on mood, HPA axis, and autonomic response: comparison of three psychosocial stress paradigms.

    Directory of Open Access Journals (Sweden)

    Grace E Giles

    Full Text Available Extensive experimental psychology research has attempted to parse the complex relationship between psychosocial stress, mood, cognitive performance, and physiological changes. To do so, it is necessary to have effective, validated methods to experimentally induce psychosocial stress. The Trier Social Stress Test (TSST is the most commonly used method of experimentally inducing psychosocial stress, but it is resource intensive. Less resource intense psychosocial stress tasks include the Socially Evaluative Cold Pressor Task (SECPT and a computerized mental arithmetic task (MAT. These tasks effectively produce a physiological and psychological stress response and have the benefits of requiring fewer experimenters and affording data collection from multiple participants simultaneously. The objective of this study was to compare the magnitude and duration of these three experimental psychosocial stress induction paradigms. On each of four separate days, participants completed either a control non-stressful task or one of the three experimental stressors: the TSST, SECPT, or MAT. We measured mood, working memory performance, salivary cortisol and alpha-amylase (AA, and heart rate. The TSST and SECPT exerted the most robust effects on mood and physiological measures. TSST effects were generally evident immediately post-stress as well as 10- and 20-minutes after stress cessation, whereas SECPT effects were generally limited to the duration of the stressor. The stress duration is a key determinant when planning a study that utilizes an experimental stressor, as researchers may be interested in collecting dependent measures prior to stress cessation. In this way, the TSST would allow the investigator a longer window to administer tasks of interest.

  6. Work-related social support modulates effects of early life stress on limbic reactivity during stress.

    Science.gov (United States)

    Leicht-Deobald, Ulrich; Bruch, Heike; Bönke, Luisa; Stevense, Amie; Fan, Yan; Bajbouj, Malek; Grimm, Simone

    2017-12-15

    Early life stress (ELS) affects stress- reactivity via limbic brain regions implicated such as hippocampus and amygdala. Social support is a major protective factor against ELS effects, while subjects with ELS experience reportedly perceive less of it in their daily life. The workplace, where most adults spend a substantial amount of time in their daily lives, might serve as a major resource for social support. Since previous data demonstrated that social support attenuates stress reactivity, we here used a psychosocial stress task to test the hypothesis that work-related social support modulates the effects of ELS. Results show decreased amygdala reactivity during stress in ELS subjects who report high levels of work- related social support, thereby indicating a signature for reduced stress reactivity. However, this effect was only observable on the neural, but not on the behavioral level, since social support had no buffering effect regarding the subjective experience of stress in daily life as well as regarding feelings of uncontrollability induced by the stress task. Accordingly, our data suggest that subjects with ELS experiences might benefit from interventions targeted at lowering their subjective stress levels by helping them to better perceive the availability of social support in their daily lives.

  7. Effect of Dynamic Meditation on Mental Health.

    Science.gov (United States)

    Iqbal, Naved; Singh, Archana; Aleem, Sheema

    2016-02-01

    Although traditional meditation has been found to be effective in improving physical and mental health of subjects, there was a paucity of research of the effect of active or dynamic meditation on these variables. Therefore, the present study was aimed at studying the effect of dynamic meditation on mental health of the subjects. Total sample of the present study comprised 60 subjects, 30 each in experimental and control group. Subjects in experimental group were given 21-day training in dynamic meditation. Mental health of the experimental and control group subjects was measured in pre- and post-condition with the help of Mental Health Inventory developed by Jagadish and Srivastava (Mental Health inventory, Manovaigyanik Parikshan Sansthan, Varanasi, 1983). Obtained data were analyzed with the help of ANCOVA. In post-condition, experimental group scored better than control group on integration of personality, autonomy and environmental mastery. Effect sizes of dynamic meditation on these dimensions of mental health were large. However, experimental group and control group did not differ significantly on positive self-evaluation, perception of reality and group-oriented attitude dimensions of mental health in post-condition. Overall, dynamic meditation training was effective in improving mental health of the subjects.

  8. Short-term salt stress strongly affects dynamic photosynthesis, but not steady-state photosynthesis, in tomato (Solanum lycopersicum)

    NARCIS (Netherlands)

    Zhang, Yuqi; Kaiser, Elias; Zhang, Yating; Yang, Qichang; Li, Tao

    2018-01-01

    Salt stress occurs worldwide due to widespread soil salinization. Also, plants are often subjected to rapidly alternating periods of sun and shade (sunflecks). Despite this combined occurrence of salt stress and sunflecks, dynamic photosynthetic responses to sunflecks under salt stress remain

  9. Effects of nutrient and light stress on some morphological ...

    African Journals Online (AJOL)

    Tomato seedlings were subjected to light and nutrient stress to determine the effects of each of these stress factors as well as their combined effects on some morphological parameters of the plant. A two-way Analysis of Variance (ANOVA) carried out on the data obtained showed that light produced significant effect on all ...

  10. Effectiveness of stress release geometries on reducing residual stress in electroforming metal microstructure

    Science.gov (United States)

    Song, Chang; Du, Liqun; Zhao, Wenjun; Zhu, Heqing; Zhao, Wen; Wang, Weitai

    2018-04-01

    Micro electroforming, as a mature micromachining technology, is widely used to fabricate metal microdevices in micro electro mechanical systems (MEMS). However, large residual stress in the local positions of the micro electroforming layer often leads to non-uniform residual stress distributions, dimension accuracy defects and reliability issues during fabrication of the metal microdevice. To solve this problem, a novel design method of presetting stress release geometries in the topological structure of the metal microstructure is proposed in this paper. First, the effect of stress release geometries (circular shape, annular groove shape and rivet shape) on the residual stress in the metal microstructure was investigated by finite element modeling (FEM) analysis. Two evaluation parameters, stress concentration factor K T and stress non-uniformity factor δ were calculated. The simulation results show that presetting stress release geometries can effectively reduce and homogenize the residual stress in the metal microstructures were measured metal microstructure. By combined use with stress release geometries of annular groove shape and rivet shape, the stress concentration factor K T and the stress non-uniformity factor δ both decreased at a maximum of 49% and 53%, respectively. Meanwhile, the average residual stress σ avg decreased at a maximum of 20% from  -292.4 MPa to  -232.6 MPa. Then, micro electroforming experiments were carried out corresponding to the simulation models. The residual stresses in the metal microstructures were measured by micro Raman spectroscopy (MRS) method. The results of the experiment proved that the stress non-uniformity factor δ and the average residual stress σ avg also decreased at a maximum with the combination use of annular groove shape and rivet shape stress release geometries, which is in agreement with the results of FEM analysis. The stress non-uniformity factor δ has a maximum decrease of 49% and the

  11. When does stress help or harm? The effects of stress controllability and subjective stress response on Stroop performance.

    Directory of Open Access Journals (Sweden)

    Roselinde Kaiser Henderson

    2012-06-01

    Full Text Available The ability to engage in goal-directed behavior despite exposure to stress is critical to resilience. Questions of how stress can impair or improve behavioral functioning are important in diverse settings, from athletic competitions to academic testing to clinical therapy. Previous research suggests that controllability is a key factor in the impact of stress on behavior: learning how to control stressors buffers people from the negative effects of stress on subsequent cognitively demanding tasks. In addition, research suggests that the impact of stress on cognitive functioning depends on an individual’s response to stressors: moderate responses to stress can lead to improved performance while extreme (high or low responses can lead to impaired performance. The present studies tested the hypothesis that 1 learning to behaviorally control stressors leads to improved performance on a test of general executive functioning, the color-word Stroop, and that 2 this improvement emerges specifically for people who report moderate (subjective responses to stress. Experiment 1: Stroop performance, measured before and after a stress manipulation, was compared across groups of undergraduate participants (n=109. People who learned to control a noise stressor and received accurate performance feedback demonstrated reduced Stroop interference compared with people exposed to uncontrollable noise stress and feedback indicating an exaggerated rate of failure. In the group who learned behavioral control, those who reported moderate levels of stress showed the greatest reduction in Stroop interference. In contrast, in the group exposed to uncontrollable events, self-reported stress failed to predict performance. Experiment 2: In a second sample (n=90, we specifically investigated the role of controllability by keeping the rate of failure feedback constant across groups. In the group who learned behavioral control, those who reported moderate levels of stress

  12. Salubrious effects of oxytocin on social stress-induced deficits

    Science.gov (United States)

    Smith, Adam S.; Wang, Zuoxin

    2012-01-01

    Social relationships are a fundamental aspect of life, affecting social, psychological, physiological, and behavioral functions. While social interactions can attenuate stress and promote health, disruption, confrontations, isolation, or neglect in the social environment can each be major stressors. Social stress can impair the basal function and stress-induced activation of the hypothalamic-pituitary-adrenal (HPA) axis, impairing function of multiple biological systems and posing a risk to mental and physical health. In contrast, social support can ameliorate stress-induced physiological and immunological deficits, reducing the risk of subsequent psychological distress and improving an individual's overall well-being. For better clinical treatment of these physiological and mental pathologies, it is necessary to understand the regulatory mechanisms of stress-induced pathologies as well as determine the underlying biological mechanisms that regulate social buffering of the stress system. A number of ethologically relevant animal models of social stress and species that form strong adult social bonds have been utilized to study the etiology, treatment, and prevention of stress-related disorders. While undoubtedly a number of biological pathways contribute to the social buffering of the stress response, the convergence of evidence denotes the regulatory effects of oxytocin in facilitating social bond-promoting behaviors and their effect on the stress response. Thus, oxytocin may be perceived as a common regulatory element of the social environment, stress response, and stress-induced risks on mental and physical health. PMID:22178036

  13. Photoelastic stress investigation in underground large hole in permafrost soil (statics, thermoelasticity, dynamics, photoelastic strain-gauges)

    Science.gov (United States)

    Savostjanov, V. N.; Dvalishvili, V. V.; Sakharov, V. N.; Isajkin, A. S.; Frishter, L.; Starchevsky, A. V.

    1991-12-01

    The development of many-year-frost rock (MYFR) region hydrotechnic construction, the MYFR being quite a reliable construction based provided it is situated outside the seasonal temperature fluctuation layer, requires the rock stress-deformed state evaluating criteria working out with maximal possible account of static, dynamic, blast-hole drilling, and temperature effect on their properties. In estimating the hydroelectrical power station (HPS) underground building stress-deformed state the present work refers to experimental data and calculations, received by solving a linear task with further account of the building profile changing effect in the process of construction and the concrete and rock mechanic properties heterogeneity. The proposed order is justified, provided the rock mass defrosting depth value is small as compared to the rock separate block dimensions and it corresponds to the building construction period. The results are given for the Kolymskaya Hydroelectrical Power Station building cross-section, considered under flat deformation conditions.

  14. Effectiveness of a Dental Students Stress Management Program

    Directory of Open Access Journals (Sweden)

    Abdullah M. Alzahem

    2015-12-01

    Full Text Available The dental education stress effects and sources were explored thoroughly in the literature, but the effectiveness of stress management programs received less attention. This study introduced a new stress management program, named Dental Education Stress Management (DESM program. It showed its effectiveness in a quasi-experimental pretest-posttest-follow-up-control group design. The new program was based on the principle of psychoeducation and consisted of three 90-min sessions, to teach dental students how to better deal with their stress symptoms and to reduce their general stress level. Two instruments were used to assess the level of stress of the dental students, namely the Dental Environment Stress questionnaire (DES, and the Psychological Stress Measure (PSM-9. Results show that the DESM program has the desired effect of decreasing the stress levels of its participants, and these effects lasted for at least two weeks. Because of several methodological limitations of the study more research is needed to draw more generalizable conclusions.

  15. The Dichotomous Effect of Chronic Stress on Obesity.

    Science.gov (United States)

    Razzoli, Maria; Bartolomucci, Alessandro

    2016-07-01

    Obesity and metabolic diseases are linked to chronic stress and low socioeconomic status. The mechanistic link between stress and obesity has not been clarified, partly due to the inherent complexity exemplified by the bidirectional effect of stress on eating and body weight. Recent studies focusing on adaptive thermogenesis and brown adipose tissue (BAT) function support a dichotomous relation to explain the impact of stress on obesity: stress promotes obesity in the presence of hyperphagia and unchanged BAT function; stress results in weight loss and/or obesity resistance in the presence of hypophagia, or when hyperphagia is associated with BAT recruitment and enhanced thermogenesis. Mechanistically dissecting the bidirectional effects of stress on metabolic outcomes might open new avenues for innovative pharmacotherapies for the treatment of obesity-associated diseases. Copyright © 2016 Elsevier Ltd. All rights reserved.

  16. Effects of stress typicality during speeded grammatical classification.

    Science.gov (United States)

    Arciuli, Joanne; Cupples, Linda

    2003-01-01

    The experiments reported here were designed to investigate the influence of stress typicality during speeded grammatical classification of disyllabic English words by native and non-native speakers. Trochaic nouns and iambic gram verbs were considered to be typically stressed, whereas iambic nouns and trochaic verbs were considered to be atypically stressed. Experiments 1a and 2a showed that while native speakers classified typically stressed words individual more quickly and more accurately than atypically stressed words during differences reading, there were no overall effects during classification of spoken stimuli. However, a subgroup of native speakers with high error rates did show a significant effect during classification of spoken stimuli. Experiments 1b and 2b showed that non-native speakers classified typically stressed words more quickly and more accurately than atypically stressed words during reading. Typically stressed words were classified more accurately than atypically stressed words when the stimuli were spoken. Importantly, there was a significant relationship between error rates, vocabulary size and the size of the stress typicality effect in each experiment. We conclude that participants use information about lexical stress to help them distinguish between disyllabic nouns and verbs during speeded grammatical classification. This is especially so for individuals with a limited vocabulary who lack other knowledge (e.g., semantic knowledge) about the differences between these grammatical categories.

  17. Effect of food intake on left ventricular wall stress.

    Science.gov (United States)

    Gårdinger, Ylva; Hlebowicz, Joanna; Björgell, Ola; Dencker, Magnus

    2014-01-28

    Left ventricular wall stress has been investigated in a variety of populations, but the effect of food intake has not been evaluated. We assessed whether left ventricular wall stress is affected by food intake in healthy subjects. Twenty-three healthy subjects aged 25.6 ± 4.5 years were investigated. Meridional end-systolic wall stress (ESS) and circumferential end-systolic wall stress (cESS) were measured before, 30 minutes after, and 110 minutes after a standardised meal. Both ESS and cESS decreased significantly (P stress is affected by food intake in healthy subjects.

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

    DEFF Research Database (Denmark)

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

    2012-01-01

    The Effective stress coefficient is a measure of how chalk grains are connected with each other. The stiffness of chalk may decrease if the amount of contact cements between the grains decreases, which may lead to an increase of the effective stress coefficient. We performed CO2 injection in chal...... precise failure strength of chalk during changed stress state and under the influence of chemically reactive fluids during production of hydrocarbon and geological storage CO2....

  19. Effect of magnetic attachment with stress breaker on lateral stress to abutment tooth under overdenture.

    Science.gov (United States)

    Gonda, T; Ikebe, K; Ono, T; Nokubi, T

    2004-10-01

    Recently, a newly developed magnetic attachment with stress breaker was used in retentive components in overdentures. Excessive lateral stress has a more harmful effect on natural teeth than axial stress, and the magnetic attachment with stress breaker is expected to reduce lateral forces on abutment teeth and protect it teeth from excessive stress. However, the properties of this retainer have not yet been determined experimentally. This study compares the lateral forces on abutment teeth for three retainers under loading on the denture base in a model study. A mandibular simulation model is constructed to measure lateral stress. Three types of retentive devices are attached to the canine root. These devices include the conventional root coping, the conventional magnetic attachment and the new magnetic attachment with stress breaker. For each retentive device, load is generated on the occlusal table of the model overdenture, and the lateral stress on the canine root and the displacement of the overdenture measured. The magnetic attachment with stress breaker does not displace the denture and exhibits lower lateral stress in the canine root than conventional root coping and magnetic attachments.

  20. Effects of Stress Inoculation Training on Anxiety, Stress, and Academic Performance among Adolescents.

    Science.gov (United States)

    Kiselica, Mark S.; And Others

    1994-01-01

    Examined effectiveness of preventive stress inoculation program for adolescents (n=48) that consisted of progressive muscle relaxation, cognitive restructuring, and assertiveness training. Compared with control subjects, trainees showed significantly greater improvements on self-report measures of trait anxiety and stress-related symptoms at…

  1. Effective Stress Management: A Model of Emotional Intelligence, Self-Leadership, and Student Stress Coping

    Science.gov (United States)

    Houghton, Jeffery D.; Wu, Jinpei; Godwin, Jeffrey L.; Neck, Christopher P.; Manz, Charles C.

    2012-01-01

    This article develops and presents a model of the relationships among emotional intelligence, self-leadership, and stress coping among management students. In short, the authors' model suggests that effective emotion regulation and self-leadership, as mediated through positive affect and self-efficacy, has the potential to facilitate stress coping…

  2. Stressful life events and depression symptoms: the effect of childhood emotional abuse on stress reactivity.

    Science.gov (United States)

    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.

  3. The effect of additional equilibrium stress functions on the three-node hybrid-mixed curved beam element

    International Nuclear Information System (INIS)

    Kim, Jin Gon; Park, Yong Kuk

    2008-01-01

    To develop an effective hybrid-mixed element, it is extremely critical as to how to assume the stress field. This research article demonstrates the effect of additional equilibrium stress functions to enhance the numerical performance of the locking-free three-node hybrid-mixed curved beam element, proposed in Saleeb and Chang's previous work. It is exceedingly complicated or even infeasible to determine the stress functions to satisfy fully both the equilibrium conditions and suppression of kinematic deformation modes in the three-node hybrid-mixed formulation. Accordingly, the additional stress functions to satisfy partially or fully equilibrium conditions are incorporated in this study. Several numerical examples for static and dynamic problems confirm that the newly proposed element with these additional stress functions is highly effective regardless of the slenderness ratio and curvature of arches in static and dynamic analyses

  4. A Modified Split Hopkinson Pressure Bar Approach for Mimicking Dynamic Oscillatory Stress Fluctuations During Earthquake Rupture

    Science.gov (United States)

    Braunagel, M. J.; Griffith, W. A.

    2017-12-01

    Past experimental work has demonstrated that rock failure at high strain rates occurs by fragmentation rather than discrete fracture and is accompanied by a dramatic increase in rock strength. However, these observations are difficult to reconcile with the assertion that pulverized rocks in fault zones are the product of impulsive stresses during the passage of earthquake ruptures, as the distance from the principal slip zones of some pulverized rock is too great to exceed fragmentation transition. One potential explanation to this paradox that has been suggested is that repeated loading over the course of multiple earthquake ruptures may gradually reduce the pulverization threshold, in terms of both strain rate and strength. We propose that oscillatory loading during a single earthquake rupture may further lower these pulverization thresholds, and that traditional dynamic experimental approaches, such as the Split Hopkinson Pressure Bar (SHPB) wherein load is applied as a single, smooth, sinusoidal compressive wave, may not reflect natural loading conditions. To investigate the effects of oscillatory compressive loading expected during earthquake rupture propagation, we develop a controlled cyclic loading model on a SHPB apparatus utilizing two striker bars connected by an elastic spring. Unlike traditional SHPB experiments that utilize a gas gun to fire a projectile bar and generate a single compressive wave on impact with the incident bar, our modified striker bar assembly oscillates while moving down the gun barrel and generates two separate compressive pulses separated by a lag time. By modeling the modified assembly as a mass-spring-mass assembly accelerating due to the force of the released gas, we can predict the compression time of the spring upon impact and therefore the time delay between the generation of the first and second compressive waves. This allows us to predictably control load cycles with durations of only a few hundred microseconds. Initial

  5. Biological effects of laser-induced stress waves

    International Nuclear Information System (INIS)

    Doukas, A.; Lee, S.; McAuliffe, D.

    1995-01-01

    Laser-induced stress waves can be generated by one of the following mechanisms: Optical breakdown, ablation or rapid heating of an absorbing medium. These three modes of laser interaction with matter allow the investigation of cellular and tissue responses to stress waves with different characteristics and under different conditions. The most widely studied phenomena are those of the collateral damage seen in photodisruption in the eye and in 193 run ablation of cornea and skin. On the other hand, the therapeutic application of laser-induced stress waves has been limited to the disruption of noncellular material such as renal stones, atheromatous plaque and vitreous strands. The effects of stress waves to cells and tissues can be quite disparate. Stress waves can fracture tissue, damage cells, and increase the permeability of the plasma membrane. The viability of cell cultures exposed to stress waves increases with the peak stress and the number of pulses applied. The rise time of the stress wave also influences the degree of cell injury. In fact, cell viability, as measured by thymidine incorporation, correlates better with the stress gradient than peak stress. Recent studies have also established that stress waves induce a transient increase of the permeability of the plasma membrane in vitro. In addition, if the stress gradient is below the damage threshhold, the cells remain viable. Thus, stress waves can be useful as a means of drug delivery, increasing the intracellular drug concentration and allowing the use of drugs which are impermeable to the cell membrane. The present studies show that it is important to create controllable stress waves. The wavelength tunability and the micropulse structure of the free electron laser is ideal for generating stress waves with independently adjustable parameters, such as rise time, duration and peak stress

  6. A Dynamic Model of Post-Traumatic Stress Disorder for Military Personnel and Veterans.

    Directory of Open Access Journals (Sweden)

    Navid Ghaffarzadegan

    Full Text Available Post-traumatic stress disorder (PTSD stands out as a major mental illness; however, little is known about effective policies for mitigating the problem. The importance and complexity of PTSD raise critical questions: What are the trends in the population of PTSD patients among military personnel and veterans in the postwar era? What policies can help mitigate PTSD? To address these questions, we developed a system dynamics simulation model of the population of military personnel and veterans affected by PTSD. The model includes both military personnel and veterans in a "system of systems." This is a novel aspect of our model, since many policies implemented at the military level will potentially influence (and may have side effects on veterans and the Department of Veterans Affairs. The model is first validated by replicating the historical data on PTSD prevalence among military personnel and veterans from 2000 to 2014 (datasets from the Department of Defense, the Institute of Medicine, the Department of Veterans Affairs, and other sources. The model is then used for health policy analysis. Our results show that, in an optimistic scenario based on the status quo of deployment to intense/combat zones, estimated PTSD prevalence among veterans will be at least 10% during the next decade. The model postulates that during wars, resiliency-related policies are the most effective for decreasing PTSD. In a postwar period, current health policy interventions (e.g., screening and treatment have marginal effects on mitigating the problem of PTSD, that is, the current screening and treatment policies must be revolutionized to have any noticeable effect. Furthermore, the simulation results show that it takes a long time, on the order of 40 years, to mitigate the psychiatric consequences of a war. Policy and financial implications of the findings are discussed.

  7. A Dynamic Model of Post-Traumatic Stress Disorder for Military Personnel and Veterans

    Science.gov (United States)

    Ghaffarzadegan, Navid; Ebrahimvandi, Alireza; Jalali, Mohammad S.

    2016-01-01

    Post-traumatic stress disorder (PTSD) stands out as a major mental illness; however, little is known about effective policies for mitigating the problem. The importance and complexity of PTSD raise critical questions: What are the trends in the population of PTSD patients among military personnel and veterans in the postwar era? What policies can help mitigate PTSD? To address these questions, we developed a system dynamics simulation model of the population of military personnel and veterans affected by PTSD. The model includes both military personnel and veterans in a “system of systems.” This is a novel aspect of our model, since many policies implemented at the military level will potentially influence (and may have side effects on) veterans and the Department of Veterans Affairs. The model is first validated by replicating the historical data on PTSD prevalence among military personnel and veterans from 2000 to 2014 (datasets from the Department of Defense, the Institute of Medicine, the Department of Veterans Affairs, and other sources). The model is then used for health policy analysis. Our results show that, in an optimistic scenario based on the status quo of deployment to intense/combat zones, estimated PTSD prevalence among veterans will be at least 10% during the next decade. The model postulates that during wars, resiliency-related policies are the most effective for decreasing PTSD. In a postwar period, current health policy interventions (e.g., screening and treatment) have marginal effects on mitigating the problem of PTSD, that is, the current screening and treatment policies must be revolutionized to have any noticeable effect. Furthermore, the simulation results show that it takes a long time, on the order of 40 years, to mitigate the psychiatric consequences of a war. Policy and financial implications of the findings are discussed. PMID:27716776

  8. Overcoming the effects of stress on reactor operator performance

    International Nuclear Information System (INIS)

    He Xuhong; Wei Li; Zhao Bingquan

    2003-01-01

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

  9. Effect of stress on turbine fish passage mortality estimates

    International Nuclear Information System (INIS)

    Ruggles, C.P.

    1993-01-01

    Tests were conducted with juvenile alewife to determine the effects of four experimental protocols upon turbine fish passage mortality estimates. Three protocols determined the effect of cumulative stresses upon fish, while the fourth determined the effect of long range truck transportation prior to release into the penstock or tailrace. The wide range in results were attributed to the presence or absence of additional stress factors associated with the experiments. For instance, fish may survive passage through a turbine, or non-turbine related stresses imposed by the investigator; however, when both are imposed, the cumulative stresses may be lethal. The impact of protocol stress on turbine mortality estimates becomes almost exponential after control mortality exceeds 10%. Valid turbine related mortalities may be determined only after stresses associated with experimental protocol are adequately reduced. This is usually indicated by a control mortality of less than 10%. 14 refs., 5 figs., 6 tabs

  10. Overcoming the effects of stress on reactor operator performance

    Energy Technology Data Exchange (ETDEWEB)

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

    2003-03-01

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

  11. Contrast-induced nephrotoxicity: possible synergistic effect of stress hyperglycemia.

    LENUS (Irish Health Repository)

    O'Donnell, David H

    2010-07-01

    Oxidative stress on the renal tubules has been implicated as a mechanism of injury in both stress hyperglycemia and contrast-induced nephrotoxicity. The purpose of this study was to determine whether the combination of these effects has a synergistic effect on accentuating renal tubular apoptosis and therefore increasing the risk of contrast-induced nephrotoxicity.

  12. [Effect of occupational stress on neurotransmitters in petroleum workers].

    Science.gov (United States)

    Jiang, Yu; Lian, Yulong; Tao, Ning; Ge, Hua; Liu, Jiwen

    2015-09-01

    To explore the effects of occupational stress on neurotransmitters in petroleum workers. 178 petroleum workers with the length of service ≥ 1 year were recruited to the subjects by the questionnaire of OSI-R. The levels of 5-hydroxy tryptamine (5-HT), norepinephrine (NE), neuropeptide Y (NPY) and substance P (SP) in serum were measured. The subjects were classified into 3 groups according to the scores of occupational stress. The levels of 5-HT NE and SP for over 15 working years were higher than those of less than 15 years (P occupational stress degree groups, multiple comparison showed high. occupational stress group was higher than those of low occupational stress group. Multivariate correlation analysis showed that the occupational stress and sleep quality component scores correlated positively with the 5-HT, NE and SP (P Occupational stress in petroleum workers is correlated with serum monoamine and neuropeptides neurotransmitters, and it may affect serum levels of monoamine and neuropeptides neurotransmitters.

  13. Nonlinear dynamics of a flexible rotor supported by turbulent journal bearings with couple stress fluid

    International Nuclear Information System (INIS)

    Lo, C.-Y.; Chang-Jian, C.-W.

    2008-01-01

    This study presents a dynamic analysis of a rotor supported by two turbulent flow model journal bearings and lubricated with couple stress fluid under nonlinear suspension. The dynamics of the rotor center and bearing center is studied. The dynamic equations are solved using the Runge-Kutta method. The analysis methods employed in this study is inclusive of the dynamic trajectories of the rotor center and bearing center, power spectra, Poincare maps and bifurcation diagrams. The maximum Lyapunov exponent analysis is also used to identify the onset of chaotic motion. The results show that the values of dimensionless parameters l* strongly influence dynamic motions of bearing and rotor centre. It is found that couple stress fluid improve the stability of the system when l* > 0.4 even if the flow of this system is turbulent. We also demonstrated that the dimensionless rotational speed ratios s and the dimensionless unbalance parameter β are also significant system parameters. The modeling results thus obtained by using the method proposed in this paper can be employed to predict the stability of the rotor-bearing system and the undesirable behavior of the rotor and bearing center can be avoided

  14. Dynamics of Mount Somma-Vesuvius edifice: from stress field inversion to analogue and numerical modelling

    Science.gov (United States)

    De Matteo, Ada; Massa, Bruno; D'Auria, Luca; Castaldo, Raffaele

    2017-04-01

    Geological processes are generally very complex and too slow to be directly observed in their completeness; modelling procedures overcome this limit. The state of stress in the upper lithosphere is the main responsible for driving geodynamical processes; in order to retrieve the active stress field in a rock volume, stress inversion techniques can be applied on both seismological and structural datasets. This approach has been successfully applied to active tectonics as well as volcanic areas. In this context the best approach in managing heterogeneous datasets in volcanic environments consists in the analysis of spatial variations of the stress field by applying robust techniques of inversion. The study of volcanic seismicity is an efficient tool to retrieve spatial and temporal pattern of the pre-, syn- and inter-eruptive stress field: magma migration as well as dynamics of magma chamber and hydrothermal system are directly connected to the volcanic seismicity. Additionally, analysis of the temporal variations of stress field pattern in volcanoes could be a useful monitoring tool. Recently the stress field acting on several active volcanoes has been investigated by using stress inversion techniques on seismological datasets (Massa et al., 2016). The Bayesian Right Trihedra Method (BRTM; D'Auria and Massa, 2015) is able to successfully manage heterogeneous datasets allowing the identification of regional fields locally overcame by the stress field due to volcano specific dynamics. In particular, the analysis of seismicity and stress field inversion at the Somma-Vesuvius highlighted the presence of two superposed volumes characterized by different behaviour and stress field pattern: a top volume dominated by an extensional stress field, in accordance with a gravitational spreading-style of deformation, and a bottom volume related to a regional extensional stress field. In addition, in order to evaluate the dynamics of deformation, both analogue and numerical

  15. Extension to linear dynamics for hybrid stress finite element formulation based on additional displacements

    Science.gov (United States)

    Sumihara, K.

    Based upon legitimate variational principles, one microscopic-macroscopic finite element formulation for linear dynamics is presented by Hybrid Stress Finite Element Method. The microscopic application of Geometric Perturbation introduced by Pian and the introduction of infinitesimal limit core element (Baby Element) have been consistently combined according to the flexible and inherent interpretation of the legitimate variational principles initially originated by Pian and Tong. The conceptual development based upon Hybrid Finite Element Method is extended to linear dynamics with the introduction of physically meaningful higher modes.

  16. Stability of cracked pipe under seismic/dynamic displacement-controlled stresses. Subtask 1.2 final report

    International Nuclear Information System (INIS)

    Kramer, G.; Veith, P.; Marschall, C.

    1997-06-01

    Results of displacement-controlled pipe fracture experiments, analyses, and material characterization efforts performed within the International Piping Integrity Research Group, IPIRG, Program Subtask 1.2 are discussed. Effects of dynamic versus quasi-static and monotonic versus cyclic loading were evaluated for ductile tearing of two materials, A106 Grade B ferritic steel and TP304 austenitic steel. Twelve through-wall-cracked pipe experiments were conducted on 6-inch diameter Schedule 120 pipe at 288 C (550 F). The results indicated dynamic loading at seismic strain rates marginally increased the load-carrying capacity of austenitic steel. The ferritic steel tested was sensitive to dynamic strain-aging, and consequently, its load-carrying capacity decreased at dynamic strain rates. Two parameters were found to affect the apparent ductile crack growth resistance during cyclic loading, load ratio (R) and incremental plastic displacement that occurs in a cycle. Cyclic (R = 0) loading had minimal effect on ductile tearing for both materials. However, fully reversed loading decreased the load-carrying capacity and toughness for both materials. The incremental plastic displacement can be as important as the load ratio; however, it is harder to quantify from design stress reports. Large plastic displacements will minimize the effect of negative load ratios

  17. Effects of anger regulation and social anxiety on perceived stress

    Directory of Open Access Journals (Sweden)

    Ayano Yamaguchi

    2015-08-01

    Full Text Available The mediating role of social anxiety was explored within the effect of anger regulation on perceived stress in the national sample of American and Japanese older adults. Results indicated that anger suppression is a significant factor in perceived stress mediated by social anxiety. Anger suppression was also directly related to perceived stress. The correlation of anger suppression with social anxiety was stronger in Japan than in the United States. Understanding both universal and culture-specific aspects of emotion regulation and perceived stress will be essential for the development of sound theory, future research, and effective prevention and intervention efforts.

  18. Cardiorespiratory dynamic response to mental stress: a multivariate time-frequency analysis.

    Science.gov (United States)

    Widjaja, Devy; Orini, Michele; Vlemincx, Elke; Van Huffel, Sabine

    2013-01-01

    Mental stress is a growing problem in our society. In order to deal with this, it is important to understand the underlying stress mechanisms. In this study, we aim to determine how the cardiorespiratory interactions are affected by mental arithmetic stress and attention. We conduct cross time-frequency (TF) analyses to assess the cardiorespiratory coupling. In addition, we introduce partial TF spectra to separate variations in the RR interval series that are linearly related to respiration from RR interval variations (RRV) that are not related to respiration. The performance of partial spectra is evaluated in two simulation studies. Time-varying parameters, such as instantaneous powers and frequencies, are derived from the computed spectra. Statistical analysis is carried out continuously in time to evaluate the dynamic response to mental stress and attention. The results show an increased heart and respiratory rate during stress and attention, compared to a resting condition. Also a fast reduction in vagal activity is noted. The partial TF analysis reveals a faster reduction of RRV power related to (3 s) than unrelated to (30 s) respiration, demonstrating that the autonomic response to mental stress is driven by mechanisms characterized by different temporal scales.

  19. Topography on a subcellular scale modulates cellular adhesions and actin stress fiber dynamics in tumor associated fibroblasts

    Science.gov (United States)

    Azatov, Mikheil; Sun, Xiaoyu; Suberi, Alexandra; Fourkas, John T.; Upadhyaya, Arpita

    2017-12-01

    Cells can sense and adapt to mechanical properties of their environment. The local geometry of the extracellular matrix, such as its topography, has been shown to modulate cell morphology, migration, and proliferation. Here we investigate the effect of micro/nanotopography on the morphology and cytoskeletal dynamics of human pancreatic tumor-associated fibroblast cells (TAFs). We use arrays of parallel nanoridges with variable spacings on a subcellular scale to investigate the response of TAFs to the topography of their environment. We find that cell shape and stress fiber organization both align along the direction of the nanoridges. Our analysis reveals a strong bimodal relationship between the degree of alignment and the spacing of the nanoridges. Furthermore, focal adhesions align along ridges and form preferentially on top of the ridges. Tracking actin stress fiber movement reveals enhanced dynamics of stress fibers on topographically patterned surfaces. We find that components of the actin cytoskeleton move preferentially along the ridges with a significantly higher velocity along the ridges than on a flat surface. Our results suggest that a complex interplay between the actin cytoskeleton and focal adhesions coordinates the cellular response to micro/nanotopography.

  20. QTAIM and Stress Tensor Characterization of Intramolecular Interactions Along Dynamics Trajectories of a Light-Driven Rotary Molecular Motor.

    Science.gov (United States)

    Wang, Lingling; Huan, Guo; Momen, Roya; Azizi, Alireza; Xu, Tianlv; Kirk, Steven R; Filatov, Michael; Jenkins, Samantha

    2017-06-29

    A quantum theory of atoms in molecules (QTAIM) and stress tensor analysis was applied to analyze intramolecular interactions influencing the photoisomerization dynamics of a light-driven rotary molecular motor. For selected nonadiabatic molecular dynamics trajectories characterized by markedly different S 1 state lifetimes, the electron densities were obtained using the ensemble density functional theory method. The analysis revealed that torsional motion of the molecular motor blades from the Franck-Condon point to the S 1 energy minimum and the S 1 /S 0 conical intersection is controlled by two factors: greater numbers of intramolecular bonds before the hop-time and unusually strongly coupled bonds between the atoms of the rotor and the stator blades. This results in the effective stalling of the progress along the torsional path for an extended period of time. This finding suggests a possibility of chemical tuning of the speed of photoisomerization of molecular motors and related molecular switches by reshaping their molecular backbones to decrease or increase the degree of coupling and numbers of intramolecular bond critical points as revealed by the QTAIM/stress tensor analysis of the electron density. Additionally, the stress tensor scalar and vector analysis was found to provide new methods to follow the trajectories, and from this, new insight was gained into the behavior of the S 1 state in the vicinity of the conical intersection.

  1. A Laboratory Study of the Effect of Stress State on the Elastic Moduli of Sand

    Science.gov (United States)

    1990-01-01

    frequency. Drnevich (1967) investigated the effect of strain history on the dynamic properties of a dry Ottawa sand. One finding of his work was that the...2.2) in which jo = effective octahedral normal stress, e = void ratio, H = ambient stress and vibration history , S - de9,ee of saturation, To...zt) = ik[Cei(kz-wt) - De-i(kz+Wt) (3.20) dz I Substituting Eqs. 3.19 and 3.20 into the second boundary condition at z - L yields ikEA [Cei(kL-cot

  2. Dying piece by piece: carbohydrate dynamics in aspen seedlings under severe carbon stress and starvation

    Science.gov (United States)

    Wiley, Erin; Chow, Pak; Landhäusser, Simon

    2016-04-01

    Carbon stress and starvation remain poorly understood in trees, despite their potential role in mortality from a variety of agents. To explore the effects of carbon stress on nonstructural carbohydrate (NSC) dynamics and recovery potential and to examine the process of starvation, we grew aspen seedlings under one of three levels of shade: 40% (light shade), 8% (medium shade), and 4% (dark shade) of full sunlight. We then exposed seedlings to 24 hours darkness at either 20° or 28° C until trees had died. Periodically, seedlings were harvested for NSC analysis and to measure stem and root respiration. In addition, some seedlings were moved back into the light to determine if recovery was possible at certain points during starvation. Specifically, we sought to address the following questions: 1) Do NSC concentrations or mass influence tree survival under carbon stress? 2) At what carbohydrate levels do trees fail to recover and starve? 3) Does temperature affect the NSC level at which trees starve? Increasing shade reduced growth, but surprisingly did not reduce NSC levels, except in a portion of deep shade seedlings that experienced dieback. Once in darkness, leaves died first, with final NSC levels ranging from ~4% (Medium shade, 28 degrees) to 7.5% (Light shade). Stem death generally occurred gradually down the stem. Stem tissues retained ~1-2% NSC when dead. Recovery was still possible when only the upper half of the stem had died; at this point, seedlings had relatively high root NSC levels in their remaining roots (7-10%), with 1-3% starch. No trees recovered after the whole stem had died, at which point, some trees root systems were completely dead. However, most retained substantial amounts of live roots, averaging 5-6% NSC, with 0.25-1.5% starch. Despite the initially similar NSC concentrations, light shade seedlings took longer to reach half stem and whole stem death than seedlings from medium and dark shade. Longer survival times were associated with

  3. Stress and Memory: Behavioral Effects and Neurobiological Mechanisms

    Directory of Open Access Journals (Sweden)

    M. Teresa Pinelo-Nava

    2007-04-01

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

  4. Stress

    Science.gov (United States)

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

  5. Inertial effects on the stress generation of active fluids

    Science.gov (United States)

    Takatori, S. C.; Brady, J. F.

