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Sample records for hertz stress-life exponent

Relation Between Hertz Stress-Life Exponent, Ball-Race Conformity, and Ball Bearing Life

Science.gov (United States)

Zaretsky, Erwin V.; Poplawski, Joseph V.; Root, Lawrence E.

2008-01-01

ANSI/ABMA and ISO standards based on Lundberg-Palmgren bearing life theory are normalized for ball bearings having inner- and outerrace conformities of 52 percent (0.52) and made from pre-1940 bearing steel. The Lundberg-Palmgren theory incorporates an inverse 9th power relation between Hertz stress and fatigue life for ball bearings. The effect of race conformity on ball set life independent of race life is not incorporated into the Lundberg-Palmgren theory. In addition, post-1960 vacuum-processed bearing steel exhibits a 12th power relation between Hertz stress and life. The work reported extends the previous work of Zaretsky, Poplawski, and Root to calculate changes in bearing life--that includes the life of the ball set--caused by race conformity, Hertz stress-life exponent, ball bearing type and bearing series. The bearing fatigue life in actual application will usually be equal to or greater than that calculated using the ANSI/ABMA and ISO standards that incorporate the Lundberg-Palmgren theory. The relative fatigue life of an individual race is more sensitive to changes in race conformity for Hertz stress-life exponent n of 12 than where n = 9. However, when the effects are combined to predict actual bearing life for a specified set of conditions and bearing geometry, the predicted life of the bearing will be greater for a value of n = 12 than n = 9.
Relation Between Residual and Hoop Stresses and Rolling Bearing Fatigue Life

Science.gov (United States)

Oswald, Fred B.; Zaretsky, Erwin V.; Poplawski, Joseph V.

2015-01-01

Rolling-element bearings operated at high speed or high vibration may require a tight interference fit between the bore of the bearing and shaft to prevent rotation of the bearing bore around the shaft and fretting damage at the interfaces. Previous work showed that the hoop stresses resulting from tight interference fits can reduce bearing lives by as much as 65 percent. Where tight interference fits are required, case-carburized steel such as AISI 9310 or M50 NiL is often used because the compressive residual stresses inhibit subsurface crack formation and the ductile core inhibits inner-ring fracture. The presence of compressive residual stress and its combination with hoop stress also modifies the Hertz stress-life relation. This paper analyzes the beneficial effect of residual stresses on rolling-element bearing fatigue life in the presence of high hoop stresses for three bearing steels. These additional stresses were superimposed on Hertzian principal stresses to calculate the inner-race maximum shearing stress and the resulting fatigue life of the bearing. The load-life exponent p and Hertz stress-life exponent n increase in the presence of compressive residual stress, which yields increased life, particularly at lower stress levels. The Zaretsky life equation is described and is shown to predict longer bearing lives and greater load- and stress-life exponents, which better predicts observed life of bearings made from vacuum-processed steel.
Reevaluation of the stress-life relation in rolling-element bearings

Science.gov (United States)

Parker, R. J.; Zaretsky, E. V.

1972-01-01

Four groups of 12.7 millimeter diameter vacuum-degassed AISI 52100 balls were tested, each at a maximum Hertz stress in the range of 4.5 times 10 to 9th power to 6.0 times 10 to 9th power N/m2. Tests were run in the five-ball fatigue tester at a contact angle of 30 deg and a shaft speed of 10,000 rpm. The 10 percent fatigue lives at the four stress levels indicated that fatigue life is inversely proportional to maximum Hertz stress raised to the power of 12. This result agrees with a survey of the literature which suggests that a stress-life exponent of approximately 12 is typical of vacuum-processed bearing steels rather than the exponent of 9 which has been generally accepted by the bearing industry.
Profiled Roller Stress/Fatigue Life Analysis Methodology and Establishment of an Appropriate Stress/Life Exponent

Science.gov (United States)

1997-01-01

The objective of this work was to determine the three dimensional volumetric stress field, surface pressure distribution and actual contact area between a 0.50" square roller with different crown profiles and a flat raceway surface using Finite Element Analysis. The 3-dimensional stress field data was used in conjunction with several bearing fatigue life theories to extract appropriate values for stress-life exponents. Also, results of the FEA runs were used to evaluate the laminated roller model presently used for stress and life prediction.
Stress-life relation of the rolling-contact fatigue spin rig

Science.gov (United States)

Butler, Robert H; Carter, Thomas L

1957-01-01

The rolling-contact fatigue spin rig was used to test groups of SAE 52100 9.16-inch-diameter balls lubricated with a mineral oil at 600,000-, 675,000-, and 750,000-psi maximum Hertz stress. Cylinders of AISI M-1 vacuum and commercial melts and MV-1 (AISI M-50) were used as race specimens. Stress-life exponents produced agree closely with values accepted in industry. The type of failure obtained in the spin rig was similar to the subsurface fatigue spells found in bearings.
Rolling Bearing Life Prediction, Theory, and Application

Science.gov (United States)

Zaretsky, Erwin V.

2016-01-01

A tutorial is presented outlining the evolution, theory, and application of rolling-element bearing life prediction from that of A. Palmgren, 1924; W. Weibull, 1939; G. Lundberg and A. Palmgren, 1947 and 1952; E. Ioannides and T. Harris, 1985; and E. Zaretsky, 1987. Comparisons are made between these life models. The Ioannides-Harris model without a fatigue limit is identical to the Lundberg-Palmgren model. The Weibull model is similar to that of Zaretsky if the exponents are chosen to be identical. Both the load-life and Hertz stress-life relations of Weibull, Lundberg and Palmgren, and Ioannides and Harris reflect a strong dependence on the Weibull slope. The Zaretsky model decouples the dependence of the critical shear stress-life relation from the Weibull slope. This results in a nominal variation of the Hertz stress-life exponent. For 9th- and 8th-power Hertz stress-life exponents for ball and roller bearings, respectively, the Lundberg-Palmgren model best predicts life. However, for 12th- and 10th-power relations reflected by modern bearing steels, the Zaretsky model based on the Weibull equation is superior. Under the range of stresses examined, the use of a fatigue limit would suggest that (for most operating conditions under which a rolling-element bearing will operate) the bearing will not fail from classical rolling-element fatigue. Realistically, this is not the case. The use of a fatigue limit will significantly overpredict life over a range of normal operating Hertz stresses. (The use of ISO 281:2007 with a fatigue limit in these calculations would result in a bearing life approaching infinity.) Since the predicted lives of rolling-element bearings are high, the problem can become one of undersizing a bearing for a particular application. Rules had been developed to distinguish and compare predicted lives with those actually obtained. Based upon field and test results of 51 ball and roller bearing sets, 98 percent of these bearing sets had acceptable
Gustav Hertz in Berlin

International Nuclear Information System (INIS)

Rompe, R.

1987-01-01

A brief account of the life and work of the physicist Gustav Hertz (1887-1975) is given with regard to the Franck-Hertz experiment, work on isotope separation by diffusion, and activities as chairman of the council for the peaceful uses of atomic energy
Interference-Fit Life Factors for Ball Bearings

Science.gov (United States)

Oswald, Fred B.; Zaretsky, Erwin V.; Poplawski, Joseph V.

2010-01-01

The effect of hoop stresses on the rolling-element fatigue life of angular-contact and deep-groove ball bearings was determined for common inner-ring interference fits at the ABEC-5 tolerance level. The analysis was applied to over 1150 bearing configurations and load cases. Hoop stresses were superimposed on the Hertzian principal stresses created by the applied bearing load to calculate the inner-race maximum shearing stress. The resulting fatigue life of the bearing was recalculated through a series of equations. The reduction in the fatigue life is presented as life factors that are applied to the unfactored bearing life. The life factors found in this study ranged from 1.00 (no life reduction)--where there was no net interface pressure--to a worst case of 0.38 (a 62-percent life reduction). For a given interference fit, the reduction in life is different for angular-contact and deep-groove ball bearings. Interference fits also affect the maximum Hertz stress-life relation. Experimental data of Czyzewski, showing the effect of interference fit on rolling-element fatigue life, were reanalyzed to determine the shear stress-life exponent. The Czyzewski data shear stress-life exponent c equals 8.77, compared with the assumed value of 9. Results are presented as tables and charts of life factors for angular-contact and deep-groove ball bearings with light, normal, and heavy loads and interference fits ranging from extremely light to extremely heavy.
Development of a high hertz-stress contact for conventional batch production using a unique scribing technology

International Nuclear Information System (INIS)

Bhuiyan, M M I; Alamgir, T; Bhuiyan, M; Kajihara, M

2013-01-01

Gradually the electronic devices are getting more compact dimension with respect to the width and thickness. As a result, the contacts are becoming thinner and which leads the contact to be loose and unstable contact. In comercial stamping methode, connector tip diameter should be more than 300μm due to its size limitation. Consequently, the connector contact resistance is becoming higher due to weak contact force. To overcome this problem there were few more basic research using MEMS and Electro Fine Forming (EFF) technology to make high Hertz-Stress Contact (5μm) due to the limitation in the commercial stamping process and the result was in satisfactory level. However, since the MEMS and EFF fabrication is costly therefore, a new method is introduced in this paper using the commercial Phosphor Bronze stamping method to reduce the production cost. Moreover, scribing method is used to make tip on the contact. Accordingly, more compact fine pitch contact is successfully fabricated and tested with 5μm High Hertz Stress without using the MEMS and EFF technology. Hence the manufactured contact resistance becomes less than 20mΩ ±5mΩ
Effect of residual stresses induced by prestressing on rolling element fatigue life

Science.gov (United States)

Parker, R. J.; Zaretsky, E. V.

1972-01-01

A mechanical prestress cycle suitable to induce compressive stress beneath the surface of the inner race of radially loaded 207-size bearings was determined. Compressive residual stress in excess 0.69 x 10 to the 9th power N/sq m (100,000 psi), as measured by X-ray diffraction, were induced at the depth of maximum shearing stress. The prestress cycle consisted of running the bearings for 25 hours at 2750 rpm at a radial load which produced a maximum Hertz stress of 3.3 x 10 to the 9th power N/sq m (480,000 psi) at the contact of the inner race and the heaviest loaded ball. Bearings subjected to this prestress cycle and subsequently fatigue tested gave a 10 percent fatigue life greater than twice that of a group of baseline bearings.
Remembering Gustav Hertz

International Nuclear Information System (INIS)

Rompe, R.

1987-01-01

The scientific achievements of Gustav Hertz are appreciated on the basis of personal memories. Emphasis is laid on the work of this strong personality with regard to industry- and technology-oriented research and as chairman of the 'Council for peaceful uses of nuclear energy in the GDR'. (author)
Franck--Hertz experiment with higher excitation level measurements

International Nuclear Information System (INIS)

Liu, F.H.

1987-01-01

The measurement of the higher levels of 6 3 P 2 and 6 1 P 1 of the mercury atom in the Franck--Hertz experiment has been introduced into the junior and senior laboratory course by using a homemade tetrode Franck--Hertz tube. The main structure of the tube is described. The optimum operating conditions are in the temperature range between 130 and 150 0 C and the collector currents are of the order of 10 -9 A. The additional observations of the famous Franck--Hertz experiment in the laboratory course will give the students more familiarity with the quantum behavior of atoms
Reading Hertz's own dipole theory

International Nuclear Information System (INIS)

Anicin, B A

2008-01-01

It is well known that the discoverer of radio waves, Heinrich Hertz, was the first man to apply Maxwell's electrodynamic theory to a problem in radio wave propagation. In this paper, we scrutinize his near-field lines of force using computers and his theory. In one of his four figures, a feature was found which was not to be obtained by computation. This feature, a self-intersecting line of force, more or less a figure of eight, appears strange to the eye. The clarity of the original work by H Hertz on electromagnetic waves should be of great value in both physics and engineering courses. This holds in particular for his Q function, almost completely forgotten today
Reading Hertz's own dipole theory

Science.gov (United States)

Aničin, B. A.

2008-01-01

It is well known that the discoverer of radio waves, Heinrich Hertz, was the first man to apply Maxwell's electrodynamic theory to a problem in radio wave propagation. In this paper, we scrutinize his near-field lines of force using computers and his theory. In one of his four figures, a feature was found which was not to be obtained by computation. This feature, a self-intersecting line of force, more or less a figure of eight, appears strange to the eye. The clarity of the original work by H Hertz on electromagnetic waves should be of great value in both physics and engineering courses. This holds in particular for his Q function, almost completely forgotten today.
Geometrizing configurations. Heinrich Hertz and his mathematical precursors

DEFF Research Database (Denmark)

Lützen, Jesper

1999-01-01

A comparison between the methods used by Heinrich hertz and his mathematician precursors such as Liouville, Lipschitz and Darboux in order to apply differential geometry in mechanics......A comparison between the methods used by Heinrich hertz and his mathematician precursors such as Liouville, Lipschitz and Darboux in order to apply differential geometry in mechanics...
Predicting guar seed splitting by compression between two plates using Hertz theory of contact stresses.

Science.gov (United States)

Vishwakarma, R K; Shivhare, U S; Nanda, S K

2012-09-01

Hertz's theory of contact stresses was applied to predict the splitting of guar seeds during uni-axial compressive loading between 2 rigid parallel plates. The apparent modulus of elasticity of guar seeds varied between 296.18 and 116.19 MPa when force was applied normal to hilum joint (horizontal position), whereas it varied between 171.86 and 54.18 MPa when force was applied in the direction of hilum joint (vertical position) with in moisture content range of 5.16% to 15.28% (d.b.). At higher moisture contents, the seeds yielded after considerable deformation, thus showing ductile nature. Distribution of stresses below the point of contact were plotted to predict the location of critical point, which was found at 0.44 to 0.64 mm and 0.37 to 0.53 mm below the contact point in vertical and horizontal loading, respectively, depending upon moisture content. The separation of cotyledons from each other initiated before yielding of cotyledons and thus splitting of seed took place. The relationships between apparent modulus of elasticity, principal stresses with moisture content were described using second-order polynomial equations and validated experimentally. Manufacture of guar gum powder requires dehulling and splitting of guar seeds. This article describes splitting behavior of guar seeds under compressive loading. Results of this study may be used for design of dehulling and splitting systems of guar seeds. © 2012 Institute of Food Technologists®
The Creation of Scientific Effects Heinrich Hertz and Electric Waves

CERN Document Server

Buchwald, Jed Z

1994-01-01

This book is an attempt to reconstitute the tacit knowledge—the shared, unwritten assumptions, values, and understandings—that shapes the work of science. Jed Z. Buchwald uses as his focus the social and intellectual world of nineteenth-century German physics. Drawing on the lab notes, published papers, and unpublished manuscripts of Heinrich Hertz, Buchwald recreates Hertz's 1887 invention of a device that produced electromagnetic waves in wires. The invention itself was serendipitous and the device was quickly transformed, but Hertz's early experiments led to major innovations in electrodyna
Gustav-Hertz-Prize for CERN Physicist

CERN Multimedia

2004-01-01

Klaus Blaum, of GSI Darmstadt and project leader of the ISOLTRAP experiment at CERN, will receive the 2004 Gustav-Hertz-Prize for his outstanding work on the mass determination of unstable atomic nuclei. Blaum extended the measuring capability of the ISOLTRAP experiment at the ISOLDE facility, which studies short-lived isotopes, by installing a source of carbon clusters. Using these carbon clusters as mass reference allows researchers to obtain higher-precision and absolute atomic mass measurements which are important to understand the weak interaction and the synthesis of chemical elements. The Gustav-Hertz-Prize is awarded to outstanding young physicists and is endowed with 7500 euro. It will be awarded at the Spring Conference of the German Physical Society in Munich on 24 March.
Celebrando São Besso ou o que Robert Hertz e a Escola Francesa de Sociologia têm a nos dizer sobre festas, rituais e simbolismo

Directory of Open Access Journals (Sweden)

Renata de Castro Menezes

2009-01-01

Full Text Available Este artigo apresenta reflexões sobre as possibilidades e as dificuldades do estudo de festas religiosas através da interpretação de um texto de Robert Hertz (um dos pesquisadores da Escola Francesa de Sociologia, originalmente publicado em 1913, que versa sobre a festa de São Besso, um evento religioso que ocorre nos alpes italianos. O objetivo do presente trabalho é destacar as pistas que Hertz deixou abertas em seu estudo e sugerir maneiras de nos apropriarmos de seus insights em nossas análises atuais.This article presents some reflections about the possibilities and difficulties in the study of religious festivals. It does so by reinterpreting a text written by Robert Hertz, one of the researches of the French School of Sociology. It is a text about Saint Besso’s festival, originally published in 1913. The aim of the article is to stress some of the clues that Hertz opened with his work and to suggest how his insights can be useful for our own analyses about festivals.
Deficit or creativity: Cesare Lombroso, Robert Hertz, and the meanings of left-handedness.

Science.gov (United States)

Kushner, Howard I

2013-01-01

In the first decade of the twentieth century two influential researchers attempted to explain the origin and impact of left-handedness in human history. The first, the Turin physician Cesare Lombroso, often referred to as the father of modern criminology, was nearing the end of his long distinguished career. Lombroso tied left-handedness to criminality, insanity, and feeble mindedness. According to Lombroso, these groups shared biological regressions to primitive mentalities that could not be reversed by education or training. The second, French sociologist Robert Hertz, was at the beginning of a career cut short by his death in combat during the First World War. Hertz challenged Lombroso's claims, insisting that the predominance of right-handedness, whatever its biological substrate, was ultimately a cultural artefact driven by a primitive human urge to make sense of the world by dividing it into binary oppositions in which the right was viewed as sacred and the left as profane. Ending discrimination against left-handedness would, according to Hertz, unleash access to both hands and thus both hemispheres. The results, he insisted, would allow repressed talents and creativity to flourish. The conflicting views of Lombroso and Hertz have informed investigations of the causes and consequences of left-handedness until today. While the language of the debate has been reframed in current scientific discourses, left-handedness continues to be portrayed in the contradictory ways first elaborated by Lombroso and Hertz more than a century ago as either the cause of a variety of learning disabilities or as the key that can unlock creativity and talent. The debate also exposed the extent to which other cultural concerns, particularly anti-Semitism, informed theories of handedness.

Does the Hertz solution estimate pressures correctly in diamond indentor experiments?

Science.gov (United States)

Bruno, M. S.; Dunn, K. J.

1986-05-01

The Hertz solution has been widely used to estimate pressures in a spherical indentor against flat matrix type high pressure experiments. It is usually assumed that the pressure generated when compressing a sample between the indentor and substrate is the same as that generated when compressing an indentor against a flat surface with no sample present. A non-linear finite element analysis of this problem has shown that the situation is far more complex. The actual peak pressure in the sample is highly dependent on plastic deformation and the change in material properties due to hydrostatic pressure. An analysis with two material models is presented and compared with the Hertz solution.
[A historic case of Wegener's granulomatosis: the physicist who discovered the electromagnetic waves: Heinrich Hertz].

Science.gov (United States)

Feldmann, H

2005-06-01

A diary and an extensive correspondence of Heinrich Hertz and his family provide a meticulous documentation of his life, made available by Albrecht Folsing in 1997 through a carefully investigated biography, which permit the conclusion that H. Hertz died of Wegener's granulomatosis, 45 years before this disease had been explored. WEGENER'S GRANULOMATOSIS: The symptoms of the granulomatosis, that was first described by Friedrich Wegener in 1936 and 1939 are presented in short with literal quotations of the author: It begins with a refractory cold that will last until the end, then follow involvement of the paranasal sinuses, ears, mucous lining of mouth and pharynx, slight fever, weakness, in the final phase dissemination with nephritis, septic fever, arthritis, myalgia, paralyses leading to total immobility, exitus. The etiology is not fully understood but probably based on immunoreaction. H. HERTZ: CURRICULUM VITAE: Born in Hamburg, Germany, in 1857: after secondary school academic training in physics at Dresden, Munic and Berlin. 1885 professor of physics in Karlsruhe, then starting in 1889 at Bonn. 1887/88 exploration of the electromagnetic waves, now the basis for all radio communication, and exploration of the photoelectric effect, the basis of solar techniques. Numerous highranking distinctions. H. HERTZ: The case history is presented in detail based on numerous literal quotations from personal letters and the diary. After a few banal affections involving the teeth and toes the systemic disease became manifest in summer 1892 with a refractory cold which remained the focus of treatment until death. Granulation tissue in the nose that was excised several times: no tuberculosis, no carcinoma. Otitis with purulent mastoiditis, in October 1892 mastoidectomy, persistent purulence. Early in 1893 diagnosis of nephritis. Extraction of a superior tooth, punturing of the maxillary sinus, then twice radical opening of the maxillary sinus. Painful ankylosis and paralyses
Lyapunov Exponents

CERN Document Server

Crauel, Hans; Eckmann, Jean-Pierre

1991-01-01

Since the predecessor to this volume (LNM 1186, Eds. L. Arnold, V. Wihstutz)appeared in 1986, significant progress has been made in the theory and applications of Lyapunov exponents - one of the key concepts of dynamical systems - and in particular, pronounced shifts towards nonlinear and infinite-dimensional systems and engineering applications are observable. This volume opens with an introductory survey article (Arnold/Crauel) followed by 26 original (fully refereed) research papers, some of which have in part survey character. From the Contents: L. Arnold, H. Crauel: Random Dynamical Systems.- I.Ya. Goldscheid: Lyapunov exponents and asymptotic behaviour of the product of random matrices.- Y. Peres: Analytic dependence of Lyapunov exponents on transition probabilities.- O. Knill: The upper Lyapunov exponent of Sl (2, R) cocycles:Discontinuity and the problem of positivity.- Yu.D. Latushkin, A.M. Stepin: Linear skew-product flows and semigroups of weighted composition operators.- P. Baxendale: Invariant me...
Creep properties of annealed Zr-Nb-O and stress-relieved Zr-Nb-Sn-Fe cladding tubes and their performance comparison

International Nuclear Information System (INIS)

Ko, S.; Hong, S.I.; Kim, K.T.

2010-01-01

Creep properties of annealed Zr-Nb-O and stress-relieved Zr-Nb-Sn-Fe cladding tubes were studied and compared. The creep rates of the annealed Zr-Nb-O alloy were found to be greater than those of the stress-relieved Zr-Nb-Sn-Fe alloy. Zr-Nb-O alloy was found to have stress exponents of 5-7 independent of stress level whereas Zr-Nb-Sn-Fe alloy exhibited the transition of the stress exponent from 6.5 to 7.5 in the lower stress region to ∼4.2 in the higher stress region. The reduction of stress exponent at high stresses in Zr-Nb-Sn-Fe can be explained in terms of the dynamic solute-dislocation effect caused by Sn atoms. The constancy of stress exponent without the transition was observed in Zr-Nb-O alloy, supporting that the decrease of the stress exponent with increasing stress in Zr-Nb-Sn-Fe is associated with Sn atoms. The difference of creep life between annealed Zr-Nb-O and stress-relieved Zr-Nb-Sn-Fe is not large considering the large difference of strength level between annealed Zr-Nb-O and annealed stress-relieved Zr-Nb-Sn-Fe. The better-than-expected creep life of annealed Zr-Nb-O alloy can be attributable to the combined effects of creep ductility enhancement associated with softening and the decreased contribution of grain boundary diffusion due to the increased grain size.
Life prediction of Ni-base superalloy

Indian Academy of Sciences (India)

mean stress exponent, n, and the mean activation energy for creep were calculated from the experimental results. The accelerated creep life of the alloy was evaluated by using iso-stress parametric equations and Monkman–Grant method. Keywords. ... This alloy is age-hardenable by a fine dispersion of γ par- ticles, which ...
The application of the consecutive-Woehler-curve-concept in computation of the life values for multi-stage creep

International Nuclear Information System (INIS)

Schott, G.

1991-01-01

It is known that at multi-stage creep load there cannot be calculated any reliable life values by means of linear damage accumulation hypotheses. A practicable non-linear statement was proposed by Pantelakis. Besides the one-stage creep life curve, results from two-stage tests are required for determining the damage exponent. With this exponent, which is a function of temperature and stress in the load stage applied first, the life values can be calculated only for two-stage sequences whose stress stages have to be identical to those of the two-stage tests. For the application of the consecutive Woehler curve concept described in the following there is required the knowledge of the one-stage creep life curve and of the creep function for increasing and decreasing stress sequences derived from two-stage tests. Then, the life values can be calculated for the most different multi-stage loads. The stress stages should lie within the stress range used in the two-stage tests. (orig.) [de
The harmonic oscillator in the forceless mechanics of Hertz and in the Riemannian space-time geometry

International Nuclear Information System (INIS)

Fueloep, L.

1987-10-01

The forceless mechanics of Hertz is a reformulation of the classical mechanics in a curved configuration space. The relationship between the forceless mechanics and the general relativity theory which uses curved Riemann spaces as well is investigated on the simple example of the harmonic oscillator. The mathematical similarities and differences and the different interpretations of similar formulas are discussed. Some formal constants of the Hertz mechanics have got concrete physical meanings in the general relativity. (D.Gy.)
A Matter of Matter or a Matter of Space? Heinrich Hertz's Image of Mass in his Prinzipien der Mechanik

DEFF Research Database (Denmark)

Lützen, Jesper

1999-01-01

It is argued that Hertz introduced Massenteilchen in his Principles of Mechanics because they allowed him to deduce the line element of his differential geometric formalism......It is argued that Hertz introduced Massenteilchen in his Principles of Mechanics because they allowed him to deduce the line element of his differential geometric formalism...
Stressful life events, vulnerable to stress and depression among ...

African Journals Online (AJOL)

The present study was carried out to observe the difference between male and female Eritrean students on the basis of stressful life events, vulnerable to stress and depression. Stressful life Events Questionnaire, Vulnerable to Stress Instrument and Beck Depression Scale were administered to gather information. The data ...
Life stress and mental disorders in the South African Stress and ...

African Journals Online (AJOL)

Life stress and mental disorders in the South African Stress and Health study. ... Although stressful life events (SLEs) are associated with psychopathology, the ... life stress and sociodemographic predictors of 12-month and lifetime disorder.
Prediction of life stress on athletes' burnout: the dual role of perceived stress.

Science.gov (United States)

Chyi, Theresa; Lu, Frank Jing-Horng; Wang, Erica T W; Hsu, Ya-Wen; Chang, Ko-Hsin

2018-01-01

Although many studies adopted Smith's (1986) cognitive-affective model of athletic burnout in examining stress-burnout relationship, very few studies examined the mediating/moderating role of perceived stress on the stress-burnout relationship. We sampled 195 college student-athletes and assessed their life stress, perceived stress, and burnout. Correlation analyses found all study variables correlated. Two separate hierarchical regression analyses found that the "distress" component of perceived stress mediated athletes' two types of life stress-burnout relationship but "counter-stress" component of perceived stress-moderated athletes' general-life stress-burnout relationship. We concluded that interweaving relationships among athletes' life stress, perceived stress, and burnout are not straightforward. Future research should consider the nature of athletes life stress, and dual role of perceived stress in examining its' association with related psychological responses in athletic settings.
WeChat Addiction Suppresses the Impact of Stressful Life Events on Life Satisfaction.

Science.gov (United States)

Li, Bi; Wu, Yan; Jiang, Shengyi; Zhai, Huizhen

2018-03-01

The current study examined the influences of stressful life events and WeChat addiction on life satisfaction, and investigated the mediating role of WeChat addiction on the relationship between the two research variables. A total of 463 undergraduates completed self-reported scales for stressful life events, WeChat addiction, and life satisfaction. Structural equation modeling was used to analyze the questionnaire data. The results showed the suppressing effect of WeChat addiction on the negative impact of stressful life events on life satisfaction. Stressful life events affect life satisfaction both directly and indirectly. Stressful life events are positively associated with WeChat addiction, which exerts positive impact on life satisfaction. The contributions of the findings are discussed.
Relating Lagrangian passive scalar scaling exponents to Eulerian scaling exponents in turbulence

OpenAIRE

Schmitt , François G

2005-01-01

Intermittency is a basic feature of fully developed turbulence, for both velocity and passive scalars. Intermittency is classically characterized by Eulerian scaling exponent of structure functions. The same approach can be used in a Lagrangian framework to characterize the temporal intermittency of the velocity and passive scalar concentration of a an element of fluid advected by a turbulent intermittent field. Here we focus on Lagrangian passive scalar scaling exponents, and discuss their p...
Life Stress, the "Kindling" Hypothesis, and the Recurrence of Depression: Considerations From a Life Stress Perspective

Science.gov (United States)

Monroe, Scott M.; Harkness, Kate L.

2005-01-01

Major depression is frequently characterized by recurrent episodes over the life course. First lifetime episodes of depression, however, are typically more strongly associated with major life stress than are successive recurrences. A key theoretical issue involves how the role of major life stress changes from an initial episode over subsequent…
Stress, Adaptive Coping, and Life Satisfaction

Science.gov (United States)

Buser, Juleen K.; Kearney, Anne

2017-01-01

The authors examined the relationship between stress, adaptive coping, and life satisfaction among college students who reported having a friend or family member with eating disorder symptomatology. A hierarchical regression confirmed the study's hypotheses. Higher stress was linked with less life satisfaction. After stress was controlled, plan…
The stress of life

National Research Council Canada - National Science Library

Selye, H

1978-01-01

.... This is also a dependable personal guide that tells you how to combat both physical and mental stress, how to handle yourself during the stress of everyday life, and how your bodily changes can help...
Prediction of life stress on athletes’ burnout: the dual role of perceived stress

Science.gov (United States)

Wang, Erica T.W.; Hsu, Ya-Wen; Chang, Ko-Hsin

2018-01-01

Although many studies adopted Smith’s (1986) cognitive–affective model of athletic burnout in examining stress–burnout relationship, very few studies examined the mediating/moderating role of perceived stress on the stress–burnout relationship. We sampled 195 college student-athletes and assessed their life stress, perceived stress, and burnout. Correlation analyses found all study variables correlated. Two separate hierarchical regression analyses found that the “distress” component of perceived stress mediated athletes’ two types of life stress–burnout relationship but “counter-stress” component of perceived stress-moderated athletes’ general-life stress–burnout relationship. We concluded that interweaving relationships among athletes’ life stress, perceived stress, and burnout are not straightforward. Future research should consider the nature of athletes life stress, and dual role of perceived stress in examining its’ association with related psychological responses in athletic settings. PMID:29362691
Prediction of life stress on athletes’ burnout: the dual role of perceived stress

Directory of Open Access Journals (Sweden)

Theresa Chyi

2018-01-01

Full Text Available Although many studies adopted Smith’s (1986 cognitive–affective model of athletic burnout in examining stress–burnout relationship, very few studies examined the mediating/moderating role of perceived stress on the stress–burnout relationship. We sampled 195 college student-athletes and assessed their life stress, perceived stress, and burnout. Correlation analyses found all study variables correlated. Two separate hierarchical regression analyses found that the “distress” component of perceived stress mediated athletes’ two types of life stress–burnout relationship but “counter-stress” component of perceived stress-moderated athletes’ general-life stress–burnout relationship. We concluded that interweaving relationships among athletes’ life stress, perceived stress, and burnout are not straightforward. Future research should consider the nature of athletes life stress, and dual role of perceived stress in examining its’ association with related psychological responses in athletic settings.
A modified approach to predict pore pressure using the D exponent method: An example from the Carbonera Formation, Colombia

International Nuclear Information System (INIS)

Solano, Yully P; Uribe, Rodolfo; Frydman, Marcelo; Saavedra, Nestor F; Calderon, Zuly H

2007-01-01

The methodology for the pore pressure prediction known as an exponent is o function of an exponent of adjustment that was originally defined for the Gulf of Mexico (Jorden and Shirley, 1966; Eaton, 1972). A limiting factor of this methodology is the definition of the normal compaction trend (NCT), which needs to be interpreted from the data (Mouchet and Mitchell, 1989). In this study, the D exponent methodology was modified to make it applicable to the Oligocene Carbonera Formation in an oil field of the llanos foothills Colombia. The approach consisted of calculating the ratio between affective stress and the D exponent of each wall, in order to find a robust NCT for the entire field, thus reducing subjectivity in the traditional d exponent methodology. Pore pressure determinations from Measured Direct Tests (MDT) at one wall confirm the predictive capability of our approach
Posttraumatic Stress Disorder and Stressful Life Events Among Rural Women With HIV Disease.

Science.gov (United States)

Kemppainen, Jeanne K; MacKain, Sally; Alexander, Melissa; Reid, Paula; Jackson, Morgan Parks

Posttraumatic stress disorder (PTSD) and stressful life events are frequent and distressing problems for women living with HIV (WLWH). Studies have independently focused on the impact of these problems, but little work has examined the relationship between PTSD and stressful life events. Our cross-sectional study examined relationships between PTSD and recent stressful life events in WLWH. A sample of 60 women recruited through HIV community agencies in southeastern North Carolina completed the Stressful Life Events Questionnaire and the PTSD Checklist-Civilian Version (PCL-C). PTSD prevalence was high (43.2%). Two-thirds (66%) reported three or more recent life stressors. Women who experienced a higher number of recent life stressors scored higher on the PCL-C than those with fewer life stressors (p stressful life events may accelerate PTSD symptoms. Findings underscore the importance of addressing mental health issues in HIV treatment settings. Implications for nursing practice are provided. Copyright © 2016 Association of Nurses in AIDS Care. Published by Elsevier Inc. All rights reserved.

Relation between the Hurst Exponent and the Efficiency of Self-organization of a Deformable System

Science.gov (United States)

Alfyorova, E. A.; Lychagin, D. V.

2018-04-01

We have established the degree of self-organization of a system under plastic deformation at different scale levels. Using fractal analysis, we have determined the Hurst exponent and correlation lengths in the region of formation of a corrugated (wrinkled) structure in [111] nickel single crystals under compression. This has made it possible to single out two (micro-and meso-) levels of self-organization in the deformable system. A qualitative relation between the values of the Hurst exponent and the stages of the stress-strain curve has been established.
Work stress, life stress, and smoking among rural–urban migrant workers in China

Directory of Open Access Journals (Sweden)

Cui Xiaobo

2012-11-01

Full Text Available Abstract Background Stimulated by rapid modernization and industrialization, there is massive rural–urban migration in China. The migrants are highly susceptible to smoking and mental health problems. This study examined the association between both perceived work stress and perceived life stress with smoking behavior among this group during the period of migration. Methods Participants (n = 1,595 were identified through stratified, multi-stage, systematic sampling. Smoking status separated non-smokers from daily and occasional smokers, and migration history, work stress, and life stress were also measured. Analyses were conducted using the Chi-square test and multiple logistic regression. Two models were utilized. The first was the full model that comprised sociodemographic and migration-related characteristics, as well as the two stress variables. In addressing potential overlap between life and work stress, the second model eliminated one of the two stress variables as appropriate. Results Overall smoking prevalence was 64.9% (95% CI: 62.4-67.2%. In the regression analysis, under the full model, migrants with high perceived life stress showed a 45% excess likelihood to be current smokers relative to low-stress counterparts (OR: 1.45; 95% CI: 1.05 – 2.06. Applying the second model, which excluded the life stress variable, migrants with high perceived work stress had a 75% excess likelihood to be current smokers relative to opposites (OR: 1.75; 95% CI: 1.26–2.45. Conclusions Rural–urban migrant workers manifested a high prevalence of both life stress and work stress. While both forms of stress showed associations with current smoking, life stress appeared to outweigh the impact of work stress. Our findings could inform the design of tobacco control programs that would target Chinese rural–urban migrant workers as a special population.
Monte Carlo-based tail exponent estimator

Science.gov (United States)

Barunik, Jozef; Vacha, Lukas

2010-11-01

In this paper we propose a new approach to estimation of the tail exponent in financial stock markets. We begin the study with the finite sample behavior of the Hill estimator under α-stable distributions. Using large Monte Carlo simulations, we show that the Hill estimator overestimates the true tail exponent and can hardly be used on samples with small length. Utilizing our results, we introduce a Monte Carlo-based method of estimation for the tail exponent. Our proposed method is not sensitive to the choice of tail size and works well also on small data samples. The new estimator also gives unbiased results with symmetrical confidence intervals. Finally, we demonstrate the power of our estimator on the international world stock market indices. On the two separate periods of 2002-2005 and 2006-2009, we estimate the tail exponent.
Quantum critical Hall exponents

CERN Document Server

Lütken, C A

2014-01-01

We investigate a finite size "double scaling" hypothesis using data from an experiment on a quantum Hall system with short range disorder [1-3]. For Hall bars of width w at temperature T the scaling form is w(-mu)T(-kappa), where the critical exponent mu approximate to 0.23 we extract from the data is comparable to the multi-fractal exponent alpha(0) - 2 obtained from the Chalker-Coddington (CC) model [4]. We also use the data to find the approximate location (in the resistivity plane) of seven quantum critical points, all of which closely agree with the predictions derived long ago from the modular symmetry of a toroidal sigma-model with m matter fields [5]. The value nu(8) = 2.60513 ... of the localisation exponent obtained from the m = 8 model is in excellent agreement with the best available numerical value nu(num) = 2.607 +/- 0.004 derived from the CC-model [6]. Existing experimental data appear to favour the m = 9 model, suggesting that the quantum Hall system is not in the same universality class as th...
Negative life events and symptoms of depression and anxiety: stress causation and/or stress generation.

Science.gov (United States)

Phillips, Anna C; Carroll, Douglas; Der, Geoff

2015-01-01

Stressful life events are known to contribute to development of depression; however, it is possible this link is bidirectional. The present study examined whether such stress generation effects are greater than the effects of stressful life events on depression, and whether stress generation is also evident with anxiety. Participants were two large age cohorts (N = 732 aged 44 years; N = 705 aged 63 years) from the West of Scotland Twenty-07 study. Stressful life events, depression, and anxiety symptoms were measured twice five years apart. Cross-lagged panel analysis examined the mutual influences of stressful life events on depression and on anxiety over time. Life events predicted later depressive symptomatology (p = .01), but the depression predicting life events relationship was less strong (p = .06), whereas earlier anxiety predicted life events five years later (p = .001). There was evidence of sex differences in the extent to which life events predicted later anxiety. This study provides evidence of stress causation for depression and weaker evidence for stress generation. In contrast, there was strong evidence of stress generation for anxiety but weaker evidence for stress causation, and that differed for men and women.
Nuclear multifragmentation critical exponents

International Nuclear Information System (INIS)

Bauer, W.; Friedman, W.A.; Univ. of Wisconsin, Madison, WI

1995-01-01

In a recent Letter, cited in a reference, the EoS collaboration presented data of fragmentation of 1 A GeV gold nuclei incident on carbon. By analyzing moments of the fragment charge distribution, the authors claim to determine the values of the critical exponents γ, β, and τ for finite nuclei. These data represent a crucial step forward in the understanding of the physics of nuclear fragmentation. However, as shown in this paper, the analysis presented in the cited reference is not sufficient to support the claim that the critical exponents for nuclear fragmentation have been unambiguously determined
An inquiry-based approach to the Franck-Hertz experiment

International Nuclear Information System (INIS)

Persano Adorno, Dominique; Pizzolato, Nicola

2015-01-01

The practice of scientists and engineers is today exerted within interdisciplinary contexts, placed at the intersections of different research fields, including nanoscale science. The development of the required competencies is based on an effective science and engineering instruction, which should be able to drive the students towards a deeper understanding of quantum mechanics fundamental concepts and, at the same time, strengthen their reasoning skills and transversal abilities. In this study we report the results of an inquiry-driven learning path experienced by a sample of 12 electronic engineering undergraduates engaged to perform the Franck-Hertz experiment. Before being involved in this experimental activity, the students received a traditional lecture-based instruction on the fundamental concepts of quantum mechanics, but their answers to an open-ended questionnaire, administered at the beginning of the inquiry activity, demonstrated that the acquired knowledge was characterized by a strictly theoretical vision of quantum science, basically in terms of an artificial mathematical framework having very poor connections with the real world. The Franck Hertz experiment was introduced to the students by starting from the problem of finding an experimental confirmation of the Bohr’s postulates asserting that atoms can absorb energy only in quantum portions. The whole activity has been videotaped and this allowed us to deeply analyse the student perception’s change about the main concepts of quantum mechanics. We have found that the active participation to this learning experience favored the building of cognitive links among student theoretical perceptions of quantum mechanics and their vision of quantum phenomena, within an everyday context of knowledge. Furthermore, our findings confirm the benefits of integrating traditional lecture-based instruction on quantum mechanics with learning experiences driven by inquiry-based teaching strategies.
An inquiry-based approach to the Franck-Hertz experiment

Science.gov (United States)

Persano Adorno, Dominique; Pizzolato, Nicola

2016-05-01

The practice of scientists and engineers is today exerted within interdisciplinary contexts, placed at the intersections of different research fields, including nanoscale science. The development of the required competences is based on an effective science and engineering instruction, which should be able to drive the students towards a deeper understanding of quantum mechanics fundamental concepts and, at the same time, strengthen their reasoning skills and transversal abilities. In this study we report the results of an inquiry-driven learning path experienced by a sample of 12 electronic engineering undergraduates engaged to perform the Franck-Hertz experiment. Before being involved in this experimental activity, the students received a traditional lecture-based instruction on the fundamental concepts of quantum mechanics, but their answers to an open-ended questionnaire, administered at the beginning of the inquiry activity, demonstrated that the acquired knowledge was characterized by a strictly theoretical vision of quantum science, basically in terms of an artificial mathematical framework having very poor connections with the real world. The Franck Hertz experiment was introduced to the students by starting from the problem of finding an experimental confirmation of the Bohr's postulates asserting that atoms can absorb energy only in quantum portions. The whole activity has been videotaped and this allowed us to deeply analyse the student perception's change about the main concepts of quantum mechanics. We have found that the active participation to this learning experience favored the building of cognitive links among student theoretical perceptions of quantum mechanics and their vision of quantum phenomena, within an everyday context of knowledge. Furthermore, our findings confirm the benefits of integrating traditional lecture-based instruction on quantum mechanics with learning experiences driven by inquiry-based teaching strategies.
Diophantine exponents for mildly restricted approximation

DEFF Research Database (Denmark)

Bugeaud, Yann; Kristensen, Simon

We are studying the Diophantine exponent defined for integers and a vector by letting , where is the scalar product and denotes the distance to the nearest integer and is the generalised cone consisting of all vectors with the height attained among the first coordinates. We show that the exponent...
Role of stress areas, stress severity, and stressful life events on the onset of depressive disorder: a case-control study.

Science.gov (United States)

Lueboonthavatchai, Peeraphon

2009-09-01

Although the stress and stressful life events are known as the precipitation of depressive disorder, the areas of stress and types of stressful life events found in depression are varied by different socio-cultural context. Identify the stress areas, stress severity, and types of stressful life events associated with the onset of depressive disorder in Thai depressed patients. Ninety depressed and ninety non-depressed subjects, aged above 18 years old, from the Department of Psychiatry, King Chulalongkorn Memorial Hospital, were recruited into the present study between July 2007 and January 2008. All subjects completed a demographic data form, and a 1-Year Life Stress Event Questionnaire. The association between the number of stressful life events, stress areas, stress severity, types of stressful life events, and the onset of depressive disorder were analyzed by independent t-test and chi-square test. Logistic regression was performed to identify the predictors of depressive disorder. Most of the subjects were young and middle-aged women, living in Bangkok and the central region. The depressed subjects experienced more stressful life events than the non-depressed subjects (5.81 +/- 3.19 vs. 3.24 +/- 2.80 events in one year) (p stress areas (health-related, family-related, financial, occupational, and social stress), and overall stress were associated with the onset of depressive disorder (p stress in all areas were at the higher risk of depressive disorder than those with the mild stress (p stress was the stress area highest associated with the depressive disorder (OR = 5.93, 95% CI = 2.33-16.92, p stressful life events associated with the onset of depressive disorder were the medical hospitalization, medical illness leading to missing work or disturbed daily routine, change in sleeping habits, absence of recreation, arguments with spouse, sexual difficulties with spouse, family financial problems, job loss, and trouble with boss (p stress was the significant
Merit exponents and control area diagrams in materials selection

International Nuclear Information System (INIS)

Zander, Johan; Sandstroem, Rolf

2011-01-01

Highlights: → Merit exponents are introduced to generalise the merit indices commonly used in materials selection. → The merit exponents can rank materials in general design situations. → To allow identification of the active merit exponent(s), control area diagrams are used. → Principles for generating the control area diagrams are presented. -- Abstract: Merit indices play a fundamental role in materials selection, since they enable ranking of materials. However, the conventional formulation of merit indices is associated with severe limitations. They are dependent on the explicit solution of the variables in the equations for the constraints from the design criteria. Furthermore, it is not always easy to determine which the controlling merit index is. To enable the ranking of materials in more general design cases, merit exponents are introduced as generalisations of the merit indices. Procedures are presented for how to compute the merit exponents numerically without having to solve equations algebraically. Merit exponents (and indices) are only valid in a certain range of property values. To simplify the identification of the controlling merit exponent, it is suggested that so called control area diagrams are used. These diagrams consist of a number of domains, each showing the active constraints and the controlling merit exponent. It is shown that the merit exponents play a crucial role when the control area diagram (CAD) is set up. The principles in the paper are developed for mechanically loaded components and are illustrated for engineering beams with two or three geometric variables.
Racism-Related Stress, General Life Stress, and Psychological Functioning among Black American Women

Science.gov (United States)

Pieterse, Alex L.; Carter, Robert T.; Ray, Kilynda V.

2013-01-01

The relationship between general life stress, perceived racism, and psychological functioning was explored in a sample of 118 Black American women. Findings indicate that racism-related stress was not a significant predictor of psychological functioning when controlling for general life stress. Perceived racism was positively associated with…
Life Satisfaction and Hemodynamic Reactivity to Mental Stress.

Science.gov (United States)

Schwerdtfeger, Andreas; Gaisbachgrabner, Kerstin; Traunmüller, Claudia

2017-06-01

Satisfaction with life has been considered a health-protective variable, which could impact cardiovascular morbidity and mortality. However, few studies have examined the physiological pathways involved in the potentially salutary effect of life satisfaction. It was hypothesized that life satisfaction should be associated with a cardiovascular response profile that signals challenge (i.e., higher cardiac output, lower peripheral resistance), rather than threat during a mental stress task. A sample of 75 healthy, medication-free men without clinical signs of psychological disorders who worked full-time and occupied highly demanding positions participated in this study. They performed two mental stress tasks (n-back) with varying degrees of difficulty. The tasks were embedded between a baseline and a recovery period. Cardiovascular and hemodynamic variables (heart rate, blood pressure, cardiac output, total peripheral resistance) were recorded by means of impedance cardiography. Individuals who were more satisfied with their life displayed higher cardiac output and lower peripheral resistance levels during the stress tasks, indicating a challenge rather than a threat profile. Findings were robust when controlled for physical activity, smoking, age, and depressive symptoms. Life satisfaction could be positively correlated with beneficial hemodynamic stress reactivity, indicating that individuals with higher levels of life satisfaction can more adaptively cope with stress. Increased cardiac output and decreased peripheral resistance during stress may constitute one route through which life satisfaction can benefit health.
Evaluating Lyapunov exponent spectra with neural networks

International Nuclear Information System (INIS)

Maus, A.; Sprott, J.C.

2013-01-01

Highlights: • Cross-correlation is employed to remove spurious Lyapunov exponents from a spectrum. • Neural networks are shown to accurately model Lyapunov exponent spectra. • Neural networks compare favorably to local linear fits in modeling Lyapunov exponents. • Numerical experiments are performed with time series of varying length and noise. • Methods perform reasonably well on discrete time series. -- Abstract: A method using discrete cross-correlation for identifying and removing spurious Lyapunov exponents when embedding experimental data in a dimension greater than the original system is introduced. The method uses a distribution of calculated exponent values produced by modeling a single time series many times or multiple instances of a time series. For this task, global models are shown to compare favorably to local models traditionally used for time series taken from the Hénon map and delayed Hénon map, especially when the time series are short or contaminated by noise. An additional merit of global modeling is its ability to estimate the dynamical and geometrical properties of the original system such as the attractor dimension, entropy, and lag space, although consideration must be taken for the time it takes to train the global models
Stress, Emotional Intelligence, and Life Satisfaction in College Students

Science.gov (United States)

Holinka, Cassandra

2015-01-01

Prior studies have examined stress, life satisfaction, and emotional intelligence in college students. Research on stress in college students has focused on the sources of stress, coping styles, and relevant outcomes. Research on life satisfaction has focused on specific relationships between life satisfaction and concepts like worry,…
Stressful life events and cancer risk

DEFF Research Database (Denmark)

Bergelt, C; Prescott, E; Grønbaek, M

2006-01-01

In a prospective cohort study in Denmark of 8736 randomly selected people, no evidence was found among 1011 subjects who developed cancer that self-reported stressful major life events had increased their risk for cancer.......In a prospective cohort study in Denmark of 8736 randomly selected people, no evidence was found among 1011 subjects who developed cancer that self-reported stressful major life events had increased their risk for cancer....
Life Stress and Academic Burnout

Science.gov (United States)

Lin, Shu-Hui; Huang, Yun-Chen

2014-01-01

Stress has been shown to negatively affect learning. Academic burnout is a significant problem associated with poor academic performance. Although there has been increased attention on these two issues, literature on the relationship between students' life stress and burnout is relatively limited. This study surveys academic burnout and life…
Stress and Protists: No life without stress.

Science.gov (United States)

Slaveykova, Vera; Sonntag, Bettina; Gutiérrez, Juan Carlos

2016-08-01

We report a summary of the symposium "Stress and Protists: No life without stress", which was held in September 2015 on the VII European Congress of Protistology in partnership with the International Society of Protistologists (Seville, Spain). We present an overview on general comments and concepts on cellular stress which can be also applied to any protist. Generally, various environmental stressors may induce similar cell responses in very different protists. Two main topics are reported in this manuscript: (i) metallic nanoparticles as environmental pollutants and stressors for aquatic protists, and (ii) ultraviolet radiation - induced stress and photoprotective strategies in ciliates. Model protists such as Chlamydomonas reinhardtii and Tetrahymena thermophila were used to assess stress caused by nanoparticles while stress caused by ultraviolet radiation was tested with free living planktonic ciliates as well as with the symbiont-bearing model ciliate Paramecium bursaria. For future studies, we suggest more intensive analyses on protist stress responses to specific environmental abiotic and/or biotic stressors at molecular and genetic levels up to ecological consequences and food web dynamics. Copyright © 2016 Elsevier GmbH. All rights reserved.
The Influence of Exercise Empowerment on Life Stress

Directory of Open Access Journals (Sweden)

Tonya M. Parker

2017-10-01

Full Text Available Background: Psychological stress – when an individual perceives that the environment exceeds their ability to meet the demands placed on them - is common in college students and exercise, and specifically instructional physical activity courses, is frequently cited as a one method of stress reduction. Objective: Determine any relationship between exercise empowerment and perceived life stress for those participating in instructional physical activity courses (IPAC. Methods: All undergraduate students (n = 3388 enrolled in IPAC in 15-week IPAC at a large university were surveyed on perceived life stress (PSS, empowerment in exercise (EES, and specific demographic variables. Results: 944 of 3388 enrolled students (Nov. 2015, April 2016 completed the survey. The data revealed GPA (p < 0.002, sex (p < 0.000, and EES (p < 0.001 showed differences for PSS. It was determined that EES, sex, and GPA predicted PSS differently for students according to their year in college. Conclusions: For freshman and seniors, sex and lower GPA were a stronger predictor of PSS with no mitigating effect of exercise empowerment. For sophomores and juniors the level of life stress was lower at higher levels of exercise empowerment. These findings support a complex relationship between exercise empowerment and life stress. While exercise is cited as a method for stress reduction the relationship between exercise empowerment and life stress for college-aged students is not as straightforward as it may seem.
A Sikh Perspective on Life-Stress: Implications for Counselling

Science.gov (United States)

Sandhu, Jaswinder Singh

2005-01-01

This paper presents the Sikh life-stress model as a culture-specific intervention. The paper looks at the Sikh world-view, from which it delineates the Sikh perspective on life-stress. It further outlines a framework for incorporating the Sikh life-stress model into the Western counselling context, and concludes with a case vignette to demonstrate…

College Student Stress and Satisfaction with Life

Science.gov (United States)

Weinstein, Lawrence; Laverghetta, Antonio

2009-01-01

The following study was performed to determine if general life satisfaction is negatively correlated with college student stress. We administered the satisfaction with life scale (Diener et al., 1985), college student stress scale (Feldt, 2008) and a brief demographics survey to a sample of college students at a regional southwestern university in…
Fatigue life estimation considering welding residual stress and hot-spot stress of welded components

International Nuclear Information System (INIS)

Han, S. H.; Lee, T. K.; Shin, B. C.

2002-01-01

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

Science.gov (United States)

Zascavage, Victoria; Winterman, Kathleen G.; Buot, Max; Wies, Jennifer R.; Lyzinski, Natalie

2012-01-01

In order to better understand the effects of student-life stress on Education and Health Service majors (n = 195) at a private, religious, Midwestern university in the USA, we assessed student perception of overall stress level and physical stress level using the Student-life Stress Inventory. The targeted sample consisted of students with…
Non-universal spreading exponents in a catalytic reaction model

International Nuclear Information System (INIS)

De Andrade, Marcelo F; Figueiredo, W

2011-01-01

We investigated the dependence of the spreading critical exponents and the ultimate survival probability exponent on the initial configuration of a nonequilibrium catalytic reaction model. The model considers the competitive reactions between two different monomers, A and B, where we take into account the energy couplings between nearest neighbor monomers, and the adsorption energies, as well as the temperature T of the catalyst. For each value of T the model shows distinct absorbing states, with different concentrations of the two monomers. Employing an epidemic analysis, we established the behavior of the spreading exponents as we started the Monte Carlo simulations with different concentrations of the monomers. The exponents were determined as a function of the initial concentration ρ A, ini of A monomers. We have also considered initial configurations with correlations for a fixed concentration of A monomers. From the determination of three spreading exponents, and the ultimate survival probability exponent, we checked the validity of the generalized hyperscaling relation for a continuous set of initial states, random and correlated, which are dependent on the temperature of the catalyst
Multiscale Lyapunov exponent for 2-microlocal functions

International Nuclear Information System (INIS)

Dhifaoui, Zouhaier; Kortas, Hedi; Ammou, Samir Ben

2009-01-01

The Lyapunov exponent is an important indicator of chaotic dynamics. Using wavelet analysis, we define a multiscale representation of this exponent which we demonstrate the scale-wise dependence for functions belonging to C x 0 s,s ' spaces. An empirical study involving simulated processes and financial time series corroborates the theoretical findings.
Effects of work and life stress on semen quality.

Science.gov (United States)

Janevic, Teresa; Kahn, Linda G; Landsbergis, Paul; Cirillo, Piera M; Cohn, Barbara A; Liu, Xinhua; Factor-Litvak, Pam

2014-08-01

To evaluate associations between work-related stress, stressful life events, and perceived stress and semen quality. Cross-sectional analysis. Northern California. 193 men from the Child Health and Development Studies evaluated between 2005-2008. None. Measures of stress including job strain, perceived stress, and stressful life events; outcome measures of sperm concentration, percentage of motile sperm, and percentage of morphologically normal sperm. We found an inverse association between perceived stress score and sperm concentration (estimated coefficient b=-0.09×10(3)/mL; 95% confidence interval [CI]=-0.18, -0.01), motility (b=-0.39; 95% CI=-0.79, 0.01), and morphology (b=-0.14; 95% CI, -0.25, -0.04) in covariate-adjusted linear regression analyses. Men who experienced two or more stressful life events in the past year compared with no stressful events had a lower percentage of motile sperm (b=-8.22; 95% CI, -14.31, -2.13) and a lower percentage of morphologically normal sperm (b=-1.66; 95% CI, -3.35, 0.03) but a similar sperm concentration. Job strain was not associated with semen parameters. In this first study to examine all three domains of stress, perceived stress and stressful life events but not work-related stress were associated with semen quality. Copyright © 2014 American Society for Reproductive Medicine. Published by Elsevier Inc. All rights reserved.
The Critical Exponent is Computable for Automatic Sequences

Directory of Open Access Journals (Sweden)

Jeffrey Shallit

2011-08-01

Full Text Available The critical exponent of an infinite word is defined to be the supremum of the exponent of each of its factors. For k-automatic sequences, we show that this critical exponent is always either a rational number or infinite, and its value is computable. This generalizes or recovers previous results of Krieger and others. Our technique is applicable to other situations; e.g., the computation of the optimal recurrence constant for a linearly recurrent k-automatic sequence.
Stress and Life Satisfaction of Turkish College Students

Science.gov (United States)

Kaya, Cahit; Tansey, Timothy N.; Melekoglu, Macid; Çakiroglu, Orhan

2015-01-01

This study investigated the association between perceived stress and life satisfaction of Turkish college students. The "Satisfaction with Life Scale" (Diener, Emmons, Larsen, & Griffin, 1985), the "Perceived Stress Scale" (Cohen & Williamson, 1988), and a brief demographic questionnaire were administered to 235 college…
Lyapunov exponents and smooth ergodic theory

CERN Document Server

Barreira, Luis

2001-01-01

This book is a systematic introduction to smooth ergodic theory. The topics discussed include the general (abstract) theory of Lyapunov exponents and its applications to the stability theory of differential equations, stable manifold theory, absolute continuity, and the ergodic theory of dynamical systems with nonzero Lyapunov exponents (including geodesic flows). The authors consider several non-trivial examples of dynamical systems with nonzero Lyapunov exponents to illustrate some basic methods and ideas of the theory. This book is self-contained. The reader needs a basic knowledge of real analysis, measure theory, differential equations, and topology. The authors present basic concepts of smooth ergodic theory and provide complete proofs of the main results. They also state some more advanced results to give readers a broader view of smooth ergodic theory. This volume may be used by those nonexperts who wish to become familiar with the field.
[Association of occupational stress with quality of working life].

Science.gov (United States)

Zhang, Qin; Lan, Ya-Jia; Chen, Hong-Mei

2011-07-01

To assess occupational stress and quality of working life (QWL) and their association in workers with different jobs. The Occupational Stress Inventory Revised Edition (OSI-R) and Quality of Working Life Scale (QWL7-32) were administered to 194 workers in the Liaohe Oilfield. The association between occupational stress and quality of working life was analysed by controlling job types and other confounding variables. Office workers had significantly lower scores in occupational role questionnaire (ORQ) and personal strain questionnaire (PSQ) and higher scores in personal resources questionnaire (PRQ) and QWL than physical laborers (P<0.05). The PSQ scores were positively correlated with the ORQ scores and negatively correlated with the PRQ scores. The QWL scores were negatively correlated with the ORQ and PSQ scores, and positively correlated with the PRQ scores (P<0.001). The QWL scores changed with job types. The QWL scores declined with the increase of stress levels (P<0.01). ORQ, role boundary (RB), role insufficiency (RI), physical environment (PE), PSQ, vocational strain (VS), interpersonal strain (IS) and PRQ had a significant impact on quality of working life (P<0.01). Occupational stress is associated with quality of working life. Quality of working life can be improved through control of occupational stress.
Cryptanalysis of 'less short' RSA secret exponents

NARCIS (Netherlands)

Verheul, E.R.; Tilborg, van H.C.A.

1997-01-01

In some applications of RSA, it is desirable to have a short secret exponent d. Wiener [6], describes a technique to use continued fractions (CF) in a cryptanalytic attack on an RSA cryptosystem having a ‘short’ secret exponent. Let n=p¿·¿q be the modulus of the system. In the typical case that
Lyapunov exponent for aging process in induction motor

Science.gov (United States)

Bayram, Duygu; Ünnü, Sezen Yıdırım; Şeker, Serhat

2012-09-01

Nonlinear systems like electrical circuits and systems, mechanics, optics and even incidents in nature may pass through various bifurcations and steady states like equilibrium point, periodic, quasi-periodic, chaotic states. Although chaotic phenomena are widely observed in physical systems, it can not be predicted because of the nature of the system. On the other hand, it is known that, chaos is strictly dependent on initial conditions of the system [1-3]. There are several methods in order to define the chaos. Phase portraits, Poincaré maps, Lyapunov Exponents are the most common techniques. Lyapunov Exponents are the theoretical indicator of the chaos, named after the Russian mathematician Aleksandr Lyapunov (1857-1918). Lyapunov Exponents stand for the average exponential divergence or convergence of nearby system states, meaning estimating the quantitive measure of the chaotic attractor. Negative numbers of the exponents stand for a stable system whereas zero stands for quasi-periodic systems. On the other hand, at least if one of the exponents is positive, this situation is an indicator of the chaos. For estimating the exponents, the system should be modeled by differential equation but even in that case mathematical calculation of Lyapunov Exponents are not very practical and evaluation of these values requires a long signal duration [4-7]. For experimental data sets, it is not always possible to acquire the differential equations. There are several different methods in literature for determining the Lyapunov Exponents of the system [4, 5]. Induction motors are the most important tools for many industrial processes because they are cheap, robust, efficient and reliable. In order to have healthy processes in industrial applications, the conditions of the machines should be monitored and the different working conditions should be addressed correctly. To the best of our knowledge, researches related to Lyapunov exponents and electrical motors are mostly
Stressful life events and neuroticism as predictors of late-life versus early-life depression.

Science.gov (United States)

Weber, Kerstin; Giannakopoulos, Panteleimon; Herrmann, François R; Bartolomei, Javier; Digiorgio, Sergio; Ortiz Chicherio, Nadia; Delaloye, Christophe; Ghisletta, Paolo; Lecerf, Thierry; De Ribaupierre, Anik; Canuto, Alessandra

2013-12-01

The occurrence of depression in younger adults is related to the combination of long-standing factors such as personality traits (neuroticism) and more acute factors such as the subjective impact of stressful life events. Whether an increase in physical illnesses changes these associations in old age depression remains a matter of debate. We compared 79 outpatients with major depression and 102 never-depressed controls; subjects included both young (mean age: 35 years) and older (mean age: 70 years) adults. Assessments included the Social Readjustment Rating Scale, NEO Personality Inventory and Cumulative Illness Rating Scale. Logistic regression models analyzed the association between depression and subjective impact of stressful life events while controlling for neuroticism and physical illness. Patients and controls experienced the same number of stressful life events in the past 12 months. However, in contrast to the controls, patients associated the events with a subjective negative emotional impact. Negative stress impact and levels of neuroticism, but not physical illness, significantly predicted depression in young age. In old age, negative stress impact was weakly associated with depression. In this age group, depressive illness was also determined by physical illness burden and neuroticism. Our data suggest that the subjective impact of life stressors, although rated as of the same magnitude, plays a less important role in accounting for depression in older age compared to young age. They also indicate an increasing weight of physical illness burden in the prediction of depression occurrence in old age. © 2013 The Authors. Psychogeriatrics © 2013 Japanese Psychogeriatric Society.
Life stress and atherosclerosis: a pathway through unhealthy lifestyle.

