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Sample records for hertz stress-life exponent

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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

  6. 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)

  7. 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...

  8. 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.

  9. 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

  10. 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.

  11. 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.

  12. 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...

  13. 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

  14. 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

  15. 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

  16. 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

  17. 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

  18. 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...

  19. 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.

  20. Personality, Stressful Life Events, and Treatment Response in Major Depression

    Science.gov (United States)

    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…

  1. 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 ...

  2. 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)

  3. 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...

  4. 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 ...

  5. 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.

  6. 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...

  7. 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

  8. Error exponents for entanglement concentration

    International Nuclear Information System (INIS)

    Hayashi, Masahito; Koashi, Masato; Matsumoto, Keiji; Morikoshi, Fumiaki; Winter, Andreas

    2003-01-01

    Consider entanglement concentration schemes that convert n identical copies of a pure state into a maximally entangled state of a desired size with success probability being close to one in the asymptotic limit. We give the distillable entanglement, the number of Bell pairs distilled per copy, as a function of an error exponent, which represents the rate of decrease in failure probability as n tends to infinity. The formula fills the gap between the least upper bound of distillable entanglement in probabilistic concentration, which is the well-known entropy of entanglement, and the maximum attained in deterministic concentration. The method of types in information theory enables the detailed analysis of the distillable entanglement in terms of the error rate. In addition to the probabilistic argument, we consider another type of entanglement concentration scheme, where the initial state is deterministically transformed into a (possibly mixed) final state whose fidelity to a maximally entangled state of a desired size converges to one in the asymptotic limit. We show that the same formula as in the probabilistic argument is valid for the argument on fidelity by replacing the success probability with the fidelity. Furthermore, we also discuss entanglement yield when optimal success probability or optimal fidelity converges to zero in the asymptotic limit (strong converse), and give the explicit formulae for those cases

  9. TeraHertz Time Domain Spectroscopy of Astrophysical Analog Materials

    Science.gov (United States)

    Blake, Geoffrey

    The section of the electromagnetic spectrum extending roughly from wavelengths of 3 millimeters to 30 microns is commonly known as the far-infrared or TeraHertz (THz) region. It contains the great majority of the photons emitted by the universe, and THz observations of molecules and dust are able penetrate deeply into molecular clouds, thus revealing the full history of star and planet formation. Accordingly, the successful deployments of the Herschel and SOFIA observatories, and the emerging capabilities of ALMA, are both revolutionizing our understanding of THz astrophysics and placing stringent demands on the generation of accurate laboratory data on the relevant gas phase and solid state materials detected. With APRA support, we have constructed a combined high bandwidth and high spectral resolution femtosecond THz Time Domain Spectroscopy (THz TDS) system and an FT-IR spectrometer, and coupled these instruments to a high vacuum chamber and cryostat and to gas phase cells including a molecular beam system. We have investigated solid materials from room temperature to 10 K, and can examine both refractory matter such as silicates and molecular ices. For the latter, we have demonstrated that the THz bands observed are uniquely sensitive to both the molecular structure of the ice and its thermal history, and thus that THz observations can provide novel insight into the dominant condensable materials in dense, cold regions. In the gas phase we can record doppler-limited data over at least a decade in bandwidth. While quite capable, the high vacuum cryostat can only study thick samples, especially ices, due to the fairly rapid adsorption of gases onto surfaces at low temperature under such conditions. It is therefore not possible to examine highly layered/structured samples or reactive species. We therefore propose here to upgrade the chamber/cryostat to ultrahigh vacuum, and implement additional sample preparation and characterization tools. With such modifications

  10. A Sub-Hertz, Low-Frequency Vibration Isolation Platform

    Science.gov (United States)

    Ortiz, Gerardo, G.; Farr, William H.; Sannibale, Virginio

    2011-01-01

    One of the major technical problems deep-space optical communication (DSOC) systems need to solve is the isolation of the optical terminal from vibrations produced by the spacecraft navigational control system and by the moving parts of onboard instruments. Even under these vibration perturbations, the DSOC transceivers (telescopes) need to be pointed l000 fs of times more accurately than an RF communication system (parabolic antennas). Mechanical resonators have been extensively used to provide vibration isolation for groundbased, airborne, and spaceborne payloads. The effectiveness of these isolation systems is determined mainly by the ability of designing a mechanical oscillator with the lowest possible resonant frequency. The Low-Frequency Vibration Isolation Platform (LFVIP), developed during this effort, aims to reduce the resonant frequency of the mechanical oscillators into the sub-Hertz region in order to maximize the passive isolation afforded by the 40 dB/decade roll-off response of the resonator. The LFVIP also provides tip/tilt functionality for acquisition and tracking of a beacon signal. An active control system is used for platform positioning and for dampening of the mechanical oscillator. The basic idea in the design of the isolation platform is to use a passive isolation strut with an approximately equal to 100-mHz resonance frequency. This will extend the isolation range to lower frequencies. The harmonic oscillator is a second-order lowpass filter for mechanical disturbances. The resonance quality depends on the dissipation mechanisms, which are mainly hysteretic because of the low resonant frequency and the absence of any viscous medium. The LFVIP system is configured using the well-established Stewart Platform, which consists of a top platform connected to a base with six extensible struts (see figure). The struts are attached to the base and to the platform via universal joints, which permit the extension and contraction of the struts. The

  11. 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.

  12. 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

  13. 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...

  14. 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.

  15. 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…

  16. 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

  17. 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.

  18. 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 ...

  19. 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.

  20. 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.

  1. 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.)

  2. 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...

  3. 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.

  4. 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

  5. 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.

  6. Lyapunov exponents for infinite dimensional dynamical systems

    Science.gov (United States)

    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.

  7. 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

  8. 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.

  9. 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.)

  10. 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...

  11. 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)

  12. 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

  13. 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

  14. 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...

  15. [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

  16. 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.

  17. Beyond Critical Exponents in Neuronal Avalanches

    Science.gov (United States)

    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.

  18. 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

  19. 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

  20. Geodesic stability, Lyapunov exponents, and quasinormal modes

    International Nuclear Information System (INIS)

    Cardoso, Vitor; Miranda, Alex S.; Berti, Emanuele; Witek, Helvi; Zanchin, Vilson T.

    2009-01-01

    Geodesic motion determines important features of spacetimes. Null unstable geodesics are closely related to the appearance of compact objects to external observers and have been associated with the characteristic modes of black holes. By computing the Lyapunov exponent, which is the inverse of the instability time scale associated with this geodesic motion, we show that, in the eikonal limit, quasinormal modes of black holes in any dimensions are determined by the parameters of the circular null geodesics. This result is independent of the field equations and only assumes a stationary, spherically symmetric and asymptotically flat line element, but it does not seem to be easily extendable to anti-de Sitter spacetimes. We further show that (i) in spacetime dimensions greater than four, equatorial circular timelike geodesics in a Myers-Perry black-hole background are unstable, and (ii) the instability time scale of equatorial null geodesics in Myers-Perry spacetimes has a local minimum for spacetimes of dimension d≥6.

  1. Critical exponents for diluted resistor networks.

    Science.gov (United States)

    Stenull, O; Janssen, H K; Oerding, K

    1999-05-01

    An approach by Stephen [Phys. Rev. B 17, 4444 (1978)] is used to investigate the critical properties of randomly diluted resistor networks near the percolation threshold by means of renormalized field theory. We reformulate an existing field theory by Harris and Lubensky [Phys. Rev. B 35, 6964 (1987)]. By a decomposition of the principal Feynman diagrams, we obtain diagrams which again can be interpreted as resistor networks. This interpretation provides for an alternative way of evaluating the Feynman diagrams for random resistor networks. We calculate the resistance crossover exponent phi up to second order in epsilon=6-d, where d is the spatial dimension. Our result phi=1+epsilon/42+4epsilon(2)/3087 verifies a previous calculation by Lubensky and Wang, which itself was based on the Potts-model formulation of the random resistor network.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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)

  8. 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

  9. 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.

  10. 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).

  11. The Hurst exponent in energy futures prices

    Science.gov (United States)

    Serletis, Apostolos; Rosenberg, Aryeh Adam

    2007-07-01

    This paper extends the work in Elder and Serletis [Long memory in energy futures prices, Rev. Financial Econ., forthcoming, 2007] and Serletis et al. [Detrended fluctuation analysis of the US stock market, Int. J. Bifurcation Chaos, forthcoming, 2007] by re-examining the empirical evidence for random walk type behavior in energy futures prices. In doing so, it uses daily data on energy futures traded on the New York Mercantile Exchange, over the period from July 2, 1990 to November 1, 2006, and a statistical physics approach-the ‘detrending moving average’ technique-providing a reliable framework for testing the information efficiency in financial markets as shown by Alessio et al. [Second-order moving average and scaling of stochastic time series, Eur. Phys. J. B 27 (2002) 197-200] and Carbone et al. [Time-dependent hurst exponent in financial time series. Physica A 344 (2004) 267-271; Analysis of clusters formed by the moving average of a long-range correlated time series. Phys. Rev. E 69 (2004) 026105]. The results show that energy futures returns display long memory and that the particular form of long memory is anti-persistence.

  12. 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...

  13. 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.

  14. 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....

  15. Self reported stressful life events and exacerbations in multiple sclerosis: prospective study

    NARCIS (Netherlands)

    D. Buljevac (Dragan); W.C.J. Hop (Wim); W. Reedeker; A.C.J.W. Janssens (Cécile); F.G.A. van der Meché (Frans); P.A. van Doorn (Pieter); R.Q. Hintzen (Rogier)

    2003-01-01

    textabstractOBJECTIVE: To study the relation between self reported stressful life events not related to multiple sclerosis and the occurrence of exacerbations in relapsing-remitting multiple sclerosis. DESIGN: Longitudinal, prospective cohort study. SETTING: Outpatient clinic of

  16. 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.

  17. 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.

  18. Stressful life events and depressive symptoms in mothers and fathers of young children.

    Science.gov (United States)

    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.

  19. 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.

  20. 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.

  1. 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.

  2. 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

  3. 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®

  4. 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.

  5. 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)

  6. 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.

  7. [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.

  8. 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

  9. ACCURATE ESTIMATES OF CHARACTERISTIC EXPONENTS FOR SECOND ORDER DIFFERENTIAL EQUATION

    Institute of Scientific and Technical Information of China (English)

    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.

  10. 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.

  11. 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

  12. 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)

  13. 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

  14. 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)

  15. Studies on omnidirectional enhancement of giga-hertz radiation by sub-wavelength plasma modulation

    Science.gov (United States)

    Fanrong, KONG; Qiuyue, NIE; Shu, LIN; Zhibin, WANG; Bowen, LI; Shulei, ZHENG; Binhao, JIANG

    2018-01-01

    The technology of radio frequency (RF) radiation intensification for radio compact antennas based on modulation and enhancement effects of sub-wavelength plasma structures represents an innovative developing strategy. It exhibits important scientific significance and promising potential of broad applications in various areas of national strategic demands, such as electrical information network and microwave communication, detection and control technology. In this paper, laboratory experiments and corresponding analyses have been carried out to investigate the modulation and enhancement technology of sub-wavelength plasma structure on the RF electromagnetic radiation. An application focused sub-wavelength plasma-added intensification up to ∼7 dB higher than the free-space radiation is observed experimentally in giga-hertz (GHz) RF band. The effective radiation enhancement bandwidth covers from 0.85 to 1.17 GHz, while the enhanced electromagnetic signals transmitted by sub-wavelength plasma structures maintain good communication quality. Particularly, differing from the traditional RF electromagnetic radiation enhancement method characterized by focusing the radiation field of antenna in a specific direction, the sub-wavelength plasma-added intensification of the antenna radiation presents an omnidirectional enhancement, which is reported experimentally for the first time. Corresponding performance characteristics and enhancement mechanism analyses are also conducted in this paper. The results have demonstrated the feasibility and promising potential of sub-wavelength plasma modulation in application focused RF communication, and provided the scientific basis for further research and development of sub-wavelength plasma enhanced compact antennas with wide-range requests and good quality for communication.

  16. 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

  17. 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...

  18. 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.

  19. Stressful Life Events and Psychosomatic Symptoms among Students Smokers and Non-smokers

    Science.gov (United States)

    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…

  20. 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…

  1. Green space as a buffer between stressful life events and health

    NARCIS (Netherlands)

    Berg, van den A.E.; Maas, J.; Verheij, R.A.; Groenewegen, P.P.

    2010-01-01

    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

  2. Green space as a buffer between stressful life events and health

    NARCIS (Netherlands)

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

    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

  3. Green space as a buffer between stressful life events and health.

    NARCIS (Netherlands)

    Maas, J.; Berg, A. van den; Verheij, R.A.; Groenewegen, P.P.

    2010-01-01

    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

  4. Risk Factors for Preschool Depression: The Mediating Role of Early Stressful Life Events

    Science.gov (United States)

    Luby, Joan L.; Belden, Andy C.; Spitznagel, Edward

    2006-01-01

    Background: Family history of mood disorders and stressful life events are both established risk factors for childhood depression. However, the role of mediators in risk trajectories, which are potential targets for intervention, remains understudied. To date, there have been no investigations of mediating relationships between risk factors and…

  5. The Relationship Between Stressful Life Events, Locus of Control, and Suicidal Ideation.

    Science.gov (United States)

    Crepeau, James J.

    Numerous studies involving suicide attempters and those who commit suicide suggest that the suicidal individual perceives limited control over the environment, the occurrence of stressful life events and a diminished probability of future success. Results of the present study indicate a relationship between the frequency of suicidal thoughts among…

  6. Origins of Early Adolescents' Hope: Personality, Parental Attachment, and Stressful Life Events

    Science.gov (United States)

    Otis, Kristin L.; Huebner, E. Scott; Hills, Kimberly J.

    2016-01-01

    Psychology has recently increased attention to identifying psychological qualities in individuals that indicate positive mental health, such as hope. In an effort to understand further the origins of hope, we examined the relations among parental attachment, stressful life events, personality variables, and hope in a sample of 647 middle school…

  7. 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....

  8. 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.

  9. Using Focus Groups to Explore the Stressful Life Events of Black College Men

    Science.gov (United States)

    Watkins, Daphne C.; Green, B. Lee; Goodson, Patricia; Guidry, Jeffrey Joseph; Stanley, Christine A.

    2007-01-01

    Black students who attend predominately White institutions (PWI) face many obstacles. This study identified the stressful life events of Black college men via focus group discussions and examined how these events impact their mental health and health behaviors. Forty-six participants from a PWI and a historically Black college/university (HBCU)…

  10. Potentially Stressful Life Events and Emotional Closeness between Grandparents and Adult Grandchildren

    Science.gov (United States)

    Wood, Suzanne; Liossis, Poppy

    2007-01-01

    The purpose of this study is to explore the variation in emotional closeness in the adult grandchild and grandparent relationship in relation to the occurrence of potentially stressful life events in childhood. A sample of university students (N = 119) completed a questionnaire measuring elements of intergenerational solidarity. Comparisons were…

  11. 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....

  12. 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).

  13. 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.

  14. 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

  15. 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)

  16. 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.

  17. 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.

  18. 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

  19. 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

  20. 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.

  1. 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 ...

  2. 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

  3. Analysis of Human Standing Balance by Largest Lyapunov Exponent

    Directory of Open Access Journals (Sweden)

    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.

  4. Nonlinear anisotropic elliptic equations with variable exponents and degenerate coercivity

    Directory of Open Access Journals (Sweden)

    Hocine Ayadi

    2018-02-01

    Full Text Available In this article, we prove the existence and the regularity of distributional solutions for a class of nonlinear anisotropic elliptic equations with $p_i(x$ growth conditions, degenerate coercivity and $L^{m(\\cdot}$ data, with $m(\\cdot$ being small, in appropriate Lebesgue-Sobolev spaces with variable exponents. The obtained results extend some existing ones [8,10].

  5. 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.

  6. 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…

  7. 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.

  8. 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

  9. 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)

  10. 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.

  11. Interaction between genetic polymorphisms and stressful life events in first episode depression

    DEFF Research Database (Denmark)

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

    2009-01-01

    of depression among participants. METHOD: We applied a case-only design, including 290 ethnically homogeneous patients suffering exclusively from first episode depression. Psychiatric mo-morbidity, personality traits and disorders and stressful life events in a six months period preceding onset of depression......BACKGROUND: A polymorphism in the serotonin transporter (5-HTT) gene seems to moderate the influence of stressful life events on depression. However, the results from previous studies of gene-environment interactions in depression are inconsistent and might be confounded by the history......A, 2A, and 2C. RESULTS: The low activity variants of the 5-HTT-linked polymorphic region in the serotonin transporter gene and the Met-allele of a single nucleotide polymorphism (Val66Met) in the gene encoding brain derived neurotrophic factor were independently associated with the presence...

  12. 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.

  13. 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.

  14. 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

  15. 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.

  16. "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...

  17. 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...

  18. Perfectionism and Stressful Life Events as Vulnerabilities to Depression Symptoms in Students

    OpenAIRE

    Fariba Kiani; Mohamad Reza Khodabakhsh

    2014-01-01

    IntroductionThe mood disorders such as depression are the most common mental disorders among individuals. In addition to, girls’ students as a group at high risk are known for developing this disorder. The aim of this study was to investigate the role of perfectionism and stressful life events in predicting disordered depression symptoms among girls’ students. Materials and Methods: This cross-sectional study on 344 girl students of Tehran’s high schools, who were selected by multiple cluster...

  19. 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.

  20. 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

  1. 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.

  2. 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.

  3. 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...

  4. 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.)

  5. 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.

  6. 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.

  7. 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

  8. 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.

  9. 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.

  10. 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.

  11. 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

  12. Lyapunov exponent and topological entropy plateaus in piecewise linear maps

    International Nuclear Information System (INIS)

    Botella-Soler, V; Oteo, J A; Ros, J; Glendinning, P

    2013-01-01

    We consider a two-parameter family of piecewise linear maps in which the moduli of the two slopes take different values. We provide numerical evidence of the existence of some parameter regions in which the Lyapunov exponent and the topological entropy remain constant. Analytical proof of this phenomenon is also given for certain cases. Surprisingly however, the systems with that property are not conjugate as we prove by using kneading theory. (paper)

  13. 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

  14. 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

  15. On nonlinear evolution variational inequalities involving variable exponent

    Directory of Open Access Journals (Sweden)

    Mingqi Xiang

    2013-12-01

    Full Text Available In this paper, we discuss a class of quasilinear evolution variational inequalities with variable exponent growth conditions in a generalized Sobolev space. We obtain the existence of weak solutions by means of penalty method. Moreover, we study the extinction properties of weak solutions to parabolic inequalities and provide a sufficient condition that makes the weak solutions vanish in a finite time. The existence of global attractors for weak solutions is also obtained via the theories of multi-valued semiflow.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. Major stressful life events and other risk factors for first admission with mania

    DEFF Research Database (Denmark)

    Kessing, L.V.; Agerbo, E.; Mortensen, P.B.

    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...... was found on the association between life events and the first admission with mania, totally, or for men or women, separately regarding ageing. CONCLUSIONS: The occurrence of death in the family and the experience of major life events are associated with increased risk of first admission with bipolar...

  1. 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...

  2. Zipf exponent of trajectory distribution in the hidden Markov model

    Science.gov (United States)

    Bochkarev, V. V.; Lerner, E. Yu

    2014-03-01

    This paper is the first step of generalization of the previously obtained full classification of the asymptotic behavior of the probability for Markov chain trajectories for the case of hidden Markov models. The main goal is to study the power (Zipf) and nonpower asymptotics of the frequency list of trajectories of hidden Markov frequencys and to obtain explicit formulae for the exponent of the power asymptotics. We consider several simple classes of hidden Markov models. We prove that the asymptotics for a hidden Markov model and for the corresponding Markov chain can be essentially different.

  3. Zipf exponent of trajectory distribution in the hidden Markov model

    International Nuclear Information System (INIS)

    Bochkarev, V V; Lerner, E Yu

    2014-01-01

    This paper is the first step of generalization of the previously obtained full classification of the asymptotic behavior of the probability for Markov chain trajectories for the case of hidden Markov models. The main goal is to study the power (Zipf) and nonpower asymptotics of the frequency list of trajectories of hidden Markov frequencys and to obtain explicit formulae for the exponent of the power asymptotics. We consider several simple classes of hidden Markov models. We prove that the asymptotics for a hidden Markov model and for the corresponding Markov chain can be essentially different

  4. 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.

  5. 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.

  6. Reading the Bible for guidance, comfort, and strength during stressful life events.

    Science.gov (United States)

    Hamilton, Jill B; Moore, Angelo D; Johnson, Khishaana A; Koenig, Harold G

    2013-01-01

    The use of religious practices to promote mental health among African Americans is well documented. African Americans are more likely to report strong religious affiliations and to use religion over prescribed medications for mental health problems. However, few studies have explored how African Americans use religious practices in response to stressful life events. The aim of this study is to examine how African American women and men find comfort in using scripture passages from The Bible. Fifty-four African American adults residing in the Southeastern United States participated in a qualitative descriptive study using open-ended semistructured interviews. Participants were asked to describe their use of scripture passages from The Bible and the personal meanings associated with these scriptures in the context of a family death or life-threatening illness. These participants used scripture passages categorized as God as Protector, God as Beneficent, Praise and Thanksgiving, God as Healer, Memory of Forefathers, Prayers to God, and Life after Death. Few gender differences were noted. However, women were more likely to use scripture passages of God as Protector and Life after Death, whereas men were more likely to use God as Beneficent and God as Healer. The religious practice of reading scripture passages from The Bible is a mental health-promoting strategy used during stressful life events. The findings of this study have practical uses for nurses and can be used to inform acceptable and sensitive approaches in addressing mental health issues and spiritual care needs in African American patients.

  7. Association Between Stressful Life Events and Depression; Intersection of Race and Gender.

    Science.gov (United States)

    Assari, Shervin; Lankarani, Maryam Moghani

    2016-06-01

    Although stressful life events (SLEs) and depression are associated, we do not know if the intersection of race and gender modifies the magnitude of this link. Using a nationally representative sample of adults in the USA, we tested if the association between SLE and major depressive episode (MDE) depends on the intersection of race and gender. Data came from the National Survey of American Life (NSAL), 2003, a cross-sectional survey that enrolled 5899 adults including 5008 Blacks (African-Americans or Caribbean Blacks), and 891 Non-Hispanic Whites. Logistic regression was used for data analysis. Stressful life events (past 30 days) was the independent variable, 12-month MDE was the dependent variable, and age, educational level, marital status, employment, and region of country were controls. In the pooled sample, SLE was associated with MDE above and beyond all covariates, without the SLE × race interaction term being significant. Among men, the SLE × race interaction was significant, suggesting a stronger association between SLE and MDE among White men compared to Black men. Such interaction between SLE × race could not be found among women. The association between SLE and depression may be stronger for White men than Black men; however, this link does not differ between White and Black women. More research is needed to better understand the mechanism behind race by gender variation in the stress-depression link.

  8. Quality of Life and Stressful Life Events in First and Second Generation Immigrant Adolescents

    Directory of Open Access Journals (Sweden)

    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.

  9. Stressful life events predict delayed functional recovery following treatment for mania in bipolar disorder.

    Science.gov (United States)

    Yan-Meier, Leslie; Eberhart, Nicole K; Hammen, Constance L; Gitlin, Michael; Sokolski, Kenneth; Altshuler, Lori

    2011-04-30

    Identifying predictors of functional recovery in bipolar disorder is critical to treatment efforts to help patients re-establish premorbid levels of role adjustment following an acute manic episode. The current study examined the role of stressful life events as potential obstacles to recovery of functioning in various roles. 65 patients with bipolar I disorder participated in a longitudinal study of functional recovery following clinical recovery from a manic episode. Stressful life events were assessed as predictors of concurrent vs. delayed recovery of role functioning in 4 domains (friends, family, home duties, work/school). Despite clinical recovery, a subset of patients experienced delayed functional recovery in various role domains. Moreover, delayed functional recovery was significantly associated with presence of one or more stressors in the prior 3 months, even after controlling for mood symptoms. Presence of a stressor predicted longer time to functional recovery in life domains, up to 112 days in work/school. Interventions that provide monitoring, support, and problem-solving may be needed to help prevent or mitigate the effects of stress on functional recovery. Copyright © 2010 Elsevier Ireland Ltd. All rights reserved.

  10. 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.

  11. Exponent and scrambling index of double alternate circular snake graphs

    Science.gov (United States)

    Rahmayanti, Sri; Pasaribu, Valdo E.; Nasution, Sawaluddin; Liani Salnaz, Sishi

    2018-01-01

    A graph is primitive if it contains a cycle of odd length. The exponent of a primitive graph G, denoted by exp(G), is the smallest positive integer k such that for each pair of vertices u and v in G there is a uv-walk length k. The scrambling index of a primitive graph G, denoted by k(G), is the smallest positive integer k such that for each pair of vertices u and v in G there is a uv-walk of length 2k. For an even positive integer n and an odd positive integer r, a (n,r)-double alternate circular snake graph, denoted by DA(C r,n ), is a graph obtained from a path u 1 u 2 ... u n by replacing each edge of the form u 2i u 2i+1 by two different r-cycles. We study the exponent and scrambling index of DA(C r,n ) and show that exp(DA(C r,n )) = n + r - 4 and k(DA(C r,n )) = (n + r - 3)/2.

  12. Riemannian theory of Hamiltonian chaos and Lyapunov exponents

    Science.gov (United States)

    Casetti, Lapo; Clementi, Cecilia; Pettini, Marco

    1996-12-01

    A nonvanishing Lyapunov exponent λ1 provides the very definition of deterministic chaos in the solutions of a dynamical system; however, no theoretical mean of predicting its value exists. This paper copes with the problem of analytically computing the largest Lyapunov exponent λ1 for many degrees of freedom Hamiltonian systems as a function of ɛ=E/N, the energy per degree of freedom. The functional dependence λ1(ɛ) is of great interest because, among other reasons, it detects the existence of weakly and strongly chaotic regimes. This aim, the analytic computation of λ1(ɛ), is successfully reached within a theoretical framework that makes use of a geometrization of Newtonian dynamics in the language of Riemannian differential geometry. An alternative point of view about the origin of chaos in these systems is obtained independently of the standard explanation based on homoclinic intersections. Dynamical instability (chaos) is here related to curvature fluctuations of the manifolds whose geodesics are natural motions and is described by means of the Jacobi-Levi-Civita equation (JLCE) for geodesic spread. In this paper it is shown how to derive from the JLCE an effective stability equation. Under general conditions, this effective equation formally describes a stochastic oscillator; an analytic formula for the instability growth rate of its solutions is worked out and applied to the Fermi-Pasta-Ulam β model and to a chain of coupled rotators. Excellent agreement is found between the theoretical prediction and numeric values of λ1(ɛ) for both models.

  13. Truncatable bootstrap equations in algebraic form and critical surface exponents

    Energy Technology Data Exchange (ETDEWEB)

    Gliozzi, Ferdinando [Dipartimento di Fisica, Università di Torino andIstituto Nazionale di Fisica Nucleare - sezione di Torino,Via P. Giuria 1, Torino, I-10125 (Italy)

    2016-10-10

    We describe examples of drastic truncations of conformal bootstrap equations encoding much more information than that obtained by a direct numerical approach. A three-term truncation of the four point function of a free scalar in any space dimensions provides algebraic identities among conformal block derivatives which generate the exact spectrum of the infinitely many primary operators contributing to it. In boundary conformal field theories, we point out that the appearance of free parameters in the solutions of bootstrap equations is not an artifact of truncations, rather it reflects a physical property of permeable conformal interfaces which are described by the same equations. Surface transitions correspond to isolated points in the parameter space. We are able to locate them in the case of 3d Ising model, thanks to a useful algebraic form of 3d boundary bootstrap equations. It turns out that the low-lying spectra of the surface operators in the ordinary and the special transitions of 3d Ising model form two different solutions of the same polynomial equation. Their interplay yields an estimate of the surface renormalization group exponents, y{sub h}=0.72558(18) for the ordinary universality class and y{sub h}=1.646(2) for the special universality class, which compare well with the most recent Monte Carlo calculations. Estimates of other surface exponents as well as OPE coefficients are also obtained.

  14. Prevalence of internet addiction and its association with stressful life events and psychological symptoms among adolescent internet users.

    Science.gov (United States)

    Tang, Jie; Yu, Yizhen; Du, Yukai; Ma, Ying; Zhang, Dongying; Wang, Jiaji

    2014-03-01

    Internet addiction (IA) among adolescents is a serious public health problem around the world. However, there have been few studies that examine the association between IA and stressful life events and psychological symptoms among Chinese adolescent internet users. We examined the association between IA and stressful life events and psychological symptoms among a random sample of school students who were internet users (N=755) in Wuhan, China. Internet addiction, stressful life events, coping style and psychological symptoms were measured by self-rated scales. The prevalence rate of internet addiction was 6.0% among adolescent internet users. Logistic regression analyses indicated that stressors from interpersonal problem and school related problem and anxiety symptoms were significantly associated with IA after controlling for demographic characteristics. Analyses examining the coping style with the IA revealed that negative coping style may mediate the effects of stressful life events to increase the risk of IA. However, no significant interaction of stressful life events and psychological symptoms was found. These findings of the current study indicate a high prevalence of internet addiction among Chinese adolescent internet users and highlight the importance of stressors from interpersonal problem and school related problem as a risk factor for IA which mainly mediated through negative coping style. Copyright © 2013 Elsevier Ltd. All rights reserved.

  15. Revealing the Formation of Stellar-mass Black Hole Binaries: The Need for Deci-Hertz Gravitational-wave Observatories

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Xian [Astronomy Department, School of Physics, Peking University, 100871 Beijing (China); Amaro-Seoane, Pau, E-mail: xian.chen@pku.edu.cn, E-mail: pau@ice.cat [Institut de Ciències de l’Espai (CSIC-IEEC) at Campus UAB, Carrer de Can Magrans s/n, E-08193 Barcelona (Spain)

    2017-06-10

    The formation of compact stellar-mass binaries is a difficult, but interesting problem in astrophysics. There are two main formation channels: in the field via binary star evolution, or in dense stellar systems via dynamical interactions. The Laser Interferometer Gravitational-wave Observatory (LIGO) has detected black hole binaries (BHBs) via their gravitational radiation. These detections provide us with information about the physical parameters of the system. It has been claimed that when the Laser Interferometer Space Antenna (LISA) is operating, the joint observation of these binaries with LIGO will allow us to derive the channels that lead to their formation. However, we show that for BHBs in dense stellar systems dynamical interactions could lead to high eccentricities such that a fraction of the relativistic mergers are not audible to LISA. A non-detection by LISA puts a lower limit of about 0.005 on the eccentricity of a BHB entering the LIGO band. On the other hand, a deci-Hertz observatory, like DECIGO or Tian Qin, would significantly enhance the chances of a joint detection and shed light on the formation channels of these binaries.

  16. Dynamic dilution exponent in monodisperse entangled polymer solutions

    DEFF Research Database (Denmark)

    Shahid, T.; Huang, Qian; Oosterlinck, F.

    2017-01-01

    of concentration but also depends on the molar mass of the chains. While the proposed approach successfully explains the viscoelastic properties of a large number of semi-dilute solutions of polymers in their own oligomers, important discrepancies are found for semi-dilute entangled polymers in small-molecule......We study and model the linear viscoelastic properties of several entangled semi-dilute and concentrated solutions of linear chains of different molar masses and at different concentrations dissolved in their oligomers. We discuss the dilution effect of the oligomers on the entangled long chains....... In particular, we investigate the influence of both concentration and molar mass on the value of the effective dynamic dilution exponent determined from the level of the storage plateau at low and intermediate frequencies. We show that the experimental results can be quantitatively explained by considering...

  17. Hybrid Percolation Transition in Cluster Merging Processes: Continuously Varying Exponents

    Science.gov (United States)

    Cho, Y. S.; Lee, J. S.; Herrmann, H. J.; Kahng, B.

    2016-01-01

    Consider growing a network, in which every new connection is made between two disconnected nodes. At least one node is chosen randomly from a subset consisting of g fraction of the entire population in the smallest clusters. Here we show that this simple strategy for improving connection exhibits a more unusual phase transition, namely a hybrid percolation transition exhibiting the properties of both first-order and second-order phase transitions. The cluster size distribution of finite clusters at a transition point exhibits power-law behavior with a continuously varying exponent τ in the range 2 power-law behavior of the avalanche size distribution arising in models with link-deleting processes in interdependent networks.

  18. A Hyperchaotic Attractor with Multiple Positive Lyapunov Exponents

    International Nuclear Information System (INIS)

    Guo-Si, Hu

    2009-01-01

    There are many hyperchaotic systems, but few systems can generate hyperchaotic attractors with more than three PLEs (positive Lyapunov exponents). A new hyperchaotic system, constructed by adding an approximate time-delay state feedback to a five-dimensional hyperchaotic system, is presented. With the increasing number of phase-shift units used in this system, the number of PLEs also steadily increases. Hyperchaotic attractors with 25 PLEs can be generated by this system with 32 phase-shift units. The sum of the PLEs will reach the maximum value when 23 phase-shift units are used. A simple electronic circuit, consisting of 16 operational amplifiers and two analogy multipliers, is presented for confirming hyperchaos of order 5, i.e., with 5 PLEs

  19. Generalized Hurst exponent approach to efficiency in MENA markets

    Science.gov (United States)

    Sensoy, A.

    2013-10-01

    We study the time-varying efficiency of 15 Middle East and North African (MENA) stock markets by generalized Hurst exponent analysis of daily data with a rolling window technique. The study covers a time period of six years from January 2007 to December 2012. The results reveal that all MENA stock markets exhibit different degrees of long-range dependence varying over time and that the Arab Spring has had a negative effect on market efficiency in the region. The least inefficient market is found to be Turkey, followed by Israel, while the most inefficient markets are Iran, Tunisia, and UAE. Turkey and Israel show characteristics of developed financial markets. Reasons and implications are discussed.

  20. Nonlinearity exponent of ac conductivity in disordered systems

    International Nuclear Information System (INIS)

    Nandi, U N; Sircar, S; Karmakar, A; Giri, S

    2012-01-01

    We measured the real part of ac conductance Σ(x,f) or Σ(T,f) of iron-doped mixed-valent polycrystalline manganite oxides LaMn 1-x Fe x O 3 as a function of frequency f by varying initial conductance Σ 0 by quenched disorder x at a fixed temperature T (room) and by temperature T at a fixed quenched disorder x. At a fixed temperature T, Σ(x,f) of a sample with fixed x remains almost constant at its zero-frequency dc value Σ 0 at lower frequency. With increase in f, Σ(x,f) increases slowly from Σ 0 and finally increases rapidly following a power law with an exponent s at high frequency. Scaled appropriately, the data for Σ(T,f) and Σ(x,f) fall on the same universal curve, indicating the existence of a general scaling formalism for the ac conductivity in disordered systems. The characteristic frequency f c at which Σ(x,f) or Σ(T,f) increases for the first time from Σ 0 scales with initial conductance Σ 0 as f c ∼ Σ 0 x f , where x f is the onset exponent. The value of x f is nearly equal to one and is found to be independent of x and T. Further, an inverse relationship between x f and s provides a self-consistency check of the systematic description of Σ(x,f) or Σ(T,f). This apparent universal value of x f is discussed within the framework of existing theoretical models and scaling theories. The relevance to other similar disordered systems is also highlighted. (paper)

  1. Assessing traumatic event exposure: general issues and preliminary findings for the Stressful Life Events Screening Questionnaire.

    Science.gov (United States)

    Goodman, L A; Corcoran, C; Turner, K; Yuan, N; Green, B L

    1998-07-01

    This article reviews the psychometric properties of the Stressful Life Events Screening Questionnaire (SLESQ), a recently developed trauma history screening measure, and discusses the complexities involved in assessing trauma exposure. There are relatively few general measures of exposure to a variety of types of traumatic events, and most of those that exist have not been subjected to rigorous psychometric evaluation. The SLESQ showed good test-retest reliability, with a median kappa of .73, adequate convergent validity (with a lengthier interview) with a median kappa of .64, and good discrimination between Criterion A and non-Criterion A events. The discussion addresses some of the challenges of assessing traumatic event exposure along the dimensions of defining traumatic events, assessment methodologies, reporting consistency, and incident validation.

  2. 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.

  3. 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.

  4. The association between stressful life events and depressive symptoms among Cypriot university students: a cross-sectional descriptive correlational study.

    Science.gov (United States)

    Sokratous, Sokratis; Merkouris, Anastasios; Middleton, Nicos; Karanikola, Maria

    2013-12-05

    Previous findings suggest that stressful life events have a causal relationship with depressive symptoms. However, to date little is known concerning the contribution of the number and severity of recent stressful life events on the prevalence of depressive symptoms among university students. The aim of this study was to investigate the prevalence of depressive symptoms and its association with the number and the severity of self-reported stressful life events among university students in Cyprus. A descriptive correlational design with cross sectional comparison was used. The CES-D scale was applied for the assessment of depressive symptoms and the LESS instrument for stressful life events. Both scales were completed anonymously and voluntarily by 1.500 students (response rate 85%). The prevalence of mild to moderate depressive symptoms [CES-D score between 16 and 21] and of clinically significant depressive symptoms [CES-D score ≥ 22] were 18.8% and 25.3% respectively. There were statistically significant differences in clinically significant depressive symptoms by gender, with higher rates among women (x(2) = 8.53, df = 1, p = 0.003). Higher scores on the LESS scale were associated with more frequent reports of clinical depressive symptoms (x(2) = 70.63, df = 4, p life events and clinical depressive symptoms (x(2) = 40.06, df = 4, p stressful life events during the previous year (OR = 2.64 95% CI: 1.02, 6.83) and a severe degree of stress due to these events (total LESS score > 351, OR = 3.03 95% CI: 1.66, 5.39) were more likely to manifest clinical depressive symptoms. The high frequency of occurrence of depressive symptoms among Cypriot university students, as well as the strong association with stressful life events, highlights the need for psychological empowerment strategies towards students by institutional counseling services.

