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Sample records for stress relaxation testing

  1. Stress relaxation in tempered glass caused by heat soak testing

    DEFF Research Database (Denmark)

    Schneider, Jens; Hilcken, Jonas; Aronen, Antti

    2016-01-01

    of commercial soda-lime-silica glass, it causes stress relaxation in tempered glass and the fracture pattern of the glass changes accordingly, especially thin glasses are affected. Based on the Tool-Narayanaswamy-Model, this paper comprises the theoretical background of the stress......Heat soak testing of tempered glass is a thermal process required after the tempering process itself to bring glasses of commercial soda-lime-silica-glass to failure that are contaminated with nickel sulphide inclusions, diameter 50 mm to 500 mm typically. Thus, the tests avoid a so...

  2. Stress Testing Recovery EMG for Evaluation of Biofeedback and Progressive Muscle Relaxation Training Effects.

    Science.gov (United States)

    Sime, Wesley E.; DeGood, Douglas E.

    The purpose of this investigation was to assess biofeedback (BF) and progressive muscle relaxation (PMR) and placebo-control training by means of a post-training transfer test. The subjects for the research were 30 women. Initial tests consisted of measuring the electromyographic response of the frontalis muscle of the forehead to stress. After…

  3. The Application of Stress-Relaxation Test to Life Assessment of T911/T22 Weld Metal

    Science.gov (United States)

    Cao, Tieshan; Zhao, Jie; Cheng, Congqian; Li, Huifang

    2016-03-01

    A dissimilar weld metal was obtained through submerged arc welding of a T911 steel to a T22 steel, and its creep property was explored by stress-relaxation test assisted by some conventional creep tests. The creep rate information of the stress-relaxation test was compared to the minimum and the average creep rates of the conventional creep test. Log-log graph showed that the creep rate of the stress-relaxation test was in a linear relationship with the minimum creep rate of the conventional creep test. Thus, the creep rate of stress-relaxation test could be used in the Monkman-Grant relation to calculate the rupture life. The creep rate of the stress-relaxation test was similar to the average creep rate, and thereby the rupture life could be evaluated by a method of "time to rupture strain." The results also showed that rupture life which was assessed by the Monkman-Grant relation was more accurate than that obtained through the method of "time to rupture strain."

  4. Sleep, Stress & Relaxation: Rejuvenate Body & Mind

    Science.gov (United States)

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  5. The relaxation & stress reduction workbook

    National Research Council Canada - National Science Library

    Davis, Martha; Eshelman, Elizabeth Robbins; McKay, Matthew

    2008-01-01

    "The Relaxation & Stress Reduction Workbook broke new ground when it was first published in 1980, detailing easy, step-by-step techniques for calming the body and mind in an increasingly overstimulated world...

  6. Modelling of Creep and Stress Relaxation Test of a Polypropylene Microfibre by Using Fraction-Exponential Kernel

    Directory of Open Access Journals (Sweden)

    Andrea Sorzia

    2016-01-01

    Full Text Available A tensile test until breakage and a creep and relaxation test on a polypropylene fibre are carried out and the resulting creep and stress relaxation curves are fit by a model adopting a fraction-exponential kernel in the viscoelastic operator. The models using fraction-exponential functions are simpler than the complex ones obtained from combination of dashpots and springs and, furthermore, are suitable for fitting experimental data with good approximation allowing, at the same time, obtaining inverse Laplace transform in closed form. Therefore, the viscoelastic response of polypropylene fibres can be modelled straightforwardly through analytical methods. Addition of polypropylene fibres greatly improves the tensile strength of composite materials with concrete matrix. The proposed analytical model can be employed for simulating the mechanical behaviour of composite materials with embedded viscoelastic fibres.

  7. The Relationship of Relaxation Technique, Test Anxiety, Academic Stress, and Nursing Students Intention to Stay in a Baccalaureate Degree Nursing Program

    Science.gov (United States)

    Manansingh, Sherry

    2017-01-01

    The purpose of this study was to examine the effect of relaxation techniques among first semester Baccalaureate Degree nursing students' test anxiety and academic stress. Additionally, this study examined if there was a relationship among demographic characteristics of the respondents and test anxiety and academic stress. The pretest and posttest…

  8. Measuring Propellant Stress Relaxation Modulus Using Dynamic Mechanical Analyzer

    Science.gov (United States)

    2017-03-29

    Article 3. DATES COVERED (From - To) 04 August 2016 – 29 March 2017 4. TITLE AND SUBTITLE Measuring Propellant Stress Relaxation Modulus Using Dynamic...ERC 14. ABSTRACT A method for determining the stress relaxation master curve of solid rocket propellants was developed. The propellant was tested in... stress relaxation modulus, Mpa; E∞ = long-term equilibrium modulus, Mpa; E0 = storage modulus, Mpa; E0 0 = loss modulus, Mpa; F = Fisher test

  9. Stress relaxation in viscous soft spheres.

    Science.gov (United States)

    Boschan, Julia; Vasudevan, Siddarth A; Boukany, Pouyan E; Somfai, Ellák; Tighe, Brian P

    2017-10-04

    We report the results of molecular dynamics simulations of stress relaxation tests in athermal viscous soft sphere packings close to their unjamming transition. By systematically and simultaneously varying both the amplitude of the applied strain step and the pressure of the initial condition, we access both linear and nonlinear response regimes and control the distance to jamming. Stress relaxation in viscoelastic solids is characterized by a relaxation time τ* that separates short time scales, where viscous loss is substantial, from long time scales, where elastic storage dominates and the response is essentially quasistatic. We identify two distinct plateaus in the strain dependence of the relaxation time, one each in the linear and nonlinear regimes. The height of both plateaus scales as an inverse power law with the distance to jamming. By probing the time evolution of particle velocities during relaxation, we further identify a correlation between mechanical relaxation in the bulk and the degree of non-affinity in the particle velocities on the micro scale.

  10. Stress relaxation of constructions elements

    Directory of Open Access Journals (Sweden)

    Larionov Evgeniy

    2017-01-01

    Full Text Available A relaxation of stress in the elements of constructions is considered and an approach is proposed for solution of corresponding problems. It is notable that this approach is based on a modification Boltzmann’s principle superposition of fraction creep deformations. This modification reduces the noted problems to solution of linear relative to so-called structural stress integral equations. Next a desired stress is defined by solution of algebraic equations. It should be underline that a material (concrete, steel, graph of elements a considered as a union of its fractions with statistical disturbed strengths. This ascending to Weibull conception [1] permits to modify Boltzmann’s principle superposition [2]. As a result this principle is applicable when a dependence on deformations from the stresses is nonlinear [3-7].

  11. Stress relaxation and estimation of activation volume in a ...

    Indian Academy of Sciences (India)

    Abstract. The stress relaxation of ferroelectric/piezoelectric material was studied using compression testing. The deformation was produced by the switching of ferroelectric domains. The internal stresses were estimated by decremental stress relaxation during unloading. The results were interpreted in terms of reversible and ...

  12. High Temperature Performance Evaluation of As-serviced 25Cr35Ni Type Heat-resistant Steel Based on Stress Relaxation Tests

    Directory of Open Access Journals (Sweden)

    XU Jun

    2017-08-01

    Full Text Available Based on an as-serviced 25Cr35Ni type steel, the high temperature property evaluation using stress relaxation test(SRT method and residual life prediction were studied. The results show that creep rupture property decreases because of the formation of network carbides along grain boundaries and coarsening of secondary carbides in the austenitic matrix. Based on the relationship of stress relaxation strain rate curves obtained at different temperatures, and the extrapolation equation of stress relaxation rate-rupture time, it is capable to perform residual life evaluation by combining SRT data and a small amount of creep rupture test(CRT. Good agreement is observed for predicting results performed by current method and traditional method.

  13. Stress and Relaxation in Relation to Personality

    OpenAIRE

    Harish Kumar Sharma

    2011-01-01

    Relaxation plays a significant role in facing stress. The aim of the present study is to see whether personality patterns determine an individual’s ability to relax. As a reaction to stress, coping is the best way to handle stress, which requires rational and conscious thinking. Does this ability to relax anyway facilitate coping reactions? A study was conducted on 100 college students. Results revealed that extraverts...

  14. Stress and Relaxation in Relation to Personality

    Directory of Open Access Journals (Sweden)

    Harish Kumar Sharma

    2011-09-01

    Full Text Available Relaxation plays a significant role in facing stress. The aim of the present study is to see whether personality patterns determine an individual’s ability to relax. As a reaction to stress, coping is the best way to handle stress, which requires rational and conscious thinking. Does this ability to relax anyway facilitate coping reactions? A study was conducted on 100 college students. Results revealed that extraverts relax easily than introverts. In addition, if intelligence level is average or above average, relaxation does play a role in facilitating coping reactions. It suggests that in designing techniques of stress management, the personality and intelligence level must be taken into consideration to make techniques effective.

  15. Effectiveness of Indonesian Essential Oil Mixture of Lemongrass, Cananga, and Patchouli in Relaxation through Inhalation: A Clinical Test on Healthy Woman with High Potential for Stress

    Directory of Open Access Journals (Sweden)

    Richard Siahaan

    2014-12-01

    Full Text Available Relaxation is one of many mechanisms for coping with stress. One of the most widely used methods for relaxation is aromatherapy with the application of essential oils. Known for their therapeutic benefits, essential oils can be extracted from various Indonesian native herbs such as lemongrass (sereh wangi or Cymbopogon winterianus, cananga or ylang-ylang (kenanga or Canarium odoratum, and patchouli (nilam or Pogostemon cabin. This study aims to examine the effectiveness of a mixture of Indonesian essential oil made of lemongrass, cananga, and patchouli extracts. Experiment was conducted by asking a number of subjects to inhale the oil mixture and assessing its effectiveness in terms of psychological relaxation by using Visual Analog Scale or VAS and of physical relaxation by examining the subjects’ blood pressure (MAP, pulse frequency, and breathing frequency. The result was then compared with that of lavender oil and with the control group. The study was conducted on 60 healthy women through single-blind clinical trials (before and after using the “intent to treat” approach, followed by a startle test. Participants were divided into three groups: (1 20 participants who were treated with Indonesian essential oil mixture, (2 20 participants who were treated with lavender oil, and (3 20 participants who served as the control group. Psychological relaxation measurement showed that Indonesian essential oil mixture produced the same degree of effectiveness as lavender oil and the control groups did, although both treatments tended to produce better results than the control group did. However, physical relaxation measurement showed that Indonesian essential oil mixture produced a higher degree of effectiveness than lavender oil and tended to produce a better result than the control group did, especially in terms of blood pressure based on MAP scores.

  16. Transformation fatigue and stress relaxation of shape memory alloy wires

    Science.gov (United States)

    Pappas, P.; Bollas, D.; Parthenios, J.; Dracopoulos, V.; Galiotis, C.

    2007-12-01

    The present work deals with the stress generation capability of nickel-titanium shape memory alloys (SMAs) under constrained conditions for two well-defined loading modes: recurrent crystalline transformation (transformation fatigue) and a one-step continuous activation (generated stress relaxation). The data acquired will be very useful during the design process of an SMA Ni-Ti element as a functional part of an assembly. Differential scanning calorimetry (DSC) was employed in order to investigate the transformation characteristics of the alloy before and after the tests. Transformation fatigue tests revealed that the parameter that affects more the rate of the functional degradation is the number of crystalline transitions the wire undergoes. Thus, the service life limit of this material as a stress generator can be reduced to a few thousand working cycles. For stress relaxation, the main factor that affects the ability for stress generation is the working temperature: the higher the temperature above the austenite finish (TAf) limit the higher the relaxation effect. Thermomechanical treatment of the alloy during the tests reveals the 'hidden' transformation from the cubic structure (B2) of austenite to the rhombohedral structure of the R-phase. It is believed that the gradual loss of the stress generation capability of the material under constrained conditions must be associated to a gradual slipping relaxation mechanism. Scanning electron microscopy (SEM) observations on as-received, re-trained, fatigued and stress-relaxed specimens in the martensitic state provide further support for this hypothesis.

  17. Stress Relaxation in Entangled Polymer Melts

    DEFF Research Database (Denmark)

    Hou, Ji-Xuan; Svaneborg, Carsten; Everaers, Ralf

    2010-01-01

    We present an extensive set of simulation results for the stress relaxation in equilibrium and step-strained bead-spring polymer melts. The data allow us to explore the chain dynamics and the shear relaxation modulus, G(t), into the plateau regime for chains with Z=40 entanglements and into the t......We present an extensive set of simulation results for the stress relaxation in equilibrium and step-strained bead-spring polymer melts. The data allow us to explore the chain dynamics and the shear relaxation modulus, G(t), into the plateau regime for chains with Z=40 entanglements...... excellent agreement for the Likhtman-McLeish theory using the double reptation approximation for constraint release, if we remove the contribution of high-frequency modes to contour length fluctuations of the primitive chain....

  18. The relaxation & stress reduction workbook

    National Research Council Canada - National Science Library

    Davis, Martha; Eshelman, Elizabeth Robbins; McKay, Matthew

    2008-01-01

    .... Now in its sixth edition, this workbook, highly regarded by therapists and their clients, remains the "go-to" source for stress reduction strategies that can be incorporated into even the busiest lives...

  19. The Effects of Stress Inoculation, Physical Relaxation and Skills ...

    African Journals Online (AJOL)

    ... the physical relaxation was more effective than the other treatment conditions in reducing psychophysiological symptoms, the stress inoculation was more effective in reducing the participants worry and emotionality reactions to evaluative situations. Keywords: Stress Inoculation; Physical Relaxation; Stress Management.

  20. Stress Relaxation in Entangled Polymer Melts

    DEFF Research Database (Denmark)

    Hou, Ji-Xuan; Svaneborg, Carsten; Everaers, Ralf

    2010-01-01

    We present an extensive set of simulation results for the stress relaxation in equilibrium and step-strained bead-spring polymer melts. The data allow us to explore the chain dynamics and the shear relaxation modulus, G(t), into the plateau regime for chains with Z=40 entanglements and into the t...... excellent agreement for the Likhtman-McLeish theory using the double reptation approximation for constraint release, if we remove the contribution of high-frequency modes to contour length fluctuations of the primitive chain....

  1. Effect of residual stress relaxation by means of local rapid induction heating on stress corrosion cracking behavior and electrochemical characterization of welded Ti-6Al-4V alloy under slow strain rate test

    Science.gov (United States)

    Liu, Yan; Tang, Shawei; Liu, Guangyi; Sun, Yue; Hu, Jin

    2017-05-01

    In this study, a welded Ti-6Al-4V alloy was treated by means of local rapid induction heating in order to relax the residual stress existed in the weldment. The welded samples were heat treated at the different temperatures. The stress corrosion cracking behavior and electrochemical characterization of the as-welded samples before and after the post weld heat treatment as a function of residual stress were investigated. Electrochemical impedance spectroscopy measurements of the samples under slow strain rate test were performed in a LiCl-methanol solution. The results demonstrated that the residual stress in the as-welded sample was dramatically reduced after the post weld heat treatment, and the residual stress decreased with the increase in the heat treatment temperature. The stress corrosion cracking susceptibility and electrochemical activity of the as-welded sample were significantly reduced after the heat treatment due to the relaxation of the residual stress, which gradually decreased with the decreasing value of the residual stress distributed in the heat treated samples.

  2. Nuclear stress test

    Science.gov (United States)

    ... Persantine stress test; Thallium stress test; Stress test - nuclear; Adenosine stress test; Regadenoson stress test; CAD - nuclear stress; Coronary artery disease - nuclear stress; Angina - nuclear ...

  3. Effects of progressive muscle relaxation on postmenopausal stress

    Directory of Open Access Journals (Sweden)

    Arunima Chaudhuri

    2015-01-01

    Full Text Available Background: Menopause increases stress level among females and this may be a contributing factor in developing metabolic syndrome. Objectives: The objective of this study is to study the effects of progressive muscle relaxation on cardiorespiratory efficiency and autonomic functions in over weight and obese working stressed postmenopausal females. Materials and Methods: A total of 30 postmenopausal overweight or obese (body mass index [BMI]: 24.97 ± 1.28 females belonging to the age group 50-55 years were included. Stress level in the subjects was assessed according to the presumptive life event stress scale. The perceived stress scale (PSS of Sheldon Cohen was used for measuring the perception of stress. Fasting blood samples were collected to exclude diabetic subjects and analyze lipid profile. BMI and waist/hip ratio were calculated. Resting pulse rate and blood pressure, respiratory rate were measured. VO 2 max, physical fitness index, breath holding time and 40 mm endurance test time were calculated for estimation of cardiopulmonary efficiency. Autonomic function tests were carried. Subjects were given progressive muscle relaxation training for 3 months and all parameters were reevaluated. Data was analyzed using SPSS version 16 (SPSS Inc., Chicago, USA. Results: PSS in pre-training session was 26.16 ± 1.7 and in post-training session was 14.33 ± 2.01 and the difference was statistically significant. There was a significant decrease in pulse rate, blood pressure, BMI, waist/hip ratio, cholesterol, low-density lipoprotein following preventive medicine residency training. Results of autonomic function tests and cardiopulmonary efficiency test improved significantly following relaxation training. Conclusions: Increased stress levels may increase BMI and waist/hip ratio, dyslipidemia and lead to autonomic dysfunctions and increase incidence of cardiovascular disease in postmenopausal females. Lifestyle modification with relaxation exercises

  4. Experimental characterization of stress relaxation in glass

    Science.gov (United States)

    Kadali, Hemanth C.

    Glass viscoelasticity has gained importance in recent years as glass lens molding appeared as a valuable alternative to the traditional grinding and polishing process for manufacturing glass lenses. In the precision lens molding process, knowledge of viscoelastic properties of glass in the transition region, which affect the stress relaxation behavior, is required to precisely predict the final size and shape of molded lenses. The purpose of this study is to establish a step-by-step procedure for characterizing the viscoelastic behavior of glass in the glass transition region using a finite term Prony series of a Generalized Maxwell model. This study focuses on viscoelastic characterization of stabilized glass samples at lower stress levels between 3 and 12 MPa where it demonstrates linearity. Analysis and post-processing of creep data, performed in MATLAB and MAPLE, include displacement-to-strain conversion, determination of viscoelastic moments and constants, normalization, curve fitting and retardation-to-relaxation conversion. The process of curve fitting is carried out using a constrained optimization scheme to satisfy the constraint equations involving viscoelastic constants and functions. A set of relaxation parameters needed in numerical modeling, i.e., weights and times of the Prony series are presented in this thesis for borosilicate glass at different temperatures. Additionally, the issues related to the characterization of optical glasses were identified and discussed.

  5. Magneto-dependent stress relaxation of magnetorheological gels

    KAUST Repository

    Xu, Yangguang

    2017-09-01

    The stress relaxation behaviors of magnetorheological (MR) gels under stepwise shear loading are systematically investigated. The particle-enhanced effect, the magneto-induced effect, and the temperature-enhanced effect on the stress relaxation of MR gels are discussed. For further analysis of the magneto-induced stress relaxation mechanism in MR gels, a phenomenological model is established to describe the stress relaxation behavior of the matrix and the magnetic particle chains. All characteristic parameters introduced in the model, i.e. relaxation time, instantaneous modulus, and stable modulus, have well-defined physical meanings and are fitted based on the experimental results. The influence of each parameter on the macroscopic response is discussed and it is found that the relaxation stress induced by the magneto-mechanical coupling effect plays an important role in the stress relaxation process of MR gels.

  6. Magneto-dependent stress relaxation of magnetorheological gels

    Science.gov (United States)

    Xu, Yangguang; Liu, Taixiang; Liao, Guojiang; Lubineau, Gilles

    2017-11-01

    The stress relaxation behaviors of magnetorheological (MR) gels under stepwise shear loading are systematically investigated. The particle-enhanced effect, the magneto-induced effect, and the temperature-enhanced effect on the stress relaxation of MR gels (MRG) are discussed. For further analysis of the magneto-induced stress relaxation mechanism in MRG, a phenomenological model is established to describe the stress relaxation behavior of the matrix and the magnetic particle chains. All characteristic parameters introduced in the model, i.e. relaxation time, instantaneous modulus, and stable modulus, have well-defined physical meanings and are fitted based on the experimental results. The influence of each parameter on the macroscopic response is discussed and it is found that the relaxation stress induced by the magneto-mechanical coupling effect plays an important role in the stress relaxation process of MRG.

  7. Composite Analysis of Concrete - Creep, Relaxation and Eigenstrain/stress

    DEFF Research Database (Denmark)

    Nielsen, Lauge Fuglsang

    1996-01-01

    approach.The model is successfully justified comparing predicted results with recent experimental data obtained in tests made at the Danish Technological Institute and at the Technical University of Denmark on creep, relaxation, and shrinkage of very young concretes (hours) - and also with experimental...... results on creep, shrinkage, and internal stresses caused by drying shrinkage reported in the literature on the mechanical behavior of mature concretes.Shrinkage (autogeneous or drying) of mortar and concrete and associated internal stress states are examples of analysis made in this report......A composite-rheological model of concrete is presented by which consistent predictions of creep, relaxation, and internal stresses can be made from known concrete composition, age at loading, and climatic conditions. No other existing "creep prediction method" offers these possibilities in one...

  8. Stress relaxation and estimation of activation volume in a ...

    Indian Academy of Sciences (India)

    Unknown

    Stress relaxation and estimation of activation volume in a commercial hard PZT piezoelectric ceramic. B L CHENG and M J REECE*. Department of Materials, Queen Mary and Westfield College, Mile End Road, E1 4NS, London, UK. Abstract. The stress relaxation of ferroelectric/piezoelectric material was studied using ...

  9. Stress relaxation of bi-disperse polystyrene melts

    DEFF Research Database (Denmark)

    Hengeller, Ludovica; Huang, Qian; Dorokhin, Andriy

    2016-01-01

    We present start-up of uniaxial extension followed by stress relaxation experiments of a bi-disperse 50 % by weight blend of 95k and 545k molecular weight polystyrene. We also show, for comparison, stress relaxation measurements of the polystyrene melts with molecular weight 95k and 545k, which...

  10. Stress relaxation functions: Methods of approximation

    Science.gov (United States)

    Bower, Mark V.; Gant, Frederick S.

    1994-04-01

    A new method of determining Prony series coefficients is presented. This method, the domain of influence method (DOI), capitalizes on characteristics of the exponential decay curve to adjust its parameters to fit a set of data. This method was applied to viscoelastic stress relaxation data. The method is general and can be used to develop exponential decay curves to represent other types of data where appropriate. The DOI method does not include any error correction within itself. To improve the results of the DOI method some form of error correction is necessary. The nonlinearity of the Prony series does not lend itself to common methods of error minimization. Optimization methods can be applied to this problem. These methods use the functional behavior of the problem under study to minimize or maximize some characteristic of the problem. Here the function minimized was an error function between the DOI estimated Prony series and the viscoelastic data. Optimization was achieved by adjusting the Prony series coefficients to minimize that error. The DOI method was encoded in FORTRAN and integrated with commercially available optimization routines to produce a tool called Viscoelastic Coefficient Determination or VCD. A description of this code including a discussion of the salient features is presented. An example is used to demonstrate the DOI method, illustrate the operation of VCD, and demonstrate the capabilities of the method and the software. A code listing appears in the appendix.

  11. Multiple sources of passive stress relaxation in muscle fibres

    Energy Technology Data Exchange (ETDEWEB)

    Linke, Wolfgang A; Leake, Mark C [Physiology and Biophysics Laboratory, University of Muenster, Schlossplatz 5, D-48149 Muenster (Germany)

    2004-08-21

    The forces developed during stretch of nonactivated muscle consist of velocity-sensitive (viscous/viscoelastic) and velocity-insensitive (elastic) components. At the myofibrillar level, the elastic-force component has been described in terms of the entropic-spring properties of the giant protein titin, but entropic elasticity cannot account for viscoelastic properties, such as stress relaxation. Here we examine the contribution of titin to passive stress relaxation of isolated rat-cardiac myofibrils depleted of actin by gelsolin treatment. Monte Carlo simulations show that, up to {approx}5 s after a stretch, the time course of stress relaxation can be described assuming unfolding of 1-2 immunoglobulin domains per titin molecule. For extended periods of stress relaxation, the simulations failed to correctly describe the myofibril data, suggesting that in situ, titin-Ig domains may be more stable than predicted in earlier single-molecule atomic-force-microscopy studies. The reasons behind this finding remain unknown; simply assuming a reduced unfolding probability of domains-an effect found here by AFM force spectroscopy on titin-Ig domains in the presence of a chaperone, alpha-B-crystallin-did not help correctly simulate the time course of stress relaxation. We conclude that myofibrillar stress relaxation likely has multiple sources. Evidence is provided that in intact myofibrils, an initial, rapid phase of stress relaxation results from viscous resistance due to the presence of actin filaments.

  12. Mozart versus new age music: relaxation states, stress, and ABC relaxation theory.

    Science.gov (United States)

    Smith, Jonathan C; Joyce, Carol A

    2004-01-01

    Smith's (2001) Attentional Behavioral Cognitive (ABC) relaxation theory proposes that all approaches to relaxation (including music) have the potential for evoking one or more of 15 factor-analytically derived relaxation states, or "R-States" (Sleepiness, Disengagement, Rested / Refreshed, Energized, Physical Relaxation, At Ease/Peace, Joy, Mental Quiet, Childlike Innocence, Thankfulness and Love, Mystery, Awe and Wonder, Prayerfulness, Timeless/Boundless/Infinite, and Aware). The present study investigated R-States and stress symptom-patterns associated with listening to Mozart versus New Age music. Students (N = 63) were divided into three relaxation groups based on previously determined preferences. Fourteen listened to a 28-minute tape recording of Mozart's Eine Kleine Nachtmusik and 14 listened to a 28-minute tape of Steven Halpern's New Age Serenity Suite. Others (n = 35) did not want music and instead chose a set of popular recreational magazines. Participants engaged in their relaxation activity at home for three consecutive days for 28 minutes a session. Before and after each session, each person completed the Smith Relaxation States Inventory (Smith, 2001), a comprehensive questionnaire tapping 15 R-States as well as the stress states of somatic stress, worry, and negative emotion. Results revealed no differences at Session 1. At Session 2, those who listened to Mozart reported higher levels of At Ease/Peace and lower levels of Negative Emotion. Pronounced differences emerged at Session 3. Mozart listeners uniquely reported substantially higher levels of Mental Quiet, Awe and Wonder, and Mystery. Mozart listeners reported higher levels, and New Age listeners slightly elevated levels, of At Ease/Peace and Rested/Refreshed. Both Mozart and New Age listeners reported higher levels of Thankfulness and Love. In summary, those who listened to Mozart's Eine Kleine Nachtmusik reported more psychological relaxation and less stress than either those who listened to

  13. The Stress Relaxation Process in Sutures Tied with a Surgeon's Knot in a Simulated Biological Environment.

    Science.gov (United States)

    Liber-Kneć, Aneta; Łagan, Sylwia

    2016-01-01

    The exact characteristics of sutures are not only the basis for selecting from among different types of suture, but also provide the necessary information for the design of new surgical sutures. Apart from information relating to the breaking load of a suture reported in pharmacopoeias, the viscoelastic properties of sutures can be an additional selection criterium - one that influences stitching quality, especially when there is a risk of wound dehiscence. The aim of the study was to assess the stress relaxation process for 3 polymeric sutures in an environment simulating the conditions in a living organism and (for comparison) in room conditions. Stress relaxation testing was carried out on 3 polymeric sutures: polypropylene (PP), polydioxanone (PDS) and polyglycolic acid (PGA). To identify the mechanical properties of the sutures, uniaxial tensile tests were conducted according to the Polish Pharmacopoeia. The relaxation test was carried out in room conditions and in the bath simulating a biological environment. The sutures being tested were tied with a surgeon's knot. The PP suture exhibited the greatest stress relaxation (18% of the initial stress in room conditions and 21% of the initial stress in the bath). The PGA suture exhibited the least stress relaxation (approximately 60% of the initial stress in room conditions and 59% of the initial stress in the bath). The PDS suture was tested at a lower strain level and showed stress relaxation similar to the PGA suture (approximately 63% of the initial stress in room conditions and 55% in the bath). Multifilament braided absorbable (PGA) sutures and monofilament absorbable (PDS) sutures had a higher stress relaxation ratio over time than monofilament non-absorbable (PP) sutures. These findings may indicate higher stress maintained over time in PDS and PGA sutures, and thus higher tension at wound edges, sufficient to resist wound dehiscence.

  14. Stress relaxation in the region of microplastic deformation of polycrystals

    Science.gov (United States)

    Pochivalova, G. P.; Dudarev, E. F.; Nikitina, N. V.

    1987-07-01

    Stress relaxation equations are derived to predict the relaxation capacity of a material on the basis of studies of microplastic deformation under static loading. The approach was checked experimentally on spring steels LANKMts, ÉI702, ÉP637, and 50KhFA.

  15. Relaxation of stresses during reduction of anode supported SOFCs

    DEFF Research Database (Denmark)

    Frandsen, Henrik Lund; Chatzichristodoulou, Christodoulos; Jørgensen, Peter Stanley

    2016-01-01

    To assess the reliability of solid oxide fuel cell (SOFC) stacks during operation, the stress field in the stack must be known. During operation the stress field will depend on time as creep processes relax stresses. This work reports further details on a newly discovered creep phenomenon...

  16. The effect of progressive muscle relaxation method on test anxiety in nursing students

    National Research Council Canada - National Science Library

    Zargarzadeh, Maryam; Shirazi, Maryam

    2014-01-01

    Concerning the prevalence of test anxiety among nursing students and presence of stress in nursing education years, this study was conducted to determine the effect of progressive muscle relaxation...

  17. STRUCTURAL STRESS RELAXATION IN STAINLESS INSTABILITY STEEL

    Directory of Open Access Journals (Sweden)

    S. Lyabuk

    2017-06-01

    Full Text Available The approach to the description of conditions of martensitic transformation in austenitic steel is advanced. Transformation induced hardening is the result of Le Chatelier principle in instability alloys. The phase transformation in austenitic instability stainless steel is the cause of reduction of grain refining and increase of strength. It was experimentally shown that physical-mechanical characteristics of the prepared materials were defined by the structure and inhomogeneous distribution of the hardening phase within a grain. The reasons for high thermal stability of inverse austenitic were established. The factors determining the inverse austenitic relaxation resistibility and resources for its increasing were revealed.

  18. Unexpected power-law stress relaxation of entangled ring polymers

    Science.gov (United States)

    KAPNISTOS, M.; LANG, M.; PYCKHOUT-HINTZEN, W.; RICHTER, D.; CHO, D.; CHANG, T.

    2016-01-01

    After many years of intense research, most aspects of the motion of entangled polymers have been understood. Long linear and branched polymers have a characteristic entanglement plateau and their stress relaxes by chain reptation or branch retraction, respectively. In both mechanisms, the presence of chain ends is essential. But how do entangled polymers without ends relax their stress? Using properly purified high-molar-mass ring polymers, we demonstrate that these materials exhibit self-similar dynamics, yielding a power-law stress relaxation. However, trace amounts of linear chains at a concentration almost two decades below their overlap cause an enhanced mechanical response. An entanglement plateau is recovered at higher concentrations of linear chains. These results constitute an important step towards solving an outstanding problem of polymer science and are useful for manipulating properties of materials ranging from DNA to polycarbonate. They also provide possible directions for tuning the rheology of entangled polymers. PMID:18953345

  19. Surface relaxation and stress for 5d transition metals

    Science.gov (United States)

    Zólyomi, V.; Vitos, L.; Kwon, S. K.; Kollár, J.

    2009-03-01

    Using the density functional theory, we present a systematic theoretical study of the layer relaxation and surface stress of 5d transition metals. Our calculations predict layer contractions for all surfaces, except for the (111) surface of face centered cubic Pt and Au, where slight expansions are obtained similarly to the case of the 4d series. We also find that the relaxations of the close packed surfaces decrease with increasing occupation number through the 5d series. The surface stress for the relaxed, most closely packed surfaces shows similar atomic number dependence as the surface energy. Using Cammarata's model and our calculated surface stress and surface energy values, we examine the possibility of surface reconstructions, which is in reasonable agreement with the experimental observations.

  20. Plate-wide stress relaxation explains European Palaeocene basin inversions

    DEFF Research Database (Denmark)

    Nielsen, S.B.; Thomsen, Erik; Hansen, D.L.

    2005-01-01

    of the in-plane tectonic stress. The onset of relaxation inversions was plate-wide and simultaneous, and may have been triggered by stress changes caused by elevation of the North Atlantic lithosphere by the Iceland plume or the drop in NS convergence rate between Africa and Europe....... Paleocene phase was characterized by domal uplift of a wider area with only mild fault movements, and formation of more distal and shallow marginal troughs. A simple flexural model explains how domal, secondary inversion follows inevitably from primary, convergence related inversion upon relaxation...

  1. Thermal stress relaxation in magnesium composites during thermal cycling

    Energy Technology Data Exchange (ETDEWEB)

    Trojanova, Z.; Lukac, P. (Karlova Univ., Prague (Czech Republic)); Kiehn, J.; Kainer, K.U.; Mordike, B.L. (Technische Univ. Clausthal, Clausthal-Zellerfeld (Germany))

    1998-01-01

    It has been shown that the internal friction of Mg - Saffil metal matrix composites can be influenced by thermal stresses, if MMCc are submitted to thermal cycling between room temperature and an upper temperature of cycling. These stresses can be accommodated by generation and motion of dislocations giving the formation of the microplastic zones. The thermal stress relaxation depends on the upper temperature of cycling, the volume fraction of reinforcement and the matrix composition and can result in plastic deformation and strain hardening of the matrix without applied stress. The internal friction measurements can be used for non destructive investigation of processes which influence the mechanical properties. (orig.)

  2. Relaxation of stress and density, strength (fatigue)

    CERN Document Server

    Gräfe, Wolfgang

    2015-01-01

    This treatment of ""Time-Dependent Mechanical Properties of Solids"" beginswith a phenomenological description of the transport of some unspecifiedentity. It is assumed that the transport is caused by mechanical stresses ortemperature fields. Using these assumptions, it is possible to deduceformulae for a theoretically based description of several phenomena withoutreferring to any specific process or entity. These theoretical results thenprovide the tools for performing methodologically better scientific work andfor a better analysis of data in the practical application of materials. Bypublish

  3. A progressive rupture model of soft tissue stress relaxation.

    Science.gov (United States)

    Bates, Jason H T; Ma, Baoshun

    2013-06-01

    A striking feature of stress relaxation in biological soft tissue is that it frequently follows a power law in time with an exponent that is independent of strain even when the elastic properties of the tissue are highly nonlinear. This kind of behavior is an example of quasi-linear viscoelasticity, and is usually modeled in a purely empirical fashion. The goal of the present study was to account for quasi-linear viscoelasticity in mechanistic terms based on our previously developed hypothesis that it arises as a result of isolated micro-yield events occurring in sequence throughout the tissue, each event passing the stress it was sustaining on to other regions of the tissue until they themselves yield. We modeled stress relaxation computationally in a collection of stress-bearing elements. Each element experiences a stochastic sequence of either increases in elastic equilibrium length or decreases in stiffness according to the stress imposed upon it. This successfully predicts quasi-linear viscoelastic behavior, and in addition predicts power-law stress relaxation that proceeds at the same slow rate as observed in real biological soft tissue.

  4. Time and Temperature Dependence of Viscoelastic Stress Relaxation in Gold and Gold Alloy Thin Films

    Science.gov (United States)

    Mongkolsuttirat, Kittisun

    Radio frequency (RF) switches based on capacitive MicroElectroMechanical System (MEMS) devices have been proposed as replacements for traditional solid-state field effect transistor (FET) devices. However, one of the limitations of the existing capacitive switch designs is long-term reliability. Failure is generally attributed to electrical charging in the capacitor's dielectric layer that creates an attractive electrostatic force between a moving upper capacitor plate (a metal membrane) and the dielectric. This acts as an attractive stiction force between them that may cause the switch to stay permanently in the closed state. The force that is responsible for opening the switch is the elastic restoring force due to stress in the film membrane. If the restoring force decreases over time due to stress relaxation, the tendency for stiction failure behavior will increase. Au films have been shown to exhibit stress relaxation even at room temperature. The stress relaxation observed is a type of viscoelastic behavior that is more significant in thin metal films than in bulk materials. Metal films with a high relaxation resistance would have a lower probability of device failure due to stress relaxation. It has been shown that solid solution and oxide dispersion can strengthen a material without unacceptable decreases in electrical conductivity. In this study, the viscoelastic behavior of Au, AuV solid solution and AuV2O5 dispersion created by DC magnetron sputtering are investigated using the gas pressure bulge testing technique in the temperature range from 20 to 80°C. The effectiveness of the two strengthening approaches is compared with the pure Au in terms of relaxation modulus and 3 hour modulus decay. The time dependent relaxation curves can be fitted very well with a four-term Prony series model. From the temperature dependence of the terms of the series, activation energies have been deduced to identify the possible dominant relaxation mechanism. The measured

  5. Stress Management and Anxiety Reduction Through EMG Biofeedback/Relaxation Training upon Junior High School Students.

    Science.gov (United States)

    Lang, Darrel

    The effectiveness of electromyographic (EMG) biofeedback/relaxation training on the stress management and anxiety levels of 18 eighth-grade students was tested. Chapter I serves as an introduction and presents information on the need for the study, hypotheses, limitations, and definition of terms. Chapter II contains a review of related…

  6. Transformation-Induced Relaxation and Stress Recovery of TiNi Shape Memory Alloy.

    Science.gov (United States)

    Takeda, Kohei; Matsui, Ryosuke; Tobushi, Hisaaki; Pieczyska, Elzbieta A

    2014-03-06

    The transformation-induced stress relaxation and stress recovery of TiNi shape memory alloy (SMA) in stress-controlled subloop loading were investigated based on the local variation in temperature and transformation band on the surface of the tape in the tension test. The results obtained are summarized as follows. (1) In the loading process, temperature increases due to the exothermic martensitic transformation (MT) until the holding strain and thereafter temperature decreases while holding the strain constant, resulting in stress relaxation due to the MT; (2) In the unloading process, temperature decreases due to the endothermic reverse transformation until the holding strain and thereafter temperature increases while holding the strain constant, resulting in stress recovery due to the reverse transformation; (3) Stress varies markedly in the initial stage followed by gradual change while holding the strain constant; (4) If the stress rate is high until the holding strain in the loading and unloading processes, both stress relaxation and stress recovery are large; (5) It is important to take into account this behavior in the design of SMA elements, since the force of SMA elements varies even if the atmospheric temperature is kept constant.

  7. STRESS RELAXATION CHARACTERISTICS OF SELECTED COMMERCIALLY PRODUCED GLASSES

    Directory of Open Access Journals (Sweden)

    Chocholoušek J.

    2013-06-01

    Full Text Available This paper describes a quantitative method of stress relaxation measurement in prismatic glass samples during two different time-temperature regimes using the Sénarmont compensator. Four types of glass (Barium crystal glass, Eutal, Simax, and Container glass were subjected to observation in an assembled measuring device. Results will be used for parameterization of the Tool-Narayanaswamy-Mazurin model and consequently implemented in a finite element method code.

  8. Stress Relaxation Behavior and Its Prediction of CrMoWV Steel

    Directory of Open Access Journals (Sweden)

    CAO Tie-shan

    2017-05-01

    Full Text Available The stress relaxation data up to 8760h at 550℃ and 600℃of 12Cr-1Mo-1W-0.25V heat-resistant steel were used as the object to study the method of how to accurately and effectively predict long-term relaxation stress by using short-time relaxation data. When relaxation model is used to extrapolate the long-term relaxation stress directly, it is found that the parameters of the relaxation model depend on the length of the fitted data. The time-dependent parameter model, naming as timing parameter method, is proposed to predict the long-term relaxation stress with high accuracy. By comparison of the results of timing parameter method and direct extrapolation method, timing parameter method has obvious advantages in predicting long time relaxation stress with short time relaxation data, as the timing parameter method has a more accurate prediction than that of direct extrapolation method.

  9. What Is Stress Testing?

    Science.gov (United States)

    ... However, your doctor may want to use a stress test to screen for CHD if you have diabetes. This disease increases your risk of CHD. Currently, though, no evidence shows that having a stress test will improve your outcome if you have diabetes. What To Expect Before Stress Testing Stress testing ...

  10. Effects of γ' Precipitation, Dislocation Density, and Grain Size on Stress-Relaxation Properties of INCONEL X-750 Helical Springs

    Science.gov (United States)

    Ha, Jeong Won; Seong, Baek Seok; Woo, Wanchuck; Jeong, Hi Won; Choi, Yoon Suk; Kang, Namhyun

    2017-08-01

    INCONEL X-750 specimens were manufactured into helical springs by drawing and coiling followed by aging. They were subsequently subjected to stress-relaxation tests. Stress relaxation is the important property of springs that are compressed at elevated temperatures. To understand stress relaxation, this study investigated the effect of the drawing ratio (DR) on the γ' size and volume fraction, grain size, carbide volume fraction, and dislocation density. Small-angle neutron scattering was used to measure the size and volume fraction of γ' phase, and X-ray diffraction was employed to analyze the dislocation density in the springs as a function of the DR. The smallest DR specimen (DR0) had a longer free length than the larger DR specimens (DR17 and DR42) after the stress-relaxation test was completed at 773 K (500 °C) for 300 hours. However, the size and volume fraction of γ', along with the dislocation density, had no influence on the stress relaxation of the INCONEL X-750 springs. The decreased grain size ( d) due to an increase in the DR was the main factor in the increase in the stress relaxation of the springs. The decrease in grain size displayed a nonlinear relationship with the increase in stress relaxation. The stress-relaxation behavior relationship was d -3. Grain boundaries were determined to play a role in dislocation sink via transmission electron microscopy (TEM) observations. Grain boundary diffusion accommodated by slip was responsible for the stress-relaxation properties of the spring at an elevated temperature (773 K = 500 °C).

  11. Blue lighting accelerates post-stress relaxation: Results of a preliminary study.

    Directory of Open Access Journals (Sweden)

    Jesus Minguillon

    Full Text Available Several authors have studied the influence of light on both human physiology and emotions. Blue light has been proved to reduce sleepiness by suppression of melatonin secretion and it is also present in many emotion-related studies. Most of these have a common lack of objective methodology since results and conclusions are based on subjective perception of emotions. The aim of this work was the objective assessment of the effect of blue lighting in post-stress relaxation, in comparison with white lighting, by means of bio-signals and standardized procedures. We conducted a study in which twelve healthy volunteers were stressed and then performed a relaxation session within a chromotherapy room with blue (test group or white (control group lighting. We conclude that the blue lighting accelerates the relaxation process after stress in comparison with conventional white lighting. The relaxation time decreased by approximately three-fold (1.1 vs. 3.5 minutes. We also observed a convergence time (3.5-5 minutes after which the advantage of blue lighting disappeared. This supports the relationship between color of light and stress, and the observations reported in previous works. These findings could be useful in clinical and educational environments, as well as in daily-life context and emerging technologies such as neuromarketing. However, our study must be extended to draw reliable conclusions and solid scientific evidence.

  12. Blue lighting accelerates post-stress relaxation: Results of a preliminary study.

    Science.gov (United States)

    Minguillon, Jesus; Lopez-Gordo, Miguel Angel; Renedo-Criado, Diego A; Sanchez-Carrion, Maria Jose; Pelayo, Francisco

    2017-01-01

    Several authors have studied the influence of light on both human physiology and emotions. Blue light has been proved to reduce sleepiness by suppression of melatonin secretion and it is also present in many emotion-related studies. Most of these have a common lack of objective methodology since results and conclusions are based on subjective perception of emotions. The aim of this work was the objective assessment of the effect of blue lighting in post-stress relaxation, in comparison with white lighting, by means of bio-signals and standardized procedures. We conducted a study in which twelve healthy volunteers were stressed and then performed a relaxation session within a chromotherapy room with blue (test group) or white (control group) lighting. We conclude that the blue lighting accelerates the relaxation process after stress in comparison with conventional white lighting. The relaxation time decreased by approximately three-fold (1.1 vs. 3.5 minutes). We also observed a convergence time (3.5-5 minutes) after which the advantage of blue lighting disappeared. This supports the relationship between color of light and stress, and the observations reported in previous works. These findings could be useful in clinical and educational environments, as well as in daily-life context and emerging technologies such as neuromarketing. However, our study must be extended to draw reliable conclusions and solid scientific evidence.

  13. Separating the Influence of Environment from Stress Relaxation Effects on Dwell Fatigue Crack Growth

    Science.gov (United States)

    Telesman, Jack; Gabb, Tim; Ghosn, Louis J.

    2016-01-01

    Seven different microstructural variations of LSHR were produced by controlling the cooling rate and the subsequent aging and thermal exposure heat treatments. Through cyclic fatigue crack growth testing performed both in air and vacuum, it was established that four out of the seven LSHR heat treatments evaluated, possessed similar intrinsic environmental resistance to cyclic crack growth. For these four heat treatments, it was further shown that the large differences in dwell crack growth behavior which still persisted, were related to their measured stress relaxation behavior. The apparent differences in their dwell crack growth resistance were attributed to the inability of the standard linear elastic fracture mechanics (LEFM) stress intensity parameter to account for visco-plastic behavior. Crack tip stress relaxation controls the magnitude of the remaining local tensile stresses which are directly related to the measured dwell crack growth rates. It was hypothesized that the environmentally weakened grain boundary crack tip regions fail during the dwells when their strength is exceeded by the remaining local crack tip tensile stresses. It was shown that the classical creep crack growth mechanisms such as grain boundary sliding did not contribute to crack growth, but the local visco-plastic behavior still plays a very significant role by determining the crack tip tensile stress field which controls the dwell crack growth behavior. To account for the influence of the visco-plastic behavior on the crack tip stress field, an empirical modification to the LEFM stress intensity parameter, Kmax, was developed by incorporating into the formulation the remaining stress level concept as measured by simple stress relaxation tests. The newly proposed parameter, Ksrf, did an excellent job in correlating the dwell crack growth rates for the four heat treatments which were shown to have similar intrinsic environmental cyclic fatigue crack growth resistance.

  14. Immune modulation in response to stress and relaxation.

    Science.gov (United States)

    Mahbub-E-Sobhani; Haque, N; Salma, U; Ahmed, A

    2011-03-15

    Traditional medical science has kept the mind separate from the body. Recently people realize the effect of mind on health and psychoneuroimmunology is the new evolved science that describes the interactions between psyche and soma. In this review through a typical psycho-neuro-endocrino-immune network the effects of psychological stress (acute, brief naturalistic and chronic) and relaxation on immune modulation has been shown. From this network Corticotrophin Releasing Factor (CRF), Adrenocorticotrophic Hormone (ACTH), Glucocorticoids (GC), alpha-endorphin and Met-enkephalin are found as important endocrine components and T cells, B cells, monocytes/macrophages, Natural Killer (NK) cells and their cytokines that is Tumor Necrosis Factor-alpha (TNF-alpha), Interferon Gamma (IFN-alpha) and interleukins such as IL-1, IL-2, IL-4, IL-6, IL-10, IL-12 etc. are found as important immune components. Finally, it has been shown that, acute, brief naturalistic and chronic stress have different immune modulatory activities which are harmful to one's homeostasis and relaxation can help to maintain that homeostasis.

  15. Stress relaxation analysis of single chondrocytes using porohyperelastic model based on AFM experiments

    Directory of Open Access Journals (Sweden)

    Trung Dung Nguyen

    2014-01-01

    Full Text Available Based on atomic force microscopytechnique, we found that the chondrocytes exhibits stress relaxation behavior. We explored the mechanism of this stress relaxation behavior and concluded that the intracellular fluid exuding out from the cells during deformation plays the most important role in the stress relaxation. We applied the inverse finite element analysis technique to determine necessary material parameters for porohyperelastic (PHE model to simulate stress relaxation behavior as this model is proven capable of capturing the non-linear behavior and the fluid-solid interaction during the stress relaxation of the single chondrocytes. It is observed that PHE model can precisely capture the stress relaxation behavior of single chondrocytes and would be a suitable model for cell biomechanics.

  16. Stress Relaxation Effects in TiNi SMA During Superelastic Deformation: Experiment and Constitutive Model

    Science.gov (United States)

    Pieczyska, Elżbieta A.; Kowalewski, Zbigniew L.; Dunić, Vladimir Lj.

    2017-12-01

    This paper presents an investigation of thermomechanical effects related to the phenomena of stress relaxation occurring in TiNi SMA subjected to modified program of displacement-controlled tension. The deformation data were taken from testing machine, whereas the temperature changes accompanying the exothermic/endothermic martensite forward/reverse transformation were measured by infrared camera. At the advanced stages of the transformations, the strain was kept constant for a few minutes and the SMA load and temperature were recorded continuously. As a consequence, the stress and temperature changed significantly during the loading stops. A large stress drop, caused by the transformation, was observed during the relaxation stage in both courses of the SMA loading and unloading. Moreover, the non-uniform temperature distribution, reflecting macroscopically inhomogeneous transformation, lapsed while the strain was kept constant, yet restarted at the end of the relaxation stop and developed at the reloading stage. Along with the experimental results, the mechanical and thermal responses induced by the transformation were obtained by 3D coupled thermomechanical numerical analysis, realized in partitioned approach. Latent heat production was correlated with an amount of the martensitic volume fraction. The stress and temperature drops recorded during the experiment were satisfactorily reproduced by the model proposed for the SMA thermomechanical coupling.

  17. Characterization of bovine cartilage by fiber Bragg grating-based stress relaxation measurements

    Science.gov (United States)

    Baier, V.; Marchi, G.; Foehr, P.; Burgkart, R.; Roths, J.

    2017-04-01

    A fiber-based device for testing mechanical properties of cartilage is presented within this study. The measurement principle is based on stepwise indentation into the tissue and observing of corresponding relaxation of the stress. The indenter tip is constituted of a cleaved optical fiber that includes a fiber Bragg grating which is used as the force sensor. Stress relaxation measurements at 25 different positions on a healthy bovine cartilage sample were performed to assess the behavior of healthy cartilage. For each indentation step a good agreement was found with a viscoelastic model that included two time constants. The model parameters showed low variability and a clear dependence with indentation depth. The parameters can be used as reference values for discriminating healthy and degenerated cartilage.

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

    Directory of Open Access Journals (Sweden)

    Carlos Vilorio

    2015-12-01

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

  19. Residual stresses relaxation in surface-hardened half-space under creep conditions

    Directory of Open Access Journals (Sweden)

    Vladimir P. Radchenko

    2015-09-01

    Full Text Available We developed the method for solving the problem of residual stresses relaxation in surface-hardened layer of half-space under creep conditions. At the first stage we made the reconstruction of stress-strain state in half-space after plastic surface hardening procedure based on partial information about distribution for one residual stress tensor component experimentally detected. At the second stage using a numerical method we solve the problem of relaxation of self-balanced residual stresses under creep conditions. To solve this problem we introduce the following Cartesian system: x0y plane is aligned with hardened surface of half-space and 0z axis is directed to the depth of hardened layer. We also introduce the hypotheses of plane sections parallel to x0z and y0z planes. Detailed analysis of the problem has been done. Comparison of the calculated data with the corresponding test data was made for plane specimens (rectangular parallelepipeds made of EP742 alloy during T=650°C after the ultrasonic hardening with four hardening modes. We use half-space to model these specimens because penetration's depth of residual stresses is less than specimen general size in two digit exponent. There is enough correspondence of experimental and calculated data. It is shown that there is a decay (in modulus of pressing residual stresses under creep in 1.4–1.6 times.

  20. Effects of Stress and Relaxation on Time Perception

    Science.gov (United States)

    2003-01-01

    1998). Common relaxation methods include progressive muscle relaxation, meditation, imaging, autogenic training (self- hypnosis ), listening to 14 music...2001). Menstrual and circadian rythms in time perception in healthy women and women with premenstrual syndrome. Neuroscience Research, 41(4), 339

  1. Stress relaxation and reversed flow of low-density polyethylene melts following uniaxial extension

    DEFF Research Database (Denmark)

    Huang, Qian; Rasmussen, Henrik K.; Skov, Anne Ladegaard

    2012-01-01

    The extensional dynamics of two low-density polyethylene melts Lupolen 3020D and Lupolen 1840D, both showing a stress overshoot in start-up of uniaxial extension [Rasmussen, H. K., J. K. Nielsen, A. Bach, and O.Hassager, 'Viscosity overshoot in the start-up of uniaxial elongation of low density...... polyethylene melts,' J. Rheol. 49(2), 369-381 (2005)], have been further investigated in stress relaxation and reversed flow. After the overshoot, the stress relaxation has a remarkably faster decrease of the transient stress than when the relaxation is initiated before the overshoot. The measurements from...

  2. Creep and stress relaxation of human red cell membrane.

    Science.gov (United States)

    Fischer, Thomas M

    2017-02-01

    In contrast to most mechanical properties of the red cell, experimental information on stress relaxation (SR) of the membrane skeleton is scarce. On the other hand, many postulates or assumptions as to the value of the characteristic time of SR [Formula: see text] can be found in the literature. Here, an experiment is presented that allows measurement of [Formula: see text] up to values of about 10 h. The membrane skeleton was deformed passively by changing the spontaneous curvature of the bilayer thus transforming the natively biconcave red cells into echinocytes. This shape and the concomitant deformation of the skeleton were kept up to 4 h by incubation at 37 ℃. During this period, no plastic deformation (creep) was observed. After the incubation, the spontaneous curvature was returned to normal. The resulting shape was smooth showing no remnants of the echinocytic shape. Both observations indicate [Formula: see text] 10 h. This result is in gross disagreement to postulates or assumptions existing in the literature.

  3. Density dependence of the stress relaxation function of a simple fluid

    NARCIS (Netherlands)

    Hartkamp, Remco; Daivis, P.J.; Todd, B.D.

    2013-01-01

    We present accurate molecular dynamics calculations of the shear stress relaxation modulus of a simple atomic fluid over a wide range of densities. The high accuracy of the data enables us to study changes in the functional form of the shear relaxation modulus, and the properties that are derived

  4. Stress-relaxation behavior of lignocellulosic high-density polyethlene composites

    Science.gov (United States)

    Babak Mirzaei; Mehdi Tajvidi; Robert H. Falk; Colin. Felton

    2011-01-01

    In this study, stress-relaxation performance of HDPE-based injection-molded composites containing four types of natural fibers (i.e., wood flour, rice hulls, newsprint, and kenaf fiber) at 25 and 50 wt% contents, and the effect of prescribed strain levels were investigated. The results indicated that incorporating more filler causes lower relaxation values and rates,...

  5. Effects of a relaxation training programme on immediate and prolonged stress responses in women with preterm labour.

    Science.gov (United States)

    Chuang, Li-Lan; Lin, Li-Chan; Cheng, Po-Jen; Chen, Chung-Hey; Wu, Shiao-Chi; Chang, Chuan-Lin

    2012-01-01

    This paper is a report of an experimental study of the effects of relaxation-training programme on immediate and prolonged stress responses in women with preterm labour. Hospitalized pregnant women with preterm labour experience developmental and situational stress. However, few studies have been performed on stress management in such women. An experimental pretest and repeated post-test design was used to compare the outcomes for two groups in northern Taiwan from December 2008, to May 2010. A total of 129 women were randomly assigned to an experimental (n = 68) or control (n = 61) group. The experimental group participants were instructed to listen daily to a 13-minute relaxation programme. Measurements involved the stress visual analogue scale, finger temperatures, State Trait Anxiety Inventory, Perceived Stress Scale and Pregnancy-related Anxiety. Two-way analysis of variance and hierarchical linear modelling were used to analyse the group differences. Compared with those in the control group, participants in the experimental group showed immediate improvements in the stress visual analogue scale scores and finger temperatures. The State Trait Anxiety Inventory-State subscale score for the experimental group was significantly lower than that for the control group (P = 0·03). However, no statistically significant differences for the Perceived Stress Scale and Pregnancy-related Anxiety scores were found between the experimental group and the control group. The relaxation-training programme could improve the stress responses of women with preterm labour. © 2011 The Authors. Journal of Advanced Nursing © 2011 Blackwell Publishing Ltd.

  6. Influence of pudendal nerve blockade on stress relaxation in the female urethra

    DEFF Research Database (Denmark)

    Thind, P; Bagi, P; Mieszczak, C

    1996-01-01

    The urethral pressure decay following a sudden and sustained dilatation corresponds to stress relaxation. Urethral stress relaxation can be described by the equation Pt = Pequ + P alpha e-t/tau alpha + P beta e-t/tau beta, where Pt is the pressure at time t, Pequ is the equilibrium pressure after...... dilatation, P alpha and P beta are pressure decay, and tau alpha and tau beta are time constants. The time constants have previously proved independent of the way the dilatation is performed. The urethral stress relaxation obtained in 10 healthy women before and after pudendal nerve blockade was analysed...... by the mathematical model and the pressure parameters and time constants determined. The fast time constant, tau beta, was reduced by the nerve blockade, whereas tau alpha was unaffected, however, both P alpha and P beta were reduced. No single stress relaxation parameter can therefore be related to the muscle...

  7. How Do You #relax When You're #stressed? A Content Analysis and Infodemiology Study of Stress-Related Tweets.

    Science.gov (United States)

    Doan, Son; Ritchart, Amanda; Perry, Nicholas; Chaparro, Juan D; Conway, Mike

    2017-06-13

    Stress is a contributing factor to many major health problems in the United States, such as heart disease, depression, and autoimmune diseases. Relaxation is often recommended in mental health treatment as a frontline strategy to reduce stress, thereby improving health conditions. Twitter is a microblog platform that allows users to post their own personal messages (tweets), including their expressions about feelings and actions related to stress and stress management (eg, relaxing). While Twitter is increasingly used as a source of data for understanding mental health from a population perspective, the specific issue of stress-as manifested on Twitter-has not yet been the focus of any systematic study. The objective of our study was to understand how people express their feelings of stress and relaxation through Twitter messages. In addition, we aimed at investigating automated natural language processing methods to (1) classify stress versus nonstress and relaxation versus nonrelaxation tweets, and (2) identify first-hand experience-that is, who is the experiencer-in stress and relaxation tweets. We first performed a qualitative content analysis of 1326 and 781 tweets containing the keywords "stress" and "relax," respectively. We then investigated the use of machine learning algorithms-in particular naive Bayes and support vector machines-to automatically classify tweets as stress versus nonstress and relaxation versus nonrelaxation. Finally, we applied these classifiers to sample datasets drawn from 4 cities in the United States (Los Angeles, New York, San Diego, and San Francisco) obtained from Twitter's streaming application programming interface, with the goal of evaluating the extent of any correlation between our automatic classification of tweets and results from public stress surveys. Content analysis showed that the most frequent topic of stress tweets was education, followed by work and social relationships. The most frequent topic of relaxation tweets

  8. Stress Management for Special Educators: The Self-Administered Tool for Awareness and Relaxation (STAR)

    Science.gov (United States)

    Williams, Krista; Poel, Elissa Wolfe

    2006-01-01

    The Self-Administered Tool for Awareness and Relaxation (STAR) is a stress management strategy designed to facilitate awareness of the physical, mental, emotional, and physiological effects of stress through the interconnectedness of the brain, body, and emotions. The purpose of this article is to present a stress-management model for teachers,…

  9. Effect of physical aging on stress relaxation of poly/methyl methacrylate/

    Science.gov (United States)

    Cizmecioglu, M.; Fedors, R. F.; Hong, S. D.; Moacanin, J.

    1981-01-01

    A study was made on the stress relaxation behavior at 25 C of poly(methyl methacrylate) in uniaxial tension as a function of physical aging at both room temperature and 60 C. Test specimens were compression molded at 165 C, then quenched to room temperature and allowed to age for up to 30 days prior to testing. Stress relaxation curves measured after different aging times could be superposed to a single master curve for each aging temperature. Superposition was achieved by applying vertical and horizontal shifts. Hence, the shape of the response curves was not changed by aging. This is in accordance with observations made by Struik for tensile creep curves. Volume changes as a function of physical aging were also determined. Simple exponential relationships were observed between volume and both horizontal and vertical shifts. The horizontal shift implies a shift in the effective time scale caused by a change in free volume. The vertical shifts could be correlated with changes in Young's modulus caused by a change in density. For the range of aging studied, the response time scale varied over nearly two decades of log-time. For the same conditions modulus varied by 30 percent.

  10. The Effects of Progressive Relaxation and Music on Attention, Relaxation and Stress Responses: An Investigation of the Cognitive-Behavioral Model of Relaxation

    Science.gov (United States)

    1999-01-28

    In order to test the cognitive behavioral model of relaxation in the present experiment, additional information on attention and attention measurement...gathered from brain-Iesioned patients, as well as component analyses of neuropsychological test battery data. Specific functions of the attention...of the Weschler Memory Scale (WMS-III; The Psychological Corporation, San Antonio, Texas), and a "Silly Sentence Task" (Mesulam, 1985) as prompted by

  11. The effects of music relaxation and muscle relaxation techniques on sleep quality and emotional measures among individuals with post-traumatic stress disorder

    OpenAIRE

    Ilana Kremer; Naomi Ziv; Zahi Arnon; Boaz Bloch; Limor Vadas; Iris Haimov

    2012-01-01

    The aim of the present study was to examine the effects of music and muscle relaxation techniques on sleep quality and emotional measures in individuals with Post-traumatic stress disorder (PTSD). Thirteen PTSD patients, who had no other major psychiatric, sleep, or neurological disorders, participated in the study. The study comprised one 7-day, running-in, no-treatment period, followed by two 7-day experimental periods. The treatments were either music relaxation or muscle relaxation techni...

  12. Effect of extender oils on the stress relaxation behavior of thermoplastic vulcanizates

    Directory of Open Access Journals (Sweden)

    2008-11-01

    Full Text Available The long term mechanical behavior of oil extended thermoplastic vulcanizates (TPV based on polypropylene (PP and acrylonitrile-butadiene rubber (NBR has been characterized by means of stress relaxation experiments. The morphology of TPV and the phase specific oil distribution which depend on the content and type of oil as well as on the mixing regime have been characterized by means of Atomic Force Microscopy (AFM, Dynamic Mechanical Thermal Analysis (DMTA and Differential Scanning Calorimetrie (DSC. The discussion of the stress relaxation behavior was carried out using the two-component model, which allows splitting the initial stress into two components: a thermal activated stress component and an athermal one. A master curve was created by shifting the relaxation curves vertically and horizontally towards the reference curve. The vertical shift factor bT is a function of the temperature dependence of the athermal stress components. It was found that the oil distribution strongly affects the athermal stress component which is related to the contribution of the structural changes, e.g. crystallinity of the PP phase and the average molecular weight between the crosslinks of the NBR phase. From the temperature dependence of the horizontal shift factor aT the main viscoelastic relaxation process was determined as the α-relaxation process of the crystalline PP phase. It is not dependent on the polarity and content of the oil as well as the mixing regime.

  13. Effects of patterning induced stress relaxation in strained SOI/SiGe layers and substrate

    Science.gov (United States)

    Hermann, P.; Hecker, M.; Renn, F.; Rölke, M.; Kolanek, K.; Rinderknecht, J.; Eng, L. M.

    2011-06-01

    Local stress fields in strained silicon structures important for CMOS technology are essentially related to size effects and properties of involved materials. In the present investigation, Raman spectroscopy was utilized to analyze the stress distribution within strained silicon (sSi) and silicon-germanium (SiGe) island structures. As a result of the structuring of initially unpatterned strained films, a size-dependent relaxation of the intrinsic film stresses was obtained in agreement with model calculations. This changed stress state in the features also results in the appearance of opposing stresses in the substrate underneath the islands. Even for strained island structures on top of silicon-on-insulator (SOI) wafers, corresponding stresses in the silicon substrate underneath the oxide were detected. Within structures, the stress relaxation is more pronounced for islands on SOI substrates as compared to those on bulk silicon substrates.

  14. Influence of pudendal nerve blockade on stress relaxation in the female urethra

    DEFF Research Database (Denmark)

    Thind, P; Bagi, P; Mieszczak, C

    1996-01-01

    The urethral pressure decay following a sudden and sustained dilatation corresponds to stress relaxation. Urethral stress relaxation can be described by the equation Pt = Pequ + P alpha e-t/tau alpha + P beta e-t/tau beta, where Pt is the pressure at time t, Pequ is the equilibrium pressure after...... or the connective tissue components. The method may prove useful in the further evaluation of the closure function of the urethra with special reference to the pathophysiology of stress urinary incontinence....