    2017-09-01

    Suspensions of self-propelled bodies generate a unique mechanical stress owing to their motility that impacts their large-scale collective behavior. For microswimmers suspended in a fluid with negligible particle inertia, we have shown that the virial swim stress is a useful quantity to understand the rheology and nonequilibrium behaviors of active soft matter systems. For larger self-propelled organisms such as fish, it is unclear how particle inertia impacts their stress generation and collective movement. Here we analyze the effects of finite particle inertia on the mechanical pressure (or stress) generated by a suspension of self-propelled bodies. We find that swimmers of all scales generate a unique swim stress and Reynolds stress that impact their collective motion. We discover that particle inertia plays a similar role as confinement in overdamped active Brownian systems, where the reduced run length of the swimmers decreases the swim stress and affects the phase behavior. Although the swim and Reynolds stresses vary individually with the magnitude of particle inertia, the sum of the two contributions is independent of particle inertia. This points to an important concept when computing stresses in computer simulations of nonequilibrium systems: The Reynolds and the virial stresses must both be calculated to obtain the overall stress generated by a system.

  6. Stretching the Stress Boundary: Linking Air Pollution Health Effects to a Neurohormonal Stress Response

    Science.gov (United States)

    Inhaled pollutants produce effects in virtually all organ systems in our body and have been linked to chronic diseases including hypertension, atherosclerosis, Alzheimer’s and diabetes. A neurohormonal stress response (referred here as a systemic response produced by activation ...

  7. Dynamic interaction effects in cooling tower groups

    International Nuclear Information System (INIS)

    Riera, J.D.

    1984-01-01

    A theoretical and experimental determination of the dynamic response of reinforced concrete cooling towers, taking into consideration group effects, are described. The results for an individual tower are thoroughly examined. A complete analysis is then performed for the critical wind orientations, for each tower in a six towers group. It's shown that ignoring group effects in the analysis may lead to a significant underestimation of the structural response. (E.G.) [pt

  8. Effect of coal stress on grain size of the gotten

    Energy Technology Data Exchange (ETDEWEB)

    Sikora, W; Tront, A

    1988-09-01

    Presents investigation results on the effect of seam stress and strain state on winning as measured by the grain size of the gotten. The investigations were carried out at the Institute of Mining Mechanization of the Silesian Politechnical where the relations between parameters of seams and cutters and their effect on coal grain size and energy consumption have been studied for several years. The effect was examined on coal samples taken from 4 mines in the Upper Silesian coal basin using a model of the system: seam - cutter. Cubic samples (400x400x400 mm) were tested on the CMG KOMAG test stand equipped with the POS-1 cutting apparatus. Two types of coal were distinguished: that particularly sensitive to increased pressure on seam and that only negligibly susceptible. Corresponding graphs of coal grain size versus vertical pressure are shown. A function has been developed that characterizes this sensitivity depending on a material parameter that can be determined by workability tests. The relationship between coal strength and grain size yield greater than 10 mm in the gotten depending on dynamic crushability of coal is shown in graphs. 6 refs.

  9. Environmental stresses can alleviate the average deleterious effect of mutations

    Directory of Open Access Journals (Sweden)

    Leibler Stanislas

    2003-05-01

    Full Text Available Abstract Background Fundamental questions in evolutionary genetics, including the possible advantage of sexual reproduction, depend critically on the effects of deleterious mutations on fitness. Limited existing experimental evidence suggests that, on average, such effects tend to be aggravated under environmental stresses, consistent with the perception that stress diminishes the organism's ability to tolerate deleterious mutations. Here, we ask whether there are also stresses with the opposite influence, under which the organism becomes more tolerant to mutations. Results We developed a technique, based on bioluminescence, which allows accurate automated measurements of bacterial growth rates at very low cell densities. Using this system, we measured growth rates of Escherichia coli mutants under a diverse set of environmental stresses. In contrast to the perception that stress always reduces the organism's ability to tolerate mutations, our measurements identified stresses that do the opposite – that is, despite decreasing wild-type growth, they alleviate, on average, the effect of deleterious mutations. Conclusions Our results show a qualitative difference between various environmental stresses ranging from alleviation to aggravation of the average effect of mutations. We further show how the existence of stresses that are biased towards alleviation of the effects of mutations may imply the existence of average epistatic interactions between mutations. The results thus offer a connection between the two main factors controlling the effects of deleterious mutations: environmental conditions and epistatic interactions.

  10. The dynamics of stress and fatigue across menopause: attractors, coupling, and resilience.

    Science.gov (United States)

    Taylor-Swanson, Lisa; Wong, Alexander E; Pincus, David; Butner, Jonathan E; Hahn-Holbrook, Jennifer; Koithan, Mary; Wann, Kathryn; Woods, Nancy F

    2018-04-01

    The objective of this study was to evaluate the regulatory dynamics between stress and fatigue experienced by women during the menopausal transition (MT) and early postmenopause (EPM). Fatigue and perceived stress are commonly experienced by women during the MT and EPM. We sought to discover relationships between these symptoms and to employ these symptoms as possible markers for resilience. Participants were drawn from the longitudinal Seattle Midlife Women's Health Study. Eligible women completed questionnaires on 60+ occasions (annual health reports and monthly health diaries) (n = 56 women). The total number of observations across the sample was 4,224. STRAW+10 criteria were used to stage women in either in late reproductive, early or late transition, or EPM stage. Change values were generated for fatigue and stress and analyzed with a multilevel structural equation model; slopes indicate how quickly a person returns to homeostasis after a perturbation. Coupling of stress and fatigue was modeled to evaluate resilience, the notion of maintaining stability during change. Eligible women were on average 35 years old (SD = 4.71), well educated, employed, married or partnered, and white. Fit indices suggested the model depicts the relationships of stress and fatigue (χ(9 df) = 7.638, P = 0.57, correction factor = 4.9244; root mean square error of approximation (RMSEA) 90% CI = 0.000 ≤ 0.000 ≤ 0.032; comparative fit index (CFI) = 1.00). A loss in model fit across stages suggests that the four stages differed in their dynamics (χΔ(12 df) = 21.181, P = .048). All stages showed fixed-point attractor dynamics: fatigue became less stable over time; stress generally became more stable over time. Coupling relationships of stress on fatigue show evidence for shifts in regulatory relationships with one another across the MT. Results are suggestive of general dysregulation via disruptions to coupling relationships of stress and

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

    International Nuclear Information System (INIS)

    Mumaw, R.J.

    1994-08-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

    Mumaw, R.J.

    1994-08-01

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

  13. Effects of Stress and MDMA on Hippocampal Gene Expression

    OpenAIRE

    Weber, Georg F.; Johnson, Bethann N.; Yamamoto, Bryan K.; Gudelsky, Gary A.

    2014-01-01

    MDMA (3,4-methylenedioxymethamphetamine) is a substituted amphetamine and popular drug of abuse. Its mood-enhancing short-term effects may prompt its consumption under stress. Clinical studies indicate that MDMA treatment may mitigate the symptoms of stress disorders such as posttraumatic stress syndrome (PTSD). On the other hand, repeated administration of MDMA results in persistent deficits in markers of serotonergic (5-HT) nerve terminals that have been viewed as indicative of 5-HT neuro...

  14. A study on the evaluation of dynamic stress intensity factor in repeated impact bending test

    International Nuclear Information System (INIS)

    Sim, Jae Ki; Cho, Gyu Jae; Han, Gill Young

    1988-01-01

    The purpose of the present paper was to establish the evaluation of the dynamic stress intensity factor in repeated impact three point bending test. Contact force between the impact bar and the cracked beam (simple supported beam) was analyzed by the using Hertz's contact law. In order to clarify the validity of theoretical analysis, experiments of dynamic stress intensity factir k I (t) are made on the cracked beam. The results obtained from this study are as follow: 1. In case of impact force analysis the theoretical result was obtained by the use of the Hertz's contact law. It's result was agreemant with the experimental result. Particularly, it was good agreement in the low impact velocity range. 2. The time variation of the dynamic stress intensity was determined by using the simple formula developed in this pqper. And the validity of it's result can be confirmed by experiment. Particlarly, this theoretical analysis was a good agreement to actual phenomena on from 0.3 msec to 0.65 msec. (Author)

  15. The Role of Musculoskeletal Dynamics and Neuromuscular Control in Stress Development in Bone

    Science.gov (United States)

    DeWoody, Yssa

    1996-01-01

    The role of forces produced by the musculotendon units in the stress development of the long bones during gait has not been fully analyzed. It is well known that the musculotendons act as actuators producing the joint torques which drive the body. Although the joint torques required to perform certain motor tasks can be recovered through a kinematic analysis, it remains a difficult problem to determine the actual forces produced by each muscle that resulted in these torques. As a consequence, few studies have focused on the role of individual muscles in the development of stress in the bone. This study takes a control theoretic approach to the problem. A seven-link, eight degrees of freedom model of the body is controlled by various muscle groups on each leg to simulate gait. The simulations incorporate Hill-type models of muscles with activation and contraction dynamics controlled through neural inputs. This direct approach allows one to know the exact muscle forces exerted by each musculotendon throughout the gait cycle as well the joint torques and reaction forces at the ankle and knee. Stress and strain computed by finite element analysis on skeletal members will be related to these derived loading conditions. Thus the role of musculoskeletal dynamics and neuromuscular control in the stress development of the tibia during gait can be analyzed.

  16. Forgiveness, Stress, and Health: a 5-Week Dynamic Parallel Process Study.

    Science.gov (United States)

    Toussaint, Loren L; Shields, Grant S; Slavich, George M

    2016-10-01

    Psychological stress is a well-known risk factor for poor health, and recent research has suggested that the emotion-focused coping process of forgiveness may help mitigate these effects. To date, however, no studies have examined how levels of forgiveness, stress, and health fluctuate and interrelate over time. We addressed this issue by examining how forgiveness, stress, and mental and physical health symptoms change and relate to one another over 5 weeks. We hypothesized that increases in state levels of forgiveness would be associated with decreases in perceptions of stress, which would in turn be related to decreases in mental and physical health symptoms. A reverse effects model was also tested. We recruited a large, community-based sample of 332 young, middle-aged, and older adults (16-79 years old; M age  = 27.9). Each week for 5 weeks, participants reported on their levels of state forgiveness, perceived stress, and mental and physical health symptoms. Levels of forgiveness, stress, and mental and physical health symptoms each showed significant change and individual variability in change over time. As hypothesized, increases in forgiveness were associated with decreases in stress, which were in turn related to decreases in mental (but not physical) health symptoms (i.e., forgiveness → stress → health). The reverse effects model (i.e., health → stress → forgiveness) provided a relatively poorer fit. This study is the first to provide prospective, longitudinal evidence showing that greater forgiveness is associated with less stress and, in turn, better mental health. Strategies for cultivating forgiveness may thus have beneficial effects on stress and health.

  17. Effects of Hospital Workers' Friendship Networks on Job Stress.

    Directory of Open Access Journals (Sweden)

    Sung Yae Shin

    Full Text Available This study attempted to identify the sources of job stress according to job position and investigate how friendship networks affect job stress.Questionnaires based on The Health Professions Stress Inventory (HPSI developed by Wolfgang experienced by healthcare providers were collected from 420 nurses, doctors and radiological technologists in two general hospitals in Korea by a multistage cluster sampling method. Multiple regression analysis was used to examine the effects of friendship networks on job stress after controlling for other factors.The severity of job stress differed according to level of job demands (p = .006; radiologic technologists experienced the least stress (45.4, nurses experienced moderate stress (52.4, and doctors experienced the most stress (53.6. Those with long-term friendships characterized by strong connections reported lower levels of stress than did those with weak ties to friends among nurses (1.3, p < .05 and radiological technologists (11.4, p < .01. The degree of cohesion among friends had a positive impact on the level of job stress experienced by nurses (8.2, p < .001 and radiological technologists (14.6, p < .1. Doctors who participated in workplace alumni meetings scored higher than those who did not. However, those who participated in alumni meetings outside the workplace showed the opposite tendency, scoring 9.4 (p < .05 lower than those who did not. The resources from their friendship network include both information and instrumental support. As most radiological technologists were male, their instrumental support positively affected their job stress (9.2, p < .05. Life information support was the primary positive contributor to control of nurses' (4.1, p < .05, radiological technologists' (8.0, p < .05 job stress.The strength and density of such friendship networks were related to job stress. Life information support from their friendship network was the primary positive contributor to control of job

  18. Salinity effects on the dynamics and patterns of desiccation cracks

    Science.gov (United States)

    Shokri, N.; Zhou, P.

    2012-12-01

    Cracking arising from desiccation is a ubiquitous phenomenon encountered in various industrial and geo-environmental applications including drying of clayey soil, cement, ceramics, gels, and many more colloidal suspensions. Presence of cracks in muddy sediments modifies the characteristics of the medium such as pore structure, porosity, and permeability which in turn influence various flow and transport processes. Thus it remains a topic of great interest in many disciplines to describe the dynamics of desiccation cracking under various boundary conditions. To this end, we conducted a comprehensive study to investigate effects of NaCl concentrations on cracking dynamics and patterns during desiccation of Bentonite. Mixtures of Bentonite and NaCl solutions were prepared with NaCl concentration varying from 2 to 10 percent in 0.5 percent increment (totally 17 configurations). The slurry was placed in a Petri dish mounted on a digital balance to record the evaporation dynamics. The atmospheric conditions were kept constant using an environmental chamber. An automatic camera was used to record the dynamics of macro-cracks (mm scale) at the surface of desiccating clay each minute. The obtained results illustrate the significant effects of salt concentration on the initiation, propagation, morphology and general dynamics of macro-cracks. We found that higher salt concentrations results in larger macro cracks' lengths attributed to the effects of NaCl on compressing the electric double layer of particles at increasing electrolyte concentrations which reduce considerably the repulsive forces among the particles and causing instability of the slurry and flocculation of the colloidal particles. Rheological measurements by means of a stress controlled rheometer revealed that the yield stress of the slurry decreases as NaCl concentration increases which may indicate aggregation of larger units in the slurry as a result of flocculation causing larger cracks' lengths due to

  19. Anti-stress effect of ethyl acetate soluble fraction of Morus alba in chronic restraint stress.

    Science.gov (United States)

    Nade, Vandana S; Yadav, Adhikrao V

    2010-09-01

    Restraint stress is a well-known method to induce chronic stress which leads to alterations in various behavioral and biochemical parameters. The present work was designed to study anti-stress effects of Morus alba in chronic restraint stress (RS)-induced perturbations in behavioral, biochemical and brain oxidative stress status. The stress was produced by restraining the animals inside an adjustable cylindrical plastic tube for 3 h once daily for ten consecutive days. The ethyl acetate soluble fraction of Morus alba (EASF) 25, 50, 100 mg/kg and diazepam (1 mg/kg) per day was administered 60 min prior to the stress procedure. The behavioral and biochemical parameters such as open field, cognitive dysfunction; leucocytes count; blood glucose and corticosteroid levels were determined. On day 10, the rats were sacrificed and biochemical assessment of superoxide dismutase (SOD), lipid peroxidation (LPO), catalase (CAT), and glutathione reductase (GSH) in whole rat brain were performed. Chronic restraint stress produced cognitive dysfunction, altered behavioral parameters, increased leucocytes count, SOD, LPO, glucose and corticosterone levels, with concomitant decrease in CAT and GSH activities. Gastric ulceration, adrenal gland and spleen weights were also used as the stress indices. All these RS induced perturbations were attenuated by EASF of Morus alba. The results of the study suggest that in addition to its classically established pharmacological activities, the plant also has immense potential as an anti-stress agent of great therapeutic relevance. This study indicates the beneficial role of Morus alba for the treatment of oxidative stress-induced disorders.

  20. Elevated nonlinearity as an indicator of shifts in the dynamics of populations under stress.

    Science.gov (United States)

    Dakos, Vasilis; Glaser, Sarah M; Hsieh, Chih-Hao; Sugihara, George

    2017-03-01

    Populations occasionally experience abrupt changes, such as local extinctions, strong declines in abundance or transitions from stable dynamics to strongly irregular fluctuations. Although most of these changes have important ecological and at times economic implications, they remain notoriously difficult to detect in advance. Here, we study changes in the stability of populations under stress across a variety of transitions. Using a Ricker-type model, we simulate shifts from stable point equilibrium dynamics to cyclic and irregular boom-bust oscillations as well as abrupt shifts between alternative attractors. Our aim is to infer the loss of population stability before such shifts based on changes in nonlinearity of population dynamics. We measure nonlinearity by comparing forecast performance between linear and nonlinear models fitted on reconstructed attractors directly from observed time series. We compare nonlinearity to other suggested leading indicators of instability (variance and autocorrelation). We find that nonlinearity and variance increase in a similar way prior to the shifts. By contrast, autocorrelation is strongly affected by oscillations. Finally, we test these theoretical patterns in datasets of fisheries populations. Our results suggest that elevated nonlinearity could be used as an additional indicator to infer changes in the dynamics of populations under stress. © 2017 The Author(s).

  1. Dynamic effective connectivity of inter-areal brain circuits.

    Directory of Open Access Journals (Sweden)

    Demian Battaglia

    Full Text Available Anatomic connections between brain areas affect information flow between neuronal circuits and the synchronization of neuronal activity. However, such structural connectivity does not coincide with effective connectivity (or, more precisely, causal connectivity, related to the elusive question "Which areas cause the present activity of which others?". Effective connectivity is directed and depends flexibly on contexts and tasks. Here we show that dynamic effective connectivity can emerge from transitions in the collective organization of coherent neural activity. Integrating simulation and semi-analytic approaches, we study mesoscale network motifs of interacting cortical areas, modeled as large random networks of spiking neurons or as simple rate units. Through a causal analysis of time-series of model neural activity, we show that different dynamical states generated by a same structural connectivity motif correspond to distinct effective connectivity motifs. Such effective motifs can display a dominant directionality, due to spontaneous symmetry breaking and effective entrainment between local brain rhythms, although all connections in the considered structural motifs are reciprocal. We show then that transitions between effective connectivity configurations (like, for instance, reversal in the direction of inter-areal interactions can be triggered reliably by brief perturbation inputs, properly timed with respect to an ongoing local oscillation, without the need for plastic synaptic changes. Finally, we analyze how the information encoded in spiking patterns of a local neuronal population is propagated across a fixed structural connectivity motif, demonstrating that changes in the active effective connectivity regulate both the efficiency and the directionality of information transfer. Previous studies stressed the role played by coherent oscillations in establishing efficient communication between distant areas. Going beyond these early

  2. Micromagnetic modeling of the effects of stress on magnetic properties

    International Nuclear Information System (INIS)

    Zhu, B.; Lo, C. C. H.; Lee, S. J.; Jiles, D. C.

    2001-01-01

    A micromagnetic model has been developed for investigating the effect of stress on the magnetic properties of thin films. This effect has been implemented by including the magnetoelastic energy term into the Landau - Lifshitz - Gilbert equation. Magnetization curves of a nickel film were calculated under both tensile and compressive stresses of various magnitudes applied along the field direction. The modeling results show that coercivity increased with increasing compressive stress while remanence decreased with increasing tensile stress. The results are in agreement with the experimental data in the literature and can be interpreted in terms of the effects of the applied stress on the irreversible rotation of magnetic moments during magnetization reversal under an applied field. [copyright] 2001 American Institute of Physics

  3. Effects of location, thermal stress and residual stress on corner cracks in nozzles with cladding

    International Nuclear Information System (INIS)

    McLean, J.L.; Cohen, L.M.; Besuner, P.M.

    1979-01-01

    The stress intensity factors (K 1 ) for corner cracks in a boiling water reactor feedwater nozzle with stainless steel cladding are obtained for loading by internal pressure and a fluid quench in the nozzle. Conditions both with and without residual stress in the component are considered. The residual stress is simulated by means of a reference temperature change. The stress distribution for the uncracked structure is obtained from a three-dimensional finite element model. A three-dimensional influence function (IF) method, in conjunction with the boundary-integral equation method for structural analysis, is employed to compute K 1 values from the uncracked stress distribution. For each type of loading K 1 values are given for cracks at 15 nozzle locations and for 6 crack depths. Reasonable agreement is noted between calculated and previously published pressure-induced K 1 values. Comparisons are made to determine the effect on K 1 of crack location, thermal stress and residual stress, as compared with pressure stress. For the thermal transient it is shown that K 1 for small crack depths is maximised early in the transient, while K 1 for large cracks is maximised later under steady state conditions. Computation should, therefore, be made for several transient time points and the maximum K 1 for a given crack depth should be used for design analysis. It is concluded that the effects on K 1 of location, thermal stresses and residual stresses are significant and generally too complex to evaluate without advanced numerical procedures. The utilised combination of finite element analysis of the uncracked structure and three-dimensional influence function analysis of the cracked structure is demonstrated and endorsed. (author)

  4. The effects of location, thermal stress, and residual stress on corner cracks in nozzles with cladding

    International Nuclear Information System (INIS)

    Besuner, P.M.; Cohen, L.M.; McLean, J.L.

    1977-01-01

    The stress intensity factors (Ksub(I)) for corner cracks in a boiling water reactor feedwater nozzle with stainless steel cladding are obtained for loading by internal pressure, and a fluid quench in the nozzle. Conditions with and without residual stress in the component are considered. The residual stress is simulated by means of a reference temperature change. The stress distribution for the uncracked structure is obtained from a three-dimensional finite element model. A three-dimensional influence function (IF) method, in conjunction with the boundary-integral equation method for structural analysis, is employed to compute Ksub(I) values from the uncracked structure's stress distribution. For each type of loading Ksub(I) values are given for cracks at 15 nozzle locations and for six crack depths. Reasonable agreement is noted between calculated and previously published pressure-induced Ksub(I) values. Comparisons are made to determine the effect on Ksub(I) of crack location, thermal stress, and residual stress as compared to pressure stress. For the thermal transient it is shown that Ksub(I) for small crack depths is maximized early in the transient while Ksub(I) for large cracks is maximized later, under steady state conditions. Ksub(I) computations should, therefore, be made for several transient time points and the maximum Ksub(I) for a given crack depth should be used for design analysis. It is concluded that the effects on Ksub(I) of location, thermal stresses, and residual stresses are significant and generally too complex to evalute without advanced numerical procedures. The utilized combination of finite element analysis of the uncracked structure and three-dimensional influence function analysis of the cracked structure is demonstrated

  5. Effect of stress on structural brain asymmetry

    Czech Academy of Sciences Publication Activity Database

    Zach, P.; Valeš, Karel; Stuchlík, Aleš; Čermáková, P.; Mrzílková, J.; Koutella, A.; Kutová, M.

    2016-01-01

    Roč. 37, č. 4 (2016), s. 253-264 ISSN 0172-780X R&D Projects: GA ČR(CZ) GBP304/12/G069 Institutional support: RVO:67985823 Keywords : laterality * asymmetry * brain * evolution * stress * neuropsychiatric disorders Subject RIV: FH - Neurology Impact factor: 0.918, year: 2016

  6. Scale effect in fatigue resistance under complex stressed state

    International Nuclear Information System (INIS)

    Sosnovskij, L.A.

    1979-01-01

    On the basis the of the fatigue failure statistic theory obtained is the formula for calculated estimation of probabillity of failure under complex stressed state according to partial probabilities of failure under linear stressed state with provision for the scale effect. Also the formula for calculation of equivalent stress is obtained. The verification of both formulae using literary experimental data for plane stressed state torsion has shown that the error of estimations does not exceed 10% for materials with the ultimate strength changing from 61 to 124 kg/mm 2

  7. Effect of food intake on left ventricular wall stress

    OpenAIRE

    Gårdinger, Ylva; Hlebowicz, Joanna; Björgell, Ola; Dencker, Magnus

    2014-01-01

    Objective: Left ventricular wall stress has been investigated in a variety of populations, but the effect of food intake has not been evaluated. We assessed whether left ventricular wall stress is affected by food intake in healthy subjects. Methods: Twenty-three healthy subjects aged 25.6 +/- 4.5 years were investigated. Meridional end-systolic wall stress (ESS) and circumferential end-systolic wall stress (cESS) were measured before, 30 minutes after, and 110 minutes after a standardised me...

  8. Size-effect on stress behavior of the AlN/TiN film

    International Nuclear Information System (INIS)

    Chen, D.; Wang, Y.M.; Ma, X.L.

    2009-01-01

    The stress behavior of AlN/TiN superlattice film has been studied by means of a crystal-chemical atomic dynamics simulation based on first-principles calculations. The size-effects on stress behavior are demonstrated and discussed in detail. Stress behavior depends not only on AlN thickness but also on structural relaxation and strain distribution in the film. When the AlN thickness exceeds a critical one, the superlattice film is metastable. Stress behavior can be traced to the AlN/TiN interface structure and its variation with strain relaxation, which may reflect the main strain characteristics caused by AlN structural transformation in this film.

  9. Effect of texture and grain size on the residual stress of nanocrystalline thin films

    Science.gov (United States)

    Cao, Lei; Sengupta, Arkaprabha; Pantuso, Daniel; Koslowski, Marisol

    2017-10-01

    Residual stresses develop in thin film interconnects mainly as a result of deposition conditions and multiple thermal loading cycles during the manufacturing flow. Understanding the relation between the distribution of residual stress and the interconnect microstructure is of key importance to manage the nucleation and growth of defects that can lead to failure under reliability testing and use conditions. Dislocation dynamics simulations are performed in nanocrystalline copper subjected to cyclic loading to quantify the distribution of residual stresses as a function of grain misorientation and grain size distribution. The outcomes of this work help to evaluate the effect of microstructure in thin films failure by identifying potential voiding sites. Furthermore, the simulations show how dislocation structures are influenced by texture and grain size distribution that affect the residual stress. For example, when dislocation loops reach the opposite grain boundary during loading, these dislocations remain locked during unloading.

  10. Effects of prenatal stress on vulnerability to stress in prepubertal and adult rats.

    Science.gov (United States)

    Fride, E; Dan, Y; Feldon, J; Halevy, G; Weinstock, M

    1986-01-01

    This study investigated the hypotheses that unpredictable prenatal stress has effects on the offspring, similar to those induced by perinatal administration of glucocorticoids and increases the vulnerability to stressful situations at adulthood. Rats were exposed to random noise and light stress throughout pregnancy. Offspring were tested for the development of spontaneous alternation behavior (SA) and at adulthood, their response to novel or aversive situations, open field, extinction and punishment following acquisition of an appetitive response and two-way active avoidance, were assessed. In prenatally stressed rats, the development of SA was significantly delayed. On repeated exposure to an open field they were less active; control rats had elevated plasma corticosterone (CCS) on days 2 and 4 of open field exposure, while prenatally stressed rats had significantly raised plasma CCS after each exposure (days 1-8). Furthermore, punishment-induced suppression of an appetitive response was enhanced. Acquisition of active avoidance was faciliated in female but reduced in male prenatally stressed offspring. It is suggested that random prenatal noise and light stress may cause impairment of development of hippocampal function which lasts into adulthood. This impairment is manifested as an increase in vulnerability and a decrease in habituation to stressful stimuli.

  11. Effect of salt stress on growth, inorganic ion and proline ...

    African Journals Online (AJOL)

    The inhibitory effect of salt stress in rice is complex and is one of the main reasons for reduction of plant growth and crop productivity. In the present study, the response of rice callus cultivar Khao Dawk Mali 105 (KDML105), commonly known as Thai jasmine rice, to salt stress was examined. Callus cultures of KDML105 rice ...

  12. Effect of salinity stress on plant fresh weight and nutrient ...

    African Journals Online (AJOL)

    Effect of salinity stress on plant fresh weight and nutrient composition of some Canola ( Brassica napus L.) cultivars. ... K+, Ca2+ and K+/Na+ contents in plants decreased by salt stress, but Na+ and Cl- content in the roots, ... from 32 Countries:.

  13. Effect of supplemental Ascorbic acid and disturbance stress on the ...

    African Journals Online (AJOL)

    Effect of supplemental Ascorbic acid and disturbance stress on the performance of broiler chickens. ... Nigerian Journal of Animal Production ... Results showed that there were no significant interactions between dietary ascorbic acid supplementation and disturbance stress levels on any of the performance data considered.

  14. Effects of induced stress on seismic forward modelling and inversion

    Science.gov (United States)

    Tromp, Jeroen; Trampert, Jeannot

    2018-05-01

    We demonstrate how effects of induced stress may be incorporated in seismic modelling and inversion. Our approach is motivated by the accommodation of pre-stress in global seismology. Induced stress modifies both the equation of motion and the constitutive relationship. The theory predicts that induced pressure linearly affects the unstressed isotropic moduli with a slope determined by their adiabatic pressure derivatives. The induced deviatoric stress produces anisotropic compressional and shear wave speeds; the latter result in shear wave splitting. For forward modelling purposes, we determine the weak form of the equation of motion under induced stress. In the context of the inverse problem, we determine induced stress sensitivity kernels, which may be used for adjoint tomography. The theory is illustrated by considering 2-D propagation of SH waves and related Fréchet derivatives based on a spectral-element method.

  15. Dynamical effects prior to heavy ion fusion

    International Nuclear Information System (INIS)

    Mikhajlova, T.I.; Mikhajlov, I.N.; Molodtsova, I.V.; Di Toro, M.

    2002-01-01

    Dynamical effects in the initial phase of fusion reactions are studied following the evolution of two colliding 100 Mo ions. The role of elastic forces associated with the Fermi-surface deformation is shown by comparing the results obtained with and without taking the memory effects into account. The Bass barrier separating fused and scattered configurations and the lower bound for the extra push energy are estimated. Examples of cases are shown in which the excitation energy and deformation dependence of the friction parameter are fictitious and simulate the effects of collective motion related with the Fermi-surface deformations

  16. Analysis of creep effective stress in austenitic heat resistant steel

    International Nuclear Information System (INIS)

    Park, In Duck; Nam, Ki Woo

    2002-01-01

    This paper describes the comparison of calculated effective stress with experimental one in austenitic heat resistant steels, STS310J1TB and STS310S with and without a small amount of Nb and N. Based on a solute atoms diffusion model, contribution from soluble nitrogen to the high-temperature strength was numerically examined for austenitic heat-resisting Fe-Cr-Ni-N(STS310J1TB) and Fe-Cr-Ni(STS310S) alloys. The solute atmosphere dragging stress of dislocation was calculated in optional dislocation velocity of STS310J1TB and STS310S at 650 degree C, 675 degree C and 700 degree C. As a result of the numerical calculation, the solute atmosphere dragging stress of STS310J1TB was about 50 times larger than that of STS310S. When the temperature became high, the maximum value of solute atmosphere dragging stress was small and the velocity of moving dislocation was fast. From the relationship between the dislocation rate and the solute atmosphere dragging stress, the relation of both was proportional and the inclination is about 1 in the level with low velocity of moving dislocation. From above results, the mechanism of dislocation movement in STS310J1TB was the solute atmosphere dragging stress. The solute atmosphere dragging stress, which was calculated from the numerical calculation was close to the effect stress in stress relaxation tests

  17. No effects of psychosocial stress on intertemporal choice.

    Directory of Open Access Journals (Sweden)

    Johannes Haushofer

    Full Text Available Intertemporal choices - involving decisions which trade off instant and delayed outcomes - are often made under stress. It remains unknown, however, whether and how stress affects intertemporal choice. We subjected 142 healthy male subjects to a laboratory stress or control protocol, and asked them to make a series of intertemporal choices either directly after stress, or 20 minutes later (resulting in four experimental groups. Based on theory and evidence from behavioral economics and cellular neuroscience, we predicted a bidirectional effect of stress on intertemporal choice, with increases in impatience or present bias immediately after stress, but decreases in present bias or impatience when subjects are tested 20 minutes later. However, our results show no effects of stress on intertemporal choice at either time point, and individual differences in stress reactivity (changes in stress hormone levels over time are not related to individual differences in intertemporal choice. Together, we did not find support for the hypothesis that psychosocial laboratory stressors affect intertemporal choice.

  18. Effect of tensile stress on cavitation damage formation in mercury

    Energy Technology Data Exchange (ETDEWEB)

    Naoe, Takashi, E-mail: naoe.takashi@jaea.go.j [J-PARC Center, Japan Atomic Energy Agency, Tokai-mura, Naka-gun, Ibaraki 319-1195 (Japan); Kogawa, Hiroyuki [J-PARC Center, Japan Atomic Energy Agency, Tokai-mura, Naka-gun, Ibaraki 319-1195 (Japan); Yamaguchi, Yoshihito [Nuclear Safety Research Center, Japan Atomic Energy Agency, Tokai-mura, Naka-gun, Ibaraki 319-1195 (Japan); Futakawa, Masatoshi [J-PARC Center, Japan Atomic Energy Agency, Tokai-mura, Naka-gun, Ibaraki 319-1195 (Japan)

    2010-03-15

    Cavitation erosion or so called pitting damage was investigated under tensile stress conditions in mercury. In MW-class liquid metal spallation targets, pitting damage is a critical issue to satisfy required power and/or lifetime of the target vessel. Cavitation occurs by negative pressure which is induced through pressure wave propagation due to proton beam injection. Pitting damage is formed by microjet and/or shock wave during cavitation bubble collapse. A mercury target vessel suffers tensile stress due to thermal stress or welding. In order to investigate the effect of tensile stress on pitting damage formation, cavitation erosion tests were performed using stress imposed specimens in mercury. An ultrasonic vibratory horn and electro-Magnetic IMpact Testing Machine (MIMTM) were used to vary the cavitation intensity. In the incubation period of pitting damage, damaged area was slightly increased with increasing imposed tensile stress. In the steady state period, a mean depth of erosion was increased by the tensile stress. Additionally, in order to quantitatively evaluate the effect of tensile stress, an indentation test with Vickers indenter was carried out to quasi-statically simulate the impact load. From the measurement of the diagonal length of the indent aspect ratio and hardness, it is recognized that the threshold of the deformation, i.e. pitting damage formation, was decreased by the tensile stress.

  19. Effects of stress and MDMA on hippocampal gene expression.

    Science.gov (United States)

    Weber, Georg F; Johnson, Bethann N; Yamamoto, Bryan K; Gudelsky, Gary A

    2014-01-01

    MDMA (3,4-methylenedioxymethamphetamine) is a substituted amphetamine and popular drug of abuse. Its mood-enhancing short-term effects may prompt its consumption under stress. Clinical studies indicate that MDMA treatment may mitigate the symptoms of stress disorders such as posttraumatic stress syndrome (PTSD). On the other hand, repeated administration of MDMA results in persistent deficits in markers of serotonergic (5-HT) nerve terminals that have been viewed as indicative of 5-HT neurotoxicity. Exposure to chronic stress has been shown to augment MDMA-induced 5-HT neurotoxicity. Here, we examine the transcriptional responses in the hippocampus to MDMA treatment of control rats and rats exposed to chronic stress. MDMA altered the expression of genes that regulate unfolded protein binding, protein folding, calmodulin-dependent protein kinase activity, and neuropeptide signaling. In stressed rats, the gene expression profile in response to MDMA was altered to affect sensory processing and responses to tissue damage in nerve sheaths. Subsequent treatment with MDMA also markedly altered the genetic responses to stress such that the stress-induced downregulation of genes related to the circadian rhythm was reversed. The data support the view that MDMA-induced transcriptional responses accompany the persistent effects of this drug on neuronal structure/function. In addition, MDMA treatment alters the stress-induced transcriptional signature.

  20. Effects of Stress and MDMA on Hippocampal Gene Expression

    Directory of Open Access Journals (Sweden)

    Georg F. Weber

    2014-01-01

    Full Text Available MDMA (3,4-methylenedioxymethamphetamine is a substituted amphetamine and popular drug of abuse. Its mood-enhancing short-term effects may prompt its consumption under stress. Clinical studies indicate that MDMA treatment may mitigate the symptoms of stress disorders such as posttraumatic stress syndrome (PTSD. On the other hand, repeated administration of MDMA results in persistent deficits in markers of serotonergic (5-HT nerve terminals that have been viewed as indicative of 5-HT neurotoxicity. Exposure to chronic stress has been shown to augment MDMA-induced 5-HT neurotoxicity. Here, we examine the transcriptional responses in the hippocampus to MDMA treatment of control rats and rats exposed to chronic stress. MDMA altered the expression of genes that regulate unfolded protein binding, protein folding, calmodulin-dependent protein kinase activity, and neuropeptide signaling. In stressed rats, the gene expression profile in response to MDMA was altered to affect sensory processing and responses to tissue damage in nerve sheaths. Subsequent treatment with MDMA also markedly altered the genetic responses to stress such that the stress-induced downregulation of genes related to the circadian rhythm was reversed. The data support the view that MDMA-induced transcriptional responses accompany the persistent effects of this drug on neuronal structure/function. In addition, MDMA treatment alters the stress-induced transcriptional signature.