  5. Development and validation of a Thai stressful life events rating scale for patients with a diagnosis of schizophrenic methamphetamine abuse

    Directory of Open Access Journals (Sweden)

    Ek-uma Imkome

    2017-04-01

    Full Text Available This study aimed to psychometrically test a Thai Stressful Life Events Rating Scale (TSLERS. Factor analysis was done on data collected from 313 patients with schizophrenia and methamphetamine abuse in Thailand from April to May, 2015. Results identified the following problems impacting physical and mental health: social relationship and social concerns, money, family life, life security, and career. Evaluation of the psychometric scale properties demonstrated acceptable validity and reliability. TSLERS provided scientific and empirical data about stressful life events of patients with schizophrenia and methamphetamine abuse, and was suitable for stress detection and suggesting further innovations.

  6. The '0.4 eV' shape resonance of electron scattering from mercury in a Franck-Hertz tube

    International Nuclear Information System (INIS)

    Nicoletopoulos, Peter

    2004-01-01

    The alternative version of the Franck-Hertz experiment with mercury, in which a two-grid tube is used as a combination of electron gun, equipotential collision space and detection cell, was analysed recently in considerable detail. In particular, it was inferred that, at optimal pressure, the formation of peaks in the anode current at inelastic thresholds is mediated inside the detection cell by the large variation, a maximum at 0.4 eV, in the cross section for elastic scattering. This variation is due to a shape resonance in the electron-mercury system and is observable persuasively at the onset of anode current as a sharp peak followed by a clear minimum. In this paper, the passage of electrons through the second grid to the anode region is analysed in terms of kinetic theory. The discussion is based on a simplified expression for the electron current derivable from an approximate form of the Boltzmann transport equation that maintains the spatial density gradient but omits elastic energy losses. The estimated range of pressure underlying this kind of idealization is in good agreement with experiment. An explicit solution is obtained by constructing an analytic expression for the momentum transfer cross section of mercury using a recent theory of generalized Fano profiles for overlapping resonances. This solution is used in order to model successfully the formation of peaks at the threshold of anode current and at excitation potentials, and to explain the dependence of the observed profiles on the pressure and on the sign and magnitude of the potential across the detection cell

  7. 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)

  8. 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.

  9. 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

  10. Stressful Life Event Experiences of Homeless Adults: A Comparison of Single Men, Single Women, and Women with Children

    Science.gov (United States)

    Zugazaga, Carole

    2004-01-01

    This article describes stressful life events experienced by a multi-shelter sample of 162 homeless adults in the Central Florida area. Participants included homeless single men (n = 54), homeless single women (n = 54), and homeless women with children (n = 54). Subjects were interviewed with a modified version of the List of Threatening…

  11. Gene-Environment Interaction Effects of Peer Deviance, Parental Knowledge and Stressful Life Events on Adolescent Alcohol Use.

    Science.gov (United States)

    Cooke, Megan E; Meyers, Jacquelyn L; Latvala, Antti; Korhonen, Tellervo; Rose, Richard J; Kaprio, Jaakko; Salvatore, Jessica E; Dick, Danielle M

    2015-10-01

    The purpose of this study was to address two methodological issues that have called into question whether previously reported gene-environment interaction (GxE) effects for adolescent alcohol use are 'real'. These issues are (1) the potential correlation between the environmental moderator and the outcome across twins and (2) non-linear transformations of the behavioral outcome. Three environments that have been previously studied (peer deviance, parental knowledge, and potentially stressful life events) were examined here. For each moderator (peer deviance, parental knowledge, and potentially stressful life events), a series of models was fit to both a raw and transformed measure of monthly adolescent alcohol use in a sample that included 825 dizygotic (DZ) and 803 monozygotic (MZ) twin pairs. The results showed that the moderating effect of peer deviance was robust to transformation, and that although the significance of moderating effects of parental knowledge and potentially stressful life events were dependent on the scale of the adolescent alcohol use outcome, the overall results were consistent across transformation. In addition, the findings did not vary across statistical models. The consistency of the peer deviance results and the shift of the parental knowledge and potentially stressful life events results between trending and significant, shed some light on why previous findings for certain moderators have been inconsistent and emphasize the importance of considering both methodological issues and previous findings when conducting and interpreting GxE analyses.

  12. 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.

  13. Validation of the Revised Stressful Life Event Questionnaire Using a Hybrid Model of Genetic Algorithm and Artificial Neural Networks

    Directory of Open Access Journals (Sweden)

    Rasoul Sali

    2013-01-01

    Full Text Available Objectives. Stressors have a serious role in precipitating mental and somatic disorders and are an interesting subject for many clinical and community-based studies. Hence, the proper and accurate measurement of them is very important. We revised the stressful life event (SLE questionnaire by adding weights to the events in order to measure and determine a cut point. Methods. A total of 4569 adults aged between 18 and 85 years completed the SLE questionnaire and the general health questionnaire-12 (GHQ-12. A hybrid model of genetic algorithm (GA and artificial neural networks (ANNs was applied to extract the relation between the stressful life events (evaluated by a 6-point Likert scale and the GHQ score as a response variable. In this model, GA is used in order to set some parameter of ANN for achieving more accurate results. Results. For each stressful life event, the number is defined as weight. Among all stressful life events, death of parents, spouse, or siblings is the most important and impactful stressor in the studied population. Sensitivity of 83% and specificity of 81% were obtained for the cut point 100. Conclusion. The SLE-revised (SLE-R questionnaire despite simplicity is a high-performance screening tool for investigating the stress level of life events and its management in both community and primary care settings. The SLE-R questionnaire is user-friendly and easy to be self-administered. This questionnaire allows the individuals to be aware of their own health status.

  14. The Moderating Effect of Impulsivity on the Relationship between Stressful Life Events and Depression among College Women

    Science.gov (United States)

    Clarke, Dave

    2012-01-01

    Based on the transpersonal model of stress, the purpose of the study was to investigate the moderating effect of impulsivity on the relationship between stressful life events (SLE) and depression among first year university women. Impulsivity consists of tendencies towards lack of premeditation, lack of perseverance, urgency and sensation seeking.…

  15. Stressful life events and onset of mood disorders in children of bipolar parents during 14-month follow-up

    NARCIS (Netherlands)

    Wals, M; Hillegers, MHJ; Reichart, CG; Verhulst, FC; Nolen, WA; Ormel, J

    Background: Although multiple studies have examined the association between stressful life events (SLEs) and the development of mood disorders, the exact nature of the association and the degree to which it is independent from familial loading (FL) and gender-specific are still not fully elucidated.

  16. Microscopic processes controlling the Herschel-Bulkley exponent

    Science.gov (United States)

    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.

  17. Regularized semiclassical limits: Linear flows with infinite Lyapunov exponents

    KAUST Repository

    Athanassoulis, Agissilaos; Katsaounis, Theodoros; Kyza, Irene

    2016-01-01

    Semiclassical asymptotics for Schrödinger equations with non-smooth potentials give rise to ill-posed formal semiclassical limits. These problems have attracted a lot of attention in the last few years, as a proxy for the treatment of eigenvalue crossings, i.e. general systems. It has recently been shown that the semiclassical limit for conical singularities is in fact well-posed, as long as the Wigner measure (WM) stays away from singular saddle points. In this work we develop a family of refined semiclassical estimates, and use them to derive regularized transport equations for saddle points with infinite Lyapunov exponents, extending the aforementioned recent results. In the process we answer a related question posed by P.L. Lions and T. Paul in 1993. If we consider more singular potentials, our rigorous estimates break down. To investigate whether conical saddle points, such as -|x|, admit a regularized transport asymptotic approximation, we employ a numerical solver based on posteriori error control. Thus rigorous upper bounds for the asymptotic error in concrete problems are generated. In particular, specific phenomena which render invalid any regularized transport for -|x| are identified and quantified. In that sense our rigorous results are sharp. Finally, we use our findings to formulate a precise conjecture for the condition under which conical saddle points admit a regularized transport solution for the WM. © 2016 International Press.

  18. Regularized semiclassical limits: Linear flows with infinite Lyapunov exponents

    KAUST Repository

    Athanassoulis, Agissilaos

    2016-08-30

    Semiclassical asymptotics for Schrödinger equations with non-smooth potentials give rise to ill-posed formal semiclassical limits. These problems have attracted a lot of attention in the last few years, as a proxy for the treatment of eigenvalue crossings, i.e. general systems. It has recently been shown that the semiclassical limit for conical singularities is in fact well-posed, as long as the Wigner measure (WM) stays away from singular saddle points. In this work we develop a family of refined semiclassical estimates, and use them to derive regularized transport equations for saddle points with infinite Lyapunov exponents, extending the aforementioned recent results. In the process we answer a related question posed by P.L. Lions and T. Paul in 1993. If we consider more singular potentials, our rigorous estimates break down. To investigate whether conical saddle points, such as -|x|, admit a regularized transport asymptotic approximation, we employ a numerical solver based on posteriori error control. Thus rigorous upper bounds for the asymptotic error in concrete problems are generated. In particular, specific phenomena which render invalid any regularized transport for -|x| are identified and quantified. In that sense our rigorous results are sharp. Finally, we use our findings to formulate a precise conjecture for the condition under which conical saddle points admit a regularized transport solution for the WM. © 2016 International Press.

  19. 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

  20. Stressful life events and social health factors in women using anxiolytics and antidepressants: an Italian observational study in community pharmacies.

    Science.gov (United States)

    D'Incau, Paola; Barbui, Corrado; Tubini, Jacopo; Conforti, Anita

    2011-04-01

    In Italy, as in all of Europe, women differ from men in that they are somewhat more sensitive to the depressogenic effects of stressful life events related to their social networks and emotional sphere. Women are more likely than men to have experienced poverty, gender discrimination, and physical and sexual abuse. The purpose of this study was to expand the knowledge about the occurrence of stressful life events in women exposed and not exposed to anxiolytics and antidepressants in a community pharmacy setting. Women attending 100 community pharmacies in the Italian Veneto region were surveyed by pharmacists with regard to a number of general features of their current pharmacologic treatment. Women independently completed a written self-assessment questionnaire that focused on stressful life events. Unconditional logistic regression analysis was performed to investigate the association between anxiolytics and antidepressants use and potential factors, including stressful life events. The study population comprised 11,357 women. One or more stressful life events occurred in 90% of the women treated with anxiolytics and/or antidepressants (users [n = 3848]) and in 74% of the women not treated with these drugs (nonusers [n = 7509]) (odds ratio = 3.19; 95% CI, 2.83-3.60). On average, the life events occurred during the previous 6 months and the women considered the influence of these events on their well-being to be severe. After the unconditional logistic regression analysis, the association between anxiolytics and/or antidepressants use remained positive for most of the stressful life events studied as well as for other factors: separation/divorce, living alone or with others (family or friends), unemployment, whether currently being seen by a psychologist/psychiatrist, and treatment with drugs for the alimentary tract and metabolism, cardiovascular system, or nervous system. A significant association between stressful life events and anxiolytics and

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

    Science.gov (United States)

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

    2012-06-01

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

  2. Stressful life-events in childhood and risk of multiple sclerosis: a Danish nationwide cohort study.

    Science.gov (United States)

    Nielsen, Nete Munk; Pedersen, Bo V; Stenager, Egon; Koch-Henriksen, Nils; Frisch, Morten

    2014-10-01

    Current knowledge concerning the association between exposure to stressful life-events (SFLEs) in childhood and later risk of multiple sclerosis (MS) is sparse. We studied the associations between SFLEs in childhood and subsequent risk of MS in a nationwide cohort of 2.9 million Danes born from 1968 to 2011. A SFLE in childhood was defined as exposure before age 18 years to parental divorce, parental death, or death of a sibling, using information from the Danish Civil Registration System. MS cases in the cohort were identified in the Danish Multiple Sclerosis Registry. Associations of SFLE with MS risk were evaluated by incidence rate ratios (RR) of MS obtained in log-linear Poisson regression models. Persons exposed to any SFLE in childhood were at 11% elevated risk of MS (RR = 1.11; 95% confidence interval: 1.03-1.20), compared to non-exposed persons. Stratification by subtype of SFLE showed that parental death and death of a sibling were not associated with MS risk. However, persons exposed to parental divorce were at 13% increased risk of developing MS compared to non-exposed (RR = 1.13; 1.04-1.23). Associations of SFLEs in childhood with risk of MS are weak. However, parental divorce is somehow associated with modestly increased risk of MS. © The Author(s), 2014.

  3. Negative relationship behavior is more important than positive: Correlates of outcomes during stressful life events.

    Science.gov (United States)

    Rivers, Alannah Shelby; Sanford, Keith

    2018-04-01

    When people who are married or cohabiting face stressful life situations, their ability to cope may be associated with two separate dimensions of interpersonal behavior: positive and negative. These behaviors can be assessed with the Couple Resilience Inventory (CRI). It was expected that scales on this instrument would correlate with outcome variables regarding life well-being, stress, and relationship satisfaction. It was also expected that effects for negative behavior would be larger than effects for positive and that the effects might be curvilinear. Study 1 included 325 married or cohabiting people currently experiencing nonmedical major life stressors and Study 2 included 154 married or cohabiting people with current, serious medical conditions. All participants completed an online questionnaire including the CRI along with an alternate measure of couple behavior (to confirm scale validity), a measure of general coping style (to serve as a covariate), and measures of outcome variables regarding well-being, quality of life, perceived stress, and relationship satisfaction. The effects for negative behavior were larger than effects for positive in predicting most outcomes, and many effects were curvilinear. Notably, results remained significant after controlling for general coping style, and scales measuring positive and negative behavior demonstrated comparable levels of validity. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

  4. Association of plasma hormones, nutritional status, and stressful life events in anorexia nervosa patients.

    Science.gov (United States)

    Śmiarowska, Małgorzata; Safranow, Krzysztof; Dziedziejko, Violetta; Bialecka, Monika; Koziołek, Monika; Samochowiec, Jerzy

    2014-02-06

    The aim of the current study was to analyze the relationships between plasma hormones, body weight parameters and stressful life events in anorexia nervosa (AN). 72 females in the active phase of AN were evaluated. 52 healthy women constituted the control group. RIA kits were used to measure plasma hormone levels. The concentrations of leptin, insulin, IGF-1, triiodothyronine, LH, FSH, estradiol, and testosterone were significantly lower and those of cortisol and growth hormone significantly higher in the AN than the control group. No hormonal differences between restrictive and binge-purging AN subtypes were found. Leptin, IGF-1, gonadotropins, and sex steroids correlated significantly negatively and growth hormone positively with total reduction of body weight or the degree of undernutrition. Associations were also found between lower insulin concentration and family violence, lower cortisol and psychiatric diseases in the family, higher testosterone and patient's alcohol or drug abuse. The changed activity of the somatotropin-somatomedin, gonadal, and corticotrophin axes corresponds to the clinical stage of AN. Plasma IGF-1 seems to be the most sensitive and useful independent hormonal marker of cachexia.

  5. Association of plasma hormones, nutritional status, and stressful life events in anorexia nervosa patients

    Directory of Open Access Journals (Sweden)

    Małgorzata Śmiarowska

    2014-02-01

    Full Text Available Objective: The aim of the current study was to analyze the relationships between plasma hormones, body weight parameters and stressful life events in anorexia nervosa (AN. Material and Methods: 72 females in the active phase of AN were evaluated. 52 healthy women constituted the control group. RIA kits were used to measure plasma hormone levels. Results: The concentrations of leptin, insulin, IGF-1, triiodothyronine, LH, FSH, estradiol, and testosterone were significantly lower and those of cortisol and growth hormone significantly higher in the AN than the control group. No hormonal differences between restrictive and binge-purging AN subtypes were found. Leptin, IGF-1, gonadotropins, and sex steroids correlated significantly negatively and growth hormone positively with total reduction of body weight or the degree of undernutrition. Associations were also found between lower insulin concentration and family violence, lower cortisol and psychiatric diseases in the family, higher testosterone and patient’s alcohol or drug abuse. Discussion: The changed activity of the somatotropin-somatomedin, gonadal, and corticotrophin axes corresponds to the clinical stage of AN. Plasma IGF-1 seems to be the most sensitive and useful independent hormonal marker of cachexia.

  6. Stressful Life Events Predict Eating Disorder Relapse Following Remission: Six-Year Prospective Outcomes

    Science.gov (United States)

    Grilo, Carlos M.; Pagano, Maria E.; Stout, Robert L.; Markowitz, John C.; Ansell, Emily B.; Pinto, Anthony; Zanarini, Mary C.; Yen, Shirley; Skodol, Andrew E.

    2012-01-01

    Objective To examine prospectively the natural course of bulimia nervosa (BN) and eating disorder not-otherwise-specified (EDNOS) and test for the effects of stressful life events (SLE) on relapse after remission from these eating disorders. Method 117 female patients with BN (N = 35) or EDNOS (N = 82) were prospectively followed for 72 months using structured interviews performed at baseline, 6- and 12-months, and then yearly thereafter. ED were assessed with the structured clinical interview for DSM-IV, and monitored over time with the longitudinal interval follow-up evaluation. Personality disorders were assessed with the diagnostic interview for DSM-IV-personality-disorders, and monitored over time with the follow-along-version. The occurrence and specific timing of SLE were assessed with the life events assessment interview. Cox proportional-hazard-regression-analyses tested associations between time-varying levels of SLE and ED relapse, controlling for comorbid psychiatric disorders, ED duration, and time-varying personality-disorder status. Results ED relapse probability was 43%; BN and EDNOS did not differ in time to relapse. Negative SLE significantly predicted ED relapse; elevated work and social stressors were significant predictors. Psychiatric comorbidity, ED duration, and time-varying personality-disorder status were not significant predictors. Discussion Higher work and social stress represent significant warning signs for triggering relapse for women with remitted BN and EDNOS. PMID:21448971

  7. THE IMPACT OF STRESSFUL LIFE EVENTS ON RELAPSE OF GENERALIZED ANXIETY DISORDER

    Science.gov (United States)

    Francis, Jennifer L.; Moitra, Ethan; Dyck, Ingrid; Keller, Martin B.

    2013-01-01

    Background Stressful life events (SLEs) are associated with the onset of psychiatric disorders but little is known about the effects of SLEs on individuals already diagnosed with an anxiety disorder, particularly generalized anxiety disorder (GAD) in which worry about life events is a defining characteristic. This study examined the impact of SLEs on relapse in adults already diagnosed with GAD. Methods Data are obtained from the Harvard/Brown Anxiety Research Project (HARP), a naturalistic longitudinal study of adults with a current or past history of anxiety disorders. One hundred and twelve adults recovered from an episode of GAD and 27 subsequently relapsed during the study. Eight categories of SLEs were assessed via interview and were examined as predictors of GAD relapse. Results An increased total number of SLEs was associated with a higher cumulative probability of relapse into episode of GAD and there was a nonsignificant statistical trend indicating specific categories of SLEs including health, death, and family/friends/household were related to an increased probability of relapse into episodes of GAD. Conclusions SLEs impact the course of GAD and certain types of stressors may be more relevant to symptomatology than others. The change and uncertainty associated with SLEs may exacerbate existing worry tendencies even among those who have recovered from GAD. PMID:22431499

  8. 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.

  9. The interplay of stressful life events and coping skills on risk for suicidal behavior among youth students in contemporary China: a large scale cross-sectional study

    OpenAIRE

    Tang, Fang; Xue, Fuzhong; Qin, Ping

    2015-01-01

    Background Stressful life events are common among youth students and may induce psychological problems and even suicidal behaviors in those with poor coping skills. This study aims to assess the influence of stressful life events and coping skills on risk for suicidal behavior and to elucidate the underlying mechanism using a large sample of university students in China. Methods 5972 students, randoml...

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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

  15. Stressful life events in childhood and risk of infectious disease hospitalization.

    Science.gov (United States)

    Nielsen, Nete Munk; Hansen, Anne Vinkel; Simonsen, Jacob; Hviid, Anders

    2012-01-01

    Individuals exposed to high levels of stress might have an increased risk of infectious diseases. However, most of the previous studies have been conducted among adults. To examine the effect of childhood stress, we conducted a nationwide cohort study including all Danish children born from 1977 to 2004. Stressful life events (SFLE) included parental death, death of sibling or parental divorce. Outcome was defined as hospitalizations due to less severe (LSID) or severe infectious diseases (SID). Children were followed until the age of 15 years. The association between SFLE and risk of infections was evaluated through rate ratios (RR) comparing infectious disease incidence ratios in children with and without a history of SFLE. Overall, children exposed to SFLE were at 13% increased risk of LSID (RR = 1.13 (1.10-1.15)), but at no increased risk of SID hospitalization (RR = 1.05 (0.97-1.14)). Looking at the specific type of SFLE, parental divorce increased the risk of LSID (RR = 1.11 (1.09-1.14)) and SID hospitalization (1.11 (1.02-1.21)) by 11%, whereas no increased risk of LSID and SID hospitalization was observed following parental death. Finally, a 34% increased risk of LSID hospitalization (RR = 1.34 (1.23-1.45)) was observed following death of sibling, in contrast to no increased risk of SID hospitalization. Childhood exposure to SFLE, especially parental divorce seems to increase the risk of infectious disease hospitalization. Although we cannot determine whether our observations are the result of a biological effect of stress, adoption of unhealthy behaviours or increased likelihood of hospitalization, our findings do have public health relevance as a considerable proportion of the children today will be exposed to SFLE, the majority to parental divorce.

  16. The impact of resilience and subsequent stressful life events on MDD and GAD.

    Science.gov (United States)

    Sheerin, Christina M; Lind, Mackenzie J; Brown, Emily A; Gardner, Charles O; Kendler, Kenneth S; Amstadter, Ananda B

    2018-02-01

    There remains a dearth of research examining the "buffering" effect of resilience, wherein resilience at one point in time would be expected to protect an individual against development of psychopathology following future adverse life events. Using longitudinal data from an epidemiological twin sample (N = 7463), this study tested whether resilience would act as a buffer for stressful life events (SLEs) against risk for major depressive disorder (MDD) and generalized anxiety disorder (GAD). Resilience, demographics, and psychopathology were measured at Time 1 and recent SLEs and current MDD and GAD were measured at Time 2. Final models, controlling for demographic covariates and Time 1 diagnosis, examined the impact of Time 1 resilience, recent SLEs, their interaction, and a three-way interaction adding sex on MDD and GAD. The pattern of findings was the same for MDD and GAD, wherein main effects and two-way interactions of resilience and SLEs were significant, such that greater resilience was protective even in the context of high numbers of past-year SLEs. The three-way interaction was not significant, suggesting that the relationship between SLEs and resilience on psychopathology was the same for both men and women. Findings support the conceptualization of resilience as a buffer against the impact of future life stressors on common internalizing psychopathology. Longitudinal designs and trajectory-based studies that include recurring measures of SLEs could inform conceptualizations of resilience in the context of ongoing adversity and aid in developing interventions aimed at fostering healthy adaptation in the face of stressors. © 2017 Wiley Periodicals, Inc.

  17. Infant Birthweight in the US: The Role of Preconception Stressful Life Events and Substance Use

    Science.gov (United States)

    Witt, Whitney P.; Mandell, Kara C.; Wisk, Lauren E.; Cheng, Erika R.; Chatterjee, Debanjana; Wakeel, Fathima; Park, Hyojun; Zarak, Dakota

    2017-01-01

    PURPOSE The purpose of this study was to determine the relationships among preconception stressful life events (PSLEs), women’s alcohol and tobacco use before and during pregnancy, and infant birthweight. METHODS Data were from the Early Childhood Longitudinal Study-Birth Cohort (n=9,350). Data were collected in 2001. Exposure to PSLEs was defined by indications of death of a parent, spouse, or previous live born child; divorce or marital separation; or fertility problems prior to conception. Survey data determined alcohol and tobacco usage during the three months prior to and in the final three months of pregnancy. We used staged multivariable logistic regression to estimate the effects of women’s substance use and PSLEs on the risk of having a very low (<1,500 grams, VLBW) or low (1,500–2,499 grams, LBW) birthweight infant, adjusting for confounders. RESULTS Women who experienced any PSLE were more likely to give birth to VLBW infants (adjusted odds ratio [AOR]: 1.35; 95% confidence interval [CI]: 1.10–1.66) than women who did not experience any PSLE. Compared to women who never smoked, women who smoked prior to conception (AOR: 1.31; 95% CI: 1.04–1.66) or during their last trimester (AOR: 1.98; 95% CI: 1.56–2.52) were more likely to give birth to LBW infants. CONCLUSIONS PSLEs and women’s tobacco use before and during pregnancy are independent risk factors for having a lower birthweight baby. Interventions to improve birth outcomes may need to address women’s health and health behaviors in the preconception period. PMID:26767530

  18. Social connectedness, stressful life events, and self-injurious thoughts and behaviors among young adults.

    Science.gov (United States)

    Macrynikola, Natalia; Miranda, Regina; Soffer, Ariella

    2018-01-01

    Preventing self-injurious thoughts and behaviors (SITBs) is particularly challenging on commuter campuses, given lower social cohesion and higher levels of stress than among traditional college populations. The present study examined the relationship between stressful life events (SLEs) and risk for different forms of SITBs, along with the potential buffering role of social connectedness, in a diverse sample of young adults from a commuter college. Participants were 1712 (81% female; 61% racial/ethnic minority; 20% sexual minority) undergraduate and graduate students from a public commuter college in New York City. Participants completed an anonymous survey that inquired about lifetime and recent (past 12months) history of suicidal ideation, suicide attempts, and non-suicidal self-injury (NSSI), along with social connectedness and lifetime history of SLEs. Lower levels of social connectedness and exposure to a higher number of SLEs were associated with engaging in SITBs in the past year, particularly both suicide attempts and non-suicidal self-injury. However, social connectedness did not buffer against the impact of SLEs on SITBs. Data are cross-sectional, limiting conclusions about directionality, and females were overrepresented. Identifying ways to increase social connectedness on diverse commuter campuses may help decrease risk of SITBs. However, it may not buffer against the impact of SLEs on risk of SITBs. Future studies should examine contextual variables (e.g., type and timing of social support) that may play a role in protecting against SITBs, particularly for those with a history of adversity. Copyright © 2017 Elsevier Inc. All rights reserved.

  19. Development and validation of a Thai stressful life events rating scale for patients with a diagnosis of schizophrenic methamphetamine abuse

    OpenAIRE

    Ek-uma Imkome; JintanaYunibhand; Waraporn Chaiyawat

    2017-01-01

    This study aimed to psychometrically test a Thai Stressful Life Events Rating Scale (TSLERS). Factor analysis was done on data collected from 313 patients with schizophrenia and methamphetamine abuse in Thailand from April to May, 2015. Results identified the following problems impacting physical and mental health: social relationship and social concerns, money, family life, life security, and career. Evaluation of the psychometric scale properties demonstrated acceptable validity ...

  20. 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)

  1. 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

  2. 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

  3. Condensation and critical exponents of an ideal non-Abelian gas

    Science.gov (United States)

    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.

  4. Symptoms of borderline personality disorder predict interpersonal (but not independent) stressful life events in a community sample of older adults.

    Science.gov (United States)

    Powers, Abigail D; Gleason, Marci E J; Oltmanns, Thomas F

    2013-05-01

    Individuals with borderline personality disorder (BPD) often experience stressful life events at a higher frequency than those without BPD. It is less clear what specific types of events are involved in this effect, and it has not been determined whether some features of BPD are more important than others in accounting for this effect. The latter issue is important in light of the heterogeneous nature of this diagnostic construct. These issues were examined in a large, representative community sample of men and women, ages 55-64. Ten Diagnostic and Statistical Manual of Mental Disorders (4th ed., text rev., DSM-IV-TR, Washington, DC, American Psychiatric Association, 2000) personality disorders were assessed at baseline using the Structured Interview for DSM-IV Personality: SIDP-IV (B. Pfohl, N. Blum, & M. Zimmerman, 1997, Washington, DC, American Psychiatric Press). Life events were measured at three sequential assessments following baseline at 6-month (N = 1,294), 12-month (N = 1,070), and 18-month (N = 837) follow-ups. Stressful life events were identified using a self-report questionnaire (LTE-Q; List of Threatening Experiences Questionnaire: A subset of prescribed life events with considerable long-term contextual threat by T. Brugha, C. Bebbington, P. Tennant, and J. Hurry, 1985, Psychological Medicine, Vol. 15, pp. 189-194.) followed by a telephone interview. Only borderline personality pathology was related to an increase in the frequency of interpersonal stressful life events. Three specific symptoms of BPD were largely responsible for this connection: unstable interpersonal relationships, impulsivity, and chronic feelings of emptiness (negative association). Symptoms of avoidant and schizoid personality disorders were associated with a reduced number of stressful life events that are considered to be outside a person's control (e.g., serious illness, injury, or death of a loved one). None of the personality disorders predicted an increase in the number of

  5. 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.

  6. 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

  7. 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.

  8. 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.

  9. 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

  10. 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.

  11. 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

  12. 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)

  13. Culture and context: buffering the relationship between stressful life events and risky behaviors in American Indian youth.

    Science.gov (United States)

    Baldwin, Julie A; Brown, Betty G; Wayment, Heidi A; Nez, Ramona Antone; Brelsford, Kathleen M

    2011-01-01

    The Sacred Mountain Youth Project was conducted to investigate risk and protective factors related to alcohol and drug use among American Indian youth. Findings indicated that stressful life events were positively associated with depressed mood, substance use, and risky behavior; cultural identity had no direct effects, but a secondary model showed that social support and protective family and peer influences were related to cultural identity. These findings suggest that the relationships between stressors and their negative sequelae are complex. Emphasis on protective processes that are culturally specific to American Indian youth may lead to effective alcohol and drug use prevention programs.

  14. Regional and national differences in stressful life events: The role of cultural factors, economic development, and gender.

    Science.gov (United States)

    Vázquez, José Juan; Panadero, Sonia; Martín, Rosa M

    2015-07-01

    The study analyzed differences in the risk of experiencing stressful life events (SLE) according to cultural factors, the level of economic development of the region inhabited, and gender. Information was gathered on the number and nature of SLE experienced by a sample of 604 undergraduates from 3 regions with very different levels of economic development: Madrid (Spain), León (Nicaragua), and Bilwi (Nicaragua). The results indicated a greater risk of experiencing SLE among undergraduates from Nicaragua, but few differences attributed to the undergraduates' gender or the level of economic development in the region they inhabit within the same country. (c) 2015 APA, all rights reserved).

  15. The relationship between stressful life events and Axis I diagnoses among adolescent offspring of probands with bipolar and non-bipolar psychiatric disorders and healthy controls

    Science.gov (United States)

    Pan, Lisa A.; Goldstein, Tina R.; Rooks, Brian T.; Hickey, Mary; Fan, Jie Yu; Merranko, John; Monk, Kelly; Diler, Rasim S.; Sakolsky, Dara J.; Hafeman, Daniella; Iyengar, Satish; Goldstein, Benjamin; Kupfer, David J.; Axelson, David; Brent, David A.; Birmaher, Boris

    2018-01-01

    Background Previous studies have explored the role of stressful life events in the development of mood disorders. We examined the frequency and nature of stressful life events as measured by the Stressful Life Events Scale(SLES) among three groups of adolescent offspring of probands: with bipolar(BD), with non-BD psychiatric disorders, and healthy control(HC). Furthermore, we examined the relationship between stressful life events and presence of DSM-IV Axis I disorders in these offspring. Stressful life events were characterized as dependent, independent, or uncertain (neither dependent or independent), and positive, negative, and neutral (neither positive or negative). Method Offspring of probands with BD aged 13–18 years(N=269), demographically-matched offspring of probands with non-BD Axis I disorders(N=88), and HC probands(N=81) from the Pittsburgh Bipolar Offspring Study were assessed from 2002–2007 with standardized instruments at intake. Probands completed the SLES for their offspring for life events within the prior year. Life events were evaluated with regard to current offspring Axis I diagnoses after adjusting for confounds. Results After adjusting for demographic and clinical between-group differences(in probands and offspring), offspring of BD probands had greater independent and neutral life events compared with HC offspring and greater number of more severe stressful life events than HC offspring, but not non-BD offspring. Offspring of BD probands with comorbid substance use disorder reported more independent stressful life events. Greater frequency and severity of stressful life events were associated with current Axis I disorder in offspring of both BD and non-BD affected probands regardless of dependency or valence. Greater frequency and severity of stressful life events were associated with greater current Axis I disorder in all offspring. Conclusions Offspring of BD probands have greater exposure to independent and neutral life events than

  16. Psychological adjustment and victim-blaming among intimate partner violence offenders: The role of social support and stressful life events

    Directory of Open Access Journals (Sweden)

    Sergio Murgui

    2013-07-01

    Full Text Available Intimate partner violence offenders often use victim-blaming attributions to explain their own violentbehavior. These attributions represent an important challenge for intervention programs for intimatepartnerviolence offenders. The main objectives of this study were to analyze both the influence of socialsupport and stressful life events on the psychological adjustment (self-esteem and depressivesymptomatology of intimate partner violence offenders and the relationship between offenders’psychological adjustment and their victim-blaming attributions. The sample consists of 314 men convictedof intimate partner violence who were referred to a community-based intervention program. Results froma structural equation model showed that social support and stressful life events were related topsychological adjustment. Psychological adjustment also was related to victim-blaming attributions amongintimate partner violence offenders. A better understanding of the relationships between psychologicaladjustment of intimate partner violence offenders and its determinants, as well as its impact on victimblamingattributions, may provide support to new intervention strategies. Implications of these results forimproving the effectiveness of intervention programs are discussed.

  17. 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.

  18. 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.

  19. 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.

  20. Subdiffusive master equation with space-dependent anomalous exponent and structural instability

    Science.gov (United States)

    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.

  1. Magnetic entropy change and critical exponents in double perovskite Y2NiMnO6

    Science.gov (United States)

    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.

  2. 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

  3. Association of stressful life events with incident falls and fractures in older men: the Osteoporotic Fractures in Men (MrOS) Study

    Science.gov (United States)

    Fink, Howard A.; Kuskowski, Michael A.; Marshall, Lynn M.

    2014-01-01

    Background: small, retrospective studies suggest that major life events and/or sudden emotional stress may increase fall and fracture risk. The current study examines these associations prospectively. Methods: a total of 5,152 men aged ≥65 years in the Osteoporotic Fractures in Men study self-reported data on stressful life events for 1 year prior to study Visit 2. Incident falls and fractures were ascertained for 1 year after Visit 2. Fractures were centrally confirmed. Results: a total of 2,932 (56.9%) men reported ≥1 type of stressful life event. In men with complete stressful life event, fall and covariate data (n = 3,949), any stressful life event was associated with a 33% increased risk of incident fall [relative risk (RR) 1.33, 95% confidence interval (CI) 1.19–1.49] and 68% increased risk of multiple falls (RR = 1.68, 95% CI = 1.40–2.01) in the year following Visit 2 after adjustment for age, education, Parkinson's disease, diabetes, stroke, instrumental activities of daily living (IADL) impairment, chair stand time, walk speed, multiple past falls, depressive symptoms and antidepressant use. Risk increased with the number of types of stressful life events. Though any stressful life event was associated with a 58% increased age-adjusted risk for incident fracture, this association was attenuated and no longer statistically significant after additional adjustment for total hip bone mineral density, fracture after age 50, Parkinson's disease, stroke and IADL impairment. Conclusions: in this cohort of older men, stressful life events significantly increased risk of incident falls independent of other explanatory variables, but did not independently increase incident fracture risk. PMID:24002237

  4. 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.

  5. 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.

  6. 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.

  7. 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.)

  8. 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.

  9. 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

  10. 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

  11. 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.

  12. 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

  13. 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.

  14. Brief communication: Possible explanation of the values of Hack's drainage basin, river length scaling exponent

    Science.gov (United States)

    Hunt, Allen G.

    2016-04-01

    Percolation theory can be used to find water flow paths of least resistance. 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 may allow interpretation of the range of exponent values based on an assessment of the heterogeneity of the substrate.

  15. 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.

  16. 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.

  17. 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.)

  18. 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.

  19. 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)

  20. 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)

  1. The Hausdorff dimension of random walks and the correlation length critical exponent in Euclidean field theory

    International Nuclear Information System (INIS)

    Kiskis, J.; Narayanan, R.; Vranas, P.

    1993-01-01

    The authors study the random walk representation of the two-point function in statistical mechanics models near the critical point. Using standard scaling arguments, the authors show that the critical exponent v describing the vanishing of the physical mass at the critical point is equal to v θ /d w , where d w is the Hausdorff dimension of the walk, and v θ = var-phi, where var-phi is the crossover exponent known in the context of field theory. This implies that the Hausdorff dimension of the walk is var-phi/v for O(N) models. 3 refs

  2. The effects of poverty on childhood brain development: the mediating effect of caregiving and stressful life events.

    Science.gov (United States)

    Luby, Joan; Belden, Andy; Botteron, Kelly; Marrus, Natasha; Harms, Michael P; Babb, Casey; Nishino, Tomoyuki; Barch, Deanna

    2013-12-01

    IMPORTANCE The study provides novel data to inform the mechanisms by which poverty negatively impacts childhood brain development. OBJECTIVE To investigate whether the income-to-needs ratio experienced in early childhood impacts brain development at school age and to explore the mediators of this effect. DESIGN, SETTING, AND PARTICIPANTS This study was conducted at an academic research unit at the Washington University School of Medicine in St Louis. Data from a prospective longitudinal study of emotion development in preschool children who participated in neuroimaging at school age were used to investigate the effects of poverty on brain development. Children were assessed annually for 3 to 6 years prior to the time of a magnetic resonance imaging scan, during which they were evaluated on psychosocial, behavioral, and other developmental dimensions. Preschoolers included in the study were 3 to 6 years of age and were recruited from primary care and day care sites in the St Louis metropolitan area; they were annually assessed behaviorally for 5 to 10 years. Healthy preschoolers and those with clinical symptoms of depression participated in neuroimaging at school age/early adolescence. EXPOSURE Household poverty as measured by the income-to-needs ratio. MAIN OUTCOMES AND MEASURES Brain volumes of children's white matter and cortical gray matter, as well as hippocampus and amygdala volumes, obtained using magnetic resonance imaging. Mediators of interest were caregiver support/hostility measured observationally during the preschool period and stressful life events measured prospectively. RESULTS Poverty was associated with smaller white and cortical gray matter and hippocampal and amygdala volumes. The effects of poverty on hippocampal volume were mediated by caregiving support/hostility on the left and right, as well as stressful life events on the left. CONCLUSIONS AND RELEVANCE The finding that exposure to poverty in early childhood materially impacts brain

  3. 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...