  15. Stress relaxation following uniaxial extension of polystyrene melt and oligomer dilutions

    DEFF Research Database (Denmark)

    Huang, Qian; Rasmussen, Henrik K.

    2016-01-01

    The filament stretching rheometer has been used to measure the stress relaxation following the startup of uniaxial extensional flow, on anarrow molar mass distribution (NMMD) polystyrene melt and styrene oligomer dilutions thereof. All samples used here were characterizedin molecular weight......, mechanical spectroscopy, and constant strain rate uniaxial extension in the work of Huang et al. [Macromolecules 46,5026–5035 (2013); ACS Macro Lett. 2, 741–744 (2013)]. The stress relaxation following the steady extensional stress was measured on a285 kg/mole NMMD polystyrene and two 1.92 kg/mole styrene...... oligomer dilutions thereof {PS-285k, PS-285k/2k-72, and PS-285k/2k-44 inthe work of Huang et al. [Macromolecules 46, 5026–5035 (2013)]}. The two dilutions contained 28 and 56 wt. % oligomer, respectively.Further, the stress relaxation on a 545 kg/mole NMMD polystyrene diluted with 48 wt. % 0.972 kg...

  16. Effects of suryanamaskar on relaxation among college students with high stress in Pune, India.

    Science.gov (United States)

    Godse, Anand Sharad; Shejwal, Bhaskar R; Godse, Amruta Anand

    2015-01-01

    Suryanamaskar is a yogic practice widely practiced across India. Along with the available studies on physiology, there is a need to study its psychological effects. This research aims at studying the effects of suryanamaskar on relaxation dispositions (R-dispositions) among college students with high stress in Pune, India. The present study was conducted in a college setting and used a randomized control group design. A group of 419 college students (age 17-22 years) were assessed on stress symptoms using the ABC relaxation theory. A total of 124 out of 419 students who were identified as high on stress were randomly assigned to an experimental and control group. And 40 participants each in both the group completed the program and were assessed on R-dispositions and stress dispositions before and after the suryanamaskar program. Analysis of covariance (ANCOVA) was used to study the differences in R-dispositions and stress dispositions between the experimental and control groups. The experimental group was found to be higher on the R-dispositions of physical relaxation, mental quiet, at ease/peace, rested and refreshed, strength and awareness and joy and lower on sleepiness, and stress dispositions-somatic stress, worry, and negative emotion compared with the control group. It was concluded that suryanamaskar is effective in leading to R-Dispositions like physical relaxation, mental quiet, at ease/peace, rested and refreshed, strength and awareness and joy and reduces sleepiness, somatic stress, worry and negative emotion at a dispositional level.

  17. Stress relaxation of narrow molar mass distribution polystyrene following uniaxial extension

    DEFF Research Database (Denmark)

    Nielsen, Jens Kromann; Rasmussen, Henrik K.; Hassager, Ole

    2008-01-01

    The stress in the startup of uniaxial elongational flow until steady state, followed by stress relaxation, has been measured for a narrow molar mass distribution polystyrene inelt with a molecular weight of 145 kg/mol. The experiments are conducted on a filament stretching rheometer, where a closed...

  18. Understanding the Stress Relaxation Behavior of Polymers Reinforced with Short Elastic Fibers.

    Science.gov (United States)

    Obaid, Numaira; Kortschot, Mark T; Sain, Mohini

    2017-04-28

    Although it has been experimentally shown that the addition of short-fibers slows the stress relaxation process in composites, the underlying phenomenon is complex and not well understood. Previous studies have proposed that fibers slow the relaxation process by either hindering the movement of nearby polymeric chains or by creating additional covalent bonds at the fiber-matrix interface that must be broken before bulk relaxation can occur. In this study, we propose a simplified analytical model that explicitly accounts for the influence of polymer viscoelasticity on shear stress transfer to the fibers. This model adequately explains the effect of fiber addition on the relaxation behavior without the need to postulate structural changes at the fiber-matrix interface. The model predictions were compared to those from Monte Carlo finite-element simulations, and good agreement between the two was observed.

  19. Anaphylaxis to muscle relaxants: rational for skin tests.

    Science.gov (United States)

    Moneret-Vautrin, D A; Kanny, G

    2002-09-01

    IgE-dependent allergy to muscle relaxants (MR) has an estimated prevalence of 1 out of 6500 General Anesthesias (GA). 62% of anaphylaxis during surgery are due to MR anaphylaxis. All the molecules are divalent, carrying two NH4+ epitopes (quaternary ammonium ions), either structurally or after rapid in vivo protonization (vecuronium). The excellent overall performance of skin test makes them the golden standard for the diagnosis of anaphylactoid reactions. Techniques include intradermal tests and prick-tests. The current localizations are the forearm and the back. Positivity criteria are 3 mm for prick-tests. For IDTs, the criterium is the doubling of the size of the injection papula, when 0.02 to 0.04 ml is injected: 8 mm. The recommended concentrations are not falsely negative. Commercial concentrations can be tested by prick tests, except for mivacurium and atracurium tested of 1:10 dilution. A scale of concentrations is advised for IDT starting with 1:10,000, up to a normally non reactive concentration that is: 100 micrograms/ml (succinylcholine), 200 micrograms/ml (gallamine), 10 micrograms/ml (atracurium), 2 micrograms/ml (mivacurium), 200 micrograms/ml (pancuronium), 400 micrograms/ml (vecuronium), 1,000 micrograms/ml (rocuronium), 200 micrograms/ml (cis atracurium). The specificity and sensitivity of the skin tests to MRs are greater than 95%. The reproducibility over years is 88%. The overall concordance of PT and IDR is 97%. Both types of tests can be used for the diagnosis. IDT have to be carried out for the search of the cross sensitization. 84% of patients do have cross sensitization to MRs but only 16% react to all MRs. The further use of MRs selected by negative IDTs has been proved to be safe.

  20. Stress relaxation at a gelatin hydrogel-glass interface in direct shear sliding

    Science.gov (United States)

    Gupta, Vinit; Singh, Arun K.

    2018-01-01

    In this paper, we study experimentally the stress relaxation behavior of soft solids such as gelatin hydrogels on a smooth glass surface in direct shear sliding. It is observed experimentally that irrespective of pulling velocity, the sliding block relaxes to the same level of nonzero residual stress. However, residual stress increases with increasing gelatin concentration in the hydrogels. We have also validated a friction model for strong bond formation during steady relaxation in light of the experimental observations. Our theoretical analysis establishes that population of dangling chains at the sliding interface significantly affects the relaxation process. As a result, residual stress increases with increasing gelatin concentration or decreasing mesh size of the three-dimensional structures in the hydrogels. It is also found that the transition time, at which a weak bond converts to strong bond, increases with increasing mesh size of the hydrogels. Moreover, relaxation time constant of a strong bond decreases with increasing mesh size. However, activation length of a strong bond increases with mesh size. Finally, this study signifies the role of residual strength in frictional shear sliding and it is believed that these results should be useful to understand the role of residual stress in stick-slip instability.

  1. Viscoelastic properties of passive skeletal muscle in compression: stress-relaxation behaviour and constitutive modelling.

    Science.gov (United States)

    Van Loocke, M; Lyons, C G; Simms, C K

    2008-01-01

    The compressive properties of skeletal muscle are important in impact biomechanics, rehabilitation engineering and surgical simulation. However, the mechanical behaviour of muscle tissue in compression remains poorly characterised. In this paper, the time-dependent properties of passive skeletal muscle were investigated using a combined experimental and theoretical approach. Uniaxial ramp and hold compression tests were performed in vitro on fresh porcine skeletal muscle at various rates and orientations of the tissue fibres. Results show that above a very small compression rate, the viscoelastic component plays a significant role in muscle mechanical properties; it represents approximately 50% of the total stress reached at a compression rate of 0.5% s(-1). A stiffening effect with compression rate is observed especially in directions closer to the muscle fibres. Skeletal muscle viscoelastic behaviour is thus dependent on compression rate and fibre orientation. A model is proposed to represent the observed experimental behaviour, which is based on the quasi-linear viscoelasticity framework. A previously developed strain-dependent Young's Moduli formulation was extended with Prony series to account for the tissue viscoelastic properties. Parameters of the model were obtained by fitting to stress-relaxation data obtained in the muscle fibre, cross-fibre and 45 degrees directions. The model then successfully predicted stress-relaxation behaviour at 60 degrees from the fibre direction (errors fitting to data obtained at compression rates of 0.5% s(-1), 1%s(-1) and 10% s(-1) was performed and the model provided a good fit to the data as well as good predictions of muscle behaviour at rates of 0.05% s(-1) and 5% s(-1) (errors <25%).

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

    Directory of Open Access Journals (Sweden)

    George Hloupis

    2012-04-01

    Full Text Available

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

  3. Stress relaxation measurements of meta-dynamic and static recrystallization of alloy 80A

    Energy Technology Data Exchange (ETDEWEB)

    Kleber, S.; Sommitsch, C. [Boehler Edelstahl GmbH Kapfenberg (Australia)

    2004-07-01

    The stress relaxation method has been applied to the nickel-based alloy 80A to predict meta-dynamic (MDRX) and static recrystallization (SRX) kinetics. Compression tests were performed on a Gleeble 3800 system atr different temperatures (950-1200 C). The strain rate was varied in the case of MDRX and the pre-strain in the case of SRX. To investigate MDRX, the prestrain was set to twice the peak strain in order to reach steady state before holding. To focus on the interaction of MDRX and SRX, the pre-strain was set to the peak strain, where dynamic recrystallization (DRX) starts but does not yet reach steady state. Avrami type equations for the prediction of both the MDRX and SRX were adapted to feed a semi-empirical grain structure model. (orig.)

  4. Tunable stress relaxation behavior of an alginate-polyacrylamide hydrogel: comparison with muscle tissue.

    Science.gov (United States)

    Fitzgerald, Martha M; Bootsma, Katherine; Berberich, Jason A; Sparks, Jessica L

    2015-05-11

    Factors controlling the time-dependent mechanical properties of interpenetrating network (IPN) hydrogel materials are not well understood. In this study, alginate-polyacrylamide IPN were synthesized to mimic the stress relaxation behavior and elastic modulus of porcine muscle tissue. Hydrogel samples were created with single-parameter chemical concentration variations from a baseline formula to establish trends. The concentration of total monomer material had the largest effect on the elastic modulus, while concentration of the acrylamide cross-linker, N,N-methylenebis(acrylamide) (MBAA), changed the stress relaxation behavior most effectively. The IPN material was then tuned to mimic the mechanical response of muscle tissue using these trends. Swelling the hydrogel samples to equilibrium resulted in a dramatic decrease in both elastic modulus and stress relaxation behavior. Collectively, the results demonstrate that alginate-polyacrylamide IPN hydrogels can be tuned to closely mimic both the elastic and the viscoelastic behaviors of muscle tissue, although swelling detrimentally affects these desired properties.

  5. Night eating syndrome: effects of brief relaxation training on stress, mood, hunger, and eating patterns.

    Science.gov (United States)

    Pawlow, L A; O'Neil, P M; Malcolm, R J

    2003-08-01

    Night eating syndrome (NES) is characterized by a lack of appetite in the morning, consumption of 50% or more of daily food intake after 6:00 p.m., and difficulty falling and/or staying asleep. It has been associated with stress and with poor results at attempts to lose weight. The purpose of this study was to determine whether a relaxation intervention (Abbreviated Progressive Muscle Relaxation Therapy, APRT) that has been shown to significantly reduce stress levels in normal, healthy adults would also benefit an NES sample. A total of 20 adults with NES were randomly assigned to either a relaxation training (APRT) or a Control (quietly sitting for the same amount of time) group, and all subjects attended two laboratory sessions 1 week apart. Pre- and postsession indices of stress, anxiety, relaxation, and salivary cortisol were obtained, as well as Day 1 and Day 8 indices of mood. Food diaries and hunger ratings were also obtained. The results indicated that 20 min of a muscle relaxation exercise significantly reduced stress, anxiety, and salivary cortisol immediately postsession. After practicing these exercises daily for a week, subjects exhibited lowered stress, anxiety, fatigue, anger, and depression on Day 8. APRT was also associated with significantly higher a.m. and lower p.m. ratings of hunger, and a trend of both more breakfast and less night-time eating. These data support the role of stress and anxiety in NES and suggest that practicing relaxation may be an important component of treatment for this condition.

  6. Phase-Field Relaxation of Topology Optimization with Local Stress Constraints

    DEFF Research Database (Denmark)

    Stainko, Roman; Burger, Martin

    2006-01-01

    We introduce a new relaxation scheme for structural topology optimization problems with local stress constraints based on a phase-field method. In the basic formulation we have a PDE-constrained optimization problem, where the finite element and design analysis are solved simultaneously. The star......We introduce a new relaxation scheme for structural topology optimization problems with local stress constraints based on a phase-field method. In the basic formulation we have a PDE-constrained optimization problem, where the finite element and design analysis are solved simultaneously...

  7. The influence of strengthening mechanisms on stress relaxation in thin aluminum metallization

    Energy Technology Data Exchange (ETDEWEB)

    Gorrell, J.; Holloway, P. [Univ. of Florida, Gainesville, FL (United States). Dept. of Materials Science and Engineering; Jerman, H. [EG and G IC Sensors, Milpitas, CA (United States)

    1997-05-01

    The objective of this research is to identify ways of strengthening aluminum thin films for use in bimetallic actuators. With the development of microelectromechanical systems there is a need for stronger aluminium thin films that resist stress relaxation. A number of strengthening mechanisms are used extensively for bulk aluminum alloys, but very few have been used to improve the performance of thin films. Pure aluminum, standard microelectronics metallization (Al-.04Cu-.017Si), alloy T201 (Al-.046Cu-.006Ag-.004Mn-.003Mg-.003Ti), and alloy 2090 (Al-.026Cu-.021Li-.001Zr) were electron beam evaporated or sputter deposited onto (100) silicon substrates. Stress versus temperature and stress relaxation were measured in the films. Pure aluminum and AlSiCu alloy films exhibited plastic deformation at low stresses and low temperatures. The T201 and 2090 films exhibited residual elastic stresses at room temperature of 350 MPa and 500 MPa, and did not plastically deform until 240 C at 100 MPa stress, or 270 C at 200 MPa stress, respectively. The T201 film also showed a low stress relaxation rate. The authors speculate that solid solution strengthening caused the increase in strength of the T201 film, and that age hardening caused the increase in strength of the 2090 film.

  8. A study into stress relaxation in oxides formed on zirconium alloys

    Science.gov (United States)

    Platt, P.; Polatidis, E.; Frankel, P.; Klaus, M.; Gass, M.; Howells, R.; Preuss, M.

    2015-01-01

    Pressurised and boiling water reactors contain zirconium alloys, which are used as nuclear fuel cladding. Oxidation of these alloys, and the associated hydrogen pick-up, is a limiting factor in the lifetime of the fuel. To extend the burn-up of nuclear fuel requires control of the oxidation, and therefore development of a mechanistic understanding of the cladding corrosion process. Synchrotron X-ray diffraction (S-XRD) has been used to analyse oxide layers formed during in-situ air oxidation of Zircaloy-4 and ZIRLO™. Analysis shows that as the oxide thickness increases over time there is a relaxation of the stresses present in both the monoclinic and meta-stable tetragonal phases, and a reduction in the tetragonal phase fraction. To better understand the mechanisms behind stress relaxation in the oxide layer, finite element analysis has been used to simulate mechanical aspects of the oxidation process. This simulation was first developed based on stress relaxation in oxides formed in autoclave, and analysed ex-situ using S-XRD. Relaxation mechanisms include creep and hydrogen-induced lattice strain in the metal substrate and creep in the oxide layer. Subsequently the finite element analysis has been extended to stress relaxation observed by in-situ S-XRD oxidation experiments. Finite element analysis indicates that the impact of creep in the oxide is negligible, and the impact of both creep and hydrogen-induced lattice strain in the metal substrate metal is small. The implication is that stress relaxation must result from another source such as the development of roughness at the metal-oxide interface, or fracture in the oxide layer.

  9. The effect of progressive muscle relaxation method on test anxiety in nursing students.

    Science.gov (United States)

    Zargarzadeh, Maryam; Shirazi, Maryam

    2014-11-01

    Concerning the prevalence of test anxiety among nursing students and presence of stress in nursing education years, this study was conducted to determine the effect of progressive muscle relaxation method on test anxiety among nursing students of Isfahan University of Medical Sciences in 2013. This was a quasi-experimental study conducted in three stages on 49 male and female nursing students divided into two groups (study and control). In the pre-test stage, demographic data and Sarason anxiety questionnaires were filled by 94 students (of terms 3 and 4). Then, in the intervention stage, the students having test anxiety were assigned to two groups (study and control), and the progressive muscle relaxation method was performed in the experiment group in four sessions. Then, the students did this method two times a day until final exams, immediately following which they filled the self-reported checklists. On the first day of the final exams, test anxiety questionnaire was filled by the two groups again. The collected data were analyzed by the statistical tests, i.e. χ(2), paired t-test, independent sample t-test, Mann-Whitney and Wilcoxon tests, using SPSS 18. Independent t-test showed a significant difference in the mean scores of test anxiety after intervention between the two groups of study and control (P = 0.00), but this difference was not significant before intervention (P = 0.76). Also, in the study group, there was a significant difference in the mean scores of test anxiety before and after intervention (P = 0.00), but this difference was not significant in the control group (P = 0.09). Mann-Whitney test showed no significant difference in categorization of test anxiety scores before intervention in the study and control groups (P = 0.60), but the difference was significant after intervention (P = 0.00). Wilcoxon test showed a significant difference in categorization of test anxiety scores in the study group before and after intervention (P = 0.00), but

  10. The impact of hydrodynamics on stress formation, relaxation, and memory in colloidal dispersions: Transient, nonlinear microrheology

    Science.gov (United States)

    Mohanty, Ritesh P.; Zia, Roseanna N.

    2015-03-01

    In active microrheology, a probe is driven through a complex medium. Most work thus far has focused on steady behavior and established the relationship between the microstructure, probe speed, and rheology. But important information about structural development and relaxation are captured by startup and cessation of flows in the non-linear regime, where the structure is driven far from equilibrium. Here we study theoretically the rate of stress formation and relaxation under non-linear microrheological forcing of hydrodynamically interacting colloids. We study the behavior analytically in the dual limits of weak and strong probe forcing and weak and strong hydrodynamic interactions and numerically in between. To elucidate the detailed role of hydrodynamic, Brownian, and interparticle forces in stress formation and relaxation, we employ an excluded annulus model to introduce each systematically, and study the rheological and structural response for arbitrary forcing and strength of hydrodynamic interactions. Hydrodynamics introduce an additional mode of dissipation, which manifests as a reduction in the rate of stress formation during startup. While this non-equilibrium contribution vanishes instantly upon flow shutoff, a delicate interplay between Brownian and interparticle forces influences relaxation, revealing multiple relaxation modes. The recovery of entropically stored energy is studied.

  11. RELAX! inherent feedback during product interaction to reduce stress

    NARCIS (Netherlands)

    Bruns, M.

    2010-01-01

    For this research different experiments were conducted that indicate that people make rocking and rolling movements with a pen when they feel stressed; that when nervous movements are counteracted this results in more control over a situation; and that people prefer objects with moving parts when

  12. Comparing brief stress management courses in a community sample: mindfulness skills and progressive muscle relaxation.

    Science.gov (United States)

    Agee, John D; Danoff-Burg, Sharon; Grant, Christoffer A

    2009-01-01

    This study sought to compare a five-week mindfulness meditation (MM) course to a five-week course that taught progressive muscle relaxation (PMR). Forty-three adults from the community were randomly assigned to either MM (n = 19) or PMR (n = 24) courses after responding to flyers and other advertisements for a free stress management course. Mindfulness meditation participants practiced meditation significantly more often than PMR participants practiced relaxation during the intervention period (F[1, 43] = 7.42; P relaxation or mindfulness. Although there were no differences between groups on any of the primary outcome measures, across both treatment conditions there were statistically significant reductions from pretreatment to posttreatment in general psychological distress. Thus, although MM did not emerge as clearly superior to PMR, results of this study suggest that a brief mindfulness skills course may be effective for stress management.

  13. The effects of progressive muscular relaxation as a nursing procedure used for those who suffer from stress due to multiple sclerosis

    Directory of Open Access Journals (Sweden)

    Paolla Gabrielle Nascimento Novais

    Full Text Available ABSTRACT Objective: to evaluate the effect of progressive muscle relaxation as a nursing procedure on the levels of stress for sufferers of multiple sclerosis. Method: random clinical trials conducted at the Neurology outpatients unit at a University Hospital. The sample consisted of 40 patients who were being monitored as outpatients (20 in a control group and 20 in an experimental group. The Progressive Muscle Relaxation technique was used. The control variables were collected through interviews that were recorded on forms and on the Perceived Stress Scale that we used. Five meetings were held every fortnight covering a period of eight weeks. The experimental group was advised to carry out daily progressive muscle relaxation activities. After eight weeks of these activities, they were evaluated again to measure their levels of stress. In order to analyze the data used, the software package Statistics for Social Sciences version 19.0 was used. Results: the application of the t test showed a significant reduction in the Perceived Stress Scale scores in the experimental group (p<0.001, which in turn proved that there was a reduction in the levels of stress after the application of the relaxation practic-es. Conclusion: the progressive muscle relaxation activities contributed to the reduction in stress levels for multiple sclerosis suffers and thus can be used in nursing for patients. Clinical Trials Identifier: NCT 02673827.

  14. Measuring permeability, Young's modulus, and stress relaxation by the beam-bending technique

    Science.gov (United States)

    Vichit-Vadakan, Wilasa

    Recent interest in the permeability of cement paste, mortars, and concrete lies in the need to gain further understanding of mechanisms affecting the durability of these materials. Conventional techniques for measuring permeability are cumbersome and often take days to complete just one measurement. This thesis proposes a new technique for measuring the permeability. The advantage of this technique is that the results are obtained in a few minutes to a few hours; moreover, there is no problem with leaks or need for high pressures. The method is particularly well suited for examining the changes in permeability and viscoelastic properties of young cement paste samples. When a saturated rod of a porous material is instantaneously deflected under three-point bending, two types of relaxation processes occur simultaneously: hydrodynamic relaxation, caused by the flow of liquid in the porous body to restore ambient pressure, and viscoelastic relaxation of the solid network. By measuring the decrease in the force required to sustain a constant deflection, it is possible to obtain the permeability and Young's modulus from the hydrodynamic relaxation function, in addition to the stress relaxation function of the sample. The exact viscoelastic solution is developed and the total relaxation is shown to be very closely approximated as the product of the hydrodynamic and stress relaxation functions. The analytical results are verified on porous VycorRTM glass saturated in various solvents, including normal alcohols, water, and glycerol. The results show excellent agreement with the theory. Consistent with observations of previous workers, the permeability is found to be influenced by the size of the solvent molecule; by assuming that the pore surfaces are covered with a monolayer of immobile solvent, the observed variation can be explained. The evolution of the permeability, Young's modulus, and stress relaxation function are reported for Type III Portland cement paste with

  15. A unified aggregation and relaxation approach for stress-constrained topology optimization

    NARCIS (Netherlands)

    Verbart, A.; Langelaar, M.; van Keulen, A.

    2017-01-01

    In this paper, we propose a unified aggregation and relaxation approach for topology optimization with stress constraints. Following this approach, we first reformulate the original optimization problem with a design-dependent set of constraints into an equivalent optimization problem with a fixed

  16. Megathrust Earthquakes : Study of Fault Slip and Stress Relaxation Using Satellite Gravity Observations

    NARCIS (Netherlands)

    Broerse, D.B.T.

    2014-01-01

    During earthquakes large scale mass displacements take place when slip on a fault deforms the earth’s crust. Besides, in the days to decades after the main shock ongoing deformation is usually observed that is related to relaxation of stresses caused by the earthquake. In this thesis I relate

  17. Effects of suryanamaskar on relaxation among college students with high stress in Pune, India

    Directory of Open Access Journals (Sweden)

    Anand Sharad Godse

    2015-01-01

    Conclusions: It was concluded that suryanamaskar is effective in leading to R-Dispositions like physical relaxation, mental quiet, at ease/peace, rested and refreshed, strength and awareness and joy and reduces sleepiness, somatic stress, worry and negative emotion at a dispositional level.

  18. Stress relaxation of entangled polystyrene solution after constant-rate, uniaxial elongation

    DEFF Research Database (Denmark)

    Matsumiya, Yumi; Masubuchi, Yuichi; Watanabe, Hiroshi

    For an entangled solution of linear polystyrene (PS 545k; M = 545k) in dibutyl phthalate (DBP), the stress relaxation after constant-rate uniaxial elongation was examined with an extensional viscosity fixture mounted on ARES (TA Instruments). The PS concentration, c = 52 wt%, was chosen in a way...

  19. An Evaluation of Progressive Muscle Relaxation on Stress Related Symptoms in a Geriatric Population.

    Science.gov (United States)

    De Berry, Stephen

    1981-01-01

    Studied the effect of progressive muscle relaxation training on a group of anxious older widows (N=10). Found training decreased the severity of stress-related disorders when compared with controls. Results indicated, with state anxiety, improvement continued during home practice after treatment. (Author/JAC)

  20. Stress relaxation and cartilage shaping under laser radiation

    Science.gov (United States)

    Sobol, Emil N.; Sviridov, Alexander P.; Bagratashvili, Victor N.; Omelchenko, Alexander I.; Ovchinnikov, Yuriy M.; Shekhter, Anatoliy B.; Downes, S.; Howdle, Steven; Jones, Nicholas; Lowe, J.

    1996-05-01

    The problem of a purposeful change of the shape of cartilage is of great importance for otolaryngology, orthopaedics, and plastic surgery. In 1992 we have found a possibility of controlled shaping of cartilage under moderate laser heating. This paper presents new results in studies of that phenomenon. We have measured temperature and stress in a tissue undergoing to irradiation with a Holmium laser. Study of cartilage structure allowed us to find conditions for laser shaping without pronounced alterations in the structure of matrix.

  1. Ion-induced stress relaxation during the growth of cubic boron nitride thin films

    Energy Technology Data Exchange (ETDEWEB)

    Abendroth, B.E.

    2004-08-01

    in this thesis the deposition of cubic boron nitride films by magnetron sputtering is described. The deposition process is analyzed by Langmuir-probe measurement and energy resolved mass spectroscopy. the films are studied by stress measurement, spectroscopic ellipsometry, infrared spectroscopy, elastic recoil detection analysis, Rutherford backscattering spectroscopy, X-ray absorption near edge spectroscopy, X-ray diffraction, and transmission electron microscopy. Discussed are the stress relaxation and the microstructure and bonding characteristics together with the effects of ion bombardement. (HSI)

  2. Stress-induced eating and the relaxation response as a potential antidote: A review and hypothesis.

    Science.gov (United States)

    Masih, Tasmiah; Dimmock, James A; Epel, Elissa S; Guelfi, Kym J

    2017-11-01

    There is an accumulating body of evidence to indicate that stress leads to the consumption of unhealthy, energy-dense, palatable food, potentially contributing to the alarming global prevalence of chronic diseases, including obesity. However, comparatively little research has been devoted to addressing how best to remedy this growing problem. We provide an overview of the influence of stress on dietary intake, and then explore the novel, yet simple, possibility that regular elicitation of the relaxation response may effectively reduce stress-induced eating via both physiological neuroendocrine and reward pathways and psychological pathways involving emotion regulation, and habitual coping. If shown to be effective, the regular practice of relaxation may provide a convenient, cost efficient, patient-centered therapeutic practice to assist in the prevention of unhealthy weight gain and other negative consequences of unhealthy food intake. Copyright © 2017 Elsevier Ltd. All rights reserved.

  3. Stress growth and relaxation of dendritically branched macromolecules in shear and uniaxial extension

    DEFF Research Database (Denmark)

    Huang, Qian; Costanzo, S.; Das, C.

    2017-01-01

    stress relaxation, suggesting a strong ‘elastic memory’ of the material. These results are 2 described by BoB semi-quantitatively, both in linear and nonlinear shear and extensional regimes. Given the fact that the segments between branch points are less than 3 entanglements long, this is a very...... of the remarkable properties of these highly branched macromolecules. In particular, we address three questions pertinent to the specific molecular structure: (i) is steady state attainable during uniaxial extension? (ii) what is the respective transient response in simple shear? and (iii) how does stress relax...... the Branch-on-Branch (BoB) algorithm. The data indicates that the extensional viscosity reaches a steady state value, whose dependence on extension rate is identical to that of entangled linear and other branched polymer melts. Nonlinear shear is characterized by transient stress overshoots and the validity...

  4. Parental stress management using relaxation techniques in a neonatal intensive care unit: A randomised controlled trial.

    Science.gov (United States)

    Fotiou, Catherine; Vlastarakos, Petros V; Bakoula, Chrysa; Papagaroufalis, Konstantinos; Bakoyannis, George; Darviri, Christine; Chrousos, George

    2016-02-01

    The objective of this study was to investigate the effect of relaxation techniques on the stress/anxiety of parents with hospitalised premature infants, three months following discharge from the neonatal intensive care unit. A randomised controlled trial was conducted in the neonatal intensive care unit of a tertiary maternity hospital including 59 parents, who were randomised into two groups: 31 in the intervention group and 28 in the control group. Parents in the intervention group practiced three different relaxation techniques, in addition to undergoing the same information-based training courses as did the parents of the control group. Data were collected 10-15 days post delivery and three months post discharge. The assessment measures included the Perceived Stress Scale, the State and Trait Anxiety Inventory 1 and 2 and salivary cortisol levels. The psychometric assessment at baseline was comparable between the two groups. The intervention group showed a significant reduction in trait anxiety (p=0.02) compared with the control group three months post discharge. The perceived stress decreased in both groups (p=0.699). No difference in salivary cortisol levels was detected. The multivariate analysis revealed that higher initial stress levels (pintensive care unit experience could assess more delayed effects of stress management by relaxation techniques. Copyright © 2015 Elsevier Ltd. All rights reserved.

  5. Deformation, Stress Relaxation, and Crystallization of Lithium Silicate Glass Fibers Below the Glass Transition Temperature

    Science.gov (United States)

    Ray, Chandra S.; Brow, Richard K.; Kim, Cheol W.; Reis, Signo T.

    2004-01-01

    The deformation and crystallization of Li(sub 2)O (center dot) 2SiO2 and Li(sub 2)O (center dot) 1.6SiO2 glass fibers subjected to a bending stress were measured as a function of time over the temperature range -50 to -150 C below the glass transition temperature (Tg). The glass fibers can be permanently deformed at temperatures about 100 C below T (sub)g, and they crystallize significantly at temperatures close to, but below T,, about 150 C lower than the onset temperature for crystallization for these glasses in the no-stress condition. The crystallization was found to occur only on the surface of the glass fibers with no detectable difference in the extent of crystallization in tensile and compressive stress regions. The relaxation mechanism for fiber deformation can be best described by a stretched exponential (Kohlrausch-Williams-Watt (KWW) approximation), rather than a single exponential model.The activation energy for stress relaxation, Es, for the glass fibers ranges between 175 and 195 kJ/mol, which is considerably smaller than the activation energy for viscous flow, E, (about 400 kJ/mol) near T, for these glasses at normal, stress-free condition. It is suspected that a viscosity relaxation mechanism could be responsible for permanent deformation and crystallization of the glass fibers below T,

  6. A Microstructural Study of Load Distribution in Cartilage: A Comparison of Stress Relaxation versus Creep Loading

    Directory of Open Access Journals (Sweden)

    Ashvin Thambyah

    2015-01-01

    Full Text Available The compressive response of articular cartilage has been extensively investigated and most studies have focussed largely on the directly loaded matrix. However, especially in relation to the tissue microstructure, less is known about load distribution mechanisms operating outside the directly loaded region. We have addressed this issue by using channel indentation and DIC microscopy techniques that provide visualisation of the matrix microstructural response across the regions of both direct and nondirect loading. We hypothesise that, by comparing the microstructural response following stress relaxation and creep compression, new insights can be revealed concerning the complex mechanisms of load bearing. Our results indicate that, with stress relaxation, the initial mode of stress decay appears to primarily involve relaxation of the surface layer. In the creep loading protocol, the main mode of stress release is a lateral distribution of load via the mid matrix. While these two modes of stress redistribution have a complex relationship with the zonally differentiated tissue microstructure and the depth of strain, four mechanostructural mechanisms are proposed to describe succinctly the load responses observed.

  7. Strain-enhanced stress relaxation impacts nonlinear elasticity in collagen gels.

    Science.gov (United States)

    Nam, Sungmin; Hu, Kenneth H; Butte, Manish J; Chaudhuri, Ovijit

    2016-05-17

    The extracellular matrix (ECM) is a complex assembly of structural proteins that provides physical support and biochemical signaling to cells in tissues. The mechanical properties of the ECM have been found to play a key role in regulating cell behaviors such as differentiation and malignancy. Gels formed from ECM protein biopolymers such as collagen or fibrin are commonly used for 3D cell culture models of tissue. One of the most striking features of these gels is that they exhibit nonlinear elasticity, undergoing strain stiffening. However, these gels are also viscoelastic and exhibit stress relaxation, with the resistance of the gel to a deformation relaxing over time. Recent studies have suggested that cells sense and respond to both nonlinear elasticity and viscoelasticity of ECM, yet little is known about the connection between nonlinear elasticity and viscoelasticity. Here, we report that, as strain is increased, not only do biopolymer gels stiffen but they also exhibit faster stress relaxation, reducing the timescale over which elastic energy is dissipated. This effect is not universal to all biological gels and is mediated through weak cross-links. Mechanistically, computational modeling and atomic force microscopy (AFM) indicate that strain-enhanced stress relaxation of collagen gels arises from force-dependent unbinding of weak bonds between collagen fibers. The broader effect of strain-enhanced stress relaxation is to rapidly diminish strain stiffening over time. These results reveal the interplay between nonlinear elasticity and viscoelasticity in collagen gels, and highlight the complexity of the ECM mechanics that are likely sensed through cellular mechanotransduction.

  8. Exposure of natural rubber to personal lubricants--swelling and stress relaxation as potential indicators of reduced seal integrity of non-lubricated male condoms.

    Science.gov (United States)

    Sarkar Das, Srilekha; Coburn, James C; Tack, Charles; Schwerin, Matthew R; Richardson, D Coleman

    2014-07-01

    Male condoms act as mechanical barriers to prevent passage of body fluids. For effective use of condoms the mechanical seal is also expected to remain intact under reasonable use conditions, including with personal lubricants. Absorption of low molecular weight lubricant components into the material of male condoms may initiate material changes leading to swelling and stress relaxation of the polymer network chains that could affect performance of the sealing function of the device. Swelling indicates both a rubber-solvent interaction and stress relaxation, the latter of which may indicate and/or result in a reduced seal pressure in the current context. Swelling and stress relaxation of natural rubber latex condoms were assessed in a laboratory model in the presence of silicone-, glycol-, and water-based lubricants. Within 15 minutes, significant swelling (≥6 %) and stress reduction (≥12 %) of condoms were observed with 2 out of 4 silicone-based lubricants tested, but neither was observed with glycol- or water-based lubricants tested. Under a given strain, reduction in stress was prominent during the swelling processes, but not after the process was complete. Lubricant induced swelling and stress relaxation may loosen the circumferential stress responsible for the mechanical seal. Swelling and stress relaxation behavior of latex condoms in the presence of personal lubricants may be useful tests to identify lubricant-rooted changes in condom-materials. For non-lubricated latex condoms, material characteristics--which are relevant to failure--may change in the presence of a few silicone-based personal lubricants. These changes may in turn induce a loss of condom seal during use, specifically at low strain conditions. Published by Elsevier Inc.

  9. Shrinkage stress compensation in composite-restored teeth: relaxation or hygroscopic expansion?

    Science.gov (United States)

    Meriwether, Laurel A; Blen, Bernard J; Benson, Jarred H; Hatch, Robert H; Tantbirojn, Daranee; Versluis, Antheunis

    2013-05-01

    Polymerization of composite restorations causes shrinkage, which deforms and thus stresses restored teeth. This shrinkage deformation, however, has been shown to decrease over time. The objective was to investigate whether this reduction was caused by hygroscopic expansion or stress relaxation of the composite/tooth complex. Extracted molars were mounted in rigid stainless steel rings with four spherical reference areas. Twelve molars were prepared with large mesioocclusodistal slots, etched, bonded, and restored with a composite material (Filtek Supreme, 3M ESPE) in two horizontal layers. Ten intact molars were the controls. The teeth were stored either in deionized water or silicone oil. They were scanned after preparation (baseline), restoration (0-week), and after 1, 2, and 4 weeks storage. Scanned tooth surfaces were aligned with the baseline using the unchanged reference areas. Cuspal flexure was calculated from lingual and buccal surface deformation. To verify that the restorations had remained bonded, dye penetration at the interfaces was assessed using basic fuchsin dye. Statistical assessment was done by ANOVA followed by Student-Newman-Keuls post hoc test (p=0.05). Substantial cuspal contraction was found for restored teeth after the composite was cured (13-14 μm cuspal flexure). After 4 weeks cuspal contraction decreased significantly for restored teeth stored in water (7.3 ± 3.2) but not for those stored in silicone oil (11.4 ± 5.0). Dye penetration of the occlusal interface was minimal in both groups (106 ± 87 and 21 ± 28 μm in water and silicone oil, respectively). The results suggest that hygroscopic expansion was the main mechanism for shrinkage stress compensation. Copyright © 2013 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  10. Stress Relaxation Analysis Facilitates a Quantitative Approach towards Antimicrobial Penetration into Biofilms

    Science.gov (United States)

    He, Yan; Peterson, Brandon W.; Jongsma, Marije A.; Ren, Yijin; Sharma, Prashant K.; Busscher, Henk J.; van der Mei, Henny C.

    2013-01-01

    Biofilm-related infections can develop everywhere in the human body and are rarely cleared by the host immune system. Moreover, biofilms are often tolerant to antimicrobials, due to a combination of inherent properties of bacteria in their adhering, biofilm mode of growth and poor physical penetration of antimicrobials through biofilms. Current understanding of biofilm recalcitrance toward antimicrobial penetration is based on qualitative descriptions of biofilms. Here we hypothesize that stress relaxation of biofilms will relate with antimicrobial penetration. Stress relaxation analysis of single-species oral biofilms grown in vitro identified a fast, intermediate and slow response to an induced deformation, corresponding with outflow of water and extracellular polymeric substances, and bacterial re-arrangement, respectively. Penetration of chlorhexidine into these biofilms increased with increasing relative importance of the slow and decreasing importance of the fast relaxation element. Involvement of slow relaxation elements suggests that biofilm structures allowing extensive bacterial re-arrangement after deformation are more open, allowing better antimicrobial penetration. Involvement of fast relaxation elements suggests that water dilutes the antimicrobial upon penetration to an ineffective concentration in deeper layers of the biofilm. Next, we collected biofilms formed in intra-oral collection devices bonded to the buccal surfaces of the maxillary first molars of human volunteers. Ex situ chlorhexidine penetration into two weeks old in vivo formed biofilms followed a similar dependence on the importance of the fast and slow relaxation elements as observed for in vitro formed biofilms. This study demonstrates that biofilm properties can be derived that quantitatively explain antimicrobial penetration into a biofilm. PMID:23723995

  11. Credibility and Crisis Stress Testing

    Directory of Open Access Journals (Sweden)

    Li Lian Ong

    2014-02-01

    Full Text Available Credibility is the bedrock of any crisis stress test. The use of stress tests to manage systemic risk was introduced by the U.S. authorities in 2009 in the form of the Supervisory Capital Assessment Program. Since then, supervisory authorities in other jurisdictions have also conducted similar exercises. In some of those cases, the design and implementation of certain elements of the framework have been criticized for their lack of credibility. This paper proposes a set of guidelines for constructing an effective crisis stress test. It combines financial markets impact studies of previous exercises with relevant case study information gleaned from those experiences to identify the key elements and to formulate their appropriate design. Pertinent concepts, issues and nuances particular to crisis stress testing are also discussed. The findings may be useful for country authorities seeking to include stress tests in their crisis management arsenal, as well as for the design of crisis programs.

  12. The effects of music relaxation and muscle relaxation techniques on sleep quality and emotional measures among individuals with posttraumatic stress disorder.

    Science.gov (United States)

    Blanaru, Monica; Bloch, Boaz; Vadas, Limor; Arnon, Zahi; Ziv, Naomi; Kremer, Ilana; Haimov, Iris

    2012-07-26

    Posttraumatic stress disorder (PTSD), an anxiety disorder with lifetime prevalence of 7.8%, is characterized by symptoms that develop following exposure to traumatic life events and that cause an immediate experience of intense fear, helplessness or horror. PTSD is marked by recurrent nightmares typified by the recall of intrusive experiences and by extended disturbance throughout sleep. Individuals with PTSD respond poorly to drug treatments for insomnia. The disadvantages of drug treatment for insomnia underline the importance of non-pharmacological alternatives. Thus, the present study had three aims: first, to compare the efficiency of two relaxation techniques (muscular relaxation and progressive music relaxation) in alleviating insomnia among individuals with PTSD using both objective and subjective measures of sleep quality; second, to examine whether these two techniques have different effects on psychological indicators of PTSD, such as depression and anxiety; and finally, to examine how initial PTSD symptom severity and baseline emotional measures are related to the efficiency of these two relaxation methods. Thirteen PTSD patients with no other major psychiatric or neurological disorders participated in the study. The study comprised one seven-day running-in, no-treatment period, followed by two seven-day experimental periods. The treatments constituted either music relaxation or muscle relaxation techniques at desired bedtime. These treatments were randomly assigned. During each of these three experimental periods, subjects' sleep was continuously monitored with a wrist actigraph (Ambulatory Monitoring, Inc.), and subjects were asked to fill out several questionnaires concerned with a wide spectrum of issues, such as sleep, depression, and anxiety. Analyses revealed a significant increase in objective and subjective sleep efficiency and a significant reduction in depression level following music relaxation. Moreover, following music relaxation, a highly

  13. The effects of music relaxation and muscle relaxation techniques on sleep quality and emotional measures among individuals with posttraumatic stress disorder

    Directory of Open Access Journals (Sweden)

    Iris Haimov

    2012-07-01

    Full Text Available Posttraumatic stress disorder (PTSD, an anxiety disorder with lifetime prevalence of 7.8%, is characterized by symptoms that develop following exposure to traumatic life events and that cause an immediate experience of intense fear, helplessness or horror. PTSD is marked by recurrent nightmares typified by the recall of intrusive experiences and by extended disturbance throughout sleep. Individuals with PTSD respond poorly to drug treatments for insomnia. The disadvantages of drug treatment for insomnia underline the importance of non-pharmacological alternatives. Thus, the present study had three aims: first, to compare the efficiency of two relaxation techniques (muscular relaxation and progressive music relaxation in alleviating insomnia among individuals with PTSD using both objective and subjective measures of sleep quality; second, to examine whether these two techniques have different effects on psychological indicators of PTSD, such as depression and anxiety; and finally, to examine how initial PTSD symptom severity and baseline emotional measures are related to the efficiency of these two relaxation methods. Thirteen PTSD patients with no other major psychiatric or neurological disorders participated in the study. The study comprised one seven-day running-in, no-treatment period, followed by two seven-day experimental periods. The treatments constituted either music relaxation or muscle relaxation techniques at desired bedtime. These treatments were randomly assigned. During each of these three experimental periods, subjects’ sleep was continuously monitored with a wrist actigraph (Ambulatory Monitoring, Inc., and subjects were asked to fill out several questionnaires concerned with a wide spectrum of issues, such as sleep, depression, and anxiety. Analyses revealed a significant increase in objective and subjective sleep efficiency and a significant reduction in depression level following music relaxation. Moreover, following music

  14. Restoring range of motion via stress relaxation and static progressive stretch in posttraumatic elbow contractures.

    Science.gov (United States)

    Ulrich, Slif D; Bonutti, Peter M; Seyler, Thorsten M; Marker, David R; Morrey, Bernard F; Mont, Michael A

    2010-03-01

    Loss of range of motion after injury or surgery of the elbow is a common complication. We hypothesized that an orthosis that used progressive stretch and stress relaxation principles would improve elbow range of motion. This study evaluated the result of a patient-directed, bidirectional orthosis that uses static progressive stretch and stress relaxation principles to improve elbow range of motion in patients who had posttraumatic elbow contractures. Treatment in 37 elbows consisted of a 30-minute stretching protocol performed in 1 to 3 sessions daily for a mean of 10 weeks (range, 2-22 weeks). The mean gain in range of motion was 26 degrees (range, 2 degrees -60 degrees ). Gains of motion were noted in 35 of 37 elbows. Patients lowered their analgesic use and were highly satisfied with the device (mean satisfaction score of 8.5 of 10 points possible). This device compared favorably with reports of other devices. Consistent improvements in restoring range of motion can be achieved with short treatment times by using a device based on the principles of static progressive stretch and stress relaxation in patients with posttraumatic elbow contractures. Copyright 2010 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Mosby, Inc. All rights reserved.

  15. Combining walking and relaxation for stress reduction-A randomized cross-over trial in healthy adults.

    Science.gov (United States)

    Matzer, Franziska; Nagele, Eva; Lerch, Nikolaus; Vajda, Christian; Fazekas, Christian

    2017-08-25

    Both physical activity and relaxation have stress-relieving potential. This study investigates their combined impact on the relaxation response while considering participants' initial stress level. In a randomized cross-over trial, 81 healthy adults completed 4 types of short-term interventions for stress reduction, each lasting for 1 hr: (1) physical activity (walking) combined with resting, (2) walking combined with balneotherapy, (3) combined resting and balneotherapy, and (4) resting only. Saliva cortisol, blood pressure, state of mood, and relaxation were measured preintervention and postintervention. Stress levels were determined by validated questionnaires. All interventions were associated with relaxation responses in the variables saliva cortisol, blood pressure, state of mood, and subjective relaxation. No significant differences were found regarding the reduction of salivary cortisol (F = 1.30; p = .281). The systolic blood pressure was reduced best when walking was combined with balneotherapy or resting (F = 7.34; p < .001). Participants with high stress levels (n = 25) felt more alert after interventions including balneotherapy, whereas they reported an increase of tiredness when walking was combined with resting (F = 3.20; p = .044). Results suggest that combining physical activity and relaxation (resting or balneotherapy) is an advantageous short-term strategy for stress reduction as systolic blood pressure is reduced best while similar levels of relaxation can be obtained. Copyright © 2017 John Wiley & Sons, Ltd.

  16. The influence of stress and energy level on learning muscle relaxation during gross-motor task performance using electromyographic feedback

    NARCIS (Netherlands)

    van Dijk, H; Voerman, Gerlienke; Hermens, Hermanus J.

    The aim was to investigate the influence of mood on learning muscle relaxation. Self-reported mood (assessed by the Stress-Energy Checklist) at baseline was related to learning muscle relaxation induced by electromyographic feedback training during performance of a gross-motor task. Feedback

  17. The use of self-Reiki for stress reduction and relaxation.

    Science.gov (United States)

    Bukowski, Elaine L

    2015-09-01

    More than one-third of college students reported the desire for stress reduction techniques and education. The purpose of this study was to determine the effects of a 20-week structured self-Reiki program on stress reduction and relaxation in college students. Students were recruited from Stockton University and sessions were conducted in the privacy of their residence. Twenty students completed the entire study consisting of 20 weeks of self-Reiki done twice weekly. Each participant completed a Reiki Baseline Credibility Scale, a Reiki Expectancy Scale, and a Perceived Stress Scale (PSS) after acceptance into the study. The PSS was completed every four weeks once the interventions were initiated. A global assessment questionnaire was completed at the end of the study. Logs summarizing the outcome of each session were submitted at the end of the study. With the exception of three participants, participants believed that Reiki is a credible technique for reducing stress levels. Except for two participants, participants agreed that Reiki would be effective in reducing stress levels. All participants experienced stress within the month prior to completing the initial PSS. There was a significant reduction in stress levels from pre-study to post-study. There was a correlation between self-rating of improvement and final PSS scores. With one exception, stress levels at 20 weeks did not return to pre-study stress levels. This study supports the hypothesis that the calming effect of Reiki may be achieved through the use of self-Reiki.

  18. Diazepam and Jacobson's progressive relaxation show similar attenuating short-term effects on stress-related brain glucose consumption

    National Research Council Canada - National Science Library

    Pifarré, P; Simó, M; Gispert, J-D; Plaza, P; Fernández, A; Pujol, J

    2015-01-01

    A non-pharmacological method to reduce anxiety is "progressive relaxation" (PR). The aim of the method is to reduce mental stress and associated mental processes by means of progressive suppression of muscle tension...

  19. [Relaxation treatments and biofeedback for anxiety and somatic stress-related disorders].

    Science.gov (United States)

    Biondi, Massimo; Valentini, Martina

    2014-01-01

    Relaxation techniques (TR) and biofeedback (BFB) are widely used in psychiatric and psychological practice for the treatment for anxiety and stress-related disorders. An examination of studies focusing on the correlates of psychophysiology of relaxation and biofeedback has been done, in addiction to controlled therapeutic studies that describes clinical aspects, efficacy and limits. There are different TR and BFB procedures, but they have the same goal and same physiological modifications, resulting in stress and anxiety reduction. There is a proven action to musculoskeletal, neuroendocrine and autonomic nervous system, showing similar results. Very few data on immune changes are available. Meta-Analysis show superior efficacy to no treatment or placebo in anxiety disorders, tension headache, bruxism, temporomandibular pain syndrome, rehabilitation and prevention of ischemic heart disease. Moderate efficacy is shown for chronic low back pain, cancer-related pain, rheumatoid arthritis and gastrointestinal disorders; data for essential hypertension are controversial. Variability of techniques, procedures, sampling problems, non-systematic make definitive conclusions difficult. TR and BFB are often used in combination with cognitive-behavioral and educational techniques. The association of the active relaxation technique facilitates generalization and self-control during stress situation and outside the training session. TR and BFB are effective for anxiety and somatic stress-related disorders, associated with coping and quality of life improvement and affordable costs; they are minimally invasive but needing an active participation in the treatment process. Some limits are responders' prediction, continuity of practice and limited effectiveness for depression disorders. Finally, it is shown that they are real psychosomatic therapies that are able to produce somatic peripheral changes (neuroendocrine, neurovegetative and muscular systems) generated by the mind and

  20. Strain modulations as a mechanism to reduce stress relaxation in laryngeal tissues.

    Directory of Open Access Journals (Sweden)

    Eric J Hunter

    Full Text Available Vocal fold tissues in animal and human species undergo deformation processes at several types of loading rates: a slow strain involved in vocal fold posturing (on the order of 1 Hz or so, cyclic and faster posturing often found in speech tasks or vocal embellishment (1-10 Hz, and shear strain associated with vocal fold vibration during phonation (100 Hz and higher. Relevant to these deformation patterns are the viscous properties of laryngeal tissues, which exhibit non-linear stress relaxation and recovery. In the current study, a large strain time-dependent constitutive model of human vocal fold tissue is used to investigate effects of phonatory posturing cyclic strain in the range of 1 Hz to 10 Hz. Tissue data for two subjects are considered and used to contrast the potential effects of age. Results suggest that modulation frequency and extent (amplitude, as well as the amount of vocal fold overall strain, all affect the change in stress relaxation with modulation added. Generally, the vocal fold cover reduces the rate of relaxation while the opposite is true for the vocal ligament. Further, higher modulation frequencies appear to reduce the rate of relaxation, primarily affecting the ligament. The potential benefits of cyclic strain, often found in vibrato (around 5 Hz modulation and intonational inflection, are discussed in terms of vocal effort and vocal pitch maintenance. Additionally, elderly tissue appears to not exhibit these benefits to modulation. The exacerbating effect such modulations may have on certain voice disorders, such as muscle tension dysphonia, are explored.

  1. Numerical simulation of a relaxation test designed to fit a quasi-linear viscoelastic model for temporomandibular joint discs.

    Science.gov (United States)

    Commisso, Maria S; Martínez-Reina, Javier; Mayo, Juana; Domínguez, Jaime

    2013-02-01

    The main objectives of this work are: (a) to introduce an algorithm for adjusting the quasi-linear viscoelastic model to fit a material using a stress relaxation test and (b) to validate a protocol for performing such tests in temporomandibular joint discs. This algorithm is intended for fitting the Prony series coefficients and the hyperelastic constants of the quasi-linear viscoelastic model by considering that the relaxation test is performed with an initial ramp loading at a certain rate. This algorithm was validated before being applied to achieve the second objective. Generally, the complete three-dimensional formulation of the quasi-linear viscoelastic model is very complex. Therefore, it is necessary to design an experimental test to ensure a simple stress state, such as uniaxial compression to facilitate obtaining the viscoelastic properties. This work provides some recommendations about the experimental setup, which are important to follow, as an inadequate setup could produce a stress state far from uniaxial, thus, distorting the material constants determined from the experiment. The test considered is a stress relaxation test using unconfined compression performed in cylindrical specimens extracted from temporomandibular joint discs. To validate the experimental protocol, the test was numerically simulated using finite-element modelling. The disc was arbitrarily assigned a set of quasi-linear viscoelastic constants (c1) in the finite-element model. Another set of constants (c2) was obtained by fitting the results of the simulated test with the proposed algorithm. The deviation of constants c2 from constants c1 measures how far the stresses are from the uniaxial state. The effects of the following features of the experimental setup on this deviation have been analysed: (a) the friction coefficient between the compression plates and the specimen (which should be as low as possible); (b) the portion of the specimen glued to the compression plates (smaller

  2. Endothelial relaxation mechanisms and oxidative stress are restored by atorvastatin therapy in ovariectomized rats.

    Directory of Open Access Journals (Sweden)

    Izabela Facco Caliman

    Full Text Available The studies on hormone replacement therapy (HRT in females with estrogen deficiency are not conclusive. Thus, non-estrogen therapies, such as atorvastatin (ATO, could be new strategies to substitute or complement HRT. This study evaluated the effects of ATO on mesenteric vascular bed (MVB function from ovariectomized (OVX female rats. Female rats were divided into control SHAM, OVX, and OVX treated with 17β-estradiol (EST or ATO groups. The MVB reactivity was determined in organ chambers, vascular oxidative stress by dihydroethidine staining, and the expression of target proteins by western blot. The reduction in acetylcholine-induced relaxation in OVX rats was restored by ATO or EST treatment. The endothelium-dependent nitric oxide (NO component was reduced in OVX rats, whereas the endothelium-derived hyperpolarizing factor (EDHF component or prostanoids were not altered in the MVBs. Endothelial dysfunction in OVX rats was associated with oxidative stress, an up-regulation of iNOS and NADPH oxidase expression and a down-regulation of eNOS expression. Treatment with ATO or EST improved the NO component of the relaxation and normalized oxidative stress and the expression of those signaling pathways enzymes. Thus, the protective effect of ATO on endothelial dysfunction caused by estrogen deficiency highlights a significant therapeutic benefit for statins independent of its effects on cholesterol, thus providing evidence that non-estrogen therapy could be used for cardiovascular benefit in an estrogen-deficient state, such as menopause.

  3. Stress relaxation and creep experiments with the atomic force microscope: a unified method to calculate elastic moduli and viscosities of biomaterials (and cells)

    CERN Document Server

    Moreno-Flores, Susana; Vivanco, Maria dM; Toca-Herrera, Jose Luis

    2010-01-01

    We show that the atomic force microscope can perform stress relaxation and creep compliance measurements on living cells. We propose a method to obtain the mechanical properties of the studied biomaterial: the relaxation time, the elastic moduli and the viscosity.

  4. The Effects of Relaxation Instructions and EMG Biofeedback of Test Anxiety, General Anxiety, and Locus of Control.

    Science.gov (United States)

    Reed, Michael; Saslow, Carol

    1980-01-01

    Brief relaxation instruction alone and instructions plus electromyographic (EMG) feedback produced significant decreases in general and test-specific anxiety. EMG feedback added little to the effectiveness of relaxation instructions and practice. Relaxation instruction without EMG biofeedback shifted subjects toward a more internal locus of…

  5. Stress testing in financial institutions

    Directory of Open Access Journals (Sweden)

    Mirković Vladimir

    2014-01-01

    Full Text Available In 2000 the Basle Committee on the Global Financial System defined stress testing as 'a generic term describing various techniques used by financial firms to gauge their potential vulnerability to exceptional but plausible events'. Exceptional events refer to one-off or recurring events with far-reaching consequences for the concerned financial institution and the financial sector s stability overall. Such unexpected (exceptional events include, for instance: bankruptcy in Argentina in 2001, stock markets collapse ('Black Monday' on 19 October 1987, or the fall of the energy giant Enron in 2001. The adoption of the new Basle Accord (better known as Basle II in 2001 envisaged the implementation of stress tests for the identification of events and future changes in economic circumstances that could cause some unfavorable effects on banks' credit exposure, along with the assessment of banks' ability to survive in the new circumstances. Negative experiences from the past, having undermined the stability of financial systems worldwide, made a decisive impact on regulators at all levels to additionally consider the issue of increasing the financial system's resistance to the occurrence of unexpected - exceptional events. To this end, the introduction of stress tests was the turning point in the process of increased banking systems' resistance to shocks. This paper primarily deals with stress testing methodology and bank risk measurement techniques, along with the main results of conducted tests, directly impacting the entire financial system.

  6. Abbreviated Upright Behavioral Relaxation Training for Test Anxiety among College Students: Initial Results

    Science.gov (United States)

    Tatum, Teresa; Lundervold, Duane A.; Ament, Patrick

    2006-01-01

    Effect of abbreviated upright Behavioral Relaxation Training (BRT) on two self-report measures of test anxiety was examined using a quasi-experimental pre-post between groups (N = 20) research design with self-referred college students. At time 1 (T1) assessment, all participants completed the Abbreviated Test Anxiety Scale (ATAS) and were trained…

  7. Functionally distinct tendon fascicles exhibit different creep and stress relaxation behaviour.

    Science.gov (United States)

    Shepherd, Jennifer H; Legerlotz, Kirsten; Demirci, Taylan; Klemt, Christian; Riley, Graham P; Screen, Hazel R C

    2014-01-01

    Most overuse tendinopathies are thought to be associated with repeated microstrain below the failure threshold, analogous to the fatigue failure that affects materials placed under repetitive loading. Investigating the progression of fatigue damage within tendons is therefore of critical importance. There are obvious challenges associated with the sourcing of human tendon samples for in vitro analysis so animal models are regularly adopted. However, data indicates that fatigue life varies significantly between tendons of different species and with different stresses in life. Positional tendons such as rat tail tendon or the bovine digital extensor are commonly applied in in vitro studies of tendon overuse, but there is no evidence to suggest their behaviour is indicative of the types of human tendon particularly prone to overuse injuries. In this study, the fatigue response of the largely positional digital extensor and the more energy storing deep digital flexor tendon of the bovine hoof were compared to the semitendinosus tendon of the human hamstring. Fascicles from each tendon type were subjected to either stress or strain controlled fatigue loading (cyclic creep or cyclic stress relaxation respectively). Gross fascicle mechanics were monitored after cyclic stress relaxation and the mean number of cycles to failure investigated with creep loading. Bovine extensor fascicles demonstrated the poorest fatigue response, while the energy storing human semitendinosus was the most fatigue resistant. Despite the superior fatigue response of the energy storing tendons, confocal imaging suggested a similar degree of damage in all three tendon types; it appears the more energy storing tendons are better able to withstand damage without detriment to mechanics.

  8. Power-Law Stress and Creep Relaxations of Single Cells Measured by Colloidal Probe Atomic Force Microscopy

    OpenAIRE

    Hiratsuka, Shinichiro; Mizutani, Yusuke; Toda, Akitoshi; Fukushima, Norichika; Kawahara, Koichi; Tokumoto, Hiroshi; Okajima, Takaharu

    2009-01-01

    We measured stress and creep relaxations of mouse fibroblast cells arranged and cultured on a microarray, by colloidal probe atomic force microscopy (AFM). A hydrophobic monolayer coating of perfluorodecyltrichlorosilane (FDTS) on the surface of colloidal silica beads significantly reduced the adhesion force of live cells, compared with untreated beads. The rheological behaviors of cells were estimated by averaging several relaxation curves of cells measured by the AFM. Longer-time tailing of...

  9. Creep and stress relaxation induced by interface diffusion in metal matrix composites

    Science.gov (United States)

    Li, Yinfeng; Li, Zhonghua

    2013-03-01

    An analytical solution is developed to predict the creep rate induced by interface diffusion in unidirectional fiber-reinforced and particle reinforced composites. The driving force for the interface diffusion is the normal stress acting on the interface, which is obtained from rigorous Eshelby inclusion theory. The closed-form solution is an explicit function of the applied stress, volume fraction and radius of the fiber, as well as the modulus ratio between the fiber and the matrix. It is interesting that the solution is formally similar to that of Coble creep in polycrystalline materials. For the application of the present solution in the realistic composites, the scale effect is taken into account by finite element analysis based on a unit cell. Based on the solution, a closed-form solution is also given as a description of stress relaxation induced by interfacial diffusion under constant strain. In addition, the analytical solution for the interface stress presented in this study gives some insight into the relationship between the interface diffusion and interface slip. This work was supported by the financial support from the Nature Science Foundation of China (No. 10932007), the National Basic Research Program of China (No. 2010CB631003/5), and the Doctoral Program of Higher Education of China (No. 20100073110006).

  10. Fitting stress relaxation experiments with fractional Zener model to predict high frequency moduli of polymeric acoustic foams

    Science.gov (United States)

    Guo, Xinxin; Yan, Guqi; Benyahia, Lazhar; Sahraoui, Sohbi

    2016-11-01

    This paper presents a time domain method to determine viscoelastic properties of open-cell foams on a wide frequency range. This method is based on the adjustment of the stress-time relationship, obtained from relaxation tests on polymeric foams' samples under static compression, with the four fractional derivatives Zener model. The experimental relaxation function, well described by the Mittag-Leffler function, allows for straightforward prediction of the frequency-dependence of complex modulus of polyurethane foams. To show the feasibility of this approach, complex shear moduli of the same foams were measured in the frequency range between 0.1 and 16 Hz and at different temperatures between -20 °C and 20 °C. A curve was reconstructed on the reduced frequency range (0.1 Hz-1 MHz) using the time-temperature superposition principle. Very good agreement was obtained between experimental complex moduli values and the fractional Zener model predictions. The proposed time domain method may constitute an improved alternative to resonant and non-resonant techniques often used for dynamic characterization of polymers for the determination of viscoelastic moduli on a broad frequency range.

  11. Separating the Influence of Environment from Stress Relaxation Effects on Dwell Fatigue Crack Growth in a Nickel-Base Disk Alloy

    Science.gov (United States)

    Telesman, J.; Gabb, T. P.; Ghosn, L. J.

