Science.gov

Sample records for adults structural equation

  1. A structural equation model relating physical function, pain, impaired mobility (IM), and falls in older adults.

    PubMed

    Dai, Boyi; Ware, William B; Giuliani, Carol A

    2012-01-01

    The current study used a structural equation model to investigate the interrelationships among physical function, pain, IM, and falls in 511 American older adults. The model included 11 measurement variables (tandem stance, single leg stance, 360° turn, chair stand, arm curl, sit and reach, back scratch, normative score of 6-min walk or 2-min step, timed up and go, pain, and fall) and four latent variables (balance, strength, flexibility, and IM). The final model with the combined sample demonstrated good fit with the participant data (χ(2)(31)=30.0, N=499, p=0.52; Goodness of Fit Index (GFI)=0.99). Balance had a significant and the largest effect on IM (standardized regression weights=-1.05, p<0.001). Strength, endurance, flexibility, and pain had small effects on IM (standardized regression weights<0.2). The findings suggest that balance and mobility testing should be a priority in fall screening and prevention programs. PMID:22766209

  2. Young adults' knowledge of politics: evaluating the role of socio-cognitive variables using structural equations.

    PubMed

    Brussino, Silvina; Medrano, Leonardo; Sorribas, Patricia; Rabbia, Hugo H

    2011-05-01

    The aim of this study was to create an explanatory model that allows analyzing the predictive power of a set of variables related to political knowledge; more specifically, to analyze the relationship between the education level of young adults and the variables, interest in politics and internal political efficacy. We also analyzed the combined relationship between these variables, together with age, and political knowledge. We worked with a sample group of 280 young adults between the ages of 18-30 from the city of Córdoba (Argentina). The data was subjected to a structural equation modelling SEM analysis, which allowed for the corroboration of the following hypotheses: the higher the education level, the more the interest in politics; the higher the education level, the better the perception of internal political efficacy; the higher the education level, the more the political knowledge; the more the interest in politics, the more the political knowledge; and the better the perception of internal political efficacy, the more interest in politics. Moreover, the following hypotheses could not be verified: the older an individual, the more the political knowledge; and the better the perception of internal political efficacy, the more the political knowledge. The model obtained allows for discussion of the explanatory value of these socio-cognitive variables. PMID:21568176

  3. A Structural Equation Modeling Approach to the Study of Stress and Psychological Adjustment in Emerging Adults

    ERIC Educational Resources Information Center

    Asberg, Kia K.; Bowers, Clint; Renk, Kimberly; McKinney, Cliff

    2008-01-01

    Today's society puts constant demands on the time and resources of all individuals, with the resulting stress promoting a decline in psychological adjustment. Emerging adults are not exempt from this experience, with an alarming number reporting excessive levels of stress and stress-related problems. As a result, the present study addresses the…

  4. Regularized Structural Equation Modeling

    PubMed Central

    Jacobucci, Ross; Grimm, Kevin J.; McArdle, John J.

    2016-01-01

    A new method is proposed that extends the use of regularization in both lasso and ridge regression to structural equation models. The method is termed regularized structural equation modeling (RegSEM). RegSEM penalizes specific parameters in structural equation models, with the goal of creating easier to understand and simpler models. Although regularization has gained wide adoption in regression, very little has transferred to models with latent variables. By adding penalties to specific parameters in a structural equation model, researchers have a high level of flexibility in reducing model complexity, overcoming poor fitting models, and the creation of models that are more likely to generalize to new samples. The proposed method was evaluated through a simulation study, two illustrative examples involving a measurement model, and one empirical example involving the structural part of the model to demonstrate RegSEM’s utility. PMID:27398019

  5. Structural Equation Model Trees

    ERIC Educational Resources Information Center

    Brandmaier, Andreas M.; von Oertzen, Timo; McArdle, John J.; Lindenberger, Ulman

    2013-01-01

    In the behavioral and social sciences, structural equation models (SEMs) have become widely accepted as a modeling tool for the relation between latent and observed variables. SEMs can be seen as a unification of several multivariate analysis techniques. SEM Trees combine the strengths of SEMs and the decision tree paradigm by building tree…

  6. Structural Equation Model Trees

    PubMed Central

    Brandmaier, Andreas M.; von Oertzen, Timo; McArdle, John J.; Lindenberger, Ulman

    2015-01-01

    In the behavioral and social sciences, structural equation models (SEMs) have become widely accepted as a modeling tool for the relation between latent and observed variables. SEMs can be seen as a unification of several multivariate analysis techniques. SEM Trees combine the strengths of SEMs and the decision tree paradigm by building tree structures that separate a data set recursively into subsets with significantly different parameter estimates in a SEM. SEM Trees provide means for finding covariates and covariate interactions that predict differences in structural parameters in observed as well as in latent space and facilitate theory-guided exploration of empirical data. We describe the methodology, discuss theoretical and practical implications, and demonstrate applications to a factor model and a linear growth curve model. PMID:22984789

  7. Adult attention deficit hyperactivity disorder symptoms and five-factor model traits in a clinical sample: a structural equation modeling approach.

    PubMed

    Knouse, Laura E; Traeger, Lara; O'Cleirigh, Conall; Safren, Steven A

    2013-10-01

    Relationships among attention deficit hyperactivity disorder (ADHD) symptoms and adult personality traits have not been examined in larger clinically diagnosed samples. We collected multisource ADHD symptom and self-report NEO Five-Factor Inventory (Costa and McCrae [Odessa, FL: Psychological Assessment Resources, Inc, 1992) data from 117 adults with ADHD and tested symptom-trait associations using structural equation modeling. The final model fit the data. Inattention was positively associated with neuroticism and negatively associated with conscientiousness. On the basis of ADHD expression in adulthood, hyperactivity and impulsivity were estimated as separate constructs and showed differential relationships to extraversion and agreeableness. A significant positive relationship between hyperactivity and conscientiousness arose in the context of other pathways. ADHD symptoms are reliably associated with personality traits, suggesting a complex interplay across development that warrants prospective study into adulthood. PMID:24080671

  8. Generalized Multilevel Structural Equation Modeling

    ERIC Educational Resources Information Center

    Rabe-Hesketh, Sophia; Skrondal, Anders; Pickles, Andrew

    2004-01-01

    A unifying framework for generalized multilevel structural equation modeling is introduced. The models in the framework, called generalized linear latent and mixed models (GLLAMM), combine features of generalized linear mixed models (GLMM) and structural equation models (SEM) and consist of a response model and a structural model for the latent…

  9. The Designing of CALM (Computer Anxiety and Learning Measure): Validation of a Multidimensional Measure of Anxiety and Cognitions Relating to Adult Learning of Computing Skills Using Structural Equation Modeling.

    ERIC Educational Resources Information Center

    McInerney, Valentina; Marsh, Herbert W.; McInerney, Dennis M.

    This paper discusses the process through which a powerful multidimensional measure of affect and cognition in relation to adult learning of computing skills was derived from its early theoretical stages to its validation using structural equation modeling. The discussion emphasizes the importance of ensuring a strong substantive base from which to…

  10. Helicobacter pylori Seropositivity’s Association with Markers of Iron, 1-Carbon Metabolism, and Antioxidant Status among US Adults: A Structural Equations Modeling Approach

    PubMed Central

    Beydoun, May A.; Dore, Greg A.; Canas, Jose A.; Beydoun, Hind A.; Zonderman, Alan B.

    2015-01-01

    Objectives We tested a model in which Helicobacter pylori seropositivity (Hps) predicted iron status, which in turn acted as a predictor for markers of 1-C metabolism that were then allowed to predict antioxidant status. Methods National Health and Nutrition Examination Surveys (NHANES 1999–2000) cross-sectional data among adults aged 20–85 y were analyzed (n = 3,055). Markers of Hps, iron status (serum ferritin and transferrin saturation (TS)); 1-C metabolism (serum folate (FOLserum), B-12, total homocysteine (tHcy), methylmalonic acid (MMA)) and antioxidant status (vitamins A and E) were entered into a structural equations model (SEM). Results Predictors of Hps included older age, lower education and income, racial/ethnic groups (lowest among Non-Hispanic Whites), and lifetime cigarette smoking. SEM modeling indicated that Hps had a direct inverse relationship with iron status (combining serum ferritin and TS) which in turn was positively related to 1-C metabolites (higher serum folate, B-12 or lower tHcy/MMA) that were positively associated with antioxidant status (combining serum vitamins A and E). Another pathway that was found bypassed 1-C metabolites (Hps → Iron_st → Antiox). The sum of all indirect effects from Hps combining both pathways and the other indirect pathways in the model (Hps → Iron_st → OneCarbon; Hps →OneCarbon →Antiox) was estimated at β = -0.006±0.003, p<0.05. Conclusions In sum, of the total effect of H. pylori seropositivity on antioxidant status, two significant indirect pathways through Iron status and 1-Carbon metabolites were found. Randomized controlled trials should be conducted to uncover the concomitant causal effect of H. pylori eradication on improving iron status, folate, B-12 and antioxidant status among H. pylori seropositive individuals. PMID:25815731

  11. On a Equation in Finite Algebraically Structures

    ERIC Educational Resources Information Center

    Valcan, Dumitru

    2013-01-01

    Solving equations in finite algebraically structures (semigroups with identity, groups, rings or fields) many times is not easy. Even the professionals can have trouble in such cases. Therefore, in this paper we proposed to solve in the various finite groups or fields, a binomial equation of the form (1). We specify that this equation has been…

  12. The Specific Analysis of Structural Equation Models

    ERIC Educational Resources Information Center

    McDonald, Roderick P.

    2004-01-01

    Conventional structural equation modeling fits a covariance structure implied by the equations of the model. This treatment of the model often gives misleading results because overall goodness of fit tests do not focus on the specific constraints implied by the model. An alternative treatment arising from Pearl's directed acyclic graph theory…

  13. Systems of fuzzy equations in structural mechanics

    NASA Astrophysics Data System (ADS)

    Skalna, Iwona; Rama Rao, M. V.; Pownuk, Andrzej

    2008-08-01

    Systems of linear and nonlinear equations with fuzzy parameters are relevant to many practical problems arising in structure mechanics, electrical engineering, finance, economics and physics. In this paper three methods for solving such equations are discussed: method for outer interval solution of systems of linear equations depending linearly on interval parameters, fuzzy finite element method proposed by Rama Rao and sensitivity analysis method. The performance and advantages of presented methods are described with illustrative examples. Extended version of the present paper can be downloaded from the web page of the UTEP [I. Skalna, M.V. Rama Rao, A. Pownuk, Systems of fuzzy equations in structural mechanics, The University of Texas at El Paso, Department of Mathematical Sciences Research Reports Series, , Texas Research Report No. 2007-01, 2007].

  14. Multiplicity Control in Structural Equation Modeling

    ERIC Educational Resources Information Center

    Cribbie, Robert A.

    2007-01-01

    Researchers conducting structural equation modeling analyses rarely, if ever, control for the inflated probability of Type I errors when evaluating the statistical significance of multiple parameters in a model. In this study, the Type I error control, power and true model rates of famsilywise and false discovery rate controlling procedures were…

  15. Structural Equation Modeling in Rehabilitation Counseling Research

    ERIC Educational Resources Information Center

    Chan, Fong; Lee, Gloria K.; Lee, Eun-Jeong; Kubota, Coleen; Allen, Chase A.

    2007-01-01

    Structural equation modeling (SEM) has become increasingly popular in counseling, psychology, and rehabilitation research. The purpose of this article is to provide an overview of the basic concepts and applications of SEM in rehabilitation counseling research using the AMOS statistical software program.

  16. A Brief Guide to Structural Equation Modeling

    ERIC Educational Resources Information Center

    Weston, Rebecca; Gore, Paul A., Jr.

    2006-01-01

    To complement recent articles in this journal on structural equation modeling (SEM) practice and principles by Martens and by Quintana and Maxwell, respectively, the authors offer a consumer's guide to SEM. Using an example derived from theory and research on vocational psychology, the authors outline six steps in SEM: model specification,…

  17. Causality, Confirmation, Credulity, and Structural Equation Modeling.

    ERIC Educational Resources Information Center

    Biddle, Bruce J.; Marlin, Marjorie M.

    1987-01-01

    Defines structural equation modeling (SEM) and points out its relation to other more familiar data-analytic techniques, as well as some of the potentials and pitfalls of SEM in the analysis of developmental data. Discussion focuses on causal modeling, path diagrams, ordinary least-squares regression analysis, and powerful methods for model…

  18. Mediation from Multilevel to Structural Equation Modeling

    PubMed Central

    MacKinnon, David P.; Valente, Matthew J.

    2016-01-01

    Background/Aims The purpose of this article is to outline multilevel structural equation modeling (MSEM) for mediation analysis of longitudinal data. The introduction of mediating variables can improve experimental and nonexperimental studies of child growth in several ways as discussed throughout this article. Single-mediator individual-level and multilevel mediation models illustrate several current issues in the estimation of mediation with longitudinal data. The strengths of incorporating structural equation modeling (SEM) with multilevel mediation modeling are described. Summary and Key Messages Longitudinal mediation models are pervasive in many areas of research including child growth. Longitudinal mediation models are ideally modeled as repeated measurements clustered within individuals. Further, the combination of MSEM and SEM provides an ideal approach for several reasons, including the ability to assess effects at different levels of analysis, incorporation of measurement error and possible random effects that vary across individuals. PMID:25413658

  19. Model Comparison of Bayesian Semiparametric and Parametric Structural Equation Models

    ERIC Educational Resources Information Center

    Song, Xin-Yuan; Xia, Ye-Mao; Pan, Jun-Hao; Lee, Sik-Yum

    2011-01-01

    Structural equation models have wide applications. One of the most important issues in analyzing structural equation models is model comparison. This article proposes a Bayesian model comparison statistic, namely the "L[subscript nu]"-measure for both semiparametric and parametric structural equation models. For illustration purposes, we consider…

  20. AN ATMOSPHERIC STRUCTURE EQUATION FOR GRAIN GROWTH

    SciTech Connect

    Ormel, C.W.

    2014-07-01

    We present a method to include the evolution of the grain size and grain opacity κ{sub gr} in the equations describing the structure of protoplanetary atmospheres. The key assumption of this method is that a single grain size dominates the grain size distribution at any height r. In addition to following grain growth, the method accounts for mass deposition by planetesimals and grain porosity. We illustrate this method by computation of a simplified atmosphere structure model. In agreement with previous works, grain coagulation is seen to be very efficient. The opacity drops to values much below the often-used ''interstellar medium opacities'' (∼1 cm{sup 2} g{sup –1}) and the atmosphere structure profiles for temperature and density resemble that of the grain-free case. Deposition of planetesimals in the radiative part of the atmosphere hardly influences this outcome as the added surface is quickly coagulated away. We observe a modest dependence on the internal structure (porosity), but show that filling factors cannot become too large because of compression by gas drag.

  1. Structural equation modeling: strengths, limitations, and misconceptions.

    PubMed

    Tomarken, Andrew J; Waller, Niels G

    2005-01-01

    Because structural equation modeling (SEM) has become a very popular data-analytic technique, it is important for clinical scientists to have a balanced perception of its strengths and limitations. We review several strengths of SEM, with a particular focus on recent innovations (e.g., latent growth modeling, multilevel SEM models, and approaches for dealing with missing data and with violations of normality assumptions) that underscore how SEM has become a broad data-analytic framework with flexible and unique capabilities. We also consider several limitations of SEM and some misconceptions that it tends to elicit. Major themes emphasized are the problem of omitted variables, the importance of lower-order model components, potential limitations of models judged to be well fitting, the inaccuracy of some commonly used rules of thumb, and the importance of study design. Throughout, we offer recommendations for the conduct of SEM analyses and the reporting of results. PMID:17716081

  2. String gravitational equations with Hermitian structure

    NASA Astrophysics Data System (ADS)

    Naderi, F.; Rezaei-Aghdam, A.; Darabi, F.

    2016-02-01

    We consider a string model at one-loop related to a σ-model whose antisymmetric tensor field is constructed as complex structure on the background manifold, especially on a manifold R × N where N is a complex manifold. As an example, we consider a homogeneous anisotropic (1 + 4)-dimensional σ-model where space part of the background is a four-dimensional complex manifold. By solving the related one-loop β-functions, we obtain a static solution so that by reduction of this solution to (1 + 3)-dimension, we obtain a static solution of Einstein equation where the matter sector is effectively interpreted as an inhomogeneous, anisotropic and barotropic matter satisfying all the energy conditions. Finally, the T-dual background of the solution is investigated and it is shown that the duality transformation and reduction processes commute with each other.

  3. Structuring an Adult Learning Environment.

    ERIC Educational Resources Information Center

    Frankel, Alan D.; Lindsey, William L.

    Mercy College in New York has devised a program that seeks to meet the special needs of returning adult students. To ease the restraints on the adult student's time and travel needs, the college holds classes in branches and extension centers throughout the urban area. It also offers eight-week courses that carry the same contact time requirements…

  4. Integrable systems of partial differential equations determined by structure equations and Lax pair

    NASA Astrophysics Data System (ADS)

    Bracken, Paul

    2010-01-01

    It is shown how a system of evolution equations can be developed both from the structure equations of a submanifold embedded in three-space as well as from a matrix SO(6) Lax pair. The two systems obtained this way correspond exactly when a constraint equation is selected and imposed on the system of equations. This allows for the possibility of selecting the coefficients in the second fundamental form in a general way.

  5. Exploratory structural equation modeling of personality data.

    PubMed

    Booth, Tom; Hughes, David J

    2014-06-01

    The current article compares the use of exploratory structural equation modeling (ESEM) as an alternative to confirmatory factor analytic (CFA) models in personality research. We compare model fit, factor distinctiveness, and criterion associations of factors derived from ESEM and CFA models. In Sample 1 (n = 336) participants completed the NEO-FFI, the Trait Emotional Intelligence Questionnaire-Short Form, and the Creative Domains Questionnaire. In Sample 2 (n = 425) participants completed the Big Five Inventory and the depression and anxiety scales of the General Health Questionnaire. ESEM models provided better fit than CFA models, but ESEM solutions did not uniformly meet cutoff criteria for model fit. Factor scores derived from ESEM and CFA models correlated highly (.91 to .99), suggesting the additional factor loadings within the ESEM model add little in defining latent factor content. Lastly, criterion associations of each personality factor in CFA and ESEM models were near identical in both inventories. We provide an example of how ESEM and CFA might be used together in improving personality assessment. PMID:24682748

  6. Structural Determinants of Publicly Subsidized Adult Education.

    ERIC Educational Resources Information Center

    Nordhaug, Odd

    1990-01-01

    Data on the amount of adult education activity were collected from 454 Norwegian municipalities. Variables were geographic centrality, population density, commuting status, educational resources, municipal finances, and municipal subsidies for adult education. Material and population structures had more effect on activity level than did economic…

  7. Model Specification Searches in Structural Equation Modeling Using Tabu Search.

    ERIC Educational Resources Information Center

    Marcoulides, George A.; Drezner, Zvi; Schumacker, Randall E.

    1998-01-01

    Introduces an alternative structural equation modeling (SEM) specification search approach based on the Tabu search procedure. Using data with known structure, the procedure is illustrated, and its capabilities for specification searches in SEM are demonstrated. (Author/SLD)

  8. Two Rules of Identification for Structural Equation Models

    ERIC Educational Resources Information Center

    Bollen, Kenneth A.; Davis, Walter R.

    2009-01-01

    Identification of structural equation models remains a challenge to many researchers. Although empirical tests of identification are readily available in structural equation modeling software, these examine local identification and rely on sample estimates of parameters. Rules of identification are available, but do not include all models…

  9. Fitting ARMA Time Series by Structural Equation Models.

    ERIC Educational Resources Information Center

    van Buuren, Stef

    1997-01-01

    This paper outlines how the stationary ARMA (p,q) model (G. Box and G. Jenkins, 1976) can be specified as a structural equation model. Maximum likelihood estimates for the parameters in the ARMA model can be obtained by software for fitting structural equation models. The method is applied to three problem types. (SLD)

  10. A Structural Equation Modeling Analysis of Influences on Juvenile Delinquency

    ERIC Educational Resources Information Center

    Barrett, David E.; Katsiyannis, Antonis; Zhang, Dalun; Zhang, Dake

    2014-01-01

    This study examined influences on delinquency and recidivism using structural equation modeling. The sample comprised 199,204 individuals: 99,602 youth whose cases had been processed by the South Carolina Department of Juvenile Justice and a matched control group of 99,602 youth without juvenile records. Structural equation modeling for the…

  11. Sensitivity of rocky planet structures to the equation of state

    SciTech Connect

    Swift, D C

    2009-06-10

    Structures were calculated for Mercury, Venus, Earth, the Moon, and Mars, using a core-mantle model and adjusting the core radius to reproduce the observed mass and diameter of each body. Structures were calculated using Fe and basalt equations of state of different degrees of sophistication for the core and mantle. The choice of equation of state had a significant effect on the inferred structure. For each structure, the moment of inertia ratio was calculated and compared with observed values. Linear Grueneisen equations of state fitted to limited portions of shock data reproduced the observed moments of inertia significantly better than did more detailed equations of state incorporating phase transitions, presumably reflecting the actual compositions of the bodies. The linear Grueneisen equations of state and corresponding structures seem however to be a reasonable starting point for comparative simulations of large-scale astrophysical impacts.

  12. Surfaces specified by integrable systems of partial differential equations determined by structure equations and Lax pair

    NASA Astrophysics Data System (ADS)

    Bracken, Paul

    2010-04-01

    A system of evolution equations can be developed from the structure equations for a submanifold embedded in a three-dimensional space. It is seen how these same equations can be obtained from a generalized matrix Lax pair provided a single constraint equation is imposed. This can be done in Euclidean space as well as in Minkowski space. The integrable systems which result from this process can be thought of as generalizing the SO(3) and SO(2,1) Lax pairs which have been studied previously.

  13. Hamiltonian structures for the Ostrovsky-Vakhnenko equation

    NASA Astrophysics Data System (ADS)

    Brunelli, J. C.; Sakovich, S.

    2013-01-01

    We obtain a bi-Hamiltonian formulation for the Ostrovsky-Vakhnenko (OV) equation using its higher order symmetry and a new transformation to the Caudrey-Dodd-Gibbon-Sawada-Kotera equation. Central to this derivation is the relation between Hamiltonian structures when dependent and independent variables are transformed.

  14. The relativistic equations of stellar structure and evolution

    NASA Technical Reports Server (NTRS)

    Thorne, K. S.

    1977-01-01

    The general-relativistic equations of stellar structure and evolution are reformulated in a notation which makes easy contact with Newtonian theory. Also, a general-relativistic version of the mixing-length formalism for convection is presented.

  15. USING STRUCTURAL EQUATION MODELING TO INVESTIGATE RELATIONSHIPS AMONG ECOLOGICAL VARIABLES

    EPA Science Inventory

    This paper gives an introductory account of Structural Equation Modeling (SEM) and demonstrates its application using LISREL< with a model utilizing environmental data. Using nine EMAP data variables, we analyzed their correlation matrix with an SEM model. The model characterized...

  16. Case Residuals in Structural Equation Modeling

    ERIC Educational Resources Information Center

    Cardinale, John

    2011-01-01

    From the beginning, lead methodologists in psychometrics and quantitative psychology have been well aware of the problems of fitting structural and confirmatory factor models. The question we approach in our research is how to best detect this misfit and how to identify specific sources of misfit by scrutinizing the data at the case level. Since…

  17. Computation of Neutron Star Structure Using Modern Equation of State

    NASA Astrophysics Data System (ADS)

    Bordbar, G. H.; Hayati, M.

    Using the modern equations of state derived from microscopic calculations, we have calculated the neutron star structure. For the neutron star, we have obtained a minimum mass about 0.1 M⊙ which is nearly independent of the equation of state, and a maximum mass between 1.47 M⊙ and 1.98 M⊙ which is strongly dependent on the equation of state. It is shown that among the equations of state of neutron star matter which we have used, the stiffest one leads to higher maximum mass and radius and lower central density. It is seen that the given maximum mass for the Reid-93 equation of state shows a good consistency with the accurate observations of radio pulsars. We have indicated that the thickness of neutron star crust is very small compared to the predicted neutron star radius.

  18. Structural Equation Modelling: A Primer for Music Education Researchers

    ERIC Educational Resources Information Center

    Teo, Timothy

    2010-01-01

    Structural equation modelling (SEM) is a method for analysis of multivariate data from both non-experimental and experimental research. The method combines a structural model linking latent variables and a measurement model linking observed variables with latent variables. Its use in social science and educational research has grown since the…

  19. Bayesian Semiparametric Structural Equation Models with Latent Variables

    ERIC Educational Resources Information Center

    Yang, Mingan; Dunson, David B.

    2010-01-01

    Structural equation models (SEMs) with latent variables are widely useful for sparse covariance structure modeling and for inferring relationships among latent variables. Bayesian SEMs are appealing in allowing for the incorporation of prior information and in providing exact posterior distributions of unknowns, including the latent variables. In…

  20. Paraconformal structures, ordinary differential equations and totally geodesic manifolds

    NASA Astrophysics Data System (ADS)

    Kryński, Wojciech

    2016-05-01

    We construct point invariants of ordinary differential equations of arbitrary order that generalise the Tresse and Cartan invariants of equations of order two and three, respectively. The vanishing of the invariants is equivalent to the existence of a totally geodesic paraconformal structure which consists of a paraconformal structure, an adapted GL(2 , R) -connection and a two-parameter family of totally geodesic hypersurfaces on the solution space. The structures coincide with the projective structures in dimension 2 and with the Einstein-Weyl structures of Lorentzian signature in dimension 3. We show that the totally geodesic paraconformal structures in higher dimensions can be described by a natural analogue of the Hitchin twistor construction. We present a general example of Veronese webs that generalise the hyper-CR Einstein-Weyl structures in dimension 3. The Veronese webs are described by a hierarchy of integrable systems.

  1. On third Poisson structure of KdV equation

    SciTech Connect

    Gorsky, A.; Marshakov, A.; Orlov, A.

    1995-12-01

    The third Poisson structure of the KdV equation in terms of canonical {open_quote}free fields{close_quote} and the reduced WZNW model is discussed. We prove that it is {open_quotes}diagonalized{close_quotes} in the Lagrange variables which were used before in the formulation of 2d gravity. We propose a quantum path integral for the KdV equation based on this representation.

  2. A Structural Equation Model of Expertise in College Physics

    ERIC Educational Resources Information Center

    Taasoobshirazi, Gita; Carr, Martha

    2009-01-01

    A model of expertise in physics was tested on a sample of 374 college students in 2 different level physics courses. Structural equation modeling was used to test hypothesized relationships among variables linked to expert performance in physics including strategy use, pictorial representation, categorization skills, and motivation, and these…

  3. The relativistic equations of stellar structure and evolution

    NASA Technical Reports Server (NTRS)

    Thorne, K. S.

    1975-01-01

    The general relativistic equations of stellar structure and evolution are reformulated in a notation which makes easy contact with Newtonian theory. A general relativistic version of the mixing-length formalism for convection is presented. It is argued that in work on spherical systems, general relativity theorists have identified the wrong quantity as total mass-energy inside radius r.

  4. Analyzing Mixed-Dyadic Data Using Structural Equation Models

    ERIC Educational Resources Information Center

    Peugh, James L.; DiLillo, David; Panuzio, Jillian

    2013-01-01

    Mixed-dyadic data, collected from distinguishable (nonexchangeable) or indistinguishable (exchangeable) dyads, require statistical analysis techniques that model the variation within dyads and between dyads appropriately. The purpose of this article is to provide a tutorial for performing structural equation modeling analyses of cross-sectional…

  5. Gender Differences in Explaining Grades Using Structural Equation Modeling

    ERIC Educational Resources Information Center

    Ruban, Lilia M.; McCoach, D. Betsy

    2005-01-01

    This study examined the differential impacts of SAT scores and high school rank, college academic level, motivational variables, and self-regulatory variables in explaining variance in the academic achievement of male and female collegians using structural equation modeling and multiple groups analyses. Significantly, in light of earlier research,…

  6. Structural Equation Modeling Reporting Practices for Language Assessment

    ERIC Educational Resources Information Center

    Ockey, Gary J.; Choi, Ikkyu

    2015-01-01

    Studies that use structural equation modeling (SEM) techniques are increasingly encountered in the language assessment literature. This popularity has created the need for a set of guidelines that can indicate what should be included in a research report and make it possible for research consumers to judge the appropriateness of the…

  7. Sensitivity Analysis in Structural Equation Models: Cases and Their Influence

    ERIC Educational Resources Information Center

    Pek, Jolynn; MacCallum, Robert C.