Science.gov (United States)

Mainous, Arch G; Everett, Charles J; Diaz, Vanessa A; Player, Marty S; Gebregziabher, Mulugeta; Smith, Daniel W

2010-01-01

To examine the relationship between a general measure of chronic life stress and atherosclerosis among middle aged adults without clinical cardiovascular disease via pathways through unhealthy lifestyle characteristics. We conducted an analysis of The Multi-Ethnic Study of Atherosclerosis (MESA). The MESA collected in 2000 includes 5,773 participants, aged 45-84. We computed standard regression techniques to examine the relationship between life stress and atherosclerosis as well as path analysis with hypothesized paths from stress to atherosclerosis through unhealthy lifestyle. Our outcome was sub-clinical atherosclerosis measured as presence of coronary artery calcification (CAC). A logistic regression adjusted for potential confounding variables along with the unhealthy lifestyle characteristics of smoking, excessive alcohol use, high caloric intake, sedentary lifestyle, and obesity yielded no significant relationship between chronic life stress (OR 0.93, 95% CI 0.80-1.08) and CAC. However, significant indirect pathways between chronic life stress and CAC through smoking (p = .007), and sedentary lifestyle (p = .03) and caloric intake (.002) through obesity were found. These results suggest that life stress is related to atherosclerosis once paths of unhealthy coping behaviors are considered.
Work-related stress, work/life balance and personal life coaching.

Science.gov (United States)

Hawksley, Barbara

2007-01-01

Work-related stress adversely affects personal performance, organizational efficiency and patient care as well as costing the NHS millions of pounds each year. Reducing the effects of work-related stress is a legal duty for all employers. There are a number of resources available to help both employees and employers, such as the Health and Safety Executive stress management standards. Personal life coaching is one approach to reducing work-related stress, which is well established amongst business and management executives as well as some public sector organizations.
Images and Conventions: Kantianism, empiricism, and conventionalism in Hertz's and Poincaré's philosophies of space and mechanics

DEFF Research Database (Denmark)

Lützen, Jesper

2007-01-01

Artiklen analyserer kantianske, empiricistiske og konventionalistiske tendenser i Heinrich Hertz's Prinzipien der Mechanik (1894) og sammenligner dem med tilsvarende tendenser i Henri Poincaré's La science et l'hypothèse (1902). Derved belyses Poincaré's reaktion på kantianismen...
The Exponent of High-frequency Source Spectral Falloff and Contribution to Source Parameter Estimates

Science.gov (United States)

Kiuchi, R.; Mori, J. J.

2015-12-01

As a way to understand the characteristics of the earthquake source, studies of source parameters (such as radiated energy and stress drop) and their scaling are important. In order to estimate source parameters reliably, often we must use appropriate source spectrum models and the omega-square model is most frequently used. In this model, the spectrum is flat in lower frequencies and the falloff is proportional to the angular frequency squared. However, Some studies (e.g. Allmann and Shearer, 2009; Yagi et al., 2012) reported that the exponent of the high frequency falloff is other than -2. Therefore, in this study we estimate the source parameters using a spectral model for which the falloff exponent is not fixed. We analyze the mainshock and larger aftershocks of the 2008 Iwate-Miyagi Nairiku earthquake. Firstly, we calculate the P wave and SH wave spectra using empirical Green functions (EGF) to remove the path effect (such as attenuation) and site effect. For the EGF event, we select a smaller earthquake that is highly-correlated with the target event. In order to obtain the stable results, we calculate the spectral ratios using a multitaper spectrum analysis (Prieto et al., 2009). Then we take a geometric mean from multiple stations. Finally, using the obtained spectra ratios, we perform a grid search to determine the high frequency falloffs, as well as corner frequency of both of events. Our results indicate the high frequency falloff exponent is often less than 2.0. We do not observe any regional, focal mechanism, or depth dependencies for the falloff exponent. In addition, our estimated corner frequencies and falloff exponents are consistent between the P wave and SH wave analysis. In our presentation, we show differences in estimated source parameters using a fixed omega-square model and a model allowing variable high-frequency falloff.
Stressful life events and depression symptoms: the effect of childhood emotional abuse on stress reactivity.

Science.gov (United States)

Shapero, Benjamin G; Black, Shimrit K; Liu, Richard T; Klugman, Joshua; Bender, Rachel E; Abramson, Lyn Y; Alloy, Lauren B

2014-03-01

Stressful life events are associated with an increase in depressive symptoms and the onset of major depression. Importantly, research has shown that the role of stress changes over the course of depression. The present study extends the current literature by examining the effects of early life stress on emotional reactivity to current stressors. In a multiwave study (N = 281, mean age = 18.76; 68% female), we investigated the proximal changes that occur in depressive symptoms when individuals are faced with life stress and whether a history of childhood emotional abuse moderates this relationship. Results support the stress sensitivity hypothesis for early emotional abuse history. Individuals with greater childhood emotional abuse severity experienced greater increases in depressive symptoms when confronted with current dependent stressors, controlling for childhood physical and sexual abuse. This study highlights the importance of emotional abuse as an indicator for reactivity to stressful life events. © 2013 Wiley Periodicals, Inc.
What is the cementation exponent? A new differential interpretation

Science.gov (United States)

Glover, P. W. J.

2009-04-01

Between 1950 and 2002 the total volume of reserves discovered has run to over 1500 Bbbl. for oil and 7.5 Tcf. for gas. Over half of these resources has already been produced, and has driven the global economy for the last fifty years. All of the assessments of the volume of hydrocarbon reserves were made using Archie's relationships (1942). It would be difficult, therefore, to overestimate the impact of either the petrophysical techniques or Archie's relationships on the worldwide economy. Archie's laws link the electrical resistivity of a rock to its porosity, to the resistivity of the water that saturates its pores, and to the fractional saturation of the pore space with the water, and are used to calculate the hydrocarbon saturation of the reservoir rock from which the reserves are then calculated. Archie's laws contain two exponents, m and n, which Archie called the cementation exponent and the saturation exponent, respectively. The conductivity of the hydrocarbon saturated rock is highly sensitive to changes in either exponent. However, despite the importance of the cementation exponent, few petrophysicists, commercial or academic, are able to describe its real physical meaning. The purpose of this contribution is to investigate the elusive physical meaning of the cementation exponent. We review the traditional interpretation of the cementation exponent and consider the extension of Archie's first law to two conducting phases. Consequently, we develop a new differential interpretation of the cementation exponent that is based on a new definition for the connectedness of the conducting phases in a porous medium. In this interpretation the connectedness of a porous medium is defined as the availability of pathways for transport, where the connectedness is the inverse of the formation resistivity factor, G = σo σw = 1 F (and may also be called the conductivity formation factor). Porosity is defined as the fractional amount of pore space in the usual manner
First-passage exponents of multiple random walks

International Nuclear Information System (INIS)

Ben-Naim, E; Krapivsky, P L

2010-01-01

We investigate first-passage statistics of an ensemble of N noninteracting random walks on a line. Starting from a configuration in which all particles are located in the positive half-line, we study S n (t), the probability that the nth rightmost particle remains in the positive half-line up to time t. This quantity decays algebraically, S n (t)∼t -β n , in the long-time limit. Interestingly, there is a family of nontrivial first-passage exponents, β 1 2 N-1 ; the only exception is the two-particle case where β 1 = 1/3. In the N → ∞ limit, however, the exponents attain a scaling form, β n (N) → β(z) with z=(n-N/2)/√N. We also demonstrate that the smallest exponent decays exponentially with N. We deduce these results from first-passage kinetics of a random walk in an N-dimensional cone and confirm them using numerical simulations. Additionally, we investigate the family of exponents that characterizes leadership statistics of multiple random walks and find that in this case, the cone provides an excellent approximation.

A new theoretical interpretation of Archie's saturation exponent

Directory of Open Access Journals (Sweden)

P. W. J. Glover

2017-07-01

Full Text Available This paper describes the extension of the concepts of connectedness and conservation of connectedness that underlie the generalized Archie's law for n phases to the interpretation of the saturation exponent. It is shown that the saturation exponent as defined originally by Archie arises naturally from the generalized Archie's law. In the generalized Archie's law the saturation exponent of any given phase can be thought of as formally the same as the phase (i.e. cementation exponent, but with respect to a reference subset of phases in a larger n-phase medium. Furthermore, the connectedness of each of the phases occupying a reference subset of an n-phase medium can be related to the connectedness of the subset itself by Gi = GrefSini. This leads naturally to the idea of the term Sini for each phase i being a fractional connectedness, where the fractional connectednesses of any given reference subset sum to unity in the same way that the connectednesses sum to unity for the whole medium. One of the implications of this theory is that the saturation exponent of any phase can be now be interpreted as the rate of change of the fractional connectedness with saturation and connectivity within the reference subset.
A new exponent in self-avoiding walks

International Nuclear Information System (INIS)

Srivastava, V.

1983-06-01

Existence of a new exponent is reported in the problem of nonintersecting self-avoiding random walks. It is connected with the asymptotic behaviour of the growth of number of such walks of larger and larger length. The value of the exponent is found to be nearly 0.90 for all two-dimensional and nearly 0.96 for all three-dimensional lattices studied here. (author)
Student-Life Stress Inventory.

Science.gov (United States)

Gadzella, Bernadette M.; And Others

The reliability of the Student-Life Stress Inventory of B. M. Gadzella (1991) was studied. The inventory consists of 51 items listed in 9 sections indicating different types of stressors (frustrations, conflicts, pressures, changes, and self-imposed stressors) and reactions to the stressors (physiological, emotional, behavioral, and cognitive) as…
On Schrödinger's equation, Hertz's mechanics and Van Vleck's determinant

International Nuclear Information System (INIS)

Coelho, R Lopes; Stachel, John

2013-01-01

There has been much research on Schrödinger's route to what we now call Schrödinger's equation. Various authors disagree as to the exact nature of the influence of each of the physicists he cites—and of some that he does not. This paper, intended for graduate students of and researchers in quantum theory, clarifies Schrödinger's original aims in formulating a wave equation for matter, discusses how far he fulfilled his original aspirations and in what respects he fell short of his goal. An analysis of Schrödinger's foundational paper enables us to distinguish between a formal and an epistemological part, and consider the input of the physicists cited on the basis of the part in which each reference occurs. It turns out, for instance, that Hamilton's optical-mechanical analogy belongs entirely to the epistemological part. Indeed, no element of this analogy plays any role in the formal part of Schrödinger's argument. Instead of basing his theory on this analogy, as is often done nowadays in the physics literature and even in the history of science, we maintain that the aim of Schrödinger's project was to represent wave phenomena by a ‘wave’ in configuration- or q-space, paralleling Hertz's treatment in his Mechanics (1894). The influence of this book on Schrödinger's foundational paper is demonstrated by an analysis of his unpublished paper: Hertz's Mechanics and Einstein's Theory of Gravitation. This approach enables us to dispense with the optical-mechanical analogy in tracing the route to Schrödinger's equation. We also discuss the curious role of the Van Vleck determinant as the ‘missing link’ in taking the classical limit of Schrödinger's wavefunction. A concluding section discusses the relation of some of Schrödinger's earlier and later work to the development of quantum field theory. (paper)
Resistance to early-life stress in mice: effects of genetic background and stress duration

Directory of Open Access Journals (Sweden)

Helene M. Savignac

2011-04-01

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

Science.gov (United States)

Santarelli, Sara; Zimmermann, Christoph; Kalideris, Georgia; Lesuis, Sylvie L; Arloth, Janine; Uribe, Andrés; Dournes, Carine; Balsevich, Georgia; Hartmann, Jakob; Masana, Mercè; Binder, Elisabeth B; Spengler, Dietmar; Schmidt, Mathias V

2017-04-01

Chronic stress is a major risk factor for depression. Interestingly, not all individuals develop psychopathology after chronic stress exposure. In contrast to the prevailing view that stress effects are cumulative and increase stress vulnerability throughout life, the match/mismatch hypothesis of psychiatric disorders. The match/mismatch hypothesis proposes that individuals who experience moderate levels of early life psychosocial stress can acquire resilience to renewed stress exposure later in life. Here, we have tested this hypothesis by comparing the developmental effects of 2 opposite early life conditions, when followed by 2 opposite adult environments. Male Balb/c mice were exposed to either adverse early life conditions (limited nesting and bedding material) or a supportive rearing environment (early handling). At adulthood, the animals of each group were either housed with an ovariectomized female (supportive environment) or underwent chronic social defeat stress (socially adverse environment) for 3 weeks. At the end of the adult manipulations, all of the animals were returned to standard housing conditions. Then, we compared the neuroendocrine, behavioral and molecular effects of the interaction between early and adult environment. Our study shows that early life adversity does not necessarily result in increased vulnerability to stress. Specific endophenotypes, like hypothalamic-pituitary-adrenal axis activity, anxiety-related behavior and glucocorticoid receptor expression levels in the hippocampus were not significantly altered when adversity is experienced during early life and in adulthood, and are mainly affected by either early life or adult life adversity alone. Overall our data support the notion that being raised in a stressful environment prepares the offspring to better cope with a challenging adult environment and emphasize the role of early life experiences in shaping adult responsiveness to stress. Copyright © 2017 Elsevier Ltd. All rights
Childhood maltreatment, stressful life events, and alcohol craving in adult drinkers

Science.gov (United States)

Kim, June H.; Martins, Silvia S.; Shmulewitz, Dvora; Santaella, Julian; Wall, Melanie M.; Keyes, Katherine M.; Eaton, Nicholas R.; Krueger, Robert; Grant, Bridget F.; Hasin, Deborah S.

2014-01-01

Background Little is known about the relationship of stressful life events and alcohol craving in the general population, and whether a history of childhood maltreatment sensitizes individuals to crave alcohol after adult stressors. Methods Participants were 22,147 past-year drinkers from Wave 2 (2004-2006) of the National Epidemiologic Survey on Alcohol and Related Conditions. A structured, face-to-face interview assessed past-year stressful life events, alcohol craving, and history of childhood maltreatment. Logistic regression was used to generate adjusted odds ratios (aOR) to evaluate the relationship between stressful life events and craving, adjusting for demographic characteristics and parental history of alcoholism. Interaction between stressful life events and childhood maltreatment was also assessed. Results Compared to participants with no stressful life events, those with ≥3 events had increased odds of moderate alcohol craving (aOR=3.15 [95% CI=2.30-4.33]) and severe craving (aOR=8.47 [95% CI=4.78-15.01]). Stressful life events and childhood maltreatment interacted in predicting severe craving (p=0.017); those with ≥3 events were at higher risk for craving if they had been exposed to childhood maltreatment. Conclusion A direct relationship between stressful life events and risk for alcohol craving was observed. Further, history of childhood maltreatment increased the salience of stressful life events in adulthood. Future studies should examine the role of psychiatric comorbidity in more complex models of stress sensitization and alcohol craving. PMID:24961735
Perceived life stress exposure modulates reward-related medial prefrontal cortex responses to acute stress in depression.

Science.gov (United States)

Kumar, Poornima; Slavich, George M; Berghorst, Lisa H; Treadway, Michael T; Brooks, Nancy H; Dutra, Sunny J; Greve, Douglas N; O'Donovan, Aoife; Bleil, Maria E; Maninger, Nicole; Pizzagalli, Diego A

2015-07-15

Major depressive disorder (MDD) is often precipitated by life stress and growing evidence suggests that stress-induced alterations in reward processing may contribute to such risk. However, no human imaging studies have examined how recent life stress exposure modulates the neural systems that underlie reward processing in depressed and healthy individuals. In this proof-of-concept study, 12 MDD and 10 psychiatrically healthy individuals were interviewed using the Life Events and Difficulties Schedule (LEDS) to assess their perceived levels of recent acute and chronic life stress exposure. Additionally, each participant performed a monetary incentive delay task under baseline (no-stress) and stress (social-evaluative) conditions during functional MRI. Across groups, medial prefrontal cortex (mPFC) activation to reward feedback was greater during acute stress versus no-stress conditions in individuals with greater perceived stressor severity. Under acute stress, depressed individuals showed a positive correlation between perceived stressor severity levels and reward-related mPFC activation (r=0.79, p=0.004), whereas no effect was found in healthy controls. Moreover, for depressed (but not healthy) individuals, the correlations between the stress (r=0.79) and no-stress (r=-0.48) conditions were significantly different. Finally, relative to controls, depressed participants showed significantly reduced mPFC gray matter, but functional findings remained robust while accounting for structural differences. Small sample size, which warrants replication. Depressed individuals experiencing greater recent life stress recruited the mPFC more under stress when processing rewards. Our results represent an initial step toward elucidating mechanisms underlying stress sensitization and recurrence in depression. Copyright © 2015 Elsevier B.V. All rights reserved.
Perceptions of Parental Awareness of Emotional Responses to Stressful Life Events.

Science.gov (United States)

Jobe-Shields, Lisa; Parra, Gilbert R; Buckholdt, Kelly E

2013-10-01

There is a need to better understand family processes related to recovery from past stressful life events. The present study aimed to investigate links between perceptions of parental awareness regarding stressful life events, continued event-related rumination, and current symptoms of depression. Students at a diverse, urban university completed a life events checklist and a semi-structured interview regarding family processing of stressful life events, as well as self-report measures of event-related rumination and depression. Results indicated that perceptions of mothers' and fathers' awareness of sadness regarding stressful life events as well as mothers' and fathers' verbal event processing predicted symptoms of event-related rumination and depression. Results support the inclusion of perceptions of parental awareness in the understanding of how emerging adults continue to cope with past stressful life events.
Effect of Silicon Nitride Balls and Rollers on Rolling Bearing Life

Science.gov (United States)

Zaretsky, Erwin V.; Vlcek, Brian L.; Hendricks, Robert C.

2005-01-01

Three decades have passed since the introduction of silicon nitride rollers and balls into conventional rolling-element bearings. For a given applied load, the contact (Hertz) stress in a hybrid bearing will be higher than an all-steel rolling-element bearing. The silicon nitride rolling-element life as well as the lives of the steel races were used to determine the resultant bearing life of both hybrid and all-steel bearings. Life factors were determined and reported for hybrid bearings. Under nominal operating speeds, the resultant calculated lives of the deep-groove, angular-contact, and cylindrical roller hybrid bearings with races made of post-1960 bearing steel increased by factors of 3.7, 3.2, and 5.5, respectively, from those calculated using the Lundberg-Palmgren equations. An all-steel bearing under the same load will have a longer life than the equivalent hybrid bearing under the same conditions. Under these conditions, hybrid bearings are predicted to have a lower fatigue life than all-steel bearings by 58 percent for deep-groove bearings, 41 percent for angular-contact bearings, and 28 percent for cylindrical roller bearings.
Evaluating personality as a moderator of the association between life events stress and cardiovascular reactivity to acute stress.

Science.gov (United States)

Gallagher, Stephen; O'Riordan, Adam; McMahon, Grace; Creaven, Ann-Marie

2018-04-01

The present study investigated the possible interaction between life events stress and personality in predicting cardiovascular stress responses. Participants (N = 184) completed psychometric measures of life event stress and personality styles and had cardiovascular responses monitored during a standardised stress testing protocol. In adjusted models, the observed blunted association between life event stress and SBP and DBP was moderated by openness; this was more evident at -1SD below the mean openness value. Further, the association between life event stress and TPR vascular resistance was found to be moderated by conscientiousness. In particular, we found conscientiousness at both the mean and 1SD above the mean buffered against the negative impact of life stress on TPR reactivity. The findings are discussed in relation to theory and future directions. Copyright © 2018 Elsevier B.V. All rights reserved.
How We Tend To Overestimate Powerlaw Tail Exponents

OpenAIRE

Nassim N. Taleb

2012-01-01

In the presence of a layer of metaprobabilities (from uncertainty concerning the parameters), the asymptotic tail exponent corresponds to the lowest possible tail exponent regardless of its probability. The problem explains "Black Swan" effects, i.e., why measurements tend to chronically underestimate tail contributions, rather than merely deliver imprecise but unbiased estimates.
Negative life events and symptoms of depression and anxiety: stress causation and/or stress generation

OpenAIRE

Phillips, Anna C.; Carroll, Douglas; Der, Geoffrey

2015-01-01

Background and Objectives: Stressful life events are known to contribute to development of depression, however, it is possible this link is bi-directional. The present study examined whether such stress generation effects are greater than the effects of stressful life events on depression, and whether stress generation is also evident with anxiety. Design: Participants were two large age cohorts (N = 732 aged 44 years; N = 705 aged 63 years) from the West of Scotland Twenty-07 study. Methods:...
Fatigue life estimation of welded components considering welding residual stress relaxation and its mean stress effect

International Nuclear Information System (INIS)

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

2003-01-01

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

Science.gov (United States)

Lu, Frank Jing-Horng; Hsu, Ya-Wen; Chan, Yuan-Shuo; Cheen, Jang-Rong; Kao, Kuei-Tsu

2012-01-01

College student-athletes have unique life stress that warrants close attention. The purpose of this study was to develop a reliable and valid measurement assessing college student-athletes' life stress. In Study 1, a focus group discussion and Delphi method produced a questionnaire draft, termed the College Student-Athletes' Life Stress Scale. In…
The Association of Sever Stressful Life Events and Multiple Sclerosis

Directory of Open Access Journals (Sweden)

Rozita Naeeni

2015-04-01

Full Text Available Background: Stressful life events have suggested as one of etiologic cause of the disease from the middle of last century, but controversies still is going on. Materials and Methods: This study is a case- control study conducted on 100 MS patients in neurology clinic of Shariati Hospital during one year. History of stressful life events one year before beginning of the disease was questioned. These events, according to Holmes and Rahe Stress Scale, were severe and affected the disease progression. The analysis of data was performed using SPSS 15. Results: The mean age of patients was 30.9 ± 7.1. Most of them (n=87 had relapsing- remitting MS. 51% of patients and 26% of controls had stressful life events (P<0.001. Odd's Ratio with confidence interval of 95% was 2.71. The most frequent stressful events were family problems and death of first degree relatives. Conclusion: This study showed that stressful life events were significantly more prevalent in MS, but we cannot conclude that stress lonely is a cause of MS. Although, major stress along with multiple other risk factors may be related to MS.
The Evolution of the Exponent of Zipf's Law in Language Ontogeny

Science.gov (United States)

Baixeries, Jaume; Elvevåg, Brita; Ferrer-i-Cancho, Ramon

2013-01-01

It is well-known that word frequencies arrange themselves according to Zipf's law. However, little is known about the dependency of the parameters of the law and the complexity of a communication system. Many models of the evolution of language assume that the exponent of the law remains constant as the complexity of a communication systems increases. Using longitudinal studies of child language, we analysed the word rank distribution for the speech of children and adults participating in conversations. The adults typically included family members (e.g., parents) or the investigators conducting the research. Our analysis of the evolution of Zipf's law yields two main unexpected results. First, in children the exponent of the law tends to decrease over time while this tendency is weaker in adults, thus suggesting this is not a mere mirror effect of adult speech. Second, although the exponent of the law is more stable in adults, their exponents fall below 1 which is the typical value of the exponent assumed in both children and adults. Our analysis also shows a tendency of the mean length of utterances (MLU), a simple estimate of syntactic complexity, to increase as the exponent decreases. The parallel evolution of the exponent and a simple indicator of syntactic complexity (MLU) supports the hypothesis that the exponent of Zipf's law and linguistic complexity are inter-related. The assumption that Zipf's law for word ranks is a power-law with a constant exponent of one in both adults and children needs to be revised. PMID:23516390
Forebrain CRF1 Modulates Early-Life Stress-Programmed Cognitive Deficits

Science.gov (United States)

Wang, Xiao-Dong; Rammes, Gerhard; Kraev, Igor; Wolf, Miriam; Liebl, Claudia; Scharf, Sebastian H.; Rice, Courtney J.; Wurst, Wolfgang; Holsboer, Florian; Deussing, Jan M.; Baram, Tallie Z.; Stewart, Michael G.; Müller, Marianne B.; Schmidt, Mathias V.

2012-01-01

Childhood traumatic events hamper the development of the hippocampus and impair declarative memory in susceptible individuals. Persistent elevations of hippocampal corticotropin-releasing factor (CRF), acting through CRF receptor 1 (CRF1), in experimental models of early-life stress have suggested a role for this endogenous stress hormone in the resulting structural modifications and cognitive dysfunction. However, direct testing of this possibility has been difficult. In the current study, we subjected conditional forebrain CRF1 knock-out (CRF1-CKO) mice to an impoverished postnatal environment and examined the role of forebrain CRF1 in the long-lasting effects of early-life stress on learning and memory. Early-life stress impaired spatial learning and memory in wild-type mice, and postnatal forebrain CRF overexpression reproduced these deleterious effects. Cognitive deficits in stressed wild-type mice were associated with disrupted long-term potentiation (LTP) and a reduced number of dendritic spines in area CA3 but not in CA1. Forebrain CRF1 deficiency restored cognitive function, LTP and spine density in area CA3, and augmented CA1 LTP and spine density in stressed mice. In addition, early-life stress differentially regulated the amount of hippocampal excitatory and inhibitory synapses in wild-type and CRF1-CKO mice, accompanied by alterations in the neurexin-neuroligin complex. These data suggest that the functional, structural and molecular changes evoked by early-life stress are at least partly dependent on persistent forebrain CRF1 signaling, providing a molecular target for the prevention of cognitive deficits in adults with a history of early-life adversity. PMID:21940453
Prenatal stress may increase vulnerability to life events

DEFF Research Database (Denmark)

Hougaard, Karin S; Andersen, Maibritt B; Kjaer, Sanna L

2005-01-01

Prenatal stress has been associated with a variety of alterations in the offspring. The presented observations suggest that rather than causing changes in the offspring per se, prenatal stress may increase the organism's vulnerability to aversive life events. Offspring of rat dams stressed...
Life stress and hysterectomy-oophorectomy

NARCIS (Netherlands)

Kraaimaat, F.W.; Veeninga, A.T.

1984-01-01

The effects of hysterectomy-oophorectomy and life stress in regard to physical and psychological discomfort were investigated. Oophorectomized women reported more physical complaints and more frequent loss of sexual interest than a control group of cholecystectomized women. No differences between

Perceptions of Parental Awareness of Emotional Responses to Stressful Life Events

OpenAIRE

Jobe-Shields, Lisa; Parra, Gilbert R.; Buckholdt, Kelly E.

2013-01-01

There is a need to better understand family processes related to recovery from past stressful life events. The present study aimed to investigate links between perceptions of parental awareness regarding stressful life events, continued event-related rumination, and current symptoms of depression. Students at a diverse, urban university completed a life events checklist and a semi-structured interview regarding family processing of stressful life events, as well as self-report measures of eve...
Oxidative stress and life histories: unresolved issues and current needs.

Science.gov (United States)

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

2015-12-01

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

Energy Technology Data Exchange (ETDEWEB)

Alvarez-Llamoza, O. [Departamento de Fisica, FACYT, Universidad de Carabobo, Valencia (Venezuela); Centro de Fisica Fundamental, Grupo de Caos y Sistemas Complejos, Universidad de Los Andes, Merida 5251, Merida (Venezuela)], E-mail: llamoza@ula.ve; Cosenza, M.G. [Centro de Fisica Fundamental, Grupo de Caos y Sistemas Complejos, Universidad de Los Andes, Merida 5251, Merida (Venezuela); Ponce, G.A. [Departamento de Fisica, Universidad Nacional Autonoma de Honduras (Honduras); Departamento de Ciencias Naturales, Universidad Pedagogica Nacional Francisco Morazan, Tegucigalpa (Honduras)

2008-04-15

The critical behavior of the Lyapunov exponent near the transition to robust chaos via type-III intermittency is determined for a family of one-dimensional singular maps. Critical boundaries separating the region of robust chaos from the region where stable fixed points exist are calculated on the parameter space of the system. A critical exponent {beta} expressing the scaling of the Lyapunov exponent is calculated along the critical curve corresponding to the type-III intermittent transition to chaos. It is found that {beta} varies on the interval 0 {<=} {beta} < 1/2 as a function of the order of the singularity of the map. This contrasts with earlier predictions for the scaling behavior of the Lyapunov exponent in type-III intermittency. The variation of the critical exponent {beta} implies a continuous change in the nature of the transition to chaos via type-III intermittency, from a second-order, continuous transition to a first-order, discontinuous transition.
Critical behavior of the Lyapunov exponent in type-III intermittency

International Nuclear Information System (INIS)

Alvarez-Llamoza, O.; Cosenza, M.G.; Ponce, G.A.

2008-01-01

The critical behavior of the Lyapunov exponent near the transition to robust chaos via type-III intermittency is determined for a family of one-dimensional singular maps. Critical boundaries separating the region of robust chaos from the region where stable fixed points exist are calculated on the parameter space of the system. A critical exponent β expressing the scaling of the Lyapunov exponent is calculated along the critical curve corresponding to the type-III intermittent transition to chaos. It is found that β varies on the interval 0 ≤ β < 1/2 as a function of the order of the singularity of the map. This contrasts with earlier predictions for the scaling behavior of the Lyapunov exponent in type-III intermittency. The variation of the critical exponent β implies a continuous change in the nature of the transition to chaos via type-III intermittency, from a second-order, continuous transition to a first-order, discontinuous transition
Lyapunov, attractors and exponents

International Nuclear Information System (INIS)

Oliveira, C.R. de.

1987-01-01

Based on the fundamental principles of statistical mechanics and ergodic theory a definition is given to atractor, as an invariant measure. Many results which reinforce this definition are demonstrated. Chaos is related to the presence of an atractor with entropy above zero. The role of Lyapunov exponents is analyzed. (A.C.A.S.) [pt
Perceived pregnancy stress and quality of life amongst Iranian women.

Science.gov (United States)

Shishehgar, Sara; Dolatian, Mahrokh; Majd, Hamid Alavi; Bakhtiary, Maryam

2014-04-24

Stress during pregnancy can result in critical negative outcomes on the mother, the fetus, the newborn, the child and even the adolescent. Quality of life has been recognized as a predictor of stress amongst pregnant women. The first aim of this study was to investigate the role of quality of life in pregnancy stress rates. The second aim was to explore the relationship between maternal stress rate and the four domains of quality of life namely physical health, psychological status, social relationships and environmental conditions. The present study was a quantitative cross-sectional research. It was conducted on 210 pregnant women in all trimesters of pregnancy who attended a hospital located in the west of Tehran for prenatal care between August and October 2012. Two questionnaires of The WHO QOL-BREF and Specific Pregnancy Stress were given to respondents to complete. The collected data was analyzed by SPSS version 22 using one-way ANOVA and Spearman correlation and Lisrel 8.8 using statistical path analyzing to describe the direct dependencies among variables. In the current study, we hypothesized that quality of life may influence the perceived stress during pregnancy. The mean age of the women surveyed was estimated 27±4.8 years. The ultimate result showed that there is a significant relationship between quality of life and pregnancy stress level (Pvalue life and the financial and environmental dimensions of specific pregnancy stress (Pvalue < 0.05, r=-0.365, r=-0.181). Further investigations may be considered for extending the results to all pregnant women. Thus, further research across country would be required to validate the results of this study and to generalize the findings to wider population.
Early Life Stress, Nicotinic Acetylcholine Receptors and Alcohol Use Disorders

Directory of Open Access Journals (Sweden)

Joan Y. Holgate

2015-06-01

Full Text Available Stress is a major driving force in alcohol use disorders (AUDs. It influences how much one consumes, craving intensity and whether an abstinent individual will return to harmful alcohol consumption. We are most vulnerable to the effects of stress during early development, and exposure to multiple traumatic early life events dramatically increases the risk for AUDs. However, not everyone exposed to early life stress will develop an AUD. The mechanisms determining whether an individual’s brain adapts and becomes resilient to the effects of stress or succumbs and is unable to cope with stress remain elusive. Emerging evidence suggests that neuroplastic changes in the nucleus accumbens (NAc following early life stress underlie the development of AUDs. This review discusses the impact of early life stress on NAc structure and function, how these changes affect cholinergic signaling within the mesolimbic reward pathway and the role nicotinic acetylcholine receptors (nAChRs play in this process. Understanding the neural pathways and mechanism determining stress resilience or susceptibility will improve our ability to identify individuals susceptible to developing AUDs, formulate cognitive interventions to prevent AUDs in susceptible individuals and to elucidate and enhance potential therapeutic targets, such as the nAChRs, for those struggling to overcome an AUD.
Lyapunov exponents

CERN Document Server

Barreira, Luís

2017-01-01

This book offers a self-contained introduction to the theory of Lyapunov exponents and its applications, mainly in connection with hyperbolicity, ergodic theory and multifractal analysis. It discusses the foundations and some of the main results and main techniques in the area, while also highlighting selected topics of current research interest. With the exception of a few basic results from ergodic theory and the thermodynamic formalism, all the results presented include detailed proofs. The book is intended for all researchers and graduate students specializing in dynamical systems who are looking for a comprehensive overview of the foundations of the theory and a sample of its applications.
Composite Overwrap Pressure Vessels: Mechanics and Stress Rupture Lifing Philosophy

Science.gov (United States)

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

2007-01-01

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

International Nuclear Information System (INIS)

Ha Huy Vui; Pham Tien Son

2007-07-01

Let f : R n → R be a nonconstant polynomial function. In this paper, using the information from 'the curve of tangency' of f, we provide a method to determine the Lojasiewicz exponent at infinity of f. As a corollary, we give a computational criterion to decide if the Lojasiewicz exponent at infinity is finite or not. Then, we obtain a formula to calculate the set of points at which the polynomial f is not proper. Moreover, a relation between the Lojasiewicz exponent at infinity of f with the problem of computing the global optimum of f is also established. (author)
Early life stress, HPA axis adaptation and mechanisms contributing to later health outcomes

Directory of Open Access Journals (Sweden)

Jayanthi eManiam

2014-05-01

Full Text Available Stress activates the hypothalamic-pituitary-adrenal (HPA axis, which then modulates the degree of adaptation and response to a later stressor. It is known that early life stress can impact on later health but less is known about how early life stress impairs HPA axis activity, contributing to maladaptation of the stress response system. Early life stress exposure (either prenatally or in the early postnatal period can impact developmental pathways resulting in lasting structural and regulatory changes that predispose to adulthood disease. Epidemiological, clinical and experimental studies have demonstrated that early life stress produces long-term hyper responsiveness to stress with exaggerated circulating glucocorticoids, and enhanced anxiety and depression-like behaviours. Recently, evidence has emerged on early life stress induced metabolic derangements, for example hyperinsulinemia and altered insulin sensitivity on exposure to a high energy diet later in life. This draws our attention to the contribution of later environment to disease vulnerability. Early life stress can alter the expression of genes in peripheral tissues, such as the glucocorticoid receptor and 11-beta hydroxysteroid dehydrogenase (11β-HSD1. We propose that interactions between altered HPA axis activity and liver 11β-HSD1 modulates both tissue and circulating glucocorticoid availability, with adverse metabolic consequences. This review discusses the potential mechanisms underlying early life stress induced maladaptation of the HPA axis, and its subsequent effects on energy utilisation and expenditure. The effects of positive later environments as a means of ameliorating early life stress induced health deficits, and proposed mechanisms underpinning the interaction between early life stress and subsequent detrimental environmental exposures on metabolic risk will be outlined. Limitations in current methodology linking early life stress and later health outcomes will also
Psychotherapeutic Methods of Coping with Stress in Everyday Life

Directory of Open Access Journals (Sweden)

Senol TURAN

2015-12-01

Full Text Available Stress is an inevitable part of life. Knowing the ways of coping with stress are necessary to preserve our mental and physical health and to maintain good social and/or occupational functioning in daily life activities. Different ways of coping with stress have been developed throughout history. Various type of therapies offer quite effective remedies for coping with stress in everyday life. Among psychotherapeutic treatments cognitive behavioral therapy which involves teaching stressful individuals to develop coping strategies have yielded very promising results. It is helpful to determine first whether stress source can be changed, several therapeutic approaches may then be used. Lazarus and Folkman have identified two major approaches for coping with stress so-called "problem-focused" and "emotion-focused". In "problem-focused" approaches targets are acquiring time management, self-monitoring, problem-solving skills, while in "emotion-focused" approaches, through ways of accepting or rejecting of stress associated negative emotions, or reconciling with these emotions, the target is learning how to keep emotions under control. "Problem-focused" and "emotion-focused" approaches may independently be used effectively in appropriate cases, their simultaneous practice may increase chances of successful treatment. Apart from this methods, psychodynamic therapy may be indicated in some cases. [JCBPR 2015; 4(3.000: 133-140
Self-esteem, narcissism, and stressful life events: Testing for selection and socialization.

Science.gov (United States)

Orth, Ulrich; Luciano, Eva C

2015-10-01

We examined whether self-esteem and narcissism predict the occurrence of stressful life events (i.e., selection) and whether stressful life events predict change in self-esteem and narcissism (i.e., socialization). The analyses were based on longitudinal data from 2 studies, including samples of 328 young adults (Study 1) and 371 adults (Study 2). The effects of self-esteem and narcissism were mutually controlled for each other and, moreover, controlled for effects of depression. After conducting the study-level analyses, we meta-analytically aggregated the findings. Self-esteem had a selection effect, suggesting that low self-esteem led to the occurrence of stressful life events; however, this effect became nonsignificant when depression was controlled for. Regardless of whether depression was controlled for or not, narcissism had a selection effect, suggesting that high narcissism led to the occurrence of stressful life events. Moreover, stressful life events had a socialization effect on self-esteem, but not on narcissism, suggesting that the occurrence of stressful life events decreased self-esteem. Analyses of trait-state models indicated that narcissism consisted almost exclusively of perfectly stable trait variance, providing a possible explanation for the absence of socialization effects on narcissism. The findings have significant implications because they suggest that a person's level of narcissism influences whether stressful life events occur, and that self-esteem is shaped by the occurrence of stressful life events. Moreover, we discuss the possibility that depression mediates the selection effect of low self-esteem on stressful life events. (PsycINFO Database Record (c) 2015 APA, all rights reserved).
Work-related social support modulates effects of early life stress on limbic reactivity during stress.

Science.gov (United States)

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

2017-12-15

Early life stress (ELS) affects stress- reactivity via limbic brain regions implicated such as hippocampus and amygdala. Social support is a major protective factor against ELS effects, while subjects with ELS experience reportedly perceive less of it in their daily life. The workplace, where most adults spend a substantial amount of time in their daily lives, might serve as a major resource for social support. Since previous data demonstrated that social support attenuates stress reactivity, we here used a psychosocial stress task to test the hypothesis that work-related social support modulates the effects of ELS. Results show decreased amygdala reactivity during stress in ELS subjects who report high levels of work- related social support, thereby indicating a signature for reduced stress reactivity. However, this effect was only observable on the neural, but not on the behavioral level, since social support had no buffering effect regarding the subjective experience of stress in daily life as well as regarding feelings of uncontrollability induced by the stress task. Accordingly, our data suggest that subjects with ELS experiences might benefit from interventions targeted at lowering their subjective stress levels by helping them to better perceive the availability of social support in their daily lives.
Life stress versus traumatic stress: The impact of life events on psychological functioning in children with and without serious illness.

Science.gov (United States)

Willard, Victoria W; Long, Alanna; Phipps, Sean

2016-01-01

To determine the differential impact of potentially traumatic events (PTEs) and other stressful life events on psychological functioning in 2 groups of children: those with cancer and those without history of serious illness. Children with cancer age 8-17 (n = 254) and age-, sex-, and race/ethnicity-matched controls (n = 142) completed self-report measures of stressful life events and psychological functioning. Stressful life events included those that may meet Diagnostic and Statistical Manual of Mental Disorders (4th ed.; DSM-IV; American Psychiatric Association, 2000) A1 criteria (PTEs; 9 events) and others that would likely not (other events; 21 events). Children with cancer endorsed significantly more PTEs than control children. There were no differences between groups in number of other events experienced. Hierarchical regression analyses revealed that number of other events accounted for significant variance in psychological functioning, above and beyond group status, demographic factors (age and socioeconomic status), and number of PTEs. The number of cumulative other events experienced is a significant predictor of psychological functioning in both youth with serious illness and controls. In contrast, cumulative PTEs appear to have a minor (albeit significant) impact on children's psychological functioning. Assessment of psychological functioning would benefit from a thorough history of stressful life events, regardless of their potential traumatic impact. (c) 2016 APA, all rights reserved).
Full spectrum of Lyapunov exponents in gauge field theories

International Nuclear Information System (INIS)

Biro, T.S.; Markum, H.; Pullirsch, R.

2003-01-01

Full text: Results are presented for the full spectrum of Lyapunov exponents of the compact U(1) gauge system in classical field theory. Instead of the determination of the largest Lyapunov exponent by the rescaling method we now use the monodromy matrix approach. The Lyapunov spectrum L i is expressed in terms of the eigenvalues Λ i of the monodromy matrix M. In the confinement phase the eigenvalues lie on either the real or on the imaginary axes. This is a nice illustration of a strange attractor of a chaotic system. Positive Lyapunov exponents eject the trajectories from oscillating orbits provided by the imaginary eigenvalues. Negative Lyapunov exponents attract the trajectories keeping them confined in the basin. Latest studies concern the time (in)dependence of the monodromy matrix. Further, we show that monopoles are created and annihilated in pairs as a function of real time in access to a fixed average monopole number. (author)
Early-Life Stress, HPA Axis Adaptation, and Mechanisms Contributing to Later Health Outcomes

Science.gov (United States)

Maniam, Jayanthi; Antoniadis, Christopher; Morris, Margaret J.

2014-01-01

Stress activates the hypothalamic–pituitary–adrenal (HPA) axis, which then modulates the degree of adaptation and response to a later stressor. It is known that early-life stress can impact on later health but less is known about how early-life stress impairs HPA axis activity, contributing to maladaptation of the stress–response system. Early-life stress exposure (either prenatally or in the early postnatal period) can impact developmental pathways resulting in lasting structural and regulatory changes that predispose to adulthood disease. Epidemiological, clinical, and experimental studies have demonstrated that early-life stress produces long term hyper-responsiveness to stress with exaggerated circulating glucocorticoids, and enhanced anxiety and depression-like behaviors. Recently, evidence has emerged on early-life stress-induced metabolic derangements, for example hyperinsulinemia and altered insulin sensitivity on exposure to a high energy diet later in life. This draws our attention to the contribution of later environment to disease vulnerability. Early-life stress can alter the expression of genes in peripheral tissues, such as the glucocorticoid receptor and 11-beta hydroxysteroid dehydrogenase (11β-HSD1). We propose that interactions between altered HPA axis activity and liver 11β-HSD1 modulates both tissue and circulating glucocorticoid availability, with adverse metabolic consequences. This review discusses the potential mechanisms underlying early-life stress-induced maladaptation of the HPA axis, and its subsequent effects on energy utilization and expenditure. The effects of positive later environments as a means of ameliorating early-life stress-induced health deficits, and proposed mechanisms underpinning the interaction between early-life stress and subsequent detrimental environmental exposures on metabolic risk will be outlined. Limitations in current methodology linking early-life stress and later health outcomes will also be
The role of maternal care in borderline personality disorder and dependent life stress.

Science.gov (United States)

Ball Cooper, Ericka; Venta, Amanda; Sharp, Carla

2018-01-01

Borderline Personality Disorder (BPD) affects 0.9%-3.2% of adolescents, and more than 20% of inpatient adolescents. Life stress has been linked to BPD across the lifespan, and previous research in adults has linked BPD to dependent stress (i.e., stress induced by the individual). However, prior research has not examined dependent stress alongside BPD in adolescents. Additionally, the potential protective effect of maternal care has not been considered in this relation. This study tested a moderation model expecting that (1) BPD would be positively associated with dependent life stress, (2) maternal care would be negatively associated with BPD, and (3) maternal care would moderate the relation between BPD and dependent life stress. The sample consisted of 184 adolescents recruited from an inpatient psychiatric facility serving a diverse population in the Southwestern United States. Dependent life stress, BPD, and maternal care were measured using the UCLA Life Stress Interview, DSM-IV Childhood Interview for BPD, and Kerns Security Scale, respectively. Results supported the first two hypotheses; BPD diagnosis was significantly, positively associated with dependent life stress, and negatively associated with maternal availability and dependability. Contrary to the third hypothesis, no significant evidence that maternal care acts as a buffer in the relation between BPD and dependent life stress was found. Although maternal care was not found to moderate the association between BPD and dependent life stress, results supported previously found relations between BPD, dependent life stress, and maternal care, and did so within a diverse inpatient adolescent sample.
Early life stress determines the effects of glucocorticoids and stress on hippocampal function: Electrophysiological and behavioral evidence respectively.

Science.gov (United States)

Pillai, Anup G; Arp, Marit; Velzing, Els; Lesuis, Sylvie L; Schmidt, Mathias V; Holsboer, Florian; Joëls, Marian; Krugers, Harm J

2018-05-01

Exposure to early-life adversity may program brain function to prepare individuals for adaptation to matching environmental contexts. In this study we tested this hypothesis in more detail by examining the effects of early-life stress - induced by raising offspring with limited nesting and bedding material from postnatal days 2-9 - in various behavioral tasks and on synaptic function in adult mice. Early-life stress impaired adult performance in the hippocampal dependent low-arousing object-in-context recognition memory task. This effect was absent when animals were exposed to a single stressor before training. Early-life stress did not alter high-arousing context and auditory fear conditioning. Early-life stress-induced behavioral modifications were not associated with alterations in the dendritic architecture of hippocampal CA1 pyramidal neurons or principal neurons of the basolateral amygdala. However, early-life stress reduced the ratio of NMDA to AMPA receptor-mediated excitatory postsynaptic currents and glutamate release probability specifically in hippocampal CA1 neurons, but not in the basolateral amygdala. These ex vivo effects in the hippocampus were abolished by acute glucocorticoid treatment. Our findings support that early-life stress can hamper object-in-context learning via pre- and postsynaptic mechanisms that affect hippocampal function but these effects are counteracted by acute stress or elevated glucocorticoid levels. Copyright © 2018. Published by Elsevier Ltd.
Life stress as potential risk factor for depression and burnout

Directory of Open Access Journals (Sweden)

T. Plieger

2015-03-01

Conclusion: By considering the influence of life stress it could be demonstrated that depression and burnout are not identical although they share substantial phenotypic variance (r = .46–.61. Most important, the trivariate associations are the same in a representative employee sample and in an inpatient clinical sample suggesting the same underlying mechanisms covering the whole range from normal behavior to psychopathology. However, only longitudinal data can show if burnout necessarily turns into depression with the consequence that the burnout – life stress association approaches the depression – life stress association over time.

Infrared catastrophe averted by Hertz potential

International Nuclear Information System (INIS)

Zwanziger, D.

1979-01-01

A computational scheme for quantum electrodynamics is developed from first principles in which infrared divergences are not encountered. The gist of the method is that the photon propagator is properly -ig/sub munu/(k 2 + iepsilon) -1 (1/2k/sup sigma/partial/partialk/sup sigma/)/sub w/ln(-lambda -2 k 2 - iepsilon). Here lambda is a parameter which plays the role of the photon mass, but which cancels out of cross sections for any finite value (lambda → 0 is never taken). The subscript w means weak derivative, so a partial integration on k, with neglect of boundary terms, is always understood in Feynman integrals. This makes integrals converge which otherwise would be logarithmically divergent. For sufficiently convergent integrals the partial integration may be undone and the conventional value results because (1/2k/sup sigma/partial/partialk/sup sigma/)ln(-lambda -2 k 2 - iepsilon) = 1. It is shown that the above propagator is not merely an artificial device, but results if the vector potential A/sup μ/ is derived from a Hertz potential π/sup lambdamu/ = -π/sup mulambda/, A/sup μ/ = partial/sub μ/π/sup lambdamu/, which is a local field. The real-photon infrared divergences do not occur when the integral over real photons is obtained from the discontinuity in the k 0 plane of the above propagator. A contribution to the real-photon integral at strictly zero frequency, resembling a third polarization state of the photon, is isolated and evaluated explicitly. The S matrix and physical subspaces are defined
Life Balance and Stress in Adults With Medical Conditions or Obesity.

Science.gov (United States)

Matuska, Kathleen; Bass, Julie

2016-04-01

This cross-sectional research examined differences in life balance and perceived stress by body mass index (BMI) levels and self-reported medical conditions that limited physical activity. The sample consisted of 2,338 participants between the ages of 18 and 49 years who took the Life Balance Inventory, the Perceived Stress Scale, and provided demographic information including height and weight. Findings showed that individuals who were obese (BMI > 30.0) reported significantly lower life balance scores and higher stress scores than participants without obesity (p life balance and more stress than individuals without medical conditions (p < .001). These findings highlight the importance of addressing activity participation as a means to promote health and wellness. © The Author(s) 2016.
Sub-millimeter science with the Heinrich-Hertz-Telescope

Science.gov (United States)

Dumke, Michael

The Heinrich-Hertz-Telescope on Mt. Graham, Arizona, is a state-of-the-art single-dish radio telescope for observations in the sub-millimeter wavelength range. It is operated by the Sub-Millimeter Telescope Observatory (SMTO), which is a collaboration between the University of Arizona, Tucson, and the Max-Planck-Institut für Radioastronomie, Bonn. In this talk I give an overview over the telescope and its instrumentation, and show some examples of forefront research performed by astronomers from both the U.S. and Europe using this instrument. The telescope is located on Mt. Graham, Arizona, at an altitude of 3178 m, which ensures sub-mm weather conditions during a significant amount of available observing time. It has a primary reflector of 10 m diameter, mounted on a carbon fiber backup structure, and is equipped with a corotating enclosure. The surface accuracy of the primary reflector is 12 microns rms, what makes the HHT the most accurate radio telescope ever built. For spectral line observations, SIS receivers covering the frequency range from 200 to 500 GHz are available. Furthermore, a Hot-Electron-Bolometer, developed at the CfA, can be used for spectral line observations above 800 GHz. The continuum receivers are a 4-color bolometer, observing at 1300, 870, 450, and 350 microns, and a 19-channel bolometer array, developed at the MPIfR, which is sensitive around 850 microns. In the last few years, the HHT has been used by several groups to perform astronomical research. The most notable result was the measurement of the CO(9--8) line in Orion at 1.037 THz with the Hot-Electron Bolometer -- the first radioastronomical observation above 1 THz from a ground-based telescope. Several galactic molecular line sources have been mapped in the CO(7--6) line at 806 GHz, and in two fine-structure lines of atomic carbon. A continuum map of the galactic center at 850 microns could be produced using the new 19-channel bolometer array. Even external galaxies, where
Suicide in Relation to the Experience of Stressful Life Events

DEFF Research Database (Denmark)

Fjeldsted, Rita; Teasdale, Thomas William; Jensen, Martin

2017-01-01

Stressful life events have been associated with high risk of suicidal behavior. The aim of this study was to examine whether persons who died by suicide in Denmark had more frequently been exposed to stressful life events, specifically divorce, death of a close relative, exposure to violence......, and imprisonment, when compared to gender and age-matched controls. Data from Danish national registers were obtained for the period of 2000-2010 and a nested case-control design was applied. The association between exposure to stressful life events and suicide was examined using logistic regression analysis...... compared to controls. People who died by suicide had 1.5-fold (CI-95%: 1.3-1.6) higher risk of having experienced a divorce. Stressful life events, such as divorce and imprisonment, were more frequent in temporal proximity to the date of death among the suicide cases than for end of exposure for controls...
OBSERVING LYAPUNOV EXPONENTS OF INFINITE-DIMENSIONAL DYNAMICAL SYSTEMS.

Science.gov (United States)

Ott, William; Rivas, Mauricio A; West, James

2015-12-01

Can Lyapunov exponents of infinite-dimensional dynamical systems be observed by projecting the dynamics into ℝ N using a 'typical' nonlinear projection map? We answer this question affirmatively by developing embedding theorems for compact invariant sets associated with C 1 maps on Hilbert spaces. Examples of such discrete-time dynamical systems include time- T maps and Poincaré return maps generated by the solution semigroups of evolution partial differential equations. We make every effort to place hypotheses on the projected dynamics rather than on the underlying infinite-dimensional dynamical system. In so doing, we adopt an empirical approach and formulate checkable conditions under which a Lyapunov exponent computed from experimental data will be a Lyapunov exponent of the infinite-dimensional dynamical system under study (provided the nonlinear projection map producing the data is typical in the sense of prevalence).
Hypergeometric continuation of divergent perturbation series: I. Critical exponents of the Bose–Hubbard model

International Nuclear Information System (INIS)

Sanders, Sören; Holthaus, Martin

2017-01-01

We study the connection between the exponent of the order parameter of the Mott insulator-to-superfluid transition occurring in the two-dimensional Bose–Hubbard model, and the divergence exponents of its one- and two-particle correlation functions. We find that at the multicritical points all divergence exponents are related to each other, allowing us to express the critical exponent in terms of one single divergence exponent. This approach correctly reproduces the critical exponent of the three-dimensional XY universality class. Because divergence exponents can be computed in an efficient manner by hypergeometric analytic continuation, our strategy is applicable to a wide class of systems. (paper)
Hypergeometric continuation of divergent perturbation series: I. Critical exponents of the Bose-Hubbard model

Science.gov (United States)

Sanders, Sören; Holthaus, Martin

2017-10-01

We study the connection between the exponent of the order parameter of the Mott insulator-to-superfluid transition occurring in the two-dimensional Bose-Hubbard model, and the divergence exponents of its one- and two-particle correlation functions. We find that at the multicritical points all divergence exponents are related to each other, allowing us to express the critical exponent in terms of one single divergence exponent. This approach correctly reproduces the critical exponent of the three-dimensional XY universality class. Because divergence exponents can be computed in an efficient manner by hypergeometric analytic continuation, our strategy is applicable to a wide class of systems.
The Social and Spatial Patterning of Life Stress Among Immigrants in Canada.

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Wang, Lu; Palacios, Elmer Lara

2017-06-01

While much literature has examined immigrants' health in Canada, less attention has focused specifically on the life stress, an important yet understudied post-migration challenge which may lead to poor coping strategies and negative health consequences. For this study, the pooled 2009-2014 Canadian Community Health Survey (CCHS) was analyzed, using multilevel logistic regression to examine the compositional effects (at an individual level) and areal effects (at a CMA/CA level) on reported high life stress. Separate models have been run for immigrants and non-immigrants for comparative purposes. The results reveal different ways in which select individual socioeconomic and lifestyle factors affect life stress. A statistically significant yet small areal effect at the CMA/CA level on life stress was identified for both immigrants and non-immigrants. When comparing immigrants to non-immigrants, factors such as smoking, length of residency in Canada, and mental health status were found to be particularly informative for predicting high life stress among immigrants. A Healthy Immigrant Effect (HIE) is partially evident, as immigrants with a longer stay in Canada are more likely to be highly stressed than recent arrivals. The areal effect on variances in high life stress is minimal, suggesting the importance of focusing on individual-level effects as stress predictors.
A study on the evaluation of dynamic stress intensity factor in repeated impact bending test

International Nuclear Information System (INIS)

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

1988-01-01

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

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Gupchup, Gireesh V.; Borrego, Matthew E.; Konduri, Niranjan

2004-01-01

The purpose of this study was to examine the association between student-life stress and health related quality of life (HRQOL) among Doctor of Pharmacy (Pharm.D.) students. Data were collected for 166 students in the first three years of a Pharm.D. curriculum. Student-Life Stress Inventory scores were significantly negatively correlated to mental…
Design for limit stresses of orange fruits (Citrus sinensis under axial and radial compression as related to transportation and storage design

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Christopher Chukwutoo Ihueze

2017-01-01

Full Text Available This article employed the Hertz contact stress theory and the finite element method to evaluate the maximum contact pressure and the limit stresses of orange fruit under transportation and storage. The elastic properties of orange fruits subjected to axial and axial contact were measured such that elastic limit force, elastic modulus, Poisson’s ratio and bioyield stress were obtained as 18 N, 0.691 MPa, 0.367, 0.009 MPa for axial compression and for radial loading were 15.69 N, 0.645 MPa, 0.123, 0.010 MPa. The Hertz maximum contact pressure was estimated for axial and radial contacts as 0.036 MPa. The estimated limiting yield stress estimated as von Mises stresses for the induced surface stresses of the orange topologies varied from 0.005 MPa–0.03 MPa. Based on the distortion energy theory (DET the yield strength of orange fruit is recommended as 0.03 MPa while based on the maximum shear stress theory (MSST is 0.01 MPa for the design of orange transportation and storage system.
Quality of Life and Stressful Life Events in First and Second Generation Immigrant Adolescents

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Ida Lemos

2013-09-01

Full Text Available The aim of this study was to examine differences in quality of life and stressful life events, in first and second generation immigrant adolescents living in Algarve. A total of 172 immigrant adolescents participated in the study, completing the kidscreen-52, the stressful and negative life events inventory and a socio-demographic questionnaire. Results suggest that younger immigrant adolescents report more physical well-being and a higher mood level. Concerning gender differences, girls scored higher than boys in physical well-being, mood and self-perception, but no differences were found on the other kidscreen subscales. First generation immigrants scored significantly higher than second generation ones on the general quality of life index, psychological well-being, autonomy, financial resources and school environment. However, the second-generation immigrants did not seem to be more exposed to stressful life events than the first-generation group. When selecting relevant variables for well-being promotion and for intervention, we must consider that immigrants are more exposed to economic vulnerability, may experience difficulties in adapting to a different school context, and are at higher risk of social exclusion.
Lyapunov exponents for infinite dimensional dynamical systems

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Mhuiris, Nessan Mac Giolla

1987-01-01

Classically it was held that solutions to deterministic partial differential equations (i.e., ones with smooth coefficients and boundary data) could become random only through one mechanism, namely by the activation of more and more of the infinite number of degrees of freedom that are available to such a system. It is only recently that researchers have come to suspect that many infinite dimensional nonlinear systems may in fact possess finite dimensional chaotic attractors. Lyapunov exponents provide a tool for probing the nature of these attractors. This paper examines how these exponents might be measured for infinite dimensional systems.
The hurst exponent and long-time correlation

International Nuclear Information System (INIS)

Wang, G.; Antar, G.; Devynck, P.

1999-10-01

The rescaled range statistics (R/S) method is applied to the ion saturation current fluctuations measured by Langmuir probe at edge on Tore Supra to evaluate the Hurst exponent. Data block randomization is carried out to the data sets in order to investigate the relationship between the Hurst exponent and long time correlation. It is observed that h is well above 0.5 in the long time self-similar range. However, it is found that the information which leads to H > 0.5 is totally contained in the short-time correlation and no link to long times is found. (authors)
Occupational Stress and Quality of Life in Nursing

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Aline Moraes da Silva

2016-04-01

Full Text Available Abstract To reduce the work related to stress and the psychosocial risk is not only an imperative question, but also moral. This epistemological study aims to verify the presence of the occupational stress and quality of life related to health in nursing professionals. We used three questionnaires: (a Socio Demographic Questionnaire, (b Job Strain Scale, and (c Item Short Form Health Survey. Statistical analysis was performed between the questionnaires, analysis of variance (ANOVA and simple and multiple linear regression. It was found that 60.8% of the participants see the high demand of work, 71.8% high control on the developed activity and 85.5% low social support. Related to eight dominant of quality of life, the most damaged are: pain (µ = 61.87 and vitality (µ = 62.25. It was concluded that although in most sample experiences an intermediary risk situation to stress, the quality of life showed a damaged.
Personality, Stressful Life Events, and Treatment Response in Major Depression

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Bulmash, Eric; Harkness, Kate L.; Stewart, Jeremy G.; Bagby, R. Michael

2009-01-01

The current study examined whether the personality traits of self-criticism or dependency moderated the effect of stressful life events on treatment response. Depressed outpatients (N = 113) were randomized to 16 weeks of cognitive-behavioral therapy, interpersonal psychotherapy, or antidepressant medication (ADM). Stressful life events were…
Subdiffusive master equation with space-dependent anomalous exponent and structural instability

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Fedotov, Sergei; Falconer, Steven

2012-03-01

We derive the fractional master equation with space-dependent anomalous exponent. We analyze the asymptotic behavior of the corresponding lattice model both analytically and by Monte Carlo simulation. We show that the subdiffusive fractional equations with constant anomalous exponent μ in a bounded domain [0,L] are not structurally stable with respect to the nonhomogeneous variations of parameter μ. In particular, the Gibbs-Boltzmann distribution is no longer the stationary solution of the fractional Fokker-Planck equation whatever the space variation of the exponent might be. We analyze the random distribution of μ in space and find that in the long-time limit, the probability distribution is highly intermediate in space and the behavior is completely dominated by very unlikely events. We show that subdiffusive fractional equations with the nonuniform random distribution of anomalous exponent is an illustration of a “Black Swan,” the low probability event of the small value of the anomalous exponent that completely dominates the long-time behavior of subdiffusive systems.
Global life satisfaction predicts ambulatory affect, stress, and cortisol in daily life in working adults.

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Smyth, Joshua M; Zawadzki, Matthew J; Juth, Vanessa; Sciamanna, Christopher N

2017-04-01

Global life satisfaction has been linked with long-term health advantages, yet how life satisfaction impacts the trajectory of long-term health is unclear. This paper examines one such possible mechanism-that greater life satisfaction confers momentary benefits in daily life that accumulate over time. A community sample of working adults (n = 115) completed a measure of life satisfaction and then three subsequent days of ecological momentary assessment surveys (6 times/day) measuring affect (i.e., emotional valence, arousal), and perceived stress, and also provided salivary cortisol samples. Multilevel models indicated that people with higher (vs. lower) levels of life satisfaction reported better momentary affect, less stress, marginally lower momentary levels and significantly altered diurnal slopes of cortisol. Findings suggest individuals with high global life satisfaction have advantageous daily experiences, providing initial evidence for potential mechanisms through which global life satisfaction may help explain long-term health benefits.
Stress and Quality of Life for Taiwanese Women Who Underwent Infertility Treatment.