    2016-01-01

    Both environmental embrittlement and crack tip visco-plastic stress relaxation play a significant role in determining the dwell fatigue crack growth (DFCG) resistance of nickel-based disk superalloys. In the current study performed on the Low Solvus High Refractory (LSHR) disk alloy, the influence of these two mechanisms were separated so that the effects of each could be quantified and modeled. Seven different microstructural variations of LSHR were produced by controlling the cooling rate and the subsequent aging and thermal exposure heat treatments. Through cyclic fatigue crack growth testing performed both in air and vacuum, it was established that four out of the seven LSHR heat treatments evaluated, possessed similar intrinsic environmental resistance to cyclic crack growth. For these four heat treatments, it was further shown that the large differences in dwell crack growth behavior which still persisted, were related to their measured stress relaxation behavior. The apparent differences in their dwell crack growth resistance were attributed to the inability of the standard linear elastic fracture mechanics (LEFM) stress intensity parameter to account for visco-plastic behavior. Crack tip stress relaxation controls the magnitude of the remaining local tensile stresses which are directly related to the measured dwell crack growth rates. It was hypothesized that the environmentally weakened grain boundary crack tip regions fail during the dwells when their strength is exceeded by the remaining local crack tip tensile stresses. It was shown that the classical creep crack growth mechanisms such as grain boundary sliding did not contribute to crack growth, but the local visco-plastic behavior still plays a very significant role by determining the crack tip tensile stress field which controls the dwell crack growth behavior. To account for the influence of the visco-plastic behavior on the crack tip stress field, an empirical modification to the LEFM stress

  12. ASSESSMENT OF CRACKING RESISTANCE OF CELLULAR CONCRETE PRODUCTS UNDER MOISTURE AND CARBONISATION DEFORMATIONS WITH STRESS RELAXATION

    Directory of Open Access Journals (Sweden)

    Sh. I. Apkarov

    2017-01-01

    Full Text Available Objectives. On the basis of the experimental, theoretical and field studies, an engineering calculation method was developed for assessing the cracking resistance of external enclosing constructions made of cellular concrete, with the maximum gradient development of moisture and carbonisation forced deformations along their thickness, taking into account the relaxation of the shrinkage stresses. In this regard, the aim of the work is to provide technological measures at the manufacturing stage in order to increase the operational cracking resistance of the construction's outer surface layers by reducing the moisture and carbonation shrinkage of cellular concrete by introducing a large or fine porous aggregate in calculated amounts.Methods. A number of analytical equations were applied to establish the dependence of the shrinkage of heavy concrete of conventional hardness on the amount of aggregate introduced and its elasticity modulus, water-cement ratio and cement consumption, as well as the concrete's moisture content.Results. Knowing the volumes of the structural aggregate and the cellular concrete mass, as well as their modulus of elasticity, the shrinkage reduction factor of the cellular concrete was calculated with the addition of a lightweight porous aggregate. Subsequently, the shrinkage deformations of concrete in the surface layer of the outer enclosing construction, maximising crack resistance due to moisture exchange and carbonation influences under operating conditions, were defined, taking into account the relaxation of tensile stresses due to creep of concrete.Conclusion. Theoretical calculations, based on the recommended method of assessing the cracking resistance of cellular concrete enclosing constructions under moisture exchange and carbonisation processes, taking into account the relaxation of shrinkage stresses, showed that in order to exclude the appearance of cracks in wall panels 280 mm thick made of 700 kg/m3 gas ash

  13. Influence of Stress Relaxation in Hybrid Composite/Metal Bolted Connections

    Science.gov (United States)

    2005-01-15

    Composite Constituent Volume Test (Bum Off) - ASTM D2584 * Tension Test - ASTM D3039 • Compression Test - ASTM D3410 Pelletier, Caccese and Berube 32 UM...Kim and McMeeking [1994] performed testing on creep in composite materials in the fiber direction. They found that the matrix followed the following...composites using short-term test data obtained for accelerated testing conditions such as higher temperature, stress, and humidity. Continuous carbon

  14. Simulation of the Relaxation Potential Profile of an ac-dc-ac Test

    Directory of Open Access Journals (Sweden)

    Kerry N. Allahar

    2014-01-01

    Full Text Available The relaxation period of the accelerated ac-dc-ac test for coatings is associated with the transient electrochemistry that occurs when the immersed coated system is allowed to return to a stable open-circuit condition after being subjected to a cathodic potential. A mathematical model of the transient electrochemistry that occurs during this relaxation period is presented for coated aluminum. Expressions for the corrosion potential and corrosion current as functions of the local pH at the metal-coating interface were developed using reported experimental results. These expressions enabled the simulation of the transient electrochemistry under the constraint of balanced anodic and cathodic current densities. Regression of the transient relaxation potential profiles to exponential decay functions provided time-constant characterization of the profiles. Simulated results are presented that demonstrate the influences of the coating's porosity and thickness, the applied dc potential and the metal-coating interface condition on the time-constants associated with the relaxation profile. Interpretation of experimentally reported relaxation potential profiles supported the analysis of the simulated results.

  15. Mechanical spectroscopy of thermal stress relaxation in aluminium alloys reinforced with short alumina fibres

    Energy Technology Data Exchange (ETDEWEB)

    Carreno-Morelli, E.; Schaller, R. [Ecole Polytechnique Federale, Lausanne (Switzerland). Inst. de Genie Atomique; Urreta, S.E.

    1998-05-01

    The mechanical behaviour under low temperature thermal cycling of aluminium-based composites reinforced with short Al{sub 2}O{sub 3} SAFFIL fibres has been investigated by mechanical spectroscopy (mechanical loss and elastic shear modulus measurements). A mechanical loss maximum has been observed during cooling which originates in the relaxation of thermal stresses at the interfaces due to the differential thermal expansion between matrix and reinforcement. The maximum height increases with the volumetric fibre content. In addition, if the matrix strength is increased by the appropriated choice of alloy and thermal treatment, the maximum diminishes and shifts to lower temperatures. No damage accumulation at the interfaces has been detected during long period thermal cycling in the range 100 to 500 K. A description of the damping behaviour is made in terms of the development of microplastic zones which surround the fibres. (orig.) 9 refs.

  16. Stress-Relaxation Behavior of Magnesium-3Gadolinium-2Calcium-Based Alloys at Elevated Temperatures

    Science.gov (United States)

    Mo, Ning; Tan, Qiyang; Jiang, Bin; Pan, Fusheng; Zhang, Ming-Xing

    2017-11-01

    Based on previously published work on binary Mg alloys by Abaspour et al. and on the magnesium (Mg)-6gadolinium (Gd)-2zinc (Zn)-0.6zirconium (Zr) (wt pct) alloy reported by Nie et al., a number of new lower-cost Mg-3Gd-2calcium (Ca) (wt pct)-based creep-resistant magnesium alloys were developed by replacing part of the Gd with Ca. After solution treatment at 793 K (520 °C), the Ca-containing alloys exhibited an increased strength and a reduced stress relaxation at 453 K (180 °C) compared with the Mg-6Gd-2Zn-0.6Zr (wt pct) alloy. This work indicates that the replacement of Gd with Ca is a promising approach to develop lower-cost Mg alloys with an improved creep resistance. The results support the hypothesis that the short-range order of solutes governs the creep behavior of magnesium alloys.

  17. The change in body stressed to relaxed body through breathing, visualization and a protective environment together

    Directory of Open Access Journals (Sweden)

    Evelyn I. Rodríguez Morrill

    2009-11-01

    Full Text Available This work shows several ways to meet and relax the body through personal knowledge and techniques encounter with nature. Modern life and fast, the constant pressure from childhood to adulthood, in the modes of interaction between individuals and groups, they lead to construction of bodies that reflect emotional anatomy visible loss of balance, contractures, inflammation, multiple imbalances by lack of knowledge and awareness especially being in the world fully, the person has moved away from its ecological relationship with itself and the environment. Methods are shown to positively change a condition of constant stress and chronic discomfort, a learned condition of physical and psychological wellbeing, with a series of movements, recovering the body through exercise, to tend to personal balance, obtaining a positive relationship with the environment and the people attended. The proposal starts promoting new habits that can be saved in consciousness. Partly, mainly of breath, alignment with the music and the environment and personal and group work

  18. Statistics of energy dissipation and stress relaxation in a crumpling network of randomly folded aluminum foils

    Science.gov (United States)

    Balankin, Alexander S.; Susarrey Huerta, Orlando; Tapia, Viktor

    2013-09-01

    We study stress relaxation in hand folded aluminum foils subjected to the uniaxial compression force F(λ). We found that once the compression ratio is fixed (λ=const) the compression force decreases in time as F∝F0P(t), where P(t) is the survival probability time distribution belonging to the domain of attraction of max-stable distribution of the Fréchet type. This finding provides a general physical picture of energy dissipation in the crumpling network of a crushed elastoplastic foil. The difference between energy dissipation statistics in crushed viscoelastic papers and elastoplastic foils is outlined. Specifically, we argue that the dissipation of elastic energy in crushed aluminum foils is ruled by a multiplicative Poisson process governed by the maximum waiting time distribution. The mapping of this process into the problem of transient random walk on a fractal crumpling network is suggested.

  19. Contribution to viscosity from the structural relaxation via the atomic scale Green-Kubo stress correlation function.

    Science.gov (United States)

    Levashov, V A

    2017-11-14

    We studied the connection between the structural relaxation and viscosity for a binary model of repulsive particles in the supercooled liquid regime. The used approach is based on the decomposition of the macroscopic Green-Kubo stress correlation function into the correlation functions between the atomic level stresses. Previously we used the approach to study an iron-like single component system of particles. The role of vibrational motion has been addressed through the demonstration of the relationship between viscosity and the shear waves propagating over large distances. In our previous considerations, however, we did not discuss the role of the structural relaxation. Here we suggest that the contribution to viscosity from the structural relaxation can be taken into account through the consideration of the contribution from the atomic stress auto-correlation term only. This conclusion, however, does not mean that only the auto-correlation term represents the contribution to viscosity from the structural relaxation. Previously the role of the structural relaxation for viscosity has been addressed through the considerations of the transitions between inherent structures and within the mode-coupling theory by other authors. In the present work, we study the structural relaxation through the considerations of the parent liquid and the atomic level stress correlations in it. The comparison with the results obtained on the inherent structures also is made. Our current results suggest, as our previous observations, that in the supercooled liquid regime, the vibrational contribution to viscosity extends over the times that are much larger than the Einstein's vibrational period and much larger than the times that it takes for the shear waves to propagate over the model systems. Besides addressing the atomic level shear stress correlations, we also studied correlations between the atomic level pressure elements.

  20. Contribution to viscosity from the structural relaxation via the atomic scale Green-Kubo stress correlation function

    Science.gov (United States)

    Levashov, V. A.

    2017-11-01

    We studied the connection between the structural relaxation and viscosity for a binary model of repulsive particles in the supercooled liquid regime. The used approach is based on the decomposition of the macroscopic Green-Kubo stress correlation function into the correlation functions between the atomic level stresses. Previously we used the approach to study an iron-like single component system of particles. The role of vibrational motion has been addressed through the demonstration of the relationship between viscosity and the shear waves propagating over large distances. In our previous considerations, however, we did not discuss the role of the structural relaxation. Here we suggest that the contribution to viscosity from the structural relaxation can be taken into account through the consideration of the contribution from the atomic stress auto-correlation term only. This conclusion, however, does not mean that only the auto-correlation term represents the contribution to viscosity from the structural relaxation. Previously the role of the structural relaxation for viscosity has been addressed through the considerations of the transitions between inherent structures and within the mode-coupling theory by other authors. In the present work, we study the structural relaxation through the considerations of the parent liquid and the atomic level stress correlations in it. The comparison with the results obtained on the inherent structures also is made. Our current results suggest, as our previous observations, that in the supercooled liquid regime, the vibrational contribution to viscosity extends over the times that are much larger than the Einstein's vibrational period and much larger than the times that it takes for the shear waves to propagate over the model systems. Besides addressing the atomic level shear stress correlations, we also studied correlations between the atomic level pressure elements.

  1. Effects of stress and relaxation on pain perception in subjects with pain-free occlusional disharmony compared with healthy controls.

    Science.gov (United States)

    Ruscheweyh, R; Becker, T; Born, Y; Çolak-Ekici, R; Marziniak, M; Evers, S; Gerlach, A L; Wolowski, A

    2015-04-01

    The significance of occlusal disharmony for the development of painful temporomandibular disorder (TMD) is controversial. The ongoing biomechanical strain caused by occlusal disharmony might lead to sensitization processes in the nociceptive system. Understanding these processes might be an important step toward understanding the possible relationship between occlusal disharmony and TMD. In this study, we therefore investigated whether subjects with occlusal disharmony (n = 22) differ from healthy controls (n = 26) in their pain perception and pain modulation by stress and relaxation. Trigeminal and extratrigeminal experimental pain perception (pinprick, heat, and pressure pain) was assessed before and after stress (mental arithmetic) and relaxation (viewing of low-arousal pictures). There were no group differences in pain perception at baseline or during the stress task. Compared with controls, the occlusal disharmony group exhibited an inadequate reduction in pain perception during relaxation, which was significant for the extratrigeminal site (P < 0.01) and reached a trend for significance at the trigeminal site (P = 0.1). These results suggest that subjects with occlusal disharmony show signs of disturbed endogenous pain inhibition during relaxation. There is evidence for the presence of sensitization of the nociceptive system in subjects with occlusal disharmony. Possibly, deficient inhibition of extratrigeminal and trigeminal pain perception by relaxation might contribute to the development of TMD or other chronic pain disorders. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  2. Mesures de contraintes in-situ. Méthode de relaxation des carottes Measuring in-Situ Stresses. Relaxation Method with Core Samples

    Directory of Open Access Journals (Sweden)

    Perreau P.

    2006-11-01

    Full Text Available Dans cet article, on se propose de présenter les premiers résultats de l'étude de la méthode d'évaluation des contraintes par mesure de déformations différées d'une carotte après son extraction. Le travail correspondant a été réalisé dans le cadre du projet ARTEP Fracturation hydraulique . Les principes de cette méthode et les quelques éléments d'interprétation récemment publiés dans la littérature sont exposés dans un premier temps. Les résultats de deux campagnes de mesures sur deux puits de la SNEA-P (Soudron, novembre 1985 et Lanot, juillet 1986 sont ensuite présentés. Ces essais ont mis en évidence que les déformations différées d'une carotte dues au relachement des contraintes sont effectivement mesurables. Cependant, une interprétation quantitative de ces mesures nécessite une amélioration des conditions expérimentales (stabilisation thermique, stabilisation de l'état de saturation. This article describes the first results of research on a method of evaluating stresses by measuring the differred deformations of a core sample after it has been extracted. The corresponding research was done within the framework of an ARTEP project on Hydraulic Fracturing . The principles of this method and several interpretation aspects published recently in the literature are described in the first part. Then the results of two measurement campaigns using two SNEA-P wells (Soudron in November 1985 and Lanot in July 1986 are described. These tests revealed that the differed deformations of a core sample due to the relaxing of stresses can effectively be measured. However, a quantitative interpretation of these measurements requires an improvement to be made in the experimental conditions (thermal stabilization, stabilization of the state of saturation.

  3. 77 FR 61238 - Annual Stress Test

    Science.gov (United States)

    2012-10-09

    ... Office of the Comptroller of the Currency 12 CFR Part 46 RIN 1557-AD58 Annual Stress Test AGENCY: Office...'') which requires certain companies to conduct annual stress tests pursuant to regulations prescribed by... ``covered institutions'') to conduct an annual stress test as prescribed by this rule. Under the final rule...

  4. 77 FR 16484 - Annual Stress Test

    Science.gov (United States)

    2012-03-21

    ... Office of the Comptroller of the Currency 12 CFR Part 46 RIN 1557-AD58 Annual Stress Test AGENCY: Office... with total consolidated assets of more than $10 billion to conduct an annual stress test and comply... consolidated assets in excess of $10 billion to conduct annual stress tests pursuant to regulations prescribed...

  5. Functional Connectivity During Exposure to Favorite-Food, Stress, and Neutral-Relaxing Imagery Differs Between Smokers and Nonsmokers.

    Science.gov (United States)

    Garrison, Kathleen A; Sinha, Rajita; Lacadie, Cheryl M; Scheinost, Dustin; Jastreboff, Ania M; Constable, R Todd; Potenza, Marc N

    2016-09-01

    Tobacco-use disorder is a complex condition involving multiple brain networks and presenting with multiple behavioral correlates including changes in diet and stress. In a previous functional magnetic resonance imaging (fMRI) study of neural responses to favorite-food, stress, and neutral-relaxing imagery, smokers versus nonsmokers demonstrated blunted corticostriatal-limbic responses to favorite-food cues. Based on other recent reports of alterations in functional brain networks in smokers, the current study examined functional connectivity during exposure to favorite-food, stress, and neutral-relaxing imagery in smokers and nonsmokers, using the same dataset. The intrinsic connectivity distribution was measured to identify brain regions that differed in degree of functional connectivity between groups during each imagery condition. Resulting clusters were evaluated for seed-to-voxel connectivity to identify the specific connections that differed between groups during each imagery condition. During exposure to favorite-food imagery, smokers versus nonsmokers showed lower connectivity in the supramarginal gyrus, and differences in connectivity between the supramarginal gyrus and the corticostriatal-limbic system. During exposure to neutral-relaxing imagery, smokers versus nonsmokers showed greater connectivity in the precuneus, and greater connectivity between the precuneus and the posterior insula and rolandic operculum. During exposure to stress imagery, smokers versus nonsmokers showed lower connectivity in the cerebellum. These findings provide data-driven insights into smoking-related alterations in brain functional connectivity patterns related to appetitive, relaxing, and stressful states. This study uses a data-driven approach to demonstrate that smokers and nonsmokers show differential patterns of functional connectivity during guided imagery related to personalized favorite-food, stress, and neutral-relaxing cues, in brain regions implicated in attention

  6. No Stress! Relax! Mechanisms Governing Growth and Shape in Plant Cells

    Directory of Open Access Journals (Sweden)

    Gea Guerriero

    2014-03-01

    Full Text Available The mechanisms through which plant cells control growth and shape are the result of the coordinated action of many events, notably cell wall stress relaxation and turgor-driven expansion. The scalar nature of turgor pressure would drive plant cells to assume spherical shapes; however, this is not the case, as plant cells show an amazing variety of morphologies. Plant cell walls are dynamic structures that can display alterations in matrix polysaccharide composition and concentration, which ultimately affect the wall deformation rate. The wide varieties of plant cell shapes, spanning from elongated cylinders (as pollen tubes and jigsaw puzzle-like epidermal cells, to very long fibres and branched stellate leaf trichomes, can be understood if the underlying mechanisms regulating wall biosynthesis and cytoskeletal dynamics are addressed. This review aims at gathering the available knowledge on the fundamental mechanisms regulating expansion, growth and shape in plant cells by putting a special emphasis on the cell wall-cytoskeleton system continuum. In particular, we discuss from a molecular point of view the growth mechanisms characterizing cell types with strikingly different geometries and describe their relationship with primary walls. The purpose, here, is to provide the reader with a comprehensive overview of the multitude of events through which plant cells manage to expand and control their final shapes.

  7. The nonlinear Maxwell-type model for viscoelastoplastic materials: simulation of temperature influence on creep, relaxation and strain-stress curves

    Directory of Open Access Journals (Sweden)

    Andrew V. Khokhlov

    2017-04-01

    restrictions on material functions and their comparison to typical test curves of stable viscoelastoplastic materials. It is proved that the viscosity coefficient and the “modulus of elasticity” of the model and their ratio (i.e. relaxation time of the associated linear Maxwell model should be decreasing functions of temperature. This requirements are proved to provide an adequate qualitative simulation of a dozen basic phenomena expressing an increase of material compliance (a decrease of tangent modulus and yield stress, in particular, strengthening of strain rate sensitivity and acceleration of dissipation, relaxation, creep and plastic strain accumulation with temperature growth.

  8. Analysis of Cantilever-Beam Bending Stress Relaxation Properties of Thin Wood Composites

    Science.gov (United States)

    John F. Hunt; Houjiang Zhang; Yan Huang

    2015-01-01

    An equivalent strain method was used to analyze and determine material relaxation properties for specimens from particleboard, high density fiberboard, and medium density fiberboard. Cantilever beams were clamped and then deflected to 11 m and held for either 2 h or 3 h, while the load to maintain that deflection was measured vs. time. Plots of load relaxation for each...

  9. Work-related stress, inability to relax after work and risk of adult asthma: a population-based cohort study.

    Science.gov (United States)

    Loerbroks, A; Gadinger, M C; Bosch, J A; Stürmer, T; Amelang, M

    2010-10-01

    There is an extensive literature linking stressful work conditions to adverse health outcomes. Notwithstanding, the relationship with asthma has not been examined, although various other measures of psychological stress have been associated with asthma. Therefore, we aimed to investigate the relation between work stress and asthma prevalence and incidence. We used data from a population-based cohort study (n = 5114 at baseline in 1992-1995 and n = 4010 at follow-up in 2002/2003). Asthma was measured by self-reports. Two scales that assessed psychologically adverse work conditions were extracted from a list of work-condition items by factor analysis (these scales were termed 'work stress' and 'inability to relax after work'). For each scale, the derived score was employed both as continuous z-score and as categorized variable in analyses. Associations with asthma were estimated by prevalence ratios (PRs) and risk ratios (RRs) using Poisson regression with a log-link function adjusting for demographics, health-related lifestyles, body mass index and family history of asthma. Analyses were restricted to those in employment (n = 3341). Work stress and inability to relax z-scores were positively associated with asthma prevalence (PR = 1.15, 95%CI = 0.97, 1.36 and PR = 1.43, 95%CI = 1.12, 1.83, respectively). Prospective analyses using z-scores showed that for each 1 standard deviation increase in work stress and inability to relax, the risk of asthma increased by approximately 40% (RR for work stress = 1.46, 95%CI = 1.06, 2.00; RR for inability to relax = 1.39, 95%CI = 1.01, 1.91). Similar patterns of associations were observed in analyses of categorized exposures. This is the first study to show a cross-sectional and longitudinal association of work stress with asthma.

  10. The effects of progressive muscular relaxation as a nursing procedure used for those who suffer from stress due to multiple sclerosis.

    Science.gov (United States)

    Novais, Paolla Gabrielle Nascimento; Batista, Karla de Melo; Grazziano, Eliane da Silva; Amorim, Maria Helena Costa

    2016-09-01

    to evaluate the effect of progressive muscle relaxation as a nursing procedure on the levels of stress for sufferers of multiple sclerosis. random clinical trials conducted at the Neurology outpatients unit at a University Hospital. The sample consisted of 40 patients who were being monitored as outpatients (20 in a control group and 20 in an experimental group). The Progressive Muscle Relaxation technique was used. The control variables were collected through interviews that were recorded on forms and on the Perceived Stress Scale that we used. Five meetings were held every fortnight covering a period of eight weeks. The experimental group was advised to carry out daily progressive muscle relaxation activities. After eight weeks of these activities, they were evaluated again to measure their levels of stress. In order to analyze the data used, the software package Statistics for Social Sciences version 19.0 was used. the application of the t test showed a significant reduction in the Perceived Stress Scale scores in the experimental group (pCiencias Sociales versión 19.0. la aplicación de la Prueba t demostró una disminución significativa de los puntajes de la Escala de Estrés Percibido en el grupo experimental (p<0,001), evidenciando la disminución de los niveles de estrés después de la práctica del relajamiento. la intervención Relajamiento Muscular Progresivo contribuye para reducir los niveles de estrés en personas con Esclerosis Múltiple, pudiendo ésta ser incluida como práctica en la asistencia de enfermería prestada a esos pacientes. NCT 02673827.

  11. β-distribution for Reynolds stress and turbulent heat flux in relaxation turbulent boundary layer of compression ramp

    Science.gov (United States)

    Hu, YanChao; Bi, WeiTao; Li, ShiYao; She, ZhenSu

    2017-12-01

    A challenge in the study of turbulent boundary layers (TBLs) is to understand the non-equilibrium relaxation process after sep-aration and reattachment due to shock-wave/boundary-layer interaction. The classical boundary layer theory cannot deal with the strong adverse pressure gradient, and hence, the computational modeling of this process remains inaccurate. Here, we report the direct numerical simulation results of the relaxation TBL behind a compression ramp, which reveal the presence of intense large-scale eddies, with significantly enhanced Reynolds stress and turbulent heat flux. A crucial finding is that the wall-normal profiles of the excess Reynolds stress and turbulent heat flux obey a β-distribution, which is a product of two power laws with respect to the wall-normal distances from the wall and from the boundary layer edge. In addition, the streamwise decays of the excess Reynolds stress and turbulent heat flux also exhibit power laws with respect to the streamwise distance from the corner of the compression ramp. These results suggest that the relaxation TBL obeys the dilation symmetry, which is a specific form of self-organization in this complex non-equilibrium flow. The β-distribution yields important hints for the development of a turbulence model.

  12. Diazepam and Jacobson's progressive relaxation show similar attenuating short-term effects on stress-related brain glucose consumption.

    Science.gov (United States)

    Pifarré, P; Simó, M; Gispert, J-D; Plaza, P; Fernández, A; Pujol, J

    2015-02-01

    A non-pharmacological method to reduce anxiety is "progressive relaxation" (PR). The aim of the method is to reduce mental stress and associated mental processes by means of progressive suppression of muscle tension. The study was addressed to evaluate changes in brain glucose metabolism induced by PR in patients under a stressing state generated by a diagnostic medical intervention. The effect of PR was compared to a dose of sublingual diazepam, with the prediction that both interventions would be associated with a reduction in brain metabolism. Eighty-four oncological patients were assessed with 18F-fluorodeoxyglucose-positron emission tomography. Maps of brain glucose distribution from 28 patients receiving PR were compared with maps from 28 patients receiving sublingual diazepam and with 28 patients with no treatment intervention. Compared to reference control subjects, the PR and diazepam groups showed a statistically significant, bilateral and generalized cortical hypometabolism. Regions showing the most prominent changes were the prefrontal cortex and anterior cingulate cortex. No significant differences were identified in the direct comparison between relaxation technique and sublingual diazepam. Our findings suggest that relaxation induced by a physical/psychological procedure can be as effective as a reference anxiolytic in reducing brain activity during a stressful state. Copyright © 2014 Elsevier Masson SAS. All rights reserved.

  13. Multistep stress-relaxation study of a single crystal of n-eicosane (C20H42) in torsion

    Science.gov (United States)

    Crissman, J. M.

    1989-07-01

    Multistep stress-relaxation experiments in torsion have been done on a single crystal of the long-chain hydrocarbon compound n-eicosane. It was found that at very small strains the behavior approaches that of a linear viscoelastic material, whereas at larger strains the behavior becomes increasingly nonlinear and time dependent. In the region where the stress-strain behavior becomes nonlinear, it is shown that the second-step response, in an experiment in which the magnitude of the second step is one half that of the first step, can be described very well using a recent constitutive equation proposed by Zapas.

  14. Numerical Investigation of the Role of Volumetric Transformation Strain on the Relaxation Stress and the Corresponding Hydrogen Interstitial Concentration in Niobium Matrix

    Directory of Open Access Journals (Sweden)

    Burak Bal

    2017-01-01

    Full Text Available The effects of relaxation stress on the hydrogen concentration in Niobium- (Nb- H media were investigated by iterative numerical modeling approach. To calculate the transformation strain, relaxation stress, and corresponding relaxed hydrogen concentration around an edge dislocation, a new third-order polynomial formulation was utilized in the model. With the aid of this polynomial, hydrogen induced relaxation stress never exceeds the dislocation stress, which indicates that the total stress field never turns to compressive state and diverges the results. The current model calculates the hydrogen concentration not only in the vicinity of an edge dislocation but also far away from the dislocation. Furthermore, the effect of relaxation stress on the interaction energy was also captured in the model. Overall, the current findings shed light on the complicated hydrogen embrittlement mechanisms of metallic materials by demonstrating that hydrogen induced relaxation has a significant effect on the hydrogen atom concentration and the interaction energy between the existing internal stress field and the solute hydrogen atom.

  15. Stress Testing with Student's t Dependence

    NARCIS (Netherlands)

    H.J.W.G. Kole (Erik); C.G. Koedijk (Kees); M.J.C.M. Verbeek (Marno)

    2003-01-01

    textabstractIn this study we propose the use of the Student's t dependence function to model dependence between asset returns when conducting stress tests. To properly include stress testing in a risk management system, it is important to have accurate information about the (joint) probabilities of

  16. Prevalence and pattern of stress relaxation practices in Ahmedabad city: A cross-sectional study

    Science.gov (United States)

    Nayak, Himanshu K; Sonia, Batra; Kapoor, Rachna; Gadhavi, Rajendra; Solanki, Anand; Vyas, Sheetal; Tiwari, Hemant

    2011-01-01

    Background: Research has shown the growing importance of stress relaxation practices (SRPs) in many noncommunicable diseases. But there is little information on the prevalence of SRPs in Indian population. Objectives: To study the prevalence of different types of SRPs and their sociodemographic profile. Materials and Methods: A community-based cross-sectional study was carried out in Ahmedabad city, Gujarat, India. One ward from each zone of the city was selected by stratified sampling. All individuals above 20 years were included in the study. Detailed information regarding different SRPs practiced by the participants was collected in a standard pretested proforma by house-to-house survey. Univariate regression analysis was applied to compare the groups. Results: Of 1157 persons surveyed, 904 were included in the final analysis. Of these, 310 (34.3%) were doing SRPs and 594 (65.7%) were not doing any type of SRPs. Respondents doing SRPs were compared with non-SRP group. Significant (P<0.05) differences were noticed between the two groups; in females, it was (SRP 58.4% vs non-SRP 49.8%) in the age group 40 to 59 years (44.2 vs 33.8%), those from sedentary occupation (93.9% vs 85.4%), the persons belonging to upper socioeconomic status (70.6% vs 61.8%), and living in central and western zones (66.5% vs 24.6%) and had less number of diabetes (SRP 10.8% vs non-SRP 19.7%) and hypertension (20.7% vs 34.2%). People doing SRPs were able to maintain balance between work and other activities than non-SRPs group (198/310, 63.9% vs 42/594, 7.1%). Among SRPs, majority (243, 78.4%) were involved in religious activities followed by yoga, 36(11.6%), and meditation, 15 (4.8%). Conclusion: Persons practicing SRPs in Ahmedabad are more likely to be above 40 years of age, females, college educated, in sedentary occupation, from upper and middle class, married and living in new-west and central zones, and were less likely to have diabetes and hypertension as compared with those who do

  17. Stress relaxation experiments on a lamellar polystyrene-polyisoprene diblock copolymer melt

    DEFF Research Database (Denmark)

    Holmqvist, P.; Castelletto, V.; Hamley, I.W.

    2001-01-01

    via dynamic light scattering experiments. The slowest relaxation process may be related to the shear-induced orientation of the lamellae. It is shown that time-strain separability G(t, gamma)= G(t)h(gamma) can be applied, and the damping function h(gamma) is consistent with a strongly strain...

  18. Coping with a stressful sigmoidoscopy: evaluation of cognitive and relaxation preparations.

    Science.gov (United States)

    Kaplan, R M; Atkins, C J; Lenhard, L

    1982-03-01

    Sigmoidoscopy involves the insertion of a small scope into the anal cavity to inspect for abnormalities in the colon. Although the procedure is not believed to be painful, it is often noxious for patients because it produces embarassment and discomfort. We examined the effectiveness of two brief interventions designed to enhance coping: self-instructional training and relaxation. In the self-instructional conditions patients were given brief training to focus their attention on either their own (internal) or the doctor's (external) ability to regulate the situation. A third (control) group received attention but did not experience self-instructional training. Half of each of these three groups also received relaxation training, while the other half did not. Planned comparisons demonstrated that subjects in the self-instructional strategies rated themselves as less anxious, had fewer body movements during the exam, and emitted fewer verbalization than those in an attention control group. Patients in the external condition estimated that the exam took less time but tended to have elevated heart rates during the procedure. Those experiencing relaxation training tended to overestimate the duration of the exam, but made fewer requests to stop the exam and rated themselves as less anxious than patients who did not receive relaxation training.

  19. The contribution of time-dependent stress relaxation in protein gels to the recoverable energy that is used as a tool to describe food texture

    Science.gov (United States)

    de Jong, Saskia; van Vliet, Ton; de Jongh, Harmen H. J.

    2015-11-01

    The recoverable energy (RE), defined as the ratio of the work exerted on a test specimen during compression and recovered upon subsequent decompression, has been shown to correlate to sensory profiling of protein-based food products. Understanding the mechanism determining the time-dependency of RE is primordial. This work aims to identify the protein-specific impact on the recoverable energy by stress dissipation via relaxation of (micro)structural rearrangements within protein gels. To this end, caseinate and gelatin gels are studied for their response to time-dependent mechanical deformation as they are known to develop structurally distinct network morphologies. This work shows that in gelatin gels no significant stress relaxation occurs on the seconds timescale, and consequently no time-dependency of the amount of energy stored in this material is observed. In caseinate gels, however, the energy dissipation via relaxation processes does contribute significantly to the time-dependency of reversible stored energy in the network. This can explain the obtained RE as a function of applied deformation at slow deformation rates. At faster deformation, an additional contribution to the dissipated energy is apparent, that increases with the deformation rate, which might point to the role of energy dissipation related to friction of the serum entrapped by the protein-network. This work shows that engineering strategies focused on controlling viscous flow in protein gels could be more effective to dictate the ability to elastically store energy in protein gels than routes that direct protein-specific aggregation and/or network-assembly.

  20. Stress testing - ettevaatliku investori abimees / Peeter Teder

    Index Scriptorium Estoniae

    Teder, Peeter

    2005-01-01

    Autor selgitab stress testingut kui investeerimisportfelli varade väärtuse hindamist ning tutvustab selle võimalusi ja ohtusid. Diagrammid: Portfelli testimis-stsenaariumiks sobivad hästi börsikrahhid. Vt. samas: Stress testing toimib ka mujal

  1. On the effects of thermal history on the development and relaxation of thermo-mechanical stress in cryopreservation

    Science.gov (United States)

    Eisenberg, David P.; Steif, Paul S.; Rabin, Yoed

    2014-11-01

    This study investigates the effects of the thermal protocol on the development and relaxation of thermo-mechanical stress in cryopreservation by means of glass formation, also known as vitrification. The cryopreserved medium is modeled as a homogeneous viscoelastic domain, constrained within either a stiff cylindrical container or a highly compliant bag. Annealing effects during the cooling phase of the cryopreservation protocol are analyzed. Results demonstrate that an intermediate temperature-hold period can significantly reduce the maximum tensile stress, thereby decreasing the potential for structural damage. It is also demonstrated that annealing at temperatures close to glass transition significantly weakens the dependency of thermo-mechanical stress on the cooling rate. Furthermore, a slower initial rewarming rate after cryogenic storage may drastically reduce the maximum tensile stress in the material, which supports previous experimental observations on the likelihood of fracture at this stage. This study discusses the dependency of the various stress components on the storage temperature. Finally, it is demonstrated that the stiffness of the container wall can affect the location of maximum stress, with implications on the development of cryopreservation protocols.

  2. Study on the effect of post weld heat treatment parameters on the relaxation of welding residual stresses in electron beam welded P91 steel plates

    OpenAIRE

    Venkata, K. Abburi; Kumar, S.; Dey, H.C.; Smith, D. J.; Bouchard, P J; Truman, C.E

    2014-01-01

    Residual stresses are created by localised heating effects that occur during the welding process. Post weld heat treatment (PWHT) is the most convenient method for stress relief of welds. But PWHT cannot completely eliminate the residual stresses. So, it is essential to determine the influence of PWHT parameters like holding temperature and time on the stress relaxation for optimising the process. The selected material is modified 9Cr-1Mo (Grade 91) steel in the form of plates welded together...

  3. Modeling Reliability Growth in Accelerated Stress Testing

    Science.gov (United States)

    2013-12-01

    and E. Elsayed, "A general accelerated life model for step stress testing," IIE Transactions , vol. 37, no. 11, pp. 1059-1069, 2005. [57] D. Nicholls...W. Nelson, "Accelerated Life Testing - step-stress models and data analyses," IEEE Transactions on Reliability, vol. 29, pp. 103-108, 1980. [19] G...34 IEEE Transactions on Reliability, Vols. R-26, no. 5, pp. 348-351, 1977. [35] D. E. Olsen, "Estimating reliability growth," IEEE Transactions on

  4. Liquid salt environment stress-rupture testing

    Energy Technology Data Exchange (ETDEWEB)

    Ren, Weiju; Holcomb, David E.; Muralidharan, Govindarajan; Wilson, Dane F.

    2016-03-22

    Disclosed herein are systems, devices and methods for stress-rupture testing selected materials within a high-temperature liquid salt environment. Exemplary testing systems include a load train for holding a test specimen within a heated inert gas vessel. A thermal break included in the load train can thermally insulate a load cell positioned along the load train within the inert gas vessel. The test specimen can include a cylindrical gage portion having an internal void filled with a molten salt during stress-rupture testing. The gage portion can have an inner surface area to volume ratio of greater than 20 to maximize the corrosive effect of the molten salt on the specimen material during testing. Also disclosed are methods of making a salt ingot for placement within the test specimen.

  5. Seedling quality tests: plant moisture stress

    Science.gov (United States)

    Gary Ritchie; Thomas D. Landis

    2005-01-01

    This is the fifth installment in our review of seedling quality tests. Here we focus on what is commonly known as "plant moisture stress" or PMS. Although PMS is not routinely used for seedling quality testing per se, it is nevertheless the most common physiological measurement made on reforestation stock. This is because the measurement itself is simple and...

  6. Analysis/test correlation using VAWT-SDS on a step-relaxation test for the rotating Sandia 34 m test bed

    Energy Technology Data Exchange (ETDEWEB)

    Argueello, J.G.; Dohrmann, C.R.; Carne, T.G.; Veers, P.S.

    1993-11-01

    The combined analysis/test effort described in this paper compares predictions with measured data from a step-relaxation test in the absence of significant wind-driven aerodynamic loading. The process described here is intended to illustrate a method for validation of time domain codes for structural analysis of wind turbine structures. Preliminary analyses were performed to investigate the transient dynamic response that the rotating Sandia 34 m Vertical Axis Wind Turbine (VAWT) would undergo when one of the two blades was excited by step-relaxation. The calculations served two purposes. The first was for pretest planning to evaluate the relative importance of the various forces that would be acting on the structure during the test and to determine if the applied force in the step-relaxation would be sufficient to produce an excitation that was distinguishable from that produced by the aerodynamic loads. The second was to provide predictions that could subsequently be compared to the data from the test. The test was carried out specifically to help in the validation of the time-domain structural dynamics code, VAWT-SDS, which predicts the dynamic response of VAWTs subject to transient events. Post-test comparisons with the data were performed and showed a qualitative agreement between pretest predictions and measured response. However, they also showed that there was significantly more damping in the measurements than included in the predictions. Efforts to resolve this difference, including post-test analyses, were undertaken and are reported herein. The overall effort described in this paper represents a major step in the process of arriving at a validated structural dynamics code.

  7. Stress Relaxation by Addition-Fragmentation Chain Transfer in Highly Crosslinked Thiol-Yne Networks

    OpenAIRE

    Park, Hee Young; Kloxin, Christopher J.; Scott, Timothy F.; Bowman, Christopher N.

    2010-01-01

    Radical mediated addition-fragmentation chain transfer of mid-chain allyl sulfide functional groups was utilized to reduce polymerization-induced shrinkage stress in thiol-yne step-growth photopolymerization reactions. In previous studies, the addition-fragmentation of allyl sulfide during the polymerization of a step-growth thiol-ene network demonstrated reduced polymerization stress; however, the glass transition temperature of the material was well below room temperature (~ −20°C). Many ap...

  8. Pad stress tests with increasing load for the diagnosis of stress urinary incontinence.

    Science.gov (United States)

    Rimstad, Liv; Larsen, Elsa Skjønhaug; Schiøtz, Hjalmar A; Kulseng-Hanssen, Sigurd

    2014-09-01

    The aim of the study was to test the ability of pad stress tests with increasing load (supine, jumping on the floor, and jumping on a trampoline) to document stress incontinence in subjectively stress incontinent women. In this prospective study 147 subjectively stress and mixed incontinent women performed consecutively the three pad stress tests with a bladder volume of 300 ml. Nineteen women performed a second trampoline pad stress test to test repeatability of the test. Nine continent women performed a trampoline pad stress test in order to determine if subjectively continent women would leak during the test. Seventy-two women (49%) leaked during the supine, 136 (93%) leaked during the jumping, and 146 (99%) leaked during the trampoline pad stress test. The differences between pad stress tests were significant with P trampoline pad stress tests was high at 0.8. None of the nine continent women leaked during the trampoline pad stress test. The supine pad stress test has low sensitivity and is therefore often falsely negative. The jumping pad stress test is a simple test to perform and is satisfactory for everyday use. Subjectively stress incontinent women who do not leak during the jumping pad stress test may perform a trampoline pad stress test to document stress incontinence. The trampoline pad stress test is also simple to perform and detected leakage in 91% of the women who did not leak during the jumping pad stress test. © 2013 Wiley Periodicals, Inc.

  9. The contrasting roles of creep and stress relaxation in the time-dependent deformation during in-situ cooling of a nickel-base single crystal superalloy.

    Science.gov (United States)

    Panwisawas, Chinnapat; D'Souza, Neil; Collins, David M; Bhowmik, Ayan

    2017-09-11

    Time dependent plastic deformation in a single crystal nickel-base superalloy during cooling from casting relevant temperatures has been studied using a combination of in-situ neutron diffraction, transmission electron microscopy and modelling. Visco-plastic deformation during cooling was found to be dependent on the stress and constraints imposed to component contraction during cooling, which mechanistically comprises creep and stress relaxation. Creep results in progressive work hardening with dislocations shearing the γ' precipitates, a high dislocation density in the γ channels and near the γ/γ' interface and precipitate shearing. When macroscopic contraction is restricted, relaxation dominates. This leads to work softening from a decreased dislocation density and the presence of long segment stacking faults in γ phase. Changes in lattice strains occur to a similar magnitude in both the γ and γ' phases during stress relaxation, while in creep there is no clear monotonic trend in lattice strain in the γ phase, but only a marginal increase in the γ' precipitates. Using a visco-plastic law derived from in-situ experiments, the experimentally measured and calculated stresses during cooling show a good agreement when creep predominates. However, when stress relaxation dominates accounting for the decrease in dislocation density during cooling is essential.

  10. 77 FR 3408 - Annual Stress Test

    Science.gov (United States)

    2012-01-24

    ... risks to the financial soundness of the covered institution, and may require a covered institution to... adverse outcomes across a set of risk types affecting aspects of the covered institution's financial... supervisory stress tests where applicable, and market assessments. B. Covered Institutions 1. National Banks...

  11. 77 FR 62417 - Annual Stress Test

    Science.gov (United States)

    2012-10-15

    ... because, due to the complexity of the rule's stress testing requirements, regional and community banks... covered banks no later than November 15 of each year, which aligns the development and issuance of the... geographic footprints be permitted to develop economic scenarios relevant to banks' regional operations. One...

  12. Modeling and adapting production environmental stress testing

    OpenAIRE

    Wilson, Simon

    2009-01-01

    PUBLISHED This study describes the production sampling environmental stress test (PSEST) process and the offline analysis conducted. Some of the key characteristics and parameters of the test are outlined. The analytical process is based on two types of regression model, each of which links a dependent variable (the log of time to failure in each dwell, or the log of the number failed in each dwell) to independent variables such as temperature and age. These two types of regres...

  13. THE EFFECT OF PROGRESSIVE MUSCULAR RELAXATION AND PSYCHOLOGICAL COUNSELING ON PHYSIOLOGICAL PARAMETERS DURING SURGICAL STRESS

    Directory of Open Access Journals (Sweden)

    Avnish

    2015-10-01

    Full Text Available Present study was carried out to study the effect of muscular relaxation technique and counseling on physiological parameters on subjects undergoing surgery. The study was conducted in 32 individuals between ages of 20 – 70 at Civil hospital, GMERS, Valsad and was compared with a control group (N=32 of the same age. The parameters recorded were arterial pulse, arterial blood pressure. The results show the significant differences in the recorded parameters in control ( n=34 and study group (n=33. Pulse rat e ( 75.54 to 80.17 , systolic ( 121.49 to 126.29 and diastolic blood pressure ( 80.4 to 84.23 values increased in preoperative period than on admission in the control group while study group showed decrease in the preoperative value compared to that on admi ssion Pulse rate ( 77.94 to 74.80, systolic ( 124.50 to 122.19 and diastolic blood pressure ( 82.88 to 81. The results obtained were analyzed for statistical significance. The results obtained were statistically significant

  14. Study of stress relief cracking in titanium stabilized austenitic stainless steel; Etude de la fissuration differee par relaxation d'un acier inoxydable austenitique stabilise au titane

    Energy Technology Data Exchange (ETDEWEB)

    Chabaud-Reytier, M

    1999-07-01

    The heat affected zone (HAZ) of titanium stabilised austenitic stainless steel welds (AISI 321) may exhibit a serious form of intercrystalline cracking during service at high temperature. This type of cracking, called 'stress relief cracking', is known to be due to work hardening but also to ageing: a fine and abundant intragranular Ti(C,N) precipitation appears near the fusion line and modifies the mechanical behaviour of the HAZ. This study aims to better know the accused mechanism and to succeed in estimating the risk of such cracking in welded junctions of 321 stainless steel. To analyse this embrittlement mechanism, and to assess the lifetime of real components, different HAZ are simulated by heat treatments applied to the base material which is submitted to various cold rolling and ageing conditions in order to reproduce the HAZ microstructure. Then, we study the effects of work hardening and ageing on the titanium carbide precipitation, on the mechanical (tensile and creep) behaviour of the resulting material and on its stress relief cracking sensitivity. It is shown that work hardening is the main parameter of the mechanism and that ageing do not favour crack initiation although it leads to titanium carbide precipitation. The role of this precipitation is also discussed. Moreover, a creep damage model is identified by a local approach to fracture. Materials sensitive to stress relief cracking are selected. Then, creep tests are carried out on notched bars in order to quantify the intergranular damage of these different materials; afterwards, these measurements are combined with calculated mechanical fields. Finally, it is shown that the model gives good results to assess crack initiation for a compact tension (CT) specimen during relaxation tests, as well as for a notched tubular specimen tested at 600 deg. C under a steady torque. (author)

  15. The contrasting roles of creep and stress relaxation in the time-dependent deformation during in-situ cooling of a nickel-base single crystal superalloy

    OpenAIRE

    Panwisawas, Chinnapat; D?Souza, Neil; David M. Collins; Bhowmik, Ayan

    2017-01-01

    Time dependent plastic deformation in a single crystal nickel-base superalloy during cooling from casting relevant temperatures has been studied using a combination of in-situ neutron diffraction, transmission electron microscopy and modelling. Visco-plastic deformation during cooling was found to be dependent on the stress and constraints imposed to component contraction during cooling, which mechanistically comprises creep and stress relaxation. Creep results in progressive work hardening w...

  16. Electrical resistivity change in amorphous Ta42Si13N45 films by stress relaxation

    Science.gov (United States)

    Nicolet, M.-A.; Ryser, M.; Romano, V.

    2015-03-01

    In a first experiment, a reactively sputtered amorphous Ta42Si13N45 film about 260 nm thick deposited on a flat and smooth alumina substrate was thermally annealed in air for 30 min and let cooled again repeatedly at successively higher temperatures from 200 to 500 °C. This treatment successively and irreversibly increases the room temperature resistivity of the film monotonically from its initial value of 670 μΩ cm to a maximum of 705 μΩ cm (+5.2 %). Subsequent heat treatments at temperatures below 500 °C and up to 6 h have no further effect on the room temperature resistivity. The new value remains unchanged after 3.8 years of storage at room temperature. In a second experiment, the evolution of the initially compressive stress of a film similarly deposited by reactive sputtering on a 2-inch silicon wafer was measured by tracking the wafer curvature during similar thermal annealing cycles. A similar pattern of irreversible and reversible changes of stress was observed as for the film resistivity. Transmission electron micrographs and secondary ion mass profiles of the film taken before and after thermal annealing in air establish that both the structure and the composition of the film scarcely change during the annealing cycles. We reason that the film stress is implicated in the resistivity change. In particular, to interpret the observations, a model is proposed where the interface between the film and the substrate is mechanically unyielding.

  17. Stress Relaxation in a Perfect Nanocrystal by Coherent Ejection of Lattice Layers

    Science.gov (United States)

    Chaudhuri, Abhishek; Sengupta, Surajit; Rao, Madan

    2005-12-01

    We show that a small crystal trapped within a potential well and in contact with its own fluid responds to large compressive stresses by a novel mechanism—the transfer of complete lattice layers across the solid-fluid interface. Further, when the solid is impacted by a momentum impulse set up in the fluid, a coherently ejected lattice layer carries away a definite quantity of energy and momentum, resulting in a sharp peak in the calculated phonon absorption spectrum. Apart from its relevance to studies of stability and failure of small sized solids, such coherent nanospallation may be used to make atomic wires or monolayer films.

  18. Conduction abnormalities during dipyridamole stress testing.

    Science.gov (United States)

    Massalha, Samia; Reizberg, Ilya; Israel, Ora; Kapeliovich, Michael; Sholy, Haitham; Koskosi, Amjad; Keidar, Zohar; Marai, Ibrahim

    2017-04-01

    Pharmacological stress tests using dipyridamole are considered to be safe. However, cases of atrioventricular (AV) block have been reported. We retrospectively analyzed ECG at baseline and during dipyridamole stress tests of 2010 consecutive patients (patients with second or third degree AV block were excluded). At baseline, 350 (17.4%) patients had conduction abnormalities. Following dipyridamole infusion 16 patients (0.8%) developed a transient change in AV conduction (15 patients) and or sinus arrest (1 patient). Compared to patients without baseline conduction abnormalities, patients with any conduction abnormalities at baseline were at a higher risk for the development of AV block after dipyridamole infusion [0.3% vs 3.14%, respectively; P < .0001].

  19. Pathophysiological rationale and diagnostic targets for diastolic stress testing.

    Science.gov (United States)

    Erdei, Tamás; Aakhus, Svend; Marino, Paolo; Paulus, Walter J; Smiseth, Otto A; Fraser, Alan G

    2015-09-01

    Cardiopulmonary functional reserve measured as peak oxygen uptake is predicted better at rest by measures of cardiac diastolic function than by systolic function. Normal adaptations in the trained heart include resting bradycardia, increased LV end-diastolic volume and augmented early diastolic suction on exercise. In normal populations early diastolic relaxation declines with age and end-diastolic stiffness increases, but in healthy older subjects who have exercised throughout their lives diastolic function can be well preserved. The mechanisms by which LV diastolic filling and pressures can be impaired during exercise include reduced early diastolic recoil and suction (which can be exacerbated by increased late systolic loading), increased preload and reduced compliance. Abnormal ventricular-arterial coupling and enhanced ventricular interaction may contribute in particular circumstances. One common final pathway that causes breathlessness is an increase in LV filling pressure and left atrial pressure. Testing elderly subjects with breathlessness of unknown aetiology in order to detect worsening diastolic function during stress is proposed to diagnose heart failure with preserved EF. In invasive studies, the most prominent abnormality is an early and rapid rise in pulmonary capillary wedge pressure. A systematic non-invasive diagnostic strategy would use validated methods to assess different mechanisms of inducible diastolic dysfunction and not just single parameters that offer imprecise estimates of mean LV filling pressure. Protocols should assess early diastolic relaxation and filling as well as late diastolic filling and compliance, as these may be affected separately. Better refined diagnostic targets may translate to more focused treatment. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

  20. Estimating material elasticity by spherical indentation load-relaxation tests on viscoelastic samples of finite thickness.

    Science.gov (United States)

    Qiang, Bo; Greenleaf, James; Oyen, Michelle; Zhang, Xiaoming

    2011-07-01

    A two-step viscoelastic spherical indentation method is proposed to compensate for 1) material relaxation and 2) sample thickness. In the first step, the indenter is moved at a constant speed and the reaction force is measured. In the second step, the indenter is held at a constant position and the relaxation response of the material is measured. Then the relaxation response is fit with a multi-exponential function which corresponds to a three-branch general Maxwell model. The relaxation modulus is derived by correcting the finite ramp time introduced in the first step. The proposed model takes into account the sample thickness, which is important for applications in which the sample thickness is less than ten times the indenter radius. The model is validated numerically by finite element simulations. Experiments are carried out on a 10% gelatin phantom and a chicken breast sample with the proposed method. The results for both the gelatin phantom and the chicken breast sample agree with the results obtained from a surface wave method. Both the finite element simulations and experimental results show improved elasticity estimations by incorporating the sample thickness into the model. The measured shear elasticities of the 10% gelatin sample are 6.79 and 6.93 kPa by the proposed finite indentation method at sample thickness of 40 and 20 mm, respectively. The elasticity of the same sample is estimated to be 6.53 kPa by the surface wave method. For the chicken breast sample, the shear elasticity is measured to be 4.51 and 5.17 kPa by the proposed indentation method at sample thickness of 40 and 20 mm, respectively. Its elasticity is measured by the surface wave method to be 4.14 kPa.

  1. Hydrogen-induced stress relaxation in thin Pd films: influence of carbon implementation.

    Science.gov (United States)

    Nowakowski, Robert; Grzeszczak, Patrycja; Dus, Ryszard

    2007-02-13

    The influence of carbon impurities on mechanical properties of thin Pd film in the process of hydride formation and its disintegration has been investigated "in situ" by means of atomic force microscopy (AFM). Pd interaction with hydrogen leads to the formation of hydride PdHx, if critical conditions of pressure and temperature are reached (equilibrium hydrogen pressure over PdHx at 298 K is approximately 1 kPa). The lattice constant of PdHx is larger than that of the original metal, and the hydride formation generates high stress within the film. As a consequence, the reversible formation of well organized mesoscopic protrusions on the film surface is observed. In this paper, we focus our investigation on the mechanical response which occurs when, prior to hydride generation, carbon atoms are incorporated into the bulk of the film. The systems characterized by carbon incorporation from the two opposite sides of thin palladium film (HOPG substrate and hydrocarbon fragments deposit from a gas-phase reached by preadsorption of ethylene) are compared. For both cases the mechanism of mechanical response is the same, but very different from that registered for pure thin palladium film. Carbon impurities induce, during PdHx decomposition, creation of an organized network of cracks which divides the continuous film into separated domains. The mechanisms of carbon introduction occurring in both cases have been proposed.

  2. Laboratory observations of time-dependent frictional strengthening and stress relaxation in natural and synthetic fault gouges

    Science.gov (United States)

    Carpenter, B. M.; Ikari, M. J.; Marone, C.

    2016-02-01

    Interseismic recovery of fault strength (healing) following earthquake failure is a fundamental requirement of the seismic cycle and likely plays a key role in determining the stability and slip behavior of tectonic faults. We report on laboratory measurements of time- and slip-dependent frictional strengthening for natural and synthetic gouges to evaluate the role of mineralogy in frictional strengthening. We performed slide-hold-slide (SHS) shearing experiments on nine natural fault gouges and eight synthetic gouges at conditions of 20 MPa normal stress, 100% relative humidity (RH), large shear strain (~15), and room temperature. Phyllosilicate-rich rocks show the lowest rates of frictional strengthening. Samples rich in quartz and feldspar exhibit intermediate rates of frictional strengthening, and calcite-rich gouges show the largest values. Our results show that (1) the rates of frictional strengthening and creep relaxation scale with frictional strength, (2) phyllosilicate-rich fault gouges have low strength and healing characteristics that promote stable, aseismic creep, (3) most natural fault gouges exhibit intermediate rates of frictional strengthening, consistent with a broad range of fault slip behaviors, and (4) calcite-rich fault rocks show the highest rates of frictional strengthening, low values of dilation upon reshear, and high frictional strengths, all of which would promote seismogenic behavior.

  3. Assessing the P-wave attenuation and phase velocity characteristics of fractured media based on creep and relaxation tests

    Science.gov (United States)

    Milani, Marco; Germán Rubino, J.; Müller, Tobias M.; Quintal, Beatriz; Holliger, Klaus

    2014-05-01

    Fractures are present in most geological formations and they tend to dominate not only their mechanical but also, and in particular, their hydraulic properties. For these reasons, the detection and characterization of fractures are of great interest in several fields of Earth sciences. Seismic attenuation has been recognized as a key attribute for this purpose, as both laboratory and field experiments indicate that the presence of fractures typically produces significant energy dissipation and that this attribute tends to increase with increasing fracture density. This energy loss is generally considered to be primarily due to wave-induced pressure diffusion between the fractures and the embedding porous matrix. That is, due to the strong compressibility contrast between these two domains, the propagation of seismic waves can generate a strong fluid pressure gradient and associated pressure diffusion, which leads to fluid flow and in turn results in frictional energy dissipation. Numerical simulations based on Biot's poroelastic wave equations are computationally very expensive. Alternative approaches consist in performing numerical relaxation or creep tests on representative elementary volumes (REV) of the considered medium. These tests are typically based on Biot's consolidation equations. Assuming that the heterogeneous poroelastic medium can be replaced by an effective, homogeneous viscoelastic solid, these numerical creep and relaxation tests allow for computing the equivalent seismic P-wave attenuation and phase velocity. From a practical point of view, an REV is typically characterized by the smallest volume for which rock physical properties are statistically stationary and representative of the probed medium in its entirety. A more general definition in the context of wavefield attributes is to consider an REV as the smallest volume over which the P-wave attenuation and phase velocity dispersion are independent of the applied boundary conditions. That is

  4. Brief relaxation training program for hospital employees.

    Science.gov (United States)

    Balk, Judith L; Chung, Sheng-Chia; Beigi, Richard; Brooks, Maria

    2009-01-01

    Employee stress leads to attrition, burnout, and increased medical costs. We aimed to assess if relaxation training leads to decreased stress levels based on questionnaire and thermal biofeedback. Thirty-minute relaxation training sessions were conducted for hospital employees and for cancer patients. Perceived Stress levels and skin temperature were analyzed before and after relaxation training.

  5. 40 CFR 91.329 - Catalyst thermal stress test.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 20 2010-07-01 2010-07-01 false Catalyst thermal stress test. 91.329....329 Catalyst thermal stress test. (a) Oven characteristics. The oven used for termally stressing the test catalyst must be capable of maintaining a temperature of 500 ±5 °C and 1000 ±10 °C. (b) Evaluation...

  6. 40 CFR 90.329 - Catalyst thermal stress test.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 20 2010-07-01 2010-07-01 false Catalyst thermal stress test. 90.329... Equipment Provisions § 90.329 Catalyst thermal stress test. (a) Oven characteristics. The oven used for thermally stressing the test catalyst must be capable of maintaining a temperature of 500 ±5 °C and 1000 ±10...

  7. Interpretation of Offshore Crustal Movements Following the 2011 Tohoku-Oki Earthquake by the Combined Effect of Afterslip and Viscoelastic Stress Relaxation

    Science.gov (United States)

    Noda, Akemi; Takahama, Tsutomu; Kawasato, Takeshi; Matsu'ura, Mitsuhiro

    2017-10-01

    On the 11th March 2011, a megathrust event, called the Tohoku-oki earthquake, occurred at the North American-Pacific plate interface off northeast Japan. Transient crustal movements following this earthquake were clearly observed by a dense GPS network (GEONET) on land and a sparse GPS/Acoustic positioning network on seafloor. The observed crustal movements are in accordance with ordinary expectations on land, but not on seafloor; that is, slowly decaying landward movements above the main rupture area and rapidly decaying trench-ward movements in its southern extension. To reveal the cause of such curious offshore crustal movements, we analyzed the coseismic and postseismic GPS array data on land with a sequential stepwise inversion method considering viscoelastic stress relaxation in the asthenosphere, and obtained the following results: The afterslip of the Tohoku-oki earthquake rapidly proceeds for the first 1 year on a high-angle downdip extension of the main rupture, which occurred on the low-angle offshore plate interface. The theoretical patterns of seafloor horizontal movements due to the afterslip and the viscoelastic relaxation of coseismic stress changes in the asthenosphere are essentially different both in space and time; inshore trench-ward movements and offshore landward movements for the afterslip, while overall landward movements for the viscoelastic stress relaxation. General agreement between the computed horizontal movements and the GPS/Acoustic observations demonstrates that the postseismic curious offshore crustal movements can be ascribed to the combined effect of afterslip on a high-angle downdip extension of the main rupture and viscoelastic stress relaxation in the asthenosphere.

  8. Relaxation techniques for stress

    Science.gov (United States)

    ... Yoga is an ancient practice rooted in Indian philosophy. The practice of yoga combines postures or movements ... Updated June 2013. nccih.nih.gov/health/yoga/introduction.htm . Accessed October 18, 2016. Review Date 9/ ...

  9. Stress relaxing hyaluronic acid-collagen hydrogels promote cell spreading, fiber remodeling, and focal adhesion formation in 3D cell culture.

    Science.gov (United States)

    Lou, Junzhe; Stowers, Ryan; Nam, Sungmin; Xia, Yan; Chaudhuri, Ovijit

    2018-02-01

    The physical and architectural cues of the extracellular matrix (ECM) play a critical role in regulating important cellular functions such as spreading, migration, proliferation, and differentiation. Natural ECM is a complex viscoelastic scaffold composed of various distinct components that are often organized into a fibrillar microstructure. Hydrogels are frequently used as synthetic ECMs for 3D cell culture, but are typically elastic, due to covalent crosslinking, and non-fibrillar. Recent work has revealed the importance of stress relaxation in viscoelastic hydrogels in regulating biological processes such as spreading and differentiation, but these studies all utilize synthetic ECM hydrogels that are non-fibrillar. Key mechanotransduction events, such as focal adhesion formation, have only been observed in fibrillar networks in 3D culture to date. Here we present an interpenetrating network (IPN) hydrogel system based on HA crosslinked with dynamic covalent bonds and collagen I that captures the viscoelasticity and fibrillarity of ECM in tissues. The IPN hydrogels exhibit two distinct processes in stress relaxation, one from collagen and the other from HA crosslinking dynamics. Stress relaxation in the IPN hydrogels can be tuned by modulating HA crosslinker affinity, molecular weight of the HA, or HA concentration. Faster relaxation in the IPN hydrogels promotes cell spreading, fiber remodeling, and focal adhesion (FA) formation - behaviors often inhibited in other hydrogel-based materials in 3D culture. This study presents a new, broadly adaptable materials platform for mimicking key ECM features of viscoelasticity and fibrillarity in hydrogels for 3D cell culture and sheds light on how these mechanical and structural cues regulate cell behavior. Copyright © 2017 Elsevier Ltd. All rights reserved.

  10. Impact of applied progressive deep muscle relaxation training on the level of depression, anxiety and stress among prostate cancer patients: a quasi-experimental study.

    Science.gov (United States)

    Isa, Mohamad Rodi; Moy, Foong Ming; Abdul Razack, Azad Hassan; Zainuddin, Zulkifli Md; Zainal, Nor Zuraida

    2013-01-01

    The aim of this study was to determine the impact of applied progressive muscle relaxation training on the levels of depression, anxiety and stress among prostate cancer patients. A quasi-experimental study was conducted at the University Malaya Medical Centre (UMMC) and Universiti Kebangsaan Malaysia Medical Centre (UKMMC) over six months. Prostate cancer patients from UMMC received the intervention and patients from UKMMC were taken as controls. The level of depression, anxiety and stress were measured using Depression, Anxiety Stress Scales - 21 (DASS-21). A total of 77 patients from the UMMC and 78 patients from the UKMMC participated. At the end of the study, 90.9% and 87.2% of patients from the UMMC and UKMMC groups completed the study respectively. There were significant improvements in anxiety (prelaxation therapy among prostate cancer patients as a coping strategy to improve their anxiety and stress.

  11. Characterization of Stress Relaxation, Dislocations and Crystallographic Tilt Via X-ray Microdiffraction in GaN (0001) Layers Grown by Maskless Pendeo-Epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Barabash, R.I.; Ice, G.E.; Liu, W.; Einfeldt, S.; Hommel, D.; Roskowski, A.M.; Davis, R.F. (ORNL)

    2010-06-25

    Intrinsic stresses due to lattice mismatch and high densities of threading dislocations and extrinsic stresses resulting from the mismatch in the coefficients of thermal expansion are present in almost all III-Nitride heterostructures. Stress relaxation in the GaN layers occurs in conventional and in pendeo-epitaxial films via the formation of additional misfit dislocations, domain boundaries, elastic strain and wing tilt. Polychromatic X-ray microdiffraction, high resolution monochromatic X-ray diffraction and finite element simulations have been used to determine the distribution of strain, dislocations, sub-boundaries and crystallographic wing tilt in uncoalesced and coalesced GaN layers grown by maskless pendeo-epitaxy. An important parameter was the width-to-height ratio of the etched columns of GaN from which the lateral growth of the wings occurred. The strain and tilt across the stripes increased with the width-to-height ratio. Tilt boundaries formed in the uncoalesced GaN layers at the column/wing interfaces for samples with a large ratio. Sharper tilt boundaries were observed at the interfaces formed by the coalescence of two laterally growing wings. The wings tilted upward during cooling to room temperature for both the uncoalesced and the coalesced GaN layers. It was determined that finite element simulations that account for extrinsic stress relaxation can explain the experimental results for uncoalesced GaN layers. Relaxation of both extrinsic and intrinsic stress components in the coalesced GaN layers contribute to the observed wing tilt and the formation of sub-boundaries.