    2011-01-01

    The detection of outliers and influential observations is routine practice in linear regression. Despite ongoing extensions and development of case diagnostics in structural equation models (SEM), their application has received limited attention and understanding in practice. The use of case diagnostics informs analysts of the uncertainty of model…

  8. Testing Structural Equation Models or Detection of Misspecifications?

    ERIC Educational Resources Information Center

    Saris, Willem E.; Satorra, Albert; van der Veld, William M.

    2009-01-01

    Assessing the correctness of a structural equation model is essential to avoid drawing incorrect conclusions from empirical research. In the past, the chi-square test was recommended for assessing the correctness of the model but this test has been criticized because of its sensitivity to sample size. As a reaction, an abundance of fit indexes…

  9. Multiplicity Control in Structural Equation Modeling: Incorporating Parameter Dependencies

    ERIC Educational Resources Information Center

    Smith, Carrie E.; Cribbie, Robert A.

    2013-01-01

    When structural equation modeling (SEM) analyses are conducted, significance tests for all important model relationships (parameters including factor loadings, covariances, etc.) are typically conducted at a specified nominal Type I error rate ([alpha]). Despite the fact that many significance tests are often conducted in SEM, rarely is…

  10. Implementing Restricted Maximum Likelihood Estimation in Structural Equation Models

    ERIC Educational Resources Information Center

    Cheung, Mike W.-L.

    2013-01-01

    Structural equation modeling (SEM) is now a generic modeling framework for many multivariate techniques applied in the social and behavioral sciences. Many statistical models can be considered either as special cases of SEM or as part of the latent variable modeling framework. One popular extension is the use of SEM to conduct linear mixed-effects…

  11. A Note on Structural Equation Modeling Estimates of Reliability

    ERIC Educational Resources Information Center

    Yang, Yanyun; Green, Samuel B.

    2010-01-01

    Reliability can be estimated using structural equation modeling (SEM). Two potential problems with this approach are that estimates may be unstable with small sample sizes and biased with misspecified models. A Monte Carlo study was conducted to investigate the quality of SEM estimates of reliability by themselves and relative to coefficient…

  12. Introduction to Structural Equation Modeling: Issues and Practical Considerations

    ERIC Educational Resources Information Center

    Lei, Pui-Wa; Wu, Qiong

    2007-01-01

    Structural equation modeling (SEM) is a versatile statistical modeling tool. Its estimation techniques, modeling capacities, and breadth of applications are expanding rapidly. This module introduces some common terminologies. General steps of SEM are discussed along with important considerations in each step. Simple examples are provided to…

  13. Structural Equations and Causal Explanations: Some Challenges for Causal SEM

    ERIC Educational Resources Information Center

    Markus, Keith A.

    2010-01-01

    One common application of structural equation modeling (SEM) involves expressing and empirically investigating causal explanations. Nonetheless, several aspects of causal explanation that have an impact on behavioral science methodology remain poorly understood. It remains unclear whether applications of SEM should attempt to provide complete…

  14. Maximum Likelihood Estimation of Nonlinear Structural Equation Models.

    ERIC Educational Resources Information Center

    Lee, Sik-Yum; Zhu, Hong-Tu

    2002-01-01

    Developed an EM type algorithm for maximum likelihood estimation of a general nonlinear structural equation model in which the E-step is completed by a Metropolis-Hastings algorithm. Illustrated the methodology with results from a simulation study and two real examples using data from previous studies. (SLD)

  15. Model Comparison of Nonlinear Structural Equation Models with Fixed Covariates.

    ERIC Educational Resources Information Center

    Lee, Sik-Yum; Song, Xin-Yuan

    2003-01-01

    Proposed a new nonlinear structural equation model with fixed covariates to deal with some complicated substantive theory and developed a Bayesian path sampling procedure for model comparison. Illustrated the approach with an illustrative example using data from an international study. (SLD)

  16. Local Influence Analysis of Nonlinear Structural Equation Models

    ERIC Educational Resources Information Center

    Lee, Sik-Yum; Tang, Nian-Sheng

    2004-01-01

    By regarding the latent random vectors as hypothetical missing data and based on the conditional expectation of the complete-data log-likelihood function in the EM algorithm, we investigate assessment of local influence of various perturbation schemes in a nonlinear structural equation model. The basic building blocks of local influence analysis…

  17. The Use of Structural Equation Modeling in Counseling Psychology Research

    ERIC Educational Resources Information Center

    Martens, Matthew P.

    2005-01-01

    Structural equation modeling (SEM) has become increasingly popular for analyzing data in the social sciences, although several broad reviews of psychology journals suggest that many SEM researchers engage in questionable practices when using the technique. The purpose of this study is to review and critique the use of SEM in counseling psychology…

  18. Robust Structural Equation Modeling with Missing Data and Auxiliary Variables

    ERIC Educational Resources Information Center

    Yuan, Ke-Hai; Zhang, Zhiyong

    2012-01-01

    The paper develops a two-stage robust procedure for structural equation modeling (SEM) and an R package "rsem" to facilitate the use of the procedure by applied researchers. In the first stage, M-estimates of the saturated mean vector and covariance matrix of all variables are obtained. Those corresponding to the substantive variables are then…

  19. A Structural Equation Model for Predicting Business Student Performance

    ERIC Educational Resources Information Center

    Pomykalski, James J.; Dion, Paul; Brock, James L.

    2008-01-01

    In this study, the authors developed a structural equation model that accounted for 79% of the variability of a student's final grade point average by using a sample size of 147 students. The model is based on student grades in 4 foundational business courses: introduction to business, macroeconomics, statistics, and using databases. Educators and…

  20. A Bayesian Approach for Analyzing Longitudinal Structural Equation Models

    ERIC Educational Resources Information Center

    Song, Xin-Yuan; Lu, Zhao-Hua; Hser, Yih-Ing; Lee, Sik-Yum

    2011-01-01

    This article considers a Bayesian approach for analyzing a longitudinal 2-level nonlinear structural equation model with covariates, and mixed continuous and ordered categorical variables. The first-level model is formulated for measures taken at each time point nested within individuals for investigating their characteristics that are dynamically…

  1. People Are Variables Too: Multilevel Structural Equations Modeling

    ERIC Educational Resources Information Center

    Mehta, Paras D.; Neale, Michael C.

    2005-01-01

    The article uses confirmatory factor analysis (CFA) as a template to explain didactically multilevel structural equation models (ML-SEM) and to demonstrate the equivalence of general mixed-effects models and ML-SEM. An intuitively appealing graphical representation of complex ML-SEMs is introduced that succinctly describes the underlying model and…

  2. A Structural Equation Model of Conceptual Change in Physics

    ERIC Educational Resources Information Center

    Taasoobshirazi, Gita; Sinatra, Gale M.

    2011-01-01

    A model of conceptual change in physics was tested on introductory-level, college physics students. Structural equation modeling was used to test hypothesized relationships among variables linked to conceptual change in physics including an approach goal orientation, need for cognition, motivation, and course grade. Conceptual change in physics…

  3. Structural Equation Modeling Diagnostics Using R Package Semdiag and EQS

    ERIC Educational Resources Information Center

    Yuan, Ke-Hai; Zhang, Zhiyong

    2012-01-01

    Yuan and Hayashi (2010) introduced 2 scatter plots for model and data diagnostics in structural equation modeling (SEM). However, the generation of the plots requires in-depth understanding of their underlying technical details. This article develops and introduces an R package semdiag for easily drawing the 2 plots. With a model specified in EQS…

  4. Bayesian Data-Model Fit Assessment for Structural Equation Modeling

    ERIC Educational Resources Information Center

    Levy, Roy

    2011-01-01

    Bayesian approaches to modeling are receiving an increasing amount of attention in the areas of model construction and estimation in factor analysis, structural equation modeling (SEM), and related latent variable models. However, model diagnostics and model criticism remain relatively understudied aspects of Bayesian SEM. This article describes…

  5. Latent Growth Curves within Developmental Structural Equation Models.

    ERIC Educational Resources Information Center

    McArdle, J. J.; Epstein, David

    1987-01-01

    Uses structural equation modeling to combine traditional ideas from repeated-measures ANOVA with some traditional ideas from longitudinal factor analysis. The model describes a latent growth curve model that permits the estimation of parameters representing individual and group dynamics. (Author/RH)

  6. Peculiar symmetry structure of some known discrete nonautonomous equations

    NASA Astrophysics Data System (ADS)

    Garifullin, R. N.; Habibullin, I. T.; Yamilov, R. I.

    2015-06-01

    We study the generalized symmetry structure of three known discrete nonautonomous equations. One of them is the semidiscrete dressing chain of Shabat. Two others are completely discrete equations defined on the square lattice. The first one is a discrete analogue of the dressing chain introduced by Levi and Yamilov. The second one is a nonautonomous generalization of the potential discrete KdV equation or, in other words, the H1 equation of the well-known Adler-Bobenko-Suris list. We demonstrate that these equations have generalized symmetries in both directions if and only if their coefficients, depending on the discrete variables, are periodic. The order of the simplest generalized symmetry in at least one direction depends on the period and may be arbitrarily high. We substantiate this picture by some theorems in the case of small periods. In case of an arbitrarily large period, we show that it is possible to construct two hierarchies of generalized symmetries and conservation laws. The same picture should take place in case of any nonautonomous equation of the Adler-Bobenko-Suris list.

  7. Signal processing in the cochlea: The structure equations

    PubMed Central

    2011-01-01

    Background Physical and physiological invariance laws, in particular time invariance and local symmetry, are at the outset of an abstract model. Harmonic analysis and Lie theory are the mathematical prerequisites for its deduction. Results The main result is a linear system of partial differential equations (referred to as the structure equations) that describe the result of signal processing in the cochlea. It is formulated for phase and for the logarithm of the amplitude. The changes of these quantities are the essential physiological observables in the description of signal processing in the auditory pathway. Conclusions The structure equations display in a quantitative way the subtle balance for processing information on the basis of phase versus amplitude. From a mathematical point of view, the linear system of equations is classified as an inhomogeneous - equation. In suitable variables the solutions can be represented as the superposition of a particular solution (determined by the system) and a holomorphic function (determined by the incoming signal). In this way, a global picture of signal processing in the cochlea emerges. PMID:22656650

  8. Shock-wave structure using nonlinear model Boltzmann equations.

    NASA Technical Reports Server (NTRS)

    Segal, B. M.; Ferziger, J. H.

    1972-01-01

    The structure of strong plane shock waves in a perfect monatomic gas was studied using four nonlinear models of the Boltzmann equation. The models involved the use of a simplified collision operator with velocity-independent collision frequency, in place of the complicated Boltzmann collision operator. The models employed were the BGK and ellipsoidal models developed by earlier authors, and the polynomial and trimodal gain function models developed during the work. An exact set of moment equations was derived for the density, velocity, temperature, viscous stress, and heat flux within the shock. This set was reduced to a pair of coupled nonlinear integral equations and solved using specially adapted numerical techniques. A new and simple Gauss-Seidel iteration was developed during the work and found to be as efficient as the best earlier iteration methods.

  9. Annotated bibliography of structural equation modelling: technical work.

    PubMed

    Austin, J T; Wolfle, L M

    1991-05-01

    Researchers must be familiar with a variety of source literature to facilitate the informed use of structural equation modelling. Knowledge can be acquired through the study of an expanding literature found in a diverse set of publishing forums. We propose that structural equation modelling publications can be roughly classified into two groups: (a) technical and (b) substantive applications. Technical materials focus on the procedures rather than substantive conclusions derived from applications. The focus of this article is the former category; included are foundational/major contributions, minor contributions, critical and evaluative reviews, integrations, simulations and computer applications, precursor and historical material, and pedagogical textbooks. After a brief introduction, we annotate 294 articles in the technical category dating back to Sewall Wright (1921). PMID:1873237

  10. Multidisciplinary optimization of controlled space structures with global sensitivity equations

    NASA Technical Reports Server (NTRS)

    Padula, Sharon L.; James, Benjamin B.; Graves, Philip C.; Woodard, Stanley E.

    1991-01-01

    A new method for the preliminary design of controlled space structures is presented. The method coordinates standard finite element structural analysis, multivariable controls, and nonlinear programming codes and allows simultaneous optimization of the structures and control systems of a spacecraft. Global sensitivity equations are a key feature of this method. The preliminary design of a generic geostationary platform is used to demonstrate the multidisciplinary optimization method. Fifteen design variables are used to optimize truss member sizes and feedback gain values. The goal is to reduce the total mass of the structure and the vibration control system while satisfying constraints on vibration decay rate. Incorporating the nonnegligible mass of actuators causes an essential coupling between structural design variables and control design variables. The solution of the demonstration problem is an important step toward a comprehensive preliminary design capability for structures and control systems. Use of global sensitivity equations helps solve optimization problems that have a large number of design variables and a high degree of coupling between disciplines.

  11. Universal structure and universal equations (PDE) for unitary ensembles

    NASA Astrophysics Data System (ADS)

    Rumanov, Igor

    2010-08-01

    Random matrix ensembles with unitary invariance of measure (UE) are described in a unified way using a combination of Tracy-Widom (TW) and Adler-Shiota-van Moerbeke approaches to the derivation of partial differential equations (PDEs) for spectral gap probabilities. First, general three-term recurrence relations for UE restricted to subsets of real line, or, in other words, for functions in the resolvent kernel, are obtained. Using them, simple universal relations between all TW dependent variables and one-dimensional Toda lattice τ-functions are found. A universal system of PDE for UE is derived from previous relations, which leads also to a single independent PDE for spectral gap probability of various UE. Thus, orthogonal function bases and Toda lattice are seen at the core of correspondence of different approaches. Moreover, Toda-AKNS system provides a common structure of PDE for unitary ensembles. Interestingly, this structure can be seen in two very different forms: one arises from orthogonal function-Toda lattice considerations, while the other comes from Schlesinger equations for isomonodromic deformations and their relation to TW equations. The simple example of Gaussian matrices most neatly exposes this structure.

  12. Structure and Calibration of Constitutive Equations for Granular Soils

    NASA Astrophysics Data System (ADS)

    Sawicki, Andrzej; Sławińska, Justyna; Mierczyński, Jacek

    2015-02-01

    The form of incremental constitutive equations for granular soils is discussed for the triaxial configuration. The classical elasto-plastic approach and the semi-empirical model are discussed on the basis of constitutive relations determined directly from experimental data. First, the general structure of elasto-plastic constitutive equations is presented. Then, the structure of semiempirical constitutive equations is described, and a method of calibrating the model is presented. This calibration method is based on a single experiment, performed in the triaxial apparatus, which also involves a partial verification of the model, on an atypical stress path. The model is shown to give reasonable predictions. An important feature of the semi-empirical incremental model is the definition of loading and unloading, which is different from that assumed in elasto-plasticity. This definition distinguishes between spherical and deviatoric loading/unloading. The definition of deviatoric loading/unloading has been subject to some criticism. It was therefore discussed and clarified in this paper on the basis of the experiment presented.

  13. Crystal structure optimisation using an auxiliary equation of state.

    PubMed

    Jackson, Adam J; Skelton, Jonathan M; Hendon, Christopher H; Butler, Keith T; Walsh, Aron

    2015-11-14

    Standard procedures for local crystal-structure optimisation involve numerous energy and force calculations. It is common to calculate an energy-volume curve, fitting an equation of state around the equilibrium cell volume. This is a computationally intensive process, in particular, for low-symmetry crystal structures where each isochoric optimisation involves energy minimisation over many degrees of freedom. Such procedures can be prohibitive for non-local exchange-correlation functionals or other "beyond" density functional theory electronic structure techniques, particularly where analytical gradients are not available. We present a simple approach for efficient optimisation of crystal structures based on a known equation of state. The equilibrium volume can be predicted from one single-point calculation and refined with successive calculations if required. The approach is validated for PbS, PbTe, ZnS, and ZnTe using nine density functionals and applied to the quaternary semiconductor Cu2ZnSnS4 and the magnetic metal-organic framework HKUST-1. PMID:26567640

  14. Crystal structure optimisation using an auxiliary equation of state

    SciTech Connect

    Jackson, Adam J.; Skelton, Jonathan M.; Hendon, Christopher H.; Butler, Keith T.; Walsh, Aron

    2015-11-14

    Standard procedures for local crystal-structure optimisation involve numerous energy and force calculations. It is common to calculate an energy–volume curve, fitting an equation of state around the equilibrium cell volume. This is a computationally intensive process, in particular, for low-symmetry crystal structures where each isochoric optimisation involves energy minimisation over many degrees of freedom. Such procedures can be prohibitive for non-local exchange-correlation functionals or other “beyond” density functional theory electronic structure techniques, particularly where analytical gradients are not available. We present a simple approach for efficient optimisation of crystal structures based on a known equation of state. The equilibrium volume can be predicted from one single-point calculation and refined with successive calculations if required. The approach is validated for PbS, PbTe, ZnS, and ZnTe using nine density functionals and applied to the quaternary semiconductor Cu{sub 2}ZnSnS{sub 4} and the magnetic metal-organic framework HKUST-1.

  15. Crystal structure optimisation using an auxiliary equation of state

    NASA Astrophysics Data System (ADS)

    Jackson, Adam J.; Skelton, Jonathan M.; Hendon, Christopher H.; Butler, Keith T.; Walsh, Aron

    2015-11-01

    Standard procedures for local crystal-structure optimisation involve numerous energy and force calculations. It is common to calculate an energy-volume curve, fitting an equation of state around the equilibrium cell volume. This is a computationally intensive process, in particular, for low-symmetry crystal structures where each isochoric optimisation involves energy minimisation over many degrees of freedom. Such procedures can be prohibitive for non-local exchange-correlation functionals or other "beyond" density functional theory electronic structure techniques, particularly where analytical gradients are not available. We present a simple approach for efficient optimisation of crystal structures based on a known equation of state. The equilibrium volume can be predicted from one single-point calculation and refined with successive calculations if required. The approach is validated for PbS, PbTe, ZnS, and ZnTe using nine density functionals and applied to the quaternary semiconductor Cu2ZnSnS4 and the magnetic metal-organic framework HKUST-1.

  16. Bidirectional relationship between chronic kidney and periodontal disease: a study using structural equation modeling.

    PubMed

    Fisher, Monica A; Taylor, George W; West, Brady T; McCarthy, Ellen T

    2011-02-01

    Periodontal disease is associated with diabetes, heart disease, and chronic kidney disease (CKD), relationships postulated to be due in part to vascular inflammation. A bidirectional relationship between CKD and periodontal disease is plausible, though this relationship has not been previously reported. In this study, we assessed the potential for connections between CKD and periodontal disease, and mediators of these relationships using structural equation models of data from 11,211 adults ≥ 18 years of age who participated in the Third National Health and Nutrition Examination Survey. Multivariable logistic regression models were used to test the hypothesis that periodontal disease was independently associated with CKD. Given the potential that the periodontal disease and CKD relationship may be bidirectional, a two-step analytic approach was used that involved tests for mediation and structural equation models to examine more complex direct and indirect effects of periodontal disease on CKD, and vice versa. In two separate models, periodontal disease (adjusted odds ratio of 1.62), edentulism (adjusted odds ratio of 1.83), and the periodontal disease score were associated with CKD when simultaneously adjusting for 14 other factors. Altogether, three of four structural equation models support the hypothesized relationship. Thus, our analyses support a bidirectional relationship between CKD and periodontal disease, mediated by hypertension and the duration of diabetes. PMID:20927035

  17. Reliability of Scales with General Structure: Point and Interval Estimation Using a Structural Equation Modeling Approach.

    ERIC Educational Resources Information Center

    Raykov, Tenko; Shrout, Patrick E.

    2002-01-01

    Discusses a method for obtaining point and interval estimates of reliability for composites of measures with a general structure. The approach is based on fitting a correspondingly constrained structural equation model and generalizes earlier covariance structure analysis methods for scale reliability estimation with congeneric tests. (SLD)

  18. Structural relaxation in atomic clusters: Master equation dynamics

    NASA Astrophysics Data System (ADS)

    Miller, Mark A.; Doye, Jonathan P. K.; Wales, David J.

    1999-10-01

    The role of the potential energy landscape in determining the relaxation dynamics of model clusters is studied using a master equation. Two types of energy landscape are examined: a single funnel, as exemplified by 13-atom Morse clusters, and the double funnel landscape of the 38-atom Lennard-Jones cluster. Interwell rate constants are calculated using Rice-Ramsperger-Kassel-Marcus theory within the harmonic approximation, but anharmonic model partition functions are also considered. Decreasing the range of the potential in the Morse clusters is shown to hinder relaxation toward the global minimum, and this effect is related to the concomitant changes in the energy landscape. The relaxation modes that emerge from the master equation are interpreted and analyzed to extract interfunnel rate constants for the Lennard-Jones cluster. Since this system is too large for a complete characterization of the energy landscape, the conditions under which the master equation can be applied to a limited database are explored. Connections are made to relaxation processes in proteins and structural glasses.

  19. Structural Equation Modeling: Applications in ecological and evolutionary biology research

    USGS Publications Warehouse

    Pugesek, Bruce H.; von Eye, Alexander; Tomer, Adrian

    2003-01-01

    This book presents an introduction to the methodology of structural equation modeling, illustrates its use, and goes on to argue that it has revolutionary implications for the study of natural systems. A major theme of this book is that we have, up to this point, attempted to study systems primarily using methods (such as the univariate model) that were designed only for considering individual processes. Understanding systems requires the capacity to examine simultaneous influences and responses. Structural equation modeling (SEM) has such capabilities. It also possesses many other traits that add strength to its utility as a means of making scientific progress. In light of the capabilities of SEM, it can be argued that much of ecological theory is currently locked in an immature state that impairs its relevance. It is further argued that the principles of SEM are capable of leading to the development and evaluation of multivariate theories of the sort vitally needed for the conservation of natural systems. Supplementary information can be found at the authors website, http://www.jamesbgrace.com/. • Details why multivariate analyses should be used to study ecological systems • Exposes unappreciated weakness in many current popular analyses • Emphasizes the future methodological developments needed to advance our understanding of ecological systems.

  20. Spectral analysis and structure preserving preconditioners for fractional diffusion equations

    NASA Astrophysics Data System (ADS)

    Donatelli, Marco; Mazza, Mariarosa; Serra-Capizzano, Stefano

    2016-02-01

    Fractional partial order diffusion equations are a generalization of classical partial differential equations, used to model anomalous diffusion phenomena. When using the implicit Euler formula and the shifted Grünwald formula, it has been shown that the related discretizations lead to a linear system whose coefficient matrix has a Toeplitz-like structure. In this paper we focus our attention on the case of variable diffusion coefficients. Under appropriate conditions, we show that the sequence of the coefficient matrices belongs to the Generalized Locally Toeplitz class and we compute the symbol describing its asymptotic eigenvalue/singular value distribution, as the matrix size diverges. We employ the spectral information for analyzing known methods of preconditioned Krylov and multigrid type, with both positive and negative results and with a look forward to the multidimensional setting. We also propose two new tridiagonal structure preserving preconditioners to solve the resulting linear system, with Krylov methods such as CGNR and GMRES. A number of numerical examples show that our proposal is more effective than recently used circulant preconditioners.

  1. A New Look at the Big Five Factor Structure through Exploratory Structural Equation Modeling

    ERIC Educational Resources Information Center

    Marsh, Herbert W.; Ludtke, Oliver; Muthen, Bengt; Asparouhov, Tihomir; Morin, Alexandre J. S.; Trautwein, Ulrich; Nagengast, Benjamin

    2010-01-01

    NEO instruments are widely used to assess Big Five personality factors, but confirmatory factor analyses (CFAs) conducted at the item level do not support their a priori structure due, in part, to the overly restrictive CFA assumptions. We demonstrate that exploratory structural equation modeling (ESEM), an integration of CFA and exploratory…

  2. Incremental shuttle walk test: Reference values and predictive equation for healthy Indian adults

    PubMed Central

    Agarwal, Bela; Shah, Monal; Andhare, Nilesh; Mullerpatan, Rajani

    2016-01-01

    Purpose: Physical inactivity in Indians is leading to an increase in noncommunicable disorders at an early age in life. Early identification and quantification of the lack of physical activity using simple and reliable exercise testing is the need of the hour. The incremental shuttle walk test (ISWT) is an externally paced walk test widely used for the evaluation of exercise capacity. Currently the normative values available for clinical reference are generated from Western populations. Hence, the study was conducted to find normative values for the ISWT in healthy Indian adults (17-75 years). Materials and Methods: A convenience sample of 862 subjects was recruited after ethical approval was obtained. All subjects were divided into groups as per age and gender. For age, the grouping was as follows: Group 1: Young adulthood (17-40 years), group 2: Middle adulthood (40-65 years), and group 3: Old adulthood (>65 years). The ISWT was performed as per standard protocol by Sally Singh. Results: The average distance walked were 709.2m,556.4m and 441.3m in females and 807.9 m, 639.6 m and 478.2 m in males in the three respective age groups. Stepwise regression analysis revealed age and gender as key variables correlating with incremental shuttle walk distance (ISWD). The derived predictive equations for males and females may be given as follows: 740.351 - (5.676 × age) + (99.007 × gender). Conclusion: Reference values were generated for healthy Indian adults. Physiological response to the ISWT was shown to be affected by gender and increasing age. Easily measurable variables explained 68% of the variance seen in the test, making the reference equation a relevant part of the evaluation of the ISWT. PMID:26933305

  3. Bayesian structural equation modeling in sport and exercise psychology.

    PubMed

    Stenling, Andreas; Ivarsson, Andreas; Johnson, Urban; Lindwall, Magnus

    2015-08-01

    Bayesian statistics is on the rise in mainstream psychology, but applications in sport and exercise psychology research are scarce. In this article, the foundations of Bayesian analysis are introduced, and we will illustrate how to apply Bayesian structural equation modeling in a sport and exercise psychology setting. More specifically, we contrasted a confirmatory factor analysis on the Sport Motivation Scale II estimated with the most commonly used estimator, maximum likelihood, and a Bayesian approach with weakly informative priors for cross-loadings and correlated residuals. The results indicated that the model with Bayesian estimation and weakly informative priors provided a good fit to the data, whereas the model estimated with a maximum likelihood estimator did not produce a well-fitting model. The reasons for this discrepancy between maximum likelihood and Bayesian estimation are discussed as well as potential advantages and caveats with the Bayesian approach. PMID:26442771

  4. Malignant Potential of Gastrointestinal Cancers Assessed by Structural Equation Modeling

    PubMed Central

    Onodera, Kei; Takahashi, Hiroaki; Okahara, Satoshi; Kodaira, Junichi; Oohashi, Hirokazu; Isshiki, Hiroyuki; Kawakami, Kentaro; Yamashita, Kentaro; Shinomura, Yasuhisa; Hosokawa, Masao

    2016-01-01

    Background Parameters reported in pathologic reviews have been failing to assess exactly the malignant potential of gastrointestinal cancers. We hypothesized that malignant potential could be defined by common latent variables (hypothesis I), but there are substantial differences in the associations between malignant potential and pathologic parameters according to the origin of gastrointestinal cancers (hypothesis II). We shed light on these issues by structural equation modeling. Materials and Methods We conducted a cross-sectional survey of 217 esophageal, 192 gastric, and 175 colorectal cancer patients who consecutively underwent curative surgery for their pathologic stage I cancers at Keiyukai Sapporo Hospital. Latent variables identified by factor analysis and seven conventional pathologic parameters were introduced in the structural equation modeling analysis. Results Because latent variables were disparate except for their number, 'three' in the examined gastrointestinal cancers, the first hypothesis was rejected. Because configural invariance across gastrointestinal cancers was not approved, the second hypothesis was verified. We could trace the three significant paths on the causal graph from latent variables to lymph node metastasis, which were mediated through depth, lymphatic invasion, and matrilysin expression in esophageal cancer, whereas only one significant path could be traced in both gastric and colorectal cancer. Two of the three latent variables were exogenous in esophageal cancer, whereas one factor was exogenous in the other gastrointestinal cancers. Cancer stemness promoted viability in esophageal cancer, but it was suppressed in others. Conclusion These results reflect the malignant potential of esophageal cancer is higher than that of the other gastrointestinal cancers. Such information might contribute to refining clinical treatments for gastrointestinal cancers. PMID:26889682

  5. Validation of an equation for estimating maximal oxygen consumption of nonexpert adult swimmers

    PubMed Central

    da Costa, Adalberto Veronese; Costa, Manoel da Cunha; de Oliveira, Saulo Fernandes Melo; de Albuquerque, Fabíola Lima; de Sá Pereira Guimarães, Fernando José; Barbosa, Tiago Manuel

    2013-01-01

    Objective To validate an equation to estimate the maximal oxygen consumption (VO2max) of nonexpert adult swimmers. Methods Participants were 22 nonexpert swimmers, male, aged between 18 and 30 years (age: 23.1 ± 3:59 years; body mass: 73.6 ± 7:39 kg; height 176.6 ± 5.53 cm; and body fat percentage: 15.9% ± 4.39%), divided into two subgroups: G1 – eleven swimmers for the VO2max oximetry and modeling of the equation; and G2 – eleven swimmers for application of the equation modeled on G1 and verification of their validation. The test used was the adapted Progressive Swim Test, in which there occurs an increase in the intensity of the swim every two laps. For normality and homogeneity of data, Shapiro-Wilk and Levene tests were used, the descriptive values of the average and standard deviation. The statistical steps were: (1) reliability of the Progressive Swim Test – through the paired t-test, intraclass correlation coefficient (ICC), and the Pearson linear correlation (R) relative to the reproducibility, the coefficient of variation (CV), and standard error measurement (SEM) for the absolute reproducibility; (2) in the model equation to estimate VO2max, a relative VO2 was established, and a stepwise multiple regression model was performed with G1 – so the variables used were analysis of variance regression (AR), coefficient of determination (R2), adjusted coefficient of determination (R2a), standard error of estimate (SEE), and Durbin–Watson (DW); (3) validation of the equation – the results were presented in graphs, where direct (G1) and estimated (G2) VO2max were compared using independent t-test, linear regression (stressing the correlation between groups), and Bland–Altman (the bias agreement of the results). All considered a statistical significance level of P < 0.05. Results On the trustworthiness of the Progressive Swim Test adapted presented as high as observed (R and ICC > 0.80, CV < 10%, and SEM < 2%). In the equation model, VO2max has

  6. Infants' and adults' perception of scale structure.

    PubMed

    Trehub, S E; Schellenberg, E G; Kamenetsky, S B

    1999-08-01

    Adults and 9-month-old infants were required to detect mistuned tones in multitone sequences. When 7-tone versions of a common nursery tune were generated from the Western major scale (unequal scale steps) or from an alternative scale (equal steps), infants detected the mistuned tones more accurately in the unequal-step context than in the equal-step context (Experiment 1). Infants and adults were subsequently tested with 1 of 3 ascending-descending scales (15 tones): (a) a potentially familiar scale (major) with unequal steps, (b) an unfamiliar scale with unequal steps, and (c) an unfamiliar scale with equal steps. Infants detected mistuned tones only in the scales with unequal steps (Experiment 2). Adults performed better on the familiar (major) unequal-step scale and equally poorly on both unfamiliar scales (Experiments 3 and 4). These findings are indicative of an inherent processing bias favoring unequal-step scales. PMID:10464941

  7. Geometric Structures and Field Equations of Dirac Lu Space

    NASA Astrophysics Data System (ADS)

    Ren, Xin-An; Zhang, Li-You

    2008-11-01

    In this paper, a fraktur G-invariant Lorentz metric on the Dirac Lu space is given, and then the geodesic equation is investigated. Finally, we discuss the field equations and find their solutions by the method of separating variables.