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Cheng, Ching-Yu; Stevenson, Eleanor Lowndes; Yang, Cheng-Ta; Liou, Shwu-Ru

2018-04-28

To describe the psychological stress and quality of life experienced by women who underwent fertility treatment in Taiwan. Cross-sectional, correlational study. Recruitment was conducted and questionnaires administered at a reproductive medicine center in Chiayi City, Taiwan. Informed consent to participate was obtained from 126 women who sought fertility treatment at the center. The Chinese Fertility Problem Inventory and Fertility Quality of Life scale were used to measure participants' levels of fertility-related stress and fertility-related quality of life. Descriptive statistics, correlation, and regression analysis were used. Overall, participants reported low levels of fertility-related stress and fertility-related quality of life; however, they had relatively high levels of stress related to need for parenthood. Women who were older, had greater body mass indexes, and consumed coffee regularly had lower fertility-related quality of life. Social and relationship concerns and stress related to need for parenthood were significant predictors of low fertility-related quality of life. In a culture in which childbearing is generally an expectation and an important part of family life, women who experience infertility are at risk to experience fertility-related stress. Social support and family consultation might be offered to improve women's fertility-related quality of life. Copyright © 2018 AWHONN, the Association of Women’s Health, Obstetric and Neonatal Nurses. Published by Elsevier Inc. All rights reserved.
Transgenerational transmission of a stress-coping phenotype programmed by early-life stress in the Japanese quail

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Zimmer, Cédric; Larriva, Maria; Boogert, Neeltje J.; Spencer, Karen A.

2017-01-01

An interesting aspect of developmental programming is the existence of transgenerational effects that influence offspring characteristics and performance later in life. These transgenerational effects have been hypothesized to allow individuals to cope better with predictable environmental fluctuations and thus facilitate adaptation to changing environments. Here, we test for the first time how early-life stress drives developmental programming and transgenerational effects of maternal exposure to early-life stress on several phenotypic traits in their offspring in a functionally relevant context using a fully factorial design. We manipulated pre- and/or post-natal stress in both Japanese quail mothers and offspring and examined the consequences for several stress-related traits in the offspring generation. We show that pre-natal stress experienced by the mother did not simply affect offspring phenotype but resulted in the inheritance of the same stress-coping traits in the offspring across all phenotypic levels that we investigated, shaping neuroendocrine, physiological and behavioural traits. This may serve mothers to better prepare their offspring to cope with later environments where the same stressors are experienced. PMID:28387355

Life Stress and Health: A Review of Conceptual Issues and Recent Findings.

Science.gov (United States)

Slavich, George M

2016-10-01

Life stress is a central construct in many models of human health and disease. The present article reviews research on stress and health, with a focus on (a) how life stress has been conceptualized and measured over time, (b) recent evidence linking stress and disease, and (c) mechanisms that might underlie these effects. Emerging from this body of work is evidence that stress is involved in the development, maintenance, or exacerbation of several mental and physical health conditions, including asthma, rheumatoid arthritis, anxiety disorders, depression, cardiovascular disease, chronic pain, human immunodeficiency virus/AIDS, stroke, and certain types of cancer. Stress has also been implicated in accelerated biological aging and premature mortality. These effects have been studied most commonly using self-report checklist measures of life stress exposure, although interview-based approaches provide a more comprehensive assessment of individuals' exposure to stress. Most recently, online systems like the Stress and Adversity Inventory (STRAIN) have been developed for assessing lifetime stress exposure, and such systems may provide important new information to help advance our understanding of how stressors occurring over the life course get embedded in the brain and body to affect lifespan health.
Microscopic processes controlling the Herschel-Bulkley exponent

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Lin, Jie; Wyart, Matthieu

2018-01-01

The flow curve of various yield stress materials is singular as the strain rate vanishes and can be characterized by the so-called Herschel-Bulkley exponent n =1 /β . A mean-field approximation due to Hebraud and Lequeux (HL) assumes mechanical noise to be Gaussian and leads to β =2 in rather good agreement with observations. Here we prove that the improved mean-field model where the mechanical noise has fat tails instead leads to β =1 with logarithmic correction. This result supports that HL is not a suitable explanation for the value of β , which is instead significantly affected by finite-dimensional effects. From considerations on elastoplastic models and on the limitation of speed at which avalanches of plasticity can propagate, we argue that β =1 +1 /(d -df) , where df is the fractal dimension of avalanches and d the spatial dimension. Measurements of df then supports that β ≈2.1 and β ≈1.7 in two and three dimensions, respectively. We discuss theoretical arguments leading to approximations of β in finite dimensions.
Stressful life events and depressive symptoms in mothers and fathers of young children.

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Flouri, Eirini; Narayanan, Martina K; Nærde, Ane

2018-04-01

Parents of young children generally report more depressive symptoms than parents of adult children or people without children, mainly because the presence of young children increases exposure to significant stressors (such as stressful life events). However, most studies on the depressogenic role of stressful life events in parents of young children have focussed on mothers. Using data from 1138 families with young children in Norway, we investigated gender differences in the effect of stressful life events after a child's birth on the development of parental depressive symptoms in 3 follow-ups at child's ages 3-6 years. We also explored if gender differences in disposition (personality) may explain any gender differences in the depressogenic effect of life events. Nesting parents within families, we found a female gender bias for both neuroticism and depressive symptoms but no gender difference in the number of life events reported. Importantly, the number of stressful life events predicted the level and course of depressive symptoms similarly for mothers and fathers. Personality traits did not change the association between stressful life events and depressive symptoms in either mothers or fathers. Given the study design, causality cannot be inferred. There was no gender difference in the depressogenic effect of stressful life events in our sample. There was no evidence for a female dispositional sensitivity to the depressogenic effect of stressful life events, either. Stressful life events put both mothers and fathers of young children at risk of depression. Copyright © 2018 The Authors. Published by Elsevier B.V. All rights reserved.
Condensation and critical exponents of an ideal non-Abelian gas

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Talaei, Zahra; Mirza, Behrouz; Mohammadzadeh, Hosein

2017-11-01

We investigate an ideal gas obeying non-Abelian statistics and derive the expressions for some thermodynamic quantities. It is found that thermodynamic quantities are finite at the condensation point where their derivatives diverge and, near this point, they behave as \\vert T-Tc\\vert^{-ρ} in which Tc denotes the condensation temperature and ρ is a critical exponent. The critical exponents related to the heat capacity and compressibility are obtained by fitting numerical results and others are obtained using the scaling law hypothesis for a three-dimensional non-Abelian ideal gas. This set of critical exponents introduces a new universality class.
The relationship between sex life satisfaction and job stress of married nurses.

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Lee, Hsiu-Hui; Lung, For-Wey; Lee, Pei-Rong; Kao, Wei-Tsung; Lee, Yu-Lan

2012-08-19

The purpose of this study was to investigate the relationship among work stress, sex life satisfaction, and mental health of married nurses. Demographic information, work stress, sex life satisfaction, sexual desire and mental health measured using the Chinese Health Questionnaire, data were collected from 100 married nurses in Taiwan. Sex life satisfaction and age were negatively correlated, but sex life satisfaction and sexual desire were positively correlated. The mental health of over-committed nursing staff was not affected. Higher reward for effort was positively correlated with sex life satisfaction. No matter whether job stress was high or low, receiving a higher reward for effort led to better sex life satisfaction, which had a satisfying positive effect on the nurses' lives. To improve nursing care quality at the hospital, nursing administrators should assist nurses in confronting work stress via positive adjustment, which is associated with the nurses' sexual harmony, and quality of life.
The relationship between sex life satisfaction and job stress of married nurses

Directory of Open Access Journals (Sweden)

Lee Hsiu-Hui

2012-08-01

Full Text Available Abstract Background The purpose of this study was to investigate the relationship among work stress, sex life satisfaction, and mental health of married nurses. Demographic information, work stress, sex life satisfaction, sexual desire and mental health measured using the Chinese Health Questionnaire, data were collected from 100 married nurses in Taiwan. Findings Sex life satisfaction and age were negatively correlated, but sex life satisfaction and sexual desire were positively correlated. The mental health of over-committed nursing staff was not affected. Higher reward for effort was positively correlated with sex life satisfaction. Conclusions No matter whether job stress was high or low, receiving a higher reward for effort led to better sex life satisfaction, which had a satisfying positive effect on the nurses' lives. To improve nursing care quality at the hospital, nursing administrators should assist nurses in confronting work stress via positive adjustment, which is associated with the nurses’ sexual harmony, and quality of life.
Analysis of Human Standing Balance by Largest Lyapunov Exponent

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Kun Liu

2015-01-01

Full Text Available The purpose of this research is to analyse the relationship between nonlinear dynamic character and individuals’ standing balance by the largest Lyapunov exponent, which is regarded as a metric for assessing standing balance. According to previous study, the largest Lyapunov exponent from centre of pressure time series could not well quantify the human balance ability. In this research, two improvements were made. Firstly, an external stimulus was applied to feet in the form of continuous horizontal sinusoidal motion by a moving platform. Secondly, a multiaccelerometer subsystem was adopted. Twenty healthy volunteers participated in this experiment. A new metric, coordinated largest Lyapunov exponent was proposed, which reflected the relationship of body segments by integrating multidimensional largest Lyapunov exponent values. By using this metric in actual standing performance under sinusoidal stimulus, an obvious relationship between the new metric and the actual balance ability was found in the majority of the subjects. These results show that the sinusoidal stimulus can make human balance characteristics more obvious, which is beneficial to assess balance, and balance is determined by the ability of coordinating all body segments.
Life Stress and Health: A Review of Conceptual Issues and Recent Findings

Science.gov (United States)

Slavich, George M.

2016-01-01

Life stress is a central construct in many models of human health and disease. The present article reviews research on stress and health, with a focus on (a) how life stress has been conceptualized and measured over time, (b) recent evidence linking stress and disease, and (c) mechanisms that might underlie these effects. Emerging from this body…
Effect of heating method on stress-rupture life

Science.gov (United States)

Bizon, P. T.; Calfo, F. D.

1977-01-01

The effect of radiant(furnace), resistance(electric current), burner(hot gas stream), and a combination of resistance and burner heating on intermediate time (100 to 300 hr) stress-rupture life and reduction of area was evaluated. All heating methods were studied using the nickel-based alloy Udimet 700 while all but burner heating were evaluated with the cobalt-based alloy Mar-M 509. Limited test results of eight other superalloys were also included in this study. Resistance heated specimens had about 20 to 30 percent of the stress-rupture life of radiant heated specimens. The limited burner heating data showed about a 50 percent life reduction as compared to the radiant heated tests. A metallurgical examination gave no explanation for these reductions.
The surface fatigue life of contour induction hardened AISI 1552 gears

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Townsend, Dennis P.; Turza, Alan; Chaplin, Mike

1995-07-01

Two groups of spur gears manufactured from two different materials and heat treatments were endurance tested for surface fatigue life. One group was manufactured from AISI 1552 and was finished ground to a 0.4 micron (16 micro-in.) rms surface finish and then dual frequency contour induction hardened. The second group was manufactured from CEVM AISI 9310 and was carburized, hardened, and ground to a 0.4 micron (16 micro-in.) rms surface finish. The gear pitch diameter was 8.89 cm (3.5 in.). Test conditions were a maximum Hertz stress of 1.71 GPa (248 ksi), a bulk gear temperature of approximately 350 K (170 F) and a speed of 10,000 rpm. The lubricant used for the tests was a synthetic paraffinic oil with an additive package. The test results showed that the 10 percent surface fatigue (pitting) life of the contour hardened AISI 1552 test gears was 1.7 times that of the carburized and hardened AISI 9310 test gears. Also there were two early failures of the AISI 1552 gears by bending fatigue.
Early life trauma exposure and stress sensitivity in young children.

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Grasso, Damion J; Ford, Julian D; Briggs-Gowan, Margaret J

2013-01-01

The current study replicates and extends work with adults that highlights the relationship between trauma exposure and distress in response to subsequent, nontraumatic life stressors. The sample included 213 2-4-year-old children in which 64.3% had a history of potential trauma exposure. Children were categorized into 4 groups based on trauma history and current life stress. In a multivariate analysis of variance, trauma-exposed children with current life stressors had elevated internalizing and externalizing problems compared with trauma-exposed children without current stress and nontrauma-exposed children with and without current stressors. The trauma-exposed groups with or without current stressors did not differ on posttraumatic stress disorder symptom severity. Accounting for number of traumatic events did not change these results. These findings suggest that early life trauma exposure may sensitize young children and place them at risk for internalizing or externalizing problems when exposed to subsequent, nontraumatic life stressors.
Stressful Life Events and Child Anxiety: Examining Parent and Child Mediators

Science.gov (United States)

Platt, Rheanna; Williams, Sarah R.; Ginsburg, Golda S.

2015-01-01

While a number of factors have been linked with excessive anxiety (e.g., parenting, child temperament), the impact of stressful life events remains under-studied. Moreover, much of this literature has examined bivariate associations rather than testing more complex theoretical models. The current study extends the literature on life events and child anxiety by testing a theory-driven meditational model. Specifically, one child factor (child cognitions/locus of control), two parent factors (parent psychopathology and parenting stress), and two parent-child relationship factors (parent-child dysfunctional interaction and parenting style) were examined as mediators in the relationship between stressful life events and severity of child anxiety. One hundred and thirty anxious parents and their nonanxious, high-risk children (ages ranged from 7 to 13 years) participated in this study. Results indicated that levels of parenting stress, parental anxious rearing, and dysfunctional parent-child interaction mediated the association between stressful life events and severity of anxiety symptoms. Child cognition and parent psychopathology factors failed to emerge as mediators. Findings provide support for more complex theoretical models linking life events and child anxiety and suggest potential targets of intervention. PMID:25772523
Dissecting molecular stress networks: identifying nodes of divergence between life-history phenotypes.

Science.gov (United States)

Schwartz, Tonia S; Bronikowski, Anne M

2013-02-01

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

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Jolanta Adamczuk

2015-09-01

Full Text Available Introduction: Urinary incontinence (UI involves uncontrolled leakage of urine through the urethra as a result of damage to its sphincter muscle and a disturbed function of the urogenital diaphragm within the pelvis minor. The symptoms of UI radically impair psychological, somatic, and social functioning. The aim of each disease stress coping process is to reduce the impact of harmful agents as well as the acquisition of necessary preventive measures in order to combat the disorder. Aim of the study was to assess the relationship between coping styles used when dealing with stress associated with disease and the quality of life. Material and methods: The study was carried out at an outpatients’ clinic located in the Lublin Province (eastern Poland, covering 150 women with diagnosed stress urinary incontinence, aged between 32 and 79. The following methods were used: (a Coping Inventory for Stressful Situations (Endler, Parker to assess coping styles, (b CASP-19 scale (Higgins, Hyde, Wiggins, Blade to measure the overall quality of life, and (c Urinary Incontinence Life Quality Scale (Szymona-Pałkowska, Kraczkowski. Results : The preferred style in the studied group of women was Task-Oriented Coping. This style is associated with a low score on the Independence from Symptoms scale and low Control, being simultaneously correlated with Autonomy and Self-Realisation. Emotion-Oriented Coping is associated with low psychological, physical and social well-being, as well as with little independence from the disease symptoms, little pleasure and self-realisation, but it gives a sense of internal control. Avoidance-Oriented Coping does not significantly correlate with any of the Overall Quality of Life dimensions. Conclusions : Women suffering from UI tend to try to solve their problem by means of cognitive transformation. In their situation, clinging to the problem turns out to be a depressing factor and entails a lower quality of their life.
Influence of hydrogen-ion concentration exponent on undrained shear behaviour of bentonites; Bentonaito no hihaisui sendan kyodo ni oyobosu suiso ion nodo shisu no eikyo

Energy Technology Data Exchange (ETDEWEB)

Kamei, T [Kiso Jiban Consultants Co. Ltd., Tokyo (Japan); Tokida, M [Nagano National College of Technology, Nagano (Japan)

1994-12-21

Because there is a report example that the yield stress of a landslide clay increases along with a decrease of a hydrogen-ion concentration exponent, it is thought that a shear strength of the landslide clay depends on the hydrogen-ion concentration exponent. Furthermore, when the soil stabilization method by lime is applied to the soft ground and high organic earth, it is pointed out that the hydrogen-ion concentration exponent will become one of the harmful factors. Accordingly, it is understood that revealing an influence of a hydrogen-ion concentration exponent affects on the characteristics of an earth is one of the important factors, to evaluate a strength, deformation and so forth of the viscous ground. In this study, in order to examine an influence of a hydrogen-ion concentration exponent affecting on an undrained shear behavior of the bentonites, for the artificially adjusted bentonite specimens with 5 kinds of different pH, the isotropic consolidated undrained triaxial compression tests were performed, and consequently an influence of pH affecting on the engineering characteristics of the bentonites was made clear quantitatively. 28 refs., 16 figs., 5 tabs.
The Association of Sever Stressful Life Events and Multiple Sclerosis

OpenAIRE

Rozita Naeeni; Zlbar Soltanzadeh; Homan Salimipour; Zahra Vahhabi; Samira Yadegari

2015-01-01

Background: Stressful life events have suggested as one of etiologic cause of the disease from the middle of last century, but controversies still is going on. Materials and Methods: This study is a case- control study conducted on 100 MS patients in neurology clinic of Shariati Hospital during one year. History of stressful life events one year before beginning of the disease was questioned. These events, according to Holmes and Rahe Stress Scale, were severe and affected the disease progres...
Prediction of life stress on athletes’ burnout: the dual role of perceived stress

OpenAIRE

Chyi, Theresa; Lu, Frank Jing-Horng; Wang, Erica T.W.; Hsu, Ya-Wen; Chang, Ko-Hsin

2018-01-01

Although many studies adopted Smith’s (1986) cognitive–affective model of athletic burnout in examining stress–burnout relationship, very few studies examined the mediating/moderating role of perceived stress on the stress–burnout relationship. We sampled 195 college student-athletes and assessed their life stress, perceived stress, and burnout. Correlation analyses found all study variables correlated. Two separate hierarchical regression analyses found that the “distress” component of perce...
Optimization of a coherent synchrotron radiation source in the Tera-hertz range for high-resolution spectroscopy of molecules of astrophysical interest

International Nuclear Information System (INIS)

Barros, J.

2012-01-01

Fourier Transform spectroscopy is the most used multiplex tool for high-resolution measurements in the infrared range. Its extension to the Tera-hertz domain is of great interest for spectroscopic studies of interstellar molecules. This application is however hampered by the lack of dedicated, broadband sources with a sufficient intensity and stability. In this work, Coherent Synchrotron Radiation (CSR) was used as a source for molecular spectroscopy at high resolution on the AILES infrared and Tera-hertz beamline of SOLEIL synchrotron. The beamline being optimized for far-infrared, we could characterize the properties of CSR and compare them to the incoherent synchrotron radiation. A double detection system allowed to correct the effect of the source-related instabilities, hence to significantly increase the signal-to-noise ratio. Pure rotational spectra were measured using these developments. The case of the propynal molecule, for which a refined set of rotational and centrifugal distortion constants was calculated, proves the complementarity between CSR and the classical microwave or infrared sources. (author)
Partial differential equations with variable exponents variational methods and qualitative analysis

CERN Document Server

Radulescu, Vicentiu D

2015-01-01

Partial Differential Equations with Variable Exponents: Variational Methods and Qualitative Analysis provides researchers and graduate students with a thorough introduction to the theory of nonlinear partial differential equations (PDEs) with a variable exponent, particularly those of elliptic type. The book presents the most important variational methods for elliptic PDEs described by nonhomogeneous differential operators and containing one or more power-type nonlinearities with a variable exponent. The authors give a systematic treatment of the basic mathematical theory and constructive meth
Work stress and cardiovascular disease: a life course perspective.

Science.gov (United States)

Li, Jian; Loerbroks, Adrian; Bosma, Hans; Angerer, Peter

2016-05-25

Individuals in employment experience stress at work, and numerous epidemiological studies have documented its negative health effects, particularly on cardiovascular disease (CVD). Although evidence on the various interrelationships between work stress and CVD has been accumulated, those observations have not yet been conceptualized in terms of a life course perspective. Using the chain of risk model, we would like to propose a theoretical model incorporating six steps: (1) work stress increases the risk of incident CVD in healthy workers. (2) Among those whose work ability is not fully and permanently damaged, work stress acts as a determinant of the process of return to work after CVD onset. (3) CVD patients experience higher work stress after return to work. (4) Work stress increases the risk of recurrent CVD in workers with prior CVD. (5) CVD patients who fully lose their work ability transit to disability retirement. (6) Disability retirees due to CVD have an elevated risk of CVD mortality. The life course perspective might facilitate an in-depth understanding of the diverse interrelationships between work stress and CVD, thereby leading to work stress management interventions at each period of the lifespan and three-level prevention of CVD.

Stressful life events and Graves' disease: Results of a case control study

International Nuclear Information System (INIS)

Pintor, A.B.; Barrenechea, E.A.; Laureta, E.G.; Ligon, R.A.

2003-01-01

Prolonged worry has generally been acknowledged as one of the main precipitating factors of the onset of Graves' disease. A review of literature reveals that emotional stresses of considerable severity precede the onset of hyperthyroidism in about 90% of cases. However, not everyone subscribes to the Stress/Graves' disease hypothesis. Attempts to resolve this issue have tended to focus on whether a correlation can be shown between the magnitude of antecedent life events and the disease. Hence the main objective of the present study was to identify the possible association between stressful life events and Graves' disease. This paper presents the results of a case-control study, involving patents and subjects from the Veterans Memorial Medical Centre of Manila. A total of 224 patients of Graves' disease, newly or previously diagnosed, representing the 'patient's' arm were interviewed. All patients were questioned regarding various stresses, which greatly affected their life style spanning over a 12-month period prior to the onset of the disease. Simultaneously, 224 control subjects were also interviewed, and their stresses spanning over a similar period preceding the dates of interviews were recorded in quantifiable terms. Different stresses were given different intensity scores based on a social readjustment scale taking into consideration the life situations, emotions and diseases. In cases of multiple stresses, intensity scores were added to obtain the total stress intensity. Results were expressed as mean, standard deviation, median, frequency and percent distribution. Scatter plot was also constructed for intensity of stressful life events. To determine association of different factors with Graves' disease, Students t-test and chi-square tests were applied to the data. Odds ratio (OR) was also computed to determine risk attributed to each factor. Since there was significant difference in gender distribution between the patients and controls, stratified Mantel
Stressful life events are not associated with the development of dementia

OpenAIRE

Sundstr?m, Anna; R?nnlund, Michael; Adolfsson, Rolf; Nilsson, Lars-G?ran

2014-01-01

Background: The impact of stressful life events as a risk factor of dementia diseases is inconclusive. We sought to determine whether stressful negative life events are associated with incidental dementia in a population-based study with long-term follow-up. We also tested the hypothesis that the occurrence of positive life events could mitigate or overcome the possible adverse effects of negative life events on dementia conversion. Methods: The study involved 2,462 dementia-free participants...
Associations among everyday stress, critical life events, and sexual problems.

Science.gov (United States)

Bodenmann, Guy; Ledermann, Thomas; Blattner, Denise; Galluzzo, Claudia

2006-07-01

This study addresses the question of how stress is linked to sexual problems among women and men in close relationships. Psychological symptoms, relationship quality, internal daily stress (i.e., originating within the couple such as conflicts, worry for the partner), external daily stress (i.e., stress arising outside the couple such as job stress, stressful relatives, and so forth), and critical life events were examined with regard to their association with different sexual problems. The results support the hypotheses that (1) there is an incremental effect of stress on sexual problems after controlling for psychological symptoms and relationship quality, and that (2) it is primarily internal daily stress and in some cases critical life events rather than external daily stress that are related to sexual problems, particularly hypoactive sexual desire in women and men, sexual aversion in women, vaginismus in women, and premature ejaculation in men. Our findings indicate that the treatment of these sexual problems should address relationship issues and include a focus on helping individuals improve their stress management skills within their couple relationship.
Endogenous ROS levels in C. elegans under exogenous stress support revision of oxidative stress theory of life-history tradeoffs.

Science.gov (United States)

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

2014-07-24

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

International Nuclear Information System (INIS)

Grond, Florian; Diebner, Hans H.

2005-01-01

We analyze a recently proposed algorithm for computing Lyapunov exponents focusing on its capability to calculate reliable local values for chaotic attractors. The averaging process of local contributions to the global measure becomes interpretable, i.e. they are related to the local topological structure in phase space. We compare the algorithm with the commonly used Wolf algorithm by means of analyzing correlations between coordinates of the chaotic attractor and local values of the Lyapunov exponents. The correlations for the new algorithm turn out to be significantly stronger than those for the Wolf algorithm. Since the usage of scalar measures to capture complex structures can be questioned we discuss these entities along with a more phenomenological description of scatter plots
Stress and Quality of Life Among University Students: A Systematic Literature Review

Directory of Open Access Journals (Sweden)

Ícaro J.S. Ribeiro

2018-06-01

Full Text Available Purpose: Excessive and continuous stress has effects that go beyond mere health commitment, by triggering various diseases, and it is well stablish that this stress-related somatic events can affect the quality of life. Based on the exposed, the following questions were raised: There is association between quality of life and stress level in university students? What are the potential variables that influences this association? Therefore, this research aimed to analyze recent scientific productions about stress and quality of life in university students. Methods: A systematic review was conducted on the recent scientific production (i.e., published papers along the last five (5 years in Scopus, Web of Science, Science Direct, PubMed and Virtual Health Library (BVS. For this it was used the following search terms: ''quality of life'', restricted to the title, ''Stress'' and ''students'' in the title, abstract or keywords, all entered in a single search and connected by the Boolean operator ''AND''. Results: This study identified 142 articles in the scientific literature, but only 13 articles were classified as eligible according to the previously established criteria, highlighting the lack of studies that address the theme under investigation. Among these, quality of life was frequently negatively associated to stress and factors as insomnia and burnout were also associated with its deterioration. Discussion: This systematic review highlights the negative association between stress and QoL in university students, through the deterioration of various aspects related to physical and mental health. Keywords: Quality of life, Psychological stress, Undergraduate
Adaptive control of nonlinear in parameters chaotic system via Lyapunov exponents placement

Energy Technology Data Exchange (ETDEWEB)

Ayati, Moosa [Department of Electrical Engineering, K.N. Toosi University of Technology, Sayyed Khandan Bridge, Shariati Street, Tehran (Iran, Islamic Republic of)], E-mail: Ayati@dena.kntu.ac.ir; Khaki-Sedigh, Ali [Department of Electrical Engineering, K.N. Toosi University of Technology, Sayyed Khandan Bridge, Shariati Street, Tehran (Iran, Islamic Republic of)], E-mail: sedigh@kntu.ac.ir

2009-08-30

This paper proposes a new method for the adaptive control of nonlinear in parameters (NLP) chaotic systems. A method based on Lagrangian of a cost function is used to identify the parameters of the system. Estimation results are used to calculate the Lyapunov exponents adaptively. Finally, the Lyapunov exponents placement method is used to assign the desired Lyapunov exponents of the closed loop system.
Adaptive control of nonlinear in parameters chaotic system via Lyapunov exponents placement

International Nuclear Information System (INIS)

Ayati, Moosa; Khaki-Sedigh, Ali

2009-01-01

This paper proposes a new method for the adaptive control of nonlinear in parameters (NLP) chaotic systems. A method based on Lagrangian of a cost function is used to identify the parameters of the system. Estimation results are used to calculate the Lyapunov exponents adaptively. Finally, the Lyapunov exponents placement method is used to assign the desired Lyapunov exponents of the closed loop system.
Early-life stress origins of gastrointestinal disease: animal models, intestinal pathophysiology, and translational implications

Science.gov (United States)

Pohl, Calvin S.; Medland, Julia E.

2015-01-01

Early-life stress and adversity are major risk factors in the onset and severity of gastrointestinal (GI) disease in humans later in life. The mechanisms by which early-life stress leads to increased GI disease susceptibility in adult life remain poorly understood. Animal models of early-life stress have provided a foundation from which to gain a more fundamental understanding of this important GI disease paradigm. This review focuses on animal models of early-life stress-induced GI disease, with a specific emphasis on translational aspects of each model to specific human GI disease states. Early postnatal development of major GI systems and the consequences of stress on their development are discussed in detail. Relevant translational differences between species and models are highlighted. PMID:26451004
Spacetime dependence of the anomalous exponent of electric transport in the disorder model

International Nuclear Information System (INIS)

Egami, Takeshi; Suzuki, Koshiro; Watanabe, Katsuhiro

2012-01-01

Spacetime dependence of the anomalous exponent of electric transport in the disorder model is investigated. We show that the anomalous exponent evolves with time, according to the time evolution of the number of the effective neighbouring sites. Transition from subdiffusive to normal transport is recovered at macroscopic timescales. Plateaus appear in the history of the anomalous exponent due to the discreteness of the hopping sites, which is compatible with the conventional treatment to regard the anomalous exponent as a constant. We also show that, among various microscopic spatial structures, the number of the effective neighbouring sites is the only element which determines the anomalous exponent. This is compatible with the mesoscopic model of Scher–Montroll. These findings are verified by means of Monte Carlo simulation. The well-known expression of the anomalous exponent in the conventional multiple trapping model is derived by deducing it as a special case of the disorder model. (paper)
Life Stress and Health: A Review of Conceptual Issues and Recent Findings

OpenAIRE

Slavich, George M.

2016-01-01

Life stress is a central construct in many models of human health and disease. The present article reviews research on stress and health, with a focus on (a) how life stress has been conceptualized and measured over time, (b) recent evidence linking stress and disease, and (c) mechanisms that might underlie these effects. Emerging from this body of work is evidence that stress is involved in the development, maintenance, or exacerbation of several mental and physical health conditions, includ...
Anisotropies in magnetic field evolution and local Lyapunov exponents

International Nuclear Information System (INIS)

Tang, X.Z.; Boozer, A.H.

2000-01-01

The natural occurrence of small scale structures and the extreme anisotropy in the evolution of a magnetic field embedded in a conducting flow is interpreted in terms of the properties of the local Lyapunov exponents along the various local characteristic (un)stable directions for the Lagrangian flow trajectories. The local Lyapunov exponents and the characteristic directions are functions of Lagrangian coordinates and time, which are completely determined once the flow field is specified. The characteristic directions that are associated with the spatial anisotropy of the problem, are prescribed in both Lagrangian and Eulerian frames. Coordinate transformation techniques are employed to relate the spatial distributions of the magnetic field, the induced current density, and the Lorentz force, which are usually followed in Eulerian frame, to those of the local Lyapunov exponents, which are naturally defined in Lagrangian coordinates
Laminar Flame Velocity and Temperature Exponent of Diluted DME-Air Mixture

Science.gov (United States)

Naseer Mohammed, Abdul; Anwar, Muzammil; Juhany, Khalid A.; Mohammad, Akram

2017-03-01

In this paper, the laminar flame velocity and temperature exponent diluted dimethyl ether (DME) air mixtures are reported. Laminar premixed mixture of DME-air with volumetric dilutions of carbon dioxides (CO2) and nitrogen (N2) are considered. Experiments were conducted using a preheated mesoscale high aspect-ratio diverging channel with inlet dimensions of 25 mm × 2 mm. In this method, flame velocities are extracted from planar flames that were stabilized near adiabatic conditions inside the channel. The flame velocities are then plotted against the ratio of mixture temperature and the initial reference temperature. A non-linear power law regression is observed suitable. This regression analysis gives the laminar flame velocity at the initial reference temperature and temperature exponent. Decrease in the laminar flame velocity and increase in temperature exponent is observed for CO2 and N2 diluted mixtures. The addition of CO2 has profound influence when compared to N2 addition on both flame velocity and temperature exponent. Numerical prediction of the similar mixture using a detailed reaction mechanism is obtained. The computational mechanism predicts higher magnitudes for laminar flame velocity and smaller magnitudes of temperature exponent compared to experimental data.
Better executive function under stress mitigates the effects of recent life stress exposure on health in young adults.

Science.gov (United States)

Shields, Grant S; Moons, Wesley G; Slavich, George M

2017-01-01

Executive function is a neuropsychological construct that enables controlled cognitive processing, which has been hypothesized to enhance individuals' resilience to stress. However, little empirical work has directly examined how executive function under different conditions mitigates the negative effects of stress exposure on health. To address this issue, we recruited 110 healthy young adults and assessed their recent life stress exposure, executive function in either a stressful or non-stressful context, and current health complaints. Based on existing research, we hypothesized that individuals exhibiting better executive function following a laboratory-based stressor (but not a control task) would demonstrate weaker associations between recent stress exposure and health because they perceived recent life stressors as being less severe. Consistent with this hypothesis, better executive function during acute stress, but not in the absence of stress, was associated with an attenuated link between participants' recent life stress exposure and their current health complaints. Moreover, this attenuating effect was mediated by lesser perceptions of stressor severity. Based on these data, we conclude that better executive function under stress is associated with fewer health complaints and that these effects may occur by reducing individuals' perceptions of stressor severity. The data thus suggest the possibility of reducing stress-related health problems by enhancing executive function.
A comment on measuring the Hurst exponent of financial time series

Science.gov (United States)

Couillard, Michel; Davison, Matt

2005-03-01

A fundamental hypothesis of quantitative finance is that stock price variations are independent and can be modeled using Brownian motion. In recent years, it was proposed to use rescaled range analysis and its characteristic value, the Hurst exponent, to test for independence in financial time series. Theoretically, independent time series should be characterized by a Hurst exponent of 1/2. However, finite Brownian motion data sets will always give a value of the Hurst exponent larger than 1/2 and without an appropriate statistical test such a value can mistakenly be interpreted as evidence of long term memory. We obtain a more precise statistical significance test for the Hurst exponent and apply it to real financial data sets. Our empirical analysis shows no long-term memory in some financial returns, suggesting that Brownian motion cannot be rejected as a model for price dynamics.
Stressful life events in pregnancy and head circumference at birth

DEFF Research Database (Denmark)

Obel, Carsten; Hedegaard, Morten; Henriksen, Tine Brink

2003-01-01

A strong association between stress in pregnancy and small head circumference in infants at birth was reported in 1994. This important finding has never been replicated. In a follow-up study of 4211 participants with singleton pregnancies, information on life events was collected twice during...... pregnancy and head circumference measured shortly after birth following standard procedures. No association was found between experienced or perceived stress as a result of life events during pregnancy and head circumference in the infants. In conclusion, stress in pregnancy may influence foetal brain...
Can the bivariate Hurst exponent be higher than an average of the separate Hurst exponents?

Czech Academy of Sciences Publication Activity Database

Krištoufek, Ladislav

2015-01-01

Roč. 431, č. 1 (2015), s. 124-127 ISSN 0378-4371 R&D Projects: GA ČR(CZ) GP14-11402P Institutional support: RVO:67985556 Keywords : Correlations * Power- law cross-correlations * Bivariate Hurst exponent * Spectrum coherence Subject RIV: AH - Economics Impact factor: 1.785, year: 2015 http://library.utia.cas.cz/separaty/2015/E/kristoufek-0452314.pdf
Inverted rank distributions: Macroscopic statistics, universality classes, and critical exponents

Science.gov (United States)

Eliazar, Iddo; Cohen, Morrel H.

2014-01-01

An inverted rank distribution is an infinite sequence of positive sizes ordered in a monotone increasing fashion. Interlacing together Lorenzian and oligarchic asymptotic analyses, we establish a macroscopic classification of inverted rank distributions into five “socioeconomic” universality classes: communism, socialism, criticality, feudalism, and absolute monarchy. We further establish that: (i) communism and socialism are analogous to a “disordered phase”, feudalism and absolute monarchy are analogous to an “ordered phase”, and criticality is the “phase transition” between order and disorder; (ii) the universality classes are characterized by two critical exponents, one governing the ordered phase, and the other governing the disordered phase; (iii) communism, criticality, and absolute monarchy are characterized by sharp exponent values, and are inherently deterministic; (iv) socialism is characterized by a continuous exponent range, is inherently stochastic, and is universally governed by continuous power-law statistics; (v) feudalism is characterized by a continuous exponent range, is inherently stochastic, and is universally governed by discrete exponential statistics. The results presented in this paper yield a universal macroscopic socioeconophysical perspective of inverted rank distributions.
Early-life stress origins of gastrointestinal disease: animal models, intestinal pathophysiology, and translational implications.

Science.gov (United States)

Pohl, Calvin S; Medland, Julia E; Moeser, Adam J

2015-12-15

Early-life stress and adversity are major risk factors in the onset and severity of gastrointestinal (GI) disease in humans later in life. The mechanisms by which early-life stress leads to increased GI disease susceptibility in adult life remain poorly understood. Animal models of early-life stress have provided a foundation from which to gain a more fundamental understanding of this important GI disease paradigm. This review focuses on animal models of early-life stress-induced GI disease, with a specific emphasis on translational aspects of each model to specific human GI disease states. Early postnatal development of major GI systems and the consequences of stress on their development are discussed in detail. Relevant translational differences between species and models are highlighted. Copyright © 2015 the American Physiological Society.
Effects of stress management training and problem solving on quality of life and life expectancy among infertile women

Directory of Open Access Journals (Sweden)

Mohammad Reza Zarbakhsh Bahri

2013-08-01

Full Text Available Introduction: This study aims to evaluate the effectiveness of stress management training and problem-solving training on quality of life and life expectancy of infertile women was conducted.Material and Methods: The method of this study was experimental with pretest – posttest design with a control group. population of 400 infertile women who referred to infertility center in Rasht were randomized to 250 of them were selected and the quality of life and life expectancy of the study were the 45 members of the quality of life and life expectancy lower were more randomly in three groups of 15 people, including two experimental groups and one control group were replaced. Each experimental groups were trained for 10 sessions of 90 minutes, respectively, stress management and problem-solving. Upon completion of the training program, participants were assessed again.Results: The result of present study showed that there was a significant difference between the experimental groups and control group in the scores of quality of life and life expectancy (p0.05.Conclusion: Stress management and problem solving training were effective on life expectancy and quality of life of infertile women but there was no significant difference between the effectiveness of these two methods on life expectancy and quality of life of infertile women.

Development of an Accelerated Test Design for Predicting the Service Life of the Solar Array at Mead, Nebraska

Science.gov (United States)

Gaines, G. B.; Thomas, R. E.; Noel, G. T.; Shilliday, T. S.; Wood, V. E.; Carmichael, D. C.

1979-01-01

An accelerated life test is described which was developed to predict the life of the 25 kW photovoltaic array installed near Mead, Nebraska. A quantitative model for accelerating testing using multiple environmental stresses was used to develop the test design. The model accounts for the effects of thermal stress by a relation of the Arrhenius form. This relation was then corrected for the effects of nonthermal environmental stresses, such as relative humidity, atmospheric pollutants, and ultraviolet radiation. The correction factors for the nonthermal stresses included temperature-dependent exponents to account for the effects of interactions between thermal and nonthermal stresses on the rate of degradation of power output. The test conditions, measurements, and data analyses for the accelerated tests are presented. Constant-temperature, cyclic-temperature, and UV types of tests are specified, incorporating selected levels of relative humidity and chemical contamination and an imposed forward-bias current and static electric field.
Gender/Sex Differences in the Relationship between Psychosocial Work Exposures and Work and Life Stress.

Science.gov (United States)

Padkapayeva, Kathy; Gilbert-Ouimet, Mahée; Bielecky, Amber; Ibrahim, Selahadin; Mustard, Cameron; Brisson, Chantal; Smith, Peter

2018-04-18

Stress is an important factor affecting the health of working population. While work exposures are determinants of levels of work and life stress, we do not know whether similar or different exposures are related to stress levels for men and women. This study aimed to formally examine male/female differences in the relationships between psychosocial work exposures and work and life stress in a representative sample of Canadian labour market participants. We used data from 2012 cycle of the Canadian Community Health Survey (CCHS), a representative population-based survey conducted by Statistics Canada. The sample was restricted to employed labour force participants working 15+ hours per week (N = 8328, 48% female). To examine the relationship between work exposures and work and life stress, we conducted path analyses. Psychosocial work exposures included social support, job insecurity, job control, and job strain. Differences between estimates for men and women were explored using multigroup analyses, constraining paths between male and female models to be equivalent and examining the impact on change in model fit. Male/female differences were observed in the relationships between supervisor support and work stress levels as well as between job control, job insecurity, job strain, and life stress levels. Higher levels of supervisor support at work were associated with lower work stress among women, but not among men. Low job control had a direct protective effect on life stress for men but not for women, while high job strain had a direct adverse effect on life stress among women but not among men. Higher job insecurity was more strongly associated with higher life stress among men compared with women. The relationship between work stress and life stress was similar among men and women. The findings of this study suggest that the relationships between psychosocial exposures and work and life stress differ for men and women. Our study also raised important questions
Results of fatigue tests and prediction of fatigue life under superposed stress wave and combined superposed stress wave

International Nuclear Information System (INIS)

Takasugi, Shunji; Horikawa, Takeshi; Tsunenari, Toshiyasu; Nakamura, Hiroshi

1983-01-01

In order to examine fatigue life prediction methods at high temperatures where creep damage need not be taken into account, fatigue tests were carried out on plane bending specimens of alloy steels (SCM 435, 2 1/4Cr-1Mo) under superposed and combined superposed stress waves at room temperature and 500 0 C. The experimental data were compared with the fatigue lives predicted by using the cycle counting methods (range pair, range pair mean and zero-cross range pair mean methods), the modified Goodman's equation and the modified Miner's rule. The main results were as follows. (1) The fatigue life prediction method which is being used for the data at room temperature is also applicable to predict the life at high temperatures. The range pair mean method is especially better than other cycle counting methods. The zero-cross range pair mean method gives the estimated lives on the safe side of the experimental lives. (2) The scatter bands of N-bar/N-barsub(es) (experimental life/estimated life) becomes narrower when the following equation is used instead of the modified Goodman's equation for predicting the effect of mean stress on fatigue life. σ sub(t) = σ sub(a) / (1 - Sigma-s sub(m) / kσ sub(B)) σ sub(t); stress amplitude at zero mean stress (kg/mm 2 ) σ sub(B); tensile strength (kg/mm 2 ) σ sub(m); mean stress (kg/mm 2 ) σ sub(a); stress amplitude (kg/mm 2 ) k; modified coefficient of σ sub(B) (author)
Relationship between the quality of life and stress in health area students

Directory of Open Access Journals (Sweden)

Rita de Cassia Calderani Borine

2015-08-01

Full Text Available The present work aimed to comprehend the relationship between quality of life and the stress of healthcare academics from a private college in the interior of Rondônia. Were involved 208 students, with 133 females and 75 males between 17 to 55 years old. To achieve the research proposal the scale used was Whogol-Bref to evaluate the quality of live and the Inventário de Sintomas de Stress para Adultos for the respondent the level of stress. The conclusion is that academics as higher level quality of life lower stress levels, the course of Veterinary Medicine presents highest life quality and the Physiotherapy course is the with highest level of stress, there is also a significant difference between genders, where the female presented more levels of stress comparing to male gender.
Coping with a changing environment: The effects of early life stress

DEFF Research Database (Denmark)

Vindas, Marco A.; Madaro, Angelico; Fraser, Thomas W.K.

2016-01-01

to environmental changes is particularly evident at early life stages. We investigated the performance of salmon, previously subjected to an unpredictable chronic stress (UCS) treatment at an early age (10 month old parr), over several months and life stages. The UCS fish showed overall higher specific growth...... rates compared with unstressed controls after smoltification, a particularly challenging life stage, and after seawater transfer. Furthermore, subjecting fish to acute stress at the end of the experiment, we found that UCS groups had an overall lower hypothalamic catecholaminergic and brain stem...... serotonergic response to stress compared with control groups. In addition, serotonergic activity was negatively correlated with final growth rates,which implies that serotonin responsive individuals have growth disadvantages. Altogether, our results may imply that a subduedmonoaminergic response in stressful...
The serotonin transporter and early life stress : Translational perspectives

NARCIS (Netherlands)

Houwing, Danielle J; Buwalda, Bauke; Zee, van der Eddy; de Boer, Sietse F; Olivier, Jocelien D A

2017-01-01

The interaction between the serotonin transporter (SERT) linked polymorphic region (5-HTTLPR) and adverse early life stressing (ELS) events is associated with enhanced stress susceptibility and risk to develop mental disorders like major depression, anxiety, and aggressiveness. In particular, human
Controlled test for predictive power of Lyapunov exponents: their inability to predict epileptic seizures.

Science.gov (United States)

Lai, Ying-Cheng; Harrison, Mary Ann F; Frei, Mark G; Osorio, Ivan

2004-09-01

Lyapunov exponents are a set of fundamental dynamical invariants characterizing a system's sensitive dependence on initial conditions. For more than a decade, it has been claimed that the exponents computed from electroencephalogram (EEG) or electrocorticogram (ECoG) signals can be used for prediction of epileptic seizures minutes or even tens of minutes in advance. The purpose of this paper is to examine the predictive power of Lyapunov exponents. Three approaches are employed. (1) We present qualitative arguments suggesting that the Lyapunov exponents generally are not useful for seizure prediction. (2) We construct a two-dimensional, nonstationary chaotic map with a parameter slowly varying in a range containing a crisis, and test whether this critical event can be predicted by monitoring the evolution of finite-time Lyapunov exponents. This can thus be regarded as a "control test" for the claimed predictive power of the exponents for seizure. We find that two major obstacles arise in this application: statistical fluctuations of the Lyapunov exponents due to finite time computation and noise from the time series. We show that increasing the amount of data in a moving window will not improve the exponents' detective power for characteristic system changes, and that the presence of small noise can ruin completely the predictive power of the exponents. (3) We report negative results obtained from ECoG signals recorded from patients with epilepsy. All these indicate firmly that, the use of Lyapunov exponents for seizure prediction is practically impossible as the brain dynamical system generating the ECoG signals is more complicated than low-dimensional chaotic systems, and is noisy. Copyright 2004 American Institute of Physics
World assumptions, posttraumatic stress and quality of life after a natural disaster: A longitudinal study

Science.gov (United States)

2012-01-01

Background Changes in world assumptions are a fundamental concept within theories that explain posttraumatic stress disorder. The objective of the present study was to gain a greater understanding of how changes in world assumptions are related to quality of life and posttraumatic stress symptoms after a natural disaster. Methods A longitudinal study of 574 Norwegian adults who survived the Southeast Asian tsunami in 2004 was undertaken. Multilevel analyses were used to identify which factors at six months post-tsunami predicted quality of life and posttraumatic stress symptoms two years post-tsunami. Results Good quality of life and posttraumatic stress symptoms were negatively related. However, major differences in the predictors of these outcomes were found. Females reported significantly higher quality of life and more posttraumatic stress than men. The association between level of exposure to the tsunami and quality of life seemed to be mediated by posttraumatic stress. Negative perceived changes in the assumption “the world is just” were related to adverse outcome in both quality of life and posttraumatic stress. Positive perceived changes in the assumptions “life is meaningful” and “feeling that I am a valuable human” were associated with higher levels of quality of life but not with posttraumatic stress. Conclusions Quality of life and posttraumatic stress symptoms demonstrate differences in their etiology. World assumptions may be less specifically related to posttraumatic stress than has been postulated in some cognitive theories. PMID:22742447
Critical exponents from the effective average action

International Nuclear Information System (INIS)

Tetradis, N.; Wetterich, C.

1993-07-01

We compute the critical behaviour of three-dimensional scalar theories using a new exact non-perturbative evolution equation. Our values for the critical exponents agree well with previous precision estimates. (orig.)
Stressful Life Events in Children With Functional Defecation Disorders.

Science.gov (United States)

Philips, Elise M; Peeters, Babette; Teeuw, Arianne H; Leenders, Arnold G E; Boluyt, Nicole; Brilleslijper-Kater, Sonja N; Benninga, Marc A

2015-10-01

The aim of the study was to determine the prevalence of stressful life events including (sexual) abuse in children with functional defecation disorders by performing a systematic review. We searched MEDLINE, EMBASE, and PsycINFO for cohort, case-control and cross-sectional studies investigating the prevalence of stressful life events, including (sexual) abuse in children with functional defecation disorders. The search yielded 946 articles, of which 8 were included with data from 654 children with functional constipation and 1931 children with (constipation-associated) fecal incontinence (FI). Overall, children with functional defecation disorders had been significantly more exposed to stressful life events than healthy children, with prevalence rates ranging from 1.6% to 90.9%. Being bullied, being a relational victim, interruption of toilet training, punishment by parents during toilet training, and hospitalization were significantly related to FI, whereas separation from the best friend, failure in an examination, severe illness in a close family member, loss of job by a parent, frequent punishment, and living in a war-affected area were significantly related to constipation. Only 1 study measured the prevalence of child abuse, which reported a significantly higher prevalence of child (sexual) abuse in children with FI compared with controls. The prevalence of stressful life events, including (sexual) abuse is significantly higher in children with functional defecation disorders compared with healthy children. To gain more insight into the true prevalence of child (sexual) abuse in children with functional defecation disorders, more studies are clearly needed.
Stress, depression, quality of life and salivary cortisol levels in community health agents.

Science.gov (United States)

Knuth, Berenice Scaletzky; Cocco, Rafaela Abreu; Radtke, Vinicius Augusto; Medeiros, João Ricardo Carvalho; Oses, Jean Pierre; Wiener, Carolina David; Jansen, Karen

2016-06-01

To determine the prevalence of and factors associated with depression and stress with perceived quality of life and the salivary cortisol levels in Community Health Agent (CHA). Materials and Methods Cross-sectional descriptive study of CHAs in Pelotas-RS, Brazil. Data collection, including sociodemographic information and factors related to work and health. Beck Depression Inventory (BDI) II was used to assess depressive symptoms, Inventory of Stress Symptoms Lipp (ISSL) was used for the analysis of stress and the WHOQOL-BREF was used to investigate quality of life. Salivary cortisol was quantified via ELISA test. The assessments showed that 71.0% are in a state of stress resistance, 30.5% were in the alert state of stress and 32.8% were in the stress state of exhaustion. Depressive episodes (BDI≥12) were observed in 28.2%. The environmental domain had the lowest score for quality of life. We observed significantly higher salivary cortisol levels in CHAs with less than 1 year of service and with the lowest quality of life scores in the environmental subsection. A high prevalence of stress and depression was observed in this sample of CHAs. In addition, the worst levels of quality of life were identified in the environmental subsection. Cortisol levels corroborate these findings regarding quality of life within the environmental domain and began working less than a year previously.
Depression, anxiety and stress as negative predictors of life satisfaction in university students

International Nuclear Information System (INIS)

Bukhari, S.R.; Saba, F.

2017-01-01

Objective: To study the role of depression, anxiety and stress in prediction of life satisfaction in male and female university students. Methodology: The study involved 200 students, 100 males and 100 females selected by using purposive sampling technique from different universities of Islamabad. Age range of participants was 19-30 years (mean 21.79+-2.970). Depression anxiety stress scale-21 (DASS-21 and Life Satisfaction scale were administered. Data were analyzed on SPSS version 19. Results: The result of present study indicated that depression anxiety and stress significantly predict life satisfaction among male and female university students. Conclusion: University students who are facing depression, anxiety and stress are more vulnerable to low levels of life satisfaction. (author)
On the Topological Changes of Local Hurst Exponent in Polar Regions

Science.gov (United States)

Consolini, G.; De Michelis, P.

2014-12-01

Geomagnetic activity during magnetic substorms and storms is related to the dinamical and topological changes of the current systems flowing in the Earth's magnetosphere-ionosphere. This is particularly true in the case of polar regions where the enhancement of auroral electrojet current system is responsible for the observed geomagnetic perturbations. Here, using the DMA-technique we evaluate the local Hurst exponent (H"older exponent) for a set of 46 geomagnetic observatories, widely distributed in the northern hemisphere, during one of the most famous and strong geomagnetic storm, the Bastille event, and reconstruct a sequence of polar maps showing the dinamical changes of the topology of the local Hurst exponent with the geomagnetic activity level. The topological evolution of local Hurst exponent maps is discussed in relation to the dinamical changes of the current systems flowing in the polar ionosphere. G. Consolini has received funding from the European Community's Seventh Framework Programme (FP7/2007-2013) under Grant agreement no. 313038/STORM for this research.
Variation of CRE with exponents of time and number of fractions

International Nuclear Information System (INIS)

Supe, S.J.; Rao, S.M.; Sawant, S.G.; Bisht, J.S.

1976-01-01

The concept of NSD has been modified into TDF's by Orton and Ellis and CRE's by Kirk et al. It was aimed to study the variability of these new concepts on the exponents of time and number of fractions. It was found that TDF has larger variation with the exponents compared to that of CRE. The use of CRE and NSD for solving the treatment scheduling problems or for intercomparison of various regimes has been simplified by providing readymade estimation of CRE for various doses/fraction with increasing number of fractions. As there is increasing evidence for the change of exponents J and H, nomograms are presented to determine the CRE for various values of J and H. The variation of decay correction factors with the exponent H is also evaluated and is presented. This will help various radiotherapists to use CRE and the decay correction factors consistent with their clinical findings. (orig.) [de
The major stressful life events and cancer: stress history and cancer.

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

2012-06-01

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

Science.gov (United States)

Hobson, Charles J.; Delunas, Linda; Kesic, Dawn

2001-01-01

Considers how failure to balance excessive work and life/family demands can lead to negative consequences for both individuals and organizations, including higher stress levels, increased absenteeism, and lower productivity. Discusses results of a survey on stressful life events that offers an explanation of why work/life balance programs are so…
Effects of stress conditions on the generation of negative bias temperature instability-associated interface traps

International Nuclear Information System (INIS)

Zhang Yue; Pu Shi; Lei Xiao-Yi; Chen Qing; Ma Xiao-Hua; Hao Yue

2013-01-01

The exponent n of the generation of an interface trap (N it ), which contributes to the power-law negative bias temperature instability (NBTI) degradation, and the exponent's time evolution are investigated by simulations with varying the stress voltage V g and temperature T. It is found that the exponent n in the diffusion-limited phase of the degradation process is irrelevant to both V g and T. The time evolution of the exponent n is affected by the stress conditions, which is reflected in the shift of the onset of the diffusion-limited phase. According to the diffusion profiles, the generation of the atomic hydrogen species, which is equal to the buildup of N it , is strongly correlated with the stress conditions, whereas the diffusion of the hydrogen species shows V g -unaffected but T-affected relations through the normalized results
The Role of Perceived Stress and Self-Efficacy in Young People's Life Satisfaction: A Longitudinal Study.

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Burger, Kaspar; Samuel, Robin

2017-01-01

Life satisfaction is an important indicator of successful development. However, adolescents' life satisfaction tends to be relatively unsteady, and environmental influences play a critical role in shaping life satisfaction among adolescents in the transition to young adulthood. Given the paramount importance that education plays in adolescents' lives, adolescents' life satisfaction may vary as a function of school-related stress experience. At the same time, coping resources may help reduce adverse effects of stress on life satisfaction. With this in mind, we examined whether, and to what extent, perceived stress in education and general self-efficacy (a resource that facilitates coping) affect the life satisfaction of adolescents in transition to young adulthood. We distinguished between baseline levels of stress and self-efficacy and within-person change in stress and self-efficacy to determine whether life satisfaction is sensitive to fluctuations in stress and self-efficacy when person-specific levels of stress and self-efficacy are taken into account. Estimating growth curve models on data from a panel study on the life trajectories of compulsory-school leavers (n = 5126, 55.3 % female), we found that baseline levels of stress and self-efficacy, as well as within-person change in stress and self-efficacy, affected adolescents' life satisfaction. Moreover, our results showed that baseline self-efficacy mitigated the negative effect of baseline stress on life satisfaction. These findings improve our understanding of two major psychological determinants of adolescents' life satisfaction and extend our knowledge of life satisfaction trajectories during the transition to young adulthood.
Alcohol, psychomotor-stimulants and behaviour: methodological considerations in preclinical models of early-life stress.

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McDonnell-Dowling, Kate; Miczek, Klaus A

2018-04-01

In order to assess the risk associated with early-life stress, there has been an increase in the amount of preclinical studies investigating early-life stress. There are many challenges associated with investigating early-life stress in animal models and ensuring that such models are appropriate and clinically relevant. The purpose of this review is to highlight the methodological considerations in the design of preclinical studies investigating the effects of early-life stress on alcohol and psychomotor-stimulant intake and behaviour. The protocols employed for exploring early-life stress were investigated and summarised. Experimental variables include animals, stress models, and endpoints employed. The findings in this paper suggest that there is little consistency among these studies and so the interpretation of these results may not be as clinically relevant as previously thought. The standardisation of these simple stress procedures means that results will be more comparable between studies and that results generated will give us a more robust understanding of what can and may be happening in the human and veterinary clinic.
Four-loop critical exponents for the Gross-Neveu-Yukawa models

International Nuclear Information System (INIS)

Zerf, Nikolai; Mihaila, Luminita N.; Herbut, Igor F.; Scherer, Michael M.

2017-09-01

We study the chiral Ising, the chiral XY and the chiral Heisenberg models at four-loop order with the perturbative renormalization group in 4-ε dimensions and compute critical exponents for the Gross-Neveu-Yukawa fixed points to order O(ε 4 ). Further, we provide Pade estimates for the correlation length exponent, the boson and fermion anomalous dimension as well as the leading correction to scaling exponent in 2+1 dimensions. We also confirm the emergence of supersymmetric field theories at four loops for the chiral Ising and the chiral XY models with N=1/4 and N=1/2 fermions, respectively. Furthermore, applications of our results relevant to various quantum transitions in the context of Dirac and Weyl semimetals are discussed, including interaction-induced transitions in graphene and surface states of topological insulators.

Four-loop critical exponents for the Gross-Neveu-Yukawa models

Energy Technology Data Exchange (ETDEWEB)

Zerf, Nikolai; Mihaila, Luminita N. [Heidelberg Univ. (Germany). Inst. fuer Theoretische Physik; Marquard, Peter [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany); Herbut, Igor F. [Simon Fraser Univ., Burnaby, BC (Canada). Dept. of Physics; Scherer, Michael M. [Koeln Univ. (Germany). Inst. for Theoretical Physics

2017-09-15

We study the chiral Ising, the chiral XY and the chiral Heisenberg models at four-loop order with the perturbative renormalization group in 4-ε dimensions and compute critical exponents for the Gross-Neveu-Yukawa fixed points to order O(ε{sup 4}). Further, we provide Pade estimates for the correlation length exponent, the boson and fermion anomalous dimension as well as the leading correction to scaling exponent in 2+1 dimensions. We also confirm the emergence of supersymmetric field theories at four loops for the chiral Ising and the chiral XY models with N=1/4 and N=1/2 fermions, respectively. Furthermore, applications of our results relevant to various quantum transitions in the context of Dirac and Weyl semimetals are discussed, including interaction-induced transitions in graphene and surface states of topological insulators.
Determining the Walker exponent and developing a modified Smith-Watson-Topper parameter model

Energy Technology Data Exchange (ETDEWEB)

Lv, Zhiqiang; Huang, Hong Zhong; Wang, Hai Kun; Gao, Huiying; Zuo, Fang Jun [University of Electronic Science and Technology of China, Chengdu (China)

2016-03-15

Mean stress effects significantly influence the fatigue life of components. In general, tensile mean stresses are known to reduce the fatigue life of components, whereas compressive mean stresses are known to increase it. To date, various methods that account for mean stress effects have been studied. In this research, considering the high accuracy of mean stress correction and the difficulty in obtaining the material parameter of the Walker method, a practical method is proposed to describe the material parameter of this method. The test data of various materials are then used to verify the proposed practical method. Furthermore, by applying the Walker material parameter and the Smith-Watson-Topper (SWT) parameter, a modified strain-life model is developed to consider sensitivity to mean stress of materials. In addition, three sets of experimental fatigue data from super alloy GH4133, aluminum alloy 7075-T651, and carbon steel are used to estimate the accuracy of the proposed model. A comparison is also made between the SWT parameter method and the proposed strainlife model. The proposed strain-life model provides more accurate life prediction results than the SWT parameter method.
Statistical-mechanical formulation of Lyapunov exponents

International Nuclear Information System (INIS)

Tanase-Nicola, Sorin; Kurchan, Jorge

2003-01-01

We show how the Lyapunov exponents of a dynamic system can, in general, be expressed in terms of the free energy of a (non-Hermitian) quantum many-body problem. This puts their study as a problem of statistical mechanics, whose intuitive concepts and techniques of approximation can hence be borrowed
Fujita Exponent for a Nonlinear Degenerate Parabolic Equation with Localized Source

Directory of Open Access Journals (Sweden)

Yulan Wang

2014-01-01

Full Text Available This paper is devoted to understand the blow-up properties of reaction-diffusion equations which combine a localized reaction term with nonlinear diffusion. In particular, we study the critical exponent of a p-Laplacian equation with a localized reaction. We obtain the Fujita exponent qc of the equation.
Stressful life events and occupational accidents.

Science.gov (United States)

Cordeiro, Ricardo; Dias, Adriano

2005-10-01

The purpose of this study was to examine the association between stressful life events and occupational accidents. This was a population-based case-control study, carried out in the city of Botucatu, in southeast Brazil. The cases consisted of 108 workers who had recently experienced occupational accidents. Each case was matched with three controls. The cases and controls answered a questionnaire about recent exposure to stressful life events. Reporting of "environmental problems", "being a victim of assault", "not having enough food at home" and "nonoccupational fatigue" were found to be risk factors for work-related accidents with estimated incidence rate ratios of 1.4 [95% confidence interval (95% CI) 1.1-1.7], 1.3 (95% CI 1.1-1.7), 1.3 (95% CI 1.1-1.6), and 1.4 (95% CI 1.2-1.7) respectively. The findings of the study suggested that nonwork variables contribute to occupational accidents, thus broadening the understanding of these phenomena, which can support new approaches to the prevention of occupational accidents.
A Comparative Study of Stressful Life Events and Stress Coping Strategies in Coronary Heart Disease Patients and Non-Patients

Directory of Open Access Journals (Sweden)

A. Heidari Pahlavian

2010-10-01

Full Text Available Introduction & Objective: Etiological researches suggest that biopsychosocial dimensions are responsible for coronary heart disease (CHD. The main goal of the present research was to compare stressful life events and stress coping strategies in coronary heart patients (Acute Myocardial Infarction and non-patients. Materials & Methods: In this cross sectional research 102 patients (all males suffering from acute myocardial infarction and 162 non-patient individuals after matching were studied and compared with regard to psychosocial life events and stress coping strategies through coping response inventory (Moos, 1993 , scaling of life Events (paykel , 1971 and researcher made questionnaire. Results: The result established that myocardial infarction patients experienced more stress than the control group during one year before heart- attack and they used more inadequate stress coping strategies comparing with the control individuals. Conclusion: This study showed that stress and inadequate coping strategies are important variables for the development of coronary heart diseases. (Sci J Hamadan Univ Med Sci 2010;17(3:33-38
Life stress and symptoms of anxiety and depression in women after cancer: The mediating effect of stress appraisal and coping.