  12. Characterization of Stress Relaxation, Dislocations and Crystallographic Tilt Via X-ray Microdiffraction in GaN (0001) Layers Grown by Maskless Pendeo-Epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Barabash, Rozaliya [ORNL; Ice, Gene E [ORNL; Liu, Wenjun [ORNL; Einfeldt, S. [University of Bremen, Bremen, Germany; Hommel, D. [University of Bremen, Bremen, Germany; Roskowski, A. M. [North Carolina State University; Davis, R. F. [North Carolina State University

    2005-01-01

    Intrinsic stresses due to lattice mismatch and high densities of threading dislocations and extrinsic stresses resulting from the mismatch in the coefficients of thermal expansion are present in almost all III-Nitride heterostructures. Stress relaxation in the GaN layers occurs in conventional and in pendeo-epitaxial films via the formation of additional misfit dislocations, domain boundaries, elastic strain and wing tilt. Polychromatic X-ray microdiffraction, high resolution monochromatic X-ray diffraction and finite element simulations have been used to determine the distribution of strain, dislocations, sub-boundaries and crystallographic wing tilt in uncoalesced and coalesced GaN layers grown by maskless pendeo-epitaxy. An important parameter was the width-to-height ratio of the etched columns of GaN from which the lateral growth of the wings occurred. The strain and tilt across the stripes increased with the width-to-height ratio. Tilt boundaries formed in the uncoalesced GaN layers at the column/wing interfaces for samples with a large ratio. Sharper tilt boundaries were observed at the interfaces formed by the coalescence of two laterally growing wings. The wings tilted upward during cooling to room temperature for both the uncoalesced and the coalesced GaN layers. It was determined that finite element simulations that account for extrinsic stress relaxation can explain the experimental results for uncoalesced GaN layers. Relaxation of both extrinsic and intrinsic stress components in the coalesced GaN layers contribute to the observed wing tilt and the formation of sub-boundaries.

  13. Endothelial relaxation mechanisms and nitrative stress are partly restored by Vitamin D3 therapy in a rat model of polycystic ovary syndrome.

    Science.gov (United States)

    Masszi, Gabriella; Benko, Rita; Csibi, Noemi; Horvath, Eszter M; Tokes, Anna-Maria; Novak, Agnes; Beres, Nora Judit; Tarszabo, Robert; Buday, Anna; Repas, Csaba; Bekesi, Gabor; Patocs, Attila; Nadasy, Gyorgy L; Hamar, Peter; Benyo, Zoltan; Varbiro, Szabolcs

    2013-08-06

    In polycystic ovary syndrome (PCOS), metabolic and cardiovascular dysfunction is related to hyperandrogenic status and insulin resistance, however, Vitamin D3 has a beneficial effect partly due to its anti-oxidant capacity. Nitrative stress is a major factor in the development of cardiovascular dysfunction and insulin resistance in various diseases. Our aim was to determine the effects of vitamin D3 in a rat model of PCOS, particularly the pathogenic role of nitrative stress. Female Wistar rats weighing 100-140g were administered vehicle (C), dihydrotestosterone (DHT) or dihydrotestosterone plus vitamin D3 (DHT+D) (n=10 per group). On the 10th week, acetylcholine (Ach) induced relaxation ability of the isolated thoracic aorta rings was determined. In order to examine the possible role of endothelial nitric oxide synthase (eNOS) and cyclooxygenase-2 (COX-2) pathways in the impaired endothelial function, immunohistochemical labeling of aortas with anti-eNOS and anti-COX-2 antibodies was performed. Leukocyte smears, aorta and ovary tissue sections were also immunostained with anti-nitrotyrosine antibody to determine nitrative stress. Relaxation ability of aorta was reduced in group DHT, and vitamin D3 partly restored Ach induced relaxation. eNOS labeling was significantly lower in DHT rats compared to the other two groups, however COX-2 staining showed an increment. Nitrative stress showed a significant increase in response to dihydrotestosterone, while vitamin D3 treatment, in case of the ovaries, was able to reverse this effect. Nitrative stress may play a role in the pathogenesis of PCOS and in the development of the therapeutic effect of vitamin D3. Copyright © 2013 Elsevier Inc. All rights reserved.

  14. [Development of the "Mannheim Multicomponent Stress Test" (MMST)].

    Science.gov (United States)

    Kolotylova, Tatyana; Koschke, Mandy; Bär, Karl-Jürgen; Ebner-Priemer, Ulrich; Kleindienst, Nikolaus; Bohus, Martin; Schmahl, Christian

    2010-02-01

    The aim of the present study was to develop and evaluate an economical stress paradigm, which can be used for the investigation of stress reactions in a laboratory setting. Different stressors were combined to investigate the changes of heart frequency and subjective stress levels as response to stressful stimulation. A combination of mental stress, noise and emotional pictures presented in the background during performing a mental arithmetic task showed significant increases in heart rate and subjective stress levels. Furthermore we tested the stress combination in 32 healthy subjects to evaluate the physiological response. We found significant changes in the cardiovascular parameters such as heart rate variability, baroreflex sensitivity and cardiac output. We conclude that the Mannheim Multicomponent Stress Test (MMST) induces high levels of physiological and psychological stress and can serve as an economical method to investigate stress reactions in a laboratory setting.

  15. COX-2-derived prostanoids and oxidative stress additionally reduce endothelium-mediated relaxation in old type 2 diabetic rats.

    Directory of Open Access Journals (Sweden)

    Emilie Vessières

    Full Text Available Endothelial dysfunction in resistance arteries alters end organ perfusion in type 2 diabetes. Superoxides and cyclooxygenase-2 (COX-2 derivatives have been shown separately to alter endothelium-mediated relaxation in aging and diabetes but their role in the alteration of vascular tone in old diabetic subjects is not clear, especially in resistance arteries. Consequently, we investigated the role of superoxide and COX-2-derivatives on endothelium-dependent relaxation in 3 and 12 month-old Zucker diabetic fatty (ZDF and lean (LZ rats. Mesenteric resistance arteries were isolated and vascular tone was investigated using wire-myography. Endothelium (acetylcholine-dependent relaxation was lower in ZDF than in LZ rats (60 versus 84% maximal relaxation in young rats and 41 versus 69% in old rats. Blocking NO production with L-NAME was less efficient in old than in young rats. L-NAME had no effect in old ZDF rats although eNOS expression level in old ZDF rats was similar to that in old LZ rats. Superoxide level and NADPH-oxidase subunits (p67phox and gp91phox expression level were greater in ZDF than in LZ rats and were further increased by aging in ZDF rats. In young ZDF rats reducing superoxide level with tempol restored acetylcholine-dependent relaxation to the level of LZ rats. In old ZDF rats tempol improved acetylcholine-dependent relaxation without increasing it to the level of LZ rats. COX-2 (immunolabelling and Western-blot was present in arteries of ZDF rats and absent in LZ rats. In old ZDF rats arterial COX-2 level was higher than in young ZDF rats. COX-2 blockade with NS398 restored in part acetylcholine-dependent relaxation in arteries of old ZDF rats and the combination of tempol and NS398 fully restored relaxation in control (LZ rats level. Accordingly, superoxide production and COX-2 derivatives together reduced endothelium-dependent relaxation in old ZDF rats whereas superoxides alone attenuated relaxation in young ZDF or old LZ rats.

  16. Stress relaxation and creep on living cells with the atomic force microscope: a means to calculate elastic moduli and viscosities of cell components

    Energy Technology Data Exchange (ETDEWEB)

    Moreno-Flores, Susana; Toca-Herrera, Jose Luis [Biosurfaces Unit, CIC BiomaGUNE, Paseo Miramon 182, E-20009 San Sebastian-Donostia (Spain); Benitez, Rafael [Departamento Matematicas, Centro Universitario de Plasencia, Universidad de Extremadura, Avenida Virgen del Puerto 2, E-10600 Plasencia (Spain); Vivanco, Maria dM, E-mail: jltocaherrera@cicbiomagune.es, E-mail: jose.toca-herrera@boku.ac.at [Cell Biology and Stem Cells Unit, CIC BioGUNE, Parque tecnologico de Bizkaia, Ed. 801A, E-48160 Derio (Spain)

    2010-11-05

    In this work we present a unified method to study the mechanical properties of cells using the atomic force microscope. Stress relaxation and creep compliance measurements permitted us to determine, the relaxation times, the Young moduli and the viscosity of breast cancer cells (MCF-7). The results show that the mechanical behaviour of MCF-7 cells responds to a two-layered model of similar elasticity but differing viscosity. Treatment of MCF-7 cells with an actin-depolymerising agent results in an overall decrease in both cell elasticity and viscosity, however to a different extent for each layer. The layer that undergoes the smaller decrease (36-38%) is assigned to the cell membrane/cortex while the layer that experiences the larger decrease (70-80%) is attributed to the cell cytoplasm. The combination of the method presented in this work, together with the approach based on stress relaxation microscopy (Moreno-Flores et al 2010 J. Biomech. 43 349-54), constitutes a unique AFM-based experimental framework to study cell mechanics. This methodology can also be extended to study the mechanical properties of biomaterials in general.

  17. Stress relaxation and creep on living cells with the atomic force microscope: a means to calculate elastic moduli and viscosities of cell components

    Science.gov (United States)

    Moreno-Flores, Susana; Benitez, Rafael; Vivanco, María dM; Toca-Herrera, José Luis

    2010-11-01

    In this work we present a unified method to study the mechanical properties of cells using the atomic force microscope. Stress relaxation and creep compliance measurements permitted us to determine, the relaxation times, the Young moduli and the viscosity of breast cancer cells (MCF-7). The results show that the mechanical behaviour of MCF-7 cells responds to a two-layered model of similar elasticity but differing viscosity. Treatment of MCF-7 cells with an actin-depolymerising agent results in an overall decrease in both cell elasticity and viscosity, however to a different extent for each layer. The layer that undergoes the smaller decrease (36-38%) is assigned to the cell membrane/cortex while the layer that experiences the larger decrease (70-80%) is attributed to the cell cytoplasm. The combination of the method presented in this work, together with the approach based on stress relaxation microscopy (Moreno-Flores et al 2010 J. Biomech. 43 349-54), constitutes a unique AFM-based experimental framework to study cell mechanics. This methodology can also be extended to study the mechanical properties of biomaterials in general.

  18. Stress Optical Coefficient, Test Methodology, and Glass Standard Evaluation

    Science.gov (United States)

    2016-05-01

    ARL-TN-0756 ● MAY 2016 US Army Research Laboratory Stress Optical Coefficient, Test Methodology, and Glass Standard Evaluation...Stress Optical Coefficient, Test Methodology, and Glass Standard Evaluation by Clayton M Weiss Oak Ridge Institute for Science and Education...materials under stress, which is represented by the material property of stress optical coefficient, can be used to evaluate glass samples of known and

  19. Strain, stress, and mechanical relaxation in fin-patterned Si/SiGe multilayers for sub-7 nm nanosheet gate-all-around device technology

    Science.gov (United States)

    Reboh, S.; Coquand, R.; Barraud, S.; Loubet, N.; Bernier, N.; Audoit, G.; Rouviere, J.-L.; Augendre, E.; Li, J.; Gaudiello, J.; Gambacorti, N.; Yamashita, T.; Faynot, O.

    2018-01-01

    Pre-strained fin-patterned Si/SiGe multilayer structures for sub-7 nm stacked gate-all-around Si-technology transistors that have been grown onto bulk-Si, virtually relaxed SiGe, strained Silicon-On-Insulator, and compressive SiGe-On-Insulator were investigated. From strain maps with a nanometer spatial resolution obtained by transmission electron microscopy, we developed 3D quantitative numerical models describing the mechanics of the structures. While elastic interactions describe every other system reported here, the patterning on the compressive SiGe-On-Insulator substrate that is fabricated by Ge-condensation results in relaxation along the semiconductor/insulator interface, revealing a latent plasticity mechanism. As a consequence, Si layers with a uniaxial stress of 1.4 GPa are obtained, bringing fresh perspectives for strain engineering in advanced devices. These findings could be extended to other semiconductor technologies.

  20. Ultrasonic test of highly stressed gear shafts

    Energy Technology Data Exchange (ETDEWEB)

    Schreiner, T. [Siemens AG, Power Generation, KWU, Muelheim (Germany); Heinrich, W. [Siemens AG, Power Generation, KWU, Berlin (Germany); Achtzehn, J. [Siemens AG, Power Generation, ICVW, Erlangen (Germany); Hensley, H. [Siemens Power Generation (Germany)

    1998-12-31

    In the power plant industry, gears are used for increasingly higher turbine capacities. Efficiency enhancements, particularly for the combined gas and steam turbine process, lead to an increase in stresses, even for high-performance gears. Consequently, the requirements for non-destructive material testing are on the increase as well. At Siemens KWU, high-performance gears are used so far only for gas turbines with lower rating (65 MW) to adapt the gas turbine speed (5413 rpm) to the generator speed (3000 rpm/ 50 Hz or 3600 rpm/60 Hz). The gear train consists of a forged and case-hardened wheel shaft and pinion shaft made of material 17 CrNiMo 6, where the wheel shaft can be either a solid or a hollow shaft. Dimensions are typically 2.3 m length and 1 m diameter. As a rule, pinion shafts are solid. The gear design, calling for an additional torsion shaft turning inside the hollow wheel shaft, can absorb more torsional load surges and is more tolerant of deviations during gear train alignment. This design requires two additional forgings (torsion shaft and hub) and an additional bearing 2 refs.

  1. Regularities of the effect of the value of initial bending stresses on their relaxation under the annealing of amorphous magnetically soft alloys of various classes

    Science.gov (United States)

    Kekalo, I. B.; Mogil'nikov, P. S.

    2017-02-01

    It has been shown that, in some amorphous alloys, the value of initial bending stresses σm can influence the development of the relaxation of these stresses during the annealing of the alloys. These alloys include Co69Fe3.7Cr3.8Si12.5B11, with a nearly zero saturation magnetostriction (λs saturation magnetostriction λs. When this effect manifests itself, the activation energy U of the given process becomes a function of two factors; i.e., this energy depends on both the composition of the alloy (that is, interatomic forces) and the value of the initial bending stresses. In this case, the activation energy U cannot be considered to be characteristic of the material.

  2. Covalent adaptable networks as dental restorative resins: stress relaxation by addition-fragmentation chain transfer in allyl sulfide-containing resins.

    Science.gov (United States)

    Park, Hee Young; Kloxin, Christopher J; Scott, Timothy F; Bowman, Christopher N

    2010-10-01

    The aim is to demonstrate significant polymerization shrinkage stress reduction in model resins through incorporation of addition-fragmentation chain transfer moieties that promote network stress accommodation by molecular rearrangement. Monomers containing allyl sulfide linkages are incorporated to affect the shrinkage stress that arises during photopolymerization of model resins that contain an initiator and dimethacrylates. Radical-mediated allyl sulfide addition-fragmentation is enabled during polymerization. We hypothesize that allyl sulfide incorporation into methacrylate polymerizations promotes stress relaxation by enabling network adaptation. A 1:2 mixture of tetrathiol and allyl sulfide-containing divinyl ethers is formulated with glass-forming dimethacrylates and compared to controls where the allyl sulfide is replaced with a propyl sulfide that is incapable of undergoing addition-fragmentation. Simultaneous shrinkage stress and functional group conversion measurements are performed. The T(g) is determined by DMA. Increasing allyl sulfide concentration reduces the relative stress by up to 75% in the resins containing the maximum amount of allyl sulfide. In glassy systems, at much lower allyl sulfide concentrations, the stress is reduced by up to 20% as compared to propyl sulfide-containing systems incapable of undergoing addition-fragmentation chain transfer. Shrinkage stress reduction, typically accompanying free-radical polymerization, is a primary focus in dental materials research and new product development. Allyl sulfide addition-fragmentation chain transfer is utilized as a novel approach to reduce stress in ternary thiol-ene-methacrylate polymerizations. The stress reduction effect depends directly on the allyl sulfide concentration in the given ternary systems, with stress reduction observed even in systems possessing super-ambient T(g)s and low allyl sulfide concentrations. Published by Elsevier Ltd.

  3. Effects of cognitive behavioral therapy with relaxation vs. imagery rescripting on test anxiety: A randomized controlled trial.

    Science.gov (United States)

    Reiss, Neele; Warnecke, Irene; Tolgou, Theano; Krampen, Dorothea; Luka-Krausgrill, Ursula; Rohrmann, Sonja

    2017-01-15

    Test anxiety is a common condition in students, which may lead to impaired academic performance as well as to distress. The primary objective of this study was to evaluate the effectiveness of two cognitive-behavioral interventions designed to reduce test anxiety. Test anxiety in the participants was diagnosed as social or specific phobia according to DSM-IV. Subsequently subjects were randomized to three groups: a moderated self-help group, which served as a control group, and two treatment groups, where either relaxation techniques or imagery rescripting were applied. Students suffering from test anxiety were recruited at two German universities (n=180). The randomized controlled design comprised three groups which received test anxiety treatment in weekly three-hour sessions over a period of five weeks. Treatment outcome was assessed with a test anxiety questionnaire, which was administered before and after treatment, as well as in a six-month follow-up. A repeated-measures ANOVA for participants with complete data (n=59) revealed a significant reduction of test anxiety from baseline to six-month follow-up in all three treatment groups (p<.001). Participants were included if they had a clinical diagnosis of test anxiety. The sample may therefore represent only more severe forms of text anxiety . Moreover, the sample size in this study was small, the numbers of participants per group differed, and treatment results were based on self-report. Due to the length of the treatment, an implementation of the group treatments used in this study might not be feasible in all settings. Group treatments constitute an effective method of treating test anxiety, e.g. in university settings. Imagery rescripting may particularly contribute to treatment efficacy. Copyright © 2016 Elsevier B.V. All rights reserved.

  4. Uses and Abuses of Progressive Relaxation and Biofeedback in Treating Effects of Stress: The Cognitive vs. Psychophysiological vs. Behavioral Distinction.

    Science.gov (United States)

    Lehrer, Paul M.

    Experimental, clinical, and personal observations give some support to the notions that: (1) intensive live training with anxious subjects is required in order to demonstrate that perspective relaxation has physiological effects; (2) physiological, cognitive, and behavioral symptoms of anxiety are separable and may respond differentially to…

  5. Relaxation Techniques to Manage IBS Symptoms

    Science.gov (United States)

    ... Day Art of IBS Gallery Contact Us Relaxation Techniques to Manage IBS Symptoms Details Content Last Updated: ... Psychological Treatments Understanding Stress Cognitive Behavioral Therapy Relaxation Techniques for IBS You’ve been to the doctor ...

  6. Critical wall shear stress for the EHEDG test method

    DEFF Research Database (Denmark)

    Jensen, Bo Boye Busk; Friis, Alan

    2004-01-01

    In order to simulate the results of practical cleaning tests on closed processing equipment, based on wall shear stress predicted by computational fluid dynamics, a critical wall shear stress is required for that particular cleaning method. This work presents investigations that provide a critical...... wall shear stress of 3 Pa for the standardised EHEDG cleaning test method. The cleaning tests were performed on a test disc placed in a radial flowcell assay. Turbulent flow conditions were generated and the corresponding wall shear stresses were predicted from CFD simulations. Combining wall shear...... stress predictions from a simulation using the low Re k-epsilon and one using the two-layer model of Norris and Reynolds were found to produce reliable predictions compared to empirical solutions for the ideal flow case. The comparison of wall shear stress curves predicted for the real RFC...

  7. 78 FR 65583 - Capital Planning and Stress Testing

    Science.gov (United States)

    2013-11-01

    ... ADMINISTRATION 12 CFR Part 702 RIN 3133-AE27 Capital Planning and Stress Testing AGENCY: National Credit Union... [email protected] . Include ``[Your name]-- Comments on Proposed Rule--Capital Planning and Stress Testing... Examination and Insurance, at the above address or telephone (703) 518-6360; or Lisa Henderson, Staff Attorney...

  8. 12 CFR 652.40 - Stress tests for mortgage securities.

    Science.gov (United States)

    2010-01-01

    ... 12 Banks and Banking 6 2010-01-01 2010-01-01 false Stress tests for mortgage securities. 652.40... MORTGAGE CORPORATION FUNDING AND FISCAL AFFAIRS Investment Management § 652.40 Stress tests for mortgage... and price of each mortgage security that you purchase and hold, except for adjustable rate mortgage...

  9. Coping with the Stress of High Stakes Testing

    Science.gov (United States)

    Kruger, Louis J.; Wandle, Caroline; Struzziero, Joan

    2007-01-01

    High stakes testing puts considerable pressure on schools, teachers, and students to achieve at high levels. Therefore, how schools and individuals cope with this major source of stress may have important implications for the success of high stakes testing. This article reviews relevant theory and research on stress as they relate to public…

  10. Relationships between adolescents' test anxiety, stress and sleep

    NARCIS (Netherlands)

    Dewald, J.F.; Meijer, A.M.; Oort, F.J.; Bögels, S.M.

    2012-01-01

    Objective. This study aims to investigate the relationship between adolescents' test anxiety, stress and different aspects of sleep. Method. 175 adolescents (70.8% girls, mean age 15.14 years) participated in the study. Test anxiety, stress and chronic sleep reduction were assessed at baseline using

  11. Model of electronic energy relaxation in the test-particle Monte Carlo method

    Energy Technology Data Exchange (ETDEWEB)

    Roblin, P.; Rosengard, A. [CEA Centre d`Etudes de Saclay, 91 - Gif-sur-Yvette (France). Dept. des Procedes d`Enrichissement; Nguyen, T.T. [Compagnie Internationale de Services en Informatique (CISI) - Centre d`Etudes Nucleaires de Saclay, 91 - Gif-sur-Yvette (France)

    1994-12-31

    We previously presented a new test-particle Monte Carlo method (1) (which we call PTMC), an iterative method for solving the Boltzmann equation, and now improved and very well-suited to the collisional steady gas flows. Here, we apply a statistical method, described by Anderson (2), to treat electronic translational energy transfer by a collisional process, to atomic uranium vapor. For our study, only three levels of its multiple energy states are considered: 0,620 cm{sup -1} and an average level grouping upper levels. After presenting two-dimensional results, we apply this model to the evaporation of uranium by electron bombardment and show that the PTMC results, for given initial electronic temperatures, are in good agreement with experimental radial velocity measurements. (author). 12 refs., 1 fig.

  12. The Trier Social Stress Test: Principles and practice.

    Science.gov (United States)

    Allen, Andrew P; Kennedy, Paul J; Dockray, Samantha; Cryan, John F; Dinan, Timothy G; Clarke, Gerard

    2017-02-01

    Researchers interested in the neurobiology of the acute stress response in humans require a valid and reliable acute stressor that can be used under experimental conditions. The Trier Social Stress Test (TSST) provides such a testing platform. It induces stress by requiring participants to make an interview-style presentation, followed by a surprise mental arithmetic test, in front of an interview panel who do not provide feedback or encouragement. In this review, we outline the methodology of the TSST, and discuss key findings under conditions of health and stress-related disorder. The TSST has unveiled differences in males and females, as well as different age groups, in their neurobiological response to acute stress. The TSST has also deepened our understanding of how genotype may moderate the cognitive neurobiology of acute stress, and exciting new inroads have been made in understanding epigenetic contributions to the biological regulation of the acute stress response using the TSST. A number of innovative adaptations have been developed which allow for the TSST to be used in group settings, with children, in combination with brain imaging, and with virtual committees. Future applications may incorporate the emerging links between the gut microbiome and the stress response. Future research should also maximise use of behavioural data generated by the TSST. Alternative acute stress paradigms may have utility over the TSST in certain situations, such as those that require repeat testing. Nonetheless, we expect that the TSST remains the gold standard for examining the cognitive neurobiology of acute stress in humans.

  13. Current trends and future development in pharmacologic stress testing

    Energy Technology Data Exchange (ETDEWEB)

    Bae, Jin Ho; Lee, Jae Tae [Kyungpook National University Medical School, Daegu (Korea, Republic of)

    2005-02-15

    Pharmacologic stress testing for myocardial perfusion imaging is a widely used noninvasive method for the evaluation of known or suspected coronary artery disease. The use of exercise for cardiac stress has been practiced for over 60 years and clinicians are familiar with its using. However, there are inevitable situations in which exercise stress is inappropriate. A large number of patients with cardiac problems are unable to exercise to their full potential due to comorbidity such as osteoarthritis, vascular disease and pulmonary disease and a standard exercise stress test for myocardial perfusion imaging is suboptimal means for assessment of coronary artery disease. This problem has led to the development of the pharmacologic stress test and to a great increase in its popularity. All of the currently used pharmacologic agents have well-documented diagnostic value. This review deals the physiological actions, clinical protocols, safety, nuclear imaging applications of currently available stress agents and future development of new vasodilating agents.

  14. Strain Rate and Stress Relaxation Effects on Pressuremeter Testing in Clays

    Science.gov (United States)

    1992-03-01

    and a vacuuming system. According to Sheeran and Krizek (1971), samples prepared from the higher water content slurry will not be influenced by the...and larger loading frame. From their experiments, Sheeran and Krizek found out that a water content of 2 to 2.5 times the liquid limit of the soil...213. Sheeran , D.E. and Krizek, R.J. (1971). "Preparation of Homogeneous Soil Samples by Slurry Consolidation," J. of Materials, JMLSA, 6(2), 356-373

  15. Technological patterns of preventive relaxation of workings

    Energy Technology Data Exchange (ETDEWEB)

    Kaufman, L.L.; Bakhtin, A.F.; Zel' vyanskii, M.Sh. (Donetskaya Proektnaya Kontora (USSR))

    1991-09-01

    Presents stress relaxation patterns of workings. The patterns are used at horizon layouts and panel development of mine-take in stone inclines, boundary entries, mine drainage galleries and main galleries. The stress relaxation variants are: stress relaxing longwalls with complete mining with two or three winning galleries, longwalls worked by long pillars on the strike, and longwalls worked with advance mining on the strike. The individual variants differ by the ventilation system adopted.

  16. A new paradigm to induce mental stress: The Sing-a-Song Stress Test (SSST

    Directory of Open Access Journals (Sweden)

    Anne-Marie eBrouwer

    2014-07-01

    Full Text Available We here introduce a new experimental paradigm to induce mental stress in a quick and easy way while adhering to ethical standards and controlling for potential confounds resulting from sensory input and body movements. In our Sing-a-Song Stress Test, participants are presented with neutral messages on a screen, interleaved with 1-minute time intervals. The final message is that the participant should sing a song aloud after the interval has elapsed. Participants sit still during the whole procedure. We found that heart rate and skin conductance during the 1-minute intervals following the sing-a-song stress message are substantially higher than during intervals following neutral messages. The order of magnitude of the rise is comparable to that achieved by the Trier Social Stress Test. Skin conductance increase correlates positively with experienced stress level as reported by participants. We also simulated stress detection in real time. When using both skin conductance and heart rate, stress is detected for 18 out of 20 participants, approximately 10s after onset of the sing-a-song message. In conclusion, the Sing-a-Song Stress Test provides a quick, easy, controlled and potent way to induce mental stress and could be helpful in studies ranging from examining physiological effects of mental stress to evaluating interventions to reduce stress.

  17. Stress Tests for Chest Pain: When You Need an Imaging Test -- and When You Don't

    Science.gov (United States)

    ... Resources Adult , Geriatric Stress Tests for Chest Pain Stress Tests for Chest Pain When you need an ... pain isn’t from heart disease. A cardiac stress test makes the heart work hard so your ...

  18. Effects of test stress during an objective structured clinical examination.

    Science.gov (United States)

    Zhang, Niu; Rabatsky, Ali

    2015-10-01

    The existence of test stress has been widely reported among professional students. To our knowledge, no studies exist that explore student stress response to objective structured clinical examinations. The aim of this study was to evaluate possible correlations between stress and objective structured clinical examination performance in a sample of chiropractic students. A total of 116 students completed a 2-part questionnaire to assess test stress and the physiological symptoms and signs of stress. Heart rate, systolic blood pressure, and diastolic were measured during the physical examination laboratory class within the first 3 weeks and then again just prior to their objective structured clinical examination in week 5. Statistical tests were then performed for questionnaire data, heart rate and blood pressure differences, and correlation between the objective structured clinical examination grade and symptoms and signs. Questionnaire results showed that 5.1%-22.4% of students sometimes or often felt a certain degree of stress. More than 50% had 1 or more physiological symptoms and signs of stress. The objective structured clinical examination heart rate (75.23 ± 11.20 vs 68.16 ± 8.82, p examination grades and physiological symptoms and signs and between objective structured clinical examination grades and feeling statement score. The results support our hypothesis that chiropractic students experience stress when performing the objective structured clinical examination and that high levels of stress had a negative impact on performance.

  19. Shear-Panel Test Fixture Eliminates Corner Stresses

    Science.gov (United States)

    Kiss, J. J.; Farley, G. L.; Baker, D. J.

    1984-01-01

    New design eliminates corner stresses while maintaining uniform stress across panel. Shear panel test fixture includes eight frames and eight corner pins. Fixture assembled in two halves with shear panel sandwiched in between. Results generated from this fixture will result in good data base for design of efficient aircraft structures and other applications.

  20. Sympathetic Hyperactivity, Increased Tyrosine Hydroxylase and Exaggerated Corpus Cavernosum Relaxations Associated with Oxidative Stress Plays a Major Role in the Penis Dysfunction in Townes Sickle Cell Mouse.

    Directory of Open Access Journals (Sweden)

    Fábio H Silva

    Full Text Available Sickle cell disease patients display priapism that may progress to erectile dysfunction. However, little is known about the pathophysiological alterations of corpus cavernosum in sickle cell disease.Thus, this study aimed to evaluate the functional and molecular alterations of sympathetic machinery and nitric oxide-cyclic guanosine monophosphate signaling pathway in Townes transgenic sickle cell disease mice.Concentration-response curves to contractile (phenylephrine and relaxant agents (acetylcholine and sodium nitroprusside were obtained in corpus cavernosum strips from sickle and C57BL/6 (control mice. Neurogenic contractions and nitrergic relaxations were obtained using electrical-field stimulation. Measurements of endothelial nitric oxide synthase (eNOS, neuronal nitric oxide synthase (nNOS, phosphodiesterase-5 (PDE5 and α1A-, α1B- and α1D-adrenoceptor mRNA expressions and reactive-oxygen species were performed. Tyrosine hydroxylase phosphorylated at Ser-31 and total tyrosine hydroxylase protein expressions in cavernosal tissues were also measured.The neurogenic contractions were higher in the sickle cell disease group, in association with elevated tyrosine hydroxylase phosphorylated at Ser-31 and total tyrosine hydroxylase protein expression, as well as increased tyrosine hydroxylase mRNA expression. Likewise, phenylephrine-induced contractions were greater in the sickle mice, whereas α1A-, α1B- and α1D-adrenoceptor mRNA expression remained unchanged. Cavernosal relaxations to acetylcholine, sodium nitroprusside and EFS were higher in sickle mice, accompanied by decreased eNOS and nNOS, along with lower PDE5 mRNA expression. An increase of about 40% in reactive-oxygen species generation in corpus cavernosum from sickle mice was also detected.Our study shows that decreased nitric oxide bioavailability in erectile tissue due to increased oxidative stress leads to both sympathetic hyperactivity and dysregulation of nitric oxide

  1. Sympathetic Hyperactivity, Increased Tyrosine Hydroxylase and Exaggerated Corpus Cavernosum Relaxations Associated with Oxidative Stress Plays a Major Role in the Penis Dysfunction in Townes Sickle Cell Mouse.

    Science.gov (United States)

    Silva, Fábio H; Claudino, Mário A; Calmasini, Fabiano B; Alexandre, Eduardo C; Franco-Penteado, Carla; Burnett, Arthur L; Antunes, Edson; Costa, Fernando F

    2016-01-01

    Sickle cell disease patients display priapism that may progress to erectile dysfunction. However, little is known about the pathophysiological alterations of corpus cavernosum in sickle cell disease. Thus, this study aimed to evaluate the functional and molecular alterations of sympathetic machinery and nitric oxide-cyclic guanosine monophosphate signaling pathway in Townes transgenic sickle cell disease mice. Concentration-response curves to contractile (phenylephrine) and relaxant agents (acetylcholine and sodium nitroprusside) were obtained in corpus cavernosum strips from sickle and C57BL/6 (control) mice. Neurogenic contractions and nitrergic relaxations were obtained using electrical-field stimulation. Measurements of endothelial nitric oxide synthase (eNOS), neuronal nitric oxide synthase (nNOS), phosphodiesterase-5 (PDE5) and α1A-, α1B- and α1D-adrenoceptor mRNA expressions and reactive-oxygen species were performed. Tyrosine hydroxylase phosphorylated at Ser-31 and total tyrosine hydroxylase protein expressions in cavernosal tissues were also measured. The neurogenic contractions were higher in the sickle cell disease group, in association with elevated tyrosine hydroxylase phosphorylated at Ser-31 and total tyrosine hydroxylase protein expression, as well as increased tyrosine hydroxylase mRNA expression. Likewise, phenylephrine-induced contractions were greater in the sickle mice, whereas α1A-, α1B- and α1D-adrenoceptor mRNA expression remained unchanged. Cavernosal relaxations to acetylcholine, sodium nitroprusside and EFS were higher in sickle mice, accompanied by decreased eNOS and nNOS, along with lower PDE5 mRNA expression. An increase of about 40% in reactive-oxygen species generation in corpus cavernosum from sickle mice was also detected. Our study shows that decreased nitric oxide bioavailability in erectile tissue due to increased oxidative stress leads to both sympathetic hyperactivity and dysregulation of nitric oxide signaling in

  2. Cold Stress and the Cold Pressor Test

    Science.gov (United States)

    Silverthorn, Dee U.; Michael, Joel

    2013-01-01

    Temperature and other environmental stressors are known to affect blood pressure and heart rate. In this activity, students perform the cold pressor test, demonstrating increased blood pressure during a 1- to 2-min immersion of one hand in ice water. The cold pressor test is used clinically to evaluate autonomic and left ventricular function. This…

  3. Methods of Stress Testing of Financial Stability of Ukrainian Enterprises

    Directory of Open Access Journals (Sweden)

    Lukianenko Iryna G.

    2013-11-01

    Full Text Available The goal of the article lies in adaptation of the procedure of stress testing for assessment of financial stability of enterprises and development of adequate economic and mathematical instruments for its conduct. It was revealed during the study that the proposed approach allows not only obtaining a forecast assessment of financial stability in future periods of enterprise activity but also all-sided study and quantitative assessment of its reaction on action of internal and external stresses in short-term and long-term prospects. This article proves that main stages of the conduct of a stress test at the enterprise level are analysis of external environment and identification of potential markets; identification of indicators that meet the detected risks and stresses; development and specification of the economic and mathematical model, that is used for running scenarios, which should be oriented at unfavourable but quite probable events. The conducted studies confirmed prospectiveness of the use of longitudinal data models and vector auto-regression models, including error correction models when conducting stress testing at the level of the branch and an individual enterprise. The obtained results could be used as a basis for further development and improvement of the method of stress testing of financial stability of economic subjects and also for identification of the model of stress testing of individual branches of the Ukrainian economy.

  4. A prognostic scoring system for arm exercise stress testing

    National Research Council Canada - National Science Library

    Xie, Yan; Xian, Hong; Chandiramani, Pooja; Bainter, Emily; Wan, Leping; Martin, 3rd, Wade H

    2016-01-01

    ...% for patients unable to perform leg exercise. Thus, our objective was to develop an arm exercise ECG stress test scoring system, analogous to the Duke Treadmill Score, for predicting outcome in these individuals...

  5. Stope Stability Assessment and Effect of Horizontal to Vertical Stress Ratio on the Yielding and Relaxation Zones Around Underground Open Stopes Using Empirical and Finite Element Methods

    Science.gov (United States)

    Sepehri, Mohammadali; Apel, Derek; Liu, Wei

    2017-09-01

    Predicting the stability of open stopes can be a challenging task for underground mine engineers. For decades, the stability graph method has been used as the first step of open stope design around the world. However, there are some shortcomings with this method. For instance, the stability graph method does not account for the relaxation zones around the stopes. Another limitation of the stability graph is that this method cannot to be used to evaluate the stability of the stopes with high walls made of backfill materials. However, there are several analytical and numerical methods that can be used to overcome these limitations. In this study, both empirical and numerical methods have been used to assess the stability of an open stope located between mine levels N9225 and N9250 at Diavik diamond underground mine. It was shown that the numerical methods can be used as complementary methods along with other analytical and empirical methods to assess the stability of open stopes. A three dimensional elastoplastic finite element model was constructed using Abaqus software. In this paper a sensitivity analysis was performed to investigate the impact of the stress ratio "k" on the extent of the yielding and relaxation zones around the hangingwall and footwall of the understudy stope.

  6. [Stress-corrosion test of TIG welded CP-Ti].

    Science.gov (United States)

    Li, H; Wang, Y; Zhou, Z; Meng, X; Liang, Q; Zhang, X; Zhao, Y

    2000-12-01

    In this study TIG (Tungsten Inert Gas) welded CP-Ti were subjected to stress-corrosion test under 261 MPa in artificial saliva of 37 degrees C for 3 months. No significant difference was noted on mechanical test (P > 0.05). No color-changed and no micro-crack on the sample's surface yet. These results indicate that TIG welded CP-Ti offers excellent resistance to stress corrosion.

  7. The Trier Social Stress Test: Principles and practice

    Directory of Open Access Journals (Sweden)

    Andrew P. Allen

    2017-02-01

    Full Text Available Researchers interested in the neurobiology of the acute stress response in humans require a valid and reliable acute stressor that can be used under experimental conditions. The Trier Social Stress Test (TSST provides such a testing platform. It induces stress by requiring participants to make an interview-style presentation, followed by a surprise mental arithmetic test, in front of an interview panel who do not provide feedback or encouragement. In this review, we outline the methodology of the TSST, and discuss key findings under conditions of health and stress-related disorder. The TSST has unveiled differences in males and females, as well as different age groups, in their neurobiological response to acute stress. The TSST has also deepened our understanding of how genotype may moderate the cognitive neurobiology of acute stress, and exciting new inroads have been made in understanding epigenetic contributions to the biological regulation of the acute stress response using the TSST. A number of innovative adaptations have been developed which allow for the TSST to be used in group settings, with children, in combination with brain imaging, and with virtual committees. Future applications may incorporate the emerging links between the gut microbiome and the stress response. Future research should also maximise use of behavioural data generated by the TSST. Alternative acute stress paradigms may have utility over the TSST in certain situations, such as those that require repeat testing. Nonetheless, we expect that the TSST remains the gold standard for examining the cognitive neurobiology of acute stress in humans.

  8. Utility and tolerance of stress testing in geriatric patients.

    Science.gov (United States)

    Aparici, M; Peteiro, J; Fernandez de Almeida, C A; Hidalgo, R; Cabañero, J; Barba, J

    1990-10-01

    To determine the sensitivity and specificity of stress testing in geriatric patients and to estimate the tolerance of these patients to exercise. A prospective study done in two populations with different ages. Cardiologists and a stress testing laboratory. Persons with ages above and under 65 years who were admitted in our center and submitted to stress testing and coronary angiography for suspicion of ischemic heart disease. All stress tests were performed on a Siemens Elama cicloergometer model 380-B adapted to a Hewlett Packard 1517 A ECG recorder. Our protocol started with an initial work load of 30 Watts with increments of other 30 Watts every three minutes. A 12 lead ECG was registered at rest, at maximum effort and in the recovery phase (approx. eight minutes after maximum effort). Three leads ECG's (V2, aVF, V5) were registered every three minutes. Stress finishing criteria were: symptom's limited, fatigue and maximum heart rate (220-age). Blood pressure was also controlled every three minutes during exercise and every two minutes during the recovery phase. Coronary angiographies were performed on a Siemens Cardoskop U (cine) using the Judkins technique. Left anterior oblique, right anterior oblique and postero anterior projections were used in all the procedures. Stress testing presents high sensitivity and low specificity in geriatric patients. A good tolerance to exercise was observed in this group of patients. A similar sensitivity was observed in the stress tests performed by patients with ages above and under 65 years. Sensitivity seems to be related to the severity of the coronary lesion. On the other hand stress testing presented a lower specificity in the geriatric patient. Finally, good tolerance to exercise was observed in patients older than 65 years.

  9. Effect of angiotensin II and its receptor antagonists on human corpus cavernous contractility and oxidative stress: modulation of nitric oxide mediated relaxation.

    Science.gov (United States)

    Ertemi, Hani; Mumtaz, Faiz H; Howie, Alexander J; Mikhailidis, Dimitri P; Thompson, Cecil S

    2011-06-01

    To our knowledge the interaction between angiotensin II and nitric oxide in the control of human corpus cavernous function has not been assessed previously. We determined the presence and role of angiotensin II and its receptors in human penile function. Corpus cavernous tissue was obtained from 35 patients undergoing gender reassignment surgery. Immunohistochemical analysis was done to determine angiotensin II peptide tissue distribution. Organ bath studies were done to determine the angiotensin II/nitric oxide interaction on corpus cavernous smooth muscle function. The role of oxidative stress in the angiotensin II response was also examined using the nicotinamide adenine dinucleotide phosphate oxidase inhibitor apocynin. Angiotensin II was distributed in arteriolar endothelium, endothelium lining sinusoids and smooth muscle cells, and caused dose dependent contraction of human corpus cavernous smooth muscle strips that was inhibited by the angiotensin type 1 receptor antagonist losartan. Relaxation of corpus cavernous smooth muscle induced by the nitric oxide donor sodium nitroprusside or electrical field stimulation was potentiated by losartan. Apocynin decreased angiotensin II induced corpus cavernous contraction. Angiotensin II and nitric oxide interact to modulate human cavernous function since losartan potentiated sodium nitroprusside and electrical field stimulation mediated corpus cavernous smooth muscle relaxation. The angiotensin II response involves the production of superoxide and the development of oxidative stress. These findings support the role of angiotensin II in the regulation of human penile smooth muscle tone and suggest that angiotensin type 1 receptor inhibition may be a therapeutic approach to erectile dysfunction. Copyright © 2011 American Urological Association Education and Research, Inc. Published by Elsevier Inc. All rights reserved.

  10. A new paradigm to induce mental stress : the Sing-a-Song Stress Test(SSST)

    NARCIS (Netherlands)

    Brouwer, A.M.; Hogervorst, M.A.

    2014-01-01

    We here introduce a new experimental paradigm to induce mental stress in a quick and easy way while adhering to ethical standards and controlling for potential confounds resulting from sensory input and body movements. In our Sing-a-Song Stress Test, participants are presented with neutral messages

  11. Conversion of engineering stresses to Cauchy stresses in tensile and compression tests of thermoplastic polymers

    Directory of Open Access Journals (Sweden)

    Schümann Kerstin

    2016-09-01

    Full Text Available Thermoplastic polymers exhibit non-isochoric behaviour during tensile and compression testing as well as particular deformations like local necking (tension or buckling (compression. A method for the determination of Cauchy stresses from tensile and compression tests is presented, that considers the actual deformations of the test specimens. The exact geometry of the specimens in the respective present configuration is determined in photographs, which are taken continuously throughout the test. The engineering stresses at several time points are converted into Cauchy stresses using newly developed formulas in consideration of the actual specimen geometry. For validation finite element analyses of the tensile and compression tests are performed using the identified stress-strain curves. The numerical results show good agreement with the experiments for the tested polymers. Thus a method for conversion of engineering to Cauchy stresses in tensile and compression tests could be established considering the non-isochoric deformation in plasticity. With this method “true” stress-strain curves as input for finite element material models can be identified for arbitrary materials.

  12. Accelerated Stress Testing of Solar Photovoltaic Modules

    Science.gov (United States)

    1981-09-01

    Same Same. Also extensive internal corrosion where screw meets busbar . Loss of fill factor in 1-V curves after Not observed. No loss in fill factor...observed. Not observed. Extensive corrosion on oack ot ill cells 4tarting after 494 cycles. Teflon wire wicks water into busbar Same SAme where water...oxidizes busbar . 12 7 L L DI R< T. E: IZ -C& S E: RNI q - 0CT0 N R 0 L--F R 0F S T--- T .I ., F i T C YC LES FIGURE 3-2 Freeze Test Effects on OCLI Module 13

  13. Pilot Testing of the NURSE Stress Management Intervention.

    Science.gov (United States)

    Delaney, Colleen; Barrere, Cynthia; Robertson, Sue; Zahourek, Rothlyn; Diaz, Desiree; Lachapelle, Leeanne

    2016-12-01

    Student nurses experience significant stress during their education, which may contribute to illness and alterations in health, poor academic performance, and program attrition. The aim of this pilot study was to evaluate the feasibility and potential efficacy of an innovative stress management program in two baccalaureate nursing programs in Connecticut, named NURSE (Nurture nurse, Use resources, foster Resilience, Stress and Environment management), that assists nursing students to develop stress management plans. An explanatory sequential mixed-methods design was used to evaluate the effects of the intervention with 40 junior nursing students. Results from this study provide evidence that the NURSE intervention is highly feasible, and support further testing to examine the effect of the intervention in improving stress management in nursing students. © The Author(s) 2015.

  14. 12 CFR 615.5141 - Stress tests for mortgage securities.

    Science.gov (United States)

    2010-01-01

    ... 12 Banks and Banking 6 2010-01-01 2010-01-01 false Stress tests for mortgage securities. 615.5141... tests for mortgage securities. Mortgage securities are not eligible investments unless they pass a... cashflow and price of each mortgage security that you purchase and hold, except for adjustable rate...

  15. Market risk stress testing for internationally active financial institutions

    Directory of Open Access Journals (Sweden)

    Marković Petar

    2011-01-01

    Full Text Available The paper develops a comprehensive framework for market risk stress testing in internationally active financial institutions. We begin by defining the scope and type of the stress test and explaining how to select risk factors and the stress time horizon. We then address challenges related to data gathering, followed by in-depth discussion of techniques for developing realistic shock scenarios. Next the process of shock application to a particular portfolio is described, followed by determination of portfolio profit and loss. We conclude by briefly discussing the issue of assigning probability to stress scenarios. We illustrate the framework by considering the development of a ‘worst case’ scenario using global financial market data from Thomson Reuters Datastream.

  16. A Coupled Creep-Plasticity Model for Residual Stress Relaxation of a Shot-Peened Nickel-Base Superalloy

    Science.gov (United States)

    2007-05-01

    those attributed to Ludwik [118] and Ramberg - Osgood [119]. The function that best fits the tensile data is the Ramberg - Osgood model, n o KE 1...Peening Analytical Development, UDRI-TR-1999-47, August 1999. 118. Ludwik, P., Elemente der technologishen Mechanik, Springer, Berlin, 1909. 119. Ramberg ...W., and Osgood , W. R., “Description of Stress-Strain Curves by Three Parameters,” NACA Technical Note, No. 902, July, 1943. 120. Kirk, D

  17. Dislocation Reduction and Stress Relaxation of GaN and InGaN Multiple Quantum Wells with Improved Performance via Serpentine Channel Patterned Mask.

    Science.gov (United States)

    Ji, Qingbin; Li, Lei; Zhang, Wei; Wang, Jia; Liu, Peichi; Xie, Yahong; Yan, Tongxing; Yang, Wei; Chen, Weihua; Hu, Xiaodong

    2016-08-24

    The existence of high threading dislocation density (TDD) in GaN-based epilayers is a long unsolved problem, which hinders further applications of defect-sensitive GaN-based devices. Multiple-modulation of epitaxial lateral overgrowth (ELOG) is used to achieve high-quality GaN template on a novel serpentine channel patterned sapphire substrate (SCPSS). The dislocation blocking brought by the serpentine channel patterned mask, coupled with repeated dislocation bending, can reduce the dislocation density to a yet-to-be-optimized level of ∼2 × 10(5) to 2 × 10(6) cm(-2). About 80% area utilization rate of GaN with low TDD and stress relaxation is obtained. The periodical variations of dislocation density, optical properties and residual stress in GaN-based epilayers on SCPSS are analyzed. The quantum efficiency of InGaN/GaN multiple quantum wells (MQWs) on it can be increased by 52% compared with the conventional sapphire substrate. The reduced nonradiative recombination centers, the enhanced carrier localization, and the suppressed quantum confined Stark effect, are the main determinants of improved luminous performance in MQWs on SCPSS. This developed ELOG on serpentine shaped mask needs no interruption and regrowth, which can be a promising candidate for the heteroepitaxy of semipolar/nonpolar GaN and GaAs with high quality.

  18. A prognostic scoring system for arm exercise stress testing.

    Science.gov (United States)

    Xie, Yan; Xian, Hong; Chandiramani, Pooja; Bainter, Emily; Wan, Leping; Martin, Wade H

    2016-01-01

    Arm exercise stress testing may be an equivalent or better predictor of mortality outcome than pharmacological stress imaging for the ≥50% for patients unable to perform leg exercise. Thus, our objective was to develop an arm exercise ECG stress test scoring system, analogous to the Duke Treadmill Score, for predicting outcome in these individuals. In this retrospective observational cohort study, arm exercise ECG stress tests were performed in 443 consecutive veterans aged 64.1 (11.1) years. (mean (SD)) between 1997 and 2002. From multivariate Cox models, arm exercise scores were developed for prediction of 5-year and 12-year all-cause and cardiovascular mortality and 5-year cardiovascular mortality or myocardial infarction (MI). Arm exercise capacity in resting metabolic equivalents (METs), 1 min heart rate recovery (HRR) and ST segment depression ≥1 mm were the stress test variables independently associated with all-cause and cardiovascular mortality by step-wise Cox analysis (all pArm exercise scores for the other outcome end points yielded C-statistic values of 0.77-0.79 before and 0.82-0.86 after adjustment for significant covariates versus 0.64-0.72 for best fit pharmacological myocardial perfusion imaging models in a cohort of 1730 veterans who were evaluated over the same time period. Arm exercise scores, analogous to the Duke Treadmill Score, have good power for prediction of mortality or MI in patients who cannot perform leg exercise.

  19. Negative Exercise Stress Test: Does it Mean Anything? Case study

    Directory of Open Access Journals (Sweden)

    Hassan A. Mohamed

    2007-01-01

    Full Text Available Despite its low sensitivity and specificity (67% and 72%, respectively, exercise testing has remained one of the most widely used noninvasive tests to determine the prognosis in patients with suspected or established coronary disease.As a screening test for coronary artery disease, the exercise stress test is useful in that it is relatively simple and inexpensive. It has been considered particularly helpful in patients with chest pain syndromes who have moderate probability for coronary artery disease, and in whom the resting electrocardiogram (ECG is normal. The following case presentation and discussion will question the predictive value of a negative stress testing in patients with moderate probability for coronary artery disease.

  20. NUMERICAL SIMULATION OF AN AGRICULTURAL SOIL SHEAR STRESS TEST

    Directory of Open Access Journals (Sweden)

    Andrea Formato

    2007-03-01

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

  1. In-situ Curing Strain Monitoring of a Flat Plate Residual Stress Specimen Using a Chopped Stand Mat Glass/Epoxy Composite as Test Material

    Science.gov (United States)

    Jakobsen, J.; Skordos, A.; James, S.; Correia, R. G.; Jensen, M.

    2015-12-01

    The curing stresses in a newly proposed bi-axial residual stress testing configuration are studied using a chopped strand mat glass/epoxy specimen. In-situ monitoring of the curing is conducted using dielectric and fibre Bragg grating sensors. It is confirmed that a bi-axial residual stress state can be introduced in the specimens during curing and a quantification of its magnitude is presented. An alternative decomposition method used for converting the dielectric signal into a material state variable is proposed and good agreement with models found in the literature is obtained. From the cure cycles chosen it is suggested that any stress build up in the un-vitrified state is relaxed immediately and only stress build up in the vitrified state contributes to the residual stress state in the specimen.

  2. Using the Relaxation Test to Study Variation in the Time-Dependent Property of Rock and the Consequent Effect on Time-Dependent Roof Failure

    Science.gov (United States)

    Xue, Yuting; Mishra, Brijes; Gao, Danqing

    2017-09-01

    Field observations have demonstrated that roof failure occurs spatially in a mine from the time of excavation. It is suspected that time-dependent deformation propagates failure in the rock mass. In this paper, the relaxation test is used to study variation in the time-dependent property of rock and the consequent effect on time-dependent roof failure. This investigation uses a numerical simulation in 3DEC. The relaxation equation is developed from Burgers model. Variations in the time-dependent property in the post-failure region show negligible variation and, therefore, are averaged to represent the time-dependent property of the failed rock. Finally, these parameters are used in the numerical simulation of underground excavations. Two groups of parameters are used to represent the time-dependent property for pre- and post-failure conditions. FISH functions within 3DEC are used to monitor the state of each zone. Once failure is detected, the parameters are changed to the values corresponding to failed rock. The results show that the new relaxation model accurately predicts the time-dependent propagation of the failure zone. The variation of the time-dependent parameters significantly affects the rock mass behavior and roof convergence.

  3. Use of controlled dynamic impacts on hierarchically structured seismically hazardous faults for seismically safe relaxation of shear stresses

    Science.gov (United States)

    Ruzhich, Valery V.; Psakhie, Sergey G.; Levina, Elena A.; Shilko, Evgeny V.; Grigoriev, Alexandr S.

    2017-12-01

    In the paper we briefly outline the experience in forecasting catastrophic earthquakes and the general problems in ensuring seismic safety. The purpose of our long-term research is the development and improvement of the methods of man-caused impacts on large-scale fault segments to safely reduce the negative effect of seismodynamic failure. Various laboratory and large-scale field experiments were carried out in the segments of tectonic faults in Baikal rift zone and in main cracks in block-structured ice cove of Lake Baikal using the developed measuring systems and special software for identification and treatment of deformation response of faulty segments to man-caused impacts. The results of the study let us to ground the necessity of development of servo-controlled technologies, which are able to provide changing the shear resistance and deformation regime of fault zone segments by applying vibrational and pulse triggering impacts. We suppose that the use of triggering impacts in highly stressed segments of active faults will promote transferring the geodynamic state of these segments from a metastable to a more stable and safe state.

  4. New method of diagnosis for chronic ankle instability: comparison of manual anterior drawer test, stress radiography and stress ultrasound.

    Science.gov (United States)

    Lee, Kyung Tai; Park, Young Uk; Jegal, Hyuk; Park, Jong Won; Choi, Jung Pil; Kim, Jin Su

    2014-07-01

    To diagnose chronic ankle instability, clinicians frequently use manual anterior drawer test and stress radiography. However, both exams can yield incorrect results and do not reveal the extent of ankle instability. The use of stress ultrasound during a manual anterior drawer stress procedure might enable the diagnosis of chronic ankle instability. Seventy-three patients with chronic ankle pain or laxity after remote ankle sprain were included. The study population included 41 males and 32 females. The mean age of the patients at the time of the operation was 29 years. A standardized physical examination (manual anterior drawer test), stress radiography and stress ultrasonography were performed to assess the anterior talofibular ligament (ATFL). Ultrasound images were taken in the resting position and the maximal anterior drawer position. The statistical significance of stress ultrasound among the three groups according to manual anterior drawer test and a specific degree (5 mm) of anterior translation of stress radiography were analysed. Correlation coefficients between stress ultrasound, stress radiography and manual anterior drawer test were calculated. There was a significant difference for ATFL length (ATFL stress) and ATFL ratio (ATFL stress/ATFL resting) among the three groups (both p stress radiography among three groups according to manual anterior drawer test (p = 0.159). There was a significant difference for ATFL length (ATFL stress) and ATFL ratio between two groups with 5-mm anterior translation of stress radiography (p = 0.002 and p = 0.011, respectively). The mean value of grade of manual anterior drawer test between the two groups also differed (p = 0.021). There was a moderately positive linear relationship between stress ultrasound and manual anterior drawer test. Also, there was a positive linear relationship between stress ultrasound and stress radiography. The results suggest that the value of ATFL length (ATFL stress) and ATFL ratio of stress

  5. Testing the Elliott-Yafet spin-relaxation mechanism in KC8: A model system of biased graphene

    Science.gov (United States)

    Fábián, G.; Dóra, B.; Antal, Á.; Szolnoki, L.; Korecz, L.; Rockenbauer, A.; Nemes, N. M.; Forró, L.; Simon, F.

    2012-06-01

    Temperature-dependent electron spin resonance (ESR) measurements are reported on stage-1 potassium-doped graphite, a model system of biased graphene. The ESR linewidth is nearly isotropic, and although the g factor has a sizable anisotropy, its majority is shown to arise due to macroscopic magnetization. Even though the homogeneous ESR linewidth shows an unusual, nonlinear temperature dependence, it appears to be proportional to the resistivity which is a quadratic function of the temperature. These observations suggests the validity of the Elliott-Yafet relaxation mechanism in KC8 and allows us to place KC8 on the empirical Beuneu-Monod plot among ordinary elemental metals.

  6. Prognostic impact of stress testing in coronary artery disease

    Energy Technology Data Exchange (ETDEWEB)

    Severi, S.; Michelassi, C. (CNR Clinical Physiology Institute, Pisa, (Italy))

    1991-05-01

    Observational data prospectively collected permit the examination of a complex set of decisions, including the decision not to perform any stress testing. Patients with or without previous myocardial infarction admitted for coronary evaluation and not submitted to any stress testing because of clinical reasons are at a higher risk for subsequent death. For prognostication, no test has been better validated than exercise electrocardiography: it can identify patients at low and high risk for future cardiac events among those without symptoms, with typical chest pain, and with previous myocardial infarction. In patients with triple-vessel disease, the results of exercise also allow those at low and high risk to be recognized. Both exercise radionuclide angiography and {sup 201}Tl scintigraphy (the latter in larger patient populations) have also demonstrated significant prognostic value on patients with or without previous myocardial infarction. Neither one has shown superiority to the other in prognostication. So far, they have been considered the only viable alternatives to exercise electrocardiography stress testing for diagnosis and prognostication. However, their costs limit their extensive application. Preliminary data suggest that intravenous dipyridamole echocardiography can be used for both diagnosis and prognostication of coronary artery disease; moreover, the prognostic information derived from dipyridamole echocardiography testing seems independent of and additive to that provided by exercise electrocardiography. Further prospective studies on larger patient populations are needed to better define the prognostic value of dipyridamole echocardiography testing.47 references.

  7. Heart-Kidney Biomarkers in Patients Undergoing Cardiac Stress Testing

    Directory of Open Access Journals (Sweden)

    Mikko Haapio

    2011-01-01

    Full Text Available We examined association of inducible myocardial perfusion defects with cardiorenal biomarkers, and of diminished left ventricular ejection fraction (LVEF with kidney injury marker plasma neutrophil gelatinase-associated lipocalin (NGAL. Patients undergoing nuclear myocardial perfusion stress imaging were divided into 2 groups. Biomarkers were analyzed pre- and poststress testing. Compared to the patients in the low ischemia group (n=16, the patients in the high ischemia group (n=18 demonstrated a significantly greater rise in cardiac biomarkers plasma BNP, NT-proBNP and cTnI. Subjects were also categorized based on pre- or poststress test detectable plasma NGAL. With stress, the group with no detectable NGAL had a segmental defect score 4.2 compared to 8.2 (P=.06 in the detectable NGAL group, and 0.9 vs. 3.8 (P=.03 at rest. BNP rose with stress to a greater degree in patients with detectable NGAL (10.2 vs. 3.5 pg/mL, P=.03. LVEF at rest and with stress was significantly lower in the detectable NGAL group; 55.8 versus 65.0 (P=.03 and 55.1 vs. 63.8 (P=.04, respectively. Myocardial perfusion defects associate with biomarkers of cardiac stress, and detectable plasma NGAL with significantly lower LVEF, suggesting a specific heart-kidney link.

  8. Treating Post-traumatic Stress Disorder in Patients with Multiple Sclerosis: A Randomized Controlled Trial Comparing the Efficacy of Eye Movement Desensitization and Reprocessing and Relaxation Therapy.

    Science.gov (United States)

    Carletto, Sara; Borghi, Martina; Bertino, Gabriella; Oliva, Francesco; Cavallo, Marco; Hofmann, Arne; Zennaro, Alessandro; Malucchi, Simona; Ostacoli, Luca

    2016-01-01

    Multiple Sclerosis (MS) is a demyelinating autoimmune disease that imposes a significant emotional burden with heavy psychosocial consequences. Several studies have investigated the association between MS and mental disorders such as depression and anxiety, and recently researchers have focused also on Post-traumatic Stress Disorder (PTSD). This is the first study that investigates the usefulness of proposing a treatment for PTSD to patients with MS. A randomized controlled trial with patients with MS diagnosed with PTSD comparing Eye Movement Desensitization and Reprocessing (EMDR; n = 20) and Relaxation Therapy (RT; n = 22). The primary outcome measure was the proportion of participants that no longer meet PTSD diagnosis as measured with Clinician Administered PTSD Scale 6-months after the treatment. The majority of patients were able to overcome their PTSD diagnosis after only 10 therapy sessions. EMDR treatment appears to be more effective than RT in reducing the proportion of patients with MS suffering from PTSD. Both treatments are effective in reducing PTSD severity, anxiety and depression symptoms, and to improve Quality of Life. Although our results can only be considered preliminary, this study suggests that it is essential that PTSD symptoms are detected and that brief and cost-effective interventions to reduce PTSD and associated psychological symptoms are offered to patients, in order to help them to reduce the psychological burden associated with their neurological condition. NCT01743664, https://clinicaltrials.gov/ct2/show/NCT01743664.

  9. Treating Post-traumatic Stress Disorder in patients with Multiple Sclerosis: a randomized controlled trial comparing the efficacy of Eye Movement Desensitization and Reprocessing and Relaxation Therapy.

    Directory of Open Access Journals (Sweden)

    Sara eCarletto

    2016-04-01

    Full Text Available Objective: Multiple Sclerosis (MS is a demyelinating autoimmune disease that imposes a significant emotional burden with heavy psychosocial consequences. Several studies have investigated the association between MS and mental disorders such as depression and anxiety, and recently researchers have focused also on Post-traumatic Stress Disorder (PTSD. This is the first study that investigates the usefulness of proposing a treatment for PTSD to patients with MS. Methods: A randomized controlled trial with patients with MS diagnosed with PTSD comparing Eye Movement Desensitization and Reprocessing (EMDR; n = 20 and Relaxation Therapy (RT; n = 22. The primary outcome measure was the proportion of participants that no longer meet PTSD diagnosis as measured with Clinician Administered PTSD Scale six-months after the treatment.Results: The majority of patients were able to overcome their PTSD diagnosis after only 10 therapy sessions. EMDR treatment appears to be more effective than RT in reducing the proportion of patients with MS suffering from PTSD. Both treatments are effective in reducing PTSD severity, anxiety symptoms and to improve Quality of Life (QoL. Conclusions: Although our results can only be considered preliminary, this study suggests that it is essential that PTSD symptoms are detected and that brief and cost-effective interventions to reduce PTSD and associated psychological symptoms are offered to patients, in order to help them to reduce the psychological burden associated with their neurological condition.Trail registration: NCT01743664, https://clinicaltrials.gov/ct2/show/NCT01743664

  10. Color Shift Modeling of Light-Emitting Diode Lamps in Step-Loaded Stress Testing

    NARCIS (Netherlands)

    Cai, Miao; Yang, Daoguo; Huang, J.; Zhang, Maofen; Chen, Xianping; Liang, Caihang; Koh, S.W.; Zhang, G.Q.