  8. The structure of constitutive equations for semiconductor devices

    SciTech Connect

    Buchanan, G.R.; Girrens, S.P.; Bennett, J.G.

    1987-01-01

    The fundamental equations that describe carrier transport in semiconductor materials are developed using the methods of continuum mixture theory and Maxwell's equations for electrodynamics. There are five basic equations that govern the behavior of current flux, electrostatic potential, electrons, and holes. The bahavior of the electrical chemical potentials are introduced and their relation to the current flux is discussed.

  9. Shock wave structure using nonlinear model Boltzmann equations

    NASA Technical Reports Server (NTRS)

    Segal, Ben Maurice

    1971-01-01

    The structure of a strong plane shock wave in a monatomic rarefied perfect gas is one of the simplest problems able to be posed in kinetic theory, and one of the hardest to solve. Its simplicity lies in the absence of solid boundaries, geometrical complications, or internal molecular energy. Its difficulty arises from the great departure of the gas from equilibrium within the shock, which invalidates many of the techniques used successfully elsewhere in kinetic theory. In addition to this theoretical challenge, the modern development of ballistics and hypersonic flight has helped to stimulate extensive theoretical and experimental interest in the shock problem. The experimenters in turn have encountered great difficulties on account of the very small physical dimensions of shocks. In fact, until very recently indeed, any close comparisons of theoretical and experimental shock structure results have been rather unprofitable due to the inadequacies of both theory and experiment. During the last few years this situation has been appreciably improved by development of the Monte Carlo method. This allows idealized 'experiments' to be performed on large computers instead of in wind tunnels, using a known intermolecular force law. The most developed of these methods has been shown to be equivalent theoretically to the Boltzmann equation and to give results which agree extremely closely with measurements of high accuracy. Thus Monte Carlo results not only form the soundest basis for our present theoretical knowledge of shock wave structure, but, for purposes of developing other theories, can also be considered a very valuable experimental resource. However, such results remain very expensive to obtain. In this thesis we develop more economical kinetic theory methods for the approximate prediction of shock structure, and compare our results with those of the Monte Carlo method.

  10. Occupants' satisfaction toward building environmental quality: structural equation modeling approach.

    PubMed

    Kamaruzzaman, Syahrul Nizam; Egbu, C O; Zawawi, Emma Marinie Ahmad; Karim, Saipol Bari Abd; Woon, Chen Jia

    2015-05-01

    It is accepted that occupants who are more satisfied with their workplace's building internal environment are more productive. The main objective of the study was to measure the occupants' level of satisfaction and the perceived importance of the design or refurbishment on office conditions. The study also attempted to determine the factors affecting the occupants' satisfaction with their building or office conditions. Post-occupancy evaluations were conducted using a structured questionnaire developed by the Built Environment Research Group at the University of Manchester, UK. Our questionnaires incorporate 22 factors relating to the internal environment and rate these in terms of "user satisfaction" and "degree of importance." The questions were modified to reflect the specific setting of the study and take into consideration the local conditions and climate in Malaysia. The overall mean satisfaction of the occupants toward their office environment was 5.35. The results were measured by a single item of overall liking of office conditions in general. Occupants were more satisfied with their state of health in the workplace, but they were extremely dissatisfied with the distance away from a window. The factor analysis divided the variables into three groups, namely intrusion, air quality, and office appearance. Structural equation modeling (SEM) was then used to determine which factor had the most significant influence on occupants' satisfaction: appearance. The findings from the study suggest that continuous improvement in aspects of the building's appearance needs to be supported with effective and comprehensive maintenance to sustain the occupants' satisfaction. PMID:25864077

  11. Equation of State of Structured Matter at Finite Temperature

    NASA Astrophysics Data System (ADS)

    Maruyama, T.; Yasutake, N.; Tatsumi, T.

    We investigate the properties of nuclear matter at the first-order phase transitions such as liquid-gas phase transition and hadron-quark phase transition. As a general feature of the first-order phase transitions of matter consisting of many species of charged particles, there appears a mixed phases with geometrical structures called ``pasta'' due to the balance of the Coulomb repulsion and the surface tension between two phases [G.~D.~Ravenhall, C.~J.~Pethick and J.~R.~Wilson, Phys. Rev. Lett. 50 (1983), 2066. M.~Hashimoto, H.~Seki and M.~Yamada, Prog. Theor. Phys. 71 (1984), 320.] The equation of state (EOS) of mixed phase is different from the one obtained by a bulk application of the Gibbs conditions or by the Maxwell construction due to the effects of the non-uniform structure. We show that the charge screening and strong surface tension make the EOS close to that of the Maxwell construction. The thermal effects are elucidated as well as the above finite-size effects.

  12. Bayesian Analysis of Structural Equation Models with Nonlinear Covariates and Latent Variables

    ERIC Educational Resources Information Center

    Song, Xin-Yuan; Lee, Sik-Yum

    2006-01-01

    In this article, we formulate a nonlinear structural equation model (SEM) that can accommodate covariates in the measurement equation and nonlinear terms of covariates and exogenous latent variables in the structural equation. The covariates can come from continuous or discrete distributions. A Bayesian approach is developed to analyze the…

  13. Searching for the full picture: structural equation modeling in alcohol research.

    PubMed

    Schuckit, Marc A; Windle, Michael; Smith, Tom L; Hesselbrock, Victor; Ohannessian, Christine; Averna, Susan; Bauer, Lance; Kramer, John; Bucholz, Kathleen; Sher, Kenneth J

    2006-02-01

    This article summarizes the proceedings of a symposium presented at the 2005 Research Society on Alcoholism meeting in Santa Barbara, California. This symposium begins with a description by Michael Windle of structural equation modeling (SEM), including the assets and liabilities of this approach. Next, Marc Schuckit and Tom Smith demonstrate the application of an SEM approach to understanding the impact of a low level of response to alcohol, using data from both adolescent and adult populations. Victor Hesselbrock and colleagues next review the results when an SEM approach is used in the longitudinal study of externalizing behaviors. This is followed by a description of the application of SEM to an affect-related model as discussed by John Kramer and Kathleen Bucholz. Finally, Kenneth Sher offers thoughts on how to place these findings into perspective. PMID:16441268

  14. Using structural equation modeling to investigate relationships among ecological variables

    USGS Publications Warehouse

    Malaeb, Z.A.; Kevin, Summers J.; Pugesek, B.H.

    2000-01-01

    Structural equation modeling is an advanced multivariate statistical process with which a researcher can construct theoretical concepts, test their measurement reliability, hypothesize and test a theory about their relationships, take into account measurement errors, and consider both direct and indirect effects of variables on one another. Latent variables are theoretical concepts that unite phenomena under a single term, e.g., ecosystem health, environmental condition, and pollution (Bollen, 1989). Latent variables are not measured directly but can be expressed in terms of one or more directly measurable variables called indicators. For some researchers, defining, constructing, and examining the validity of latent variables may be the end task of itself. For others, testing hypothesized relationships of latent variables may be of interest. We analyzed the correlation matrix of eleven environmental variables from the U.S. Environmental Protection Agency's (USEPA) Environmental Monitoring and Assessment Program for Estuaries (EMAP-E) using methods of structural equation modeling. We hypothesized and tested a conceptual model to characterize the interdependencies between four latent variables-sediment contamination, natural variability, biodiversity, and growth potential. In particular, we were interested in measuring the direct, indirect, and total effects of sediment contamination and natural variability on biodiversity and growth potential. The model fit the data well and accounted for 81% of the variability in biodiversity and 69% of the variability in growth potential. It revealed a positive total effect of natural variability on growth potential that otherwise would have been judged negative had we not considered indirect effects. That is, natural variability had a negative direct effect on growth potential of magnitude -0.3251 and a positive indirect effect mediated through biodiversity of magnitude 0.4509, yielding a net positive total effect of 0

  15. Bidirectional Relationship between Chronic Kidney Disease and Periodontal Disease: Structural Equation Modeling

    PubMed Central

    Fisher, Monica A.; Taylor, George W.; West, Brady T.; McCarthy, Ellen T.

    2011-01-01

    Periodontal disease is associated with diabetes, heart disease, and chronic kidney disease (CKD), an effect postulated to be due in part to endovascular inflammation. While a bidirectional relationship between CKD and periodontal disease is plausible, it has not been previously reported in the literature. Over 11 200 adults 18 years or older were identified in the Third National Health and Nutrition Examination Survey. Analyses were conducted in two stages. First, multivariable logistic regression models were fitted to test the hypothesis that periodontal disease was independently associated with CKD. Given the potential that the periodontal disease and CKD relationship may be bidirectional, a two-step analytic approach was used that involved 1) tests for mediation, and 2) structural equation models to examine more complex direct and indirect effects of periodontal disease on CKD, and vice versa. In two separate models periodontal disease (ORAdj =1.62 (95% CI: 1.17-2.26) and edentulism (ORAdj = 1.83 (1.31-2.55) and periodontal disease score (ORAdj = 1.01 (1.01-1.02) were associated with CKD, when simultaneously adjusting for 14 other factors. Three of four structural equation models were most plausible suggesting bidirectional relationships. Collectively, these analyses provide for the first time empirical support for a bidirectional relationship between CKD and periodontal disease, and mediation of that relationship by diabetes duration and hypertension. PMID:20927035

  16. Is racism dead? Comparing (expressive) means and (structural equation) models.

    PubMed

    Leach, C W; Peng, T R; Volckens, J

    2000-09-01

    Much scholarship suggests that racism--belief in out-group inferiority--is unrelated to contemporary attitudes. Purportedly, a new form of racism, one which relies upon a belief in cultural difference, has become a more acceptable basis for such attitudes. The authors argue that an appropriate empirical assessment of racism (both 'old' and 'new') depends upon (1) clear conceptualization and operationalization, and (2) attention to both mean-level expression and explanatory value in structural equation models. This study assessed the endorsement of racism and belief in cultural difference as well as their association with a measure of general attitude in a secondary analysis of parallel representative surveys of attitudes toward different ethnic out-groups in France, The Netherlands, Western Germany and Britain (N = 3242; see Reif & Melich, 1991). For six of the seven out-group targets, racism was strongly related to ethnic majority attitudes, despite low mean-level endorsement. In a pattern consistent with a 'new', indirect racism, the relationship between British racism and attitudes toward Afro-Caribbeans was mediated by belief in cultural difference. PMID:11041013

  17. Applications of Multilevel Structural Equation Modeling to Cross-Cultural Research

    ERIC Educational Resources Information Center

    Cheung, Mike W.-L.; Au, Kevin

    2005-01-01

    Multilevel structural equation modeling (MSEM) has been proposed as an extension to structural equation modeling for analyzing data with nested structure. We have begun to see a few applications in cross-cultural research in which MSEM fits well as the statistical model. However, given that cross-cultural studies can only afford collecting data…

  18. Factors of home dream recall: a structural equation model.

    PubMed

    Schredl, Michael; Wittmann, Lutz; Ciric, Petra; Götz, Simon

    2003-06-01

    Previous research has indicated that personality factors such as openness to experience, creativity, visual memory, attitude toward dreams, and sleep behavior is related to home dream recall frequency (DRF). However, a study investigating all areas simultaneously within one sample in order to determine the percentage of variance explained by all variables and to take intercorrelations between the influencing factors into account has not been performed till now. The present study with 444 participants fills this gap. Using several indicators for each of the variables mentioned above, a structural equation model was tested. Although the model fit was satisfying, the four factors which were significantly related to DRF: personality (openness to experience, thin boundaries, absorption), creativity, nocturnal awakenings, and attitude toward dreams, explained only 8.4% of the total variance. As this value is considerably lower than those of studies investigating a single influencing factor and using similar measurement instruments in similar samples, one might speculate about possible expectancy effects in these previous studies, an effect which has been demonstrated for DRF in the laboratory setting. In addition, the small percentage of explained variance of each single factors (<3%) may indicate that other, in this study unmeasured, variables such as sleep duration (state aspect), introspection, and cognitive functioning immediately upon awakening (sleep inertia) show substantial covariance with the interindividual differences in DRF. Future studies should focus on longitudinal aspects in order to differentiate between state versus trait factors (although methodologic issues, e.g. the effect of the measurement technique on DRF itself, have to be clarified) and investigate additional variables which might be associated with DRF (see above). PMID:12753350

  19. Habitat fragmentation and reproductive success: a structural equation modelling approach.

    PubMed

    Le Tortorec, Eric; Helle, Samuli; Käyhkö, Niina; Suorsa, Petri; Huhta, Esa; Hakkarainen, Harri

    2013-09-01

    1. There is great interest on the effects of habitat fragmentation, whereby habitat is lost and the spatial configuration of remaining habitat patches is altered, on individual breeding performance. However, we still lack consensus of how this important process affects reproductive success, and whether its effects are mainly due to reduced fecundity or nestling survival. 2. The main reason for this may be the way that habitat fragmentation has been previously modelled. Studies have treated habitat loss and altered spatial configuration as two independent processes instead of as one hierarchical and interdependent process, and therefore have not been able to consider the relative direct and indirect effects of habitat loss and altered spatial configuration. 3. We investigated how habitat (i.e. old forest) fragmentation, caused by intense forest harvesting at the territory and landscape scales, is associated with the number of fledged offspring of an area-sensitive passerine, the Eurasian treecreeper (Certhia familiaris). We used structural equation modelling (SEM) to examine the complex hierarchical associations between habitat loss and altered spatial configuration on the number of fledged offspring, by controlling for individual condition and weather conditions during incubation. 4. Against generally held expectations, treecreeper reproductive success did not show a significant association with habitat fragmentation measured at the territory scale. Instead, our analyses suggested that an increasing amount of habitat at the landscape scale caused a significant increase in nest predation rates, leading to reduced reproductive success. This effect operated directly on nest predation rates, instead of acting indirectly through altered spatial configuration. 5. Because habitat amount and configuration are inherently strongly collinear, particularly when multiple scales are considered, our study demonstrates the usefulness of a SEM approach for hierarchical partitioning

  20. Stress and Resilience in Functional Somatic Syndromes – A Structural Equation Modeling Approach

    PubMed Central

    Fischer, Susanne; Lemmer, Gunnar; Gollwitzer, Mario; Nater, Urs M.

    2014-01-01

    Background Stress has been suggested to play a role in the development and perpetuation of functional somatic syndromes. The mechanisms of how this might occur are not clear. Purpose We propose a multi-dimensional stress model which posits that childhood trauma increases adult stress reactivity (i.e., an individual's tendency to respond strongly to stressors) and reduces resilience (e.g., the belief in one's competence). This in turn facilitates the manifestation of functional somatic syndromes via chronic stress. We tested this model cross-sectionally and prospectively. Methods Young adults participated in a web survey at two time points. Structural equation modeling was used to test our model. The final sample consisted of 3′054 participants, and 429 of these participated in the follow-up survey. Results Our proposed model fit the data in the cross-sectional (χ2(21)  = 48.808, p<.001, CFI  = .995, TLI  = .992, RMSEA  = .021, 90% CI [.013.029]) and prospective analyses (χ2(21)  = 32.675, p<.05, CFI  = .982, TLI  = .969, RMSEA  = .036, 90% CI [.001.059]). Discussion Our findings have several clinical implications, suggesting a role for stress management training in the prevention and treatment of functional somatic syndromes. PMID:25396736

  1. Dynamic Spectral Structure Specifies Vowels for Adults and Children

    PubMed Central

    Nittrouer, Susan; Lowenstein, Joanna H.

    2014-01-01

    The dynamic specification account of vowel recognition suggests that formant movement between vowel targets and consonant margins is used by listeners to recognize vowels. This study tested that account by measuring contributions to vowel recognition of dynamic (i.e., time-varying) spectral structure and coarticulatory effects on stationary structure. Adults and children (four-and seven-year-olds) were tested with three kinds of consonant-vowel-consonant syllables: (1) unprocessed; (2) sine waves that preserved both stationary coarticulated and dynamic spectral structure; and (3) vocoded signals that primarily preserved that stationary, but not dynamic structure. Sections of two lengths were removed from syllable middles: (1) half the vocalic portion; and (2) all but the first and last three pitch periods. Adults performed accurately with unprocessed and sine-wave signals, as long as half the syllable remained; their recognition was poorer for vocoded signals, but above chance. Seven-year-olds performed more poorly than adults with both sorts of processed signals, but disproportionately worse with vocoded than sine-wave signals. Most four-year-olds were unable to recognize vowels at all with vocoded signals. Conclusions were that both dynamic and stationary coarticulated structures support vowel recognition for adults, but children attend to dynamic spectral structure more strongly because early phonological organization favors whole words. PMID:25536845

  2. N = 4 superextension of the Liouville equation with quaternion structure

    SciTech Connect

    Ivanov, E.A.; Krivonos, S.O.

    1985-11-01

    The authors construct an N = 4 supersymmetric extension of the Liouville equation. It has internal SU(2) x SU(2) gauge symmetry and can be adequately formulated in terms of a real quaternion N = 4 superfield on which definite conditions of Grassmann analyticity are imposed. Both the dynamic equations as well as the analyticity conditions follow from the zero-curvature representation on the superalgebra SU(1,1/2). It is shown that the obtained system is invariant with respect to transformations of the infinitedimensional superalgebra of the SU(2) superstring, the realization of these transformations differing from those previously known. The possible connection between the N = 4 Liouville equation and the theory of the SU(2) superstring is discussed.

  3. A Structural Equation Model of Predictors of Online Learning Retention

    ERIC Educational Resources Information Center

    Lee, Youngju; Choi, Jaeho

    2013-01-01

    This study examined the effects of internal academic locus of control (ALOC), learning strategies, flow experience, and student satisfaction on student retention in online learning courses. A total number of 282 adult students at the Korea National Open University participated in the study by completing an online survey adopted from previous…

  4. Poisson structures for lifts and periodic reductions of integrable lattice equations

    NASA Astrophysics Data System (ADS)

    Kouloukas, Theodoros E.; Tran, Dinh T.

    2015-02-01

    We introduce and study suitable Poisson structures for four-dimensional maps derived as lifts and specific periodic reductions of integrable lattice equations. These maps are Poisson with respect to these structures and the corresponding integrals are in involution.

  5. Estimating and Interpreting Latent Variable Interactions: A Tutorial for Applying the Latent Moderated Structural Equations Method

    ERIC Educational Resources Information Center

    Maslowsky, Julie; Jager, Justin; Hemken, Douglas

    2015-01-01

    Latent variables are common in psychological research. Research questions involving the interaction of two variables are likewise quite common. Methods for estimating and interpreting interactions between latent variables within a structural equation modeling framework have recently become available. The latent moderated structural equations (LMS)…

  6. The fermionic covariant prolongation structure of the super generalized Hirota equation

    NASA Astrophysics Data System (ADS)

    Yan, Zhaowen; Yao, Shaokui; Zhang, Chunhong; Gegenhasi

    2016-07-01

    The integrability of a super generalized Hirota equation (GHE) is investigated by means of the fermionic covariant prolongation structure theory. We construct the su(2/1) × R(λ) prolongation structure for the super GHE and derive the corresponding Lax representation and the Bäcklund transformation. In addition, a solution of the super integrable equation is presented.

  7. Evaluation of Structural Equation Mixture Models: Parameter Estimates and Correct Class Assignment

    ERIC Educational Resources Information Center

    Tueller, Stephen; Lubke, Gitta

    2010-01-01

    Structural equation mixture models (SEMMs) are latent class models that permit the estimation of a structural equation model within each class. Fitting SEMMs is illustrated using data from 1 wave of the Notre Dame Longitudinal Study of Aging. Based on the model used in the illustration, SEMM parameter estimation and correct class assignment are…

  8. On bi-Hamiltonian structure of two-component Novikov equation

    NASA Astrophysics Data System (ADS)

    Li, Nianhua; Liu, Q. P.

    2013-01-01

    In this Letter, we present a bi-Hamiltonian structure for the two-component Novikov equation. We also show that proper reduction of this bi-Hamiltonian structure leads to the Hamiltonian operators found by Hone and Wang for the Novikov equation.

  9. A Bayesian Approach for Analyzing Hierarchical Data with Missing Outcomes through Structural Equation Models

    ERIC Educational Resources Information Center

    Song, Xin-Yuan; Lee, Sik-Yum

    2008-01-01

    Structural equation models are widely appreciated in behavioral, social, and psychological research to model relations between latent constructs and manifest variables, and to control for measurement errors. Most applications of structural equation models are based on fully observed data that are independently distributed. However, hierarchical…

  10. General structure of the gravitational equations of motion in conformal Weyl gravity

    NASA Technical Reports Server (NTRS)

    Kazanas, Demosthenes; Mannheim, Philip D.

    1991-01-01

    A general method for determining the structure of the gravitational equations of motion is presented in the fourth-order theory of gravity based on local conformal Weyl invariance of the gravitational action. The explicit structure for these equations is given for a time-dependent, spherically symmetric geometry.

  11. Meta-Analytic Structural Equation Modeling (MASEM): Comparison of the Multivariate Methods

    ERIC Educational Resources Information Center

    Zhang, Ying

    2011-01-01

    Meta-analytic Structural Equation Modeling (MASEM) has drawn interest from many researchers recently. In doing MASEM, researchers usually first synthesize correlation matrices across studies using meta-analysis techniques and then analyze the pooled correlation matrix using structural equation modeling techniques. Several multivariate methods of…

  12. Factor Structure of Deterrents to Adult Participation in Higher Education

    ERIC Educational Resources Information Center

    Malhotra, Naveen K.; Shapero, Morris; Sizoo, Steve; Munro, Tom

    2007-01-01

    As institutions of higher learning have seen the aging of American college students, they have been increasingly concerned about helping them overcome what deters their reentry. Adult perception of deterrents is identified in this study. Analysis and the factor structure underlying these deterrents is examined in the Situational, Institutional,…

  13. Factorial structure of two health belief measures among older adults.

    PubMed

    Robinson-Whelen, S; Storandt, M

    1992-06-01

    Confirmatory factor analysis of Wallston's Multidimensional Health Locus of Control Scale and Krantz's Health Opinion Survey was conducted using 197 nondiabetic and 171 diabetic older adults. Qualified support was found for the 3-factor structure of the Wallston measure when applied to older adults. The Krantz model provided a less-than-adequate representation of the older sample's data. When the items from these 2 measures were combined, a 4-factor structure was found. Multisample simultaneous factor analyses using LISREL revealed that the factor structures of the Wallston and the Krantz measures fit the diabetic and the nondiabetic samples fairly equivalently. Despite the similarities in factor structures, diabetic individuals reported greater belief in powerful others and less desire for behavioral involvement in the health-care process than did nondiabetics. PMID:1610510

  14. Discrete integration of continuous Kalman filtering equations for time invariant second-order structural systems

    NASA Technical Reports Server (NTRS)

    Park, K. C.; Belvin, W. Keith

    1990-01-01

    A general form for the first-order representation of the continuous second-order linear structural-dynamics equations is introduced to derive a corresponding form of first-order continuous Kalman filtering equations. Time integration of the resulting equations is carried out via a set of linear multistep integration formulas. It is shown that a judicious combined selection of computational paths and the undetermined matrices introduced in the general form of the first-order linear structural systems leads to a class of second-order discrete Kalman filtering equations involving only symmetric sparse N x N solution matrices.