  1. Sex differences in stress effects on emotional learning.

    Science.gov (United States)

    Merz, Christian J; Wolf, Oliver T

    2017-01-02

    Stress influences emotional learning and memory processes. These effects are thought to underlie stress-associated mental disorders. Sex differences in stress reactivity and in central nervous system stress sensitivity illustrate the important modulatory role of sex hormones. This Review outlines how stress hormones influence different stages of the fear conditioning process, such as fear acquisition, extinction, and retrieval. Results will be compared with findings on the impact of stress on episodic memory. The focus is on the available human data on sex differences and the impact sex hormones have on the stress effects on emotional learning and memory. It will become apparent that the menstrual cycle but also the intake of hormonal contraceptives modulates the impact of stress on brain and behavior. Additional basic research is needed for a deeper insight regarding the interplay between stress and sex hormones in emotion and cognition. In addition, new treatment options might be derived to optimize existing strategies such as exposure therapy, which relies on the principles of fear conditioning. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

  2. Effective long wavelength scalar dynamics in de Sitter

    Energy Technology Data Exchange (ETDEWEB)

    Moss, Ian; Rigopoulos, Gerasimos, E-mail: ian.moss@newcastle.ac.uk, E-mail: gerasimos.rigopoulos@ncl.ac.uk [School of Mathematics and Statistics, Newcastle University, Herschel Building, Newcastle upon Tyne, NE1 7RU U.K. (United Kingdom)

    2017-05-01

    We discuss the effective infrared theory governing a light scalar's long wavelength dynamics in de Sitter spacetime. We show how the separation of scales around the physical curvature radius k / a ∼ H can be performed consistently with a window function and how short wavelengths can be integrated out in the Schwinger-Keldysh path integral formalism. At leading order, and for time scales Δ t >> H {sup −1}, this results in the well-known Starobinsky stochastic evolution. However, our approach allows for the computation of quantum UV corrections, generating an effective potential on which the stochastic dynamics takes place. The long wavelength stochastic dynamical equations are now second order in time, incorporating temporal scales Δ t ∼ H {sup −1} and resulting in a Kramers equation for the probability distribution—more precisely the Wigner function—in contrast to the more usual Fokker-Planck equation. This feature allows us to non-perturbatively evaluate, within the stochastic formalism, not only expectation values of field correlators, but also the stress-energy tensor of φ.

  3. Cytoprotective Effects of Pumpkin (Cucurbita Moschata) Fruit Extract against Oxidative Stress and Carbonyl Stress.

    Science.gov (United States)

    Shayesteh, Reyhaneh; Kamalinejad, Mohammad; Adiban, Hasan; Kardan, Azin; Keyhanfar, Fariborz; Eskandari, Mohammad Reza

    2017-10-01

    Background Diabetes mellitus is a chronic endocrine disorder that is associated with significant mortality and morbidity due to microvascular and macrovascular complications. Diabetes complications accompanied with oxidative stress and carbonyl stress in different organs of human body because of the increased generation of free radicals and impaired antioxidant defense systems. In the meantime, reactive oxygen species (ROS) and reactive carbonyl species (RCS) have key mediatory roles in the development and progression of diabetes complications. Therapeutic strategies have recently focused on preventing such diabetes-related abnormalities using different natural and chemical compounds. Pumpkin ( Cucurbita moschata ) is one of the most important vegetables in the world with a broad-range of pharmacological activities such as antihyperglycemic effect. Methods In the present study, the cytoprotective effects of aqueous extract of C. moschata fruit on hepatocyte cytotoxicity induced by cumene hydroperoxide (oxidative stress model) or glyoxal (carbonylation model) were investigated using freshly isolated rat hepatocytes. Results The extract of C. moschata (50 μg/ml) excellently prevented oxidative and carbonyl stress markers, including hepatocyte lysis, ROS production, lipid peroxidation, glutathione depletion, mitochondrial membrane potential collapse, lysosomal damage, and cellular proteolysis. In addition, protein carbonylation was prevented by C. moschata in glyoxal-induced carbonyl stress. Conclusion It can be concluded that C. moschata has cytoprotective effects in oxidative stress and carbonyl stress models and this valuable vegetable can be considered as a suitable herbal product for the prevention of toxic subsequent of oxidative stress and carbonyl stress seen in chronic hyperglycemia. © Georg Thieme Verlag KG Stuttgart · New York.

  4. The effect of salinity and moisture stress on pea plant

    International Nuclear Information System (INIS)

    Abdalla, A.Abd-El Ghany

    1985-01-01

    Four experiments were carried out in the green house in Inchas, Atomic Energy Establishment, to study the effect os salinity and moisture stress on pea plants. Salinity experiments were conducted in 1981/1982, 1982/1983 and 1983/1984 seasons to study the effect of NaCl and/or CaC l 2 as single or mixed salts and radiation combined with salinity. Water stress studies were conducted in 1983/1984 growing season to investigate the effect of soil moisture stress on growth, yield and water use efficiency

  5. Macro design effects on stress distribution around implants: a photoelastic stress analysis.

    Science.gov (United States)

    Ozkir, Serhat Emre; Terzioglu, Hakan

    2012-01-01

    Biomechanics is one of the main factors for achieving long-term success of implant supported prostheses. Long-term failures mostly depend on biomechanical complications. It is important to distinguish the effects of macro design of the implants. In this study, the photoelastic response of four different types of implants that were inserted with different angulations were comparatively analyzed. The implant types investigated were screw cylinder (ITI, Straumann AG, Basel, Switzerland), stepped cylinder (Frialit2, Friadent GmbH, Manheim, Germany), root form (Camlog Rootline, Alatatec, Wilshelm, Germany), and cylindrical implant, with micro-threads on the implant neck (Astra, AstraTech, Mölndal, Sweden). In the test models, one of the implants was inserted straight, while the other one was aligned mesially with 15° angles. The superstructures were prepared as single crowns. A 150N loading was applied to the restorations throughout the test. A comparison of the implant designs showed that there were no significant differences between the straight implants; however, between the inclined implants, the most favorable stress distribution was seen with the stepped cylinder implants. The least favorable stress concentration was observed around the root formed implants. Microthreads around the implant neck appeared to be effective in a homogenous stress distribution. Observations showed that misaligned implants caused less stress than straight implants, but the stress concentrations were not homogenous. As there were observable differences between the implant types, straight placed cylindrical implants showed better stress distribution characteristics, while inclined tapering implants had better stress distribution characteristics.

  6. ALS mutant SOD1 interacts with G3BP1 and affects stress granule dynamics.

    Science.gov (United States)

    Gal, Jozsef; Kuang, Lisha; Barnett, Kelly R; Zhu, Brian Z; Shissler, Susannah C; Korotkov, Konstantin V; Hayward, Lawrence J; Kasarskis, Edward J; Zhu, Haining

    2016-10-01

    Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease. Mutations in Cu/Zn superoxide dismutase (SOD1) are responsible for approximately 20 % of the familial ALS cases. ALS-causing SOD1 mutants display a gain-of-toxicity phenotype, but the nature of this toxicity is still not fully understood. The Ras GTPase-activating protein-binding protein G3BP1 plays a critical role in stress granule dynamics. Alterations in the dynamics of stress granules have been reported in several other forms of ALS unrelated to SOD1. To our surprise, the mutant G93A SOD1 transgenic mice exhibited pathological cytoplasmic inclusions that co-localized with G3BP1-positive granules in spinal cord motor neurons. The co-localization was also observed in fibroblast cells derived from familial ALS patient carrying SOD1 mutation L144F. Mutant SOD1, unlike wild-type SOD1, interacted with G3BP1 in an RNA-independent manner. Moreover, the interaction is specific for G3BP1 since mutant SOD1 showed little interaction with four other RNA-binding proteins implicated in ALS. The RNA-binding RRM domain of G3BP1 and two particular phenylalanine residues (F380 and F382) are critical for this interaction. Mutant SOD1 delayed the formation of G3BP1- and TIA1-positive stress granules in response to hyperosmolar shock and arsenite treatment in N2A cells. In summary, the aberrant mutant SOD1-G3BP1 interaction affects stress granule dynamics, suggesting a potential link between pathogenic SOD1 mutations and RNA metabolism alterations in ALS.

  7. Some Dynamical Effects of the Cosmological Constant

    Science.gov (United States)

    Axenides, M.; Floratos, E. G.; Perivolaropoulos, L.

    Newton's law gets modified in the presence of a cosmological constant by a small repulsive term (antigravity) that is proportional to the distance. Assuming a value of the cosmological constant consistent with the recent SnIa data (Λ~=10-52 m-2), we investigate the significance of this term on various astrophysical scales. We find that on galactic scales or smaller (less than a few tens of kpc), the dynamical effects of the vacuum energy are negligible by several orders of magnitude. On scales of 1 Mpc or larger however we find that the vacuum energy can significantly affect the dynamics. For example we show that the velocity data in the local group of galaxies correspond to galactic masses increased by 35% in the presence of vacuum energy. The effect is even more important on larger low density systems like clusters of galaxies or superclusters.

  8. Quantitative analysis of localized stresses in irradiated stainless steels using high resolution electron backscatter diffraction and molecular dynamics modeling

    International Nuclear Information System (INIS)

    Johnson, D.C.; Kuhr, B.; Farkas, D.; Was, G.S.

    2016-01-01

    Quantitative measurements of stress near dislocation channel–grain boundary (DC–GB) interaction sites were made using high resolution electron backscatter diffraction (HREBSD) and have been compared with molecular dynamics (MD) simulations. Tensile stress normal to the grain boundary was significantly elevated at discontinuous DC–GB intersections with peak magnitudes roughly an order of magnitude greater than at sites where slip transfer occurred. These results constitute the first measurement of stress amplification at DC–GB intersections and provide support to the theory that high normal stress at the grain boundary may be a key driver for the initiation of irradiation assisted stress corrosion cracks.

  9. Dextran's effects on stressed lenses: water, electrolyte, and radioisotope studies

    International Nuclear Information System (INIS)

    Sanders, D.R.; Bokosky, J.; Peyman, G.A.; Gray, D.

    1979-01-01

    To evaluate the beneficial effects of dextran 40 as an additive to infusion solutions, we studied an experimental model of lens stress with use of buffered, low calcium (Ca ++ )-containing solutions. Incubation in low Ca ++ solutions (pCa = 10.7) for ten hours (stress period) resulted in lens swelling and electrolyte imbalances that were irreversible even with reincubation in physiologic, normal Ca ++ -containing media (pCa = 2.7) (recovery period). The addition of 6% or more of dextran to the media inhibited lens water gain during the stress period. It also rendered the resultant electrolyte imbalances reversible during the recovery period, thus exerting a protective effect. Radioisotope-tracer studies showed that dextran improved the ability of the lens to accumulate rubidium chloride Rb 86 and reduced its efflux during both the stress and recovery periods. Dextran did not markedly decrease sodium chloride Na 22 uptake by lenses under stress

  10. Effect of Stress State on Fracture Features

    Science.gov (United States)

    Das, Arpan

    2018-02-01

    Present article comprehensively explores the influence of specimen thickness on the quantitative estimates of different ductile fractographic features in two dimensions, correlating tensile properties of a reactor pressure vessel steel tested under ambient temperature where the initial crystallographic texture, inclusion content, and their distribution are kept unaltered. It has been investigated that the changes in tensile fracture morphology of these steels are directly attributable to the resulting stress-state history under tension for given specimen dimensions.

  11. Analysis of domain wall dynamics based on skewness of magnetic Barkhausen noise for applied stress determination

    Energy Technology Data Exchange (ETDEWEB)

    Ding, Song [College of Electrical Engineering and Control Science, Nanjing Tech University, Nanjing, Jiangsu 211816 (China); School of Automation Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing, Jiangsu 210016 (China); Tian, GuiYun, E-mail: tian280@hotmail.com [School of Automation Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing, Jiangsu 210016 (China); School of Electrical and Electronic Engineering, Merz Court, University of Newcastle upon Tyne, Newcastle NE1 7RU (United Kingdom); Dobmann, Gerd; Wang, Ping [School of Automation Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing, Jiangsu 210016 (China)

    2017-01-01

    Skewness of Magnetic Barkhausen Noise (MBN) signal is used as a new feature for applied stress determination. After experimental studies, skewness presents its ability for measuring applied tensile stress compared with conventional feature, meanwhile, a non-linear behavior of this new feature and an independence of the excitation conditions under compressive stress are found and discussed. Effective damping during domain wall motion influencing the asymmetric shape of the MBN statistical distribution function is discussed under compressive and tensile stress variation. Domain wall (DW) energy and distance between pinning edges of the DW are considered altering the characteristic relaxation time, which is the reason for the non-linear phenomenon of skewness. - Highlights: • The skewness of magnetic Barkhausen noise profile is proposed as a new feature for applied stress determination. • The skewness is sensitive to applied stress and independent to excitation frequency. • Domain wall energy and pinning distance influence the relaxation time of domain wall, which leads to a non-linear behavior of skewness under compressive stress.

  12. Effect of the weld joint configuration on stressed components, residual stresses and mechanical properties

    Energy Technology Data Exchange (ETDEWEB)

    Cevik, Bekir; Oezer, Alpay; Oezcatalbas, Yusuf [Gazi Univ., Ankara (Turkey)

    2014-03-01

    The effect of the weld joint configuration on components has been studied, which are under service loads, under repair or construction and the residual stresses as well as the mechanical properties of the joint have been determined. For this purpose, a horizontal positioned tensile testing device and a semi-automatic MIG welding machine have been used and then the weld joints of the plates were subjected to different elastic stresses. When the temperature of the joined elements decreased to room temperature, applied elastic stresses were released. By this means, the effects of the existing tensile stresses in the joined parts and the tensile stresses created by the welding processes were investigated. The tensile stresses occurring in the joined elements were determined by using the photo-elasticity analysis method and the hole-drilling method. Also, tensile-shear tests were applied in order to determine the effect of permanent tensile loads on the mechanical properties of the joint. Experimental results showed that the application of corner welded lap joints for components under tensile loading significantly decrease the shear strength and yielding capacities of the joint. (orig.)

  13. Psychological stress-relieving effects of chewing - Relationship between masticatory function-related factors and stress-relieving effects.

    Science.gov (United States)

    Tasaka, Akinori; Kikuchi, Manaki; Nakanishi, Kousuke; Ueda, Takayuki; Yamashita, Shuichiro; Sakurai, Kaoru

    2018-01-01

    The objective of the present study was to investigate the relationship between masticatory function-related factors (masticatory performance, occlusal contact area, maximum bite force, number of chewing strokes, and muscle activity) and the stress-relieving effects of chewing. A total of 28 healthy male subjects were instructed to rest or chew for 10min after 30min of stress loading with arithmetic calculations. Their stress state was assessed by measuring salivary cortisol levels. Saliva was collected at three time points: before stress loading, immediately after stress loading, and 10min after stress loading. Compared to resting, chewing produced a significantly greater reduction in the rate of change in salivary cortisol levels 10min after stress loading. A negative correlation was observed between the rate of decrease in salivary cortisol levels and the number of chewing strokes. No significant correlation was observed between the rate of decrease in salivary cortisol levels and other measurement items. In healthy dentulous people, the number of chewing strokes has been shown to be a masticatory function-related factor that affects stress relief from chewing, suggesting the possibility that more appropriate chewing would produce a greater effect psychological stress relief. Copyright © 2017 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.

  14. Stat5 signaling specifies basal versus stress erythropoietic responses through distinct binary and graded dynamic modalities.

    Directory of Open Access Journals (Sweden)

    Ermelinda Porpiglia

    2012-08-01

    Full Text Available Erythropoietin (Epo-induced Stat5 phosphorylation (p-Stat5 is essential for both basal erythropoiesis and for its acceleration during hypoxic stress. A key challenge lies in understanding how Stat5 signaling elicits distinct functions during basal and stress erythropoiesis. Here we asked whether these distinct functions might be specified by the dynamic behavior of the Stat5 signal. We used flow cytometry to analyze Stat5 phosphorylation dynamics in primary erythropoietic tissue in vivo and in vitro, identifying two signaling modalities. In later (basophilic erythroblasts, Epo stimulation triggers a low intensity but decisive, binary (digital p-Stat5 signal. In early erythroblasts the binary signal is superseded by a high-intensity graded (analog p-Stat5 response. We elucidated the biological functions of binary and graded Stat5 signaling using the EpoR-HM mice, which express a "knocked-in" EpoR mutant lacking cytoplasmic phosphotyrosines. Strikingly, EpoR-HM mice are restricted to the binary signaling mode, which rescues these mice from fatal perinatal anemia by promoting binary survival decisions in erythroblasts. However, the absence of the graded p-Stat5 response in the EpoR-HM mice prevents them from accelerating red cell production in response to stress, including a failure to upregulate the transferrin receptor, which we show is a novel stress target. We found that Stat5 protein levels decline with erythroblast differentiation, governing the transition from high-intensity graded signaling in early erythroblasts to low-intensity binary signaling in later erythroblasts. Thus, using exogenous Stat5, we converted later erythroblasts into high-intensity graded signal transducers capable of eliciting a downstream stress response. Unlike the Stat5 protein, EpoR expression in erythroblasts does not limit the Stat5 signaling response, a non-Michaelian paradigm with therapeutic implications in myeloproliferative disease. Our findings show how the

  15. Dynamic stresses in a Francis model turbine at deep part load

    Science.gov (United States)

    Weber, Wilhelm; von Locquenghien, Florian; Conrad, Philipp; Koutnik, Jiri

    2017-04-01

    A comparison between numerically obtained dynamic stresses in a Francis model turbine at deep part load with experimental ones is presented. Due to the change in the electrical power mix to more content of new renewable energy sources, Francis turbines are forced to operate at deep part load in order to compensate stochastic nature of wind and solar power and to ensure grid stability. For the extension of the operating range towards deep part load improved understanding of the harsh flow conditions and their impact on material fatigue of hydraulic components is required in order to ensure long life time of the power unit. In this paper pressure loads on a model turbine runner from unsteady two-phase computational fluid dynamics simulation at deep part load are used for calculation of mechanical stresses by finite element analysis. Therewith, stress distribution over time is determined. Since only few runner rotations are simulated due to enormous numerical cost, more effort has to be spent to evaluation procedure in order to obtain objective results. By comparing the numerical results with measured strains accuracy of the whole simulation procedure is verified.

  16. The Dynamics of Migration-Related Stress and Coping of Female Domestic Workers from the Philippines: An Exploratory Study

    NARCIS (Netherlands)

    van der Ham, A.J.; Ujano-Batangan, M.T.; Ignacio, R.; Wolffers, I.N.

    2015-01-01

    Female domestic workers face many migration-related stressors that affect their mental health, but we know little about the dynamics of stress and coping in different migration phases. This exploratory study aims to assess stress and coping of female migrant domestic workers from the Philippines in

  17. Handling magnetic anisotropy and magnetoimpedance effect in flexible multilayers under external stress

    Energy Technology Data Exchange (ETDEWEB)

    Agra, K.; Bohn, F. [Departamento de Física Teórica e Experimental, Universidade Federal do Rio Grande do Norte, 59078-900 Natal, RN (Brazil); Mori, T.J.A. [Laboratório Nacional de Luz Síncrotron, Rua Giuseppe Máximo Scolfaro, 1000, Guará, 13083-100 Campinas, SP (Brazil); Callegari, G.L.; Dorneles, L.S. [Departamento de Física, Universidade Federal de Santa Maria, 97105-900 Santa Maria, RS (Brazil); Correa, M.A., E-mail: marciocorrea@dfte.ufrn.br [Departamento de Física Teórica e Experimental, Universidade Federal do Rio Grande do Norte, 59078-900 Natal, RN (Brazil)

    2016-12-15

    We investigate the dynamic magnetic response though magnetoimpedance effect of ferromagnetic flexible NiFe/Ta and FeCuNbSiB/Ta multilayers under external stress. We explore the possibility of handling magnetic anisotropy, and consequently the magnetoimpedance effect, of magnetostrictive multilayers deposited onto flexible substrates. We quantify the sensitivity of the multilayers under external stress by calculating the ratio between impedance variations and external stress changes, and show that considerable values can be reached by tuning the magnetic field, frequency, magnetostriction constant, and external stress. The results extend possibilities of application of magnetostrictive multilayers deposited onto flexible substrates when under external stress and place them as very attractive candidates as element sensor for the development of sensitive smart touch sensors. - Highlights: • We investigate the magnetoimpedance effect in magnetostrictive flexible multilayers grown on flexible substrates. • The external applied stress enables to tuning the samples anisotropies, and consequently the MI performance. • The flexible substrate becomes promising candidate for RF-frequency devices.

  18. Effect of water deficit stress on proline contents, soluble sugars ...

    African Journals Online (AJOL)

    Effect of water deficit stress on proline contents, soluble sugars, chlorophyll and grain yield of sunflower ... Journal Home > Vol 11, No 1 (2012) > ... The objective of the present work was to determine the mechanisms of tolerance of four ...

  19. Dynamic of bioelectric activity back hypothalamus changes in conditions of pyroxan application on the background of stress-reaction developmen

    Directory of Open Access Journals (Sweden)

    T. G. Chaus

    2005-04-01

    Full Text Available The dynamic of changes of capacity of electroencephalogram’s rhythms back hypothalamus at animals of control group and group in stress conditions in parallel with rats who on a background of stress development accepted pyroxan is analyzed. The submitted results have shown influence of a pharmacological preparation pyroxan on bioelectric activity of back hypothalamus in stress conditions that restoration of electric activity under action of this preparation was more shown at 3 weeks of its application.

  20. The effects of location, thermal stress, and residual stress on corner cracks in nozzles with cladding

    International Nuclear Information System (INIS)

    Besuner, P.M.; Cohen, L.M.; McLean, J.L.

    1977-01-01

    The stress intensity factors (Ksub(I)) for corner cracks in a boiling water reactor feedwater nozzle with stainless steel cladding are obtained for loading by internal pressure, and a fluid quench in the nozzle. Conditions with and without residual stress in the component are considered. The residual stress is simulated by means of a reference temperature change. The stress distribution for the uncracked structure is obtained from a three-dimensional finite element model. A three-dimensional influence function (IF) method, in conjunction with the boundary-integral equation method for structural analysis is employed to compute Ksub(I) values from the uncracked structure's stress distribution. It is concluded that the effects on Ksub(I) of location, thermal stresses, and residual stresses are significant and generally too complex to evaluate without advanced numerical procedures. The ulilized combination of finite element analysis of the uncracked structure and three-dimensional influence function analysis of the cracked structure is demonstrated and endorsed. (Auth.)

  1. Resistance to early-life stress in mice: effects of genetic background and stress duration

    Directory of Open Access Journals (Sweden)

    Helene M. Savignac

    2011-04-01

    Full Text Available Early-life stress can induce marked behavioural and physiological impairments in adulthood including cognitive deficits, depression, anxiety and gastrointestinal dysfunction. Although robust rat models of early-life stress exist there are few established effective paradigms in the mouse. Genetic background and protocol parameters used are two critical variables in such model development.Thus we investigated the impact of two different early-life stress protocols in two commonly used inbred mouse strains. C57BL/6 and innately anxious BALB/c male mice were maternally deprived 3 hrs daily, either from postnatal day 1 to 14 (Protocol 1 or 6 to 10 (Protocol 2. Animals were assessed in adulthood for cognitive performance (spontaneous alternation behaviour test, anxiety (open field, light/dark box and elevated plus maze tests and depression-related behaviours (forced swim test in addition to stress-sensitive physiological changes. Overall, the results showed that early-life stressed mice from both strains displayed good cognitive ability and no elevations in anxiety. However, paradoxical changes occurred in C57BL/6 mice as the longer protocol (protocol 1 decreased anxiety in the light-dark box and increased exploration in the elevated plus maze. In BALB/c mice there were also limited effects of maternal separation with both separation protocols inducing reductions in stress-induced defecation and protocol 1 reducing the colon length. These data suggest that, independent of stress duration, mice from both strains were on the whole resilient to the maladaptive effects of early-life stress. Thus maternal-separation models of brain-gut axis dysfunction should rely on either different stressor protocols or other strains of mice.

  2. Effects of heat stress on baroreflex function in humans

    Science.gov (United States)

    Crandall, Craig G.; Cui, Jian; Wilson, Thad E.

    2003-01-01

    INTRODUCTION: Heat stress significantly reduces orthostatic tolerance in humans. The mechanism(s) causing this response remain unknown. The purpose of this review article is to present data pertaining to the hypothesis that reduced orthostatic tolerance in heat stressed individuals is a result of heat stress induced alterations in baroflex function. METHODS: In both normothermic and heat stressed conditions baroreflex responsiveness was assessed via pharmacological and non-pharmacological methods. In addition, the effects of heat stress on post-synaptic vasoconstrictor responsiveness were assessed. RESULTS: Generally, whole body heating did not alter baroreflex sensitivity defined as the gain of the linear portion of the baroreflex curve around the operating point. However, whole body heating shifted the baroreflex curve to the prevailing (i.e. elevated) heart rate and muscle sympathetic nerve activity. Finally, the heat stress impaired vasoconstrictor responses to exogenous administration of adrenergic agonists. CONCLUSION: Current data do not support the hypothesis that reduced orthostatic tolerance associated with heat stress in humans is due to impaired baroreflex responsiveness. This phenomenon may be partially due to the effects of heat stress on reducing vasoconstrictor responsiveness.

  3. Effects of Consolidation Stress State on Normally Consolidated Clay

    DEFF Research Database (Denmark)

    Lade, Poul V.

    2000-01-01

    The effect of consolidation stress state on the stress-strain and strength characteristics has been studied from experiments on undisturbed block samples of a natural, normally consolidated clay known as San Francisco Bay Mud. The results of experiments on K0-consolidated, hollow cylinder specimens...... and on isotropically consolidated, cubical specimens, both tested in triaxial compression and extension, clearly showed the influence of the undisturbed fabric as well as the effect of the initial consolidation stress states. While the K0-consolidated specimens appeared to retain their original fabric and exhibit...

  4. Effects of Social Defeat Stress on Sleep in Mice

    OpenAIRE

    Henderson, Fiona; Vialou, Vincent; El Mestikawy, Salah; Fabre, Véronique

    2017-01-01

    Stress plays a key role in the development of psychiatric disorders and has a negative impact on sleep integrity. In mice, chronic social defeat stress (CSDS) is an ethologically valid model of stress-related disorders but little is known about its effects on sleep regulation. Here, we investigated the immediate and long-term effects of 10 consecutive days of social defeat (SD) on vigilance states in C57Bl/6J male mice. Social behavior was assessed to identify susceptible mice, i.e., mice tha...

  5. Stretching the stress boundary: Linking air pollution health effects to a neurohormonal stress response.

    Science.gov (United States)

    Kodavanti, Urmila P

    2016-12-01

    Inhaled pollutants produce effects in virtually all organ systems in our body and have been linked to chronic diseases including hypertension, atherosclerosis, Alzheimer's and diabetes. A neurohormonal stress response (referred to here as a systemic response produced by activation of the sympathetic nervous system and hypothalamus-pituitary-adrenal (HPA)-axis) has been implicated in a variety of psychological and physical stresses, which involves immune and metabolic homeostatic mechanisms affecting all organs in the body. In this review, we provide new evidence for the involvement of this well-characterized neurohormonal stress response in mediating systemic and pulmonary effects of a prototypic air pollutant - ozone. A plethora of systemic metabolic and immune effects are induced in animals exposed to inhaled pollutants, which could result from increased circulating stress hormones. The release of adrenal-derived stress hormones in response to ozone exposure not only mediates systemic immune and metabolic responses, but by doing so, also modulates pulmonary injury and inflammation. With recurring pollutant exposures, these effects can contribute to multi-organ chronic conditions associated with air pollution. This review will cover, 1) the potential mechanisms by which air pollutants can initiate the relay of signals from respiratory tract to brain through trigeminal and vagus nerves, and activate stress responsive regions including hypothalamus; and 2) the contribution of sympathetic and HPA-axis activation in mediating systemic homeostatic metabolic and immune effects of ozone in various organs. The potential contribution of chronic environmental stress in cardiovascular, neurological, reproductive and metabolic diseases, and the knowledge gaps are also discussed. This article is part of a Special Issue entitled Air Pollution, edited by Wenjun Ding, Andrew J. Ghio and Weidong Wu. Published by Elsevier B.V.

  6. Effects of mobility on ordering dynamics

    International Nuclear Information System (INIS)

    Baronchelli, Andrea; Pastor-Satorras, Romualdo

    2009-01-01

    Models of ordering dynamics allow us to understand natural systems in which an initially disordered population homogenizes some traits via local interactions. The simplest of these models, with wide applications ranging from evolutionary to social dynamics, are the Voter and Moran processes, usually defined in terms of static or randomly mixed individuals that interact with a neighbor to copy or modify a discrete trait. Here we study the effects of diffusion in Voter/Moran processes by proposing a generalization of ordering dynamics in a metapopulation framework, in which individuals are endowed with mobility and diffuse through a spatial structure represented as a graph of patches upon which interactions take place. We show that diffusion dramatically affects the time to reach the homogeneous state, independently of the underlying network's topology, while the final consensus emerges through different local/global mechanisms, depending on the mobility strength. Our results highlight the crucial role played by mobility in ordering processes and set up a general framework that allows its effect to be studied on a large class of models, with implications in the understanding of evolutionary and social phenomena. (letter)

  7. Kinetics of interstitial defects in α-Fe: The effect from uniaxial stress

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Changwoo [Department of Nuclear Engineering, Texas A& M University, College Station, TX 77843 (United States); Wang, Qingyu [College of Nuclear Science and Technology, Harbin Engineering University, Harbin 150001 (China); Shao, Lin, E-mail: lshao@tamu.edu [Department of Nuclear Engineering, Texas A& M University, College Station, TX 77843 (United States)

    2017-03-15

    Understanding defect kinetics in a stress field is important for multiscale modeling of materials degradation of nuclear materials. By means of molecular dynamics and molecular statics simulations, we calculate formation and migration energies of self-interstitial atoms (SIA) and SIA clusters (up to size of 5 interstitials) in alpha Fe and identify their stable configurations under uniaxial tensile strains. By applying uniaxial stress along [111], <111> oriented single SIA defects become more stable than <110> oriented SIA, which is opposite to stress-free condition. Diffusion of single SIA defects under [111] tensile stress is facilitated along [111] direction and the diffusion becomes one dimensional (1D). For SIA clusters, their diffusion under zero stress has gradual transition from three dimensional (3D) for small clusters to one dimensional (1D) for large clusters. Under the tensile stress along [111], the 3D to 1D transition is accelerated. For large SIA clusters, the stress effect is quickly saturated with less diffusivity enhancement in comparison with small SIA clusters.

  8. Dynamics of the Chemotactic Boycott Effect

    Science.gov (United States)

    Cisneros, Luis; Wolgemuth, Charles; Tuval, Idan

    2005-03-01

    Aerobic bacteria often live in thin fluid layers on irregular surfaces, near solid-air-water contact lines where the interplay between fluid interface geometry, nutrient transport, and chemotaxis is central to the micro-ecology. To elucidate these processes, we use the simplified geometry of a sessile drop and provide direct experimental evidence for the ``chemotactic Boycott effect" in suspensions of B. subtilis: upward oxygentaxis toward the drop surface leads to accumulation of cells in a thin layer, which flows down to the contact line and produces there a persistent vortex which traps cells near the meniscus. These phenomena are explained quantitatively with a mathematical model consisting of coupled oxygen diffusion and consumption, chemotaxis, and viscous fluid dynamics; they are shown to be associated with a singularity in the chemotactic dynamics at the contact line.

  9. Gene expression dynamics in the oxidative stress response of fission yeast

    DEFF Research Database (Denmark)

    Papadakis, Emmanouil

    Changes in the environment continuously challenge living organisms during their lifetime. A cell’s survival depends on its ability to coordinate a rapid and successful stress response when exposed to acute doses of damaging agents. Oxidative stress caused by an excess of reactive oxygen species......, especially using model organisms. The fission yeast Schizosaccharomyces pombe is a unicellular eukaryotic organism that possesses genome features and molecular pathways that are highly conserved in humans. Moreover, the limited redundancy of its genome make S. pombe well suited for phenotypic studies...... (HP, 0.5 mM). The applied experimental design allowed us to measure both the activation and recovery phases of the response at a sufficiently high time resolution to model transcription and translation dynamics. Absolute expression levels (copies per cell) and time-resolved expression profiles for 4...

  10. Dynamic Stresses in the LHC TCDS Diluter from 7 TeV Beam Loading

    CERN Document Server

    Goddard, B; Presland, A; Weterings, W

    2006-01-01

    In the event of an unsynchronised beam abort, the MSD extraction septum of the LHC beam dumping system is protected from damage by the TCDS diluter. The simultaneous constraints of obtaining sufficient beam dilution while ensuring the survival of the TCDS make the design difficult, with high thermally induced dynamic stresses occurring in the material needed to attenuate the particle showers induced by the primary beam impact. In this paper, full 3D simulations are described where the worst-case beam loading has been used to generate the local temperature rise and to follow the resulting time evolution of the mechanical stresses. The results and the accompanying design changes for the TCDS, to provide an adequate performance margin, are detailed.

  11. Temporal dynamics of the response to Al stress in Eucalyptus grandis × Eucalyptus camaldulensis

    Directory of Open Access Journals (Sweden)

    Berenice K. de Alcântara

    2015-06-01

    Full Text Available Lipid peroxidation and root elongation of Eucalyptus grandis × Eucalyptus camaldulensis were studied under stress conditions in response to aluminum (Al, a metal known to limit agricultural productivity in acidic soils primarily due to reduced root elongation. In Brazil, the Grancam 1277 hybrid (E. grandis × E. camaldulensis has been planted in the "Cerrado", a region of the country with a wide occurrence of acidic soils. The present study demonstrated that the hybrid exhibited root growth reduction and increased levels of lipid peroxidation after 24h of treatment with 100 µM of Al, which was followed by a reduction in lipid peroxidation levels and the recovery of root elongation after 48h of Al exposure, suggesting a rapid response to the early stressful conditions induced by Al. The understanding of the temporal dynamics of Al tolerance may be useful for selecting more tolerant genotypes and for identifying genes of interest for applications in bioengineering.

  12. Psychophysiological effects of yoga on stress in college students.

    Science.gov (United States)

    Tripathi, Mahesh Narain; Kumari, Sony; Ganpat, Tikhe Sham

    2018-01-01

    College students are vulnerable to a critical period in developmental maturation, facing rigorous academic work, and learning how to function independently. Physical activities such as running and bicycling have been shown to improve mood and relieve stress. However, college students often have low levels of physical activity. Yoga is an ancient physical and mental activity that affects mood and stress. However, studies examining the psychophysiological effects of yoga are rare in peer-reviewed journals. The aim of this study is to establish preliminary evidence for the psychophysiological effects of yoga on stress in young-adult college students. The present study suggests that yoga has positive effects on a psychophysiological level that leads to decreased levels of stress in college student. Further research is needed to examine the extent to which different types of yogic practices address the needs of different college subpopulations (e.g., overweight, sedentary, and smokers).

  13. Psychophysiological effects of yoga on stress in college students

    Directory of Open Access Journals (Sweden)

    Mahesh Narain Tripathi

    2018-01-01

    Full Text Available College students are vulnerable to a critical period in developmental maturation, facing rigorous academic work, and learning how to function independently. Physical activities such as running and bicycling have been shown to improve mood and relieve stress. However, college students often have low levels of physical activity. Yoga is an ancient physical and mental activity that affects mood and stress. However, studies examining the psychophysiological effects of yoga are rare in peer-reviewed journals. The aim of this study is to establish preliminary evidence for the psychophysiological effects of yoga on stress in young-adult college students. The present study suggests that yoga has positive effects on a psychophysiological level that leads to decreased levels of stress in college student. Further research is needed to examine the extent to which different types of yogic practices address the needs of different college subpopulations (e.g., overweight, sedentary, and smokers.

  14. The effective stress concept in saturated sand-clay buffer

    International Nuclear Information System (INIS)

    Graham, J.; Oswell, J.M.; Gray, M.N.

    1992-01-01

    Tests were performed on mixtures of sand and bentonite, to investigate whether the behavior of the mixture can be expressed in terms of effective stresses, defined as the tensor difference between externally applied total stresses and pore water pressures measured outside the cell. Within acceptable bounds of experimental error, the tests show that effective stress can be used to describe consolidation and shear behaviour. However, because part of the effective stress in the clay is derived from net interparticle repulsive (unit) forces seated in diffuse double layers around aggregations of bentonite particles, the applicability of the concept has at this stage been restricted to conditions of constant volume (or possibly constant straining rate), constant chemistry, and constant temperature

  15. Effect of residual stresses on hydrogen permeation in iron

    International Nuclear Information System (INIS)

    Mouanga, M.; Bercot, P.; Takadoum, J.

    2010-01-01

    The effect of residual stresses on electrochemical permeation in iron membrane was investigated. Four thermal and mechanical treatments were chosen to obtain different surface states in relation to the residual stresses. Residual stresses were determined by X-ray diffraction (XRD) using the Macherauch and Mueller method. The results were completed by the microhardness measurements. For all iron membranes, compressive residual stresses were obtained. Electrochemical permeation experiments using a Devanathan and Stachurski cell were employed to determine the hydrogen permeation behaviour of the various iron membranes. The latter was charged with hydrogen by galvanostatic cathodic polarization in 0.1 M NaOH at 25 deg. C. The experimental results revealed that hydrogen permeation rate increases with increasing residual stresses introduced in iron membranes.

  16. Effects of stress on swelling in reactor fuel cladding

    International Nuclear Information System (INIS)

    Bates, J.F.; Gilbert, E.R.

    1977-01-01

    The purpose of this report is to describe the effect of stress on swelling in both annealed and 20% cold worked 316 stainless steel. An effect of stress on swelling in irradiated metals has been postulated for some time. Low fluence data confirmed that indeed a tensile stress can increase swelling in irradiated annealed 316 stainless steel and that the maximum swelling occurs at an intermediate stress level which is approximately equal to the proportional elastic limit of the material. The specimens discussed above were examined by transmission electron microscopy and an effect of stress on the microstructure of the annealed and 20% cold worked 316 specimens has been observed. Howver, as yet, copious swelling had not occurred in the 20% cold worked material. Specimens of 20% cold worked 316 fabricated from the same heat of material as those described above have now been irradiated to sufficiently high neutron fluences that swelling has occurred in both the annealed and cold worked conditions. Swelling increases linearly with stress for both materials. However, for solution annealed 316, swelling reaches a maximum at approximately 136 MPa, whereupon further increases in stress result in reduced swelling. It is felt that this reduction in swelling is related to the onset of plastic yielding in the material. The swelling observed in the 20% CW 316 and the solution annealed 316 below the maximum swelling stress can be adequately described by an equation of the form: S = S 0 (1 + Psigma). No strong effect of stress on changing the incubation period associated with void nucleation was found. (Auth.)