  4. Stressful Life Events and Predictors of Post-traumatic Growth among High-Risk Early Emerging Adults.

    Science.gov (United States)

    Arpawong, Thalida E; Rohrbach, Louise A; Milam, Joel E; Unger, Jennifer B; Land, Helen; Sun, Ping; Spruijt-Metz, Donna; Sussman, Steve

    2016-01-01

    Stressful life events (SLEs) may elicit positive psychosocial change among youth, referred to as Post-traumatic Growth (PTG). We assessed types of SLEs experienced, degree to which participants reported PTG, and variables predicting PTG across 24 months among a sample of high risk, ethnically diverse early emerging adults. Participants were recruited from alternative high schools ( n = 564; mean age=16.8; 65% Hispanic). Multi-level regression models were constructed to examine the impact of environmental (SLE quantity, severity) and personal factors (hedonic ability, perceived stress, developmental stage, future time orientation) on a composite score of PTG. The majority of participants reported positive changes resulted from their most life-altering SLE of the past two years. Predictors of PTG included fewer SLEs, less general stress, having a future time perspective, and greater identification with the developmental stage of Emerging Adulthood. Findings suggest intervention targets to foster positive adaptation among early emerging adults who experience frequent SLEs.

  5. The impact of stressful life events on excessive alcohol consumption in the French population: findings from the GAZEL cohort study.

    Science.gov (United States)

    Tamers, Sara L; Okechukwu, Cassandra; Bohl, Alex A; Guéguen, Alice; Goldberg, Marcel; Zins, Marie

    2014-01-01

    Major life changes may play a causative role in health through lifestyle factors, such as alcohol. The objective was to examine the impact of stressful life events on heavy alcohol consumption among French adults. Trajectories of excessive alcohol consumption in 20,625 employees of the French national gas and electricity company for up to 5 years before and 5 years after an event, with annual measurements from 1992. We used repeated measures analysis of time series data indexed to events, employing generalized estimating equations. For women, excessive alcohol use increased before important purchase (p = 0.021), children leaving home (pdivorce, widowhood, and death of loved one (all pchildren leaving home and retirement, where we observed an increase (all pdivorce and increased after (all pimpact alcohol intake temporarily while others have longer-term implications. Research should disentangle women's and men's distinct perceptions of events over time.

  6. The Role of Rumination and Stressful Life Events in the Relationship between the Qi Stagnation Constitution and Depression in Women: A Moderated Mediation Model

    Science.gov (United States)

    Liu, Qiaosheng

    2017-01-01

    The qi stagnation constitution is associated with depression in traditional Chinese medicine. It is unclear how rumination and stressful life events affect the relationship between the qi stagnation constitution and depression. The Qi Stagnation Constitution Scale, Ruminative Response Scale, Center for Epidemiologic Studies Depression Scale, and Adolescent Self-Rating Life Events Checklist were used to assess this association in 1200 female college students. The results revealed that the qi stagnation constitution was positively associated with depression. Furthermore, rumination was a partial mediator of the relationship between the qi stagnation constitution and depression. In addition, stressful life events moderated the direct effect and mediating effect of the qi stagnation constitution on depression. These findings indicate that rumination and stressful life events may affect the relationship between the qi stagnation constitution and depression in women. PMID:28757889

  7. The Role of Rumination and Stressful Life Events in the Relationship between the Qi Stagnation Constitution and Depression in Women: A Moderated Mediation Model

    Directory of Open Access Journals (Sweden)

    Mingfan Liu

    2017-01-01

    Full Text Available The qi stagnation constitution is associated with depression in traditional Chinese medicine. It is unclear how rumination and stressful life events affect the relationship between the qi stagnation constitution and depression. The Qi Stagnation Constitution Scale, Ruminative Response Scale, Center for Epidemiologic Studies Depression Scale, and Adolescent Self-Rating Life Events Checklist were used to assess this association in 1200 female college students. The results revealed that the qi stagnation constitution was positively associated with depression. Furthermore, rumination was a partial mediator of the relationship between the qi stagnation constitution and depression. In addition, stressful life events moderated the direct effect and mediating effect of the qi stagnation constitution on depression. These findings indicate that rumination and stressful life events may affect the relationship between the qi stagnation constitution and depression in women.

  8. Exponent Rummy

    Science.gov (United States)

    Griffith, Leah

    2016-01-01

    Classroom teachers try to provide opportunities for students to practice and use the algebra skills they are learning in ways that are nonroutine. They also want to help students connect the big ideas of math with the skills they are learning as part of the balance between understanding concepts and procedures. Math games can be used to accomplish…

  9. Associations among depressive symptoms, childhood abuse, neuroticism, and adult stressful life events in the general adult population

    Directory of Open Access Journals (Sweden)

    Ono K

    2017-02-01

    Full Text Available Kotaro Ono,1 Yoshikazu Takaesu,1 Yukiei Nakai,2 Akiyoshi Shimura,1 Yasuyuki Ono,1 Akiko Murakoshi,1 Yasunori Matsumoto,1 Hajime Tanabe,3 Ichiro Kusumi,2 Takeshi Inoue1 1Department of Psychiatry, Tokyo Medical University, Tokyo, 2Department of Psychiatry, Hokkaido University Graduate School of Medicine, Hokkaido, 3Department of Clinical Human Sciences, Graduate school of Humanities and Social Sciences, Shizuoka University, Shizuoka, Japan Background: Recent studies have suggested that the interactions among several factors affect the onset, progression, and prognosis of major depressive disorder. This study investigated how childhood abuse, neuroticism, and adult stressful life events interact with one another and affect depressive symptoms in the general adult population. Subjects and methods: A total of 413 participants from the nonclinical general adult population completed the Patient Health Questionnaire-9, the Child Abuse and Trauma Scale, the neuroticism subscale of the shortened Eysenck Personality Questionnaire – Revised, and the Life Experiences Survey, which are self-report scales. Structural equation modeling (Mplus version 7.3 and single and multiple regressions were used to analyze the data. Results: Childhood abuse, neuroticism, and negative evaluation of life events increased the severity of the depressive symptoms directly. Childhood abuse also indirectly increased the negative appraisal of life events and the severity of the depressive symptoms through enhanced neuroticism in the structural equation modeling. Limitations: There was recall bias in this study. The causal relationship was not clear because this study was conducted using a cross-sectional design. Conclusion: This study suggested that neuroticism is the mediating factor for the two effects of childhood abuse on adulthood depressive symptoms and negative evaluation of life events. Childhood abuse directly and indirectly predicted the severity of depressive symptoms

  10. 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.

  11. Rigorous lower bound on the dynamic critical exponent of some multilevel Swendsen-Wang algorithms

    International Nuclear Information System (INIS)

    Li, X.; Sokal, A.D.

    1991-01-01

    We prove the rigorous lower bound z exp ≥α/ν for the dynamic critical exponent of a broad class of multilevel (or ''multigrid'') variants of the Swendsen-Wang algorithm. This proves that such algorithms do suffer from critical slowing down. We conjecture that such algorithms in fact lie in the same dynamic universality class as the stanard Swendsen-Wang algorithm

  12. The critical 1-arm exponent for the ferromagnetic Ising model on the Bethe lattice

    Science.gov (United States)

    Heydenreich, Markus; Kolesnikov, Leonid

    2018-04-01

    We consider the ferromagnetic nearest-neighbor Ising model on regular trees (Bethe lattice), which is well-known to undergo a phase transition in the absence of an external magnetic field. The behavior of the model at critical temperature can be described in terms of various critical exponents; one of them is the critical 1-arm exponent ρ which characterizes the rate of decay of the (root) magnetization as a function of the distance to the boundary. The crucial quantity we analyze in this work is the thermal expectation of the root spin on a finite subtree, where the expected value is taken with respect to a probability measure related to the corresponding finite-volume Hamiltonian with a fixed boundary condition. The spontaneous magnetization, which is the limit of this thermal expectation in the distance between the root and the boundary (i.e., in the height of the subtree), is known to vanish at criticality. We are interested in a quantitative analysis of the rate of this convergence in terms of the critical 1-arm exponent ρ. Therefore, we rigorously prove that ⟨σ0⟩ n +, the thermal expectation of the root spin at the critical temperature and in the presence of the positive boundary condition, decays as ⟨σ0 ⟩ n +≈n-1/2 (in a rather sharp sense), where n is the height of the tree. This establishes the 1-arm critical exponent for the Ising model on regular trees (ρ =1/2 ).

  13. 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.

  14. 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 ...

  15. 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.

  16. A new interpretation of zero Lyapunov exponents in BKL time for Mixmaster cosmology

    International Nuclear Information System (INIS)

    Wu Xin

    2010-01-01

    A global relationship between cosmological time and Belinskii-Khalatnikov-Lifshitz (BKL) time during the entire evolution of the Mixmaster Bianchi IX universe is used to explain why all the Lyapunov exponents are zero at the BKL time. The actual reason is that the domain of the cosmological time is finite as the BKL time runs from minus infinity to infinity.

  17. Phase space reconstruction and estimation of the largest Lyapunov exponent for gait kinematic data

    Energy Technology Data Exchange (ETDEWEB)

    Josiński, Henryk [Silesian University of Technology, Akademicka 16, 44-100 Gliwice (Poland); Świtoński, Adam [Polish-Japanese Institute of Information Technology, Aleja Legionów 2, 41-902 Bytom (Poland); Silesian University of Technology, Akademicka 16, 44-100 Gliwice (Poland); Michalczuk, Agnieszka; Wojciechowski, Konrad [Polish-Japanese Institute of Information Technology, Aleja Legionów 2, 41-902 Bytom (Poland)

    2015-03-10

    The authors describe an example of application of nonlinear time series analysis directed at identifying the presence of deterministic chaos in human motion data by means of the largest Lyapunov exponent. The method was previously verified on the basis of a time series constructed from the numerical solutions of both the Lorenz and the Rössler nonlinear dynamical systems.

  18. Using machine learning to replicate chaotic attractors and calculate Lyapunov exponents from data

    Science.gov (United States)

    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.

  19. Extraction of the power law exponent for 1 GeV/nucleon Au + C projectile multifragmentation

    International Nuclear Information System (INIS)

    Gilkes, M.L.; Elliott, J.B.; Huager, A.; Hirsch, A.S.; Hjort, E.

    1993-01-01

    Using moments of the measured charge distribution in exclusive gold multifragmentation events, we present a preliminary determination of the power law exponent τ. For a system undergoing a phase transition near the critical point, τ governs the cluster size distribution and is expected on rather general grounds to lie in the range 2 < τ < 3

  20. Adiabatic invariants and asymptotic behavior of Lyapunov exponents of the Schrodinger equation

    International Nuclear Information System (INIS)

    Delyon, F.; Foulon, P.

    1986-01-01

    We give an upper bound for the high-energy behavior of the Lyapunov exponent of the one-dimensional Schrodinger equation. We relate this behavior to the diffrentiability properties of the potential. As an application, this result provides an upper bound for the asymptotic length of the gaps of the Schrodinger equation

  1. 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

  2. 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.

  3. 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.

  4. Singular elliptic systems involving concave terms and critical Caffarelli-Kohn-Nirenberg exponents

    Directory of Open Access Journals (Sweden)

    Mohammed E. O. El Mokhtar

    2012-03-01

    Full Text Available In this article, we establish the existence of at least four solutions to a singular system with a concave term, a critical Caffarelli-Kohn-Nirenberg exponent, and sign-changing weight functions. Our main tools are the Nehari manifold and the mountain pass theorem.

  5. Effect of interband interaction on isotope effect exponent of MgB2 ...

    Indian Academy of Sciences (India)

    The interband interaction of the electron–phonon interaction shows more effect on the isotope exponent than on the non-phonon interaction. Acknowledgement. The authors would like to thank Thailand Research Fund for financial support and the University of the Thai Chamber of Commerce for partial financial support and.

  6. 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

  7. Dynamical generalized Hurst exponent as a tool to monitor unstable periods in financial time series

    Science.gov (United States)

    Morales, Raffaello; Di Matteo, T.; Gramatica, Ruggero; Aste, Tomaso

    2012-06-01

    We investigate the use of the Hurst exponent, dynamically computed over a weighted moving time-window, to evaluate the level of stability/instability of financial firms. Financial firms bailed-out as a consequence of the 2007-2008 credit crisis show a neat increase with time of the generalized Hurst exponent in the period preceding the unfolding of the crisis. Conversely, firms belonging to other market sectors, which suffered the least throughout the crisis, show opposite behaviors. We find that the multifractality of the bailed-out firms increase at the crisis suggesting that the multi fractal properties of the time series are changing. These findings suggest the possibility of using the scaling behavior as a tool to track the level of stability of a firm. In this paper, we introduce a method to compute the generalized Hurst exponent which assigns larger weights to more recent events with respect to older ones. In this way large fluctuations in the remote past are less likely to influence the recent past. We also investigate the scaling associated with the tails of the log-returns distributions and compare this scaling with the scaling associated with the Hurst exponent, observing that the processes underlying the price dynamics of these firms are truly multi-scaling.

  8. The interplay of stressful life events and coping skills on risk for suicidal behavior among youth students in contemporary China: a large scale cross-sectional study.

    Science.gov (United States)

    Tang, Fang; Xue, Fuzhong; Qin, Ping

    2015-07-31

    Stressful life events are common among youth students and may induce psychological problems and even suicidal behaviors in those with poor coping skills. This study aims to assess the influence of stressful life events and coping skills on risk for suicidal behavior and to elucidate the underlying mechanism using a large sample of university students in China. 5972 students, randomly selected from 6 universities, completed the questionnaire survey. Logistic regression analysis was performed to estimate the effect of stressful life events and coping skills on risk for suicidal behavior. Bayesian network was further adopted to probe their probabilistic relationships. Of the 5972 students, 7.64% reported the presence of suicidal behavior (attempt or ideation) within the past one year period. Stressful life events such as strong conflicts with classmates and a failure in study exam constituted strong risk factors for suicidal behavior. The influence of coping skills varied according to the strategies adapted toward problems with a high score of approach coping skills significantly associated with a reduced risk of suicidal behavior. The Bayesian network indicated that the probability of suicidal behavior associated with specific life events was to a large extent conditional on coping skills. For instance, a stressful experience of having strong conflicts with classmates could result in a probability of suicidal behavior of 21.25% and 15.36% respectively, for female and male students with the score of approach coping skills under the average. Stressful life events and deficient coping skills are strong risk factors for suicidal behavior among youth students. The results underscore the importance of prevention efforts to improve coping skills towards stressful life events.

  9. Impact of new traumatic or stressful life events on pre-existing PTSD in traumatized refugees: results of a longitudinal study

    Directory of Open Access Journals (Sweden)

    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

  10. 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

  11. 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.

  12. 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

  13. 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.

  14. 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.

  15. 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 ɛ) (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 ɛ and h. In this study, we expand this to a more general ɛ-η-h relationship. We approach ɛ-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.

  16. 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.

  17. Fractional Black–Scholes option pricing, volatility calibration and implied Hurst exponents in South African context

    Directory of Open Access Journals (Sweden)

    Emlyn Flint

    2017-03-01

    Full Text Available Background: Contingent claims on underlying assets are typically priced under a framework that assumes, inter alia, that the log returns of the underlying asset are normally distributed. However, many researchers have shown that this assumption is violated in practice. Such violations include the statistical properties of heavy tails, volatility clustering, leptokurtosis and long memory. This paper considers the pricing of contingent claims when the underlying is assumed to display long memory, an issue that has heretofore not received much attention. Aim: We address several theoretical and practical issues in option pricing and implied volatility calibration in a fractional Black–Scholes market. We introduce a novel eight-parameter fractional Black–Scholes-inspired (FBSI model for the implied volatility surface, and consider in depth the issue of calibration. One of the main benefits of such a model is that it allows one to decompose implied volatility into an independent long-memory component – captured by an implied Hurst exponent – and a conditional implied volatility component. Such a decomposition has useful applications in the areas of derivatives trading, risk management, delta hedging and dynamic asset allocation. Setting: The proposed FBSI volatility model is calibrated to South African equity index options data as well as South African Rand/American Dollar currency options data. However, given the focus on the theoretical development of the model, the results in this paper are applicable across all financial markets. Methods: The FBSI model essentially combines a deterministic function form of the 1-year implied volatility skew with a separate deterministic function for the implied Hurst exponent, thus allowing one to model both observed implied volatility surfaces as well as decompose them into independent volatility and long-memory components respectively. Calibration of the model makes use of a quasi-explicit weighted

  18. Investigations in the field electron emission at the Siemens research laboratory directed by Gustav Hertz between 1935 and 1945 and their significance for the present-day surface physics

    International Nuclear Information System (INIS)

    Haefer, R.A.

    1987-01-01

    The author, who was a co-worker of Gustav Hertz, describes briefly the early history of field emission research and the fundamental results, i.e. the invention of the field electron microscope by E. W. Mueller and the first confirmation of the quantum mechanical Fowler-Nordheim theory by R. A. Haefer, and points out their significance for present-day surface physics and technology. (author)

  19. 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…

  20. Role of stressful life events, avoidant coping styles, and neuroticism in online game addiction among college students: a moderated mediation model

    Directory of Open Access Journals (Sweden)

    Li Huanhuan

    2016-11-01

    Full Text Available Online game addiction (OGA is becoming a significant problem worldwide. The aim of this study was to explore the incidence of OGA and the roles of stressful life events, avoidant coping styles (ACSs, and neuroticism in OGA. A total of 651 Chinese college students were selected by random cluster sampling. Subjects completed the Chinese version of Young’s eight-item Internet Addiction Scale (CIAS, Online Game Cognition Addiction Scale (OGCAS, Revised Eysenck Personality Questionnaire Short Scale in Chinese (EPQ-RSC, Chinese College-student Stress Questionnaire (CCSQ, and Coping Style Questionnaire (CSQ. Structural equation modeling (SEM was used to explore the interactive effects of stressful life events, ACSs, and neuroticism on OGA. Of the 651 participants in the sample, 31 (4.8% were identified as addicts. The incidence of OGA was two times higher for males than females. The addicts had markedly higher scores on the neuroticism subscale of the EPQ-RSC than non-addicts. Compared to non-addicts, addicts were more apt to use ACSs. Having an avoidant coping strategy mediated the effect of stressful life events on OGA. Furthermore, neuroticism moderated the indirect effect of stressful life events on OGA via ACSs. Applications of these findings to etiological research and clinical treatment programs are discussed.

  1. The Effects of Depression and Stressful Life Events on the Development and Maintenance of Syndromal Social Anxiety: Sex and Age Differences

    Science.gov (United States)

    Aune, Tore; Stiles, Tore C.

    2009-01-01

    This study assessed age and sex differences in the prevalence and incidence rates of syndromal social anxiety (SSA), as well as the predictive role of depressive symptoms and stressful life events on the development and persistence of SSA. A sample of 1,439 young people, between 11 and 14 years of age, was assessed twice within a 12-month…

  2. Gender Differences in Depressive Symptoms during Adolescence: Role of Gender-Typed Characteristics, Self-Esteem, Body Image, Stressful Life Events, and Pubertal Status.

    Science.gov (United States)

    Marcotte, Diane; Fortin, Laurier; Potvin, Pierre; Papillon, Myra

    2002-01-01

    In a study of French-speaking adolescents (n=547), five measures designed to examine psychological well being found that body image, self-esteem, and negative stressful life events mediate the relationship between gender and depressive symptoms during adolescence. Further analysis of a subsample who recently transitioned to high school also found…

  3. Investigating the interactive role of stressful life events, reinforcement sensitivity and personality traits in prediction of the severity of Multiple Sclerosis (MS symptoms

    Directory of Open Access Journals (Sweden)

    2017-06-01

    Full Text Available Background & Objective: Multiple sclerosis is a chronic neurological condition recognized by demyelination in the central nervous system. The present study was conducted to investigate the interactive role of stressful life events, reinforcement sensitivity, and personality traits in prediction of the severity of symptoms of Multiple sclerosis (MS symptoms. Materials & Methods: This is a correlational study whose statistical population consisted of all the patients suffering from Multiple Sclerosis in Shiraz in the first half of 1394, among whom 162 patients were included in this research by means of purposive sampling method. Five-Factor Personality Inventory, Jackson Personality Inventory, Stressful Life Events Scale, and Expanded Disability Status Scale (EDSS were utilised as research tools. In order to analyze the data, descriptive and inferential methods were used. The data were analysed using Pearson correlation and hierarchical regression. Results: The findings revealed that stressful life events (β = 0.41, p <0.001, Behavioral Inhibition System (β = 0.26, p<0.05, and neuroticism index (β = 0.92, p <0.05 were able to predict variance of scores of the severity of symptoms of Multiple Sclerosis significantly. Conclusion: Stressful life events, Behavioral Inhibition System, and neuroticism showed a significant relationship with the severity of symptoms of Multiple Sclerosis; thus, it seems that interaction of personality traits and environmental conditions are among influential factors of the severity of symptoms of Multiple Sclerosis. This fact implies that individuals' personal traits play an eminent role in the progression of the disease.

  4. Stressful Life Events: Moderators of the Relationships of Gender and Gender Roles to Self-Reported Depression and Suicidality among College Students.

    Science.gov (United States)

    Waelde, Lynn C.; And Others

    1994-01-01

    Examines whether relationships of self-reported depression and suicidality to gender roles or gender are moderated by stressful life events. Results with 290 female and 247 male undergraduates support the androgyny model of adjustment and a self-schema model of depression. (SLD)

  5. Role of Stressful Life Events, Avoidant Coping Styles, and Neuroticism in Online Game Addiction among College Students: A Moderated Mediation Model.

    Science.gov (United States)

    Li, Huanhuan; Zou, Yingmin; Wang, Jiaqi; Yang, Xuelin

    2016-01-01

    Online game addiction (OGA) is becoming a significant problem worldwide. The aim of this study was to explore the incidence of OGA and the roles of stressful life events, avoidant coping styles (ACSs), and neuroticism in OGA. A total of 651 Chinese college students were selected by random cluster sampling. Subjects completed the Chinese version of Young's eight-item Internet Addiction Scale (CIAS), Online Game Cognition Addiction Scale (OGCAS), Revised Eysenck Personality Questionnaire Short Scale in Chinese (EPQ-RSC), Chinese College-student Stress Questionnaire, and Coping Style Questionnaire. Structural equation modeling (SEM) was used to explore the interactive effects of stressful life events, ACSs, and neuroticism on OGA. Of the 651 participants in the sample, 31 (4.8%) were identified as addicts. The incidence of OGA was two times higher for males than females. The addicts had markedly higher scores on the neuroticism subscale of the EPQ-RSC than non-addicts. Compared to non-addicts, addicts were more apt to use ACSs. Having an avoidant coping strategy mediated the effect of stressful life events on OGA. Furthermore, neuroticism moderated the indirect effect of stressful life events on OGA via ACSs. Applications of these findings to etiological research and clinical treatment programs are discussed.

  6. Role of Stressful Life Events, Avoidant Coping Styles, and Neuroticism in Online Game Addiction among College Students: A Moderated Mediation Model

    Science.gov (United States)

    Li, Huanhuan; Zou, Yingmin; Wang, Jiaqi; Yang, Xuelin

    2016-01-01

    Online game addiction (OGA) is becoming a significant problem worldwide. The aim of this study was to explore the incidence of OGA and the roles of stressful life events, avoidant coping styles (ACSs), and neuroticism in OGA. A total of 651 Chinese college students were selected by random cluster sampling. Subjects completed the Chinese version of Young’s eight-item Internet Addiction Scale (CIAS), Online Game Cognition Addiction Scale (OGCAS), Revised Eysenck Personality Questionnaire Short Scale in Chinese (EPQ-RSC), Chinese College-student Stress Questionnaire, and Coping Style Questionnaire. Structural equation modeling (SEM) was used to explore the interactive effects of stressful life events, ACSs, and neuroticism on OGA. Of the 651 participants in the sample, 31 (4.8%) were identified as addicts. The incidence of OGA was two times higher for males than females. The addicts had markedly higher scores on the neuroticism subscale of the EPQ-RSC than non-addicts. Compared to non-addicts, addicts were more apt to use ACSs. Having an avoidant coping strategy mediated the effect of stressful life events on OGA. Furthermore, neuroticism moderated the indirect effect of stressful life events on OGA via ACSs. Applications of these findings to etiological research and clinical treatment programs are discussed. PMID:27920734

  7. Serotonin Transporter-Linked Polymorphic Region (5-HTTLPR) Genotype and Stressful Life Events Interact to Predict Preschool-Onset Depression: A Replication and Developmental Extension

    Science.gov (United States)

    Bogdan, Ryan; Agrawal, Arpana; Gaffrey, Michael S.; Tillman, Rebecca; Luby, Joan L.

    2014-01-01

    Background: Scientific enthusiasm about gene × environment interactions, spurred by the 5-HTTLPR (serotonin transporter-linked polymorphic region) × SLEs (stressful life events) interaction predicting depression, have recently been tempered by sober realizations of small effects and meta-analyses reaching opposing conclusions. These mixed findings…

  8. Estimation of time-dependent Hurst exponents with variational smoothing and application to forecasting foreign exchange rates

    Science.gov (United States)

    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.

  9. 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

  10. Momentum distribution critical exponents for one dimensional large U hubbard model in thermodynamic limit

    International Nuclear Information System (INIS)

    Qin Shaojin; Yu Lu.

    1996-03-01

    The critical exponent of the momentum distribution near k F , 3k F and 5k F are studied numerically for one-dimensional U → ∞ Hubbard model, using finite size systems and extrapolating them to the thermodynamic limit. Results at k F agree with earlier calculations, while at 3k F exponents less than 1 are obtained for finite size systems with extrapolation to 1 (regular behaviour) in the thermodynamic limit, in contrast to earlier analytic prediction 9/8. The distribution is regular at 5k F even for finite systems. The singularity near 3k F is interpreted as due to low energy excitations near 3k F in finite systems. (author). 18 refs, 4 figs, 1 tab

  11. Analysis of Multiple Structural Changes in Financial Contagion Based on the Largest Lyapunov Exponents

    Directory of Open Access Journals (Sweden)

    Rui Wang

    2014-01-01

    Full Text Available A modified multiple structural changes model is built to test structural breaks of the financial system based on calculating the largest Lyapunov exponents of the financial time series. Afterwards, the Lorenz system is used as a simulation example to inspect the new model. As the Lorenz system has strong nonlinearity, the verification results show that the new model has good capability in both finding the breakpoint and revealing the changes in nonlinear characteristics of the time series. The empirical study based on the model used daily data from the S&P 500 stock index during the global financial crisis from 2005 to 2012. The results provide four breakpoints of the period, which divide the contagion into four stages: stationary, local outbreak, global outbreak, and recovery period. An additional significant result is the obvious chaos characteristic difference in the largest Lyapunov exponents and the standard deviation at various stages, particularly at the local outbreak stage.

  12. Critical exponents of the transition from incoherence to partial oscillation death in the Winfree model

    International Nuclear Information System (INIS)

    Basnarkov, Lasko; Urumov, Viktor

    2009-01-01

    We consider an analytically solvable version of the Winfree model of synchronization of phase oscillators (proposed by Ariaratnam and Strogatz 2001 Phys. Rev. Lett. 86 4278). It is obtained that the transition from incoherence to a partial death state is characterized by third-order or higher phase transitions according to the Ehrenfest classification. The order of the transition depends on the shape of the distribution function for natural frequencies of oscillators in the vicinity of their lowest frequency. The corresponding critical exponents are found analytically and verified with numerical simulations of equations of motion. We also consider the generalized Winfree model with the interaction strength proportional to a power of the Kuramoto order parameter and find the domain where the critical exponent remains unchanged by this modification

  13. Dependence of exponents on text length versus finite-size scaling for word-frequency distributions

    Science.gov (United States)

    Corral, Álvaro; Font-Clos, Francesc

    2017-08-01

    Some authors have recently argued that a finite-size scaling law for the text-length dependence of word-frequency distributions cannot be conceptually valid. Here we give solid quantitative evidence for the validity of this scaling law, using both careful statistical tests and analytical arguments based on the generalized central-limit theorem applied to the moments of the distribution (and obtaining a novel derivation of Heaps' law as a by-product). We also find that the picture of word-frequency distributions with power-law exponents that decrease with text length [X. Yan and P. Minnhagen, Physica A 444, 828 (2016), 10.1016/j.physa.2015.10.082] does not stand with rigorous statistical analysis. Instead, we show that the distributions are perfectly described by power-law tails with stable exponents, whose values are close to 2, in agreement with the classical Zipf's law. Some misconceptions about scaling are also clarified.

  14. Evaluating Noise Sensitivity on the Time Series Determination of Lyapunov Exponents Applied to the Nonlinear Pendulum

    Directory of Open Access Journals (Sweden)

    L.F.P. Franca

    2003-01-01

    Full Text Available This contribution presents an investigation on noise sensitivity of some of the most disseminated techniques employed to estimate Lyapunov exponents from time series. Since noise contamination is unavoidable in cases of data acquisition, it is important to recognize techniques that could be employed for a correct identification of chaos. State space reconstruction and the determination of Lyapunov exponents are carried out to investigate the response of a nonlinear pendulum. Signals are generated by numerical integration of the mathematical model, selecting a single variable of the system as a time series. In order to simulate experimental data sets, a random noise is introduced in the signal. Basically, the analyses of periodic and chaotic motions are carried out. Results obtained from mathematical model are compared with the one obtained from time series analysis, evaluating noise sensitivity. This procedure allows the identification of the best techniques to be employed in the analysis of experimental data.

  15. Phase Transitions, Geometrothermodynamics, and Critical Exponents of Black Holes with Conformal Anomaly

    Directory of Open Access Journals (Sweden)

    Jie-Xiong Mo

    2014-01-01

    Full Text Available We investigate the phase transitions of black holes with conformal anomaly in canonical ensemble. Some interesting and novel phase transition phenomena have been discovered. It is shown that there are striking differences in both Hawking temperature and phase structure between black holes with conformal anomaly and those without it. Moreover, we probe in detail the dependence of phase transitions on the choice of parameters. The results show that black holes with conformal anomaly have much richer phase structure than those without it. There would be two, only one, or no phase transition points depending on the parameters. The corresponding parameter regions are derived both numerically and graphically. Geometrothermodynamics are built up to examine the phase structure we have discovered. It is shown that Legendre invariant thermodynamic scalar curvature diverges exactly where the specific heat diverges. Furthermore, critical behaviors are investigated by calculating the relevant critical exponents. And we prove that these critical exponents satisfy the thermodynamic scaling laws.

  16. The brief time-reversibility of the local Lyapunov exponents for a small chaotic Hamiltonian system

    International Nuclear Information System (INIS)

    Waldner, Franz; Hoover, William G.; Hoover, Carol G.

    2014-01-01

    Highlights: •We consider the local Lyapunov spectrum for a four-dimensional Hamilton system. •Its stable periodic motion can be reversed for long times. •In the chaotic motion, time reversal occurs only for a short time. •Perturbations will change this short unstable case into a different stable case. •These observations might relate chaos to the Second Law of Thermodynamics. - Abstract: We consider the local (instantaneous) Lyapunov spectrum for a four-dimensional Hamiltonian system. Its stable periodic motion can be reversed for long times. Its unstable chaotic motion, with two symmetric pairs of exponents, cannot. In the latter case reversal occurs for more than a thousand fourth-order Runge–Kutta time steps, followed by a transition to a new set of paired Lyapunov exponents, unrelated to those seen in the forward time direction. The relation of the observed chaotic dynamics to the Second Law of Thermodynamics is discussed

  17. Anomalous roughness of turbulent interfaces with system size dependent local roughness exponent

    International Nuclear Information System (INIS)

    Balankin, Alexander S.; Matamoros, Daniel Morales

    2005-01-01

    In a system far from equilibrium the system size can play the role of control parameter that governs the spatiotemporal dynamics of the system. Accordingly, the kinetic roughness of interfaces in systems far from equilibrium may depend on the system size. To get an insight into this problem, we performed a detailed study of rough interfaces formed in paper combustion experiments. Using paper sheets of different width λ, we found that the turbulent flame fronts display anomalous multi-scaling characterized by non-universal global roughness exponent α and by the system size dependent spectrum of local roughness exponents, ζ q (λ)=ζ 1 (1)q -ω λ φ q =0.93q -0.15 . The structure factor of turbulent flame fronts also exhibits unconventional scaling dependence on λ. These results are expected to apply to a broad range of far from equilibrium systems when the kinetic energy fluctuations exceed a certain critical value.

  18. Robust uniform persistence in discrete and continuous dynamical systems using Lyapunov exponents.

    Science.gov (United States)

    Salceanu, Paul L

    2011-07-01

    This paper extends the work of Salceanu and Smith [12, 13] where Lyapunov exponents were used to obtain conditions for uniform persistence ina class of dissipative discrete-time dynamical systems on the positive orthant of R(m), generated by maps. Here a united approach is taken, for both discrete and continuous time, and the dissipativity assumption is relaxed. Sufficient conditions are given for compact subsets of an invariant part of the boundary of R(m+) to be robust uniform weak repellers. These conditions require Lyapunov exponents be positive on such sets. It is shown how this leads to robust uniform persistence. The results apply to the investigation of robust uniform persistence of the disease in host populations, as shown in an application.

  19. Application of the Lyapunov exponent to detect noise-induced chaos in oscillating microbial cultures

    International Nuclear Information System (INIS)

    Patnaik, P.R.

    2005-01-01

    Oscillating microbial processes can, under certain conditions, gravitate into chaotic behavior induced by external noise. Detection and control of chaos are important for the survival of the microorganisms and to operate a process usefully. In this study the largest Lyapunov exponent is recommended as a convenient and reliable index of chaos in continuous oscillating cultures. For the growth of Saccharomyces cerevisiae as a model system, the exponents increase with the oxygen mass transfer coefficient and decrease as the dilution rate increases. By comparing with the corresponding time-domain oscillations determined earlier, it is inferred that weakly oscillating cultures are less likely to be driven to chaotic behavior. The main carbon source, glucose, is quite robust to chaotic destabilization, thus enhancing its suitability as a manipulated variable for bioreactor control

  20. Using largest Lyapunov exponent to confirm the intrinsic stability of boiling water reactors

    International Nuclear Information System (INIS)

    Gavilian-Moreno, Carlos; Espinosa-Paredes, Gilberto

    2016-01-01

    The aim of this paper is the study of instability state of boiling water reactors with a method based in largest Lyapunov exponents (LLEs). Detecting the presence of chaos in a dynamical system is an important problem that is solved by measuring the LLE. Lyapunov exponents quantify the exponential divergence of initially close state-space trajectories and estimate the amount of chaos in a system. This method was applied to a set of signals from several nuclear power plant (NPP) reactors under commercial operating conditions that experienced instabilities events, apparently each of a different nature. Laguna Verde and Forsmark NPPs with in-phase instabilities, and Cofrentes NPP with out-of-phases instability. This study presents the results of intrinsic instability in the boiling water reactors of three NPPs. In the analyzed cases the limit cycle was not reached, which implies that the point of equilibrium exerts influence and attraction on system evolution

  1. Using largest Lyapunov exponent to confirm the intrinsic stability of boiling water reactors

    Energy Technology Data Exchange (ETDEWEB)

    Gavilian-Moreno, Carlos [Iberdrola Generacion, S.A., Cofrentes Nuclear Power Plant, Project Engineering Department, Paraje le Plano S/N, Valencia (Spain); Espinosa-Paredes, Gilberto [Area de ingeniera en Recursos Energeticos, Universidad Autonoma Metropolitana-Iztapalapa, Mexico city (Mexico)

    2016-04-15

    The aim of this paper is the study of instability state of boiling water reactors with a method based in largest Lyapunov exponents (LLEs). Detecting the presence of chaos in a dynamical system is an important problem that is solved by measuring the LLE. Lyapunov exponents quantify the exponential divergence of initially close state-space trajectories and estimate the amount of chaos in a system. This method was applied to a set of signals from several nuclear power plant (NPP) reactors under commercial operating conditions that experienced instabilities events, apparently each of a different nature. Laguna Verde and Forsmark NPPs with in-phase instabilities, and Cofrentes NPP with out-of-phases instability. This study presents the results of intrinsic instability in the boiling water reactors of three NPPs. In the analyzed cases the limit cycle was not reached, which implies that the point of equilibrium exerts influence and attraction on system evolution.

  2. The use of the Hurst exponent to predict changes in trends on the Warsaw Stock Exchange

    Science.gov (United States)

    Domino, Krzysztof

    2011-01-01

    The local properties of the time series of the evolution of share prices of 126 significant companies traded on the Warsaw Stock Exchange during the period between 1991-2008 have been investigated. The analysis was applied to daily financial returns. I have used the local DFA to obtain the Hurst exponent (diffusion coefficient) while searching for negative correlations by which changes of long-term trends would be effected. A certain evidence, proving that after the signature of anti-correlation-the drop in the Hurst exponent-the change in the trend and in the return rate of an investment is probable, was pointed out. Hence after further investigation this method may be useful as a part of an investment strategy. As the Warsaw Stock Exchange is relatively smaller and younger than other significant world Stock Exchanges-and as the developing market is less efficient-the generalization for others markets needs further investigation.