  15. Using SAS PROC TCALIS for multigroup structural equation modelling with mean structures.

    PubMed

    Gu, Fei; Wu, Wei

    2011-11-01

    Multigroup structural equation modelling (SEM) is a technique frequently used to evaluate measurement invariance in social and behavioural science research. Before version 9.2, SAS was incapable of handling multigroup SEM. However, this limitation is resolved in PROC TCALIS in SAS 9.2. For the purpose of illustration, this paper provides a step-by-step guide to programming the tests of measurement invariance and partial invariance using PROC TCALIS for multigroup SEM with mean structures. Fit indices and parameter estimates are validated, thus providing an alternative tool for researchers conducting both applied and simulated studies. Other new features (e.g., different types of modelling languages and estimation methods) and limitations (e.g., ordered-categorical SEM and multilevel SEM) of the TCALIS procedure are also briefly discussed. PMID:21973099

  16. Individual- and Structural-Level Risk Factors for Suicide Attempts among Transgender Adults

    PubMed Central

    Perez-Brumer, Amaya; Hatzenbuehler, Mark L.; Oldenburg, Catherine E.; Bockting, Walter

    2016-01-01

    This study assessed individual (i.e., internalized transphobia) and structural forms of stigma as risk factors for suicide attempts among transgender adults. Internalized transphobia was assessed through a 26-item scale including four dimensions: pride, passing, alienation and shame. State-level structural stigma was operationalized as a composite index, including: density of same-sex couples; proportion of Gay-Straight Alliances per public high school; 5 policies related to sexual orientation discrimination; and aggregated public opinion towards homosexuality. Multivariable logistic generalized estimating equation models assessed associations of interest among an online sample of transgender adults (N=1,229) representing 48 states and the District of Columbia. Lower levels of structural stigma were associated with fewer lifetime suicide attempts (AOR 0.96, 95% CI 0.92–0.997), and a higher score on the internalized transphobia scale was associated with greater lifetime suicide attempts (AOR 1.18, 95% CI 1.04–1.33). Addressing stigma at multiple levels is necessary to reduce the vulnerability of suicide attempts among transgender adults. PMID:26287284

  17. Individual- and Structural-Level Risk Factors for Suicide Attempts Among Transgender Adults.

    PubMed

    Perez-Brumer, Amaya; Hatzenbuehler, Mark L; Oldenburg, Catherine E; Bockting, Walter

    2015-01-01

    This study assessed individual (ie, internalized transphobia) and structural forms of stigma as risk factors for suicide attempts among transgender adults. Internalized transphobia was assessed through a 26-item scale including four dimensions: pride, passing, alienation, and shame. State-level structural stigma was operationalized as a composite index, including density of same-sex couples; proportion of Gay-Straight Alliances per public high school; 5 policies related to sexual orientation discrimination; and aggregated public opinion toward homosexuality. Multivariable logistic generalized estimating equation models assessed associations of interest among an online sample of transgender adults (N = 1,229) representing 48 states and the District of Columbia. Lower levels of structural stigma were associated with fewer lifetime suicide attempts (AOR 0.96, 95% CI 0.92-0.997), and a higher score on the internalized transphobia scale was associated with greater lifetime suicide attempts (AOR 1.18, 95% CI 1.04-1.33). Addressing stigma at multiple levels is necessary to reduce the vulnerability of suicide attempts among transgender adults. PMID:26287284

  18. Individual and environmental correlates of dietary fat intake in rural communities: a structural equation model analysis.

    PubMed

    Hermstad, April K; Swan, Deanne W; Kegler, Michelle C; Barnette, J K; Glanz, Karen

    2010-07-01

    Total dietary fat and saturated fat intake are associated with obesity, elevated cholesterol, and heart disease. This study tested a multi-group structural equation model to explore differences in the relative influence of individual, social, and physical environment factors on dietary fat intake amongst adults aged 40-70 years. Participants from four rural Georgia, U.S., counties (n=527) completed a cross-sectional survey that included questions about eating patterns and individual and social influences on healthy eating. Observational measures of nutrition environments in stores and restaurants in these counties also were completed. Models for both women and men found significant positive relationships between self-efficacy for healthy eating and perceived nutrition environments and family support for healthy eating. The association between self-efficacy for eating a low-fat diet and frequency of eating out and grocery shopping was negative for both genders. The home nutrition environment was associated with dietary fat intake for women but not men. The results indicate that the influence of individual and environmental factors on dietary fat intake differs for men and women, with the home environment playing a larger role for women in rural communities. PMID:20462682

  19. Using Structural Equation Modeling To Test for Differential Reliability and Validity: An Empirical Demonstration.

    ERIC Educational Resources Information Center

    Raines-Eudy, Ruth

    2000-01-01

    Demonstrates empirically a structural equation modeling technique for group comparison of reliability and validity. Data, which are from a study of 495 mothers' attitudes toward pregnancy, have a one-factor measurement model and three sets of subpopulation comparisons. (SLD)

  20. Effect of the Number of Variables on Measures of Fit in Structural Equation Modeling.

    ERIC Educational Resources Information Center

    Kenny, David A.; McCoach, D. Betsy

    2003-01-01

    Used three approaches to understand the effect of the number of variables in the model on model fit in structural equation modeling through computer simulation. Developed a simple formula for the theoretical value of the comparative fit index. (SLD)

  1. Nonlinear static and dynamic analysis of beam structures using fully intrinsic equations

    NASA Astrophysics Data System (ADS)

    Sotoudeh, Zahra

    2011-07-01

    Beams are structural members with one dimension much larger than the other two. Examples of beams include propeller blades, helicopter rotor blades, and high aspect-ratio aircraft wings in aerospace engineering; shafts and wind turbine blades in mechanical engineering; towers, highways and bridges in civil engineering; and DNA modeling in biomedical engineering. Beam analysis includes two sets of equations: a generally linear two-dimensional problem over the cross-sectional plane and a nonlinear, global one-dimensional analysis. This research work deals with a relatively new set of equations for one-dimensional beam analysis, namely the so-called fully intrinsic equations. Fully intrinsic equations comprise a set of geometrically exact, nonlinear, first-order partial differential equations that is suitable for analyzing initially curved and twisted anisotropic beams. A fully intrinsic formulation is devoid of displacement and rotation variables, making it especially attractive because of the absence of singularities, infinite-degree nonlinearities, and other undesirable features associated with finite rotation variables. In spite of the advantages of these equations, using them with certain boundary conditions presents significant challenges. This research work will take a broad look at these challenges of modeling various boundary conditions when using the fully intrinsic equations. Hopefully it will clear the path for wider and easier use of the fully intrinsic equations in future research. This work also includes application of fully intrinsic equations in structural analysis of joined-wing aircraft, different rotor blade configuration and LCO analysis of HALE aircraft.

  2. On the structure of nonlinear constitutive equations for fiber reinforced composites

    NASA Technical Reports Server (NTRS)

    Jansson, Stefan

    1992-01-01

    The structure of constitutive equations for nonlinear multiaxial behavior of transversely isotropic fiber reinforced metal matrix composites subject to proportional loading was investigated. Results from an experimental program were combined with numerical simulations of the composite behavior for complex stress to reveal the full structure of the equations. It was found that the nonlinear response can be described by a quadratic flow-potential, based on the polynomial stress invariants, together with a hardening rule that is dominated by two different hardening mechanisms.

  3. The abundant symmetry structure of hierarchies of nonlinear equations obtained by reciprocal links

    NASA Astrophysics Data System (ADS)

    Carillo, Sandra; Fuchssteiner, Benno

    1989-07-01

    Explicit computation for a Kawamoto-type equation shows that there is a rich associated symmetry structure for four separate hierarchies of nonlinear integrodifferential equations. Contrary to the general belief that symmetry groups for nonlinear evolution equations in 1+1 dimensions have to be Abelian, it is shown that, in this case, the symmetry group is noncommutative. Its semisimple part is isomorphic to the affine Lie algebra A(1)1 associated to sl(2,C). In two of the additional hierarchies that were found, an explicit dependence of the independent variable occurs. Surprisingly, the generic invariance for the Kawamoto-type equation obtained in Rogers and Carillo [Phys. Scr. 36, 865 (1987)] via a reciprocal link to the Möbius invariance of the singularity equation of the Kaup-Kupershmidt (KK) equation only holds for one of the additional hierarchies of symmetry groups. Thus the generic invariance is not a universal property for the complete symmetry group of equations obtained by reciprocal links. In addition to these results, the bi-Hamiltonian formulation of the hierarchy is given. A direct Bäcklund transformation between the (KK) hierarchy and the hierarchy of singularity equation for the Caudrey-Dodd-Gibbon-Sawada-Kotera equation is exhibited: This shows that the abundant symmetry structure found for the Kawamoto equation must exist for all fifth-order equations, which are known to be completely integrable since these equations are connected either by Bäcklund transformations or reciprocal links. It is shown that similar results must hold for all hierarchies emerging out of singularity hierarchies via reciprocal links. Furthermore, general aspects of the results are discussed.

  4. A homotopy algorithm for synthesizing robust controllers for flexible structures via the maximum entropy design equations

    NASA Technical Reports Server (NTRS)

    Collins, Emmanuel G., Jr.; Richter, Stephen

    1990-01-01

    One well known deficiency of LQG compensators is that they do not guarantee any measure of robustness. This deficiency is especially highlighted when considering control design for complex systems such as flexible structures. There has thus been a need to generalize LQG theory to incorporate robustness constraints. Here we describe the maximum entropy approach to robust control design for flexible structures, a generalization of LQG theory, pioneered by Hyland, which has proved useful in practice. The design equations consist of a set of coupled Riccati and Lyapunov equations. A homotopy algorithm that is used to solve these design equations is presented.

  5. Integrating affective and cognitive correlates of heart rate variability: A structural equation modeling approach.

    PubMed

    Mann, Sarah L; Selby, Edward A; Bates, Marsha E; Contrada, Richard J

    2015-10-01

    High frequency heart rate variability (HRV) is a measure of neurocardiac communication thought to reflect predominantly parasympathetic cardiac regulation. Low HRV has been associated empirically with clinical and subclinical levels of anxiety and depression and, more recently, high levels of HRV have been associated with better performance on some measures of executive functioning (EF). These findings have offered support for theories proposing HRV as an index measure of a broad, self-regulatory capacity underlying aspects of emotion regulation and executive control. This study sought to test that proposition by using a structural equation modeling approach to examine the relationships of HRV to negative affect (NA) and EF in a large sample of U.S. adults ages 30s-80s. HRV was modeled as a predictor of an NA factor (self-reported trait anxiety and depression symptoms) and an EF factor (performance on three neuropsychological tests tapping facets of executive abilities). Alternative models also were tested to determine the utility of HRV for predicting NA and EF, with and without statistical control of demographic and health-related covariates. In the initial structural model, HRV showed a significant positive relationship to EF and a nonsignificant relationship to NA. In a covariate-adjusted model, HRV's associations with both constructs were nonsignificant. Age emerged as the only significant predictor of NA and EF in the final model, showing inverse relationships to both. Findings may reflect population and methodological differences from prior research; they also suggest refinements to the interpretations of earlier findings and theoretical claims regarding HRV. PMID:26168884

  6. Calcium exchange, structure, and function in cultured adult myocardial cells

    SciTech Connect

    Langer, G.A.; Frank, J.S.; Rich, T.L.; Orner, F.B.

    1987-02-01

    Cells digested from adult rat heart and cultured for 14 days demonstrate all the structural elements, in mature form, associated with the process of excitation-contraction (EC) coupling. The transverse tubular (TT) system is well developed with an extensive junctional sarcoplasmic reticulum (JSR). In nonphosphate-containing buffer contraction of the cells is lost as rapidly as zero extracellular Ca concentration ((Ca)/sup 0/) solution is applied and a negative contraction staircase is produced on increase of stimulation frequency. Structurally and functionally the cells have the characteristics of adult cells in situ. /sup 45/Ca exchange and total /sup 45/Ca measurement in N-2-hydroxyethylpiperazine N'-2-ethanesulfonic acid (HEPES)-buffered perfusate define three components of cellular Ca: 1) a rapidly exchangeable component accounting for 36% of total Ca, 2) a slowly exchangeable component (t/sub 1/2/ 53 min) accounting for 7% total Ca, and 3) the remaining 57% cellular Ca is inexchangeable (demonstrates no significant exchange within 60 min). The slowly exchangeable component can be increased 10-fold within 60 min by addition of phosphate to the perfusate. The Ca distribution and exchange characteristics are little different from those of 3-day cultures of neonatal rat heart previously studied. The results suggest that the cells are representative of adult cells in situ and that both sarcolemmal-bound and sarcoplasmic reticular Ca contribute to the component of Ca that is rapidly exchangeable.

  7. White matter structure changes as adults learn a second language.

    PubMed

    Schlegel, Alexander A; Rudelson, Justin J; Tse, Peter U

    2012-08-01

    Traditional models hold that the plastic reorganization of brain structures occurs mainly during childhood and adolescence, leaving adults with limited means to learn new knowledge and skills. Research within the last decade has begun to overturn this belief, documenting changes in the brain's gray and white matter as healthy adults learn simple motor and cognitive skills [Lövdén, M., Bodammer, N. C., Kühn, S., Kaufmann, J., Schütze, H., Tempelmann, C., et al. Experience-dependent plasticity of white-matter microstructure extends into old age. Neuropsychologia, 48, 3878-3883, 2010; Taubert, M., Draganski, B., Anwander, A., Müller, K., Horstmann, A., Villringer, A., et al. Dynamic properties of human brain structure: Learning-related changes in cortical areas and associated fiber connections. The Journal of Neuroscience, 30, 11670-11677, 2010; Scholz, J., Klein, M. C., Behrens, T. E. J., & Johansen-Berg, H. Training induces changes in white-matter architecture. Nature Neuroscience, 12, 1370-1371, 2009; Draganski, B., Gaser, C., Busch, V., Schuirer, G., Bogdahn, U., & May, A. Changes in grey matter induced by training. Nature, 427, 311-312, 2004]. Although the significance of these changes is not fully understood, they reveal a brain that remains plastic well beyond early developmental periods. Here we investigate the role of adult structural plasticity in the complex, long-term learning process of foreign language acquisition. We collected monthly diffusion tensor imaging scans of 11 English speakers who took a 9-month intensive course in written and spoken Modern Standard Chinese as well as from 16 control participants who did not study a language. We show that white matter reorganizes progressively across multiple sites as adults study a new language. Language learners exhibited progressive changes in white matter tracts associated with traditional left hemisphere language areas and their right hemisphere analogs. Surprisingly, the most significant changes

  8. The Lattice Structure of Connection Preserving Deformations for q-Painlevé Equations I

    NASA Astrophysics Data System (ADS)

    Ormerod, Christopher M.

    2011-05-01

    We wish to explore a link between the Lax integrability of the q-Painlevé equations and the symmetries of the q-Painlevé equations. We shall demonstrate that the connection preserving deformations that give rise to the q-Painlevé equations may be thought of as elements of the groups of Schlesinger transformations of their associated linear problems. These groups admit a very natural lattice structure. Each Schlesinger transformation induces a Bäcklund transformation of the q-Painlevé equation. Each translational Bäcklund transformation may be lifted to the level of the associated linear problem, effectively showing that each translational Bäcklund transformation admits a Lax pair. We will demonstrate this framework for the q-Painlevé equations up to and including q-PVI.

  9. High-accuracy deterministic solution of the Boltzmann equation for the shock wave structure

    NASA Astrophysics Data System (ADS)

    Malkov, E. A.; Bondar, Ye. A.; Kokhanchik, A. A.; Poleshkin, S. O.; Ivanov, M. S.

    2015-07-01

    A new deterministic method of solving the Boltzmann equation has been proposed. The method has been employed in numerical studies of the plane shock wave structure in a hard sphere gas. Results for Mach numbers and have been compared with predictions of the direct simulation Monte Carlo (DSMC) method, which has been used to obtain the reference solution. Particular attention in estimating the solution accuracy has been paid to a fine structural effect: the presence of a total temperature peak exceeding the temperature value further downstream. The results of solving the Boltzmann equation for the shock wave structure are in excellent agreement with the DSMC predictions.

  10. Genotypic structure of a Drosophila population for adult locomotor activity

    SciTech Connect

    Grechanyi, G.V.; Korzun, V.M.

    1995-01-01

    Analysis of the variation of adult locomotor activity in four samples taken at different times from a natural population of Drosophila melanogaster showed that the total variation of this trait is relatively stable in time and has a substantial genetic component. Genotypic structure of the population for locomotor activity is characterized by the presence of large groups of genotypes with high and low values of this trait. A possible explanation for the presence of such groups in a population is cyclic density-dependent selection.

  11. Discrete Kalman filtering equations of second-order form for control-structure interaction simulations

    NASA Technical Reports Server (NTRS)

    Park, K. C.; Alvin, K. F.; Belvin, W. Keith

    1991-01-01

    A second-order form of discrete Kalman filtering equations is proposed as a candidate state estimator for efficient simulations of control-structure interactions in coupled physical coordinate configurations as opposed to decoupled modal coordinates. The resulting matrix equation of the present state estimator consists of the same symmetric, sparse N x N coupled matrices of the governing structural dynamics equations as opposed to unsymmetric 2N x 2N state space-based estimators. Thus, in addition to substantial computational efficiency improvement, the present estimator can be applied to control-structure design optimization for which the physical coordinates associated with the mass, damping and stiffness matrices of the structure are needed instead of modal coordinates.

  12. Multilevel Structural Equation Models for the Analysis of Comparative Data on Educational Performance

    ERIC Educational Resources Information Center

    Goldstein, Harvey; Bonnet, Gerard; Rocher, Thierry

    2007-01-01

    The Programme for International Student Assessment comparative study of reading performance among 15-year-olds is reanalyzed using statistical procedures that allow the full complexity of the data structures to be explored. The article extends existing multilevel factor analysis and structural equation models and shows how this can extract richer…

  13. Introducing Algebraic Structures through Solving Equations: Vertical Content Knowledge for K-12 Mathematics Teachers

    ERIC Educational Resources Information Center

    Wasserman, Nicholas H.

    2014-01-01

    Algebraic structures are a necessary aspect of algebraic thinking for K-12 students and teachers. An approach for introducing the algebraic structure of groups and fields through the arithmetic properties required for solving simple equations is summarized; the collective (not individual) importance of these axioms as a foundation for algebraic…

  14. The Effect of Perceived Instructional Effectiveness on Student Loyalty: A Multilevel Structural Equation Model

    ERIC Educational Resources Information Center

    Simsek, Gulhayat Golbasi; Noyan, Fatma

    2009-01-01

    Social sciences research often entails the analysis of data with a multilevel structure. An example of multilevel data is containing measurement on university students nested within instructors. This paper concentrates on multilevel analysis of structural equation modeling with educational data. Data used in this study were gathered from 17647…

  15. Application of Exploratory Structural Equation Modeling to Evaluate the Academic Motivation Scale

    ERIC Educational Resources Information Center

    Guay, Frédéric; Morin, Alexandre J. S.; Litalien, David; Valois, Pierre; Vallerand, Robert J.

    2015-01-01

    In this research, the authors examined the construct validity of scores of the Academic Motivation Scale using exploratory structural equation modeling. Study 1 and Study 2 involved 1,416 college students and 4,498 high school students, respectively. First, results of both studies indicated that the factor structure tested with exploratory…

  16. Structural Equation Modeling in Assessing Students' Understanding of the State Changes of Matter

    ERIC Educational Resources Information Center

    Stamovlasis, Dimitrios; Tsitsipis, Georgios; Papageorgiou, George

    2012-01-01

    In this study, structural equation modeling (SEM) is applied to an instrument assessing students' understanding of the particulate nature of matter, the collective properties and physical changes, such as melting, evaporation, boiling and condensation. The structural relationships among particular groups of items were investigated. In addition,…

  17. OpenMx: An Open Source Extended Structural Equation Modeling Framework

    ERIC Educational Resources Information Center

    Boker, Steven; Neale, Michael; Maes, Hermine; Wilde, Michael; Spiegel, Michael; Brick, Timothy; Spies, Jeffrey; Estabrook, Ryne; Kenny, Sarah; Bates, Timothy; Mehta, Paras; Fox, John

    2011-01-01

    OpenMx is free, full-featured, open source, structural equation modeling (SEM) software. OpenMx runs within the "R" statistical programming environment on Windows, Mac OS-X, and Linux computers. The rationale for developing OpenMx is discussed along with the philosophy behind the user interface. The OpenMx data structures are introduced--these…

  18. Superwoman Schema: Using Structural Equation Modeling to Investigate Measurement Invariance in a Questionnaire

    ERIC Educational Resources Information Center

    Steed, Teneka C.

    2013-01-01

    Evaluating the psychometric properties of a newly developed instrument is critical to understanding how well an instrument measures what it intends to measure, and ensuring proposed use and interpretation of questionnaire scores are valid. The current study uses Structural Equation Modeling (SEM) techniques to examine the factorial structure and…

  19. Fitting Data to Model: Structural Equation Modeling Diagnosis Using Two Scatter Plots

    ERIC Educational Resources Information Center

    Yuan, Ke-Hai; Hayashi, Kentaro

    2010-01-01

    This article introduces two simple scatter plots for model diagnosis in structural equation modeling. One plot contrasts a residual-based M-distance of the structural model with the M-distance for the factor score. It contains information on outliers, good leverage observations, bad leverage observations, and normal cases. The other plot contrasts…

  20. Direct and Indirect Effects of Parental Influence upon Adolescent Alcohol Use: A Structural Equation Modeling Analysis

    ERIC Educational Resources Information Center

    Kim, Young-Mi; Neff, James Alan

    2010-01-01

    A model incorporating the direct and indirect effects of parental monitoring on adolescent alcohol use was evaluated by applying structural equation modeling (SEM) techniques to data on 4,765 tenth-graders in the 2001 Monitoring the Future Study. Analyses indicated good fit of hypothesized measurement and structural models. Analyses supported both…

  1. Application of partial differential equation modeling of the control/structural dynamics of flexible spacecraft

    NASA Technical Reports Server (NTRS)

    Taylor, Lawrence W., Jr.; Rajiyah, H.

    1991-01-01

    Partial differential equations for modeling the structural dynamics and control systems of flexible spacecraft are applied here in order to facilitate systems analysis and optimization of these spacecraft. Example applications are given, including the structural dynamics of SCOLE, the Solar Array Flight Experiment, the Mini-MAST truss, and the LACE satellite. The development of related software is briefly addressed.

  2. A family of solution algorithms for nonlinear structural analysis based on relaxation equations

    NASA Technical Reports Server (NTRS)

    Park, K. C.

    1981-01-01

    A family of hierarchical algorithms for nonlinear structural equations are presented. The algorithms are based on the Davidenko-Branin type homotopy and shown to yield consistent hierarchical perturbation equations. The algorithms appear to be particularly suitable to problems involving bifurcation and limit point calculations. An important by-product of the algorithms is that it provides a systematic and economical means for computing the stepsize at each iteration stage when a Newton-like method is employed to solve the systems of equations. Some sample problems are provided to illustrate the characteristics of the algorithms.

  3. The second Hamiltonian structure for a special case of the Lotka-Volterra equations

    NASA Astrophysics Data System (ADS)

    Bibik, Yu. V.

    2007-08-01

    A special case of the Lotka-Volterra equations is considered for which it is possible to find the second Hamiltonian structure that is complementary to the known one. The form of the new Hamiltonian makes it possible to solve the equations by quadratures, which is the main feature of the case under examination. As a consequence, the period can also be represented by quadratures. In terms of the new variables, the equations of motion admit a mechanical analogy with the oscillations of a mass on a nonlinear spring.

  4. Towards a gauge-equivalent magnetic structure of the nonlocal nonlinear Schrödinger equation

    NASA Astrophysics Data System (ADS)

    Gadzhimuradov, T. A.; Agalarov, A. M.

    2016-06-01

    It is shown that the nonlocal nonlinear Schrödinger equation recently proposed by Ablowitz and Musslimani [Phys. Rev. Lett. 110, 064105 (2013), 10.1103/PhysRevLett.110.064105] is gauge equivalent to the unconventional system of coupled Landau-Lifshitz equations. The first integrals of motion and one-soliton solution of an obtained model are given. The physical and geometrical aspects of model and their effect on expected metamagnetic structures are studied.

  5. Predictive equations for central obesity via anthropometrics, stereovision imaging, and MRI in adults

    PubMed Central

    Lee, Jane J; Freeland-Graves, Jeanne H; Pepper, M Reese; Yao, Ming; Xu, Bugao

    2013-01-01

    Objective Abdominal visceral adiposity is related to risks for insulin resistance and metabolic perturbations. Magnetic resonance imaging (MRI) and computed tomography are advanced instruments that quantify abdominal adiposity; yet field use is constrained by their bulkiness and costliness. The purpose of this study is to develop prediction equations for total abdominal, subcutaneous, and visceral adiposity via anthropometrics, stereovision body imaging (SBI), and MRI. Design and Methods Participants (67 men and 55 women) were measured for anthropometrics, and abdominal adiposity volumes evaluated by MRI umbilicus scans. Body circumferences and central obesity were obtained via SBI. Prediction models were developed via multiple linear regression analysis, utilizing body measurements and demographics as independent predictors, and abdominal adiposity as a dependent variable. Cross-validation was performed by the data-splitting method. Results The final total abdominal adiposity prediction equation was –470.28+7.10waist circumference–91.01gender+5.74sagittal diameter (R²=89.9%); subcutaneous adiposity was –172.37+8.57waist circumference–62.65gender–450.16stereovision waist-to-hip ratio (R²=90.4%); and visceral adiposity was –96.76+11.48central obesity depth–5.09 central obesity width+204.74stereovision waist-to-hip ratio–18.59gender (R²=71.7%). R² significantly improved for predicting visceral fat when SBI variables were included, but not for total abdominal or subcutaneous adiposity. Conclusions SBI is effective for predicting visceral adiposity and the prediction equations derived from SBI measurements can assess obesity. PMID:23613161

  6. Analysing the socioeconomic determinants of hypertension in South Africa: a structural equation modelling approach

    PubMed Central

    2014-01-01

    Background Epidemiological research has long observed a varying prevalence of hypertension across socioeconomic strata. However, patterns of association and underlying causal mechanisms are poorly understood in sub-Saharan Africa. Using education and income as indicators, we investigated the extent to which socioeconomic status is linked to blood pressure in the first wave of the National Income Dynamics Study — a South African longitudinal study of more than 15000 adults – and whether bio-behavioural risk factors mediate the association. Methods In a cross-sectional analysis, structural equation modelling was employed to estimate the effect of socioeconomic status on systolic and diastolic blood pressure and to assess the role of a set of bio-behavioural risk factors in explaining the observed relationships. Results After adjustment for age, race and antihypertensive treatment, higher education and income were independently associated with higher diastolic blood pressure in men. In women higher education predicted lower values of both diastolic and systolic blood pressure while higher income predicted lower systolic blood pressure. In both genders, body mass index was a strong mediator of an adverse indirect effect of socioeconomic status on blood pressure. Together with physical exercise, alcohol use, smoking and resting heart rate, body mass index therefore contributed substantially to mediation of the observed relationships in men. By contrast, in women unmeasured factors played a greater role. Conclusion In countries undergoing epidemiological transition, effects of socioeconomic status on blood pressure may vary by gender. In women, factors other than those listed above may have substantial role in mediating the association and merit investigation. PMID:24885860

  7. The developmental antecedents of sexual coercion against women: testing alternative hypotheses with structural equation modeling.

    PubMed

    Knight, Raymond A; Sims-Knight, Judith E

    2003-06-01

    A unified model of the origin of sexual aggression against women on both adult and juvenile sexual offender samples has been developed and successfully tested. This model proposed three major causal paths to sexual coercion against women. In the first path, physical and verbal abuse was hypothesized to produce callousness and lack of emotionality, which disinhibited sexual drive and sexual fantasies. These in turn disinhibited hostile sexual fantasies, and led to sexual coercion. In the second causal path, sexual abuse contributed directly to the disinhibition of sexual drive and sexual fantasies, which through hostile sexual fantasies led to sexual coercion. The third path operated through early antisocial behavior, including aggressive acts. It developed as a result of both physical/verbal abuse and callousness/lack of emotion. It in turn directly affected sexual coercion and worked indirectly through the hostile sexual fantasies path. In the present study, the anonymous responses of a group of 168 blue-collar, community males to an inventory (the Multidimensional Assessment of Sex and Aggression) were used in a structural equation model to test the validity of this model. Moreover, this model was pitted against (Malamuth's (1998)) two-path model. Whereas the three-path model had an excellent fit with the data (CFI =.951, RMSEA =.047), the two-path model fit less well (CFI =.857, RMSEA =.079). These results indicate the superiority of the three-path model and suggest that it constitutes a solid, empirically disconfirmable heuristic for the etiology of sexual coercion against women. PMID:12839887

  8. From network structure to network reorganization: implications for adult neurogenesis

    NASA Astrophysics Data System (ADS)

    Schneider-Mizell, Casey M.; Parent, Jack M.; Ben-Jacob, Eshel; Zochowski, Michal R.; Sander, Leonard M.