  17. Effect of the plate surface characteristics and gap height on yield stresses of a magnetorheological fluid

    International Nuclear Information System (INIS)

    Jonkkari, I; Syrjala, S; Kostamo, E; Kostamo, J; Pietola, M

    2012-01-01

    Effects of the plate material, surface roughness and measuring gap height on static and dynamic yield stresses of a magnetorheological (MR) fluid were investigated with a commercial plate–plate magnetorheometer. Magnetic and non-magnetic plates with smooth (Ra ∼ 0.3 μm) and rough (Ra ∼ 10 μm) surface finishes were used. It was shown by Hall probe measurements and finite element simulations that the use of magnetic plates or higher gap heights increases the level of magnetic flux density and changes the shape of the radial flux density profile. The yield stress increase caused by these factors was determined and subtracted from the measured values in order to examine only the effect of the wall characteristics or the gap height. Roughening of the surfaces offered a significant increase in the yield stresses for non-magnetic plates. With magnetic plates the yield stresses were higher to start with, but roughening did not increase them further. A significant part of the difference in measured stresses between rough non-magnetic and magnetic plates was caused by changes in magnetic flux density rather than by better contact of the particles to the plate surfaces. In a similar manner, an increase in gap height from 0.25 to 1.00 mm can lead to over 20% increase in measured stresses due to changes in the flux density profile. When these changes were compensated the dynamic yield stresses generally remained independent of the gap height, even in the cases where it was obvious that the wall slip was present. This suggests that with MR fluids the wall slip cannot be reliably detected by comparison of flow curves measured at different gap heights. (paper)

  18. Effective gravitational wave stress-energy tensor in alternative theories of gravity

    International Nuclear Information System (INIS)

    Stein, Leo C.; Yunes, Nicolas

    2011-01-01

    The inspiral of binary systems in vacuum is controlled by the stress-energy of gravitational radiation and any other propagating degrees of freedom. For gravitational waves, the dominant contribution is characterized by an effective stress-energy tensor at future null infinity. We employ perturbation theory and the short-wavelength approximation to compute this stress-energy tensor in a wide class of alternative theories. We find that this tensor is generally a modification of that first computed by Isaacson, where the corrections can dominate over the general relativistic term. In a wide class of theories, however, these corrections identically vanish at asymptotically flat, future, null infinity, reducing the stress-energy tensor to Isaacson's. We exemplify this phenomenon by first considering dynamical Chern-Simons modified gravity, which corrects the action via a scalar field and the contraction of the Riemann tensor and its dual. We then consider a wide class of theories with dynamical scalar fields coupled to higher-order curvature invariants and show that the gravitational wave stress-energy tensor still reduces to Isaacson's. The calculations presented in this paper are crucial to perform systematic tests of such modified gravity theories through the orbital decay of binary pulsars or through gravitational wave observations.

  19. Effects of residual stress on irradiation hardening in stainless steels

    Energy Technology Data Exchange (ETDEWEB)

    Okubo, N.; Kondo, K.; Kaji, Y. [Japan Atomic Energy Agency, Tokai-mura, Naga-gun, Ibaraki-ken (Japan); Miwa, Y. [Nuclear Energy and Science Directorate, Japan Atomic Energy Agency, Tokai-mura, Ibaraki-ken (Japan)

    2007-07-01

    Full text of publication follows: Structural materials in fusion reactor with water cooling system will undergo corrosion in aqueous environment and heavier irradiation than that in LWR. Irradiation assisted stress corrosion (IASCC) may be induced in stainless steels exposed in these environment for a long term of reactor operation. The IASCC is considered to be caused in a welding zone. It is difficult to predict and estimate the IASCC, because several irradiation effects (irradiation hardening, swelling, irradiation induced stress relaxation, etc) work intricately. Firstly, effects of residual stress on irradiation hardening were investigated in stainless steels. Specimens used in this study were SUS316 and SUS316L. By bending deformation, the specimens with several % plastic strain, which corresponds to weld residual stress, were prepared. Ion irradiations of 12 MeV Ni{sup 3+} were performed at 330, 400 and 550 deg. C to 45 dpa in TIARA facility at JAEA. No bent specimen was simultaneously irradiated with the bent specimen. The residual stress was estimated by X-ray residual stress measurements before and after the irradiation. The micro-hardness was measured by using nano-indenter. The irradiation hardening and the stress relaxation were changed by irradiation under bending deformation. The residual stress did not relax even for the case of the higher temperature aging at 500 deg. C for the same time of irradiation. The residual stress after ion irradiation, however, relaxed at these experimental temperatures in SUS316L. The hardness was obviously suppressed in bent SUS316L irradiated at 300 deg. C to 6 or 12 dpa. It was evident that irradiation induced stress relaxation occasionally suppressed the irradiation hardening in SUS316L. (authors)

  20. Transient electromagnetic and dynamic structural analyses of a blanket structure with coupling effects

    Energy Technology Data Exchange (ETDEWEB)

    Koganezawa, K. [Mitsubishi Atomic Power Industries, Inc., Yokohama (Japan); Kushiyama, M. [Mitsubishi Atomic Power Industries, Inc., Yokohama (Japan); Niikura, S. [Mitsubishi Atomic Power Industries, Inc., Yokohama (Japan); Kudough, F. [Mitsubishi Atomic Power Industries, Inc., Yokohama (Japan); Onozuka, M. [Mitsubishi Heavy Industries Ltd., Yokohama (Japan); Koizumi, K. [Japan Atomic Energy Research Inst., Ibaraki (Japan)

    1995-12-31

    Transient electromagnetic and dynamic structural analyses of a blanket structure in the fusion experimental reactor (FER) under a plasma disruption event and a vertical displacement event (VDE) have been performed to investigate the dynamic structural characteristics and the feasibility of the structure. Coupling effects between eddy currents and dynamic deflections have also been taken into account in these analyses. In this study, the inboard blanket was employed because of our computer memory limitation. A 1/192 segment model of a full torus was analyzed using the analytical code, EDDYCUFF. In the plasma disruption event, the maximum magnetic pressure caused by eddy currents and poloidal fields was 1.2MPa. The maximum stress intensity by this magnetic pressure was 114MPa. In the VDE, the maximum magnetic pressure was 2.4MPa and the maximum stress intensity was 253MPa. This stress was somewhat beyond the allowable stress limit. Therefore, the blanket structure and support design should be reviewed to reduce the stress to a suitable value. In summary, the dynamic structural characteristics and design issues of the blanket structure have been identified. (orig.).

  1. Effect of yoga on academic performance in relation to stress

    Directory of Open Access Journals (Sweden)

    Kauts Amit

    2009-01-01

    Full Text Available Background: Academic performance is concerned with the quantity and quality of learning attained in a subject or group of subjects after a long period of instruction. Excessive stress hampers students′ performance. Improvement in academic performance and alertness has been reported in several yogic studies. Aims and Objectives: The main objective of the study was to assess the effect of yoga on academic performance in relation to stress. Materials and Methods: The study started with 800 adolescent students; 159 high-stress students and 142 low-stress students were selected on the basis of scores obtained through Stress Battery. Experimental group and control group were given pre test in three subjects, i.e., Mathematics, Science, and Social Studies. A yoga module consisting of yoga asanas, pranayama, meditation, and a value orientation program was administered on experimental group for 7 weeks. The experimental and control groups were post-tested for their performance on the three subjects mentioned above. Results: The results show that the students, who practiced yoga performed better in academics. The study further shows that low-stress students performed better than high-stress students, meaning thereby that stress affects the students′ performance.

  2. Dynamic Fungal Cell Wall Architecture in Stress Adaptation and Immune Evasion.

    Science.gov (United States)

    Hopke, Alex; Brown, Alistair J P; Hall, Rebecca A; Wheeler, Robert T

    2018-04-01

    Deadly infections from opportunistic fungi have risen in frequency, largely because of the at-risk immunocompromised population created by advances in modern medicine and the HIV/AIDS pandemic. This review focuses on dynamics of the fungal polysaccharide cell wall, which plays an outsized role in fungal pathogenesis and therapy because it acts as both an environmental barrier and as the major interface with the host immune system. Human fungal pathogens use architectural strategies to mask epitopes from the host and prevent immune surveillance, and recent work elucidates how biotic and abiotic stresses present during infection can either block or enhance masking. The signaling components implicated in regulating fungal immune recognition can teach us how cell wall dynamics are controlled, and represent potential targets for interventions designed to boost or dampen immunity. Copyright © 2018 Elsevier Ltd. All rights reserved.

  3. Framing Effects: Dynamics and Task Domains

    Science.gov (United States)

    Wang

    1996-11-01

    The author examines the mechanisms and dynamics of framing effects in risky choices across three distinct task domains (i.e., life-death, public property, and personal money). The choice outcomes of the problems presented in each of the three task domains had a binary structure of a sure thing vs a gamble of equal expected value; the outcomes differed in their framing conditions and the expected values, raging from 6000, 600, 60, to 6, numerically. It was hypothesized that subjects would become more risk seeking, if the sure outcome was below their aspiration level (the minimum requirement). As predicted, more subjects preferred the gamble when facing the life-death choice problems than facing the counterpart problems presented in the other two task domains. Subjects' risk preference varied categorically along the group size dimension in the life-death domain but changed more linearly over the expected value dimension in the monetary domain. Framing effects were observed in 7 of 13 pairs of problems, showing a positive frame-risk aversion and negative frame-risk seeking relationship. In addition, two types of framing effects were theoretically defined and empirically identified. A bidirectional framing effect involves a reversal in risk preference, and occurs when a decision maker's risk preference is ambiguous or weak. Four bidirectional effects were observed; in each case a majority of subjects preferred the sure outcome under a positive frame but the gamble under a negative frame. In contrast, a unidirectional framing effect refers to a preference shift due to the framing of choice outcomes: A majority of subjects preferred one choice outcome (either the sure thing or the gamble) under both framing conditions, with positive frame augmented the preference for the sure thing and negative frame augmented the preference for the gamble. These findings revealed some dynamic regularities of framing effects and posed implications for developing predictive and testable

  4. The Effect of Music on the Human Stress Response

    Science.gov (United States)

    Thoma, Myriam V.; La Marca, Roberto; Brönnimann, Rebecca; Finkel, Linda; Ehlert, Ulrike; Nater, Urs M.

    2013-01-01

    Background Music listening has been suggested to beneficially impact health via stress-reducing effects. However, the existing literature presents itself with a limited number of investigations and with discrepancies in reported findings that may result from methodological shortcomings (e.g. small sample size, no valid stressor). It was the aim of the current study to address this gap in knowledge and overcome previous shortcomings by thoroughly examining music effects across endocrine, autonomic, cognitive, and emotional domains of the human stress response. Methods Sixty healthy female volunteers (mean age = 25 years) were exposed to a standardized psychosocial stress test after having been randomly assigned to one of three different conditions prior to the stress test: 1) relaxing music (‘Miserere’, Allegri) (RM), 2) sound of rippling water (SW), and 3) rest without acoustic stimulation (R). Salivary cortisol and salivary alpha-amylase (sAA), heart rate (HR), respiratory sinus arrhythmia (RSA), subjective stress perception and anxiety were repeatedly assessed in all subjects. We hypothesized that listening to RM prior to the stress test, compared to SW or R would result in a decreased stress response across all measured parameters. Results The three conditions significantly differed regarding cortisol response (p = 0.025) to the stressor, with highest concentrations in the RM and lowest in the SW condition. After the stressor, sAA (p=0.026) baseline values were reached considerably faster in the RM group than in the R group. HR and psychological measures did not significantly differ between groups. Conclusion Our findings indicate that music listening impacted the psychobiological stress system. Listening to music prior to a standardized stressor predominantly affected the autonomic nervous system (in terms of a faster recovery), and to a lesser degree the endocrine and psychological stress response. These findings may help better understanding the

  5. A new formulation of mean stress effects in fatigue

    Science.gov (United States)

    Manson, S. S.; Heidmann, K. R.

    1987-01-01

    A common method of treating the mean stress effect on fatigue life is to displace the elastic line on a Manson-Coffin-Basquin diagram while retaining the position of the plastic line. Manson and Halford pointed out that this procedure implies that mean stress significantly affects the cyclic stress-strain curve. Actually, however, they showed experimentally and by more general reasoning, that mean stress has little, if any, effect on the cyclic stress-strain curve. Thus, they concluded that it is necessary to displace the plastic line as well as the elastic line in order to keep the cyclic stress-strain curve unaltered. Another way to express the common displacement of the two lines is to keep the lines in place and change the horizontal coordinate to include a term relating to the displacement. Thus, instead of life, 2N sub f, as the horizontal coordinate, a new coordinate can become 2N sub f (1-sigma sub m/sigma sub f) superscript 1/b, thereby displacing both the elastic and plastic lines by an amount (1-sigma sub m/sigma sub f) superscript 1/b where sigma sub m is the mean stress and sigma sub f is the intercept of the elastic line at N sub f = 1/2 cycles and b is the slope of the elastic line.

  6. Dynamic stall and 3D effects

    Energy Technology Data Exchange (ETDEWEB)

    Bjoerck, A.; Thor, S.E. [Aeronautical Research Inst. of Sweden, Bromma (Sweden)

    1996-12-01

    The JOULE II project `Dynamic stall and 3D effects` started in January 1994 and was completed in September 1995. The objective of the project has been to increase the understanding of the three-dimensional and unsteady aerodynamics of stall controlled HAWT`s. The objectives have also been to develop `engineering models` suitable for inclusion into aero-elastic codes. The project included the participation of 13 parties within Europe. This paper describes an overview of the work carried out within the project and key results. 3 refs, 4 figs

  7. TIA-1 Self-Multimerization, Phase Separation, and Recruitment into Stress Granules Are Dynamically Regulated by Zn2+

    Directory of Open Access Journals (Sweden)

    Joseph B. Rayman

    2018-01-01

    Full Text Available Summary: Stress granules are non-membranous structures that transiently form in the cytoplasm during cellular stress, where they promote translational repression of non-essential RNAs and modulate cell signaling by sequestering key signal transduction proteins. These and other functions of stress granules facilitate an adaptive cellular response to environmental adversity. A key component of stress granules is the prion-related RNA-binding protein, T cell intracellular antigen-1 (TIA-1. Here, we report that recombinant TIA-1 undergoes rapid multimerization and phase separation in the presence of divalent zinc, which can be reversed by the zinc chelator, TPEN. Similarly, the formation and maintenance of TIA-1-positive stress granules in arsenite-treated cells are inhibited by TPEN. In addition, Zn2+ is released in cells treated with arsenite, before stress granule formation. These findings suggest that Zn2+ is a physiological ligand of TIA-1, acting as a stress-inducible second messenger to promote multimerization of TIA-1 and subsequent localization into stress granules. : Rayman et al. show that Zn2+ is a stress-inducible second messenger that triggers self-multimerization and phase separation of TIA-1 and regulates dynamic recruitment of TIA-1 into stress granules. This mechanism is part of an adaptive cellular response to environmental adversity. Keywords: TIA-1, TIA1, stress granules, cellular stress, functional prion, phase separation, zinc regulation

  8. Research on Formation Mechanism of Dynamic Response and Residual Stress of Sheet Metal Induced by Laser Shock Wave

    Science.gov (United States)

    Feng, Aixin; Cao, Yupeng; Wang, Heng; Zhang, Zhengang

    2018-01-01

    In order to reveal the quantitative control of the residual stress on the surface of metal materials, the relevant theoretical and experimental studies were carried out to investigate the dynamic response of metal thin plates and the formation mechanism of residual stress induced by laser shock wave. In this paper, the latest research trends on the surface residual stress of laser shock processing technology were elaborated. The main progress of laser shock wave propagation mechanism and dynamic response, laser shock, and surface residual stress were discussed. It is pointed out that the multi-scale characterization of laser and material, surface residual stress and microstructure change is a new hotspot in laser shock strengthening technology.

  9. Stress distribution in dental prosthesis under an occlusal combined dynamic loading

    International Nuclear Information System (INIS)

    Merdji, A.; Bachir Bouiadjra, B.; Ould Chikh, B.; Mootanah, R.; Aminallah, L.; Serier, B.; Muslih, I.M.

    2012-01-01

    Highlights: ► The mechanical stress reaches the highest in areas of cortical bones. ► The mechanical stress in the cancellous bone reaches greatest in the bottom of the dental implant. ► Implant with low-volume bone might cause increased stress concentration in the cortical bone. -- Abstract: The biomechanical behavior of osseointegrated dental prostheses systems plays an important role in its functional longevity inside the bone. Simulation of these systems requires an accurate modeling of the prosthesis components, the jaw bone, the implant–bone interface, and the response of the system to different types of applied forces. The purpose of this study was to develop a new three-dimensional model of an osseointegrated molar dental prosthesis and to carry out finite element analysis to evaluate stress distributions in the bone and the dental prosthesis compounds under an occlusal combined dynamic load was applied to the top of the occlusale face of the prosthesis crown. The jaw bone model containing cortical bone and cancellous bone was constructed by using computer tomography scan pictures and Computer Aided Design tools. The dental prosthesis compounds were constructed, simulating the commercially available cylindrical implant of 4.8 mm diameter and 10 mm length. Both finite element models were created in Abaqus finite element software. All materials used in the models were considered to be isotropic, homogeneous and linearly elastic. The elastic properties, loads and constraints used in the model were taken from published data. Results of our finite element analyses, indicated that the maximum stresses were located around the mesial neck of the implant, in the marginal bone. Thus, this area should be preserved clinically in order to maintain the bone–implant interface structurally and functionally.

  10. The effects of stress on physical activity and exercise.

    Science.gov (United States)

    Stults-Kolehmainen, Matthew A; Sinha, Rajita

    2014-01-01

    Psychological stress and physical activity (PA) are believed to be reciprocally related; however, most research examining the relationship between these constructs is devoted to the study of exercise and/or PA as an instrument to mitigate distress. The aim of this paper was to review the literature investigating the influence of stress on indicators of PA and exercise. A systematic search of Web of Science, PubMed, and SPORTDiscus was employed to find all relevant studies focusing on human participants. Search terms included "stress", "exercise", and "physical activity". A rating scale (0-9) modified for this study was utilized to assess the quality of all studies with multiple time points. The literature search found 168 studies that examined the influence of stress on PA. Studies varied widely in their theoretical orientation and included perceived stress, distress, life events, job strain, role strain, and work-family conflict but not lifetime cumulative adversity. To more clearly address the question, prospective studies (n = 55) were considered for further review, the majority of which indicated that psychological stress predicts less PA (behavioral inhibition) and/or exercise or more sedentary behavior (76.4 %). Both objective (i.e., life events) and subjective (i.e., distress) measures of stress related to reduced PA. Prospective studies investigating the effects of objective markers of stress nearly all agreed (six of seven studies) that stress has a negative effect on PA. This was true for research examining (a) PA at periods of objectively varying levels of stress (i.e., final examinations vs. a control time point) and (b) chronically stressed populations (e.g., caregivers, parents of children with a cancer diagnosis) that were less likely to be active than controls over time. Studies examining older adults (>50 years), cohorts with both men and women, and larger sample sizes (n > 100) were more likely to show an inverse association. 85.7 % of higher

  11. Cross-talk between lipid and protein carbonylation in a dynamic cardiomyocyte model of mild nitroxidative stress

    Directory of Open Access Journals (Sweden)

    Eva Griesser

    2017-04-01

    Full Text Available Reactive oxygen and nitrogen species (ROS/RNS play an important role in the regulation of cardiac function. Increase in ROS/RNS concentration results in lipid and protein oxidation and is often associated with onset and/or progression of many cardiovascular disorders. However, interplay between lipid and protein modifications has not been simultaneously studied in detail so far. Biomolecule carbonylation is one of the most common biomarkers of oxidative stress. Using a dynamic model of nitroxidative stress we demonstrated rapid changes in biomolecule carbonylation in rat cardiomyocytes. Levels of carbonylated species increased as early as 15 min upon treatment with the peroxynitrite donor, 3-morpholinosydnonimine (SIN-1, and decreased to values close to control after 16 h. Total (lipids+proteins vs. protein-specific carbonylation showed different dynamics, with a significant increase in protein-bound carbonyls at later time points. Treatment with SIN-1 in combination with inhibitors of proteasomal and autophagy/lysosomal degradation pathways allowed confirmation of a significant role of the proteasome in the degradation of carbonylated proteins, whereas lipid carbonylation increased in the presence of autophagy/lysosomal inhibitors. Electrophilic aldehydes and ketones formed by lipid peroxidation were identified and relatively quantified using LC-MS/MS. Molecular identity of reactive species was used for data-driven analysis of their protein targets. Combination of different enrichment strategies with LC-MS/MS analysis allowed identification of more than 167 unique proteins with 332 sites modified by electrophilic lipid peroxidation products. Gene ontology analysis of modified proteins demonstrated enrichment of several functional categories including proteins involved in cytoskeleton, extracellular matrix, ion channels and their regulation. Using calcium mobilization assays, the effect of nitroxidative stress on the activity of several ion

  12. EFFECT OF HEEL LIFTS ON PATELLOFEMORAL JOINT STRESS DURING RUNNING.

    Science.gov (United States)

    Mestelle, Zachary; Kernozek, Thomas; Adkins, Kelly S; Miller, Jessica; Gheidi, Naghmeh

    2017-10-01

    Patellofemoral pain is a debilitating injury for many recreational runners. Excessive patellofemoral joint stress may be the underlying source of pain and interventions often focus on ways to reduce patellofemoral joint stress. Heel lifts have been used as an intervention within Achilles tendon rehabilitation programs and to address leg length discrepancies. The purpose of this study was to examine the effect of running with heel lifts on patellofemoral joint stress, patellofemoral stress impulse, quadriceps force, step length, cadence, and other related kinematic and spatiotemporal variables. A repeated-measures research design. Sixteen healthy female runners completed five running trials in a controlled laboratory setting with and without 11mm heel lifts inserted in a standard running shoe. Kinetic and kinematic data were used in combination with a static optimization technique to estimate individual muscle forces. These data were inserted into a patellofemoral joint model which was used to estimate patellofemoral joint stress and other variables during running. When running with heel lifts, peak patellofemoral joint stress and patellofemoral stress impulse were reduced by a 4.2% (p=0.049) and 9.3% (p=0.002). Initial center of pressure was shifted anteriorly 9.1% when running with heel lifts (p0.05) were shown between conditions. Heel lift use resulted in decreased patellofemoral joint stress and impulse without associated changes in step length or frequency, or other variables shown to influence patellofemoral joint stress. The center of pressure at initial contact was also more anterior using heel lifts. The use of heel lifts may have therapeutic benefits for runners with patellofemoral pain if the primary goal is to reduce patellofemoral joint stress. 3b.

  13. Effects of Uric Acid on Exercise-induced Oxidative Stress

    OpenAIRE

    平井, 富弘

    2001-01-01

    We studied effects of uric acid on exercise― induced oxidative stress in humans based on a hypothesis that uric acid acts as an antioxidant to prevent from exercise―induced oxidative stress. Relation between uric acid level in plasma and increase of thiobarbituric acid reactive substance (TBARS)after the cycle ergometer exercise was examined. Thiobarbituricacid reactive substance in plasma increased after the ergometer exercise. High uric acid in plasma did not result in low increase of TBARS...

  14. Investigating The Effect Of Job Stress On Performance Of Employees

    OpenAIRE

    Oyungerel Altangerel; Wang Ruimei; Ehsan Elahi; Bayandalai Dash

    2015-01-01

    Abstract This study is conducted to investigate the effect of job stress on job performance. A random sampling technique is used to collect primary data of 120 employees of four telecommunication companies of Mongolia i.e. Mobicom Unitel Skytel and G-mobile. A well-structured questionnaire is utilized to collect relevant data descriptive and logistic analysis is used to estimate and describe the findings of results. It is found that work overload is major reason of stress among employees and ...

  15. Behavioural and Neuroendocrine Effects of Stress in Salmonid Fish

    OpenAIRE

    Øverli, Øyvind

    2001-01-01

    Stress can affect several behavioural patterns, such as food intake and the general activity level of an animal. The central monoamine neurotransmitters serotonin, dopamine, and norepinephrine are important in the mediation of both behavioural and neuroendocrine stress effects. This thesis describes studies of two salmonid fish model systems: Fish that become socially dominant or subordinate when reared in pairs, and rainbow trout (Oncorhynchus mykiss) genetically selected for high (HR) and l...

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

    International Nuclear Information System (INIS)

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

    1977-11-01

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

  17. The Effects of Stress on Physical Activity and Exercise

    Science.gov (United States)

    Stults-Kolehmainen, Matthew A.; Sinha, Rajita

    2013-01-01

    Background Psychological stress and physical activity (PA) are believed to be reciprocally related; however, most research examining the relationship between these constructs is devoted to the study of exercise and/or PA as an instrument to mitigate distress. Objective The aim of this paper was to review the literature investigating the influence of stress on indicators of PA and exercise. Methods A systematic search of Web of Science, Pub-Med, and SPORTDiscus was employed to find all relevant studies focusing on human participants. Search terms included “stress”, “exercise”, and “physical activity”. A rating scale (0–9) modified for this study was utilized to assess the quality of all studies with multiple time points. Results The literature search found 168 studies that examined the influence of stress on PA. Studies varied widely in their theoretical orientation and included perceived stress, distress, life events, job strain, role strain, and work–family conflict but not lifetime cumulative adversity. To more clearly address the question, prospective studies (n = 55) were considered for further review, the majority of which indicated that psychological stress predicts less PA (behavioral inhibition) and/or exercise or more sedentary behavior (76.4 %). Both objective (i.e., life events) and subjective (i.e., distress) measures of stress related to reduced PA. Prospective studies investigating the effects of objective markers of stress nearly all agreed (six of seven studies) that stress has a negative effect on PA. This was true for research examining (a) PA at periods of objectively varying levels of stress (i.e., final examinations vs. a control time point) and (b) chronically stressed populations (e.g., caregivers, parents of children with a cancer diagnosis) that were less likely to be active than controls over time. Studies examining older adults (>50 years), cohorts with both men and women, and larger sample sizes (n > 100) were more likely

  18. Dynamics of food availability, body condition and physiological stress response in breeding Black-legged Kittiwakes

    Science.gov (United States)

    Kitaysky, A.S.; Wingfield, J.C.; Piatt, John F.

    1999-01-01

    1. The seasonal dynamics of body condition (BC), circulating corticosterone levels (baseline, BL) and the adrenocortical response to acute stress (SR) were examined in long-lived Black-legged Kittiwakes, Rissa tridactyla, breeding at Duck (food-poor colony) and Gull (food-rich colony) Islands in lower Cook Inlet, Alaska. It was tested whether the dynamics of corticosterone levels reflect a seasonal change in bird physiological condition due to reproduction and/or variation in foraging conditions. 2. BC declined seasonally, and the decline was more pronounced in birds at the food-poor colony. BL and SR levels of corticosterone rose steadily through the reproductive season, and BL levels were significantly higher in birds on Duck island compared with those on Gull Island. During the egg-laying and chick-rearing stages, birds had lower SR on Duck Island than on Gull Island. 3. The results suggest that, in addition to a seasonal change in bird physiology during reproduction, local ecological factors such as food availability affect circulating levels of corticosterone and adrenal response to acute stress.

  19. Effects of Telecoupling on Global Vegetation Dynamics

    Science.gov (United States)

    Viña, A.; Liu, J.

    2016-12-01

    With the ever increasing trend in telecoupling processes, such as international trade, all countries around the world are becoming more interdependent. However, the effects of this growing interdependence on vegetation (e.g., shifts in the geographic extent and distribution) remain unknown even though vegetation dynamics are crucially important for food production, carbon sequestration, provision of other ecosystem services, and biodiversity conservation. In this study we evaluate the effects of international trade on the spatio-temporal trajectories of vegetation at national and global scales, using vegetation index imagery collected over more than three decades by the Advanced Very High Resolution Radiometer (AVHRR) satellite sensor series together with concurrent national and international data on international trade (and its associated movement of people, goods, services and information). The spatio-temporal trajectories of vegetation are obtained using the scale of fluctuation technique, which is based on the decomposition of the AVHRR image time series to obtain information on its spatial dependence structure over time. Similar to the correlation length, the scale of fluctuation corresponds to the range over which fluctuations in the vegetation index are spatially correlated. Results indicate that global vegetation has changed drastically over the last three decades. These changes are not uniform across space, with hotspots in active trading countries. This study not only has direct implications for understanding global vegetation dynamics, but also sheds important insights on the complexity of human-nature interactions across telecoupled systems.

  20. Effect of pairing on nuclear dynamics

    International Nuclear Information System (INIS)

    Scamps, Guillaume

    2014-01-01

    Pairing correlations is an essential component for the description of the atomic nuclei. The effects of pairing on static property of nuclei are now well known. In this thesis, the effect of pairing on nuclear dynamics is investigated. Theories that includes pairing are benchmarked in a model case. The TDHF+BCS theory turns out to be a good compromise between the physics taken into account and the numerical cost. This TDHF+BCS theory was retained for realistic calculations. Nevertheless, the application of pairing in the BCS approximation may induce new problems due to (1) the particle number symmetry breaking, (2) the non-conservation of the continuity equation. These difficulties are analysed in detail and solutions are proposed. In this thesis, a 3 dimensional TDHF+BCS code is developed to simulate the nuclear dynamic. Applications to giant resonances show that pairing modify only the low lying peaks. The high lying collective components are only affected by the initial conditions. An exhaustive study of the giant quadrupole resonances with the TDHF+BCS theory is performed on more than 700 spherical or deformed nuclei. Is is shown that the TDHF+BCS theory reproduces well the collective energy of the resonance. After validation on the small amplitude limit problem, the approach was applied to study nucleon transfer in heavy ion reactions. A new method to extract transfer probabilities is introduced. It is demonstrated that pairing significantly increases the two-nucleon transfer probability. (author) [fr

  1. Dynamics of seed germination, seedling growth and physiological responses of sweet corn under peg-induced water stress

    International Nuclear Information System (INIS)

    Li, W.; Zhang, X.; Li, G.; Suo, H.; Ashraf, U.; Mo, Z.

    2017-01-01

    Stress induced variations in seed germination of various crops has been well reported but germination potential of sweet corn seeds under osmotic stress with relation to time dynamics is still elusive. Present study explored the water absorption, germination potential and physiological indices and of sweet corn seeds exposed to five different levels of PEG-induced water stress i.e., 0, -0.3, -0.6, -0.9 and -1.2 M Pa water potential (Psi /sub w/) with respect to time dynamics. Results showed that enhanced water stress for prolonged time period (96 h) led to substantial reduction in water absorption and seed moisture contents, seed germination and vigor index as well as seedlings growth and fresh and dry biomass. Osmotic stress triggered antioxidant defense system like super-oxide dismutase (SOD), peroxidase (POD) and catalase (CAT) and accumulation of soluble sugars, proline and protein contents considerably. Initially, activities of SOD and CAT were higher but then reduced as stress persisted, however, POD showed a linear increase with respect to stress exposure time. Water stress also increased MDA contents up to 36 h then declined. Further, alpha-amylase activity and soluble protein showed significant correlations with maize seed germination. Overall, germination potential decreased with increase in osmotic stress in sweet corn seeds. (author)

  2. The effects of acute stress on the calibration of persistence.

    Science.gov (United States)

    Lempert, Karolina M; McGuire, Joseph T; Hazeltine, Danielle B; Phelps, Elizabeth A; Kable, Joseph W

    2018-02-01

    People frequently fail to wait for delayed rewards after choosing them. These preference reversals are sometimes thought to reflect self-control failure. Other times, however, continuing to wait for a delayed reward may be counterproductive (e.g., when reward timing uncertainty is high). Research has demonstrated that people can calibrate how long to wait for rewards in a given environment. Thus, the role of self-control might be to integrate information about the environment to flexibly adapt behavior, not merely to promote waiting. Here we tested effects of acute stress, which has been shown to tax control processes, on persistence, and the calibration of persistence, in young adult human participants. Half the participants (n = 60) performed a task in which persistence was optimal, and the other half (n = 60) performed a task in which it was optimal to quit waiting for reward soon after each trial began. Each participant completed the task either after cold pressor stress or no stress. Stress did not influence persistence or optimal calibration of persistence. Nevertheless, an exploratory analysis revealed an "inverted-U" relationship between cortisol increase and performance in the stress groups, suggesting that choosing the adaptive waiting policy may be facilitated with some stress and impaired with severe stress.

  3. Residual stress effects in LMFBR fracture assessment procedures

    International Nuclear Information System (INIS)

    Hooton, D.G.

    1984-01-01

    Two post-yield fracture mechanics methods, which have been developed into fully detailed failure assessment procedures for ferritic structures, have been reviewed from the point of view of the manner in which as-welded residual stress effects are incorporated, and comparisons then made with finite element and theoretical models of centre-cracked plates containing residual/thermal stresses in the form of crack-driving force curves. Applying the procedures to austenitic structures, comparisons are made in terms of failure assessment curves and it is recommended that the preferred method for the prediction of critical crack sizes in LMFBR austenitic structures containing as-welded residual stresses is the CEGB-R6 procedure based on a flow stress defined at 3% strain in the parent plate. When the prediction of failure loads in such structures is required, it is suggested that the CEGB-R6 procedure be used with residual/thermal stresses factored to give a maximum total stress of flow stress magnitude

  4. Probabilistic molecular dynamics evaluation of the stress-strain behavior of polyethylene

    International Nuclear Information System (INIS)

    Stowe, J.Q.; Predecki, P.K.; Laz, P.J.; Burks, B.M.; Kumosa, M.

    2009-01-01

    The primary goal of this study was to utilize molecular dynamics to predict the mechanical behavior of polyethylene. In particular, stress-strain relationships, the Young's modulus and Poisson ratio were predicted for low-density polyethylene at several molecular weights and polymer configurations with the number of united CH 2 atoms ranging between 500 and 5000. Probabilistic Monte Carlo methods were also used to identify the extent of uncertainty in mechanical property predictions. In general, asymptotic behavior was observed for stress and the Young's modulus as the molecular weight of the models increased. At the same time, significant variability, of the order of 1000% of the mean, in the stress-strain relationships and the Young's modulus predictions was observed, especially for low molecular weight models. The variability in the Young's modulus predictions ranged from 17.9 to 3.2 GPa for the models ranging from 100 to 5000 CH 2 atom models. However, it was also found that the mean value of the Young's modulus approached a physically possible value of 194 MPa for the 5000 atom model. Poisson ratio predictions also resulted in significant variability, from 200% to 425% of the mean, and ranged from 0.75 to 1.30. The mean value of the Poisson ratios calculated in this study ranged from 0.32 to 0.44 for the 100 to 5000 atom models, respectively.

  5. Angiogenin enhances cell migration by regulating stress fiber assembly and focal adhesion dynamics.

    Directory of Open Access Journals (Sweden)

    Saisai Wei

    Full Text Available Angiogenin (ANG acts on both vascular endothelial cells and cancer cells, but the underlying mechanism remains elusive. In this study, we carried out a co-immunoprecipitation assay in HeLa cells and identified 14 potential ANG-interacting proteins. Among these proteins, β-actin, α-actinin 4, and non-muscle myosin heavy chain 9 are stress fiber components and involved in cytoskeleton organization and movement, which prompted us to investigate the mechanism of action of ANG in cell migration. Upon confirmation of the interactions between ANG and the three proteins, further studies revealed that ANG co-localized with β-actin and α-actinin 4 at the leading edge of migrating cells. Down-regulation of ANG resulted in fewer but thicker stress fibers with less dynamics, which was associated with the enlargements of focal adhesions. The focal adhesion kinase activity and cell migration capacity were significantly decreased in ANG-deficient cells. Taken together, our data demonstrated that the existence of ANG in the cytoplasm optimizes stress fiber assembly and focal adhesion formation to accommodate cell migration. The finding that ANG promoted cancer cell migration might provide new clues for tumor metastasis research.

  6. Combined effect of gamma radiation and stress cracking in polystyrene

    International Nuclear Information System (INIS)

    Amorim, Fernando A.; Rabello, Marcelo S.; Silva, Leonardo G.A.

    2011-01-01

    This study aimed to evaluate the combined effect of gamma radiation and stress cracking in polystyrene. Three different grades of polystyrene were analysed. The material was submitted to tensile tests and relaxation, analysis of molecular weight and determination of crosslinking. The results showed an increase in tensile strength in the specimens that had been exposed to radiation. The higher the molecular weight polystyrene showed better mechanical properties and after suffering the effects of gamma radiation there was an increase of 5.67% in the resistance to stress cracking effects. (author)

  7. Stress- and temperature-dependent scaling behavior of dynamic hysteresis in soft PZT bulk ceramics

    International Nuclear Information System (INIS)

    Yimnirun, R; Wongsaenmai, S; Wongmaneerung, R; Wongdamnern, N; Ngamjarurojana, A; Ananta, S; Laosiritaworn, Y

    2007-01-01

    Effects of electric field-frequency, electric field-amplitude, mechanical stress, and temperature on the hysteresis area, especially the scaling form, were investigated in soft lead zirconate titanate (PZT) bulk ceramics. The hysteresis area was found to depend on the frequency and field-amplitude with the same set of exponents as the power-law scaling for both with and without stresses. The inclusion of stresses into the power-law was obtained in the form of σ=0 > ∝ f -0.25 E 0 σ 0.45 which indicates the difference in energy dissipation between the under-stress and stress-free conditions. The power-law temperature scaling relations were obtained for hysteresis area (A) and remanent polarization P r , while the coercivity E C was found to scale linearly with temperature T. The three temperature scaling relations were also field-dependent. At fixed field amplitude E 0 , the scaling relations take the forms of ∝ T -1.1024 , P r ∼T -1.2322 and (E C0 - E C ) ∼T

  8. The impact of stress on tumor growth: peripheral CRF mediates tumor-promoting effects of stress

    Directory of Open Access Journals (Sweden)

    Stathopoulos Efstathios N

    2010-09-01

    effect. Moreover, antalarmin suppressed neoangiogenesis in 4T1 tumors in vivo. Conclusion This is the first report demonstrating that peripheral CRF, at least in part, mediates the tumor-promoting effects of stress and implicates CRF in SMAD2 and β-catenin expression.

  9. Stress

    Science.gov (United States)

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

  10. Protracted effects of chronic stress on serotonin dependent thermoregulation

    Science.gov (United States)

    Natarajan, Reka; Northrop, Nicole A.; Yamamoto, Bryan K.