Science.gov (United States)

Seib, Charrlotte; Porter-Steele, Janine; Ng, Shu-Kay; Turner, Jane; McGuire, Amanda; McDonald, Nicole; Balaam, Sarah; Yates, Patsy; McCarthy, Alexandra; Anderson, Debra

2018-04-06

This paper examines the direct and intermediary relationships between life stress, stress appraisal, and resilience, and increased anxiety and depressive symptoms in Australian women after cancer treatment. Data examined from 278 women aged 18 years and older previously treated for breast, gynaecological, or blood cancer, participating in the Australian Women's Wellness after Cancer Program. Serial mediation models interrogated the effect of stressful life events (List of Threatening Experiences-Modified) mediated by appraisal and coping (Perceived Stress Scale and Connor-Davidson Resilience Scale), on symptoms of anxiety and depression (Zung Self-rating Anxiety Scale and Center for Epidemiologic Studies Depression Scale). Over one-quarter (30.2%) of participants reported 1 or more stressful life events, other than their cancer, in the previous 6 months. Results indicate that perceived stress fully mediated the relationships between life stress, anxiety (indirect effect = 0.09, Bias-corrected bootstrap 95% CI 0.02-0.18, Percent mediation = 0.51), and depressive symptoms (indirect effect = 0.11, Bias-corrected bootstrap 95% CI 0.02-0.23, Percent mediation = 0.71) and accounted for more than half of the relationship between predictor and outcome. Findings indicate that stress appraisal mediated the relationship between past life stressors and anxiety and depressive symptoms. This analysis also highlights the need to consider wellness within a broader care context to identify potentially vulnerable patients to possibly avert future health concerns. Copyright © 2018 John Wiley & Sons, Ltd.
High-accuracy critical exponents for O(N) hierarchical 3D sigma models

International Nuclear Information System (INIS)

Godina, J. J.; Li, L.; Meurice, Y.; Oktay, M. B.

2006-01-01

The critical exponent γ and its subleading exponent Δ in the 3D O(N) Dyson's hierarchical model for N up to 20 are calculated with high accuracy. We calculate the critical temperatures for the measure δ(φ-vector.φ-vector-1). We extract the first coefficients of the 1/N expansion from our numerical data. We show that the leading and subleading exponents agree with Polchinski equation and the equivalent Litim equation, in the local potential approximation, with at least 4 significant digits
Effects of early life stress: Opportunities for pharmacological intervention

NARCIS (Netherlands)

Loi, M

2016-01-01

Moderate acute activation of the body’s stress response system is considered an adaptive mechanism that increases the chance of survival, but severe stressors early in life may disturb brain development. In agreement, epidemiological data suggest that adverse experiences early in life, such as
Negative inferential style, emotional clarity, and life stress: integrating vulnerabilities to depression in adolescence.

Science.gov (United States)

Stange, Jonathan P; Alloy, Lauren B; Flynn, Megan; Abramson, Lyn Y

2013-01-01

Negative inferential style and deficits in emotional clarity have been identified as vulnerability factors for depression in adolescence, particularly when individuals experience high levels of life stress. However, previous research has not integrated these characteristics when evaluating vulnerability to depression. In the present study, a racially diverse community sample of 256 early adolescents (ages 12 and 13) completed a baseline visit and a follow-up visit 9 months later. Inferential style, emotional clarity, and depressive symptoms were assessed at baseline, and intervening life events and depressive symptoms were assessed at follow-up. Hierarchical linear regressions indicated that there was a significant three-way interaction between adolescents' weakest-link negative inferential style, emotional clarity, and intervening life stress predicting depressive symptoms at follow-up, controlling for initial depressive symptoms. Adolescents with low emotional clarity and high negative inferential styles experienced the greatest increases in depressive symptoms following life stress. Emotional clarity buffered against the impact of life stress on depressive symptoms among adolescents with negative inferential styles. Similarly, negative inferential styles exacerbated the impact of life stress on depressive symptoms among adolescents with low emotional clarity. These results provide evidence of the utility of integrating inferential style and emotional clarity as constructs of vulnerability in combination with life stress in the identification of adolescents at risk for depression. They also suggest the enhancement of emotional clarity as a potential intervention technique to protect against the effects of negative inferential styles and life stress on depression in early adolescence.
Embedded spirituality: gardening in daily life and stressful life experiences.

Science.gov (United States)

Unruh, Anita; Hutchinson, Susan

2011-09-01

There is a limited body of research examining the relationship between spirituality and leisure, or the impact of leisure in the context of daily life, and life with stressful events. To examine the meaning of gardens and gardening across different life experiences using hermeneutic phenomenology to focus on the lived experience of leisure gardening. Most participants were interviewed once in each season over a 1 year period usually in their home. There were 42 participants (27 women and 15 men) in this study. Fifteen individuals had been diagnosed with cancer and were in varying stages of diagnosis and treatment. Three people had a chronic and progressive disease. Four women were grieving the death of their spouse. Participants ranged in age from 32 to 80 years. In this paper, we focus on the spirituality-related themes in this study: spirituality as connectedness; spirituality as an expression of inner being; the garden as a spiritual place and gardening as spiritual activity; gardening as a spiritual journey; and, stewardship. Participants with religious views saw their garden as an extension of their spirituality and a confirmation of their beliefs. Participants with secular or sacred views of spirituality that was not related to any religious beliefs were more likely to embed their spirituality in their relationship with nature as manifested in their garden. This study extends current theory regarding leisure and its contribution to meaning focused coping, and spirituality as a significant component of leisure in living with stressful health and life events. © 2011 The Authors. Scandinavian Journal of Caring Sciences © 2011 Nordic College of Caring Science.
Influence of life stress on immunological reactivity to mild psychological stress

NARCIS (Netherlands)

Brosschot, J. F.; Benschop, R. J.; Godaert, G. L.; Olff, M.; de Smet, M.; Heijnen, C. J.; Ballieux, R. E.

1994-01-01

This study investigated the effects of self-reported life stress and locus of control on reactivity of several immune parameters to a mild and short-lasting interpersonal stressor. Subjects were 86 male teachers aged 24 to 55 years. Immune reactivity was defined as changes in numbers of monocytes.
Toward Understanding How Early-Life Stress Reprograms Cognitive and Emotional Brain Networks.

Science.gov (United States)

Chen, Yuncai; Baram, Tallie Z

2016-01-01

Vulnerability to emotional disorders including depression derives from interactions between genes and environment, especially during sensitive developmental periods. Adverse early-life experiences provoke the release and modify the expression of several stress mediators and neurotransmitters within specific brain regions. The interaction of these mediators with developing neurons and neuronal networks may lead to long-lasting structural and functional alterations associated with cognitive and emotional consequences. Although a vast body of work has linked quantitative and qualitative aspects of stress to adolescent and adult outcomes, a number of questions are unclear. What distinguishes 'normal' from pathologic or toxic stress? How are the effects of stress transformed into structural and functional changes in individual neurons and neuronal networks? Which ones are affected? We review these questions in the context of established and emerging studies. We introduce a novel concept regarding the origin of toxic early-life stress, stating that it may derive from specific patterns of environmental signals, especially those derived from the mother or caretaker. Fragmented and unpredictable patterns of maternal care behaviors induce a profound chronic stress. The aberrant patterns and rhythms of early-life sensory input might also directly and adversely influence the maturation of cognitive and emotional brain circuits, in analogy to visual and auditory brain systems. Thus, unpredictable, stress-provoking early-life experiences may influence adolescent cognitive and emotional outcomes by disrupting the maturation of the underlying brain networks. Comprehensive approaches and multiple levels of analysis are required to probe the protean consequences of early-life adversity on the developing brain. These involve integrated human and animal-model studies, and approaches ranging from in vivo imaging to novel neuroanatomical, molecular, epigenomic, and computational
Toward Understanding How Early-Life Stress Reprograms Cognitive and Emotional Brain Networks

Science.gov (United States)

Chen, Yuncai; Baram, Tallie Z

2016-01-01

Vulnerability to emotional disorders including depression derives from interactions between genes and environment, especially during sensitive developmental periods. Adverse early-life experiences provoke the release and modify the expression of several stress mediators and neurotransmitters within specific brain regions. The interaction of these mediators with developing neurons and neuronal networks may lead to long-lasting structural and functional alterations associated with cognitive and emotional consequences. Although a vast body of work has linked quantitative and qualitative aspects of stress to adolescent and adult outcomes, a number of questions are unclear. What distinguishes ‘normal' from pathologic or toxic stress? How are the effects of stress transformed into structural and functional changes in individual neurons and neuronal networks? Which ones are affected? We review these questions in the context of established and emerging studies. We introduce a novel concept regarding the origin of toxic early-life stress, stating that it may derive from specific patterns of environmental signals, especially those derived from the mother or caretaker. Fragmented and unpredictable patterns of maternal care behaviors induce a profound chronic stress. The aberrant patterns and rhythms of early-life sensory input might also directly and adversely influence the maturation of cognitive and emotional brain circuits, in analogy to visual and auditory brain systems. Thus, unpredictable, stress-provoking early-life experiences may influence adolescent cognitive and emotional outcomes by disrupting the maturation of the underlying brain networks. Comprehensive approaches and multiple levels of analysis are required to probe the protean consequences of early-life adversity on the developing brain. These involve integrated human and animal-model studies, and approaches ranging from in vivo imaging to novel neuroanatomical, molecular, epigenomic, and computational
Economic stress and low leisure-time physical activity: Two life course hypotheses

Directory of Open Access Journals (Sweden)

Martin Lindström

2018-04-01

Full Text Available The aim was to investigate associations between economic stress in childhood and adulthood, and low leisure-time physical activity (LTPA in adulthood from two life course perspectives. The public health survey in Scania in the southernmost part of Sweden in 2012 is a cross-sectional study based on a stratified random sample with 28,029 respondents aged 18–80 (51.7% response rate. Associations between childhood and adult economic stress, and low LTPA were analyzed with logistic regressions. A 14.8% prevalence of men and 13.5% of women had low LTPA (sedentary lifestyle. Low LTPA was associated with higher age, being born abroad, low socioeconomic status, low trust, smoking, poor self-rated health, and economic stress in childhood and adulthood. The odds ratios of low LTPA increased with more accumulated economic stress across the life course in a dose-response relationship. There was no specific critical period (childhood or adulthood, because economic stress in childhood and adulthood were both associated with low LTPA but the associations were attenuated after the introduction of smoking and self-rated health. The accumulation hypothesis was supported because the odds ratios of low LTPA indicated a graded response to life course economic stress. The critical period hypothesis was thus not supported. Economic stress across the life course seems to be associated with low LTPA in adulthood. Keywords: Economic stress, Leisure-time physical activity, Accumulation, Critical period, Social capital, Sweden
Age- and sex-dependent effects of early life stress on hippocampal neurogenesis

NARCIS (Netherlands)

Loi, M.; Koricka, S.; Lucassen, P.J.; Joëls, M.

2014-01-01

Early life stress is a well-documented risk factor for the development of psychopathology in genetically predisposed individuals. As it is hard to study how early life stress impacts human brain structure and function, various animal models have been developed to address this issue. The models
Sugar consumption produces effects similar to early life stress exposure on hippocampal markers of neurogenesis and stress response

Directory of Open Access Journals (Sweden)

Jayanthi eManiam

2016-01-01

Full Text Available Adverse early life experience is a known risk factor for psychiatric disorders. It is also known that stress influences food preference. We were interested in exploring whether the choice of diet following early life stress exerts long-lasting molecular changes in the brain, particularly the hippocampus, a region critically involved in stress regulation and behavioural outcomes. Here, we examined the impact of early life stress induced by limited nesting material (LN and chronic sucrose availability post-weaning on an array of hippocampal genes related to plasticity, neurogenesis, stress and inflammatory responses and mitochondrial biogenesis. To examine mechanisms underlying the impact of LN and sugar intake on hippocampal gene expression, we investigated the role of DNA methylation. As females are more likely to experience adverse life events, we studied female Sprague-Dawley rats. After mating LN was imposed from days 2-9 postpartum. From 3-15 weeks of age, female Control and LN siblings had unlimited to access to either chow and water, or chow, water and 25% sucrose solution. LN markedly reduced glucocorticoid receptor (GR and neurogenic differentiation 1 (Neurod1 mRNA, markers involved in stress and hippocampal plasticity respectively, by more than 40%, with a similar effect of sugar intake in control rats. However, no further impact was observed in LN rats consuming sugar. Hippocampal Akt3 mRNA expression was similarly affected by LN and sucrose consumption. Interestingly, DNA methylation across 4 CpG sites of the GR and Neurod1 promoters was similar in LN and control rats. In summary, early life stress and post-weaning sugar intake produced long-term effects on hippocampal GR and Neurod1 expression. Moreover we found no evidence of altered promoter DNA methylation. We demonstrate for the first time that chronic sucrose consumption alone produces similar detrimental effects on the expression of hippocampal genes as LN exposure.
Early life adversity influences stress response association with smoking relapse.

Science.gov (United States)

al'Absi, Mustafa; Lemieux, Andrine; Westra, Ruth; Allen, Sharon

2017-11-01

We examined the hypothesis that stress-related blunting of cortisol in smokers is particularly pronounced in those with a history of severe life adversity. The two aims of this study were first to examine hormonal, craving, and withdrawal symptoms during ad libitum smoking and after the first 24 h of abstinence in smokers who experienced high or low levels of adversity. Second, we sought to examine the relationship between adversity and hypothalamic-pituitary-adrenal (HPA) hormones to predict relapse during the first month of a smoking cessation attempt. Hormonal and self-report measures were collected from 103 smokers (49 women) during ad libitum smoking and after the first 24 h of abstinence. HPA hormones were measured during baseline rest and in response to acute stress in both conditions. All smokers were interested in smoking cessation, and we prospectively used stress response measures to predict relapse during the first 4 weeks of the smoking cessation attempt. The results showed that high adversity was associated with higher distress and smoking withdrawal symptoms. High level of early life adversity was associated with elevated HPA activity, which was found in both salivary and plasma cortisol. Enhanced adrenocorticotropic hormone (ACTH) stress response was evident in high-adversity but not in low-adversity relapsers. This study demonstrated that early life adversity is associated with stress-related HPA responses. The study also demonstrated that, among smokers who experienced a high level of life adversity, heightened ACTH and cortisol responses were linked with increased risk for smoking relapse.
Effects of Aerobic Exercise Training on Stress Reactivity in Every-Day Life

OpenAIRE

Haaren, Birte von

2015-01-01

The current thesis investigated the effects of a 20-week aerobic exercise training on physiological and emotional responses to real-life stress using a randomized, controlled trial and an inactive sample. To assess participants' physiological and psychological responses during everyday life, ambulatory assessment was used. In summary, the present thesis provides empirical support that regular exercise can lead to improved emotional and physiological responses during real-life stress.
Increased amygdala reactivity following early life stress: a potential resilience enhancer role.

Science.gov (United States)

Yamamoto, Tetsuya; Toki, Shigeru; Siegle, Greg J; Takamura, Masahiro; Takaishi, Yoshiyuki; Yoshimura, Shinpei; Okada, Go; Matsumoto, Tomoya; Nakao, Takashi; Muranaka, Hiroyuki; Kaseda, Yumiko; Murakami, Tsuneji; Okamoto, Yasumasa; Yamawaki, Shigeto

2017-01-18

Amygdala hyper-reactivity is sometimes assumed to be a vulnerability factor that predates depression; however, in healthy people, who experience early life stress but do not become depressed, it may represent a resilience mechanism. We aimed to test these hypothesis examining whether increased amygdala activity in association with a history of early life stress (ELS) was negatively or positively associated with depressive symptoms and impact of negative life event stress in never-depressed adults. Twenty-four healthy participants completed an individually tailored negative mood induction task during functional magnetic resonance imaging (fMRI) assessment along with evaluation of ELS. Mood change and amygdala reactivity were increased in never-depressed participants who reported ELS compared to participants who reported no ELS. Yet, increased amygdala reactivity lowered effects of ELS on depressive symptoms and negative life events stress. Amygdala reactivity also had positive functional connectivity with the bilateral DLPFC, motor cortex and striatum in people with ELS during sad memory recall. Increased amygdala activity in those with ELS was associated with decreased symptoms and increased neural features, consistent with emotion regulation, suggesting that preservation of robust amygdala reactions may reflect a stress buffering or resilience enhancing factor against depression and negative stressful events.

The role of early adversity and recent life stress in depression severity in an outpatient sample.

Science.gov (United States)

Vogt, Dominic; Waeldin, Sandra; Hellhammer, Dirk; Meinlschmidt, Gunther

2016-12-01

Pre-, peri-, and postnatal stress have frequently been reported to be associated with negative health outcomes during adult life. However, it is unclear, if these factors independently predict mental health in adulthood. We estimated potential associations between reports of pre-, peri-, and postnatal stress and depression severity in outpatients (N = 473) diagnosed with depression, anxiety or somatoform disorders by their family physician. We retrospectively assessed pre-, peri-, and postnatal stress and measured depression severity as well as recent life stress using questionnaires. First, we estimated if depression severity was predicted by pre-, peri- and/or postnatal stress using multiple regression models. Second, we compared pre- and postnatal stress levels between patient subgroups of different degrees of depression severity, performing multilevel linear modeling. Third, we analyzed if an association between postnatal stress and current depression severity was mediated by recent life stress. We found no associations of pre-, or perinatal stress with depression severity (all p > 0.05). Higher postnatal stress was associated with higher depression severity (p stress as compared to patients with none to minimal, or mild depression (all p life stress of the association between postnatal stress and depression severity (p stress predicted depression severity in adult life. This association was mediated by recent life stress. Copyright © 2016 Elsevier Ltd. All rights reserved.
Voice, stress, work and quality of life of soccer coaches and physical trainers.

Science.gov (United States)

Penteado, Regina Zanella; Silva, Noelle Bernardi da; Montebello, Maria Imaculada de Lima

2015-01-01

To assess aspects related to work, stress and quality of life related to voice in soccer coaches (C) and physical trainers (T), comparing the categories. Qualitative and quantitative studies with 13 C and 13 T of teams competing in Phase One of the highest level (Série A ) of the 2012 Campeonato Paulista (São Paulo State Soccer Championship). The questions were open ended and related to complaints, difficulties, and/or problems regarding voice use during work and to the relations between voice, work, stress, and quality of life. Stress at work was analyzed by the Job Stress Scale (JSS) questionnaire. The perception of the impact of the voice on quality of life was evaluated by the Voice-Related Quality of Life (V-RQOL) protocol. The answers to the questions were transcribed and submitted to content analysis, and regarding the questionnaire, descriptive data and analytical statistics were used. Content analysis showed lack of preparation for voice care; voice complaints; and intense vocal use demand under stressful work, in addition to the absence of healthy habits and social/family support. The JSS dimensions showed that the Active Work situation and the high V-RQOL scores are compatible with vocal health without complaints. There were no statistical differences between the categories. Both categories reported complaints/problems linked to professional voice use and stressful workload. However, the perception of vocal impact on the quality of life was positive, and the analysis of stress at work resulted in "good" and favorable conditions. The relationship between voice, work, stress, and quality of life in both the categories require further investigations.
Chronic daily headache: stress and impact on the quality of life.

Science.gov (United States)

Galego, José Carlos Busto; Moraes, Avelina Maria; Cordeiro, José Antonio; Tognola, Waldir Antonio

2007-12-01

To evaluate the stress presence and its influence in the quality of life of patients with chronic daily headache (CDH). A hundred patients with at least 18 years old, with primary headache with duration greater than 4 hours a day, and frequency of 15 or more days monthly for at least three months were studied. Lipp's Inventory of Stress Symptoms and the Medical Outcomes Study Short Form (SF-36) were used. Stress was observed in 90% of the patients; nearly half of them was in the phase almost exhaustion. Patients with stress when compared with the ones with no stress presented significantly lower scores in all the domains of SF-36; except in physical functioning. The resistance phase presented scores significantly higher than almost exhaustion; except for bodily pain. The majority of the patients presented stress with significant reduction in their quality of life. Consequently, the stress could be related with both the development and the maintenance of CDH.
Herbal supplement extends life span under some environmental conditions and boosts stress resistance.

Directory of Open Access Journals (Sweden)

Bryant Villeponteau

Full Text Available Genetic studies indicate that aging is modulated by a great number of genetic pathways. We have used Drosophila longevity and stress assays to test a multipath intervention strategy. To carry out this strategy, we supplemented the flies with herbal extracts (SC100 that are predicted to modulate the expression of many genes involved in aging and stress resistance, such as mTOR, NOS, NF-KappaB, and VEGF. When flies were housed in large cages with SC100 added, daily mortality rates of both male and female flies were greatly diminished in mid to late life. Surprisingly, SC100 also stabilized midlife mortality rate increases so as to extend the maximum life span substantially beyond the limits previously reported for D. melanogaster. Under these conditions, SC100 also promoted robust resistance to partial starvation stress and to heat stress. Fertility was the same initially in both treated and control flies, but it became significantly higher in treated flies at older ages as the fertility of control flies declined. Mean and maximum life spans of flies in vials at the same test site were also extended by SC100, but the life spans were short in absolute terms. In contrast, at an independent test site where stress was minimized, the flies exhibited much longer mean life spans, but the survival curves became highly rectangular and the effects of SC100 on both mean and maximum life spans declined greatly or were abolished. The data indicate that SC100 is a novel herbal mix with striking effects on enhancing Drosophila stress resistance and life span in some environments, while minimizing mid to late life mortality rates. They also show that the environment and other factors can have transformative effects on both the length and distribution of survivorship, and on the ability of SC100 to extend the life span.
Depression, post-traumatic stress disorder, and life satisfaction in Greenlandic adults

DEFF Research Database (Denmark)

Zaragoza Scherman, Alejandra

2017-01-01

problems or a sense of wellbeing. In this study, a group of 137 Greenlandic adults completed measures of depression, PTSD, and life satisfaction. In addition, they also provided memories of traumatic or stressful and positive life events they had xperienced during their lives. No sex differences were found......Suicide is a major public health problem in Greenland. Despite the fact that suicide is highly associated with depression, posttraumatic stress disorder (PTSD), and life satisfaction there are virtually no data about the extent to which Greenlandic individuals experience these mental health...
Behaviour of Lyapunov exponents near crisis points in the dissipative standard map

Science.gov (United States)

Pompe, B.; Leven, R. W.

1988-11-01

We numerically study the behaviour of the largest Lyapunov characteristic exponent λ1 in dependence on a control parameter in the 2D standard map with dissipation. In order to investigate the system's motion in parameter intervals slightly above crisis points we introduce "partial" Lyapunov exponents which characterize the average exponential divergence of nearby orbits on a semi-attractor at a boundary crisis and on distinct parts of a "large" chaotic attractor near an interior crisis. In the former case we find no significant difference between λ1 in the pre-crisis regime and the partial Lyapunov exponent describing transient chaotic motions slightly above the crisis. For the latter case we give a quantitative description of the drastic increase of λ1. Moreover, a formula which connects the critical exponent of a chaotic transient above a boundary crisis with a pointwise dimension is derived.
Having the Time of Their Life: College Student Stress, Dating and Satisfaction with Life.

Science.gov (United States)

Coccia, Catherine; Darling, Carol A

2016-02-01

A cross-sectional design based on the family ecosystem framework was used to examine how students' time spent engaging in social interactions and personal behaviours was related to dating, stress and satisfaction with life. The data were extracted from the Parental Indulgence of Emerging Adults study and consisted of 534 students at a southeastern university. The findings indicated that the amount of time involved in non-verbal social interactions, such as texting and social networking, along with solitary activities, such as watching TV and studying, was negatively related to students' life satisfaction. In comparison, being in a relationship and talking to people on the phone were positively related to students' life satisfaction. These results have implications for family and health professionals along with university wellness centres that facilitate student health by incorporating preventative measures to help students deal with their stress. Copyright © 2014 John Wiley & Sons, Ltd.
A reliability based stress-life evaluation of aluminium-graphite particulate composites

International Nuclear Information System (INIS)

Achutha, M.V.; Sridhara, B.K.; Abdul Budan, D.

2008-01-01

Fatigue tests were conducted on sand cast aluminium-graphite composite specimens on Rotating Beam Fatigue Testing Machine with three different stress levels. Aluminium-graphite (LM 25-5% graphite) composite was processed by closed mould sand casting method. Three-stress level fatigue test program was planned for carrying out fatigue experiments. Three different stress levels selected for fatigue experiments were a fraction of ultimate tensile strength. Statistical design of fatigue experiments was carried out to determine the sample size at each stress level. Experimental results are presented in the form of stress-life (S-N) curves and reliability-stress-life (R-S-N) curves, which are helpful for designers. The S-N curve of the aluminium-graphite composite was compared with its matrix alloy LM 25. Comparison revealed that the fatigue behaviour of the aluminium-graphite composite is superior to that of the matrix alloy
Hurst exponent and prediction based on weak-form efficient market hypothesis of stock markets

Science.gov (United States)

Eom, Cheoljun; Choi, Sunghoon; Oh, Gabjin; Jung, Woo-Sung

2008-07-01

We empirically investigated the relationships between the degree of efficiency and the predictability in financial time-series data. The Hurst exponent was used as the measurement of the degree of efficiency, and the hit rate calculated from the nearest-neighbor prediction method was used for the prediction of the directions of future price changes. We used 60 market indexes of various countries. We empirically discovered that the relationship between the degree of efficiency (the Hurst exponent) and the predictability (the hit rate) is strongly positive. That is, a market index with a higher Hurst exponent tends to have a higher hit rate. These results suggested that the Hurst exponent is useful for predicting future price changes. Furthermore, we also discovered that the Hurst exponent and the hit rate are useful as standards that can distinguish emerging capital markets from mature capital markets.
Stress-life interrelationships associated with alkaline fuel cells

Science.gov (United States)

Thaller, Lawrence H.; Martin, Ronald E.; Stedman, James K.

1987-01-01

A review is presented concerning the interrelationships between applied stress and the expected service life of alkaline fuel cells. Only the physical, chemical, and electrochemical phenomena that take place within the fuel cell stack portion of an overall fuel cell system will be discussed. A brief review will be given covering the significant improvements in performance and life over the past two decades as well as summarizing the more recent advances in understanding which can be used to predict the performance and life characteristics of fuel cell systems that have yet to be built.
Lyapunov exponent and criticality in the Hamiltonian mean field model

Science.gov (United States)

Filho, L. H. Miranda; Amato, M. A.; Rocha Filho, T. M.

2018-03-01

We investigate the dependence of the largest Lyapunov exponent (LLE) of an N-particle self-gravitating ring model at equilibrium with respect to the number of particles and its dependence on energy. This model has a continuous phase-transition from a ferromagnetic to homogeneous phase, and we numerically confirm with large scale simulations the existence of a critical exponent associated to the LLE, although at variance with the theoretical estimate. The existence of strong chaos in the magnetized state evidenced by a positive Lyapunov exponent is explained by the coupling of individual particle oscillations to the diffusive motion of the center of mass of the system and also results in a change of the scaling of the LLE with the number of particles. We also discuss thoroughly for the model the validity and limits of the approximations made by a geometrical model for their analytic estimate.
Maternal life event stress and congenital anomalies.

Science.gov (United States)

Carmichael, S L; Shaw, G M

2000-01-01

We used data from a population-based case-control study to explore the relation between certain life events during the periconceptional period and several types of congenital anomalies. We ascertained cases from pregnancies ending in 1987-1989 and randomly selected controls from eligible liveborn infants. In telephone interviews, women reported deaths of anyone close to them. They also reported job losses or separations/divorces, for themselves or anyone close to them. Experiencing at least one stressful event during the periconceptional period was associated with a prevalence odds ratio of 1.4-1.5 for the delivery of infants with conotruncal heart defects, neural tube defects, and isolated cleft lip with or without palate. These associations tended to be restricted to women who were not obese and women with less than or equal to a high school education. This study suggests that women who experience stressful life events around the time of conception or early gestation may be at increased risk of delivering infants with certain congenital anomalies.
Intermittency exponent of the turbulent energy cascade

International Nuclear Information System (INIS)

Cleve, J.; Greiner, M.; Pearson, B.R.; Sreenivasan, K.R.

2006-12-01

We consider the turbulent energy dissipation from one-dimensional records in experiments using air and gaseous helium at cryogenic temperatures, and obtain the intermittency exponent via the two-point correlation function of the energy dissipation. The air data are obtained in a number of flows in a wind tunnel and the atmospheric boundary layer at a height of about 35 m above the ground. The helium data correspond to the centerline of a jet exhausting into a container. The air data on the intermittency exponent are consistent with each other and with a trend that increases with the Taylor microscale Reynolds number, R λ , of up to about 1000 and saturates thereafter. On the other hand, the helium data cluster around a constant value at nearly all R λ , this being about half of the asymptotic value for the air data. Some possible explanation is offered for this anomaly. (author)
Influence of stress on creep deformation properties of 9-12Cr ferritic creep resistant steels

Energy Technology Data Exchange (ETDEWEB)

Kimura, K.; Sawada, K.; Kushima, H. [National Institute for Materials Science (Japan)

2008-07-01

Creep deformation property of 9-12Cr ferritic creep resistant steels was investigated. With decrease in stress, a magnitude of creep strain at the onset of accelerating creep stage decreased from about 2% in the short-term to less than 1% in the longterm. A time to 1% total strain was observed in the transient creep stage in the short term regime, however, it shifted to the accelerating creep stage in the long-term regime. Life fraction of the times to 1% creep strain and 1% total strain tended to increase with decrease in stress. Difference in stress dependence of the minimum creep rate was observed in the high- and low-stress regimes with a boundary condition of 50% of 0.2% offset yield stress. Stress dependence of the minimum creep rate in the high stress regime was equivalent to a strain rate dependence of the flow stress evaluated by tensile test, and a magnitude of stress exponent, n, in the high stress regime decreased with increase in temperature from 20 at 550 C to 10 at 700 C. On the other hand, n value in the low stress regime was about 5, and creep deformation in the low stress regime was considered to be controlled by dislocation climb. Creep rupture life was accurately predicted by a region splitting method by considering a change in stress dependence of creep deformation. (orig.)
The anomalous scaling exponents of turbulence in general dimension from random geometry

Energy Technology Data Exchange (ETDEWEB)

Eling, Christopher [Rudolf Peierls Centre for Theoretical Physics, University of Oxford, 1 Keble Road, Oxford OX1 3NP (United Kingdom); Oz, Yaron [Raymond and Beverly Sackler School of Physics and Astronomy, Tel Aviv University, Tel Aviv 69978 (Israel)

2015-09-22

We propose an analytical formula for the anomalous scaling exponents of inertial range structure functions in incompressible fluid turbulence. The formula is a Knizhnik-Polyakov-Zamolodchikov (KPZ)-type relation and is valid in any number of space dimensions. It incorporates intermittency in a novel way by dressing the Kolmogorov linear scaling via a coupling to a lognormal random geometry. The formula has one real parameter γ that depends on the number of space dimensions. The scaling exponents satisfy the convexity inequality, and the supersonic bound constraint. They agree with the experimental and numerical data in two and three space dimensions, and with numerical data in four space dimensions. Intermittency increases with γ, and in the infinite γ limit the scaling exponents approach the value one, as in Burgers turbulence. At large n the nth order exponent scales as √n. We discuss the relation between fluid flows and black hole geometry that inspired our proposal.
Nature of exponents found in the critical regime of YBCO

International Nuclear Information System (INIS)

Marhas, Manmeet Kaur; Saravanan, P.; Balakrishnan, K.; Srinivasan, R.; Kanjilal, D.; Metha, G.K.; Pai, S.P.; Pinto, R.; Vedvyas, M.; Ogale, S.B.; Mohan Rao, G.; Nathan, Senthil; Mohan, S.

1997-01-01

Full text: Fluctuation effects in electrical conductivity near T c is an important tool for studying the nature of phase transition in high T c ceramics. Probing critical regime by way of experiments demand data of good precision. Measurements were carried out on well characterised high T c films prepared by laser ablation and high pressure oxygen sputtering. High energy ion irradiation carried out to see the effect of disorder. Precise electrical resistivity measurements were carried out near T c with a temperature control accuracy better than 10 mK and large number of data points were collected in this regime. 100 MeV oxygen and 200 MeV Ag ions were used with varying fluences for irradiation at 77K. The data was analysed using existing models of critical fluctuation effects. The exponent of electrical conductivity in laser ablated thin films whose transition widths are less than 1 K was 1.33 and is independent of disorder caused by high energy ion irradiation and this could be identified as the exponent for excess conductivity in the critical intermediate charged fluctuation regime as proposed by Fisher. The exponent is around 2.7 in those films whose transition widths are greater than 1 K and also was independent of disorder and this could be identified as exponent in the para coherence regime
Scaling exponents for fracture surfaces in opal glass

Energy Technology Data Exchange (ETDEWEB)

Chavez-Guerrero, L., E-mail: guerreroleo@hotmail.com [Facultad de Ingenieria Mecanica y Electrica. Cd. Universitaria s/n, C.P. 66450, Universidad Autonoma de Nuevo Leon, Nuevo Leon (Mexico); Center of Innovation, Research and Development on Engineering and Technology, Universidad Autonoma de Nuevo Leon Monterrey, C.P. 66600, Apodaca, Nuevo Leon (Mexico); Garza, F.J., E-mail: fjgarza@gama.fime.uanl.mx [Facultad de Ciencias Quimicas, Cd. Universitaria s/n, C.P. 66450, Universidad Autonoma de Nuevo Leon, Nuevo Leon (Mexico); Hinojosa, M., E-mail: hinojosa@gama.fime.uanl.mx [Facultad de Ingenieria Mecanica y Electrica. Cd. Universitaria s/n, C.P. 66450, Universidad Autonoma de Nuevo Leon, Nuevo Leon (Mexico); Center of Innovation, Research and Development on Engineering and Technology, Universidad Autonoma de Nuevo Leon Monterrey, C.P. 66600, Apodaca, Nuevo Leon (Mexico)

2010-09-25

We have investigated the scaling properties of fracture surfaces in opal glass. Specimens with two different opacifying particle sizes (1 {mu}m and 0.4 {mu}m) were broken by three-point bending test and the resulting fracture surfaces were analyzed using Atomic Force Microscopy. The analysis of the self-affine behavior was performed using the Variable Bandwidth and Height-Height Correlation Methods, and both the roughness exponent, {zeta}, and the correlation length, {xi}, were determined. It was found that the roughness exponent obtained in both samples is {zeta} {approx} 0.8; whereas the correlation length in both fractures is of the order of the particle size, demonstrating the dependence of this self-affine parameter on the microstructure of opal glass.
Scaling exponents for fracture surfaces in opal glass

International Nuclear Information System (INIS)

Chavez-Guerrero, L.; Garza, F.J.; Hinojosa, M.

2010-01-01

We have investigated the scaling properties of fracture surfaces in opal glass. Specimens with two different opacifying particle sizes (1 μm and 0.4 μm) were broken by three-point bending test and the resulting fracture surfaces were analyzed using Atomic Force Microscopy. The analysis of the self-affine behavior was performed using the Variable Bandwidth and Height-Height Correlation Methods, and both the roughness exponent, ζ, and the correlation length, ξ, were determined. It was found that the roughness exponent obtained in both samples is ζ ∼ 0.8; whereas the correlation length in both fractures is of the order of the particle size, demonstrating the dependence of this self-affine parameter on the microstructure of opal glass.
Determination of critical exponents of inhomogeneous Gd films

Energy Technology Data Exchange (ETDEWEB)

Rosales-Rivera, A., E-mail: arosalesr@unal.edu.co [Laboratorio de Magnetismo y Materiales Avanzados, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Colombia, Sede Manizales, Manizales (Colombia); Salazar, N.A. [Laboratorio de Magnetismo y Materiales Avanzados, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Colombia, Sede Manizales, Manizales (Colombia); Hovorka, O.; Idigoras, O.; Berger, A. [CIC nanoGUNE Consolider, Tolosa Hiribidea 76, E-20018 Donostia-San Sebastian (Spain)

2012-08-15

The role of inhomogeneity on the critical behavior is studied for non-epitaxial Gd films. For this purpose, the film inhomogeneity was varied experimentally by annealing otherwise identical samples at different temperatures T{sub AN}=200, 400, and 500 Degree-Sign C. Vibrating sample magnetometry (VSM) was used for magnetization M vs. T measurements at different external fields H. A method based upon the linear superposition of different sample parts having different Curie temperatures T{sub C} was used to extract the critical exponents and the intrinsic distribution of Curie temperatures. We found that this method allows extracting reliable values of the critical exponents for all annealing temperatures, which enabled us to study the effects of disorder onto the universality class of Gd films.
Determination of critical exponents of inhomogeneous Gd films

International Nuclear Information System (INIS)

Rosales-Rivera, A.; Salazar, N.A.; Hovorka, O.; Idigoras, O.; Berger, A.

2012-01-01

The role of inhomogeneity on the critical behavior is studied for non-epitaxial Gd films. For this purpose, the film inhomogeneity was varied experimentally by annealing otherwise identical samples at different temperatures T AN =200, 400, and 500 °C. Vibrating sample magnetometry (VSM) was used for magnetization M vs. T measurements at different external fields H. A method based upon the linear superposition of different sample parts having different Curie temperatures T C was used to extract the critical exponents and the intrinsic distribution of Curie temperatures. We found that this method allows extracting reliable values of the critical exponents for all annealing temperatures, which enabled us to study the effects of disorder onto the universality class of Gd films.

Major stressful life events in adulthood and risk of multiple sclerosis

DEFF Research Database (Denmark)

Nielsen, Nete Munk; Bager, Peter; Simonsen, Jacob

2014-01-01

It is unclear whether psychological stress is associated with increased risk of multiple sclerosis (MS). We studied the association between major stressful life events and MS in a nationwide cohort study using death of a child or a spouse or marital dissolution as indicators of severe stress....
Negative cognitive style and cortisol recovery accentuate the relationship between life stress and depressive symptoms.

Science.gov (United States)

Quinn, Meghan E; Grant, Kathryn E; Adam, Emma K

2018-03-01

When exposed to stressful life events, a significant number of adolescents will experience depressive symptoms. One model of depression suggests that individuals with a negative cognitive style are most vulnerable to depression following life stress. Alternatively, altered activation of the hypothalamic-pituitary-adrenal axis may explain vulnerability to depression following life stress. Each of these models plausibly explains the emergence of depressive symptoms during adolescence and have been investigated largely independently. The current study recruited a sample of urban adolescents (N = 179) to evaluate whether cortisol response to a laboratory stress induction and negative cognitive style are related and whether they independently interact with exposure to stressful life events to predict symptoms of depression. Negative cognitive style was not associated with cortisol response to the laboratory stressor. Rather, negative cognitive style and cortisol recovery independently interacted with stressful life events to predict current symptoms of depression. Results support a heterogeneous etiology of depression.
Les rites de la mort à Bornéo : séparation ou renaissance ? Actualité de Robert Hertz Death Rites in Borneo: Separation or Rebirth? Robert Hertz’ Legacy

Directory of Open Access Journals (Sweden)

Pascal Couderc

2012-12-01

Full Text Available La publication récente par le Borneo Research Council d’un ouvrage collectif sur la mort fournit l’occasion de réévaluer l’apport de Robert Hertz à la compréhension des rites funéraires à Bornéo. Si la traduction en anglais, dans les années 1960, de l’essai de Hertz sur la représentation collective de la mort avait consacré, grâce notamment aux travaux de Peter Metcalf sur les Berawan, la puissance du modèle analytique hertzien, ce nouvel ouvrage semble signaler que le moment de la célébration finale est venu, où les héritiers se libèrent de l’emprise spirituelle du défunt. Tout en conservant une grande part de sa valeur comme théorie du deuil, le paradigme transitionnel ou « réactif » de Hertz révèle ses limites, mises ici en lumière par des données ethnographiques encore peu connues ou inédites, qui démontrent, par exemple, l’existence d’une circulation des composantes de la personne par delà l’opposition entre la vie et la mort, ou encore l’influence directe des secondes funérailles sur la renaissance des défunts. Cet article aborde le dépassement du modèle hertzien en retournant à la lettre de l’essai, dont il met en relief l’intelligence ethnographique et la finesse théorique.The recent publication by the Borneo Research Council of a collection of essays on death provides an opportunity to reassess the heritage of Robert Hertz, whose theory of the double obsequies relies heavily on the ethnography of the Ngaju and other Borneo peoples. The translation of Hertz’s essay on the collective representation of death in the 1960s, prompting in particular Peter Metcalf’s work on the Berawan, has consecrated the explanatory power of Hertz’s model. With this new book, however, time seems to have come for the final celebration that marks the heirs’ liberation from the deceased’s spiritual influence. While still largely valid as a general theory of mourning, Hertz’s paradigm of
PHYSIOLOGICAL RESPONSES DURING MATCHES AND PROFILE OF ELITE PENCAK SILAT EXPONENTS

Directory of Open Access Journals (Sweden)

Benedict Tan

2002-12-01

Full Text Available This is a descriptive, cross-sectional study describing the physiological responses during competitive matches and profile of elite exponents of an emerging martial art sport, pencak silat. Thirty exponents (21 males and 9 females were involved in the study. Match responses (i.e. heart rate (HR throughout match and capillary blood lactate concentration, [La], at pre-match and at the end of every round were obtained during actual competitive duels. Elite silat exponents' physiological attributes were assessed via anthropometry, vertical jump, isometric grip strength, maximal oxygen uptake, and the Wingate 30 s anaerobic test of the upper and lower body, in the laboratory. The match response data showed that silat competitors' mean HR was > 84% of estimated HR maximum and levels of [La] ranged from 6.7 - 18.7 mMol-1 during matches. This suggests that competitive silat matches are characterised by high aerobic and anaerobic responses. In comparison to elite taekwondo and judo athletes' physiological characteristics, elite silat exponents have lower aerobic fitness and grip strength, but greater explosive leg power (vertical jump. Generally, they also possessed a similar anaerobic capability in the lower but markedly inferior anaerobic capability in the upper body
Quantum computation of multifractal exponents through the quantum wavelet transform

International Nuclear Information System (INIS)

Garcia-Mata, Ignacio; Giraud, Olivier; Georgeot, Bertrand

2009-01-01

We study the use of the quantum wavelet transform to extract efficiently information about the multifractal exponents for multifractal quantum states. We show that, combined with quantum simulation algorithms, it enables to build quantum algorithms for multifractal exponents with a polynomial gain compared to classical simulations. Numerical results indicate that a rough estimate of fractality could be obtained exponentially fast. Our findings are relevant, e.g., for quantum simulations of multifractal quantum maps and of the Anderson model at the metal-insulator transition.
DNA methyltransferase 3A gene polymorphism contributes to daily life stress susceptibility

Directory of Open Access Journals (Sweden)

Barliana MI

2017-12-01

Full Text Available Melisa I Barliana,1,2 Shintya N Amalya,1 Ivan S Pradipta,3 Sofa D Alfian,3 Arif SW Kusuma,1,2 Tiana Milanda,1,4 Rizky Abdulah3,4 1Department of Biological Pharmacy, Biotechnology Pharmacy Laboratory, 2Pharmacy Services Development Research Center, 3Department of Pharmacology and Clinical Pharmacy, Clinical Pharmacy Laboratory, 4Center for Drug Discovery and Product Development, Faculty of Pharmacy, Universitas Padjadjaran, Jatinangor, West Java, Indonesia Abstract: Daily life stress markedly affects the response toward stressful stimuli. DNA methylation is one of the factors that regulate this response, and is a normal mechanism of somatic cell growth, but its regulatory gene variations may cause alterations in the stress response. The aim of the present study was to investigate genotypic variants of the DNA methyltransferase 3A (DNMT3A gene in 129 healthy subjects and evaluate its association with daily life stress. Blood samples were collected, and genomic DNA was isolated. DNA was amplified using specific tetra primers for DNMT3A (C/T rs11683424 and visualized following 2% agarose gel electrophoresis. The association of DNMT3A genetic variants with daily life stress was analyzed using the Kessler Psychological Distress Scale (K10. We observed that the distribution of subjects with genotype CC (wild type, CT (heteromutant, and TT (homomutant was 13.95%, 81.4%, and 4.65%, respectively. Genetic variations significantly affected the daily life stress condition (p=0.04 in Indonesian healthy subjects, but most of the subjects with the CT phenotype were classified in a stress condition. Keywords: daily life stressor, DNA methylation, epigenetic, Kessler Psychological Distress Scale (K10, rs11683424, DNMT3A
Early life stress as an influence on limbic epilepsy: an hypothesis whose time has come?

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Amelia S Koe

2009-10-01

Full Text Available The pathogenesis of mesial temporal lobe epilepsy (MTLE, the most prevalent form of refractory focal epilepsy in adults, is thought to begin in early life, even though seizures may not commence until adolescence or adulthood. Amongst the range of early life factors implicated in MTLE causation (febrile seizures, traumatic brain injury, etc., stress may be one important contributor. Early life stress is an a priori agent deserving study because of the large amount of neuroscientific data showing enduring effects on structure and function in hippocampus and amygdala, the key structures involved in MTLE. An emerging body of evidence directly tests hypotheses concerning early life stress and limbic epilepsy: early life stressors, such as maternal separation, have been shown to aggravate epileptogenesis in both status epilepticus and kindling models of limbic epilepsy. In addition to elucidating its influence on limbic epileptogenesis itself, the study of early life stress has the potential to shed light on the psychiatric disorder that accompanies MTLE. For many years, psychiatric comorbidity was viewed as an effect of epilepsy, mediated psychologically and/or neurobiologically. An alternative – or complementary – perspective is that of shared causation. Early life stress, implicated in the pathogenesis of several psychiatric disorders, may be one such causal factor. This paper aims to critically review the body of experimental evidence linking early life stress and epilepsy; to discuss the direct studies examining early life stress effects in current models of limbic seizures/epilepsy; and to suggest priorities for future research.
Thickness dependence of effective critical exponents in three-dimensional Ising plates

International Nuclear Information System (INIS)

Marques, M.I.; Gonzalo, J.A.

2000-01-01

Phase transitions in ising plates of equal area and different thickness have been studied by the Monte Carlo approach. The evolution of the critical temperature and of the effective critical exponents with the thickness of the lattice has been numerically determined. The thickness dependence of the maximum value of the effective critical exponents is well described by an exponential decay towards the respective three-dimensional value. (author)
No interactions between genetic polymorphisms and stressful life events on outcome of antidepressant treatment

DEFF Research Database (Denmark)

Bukh, Jens Drachmann; Bock, Camilla; Vinberg, Maj

2009-01-01

Genetic polymorphisms seem to influence the response on antidepressant treatment and moderate the impact of stress on depression. The present study aimed to assess, whether allelic variants and stressful life events interact on the clinical outcome of depression. In a sample of 290 systematically...... recruited patients diagnosed with a single depressive episode according to ICD-10, we assessed the outcome of antidepressant treatment and the presence of stressful life events in a 6-month period preceding onset of depression by means of structured interviews. Further, we genotyped nine polymorphisms...... dependent on stressful life events experienced by the individual prior to onset of depression....
The brain-derived neurotrophic factor pathway, life stress, and chronic multi-site musculoskeletal pain.

Science.gov (United States)

Generaal, Ellen; Milaneschi, Yuri; Jansen, Rick; Elzinga, Bernet M; Dekker, Joost; Penninx, Brenda W J H

2016-01-01

Brain-derived neurotrophic factor (BDNF) disturbances and life stress, both independently and in interaction, have been hypothesized to induce chronic pain. We examined whether (a) the BDNF pathway (val(66)met genotype, gene expression, and serum levels), (b) early and recent life stress, and (c) their interaction are associated with the presence and severity of chronic multi-site musculoskeletal pain. Cross-sectional data are from 1646 subjects of the Netherlands Study of Depression and Anxiety. The presence and severity of chronic multi-site musculoskeletal pain were determined using the Chronic Pain Grade (CPG) questionnaire. The BDNF val(66)met polymorphism, BDNF gene expression, and BDNF serum levels were measured. Early life stress before the age of 16 was assessed by calculating a childhood trauma index using the Childhood Trauma Interview. Recent life stress was assessed as the number of recent adverse life events using the List of Threatening Events Questionnaire. Compared to val(66)val, BDNF met carriers more often had chronic pain, whereas no differences were found for BDNF gene expression and serum levels. Higher levels of early and recent stress were both associated with the presence and severity of chronic pain (p stress in the associations with chronic pain presence and severity. This study suggests that the BDNF gene marks vulnerability for chronic pain. Although life stress did not alter the impact of BDNF on chronic pain, it seems an independent factor in the onset and persistence of chronic pain. © The Author(s) 2016.
The Effects of Discrimination Experience on Life Satisfaction of North Korean Refugees: Mediating Effect of Stress.

Science.gov (United States)

Noh, Jin-Won; Park, Hyunchun; Kim, Minji; Kwon, Young Dae; Kim, Jin-Seok; Yu, Shieun

2018-01-01

This study investigated the mediation effect of stress between the experience of discrimination and life satisfaction among North Korean refugees who resettled in South Korea. The findings of the current study provide empirical evidence for the need of social interventions to mitigate adverse effects of stress on North Korean refugees who are subject to social discrimination on a daily basis. In this study, we included 500 subjects among 2,138 North Korean refugees who took refuge in South Korea in 2007. The interview started from April 6th 2009 and finished on May 25th 2009. We conducted moderator effect analysis with Path analysis was conducted because we confirm the experience of discrimination was affected by life satisfaction and stress can affected life satisfaction as a moderator. The experience of discrimination significantly affects stress and stress significantly affects life satisfaction. However, the experience of discrimination was not directly related to life satisfaction. The more stress the study respondents experienced, the lower the life satisfaction they reported. The present finding suggests that the effects of discriminating experiences on the life satisfaction of North Korean refugees in South Korea were mediated by their own perceived stress.
Exposure to stressful life events during pregnancy predicts psychotic experiences via behaviour problems in childhood.

Science.gov (United States)

Betts, Kim S; Williams, Gail M; Najman, Jakob M; Scott, James; Alati, Rosa

2014-12-01

Exposure to stressful life events during pregnancy has been associated with later schizophrenia in offspring. We explore how prenatal stress and neurodevelopmental abnormalities in childhood associate to increase the risk of later psychotic experiences. Participants from the Mater University Study of Pregnancy (MUSP), an Australian based, pre-birth cohort study were examined for lifetime DSM-IV positive psychotic experiences at 21 years by a semi-structured interview (n = 2227). Structural equation modelling suggested psychotic experiences were best represented with a bifactor model including a general psychosis factor and two group factors. We tested for an association between prenatal stressful life events with the psychotic experiences, and examined for potential moderation and mediation by behaviour problems and cognitive ability in childhood. Prenatal stressful life events predicted psychotic experiences indirectly via behaviour problems at child age five years, and this relationship was not confounded by maternal stressful life events at child age five. We found no statistical evidence for an interaction between prenatal stressful life events and behaviour problems or cognitive ability. The measurable effect of prenatal stressful life events on later psychotic experiences in offspring manifested as behaviour problems by age 5. By identifying early abnormal behavioural development as an intermediary, this finding further confirms the role of prenatal stress to later psychotic disorders. Copyright © 2014 Elsevier Ltd. All rights reserved.
Psychological distress and stressful life events in pediatric complex regional pain syndrome

Science.gov (United States)

Wager, Julia; Brehmer, Hannah; Hirschfeld, Gerrit; Zernikow, Boris

2015-01-01

BACKGROUND: There is little knowledge regarding the association between psychological factors and complex regional pain syndrome (CRPS) in children. Specifically, it is not known which factors precipitate CRPS and which result from the ongoing painful disease. OBJECTIVES: To examine symptoms of depression and anxiety as well as the experience of stressful life events in children with CRPS compared with children with chronic primary headaches and functional abdominal pain. METHODS: A retrospective chart study examined children with CRPS (n=37) who received intensive inpatient pain treatment between 2004 and 2010. They were compared with two control groups (chronic primary headaches and functional abdominal pain; each n=37), who also received intensive inpatient pain treatment. Control groups were matched with the CRPS group with regard to admission date, age and sex. Groups were compared on symptoms of depression and anxiety as well as stressful life events. RESULTS: Children with CRPS reported lower anxiety and depression scores compared with children with abdominal pain. A higher number of stressful life events before and after the onset of the pain condition was observed for children with CRPS. CONCLUSIONS: Children with CRPS are not particularly prone to symptoms of anxiety or depression. Importantly, children with CRPS experienced more stressful life events than children with chronic headaches or abdominal pain. Prospective long-term studies are needed to further explore the potential role of stressful life events in the etiology of CRPS. PMID:26035287
Recent life stress exposure is associated with poorer long-term memory, working memory, and self-reported memory.

Science.gov (United States)

Shields, Grant S; Doty, Dominique; Shields, Rebecca H; Gower, Garrett; Slavich, George M; Yonelinas, Andrew P

2017-11-01

Although substantial research has examined the effects of stress on cognition, much of this research has focused on acute stress (e.g. manipulated in the laboratory) or chronic stress (e.g. persistent interpersonal or financial difficulties). In contrast, the effects of recent life stress on cognition have been relatively understudied. To address this issue, we examined how recent life stress is associated with long-term, working memory, and self-reported memory in a sample of 142 healthy young adults who were assessed at two time points over a two-week period. Recent life stress was measured using the newly-developed Stress and Adversity Inventory for Daily Stress (Daily STRAIN), which assesses the frequency of relatively common stressful life events and difficulties over the preceding two weeks. To assess memory performance, participants completed both long-term and working memory tasks. Participants also provided self-reports of memory problems. As hypothesized, greater recent life stress exposure was associated with worse performance on measures of long-term and working memory, as well as more self-reported memory problems. These associations were largely robust while controlling for possible confounds, including participants' age, sex, and negative affect. The findings indicate that recent life stress exposure is broadly associated with worse memory. Future studies should thus consider assessing recent life stress as a potential predictor, moderator, or covariate of memory performance.
[The influence of meaning making following stressful life experiences on change of self-concept].

Science.gov (United States)

Horita, Ryo; Sugie, Masashi

2013-10-01

As interest in meaning making following stressful life experiences continues to grow, it is important to clarify the features and functions of the meaning- making process. We examined the influence of meaning making following stressful life experiences on change of self-concept. In two studies, university students selected their most stressful life experience and completed the Assimilation and Accommodation of Meaning Making Scale. In Study 1, 235 university students also completed questionnaires regarding post-traumatic growth and positive change of the sense of identity following their stressful life experience. The results of covariance structure analysis indicated that accommodation promoted a positive change of self-concept. In Study 2, 199 university students completed questionnaires regarding change of self-concept and emotion as a positive or negative change following stressful life experiences. The results of covariance structure analysis indicated that accommodation promoted a positive change, similar to the results of Study 1. In addition, accommodation also promoted negative change. However, assimilation did not promote positive change but did restrain negative change.
Stressful life events and psychological dysfunction in complex regional pain syndrome type I

NARCIS (Netherlands)

Geertzen, JHB; de Bruijn-Kofman, AT; de Bruijn, HP; van de Wiel, HBM; Dijkstra, PU

Objective: To determine to what extent stressful life events and psychological dysfunction play a role in the pathogenesis of Complex Regional Pain Syndrome type I (CRPS). Design: A comparative study between a CRPS group and a control group. Stressful life events and psychological dysfunction
Impact of medical intervention on stress and quality of life in patients with cancer

Directory of Open Access Journals (Sweden)

Vijay Prasad Barre

2015-01-01

Full Text Available Context: Many studies have explored stress and quality of life in (QOL patients with cancer, under several phases of disease and treatment. However, the impact of medical intervention on psychological parameters, such as stress and quality of life focusing on psychological intervention has been sparsely studied. Aims: The main aim of the study was to examine the impact of medical intervention on the level of stress and quality of life of patients with lung, breast, and head and neck cancers. Settings and Design: The study was carried out in hospital settings by following a one-group pre-test-post-test pre-experimental design. Statistical analysis used: The quantitative data were analysed by means of descriptive statistics, paired t-tests, Cohen′s d, and bar graphs accordingly. Results: The effect of medical intervention was medium in case of reduction of overall stress in participants. So far as the components are concerned, the effect was high in case of psychosomatic complaints, medium in case of fear and information deficit, and low in case of everyday life restrictions. The effect of medical intervention in respect of the quality of life was found to be high in case of symptom scale (pain and additional symptoms (constipation; medium in case of functional scale (emotional functioning, cognitive functioning and symptoms scale (nausea, vomiting. In additional symptoms scale the effect of medical intervention was found to be medium in dyspnoea and appetite loss. Conclusions: The findings revealed that though the medical intervention reduced stress and improved the quality of life, it was not instrumental in bringing down the stress to minimal level and enhancing the quality of life to optimum level. Therefore, the findings point to the need of inclusion of psychological intervention along with the medical intervention for minimizing stress and optimizing the quality of life of patients with cancer.
Stressful life events in countries of differing economic development: Nicaragua, Chile, and Spain.

Science.gov (United States)

Vazquez, José Juan; Panadero, Sonia; Rincón, Paulina Paz

2007-08-01

the aim was to describe a study involving 481 psychology students in the last courses of their degrees (M age = 21.9 yr., SD=4.2; 94 men and 386 women) from Nicaragua, Chile, and Spain. The study examined the potential risk of experiencing certain stressful life events, the number of stressors, and their characteristics. Also were analyzed the strength of their relation to social class and stressful life events experienced. Greater presence of stressful life events were reported among people from less developed countries, Chile and Nicaragua, and among people belonging to lower social class.
Damage assessment of low-cycle fatigue by crack growth prediction. Fatigue life under cyclic thermal stress

International Nuclear Information System (INIS)

Kamaya, Masayuki

2013-01-01

The number of cycles to failure of specimens in fatigue tests can be estimated by predicting crack growth. Under a cyclic thermal stress caused by fluctuation of fluid temperature, due to the stress gradient in the thickness direction, the estimated fatigue life differs from that estimated for mechanical fatigue tests. In this paper, the influence of crack growth under cyclic thermal loading on the fatigue life was investigated. First, the thermal stress was derived by superposing analytical solutions, and then, the stress intensity factor was obtained by the weight function method. It was shown that the thermal stress depended not on the rate of the fluid temperature change but on the rise time, and the magnitude of the stress was increased as the rise time was decreased. The stress intensity factor under the cyclic thermal stress was smaller than that under the uniform stress distribution. The change in the stress intensity factor with the crack depth was almost the same regardless of the rise time. The estimated fatigue life under the cyclic thermal loading could be 1.6 times longer than that under the uniform stress distribution. The critical size for the fatigue life determination was assumed to be 3 mm for fatigue test specimens of 10 mm diameter. By evaluating the critical size by structural integrity analyses, the fatigue life was increased and the effect of the critical size on the fatigue life was more pronounced for the cyclic thermal stress. (author)
New relation for critical exponents in the Ising model

International Nuclear Information System (INIS)

Pishtshev, A.

2007-01-01

The Ising model in a transverse field is considered at T=0. From the analysis of the power low behaviors of the energy gap and the order parameter as functions of the field a new relation between the respective critical exponents, β>=1/(8s 2 ), is derived. By using the Suzuki equivalence from this inequality a new relation for critical exponents in the Ising model, β>=1/(8ν 2 ), is obtained. A number of numerical examples for different cases illustrates the generality and validity of the relation. By applying this relation the estimation ν=(1/4) 1/3 ∼0.62996 for the 3D-Ising model is proposed

Stress in the City: Influence of Urban Social Stress and Violence on Pregnancy and Postpartum Quality of Life among Adolescent and Young Mothers.

Science.gov (United States)

Willie, Tiara C; Powell, Adeya; Kershaw, Trace

2016-02-01

Adolescent and young mothers transitioning from pregnancy to postpartum need to maintain an optimal quality of life. Stress and exposure to violence (e.g., intimate partner violence (IPV), nonpartner violence) are predictors of poor quality of life for adult women; however, these associations remain understudied among adolescent and young mothers in urban areas. Guided by the social ecological model, the current study created a latent variable, urban social stress, to examine the impact of the urban social environment (i.e., stressful life events, discrimination, family stress, and neighborhood problems) on the quality of life of adolescent and young mothers during both pregnancy and postpartum. The current study is a secondary data analysis of a prospective cohort study of 296 expectant young mothers recruited at obstetrics and gynecology clinics. Results from structural equation and multigroup models found that higher urban social stress predicted lower mental and physical quality of life during pregnancy, but these associations were significantly stronger for IPV-exposed and nonpartner violence-exposed mothers. In the postpartum period, higher urban social stress predicted lower mental and physical quality of life, but these associations were significantly stronger for IPV-unexposed and nonpartner violence-exposed mothers. Stress reduction programs need to help adolescent and young mothers in urban areas develop stress management skills specific to urban social stress. Pregnancy and parenting programs need to be tailored to the specific needs of young mothers in urban areas by becoming sensitive to the role of IPV and nonpartner violence in these young women's lives.
Critical exponents for the Reggeon quantum spin model

International Nuclear Information System (INIS)

Brower, R.C.; Furman, M.A.

1978-01-01

The Reggeon quantum spin (RQS) model on the transverse lattice in D dimensional impact parameter space has been conjectured to have the same critical behaviour as the Reggeon field theory (RFT). Thus from a high 'temperature' series of ten (D=2) and twenty (D=1) terms for the RQS model the authors extrapolate to the critical temperature T=Tsub(c) by Pade approximants to obtain the exponents eta=0.238 +- 0.008, z=1.16 +- 0.01, γ=1.271 +- 0.007 for D=2 and eta=0.317 +- 0.002, z=1.272 +- 0.007, γ=1.736 +- 0.001, lambda=0.57 +- 0.03 for D=1. These exponents naturally interpolate between the D=0 and D=4-epsilon results for RFT as expected on the basis of the universality conjecture. (Auth.)
Influence of the non-singular stress on the crack extension and fatigue life

International Nuclear Information System (INIS)

Cheng, C.Z.; Recho, N.; Niu, Z.R.