  3. The Hurst exponent over time: testing the assertion that emerging markets are becoming more efficient

    Science.gov (United States)

    Cajueiro, Daniel O.; Tabak, Benjamin M.

    2004-05-01

    This paper is concerned with the assertion found in the financial literature that emerging markets are becoming more efficient over time. To verify whether this assertion is true or not, we propose the calculation of the Hurst exponent over time using a time window with 4 years of data. The data used here comprises the bulk of emerging markets for Latin America and Asia. Our empirical results show that this assertion seems to be true for most countries, but it does not hold for countries such as Brazil, The Philippines and Thailand. Moreover, in order to check whether or not these results depend on the short term memory and the volatility of returns common in such financial asset return data, we filter the data by an AR-GARCH procedure and present the Hurst exponents for this filtered data.

  4. Using Largest Lyapunov Exponent to Confirm the Intrinsic Stability of Boiling Water Reactors

    Directory of Open Access Journals (Sweden)

    Carlos J. Gavilán-Moreno

    2016-04-01

    Full Text Available The aim of this paper is the study of instability state of boiling water reactors with a method based in largest Lyapunov exponents (LLEs. Detecting the presence of chaos in a dynamical system is an important problem that is solved by measuring the LLE. Lyapunov exponents quantify the exponential divergence of initially close state-space trajectories and estimate the amount of chaos in a system. This method was applied to a set of signals from several nuclear power plant (NPP reactors under commercial operating conditions that experienced instabilities events, apparently each of a different nature. Laguna Verde and Forsmark NPPs with in-phase instabilities, and Cofrentes NPP with out-of-phases instability. This study presents the results of intrinsic instability in the boiling water reactors of three NPPs. In the analyzed cases the limit cycle was not reached, which implies that the point of equilibrium exerts influence and attraction on system evolution.

  5. The path integral formulation of fractional Brownian motion for the general Hurst exponent

    International Nuclear Information System (INIS)

    Calvo, I; Sanchez, R

    2008-01-01

    In 1995, Sebastian (1995 J. Phys. A: Math. Gen. 28 4305) gave a path integral computation of the propagator of subdiffusive fractional Brownian motion (fBm), i.e. fBm with a Hurst or self-similarity exponent H element of (0, 1/2). The extension of Sebastian's calculation to superdiffusion, H element of (1/2, 1], becomes however quite involved due to the appearance of additional boundary conditions on fractional derivatives of the path. In this communication, we address the construction of the path integral representation in a different fashion, which allows us to treat both subdiffusion and superdiffusion on an equal footing. The derivation of the propagator of fBm for the general Hurst exponent is then performed in a neat and unified way. (fast track communication)

  6. Perturbation theory for Lyapunov exponents of an Anderson model on a strip

    CERN Document Server

    Schulz-Baldes, H

    2003-01-01

    It is proven that the localization length of an Anderson model on a strip of width $L$ is bounded above by $L/\\lambda^2$ for small values of the coupling constant $\\lambda$ of the disordered potential. For this purpose, a new formalism is developed in order to calculate the bottom Lyapunov exponent associated with random products of large symplectic matrices perturbatively in the coupling constant of the randomness.

  7. Modeling the Effect of Privatization on Behavior of Hurst Exponent Using Stochastic Catastrophe Theory

    Science.gov (United States)

    Bolgorian, Meysam; Raei, Reza

    In this paper using the global Hurst exponent, the impact of privatization of public companies in Iran on the degree of efficiency in Tehran Stock Exchange is assessed. The results show that selling public companies' share in Tehran Stock Exchange (TSE) leads to a structural break in degree of market development. To model this phenomenon a catastrophe approach is used and it is demonstrated that this structural break can be better explained by a cusp catastrophe model.

  8. 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.

  9. 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.

  10. Lyapunov Exponent and Out-of-Time-Ordered Correlator's Growth Rate in a Chaotic System.

    Science.gov (United States)

    Rozenbaum, Efim B; Ganeshan, Sriram; Galitski, Victor

    2017-02-24

    It was proposed recently that the out-of-time-ordered four-point correlator (OTOC) may serve as a useful characteristic of quantum-chaotic behavior, because, in the semiclassical limit ℏ→0, its rate of exponential growth resembles the classical Lyapunov exponent. Here, we calculate the four-point correlator C(t) for the classical and quantum kicked rotor-a textbook driven chaotic system-and compare its growth rate at initial times with the standard definition of the classical Lyapunov exponent. Using both quantum and classical arguments, we show that the OTOC's growth rate and the Lyapunov exponent are, in general, distinct quantities, corresponding to the logarithm of the phase-space averaged divergence rate of classical trajectories and to the phase-space average of the logarithm, respectively. The difference appears to be more pronounced in the regime of low kicking strength K, where no classical chaos exists globally. In this case, the Lyapunov exponent quickly decreases as K→0, while the OTOC's growth rate may decrease much slower, showing a higher sensitivity to small chaotic islands in the phase space. We also show that the quantum correlator as a function of time exhibits a clear singularity at the Ehrenfest time t_{E}: transitioning from a time-independent value of t^{-1}lnC(t) at ttime at t>t_{E}. We note that the underlying physics here is the same as in the theory of weak (dynamical) localization [Aleiner and Larkin, Phys. Rev. B 54, 14423 (1996)PRBMDO0163-182910.1103/PhysRevB.54.14423; Tian, Kamenev, and Larkin, Phys. Rev. Lett. 93, 124101 (2004)PRLTAO0031-900710.1103/PhysRevLett.93.124101] and is due to a delay in the onset of quantum interference effects, which occur sharply at a time of the order of the Ehrenfest time.

  11. Effective Power-Law Dependence of Lyapunov Exponents on the Central Mass in Galaxies

    Science.gov (United States)

    Delis, N.; Efthymiopoulos, C.; Kalapotharakos, C.

    2015-01-01

    Using both numerical and analytical approaches, we demonstrate the existence of an effective power-law relation L alpha m(sup p) between themean Lyapunov exponent L of stellar orbits chaotically scattered by a supermassive black hole (BH) in the centre of a galaxy and the mass parameter m, i.e. ratio of the mass of the BH over the mass of the galaxy. The exponent p is found numerically to obtain values in the range p approximately equals 0.3-0.5. We propose a theoretical interpretation of these exponents, based on estimates of local 'stretching numbers', i.e. local Lyapunov exponents at successive transits of the orbits through the BH's sphere of influence. We thus predict p = 2/3 - q with q approximately equaling 0.1-0.2. Our basic model refers to elliptical galaxy models with a central core. However, we find numerically that an effective power-law scaling of L with m holds also in models with central cusp, beyond a mass scale up to which chaos is dominated by the influence of the cusp itself. We finally show numerically that an analogous law exists also in disc galaxies with rotating bars. In the latter case, chaotic scattering by the BH affects mainly populations of thick tube-like orbits surrounding some low-order branches of the x(sub 1) family of periodic orbits, as well as its bifurcations at low-order resonances, mainly the inner Lindblad resonance and the 4/1 resonance. Implications of the correlations between L and m to determining the rate of secular evolution of galaxies are discussed.

  12. Wilson's theory of critical phenomena. Higher order corrections to critical exponents

    International Nuclear Information System (INIS)

    Zinn-Justin, J.

    1973-01-01

    The Wilson's theory of critical phenomena is presented, in the context of renormalized field theory in d dimension and of the Callan-Symanzik equations. This theory allows in particular to compute critical exponents that govern the behavior of some correlation functions near the critical temperature, as power series in epsilon=4-d, using the standard perturbation theory. Owing to the large value of the expansion parameter epsilon, whose physical value is one, it is very important to perform higher order calculations [fr

  13. Gaussian fluctuation of the diffusion exponent of virus capsid in a living cell nucleus

    Science.gov (United States)

    Itto, Yuichi

    2018-05-01

    In their work [4], Bosse et al. experimentally showed that virus capsid exhibits not only normal diffusion but also anomalous diffusion in nucleus of a living cell. There, it was found that the distribution of fluctuations of the diffusion exponent characterizing them takes the Gaussian form, which is, quite remarkably, the same form for two different types of the virus. This suggests high robustness of such fluctuations. Here, the statistical property of local fluctuations of the diffusion exponent of the virus capsid in the nucleus is studied. A maximum-entropy-principle approach (originally proposed for a different virus in a different cell) is applied for obtaining the fluctuation distribution of the exponent. Largeness of the number of blocks identified with local areas of interchromatin corrals is also examined based on the experimental data. It is shown that the Gaussian distribution of the local fluctuations can be derived, in accordance with the above form. In addition, it is quantified how the fluctuation distribution on a long time scale is different from the Gaussian distribution.

  14. Sensitivity of TDF and CRE to variations in exponents of N and T

    International Nuclear Information System (INIS)

    Orton, C.G.

    1976-01-01

    A typical example is given of the calculation by two methods of the value of the radiation dose given in 20 treatments at 5 fractions per week to be equivalent to 6000 rad given in 30 treatments also at 5 fractions per week. The solutions obtained were identical and demonstrated that, in normal clinical practice, whatever values are chosen for the exponents of N and T in the basic NSD equation, the CRE (Kirk, J., Gray, W.M., and Watson, E.R., 1971, Clinical Radiology, vol. 22, 145) and TDF (Orton, C.G., and Ellis, F., 1973, Br. J. Radiol., vol. 46, 529) methods are exactly equivalent. The variations in the values calculated by the TDF method of the dose/fraction in the same example for differing values of the exponents of N and T were typically less than +- 3%, and even for more drastic changes a variation of less than 5% resulted. The TDF and CRE methods are not therefore very sensitive to changes in these exponents. It is emphasized that since CREs are not linearly additive, application of the TDF method greatly reduces the probability of arithmetical error, particularly for more complex treatment regimes. The TDF method should however be applied with great caution if the time, dose or fractionation differ significantly from that used in conventional radiotherapeutic practice, since the theory was based on clinical evidence obtained by retrospective analysis of typical radiotherapy data. (U.K.)

  15. Critical exponents for square lattice trails with a fixed number of vertices of degree 4

    International Nuclear Information System (INIS)

    James, E W; Soteros, C E

    2002-01-01

    We prove several previously conjectured results about the number of n-edge trails and n-edge embeddings of Eulerian graphs, each with a fixed number, k, of degree 4 vertices, in the lattice Z 2 . In particular, under the assumption that the relevant critical exponents exist, we prove that the difference between the critical exponent for closed trails (Eulerian graph embeddings) and that for self-avoiding circuits (polygons) is exactly k, the number of degree 4 vertices. Similarly, we prove that the difference between the critical exponent for either open trails or open Eulerian graph embeddings and that for self-avoiding walks is also k. These results are proved by establishing upper and lower bounds for the number of n-edge embeddings of closed (open) Eulerian graphs with k vertices of degree 4 in terms of the number of n-edge self-avoiding polygons (walks). The lower bounds are proved using a Kesten pattern theorem argument and the upper bounds are established by developing (based on a detailed case analysis) a method for removing vertices of degree 4 from an embedding by altering at most a constant (independent of n) number of vertices and edges of the embedding. The work presented here extends and improves the arguments first given in the work of Zhao and Lookman (1993 J. Phys. A: Math. Gen. 26 1067-76)

  16. 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

  17. 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)

  18. 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.

  19. 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.

  20. Sensitivity of TDF and CRE to variations in exponents of N and T

    Energy Technology Data Exchange (ETDEWEB)

    Orton, C G [Rhode Island Hospital, Providence (USA). Dept. of Radiation Oncology

    1976-10-01

    A typical example is given of the calculation by two methods of the value of the radiation dose given in 20 treatments at 5 fractions per week to be equivalent to 6000 rad given in 30 treatments also at 5 fractions per week. The solutions obtained were identical and demonstrated that, in normal clinical practice, whatever values are chosen for the exponents of N and T in the basic NSD equation, the CRE (Kirk, J., Gray, W.M., and Watson, E.R., 1971, Clinical Radiology, vol. 22, 145) and TDF (Orton, C.G., and Ellis, F., 1973, Br. J. Radiol., vol. 46, 529) methods are exactly equivalent. The variations in the values calculated by the TDF method of the dose/fraction in the same example for differing values of the exponents of N and T were typically less than +- 3%, and even for more drastic changes a variation of less than 5% resulted. The TDF and CRE methods are not therefore very sensitive to changes in these exponents. It is emphasized that since CREs are not linearly additive, application of the TDF method greatly reduces the probability of arithmetical error, particularly for more complex treatment regimes. The TDF method should however be applied with great caution if the time, dose or fractionation differ significantly from that used in conventional radiotherapeutic practice, since the theory was based on clinical evidence obtained by retrospective analysis of typical radiotherapy data.

  1. The Impact of Stressful Life Events on Alcohol Relapse: Findings from the Collaborative Longitudinal Personality Disorders Study.

    Science.gov (United States)

    Reyes, Christina Delos; Pagano, Maria Elizabeth; Ronis, Robert J

    2009-04-01

    Alcohol relapse is impacted by a variety of environmental, interpersonal, and intrapersonal factors. We examined the interaction between stressful life events, personality disorder subtype, and alcohol relapse among individuals enrolled in the Collaborative Longitudinal Personality Disorders Study (CLPS). Negative life events predicted relapse in all subjects. In individuals with a history of an alcohol use disorder prior to study entry, positive life events also predicted alcohol relapse. Individuals with Antisocial Personality Disorder (ASPD) were found to be twice as likely to relapse in response to life stressors compared to individuals with Obsessive-Compulsive Personality Disorder (OCPD), who were half as likely to relapse in response to life stressors. Further analysis revealed that individuals with OCPD and no history of an alcohol use disorder were almost 10 times more likely to relapse in the face of a stressful romantic problem, while those with ASPD and a history of an alcohol use disorder were six times more likely to relapse in response to a stressful financial event. These findings have implications for both the assessment and the treatment of individuals who present with co-morbid personality and alcohol use disorders.

  2. [Association between MAOA-u VNTR polymorphism and its interaction with stressful life events and major depressive disorder in adolescents].

    Science.gov (United States)

    Ma, Jing; Yu, Shun-Ying; Liang, Shan; Ding, Jun; Feng, Zhe; Yang, Fan; Gao, Wei-Jia; Lin, Jia-Ni; Huang, Chun-Xiang; Liu, Xue-Jun; Su, Lin-Yan

    2013-07-01

    To investigate whether the genetic polymorphism, upstream variable number of tandem repeats (uVNTR), in the monoamine oxidase A (MAOA) gene, is associated with major depressive disorder (MDD) in adolescents and to test whether there is gene-environment interaction between MAOA-uVNTR polymorphism and stressful life events (SLEs). A total of 394 Chinese Han subjects, including 187 adolescent patients with MDD and 207 normal students as a control group, were included in the study. Genotyping was performed by SNaP-shot assay. SLEs in the previous 12 months were evaluated. The groups were compared in terms of the frequency distributions of MAOA-uVNTR genotypes and alleles using statistical software. The binary logistic regression model of gene-environment interaction was established to analyze the association of the gene-environment interaction between MAOA-u VNTR genotypes and SLEs with adolescent MDD. The distribution profiles of MAOA-u VNTR genotypes and alleles were not related to the onset of MDD, severity of depression, comorbid anxiety and suicidal ideation/behavior/attempt in adolescents. The gene-environment interaction between MAOA-u VNTR genotypes and SLEs was not associated with MDD in male or female adolescents. It is not proven that MAOA-u VNTR polymorphism is associated with adolescent MDD. There is also no gene-environment interaction between MAOA-u VNTR polymorphism and SLEs that is associated with adolescent MDD.

  3. Examining the relationship between lifetime stressful life events and the onset of major depression in Chinese women☆

    Science.gov (United States)

    Tao, Ming; Li, Yihan; Xie, Dong; Wang, Zhiyang; Qiu, Jianying; Wu, Wenyuan; Sun, Jing; Wang, Zhoubing; Tao, Danhong; Zhao, Hongsu; Tian, Tian; Zhang, Jingxuan; Gao, Chengge; Niu, Qihui; Li, Qiang; Liu, Shanming; Liu, Jia; Zhang, Yunshu; He, Qiang; Rong, Han; Gan, Zhaoyu; Li, Jianying; Chen, Xiansheng; Pan, Jiyang; Li, Yi; Cui, Yanping; Han, Wei; Ma, Huan; Xie, Shoufu; Jin, Guixing; Li, Ling; Zhang, Ruiling; Tan, Qingrong; Zhang, Jun; Guan, Jing; Shi, Shenxun; Chen, Yiping; Kendler, Kenneth S.; Flint, Jonathan; Gao, Jingfang

    2011-01-01

    Background In European and US studies, patients with major depressive disorder (MDD) report more stressful life events (SLEs) than controls, but this relationship has rarely been studied in Chinese populations. Methods Sixteen lifetime SLEs were assessed at interview in two groups of Han Chinese women: 1970 clinically ascertained with recurrent MDD and 2597 matched controls. Diagnostic and other risk factor information was assessed at personal interview. Odds ratios (ORs) were calculated by logistic regression. Results 60% of controls and 72% of cases reported at least one lifetime SLE. Fourteen of the sixteen SLEs occurred significantly more frequently in those with MDD (median odds ratio of 1.6). The three SLEs most strongly associated with risk for MDD (OR > 3.0) preceded the onset of MDD the majority of the time: rape (82%), physical abuse (100%) and serious neglect (99%). Limitations Our results may apply to females only. SLEs were rated retrospectively and are subject to biases in recollection. We did not assess contextual information for each life event. Conclusions More severe SLEs are more strongly associated with MDD. These results support the involvement of psychosocial adversity in the etiology of MDD in China. PMID:21821294

  4. Examining the relationship between lifetime stressful life events and the onset of major depression in Chinese women.

    Science.gov (United States)

    Tao, Ming; Li, Yihan; Xie, Dong; Wang, Zhiyang; Qiu, Jianying; Wu, Wenyuan; Sun, Jing; Wang, Zhoubing; Tao, Danhong; Zhao, Hongsu; Tian, Tian; Zhang, Jingxuan; Gao, Chengge; Niu, Qihui; Li, Qiang; Liu, Shanming; Liu, Jia; Zhang, Yunshu; He, Qiang; Rong, Han; Gan, Zhaoyu; Li, Jianying; Chen, Xiansheng; Pan, Jiyang; Li, Yi; Cui, Yanping; Han, Wei; Ma, Huan; Xie, Shoufu; Jin, Guixing; Li, Ling; Zhang, Ruiling; Tan, Qingrong; Zhang, Jun; Guan, Jing; Shi, Shenxun; Chen, Yiping; Kendler, Kenneth S; Flint, Jonathan; Gao, Jingfang

    2011-12-01

    In European and US studies, patients with major depressive disorder (MDD) report more stressful life events (SLEs) than controls, but this relationship has rarely been studied in Chinese populations. Sixteen lifetime SLEs were assessed at interview in two groups of Han Chinese women: 1970 clinically ascertained with recurrent MDD and 2597 matched controls. Diagnostic and other risk factor information was assessed at personal interview. Odds ratios (ORs) were calculated by logistic regression. 60% of controls and 72% of cases reported at least one lifetime SLE. Fourteen of the sixteen SLEs occurred significantly more frequently in those with MDD (median odds ratio of 1.6). The three SLEs most strongly associated with risk for MDD (OR>3.0) preceded the onset of MDD the majority of the time: rape (82%), physical abuse (100%) and serious neglect (99%). Our results may apply to females only. SLEs were rated retrospectively and are subject to biases in recollection. We did not assess contextual information for each life event. More severe SLEs are more strongly associated with MDD. These results support the involvement of psychosocial adversity in the etiology of MDD in China. Copyright © 2011 Elsevier B.V. All rights reserved.

  5. 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

  6. Couple adjustment to a stressful life event: a dyadic investigation of the roles of positive reframing and perceived benefits.

    Science.gov (United States)

    Samios, Christina; Baran, Shayne

    2018-03-01

    This study examines positive reframing (a form of meaning making), perceived benefits (a form of meanings made) and adjustment in couples who experienced a stressful life event in the past year. This study tested whether couple members' scores were nonindependent and whether one's own perceived benefits was predicted by their own positive reframing (actor effect) as well as their partner's positive reframing (partner effect). Further, this study tested actor and partner effects for the link between perceived benefits and adjustment and whether positive reframing (the initial variable) works through perceived benefits (the mediator) to affect adjustment (the outcome) at the dyadic level. A standard dyadic design was used. Eighty couples completed measures of positive reframing, perceived benefits, and adjustment (depression, anxiety, positive affect, life satisfaction, and relationship satisfaction). Partners' scores on study variables were related, and although only actor effects were found for the path between positive reframing and perceived benefits, both actor and partner effects were found for the path between perceived benefits and adjustment. Mediation was found for actor-actor and actor-partner indirect effects. Results indicate that a greater focus on interpersonal factors is needed to further meaning-making theory and inform practice.

  7. Incidence of stressful life events and influence of sociodemographic and clinical variables on the onset of first-episode psychosis.

    Science.gov (United States)

    Butjosa, Anna; Gómez-Benito, Juana; Huerta-Ramos, Elena; Del Cacho, Núria; Barajas, Ana; Baños, Iris; Usall, Judith; Dolz, Montserrat; Sánchez, Bernardo; Carlson, Janina; Maria Haro, Josep; Ochoa, Susana

    2016-11-30

    This study presents a quantitative analysis of the incidence of stressful life events (SLEs) and the variables gender, age at onset, family history and psychotic symptoms in patients with first-episode psychosis (FEP). A descriptive, cross-sectional methodology was used to interview 68 patients with FEP between 13 and 47 years of age. The Psychiatric Epidemiology Research Interview Life Events Scale collected one-year period prior to onset of FEP - used to analyse the subcategories academic, work, love and marriage, children, residence, legal affairs, finances and social activities-, Positive and Negative Syndrome Scale, and Clinical Global Impression-Schizophrenia scale were used to assess the relevance of certain SLEs during adolescence. Age at onset showed a significant negative correlation with the categories academic and social activities. By contrast, it showed a positive correlation with work and children. A significant relationship was found between paternal family history and social activities and between maternal family history and academic and love and marriage. Finally, an inverse relationship was observed between negative symptoms and the categories children and finance. Depressive symptoms were significantly correlated with the category academic. Our results show the importance of SLEs during adolescence and suggest that there is a clear need to develop preventive actions that promote effective strategies for dealing with the accumulation of psychosocial stress. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

  8. The role of stressful life events preceding death by suicide: Evidence from two samples of suicide decedents.

    Science.gov (United States)

    Buchman-Schmitt, Jennifer M; Chu, Carol; Michaels, Matthew S; Hames, Jennifer L; Silva, Caroline; Hagan, Christopher R; Ribeiro, Jessica D; Selby, Edward A; Joiner, Thomas E

    2017-10-01

    Stressful life events (SLEs) are associated with increased risk for suicidal behavior. Less is known regarding the intensity of SLEs and how this may vary as a function of suicide attempt history. As a large percentage of suicide decedents do not have a history of suicidal behavior, SLEs precipitating suicide may help characterize suicidality in this understudied population. This paper examines the intensity, number, and accumulation of SLEs preceding death by suicide among decedents with varying suicide attempt histories. Suicide attempts, SLEs, and suicide methods were examined in two samples: 62 prison-based and 117 community-based suicide decedents. Regression was used to compare the level of stressor precipitating death by suicide in decedents who died on a first attempt versus multiple previous attempts. A non-significant trend was observed in the prison population which was supported by significant findings in the community-based sample. Decedents who died on a first attempt experienced a stressor of a lower magnitude when compared to decedents with multiple previous suicide attempts. We discuss the implications of these findings in relation to the stress-diathesis model for suicide. Copyright © 2017 Elsevier B.V. All rights reserved.

  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.

  10. Association of stressful life events with acute myocardial infarction in population in the city of Niš within the period from 1998-2000.

    Directory of Open Access Journals (Sweden)

    Deljanin Zorana

    2007-01-01

    Full Text Available Background/Aim. Stressful life events present a very important category of psychosocial stress. A few studies have showed that a psychosocial stress represents a very important risk factor for acute myocardial infarction (AMI, but measures of stress may not be suitable for different countries, cultures and ethnic groups. The aim of this study was to investigate the relation of stressful life events with AMI in the period of 1998-2000 in the population of the city of Niš. Methods. A case-control study included 100 patients with the first MI (in the period 1998-2000 and 100 healthy subjects, matched with respect to sex and age (± 2 years from the city of Niš. The data of stressful life events were obtained by the Scaling of life events by Paykel ES, modified by the authors consistent with the examined population and the period of investigation. The Yates χ2 test, odds ratio - OR and their 99% interval of confidence were used as statistical procedures. Results. The results showed that stressful life events in the period of investigation were very important risk factors for AMI with a statistically significant level (p = 0.000. Huge financial problems (OR = 202.36, Ci = 24.82-4387.58, violation of law (OR = 168.00, Ci = 10.66-6658.96 and serious illness of family members (OR = 159.60, Ci = 19.05- 3514.81 were the highest risk for AMI. The patients who reported that his/her son or other member of family had been gone to the army (or mobilization before the illness onset, had 138 times higher risk of AMI (Ci = 14.98-3222.47, χ2 = 40.95, p = 0.000, while the patients who had mobilized themselves had 84 times higher risk (Ci = 7.00- 2363.06, χ2 = 23.87, p = 0.000. Effect of several stressful life events lead to significantly increased risk of AMI and that significance is larger as the number of life events is more frequent (one life event: OR = 28.41, Ci = 3.73- 593.52; χ2 = 17.40, p = 0.000; ≥ 4: OR = 336.00, Ci = 28.31- 9760.28, χ2 = 50

  11. 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)

  12. Unified approach for estimating the probabilistic design S-N curves of three commonly used fatigue stress-life models

    International Nuclear Information System (INIS)

    Zhao Yongxiang; Wang Jinnuo; Gao Qing

    2001-01-01

    A unified approach, referred to as general maximum likelihood method, is presented for estimating probabilistic design S-N curves and their confidence bounds of the three commonly used fatigue stress-life models, namely three parameter, Langer and Basquin. The curves are described by a general form of mean and standard deviation S-N curves of the logarithm of fatigue life. Different from existent methods, i.e., the conventional method and the classical maximum likelihood method,present approach considers the statistical characteristics of whole test data. The parameters of the mean curve is firstly estimated by least square method and then, the parameters of the standard deviation curve is evaluated by mathematical programming method to be agreement with the maximum likelihood principle. Fit effects of the curves are assessed by fitted relation coefficient, total fitted standard error and the confidence bounds. Application to the virtual stress amplitude-crack initiation life data of a nuclear engineering material, Chinese 1Cr18Ni9Ti stainless steel pipe-weld metal, has indicated the validity of the approach to the S-N data where both S and N show the character of random variable. Practices to the two states of S-N data of Chinese 45 carbon steel notched specimens (k t = 2.0) have indicated the validity of present approach to the test results obtained respectively from group fatigue test and from maximum likelihood fatigue test. At the practices, it was revealed that in general the fit is best for the three-parameter model,slightly inferior for the Langer relation and poor for the Basquin equation. Relative to the existent methods, present approach has better fit. In addition, the possible non-conservative predictions of the existent methods, which are resulted from the influence of local statistical characteristics of the data, are also overcome by present approach

  13. The 5-HTTLPR polymorphism moderates the effect of stressful life events on drinking behavior in college students of African descent.

    Science.gov (United States)

    Kranzler, Henry R; Scott, Denise; Tennen, Howard; Feinn, Richard; Williams, Carla; Armeli, Stephen; Taylor, Robert E; Briggs-Gowan, Margaret J; Covault, Jonathan

    2012-07-01

    Covault et al. [Covault et al. (2007); Biol Psychiatry 61(5): 609-616] reported that the common functional polymorphism, 5-HTTLPR, in the serotonin transporter gene moderated the association between past-year stressful events and daily reports of drinking in a sample of European-American (EA) college students. We examined this effect in college students of African descent. Students recruited at a Historically Black University (n = 564) completed web-based measures of past-year stressful life experiences and daily reports of drinking and heavy drinking over a 30-day period. Participants were genotyped for the tri-allelic 5-HTTLPR polymorphism and dichotomized as low-activity S' allele carriers or high-activity L' homozygotes. Generalized linear models were used to examine the effects of life stress, genotype, and their interaction on the two drinking measures. In students who completed 15 or more daily surveys (n = 393), there was a significant interaction of past-year stressful events, 5-HTTLPR genotype, and gender on the number of drinking days (P = 0.002). Similar findings were obtained in relation to heavy drinking days (P = 0.007). Men showed a main effect of past-year stressful events on both drinking outcomes (P's life stressors on the frequency of drinking and heavy drinking days (P's stressful events were associated with more frequent drinking and heavy drinking, an effect that was moderated by the 5-HTTLPR polymorphism. However, in contrast to the findings in EA students, in the current sample, 5-HTTLPR moderated the association only among women. Copyright © 2012 Wiley Periodicals, Inc.

  14. The Role of Trauma and Stressful Life Events among Individuals at Clinical High Risk for Psychosis: A Review

    Directory of Open Access Journals (Sweden)

    Danessa Mayo

    2017-04-01

    Full Text Available The experience of childhood trauma (CT and stressful life events (SLEs is associated with subsequent development of a variety of mental health conditions, including psychotic illness. Recent research identifying adolescents and young adults at clinical high risk (CHR for psychosis allows for prospective evaluation of the impact of trauma and adverse life events on psychosis onset and other outcomes, addressing etiological questions that cannot be answered in studies of fully psychotic or non-clinical populations. This article provides a comprehensive review of the current emerging literature on trauma and adverse life events in the CHR population. Up to 80% of CHR youth endorse a lifetime history of childhood traumatic events and victimization (e.g., bullying. Several studies have shown that the experience of CT predicts psychosis onset among CHR individuals, while the literature on the influence of recent SLEs (e.g., death of a loved one remains inconclusive. Multiple models have been proposed to explain the link between trauma and psychosis, including the stress-vulnerability and stress-sensitivity hypotheses, with emphases on both cognitive processes and neurobiological mechanisms (e.g., the hypothalamic–pituitary–adrenal axis. Despite the preponderance of CHR individuals who endorse either CT or SLEs, no clinical trials have been conducted evaluating interventions for trauma in CHR youth to date. Furthermore, the current process of formal identification and assessment of trauma, SLEs, and their impact on CHR youth is inconsistent in research and clinical practice. Recommendations for improving trauma assessment, treatment, and future research directions in the CHR field are provided.

  15. Hyperbolicity and integral expression of the Lyapunov exponents for linear cocycles

    Science.gov (United States)

    Dai, Xiongping

    Consider in this paper a linear skew-product system (θ,Θ) :T×W×R→W×R; (t,w,x)↦(tw,Θ(t,w)ṡx) where T=R or Z, and θ :(t,w)↦tw is a topological dynamical system on a compact metrizable space W, and where Θ(t,w)∈GL(n,R) satisfies the cocycle condition based on θ and is continuously differentiable in t if T=R. We show that 'semi λ-exponential dichotomy' of (θ,Θ) implies ' λ-exponential dichotomy.' Precisely, if Θ has no Lyapunov exponent λ and is almost uniformly λ-contracting along the λ-stable direction E(w;λ) and if dimE(w;λ) is constant a.e., then Θ is almost λ-exponentially dichotomous. To prove this, we first use Liao's spectrum theorem, which gives integral expression of the Lyapunov exponents, and then use the semi-uniform ergodic theorem by Sturman and Stark, which allows one to derive uniform estimates from nonuniform ones. As a consequence, we obtain the open-and-dense hyperbolicity of eventual GL(2,R)-cocycles based on a uniquely ergodic endomorphism, and of GL(2,R)-cocycles based on a uniquely ergodic equi-continuous endomorphism, respectively. On the other hand, in the sense of C-topology we obtain the density of SL(2,R)-cocycles having positive Lyapunov exponent based on a minimal subshift satisfying the Boshernitzan condition.

  16. Control of chaos in permanent magnet synchronous motor by using optimal Lyapunov exponents placement

    Energy Technology Data Exchange (ETDEWEB)

    Ataei, Mohammad, E-mail: ataei@eng.ui.ac.i [Department of Electrical Engineering, Faculty of Engineering, University of Isfahan, Hezar-Jerib St., Postal Code 8174673441, Isfahan (Iran, Islamic Republic of); Kiyoumarsi, Arash, E-mail: kiyoumarsi@eng.ui.ac.i [Department of Electrical Engineering, Faculty of Engineering, University of Isfahan, Hezar-Jerib St., Postal Code 8174673441, Isfahan (Iran, Islamic Republic of); Ghorbani, Behzad, E-mail: behzad.ghorbani63@gmail.co [Department of Control Engineering, Najafabad Azad University, Najafabad, Isfahan (Iran, Islamic Republic of)

    2010-09-13

    Permanent Magnet Synchronous Motor (PMSM) experiences chaotic behavior for a certain range of its parameters. In this case, since the performance of the PMSM degrades, the chaos should be eliminated. In this Letter, the control of the undesirable chaos in PMSM using Lyapunov exponents (LEs) placement is proposed that is also improved by choosing optimal locations of the LEs in the sense of predefined cost function. Moreover, in order to provide the physical realization of the method, nonlinear parameter estimator for the system is suggested. Finally, to show the effectiveness of the proposed methodology, the simulation results for applying this control strategy are provided.

  17. The high exponent limit $p \\to \\infty$ for the one-dimensional nonlinear wave equation

    OpenAIRE

    Tao, Terence

    2009-01-01

    We investigate the behaviour of solutions $\\phi = \\phi^{(p)}$ to the one-dimensional nonlinear wave equation $-\\phi_{tt} + \\phi_{xx} = -|\\phi|^{p-1} \\phi$ with initial data $\\phi(0,x) = \\phi_0(x)$, $\\phi_t(0,x) = \\phi_1(x)$, in the high exponent limit $p \\to \\infty$ (holding $\\phi_0, \\phi_1$ fixed). We show that if the initial data $\\phi_0, \\phi_1$ are smooth with $\\phi_0$ taking values in $(-1,1)$ and obey a mild non-degeneracy condition, then $\\phi$ converges locally uniformly to a piecewis...

  18. Uniform persistence and upper Lyapunov exponents for monotone skew-product semiflows

    International Nuclear Information System (INIS)

    Novo, Sylvia; Obaya, Rafael; Sanz, Ana M

    2013-01-01

    Several results of uniform persistence above and below a minimal set of an abstract monotone skew-product semiflow are obtained. When the minimal set has a continuous separation the results are given in terms of the principal spectrum. In the case that the semiflow is generated by the solutions of a family of non-autonomous differential equations of ordinary, delay or parabolic type, the former results are strongly improved. A method of calculus of the upper Lyapunov exponent of the minimal set is also determined. (paper)

  19. Analytic Quasi-Perodic Cocycles with Singularities and the Lyapunov Exponent of Extended Harper's Model

    Science.gov (United States)

    Jitomirskaya, S.; Marx, C. A.

    2012-11-01

    We show how to extend (and with what limitations) Avila's global theory of analytic SL(2,C) cocycles to families of cocycles with singularities. This allows us to develop a strategy to determine the Lyapunov exponent for the extended Harper's model, for all values of parameters and all irrational frequencies. In particular, this includes the self-dual regime for which even heuristic results did not previously exist in physics literature. The extension of Avila's global theory is also shown to imply continuous behavior of the LE on the space of analytic {M_2({C})}-cocycles. This includes rational approximation of the frequency, which so far has not been available.

  20. Estimating the density-scaling exponent of a monatomic liquid from its pair potential

    DEFF Research Database (Denmark)

    Bøhling, Lasse; Bailey, Nicholas; Schrøder, Thomas

    2014-01-01

    This paper investigates two conjectures for calculating the density dependence of the density-scaling exponent γ of a single-component, pair-potential liquid with strong virial potential-energy correlations. The first conjecture gives an analytical expression for γ directly in terms of the pair...... potential. The second conjecture is a refined version of this involving the most likely nearest-neighbor distance determined from the pair-correlation function. The conjectures are tested by simulations of three systems, one of which is the standard Lennard-Jones liquid. While both expressions give...

  1. Some existence results for a fourth order equation involving critical exponent

    CERN Document Server

    Ben-Ayed, M; Hammami, M

    2003-01-01

    In this paper a fourth order equation involving critical growth is considered under the Navier boundary condition: DELTA sup 2 u = Ku sup p , u > 0 in OMEGA, u = DELTA u = 0 on partial deriv OMEGA, where K is a positive function, OMEGA is a bounded smooth domain in R sup n , n >= 5 and p + 1 2n/(n - 4) is the critical Sobolev exponent. We give some topological conditions on K to ensure the existence of solutions. Our methods involve the study of the critical points at infinity and their contribution to the topology of the level sets of the associated Euler Lagrange functional.

  2. Modulational estimate for the maximal Lyapunov exponent in Fermi-Pasta-Ulam chains

    Science.gov (United States)

    Dauxois, Thierry; Ruffo, Stefano; Torcini, Alessandro

    1997-12-01

    In the framework of the Fermi-Pasta-Ulam (FPU) model, we show a simple method to give an accurate analytical estimation of the maximal Lyapunov exponent at high energy density. The method is based on the computation of the mean value of the modulational instability growth rates associated to unstable modes. Moreover, we show that the strong stochasticity threshold found in the β-FPU system is closely related to a transition in tangent space, the Lyapunov eigenvector being more localized in space at high energy.

  3. Some comments on Hurst exponent and the long memory processes on capital markets

    Science.gov (United States)

    Sánchez Granero, M. A.; Trinidad Segovia, J. E.; García Pérez, J.