    2016-01-01

    Chronic stress is known to affect serotonin (5HT) neurotransmission in the brain and to alter body temperature. Body temperature is controlled in part, by the medial preoptic area of the hypothalamus (mPOA). To investigate the effect of chronic stress on 5HT and how it affects body temperature regulation, we examined whether exposure to a chronic unpredictable stress paradigm (CUS) produces long-term alterations in thermoregulatory function of the mPOA through decreased 5HT neurotransmission. Adult male Sprague-Dawley rats underwent 21 days of CUS. Four days after last stress exposure, basal body temperature in the home cage and body temperature in a cold room maintained at 10°C were recorded. CUS rats had significantly higher subcutaneous basal body temperature at 13:00 h compared to unstressed (NoStress) rats. Whereas the NoStress rats were able to significantly elevate body temperature from basal levels at 30 and 60 min of exposure to the cold room, the CUS rats showed a hypothermic response to the cold. Treatment during CUS with metyrapone, a corticosterone synthesis inhibitor, blocked stress-induced decrease in body temperature in response to the cold challenge. CUS also decreased 5HT transporter protein immunoreactivity in the mPOA and 5HT2A/C agonist injection into the mPOA after CUS exposure caused stressed rats to exhibit a sensitized hyperthermic response to cold. These results indicate that CUS induced changes to the 5HTergic system alters mPOA function in thermoregulation. These findings help explain mechanisms underlying chronic stress induced disorders such as chronic fatigue syndrome wherein long lasting thermoregulatory deficits are observed. PMID:26414686

  11. Protracted effects of chronic stress on serotonin-dependent thermoregulation.

    Science.gov (United States)

    Natarajan, Reka; Northrop, Nicole A; Yamamoto, Bryan K

    2015-01-01

    Chronic stress is known to affect serotonin (5HT) neurotransmission in the brain and to alter body temperature. The body temperature is controlled in part, by the medial preoptic area (mPOA) of the hypothalamus. To investigate the effect of chronic stress on 5HT and how it affects body temperature regulation, we examined whether exposure to a chronic unpredictable stress (CUS) paradigm produces long-term alterations in thermoregulatory function of the mPOA through decreased 5HT neurotransmission. Adult male Sprague-Dawley rats underwent 21 d of CUS. Four days after the last stress exposure, basal body temperature in the home cage and body temperature in a cold room maintained at 10 °C were recorded. The CUS rats had significantly higher subcutaneous basal body temperature at 13:00 h compared to unstressed (NoStress) rats. Whereas the NoStress rats were able to significantly elevate body temperature from basal levels at 30 and 60 min of exposure to the cold room, the CUS rats showed a hypothermic response to the cold. Treatment during CUS with metyrapone, a corticosterone synthesis inhibitor, blocked stress-induced decrease in body temperature in response to the cold challenge. CUS also decreased 5HT transporter protein immunoreactivity in the mPOA and 5HT2A/C agonist injection into the mPOA after CUS exposure caused stressed rats to exhibit a sensitized hyperthermic response to cold. These results indicate that the CUS induced changes to the 5HTergic system alter mPOA function in thermoregulation. These findings help us to explain the mechanisms underlying chronic stress-induced disorders such as chronic fatigue syndrome wherein long lasting thermoregulatory deficits are observed.

  12. Sex differences in chronic stress effects on cognition in rodents.

    Science.gov (United States)

    Luine, Victoria; Gomez, Juan; Beck, Kevin; Bowman, Rachel

    2017-01-01

    Chronic stress causes deleterious changes in physiological function in systems ranging from neural cells in culture to laboratory rodents, sub-human primates and humans. It is notable, however, that the vast majority of research in this area has been conducted in males. In this review, we provide information about chronic stress effects on cognition in female rodents and contrast it with responses in male rodents. In general, females show cognitive resilience to chronic stressors which impair male cognitive function using spatial tasks including the radial arm maze, radial arm water maze, Morris water maze, Y-maze and object placement. Moreover, stress often enhances female performance in some of these cognitive tasks. Memory in females is not affected by stress in non-spatial memory tasks like recognition memory and temporal order recognition memory while males show impaired memory following stress. We discuss possible bases for these sex-dependent differences including the use of different strategies by the sexes to solve cognitive tasks. Whether the sex differences result from changes in non-mnemonic factors is also considered. Sex-dependent differences in alcohol and drug influences on stress responses are also described. Finally, the role of neurally derived estradiol in driving sex differences and providing resilience to stress in females is shown. The importance of determining the nature and extent of sex differences in stress responses is that such differences may provide vital information for understanding why some stress related diseases have different incidence rates between the sexes and for developing novel therapeutic treatments. Copyright © 2016 Elsevier Inc. All rights reserved.

  13. The dynamics of migration-related stress and coping of female domestic workers from the Philippines: an exploratory study.

    Science.gov (United States)

    van der Ham, Alida Joanna; Ujano-Batangan, Maria Theresa; Ignacio, Raquel; Wolffers, Ivan

    2015-01-01

    Female domestic workers face many migration-related stressors that affect their mental health, but we know little about the dynamics of stress and coping in different migration phases. This exploratory study aims to assess stress and coping of female migrant domestic workers from the Philippines in different phases of the migration process; prior to migration, in the country of destination and upon return to the Philippines. Data were collected in 2010 using questionnaires (N = 500). Validation of findings took place in a work shop (23 participants) and two focus groups (13 and 8 participants). Stress levels of women were significantly higher abroad than in the Philippines. Stress and coping in the Philippines was primarily related to financial issues, while stress and coping abroad related more strongly loneliness, working conditions and employers. Findings from this study provide insight in the phase-specific and transnational dimensions of stress and coping.

  14. Retirement and drinking outcomes: lingering effects of workplace stress?

    Science.gov (United States)

    Richman, Judith A; Zlatoper, Kenneth W; Zackula Ehmke, Jennifer L; Rospenda, Kathleen M

    2006-05-01

    This study assesses the degree to which sexual harassment (SH), generalized workplace abuse (GWA), and psychological workload (PWL) impact drinking behaviors in retirement. A mail survey was completed at four points in time by a cohort of 1654 employees initially drawn from a university workplace. Questionnaires assessed experiences of SH, GWA, PWL and drinking behaviors. Hypotheses were tested involving (1) the extent to which SH, GWA, and PWL experienced while working were associated with frequency and quantity of drinking in retirement, (2) the extent to which drinking levels of retirees differed from those of current employees experiencing similar stress levels, and (3) the extent to which gender moderated these relationships. Retirees reporting earlier stressful work environments report higher levels of alcohol consumption during retirement compared to those retirees reporting less stressful earlier work environments. Gender moderated these relationships. The findings of this study suggest that there may be a residual effect of workplace stress during retirement.

  15. Stress Effects on Stop Bursts in Five Languages

    Directory of Open Access Journals (Sweden)

    Marija Tabain

    2016-11-01

    Full Text Available This study examines the effects of stress on the stop burst in five languages differing in number of places of articulation, as reflected in burst duration, spectral centre of gravity, and ­spectral standard deviation. The languages studied are English (three places of articulation /p t k/, the Indonesian language Makasar (four places /p t c k/, and the Central Australian languages ­Pitjantjatjara, Warlpiri (both five places /p t ʈ c k/, and Arrernte (six places /p t̪ t ʈ c k/. We find that languages differ in how they manifest stress on the consonant, with Makasar not ­showing any effect of stress at all, and Warlpiri showing an effect on burst duration, but not on the ­spectral measures. For the other languages, the velar /k/ has a “darker” quality (i.e., lower spectral centre of gravity, and/or a less diffuse spectrum (i.e., lower standard deviation under stress; while the alveolar /t/ has a “lighter” quality under stress. In addition, the dental /t̪/ has a more diffuse spectrum under stress. We suggest that this involves enhancement of the features [grave] and [diffuse] under stress, with velars being [+grave] and [–diffuse], alveolars being [–grave], and dentals being [+diffuse]. We discuss the various possible spectral effects of enhancement of these features. Finally, in the languages with five or six places of articulation, the stop burst is longer only for the palatal /c/ and the velar /k/, which have intrinsically long burst durations, and not for the anterior coronals /t̪ t ʈ/, which have intrinsically short burst durations. We suggest that in these systems, [burst duration] is a feature that separates these two groups of consonants.

  16. Effective Stress Law in Unconventional Reservoirs under Different Boundary Conditions

    Science.gov (United States)

    Saurabh, S.; Harpalani, S.

    2017-12-01

    Unconventional reservoirs have attracted a great deal of research interest worldwide during the past two decades. Low permeability and specialized techniques required to exploit these resources present opportunities for improvement in both production rates and ultimate recovery. Understanding subsurface stress modifications and permeability evolution are valuable when evaluating the prospects of unconventional reservoirs. These reservoir properties are functions of effective stress. As a part of this study, effective stress law, specifically the variation of anisotropic Biot's coefficient under various boundary conditions believed to exist in gas reservoirs by different researchers, has been established. Pressure-dependent-permeability (PdK) experiments were carried out on San Juan coal under different boundary conditions, that is, uniaxial strain condition and constant volume condition. Stress and strain in the vertical and horizontal directions were monitored throughout the experiment. Data collected during the experiments was used to determine the Biot's coefficient in vertical and horizontal directions under these two boundary conditions, treating coal as transversely isotropic. The variation of Biot's coefficient was found to be well correlated with the variation in coal permeability. Based on the estimated values of Biot's coefficients, a theory of variation in its value is presented for other boundary conditions. The findings of the study shed light on the inherent behavior of Biot's coefficient under different reservoir boundary conditions. This knowledge can improve the modeling work requiring estimation of effective stress in reservoirs, such as, pressure-/stress- dependent permeability. At the same time, if the effective stresses are known with more certainty by other methods, it enables assessment of the unknown reservoir boundary conditions.

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

    Science.gov (United States)

    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.

  18. SAP-4, Static and Dynamic Linear System Stress Analysis for Various Structures

    International Nuclear Information System (INIS)

    Zawadzki, S.

    1984-01-01

    1 - Description of problem or function: SAP4 is a structural analysis program for determining the static and dynamic response of linear systems. The structural systems to be analyzed may be composed of combinations of a number of different structural elements. Currently the program contains the following element types - (a) three-dimensional truss element, (b) three-dimensional beam element, (c) plane stress and plane strain element, (d) two-dimensional axisymmetric solid, (e) three-dimensional solid, (f) variable-number nodes thick shell and three-dimensional element, (g) thin-plate or thin-shell element, (h) boundary element, and (i) pipe element (tangent and bend). 2 - Method of solution: The formation of the structure matrices is carried out in the same way in a static or dynamic analysis. The static analysis is continued by solving the equations of equilibrium followed by the computation of element stresses. In a dynamic analysis the choice is between frequency calculations only, frequency calculations followed by response history analysis, frequency calculations followed by response spectrum analysis, or response history analysis by direct integration. To obtain the frequencies and vibration mode shapes, solution routines are used which calculate the required eigenvalues and eigenvectors directly without a transformation of the structure stiffness matrix and mass matrix to a reduced form. To perform the direct integration an unconditionally stable scheme is used, which also operates on the original structure stiffness matrix and mass matrix. In this manner the program operation and input data required for a dynamic analysis are simple extensions of those needed for a static analysis. 3 - Restrictions on the complexity of the problem: The capacity of the program depends mainly on the total number of nodal points in the system, the number of eigenvalues needed in the dynamic analysis, and the computer used. There is practically no restriction on the number of

  19. Effects of Social Defeat Stress on Sleep in Mice.

    Science.gov (United States)

    Henderson, Fiona; Vialou, Vincent; El Mestikawy, Salah; Fabre, Véronique

    2017-01-01

    Stress plays a key role in the development of psychiatric disorders and has a negative impact on sleep integrity. In mice, chronic social defeat stress (CSDS) is an ethologically valid model of stress-related disorders but little is known about its effects on sleep regulation. Here, we investigated the immediate and long-term effects of 10 consecutive days of social defeat (SD) on vigilance states in C57Bl/6J male mice. Social behavior was assessed to identify susceptible mice, i.e., mice that develop long-lasting social avoidance, and unsusceptible mice. Sleep-wake stages in mice of both groups were analyzed by means of polysomnographic recordings at baseline, after the first, third, and tenth stress sessions and on the 5th recovery day (R5) following the 10-day CSDS. In susceptible mice, each SD session produced biphasic changes in sleep-wake states that were preserved all along 10-day CSDS. These sessions elicited a short-term enhancement of wake time while rapid eye-movement (REM) sleep was strongly inhibited. Concomitantly, delta power was increased during non REM (NREM) sleep. During the following dark period, an increase in total sleep time, as well as wake fragmentation, were observed after each analyzed SD session. Similar changes were observed in unsusceptible mice. At R5, elevated high-frequency EEG activity, as observed in insomniacs, emerged during NREM sleep in both susceptible and unsusceptible groups suggesting that CSDS impaired sleep quality. Furthermore, susceptible but not unsusceptible mice displayed stress-anticipatory arousal during recovery, a common feature of anxiety disorders. Altogether, our findings show that CSDS has profound impacts on vigilance states and further support that sleep is tightly regulated by exposure to stressful events. They also revealed that susceptibility to chronic psychological stress is associated with heightened arousal, a physiological feature of stress vulnerability.

  20. Effects of Social Defeat Stress on Sleep in Mice

    Directory of Open Access Journals (Sweden)

    Fiona Henderson

    2017-11-01

    Full Text Available Stress plays a key role in the development of psychiatric disorders and has a negative impact on sleep integrity. In mice, chronic social defeat stress (CSDS is an ethologically valid model of stress-related disorders but little is known about its effects on sleep regulation. Here, we investigated the immediate and long-term effects of 10 consecutive days of social defeat (SD on vigilance states in C57Bl/6J male mice. Social behavior was assessed to identify susceptible mice, i.e., mice that develop long-lasting social avoidance, and unsusceptible mice. Sleep-wake stages in mice of both groups were analyzed by means of polysomnographic recordings at baseline, after the first, third, and tenth stress sessions and on the 5th recovery day (R5 following the 10-day CSDS. In susceptible mice, each SD session produced biphasic changes in sleep-wake states that were preserved all along 10-day CSDS. These sessions elicited a short-term enhancement of wake time while rapid eye-movement (REM sleep was strongly inhibited. Concomitantly, delta power was increased during non REM (NREM sleep. During the following dark period, an increase in total sleep time, as well as wake fragmentation, were observed after each analyzed SD session. Similar changes were observed in unsusceptible mice. At R5, elevated high-frequency EEG activity, as observed in insomniacs, emerged during NREM sleep in both susceptible and unsusceptible groups suggesting that CSDS impaired sleep quality. Furthermore, susceptible but not unsusceptible mice displayed stress-anticipatory arousal during recovery, a common feature of anxiety disorders. Altogether, our findings show that CSDS has profound impacts on vigilance states and further support that sleep is tightly regulated by exposure to stressful events. They also revealed that susceptibility to chronic psychological stress is associated with heightened arousal, a physiological feature of stress vulnerability.

  1. Optimization Design of Structures Subjected to Transient Loads Using First and Second Derivatives of Dynamic Displacement and Stress

    Directory of Open Access Journals (Sweden)

    Qimao Liu

    2012-01-01

    Full Text Available This paper developed an effective optimization method, i.e., gradient-Hessian matrix-based method or second order method, of frame structures subjected to the transient loads. An algorithm of first and second derivatives of dynamic displacement and stress with respect to design variables is formulated based on the Newmark method. The inequality time-dependent constraint problem is converted into a sequence of appropriately formed time-independent unconstrained problems using the integral interior point penalty function method. The gradient and Hessian matrixes of the integral interior point penalty functions are also computed. Then the Marquardt's method is employed to solve unconstrained problems. The numerical results show that the optimal design method proposed in this paper can obtain the local optimum design of frame structures and sometimes is more efficient than the augmented Lagrange multiplier method.

  2. Non-Destructive Evaluation Method Based On Dynamic Invariant Stress Resultants

    Directory of Open Access Journals (Sweden)

    Zhang Junchi

    2015-01-01

    Full Text Available Most of the vibration based damage detection methods are based on changes in frequencies, mode shapes, mode shape curvature, and flexibilities. These methods are limited and typically can only detect the presence and location of damage. Current methods seldom can identify the exact severity of damage to structures. This paper will present research in the development of a new non-destructive evaluation method to identify the existence, location, and severity of damage for structural systems. The method utilizes the concept of invariant stress resultants (ISR. The basic concept of ISR is that at any given cross section the resultant internal force distribution in a structural member is not affected by the inflicted damage. The method utilizes dynamic analysis of the structure to simulate direct measurements of acceleration, velocity and displacement simultaneously. The proposed dynamic ISR method is developed and utilized to detect the damage of corresponding changes in mass, damping and stiffness. The objectives of this research are to develop the basic theory of the dynamic ISR method, apply it to the specific types of structures, and verify the accuracy of the developed theory. Numerical results that demonstrate the application of the method will reflect the advanced sensitivity and accuracy in characterizing multiple damage locations.

  3. Using the Dynamic Model of Affect (DMA) to examine leisure time as a stress coping resource: Taking into account stress severity and gender difference

    Science.gov (United States)

    Qian, Xinyi Lisa; Yarnal, Careen M.; Almeida, David M.

    2014-01-01

    Affective complexity (AC) is a marker of psychological well-being. According to the Dynamic Model of Affect (DMA), stressful experiences reduce AC while positive events increase AC. One type of positive events is leisure, which was also identified as a coping resource. This study extended the DMA and leisure coping research by assessing gender difference in how daily stress severity and leisure time influence AC. Analyzing eight-day diary data, we found that females, compared to males, experienced greater decrease in AC with increase in stress severity but also bigger increase in AC with increase in leisure time. The finding highlights gender difference in affective reactivity to and coping with daily stress, the value of the DMA, and the importance of severity appraisal. PMID:25242824

  4. Dynamic thermo-chemo-mechanical strain of Zircaloy-4 slotted rings for evaluating strategies that mitigate stress corrosion cracking

    Energy Technology Data Exchange (ETDEWEB)

    Ferrier, G.A.; Metzler, J.; Farahani, M.; Chan, P.K.; Corcoran, E.C. [Royal Military College of Canada, Kingston, ON (Canada)

    2014-07-01

    Stress corrosion cracking (SCC) in Zircaloy-4 fuel sheaths has been investigated by static loading of slotted ring samples under hot and corrosive conditions. However, in nuclear reactors, power ramps can have short (e.g., 10-20 minutes) and recurring time frames due to dynamic processes such as on-power refuelling, adjuster rod manoeuvres, and load following. Therefore, to enable out-reactor dynamic testing, an apparatus was designed to dynamically strain slotted ring samples under SCC conditions. This apparatus can additionally be used to test fatigue properties. Unique capabilities of this apparatus and preliminary results obtained from static and dynamic tests are presented. (author)

  5. Interactive effects of environmental stress and inbreeding on reproductive traits in a wild bird population.

    Science.gov (United States)

    Marr, A B; Arcese, P; Hochachka, W M; Reid, J M; Keller, L F

    2006-11-01

    1. Conservation biologists are concerned about the interactive effects of environmental stress and inbreeding because such interactions could affect the dynamics and extinction risk of small and isolated populations, but few studies have tested for these interactions in nature. 2. We used data from the long-term population study of song sparrows Melospiza melodia on Mandarte Island to examine the joint effects of inbreeding and environmental stress on four fitness traits that are known to be affected by the inbreeding level of adult birds: hatching success, laying date, male mating success and fledgling survival. 3. We found that inbreeding depression interacted with environmental stress to reduce hatching success in the nests of inbred females during periods of rain. 4. For laying date, we found equivocal support for an interaction between parental inbreeding and environmental stress. In this case, however, inbred females experienced less inbreeding depression in more stressful, cooler years. 5. For two other traits, we found no evidence that the strength of inbreeding depression varied with environmental stress. First, mated males fathered fewer nests per season if inbred or if the ratio of males to females in the population was high, but inbreeding depression did not depend on sex ratio. Second, fledglings survived poorly during rainy periods and if their father was inbred, but the effects of paternal inbreeding and rain did not interact. 6. Thus, even for a single species, interactions between the inbreeding level and environmental stress may not occur in all traits affected by inbreeding depression, and interactions that do occur will not always act synergistically to further decrease fitness.

  6. Effects of stress on heart rate complexity--a comparison between short-term and chronic stress.

    Science.gov (United States)

    Schubert, C; Lambertz, M; Nelesen, R A; Bardwell, W; Choi, J-B; Dimsdale, J E

    2009-03-01

    This study examined chronic and short-term stress effects on heart rate variability (HRV), comparing time, frequency and phase domain (complexity) measures in 50 healthy adults. The hassles frequency subscale of the combined hassles and uplifts scale (CHUS) was used to measure chronic stress. Short-term stressor reactivity was assessed with a speech task. HRV measures were determined via surface electrocardiogram (ECG). Because respiration rate decreased during the speech task (pshort-term stress decreased HR D2 (calculated via the pointwise correlation dimension PD2) (pshort-term stress. Partial correlation adjusting for respiration rate showed that HR D2 was associated with chronic stress (r=-.35, p=.019). Differential effects of chronic and short-term stress were observed on several HRV measures. HR D2 decreased under both stress conditions reflecting lowered functionality of the cardiac pacemaker. The results confirm the importance of complexity metrics in modern stress research on HRV.

  7. Effectiveness of stress management training on stress reduction in pregnant women

    Directory of Open Access Journals (Sweden)

    Mahboobeh Shirazi

    2016-10-01

    .1 for moderated level stress (P= 0.001 and 40.1 to 16.6 for high level of stress (P= 0.0001 respectively. Conclusion: First trimester of pregnancy is a crucial stage of fetal growth and development. Based on our findings, stress management training in this period has beneficial effects on stress reduction and enhances maternal health status.

  8. Effect of mindfulness-based stress reduction on sleep quality

    DEFF Research Database (Denmark)

    Andersen, Signe; Würtzen, Hanne; Steding-Jessen, Marianne

    2013-01-01

    The prevalence of sleep disturbance is high among cancer patients, and the sleep problems tend to last for years after the end of treatment. As part of a large randomized controlled clinical trial (the MICA trial, NCT00990977) of the effect of mindfulness-based stress reduction (MBSR) on psycholo......The prevalence of sleep disturbance is high among cancer patients, and the sleep problems tend to last for years after the end of treatment. As part of a large randomized controlled clinical trial (the MICA trial, NCT00990977) of the effect of mindfulness-based stress reduction (MBSR...

  9. The effect of morphine on biliary dynamics

    International Nuclear Information System (INIS)

    Pedersen, S.A.; Oester-Joergensen, E.; Kraglund, K.

    1987-01-01

    The effect of morphine on biliary dynamics was studied by cholescintigraphy with 99m Tc-HIDA. Among 30 normals without morphine injection 3 did not demonstrate intestinal radioactivity after 1 h, whereas all visualized the gallbladder. Eight normals with morphine injection did not demonstrate intestinal radioactivity after 2 h, but all had gallbladder visualization very early. Variables of the time-activity curves from liver areas did not point to impaired uptake or excretion. Morphine-induced increase in resistance to passage from the common duct to the intestines in normals is of a magnitude that forces the total amount of bile to accumulate in the gallbladder. Results from 11 patients after cholecystectomy indicate that the increase in pressure is less than the maximal secretory pressure of the liver. The resorptive capacity and the compliance of the gallbladder enable these events to take place without signs of secondary liver impairment

  10. Noise-induced effects in population dynamics

    Science.gov (United States)

    Spagnolo, Bernardo; Cirone, Markus; La Barbera, Antonino; de Pasquale, Ferdinando

    2002-03-01

    We investigate the role of noise in the nonlinear relaxation of two ecosystems described by generalized Lotka-Volterra equations in the presence of multiplicative noise. Specifically we study two cases: (i) an ecosystem with two interacting species in the presence of periodic driving; (ii) an ecosystem with a great number of interacting species with random interaction matrix. We analyse the interplay between noise and periodic modulation for case (i) and the role of the noise in the transient dynamics of the ecosystem in the presence of an absorbing barrier in case (ii). We find that the presence of noise is responsible for the generation of temporal oscillations and for the appearance of spatial patterns in the first case. In the other case we obtain the asymptotic behaviour of the time average of the ith population and discuss the effect of the noise on the probability distributions of the population and of the local field.

  11. Thermofield dynamics and Casimir effect for fermions

    International Nuclear Information System (INIS)

    Queiroz, H.; Silva, J.C. da; Khanna, F.C.; Malbouisson, J.M.C.; Revzen, M.; Santana, A.E.

    2005-01-01

    A generalization of the Bogoliubov transformation is developed to describe a space compactified fermionic field. The method is the fermionic counterpart of the formalism introduced earlier for bosons [Phys. Rev. A 66 (2002) 052101], and is based on the thermofield dynamics approach. We analyze the energy-momentum tensor for the Casimir effect of a free massless fermion field in a d-dimensional box at finite temperature. As a particular case the Casimir energy and pressure for the field confined in a three-dimensional parallelepiped box are calculated. It is found that the attractive or repulsive nature of the Casimir pressure on opposite faces changes depending on the relative magnitude of the edges. We also determine the temperature at which the Casimir pressure in a cubic box changes sign and estimate its value when the edge of the cube is of the order of the confining lengths for baryons

  12. Investigation into Mechanism of Floor Dynamic Rupture by Evolution Characteristics of Stress and Mine Tremors: A Case Study in Guojiahe Coal Mine, China

    Directory of Open Access Journals (Sweden)

    Guangjian Liu

    2018-01-01

    Full Text Available In order to explore the mechanism of floor dynamic rupture, the current study adopts a thin plate model to further investigate the condition of floor failure. One of the possible explanations could be floor buckling due to high horizontal stress and dynamic disturbance ultimately leading to rapid and massive release of elastic energy thus inducing dynamic rupture. Seismic computed tomography and 3D location were employed to explore the evolution characteristics of floor stress distribution and positions of mine tremors. In the regions of floor dynamic rupture, higher P-wave velocity was recorded prior to the dynamic rupture. On the contrary, relatively lower reading was observed after the dynamic rupture thus depicting a high stress concentration condition. Meanwhile, evolution of mine tremors revealed the accumulation and subsequent release of energy during the dynamic rupture process. It was further revealed that dynamic rupture was induced due to the superposition of static and dynamic stresses: (i the high static stress concentration due to frontal and lateral abutment stress from coal pillar and (ii dynamic stress from the fracture and caving of coal pillar, hard roof, and key stratum. In the later part of this study, the floor dynamic rupture occurrence process would be reproduced through numerical simulations within a 0.6 sec time frame. The above-mentioned findings would be used to propose a feasible mechanism for prewarning and prevention of floor dynamic rupture using seismic computed tomography and mine tremors 3D location.

  13. The effect of occupational stress, psychological stress and burnout on employee performance: Evidence from banking industry

    Directory of Open Access Journals (Sweden)

    Shahram Hashemnia

    2014-09-01

    Full Text Available This paper presents an empirical investigation on the effects of occupational stress, psychological stress as well as job burnout on women’s employee performance in city of Karaj, Iran. The proposed study designs a questionnaire in Likert scale and distributes it among all female employees who worked for Bank Maskan in this city. In our survey, employee performance consists of three parts of interpersonal performance, job performance as well as organizational performance. Cronbach alpha has been used to verify the overall questionnaire, all components were within acceptable levels, and the implementation of Kolmogorov-Smirnov test has indicated that the data were not normally distributed. Using Spearman correlation ratio as well as regression techniques, the study has determined that while psychological stress influenced significantly on all three components of employee performance including interpersonal performance, job performance as well as organizational performance, the effect on job performance was greater than the other components. In addition, occupational stress only influences on organizational as well as interpersonal performance. Finally, employee burnout has no impact on any components of employee performance.

  14. Neuroprotective effects of sildenafil against oxidative stress and memory dysfunction in mice exposed to noise stress.

    Science.gov (United States)

    Sikandaner, Hu Erxidan; Park, So Young; Kim, Min Jung; Park, Shi Nae; Yang, Dong Won

    2017-02-15

    Noise exposure has been well characterized as an environmental stressor, and is known to have auditory and non-auditory effects. Phosphodiesterase 5 (PDE5) inhibitors affect memory and hippocampus plasticity through various signaling cascades which are regulated by cGMP. In this study, we investigated the effects of sildenafil on memory deficiency, neuroprotection and oxidative stress in mice caused by chronic noise exposure. Mice were exposed to noise for 4h every day up to 14days at 110dB SPL of noise level. Sildenafil (15mg/kg) was orally administered 30min before noise exposure for 14days. Behavioral assessments were performed using novel object recognition (NOR) test and radial arm maze (RAM) test. Higher levels of memory dysfunction and oxidative stress were observed in noise alone-induced mice compared to control group. Interestingly, sildenafil administration increased memory performance, decreased oxidative stress, and increased neuroprotection in the hippocampus region of noise alone-induced mice likely through affecting memory related pathways such as cGMP/PKG/CREB and p25/CDK5, and induction of free radical scavengers such as SOD1, SOD2, SOD3, Prdx5, and catalase in the brain of stressed mice. Copyright © 2016. Published by Elsevier B.V.

  15. Effect of Coulomb stress on the Gutenberg-Richter law

    Science.gov (United States)

    Navas-Portella, V.; Corral, A.; Jimenez, A.

    2017-12-01

    Coulomb stress theory has been used for years in seismology to understand how earthquakes trigger each other. Whenever an earthquake occurs, the stress field changes in its neighbourhood, with places with positive values brought closer to failure, whereas negative values distance away that location from failure. Earthquake models that relate rate changes and Coulomb stress after a main event, such as the rate-and-state model, assume negative and positive stress values affect rate changes according to the same functional form. As a first order approximation, under uniform background seismicity before the main event, different values of the b-exponent in the Gutenberg-Richter law would indicate different behaviour for positive and negative stress. In this work, we study the Gutenberg-Richter law in the aftershock sequence of the Landers earthquake (California, 1992, MW=7.3). By using a statistically based fitting method, we discuss whether the sign of Coulomb stresses and the distance to the fault have a significant effect on the value of the b-exponent.

  16. Effects of lifetime stress exposure on mental and physical health in young adulthood: How stress degrades and forgiveness protects health.

    Science.gov (United States)

    Toussaint, Loren; Shields, Grant S; Dorn, Gabriel; Slavich, George M

    2016-06-01

    To examine risk and resilience factors that affect health, lifetime stress exposure histories, dispositional forgiveness levels, and mental and physical health were assessed in 148 young adults. Greater lifetime stress severity and lower levels of forgiveness each uniquely predicted worse mental and physical health. Analyses also revealed a graded Stress × Forgiveness interaction effect, wherein associations between stress and mental health were weaker for persons exhibiting more forgiveness. These data are the first to elucidate the interactive effects of cumulative stress severity and forgiveness on health, and suggest that developing a more forgiving coping style may help minimize stress-related disorders. © The Author(s) 2014.

  17. Respiratory Effects and Systemic Stress Response Following ...

    Science.gov (United States)

    Previous studies have demonstrated that exposure to the pulmonary irritant ozone causes myriad systemic metabolic and pulmonary effects attributed to sympathetic and hypothalamus-pituitary-adrenal (HPA) axis activation, which are exacerbated in metabolically impaired models. We examined respiratory and systemic effects following exposure to a sensory irritant acrolein to elucidate the systemic and pulmonary consequences in healthy and diabetic rat models. Male Wistar and Goto Kakizaki (GK) rats, a nonobese type II diabetic Wistar-derived model, were exposed by inhalation to 0, 2, or 4 ppm acrolein, 4 h/d for 1 or 2 days. Exposure at 4 ppm significantly increased pulmonary and nasal inflammation in both strains with vascular protein leakage occurring only in the nose. Acrolein exposure (4 ppm) also caused metabolic impairment by inducing hyperglycemia and glucose intolerance (GK > Wistar). Serum total cholesterol (GKs only), low-density lipoprotein (LDL) cholesterol (both strains), and free fatty acids (GK > Wistar) levels increased; however, no acrolein-induced changes were noted in branched-chain amino acid or insulin levels. These responses corresponded with a significant increase in corticosterone and modest but insignificant increases in adrenaline in both strains, suggesting activation of the HPA axis. Collectively, these data demonstrate that acrolein exposure has a profound effect on nasal and pulmonary inflammation, as well as glucose and lipid metabolis

  18. Respiratory Effects and Systemic Stress Response Following ...

    Science.gov (United States)

    Previous studies have demonstrated that exposure to ozone, a pulmonary irritant, causes myriad systemic metabolic and pulmonary effects that are attributed to neuronal and hypothalamus-pituitary-adrenal (HPA) axis activation, which are exacerbated in metabolically-impaired models. In order to elucidate the systemic consequences and the contribution of the HPA axis in mediating metabolic and respiratory effects of acrolein, a sensory irritant, we examined pulmonary, nasal, and systemic effects in rats following exposure. Male, 10 week old Wistar and Goto Kakizaki (GK) rats, a non-obese type II diabetic Wistar-derived model, were exposed to 0, 2 or 4 ppm acrolein, 4h/day for 1 or 2 days. Acrolein exposure at 4 ppm significantly increased pulmonary and nasal damage in both strains as demonstrated by increased inspiratory and expiratory times indicating labored breathing, elevated biomarkers of injury, and neutrophilic inflammation. Overall, at both time points acrolein exposure caused noticeably more damage in the nasal passages as opposed to the lung with vascular protein leakage occurring only in the nose. Acrolein exposure (4 ppm) also led to metabolic impairment by inducing hyperglycemia and glucose intolerance (GK>Wistar) as indicated by glucose tolerance testing. In addition, serum total cholesterol (GKs only), LDL cholesterol (both strains), and free fatty acids (GK>Wistar) levels increased; however, no acrolein-induced changes were noted in branched-c

  19. Simulation of bending stress variation in long buried thick-walled pipes under the earth’s movement using combined linear dynamics and beam theories

    Directory of Open Access Journals (Sweden)

    Salau Tajudeen A.O.

    2014-01-01

    Full Text Available This study reported a simulation approach to the understanding of the interactions between a buried pipe and the soil system by computing the bending stress variation of harmonically-excited buried pipes. The established principles of linear dynamics theory and simple beam theory were utilised in the analysis of the problem of buried pipe bending stress accumulation and its dynamics. With regards to the parameters that influence the bending stress variations, the most important are the isolation factor, uniform external load, and the corresponding limiting conditions. The simulated mathematical expressions, containing static and dynamic parameters of the buried pipe and earth, were coded in Fortran programming language and applied in the simulation experiment. The results obtained showed that harmonically-excited buried thick-walled pipe became stable and effective when the ratio of the natural frequency of vibration to the forced frequency is greater than 2.0, whenever the damped factor is used as the control parameter for the maximum bending stress. The mirror image of the stress variation produces variation in the location of the maximum bending stress in quantitative terms. The acceptable pipe materials for the simulated cases must have yield strength in bending greater than or equal to 13.95 MPa. The results obtained in this work fill a gap in the literature and will be useful to pipeline engineers and designers, as well as to environmental scientists in initialising and controlling environmental issues and policy formulation concerning the influence of buried pipe on the soil and water in the environment.

  20. Study of stress, self-esteem and depression in medical students and effect of music on perceived stress.

    Science.gov (United States)

    Baste, Vrushali S; Gadkari, Jayashree V

    2014-01-01

    Medical students are exposed to many stressors and if stress is perceived negatively or becomes excessive can affect academic performance and health adversely. The objective of this study was to assess stress, predominant stressor and effect of music on perceived stress. 90 undergraduate students were selected randomly. A written questionnaire about personal information, stressful factors, ways to cope up stress, Rosenberg self-esteem scale (Rosenberg, 1965) and 'Quick Inventory of Depressive Symptomatology' self-rated 16 (QIDS-SR-16) was given.45.6% Students had mild stress, 7.7% students had moderate stress and 1.1% students had severe stress. Academic factors were the predominant cause of stress in most students, followed by physical, social and emotional. On Rosenberg self-esteem scale (Rosenberg, 1965) 85.6% students had high self-esteem and on QIDS-SR16 50% students had depression. Effect of music on perceived stress was statistically significant. Medical curriculum is associated with increased stress in students. Music can be used as simple, inexpensive and effective therapy for stress.

  1. Effects of couple stresses on MHD Couette flow

    International Nuclear Information System (INIS)

    Soundalgekar, V.M.; Aranake, R.N.

    1978-01-01

    An exact analysis of the effects of the couple stresses on the MHD Couette flow of an electrically conducting, viscous incompressible fluid is carried out. Closed form solutions are derived for the velocity, the current density, the skin-friction at the lower plate, the force to move the upper plate, and the coefficient of mass flux for (i) A→infinity, and (ii) 2M/A 1, where a is the couple stress parameter and M is the Hartmann number. These are shown graphically followed by a discussion. During the course of discussion the effects of A are quantitatively compared with those in the ordinary case. It is observed that in the presence of a magnetic field the skin friction is affected by the couple stresses. (Auth.)

  2. Pipe stress intensity factors and coupled depressurization and dynamic crack propagation. 1976 Annual report

    International Nuclear Information System (INIS)

    Emery, A.F.; Kobayashi, A.S.; Love, W.J.

    1978-04-01

    This report contains the description of predictive models for the initiation and propagation of cracks in pipes and the numerical results obtained. The initiation of the crack was studied by evaluating stress intensity factors under static conditions for a series of representative flaws. Three-dimensional static stress intensity factors were determined for quarter-elliptical cracks at the corner of a hole in an infinite plate and at the corner of a bore in a rotating disk. Semi-elliptical cracks for plates in bending and in pressurized and thermally stressed hollow cylinders were also evaluated. The stress fields, in the absence of a crack, were used in the ''alternating technique'' to compute the stress intensity factors along the crack front. Parametric studies were made to assess the effects of crack thickness, the ratio of the major and minor axes of the ellipse and the thickness of the cylinders or plates. These parametric results may be used to predict critical flaw sizes for the initiation of the running crack. The initiation and propagation of axial through cracks in pressurized pipes was studied by using an elastic-plastic finite different shell code coupled with a one-dimensional thermal-hydraulic code which computed the leakage through the crack opening and the depressurization of the fluid in the pipe. The effects of large deflections and different fluid pressure profiles were investigated. The results showed that the crack opening shape is dependent upon the fracture criterion used and upon the average pressure on the crack flaps, but not upon the specific pressure profile. The consideration of large deflections changed the opening size of the crack and through the coupling with the pipe pressures, strongly affected the crack tip speed. However, for equal crack lengths, there was little difference between calculations made for large and small deflection

  3. Evaluation of Rock Stress Estimation by the Kaiser effect

    International Nuclear Information System (INIS)

    Lehtonen, A.