    2017-01-01

    The color coordinate shift of light-emitting diode (LED) lamps is investigated by running three stress-loaded testing methods, namely step-up stress accelerated degradation testing, step-down stress accelerated degradation testing, and constant stress accelerated degradation testing. A power

  11. Anorexic Behavior, Female Competition and Stress: Developing the Female Competition Stress Test

    Directory of Open Access Journals (Sweden)

    Catherine Salmon

    2008-01-01

    Full Text Available The FCST (Female-Female Competition Stress Test was constructed to assess stress from adolescent female-female competition. Such stress is particularly relevant to the Reproductive Suppression Hypothesis that has been suggested as one possible explanation for the development of anorexic type behavior in young women. A series of items generated an initial test in the first phase of development. In the second phase, three studies were conducted to assess reliability and validity. Female undergraduates retrospectively rated the female-female competition stress they had experienced as adolescents, and their responses were factor-analyzed. In a second group of subjects, FCST scores were correlated with a measure of anxiety. In the third study, three samples provided prototypicality ratings of the test items to determine both the agreement among raters and which items were not sufficiently prototypical of female-female competition stress to be retained. In the final phase, the responses of adolescent girls to the FCST and several measures of body image were factor analyzed, showing the utility of the FCST.

  12. Oxidative stress increases in overweight individuals following an exercise test.

    Science.gov (United States)

    Andrews, Anne M; Kantor, Mark A

    2010-12-01

    The objective of this study was to determine whether the Army Physical Fitness Test (APFT) causes oxidative stress and evaluate the impact of dietary antioxidant intake, fitness level, and body composition on changes in oxidative stress. Forty-seven overweight subjects were asked to perform an APFT. Creatine kinase (CK), C-reactive protein (CRP), glutathione peroxidase (GPX), and superoxide dismutase (SOD) were measured before, immediately after, and 24 hr postexercise. CK significantly increased immediately postexercise and at 24 hr postexercise. CRP and GPX significantly increased immediately postexercise, whereas SOD did not change significantly. Antioxidant intake, fitness level, and body composition were found to significantly influence changes in CK, GPX, and SOD after exercise. In conclusion, the APFT causes oxidative stress in overweight subjects. The associations between dietary antioxidants, fitness level, and body composition seen with each of the biomarkers provide support for future research in this area.

  13. Impulsivity and Stress Response in Pathological Gamblers During the Trier Social Stress Test

    NARCIS (Netherlands)

    Maniaci, G.; Goudriaan, A. E.; Cannizzaro, C.; van Holst, R. J.

    2017-01-01

    Gambling has been associated with increased sympathetic nervous system output and stimulation of the hypothalamic-pituitary-adrenal axis. However it is unclear how these systems are affected in pathological gambling. This study aimed to investigate the effect of the Trier Social Stress Test (TSST)

  14. Stress Free Temperature Testing and Residual Stress Calculations on Out-of-Autoclave Composites

    Science.gov (United States)

    Cox, Sarah; Tate, LaNetra C.; Danley, Susan; Sampson, Jeff; Taylor, Brian; Miller, Sandi

    2012-01-01

    Future launch vehicles will require the incorporation large composite parts that will make up primary and secondary components of the vehicle. NASA has explored the feasibility of manufacturing these large components using Out-of-Autoclave impregnated carbon fiber composite systems through many composites development projects. Most recently, the Composites for Exploration Project has been looking at the development of a 10 meter diameter fairing structure, similar in size to what will be required for a heavy launch vehicle. The development of new material systems requires the investigation of the material properties and the stress in the parts. Residual stress is an important factor to incorporate when modeling the stresses that a part is undergoing. Testing was performed to verify the stress free temperature with two-ply asymmetric panels. A comparison was done between three newly developed out of autoclave IM7 /Bismalieimide (BMI) systems. This paper presents the testing results and the analysis performed to determine the residual stress of the materials.

  15. Major outcomes of the stress tests. Learning from each other

    Energy Technology Data Exchange (ETDEWEB)

    Anon.

    2013-11-15

    Performed by the EU's 'nuclear' member states plus Switzerland and Ukraine, the European stress tests were carried out with some differences, notably in the scope considered. The action plans derived from the conclusions of the national reports peer-reviewed by TSO experts also differ in terms of scope, priorities and scheduling. Similar safety reassessments were performed in other countries such as Japan or Russia. The country-specific focuses described below provide an overview of the similarities and dissimilarities between twelve countries which are represented at EUROSAFE. One common denominator among them might be the fact that the conclusions from the stress tests did not reveal any major deficiency calling for immediate steps to be taken. (orig.)

  16. INTERFACE DEVICE FOR NONDESTRUCTIVE TESTING OF RESIDUAL SURFACE STRESSES

    Directory of Open Access Journals (Sweden)

    Gennady A. Perepelkin

    2016-01-01

    Full Text Available The paper considers the organization of connection of a personal computer with a device for nondestructive testing of residual surface stresses. The device works is based on the phenomenon of diffraction of ionizing radiation from the crystal lattice near the surface of the crystallites. Proposed software interface to the organization for each type of user: the device developers, administrators, users. Some aspects of the organization of communication microcontroller to a PC via USB-port

  17. Step-Stress Accelerated Degradation Testing (SSADT) for Photovoltaic (PV) Devices and Cells (Presentation)

    Energy Technology Data Exchange (ETDEWEB)

    Lee, J.; Elmore, R.; Suh, C.; Jones, W.

    2010-10-01

    Presentation on step-stress accelerated degradation testing (SSADT) for photovoltaics (PV). Developed are a step-stress degradation test (SSADT) for PV reliability tests and a lifetime prediction model for PV products.

  18. Stress relaxation resistance of Cu-1Ni-0.9Sn-0.05P alloy (C19025); Cu-1Ni-0.9Sn-0.05P gokin ( C19025 ) no taioryoku kanwa tokusei

    Energy Technology Data Exchange (ETDEWEB)

    Sugawara, A.; Hana, Y. [Dowa Mining Co. Ltd., Tokyo (Japan)

    1998-04-20

    Wire harness is a combination of cable and terminal and is an important part having a function of cable inside the vehicle. Development of car electronics demand diversification and high density of wiring, and connector of joints is obliged to multipolarization. Extremely small terminal is required in multipolarized connector, and further, thickness of the plate of copper alloy by which terminal is made is becoming thin. Further, connection of the wiring inside the engine room has been necessary with the increase of various types of sensors or with the development of engine combustion control system, and a material that can resist the heat effect from engine or exhaust system, stress relaxation resistance, has been necessary. Cu-1Ni-0.9Sn-0.05P alloy developed by authors possess extremely good stress relaxation resistance and is bearing sufficiently the temperature of 150degC. In this report, the details of the development of C 19025 are introduced and temperature resistance for more than 150degC and stress relaxation resistance are studied. 7 refs., 4 figs., 2 tabs.

  19. The Effects of Prone with Respect to Supine Position on Stress Relaxation, Respiratory Mechanics, and the Work of Breathing Measured by the End-Inflation Occlusion Method in the Rat.

    Science.gov (United States)

    Rubini, Alessandro

    2016-02-01

    The working hypothesis is that the prone position with respect to supine may change the geometric configuration of the lungs inside the chest wall, thus their reciprocal mechanical interactions, leading to possible effects on stress relaxation phenomena and respiratory mechanics. The effects of changing body posture from supine to prone on respiratory system mechanics, particularly on stress relaxation, were investigated in the rat by the end-inflation occlusion method. In the prone with respect to supine position, an increment of the frictional resistance of the airway (from 0.13 ± 0.01 to 0.19 ± 0.02 cm H2O/l sec(-1), p Respiratory system elastance and total resistive pressure dissipation did not change significantly. Accordingly, a significant increase of the frictional "ohmic" mechanical inspiratory work of breathing and a decrease of the visco-elastic work of inspiration were demonstrated, while no significant changes occurred for the total mechanical work of breathing and its total resistive and elastic components. It is concluded that postural changes affect the visco-elastic characteristics of the respiratory system and the related stress relaxation phenomena by influencing the disposition and relation of the lungs inside the chest wall and their relative geometrical configuration, and the interaction phenomena of the constitutive parenchymal structures, i.e., elastin and collagen fibers. Since the prone position resulted in no serious or disadvantageous respiratory system mechanical derangement, it is suggested it may be usefully applied in nursing or for therapeutic goals.

  20. A test of stress theory: relief workers in refugee camps.

    Science.gov (United States)

    Soliman, Hussein H; Gillespie, David F

    2011-10-01

    The purpose of this paper is to apply a stress model drawn from the literature to the relief and social service workers who have been active in refugee camps for a prolonged period of time. Working in difficult environments, social service workers deliver essential services to refugee populations around the world. A model of four work-stress determinants--tasks, management, appreciation and collaboration--was tested on 274 social workers in five regions of the Middle East (Jordan, Lebanon and Syria, as well as the occupied Palestinian territories of the Gaza Strip and the West Bank). Statistical fit indices were adequate but two relationships were statistically insignificant. The collaboration variable was dropped to create a modified model with tasks indirectly and management and appreciation directly affecting work-related stress. The five direct relationships and two indirect relationships of this modified model are consistent with stress theory, and all relationships--direct and indirect--are statistically significant. © 2011 The Author(s). Disasters © Overseas Development Institute, 2011.

  1. Effect of Progressive Muscle Relaxation in Female Health Care ...

    African Journals Online (AJOL)

    Keywords: Female stress, relaxation techniques, health care professionals. Original Article ... Stress management programs such as meditation, yoga, hypnosis ..... stress in undergraduate medical students at S. N. Medical College,. Bagalkot ...

  2. Idiosyncratic reality claims, relaxation dispositions, and ABC relaxation theory: happiness, literal christianity, miraculous powers, metaphysics, and the paranormal.

    Science.gov (United States)

    Smith, Jonathan C; Karmin, Aaron D

    2002-12-01

    This study examined idiosyncratic reality claims, that is, irrational or paranormal beliefs often claimed to enhance relaxation and happiness and reduce stress. The Smith Idiosyncratic Reality Claims Inventory and the Smith Relaxation Dispositions Inventory (which measures relaxation and stress dispositions, or enduring states of mind frequently associated with relaxation or stress) were given to 310 junior college student volunteers. Principal components factor analysis with varimax rotation identified five idiosyncratic reality claim factors: belief in Literal Christianity; Magic; Space Aliens: After Death experiences; and Miraculous Powers of Meditation, Prayer, and Belief. No factor correlated with increased relaxation dispositions Peace, Energy, or Joy, or reduced dispositional somatic stress, worry, or negative emotion on the Smith Relaxation Dispositions Inventory. It was concluded that idiosyncratic reality claims may not be associated with reported relaxation, happiness, or stress. In contrast, previous research strongly supported self-affirming beliefs with few paranormal assumptions display such an association.

  3. Learn to manage stress

    Science.gov (United States)

    Stress - managing; Stress - recognizing; Stress - relaxation techniques ... LEARN TO RECOGNIZE STRESS The first step in managing stress is recognizing it in your life. Everyone feels stress in a different way. ...

  4. STRESS TESTS FOR VIDEOSTREAMING SERVICES BASED ON RTSP PROTOCOL

    Directory of Open Access Journals (Sweden)

    Gabriel Elías Chanchí Golondrino

    2015-11-01

    Full Text Available Video-streaming is a technology with major implications these days in such diverse contexts as education, health and the business sector; all of this regarding the ease it provides for remote access to live or recorded media content, allowing communication regardless of geographic location. One standard protocol that enables implementation of this technology is real time streaming protocol, or RTSP. However, since most application servers and Internet services are supported on HTTP requests, very little research has been done on generating tools for carrying out stress tests on streaming servers. This paper presents a stress measuring tool called Hermes, developed in Python, which allows calculation of response times for establishing RTSP connections to streaming servers, as well as obtaining RAM memory consumption and CPU usage rate data from these servers. Hermes was deployed in a video-streaming environment where stress testing was carried out on the LIVE555 server, using calls in the background to VLC and OpenRTSP open source clients. 

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

    Science.gov (United States)

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

    2018-01-01

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

  6. Constrictive pericarditis causing a positive TI-201 SPECT stress test for myocardial ischemia

    Energy Technology Data Exchange (ETDEWEB)

    Matthews, R.J.; Lightfoote, J.; Grusd, R.S. (Diagnostic Imaging of Southern California Medical Group, Sherman Oaks (USA))

    1990-08-01

    A case of constritive pericarditis was demonstrated by a positive thallium SPECT stress test for myocardial ischemia. After pericardiectomy, the repeat thallium stress test was normal. The disappearance of the criteria for a positive test suggests that constrictive pericarditis can cause myocardial ischemia, which can be demonstrated by thallium SPECT stress testing.

  7. Liquidity Stress-Tester: A macro model for stress-testing banks' liquidity risk

    OpenAIRE

    Jan Willem van den End

    2008-01-01

    This paper presents a macro stress-testing model for market and funding liquidity risks of banks, which have been main drivers of the recent financial crisis. The model takes into account the first and second round (feedback) effects of shocks, induced by behavioural reactions of heterogeneous banks, and idiosyncratic reputation effects. The impact on liquidity risk is simulated by a Monte Carlo approach. This generates distributions of liquidity buffers for each scenario round, including the...

  8. Step-Stress Accelerated Degradation Testing for Solar Reflectors: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Jones, W.; Elmore, R.; Lee, J.; Kennedy, C.

    2011-09-01

    To meet the challenge to reduce the cost of electricity generated with concentrating solar power (CSP) new low-cost reflector materials are being developed including metalized polymer reflectors and must be tested and validated against appropriate failure mechanisms. We explore the application of testing methods and statistical inference techniques for quantifying estimates and improving lifetimes of concentrating solar power (CSP) reflectors associated with failure mechanisms initiated by exposure to the ultraviolet (UV) part of the solar spectrum. In general, a suite of durability and reliability tests are available for testing a variety of failure mechanisms where the results of a set are required to understand overall lifetime of a CSP reflector. We will focus on the use of the Ultra-Accelerated Weathering System (UAWS) as a testing device for assessing various degradation patterns attributable to accelerated UV exposure. Depending on number of samples, test conditions, degradation and failure patterns, test results may be used to derive insight into failure mechanisms, associated physical parameters, lifetimes and uncertainties. In the most complicated case warranting advanced planning and statistical inference, step-stress accelerated degradation (SSADT) methods may be applied.

  9. Stress Reactivity to an Electronic Version of the Trier Social Stress Test: A Pilot Study

    Directory of Open Access Journals (Sweden)

    Sage E Hawn

    2015-05-01

    Full Text Available Social stressors that rely on the inclusion of confederates (i.e., Trier Social Stress Test; TSST are often used in clinical laboratory research paradigms to elicit a measurable stress response in participants. Although effective, the TSST is labor intensive and may introduce error variance as a function of confederate race, gender, and/or response characteristics. The present study aimed to develop and validate an electronic version of the TSST (e-TSST. The primary aim was to compare the e-TSST to an e-neutral control condition; the exploratory aim was to compare the magnitude of stress response elicited by the e-TSST to that elicited by the traditional TSST. Forty-three healthy adults were randomized to the e-TSST or e-neutral condition. Subjective (participant-rated distress and objective (cortisol, heart rate and blood pressure indices of stress were collected prior to, and multiple times following, the stressor. Using archival data collected from 19 healthy participants exposed to the traditional TSST in a prior study, stress reactivity was compared between the electronic and traditional versions of the TSST. The e-TSST elicited significant increases in all measures of stress reactivity compared to the e-neutral condition, with the exception of heart rate (HR. Results showed that the magnitude of subjective distress, BP, and HR responses elicited by the e-TSST did not differ significantly from that elicited by the traditional TSST. The traditional TSST elicited significantly higher cortisol than the e-TSST. Although these findings provide initial support for the development of electronic versions of the TSST, further refinement of the e-TSST is warranted prior to broad adoption of this technology. A refined, reliable e-TSST could allow for increased utilization of the TSST by enhancing convenience, reducing labor costs, and limiting potential error variance introduced by human confederates.

  10. Soil precompression stress: II a comparison of different compaction tests and stress-displacement behaviour of the soil during wheeling

    NARCIS (Netherlands)

    Keller, T.; Arvidsson, J.; Dawidowski, J.B.; Koolen, A.J.

    2004-01-01

    Precompression stress is often used as a criterion for soil susceptibility to compaction. The objective of this study was to compare precompression stresses derived from different compression test methods and relate these values to measured stress and displacement during wheeling in the field.

  11. Learning aptitude, spatial orientation and cognitive flexibility tested in a virtual labyrinth after virtual stress induction

    National Research Council Canada - National Science Library

    Delahaye, Marcel; Lemoine, Patrick; Cartwright, Shanique; Deuring, Gunnar; Beck, Johannes; Pflueger, Marlon; Graf, Marc; Hachtel, Henning

    2015-01-01

    .... A VR task was developed to induce stress following the Trier Social Stress Test (TSST) protocol and two VR cognitive performance tests to measure learning aptitude, spatial orientation and cognitive flexibility...

  12. Testing and Evaluation of a Predeployment Stress Inoculation Training Program (PreSTINT)

    Science.gov (United States)

    2016-07-01

    The next set of questions asks about your mental or emotional health, stress, and some other things that affect ...briefed site POCs and finalized data collection room locations and facilities at Ft. Bragg. b) Study team prepared human studies protocol documents for...relaxation music or other audio recordings. Sample Size. Based on the response rates from the pilot study, the expected follow-up rate was around

  13. Experimentally testing Taylor's stress, coping and adaptation framework.

    Science.gov (United States)

    Gidron, Yori; Nyklicek, Ivan

    2009-10-01

    Taylor (1995) constructed a comprehensive framework of stress and adaptation, which considers internal and external resources/impediments as moderators, based on previous studies and models. However, most past research used correlation designs and has not taken into account all of the framework's components within one study. This study tested the effects of the event (minor, major), primary appraisal (benign, severe), coping (problem-focused coping (PFC) versus emotion-focused coping), external resources (with/without social support), and internal impediments (hostility), on estimated distress (dependent variable) in written imagined stressful daily scenarios. All components except hostility were experimentally manipulated within subjects in the scenarios. The scenarios were rated by 281 Dutch students. The variables event, appraisal, and social support significantly and independently affected estimated distress. Event and appraisal synergistically interacted in relation to estimated distress. Finally, appraisal interacted with coping such that the distress-reducing effects of PFC occurred only in benign events, while coping did not affect estimated distress in severely appraised events. This study experimentally tested most components of Taylor's framework, and showed that events, appraisal, and social resources were independent determinants of estimated distress, and that appraisal interacts in a complex manner with the event and with coping.

  14. Testing the ecological validity of the Trier Social Stress Test: Association with real-life exam stress.

    Science.gov (United States)

    Henze, Gina-Isabelle; Zänkert, Sandra; Urschler, David F; Hiltl, Tanja J; Kudielka, Brigitte M; Pruessner, Jens C; Wüst, Stefan

    2017-01-01

    The Trier Social Stress Test (TSST) is the most widely used laboratory stress protocol in psychoneuroendocrinology. Despite its popularity, surprisingly few attempts have been made to explore the ecological validity of the TSST. In the present study, 31 young healthy subjects (24 females) were exposed to the TSST about 4 weeks before completing an oral exam on a separate day. Salivary cortisol levels increased significantly in response to both stimuli (TSST: F(2.21, 66.33)=5.73, p=0.004; oral exam: F(1.98, 59.28)=4.38, p=0.017) with similar mean response curves and significant correlations between cortisol increases and areas under the response curves (increase: r=0.67; AUC: r=0.56; both p≤0.01). Correspondingly, changes in positive and negative affect did also show significant correlations between conditions (increase: positive affect: r=0.36; negative affect: r=0.50; both: p≤0.05; AUC: positive affect: r=0.81; negative affect: r=0.70; both p≤0.01) while mean time course dynamics were significantly different (positive affect: F(2.55, 76.60)=10.15, p=0.001; negative affect: F(1.56, 46.82)=23.32, p=0.001), indicating that the oral exam had a more pronounced impact on affect than the TSST. Our findings provide new evidence for the view that cortisol as well as subjective stress responses to the TSST are indeed significantly associated with acute stress responses in real life. Copyright © 2016 Elsevier Ltd. All rights reserved.

  15. Safety of regadenoson stress testing in patients with pulmonary hypertension.

    Science.gov (United States)

    Moles, Victor M; Cascino, Thomas; Saleh, Ashraf; Mikhova, Krasimira; Lazarus, John J; Ghannam, Michael; Yun, Hong J; Konerman, Matthew; Weinberg, Richard L; Ficaro, Edward P; Corbett, James R; McLaughlin, Vallerie V; Murthy, Venkatesh L

    2016-11-28

    We sought to determine the safety of regadenoson stress testing in patients with PH. PH is increasingly recognized at more advanced ages. As many as one-third of patients with PH have coronary artery disease. Because of their physical limitations, patients with PH are unable to adequately exercise. Regadenoson can potentially have an adverse impact due to their tenuous hemodynamics. Current guidelines suggest performing a coronary angiography in patients with PH who have angina or multiple coronary risk factors. We identified 67 consecutive patients with confirmed PH by catheterization (mean PA > 25 mmHg not due to left heart disease) who underwent MPI with regadenoson stress. Medical records were reviewed to determine hemodynamic and ECG response to regadenoson. No serious events occurred. Common side effects related to regadenoson were observed, dyspnea being the most common (70.6%). No syncope occurred. Heart rate increased from 74.6 ± 14 to 96.3 ± 18.3 bpm, systolic blood pressure increased from 129.8 ± 20.9 to 131.8 ± 31 mmHg, and diastolic blood pressure decreased from 77.1 ± 11.4 to 72.9 ± 15.3 mmHg. There was no ventricular tachycardia, ventricular fibrillation, or second- or third-degree atrioventricular block. Regadenoson stress MPI appears to be well tolerated and safe in patients with PH.

  16. Dielectric and shear mechanical relaxations in glass-forming liquids: A test of the Gemant-DiMarzio-Bishop model

    DEFF Research Database (Denmark)

    Niss, K.; Jakobsen, B.; Olsen, N.B.

    2005-01-01

    The Gemant-DiMarzio-Bishop model, which connects the frequency-dependent shear modulus to the frequency-dependent dielectric constant, is reviewed and a new consistent macroscopic formulation is derived. It is moreover shown that this version of the model can be tested without fitting parameters....

  17. Exercise stress testing. An overview of current guidelines.

    Science.gov (United States)

    Lear, S A; Brozic, A; Myers, J N; Ignaszewski, A

    1999-05-01

    Exercise stress testing (ET) is an inexpensive noninvasive tool that provides valuable cardiopulmonary information in healthy and diseased populations. It is most commonly used for diagnosing coronary artery disease (CAD) and developing appropriate exercise prescriptions (EP). With its widespread use and application, it is imperative that safe and appropriate guidelines and procedures are used, as there are a number of risks associated with testing in a population with or suspected of having CAD. The focus should be on the patient's safety: personnel must be properly trained and aware of all emergency procedures, contra-indications for ET and indications for test termination must be strictly adhered to. Three main types of testing are prevalent: submaximal, maximal and maximal utilising gas exchange. The maximal test is most commonly used, and the submaximal is appropriate for hospitalised patients. Gas exchange data is essential when assessing congestive heart failure and timing for heart transplantation. ET is commonly performed using a treadmill or a bicycle ergometer. The treadmill provides a more familiar exercise modality and has been shown to have greater diagnostic sensitivity than the bicycle ergometer; it is, however, more expensive and requires more space in the testing room. The bicycle ergometer is more appropriate for those individuals who are severely obese or have problems with extended periods of walking. Regardless of the modality used, an appropriate exercise protocol should be used. In North America, the Bruce protocol is the most common. However, the Bruce protocol, and others that estimate exercise capacity based on equations, tend to overestimate exercise capacity. They may be too demanding for those with limited exercise capacity, and too long for those with high exercise capacity. For these people, an exercise protocol that reaches maximal capacity in 8 to 12 minutes using smaller increments in workload should be considered. Once completed

  18. A climate stress-test of the financial system

    Science.gov (United States)

    Battiston, Stefano; Mandel, Antoine; Monasterolo, Irene; Schütze, Franziska; Visentin, Gabriele

    2017-03-01

    The urgency of estimating the impact of climate risks on the financial system is increasingly recognized among scholars and practitioners. By adopting a network approach to financial dependencies, we look at how climate policy risk might propagate through the financial system. We develop a network-based climate stress-test methodology and apply it to large Euro Area banks in a `green' and a `brown' scenario. We find that direct and indirect exposures to climate-policy-relevant sectors represent a large portion of investors' equity portfolios, especially for investment and pension funds. Additionally, the portion of banks' loan portfolios exposed to these sectors is comparable to banks' capital. Our results suggest that climate policy timing matters. An early and stable policy framework would allow for smooth asset value adjustments and lead to potential net winners and losers. In contrast, a late and abrupt policy framework could have adverse systemic consequences.

  19. Adaptive Stress Testing of Airborne Collision Avoidance Systems

    Science.gov (United States)

    Lee, Ritchie; Kochenderfer, Mykel J.; Mengshoel, Ole J.; Brat, Guillaume P.; Owen, Michael P.

    2015-01-01

    This paper presents a scalable method to efficiently search for the most likely state trajectory leading to an event given only a simulator of a system. Our approach uses a reinforcement learning formulation and solves it using Monte Carlo Tree Search (MCTS). The approach places very few requirements on the underlying system, requiring only that the simulator provide some basic controls, the ability to evaluate certain conditions, and a mechanism to control the stochasticity in the system. Access to the system state is not required, allowing the method to support systems with hidden state. The method is applied to stress test a prototype aircraft collision avoidance system to identify trajectories that are likely to lead to near mid-air collisions. We present results for both single and multi-threat encounters and discuss their relevance. Compared with direct Monte Carlo search, this MCTS method performs significantly better both in finding events and in maximizing their likelihood.

  20. Mortality in Medicare patients undergoing elective percutaneous coronary intervention with or without antecedent stress testing.

    Science.gov (United States)

    Lin, Grace A; Lucas, F Lee; Malenka, David J; Skinner, Jonathan; Redberg, Rita F

    2013-05-01

    Guidelines advise testing for ischemia, such as with stress testing, before elective percutaneous coronary intervention (PCI). However, pre-PCI stress testing is not always done; the implications of this practice are not known. Our objective was to evaluate whether receipt of stress testing before elective PCI predicts mortality. Using claims data from a 20% random sample of Medicare beneficiaries, we identified patients who had elective PCI in 2004 and followed them for a median of 3.4 years (n=23 887). Cox proportional hazards models were used to test the relationship of pre-PCI stress testing to survival. Population-based rates of elective PCI and stress testing were calculated for 306 hospital referral regions and categorized into 4 groups: high stress test/high PCI, low stress test/low PCI, low stress test/high PCI, and high stress/low PCI regions. Cox modeling was used to test whether category of hospital referral regions is related to survival. Patients who underwent pre-PCI stress testing had a 13% lower risk of mortality than those who did not (adjusted hazard ratio, 0.87; 95% confidence interval, 0.81-0.92) after median follow-up of 3.4 years. Patients in low stress test/high PCI regions had a 14% higher risk of mortality than those in high stress test/high PCI regions (adjusted hazard ratio, 1.14; 95% confidence interval, 1.03-1.26). Pre-PCI stress testing is associated with lower mortality in patients undergoing elective PCI. Greater adherence to guidelines with respect to documenting ischemia before elective PCI may result in improved outcomes for patients.

  1. The effects of progressive muscle relaxation and autogenic relaxation on young soccer players' mood states.

    Science.gov (United States)

    Hashim, Hairul Anuar; Hanafi Ahmad Yusof, Hazwani

    2011-06-01

    This study was designed to compare the effects of two different relaxation techniques, namely progressive muscle relaxation (PMR) and autogenic relaxation (AGR) on moods of young soccer players. sixteen adolescent athletes (mean age: 14.1 ± 1.3) received either PMR or AGR training. Using Profile of Mood States- Adolescents, their mood states were measured one week before relaxation training, before the first relaxation session, and after the twelfth relaxation session. Mixed ANOVA revealed no significant interaction effects and no significant main effects in any of the subscales. However, significant main effects for testing sessions were found for confusion, depression, fatigue, and tension subscales. Post hoc tests revealed post-intervention reductions in the confusion, depression, fatigue, and tension subscale scores. These two relaxation techniques induce equivalent mood responses and may be used to regulate young soccer players' mood states.

  2. The Effects of Progressive Muscle Relaxation and Autogenic Relaxation on Young Soccer Players’ Mood States

    Science.gov (United States)

    Hashim, Hairul Anuar; Hanafi@Ahmad Yusof, Hazwani

    2011-01-01

    Purpose This study was designed to compare the effects of two different relaxation techniques, namely progressive muscle relaxation (PMR) and autogenic relaxation (AGR) on moods of young soccer players. Methods Sixteen adolescent athletes (mean age: 14.1 ± 1.3) received either PMR or AGR training. Using Profile of Mood States- Adolescents, their mood states were measured one week before relaxation training, before the first relaxation session, and after the twelfth relaxation session. Results Mixed ANOVA revealed no significant interaction effects and no significant main effects in any of the subscales. However, significant main effects for testing sessions were found for confusion, depression, fatigue, and tension subscales. Post hoc tests revealed post-intervention reductions in the confusion, depression, fatigue, and tension subscale scores. Conclusion These two relaxation techniques induce equivalent mood responses and may be used to regulate young soccer players’ mood states. PMID:22375225

  3. Randomized Test of an Implementation Intention-Based Tool to Reduce Stress-Induced Eating

    OpenAIRE

    O'Connor, DB; Armitage, CJ; Ferguson, E.

    2015-01-01

    Background: Stress may indirectly contribute to disease (e.g., cardiovascular disease, cancer by producing deleterious changes to diet. Purpose: To test effectiveness of a stress management support (SMS) tool to reduce stress-related unhealthy snacking and to promote stress-related healthy snacking. Methods: Participants were randomized to complete a SMS tool with instruction to link stressful situations with healthy snack alternatives (experimental) or a SMS tool without a linking instructio...

  4. Methods and Models of Market Risk Stress-Testing of the Portfolio of Financial Instruments

    Directory of Open Access Journals (Sweden)

    Alexander M. Karminsky

    2015-01-01

    Full Text Available Amid instability of financial markets and macroeconomic situation the necessity of improving bank risk-management instrument arises. New economic reality defines the need for searching for more advanced approaches of estimating banks vulnerability to exceptional, but plausible events. Stress-testing belongs to such instruments. The paper reviews and compares the models of market risk stress-testing of the portfolio of different financial instruments. These days the topic of the paper is highly acute due to the fact that now stress-testing is becoming an integral part of anticrisis risk-management amid macroeconomic instability and appearance of new risks together with close interest to the problem of risk-aggregation. The paper outlines the notion of stress-testing and gives coverage of goals, functions of stress-tests and main criteria for market risk stress-testing classification. The paper also stresses special aspects of scenario analysis. Novelty of the research is explained by elaborating the programme of aggregated complex multifactor stress-testing of the portfolio risk based on scenario analysis. The paper highlights modern Russian and foreign models of stress-testing both on solo-basis and complex. The paper lays emphasis on the results of stress-testing and revaluations of positions for all three complex models: methodology of the Central Bank of stress-testing portfolio risk, model relying on correlations analysis and copula model. The models of stress-testing on solo-basis are different for each financial instrument. Parametric StressVaR model is applicable to shares and options stress-testing;model based on "Grek" indicators is used for options; for euroobligation regional factor model is used. Finally some theoretical recommendations about managing market risk of the portfolio are given.

  5. Salivary cortisol, heart rate, electrodermal activity and subjective stress responses to the Mannheim Multicomponent Stress Test (MMST).

    Science.gov (United States)

    Reinhardt, Tatyana; Schmahl, Christian; Wüst, Stefan; Bohus, Martin

    2012-06-30

    The availability of effective laboratory paradigms for inducing psychological stress is an important requirement for experimental stress research. Reliable protocols are scarce, usually laborious and manpower-intensive. In order to develop an economical, easily applicable standardized stress protocol, we have recently tailored the Mannheim Multicomponent Stress Test (MMST). This test has been shown to induce relatively high stress responses without focusing on social-evaluative components. In this study we evaluated changes in electrodermal activity and salivary cortisol in response to the MMST. The MMST simultaneously combines cognitive (mental arithmetic), emotional (affective pictures), acoustic (white noise) and motivational stressors (loss of money). This study comprised two independent experiments. For experiment 1, 80 female subjects were recruited; 30 subjects (15 females) participated in experiment 2. Significant changes in electrodermal activity and salivary cortisol levels in response to MMST exposure were found. Subjective stress and heart rate responses were significantly increased in both experiments. These results indicate that the MMST is an economical stress paradigm which is also applicable in larger cohorts or multicenter studies for investigating stress reactions. As social-evaluative threat is not the main stress component of the MMST, this procedure represents a useful and complementary alternative to other established stress protocols. Copyright © 2012 Elsevier Ltd. All rights reserved.

  6. Testing of Carbon Fiber Composite Overwrapped Pressure Vessel Stress-Rupture Lifetime

    Science.gov (United States)

    Grimes-Ledesma, Lorie; Phoenix, S. Leigh; Beeson, Harold; Yoder, Tommy; Greene, Nathaniel

    2006-01-01

    This paper contains summaries of testing procedures and analysis of stress rupture life testing for two stress rupture test programs, one for Kevlar COPVs performed at Lawrence Livermore National Laboratory, and the other a joint study between NASA JSC White Sands Test Facility and the Jet Propulsion Laboratory. These will be discussed in detail including test setup and issues encountered during testing. Lessons learned from testing in these two programs will be discussed.

  7. BREATHING EXERCISE RELAXATION INCREASE PHSYCOLOGICAL RESPONSE PRESCHOOL CHILDREN

    Directory of Open Access Journals (Sweden)

    Yuni Sufyanti Arief

    2017-07-01

    Full Text Available Introduction: Being hospitalize will be made the children become stress. Hospitalization response of the child particularly is afraid sense regard to painfull procedure and increase to attack the invasive procedure. The aimed of this study was to describe the influence of breathing exercise relaxation technique regarded to phsycological receiving responses in the preeliminary school chidren while they were receiving invasive procedure. Method: A quasy experimental purposive sampling design was used in this study. There were 20 respondents who met to the inclusion criteria. The independent variable was the breathing exercise relaxation technique and the dependent variable was phsycological receiving responses. Data for phsylogical response were collected by using observation form then analyzed by using Wilcoxon Signed Rank Test and Mann Whitney U Test with significance level α≤0.05. Result :  The result showed that breathing exercise relaxation technique had significance influence to phsycological response (p=0.000. Discussion: It,s can be concluded that breathing exercise relaxation technique has an effect to increase pshycological response in preeliminary school children who received invasive procedure.

  8. Impulsivity and Stress Response in Pathological Gamblers During the Trier Social Stress Test.

    Science.gov (United States)

    Maniaci, G; Goudriaan, A E; Cannizzaro, C; van Holst, R J

    2017-03-18

    Gambling has been associated with increased sympathetic nervous system output and stimulation of the hypothalamic-pituitary-adrenal axis. However it is unclear how these systems are affected in pathological gambling. This study aimed to investigate the effect of the Trier Social Stress Test (TSST) on cortisol and on cardiac interbeat intervals in relation to impulsivity, in a sample of male pathological gamblers compared to healthy controls. In addition, we investigated the correlation between the TSST, duration of the disorder and impulsivity. A total of 35 pathological gamblers and 30 healthy controls, ranging from 19 to 58 years old and all male, participated in this study. Stress response was measured during and after the TSST by salivary cortisol and cardiac interbeat intervals; impulsivity was assessed with the Barratt Impulsiveness Scale (BIS-11). Exposure to the TSST produced a significant increase in salivary cortisol and interbeat intervals in both groups, without differences between groups. We found a negative correlation between baseline cortisol and duration of pathological gambling indicating that the longer the duration of the disorder the lower the baseline cortisol levels. Additionally, we found a main effect of impulsivity across groups on interbeat interval during the TSST, indicating an association between impulsivity and the intensity of the neurovegetative stress response during the TSST. Involvement of the hypothalamic-pituitary-adrenal axis in pathological gambling was confirmed together with evidence of a correlation between length of the disorder and diminished baseline cortisol levels. Impulsivity emerged as a personality trait expressed by pathological gamblers; however the neurovegetative response to the TSST, although associated with impulsivity, appeared to be independent of the presence of pathological gambling.

  9. Validation of the German version of the Ford Insomnia Response to Stress Test.

    Science.gov (United States)

    Dieck, Arne; Helbig, Susanne; Drake, Christopher L; Backhaus, Jutta

    2017-10-19

    The purpose of this study was to assess the psychometric properties of a German version of the Ford Insomnia Response to Stress Test with groups with and without sleep problems. Three studies were analysed. Data set 1 was based on an initial screening for a sleep training program (n = 393), data set 2 was based on a study to test the test-retest reliability of the Ford Insomnia Response to Stress Test (n = 284) and data set 3 was based on a study to examine the influence of competitive sport on sleep (n = 37). Data sets 1 and 2 were used to test internal consistency, factor structure, convergent validity, discriminant validity and test-retest reliability of the Ford Insomnia Response to Stress Test. Content validity was tested using data set 3. Cronbach's alpha of the Ford Insomnia Response to Stress Test was good (α = 0.80) and test-retest reliability was satisfactory (r = 0.72). Overall, the one-factor model showed the best fit. Furthermore, significant positive correlations between the Ford Insomnia Response to Stress Test and impaired sleep quality, depression and stress reactivity were in line with the expectations regarding the convergent validity. Subjects with sleep problems had significantly higher scores in the Ford Insomnia Response to Stress Test than subjects without sleep problems (P Ford Insomnia Response to Stress Test had significantly lower sleep quality (P = 0.01), demonstrating that vulnerability for stress-induced sleep disturbances accompanies poorer sleep quality in stressful episodes. The findings show that the German version of the Ford Insomnia Response to Stress Test is a reliable and valid questionnaire to assess the vulnerability to stress-induced sleep disturbances. © 2017 European Sleep Research Society.

  10. Influence of the clay in the stress cracking resistance of PET; Influencia de silicatos em camadas na resistencia ao 'stress cracking' do PET

    Energy Technology Data Exchange (ETDEWEB)

    Teofilo, Edvania T. [Programa de Pos-Graduacao em Ciencia e Engenharia de Materiais, Universidade Federal de Campina Grande, PB (Brazil); Silva, Emanuela S.; Silva, Suedina M.L.; Rabello, Marcelo S., E-mail: marcelo@dema.ufcg.edu.b [Unidade Academica de Engenharia de Materiais, Universidade Federal de Campina Grande, PB (Brazil)

    2011-07-01

    The environmental stress cracking resistance in PET and hybrid PET/clay were conducted under stress relaxation test. X-ray diffraction analysis show that was obtained immiscible system. In the absence of aggressive fluids the hybrid exhibited higher relaxation rates than the PET. Already in contact with aggressive fluids showed a similar or lower relaxation rate than the PET, being more resistant. Suggesting that the clay, though not interlayer, interferes with the distribution of the stress cracking agent. Thus, the barrier effect caused by the clay was more significant than the stress concentration caused by it. (author)

  11. Disparity between online and offline tests in accelerated aging tests of LED lamps under electric stress.

    Science.gov (United States)

    Wang, Yao; Jing, Lei; Ke, Hong-Liang; Hao, Jian; Gao, Qun; Wang, Xiao-Xun; Sun, Qiang; Xu, Zhi-Jun

    2016-09-20

    The accelerated aging tests under electric stress for one type of LED lamp are conducted, and the differences between online and offline tests of the degradation of luminous flux are studied in this paper. The transformation of the two test modes is achieved with an adjustable AC voltage stabilized power source. Experimental results show that the exponential fitting of the luminous flux degradation in online tests possesses a higher fitting degree for most lamps, and the degradation rate of the luminous flux by online tests is always lower than that by offline tests. Bayes estimation and Weibull distribution are used to calculate the failure probabilities under the accelerated voltages, and then the reliability of the lamps under rated voltage of 220 V is estimated by use of the inverse power law model. Results show that the relative error of the lifetime estimation by offline tests increases as the failure probability decreases, and it cannot be neglected when the failure probability is less than 1%. The relative errors of lifetime estimation are 7.9%, 5.8%, 4.2%, and 3.5%, at the failure probabilities of 0.1%, 1%, 5%, and 10%, respectively.

  12. Molecular relaxations in amorphous phenylbutazone

    Science.gov (United States)

    Sahra, M.; Thayyil, M. Shahin; Capaccioli, S.

    2016-05-01

    Molecular dynamics of phenylbutazone in the supercooled liquid and glassy state is studied using broadband dielectric spectroscopy for test frequencies 1 kHz, 10 kHz and 100 kHz over a wide temperature range. Above the glass transition temperature Tg, the presence of the structural α-relaxation peak was observed which shifts towards lower frequencies as the temperature decreases and kinetically freezes at Tg. Besides the structural α-relaxation peak, a β-process which arises due to the localized molecular fluctuations is observed at lower temperature.

  13. Effect of progressive muscle relaxation in female health care professionals.

    Science.gov (United States)

    Chaudhuri, A; Ray, M; Saldanha, D; Bandopadhyay, Ak

    2014-09-01

    Increasing population, fast paced industrialization, increased, competitiveness, unanticipated problems in the work place have increased the stress among the females working in health care in recent times. The aim of the following study is to detect the stress levels among female health care professionals in the age group of 25-35 years and its impact on health. A prospective cross-sectional pilot project was conducted in a tertiary care hospital in Eastern part of India, after receiving approval from the Institutional Ethics Committee and informed consent form was taken from the subjects. Stress level in the subjects was assessed according to the presumptive life event stress scale. Females with scores above 200 were selected. For these, initial assessment of anthropometric measurement, electrocardiogram and lipid profile analysis, resting pulse rate, blood pressure, physical fitness index (PFI), breath holding time (BHT), isometric hand grip (IHG) test results were evaluated and recorded. All subjects were given training of progressive muscle relaxation (PMR) for 3 months. After 3 months, the lipid profile and vital parameters, Perceived Stress Scale values were re-evaluated and subjects were asked to repeat the same exercises and data thus recorded were analyzed using Statistical Package for the Social Sciences (SPSS) version 16 (SPSS Inc. Released 2007. SPSS for Windows, Version 16.0. Chicago, SPSS Inc.). Significant decrease in resting heart rate, blood pressure and Perceived Stress Scale levels was seen after PMR training in the subjects. Results of BHT, IHG tests and PFI were significantly increased after PMR training. There was a significant decrease in total cholesterol, triglyceride and low-density lipoprotein cholesterol in subjects after practicing PMR for 3 months. Increasing stress among female health care professionals is a cause for concern and there is a need to adopt early life-style modification by practicing relaxation exercises to ameliorate

  14. Canada; Financial Sector Assessment Program-Stress Testing-Technical Note

    OpenAIRE

    International Monetary Fund

    2014-01-01

    This paper examines the stress testing module of the 2013 Financial Sector Assessment Program (FSAP) update for Canada. The IMF report highlights the three major segments of the domestic financial covered during the stress tests. The bank solvency stress tests suggest that while all banks would fall below the Canadian “all-in” Common Equity Tier 1 (CET1) supervisory threshold during severe economic distress, the resulting recapitalization needs are manageable. This IMF report provides recomme...

  15. Bulk Modulus Relaxation in Partially Molten Dunite?

    Science.gov (United States)

    Jackson, I.; Cline, C. J., II

    2016-12-01

    Synthetic solgel-derived Fo90 olivine was mixed with 3.5 wt % basaltic glass and hot-pressed within Ni/Fe foil to produce a dense aggregate expected to contain a small melt fraction at temperatures ≥ 1100°C. This specimen was precision ground and tested in both torsional and flexural forced oscillation to determine the relaxation behavior of both shear (G) and bulk (K) moduli at seismic frequencies. A recent upgrade of our experimental facility allows such measurements to be made without alteration of the driver/detector geometry, and uses an oscillating bending force rather than a bending moment, as previously described. The torsional and flexural tests were conducted in a gas apparatus at 200 MPa confining pressure, with oscillation periods ranging between 1 and 1000 s, during slow staged-cooling from 1300 to 25°C. Shear modulus and associated dissipation data are consistent with those for melt-bearing olivine specimens previously tested in torsion, with a pronounced dissipation peak superimposed on high-temperature background within the 1-1000 s observational window at temperatures of 1100-1200°C. A filament elongation model relates the observed flexural measurements to the variations along the experimental assembly of the complex Young's modulus (E*), bending moment and diametral moment of inertia. With E* given by 1/E*=1/(3G*) + 1/(9K*), and the complex shear modulus (G*) derived from torsional oscillation, any relaxation of K can be identified. Preliminary modeling shows that the viscoelastic properties in flexure are broadly consistent with those expected from the shear-mode viscoelasticity with anharmonic (real) values of K. However, some discrepancies between modeled results and flexure data at super-solidus temperatures require further investigation of possible differences in shear modulus relaxation between the torsional and flexural modes, and of potential relaxation of the bulk modulus through stress-induced changes in melt redistribution and

  16. Test anxiety and intelligence testing: a closer examination of the stage-fright hypothesis and the influence of stressful instruction.

    Science.gov (United States)

    Meijer, Joost; Oostdam, Ron

    2007-03-01

    The influence of test anxiety and the content of instruction (stressful versus reassuring) on measurements of intelligence were investigated. It was expected that components of test anxiety would show differential effects on test performance. A Latin Square design was used to unravel the effects of test type and test order. Furthermore, effects of type of instruction, stressful versus reassuring, were studied by means of a within-subjects design. Test anxiety was measured with the Revised Worry-Emotionality Questionnaire. Measurements for verbal ability, reasoning, and memory were administered. Performance on memory tests showed less vulnerability to test anxiety compared with the other tests, with a picture recall test being insensitive. The negative effect of test anxiety was mostly confined to the beginning of a test session, independent of the type of test. Partial support for the so-called stage-fright hypothesis was found. The effect of instructional content was equivocal.

  17. High-Temperature Slow Crack Growth of Silicon Carbide Determined by Constant-Stress-Rate and Constant-Stress Testing

    Science.gov (United States)

    Choi, Sung H.; Salem, J. A.; Nemeth, N. N.

    1998-01-01

    High-temperature slow-crack-growth behaviour of hot-pressed silicon carbide was determined using both constant-stress-rate ("dynamic fatigue") and constant-stress ("static fatigue") testing in flexure at 1300 C in air. Slow crack growth was found to be a governing mechanism associated with failure of the material. Four estimation methods such as the individual data, the Weibull median, the arithmetic mean and the median deviation methods were used to determine the slow crack growth parameters. The four estimation methods were in good agreement for the constant-stress-rate testing with a small variation in the slow-crack-growth parameter, n, ranging from 28 to 36. By contrast, the variation in n between the four estimation methods was significant in the constant-stress testing with a somewhat wide range of n= 16 to 32.

  18. Help-Seeking Decisions of Battered Women: A Test of Learned Helplessness and Two Stress Theories.

    Science.gov (United States)

    Wauchope, Barbara A.

    This study tested the learned helplessness theory, stress theory, and a modified stress theory to determine the best model for predicting the probability that a woman would seek help when she experienced severe violence from a male partner. The probability was hypothesized to increase as the stress of the violence experienced increased. Data were…

  19. High-Stakes Testing and Its Relationship to Stress Levels of Coastal Secondary Teachers

    Science.gov (United States)

    McDaniel, Sheneatha Lashelle Alexander

    2012-01-01

    The purpose of this research was to examine the relationship between high-stakes tests and stress with secondary teachers. Furthermore, this study investigated whether veteran teachers experience more stress than novice teachers and whether or not self-efficacy, gender, accountability status, and years of experience influence teacher stress as it…

  20. Stress and Mood

    Science.gov (United States)

    ... Relaxation Emotions & Relationships HealthyYouTXT Tools Home » Stress & Mood Stress & Mood Many people who go back to smoking ... story: Time Out Times 10 >> share What Causes Stress? Read full story: What Causes Stress? >> share The ...

  1. Strain test and stress intensity assessment of a CPR1000 Nuclear Power Plant pressurizer during pre-delivery hydrostatic test

    OpenAIRE

    Lin, Lei; Xu, Decheng; Yu, Min; Xue, Fei; Jiang, Jiawang; Zhang,Guodong; Zhao, Wensheng

    2014-01-01

    Strain gages are applied to get the strain and stress of a CPR1000 Nuclear Power Plant (NPP) pressurizer during the pre-delivery hydrostatic test. The measured strain curves are discussed to find the deformation features of the cylinder. The stresses of cylindrical base metal, longitudinal welds and girth welds are calculated and compared with the theoretical values. The stresses in girth welds and upper head nozzle welds show non-uniformity at these areas. The possible reasons are discussed ...

  2. Residual Stress Test and Finite Element Analysis of Titanium Alloy Surface Obtained by Electron Beam Welding

    Directory of Open Access Journals (Sweden)

    LIU Xiaojia

    2016-08-01

    Full Text Available Ti60 titanium alloy plates were welded by electron beam,and the welding residual stress was tested and simulated by the residual stress tester and finite element analysis. The comparison of the residual stress values caused in the three kinds of welding processes of pre-heating, slow cooling and both pre-heating and slow cooling was carried out. The residual stress distribution law was also studied. Results show that in the vertical welding section, the longitudinal welding residual stress tested is similar to that simulated as to the change trend; in the parallel welding section, the distributions of the tested and simulated longitudinal welding residual stress are similar. These prove that the finite element analysis is reasonable and reliable. The process of pre-heating has little influence on the welding residual stress, but the slow cooling process can change its distribution.

  3. A novel method for estimating soil precompression stress from uniaxial confined compression tests

    DEFF Research Database (Denmark)

    Lamandé, Mathieu; Schjønning, Per; Labouriau, Rodrigo

    2017-01-01

    obtained from the new method were linearly related to the maximum stress experienced by the soil samples prior to the uniaxial, confined compression test at each soil condition with a slope close to 1. Precompression stress determined with the new method was not related to soil type or dry bulk density......The concept of precompression stress is used for estimating soil strength of relevance to fieldtraffic. It represents the maximum stress experienced by the soil. The most recently developed fitting method to estimate precompression stress (Gompertz) is based on the assumption of an S-shape stress......-strain curve, which is not always fulfilled. A new simple numerical method was developed to estimate precompression stress from stress-strain curves, based solely on the sharp bend on the stress-strain curve partitioning the curve into an elastic and a plastic section. Our study had three objectives: (i...

  4. Advanced holographic nondestructive testing system for residual stress analysis

    CERN Document Server

    Kniazkov, Anatoli; Dovgalenko, George; Salamo, Gregory; Latychevskaia, Tatiana; 10.1117/12.347399

    2013-01-01

    The design and operating of a portable holographic interferometer for residual stress analysis by creating a small scratch along with a new mathematical algorithm of calculations are discussed. Preliminary data of the stress investigations on aluminum and steel alloys have been obtained by the automatic processing of the interference pattern using a notebook computer. A phase-shift compensation technique in real-time reflection interferometry is used to measure the out-of-plane stress release surface displacement surrounding a small scratch (25 um depth and 0.5 mm width) in a plate with residual stress of around 50 MPa. Comparison between theoretical models for a rectangular and triangular shaped scratch with the experimental data are presented.

  5. Pegasus Rocket Wing and PHYSX Glove Undergoes Stress Loads Testing

    Science.gov (United States)

    1997-01-01

    The Pegasus Hypersonic Experiment (PHYSX) Project's Pegasus rocket wing with attached PHYSX glove rests after load-tests at Scaled Composites, Inc., in Mojave, California, in January 1997. Technicians slowly filled water bags beneath the wing, to create the pressure, or 'wing-loading,' required to determine whether the wing could withstand its design limit for stress. The wing sits in a wooden triangular frame which serves as the test-rig, mounted to the floor atop the waterbags. Pegasus is an air-launched space booster produced by Orbital Sciences Corporation and Hercules Aerospace Company (initially; later, Alliant Tech Systems) to provide small satellite users with a cost-effective, flexible, and reliable method for placing payloads into low earth orbit. Pegasus has been used to launch a number of satellites and the PHYSX experiment. That experiment consisted of a smooth glove installed on the first-stage delta wing of the Pegasus. The glove was used to gather data at speeds of up to Mach 8 and at altitudes approaching 200,000 feet. The flight took place on October 22, 1998. The PHYSX experiment focused on determining where boundary-layer transition occurs on the glove and on identifying the flow mechanism causing transition over the glove. Data from this flight-research effort included temperature, heat transfer, pressure measurements, airflow, and trajectory reconstruction. Hypersonic flight-research programs are an approach to validate design methods for hypersonic vehicles (those that fly more than five times the speed of sound, or Mach 5). Dryden Flight Research Center, Edwards, California, provided overall management of the glove experiment, glove design, and buildup. Dryden also was responsible for conducting the flight tests. Langley Research Center, Hampton, Virginia, was responsible for the design of the aerodynamic glove as well as development of sensor and instrumentation systems for the glove. Other participating NASA centers included Ames Research

  6. The incremental value of stress testing in patients with acute chest pain beyond serial cardiac troponin testing.

    Science.gov (United States)

    Aldous, Sally; Richards, A Mark; Cullen, Louise; Pickering, John W; Than, Martin

    2016-05-01

    In patients with acute chest pain and normal range cardiac troponin (cTn), accurate risk stratification for acute coronary syndrome is challenging. This study assesses the incremental value of stress testing to identify patients for angiography with a view to revascularisation. A single-centre observational study recruited patients with acute chest pain in whom serial cTn tests were negative and stress testing (exercise tolerance testing/dobutamine stress echocardiography) was performed. Stress tests were reported as negative, non-diagnostic or positive. The primary outcomes were revascularisation on index admission, or cardiac death and myocardial infarction over 1 year follow-up. Of 749 patients recruited, 709 underwent exercise tolerance testing and 40 dobutamine stress echo of which 548 (73.2%) were negative, 169 (22.6%) were non-diagnostic and 32 (4.3%) were positive. Patients with positive tests (n=19 (59.4%)) were more likely to undergo index admission revascularisation than patients with non-diagnostic (n=15 (8.9%)) (pacute myocardial infarction were low and were similar across stress test outcomes. The incremental value of stress testing was the identification of an additional 34 (4.5% (95% CI 3.0% to 6.0%)) patients who underwent index admission revascularisation with a view to preventing future adverse events. Uncertainty in whether revascularisation prevents adverse events in patients with negative cTn means the choice to undertake stress testing depends on whether clinicians perceive value in identifying 4.5% of these patients for revascularisation. ACTRN1260900028327, ACTRN12611001069943. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/

  7. Learning aptitude, spatial orientation and cognitive flexibility tested in a virtual labyrinth after virtual stress induction.

    Science.gov (United States)

    Delahaye, Marcel; Lemoine, Patrick; Cartwright, Shanique; Deuring, Gunnar; Beck, Johannes; Pflueger, Marlon; Graf, Marc; Hachtel, Henning

    2015-01-01

    Under stressful conditions such as in an emergency situation, efficient information processing is essential for reasonable responses. Virtual Reality (VR) technology is used to induce stress and to test three main cognitive functions for decision making in stressful situations. A VR task was developed to induce stress following the Trier Social Stress Test (TSST) protocol and two VR cognitive performance tests to measure learning aptitude, spatial orientation and cognitive flexibility. Participants (N = 31) gave a public speech in front of a virtual audience (TSST) and later had to find their way out of different VR labyrinths. The first exercise tested spatial orientation and learning aptitude where participants had to learn aspects of the ground layout and geometric icons had to be identified as correct in order to be able to exit. The second labyrinth tested cognitive flexibility on the background of the Wisconsin Card Sorting Test. Correlations were analyzed using Kendall Tau Correlation (One-tailed tests with p set to 0.05 for all analyses). Heart rate (HR) was calculated from the RR time values and averaged across the TSST- speech and the post-stress period. Autonomic nervous system reactivity was defined as the deviation of HR during TSST- speech condition from post-stress baseline measurement. A repeated-measures t-test was used to analyze differences. The newly developed virtual stress test was successfully adapted from the original TSST. Participants perceived the task as stressful and scored an average of 5.7 points on a 1-8 Likert Scale. As a physiological stress parameter, increased heart rates of the participants showed that they were more stressed during the TSST procedure compared to the post-stress period. Also, the subjective stress perception, has a strong correlation with the results of the cognitive tasks performed after the stress induction. The more a participant experienced the TSST as stressful, the lower their learning aptitude and

  8. Standard practice for preparation and use of Bent-Beam stress-corrosion test specimens

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2011-01-01

    1.1 This practice covers procedures for designing, preparing, and using bent-beam stress-corrosion specimens. 1.2 Different specimen configurations are given for use with different product forms, such as sheet or plate. This practice applicable to specimens of any metal that are stressed to levels less than the elastic limit of the material, and therefore, the applied stress can be accurately calculated or measured (see Note 1). Stress calculations by this practice are not applicable to plastically stressed specimens. Note 1—It is the nature of these practices that only the applied stress can be calculated. Since stress-corrosion cracking is a function of the total stress, for critical applications and proper interpretation of results, the residual stress (before applying external stress) or the total elastic stress (after applying external stress) should be determined by appropriate nondestructive methods, such as X-ray diffraction (1). 1.3 Test procedures are given for stress-corrosion testing by ex...

  9. Effect of crosslinking density on biaxial relaxation of SBR by using reduced variables. [Styrene-Butadiene Rubber

    Science.gov (United States)

    Arenz, R. J.

    1974-01-01

    The use of reduced variables to account for the effect of crosslinking density in a styrene-butadiene rubber (SBR) system is demonstrated for general biaxial stress states. Recently published results from stress relaxation tests on five SBR vulcanizates crosslinked to different degrees by tetramethylthiuram disulfide were superposed by using the crosslinking density as a reduction variable. The equilibrium shear modulus calculated from the master relaxation curve at long reduced times was in satisfactory agreement with other results for SBR. The time-axis shifts were related in a linear logarithmic manner to the crosslinking density but had a slope slightly less than values previously reported for elastomer systems.

  10. Cornea stress test--evaluation of corneal endothelial function in vivo by contact lens induced stress

    Directory of Open Access Journals (Sweden)

    Saini Jagjit

    1997-01-01

    Full Text Available Reliable and valid assessment of corneal endothelial function is a critical input for diagnosing, prognosticating and monitoring progression of disorders affecting corneal endothelium. In 123 eyes, corneal endothelial function was assessed employing data from the corneal hydration recovery dynamics. Serial pachometric readings were recorded on Haag-Striet pachometer with Mishima-Hedbys modification before and after two hours of thick soft contact lens wear. Percentage Recovery Per Hour (PRPH was derived from raw data as an index of endothelial function. Assessed PRPH in pseudophakic corneal oedema and Fuchs′ endothelial dystrophy eyes (35.9 +/- 9.8% was significantly lower than normal controls (61.9 +/- 10.5%. On employing receiver operation characteristics curve analysis the tested results demonstrated high sensitivity (87% and specificity (92% for detection of low endothelial function at PRPH cut off of 47.5%. Using this PRPH cut off, 80% of Fuchs′ endothelial dystrophy and 93.3% of pseudophakic corneal oedema eyes could be demonstrated to have low endothelial function. A total of 66.7% of diabetic eyes also demonstrated PRPH of lower than 47.5%. Clear corneal grafts demonstrated PRPH values of 24.6% to 73.0%. Of 6 corneal grafts that demonstrated initial PRPH of lower than 47.5%, 4 failed within 4 to 6 months. Our data demonstrated high sensitivity and specificity of this corneal stress test. PRPH index was useful in quantifying endothelial function in clinical disorders including diabetes mellitus. The index PRPH was demonstrated to be useful in monitoring and prognosticating outcome of corneal grafts.

  11. Circumferential Notched Tensile Testing for Correlation of the Stress Intensity Factor ( K I ) and Stress Corrosion Crack Growth Rate

    Science.gov (United States)

    Rihan, R.; Singh Raman, R. K.; Ibrahim, R. N.

    2008-07-01

    A novel fracture mechanics technique has been employed for the determination of crack growth rate and threshold stress intensity factor ( K ISCC) for stress corrosion cracking (SCC) using small circumferential notch tensile (CNT) specimens. The technique was applied successfully for testing SCC susceptibility of AISI 1020 mild steel in 12.5 M NaOH at 150 °C. The crack growth rate of mild steel in 12.5 M NaOH solution at 150 °C has been determined at different stress intensity factors ( K I ), and the K ISCC has been determined to be 29 MPa·m1/2. The surfaces of fractured specimens have been examined by scanning electron microscopy (SEM) in order to establish intergranular propagation of stress corrosion cracks. The CNT testing is a simple, relatively fast, and cost-advantageous approach for generating crack growth rate and K ISCC data.

  12. Stress Testing German Industry Sectors: Results from a Vine Copula Based Quantile Regression

    OpenAIRE

    Fischer, Matthias; Kraus, Daniel; Pfeuffer, Marius; Czado, Claudia

    2017-01-01

    Measuring interdependence between probabilities of default (PDs) in different industry sectors of an economy plays a crucial role in financial stress testing. Thereby, regression approaches may be employed to model the impact of stressed industry sectors as covariates on other response sectors. We identify vine copula based quantile regression as an eligible tool for conducting such stress tests as this method has good robustness properties, takes into account potential nonlinearities of cond...

  13. 12 CFR 652.100 - Audit of the risk-based capital stress test.

    Science.gov (United States)

    2010-01-01

    ... 12 Banks and Banking 6 2010-01-01 2010-01-01 false Audit of the risk-based capital stress test... AGRICULTURAL MORTGAGE CORPORATION FUNDING AND FISCAL AFFAIRS Risk-Based Capital Requirements § 652.100 Audit of the risk-based capital stress test. You must have a qualified, independent external auditor review...

  14. A preliminary investigation of the dynamic viscoelastic relaxation of bovine cortical bone

    Directory of Open Access Journals (Sweden)

    Loete T.J.C.

    2015-01-01

    Full Text Available A new experimental approach is proposed to characterize the dynamic viscoelastic relaxation behaviour of cortical bone. Theoretical models are presented to show that a linear viscoelastic material, when allowed to relax between two long elastic bars, will produce stress, strain and strain rate histories that contain characteristic features. Furthermore, typical experimental results are presented to show that these characteristic features are observed during split Hopkinson bar tests on bovine cortical bone using a Cone-in-Tube striker. The interpretation of this behaviour in the context of a standard linear viscoelastic model is discussed.

  15. Summary report - development of laboratory tests and the stress- strain behaviour of Olkiluoto mica gneiss

    Energy Technology Data Exchange (ETDEWEB)

    Hakala, M.; Heikkilae, E. [Helsinki Univ. of Technology, Espoo (Finland). Lab. of Rock Engineering

    1997-05-01

    This work summarizes the project aimed at developing and qualifying a suitable combination of laboratory tests to establish a statistically reliable stress-strain behaviour of the main rock types at Posiva Oy`s detailed investigation sites for disposal of spent nuclear fuel. The work includes literature study of stress-strain behaviour of brittle rock, development and qualification of laboratory tests, suggested test procedures and interpretation methods and finally testing of Olkiluoto mica gneiss. The Olkiluoto study includes over 130 loading tests. Besides the commonly used laboratory tests, direct tensile tests, damage controlled tests and acoustic emission measurements were also carried out. (orig.) (54 refs.).

  16. Progress and Challenges of Ultrasonic Testing for Stress in Remanufacturing Laser Cladding Coating.

    Science.gov (United States)

    Yan, Xiao-Ling; Dong, Shi-Yun; Xu, Bin-Shi; Cao, Yong

    2018-02-13

    Stress in laser cladding coating is an important factor affecting the safe operation of remanufacturing components. Ultrasonic testing has become a popular approach in the nondestructive evaluation of stress, because it has the advantages of safety, nondestructiveness, and online detection. This paper provides a review of ultrasonic testing for stress in remanufacturing laser cladding coating. It summarizes the recent research outcomes on ultrasonic testing for stress, and analyzes the mechanism of ultrasonic testing for stress. Remanufacturing laser cladding coating shows typical anisotropic behaviors. The ultrasonic testing signal in laser cladding coating is influenced by many complex factors, such as microstructure, defect, temperature, and surface roughness, among others. At present, ultrasonic testing for stress in laser cladding coating can only be done roughly. This paper discusses the active mechanism of micro/macro factors in the reliability of stress measurement, as well as the impact of stress measurement on the quality and safety of remanufacturing components. Based on the discussion, this paper proposes strategies to nondestructively, rapidly, and accurately measure stress in remanufacturing laser cladding coating.