    2008-09-01

    The analysis of long memory processes in capital markets has been one of the topics in finance, since the existence of the market memory could implicate the rejection of an efficient market hypothesis. The study of these processes in finance is realized through Hurst exponent and the most classical method applied is R/S analysis. In this paper we will discuss the efficiency of this methodology as well as some of its more important modifications to detect the long memory. We also propose the application of a classical geometrical method with short modifications and we compare both approaches.

  4. Exponence, allomorphy and haplology in the number and State morphology of Modern Hebrew

    OpenAIRE

    Faust, Noam

    2018-01-01

    This paper provides an account of the regularities of plural exponence in Modern Hebrew. There are two genders in Modern Hebrew, each with its specific plural marker. Nouns can appear in the Construct or Free states, and the State of a noun also has an effect on the plural marking, though only in the case of masculine nouns. Finally, in nouns with possessive suffixes and in newly-formed dual nouns, plural number seems to be marked twice in the feminine noun, but only once in the masculine nou...

  5. Estimation of Spectral Exponent Parameter of 1/f Process in Additive White Background Noise

    Directory of Open Access Journals (Sweden)

    Semih Ergintav

    2007-01-01

    Full Text Available An extension to the wavelet-based method for the estimation of the spectral exponent, γ, in a 1/fγ process and in the presence of additive white noise is proposed. The approach is based on eliminating the effect of white noise by a simple difference operation constructed on the wavelet spectrum. The γ parameter is estimated as the slope of a linear function. It is shown by simulations that the proposed method gives reliable results. Global positioning system (GPS time-series noise is analyzed and the results provide experimental verification of the proposed method.

  6. Conditional Lyapunov exponents and transfer entropy in coupled bursting neurons under excitation and coupling mismatch

    Science.gov (United States)

    Soriano, Diogo C.; Santos, Odair V. dos; Suyama, Ricardo; Fazanaro, Filipe I.; Attux, Romis

    2018-03-01

    This work has a twofold aim: (a) to analyze an alternative approach for computing the conditional Lyapunov exponent (λcmax) aiming to evaluate the synchronization stability between nonlinear oscillators without solving the classical variational equations for the synchronization error dynamical system. In this first framework, an analytic reference value for λcmax is also provided in the context of Duffing master-slave scenario and precisely evaluated by the proposed numerical approach; (b) to apply this technique to the study of synchronization stability in chaotic Hindmarsh-Rose (HR) neuronal models under uni- and bi-directional resistive coupling and different excitation bias, which also considered the root mean square synchronization error, information theoretic measures and asymmetric transfer entropy in order to offer a better insight of the synchronization phenomenon. In particular, statistical and information theoretical measures were able to capture similarity increase between the neuronal oscillators just after a critical coupling value in accordance to the largest conditional Lyapunov exponent behavior. On the other hand, transfer entropy was able to detect neuronal emitter influence even in a weak coupling condition, i.e. under the increase of conditional Lyapunov exponent and apparently desynchronization tendency. In the performed set of numerical simulations, the synchronization measures were also evaluated for a two-dimensional parameter space defined by the neuronal coupling (emitter to a receiver neuron) and the (receiver) excitation current. Such analysis is repeated for different feedback couplings as well for different (emitter) excitation currents, revealing interesting characteristics of the attained synchronization region and conditions that facilitate the emergence of the synchronous behavior. These results provide a more detailed numerical insight of the underlying behavior of a HR in the excitation and coupling space, being in accordance

  7. Percolation with first-and-second neighbour bonds: a renormalization-group calculation of critical exponents

    International Nuclear Information System (INIS)

    Riera, R.; Oliveira, P.M.C. de; Chaves, C.M.G.F.; Queiroz, S.L.A. de.

    1980-04-01

    A real-space renormalization group approach for the bond percolation problem in a square lattice with first- and second- neighbour bonds is proposed. The respective probabilities are treated, as independent variables. Two types of cells are constructed. In one of them the lattice is considered as two interpenetrating sublattices, first-neighbour bonds playing the role of intersublattice links. This allows the calculation of both critical exponents ν and γ, without resorting to any external field. Values found for the critical indices are in good agreement with data available in the literature. The phase diagram in parameter space is also obtained in each case. (Author) [pt

  8. The relation between mass-gap amplitudes and critical exponents in the Heisenberg model

    International Nuclear Information System (INIS)

    Alcaraz, F.C.; Felicio, J.R.D. de

    1985-01-01

    A recent result concerning the universality of the ratio of mass-gap amplitudes using the well known 1-D Heisenberg model which is the quantum version of the two-dimensional eight-vertex model is discussed. The believed extended scaling relation (x sub(p) = x sub(is an element of)/4) relating the polarization and energy anomalous dimensions is confirmed. The exponent, α, ν, γ sub(m) and γ sub(p) is also obtained by usual phenomenological renormalization group methods. (Author) [pt

  9. Self rating of health is associated with stressful life events, social support and residency in East and West Berlin shortly after the fall of the wall

    OpenAIRE

    Hillen, T.; Schaub, R.; Hiestermann, A.; Kirschner, W.; Robra, B.

    2000-01-01

    STUDY OBJECTIVE—To compare the health status and factors influencing the health of populations that had previously lived under different political systems.
DESIGN—Cross sectional health and social survey using postal interviews. The relation between self reported health and psychosocial factors (stressful life events, social support, education, health promoting life style and health endangering behaviour) was investigated. To determine East-West differences a logistic regression model includi...

  10. Food insecurity, stressful life events and symptoms of anxiety and depression in east Africa: evidence from the Gilgel Gibe growth and development study.

    Science.gov (United States)

    Hadley, C; Tegegn, A; Tessema, F; Cowan, J A; Asefa, M; Galea, S

    2008-11-01

    Common mental disorders are a major contributor to the burden of disease in developing countries. An assessment was carried out of whether food insecurity and exposure to stressful life events, two common features of life in sub-Saharan Africa (SSA), are associated with symptoms of mental disorders among adults. The Gilgel Gibe Growth and Development Study (GGGDS) is an ongoing cohort study in rural Ethiopia. Participants of the GGGDS were randomly selected from households from a complete census of persons living in the area. The Hopkins Symptom Checklist and the Harvard Trauma Questionnaire were used to assess anxiety and depression and post-traumatic stress symptoms. Among 902 adult participants, food insecurity, stressful life events and symptoms of common mental disorders were highly prevalent. In separate multivariate models adjusting for potential confounders, food insecurity and stressful life events were independently associated with high symptoms of depression, anxiety and post-traumatic stress. Potentially modifiable stressors may influence variation in common mental disorders in Ethiopia, and SSA more generally. These findings suggest that the negative effects of food insecurity extend beyond nutritional outcomes and that interventions that promote food security may also positively influence adult mental health in the region.

  11. Determination of the Lyapunov exponents and the information dimension in some dynamical systems

    International Nuclear Information System (INIS)

    Ziar, A.

    1992-01-01

    Classical phase space for some dynamical systems relevant in nuclear physics are studied. The nuclei is described by convex billiards or in the mean field theory. In both cases, besides the Poincare surface of sections which gives a qualitative description, each trajectory is characterized by its maximum Lyapunov exponent. The analytic monodromy matrix for a free particle in convex billiards rotating around an axis perpendicular to the plan of billiards, is determined, generalizing a previous result obtained for static billiards. In the frame of the mean field theory, it is shown an interesting alternative to the Lyapunov exponent, which is the dimension of the manifold in the phase space associated to the trajectory, leading to the evaluation of the relative chaotic volume in phase space as a function of the different parameters. The dimension appears as a character which could be determined easily for the rotating mean field, where the dimension of the manifold on which the trajectory is lying could be equal to 5 or 4 for chaotic trajectories, and less or equal to 3 for regular ones

  12. Relationship between deficiency of vitamin D and exponents of metabolic syndrome.

    Science.gov (United States)

    Kramkowska, M; Grzelak, T; Walczak, M; Bogdanski, P; Pupek-Musialik, D; Czyzewska, K

    2015-06-01

    Widespread hypovitaminosis D and an increased incidence of metabolic syndrome (MetS) represent significant problems of contemporary medicine but link between them remain unresolved. We aimed to define relationship between vitamin D serum concentration and exponents of MetS. The studies were conducted on 70 individuals (51 with and 19 without MetS). Concentrations of 25(OH)D (25-hydroxyergocalciferol and 25-hydroxycholecalciferol), calcium, cholesterol, HDL, cholesterol LDL, triglycerides, fasting glucose, blood pressure and anthropometric parameters were measured. Median concentration of vitamin D in the research population amounted to 41.46 nmol/L. Concentration of 25(OH)D in MetS group was lower than in remainder participants (38.45 nmol/L vs. 58.50 nmol/L, p = 0.0104). An inverse correlation was demonstrated between 25(OH)D level on one hand and body weight, waist and hips circumference, adipose body weight, Body Mass Index, Waist to Height Ratio (WHtR), glycaemia and number of MetS components on the other in persons free of MetS. No such relationships could be documented in MetS group. In the entire population values of Waist to Hip Ratio (WHpR) and WHtR indices manifested correlation with hyperglycaemia, hypertriglyceridaemia, low HDL concentrations. In persons without MetS a relationship was detected between vitamin D concentration and exponents of metabolic syndrome, although further studies on this problem are required.

  13. Automatic detection of ischemic stroke based on scaling exponent electroencephalogram using extreme learning machine

    Science.gov (United States)

    Adhi, H. A.; Wijaya, S. K.; Prawito; Badri, C.; Rezal, M.

    2017-03-01

    Stroke is one of cerebrovascular diseases caused by the obstruction of blood flow to the brain. Stroke becomes the leading cause of death in Indonesia and the second in the world. Stroke also causes of the disability. Ischemic stroke accounts for most of all stroke cases. Obstruction of blood flow can cause tissue damage which results the electrical changes in the brain that can be observed through the electroencephalogram (EEG). In this study, we presented the results of automatic detection of ischemic stroke and normal subjects based on the scaling exponent EEG obtained through detrended fluctuation analysis (DFA) using extreme learning machine (ELM) as the classifier. The signal processing was performed with 18 channels of EEG in the range of 0-30 Hz. Scaling exponents of the subjects were used as the input for ELM to classify the ischemic stroke. The performance of detection was observed by the value of accuracy, sensitivity and specificity. The result showed, performance of the proposed method to classify the ischemic stroke was 84 % for accuracy, 82 % for sensitivity and 87 % for specificity with 120 hidden neurons and sine as the activation function of ELM.

  14. Hopf bifurcations, Lyapunov exponents and control of chaos for a class of centrifugal flywheel governor system

    International Nuclear Information System (INIS)

    Zhang Jiangang; Li Xianfeng; Chu Yandong; Yu Jianning; Chang Yingxiang

    2009-01-01

    In this paper, complex dynamical behavior of a class of centrifugal flywheel governor system is studied. These systems have a rich variety of nonlinear behavior, which are investigated here by numerically integrating the Lagrangian equations of motion. A tiny change in parameters can lead to an enormous difference in the long-term behavior of the system. Bubbles of periodic orbits may also occur within the bifurcation sequence. Hyperchaotic behavior is also observed in cases where two of the Lyapunov exponents are positive, one is zero, and one is negative. The routes to chaos are analyzed using Poincare maps, which are found to be more complicated than those of nonlinear rotational machines. Periodic and chaotic motions can be clearly distinguished by all of the analytical tools applied here, namely Poincare sections, bifurcation diagrams, Lyapunov exponents, and Lyapunov dimensions. This paper proposes a parametric open-plus-closed-loop approach to controlling chaos, which is capable of switching from chaotic motion to any desired periodic orbit. The theoretical work and numerical simulations of this paper can be extended to other systems. Finally, the results of this paper are of practical utility to designers of rotational machines.

  15. Scaling exponents of the velocity structure functions in the interplanetary medium

    Directory of Open Access Journals (Sweden)

    V. Carbone

    Full Text Available We analyze the scaling exponents of the velocity structure functions, obtained from the velocity fluctuations measured in the interplanetary space plasma. Using the expression for the energy transfer rate which seems the most relevant in describing the evolution of the pseudo-energy densities in the interplanetary medium, we introduce an energy cascade model derived from a simple fragmentation process, which takes into account the intermittency effect. In the absence and in the presence of the large-scale magnetic field decorrelation effect the model reduces to the fluid and the hydromagnetic p-model, respectively. We show that the scaling exponents of the q-th power of the velocity structure functions, as obtained by the model in the absence of the decorrelation effect, furnishes the best-fit to the data analyzed from the Voyager 2 velocity field measurements at 8.5 AU. Our results allow us to hypothesize a new kind of scale-similarity for magnetohydrodynamic turbulence when the decorrelation effect is at work, related to the fourth-order velocity structure function.

  16. Predicting the long tail of book sales: Unearthing the power-law exponent

    Science.gov (United States)

    Fenner, Trevor; Levene, Mark; Loizou, George

    2010-06-01

    The concept of the long tail has recently been used to explain the phenomenon in e-commerce where the total volume of sales of the items in the tail is comparable to that of the most popular items. In the case of online book sales, the proportion of tail sales has been estimated using regression techniques on the assumption that the data obeys a power-law distribution. Here we propose a different technique for estimation based on a generative model of book sales that results in an asymptotic power-law distribution of sales, but which does not suffer from the problems related to power-law regression techniques. We show that the proportion of tail sales predicted is very sensitive to the estimated power-law exponent. In particular, if we assume that the power-law exponent of the cumulative distribution is closer to 1.1 rather than to 1.2 (estimates published in 2003, calculated using regression by two groups of researchers), then our computations suggest that the tail sales of Amazon.com, rather than being 40% as estimated by Brynjolfsson, Hu and Smith in 2003, are actually closer to 20%, the proportion estimated by its CEO.

  17. Aging Wiener-Khinchin theorem and critical exponents of 1/f^{β} noise.

    Science.gov (United States)

    Leibovich, N; Dechant, A; Lutz, E; Barkai, E

    2016-11-01

    The power spectrum of a stationary process may be calculated in terms of the autocorrelation function using the Wiener-Khinchin theorem. We here generalize the Wiener-Khinchin theorem for nonstationary processes and introduce a time-dependent power spectrum 〈S_{t_{m}}(ω)〉 where t_{m} is the measurement time. For processes with an aging autocorrelation function of the form 〈I(t)I(t+τ)〉=t^{Υ}ϕ_{EA}(τ/t), where ϕ_{EA}(x) is a nonanalytic function when x is small, we find aging 1/f^{β} noise. Aging 1/f^{β} noise is characterized by five critical exponents. We derive the relations between the scaled autocorrelation function and these exponents. We show that our definition of the time-dependent spectrum retains its interpretation as a density of Fourier modes and discuss the relation to the apparent infrared divergence of 1/f^{β} noise. We illustrate our results for blinking-quantum-dot models, single-file diffusion, and Brownian motion in a logarithmic potential.

  18. Effect of parameter calculation in direct estimation of the Lyapunov exponent in short time series

    Directory of Open Access Journals (Sweden)

    A. M. López Jiménez

    2002-01-01

    Full Text Available The literature about non-linear dynamics offers a few recommendations, which sometimes are divergent, about the criteria to be used in order to select the optimal calculus parameters in the estimation of Lyapunov exponents by direct methods. These few recommendations are circumscribed to the analysis of chaotic systems. We have found no recommendation for the estimation of λ starting from the time series of classic systems. The reason for this is the interest in distinguishing variability due to a chaotic behavior of determinist dynamic systems of variability caused by white noise or linear stochastic processes, and less in the identification of non-linear terms from the analysis of time series. In this study we have centered in the dependence of the Lyapunov exponent, obtained by means of direct estimation, of the initial distance and the time evolution. We have used generated series of chaotic systems and generated series of classic systems with varying complexity. To generate the series we have used the logistic map.

  19. Asymptotic scaling properties and estimation of the generalized Hurst exponents in financial data

    Science.gov (United States)

    Buonocore, R. J.; Aste, T.; Di Matteo, T.

    2017-04-01

    We propose a method to measure the Hurst exponents of financial time series. The scaling of the absolute moments against the aggregation horizon of real financial processes and of both uniscaling and multiscaling synthetic processes converges asymptotically towards linearity in log-log scale. In light of this we found appropriate a modification of the usual scaling equation via the introduction of a filter function. We devised a measurement procedure which takes into account the presence of the filter function without the need of directly estimating it. We verified that the method is unbiased within the errors by applying it to synthetic time series with known scaling properties. Finally we show an application to empirical financial time series where we fit the measured scaling exponents via a second or a fourth degree polynomial, which, because of theoretical constraints, have respectively only one and two degrees of freedom. We found that on our data set there is not clear preference between the second or fourth degree polynomial. Moreover the study of the filter functions of each time series shows common patterns of convergence depending on the momentum degree.

  20. 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.

  1. 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

  2. Dynamic stability of running: The effects of speed and leg amputations on the maximal Lyapunov exponent

    International Nuclear Information System (INIS)

    Look, Nicole; Arellano, Christopher J.; Grabowski, Alena M.; Kram, Rodger; McDermott, William J.; Bradley, Elizabeth

    2013-01-01

    In this paper, we study dynamic stability during running, focusing on the effects of speed, and the use of a leg prosthesis. We compute and compare the maximal Lyapunov exponents of kinematic time-series data from subjects with and without unilateral transtibial amputations running at a wide range of speeds. We find that the dynamics of the affected leg with the running-specific prosthesis are less stable than the dynamics of the unaffected leg and also less stable than the biological legs of the non-amputee runners. Surprisingly, we find that the center-of-mass dynamics of runners with two intact biological legs are slightly less stable than those of runners with amputations. Our results suggest that while leg asymmetries may be associated with instability, runners may compensate for this effect by increased control of their center-of-mass dynamics

  3. Decrease in Hurst exponent of human gait with aging and neurodegenerative diseases

    International Nuclear Information System (INIS)

    Zhauang Jianjun; Ning Xinbao; Yang Xiaodong; Huo Chengyu; Hou Fengzhen

    2008-01-01

    In this paper the decrease in the Hurst exponent of human gait with aging and neurodegenerative diseases was observed by using an improved rescaled range (R/S) analysis method. It indicates that the long-range correlations of gait rhythm from young healthy people are stronger than those from the healthy elderly and the diseased. The result further implies that fractal dynamics in human gait will be altered due to weakening or impairment of neural control on locomotion resulting from aging and neurodegenerative diseases. Due to analysing short-term data sequences rather than long datasets required by most nonlinear methods, the algorithm has the characteristics of simplicity and sensitivity, most importantly, fast calculation as well as powerful anti-noise capacities. These findings have implications for modelling locomotor control and also for quantifying gait dynamics in varying physiologic and pathologic states

  4. Universal Scaling and Critical Exponents of the Anisotropic Quantum Rabi Model

    Science.gov (United States)

    Liu, Maoxin; Chesi, Stefano; Ying, Zu-Jian; Chen, Xiaosong; Luo, Hong-Gang; Lin, Hai-Qing

    2017-12-01

    We investigate the quantum phase transition of the anisotropic quantum Rabi model, in which the rotating and counterrotating terms are allowed to have different coupling strengths. The model interpolates between two known limits with distinct universal properties. Through a combination of analytic and numerical approaches, we extract the phase diagram, scaling functions, and critical exponents, which determine the universality class at finite anisotropy (identical to the isotropic limit). We also reveal other interesting features, including a superradiance-induced freezing of the effective mass and discontinuous scaling functions in the Jaynes-Cummings limit. Our findings are extended to the few-body quantum phase transitions with N >1 spins, where we expose the same effective parameters, scaling properties, and phase diagram. Thus, a stronger form of universality is established, valid from N =1 up to the thermodynamic limit.

  5. On the improvement of Wiener attack on RSA with small private exponent.

    Science.gov (United States)

    Wu, Mu-En; Chen, Chien-Ming; Lin, Yue-Hsun; Sun, Hung-Min

    2014-01-01

    RSA system is based on the hardness of the integer factorization problem (IFP). Given an RSA modulus N = pq, it is difficult to determine the prime factors p and q efficiently. One of the most famous short exponent attacks on RSA is the Wiener attack. In 1997, Verheul and van Tilborg use an exhaustive search to extend the boundary of the Wiener attack. Their result shows that the cost of exhaustive search is 2r + 8 bits when extending the Weiner's boundary r bits. In this paper, we first reduce the cost of exhaustive search from 2r + 8 bits to 2r + 2 bits. Then, we propose a method named EPF. With EPF, the cost of exhaustive search is further reduced to 2r - 6 bits when we extend Weiner's boundary r bits. It means that our result is 2(14) times faster than Verheul and van Tilborg's result. Besides, the security boundary is extended 7 bits.

  6. Fractality Evidence and Long-Range Dependence on Capital Markets: a Hurst Exponent Evaluation

    Science.gov (United States)

    Oprean, Camelia; Tănăsescu, Cristina

    2014-07-01

    Since the existence of market memory could implicate the rejection of the efficient market hypothesis, the aim of this paper is to find any evidence that selected emergent capital markets (eight European and BRIC markets, namely Hungary, Romania, Estonia, Czech Republic, Brazil, Russia, India and China) evince long-range dependence or the random walk hypothesis. In this paper, the Hurst exponent as calculated by R/S fractal analysis and Detrended Fluctuation Analysis is our measure of long-range dependence in the series. The results reinforce our previous findings and suggest that if stock returns present long-range dependence, the random walk hypothesis is not valid anymore and neither is the market efficiency hypothesis.

  7. Importance sampling with imperfect cloning for the computation of generalized Lyapunov exponents

    Science.gov (United States)

    Anteneodo, Celia; Camargo, Sabrina; Vallejos, Raúl O.

    2017-12-01

    We revisit the numerical calculation of generalized Lyapunov exponents, L (q ) , in deterministic dynamical systems. The standard method consists of adding noise to the dynamics in order to use importance sampling algorithms. Then L (q ) is obtained by taking the limit noise-amplitude → 0 after the calculation. We focus on a particular method that involves periodic cloning and pruning of a set of trajectories. However, instead of considering a noisy dynamics, we implement an imperfect (noisy) cloning. This alternative method is compared with the standard one and, when possible, with analytical results. As a workbench we use the asymmetric tent map, the standard map, and a system of coupled symplectic maps. The general conclusion of this study is that the imperfect-cloning method performs as well as the standard one, with the advantage of preserving the deterministic dynamics.

  8. Connection of optimum temporal exponents with a principle of least action

    Science.gov (United States)

    Sergeev, E. V.; Karzanov, A. V.; Tremaskin, A. V.

    2008-06-01

    The principle of the least action states, that the motion of objects on optimum trajectories conjugates to the underload expenditure of activity. In the canonical approach this statement is reduced to searching extreme activity. For the immediate proof of the underload expenditure of activity on optimum trajectories the relevant mathematical algorithm in the basis of which bottom the concept of optimum time exponents lays is offered. Using this algorithm, various modes of a motion of charged particles are explored: the harmonic motion, a motion in the homogeneous force field, a motion in a central force field and a motion on inertia. The terrain clearance minimum under the rate of flux of activity for the harmonic motions is detected.

  9. Detection of the onset of numerical chaotic instabilities by lyapunov exponents

    Directory of Open Access Journals (Sweden)

    Alicia Serfaty De Markus

    2001-01-01

    Full Text Available It is commonly found in the fixed-step numerical integration of nonlinear differential equations that the size of the integration step is opposite related to the numerical stability of the scheme and to the speed of computation. We present a procedure that establishes a criterion to select the largest possible step size before the onset of chaotic numerical instabilities, based upon the observation that computational chaos does not occur in a smooth, continuous way, but rather abruptly, as detected by examining the largest Lyapunov exponent as a function of the step size. For completeness, examination of the bifurcation diagrams with the step reveals the complexity imposed by the algorithmic discretization, showing the robustness of a scheme to numerical instabilities, illustrated here for explicit and implicit Euler schemes. An example of numerical suppression of chaos is also provided.

  10. Scaling behavior of knotted random polygons and self-avoiding polygons: Topological swelling with enhanced exponent.

    Science.gov (United States)

    Uehara, Erica; Deguchi, Tetsuo

    2017-12-07

    We show that the average size of self-avoiding polygons (SAPs) with a fixed knot is much larger than that of no topological constraint if the excluded volume is small and the number of segments is large. We call it topological swelling. We argue an "enhancement" of the scaling exponent for random polygons with a fixed knot. We study them systematically through SAP consisting of hard cylindrical segments with various different values of the radius of segments. Here we mean by the average size the mean-square radius of gyration. Furthermore, we show numerically that the topological balance length of a composite knot is given by the sum of those of all constituent prime knots. Here we define the topological balance length of a knot by such a number of segments that topological entropic repulsions are balanced with the knot complexity in the average size. The additivity suggests the local knot picture.

  11. On the Improvement of Wiener Attack on RSA with Small Private Exponent

    Directory of Open Access Journals (Sweden)

    Mu-En Wu

    2014-01-01

    Full Text Available RSA system is based on the hardness of the integer factorization problem (IFP. Given an RSA modulus N=pq, it is difficult to determine the prime factors p and q efficiently. One of the most famous short exponent attacks on RSA is the Wiener attack. In 1997, Verheul and van Tilborg use an exhaustive search to extend the boundary of the Wiener attack. Their result shows that the cost of exhaustive search is 2r+8 bits when extending the Weiner's boundary r bits. In this paper, we first reduce the cost of exhaustive search from 2r+8 bits to 2r+2 bits. Then, we propose a method named EPF. With EPF, the cost of exhaustive search is further reduced to 2r-6 bits when we extend Weiner's boundary r bits. It means that our result is 214 times faster than Verheul and van Tilborg's result. Besides, the security boundary is extended 7 bits.

  12. Spectral analysis of structure functions and their scaling exponents in forced isotropic turbulence

    Science.gov (United States)

    Linkmann, Moritz; McComb, W. David; Yoffe, Samuel; Berera, Arjun

    2014-11-01

    The pseudospectral method, in conjunction with a new technique for obtaining scaling exponents ζn from the structure functions Sn (r) , is presented as an alternative to the extended self-similarity (ESS) method and the use of generalized structure functions. We propose plotting the ratio | Sn (r) /S3 (r) | against the separation r in accordance with a standard technique for analysing experimental data. This method differs from the ESS technique, which plots the generalized structure functions Gn (r) against G3 (r) , where G3 (r) ~ r . Using our method for the particular case of S2 (r) we obtain the new result that the exponent ζ2 decreases as the Taylor-Reynolds number increases, with ζ2 --> 0 . 679 +/- 0 . 013 as Rλ --> ∞ . This supports the idea of finite-viscosity corrections to the K41 prediction for S2, and is the opposite of the result obtained by ESS. The pseudospectral method permits the forcing to be taken into account exactly through the calculation of the energy input in real space from the work spectrum of the stirring forces. The combination of the viscous and the forcing corrections as calculated by the pseudospectral method is shown to account for the deviation of S3 from Kolmogorov's ``four-fifths''-law at all scales. This work has made use of the resources provided by the UK supercomputing service HECToR, made available through the Edinburgh Compute and Data Facility (ECDF). A. B. is supported by STFC, S. R. Y. and M. F. L. are funded by EPSRC.

  13. Psychological characteristics, stressful life events and deliberate self-harm: findings from the Child & Adolescent Self-harm in Europe (CASE) Study.

    Science.gov (United States)

    Madge, Nicola; Hawton, Keith; McMahon, Elaine M; Corcoran, Paul; De Leo, Diego; de Wilde, Erik Jan; Fekete, Sandor; van Heeringen, Kees; Ystgaard, Mette; Arensman, Ella

    2011-10-01

    There is evidence to suggest that both psychological characteristics and stressful life events are contributory factors in deliberate self-harm among young people. These links, and the possibility of a dose-response relationship between self-harm and both psychological health and life events, were investigated in the context of a seven-country school-based study. Over 30,000, mainly 15 and 16 year olds, completed anonymous questionnaires at secondary schools in Belgium, England, Hungary, Ireland, the Netherlands, Norway and Australia. Pupils were asked to report on thoughts and episodes of self-harm, complete scales on depression and anxiety symptoms, impulsivity and self-esteem and indicate stressful events in their lives. Level and frequency of self-harm was judged according to whether they had thought about harming themselves or reported single or multiple self-harm episodes. Multinomial logistic regression assessed the extent to which psychological characteristics and stressful life events distinguished between adolescents with different self-harm histories. Increased severity of self-harm history was associated with greater depression, anxiety and impulsivity and lower self-esteem and an increased prevalence of all ten life event categories. Female gender, higher impulsivity and experiencing the suicide or self-harm of others, physical or sexual abuse and worries about sexual orientation independently differentiated single-episode self-harmers from adolescents with self-harm thoughts only. Female gender, higher depression, lower self-esteem, experiencing the suicide or self-harm of others, and trouble with the police independently distinguished multiple- from single-episode self-harmers. The findings reinforce the importance of psychological characteristics and stressful life events in adolescent self-harm but nonetheless suggest that some factors are more likely than others to be implicated.

  14. Association of Stressful Life Events with Psychological Problems: A Large-Scale Community-Based Study Using Grouped Outcomes Latent Factor Regression with Latent Predictors

    Directory of Open Access Journals (Sweden)

    Akbar Hassanzadeh

    2017-01-01

    Full Text Available Objective. The current study is aimed at investigating the association between stressful life events and psychological problems in a large sample of Iranian adults. Method. In a cross-sectional large-scale community-based study, 4763 Iranian adults, living in Isfahan, Iran, were investigated. Grouped outcomes latent factor regression on latent predictors was used for modeling the association of psychological problems (depression, anxiety, and psychological distress, measured by Hospital Anxiety and Depression Scale (HADS and General Health Questionnaire (GHQ-12, as the grouped outcomes, and stressful life events, measured by a self-administered stressful life events (SLEs questionnaire, as the latent predictors. Results. The results showed that the personal stressors domain has significant positive association with psychological distress (β=0.19, anxiety (β=0.25, depression (β=0.15, and their collective profile score (β=0.20, with greater associations in females (β=0.28 than in males (β=0.13 (all P<0.001. In addition, in the adjusted models, the regression coefficients for the association of social stressors domain and psychological problems profile score were 0.37, 0.35, and 0.46 in total sample, males, and females, respectively (P<0.001. Conclusion. Results of our study indicated that different stressors, particularly those socioeconomic related, have an effective impact on psychological problems. It is important to consider the social and cultural background of a population for managing the stressors as an effective approach for preventing and reducing the destructive burden of psychological problems.

  15. Association of Stressful Life Events with Psychological Problems: A Large-Scale Community-Based Study Using Grouped Outcomes Latent Factor Regression with Latent Predictors

    Science.gov (United States)

    Hassanzadeh, Akbar; Heidari, Zahra; Hassanzadeh Keshteli, Ammar; Afshar, Hamid

    2017-01-01

    Objective The current study is aimed at investigating the association between stressful life events and psychological problems in a large sample of Iranian adults. Method In a cross-sectional large-scale community-based study, 4763 Iranian adults, living in Isfahan, Iran, were investigated. Grouped outcomes latent factor regression on latent predictors was used for modeling the association of psychological problems (depression, anxiety, and psychological distress), measured by Hospital Anxiety and Depression Scale (HADS) and General Health Questionnaire (GHQ-12), as the grouped outcomes, and stressful life events, measured by a self-administered stressful life events (SLEs) questionnaire, as the latent predictors. Results The results showed that the personal stressors domain has significant positive association with psychological distress (β = 0.19), anxiety (β = 0.25), depression (β = 0.15), and their collective profile score (β = 0.20), with greater associations in females (β = 0.28) than in males (β = 0.13) (all P < 0.001). In addition, in the adjusted models, the regression coefficients for the association of social stressors domain and psychological problems profile score were 0.37, 0.35, and 0.46 in total sample, males, and females, respectively (P < 0.001). Conclusion Results of our study indicated that different stressors, particularly those socioeconomic related, have an effective impact on psychological problems. It is important to consider the social and cultural background of a population for managing the stressors as an effective approach for preventing and reducing the destructive burden of psychological problems. PMID:29312459

  16. Adaptation of the Recent Life Changes Questionnaire (RLCQ) to measure stressful life events in adults residing in an urban megapolis in Pakistan.

    Science.gov (United States)

    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

  17. Stressful life events and maltreatment in conversion (functional neurological) disorder: systematic review and meta-analysis of case-control studies.

    Science.gov (United States)

    Ludwig, Lea; Pasman, Joëlle A; Nicholson, Timothy; Aybek, Selma; David, Anthony S; Tuck, Sharon; Kanaan, Richard A; Roelofs, Karin; Carson, Alan; Stone, Jon

    2018-04-01

    Stressful life events and maltreatment have traditionally been considered crucial in the development of conversion (functional neurological) disorder, but the evidence underpinning this association is not clear. We aimed to assess the association between stressors and functional neurological disorder. We systematically reviewed controlled studies reporting stressors occurring in childhood or adulthood, such as stressful life events and maltreatment (including sexual, physical abuse, and emotional neglect) and functional neurological disorder. We did a meta-analysis, with assessments of methodology, sources of bias, and sensitivity analyses. 34 case-control studies, with 1405 patients, were eligible. Studies were of moderate-to-low quality. The frequency of childhood and adulthood stressors was increased in cases compared with controls. Odds ratios (OR) were higher for emotional neglect in childhood (49% for cases vs 20% for controls; OR 5·6, 95% CI 2·4-13·1) compared with sexual abuse (24% vs 10%; 3·3, 2·2-4·8) or physical abuse (30% vs 12%; 3·9, 2·2-7·2). An association with stressful life events preceding onset (OR 2·8, 95% CI 1·4-6·0) was stronger in studies with better methods (interviews; 4·3, 1·4-13·2). Heterogeneity was significant between studies (I 2 21·1-90·7%). 13 studies that specifically ascertained that the participants had not had either severe life events or any subtype of maltreatment all found a proportion of patients with functional neurological disorder reporting no stressor. Stressful life events and maltreatment are substantially more common in people with functional neurological disorder than in healthy controls and patient controls. Emotional neglect had a higher risk than traditionally emphasised sexual and physical abuse, but many cases report no stressors. This outcome supports changes to diagnostic criteria in DSM-5; stressors, although relevant to the cause in many patients, are not a core diagnostic feature. This

  18. Job loss and broken partnerships: do the number of stressful life events influence the risk of ischemic heart disease in men?

    DEFF Research Database (Denmark)

    Kriegbaum, Margit; Christensen, Ulla; Lund, Rikke

    2008-01-01

    % confidence interval 1.02-1.85). We found no indication of dose-response relationship between number of events and risk of IHD. CONCLUSION: In this study of middle-aged men, we found only weak support for the effect of psychosocial stress on IHD measured with register based life events; we found that IHD...... was associated with broken partnerships but not with job loss. We did not find that the risk of incident IHD varied with the number of these stressful life events....

  19. On the curve of critical exponents for nonlinear elliptic problems in the case of a zero mass

    Science.gov (United States)

    Il'yasov, Ya. Sh.

    2017-03-01

    For semilinear elliptic equations -Δ u = λ| u| p-2 u-| u| q-2 u, boundary value problems in bounded and unbounded domains are considered. In the plane of exponents p × q, the so-called curves of critical exponents are defined that divide this plane into domains with qualitatively different properties of the boundary value problems and the corresponding parabolic equations. New solvability conditions for boundary value problems, conditions for the stability and instability of stationary solutions, and conditions for the existence of global solutions to parabolic equations are found.

  20. Comment on 'Exact analytical solution for the generalized Lyapunov exponent of the two-dimensional Anderson localization'

    International Nuclear Information System (INIS)

    Markos, P; Schweitzer, L; Weyrauch, M

    2004-01-01

    In a recent publication, Kuzovkov et al (2002 J. Phys.: Condens. Matter. 14 13777) announced an analytical solution of the two-dimensional Anderson localization problem via the calculation of a generalized Lyapunov exponent using signal theory. Surprisingly, for certain energies and small disorder strength they observed delocalized states. We study the transmission properties of the same model using well-known transfer matrix methods. Our results disagree with the findings obtained using signal theory. We point to the possible origin of this discrepancy and comment on the general strategy of using a generalized Lyapunov exponent for studying Anderson localization. (comment)

  1. The Ising model on a random planar lattice: The structure of the phase transition and the exact critical exponents

    International Nuclear Information System (INIS)

    Boulatov, D.V.; Kazakov, V.A.

    1987-01-01

    We investigate the critical properties of a recently proposed exactly soluble Ising model on a planar random dynamical lattice representing a regularization of the zero-dimensional string with internal fermions. The sum over all lattices gives rise to a new quantum degree of freedom - fluctuation of the metric. The whole system of critical exponents is found: α = -1, β = 1/2, γ = 2, δ = 5, v . D = 3. To test the universality we have used the planar graphs with the coordination number equal to 4 (Φ 4 theory graphs) as well as with the equal to 3 (Φ 3 theory graphs or triangulations). The critical exponents coincide for both cases. (orig.)

  2. Anxiety, depression, suicidal ideation, and stressful life events in non-cardiac adolescent chest pain: a comparative study about the hidden part of the iceberg.

    Science.gov (United States)

    Eliacik, Kayi; Kanik, Ali; Bolat, Nurullah; Mertek, Hilal; Guven, Baris; Karadas, Ulas; Dogrusoz, Buket; Bakiler, Ali Rahmi

    2017-08-01

    Chest pain in adolescents is rarely associated with cardiac disease. Adolescents with medically unexplained chest pain usually have high levels of anxiety and depression. Psychological stress may trigger non-cardiac chest pain. This study evaluated risk factors that particularly characterise adolescence, such as major stressful events, in a clinical population. The present study was conducted on 100 adolescents with non-cardiac chest pain and 76 control subjects. Stressful life events were assessed by interviewing patients using a 36-item checklist, along with the Children's Depression Inventory and Spielberger's State-Trait Anxiety Inventory for children, in both groups. Certain stressful life events, suicidal thoughts, depression, and anxiety were more commonly observed in adolescents with non-cardiac chest pain compared with the control group. Moreover, binary logistic regression analysis showed that trouble with bullies, school-related problems, and depression may trigger non-cardiac chest pain in adolescents. Non-cardiac chest pain on the surface may point to the underlying psychosocial health problems such as depression, suicidal ideas, or important life events such as academic difficulties or trouble with bullies. The need for a psychosocial evaluation that includes assessment of negative life events and a better management have been discussed in light of the results.