    2010-12-01

    Networks can be dynamical systems that undergo functional and structural reorganization. One example of such a process is adult hippocampal neurogenesis, in which new cells are continuously born and incorporate into the existing network of the dentate gyrus region of the hippocampus. Many of these introduced cells mature and become indistinguishable from established neurons, joining the existing network. Activity in the network environment is known to promote birth, survival and incorporation of new cells. However, after epileptogenic injury, changes to the connectivity structure around the neurogenic niche are known to correlate with aberrant neurogenesis. The possible role of network-level changes in the development of epilepsy is not well understood. In this paper, we use a computational model to investigate how the structural and functional outcomes of network reorganization, driven by addition of new cells during neurogenesis, depend on the original network structure. We find that there is a stable network topology that allows the network to incorporate new neurons in a manner that enhances activity of the persistently active region, but maintains global network properties. In networks having other connectivity structures, new cells can greatly alter the distribution of firing activity and destroy the initial activity patterns. We thus find that new cells are able to provide focused enhancement of network only for small-world networks with sufficient inhibition. Network-level deviations from this topology, such as those caused by epileptogenic injury, can set the network down a path that develops toward pathological dynamics and aberrant structural integration of new cells.

  9. A developmentally plastic adult mouse kidney cell line spontaneously generates multiple adult kidney structures

    PubMed Central

    Webb, Carol F.; Wirsig-Wiechmann, Celeste R.; Lakiza, Olga; Obara, Tomoko

    2015-01-01

    Despite exciting new possibilities for regenerative therapy posed by the ability to induce pluripotent stem cells, recapitulation of three-dimensional kidneys for repair or replacement has not been possible. ARID3a-deficient mouse tissues generated multipotent, developmentally plastic cells. Therefore, we assessed the adult mouse ARID3a−/− kidney cell line, KKPS5, which expresses renal progenitor surface markers as an alternative cell source for modeling kidney development. Remarkably, these cells spontaneously developed into multicellular nephron-like structures in vitro, and engrafted into immunocompromised medaka mesonephros, where they formed mouse nephron structures. These data implicate KKPS5 cells as a new model system for studying kidney development. PMID:26111446

  10. Fluid/Structure Interaction Studies of Aircraft Using High Fidelity Equations on Parallel Computers

    NASA Technical Reports Server (NTRS)

    Guruswamy, Guru; VanDalsem, William (Technical Monitor)

    1994-01-01

    Abstract Aeroelasticity which involves strong coupling of fluids, structures and controls is an important element in designing an aircraft. Computational aeroelasticity using low fidelity methods such as the linear aerodynamic flow equations coupled with the modal structural equations are well advanced. Though these low fidelity approaches are computationally less intensive, they are not adequate for the analysis of modern aircraft such as High Speed Civil Transport (HSCT) and Advanced Subsonic Transport (AST) which can experience complex flow/structure interactions. HSCT can experience vortex induced aeroelastic oscillations whereas AST can experience transonic buffet associated structural oscillations. Both aircraft may experience a dip in the flutter speed at the transonic regime. For accurate aeroelastic computations at these complex fluid/structure interaction situations, high fidelity equations such as the Navier-Stokes for fluids and the finite-elements for structures are needed. Computations using these high fidelity equations require large computational resources both in memory and speed. Current conventional super computers have reached their limitations both in memory and speed. As a result, parallel computers have evolved to overcome the limitations of conventional computers. This paper will address the transition that is taking place in computational aeroelasticity from conventional computers to parallel computers. The paper will address special techniques needed to take advantage of the architecture of new parallel computers. Results will be illustrated from computations made on iPSC/860 and IBM SP2 computer by using ENSAERO code that directly couples the Euler/Navier-Stokes flow equations with high resolution finite-element structural equations.

  11. Matching structural, effective, and functional connectivity: a comparison between structural equation modeling and ancestral graphs.

    PubMed

    Bringmann, Laura F; Scholte, H Steven; Waldorp, Lourens J

    2013-01-01

    In this study, we examined the accuracy of ancestral graphs (AGs) to study effective connectivity in the brain. Unlike most other methods that estimate effective connectivity, an AG is able to explicitly model missing brain regions in a network model. We compared AGs with the conventional structural equation models (SEM). We used both methods to estimate connection strengths between six regions of interest of the visual cortex based on functional magnetic resonance imaging data of a motion perception task. In order to examine which method is more accurate to estimate effective connectivity, we compared the connection strengths of the AG and SEM models with connection probabilities resulting from probabilistic tractography obtained from diffusion tensor images. This was done by correlating the connection strengths of the best fitting AG and SEM models with the connection probabilities of the probabilistic tractography models. We show that, in general, AGs result in more accurate models to estimate effective connectivity than SEM. The reason for this is that missing regions are taken into account when modeling with AG but not when modeling with SEM: AG can be used to explicitly test the assumption of missing regions. If the set of regions is complete, SEM and AG perform about equally well. PMID:23662916

  12. Dynamics of a neutral delay equation for an insect population with long larval and short adult phases

    NASA Astrophysics Data System (ADS)

    Gourley, Stephen A.; Kuang, Yang

    We present a global study on the stability of the equilibria in a nonlinear autonomous neutral delay differential population model formulated by Bocharov and Hadeler. This model may be suitable for describing the intriguing dynamics of an insect population with long larval and short adult phases such as the periodical cicada. We circumvent the usual difficulties associated with the study of the stability of a nonlinear neutral delay differential model by transforming it to an appropriate non-neutral nonautonomous delay differential equation with unbounded delay. In the case that no juveniles give birth, we establish the positivity and boundedness of solutions by ad hoc methods and global stability of the extinction and positive equilibria by the method of iteration. We also show that if the time adjusted instantaneous birth rate at the time of maturation is greater than 1, then the population will grow without bound, regardless of the population death process.

  13. Testing strong factorial invariance using three-level structural equation modeling.

    PubMed

    Jak, Suzanne

    2014-01-01

    Within structural equation modeling, the most prevalent model to investigate measurement bias is the multigroup model. Equal factor loadings and intercepts across groups in a multigroup model represent strong factorial invariance (absence of measurement bias) across groups. Although this approach is possible in principle, it is hardly practical when the number of groups is large or when the group size is relatively small. Jak et al. (2013) showed how strong factorial invariance across large numbers of groups can be tested in a multilevel structural equation modeling framework, by treating group as a random instead of a fixed variable. In the present study, this model is extended for use with three-level data. The proposed method is illustrated with an investigation of strong factorial invariance across 156 school classes and 50 schools in a Dutch dyscalculia test, using three-level structural equation modeling. PMID:25120499

  14. Reformulation of Maxwell's equations to incorporate near-solute solvent structure.

    PubMed

    Yang, Pei-Kun; Lim, Carmay

    2008-09-01

    Maxwell's equations, which treat electromagnetic interactions between macroscopic charged objects in materials, have explained many phenomena and contributed to many applications in our lives. Derived in 1861 when no methods were available to determine the atomic structure of macromolecules, Maxwell's equations assume the solvent to be a structureless continuum. However, near-solute solvent molecules are highly structured, unlike far-solute bulk solvent molecules. Current methods cannot treat both the near-solute solvent structure and time-dependent electromagnetic interactions in a macroscopic system. Here, we derive "microscopic" electrodynamics equations that can treat macroscopic time-dependent electromagnetic field problems like Maxwell's equations and reproduce the solvent molecular and dipole density distributions observed in molecular dynamics simulations. These equations greatly reduce computational expense by not having to include explicit solvent molecules, yet they treat the solvent electrostatic and van der Waals effects more accurately than continuum models. They provide a foundation to study electromagnetic interactions between molecules in a macroscopic system that are ubiquitous in biology, bioelectromagnetism, and nanotechnology. The general strategy presented herein to incorporate the near-solute solvent structure would enable studies on how complex cellular protein-ligand interactions are affected by electromagnetic radiation, which could help to prevent harmful electromagnetic spectra or find potential therapeutic applications. PMID:18698705

  15. A ballistic limit equation for hypervelocity impacts on CFRP Al H/C satellite structures

    NASA Astrophysics Data System (ADS)

    Ryan, S.; Schäfer, F.; Destefanis, R.; Lambert, M.

    Composite sandwich panels consisting of Carbon Fiber Reinforced Plastic facesheets bonded to Aluminum honeycomb cores CFRP Al H C SP are amongst the most commonly used structures for satellites due to their relative low mass and high thermal and mechanical stability To assess the threat of micrometeoroid orbital debris M OD on a satellite mission equations which define the limits of structural perforation in terms of impactor mass velocity and angle are required This type of equation is referred to as a Ballistic Limit Equation BLE There is presently no validated BLE existing for application in the risk assessment of CFRP Al H C SP structures During a recent experimental test campaign performed in the framework of ESA Contract 16721 e g 1 using EMI s two-stage light-gas guns the ballistic performance of multiple representative CFRP Al HC SP structural configurations GOCE Radarsat-2 Herschel Planck BeppoSax was investigated The experimental results have been used to adjust and validate a new empirical BLE derived from an existing Whipple Shield BLE which provides a significant improvement in the accuracy of ballistic performance prediction over existing techniques Additionally the equation is capable of predicting the ballistic limit of an Electronic-box representative structure located behind the structural wall Good agreement with the experimental results is achieved for the vast majority of test set-ups For some set-ups the ballistic limit was conservatively predicted however this is attributed to the additional

  16. Second-order discrete Kalman filtering equations for control-structure interaction simulations

    NASA Technical Reports Server (NTRS)

    Park, K. C.; Belvin, W. Keith; Alvin, Kenneth F.

    1991-01-01

    A general form for the first-order representation of the continuous, second-order linear structural dynamics equations is introduced in order to derive a corresponding form of first-order Kalman filtering equations (KFE). Time integration of the resulting first-order KFE is carried out via a set of linear multistep integration formulas. It is shown that a judicious combined selection of computational paths and the undetermined matrices introduced in the general form of the first-order linear structural systems leads to a class of second-order discrete KFE involving only symmetric, N x N solution matrix.

  17. First-principles prediction of the equation of state for TcC with rocksalt structure

    NASA Astrophysics Data System (ADS)

    Sun, Xiao-Wei; Chu, Yan-Dong; Liu, Zi-Jiang; Song, Ting; Tian, Jun-Hong; Wei, Xiao-Ping

    2014-10-01

    The equation of state of TcC with rocksalt structure is investigated by means of first-principles density functional theory calculations combined with the quasi-harmonic Debye model in which the phononic effects are considered. Particular attention is paid to the predictions of the compressibility, the isothermal bulk modulus and its first pressure derivative which play a central role in the formulation of approximate equations of state for the first time. The properties of TcC with rocksalt structure are summarized in the pressure range of 0-80 GPa and the temperature up to 2500 K.

  18. A developmentally plastic adult mouse kidney cell line spontaneously generates multiple adult kidney structures

    SciTech Connect

    Webb, Carol F.; Ratliff, Michelle L.; Powell, Rebecca; Wirsig-Wiechmann, Celeste R.; Lakiza, Olga; Obara, Tomoko

    2015-08-07

    Despite exciting new possibilities for regenerative therapy posed by the ability to induce pluripotent stem cells, recapitulation of three-dimensional kidneys for repair or replacement has not been possible. ARID3a-deficient mouse tissues generated multipotent, developmentally plastic cells. Therefore, we assessed the adult mouse ARID3a−/− kidney cell line, KKPS5, which expresses renal progenitor surface markers as an alternative cell source for modeling kidney development. Remarkably, these cells spontaneously developed into multicellular nephron-like structures in vitro, and engrafted into immunocompromised medaka mesonephros, where they formed mouse nephron structures. These data implicate KKPS5 cells as a new model system for studying kidney development. - Highlights: • An ARID3a-deficient mouse kidney cell line expresses multiple progenitor markers. • This cell line spontaneously forms multiple nephron-like structures in vitro. • This cell line formed mouse kidney structures in immunocompromised medaka fish kidneys. • Our data identify a novel model system for studying kidney development.

  19. Thermodynamics and structure of a two-dimensional electrolyte by integral equation theory.

    PubMed

    Aupic, Jana; Urbic, Tomaz

    2014-05-14

    Monte Carlo simulations and integral equation theory were used to predict the thermodynamics and structure of a two-dimensional Coulomb fluid. We checked the possibility that integral equations reproduce Kosterlitz-Thouless and vapor-liquid phase transitions of the electrolyte and critical points. Integral equation theory results were compared to Monte Carlo data and the correctness of selected closure relations was assessed. Among selected closures hypernetted-chain approximation results matched computer simulation data best, but these equations unfortunately break down at temperatures well above the Kosterlitz-Thouless transition. The Kovalenko-Hirata closure produces results even at very low temperatures and densities, but no sign of phase transition was detected. PMID:24832290

  20. Thermodynamics and structure of a two-dimensional electrolyte by integral equation theory

    SciTech Connect

    Aupic, Jana; Urbic, Tomaz

    2014-05-14

    Monte Carlo simulations and integral equation theory were used to predict the thermodynamics and structure of a two-dimensional Coulomb fluid. We checked the possibility that integral equations reproduce Kosterlitz-Thouless and vapor-liquid phase transitions of the electrolyte and critical points. Integral equation theory results were compared to Monte Carlo data and the correctness of selected closure relations was assessed. Among selected closures hypernetted-chain approximation results matched computer simulation data best, but these equations unfortunately break down at temperatures well above the Kosterlitz-Thouless transition. The Kovalenko-Hirata closure produces results even at very low temperatures and densities, but no sign of phase transition was detected.

  1. Some Poisson structures and Lax equations associated with the Toeplitz lattice and the Schur lattice

    NASA Astrophysics Data System (ADS)

    Lemarie, Caroline

    2016-01-01

    The Toeplitz lattice is a Hamiltonian system whose Poisson structure is known. In this paper, we unveil the origins of this Poisson structure and derive from it the associated Lax equations for this lattice. We first construct a Poisson subvariety H n of GL n (C), which we view as a real or complex Poisson-Lie group whose Poisson structure comes from a quadratic R-bracket on gl n (C) for a fixed R-matrix. The existence of Hamiltonians, associated to the Toeplitz lattice for the Poisson structure on H n , combined with the properties of the quadratic R-bracket allow us to give explicit formulas for the Lax equation. Then we derive from it the integrability in the sense of Liouville of the Toeplitz lattice. When we view the lattice as being defined over R, we can construct a Poisson subvariety H n τ of U n which is itself a Poisson-Dirac subvariety of GL n R (C). We then construct a Hamiltonian for the Poisson structure induced on H n τ , corresponding to another system which derives from the Toeplitz lattice the modified Schur lattice. Thanks to the properties of Poisson-Dirac subvarieties, we give an explicit Lax equation for the new system and derive from it a Lax equation for the Schur lattice. We also deduce the integrability in the sense of Liouville of the modified Schur lattice.

  2. Discussions on equivalent solutions and localized structures via the mapping method based on Riccati equation

    NASA Astrophysics Data System (ADS)

    Xu, Ling; Cheng, Xuan; Dai, Chao-Qing

    2015-12-01

    Although the mapping method based on Riccati equation was proposed to obtain variable separation solutions many years ago, two important problems have not been studied: i) the equivalence of variable separation solutions by means of the mapping method based on Riccati equation with the radical sign combined ansatz; and ii) lack of physical meanings for some localized structures constructed by variable separation solutions. In this paper, we re-study the (2+1)-dimensional Boiti-Leon-Pempinelli equation via the mapping method based on Riccati equation and prove that nine types of variable separation solutions are actually equivalent to each other. Moreover, we also re-study localized structures constructed by variable separation solutions. Results indicate that some localized structures reported in the literature are lacking real values due to the appearance of the divergent and un-physical phenomenon for the initial field. Therefore, we must be careful with the initial field to avoid the appearance of some un-physical or even divergent structures in it when we construct localized structures for the potential field.

  3. Biological fitness and the Price Equation in class-structured populations.

    PubMed

    Grafen, Alan

    2015-05-21

    Price׳s extended covariance selection mathematics is applied to class-structured populations with additional assumptions, to derive the 'genetic Price Equation with class structure'. Each individual belongs to a class, and there may be overlapping generations; the equation is genetic because the trait is restricted to an arbitrary weighted sum of allele frequencies. Two special cases are then considered, a demography-like case corresponding to Fisher's fundamental theorem of natural selection, and a sex-ratio-like case corresponding to Fisher's sex ratio argument: these differ in whether it is natural to assume that the per-capita or the total reproductive values of each class are maintained from the parental to the descendant population. These cases also match the two existing attempts to eliminate from the effects of natural selection those passive changes in allele frequencies that are caused by the class structure, and suggest improvements in one of them. In each case a more specialised Price Equation, and a 'fundamental theorem of natural selection', are proved, which hold out of class-structure equilibrium, showing that passive changes can be eliminated in more than one way, and hinting at the possibility of a more general formulation. Previous class-structured Price Equations and a 'fundamental theorem' are linked to these results. The power of Price's formal approach is vividly illustrated by this lucid conspectus of otherwise self-standing theories with confusing interconnections. PMID:25701635

  4. An analysis of the vertical structure equation for arbitrary thermal profiles

    NASA Technical Reports Server (NTRS)

    Cohn, Stephen E.; Dee, Dick P.

    1989-01-01

    The vertical structure equation is a singular Sturm-Liouville problem whose eigenfunctions describe the vertical dependence of the normal modes of the primitive equations linearized about a given thermal profile. The eigenvalues give the equivalent depths of the modes. The spectrum of the vertical structure equation and the appropriateness of various upper boundary conditions, both for arbitrary thermal profiles were studied. The results depend critically upon whether or not the thermal profile is such that the basic state atmosphere is bounded. In the case of a bounded atmosphere it is shown that the spectrum is always totally discrete, regardless of details of the thermal profile. For the barotropic equivalent depth, which corresponds to the lowest eigen value, upper and lower bounds which depend only on the surface temperature and the atmosphere height were obtained. All eigenfunctions are bounded, but always have unbounded first derivatives. It was proved that the commonly invoked upper boundary condition that vertical velocity must vanish as pressure tends to zero, as well as a number of alternative conditions, is well posed. It was concluded that the vertical structure equation always has a totally discrete spectrum under the assumptions implicit in the primitive equations.

  5. An analysis of the vertical structure equation for arbitrary thermal profiles

    NASA Technical Reports Server (NTRS)

    Cohn, Stephen E.; Dee, Dick P.

    1987-01-01

    The vertical structure equation is a singular Sturm-Liouville problem whose eigenfunctions describe the vertical dependence of the normal modes of the primitive equations linearized about a given thermal profile. The eigenvalues give the equivalent depths of the modes. The spectrum of the vertical structure equation and the appropriateness of various upper boundary conditions, both for arbitrary thermal profiles were studied. The results depend critically upon whether or not the thermal profile is such that the basic state atmosphere is bounded. In the case of a bounded atmosphere it is shown that the spectrum is always totally discrete, regardless of details of the thermal profile. For the barotropic equivalent depth, which corresponds to the lowest eigen value, upper and lower bounds which depend only on the surface temperature and the atmosphere height were obtained. All eigenfunctions are bounded, but always have unbounded first derivatives. It was proved that the commonly invoked upper boundary condition that vertical velocity must vanish as pressure tends to zero, as well as a number of alternative conditions, is well posed. It was concluded that the vertical structure equation always has a totally discrete spectrum under the assumptions implicit in the primitive equations.

  6. Evaluation of structural equation mixture models Parameter estimates and correct class assignment

    PubMed Central

    Tueller, Stephen; Lubke, Gitta

    2009-01-01

    Structural Equation Mixture Models(SEMMs) are latent class models that permit the estimation of a structural equation model within each class. Fitting SEMMs is illustrated using data from one wave of the Notre Dame Longitudinal Study of Aging. Based on the model used in the illustration, SEMM parameter estimation and correct class assignment are investigated in a large scale simulation study. Design factors of the simulation study are (im)balanced class proportions, (im)balanced factor variances, sample size, and class separation. We compare the fit of models with correct and misspecified within-class structural relations. In addition, we investigate the potential to fit SEMMs with binary indicators. The structure of within-class distributions can be recovered under a wide variety of conditions, indicating the general potential and flexibility of SEMMs to test complex within-class models. Correct class assignment is limited. PMID:20582328

  7. Comparison of Approaches to Constructing Confidence Intervals for Mediating Effects Using Structural Equation Models

    ERIC Educational Resources Information Center

    Cheung, Mike W. L.

    2007-01-01

    Mediators are variables that explain the association between an independent variable and a dependent variable. Structural equation modeling (SEM) is widely used to test models with mediating effects. This article illustrates how to construct confidence intervals (CIs) of the mediating effects for a variety of models in SEM. Specifically, mediating…

  8. Structural Equation Modelling of Multiple Facet Data: Extending Models for Multitrait-Multimethod Data

    ERIC Educational Resources Information Center

    Bechger, Timo M.; Maris, Gunter

    2004-01-01

    This paper is about the structural equation modelling of quantitative measures that are obtained from a multiple facet design. A facet is simply a set consisting of a finite number of elements. It is assumed that measures are obtained by combining each element of each facet. Methods and traits are two such facets, and a multitrait-multimethod…

  9. Using Structural Equation Modeling to Assess Functional Connectivity in the Brain: Power and Sample Size Considerations

    ERIC Educational Resources Information Center

    Sideridis, Georgios; Simos, Panagiotis; Papanicolaou, Andrew; Fletcher, Jack

    2014-01-01

    The present study assessed the impact of sample size on the power and fit of structural equation modeling applied to functional brain connectivity hypotheses. The data consisted of time-constrained minimum norm estimates of regional brain activity during performance of a reading task obtained with magnetoencephalography. Power analysis was first…

  10. Organizational Cynicism, School Culture, and Academic Achievement: The Study of Structural Equation Modeling

    ERIC Educational Resources Information Center

    Karadag, Engin; Kilicoglu, Gökhan; Yilmaz, Derya

    2014-01-01

    The purpose of this study is to explain constructed theoretical models that organizational cynicism perceptions of primary school teachers affect school culture and academic achievement, by using structural equation modeling. With the assumption that there is a cause-effect relationship between three main variables, the study was constructed with…

  11. Testing Mediation Using Multiple Regression and Structural Equation Modeling Analyses in Secondary Data

    ERIC Educational Resources Information Center

    Li, Spencer D.

    2011-01-01

    Mediation analysis in child and adolescent development research is possible using large secondary data sets. This article provides an overview of two statistical methods commonly used to test mediated effects in secondary analysis: multiple regression and structural equation modeling (SEM). Two empirical studies are presented to illustrate the…

  12. A Polychoric Instrumental Variable (PIV) Estimator for Structural Equation Models with Categorical Variables

    ERIC Educational Resources Information Center

    Bollen, Kenneth A.; Maydeu-Olivares, Albert

    2007-01-01

    This paper presents a new polychoric instrumental variable (PIV) estimator to use in structural equation models (SEMs) with categorical observed variables. The PIV estimator is a generalization of Bollen's (Psychometrika 61:109-121, 1996) 2SLS/IV estimator for continuous variables to categorical endogenous variables. We derive the PIV estimator…

  13. Bayesian Structural Equation Modeling: A More Flexible Representation of Substantive Theory

    ERIC Educational Resources Information Center

    Muthen, Bengt; Asparouhov, Tihomir

    2012-01-01

    This article proposes a new approach to factor analysis and structural equation modeling using Bayesian analysis. The new approach replaces parameter specifications of exact zeros with approximate zeros based on informative, small-variance priors. It is argued that this produces an analysis that better reflects substantive theories. The proposed…

  14. A Study of Factors that Influence College Academic Achievement: A Structural Equation Modeling Approach

    ERIC Educational Resources Information Center

    Rugutt, John K.; Chemosit, Caroline C.

    2005-01-01

    The authors of this study used the structural equation model (SEM) approach to test a model that hypothesized the influence of student learning strategies, internet and campus technology, quality of instruction and overall college experience, and student-faculty interaction on student academic achievement. Further a SEM model was developed to link…

  15. Teacher's Corner: Structural Equation Modeling with the Sem Package in R

    ERIC Educational Resources Information Center

    Fox, John

    2006-01-01

    R is free, open-source, cooperatively developed software that implements the S statistical programming language and computing environment. The current capabilities of R are extensive, and it is in wide use, especially among statisticians. The sem package provides basic structural equation modeling facilities in R, including the ability to fit…

  16. Using a Structural Equation Model to Examine Factors Affecting Married Individuals' Sexual Embarrassment

    ERIC Educational Resources Information Center

    Celik, Eyup; Arici, Neslihan

    2014-01-01

    This study aimed to predict the effects of levels of sexual awareness, sexual courage, and sexual self-disclosure on sexual embarrassment. Data was collected from 336 married individuals, who have students in the Sultangazi District of Istanbul. According to the structural equation model (SEM), sexual self-disclosure, directly, and sexual courage…

  17. Sample Size Requirements for Structural Equation Models: An Evaluation of Power, Bias, and Solution Propriety

    ERIC Educational Resources Information Center

    Wolf, Erika J.; Harrington, Kelly M.; Clark, Shaunna L.; Miller, Mark W.

    2013-01-01

    Determining sample size requirements for structural equation modeling (SEM) is a challenge often faced by investigators, peer reviewers, and grant writers. Recent years have seen a large increase in SEMs in the behavioral science literature, but consideration of sample size requirements for applied SEMs often relies on outdated rules-of-thumb.…

  18. Psychological Separation, Attachment Security, Vocational Self-Concept Crystallization, and Career Indecision: A Structural Equation Analysis.

    ERIC Educational Resources Information Center

    Tokar, David M.; Withrow, Jason R.; Hall, Rosalie J.; Moradi, Bonnie

    2003-01-01

    Structural equation modeling was used to test theoretically based models in which psychological separation and attachment security variables were related to career indecision and those relations were mediated through vocational self-concept crystallization. Results indicated that some components of separation and attachment security did relate to…

  19. A Program Implementing Mardia's Multivariate Normality Test for Use in Structural Equation Modeling with Latent Variables.

    ERIC Educational Resources Information Center

    MacIntosh, Randall

    1997-01-01

    Presents KANT, a FORTRAN 77 software program that tests assumptions of multivariate normality in a data set. Based on the test developed by M. V. Mardia (1985), the KANT program is useful for those engaged in structural equation modeling with latent variables. (SLD)

  20. Understanding the Impact of Trauma Exposure on Posttraumatic Stress Symptomatology: A Structural Equation Modeling Approach

    ERIC Educational Resources Information Center

    Chen, Wei; Wang, Long; Zhang, Xing-Li; Shi, Jian-Nong

    2012-01-01

    The objective of this study was to investigate the impact of trauma exposure on the posttraumatic stress symptomatology (PTSS) of children who resided near the epicenter of the 2008 Wenchuan earthquake. The mechanisms of this impact were explored via structural equation models with self-esteem and coping strategies included as mediators. The…

  1. A Robust Bayesian Approach for Structural Equation Models with Missing Data

    ERIC Educational Resources Information Center

    Lee, Sik-Yum; Xia, Ye-Mao

    2008-01-01

    In this paper, normal/independent distributions, including but not limited to the multivariate t distribution, the multivariate contaminated distribution, and the multivariate slash distribution, are used to develop a robust Bayesian approach for analyzing structural equation models with complete or missing data. In the context of a nonlinear…

  2. Structural Equation Modeling in Language Testing and Learning Research: A Review

    ERIC Educational Resources Information Center

    In'nami, Yo; Koizumi, Rie

    2011-01-01

    Despite the recent increase of structural equation modeling (SEM) in language testing and learning research and Kunnan's (1998) call for the proper use of SEM to produce useful findings, there seem to be no reviews about how SEM is applied in these areas or about the extent to which the current application accords with appropriate practices. To…

  3. Reliability of Summed Item Scores Using Structural Equation Modeling: An Alternative to Coefficient Alpha

    ERIC Educational Resources Information Center

    Green, Samuel B.; Yang, Yanyun

    2009-01-01

    A method is presented for estimating reliability using structural equation modeling (SEM) that allows for nonlinearity between factors and item scores. Assuming the focus is on consistency of summed item scores, this method for estimating reliability is preferred to those based on linear SEM models and to the most commonly reported estimate of…

  4. Self-Conscious Emotions in Response to Perceived Failure: A Structural Equation Model

    ERIC Educational Resources Information Center

    Bidjerano, Temi

    2010-01-01

    This study explored the occurrence of self-conscious emotions in response to perceived academic failure among 4th-grade students from the United States and Bulgaria, and the author investigated potential contributors to such negative emotional experiences. Results from structural equation modeling indicated that regardless of country, negative…

  5. Quasi-Maximum Likelihood Estimation of Structural Equation Models with Multiple Interaction and Quadratic Effects

    ERIC Educational Resources Information Center

    Klein, Andreas G.; Muthen, Bengt O.