  17. Nonlinear fractional relaxation

    Indian Academy of Sciences (India)

    Nonlinear fractional equation; nonlinear fractional relaxation; -expansion. Abstract. We define a nonlinear model for fractional relaxation phenomena. We use -expansion method to analyse this model. By studying the fundamental solutions of this model we find that when → 0 the model exhibits a fast decay rate and ...

  18. Determination of in situ stress in U12g tunnel, Rainier Mesa, Nevada Test Site, Nevada

    Energy Technology Data Exchange (ETDEWEB)

    Ellis, W.L.; Ege, J.R.

    1976-01-01

    Stress relief borehole-deformation measurements using the U. S. Bureau of Mines overcore technique were made at a depth of 442 m below Rainier Mesa, Nevada Test Site. The measurements, made in three noncoplaner boreholes drilled in low-modulus, low-density, volcanic rocks, were used to calculate the three-dimensional stress field. All stresses were found to be compressive. The calculated vertical stress component of 67 bars is consistent with the estimated vertical stress attributed to overburden. The maximum principal stress(85 bars) trends N 21/sup 0/E and the minimum principal stress (26 bars) trends N 68/sup 0/W; both are nearly horizontal. Synthesis of geologic and geophysical data by other workers indicates a similar orientation of the maximum and minimum horizontal stresses on a regional scale. (auth)

  19. Effects of Progressive Muscle Relaxation Therapy in Colorectal Cancer Patients.

    Science.gov (United States)

    Kim, Kyeng Jin; Na, Yeon Kyung; Hong, Hae Sook

    2016-08-01

    This study aimed to examine the effect of progressive muscle relaxation therapy (PMRT) on cortisol level, the Stress Arousal Checklist (SACL) score, blood pressure, and heart rate in colorectal cancer patients undergoing laparoscopic surgery. Forty-six patients were divided into control and experimental groups. Cortisol levels, blood pressure, and heart rate were measured before surgery and between 8:00 and 11:00 a.m. on the first, third, and fifth days after surgery. SACL score was measured before surgery and on the fifth day after surgery at the same time points. PMRT was performed twice a day for 5 days. Analyses of covariance with advanced covariate levels and t tests showed that PMRT helps colorectal cancer patients achieve a lower stress response and provides an important basis for stress control. © The Author(s) 2016.

  20. Stress Level Testing of Electronics, Avionics Communications and C3I Equipments.

    Science.gov (United States)

    1985-08-30

    mater- ials; these types of stress testing are covered in MIL-STO- BlOD ._ Acce j n To - ( Th_ _ WTIS iiA DT, A Unnnuned 1 justiicaK’ AcOstruiol Dist...GOVT ACCESSION NO 3. RECIPIENT’S CATALOG NUMBER TOP 6-1-0021 4. TITLE (and Subtitle) S. TYPE OF REPORT & PERIOD COVERED U.S. Army Test and Evaluation...environmental and mechan- ical stress testing of materials; these types of stress testing are covered in MIL-STD-810D. 2.0 FACILITIES AND

  1. Short-term effects of a randomized controlled worksite relaxation intervention in Greece

    Directory of Open Access Journals (Sweden)

    Evangelos C Alexopoulos

    2014-06-01

    Full Text Available objective. To evaluate the short-term benefits of simple relaxation techniques in white-collar employees. materials and methods. The study was a two-arm parallel group randomized controlled trial. 152 employees were randomly assigned to receive the 8-week programme (N=80 (relaxation breathing and progressive muscle relaxation, twice a day or not (wait-list group N=72. Self-reported validated measures were used to evaluate perceived stress, health locus of control, job and lifestyle related variables. Saliva cortisol were also sampled and measured. Adjusted mean changes on outcomes were estimated by linear mixed model analysis. 127 employees were finally analyzed (68 in the intervention and 59 in the control group. results. Specific stress-related symptoms, psychological job demands and cortisol levels were found to be significantly decreased after 8-weeks in the intervention group. The result was probably affected by the general socio-economic condition during the study period. Cortisol levels were also significantly related with age, family situation, gender and sampling time. conclusions. Simple relaxation training (diaphragmatic breathing and progressive muscle relaxation could benefit employees and it is strongly proposed that these and other similar techniques should be tested in various labour settings

  2. Depressive symptoms and perceived chronic stress predict test anxiety in nursing students

    Directory of Open Access Journals (Sweden)

    Christoph Augner

    2015-09-01

    Full Text Available Aim: The aim of this study is to identify predictors of test anxiety in nursing students. Design: Cross sectional pilot study. Methods: A questionnaire was administered to 112 students of an Austrian nursing school (mean age = 21.42, SD = 5.21. Test anxiety (measured by the standardized PAF Test Anxiety Questionnaire, perceived chronic stress, depressive symptoms, pathological eating and further psychological and health parameters were measured. Results: We found highly significant correlations between test anxiety and working hours (0.25, depression score (0.52, emotional stability (-0.31, and perceived chronic stress (0.65 (p < 0.01, for all. Regression analysis revealed chronic stress and emotional instability as best predictors for test anxiety. Furthermore, path analysis revealed that past negative academic performance outcomes contribute to test anxiety via depressive symptoms and perceived chronic stress. Conclusion: Depressive symptoms and perceived chronic stress are strongly related to test anxiety. Therefore therapy and training methods that address depressive symptoms and perceived chronic stress, and thereby aim to modify appraisal of potential stressful situations, may be successful in addressing test anxiety.

  3. Standard test method for determining residual stresses by the hole-drilling strain-gage method

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2008-01-01

    1.1 Residual Stress Determination: 1.1.1 This test method specifies a hole-drilling procedure for determining residual stress profiles near the surface of an isotropic linearly elastic material. The test method is applicable to residual stress profile determinations where in-plane stress gradients are small. The stresses may remain approximately constant with depth (“uniform” stresses) or they may vary significantly with depth (“non-uniform” stresses). The measured workpiece may be “thin” with thickness much less than the diameter of the drilled hole or “thick” with thickness much greater than the diameter of the drilled hole. Only uniform stress measurements are specified for thin workpieces, while both uniform and non-uniform stress measurements are specified for thick workpieces. 1.2 Stress Measurement Range: 1.2.1 The hole-drilling method can identify in-plane residual stresses near the measured surface of the workpiece material. The method gives localized measurements that indicate the...

  4. Stress transfer in microdroplet tensile test: PVC-coated and uncoated Kevlar-29 single fiber

    Science.gov (United States)

    Zhenkun, Lei; Quan, Wang; Yilan, Kang; Wei, Qiu; Xuemin, Pan

    2010-11-01

    The single fiber/microdroplet tensile test is applied for evaluating the interfacial mechanics between a fiber and a resin substrate. It is used to investigate the influence of a polymer coating on a Kevlar-29 fiber surface, specifically the stress transfer between the fiber and epoxy resin in a microdroplet. Unlike usual tests, this new test ensures a symmetrical axial stress on the embedded fiber and reduces the stress singularity that appears at the embedded fiber entry. Using a homemade loading device, symmetrical tensile tests are performed on a Kevlar-29 fiber with or without polyvinylchloride (PVC) coating, the surface of which is in contact with two epoxy resin microdroplets during curing. Raman spectra on the embedded fiber are recorded by micro-Raman Spectroscopy under different strain levels. Then they are transformed to the distributions of fiber axis stress based on the relationship between stress and Raman shift. The Raman results reveal that the fiber axial stresses increase with the applied loads, and the antisymmetric interfacial shear stresses, obtained by a straightforward balance of shear-to-axial forces argument, lead to the appearance of shear stress concentrations at a distance to the embedded fiber entry. The load is transferred from the outer fiber to the embedded fiber in the epoxy microdroplet. As is observed by scanning electronic microscopy (SEM), the existence of a flexible polymer coating on the fiber surface reduces the stress transfer efficiency.

  5. Epitaxial growth of GaSb on V-grooved Si (001) substrates with an ultrathin GaAs stress relaxing layer

    Science.gov (United States)

    Li, Qiang; Lai, Billy; Lau, Kei May

    2017-10-01

    We report epitaxial growth of GaSb nano-ridge structures and planar thin films on V-groove patterned Si (001) substrates by leveraging the aspect ratio trapping technique. GaSb was deposited on {111} Si facets of the V-shaped trenches using metal-organic chemical vapor deposition with a 7 nm GaAs growth initiation layer. Transmission electron microscopy analysis reveals the critical role of the GaAs layer in providing a U-shaped surface for subsequent GaSb epitaxy. A network of misfit dislocations was uncovered at the GaSb/GaAs hetero-interface. We studied the evolution of the lattice relaxation as the growth progresses from closely pitched GaSb ridges to coalesced thin films using x-ray diffraction. The omega rocking curve full-width-at-half-maximum of the resultant GaSb thin film is among the lowest values reported by molecular beam epitaxy, substantiating the effectiveness of the defect necking mechanism. These results thus present promising opportunities for the heterogeneous integration of devices based on 6.1 Å family compound semiconductors.

  6. The effects of the transcendental mediation technique and progressive muscle relaxation on EEG coherence, stress reactivity, and mental health in black adults.

    Science.gov (United States)

    Gaylord, C; Orme-Johnson, D; Travis, F

    1989-05-01

    Eighty-three black college students, staff and adults were pretested on EEG coherence, skin potential (SP) habituation to a series of loud tones, psychometric measures of mental health (Tennessee Self-Concept Empirical Scales and Spielberger State-Trait Anxiety Inventory) and IQ. They were then randomly assigned to one of the three treatment groups: the Transcendental Meditation technique (TM); Progressive Muscle Relaxation (PR); or cognitive-behavioral strategies (C). Approximately one year later, they were posttested. TM and PR increased significantly on an overall mental health factor (p less than .036) and anxiety (p less than .0006). TM showed a greater reduction in neuroticism than PR and C (p less than .032). TM also showed global increases in alpha and theta coherence among frontal and central leads during the TM period compared to eyes closed (p less than .016), whereas PR and C did not show EEG state changes. The coherence increases during TM were most marked in the right hemisphere (F4C4). TM showed faster SP habituation at posttest compared to pretest (p less than .047) whereas PR did not (data was missing for C). None of the groups showed longitudinal changes in EEG, perhaps due to lack of regularity of participation in the treatment programs.

  7. Temperature, stress, and structural-relaxation dependence of the magnetostriction in (Co0.94/BFe0.06)75/BSi15B10 glasses

    DEFF Research Database (Denmark)

    Barandiarán, J. M.; Hernando, A.; Madurga, V.

    1987-01-01

    High-sensitivity measurements of the magnetostriction constant λs have been performed in the nearly zero magnetostriction (Co0.94Fe0.06)75Si15B10 metallic glass as a function of the stress and temperature after pulse-annealing treatments. A stress dependence of λs in this amorphous alloy is repor......High-sensitivity measurements of the magnetostriction constant λs have been performed in the nearly zero magnetostriction (Co0.94Fe0.06)75Si15B10 metallic glass as a function of the stress and temperature after pulse-annealing treatments. A stress dependence of λs in this amorphous alloy...... is reported for the first time. At room temperature a slope of about -2×10-7 GPa-1 has been determined leading to a change in the sign of the magnetostriction constant in some circumstances. For determination of the thermal variation of λs, the temperature was changed by means of the alternating current...... flowing through the sample during the measurement, which was done by the small-angle magnetization-rotation (SAMR) method. The compensation temperatures, i.e., those temperatures at which the value of λs vanishes in going from negative to positive, were determined after isochronal annealing. In this way...

  8. Research on remote stress test system of lifting machinery metal structure

    Science.gov (United States)

    Tang, Zhifen

    2013-03-01

    This paper introduces a new remote wireless stress testing system, wireless sensor network node principle and key technology are discussed in this system, combining with WSN (wireless sensor networks) technology and GPRS network data transmission technology, realizing the remote testing of lifting machinery metal structure. to MDEL900B handling machine for the testing object, on the base of finite element analysis, test the metal structure stress of key parts on the MDEL900B handling machine in working condition, by comparition between the results of test and finite element analysis , the reliability of the testing system is shown .

  9. The Application of Normal Stress Reduction Function in Tilt Tests for Different Block Shapes

    Science.gov (United States)

    Kim, Dong Hyun; Gratchev, Ivan; Hein, Maw; Balasubramaniam, Arumugam

    2016-08-01

    This paper focuses on the influence of the shapes of rock cores, which control the sliding or toppling behaviours in tilt tests for the estimation of rock joint roughness coefficients (JRC). When the JRC values are estimated by performing tilt tests, the values are directly proportional to the basic friction of the rock material and the applied normal stress on the sliding planes. Normal stress obviously varies with the shape of the sliding block, and the basic friction angle is also affected by the sample shapes in tilt tests. In this study, the shapes of core blocks are classified into three representative shapes and those are created using plaster. Using the various shaped artificial cores, a set of tilt tests is carried out to identify the shape influences on the normal stress and the basic friction angle in tilt tests. The test results propose a normal stress reduction function to estimate the normal stress for tilt tests according to the sample shapes based on Barton's empirical equation. The proposed normal stress reduction functions are verified by tilt tests using artificial plaster joints and real rock joint sets. The plaster joint sets are well matched and cast in detailed printed moulds using a 3D printing technique. With the application of the functions, the obtained JRC values from the tilt tests using the plaster samples and the natural rock samples are distributed within a reasonable JRC range when compared with the measured values.

  10. Collection Development: Relaxation & Meditation, September 1, 2010

    Science.gov (United States)

    Lettus, Dodi

    2010-01-01

    One of the first books to document the relationship between stress and physical and emotional health was "The Relaxation Response" by Herbert Benson, M.D., with Miriam Z. Klipper. Originally published in 1975, the book grew out of Benson's observations as a cardiologist and his research as a fellow at Harvard Medical School. Benson's study of…

  11. Cardiac stress testing for the diagnosis and management of coronary artery disease: a reference for the primary care physician.

    Science.gov (United States)

    Gajulapalli, Rama Dilip; Aneja, Ashish; Rovner, Aleksandr

    2012-02-01

    Choosing the appropriate stress test is important in the workup of patients with possible myocardial ischemia. This choice often is challenging and sometimes confusing because of the plethora of tests and guidelines available. We present a broad overview of commonly available stress tests and indications to help physicians select the most appropriate stress test for their patients.

  12. [A study on Korean concepts of relaxation].

    Science.gov (United States)

    Park, J S

    1992-01-01

    Relaxation technique is an independent nursing intervention used in various stressful situations. The concept of relaxation must be explored for the meaning given by the people in their traditional thought and philosophy. Korean relaxation technique, wanting to become culturally acceptable and effective, is learning to recognize and develop Korean concepts, experiences, and musics of relaxation. This study was aimed at discovering Korean concepts, experiences and musics of relaxation and contributing the development of the relaxation technique for Korean people. The subjects were 59 nursing students, 39 hospitalized patients, 61 housewives, 21 rural residents and 16 researchers. Data were collected from September 4th to October 24th, 1991 by interviews or questionnaires. The data analysis was done by qualitative research method, and validity assured by conformation of the concept and category by 2 nursing scientists who had written a Master's thesis on the relaxation technique. The results of the study were summarized as follows; 1. The meaning of the relaxation concept; From 298 statements, 107 concepts were extracted and then 5 categories "Physical domain", "Psychological domain", "Complex domain", "Situation", and "environment" were organized. 'Don't have discomforts, 'don't have muscle tension', 'don't have energy (him in Korean)', 'don't have activities' subcategories were included in "Physical domain". 'Don't have anxiety', 'feel good', 'emotional stability', 'don't have wordly thoughts', 'feel one's brain muddled', 'loss of desire' subcategories were included in "physical domain" 'Comfort body and mind', 'don't have tension of body and mind', 'be sagged' 'liveliness of thoughts' subcategories were included in "Complex domain". 'Rest', 'sleep', 'others' subcategories were included in "Situation domain". And 'quite environment' & 'comfortable environment' subcategories were included in "Environmental domain". 2. The experiences of the relaxation; From 151

  13. Models for multiple relaxation processes in collagen fiber

    Indian Academy of Sciences (India)

    First page Back Continue Last page Overview Graphics. Models for multiple relaxation processes in collagen fiber. Two element model suits best the dimensional relaxation processes, of which one event appears to originate from stress strain induced changes in hydrogen bond network whereas the other seems to be more ...

  14. Effects of flotation-restricted environmental stimulation technique on stress-related muscle pain: what makes the difference in therapy--attention-placebo or the relaxation response?

    Science.gov (United States)

    Bood, Sven A; Sundequist, Ulf; Kjellgren, Anette; Nordstrom, Gun; Norlander, Torsten

    2005-01-01

    The purpose of the present study was to examine the potential effects of attention-placebo on flotation tank therapy. Flotation-restricted environmental stimulation technique is a method whereby an individual lies in a floating tank and all stimuli are reduced to a minimum. Thirty-two patients were diagnosed as having stress-related muscular pain. In addition, 16 of the participants had received the diagnosis of burnout depression. The patients were treated with flotation-restricted environmental stimulation technique for six weeks. One-half of the patients were also given special attention for 12 weeks (high attention), while the remainder received attention for only six weeks (normal attention). The participants exhibited lowered blood pressure, reduced pain, anxiety, depression, stress and negative affectivity, as well as increased optimism, energy and positive affectivity. The results were largely unaffected by the degree of attention-placebo or diagnosis. It was concluded that flotation therapy is an effective, noninvasive method for treating stress-related pain, and that the method is not more affected by placebo than by other methods currently used in pain treatment. The treatment of both burnout depression and pain related to muscle tension constitutes a major challenge for the patient as well as the care provider, an area in which great gains can be made if the treatment is effective. Flotation therapy may constitute an integral part of such treatment.

  15. Social Support for Divorced Fathers' Parenting: Testing a Stress-Buffering Model

    Science.gov (United States)

    DeGarmo, David S.; Patras, Joshua; Eap, Sopagna

    2008-01-01

    A stress-buffering hypothesis for parenting was tested in a county-representative sample of 218 divorced fathers. Social support for parenting (emergency and nonemergency child care, practical support, financial support) was hypothesized to moderate effects of stress (role overload, coparental conflict, and daily hassles) on fathers' quality…

  16. The Rodent Forced Swim Test Measures Stress-Coping Strategy, Not Depression-like Behavior.

    Science.gov (United States)

    Commons, Kathryn G; Cholanians, Aram B; Babb, Jessica A; Ehlinger, Daniel G

    2017-05-17

    The forced swim test (FST) measures coping strategy to an acute inescapable stress and thus provides unique insight into the neural limb of the stress response. Stress, particularly chronic stress, is a contributing factor to depression in humans and depression is associated with altered response to stress. In addition, drugs that are effective antidepressants in humans typically promote active coping strategy in the FST. As a consequence, passive coping in the FST has become loosely equated with depression and is often referred to as "depression-like" behavior. This terminology oversimplifies complex biology and misrepresents both the utility and limitations of the FST. The FST provides little construct- or face-validity to support an interpretation as "depression-like" behavior. While stress coping and the FST are arguably relevant to depression, there are likely many factors that can influence stress coping strategy. Importantly, there are other neuropsychiatric disorders characterized by altered responses to stress and difficulty in adapting to change. One of these is autism spectrum disorder (ASD), and several mouse genetic models of ASD exhibit altered stress-coping strategies in the FST. Here we review evidence that argues a more thoughtful consideration of the FST, and more precise terminology, would benefit the study of stress and disorders characterized by altered response to stress, which include but are not limited to depression.

  17. FlowPing - The New Tool for Throughput and Stress Testing

    Directory of Open Access Journals (Sweden)

    Ondrej Vondrous

    2015-01-01

    Full Text Available This article presents a new tool for network throughput and stress testing. The FlowPing tool is easy to use, and its basic output is very similar to standard Linux ping application. The FlowPing tool is not limited to reach-ability or round trip time testing but is capable of complex UDP based throughput stress testing with rich reporting capabilities on client and server sides. Our new tool implements features, which allow the user to perform tests with variable packet size and traffic rate. All these features can be used in one single test run. This allows the user to use and develop new methodologies for network throughput and stress testing. With the FlowPing tool, it is easy to perform the test with the slowly increasing the amount of network traffic and monitor the behavior of network when the congestion occurs.

  18. Present-day stress magnitude at depth from leak-off tests in Italy

    Science.gov (United States)

    Mariucci, M. T.; Montone, P.; Pierdominici, S.

    2012-04-01

    We present new results from the analysis of leak-off tests, performed in deep oil wells in Italy, to characterize the present-day stress magnitude and regime in the crust. In the last years we have collected a large number of data (more than 500) from different stress indicators, mainly borehole breakouts, earthquake focal mechanisms and fault data, which provided information on the present-day stress orientations. In some areas the tectonic regime has been inferred either from fault plane solutions of M≥4 earthquakes or from stress inversions of smaller earthquakes. Where seismicity lacks, the regime is not well constrained and little or no information on the magnitude of the crustal stresses is available. In order to improve our knowledge in stress regime and its magnitude in Italy, in this work we use the leak-off test technique. Each test is performed at the bottom of an open hole by sealing off a section and then slowly pressurizing with a fluid until hydraulic tensile fractures develop. The minimum horizontal stress is inferred by leak-off pressure record, the vertical stress is computed by rock density data and the maximum horizontal stress is estimated applying a specific formula from the literature. Thanks to ENI S.p.A. (Italian oil company), that kindly provided new well data, we have been able to perform a critical review of our preliminary calculations and to enhance our previous results concerning stress magnitudes. Totally, we have analyzed 192 leak-off tests at depth between 200 and 5400m (average 1800m). In particular, wells are located along the Italian peninsula and in Sicily: most of them are in the Po Plain and along the Apenninic foredeep; few are in southern Apenninic belt and a few tens are in Sicily. After an accurate selection of the most robust results, we better characterize the Italian stress regime at depth.

  19. Validity of multiple stress creep recovery test for LADOTD asphalt binder specification.

    Science.gov (United States)

    2010-09-01

    The objectives of this research are to characterize the elastic response of various binders used by LADOTD to determine the feasibility of the Multiple Stress Creep Recovery (MSCR) test to be included in the LADOTD asphalt binder specification and to...

  20. Delayed heart rate recovery after adenosine stress testing with supplemental arm exercise predicts mortality.

    Science.gov (United States)

    Akutsu, Yasushi; Gregory, Shawn A; Kardan, Arash; Zervos, Gerasimos D; Thomas, Gregory S; Gewirtz, Henry; Yasuda, Tsunehiro

    2009-01-01

    Delayed heart rate (HR) recovery after treadmill exercise testing predicts mortality. Patients with suspected ischemic heart disease who cannot perform adequate treadmill exercise are typically evaluated with pharmacological stress myocardial perfusion imaging (MPI) studies, but little prognostic significance has been attributed to the hemodynamic response to vasodilator stress testing with low-level exercise. We hypothesized that a delay in HR recovery after adenosine stress testing with arm exercise is associated with increased mortality. Technetium 99m-Sestamibi MPI was performed in 1,455 consecutive patients (70 +/- 12 years, 50.2% men) with adenosine stress and supplemental arm exercise. HRs were recorded at rest, continuously during infusion, and then 5 minutes post-infusion. Delayed HR recovery was defined as a decline of mortality (16.5% vs 5.3% in those with normal HR recovery, P testing with arm exercise is a readily available and powerful predictor of all-cause mortality.

  1. To What Extent Is Stress Testing of Android TV Applications Automated in Industrial Environments?

    OpenAIRE

    Jiang, Bo; Chen, Peng; Chan, W. K.; Zhang, Xinchao

    2015-01-01

    An Android-based smart Television (TV) must reliably run its applications in an embedded program environment under diverse hardware resource conditions. Owing to the diverse hardware components used to build numerous TV models, TV simulators are usually not high enough in fidelity to simulate various TV models, and thus are only regarded as unreliable alternatives when stress testing such applications. Therefore, even though stress testing on real TV sets is tedious, it is the de facto approa...

  2. Stress transfer of a Kevlar 49 fiber pullout test studied by micro-Raman spectroscopy.

    Science.gov (United States)

    Lei, Zhenkun; Wang, Quan; Qiu, Wei

    2013-06-01

    The interfacial stress transfer behavior of a Kevlar 49 aramid fiber-epoxy matrix was studied with fiber pullout tests, the fibers of which were stretched by a homemade microloading device. Raman spectra on the embedded fiber were recorded by micro-Raman spectroscopy, under different strain levels. Then, the fiber axial stress was obtained by the relationship between the stress and Raman shift of the aramid fiber. Experimental results revealed that the fiber axial stress increased significantly with the load. The shear stress concentration occurred at the fiber entry to the epoxy resin. Thus, interfacial friction stages exist in the debonded fiber segment, and the interfacial friction shear stress is constant within one stage. The experimental results are consistent with the theoretical model predictions.

  3. Effect of Benson Relaxation Techniques on Hemodynamic Variables of Patient Undergoing Coronary Angiography

    Directory of Open Access Journals (Sweden)

    M khani

    2005-01-01

    Full Text Available Introduction: Invasive diagnostic procedures such as coronary angiography, in most cases, are accompanied by stress and anxiety for patients,which may effect on hemodynamic signs. Materials and Methods:This research, as a quasi experimental study, has the objective to determine the influence of applying methods of relaxation on hemodynamic signs in hospitalized 40 patients, experienciny coronary angiography (CA,, has been studied, in regard to existing conditions and methods of sampling and random allocation to two groups of control and relaxation at 2003 . Data collection tool included demographic and disease related information sheet, as well as record sheets for hemodynamic parameters at intervals of 8-12 and ½ hrs before, during and after the angiography. For relaxation group, the researcher would speak individually about the influence of relaxation, the day before angiography; Then with the aid of client himself/herself, performed relaxation instances in a single bout, and eventually asked client to perform relaxation technique 2-3 times before going for angiography. In control group was attended in the usual manner preangiographically. Homodynamic parameters were measured in both groups 8-12 and ½ hrs, before during and after CA. Afterward, resulted data were analyzed statistically by T-Test Chi-squre. Results: With T-Test, respiratory rates½ hrs, beforeAngiography, diastolic blood pressure and Respiratory Rate after Angiography showed statisticaly significant difference between two groups (P0.05.but most of parameters showed clinically significant difference between two groups. Conclusion: Therfore it is offered that relaxation method is applied after invasive procedures.

  4. Comparison of the Safety of Adenosine and Regadenoson in Patients Undergoing Outpatient Cardiac Stress Testing.

    Science.gov (United States)

    Brink, Heidi L; Dickerson, Jennifer A; Stephens, Julie A; Pickworth, Kerry K

    2015-12-01

    To compare the adverse effect profiles of adenosine and regadenoson in patients undergoing outpatient cardiac stress testing. Single-center retrospective cohort study. Two outpatient clinics, both of which are part of a single tertiary academic medical health system; one clinic exclusively used adenosine for cardiac stress testing, and the other clinic exclusively used regadenoson. A total of 489 patients who underwent an outpatient cardiac stress test between January 1, 2014, and December 31, 2014; of those patients, 254 received adenosine and 235 received regadenoson. Baseline characteristics were similar between groups, except for chronic kidney disease (pregadenoson groups. A significantly higher proportion of patients who were given regadenoson during cardiac stress testing experienced at least one adverse effect compared with patients who underwent an adenosine stress test (79.6% vs 31.5%, pregadenoson experienced a significantly higher occurrence of arrhythmia (30.6% vs 16.1%, pregadenoson based on the average wholesale price. Among patients undergoing an outpatient pharmacologic stress test, the use of adenosine was associated with a lower occurrence of adverse effects and lower rate of a rescue agent use and may provide a potential medication cost savings opportunity compared with regadenoson. © 2015 Pharmacotherapy Publications, Inc.

  5. The influence of clopidogrel on ischemia diagnosed by myocardial perfusion stress testing.

    Science.gov (United States)

    Jovin, Ion S; Ebisu, Keita A; Oprea, Adriana D; Brandt, Cynthia A; Natale, Donna; Finta, Laurie A; Dziura, James; Wackers, Frans J

    2016-08-01

    Clopidogrel is a platelet adenosine receptor antagonist which can influence coronary vascular tone and thus can potentially interfere with myocardial perfusion imaging. We investigated whether clopidogrel can hamper the diagnosis of ischemia in patients undergoing myocardial perfusion testing. Data from a database of 6349 myocardial perfusion stress tests were analyzed. Using a propensity analysis, patients who were taking clopidogrel were compared with patients not taking clopidogrel for the presence of reversible perfusion defects on myocardial single-photon emission computed tomography scans. Of the 6349 tests, the stress technique was adenosine in 2713 patients and exercise in 3636. At the time of the stress test, 277 (4.3%) of the patients were taking clopidogrel. The odds ratio (OR) for patients taking clopidogrel to have a reversible perfusion defect was 2.75 (95% confidence interval [CI] 2.09-3.62; P clopidogrel, the OR was 1.06 (CI 0.76-1.49; P = .73) for patients undergoing adenosine stress tests and 1.60 (CI 0.85-3.00; P = .14) for patients undergoing exercise stress tests. We found no evidence that the use of clopidogrel decreases the likelihood of ischemia on adenosine or exercise stress myocardial perfusion scans.

  6. Relaxation of jammed colloidal suspensions after shear cessation.

    Science.gov (United States)

    Ianni, Francesca; Lasne, David; Sarcia, Régis; Hébraud, Pascal

    2006-07-01

    The dynamics of heterogeneities in a shear thickening, concentrated colloidal suspension is investigated through speckle visibility spectroscopy, a dynamic light scattering technique recently introduced [P. K. Dixon and D. J. Durian, Phys. Rev. Lett. 90, 184302 (2003)]. Formation of shear-induced heterogeneities is observed in the jamming regime, and their relaxation after shear cessation is monitored as a function of the applied shear stress. The relaxation time of these heterogeneities increases when a higher stress is applied.

  7. 78 FR 47217 - Proposed Supervisory Guidance on Implementing Dodd-Frank Act Company-Run Stress Tests for Banking...

    Science.gov (United States)

    2013-08-05

    ... Company-Run Stress Tests for Banking Organizations With Total Consolidated Assets of More Than $10 Billion... Implementing Dodd-Frank Act Company-Run Stress Tests for Banking Organizations with Total Consolidated Assets... Stress Tests for Banking Organizations with Total Consolidated Assets of more than $10 Billion but less...

  8. Stress relaxation in thick-film GaN grown by hydride vapor phase epitaxy on sapphire and spinel substrates as studied by photoluminescence and raman spectroscopy

    CERN Document Server

    Kim, S T; Lee, C; Kim, J E; Park, H Y

    1999-01-01

    The residual strains in thick-film GaN grown on both sapphire and spinel substrates has been evaluated by photoluminescence (PL) and raman spectroscopy . The strain-free shallow donor bound exciton recombination energy (I sub 2) is 3.468 eV at 10 K. The raman mode frequency shift with residual strain with estimated as DELTA w = 3.93 cm sup - sup 1 per one GPa for GaN layers on both substrates . The linear relationship between the PL I sub 2 line and the raman E sub 2 mode frequency is DELTA E/DELTA w = 5.12 meV/cm sup - sup 1 , which leads to a stress-induced PL line shift of DELTA E = 20 meV/GPa.

  9. Frequency of stress testing to document ischemia prior to elective percutaneous coronary intervention.

    Science.gov (United States)

    Lin, Grace A; Dudley, R Adams; Lucas, F L; Malenka, David J; Vittinghoff, Eric; Redberg, Rita F

    2008-10-15

    Guidelines call for documenting ischemia in patients with stable coronary artery disease prior to elective percutaneous coronary intervention (PCI). To determine the frequency and predictors of stress testing prior to elective PCI in a Medicare population. Retrospective, observational cohort study using claims data from a 20% random sample of 2004 Medicare fee-for-service beneficiaries aged 65 years or older who had an elective PCI (N = 23 887). Percentage of patients who underwent stress testing within 90 days prior to elective PCI; variation in stress testing prior to PCI across 306 hospital referral regions; patient, physician, and hospital characteristics that predicted the appropriate use of stress testing prior to elective PCI. In the United States, 44.5% (n = 10 629) of patients underwent stress testing within the 90 days prior to elective PCI. There was wide regional variation among the hospital referral regions with stress test rates ranging from 22.1% to 70.6% (national mean, 44.5%; interquartile range, 39.0%-50.9%). Female sex (adjusted odds ratio [AOR], 0.91; 95% confidence interval [CI], 0.86-0.97), age of 85 years or older (AOR, 0.83; 95% CI, 0.72-0.95), a history of congestive heart failure (AOR, 0.85; 95% CI, 0.79-0.92), and prior cardiac catheterization (AOR, 0.45; 95% CI, 0.38-0.54) were associated with a decreased likelihood of prior stress testing. A history of chest pain (AOR, 1.28; 95% CI, 1.09-1.54) and black race (AOR, 1.26; 95% CI, 1.09-1.46) increased the likelihood of stress testing prior to PCI. Patients treated by physicians performing 150 or more PCIs per year were less likely to have stress testing prior to PCI (AOR, 0.84; 95% CI, 0.77-0.93). No hospital characteristics were associated with receipt of stress testing. The majority of Medicare patients with stable coronary artery disease do not have documentation of ischemia by noninvasive testing prior to elective PCI.

  10. Testing the relationship between job stress and satisfaction in correctional nurses.

    Science.gov (United States)

    Flanagan, Nancy A

    2006-01-01

    Correctional nurses function in a high stress environment due to the nature of their clients and the primacy of environmental security. Job stress and satisfaction are theorized relational concepts that influence intent to stay and turnover as described in the anticipated turnover model. An increased understanding of the nature and sources of stress and satisfaction provides necessary information about correctional nursing. To (a) replicate an earlier study of correctional nurses to determine whether similar findings could be duplicated in a study of prison nurses from another state and (b) test the concepts of stress and satisfaction as represented in the anticipated turnover model. Using the Index of Work Satisfaction and the Nurse Stress Index, a correlational mail survey was designed to assess job stress and satisfaction among 454 nurses in a northeastern state prison system. Overall stress scores were not significantly different from the original study despite differences in demographic characteristics. Highest to lowest mean scores on actual sources of satisfaction include physician-nurse interaction, autonomy, professional status, task requirements, organizational policies, and pay. Satisfaction scores were significantly higher in the original study. An inverse relationship exists between job stress and satisfaction among correctional nurses. Job stress was a significant predictor of job satisfaction, supporting the theorized conceptual relationship between job stress and job satisfaction as described in the anticipated turnover model. Stress levels and the top two sources of stress were essentially the same for both groups of correctional nurses. Sources of satisfaction are ranked similarly but subscale and overall scores indicate that the nurses in the replication study were more dissatisfied. Findings validate the theoretical proposition in the anticipated turnover model that job stress is a major predictor variable in explaining job satisfaction.

  11. Residual stresses in high temperature corrosion of pure zirconium using elasto-viscoplastic model: Application to the deflection test in monofacial oxidation

    Science.gov (United States)

    Fettré, D.; Bouvier, S.; Favergeon, J.; Kurpaska, L.

    2015-12-01

    The paper is devoted to modeling residual stresses and strains in an oxide film formed during high temperature oxidation. It describes the deflection test in isothermal high-temperature monofacial oxidation (DTMO) of pure zirconium. The model incorporates kinetics and mechanism of oxidation and takes into account elastic, viscoplastic, growth and chemical strains. Different growth strains models are considered, namely, isotropic growth strains given by Pilling-Bedworth ratio, anisotropic growth strains defined by Parise and co-authors and physically based model for growth strain proposed by Clarke. Creep mechanisms based on dislocation slip and core diffusion, are used. A mechanism responsible for through thickness normal stress gradient in the oxide film is proposed. The material parameters are identified using deflection tests under 400 °C, 500 °C and 600 °C. The effect of temperature on creep and stress relaxation is analyzed. Numerical sensitivity study of the DTMO experiment is proposed in order to investigate the effects of the initial foil thickness and platinum coating on the deflection curves.

  12. Organizational and media stress among professional football players: testing an achievement goal theory model.

    Science.gov (United States)

    Kristiansen, E; Halvari, H; Roberts, G C

    2012-08-01

    The purpose of this study was to investigate media and coach-athlete stress experienced by professional football players and their relationship to motivational variables by testing an achievement goal theory (AGT) stress model. In order to do so, we developed scales specifically designed to assess media and coach-athlete stress. Eighty-two elite football players (M(age) =25.17 years, SD=5.19) completed a series of questionnaires. Correlations and bootstrapping were used as primary statistical analyses, supplemented by LISREL, to test the hypotheses. Results revealed that a mastery climate was directly and negatively associated with coach-athlete stress, while a performance climate was directly and positively associated with coach-athlete stress. In addition, an indirect positive path between the performance climate and media stress was revealed through ego orientation. These findings support some of the key postulates of AGT; a mastery climate reduces the perception of stress among athletes, and the converse is true for a performance climate. Coaches of elite footballers are advised to try to reduce the emphasis on performance criteria because of its stress-reducing effects. © 2011 John Wiley & Sons A/S.

  13. The Effectiveness of Stress Management and Test-Taking Workshops in Reducing Test Anxiety of Community College Students.

    Science.gov (United States)

    Price, Elsa C.

    A study was conducted to determine the effectiveness of a Stress Management Seminar and a Test-Taking Skills Workshop in improving the scores of pre-nursing and guidance examinees at Wallace Community College in Dothan, Alabama. The 73 subjects took the Pre-Nursing and Guidance Examination (PNGE) in June 1984, September 1984, or January 1985.…

  14. Molecular Relaxation in Liquids

    CERN Document Server

    Bagchi, Biman

    2012-01-01

    This book brings together many different relaxation phenomena in liquids under a common umbrella and provides a unified view of apparently diverse phenomena. It aligns recent experimental results obtained with modern techniques with recent theoretical developments. Such close interaction between experiment and theory in this area goes back to the works of Einstein, Smoluchowski, Kramers' and de Gennes. Development of ultrafast laser spectroscopy recently allowed study of various relaxation processes directly in the time domain, with time scales going down to picosecond (ps) and femtosecond (fs

  15. Impaired gastric relaxation in patients with achalasia.

    Science.gov (United States)

    Mearin, F; Papo, M; Malagelada, J R

    1995-03-01

    Achalasia is considered a primary motility disorder confined to the oesophagus. The lower oesophageal sphincter (LOS) in achalasia is frequently hypertonic and manifests absent or incomplete relaxation in response to deglution. On the other hand, the LOS and the proximal stomach act physiologically as a functional unit whereby relaxation of the LOS during deglution is associated with receptive relaxation of the proximal stomach. Thus, this study investigated the hypothesis that impaired LOS relaxation in patients with achalasia might be associated with impaired relaxation of the proximal stomach. The study consisted of 20 patients with achalasia and 10 healthy controls. Gastric tone variations were quantified using an electronic barostat. Firstly, the study established the basal gastric tone (intragastric volume at the minimal distending pressure+1 mm Hg) and gastric compliance (volume/pressure relation) during isobaric distension (increasing stepwise the intragastric pressure from 0 to 20 mm Hg up to 600 ml). Secondly, the gastric tone response to cold stress (hand immersion into ice water for five minutes) or to control stimuli (water at 37 degrees) was determined. Basal gastric tone mean (SEM) was similar in achalasia and in healthy controls (125 (9) ml v 138 (9) ml, respectively). Compliance was linear and similar in both groups, which also showed similar gastric extension ratios (58 (7) ml/mm Hg v 57 (6) ml/mm Hg). Cold stress induced a gastric relaxatory response that, as a group, was significantly lower in achalasia than in healthy controls (volume: 43 (20) ml v 141 (42) ml; p 100 ml) relaxatory responses whereas four of the 10 healthy controls did not. In conclusion, reflex gastric relaxation is impaired in most patients with achalasia showing that the proximal stomach, and not exclusively the oesophagus, may be effected by the disease.

  16. Stress testing in patients with implantable cardioverter-defibrillators: a preliminary report.

    Science.gov (United States)

    Chinnaiyan, Kavitha M; Trivax, Justin; Franklin, Barry A; Williamson, Brian; Kahn, Joel K

    2007-01-01

    This retrospective study was undertaken to assess the responses to, and complications associated with, stress testing in patients with implantable cardioverter-defibrillators (ICDs). Primary end points were occurrence of malignant ventricular arrhythmias, onset of burst pacing or ICD firing, cardiopulmonary resuscitation, or death during or soon after stress testing. Secondary end points were urgent coronary revascularization and/or hospital readmission for cardiovascular complications. During a 4-year period, 1734 patients underwent ICD implantation or generator replacement at our institution; 84 patients (mean age +/- SD, 67+/-12 years; 76% men) subsequently underwent 107 stress tests, including 44 exercise and 63 pharmacologic (22 dobutamine, 41 dipyridamole) evaluations. None of the ICDs were inactivated before testing. All tests were supervised by specially trained paramedical personnel, with a physician immediately available. Four patients had self-terminating, nonsustained ventricular tachycardia at peak stress. None had sustained ventricular tachycardia requiring emergent therapy. There were no deaths or hospital readmissions for ventricular arrhythmias. These findings suggest that stress testing is feasible in patients with ICDs and that it can be performed without pretest inactivation.

  17. [Magnesium deficiency and stress: Issues of their relationship, diagnostic tests, and approaches to therapy].

    Science.gov (United States)

    Tarasov, E A; Blinov, D V; Zimovina, U V; Sandakova, E A

    2015-01-01

    Magnesium plays an important role in the functions of the central nervous system. It takes part in the regulation of the cell membrane, the transmembrane transport of calcium and sodium ions, and metabolic reactions that produce, accumulate, transfer, and utilize energy, free radicals, and their oxidation products. The magnesium-containing substances include many sequestered antigens, such as glial fibrillary acidic protein, S100, and neuron-specific enolase; magnesium may act as a neuroprotector that is able to modulate the regulation of blood-brain barrier permeability. Investigations have demonstrated a relationship between the manifestations of stress reactions (anxiety, autonomic dysfunction, and maladjustment) and magnesium deficiency (MD). Thus, mental and physical stresses cause an increase in magnesium elimination from the body. MD in turn enhances a response to stress, by paradoxically aggravating its sequels. Compensation for MD increases the ability of the nervous system to resist stress. The valid diagnosis of MD present difficulties; namely, a blood magnesium concentration decrease below 0.8 mmol/l is evidence of MD; but the constant blood level of magnesium may be long maintained due to its release from the bone tissue depot. So it is necessary to keep in mind the clinical manifestations of MD. The authors have developed and tested a simple rapid MD assessment test and a stress resistance self-rating test. The proposed tests will help to screen stress resistance and MD in outpatient settings.

  18. An Exploration of the Relationship between Wrist Temperature and Relaxation Training.

    Science.gov (United States)

    Matthews, Doris B.; Casteel, Jim Frank

    Research supports skin temperature changes (increases) as indicators of stress reduction or relaxation. To study the utility of skin temperature at the wrist as a measure of relaxation, 226 seventh grade students recorded their wrist temperatures before and after a 15-minute relaxation training exercise each morning for 29 weeks. Teachers checked…

  19. Development of the Stress of Immigration Survey (SOIS): a Field Test among Mexican Immigrant Women

    Science.gov (United States)

    Sternberg, Rosa Maria; Nápoles, Anna Maria; Gregorich, Steven; Paul, Steven; Lee, Kathryn A.; Stewart, Anita L.

    2016-01-01

    The Stress of Immigration Survey (SOIS) is a screening tool used to assess immigration-related stress. The mixed methods approach included concept development, pretesting, field-testing, and psychometric evaluation in a sample of 131 low-income women of Mexican descent. The 21-item SOIS screens for stress related to language; immigrant status; work issues; yearning for family and home country; and cultural dissonance. Mean scores ranged from 3.6 to 4.4 (1-5 scale, higher is more stress). Cronbach's alphas >.80 for all sub-scales. The SOIS may be a useful screening tool for detecting high levels of immigration-related stress in low-income Mexican immigrant women. PMID:26605954

  20. Development of the Stress of Immigration Survey: A Field Test Among Mexican Immigrant Women.

    Science.gov (United States)

    Sternberg, Rosa Maria; Nápoles, Anna Maria; Gregorich, Steven; Paul, Steven; Lee, Kathryn A; Stewart, Anita L

    2016-01-01

    The Stress of Immigration Survey (SOIS) is a screening tool used to assess immigration-related stress. The mixed methods approach included concept development, pretesting, field testing, and psychometric evaluation in a sample of 131 low-income women of Mexican descent. The 21-item SOIS screens for stress related to language, immigrant status, work issues, yearning for family and home country, and cultural dissonance. Mean scores ranged from 3.6 to 4.4 (a scale of 1-5, higher is more stress). Cronbach α values were more than 0.80 for all subscales. The SOIS may be a useful screening tool for detecting high levels of immigration-related stress in low-income Mexican immigrant women.

  1. Stress mitigation of x-ray beamline monochromators using topography test unit.

    Energy Technology Data Exchange (ETDEWEB)

    Maj, J.; Waldschmidt, G.; Baldo, P.; Macrander, A.; Koshelev, I.; Huang, R.; Maj, L.; Maj, A.; Univ. of Chicago; Northeastern Ohio Univ. Coll. of Medicine; Rosalind Franklin Univ. of Medicine and Science

    2007-01-01

    Silicon and diamond monochromators (crystals), often used in the Advanced Photon Source X-ray beamlines, require a good quality surface finish and stress-free installation to ensure optimal performance. The device used to mount the crystal has been shown to be ajor contributing source of stress. In this case, an adjustable mounting device is an effective method of reducing stresses and improve the rocking curve to levels much closer to ideal. Analysis by a topography test unit has been used to determine the distribution of stresses and to measure the rocking curve, as well as create CCD images of the crystal. This paper describes the process of measuring these stresses and manipulating the mounting device and crystal to create a substantially improved monochromator.

  2. A Study on the Storage Reliability of LSINS Based on Step-stress Accelerated Life Test

    Directory of Open Access Journals (Sweden)

    Teng Fei

    2015-01-01

    Full Text Available Based on the step-stress accelerated life test and the laser strap-down inertial navigation system, this paper studies the accelerated life model and the test method, provides the likelihood function, the likelihood equation and the two-order derivative when the stress level is k, evaluates the effectiveness of the method with the simulation test model established by MATLAB, applies the research findings in the storage reliability study of the XX laser strap-down inertial navigation system, and puts forward an effective evaluation method of the storage life of the inertial navigation system.

  3. Standard test method for calibration of surface/stress measuring devices

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    1997-01-01

    Return to Contents page 1.1 This test method covers calibration or verification of calibration, or both, of surface-stress measuring devices used to measure stress in annealed and heat-strengthened or tempered glass using polariscopic or refractometry based principles. 1.2 This test method is nondestructive. 1.3 This test method uses transmitted light, and therefore, is applicable to light-transmitting glasses. 1.4 This test method is not applicable to chemically tempered glass. 1.5 Using the procedure described, surface stresses can be measured only on the “tin” side of float glass. 1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

  4. Partial Shade Stress Test for Thin-Film Photovoltaic Modules: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Silverman, Timothy J.; Deceglie, Michael G.; Deline, Chris; Kurtz, Sarah

    2015-09-02

    Partial shade of monolithic thin-film PV modules can cause reverse-bias conditions leading to permanent damage. In this work, we propose a partial shade stress test for thin-film PV modules that quantifies permanent performance loss. We designed the test with the aid of a computer model that predicts the local voltage, current and temperature stress that result from partial shade. The model predicts the module-scale interactions among the illumination pattern, the electrical properties of the photovoltaic material and the thermal properties of the module package. The test reproduces shading and loading conditions that may occur in the field. It accounts for reversible light-induced performance changes and for additional stress that may be introduced by light-enhanced reverse breakdown. We present simulated and experimental results from the application of the proposed test.

  5. Assessing corrosion problems in photovoltaic cells via electrochemical stress testing

    Science.gov (United States)

    Shalaby, H.

    1985-01-01

    A series of accelerated electrochemical experiments to study the degradation properties of polyvinylbutyral-encapsulated silicon solar cells has been carried out. The cells' electrical performance with silk screen-silver and nickel-solder contacts was evaluated. The degradation mechanism was shown to be electrochemical corrosion of the cell contacts; metallization elements migrate into the encapsulating material, which acts as an ionic conducting medium. The corrosion products form a conductive path which results in a gradual loss of the insulation characteristics of the encapsulant. The precipitation of corrosion products in the encapsulant also contributes to its discoloration which in turn leads to a reduction in its transparency and the consequent optical loss. Delamination of the encapsulating layers could be attributed to electrochemical gas evolution reactions. The usefulness of the testing technique in qualitatively establishing a reliability difference between metallizations and antireflection coating types is demonstrated.

  6. Predischarge stress test after myocardial infarction in the old stage : results and prognostic value

    NARCIS (Netherlands)

    P.M. Fioretti (Paolo); J.W. Deckers (Jaap); R.W. Brower (Ronald); M.L. Simoons (Maarten); J.A.J.M. Beelen; P.G. Hugenholtz (Paul)

    1984-01-01

    textabstractThe aim of this study was to evaluate the results of predischarge stress testing in the elderly, and to assess the prognostic value of the test during one-year follow-up. The database consisted of 48 patients older than 64 years of age and 109 patients 55-64 years of age, who survived

  7. Stress Corrosion Cracking of Steel and Aluminum in Sodium Hydroxide: Field Failure and Laboratory Test

    Directory of Open Access Journals (Sweden)

    Y. Prawoto

    2012-01-01

    Full Text Available Through an investigation of the field failure analysis and laboratory experiment, a study on (stress corrosion cracking SCC behavior of steel and aluminum was performed. All samples were extracted from known operating conditions from the field failures. Similar but accelerated laboratory test was subsequently conducted in such a way as to mimic the field failures. The crack depth and behavior of the SCC were then analyzed after the laboratory test and the mechanism of stress corrosion cracking was studied. The results show that for the same given stress relative to ultimate tensile strength, the susceptibility to SCC is greatly influenced by heat treatment. Furthermore, it was also concluded that when expressed relative to the (ultimate tensile strength UTS, aluminum has similar level of SCC susceptibility to that of steel, although with respect to the same absolute value of applied stress, aluminum is more susceptible to SCC in sodium hydroxide environment than steel.

  8. Nuclear Spin Relaxation

    Indian Academy of Sciences (India)

    IAS Admin

    and almost completely destroyed by the chaotic thermal environ- ment. Fortunately, the havoc wreaked by thermal molecular motion is not complete. The tiny residual nuclear magnetism (of the order of 10–5), which is established through spin–lattice relaxation, is the basis of almost all NMR and MRI experiments. [1].

  9. How acute sport influences the response to a social stress test

    OpenAIRE

    Fischer, Elisabeth

    2012-01-01

    The high level of both chronic and acute stress in daily life can endanger our health. Therefore it is important to develop strategies to cope with the stress one cannot evade. In this thesis we investigate whether acute sport changes the response of healthy individuals to a social stress test. To answer this question 34 healthy individuals were placed in either the placebo or verum group by chance. The verum group had to exercise for 30 minutes on a treadmill. After this treatment both group...

  10. A Modified Constant-Stress Coupon for Enhanced Natural Crack Start during Fatigue Testing

    Science.gov (United States)

    2016-05-01

    elimination of the highly-localised stress concentration that is a characteristic feature of a traditional dog -bone coupon. The presence of an extensive...greatly reduced costs in conducting fatigue testing programs studying the initiation and growth behaviour of small cracks. RELEASE LIMITATION...of the notch, resulting in the elimination of the highly-localised stress concentration that is a characteristic feature of a traditional dog -bone

  11. Stress Testing of the Philips 60W Replacement Lamp L Prize Entry

    Energy Technology Data Exchange (ETDEWEB)

    Poplawski, Michael E.; Ledbetter, Marc R.; Smith, Mark

    2012-04-24

    The Pacific Northwest National Laboratory, operated by Battelle for the U.S. Department of Energy, worked with Intertek to develop a procedure for stress testing medium screw-base light sources. This procedure, composed of alternating stress cycles and performance evaluation, was used to qualitatively compare and contrast the durability and reliability of the Philips 60W replacement lamp L Prize entry with market-proven compact fluorescent lamps (CFLs) with comparable light output and functionality. The stress cycles applied simultaneous combinations of electrical, thermal, vibration, and humidity stresses of increasing magnitude. Performance evaluations measured relative illuminance, x chromaticity and y chromaticity shifts after each stress cycle. The Philips L Prize entry lamps appear to be appreciably more durable than the incumbent energy-efficient technology, as represented by the evaluated CFLs, and with respect to the applied stresses. Through the course of testing, all 15 CFL samples permanently ceased to function as a result of the applied stresses, while only 1 Philips L Prize entry lamp exhibited a failure, the nature of which was minor, non-destructive, and a consequence of a known (and resolved) subcontractor issue. Given that current CFL technology appears to be moderately mature and no Philips L Prize entry failures could be produced within the stress envelope causing 100 percent failure of the benchmark CFLs, it seems that, in this particular implementation, light-emitting diode (LED) technology would be much more durable in the field than current CFL technology. However, the Philips L Prize entry lamps used for testing were carefully designed and built for the competition, while the benchmark CFLs were mass produced for retail sale—a distinction that should be taken into consideration. Further reliability testing on final production samples would be necessary to judge the extent to which the results of this analysis apply to production versions

  12. Stress-testing the Standard Model at the LHC

    CERN Document Server

    2016-01-01

    With the high-energy run of the LHC now underway, and clear manifestations of beyond-Standard-Model physics not yet seen in data from the previous run, the search for new physics at the LHC may be a quest for small deviations with big consequences. If clear signals are present, precise predictions and measurements will again be crucial for extracting the maximum information from the data, as in the case of the Higgs boson. Precision will therefore remain a key theme for particle physics research in the coming years. The conference will provide a forum for experimentalists and theorists to identify the challenges and refine the tools for high-precision tests of the Standard Model and searches for signals of new physics at Run II of the LHC. Topics to be discussed include: pinning down Standard Model corrections to key LHC processes; combining fixed-order QCD calculations with all-order resummations and parton showers; new developments in jet physics concerning jet substructure, associated jets and boosted je...

  13. Exercise Testing and Stress Imaging in Mitral Valve Disease.

    Science.gov (United States)

    Voilliot, Damien; Lancellotti, Patrizio

    2017-03-01

    Mitral valve disease represented by mitral stenosis and mitral regurgitation is the second most frequent valvulopathy. Mitral stenosis leads to an increased left atrial pressure whereas mitral regurgitation leads to an increased left atrial pressure associated with a volume overload. Secondary to an upstream transmission of this overpressure, both mitral stenosis and regurgitation lead to pulmonary hypertension and right heart failure. In addition, mitral regurgitation also leads to left ventricular dilatation and dysfunction with left heart failure. Depending on the anatomy of the valvular and subvalvular apparatus, valve repair (percutaneous mitral commissurotomy for mitral stenosis and valvuloplasty for mitral regurgitation) might be possible. If the anatomy is not favorable, valve replacement by mechanical or biological prosthesis is indicated. Most of the intervention indications are based on clinical symptoms and resting transthoracic echocardiography. Outcomes of patients operated based upon resting echo abnormalities might however not be optimal. Therefore early intervention might be beneficial based upon abnormal exercise testing, which has been demonstrated to more sensitive to identify high-risk patients. In this last decade, especially exercise echocardiography has been found to be a crucial tool in the management of patients with mitral valve disease.

  14. Testing the Coulomb stress triggering hypothesis for three recent megathrust earthquakes

    Science.gov (United States)

    Ishibe, Takeo; Ogata, Yosihiko; Tsuruoka, Hiroshi; Satake, Kenji

    2017-12-01

    We test the static Coulomb stress triggering hypothesis for three recent megathrust earthquakes (the 2004 Sumatra-Andaman earthquake, the 2010 Maule earthquake, and the 2011 Tohoku-Oki earthquake) using focal mechanism solutions for actual earthquakes as receiver faults to calculate Coulomb stress changes. For the 2004 Sumatra-Andaman and 2011 Tohoku-Oki earthquakes, the median values of the Coulomb stress changes for 100 consecutive earthquakes revealed temporal changes from approximately zero before the megathrust earthquake to significant positive values following the mainshock, followed by decay over time. Furthermore, the ratio of the number of positively to negatively stressed receiver faults increased after the megathrust. These results support the triggering hypothesis that the static stress changes imparted by megathrust earthquakes cause seismicity changes. This is in contrast to the results of a previous study that used optimally orientated receiver faults to calculate Coulomb stress changes, and this difference indicates the importance of considering the spatial and temporal heterogeneities of receiver fault distributions. For the 2010 Maule earthquake, however, the results are strongly dependent on fault-slip models. Since most receiver faults are concentrated in the mainshock source region, slip models significantly affect the computed Coulomb stress changes and sometimes cause anomalous stress concentrations along the edge of each sub-fault.

  15. Stress

    Science.gov (United States)

    ... natural disaster. This type of stress can cause post-traumatic stress disorder (PTSD). Different people may feel stress in different ways. Some people experience digestive symptoms. Others may have headaches, sleeplessness, depressed mood, anger, ...

  16. [Evaluation of the empty bladder stress test in supine position as a marker of severity and quality of life in women with stress urinary incontinence].

    Science.gov (United States)

    Arribillaga, Leandro; Ledesma, Marta; Bengió, Rubén G; Montedoro, Ariel; Pisano, Florencia; Orellana, Sergio; García Önto, Hernán; Bengió, Rubén H

    2016-06-01

    To assess the association between empty bladder stress test and objective and subjective measures of stress urinary incontinence (SUI) severity. Prospective, analytic and descriptive study of females with diagnosis of stress urinary incontinence referred for urodynamics study. Every patient underwent medical history (including number of daily pads) and physical examination, ISIQ-SF and short IIQ-7 questionnaires, and full urodynamic study, including the measurment of the abdominal leak pressure point (ALPP). Positive empty stress test was defined as stress urine leak on physical exam after uroflowmetry evacuation and in absence of significant post-void residual. To evaluate the relationship between empty bladder stress test and each one of the stress urinary incontinence severity measures, Stundent's t test was performed, considering a 〈0.05 value statistically significant. 107 patients were studied in the final analysis; of them 49 had empty bladder stress test (+) and 58 (-). Patients with positive test wet a greater number of protectors per day (3.9 vs 2.8; p 0.013), higher ICIQSF score (15.04 vs 12.22; p 0.0007), higher IIQ-7 score (52.2 vs 37.5; p 0.0049) and lower urodynamics ALPP (73 cm H2O vs 91 cm H2O; p 0.0002). Patients with SUI and positive empty bladder stress test had a strong association with the objective and subjective perception of urine incontinence severity with a negative impact in patients quality of life.

  17. A test case of the deformation rate analysis (DRA) stress measurement method

    Energy Technology Data Exchange (ETDEWEB)

    Dight, P.; Hsieh, A. [Australian Centre for Geomechanics, Univ. of WA, Crawley (Australia); Johansson, E. [Saanio and Riekkola Oy, Helsinki (Finland); Hudson, J.A. [Rock Engineering Consultants (United Kingdom); Kemppainen, K.

    2012-01-15

    As part of Posiva's site and ONKALO investigations, the in situ rock stress has been measured by a variety of techniques, including hydraulic fracturing, overcoring, and convergence measurements. All these techniques involve direct measurements in a drillhole or at the rock surface. An alternative method is to test drillhole core in a way that enables estimation of the magnitudes and orientations of the in situ rock stress. The Kaiser Effect (KE) and Deformation Rate Analysis (DRA) are two ways to do this. In the work reported here, a 'blind' DRA test was conducted on core obtained from the POSE (Posiva's Olkiluoto Spalling Experiment) niche in the ONKALO. The term 'blind' means that the two first authors of this report, who conducted the tests at the Australian Centre for Geomechanics, did not know the depths below surface at which the cores had been obtained. The results of this DRA Test Case are presented, together with an explanation of the DRA procedure. Also, additional information that would help in such DRA testing and associated analysis is explained. One of the problems in comparing the DRA results with the known Olkiluoto stress field is that the latter is highly variable across the site, as experienced by the previous in situ stress measurements and as predicted by numerical analysis. The variability is mainly caused by the presence of the large brittle deformation zones which perturb the local stress state. However, this variability reduces with depth and the stress field becomes more stable at the {approx} 350 m at which the drillhole cores were obtained. Another compounding difficulty is that the stress quantity, being a second order tensor, requires six independent components for its specification. In other words, comparison of the DRA results and the known stress field requires comparison of six different quantities. In terms of the major principal stress orientation, the DRA results predict an orientation completely

  18. A microfluidic platform for rapid, stress-induced antibiotic susceptibility testing of Staphylococcus aureus

    OpenAIRE

    Kalashnikov, Maxim; Lee, Jean C.; Campbell, Jennifer; Sharon, Andre; Sauer-Budge, Alexis F.

    2012-01-01

    The emergence and spread of bacterial resistance to ever increasing classes of antibiotics intensifies the need for fast phenotype-based clinical tests for determining antibiotic susceptibility. Standard susceptibility testing relies on the passive observation of bacterial growth inhibition in the presence of antibiotics. In this paper, we present a novel microfluidic platform for antibiotic susceptibility testing basedon stress-activation of biosynthetic pathways that are the primary targets...

  19. Direct Shear Tests of Sandstone Under Constant Normal Tensile Stress Condition Using a Simple Auxiliary Device

    Science.gov (United States)

    Cen, Duofeng; Huang, Da

    2017-06-01

    Tension-shear failure is a typical failure mode in the rock masses in unloading zones induced by excavation or river incision, etc., such as in excavation-disturbed zone of deep underground caverns and superficial rocks of high steep slopes. However, almost all the current shear failure criteria for rock are usually derived on the basis of compression-shear failure. This paper proposes a simple device for use with a servo-controlled compression-shear testing machine to conduct the tension-shear tests of cuboid rock specimens, to test the direct shear behavior of sandstone under different constant normal tensile stress conditions ( σ = -1, -1.5, -2, -2.5 and -3 MPa) as well as the uniaxial tension behavior. Generally, the fracture surface roughness decreases and the proportion of comminution areas in fracture surface increases as the change of stress state from tension to tension-shear and to compression-shear. Stepped fracture is a primary fracture pattern in the tension-shear tests. The shear stiffness, shear deformation and normal deformation (except the normal deformation for σ = -1 MPa) decrease during shearing, while the total normal deformation containing the pre-shearing portion increases as the normal tensile stress level (| σ|) goes up. Shear strength is more sensitive to the normal tensile stress than to the normal compressive stress, and the power function failure criterion (or Mohr envelope form of Hoek-Brown criterion) is examined to be the optimal criterion for the tested sandstone in the full region of tested normal stress in this study.

  20. Physical Stress Echocardiography: Prediction of Mortality and Cardiac Events in Patients with Exercise Test showing Ischemia

    Directory of Open Access Journals (Sweden)

    Ana Carla Pereira de Araujo

    2014-11-01

    Full Text Available Background: Studies have demonstrated the diagnostic accuracy and prognostic value of physical stress echocardiography in coronary artery disease. However, the prediction of mortality and major cardiac events in patients with exercise test positive for myocardial ischemia is limited. Objective: To evaluate the effectiveness of physical stress echocardiography in the prediction of mortality and major cardiac events in patients with exercise test positive for myocardial ischemia. Methods: This is a retrospective cohort in which 866 consecutive patients with exercise test positive for myocardial ischemia, and who underwent physical stress echocardiography were studied. Patients were divided into two groups: with physical stress echocardiography negative (G1 or positive (G2 for myocardial ischemia. The endpoints analyzed were all-cause mortality and major cardiac events, defined as cardiac death and non-fatal acute myocardial infarction. Results: G2 comprised 205 patients (23.7%. During the mean 85.6 ± 15.0-month follow-up, there were 26 deaths, of which six were cardiac deaths, and 25 non-fatal myocardial infarction cases. The independent predictors of mortality were: age, diabetes mellitus, and positive physical stress echocardiography (hazard ratio: 2.69; 95% confidence interval: 1.20 - 6.01; p = 0.016. The independent predictors of major cardiac events were: age, previous coronary artery disease, positive physical stress echocardiography (hazard ratio: 2.75; 95% confidence interval: 1.15 - 6.53; p = 0.022 and absence of a 10% increase in ejection fraction. All-cause mortality and the incidence of major cardiac events were significantly higher in G2 (p < 0. 001 and p = 0.001, respectively. Conclusion: Physical stress echocardiography provides additional prognostic information in patients with exercise test positive for myocardial ischemia.