  3. Wavefunctions, quantum diffusion, and scaling exponents in golden-mean quasiperiodic tilings.

    Science.gov (United States)

    Thiem, Stefanie; Schreiber, Michael

    2013-02-20

    We study the properties of wavefunctions and the wavepacket dynamics in quasiperiodic tight-binding models in one, two, and three dimensions. The atoms in the one-dimensional quasiperiodic chains are coupled by weak and strong bonds aligned according to the Fibonacci sequence. The associated d-dimensional quasiperiodic tilings are constructed from the direct product of d such chains, which yields either the hypercubic tiling or the labyrinth tiling. This approach allows us to consider fairly large systems numerically. We show that the wavefunctions of the system are multifractal and that their properties can be related to the structure of the system in the regime of strong quasiperiodic modulation by a renormalization group (RG) approach. We also study the dynamics of wavepackets to get information about the electronic transport properties. In particular, we investigate the scaling behaviour of the return probability of the wavepacket with time. Applying again the RG approach we show that in the regime of strong quasiperiodic modulation the return probability is governed by the underlying quasiperiodic structure. Further, we also discuss lower bounds for the scaling exponent of the width of the wavepacket and propose a modified lower bound for the absolute continuous regime.

  4. Generalized Hurst exponent estimates differentiate EEG signals of healthy and epileptic patients

    Science.gov (United States)

    Lahmiri, Salim

    2018-01-01

    The aim of our current study is to check whether multifractal patterns of the electroencephalographic (EEG) signals of normal and epileptic patients are statistically similar or different. In this regard, the generalized Hurst exponent (GHE) method is used for robust estimation of the multifractals in each type of EEG signals, and three powerful statistical tests are performed to check existence of differences between estimated GHEs from healthy control subjects and epileptic patients. The obtained results show that multifractals exist in both types of EEG signals. Particularly, it was found that the degree of fractal is more pronounced in short variations of normal EEG signals than in short variations of EEG signals with seizure free intervals. In contrary, it is more pronounced in long variations of EEG signals with seizure free intervals than in normal EEG signals. Importantly, both parametric and nonparametric statistical tests show strong evidence that estimated GHEs of normal EEG signals are statistically and significantly different from those with seizure free intervals. Therefore, GHEs can be efficiently used to distinguish between healthy and patients suffering from epilepsy.

  5. Wavefunctions, quantum diffusion, and scaling exponents in golden-mean quasiperiodic tilings

    International Nuclear Information System (INIS)

    Thiem, Stefanie; Schreiber, Michael

    2013-01-01

    We study the properties of wavefunctions and the wavepacket dynamics in quasiperiodic tight-binding models in one, two, and three dimensions. The atoms in the one-dimensional quasiperiodic chains are coupled by weak and strong bonds aligned according to the Fibonacci sequence. The associated d-dimensional quasiperiodic tilings are constructed from the direct product of d such chains, which yields either the hypercubic tiling or the labyrinth tiling. This approach allows us to consider fairly large systems numerically. We show that the wavefunctions of the system are multifractal and that their properties can be related to the structure of the system in the regime of strong quasiperiodic modulation by a renormalization group (RG) approach. We also study the dynamics of wavepackets to get information about the electronic transport properties. In particular, we investigate the scaling behaviour of the return probability of the wavepacket with time. Applying again the RG approach we show that in the regime of strong quasiperiodic modulation the return probability is governed by the underlying quasiperiodic structure. Further, we also discuss lower bounds for the scaling exponent of the width of the wavepacket and propose a modified lower bound for the absolute continuous regime.

  6. The Fermi-Pasta-Ulam Problem and Its Underlying Integrable Dynamics: An Approach Through Lyapunov Exponents

    Science.gov (United States)

    Benettin, G.; Pasquali, S.; Ponno, A.

    2018-05-01

    FPU models, in dimension one, are perturbations either of the linear model or of the Toda model; perturbations of the linear model include the usual β -model, perturbations of Toda include the usual α +β model. In this paper we explore and compare two families, or hierarchies, of FPU models, closer and closer to either the linear or the Toda model, by computing numerically, for each model, the maximal Lyapunov exponent χ . More precisely, we consider statistically typical trajectories and study the asymptotics of χ for large N (the number of particles) and small ɛ (the specific energy E / N), and find, for all models, asymptotic power laws χ ˜eq Cɛ ^a, C and a depending on the model. The asymptotics turns out to be, in general, rather slow, and producing accurate results requires a great computational effort. We also revisit and extend the analytic computation of χ introduced by Casetti, Livi and Pettini, originally formulated for the β -model. With great evidence the theory extends successfully to all models of the linear hierarchy, but not to models close to Toda.

  7. Competitive autocatalytic reactions in chaotic flows with diffusion: Prediction using finite-time Lyapunov exponents

    International Nuclear Information System (INIS)

    Schlick, Conor P.; Umbanhowar, Paul B.; Ottino, Julio M.; Lueptow, Richard M.

    2014-01-01

    We investigate chaotic advection and diffusion in autocatalytic reactions for time-periodic sine flow computationally using a mapping method with operator splitting. We specifically consider three different autocatalytic reaction schemes: a single autocatalytic reaction, competitive autocatalytic reactions, which can provide insight into problems of chiral symmetry breaking and homochirality, and competitive autocatalytic reactions with recycling. In competitive autocatalytic reactions, species B and C both undergo an autocatalytic reaction with species A such that A+B→2B and A+C→2C. Small amounts of initially spatially localized B and C and a large amount of spatially homogeneous A are advected by the velocity field, diffuse, and react until A is completely consumed and only B and C remain. We find that local finite-time Lyapunov exponents (FTLEs) can accurately predict the final average concentrations of B and C after the reaction completes. The species that starts in the region with the larger FTLE has, with high probability, the larger average concentration at the end of the reaction. If B and C start in regions with similar FTLEs, their average concentrations at the end of the reaction will also be similar. When a recycling reaction is added, the system evolves towards a single species state, with the FTLE often being useful in predicting which species fills the entire domain and which is depleted. The FTLE approach is also demonstrated for competitive autocatalytic reactions in journal bearing flow, an experimentally realizable flow that generates chaotic dynamics

  8. 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.

  9. Landau-Ginzburg Limit of Black Hole's Quantum Portrait: Self Similarity and Critical Exponent

    CERN Document Server

    Dvali, Gia

    2012-01-01

    Recently we have suggested that the microscopic quantum description of a black hole is an overpacked self-sustained Bose-condensate of N weakly-interacting soft gravitons, which obeys the rules of 't Hooft's large-N physics. In this note we derive an effective Landau-Ginzburg Lagrangian for the condensate and show that it becomes an exact description in a semi-classical limit that serves as the black hole analog of 't Hooft's planar limit. The role of a weakly-coupled Landau-Ginzburg order parameter is played by N. This description consistently reproduces the known properties of black holes in semi-classical limit. Hawking radiation, as the quantum depletion of the condensate, is described by the slow-roll of the field N. In the semiclassical limit, where black holes of arbitrarily small size are allowed, the equation of depletion is self similar leading to a scaling law for the black hole size with critical exponent 1/3.

  10. Influence of finite-time Lyapunov exponents on winter precipitation over the Iberian Peninsula

    Science.gov (United States)

    Garaboa-Paz, Daniel; Lorenzo, Nieves; Pérez-Muñuzuri, Vicente

    2017-05-01

    Seasonal forecasts have improved during the last decades, mostly due to an increase in understanding of the coupled ocean-atmosphere dynamics, and the development of models able to predict the atmosphere variability. Correlations between different teleconnection patterns and severe weather in different parts of the world are constantly evolving and changing. This paper evaluates the connection between winter precipitation over the Iberian Peninsula and the large-scale tropospheric mixing over the eastern Atlantic Ocean. Finite-time Lyapunov exponents (FTLEs) have been calculated from 1979 to 2008 to evaluate this mixing. Our study suggests that significant negative correlations exist between summer FTLE anomalies and winter precipitation over Portugal and Spain. To understand the mechanisms behind this correlation, summer anomalies of the FTLE have also been correlated with other climatic variables such as the sea surface temperature (SST), the sea level pressure (SLP) or the geopotential. The East Atlantic (EA) teleconnection index correlates with the summer FTLE anomalies, confirming their role as a seasonal predictor for winter precipitation over the Iberian Peninsula.

  11. Variability of aerosol optical depth and Angstrom wavelength exponent derived from AERONET observations in recent decades

    International Nuclear Information System (INIS)

    Xia Xiangao

    2011-01-01

    Using aerosol loading data from 79 Aerosol Robotic Network (AERONET) stations with observations from more than six years, changes in aerosol optical depth (AOD) and Angstrom wavelength exponent (AWE) were studied. A statistical method was developed to determine whether AOD changes were due to increased background AOD values and/or an increased number of high AOD events. AOD decreased significantly at AERONET sites in northeastern North American and in Western Europe, which was accompanied by decreased AWE. Reduction of AOD there was mainly due to a decreased frequency of high AOD events and an increased frequency of background AOD events. In addition, decreased AOD values for high AOD events also accounted for ∼ 16–32% of the AOD reduction. This is indicative of significant meteorological effects on AOD variability. AOD trends in other regions were marginal and most were not significant; however, AOD increased significantly at one site in the Sahel and another in Saudi Arabia, predominantly due to the increased frequency of high AOD events and their average AOD.

  12. Designing Hyperchaotic Cat Maps With Any Desired Number of Positive Lyapunov Exponents.

    Science.gov (United States)

    Hua, Zhongyun; Yi, Shuang; Zhou, Yicong; Li, Chengqing; Wu, Yue

    2018-02-01

    Generating chaotic maps with expected dynamics of users is a challenging topic. Utilizing the inherent relation between the Lyapunov exponents (LEs) of the Cat map and its associated Cat matrix, this paper proposes a simple but efficient method to construct an -dimensional ( -D) hyperchaotic Cat map (HCM) with any desired number of positive LEs. The method first generates two basic -D Cat matrices iteratively and then constructs the final -D Cat matrix by performing similarity transformation on one basic -D Cat matrix by the other. Given any number of positive LEs, it can generate an -D HCM with desired hyperchaotic complexity. Two illustrative examples of -D HCMs were constructed to show the effectiveness of the proposed method, and to verify the inherent relation between the LEs and Cat matrix. Theoretical analysis proves that the parameter space of the generated HCM is very large. Performance evaluations show that, compared with existing methods, the proposed method can construct -D HCMs with lower computation complexity and their outputs demonstrate strong randomness and complex ergodicity.

  13. Spike solutions in Gierer#x2013;Meinhardt model with a time dependent anomaly exponent

    Science.gov (United States)

    Nec, Yana

    2018-01-01

    Experimental evidence of complex dispersion regimes in natural systems, where the growth of the mean square displacement in time cannot be characterised by a single power, has been accruing for the past two decades. In such processes the exponent γ(t) in ⟨r2⟩ ∼ tγ(t) at times might be approximated by a piecewise constant function, or it can be a continuous function. Variable order differential equations are an emerging mathematical tool with a strong potential to model these systems. However, variable order differential equations are not tractable by the classic differential equations theory. This contribution illustrates how a classic method can be adapted to gain insight into a system of this type. Herein a variable order Gierer-Meinhardt model is posed, a generic reaction- diffusion system of a chemical origin. With a fixed order this system possesses a solution in the form of a constellation of arbitrarily situated localised pulses, when the components' diffusivity ratio is asymptotically small. The pattern was shown to exist subject to multiple step-like transitions between normal diffusion and sub-diffusion, as well as between distinct sub-diffusive regimes. The analytical approximation obtained permits qualitative analysis of the impact thereof. Numerical solution for typical cross-over scenarios revealed such features as earlier equilibration and non-monotonic excursions before attainment of equilibrium. The method is general and allows for an approximate numerical solution with any reasonably behaved γ(t).

  14. Black Carbon, Aerosol optical depth and Angstrom Exponent in São Paulo, Brazil

    Science.gov (United States)

    Miranda, R. M.; Perez-Martinez, P. J.; Andrade, M. D. F.

    2017-12-01

    Black carbon (BC) is a major absorber of solar radiation, and its impact on the radiative balance is therefore considered important. Fossil fuel combustion processes and biomass burning result in the emission of BC. Black carbon is being monitored since 2014 with a Multi-Angle Absorption Photometer-MAAP (5012; Thermo Scientific) in the East Zone of São Paulo, Brazil. São Paulo Metropolitan Area with more than 19 million inhabitants, 7 million vehicles, has high concentrations of air pollutants, especially in the winter. Vehicles can be considered the principal source of particles emitted to the atmosphere. Concentration of the pollutant had an average of 1.95 ug.m-3 ± 2.06 and a maximum value of 19.93 ug.m-3. These large variations were due to meteorological effects and to the influence of anthropogenic activities, since samples were collected close to important highways. Winds coming from the East part predominate. Higher concentrations were found in the winter months (June, July and August). Optical data from AERONET (Aerosol Optical Depth-AOD 550 nm and Angstrom Exponent 440-675 nm) were related to BC concentrations for the period from August, 2016. Average values of AOD at 500 nm and Angstrom Parameter (440-675nm) were 0.16±0.11 and 1.44±0.23, respectively. Higher BC concentrations were related to lower Angstrom values.

  15. Reliability of Lyapunov characteristic exponents computed by the two-particle method

    Science.gov (United States)

    Mei, Lijie; Huang, Li

    2018-03-01

    For highly complex problems, such as the post-Newtonian formulation of compact binaries, the two-particle method may be a better, or even the only, choice to compute the Lyapunov characteristic exponent (LCE). This method avoids the complex calculations of variational equations compared with the variational method. However, the two-particle method sometimes provides spurious estimates to LCEs. In this paper, we first analyze the equivalence in the definition of LCE between the variational and two-particle methods for Hamiltonian systems. Then, we develop a criterion to determine the reliability of LCEs computed by the two-particle method by considering the magnitude of the initial tangent (or separation) vector ξ0 (or δ0), renormalization time interval τ, machine precision ε, and global truncation error ɛT. The reliable Lyapunov characteristic indicators estimated by the two-particle method form a V-shaped region, which is restricted by d0, ε, and ɛT. Finally, the numerical experiments with the Hénon-Heiles system, the spinning compact binaries, and the post-Newtonian circular restricted three-body problem strongly support the theoretical results.

  16. A perturbation method to the tent map based on Lyapunov exponent and its application

    Science.gov (United States)

    Cao, Lv-Chen; Luo, Yu-Ling; Qiu, Sen-Hui; Liu, Jun-Xiu

    2015-10-01

    Perturbation imposed on a chaos system is an effective way to maintain its chaotic features. A novel parameter perturbation method for the tent map based on the Lyapunov exponent is proposed in this paper. The pseudo-random sequence generated by the tent map is sent to another chaos function — the Chebyshev map for the post processing. If the output value of the Chebyshev map falls into a certain range, it will be sent back to replace the parameter of the tent map. As a result, the parameter of the tent map keeps changing dynamically. The statistical analysis and experimental results prove that the disturbed tent map has a highly random distribution and achieves good cryptographic properties of a pseudo-random sequence. As a result, it weakens the phenomenon of strong correlation caused by the finite precision and effectively compensates for the digital chaos system dynamics degradation. Project supported by the Guangxi Provincial Natural Science Foundation, China (Grant No. 2014GXNSFBA118271), the Research Project of Guangxi University, China (Grant No. ZD2014022), the Fund from Guangxi Provincial Key Laboratory of Multi-source Information Mining & Security, China (Grant No. MIMS14-04), the Fund from the Guangxi Provincial Key Laboratory of Wireless Wideband Communication & Signal Processing, China (Grant No. GXKL0614205), the Education Development Foundation and the Doctoral Research Foundation of Guangxi Normal University, the State Scholarship Fund of China Scholarship Council (Grant No. [2014]3012), and the Innovation Project of Guangxi Graduate Education, China (Grant No. YCSZ2015102).

  17. The Tail Exponent for Stock Returns in Bursa Malaysia for 2003-2008

    Science.gov (United States)

    Rusli, N. H.; Gopir, G.; Usang, M. D.

    2010-07-01

    A developed discipline of econophysics that has been introduced is exhibiting the application of mathematical tools that are usually applied to the physical models for the study of financial models. In this study, an analysis of the time series behavior of several blue chip and penny stock companies in Main Market of Bursa Malaysia has been performed. Generally, the basic quantity being used is the relative price changes or is called the stock price returns, contains daily-sampled data from the beginning of 2003 until the end of 2008, containing 1555 trading days recorded. The aim of this paper is to investigate the tail exponent in tails of the distribution for blue chip stocks and penny stocks financial returns in six years period. By using a standard regression method, it is found that the distribution performed double scaling on the log-log plot of the cumulative probability of the normalized returns. Thus we calculate α for a small scale return as well as large scale return. Based on the result obtained, it is found that the power-law behavior for the probability density functions of the stock price absolute returns P(z)˜z-α with values lying inside and outside the Lévy stable regime with values α>2. All the results were discussed in detail.

  18. Density-scaling exponents and virial potential-energy correlation coefficients for the (2n, n) Lennard-Jones system

    DEFF Research Database (Denmark)

    Friisberg, Ida Marie; Costigliola, Lorenzo; Dyre, Jeppe C.

    2017-01-01

    This paper investigates the relation between the density-scaling exponent γ and the virial potentialenergy 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 syste...

  19. Orbital Exponent Optimization in Elementary VB Calculations of the Chemical Bond in the Ground State of Simple Molecular Systems

    Science.gov (United States)

    Magnasco, Valerio

    2008-01-01

    Orbital exponent optimization in the elementary ab-initio VB calculation of the ground states of H[subscript 2][superscript +], H[subscript 2], He[subscript 2][superscript +], He[subscript 2] gives a fair description of the exchange-overlap component of the interatomic interaction that is important in the bond region. Correct bond lengths and…

  20. 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.

  1. Estimate of the largest Lyapunov characteristic exponent of a high dimensional atmospheric global circulation model: a sensitivity analysis

    International Nuclear Information System (INIS)

    Guerrieri, A.

    2009-01-01

    In this report the largest Lyapunov characteristic exponent of a high dimensional atmospheric global circulation model of intermediate complexity has been estimated numerically. A sensitivity analysis has been carried out by varying the equator-to-pole temperature difference, the space resolution and the value of some parameters employed by the model. Chaotic and non-chaotic regimes of circulation have been found. [it

  2. 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

  3. Effect of noise and filtering on largest Lyapunov exponent of time series associated with human walking.

    Science.gov (United States)

    Mehdizadeh, Sina; Sanjari, Mohammad Ali

    2017-11-07

    This study aimed to determine the effect of added noise, filtering and time series length on the largest Lyapunov exponent (LyE) value calculated for time series obtained from a passive dynamic walker. The simplest passive dynamic walker model comprising of two massless legs connected by a frictionless hinge joint at the hip was adopted to generate walking time series. The generated time series was used to construct a state space with the embedding dimension of 3 and time delay of 100 samples. The LyE was calculated as the exponential rate of divergence of neighboring trajectories of the state space using Rosenstein's algorithm. To determine the effect of noise on LyE values, seven levels of Gaussian white noise (SNR=55-25dB with 5dB steps) were added to the time series. In addition, the filtering was performed using a range of cutoff frequencies from 3Hz to 19Hz with 2Hz steps. The LyE was calculated for both noise-free and noisy time series with different lengths of 6, 50, 100 and 150 strides. Results demonstrated a high percent error in the presence of noise for LyE. Therefore, these observations suggest that Rosenstein's algorithm might not perform well in the presence of added experimental noise. Furthermore, findings indicated that at least 50 walking strides are required to calculate LyE to account for the effect of noise. Finally, observations support that a conservative filtering of the time series with a high cutoff frequency might be more appropriate prior to calculating LyE. Copyright © 2017 Elsevier Ltd. All rights reserved.

  4. ANTHIM THE IVIRITE AN EXPONENT OF CAUCASIAN AND ROMANIAN SPIRITUALITY IN THE 18TH CENTURY

    Directory of Open Access Journals (Sweden)

    Angela BOTEZ

    2016-10-01

    Full Text Available The paper approaches the theme about Anthim the Ivirite is an exponent of Romanian and Caucasian spirituality. Honouring this personality we start from the observation that his spiritual heritage remains relevant over the ages. Some biographers claim that Anthim the Ivirite was from a noble family. His life was as well dramatic, as noble. Anthim the Ivirite remains in Romanian history as a deeply religious man and a man of many talents. He spoke several foreign languages among which Romanian, Greek, Arabic and Turkish. Saint Anthim was a scholar, a printer of religious writings, he wrote religious literature and succeeded to leave a deep mark in the Romanian culture that times undimmed. We consider relevant also that among the important anniversaries of the year 2016 along with the anniversary of Saint Anthim the Ivirite the Romanian Orthodox Church celebrates all the Romanian Church typographers who have contributed fundamentally to a rich religious culture in Romanian. A religious journalist notice for a specialized publication that The fact that the Romanian Orthodox Church, under the clear vision of His Beatitude Patriarch Daniel has chosen to inscribe amongst the paramount holidays of the year 2016 the Church typographers represents a memorable and soul-uplifting gesture, a gesture of conscience in agreement with all who wanted and succeeded to conquer time through the eternity of the typed letter, taking the Word of God in all the four skies and seeding the values of Christian faith and Christian moral in the hearts and thoughts of all Romanians. Posterity’s judgment was warm, respectful and fair in what concerns Saint Hierarch Anthim, and the Holy Synod of the Romanian Orthodox Church glorified him, as a saint and martyr of our Romanian Orthodox Church and this is the reason why the final part of the paper is dedicated to the identification of a string of interesting Anthim anniversaries over the times.

  5. Hurst Exponent Analysis of Resting-State fMRI Signal Complexity across the Adult Lifespan

    Directory of Open Access Journals (Sweden)

    Jianxin Dong

    2018-02-01

    Full Text Available Exploring functional information among various brain regions across time enables understanding of healthy aging process and holds great promise for age-related brain disease diagnosis. This paper proposed a method to explore fractal complexity of the resting-state functional magnetic resonance imaging (rs-fMRI signal in the human brain across the adult lifespan using Hurst exponent (HE. We took advantage of the examined rs-fMRI data from 116 adults 19 to 85 years of age (44.3 ± 19.4 years, 49 females from NKI/Rockland sample. Region-wise and voxel-wise analyses were performed to investigate the effects of age, gender, and their interaction on complexity. In region-wise analysis, we found that the healthy aging is accompanied by a loss of complexity in frontal and parietal lobe and increased complexity in insula, limbic, and temporal lobe. Meanwhile, differences in HE between genders were found to be significant in parietal lobe (p = 0.04, corrected. However, there was no interaction between gender and age. In voxel-wise analysis, the significant complexity decrease with aging was found in frontal and parietal lobe, and complexity increase was found in insula, limbic lobe, occipital lobe, and temporal lobe with aging. Meanwhile, differences in HE between genders were found to be significant in frontal, parietal, and limbic lobe. Furthermore, we found age and sex interaction in right parahippocampal gyrus (p = 0.04, corrected. Our findings reveal HE variations of the rs-fMRI signal across the human adult lifespan and show that HE may serve as a new parameter to assess healthy aging process.

  6. A Brainnetome Atlas Based Mild Cognitive Impairment Identification Using Hurst Exponent

    Directory of Open Access Journals (Sweden)

    Zhuqing Long

    2018-04-01

    Full Text Available Mild cognitive impairment (MCI, which generally represents the transition state between normal aging and the early changes related to Alzheimer’s disease (AD, has drawn increasing attention from neuroscientists due that efficient AD treatments need early initiation ahead of irreversible brain tissue damage. Thus effective MCI identification methods are desperately needed, which may be of great importance for the clinical intervention of AD. In this article, the range scaled analysis, which could effectively detect the temporal complexity of a time series, was utilized to calculate the Hurst exponent (HE of functional magnetic resonance imaging (fMRI data at a voxel level from 64 MCI patients and 60 healthy controls (HCs. Then the average HE values of each region of interest (ROI in brainnetome atlas were extracted and compared between MCI and HC. At last, the abnormal average HE values were adopted as the classification features for a proposed support vector machine (SVM based identification algorithm, and the classification performance was estimated with leave-one-out cross-validation (LOOCV. Our results indicated 83.1% accuracy, 82.8% sensitivity and 83.3% specificity, and an area under curve of 0.88, suggesting that the HE index could serve as an effective feature for the MCI identification. Furthermore, the abnormal HE brain regions in MCI were predominately involved in left middle frontal gyrus, right hippocampus, bilateral parahippocampal gyrus, bilateral amygdala, left cingulate gyrus, left insular gyrus, left fusiform gyrus, left superior parietal gyrus, left orbital gyrus and left basal ganglia.

  7. Magnetic entropy change and critical exponents in double perovskite Y{sub 2}NiMnO{sub 6}

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, G. [School of Physical Sciences, Jawaharlal Nehru University, New Delhi-110067 (India); Tripathi, T.S. [Inter-University Accelerator Centre, New Delhi-110067 (India); Saha, J. [School of Physical Sciences, Jawaharlal Nehru University, New Delhi-110067 (India); Patnaik, S., E-mail: spatnaik@mail.jnu.ac.in [School of Physical Sciences, Jawaharlal Nehru University, New Delhi-110067 (India)

    2014-11-15

    We report the magnetic entropy change (ΔS{sub M}) and the critical exponents in the double perovskite manganite Y{sub 2}NiMnO{sub 6} with a ferromagnetic to paramagnetic transition T{sub C}∼85K. For a magnetic field change ΔH=80kOe, a maximum magnetic entropy change ΔS{sub M}=−6.57J/kgK is recorded around T{sub C}. The critical exponents β=0.363±0.05 and γ=1.331±0.09 obtained from power law fitting to spontaneous magnetization M{sub S}(T) and the inverse initial susceptibility χ{sub 0}{sup −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 T{sub C}. 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,ϵ)=ϵ{sup β}f±(H/ϵ{sup β+γ}) according to which the magnetization-field-temperature data around T{sub C} should collapse into two curves for temperatures below and above T{sub C}. - Highlights: • The magneto-caloric (MC) effect and the critical exponent analysis in Y{sub 2}NiMnO{sub 6} are studied. • Methods such as Kouvel–Fisher, Widom's and Mean-Field scaling are used. • The magnetic ground state in Y{sub 2}NiMnO{sub 6} is based on isotropic 3D Heisenberg model. • The large MC effect can be utilized towards magnetic refrigeration around 77 K. • The nearest neighbor interaction in Y{sub 2}NiMnO{sub 6} rules out ferroelectricity.

  8. Optimism and well-being: a prospective multi-method and multi-dimensional examination of optimism as a resilience factor following the occurrence of stressful life events.

    Science.gov (United States)

    Kleiman, Evan M; Chiara, Alexandra M; Liu, Richard T; Jager-Hyman, Shari G; Choi, Jimmy Y; Alloy, Lauren B

    2017-02-01

    Optimism has been conceptualised variously as positive expectations (PE) for the future , optimistic attributions , illusion of control , and self-enhancing biases. Relatively little research has examined these multiple dimensions of optimism in relation to psychological and physical health. The current study assessed the multi-dimensional nature of optimism within a prospective vulnerability-stress framework. Initial principal component analyses revealed the following dimensions: PEs, Inferential Style (IS), Sense of Invulnerability (SI), and Overconfidence (O). Prospective follow-up analyses demonstrated that PE was associated with fewer depressive episodes and moderated the effect of stressful life events on depressive symptoms. SI also moderated the effect of life stress on anxiety symptoms. Generally, our findings indicated that optimism is a multifaceted construct and not all forms of optimism have the same effects on well-being. Specifically, our findings indicted that PE may be the most relevant to depression, whereas SI may be the most relevant to anxiety.

  9. Self rating of health is associated with stressful life events, social support and residency in East and West Berlin shortly after the fall of the wall.

    Science.gov (United States)

    Hillen, T; Schaub, R; Hiestermann, A; Kirschner, W; Robra, B P

    2000-08-01

    To compare the health status and factors influencing the health of populations that had previously lived under different political systems. Cross sectional health and social survey using postal interviews. The relation between self reported health and psychosocial factors (stressful life events, social support, education, health promoting life style and health endangering behaviour) was investigated. To determine East-West differences a logistic regression model including interaction terms was fitted. East and West Berlin shortly after reunification 1991. Representative sample of 4430 Berlin residents aged 18 years and over (response rate 63%). Of all respondents, 15.4% rated their health as unsatisfactory. Residents of East Berlin rated their health more frequently as unsatisfactory than residents of West Berlin (Or(age adjusted)= 1.29, 95%CI 1.08, 1.52), these differences occurred predominantly in the over 60 years age group. Logistic regression showed significant independent effects of stressful life events, social support, education, and health promoting life style on self rated health. The effects of education and health promoting life style were observed to be more pronounced in the western part of Berlin. Old age and female sex showed a stronger association with unsatisfactory health status in the eastern part of Berlin. For subjects aged over 60 years there was evidence that living in the former East Berlin had an adverse effect on health compared with West Berlin. The impact of education and a health promoting lifestyle on self rated health seemed to be weaker in a former socialist society compared with that of a Western democracy. This study supports an "additive model" rather than a "buffering model" in explaining the effects of psychosocial factors on health.

  10. The influence of parental care and overprotection, neuroticism and adult stressful life events on depressive symptoms in the general adult population.

    Science.gov (United States)

    Ono, Yasuyuki; Takaesu, Yoshikazu; Nakai, Yukiei; Ichiki, Masahiko; Masuya, Jiro; Kusumi, Ichiro; Inoue, Takeshi

    2017-08-01

    The quality of parenting, neuroticism, and adult stressful life events are reportedly associated with depressive symptoms. However, previous studies have not examined the complex interaction between these three factors. In this study, we hypothesized that the quality of parenting (care and overprotection) acts on depressive symptoms through 'neuroticism' and the appraisal of adult stressful life events, and this hypothesis was verified by structural equation modeling. Four hundred one participants from the general adult population were studied using the following self-administered questionnaire surveys: Patient Health Questionnaire-9 (PHQ-9), Parental Bonding Instrument (PBI), neuroticism subscale of the short version of the Eysenck Personality Questionnaire-revised (EPQ-R), and Life Experiences Survey (LES). The data were analyzed with single and multiple regression analyses and covariance structure analyses. In the covariance structure analysis, neuroticism scores and negative change scores on the LES acted on the depressive symptoms (PHQ-9 scores) directly, but care or overprotection in childhood on the PBI did not act on them directly. Low care and high overprotection of the PBI increased depressive symptoms and negative change scores on the LES through enhanced neuroticism, which is regarded as a mediator in these effects. The subjects of this study were nonclinical volunteers; the findings might not be generalizable to psychiatric patients. This research showed that low care and high overprotection of maternal and paternal parenting in childhood influence depressive symptoms indirectly through enhanced neuroticism in general adults. These findings suggest that neuroticism mediates the long-term effect of the quality of parenting on depression in adulthood. Copyright © 2017 Elsevier B.V. All rights reserved.

  11. Depression, Stressful Life Events, and the Impact of Variation in the Serotonin Transporter: Findings from the National Longitudinal Study of Adolescent to Adult Health (Add Health)

    Science.gov (United States)

    Haberstick, Brett C.; Boardman, Jason D.; Wagner, Brandon; Smolen, Andrew; Hewitt, John K.; Killeya-Jones, Ley A.; Tabor, Joyce; Halpern, Carolyn T.; Brummett, Beverly H.; Williams, Redford B.; Siegler, Ilene C.; Hopfer, Christian J.; Mullan Harris, Kathleen

    2016-01-01

    Background The low transcriptionally efficient short-allele of the 5HTTLPR serotonin transporter polymorphism has been implicated to moderate the relationship between the experience of stressful life events (SLEs) and depression. Despite numerous attempts at replicating this observation, results remain inconclusive. Methods We examined this relationship in young-adult Non-Hispanic white males and females between the ages of 22 and 26 (n = 4724) participating in the National Longitudinal Study of Adolescent to Adult Health (Add Health) with follow-up information every six years since 1995. Results Linear and logistic regression models, corrected for multiple testing, indicated that carriers of one or more of the S-alleles were more sensitive to stress than those with two L-alleles and at a higher risk for depression. This relationship behaved in a dose-response manner such that the risk for depression was greatest among those who reported experiencing higher numbers of SLEs. In post-hoc analyses we were not able to replicate an interaction effect for suicide ideation but did find suggestive evidence that the effects of SLEs and 5HTTLPR on suicide ideation differed for males and females. There were no effects of childhood maltreatment. Discussion Our results provide partial support for the original hypothesis that 5-HTTLPR genotype interacts with the experience of stressful life events in the etiology of depression during young adulthood. However, even with this large sample, and a carefully constructed a priori analysis plan, the results were still not definitive. For the purposes of replication, characterizing the 5HTTLPR in other large data sets with extensive environmental and depression measures is needed. PMID:26938215

  12. Depression, Stressful Life Events, and the Impact of Variation in the Serotonin Transporter: Findings from the National Longitudinal Study of Adolescent to Adult Health (Add Health.

    Directory of Open Access Journals (Sweden)

    Brett C Haberstick

    Full Text Available The low transcriptionally efficient short-allele of the 5HTTLPR serotonin transporter polymorphism has been implicated to moderate the relationship between the experience of stressful life events (SLEs and depression. Despite numerous attempts at replicating this observation, results remain inconclusive.We examined this relationship in young-adult Non-Hispanic white males and females between the ages of 22 and 26 (n = 4724 participating in the National Longitudinal Study of Adolescent to Adult Health (Add Health with follow-up information every six years since 1995.Linear and logistic regression models, corrected for multiple testing, indicated that carriers of one or more of the S-alleles were more sensitive to stress than those with two L-alleles and at a higher risk for depression. This relationship behaved in a dose-response manner such that the risk for depression was greatest among those who reported experiencing higher numbers of SLEs. In post-hoc analyses we were not able to replicate an interaction effect for suicide ideation but did find suggestive evidence that the effects of SLEs and 5HTTLPR on suicide ideation differed for males and females. There were no effects of childhood maltreatment.Our results provide partial support for the original hypothesis that 5-HTTLPR genotype interacts with the experience of stressful life events in the etiology of depression during young adulthood. However, even with this large sample, and a carefully constructed a priori analysis plan, the results were still not definitive. For the purposes of replication, characterizing the 5HTTLPR in other large data sets with extensive environmental and depression measures is needed.

  13. Cumulative Effective Hölder Exponent Based Indicator for Real-Time Fetal Heartbeat Analysis during Labour

    Science.gov (United States)

    Struzik, Zbigniew R.; van Wijngaarden, Willem J.

    We introduce a special purpose cumulative indicator, capturing in real time the cumulative deviation from the reference level of the exponent h (local roughness, Hölder exponent) of the fetal heartbeat during labour. We verify that the indicator applied to the variability component of the heartbeat coincides with the fetal outcome as determined by blood samples. The variability component is obtained from running real time decomposition of fetal heartbeat into independent components using an adaptation of an oversampled Haar wavelet transform. The particular filters used and resolutions applied are motivated by obstetricial insight/practice. The methodology described has the potential for real-time monitoring of the fetus during labour and for the prediction of the fetal outcome, allerting the attending staff in the case of (threatening) hypoxia.

  14. Influence of granulometry in the Hurst exponent of air liquid interfaces formed during capillary rising in a granular media

    Directory of Open Access Journals (Sweden)

    Gontijo Guilherme L.

    2017-01-01

    Full Text Available We report results concerning the fractal dimension of a air/fluid interface formed during the capillary rising of a fluid into a dense granular media. The system consists in a modified Hele-Shaw cell filled with grains at different granulometries and confined in a narrow gap between the glass plates. The system is then placed onto a water reservoir, and the liquid penetrates the medium due to capillary forces. We measure the Hurst exponent of the liquid/air interface with help of image processing, and follow the temporal evolution of the profiles. We observe that the Hurst exponent can be related with the granulometry, but the range of values are odd to the predicted values from models or theory.

  15. Moment Lyapunov Exponent and Stochastic Stability of Binary Airfoil under Combined Harmonic and Non-Gaussian Colored Noise Excitations

    Science.gov (United States)

    Hu, D. L.; Liu, X. B.

    Both periodic loading and random forces commonly co-exist in real engineering applications. However, the dynamic behavior, especially dynamic stability of systems under parametric periodic and random excitations has been reported little in the literature. In this study, the moment Lyapunov exponent and stochastic stability of binary airfoil under combined harmonic and non-Gaussian colored noise excitations are investigated. The noise is simplified to an Ornstein-Uhlenbeck process by applying the path-integral method. Via the singular perturbation method, the second-order expansions of the moment Lyapunov exponent are obtained, which agree well with the results obtained by the Monte Carlo simulation. Finally, the effects of the noise and parametric resonance (such as subharmonic resonance and combination additive resonance) on the stochastic stability of the binary airfoil system are discussed.

  16. Using the Hurst's exponent as a monitor and predictor of BWR reactor instabilities

    International Nuclear Information System (INIS)

    Gavilan Moreno, Carlos J.