2012-01-01

Highlights: ► BEM is combined by characteristic analysis to calculate the singular stress field. ► A new method is proposed to evaluate the full stress field at crack tip region. ► Effect of non-singular stress on the propagation direction of the fatigue crack is analyzed. ► The influence of non-singular stress on the fatigue crack life is evaluated. - Abstract: The complete elasticity stress field at a crack tip region can be presented by the sum of the singular stress and several non-singular stress terms according to the Williams asymptotic expansion theory. The non-singular stress has a non-negligible influence on the prediction of the crack extension direction and crack growth rate under the fatigue loading. A novel method combining the boundary element method and the singularity characteristic analysis is proposed here to evaluate the complete stress field at a crack tip region. In this new method, any non-singular stress term in the Williams series expansion can be evaluated according to the computational accuracy requirement. Then, a modified Paris law is introduced to predict the crack propagation under the mixed-mode loading for exploring the influence of the non-singular stress on the fatigue life duration. By comparing with the existed experimental results, the predicted crack fatigue life when the non-singular stress is taken into consideration is more accurate than the predicted ones only considering the singular stress.
Monte Carlo-Based Tail Exponent Estimator

Czech Academy of Sciences Publication Activity Database

Baruník, Jozef; Vácha, Lukáš

2010-01-01

Roč. 2010, č. 6 (2010), s. 1-26 R&D Projects: GA ČR GA402/09/0965; GA ČR GD402/09/H045; GA ČR GP402/08/P207 Institutional research plan: CEZ:AV0Z10750506 Keywords : Hill estimator * α-stable distributions * tail exponent estimation Subject RIV: AH - Economics http://library.utia.cas.cz/separaty/2010/E/barunik-0342493.pdf
Stress on health-related quality of life in older adults: the protective nature of mindfulness.

Science.gov (United States)

de Frias, Cindy M; Whyne, Erum

2015-01-01

The current study examined whether the link between stress and health-related quality of life was buffered by protective factors, namely mindfulness, in a sample of middle-aged and older adults. In this cross-sectional study, 134 healthy, community-dwelling adults (ages 50-85 years) were recruited from Dallas, TX. The participants were screened for depressive symptoms and severity (using the Patient Health Questionnaire [PHQ-9]). All participants completed measures of self-reported health status (i.e. SF36v2: mental and physical health composites), life stress (using the Elders Life Stress Inventory [ELSI]), and trait mindfulness (i.e. Mindful Attention Awareness Scale). Hierarchical regressions (covarying for age, gender, and education) showed that life stress was inversely related to physical and mental health. Mindfulness was positively related to mental health. The negative effect of life stress on mental health was weakened for those individuals with higher levels of trait mindfulness. The results suggest that mindfulness is a powerful, adaptive strategy that may protect middle-aged and older adults from the well-known harmful effects of stress on mental health.
A new combined approach on Hurst exponent estimate and its applications in realized volatility

Science.gov (United States)

Luo, Yi; Huang, Yirong

2018-02-01

The purpose of this paper is to propose a new estimator of Hurst exponent based on the combined information of the conventional rescaled range methods. We demonstrate the superiority of the proposed estimator by Monte Carlo simulations, and the applications in estimating the Hurst exponent of daily volatility series in Chinese stock market. Moreover, we indicate the impact of the type of estimator and structural break on the estimating results of Hurst exponent.
Stress dependence of microstructures in experimentally deformed calcite

Science.gov (United States)

Platt, John P.; De Bresser, J. H. P.

2017-12-01

Optical measurements of microstructural features in experimentally deformed Carrara marble help define their dependence on stress. These features include dynamically recrystallized grain size (Dr), subgrain size (Sg), minimum bulge size (Lρ), and the maximum scale length for surface-energy driven grain-boundary migration (Lγ). Taken together with previously published data Dr defines a paleopiezometer over the range 15-291 MPa and temperature over the range 500-1000 °C, with a stress exponent of -1.09 (CI -1.27 to -0.95), showing no detectable dependence on temperature. Sg and Dr measured in the same samples are closely similar in size, suggesting that the new grains did not grow significantly after nucleation. Lρ and Lγ measured on each sample define a relationship to stress with an exponent of approximately -1.6, which helps define the boundary between a region of dominant strain-energy-driven grain-boundary migration at high stress, from a region of dominant surface-energy-driven grain-boundary migration at low stress.
Early-life stress impacts the developing hippocampus and primes seizure occurrence: cellular, molecular, and epigenetic mechanisms

Science.gov (United States)

Huang, Li-Tung

2014-01-01

Early-life stress includes prenatal, postnatal, and adolescence stress. Early-life stress can affect the development of the hypothalamic-pituitary-adrenal (HPA) axis, and cause cellular and molecular changes in the developing hippocampus that can result in neurobehavioral changes later in life. Epidemiological data implicate stress as a cause of seizures in both children and adults. Emerging evidence indicates that both prenatal and postnatal stress can prime the developing brain for seizures and an increase in epileptogenesis. This article reviews the cellular and molecular changes encountered during prenatal and postnatal stress, and assesses the possible link between these changes and increases in seizure occurrence and epileptogenesis in the developing hippocampus. In addititon, the priming effect of prenatal and postnatal stress for seizures and epileptogenesis is discussed. Finally, the roles of epigenetic modifications in hippocampus and HPA axis programming, early-life stress, and epilepsy are discussed. PMID:24574961
Lyapunov exponent of the random frequency oscillator: cumulant expansion approach

International Nuclear Information System (INIS)

Anteneodo, C; Vallejos, R O

2010-01-01

We consider a one-dimensional harmonic oscillator with a random frequency, focusing on both the standard and the generalized Lyapunov exponents, λ and λ* respectively. We discuss the numerical difficulties that arise in the numerical calculation of λ* in the case of strong intermittency. When the frequency corresponds to a Ornstein-Uhlenbeck process, we compute analytically λ* by using a cumulant expansion including up to the fourth order. Connections with the problem of finding an analytical estimate for the largest Lyapunov exponent of a many-body system with smooth interactions are discussed.
Attentional avoidance of fearful facial expressions following early life stress is associated with impaired social functioning.

Science.gov (United States)

Humphreys, Kathryn L; Kircanski, Katharina; Colich, Natalie L; Gotlib, Ian H

2016-10-01

Early life stress is associated with poorer social functioning. Attentional biases in response to threat-related cues, linked to both early experience and psychopathology, may explain this association. To date, however, no study has examined attentional biases to fearful facial expressions as a function of early life stress or examined these biases as a potential mediator of the relation between early life stress and social problems. In a sample of 154 children (ages 9-13 years) we examined the associations among interpersonal early life stressors (i.e., birth through age 6 years), attentional biases to emotional facial expressions using a dot-probe task, and social functioning on the Child Behavior Checklist. High levels of early life stress were associated with both greater levels of social problems and an attentional bias away from fearful facial expressions, even after accounting for stressors occurring in later childhood. No biases were found for happy or sad facial expressions as a function of early life stress. Finally, attentional biases to fearful faces mediated the association between early life stress and social problems. Attentional avoidance of fearful facial expressions, evidenced by a bias away from these stimuli, may be a developmental response to early adversity and link the experience of early life stress to poorer social functioning. © 2016 Association for Child and Adolescent Mental Health.
On some properties of the discrete Lyapunov exponent

International Nuclear Information System (INIS)

Amigo, Jose M.; Kocarev, Ljupco; Szczepanski, Janusz

2008-01-01

One of the possible by-products of discrete chaos is the application of its tools, in particular of the discrete Lyapunov exponent, to cryptography. In this Letter we explore this question in a very general setting
Depression symptoms and stressful life events among college students in Puerto Rico.

Science.gov (United States)

Reyes-Rodríguez, Mae Lynn; Rivera-Medina, Carmen L; Cámara-Fuentes, Luis; Suárez-Torres, Alba; Bernal, Guillermo

2013-03-05

The transition from adolescence to adulthood is associated with stressful adaptation experiences that may increase symptoms of depression. We explored the prevalence and sex differences of depressive symptoms and suicidal ideation in freshmen Latino college students in Puerto Rico, and identified stressful life events that could contribute to symptoms of depression. Two thousand one hundred sixty-three freshmen college students from the University of Puerto Rico (UPR) public education system were assessed for depression symptoms using the Beck Depression Inventory (BDI) and stressful life events using open questions. Nine percent of the sample reported depression symptoms at a moderate or severe level (BDI>20). Chi square analyses revealed a significantly higher prevalence for three of the stressful life events in females than males: relocation (10.2% females vs. 7.3% males; X(2) (1)=4.13, p=.042), break-up of a significant relationship (25.3% females vs. 17.8% males; X(2) (1)=13.76, pstressful life events are associated with an increased prevalence of depression symptoms. Early detection of depression and tailored prevention programs should be developed to improve both mental health and academic performance among the college population. Published by Elsevier B.V.
Life Event Stress and Binge Eating Among Adolescents: The Roles of Early Maladaptive Schemas and Impulsivity.

Science.gov (United States)

Zhu, Hong; Luo, Xingwei; Cai, Taisheng; He, Jinbo; Lu, Yao; Wu, Siyao

2016-10-01

This study examined the relationships between life event stress, early maladaptive schemas, impulsivity and binge eating among adolescents and investigated the effects of early maladaptive schemas and impulsivity on the relationship between life event stress and binge eating. Specifically, we examined a moderated mediation model in which early maladaptive schemas mediated this relationship and impulsivity moderated the mediation effect. Life event stress, early maladaptive schemas, impulsivity and binge eating were investigated in a sample of 2172 seventh-, eighth- and tenth-grade middle and high school students (mean age = 14.55 years, standard deviation = 1.29). The results indicated that adolescents with greater life event stress, more early maladaptive schemas and higher levels of impulsivity displayed more severe binge eating. In addition, early maladaptive schemas mediated the relationship between life event stress and binge eating, while impulsivity moderated this relationship. Furthermore, impulsivity also moderated the mediation effect of early maladaptive schemas; as impulsivity levels increased, the strength of the association between life event stress and early maladaptive schemas increased. This study illustrates the importance of understanding individual differences and their effects on the relationship between life event stress and binge eating. Copyright © 2015 John Wiley & Sons, Ltd. Copyright © 2015 John Wiley & Sons, Ltd.
Design of PH-based accelerated life testing plans under multiple-stress-type

International Nuclear Information System (INIS)

Elsayed, E.A.; Zhang Hao

2007-01-01

Accelerated life testing (ALT) is used to obtain failure time data quickly under high stress levels in order to predict product life performance under design stress conditions. Most of the previous work on designing ALT plans is focused on the application of a single stress. However, as components or products become more reliable due to technological advances, it becomes more difficult to obtain significant amount of failure data within reasonable amount of time using single stress only. Multiple-stress-type ALTs have been employed as a means of overcoming such difficulties. In this paper, we design optimum multiple-stress-type ALT plans based on the proportional hazards model. The optimum combinations of stresses and their levels are determined such that the variance of the reliability estimate of the product over a specified period of time is minimized. The use of the model is illustrated using numerical example, and sensitivity analysis shows that the resultant optimum ALT plan is robust to the deviation in model parameters
Damage assessment of low-cycle fatigue by crack growth prediction. Fatigue life under cyclic thermal stress

International Nuclear Information System (INIS)

Kamaya, Masayuki

2013-01-01

The number of cycles to failure of specimens in fatigue tests can be estimated by predicting crack growth. Under a cyclic thermal stress caused by fluctuation of fluid temperature, due to the stress gradient in the thickness direction, the estimated fatigue life differs from that estimated for mechanical fatigue tests. In this paper, the influence of crack growth under cyclic thermal loading on the fatigue life was investigated. First, the thermal stress was derived by superposing analytical solutions, and then, the stress intensity factor was obtained by the weight function method. It was shown that the thermal stress depended not on the rate of the fluid temperature change but on the rise time, and the magnitude of the stress was increased as the rise time was decreased. The stress intensity factor under the cyclic thermal stress was smaller than that under the uniform stress distribution. The change in the stress intensity factor with the crack depth did not depend on the heat transfer coefficient and only slightly depended on the rise time. The estimated fatigue life under the cyclic thermal loading could be 1.6 times longer than that under the uniform stress distribution. The critical size for the fatigue life determination was assumed to be 3 mm for fatigue test specimens of 10 mm diameter. By evaluating the critical size by structural integrity analyses, the fatigue life was increased and the effect of the critical size on the fatigue life was more pronounced for the cyclic thermal stress. (author)
How Accumulated Real Life Stress Experience and Cognitive Speed Interact on Decision-Making Processes

Directory of Open Access Journals (Sweden)

Eva Friedel

2017-06-01

Full Text Available Rationale: Advances in neurocomputational modeling suggest that valuation systems for goal-directed (deliberative on one side, and habitual (automatic decision-making on the other side may rely on distinct computational strategies for reinforcement learning, namely model-free vs. model-based learning. As a key theoretical difference, the model-based system strongly demands cognitive functions to plan actions prospectively based on an internal cognitive model of the environment, whereas valuation in the model-free system relies on rather simple learning rules from operant conditioning to retrospectively associate actions with their outcomes and is thus cognitively less demanding. Acute stress reactivity is known to impair model-based but not model-free choice behavior, with higher working memory capacity protecting the model-based system from acute stress. However, it is not clear which impact accumulated real life stress has on model-free and model-based decision systems and how this influence interacts with cognitive abilities.Methods: We used a sequential decision-making task distinguishing relative contributions of both learning strategies to choice behavior, the Social Readjustment Rating Scale questionnaire to assess accumulated real life stress, and the Digit Symbol Substitution Test to test cognitive speed in 95 healthy subjects.Results: Individuals reporting high stress exposure who had low cognitive speed showed reduced model-based but increased model-free behavioral control. In contrast, subjects exposed to accumulated real life stress with high cognitive speed displayed increased model-based performance but reduced model-free control.Conclusion: These findings suggest that accumulated real life stress exposure can enhance reliance on cognitive speed for model-based computations, which may ultimately protect the model-based system from the detrimental influences of accumulated real life stress. The combination of accumulated real life
How Accumulated Real Life Stress Experience and Cognitive Speed Interact on Decision-Making Processes.

Science.gov (United States)

Friedel, Eva; Sebold, Miriam; Kuitunen-Paul, Sören; Nebe, Stephan; Veer, Ilya M; Zimmermann, Ulrich S; Schlagenhauf, Florian; Smolka, Michael N; Rapp, Michael; Walter, Henrik; Heinz, Andreas

2017-01-01

Rationale: Advances in neurocomputational modeling suggest that valuation systems for goal-directed (deliberative) on one side, and habitual (automatic) decision-making on the other side may rely on distinct computational strategies for reinforcement learning, namely model-free vs. model-based learning. As a key theoretical difference, the model-based system strongly demands cognitive functions to plan actions prospectively based on an internal cognitive model of the environment, whereas valuation in the model-free system relies on rather simple learning rules from operant conditioning to retrospectively associate actions with their outcomes and is thus cognitively less demanding. Acute stress reactivity is known to impair model-based but not model-free choice behavior, with higher working memory capacity protecting the model-based system from acute stress. However, it is not clear which impact accumulated real life stress has on model-free and model-based decision systems and how this influence interacts with cognitive abilities. Methods: We used a sequential decision-making task distinguishing relative contributions of both learning strategies to choice behavior, the Social Readjustment Rating Scale questionnaire to assess accumulated real life stress, and the Digit Symbol Substitution Test to test cognitive speed in 95 healthy subjects. Results: Individuals reporting high stress exposure who had low cognitive speed showed reduced model-based but increased model-free behavioral control. In contrast, subjects exposed to accumulated real life stress with high cognitive speed displayed increased model-based performance but reduced model-free control. Conclusion: These findings suggest that accumulated real life stress exposure can enhance reliance on cognitive speed for model-based computations, which may ultimately protect the model-based system from the detrimental influences of accumulated real life stress. The combination of accumulated real life stress exposure
Finite-time braiding exponents

Science.gov (United States)

Budišić, Marko; Thiffeault, Jean-Luc

2015-08-01

Topological entropy of a dynamical system is an upper bound for the sum of positive Lyapunov exponents; in practice, it is strongly indicative of the presence of mixing in a subset of the domain. Topological entropy can be computed by partition methods, by estimating the maximal growth rate of material lines or other material elements, or by counting the unstable periodic orbits of the flow. All these methods require detailed knowledge of the velocity field that is not always available, for example, when ocean flows are measured using a small number of floating sensors. We propose an alternative calculation, applicable to two-dimensional flows, that uses only a sparse set of flow trajectories as its input. To represent the sparse set of trajectories, we use braids, algebraic objects that record how trajectories exchange positions with respect to a projection axis. Material curves advected by the flow are represented as simplified loop coordinates. The exponential rate at which a braid stretches loops over a finite time interval is the Finite-Time Braiding Exponent (FTBE). We study FTBEs through numerical simulations of the Aref Blinking Vortex flow, as a representative of a general class of flows having a single invariant component with positive topological entropy. The FTBEs approach the value of the topological entropy from below as the length and number of trajectories is increased; we conjecture that this result holds for a general class of ergodic, mixing systems. Furthermore, FTBEs are computed robustly with respect to the numerical time step, details of braid representation, and choice of initial conditions. We find that, in the class of systems we describe, trajectories can be re-used to form different braids, which greatly reduces the amount of data needed to assess the complexity of the flow.
Non-suicidal self-injury and life stress: A systematic meta-analysis and theoretical elaboration

Science.gov (United States)

Liu, Richard T.; Cheek, Shayna M.; Nestor, Bridget A.

2016-01-01

Recent years have seen a considerable growth of interest in the study of life stress and non-suicidal self-injury (NSSI). The current article presents a systematic review of the empirical literature on this association. In addition to providing a comprehensive meta-analysis, the current article includes a qualitative review of the findings for which there were too few cases (i.e., life stress and NSSI was found (pooled OR = 1.81 [95% CI = 1.49–2.21]). After an adjustment was made for publication bias, the estimated effect size was smaller but still significant (pooled OR = 1.33 [95% CI = 1.08–1.63]). This relation was moderated by sample type, NSSI measure type, and length of period covered by the NSSI measure. The empirical literature is characterized by several methodological limitations, particularly the frequent use of cross-sectional analyses involving temporal overlap between assessments of life stress and NSSI, leaving unclear the precise nature of the relation between these two phenomena (e.g., whether life stress may be a cause, concomitant, or consequence of NSSI). Theoretically informed research utilizing multi-wave designs, assessing life stress and NSSI over relatively brief intervals, and featuring interview-based assessments of these constructs holds promise for advancing our understanding of their relation. The current review concludes with a theoretical elaboration of the association between NSSI and life stress, with the aim of providing a conceptual framework to guide future study in this area. PMID:27267345
Midlife work-related stress is associated with late-life cognition.

Science.gov (United States)

Sindi, Shireen; Kåreholt, Ingemar; Solomon, Alina; Hooshmand, Babak; Soininen, Hilkka; Kivipelto, Miia

2017-09-01

To investigate the associations between midlife work-related stress and late-life cognition in individuals without dementia from the general population. The Cardiovascular Risk Factors, Aging and Dementia (CAIDE) study population (n = 2000) was randomly selected from independent Finnish population-based surveys (baseline mean age 50 years). Participants underwent two re-examinations in late life (mean age 71 and 78 years, respectively). 1511 subjects participated in at least one re-examination (mean total follow-up 25 years). Work-related stress was measured using two questions on work demands administered in midlife. Multiple cognitive domains were assessed. Analyses were adjusted for several potential confounders. Higher levels of midlife work-related stress were associated with poorer performance on global cognition [β-coefficient, -0.02; 95% confidence interval (CI), -0.05 to -0.00], and processing speed [β -0.03, CI -0.05 to -0.01]. Results remained significant after adjusting for potential confounders. Work-related stress was not significantly associated with episodic memory, executive functioning, verbal fluency or manual dexterity. This study shows that global cognition and processing speed may be particularly susceptible to the effects of midlife work-related stress.

Mental Health and Stressful Life Events in Coronary Heart Disease Patients and Non- Patients

Directory of Open Access Journals (Sweden)

Samaneh Nateghian

2008-07-01

Full Text Available "nObjective: "n The main goal of this study is to compare stressful life events and mental health in coronary heart disease (CHD patients and non-patients. "nMethod: In this research, 120 participants (n=68 male, n= 52 female were divided into two groups of patients (n=60 and non-patients (n=60. They were selected from Vali Asr Hospital of Meshginshahr (Iran and completed the General Health Questionnaire (GHQ and Stressful Life Events Inventory . "nResults: Data was analyzed using independent t-test. The results showed significant differences between CHD patients and non-patients in mental health and stressful life events. CHD patients showed high rates of physical symptoms and anxiety of GHQ . "nConclusion: CHD patients reported more stressful life events. Therefore, it can be inferred that psychological factors are important in coronary heart disease.
Stressful life events preceding the onset of depression in Asian patients with major depressive disorder.

Science.gov (United States)

Park, Subin; Hatim, Ahmad; Si, Tian-Mei; Jeon, Hong Jin; Srisurapanont, Manit; Bautista, Dianne; Liu, Shen-ing; Chua, Hong Choon; Hong, Jin Pyo

2015-12-01

Previous studies have identified the significant role of stressful life events in the onset of depressive episodes. However, there is a paucity of cross-national studies on stressful life events that precede depression. We aimed to compare types of stressful life events associated with the onset of depressive episodes in patients with major depressive disorder (MDD) in five Asian countries. A total of 507 outpatients with MDD were recruited in China (n = 114), South Korea (n = 101), Malaysia (n = 90), Thailand (n = 103) and Taiwan (n = 99). All patients were assessed with the Mini-International Neuropsychiatric Interview and the List of Threatening Experiences. The prevalence of each type of stressful life events was calculated and compared between each country. The type of stressful life event that preceded the onset of a depressive episode differed between patients in China and Taiwan and those in South Korea, Malaysia and Thailand. Patients in China and Taiwan were less likely to report interpersonal relationship problems and occupational/financial problems than patients in South Korea, Malaysia and Thailand. Understanding the nature and basis of culturally determined susceptibilities to specific stressful life events is critical for establishing a policy of depression prevention and providing effective counseling services for depressed patients. © The Author(s) 2015.
Race/ethnicity moderates the relationship between chronic life stress and quality of life in type 2 diabetes.

Science.gov (United States)

Shallcross, Amanda J; Ojie, Mary-Jane; Chaplin, William; Levy, Natalie; Odedosu, Taiye; Ogedegbe, Gbenga; Spruill, Tanya M

2015-04-01

To determine whether chronic life stress is differentially associated with quality of life (QoL) for Blacks vs. Hispanics with type 2 diabetes. We assessed self-reported chronic stress and QoL in 125 patients with type 2 diabetes who self-identified as either non-Hispanic Black or Hispanic. Separate cross-sectional two-way interaction models (stress × race/ethnicity) with physical and mental health as outcomes were examined. The two-way interaction predicted mental (b=3.12, P=.04) but not physical health. Simple slopes analyses indicated that under conditions of high stress, Blacks (b=-4.4, Pstress × race/ethnicity × social support) with physical and mental health as outcomes. Results indicated the three-way interaction predicted mental (b=.62, P=.01) but not physical health. Simple slopes analyses indicated that under conditions of high stress, high levels of social support improved mental health for Hispanics (b=1.2, Pstress. Social support buffers effects of stress on mental health in Hispanics but not Blacks, which suggests differences in the use and/or quality of social support between Hispanics and Blacks. Longitudinal investigations that examine race/ethnicity, stress, social support, and QoL should help clarify the processes that underlie these observed relations. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.
Lojasiewicz exponents and Newton polyhedra

International Nuclear Information System (INIS)

Pham Tien Son

2006-07-01

In this paper we obtain the exact value of the Lojasiewicz exponent at the origin of analytic map germs on K n (K = R or C under the Newton non-degeneracy condition, using information from their Newton polyhedra. We also give some conclusions on Newton non-degenerate analytic map germs. As a consequence, we obtain a link between Newton non-degenerate ideals and their integral closures, thus leading to a simple proof of a result of Saia. Similar results are also considered to polynomial maps which are Newton non-degenerate at infinity. (author)
The Effect of Stress Management Model in Quality of Life in Breast Cancer Women.

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Khodabakhshi Koolaee, Anahita; Falsafinejad, Mohammad Reza; Akbari, Mohammd Esmaeil

2015-08-01

Breast cancer associates with severs severe distress and stress. Since Because of that, the stress management program can train necessary skills to cope with stress; therefore, the current study investigates the effectiveness of stress management on enhancement of quality of life. The aim of the current study is to examine the effectiveness of stress management model in quality of life for breast cancer patients. This research is a quasi-experimental study with pre and post-tests. The 21 subjects were selected from cancer institute of Imam Khomeini in Tehran in 2014. The participants were allocated to two matched groups based on their pre-test scores. They were assigned randomly to the control and experimental groups. Stress management was conducted with the experimental group during 10 sessions. Then the questionnaire was administered at post-test. Statistical analysis was conducted by using the independent t-test and analysis of variance. The research instrument was the core quality of life questionnaire QLQ-C30. The results of the independent t-test showed that there is a significant difference between the pretest and post-test scores in the experimental group (P stress management can change the irrational and distortion thoughts. So, it enhances the quality of life in breast cancer patients.
Stressful Life Events and Irrational Beliefs as Predictors of ...

African Journals Online (AJOL)

Stressful Life Events and Irrational Beliefs as Predictors of Psychological Wellbeing ... characterized with negative indicators, such as, anxiety, depression. Does similar relationship is evident referring to positive indicators of Psychological ...
Adaptation of the Recent Life Changes Questionnaire (RLCQ) to measure stressful life events in adults residing in an urban megapolis in Pakistan.

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Artani, Azmina; Bhamani, Shireen Shehzad; Azam, Iqbal; AbdulSultan, Moiz; Khoja, Adeel; Kamal, Ayeesha K

2017-05-05

Contextually relevant stressful life events are integral to the quantification of stress. None such measures have been adapted for the Pakistani population. The RLCQ developed by Richard Rahe measures stress of an individual through recording the experience of life changing events. We used qualitative methodology in order to identify contextually relevant stressors in an open ended format, using serial in-depth interviews until thematic saturation of reported stressful life events was achieved. In our next phase of adaptation, our objective was to scale each item on the questionnaire, so as to weigh each of these identified events, in terms of severity of stress. This scaling exercise was performed on 200 random participants residing in the four communities of Karachi namely Kharadar, Dhorajee, Gulshan and Garden. For analysis of the scaled tool, exploratory factor analysis was used to inform structuring. Finally, to complete the process of adaption, content and face validity exercises were performed. Content validity by subject expert review and face validity was performed by translation and back translation of the adapted RLCQ. This yielded our final adapted tool. Stressful life events emerging from the qualitative phase of the study reflect daily life stressors arising from the unstable socio-political environment. Some such events were public harassment, robbery/theft, missed life opportunities due to nepotism, extortion and threats, being a victim of state sponsored brutality, lack of electricity, water, sanitation, fuel, destruction due to natural disasters and direct or media based exposure to suicide bombing in the city. Personal or societal based relevant stressors included male child preference, having an unmarried middle aged daughter, lack of empowerment and respect reported by females. The finally adapted RLCQ incorporated "Environmental Stress" as a new category. The processes of qualitative methodology, in depth interview, community based scaling and
Critical exponents predicted by grouping of Feynman diagrams in φ4 model

International Nuclear Information System (INIS)

Kaupuzs, J.

2001-01-01

Different perturbation theory treatments of the Ginzburg-Landau phase transition model are discussed. This includes a criticism of the perturbative renormalization group (RG) approach and a proposal of a novel method providing critical exponents consistent with the known exact solutions in two dimensions. The usual perturbation theory is reorganized by appropriate grouping of Feynman diagrams of φ 4 model with O(n) symmetry. As a result, equations for calculation of the two-point correlation function are obtained which allow to predict possible exact values of critical exponents in two and three dimensions by proving relevant scaling properties of the asymptotic solution at (and near) the criticality. The new values of critical exponents are discussed and compared to the results of numerical simulations and experiments. (orig.)
Nonlinear Heart Rate Variability features for real-life stress detection. Case study: students under stress due to university examination.

Science.gov (United States)

Melillo, Paolo; Bracale, Marcello; Pecchia, Leandro

2011-11-07

This study investigates the variations of Heart Rate Variability (HRV) due to a real-life stressor and proposes a classifier based on nonlinear features of HRV for automatic stress detection. 42 students volunteered to participate to the study about HRV and stress. For each student, two recordings were performed: one during an on-going university examination, assumed as a real-life stressor, and one after holidays. Nonlinear analysis of HRV was performed by using Poincaré Plot, Approximate Entropy, Correlation dimension, Detrended Fluctuation Analysis, Recurrence Plot. For statistical comparison, we adopted the Wilcoxon Signed Rank test and for development of a classifier we adopted the Linear Discriminant Analysis (LDA). Almost all HRV features measuring heart rate complexity were significantly decreased in the stress session. LDA generated a simple classifier based on the two Poincaré Plot parameters and Approximate Entropy, which enables stress detection with a total classification accuracy, a sensitivity and a specificity rate of 90%, 86%, and 95% respectively. The results of the current study suggest that nonlinear HRV analysis using short term ECG recording could be effective in automatically detecting real-life stress condition, such as a university examination.
Inter-relationship between scaling exponents for describing self-similar river networks

Science.gov (United States)

Yang, Soohyun; Paik, Kyungrock

2015-04-01

Natural river networks show well-known self-similar characteristics. Such characteristics are represented by various power-law relationships, e.g., between upstream length and drainage area (exponent h) (Hack, 1957), and in the exceedance probability distribution of upstream area (exponent É) (Rodriguez-Iturbe et al., 1992). It is empirically revealed that these power-law exponents are within narrow ranges. Power-law is also found in the relationship between drainage density (the total stream length divided by the total basin area) and specified source area (the minimum drainage area to form a stream head) (exponent η) (Moussa and Bocquillon, 1996). Considering that above three scaling relationships all refer to fundamental measures of 'length' and 'area' of a given drainage basin, it is natural to hypothesize plausible inter-relationship between these three scaling exponents. Indeed, Rigon et al. (1996) demonstrated the relationship between É and h. In this study, we expand this to a more general É-η-h relationship. We approach É-η relationship in an analytical manner while η-h relationship is demonstrated for six study basins in Korea. Detailed analysis and implications will be presented. References Hack, J. T. (1957). Studies of longitudinal river profiles in Virginia and Maryland. US, Geological Survey Professional Paper, 294. Moussa, R., & Bocquillon, C. (1996). Fractal analyses of tree-like channel networks from digital elevation model data. Journal of Hydrology, 187(1), 157-172. Rigon, R., Rodriguez-Iturbe, I., Maritan, A., Giacometti. A., Tarboton, D. G., & Rinaldo, A. (1996). On Hack's Law. Water Resources Research, 32(11), 3367-3374. Rodríguez-Iturbe, I., Ijjasz-Vasquez, E. J., Bras, R. L., & Tarboton, D. G. (1992). Power law distributions of discharge mass and energy in river basins. Water Resources Research, 28(4), 1089-1093.
Stressful life events and alcohol use among university students in ...

African Journals Online (AJOL)

In this study, the association between stressful life events and alcohol use among young adults pursuing university education in a university in Botswana was studied. A total of 312 young adults participated in the study (55.4% females, mean age = 21.58 (SD =1.87)). Student Stress Scale adapted from Holmes and Rahe's ...
Life event stress in duodenal ulcer compared with functional dyspepsia: A case-control study

OpenAIRE

Abdel Hafeiz Hassan; Al Quorain Abdulaziz; Karim Ahmed; Al-Mangoor Shuaa

1997-01-01

This is a prospective study of life event stress in 80 duodenal ulcer patients compared with 80 patients with functional dyspepsia and 80 healthy controls; matched for age, sex and marital status. A semi structured psychiatric interview was used in the psychiatric assessment of the dyspeptic patients and controls. A modified version of Life Events Scale by Tennant and Andrews was used in the assessment of life event stress. More dyspeptic patients reported life events than the controls, but, ...
Study on effect of mean stress on fatigue life prediction of thin film structure

Energy Technology Data Exchange (ETDEWEB)

Shin, Myung Soo [Ahtti Co., Seongnam (Korea, Republic of); Park, Jun Hyu [Tongmyong University, Busan (Korea, Republic of); Kim, Jung Yup [Korea Institute of Machinery and Materials, Daejeon (Korea, Republic of)

2016-04-15

This paper describes the effect of mean stress on fatigue life prediction of structure made with thin film. It is well known that the mean stress influences fatigue life prediction of mechanical structure. We investigated a reasonable method for considering mean stress when fatigue strength assessment of micro structure of thin film should be performed. Fatigue tests of smooth specimen of beryllium-copper (BeCu) thin film were performed in ambient air at R = 0.1 with 5 Hz. A micro probe was designed and made with BeCu thin film by the precision press process. Fatigue tests of micro structure were performed with 5 Hz frequency, in ambient air to verify the fatigue life predicted by computer simulation through FE analysis. The fatigue life predicted by the Sa -N curve modified by Goodman method with principal stress through FE analysis shows a more reasonable result than other methods.
Study on effect of mean stress on fatigue life prediction of thin film structure

International Nuclear Information System (INIS)

Shin, Myung Soo; Park, Jun Hyu; Kim, Jung Yup

2016-01-01

This paper describes the effect of mean stress on fatigue life prediction of structure made with thin film. It is well known that the mean stress influences fatigue life prediction of mechanical structure. We investigated a reasonable method for considering mean stress when fatigue strength assessment of micro structure of thin film should be performed. Fatigue tests of smooth specimen of beryllium-copper (BeCu) thin film were performed in ambient air at R = 0.1 with 5 Hz. A micro probe was designed and made with BeCu thin film by the precision press process. Fatigue tests of micro structure were performed with 5 Hz frequency, in ambient air to verify the fatigue life predicted by computer simulation through FE analysis. The fatigue life predicted by the Sa -N curve modified by Goodman method with principal stress through FE analysis shows a more reasonable result than other methods
On identifying relationships between the flood scaling exponent and basin attributes.

Science.gov (United States)

Medhi, Hemanta; Tripathi, Shivam

2015-07-01

Floods are known to exhibit self-similarity and follow scaling laws that form the basis of regional flood frequency analysis. However, the relationship between basin attributes and the scaling behavior of floods is still not fully understood. Identifying these relationships is essential for drawing connections between hydrological processes in a basin and the flood response of the basin. The existing studies mostly rely on simulation models to draw these connections. This paper proposes a new methodology that draws connections between basin attributes and the flood scaling exponents by using observed data. In the proposed methodology, region-of-influence approach is used to delineate homogeneous regions for each gaging station. Ordinary least squares regression is then applied to estimate flood scaling exponents for each homogeneous region, and finally stepwise regression is used to identify basin attributes that affect flood scaling exponents. The effectiveness of the proposed methodology is tested by applying it to data from river basins in the United States. The results suggest that flood scaling exponent is small for regions having (i) large abstractions from precipitation in the form of large soil moisture storages and high evapotranspiration losses, and (ii) large fractions of overland flow compared to base flow, i.e., regions having fast-responding basins. Analysis of simple scaling and multiscaling of floods showed evidence of simple scaling for regions in which the snowfall dominates the total precipitation.
LIFE EVENTS WITH STRESSFUL EFFECT ON PATIENTS WITH SCHIZOPHRENIA ACCORDING TO THE SEX AND AGE.

Directory of Open Access Journals (Sweden)

Lilia Nikolova

2012-08-01

Full Text Available According to the literature life events with stressful effect are significant both for initiation and progress of the schizophrenia. Having this in mind we set our aim to be investigating the relationship between life events (considered as stressful, sex and age trough questioning 50 patients with paranoid schizophrenia. The results of our study showed presence of correlation between some of the studied life events, assessed as stressful. The analysis of the data revealed that both sex and age are influencing the assessment of the significance of the life events and “increases” their importance both for women and men.
Stochastic model of Zipf's law and the universality of the power-law exponent.

Science.gov (United States)

Yamamoto, Ken

2014-04-01

We propose a stochastic model of Zipf's law, namely a power-law relation between rank and size, and clarify as to why a specific value of its power-law exponent is quite universal. We focus on the successive total of a multiplicative stochastic process. By employing properties of a well-known stochastic process, we concisely show that the successive total follows a stationary power-law distribution, which is directly related to Zipf's law. The formula of the power-law exponent is also derived. Finally, we conclude that the universality of the rank-size exponent is brought about by symmetry between an increase and a decrease in the random growth rate.
Perceived stress and quality of life of pharmacy students in University of Ghana.

Science.gov (United States)

Opoku-Acheampong, Adomah; Kretchy, Irene A; Acheampong, Franklin; Afrane, Barima A; Ashong, Sharon; Tamakloe, Bernice; Nyarko, Alexander K

2017-03-02

Stress among pharmacy students could greatly affect their learning activities and general well-being. It is therefore necessary to investigate how stress relates with the quality of life of students to maintain and/or improve their personal satisfaction and academic performance. A school-based longitudinal study was used to investigate the relationship between stress and quality of life of undergraduate pharmacy students. The 10-item perceived stress scale and the shorter version of the WHO quality of life scale were administered to the same participants at two time points i.e. Time 1 (4 weeks into the semester) and Time 2 (8 weeks afterwards). The correlations and differences between the study variables were tested using the Pearson's coefficient and independent sample t test. The mean stress scores were higher at Time 2 compared to Time 1 for the first and second years. However, there was no significant difference in stress for different year groups-Time 1 [F (3) = 0.410; p = 0.746] and Time 2 [F(3) = 0.909; p = 0.439]. Female students had higher stress scores at Time 2 compared to male students. The main stressors identified in the study were; large volume of material to be studied (88.2%), laboratory report writing (78.2%), constant pressure to maintain good grades (66.4%) and the lack of leisure time (46.4%). Even though most students employed positive stress management strategies such as time management (68.2%), other students resorted to emotional eating (9.1%) and alcohol/substance use (1.8%). At Time 2, perceived stress scores were significantly negatively correlated with social relationship (r = -0.40, p ≤ 0.0001), environmental health (r = -0.37, p ≤ 0.0001), physical health (r = -0.49, p ≤ 0.0001) and psychological health (r = -0.51, p ≤ 0.0001). The study reported significant correlations between stress and various domains of quality of life of undergraduate pharmacy students. It is thus necessary to institute some
Fermat's Last Theorem for Factional and Irrational Exponents

Science.gov (United States)

Morgan, Frank

2010-01-01

Fermat's Last Theorem says that for integers n greater than 2, there are no solutions to x[superscript n] + y[superscript n] = z[superscript n] among positive integers. What about rational exponents? Irrational n? Negative n? See what an undergraduate senior seminar discovered.
Effect of the combined stress on the life of components under thermal cycling conditions

International Nuclear Information System (INIS)

Zuchowski, R.; Zietkowski, L.

1987-01-01

The life of structural components subjected to temperature changes is affected, among other factors, by the nature of the stress field. If life prediction for axially stressed components can be accomplished with a number of well established techniques, the behaviour under a complex state of stress and varying temperature conditions still is the object of intensive research. The present study was aimed at assessing the influence of the stress field upon the life of specimens made of chromium-nickel H23N18 steel under thermal cycling conditions. The designation of steel is in accordance with Polish Standards. The experiments were made on thin-walled tubular specimens loaded with various combinations of a static axial force and a static torque. (orig./GL)

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

Science.gov (United States)

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

CERN Document Server

Pikovsky, Arkady

2016-01-01

Lyapunov exponents lie at the heart of chaos theory, and are widely used in studies of complex dynamics. Utilising a pragmatic, physical approach, this self-contained book provides a comprehensive description of the concept. Beginning with the basic properties and numerical methods, it then guides readers through to the most recent advances in applications to complex systems. Practical algorithms are thoroughly reviewed and their performance is discussed, while a broad set of examples illustrate the wide range of potential applications. The description of various numerical and analytical techniques for the computation of Lyapunov exponents offers an extensive array of tools for the characterization of phenomena such as synchronization, weak and global chaos in low and high-dimensional set-ups, and localization. This text equips readers with all the investigative expertise needed to fully explore the dynamical properties of complex systems, making it ideal for both graduate students and experienced researchers...
On generalized scaling laws with continuously varying exponents

International Nuclear Information System (INIS)

Sittler, Lionel; Hinrichsen, Haye

2002-01-01

Many physical systems share the property of scale invariance. Most of them show ordinary power-law scaling, where quantities can be expressed as a leading power law times a scaling function which depends on scaling-invariant ratios of the parameters. However, some systems do not obey power-law scaling, instead there is numerical evidence for a logarithmic scaling form, in which the scaling function depends on ratios of the logarithms of the parameters. Based on previous ideas by Tang we propose that this type of logarithmic scaling can be explained by a concept of local scaling invariance with continuously varying exponents. The functional dependence of the exponents is constrained by a homomorphism which can be expressed as a set of partial differential equations. Solving these equations we obtain logarithmic scaling as a special case. The other solutions lead to scaling forms where logarithmic and power-law scaling are mixed
Improvement in surface fatigue life of hardened gears by high-intensity shot peening

Science.gov (United States)

Townsend, Dennis P.

1992-04-01

Two groups of carburized, hardened, and ground spur gears that were manufactured from the same heat vacuum induction melted vacuum arc melted (VIM VAR) AISI 9310 steel were endurance tested for surface fatigue. Both groups were manufactured with a standard ground 16 rms surface finish. One group was subjected to a shot peening (SP) intensity of 7 to 9A, and the second group was subjected to a SP intensity of 15 to 17A. All gears were honed after SP to a surface finish of 16 rms. The gear pitch diameter was 8.89 cm. Test conditions were a maximum Hertz stress of 1.71 GPa, a gear temperature of 350 K, and a speed of 10000 rpm. The lubricant used for the tests was a synthetic paraffinic oil with an additive package. The following results were obtained: The 10 pct. surface fatigue (pitting) life of the high intensity (15 to 17A) SPed gears was 2.15 times that of the medium intensity (7 to 9A) SPed gears, the same as that calculated from measured residual stress at a depth of 127 microns. The measured residual stress for the high intensity SPed gears was 57 pct. higher than that for the medium intensity SPed gears at a depth of 127 microns and 540 pct. higher at a depth of 51 microns.
The Multivariate Largest Lyapunov Exponent as an Age-Related Metric of Quiet Standing Balance

Directory of Open Access Journals (Sweden)

Kun Liu

2015-01-01

Full Text Available The largest Lyapunov exponent has been researched as a metric of the balance ability during human quiet standing. However, the sensitivity and accuracy of this measurement method are not good enough for clinical use. The present research proposes a metric of the human body’s standing balance ability based on the multivariate largest Lyapunov exponent which can quantify the human standing balance. The dynamic multivariate time series of ankle, knee, and hip were measured by multiple electrical goniometers. Thirty-six normal people of different ages participated in the test. With acquired data, the multivariate largest Lyapunov exponent was calculated. Finally, the results of the proposed approach were analysed and compared with the traditional method, for which the largest Lyapunov exponent and power spectral density from the centre of pressure were also calculated. The following conclusions can be obtained. The multivariate largest Lyapunov exponent has a higher degree of differentiation in differentiating balance in eyes-closed conditions. The MLLE value reflects the overall coordination between multisegment movements. Individuals of different ages can be distinguished by their MLLE values. The standing stability of human is reduced with the increment of age.
Perceived Stress, Its Physiological Correlates, and Quality of Life in Patients With Irritable Bowel Syndrome.

Science.gov (United States)

Weaver, Kristen R; Melkus, Gail D'Eramo; Fletcher, Jason; Henderson, Wendy A

2018-05-01

Irritable bowel syndrome (IBS) is a chronic, common disorder of the gastrointestinal tract associated with high psychological comorbidity and diminished quality of life. Patients with IBS display a heightened sensitivity to stress, although the literature is inconsistent as to whether they have a dysregulated stress response. The purpose of the present investigation, a substudy of a larger research effort, was to examine physiological correlates of perceived stress in patients with IBS (cortisol and adrenocorticotropic hormone) and to explore associations between perceived stress and quality of life. A total of 101 participants (35 with IBS [predominant subtypes IBS-constipation and IBS-diarrhea] and 66 healthy controls [HCs]) completed self-report inventories regarding perceived stress and quality of life, and fasting peripheral blood was drawn. Participants with IBS did not differ from the HC in demographic or physiological measures but did differ in psychological measures, reporting significantly higher levels of perceived stress and lower levels of quality of life. Perceived stress and quality of life were not significantly associated in IBS participants. However, differential findings of the stress response were found within IBS participants by sex, race, and subtype. These findings illustrate the heterogeneity of the IBS patient population, underscore the necessity of evaluating larger sample sizes and increasing the diversity of such samples to include males and ethnic minorities, and demonstrate the importance of taking an individualized approach to evaluation and treatment in the IBS patient population.
Quality of life among post-menopausal women due to oxidative stress boosted by dysthymia and anxiety.

Science.gov (United States)

Sánchez-Rodríguez, Martha A; Castrejón-Delgado, Lizett; Zacarías-Flores, Mariano; Arronte-Rosales, Alicia; Mendoza-Núñez, Víctor Manuel

2017-01-03

Menopause is the onset of aging in women. During this process, some women experience physical changes that may impact upon their psychological and social status, also affecting their quality of life. Furthermore, several psychological changes following menopause have been shown to act as pro-oxidant, but the association between the psychological status that modify the quality of life and oxidative stress in postmenopausal women is still unclear. The aim of this study was to determinate the relationship between oxidative stress with psychological disturbances, low self-esteem, depressive mood and anxiety, and quality of life in the postmenopausal women. We carried out a cross-sectional study with101 premenopausal and 101 postmenopausal women from Mexico City. As markers of oxidative stress we measured plasma lipoperoxide levels, erythrocyte superoxide dismutase and glutathione peroxidase activities, and total antioxidant status. We calculate a stress score as global oxidative stress status, with cut-off values for each parameter; this score range from 0 to 6, representing the severity of markers modifications. All the women were rated using the Coopersmith Self-Esteem Inventory, the Zung Self-Rating Anxiety and the Zung Self-Rating Depression Scales, and the WHO Quality of Life-brief. The postmenopausal women with low quality of life in the WHO Quality of Life-brief and their subscales had higher stress score compared with premenopausal women with high quality of life (p Life-brief scores (r = -0.266, p Life-brief, after adjusted for pro-oxidant factors. Zung Self-Rating Anxiety and Zung Self-Rating Depression Scales scores also contribute to increase lipoperoxides levels, but not significant. Our findings suggest that oxidative stress is increased in postmenopausal women with psychological disturbances and low quality of life.
Life estimation of low-cycle fatigue of pipe elbows. Proposed criteria of low-cycle fatigue life under the multi-axial stress field

International Nuclear Information System (INIS)

Ando, Kotoji; Takahashi, Koji; Matsuo, Kazuya; Urabe, Yoshio

2013-01-01

Pipe elbows were important parts frequently used in the pipelines of nuclear power, thermal power and chemical plants, and their integrity needed to be assured under seismic loads and thermal stresses considering local wall thinning or complex stress distribution due to special configuration different from straight pipe. This article investigated in details elastic-plastic stress-strain state of pipe elbow using finite element analysis and clarified there existed high bi-axial stress field at side inner surface of pipe elbow axial cracks initiated. Bi-axial stress factor was around 0.6 for sound elbow and up to 0.95 for local wall thinning at crown. Fracture strain of 1.15 was reduced to around 0.15 for bi-axial stress factor from 0.6 to 0.9. Normalized fatigue life for bi-axial stress field (0.6 - 0.8) was largely reduced to around 15, 19 and 10% of fatigue life of uni-axial state dependent on material strength level. Proposed revised universal slopes taking account of multi-axial stress factor could explain qualitatively effects of strain range, internal pressure and ratchet strain (pre-strain) on low-cycle fatigue life of pipe elbow. (T. Tanaka)
Differential reproductive responses to stress reveal the role of life-history strategies within a species.

Science.gov (United States)

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

2013-11-22

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

International Nuclear Information System (INIS)

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

2016-01-01

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

DEFF Research Database (Denmark)

Bock, Camilla; Bukh, Jens Drachmann; Vinberg, Maj

2009-01-01

BACKGROUND: It is unclear whether medical treatment outcome in first episode depression differ for patients with and without stressful life events prior to onset of depression. METHODS: Patients discharged with a diagnosis of a single depressive episode from a psychiatric in- or outpatient hospital......-II) and the interview of recent life events (IRLE). Medical treatment history was assessed in detail using standardised procedures (TRAQ). Remission was defined as a score or= 4 on TRAQ following (1) first trial of antidepressant treatment (2) two adequate trials of antidepressant treatment. RESULTS: A total of 399...... patients participated in the interview and among these 301 patients obtained a SCAN diagnosis of a single depressive episode. A total of 62.8% of the 301 patients experienced at least one moderate to severe stressful life event in a 6 months period prior to symptom onset. The presence of a stressful life...
The Impact of Sleep Disturbance on the Association Between Stressful Life Events and Depressive Symptoms.

Science.gov (United States)

Leggett, Amanda; Burgard, Sarah; Zivin, Kara

2016-01-01

Sleep problems are common across the adult life span and may exacerbate depressive symptoms and the effect of common risk factors for depressive symptoms such as life stress. We examine sleep disturbance as a moderator of the association between stressful life events and depressive symptoms across five waves (25 years) of the nationally representative, longitudinal American Changing Lives Study. The sample includes 3,597 adults aged 25 years or older who were surveyed up to five times over 25 years. Multilevel models were run to examine between- and within-person variability in sleep disturbance and life event stress as predictors of depressive symptoms, and an interaction to test sleep disturbance as a moderator is included in a second step. Life events and sleep disturbance were associated with elevated depressive symptoms at the between- and within-person levels. A significant sleep disturbance by interaction of life events was found, indicating that when individuals experienced an above average number of life events and slept more restlessly than usual, they had a higher risk for depressive symptoms than individuals who experienced above average stress but slept well. Sleeping restfully may allow individuals the rejuvenation needed to manage stress adaptively and reduce depressive symptom burden. © The Author 2015. Published by Oxford University Press on behalf of The Gerontological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.
Critical applied stresses for a crack initiation from a sharp V-notch

Directory of Open Access Journals (Sweden)

L. Náhlík

2014-10-01

Full Text Available The aim of the paper is to estimate a value of the critical applied stress for a crack initiation from a sharp V-notch tip. The classical approach of the linear elastic fracture mechanics (LELM was generalized, because the stress singularity exponent differs from 0.5 in the studied case. The value of the stress singularity exponent depends on the V-notch opening angle. The finite element method was used for a determination of stress distribution in the vicinity of the sharp V-notch tip and for the estimation of the generalized stress intensity factor depending on the V-notch opening angle. Critical value of the generalized stress intensity factor was obtained using stability criteria based on the opening stress component averaged over a critical distance d from the V-notch tip and generalized strain energy density factor. Calculated values of the critical applied stresses were compared with experimental data from the literature and applicability of the LEFM concept is discussed.
Interference fits and stress-corrosion failure. [aircraft parts fatigue life analysis

Science.gov (United States)

Hanagud, S.; Carter, A. E.

1976-01-01

It is pointed out that any proper design of interference fit fastener, interference fit bushings, or stress coining processes should consider both the stress-corrosion susceptibility and fatigue-life improvement together. Investigations leading to such a methodology are discussed. A service failure analysis of actual aircraft parts is considered along with the stress-corrosion susceptibility of cold-working interference fit bushings. The optimum design of the amount of interference is considered, giving attention to stress formulas and aspects of design methodology.
An improved Corten-Dolan's model based on damage and stress state effects

International Nuclear Information System (INIS)

Gao, Huiying; Huang, Hong Zhong; Lv, Zhiqiang; Zuo, Fang Jun; Wang, Hai Kun

2015-01-01

The value of exponent d in Corten-Dolan's model is generally considered to be a constant. Nonetheless, the results predicted on the basis of this statement deviate significantly from the real values. In consideration of the effects of damage and stress state on fatigue life prediction, Corten-Dolan's model is improved by redefining the exponent d used in the traditional model. The improved model performs better than the traditional one with respect to the demonstration of a fatigue failure mechanism. Predictions of fatigue life on the basis of investigations into three metallic specimens indicate that the errors caused by the improved model are significantly smaller than those induced by the traditional model. Meanwhile, predictions derived according to the improved model fall into a narrower dispersion zone than those made as per Miner's rule and the traditional model. This finding suggests that the proposed model improves the life prediction accuracy of the other two models. The predictions obtained using the improved Corten-Dolan's model differ slightly from those derived according to a model proposed in previous literature; a few life predictions obtained on the basis of the former are more accurate than those derived according to the latter. Therefore, the improved model proposed in this paper is proven to be rational and reliable given the proven validity of the existing model. Therefore, the improved model can be feasibly and credibly applied to damage accumulation and fatigue life prediction to some extent.
An improved Corten-Dolan's model based on damage and stress state effects

Energy Technology Data Exchange (ETDEWEB)

Gao, Huiying; Huang, Hong Zhong; Lv, Zhiqiang; Zuo, Fang Jun; Wang, Hai Kun [University of Electronic Science and Technology of China, Chengdu (China)

2015-08-15

The value of exponent d in Corten-Dolan's model is generally considered to be a constant. Nonetheless, the results predicted on the basis of this statement deviate significantly from the real values. In consideration of the effects of damage and stress state on fatigue life prediction, Corten-Dolan's model is improved by redefining the exponent d used in the traditional model. The improved model performs better than the traditional one with respect to the demonstration of a fatigue failure mechanism. Predictions of fatigue life on the basis of investigations into three metallic specimens indicate that the errors caused by the improved model are significantly smaller than those induced by the traditional model. Meanwhile, predictions derived according to the improved model fall into a narrower dispersion zone than those made as per Miner's rule and the traditional model. This finding suggests that the proposed model improves the life prediction accuracy of the other two models. The predictions obtained using the improved Corten-Dolan's model differ slightly from those derived according to a model proposed in previous literature; a few life predictions obtained on the basis of the former are more accurate than those derived according to the latter. Therefore, the improved model proposed in this paper is proven to be rational and reliable given the proven validity of the existing model. Therefore, the improved model can be feasibly and credibly applied to damage accumulation and fatigue life prediction to some extent.
Stressful life events in a clinical sample of depressed children in Hungary.

Science.gov (United States)

Mayer, László; Lopez-Duran, Nestor L; Kovacs, Maria; George, Charles J; Baji, Ildikó; Kapornai, Krisztina; Kiss, Eniko; Vetró, Agnes

2009-05-01

There is limited information on the characteristics of stressful life events in depressed pediatric clinical populations and the extent to which sex, age, and their interactions may influence the relations of life events and depression. Using a very large clinical sample of children and adolescents with major depressive disorder (MDD), we therefore examined life events in various ways, as well as their relations to age and sex. The study included a clinic-based sample of 434 children (ages 7-14) with a DSM-IV diagnosis of MDD and their mothers, and a school-based comparison sample of 724 children and their mothers. Life event information was obtained from the mothers. Children with MDD had twice the number of lifetime stressful events than did the comparison group, with very high levels of stressors by the age of 7-9 that stabilized across adolescence. In contrast, the comparison sample experienced a gradual increase in stressful life events as a function of age up to mid-adolescence. Parental health events, death of close relatives, and intrafamilial events were significantly associated with MDD diagnosis. There were significantly stronger associations between parental health- as well as death-event clusters and MDD diagnosis among younger children than adolescents. Geographical differences between the clinical and comparison samples, as well as possible parental reporting biases may affect the generalizability of these findings. The association between some stressful life events and MDD seems to be moderated by age, underscoring the need to examine specific events, as well as clusters of events. Better understanding of such interactions may facilitate early identification of possible risk factors for pediatric MDD.
Variation of Zipf's exponent in one hundred live languages: A study of the Holy Bible translations

Science.gov (United States)

Mehri, Ali; Jamaati, Maryam

2017-08-01

Zipf's law, as a power-law regularity, confirms long-range correlations between the elements in natural and artificial systems. In this article, this law is evaluated for one hundred live languages. We calculate Zipf's exponent for translations of the holy Bible to several languages, for this purpose. The results show that, the average of Zipf's exponent in studied texts is slightly above unity. All studied languages in some families have Zipf's exponent lower/higher than unity. It seems that geographical distribution impresses the communication between speakers of different languages in a language family, and affect similarity between their Zipf's exponent. The Bible has unique concept regardless of its language, but the discrepancy in grammatical rules and syntactic regularities in applying stop words to make sentences and imply a certain concept, lead to difference in Zipf's exponent for various languages.
Methodology for formulating predictions of stress corrosion cracking life

International Nuclear Information System (INIS)

Yamauchi, Kiyoshi; Hattori, Shigeo; Shindo, Takenori; Kuniya, Jiro

1994-01-01

This paper presents a methodology for formulating predictions to evaluate the stress corrosion cracking (SCC) potential of each light-water reactor component, where an index is introduced as a life index or F index. The index denotes the SCC time ratio of a given SCC system to be evaluated against a reference SCC system. The life index is expressed by the products of several subdivided life indexes, which correspond to each SCC influencing factor. Each subdivided life index is constructed as a function containing the influencing factor variable, obtained by analyzing experimental SCC life data. The methodology was termed the subdivided factor method. Application of the life index to SCC life data and field data showed that it was effective for evaluating the SCC potential, i.e. the SCC life. Accordingly, the proposed methodology can potentially describe a phenomenon expressed by a function which consists of the variables of several influencing factors whether there are formulae which unite as a physical model or not. ((orig.))
Gender Differences in Perceived Social Support and Stressful Life Events in Depressed Patients.

Science.gov (United States)

Soman, S; Bhat, S M; Latha, K S; Praharaj, S K

2016-03-01

To study the gender differences in perceived social support and life events in patients with depression. A total of 118 patients aged 18 to 60 years, with depressive disorder according to the DSM-IV-TR, were evaluated using the Multidimensional Scale of Perceived Social Support and Presumptive Stressful Life Events Scale. The perceived social support score was significantly higher in males than females (p friends than females (p life events as well as specific type of life events in males that became apparent after controlling for education (p life event in both males and females. Work-related problems were more commonly reported by males, whereas family and marital conflict were more frequently reported by females. Perceived social support and stressful life events were higher in males with depression than females.

Identification of exponent from load-deformation relation for soft materials from impact tests

Science.gov (United States)

Ciornei, F. C.; Alaci, S.; Romanu, I. C.; Ciornei, M. C.; Sopon, G.

2018-01-01

When two bodies are brought into contact, the magnitude of occurring reaction forces increase together with the amplitude of deformations. The load-deformation dependency of two contacting bodies is described by a function having the form F = Cxα . An accurate illustration of this relationship assumes finding the precise coefficient C and exponent α. This representation proved to be very useful in hardness tests, in dynamic systems modelling or in considerations upon the elastic-plastic ratio concerning a Hertzian contact. The classical method for identification of the exponent consists in finding it from quasi-static tests. The drawback of the method is the fact that the accurate estimation of the exponent supposes precise identification of the instant of contact initiation. To overcome this aspect, the following observation is exploited: during an impact process, the dissipated energy is converted into heat released by internal friction in the materials and energy for plastic deformations. The paper is based on the remark that for soft materials the hysteresis curves obtained for a static case are similar to the ones obtained for medium velocities. Furthermore, utilizing the fact that for the restitution phase the load-deformation dependency is elastic, a method for finding the α exponent for compression phase is proposed. The maximum depth of the plastic deformations obtained for a series of collisions, by launching, from different heights, a steel ball in free falling on an immobile prism made of soft material, is evaluated by laser profilometry method. The condition that the area of the hysteresis loop equals the variation of kinetical energy of the ball is imposed and two tests are required for finding the exponent. Five collisions from different launching heights of the ball were taken into account. For all the possible impact-pair cases, the values of the exponent were found and close values were obtained.
Early Life Trauma Exposure and Stress Sensitivity in Young Children

OpenAIRE

Grasso, Damion J.; Ford, Julian D.; Briggs-Gowan, Margaret J.

2012-01-01

Objective The current study replicates and extends work with adults that highlights the relationship between trauma exposure and distress in response to subsequent, nontraumatic life stressors. Methods The sample included 213 2–4-year-old children in which 64.3% had a history of potential trauma exposure. Children were categorized into 4 groups based on trauma history and current life stress. Results In a multivariate analysis of variance, trauma-exposed children with current life stressors h...
Psychoneuroimmunology of Early-Life Stress: The Hidden Wounds of Childhood Trauma?

Science.gov (United States)

Danese, Andrea; J Lewis, Stephanie

2017-01-01

The brain and the immune system are not fully formed at birth, but rather continue to mature in response to the postnatal environment. The two-way interaction between the brain and the immune system makes it possible for childhood psychosocial stressors to affect immune system development, which in turn can affect brain development and its long-term functioning. Drawing from experimental animal models and observational human studies, we propose that the psychoneuroimmunology of early-life stress can offer an innovative framework to understand and treat psychopathology linked to childhood trauma. Early-life stress predicts later inflammation, and there are striking analogies between the neurobiological correlates of early-life stress and of inflammation. Furthermore, there are overlapping trans-diagnostic patterns of association of childhood trauma and inflammation with clinical outcomes. These findings suggest new strategies to remediate the effect of childhood trauma before the onset of clinical symptoms, such as anti-inflammatory interventions and potentiation of adaptive immunity. Similar strategies might be used to ameliorate the unfavorable treatment response described in psychiatric patients with a history of childhood trauma. PMID:27629365
Life satisfaction and perceived stress among young offenders in a residential therapeutic community: Latent change score analysis.

Science.gov (United States)

Tang, Kristen N S; Chan, Christian S

2017-06-01

Recent rehabilitation frameworks underscore the importance of strength-based interventions for young offenders who may lack internal and external resources to manage their stress and plan for their life. This multi-wave longitudinal study investigated the dynamic relationship between perceived stress and life satisfaction among a group of young ex-offenders in a residential therapeutic community. Four waves of data were collected from 117 Hong Kong youths (24.0% female, mean age = 17.7) over one year. Latent change score analysis was employed to examine the univairate and bivariate changes of their perceived stress and life satisfaction. Results suggest a positive growth trajectory in life satisfaction over time. The results of perceived stress were less conclusive. Bivariate models indicated that the previous level of life satisfaction was negatively linked to the subsequent perceived stress level but not vice versa. The findings suggest that improvement in life satisfaction may reduce perceived stress in young ex-offenders. Copyright © 2017 The Foundation for Professionals in Services for Adolescents. Published by Elsevier Ltd. All rights reserved.
The influence of personality traits and social support on male nursing student life stress: a cross-sectional research design.