  1. Hair Dye and Hair Relaxers

    Science.gov (United States)

    ... Consumers Consumer Information by Audience For Women Hair Dye and Hair Relaxers Share Tweet Linkedin Pin it ... If you have a bad reaction to hair dyes and relaxers, you should: Stop using the product. ...

  2. Quantification of Shear Deformations and Corresponding Stresses in the Biaxially Tested Human Myocardium.

    Science.gov (United States)

    Sommer, Gerhard; Haspinger, Daniel Ch; Andrä, Michaela; Sacherer, Michael; Viertler, Christian; Regitnig, Peter; Holzapfel, Gerhard A

    2015-10-01

    One goal of cardiac research is to perform numerical simulations to describe/reproduce the mechanoelectrical function of the human myocardium in health and disease. Such simulations are based on a complex combination of mathematical models describing the passive mechanical behavior of the myocardium and its electrophysiology, i.e., the activation of cardiac muscle cells. The problem in developing adequate constitutive models is the shortage of experimental data suitable for detailed parameter estimation in specific functional forms. A combination of shear and biaxial extension tests with different loading protocols on different specimen orientations is necessary to capture adequately the direction-dependent (orthotropic) response of the myocardium. In most experimental animal studies, where planar biaxial extension tests on the myocardium have been conducted, the generated shear stresses were neither considered nor discussed. Hence, in this study a method is presented which allows the quantification of shear deformations and related stresses. It demonstrates an approach for experimenters as to how the generation of these shear stresses can be minimized during mechanical testing. Experimental results on 14 passive human myocardial specimens, obtained from nine human hearts, show the efficiency of this newly developed method. Moreover, the influence of the clamping technique of the specimen, i.e., the load transmission between the testing device and the tissue, on the stress response is determined by testing an isotropic material (Latex). We identified that the force transmission between the testing device and the specimen by means of hooks and cords does not influence the performed experiments. We further showed that in-plane shear stresses definitely exist in biaxially tested human ventricular myocardium, but can be reduced to a minimum by preparing the specimens in an appropriate manner. Moreover, we showed whether shear stresses can be neglected when performing

  3. Enhanced memory performance on an internal-internal source monitoring test following acute psychosocial stress.

    Science.gov (United States)

    Smeets, T; Jelicic, M; Merckelbach, H; Peters, M; Fett, A; Taverniers, J; Henquet, C; Dautzenberg, J

    2006-12-01

    Research on the effect of acute stress and high levels of glucocorticoids on memory has largely focused on memory tasks involving the medial temporal lobe (e.g., declarative memory). Less is known, however, about the effects of stress and glucocorticoids on more strategic memory processes regulated by the prefrontal cortex (e.g., source monitoring). In the current study, the authors investigated whether exposure to acute psychosocial stress would result in altered source monitoring performance relative to the performance of a nonstressed control group. To this end, the authors assigned nonsmoking, healthy, young men to either a stress (n = 22) or a control (n = 18) condition, after which the men were given an internal source monitoring test. Results show that relative to control participants, stressed participants made fewer source monitoring errors. This study suggests that stress may have differential effects on memory, depending on whether the memory test is regulated by the prefrontal cortex or the medial temporal lobe. 2006 APA, all rights reserved

  4. Effects of stress on memory in children and adolescents: testing causal connections.

    Science.gov (United States)

    Quas, Jodi A; Rush, Elizabeth B; Yim, Ilona S; Nikolayev, Mariya

    2014-01-01

    Although a sizeable body of research has examined children's memory for stressful prior experiences, relatively few studies have experimentally manipulated stress during a to-be-remembered event to draw causal inferences about the effects of stress, especially across wide age ranges. We exposed children and adolescents to a more or a less arousing version of the Trier Social Stress Test-Modified (TSST-M), a widely used laboratory stress task. Two weeks later, we tested their memory for what happened. Interviewers behaved in a supportive or non-supportive manner. In adolescents, those who completed the high-arousal TSST-M provided fewer correct responses to recognition questions and fewer incorrect responses to misleading questions for which any answer would have been incorrect, compared to those who completed the lower-arousal TSST-M. Thus, arousal seemed to have reduced the adolescents' willingness to answer questions rather than having influenced their memory per se. In children, across TSST-M conditions, greater physiological arousal during the TSST-M predicted enhanced recall. Finally, interviewer support reduced the amount of factual information provided in free recall but increased correct responses to misleading questions. Results highlight the complex ways in which event stress and interviewer demeanour shape recounting of prior experiences across development.

  5. Randomized test of an implementation intention-based tool to reduce stress-induced eating.

    Science.gov (United States)

    O'Connor, Daryl B; Armitage, Christopher J; Ferguson, Eamonn

    2015-06-01

    Stress may indirectly contribute to disease (e.g. cardiovascular disease, cancer) by producing deleterious changes to diet. The purpose of this study was to test the effectiveness of a stress management support (SMS) tool to reduce stress-related unhealthy snacking and to promote stress-related healthy snacking. Participants were randomized to complete a SMS tool with instruction to link stressful situations with healthy snack alternatives (experimental) or a SMS tool without a linking instruction (control). On-line daily reports of stressors and snacking were completed for 7 days. Daily stressors were associated with unhealthy snack consumption in the control condition but not in the experimental condition. Participants highly motivated towards healthy eating consumed a greater number of healthy snacks in the experimental condition on stressful days compared to participants in the experimental condition with low and mean levels of motivation. This tool is an effective, theory driven, intervention that helps to protect against stress-induced high-calorie snack consumption.

  6. How Can I Manage Stress?

    Science.gov (United States)

    ... minutes.. How can I live a more relaxed life? Here are some positive healthy habits you may want to develop to manage stress and live a more relaxed life. Think ahead about what may upset you. Have ...

  7. Fatigue Failure Results for Multi-Axial versus Uniaxial Stress Screen Vibration Testing

    Directory of Open Access Journals (Sweden)

    Wayne E. Whiteman

    2002-01-01

    Full Text Available To date, the failure potential and prediction between simultaneous multi-axial versus sequentially applied uniaxial vibration stress screen testing has been the subject of great debate. In most applications, current vibration tests are done by sequentially applying uniaxial excitation to the test specimen along three orthogonal axes. The most common standards for testing military equipment are published in MIL-STD-810F and NAVMAT P-9492. Previous research had shown that uniaxial testing may be unrealistic and inadequate. This current research effort is a continuing effort to systematically investigate the differences between fatigue damage mechanisms and the effects of uniaxial versus tri-axial testing. This includes assessing the ability of the tri-axial method in predicting the formation of damage mechanisms, specifically looking at the effects of stress or fatigue failure. Multi-axial testing achieves the synergistic effect of exciting all modes simultaneously and induces a more realistic vibration stress loading condition. As such, it better approximates real-world operating conditions. This paper provides the latest results on the differences between multi-axial and uniaxial testing of a simple notched cantilever beam.

  8. A test procedure for determining the influence of stress ratio on fatigue crack growth

    Science.gov (United States)

    Fitzgerald, J. H.; Wei, R. P.

    1974-01-01

    A test procedure is outlined by which the rate of fatigue crack growth over a range of stress ratios and stress intensities can be determined expeditiously using a small number of specimens. This procedure was developed to avoid or circumvent the effects of load interactions on fatigue crack growth, and was used to develop data on a mill annealed Ti-6Al-4V alloy plate. Experimental data suggest that the rates of fatigue crack growth among the various stress ratios may be correlated in terms of an effective stress intensity range at given values of K max. This procedure is not to be used, however, for determining the corrosion fatigue crack growth characteristics of alloys when nonsteady-state effects are significant.

  9. Thermal stress analysis of the NASA Dryden hypersonic wing test structure

    Science.gov (United States)

    Morris, Glenn

    1990-01-01

    Present interest in hypersonic vehicles has resulted in a renewed interest in thermal stress analysis of airframe structures. While there are numerous texts and papers on thermal stress analysis, practical examples and experience on light gage aircraft structures are fairly limited. A research program has been undertaken at General Dynamics to demonstrate the present state of the art, verify methods of analysis, gain experience in their use, and develop engineering judgement in thermal stress analysis. The approach for this project has been to conduct a series of analyses of this sample problem and compare analysis results with test data. This comparison will give an idea of how to use our present methods of thermal stress analysis, and how accurate we can expect them to be.

  10. Relaxation strategies for patients during dermatologic surgery.

    Science.gov (United States)

    Shenefelt, Philip D

    2010-07-01

    Patient stress and anxiety are common preoperatively and during dermatologic procedures and surgeries. Stress and anxiety can occasionally interfere with performance of procedures or surgery and can induce hemodynamic instability, such as elevated blood pressure or syncope, as well as producing considerable discomfort for some patients. Detection of excess stress and anxiety in patients can allow the opportunity for corrective or palliative measures. Slower breathing, biofeedback, progressive muscular relaxation, guided imagery, hypnosis, meditation and music can help calm and rebalance the patient's autonomic nervous system and immune functioning. Handheld miniaturized heart rate variability biofeedback devices are now available. The relaxation response can easily be taught. Guided imagery can be recorded or live. Live rapid induction hypnosis followed by deepening and then self-guided imagery requires no experience on the part of the patient but does require training and experience on the part of a provider. Recorded hypnosis inductions may also be used. Meditation generally requires more prior experience and training, but is useful when the patient already is skilled in it. Live, guided meditation or meditation recordings may be used. Relaxing recorded music from speakers or headphones or live performance music may also be employed to ease discomfort and improve the patient's attitude for dermatologic procedures and surgeries.

  11. The relationship between gender and clinical management after exercise stress testing.

    Science.gov (United States)

    Daugherty, Stacie L; Peterson, Pamela N; Magid, David J; Ho, P Michael; Bondy, Jessica; Hokanson, John E; Ross, Colleen A; Rumsfeld, John S; Masoudi, Frederick A

    2008-08-01

    Controversy remains regarding whether gender differences exist in clinical management after exercise treadmill testing (ETT). We studied 7,506 patients (49.8% women) without documented coronary heart disease referred for ETT from July 2001 to June 2004 in a community-based setting. We assessed the relationship between gender and subsequent diagnostic testing (secondary stress testing or coronary angiography) within 6 months after ETT. Secondary outcomes included subsequent stress testing, coronary angiography, and new cardiology visits in the 6-month interval. Multivariable analyses assessed the relationship between gender and these outcomes adjusting for demographic, clinical, and stress test characteristics. In subsequent analyses, patients were stratified by Duke Treadmill Scores (Duke University, Durham, NC). Compared with men, women referred for ETT were older, had a higher prevalence of some cardiac risk factors, achieved lower peak workloads, and, more often, experienced chest pain or ST-segment changes. After accounting for differences in clinical and ETT parameters, gender was not associated with any subsequent diagnostic testing in the 6 months after ETT (OR 1.0, 95% CI 0.85-1.18). In secondary analyses, women were less likely to undergo angiography (OR 0.63, 95% CI 0.47-0.83) with a trend toward more subsequent stress testing. Stratified analyses revealed less subsequent testing in high-to-intermediate Duke Treadmill Score women compared with men (OR 0.61, 95% CI 0.48-0.79). Women and men were equally likely to die (hazards ratio 0.93, 95% CI 0.61-1.44) in the adjusted survival analysis. Overall, women and men equally underwent subsequent diagnostic testing after ETT. Although women were less likely to undergo angiography and higher-risk women were less likely to undergo subsequent testing, adverse events were not higher in women. Given these findings, assumptions regarding gender disparities in clinical management after ETT should be reevaluated in

  12. Fast relaxations in foam

    Science.gov (United States)

    Krishan, Kapilanjan; Helal, Ahmed; Höhler, Reinhard; Cohen-Addad, Sylvie

    2010-07-01

    Aqueous foams present an anomalous macroscopic viscoelastic response at high frequency, previously shown to arise from collective relaxations in the disordered bubble packing. We demonstrate experimentally how these mesoscopic dynamics are in turn tuned by physico-chemical processes on the scale of the gas-liquid interfaces. Two specific local dissipation processes are identified, and we show how the rigidity of the interfaces selects the dominant one, depending on the choice of the surfactant.

  13. Relaxation from particle production

    Science.gov (United States)

    Hook, Anson; Marques-Tavares, Gustavo

    2016-12-01

    We consider using particle production as a friction force by which to implement a "Relaxion" solution to the electroweak hierarchy problem. Using this approach, we are able to avoid superplanckian field excursions and avoid any conflict with the strong CP problem. The relaxation mechanism can work before, during or after inflation allowing for inflationary dynamics to play an important role or to be completely decoupled.

  14. Study and Test of a New Bundle-Structure Riser Stress Monitoring Sensor Based on FBG

    Directory of Open Access Journals (Sweden)

    Jian Xu

    2015-11-01

    Full Text Available To meet the requirements of riser safety monitoring in offshore oil fields, a new Fiber Bragg Grating (FBG-based bundle-structure riser stress monitoring sensor has been developed. In cooperation with many departments, a 49-day marine test in water depths of 1365 m and 1252 m was completed on the “HYSY-981” ocean oil drilling platform. No welding and pasting were used when the sensor was installed on risers. Therefore, the installation is convenient, reliable and harmless to risers. The continuous, reasonable, time-consistent data obtained indicates that the sensor worked normally under water. In all detailed working conditions, the test results show that the sensor can do well in reflecting stresses and bending moments both in and in magnitude. The measured maximum stress is 132.7 MPa, which is below the allowable stress. In drilling and testing conditions, the average riser stress was 86.6 MPa, which is within the range of the China National Offshore Oil Corporation (CNOOC mechanical simulation results.

  15. Standard Practice for Making and Using U-Bend Stress-Corrosion Test Specimens

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2009-01-01

    1.1 This practice covers procedures for making and using U-bend specimens for the evaluation of stress-corrosion cracking in metals. The U-bend specimen is generally a rectangular strip which is bent 180° around a predetermined radius and maintained in this constant strain condition during the stress-corrosion test. Bends slightly less than or greater than 180° are sometimes used. Typical U-bend configurations showing several different methods of maintaining the applied stress are shown in Fig. 1. 1.2 U-bend specimens usually contain both elastic and plastic strain. In some cases (for example, very thin sheet or small diameter wire) it is possible to form a U-bend and produce only elastic strain. However, bent-beam (Practice G 39 or direct tension (Practice G 49)) specimens are normally used to study stress-corrosion cracking of strip or sheet under elastic strain only. 1.3 This practice is concerned only with the test specimen and not the environmental aspects of stress-corrosion testing which are discus...

  16. Neurocognitive deficits or stress overload: Why do individuals with schizophrenia show poor performance in neurocognitive tests?

    Science.gov (United States)

    Krkovic, Katarina; Moritz, Steffen; Lincoln, Tania M

    2017-05-01

    Poor performance in neurocognitive tasks is consistently found across studies in all stages of schizophrenia spectrum disorders and is interpreted as an underlying, brain function-related, neurocognitive deficit. However, neurocognitive test performance in schizophrenia might be compromised by patients' increased stress level. We investigated group-differences in neurocognitive performance while accounting for psychophysiological (salivary cortisol, heart rate, skin conductance level) and self-reported stress. We included 35 patients with schizophrenia, 29 participants with attenuated psychotic symptoms, 26 first-degree relatives of individuals with schizophrenia and 28 healthy controls. Participants completed a neurocognitive test battery that assessed processing speed, task switching, attention, working memory, verbal episodic memory, and verbal comprehension. Multivariate analyses of covariance (MANCOVA) were calculated to test for main effects of group on neurocognitive performance thereby not accounting versus accounting for confounding effects of stress. As expected, patients with schizophrenia scored lower than the other groups in all neurocognitive domains. Participants with attenuated psychotic symptoms, first-degree relatives and healthy individuals did not differ from each other in their performance. After accounting for heart rate and self-reported stress, the multivariate effect of group on neurocognition remained significant, but was rendered non-significant for specific domains - working memory capacity, episodic memory, and long-term memory. The findings imply that stress is relevant to neurocognitive performance and this should be taken into account when interpreting the origin of performance deficits in schizophrenia patients. Copyright © 2016 Elsevier B.V. All rights reserved.

  17. Test with different stress measurement methods in two orthogonal bore holes in Aespoe HRL

    Energy Technology Data Exchange (ETDEWEB)

    Janson, Thomas; Stigsson, Martin [Golder Associates AB, Stockholm (Sweden)

    2002-12-01

    Within the scope of work, to provide the necessary rock mechanics support for the site investigations, SKB has studied some available pieces of equipment for in situ stress measurements in deep boreholes. A project with the objective to compare three different pieces of equipment for in situ stress measurements under similar conditions has been carried out. The main objective for the project is to compare the three different pieces of equipment for in situ stress measurements and find a strategy for SKB's Site Investigations to determine the state of stress in the rock mass. Two units of equipment use the overcoring method while the third uses the hydraulic fracturing method. The overcoring was performed by AECL, using Deep Door stopper Gauge System (DDGS), and SwedPower, using their triaxial strain measuring instrument (Borre Probe). MeSy Geo Systeme GmbH performed the hydraulic fracturing. The DDGS system is a new method to SKB while the experience of the SwedPower overcoring and the hydraulic fracturing methods are long. The tests were performed in the same orthogonal boreholes at Aespoe Hard Rock Laboratory (HRL), Oskarshamn, Sweden. The measured results have been verified against known conditions at the Aespoe HRL. The results from the three in situ stress measurement methods rose more questions than answers. Which illustrate the complexity to determine the in situ stresses in a rock mass. To understand the difference in results and answer the questions, it was necessary to do deeper investigations such as laboratory tests and theoretical calculations such as geological structure model, analysis of the influence of a nearby fracture, P-wave measurements, uniaxial tests on small cores from the HQ-3 core, theoretical and numerical analyses of the hole bottom (theoretical strains, stress concentrations and microcracking), auditing of DDGS measurements results and assumptions in the DDGS analyse and microscopy investigations on the cores. The following

  18. Modelling Creep (Relaxation of the Urinary Bladder

    Directory of Open Access Journals (Sweden)

    Zdravkovic Nebojsa

    2017-12-01

    Full Text Available We first present the results of an experiment in which the passive properties of the urinary bladder were investigated using strips of rabbit bladder. Under the assumption that the urinary bladder had orthopaedic characteristics, the strips were taken in the longitudinal and in the circumferential directions. The material was subjected to uniaxial tension, and stress-stretch curves were generated for various rates of deformation. We found that the rates did not have a significantly effect on the passive response of the material. Additionally, the stress-stretch dependence during relaxation of the material when exposed to isometric conditions was determined experimentally.

  19. Effect of Progressive Muscle Relaxation on the Adverse ...

    African Journals Online (AJOL)

    Background: The altered stress reactivity in polycystic ovarian syndrome (PCOS) may constitute a link between depression, overweight, and cardiovascular risk factors. Aims: To study the effects of progressive muscle relaxation (PMR) on the stress levels of PCOS patients and their influence on the cardiovascular risk factors ...

  20. Objective effect manifestation of pectus excavatum on load-stressed pulmonary function testing: a case report

    Directory of Open Access Journals (Sweden)

    Chan Jason

    2011-12-01

    Full Text Available Abstract Introduction Pectus excavatum is the most common congenital deformity of the anterior chest wall that, under certain conditions, may pose functional problems due to cardiopulmonary compromise and exercise intolerance. Case presentation We present the case of an otherwise physically-adept 21-year-old Chinese sportsman with idiopathic pectus excavatum, whose symptoms manifested only on bearing a loaded body vest and backpack during physical exercise. Corroborative objective evidence was obtained via load-stressed pulmonary function testing, which demonstrated restrictive lung function. Conclusion This report highlights the possible detrimental synergism of thoracic load stress and pectus excavatum on cardiopulmonary function. Thoracic load-stressed pulmonary function testing provides objective evidence in support of such a synergistic relationship.

  1. Objective effect manifestation of pectus excavatum on load-stressed pulmonary function testing: a case report

    Science.gov (United States)

    2011-01-01

    Introduction Pectus excavatum is the most common congenital deformity of the anterior chest wall that, under certain conditions, may pose functional problems due to cardiopulmonary compromise and exercise intolerance. Case presentation We present the case of an otherwise physically-adept 21-year-old Chinese sportsman with idiopathic pectus excavatum, whose symptoms manifested only on bearing a loaded body vest and backpack during physical exercise. Corroborative objective evidence was obtained via load-stressed pulmonary function testing, which demonstrated restrictive lung function. Conclusion This report highlights the possible detrimental synergism of thoracic load stress and pectus excavatum on cardiopulmonary function. Thoracic load-stressed pulmonary function testing provides objective evidence in support of such a synergistic relationship. PMID:22188608

  2. Relationship between academic stress and suicidal ideation: testing for depression as a mediator using multiple regression.

    Science.gov (United States)

    Ang, Rebecca P; Huan, Vivien S

    2006-01-01

    Relations among academic stress, depression, and suicidal ideation were examined in 1,108 Asian adolescents 12-18 years old from a secondary school in Singapore. Using Baron and Kenny's [J Pers Soc Psychol 51:1173-1192, 1986] framework, this study tested the prediction that adolescent depression mediated the relationship between academic stress and suicidal ideation in a four-step process. The previously significant relationship between academic stress and suicidal ideation was significantly reduced in magnitude when depression was included in the model providing evidence in this sample that adolescent depression was a partial mediator. The applied and practical implications for intervention and prevention work in schools are discussed. The present investigation also served as a demonstration to illustrate how multiple regression analyses can be used as one possible method for testing mediation effects within child psychology and psychiatry.

  3. Standard Practice for Making and Using C-Ring Stress-Corrosion Test Specimens

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2007-01-01

    1.1 This practice covers the essential features of the design and machining, and procedures for stressing, exposing, and inspecting C-ring type of stress-corrosion test specimens. An analysis is given of the state and distribution of stress in the C-ring. 1.2 Specific considerations relating to the sampling process and to the selection of appropriate test environments are outside the scope of this practice. 1.3 The values stated in SI units are to be regarded as the standard; The values given in parentheses are for information only. 1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

  4. The Relation of Arm Exercise Peak Heart Rate to Stress Test Results and Outcome.

    Science.gov (United States)

    Xian, Hong; Liu, Weijian; Marshall, Cynthia; Chandiramani, Pooja; Bainter, Emily; Martin, Wade H

    2016-09-01

    Arm exercise is an alternative to pharmacologic stress testing for >50% of patients unable to perform treadmill exercise, but no data exist regarding the effect of attained peak arm exercise heart rate on test sensitivity. Thus, the purpose of this investigation was to characterize the relationship of peak arm exercise heart rate responses to abnormal stress test findings, coronary revascularization, and mortality in patients unable to perform leg exercise. From 1997 until 2002, arm cycle ergometer stress tests were performed in 443 consecutive veterans age 64.1 yr (11.0 yr) (mean (SD)), of whom 253 also underwent myocardial perfusion imaging (MPI). Patients were categorized by frequency distributions of quartiles of percentage age-predicted peak heart rate (APPHR), heart rate reserve (HRR), and peak heart rate-systolic blood pressure product (PRPP). Exercise-induced ST-segment depression, abnormal MPI findings, coronary revascularization, and 12.0-yr (1.3 yr) Kaplan-Meier all-cause and cardiovascular mortality plots were then characterized by quartiles of APPHR, HRR, and PRPP. A reduced frequency of abnormal arm exercise ECG results was associated only with the lowest quartile of APPHR (≤69%) and HRR (≤43%), whereas higher frequency of abnormal MPI findings exhibited an inverse relationship trend with lower APPHR (P = 0.10) and HRR (P = 0.12). There was a strong inverse association of APPHR, HRR, and PRPP with all-cause (all P ≤ 0.01) and cardiovascular (P Arm exercise ECG stress test sensitivity is only reduced at ≤69% APPHR or ≤43% HRR, whereas arm exercise MPI sensitivity and referral for coronary revascularization after arm exercise stress testing are not adversely affected by even a severely blunted peak heart rate. However, both all-cause mortality and cardiovascular mortality are strongly and inversely related to APPHR and HRR.

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

    Science.gov (United States)

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

    2010-01-01

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

  6. Impact of peak electricity demand in distribution grids: a stress test

    NARCIS (Netherlands)

    Hoogsteen, Gerwin; Molderink, Albert; Hurink, Johann L.; Smit, Gerardus Johannes Maria; Schuring, Friso; Kootstra, Ben

    2015-01-01

    The number of (hybrid) electric vehicles is growing, leading to a higher demand for electricity in distribution grids. To investigate the effects of the expected peak demand on distribution grids, a stress test with 15 electric vehicles in a single street is conducted and described in this paper.

  7. Stress and anxiety effects on positive skin test responses in young adults with allergic rhinitis.

    Science.gov (United States)

    Heffner, Kathi L; Kiecolt-Glaser, Janice K; Glaser, Ronald; Malarkey, William B; Marshall, Gailen D

    2014-07-01

    Anxiety and psychological stress affect allergy-related immune function. How these relations influence the evaluations of patients with allergic rhinitis is unknown. To examine whether anxiety and stress exposure affect skin prick test (SPT) responses to common allergens for which patients with atopy showed no prior positive SPT response. Patients with allergic rhinitis, evidenced by clinical history and SPT results, were admitted twice to a hospital research unit for 4 hours. In a crossover design, SPT wheals were assessed before and after the Trier Social Stress Test and then the following morning; for comparison, SPT wheals were assessed before and after a laboratory session without a stressor. Analyses focused on wheal responses for common allergens that tested negative (wheal size wheal responses for allergens previously testing negative were enhanced after a stressor. Histamine (positive control) or saline (negative control) SPT responses were not affected. A laboratory stressor affected allergen SPT responses in more anxious patients with allergic rhinitis. In addition to clinical history, assessment of anxiety and current stress at the time of the SPT may provide valuable information about a patient's allergic status and aid in clinical decision making. Copyright © 2014 American College of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.

  8. Paradigm Change for Accelerated Stress Testing of Thin-Film Modules

    DEFF Research Database (Denmark)

    Hacke, Peter; Spataru, Sergiu; Johnston, Steve

    2017-01-01

    A fundamental change in the analysis for the accelerated stress testing of thin-film modules is proposed, whereby power changes due to metastability and other effects that may occur due to the thermal history are removed from the power measurement that we obtain as a function of the applied stres...

  9. Relationship between Academic Stress and Suicidal Ideation: Testing for Depression as a Mediator Using Multiple Regression

    Science.gov (United States)

    Ang, Rebecca P.; Huan, Vivien S.

    2006-01-01

    Relations among academic stress, depression, and suicidal ideation were examined in 1,108 Asian adolescents 12-18 years old from a secondary school in Singapore. Using Baron and Kenny's [J Pers Soc Psychol 51:1173-1192, 1986] framework, this study tested the prediction that adolescent depression mediated the relationship between academic stress…

  10. 77 FR 62378 - Supervisory and Company-Run Stress Test Requirements for Covered Companies

    Science.gov (United States)

    2012-10-12

    ... INFORMATION: Table of Contents I. Background II. Overview of Comments III. Description of Final Rule A. Scope... proposed rules, the Board would conduct an annual supervisory stress test of covered companies under three... year and three scenarios developed by the company. The proposed rule required each covered company to...

  11. 78 FR 67218 - Agency Information Collection Activities: Company-Run Annual Stress Test Reporting Template and...

    Science.gov (United States)

    2013-11-08

    ....gov/tools-forms/forms/bank-operations/stress-test-reporting.html ). SUPPLEMENTARY INFORMATION: The OCC... internal assessments of capital adequacy and overall capital planning. The OCC recognizes that many covered... trading shock. Securities Available-for-Sale (AFS) Market Shock Worksheet Consistent with the redefinition...

  12. High-Stakes Testing and Its Relationship to Stress Levels of Secondary Teachers

    Science.gov (United States)

    Christian, Sonya Colman

    2010-01-01

    This study investigated the relationship between high-stakes testing and the stress levels of secondary teachers in Jackson's Jackson Public School District. The independent variables of age, gender, subject taught, teaching experience, degree and school level were used to determine the differences of the various groups. A survey was piloted and…

  13. Development of a standardized battery of performance tests for the assessment of noise stress effects

    Science.gov (United States)

    Theologus, G. C.; Wheaton, G. R.; Mirabella, A.; Brahlek, R. E.

    1973-01-01

    A set of 36 relatively independent categories of human performance were identified. These categories encompass human performance in the cognitive, perceptual, and psychomotor areas, and include diagnostic measures and sensitive performance metrics. Then a prototype standardized test battery was constructed, and research was conducted to obtain information on the sensitivity of the tests to stress, the sensitivity of selected categories of performance degradation, the time course of stress effects on each of the selected tests, and the learning curves associated with each test. A research project utilizing a three factor partially repeated analysis of covariance design was conducted in which 60 male subjects were exposed to variations in noise level and quality during performance testing. Effects of randomly intermittent noise on performance of the reaction time tests were observed, but most of the other performance tests showed consistent stability. The results of 14 analyses of covariance of the data taken from the performance of the 60 subjects on the prototype standardized test battery provided information which will enable the final development and test of a standardized test battery and the associated development of differential sensitivity metrics and diagnostic classificatory system.

  14. Prerequisites, requirements, stresses and strains, training and performance tests for the horses

    OpenAIRE

    Westermann, Katharina

    2013-01-01

    One aim of this study was to investigate the emphasis (requirements, stresses and strains) and the actual qualifying (training guide, performance test) of horses in EAI. Another aim was to work out proposals for a standardizable quality management for those horses (development of a guideline for the utilisation and training as well as a performance test for horses in EAI, an instructor licence “EAI” for suppliers, additions to the education guidelines within the horse-related apprenticeships ...

  15. Accelerated Stress Testing of Thin-Film Modules with SnO2:F Transparent Conductors

    Energy Technology Data Exchange (ETDEWEB)

    Osterwald, C. R.; McMahon, T. J.; del Cueto, J. A.; Adelstein, J.; Puett, J.

    2003-05-01

    This paper reviews a testing program conducted at NREL for the past two years that applied voltage, water vapor, and light stresses to thin-film photovoltaic (PV) modules with SnO2:F transparent conducting oxides (TCOs) deposited on soda-lime glass superstrates. Electrochemical corrosion at the glass-TCO interface was observed to result in delamination of the thin-film layers. Experimental testing was directed toward accelerating the corrosion and understanding the nature of the resulting damage.

  16. Standard Test Method for Testing Polymeric Seal Materials for Geothermal and/or High Temperature Service Under Sealing Stress

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    1985-01-01

    1.1 This test method covers the initial evaluation of (screening) polymeric materials for seals under static sealing stress and at elevated temperatures. 1.2 This test method applies to geothermal service only if used in conjunction with Test Method E 1068. 1.3 The test fluid is distilled water. 1.4 The values stated in SI units are to be regarded as the standard. The values in parentheses are for information only. 1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

  17. Stress-deformed state of cylindrical specimens during indirect tensile strength testing

    Directory of Open Access Journals (Sweden)

    Levan Japaridze

    2015-10-01

    Full Text Available In this study, the interaction between cylindrical specimen made of homogeneous, isotropic, and linearly elastic material and loading jaws of any curvature is considered in the Brazilian test. It is assumed that the specimen is diametrically compressed by elliptic normal contact stresses. The frictional contact stresses between the specimen and platens are neglected. The analytical solution starts from the contact problem of the loading jaws of any curvature and cylindrical specimen. The contact width, corresponding loading angle (2θ0, and elliptical stresses obtained through solution of the contact problems are used as boundary conditions for a cylindrical specimen. The problem of the theory of elasticity for a cylinder is solved using Muskhelishvili's method. In this method, the displacements and stresses are represented in terms of two analytical functions of a complex variable. In the main approaches, the nonlinear interaction between the loading bearing blocks and the specimen as well as the curvature of their surfaces and the elastic parameters of their materials are taken into account. Numerical examples are solved using MATLAB to demonstrate the influence of deformability, curvature of the specimen and platens on the distribution of the normal contact stresses as well as on the tensile and compressive stresses acting across the loaded diameter. Derived equations also allow calculating the modulus of elasticity, total deformation modulus and creep parameters of the specimen material based on the experimental data of radial contraction of the specimen.

  18. Myocordial perfusion SPECT with dipyridamole stress test in cardiac syndrome X

    Energy Technology Data Exchange (ETDEWEB)

    Czepczynski, R.; Smolarek, I.; Sowinski, J. [Nuclear Medicine Unit, Dept. of Endocrinology and Metabolism, Poznan Univ. of Medical Sciences, Poznan (Poland); Rogacka, D.; Kazmierczak, M.; Wysocki, H. [Dept. of Intensive Care and Cardiology, Poznan Univ. of Medical Sciences, Poznan (Poland)

    2006-07-01

    Cardiac syndrome X defines patients with typical anginal chest pain, a positive exercise ECG stress test and angiographically normal coronary arteries. Aim of this study was to evaluate the role of myocardial perfusion SPECT with dipyridamole stress in the diagnosis of cardiac syndrome X. Patients, methods: 68 patients with syndrome X aged 32 to 60 years were subjected to myocardial imaging using {sup 99m}Tc-MIBI according to the two-days protocol: at rest and after dipyridamole infusion. Semiquantitative evaluation of the images was based on the assessment of {sup 99m}Tc-MIBI uptake in 17 myocardial segments using a 5-points scale (0 point - normal uptake, 4 points - no uptake). Scores obtained in each segment were summed up, constituting the summed rest score (SRS) and summed stress score (SSS). Results: mean SRS was 7.9 {+-} 4.8 and mean SSS was 7.2 {+-} 4.4 (non-significant difference). Individual comparison of SRS and SSS values revealed three patterns of scintigraphic images: (1) in 25 patients (36.8%), a paradoxical improvement of perfusion at stress images was found, (2) in 23 patients (33.8%), the myocardial perfusion deteriorated after dipyridamole, (3) in 20 patients (29.4%), no significant change of the myocordial perfusion between rest and stress images occurred. Conclusions: in cardiac syndrome X, myocardial SPECT with dipyridamole stress shows different patterns of myocardial perfusion that reflects heterogeneity of this pathology. (orig.)

  19. Mediators of compassionate goal intervention effects on human neuroendocrine responses to the Trier Social Stress Test.

    Science.gov (United States)

    Erickson, Thane M; Mayer, Stefanie E; Lopez-Duran, Nestor L; Scarsella, Gina M; McGuire, Adam P; Crocker, Jennifer; Abelson, James L

    2017-11-01

    The hypothalamic-pituitary-adrenal (HPA) axis is thought to mediate the effects of stress on illness. Research has identified a limited number of psychological variables that modulate human HPA responses to stressors (e.g. perceived control and social support). Prosocial goals can reduce subjective stress, but have not been carefully examined in experimental settings where pathways of impact on biological stress markers may be traced. Recent work demonstrated that coaching individuals to strive to help others reduced HPA responses to the Trier Social Stress Test (TSST) relative to other cognitive interventions. However, identification of mediational pathways, which were not examined in the original study, is necessary to determine whether the HPA buffering effects were due to helping motivations (compassionate goals; CGs) rather than via previously identified variables such as control or support. In this new analysis, we combined the original cortisol data with novel observer ratings of interpersonal behavior and psychological variables during the stress task, and conducted new, theory-driven analyses to determine psychological mediators for the intervention's effect on cortisol responses (N = 54; 21 females, 33 males; 486 cortisol samples). Control, support, and task ego-threat failed to account for the effects of the intervention. As hypothesized, self and observer-rated CGs, as well as observer-rated perceptions of participants' interpersonal behavior as morally desirable (but not as dominant or affiliative) were significant mediators of neuroendocrine responses. The findings suggest that stress-reduction interventions based on prosocial behavior should target particular motivational and interpersonal features.

  20. Test of the stress sensitization model in adolescents following the pipeline explosion.

    Science.gov (United States)

    Shao, Di; Gao, Qing-Ling; Li, Jie; Xue, Jiao-Mei; Guo, Wei; Long, Zhou-Ting; Cao, Feng-Lin

    2015-10-01

    The stress sensitization model states that early traumatic experiences increase vulnerability to the adverse effects of subsequent stressful life events. This study examined the effect of stress sensitization on development of posttraumatic stress disorder (PTSD) symptoms in Chinese adolescents who experienced the pipeline explosion. A total of 670 participants completed self-administered questionnaires on demographic characteristics and degree of explosion exposure, the Childhood Trauma Questionnaire (CTQ), and the Posttraumatic Stress Disorder Checklist-Civilian Version (PCL-C). Associations among the variables were explored using MANOVA, and main effects and interactions were analyzed. Overall MANOVA tests with the PCL-C indicated significant differences for gender (F=6.86, p=.000), emotional abuse (F=6.79, p=.000), and explosion exposure (F=22.40, p=.000). There were significant interactions between emotional abuse and explosion exposure (F=3.98, p=.008) and gender and explosion exposure (F=2.93, p=.033). Being female, childhood emotional abuse, and a high explosion exposure were associated with high PTSD symptom levels. Childhood emotional abuse moderated the effect of explosion exposure on PTSD symptoms. Thus, stress sensitization influenced the development of PTSD symptoms in Chinese adolescents who experienced the pipeline explosion as predicted by the model. Copyright © 2015 Elsevier Inc. All rights reserved.

  1. 78 FR 59791 - Annual Company-Run Stress Tests at Banking Organizations With Total Consolidated Assets of More...

    Science.gov (United States)

    2013-09-30

    ... ratio, implements strict eligibility criteria for regulatory capital instruments, and introduces a... more. Consistent with the stress test rules applicable to their bank holding company parents, these...

  2. Progress testing in the medical curriculum: students' approaches to learning and perceived stress.

    Science.gov (United States)

    Chen, Yan; Henning, Marcus; Yielder, Jill; Jones, Rhys; Wearn, Andy; Weller, Jennifer

    2015-09-11

    Progress Tests (PTs) draw on a common question bank to assess all students in a programme against graduate outcomes. Theoretically PTs drive deep approaches to learning and reduce assessment-related stress. In 2013, PTs were introduced to two year groups of medical students (Years 2 and 4), whereas students in Years 3 and 5 were taking traditional high-stakes assessments. Staged introduction of PTs into our medical curriculum provided a time-limited opportunity for a comparative study. The main purpose of the current study was to compare the impact of PTs on undergraduate medical students' approaches to learning and perceived stress with that of traditional high-stakes assessments. We also aimed to investigate the associations between approaches to learning, stress and PT scores. Undergraduate medical students (N = 333 and N = 298 at Time 1 and Time 2 respectively) answered the Revised Study Process Questionnaire (R-SPQ-2F) and the Perceived Stress Scale (PSS) at two time points to evaluate change over time. The R-SPQ-2F generated a surface approach and a deep approach score; the PSS generated an overall perceived stress score. We found no significant differences between the two groups in approaches to learning at either time point, and no significant changes in approaches to learning over time in either cohort. Levels of stress increased significantly at the end of the year (Time 2) for students in the traditional assessment cohort, but not in the PT cohort. In the PT cohort, surface approach to learning, but not stress, was a significant negative predictor of students' PT scores. While confirming an association between surface approaches to learning and lower PT scores, we failed to demonstrate an effect of PTs on approaches to learning. However, a reduction in assessment-associated stress is an important finding.

  3. Summary of tectonic and structural evidence for stress orientation at the Nevada Test Site

    Science.gov (United States)

    Carr, Wilfred James

    1974-01-01

    A tectonic synthesis of the NTS (Nevada Test Site) region, when combined with seismic data and a few stress and strain measurements, suggests a tentative model for stress orientation. This model proposes that the NTS is undergoing extension in a N. 50 ? W.-S. 50 ? E. direction coincident with the minimum principal stress direction. The model is supported by (1) a tectonic similarity between a belt of NTS Quaternary faulting and part of the Nevada-California seismic belt, for which northwest-southeast extension has been suggested; (2) historic northeast- trending natural- and explosion-produced fractures in the NTS; (3) the virtual absence in the NTS of northwest-trending Quaternary faults; (4) the character of north-trending faults and basin configuration in the Yucca Flat area, which suggest a component of right-lateral displacement and post-10 m.y. (million year) oblique separation of the sides of the north-trending depression; (5) seismic evidence suggesting a north- to northwest-trending tension axis; (6) strain measurements, which indicate episodes of northwest-southeast extension within a net northeast-southwest compression; (7) a stress estimate based on tectonic cracking that indicates near-surface northwest-southeast-directed tension, and two stress measurements indicating an excess (tectonic) maximum principal compressive stress in a northeast-southwest direction at depths of about 1,000 feet (305 m); and (8) enlargement of some drill holes in Yucca Flat in a northwest-southeast direction. It is inferred that the stress episode resulting in the formation of deep alluvium-filled trenches began somewhere between 10 and possibly less than 4 m.y. ago in the NTS and is currently active. In the Walker Lane of western Nevada, crystallization of plutons associated with Miocene volcanism may have increased the competency and thickness of the crust and its ability to propagate stress, thereby modulating the frequency (spacing) of basin-range faults.

  4. Testing the Adaptation to Poverty-Related Stress Model: Predicting Psychopathology Symptoms in Families Facing Economic Hardship

    Science.gov (United States)

    Wadsworth, Martha E.; Raviv, Tali; Santiago, Catherine DeCarlo; Etter, Erica M.

    2011-01-01

    This study tested the Adaptation to Poverty-related Stress Model and its proposed relations between poverty-related stress, effortful and involuntary stress responses, and symptoms of psychopathology in an ethnically diverse sample of low-income children and their parents. Prospective Hierarchical Linear Modeling analyses conducted with 98…

  5. A microfluidic platform for rapid, stress-induced antibiotic susceptibility testing of Staphylococcus aureus.

    Science.gov (United States)

    Kalashnikov, Maxim; Lee, Jean C; Campbell, Jennifer; Sharon, Andre; Sauer-Budge, Alexis F

    2012-11-07

    The emergence and spread of bacterial resistance to ever increasing classes of antibiotics intensifies the need for fast phenotype-based clinical tests for determining antibiotic susceptibility. Standard susceptibility testing relies on the passive observation of bacterial growth inhibition in the presence of antibiotics. In this paper, we present a novel microfluidic platform for antibiotic susceptibility testing based on stress-activation of biosynthetic pathways that are the primary targets of antibiotics. We chose Staphylococcus aureus (S. aureus) as a model system due to its clinical importance, and we selected bacterial cell wall biosynthesis as the primary target of both stress and antibiotic. Enzymatic and mechanical stresses were used to damage the bacterial cell wall, and a β-lactam antibiotic interfered with the repair process, resulting in rapid cell death of strains that harbor no resistance mechanism. In contrast, resistant bacteria remained viable under the assay conditions. Bacteria, covalently-bound to the bottom of the microfluidic channel, were subjected to mechanical shear stress created by flowing culture media through the microfluidic channel and to enzymatic stress with sub-inhibitory concentrations of the bactericidal agent lysostaphin. Bacterial cell death was monitored via fluorescence using the Sytox Green dead cell stain, and rates of killing were measured for the bacterial samples in the presence and absence of oxacillin. Using model susceptible (Sanger 476) and resistant (MW2) S. aureus strains, a metric was established to separate susceptible and resistant staphylococci based on normalized fluorescence values after 60 min of exposure to stress and antibiotic. Because this ground-breaking approach is not based on standard methodology, it circumvents the need for minimum inhibitory concentration (MIC) measurements and long wait times. We demonstrate the successful development of a rapid microfluidic-based and stress

  6. Rheumatoid arthritis: a study of relaxation and temperature biofeedback training as an adjunctive therapy.

    Science.gov (United States)

    Achterberg, J; McGraw, P; Lawlis, G F

    1981-06-01

    Rheumatoid arthritis (RA) is a painful systemic disease and is believed to be exacerbated by stress. Relaxation and biofeedback strategies have demonstrated utility in alleviating both pain and stress-related symptomatology, and therefore were tested for efficacy with this disease in a two-phase study. First, 24 patients were taught a relaxation technique and then trained in either temperature elevation or reduction. Second, a group of 15 patients thus trained was compared with 8 others who received traditional physiotherapy modalities. Psychological tests, functional/physical evaluations, as well as measurements related to pain, sleep, and other activities were carried out. Results of the first study revealed significant and positive changes following treatment that were primarily related to pain, tension, and sleep patterns for both groups, but no differential effects were noted between temperature elevation or reduction conditions. This was attributed to both groups having maintained temperature above baseline during biofeedback training. The results of the second study consistently favored the relaxation and biofeedback over the physiotherapy group on the physical/functional indices. The psychological measures tended to remain constant throughout both studies, leading to the conclusion that the effectiveness of treatment was specific to physical functioning rather than to a psychological enhancement of well-being.

  7. Relaxing to Three Dimensions

    CERN Document Server

    Karch, A; Karch, Andreas; Randall, Lisa

    2005-01-01

    We propose a new selection principle for distinguishing among possible vacua that we call the "relaxation principle". The idea is that the universe will naturally select among possible vacua through its cosmological evolution, and the configuration with the biggest filling fraction is the likeliest. We apply this idea to the question of the number of dimensions of space. We show that under conventional (but higher-dimensional) FRW evolution, a universe filled with equal numbers of branes and antibranes will naturally come to be dominated by 3-branes and 7-branes. We show why this might help explain the number of dimensions that are experienced in our visible universe.

  8. Effectiveness of progressive muscle relaxation therapy as a worksite health promotion program in the automobile assembly line.

    Science.gov (United States)

    Sundram, Bala Murali; Dahlui, Maznah; Chinna, Karuthan

    2016-06-10

    The aim of this study was to examine the effectiveness of Progressive Muscle Relaxation (PMR) as part of a Worksite Health Promotion Program on self-perceived stress, anxiety and depression among male automotive assembly-line workers through a quasi-experimental trial. Two assembly plants were chosen with one receiving PMR therapy and the other Pamphlets. Intention-to-treat analysis was conducted to test the effectiveness of the relaxation therapy. Stress, Depression and Anxiety levels were measured using the shortened DASS-21 questionnaire. Data were analyzed using Chi-square, Independent sample t test and Repeated-measures analysis of variance to test the significance of the effects of intervention (time * group) for the measures of Stress, Depression and Anxiety. Significant favourable intervention effects on stress were found in the PMR group (Effect size=0.6) as compared to the Pamphlet group (Effect size=0.2). There was a significant group *time interaction effect (p<0.001) on Stress levels. Depression and Anxiety levels were minimal at baseline in both the groups with mild or no reduction in levels. The improvement in stress levels showed the potential of PMR therapy as a coping strategy at the workplace. Further research in this field is necessary to examine the beneficial effects of coping strategies in the workplace.

  9. Standard practice for preparation and use of direct tension stress-corrosion test specimens

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    1985-01-01

    1.1 This practice covers procedures for designing, preparing, and using ASTM standard tension test specimens for investigating susceptibility to stress-corrosion cracking. Axially loaded specimens may be stressed quantitatively with equipment for application of either a constant load, constant strain, or with a continuously increasing strain. 1.2 Tension test specimens are adaptable for testing a wide variety of product forms as well as parts joined by welding, riveting, or various other methods. 1.3 The exposure of specimens in a corrosive environment is treated only briefly because other standards are being prepared to deal with this aspect. Meanwhile, the investigator is referred to Practices G35, G36, G37, and G44, and to ASTM Special Technical Publication 425 (1).

  10. Short duration exhaustive aerobic exercise induces oxidative stress: a novel play-oriented volitional fatigue test.

    Science.gov (United States)

    Kyparos, A; Salonikidis, K; Nikolaidis, M G; Kouretas, D

    2007-12-01

    Exercise is associated with the generation of reactive oxygen and nitrogen species. This study examined the oxidative stress in response to a novel volitional fatigue test. Eleven male college students performed a volitional fatigue test consisting of shuttle runs with a tennis racquet in the hand towards the left and right sidelines within the tennis singles court in an attempt to hit tennis balls until exhaustion. A tennis ball serving machine was adjusted to alternate feeds to the forehand and backhand sides of the subjects, standing at the baseline, at a frequency of 20 balls per minute. Mean time to volitional fatigue was 5.9+/-1.3 min and mean heart rate at volitional fatigue was 189+/-8.1 beats x min(-1). The volitional fatigue test resulted in significant increases in blood thiobarbituric acid-reactive substances (22%), protein carbonyls (58%), catalase activity (143%), total antioxidant capacity (34%) and oxidized glutathione (GSSG, 81%) concentration, as well as significant decreases in reduced glutathione (GSH, 15%) concentration and GSH/GSSG ratio (56%) immediately postexercise, as compared to the pre-exercise concentration. The data provide evidence that acute short duration exhaustive aerobic exercise in the form of a novel volitional fatigue test is capable of inducing oxidative stress. This novel test could serve as an alternative exercise modality to study oxidative stress.

  11. Business model stress testing : A practical approach to test the robustness of a business model

    NARCIS (Netherlands)

    Haaker, T.I.; Bouwman, W.A.G.A.; Janssen, W; de Reuver, G.A.

    Business models and business model innovation are increasingly gaining attention in practice as well as in academic literature. However, the robustness of business models (BM) is seldom tested vis-à-vis the fast and unpredictable changes in digital technologies, regulation and markets. The

  12. A randomized trial of urodynamic testing before stress-incontinence surgery.

    Science.gov (United States)

    Nager, Charles W; Brubaker, Linda; Litman, Heather J; Zyczynski, Halina M; Varner, R Edward; Amundsen, Cindy; Sirls, Larry T; Norton, Peggy A; Arisco, Amy M; Chai, Toby C; Zimmern, Philippe; Barber, Matthew D; Dandreo, Kimberly J; Menefee, Shawn A; Kenton, Kimberly; Lowder, Jerry; Richter, Holly E; Khandwala, Salil; Nygaard, Ingrid; Kraus, Stephen R; Johnson, Harry W; Lemack, Gary E; Mihova, Marina; Albo, Michael E; Mueller, Elizabeth; Sutkin, Gary; Wilson, Tracey S; Hsu, Yvonne; Rozanski, Thomas A; Rickey, Leslie M; Rahn, David; Tennstedt, Sharon; Kusek, John W; Gormley, E Ann

    2012-05-24

    Urodynamic studies are commonly performed in women before surgery for stress urinary incontinence, but there is no good evidence that they improve outcomes. We performed a multicenter, randomized, noninferiority trial involving women with uncomplicated, demonstrable stress urinary incontinence to compare outcomes after preoperative office evaluation and urodynamic tests or evaluation only. The primary outcome was treatment success at 12 months, defined as a reduction in the score on the Urogenital Distress Inventory of 70% or more and a response of "much better" or "very much better" on the Patient Global Impression of Improvement. The predetermined noninferiority margin was 11 percentage points. A total of 630 women were randomly assigned to undergo office evaluation with urodynamic tests or evaluation only (315 per group); the proportion in whom treatment was successful was 76.9% in the urodynamic-testing group versus 77.2% in the evaluation-only group (difference, -0.3 percentage points; 95% confidence interval, -7.5 to 6.9), which was consistent with noninferiority. There were no significant between-group differences in secondary measures of incontinence severity, quality of life, patient satisfaction, rates of positive provocative stress tests, voiding dysfunction, or adverse events. Women who underwent urodynamic tests were significantly less likely to receive a diagnosis of overactive bladder and more likely to receive a diagnosis of voiding-phase dysfunction, but these changes did not lead to significant between-group differences in treatment selection or outcomes. For women with uncomplicated, demonstrable stress urinary incontinence, preoperative office evaluation alone was not inferior to evaluation with urodynamic testing for outcomes at 1 year. (Funded by the National Institute of Diabetes and Digestive and Kidney Diseases and the Eunice Kennedy Shriver National Institute of Child Health and Human Development; ClinicalTrials.gov number, NCT00803959.).

  13. Strain Rate Dependence of Compressive Yield and Relaxation in DGEBA Epoxies

    Science.gov (United States)

    Arechederra, Gabriel K.; Reprogle, Riley C.; Clarkson, Caitlyn M.; McCoy, John D.; Kropka, Jamie M.; Long, Kevin N.; Chambers, Robert S.

    2015-03-01

    The mechanical response in uniaxial compression of two diglycidyl ether of bisphenol-A epoxies were studied. These were 828DEA (Epon 828 cured with diethanolamine (DEA)) and 828T403 (Epon 828 cured with Jeffamine T-403). Two types of uniaxial compression tests were performed: A) constant strain rate compression and B) constant strain rate compression followed by a constant strain relaxation. The peak (yield) stress was analyzed as a function of strain rate from Eyring theory for activation volume. Runs at different temperatures permitted the construction of a mastercurve, and the resulting shift factors resulted in an activation energy. Strain and hold tests were performed for a low strain rate where a peak stress was lacking and for a higher strain rate where the peak stress was apparent. Relaxation from strains at different places along the stress-strain curve was tracked and compared. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  14. Using borehole electrometry to determine the orientation of quasiprincipal stresses. II. Monitoring equipment, in situ tests

    Energy Technology Data Exchange (ETDEWEB)

    Oparin, V.N.; Kurlenya, M.V.; Matasova, G.C.; Tapsiev, A.P.

    1986-05-01

    The authors describe the testing of the theory of determining the orientation of quasiprincipal stresses by using the electrometric method. Electrometric differential sondes are described. The device is intended for electric resistivity logging of differently oriented non-waterlogged wells in mining conditions and can be used for determining the electric anisotropy of coal and orientation of quasiprincipal stresses. Operation of the device is explained and its specifications are presented. The method has several merits: ease of implementation--any single well can be used; the measurements can be conducted to any depth along the well, with a desired degree of detail; a well can be used any number of times for repeated measurements to determine the changes in the orientation of quasiprincipal stresses caused by mine advance; and a well can be drilled in any mineralogically homogeneous rock.

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

    Directory of Open Access Journals (Sweden)

    Casey Moore

    2012-04-01

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

  16. Children's implicit understanding of the stress-illness link: Testing development of health cognitions.

    Science.gov (United States)

    Cheetham, Tara J; Turner-Cobb, Julie M; Gamble, Tim

    2016-11-01

    Innate knowledge and developmental stage theory have been used to explain children's understanding of concepts relating to health, illness, and stress. The aim of this study was to investigate the degree to which children demonstrate unconscious cognitive associations between the concepts of stress and illness. The study employed an experimental design using an age appropriate implicit association task. Thirty-two children (5-11 years of age) completed the Preschool Implicit Association Test (PSIAT), a computer-based measure of reaction time to consistent (stress and illness) and inconsistent (stress and health) concept pairings. Whilst age group had a significant effect on reaction times (older children generally displaying faster reaction times than younger children), those as young as 5-6 years of age were able to demonstrate implicit associations between stress and illness using the PSIAT. There was also some indication that this association peaks at around 7-8 years of age. Findings support a combination of developmental stage theory and the innate theory of children's understanding. Whilst sample size is small, this study is the first to apply the PSIAT to the context of implicit cognitive associations between stress and illness in children. Findings have potential implications for the delivery of interventions to facilitate health promotion and development of positive health behaviours in children and indicate that even children as young as 5-6 years have some ability to relate to the concept that stress may influence illness. Statement of contribution What is already known on this subject? The way in which children understand health and illness is commensurate with their developmental stage and experience of illness. Children also appear to have a degree of innate understanding of health and illness and their causes. Furthermore, recent work suggests children have some innate understanding and knowledge of the concept of stress. What does this study add

  17. The effect of progressive muscle relaxation on pregnant women's general health.

    Science.gov (United States)

    Sadeghi, Azam; Sirati-Nir, Masoud; Ebadi, Abbas; Aliasgari, Matin; Hajiamini, Zahra

    2015-01-01

    Pregnancy may be accompanied by serious physiological and psychological changes as it is a stressful period in a woman's life. So, this study was conducted to determine the effect of progressive muscle relaxation on pregnant women's general health. In this clinical trial, 60 primigravida women admitted to the prenatal clinic of selected hospitals in Iran constituted the study population. Using purposive sampling method, the level of general health of the women was measured with General Health Questionnaire-28 (GHQ-28). Then, the samples were randomly divided into control and experimental groups. Three 1.5-2 h relaxation training sessions were held for the experimental group. After 8 weeks, the level of general health of both groups was measured again. Finally, the collected data were analyzed using Chi-square and paired t-test (P progressive muscle relaxation on pregnant women's general health, the prenatal clinics can include a training program for progressive muscle relaxation in the routine training programs for pregnant women.

  18. Ghrelin levels after a cold pressor stress test in obese women with binge eating disorder.

    Science.gov (United States)

    Gluck, Marci E; Yahav, Eric; Hashim, Sami A; Geliebter, Allan

    2014-01-01

    Ghrelin, a peptide hormone secreted mainly by the stomach, increases appetite and food intake. Surprisingly, ghrelin levels are lower in obese individuals with binge eating disorder (BED) than in obese non-BED individuals. Acute psychological stress has been shown to raise ghrelin levels in animals and humans. Our aim was to assess ghrelin levels after a cold pressor test (CPT) in women with BED. We also examined the relationship between the cortisol stress response and changes in ghrelin levels. Twenty-one obese (mean [standard deviation] body mass index = 34.9 [5.8] kg/m(2)) women (10 non-BED, 11 BED) underwent the CPT, hand submerged in ice water for 2 minutes. Blood samples were drawn for 70 minutes and assayed for ghrelin and cortisol. There were no differences between the groups in ghrelin levels at baseline (-10 minutes). Ghrelin rose significantly after the CPT (F = 2.4, p = .024) peaking at 19 minutes before declining (F = 17.9, p stress, hunger, or desire to eat after CPT. In addition, there were no observed relationships between the area under the curves for ghrelin or cortisol after stress. Although there were no differences between BED groups, there was a significant rise in ghrelin in obese humans after a stressor, consistent with other recent reports suggesting a stress-related role for ghrelin.

  19. 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.

  20. LLNL and TRW extend benchmark environmental stress testing for two alternative printed board cleaners

    Energy Technology Data Exchange (ETDEWEB)

    Hersey, R.J. Jr.; Meltzer, M.; Hofstad, H.W.; Lawrence, M.; Sanborn, R. [Lawrence Livermore National Lab., CA (United States); Arauco, H. [TRW, Inc., Redondo Beach, CA (United States). Electronic Technology Div.

    1995-03-01

    TRW Corporation and LLNL jointly conducted a testing program to evaluate the effectiveness of non-CFC defluxing chemistries on printed boards designed for high reliability military and aerospace applications. TRW assessed existing data for alternative chemistries, selected candidates for further testing, implemented the cleaning processes, and performed ionic conductivity testing on the spent solvents. LLNL designed and fabricated special circuit boards with interdigitated comb patterns to allow insulation resistance (IR) measurements under selected soldered components. LLNL designed the test and measurement setup and conducted accelerated environmental stress testing of flux residues for 28 days following cleaning. Statistical analyses of the IR measurements were correlated with visual observations and spectroscopic (FTIR) measurements. Performance of the alternative chemistries was compared with that of a standard CFC cleaning agent also included in the test program. The program was designed to follow the same environmental stress and electrical measurement requirements as the IPC/DOD/EPA Ad Hoc Solvent Working Group`s benchmark 7-day test plan, but with certain minor modifications and extension to 28 days.

  1. Possibilities of applying pharmacological stress testing in assessment of heart functional capacity in dogs

    Directory of Open Access Journals (Sweden)

    Kosić-Spasojević Ljubica

    2010-01-01

    Full Text Available Systolic and diastolic heart functions, evaluated using echocardiography, do not reflect the functional capacity of the patient and they cannot explain the occurrence of symptoms during a certain degree of activity. Evaluation of the functional capacity is an integral part of cardiological examinations in human medicine. Functional examinations of the heart can be carried out using the body burden test or pharmacologically. Investigations carried out so far into canine cardiology have not contributed to the clinical implementation of functional heart examinations in dogs. Pharmacological stress testing is an optimal way to perform a functional heart examination in dogs. Since it reflects the effects of moderate physical activity, dobutamine has been recommended as the medicine of choice for provoking a pharmacological stress test. This work presents a review of the results of the most important investigations, as well as our own investigations, of the application of the dobutamine stress test (DST in dogs, and the problems in investigations so far have been considered and future directions for DST investigations pointed out. .

  2. Active nematic gels as active relaxing solids

    Science.gov (United States)

    Turzi, Stefano S.

    2017-11-01

    I propose a continuum theory for active nematic gels, defined as fluids or suspensions of orientable rodlike objects endowed with active dynamics, that is based on symmetry arguments and compatibility with thermodynamics. The starting point is our recent theory that models (passive) nematic liquid crystals as relaxing nematic elastomers. The interplay between viscoelastic response and active dynamics of the microscopic constituents is naturally taken into account. By contrast with standard theories, activity is not introduced as an additional term of the stress tensor, but it is added as an external remodeling force that competes with the passive relaxation dynamics and drags the system out of equilibrium. In a simple one-dimensional channel geometry, we show that the interaction between nonuniform nematic order and activity results in either a spontaneous flow of particles or a self-organization into subchannels flowing in opposite directions.

  3. Perceived stress and resilience in Alzheimer's disease caregivers: testing moderation and mediation models of social support.

    Science.gov (United States)

    Wilks, Scott E; Croom, Beth

    2008-05-01

    The study examined whether social support functioned as a protective, resilience factor among Alzheimer's disease (AD) caregivers. Moderation and mediation models were used to test social support amid stress and resilience. A cross-sectional analysis of self-reported data was conducted. Measures of demographics, perceived stress, family support, friend support, overall social support, and resilience were administered to caregiver attendees (N=229) of two AD caregiver conferences. Hierarchical regression analysis showed the compounded impact of predictors on resilience. Odds ratios generated probability of high resilience given high stress and social supports. Social support moderation and mediation were tested via distinct series of regression equations. Path analyses illustrated effects on the models for significant moderation and/or mediation. Stress negatively influenced and accounted for most variation in resilience. Social support positively influenced resilience, and caregivers with high family support had the highest probability of elevated resilience. Moderation was observed among all support factors. No social support fulfilled the complete mediation criteria. Evidence of social support as a protective, moderating factor yields implications for health care practitioners who deliver services to assist AD caregivers, particularly the promotion of identification and utilization of supportive familial and peer relations.

  4. A Stress Test to Evaluate the Physical Capacity of Performing L-1 Anti-G Straining Maneuvers

    Science.gov (United States)

    1988-09-01

    according to the "Guide for the Care and Use of Laboratory Animals ," Institute of Laboratory Animal Resources, National Research Council. The...stress test and at 50% duty cycle of continuous AGSM stress test were calculated by automated open-circuit spirometry (Metabolic Cart, System 2001

  5. 78 FR 78694 - Orders: Supplemental Orders on Reporting by Regulated Entities of Stress Testing Results as of...

    Science.gov (United States)

    2013-12-27

    ... AGENCY 12 CFR Part 1238 Orders: Supplemental Orders on Reporting by Regulated Entities of Stress Testing... Analysis, Modeling and Simulations, (202) 649-3140, [email protected] ; Stefan Szilagyi, Examination... additional appendices of scenario assumptions to be used for stress testing. II. Orders For the convenience...

  6. Determination of consistent patterns of range of motion in the ankle joint with a computed tomography stress-test

    NARCIS (Netherlands)

    Tuijthof, Gabriëlle Josephine Maria; Zengerink, Maartje; Beimers, Lijkele; Jonges, Remmet; Maas, Mario; van Dijk, Cornelis Niek; Blankevoort, Leendert

    2009-01-01

    Background: Measuring the range of motion of the ankle joint can assist in accurate diagnosis of ankle laxity. A computed tomography-based stress-test (3D CT stress-test) was used that determines the three-dimensional position and orientation of tibial, calcaneal and talar bones. The goal was to

  7. In vitro blood flow model with physiological wall shear stress for hemocompatibility testing-An example of coronary stent testing.