    2005-11-01

    The knowledge of in situ stress is the key input parameter in many rock mechanics analyses. Information on stress allows the definition of boundary conditions for various modelling and engineering tasks. Presently, the estimation of stresses in bedrock is one of the most difficult, time-consuming and high-priced rock mechanical investigations. In addition, the methods used today have not evolved significantly in many years. This brings out a demand for novel, more economical and practical methods for stress estimation. In this study, one such method, Kaiser effect based on acoustic emission of core samples, has been evaluated. It can be described as a 'memory' in rock that is indicated by a change in acoustic emission emitted during uniaxial loading test. The most tempting feature of this method is the ability to estimate the in situ stress state from core specimens in laboratory conditions. This yields considerable cost savings compared to laborious borehole measurements. Kaiser effect has been studied in order to determine in situ stresses for decades without any major success. However, recent studies in Australia and China have been promising and made the estimation of stress tensor possible from differently oriented core samples. The aim of this work has been to develop a similar estimation method in Finland (including both equipment and data reduction), and to test it on samples obtained from Olkiluoto, Eurajoki. The developed measuring system proved to work well. The quality of obtained data varied, but they were still interpretable. The results obtained from these tests were compared with results of previous overcoring measurements, and they showed quite good correlation. Thus, the results were promising, but the method still needs further development and more testing before the final decision on its feasibility can be made. (orig.)

  4. [Effects of job content on psychological stress in young recruits].

    Science.gov (United States)

    Zhang, J J; Tao, N; Jia, J M; Qin, X; Tian, H; Qiu, E C; Liu, J W

    2016-04-20

    To explore the effects of job content on psychological stress in young recruits. In October 2014, 625 young recruits enrolled in one troop of Xinjiang Military Command in 2014 were chosen as subjects by multi-stage stratified random sampling. The Chinese version of the job content questionnaire (JCQ)and the psychological stress self evaluation test (PEST)were used to investigate the subjects. The subjects were divided into two groups with scores higher and lower than the mean score of three subscales (job requirement, degree of autonomy, and social support)of JCQ to explore the effects of job content on psychological stress in young recruits. The correlation of psychological stress with three subscales of job content was evaluated using the Pearson' s correlation analysis. Binary logistic regression analysis was used to analyze the influencing factors for psychological stress. The PEST score of young recruits was 49.98±9.98. Forty-five (7.68%)out of them had scores of ≥70 points and were diagnosed with high levels of psychological stress. When the subjects were grouped based on socio-demographic characteristics, a high level of psychological stress was significantly more frequent in subjects less than 20 years of age than in those not less than 20 years of age, in smoking subjects than in non-smoking subjects, and in urban residents than in rural residents (10.42% vs 5.03%, P0.05). In various job content domains that had impacts on psychological stress, subjects with a low score of social support had significantly higher PEST scores than those with a high score of social support (50.96±10.35 vs 48.49±9.22, Pautonomy and social support (r=-0.103, Pjob requirement and social support were influencing factors for psychological stress (OR=0.718, 95% CI= 0.718 (0.607~0.851), Pjob requirement subscale and social support subscale may be potential protective factor and risk factor for psychological stress, respectively.

  5. Effect of childhood physical abuse on cortisol stress response.

    Science.gov (United States)

    Carpenter, Linda L; Shattuck, Thaddeus T; Tyrka, Audrey R; Geracioti, Thomas D; Price, Lawrence H

    2011-03-01

    Abuse and neglect are highly prevalent in children and have enduring neurobiological effects. Stressful early life environments perturb the hypothalamic-pituitary-adrenal (HPA) axis, which in turn may predispose to psychiatric disorders in adulthood. However, studies of childhood maltreatment and adult HPA function have not yet rigorously investigated the differential effects of maltreatment subtypes, including physical abuse. In this study, we sought to replicate our previous finding that childhood maltreatment was associated with attenuated cortisol responses to stress and determine whether the type of maltreatment was a determinant of the stress response. Salivary cortisol response to the Trier Social Stress Test (TSST) was examined in a non-clinical sample of women (n = 110). Subjects had no acute medical problems and were not seeking psychiatric treatment. Effects of five maltreatment types, as measured by the Childhood Trauma Questionnaire, on cortisol response to the TSST were investigated. To further examine the significant (p < 0.005) effect of one maltreatment type, women with childhood physical abuse (PA) (n = 20) were compared to those without past PA (n = 90). Women reporting childhood PA displayed a significantly blunted cortisol response to the TSST compared with subjects without PA, after controlling for estrogen use, age, other forms of maltreatment, and other potential confounds. There were no differences between PA and control groups with regard to physiological arousal during the stress challenge. In a non-clinical sample of women with minimal or no current psychopathology, physical abuse is associated with a blunted cortisol response to a psychosocial stress task.

  6. A method for the dynamic and thermal stress analysis of space shuttle surface insulation

    Science.gov (United States)

    Ojalvo, I. U.; Levy, A.; Austin, F.

    1975-01-01

    The thermal protection system of the space shuttle consists of thousands of separate insulation tiles bonded to the orbiter's surface through a soft strain-isolation layer. The individual tiles are relatively thick and possess nonuniform properties. Therefore, each is idealized by finite-element assemblages containing up to 2500 degrees of freedom. Since the tiles affixed to a given structural panel will, in general, interact with one another, application of the standard direct-stiffness method would require equation systems involving excessive numbers of unknowns. This paper presents a method which overcomes this problem through an efficient iterative procedure which requires treatment of only a single tile at any given time. Results of associated static, dynamic, and thermal stress analyses and sufficient conditions for convergence of the iterative solution method are given.

  7. Protective Effect against Oxidative Stress in Medicinal Plant Extracts

    International Nuclear Information System (INIS)

    Kim, Jeong Hee; Lee, Eun Ju; Shin, Dong O; Hong, Sung Eun; Kim, Jin Kyu

    2000-01-01

    Protective effect of medicinal plant extracts against oxidative stress were screened in this study. Methanol extracts from 48 medicinal plants, which were reported to have antioxidative or anti-inflammatory effect were prepared and screened for their protective activity against chemically-induced and radiation-induced oxidative stress by using MTT assay. Thirty three samples showed protective activity against chemically-induced oxidative stress in various extent. Among those samples, extract of Glycyrrhiza uralensis revealed the strongest activity (25.9% at 100 μg/ml) with relatively lower cytotoxicity. Seven other samples showed higher than 20% protection at 100 μg/ml. These samples were tested for protection activity against radiation-induced oxidative stress. Methanol extract of Alpina officinarum showed the highest activity (17.8% at 20 μg/ml). Five fractions were prepared from the each 10 methanol extracts which showed high protective activity against oxidative stress. Among those fraction samples butanol fractions of Areca catechu var. dulcissima and Spirodela polyrrhiza showed the highest protective activities (78.8% and 77.2%, respectively, at 20 μg/ml)

  8. The effects of spatial dynamics on a wormhole throat

    Science.gov (United States)

    Alias, Anuar; Wan Abdullah, Wan Ahmad Tajuddin

    2018-02-01

    Previous studies on dynamic wormholes were focused on the dynamics of the wormhole itself, be it either rotating or evolutionary in character and also in various frameworks from classical to braneworld cosmological models. In this work, we modeled a dynamic factor that represents the spatial dynamics in terms of spacetime expansion and contraction surrounding the wormhole itself. Using an RS2-based braneworld cosmological model, we modified the spacetime metric of Wong and subsequently employed the method of Bronnikov, where it is observed that a traversable wormhole is easier to exist in an expanding brane universe, however it is difficult to exist in a contracting brane universe due to stress-energy tensors requirement. This model of spatial dynamic factor affecting the wormhole throat can also be applied on the cyclic or the bounce universe model.

  9. Microsecond molecular dynamics simulations of intrinsically disordered proteins involved in the oxidative stress response.

    Directory of Open Access Journals (Sweden)

    Elio A Cino

    Full Text Available Intrinsically disordered proteins (IDPs are abundant in cells and have central roles in protein-protein interaction networks. Interactions between the IDP Prothymosin alpha (ProTα and the Neh2 domain of Nuclear factor erythroid 2-related factor 2 (Nrf2, with a common binding partner, Kelch-like ECH-associated protein 1(Keap1, are essential for regulating cellular response to oxidative stress. Misregulation of this pathway can lead to neurodegenerative diseases, premature aging and cancer. In order to understand the mechanisms these two disordered proteins employ to bind to Keap1, we performed extensive 0.5-1.0 microsecond atomistic molecular dynamics (MD simulations and isothermal titration calorimetry experiments to investigate the structure/dynamics of free-state ProTα and Neh2 and their thermodynamics of bindings. The results show that in their free states, both ProTα and Neh2 have propensities to form bound-state-like β-turn structures but to different extents. We also found that, for both proteins, residues outside the Keap1-binding motifs may play important roles in stabilizing the bound-state-like structures. Based on our findings, we propose that the binding of disordered ProTα and Neh2 to Keap1 occurs synergistically via preformed structural elements (PSEs and coupled folding and binding, with a heavy bias towards PSEs, particularly for Neh2. Our results provide insights into the molecular mechanisms Neh2 and ProTα bind to Keap1, information that is useful for developing therapeutics to enhance the oxidative stress response.

  10. Effect of Applied Stress and Temperature on Residual Stresses Induced by Peening Surface Treatments in Alloy 600

    Science.gov (United States)

    Telang, A.; Gnäupel-Herold, T.; Gill, A.; Vasudevan, V. K.

    2018-04-01

    In this study, the effects of applied tensile stress and temperature on laser shock peening (LSP) and cavitation shotless peening (CSP)-induced compressive residual stresses were investigated using neutron and x-ray diffraction. Residual stresses on the surface, measured in situ, were lower than the applied stress in LSP- and CSP-treated Alloy 600 samples (2 mm thick). The residual stress averaged over the volume was similar to the applied stress. Compressive residual stresses on the surface and balancing tensile stresses in the interior relax differently due to hardening induced by LSP. Ex situ residual stress measurements, using XRD, show that residual stresses relaxed as the applied stress exceeded the yield strength of the LSP- and CSP-treated Alloy 600. Compressive residual stresses induced by CSP and LSP decreased by 15-25% in magnitude, respectively, on exposure to 250-450 °C for more than 500 h with 10-11% of relaxation occurring in the first few hours. Further, 80% of the compressive residual stresses induced by LSP and CSP treatments in Alloy 600 were retained even after long-term aging at 350 °C for 2400 h.

  11. The Relevance of the Dynamic Stall Effect for Transient

    DEFF Research Database (Denmark)

    Jauch, Clemens; Sørensen, Poul; Bak-Jensen, Birgitte

    2005-01-01

    This article describes a methodology to quantify the influence of dynamic stall on transient fault operations of active-stall turbines. The model of the dynamic stall effect is introduced briefly. The behaviour of the dynamic stall model during a transient fault operation is described mathematica...

  12. Stress and its effects on horses reproduction

    Directory of Open Access Journals (Sweden)

    Amal M. AboEl-Maaty

    2011-11-01

    Full Text Available A total of 90 mares and horses were subjected to blood sampling for determining the effect of management (farm, reproductive condition, sex, age, breed and month of the year during breeding on circulating levels of cortisol and sex hormones. Blood samples were collected from December to the following June from four farms. Blood sera underwent testosterone, estradiol, progesterone and cortisol assaying using ELISA kits. Cortisol levels were significantly low in lactating mares during their foal heat but significantly high levels were recorded in both repeat breeder mares and horses used for racing. High and significant testosterone and estradiol levels were recorded in both stallions used for breeding especially after semen collection and early pregnant mares. Similar testosterone levels were recorded in both early pregnant mares and racing horses but high levels were recorded in stallions. Estradiol was high in both early pregnant and mares with endometritis but the highest levels were observed in stallions. Horses held in private farms had high cortisol levels compared to those of governmental farms. In contrast to mares, horses had low cortisol and high estradiol levels. Cortisol levels were high from April to June (Spring and early summer compared to its levels from December to March (Winter. Arab horses had low cortisol compared to native and imported foreign breeds. In conclusion, environmental condition, exercise, breed, management and the purpose of raising horses all are affecting its cortisol levels.

  13. Effect of moxifloxacin on oxidative stress, paraoxonase-1 (PON1 ...

    African Journals Online (AJOL)

    Purpose: To investigate the effect of moxifloxacin on paraoxonase-1 (PON1) activity, and serum oxidative stress in patients with multiple drug-resistant tuberculosis (MDR-TB). Methods: A total ofof 130 MDR-TB patients who were treated with moxifloxacin from October 2014 to October 2010 in Eastern Medical District of Linyi ...

  14. The effect of anesthesia type on stress hormone response ...

    African Journals Online (AJOL)

    Aim: The aim of this study was to investigate the effect of different types of anesthesia on stress hormones. Materials and Methods: The study was included 60 ASAI-II cases scheduled for major lower extremity surgery. The cases were randomized into 2 groups: The EA group was administered epidural anesthesia and the ...

  15. Effects of high concentration of chromium stress on physiological ...

    African Journals Online (AJOL)

    We studied the effects of high concentration of chromium (Cr) stress on physiological and biochemical characters and accumulation of Cr in Pingyang Tezao tea [Camellia sinensis (L) O. Kutze 'Pingyangtezao'] through a pot experiment. The results show that the indicators of photosynthesis were all suppressed with ...

  16. Stress urinary incontinence: effect of pelvic muscle exercise

    NARCIS (Netherlands)

    Ferguson, K. L.; McKey, P. L.; Bishop, K. R.; Kloen, P.; Verheul, J. B.; Dougherty, M. C.

    1990-01-01

    Twenty women with stress urinary incontinence diagnosed by urodynamic testing participated in a 6-week pelvic muscle exercise program. The aim of the study was to evaluate the effectiveness of the exercise program, with or without an intravaginal balloon, on urinary leakage as determined by a

  17. EFFECT OF DROUGHT STRESS ON EARLY GROWTH OF ...

    African Journals Online (AJOL)

    Ridwan

    ABSTRACT. Drought and high temperatures are said to have triggered increased tree mortality and could be linked to the menace of climate change. This research therefore investigated the effect of drought stress on early growth of Adansonia digitata where seedlings were exposed to different watering frequencies (Once ...

  18. Evaluation of drought and salinity stress effects on germination and ...

    African Journals Online (AJOL)

    To study the effect of polyethylene glycol (PEG) and NaCl stress on germination and early seedling stages on two cultivars of maize, two separated experiment were laid out at seed laboratory in Iran in 2011. This investigation was performed as factorial experiment under completely randomized design (CRD) with three ...

  19. Effects of life event stress, exercise workload, hardiness and coping ...

    African Journals Online (AJOL)

    Effects of life event stress, exercise workload, hardiness and coping style on susceptibility to the common cold. GA Struwig, M Papaikonomou, P Kruger. Abstract. No Abstract. South African Journal for Physical, Health Education, Recreation and DanceVol. 12(4) 2006: pp. 369-383. Full Text: EMAIL FULL TEXT EMAIL FULL ...

  20. Ameliorative Effects of Neurolytic Celiac Plexus Block on Stress and ...

    African Journals Online (AJOL)

    Purpose: To investigate effects of neurolytic celiac plexus block (NCPB) on stress and inflammation in rats with partial hepatectomy (PH). Methods: A model of PH rat was established, and serum C-reactive protein (CRP); corticosterone (GC); adrenocorticotropin (ACTH); noradrenaline (NA); adrenalin (AD); aspartate ...

  1. Title: Effect of abiotic stress on reduction of microbial contamination ...

    African Journals Online (AJOL)

    TERI

    2016-03-30

    Mar 30, 2016 ... Full Length Research Paper. Effect of osmotic stress on in vitro propagation of. Musa sp. ... In vitro propagation of banana preferably use sword sucker as explant source where microbial contamination poses a great problem in ... micropropagation. Endo-bacterial contamination is one of the major problems ...

  2. Wellness Intervention Effects on Lifestyle, Attitudes and Stress.

    Science.gov (United States)

    Horowitz, Stephen M.; And Others

    The effect of an on-site health promotion program on lifestyle behavior, health, attitude, and stress was studied with 41 university faculty and nonacademic administrators. The participants were administered a maximal graded exercise tolerance test, hydrostatic weighing, and the Lifestyle Analysis Questionnaire. While 32 staff were assigned to an…

  3. Effects of Stress and Social Enrichment on Alcohol Intake, Biological and Psychological Stress Responses in Rats

    Science.gov (United States)

    2010-06-28

    used were not sophisticated enough to elucidate the pattern. Using a more advanced statistical approach (e.g., Canonical discriminitive analysis...corticotrophin-releasing factor in stress-induced relapse to alcohol- seeking behavior in rats. Psychopharmacology (Berl) 150:317-324. Lex BW (1991) Some gender ...Prunell M, Dimitsantos V, Nadal R, Escorihuela RM (2006) Environmental enrichment effects in social investigation in rats are gender dependent

  4. Food stress causes sex-specific maternal effects in mites.

    Science.gov (United States)

    Walzer, Andreas; Schausberger, Peter

    2015-08-01

    Life history theory predicts that females should produce few large eggs under food stress and many small eggs when food is abundant. We tested this prediction in three female-biased size-dimorphic predatory mites feeding on herbivorous spider mite prey: Phytoseiulus persimilis, a specialized spider mite predator; Neoseiulus californicus, a generalist preferring spider mites; Amblyseius andersoni, a broad diet generalist. Irrespective of predator species and offspring sex, most females laid only one small egg under severe food stress. Irrespective of predator species, the number of female but not male eggs decreased with increasing maternal food stress. This sex-specific effect was probably due to the higher production costs of large female than small male eggs. The complexity of the response to the varying availability of spider mite prey correlated with the predators' degree of adaptation to this prey. Most A. andersoni females did not oviposit under severe food stress, whereas N. californicus and P. persimilis did oviposit. Under moderate food stress, only P. persimilis increased its investment per offspring, at the expense of egg number, and produced few large female eggs. When prey was abundant, P. persimilis decreased the female egg sizes at the expense of increased egg numbers, resulting in a sex-specific egg size/number trade-off. Maternal effects manifested only in N. californicus and P. persimilis. Small egg size correlated with the body size of daughters but not sons. Overall, our study provides a key example of sex-specific maternal effects, i.e. food stress during egg production more strongly affects the sex of the large than the small offspring. © 2015. Published by The Company of Biologists Ltd.

  5. The effects of shear and normal stress paths on rock friction

    International Nuclear Information System (INIS)

    Olsson, W.A.

    1990-01-01

    The effect of variable normal stress on the coefficient of friction of smooth artificial surfaces in welded tuff was studied. The shear stress response to changes in normal stress during constant-velocity sliding suggests that friction depends on the history of the normal stress; or, more generally, the path in shear/normal stress space. 6 refs., 5 figs

  6. The dual role of cyclin C connects stress regulated gene expression to mitochondrial dynamics

    Directory of Open Access Journals (Sweden)

    Randy Strich

    2014-09-01

    Full Text Available Following exposure to cytotoxic agents, cellular damage is first recognized by a variety of sensor mechanisms. Thenceforth, the damage signal is transduced to the nucleus to install the correct gene expression program including the induction of genes whose products either detoxify destructive compounds or repair the damage they cause. Next, the stress signal is disseminated throughout the cell to effect the appropriate changes at organelles including the mitochondria. The mitochondria represent an important signaling platform for the stress response. An initial stress response of the mitochondria is extensive fragmentation. If the damage is prodigious, the mitochondria fragment (fission and lose their outer membrane integrity leading to the release of pro-apoptotic factors necessary for programmed cell death (PCD execution. As this complex biological process contains many moving parts, it must be exquisitely coordinated as the ultimate decision is life or death. The conserved C-type cyclin plays an important role in executing this molecular Rubicon by coupling changes in gene expression to mitochondrial fission and PCD. Cyclin C, along with its cyclin dependent kinase partner Cdk8, associates with the RNA polymerase holoenzyme to regulate transcription. In particular, cyclin C-Cdk8 repress many stress responsive genes. To relieve this repression, cyclin C is destroyed in cells exposed to pro-oxidants and other stressors. However, prior to its destruction, cyclin C, but not Cdk8, is released from its nuclear anchor (Med13, translocates from the nucleus to the cytoplasm where it interacts with the fission machinery and is both necessary and sufficient to induce extensive mitochondria fragmentation. Furthermore, cytoplasmic cyclin C promotes PCD indicating that it mediates both mitochondrial fission and cell death pathways. This review will summarize the role cyclin C plays in regulating stress-responsive transcription. In addition, we will detail

  7. Better executive function under stress mitigates the effects of recent life stress exposure on health in young adults.

    Science.gov (United States)

    Shields, Grant S; Moons, Wesley G; Slavich, George M

    2017-01-01

    Executive function is a neuropsychological construct that enables controlled cognitive processing, which has been hypothesized to enhance individuals' resilience to stress. However, little empirical work has directly examined how executive function under different conditions mitigates the negative effects of stress exposure on health. To address this issue, we recruited 110 healthy young adults and assessed their recent life stress exposure, executive function in either a stressful or non-stressful context, and current health complaints. Based on existing research, we hypothesized that individuals exhibiting better executive function following a laboratory-based stressor (but not a control task) would demonstrate weaker associations between recent stress exposure and health because they perceived recent life stressors as being less severe. Consistent with this hypothesis, better executive function during acute stress, but not in the absence of stress, was associated with an attenuated link between participants' recent life stress exposure and their current health complaints. Moreover, this attenuating effect was mediated by lesser perceptions of stressor severity. Based on these data, we conclude that better executive function under stress is associated with fewer health complaints and that these effects may occur by reducing individuals' perceptions of stressor severity. The data thus suggest the possibility of reducing stress-related health problems by enhancing executive function.

  8. Effects of couple stresses in MHD channel flow

    International Nuclear Information System (INIS)

    Soundalgekar, V.M.; Aranake, R.N.

    1977-01-01

    An analysis of fully developed MHD channel flow of an electrically conducting incompressible fluid, taking into account the couple stresses, is carried out. Exact solutions are derived for velocity profiles, current density, skin-friction and coefficient of mass flux. They are influenced by the magnetic field, the loading parameter k, and the non-dimensional parameter (a=b 1 /lambda). Their variations with respect to M, k and a are represented graphically, this is followed by a physical discussion. It is observed that the couple stresses are more effective in the presence of a very weak magnetic field. (Auth.)

  9. Stress in Irish dentists: developing effective coping strategies.

    LENUS (Irish Health Repository)

    Rogers, Cathryn

    2012-02-01

    Recent research has highlighted the need to recognise occupation-specific risk factors contributing to stress and burnout. As health professionals, it is important for dentists to recognise the symptoms and the effects of stress on physical, psychological and professional well being. This article reviews the relevant scientific evidence, and provides practical cognitive psychological measures to guide improved well-being for dentists. Any stigma-related factors need to be acknowledged and addressed for the wellbeing of dentists and their patients, and the dental profession is well placed to provide leadership on this issue. Peer support is central to meeting this challenge.

  10. Effects of magnetized walls on the particle structure and the yield stress of magnetorheological fluids

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Jianfeng, E-mail: zhoujianfeng@njtech.edu.cn [School of Mechanical and Power Engineering, Nanjing Tech University, Nanjing 211816, Jiangsu (China); Mo, Jingwen [Department of Mechanical and Aerospace Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon (Hong Kong); Shao, Chunlei [School of Mechanical and Power Engineering, Nanjing Tech University, Nanjing 211816, Jiangsu (China); Li, Zhigang [Department of Mechanical and Aerospace Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon (Hong Kong)

    2015-09-01

    In this work, we investigate the quasi-static shear deformation of magnetic particles (MPs) in a Couette flow of magnetorheological (MR) fluids through Stokesian dynamic simulations. The magnetized walls are modeled by a congregation of magnetic dipoles and their effects on the MPs are considered. The simple shear flow of the base fluid with linear velocity distribution is used to generate the shear deformation of the MP structure and the yield stresses under different shear rates are obtained. Comparing with the relatively long chains forming in base fluid without the effect of magnetized walls, the initial structure of MPs is mainly in the form of short chains due to the attractive force of walls. At the beginning of the shear deformation of the MP structure, the concentration of MPs near the walls is found. As the shear deformation develops, however, the chains concentrate at the center of the simulation domain and the MPs near wall boundaries are attracted to the center. The yield stress depends on the initial structure of MPs which is affected by the magnetized walls. It is revealed that the larger shear rate of base fluid results in the larger yield stress, and the effects of the magnetization intensity of the walls and their space distance on the yield stress are also investigated. - Highlights: • We model a Couette flow of magnetorheological fluid considering magnetized walls. • The walls are modeled by a congregation of magnetic dipoles. • Initial structure of MPs is remarkably affected by the walls, so is yield stress. • Larger base fluid shear rate causes the larger shear deformation and larger yield stress.

  11. Effects of magnetized walls on the particle structure and the yield stress of magnetorheological fluids

    International Nuclear Information System (INIS)

    Zhou, Jianfeng; Mo, Jingwen; Shao, Chunlei; Li, Zhigang

    2015-01-01

    In this work, we investigate the quasi-static shear deformation of magnetic particles (MPs) in a Couette flow of magnetorheological (MR) fluids through Stokesian dynamic simulations. The magnetized walls are modeled by a congregation of magnetic dipoles and their effects on the MPs are considered. The simple shear flow of the base fluid with linear velocity distribution is used to generate the shear deformation of the MP structure and the yield stresses under different shear rates are obtained. Comparing with the relatively long chains forming in base fluid without the effect of magnetized walls, the initial structure of MPs is mainly in the form of short chains due to the attractive force of walls. At the beginning of the shear deformation of the MP structure, the concentration of MPs near the walls is found. As the shear deformation develops, however, the chains concentrate at the center of the simulation domain and the MPs near wall boundaries are attracted to the center. The yield stress depends on the initial structure of MPs which is affected by the magnetized walls. It is revealed that the larger shear rate of base fluid results in the larger yield stress, and the effects of the magnetization intensity of the walls and their space distance on the yield stress are also investigated. - Highlights: • We model a Couette flow of magnetorheological fluid considering magnetized walls. • The walls are modeled by a congregation of magnetic dipoles. • Initial structure of MPs is remarkably affected by the walls, so is yield stress. • Larger base fluid shear rate causes the larger shear deformation and larger yield stress

  12. Stress state in the neighborhood of subways and pipe lines under the action of dynamic loads

    International Nuclear Information System (INIS)

    Alexeyeva, L.A.; Eskalieva, A.Z.; Shershnev, V.V.

    2001-01-01

    We consider the long underground constructions of deep and shallow types such as transport subways, mines, underground pipes etc. by the action of dynamic lads. Situated in areas of seismic activity, they are subjected to the influence of seismic waves during earthquakes and can be destroyed. Running loads inside constructions (transport for instance) affect upon toughness and stability of both subways and surrounding medium. If underground construction dispose near a day's surface, it acts also on nearby buildings. Evaluations of behavior of underground and pipes under dynamic influences in real conditions of usage are determined of stress state of constructions in the interaction with environment medium. Here underground constructions are simulated by infinitely long cylindrical cavities in utter ambience. As utter ambience the isotropic elastic medium and two-component medium of Biot are researched. Last one allows simulating saturated water oils. The elastic cylindrical shell simulates supporting of a tunnel (or pipeline). Both a tress state of construction and surrounding medium were investigated for a different contact conditions between support of tunnel and environment (rigid, slippery and viscous contacts). (author)

  13. Effects of profile wear on wheel–rail contact conditions and dynamic interaction of vehicle and turnout

    Directory of Open Access Journals (Sweden)

    Jingmang Xu

    2016-01-01

    Full Text Available Severe wear is a common damage mechanism in railway turnouts, which strongly affects the dynamic performance of railway vehicles and maintenance costs of tracks. This article explores the effects of profile wear on contact behaviors in the wheel–rail/switch contact and dynamic interaction, and nominal and measured worn turnout rail profiles are used as boundary conditions of wheel–rail contact. The calculation of the dynamic loads and the resultant contact stresses and internal stresses makes it possible to rationally design railway turnouts and correctly select the material to be applied for their components. For these reasons, the multi-body system SIMPACK and finite element software ANSYS are used to calculate the features of load and subsequently distributions of contact stresses and internal stresses in the regions of wheel–turnout components. The results show that profile wear disturbs the distribution of wheel–rail contact point pairs, changes the positions of wheel–rail contact points along the longitudinal direction, and affects the dynamic interaction of vehicle and turnout. For the measured profile in this article, profile wear aggravates vertical dynamic responses significantly but improves lateral dynamic responses. Profile wear disturbs the normal contact situations between the wheel and switch rail and worsens the stress state of the switch rail.

  14. Lattice dynamics approach to determine the dependence of the time-of-flight of transversal polarized acoustic waves on external stress

    Science.gov (United States)

    Tarar, K. S.; Pluta, M.; Amjad, U.; Grill, W.

    2011-04-01

    Based on the lattice dynamics approach the dependence of the time-of-flight (TOF) on stress has been modeled for transversal polarized acoustic waves. The relevant dispersion relation is derived from the appropriate mass-spring model together with the dependencies on the restoring forces including the effect of externally applied stress. The lattice dynamics approach can also be interpreted as a discrete and strictly periodic lumped circuit. In that case the modeling represents a finite element approach. In both cases the properties relevant for wavelengths large with respect to the periodic structure can be derived from the respective limit relating also to low frequencies. The model representing a linear chain with stiffness to shear and additional stiffness introduced by extensional stress is presented and compared to existing models, which so far represent each only one of the effects treated here in combination. For a string this effect is well known from musical instruments. The counteracting effects are discussed and compared to experimental results.

  15. Odors as effective retrieval cues for stressful episodes.

    Science.gov (United States)

    Wiemers, Uta S; Sauvage, Magdalena M; Wolf, Oliver T

    2014-07-01

    Olfactory information seems to play a special role in memory due to the fast and direct processing of olfactory information in limbic areas like the amygdala and the hippocampus. This has led to the assumption that odors can serve as effective retrieval cues for autobiographic memories, especially emotional memories. The current study sought to investigate whether an olfactory cue can serve as an effective retrieval cue for memories of a stressful episode. A total of 95 participants were exposed to a psychosocial stressor or a well matching but not stressful control condition. During both conditions were visual objects present, either bound to the situation (central objects) or not (peripheral objects). Additionally, an ambient odor was present during both conditions. The next day, participants engaged in an unexpected object recognition task either under the influence of the same odor as was present during encoding (congruent odor) or another odor (non-congruent odor). Results show that stressed participants show a better memory for all objects and especially for central visual objects if recognition took place under influence of the congruent odor. An olfactory cue thus indeed seems to be an effective retrieval cue for stressful memories. Copyright © 2013 Elsevier Inc. All rights reserved.

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

    Science.gov (United States)

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

    2014-11-01

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

  17. Investigating The Effect Of Job Stress On Performance Of Employees

    Directory of Open Access Journals (Sweden)

    Oyungerel Altangerel

    2015-02-01

    Full Text Available Abstract This study is conducted to investigate the effect of job stress on job performance. A random sampling technique is used to collect primary data of 120 employees of four telecommunication companies of Mongolia i.e. Mobicom Unitel Skytel and G-mobile. A well-structured questionnaire is utilized to collect relevant data descriptive and logistic analysis is used to estimate and describe the findings of results. It is found that work overload is major reason of stress among employees and majority of employees reduce their productivity and loss of interest in job due to stress. As for concern health issue eyes strain dizziness and disorder in sleep are due to job stress. According to results of logit model parameters of education experience and salary per month are statistically significant and have positive impact on employees performance but age family size no relaxation time giving to employees during working hours and work overload are statistically significant and have negative impact on employees job performance. For suggestions companies should increase salaries of employees and give reward to employees those have work overload. Workload of employees should reduce by proper work redesign and efficient management by proper allocation of job. It is also found that stress also becomes reason of several illnesses and majority of employees dont have medical facilities first aid at working place therefore it is suggested that companies should also provide medical facilities first aid for employees at work place.

  18. Approximate methods and working rules for peak stress effects

    International Nuclear Information System (INIS)

    Jobson, D.A.

    1983-01-01

    In order to assess stress concentration effects and associated strain intensification at notches, Neuber's work on this subject is used frequently. Neuber refers to a particular nonlinear stress-strain relation which, he observed, led to the same deferential equation for the lateral displacements as that found by Chaplygin for the velocity potential of compressible flow. for a linearized adiabatic law. This finding has been examined by studying torsion problems, which Involve warping displacements. Although a deformation law of the type τ(γ) has been assumed, the shear strain components remain 'proportional' to the corresponding stress components for problems of the type considered. It has been found that the governing equations and boundary conditions for φ may be made completely analogous to those for the velocity potential of a corresponding compressible flow in a prismatic cylinder of the same shape as that of the solid bar, provided that the constitutive equation. for the solid and the gas correspond in a defined sense. This embodied Neuber's observation, which was restricted to a particular stress strain law, namely that which corresponded to a linear adiabatic gas relationship. The above finding also assimilates a well-known hydrodynamic analogy, to which it reduces for linearly elastic materials. Corresponding governing equations have further been established for the stress function and these have similarly been related to those for an analogous stream function, defined by reference to the flow density of the corresponding compressible fluid

  19. Laser quench hardening of steel: Effects of superimposed elastic pre-stress on the hardness and residual stress distribution

    Science.gov (United States)

    Meserve, Justin

    Cold drawn AISI 4140 beams were LASER surface hardened with a 2 kW CO2 LASER. Specimens were treated in the free state and while restrained in a bending fixture inducing surface tensile stresses of 94 and 230 MPa. Knoop hardness indentation was used to evaluate the through thickness hardness distribution, and a layer removal methodology was used to evaluate the residual stress distribution. Results showed the maximum surface hardness attained was not affected by pre-stress during hardening, and ranged from 513 to 676 kg/mm2. The depth of effective hardening varied at different magnitudes of pre-stress, but did not vary proportionately to the pre-stress. The surface residual stress, coinciding with the maximum compressive residual stress, increased as pre-stress was increased, from 1040 MPa for the nominally treated specimens to 1270 MPa for specimens pre-stressed to 230 MPa. The maximum tensile residual stress observed in the specimens decreased from 1060 MPa in the nominally treated specimens to 760 MPa for specimens pre-stressed to 230 MPa. Similarly, thickness of the compressive residual stress region increased and the depth at which maximum tensile residual stress occurred increased as the pre-stress during treatment was increased Overall, application of tensile elastic pre-stress during LASER hardening is beneficial to the development of compressive residual stress in AISI 4140, with minimal impact to the hardness attained from the treatment. The newly developed approach for LASER hardening may support efforts to increase both the wear and fatigue resistance of parts made from hardenable steels.

  20. Nonadiabatic effects in electronic and nuclear dynamics

    Directory of Open Access Journals (Sweden)

    Martin P. Bircher

    2017-11-01

    Full Text Available Due to their very nature, ultrafast phenomena are often accompanied by the occurrence of nonadiabatic effects. From a theoretical perspective, the treatment of nonadiabatic processes makes it necessary to go beyond the (quasi static picture provided by the time-independent Schrödinger equation within the Born-Oppenheimer approximation and to find ways to tackle instead the full time-dependent electronic and nuclear quantum problem. In this review, we give an overview of different nonadiabatic processes that manifest themselves in electronic and nuclear dynamics ranging from the nonadiabatic phenomena taking place during tunnel ionization of atoms in strong laser fields to the radiationless relaxation through conical intersections and the nonadiabatic coupling of vibrational modes and discuss the computational approaches that have been developed to describe such phenomena. These methods range from the full solution of the combined nuclear-electronic quantum problem to a hierarchy of semiclassical approaches and even purely classical frameworks. The power of these simulation tools is illustrated by representative applications and the direct confrontation with experimental measurements performed in the National Centre of Competence for Molecular Ultrafast Science and Technology.

  1. Dynamic deformation and failure characteristic of rock foundation by means of effect of cyclic shear loading

    International Nuclear Information System (INIS)

    Fujiwara, Yoshikazu; Hibino, Satoshi; Kanagawa, Tadashi; Komada, Hiroya; Nakagawa, Kameichiro

    1984-01-01

    The main structures of nuclear power plants are built on hard and soft rocks. The rock-dynamic properties used for investigating the stability of the structures have been determined so far by laboratory tests for soft rocks. In hard rocks, however, joints and cracks exist, and the test including these effects is not able to be performed in laboratories at present. Therefore, a dynamic repeating shearing test equipment to be used under the condition including the joints and cracks of actual ground has been made for a base rock of tuff breccia. In this paper, the test results are reported as follows. The geological features of the testing site and the arrangement of tested rocks, the preparation for tests, test equipment, loading method, measuring method, analysis, and the result and the examination. The results of dynamic deformation and failure characteristics were as follows: (1) the dynamic shear-elasticity-modulus Gd of the base rock showed greater values as the normal stress increased, while Gd decreased and showed the strain dependence as the dynamic shear strain amplitude γ increased; (2) the relationship between Gd and γ was well represented with the equation proposed by Hardin-Drnevich; (3) damping ratio increased as γ increased, and decreased as normal stress increased; (4) When a specimen was about to break, γ suddenly increased, and the dynamic shear strain amplitude at yield point was in the range of approximately (3.4 to 4.1) x 10 -3 . (Wakatsuki, Y.)

  2. Hemodynamic Changes After Static and Dynamic Exercises and Treadmill Stress Test; Different Patterns in Patients with Primary Benign Exertional Headache?

    Directory of Open Access Journals (Sweden)

    Mohsen Rostami

    2012-06-01

    Full Text Available The pathophysiology of primary benign exertional headache (EH is not still clearly defined. Some researchers have suggested an impaired vascular response as the etiology of this disorder. In this study we investigated whether there are any differences in blood pressure (BP and heart rate (HR of the subjects in course of the static and dynamic exercises and the treadmill stress test between those with and without EH. From university students, 22 patients with EH (mean age: 19.8 ± 2.10, Female to Male: 7:15 and 20 normal subjects (mean age: 19.3 ± 1.97, Female: Male: 8:12 were recruited. All the subjects performed the static and dynamic exercises at 30 and 20 percent of the maximal voluntary contraction (MVC and Bruce treadmill stress test according to the standard protocols. HR and BP of all the cases at the baseline and during and immediately after each test were measured. No significant difference was found between the mean rise of HR, systolic and diastolic BP of the subjects with and without EH in static and dynamic exercises and also treadmill stress test. It seems that between those with and without EH, there is no significant difference in rise of HR and BP response to static and dynamic exercises and treadmill stress test. Further studies are required to find the pathophysiology and risk factors of EH.

  3. Hemodynamic changes after static and dynamic exercises and treadmill stress test; different patterns in patients with primary benign exertional headache?