Science.gov (United States)

Lou, Jiunn-Horng; Chen, Sheng-Hwang; Yu, Hsing-Yi; Li, Ren-Hau; Yang, Cheng-I; Eng, Cheng-Joo

2010-06-01

Understanding how male nursing students alleviate life stress during their academic career is conducive to their development as successful nursing professionals. This study was designed to understand the personality traits, social support, and life stresses of male nursing students. The respective influences of personality traits and social support on life stress were also explored. The study used a cross-sectional research design. A college in central Taiwan was targeted as the site for data collection. A total of 158 questionnaires were dispatched, with 145 valid copies returned (valid response rate = 91.7%). Structured questionnaires were designed to collect data on participant demographics, personality traits, social support, and life stress. Statistical methods such as descriptive statistics, one-way analysis of variance, and multiple regression analysis were applied to data analysis. Major findings of this study revealed that (a) in general, the personality traits, social support, and life stress of male nursing students scored in the medium to high range. Participants reported encountering more stress from learning and life goals than from interpersonal stress. (b) Male nursing student demographic variables (e.g., parent [father and mother considered separately] education level) and the personality traits of conscientiousness and family support, respectively, were found to impact significantly on participant life stress perceptions. And (c) the only significant predictors of life stress were support from family and education level of participant fathers and mothers, accounting for about 23.7% of variability. It is suggested that nursing students in each year of their academic career should be exposed to courses geared to reduce the life stress perceptions (especially in the areas of learning and career development) of male nursing students. Increased family support is an effective way to decrease male nursing student life stress. This study could be a
Deposition stress effects on thermal barrier coating burner rig life

Science.gov (United States)

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

1984-01-01

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

International Nuclear Information System (INIS)

Udomsamuthirun, P.; Kumvongsa, C.; Burakorn, A.; Changkanarth, P.; Yoksan, S.

2005-01-01

The exact formula of T c 's equation and the isotope effect exponent of two-band s-wave superconductors in weak-coupling limit are derived by considering the influence of two kinds of density of state: constant and van Hove singularity. The paring interaction in each band consisted of two parts: the electron-phonon interaction and non-electron-phonon interaction are included in our model. We find that the interband interaction of electron-phonon show more effect on isotope exponent than the intraband interaction and the isotope effect exponent with constant density of state can fit to experimental data, MgB 2 and high-T c superconductor, better than van Hove singularity density of state
Effect of Coulomb stress on the Gutenberg-Richter law

Science.gov (United States)

Navas-Portella, V.; Corral, A.; Jimenez, A.

2017-12-01

Coulomb stress theory has been used for years in seismology to understand how earthquakes trigger each other. Whenever an earthquake occurs, the stress field changes in its neighbourhood, with places with positive values brought closer to failure, whereas negative values distance away that location from failure. Earthquake models that relate rate changes and Coulomb stress after a main event, such as the rate-and-state model, assume negative and positive stress values affect rate changes according to the same functional form. As a first order approximation, under uniform background seismicity before the main event, different values of the b-exponent in the Gutenberg-Richter law would indicate different behaviour for positive and negative stress. In this work, we study the Gutenberg-Richter law in the aftershock sequence of the Landers earthquake (California, 1992, MW=7.3). By using a statistically based fitting method, we discuss whether the sign of Coulomb stresses and the distance to the fault have a significant effect on the value of the b-exponent.
Health-Related Quality of Life and Parental Stress in Children With Fecal Incontinence: A Normative Comparison.

Science.gov (United States)

Cushing, Christopher C; Martinez-Leo, Bruno; Bischoff, Andrea; Hall, Jennifer; Helmrath, Michael; Dickie, Belinda H; Levitt, Marc A; Peña, Alberto; Zeller, Meg H; Frischer, Jason S

2016-12-01

The aim of the present study was to describe the quality of life and parenting stress associated with a child with fecal incontinence (FI). Female caregivers (n = 170) of children of 3 to 12 years age with FI completed a broad and general measure of quality of life and a measure of parenting stress. Results were compared with proxy reports for a normative sample of healthy children. Caregivers of children with FI reported significantly impaired quality of life for their children and increased parenting stress in all of the respective domains relative to healthy controls. Impairments reported by caregivers were large in magnitude. Similarly, rates of parenting stress were at or greater than the 98th percentile for caregivers of children with FI. Children with fecal incontinence and their families are in need of interventions targeting their quality of life and the stress associated with caregiving. FI appears to be particularly stressful for caregivers who may be in need of support beyond medical management of their child's bowel. Moreover, additional refinements in disease-specific quality of life assessment are needed in this population. Such refinement would allow for more precise measurement of the quality of life processes that are unique to FI.
Number of recent stressful life events and incident cardiovascular disease: Moderation by lifetime depressive disorder.

Science.gov (United States)

Berntson, Jessica; Patel, Jay S; Stewart, Jesse C

2017-08-01

We investigated whether number of recent stressful life events is associated with incident cardiovascular disease (CVD) and whether this relationship is stronger in adults with a history of clinical depression. Prospective data from 28,583 U.S. adults (mean age=45years) initially free of CVD who participated in Waves 1 (2001-2002) and 2 (2004-2005) of the National Epidemiologic Survey on Alcohol and Related Conditions (NESARC) were examined. Number of past-year stressful life events (Wave 1), lifetime depressive disorder (Wave 1), and incident CVD (Wave 2) were determined by structured interviews. There were 1069 cases of incident CVD. Each additional stressful life event was associated with a 15% increased odds of incident CVD [Odds Ratio (OR)=1.15, 95% Confidence Interval (CI): 1.11, 1.19]. As hypothesized, a stressful life events by lifetime depressive disorder interaction was detected (P=0.003). Stratified analyses indicated that stressful life events had a stronger association with incident CVD among adults with (OR=1.18, 95% CI: 1.10, 1.27, n=4908) versus without (OR=1.10, 95% CI: 1.07, 1.14, n=23,675) a lifetime depressive disorder. Our findings suggest that a greater number of recent stressful life events elevate the risk of new-onset CVD and that this risk is potentiated in adults with a history of clinical depression. Copyright © 2017 Elsevier Inc. All rights reserved.
The Interactive Effects of Stressful Family Life Events and Cortisol Reactivity on Adolescent Externalizing and Internalizing Behaviors

Science.gov (United States)

Steeger, Christine M.; Cook, Emily C.; Connell, Christian M.

2016-01-01

This study investigated the associations between stressful family life events and adolescent externalizing and internalizing behaviors, and the interactive effects of family life events and cortisol reactivity on problem behaviors. In a sample of 100 mothers and their adolescents (M age = 15.09; SD age = 0.98; 68% girls), adolescent cortisol reactivity was measured in response to a mother-adolescent conflict interaction task designed to elicit a stress response. Mothers reported on measures of family life events and adolescent problem behaviors. Results indicated that a heightened adolescent cortisol response moderated the relations between stressful family life events and both externalizing and internalizing behaviors. Results support context-dependent theoretical models, suggesting that for adolescents with higher cortisol reactivity (compared to those with lower cortisol reactivity), higher levels of stressful family life events were associated with greater problem behaviors, whereas lower levels of stressful family life events were related to fewer problem behaviors. PMID:26961703
Estimation of Hurst Exponent for the Financial Time Series

Science.gov (United States)

Kumar, J.; Manchanda, P.

2009-07-01

Till recently statistical methods and Fourier analysis were employed to study fluctuations in stock markets in general and Indian stock market in particular. However current trend is to apply the concepts of wavelet methodology and Hurst exponent, see for example the work of Manchanda, J. Kumar and Siddiqi, Journal of the Frankline Institute 144 (2007), 613-636 and paper of Cajueiro and B. M. Tabak. Cajueiro and Tabak, Physica A, 2003, have checked the efficiency of emerging markets by computing Hurst component over a time window of 4 years of data. Our goal in the present paper is to understand the dynamics of the Indian stock market. We look for the persistency in the stock market through Hurst exponent and fractal dimension of time series data of BSE 100 and NIFTY 50.
Power-law Exponent in Multiplicative Langevin Equation with Temporally Correlated Noise

Science.gov (United States)

Morita, Satoru

2018-05-01

Power-law distributions are ubiquitous in nature. Random multiplicative processes are a basic model for the generation of power-law distributions. For discrete-time systems, the power-law exponent is known to decrease as the autocorrelation time of the multiplier increases. However, for continuous-time systems, it is not yet clear how the temporal correlation affects the power-law behavior. Herein, we analytically investigated a multiplicative Langevin equation with colored noise. We show that the power-law exponent depends on the details of the multiplicative noise, in contrast to the case of discrete-time systems.
On the relation between Lyapunov exponents and exponential decay of correlations

International Nuclear Information System (INIS)

Slipantschuk, Julia; Bandtlow, Oscar F; Just, Wolfram

2013-01-01

Chaotic dynamics with sensitive dependence on initial conditions may result in exponential decay of correlation functions. We show that for one-dimensional interval maps the corresponding quantities, that is, Lyapunov exponents and exponential decay rates, are related. More specifically, for piecewise linear expanding Markov maps observed via piecewise analytic functions, we show that the decay rate is bounded above by twice the Lyapunov exponent, that is, we establish lower bounds for the subleading eigenvalue of the corresponding Perron–Frobenius operator. In addition, we comment on similar relations for general piecewise smooth expanding maps. (paper)
Life span effects of Hypericum perforatum extracts on Caenorhabditis elegans under heat stress.

Science.gov (United States)

Kılıçgün, Hasan; Göksen, Gülden

2012-10-01

The beneficial effects of antioxidants in plants are mainly extrapolated from in vitro studies or short-term dietary supplementation studies. Due to cost and duration, relatively little is known about whether dietary antioxidants are beneficial in whole animals' life span or not. To address this question, under heat stress (35°C), Hypericum perforatum was extracted with petroleum ether and the nematodes Caenorhabditis elegans exposed to three different extract concentrations (1mg/mL, 0.1mg/mL, 0.01mg/mL) of H. perforatum. We report that Hypericum perforatum extracts did not increase life span and slow aging related increase in C. elegans. Moreover, one fraction (1mg/mL) increased declines of C. elegans life span and thermotolerance. Given this mounting evidence for life span role of H. perforatum in the presence of heat stress in vivo, the question whether H. perforatum acts as a prooxidant or an antioxidant in vivo under heat stress arises.
Service Life Of Main Piping Component Due To Low Thermal Stresses.Fatigue

International Nuclear Information System (INIS)

Miroshnik, R.; Jeager, A.; Ben Haim, H.

1998-01-01

The paper deals with estimating the service life of the power station Main piping component and describing the repair process for extending of its service life. After a long period of service, several circular fatigue cracks have been discovered at the bottom of the Main piping component chamber. Finite element analyses of transient thermal stresses, caused by power station startup, are carried out in the paper. The calculation results show good agreement between the theoretical locations of the maximum stresses and the actual locations of the cracks. There is a good agreement between theoretical evaluation and actual service life, as well. The possibility of machining out the cracks in order to prevent their growing is examined here. The machining enables us to extend the power station component's life service
Gender and Racial Differences in Stress, Coping, and Health-Related Quality of Life in Chronic Kidney Disease.

Science.gov (United States)

Gemmell, Leigh A; Terhorst, Lauren; Jhamb, Manisha; Unruh, Mark; Myaskovsky, Larissa; Kester, Lauren; Steel, Jennifer L

2016-12-01

Living with chronic kidney disease can be stressful and influence an individual's health-related quality of life. Effective coping strategies may reduce stress and improve quality of life in individuals with chronic medical conditions. Health-related quality of life (HRQOL) is an important outcome for patients living with chronic kidney disease (CKD), and it is necessary to better understand potential gender and racial differences and predictors associated with reduced HRQOL, so that effective interventions can be developed. Participants included 182 patients with CKD who were administered a battery of questions that included the Medical Outcomes Study Short-Form 36, Perceived Stress Scale, and the Brief COPE. Demographic and disease-specific information was abstracted from the patients' medical record. No differences by race were observed with regard to stress, quality of life, or coping with the exception that minority patients reported use of religious coping more often (P = 0.001) and had higher levels of energy compared with nonminority patients with CKD (P = 0.27). Women with CKD tended to use self-distraction (P = 0.002), positive reframing (P = 0.035), venting (P = 0.024), and religious coping (P = 0 stress or domains of quality of life were observed between men and women with CKD. A link between coping strategies and HRQOL was observed in women (P = 0.001-0.02) but not men. Perceived stress was associated with poorer quality of life for men (P = 0.017 to life were affected by perceived stress compared with women. The findings of the study suggest that the wider range of coping strategies used by women may be associated with buffering the link between perceived stress and quality of life. Men with CKD may benefit from interventions that not only reduce stress but also facilitate the use of a broader range of coping strategies to reduce stress and improve quality of life. Copyright © 2016 American Academy of Hospice and Palliative Medicine
Controversy in the allometric application of fixed- versus varying-exponent models: a statistical and mathematical perspective.

Science.gov (United States)

Tang, Huadong; Hussain, Azher; Leal, Mauricio; Fluhler, Eric; Mayersohn, Michael

2011-02-01

This commentary is a reply to a recent article by Mahmood commenting on the authors' article on the use of fixed-exponent allometry in predicting human clearance. The commentary discusses eight issues that are related to criticisms made in Mahmood's article and examines the controversies (fixed-exponent vs. varying-exponent allometry) from the perspective of statistics and mathematics. The key conclusion is that any allometric method, which is to establish a power function based on a limited number of animal species and to extrapolate the resulting power function to human values (varying-exponent allometry), is infused with fundamental statistical errors. Copyright © 2010 Wiley-Liss, Inc.
Landau-like theory for universality of critical exponents in quasistationary states of isolated mean-field systems.

Science.gov (United States)

Ogawa, Shun; Yamaguchi, Yoshiyuki Y

2015-06-01

An external force dynamically drives an isolated mean-field Hamiltonian system to a long-lasting quasistationary state, whose lifetime increases with population of the system. For second order phase transitions in quasistationary states, two nonclassical critical exponents have been reported individually by using a linear and a nonlinear response theories in a toy model. We provide a simple way to compute the critical exponents all at once, which is an analog of the Landau theory. The present theory extends the universality class of the nonclassical exponents to spatially periodic one-dimensional systems and shows that the exponents satisfy a classical scaling relation inevitably by using a key scaling of momentum.
Canonical Correlation Analysis on Life Stress and Learning Burnout of College Students in Taiwan

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Huang, Yun-Chen; Lin, Shu Hui

2010-01-01

With rapid social changes, stress in life has increased significantly for everyone including college students. Understanding life stress among college students and how it may affect learning burnout has become an important concern for education researchers. The purposes of this study were (1) to assess the current status and factor structures of…

Critical exponents of extremal Kerr perturbations

Science.gov (United States)

Gralla, Samuel E.; Zimmerman, Peter

2018-05-01

We show that scalar, electromagnetic, and gravitational perturbations of extremal Kerr black holes are asymptotically self-similar under the near-horizon, late-time scaling symmetry of the background metric. This accounts for the Aretakis instability (growth of transverse derivatives) as a critical phenomenon associated with the emergent symmetry. We compute the critical exponent of each mode, which is equivalent to its decay rate. It follows from symmetry arguments that, despite the growth of transverse derivatives, all generally covariant scalar quantities decay to zero.
Effects of medium renewal and handling stress on life history traits in Daphnia

NARCIS (Netherlands)

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

2010-01-01

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

Science.gov (United States)

Williamson, Nathan H; Röding, Magnus; Miklavcic, Stanley J; Nydén, Magnus

2017-05-01

Molecular mass distribution measurements by pulsed gradient spin echo nuclear magnetic resonance (PGSE NMR) spectroscopy currently require prior knowledge of scaling parameters to convert from polymer self-diffusion coefficient to molecular mass. Reversing the problem, we utilize the scaling relation as prior knowledge to uncover the scaling exponent from within the PGSE data. Thus, the scaling exponent-a measure of polymer conformation and solvent quality-and the dispersity (M w /M n ) are obtainable from one simple PGSE experiment. The method utilizes constraints and parametric distribution models in a two-step fitting routine involving first the mass-weighted signal and second the number-weighted signal. The method is developed using lognormal and gamma distribution models and tested on experimental PGSE attenuation of the terminal methylene signal and on the sum of all methylene signals of polyethylene glycol in D 2 O. Scaling exponent and dispersity estimates agree with known values in the majority of instances, leading to the potential application of the method to polymers for which characterization is not possible with alternative techniques. Copyright © 2017 Elsevier Inc. All rights reserved.
Correlation Between Stress and Quality of Life Experienced by Caregivers: Perception of a Group of Healthcare Professionals.

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Silva, Bhárbara Karolline Rodrigues; Quaresma, Fernando Rodrigues Peixoto; Maciel, Erika da Silva; Figueiredo, Francisco Winter Dos Santos; Sarraf, Jonathan Souza; Adami, Fernando

2017-01-01

This study aims to evaluate the relationship between perceived level of stress and quality of life of professionals working in Prompt Service Units in the city of Palmas, Tocantins. A cross-sectional study was performed among 164 professionals from Prompt Service Units. Stress levels were evaluated using the Perceived Stress Scale. The WHOQOL-bref was used to evaluate the perception of quality of life. Quantitative variables distribution was evaluated using Shapiro-Wilk's test. For the analyses of correlations among perceived level of stress, total quality of life score, and the physical health domain of the WHOQOL-bref, Pearson's correlation test was applied. The significance level adopted for this trial was 95%. The study was approved by the Committee of Ethics in Research with Human Beings. When assessing the perceived level of stress with the total quality of life score, there was no significant correlation between those variables. However, there was an association between the perceived level of stress and the physical health domain of quality of life. Perceived quality of life was correlated with the physical health domain, and this result reinforces the importance of the facets that make up this area.
High-resolution satellite image segmentation using Hölder exponents

Indian Academy of Sciences (India)

Keywords. High resolution image; texture analysis; segmentation; IKONOS; Hölder exponent; cluster. ... are that. • it can be used as a tool to measure the roughness ... uses reinforcement learning to learn the reward values of ..... The numerical.
Universal rescaling of flow curves for yield-stress fluids close to jamming

Science.gov (United States)

Dinkgreve, M.; Paredes, J.; Michels, M. A. J.; Bonn, D.

2015-07-01

The experimental flow curves of four different yield-stress fluids with different interparticle interactions are studied near the jamming concentration. By appropriate scaling with the distance to jamming all rheology data can be collapsed onto master curves below and above jamming that meet in the shear-thinning regime and satisfy the Herschel-Bulkley and Cross equations, respectively. In spite of differing interactions in the different systems, master curves characterized by universal scaling exponents are found for the four systems. A two-state microscopic theory of heterogeneous dynamics is presented to rationalize the observed transition from Herschel-Bulkley to Cross behavior and to connect the rheological exponents to microscopic exponents for the divergence of the length and time scales of the heterogeneous dynamics. The experimental data and the microscopic theory are compared with much of the available literature data for yield-stress systems.
Estimation of time-dependent Hurst exponents with variational smoothing and application to forecasting foreign exchange rates

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Garcin, Matthieu

2017-10-01

Hurst exponents depict the long memory of a time series. For human-dependent phenomena, as in finance, this feature may vary in the time. It justifies modelling dynamics by multifractional Brownian motions, which are consistent with time-dependent Hurst exponents. We improve the existing literature on estimating time-dependent Hurst exponents by proposing a smooth estimate obtained by variational calculus. This method is very general and not restricted to the sole Hurst framework. It is globally more accurate and easier than other existing non-parametric estimation techniques. Besides, in the field of Hurst exponents, it makes it possible to make forecasts based on the estimated multifractional Brownian motion. The application to high-frequency foreign exchange markets (GBP, CHF, SEK, USD, CAD, AUD, JPY, CNY and SGD, all against EUR) shows significantly good forecasts. When the Hurst exponent is higher than 0.5, what depicts a long-memory feature, the accuracy is higher.
Contact mechanical analysis of O-ring stresses

Energy Technology Data Exchange (ETDEWEB)

Kim, Hyung Kyu

2007-02-15

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

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Sampasa-Kanyinga, Hugues; Chaput, Jean-Philippe

2017-03-01

We investigated the associations among self-perceived work and life stress, trouble sleeping, physical activity and body weight among Canadian adults, and tested whether trouble sleeping and physical activity moderated the relationship between work/life stress and body weight, and whether work/life stress and physical activity moderated the relationship between trouble sleeping and body weight. Data on 13,926 Canadian adults aged 20years and older were derived from the nationally representative 2012 Canadian Community Health Survey. After adjusting for age, sex, education level, household income, marital status and job insecurity, self-perceived work and life stress and trouble sleeping were associated with a higher BMI. The associations of work and life stress with higher BMI were independent of trouble sleeping and physical activity in addition to other covariates, while that of trouble sleeping and higher BMI was independent of work and life stress. Results further indicated that trouble sleeping among inactive participants was related to a higher BMI; however, this relationship was almost null for adults who self-reported being physically active for about 8h/week. These findings suggest that work and life stress are both associated with excess weight in adults, regardless of physical activity level, while the link of trouble sleeping with BMI varies by physical activity level. Future research is necessary to determine whether reducing work and life stress and improving sleep habits would benefit the prevention of weight gain and obesity. Copyright © 2016 Elsevier Inc. All rights reserved.
Non-linear impact of glutathione depletion on C. elegans life span and stress resistance

Directory of Open Access Journals (Sweden)

Nadine Urban

2017-04-01

Full Text Available The redox environment in cells and organisms is set by low-molecular mass and protein-bound thiols, with glutathione (GSH representing a major intracellular redox buffer. Subtle thiol oxidation elicits signal transduction processes and adaptive responses to cope with stressors, whereas highly oxidizing conditions may provoke cell death. We here tested how thiol depletion affects life span, stress resistance and stress signaling in the model organism Caenorhabditis elegans. Diethyl maleate (DEM, an α,β-unsaturated carbonyl compound that conjugates to GSH and other thiols, decreased C. elegans life span at a concentration of 1 mM. In contrast, low and moderate doses of DEM (10–100 µM increased mean and maximum life span and improved resistance against oxidative stress. DEM-induced life span extension was not detectable in worms deficient in either the FoxO orthologue, DAF-16, or the Nrf2 orthologue, SKN-1, pointing to a collaborative role of the two transcription factors in life span extension induced by thiol depletion. Cytoprotective target genes of DAF-16 and SKN-1 were upregulated after at least 3 days of exposure to 100 µM DEM, but not 1 mM DEM, whereas only 1 mM DEM caused upregulation of egl-1, a gene controlled by a p53-orthologue, CEP-1. In order to test whether depletion of GSH may elicit effects similar to DEM, we suppressed GSH biosynthesis in worms by attenuating γ-glutamylcysteine synthetase (gcs-1 expression through RNAi. The decline in GSH levels elicited by gcs-1 knockdown starting at young adult stage did not impair viability, but increased both stress resistance and life expectancy of the worms. In contrast, gcs-1 knockdown commencing right after hatching impaired nematode stress resistance and rendered young adult worms prone to vulval ruptures during egg-laying. Thus, modest decrease in GSH levels in young adult worms may promote stress resistance and life span, whereas depletion of GSH is detrimental to freshly
Non-linear impact of glutathione depletion on C. elegans life span and stress resistance.

Science.gov (United States)

Urban, Nadine; Tsitsipatis, Dimitrios; Hausig, Franziska; Kreuzer, Katrin; Erler, Katrin; Stein, Vanessa; Ristow, Michael; Steinbrenner, Holger; Klotz, Lars-Oliver

2017-04-01

The redox environment in cells and organisms is set by low-molecular mass and protein-bound thiols, with glutathione (GSH) representing a major intracellular redox buffer. Subtle thiol oxidation elicits signal transduction processes and adaptive responses to cope with stressors, whereas highly oxidizing conditions may provoke cell death. We here tested how thiol depletion affects life span, stress resistance and stress signaling in the model organism Caenorhabditis elegans. Diethyl maleate (DEM), an α,β-unsaturated carbonyl compound that conjugates to GSH and other thiols, decreased C. elegans life span at a concentration of 1mM. In contrast, low and moderate doses of DEM (10-100µM) increased mean and maximum life span and improved resistance against oxidative stress. DEM-induced life span extension was not detectable in worms deficient in either the FoxO orthologue, DAF-16, or the Nrf2 orthologue, SKN-1, pointing to a collaborative role of the two transcription factors in life span extension induced by thiol depletion. Cytoprotective target genes of DAF-16 and SKN-1 were upregulated after at least 3 days of exposure to 100µM DEM, but not 1mM DEM, whereas only 1mM DEM caused upregulation of egl-1, a gene controlled by a p53-orthologue, CEP-1. In order to test whether depletion of GSH may elicit effects similar to DEM, we suppressed GSH biosynthesis in worms by attenuating γ-glutamylcysteine synthetase (gcs-1) expression through RNAi. The decline in GSH levels elicited by gcs-1 knockdown starting at young adult stage did not impair viability, but increased both stress resistance and life expectancy of the worms. In contrast, gcs-1 knockdown commencing right after hatching impaired nematode stress resistance and rendered young adult worms prone to vulval ruptures during egg-laying. Thus, modest decrease in GSH levels in young adult worms may promote stress resistance and life span, whereas depletion of GSH is detrimental to freshly hatched and developing worms
Randomness confidence bands of fractal scaling exponents for financial price returns

International Nuclear Information System (INIS)

Ibarra-Valdez, C.; Alvarez, J.; Alvarez-Ramirez, J.

2016-01-01

Highlights: • A robust test for randomness of price returns is proposed. • The DFA scaling exponent is contrasted against confidence bands for random sequences. • The size of the band depends of the sequence length. • Crude oil and USA stock markets have been rarely inefficient. - Abstract: The weak-form of the efficient market hypothesis (EMH) establishes that price returns behave as a pure random process and so their outcomes cannot be forecasted. The detrended fluctuation analysis (DFA) has been widely used to test the weak-form of the EMH by showing that time series of price returns are serially uncorrelated. In this case, the DFA scaling exponent exhibits deviations from the theoretical value of 0.5. This work considers the test of the EMH for DFA implementation on a sliding window, which is an approach that is intended to monitor the evolution of markets. Under these conditions, the scaling exponent exhibits important variations over the scrutinized period that can offer valuable insights in the behavior of the market provided the estimated scaling value is kept within strict statistical tests to verify the presence or not of serial correlations in the price returns. In this work, the statistical tests are based on comparing the estimated scaling exponent with the values obtained from pure Gaussian sequences with the length of the real time series. In this way, the presence of serial correlations can be guaranteed only in terms of the confidence bands of a pure Gaussian process. The crude oil (WTI) and the USA stock (DJIA) markets are used to illustrate the methodology.
Beyond Critical Exponents in Neuronal Avalanches

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Friedman, Nir; Butler, Tom; Deville, Robert; Beggs, John; Dahmen, Karin

2011-03-01

Neurons form a complex network in the brain, where they interact with one another by firing electrical signals. Neurons firing can trigger other neurons to fire, potentially causing avalanches of activity in the network. In many cases these avalanches have been found to be scale independent, similar to critical phenomena in diverse systems such as magnets and earthquakes. We discuss models for neuronal activity that allow for the extraction of testable, statistical predictions. We compare these models to experimental results, and go beyond critical exponents.
Stressful life events and acute kidney injury in intensive and semi-intensive care unities.

Science.gov (United States)

Diniz, Denise Para; Marques, Daniella Aparecida; Blay, Sérgio Luis; Schor, Nestor

2012-03-01

Several studies point out that pathophysiological changes related to stress may influence renal function and are associated with disease onset and evolution. However, we have not found any studies about the influence of stress on renal function and acute kidney injury. To evaluate the association between stressful life events and acute kidney injury diagnosis, specifying the most stressful classes of events for these patients in the past 12 months. Case-control study. The study was carried out at Hospital São Paulo, in Universidade Federal de São Paulo and at Hospital dos Servidores do Estado de São Paulo, in Brazil. Patients with acute kidney injury and no chronic disease, admitted to the intensive or semi-intensive care units were included. Controls included patients in the same intensive care units with other acute diseases, except for the acute kidney injury, and also with no chronic disease. Out of the 579 patients initially identified, 475 answered to the Social Readjustment Rating Scale (SRRS) questionnaire and 398 were paired by age and gender (199 cases and 199 controls). The rate of stressful life events was statistically similar between cases and controls. The logistic regression analysis to detect associated effects of the independent variables to the stressful events showed that: increasing age and economic classes A and B in one of the hospitals (Hospital São Paulo - UNIFESP) increased the chance of a stressful life event (SLE). This study did not show association between the Acute Kidney Injury Group with a higher frequency of stressful life events, but that old age, higher income, and type of clinical center were associated.
Magnetic entropy change and critical exponents in double perovskite Y2NiMnO6

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Sharma, G.; Tripathi, T. S.; Saha, J.; Patnaik, S.

2014-11-01

We report the magnetic entropy change (ΔSM) and the critical exponents in the double perovskite manganite Y2NiMnO6 with a ferromagnetic to paramagnetic transition TC~85 K. For a magnetic field change ΔH=80 kOe, a maximum magnetic entropy change ΔSM=-6.57 J/kg K is recorded around TC. The critical exponents β=0.363±0.05 and γ=1.331±0.09 obtained from power law fitting to spontaneous magnetization MS(T) and the inverse initial susceptibility χ0-1(T) satisfy well to values derived for a 3D-Heisenberg ferromagnet. The critical exponent δ=4.761±0.129 is determined from the isothermal magnetization at TC. The scaling exponents corresponding to second order phase transition are consistent with the exponents from Kouvel-Fisher analysis and satisfy Widom's scaling relation δ=1+(γ/β). Additionally, they also satisfy the single scaling equation M(H,ɛ)=ɛβf±(H/ɛ) according to which the magnetization-field-temperature data around TC should collapse into two curves for temperatures below and above TC.
Predicting Traffic Flow in Local Area Networks by the Largest Lyapunov Exponent

Directory of Open Access Journals (Sweden)

Yan Liu

2016-01-01

Full Text Available The dynamics of network traffic are complex and nonlinear, and chaotic behaviors and their prediction, which play an important role in local area networks (LANs, are studied in detail, using the largest Lyapunov exponent. With the introduction of phase space reconstruction based on the time sequence, the high-dimensional traffic is projected onto the low dimension reconstructed phase space, and a reduced dynamic system is obtained from the dynamic system viewpoint. Then, a numerical method for computing the largest Lyapunov exponent of the low-dimensional dynamic system is presented. Further, the longest predictable time, which is related to chaotic behaviors in the system, is studied using the largest Lyapunov exponent, and the Wolf method is used to predict the evolution of the traffic in a local area network by both Dot and Interval predictions, and a reliable result is obtained by the presented method. As the conclusion, the results show that the largest Lyapunov exponent can be used to describe the sensitivity of the trajectory in the reconstructed phase space to the initial values. Moreover, Dot Prediction can effectively predict the flow burst. The numerical simulation also shows that the presented method is feasible and efficient for predicting the complex dynamic behaviors in LAN traffic, especially for congestion and attack in networks, which are the main two complex phenomena behaving as chaos in networks.
Effects of a leisure programme on quality of life and stress of individuals with ASD.

Science.gov (United States)

García-Villamisar, D A; Dattilo, J

2010-07-01

Even though there is research demonstrating a positive relationship between leisure participation and the two constructs of quality of life and stress reduction, current conceptualisation of leisure as a contributor to quality of life is limited. In addition, in spite of improvements in accurate diagnosis of autism spectrum disorder (ASD) at increasingly earlier ages and proliferation of interventions, research associated with leisure and quality of life for people with ASD is lacking. Therefore, a study using a repeated measures design was used to measure effects of a 1-year group leisure programme intended to facilitate interaction with media, engagement in exercise, playing games and doing crafts, attending events, and participating in other recreation activities on quality of life and stress of 37 participants (22 male, 15 female), ages 17-39 (M = 31.49) years at the beginning of the programme) diagnosed with an ASD and a group of 34 adults with ASD as control group (waiting list) (19 male, 15 female), ages 24-38 (M = 30 at programme initiation) years. There was a significant decrease in overall scores of stress levels for participants over the course of the study and there was a significant increase in the four factors of quality of life that were measured (satisfaction, independence, competence and social interaction) as well as the total score for quality of life from baseline to the end of the intervention 12 months later. In contrast, the control group demonstrated no significant improvements related to stress or quality of life. Implications of these findings to leisure services and the quality of life of individuals with ASD are discussed. Findings support the contention that participation in recreation activities positively influenced the stress and quality of life of adults with ASD.
Hurst exponent: A Brownian approach to characterize the nonlinear behavior of red blood cells deformability

Science.gov (United States)

Mancilla Canales, M. A.; Leguto, A. J.; Riquelme, B. D.; León, P. Ponce de; Bortolato, S. A.; Korol, A. M.

2017-12-01

Ektacytometry techniques quantifies red blood cells (RBCs) deformability by measuring the elongation of suspended RBCs subjected to shear stress. Raw shear stress elongation plots are difficult to understand, thus most research papers apply data reduction methods characterizing the relationship between curve fitting. Our approach works with the naturally generated photometrically recorded time series of the diffraction pattern of several million of RBCs subjected to shear stress, and applies nonlinear quantifiers to study the fluctuations of these elongations. The development of new quantitative methods is crucial for restricting the subjectivity in the study of the cells behavior, mainly if they are capable of analyze at the same time biological and mechanical aspects of the cells in flowing conditions and compare their dynamics. A patented optical system called Erythrocyte Rheometer was used to evaluate viscoelastic properties of erythrocytes by Ektacytometry. To analyze cell dynamics we used the technique of Time Delay Coordinates, False Nearest Neighbors, the forecasting procedure proposed by Sugihara and May, and Hurst exponent. The results have expressive meaning on comparing healthy samples with parasite treated samples, suggesting that apparent noise associated with deterministic chaos can be used not only to distinguish but also to characterize biological and mechanical aspects of cells at the same time in flowing conditions.
Association of stressful life events with accelerated bone loss in older men: the Osteoporotic Fractures in Men (MrOS) Study

Science.gov (United States)

Fink, Howard A.; Kuskowski, Michael A.; Cauley, Jane A.; Taylor, Brent C.; Schousboe, John T.; Cawthon, Peggy M.; Ensrud, Kristine E.

2015-01-01

Purpose/Introduction Prior studies suggest that stressful life events may increase adverse health outcomes, including falls and possibly fractures. The current study builds on these findings and examines whether stressful life events are associated with increased bone loss. Methods 4388 men aged ≥65 years in the Osteoporotic Fractures in Men study completed total hip bone mineral density (BMD) measures at baseline and visit 2, approximately 4.6 years later, and self-reported stressful life events data mid-way between baseline and visit 2, and at visit 2. We used linear regression to model the association of stressful life events with concurrent annualized total hip BMD loss, and log binomial regression or Poisson regression to model risk of concurrent accelerated BMD loss (>1 SD more than mean annualized change). Results 75.3% of men reported ≥1 type of stressful life event, including 43.3% with ≥2 types of stressful life events. Mean annualized BMD loss was −0.36% (SD 0.88) and 13.9% of men were categorized with accelerated BMD loss (about 5.7% or more total loss). Rate of annualized BMD loss increased with the number of types of stressful life events after adjustment for age (pstressful life events (RR, 1.10 [95% CI, 1.04–1.16]) per increase of 1 type of stressful life event). Fracture risk was not significantly different between stressful life event-accelerated bone loss subgroups (p=0.08). Conclusions In these older men, stressful life events were associated with a small, dose-related increase in risk of concurrent accelerated hip bone loss. Low frequency of fractures limited assessment of whether rapid bone loss mediates any association of stressful life events with incident fractures. Future studies are needed to confirm these findings and to investigate the mechanism that may underlie this association. PMID:25169421
Perception of Life as Stressful, Not Biological Response to Stress, Is Associated with Greater Social Disability in Adults with Autism Spectrum Disorder

Science.gov (United States)

Bishop-Fitzpatrick, Lauren; Minshew, Nancy J.; Mazefsky, Carla A.; Eack, Shaun M.

2017-01-01

This study examined differences between adults with autism spectrum disorder (ASD; N = 40) and typical community volunteers (N = 25) on measures of stressful life events, perceived stress, and biological stress response (cardiovascular and cortisol reactivity) during a novel social stress task. Additional analyses examined the relationship between…

Intersection of Stress, Social Disadvantage, and Life Course Processes: Reframing Trauma and Mental Health.

Science.gov (United States)

Nurius, Paula S; Uehara, Edwina; Zatzick, Douglas F

2013-04-01

This paper describes the intersection of converging lines of research on the social structural, psychosocial, and physiological factors involved in the production of stress and implications for the field of mental health. Of particular interest are the stress sensitization consequences stemming from exposure to adversity over the life course. Contemporary stress sensitization theory provides important clinical utility in articulating mechanisms through which these multiple levels exert influence on mental health. Stress sensitization models (a) extend understanding of neurobiological and functional contexts within which extreme stressors operate and (b) make clear how these can influence psychologically traumatic outcomes. The value of interventions that are sensitive to current contexts as well as life course profiles of cumulative stress are illustrated through recent treatment innovations.
Stressful life events during pregnancy as risk factors for developing autistic disorder in children

Directory of Open Access Journals (Sweden)

Salman Abdi

2016-12-01

Full Text Available Introduction: This study aimed to examine the role of prenatal stressful events in mothers of children and adolescents with autistic disorder (AD. Methods: This case-control study was conducted in 2014. A total number of 115 children and adolescents with AD were selected by convenience method from the autism rehabilitation centers in Tabriz, Iran. Moreover, 112 typically developing (TD children and adolescents were selected from public schools using a random clustering method. Two groups were matched in terms of mother's and child's age and mother's educational level. The Kiddie Schedule for Affective Disorders and Schizophrenia (K-SADS semi-structured diagnostic interview was used to evaluate the presence of psychiatric disorders. The diagnosis of AD was made based on the DSM-IV criteria during separate diagnostic interviews by two child and adolescent psychiatrists. The life stressful events’ inventory was used to assess the presence of stressful events during pregnancy. Results: According to Fisher's exact test, the frequency of stressful life events including failure to achieve life goals, high debt, frequent marital conflict, conflict with spouse's family, changes in sleeping habits, and sexual difficulties in the mothers of AD children during pregnancy was significantly higher than the mothers of TD children. Also, mothers of AD children reported significantly higher frequency for the positive stressful life events including the major job progress, starting or finishing education, change of education, location, and summer vacation during pregnancy. Conclusion: Some stressful life events in mothers during pregnancy may be considered as risk factors for developing AD in their children. Further researches are needed to establish the results of this study.
Remaining life case history studies for high energy piping systems using equivalent stress

International Nuclear Information System (INIS)

Cohn, M.J.

1987-01-01

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

NARCIS (Netherlands)

Philips, Elise M.; Peeters, Babette; Teeuw, Arianne H.; Leenders, Arnold G. E.; Boluyt, Nicole; Brilleslijper-Kater, Sonja N.; Benninga, Marc A.

2015-01-01

The aim of the study was to determine the prevalence of stressful life events including (sexual) abuse in children with functional defecation disorders by performing a systematic review. We searched MEDLINE, EMBASE, and PsycINFO for cohort, case-control and cross-sectional studies investigating the
Effect of Stress Urinary Incontinence on the Sexual Function of Couples and the Quality of Life of Patients.

Science.gov (United States)

Lim, Renly; Liong, Men Long; Leong, Wing Seng; Khan, Nurzalina Abdul Karim; Yuen, Kah Hay

2016-07-01

Studies of the effects of stress urinary incontinence on the sexual function of couples are scarce. We prospectively evaluated couple sexual function and the relationship between sexual function and quality of life. We also compared quality of life in females with vs without stress urinary incontinence. Sexually active females at least 21 years old with or without stress urinary incontinence and their partners were recruited for study. To assess sexual function the couples completed GRISS (Golombok Rust Inventory of Sexual Satisfaction) and a 1-item question on overall sexual experience, "Over the past 4 weeks, how satisfied have you been with your overall sexual life?" Additionally, females completed ICIQ-LUTSqol (International Consultation on Incontinence Questionnaire-Lower Urinary Tract Symptoms Quality of Life) to assess quality of life. For sexual function assessment 66 of 134 couples with (49.3%) and 95 of 176 without (54.0%) stress urinary incontinence were recruited. Females with stress urinary incontinence had lower overall sexual function, lower frequency of sexual intercourse, less satisfaction (each p stress urinary incontinence had more problems with erectile dysfunction (p = 0.027), less satisfaction (p = 0.006) and lower frequency of sexual intercourse (p = 0.001) but no difference in overall GRISS score (p = 0.093). Couples with stress urinary incontinence had poorer overall sexual experience (p stress urinary incontinence had poorer quality of life than those without stress urinary incontinence (120 of 134, response rate 89.6% vs 145 of 176, response rate 82.4%, p life did not significantly correlate (r = 0.001, p = 0.997). Stress urinary incontinence in females is negatively associated not only with female quality of life and sexual function but also with partner sexual function. Copyright © 2016 American Urological Association Education and Research, Inc. Published by Elsevier Inc. All rights reserved.
A MONTE-CARLO METHOD FOR ESTIMATING THE CORRELATION EXPONENT

NARCIS (Netherlands)

MIKOSCH, T; WANG, QA

We propose a Monte Carlo method for estimating the correlation exponent of a stationary ergodic sequence. The estimator can be considered as a bootstrap version of the classical Hill estimator. A simulation study shows that the method yields reasonable estimates.
Early-Life Stress Triggers Juvenile Zebra Finches to Switch Social Learning Strategies.

Science.gov (United States)

Farine, Damien R; Spencer, Karen A; Boogert, Neeltje J

2015-08-17

Stress during early life can cause disease and cognitive impairment in humans and non-humans alike. However, stress and other environmental factors can also program developmental pathways. We investigate whether differential exposure to developmental stress can drive divergent social learning strategies between siblings. In many species, juveniles acquire essential foraging skills by copying others: they can copy peers (horizontal social learning), learn from their parents (vertical social learning), or learn from other adults (oblique social learning). However, whether juveniles' learning strategies are condition dependent largely remains a mystery. We found that juvenile zebra finches living in flocks socially learned novel foraging skills exclusively from adults. By experimentally manipulating developmental stress, we further show that social learning targets are phenotypically plastic. While control juveniles learned foraging skills from their parents, their siblings, exposed as nestlings to experimentally elevated stress hormone levels, learned exclusively from unrelated adults. Thus, early-life conditions triggered individuals to switch strategies from vertical to oblique social learning. This switch could arise from stress-induced differences in developmental rate, cognitive and physical state, or the use of stress as an environmental cue. Acquisition of alternative social learning strategies may impact juveniles' fit to their environment and ultimately change their developmental trajectories. Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.
The differential influence of life stress on individual symptoms of depression.

Science.gov (United States)

Fried, E I; Nesse, R M; Guille, C; Sen, S

2015-06-01

Life stress consistently increases the incidence of major depression. Recent evidence has shown that individual symptoms of major depressive disorder (MDD) differ in important dimensions such as their genetic and etiological background, but the impact of stress on individual MDD symptoms is not known. Here, we assess whether stress affects depression symptoms differentially. We used the chronic stress of medical internship to examine changes of the nine Diagnostic and Statistical Manual (DSM)-5 criterion symptoms for depression in 3021 interns assessed prior to and throughout internship. All nine depression symptoms increased in response to stress (all P stress (P Stress differentially affects the DSM-5 depressive symptoms. Analyses of individual symptoms reveal important insights obfuscated by sum-scores. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.
A cross-country comparative study on stress and quality of life in nursing students.

Science.gov (United States)

Labrague, Leodoro J; McEnroe-Petitte, Denise M; Papathanasiou, Ioanna V; Edet, Olaide B; Tsaras, Konstantinos; Christos, Kleisiaris F; Fradelos, Evangelos C; Rosales, Rheajane A; Cruz, Jonas P; Leocadio, Michael; Lucas, Katherine Vera S

2017-10-27

This study was conducted to compare perceptions of stress and quality of life (QoL) among nursing students from three countries (the Philippines, Greece, and Nigeria) and to examine the impact of stress on their QoL. A comparative, cross-sectional research design was used in this study. Data were collected from 547 nursing students from three countries using the perceived stress scale (PSS) and the quality of life evaluation skill (QOLES). Students' perceptions of stress and QoL were different across the three countries. Furthermore, higher stress perceptions were identified from taking care of patients, the clinical environment, and faculty, peer, and staff encounters, which predicted a negative QoL. The findings emphasized the need for empirically tested and culturally tailored interventions to effectively reduce stress and enhance the QoL in nursing students. © 2017 Wiley Periodicals, Inc.
Fractal characters and hurst exponent of radon exhalation rate from uranium Tailings

International Nuclear Information System (INIS)

Hu Hanqiao; Tan Kaixuan; Li Chunguang; Lv Junwen; Liu Dong

2010-01-01

The uranium tailings radon exhalation is an important environmental problem. The change of the radon exhalation rate of uranium tailings with the time through laboratory experiments is measured, and the results show that the radon exhalation rate of the tailings change obviously with time in non-periodic oscillations. Applying fractal analysis to the radon exhalation rate time-series data by R/S method, the Hurst exponent of the entire time series data is 0.83, the fractal dimension is 1.17. Mobile Hurst exponent is between 0.5 and 0.8 in most cases. The Hurst exponent of the experiments in the later part are below 0.5. The exhalation rate of uranium tailings radon does not meet the long-term trend of random walk theory, the radon exhalation rate has long-term memory, but the short-term memory is not distinct. The radon exhalation from uranium tailings is a deterministic chaotic dynamics. (authors)
Stress, lifestyle, and quality of life in midlife and older Australian women: results from the Stress and the Health of Women Study.

Science.gov (United States)

Seib, Charrlotte; Whiteside, Eliza; Lee, Kathryn; Humphreys, Janice; Tran, Tiet Hanh Dao; Chopin, Lisa; Anderson, Debra

2014-01-01

Chronic psychological stress may pose a serious threat to health, although the mechanisms are not fully understood. This study examines the impact of stress on modifiable lifestyle factors, depressive symptoms, health-related quality of life (HRQOL) and chronic illness in older Australian women. Cross-sectional data were collected from a random sample of 181 older adults aged 60 to 70 years from rural and urban areas of South-East Queensland, Australia. We used structural equation modelling to examine associations between stress, modifiable lifestyle factors, HRQOL, and chronic illness. Parameter estimates show that older women who reported life stressors where they felt helpless and feared for their life (high-magnitude stressors) also reported higher body mass index (p = .03) and more chronic illness (p unhealthy lifestyle factors. Findings highlight the need for more research on how stress reduction, a healthy lifestyle, and positive coping strategies can be used to reduce the effects of high-magnitude stress on HRQOL and chronic illness. Copyright © 2014 Jacobs Institute of Women's Health. Published by Elsevier Inc. All rights reserved.
Adolescent health, stress and life satisfaction: the paradox of indulgent parenting.

Science.gov (United States)

Coccia, Catherine; Darling, Carol A; Rehm, Marsha; Cui, Ming; Sathe, Shridhar K

2012-08-01

A survey of adolescents aged 15 to 16 years was used to examine the relationship between their perceptions of indulgent parenting and adolescent weight status to overall satisfaction with life, as associated with adolescent perceptions of body image, health and stress. In addition, perceptions of parental indulgence were examined in terms of their association with adolescent eating behaviours and health. The results revealed a paradox related to indulgent parenting, with both positive and negative outcomes for adolescents. Structural equation analyses showed that parental indulgence was not only related to lower stress and higher life satisfaction, but also to unhealthy eating behaviours. Path analysis indicated that both positive and negative eating outcomes for adolescents were related to parental indulgence. This research has many implications for both parent and adolescent health education, focusing on parenting styles, stress and healthy lifestyles. Copyright © 2011 John Wiley & Sons, Ltd.
Role of Virtues and Perceived Life Stress in Affecting Psychological Symptoms among Chinese College Students

Science.gov (United States)

Duan, Wenjie; Ho, Samuel M. Y.; Siu, Bowie P. Y.; Li, Tingting; Zhang, Yonghong

2015-01-01

Objective: This study explored the relationship among virtues, self-perceived life stress, and psychological symptoms. Participants: A total of 235 undergraduates participated in the study in March 2013. Methods: The participants were recruited to complete the Life Stress Rating Scale for College Students, the Chinese Virtues Questionnaire that…
The first experimental confirmation of the fractional kinetics containing the complex-power-law exponents: Dielectric measurements of polymerization reactions

Science.gov (United States)

Nigmatullin, R. R.; Arbuzov, A. A.; Salehli, F.; Giz, A.; Bayrak, I.; Catalgil-Giz, H.

2007-01-01

For the first time we achieved incontestable evidence that the real process of dielectric relaxation during the polymerization reaction of polyvinylpyrrolidone (PVP) is described in terms of the fractional kinetic equations containing complex-power-law exponents. The possibility of the existence of the fractional kinetics containing non-integer complex-power-law exponents follows from the general theory of dielectric relaxation that has been suggested recently by one of the authors (R.R.N). Based on the physical/geometrical meaning of the fractional integral with complex exponents there is a possibility to develop a general theory of dielectric relaxation based on the self-similar (fractal) character of the reduced (averaged) microprocesses that take place in the mesoscale region. This theory contains some essential predictions related to existence of the non-integer power-law kinetics and the results of this paper can be considered as the first confirmation of existence of the kinetic phenomena that are described by fractional derivatives with complex-power-law exponents. We want to stress here that with the help of a new complex fitting function for the complex permittivity it becomes possible to describe the whole process for real and imaginary parts simultaneously throughout the admissible frequency range (30 Hz-13 MHz). The fitting parameters obtained for the complex permittivity function for three temperatures (70, 90 and 110 °C) confirm in general the picture of reaction that was known qualitatively before. They also reveal some new features, which improve the interpretation of the whole polymerization process. We hope that these first results obtained in the paper will serve as a good stimulus for other researches to find the traces of the existence of new fractional kinetics in other relaxation processes unrelated to the dielectric relaxation. These results should lead to the reconsideration and generalization of irreversibility and kinetic phenomena that
The Effects of Early-Life Predator Stress on Anxiety- and Depression-Like Behaviors of Adult Rats

Directory of Open Access Journals (Sweden)

Lu-jing Chen

2014-01-01

Full Text Available Childhood emotional trauma contributes significantly to certain psychopathologies, such as post-traumatic stress disorder. In experimental animals, however, whether or not early-life stress results in behavioral abnormalities in adult animals still remains controversial. Here, we investigated both short-term and long-term changes of anxiety- and depression-like behaviors of Wistar rats after being exposed to chronic feral cat stress in juvenile ages. The 2-week predator stress decreased spontaneous activities immediately following stress but did not increase depression- or anxiety-like behaviors 4 weeks after the stimulation in adulthood. Instead, juvenile predator stress had some protective effects, though not very obvious, in adulthood. We also exposed genetic depression model rats, Wistar Kyoto (WKY rats, to the same predator stress. In WKY rats, the same early-life predator stress did not enhance anxiety- or depression-like behaviors in both the short-term and long-term. However, the stressed WKY rats showed slightly reduced depression-like behaviors in adulthood. These results indicate that in both normal Wistar rats and WKY rats, early-life predator stress led to protective, rather than negative, effects in adulthood.
The Effects of Early-Life Predator Stress on Anxiety- and Depression-Like Behaviors of Adult Rats

Science.gov (United States)

Chen, Lu-jing; Shen, Bing-qing; Liu, Dan-dan; Li, Sheng-tian

2014-01-01

Childhood emotional trauma contributes significantly to certain psychopathologies, such as post-traumatic stress disorder. In experimental animals, however, whether or not early-life stress results in behavioral abnormalities in adult animals still remains controversial. Here, we investigated both short-term and long-term changes of anxiety- and depression-like behaviors of Wistar rats after being exposed to chronic feral cat stress in juvenile ages. The 2-week predator stress decreased spontaneous activities immediately following stress but did not increase depression- or anxiety-like behaviors 4 weeks after the stimulation in adulthood. Instead, juvenile predator stress had some protective effects, though not very obvious, in adulthood. We also exposed genetic depression model rats, Wistar Kyoto (WKY) rats, to the same predator stress. In WKY rats, the same early-life predator stress did not enhance anxiety- or depression-like behaviors in both the short-term and long-term. However, the stressed WKY rats showed slightly reduced depression-like behaviors in adulthood. These results indicate that in both normal Wistar rats and WKY rats, early-life predator stress led to protective, rather than negative, effects in adulthood. PMID:24839560
Stress and Quality of Life in Urban Caregivers of Children With Poorly Controlled Asthma: A Longitudinal Analysis.

Science.gov (United States)

Bellin, Melissa H; Osteen, Philip; Kub, Joan; Bollinger, Mary E; Tsoukleris, Mona; Chaikind, Laurie; Butz, Arlene M

2015-01-01

The intent of this analysis was to examine the longitudinal effects of risk and protective factors on quality of life (QOL) in caregivers of minority children with asthma. Caregivers (n = 300) reported on demographics, child asthma characteristics, daily asthma caregiving stress, general life stress, social support, and QOL. Latent growth curve modeling examined changes in QOL across 12 months as a function of stress, asthma control, and social support. Caregivers were primarily the biological mother (92%), single (71%), unemployed (55%), and living in poverty. Children were African American (96%), Medicaid eligible (92%), and had poorly controlled asthma (93%). Lower QOL was associated with higher life stress, greater asthma caregiving stress, and lower asthma control over time. Findings underscore the importance of assessing objective and subjective measures of asthma burden and daily life stress in clinical encounters with urban, low-income caregivers of children with poorly controlled asthma. Copyright © 2015 National Association of Pediatric Nurse Practitioners. Published by Elsevier Inc. All rights reserved.
Alcohol craving in relation to coping with stress and satisfaction with life in the addicted

Directory of Open Access Journals (Sweden)

Krzysztof Gąsior

2015-10-01

Full Text Available Background The present study aimed at finding any relation between alcohol craving and strategies of coping with stress and satisfaction with life in the addicted. Until now, studies have shown that generalized deficits in coping with stress, and the dominance of avoidance strategies, are significantly related to the increase of the risk of addiction and the course of this disease. This relation, which could link strategies of coping with stress and quality of life with experiencing alcohol craving, has only been explained to a small extent. Also, the role of gender in explaining these relations is ambiguous. Participants and procedure The study was conducted in a group of 550 addicted subjects in out-patient or in-patient treatment (396 men and 114 women. In the present study the following instruments were used: the Craving Typology Questionnaire by Marinotti et al., the Yale-Brown Obsessive-Compulsive Drinking Scale by Modell et al., the Mini-Cope by Carver et al., SADD by Reistrick et al., and the Satisfaction with Life Scale by Diener et al. Statistical correlational analysis and structural equations were applied, namely partial least squares path modelling (PLS-PM. Results There are two types of links between craving and strategies of coping with stress among the addicted. The first dominating type is pointing at casual link between ineffective strategies of coping with stress and craving. The other weaker type indicates the diminishing influence of effective strategies of coping with stress on alcohol craving. Life satisfaction lowers alcohol craving. Conclusions Effective strategies of reacting to stress, together with life satisfaction, protect against increase of alcohol craving. Severity of dependence is an important factor which moderates the influence of strategies of coping with stress on alcohol craving.
The relative impact of work-related stress, life stress and driving environment stress on driving outcomes.

Science.gov (United States)

Rowden, Peter; Matthews, Gerald; Watson, Barry; Biggs, Herbert

2011-07-01

Previous research has shown the association between stress and crash involvement. The impact of stress on road safety may also be mediated by behaviours including cognitive lapses, errors, and intentional traffic violations. This study aimed to provide a further understanding of the impact that stress from different sources may have upon driving behaviour and road safety. It is asserted that both stress extraneous to the driving environment and stress directly elicited by driving must be considered part of a dynamic system that may have a negative impact on driving behaviours. Two hundred and forty-seven public sector employees from Queensland, Australia, completed self-report measures examining demographics, subjective work-related stress, daily hassles, and aspects of general mental health. Additionally, the Driver Behaviour Questionnaire (DBQ) and the Driver Stress Inventory (DSI) were administered. All participants drove for work purposes regularly, however the study did not specifically focus on full-time professional drivers. Confirmatory factor analysis of the predictor variables revealed three factors: DSI negative affect; DSI risk taking; and extraneous influences (daily hassles, work-related stress, and general mental health). Moderate intercorrelations were found between each of these factors confirming the 'spillover' effect. That is, driver stress is reciprocally related to stress in other domains including work and domestic life. Structural equation modelling (SEM) showed that the DSI negative affect factor influenced both lapses and errors, whereas the DSI risk-taking factor was the strongest influence on violations. The SEMs also confirmed that daily hassles extraneous to the driving environment may influence DBQ lapses and violations independently. Accordingly, interventions may be developed to increase driver awareness of the dangers of excessive emotional responses to both driving events and daily hassles (e.g. driving fast to 'blow off steam
Midwifery and nursing students' communication skills and life orientation: correlation with stress coping approaches.

Science.gov (United States)

Ozdemir, Gülsün; Kaya, Hatice

2013-06-01

Methods learnt by nursing and midwifery students' such as communication skills, optimisim and coping with stress would be used in their profeesional life. It is very important to promote their positive thinking and communication skills to raise coping with stress. This cross sectional study was performed to examine the nursing and midwifery students' communication skills and optimistic life orientation and its correlation with coping strategies with stress. The study population included 2572 students who were studying in departments of nursing and midwifery in Istanbul. The sample was included 1419 students. Three questionnaires including Communication Skills Test, Life Orientation Test and Ways of Coping Inventory were used for data collection. The data were evaluated by calculating frequency, percentage, arithmetic mean, standard deviation and Pearson correlation coefficient. Students' total mean score from the Communication Skills Scale was 165.27 ± 15.39 and for the Life Orientation Test was 18.51 ± 4.54. There was a positive correlation between their Life Orientation scores and the scores for self confidence (r = 0.34, P students in optimistic life orientation and communication skills increased self confidence approach, optimistic, and social support seeking scores increased, whereas helpless, and submissive scores decreased.

High novelty-seeking rats are resilient to negative physiological effects of the early life stress.

Science.gov (United States)

Clinton, Sarah M; Watson, Stanley J; Akil, Huda

2014-01-01

Exposure to early life stress dramatically impacts adult behavior, physiology, and neuroendocrine function. Using rats bred for novelty-seeking differences and known to display divergent anxiety, depression, and stress vulnerability, we examined the interaction between early life adversity and genetic predisposition for high- versus low-emotional reactivity. Thus, bred Low Novelty Responder (bLR) rats, which naturally exhibit high anxiety- and depression-like behavior, and bred High Novelty Responder (bHR) rats, which show low anxiety/depression together with elevated aggression, impulsivity, and addictive behavior, were subjected to daily 3 h maternal separation (MS) stress postnatal days 1-14. We hypothesized that MS stress would differentially impact adult bHR/bLR behavior, physiology (stress-induced defecation), and neuroendocrine reactivity. While MS stress did not impact bHR and bLR anxiety-like behavior in the open field test and elevated plus maze, it exacerbated bLRs' already high physiological response to stress - stress-induced defecation. In both tests, MS bLR adult offspring showed exaggerated stress-induced defecation compared to bLR controls while bHR offspring were unaffected. MS also selectively impacted bLRs' (but not bHRs') neuroendocrine stress reactivity, producing an exaggerated corticosterone acute stress response in MS bLR versus control bLR rats. These findings highlight how genetic predisposition shapes individuals' response to early life stress. Future work will explore neural mechanisms underlying the distinct behavioral and neuroendocrine consequences of MS in bHR/bLR animals.
Neighborhood Disadvantage, Stressful Life Events, and Adjustment among Mexican American Early Adolescents

Science.gov (United States)

Roosa, Mark W.; Burrell, Ginger L.; Nair, Rajni L.; Coxe, Stefany; Tein, Jenn-Yun; Knight, George P.

2010-01-01

This study examined a stress process model in which stressful life events and association with delinquent peers mediated the relationship of neighborhood disadvantage to Mexican American early adolescents' mental health. The authors also proposed that child gender, child generation, and neighborhood informal social control would moderate the…
Explanation of the values of Hack's drainage basin, river length scaling exponent

Science.gov (United States)

Hunt, A. G.

2015-08-01

Percolation theory can be used to find water flow paths of least resistance. The application of percolation theory to drainage networks allows identification of the range of exponent values that describe the tortuosity of rivers in real river networks, which is then used to generate the observed scaling between drainage basin area and channel length, a relationship known as Hack's law. Such a theoretical basis for Hack's law allows interpretation of the range of exponent values based on an assessment of the heterogeneity of the substrate.
Stressful life events are associated with a poor in vitro fertilization (IVF) - outcome: a prospective study

DEFF Research Database (Denmark)

Ebbesen, Signe Maria Schneevoigt; Zachariae, Robert; Mehlsen, Mimi Yung

2009-01-01

-fertility-related, naturally occurring stressors may influence IVF pregnancy chances. Our aim was to explore the association between IVF-outcome and negative, i.e. stressful, life-events during the previous 12 months. METHODS: Prior to IVF, 809 women (mean age: 31.2 years) completed the List of Recent Events (LRE...... number of life-events perceived as having a negative impact on quality of life may indicate chronic stress, and the results of our study indicate that stress may reduce the chances of a successful outcome following IVF, possibly through psychobiological mechanisms affecting medical end...
Effects of stress concentrations on the fatigue life of a gamma based titanium aluminide

International Nuclear Information System (INIS)

Trail, S.J.; Bowen, P.

1995-01-01

S-N curves for a gamma based titanium aluminide alloy of composition Ti-47.2Al-2.1Mn-1.9Nb(at.%)+2TiB 2 (wt.%) have been used to define fatigue life. Effects of residual stress, stressed volume, loading ratio, loading mode, elevated temperature and surface roughness have been considered. Residual tensile stresses and micro-cracking are introduced by Electro Discharge Machining and the fatigue life is reduced slightly compared with polished samples. Notched fatigue tests show a significant notch strengthening effect which increases with increasing stress concentration factor. The fracture surfaces of specimens tested at room temperature reveal fully brittle failure mechanisms and no evidence of stable crack growth is observed. The fatigue life appears, therefore, to be determined predominantly by the number of cycles to crack initiation. At the elevated temperature of 830 C, evidence for some stable fatigue crack growth has been found. Probable sites for crack initiation are addressed
Density-scaling exponents and virial potential-energy correlation ...