    2010-01-01

    Since the decade of the 1950s, when the development of boiling water reactor technology began, unstable situations have existed, which involve a high amplitude self-oscillatory process in the reactor's thermal power. As the development progressed and the reactors increased power density, the possibility of instability under certain circumstances increased. Thus, in 1985, Caorso nuclear plant (Italy) reported the first event of this type, and in 1988, such an event was reported at La Salle as well. Since then, multiple instability events have been reported. The danger of these unstable power situations resides in the possibility of exceeding a thermal limit, as expressed in Appendix A of 10FR50. Thus, the need arises to monitor and correct these situations in the industry. The most common way to monitor and control these instability situations involves the use of Decay Ratio (DR) and Resonance Frequency (RF). The use of these parameters is polemical, because their use involves certain simplifications and operations prior to the calculation which question how well they represent the reality. The most important simplifications are those which lead to the interpretation of the power time series as the result of a second order system. With regard to the previous operations, the time series needs to be standardized and filtered. The result is loss of information during prediction, due to the operations, and the results, therefore, lack accuracy. In this paper, the system is considered without simplifications, that is to say that it is treated as dynamic and, as we shall see, chaotic, in the mathematical sense of the term. The series will be used in pure form without manipulations. The parameter used for monitoring and prediction of the core's behaviour will be the Hurst's exponent (H). The concept used for this proposal is that the response of a complex dynamic system depends not only on the last excitation, but on the prior history. The processes and systems are

  17. Complexified quantum field theory and 'mass without mass' from multidimensional fractional actionlike variational approach with dynamical fractional exponents

    International Nuclear Information System (INIS)

    El-Nabulsi, Ahmad Rami

    2009-01-01

    Multidimensional fractional actionlike variational problem with time-dependent dynamical fractional exponents is constructed. Fractional Euler-Lagrange equations are derived and discussed in some details. The results obtained are used to explore some novel aspects of fractional quantum field theory where many interesting consequences are revealed, in particular the complexification of quantum field theory, in particular Dirac operators and the novel notion of 'mass without mass'.

  18. FUSION BASED MULTIMODAL AUTHENTICATION IN BIOMETRICS USING CONTEXT-SENSITIVE EXPONENT ASSOCIATIVE MEMORY MODEL : A NOVEL APPROACH

    OpenAIRE

    P. E. S. N. Krishna Prasad; Pavan Kumar K; M. V. Ramakrishna; B. D. C. N. Prasad

    2013-01-01

    Biometrics is one of the primary key concepts of real application domains such as aadhar card, passport, pan card, etc. In such applications user can provide two to three biometrics patterns like face, finger, palm, signature, iris data, and so on. We considered face and finger patterns for encoding and then also for verification. Using this data we proposed a novel model for authentication in multimodal biometrics often called Context-Sensitive Exponent Associative Memory Mode...

  19. Estimating the small-x exponent of the structure function g1NS from the Bjorken sum rule

    International Nuclear Information System (INIS)

    Knauf, Anke; Meyer-Hermann, Michael; Soff, Gerhard

    2002-01-01

    We present a new estimate of the exponent governing the small-x behavior of the nonsinglet structure function g 1 p-n derived under the assumption that the Bjorken sum rule is valid. We use the world wide average of α s and the NNNLO QCD corrections to the Bjorken sum rule. The structure function g 1 NS is found to be clearly divergent for small x

  20. 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

  1. Quantifying the degree of persistence in random amoeboid motion based on the Hurst exponent of fractional Brownian motion.

    Science.gov (United States)

    Makarava, Natallia; Menz, Stephan; Theves, Matthias; Huisinga, Wilhelm; Beta, Carsten; Holschneider, Matthias

    2014-10-01

    Amoebae explore their environment in a random way, unless external cues like, e.g., nutrients, bias their motion. Even in the absence of cues, however, experimental cell tracks show some degree of persistence. In this paper, we analyzed individual cell tracks in the framework of a linear mixed effects model, where each track is modeled by a fractional Brownian motion, i.e., a Gaussian process exhibiting a long-term correlation structure superposed on a linear trend. The degree of persistence was quantified by the Hurst exponent of fractional Brownian motion. Our analysis of experimental cell tracks of the amoeba Dictyostelium discoideum showed a persistent movement for the majority of tracks. Employing a sliding window approach, we estimated the variations of the Hurst exponent over time, which allowed us to identify points in time, where the correlation structure was distorted ("outliers"). Coarse graining of track data via down-sampling allowed us to identify the dependence of persistence on the spatial scale. While one would expect the (mode of the) Hurst exponent to be constant on different temporal scales due to the self-similarity property of fractional Brownian motion, we observed a trend towards stronger persistence for the down-sampled cell tracks indicating stronger persistence on larger time scales.

  2. Lyapunov exponent as a metric for assessing the dynamic content and predictability of large-eddy simulations

    Science.gov (United States)

    Nastac, Gabriel; Labahn, Jeffrey W.; Magri, Luca; Ihme, Matthias

    2017-09-01

    Metrics used to assess the quality of large-eddy simulations commonly rely on a statistical assessment of the solution. While these metrics are valuable, a dynamic measure is desirable to further characterize the ability of a numerical simulation for capturing dynamic processes inherent in turbulent flows. To address this issue, a dynamic metric based on the Lyapunov exponent is proposed which assesses the growth rate of the solution separation. This metric is applied to two turbulent flow configurations: forced homogeneous isotropic turbulence and a turbulent jet diffusion flame. First, it is shown that, despite the direct numerical simulation (DNS) and large-eddy simulation (LES) being high-dimensional dynamical systems with O (107) degrees of freedom, the separation growth rate qualitatively behaves like a lower-dimensional dynamical system, in which the dimension of the Lyapunov system is substantially smaller than the discretized dynamical system. Second, a grid refinement analysis of each configuration demonstrates that as the LES filter width approaches the smallest scales of the system the Lyapunov exponent asymptotically approaches a plateau. Third, a small perturbation is superimposed onto the initial conditions of each configuration, and the Lyapunov exponent is used to estimate the time required for divergence, thereby providing a direct assessment of the predictability time of simulations. By comparing inert and reacting flows, it is shown that combustion increases the predictability of the turbulent simulation as a result of the dilatation and increased viscosity by heat release. The predictability time is found to scale with the integral time scale in both the reacting and inert jet flows. Fourth, an analysis of the local Lyapunov exponent is performed to demonstrate that this metric can also determine flow-dependent properties, such as regions that are sensitive to small perturbations or conditions of large turbulence within the flow field. Finally

  3. Power spectral density and scaling exponent of high frequency global solar radiation sequences

    Science.gov (United States)

    Calif, Rudy; Schmitt, François G.; Huang, Yongxiang

    2013-04-01

    invariance: Iq(f) ~ f-?(q) , ?(q) is the scaling exponent. This allows to characterize the scaling behavior of a process: fractal or multifractal with intermittent properties. For q = 2, the Hilbert spectrum is defined. In this work, The data are collected at the University site of Guadeloupe, an island in the West Indies, located at 16°15 N latitude 60°30 W longitude. Our measurements sampled at 1 Hz were performed during one year period. The analyzed data present a power spectral density E(f) displaying a power law of the form E(f) ~ f-β with 1.6 ˜ β ˜ 2.2 for frequencies f ˜ 0.1 Hz, corresponding to time scales T × 10 s. Furthermore, global solar radiation data possesses multifractal properties. For comparison, other multifractal analysis techniques such as structure functions, MDFA, wavelet leaders are also used. This preliminary work set the basis for further investigation dedicated to simulate and forecast a sequence of solar energy fluctuation under different meteorological conditions, in the multifractal framework.

  4. The Interacting Effect of the BDNF Val66Met Polymorphism and Stressful Life Events on Adolescent Depression Is Not an Artifact of Gene-Environment Correlation: Evidence from a Longitudinal Twin Study

    Science.gov (United States)

    Chen, Jie; Li, Xinying; McGue, Matt

    2013-01-01

    Background: Confounding introduced by gene-environment correlation (rGE) may prevent one from observing a true gene-environment interaction (G × E) effect on psychopathology. The present study investigated the interacting effect of the BDNF Val66Met polymorphism and stressful life events (SLEs) on adolescent depression while controlling for the…

  5. Critical exponents of a fluid mixture in the presence of isotope exchange: Isobutyric acid/D2O

    International Nuclear Information System (INIS)

    Gulari, E.; Chu, B.; Woermann, D.

    1980-01-01

    Experiments on phase diagrams and critical opalescence of a fluid mixture, isobutyric acid in D 2 O, indicate that the presence of isotope exchange reactions can change the critical behavior of such a system from that of a simple binary fluid mixture. Appreciable amounts of additional species due to isotope exchange distort the coexistence curve, shift the critical solution concentration y/sub c/ away from the concentration (y/sub I/*) where the maximal phase separation temperature T/sub p/,max occurs, and make the critical exponents γ and ν in the one-phase region (T>T/sub c/) different from those of the coexisting two-phase region (T 0 C differing from y/sub I/*=0.310 at T/sub p/,max=45.11 0 C. In the one-phase region, γ=1.25, ν=0.633, and xi 0 =3.13 A, in excellent agreement with γ=1.24 and ν=0.633 of simple fluid systems. However, in the coexisting two-phase region, the critical exponents appear to be renormalized with γ/sub x/ =1.39, ν/sub x/approx. =0.76, and xi 0 approx. =0.6 A. These results are in agreement with the renormalized critical exponents γ/sub x/=1.40 +- 0.02 and ν/sub x/ =0.73 +- 0.04 near the plait point of a ternary liquid mixture: ethanol--water--chloroform

  6. On the effects of surrogacy of energy dissipation in determining the intermittency exponent in fully developed turbulence

    Science.gov (United States)

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

    2003-03-01

    The two-point correlation function of the energy dissipation, obtained from a one-point time record of an atmospheric boundary layer, reveals a rigorous power law scaling with intermittency exponent μ approx 0.20 over almost the entire inertial range of scales. However, for the related integral moment, the power law scaling is restricted to the upper part of the inertial range only. This observation is explained in terms of the operational surrogacy of the construction of energy dissipation, which influences the behaviour of the correlation function for small separation distances.

  7. Stressful life events, ethnic identity, historical trauma, and participation in cultural activities: Associations with smoking behaviors among American Indian adolescents in California.

    Science.gov (United States)

    Soto, Claradina; Baezconde-Garbanati, Lourdes; Schwartz, Seth J; Unger, Jennifer B

    2015-11-01

    American Indian (AI) adolescents have the highest prevalence of commercial tobacco use of any ethnic group in the United States. This study examines ethnic identity (EI), participation in cultural activities, and stressful life events (SLEs) as correlates of smoking and examines historical trauma (HT) as a mediator of these associations. California AI youth (N = 969, ages 13-19, recruited from 49 tribal youth organizations and cultural activities in urban and reservation areas in California) completed a tobacco survey. Structural equation modeling was used to test a model examining HT as a potential mediator of the associations of EI, participation in cultural activities, and SLEs with cigarette smoking. Model fit was adequate. EI, participation in cultural activities, and SLEs predicted HT. HT mediated the associations of participation in cultural activities and SLEs with past-month smoking. Stronger EI predicted greater past-month smoking and this effect was mediated by greater HT. The direct effects from HT to both smoking outcomes were positive and the direct effect from EI to past-month smoking was negative. HT is a risk factor for cigarette smoking both directly and in mediating the links of EI, cultural activities, and SLEs. More efforts are needed to help AI youth to process these thoughts and empower themselves to contribute to their own lives and those of their families and communities without resorting to unhealthy addictive behaviors such as commercial tobacco use. Published by Elsevier Ltd.

  8. A population-based longitudinal study of recent stressful life events as risk factors for suicidal behavior in major depressive disorder.

    Science.gov (United States)

    Wang, Yunqiao; Sareen, Jitender; Afifi, Tracie O; Bolton, Shay-Lee; Johnson, Edward A; Bolton, James M

    2015-01-01

    The purpose of this study is to investigate whether the type and number of stressful life events (SLEs) will be associated with suicidal behavior in a 3-year follow-up period in persons with major depressive disorder (MDD). Data came from the National Epidemiologic Survey on Alcohol and Related Conditions (NESARC), a nationally representative longitudinal survey of mental health in non-institutionalized adults in the United States. The survey consisted of two waves: Wave 1 (2001--2002) and Wave 2 (2004-2005), n = 34,653. Twelve past-year SLEs were assessed at baseline. These SLEs were categorized into the following groups based on previous research: Loss or victimization; Relationship, friendship, or interpersonal stress; Financial stress; and Legal problems. Only respondents with MDD at Wave 1 were included (n = 6,004). Several SLEs were strongly associated with suicide attempts, among which, "serious problems with neighbor, friend, or relative" (adjusted odds ratio [AOR] = 2.21; 95% confidence interval [95% CI]: 1.41, 3.45) and "major financial crisis, bankruptcy, or unable to pay bills" (AOR = 2.31; 95% CI: 1.45, 3.66) were the most robust predictors of suicide attempts even after adjusting for sociodemographic variables and any anxiety, substance use, or personality disorder. People with MDD who had been exposed to certain SLEs are at elevated risk for future suicide attempts, even after accounting for the demographic factors and psychiatric comorbidity.

  9. Differences in frontal and limbic brain activation in a small sample of monozygotic twin pairs discordant for severe stressful life events

    Directory of Open Access Journals (Sweden)

    Detre A. Godinez

    2016-12-01

    Full Text Available Monozygotic twin pairs provide a valuable opportunity to control for genetic and shared environmental influences while studying the effects of nonshared environmental influences. The question we address with this design is whether monozygotic twins selected for discordance in exposure to severe stressful life events during development (before age 18 demonstrate differences in brain activation during performance of an emotional word-face Stroop task. In this study, functional magnetic resonance imaging was used to assess brain activation in eighteen young adult twins who were discordant in exposure to severe stress such that one twin had two or more severe events compared to their control co-twin who had no severe events. Twins who experienced higher levels of stress during development, compared to their control co-twins with lower stress, exhibited significant clusters of greater activation in the ventrolateral and medial prefrontal cortex, basal ganglia, and limbic regions. The control co-twins showed only the more typical recruitment of frontoparietal regions thought to be important for executive control of attention and maintenance of task goals. Behavioral performance was not significantly different between twins within pairs, suggesting the twins with stress recruited additional neural resources associated with affective processing and updating working memory when performing at the same level. This study provides a powerful glimpse at the potential effects of stress during development while accounting for shared genetic and environmental influences.

  10. Optimism and well-being: A prospective multi-method and multi-dimensional examination of optimism as a resilience factor following the occurrence of stressful life events

    Science.gov (United States)

    Kleiman, Evan M.; Chiara, Alexandra M.; Liu, Richard T.; Jager-Hyman, Shari G.; Choi, Jimmy Y.; Alloy, Lauren B.

    2016-01-01

    Optimism has been conceptualized variously as positive expectations for the future (Scheier & Carver, 1985), optimistic attributions (Peterson & Seligman, 1984), illusion of control (Alloy & Abramson, 1979), and self-enhancing biases (Weinstein, 1980). Relatively little research has examined these multiple dimensions of optimism in relation to psychological and physical health. The current study assessed the multidimensional nature of optimism within a prospective vulnerability-stress framework. Initial principal component analyses revealed the following dimensions: Positive Expectations (PE), Inferential Style (IS), Sense of Invulnerability (SI), and Overconfidence (O). Prospective follow-up analyses demonstrated that PE was associated with fewer depressive episodes and moderated the effect of stressful life events on depressive symptoms. SI also moderated the effect of life stress on anxiety symptoms. Generally, our findings indicated that optimism is a multifaceted construct and not all forms of optimism have the same effects on well-being. Specifically, our findings indicted that PE may be the most relevant to depression, whereas SI may be the most relevant to anxiety. PMID:26558316

  11. Computation of the Lyapunov exponents in the compass-gait model under OGY control via a hybrid Poincaré map

    International Nuclear Information System (INIS)

    Gritli, Hassène; Belghith, Safya

    2015-01-01

    Highlights: • A numerical calculation method of the Lyapunov exponents in the compass-gait model under OGY control is proposed. • A new linearization method of the impulsive hybrid dynamics around a one-periodic hybrid limit cycle is achieved. • We develop a simple analytical expression of a controlled hybrid Poincaré map. • A dimension reduction of the hybrid Poincaré map is realized. • We describe the numerical computation procedure of the Lyapunov exponents via the designed hybrid Poincaré map. - Abstract: This paper aims at providing a numerical calculation method of the spectrum of Lyapunov exponents in a four-dimensional impulsive hybrid nonlinear dynamics of a passive compass-gait model under the OGY control approach by means of a controlled hybrid Poincaré map. We present a four-dimensional simplified analytical expression of such hybrid map obtained by linearizing the uncontrolled impulsive hybrid nonlinear dynamics around a desired one-periodic passive hybrid limit cycle. In order to compute the spectrum of Lyapunov exponents, a dimension reduction of the controlled hybrid Poincaré map is realized. The numerical calculation of the spectrum of Lyapunov exponents using the reduced-dimension controlled hybrid Poincaré map is given in detail. In order to show the effectiveness of the developed method, the spectrum of Lyapunov exponents is calculated as the slope (bifurcation) parameter varies and hence used to predict the walking dynamics behavior of the compass-gait model under the OGY control.

  12. Characterizing Submonolayer Growth of 6P on Mica: Capture Zone Distributions vs. Growth Exponents and the Role of Hot Precursors

    Science.gov (United States)

    Einstein, T. L.; Morales-Cifuentes, Josue; Pimpinelli, Alberto

    2015-03-01

    Analyzing capture-zone distributions (CZD) using the generalized Wigner distribution (GWD) has proved a powerful way to access the critical nucleus size i. Of the several systems to which the GWD has been applied, we consider 6P on mica, for which Winkler's group found i ~ 3 . Subsequently they measured the growth exponent α (island density ~Fα , for flux F) of this system and found good scaling but different values at small and large F, which they attributed to DLA and ALA dynamics, but with larger values of i than found from the CZD analysis. We investigate this result in some detail. The third talk of this group describes a new universal relation between α and the characteristic exponent β of the GWD. The second talk reports the results of a proposed model that takes long-known transient ballistic adsorption into account, for the first time in a quantitative way. We find several intermediate scaling regimes, with distinctive values of α and an effective activation energy. One of these, rather than ALA, gives the best fit of the experimental data and a value of i consistent with the CZD analysis. Work at UMD supported by NSF CHE 13-05892.

  13. Assessment of Effects of a Delay Block and a Nonlinear Block in Systems with Chaotic Behavior Using Lyapunov Exponents

    Directory of Open Access Journals (Sweden)

    Pablo César Rodríguez Gómez

    2017-05-01

    Full Text Available Context: Because feedback systems are very common and widely used, studies of the structural characteristics under which chaotic behavior is generated have been developed. These can be separated into a nonlinear system and a linear system at least of the third order. Methods such as the descriptive function have been used for analysis. Method: A feedback system is proposed comprising a linear system, a nonlinear system and a delay block, in order to assess his behavior using Lyapunov exponents. It is evaluated with three different linear systems, different delay values and different values for parameters of nonlinear characteristic, aiming to reach chaotic behavior. Results: One hundred experiments were carried out for each of the three linear systems, by changing the value of some parameters, assessing their influence on the dynamics of the system. Contour plots that relate these parameters to the Largest Lyapunov exponent were obtained and analyzed. Conclusions: In spite non-linearity is a condition for the existence of chaos, this does not imply that any nonlinear characteristic generates a chaotic system, it is reflected by the contour plots showing the transitions between chaotic and no chaotic behavior of the feedback system. Language: English

  14. Application of the largest Lyapunov exponent and non-linear fractal extrapolation algorithm to short-term load forecasting

    International Nuclear Information System (INIS)

    Wang Jianzhou; Jia Ruiling; Zhao Weigang; Wu Jie; Dong Yao

    2012-01-01

    Highlights: ► The maximal predictive step size is determined by the largest Lyapunov exponent. ► A proper forecasting step size is applied to load demand forecasting. ► The improved approach is validated by the actual load demand data. ► Non-linear fractal extrapolation method is compared with three forecasting models. ► Performance of the models is evaluated by three different error measures. - Abstract: Precise short-term load forecasting (STLF) plays a key role in unit commitment, maintenance and economic dispatch problems. Employing a subjective and arbitrary predictive step size is one of the most important factors causing the low forecasting accuracy. To solve this problem, the largest Lyapunov exponent is adopted to estimate the maximal predictive step size so that the step size in the forecasting is no more than this maximal one. In addition, in this paper a seldom used forecasting model, which is based on the non-linear fractal extrapolation (NLFE) algorithm, is considered to develop the accuracy of predictions. The suitability and superiority of the two solutions are illustrated through an application to real load forecasting using New South Wales electricity load data from the Australian National Electricity Market. Meanwhile, three forecasting models: the gray model, the seasonal autoregressive integrated moving average approach and the support vector machine method, which received high approval in STLF, are selected to compare with the NLFE algorithm. Comparison results also show that the NLFE model is outstanding, effective, practical and feasible.

  15. Stressful life events, perceived stress, and 12-month course of geriatric depression: direct effects and moderation by the 5-HTTLPR and COMT Val158Met polymorphisms.

    Science.gov (United States)

    Zannas, Anthony S; McQuoid, Douglas R; Steffens, David C; Chrousos, George P; Taylor, Warren D

    2012-07-01

    Although the relation between stressful life events (SLEs) and risk of major depressive disorder is well established, important questions remain about the effects of stress on the course of geriatric depression. Our objectives were (1) to examine how baseline stress and change in stress is associated with course of geriatric depression and (2) to test whether polymorphisms of serotonin transporter (5-HTTLPR) and catechol-O-methyltransferase (COMT Val158Met) genes moderate this relation. Two-hundred and sixteen depressed subjects aged 60 years or older were categorized by remission status (Montgomery-Asberg depression rating scale≤6) at 6 and 12 months. At 6 months, greater baseline numbers of self-reported negative and total SLEs and greater baseline perceived stress severity were associated with lower odds of remission. At 12 months, only baseline perceived stress predicted remission. When we examined change in stress, 12-month decrease in negative SLEs and level of perceived stress were associated with improved odds of 12-month remission. When genotype data were included, COMT Val158Met genotype did not influence these relations. However, when compared with 5-HTTLPR L/L homozygotes, S allele carriers with greater baseline numbers of negative SLEs and with greater decrease in negative SLEs were more likely to remit at 12 months. This study demonstrates that baseline SLEs and perceived stress severity may influence the 12-month course of geriatric depression. Moreover, changes in these stress measures over time correlate with depression outcomes. 5-HTTLPR S carriers appear to be more susceptible to both the effects of enduring stress and the benefit of interval stress reduction.

  16. A genetic variant in 12q13, a possible risk factor for bipolar disorder, is associated with depressive state, accounting for stressful life events.

    Directory of Open Access Journals (Sweden)

    Ayu Shimasaki

    Full Text Available Genome-wide association studies (GWASs have identified a number of susceptibility genes for schizophrenia (SCZ and bipolar disorder (BD. However, the identification of risk genes for major depressive disorder (MDD has been unsuccessful because the etiology of MDD is more influenced by environmental factors; thus, gene-environment (G × E interactions are important, such as interplay with stressful life events (SLEs. We assessed the G×E interactions and main effects of genes targeting depressive symptoms. Using a case-control design, 922 hospital staff members were evaluated for depressive symptoms according to Beck Depressive Inventory (BDI; "depression" and "control" groups were classified by scores of 10 in the BDI test, SLEs, and personality. A total of sixty-three genetic variants were selected on the basis of previous GWASs of MDD, SCZ, and BD as well as candidate-gene (SLC6A4, BDNF, DBH, and FKBP5 studies. Logistic regression analysis revealed a marginally significant interaction (genetic variant × SLE at rs4523957 (P uncorrected = 0.0034 with depression and a significant association of single nucleotide polymorphism identified from evidence of BD GWAS (rs7296288, downstream of DHH at 12q13.1 with depression as the main effect (P uncorrected = 9.4 × 10(-4, P corrected = 0.0424. We also found that SLEs had a larger impact on depression (odds ratio ∼ 3, as reported previously. These results suggest that DHH plays a possible role in depression etiology; however, variants from MDD or SCZ GWAS evidence or candidate genes showed no significant associations or minimal effects of interactions with SLEs on depression.

  17. Examining the link between women’s exposure to stressful life events prior to conception and infant and toddler health: The role of birthweight

    Science.gov (United States)

    Cheng, Erika R.; Park, Hyojun; Wisk, Lauren E.; Mandell, Kara C.; Wakeel, Fathima; Litzelman, Kristin; Chatterjee, Debanjana; Witt, Whitney P.

    2015-01-01

    Background The lifecourse perspective suggests a pathway may exist among maternal exposure to stressful life events prior to conception (PSLEs), infant birthweight, and subsequent offspring health, whereby PLSEs are part of a “chains-of-risk” that set children on a certain health pathway. No prior study has examined the link between PSLEs and offspring health in a nationally-representative sample of US mothers and their children. We used longitudinal, nationally-representative data to evaluate the relation between maternal exposure to PSLEs and subsequent measures of infant and toddler health, taking both maternal and obstetric characteristics into account. Methods We examined 6,900 mother-child dyads participating in two waves of the nationally-representative Early Childhood Longitudinal Study-Birth Cohort (n=6,900). Infant and toddler health outcomes assessed at 9 and 24 months included overall health status, special health care needs, and severe health conditions. Adjusted path analyses examined associations between PSLEs, birthweight, and child health outcomes. Results In adjusted analyses, PSLEs increased the risk for very low birthweight (VLBW, <1,500 grams), which, in turn, predicted poor health at both 9 and 24 months of age. Path analyses demonstrated that PSLEs had small indirect effects on children’s subsequent health that operated through VLBW. Conclusion Our analysis suggests a chains-of-risk model in which women’s exposure to PSLEs increases the risk for giving birth to a VLBW infant, which, in turn, adversely affects infant and toddler health. Addressing women’s preconception health may have important downstream benefits for their children, although more research is needed to replicate these findings. PMID:26500337

  18. Physical Explanation of Archie's Porosity Exponent in Granular Materials: A Process-Based, Pore-Scale Numerical Study

    Science.gov (United States)

    Niu, Qifei; Zhang, Chi

    2018-02-01

    The empirical Archie's law has been widely used in geosciences and engineering to explain the measured electrical resistivity of many geological materials, but its physical basis has not been fully understood yet. In this study, we use a pore-scale numerical approach combining discrete element-finite difference methods to study Archie's porosity exponent m of granular materials over a wide porosity range. Numerical results reveal that at dilute states (e.g., porosity ϕ > 65%), m is exclusively related to the particle shape and orientation. As the porosity decreases, the electric flow in pore space concentrates progressively near particle contacts and m increases continuously in response to the intensified nonuniformity of the local electrical field. It is also found that the increase in m is universally correlated with the volume fraction of pore throats for all the samples regardless of their particle shapes, particle size range, and porosities.

  19. A Different Statistic for the Management of Portfolios - the Hurst Exponent: Persistent, Antipersistent or Random Time Series?

    Directory of Open Access Journals (Sweden)

    Ana-Maria CALOMFIR (METESCU

    2015-12-01

    Full Text Available In recent years, research in the capital markets and management of portfolios has been producing more questions than it has been answering: the need for a new paradigm or a new way of looking at things has become more and more concludent. The existing and classical view of capital markets, based on efficient market hypothesis, has a definite theory for the last six decades, but it is still not capable of significantly increase the understanding of how capital markets function. The purpose of this article is to theoretically describe a less used statistic coefficient, having a vast area of applicability due to its robustness, and which can easily divide the random series from a non-random series, even if the random series is non-Gaussian: the Hurst exponent.

  20. Evaluation of Cognitive Complexity of Tasks for the Topic Hydrogen Exponent in the Solutions of Acids and Bases

    Directory of Open Access Journals (Sweden)

    Saša Horvat

    2018-02-01

    Full Text Available The aim of this study was evaluation of cognitive complexity of tasks for the topic hydrogen exponent in the solutions of acids and bases and its validation. The created procedure included an assessment of the difficulty of concepts and an assessment of their interactivity. There were 48 freshmen students enrolled in the study program Basic academic studies in chemistry. As a research instrument for assessing performance, test of knowledge was specifically constructed for this research. Each task in the test was followed by a seven-point Likert scale for the evaluation of invested mental effort. The evaluation of cognitive complexity was confirmed by a series of linear regression analysis where high values of correlation coefficients are obtained among the examined variables: student’s performance and invested mental effort (dependent variables and cognitive complexity (independent variable.

  1. Parameter motivated mutual correlation analysis: Application to the study of currency exchange rates based on intermittency parameter and Hurst exponent

    Science.gov (United States)

    Cristescu, Constantin P.; Stan, Cristina; Scarlat, Eugen I.; Minea, Teofil; Cristescu, Cristina M.

    2012-04-01

    We present a novel method for the parameter oriented analysis of mutual correlation between independent time series or between equivalent structures such as ordered data sets. The proposed method is based on the sliding window technique, defines a new type of correlation measure and can be applied to time series from all domains of science and technology, experimental or simulated. A specific parameter that can characterize the time series is computed for each window and a cross correlation analysis is carried out on the set of values obtained for the time series under investigation. We apply this method to the study of some currency daily exchange rates from the point of view of the Hurst exponent and the intermittency parameter. Interesting correlation relationships are revealed and a tentative crisis prediction is presented.

  2. Henry Currey FRIBA (1820-1900): leading Victorian hospital architect, and early exponent of the "pavilion principle".

    Science.gov (United States)

    Cook, G C

    2002-06-01

    The "pavilion plan" for hospital design originated in France in the 18th century and was popularised in England by John Roberton and George Godwin in the mid-19th century; the underlying rationale was that with improved ventilation the mortality rate (at that time exceedingly high) was significantly reduced. Among the enthusiasts for this new style was Florence Nightingale (herself a miasmatist)--who had experienced astronomically high death rates in the hospital at Scutari during the Crimean War (1854-6). One of the leading exponents of this style of hospital architecture was Henry Currey (1820-1900) whose greatest achievement was undoubtedly the design for the new St Thomas's Hospital on the Lambeth Palace Road.

  3. 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.

  4. Contrasting predictability of summer monsoon rainfall ISOs over the northeastern and western Himalayan region: an application of Hurst exponent

    Science.gov (United States)

    Mukherjee, Sandipan

    2017-09-01

    Due to heterogeneous nonlinear forcing of complex geomorphological features, predictability of monsoon rainfall 10-90-day intra-seasonal oscillations (ISO) over the complex terrain of northeastern and western Himalayan region (NEH and WH) remained poorly quantified. Using 72 and 61 number of station observations of monsoon rainfall ISOs of NEH and WH, respectively, this study attempts to investigate variation in the regional scale predictability of monsoon rainfall ISOs with respect to changing geomorphological features and monsoon rainfall characteristics. In view of the bimodal nonlinear dynamical structure of monsoon rainfall ISO, the fractal dynamical Hurst exponent-based predictability indices are estimated as an indicator of predictability for station observations of NEH and WH, and relationships with elevations, slopes, aspects, and average numbers of occurrences of long (short) spell of active (break) phases are investigated. Results show 10-90-day ISOs are anti-persistent throughout the IHR, although, predictability of 10-90-day ISOs is higher over the NEH region than WH. Predictabilities of ISOs are found to decrease with increasing elevation and slope for both NEH and WH regions. Predictabilities of ISOs over both regions are also found to increase linearly as the number of occurrences of monsoon rainfall ISO phases (active/break) increases.

  5. Analysis of precipitation characteristics of South and North China based on the power-law tail exponents

    International Nuclear Information System (INIS)

    Feng Guolin; Zhang Daquan; Gong Zhiqiang; Zhi Rong

    2008-01-01

    Precipitation sequence is a typical nonlinear and chaotic observational series, and studies on precipitation forecasts are restricted to the use of traditional linear statistical methods, especially when analysing the regional characteristics of precipitation. In the context of 20 stations' daily precipitation series (from 1956 to 2000) in South China (SC) and North China (NC), we divide each precipitation series into many self-stationary segments by using the heuristic segmentation algorithm (briefly BG algorithm). For each station's precipitation series, we calculate the exponent of power-law tail (EPT) of the cumulative probability distribution of segments with a length larger than l for precipitation and temperature series. Our results show that the power-law decay of the cumulative probability distribution of stationary segments might be a common attribution for precipitation and other nonstationary time series; the EPT somewhat indicates the precipitation duration and its spatial distribution that might be different from area to area. The EPT in NC is larger than in SC; Meanwhile, EPT might be another effective way to study the abrupt changes in nonlinear and nonstationary time series. (geophysics, astronomy and astrophysics)

  6. Generalized Hurst exponent and multifractal function of original and translated texts mapped into frequency and length time series

    Science.gov (United States)

    Ausloos, M.

    2012-09-01

    A nonlinear dynamics approach can be used in order to quantify complexity in written texts. As a first step, a one-dimensional system is examined: two written texts by one author (Lewis Carroll) are considered, together with one translation into an artificial language (i.e., Esperanto) are mapped into time series. Their corresponding shuffled versions are used for obtaining a baseline. Two different one-dimensional time series are used here: one based on word lengths (LTS), the other on word frequencies (FTS). It is shown that the generalized Hurst exponent h(q) and the derived f(α) curves of the original and translated texts show marked differences. The original texts are far from giving a parabolic f(α) function, in contrast to the shuffled texts. Moreover, the Esperanto text has more extreme values. This suggests cascade model-like, with multiscale time-asymmetric features as finally written texts. A discussion of the difference and complementarity of mapping into a LTS or FTS is presented. The FTS f(α) curves are more opened than the LTS ones.

  7. Fractional Diffusion, Low Exponent Lévy Stable Laws, and 'Slow Motion' Denoising of Helium Ion Microscope Nanoscale Imagery.

    Science.gov (United States)

    Carasso, Alfred S; Vladár, András E

    2012-01-01

    Helium ion microscopes (HIM) are capable of acquiring images with better than 1 nm resolution, and HIM images are particularly rich in morphological surface details. However, such images are generally quite noisy. A major challenge is to denoise these images while preserving delicate surface information. This paper presents a powerful slow motion denoising technique, based on solving linear fractional diffusion equations forward in time. The method is easily implemented computationally, using fast Fourier transform (FFT) algorithms. When applied to actual HIM images, the method is found to reproduce the essential surface morphology of the sample with high fidelity. In contrast, such highly sophisticated methodologies as Curvelet Transform denoising, and Total Variation denoising using split Bregman iterations, are found to eliminate vital fine scale information, along with the noise. Image Lipschitz exponents are a useful image metrology tool for quantifying the fine structure content in an image. In this paper, this tool is applied to rank order the above three distinct denoising approaches, in terms of their texture preserving properties. In several denoising experiments on actual HIM images, it was found that fractional diffusion smoothing performed noticeably better than split Bregman TV, which in turn, performed slightly better than Curvelet denoising.

  8. Statistical mechanics of Roskilde liquids: configurational adiabats, specific heat contours, and density dependence of the scaling exponent.

    Science.gov (United States)

    Bailey, Nicholas P; Bøhling, Lasse; Veldhorst, Arno A; Schrøder, Thomas B; Dyre, Jeppe C

    2013-11-14

    We derive exact results for the rate of change of thermodynamic quantities, in particular, the configurational specific heat at constant volume, CV, along configurational adiabats (curves of constant excess entropy Sex). Such curves are designated isomorphs for so-called Roskilde liquids, in view of the invariance of various structural and dynamical quantities along them. The slope of the isomorphs in a double logarithmic representation of the density-temperature phase diagram, γ, can be interpreted as one third of an effective inverse power-law potential exponent. We show that in liquids where γ increases (decreases) with density, the contours of CV have smaller (larger) slope than configurational adiabats. We clarify also the connection between γ and the pair potential. A fluctuation formula for the slope of the CV-contours is derived. The theoretical results are supported with data from computer simulations of two systems, the Lennard-Jones fluid, and the Girifalco fluid. The sign of dγ∕dρ is thus a third key parameter in characterizing Roskilde liquids, after γ and the virial-potential energy correlation coefficient R. To go beyond isomorph theory we compare invariance of a dynamical quantity, the self-diffusion coefficient, along adiabats and CV-contours, finding it more invariant along adiabats.

  9. Adaptive inversion algorithm for 1 . 5 μm visibility lidar incorporating in situ Angstrom wavelength exponent

    Science.gov (United States)

    Shang, Xiang; Xia, Haiyun; Dou, Xiankang; Shangguan, Mingjia; Li, Manyi; Wang, Chong

    2018-07-01

    An eye-safe 1 . 5 μm visibility lidar is presented in this work considering in situ particle size distribution, which can be deployed in crowded places like airports. In such a case, the measured extinction coefficient at 1 . 5 μm should be converted to that at 0 . 55 μm for visibility retrieval. Although several models have been established since 1962, the accurate wavelength conversion remains a challenge. An adaptive inversion algorithm for 1 . 5 μm visibility lidar is proposed and demonstrated by using the in situ Angstrom wavelength exponent, which is derived from an aerosol spectrometer. The impact of the particle size distribution of atmospheric aerosols and the Rayleigh backscattering of atmospheric molecules are taken into account. Using the 1 . 5 μm visibility lidar, the visibility with a temporal resolution of 5 min is detected over 48 h in Hefei (31 . 83∘ N, 117 . 25∘ E). The average visibility error between the new method and a visibility sensor (Vaisala, PWD52) is 5.2% with the R-square value of 0.96, while the relative error between another reference visibility lidar at 532 nm and the visibility sensor is 6.7% with the R-square value of 0.91. All results agree with each other well, demonstrating the accuracy and stability of the algorithm.