    Science.gov (United States)

    Engels, Gerwin Erik; Blok, Sjoerd Leendert Johannes; van Oeveren, Willem

    2016-09-18

    Hemocompatibility of blood contacting medical devices has to be evaluated before their intended application. To assess hemocompatibility, blood flow models are often used and can either consist of in vivo animal models or in vitro blood flow models. Given the disadvantages of animal models, in vitro blood flow models are an attractive alternative. The in vitro blood flow models available nowadays mostly focus on generating continuous flow instead of generating a pulsatile flow with certain wall shear stress, which has shown to be more relevant in maintaining hemostasis. To address this issue, the authors introduce a blood flow model that is able to generate a pulsatile flow and wall shear stress resembling the physiological situation, which the authors have coined the "Haemobile." The authors have validated the model by performing Doppler flow measurements to calculate velocity profiles and (wall) shear stress profiles. As an example, the authors evaluated the thrombogenicity of two drug eluting stents, one that was already on the market and one that was still under development. After identifying proper conditions resembling the wall shear stress in coronary arteries, the authors compared the stents with each other and often used reference materials. These experiments resulted in high contrast between hemocompatible and incompatible materials, showing the exceptional testing capabilities of the Haemobile. In conclusion, the authors have developed an in vitro blood flow model which is capable of mimicking physiological conditions of blood flow as close as possible. The model is convenient in use and is able to clearly discriminate between hemocompatible and incompatible materials, making it suitable for evaluating the hemocompatible properties of medical devices.

  8. A stress test on 235U(n, f) in adjustment with HCI and HMI benchmarks

    Science.gov (United States)

    Wu, Haicheng; Qin, Yingcan; Salvatores, Massimo

    2017-09-01

    To understand how compensation errors occur in a nuclear data adjustment mostly devoted to U-Pu fuelled fast critical experiments and with only limited information on U-235 data, a stress test on 235U(n,f) was suggested, using critical benchmarks sensitive to 235U(n,f) in 1˜ 10 keV region. The adjustment benchmark exercise with 20 integral data suggested by the NEA WPEC/SG33 was used as the reference, where practically only one experiment did give information on U-235 data. The keff of HCI4.1 and HCI6.2 experimental benchmarks were used as the 21st and 22nd integral data separately to perform stress tests. The adjusted integral values and cross sections based on 20, 21 and 22 integral data using the same nuclear data and covariance data sets were compared. The results confirm that compensation errors can be created by missing essential constraints.

  9. What do central counterparties default funds really cover? A network-based stress test answer

    CERN Document Server

    Poce, Giulia; Gabrielli, Andrea; Zaccaria, Andrea; Baldacci, Giuditta; Polito, Marco; Rizzo, Mariangela; Sabatini, Silvia

    2016-01-01

    In the last years, increasing efforts have been put into the development of effective stress tests to quantify the resilience of financial institutions. Here we propose a stress test methodology for central counterparties based on a network characterization of clearing members, whose links correspond to direct credits and debits. This network constitutes the ground for the propagation of financial distress: equity losses caused by an initial shock with both exogenous and endogenous components reverberate within the network and are amplified through credit and liquidity contagion channels. At the end of the dynamics, we determine the vulnerability of each clearing member, which represents its potential equity loss. We apply the proposed framework to the Fixed Income asset class of CC&G, the central counterparty operating in Italy whose main cleared securities are Italian Government Bonds. We consider two different scenarios: a distributed, plausible initial shock, as well as a shock corresponding to the co...

  10. Effects of chronic ethanol exposure on renal function tests and oxidative stress in kidney

    OpenAIRE

    Das, Subir Kumar; Varadhan, Sowmya; Dhanya, L.; Mukherjee, Sukhes; Vasudevan, D. M.

    2008-01-01

    After administration, ethanol and its metabolites go through the kidneys and are excreted into urine. The kidney seems to be the only vital organ generally spared in chronic alcoholics. Therefore, we investigated the multiple effects of chronic ethanol exposure on renal function tests and on oxidative stress related parameters in the kidney. Chronic ethanol (1.6 g ethanol/ kg body weight/ day) exposure did not show any significant change in relative weight (g/ 100g body weight) of kidneys, se...

  11. Relaxing Behavioural Inheritance

    Directory of Open Access Journals (Sweden)

    Nuno Amálio

    2013-05-01

    Full Text Available Object-oriented (OO inheritance allows the definition of families of classes in a hierarchical way. In behavioural inheritance, a strong version, it should be possible to substitute an object of a subclass for an object of its superclass without any observable effect on the system. Behavioural inheritance is related to formal refinement, but, as observed in the literature, the refinement constraints are too restrictive, ruling out many useful OO subclassings. This paper studies behavioural inheritance in the context of ZOO, an object-oriented style for Z. To overcome refinement's restrictions, this paper proposes relaxations to the behavioural inheritance refinement rules. The work is presented for Z, but the results are applicable to any OO language that supports design-by-contract.

  12. Acute Heat Stress Induces Differential Gene Expressions in the Testes of a Broiler-Type Strain of Taiwan Country Chickens

    Science.gov (United States)

    Wang, Shih-Han; Cheng, Chuen-Yu; Tang, Pin-Chi; Chen, Chih-Feng; Chen, Hsin-Hsin; Lee, Yen-Pai; Huang, San-Yuan

    2015-01-01

    The expression of testicular genes following acute heat stress has been reported in layer-type roosters, but few similar studies have been conducted on broilers. This study investigated the effect of acute heat stress on the gene expression in the testes of a broiler-type strain of Taiwan country chickens. Roosters were subjected to acute heat stress (38°C) for 4 h, and then exposed to 25°C, with testes collected 0, 2, and 6 h after the cessation of heat stress, using non-heat-stressed roosters as controls (n = 3 roosters per group). The body temperature and respiratory rate increased significantly (pbroiler-type and layer-type chickens. We concluded that the transcriptional responses of testes to acute heat stress may differ between the broiler-type and layer-type roosters. Whether the differential expression patterns associate with the heat-tolerance in the strains require a further exploration. PMID:25932638

  13. Simulated Service and Stress Corrosion Cracking Testing for Friction Stir Welded Spun Form Domes

    Science.gov (United States)

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

    2010-01-01

    Damage tolerance testing development was required to help qualify a new spin forming dome fabrication process for the Ares 1 program at Marshall Space Flight Center (MSFC). One challenge of the testing was due to the compound curvature of the dome. The testing was developed on a sub-scale dome with a diameter of approximately 40 inches. The simulated service testing performed was based on the EQTP1102 Rev L 2195 Aluminum Lot Acceptance Simulated Service Test and Analysis Procedure generated by Lockheed Martin for the Space Shuttle External Fuel Tank. This testing is performed on a specimen with an induced flaw of elliptical shape generated by Electrical Discharge Machining (EDM) and subsequent fatigue cycling for crack propagation to a predetermined length and depth. The specimen is then loaded in tension at a constant rate of displacement at room temperature until fracture occurs while recording load and strain. An identical specimen with a similar flaw is then proof tested at room temperature to imminent failure based on the critical offset strain achieved by the previous fracture test. If the specimen survives the proof, it is then subjected to cryogenic cycling with loads that are a percentage of the proof load performed at room temperature. If all cryogenic cycles are successful, the specimen is loaded in tension to failure at the end of the test. This standard was generated for flat plate, so a method of translating this to a specimen of compound curvature was required. This was accomplished by fabricating a fixture that maintained the curvature of the specimen rigidly with the exception of approximately one-half inch in the center of the specimen containing the induced flaw. This in conjunction with placing the center of the specimen in the center of the load train allowed for successful testing with a minimal amount of bending introduced into the system. Stress corrosion cracking (SCC) tests were performed using the typical double beam assembly and with 4

  14. Crack initiation testing of thimble tube material under PWR conditions to determine a stress threshold for IASCC

    Science.gov (United States)

    Bosch, R. W.; Vankeerberghen, M.; Gérard, R.; Somville, F.

    2015-06-01

    IASCC (Irradiation Assisted Stress Corrosion Cracking) crack initiation tests have been carried out on thimble tube material retrieved from a Belgian PWR. The crack initiation tests were carried out by constant load testing of thimble tube specimens at different stress levels. The time-to-failure was determined as a function of the applied stress to find a stress threshold under which no stress corrosion cracking will take place. The thimble tube was made of 316L cold-worked stainless steel and the dose profile along the thimble tube ranges from 45 to 80 dpa. This allows adding crack initiation data for dose values that have not been significantly reported, i.e. in the range of 45-55 dpa and at 80 dpa. The results can be used to determine whether the stress under which no IASCC occurs saturates for a dose larger than 30 dpa or whether a small further threshold decrease with dose can be observed. Over a period of four years, more than 40 specimens have been tested with doses ranging from 45 to 80 dpa at stress levels between 40% and 70% of the irradiated yield stress. Fracture occurred at all stress levels (but not all specimens) although the time-to-failure increased with decreasing stress. The results show that intergranular cracking was the main fracture mode in all failed O-rings. Three of six 80 dpa O-rings subjected to 40% and 45% of the yield stress did not fail after six months of testing. Based on these results and a comparison with literature data, an apparent stress limit for IASCC could be estimated at 40% of the irradiated yield stress.

  15. Slow viscoelastic relaxation and aging in aqueous foam

    Science.gov (United States)

    Vincent-Bonnieu, S.; Höhler, R.; Cohen-Addad, S.

    2006-05-01

    Like emulsions, pastes and many other forms of soft condensed matter, aqueous foams present slow mechanical relaxations when subjected to a stress too small to induce any plastic flow. To identify the physical origin of this viscoelastic behaviour, we have simulated how dry disordered coarsening 2D foams respond to a small applied stress. We show that the mechanism of long time relaxation is driven by coarsening-induced rearrangements of small bubble clusters. These findings are in full agreement with a scaling law previously derived from experimental creep data for 3D foams. Moreover, we find that the temporal statistics of coarsening-induced bubble rearrangements are described by a Poisson process.

  16. Dobutamine "stress" test and latent cardiac susceptibility to inhaled diesel exhaust in normal and hypertensive rats.

    Science.gov (United States)

    Hazari, Mehdi S; Callaway, Justin; Winsett, Darrell W; Lamb, Christina; Haykal-Coates, Najwa; Krantz, Q Todd; King, Charly; Costa, Daniel L; Farraj, Aimen K

    2012-08-01

    Exercise "stress" testing is a screening tool used to determine the amount of stress for which the heart can compensate before developing abnormal rhythm or ischemia, particularly in susceptible persons. Although this approach has been used to assess risk in humans exposed to air pollution, it has never been applied to rodent studies. We hypothesized that a single exposure to diesel exhaust (DE) would increase the risk of adverse cardiac events such as arrhythmia and myocardial ischemia in rats undergoing a dobutamine challenge test, which can be used to mimic exercise-like stress. Wistar-Kyoto normotensive (WKY) and spontaneously hypertensive (SH) rats implanted with radiotelemeters and a chronic intravenous catheter were whole-body exposed to 150 μg/m3 DE for 4 hr. Increasing doses of dobutamine, a β1-adrenergic agonist, were administered to conscious unrestrained rats 24 hr later to elicit the cardiac response observed during exercise while heart rate (HR) and electrocardiogram (ECG) were monitored. A single exposure to DE potentiated the HR response of WKY and SH rats during dobutamine challenge and prevented HR recovery at rest. During peak challenge, DE-exposed SH rats had lower overall HR variability when compared with controls, in addition to transient ST depression. All DE-exposed animals also had increased arrhythmias. These results are the first evidence that rats exhibit stress-induced cardiac dysrhythmia and ischemia sensitivity comparable to humans after a single exposure to a toxic air pollutant, particularly when in the presence of underlying cardiovascular disease. Thus, exposure to low concentrations of air pollution can impair the heart's ability to respond to stress and increase the risk of subsequent triggered dysfunction.

  17. Proposed Testing to Assess the Accuracy of Glass-To-Metal Seal Stress Analyses.

    Energy Technology Data Exchange (ETDEWEB)

    Chambers, Robert S.; Emery, John M; Tandon, Rajan; Antoun, Bonnie R.; Stavig, Mark E.; Newton, Clay S.; Gibson, Cory S; Bencoe, Denise N.

    2014-09-01

    The material characterization tests conducted on 304L VAR stainless steel and Schott 8061 glass have provided higher fidelity data for calibration of material models used in Glass - T o - Metal (GTM) seal analyses. Specifically, a Thermo - Multi - Linear Elastic Plastic ( thermo - MLEP) material model has be en defined for S S304L and the Simplified Potential Energy Clock nonlinear visc oelastic model has been calibrated for the S8061 glass. To assess the accuracy of finite element stress analyses of GTM seals, a suite of tests are proposed to provide data for comparison to mo del predictions.

  18. Design and Experimental Evaluation of a 3rd Generation Addressable CMOS Piezoresistive Stress Sensing Test Chip

    Energy Technology Data Exchange (ETDEWEB)

    Sweet, J.N.; Peterson, D.W.; Hsia, A.H.

    1999-04-13

    Piezoresistive stress sensing chips have been used extensively for measurement of assembly related die surface stresses. Although many experiments can be performed with resistive structures which are directly bonded, for extensive stress mapping it is necessary to have a large number of sensor cells which can be addressed using CMOS logic circuitry. Our previous test chip, the ATC04, has 100 cells, each approximately 0.012 in. on a side, on a chip with a side dimension of 0.45 in. When a cell resistor is addressed, it is connected to a four terminal measurement bus through CMOS transmission gates. In theory, the gate resistances do not affect the measurement. In practice, there may be subtle effects which appear when very high accuracy is required. At high temperatures, gate leakage can increase to a point at which the resistor measurement becomes inaccurate. For ATC04 this occurred at or above 50 C. Here, we report on the first measurements obtained with a new prototype test chip, the ATC06. This prototype was fabricated in a 0.5 micron feature size silicided CMOS process using the MOSIS prototyping facility. The cell size was approximately 0.004 in. on a side. In order to achieve piezoresistive behavior for the implanted resistors it was necessary to employ a non-standard silicide ''blocking'' process. The stress sensitivity of both implanted and polysilicon blocked resistors is discussed. Using a new design strategy for the CMOS logic, it was possible to achieve a design in which only 5 signals had to be routed to a cell for addressing vs. 9 for ATC04. With our new design, the resistor under test is more effectively electrically isolated from other resistors on the chip, thereby improving high temperature performance. We present data showing operation up to 140 C.

  19. Do positive interactions increase with abiotic stress? A test from a semi-arid steppe.

    Science.gov (United States)

    Maestre, Fernando T; Cortina, Jordi

    2004-01-01

    Theoretical models predict that the relative importance of facilitation and competition may vary inversely across gradients of abiotic stress. However, these predictions have not been thoroughly tested in the field, especially in semi-arid environments. In this study, we evaluated how the net effect of the tussock grass Stipa tenacissima on the shrub Pistacia lentiscus varied across a gradient of abiotic stress in semi-arid Mediterranean steppes. We fitted the relationship between accumulated rainfall and the relative neighbour index (our measures of abiotic stress and of the net effect of S. tenacissima on P. lentiscus, respectively), which varied across this gradient, to a quadratic model. Competitive interactions dominated at both extremes of the gradient. Our results do not support established theory. Instead, they suggest that a shift from facilitation to competition under high abiotic stress conditions is likely to occur when the levels of the most limiting resource are so low that the benefits provided by the facilitator cannot overcome its own resource uptake. PMID:15504009

  20. Edge eigen-stress and eigen-displacement of armchair molybdenum disulfide nanoribbons

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Quan; Li, Xi [Corrosion and Protection Center, Key Laboratory for Environmental Fracture (MOE), University of Science and Technology Beijing, Beijing 100083 (China); Volinsky, Alex A., E-mail: volinsky@usf.edu [Department of Mechanical Engineering, University of South Florida, Tampa, FL 33620 (United States); Su, Yanjing, E-mail: yjsu@ustb.edu.cn [Corrosion and Protection Center, Key Laboratory for Environmental Fracture (MOE), University of Science and Technology Beijing, Beijing 100083 (China)

    2017-05-10

    Edge effects on mechanical properties of armchair molybdenum disulfide nanoribbons were investigated using first principles calculations. The edge eigen-stress model was applied to explain the relaxation process of forming molybdenum disulfide nanoribbon. Edge effects on surface atoms fluctuation degree were obtained from each fully relaxed nanoribbon with different width. Changes of the relaxed armchair molybdenum disulfide nanoribbons structure can be expressed using hexagonal perimeters pattern. Based on the thickness change, relaxed armchair molybdenum disulfide nanoribbons tensile/compression tests were simulated, providing intrinsic edge elastic parameters, such as eigen-stress, Young's modulus and Poisson's ratio. - Highlights: • Edge effects on mechanical properties of armchair MoS{sub 2} nanoribbons were investigated. • Structure changes of different width armchair MoS{sub 2} nanoribbons were obtained. • Tensile/compressive tests were conducted to determine elastic constants. • Mechanical properties are compared for two and three dimensional conditions.

  1. Some important considerations in the development of stress corrosion cracking test methods.

    Science.gov (United States)

    Wei, R. P.; Novak, S. R.; Williams, D. P.

    1972-01-01

    Discussion of some of the precaution needs the development of fracture-mechanics based test methods for studying stress corrosion cracking involves. Following a review of pertinent analytical fracture mechanics considerations and of basic test methods, the implications for test corrosion cracking studies of the time-to-failure determining kinetics of crack growth and life are examined. It is shown that the basic assumption of the linear-elastic fracture mechanics analyses must be clearly recognized and satisfied in experimentation and that the effects of incubation and nonsteady-state crack growth must also be properly taken into account in determining the crack growth kinetics, if valid data are to be obtained from fracture-mechanics based test methods.

  2. Double layer relaxation in colloids

    NARCIS (Netherlands)

    Kijlstra, J.

    1992-01-01

    The purpose of the present study is to improve our insight into the relaxation of the electrical double layer around particles in hydrophobic sols. A detailed knowledge of the relaxation mechanisms is required to explain the behaviour of sols under conditions where the double layer is

  3. Magnetic relaxation in anisotropic magnets

    DEFF Research Database (Denmark)

    Lindgård, Per-Anker

    1971-01-01

    The line shape and the kinematic and thermodynamic slowing down of the critical and paramagnetic relaxation in axially anisotropic materials are discussed. Kinematic slowing down occurs only in the longitudinal relaxation function. The thermodynamic slowing down occurs in either the transverse...

  4. Parkinson's disease tremor is diminished with relaxation guided imagery.

    Science.gov (United States)

    Schlesinger, Ilana; Benyakov, Orna; Erikh, Ilana; Suraiya, Suheir; Schiller, Yitzhak

    2009-10-30

    Patients with Parkinson's disease (PD) may have pronounced tremor that exacerbates during stress. To determine whether PD tremor improves with relaxation guided imagery (RGI) and relaxing music. Twenty patients with PD with moderate to severe tremor participated in sessions where relaxation techniques were implemented. Tremor was objectively monitored using an accelerometer. RGI dramatically decreased tremor in all 20 patients (baseline 270.38 +/- 85.82 vs. RGI 35.57 +/- 43.90 movements per minute P music significantly reduced tremor but to a lesser degree than RGI (220.04 +/- 106.53 movements per minute P = 0.01). Self-relaxation had no significant effect on tremor. RGI can supplement conventional medical treatments for tremor in patients with PD on best medical treatment. (c) 2009 Movement Disorder Society.

  5. Work-related stress is associated with impaired neuropsychological test performance: a clinical cross-sectional study.

    Science.gov (United States)

    Eskildsen, Anita; Andersen, Lars Peter; Pedersen, Anders Degn; Vandborg, Sanne Kjær; Andersen, Johan Hviid

    2015-01-01

    Patients on sick leave due to work-related stress often complain about impaired concentration and memory. However, it is undetermined how widespread these impairments are, and which cognitive domains are most long-term stress sensitive. Previous studies show inconsistent results and are difficult to synthesize. The primary aim of this study was to examine whether patients with work-related stress complaints have cognitive impairments compared to a matched control group without stress. Our secondary aim was to examine whether the level of self-reported perceived stress is associated with neuropsychological test performance. We used a broad neuropsychological test battery to assess 59 outpatients with work-related stress complaints (without major depression) and 59 healthy controls. We matched the patients and controls pairwise by sex, age and educational level. Compared to controls, patients generally showed mildly reduced performance across all the measured domains of the neuropsychological test battery. However, only three comparisons reached statistical significance (p working memory. There were no statistical significant associations between self-reported perceived stress level and neuropsychological test performance. In conclusion, we recommend that cognitive functions should be considered when evaluating patients with work-related stress complaints, especially when given advice regarding return to work. Since this study had a cross-sectional design, it is still uncertain whether the impairments are permanent. Further study is required to establish causal links between work-related stress and cognitive deficits.

  6. The use of N-methylpyrrolidone as a cosolvent and oxidant in pharmaceutical stress testing.

    Science.gov (United States)

    Reynolds, Dan W; Galvani, Marina; Hicks, Simon R; Joshi, Biren J; Kennedy-Gabb, Sonya A; Kleinman, Mark H; Parmar, Paresh Z

    2012-02-01

    The use of N-methylpyrrolidone (NMP) as an oxidant and cosolvent in pharmaceutical stress testing (forced degradation) is examined. Various active pharmaceutical ingredients were heated in NMP-water solutions under nitrogen, air, and oxygen and then analyzed by high-performance liquid chromatography, usually with ultraviolet diode array detection and mass spectrometry detection. In some cases, degradation products were isolated and characterized by nuclear magnetic resonance. The NMP-water-air-heat system provided oxidative and hydrolytic degradation products. The observed oxidation products were consistent with products expected from free radical autoxidation, reactions with hydroperoxides, and possibly singlet oxygen. Oxidative and hydrolytic pathways could be distinguished by comparison of the reactions carried out under air/oxygen and nitrogen. In many cases, the oxidation products observed during stress testing were also observed during formal stability studies of drug products. The NMP-water-air-heat stress condition facilitates various oxidative degradation pathways, which are often relevant to drug product on stability. This approach facilitates stability-indicating method development and helps elucidate degradation pathways. Copyright © 2011 Wiley Periodicals, Inc.

  7. Construction and component testing of TAMU3, a 14 Tesla stress-managed Nb3Sn model dipole

    Science.gov (United States)

    Holik, Eddie Frank, III; Benson, Chris; Blackburn, Raymond; Diaczenko, Nick; Elliott, Timothy; Jaisle, Andrew; McInturff, A.; McIntyre, P.; Sattarov, Akhdiyor

    2012-06-01

    We report the construction and testing of components of TAMU3, a 14 Tesla Nb3Sn block-coil dipole. A primary goal in developing this model dipole is to test a method of stress management in which Lorentz stress is intercepted within the coil assembly and bypassed so that it cannot accumulate to a level that would cause strain degradation in the superconducting windings. Details of the fabrication, tooling, and results of construction and magnet component testing will be presented.

  8. Relaxation and music to reduce postsurgical pain.

    Science.gov (United States)

    Good, M; Stanton-Hicks, M; Grass, J A; Anderson, G C; Lai, H L; Roykulcharoen, V; Adler, P A

    2001-01-01

    We investigated the effects of relaxation, music, and the combination of relaxation and music on postoperative pain, across and between two days and two activities (ambulation and rest) and across ambulation each day. This secondary analysis of a randomized controlled trial was conducted from 1995 to 1997. After surgery, patients do not always receive sufficient relief from opioids and may have undesired side-effects. More complete relief (10-30%) was found recently with adjuvant interventions of relaxation, music, and their combination. Comparison of effects between days and treatments have not been examined longitudinally. With a repeated measures design, abdominal surgery patients (n = 468) in five US hospitals were assigned randomly to one of four groups; relaxation, music, their combination, and control. With institutional approval and written informed consent, subjects were interviewed and taught interventions preoperatively. Postoperative testing was at ambulation and rest on days 1 and 2 using visual analogue (VAS) sensation and distress of pain scales. Multivariate analysis indicated that although pain decreased by day 2, interventions were not different between days and activities. They were effective for pain across ambulation on each day, across ambulation and across rest over both days (all P pain on both postoperative days and at both ambulation and rest.

  9. Trends in referral patterns, invasive management, and mortality in elderly patients referred for exercise stress testing.

    Science.gov (United States)

    Bouzas-Mosquera, Alberto; Peteiro, Jesús; Broullón, Francisco J; Calviño-Santos, Ramón; Mosquera, Víctor X; Barbeito-Caamaño, Cayetana; Larrañaga-Moreira, José María; Maneiro-Melón, Nicolás; Álvarez-García, Nemesio; Vázquez-Rodríguez, José Manuel

    2015-12-01

    Scarce data are available on the temporal patterns in clinical characteristics and outcomes of elderly patients referred for exercise stress testing. We aimed to assess the trends in baseline characteristics, tests results, referrals for invasive management, and mortality in these patients. We evaluated 11,192 patients aged ≥65years who were referred for exercise stress testing between January 1998 and December 2013. Calendar years were grouped into four quadrennia (1998-2001, 2002-2005, 2006-2009, and 2010-2013), and trends in clinical characteristics of the patients, type and results of the tests, referrals for invasive management, and mortality across the different periods were assessed. Despite a progressive decrease in the proportion of patients with non-interpretable baseline electrocardiograms or prior history of coronary artery disease, there was a gradual and marked increase in the use of cardiac imaging from 32.8% in 1998-2001 to 67.6% in 2010-2013 (ptesting both without imaging (from 18.9 to 13.6%, pmortality also decreased progressively from 3% to 1.6% (ptesting, we observed a decline over time in the probability of inducible myocardial ischemia, an increase in the use of cardiac imaging and in the rate of coronary revascularization, and an improvement in the survival rate at 1year. Copyright © 2015 European Federation of Internal Medicine. Published by Elsevier B.V. All rights reserved.

  10. The conformity of BPP and vibroacoustic stimulation results in fetal non reactive non stress test

    Directory of Open Access Journals (Sweden)

    M. Modarres

    2006-08-01

    Full Text Available Background: The most frequently used test for evaluation of fetal health is the Non Stress Test (NST. Unfortunately it has a high incidence of false positive results. The combination of vibroacoustic stimulation with the NTS has been shown to reduce non reactive results. Methods: A tests assessment method was chosen with a simple randomized sampling. 40 pregnant women with non reactive NST in the first 20 minutes who received VAS in one of Tehran University's Hospitals were compared with BPP scores. A vibroacoustic stimulation was applied for a 3 seconds on the maternal abdomen and fallowed within 10 minutes.Data collection tools were NST, sonography instruments ,NST result paper, tooth brusher, watch, demographic questioner and check list. Data analysis was made by descriptive static and by using the Fisher's Exact Test (with level of significant at p<0/05. All statistical analysis were performed using an spss/win. Results: After VAS, 70% of non reactive tracing became reactive. All cases with fetal reactivity response after a VAS had a subsequent BPP score of 8 (negative predictive value of 100%. False positivity of VAS was lower than NST. Conclusion: VAS offers benefits, by decreasing the incidence of non reactive test and reducing test time. VAS lowers the rate of false positive NST. VAS is safe and allows more efficient of prenatal services. This test could be used as a rapid antepartum test to predict fetal well-being.

  11. 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....

  12. Testing of resveratrol microemulsion photostability and protective effect against UV induced oxidative stress

    Directory of Open Access Journals (Sweden)

    Juškaitė Vaida

    2017-06-01

    Full Text Available Resveratrol is well known for its antioxidant activity and susceptibility to ultraviolet radiation. Development of formulations providing improved stability and relevant drug delivery of resveratrol is still a challenging task. The aim of this study was to determine protective characteristics of formulated microemulsions by evaluating photoisomerization of resveratrol and to investigate the effects of resveratrol on human keratinocyte cells under oxidative stress caused by ultraviolet radiation. Incorporation of resveratrol into microemulsions resulted in increased photostability of active compounds and the results demonstrated that photodegradation of resveratrol was significantly delayed. Results of biopharmaceutical evaluation in vitro demonstrated that up to 60 % of resveratrol was released from microemulsions within 6 hours under a constant release rate profile. In vivo biological testing confirmed the ability of resveratrol to protect cells from oxidative stress and to increase cell viability. It was concluded that microemulsions might be considered in the development of UV light sensitive compounds.

  13. Testing of resveratrol microemulsion photostability and protective effect against UV induced oxidative stress.

    Science.gov (United States)

    Juškaitė, Vaida; Ramanauskienė, Kristina; Briedis, Vitalis

    2017-06-27

    Resveratrol is well known for its antioxidant activity and susceptibility to ultraviolet radiation. Development of formulations providing improved stability and relevant drug delivery of resveratrol is still a challenging task. The aim of this study was to determine protective characteristics of formulated microemulsions by evaluating photoisomerization of resveratrol and to investigate the effects of resveratrol on human keratinocyte cells under oxidative stress caused by ultraviolet radiation. Incorporation of resveratrol into microemulsions resulted in increased photostability of active compounds and the results demonstrated that photodegradation of resveratrol was significantly delayed. Results of biopharmaceutical evaluation in vitro demonstrated that up to 60 % of resveratrol was released from microemulsions within 6 hours under a constant release rate profile. In vivo biological testing confirmed the ability of resveratrol to protect cells from oxidative stress and to increase cell viability. It was concluded that microemulsions might be considered in the development of UV light sensitive compounds.

  14. Precession relaxation of viscoelastic oblate rotators

    Science.gov (United States)

    Frouard, Julien; Efroimsky, Michael

    2018-01-01

    Perturbations of all sorts destabilize the rotation of a small body and leave it in a non-principal spin state. In such a state, the body experiences alternating stresses generated by the inertial forces. This yields nutation relaxation, i.e. evolution of the spin towards the principal rotation about the maximal-inertia axis. Knowledge of the time-scales needed to damp the nutation is crucial in studies of small bodies' dynamics. In the literature hitherto, nutation relaxation has always been described with aid of an empirical quality factor Q introduced to parametrize the energy dissipation rate. Among the drawbacks of this approach was its inability to describe the dependence of the relaxation rate upon the current nutation angle. This inability stemmed from our lack of knowledge of the quality factor's dependence on the forcing frequency. In this article, we derive our description of nutation damping directly from the rheological law obeyed by the material. This renders us the nutation damping rate as a function of the current nutation angle, as well as of the shape and the rheological parameters of the body. In contradistinction from the approach based on an empirical Q factor, our development gives a zero damping rate in the spherical-shape limit. Our method is generic and applicable to any shape and to any linear rheological law. However, to simplify the developments, here we consider a dynamically oblate rotator with a Maxwell rheology.

  15. Deep postseismic viscoelastic relaxation excited by an intraslab normal fault earthquake in the Chile subduction zone

    Science.gov (United States)

    Bie, Lidong; Ryder, Isabelle; Métois, Marianne

    2017-08-01

    The 2005 Mw 7.8 Tarapaca earthquake was the result of normal faulting on a west-dipping plane at a depth of 90 km within the subducting slab down-dip of the North Chilean gap that partially ruptured in the 2014 M 8.2 Iquique earthquake. We use Envisat observations of nearly four years of postseismic deformation following the earthquake, together with some survey GPS measurements, to investigate the viscoelastic relaxation response of the surrounding upper mantle to the coseismic stress. We constrain the rheological structure by testing various 3D models, taking into account the vertical and lateral heterogeneities in viscosity that one would expect in a subduction zone environment. A viscosity of 4-8 × 1018 Pa s for the continental mantle asthenosphere fits both InSAR line-of-sight (LOS) and GPS horizontal displacements reasonably well. In order to test whether the Tarapaca earthquake and associated postseismic relaxation could have triggered the 2014 Iquique sequence, we computed the Coulomb stress change induced by the co- and postseismic deformation following the Tarapaca earthquake on the megathrust interface and nodal planes of its M 6.7 foreshock. These static stress calculations show that the Tarapaca earthquake may have an indirect influence on the Iquique earthquake, via loading of the M 6.7 preshock positively. We demonstrate the feasibility of using deep intraslab earthquakes to constrain subduction zone rheology. Continuing geodetic observation following the 2014 Iquique earthquake may further validate the rheological parameters obtained here.

  16. Stress hormones at rest and following exercise testing predict coronary artery disease severity and outcome.

    Science.gov (United States)

    Popovic, Dejana; Damjanovic, Svetozar; Djordjevic, Tea; Martic, Dejana; Ignjatovic, Svetlana; Milinkovic, Neda; Banovic, Marko; Lasica, Ratko; Petrovic, Milan; Guazzi, Marco; Arena, Ross

    2017-09-01

    Despite considerable knowledge regarding the importance of stress in coronary artery disease (CAD) pathogenesis, its underestimation persists in routine clinical practice, in part attributable to lack of a standardized, objective assessment. The current study examined the ability of stress hormones to predict CAD severity and prognosis at basal conditions as well as during and following an exertional stimulus. Forty Caucasian subjects with significant coronary artery lesions (≥50%) were included. Within 2 months of coronary angiography, cardiopulmonary exercise testing (CPET) on a recumbent ergometer was performed in conjunction with stress echocardiography (SE). At rest, peak and after 3 min of recovery following CPET, plasma levels of cortisol, adrenocorticotropic hormone (ACTH) and NT-pro-brain natriuretic peptide (NT-pro-BNP) were measured by immunoassay sandwich technique, radioimmunoassay, and radioimmunometric technique, respectively. Subjects were subsequently followed a mean of 32 ± 10 months. Mean ejection fraction was 56.7 ± 9.6%. Subjects with 1-2 stenotic coronary arteries (SCA) demonstrated a significantly lower plasma cortisol levels during CPET compared to those with 3-SCA (p  .05). Among CPET, SE, and hormonal parameters, cortisol at rest and during CPET recovery demonstrated the best predictive value in distinguishing between 1-, 2-, and 3-SCA [area under ROC curve 0.75 and 0.77 (SE = 0.11, 0.10; p = .043, .04) for rest and recovery, respectively]. ΔCortisol peak/rest predicted cumulative cardiac events (area under ROC curve 0.75, SE = 0.10, p = .049). Cortisol at rest and following an exercise test holds predictive value for CAD severity and prognosis, further demonstrating a link between stress and unwanted cardiac events.

  17. The limits of testing particle-mediated oxidative stress in vitro in predicting diverse pathologies; relevance for testing of nanoparticles

    Directory of Open Access Journals (Sweden)

    Gulumian Mary

    2009-04-01

    Full Text Available Abstract In vitro studies with particles are a major staple of particle toxicology, generally used to investigate mechanisms and better understand the molecular events underlying cellular effects. However, there is ethical and financial pressure in nanotoxicology, the new sub-specialty of particle toxicology, to avoid using animals. Therefore an increasing amount of studies are being published using in vitro approaches and such studies require careful interpretation. We point out here that 3 different conventional pathogenic particle types, PM10, asbestos and quartz, which cause diverse pathological effects, have been reported to cause very similar oxidative stress effects in cells in culture. We discuss the likely explanation and implications of this apparent paradox, and its relevance for testing in nanotoxicology.

  18. Biomolecules: Fluctuations and relaxations

    Science.gov (United States)

    Parak, F.; Ostermann, A.; Gassmann, A.; Scherk, C.; Chong, S.-H.; Kidera, A.; Go, N.

    1999-10-01

    The normal-mode refinement of X-ray crystallographic data opened a new possibility to analyze the mean-square displacements in a protein molecule. A comparison of the X-ray structure of myoglobin at several temperatures with Mössbauer data is performed. In the low-temperature regime below 180 K the iron mean-square displacements obtained by Mössbauer spectroscopy are in good agreement with a normal-mode analysis. The X-ray mean-square displacements at the position of the iron, after the motion originated from the external degrees of freedom are subtracted, have practically the same temperature dependence as those from Mössbauer spectroscopy. The difference between the X-ray mean-square displacements and those predicted by normal-mode analysis measures the distribution of molecules into conformational substates. Above 180 K the Mössbauer effect indicates fluctuations between conformational substates. The relaxation from a Fe(III) conformation to a Fe(II) conformation is shown for superoxide dismutase of Propionibacterium shermanii.

  19. Using Phylogenomic Data to Explore the Effects of Relaxed Clocks and Calibration Strategies on Divergence Time Estimation: Primates as a Test Case.

    Science.gov (United States)

    Dos Reis, Mario; Gunnell, Gregg F; Barba-Montoya, José; Wilkins, Alex; Yang, Ziheng; Yoder, Anne D

    2018-01-12

    Primates have long been a test case for the development of phylogenetic methods for divergence time estimation. Despite a large number of studies, however, the timing of origination of crown Primates relative to the K-Pg boundary and the timing of diversification of the main crown groups remain controversial. Here we analysed a dataset of 372 taxa (367 Primates and 5 outgroups, 3.4 million aligned base pairs) that includes nine primate genomes. We systematically explore the effect of different interpretations of fossil calibrations and molecular clock models on primate divergence time estimates. We find that even small differences in the construction of fossil calibrations can have a noticeable impact on estimated divergence times, especially for the oldest nodes in the tree. Notably, choice of molecular rate model (auto-correlated or independently distributed rates) has an especially strong effect on estimated times, with the independent rates model producing considerably more ancient age estimates for the deeper nodes in the phylogeny. We implement thermodynamic integration, combined with Gaussian quadrature, in the program MCMCTree, and use it to calculate Bayes factors for clock models. Bayesian model selection indicates that the auto-correlated rates model fits the primate data substantially better, and we conclude that time estimates under this model should be preferred. We show that for eight core nodes in the phylogeny, uncertainty in time estimates is close to the theoretical limit imposed by fossil uncertainties. Thus, these estimates are unlikely to be improved by collecting additional molecular sequence data. All analyses place the origin of Primates close to the K-Pg boundary, either in the Cretaceous or straddling the boundary into the Palaeogene. © The Author(s) 2018. Published by Oxford University Press, on behalf of the Society of Systematic Biologists.

  20. Microplastic relaxations of single and polycrystalline molybdenum

    Energy Technology Data Exchange (ETDEWEB)

    Pichl, W.; Weiss, B. [Wien Univ. (Austria). Inst. fuer Materialphysik; Chen, D.L.

    1998-05-01

    The microplasticity of high-purity molybdenum single crystals and of Mo polycrystals of technical purity has been investigated by relaxation step tests in uniaxial compression. A new model for the evaluation of relaxation tests in the microplastic range of b.c.c metals is presented which takes into account the decrease of the mobile dislocation density due to exhaustion of non-screw dislocations. The model allows an independent determination of the activation volume and of the microstructure parameters controlling dislocation exhaustion. The results indicate that in the high-purity single crystals the deformation rate is controlled by interactions of non-screw dislocations with the grown-in network. In the polycrystals additional interactions with impurity atoms seem to occur. In the single crystals the activity and subsequent exhaustion of two different glide systems was observed, followed by a gradual onset of screw dislocation motion. (orig.) 26 refs.

  1. RITED (Registro Italiano Test Eco-Dobutamina): side effects and complications of echo-dobutamine stress test in 3041 examinations.

    Science.gov (United States)

    Pezzano, A; Gentile, F; Mantero, A; Morabito, A; Ravizza, P

    1998-02-01

    The aim of the study was to report the incidence and clinical meaning of side-effects caused by echo-dobutamine testing in a large population and to evaluate any possible correlation between dobutamine dose and side-effects. The study population consisted of 3041 patients enrolled from January 1994 to August 1995 at 63 centers participating in the Italian Register of Echo-Dobutamine Testing (Registro Italiano Test Eco-Dobutamina, RITED). The four major indications were myocardial infarction older than one month (40.4%), recent myocardial infarction (22.7%), coronary artery disease without a history of myocardial infarction (10.8%) and suspected coronary artery disease (19.3%). Dobutamine was administered in a peripheral vein at 5, 10, 20, 30, 40 micrograms/kg/minute + atropine 1 mg in four divided doses of 0.25 mg/minute. Severe complications were asystole, which went as high as 6" in one patient, and ventricular fibrillation in two patients. The clinical side-effects were headache (2.5%), hypotension (2.2%), nausea (1.7%), bradycardia (1.4%), palpitations (0.5%), tremors (0.3%), dyspnea (0.2%), paresthesia (0.2%) and hypertension (0.2%). Atrial arrhythmia was recorded in 10.6% of patients, while ventricular arrhythmia was recorded in 26.5%. The percentage of supraventricular and ventricular repetitive arrhythmia did not increase with dosage. The cumulative incidence of supraventricular and ventricular repetitive arrhythmia, considered as an interruption criteria, was 6.6% and 5.9%, respectively. Echo-dobutamine stress test seems to be a very safe and reliable test for unmasking myocardial ischemia or viability in known or suspected coronary artery disease. It has been shown to be widely applicable in clinical practice for outpatients as well, as long as a protected environment is available.

  2. Stress, Social Support, and Depression: A Test of the Stress-Buffering Hypothesis in a Mexican Sample

    Science.gov (United States)

    Raffaelli, Marcela; Andrade, Flavia C. D.; Wiley, Angela R.; Sanchez-Armass, Omar; Edwards, Laura L.; Aradillas-Garcia, Celia

    2013-01-01

    This study examined social support as a potential moderator between stress and depressive symptoms among Mexican university applicants aged 16--21 years ("N" = 6,715; "M" age = 17.9 years; 55% female). In bivariate analyses, perceived stress was associated with higher levels of depressive symptoms, and social support with lower…

  3. Standard Test Method for Stress-Corrosion of Titanium Alloys by Aircraft Engine Cleaning Materials

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2006-01-01

    1.1 This test method establishes a test procedure for determining the propensity of aircraft turbine engine cleaning and maintenance materials for causing stress corrosion cracking of titanium alloy parts. 1.2 The evaluation is conducted on representative titanium alloys by determining the effect of contact with cleaning and maintenance materials on tendency of prestressed titanium alloys to crack when subsequently heated to elevated temperatures. 1.3 Test conditions are based upon manufacturer's maximum recommended operating solution concentration. This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. For specific precautionary statements, see and .

  4. Comparative Stress Corrosion Cracking and General Corrosion Resistance of Annealed and Hardened 440 C Stainless Steel - New Techniques in Stress Corrosion Testing

    Science.gov (United States)

    Mendreck, M. J.; Hurless, B. E.; Torres, P. D.; Danford, M. D.

    1998-01-01

    The corrosion and stress corrosion cracking (SCC) characteristics of annealed and hardened 440C stainless steel were evaluated in high humidity and 3.5-percent NaCl solution. Corrosion testing consisted of an evaluation of flat plates, with and without grease, in high humidity, as well as electrochemical testing in 3.5-percent NaCl. Stress corrosion testing consisted of conventional, constant strain, smooth bar testing in high humidity in addition to two relatively new techniques under evaluation at MSFC. These techniques involve either incremental or constant rate increases in the load applied to a precracked SE(B) specimen, monitoring the crack-opening-displacement response for indications of crack growth. The electrochemical corrosion testing demonstrated an order of magnitude greater general corrosion rate in the annealed 440C. All techniques for stress corrosion testing showed substantially better SCC resistance in the annealed material. The efficacy of the new techniques for stress corrosion testing was demonstrated both by the savings in time and the ability to better quantify SCC data.

  5. Determination of the flow stress of a magnetorheological fluid under three-dimensional stress states by using a combination of extrusion test and FEM simulation

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Peng-yi; Wang, Zhong-jin, E-mail: wangzj@hit.edu.cn

    2016-12-01

    Magnetorheological fluid (MR fluid), a kind of smart material, has been used as a new pressure-carrying medium in magnetorheological pressure forming (MRPF). The mechanical property of MR fluid under the pressure significantly affects the sheet formability. However, there is little knowledge on the deformation behavior of MR fluid under three-dimensional stress states. In this paper, a new procedure via a combination of extrusion test and FEM simulation has been proposed to determine the flow stress of MR fluids. The experimental device for extrusion test of MR fluids was designed. The flow stresses of a MR fluid (MRF-J01T) under four different magnetic fields were determined through the proposed procedure. In addition, the obtained flow stresses were used in the following FEM simulations to verify the accuracy by comparing with the experimental results. The simulation results were in good agreement with the experimental data, which supports the correctness and practicability of the proposed method. - Highlights: • An effective procedure is proposed to determine the flow stress of MR fluids. • The rheological behaviour of a MR fluid during extrusion tests is studied. • Flow stress curves of a MR fluid under different magnetic fields are obtained.

  6. Diagnostic Value of Electrocardiogram in Predicting Exaggerated Blood Pressure Response to Exercise Stress Testing.

    Science.gov (United States)

    Eshraghi, Ali; Ebdali, Reyhaneh Takalloo; Sajjadi, Seyed Sajed; Golnezhad, Reza

    2016-08-01

    It is believed that an exaggerated blood pressure response (EBPR) to exercise stress test is associated with a higher risk of cardiovascular events. It is also assumed that QT dispersion (QT-d), which was originally proposed to measure the spatial dispersion of ventricular recovery times, may have a relationship to cardiovascular events. The objective of this study was to examine the difference of changes in QT-d, Maxi-QT, Mini-QT, and QT-c (corrected QT interval) of the electrocardiogram in two groups of patients with exaggerated blood pressure responses (EBPR group) and normal responses (control group) to exercise testing. Also, the diagnostic value of each of these criteria in the prediction of EBPR was studied. This cross-sectional study was conducted from May 2015 to February 2016 on patients suspected of coronary artery disease (CAD) undergoing exercise testing who had been referred to Ghaem and Imam Reza hospitals in Mashhad (Iran). All patients underwent a treadmill exercise test with the 12-lead ECG, which was optically scanned and digitized for analysis of QT-d, QT max, and QT min. Patients were divided into two groups of normal and EBPR to exercise testing. QT changes of ECG were compared between the two groups, and the diagnostic accuracy of QT variables for prediction of EBPR to exercise testing was studied. A multiple linear regression analysis (MLR), Pearson Chi-qquare, independent samples t-test, and receiver operating characteristic (ROC) curve were used as statistical methods in IBM SPSS version 19. Sixty patients (55% male) with a mean age of 50.48 ± 10.89 years were studied in two groups of normal (n=30) and exaggerated blood pressure response (n=30) to exercise testing. Maximum QT and QT dispersion were statistically different in individuals' exaggerated blood pressure response to exercise stress test (p exercise testing. Also, a significant difference in maxi-QT and QT-d was observed between two groups of patients with normal and EBPR during

  7. Stress Testing of the Montenegrin Banking System with Aggregated and Bank-Specific Data

    Directory of Open Access Journals (Sweden)

    Vuković Sanja

    2014-05-01

    Full Text Available There are many different approaches to the process of stress testing and two of them will be investigated in this paper. The first one is a stress test performed on aggregated data i.e. the banking system as a whole. The variable of interest in both exercises is the Loan Loss Provision ratio (hereinafter: the LLP. The main goal of the thesis is to find an answer to the following question: what are the macroeconomic variables that influence LLP the most and how will LLP, as a variable of interest, behave in a situation when all these variables were to experience negative performance at the same time? The resilience of the banking system to such scenario will be tested through the capital adequacy ratio. In order to find out more about the management practices of banks, microlevel data on banks were also used in the analysis. The focus was to see which of the variables are able to explain the LLP ratio for each bank individually and how is this information helpful for possible improvements in the banking sector. The relations between these variables will be able to explain some of the banks’ losses and some of the banks’ practices regarding credit activities. The analysis there will provide for some recommendations for the banks but also for the Central Bank and its way to influence the practices in the banking sector.

  8. How stress and anxiety can alter immediate and late phase skin test responses in allergic rhinitis.

    Science.gov (United States)

    Kiecolt-Glaser, Janice K; Heffner, Kathi L; Glaser, Ronald; Malarkey, William B; Porter, Kyle; Atkinson, Cathie; Laskowski, Bryon; Lemeshow, Stanley; Marshall, Gailen D

    2009-06-01

    Allergic rhinitis (AR) is the fifth most common chronic disease, and the association between allergic disorders and anxiety is well-documented. To investigate how anxiety and stressors modulate skin prick test (SPT) responses and associated inflammatory responses, 28 men and women with AR were selected by clinical history and skin test responses. The participants were admitted twice to a hospital research unit for 4h in a crossover trial. Changes in SPT wheals were assessed before and after a standardized laboratory speech stressor, as well as again the following morning; skin responses assessed twice during a lab session without a stressor and again the following morning served as the contrast condition. Anxiety heightened the magnitude of allergen-induced wheals following the stressor. As anxiety increased, SPT wheal diameters increased after the stressor, compared to a slight decrease following the control task. Anxiety also substantially enhanced the effects of stress on late phase responses: even skin tests performed the day after the stressor reflected the continuing impact of the speech stressor among the more anxious participants. Greater anxiety was associated with more IL-6 production by Con A-stimulated leukocytes following the stressor compared to the control visit. The data suggest that stress and anxiety can enhance and prolong AR symptoms.

  9. The accuracy of the electrocardiogram during exercise stress test based on heart size.

    Directory of Open Access Journals (Sweden)

    Jason C Siegler

    Full Text Available BACKGROUND: Multiple studies have shown that the exercise electrocardiogram (ECG is less accurate for predicting ischemia, especially in women, and there is additional evidence to suggest that heart size may affect its diagnostic accuracy. HYPOTHESIS: The purpose of this investigation was to assess the diagnostic accuracy of the exercise ECG based on heart size. METHODS: We evaluated 1,011 consecutive patients who were referred for an exercise nuclear stress test. Patients were divided into two groups: small heart size defined as left ventricular end diastolic volume (LVEDV <65 mL (Group A and normal heart size defined as LVEDV ≥65 mL (Group B and associations between ECG outcome (false positive vs. no false positive and heart size (small vs. normal were analyzed using the Chi square test for independence, with a Yates continuity correction. LVEDV calculations were performed via a computer-processing algorithm. SPECT myocardial perfusion imaging was used as the gold standard for the presence of coronary artery disease (CAD. RESULTS: Small heart size was found in 142 patients, 123 female and 19 male patients. There was a significant association between ECG outcome and heart size (χ(2 = 4.7, p = 0.03, where smaller hearts were associated with a significantly greater number of false positives. CONCLUSIONS: This study suggests a possible explanation for the poor diagnostic accuracy of exercise stress testing, especially in women, as the overwhelming majority of patients with small heart size were women.

  10. Stress Wave Attenuation in Aluminum Alloy and Mild Steel Specimens Under SHPB Tensile Testing

    Science.gov (United States)

    Pothnis, J. R.; Ravikumar, G.; Arya, H.; Yerramalli, Chandra S.; Naik, N. K.

    2018-01-01

    Investigations on the effect of intensity of incident pressure wave applied through the striker bar on the specimen force histories and stress wave attenuation during split Hopkinson pressure bar (SHPB) tensile testing are presented. Details of the tensile SHPB along with Lagrangian x-t diagram of the setup are included. Studies were carried out on aluminum alloy 7075 T651 and IS 2062 mild steel. While testing specimens using the tensile SHPB setup, it was observed that the force calculated from the transmitter bar strain gauge was smaller than the force obtained from the incident bar strain gauge. This mismatch between the forces in the incident bar and the transmitter bar is explained on the basis of stress wave attenuation in the specimens. A methodology to obtain force histories using the strain gauges on the specimen during SHPB tensile testing is also presented. Further, scanning electron microscope images and photomicrographs are given. Correlation between the microstructure and mechanical properties is explained. Further, uncertainty analysis was conducted to ascertain the accuracy of the results.

  11. Laterality as an indicator of emotional stress in ewes and lambs during a separation test.

    Science.gov (United States)

    Barnard, Shanis; Matthews, Lindsay; Messori, Stefano; Podaliri-Vulpiani, Michele; Ferri, Nicola

    2016-01-01

    We assessed motor laterality in sheep to explore species-specific brain hemi-field dominance and how this could be affected by genetic or developmental factors. Further, we investigated whether directionality and strength of laterality could be linked to emotional stress in ewes and their lambs during partial separation. Forty-three ewes and their singleton lambs were scored on the (left/right) direction of turn in a y-maze to rejoin a conspecific (laterality test). Further, their behavioural response (i.e. time spent near the fence, vocalisations, and activity level) during forced separation by an open-mesh fence was assessed (separation test). Individual laterality was recorded for 44.2% ewes (significant right bias) and 81.4% lambs (equally biased to the left and the right). There was no significant association in side bias between dams and offspring. The Chi-squared test revealed a significant population bias for both groups (p separation than non-lateralised animals (p separation stress.

  12. EXPERT PANEL OVERSIGHT COMMITTEE ASSESSMENT OF FY2008 CORROSION AND STRESS CORROSION CRACKING SIMULANT TESTING PROGRAM

    Energy Technology Data Exchange (ETDEWEB)

    BOOMER KD

    2009-01-08

    The Expert Panel Oversight Committee (EPOC) has been overseeing the implementation of selected parts of Recommendation III of the final report, Expert Panel workshop for Hanford Site Double-Shell Tank Waste Chemistry Optimization, RPP-RPT-22126. Recommendation III provided four specific requirements necessary for Panel approval of a proposal to revise the chemistry control limits for the Double-Shell Tanks (DSTs). One of the more significant requirements was successful performance of an accelerated stress corrosion cracking (SCC) experimental program. This testing program has evaluated the optimization of the chemistry controls to prevent corrosion in the interstitial liquid and supernatant regions of the DSTs.

  13. Investigating the cognitive precursors of emotional response to cancer stress: re-testing Lazarus's transactional model.

    Science.gov (United States)

    Hulbert-Williams, N J; Morrison, V; Wilkinson, C; Neal, R D

    2013-02-01

    Lazarus's Transactional Model of stress and coping underwent significant theoretical development through the 1990s to better incorporate emotional reactions to stress with their appraisal components. Few studies have robustly explored the full model. This study aimed to do so within the context of a major life event: cancer diagnosis. A repeated measures design was used whereby data were collected using self-report questionnaire at baseline (soon after diagnosis), and 3- and 6-month follow-up. A total of 160 recently diagnosed cancer patients were recruited (mean time since diagnosis = 46 days). Their mean age was 64.2 years. Data on appraisals, core-relational themes, and emotions were collected. Data were analysed using both Spearman's correlation tests and multivariate regression modelling. Longitudinal analysis demonstrated weak correlation between change scores of theoretically associated components and some emotions correlated more strongly with cognitions contradicting theoretical expectations. Cross-sectional multivariate testing of the ability of cognitions to explain variance in emotion was largely theory inconsistent. Although data support the generic structure of the Transactional Model, they question the model specifics. Larger scale research is needed encompassing a wider range of emotions and using more complex statistical testing. WHAT IS ALREADY KNOWN ON THIS SUBJECT?: • Stress processes are transactional and coping outcome is informed by both cognitive appraisal of the stressor and the individual's emotional response (Lazarus & Folkman, 1984). • Lazarus (1999) made specific hypotheses about which particular stress appraisals would determine which emotional response, but only a small number of these relationships have been robustly investigated. • Previous empirical testing of this theory has been limited by design and statistical limitations. WHAT DOES THIS STUDY ADD?: • This study empirically investigates the cognitive precedents of a

  14. Anti-ischemic therapy and stress testing: pathophysiologic, diagnostic and prognostic implications

    Science.gov (United States)

    Sicari, Rosa

    2004-01-01

    Anti-ischemic therapy, in particular beta-blockers, is the most commonly employed drug for the control of myocardial ischemia in patients with stable coronary artery disease. Its widespread use also in patients with suspected coronary artery disease has important practical, clinical diagnostic and prognostic implications because diagnostic tests are heavily influenced by its effects. In the present review, the pathophysiological mechanisms of ischemia protection by antianginal therapy are described. Not all stressors are created equal in front of the different classes of antianginal drugs and on their turn the different classes of drugs exert different levels of protection on inducible ischemia. Several clinical implications can be drawn: From the diagnostic viewpoint antianginal therapy decreases test sensitivity, offsetting the real ischemic burden for a too high percentage of false negative tests. From the prognostic viewpoint test positivity in medical therapy identifies a group of subjects at higher risk of experiencing cardiac death and positivity on medical therapy can be considered a parameter of ischemia severity. Nonetheless in patients with known coronary artery disease the ability of antianginal therapy to modify the ischemic threshold at stress testing represent a powerful means to assess therapy efficacy. From a practical viewpoint, the use of antianginal therapy at time of testing has advantages and disadvantages which are largely dependent on the purpose a test is performed: if the purpose of testing is to diagnose ischemia, it should be performed in the absence of antianginal medications. If the purpose of testing is to assess the protective effects of antianginal therapy, the test should be performed on medications. PMID:15320951

  15. Testing the relationship between human occupancy in the landscape and tadpole developmental stress.

    Directory of Open Access Journals (Sweden)

    Paula C Eterovick

    Full Text Available Amphibian population declines are widespread; the main causal factors are human related and include habitat fragmentation due to agriculture, mining, fires, and urban development. Brazil is the richest country in species of amphibians, and the Brazilian regions with the greatest amphibian diversity are experiencing relatively high rates of habitat destruction, but there are presently relatively few reports of amphibian declines. It is thus important to develop research methods that will detect deterioration in population health before severe declines occur. We tested the use of measurements of fluctuating asymmetry (FA taken on amphibian larvae to detect anthropogenic stress. We hypothesized that greater human occupancy in the landscape might result in more stressful conditions for amphibians. We conducted this study at the Espinhaço mountain range in southeastern Brazil, using as a model an endemic species (Bokermannohyla saxicola, Hylidae. We chose two tadpole denticle rows and eye-nostril distance as traits for FA measurement. We measured percent cover of human-altered habitats in the landscape around tadpole sampling points and measured FA levels in sampled tadpoles. We found FA levels to differ among localities but found no relationship between human modification of the landscape and tadpole FA levels. Levels of FA in the traits we examined may not be strongly affected by environmental conditions, or may be affected by local variables that were not captured by our landscape-scale measures. Alternatively, populations may be genetically differentiated, affecting how FA levels respond to stress and obscuring the effects of anthropogenic disturbance.

  16. Testing the stress-response sequence model in paediatric oncology nursing.

    Science.gov (United States)

    Hinds, P S; Sanders, C B; Srivastava, D K; Hickey, S; Jayawardene, D; Milligan, M; Olson, M S; Puckett, P; Quargnenti, A; Randall, E A; Tyc, V

    1998-11-01

    The causes and intensity of role-related stress experienced by paediatric oncology nurses, the nurses' ability to respond to the stressors, and the professional and personal consequences of those stressors for the nurses are issues of concern for administrators and staff. The concern evolves from the anticipated relationships among stressors, the ability to cope with role-related stressors, and the expected negative outcomes such as resignation. However, the relationships among these components have not been previously measured concurrently in paediatric oncology nurses. The primary purpose of this study was to test the complete stress-response sequence model in a sample of paediatric oncology nurses by obtaining concurrent measures of the model's individual components: nurses' stressors, reactions, mediators, and consequences. A total of 126 nurses completed six questionnaires (Stressor Scale for Paediatric Oncology Nurses, Perceived Stress Scale, Measure of Job Satisfaction, Organized Commitment Questionnaire, Group Cohesion Scale, and Intent to Leave) and a demographic sheet. The majority of participating nurses were married, worked full-time and had worked 5 or more years in oncology. Qualitative data were analysed using a semantic content analysis technique. Relationships among the components of the model were examined using a two-stage least squares technique. The components were only weakly associated and unable to explain significant variation in each other. The combined qualitative and quantitative data indicate that an important explanatory variable - role-related meaning - is missing in the content model.

  17. Testing the Relationship between Human Occupancy in the Landscape and Tadpole Developmental Stress

    Science.gov (United States)

    Eterovick, Paula C.; Bar, Luís F. F.; Souza, Jorge B.; Castro, José F. M.; Leite, Felipe S. F.; Alford, Ross A.

    2015-01-01

    Amphibian population declines are widespread; the main causal factors are human related and include habitat fragmentation due to agriculture, mining, fires, and urban development. Brazil is the richest country in species of amphibians, and the Brazilian regions with the greatest amphibian diversity are experiencing relatively high rates of habitat destruction, but there are presently relatively few reports of amphibian declines. It is thus important to develop research methods that will detect deterioration in population health before severe declines occur. We tested the use of measurements of fluctuating asymmetry (FA) taken on amphibian larvae to detect anthropogenic stress. We hypothesized that greater human occupancy in the landscape might result in more stressful conditions for amphibians. We conducted this study at the Espinhaço mountain range in southeastern Brazil, using as a model an endemic species (Bokermannohyla saxicola, Hylidae). We chose two tadpole denticle rows and eye-nostril distance as traits for FA measurement. We measured percent cover of human-altered habitats in the landscape around tadpole sampling points and measured FA levels in sampled tadpoles. We found FA levels to differ among localities but found no relationship between human modification of the landscape and tadpole FA levels. Levels of FA in the traits we examined may not be strongly affected by environmental conditions, or may be affected by local variables that were not captured by our landscape-scale measures. Alternatively, populations may be genetically differentiated, affecting how FA levels respond to stress and obscuring the effects of anthropogenic disturbance. PMID:25793699

  18. Testing the stress gradient hypothesis in herbivore communities facilitation peaks at intermediate nutrient levels.

    Science.gov (United States)

    Bakker, Elisabeth S; Dobrescu, Ioana; Straile, Dietmar; Holmgren, Milena

    2013-08-01

    The role of positive interactions in structuring plant and animal communities is increasingly recognized, but the generality of current theoretical models has remained practically unexplored in animal communities. The stress gradient hypothesis predicts a linear increase in the intensity of facilitation as environmental conditions become increasingly stressful, whereas other theoretical models predict a maximum at intermediate environmental stress. We tested how competition and facilitation between herbivores change over a manipulated gradient of nutrient availability. We studied the effect of grazing by pond snails (Lymnaea stagnalis L.) as bulk grazers on aquatic caterpillars (Acentria ephemerella Denis and Schiffermüller) as small specialist grazers along an experimental gradient of environmental nutrient concentration. Higher nutrient levels increased overall total plant biomass but induced a shift toward dominance of filamentous algae at the expense of macrophytes. Facilitation of caterpillars by snail presence peaked at intermediate nutrient levels. Both caterpillar biomass and caterpillar grazing on macrophytes were highest at intermediate nutrient levels. Snails facilitated caterpillars possibly by removing filamentous algae and increasing access to the macrophyte resource, whereas they did not affect macrophyte biomass or C: nutrient ratios, a measure of food quality. We conclude that competition and facilitation in herbivore communities change along nutrient availability gradients that affect plant biomass and community composition. Understanding how interspecific interactions may change in strength and direction along environmental gradients is important to predict how the diversity and structure of communities may respond to the introduction or removal of herbivore species in ecosystems.

  19. Protective effects of melatonin against arsenic-induced apoptosis and oxidative stress in rat testes.

    Science.gov (United States)

    Uygur, Ramazan; Aktas, Cevat; Caglar, Veli; Uygur, Emine; Erdogan, Hasan; Ozen, Oguz Aslan

    2016-05-01

    This study aimed to investigate the protective effects of melatonin against arsenic-induced apoptosis and oxidative stress in rat testes. A total of 27 male rats were divided into 3 groups: control (saline: 5 ml kg(-1) day(-1), intragastrically), arsenic (sodium arsenite (NaAsO2): 5 mg kg(-1) day(-1), intragastrically), and arsenic + melatonin (sodium arsenite (NaAsO2): 5 mg kg(-1) day(-1), intragastrically and melatonin: 25 mg kg(-1) day(-1), intraperitoneally) group. At the end of 30 days, the rats were killed under anesthesia. Histopathological examination showed that testicular injury mediated by arsenic was ameliorated by the administration of melatonin. The number of apoptotic germ cell was increased, and the number of proliferating cell nuclear antigen (PCNA)-positive germ cell was decreased in testis after arsenic administration. Our data indicate a significant reduction in the activity of terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling, and there was a rise in the expression of PCNA in testis of arsenic + melatonin group. The decreased superoxide dismutase, catalase, and glutathione peroxidase activities as well as increased malondialdehyde levels in testis due to arsenic administration were also counteracted by melatonin. These data suggested that melatonin has beneficial effects against arsenic-induced testicular damage by decreasing morphological damage, germ cell apoptosis, lipid peroxidation, and oxidative stress. Our results suggest that melatonin plays a protective role against arsenic-induced testicular apoptosis and oxidative stress. © The Author(s) 2013.

  20. Stress

    OpenAIRE

    Jensen, Line Skov; Lova, Lotte; Hansen, Zandra Kulikovsky; Schønemann, Emilie; Larsen, Line Lyngby; Colberg Olsen, Maria Sophia; Juhl, Nadja; Magnussen, Bogi Roin

    2012-01-01

    Stress er en tilstand som er meget omdiskuteret i samfundet, og dette besværliggør i en vis grad konkretiseringen af mulige løsningsforslag i bestræbelsen på at forebygge den såkaldte folkesygdom. Hovedkonklusionen er, at selv om der bliver gjort meget for at forebygge, er der ikke meget der aktivt kan sættes i værk for at reducere antallet af stressramte, før en fælles forståelse af stressårsager og effektiv stresshåndtering er fremlagt. Problemformuleringen er besvaret gennem en undersø...