Indian Academy of Sciences (India)

This paper investigates the relation between the density-scaling exponent γ and the virial potential energy correlation coefficient R at several thermodynamic state points in three dimensions for the generalized (2n, n) Lennard-Jones (LJ) system for n = 4, 9, 12, 18, as well as for the standard n = 6 LJ system in two,three, and ...
Spectrum-based estimators of the bivariate Hurst exponent

Czech Academy of Sciences Publication Activity Database

Krištoufek, Ladislav

2014-01-01

Roč. 90, č. 6 (2014), art. 062802 ISSN 1539-3755 R&D Projects: GA ČR(CZ) GP14-11402P Institutional support: RVO:67985556 Keywords : bivariate Hurst exponent * power- law cross-correlations * estimation Subject RIV: AH - Economics Impact factor: 2.288, year: 2014 http://library.utia.cas.cz/separaty/2014/E/kristoufek-0436818.pdf
Life events and stress: do older men and women in Malaysia cope differently as consumers?

Science.gov (United States)

Ong, Fon Sim; Phillips, David R; Chai, Sen Tyng

2013-06-01

The study of major life events and their effects on well-being has considerable relevance for scientific disciplines and policy making in understanding the consumer behaviour of older people. There is evidence of differences in reactions to and coping with stress between males and females but relatively little knowledge about such gender differences amongst older people, especially in middle-income countries. This study of older Malaysians looked at both coping strategies and gender differences in reactions to stress when people are confronted with certain life events. Seventeen major life events were used in interviews with 645 respondents aged 50 years or older in five major urban areas in Peninsular Malaysia. The analysis showed older women tended to experience higher levels of chronic stress than older men. They also had more health problems, had lower levels of self-esteem and were less satisfied with life. Whilst the results showed little support for gender differences in coping behaviours, stress had a significant influence on the way older men and women change store preferences. A hypothesis that older women would use more emotion-focused coping strategies was not supported. Knowledge of how older Malaysians cope with life events and stress and especially in this instance with regard to consumption behaviour, is likely to be of considerable academic and policy related interest.
Association between serotonin 2A receptor genetic variations, stressful life events and suicide.

Science.gov (United States)

Ghasemi, Asghar; Seifi, Morteza; Baybordi, Fatemeh; Danaei, Nasim; Samadi Rad, Bahram

2018-06-05

Life events are series of events that disrupt a person's psychological equilibrium and may enhance the development of a disorder such as suicide. Several studies have assessed a relationship between 5-hydroxytryptamine (serotonin) 2A receptor (5-HTR2A) gene polymorphisms with an increased risk of suicide. However, there has been no study about the association between three 5-HTR2A gene polymorphisms, A1438G (rs6311), T102C (rs6313) and C1354T (rs6314), suicide, stressful life, and loss events in a same time. Relatives of 191 suicide victims were interviewed using a semi-structured questionnaire designed according to Iranian culture. Venous blood was taken from all subjects for DNA isolation. 5-HTR2A polymorphisms in a total of 191 suicide victims and 218 healthy controls were genotyped using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Chi-squared and Fisher's exact tests were used to compare genotype and allele frequencies between suicide and control groups. Correction for multiple comparisons was calculated using Bonferroni correction. There was a significant association between the 102 C/C genotype of 5-HTR2A gene and suicide (к 2  = 8.700, P = 0.012). Furthermore, we found that suicide victims with a 102 C/C genotype had a significantly higher number of stressful life and loss events (P suicide victims and control participants and there was no association between genotype distribution and higher number of stressful life and loss events (P > 0.05). Our results suggest that C102T (rs6313) polymorphism of 5-HTR2A gene may be involved in the susceptibility to suicide, higher number of stressful life and loss events, but A1438G (rs6311) and C1354T (rs6314) polymorphisms of 5-HTR2A gene were not associated with suicide, higher number of stressful life and loss events. Copyright © 2018 Elsevier B.V. All rights reserved.
Green space as a buffer between stressful life events and health.

Science.gov (United States)

van den Berg, Agnes E; Maas, Jolanda; Verheij, Robert A; Groenewegen, Peter P

2010-04-01

This study investigates whether the presence of green space can attenuate negative health impacts of stressful life events. Individual-level data on health and socio-demographic characteristics were drawn from a representative two-stage sample of 4529 Dutch respondents to the second Dutch National Survey of General Practice (DNSGP-2), conducted in 2000-2002. Health measures included: (1) the number of health complaints in the last 14 days; (2) perceived mental health (measured by the GHQ-12); and (3) a single item measure of perceived general health ranging from 'excellent' to 'poor'. Percentages of green space in a 1-km and 3-km radius around the home were derived from the 2001 National Land cover Classification database (LGN4). Data were analysed using multilevel regression analysis, with GP practices as the group-level units. All analyses were controlled for age, gender, income, education level, and level of urbanity. The results show that the relationships of stressful life events with number of health complaints and perceived general health were significantly moderated by amount of green space in a 3-km radius. Respondents with a high amount of green space in a 3-km radius were less affected by experiencing a stressful life event than respondents with a low amount of green space in this radius. The same pattern was observed for perceived mental health, although it was marginally significant. The moderating effects of green space were found only for green space within 3 km, and not for green space within 1 km of residents' homes, presumably because the 3-km indicator is more affected by the presence of larger areas of green space, that are supposed to sustain deeper forms of restoration. These results support the notion that green space can provide a buffer against the negative health impact of stressful life events. Copyright 2010 Elsevier Ltd. All rights reserved.
The interplay of early-life stress, nutrition, and immune activation programs adult hippocampal structure and function

Science.gov (United States)

Hoeijmakers, Lianne; Lucassen, Paul J.; Korosi, Aniko

2015-01-01

Early-life adversity increases the vulnerability to develop psychopathologies and cognitive decline later in life. This association is supported by clinical and preclinical studies. Remarkably, experiences of stress during this sensitive period, in the form of abuse or neglect but also early malnutrition or an early immune challenge elicit very similar long-term effects on brain structure and function. During early-life, both exogenous factors like nutrition and maternal care, as well as endogenous modulators, including stress hormones and mediator of immunological activity affect brain development. The interplay of these key elements and their underlying molecular mechanisms are not fully understood. We discuss here the hypothesis that exposure to early-life adversity (specifically stress, under/malnutrition and infection) leads to life-long alterations in hippocampal-related cognitive functions, at least partly via changes in hippocampal neurogenesis. We further discuss how these different key elements of the early-life environment interact and affect one another and suggest that it is a synergistic action of these elements that shapes cognition throughout life. Finally, we consider different intervention studies aiming to prevent these early-life adversity induced consequences. The emerging evidence for the intriguing interplay of stress, nutrition, and immune activity in the early-life programming calls for a more in depth understanding of the interaction of these elements and the underlying mechanisms. This knowledge will help to develop intervention strategies that will converge on a more complete set of changes induced by early-life adversity. PMID:25620909
New prediction of chaotic time series based on local Lyapunov exponent

International Nuclear Information System (INIS)

Zhang Yong

2013-01-01

A new method of predicting chaotic time series is presented based on a local Lyapunov exponent, by quantitatively measuring the exponential rate of separation or attraction of two infinitely close trajectories in state space. After reconstructing state space from one-dimensional chaotic time series, neighboring multiple-state vectors of the predicting point are selected to deduce the prediction formula by using the definition of the local Lyapunov exponent. Numerical simulations are carried out to test its effectiveness and verify its higher precision over two older methods. The effects of the number of referential state vectors and added noise on forecasting accuracy are also studied numerically. (general)
An Isomorphism between Lyapunov Exponents and Shannon's Channel Capacity

Energy Technology Data Exchange (ETDEWEB)

Friedland, Gerald [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Metere, Alfredo [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

2017-06-07

We demonstrate that discrete Lyapunov exponents are isomorphic to numeric overflows of the capacity of an arbitrary noiseless and memoryless channel in a Shannon communication model with feedback. The isomorphism allows the understanding of Lyapunov exponents in terms of Information Theory, rather than the traditional definitions in chaos theory. The result also implies alternative approaches to the calculation of related quantities, such as the Kolmogorov Sinai entropy which has been linked to thermodynamic entropy. This work provides a bridge between fundamental physics and information theory. It suggests, among other things, that machine learning and other information theory methods can be employed at the core of physics simulations.
Life satisfaction in people with post-traumatic stress disorder.

Science.gov (United States)

Karatzias, Thanos; Chouliara, Zoë; Power, Kevin; Brown, Keith; Begum, Millia; McGoldrick, Therese; MacLean, Rory

2013-12-01

There is limited research on the association between post-traumatic stress disorder (PTSD) and life satisfaction in community samples. We set out to investigate levels of life satisfaction and its demographic, trauma related and clinical predictors in a sample of people with PTSD (n = 46). Participants completed a battery of standardised self-report measures including Satisfaction with Life Scale, the PTSD Checklist and The Hospital Anxiety and Depression Scale. Our results indicated that people with moderately severe PTSD in the community are likely to experience lower levels of life satisfaction compared with those with other psychiatric conditions or those without any diagnoses. Multivariate analysis revealed that marital status and trauma symptoms were the only significant predictors of life satisfaction. In specific, being married and presenting with less severe posttraumatic symptomatology were both significantly associated with higher levels of life satisfaction in people with PTSD. The strong association between traumatic symptomatology and life satisfaction may indicate that routine assessment for life satisfaction or similar positive constructs in people with PTSD, referred for psychological therapies might be useful. Information on positive psychology constructs may facilitate capitalising on clients' strengths and not just on pathology.
Episodic Life Stress and the Development of Overgeneral Autobiographical Memory to Positive Cues in Youth.

Science.gov (United States)

Feurer, Cope; Woody, Mary L; Tsypes, Aliona; Burkhouse, Katie L; Champagne, Katelynn; Gibb, Brandon E

2018-02-15

Overgeneral autobiographical memory (OGM) has been established as a risk factor for depression in both youth and adults, but questions remain as to how OGM develops. Although theorists have proposed that the experience of stressful life events may contribute to the development of OGM, no studies have examined the impact of negative life events on prospective changes in OGM. The goal of the current study was to address this gap in the literature. Participants included 251 mothers and their biological children (aged 8-14 years old at the initial assessment). Using a multi-wave prospective design with assessments every 6 months for 2 years, we found that episodic life stress predicted prospective decreases in youths' autobiographical memory specificity to positive, but not negative, cues. This study supports theories proposing that negative life events may contribute to the development of OGM, but suggest that, in youth, the impact of life stress on OGM may be specific to positive rather than negative memories.
[Psychological stress and quality of life in patients with persistent asthma in Manzanillo, Cuba].

Science.gov (United States)

Rodríguez Rodríguez, María; Rodríguez Sánchez, Pedro Manuel; Brocard Arencibia, Ileana; Menéndez Porto, Lourdes

2014-07-30

Psychological stress is part of people's lives and can sometimes contribute to exacerbation of allergic diseases such as asthma. Asthma is prevalent in all age groups. Acute asthma attacks can be triggered by stress, thus impacting control of the disease and overall quality of life in these patients. The purpose of this study is to evaluate the presence of psychological stress as a trigger in poorly controlled asthma patients and its implications in their quality of life. A descriptive study was conducted in the city of Manzanillo, Cuba, in the course of one year, from January to December, 2010, which included 33 patients with persistent asthma. They were grouped according to severity as suffering from moderate or severe asthma, and all of them met the criteria for poorly controlled disease. They were surveyed to gather data about family and personal history of atopy, age of first asthma crisis, and environmental as well as other factors. Two surveys were used: a list of indicators of vulnerability to stress and the Asthma Quality of Life Questionnaire (AQLQ). Most patients with poorly controlled asthma were in their forties. Female patients were more frequently affected than men were (28 females or 84.8%, and 5 males or 15.1%), and most patients had a family history of atopic disease. Almost all patients had high vulnerability to stress as well as low overall quality of life in all the areas surveyed. Psychological counseling is advised for asthma patients in order to reduce their stress levels.
Prenatal stress may increase vulnerability to life events comparison with the effects of prenatal dexamethasone

DEFF Research Database (Denmark)

Hougaard, Karin; Andersen, Maibritt B; Kjaer, Sanna L

2005-01-01

naïve at the time of ASR testing, whereas the other had been through blood sampling for assessment of the hormonal stress response to restraint, 3 months previously. Both prenatal CMS and dexamethasone increased ASR in the offspring compared to controls, but only in prenatally stressed offspring......Prenatal stress has been associated with a variety of alterations in the offspring. The presented observations suggest that rather than causing changes in the offspring per se, prenatal stress may increase the organism's vulnerability to aversive life events. Offspring of rat dams stressed...... of the acoustic startle response. Further, a single aversive life event showed capable of changing the reactivity of prenatally stressed offspring, whereas offspring of dams going through a less stressful gestation was largely unaffected by this event. This suggests that circumstances dating back to the very...
[The relationship between stress and life-style of students at the Faculty of Medicine of Oporto].

Science.gov (United States)

Loureiro, Elizabete; McIntyre, Teresa; Mota-Cardoso, Rui; Ferreira, Maria Amélia

2008-01-01

Different studies have demonstrated that there are significant changes in the health and habits/life-style of university students, and it seems that Medical students also reveal a significant vulnerability to the adoption of health risk behaviours. The present study aims to (1) characterize the main sources of academic stress of the Medical School students of the University of Porto as well as the intensity with which they are experienced, (2) investigate the variations in academic stress and psychosocial variables, due to gender, year of course and displacement from home and (3) contribute, for the first time, to the understanding of stress and life-style of medical students in Portugal. The empirical study included a sample of 251 students from all 6 years of the course (160 females and 91 males), evaluated by the following instruments: (1) The Inventory of Sources of Academic Stress in Medical Education (ISASME), and the Portuguese versions of (2) the Brief Personal Survey (BPS), (3) the General Health Questionnaire 12 (GHQ-12), and (4) the Interpersonal Behaviour Survey-Brief (ICIBrief). In terms of overall levels of stress (GHQ-12), a prevalence of 58.2% of clinically significant stress symptoms was found, with the students from the basic cycle and those who are living away from home, presenting higher levels of stress. In terms of life-style, 47% of the students revealed health risk behaviours, with eating habits, physical exercise, alcohol and drug consumption, and body image being the main problem areas. Gender and year of course seem to have a significant influence on the variables studied, being the female students those who present higher levels of academic stress, stress responses (pressure/overload, physical distress, anxiety, anger/frustration, inefficiency, depression and loss of control), and low levels of coping confidence; the students of the basic cycle reveal higher levels of stress in managing their life-style (academic stress), general stress
Effects of loading sequences and size of repeated stress block of loads on fatigue life calculated using fatigue functions

International Nuclear Information System (INIS)

Schott, G.

1989-01-01

It is well-known that collective form, stress intensity and loading sequence of individual stresses as well as size of repeated stress blocks can influence fatigue life, significantly. The basic variant of the consecutive Woehler curve concept will permit these effects to be involved into fatigue life computation. The paper presented will demonstrate that fatigue life computations using fatigue functions reflect the loading sequence effect with multilevel loading precisely and provide reliable fatigue life data. Effects of size of repeated stress block and loading sequence on fatigue life as observed with block program tests can be reproduced using the new computation method. (orig.) [de
THE COMBINED EFFECTS OF STRESS CONCENTRATION AND TENSILE STRESSES FROM AUTOFRETTAGE ON THE LIFE OF PRESSURE VESSELS

Science.gov (United States)

2017-02-22

information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing ... hydraulically or mechanically overstrained in order to impart favorable near bore residual compressive hoop stresses in an attempt to enhance fatigue life. As a...detrimental. In the early stages of development of each system, multiple full size vessels are hydraulically fatigue tested and a safe life is

Social support buffers the effect of interpersonal life stress on suicidal ideation and self-injury during adolescence.

Science.gov (United States)

Mackin, D M; Perlman, G; Davila, J; Kotov, R; Klein, D N

2017-04-01

The effect of life stress on suicidal symptoms during adolescence is well documented. Stressful life events can trigger suicidality, but most adolescents are resilient and it is unclear which factors protect against the deleterious impact of stress. Social support is thought to be one such factor. Therefore, we investigated the buffering effect of specific sources of social support (parental and peer) on life stress (interpersonal and non-interpersonal) in predicting suicidal symptoms during adolescence. In order to test the specificity of this stress buffering, we also examined it with regard to dysphoric mood. Data come from the Adolescent Development of Emotions and Personality Traits (ADEPT) Project, a cohort of 550 adolescent females aged 13.5-15.5 recruited from Long Island. Self-reported social support, suicidality, and dysphoria were assessed at baseline and suicidality and dysphoria were assessed again at 9-month follow-up. Life stress was assessed by interview at the follow-up. High levels of parental support protected adolescent girls from developing suicidal symptoms following a stressor. This effect was less pronounced for peer support. Also, social support did not buffer the pathogenic effects of non-interpersonal stress. Finally, social support did not buffer the effect of life stress on dysphoric symptoms. Altogether, our results highlight a distinct developmental pathway for the development of suicidal symptoms involving parental support that differs from the development of dysphoria, and signifies the importance and specificity of social support in protecting against suicidality in adolescent girls.
Fatigue life prediction method for contact wire using maximum local stress

Energy Technology Data Exchange (ETDEWEB)

Kim, Yong Seok; Haochuang, Li; Seok, Chang Sung; Koo, Jae Mean [Sungkyunkwan University, Suwon (Korea, Republic of); Lee, Ki Won; Kwon, Sam Young; Cho, Yong Hyeon [Korea Railroad Research Institute, Uiwang (Korea, Republic of)

2015-01-15

Railway contact wires supplying electricity to trains are exposed to repeated mechanical strain and stress caused by their own weight and discontinuous contact with a pantograph during train operation. Since the speed of railway transportation has increased continuously, railway industries have recently reported a number of contact wire failures caused by mechanical fatigue fractures instead of normal wear, which has been a more common failure mechanism. To secure the safety and durability of contact wires in environments with increased train speeds, a bending fatigue test on contact wire has been performed. The test equipment is too complicated to evaluate the fatigue characteristics of contact wire. Thus, the axial tension fatigue test was performed for a standard specimen, and the bending fatigue life for the contact wire structure was then predicted using the maximum local stress occurring at the top of the contact wire. Lastly, the tested bending fatigue life of the structure was compared with the fatigue life predicted by the axial tension fatigue test for verification.
Fatigue life prediction method for contact wire using maximum local stress

International Nuclear Information System (INIS)

Kim, Yong Seok; Haochuang, Li; Seok, Chang Sung; Koo, Jae Mean; Lee, Ki Won; Kwon, Sam Young; Cho, Yong Hyeon

2015-01-01

Railway contact wires supplying electricity to trains are exposed to repeated mechanical strain and stress caused by their own weight and discontinuous contact with a pantograph during train operation. Since the speed of railway transportation has increased continuously, railway industries have recently reported a number of contact wire failures caused by mechanical fatigue fractures instead of normal wear, which has been a more common failure mechanism. To secure the safety and durability of contact wires in environments with increased train speeds, a bending fatigue test on contact wire has been performed. The test equipment is too complicated to evaluate the fatigue characteristics of contact wire. Thus, the axial tension fatigue test was performed for a standard specimen, and the bending fatigue life for the contact wire structure was then predicted using the maximum local stress occurring at the top of the contact wire. Lastly, the tested bending fatigue life of the structure was compared with the fatigue life predicted by the axial tension fatigue test for verification.
The effects of teaching stress management skills on the quality of life in ICU nurses

Directory of Open Access Journals (Sweden)

FARIBA GHODSBIN

2013-07-01

Full Text Available Introduction: Job stress is one of the main factors in decreasing productivity in organizations and the leading cause of psychosomatic disorders in personnel. Since job stress of nurses working in Intensive Care Units (ICUs is considered as an important segment in health and medical systems, it significantly affects the quality of care and the nurse’s quality of life. To this end, the purpose of this research is to examine the effects of teaching stress management skills on the quality of life of the nurses working at ICU of the hospitals affiliated to Shiraz University of Medical Sciences. Methods: The subjects of the study consisted of 60 ICU nurses with the average stress score in Osipow job stress exam working at the hospitals affiliated to Shiraz University of Medical Sciences. The subjects were randomly assigned to two groups (30 in the case and 30 in the control group. The intervention was performed as a teaching stress management workshop for eight hours throughout two-days (four hours per day, and the nurses were followed up for two months. The data were collected through a two part questionnaire including demographic characteristics and WHO Quality of life BREF and were analyzed in SPSS software using paired t test, and t-test. Results: The findings showed that the nurses of both the case and control groups were homogeneous considering the demographic data such as age, sex, marital status, number of children, shift position, job satisfaction, number of working hours per week, work experience and the amount of income. Moreover, there was no significant difference between the mean score of the life quality before the intervention in both groups. But after the intervention, a significant increase was revealed in the mean score of the life quality of the case group as compared to that of the control group (P<0.0001. Conclusion: The findings revealed the efficacy of the stress management workshop in improving the life quality of ICU
a Comparison of Three Hurst Exponent Approaches to Predict Nascent Bubbles in S&P500 Stocks

Science.gov (United States)

Fernández-Martínez, M.; Sánchez-Granero, M. A.; Muñoz Torrecillas, M. J.; McKelvey, Bill

Since the pioneer contributions due to Vandewalle and Ausloos, the Hurst exponent has been applied by econophysicists as a useful indicator to deal with investment strategies when such a value is above or below 0.5, the Hurst exponent of a Brownian motion. In this paper, we hypothesize that the self-similarity exponent of financial time series provides a reliable indicator for herding behavior (HB) in the following sense: if there is HB, then the higher the price, the more the people will buy. This will generate persistence in the stocks which we shall measure by their self-similarity exponents. Along this work, we shall explore whether there is some connections between the self-similarity exponent of a stock (as a HB indicator) and the stock’s future performance under the assumption that the HB will last for some time. With this aim, three approaches to calculate the self-similarity exponent of a time series are compared in order to determine which performs best to identify the transition from random efficient market behavior to HB and hence, to detect the beginning of a bubble. Generalized Hurst Exponent, Detrended Fluctuation Analysis, and GM2 algorithms have been tested. Traditionally, researchers have focused on identifying the beginning of a crash. We study the beginning of the transition from efficient market behavior to a market bubble, instead. Our empirical results support that the higher (respectively the lower) the self-similarity index, the higher (respectively the lower) the mean of the price change, and hence, the better (respectively the worse) the performance of the corresponding stock. This would imply, as a consequence, that the transition process from random efficient market to HB has started. For experimentation purposes, S&P500 stock Index constituted our main data source.
ACCURATE ESTIMATES OF CHARACTERISTIC EXPONENTS FOR SECOND ORDER DIFFERENTIAL EQUATION

Institute of Scientific and Technical Information of China (English)

无

2009-01-01

In this paper, a second order linear differential equation is considered, and an accurate estimate method of characteristic exponent for it is presented. Finally, we give some examples to verify the feasibility of our result.
Large $N$ critical exponents for the chiral Heisenberg Gross-Neveu universality class

OpenAIRE

Gracey, J. A.

2018-01-01

We compute the large N critical exponents η, ηϕ and 1/ν in d dimensions in the chiral Heisenberg Gross-Neveu model to several orders in powers of 1/N. For instance, the large N conformal bootstrap method is used to determine η at O(1/N3) while the other exponents are computed to O(1/N2). Estimates of the exponents for a phase transition in graphene are given which are shown to be commensurate with other approaches. In particular the behavior of the exponents in 2
Stressful life transitions and wellbeing: A comparison of the stress buffering hypothesis and the social identity model of identity change.

Science.gov (United States)

Praharso, Nurul F; Tear, Morgan J; Cruwys, Tegan

2017-01-01

The relationship between stressful life transitions and wellbeing is well established, however, the protective role of social connectedness has received mixed support. We test two theoretical models, the Stress Buffering Hypothesis and the Social Identity Model of Identity Change, to determine which best explains the relationship between social connectedness, stress, and wellbeing. Study 1 (N=165) was an experiment in which participants considered the impact of moving cities versus receiving a serious health diagnosis. Study 2 (N=79) was a longitudinal study that examined the adjustment of international students to university over the course of their first semester. Both studies found limited evidence for the buffering role of social support as predicted by the Stress Buffering Hypothesis; instead people who experienced a loss of social identities as a result of a stressor had a subsequent decline in wellbeing, consistent with the Social Identity Model of Identity Change. We conclude that stressful life events are best conceptualised as identity transitions. Such events are more likely to be perceived as stressful and compromise wellbeing when they entail identity loss. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.
Common stressful life events and difficulties are associated with mental health symptoms and substance use in young adolescents

Directory of Open Access Journals (Sweden)

Low Nancy CP

2012-08-01

Full Text Available Abstract Background Stressful life events are associated with mood disorders in adults in clinical settings. Less described in the literature is the association between common life stressors and a wide range of psychopathology in young adolescents. This study uses a large non-clinical sample of young adolescents to describe the associations among worry or stress about common life events/difficulties, mental health and substance use. Methods Data on lifetime stress or worry about common life events/difficulties (i.e., romantic breakups, family disruption, interpersonal difficulties, and personal stress (health, weight, school work, symptoms of depression, conduct disorder symptoms, and substance use were collected from 1025 grade 7 students (mean age 12.9 years; 45% male. The association between each source of stress and each mental health and substance use indicator was modeled in separate logistic regression analyses. Results The proportion of adolescents reporting worry or stress ranged from 7% for new family to 53% for schoolwork. Romantic breakup stress was statistically significantly associated with all the mental health and substance use indicators except illicit drug use. Family disruption was statistically significantly associated with depression symptoms, marijuana use, and cigarette use. Interpersonal difficulties stress was statistically significantly associated with depression symptoms. All sources of personal stress were statistically significantly related to depression symptoms. In addition, health-related stress was inversely related to binge drinking. Conclusion Young adolescents may benefit from learning positive coping skills to manage worry or stress about common stressors and in particular, worry or stress related to romantic breakups. Appropriate management of mental health symptoms and substance use related to common stressful life events and difficulties may help reduce emerging psychopathology.
Development and validation of the Questionnaire of Stressful Life Events (QSLE).

Science.gov (United States)

Butjosa, Anna; Gómez-Benito, Juana; Myin-Germeys, Inez; Barajas, Ana; Baños, Iris; Usall, Judith; Grau, Norma; Granell, Luis; Sola, Andrea; Carlson, Janina; Dolz, Montserrat; Sánchez, Bernardo; Haro, Josep Maria; Ochoa, Susana

2017-12-01

Stressful life events (SLEs) are important indicators prior to the onset of first-episode psychosis (FEP). Although there are well-validated interviews and self-reports for assessing SLE on proximate events, unfortunately there are no instruments to assess SLE covering an entire lifetime. This study includes detailed specific items of childhood, adolescence, and adulthood focused on the presence of SLE, emotional impact (stressfulness), and the age at which the event occurred. Our research describes 2 studies designed to develop and validate a new scale to assess SLE: the Questionnaire of Stressful Life Events (QSLE). In Study 1, an over-inclusive item pool was generated based on review of group of experts at Parc Sanitari Sant Joan de Déu and content validity was examined by an Expert Survey. The whole scale represents the content domain. In Study 2, item-level analyses revealed good distributional properties, intra-rater reliability, and convergent and discriminant validity. In the sensitivity and specificity analysis, 18 items had high relevance in the discriminability between patients with FEP and healthy controls. We note that there was an AUC of 0.676, indicating a good predictor. Using 7 as a cutoff to predict an individual as a patient would yield a sensitivity of 64.8% and a specificity of 65%. Overall, the QSLE displayed satisfactory psychometric characteristics in a Spanish population. These results suggest that QSLE gives us the opportunity to investigate childhood, adolescent, and adult life events by measuring the stress and age at the moment on a continuous scale. Copyright © 2017 Elsevier Ltd. All rights reserved.
Differential impact of Met receptor gene interaction with early-life stress on neuronal morphology and behavior in mice.

Science.gov (United States)

Heun-Johnson, Hanke; Levitt, Pat

2018-02-01

Early adversity in childhood increases the risk of anxiety, mood, and post-traumatic stress disorders in adulthood, and specific gene-by-environment interactions may increase risk further. A common functional variant in the promoter region of the gene encoding the human MET receptor tyrosine kinase (rs1858830 ' C' allele) reduces expression of MET and is associated with altered cortical circuit function and structural connectivity. Mice with reduced Met expression exhibit changes in anxiety-like and conditioned fear behavior, precocious synaptic maturation in the hippocampus, and reduced neuronal arbor complexity and synaptogenesis. These phenotypes also can be produced independently by early adversity in wild-type mice. The present study addresses the outcome of combining early-life stress and genetic influences that alter timing of maturation on enduring functional and structural phenotypes. Using a model of reduced Met expression ( Met +/- ) and early-life stress from postnatal day 2-9, social, anxiety-like, and contextual fear behaviors in later life were measured. Mice that experienced early-life stress exhibited impairments in social interaction, whereas alterations in anxiety-like behavior and fear learning were driven by Met haploinsufficiency, independent of rearing condition. Early-life stress or reduced Met expression decreased arbor complexity of ventral hippocampal CA1 pyramidal neurons projecting to basolateral amygdala. Paradoxically, arbor complexity in Met +/- mice was increased following early-life stress, and thus not different from arbors in wild-type mice raised in control conditions. The changes in dendritic morphology are consistent with the hypothesis that the physiological state of maturation of CA1 neurons in Met +/- mice influences their responsiveness to early-life stress. The dissociation of behavioral and structural changes suggests that there may be phenotype-specific sensitivities to early-life stress.
An analysis of the financial crisis in the KOSPI market using Hurst exponents

Science.gov (United States)

Yim, Kyubin; Oh, Gabjin; Kim, Seunghwan

2014-09-01

Recently, the study of the financial crisis has progressed to include the concept of the complex system, thereby improving the understanding of this extreme event from a neoclassical economic perspective. To determine which variables are related to the financial event caused by the 2008 US subprime crisis using temporal correlations, we investigate the diverse variables that may explain the financial system. These variables include return, volatility, trading volume and inter-trade duration data sets within the TAQ data for 27 highly capitalized individual companies listed on the KOSPI stock market. During 2008 and 2009, the Hurst exponent for the return time series over the whole period was less than 0.5, and the Hurst exponents for other variables, such as the volatility, trading volume and inter-trade duration, were greater than 0.5. Additionally, we analyze the relationships between the variation of temporal correlation and market instability based on these Hurst exponents and the degree of multifractality. We find that for the data related to trading volume, the Hurst exponents do not allow us to detect changes in market status, such as changes from normal to abnormal status, whereas other variables, including the return, volatility and weekly inter-trade duration, indicate a significant change in market status after the Lehman Brothers' bankruptcy. In addition, the multifractality and the measurement defined by subtracting the Hurst exponent of the return time series from that of the volatility time series decrease sharply after the US subprime event and recover approximately 50 days after the Lehman Brothers' collapse. Our findings suggest that the temporal features of financial quantities in the TAQ data set and the market complexity perform very well at diagnosing financial market stability.
An accurate algorithm to calculate the Hurst exponent of self-similar processes

International Nuclear Information System (INIS)

Fernández-Martínez, M.; Sánchez-Granero, M.A.; Trinidad Segovia, J.E.; Román-Sánchez, I.M.

2014-01-01

In this paper, we introduce a new approach which generalizes the GM2 algorithm (introduced in Sánchez-Granero et al. (2008) [52]) as well as fractal dimension algorithms (FD1, FD2 and FD3) (first appeared in Sánchez-Granero et al. (2012) [51]), providing an accurate algorithm to calculate the Hurst exponent of self-similar processes. We prove that this algorithm performs properly in the case of short time series when fractional Brownian motions and Lévy stable motions are considered. We conclude the paper with a dynamic study of the Hurst exponent evolution in the S and P500 index stocks. - Highlights: • We provide a new approach to properly calculate the Hurst exponent. • This generalizes FD algorithms and GM2, introduced previously by the authors. • This method (FD4) results especially appropriate for short time series. • FD4 may be used in both unifractal and multifractal contexts. • As an empirical application, we show that S and P500 stocks improved their efficiency
An accurate algorithm to calculate the Hurst exponent of self-similar processes

Energy Technology Data Exchange (ETDEWEB)

Fernández-Martínez, M., E-mail: fmm124@ual.es [Department of Mathematics, Faculty of Science, Universidad de Almería, 04120 Almería (Spain); Sánchez-Granero, M.A., E-mail: misanche@ual.es [Department of Mathematics, Faculty of Science, Universidad de Almería, 04120 Almería (Spain); Trinidad Segovia, J.E., E-mail: jetrini@ual.es [Department of Accounting and Finance, Faculty of Economics and Business, Universidad de Almería, 04120 Almería (Spain); Román-Sánchez, I.M., E-mail: iroman@ual.es [Department of Accounting and Finance, Faculty of Economics and Business, Universidad de Almería, 04120 Almería (Spain)

2014-06-27

In this paper, we introduce a new approach which generalizes the GM2 algorithm (introduced in Sánchez-Granero et al. (2008) [52]) as well as fractal dimension algorithms (FD1, FD2 and FD3) (first appeared in Sánchez-Granero et al. (2012) [51]), providing an accurate algorithm to calculate the Hurst exponent of self-similar processes. We prove that this algorithm performs properly in the case of short time series when fractional Brownian motions and Lévy stable motions are considered. We conclude the paper with a dynamic study of the Hurst exponent evolution in the S and P500 index stocks. - Highlights: • We provide a new approach to properly calculate the Hurst exponent. • This generalizes FD algorithms and GM2, introduced previously by the authors. • This method (FD4) results especially appropriate for short time series. • FD4 may be used in both unifractal and multifractal contexts. • As an empirical application, we show that S and P500 stocks improved their efficiency.
Early parental loss and depression history: associations with recent life stress in major depressive disorder.

Science.gov (United States)

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

2011-09-01

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

Science.gov (United States)

Peleg, Ora

2014-12-01

This study examined the relationships between stressful life events in childhood and differentiation of self and intergenerational triangulation in adulthood. The sample included 217 students (173 females and 44 males) from a college in northern Israel. Participants completed the Hebrew versions of Life Events Checklist (LEC), Differentiation of Self Inventory-Revised (DSI-R) and intergenerational triangulation (INTRI). The main findings were that levels of stressful life events during childhood and adolescence among both genders were positively correlated with the levels of fusion with others and intergenerational triangulation. The levels of positive life events were negatively related to levels of emotional reactivity, emotional cut-off and intergenerational triangulation. Levels of stressful life events in females were positively correlated with emotional reactivity. Intergenerational triangulation was correlated with emotional reactivity, emotional cut-off, fusion with others and I-position. Findings suggest that families that experience higher levels of stressful life events may be at risk for higher levels of intergenerational triangulation and lower levels of differentiation of self. © 2014 International Union of Psychological Science.
Perceived early-life maternal care and the cortisol response to repeated psychosocial stress.

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Engert, Veronika; Efanov, Simona I; Dedovic, Katarina; Duchesne, Annie; Dagher, Alain; Pruessner, Jens C

2010-11-01

In the past decade, a body of animal and human research has revealed a profound influence of early-life experiences, ranging from variations in parenting behaviour to severe adversity, on hypothalamic-pituitary-adrenal axis regulation in adulthood. In our own previous studies, we have shown how variations in early-life parental care influence the development of the hippocampus and modify the cortisol awakening response. In the present study, we investigated the influence of early-life maternal care on cortisol, heart rate and subjective psychological responses to the repeated administration of a psychosocial laboratory stressor in a population of 63 healthy young adults. Low, medium and high early-life maternal care groups were identified using the Parental Bonding Instrument. Controlling for the effect of sex, we found an inverted u-shaped relation between increasing levels of maternal care and cortisol stress responsivity. Specifically, overall and stress-induced cortisol levels went from below normal in the low maternal care, to normal in the medium care, back to below normal in the high maternal care groups. We found no group differences with respect to heart rate and subjective psychological stress measures. Whereas low and high maternal care groups exhibited similarly low endocrine stress responses, their psychological profiles were opposed with increased levels of depression and anxiety and decreased self-esteem in the low care group. Sex was unequally distributed among maternal care groups, whereby the number of men with low maternal care was too small to allow introducing sex as a second between-group variable. We discuss the potential significance of this dissociation between endocrine and psychological parameters with respect to stress vulnerability and resistance for each maternal care group.
A Dyadic Approach to Infertility Stress, Marital Adjustment, and Depression on Quality of Life in Infertile Couples.

Science.gov (United States)

Kim, Ju Hee; Shin, Hye Sook; Yun, Eun Kyoung

2018-03-01

This study was conducted to examine the level of infertility stress, marital adjustment, depression, and quality of life in infertile couples and assess the actor and partner effects in these areas using the actor-partner interdependence model. Cross-sectional study. Participants were 121 infertile couples. After pilot study, data were collected from November 2012 to March 2013 using the following questionnaires: the Fertility Quality of Life, Fertility Problem Inventory, Revised Dyadic Adjustment Scale, and Beck Depression Inventory. There was a gender difference in infertility stress, depression, and quality of life. Infertility stress had actor and partner effects on the quality of life. Marital adjustment had an actor effect on the quality of life for the wives. Depression had actor and partner effects on quality of life for the wives, but only an actor effect for the husbands. This study found that there were actor and partner effects of infertility stress, marital adjustment, and depression on the quality of life in infertile couples. These findings may help nurses be aware of such effects and can be used as a baseline data in the development of nursing interventions for infertile couples.
Using machine learning to replicate chaotic attractors and calculate Lyapunov exponents from data

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Pathak, Jaideep; Lu, Zhixin; Hunt, Brian R.; Girvan, Michelle; Ott, Edward

2017-12-01

We use recent advances in the machine learning area known as "reservoir computing" to formulate a method for model-free estimation from data of the Lyapunov exponents of a chaotic process. The technique uses a limited time series of measurements as input to a high-dimensional dynamical system called a "reservoir." After the reservoir's response to the data is recorded, linear regression is used to learn a large set of parameters, called the "output weights." The learned output weights are then used to form a modified autonomous reservoir designed to be capable of producing an arbitrarily long time series whose ergodic properties approximate those of the input signal. When successful, we say that the autonomous reservoir reproduces the attractor's "climate." Since the reservoir equations and output weights are known, we can compute the derivatives needed to determine the Lyapunov exponents of the autonomous reservoir, which we then use as estimates of the Lyapunov exponents for the original input generating system. We illustrate the effectiveness of our technique with two examples, the Lorenz system and the Kuramoto-Sivashinsky (KS) equation. In the case of the KS equation, we note that the high dimensional nature of the system and the large number of Lyapunov exponents yield a challenging test of our method, which we find the method successfully passes.
Early life stress and trauma and enhanced limbic activation to emotionally valenced faces in depressed and healthy children.

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Suzuki, Hideo; Luby, Joan L; Botteron, Kelly N; Dietrich, Rachel; McAvoy, Mark P; Barch, Deanna M

2014-07-01

Previous studies have examined the relationships between structural brain characteristics and early life stress in adults. However, there is limited evidence for functional brain variation associated with early life stress in children. We hypothesized that early life stress and trauma would be associated with increased functional brain activation response to negative emotional faces in children with and without a history of depression. Psychiatric diagnosis and life events in children (starting at age 3-5 years) were assessed in a longitudinal study. A follow-up magnetic resonance imaging (MRI) study acquired data (N = 115 at ages 7-12, 51% girls) on functional brain response to fearful, sad, and happy faces relative to neutral faces. We used a region-of-interest mask within cortico-limbic areas and conducted regression analyses and repeated-measures analysis of covariance. Greater activation responses to fearful, sad, and happy faces in the amygdala and its neighboring regions were found in children with greater life stress. Moreover, an association between life stress and left hippocampal and globus pallidus activity depended on children's diagnostic status. Finally, all children with greater life trauma showed greater bilateral amygdala and cingulate activity specific to sad faces but not the other emotional faces, although right amygdala activity was moderated by psychiatric status. These findings suggest that limbic hyperactivity may be a biomarker of early life stress and trauma in children and may have implications in the risk trajectory for depression and other stress-related disorders. However, this pattern varied based on emotion type and history of psychopathology. Copyright © 2014 American Academy of Child and Adolescent Psychiatry. Published by Elsevier Inc. All rights reserved.

Music Listening and Stress in Daily Life-a Matter of Timing.

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Linnemann, Alexandra; Wenzel, Mario; Grammes, Jennifer; Kubiak, Thomas; Nater, Urs M

2018-04-01

Despite increasing evidence suggesting that music listening in daily life has stress-reducing effects, studies mostly rely on subjective, retrospective data on music listening. Thus, the temporal dynamics underlying the stress-reducing effect of music listening remain unclear. Therefore, we aimed to examine the temporal dynamics of the associations between stress and music listening by assessing subjective and objective data on music in daily life. An exploratory Ambulatory Assessment study examining a total of 60 participants (37 women), aged 18 to 34 years (M = 22.4 years, SD = 3.5) was conducted. For 1 week, participants answered questions on music listening and stress six times per day via an electronic diary device, which additionally objectively sampled the exact time point of music listening and its duration. Self-reports on mere music listening were associated with lower stress reports, whereas objectively assessed data was not. However, concerning duration of music listening, both subjective and objective data on music listening showed associations between a minimum of 20 min of music listening and lower stress reports. Concerning the latency, objective data on music listening revealed that the association between stress reports and music listening occurs in a time-delayed manner. Although the study design does not allow for causal inferences, substantial associations among subjectively and objectively assessed data on music listening were found to differentially affect the experience of stress after music listening. In particular, when focusing on the temporal dynamics, objectively assessed data allowed for a more fine-grained analysis. In consequence, subjectively and objectively reported data on music listening should be assessed jointly when investigating effects of music listening on health. Experimental research with rigorous methodological control is required in order to corroborate our findings in a laboratory setting.
Life time forecasting method upon occurrence of stress corrosion cracking of structure and test device therefor

International Nuclear Information System (INIS)

Anzai, Hideya; Kida, Toshitaka; Urayama, Yoshinao; Kikuchi, Eiji; Shimanuki, Sei; Kuniya, Jiro; Nakata, Kiyotomo; Izumitani, Masakiyo; Hattori, Shigeo.

1993-01-01

A load stress is applied to a metal piece made of a material identical with the constituent material of a structure and having the sensitivity enhanced to a predetermined level, and plurality of such pieces are immersed in a corrosive circumstance in this state. Then, the time from the immersion till the rupture thereof and the number of ruptured pieces of the metal pieces are detected while observing them. The relation with the probability of rupture is plotted on a paper to determine the life time for the occurrence of minimum stress corrosion creacks (SSC) of the metal pieces. Based on the relationship between the previously determined stress and the life time for the occurrence of minimum SSC, the ratio between the life time for the occurrence of minimum SSC relative to estimated stress applied to the structure and the life time for the occurrence of minimum SSC relative to the stress applied to the metal pieces is determined as a first SSC acceleration rate. The ratio between the time of occurrence for minimum SSC and the sensitivity is determined as a second SSC acceleration rate. The first and the second SSC acceleration rates are multiplied to estimate the time for the occurrence of SSC of the structure. Then, the life time for the occurrence of SSC for the equipments and structures can be recognized quantitatively, to prevent ruptures of actual equipments and extend the life time. (N.H.)
Zipf's law and influential factors of the Pareto exponent of the city size distribution: Evidence from China

OpenAIRE

GAO Hongying; WU Kangping

2007-01-01

This paper estimates the Pareto exponent of the city size (population size and economy size) distribution, all provinces, and three regions in China in 1997, 2000 and 2003 by OLS, comparatively analyzes the Pareto exponent cross section and times, and empirically analyzes the factors which impacts on the Pareto exponents of provinces. Our analyses show that the size distributions of cities in China follow the Pareto distribution and are of structural features. Variations in the value of the P...
Creep-Fatigue Life Design with Various Stress and Temperature Conditions on the Basis of Lethargy Coefficient

International Nuclear Information System (INIS)

Park, Jung Eun; Yang, Sung Mo; Han, Jae Hee; Yu, Hyo Sun

2011-01-01

High temperature and stress are encounted in power plants and vehicle engines. Therefore, determination of the creep-fatigue life of a material is necessary prior to fabricating equipment. In this study, life design was determined on the basis of the lethargy coefficient for different temperatures, stress and rupture times. SP-Creep test data was compared with computed data. The SP-Creep test was performed to obtain the rupture time for X20CrMoV121 steel. The integration life equation was considered for three cases with various load, temperature and load-temperature. First, the lethargy coefficient was calculated by using the obtained rupture stress and the rupture time that were determined by carrying out the SP-Creep test. Next, life was predicted on the basis of the temperature condition. Finally, it was observed that life decreases considerably due to the coupling effect that results when fatigue and creep occur simultaneously
Impact of new traumatic or stressful life events on pre-existing PTSD in traumatized refugees: results of a longitudinal study

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Katrin Schock

2016-11-01

Full Text Available Background: A significant proportion of trauma survivors experience an additional critical life event in the aftermath. These renewed experiences of traumatic and stressful life events may lead to an increase in trauma-related mental health symptoms.Method: In a longitudinal study, the effects of renewed experiences of a trauma or stressful life event were examined. For this purpose, refugees seeking asylum in Germany were assessed for posttraumatic stress symptoms (PTS, Posttraumatic Stress Diagnostic Scale (PDS, anxiety, and depression (Hopkins Symptom Checklist [HSCL-25] before treatment start as well as after 6 and 12 months during treatment (N=46. Stressful life events and traumatic events were recorded monthly. If a new event happened, PDS and HSCL were additionally assessed directly afterwards. Mann–Whitney U-tests were performed to calculate the differences between the group that experienced an additional critical event (stressful vs. trauma during treatment (n=23 and the group that did not (n=23, as well as differences within the critical event group between the stressful life event group (n=13 and the trauma group (n=10.Results: Refugees improved significantly during the 12-month period of our study, but remained severely distressed. In a comparison of refugees with a new stressful life event or trauma, significant increases in PTS, anxiety, and depressive symptoms were found directly after the experience, compared to the group without a renewed event during the 12 months of treatment. With regard to the different critical life events (stressful vs. trauma, no significant differences were found regarding overall PTS, anxiety, and depression symptoms. Only avoidance symptoms increased significantly in the group experiencing a stressful life event.Conclusion: Although all clinicians should be aware of possible PTS symptom reactivation, especially those working with refugees and asylum seekers, who often experience new critical life
Impact of new traumatic or stressful life events on pre-existing PTSD in traumatized refugees: results of a longitudinal study.

Science.gov (United States)

Schock, Katrin; Böttche, Maria; Rosner, Rita; Wenk-Ansohn, Mechthild; Knaevelsrud, Christine

2016-01-01

A significant proportion of trauma survivors experience an additional critical life event in the aftermath. These renewed experiences of traumatic and stressful life events may lead to an increase in trauma-related mental health symptoms. In a longitudinal study, the effects of renewed experiences of a trauma or stressful life event were examined. For this purpose, refugees seeking asylum in Germany were assessed for posttraumatic stress symptoms (PTS), Posttraumatic Stress Diagnostic Scale (PDS), anxiety, and depression (Hopkins Symptom Checklist [HSCL-25]) before treatment start as well as after 6 and 12 months during treatment ( N =46). Stressful life events and traumatic events were recorded monthly. If a new event happened, PDS and HSCL were additionally assessed directly afterwards. Mann-Whitney U -tests were performed to calculate the differences between the group that experienced an additional critical event (stressful vs. trauma) during treatment ( n =23) and the group that did not ( n =23), as well as differences within the critical event group between the stressful life event group ( n =13) and the trauma group ( n =10). Refugees improved significantly during the 12-month period of our study, but remained severely distressed. In a comparison of refugees with a new stressful life event or trauma, significant increases in PTS, anxiety, and depressive symptoms were found directly after the experience, compared to the group without a renewed event during the 12 months of treatment. With regard to the different critical life events (stressful vs. trauma), no significant differences were found regarding overall PTS, anxiety, and depression symptoms. Only avoidance symptoms increased significantly in the group experiencing a stressful life event. Although all clinicians should be aware of possible PTS symptom reactivation, especially those working with refugees and asylum seekers, who often experience new critical life events, should understand symptom
The effect of residual stresses induced by prestraining on fatigue life of notched specimens

Science.gov (United States)

Sadeler, R.; Ozel, A.; Kaymaz, I.; Totik, Y.

2005-06-01

The effect of tensile prestraining-induced residual stress on the fatigue life of notched steel parts was investigated. The study was performed on AISI 4140 steel. Rotating bending fatigue tests were carried out on semicircular notched specimens with different notch radii in the as-quenched and tempered conditions. Metallography of the specimens was performed by means of light optical microscopy. The finite-element method was used to evaluate the residual stress distribution near the notch region. Fatigue tests revealed fatigue life improvement for notched specimens, which changes depending on the notch radii and applied stress. Scanning electron microscopy was used to examine the fracture surfaces of the specimens.
The doping concentration and physical properties measurement of silicon water using tera hertz wave

International Nuclear Information System (INIS)

Park, Sung Hyeon; Oh, Gyung Hwan; Kim, Hak Sung

2017-01-01

In this study, a tera hertz time domain spectroscopy (THz-TDS) imaging technique was used to measure doping concentration and physical properties (such as refractive index and permittivity) of the doped silicon (Si) wafers. The transmission and reflection modes with an incidence angle of 30° were employed to determine the physical properties of the doped Si wafers. The doping concentrations of the prepared Si wafers were varied from 10"1"4 to 10"1"8 in both N-type and P-type cases. Finally, the correlation between the doping concentration and the power of the THz wave was determined by measuring the powers of the transmitted and reflected THz waves of the doped Si wafers. Additionally, the doped thickness, the refractive index, and permittivity of each doped Si wafer were calculated using the THz time domain waveform. The results indicate that the THz-TDS imaging technique is potentially a promising technique to measure the doping concentration as well as other optical properties (such as the refractive index and permittivity) of the doped Si wafer
The doping concentration and physical properties measurement of silicon water using tera hertz wave

Energy Technology Data Exchange (ETDEWEB)

Park, Sung Hyeon; Oh, Gyung Hwan; Kim, Hak Sung [Dept. of Mechanical Convergence Engineering, Hanyang University, Seoul(Korea, Republic of)

2017-02-15

In this study, a tera hertz time domain spectroscopy (THz-TDS) imaging technique was used to measure doping concentration and physical properties (such as refractive index and permittivity) of the doped silicon (Si) wafers. The transmission and reflection modes with an incidence angle of 30° were employed to determine the physical properties of the doped Si wafers. The doping concentrations of the prepared Si wafers were varied from 10{sup 14} to 10{sup 18} in both N-type and P-type cases. Finally, the correlation between the doping concentration and the power of the THz wave was determined by measuring the powers of the transmitted and reflected THz waves of the doped Si wafers. Additionally, the doped thickness, the refractive index, and permittivity of each doped Si wafer were calculated using the THz time domain waveform. The results indicate that the THz-TDS imaging technique is potentially a promising technique to measure the doping concentration as well as other optical properties (such as the refractive index and permittivity) of the doped Si wafer.
Stressful Life Events and Psychosomatic Symptoms among Students Smokers and Non-smokers

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Dodaj, Arta; Simic, Natasa

2012-01-01

The objective of this study is to analyze the rate of stressful life events and psychosomatic symptoms among students smokers and non-smokers and examine the predictive contribution of stress and smoking to subjective health status. Methods were conducted on a convenience sample of 200 students from the University of Mostar, with a median age of…
Statistical properties of the anomalous scaling exponent estimator based on time-averaged mean-square displacement

Science.gov (United States)

Sikora, Grzegorz; Teuerle, Marek; Wyłomańska, Agnieszka; Grebenkov, Denis

2017-08-01

The most common way of estimating the anomalous scaling exponent from single-particle trajectories consists of a linear fit of the dependence of the time-averaged mean-square displacement on the lag time at the log-log scale. We investigate the statistical properties of this estimator in the case of fractional Brownian motion (FBM). We determine the mean value, the variance, and the distribution of the estimator. Our theoretical results are confirmed by Monte Carlo simulations. In the limit of long trajectories, the estimator is shown to be asymptotically unbiased, consistent, and with vanishing variance. These properties ensure an accurate estimation of the scaling exponent even from a single (long enough) trajectory. As a consequence, we prove that the usual way to estimate the diffusion exponent of FBM is correct from the statistical point of view. Moreover, the knowledge of the estimator distribution is the first step toward new statistical tests of FBM and toward a more reliable interpretation of the experimental histograms of scaling exponents in microbiology.
Stress, health and quality of life of female migrant domestic workers in Singapore: a cross-sectional study.

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Anjara, S G; Nellums, L B; Bonetto, C; Van Bortel, T

2017-10-10

There is a global increase in migrant workers. In Singapore, there are over 230,000 migrant domestic workers (MDWs). Female MDWs may experience high levels of stress and social isolation, which may negatively impact on their health and quality of life. There have also been documented cases of abuse and exploitation. However, there is a lack of empirical research with this population. This study aimed to investigate factors impacting on the health and quality of life of female MDWs in Singapore, including socio-demographic and job related characteristics, stress, social isolation, and working management style. A cross-sectional survey was carried out with 182 female MDWs in Singapore. The survey examined health and quality of life (WHOQoL-Bréf), social connectedness (the Friendship Scale), and preferred and experienced working management style (the Theory X and Theory Y Questionnaire). Descriptive analyses were carried out in addition to ANOVA, t-tests, and chi-square tests, followed by a multivariate analysis using linear regression. Participants were found to have good overall quality of life and satisfaction with health. Age and working experience were found to be significantly (p health). Agreement between experienced and preferred working management style was also found to be associated with higher quality of life scores (with the exception of the social relationships domain). Though women reported relatively good overall quality of life, more than half of participants reported feeling stressed. In addition, nearly 20% of participants reported being isolated or very isolated. Stress was identified to be associated with isolation. In the multivariate analysis, stress was found to contribute to worse quality of life in all domains except social relationships, after adjusting for confounders. Social connectedness was positively associated with all domains of quality of life, and agreement of working management style was positively associated with physical health
Bayesian Approach for Constant-Stress Accelerated Life Testing for Kumaraswamy Weibull Distribution with Censoring

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Abeer Abd-Alla EL-Helbawy

2016-09-01

Full Text Available The accelerated life tests provide quick information on the life time distributions by testing materials or products at higher than basic conditional levels of stress such as pressure, high temperature, vibration, voltage or load to induce failures. In this paper, the acceleration model assumed is log linear model. Constant stress tests are discussed based on Type I and Type II censoring. The Kumaraswmay Weibull distribution is used. The estimators of the parameters, reliability, hazard rate functions and p-th percentile at normal condition, low stress, and high stress are obtained. In addition, credible intervals for parameters of the models are constructed. Optimum test plan are designed. Some numerical studies are used to solve the complicated integrals such as Laplace and Markov Chain Monte Carlo methods.
Bayesian Approach for Constant-Stress Accelerated Life Testing for Kumaraswamy Weibull Distribution with Censoring

Directory of Open Access Journals (Sweden)

Abeer Abd-Alla EL-Helbawy

2016-12-01

Full Text Available The accelerated life tests provide quick information on the life time distributions by testing materials or products at higher than basic conditional levels of stress such as pressure, high temperature, vibration, voltage or load to induce failures. In this paper, the acceleration model assumed is log linear model. Constant stress tests are discussed based on Type I and Type II censoring. The Kumaraswmay Weibull distribution is used. The estimators of the parameters, reliability, hazard rate functions and p-th percentile at normal condition, low stress, and high stress are obtained. In addition, credible intervals for parameters of the models are constructed. Optimum test plan are designed. Some numerical studies are used to solve the complicated integrals such as Laplace and Markov Chain Monte Carlo methods.
The relationship among young adult college students' depression, anxiety, stress, demographics, life satisfaction, and coping styles.

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Mahmoud, Jihan Saber Raja; Staten, Ruth; Hall, Lynne A; Lennie, Terry A

2012-03-01

Recent research indicates that young adult college students experience increased levels of depression, anxiety, and stress. It is less clear what strategies college health care providers might use to assist students in decreasing these mental health concerns. In this paper, we examine the relative importance of coping style, life satisfaction, and selected demographics in predicting undergraduates' depression, anxiety, and stress. A total of 508 full-time undergraduate students aged 18-24 years completed the study measures and a short demographics information questionnaire. Coping strategies and life satisfaction were assessed using the Brief COPE Inventory and an adapted version of the Brief Students' Multidimensional Life Satisfaction Scale. Depression, anxiety, and stress were measured using the Depression Anxiety and Stress Scale-21 (DASS-21). Multiple regression analyses were used to examine the relative influence of each of the independent variables on depression, anxiety, and stress. Maladaptive coping was the main predictor of depression, anxiety, and stress. Adaptive coping was not a significant predictor of any of the three outcome variables. Reducing maladaptive coping behaviors may have the most positive impact on reducing depression, anxiety, and stress in this population.
Factors of subjective heat stress of urban citizens in contexts of everyday life

Science.gov (United States)

Kunz-Plapp, Tina; Hackenbruch, Julia; Schipper, Janus Willem

2016-04-01

Heat waves and the consequent heat stress of urban populations have a growing relevance in urban risk management and strategies of urban adaptation to climate change. In this context, social science studies on subjective experiencing of heat as stress by urban citizens are a new emerging field. To contribute to the understanding of self-reported subjective heat stress and its major determinants in a daily life perspective, we conducted a questionnaire survey with 323 respondents in Karlsruhe, Germany, after heat waves in July and August 2013. Statistical data analysis showed that subjective heat stress is an issue permeating everyday activities. Subjective heat stress at home was lower than at work and in general. Subjective heat stress in general, at home, and at work was determined by the health impairments experienced during the heat and the feeling of being helplessly exposed to the heat. For subjective heat stress at home, characteristics of the residential building and the built environment additionally played a role. Although the rate of implemented coping measures was rather high, coping measures showed no uniform effect for the subjective heat stress. We conclude that in terms of urban adaptation strategies, further research is needed to understand how various processes of daily social (work) life enable or limit individual coping and that communication strategies are important for building capacities to better cope with future heat waves.
The impact of life stress on adult depression and anxiety is dependent on gender and timing of exposure.

Science.gov (United States)

Herbison, Carly E; Allen, Karina; Robinson, Monique; Newnham, John; Pennell, Craig

2017-10-01

There is debate about the relative importance of timing of stressful events prenatally and over the life course and risk for subsequent depressive/anxious illness. The aim of this study was to examine the relative roles of prenatal stress and postnatal stress trajectories in predicting depression and anxiety in early adulthood in males and females. Exposure to life stress events was examined in the Western Australian Pregnancy Cohort (Raine) Study during pregnancy and ages 1, 2, 3, 5, 8, 10, 14, and 17 years. At age 20, offspring completed the Depression Anxiety Stress Scale. Prenatal stress and trajectories of stress events from age 1 to 17 were analyzed in linear regression analyses. Five postnatal stress trajectories were identified. In females, medium to high chronic stress exposure or exposure during puberty/adolescence predicted depression and anxiety symptoms while low or reduced stress exposure over the life course did not, after adjustment for relevant confounders. High stress early in pregnancy contributed to male depression/anxiety symptoms independent of postnatal stress trajectory. In females, postnatal stress trajectory was more important than prenatal stress in predicting depression/anxiety symptoms. Interventions focused on reducing and managing stress events around conception/pregnancy and exposure to chronic stress are likely to have beneficial outcomes on rates of depression and anxiety in adults.
Hurst's Exponent Determination for Radial Distribution Functions of In, Sn and In-40 wt%Sn Melt

International Nuclear Information System (INIS)

Zhou Yong-Zhi; Li Mei; Geng Hao-Ran; Yang Zhong-Xi; Sun Chun-Jing

2011-01-01

Hurst's exponent of radial distribution functions (RDFs) within the short-range scope of In, Sn and In-40 wt % Sn melts are determined by the rescaled range analysis method. Hurst's exponents H are between 0.94 and 0.97, which display long-range dependence. Within short-range scope, the number of particles from a reference particle belongs to fractional Brownian motion. After RDF serials are randomly scrambled, Hurst's exponents all dramatically dropped, which proves long-range dependence. H irregularly varies as the temperature rises, but the change tendency is not consistent with the correlation radius r c . (general)
A Multilevel Association Model for IT Employees’ Life Stress and Job Satisfaction: An Information Technology (IT Industry Case Study

Directory of Open Access Journals (Sweden)

Mehmood Khalid

2017-01-01

Full Text Available The aim of this research was to investigate the association among IT employees’ life stress and job satisfaction in information technology (IT firms. Data on 250 IT employees’ in 30 working groups was obtained from 10 Information Technology (IT Chinese firms from Beijing, and analyzed using hierarchical linear modeling (HLM. Results found momentous association among life stress of IT employees’ and their job satisfaction at an individual-level and group-level in IT firms. Furthermore, life stress in Beijing at group-level moderates the association among job satisfaction and IT employees’ life stress at an individual-level. Finally, limitations and implications of the present study are also discussed.
Bayesian Estimation of the Logistic Positive Exponent IRT Model

Science.gov (United States)

Bolfarine, Heleno; Bazan, Jorge Luis

2010-01-01

A Bayesian inference approach using Markov Chain Monte Carlo (MCMC) is developed for the logistic positive exponent (LPE) model proposed by Samejima and for a new skewed Logistic Item Response Theory (IRT) model, named Reflection LPE model. Both models lead to asymmetric item characteristic curves (ICC) and can be appropriate because a symmetric…

Living with type 1 diabetes is challenging for Zambian adolescents: qualitative data on stress, coping with stress and quality of care and life.