    Science.gov (United States)

    Kordi, Ramin; Mazaheri, Reza; Rostami, Mohsen; Mansournia, Mohammad Ali

    2012-01-01

    The pathophysiology of primary benign exertional headache (EH) is not still clearly defined. Some researchers have suggested an impaired vascular response as the etiology of this disorder. In this study we investigated whether there are any differences in blood pressure (BP) and heart rate (HR) of the subjects in course of the static and dynamic exercises and the treadmill stress test between those with and without EH. From university students, 22 patients with EH (mean age: 19.8 ± 2.10, Female to Male: 7:15) and 20 normal subjects (mean age: 19.3 ± 1.97, Female: Male: 8:12) were recruited. All the subjects performed the static and dynamic exercises at 30 and 20 percent of the maximal voluntary contraction (MVC) and Bruce treadmill stress test according to the standard protocols. HR and BP of all the cases at the baseline and during and immediately after each test were measured. No significant difference was found between the mean rise of HR, systolic and diastolic BP of the subjects with and without EH in static and dynamic exercises and also treadmill stress test. It seems that between those with and without EH, there is no significant difference in rise of HR and BP response to static and dynamic exercises and treadmill stress test. Further studies are required to find the pathophysiology and risk factors of EH.

  4. Inverse strain rate effect on cyclic stress response in annealed Zircaloy-2

    Energy Technology Data Exchange (ETDEWEB)

    Sudhakar Rao, G.; Verma, Preeti [Center of Advanced Study, Department of Metallurgical Engineering, Indian Institute of Technology (Banaras Hindu University), Varanasi 221005 (India); Chakravartty, J.K. [Mechanical Metallurgy Group, Bhabha Atomic Research Center, Trombay 400 085, Mumbai (India); Nudurupati, Saibaba [Nuclear Fuel Complex, Hyderabad 500 062 (India); Mahobia, G.S.; Santhi Srinivas, N.C. [Center of Advanced Study, Department of Metallurgical Engineering, Indian Institute of Technology (Banaras Hindu University), Varanasi 221005 (India); Singh, Vakil, E-mail: vsingh.met@itbhu.ac.in [Center of Advanced Study, Department of Metallurgical Engineering, Indian Institute of Technology (Banaras Hindu University), Varanasi 221005 (India)

    2015-02-15

    Low cycle fatigue behavior of annealed Zircaloy-2 was investigated at 300 and 400 °C at different strain amplitudes and strain rates of 10{sup −2}, 10{sup −3}, and 10{sup −4} s{sup −1}. Cyclic stress response showed initial hardening with decreasing rate of hardening, followed by linear cyclic hardening and finally secondary hardening with increasing rate of hardening for low strain amplitudes at both the temperatures. The rate as well the degree of linear hardening and secondary hardening decreased with decrease in strain rate at 300 °C, however, there was inverse effect of strain rate on cyclic stress response at 400 °C and cyclic stress was increased with decrease in strain rate. The fatigue life decreased with decrease in strain rate at both the temperatures. The occurrence of linear cyclic hardening, inverse effect of strain rate on cyclic stress response and deterioration in fatigue life with decrease in strain rate may be attributed to dynamic strain aging phenomena resulting from enhanced interaction of dislocations with solutes. Fracture surfaces revealed distinct striations, secondary cracking, and oxidation with decrease in strain rate. Deformation substructure showed parallel dislocation lines and dislocation band structure at 300 °C. Persistent slip band wall structure and development of fine Corduroy structure was observed at 400 °C.

  5. Inverse strain rate effect on cyclic stress response in annealed Zircaloy-2

    International Nuclear Information System (INIS)

    Sudhakar Rao, G.; Verma, Preeti; Chakravartty, J.K.; Nudurupati, Saibaba; Mahobia, G.S.; Santhi Srinivas, N.C.; Singh, Vakil

    2015-01-01

    Low cycle fatigue behavior of annealed Zircaloy-2 was investigated at 300 and 400 °C at different strain amplitudes and strain rates of 10 −2 , 10 −3 , and 10 −4 s −1 . Cyclic stress response showed initial hardening with decreasing rate of hardening, followed by linear cyclic hardening and finally secondary hardening with increasing rate of hardening for low strain amplitudes at both the temperatures. The rate as well the degree of linear hardening and secondary hardening decreased with decrease in strain rate at 300 °C, however, there was inverse effect of strain rate on cyclic stress response at 400 °C and cyclic stress was increased with decrease in strain rate. The fatigue life decreased with decrease in strain rate at both the temperatures. The occurrence of linear cyclic hardening, inverse effect of strain rate on cyclic stress response and deterioration in fatigue life with decrease in strain rate may be attributed to dynamic strain aging phenomena resulting from enhanced interaction of dislocations with solutes. Fracture surfaces revealed distinct striations, secondary cracking, and oxidation with decrease in strain rate. Deformation substructure showed parallel dislocation lines and dislocation band structure at 300 °C. Persistent slip band wall structure and development of fine Corduroy structure was observed at 400 °C

  6. Memory function after stress : the effects of acute stress and cortisol on memory and the inhibition of emotional distraction

    NARCIS (Netherlands)

    Oei, Nicole Yü Lan

    2010-01-01

    The present thesis contains five experimental studies into the effects of stress on memory I healthy males. Hydrocortisone (and propranolol) administration or the induction of social stress are used to heighten cortisol levels, and consequently to study its effects on working memory performance and

  7. Effective dynamics along given reaction coordinates, and reaction rate theory.

    Science.gov (United States)

    Zhang, Wei; Hartmann, Carsten; Schütte, Christof

    2016-12-22

    In molecular dynamics and related fields one considers dynamical descriptions of complex systems in full (atomic) detail. In order to reduce the overwhelming complexity of realistic systems (high dimension, large timescale spread, limited computational resources) the projection of the full dynamics onto some reaction coordinates is examined in order to extract statistical information like free energies or reaction rates. In this context, the effective dynamics that is induced by the full dynamics on the reaction coordinate space has attracted considerable attention in the literature. In this article, we contribute to this discussion: we first show that if we start with an ergodic diffusion process whose invariant measure is unique then these properties are inherited by the effective dynamics. Then, we give equations for the effective dynamics, discuss whether the dominant timescales and reaction rates inferred from the effective dynamics are accurate approximations of such quantities for the full dynamics, and compare our findings to results from approaches like Mori-Zwanzig, averaging, or homogenization. Finally, by discussing the algorithmic realization of the effective dynamics, we demonstrate that recent algorithmic techniques like the "equation-free" approach and the "heterogeneous multiscale method" can be seen as special cases of our approach.

  8. The effect of stress state on zirconium hydride reorientation

    Science.gov (United States)

    Cinbiz, Mahmut Nedim

    Prior to storage in a dry-cask facility, spent nuclear fuel must undergo a vacuum drying cycle during which the spent fuel rods are heated up to elevated temperatures of ≤ 400°C to remove moisture the canisters within the cask. As temperature increases during heating, some of the hydride particles within the cladding dissolve while the internal gas pressure in fuel rods increases generating multi-axial hoop and axial stresses in the closed-end thin-walled cladding tubes. As cool-down starts, the hydrogen in solid solution precipitates as hydride platelets, and if the multiaxial stresses are sufficiently large, the precipitating hydrides reorient from their initial circumferential orientation to radial orientation. Radial hydrides can severely embrittle the spent nuclear fuel cladding at low temperature in response to hoop stress loading. Because the cladding can experience a range of stress states during the thermo-mechanical treatment induced during vacuum drying, this study has investigated the effect of stress state on the process of hydride reorientation during controlled thermo-mechanical treatments utilizing the combination of in situ X-ray diffraction and novel mechanical testing analyzed by the combination of metallography and finite element analysis. The study used cold worked and stress relieved Zircaloy-4 sheet containing approx. 180 wt. ppm hydrogen as its material basis. The failure behavior of this material containing radial hydrides was also studied over a range of temperatures. Finally, samples from reactor-irradiated cladding tubes were examined by X-ray diffraction using synchrotron radiation. To reveal the stress state effect on hydride reorientation, the critical threshold stress to reorient hydrides was determined by designing novel mechanical test samples which produce a range of stress states from uniaxial to "near-equibiaxial" tension when a load is applied. The threshold stress was determined after thermo-mechanical treatments by

  9. Family matters: effects of birth order, culture, and family dynamics on surrogate decision-making.

    Science.gov (United States)

    Su, Christopher T; McMahan, Ryan D; Williams, Brie A; Sharma, Rashmi K; Sudore, Rebecca L

    2014-01-01

    Cultural attitudes about medical decision-making and filial expectations may lead some surrogates to experience stress and family conflict. Thirteen focus groups with racially and ethnically diverse English and Spanish speakers from county and Veterans Affairs hospitals, senior centers, and cancer support groups were conducted to describe participants' experiences making serious or end-of-life decisions for others. Filial expectations and family dynamics related to birth order and surrogate decision-making were explored using qualitative, thematic content analysis, and overarching themes from focus group transcripts were identified. The mean age of the 69 participants was 69 ± 14, and 29% were African American, 26% were white, 26% were Asian or Pacific Islander, and 19% were Latino. Seventy percent of participants engaged in unprompted discussions about birth order and family dynamics. Six subthemes were identified within three overarching categories: communication (unspoken expectations and discussion of death as taboo), emotion (emotional stress and feelings of loneliness), and conflict (family conflict and potential solutions to prevent conflict). These findings suggest that birth order and family dynamics can have profound effects on surrogate stress and coping. Clinicians should be aware of potential unspoken filial expectations for firstborns and help facilitate communication between the patient, surrogate, and extended family to reduce stress and conflict. © Published 2013. This article is a U.S. Government work and is in the public domain in the U.S.A.

  10. Family Matters: Effects of Birth Order, Culture, and Family Dynamics on Surrogate Decision Making

    Science.gov (United States)

    Su, Christopher T.; McMahan, Ryan D.; Williams, Brie A.; Sharma, Rashmi K.; Sudore, Rebecca L.

    2014-01-01

    Cultural attitudes about medical decision making and filial expectations may lead some surrogates to experience stress and family conflict. Thirteen focus groups with racially and ethnically diverse English- and Spanish-speakers from county and Veterans hospitals, senior centers, and cancer support groups were conducted to describe participants’ experiences making serious or end-of-life decisions for others. Filial expectations and family dynamics related to birth order and surrogate decision making were explored using qualitative, thematic content analysis and overarching themes from focus group transcripts were identified. The mean age of the 69 participants was 69 years ± 14 and 29% were African American, 26% were White, 26% were Asian/Pacific Islander, and 19% were Latino. Seventy percent of participants engaged in unprompted discussions about birth order and family dynamics. Six subthemes were identified within 3 overarching categories of communication, emotion, and conflict: Communication – (1) unspoken expectations and (2) discussion of death as taboo; Emotion – (3) emotional stress and (4) feelings of loneliness; and Conflict – (5) family conflict and (6) potential solutions to prevent conflict. These findings suggest that birth order and family dynamics can have profound effects on surrogate stress and coping. Clinicians should be aware of potential unspoken filial expectations for firstborns and help facilitate communication between the patient, surrogate, and extended family to reduce stress and conflict. PMID:24383459

  11. Parameter studies on the effect of pulse shape on the dynamic plastic deformation of a hexagon

    International Nuclear Information System (INIS)

    Youngdahl, C.K.

    1973-10-01

    Results of a parameter study on the dynamic plastic response of a hexagonal subassembly duct subjected to an internal pressure pulse of arbitrary shape are presented. Plastic distortion of the cross section and large-deformation geometric effects that result in redistribution of the internal forces between bending and membrane stresses in the hexagon wall are included in the analytical model. Correlation procedures are established for relating permanent plastic deformation to simple properties of the pressure pulse, for both the small- and large-deformation ranges. Characteristic response times are determined, and the dynamic load factor for large-deformation plastic response is computed

  12. Macro design effects on stress distribution around implants: A photoelastic stress analysis

    Directory of Open Access Journals (Sweden)

    Serhat Emre Ozkir

    2012-01-01

    Conclusion: As there were observable differences between the implant types, straight placed cylindrical implants showed better stress distribution characteristics, while inclined tapering implants had better stress distribution characteristics.

  13. Dynamic Effects of Diabatization in Distillation Columns

    DEFF Research Database (Denmark)

    Bisgaard, Thomas; Huusom, Jakob Kjøbsted; Abildskov, Jens

    2012-01-01

    The dynamic eects of diabatization in distillation columns are investigated in simulation with primary focus on the heat-integrated distillation column (HIDiC). A generic, dynamic, rst-principle model has been formulated, which is exible to describe various diabatic distillation congurations....... Dynamic Relative Gain Array and Singular Value Analysis have been applied in a comparative study of a conventional distillation column and a HIDiC. The study showed increased input-output coupling due to diabatization. Feasible SISO control structures for the HIDiC were also found. Control...

  14. Effect of personal and work stress on burnout, job satisfaction and ...

    African Journals Online (AJOL)

    Abstract. The majority of studies to date have focused on the effects of work stress in the nursing environment, with the effect of personal stress in nursing being less explored. This study sought to determine whether personal stress is a more significant predictor of burnout, job satisfaction and general health than work stress.

  15. Effects of Stress on Students' Physical and Mental Health and Academic Success

    Science.gov (United States)

    Shankar, Nilani L.; Park, Crystal L.

    2016-01-01

    Stress affects students in multiple ways. This article provides a conceptual overview of the direct (e.g., psychoneuroimmunological, endocrine) and indirect (health behavior) pathways through which stress affects physical health, the psychological effects of stress on mental health, and the cognitive effects of stress (e.g., attention,…

  16. Perceived heat stress and health effects on construction workers.

    Science.gov (United States)

    Dutta, Priya; Rajiva, Ajit; Andhare, Dileep; Azhar, Gulrez Shah; Tiwari, Abhiyant; Sheffield, Perry

    2015-01-01

    Increasing heat waves-particularly in urban areas where construction is most prevalent, highlight a need for heat exposure assessment of construction workers. This study aims to characterize the effects of heat on construction workers from a site in Gandhinagar. This study involved a mixed methods approach consisting of a cross sectional survey with anthropometric measurements (n = 219) and four focus groups with construction workers, as well as environmental measurements of heat stress exposure at a construction site. Survey data was collected in two seasons i.e., summer and winter months, and heat illness and symptoms were compared between the two time periods. Thematic coding of focus group data was used to identify vulnerability factors and coping mechanisms of the workers. Heat stress, recorded using a wet bulb globe temperature monitor, was compared to international safety standards. The survey findings suggest that heat-related symptoms increased in summer; 59% of all reports in summer were positive for symptoms (from Mild to Severe) as compared to 41% in winter. Focus groups revealed four dominant themes: (1) Non-occupational stressors compound work stressors; (2) workers were particularly attuned to the impact of heat on their health; (3) workers were aware of heat-related preventive measures; and (4) few resources were currently available to protect workers from heat stress. Working conditions often exceed international heat stress safety thresholds. Female workers and new employees might be at increased risk of illness or injury. This study suggests significant health impacts on construction workers from heat stress exposure in the workplace, showed that heat stress levels were higher than those prescribed by international standards and highlights the need for revision of work practices, increased protective measures, and possible development of indigenous work safety standards for heat exposure.

  17. The effect of continuous grouping of pigs in large groups on stress response and haematological parameters

    DEFF Research Database (Denmark)

    Damgaard, Birthe Marie; Studnitz, Merete; Jensen, Karin Hjelholt

    2009-01-01

    The consequences of an ‘all in-all out' static group of uniform age vs. a continuously dynamic group with litter introduction and exit every third week were examined with respect to stress response and haematological parameters in large groups of 60 pigs. The experiment included a total of 480 pigs...... from weaning at the age of 4 weeks to the age of 18 weeks after weaning. Limited differences were found in stress and haematological parameters between pigs in dynamic and static groups. The cortisol response to the stress test was increasing with the duration of the stress test in pigs from...... the dynamic group while it was decreasing in the static group. The health condition and the growth performance were reduced in the dynamic groups compared with the static groups. In the dynamic groups the haematological parameters indicated an activation of the immune system characterised by an increased...

  18. TRANSCRIPTOME DYNAMICS IN MANGO FRUIT PEEL REVEALS MECHANISMS OF CHILLING STRESS

    Directory of Open Access Journals (Sweden)

    Velu Sivankalyani

    2016-10-01

    Full Text Available Cold storage is considered the most effective method for prolonging fresh produce storage. However, subtropical fruit is sensitive to cold. Symptoms of chilling injury in mango include red and black spots that start from discolored lenticels and develop into pitting. The response of ‘Keitt’ mango fruit to chilling stress was monitored by transcriptomic, physiological and microscopic analyses. Transcriptomic changes in the mango fruit peel were evaluated during optimal (12°C and suboptimal (5°C cold storage. Two days of chilling stress upregulated genes involved in the plant stress response, including those encoding transmembrane receptors, calcium-mediated signal transduction, NADPH oxidase, MAP kinases and WRKYs, which can lead to cell death. Indeed, cell death was observed around the discolored lenticels after 19 days of cold storage at 5°C. Localized cell death and cuticular opening in the lumen of discolored lenticels were correlated with increased general decay during shelf-life storage, possibly due to fungal penetration. We also observed increased phenolics accumulation around the discolored lenticels, which was correlated with the biosynthesis of phenylpropanoids that were probably transported from the resin ducts. Increased lipid peroxidation was observed during chilling injury by both the biochemical malondialdehyde method and a new non-destructive luminescent technology, correlated to upregulation of the α-linolenic acid oxidation pathway. Genes involved in sugar metabolism were also induced, possibly to maintain osmotic balance. This analysis provides an in-depth characterization of mango fruit response to chilling stress and could lead to the development of new tools, treatments and strategies to prolong cold storage of subtropical fruit.

  19. Transcriptome Dynamics in Mango Fruit Peel Reveals Mechanisms of Chilling Stress

    Science.gov (United States)

    Sivankalyani, Velu; Sela, Noa; Feygenberg, Oleg; Zemach, Hanita; Maurer, Dalia; Alkan, Noam

    2016-01-01

    Cold storage is considered the most effective method for prolonging fresh produce storage. However, subtropical fruit is sensitive to cold. Symptoms of chilling injury (CI) in mango include red and black spots that start from discolored lenticels and develop into pitting. The response of ‘Keitt’ mango fruit to chilling stress was monitored by transcriptomic, physiological, and microscopic analyses. Transcriptomic changes in the mango fruit peel were evaluated during optimal (12°C) and suboptimal (5°C) cold storage. Two days of chilling stress upregulated genes involved in the plant stress response, including those encoding transmembrane receptors, calcium-mediated signal transduction, NADPH oxidase, MAP kinases, and WRKYs, which can lead to cell death. Indeed, cell death was observed around the discolored lenticels after 19 days of cold storage at 5°C. Localized cell death and cuticular opening in the lumen of discolored lenticels were correlated with increased general decay during shelf-life storage, possibly due to fungal penetration. We also observed increased phenolics accumulation around the discolored lenticels, which was correlated with the biosynthesis of phenylpropanoids that were probably transported from the resin ducts. Increased lipid peroxidation was observed during CI by both the biochemical malondialdehyde method and a new non-destructive luminescent technology, correlated to upregulation of the α-linolenic acid oxidation pathway. Genes involved in sugar metabolism were also induced, possibly to maintain osmotic balance. This analysis provides an in-depth characterization of mango fruit response to chilling stress and could lead to the development of new tools, treatments and strategies to prolong cold storage of subtropical fruit. PMID:27812364

  20. Reduced Insulin/IGF-1 Signaling Restores the Dynamic Properties of Key Stress Granule Proteins during Aging

    Directory of Open Access Journals (Sweden)

    Marie C. Lechler

    2017-01-01

    Full Text Available Summary: Low-complexity “prion-like” domains in key RNA-binding proteins (RBPs mediate the reversible assembly of RNA granules. Individual RBPs harboring these domains have been linked to specific neurodegenerative diseases. Although their aggregation in neurodegeneration has been extensively characterized, it remains unknown how the process of aging disturbs RBP dynamics. We show that a wide variety of RNA granule components, including stress granule proteins, become highly insoluble with age in C. elegans and that reduced insulin/insulin-like growth factor 1 (IGF-1 daf-2 receptor signaling efficiently prevents their aggregation. Importantly, stress-granule-related RBP aggregates are associated with reduced fitness. We show that heat shock transcription factor 1 (HSF-1 is a main regulator of stress-granule-related RBP aggregation in both young and aged animals. During aging, increasing DAF-16 activity restores dynamic stress-granule-related RBPs, partly by decreasing the buildup of other misfolded proteins that seed RBP aggregation. Longevity-associated mechanisms found to maintain dynamic RBPs during aging could be relevant for neurodegenerative diseases. : Lechler et al. show that RNA-binding proteins (RBPs including stress granule proteins are prone to aggregate with age in C. elegans. Aggregation of stress granule RBPs with “prion-like” domains is associated with reduced fitness. Their aggregation is prevented by longevity pathways and promoted by the aggregation of other misfolded proteins. Keywords: neurodegenerative diseases, Caenorhabditis elegans, protein aggregation, aging, RNA-binding proteins, stress granules, HSF-1, DAF-2, longevity

  1. Stress

    DEFF Research Database (Denmark)

    Keller, Hanne Dauer

    2015-01-01

    Kapitlet handler om stress som følelse, og det trækker primært på de få kvalitative undersøgelser, der er lavet af stressforløb.......Kapitlet handler om stress som følelse, og det trækker primært på de få kvalitative undersøgelser, der er lavet af stressforløb....

  2. Stress !!!

    OpenAIRE

    Fledderus, M.

    2012-01-01

    Twee op de vijf UT-studenten hebben last van ernstige studiestress, zo erg zelfs dat het ze in hun privéleven belemmert. Die cijfers komen overeen met het landelijk beeld van stress onder studenten. Samen met 14 andere universiteits- en hogeschoolbladen enquêteerde UT Nieuws bijna 5500 studenten. Opvallend is dat mannelijke studenten uit Twente zich veel minder druk lijken te maken over hun studie. Onder vrouwen ligt de stress juist erg hoog ten opzichte van het landelijk gemiddelde.

  3. In vitro potential cytogenetic and oxidative stress effects of roxithromycin.

    Science.gov (United States)

    Arslan, Mehmet; Timocin, Taygun; Ila, Hasan B

    2017-10-01

    Macrolide antibiotic roxithromycin was evaluated in terms of its genotoxic, cytotoxic and oxidative stress effects. For this purpose; 25, 50, 100 and 200 μg/mL concentrations of roxithromycin were dissolved in dimethyl sulfoxide and treated to human peripheral blood lymphocytes for two different treatment periods (24 and 48 h). In chromosome aberration (CA) and micronucleus (MN) tests, roxithromycin did not show genotoxic effect. But it induced sister chromatid exchange (SCE) at the highest concentration (200 μg/mL) for the 24-h treatment period and at all concentrations (except 25 μg/mL) for the 48-h treatment period. Looking at cytotoxic effect of roxithromycin, statistically insignificant decreases on mitotic index and proliferation index were observed. Roxithromycin decreased nuclear division index (NDI) at highest two concentrations (100 and 200 μg/mL) for the 24-h treatment period and at all concentrations (expect 25 μg/mL) for the 48-h treatment period. Total oxidant values, total antioxidant values and oxidative stress index did not change with roxithromycin treatment. Eventually, roxithromycin did not have genotoxic and oxidative stress effects in human-cultured lymphocytes.

  4. Allee effects on population dynamics in continuous (overlapping) case

    International Nuclear Information System (INIS)

    Merdan, H.; Duman, O.; Akin, O.; Celik, C.

    2009-01-01

    This paper presents the stability analysis of equilibrium points of a continuous population dynamics with delay under the Allee effect which occurs at low population density. The mathematical results and numerical simulations show the stabilizing role of the Allee effects on the stability of the equilibrium point of this population dynamics.

  5. Individual and crossover effects of stress on adjustment in medical student marriages.

    Science.gov (United States)

    Katz, J; Monnier, J; Libet, J; Shaw, D; Beach, S R

    2000-07-01

    High-stress individuals may benefit from social support, although their support providers may be adversely affected via stress crossover effects. Individual and crossover effects of perceived stress within medical student marriages (n = 30) were investigated. Perceived spousal support was positively associated with individuals' own marital and emotional adjustment, attenuating stress effects. With regard to crossover effects, medical students' perceived stress was significantly associated with their spouses' emotional adjustment. Further, medical students' own emotional adjustment fully mediated this crossover effect. Results suggest that the contagion of negative affect may serve as a key mechanism through which stress crossover effects operate in marriage.

  6. Stroop-interference effect in post-traumatic stress disorder.

    Science.gov (United States)

    Cui, Hong; Chen, Guoliang; Liu, Xiaohui; Shan, Moshui; Jia, Yanyan

    2014-12-01

    To investigate the conflict processing in posttraumatic stress disorder (PTSD) patients, we conducted the classical Stroop task by recording event-related potentials. Although the reaction time was overall slower for PTSD patients than healthy age-matched control group, the Stroop-interference effect of reaction time did not differ between the two groups. Compared with normal controls, the interference effects of N 2 and N 450 components were larger and the interference effect of slow potential component disappeared in PTSD. These data indicated the dysfunction of conflict processing in individuals with PTSD.

  7. Effects of increased rock strata stresses on coal gettability

    Energy Technology Data Exchange (ETDEWEB)

    Sikora, W; Skoczynski, W [Politechnika Slaska, Gliwice (Poland). Instytut Mechanizacji Gornictwa

    1988-01-01

    Analyzes effects of rock strata pressure on a coal seam, its cracking and on energy consumption of coal cutting by shearer loaders and coal plows. Effects of mining depth on stresses in a coal seam rib side were analyzed using formulae developed by Budryk, Chudek and Borecki. Formulae used for selecting optimum yield strength of powered supports at working faces are reviewed. Four types of spontaneous separation of coal seam blocks caused by rock strata stresses are evaluated: layers parallel to the face with constant thickness, coal blocks with thickness decreasing in the direction of the floor or roof (blocks with a planar triangle cross-cut), blocks situated in the seam layer adjacent to the floor or roof. Causes of each type of coal seam separation are analyzed. 9 refs.

  8. Effect of heating rate on caustic stress corrosion cracking

    International Nuclear Information System (INIS)

    Indig, M.E.; Hoffman, N.J.

    1977-01-01

    To evaluate effects of a large water leak into the sodium side of a steam generator in a Liquid Metal Fast Breeder Reactor the Liquid Metal Engineering Center (LMEC) at Canoga Park, California, is performing a series of tests in a Large Leak Test Rig (LLTR). This test series involves heating a large steam generator that possibly contains localized pockets of aqueous caustic retained from a previous sodium-water reaction. Such pockets of caustic solution could be in contact with welds and other components that contain residual stresses up to the yield point. The LMEC and General Electric (GE) ran a series of tests to evaluate the effect of heating rate on caustic stress corrosion cracking (SCC) for alloys either used or considered for the LLTR. A summary of the temperatures and caustic concentration ranges that can result in caustic SCC for carbon steel and Type-304 stainless steel is given

  9. A potential model for drug screening by simulating the effect of shear stress in vivo on endothelium.

    Science.gov (United States)

    Xu, Yingqian; Wang, Bochu; Deng, Jia; Liu, Zerong; Zhu, Liancai

    2013-01-01

    The purpose of this paper was to research the potential of a dynamic cell model in drug screening by studying the influence of microvascular wall shear stress on the drug absorption of endothelial cells compared to that in the static state. The cells were grown and seeded on gelatin-coated glass slides and were pretreated with extracts of Salviae miltiorrhizae (200 μg/ml) for 1 h. Then oxidative stress damage was produced by H2O2 (300 μmol/l) for 0.5 h under the 1.5 dyn/cm2 shear stress incorporated in a parallel plate flow chamber. Morphological analysis was conducted with an inverted microscope and image analysis software, and high performance liquid chromatography-mass spectrometry was used for the detection of active compounds. We compared the drug absorption in the dynamic group with that in the static group. In the dynamic model, five compounds and two new metabolite peaks were detected. However, in the static model, four compounds were absorbed by cells, and one metabolite peak was found. This study indicated that there were some effects on the absorption and metabolism of drugs under the microvascular shear stress compared to that under stasis. We infer that shear stress in the microcirculation situation in vivo played a role in causing the differences between drug screening in vitro and in vivo.

  10. The Effects of Heat Stress on Job Satisfaction, Job Performance and Occupational Stress in Casting Workers

    OpenAIRE

    Dehghan; Mobinyzadeh; Habibi

    2016-01-01

    Background Job satisfaction, job performance, job stress and heat stress affect the productivity of workers. Objectives This research aimed to study the relationship between heat stress indices with job satisfaction, job performance and job stress in casting workers. Patients and Methods This descriptive-analytical cross sectional survey was performed during summer 2013 on one hund...

  11. The effect of single overloading on stress corrosion cracking

    International Nuclear Information System (INIS)

    Ito, Yuzuru; Saito, Masahiro

    2008-01-01

    In the normal course of nuclear power plant operation in Japan, proof testing has been performed after periodic plant inspections. In this proof test procedure, the reactor pressure vessel and pipes of the primary coolant loop are subjected to a specified overload with a slightly higher hydraulic pressure than during normal operation. This specified overload is so called a single overload' in material testing. It is well known that the fatigue crack growth rate is decreased after a single overload has been applied to the specimen. However, it is not clear whether the stress corrosion cracking rate is also decreased after a single overload. In this study, the effect of a single overload on the stress corrosion cracking rate under simulated boiling water reactor environment was evaluated by examining a singly overloaded WOL (wedge opening load) specimen. The WOL specimen for the stress corrosion cracking test was machined from sensitized 304 type austenitic stainless steel. Since the crack extension length was 3.2% longer in the case of a more severely overloaded specimen, it was observed than the stress corrosion cracking rate is also decreased after the single overload has been applied to the specimen. (author)

  12. Effect of External Electric Field Stress on Gliadin Protein Conformation

    OpenAIRE

    Singh, Ashutosh; Munshi, Shirin; Raghavan, Vijaya

    2013-01-01

    A molecular dynamic (MD) modeling approach was applied to evaluate the effect of external electric field on gliadin protein structure and surface properties. Static electric field strengths of 0.001 V/nm and 0.002 V/nm induced conformational changes in the protein but had no significant effect on its surface properties. The study of hydrogen bond evolution during the course of simulation revealed that the root mean square deviation, radius of gyration and secondary structure formation, all de...

  13. Impacts of the Mesoscale Ocean-Atmosphere Coupling on the Peru-Chile Ocean Dynamics: The Current-Induced Wind Stress Modulation

    Science.gov (United States)

    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.

  14. Effects of mindfulness-based stress reduction on depression, anxiety, stress and mindfulness in Korean nursing students.

    Science.gov (United States)

    Song, Yeoungsuk; Lindquist, Ruth

    2015-01-01

    Nursing students often experience depression, anxiety, stress and decreased mindfulness which may decrease their patient care effectiveness. Mindfulness-based stress reduction (MBSR) effectively reduced depression, anxiety and stress, and increased mindfulness in previous research with other populations, but there is sparse evidence regarding its effectiveness for nursing students in Korea. To examine the effects of MBSR on depression, anxiety, stress and mindfulness in Korean nursing students. A randomized controlled trial. Fifty (50) nursing students at KN University College of Nursing in South Korea were randomly assigned to two groups. Data from 44 students, MBSR (n=21) and a wait list (WL) control (n=23) were analyzed. The MBSR group practiced mindfulness meditation for 2 h every week for 8 weeks. The WL group did not receive MBSR intervention. Standardized self-administered questionnaires of depression, anxiety, stress and mindfulness were administered at the baseline prior to the MBSR program and at completion (at 8 weeks). Compared with WL participants, MBSR participants reported significantly greater decreases in depression, anxiety and stress, and greater increase in mindfulness. A program of MBSR was effective when it was used with nursing students in reducing measures of depression, anxiety and stress, and increasing their mindful awareness. MBSR shows promise for use with nursing students to address their experience of mild depression, anxiety and stress, and to increase mindfulness in academic and clinical work, warranting further study. Copyright © 2014 Elsevier Ltd. All rights reserved.

  15. Effects of neuronal loss in the dynamic model of neural networks

    International Nuclear Information System (INIS)

    Yoon, B-G; Choi, J; Choi, M Y

    2008-01-01

    We study the phase transitions and dynamic behavior of the dynamic model of neural networks, with an emphasis on the effects of neuronal loss due to external stress. In the absence of loss the overall results obtained numerically are found to agree excellently with the theoretical ones. When the external stress is turned on, some neurons may deteriorate and die; such loss of neurons, in general, weakens the memory in the system. As the loss increases beyond a critical value, the order parameter measuring the strength of memory decreases to zero either continuously or discontinuously, namely, the system loses its memory via a second- or a first-order transition, depending on the ratio of the refractory period to the duration of action potential

  16. Notch constraint effects on the dynamic fracture toughness of an unaged beta titanium alloy

    International Nuclear Information System (INIS)

    Rack, H.J.

    1975-01-01

    The influence of notch included angle and root radius on the apparent dynamic fracture toughness of an unaged metastable beta titanium alloy, Ti--3Al--8V--6Cr--4Zr--4Mo, has been examined. The apparent fracture toughness, K/sub Id/(rho), increases with both notch radius, rho and included angle, ω. These results have been compared with the theoretical predictions of Tetelman, et al. and Smith. The comparisons show that neither theory accurately describes the effect of varying notch constraint on the apparent dynamic fracture toughness. Although preliminary considerations indicate that qualitative descriptions of notch acuity effects may be given by recent finite element analysis of the stress and strain distributions below a notch root, there is presently no quantitative basis for determining the true dynamic fracture toughness of materials from the results of blunt notch experiments. (auth)

  17. Framing of task performance strategies: effects on performance in a multiattribute dynamic decision making environment.

    Science.gov (United States)

    Nygren, T E

    1997-09-01

    It is well documented that the way a static choice task is "framed" can dramatically alter choice behavior, often leading to observable preference reversals. This framing effect appears to result from perceived changes in the nature or location of a person's initial reference point, but it is not clear how framing effects might generalize to performance on dynamic decision making tasks that are characterized by high workload, time constraints, risk, or stress. A study was conducted to examine the hypothesis that framing can introduce affective components to the decision making process and can influence, either favorably (positive frame) or adversely (negative frame), the implementation and use of decision making strategies in dynamic high-workload environments. Results indicated that negative frame participants were significantly impaired in developing and employing a simple optimal decision strategy relative to a positive frame group. Discussion focuses on implications of these results for models of dynamic decision making.

  18. Dynamic plasma screening effects on atomic collisions in dense plasmas

    International Nuclear Information System (INIS)

    Young-Dae Jung

    1999-01-01

    Dynamic plasma screening effects are investigated on electron-ion collisional excitation and Coulomb Bremsstrahlung processes in dense plasmas. The electron-ion interaction potential is considered by introduction of the plasma dielectric function. The straight-ling trajectory method is applied to the path of the projectile electron. The transition probability including the dynamic plasma screening effect is found to be always greater than that including the static plasma screening effects. It is found that the differential Bremsstrahlung radiation cross section including the dynamic plasma screening effect is also greater than that including the static plasma screening effect. When the projectile velocity is smaller than the electron thermal velocity, the dynamic polarization screening effect becomes the static plasma screening effect. However, when the projectile velocity is greater than the electron thermal velocity, the interaction potential is almost unshielded

  19. Scale and size effects in dynamic fracture of concretes and rocks

    Directory of Open Access Journals (Sweden)

    Petrov Y.

    2015-01-01

    Full Text Available Structural-temporal approach based on the notion of incubation time is used for interpretation of strain-rate effects in the fracture process of concretes and rocks. It is established that temporal dependences of concretes and rocks are calculated by the incubation time criterion. Experimentally observed different relations between ultimate stresses of concrete and mortar in static and dynamic conditions are explained. It is obtained that compressive strength of mortar at a low strain rate is greater than that of concrete, but at a high strain rate the opposite is true. Influence of confinement pressure on the mechanism of dynamic strength for concretes and rocks is discussed. Both size effect and scale effect for concrete and rocks samples subjected to impact loading are analyzed. Statistical nature of a size effect contrasts to a scale effect that is related to the definition of a spatio-temporal representative volume determining the fracture event on the given scale level.

  20. Order in cold ionic systems: Dynamic effects

    International Nuclear Information System (INIS)

    Schiffer, J.P.

    1988-01-01

    The present state and recent developments in Molecular Dynamics calculations modeling cooled heavy-ion beams are summarized. First, a frame of reference is established, summarizing what has happened in the past; then the properties of model systems of cold ions studied in Molecular Dynamics calculations are reviewed, with static boundary conditions with which an ordered state is revealed; finally, more recent results on such modelling, adding the complications in the (time-dependent) boundary conditions that begin to approach real storage rings (ion traps) are reported. 14 refs., 19 figs., 2 tabs

  1. Investigating the running abilities of Tyrannosaurus rex using stress-constrained multibody dynamic analysis

    Directory of Open Access Journals (Sweden)

    William I. Sellers

    2017-07-01

    Full Text Available The running ability of Tyrannosaurus rex has been intensively studied due to its relevance to interpretations of feeding behaviour and the biomechanics of scaling in giant predatory dinosaurs. Different studies using differing methodologies have produced a very wide range of top speed estimates and there is therefore a need to develop techniques that can improve these predictions. Here we present a new approach that combines two separate biomechanical techniques (multibody dynamic analysis and skeletal stress analysis to demonstrate that true running gaits would probably lead to unacceptably high skeletal loads in T. rex. Combining these two approaches reduces the high-level of uncertainty in previous predictions associated with unknown soft tissue parameters in dinosaurs, and demonstrates that the relatively long limb segments of T. rex—long argued to indicate competent running ability—would actually have mechanically limited this species to walking gaits. Being limited to walking speeds contradicts arguments of high-speed pursuit predation for the largest bipedal dinosaurs like T. rex, and demonstrates the power of multiphysics approaches for locomotor reconstructions of extinct animals.