  10. Phase transition in anisotropic holographic superfluids with arbitrary dynamical critical exponent z and hyperscaling violation factor α

    Energy Technology Data Exchange (ETDEWEB)

    Park, Miok [Korea Institute for Advanced Study, Seoul (Korea, Republic of); Park, Jiwon; Oh, Jae-Hyuk [Hanyang University, Department of Physics, Seoul (Korea, Republic of)

    2017-11-15

    Einstein-scalar-U(2) gauge field theory is considered in a spacetime characterized by α and z, which are the hyperscaling violation factor and the dynamical critical exponent, respectively. We consider a dual fluid system of such a gravity theory characterized by temperature T and chemical potential μ. It turns out that there is a superfluid phase transition where a vector order parameter appears which breaks SO(3) global rotation symmetry of the dual fluid system when the chemical potential becomes a certain critical value. To study this system for arbitrary z and α, we first apply Sturm-Liouville theory and estimate the upper bounds of the critical values of the chemical potential. We also employ a numerical method in the ranges of 1 ≤ z ≤ 4 and 0 ≤ α ≤ 4 to check if the Sturm-Liouville method correctly estimates the critical values of the chemical potential. It turns out that the two methods are agreed within 10 percent error ranges. Finally, we compute free energy density of the dual fluid by using its gravity dual and check if the system shows phase transition at the critical values of the chemical potential μ{sub c} for the given parameter region of α and z. Interestingly, it is observed that the anisotropic phase is more favored than the isotropic phase for relatively small values of z and α. However, for large values of z and α, the anisotropic phase is not favored. (orig.)

  11. Appropriateness of dynamical systems for the comparison of different embedding methods via calculation of the maximum Lyapunov exponent

    International Nuclear Information System (INIS)

    Franchi, M; Ricci, L

    2014-01-01

    The embedding of time series provides a valuable, and sometimes indispensable, tool in order to analyze the dynamical properties of a chaotic system. To this purpose, the choice of the embedding dimension and lag is decisive. The scientific literature describes several methods for selecting the most appropriate parameter pairs. Unfortunately, no conclusive criterion to decide which method – and thus which embedding pair – is the best has been so far devised. A widely employed quantity to compare different methods is the maximum Lyapunov exponent (MLE) because, for chaotic systems that have explicit analytic representations, MLE can be numerically evaluated independently of the embedding dimension and lag. Within this framework, we investigated the dependence on the calculated MLE on the embedding dimension and lag in the case of three dynamical systems that are also widespreadly used as reference systems, namely the Lorenz, Rössler and Mackey-Glass attractors. By also taking into account the statistical fluctuations of the calculated MLE, we propose a new method to assess which systems provide suitable test benches for the comparison of different embedding methods via MLE calculation. For example we found that, despite of its popularity in this scientific context, the Rössler attractor is not a reliable workbench to test the validity of an embedding method

  12. Robust driver heartbeat estimation: A q-Hurst exponent based automatic sensor change with interactive multi-model EKF.

    Science.gov (United States)

    Vrazic, Sacha

    2015-08-01

    Preventing car accidents by monitoring the driver's physiological parameters is of high importance. However, existing measurement methods are not robust to driver's body movements. In this paper, a system that estimates the heartbeat from the seat embedded piezoelectric sensors, and that is robust to strong body movements is presented. Multifractal q-Hurst exponents are used within a classifier to predict the most probable best sensor signal to be used in an Interactive Multi-Model Extended Kalman Filter pulsation estimation procedure. The car vibration noise is reduced using an autoregressive exogenous model to predict the noise on sensors. The performance of the proposed system was evaluated on real driving data up to 100 km/h and with slaloms at high speed. It is shown that this method improves by 36.7% the pulsation estimation under strong body movement compared to static sensor pulsation estimation and appears to provide reliable pulsation variability information for top-level analysis of drowsiness or other conditions.

  13. Characterization of coherent structures in three-dimensional turbulent flows using the finite-size Lyapunov exponent

    International Nuclear Information System (INIS)

    Bettencourt, João H; López, Cristóbal; Hernández-García, Emilio

    2013-01-01

    In this paper, we use the finite-size Lyapunov exponent (FSLE) to characterize Lagrangian coherent structures in three-dimensional (3D) turbulent flows. Lagrangian coherent structures act as the organizers of transport in fluid flows and are crucial to understand their stirring and mixing properties. Generalized maxima (ridges) of the FSLE fields are used to locate these coherent structures. 3D FSLE fields are calculated in two phenomenologically distinct turbulent flows: a wall-bounded flow (channel flow) and a regional oceanic flow obtained by the numerical solution of the primitive equations where two-dimensional (2D) turbulence dominates. In the channel flow, autocorrelations of the FSLE field show that the structure is substantially different from the near wall to the mid-channel region and relates well to the more widely studied Eulerian coherent structure of the turbulent channel flow. The ridges of the FSLE field have complex shapes due to the 3D character of the turbulent fluctuations. In the oceanic flow, strong horizontal stirring is present and the flow regime is similar to that of 2D turbulence where the domain is populated by coherent eddies that interact strongly. This in turn results in the presence of high FSLE lines throughout the domain leading to strong non-local mixing. The ridges of the FSLE field are quasi-vertical surfaces, indicating that the horizontal dynamics dominates the flow. Indeed, due to rotation and stratification, vertical motions in the ocean are much less intense than horizontal ones. This suppression is absent in the channel flow, as the 3D character of the FSLE ridges shows. This article is part of a special issue of Journal of Physics A: Mathematical and Theoretical devoted to ‘Lyapunov analysis: from dynamical systems theory to applications’. (paper)

  14. Characterization of fish sauce aroma-impact compounds using GC-MS, SPME-Osme-GCO, and Stevens' power law exponents.

    Science.gov (United States)

    Pham, A J; Schilling, M W; Yoon, Y; Kamadia, V V; Marshall, D L

    2008-05-01

    The objectives of this study were to characterize volatile compounds and to determine the characteristic aromas associated with impact compounds in 4 fish sauces using solid-phase micro-extraction, gas chromatography-mass spectrometry, Osme, and gas chromatography olfactometry (SPME-Osme-GCO) coupled with Stevens' Power Law. Compounds were separated using GCMS and GCO and were identified with the mass spectral database, aroma perceived at the sniffing port, retention indices, and verification of compounds by authentic standards in the GCMS and GCO. Aromas that were isolated and present in all 4 fish sauce samples at all concentrations included fishy (trimethylamine), pungent and dirty socks (combination of butanoic, pentanoic, hexanoic, and heptanoic acids), cooked rice and buttery popcorn (2,6-dimethyl pyrazine), and sweet and cotton candy (benzaldehyde). All fish sauces contained the same aromas as determined by GCO and GCMS (verified using authentic standard compounds), but the odor intensity associated with each compound or group of compounds was variable for different fish sauce samples. Stevens' Power Law exponents were also determined using this analytical technique, but exponents were not consistent for the same compounds that were found in all fish sauces. Stevens' Power Law exponents ranged from 0.14 to 0.37, 0.24 to 0.34, 0.09 to 0.21, and 0.10 to 0.35 for dirty socks, fishy, buttery popcorn, and sweet aromas, respectively. This demonstrates that there is variability in Stevens' Power Law exponents for odorants within fish sauce samples.

  15. Efektivita kapitálových trhů: Fraktální dimenze, Hurstův exponent a entropie

    Czech Academy of Sciences Publication Activity Database

    Krištoufek, Ladislav; Vošvrda, Miloslav

    2012-01-01

    Roč. 60, č. 2 (2012), s. 208-221 ISSN 0032-3233 R&D Projects: GA ČR GA402/09/0965 Institutional support: RVO:67985556 Keywords : capital markets efficiency * fractal dimension * long-range dependence * entropy Subject RIV: AH - Economics Impact factor: 0.722, year: 2012 http://library.utia.cas.cz/separaty/2012/E/kristoufek-capital markets efficiency fractal dimension hurst exponent and entropy.pdf

  16. Analysis and control of chaotic behavior in boost converter by ramp compensation based on Lyapunov exponents assignment: theoretical and experimental investigation

    International Nuclear Information System (INIS)

    Zamani, Najmeh; Ataei, Mohammad; Niroomand, Mehdi

    2015-01-01

    Highlights: • Applying nonlinear analysis of complex dynamics displayed by current-mode controlled boost converter. • The ramp compensation method is used to control bifurcation and chaos in these converters based on bifurcation diagram and Lyapunov exponents assignment. • A discrete-time iterative nonlinear mapping model has been derived by inserting the ramp compensation parameter in the dynamical equations of the system. • A design methodology for chaos control is provided in this converter based on Lyapunov exponents assignment in desired values theoretically by proper selection of compensator slope. • Practical results are provided to confirm the theoretical analysis and simulations. - Abstract: Nonlinear analysis of complex dynamics displayed by current mode dc–dc converter and idea of Lyapunov exponents assignment by ramp compensator in order to control chaotic behavior is proposed in this article. A discrete-time iterative nonlinear mapping model is derived. The occurrence of the complex behaviors of bifurcation and chaos generated by varying the circuit parameters are investigated through numerical analysis and software implementation of the circuit. Next, in order to control bifurcation and chaos in these converters, the ramp compensation method is used. By inserting the ramp compensation parameter in the dynamical equations of the system, these complex behaviors are examined theoretically and numerically as well. It is proved that through this method, the stable period-one operation of the converter can be extended. By evaluating the Lyapunov exponents (LEs) of the system, the impact of the slope on the location of LEs are determined analytically. This leads to a design methodology for control of chaos in this converter based on LEs assignment in desired values by proper selection of compensator slope. By developing an experimental set up, practical results are obtained to confirm the theoretical analysis and simulations.

  17. Benford analysis of quantum critical phenomena: First digit provides high finite-size scaling exponent while first two and further are not much better

    Science.gov (United States)

    Bera, Anindita; Mishra, Utkarsh; Singha Roy, Sudipto; Biswas, Anindya; Sen(De), Aditi; Sen, Ujjwal

    2018-06-01

    Benford's law is an empirical edict stating that the lower digits appear more often than higher ones as the first few significant digits in statistics of natural phenomena and mathematical tables. A marked proportion of such analyses is restricted to the first significant digit. We employ violation of Benford's law, up to the first four significant digits, for investigating magnetization and correlation data of paradigmatic quantum many-body systems to detect cooperative phenomena, focusing on the finite-size scaling exponents thereof. We find that for the transverse field quantum XY model, behavior of the very first significant digit of an observable, at an arbitrary point of the parameter space, is enough to capture the quantum phase transition in the model with a relatively high scaling exponent. A higher number of significant digits do not provide an appreciable further advantage, in particular, in terms of an increase in scaling exponents. Since the first significant digit of a physical quantity is relatively simple to obtain in experiments, the results have potential implications for laboratory observations in noisy environments.

  18. Review Article: On the relation between the seismic activity and the Hurst exponent of the geomagnetic field at the time of the 2000 Izu swarm

    Directory of Open Access Journals (Sweden)

    F. Masci

    2013-09-01

    Full Text Available Many papers document the observation of earthquake-related precursory signatures in geomagnetic field data. However, the significance of these findings is ambiguous because the authors did not adequately take into account that these signals could have been generated by other sources, and the seismogenic origin of these signals have not been validated by comparison with independent datasets. Thus, they are not reliable examples of magnetic disturbances induced by the seismic activity. Hayakawa et al. (2004 claim that at the time of the 2000 Izu swarm the Hurst exponent of the Ultra-Low-Frequency (ULF: 0.001–10 Hz band of the geomagnetic field varied in accord with the energy released by the seismicity. The present paper demonstrates that the behaviour of the Hurst exponent was insufficiently investigated and also misinterpreted by the authors. We clearly show that during the Izu swarm the changes of the Hurst exponent were strongly related to the level of global geomagnetic activity and not to the increase of the local seismic activity.

  19. Gradual multifractal reconstruction of time-series: Formulation of the method and an application to the coupling between stock market indices and their Hölder exponents

    Science.gov (United States)

    Keylock, Christopher J.

    2018-04-01

    A technique termed gradual multifractal reconstruction (GMR) is formulated. A continuum is defined from a signal that preserves the pointwise Hölder exponent (multifractal) structure of a signal but randomises the locations of the original data values with respect to this (φ = 0), to the original signal itself(φ = 1). We demonstrate that this continuum may be populated with synthetic time series by undertaking selective randomisation of wavelet phases using a dual-tree complex wavelet transform. That is, the φ = 0 end of the continuum is realised using the recently proposed iterated, amplitude adjusted wavelet transform algorithm (Keylock, 2017) that fully randomises the wavelet phases. This is extended to the GMR formulation by selective phase randomisation depending on whether or not the wavelet coefficient amplitudes exceeds a threshold criterion. An econophysics application of the technique is presented. The relation between the normalised log-returns and their Hölder exponents for the daily returns of eight financial indices are compared. One particularly noticeable result is the change for the two American indices (NASDAQ 100 and S&P 500) from a non-significant to a strongly significant (as determined using GMR) cross-correlation between the returns and their Hölder exponents from before the 2008 crash to afterwards. This is also reflected in the skewness of the phase difference distributions, which exhibit a geographical structure, with Asian markets not exhibiting significant skewness in contrast to those from elsewhere globally.

  20. Hartree-Fock study of the Anderson metal-insulator transition in the presence of Coulomb interaction: Two types of mobility edges and their multifractal scaling exponents

    Science.gov (United States)

    Lee, Hyun-Jung; Kim, Ki-Seok

    2018-04-01

    We investigate the role of Coulomb interaction in the multifractality of Anderson metal-insulator transition, where the Coulomb interaction is treated within the Hartree-Fock approximation, but disorder effects are taken into account exactly. An innovative technical aspect in our simulation is to utilize the Ewald-sum technique, which allows us to introduce the long-range nature of the Coulomb interaction into Hartree-Fock self-consistent equations of order parameters more accurately. This numerical simulation reproduces the Altshuler-Aronov correction in a metallic state and the Efros-Shklovskii pseudogap in an insulating phase, where the density of states ρ (ω ) is evaluated in three dimensions. Approaching the quantum critical point of a metal-insulator transition from either the metallic or insulting phase, we find that the density of states is given by ρ (ω ) ˜|ω| 1 /2 , which determines one critical exponent of the McMillan-Shklovskii scaling theory. Our main result is to evaluate the eigenfunction multifractal scaling exponent αq, given by the Legendre transformation of the fractal dimension τq, which characterizes the scaling behavior of the inverse participation ratio with respect to the system size L . Our multifractal analysis leads us to identify two kinds of mobility edges, one of which occurs near the Fermi energy and the other of which appears at a high energy, where the density of states at the Fermi energy shows the Coulomb-gap feature. We observe that the multifractal exponent at the high-energy mobility edge remains to be almost identical to that of the Anderson localization transition in the absence of Coulomb interactions. On the other hand, we find that the multifractal exponent near the Fermi energy is more enhanced than that at the high-energy mobility edge, suspected to result from interaction effects. However, both the multifractal exponents do not change even if the strength of the Coulomb interaction varies. We also show that the

  1. Relation of tobacco and alcohol use to stressful life events and gratitude in middle school students%中学生的烟酒使用与压力性生活事件和感恩心态

    Institute of Scientific and Technical Information of China (English)

    陈彦垒; 叶宝娟; 胡竹菁; 李义安; 姜晓芳

    2012-01-01

    目的:了解中学生烟酒使用的状况,考察感恩与中学生烟酒使用的关系,为中学生烟酒使用的教育与心理干预提供理论支持.方法:选取某地区四所初级中学的学生共565人,使用烟酒使用问卷、压力性生活事件量表、感恩问卷进行调查.结果:中学生在过去1个月中吸烟与饮酒的比例分别为18%和31%.压力性生活事件与烟酒使用呈正相关(r=0.12,P<0.01),感恩与烟酒使用呈负相关(r=-0.32,P<0.001);感恩调节压力性生活事件和烟酒使用的关系,随着压力性生活事件的增加,感恩水平高的中学生其烟酒使用变化不显著(b=0.01,P>0.05),而感恩水平低的中学生的烟酒使用表现出上升趋势(b=0.13,P<0.05).结论:中学生烟酒使用较为普遍.压力性生活事件是中学生烟酒使用的风险因素;感恩是烟酒使用的保护因素,并对压力性生活事件与烟酒使用之间的关系具有调节效应.%Objective: To explore the state of tobacco and alcohol use and its relation to gratitude, and to provide theoretical support for the psychological intervention. Methods: Totally 565 middle school students were selected and assessed with the Tobacco and Alcohol Use Questionnaire, Gratitude Questionnaire and Stressful Life Events Scale. Results: The rates of tobacco and alcohol use were 18% and 31 % respectively. Stressful life events was positively correlated with tobacco alcohol use (r =0. 12, P 0. 05), while increased significantly in those with lower gratitude (6 = 0. 13, P < 0.05) . Conclusion: It suggests that tobacco and alcohol use is common in middle school students. Stressful life event may be a risk factor of tobacco and alcohol use, while gratitude may be a protection factor and play a moderating effect on the relationship between stressful life events and tobacco and alcohol use.

  2. Beyond the Young-Laplace model for cluster growth during dewetting of thin films: effective coarsening exponents and the role of long range dewetting interactions.

    Science.gov (United States)

    Constantinescu, Adi; Golubović, Leonardo; Levandovsky, Artem

    2013-09-01

    Long range dewetting forces acting across thin films, such as the fundamental van der Waals interactions, may drive the formation of large clusters (tall multilayer islands) and pits, observed in thin films of diverse materials such as polymers, liquid crystals, and metals. In this study we further develop the methodology of the nonequilibrium statistical mechanics of thin films coarsening within continuum interface dynamics model incorporating long range dewetting interactions. The theoretical test bench model considered here is a generalization of the classical Mullins model for the dynamics of solid film surfaces. By analytic arguments and simulations of the model, we study the coarsening growth laws of clusters formed in thin films due to the dewetting interactions. The ultimate cluster growth scaling laws at long times are strongly universal: Short and long range dewetting interactions yield the same coarsening exponents. However, long range dewetting interactions, such as the van der Waals forces, introduce a distinct long lasting early time scaling behavior characterized by a slow growth of the cluster height/lateral size aspect ratio (i.e., a time-dependent Young angle) and by effective coarsening exponents that depend on cluster size. In this study, we develop a theory capable of analytically calculating these effective size-dependent coarsening exponents characterizing the cluster growth in the early time regime. Such a pronounced early time scaling behavior has been indeed seen in experiments; however, its physical origin has remained elusive to this date. Our theory attributes these observed phenomena to ubiquitous long range dewetting interactions acting across thin solid and liquid films. Our results are also applicable to cluster growth in initially very thin fluid films, formed by depositing a few monolayers or by a submonolayer deposition. Under this condition, the dominant coarsening mechanism is diffusive intercluster mass transport while the

  3. Mean-field Ising crossover and the critical exponents γ, ν, and η for a polymer blend: d-PB/PS studied by small-angle neutron scattering

    Science.gov (United States)

    Janssen, S.; Schwahn, D.; Springer, T.

    1992-05-01

    The critical behavior of the polymer blend d-PB/PS was investigated by small-angle neutron scattering experiments. 3D Ising behavior was clearly observed with the critical exponents γ=1.26+/-0.01, ν=0.59+/-0.01, and η=0.047+/-0.004. The crossover to mean-field behavior occurs at T*=Tc+5.4 K. This is compared with the results of other experiments and the Landau-Ginzburg criterion. The Q dependence of the structure factor S(Q) follows the Ornstein-Zernike form in both regimes.

  4. Retrievals of aerosol optical depth and Angström exponent from ground-based Sun-photometer data of Singapore.

    Science.gov (United States)

    Salinas, Santo V; Chew, Boon N; Liew, Soo C

    2009-03-10

    The role of aerosols in climate and climate change is one of the factors that is least understood at the present. Aerosols' direct interaction with solar radiation is a well understood mechanism that affects Earth's net radiative forcing. However, quantifying its magnitude is more problematic because of the temporal and spatial variability of aerosol particles. To enhance our understanding of the radiative effects of aerosols on the global climate, Singapore has joined the AERONET (Aerosol Robotic Network) worldwide network by contributing ground-based direct Sun measurements performed by means of a multiwavelength Sun-photometer instrument. Data are collected on an hourly basis, then are uploaded to be fully screened and quality assured by AERONET. We use a one year data record (level 1.5/2.0) of measured columnar atmospheric optical depth, spanning from November 2006 to October 2007, to study the monthly and seasonal variability of the aerosol optical depth and the Angström exponent. We performed independent retrievals of these parameters (aerosol optical depth and Angström exponent) by using the photometer's six available bands covering the near-UV to near-IR (380-1080 nm). As a validation, our independent retrievals were compared with AERONET 1.5/2.0 level direct Sun product.

  5. Stressful life events and leucocyte telomere length

    DEFF Research Database (Denmark)

    Osler, Merete; Bendix, Laila; Rask, Lene

    2016-01-01

    , and markers of low-grade inflammation. A cohort of Danish men born in 1953 has been followed since birth in the Metropolit Cohort. These men underwent a health examination including blood sampling in 2010 and a subset of 324 also had a quantitative PCR-based measurement of TL. The relation between stressful......=-0.02); P=0.05). This relation was particularly strong for being placed away from home (β=-0.16; P... (9%). This study suggests that stressful events in childhood are associated with shorter TL in middle-aged men and that part of this relation is explained by depressive mood and low grade inflammation....

  6. 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....

  7. 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.

  8. Critical exponents in nucleus breakup

    International Nuclear Information System (INIS)

    Campi, X.

    1987-01-01

    In recent years the study of cluster formation has become a new field in statistical physics. Nuclear reactions with particle number change can be viewed as a cluster formation processes. Multifragmentation decay produces a power law distribution of medium size clusters. These two cluster size distributions resemble that of many others statistical cluster formation processes. We discuss now these analogies in some details

  9. Scaling Exponents in Financial Markets

    Science.gov (United States)

    Kim, Kyungsik; Kim, Cheol-Hyun; Kim, Soo Yong

    2007-03-01

    We study the dynamical behavior of four exchange rates in foreign exchange markets. A detrended fluctuation analysis (DFA) is applied to detect the long-range correlation embedded in the non-stationary time series. It is for our case found that there exists a persistent long-range correlation in volatilities, which implies the deviation from the efficient market hypothesis. Particularly, the crossover is shown to exist in the scaling behaviors of the volatilities.

  10. Proneness to social anxiety modulates neural complexity in the absence of exposure: A resting state fMRI study using Hurst exponent.

    Science.gov (United States)

    Gentili, Claudio; Vanello, Nicola; Cristea, Ioana; David, Daniel; Ricciardi, Emiliano; Pietrini, Pietro

    2015-05-30

    To test the hypothesis that brain activity is modulated by trait social anxiety, we measured the Hurst Exponent (HE), an index of complexity in time series, in healthy individuals at rest in the absence of any social trigger. Functional magnetic resonance imaging (fMRI) time series were recorded in 36 subjects at rest. All volunteers were healthy without any psychiatric, medical or neurological disorder. Subjects completed the Liebowitz Social Anxiety Scale (LSAS) and the Brief Fear of Negative Evaluation (BFNE) to assess social anxiety and thoughts in social contexts. We also obtained the fractional Amplitude of Low Frequency Fluctuations (fALFF) of the BOLD signal as an independent control measure for HE data. BFNE scores correlated positively with HE in the posterior cingulate/precuneus, while LSAS scores correlated positively with HE in the precuneus, in the inferior parietal sulci and in the parahippocamus. Results from fALFF were highly consistent with those obtained using LSAS and BFNE to predict HE. Overall our data indicate that spontaneous brain activity is influenced by the degree of social anxiety, on a continuum and in the absence of social stimuli. These findings suggest that social anxiety is a trait characteristic that shapes brain activity and predisposes to different reactions in social contexts. Copyright © 2015. Published by Elsevier Ireland Ltd.

  11. A comparative analysis of spectral exponent estimation techniques for 1/f(β) processes with applications to the analysis of stride interval time series.

    Science.gov (United States)

    Schaefer, Alexander; Brach, Jennifer S; Perera, Subashan; Sejdić, Ervin

    2014-01-30

    The time evolution and complex interactions of many nonlinear systems, such as in the human body, result in fractal types of parameter outcomes that exhibit self similarity over long time scales by a power law in the frequency spectrum S(f)=1/f(β). The scaling exponent β is thus often interpreted as a "biomarker" of relative health and decline. This paper presents a thorough comparative numerical analysis of fractal characterization techniques with specific consideration given to experimentally measured gait stride interval time series. The ideal fractal signals generated in the numerical analysis are constrained under varying lengths and biases indicative of a range of physiologically conceivable fractal signals. This analysis is to complement previous investigations of fractal characteristics in healthy and pathological gait stride interval time series, with which this study is compared. The results of our analysis showed that the averaged wavelet coefficient method consistently yielded the most accurate results. Class dependent methods proved to be unsuitable for physiological time series. Detrended fluctuation analysis as most prevailing method in the literature exhibited large estimation variances. The comparative numerical analysis and experimental applications provide a thorough basis for determining an appropriate and robust method for measuring and comparing a physiologically meaningful biomarker, the spectral index β. In consideration of the constraints of application, we note the significant drawbacks of detrended fluctuation analysis and conclude that the averaged wavelet coefficient method can provide reasonable consistency and accuracy for characterizing these fractal time series. Copyright © 2013 Elsevier B.V. All rights reserved.

  12. Racial and ethnic differences in the relationship between antenatal stressful life events and postpartum depression among women in the United States: does provider communication on perinatal depression minimize the risk?

    Science.gov (United States)

    Mukherjee, Soumyadeep; Fennie, Kristopher; Coxe, Stefany; Madhivanan, Purnima; Trepka, Mary Jo

    2018-07-01

    Multi-state population-based studies exploring the racial/ethnic differences in the prevalence and correlates of postpartum depression (PPD), which affects 10-20% of women in the US, are rare. The aim of this study was to examine the racial/ethnic disparities in the relationship between antenatal stressful life events and PPD among US women and to explore whether antenatal health care provider communication on perinatal depression was associated with a lower risk. Data from the 2009-2011 Pregnancy Risk Assessment Monitoring System (PRAMS) were used. For each racial/ethnic group, the distribution of PPD was compared according to different levels of the stressors and socio-demographic, pre-pregnancy, antenatal, delivery, and neonatal characteristics. Multivariable logistic regression analyses were performed with PPD as the outcome and all variables that were significant in bivariate analyses as predictors. Eleven percent of 87,565 women met the criteria for PPD with the prevalence ranging from 7.9% among Asian/Pacific Islanders to 14% among American Indian/Alaska Natives. Irrespective of race/ethnicity, having many bills to pay and having more than usual arguments with husband/partner were risk factors for PPD. Among non-Hispanic black (NHB) women, having a husband/partner who did not want the pregnancy was associated with PPD (adjusted odds ratio [aOR]: 1.47; 95% confidence interval [CI]: 1.14, 1.90), and among non-Hispanic whites (NHWs), drug/drinking problems of someone close was associated with PPD (aOR: 1.37; 95% CI: 1.21, 1.55). Provider communication was inversely associated with PPD among NHWs (aOR: 0.77; 95% CI: 0.69, 0.85) and NHBs (aOR: 0.74; 95% CI: 0.60, 0.93). The protective effect of provider communication on PPD suggests the benefit of a simple conversation about perinatal depression during antenatal care. Furthermore, risk factors for PPD varied by race/ethnicity suggesting that these vulnerabilities should be taken into consideration in identifying

  13. The Role of Difficulty in Identifying and Describing Feelings in Non-Suicidal Self-Injury Behavior (NSSI): Associations With Perceived Attachment Quality, Stressful Life Events, and Suicidal Ideation.

    Science.gov (United States)

    Cerutti, Rita; Zuffianò, Antonio; Spensieri, Valentina

    2018-01-01

    . Conclusion: The ability to identify and describing feelings is important to managing emotional expression and understanding the feelings of others, both crucial in attaining successful interpersonal relationships. Our data revealed that, while controlling for stressful life events, low levels of attachment may increase adolescents' difficulty in identifying and describing their own feelings, which in turn may increase the risk of both NSSI and suicidal ideation.

  14. Gas and dust in the star-forming region ρ Oph A. The dust opacity exponent β and the gas-to-dust mass ratio g2d

    Science.gov (United States)

    Liseau, R.; Larsson, B.; Lunttila, T.; Olberg, M.; Rydbeck, G.; Bergman, P.; Justtanont, K.; Olofsson, G.; de Vries, B. L.

    2015-06-01

    Aims: We aim at determining the spatial distribution of the gas and dust in star-forming regions and address their relative abundances in quantitative terms. We also examine the dust opacity exponent β for spatial and/or temporal variations. Methods: Using mapping observations of the very dense ρ Oph A core, we examined standard 1D and non-standard 3D methods to analyse data of far-infrared and submillimetre (submm) continuum radiation. The resulting dust surface density distribution can be compared to that of the gas. The latter was derived from the analysis of accompanying molecular line emission, observed with Herschel from space and with APEX from the ground. As a gas tracer we used N2H+, which is believed to be much less sensitive to freeze-out than CO and its isotopologues. Radiative transfer modelling of the N2H+ (J = 3-2) and (J = 6-5) lines with their hyperfine structure explicitly taken into account provides solutions for the spatial distribution of the column density N(H2), hence the surface density distribution of the gas. Results: The gas-to-dust mass ratio is varying across the map, with very low values in the central regions around the core SM 1. The global average, = 88, is not far from the canonical value of 100, however. In ρ Oph A, the exponent β of the power-law description for the dust opacity exhibits a clear dependence on time, with high values of 2 for the envelope-dominated emission in starless Class -1 sources to low values close to 0 for the disk-dominated emission in Class III objects. β assumes intermediate values for evolutionary classes in between. Conclusions: Since β is primarily controlled by grain size, grain growth mostly occurs in circumstellar disks. The spatial segregation of gas and dust, seen in projection toward the core centre, probably implies that, like C18O, also N2H+ is frozen onto the grains. Based on observations with APEX, which is a 12 m diameter submillimetre telescope at 5100 m altitude on Llano Chajnantor

  15. Scaling of the distribution function and the critical exponents near the point of a marginal stability under the Vlasov-Poisson equations

    International Nuclear Information System (INIS)

    Ivanov, Alexei

    2000-08-01

    A model system, described by the consistent Vlasov-Poisson equations under periodical boundary conditions, has been studied numerically near the point of a marginal stability. The power laws, typical for a system, undergoing a second-order phase transition, hold in a vicinity of the critical point: (i) A ∝ -θ β , β=1.907±0.006 for θ ≤ 0, where A is the saturated amplitude of the marginally-stable mode; (ii) χ ∝ θ -γ as θ → 0, γ=γ - =1.020±0.008 for θ + =0.995±0.020 for θ > 0, where χ=∂A/∂F 1 at F 1 → 0 is the susceptibility to external drive of the strain F 1 ; (iii) at θ=0 the system responds to external drive as A ∝ F 1 1/δ , and δ=1.544±0.002. θ=( 2 >- cr 2 >)/ cr 2 > is the dimensionless reduced velocity dispersion. Within the error of computation these critical exponents satisfy to equality γ=β(δ-1), known in thermodynamics as the Widom equality, which is direct consequence of scaling invariance of the Fourier components f m of the distribution function f at |θ| m (λ at t, λ av v, λ aθ θ, λ aA0 A 0 , λ aF F 1 )=λf m (t, v, θ, A 0 , F 1 ) at θ approx. = 0. On the contrary to thermodynamics these critical indices indicate to a very wide critical area. In turn, it means that critical phenomena may determine macroscopic dynamics of a large fraction of systems. (author)

  16. A comparative analysis of spectral exponent estimation techniques for 1/fβ processes with applications to the analysis of stride interval time series

    Science.gov (United States)

    Schaefer, Alexander; Brach, Jennifer S.; Perera, Subashan; Sejdić, Ervin

    2013-01-01

    Background The time evolution and complex interactions of many nonlinear systems, such as in the human body, result in fractal types of parameter outcomes that exhibit self similarity over long time scales by a power law in the frequency spectrum S(f) = 1/fβ. The scaling exponent β is thus often interpreted as a “biomarker” of relative health and decline. New Method This paper presents a thorough comparative numerical analysis of fractal characterization techniques with specific consideration given to experimentally measured gait stride interval time series. The ideal fractal signals generated in the numerical analysis are constrained under varying lengths and biases indicative of a range of physiologically conceivable fractal signals. This analysis is to complement previous investigations of fractal characteristics in healthy and pathological gait stride interval time series, with which this study is compared. Results The results of our analysis showed that the averaged wavelet coefficient method consistently yielded the most accurate results. Comparison with Existing Methods: Class dependent methods proved to be unsuitable for physiological time series. Detrended fluctuation analysis as most prevailing method in the literature exhibited large estimation variances. Conclusions The comparative numerical analysis and experimental applications provide a thorough basis for determining an appropriate and robust method for measuring and comparing a physiologically meaningful biomarker, the spectral index β. In consideration of the constraints of application, we note the significant drawbacks of detrended fluctuation analysis and conclude that the averaged wavelet coefficient method can provide reasonable consistency and accuracy for characterizing these fractal time series. PMID:24200509

  17. TeraHertz imaging of hidden paint layers on canvas

    NARCIS (Netherlands)

    Adam, A.J.L.; Planken, P.C.M.; Meloni, S.; Dik, J.

    2009-01-01

    We show terahertz reflection images of hidden paint layers in a painting on canvas and compare the results with X-ray Radiography and Infrared Reflectography. Our terahertz measurements show strong reflections from both the canvas/paint interface and from the raw umber/lead white interface,

  18. Eventos de vida produtores de estresse e transtornos mentais comuns: resultados do Estudo Pró-Saúde Stressful life events and common mental disorders: results of the Pro-Saude Study

    Directory of Open Access Journals (Sweden)

    Claudia S. Lopes

    2003-12-01

    Full Text Available O objetivo do estudo é investigar a associação entre eventos de vida produtores de estresse (EVPE e transtornos mentais comuns (TMC. Dados seccionais da fase 1 de um estudo de coorte (Estudo Pró-Saúde foram coletados entre 4.030 funcionários. Informações foram obtidas por meio de um questionário multidimensional autopreenchível (General Health Questionnaire que avaliou a presença de TMC nas duas semanas anteriores, ocorrência de EVPE nos 12 meses anteriores e variáveis sociodemográficas. Após ajuste por sexo, idade, renda e situação conjugal, problemas financeiros graves foram os eventos associados a uma chance mais elevada de TMC (OR = 2,6; IC95%: 2,2-3,0, seguidos de agressão física (OR = 2,1; IC95%: 1,5-2,9, mudança forçada de moradia (OR = 1,9; IC95%: 1,5-2,4, doença grave (OR = 1,8; IC95%: 1,5-2,1, rompimento de relação amorosa (OR = 1,9; IC95%: 1,6-2,3, internação hospitalar (OR = 1,4; IC95%: 1,1-1,8 e assalto ou roubo (OR = 1,5; IC95%: 1,2-1,8. Os resultados apontam para a necessidade de se investigar efeitos de longo prazo associados a estes eventos, assim como de fatores que potencialmente modifiquem seu impacto, de forma a subsidiar ações de prevenção mais efetivas na área da saúde mental.This study investigates the association between stressful life events (SLE and common mental disorders (CMD among university employees in Rio de Janeiro, Brazil. Phase 1 sectional data from a cohort study (the Pro-Saude Study were collected among 4,030 participants. A standardized self-administered questionnaire (General Health Questionnaire assessed the presence of CMD during the previous two weeks, the occurrence of SLE in the previous 12 months, and socio-demographic characteristics. After adjustment for gender, age, income, and marital status, severe financial problems were associated with the greatest risk of CMD (OR = 2.6; 95%CI: 2.2-3.0, followed by physical aggression (OR = 2.1; 95%CI: 1.5-2.8, disruption of a

  19. Associação de eventos de vida produtores de estresse e mal-estar psicológico: um estudo de base populacional Association of stressful life events and psychological distress: a community-based study

    Directory of Open Access Journals (Sweden)

    Felipe Sparrenberger

    2004-02-01

    from socioeconomic variables (education 38.2%; family income, 32.3% and the occurrence of at least one event (36.4%. Public policies aimed at ameliorating adverse social factors such as loss of employment and crime, as well as social support to help individuals manage stressful life events are likely to improve psychological well-being.

  20. Synthetic jet flow control of two-dimensional NACA 65(1)-412 airfoil flow with finite-time lyapunov exponent analysis of Lagrangian coherent structures

    Science.gov (United States)

    Jeong, Peter Inuk

    Synthetic jet (SJ) control of a low-Reynolds number, unsteady, compressible, viscous flow over a NACA 65-(1)412 airfoil, typical for unmanned air vehicles and gas turbines, has been investigated computationally. A particular focus was placed in the development and control of Lagrangian Coherent Structures (LCS) and the associated Finite-Time Lyapunov Exponent (FTLE) fields. The FTLE fields quantitatively measure of the repulsion rate in forward-time and the attraction rate in backward-time, and provide a unique perspective on effective flow control. A Discontinuous-Galerkin (DG) methods, high-fidelity Navier-Stokes solver performs direct numerical simulation (DNS) of the airfoil flow. Three SJ control strategies have been investigated: immediately downstream of flow separation, normal to the separated shear layer; near the leading edge, normal to the airfoil suction side; near the trailing edge, normal to the airfoil pressure side. A finite difference algorithm computes the FTLE from DNS velocity data. A baseline flow without SJ control is compared to SJ actuated flows. The baseline flow forms a regular, time-periodic, asymmetric von Karman vortex street in the wake. The SJ downstream of flow separation increases recirculation region vorticity and reduces the effective angle of attack. This decreases the time-averaged lift by 2:98% and increases the time-averaged drag by 5:21%. The leading edge SJ produces small vortices that deflect the shear layer downwards, and decreases the effective angle of attack. This reduces the time-averaged lift by 1:80%, and the time-averaged drag by 1:84%. The trailing edge SJ produces perturbations that add to pressure side vortices without affecting global flow characteristics. The time-averaged lift decreases by 0:47%, and the time-averaged drag increases by 0:20%. For all SJ cases, the aerodynamic performance is much more dependent on changes to the pressure distribution than changes to the skin friction distribution. No proposed