Science.gov (United States)

Hapunda, Given; Abubakar, Amina; van de Vijver, Fons; Pouwer, Frans

2015-04-18

Psychosocial problems are common in patients with diabetes. However, data on psychosocial issues affecting patients with diabetes in Zambia are scarce. The present study explored sources of stress, stress coping strategies, stigma and perceived quality of life and care as experienced by adolescents living with Type 1 Diabetes in Zambia. Semi-structured interviews were carried out. Three groups of participants involving adolescents with Type 1 Diabetes (n = 10), caregivers (n = 8) and health practitioners (n = 4) were interviewed. Transcripts were analyzed using a thematic approach. Stress was commonly reported by adolescents mainly stemming from social, psychological and physical sources. To deal with stress, adolescents often employed different coping strategies such as adapting, accepting and avoiding among others. Both internal factors (those relating to the patients themselves) and external factors (those related to the context of the patients') influenced the patients' quality of health care. In addition, low quality of life was an issue among adolescents and their families. Poor diet, low socioeconomic status and lack of medicine were factors affecting quality of health care. Stress was an issue affecting adolescents; the coping strategies employed were sometimes maladaptive such as avoiding injecting themselves to escape stress. Several aspects of quality of life were suboptimal in both adolescents and their families, such as stigmatization, short life expectancy, low socioeconomic status and poor social participation. Findings show that there is an urgent need for a strong response from all stakeholders (governments, patients, organizations and companies) to improve diabetes care and living conditions for young people with type 1 diabetes living in Zambia.
Non-universality of critical exponents in the paraconductivity of short-coherence-length superconductors

International Nuclear Information System (INIS)

Gauzzi, A.

1993-01-01

The Aslamazov-Larkin paraconductivity term is calculated in the case of sufficiently small superconducting coherence length. It is found that the critical exponent of paraconductivity depends on the short-wavelength cut-off of the fluctuation spectrum in the whole Ginzburg-Landau mean-field region. Hence, it is predicted that the Aslamazov-Larkin universal relation between the critical exponent of paraconductivity and the dimensionality of the superconducting state is no longer valid in short-coherence-length superconductors. This prediction is confirmed by paraconductivity measurements on cuprate superconductors. (orig.)
Improvement of stress-rupture life of GTD-111 by second solution heat treatment

International Nuclear Information System (INIS)

Yang, Caixiong; Xu, Yulai; Zhang, Zixing; Nie, Heng; Xiao, Xueshan; Jia, Guoqing; Shen, Zhi

2013-01-01

Highlights: ► The second solution heat treatment promoted the solution of γ–γ′ eutectic into γ matrix. ► The volume fraction of γ′ increases significantly after adding the second solution heat treatment. ► The improved stress-rupture life is primarily due to the increased volume fraction of γ′ phase. -- Abstract: An added second solution heat treatment was conducted to investigate its effects on the microstructures and stress-rupture properties of GTD-111. The microstructures were analyzed by scanning electron microscope after each step of heat treatments. The stress-rupture life of GTD-111 dramatically increases from about 180 to 288 h at 871 °C/310 MPa after adding a second solution heat treatment. The added second solution heat treatment promoted the solution of γ–γ′ eutectic into γ matrix, and facilitated the nucleation and precipitate of the secondary γ′ particles. The distribution of γ′ phase becomes much denser, the width of γ matrix channel is also reduced, and the volume fraction of γ′ phase significantly increases from about 29.3% to 44.2%. The improved stress-rupture life is primarily due to the increased volume fraction of γ′ phase. The carbides mainly consist of MC and a small amount of M 23 C 6 , which may prevent the dislocation moving and/or grain boundary sliding, and further improve the stress-rupture properties of GTD-111.
Major stressful life events and other risk factors for first admission with mania

DEFF Research Database (Denmark)

Kessing, Lars Vedel; Agerbo, Esben; Mortensen, Preben Bo

2004-01-01

OBJECTIVES: To investigate whether first admission with mania is associated with the occurrence of death in the family or with major stressful life events and to explore whether the associations change with age. METHODS: Case register study with linkage of the Danish Psychiatric Central Research ...... disorder. The susceptibility to major life stressors of inducing mania does not seem to change throughout life....
Working conditions, self-perceived stress, anxiety, depression and quality of life: A structural equation modelling approach

Directory of Open Access Journals (Sweden)

Edimansyah Bin

2008-02-01

Full Text Available Abstract Background The relationships between working conditions [job demand, job control and social support]; stress, anxiety, and depression; and perceived quality of life factors [physical health, psychological wellbeing, social relationships and environmental conditions] were assessed using a sample of 698 male automotive assembly workers in Malaysia. Methods The validated Malay version of the Job Content Questionnaire (JCQ, Depression Anxiety Stress Scales (DASS and the World Health Organization Quality of Life-Brief (WHOQOL-BREF were used. A structural equation modelling (SEM analysis was applied to test the structural relationships of the model using AMOS version 6.0, with the maximum likelihood ratio as the method of estimation. Results The results of the SEM supported the hypothesized structural model (χ2 = 22.801, df = 19, p = 0.246. The final model shows that social support (JCQ was directly related to all 4 factors of the WHOQOL-BREF and inversely related to depression and stress (DASS. Job demand (JCQ was directly related to stress (DASS and inversely related to the environmental conditions (WHOQOL-BREF. Job control (JCQ was directly related to social relationships (WHOQOL-BREF. Stress (DASS was directly related to anxiety and depression (DASS and inversely related to physical health, environment conditions and social relationships (WHOQOL-BREF. Anxiety (DASS was directly related to depression (DASS and inversely related to physical health (WHOQOL-BREF. Depression (DASS was inversely related to the psychological wellbeing (WHOQOL-BREF. Finally, stress, anxiety and depression (DASS mediate the relationships between job demand and social support (JCQ to the 4 factors of WHOQOL-BREF. Conclusion These findings suggest that higher social support increases the self-reported quality of life of these workers. Higher job control increases the social relationships, whilst higher job demand increases the self-perceived stress and decreases
Working conditions, self-perceived stress, anxiety, depression and quality of life: a structural equation modelling approach.

Science.gov (United States)

Rusli, Bin Nordin; Edimansyah, Bin Abdin; Naing, Lin

2008-02-06

The relationships between working conditions [job demand, job control and social support]; stress, anxiety, and depression; and perceived quality of life factors [physical health, psychological wellbeing, social relationships and environmental conditions] were assessed using a sample of 698 male automotive assembly workers in Malaysia. The validated Malay version of the Job Content Questionnaire (JCQ), Depression Anxiety Stress Scales (DASS) and the World Health Organization Quality of Life-Brief (WHOQOL-BREF) were used. A structural equation modelling (SEM) analysis was applied to test the structural relationships of the model using AMOS version 6.0, with the maximum likelihood ratio as the method of estimation. The results of the SEM supported the hypothesized structural model (chi2 = 22.801, df = 19, p = 0.246). The final model shows that social support (JCQ) was directly related to all 4 factors of the WHOQOL-BREF and inversely related to depression and stress (DASS). Job demand (JCQ) was directly related to stress (DASS) and inversely related to the environmental conditions (WHOQOL-BREF). Job control (JCQ) was directly related to social relationships (WHOQOL-BREF). Stress (DASS) was directly related to anxiety and depression (DASS) and inversely related to physical health, environment conditions and social relationships (WHOQOL-BREF). Anxiety (DASS) was directly related to depression (DASS) and inversely related to physical health (WHOQOL-BREF). Depression (DASS) was inversely related to the psychological wellbeing (WHOQOL-BREF). Finally, stress, anxiety and depression (DASS) mediate the relationships between job demand and social support (JCQ) to the 4 factors of WHOQOL-BREF. These findings suggest that higher social support increases the self-reported quality of life of these workers. Higher job control increases the social relationships, whilst higher job demand increases the self-perceived stress and decreases the self-perceived quality of life related to
Working conditions, self-perceived stress, anxiety, depression and quality of life: A structural equation modelling approach

Science.gov (United States)

Rusli, Bin Nordin; Edimansyah, Bin Abdin; Naing, Lin

2008-01-01

Background The relationships between working conditions [job demand, job control and social support]; stress, anxiety, and depression; and perceived quality of life factors [physical health, psychological wellbeing, social relationships and environmental conditions] were assessed using a sample of 698 male automotive assembly workers in Malaysia. Methods The validated Malay version of the Job Content Questionnaire (JCQ), Depression Anxiety Stress Scales (DASS) and the World Health Organization Quality of Life-Brief (WHOQOL-BREF) were used. A structural equation modelling (SEM) analysis was applied to test the structural relationships of the model using AMOS version 6.0, with the maximum likelihood ratio as the method of estimation. Results The results of the SEM supported the hypothesized structural model (χ2 = 22.801, df = 19, p = 0.246). The final model shows that social support (JCQ) was directly related to all 4 factors of the WHOQOL-BREF and inversely related to depression and stress (DASS). Job demand (JCQ) was directly related to stress (DASS) and inversely related to the environmental conditions (WHOQOL-BREF). Job control (JCQ) was directly related to social relationships (WHOQOL-BREF). Stress (DASS) was directly related to anxiety and depression (DASS) and inversely related to physical health, environment conditions and social relationships (WHOQOL-BREF). Anxiety (DASS) was directly related to depression (DASS) and inversely related to physical health (WHOQOL-BREF). Depression (DASS) was inversely related to the psychological wellbeing (WHOQOL-BREF). Finally, stress, anxiety and depression (DASS) mediate the relationships between job demand and social support (JCQ) to the 4 factors of WHOQOL-BREF. Conclusion These findings suggest that higher social support increases the self-reported quality of life of these workers. Higher job control increases the social relationships, whilst higher job demand increases the self-perceived stress and decreases the self
Secure Infant-Mother Attachment Buffers the Effect of Early-Life Stress on Age of Menarche.

Science.gov (United States)

Sung, Sooyeon; Simpson, Jeffry A; Griskevicius, Vladas; Kuo, Sally I-Chun; Schlomer, Gabriel L; Belsky, Jay

2016-05-01

Prior research indicates that being reared in stressful environments is associated with earlier onset of menarche in girls. In this research, we examined (a) whether these effects are driven by exposure to certain dimensions of stress (harshness or unpredictability) during the first 5 years of life and (b) whether the negative effects of stress on the timing of menarche are buffered by secure infant-mother attachment. Results revealed that (a) exposure to greater harshness (but not unpredictability) during the first 5 years of life predicted earlier menarche and (b) secure infant-mother attachment buffered girls from this effect of harsh environments. By connecting attachment research to its evolutionary foundations, these results illuminate how environmental stressors and relationships early in life jointly affect pubertal timing. © The Author(s) 2016.
Stress relaxation in quasi-two-dimensional self-assembled nanoparticle monolayers

Science.gov (United States)

Boucheron, Leandra S.; Stanley, Jacob T.; Dai, Yeling; You, Siheng Sean; Parzyck, Christopher T.; Narayanan, Suresh; Sandy, Alec R.; Jiang, Zhang; Meron, Mati; Lin, Binhua; Shpyrko, Oleg G.

2018-05-01

We experimentally probed the stress relaxation of a monolayer of iron oxide nanoparticles at the water-air interface. Upon drop-casting onto a water surface, the nanoparticles self-assembled into islands of two-dimensional hexagonally close packed crystalline domains surrounded by large voids. When compressed laterally, the voids gradually disappeared as the surface pressure increased. After the compression was stopped, the surface pressure (as measured by a Wilhelmy plate) evolved as a function of the film aging time with three distinct timescales. These aging dynamics were intrinsic to the stressed state built up during the non-equilibrium compression of the film. Utilizing x-ray photon correlation spectroscopy, we measured the characteristic relaxation time (τ ) of in-plane nanoparticle motion as a function of the aging time through both second-order and two-time autocorrelation analysis. Compressed and stretched exponential fitting of the intermediate scattering function yielded exponents (β ) indicating different relaxation mechanisms of the films under different compression stresses. For a monolayer compressed to a lower surface pressure (between 20 mN/m and 30 mN/m), the relaxation time (τ ) decreased continuously as a function of the aging time, as did the fitted exponent, which transitioned from being compressed (>1 ) to stretched (stress release through crystalline domain reorganization. However, for a monolayer compressed to a higher surface pressure (around 40 mN/m), the relaxation time increased continuously and the compressed exponent varied very little from a value of 1.6, suggesting that the system may have been highly stressed and jammed. Despite the interesting stress relaxation signatures seen in these samples, the structural ordering of the monolayer remained the same over the sample lifetime, as revealed by grazing incidence x-ray diffraction.
Hyperchaos of four state autonomous system with three positive Lyapunov exponents

International Nuclear Information System (INIS)

Ge Zhengming; Yang, C-H.

2009-01-01

This Letter gives the results of numerical simulations of Quantum Cellular Neural Network (Quantum-CNN) autonomous system with four state variables. Three positive Lyapunov exponents confirm hyperchaotic nature of its dynamics
On Hurst exponent estimation under heavy-tailed distributions

Czech Academy of Sciences Publication Activity Database

Baruník, Jozef; Krištoufek, Ladislav

2010-01-01

Roč. 389, č. 18 (2010), s. 3844-3855 ISSN 0378-4371 R&D Projects: GA ČR GA402/09/0965 Grant - others:GA UK(CZ) 118310; GA UK(CZ) 46108 Institutional research plan: CEZ:AV0Z10750506 Keywords : high frequency data analysis * heavy tails * Hurst exponent Subject RIV: AH - Economics Impact factor: 1.521, year: 2010 http://library.utia.cas.cz/separaty/2010/E/barunik-0343525.pdf
The influence of pubertal timing and stressful life events on depression and delinquency among Chinese adolescents.

Science.gov (United States)

Chen, Jie; Yu, Jing; Wu, Yun; Zhang, Jianxin

2015-06-01

This study aimed to investigate the influences of pubertal timing and stressful life events on Chinese adolescents' depression and delinquency. Sex differences in these influences were also examined. A large sample with 4,228 participants aged 12-15 years (53% girls) was recruited in Beijing, China. Participants' pubertal development, stressful life events, depressive symptoms, and delinquency were measured using self-reported questionnaires. Both early maturing girls and boys displayed more delinquency than their same-sex on-time and late maturing peers. Early maturing girls displayed more depressive symptoms than on-time and late maturing girls, but boys in the three maturation groups showed similar levels of depressive symptoms. The interactive effects between early pubertal timing and stressful life events were significant in predicting depression and delinquency, particularly for girls. Early pubertal maturation is an important risk factor for Chinese adolescents' depression and delinquency. Stressful life events intensified the detrimental effects of early pubertal maturation on adolescents' depression and delinquency, particularly for girls. © 2015 The Institute of Psychology, Chinese Academy of Sciences and Wiley Publishing Asia Pty Ltd.
Stressful situations in life, use and abuse of alcohol and drugs by elderly in Monterrey, Mexico

OpenAIRE

Castillo,Bertha Alicia Alonso; Marziale,Maria Helena Palucci; Castillo,Maria Magdalena Alonso; Facundo,Francisco Rafael Guzmán; Meza,Marco Vinicio Gómez

2008-01-01

This is a descriptive, qualitative, and correlation study with 112 elderly aged 60 years or older. This study aimed to identify differences in alcohol consumption according to gender and marital status, and differences in the consumption of medical drugs by gender. It also aims to determine differences in stressful life events by gender, and differences in stressful life events associated to alcohol and medical drugs use and abuse, as well as to know their perceptions on the most stressful li...
Multidimensional Perfectionism, Depression, and Satisfaction with Life: Differences among Perfectionists and Tests of a Stress-Mediation Model

Science.gov (United States)

Ashby, Jeffrey S.; Noble, Christina L.; Gnilka, Philip B.

2012-01-01

This study examined the relationship between adaptive and maladaptive perfectionism, stress, depression, and satisfaction with life in a sample of undergraduate women. The authors found that maladaptive perfectionists had lower satisfaction with life and higher stress and depression scores compared with adaptive perfectionists. Results also…
Experimental determination of the micro-scale strength and stress-strain relation of an epoxy resin

DEFF Research Database (Denmark)

Zike, Sanita; Sørensen, Bent F.; Mikkelsen, Lars Pilgaard

2016-01-01

An approach is developed for determining the stress-strain law and a failure stress appropriate for micro-mechanical models of polymer materials. Double cantilever beam test specimens, made of an epoxy polymer with notches having finite root radius, were subjected to pure bending moments in an en......An approach is developed for determining the stress-strain law and a failure stress appropriate for micro-mechanical models of polymer materials. Double cantilever beam test specimens, made of an epoxy polymer with notches having finite root radius, were subjected to pure bending moments......-scale (5–6%). The hardening exponent of a power law hardening material was obtained by the use of the J-integral, estimating the strain energy density around the notch. The hardening exponent was found to be within the range of 5–6 and the corresponding micro-scale failure stress was in the range of 220...
Distribution of incremental static stress caused by earthquakes

Directory of Open Access Journals (Sweden)

Y. Y. Kagan

1994-01-01

Full Text Available Theoretical calculations, simulations and measurements of rotation of earthquake focal mechanisms suggest that the stress in earthquake focal zones follows the Cauchy distribution which is one of the stable probability distributions (with the value of the exponent α equal to 1. We review the properties of the stable distributions and show that the Cauchy distribution is expected to approximate the stress caused by earthquakes occurring over geologically long intervals of a fault zone development. However, the stress caused by recent earthquakes recorded in instrumental catalogues, should follow symmetric stable distributions with the value of α significantly less than one. This is explained by a fractal distribution of earthquake hypocentres: the dimension of a hypocentre set, ��, is close to zero for short-term earthquake catalogues and asymptotically approaches 2¼ for long-time intervals. We use the Harvard catalogue of seismic moment tensor solutions to investigate the distribution of incremental static stress caused by earthquakes. The stress measured in the focal zone of each event is approximated by stable distributions. In agreement with theoretical considerations, the exponent value of the distribution approaches zero as the time span of an earthquake catalogue (ΔT decreases. For large stress values α increases. We surmise that it is caused by the δ increase for small inter-earthquake distances due to location errors.
SICKNESS PRESENCE AND STRESSFUL LIFE EVENTS OF HEALTH CARE WORKERS.

Science.gov (United States)

Škerjanc, Alenka; Fikfak, Metoda Dodič

2015-09-01

The aim of the study is to investigate the relationship between sickness presence and stressful life events among health care workers. Data were gathered from all health care workers at the University Medical Centre Ljubljana employed there in the period between 1 January 2010 and 31 December 2010. Each employee obtained a questionnaire composed of two standardized international questionnaires. There were 57% of sickness present health care workers among the participants. The sickness present reported to have more diseases of family member than the non-sickness present (OR = 1.5; 95% CI = 1.2-2.0), loan (OR = 1.4; 95% CI = 1.1-1.6), their partner lost job (OR = 1.4; 95% CI = 1.0-1.8), or they changed the place of living (OR = 1.4; 95% CI = 1.0-2.0). The results of the study indicate that stressful life events with economic consequences might have an important influence on sickness presence.
The effect of cognitive–behavioral stress management training on improving psychological symptoms and quality of life in nurses

Directory of Open Access Journals (Sweden)

Leila Bahmanzadeh

2017-11-01

Full Text Available As a stressful profession, nursing deals with different aspects of human health and illness, and stress can threaten nurses’ health and performance. As a result, using preventive stress management programs seems necessary. The present study aimed to evaluate the effectiveness of cognitive–behavioral stress management training in improving psychological symptoms (stress, anxiety, and depression and quality of life in nurses. The design of this study was quasi-experimental with pretest-posttest and a control group. The statistical population comprised all nurses working in Bandar Abbas Shari'ati Hospital. The study sample included all 30 nurses selected through convenience sampling method. They equally and randomly were divided into experiment and control groups. Depression, anxiety, and stress scale and the Farsi version of WHOQOL-BREF were used to collect data. The results showed there was a significant difference between pretest and posttest of experimental group in the mean scores of stress, anxiety, and quality of life; however, there was no significant difference in depression. Control group mean scores did not show a significant difference between pretest and posttest. There was no significant difference between the control and experimental groups before intervention in stress, anxiety, depression, and quality of life. The findings of this study suggest that, as a useful clinical intervention, stress management skill training is an effective way to improve mental distress and quality of life.
World Trade Center disaster and sensitization to subsequent life stress: A longitudinal study of disaster responders.

Science.gov (United States)

Zvolensky, Michael J; Farris, Samantha G; Kotov, Roman; Schechter, Clyde B; Bromet, Evelyn; Gonzalez, Adam; Vujanovic, Anka; Pietrzak, Robert H; Crane, Michael; Kaplan, Julia; Moline, Jacqueline; Southwick, Steven M; Feder, Adriana; Udasin, Iris; Reissman, Dori B; Luft, Benjamin J

2015-06-01

The current study examined the role of World Trade Center (WTC) disaster exposure (hours spent working on the site, dust cloud exposure, and losing friend/loved one) in exacerbating the effects of post-disaster life stress on posttraumatic stress disorder (PTSD) symptoms and overall functioning among WTC responders. Participants were 18,896 responders (8466 police officers and 10,430 non-traditional responders) participating in the WTC Health Program who completed an initial examination between July, 2002 and April, 2010 and were reassessed an average of two years later. Among police responders, there was a significant interaction, such that the effect of post-disaster life stress on later PTSD symptoms and overall functioning was stronger among police responders who had greater WTC disaster exposure (β's=.029 and .054, respectively, for PTSD symptoms and overall functioning). This moderating effect was absent in non-traditional responders. Across both groups, post-disaster life stress also consistently was related to the dependent variables in a more robust manner than WTC exposure. The present findings suggest that WTC exposure may compound post-disaster life stress, thereby resulting in a more chronic course of PTSD symptoms and reduced functioning among police responders. Copyright © 2015 Elsevier Inc. All rights reserved.
[Effects on Stress, Problem Solving Ability and Quality of Life of as a Stress Management Program for Hospitalized Schizophrenic Patients: Based on the Stress, Appraisal-Coping Model of Lazarus & Folkman].

Science.gov (United States)

Park, Sun Ah; Sung, Kyung Mi

2016-08-01

The study was done to evaluate the effects a Stress Management Program (SMP) on stress, problem solving skills, and quality of life for hospitalized patients with Schizophrenia. A mixed method design was used: a combination of a repeated-measure design with a non-equivalent control group and qualitative data collection. The participants were 40 patients with schizophrenia admitted in three psychiatric hospitals. The experimental group (n=20) received the SMP twice a week for a total of 8 weeks. Study results revealed that the SMP was effective for stress (F=321.02, pproblem solving ability (F=246.28, peffective strategy to reduce patients' hospitalization stress, and improve problem solving skills and quality of life. Therefore, it is recommended that mental health nurses use this stress management program in clinical practice to assist adaptation to hospitalization for persons with schizophrenia.

Health and safety matters! Associations between organizational practices and personal support workers' life and work stress in Ontario, Canada.

Science.gov (United States)

Zeytinoglu, Isik U; Denton, Margaret; Brookman, Catherine; Davies, Sharon; Sayin, Firat K

2017-06-21

The home and community care sector is one of the fastest growing sectors globally and most prominently in mature industrialized countries. Personal support workers (PSWs) are the largest occupational group in the sector. This paper focuses on the emotional health of PSWs working in the home and community care sector in Ontario, Canada. The purpose of this paper is to present evidence on the associations between PSWs' life and work stress and organizational practices of full-time and guaranteed hours, and PSWs' perceptions of support at work and preference for hours. Data come from our 2015 survey of 1543 PSWs. Dependent variables are life and work stress. Independent variables are: objective organizational practices of full-time and guaranteed hours, and subjective organizational practices of perceived support at work, and preferred hours of work. Descriptive statistics, correlations and ordinary least square regression analyses with collinearity tests are conducted. Organizational practices of employing PSWs in full-time or guaranteed hours are not associated with their life and work stress. However, those who perceive support from their organizations are also the ones reporting lower life and work stress. In addition, those PSWs perceiving support from their supervisor report lower work stress. PSWs would like to work in their preferred hours, and those who prefer to work more hours report lower life and work stress, and conversely, those who prefer to work less hours report life and work stress. For PSWs in home and community care, perceived support from their organizations and supervisors, and employment in preferred hours are important factors related to their life and work stress.
"MENTAL STRAIN, MORE IMPORTANT THAN STRESSFUL LIFE EVENTS IN MYOCARDIAL INFARCTION"

OpenAIRE

M. Moosavi; M. Eslami; O. Sheikh Bagloo B. Birashk

2004-01-01

Stressful life events may play an important role in coronary heart disease and sudden cardiac death. This study was performed to compare the frequency of stressful events and mental strain in patients with acute myocardial infarction (MI) and normal population. A case-control study was performed on 50 survivors of MI and 50 controls with no evidence of cardiovascular disease, matched by age, gender, education, race, and number of family members. A questionnaire was used to determine the numbe...
Sibling Socialization: The Effects of Stressful Life Events and Experiences

Science.gov (United States)

Conger, Katherine J.; Stocker, Clare; McGuire, Shirley

2009-01-01

Stressful life events and experiences may disrupt the typical day-to-day interactions between sisters and brothers that provide the foundation of sibling socialization. This chapter examines four experiences that may affect patterns of sibling interaction: parental marital conflict, parental divorce and remarriage, foster care placement, and a…
Fast and unbiased estimator of the time-dependent Hurst exponent

Science.gov (United States)

Pianese, Augusto; Bianchi, Sergio; Palazzo, Anna Maria

2018-03-01

We combine two existing estimators of the local Hurst exponent to improve both the goodness of fit and the computational speed of the algorithm. An application with simulated time series is implemented, and a Monte Carlo simulation is performed to provide evidence of the improvement.
Directional maximum likelihood self-estimation of the path-loss exponent

NARCIS (Netherlands)

Hu, Y.; Leus, G.J.T.; Dong, Min; Zheng, Thomas Fang

2016-01-01

The path-loss exponent (PLE) is a key parameter in wireless propagation channels. Therefore, obtaining the knowledge of the PLE is rather significant for assisting wireless communications and networking to achieve a better performance. Most existing methods for estimating the PLE not only require
Early Life Stress, Depression And Parkinson's Disease: A New Approach.

Science.gov (United States)

Dallé, Ernest; Mabandla, Musa V

2018-03-19

This review aims to shed light on the relationship that involves exposure to early life stress, depression and Parkinson's disease (PD). A systematic literature search was conducted in Pubmed, MEDLINE, EBSCOHost and Google Scholar and relevant data were submitted to a meta-analysis . Early life stress may contribute to the development of depression and patients with depression are at risk of developing PD later in life. Depression is a common non-motor symptom preceding motor symptoms in PD. Stimulation of regions contiguous to the substantia nigra as well as dopamine (DA) agonists have been shown to be able to attenuate depression. Therefore, since PD causes depletion of dopaminergic neurons in the substantia nigra, depression, rather than being just a simple mood disorder, may be part of the pathophysiological process that leads to PD. It is plausible that the mesocortical and mesolimbic dopaminergic pathways that mediate mood, emotion, and/or cognitive function may also play a key role in depression associated with PD. Here, we propose that a medication designed to address a deficiency in serotonin is more likely to influence motor symptoms of PD associated with depression. This review highlights the effects of an antidepressant, Fluvoxamine maleate, in an animal model that combines depressive-like symptoms and Parkinsonism.
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.
Suicidal Ideation, Depression, Anxiety, Stress, And Life Satisfaction Of Medical, Engineering, And Social Sciences Students.

Science.gov (United States)

Naseem, Sabahat; Munaf, Seema

2017-01-01

Pursuing higher education is not an easy task as it requires hard work, dedication, and motivation. Although there are many rewards involved in growing up academically, nevertheless, it contains a few hazards too. For instance, suicidal ideation is associated with presence of depression, anxiety, and stress with low level of satisfaction with life in students finding difficulty in handling educational demands of higher education. Therefore, the present study focused on the query that whether there is any difference or not among medical, engineering, and social sciences students of city of Karachi, Pakistan in the level of suicidal ideation, depression, anxiety, stress, and life satisfaction. Using comparative group design, total 300 students (150 males and 150 females) with age range of 19-26 were selected from faculties of medical, engineering, and social sciences of different universities of Karachi, Pakistan, through purposive sampling. Respondent Profile Form, The Suicide Behaviours Questionnaire-Revised, Depression Anxiety Stress Scale-21, and Satisfaction with Life Scale were administered to assess suicidal ideation; depression, anxiety, stress; and life satisfaction, respectively, of the students. Scores were analysed through ANOVA and Post Hoc (Tukey's HSD) test using SPSS. Social sciences and engineering students were significantly higher on depression, anxiety, and stress than medical students [F (2, 297) =8.701, p=.000] whereas insignificant differences in the level of suicidal ideation [F (2, 297) =1.914, p=.149] and life satisfaction [F (2, 297) = .726, p = .485] among these students were found. With the help of these findings, it would be easier to counsel students of different disciplines in time on the lines of suggested preventive measures.
Evidence of an IFN-γ by early life stress interaction in the regulation of amygdala reactivity to emotional stimuli.

Science.gov (United States)

Redlich, Ronny; Stacey, David; Opel, Nils; Grotegerd, Dominik; Dohm, Katharina; Kugel, Harald; Heindel, Walter; Arolt, Volker; Baune, Bernhard T; Dannlowski, Udo

2015-12-01

Since numerous studies have found that exposure to early life stress leads to increased peripheral inflammation and psychiatric disease, it is thought that peripheral immune activation precedes and possibly mediates the onset of stress-associated psychiatric disease. Despite early studies, IFNγ has received little attention relative to other inflammatory cytokines in the context of the pathophysiology of affective disorders. Neuroimaging endophenotypes have emerged recently as a promising means of elucidating these types of complex relationships including the modeling of the interaction between environmental factors and genetic predisposition. Here we investigate the GxE relationship between early-life stress and genetic variants of IFNγ on emotion processing. To investigate the impact of the relationship between genetic variants of IFNγ (rs1861494, rs2069718, rs2430561) and early life stress on emotion processing, a sample of healthy adults (n=409) undergoing an emotional faces paradigm in an fMRI study were genotyped and analysed. Information on early life stress was obtained via Childhood Trauma Questionnaire (CTQ). A positive association between early life stress and amygdala reactivity was found. Specifically, the main effect of genotype of rs1861494 on amygdala reactivity indicates a higher neural response in C allele carriers compared to T homozygotes, while we did not find main effects of rs2069718 and rs2430561. Importantly, interaction analyses revealed a specific interaction between IFNγ genotype (rs1861494) and early life stress affecting amygdala reactivity to emotional faces, resulting from a positive association between CTQ scores and amygdala reactivity in C allele carriers while this association was absent in T homozygotes. Our findings indicate that firstly the genetic variant of IFNγ (rs1861494) is involved with the regulation of amygdala reactivity to emotional stimuli and secondly, that this genetic variant moderates effects of early life
Improved integrability of the gradients of solutions of elliptic equations with variable nonlinearity exponent

International Nuclear Information System (INIS)

Zhikov, Vasilii V; Pastukhova, Svetlana E

2008-01-01

Elliptic equations of p(x)-Laplacian type are investigated. There is a well-known logarithmic condition on the modulus of continuity of the nonlinearity exponent p(x), which ensures that a Laplacian with variable order of nonlinearity inherits many properties of the usual p-Laplacian of constant order. One of these is the so-called improved integrability of the gradient of the solution. It is proved in this paper that this property holds also under a slightly more general condition on the exponent p(x), although then the improvement of integrability is logarithmic rather than power-like. The method put forward is based on a new generalization of Gehring's lemma, which relies upon the reverse Hoelder inequality 'with increased support and exponent on the right-hand side'. A counterexample is constructed that reveals the extent to which the condition on the modulus of continuity obtained is sharp. Bibliography: 28 titles.
Cancer as a stressful life event: Perceptions of children with cancer and their peers.

Science.gov (United States)

Sharp, Katianne M Howard; Lindwall, Jennifer J; Willard, Victoria W; Long, Alanna M; Martin-Elbahesh, Karen M; Phipps, Sean

2017-09-01

The medical traumatic stress model is commonly applied to childhood cancer, assuming that the diagnosis of cancer is a traumatic event. However, to the authors' knowledge, little is known regarding what specifically children perceive as stressful about cancer or how it compares with other stressful events more often experienced by children. Children with cancer (254 children) and demographically similar peers without a history of serious illness (202 children) identified their most stressful life event as part of a diagnostic interview assessing for symptoms of posttraumatic stress disorder (PTSD). The events identified as most stressful were categorized thematically, with categories established separately for cancer-related and non-cancer-related events. Events also were examined to assess whether they met Diagnostic and Statistical Manual of Mental Disorders (DSM) A criteria for PTSD. In the group of children with cancer, 54% described a cancer-related event as the most stressful event they had experienced. Six distinct categories of cancer-related events and 10 categories of non-cancer-related events were identified. The same noncancer events were identified by children in both groups, and occurred at similar frequencies. The percentage of cancer-related events that met DSM A criteria for PTSD differed dramatically depending on which version of the DSM was applied. Children do not necessarily view their cancer experience as their most stressful life event. The findings of the current study suggest that the diagnosis of cancer might be better viewed as a manageable stressor rather than a major trauma, and are consistent with the change in the fifth edition of the DSM to eliminate the diagnosis of a life-threatening illness as a qualifying trauma for PTSD. Cancer 2017;123:3385-93. © 2017 American Cancer Society. © 2017 American Cancer Society.
Late-Onset Cognitive Impairments after Early-Life Stress Are Shaped by Inherited Differences in Stress Reactivity

Science.gov (United States)

McIlwrick, Silja; Pohl, Tobias; Chen, Alon; Touma, Chadi

2017-01-01

Early-life stress (ELS) has been associated with lasting cognitive impairments and with an increased risk for affective disorders. A dysregulation of the hypothalamus-pituitary-adrenal (HPA) axis, the body’s main stress response system, is critically involved in mediating these long-term consequences of adverse early-life experience. It remains unclear to what extent an inherited predisposition for HPA axis sensitivity or resilience influences the relationship between ELS and cognitive impairments, and which neuroendocrine and molecular mechanisms may be involved. To investigate this, we exposed animals of the stress reactivity mouse model, consisting of three independent lines selectively bred for high (HR), intermediate (IR), or low (LR) HPA axis reactivity to a stressor, to ELS and assessed their cognitive performance, neuroendocrine function and hippocampal gene expression in early and in late adulthood. Our results show that HR animals that were exposed to ELS exhibited an HPA axis hyper-reactivity in early and late adulthood, associated with cognitive impairments in hippocampus-dependent tasks, as well as molecular changes in transcript levels involved in the regulation of HPA axis activity (Crh) and in neurotrophic action (Bdnf). In contrast, LR animals showed intact cognitive function across adulthood, with no change in stress reactivity. Intriguingly, LR animals that were exposed to ELS even showed significant signs of enhanced cognitive performance in late adulthood, which may be related to late-onset changes observed in the expression of Crh and Crhr1 in the dorsal hippocampus of these animals. Collectively, our findings demonstrate that the lasting consequences of ELS at the level of cognition differ as a function of inherited predispositions and suggest that an innate tendency for low stress reactivity may be protective against late-onset cognitive impairments after ELS. PMID:28261058
The Effectiveness of Stress Management Program on Quality of Life among Methadone Maintenance Treatment Members

Directory of Open Access Journals (Sweden)

s Zarei

2014-11-01

Full Text Available Objective: The aim of present study was to investigate the effectiveness of stress management program on quality of life among methadone maintenance treatment members. Method: In this pre-test, post-test experimental study, 30 individual who referred to Saba MMT center in Pakdasht were randomly divided into experimental group (n=15 participants and control group (n=15 participants. The experimental group was undergone ten 90 minutes sessions of stress management program and the control group didn’t receive any treatment program. Quality of life questionnaire (SF-36 was administered. Result: The results showed that the mean sf-36 score in the experimental group had significant higher increased in comparison of control group. Conclusion: It can be concluded stress management program is effective on increasing of quality of life among methadone maintenance treatment members.
The stress of food allergy issues in daily life.

Science.gov (United States)

Peniamina, Rana L; Mirosa, Miranda; Bremer, Philip; Conner, Tamlin S

2016-06-01

Food allergies are a growing health concern, but their implications for daily psychological functioning are unknown. This micro-longitudinal study investigated the daily frequency of food allergy issues and how this related to experiences of stress, mood and physical energy. One hundred and eight adults with physician-diagnosed food allergies completed an initial Internet survey followed by a 2-week Internet daily diary survey. The initial survey collected socio-demographic and food allergy information. The daily survey collected information about the participants' experiences of stress, mood, physical energy and food allergy issues during that day. Commonly experienced allergy issues included negative physical symptoms, higher food prices, anxiety about safety of food, trouble maintaining a healthy diet and anxiety/stress at social occasions. Furthermore, multilevel modelling analyses showed that stress and negative mood were significantly higher on days with more allergy issues. Older adults experienced lower positive mood and physical energy on days with more issues. This is the first study to incorporate near to real-time tracking to examine the frequency of food allergy issues and the implications for daily psychological functioning. Targeting the issues we identified could reduce stress in patients with food allergies and improve their overall quality of life.
Instrumental learning and cognitive flexibility processes are impaired in children exposed to early life stress.

Science.gov (United States)

Harms, Madeline B; Shannon Bowen, Katherine E; Hanson, Jamie L; Pollak, Seth D

2017-10-19

Children who experience severe early life stress show persistent deficits in many aspects of cognitive and social adaptation. Early stress might be associated with these broad changes in functioning because it impairs general learning mechanisms. To explore this possibility, we examined whether individuals who experienced abusive caregiving in childhood had difficulties with instrumental learning and/or cognitive flexibility as adolescents. Fifty-three 14-17-year-old adolescents (31 exposed to high levels of childhood stress, 22 control) completed an fMRI task that required them to first learn associations in the environment and then update those pairings. Adolescents with histories of early life stress eventually learned to pair stimuli with both positive and negative outcomes, but did so more slowly than their peers. Furthermore, these stress-exposed adolescents showed markedly impaired cognitive flexibility; they were less able than their peers to update those pairings when the contingencies changed. These learning problems were reflected in abnormal activity in learning- and attention-related brain circuitry. Both altered patterns of learning and neural activation were associated with the severity of lifetime stress that the adolescents had experienced. Taken together, the results of this experiment suggest that basic learning processes are impaired in adolescents exposed to early life stress. These general learning mechanisms may help explain the emergence of social problems observed in these individuals. © 2017 The Authors. Developmental Science Published by John Wiley & Sons Ltd.
Biological Aging and Life Span Based on Entropy Stress via Organ and Mitochondrial Metabolic Loading

Directory of Open Access Journals (Sweden)

Kalyan Annamalai

2017-10-01

Full Text Available The energy for sustaining life is released through the oxidation of glucose, fats, and proteins. A part of the energy released within each cell is stored as chemical energy of Adenosine Tri-Phosphate molecules, which is essential for performing life-sustaining functions, while the remainder is released as heat in order to maintain isothermal state of the body. Earlier literature introduced the availability concepts from thermodynamics, related the specific irreversibility and entropy generation rates to metabolic efficiency and energy release rate of organ k, computed whole body specific entropy generation rate of whole body at any given age as a sum of entropy generation within four vital organs Brain, Heart, Kidney, Liver (BHKL with 5th organ being the rest of organs (R5 and estimated the life span using an upper limit on lifetime entropy generated per unit mass of body, σM,life. The organ entropy stress expressed in terms of lifetime specific entropy generated per unit mass of body organs (kJ/(K kg of organ k was used to rank organs and heart ranked highest while liver ranked lowest. The present work includes the effects of (1 two additional organs: adipose tissue (AT and skeletal muscles (SM which are of importance to athletes; (2 proportions of nutrients oxidized which affects blood temperature and metabolic efficiencies; (3 conversion of the entropy stress from organ/cellular level to mitochondrial level; and (4 use these parameters as metabolism-based biomarkers for quantifying the biological aging process in reaching the limit of σM,life. Based on the 7-organ model and Elia constants for organ metabolic rates for a male of 84 kg steady mass and using basic and derived allometric constants of organs, the lifetime energy expenditure is estimated to be 2725 MJ/kg body mass while lifetime entropy generated is 6050 kJ/(K kg body mass with contributions of 190; 1835.0; 610; 290; 700; 1470 and 95 kJ/K contributed by AT-BHKL-SM-R7 to 1 kg body
Exploring the Experience of Life Stress Among Black Women with a History of Fetal or Infant Death: a Phenomenological Study.

Science.gov (United States)

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

2017-06-01

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

Science.gov (United States)

Casu, Giulia; Ulivi, Giulia; Zaia, Victor; Fernandes Martins, Maria do Carmo; Parente Barbosa, Caio; Gremigni, Paola

2018-04-01

Infertility has a stressful impact on both partners, with adverse effects on the quality of life of infertile couples. Spirituality is a meaning-based strategy that can protect couples against infertility's negative impact on quality of life, but analysis of this mediator relationship in infertile couples has not been reported. We adopted a dyadic approach and used the actor-partner interdependence mediation model to examine whether and how women's and men's spirituality was associated with their own and their partners' infertility-related stress and quality of life. In 2014, 152 infertile couples starting their first fertility treatment at a private clinic in Brazil were recruited and completed self-reports of spirituality, infertility-related stress, and quality of life. Results indicated that women's and men's level of spirituality was positively associated with their own quality of life directly and indirectly, by reducing their own infertility-related stress. Their spirituality was associated with an increase in their partners' quality of life only indirectly, by reducing their partners' infertility-related stress. Findings highlight the importance of assessing and promoting spirituality as a coping resource that infertile women and men might use to deal with the stress of infertility and reduce its adverse effects on quality of life. © 2018 Wiley Periodicals, Inc.
Oxidative stress markers imbalance in late-life depression.

Science.gov (United States)

Diniz, Breno S; Mendes-Silva, Ana Paula; Silva, Lucelia Barroso; Bertola, Laiss; Vieira, Monica Costa; Ferreira, Jessica Diniz; Nicolau, Mariana; Bristot, Giovana; da Rosa, Eduarda Dias; Teixeira, Antonio L; Kapczinski, Flavio

2018-03-20

Oxidative stress has been implicated in the pathophysiology of mood disorders in young adults. However, there is few data to support its role in the elderly. The primary aim of this study was to evaluate whether subjects with late-life depression (LLD) presented with changes in oxidative stress response in comparison with the non-depressed control group. We then explored how oxidative stress markers associated with specific features of LLD, in particular cognitive performance and age of onset of major depressive disorder in these individuals. We included a convenience sample of 124 individuals, 77 with LLD and 47 non-depressed subjects (Controls). We measure the plasma levels of 6 oxidative stress markers: thiobarbituric acid reactive substances (TBARS), protein carbonil content (PCC), free 8-isoprostane, glutathione peroxidase (GPx) activity, glutathione reductase (GR) activity, and glutathione S-transferase (GST) activity. We found that participants with LLD had significantly higher free 8-isoprostane levels (p = 0.003) and lower glutathione peroxidase activity (p = 0.006) compared to controls. Free 8-isoprostane levels were also significantly correlated with worse scores in the initiation/perseverance (r = -0.24, p = 0.01), conceptualization (r = -0.22, p = 0.02) sub-scores, and the total scores (r = -0.21, p = 0.04) on the DRS. Our study provides robust evidence of the imbalance between oxidative stress damage, in particular lipid peroxidation, and anti-oxidative defenses as a mechanism related to LLD, and cognitive impairment in this population. Interventions aiming to reduce oxidative stress damage can have a potential neuroprotective effect for LLD subjects. Copyright © 2018 Elsevier Ltd. All rights reserved.
Perceived stress and coping skills of university student–athletes and the relationship with life satisfaction

OpenAIRE

J. Surujlal; Y. Van Zyl; V.T. Nolan

2013-01-01

Student-athletes are expected to cope with their studies and participation in sport simultaneously as well as to satisfy the expectations of coaches, teammates, friends, and family. Once student-athletes perceive a situation as stressful and struggle to cope with the anticipation thereof, their satisfaction with life will be negatively influenced. This study was conducted to determine the relationship between perceived stress and coping skills with satisfaction with life of university student...

Effects of life event stress, exercise workload, hardiness and coping ...

African Journals Online (AJOL)

Effects of life event stress, exercise workload, hardiness and coping style on susceptibility to the common cold. GA Struwig, M Papaikonomou, P Kruger. Abstract. No Abstract. South African Journal for Physical, Health Education, Recreation and DanceVol. 12(4) 2006: pp. 369-383. Full Text: EMAIL FULL TEXT EMAIL FULL ...
Numerical difficulties to obtain 3-d critical exponents from platonic solids

International Nuclear Information System (INIS)

Alcaraz, F.C.; Herrmann, H.J.

1985-01-01

The possibility to extract critical exponents of 3-d systems exploring the mass gap amplitudes of platonic solids is tested. For the Ising model the proposed method does not work for numerical reasons. (Author) [pt
The influence of mastery on mother's health in middle years: Moderating role of stressful life context.

Science.gov (United States)

King, Victoria; Wickrama, K A S; Klopack, Erick; Lorenz, Frederick O

2018-06-07

Using data from 416 middle-aged mothers gathered over the course of a decade, this study examined the influence of mastery trajectories (the initial level and change), on change in physical health. Mastery is defined as one's ability to control and influence his/her life and environment to reach a desired outcome or goal. Both the initial level and change in mastery from 1991 to 1994 were associated with decreased physical health problems over the middle years (1991-2001). Contextual moderation of this association by stressful life contexts including negative life events and work-family conflict was investigated. Moderation analysis showed that under conditions of low contextual life stressors, the level and increase in mastery significantly contributed to decreases in physical health problems in middle-aged mothers. Alternatively, conditions of high contextual life stressors inhibited the ability of mastery to influence physical health of mothers, suggesting that the positive health impact of mastery on physical health is mitigated by stressful life experiences. Implications for the need to maintain important personal resources, such as mastery, during times of stress are discussed. Copyright © 2018 John Wiley & Sons, Ltd.
Investigating textural controls on Archie's porosity exponent using process-based, pore-scale modelling

Science.gov (United States)

Niu, Q.; Zhang, C.

2017-12-01

Archie's law is an important empirical relationship linking the electrical resistivity of geological materials to their porosity. It has been found experimentally that the porosity exponent m in Archie's law in sedimentary rocks might be related to the degree of cementation, and therefore m is termed as "cementation factor" in most literatures. Despite it has been known for many years, there is lack of well-accepted physical interpretations of the porosity exponent. Some theoretical and experimental evidences have also shown that m may be controlled by the particle and/or pore shape. In this study, we conduct a pore-scale modeling of the porosity exponent that incorporates different geological processes. The evolution of m of eight synthetic samples with different particle sizes and shapes are calculated during two geological processes, i.e., compaction and cementation. The numerical results show that in dilute conditions, m is controlled by the particle shape. As the samples deviate from dilute conditions, m increases gradually due to the strong interaction between particles. When the samples are at static equilibrium, m is noticeably larger than its values at dilution condition. The numerical simulation results also show that both geological compaction and cementation induce a significant increase in m. In addition, the geometric characteristics of these samples (e.g., pore space/throat size, and their distributions) during compaction and cementation are also calculated. Preliminary analysis shows a unique correlation between the pore size broadness and porosity exponent for all eight samples. However, such a correlation is not found between m and other geometric characteristics.
Analgesia for early-life pain prevents deficits in adult anxiety and stress in rats.

Science.gov (United States)

Victoria, Nicole C; Karom, Mary C; Murphy, Anne Z

2015-01-01

Previous studies in rats have established that inflammatory pain experienced on the day of birth (P0) decreases sensitivity to acute noxious, anxiety- and stress-provoking stimuli. However, to date, the impact of early-life pain on adult responses to chronic stress is not known. Further, the ability of morphine, administered at the time of injury, to mitigate changes in adult behavioral and hormonal responses to acute or chronic stressors has not been examined. P0 male and female Sprague-Dawley rat pups were given an intraplantar injection of 1% carrageenan or handled in an identical manner in the presence or absence of morphine. As adults, rats that experienced early-life pain displayed decreased sensitivity to acute stressors, as indicated by increased time in the inner area of the Open Field, and increased latency to immobility and decreased time immobile in the Forced Swim Test (FST). An accelerated return of corticosterone to baseline was also observed. Morphine administration at the time of injury completely reversed this 'hyporesponsive' phenotype. By contrast, following 7 days of chronic variable stress, injured animals displayed a 'hyperresponsive' phenotype in that they initiated immobility and spent significantly more time immobile in the FST than controls. Responses to chronic stress were also rescued in animals that received morphine at the time of injury. These data suggest that analgesia for early-life pain prevents adult hyposensitivity to acute anxiety- and stress-provoking stimuli and increased vulnerability to chronic stress, and have important clinical implications for the management of pain in infants. © 2014 S. Karger AG, Basel.
Stress analysis and life prediction of gas turbine blade

Science.gov (United States)

Hsiung, H. C.; Dunn, A. J.; Woodling, D. R.; Loh, D. L.

1988-01-01

A stress analysis procedure is presented for a redesign of the Space Shuttle Main Engine high pressure fuel turbopump turbine blades. The analysis consists of the one-dimensional scoping analysis to support the design layout and the follow-on three-dimensional finite element analysis to confirm the blade design at operating loading conditions. Blade life is evaluated based on high-cycle fatigue and low-cycle fatigue.
Posttraumatic Stress, Depressive Emotions, and Satisfaction With Life After a Road Traffic Accident.

Science.gov (United States)

Copanitsanou, Panagiota; Drakoutos, Evagelos; Kechagias, Vasileios

The psychological response of injured people after traffic accidents includes stress and depression. To assess orthopaedic patients' stress, depression, and satisfaction with life after traffic accidents in Greece. Descriptive, longitudinal, correlational study. Patients' background factors, injury severity, scores on the Impact of Events Scale-Revised (IES-R), the Center for Epidemiologic Studies Depression (CES-D) Scale, and the Satisfaction With Life Quality (SWLQ) Scale were recorded. The principles of the Declaration of Helsinki were applied. In total, 60 patients participated in this study during hospitalization following a road traffic accident and 40 patients at 6 months after. Participants were mostly men (75%) with severe injuries (50%). The IES-R score at 6 months was significantly lower than during hospitalization. One out of 3 people had a CES-D score, which is considered of clinical significance. The SWLQ scores were considered high. As posttraumatic stress and depression seem to affect a considerable percentage of people involved in road traffic accidents in Greece, these individuals should be assessed for posttraumatic stress and depression while still hospitalized.
Effect of a vaginal device on quality of life with urinary stress incontinence

DEFF Research Database (Denmark)

Sander, P; Thyssen, H; Lose, G

1999-01-01

OBJECTIVE: To assess the effect of a vaginal device (Continence Guard) on urine leakage and quality of life. METHODS: Fifty-five women with stress incontinence participated in a 3-month study. They were assessed by the Incontinence Impact Questionnaire, two incontinence-related quality-of-life qu......OBJECTIVE: To assess the effect of a vaginal device (Continence Guard) on urine leakage and quality of life. METHODS: Fifty-five women with stress incontinence participated in a 3-month study. They were assessed by the Incontinence Impact Questionnaire, two incontinence-related quality......-to-treat basis, the vaginal device was associated with subjective cure in 11 women (20%) and improvement in 27 (49%). The mean 24-hour pad test leakage and leakage episodes in the voiding diary decreased significantly. Fifty-eight percent of the 55 women enrolled wanted to continue using the device after 3...
The Effect of Positive Thinking Training on Quality of Life, Depression, Stress and Anxiety in Delinquent Juveniles

Directory of Open Access Journals (Sweden)

Z Nikmanesh

2015-08-01

Full Text Available The aim of the present study was to investigate the effectiveness of positive thinking training on quality of life and reduction of depression, stress and anxiety in delinquent boys of Zahedan Juvenile Correction and Rehabilitation Center (ZJCRC. Method of this research was a quasi-experimental with a design of pretest- posttest- follow up test and with a control group. The sample comprised of 29 boys (17 subjects in experimental group and 12 in control. Method of sampling was the census. That is, all of statistical population were be studied as sample group. Positive thinking training was conducted on the experimental group during 8 sessions with 90 minutes. After the last session the post-test, was conducted and one month after it, the follow-up test. For data gathering, the Quality of Life of Parkerson, Broadhear & Tse et al. and the Depression, Anxiety Stress of Lovibond & Lovibond were used. The results of co-variance analysis showed that the positive thinking training effected on reducing of depression, stress and anxiety and increasing quality of life. Therefore, in regard to effectiveness of positive thinking training on reducing of depression, stress and anxiety and increasing quality of life, it is recommended for Juvenile delinquent trainers to use of the positive thinking training for increasing quality of life and reducing of depression, stress and anxiety in these juveniles.
Quality of Gaussian basis sets: direct optimization of orbital exponents by the method of conjugate gradients

International Nuclear Information System (INIS)

Kari, R.E.; Mezey, P.G.; Csizmadia, I.G.

1975-01-01

Expressions are given for calculating the energy gradient vector in the exponent space of Gaussian basis sets and a technique to optimize orbital exponents using the method of conjugate gradients is described. The method is tested on the (9/sups/5/supp/) Gaussian basis space and optimum exponents are determined for the carbon atom. The analysis of the results shows that the calculated one-electron properties converge more slowly to their optimum values than the total energy converges to its optimum value. In addition, basis sets approximating the optimum total energy very well can still be markedly improved for the prediction of one-electron properties. For smaller basis sets, this improvement does not warrant the necessary expense
Impact of a mindfulness stress management program on stress, anxiety, depression and quality of life in women with polycystic ovary syndrome: a randomized controlled trial.

Science.gov (United States)

Stefanaki, Charikleia; Bacopoulou, Flora; Livadas, Sarantis; Kandaraki, Anna; Karachalios, Athanasios; Chrousos, George P; Diamanti-Kandarakis, Evanthia

2015-01-01

Polycystic ovary syndrome (PCOS) is a common endocrine disorder with a significant psychological burden throughout the life course of affected women. Thus, use of mindful awareness may be beneficial as an adjunct to conventional medical management of women with PCOS. A randomized, controlled trial was conducted at the Evgenideion Hospital of the Athens University Medical School to explore the impact of an 8-week mindfulness stress management program on measures of depression, anxiety and stress as well as on the quality of life in reproductive age women with PCOS. The study was approved by the Research Ethics Committee. Twenty-three and 15 women with PCOS were randomly allocated to the intervention or control group, respectively. All participants were administered DASS21, PSS-14, PCOSQ, Daily Life and General Life Satisfaction Questionnaires and provided three-timed daily samples of salivary cortisol, before and after the intervention. Intervention group participants were provided with the Credibility/Expectancy Questionnaire at the day of enrolment, to check for possible placebo effect on the outcome. Post-intervention, between-group results revealed statistically significant reductions in stress, depressive and anxiety symptoms, as well as in salivary cortisol concentrations, along with an increase in Life Satisfaction and Quality of Life scores in the intervention group only. There was no significant "placebo" effect on the outcome measures. Mindfulness techniques seem promising in ameliorating stress, anxiety, depression and the quality of life in women with PCOS and could be used as an adjunct method to the conventional management of these women.
The Effectiveness of Marriage Enrichment Training on Job Stress and Quality of Work Life of working women

OpenAIRE

H; Z salak

2016-01-01

Introduction: Today, women alongside men to help their family economic cycle. So the quality of work life and job stress affect on behavioral reactions such as job satisfaction, job involvement and job performance. Because more women than men experience job stress, the purpose of this study was to investigate the effectiveness of marriage enrichment training on job stress and quality of work life of working women at Bafg Central Iron Ore Company. Methods: This study was quasi-experimental...
Early-life adversity programs emotional functions and the neuroendocrine stress system: the contribution of nutrition, metabolic hormones and epigenetic mechanisms.

Science.gov (United States)

Yam, Kit-Yi; Naninck, Eva F G; Schmidt, Mathias V; Lucassen, Paul J; Korosi, Aniko

2015-01-01

Clinical and pre-clinical studies have shown that early-life adversities, such as abuse or neglect, can increase the vulnerability to develop psychopathologies and cognitive decline later in life. Remarkably, the lasting consequences of stress during this sensitive period on the hypothalamic-pituitary-adrenal axis and emotional function closely resemble the long-term effects of early malnutrition and suggest a possible common pathway mediating these effects. During early-life, brain development is affected by both exogenous factors, like nutrition and maternal care as well as by endogenous modulators including stress hormones. These elements, while mostly considered for their independent actions, clearly do not act alone but rather in a synergistic manner. In order to better understand how the programming by early-life stress takes place, it is important to gain further insight into the exact interplay of these key elements, the possible common pathways as well as the underlying molecular mechanisms that mediate their effects. We here review evidence that exposure to both early-life stress and early-life under-/malnutrition similarly lead to life-long alterations on the neuroendocrine stress system and modify emotional functions. We further discuss how the different key elements of the early-life environment interact and affect one another and next suggest a possible role for the early-life adversity induced alterations in metabolic hormones and nutrient availability in shaping later stress responses and emotional function throughout life, possibly via epigenetic mechanisms. Such knowledge will help to develop intervention strategies, which gives the advantage of viewing the synergistic action of a more complete set of changes induced by early-life adversity.
Fatigue Life Prediction of High Modulus Asphalt Concrete Based on the Local Stress-Strain Method

Directory of Open Access Journals (Sweden)

Mulian Zheng

2017-03-01

Full Text Available Previously published studies have proposed fatigue life prediction models for dense graded asphalt pavement based on flexural fatigue test. This study focused on the fatigue life prediction of High Modulus Asphalt Concrete (HMAC pavement using the local strain-stress method and direct tension fatigue test. First, the direct tension fatigue test at various strain levels was conducted on HMAC prism samples cut from plate specimens. Afterwards, their true stress-strain loop curves were obtained and modified to develop the strain-fatigue life equation. Then the nominal strain of HMAC course determined using finite element method was converted into local strain using the Neuber method. Finally, based on the established fatigue equation and converted local strain, a method to predict the pavement fatigue crack initiation life was proposed and the fatigue life of a typical HMAC overlay pavement which runs a risk of bottom-up cracking was predicted and validated. Results show that the proposed method was able to produce satisfactory crack initiation life.
Parental Stress, Family-Professional Partnerships, and Family Quality of Life: Families of Children with Autism Spectrum Disorder

Science.gov (United States)

Hsiao, Yun-Ju

2013-01-01

The purpose of this study was to investigate the relationship among the quality of life of families that have at least one child with autism spectrum disorder, parental stress level, and partnerships between the family and professionals. Also, parent perceptions of parental stress, family quality of life, and family-professional partnerships were…
Critical exponents in the transition to chaos in one-dimensional

Indian Academy of Sciences (India)

We report the numerically evaluated critical exponents associated with the scaling of generalized fractal dimensions during the transition from order to chaos. The analysis is carried out in detail in the context of unimodal and bimodal maps representing typical one-dimensional discrete dynamical systems. The behavior of ...
The Community Child Health Network Life Stress Interview: a brief chronic stress measure for community health research.

Science.gov (United States)

Tanner Stapleton, Lynlee R; Dunkel Schetter, Christine; Dooley, Larissa N; Guardino, Christine M; Huynh, Jan; Paek, Cynthia; Clark-Kauffman, Elizabeth; Schafer, Peter; Woolard, Richard; Lanzi, Robin Gaines

2016-07-01

Chronic stress is implicated in many theories as a contributor to a wide range of physical and mental health problems. The current study describes the development of a chronic stress measure that was based on the UCLA Life Stress Interview (LSI) and adapted in collaboration with community partners for use in a large community health study of low-income, ethnically diverse parents of infants in the USA (Community Child Health Network [CCHN]). We describe the instrument, its purpose and adaptations, implementation, and results of a reliability study in a subsample of the larger study cohort. Interviews with 272 mothers were included in the present study. Chronic stress was assessed using the CCHN LSI, an instrument designed for administration by trained community interviewers to assess four domains of chronic stress, each rated by interviewers. Significant correlations ranging from small to moderate in size between chronic stress scores on this measure, other measures of stress, biomarkers of allostatic load, and mental health provide initial evidence of construct and concurrent validity. Reliability data for interviewer ratings are also provided. This relatively brief interview (15 minutes) is available for use and may be a valuable tool for researchers seeking to measure chronic stress reliably and validly in future studies with time constraints.
Intersection of Stress, Social Disadvantage, and Life Course Processes: Reframing Trauma and Mental Health

OpenAIRE

Nurius, Paula S.; Uehara, Edwina; Zatzick, Douglas F.

2013-01-01

This paper describes the intersection of converging lines of research on the social structural, psychosocial, and physiological factors involved in the production of stress and implications for the field of mental health. Of particular interest are the stress sensitization consequences stemming from exposure to adversity over the life course. Contemporary stress sensitization theory provides important clinical utility in articulating mechanisms through which these multiple levels exert influe...
Emotional intelligence, life satisfaction and subjective happiness in female student health professionals: the mediating effect of perceived stress.

Science.gov (United States)

Ruiz-Aranda, D; Extremera, N; Pineda-Galán, C

2014-03-01

The objective of the present study was to extend previous findings by examining the relationship between emotional intelligence (EI) and well-being indicators (life satisfaction and happiness) in a 12-week follow-up study. In addition, we examined the influence of perceived stress on the relationship between EI and well-being. Female students from the School of Health Sciences (n = 264) completed an ability measure of emotional intelligence. After 12 weeks, participants completed the Perceived Stress Scale, Satisfaction with Life Scale and Subjective Happiness Scale. Participants with higher EI reported less perceived stress and higher levels of life satisfaction and happiness. The results of this study suggest that perceived stress mediates the relationship between EI and well-being indicators, specifically life satisfaction and happiness. These findings suggest an underlying process by which high emotional intelligence may increase well-being in female students in nursing and allied health sciences by reducing the experience of stress. The implications of these findings for future research and for working with health professions to improve well-being outcomes are discussed. © 2013 John Wiley & Sons Ltd.
The moderating role of meaning in life in the relationship between perceived stress and diurnal cortisol.

Science.gov (United States)

Pulopulos, Matias M; Kozusznik, Malgorzata W

2018-05-01

Previous studies have suggested that meaning in life may buffer the negative effects of stress. This study is the first to investigate the moderating role of meaning in life in the relationship between the perception of stress and diurnal cortisol in two independent samples of healthy adults. In study 1 (n = 172, men = 82, women = 90, age range = 21-55 years, mean age = 37.58 years), the results of moderated regression analyses revealed that there was a significant positive relationship between overall perceived stress in the past month and both diurnal cortisol levels (area-under-the-curve with respect to the ground; AUCg) and the diurnal cortisol slope (DCS) only in individuals with low levels of meaning in life conceptualized as the degree to which one engages in activities that are personally valued and important. In study 2 (n = 259, men = 125, women = 134, age range = 18-54 years, mean age = 29.06 years), we found a non-significant interaction term between meaning in life conceptualized as having goals and a sense of excitement regarding one's future and perception of stress in a model of both adjusted AUCg and DCS. The results were independent of age, sex, body mass index, education, and race. The results shed light on the importance and the complexity of the construct of meaning in life and offer a possible explanation for why some people who face stressors may be more vulnerable than others to developing stress-related health problems.

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