  2. How does stress affect human being—a molecular dynamic simulation study on cortisol and its glucocorticoid receptor

    Directory of Open Access Journals (Sweden)

    Dan Zhang

    2017-03-01

    Full Text Available Stress can be either positive or negative to human beings. Under stressful conditions, the mental and physical conditions of human can be affected. There exists certain relation between stress and illness. The cortisol and other glucocorticoids bind to the same receptor, which is called glucocorticoid receptor. Some evidences indicated that cortisol molecule binding to its glucocorticoid receptor was necessary for the stress response. Up to now, the structure–function relationships between cortisol molecule and its glucocorticoid receptor have not been deliberated from the atomic-level. In order to get a detailed understanding of the structure–function relationships between the cortisol molecule and glucocorticoids receptor, we have carried out molecular dynamic (MD simulations on glucocorticoid receptor (Apo system and cortisol with its glucocorticoid receptor complex (HCY system. On the basis of molecular dynamic simulations, a couple of key residues were identified, which were crucial for the binding of cortisol molecule. The results of binding free energy calculations are in good agreement with the experiment data. Our research gives clear insights from atomic-level into the structural–functional aspects of cortisol molecule and its glucocorticoid receptor, and also provides valuable information for the design of drug which can treat stress related illnesses.

  3. Effect of Stress-Response Psycho-Training on the Stress Levels of Mothers with Autistic Children

    Science.gov (United States)

    Karaman, Ömer

    2018-01-01

    The aim of the study was to assess the effect of stress-response psycho-training on the stress levels of mothers with autistic children. The research was experimental in design encompassing a pretest-posttest model with control and placebo groups. Participation in the study was voluntary with a total of 28 mothers of autistic children included…

  4. Effect of Couple Stresses on the Stress Intensity Factors for Two Parallel Cracks in an Infinite Elastic Medium under Tension

    Directory of Open Access Journals (Sweden)

    Shouetsu Itou

    2012-01-01

    Full Text Available Stresses around two parallel cracks of equal length in an infinite elastic medium are evaluated based on the linearized couple-stress theory under uniform tension normal to the cracks. Fourier transformations are used to reduce the boundary conditions with respect to the upper crack to dual integral equations. In order to solve these equations, the differences in the displacements and in the rotation at the upper crack are expanded through a series of functions that are zero valued outside the crack. The unknown coefficients in each series are solved in order to satisfy the boundary conditions inside the crack using the Schmidt method. The stresses are expressed in terms of infinite integrals, and the stress intensity factors can be determined using the characteristics of the integrands for an infinite value of the variable of integration. Numerical calculations are carried out for selected crack configurations, and the effect of the couple stresses on the stress intensity factors is revealed.

  5. Effects of acute and chronic psychological stress on platelet aggregation in mice.

    Science.gov (United States)

    Matsuhisa, Fumikazu; Kitamura, Nobuo; Satoh, Eiki

    2014-03-01

    Although psychological stress has long been known to alter cardiovascular function, there have been few studies on the effect of psychological stress on platelets, which play a pivotal role in cardiovascular disease. In the present study, we investigated the effects of acute and chronic psychological stress on the aggregation of platelets and platelet cytosolic free calcium concentration ([Ca(2+)]i). Mice were subjected to both transportation stress (exposure to novel environment, psychological stress) and restraint stress (psychological stress) for 2 h (acute stress) or 3 weeks (2 h/day) (chronic stress). In addition, adrenalectomized mice were subjected to similar chronic stress (both transportation and restraint stress for 3 weeks). The aggregation of platelets from mice and [Ca(2+)]i was determined by light transmission assay and fura-2 fluorescence assay, respectively. Although acute stress had no effect on agonist-induced platelet aggregation, chronic stress enhanced the ability of the platelet agonists thrombin and ADP to stimulate platelet aggregation. However, chronic stress failed to enhance agonist-induced increase in [Ca(2+)]i. Adrenalectomy blocked chronic stress-induced enhancement of platelet aggregation. These results suggest that chronic, but not acute, psychological stress enhances agonist-stimulated platelet aggregation independently of [Ca(2+)]i increase, and the enhancement may be mediated by stress hormones secreted from the adrenal glands.

  6. Effect of soil water stress on yield and proline content of four wheat ...

    African Journals Online (AJOL)

    Effect of soil water stress on yield and proline content of four wheat lines. ... This field study was conducted to evaluate the effect of drought stress after anthesis on proline accumulation and wheat yield during 2008 at ... from 32 Countries:.

  7. Multiplied effect of heat and radiation in chemical stress relaxation

    International Nuclear Information System (INIS)

    Ito, Masayuki

    1981-01-01

    About the deterioration of rubber due to radiation, useful knowledge can be obtained by the measurement of chemical stress relaxation. As an example, the rubber coating of cables in a reactor containment vessel is estimated to be irradiated by weak radiation at the temperature between 60 and 90 deg C for about 40 years. In such case, it is desirable to establish the method of accelerated test of the deterioration. The author showed previously that the law of time-dose rate conversion holds in the case of radiation. In this study, the chemical stress relaxation to rubber was measured by the simultaneous application of heat and radiation, and it was found that there was the multiplied effect of heat and radiation in the stress relaxation speed. Therefore the factor of multiplication of heat and radiation was proposed to describe quantitatively the degree of the multiplied effect. The chloroprene rubber used was offered by Hitachi Cable Co., Ltd. The experimental method and the results are reported. The multiplication of heat and radiation is not caused by the direct cut of molecular chains by radiation, instead, it is based on the temperature dependence of various reaction rates at which the activated species reached the cut of molecular chains through complex reaction mechanism and the temperature dependence of the diffusion rate of oxygen in rubber. (Kako, I.)

  8. Stress-Softening and Residual Strain Effects in Suture Materials

    Directory of Open Access Journals (Sweden)

    Alex Elías-Zúñiga

    2013-01-01

    Full Text Available This work focuses on the experimental characterization of suture material samples of MonoPlus, Monosyn, polyglycolic acid, polydioxanone 2–0, polydioxanone 4–0, poly(glycolide-co-epsilon-caprolactone, nylon, and polypropylene when subjected to cyclic loading and unloading conditions. It is found that all tested suture materials exhibit stress-softening and residual strain effects related to the microstructural material damage upon deformation from the natural, undistorted state of the virgin suture material. To predict experimental observations, a new constitutive material model that takes into account stress-softening and residual strain effects is developed. The basis of this model is the inclusion of a phenomenological nonmonotonous softening function that depends on the strain intensity between loading and unloading cycles. The theory is illustrated by modifying the non-Gaussian average-stretch, full-network model to capture stress-softening and residual strains by using pseudoelasticity concepts. It is shown that results obtained from theoretical simulations compare well with suture material experimental data.

  9. Deposition stress effects on thermal barrier coating burner rig life

    Science.gov (United States)

    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.

  10. Effect of heating method on stress-rupture life

    Science.gov (United States)

    Bizon, P. T.; Calfo, F. D.

    1977-01-01

    The effect of radiant(furnace), resistance(electric current), burner(hot gas stream), and a combination of resistance and burner heating on intermediate time (100 to 300 hr) stress-rupture life and reduction of area was evaluated. All heating methods were studied using the nickel-based alloy Udimet 700 while all but burner heating were evaluated with the cobalt-based alloy Mar-M 509. Limited test results of eight other superalloys were also included in this study. Resistance heated specimens had about 20 to 30 percent of the stress-rupture life of radiant heated specimens. The limited burner heating data showed about a 50 percent life reduction as compared to the radiant heated tests. A metallurgical examination gave no explanation for these reductions.

  11. Dissecting long-term adjustments of photoprotective and photo-oxidative stress acclimation occurring in dynamic light environments

    Directory of Open Access Journals (Sweden)

    Shizue Matsubara

    2016-11-01

    Full Text Available Changes in light intensity directly affect the performance of the photosynthetic apparatus. Light energy absorbed in excess of cells’ needs leads to production of reactive oxygen species and photo-oxidative damage. Excess light in both constant and dynamic environments induces photoprotective acclimation in plants. Distinct sets of signals and regulatory mechanisms are involved in acclimatory adjustment of photoprotection and photosynthesis under constant and dynamic (fluctuating light conditions. We are still far away from drawing a comprehensive picture of acclimatory signal transduction pathways, particularly in dynamic environments. In this perspective article, we propose the use of Arabidopsis plants that produce H2O2 in chloroplasts (GO plants under atmospheric CO2 levels as a tool to study the mechanisms of long-term acclimation to photo-oxidative stress. In our opinion there are new avenues to future investigations on acclimatory adjustments and signal transduction occurring in plants under dynamic light environments.

  12. The Effect of Stress Management on Occupational Stress and Satisfaction among Midwives in Obstetrics and Gynecology Hospital Wards in Iran.

    Science.gov (United States)

    Karimyar Jahromi, Mahdi; Minaei, Shahnaz; Abdollahifard, Sareh; Maddahfar, Majid

    2016-09-01

    Occupational stress is one of the major problems of health care staff, substantially affecting their professional and personal performance. This research has been conducted with the aim of determining the effect of stress management on occupational stress and satisfaction among the Midwives in Obstetrics and Gynecology Hospital wards at Motahari Hospital in Jahrom, Iran 2013-2014. This is a Quasi-experimental study of the pre- and post-clinical trials type. The study population included midwives employed in the Obstetrics and Gynecology Hospital wards selected trough census. The samples were categorized into two groups randomly. The intervention group participated in the short-term training workshop of stress management. The studied samples were measured in terms of occupational stress and satisfaction before, right after, and one month after the workshop. Occupational stress measurement was measured by Toft-Anderson occupational stress questionnaire (1981). Similarly, the occupational satisfaction was measured by JDI checklist developed by Stephen Robins (1994). In order to analyze the information, SPSS 16 together with descriptive statistics tests (frequency, percentile, mean, and standard deviation), independent sample t-tests, iterative measurement and Spearman correlation coefficient were used.  A total of 70 people (two 35-person groups) of midwives participated in this study. The findings revealed that there was a significant difference between the mean of scores of occupational stress between the two groups before and after the workshop (p=0.001). There was, however, no significant difference between the scores of satisfactions across the two groups. Training of skills of coping with stress including stress management can be effective in diminishing level of occupational stress. Mitigation of stress without catering for professional, occupational, organizational, and environmental factors would not lead to development of job satisfaction.

  13. Stress in Childhood and Adulthood: Effects on Marital Quality over Time

    Science.gov (United States)

    Umberson, Debra; Williams, Kristi; Powers, Daniel A.; Liu, Hui; Needham, Belinda

    2005-01-01

    We work from a stress and life course perspective to consider how stress affects trajectories of change in marital quality over time. Specifically, we ask whether stress is more likely to undermine the quality of marital experiences at different points in the life course. In addition, we ask whether the effects of adult stress on marital quality…

  14. Effect of residual stress induced by cold expansion on fatigue crack ...

    African Journals Online (AJOL)

    Fatigue life and fatigue crack growth rate are controlled by stress ratio, stress level, orientation of crack, temper-ature, residual stress, corrosion, etc. The effects of residual stress on fatigue crack growth in aluminium (Al) alloy 2024-T351 by Mode I crack were investigated by applying constant amplitude cycles based on ...

  15. Effect of abiotic stress under light and dark conditions on carotenoid ...

    African Journals Online (AJOL)

    The aim of this study was to observe the effect of abiotic stress under light and dark conditions on pumpkin calluses carotenoid. Plant elicitors used to create abiotic stress in this study were Polyethylene Glycol 4000 for drought stress, Jasmonic Acid and Salicylic Acid for hormones stress and Murashige and Skoog Salt for ...

  16. Stress !!!

    NARCIS (Netherlands)

    Fledderus, M.

    2012-01-01

    Twee op de vijf UT-studenten hebben last van ernstige studiestress, zo erg zelfs dat het ze in hun privéleven belemmert. Die cijfers komen overeen met het landelijk beeld van stress onder studenten. Samen met 14 andere universiteits- en hogeschoolbladen enquêteerde UT Nieuws bijna 5500 studenten.

  17. Ecosystem stress response : understanding effects on the benthic invertebrate community of Alberta oil-sands wetlands

    International Nuclear Information System (INIS)

    Wytrykush, C.M.; Ciborowski, J.J.H.

    2003-01-01

    The environmental stress response of invertebrates was examined using wetlands in the Alberta oil-sands region as a model. Wetlands in this region occur naturally or they have been affected by oil-sands mining process materials such as mine-tailings, or saline process water. These materials can be toxic to aquatic organisms due to their high concentrations of sulphate ions, ammonia, polycyclic aromatic hydrocarbons (PAHs) and naphthenic acids. Wetlands are classified as either young or mature, and as having low or high sediment organic content. This study examined food web dynamics and structure in wetlands using stable isotopes to determine the effects of stress on ecological communities. Primary and secondary production in the wetlands was measured along with invertebrate diversity in order to determine a relationship. The maximum trophic position was determined using stable carbon and nitrogen isotopes to indicate food chain length which is influenced by energetic constraints, ecosystem size and stressors. The study quantifies the dynamics of vital links between the responses to environmental pressures in aquatic systems and the effects on terrestrial ecosystems

  18. The Temporal Dynamics Model of Emotional Memory Processing: A Synthesis on the Neurobiological Basis of Stress-Induced Amnesia, Flashbulb and Traumatic Memories, and the Yerkes-Dodson Law

    OpenAIRE

    Diamond, David M.; Campbell, Adam M.; Park, Collin R.; Halonen, Joshua; Zoladz, Phillip R.

    2007-01-01

    We have reviewed research on the effects of stress on LTP in the hippocampus, amygdala and prefrontal cortex (PFC) and present new findings which provide insight into how the attention and memory-related functions of these structures are influenced by strong emotionality. We have incorporated the stress-LTP findings into our “temporal dynamics†model, which provides a framework for understanding the neurobiological basis of flashbulb and traumatic memories, as well as stress-induced ...

  19. Thermomechanical Stress in Cryopreservation Via Vitrification With Nanoparticle Heating as a Stress-Moderating Effect.

    Science.gov (United States)

    Eisenberg, David P; Bischof, John C; Rabin, Yoed

    2016-01-01

    This study focuses on thermomechanical effects in cryopreservation associated with a novel approach of volumetric heating by means on nanoparticles in an alternating electromagnetic field. This approach is studied for the application of cryopreservation by vitrification, where the crystalline phase is completely avoided-the cornerstone of cryoinjury. Vitrification can be achieved by quickly cooling the material to cryogenic storage, where ice cannot form. Vitrification can be maintained at the end of the cryogenic protocol by quickly rewarming the material back to room temperature. The magnitude of the rewarming rates necessary to maintain vitrification is much higher than the magnitude of the cooling rates that are required to achieve it in the first place. The most common approach to achieve the required cooling and rewarming rates is by exposing the specimen's surface to a temperature-controlled environment. Due to the underlying principles of heat transfer, there is a size limit in the case of surface heating beyond which crystallization cannot be prevented at the center of the specimen. Furthermore, due to the underlying principles of solid mechanics, there is a size limit beyond which thermal expansion in the specimen can lead to structural damage and fractures. Volumetric heating during the rewarming phase of the cryogenic protocol can alleviate these size limitations. This study suggests that volumetric heating can reduce thermomechanical stress, when combined with an appropriate design of the thermal protocol. Without such design, this study suggests that the level of stress may still lead to structural damage even when volumetric heating is applied. This study proposes strategies to harness nanoparticles heating in order to reduce thermomechanical stress in cryopreservation by vitrification.

  20. Effectiveness of a Comprehensive Stress Management Program to Reduce Work-Related Stress in a Medium-Sized Enterprise

    Science.gov (United States)

    2014-01-01

    Objectives To assess the effectiveness of a comprehensive workplace stress management program consisting of participatory action-oriented training (PAOT) and individual management. Methods A comprehensive workplace stress management program was conducted in a medium-sized enterprise. The baseline survey was conducted in September 2011, using the Korean Occupational Stress Scale (KOSS) and Worker’s Stress Response Inventory (WSRI). After implementing both organizational and individual level interventions, the follow up evaluation was conducted in November 2011. Results Most of the workers participated in the organizational level PAOT and made Team-based improvement plans. Based on the stress survey, 24 workers were interviewed by a researcher. After the organizational and individual level interventions, there was a reduction of several adverse psychosocial factors and stress responses. In the case of blue-collar workers, psychosocial factors such as the physical environment, job demands, organizational system, lack of rewards, and occupational climate were significantly improved; in the case of white-collar workers, the occupational climate was improved. Conclusions In light of these results, we concluded that the comprehensive stress management program was effective in reducing work-related stress in a short-term period. A persistent long-term follow up is necessary to determine whether the observed effects are maintained over time. Both team-based improvement activities and individual interviews have to be sustainable and complementary to each other under the long-term plan. PMID:24524591

  1. Effectiveness of a comprehensive stress management program to reduce work-related stress in a medium-sized enterprise.

    Science.gov (United States)

    Kim, Shin-Ae; Suh, Chunhui; Park, Mi-Hee; Kim, Kunhyung; Lee, Chae-Kwan; Son, Byung-Chul; Kim, Jeong-Ho; Lee, Jong-Tae; Woo, Kuck-Hyun; Kang, Kabsoon; Jung, Hyunjin

    2014-01-01

    To assess the effectiveness of a comprehensive workplace stress management program consisting of participatory action-oriented training (PAOT) and individual management. A comprehensive workplace stress management program was conducted in a medium-sized enterprise. The baseline survey was conducted in September 2011, using the Korean Occupational Stress Scale (KOSS) and Worker's Stress Response Inventory (WSRI). After implementing both organizational and individual level interventions, the follow up evaluation was conducted in November 2011. Most of the workers participated in the organizational level PAOT and made Team-based improvement plans. Based on the stress survey, 24 workers were interviewed by a researcher. After the organizational and individual level interventions, there was a reduction of several adverse psychosocial factors and stress responses. In the case of blue-collar workers, psychosocial factors such as the physical environment, job demands, organizational system, lack of rewards, and occupational climate were significantly improved; in the case of white-collar workers, the occupational climate was improved. In light of these results, we concluded that the comprehensive stress management program was effective in reducing work-related stress in a short-term period. A persistent long-term follow up is necessary to determine whether the observed effects are maintained over time. Both team-based improvement activities and individual interviews have to be sustainable and complementary to each other under the long-term plan.

  2. Synergetic effects of radiation stress and hot-carrier stress on the current gain of npn bipolar junction transistors

    International Nuclear Information System (INIS)

    Witczak, S.C.; Kosier, S.L.; Schrimpf, R.D.; Galloway, K.F.

    1994-01-01

    The combined effects of ionizing radiation and hot-carrier stress on the current gain of npn bipolar junction transistors were investigated. The analysis was carried out experimentally by examining the consequences of interchanging the order in which the two stress types were applied to identical transistors which were stressed to various levels of damage. The results indicate that the hot-carrier response of the transistor is improved by radiation damage, whereas hot-carrier damage has little effect on subsequent radiation stress. Characterization of the temporal progression of hot-carrier effects revealed that hot-carrier stress acts initially to reduce excess base current and improve current gain in irradiated transistors. PISCES simulations show that the magnitude of the peak electric-field within the emitter-base depletion region is reduced significantly by net positive oxide charges induced by radiation. The interaction of the two stress types is explained in a qualitative model based on the probability of hot-carrier injection determined by radiation damage and on the neutralization and compensation of radiation-induced positive oxide charges by injected electrons. The result imply that a bound on damage due to the combined stress types is achieved when hot-carrier stress precedes any irradiation

  3. Expression dynamics of HSP70 during chronic heat stress in Tharparkar cattle.

    Science.gov (United States)

    Bharati, Jaya; Dangi, S S; Chouhan, V S; Mishra, S R; Bharti, M K; Verma, V; Shankar, O; Yadav, V P; Das, K; Paul, A; Bag, S; Maurya, V P; Singh, G; Kumar, P; Sarkar, M

    2017-06-01

    Six male Tharparkar cattle aged 2-3 years were selected for the study. The animals were acclimatized in the psychrometric chamber at thermoneutral zone (TNZ) for 15 days and then exposed to 42 °C temperature up to 23 days followed by 12 days of recovery period. Physiological responses were estimated, and peripheral blood mononuclear cells (PBMCs) were isolated at TNZ on day 1, day 5, and day 12; after 6 h of heat stress exposure on day 16 to day 20, day 25, day 30, day 32, day 34, day 36, and day 38; and a recovery period on day 45 and day 50. The PBMCs were cultured to study the effect of thermal challenge on HSP70 messenger RNA (mRNA) expression pattern at different temperature-time combinations. The mRNA and protein expression of HSP70 in PBMCs along with serum extracellular HSP70 (eHSP70) was increased (P cattle and the biphasic expression pattern may be providing a second window of protection during chronic heat stress.

  4. The Effects of Discrimination Experience on Life Satisfaction of North Korean Refugees: Mediating Effect of Stress.

    Science.gov (United States)

    Noh, Jin-Won; Park, Hyunchun; Kim, Minji; Kwon, Young Dae; Kim, Jin-Seok; Yu, Shieun

    2018-01-01

    This study investigated the mediation effect of stress between the experience of discrimination and life satisfaction among North Korean refugees who resettled in South Korea. The findings of the current study provide empirical evidence for the need of social interventions to mitigate adverse effects of stress on North Korean refugees who are subject to social discrimination on a daily basis. In this study, we included 500 subjects among 2,138 North Korean refugees who took refuge in South Korea in 2007. The interview started from April 6th 2009 and finished on May 25th 2009. We conducted moderator effect analysis with Path analysis was conducted because we confirm the experience of discrimination was affected by life satisfaction and stress can affected life satisfaction as a moderator. The experience of discrimination significantly affects stress and stress significantly affects life satisfaction. However, the experience of discrimination was not directly related to life satisfaction. The more stress the study respondents experienced, the lower the life satisfaction they reported. The present finding suggests that the effects of discriminating experiences on the life satisfaction of North Korean refugees in South Korea were mediated by their own perceived stress.

  5. Robust dynamical effects in traffic and chaotic maps on trees

    Indian Academy of Sciences (India)

    Here we study two types of well-defined diffusive dynamics on scale-free trees: traffic of packets as navigated random walks, and chaotic standard maps coupled along the network links. We show that in both cases robust collective dynamic effects appear, which can be measured statistically and related to non-ergodicity of ...

  6. The biomechanical and physiological effect of two dynamic workstations

    NARCIS (Netherlands)

    Botter, J.; Burford, E.M.; Commissaris, D.; Könemann, R.; Mastrigt, S.H.V.; Ellegast, R.P.

    2013-01-01

    The aim of this research paper was to investigate the effect, both biomechanically and physiologically, of two dynamic workstations currently available on the commercial market. The dynamic workstations tested, namely the Treadmill Desk by LifeSpan and the LifeBalance Station by RightAngle, were

  7. Varying parameter models to accommodate dynamic promotion effects

    NARCIS (Netherlands)

    Foekens, E.W.; Leeflang, P.S.H.; Wittink, D.R.

    1999-01-01

    The purpose of this paper is to examine the dynamic effects of sales promotions. We create dynamic brand sales models (for weekly store-level scanner data) by relating store intercepts and a brand's own price elasticity to a measure of the cumulated previous price discounts - amount and time - for

  8. Effects of regularisation priors on dynamic PET Data

    International Nuclear Information System (INIS)

    Caldeira, Liliana; Scheins, Juergen; Silva, Nuno da; Gaens, Michaela; Shah, N Jon

    2014-01-01

    Dynamic PET provides temporal information about tracer uptake. However, each PET frame has usually low statistics, resulting in noisy images. The goal is to study effects of prior regularisation on dynamic PET data. Quantification and noise in image-domain and time-domain as well as impact on parametric images is assessed.

  9. Effect of dissipation on dynamical fusion thresholds

    International Nuclear Information System (INIS)

    Sierk, A.J.

    1986-01-01

    The existence of dynamical thresholds to fusion in heavy nuclei (A greater than or equal to 200) due to the nature of the potential-energy surface is shown. These thresholds exist even in the absence of dissipative forces, due to the coupling between the various collective deformation degrees of freedom. Using a macroscopic model of nuclear shape dynamics, It is shown how three different suggested dissipation mechanisms increase by varying amounts the excitation energy over the one-dimensional barrier required to cause compound-nucleus formation. The recently introduced surface-plus-window dissipation may give a reasonable representation of experimental data on fusion thresholds, in addition to properly describing fission-fragment kinetic energies and isoscalar giant multipole widths. Scaling of threshold results to asymmetric systems is discussed. 48 refs., 10 figs

  10. MALDI-TOF Mass Spectrometry Enables a Comprehensive and Fast Analysis of Dynamics and Qualities of Stress Responses of Lactobacillus paracasei subsp. paracasei F19

    Science.gov (United States)

    Schott, Ann-Sophie; Behr, Jürgen; Quinn, Jennifer; Vogel, Rudi F.

    2016-01-01

    Lactic acid bacteria (LAB) are widely used as starter cultures in the manufacture of foods. Upon preparation, these cultures undergo various stresses resulting in losses of survival and fitness. In order to find conditions for the subsequent identification of proteomic biomarkers and their exploitation for preconditioning of strains, we subjected Lactobacillus (Lb.) paracasei subsp. paracasei TMW 1.1434 (F19) to different stress qualities (osmotic stress, oxidative stress, temperature stress, pH stress and starvation stress). We analysed the dynamics of its stress responses based on the expression of stress proteins using MALDI-TOF mass spectrometry (MS), which has so far been used for species identification. Exploiting the methodology of accumulating protein expression profiles by MALDI-TOF MS followed by the statistical evaluation with cluster analysis and discriminant analysis of principle components (DAPC), it was possible to monitor the expression of low molecular weight stress proteins, identify a specific time point when the expression of stress proteins reached its maximum, and statistically differentiate types of adaptive responses into groups. Above the specific result for F19 and its stress response, these results demonstrate the discriminatory power of MALDI-TOF MS to characterize even dynamics of stress responses of bacteria and enable a knowledge-based focus on the laborious identification of biomarkers and stress proteins. To our knowledge, the implementation of MALDI-TOF MS protein profiling for the fast and comprehensive analysis of various stress responses is new to the field of bacterial stress responses. Consequently, we generally propose MALDI-TOF MS as an easy and quick method to characterize responses of microbes to different environmental conditions, to focus efforts of more elaborate approaches on time points and dynamics of stress responses. PMID:27783652

  11. MALDI-TOF Mass Spectrometry Enables a Comprehensive and Fast Analysis of Dynamics and Qualities of Stress Responses of Lactobacillus paracasei subsp. paracasei F19.

    Directory of Open Access Journals (Sweden)

    Ann-Sophie Schott

    Full Text Available Lactic acid bacteria (LAB are widely used as starter cultures in the manufacture of foods. Upon preparation, these cultures undergo various stresses resulting in losses of survival and fitness. In order to find conditions for the subsequent identification of proteomic biomarkers and their exploitation for preconditioning of strains, we subjected Lactobacillus (Lb. paracasei subsp. paracasei TMW 1.1434 (F19 to different stress qualities (osmotic stress, oxidative stress, temperature stress, pH stress and starvation stress. We analysed the dynamics of its stress responses based on the expression of stress proteins using MALDI-TOF mass spectrometry (MS, which has so far been used for species identification. Exploiting the methodology of accumulating protein expression profiles by MALDI-TOF MS followed by the statistical evaluation with cluster analysis and discriminant analysis of principle components (DAPC, it was possible to monitor the expression of low molecular weight stress proteins, identify a specific time point when the expression of stress proteins reached its maximum, and statistically differentiate types of adaptive responses into groups. Above the specific result for F19 and its stress response, these results demonstrate the discriminatory power of MALDI-TOF MS to characterize even dynamics of stress responses of bacteria and enable a knowledge-based focus on the laborious identification of biomarkers and stress proteins. To our knowledge, the implementation of MALDI-TOF MS protein profiling for the fast and comprehensive analysis of various stress responses is new to the field of bacterial stress responses. Consequently, we generally propose MALDI-TOF MS as an easy and quick method to characterize responses of microbes to different environmental conditions, to focus efforts of more elaborate approaches on time points and dynamics of stress responses.

  12. Effects of Pre-Encoding Stress on Brain Correlates Associated with the Long-Term Memory for Emotional Scenes

    Science.gov (United States)

    Wirkner, Janine; Weymar, Mathias; Löw, Andreas; Hamm, Alfons O.

    2013-01-01

    Recent animal and human research indicates that stress around the time of encoding enhances long-term memory for emotionally arousing events but neural evidence remains unclear. In the present study we used the ERP old/new effect to investigate brain dynamics underlying the long-term effects of acute pre-encoding stress on memory for emotional and neutral scenes. Participants were exposed either to the Socially Evaluated Cold Pressure Test (SECPT) or a warm water control procedure before viewing 30 unpleasant, 30 neutral and 30 pleasant pictures. Two weeks after encoding, recognition memory was tested using 90 old and 90 new pictures. Emotional pictures were better recognized than neutral pictures in both groups and related to an enhanced centro-parietal ERP old/new difference (400–800 ms) during recognition, which suggests better recollection. Most interestingly, pre-encoding stress exposure specifically increased the ERP old/new-effect for emotional (unpleasant) pictures, but not for neutral pictures. These enhanced ERP/old new differences for emotional (unpleasant) scenes were particularly pronounced for those participants who reported high levels of stress during the SECPT. The results suggest that acute pre-encoding stress specifically strengthens brain signals of emotional memories, substantiating a facilitating role of stress on memory for emotional scenes. PMID:24039697

  13. Estimation of spacial geo-stress components in rock samples by using the Kaiser effect of acoustic emission

    International Nuclear Information System (INIS)

    Kanagawa, Tadashi; Hayashi, Masao; Nakasa, Hiroyasu.

    1976-01-01

    The spacial remaining stress component of the rock core sample is experimentally obtained by using Kaiser effect of acoustic emission (AE), and the estimated ground pressure is compared with the natural ground pressure measured by the conventional over-coring method, in order to see the feasiblity of AE method. In this experiments of AE, 111 specimens were cut out in all directions of the rock cores (tuff) sampled from the place where the ground pressure was measured by the over-coring method, and the generation of AE caused by the load was measured. Whereby, the stress components in three directions are determined. As a result of comparison, t the AE method is proved to be effective enough to estimate the ground pressure of rock geo-dynamically. In the application of the Kaiser effect to the estimation of the geo-stress in rock samples, one of the most difficult problems is how to eliminate the obstruction of erroneous AE signals caused by the strong stress concentration at the end corners of the rock specimen. As the result of comparison, the values obtained by the AE method have a tendency of greater than the values obtained by the over-coring method. It is conceived that the AE method can easily detect the maximum stress value for geo historical long time, and that the stress concentration is apt to mix in AE method by boring. (Iwakiri, K.)

  14. Effects of pre-encoding stress on brain correlates associated with the long-term memory for emotional scenes.

    Directory of Open Access Journals (Sweden)

    Janine Wirkner

    Full Text Available Recent animal and human research indicates that stress around the time of encoding enhances long-term memory for emotionally arousing events but neural evidence remains unclear. In the present study we used the ERP old/new effect to investigate brain dynamics underlying the long-term effects of acute pre-encoding stress on memory for emotional and neutral scenes. Participants were exposed either to the Socially Evaluated Cold Pressure Test (SECPT or a warm water control procedure before viewing 30 unpleasant, 30 neutral and 30 pleasant pictures. Two weeks after encoding, recognition memory was tested using 90 old and 90 new pictures. Emotional pictures were better recognized than neutral pictures in both groups and related to an enhanced centro-parietal ERP old/new difference (400-800 ms during recognition, which suggests better recollection. Most interestingly, pre-encoding stress exposure specifically increased the ERP old/new-effect for emotional (unpleasant pictures, but not for neutral pictures. These enhanced ERP/old new differences for emotional (unpleasant scenes were particularly pronounced for those participants who reported high levels of stress during the SECPT. The results suggest that acute pre-encoding stress specifically strengthens brain signals of emotional memories, substantiating a facilitating role of stress on memory for emotional scenes.

  15. Hemodynamic effects of a novel pharmacologic stress agent, Higemine

    International Nuclear Information System (INIS)

    Zhang, X.L.; Liu, X.J.; Tao, Z.H.; Shi, R.F.

    2002-01-01

    Objective: Higenamine (dl-demethylcodaurine) (HG), which was isolated from aconitum japonicum. This study was to evaluate the hemodynamic effects of HG in animal study. Methods: We compared the hemodynamic effects of HG (0.5-4μg/min/kg) with Dobutamine (Dob) (5-30μg/min/kg) in 6 dogs: heart rate (HR), blood pressure (BP), coronary blood flow (CBF), myocardial oxygen consumption (MOC) were measured. Tolerability and safety of HG (1-500μg/mg/min) were evaluated in 8 dogs. Results: Comparison of hemodynamic effects between Dob an HG was presented. SBP: systolic blood pressure; DP: diastolic blood pressure; P<0.01; P<0.05. Diastolic BP slightly decreased, but systolic BP did not change significantly during HG infusion. There was no significant ECG abnormalities and side effects during HG infusion. Conclusion: HG might be a safe and useful pharmacologic stress agent, especially for patients with severe hypertension

  16. A Method to Estimate the Dynamic Displacement and Stress of a Multi-layered Pavement with Bituminous or Concrete Materials

    Directory of Open Access Journals (Sweden)

    Zheng LU

    2014-12-01

    Full Text Available In this research work, a method to estimate the dynamic characteristics of a multilayered pavement with bituminous or concrete materials is proposed. A mechanical model is established to investigate the dynamic displacement and stress of the multi-layered pavement structure. Both the flexible and the rigid pavements, corresponding to bituminous materials and concrete materials, respectively, are studied. The theoretical solutions of the multi-layered pavement structure are deduced considering the compatibility condition at the interface of the structural layers. By introducing FFT (Fast Fourier Transform algorithm, some numerical results are presented. Comparisons of the theoretical and experimental result implied that the proposed method is reasonable in predicting the stress and displacement of a multi-layered pavement with bituminous or concrete materials. DOI: http://dx.doi.org/10.5755/j01.ms.20.4.6071

  17. On the relation between quasi-static and dynamic stress induced reversible structural relaxation of amorphous alloys

    International Nuclear Information System (INIS)

    Krueger, P.; Stucky, T.; Boewe, M.; Neuhaeuser, H.

    1993-01-01

    Quasi-static stress relaxation and dynamic internal friction measurements of stress induced reversible structural relaxation were performed on the amorphous alloy Fe 40 Ni 40 B 20 . The kinetics can be well described by a stretched exponential Kohlrausch-Williams-Watts quasi-static relaxation. The thermally activated part of the internal friction shows an Arrhenius temperature behaviour for a fixed vibration frequency and an inverse power frequency behaviour for a fixed temperature. The activation energies calculated from the Arrhenius equation and from the frequency shift method are significantly different. In order to explain this discrepancy the relation between the quasi-static and the dynamic descriptions of the reversible relaxation is reexamined. In particular it is shown that these two activation energies are connected by the Kohlrausch exponent of the quasi-static relaxation. (orig.)

  18. Effect of temperature stress on protein methyl esters

    International Nuclear Information System (INIS)

    Welch, W.; Kracaw, K.

    1986-01-01

    Protein methyl esters have been implicated in a number of physiological processes. They have measured the effect of temperature stress on the levels of protein methyl esters in the mesophilic fungus Penicillium chrysogenum (PCPS) and the thermophilic fungus P. duponti (PD). PD and PCPS were incubated with [methyl- 3 H]methionine. The mycelia were collected by filtration, frozen in liquid nitrogen and ground to a fine powder. The nitrogen powder was extracted with either phosphate buffer or with SDS, glycerol, phosphate, 2-mercaptoethanol. Insoluble material was removed by centrifugation. The supernatants were assayed for protein methyl esters. The released [ 3 H]methanol was extracted into toluene:isoamyl alcohol (3:2) and quantitated by liquid scintillation. The production of volatile methanol was confirmed by use of Conway diffusion cells. Soluble proteins accounted for about one-fourth of the total protein methyl ester extracted by SDS. In PCPS, the SDS extracted proteins have about three times the level of esterification of the soluble proteins whereas in PD there is little difference between soluble and SDS extracted protein. The level of protein esterification in PD is about one-tenth that observed in PCPS. Temperature stress caused large changes in the level of protein esterification. The data suggest protein methyl esters may contribute to the adaptation to environmental stress

  19. The Effects of Cold Stress on Photosynthesis in Hibiscus Plants

    Science.gov (United States)

    Paredes, Miriam; Quiles, María José

    2015-01-01

    The present work studies the effects of cold on photosynthesis, as well as the involvement in the chilling stress of chlororespiratory enzymes and ferredoxin-mediated cyclic electron flow, in illuminated plants of Hibiscus rosa-sinensis. Plants were sensitive to cold stress, as indicated by a reduction in the photochemistry efficiency of PSII and in the capacity for electron transport. However, the susceptibility of leaves to cold may be modified by root temperature. When the stem, but not roots, was chilled, the quantum yield of PSII and the relative electron transport rates were much lower than when the whole plant, root and stem, was chilled at 10°C. Additionally, when the whole plant was cooled, both the activity of electron donation by NADPH and ferredoxin to plastoquinone and the amount of PGR5 polypeptide, an essential component of the cyclic electron flow around PSI, increased, suggesting that in these conditions cyclic electron flow helps protect photosystems. However, when the stem, but not the root, was cooled cyclic electron flow did not increase and PSII was damaged as a result of insufficient dissipation of the excess light energy. In contrast, the chlororespiratory enzymes (NDH complex and PTOX) remained similar to control when the whole plant was cooled, but increased when only the stem was cooled, suggesting the involvement of chlororespiration in the response to chilling stress when other pathways, such as cyclic electron flow around PSI, are insufficient to protect PSII. PMID:26360248

  20. The Effects of Oxidative Stress in Urinary Tract Infection

    Directory of Open Access Journals (Sweden)

    Ergul Belge Kurutas

    2005-01-01

    Full Text Available We aimed to determine the effects of oxidative stress in urinary tract infection (UTI. One hundred sixty-four urine samples obtained from patients with the prediagnosis of acute UTI admitted to the Faculty of Medicine, Kahramanmaras Sutcu Imam University, were included in this study. Urine cultures were performed according to standard techniques. Urinary isolates were identified by using API ID 32E. The catalase and superoxide dismutase activity and the lipid peroxidation levels known as oxidative stress markers were measured in all urine samples. Thirty-six pathogen microorganisms were identified in positive urine cultures. These microorganisms were as follows: 23 (63.8% E coli, 5 (13.8% P mirabilis, 4 (11.1% K pneumoniae, 2 (5.5% Candida spp, 1 (2.7% S saprophyticus, and 1 (2.7% P aeruginosa. It was observed that lipid peroxidation levels were increased while catalase and superoxide dismutase activities were decreased in positive urine cultures, compared to negative cultures. We conclude that urinary tract infection causes oxidative stress, increases lipid peroxidation level, and leads to insufficiency of antioxidant enzymes.