    2007-01-01

    In this article, a nonlinear structural equation model is introduced and a quasi-maximum likelihood method for simultaneous estimation and testing of multiple nonlinear effects is developed. The focus of the new methodology lies on efficiency, robustness, and computational practicability. Monte-Carlo studies indicate that the method is highly…

  6. A Bayesian Approach for Nonlinear Structural Equation Models with Dichotomous Variables Using Logit and Probit Links

    ERIC Educational Resources Information Center

    Lee, Sik-Yum; Song, Xin-Yuan; Cai, Jing-Heng

    2010-01-01

    Analysis of ordered binary and unordered binary data has received considerable attention in social and psychological research. This article introduces a Bayesian approach, which has several nice features in practical applications, for analyzing nonlinear structural equation models with dichotomous data. We demonstrate how to use the software…

  7. Bayesian Analysis of Nonlinear Structural Equation Models with Nonignorable Missing Data

    ERIC Educational Resources Information Center

    Lee, Sik-Yum

    2006-01-01

    A Bayesian approach is developed for analyzing nonlinear structural equation models with nonignorable missing data. The nonignorable missingness mechanism is specified by a logistic regression model. A hybrid algorithm that combines the Gibbs sampler and the Metropolis-Hastings algorithm is used to produce the joint Bayesian estimates of…

  8. Scholastic Achievement in High School Explained? Validation of a Longitudinal Structural Equations Model

    ERIC Educational Resources Information Center

    Hellle, Laura; Tuijula, Tiina; Laakkonen, Eero

    2009-01-01

    The purpose of the study is to shed light on the mechanisms behind scholastic achievement in high school by testing a structural equations model based on the work by Vermunt (1998). It was presumed that self-regulation of learning would predict scholastic achievement and that learning orientations would predict self-regulation of learning. A…

  9. Cultural, Social, and Economic Capital Constructs in International Assessments: An Evaluation Using Exploratory Structural Equation Modeling

    ERIC Educational Resources Information Center

    Caro, Daniel H.; Sandoval-Hernández, Andrés; Lüdtke, Oliver

    2014-01-01

    The article employs exploratory structural equation modeling (ESEM) to evaluate constructs of economic, cultural, and social capital in international large-scale assessment (LSA) data from the Progress in International Reading Literacy Study (PIRLS) 2006 and the Programme for International Student Assessment (PISA) 2009. ESEM integrates the…

  10. Relationships among Adolescents' Leisure Motivation, Leisure Involvement, and Leisure Satisfaction: A Structural Equation Model

    ERIC Educational Resources Information Center

    Chen, Ying-Chieh; Li, Ren-Hau; Chen, Sheng-Hwang

    2013-01-01

    The purpose of this cross-sectional study was to test a cause-and-effect model of factors affecting leisure satisfaction among Taiwanese adolescents. A structural equation model was proposed in which the relationships among leisure motivation, leisure involvement, and leisure satisfaction were explored. The study collected data from 701 adolescent…

  11. Exploratory Structural Equation Modeling, Integrating CFA and EFA: Application to Students' Evaluations of University Teaching

    ERIC Educational Resources Information Center

    Marsh, Herbert W.; Muthen, Bengt; Asparouhov, Tihomir; Ludtke, Oliver; Robitzsch, Alexander; Morin, Alexandre J. S.; Trautwein, Ulrich

    2009-01-01

    This study is a methodological-substantive synergy, demonstrating the power and flexibility of exploratory structural equation modeling (ESEM) methods that integrate confirmatory and exploratory factor analyses (CFA and EFA), as applied to substantively important questions based on multidimentional students' evaluations of university teaching…

  12. Use of Item Parceling in Structural Equation Modeling with Missing Data

    ERIC Educational Resources Information Center

    Orcan, Fatih

    2013-01-01

    Parceling is referred to as a procedure for computing sums or average scores across multiple items. Parcels instead of individual items are then used as indicators of latent factors in the structural equation modeling analysis (Bandalos 2002, 2008; Little et al., 2002; Yang, Nay, & Hoyle, 2010). Item parceling may be applied to alleviate some…

  13. An Examination of Statistical Power in Multigroup Dynamic Structural Equation Models

    ERIC Educational Resources Information Center

    Prindle, John J.; McArdle, John J.

    2012-01-01

    This study used statistical simulation to calculate differential statistical power in dynamic structural equation models with groups (as in McArdle & Prindle, 2008). Patterns of between-group differences were simulated to provide insight into how model parameters influence power approximations. Chi-square and root mean square error of…

  14. A Two-Stage Approach to Synthesizing Covariance Matrices in Meta-Analytic Structural Equation Modeling

    ERIC Educational Resources Information Center

    Cheung, Mike W. L.; Chan, Wai

    2009-01-01

    Structural equation modeling (SEM) is widely used as a statistical framework to test complex models in behavioral and social sciences. When the number of publications increases, there is a need to systematically synthesize them. Methodology of synthesizing findings in the context of SEM is known as meta-analytic SEM (MASEM). Although correlation…

  15. Factors Affecting Higher Order Thinking Skills of Students: A Meta-Analytic Structural Equation Modeling Study

    ERIC Educational Resources Information Center

    Budsankom, Prayoonsri; Sawangboon, Tatsirin; Damrongpanit, Suntorapot; Chuensirimongkol, Jariya

    2015-01-01

    The purpose of the research is to develop and identify the validity of factors affecting higher order thinking skills (HOTS) of students. The thinking skills can be divided into three types: analytical, critical, and creative thinking. This analysis is done by applying the meta-analytic structural equation modeling (MASEM) based on a database of…

  16. On Insensitivity of the Chi-Square Model Test to Nonlinear Misspecification in Structural Equation Models

    ERIC Educational Resources Information Center

    Mooijaart, Ab; Satorra, Albert

    2009-01-01

    In this paper, we show that for some structural equation models (SEM), the classical chi-square goodness-of-fit test is unable to detect the presence of nonlinear terms in the model. As an example, we consider a regression model with latent variables and interactions terms. Not only the model test has zero power against that type of…

  17. A Demonstration of a Systematic Item-Reduction Approach Using Structural Equation Modeling

    ERIC Educational Resources Information Center

    Larwin, Karen; Harvey, Milton

    2012-01-01

    Establishing model parsimony is an important component of structural equation modeling (SEM). Unfortunately, little attention has been given to developing systematic procedures to accomplish this goal. To this end, the current study introduces an innovative application of the jackknife approach first presented in Rensvold and Cheung (1999). Unlike…

  18. Prescriptive Statements and Educational Practice: What Can Structural Equation Modeling (SEM) Offer?

    ERIC Educational Resources Information Center

    Martin, Andrew J.

    2011-01-01

    Longitudinal structural equation modeling (SEM) can be a basis for making prescriptive statements on educational practice and offers yields over "traditional" statistical techniques under the general linear model. The extent to which prescriptive statements can be made will rely on the appropriate accommodation of key elements of research design,…

  19. Evaluating Small Sample Approaches for Model Test Statistics in Structural Equation Modeling.

    ERIC Educational Resources Information Center

    Nevitt, Jonathan

    Structural equation modeling (SEM) attempts to remove the negative influence of measurement error and allows for investigation of relationships at the level of the underlying constructs of interest. SEM has been regarded as a "large sample" technique since its inception. Recent developments in SEM, some of which are currently available in popular…

  20. A Structural Equation Model at the Individual and Group Level for Assessing Faking-Related Change

    ERIC Educational Resources Information Center

    Ferrando, Pere Joan; Anguiano-Carrasco, Cristina

    2011-01-01

    This article proposes a comprehensive approach based on structural equation modeling for assessing the amount of trait-level change derived from faking-motivating situations. The model is intended for a mixed 2-wave 2-group design, and assesses change at both the group and the individual level. Theoretically the model adopts an integrative…

  1. The Trauma Outcome Process Assessment Model: A Structural Equation Model Examination of Adjustment

    ERIC Educational Resources Information Center

    Borja, Susan E.; Callahan, Jennifer L.

    2009-01-01

    This investigation sought to operationalize a comprehensive theoretical model, the Trauma Outcome Process Assessment, and test it empirically with structural equation modeling. The Trauma Outcome Process Assessment reflects a robust body of research and incorporates known ecological factors (e.g., family dynamics, social support) to explain…

  2. Bias and Efficiency in Structural Equation Modeling: Maximum Likelihood versus Robust Methods

    ERIC Educational Resources Information Center

    Zhong, Xiaoling; Yuan, Ke-Hai

    2011-01-01

    In the structural equation modeling literature, the normal-distribution-based maximum likelihood (ML) method is most widely used, partly because the resulting estimator is claimed to be asymptotically unbiased and most efficient. However, this may not hold when data deviate from normal distribution. Outlying cases or nonnormally distributed data,…

  3. Parsimonious Structural Equation Models for Repeated Measures Data, with Application to the Study of Consumer Preferences

    ERIC Educational Resources Information Center

    Elrod, Terry; Haubl, Gerald; Tipps, Steven W.

    2012-01-01

    Recent research reflects a growing awareness of the value of using structural equation models to analyze repeated measures data. However, such data, particularly in the presence of covariates, often lead to models that either fit the data poorly, are exceedingly general and hard to interpret, or are specified in a manner that is highly data…

  4. A Structural Equation Modelling of the Academic Self-Concept Scale

    ERIC Educational Resources Information Center

    Matovu, Musa

    2014-01-01

    The study aimed at validating the academic self-concept scale by Liu and Wang (2005) in measuring academic self-concept among university students. Structural equation modelling was used to validate the scale which was composed of two subscales; academic confidence and academic effort. The study was conducted on university students; males and…

  5. Band structure analysis of an analytically solvable Hill equation with continuous potential

    NASA Astrophysics Data System (ADS)

    Morozov, G. V.; Sprung, D. W. L.

    2015-03-01

    This paper concerns analytically solvable cases of Hill’s equation containing a continuously differentiable periodic potential. We outline a procedure for constructing the Floquet-Bloch fundamental system, and analyze the band structure of the system. The similarities to, and differences from, the cases of a piecewise constant periodic potential and the Mathieu potential, are illuminated.

  6. Spiritual Leadership and Organizational Culture: A Study of Structural Equation Modeling

    ERIC Educational Resources Information Center

    Karadag, Engin

    2009-01-01

    The aim of this study is to test the spiritual leadership behaviors of school principles in a structural equation model. The study is designed to test causality with the assumption that causality exists between the two variables. In this study, spiritual leadership behavior of managers is treated as the independent variable whereas the…

  7. The Issue of Isopower in Power Analysis for Tests of Structural Equation Models

    ERIC Educational Resources Information Center

    MacCallum, Robert; Lee, Taehun; Browne, Michael W.

    2010-01-01

    Two general frameworks have been proposed for evaluating statistical power of tests of model fit in structural equation modeling (SEM). Under the Satorra-Saris (1985) approach, to evaluate the power of the test of fit of Model A, a Model B, within which A is nested, is specified as the alternative hypothesis and considered as the true model. We…

  8. Exploring Mediating Effect of Metacognitive Awareness on Comprehension of Science Texts through Structural Equation Modeling Analysis

    ERIC Educational Resources Information Center

    Wang, Jing-Ru; Chen, Shin-Feng

    2014-01-01

    This study used a Chinese-language version of the Index of Science Reading Awareness (ISRA) to investigate metacognitive awareness and the Reading Comprehension of Science Test (RCST) to explore comprehension of science text by Taiwanese students. Structural equation modeling (SEM) results confirmed the validity of the underlying models of…

  9. A Structural Equation Modelling Approach for Massive Blended Synchronous Teacher Training

    ERIC Educational Resources Information Center

    Kannan, Kalpana; Narayanan, Krishnan

    2015-01-01

    This paper presents a structural equation modelling (SEM) approach for blended synchronous teacher training workshop. It examines the relationship among various factors that influence the Satisfaction (SAT) of participating teachers. Data were collected with the help of a questionnaire from about 500 engineering college teachers. These teachers…

  10. University Students' Behaviors Pertaining to Sustainability: A Structural Equation Model with Sustainability-Related Attributes

    ERIC Educational Resources Information Center

    Sahin, Elvan; Ertepinar, Hamide; Teksoz, Gaye

    2012-01-01

    The purpose of this study is to construct a structural equation model to examine the links among attitudes, values, and behaviors pertaining to sustainability, participation in outdoor recreation as well as gender and tendency to follow mass media for university students. The data were collected by on-line administration of a survey to 958…

  11. A Structural Equation Model of Burnout and Job Exit among Child Protective Services Workers.

    ERIC Educational Resources Information Center

    Drake, Brett; Yadama, Gautam N.

    1996-01-01

    Uses a structural equation model to examine the three elements of the Maslach Burnout Inventory (MBI)--emotional exhaustion, depersonalization, and personal accomplishment--in relation to job exit among child protective services workers over a 15-month period. The model was supported, showing the relevance of all three MBI elements of job exit.…

  12. Testing Time-Invariance of Variable Specificity in Repeated Measure Designs Using Structural Equation Modeling

    ERIC Educational Resources Information Center

    Raykov, Tenko; Amemiya, Yasuo

    2008-01-01

    A structural equation modeling method for examining time-invariance of variable specificity in longitudinal studies with multiple measures is outlined, which is developed within a confirmatory factor-analytic framework. The approach represents a likelihood ratio test for the hypothesis of stability in the specificity part of the residual term…

  13. Residuals and the Residual-Based Statistic for Testing Goodness of Fit of Structural Equation Models

    ERIC Educational Resources Information Center

    Foldnes, Njal; Foss, Tron; Olsson, Ulf Henning

    2012-01-01

    The residuals obtained from fitting a structural equation model are crucial ingredients in obtaining chi-square goodness-of-fit statistics for the model. The authors present a didactic discussion of the residuals, obtaining a geometrical interpretation by recognizing the residuals as the result of oblique projections. This sheds light on the…

  14. Embedding IRT in Structural Equation Models: A Comparison with Regression Based on IRT Scores

    ERIC Educational Resources Information Center

    Lu, Irene R. R.; Thomas, D. Roland; Zumbo, Bruno D.

    2005-01-01

    This article reviews the problems associated with using item response theory (IRT)-based latent variable scores for analytical modeling, discusses the connection between IRT and structural equation modeling (SEM)-based latent regression modeling for discrete data, and compares regression parameter estimates obtained using predicted IRT scores and…

  15. Structural Equation Modeling versus Ordinary Least Squares Canonical Analysis: Some Heuristic Comparisons.

    ERIC Educational Resources Information Center

    Dawson, Thomas E.

    This paper describes structural equation modeling (SEM) in comparison with another overarching analysis within the general linear model (GLM) analytic family: canonical correlation analysis. The uninitiated reader can gain an understanding of SEM's basic tenets and applications. Latent constructs discovered via a measurement model are explored and…

  16. A Graphical Method for Assessing the Identification of Linear Structural Equation Models

    ERIC Educational Resources Information Center

    Eusebi, Paolo

    2008-01-01

    A graphical method is presented for assessing the state of identifiability of the parameters in a linear structural equation model based on the associated directed graph. We do not restrict attention to recursive models. In the recent literature, methods based on graphical models have been presented as a useful tool for assessing the state of…

  17. The Relation among Fit Indexes, Power, and Sample Size in Structural Equation Modeling

    ERIC Educational Resources Information Center

    Kim, Kevin H.

    2005-01-01

    The relation among fit indexes, power, and sample size in structural equation modeling is examined. The noncentrality parameter is required to compute power. The 2 existing methods of computing power have estimated the noncentrality parameter by specifying an alternative hypothesis or alternative fit. These methods cannot be implemented easily and…

  18. Structural Equation Modeling towards Online Learning Readiness, Academic Motivations, and Perceived Learning

    ERIC Educational Resources Information Center

    Horzum, Mehmet Baris; Kaymak, Zeliha Demir; Gungoren, Ozlem Canan

    2015-01-01

    The relationship between online learning readiness, academic motivations, and perceived learning was investigated via structural equation modeling in the research. The population of the research consisted of 750 students who studied using the online learning programs of Sakarya University. 420 of the students who volunteered for the research and…

  19. Anti-Transgender Prejudice: A Structural Equation Model of Associated Constructs

    ERIC Educational Resources Information Center

    Tebbe, Esther N.; Moradi, Bonnie

    2012-01-01

    This study aimed to identify theoretically relevant key correlates of anti-transgender prejudice. Specifically, structural equation modeling was used to test the unique relations of anti-lesbian, gay, and bisexual (LGB) prejudice; traditional gender role attitudes; need for closure; and social dominance orientation with anti-transgender prejudice.…

  20. Meta-Analytic Structural Equation Modeling: A Two-Stage Approach

    ERIC Educational Resources Information Center

    Cheung, Mike W. L.; Chan, Wai

    2005-01-01

    To synthesize studies that use structural equation modeling (SEM), researchers usually use Pearson correlations (univariate r), Fisher z scores (univariate z), or generalized least squares (GLS) to combine the correlation matrices. The pooled correlation matrix is then analyzed by the use of SEM. Questionable inferences may occur for these ad hoc…

  1. Testing Mediation in Structural Equation Modeling: The Effectiveness of the Test of Joint Significance

    ERIC Educational Resources Information Center

    Leth-Steensen, Craig; Gallitto, Elena

    2016-01-01

    A large number of approaches have been proposed for estimating and testing the significance of indirect effects in mediation models. In this study, four sets of Monte Carlo simulations involving full latent variable structural equation models were run in order to contrast the effectiveness of the currently popular bias-corrected bootstrapping…

  2. A Structural Equation Model of Parental Involvement, Motivational and Aptitudinal Characteristics, and Academic Achievement.

    ERIC Educational Resources Information Center

    Gonzalez-Pienda, Julio Antonio; Nunez, Jose Carlos; Gonzalez-Pumariega, Soledad; Alvarez, Luis; Roces, Cristina; Garcia, Marta

    2002-01-01

    Used the structural equation model approach to test a model hypothesizing the influence of parental involvement on students' academic aptitudes, self-concept, and causal attributions, as well as the influence of these variables on academic achievement. Results for 261 adolescents aged 12 to 18 years suggest that cognitive-affective variables are…

  3. How To Generate Non-normal Data for Simulation of Structural Equation Models.

    ERIC Educational Resources Information Center

    Mattson, Stefan

    1997-01-01

    A procedure is proposed to generate non-normal data for simulation of structural equation models. The procedure uses a simple transformation of univariate random variables for the generation of data on latent and error variables under some restrictions for the elements of the covariance matrices for these variables. (SLD)

  4. An Application of Structural Equation Modeling for Developing Good Teaching Characteristics Ontology

    ERIC Educational Resources Information Center

    Phiakoksong, Somjin; Niwattanakul, Suphakit; Angskun, Thara

    2013-01-01

    Ontology is a knowledge representation technique which aims to make knowledge explicit by defining the core concepts and their relationships. The Structural Equation Modeling (SEM) is a statistical technique which aims to explore the core factors from empirical data and estimates the relationship between these factors. This article presents an…

  5. Structural equation modeling of the proximal–distal continuum of adherence drivers

    PubMed Central

    McHorney, Colleen A; Zhang, Ning Jackie; Stump, Timothy; Zhao, Xiaoquan

    2012-01-01

    Objectives Nonadherence to prescription medications has been shown to be significantly influenced by three key medication-specific beliefs: patients’ perceived need for the prescribed medication, their concerns about the prescribed medication, and perceived medication affordability. Structural equation modeling was used to test the predictors of these three proximal determinants of medication adherence using the proximal–distal continuum of adherence drivers as the organizing conceptual framework. Methods In Spring 2008, survey participants were selected from the Harris Interactive Chronic Illness Panel, an internet-based panel of hundreds of thousands of adults with chronic disease. Respondents were eligible for the survey if they were aged 40 years and older, resided in the US, and reported having at least one of six chronic diseases: asthma, diabetes, hyperlipidemia, hypertension, osteoporosis, or other cardiovascular disease. A final sample size of 1072 was achieved. The proximal medication beliefs were measured by three multi-item scales: perceived need for medications, perceived medication concerns, and perceived medication affordability. The intermediate sociomedical beliefs and skills included four multi-item scales: perceived disease severity, knowledge about the prescribed medication, perceived immunity to side effects, and perceived value of nutraceuticals. Generic health beliefs and skills consisted of patient engagement in their care, health information-seeking tendencies, internal health locus of control, a single-item measure of self-rated health, and general mental health. Structural equation modeling was used to model proximal–distal continuum of adherence drivers. Results The average age was 58 years (range = 40–90 years), and 65% were female and 89% were white. Forty-one percent had at least a four-year college education, and just under half (45%) had an annual income of $50,000 or more. Hypertension and hyperlipidemia were each reported

  6. Similarities and Differences in the Perceptual Structure of Facial Expressions of Children and Adults

    ERIC Educational Resources Information Center

    Gao, Xiaoqing; Maurer, Daphne; Nishimura, Mayu

    2010-01-01

    We explored the perceptual structure of facial expressions of six basic emotions, varying systematically in intensity, in adults and children aged 7 and 14 years. Multidimensional scaling suggested that three- or four-dimensional structures were optimal for all groups. Two groups of adults demonstrated nearly identical structure, which had…

  7. Pedagogical Beliefs, Activity Choice and Structure, and Adult-Child Interaction in Nursery Classrooms

    ERIC Educational Resources Information Center

    Blay, Josepha A.; Ireson, Judith

    2009-01-01

    A qualitative analysis of four cooking activities undertaken in two nursery classes reveals relationships between the adults' pedagogical beliefs, the choice and structuring of activities, and the nature of adult-child participation. Four adults each planned and carried out separately, one cooking activity of their choice with a small group of…

  8. The relativistic equations of stellar structure and evolution. Stars with degenerate neutron cores. 1: Structure of equilibrium models

    NASA Technical Reports Server (NTRS)

    Thorne, K. S.; Zytkow, A. N.

    1976-01-01

    The general relativistic equations of stellar structure and evolution are reformulated in a notation which makes easy contact with Newtonian theory. Also, a general relativistic version of the mixing-length formalism for convection is presented. Finally, it is argued that in previous work on spherical systems general relativity theorists have identified the wrong quantity as "total mass-energy inside radius r."

  9. Local Structures in Adult Education: A Discussion Paper.

    ERIC Educational Resources Information Center

    Irish National Association of Adult Education, Dublin.

    In January 2002, Ireland's minister of state announced the establishment of the National Adult Learning Council to take effect in March 2002. One of the council's priorities will be to establish local adult learning boards (LALBs) to oversee development and delivery of adult education. An Irish government white paper recommended that LALBs'…

  10. Families of solutions to the generalized Ginzburg-Landau equation and structural transitions between them

    SciTech Connect

    Ovchinnikov, Yu. N.

    2013-09-15

    Solutions to the generalized Ginzburg-Landau equations for superconductors are obtained for a Ginzburg-Landau parameter {kappa} close to unity. The families of solutions with arbitrary number n of flux quanta in a unit cell are analyzed. It is shown that under certain conditions, a cascade of phase transitions between different structures in a magnetic field appears near T{sub c}. Algebraic equations are derived for determining the boundaries of coexistence of different phases on the (T, H{sub 0}) plane.

  11. Integro-differential equations and the stability of neural networks with dendritic structure.

    PubMed

    Bressloff, P C

    1995-08-01

    We analyse the effects of dendritic structure on the stability of a recurrent neural network in terms of a set of coupled, non-linear Volterra integro-differential equations. These, which describe the dynamics of the somatic membrane potentials, are obtained by eliminating the dendritic potentials from the underlying compartmental model or cable equations. We then derive conditions for Turing-like instability as a precursor for pattern formation in a spatially organized network. These conditions depend on the spatial distribution of axo-dendritic connections across the network. PMID:7548316

  12. Cerebrovascular correlates of vitamin D deficiency in older adults living near the Equator: results from the Atahualpa Project.

    PubMed

    Del Brutto, Oscar H; Mera, Robertino M; Macias, Jorge; Morales, Gabriela; Zambrano, Mauricio

    2015-12-01

    All studies attempting to find an association between vitamin D deficiency and cerebrovascular diseases have been conducted at latitudes far away from the Equator, where living conditions, cardiovascular risk factors, and sunshine exposure are different from tropical regions. We aimed to assess cerebrovascular correlates of vitamin D deficiency in community-dwelling older adults living in Atahualpa, a village located in rural coastal Ecuador. Out of 267 individuals enrolled in the neuroimaging substudy of the Atahualpa Project, 220 (82%) signed the informed consent. Mean age of participants was 70·9 ± 7·8 years, and 126 (57%) were women. Fifty-four (25%) persons have vitamin D levels <20 ng/ml, 47 (21%) had ischemic strokes, and 53 (24%) had moderate-to-severe white matter hyperintensities of presumed vascular origin. Exposure effect models constructed with vitamin D deficiency as the exposure, white matter hyperintensities and ischemic stroke as the outcomes, and confounders--age, gender, body mass index, physical activity, blood pressure, fasting glucose, total cholesterol, ionized calcium, phosphorus, intact parathormone, and serum creatinine--as independent variables revealed a significant association of vitamin D deficiency with white matter hyperintensities (P = 0·006) but not with ischemic strokes (P = 0·359). This study shows an association of vitamin D deficiency with diffuse subcortical brain damage in older adults living in a tropical region. Lack of awareness of the importance of vitamin D deficiency might be one of the factors influencing the high prevalence of white matter hyperintensities of presumed vascular origin in underserved Latin American populations. PMID:26310517

  13. Enriched behavioral prediction equation and its impact on structured leaning and the dynamic calculus.

    PubMed

    Cattell, Raymond B; Boyle, Gregory J; Chant, David

    2002-01-01

    This theoretical note describes an expansion of the behavioral prediction equation, in line with the greater complexity encountered in models of structured learning theory (R. B. Cattell, 1996a). This presents learning theory with a vector substitute for the simpler scalar quantities by which traditional Pavlovian-Skinnerian models have hitherto been represented. Structured learning can be demonstrated by vector changes across a range of intrapersonal psychological variables (ability, personality, motivation, and state constructs). Its use with motivational dynamic trait measures (R. B. Cattell, 1985) should reveal new theoretical possibilities for scientifically monitoring change processes (dynamic calculus model: R. B. Cattell, 1996b), such as encountered within psychotherapeutic settings (R. B. Cattell, 1987). The enhanced behavioral prediction equation suggests that static conceptualizations of personality structure such as the Big Five model are less than optimal. PMID:11863038

  14. Self-assembly of nanocomponents into composite structures: Derivation and simulation of Langevin equations

    NASA Astrophysics Data System (ADS)

    Pankavich, S.; Shreif, Z.; Miao, Y.; Ortoleva, P.

    2009-05-01

    The kinetics of the self-assembly of nanocomponents into a virus, nanocapsule, or other composite structure is analyzed via a multiscale approach. The objective is to achieve predictability and to preserve key atomic-scale features that underlie the formation and stability of the composite structures. We start with an all-atom description, the Liouville equation, and the order parameters characterizing nanoscale features of the system. An equation of Smoluchowski type for the stochastic dynamics of the order parameters is derived from the Liouville equation via a multiscale perturbation technique. The self-assembly of composite structures from nanocomponents with internal atomic structure is analyzed and growth rates are derived. Applications include the assembly of a viral capsid from capsomers, a ribosome from its major subunits, and composite materials from fibers and nanoparticles. Our approach overcomes errors in other coarse-graining methods, which neglect the influence of the nanoscale configuration on the atomistic fluctuations. We account for the effect of order parameters on the statistics of the atomistic fluctuations, which contribute to the entropic and average forces driving order parameter evolution. This approach enables an efficient algorithm for computer simulation of self-assembly, whereas other methods severely limit the timestep due to the separation of diffusional and complexing characteristic times. Given that our approach does not require recalibration with each new application, it provides a way to estimate assembly rates and thereby facilitate the discovery of self-assembly pathways and kinetic dead-end structures.

  15. Self-assembly of nanocomponents into composite structures: derivation and simulation of Langevin equations.

    PubMed

    Pankavich, S; Shreif, Z; Miao, Y; Ortoleva, P

    2009-05-21

    The kinetics of the self-assembly of nanocomponents into a virus, nanocapsule, or other composite structure is analyzed via a multiscale approach. The objective is to achieve predictability and to preserve key atomic-scale features that underlie the formation and stability of the composite structures. We start with an all-atom description, the Liouville equation, and the order parameters characterizing nanoscale features of the system. An equation of Smoluchowski type for the stochastic dynamics of the order parameters is derived from the Liouville equation via a multiscale perturbation technique. The self-assembly of composite structures from nanocomponents with internal atomic structure is analyzed and growth rates are derived. Applications include the assembly of a viral capsid from capsomers, a ribosome from its major subunits, and composite materials from fibers and nanoparticles. Our approach overcomes errors in other coarse-graining methods, which neglect the influence of the nanoscale configuration on the atomistic fluctuations. We account for the effect of order parameters on the statistics of the atomistic fluctuations, which contribute to the entropic and average forces driving order parameter evolution. This approach enables an efficient algorithm for computer simulation of self-assembly, whereas other methods severely limit the timestep due to the separation of diffusional and complexing characteristic times. Given that our approach does not require recalibration with each new application, it provides a way to estimate assembly rates and thereby facilitate the discovery of self-assembly pathways and kinetic dead-end structures. PMID:19466829

  16. Derivation of the equations of motion for complex structures by symbolic manipulation

    NASA Technical Reports Server (NTRS)

    Hale, A. L.; Meirovitch, L.

    1978-01-01

    This paper outlines a computer program especially tailored to the task of deriving explicit equations of motion for structures with point-connected substructures. The special purpose program is written in FORTRAN and is designed for performing the specific algebraic operations encountered in the derivation of explicit equations of motion. The derivation is by the Lagrangian approach. Using an orderly kinematical procedure and a discretization and/or truncation scheme, it is possible to write the kinetic and potential energy of each substructure in a compact vector-matrix form. Then, if each element of the matrices and vectors encountered in the kinetic and potential energy is a known algebraic expression, the computer program performs the necessary operations to evaluate the kinetic and potential energy of the system explicitly. Lagrange's equations for small motions about equilibrium can be deduced directly from the explicit form of the system kinetic and potential energy.

  17. General features and master equations for structurization in complex dusty plasmas

    SciTech Connect

    Tsytovich, V. N.; Morfill, G. E.

    2012-02-15

    Dust structurization is considered to be typical for complex plasmas. Homogeneous dusty plasmas are shown to be universally unstable. The dusty plasma structurization instability is similar to the gravitational instability and can results in creation of different compact dust structures. A general approach for investigation of the nonlinear stage of structurization in dusty plasmas is proposed and master equations for the description of self-organized structures are formulated in the general form that can be used for any nonlinear model of dust screening. New effects due to the scattering of ions on the nonlinearly screened grains are calculated: nonlinear ion dust drag force and nonlinear ion diffusion. The physics of confinement of dust and plasma components in the equilibria of compact dust structures is presented and is supported by numerical calculations of master equations. The necessary conditions for the existence of equilibrium structures are found for an arbitrary nonlinearity in dust screening. Features of compact dust structures observed in recent experiments agree with the numerically calculated ones. Some proposals for future experiments in spherical chamber are given.

  18. Maximum pulsar mass, equation of state and structure of neutron-star cores

    NASA Astrophysics Data System (ADS)

    Haensel, P.; Zdunik, J. L.

    2016-01-01

    The structure of neutron stars is determined by the equation of state of dense matter in their interiors. Brief review of the equation of state from neutron star surface to its center is presented. Recent discovery of two two-solar-mass pulsars puts interesting constraints on the poorly known equation of state of neutron-star cores for densities greater than normal nuclear matter density. Namely, this equation of state has to be stiff enough to yield maximum allowable mass of neutron stars greater than two solar masses. There are many models of neutron stars cores involving exclusively nucleons that satisfy this constraint. However, for neutron-star models based on recent realistic baryon interaction, and allowing for the presence of hyperons, the hyperon softening of the equation of state yields maximum masses significantly lower than two solar masses. Proposed ways out from this ”hyperon puzzle” are presented. They require a very fine tuning of parameters of dense hadronic matter and quark matter models. Consequences for the mass-radius relation for neutron stars are illustrated. A summary of the present situation and possible perspectives/challenges, as well as possible observational tests, are given.

  19. Dromion-like structures and stability analysis in the variable coefficients complex Ginzburg–Landau equation

    SciTech Connect

    Wong, Pring; Pang, Li-Hui; Huang, Long-Gang; Li, Yan-Qing; Lei, Ming; Liu, Wen-Jun

    2015-09-15

    The study of the complex Ginzburg–Landau equation, which can describe the fiber laser system, is of significance for ultra-fast laser. In this paper, dromion-like structures for the complex Ginzburg–Landau equation are considered due to their abundant nonlinear dynamics. Via the modified Hirota method and simplified assumption, the analytic dromion-like solution is obtained. The partial asymmetry of structure is particularly discussed, which arises from asymmetry of nonlinear and dispersion terms. Furthermore, the stability of dromion-like structures is analyzed. Oscillation structure emerges to exhibit strong interference when the dispersion loss is perturbed. Through the appropriate modulation of modified exponent parameter, the oscillation structure is transformed into two dromion-like structures. It indicates that the dromion-like structure is unstable, and the coherence intensity is affected by the modified exponent parameter. Results in this paper may be useful in accounting for some nonlinear phenomena in fiber laser systems, and understanding the essential role of modified Hirota method.

  20. Four-Factor Structure of Obsessive-Compulsive Disorder Symptoms in Children, Adolescents, and Adults

    ERIC Educational Resources Information Center

    Stewart, S. Evelyn; Rosario, Maria C.; Baer, Lee; Carter, Alice S.; Brown, Timothy A.; Scharf, Jeremiah M.; Illmann, Cornelia; Leckman, James F.; Sukhodolsky, Denis; Katsovich, Lilya; Rasmussen, Steven; Goodman, Wayne; Delorme, Richard; Leboyer, Marion; Chabane, Nadia; Jenike, Michael A.; Geller, Daniel A.; Pauls, David L.

    2008-01-01

    A study was conducted to establish the efficacy of four-factor obsessive-compulsive disorder (OCD) symptom structure for use in child, adolescent and adult groups. Results indicated that the four-factor OCD structure is inadequate for use in children, adolescent and adult age groups.

  1. Elliptical vortex solutions, integrable Ermakov structure, and Lax pair formulation of the compressible Euler equations.

    PubMed

    An, Hongli; Fan, Engui; Zhu, Haixing

    2015-01-01

    The 2+1-dimensional compressible Euler equations are investigated here. A power-type elliptic vortex ansatz is introduced and thereby reduction obtains to an eight-dimensional nonlinear dynamical system. The latter is shown to have an underlying integral Ermakov-Ray-Reid structure of Hamiltonian type. It is of interest to notice that such an integrable Ermakov structure exists not only in the density representations but also in the velocity components. A class of typical elliptical vortex solutions termed pulsrodons corresponding to warm-core eddy theory is isolated and its behavior is simulated. In addition, a Lax pair formulation is constructed and the connection with stationary nonlinear cubic Schrödinger equations is established. PMID:25679730

  2. Quantum structure emerging from the transformation design of the Dirac equation

    SciTech Connect

    Lin, De-Hone

    2014-06-15

    It is shown that a quantum structure can be created by a set of chosen constraint conditions that emerge from the transformation design of the Dirac equation in general relativity. As an explanation, the constraints that cause novel bound states with the quantization rule of a 2D Coulomb system are presented. The discussion in this paper provides a systematic way to look for constraints that generate a required quantization rule. -- Highlights: •We perform the transformation design of space and time for spin-1/2 matter waves. •A quantum rule could naturally emerge as constraints imposed on the Dirac equation itself. •New fermion states share the quantum spectrum of a 2D Coulomb system. •Transformation design uncovers a new exact solvable model. •A quantum spectrum can be created by a geometric structure.

  3. Numerical solution of quadratic matrix equations for free vibration analysis of structures

    NASA Technical Reports Server (NTRS)

    Gupta, K. K.

    1975-01-01

    This paper is concerned with the efficient and accurate solution of the eigenvalue problem represented by quadratic matrix equations. Such matrix forms are obtained in connection with the free vibration analysis of structures, discretized by finite 'dynamic' elements, resulting in frequency-dependent stiffness and inertia matrices. The paper presents a new numerical solution procedure of the quadratic matrix equations, based on a combined Sturm sequence and inverse iteration technique enabling economical and accurate determination of a few required eigenvalues and associated vectors. An alternative procedure based on a simultaneous iteration procedure is also described when only the first few modes are the usual requirement. The employment of finite dynamic elements in conjunction with the presently developed eigenvalue routines results in a most significant economy in the dynamic analysis of structures.

  4. Prediction of Shock Wave Structure in Weakly Ionized Gas Flow by Solving MGD Equation

    NASA Technical Reports Server (NTRS)

    Deng, Z. T.; Oviedo-Rojas, Ruben; Chow, Alan; Litchford, Ron J.; Cook, Stephen (Technical Monitor)

    2002-01-01

    This paper reports the recent research results of shockwave structure predictions using a new developed code. The modified Rankine-Hugoniot relations across a standing normal shock wave are discussed and adopted to obtain jump conditions. Coupling a electrostatic body force to the Burnett equations, the weakly ionized flow field across the shock wave was solved. Results indicated that the Modified Rankine-Hugoniot equations for shock wave are valid for a wide range of ionization fraction. However, this model breaks down with small free stream Mach number and with large ionization fraction. The jump conditions also depend on the value of free stream pressure, temperature and density. The computed shock wave structure with ionization provides results, which indicated that shock wave strength may be reduced by existence of weakly ionized gas.

  5. Phylogenetic structural equation modelling reveals no need for an 'origin' of the leaf economics spectrum.

    PubMed

    Mason, Chase M; Goolsby, Eric W; Humphreys, Devon P; Donovan, Lisa A

    2016-01-01

    The leaf economics spectrum (LES) is a prominent ecophysiological paradigm that describes global variation in leaf physiology across plant ecological strategies using a handful of key traits. Nearly a decade ago, Shipley et al. (2006) used structural equation modelling to explore the causal functional relationships among LES traits that give rise to their strong global covariation. They concluded that an unmeasured trait drives LES covariation, sparking efforts to identify the latent physiological trait underlying the 'origin' of the LES. Here, we use newly developed phylogenetic structural equation modelling approaches to reassess these conclusions using both global LES data as well as data collected across scales in the genus Helianthus. For global LES data, accounting for phylogenetic non-independence indicates that no additional unmeasured traits are required to explain LES covariation. Across datasets in Helianthus, trait relationships are highly variable, indicating that global-scale models may poorly describe LES covariation at non-global scales. PMID:26563777

  6. Hamiltonian structures of nonlinear evolution equations connected with a polynomial pencil

    SciTech Connect

    Gadzhiev, I.T.; Gerdzhikov, V.S.; Ivanov, M.I.

    1986-09-10

    For a generalized Zakharov-Shabat system in which the matrix potential is a polynomial in the spectral parameter a generating operator is constructed which makes it possible to compactly write out the nonlinear evolution equations (NEE) connected with the system. The eigenfunctions of the generating operator - the squares of solutions of the original system - are found. The Hamiltonian property of the NEE and the existence of a hierarchy of Hamiltonian structures are established.

  7. Hamiltonian structures of nonlinear evolution equations associated with a polynomial bundle

    SciTech Connect

    Gadzhiev, I.T.; Gerdzhikov, V.S.; Ivanov, M.I.

    1987-05-20

    For the generalized Zakharov-Shabat system with the matrix potential a polynomial in the spectral parameter, they construct a generating operator which leads to a compact representation of the nonlinear evolution equations (NEE) associated with the system. The eigenfunctions of the generating operator are obtained as the squares of the solutions of the original system. The Hamiltonian nature of the NEE and the existence of a hierarchy of Hamiltonian structures is established.

  8. Hamiltonian structures of nonlinear evolution equations connected with a polynomial pencil

    SciTech Connect

    Gadzhiev, I.T.; Gerdzhikov, V.S.; Ivanov, M.I.

    1986-09-01

    For a generalized Zakharov-Shabat system in which the matrix potential is a polynomial in the spectral parameter a generating operator is constructed which makes it possible to compactly write out the nonlinear evolution equations (NEE) connected with the system. The eigenfunctions of the generating operator - the ''squares'' of solutions of the original system - are found. The Hamiltonian property of the NEE and the existence of a hierachy of Hamiltonian structures are established.

  9. Study of the shock wave structure by regularized Grad's set of equations

    NASA Astrophysics Data System (ADS)

    Timokhin, M. Yu.; Bondar, Ye. A.; Kokhanchik, A. A.; Ivanov, M. S.; Ivanov, I. E.; Kryukov, I. A.

    2015-03-01

    In this work, we continue to study the possibility of applying moment equations for strongly nonequilibrium flows by an example of the problem of the shock wave structure in a monatomic gas in a wide range of Mach numbers for various models of molecular interaction. The object of the study is the so-called regularized 13-moment Grad's system (R13). First time, both linear and nonlinear versions of this system of equations were considered for the problem at such wide range of parameters. The Godunov method with increased accuracy is used as a numerical tool for solving the R13 system. The numerical results for the R13 system are analyzed by using data obtained by the Direct Simulation Monte Carlo (DSMC) method, experimental data, and analytical results. As a whole, the R13 system provides an adequate description of the shock wave structure in a wide range of Mach numbers. For Mach numbers around 2, good agreement with experimental and DSMC results is observed for both linear and nonlinear versions of the system. For high Mach numbers, the result strongly depends on the molecular interaction model used: shock wave structure predictions of the nonlinear R13 system are better for Maxwell molecules and worse for hard spheres as compared to the linear version. Particular attention in this work is paid to studying nonmonotonicity of the total temperature profile (temperature overshoot) in the structure of a strong shock wave. It is shown that the moment equations correctly predict the existence of the temperature overshoot. At the same time, the solution of the moment equations overpredicts the temperature overshoot at least two-fold for Mach number M = 8, and the nonlinear version of the R13 system yields a better result for this parameter than the linear version.

  10. How Structure Sense for Algebraic Expressions or Equations Is Related to Structure Sense for Abstract Algebra

    ERIC Educational Resources Information Center

    Novotna, Jarmila; Hoch, Maureen

    2008-01-01

    Many students have difficulties with basic algebraic concepts at high school and at university. In this paper two levels of algebraic structure sense are defined: for high school algebra and for university algebra. We suggest that high school algebra structure sense components are sub-components of some university algebra structure sense…

  11. FACTOR STRUCTURE OF DSM-IV SYMPTOMS IN ADULTS

    EPA Science Inventory

    Objective: In up to 50% of clinic-referred samples of children, ADHD symptoms persist into adulthood,1-3 with the prevalence of adult ADHD currently estimated at 4.4%4. Similar to the pervasive impairments experienced by children with ADHD, adults with ADHD are less likely to com...

  12. Bayesian structural equation modeling: a more flexible representation of substantive theory.

    PubMed

    Muthén, Bengt; Asparouhov, Tihomir

    2012-09-01

    This article proposes a new approach to factor analysis and structural equation modeling using Bayesian analysis. The new approach replaces parameter specifications of exact zeros with approximate zeros based on informative, small-variance priors. It is argued that this produces an analysis that better reflects substantive theories. The proposed Bayesian approach is particularly beneficial in applications where parameters are added to a conventional model such that a nonidentified model is obtained if maximum-likelihood estimation is applied. This approach is useful for measurement aspects of latent variable modeling, such as with confirmatory factor analysis, and the measurement part of structural equation modeling. Two application areas are studied, cross-loadings and residual correlations in confirmatory factor analysis. An example using a full structural equation model is also presented, showing an efficient way to find model misspecification. The approach encompasses 3 elements: model testing using posterior predictive checking, model estimation, and model modification. Monte Carlo simulations and real data are analyzed using Mplus. The real-data analyses use data from Holzinger and Swineford's (1939) classic mental abilities study, Big Five personality factor data from a British survey, and science achievement data from the National Educational Longitudinal Study of 1988. PMID:22962886

  13. Anomalous wave structure in magnetized materials described by non-convex equations of state

    SciTech Connect

    Serna, Susana; Marquina, Antonio

    2014-01-15

    We analyze the anomalous wave structure appearing in flow dynamics under the influence of magnetic field in materials described by non-ideal equations of state. We consider the system of magnetohydrodynamics equations closed by a general equation of state (EOS) and propose a complete spectral decomposition of the fluxes that allows us to derive an expression of the nonlinearity factor as the mathematical tool to determine the nature of the wave phenomena. We prove that the possible formation of non-classical wave structure is determined by both the thermodynamic properties of the material and the magnetic field as well as its possible rotation. We demonstrate that phase transitions induced by material properties do not necessarily imply the loss of genuine nonlinearity of the wavefields as is the case in classical hydrodynamics. The analytical expression of the nonlinearity factor allows us to determine the specific amount of magnetic field necessary to prevent formation of complex structure induced by phase transition in the material. We illustrate our analytical approach by considering two non-convex EOS that exhibit phase transitions and anomalous behavior in the evolution. We present numerical experiments validating the analysis performed through a set of one-dimensional Riemann problems. In the examples we show how to determine the appropriate amount of magnetic field in the initial conditions of the Riemann problem to transform a thermodynamic composite wave into a simple nonlinear wave.

  14. Quantization of wave equations and hermitian structures in partial differential varieties

    PubMed Central

    Paneitz, S. M.; Segal, I. E.

    1980-01-01

    Sufficiently close to 0, the solution variety of a nonlinear relativistic wave equation—e.g., of the form □ϕ + m2ϕ + gϕp = 0—admits a canonical Lorentz-invariant hermitian structure, uniquely determined by the consideration that the action of the differential scattering transformation in each tangent space be unitary. Similar results apply to linear time-dependent equations or to equations in a curved asymptotically flat space-time. A close relation of the Riemannian structure to the determination of vacuum expectation values is developed and illustrated by an explicit determination of a perturbative 2-point function for the case of interaction arising from curvature. The theory underlying these developments is in part a generalization of that of M. G. Krein and collaborators concerning stability of differential equations in Hilbert space and in part a precise relation between the unitarization of given symplectic linear actions and their full probabilistic quantization. The unique causal structure in the infinite symplectic group is instrumental in these developments. PMID:16592923

  15. Nonlinear Dynamics of Layered Structures and the Generalized Sine-Lattice Equations

    NASA Astrophysics Data System (ADS)

    Soboleva, Tatyana; Zeltser, Alexander; Kivshar, Yuri; Turitsyn, Sergei

    1995-07-01

    We analyze nonlinear waves in layered (anisotropic) structures with strong interlayer interaction. One of the important physical examples of nonlinear modes in such structures is the so-called supersolitons, localized excitations of the density of a vortex lattice propagating in a system of interacting (parallel) long Josephson junctions. We show that the dynamics of these structures may be described by the so-called sine-lattice (SL) equation first introduced by S. Takeno and S. Homma [J. Phys. Soc. Jpn. 55 (1986) 65] and its various generalizations, e.g. those which include a transverse degree of freedom or more general types of the interlayer (nonlinear) interactions described by periodic Jacobi elliptic functions. We analyze nonlinear localized waves in such generalized SL equations analytically and numerically, and show that, in general, density waves may be of three types, namely kinks, dynamical solitons, and envelope solitons. We investigate also the transverse stability of quasi-one-dimensional solitons in the framework of the effective modified Boussinesq equation valid for both small amplitudes and continuous approximation, as well as investigate numerically the effects of perturbations (dissipation or point-like impurities) on the dynamics of π -kinks.

  16. Emotional dysregulation, internalizing symptoms, and self-injurious and suicidal behavior: Structural equation modeling analysis.

    PubMed

    Kranzler, Amy; Fehling, Kara B; Anestis, Michael D; Selby, Edward A

    2016-07-01

    This study used structural equation modeling to examine the relationships between emotion dysregulation, internalizing symptoms, nonsuicidal self-injury (NSSI), and suicide. One hundred forty-eight undergraduates completed a brief structured interview and self-report measures of emotion dysregulation, internalizing symptoms, and NSSI and suicidal behaviors. Results indicated a significant indirect effect of emotion dysregulation on NSSI via internalizing symptoms and on suicide attempts via NSSI. Findings provide a more nuanced understanding of the indirect association between emotion dysregulation and NSSI and suicidal behaviors. Implications for the potential utility of targeting internalizing symptoms as well as emotion dysregulation in interventions addressing NSSI and suicidal behaviors are discussed. PMID:26808092

  17. Numerical solution of the vertical structure equation in the normal mode method. [in meteorology

    NASA Technical Reports Server (NTRS)

    Sasaki, Y. K.; Chang, L. P.

    1985-01-01

    In the present model of multilayered stability stratification, aimed at obtaining the analytic eigensolutions of the vertical structure equation, each layer is characterized by its own static stability value. By requiring continuity of pressure and vertical velocity across each interface level, and by imposing suitable upper and lower boundary conditions, matching eigensolutions are obtained in terms of the Bessel functions. Attention is given to an explicit example of a double-layered stratified atmosphere which demonstrates the mathematical manipulations involved; the resultant vertical structure functions are used to check the accuracy of the numerical solutions by the finite difference and finite element methods.

  18. Kinematic assumptions and their consequences on the structure of field equations in continuum dislocation theory

    NASA Astrophysics Data System (ADS)

    Silbermann, C. B.; Ihlemann, J.

    2016-03-01

    Continuum Dislocation Theory (CDT) relates gradients of plastic deformation in crystals with the presence of geometrically necessary dislocations. Therefore, the dislocation tensor is introduced as an additional thermodynamic state variable which reflects tensorial properties of dislocation ensembles. Moreover, the CDT captures both the strain energy from the macroscopic deformation of the crystal and the elastic energy of the dislocation network, as well as the dissipation of energy due to dislocation motion. The present contribution deals with the geometrically linear CDT. More precise, the focus is on the role of dislocation kinematics for single and multi-slip and its consequences on the field equations. Thereby, the number of active slip systems plays a crucial role since it restricts the degrees of freedom of plastic deformation. Special attention is put on the definition of proper, well-defined invariants of the dislocation tensor in order to avoid any spurious dependence of the resulting field equations on the coordinate system. It is shown how a slip system based approach can be in accordance with the tensor nature of the involved quantities. At first, only dislocation glide in one active slip system of the crystal is allowed. Then, the special case of two orthogonal (interacting) slip systems is considered and the governing field equations are presented. In addition, the structure and symmetry of the backstress tensor is investigated from the viewpoint of thermodynamical consistency. The results will again be used in order to facilitate the set of field equations and to prepare for a robust numerical implementation.

  19. Exact combined traveling wave solutions and multi-symplectic structure of the variant Boussinesq-Whitham-Broer-Kaup type equations

    NASA Astrophysics Data System (ADS)

    Yang, Xiao-Feng; Deng, Zi-Chen; Li, Qing-Jun; Wei, Yi

    2016-07-01

    The homogeneous balance of undetermined coefficients method (HBUCM) is firstly proposed to construct not only the exact traveling wave solutions, three-wave solutions, homoclinic solutions, N-soliton solutions, but also multi-symplectic structures of some nonlinear partial differential equations (NLPDEs). By applying the proposed method to the variant Boussinesq equations (VBEs), the exact combined traveling wave solutions and a multi-symplectic structure of the VBEs are obtained directly. Then, the definition and a multi-symplectic structure of the variant Boussinesq-Whitham-Broer-Kaup type equations (VBWBKTEs) which can degenerate to the VBEs, the Whitham-Broer-Kaup equations (WBKEs) and the Broer-Kaup equations (BKEs) are given in the multi-symplectic sense. The HBUCM is also a standard and computable method, which can be generalized to obtain the exact solutions and multi-symplectic structures for some types of NLPDEs.

  20. Energy transfer in structured and unstructured environments: Master equations beyond the Born-Markov approximations.

    PubMed

    Iles-Smith, Jake; Dijkstra, Arend G; Lambert, Neill; Nazir, Ahsan

    2016-01-28

    We explore excitonic energy transfer dynamics in a molecular dimer system coupled to both structured and unstructured oscillator environments. By extending the reaction coordinate master equation technique developed by Iles-Smith et al. [Phys. Rev. A 90, 032114 (2014)], we go beyond the commonly used Born-Markov approximations to incorporate system-environment correlations and the resultant non-Markovian dynamical effects. We obtain energy transfer dynamics for both underdamped and overdamped oscillator environments that are in perfect agreement with the numerical hierarchical equations of motion over a wide range of parameters. Furthermore, we show that the Zusman equations, which may be obtained in a semiclassical limit of the reaction coordinate model, are often incapable of describing the correct dynamical behaviour. This demonstrates the necessity of properly accounting for quantum correlations generated between the system and its environment when the Born-Markov approximations no longer hold. Finally, we apply the reaction coordinate formalism to the case of a structured environment comprising of both underdamped (i.e., sharply peaked) and overdamped (broad) components simultaneously. We find that though an enhancement of the dimer energy transfer rate can be obtained when compared to an unstructured environment, its magnitude is rather sensitive to both the dimer-peak resonance conditions and the relative strengths of the underdamped and overdamped contributions. PMID:26827205

  1. Exact power series solutions of the structure equations of the general relativistic isotropic fluid stars with linear barotropic and polytropic equations of state

    NASA Astrophysics Data System (ADS)

    Harko, T.; Mak, M. K.

    2016-09-01

    Obtaining exact solutions of the spherically symmetric general relativistic gravitational field equations describing the interior structure of an isotropic fluid sphere is a long standing problem in theoretical and mathematical physics. The usual approach to this problem consists mainly in the numerical investigation of the Tolman-Oppenheimer-Volkoff and of the mass continuity equations, which describes the hydrostatic stability of the dense stars. In the present paper we introduce an alternative approach for the study of the relativistic fluid sphere, based on the relativistic mass equation, obtained by eliminating the energy density in the Tolman-Oppenheimer-Volkoff equation. Despite its apparent complexity, the relativistic mass equation can be solved exactly by using a power series representation for the mass, and the Cauchy convolution for infinite power series. We obtain exact series solutions for general relativistic dense astrophysical objects described by the linear barotropic and the polytropic equations of state, respectively. For the polytropic case we obtain the exact power series solution corresponding to arbitrary values of the polytropic index n. The explicit form of the solution is presented for the polytropic index n=1, and for the indexes n=1/2 and n=1/5, respectively. The case of n=3 is also considered. In each case the exact power series solution is compared with the exact numerical solutions, which are reproduced by the power series solutions truncated to seven terms only. The power series representations of the geometric and physical properties of the linear barotropic and polytropic stars are also obtained.

  2. The moser type reduction of integrable Riccati differential equations and its Lie-algebraic structure

    NASA Astrophysics Data System (ADS)

    Napora, Jolanta

    2000-10-01

    A given Riccati equation, as is well known, can be naturally reduced to a system of nonlinear evolution equations on an infinite-dimensional functional manifold with Cauchy-Goursat initial data. We describe the Lie algebraic reduction procedure of nonlocal type for this infinite-dimensional dynamical system upon the set of critical points of an invariant Lagrangian functional. As one of our main results, we show that the reduced dynamical system generates the completely integrable Hamiltonian flow on this submanifold with respect to the canonical symplectic structure upon it. The above also makes it possible to find effectively its finite-dimensional Lax type representation via both the well known Moser type reduction procedure and the dual momentum mapping scheme on some matrix manifold.

  3. New classes of integrals inherent in the mathematical structure of extended equations describing superconducting systems

    NASA Astrophysics Data System (ADS)

    Gonczarek, Ryszard; Krzyzosiak, Mateusz; Gonczarek, Adam; Jacak, Lucjan

    2015-06-01

    In this paper, we discuss the mathematical structure of the s-wave superconducting gap and other quantitative characteristics of superconducting systems. In particular, we evaluate and discuss integrals inherent in fundamental equations describing superconducting systems. The results presented here extend the approach formulated by Abrikosov and Maki, which was restricted to the first-order expansion. A few infinite families of integrals are derived and allow us to express the fundamental equations by means of analytic formulas. They can be then exploited in order to find some quantitative characteristics of superconducting systems by the method of successive approximations. We show that the results can be applied to some modern formalisms in order to study high-Tc superconductors and other superconducting materials of the new generation.

  4. Structure and decay constant of the {rho} meson within the Bethe-Salpeter equation

    SciTech Connect

    Wang, Z. G.; Wan, S. L.

    2007-08-15

    In this article, we study the structure of the {rho} meson in the framework of the coupled rainbow Schwinger-Dyson equation and ladder Bethe-Salpeter equation with a confining effective potential. The u and d quark propagators get significantly modified, the mass poles are absent in the timelike region, which implements confinement naturally. The Bethe-Salpeter amplitudes of the {rho} meson center around zero momentum and extend to the energy scale about q{sup 2}=1 GeV{sup 2}, which happens to be the energy scale of chiral symmetry breaking, strong interactions in the infrared region result in bound state. The numerical results of the mass and decay constant of the {rho} meson are in agreement with the experimental data.

  5. Examining associations between dietary patterns and metabolic CVD risk factors: a novel use of structural equation modelling.

    PubMed

    Castro, Michelle Alessandra; Baltar, Valéria Troncoso; Marchioni, Dirce Maria; Fisberg, Regina Mara

    2016-05-01

    The association between dietary patterns and metabolic cardiovascular risk factors has long been addressed but there is a lack of evidence towards the effects of the overall diet on the complex net of biological inter-relationships between risk factors. This study aimed to derive dietary patterns and examine their associations with metabolic cardiovascular risk factors following a theoretic model for the relationship between them. Participants included 417 adults of both sexes, enrolled to the cross-sectional population-based study performed in Brazil. Body weight, waist circumference, high-sensitivity C-reactive protein, blood pressure, total cholesterol:HDL-cholesterol ratio, TAG:HDL-cholesterol ratio, fasting plasma glucose and serum leptin were evaluated. Food consumption was assessed by two non-consecutive 24-h dietary recalls adjusted for the within-person variation of intake. A total of three dietary patterns were derived by exploratory structural equation modelling: 'Traditional', 'Prudent' and 'Modern'. The 'Traditional' pattern had a negative and direct effect on obesity indicators (serum LEP, body weight and waist circumference) and negative indirect effects on total cholesterol:HDL-cholesterol ratio, TAG:HDL-cholesterol ratio and fasting plasma glucose. The 'Prudent' pattern had a negative and direct effect on systolic blood pressure. No association was observed for the 'Modern' pattern and metabolic risk factors. In conclusion, the 'Traditional' and 'Prudent' dietary patterns were negatively associated with metabolic cardiovascular risk factors among Brazilian adults. Their apparent protective effects against obesity and high blood pressure may be important non-pharmacological strategies for the prevention and control of obesity-related metabolic disorders and CVD. PMID:26931638

  6. Comparison of the Schwartz and CKD-EPI Equations for Estimating Glomerular Filtration Rate in Children, Adolescents, and Adults: A Retrospective Cross-Sectional Study

    PubMed Central

    Selistre, Luciano; Rabilloud, Muriel; Cochat, Pierre; de Souza, Vandréa; Iwaz, Jean; Lemoine, Sandrine; Beyerle, Françoise; Poli-de-Figueiredo, Carlos E.; Dubourg, Laurence

    2016-01-01

    Background Estimating kidney glomerular filtration rate (GFR) is of utmost importance in many clinical conditions. However, very few studies have evaluated the performance of GFR estimating equations over all ages and degrees of kidney impairment. We evaluated the reliability of two major equations for GFR estimation, the CKD-EPI and Schwartz equations, with urinary clearance of inulin as gold standard. Methods and Findings The study included 10,610 participants referred to the Renal and Metabolic Function Exploration Unit of Edouard Herriot Hospital (Lyon, France). GFR was measured by urinary inulin clearance (only first measurement kept for analysis) then estimated with isotope dilution mass spectrometry (IDMS)–traceable CKD-EPI and Schwartz equations. The participants’ ages ranged from 3 to 90 y, and the measured GFRs from 3 to 160 ml/min/1.73 m2. A linear mixed-effects model was used to model the bias (mean ratio of estimated GFR to measured GFR). Equation reliability was also assessed using precision (interquartile range [IQR] of the ratio) and accuracy (percentage of estimated GFRs within the 10% [P10] and 30% [P30] limits above and below the measured GFR). In the whole sample, the mean ratio with the CKD-EPI equation was significantly higher than that with the Schwartz equation (1.17 [95% CI 1.16; 1.18] versus 1.08 [95% CI 1.07; 1.09], p < 0.001, t-test). At GFR values of 60–89 ml/min/1.73 m2, the mean ratios with the Schwartz equation were closer to 1 than the mean ratios with the CKD-EPI equation whatever the age class (1.02 [95% CI 1.01; 1.03] versus 1.15 [95% CI 1.13; 1.16], p < 0.001, t-test). In young adults (18–40 y), the Schwartz equation had a better precision and was also more accurate than the CKD-EPI equation at GFR values under 60 ml/min/1.73 m2 (IQR: 0.32 [95% CI 0.28; 0.33] versus 0.40 [95% CI 0.36; 0.44]; P30: 81.4 [95% CI 78.1; 84.7] versus 63.8 [95% CI 59.7; 68.0]) and also at GFR values of 60–89 ml/min/1.73 m2. In all patients

  7. Seminar on "Structures of Adult Education in Developing Countries, with Special Reference to Africa". Final Report.

    ERIC Educational Resources Information Center

    African Adult Education Association, Lusaka (Zambia).

    The Kikuyu seminar, third in a series of international meeting on the use of comparative studies as a tool of adult education, focused on the application of the comparative approach to developing countries, particularly Africa. Essential components of the structure of adult education were divided into main sectors, which are individually discussed…

  8. Characteristics of Adult to Student Structured Mentoring Programs Occurring in Christian High Schools

    ERIC Educational Resources Information Center

    Winn, Brant D.

    2010-01-01

    This research was designed to answer the question, "What are the characteristics of adult to student structured mentoring programs occurring in Christian high schools?" In the process of answering this question, the following two sub-questions were also answered: "What role does the mentor and mentee play in an adult to student structured…

  9. A ballistic limit equation for hypervelocity impacts on composite honeycomb sandwich panel satellite structures

    NASA Astrophysics Data System (ADS)

    Ryan, S.; Schaefer, F.; Destefanis, R.; Lambert, M.

    During a recent experimental test campaign performed in the framework of ESA Contract 16721, the ballistic performance of multiple satellite-representative Carbon Fibre Reinforced Plastic (CFRP)/Aluminium honeycomb sandwich panel structural configurations (GOCE, Radarsat-2, Herschel/Planck, BeppoSax) was investigated using the two-stage light-gas guns at EMI. The experimental results were used to develop and validate a new empirical Ballistic Limit Equation (BLE), which was derived from an existing Whipple-shield BLE. This new BLE provided a good level of accuracy in predicting the ballistic performance of stand-alone sandwich panel structures. Additionally, the equation is capable of predicting the ballistic limit of a thin Al plate located at a standoff behind the sandwich panel structure. This thin plate is the representative of internal satellite systems, e.g. an Al electronic box cover, a wall of a metallic vessel, etc. Good agreement was achieved with both the experimental test campaign results and additional test data from the literature for the vast majority of set-ups investigated. For some experiments, the ballistic limit was conservatively predicted, a result attributed to shortcomings in correctly accounting for the presence of high surface density multi-layer insulation on the outer facesheet. Four existing BLEs commonly applied for application with stand-alone sandwich panels were reviewed using the new impact test data. It was found that a number of these common approaches provided non-conservative predictions for sandwich panels with CFRP facesheets.

  10. Testing the Factor Structure and Measurement Invariance Across Gender of the Big Five Inventory Through Exploratory Structural Equation Modeling.

    PubMed

    Chiorri, Carlo; Marsh, Herbert W; Ubbiali, Alessandro; Donati, Deborah

    2016-01-01

    Confirmatory factor analyses (CFAs) typically fail to support the a priori 5-factor structure of Big Five self-report instruments, due in part to the overly restrictive CFA assumptions. We show that exploratory structural equation modeling (ESEM), an integration of CFA and exploratory factor analysis, overcomes these problems in relation to responses to the 44-item Big Five Inventory (BFI) administered to a large Italian community sample. ESEM fitted the data better and resulted in less correlated factors than CFA, although ESEM and CFA factor scores correlated at near unity with observed raw scores. Tests of gender invariance with a 13-model taxonomy of full measurement invariance showed that the factor structure of the BFI is gender-invariant and that women score higher on Neuroticism, Agreeableness, Extraversion, and Conscientiousness. Through ESEM one could address substantively important issues about BFI psychometric properties that could not be appropriately addressed through traditional approaches. PMID:25932664

  11. Heteroclinic Structure of Parametric Resonance in the Nonlinear Schrödinger Equation

    NASA Astrophysics Data System (ADS)

    Conforti, M.; Mussot, A.; Kudlinski, A.; Rota Nodari, S.; Dujardin, G.; De Biévre, S.; Armaroli, A.; Trillo, S.

    2016-07-01

    We show that the nonlinear stage of modulational instability induced by parametric driving in the defocusing nonlinear Schrödinger equation can be accurately described by combining mode truncation and averaging methods, valid in the strong driving regime. The resulting integrable oscillator reveals a complex hidden heteroclinic structure of the instability. A remarkable consequence, validated by the numerical integration of the original model, is the existence of breather solutions separating different Fermi-Pasta-Ulam recurrent regimes. Our theory also shows that optimal parametric amplification unexpectedly occurs outside the bandwidth of the resonance (or Arnold tongues) arising from the linearized Floquet analysis.

  12. Constrained hierarchical least square nonlinear equation solvers. [for indefinite stiffness and large structural deformations

    NASA Technical Reports Server (NTRS)

    Padovan, J.; Lackney, J.

    1986-01-01

    The current paper develops a constrained hierarchical least square nonlinear equation solver. The procedure can handle the response behavior of systems which possess indefinite tangent stiffness characteristics. Due to the generality of the scheme, this can be achieved at various hierarchical application levels. For instance, in the case of finite element simulations, various combinations of either degree of freedom, nodal, elemental, substructural, and global level iterations are possible. Overall, this enables a solution methodology which is highly stable and storage efficient. To demonstrate the capability of the constrained hierarchical least square methodology, benchmarking examples are presented which treat structure exhibiting highly nonlinear pre- and postbuckling behavior wherein several indefinite stiffness transitions occur.

  13. The harmonic-map structure of the axially symmetric stationary Einstein equations

    NASA Astrophysics Data System (ADS)

    Whitman, Andrew P.; Stoeger, William R.

    1992-06-01

    We systematically review the solutions of the vacuum Einstein equations for the axially symmetric stationary case which are harmonic maps. In particular, we show that the interesting part of the Kerr solution is a composition of a harmonic map intoH {1/2} with a totally geodesic map fromH {1/2} into SS(1,1). We also point out, relying on Sanchez' results, that there is an analogous structure for the Lorentz-domain cases involving cylindrical gravitational waves and colliding plane waves.

  14. Accurate response surface approximations for weight equations based on structural optimization

    NASA Astrophysics Data System (ADS)

    Papila, Melih

    Accurate weight prediction methods are vitally important for aircraft design optimization. Therefore, designers seek weight prediction techniques with low computational cost and high accuracy, and usually require a compromise between the two. The compromise can be achieved by combining stress analysis and response surface (RS) methodology. While stress analysis provides accurate weight information, RS techniques help to transmit effectively this information to the optimization procedure. The focus of this dissertation is structural weight equations in the form of RS approximations and their accuracy when fitted to results of structural optimizations that are based on finite element analyses. Use of RS methodology filters out the numerical noise in structural optimization results and provides a smooth weight function that can easily be used in gradient-based configuration optimization. In engineering applications RS approximations of low order polynomials are widely used, but the weight may not be modeled well by low-order polynomials, leading to bias errors. In addition, some structural optimization results may have high-amplitude errors (outliers) that may severely affect the accuracy of the weight equation. Statistical techniques associated with RS methodology are sought in order to deal with these two difficulties: (1) high-amplitude numerical noise (outliers) and (2) approximation model inadequacy. The investigation starts with reducing approximation error by identifying and repairing outliers. A potential reason for outliers in optimization results is premature convergence, and outliers of such nature may be corrected by employing different convergence settings. It is demonstrated that outlier repair can lead to accuracy improvements over the more standard approach of removing outliers. The adequacy of approximation is then studied by a modified lack-of-fit approach, and RS errors due to the approximation model are reduced by using higher order polynomials. In

  15. Analysis of factors affecting satisfaction level on problem based learning approach using structural equation modeling

    NASA Astrophysics Data System (ADS)

    Hussain, Nur Farahin Mee; Zahid, Zalina

    2014-12-01

    Nowadays, in the job market demand, graduates are expected not only to have higher performance in academic but they must also be excellent in soft skill. Problem-Based Learning (PBL) has a number of distinct advantages as a learning method as it can deliver graduates that will be highly prized by industry. This study attempts to determine the satisfaction level of engineering students on the PBL Approach and to evaluate their determinant factors. The Structural Equation Modeling (SEM) was used to investigate how the factors of Good Teaching Scale, Clear Goals, Student Assessment and Levels of Workload affected the student satisfaction towards PBL approach.

  16. The Structure of Preschoolers' Emotion Knowledge: Model Equivalence and Validity Using a Structural Equation Modeling Approach

    ERIC Educational Resources Information Center

    Bassett, Hideko Hamada; Denham, Susanne; Mincic, Melissa; Graling, Kelly

    2012-01-01

    Research Findings: A theory-based 2-factor structure of preschoolers' emotion knowledge (i.e., recognition of emotional expression and understanding of emotion-eliciting situations) was tested using confirmatory factor analysis. Compared to 1- and 3-factor models, the 2-factor model showed a better fit to the data. The model was found to be…

  17. Direct and Indirect Effects of Education on Job Satisfaction: A Structural Equation Model for the Spanish Case

    ERIC Educational Resources Information Center

    Fabra, M. Eugenia; Camison, Cesar

    2009-01-01

    Empirical literature has traditionally analyzed the effect of education on job satisfaction with single-equation models that ignore interrelationships between theoretical explanatory variables. Their results are somewhat inconclusive. We propose estimating a structural equation model to obtain both the direct effects and the set of indirect…

  18. A structural equation modeling investigation of age-related variance in executive function and DTI measured white matter damage.

    PubMed

    Charlton, R A; Landau, S; Schiavone, F; Barrick, T R; Clark, C A; Markus, H S; Morris, R G

    2008-10-01

    Cognitive changes in normal aging have been explained by the frontal-executive hypothesis, but the assumptions made by this hypothesis concerning the neurobiological causes are still a matter of debate. Executive functions (EF) may activate neural networks that include disparate grey matter regions, and rely on the integrity of white matter connections. In 118 adults (50-90 years old) from the GENIE study, white matter integrity was measured using diffusion tensor imaging, and information processing speed, fluid intelligence and EF were assessed. A theory-driven structural equation model was developed to test associations between variables. The model was revised, removing non-significant paths. The adjusted model explained well the covariance in our data; and suggested that the reduction in white matter integrity associated with age directly affected only working memory. Fluid intelligence was mediated by all measured cognitive variables. The results suggest that white matter integrity may be particularly important for abilities activating complex neural networks, as occurs in working memory. Integration of the information processing speed and frontal-executive hypotheses may provide important information regarding common, unique, and mediating factors in cognitive aging. PMID:17451845

  19. The Performance of Five Bioelectrical Impedance Analysis Prediction Equations against Dual X-ray Absorptiometry in Estimating Appendicular Skeletal Muscle Mass in an Adult Australian Population

    PubMed Central

    Yu, Solomon C. Y.; Powell, Alice; Khow, Kareeann S. F.; Visvanathan, Renuka

    2016-01-01

    Appendicular skeletal muscle mass (ASM) is a diagnostic criterion for sarcopenia. Bioelectrical impedance analysis (BIA) offers a bedside approach to measure ASM but the performance of BIA prediction equations (PE) varies with ethnicities and body composition. We aim to validate the performance of five PEs in estimating ASM against estimation by dual-energy X-ray absorptiometry (DXA). We recruited 195 healthy adult Australians and ASM was measured using single-frequency BIA. Bland-Altman analysis was used to assess the predictive accuracy of ASM as determined by BIA against DXA. Precision (root mean square error (RMSE)) and bias (mean error (ME)) were calculated according to the method of Sheiner and Beal. Four PEs (except that by Kim) showed ASM values that correlated strongly with ASMDXA (r ranging from 0.96 to 0.97, p < 0.001). The Sergi equation performed the best with the lowest ME of −1.09 kg (CI: −0.84–−1.34, p < 0.001) and the RMSE was 2.09 kg (CI: 1.72–2.47). In men, the Kyle equation performed better with the lowest ME (−0.32 kg (CI: −0.66–0.02) and RMSE (1.54 kg (CI: 1.14–1.93)). The Sergi equation is applicable in adult Australians (Caucasian) whereas the Kyle equation can be considered in males. The need remains to validate PEs in other ethnicities and to develop equations suitable for multi-frequency BIA. PMID:27043617

  20. Integral equation theory of the structure and thermodynamics of polymer blends

    NASA Astrophysics Data System (ADS)

    Schweizer, Kenneth S.; Curro, John G.

    1989-10-01

    Our recently developed RISM integral equation theory of the structure and thermodynamics of homopolymer melts is generalized to polymer mixtures. The mean spherical approximation (MSA) closure to the generalized Ornstein-Zernike equations is employed, in conjunction with the neglect of explicit chain end effects and the assumption of ideality of intramolecular structure. The theory is developed in detail for binary blends, and the random phase approximation (RPA) form for concentration fluctuation scattering is rigorously obtained by enforcing incompressibility. A microscopic, wave vector-dependent expression for the effective chi parameter measured in small angle neutron scattering (SANS) experiments is derived in terms of the species-dependent direct correlation functions of the blend. The effective chi parameter is found to depend, in general, on thermodynamic state, intermolecular forces, intramolecular structure, degree of polymerization, and global architecture. The relationship between the mean field Flory-Huggins expression for the free energy of mixing and our RISM-MSA theory is determined, along with general analytical connections between the chi parameter and intermolecular pair correlations in the liquid. Detailed numerical applications to athermal and isotopic chain polymer blend models are presented for both the chi parameter and the structure. For athermal blends a negative, concentration-dependent chi parameter is found which decreases with density, structural asymmetry, and increases with molecular weight. For isotopic blends, the effective (positive) chi parameter is found to be strongly renormalized downward from its mean field enthalpic value by long range fluctuations in monomer concentration induced by polymeric connectivity and excluded volume. Both the renormalization and composition dependence of the chi parameter increase with chain length and proximity to the spinodal instability. The critical temperature is found to be proportional to

  1. Prolongation Structure of a Generalised Inhomogeneous Gardner Equation in Plasmas and Fluids

    NASA Astrophysics Data System (ADS)

    Xie, Xi-Yang; Tian, Bo; Sun, Wen-Rong; Wang, Yun-Po

    2016-04-01

    In this article, the prolongation structure technique is applied to a generalised inhomogeneous Gardner equation, which can be used to describe certain physical situations, such as the stratified shear flows in ocean and atmosphere, ion acoustic waves in plasmas with a negative ion, interfacial solitary waves over slowly varying topographies, and wave motion in a non-linear elastic structural element with large deflection. The Lax pairs, which are derived via the prolongation structure, are more general than the Lax pairs published before. Under the Painlevé conditions, the linear-damping coefficient equals to zero, the quadratic non-linear coefficient is proportional to the dispersive coefficient c(t), the cubic non-linear coefficient is proportional to c(t), leaving no constraints on c(t) and the dissipative coefficient d(t). We establish the prolongation structure through constructing the exterior differential system. We introduce two methods to obtain the Lax pairs: (a) based on the prolongation structure, the Lax pairs are obtained, and (b) via the Lie algebra, we can derive the Pfaffian forms and Lax pairs when certain parameters are chosen. We set d(t) as a constant to discuss the influence of c(t) on the Pfaffian forms and Lax pairs, and to discuss the influence of d(t) on the Pfaffian forms and Lax pairs, we set c(t) as another constant. Then, we get different prolongation structure, Pfaffian forms and Lax pairs.

  2. Effect of structured physical activity on respiratory outcomes in sedentary elderly adults with mobility limitations

    Technology Transfer Automated Retrieval System (TEKTRAN)

    OBJECTIVES: To evaluate the effect of structured physical activity on respiratory outcomes in community dwelling elderly adults with mobility limitations. DESIGN: Multicenter, randomized trial of physical activity vs health education, with respiratory variables prespecified as tertiary outcomes over...

  3. Guidelines for a graph-theoretic implementation of structural equation modeling

    USGS Publications Warehouse

    Grace, James B.; Schoolmaster, Donald R., Jr.; Guntenspergen, Glenn R.; Little, Amanda M.; Mitchell, Brian R.; Miller, Kathryn M.; Schweiger, E. William

    2012-01-01

    Structural equation modeling (SEM) is increasingly being chosen by researchers as a framework for gaining scientific insights from the quantitative analyses of data. New ideas and methods emerging from the study of causality, influences from the field of graphical modeling, and advances in statistics are expanding the rigor, capability, and even purpose of SEM. Guidelines for implementing the expanded capabilities of SEM are currently lacking. In this paper we describe new developments in SEM that we believe constitute a third-generation of the methodology. Most characteristic of this new approach is the generalization of the structural equation model as a causal graph. In this generalization, analyses are based on graph theoretic principles rather than analyses of matrices. Also, new devices such as metamodels and causal diagrams, as well as an increased emphasis on queries and probabilistic reasoning, are now included. Estimation under a graph theory framework permits the use of Bayesian or likelihood methods. The guidelines presented start from a declaration of the goals of the analysis. We then discuss how theory frames the modeling process, requirements for causal interpretation, model specification choices, selection of estimation method, model evaluation options, and use of queries, both to summarize retrospective results and for prospective analyses. The illustrative example presented involves monitoring data from wetlands on Mount Desert Island, home of Acadia National Park. Our presentation walks through the decision process involved in developing and evaluating models, as well as drawing inferences from the resulting prediction equations. In addition to evaluating hypotheses about the connections between human activities and biotic responses, we illustrate how the structural equation (SE) model can be queried to understand how interventions might take advantage of an environmental threshold to limit Typha invasions. The guidelines presented provide for

  4. Structure and discrimination in chiral fluids: A molecular dynamics and integral equation study

    NASA Astrophysics Data System (ADS)

    Cann, N. M.; Das, B.

    2000-08-01

    An analysis of structure and discrimination in simple chiral fluids is presented. The chiral molecules consist of a central carbon bonded to four distinct groups. Molecular-dynamics simulations have been performed on a one-component chiral fluid and on two racemic mixtures. For the racemates, discrimination, as measured by differences in pair distribution functions, is present but found to be small. Intermolecular pair interaction energies are found to be good predictors of the magnitude and the sign (mirror-image pairs favored) of the differences observed in site-site distribution functions. For the one-component fluid, the quality of structural predictions from the reference-interaction-site method and Chandler-Silbey-Ladanyi (CSL) integral equation theories, with the hypernetted chain (HNC) and Percus-Yevick closures, has been examined. These theories generally provide a qualitatively correct description of the site-site distributions. Extensions beyond the HNC level have been explored: Two-field-point bridge diagrams have been explicitly evaluated and included in the CSL theory. The inclusion of these diagrams significantly improves the quality of the integral equation theories. Since the CSL theory has not been used extensively, and bridge diagrams have been evaluated in only a few instances, a detailed analysis of their impact is presented. For racemic mixtures, diagram evaluation is shown to be crucial. Specifically, the differences in site-site distributions for sites on identical and mirror-image molecules are found to originate from bridge diagrams which involve interactions between four-site, or larger, clusters. Discrimination cannot be predicted from an integral equation theory which neglects these diagrams.

  5. Normal forms for semilinear equations with non-dense domain with applications to age structured models

    NASA Astrophysics Data System (ADS)

    Liu, Zhihua; Magal, Pierre; Ruan, Shigui

    2014-08-01

    Normal form theory is very important and useful in simplifying the forms of equations restricted on the center manifolds in studying nonlinear dynamical problems. In this paper, using the center manifold theorem associated with the integrated semigroup theory, we develop a normal form theory for semilinear Cauchy problems in which the linear operator is not densely defined and is not a Hille-Yosida operator and present procedures to compute the Taylor expansion and normal form of the reduced system restricted on the center manifold. We then apply the main results and computation procedures to determine the direction of the Hopf bifurcation and stability of the bifurcating periodic solutions in a structured evolutionary epidemiological model of influenza A drift and an age structured population model.

  6. Job and Professional Leaving Among Newly Licensed RNs: A Structural Equation Model.

    PubMed

    Unruh, Lynn; Zhang, Ning Jackie; Chisolm, Latarsha

    2016-01-01

    With more than 50% of the nursing workforce close to retirement, it is especially important to keep younger nurses in nursing jobs and careers. This study empirically tests a structural equation model of registered nurse (RN) intent to leave the job and profession using data from a survey of newly licensed RNs (NLRNs). Job demands, difficulties and control, intent to leave the job, and intent to leave the profession were latent variables. A number of direct, indirect, and mediating relationships were modeled. Measurement models for all latent variables and the structural model had good fit. The final model showed a path from job demands, difficulties, and control to job satisfaction to intent to leave the job to intent to leave the profession. The results suggest that the process of an NLRN intending to leave the job and profession involves a number of mediators between the work environment and this intent. PMID:25433000

  7. Adjoint design sensitivity analysis of reduced atomic systems using generalized Langevin equation for lattice structures

    SciTech Connect

    Kim, Min-Geun; Jang, Hong-Lae; Cho, Seonho

    2013-05-01

    An efficient adjoint design sensitivity analysis method is developed for reduced atomic systems. A reduced atomic system and the adjoint system are constructed in a locally confined region, utilizing generalized Langevin equation (GLE) for periodic lattice structures. Due to the translational symmetry of lattice structures, the size of time history kernel function that accounts for the boundary effects of the reduced atomic systems could be reduced to a single atom’s degrees of freedom. For the problems of highly nonlinear design variables, the finite difference method is impractical for its inefficiency and inaccuracy. However, the adjoint method is very efficient regardless of the number of design variables since one additional time integration is required for the adjoint GLE. Through numerical examples, the derived adjoint sensitivity turns out to be accurate and efficient through the comparison with finite difference sensitivity.

  8. Multilevel structural equation models for assessing moderation within and across levels of analysis.

    PubMed

    Preacher, Kristopher J; Zhang, Zhen; Zyphur, Michael J

    2016-06-01

    Social scientists are increasingly interested in multilevel hypotheses, data, and statistical models as well as moderation or interactions among predictors. The result is a focus on hypotheses and tests of multilevel moderation within and across levels of analysis. Unfortunately, existing approaches to multilevel moderation have a variety of shortcomings, including conflated effects across levels of analysis and bias due to using observed cluster averages instead of latent variables (i.e., "random intercepts") to represent higher-level constructs. To overcome these problems and elucidate the nature of multilevel moderation effects, we introduce a multilevel structural equation modeling (MSEM) logic that clarifies the nature of the problems with existing practices and remedies them with latent variable interactions. This remedy uses random coefficients and/or latent moderated structural equations (LMS) for unbiased tests of multilevel moderation. We describe our approach and provide an example using the publicly available High School and Beyond data with Mplus syntax in Appendix. Our MSEM method eliminates problems of conflated multilevel effects and reduces bias in parameter estimates while offering a coherent framework for conceptualizing and testing multilevel moderation effects. (PsycINFO Database Record PMID:26651982

  9. Representing general theoretical concepts in structural equation models: The role of composite variables

    USGS Publications Warehouse

    Grace, J.B.; Bollen, K.A.

    2008-01-01

    Structural equation modeling (SEM) holds the promise of providing natural scientists the capacity to evaluate complex multivariate hypotheses about ecological systems. Building on its predecessors, path analysis and factor analysis, SEM allows for the incorporation of both observed and unobserved (latent) variables into theoretically-based probabilistic models. In this paper we discuss the interface between theory and data in SEM and the use of an additional variable type, the composite. In simple terms, composite variables specify the influences of collections of other variables and can be helpful in modeling heterogeneous concepts of the sort commonly of interest to ecologists. While long recognized as a potentially important element of SEM, composite variables have received very limited use, in part because of a lack of theoretical consideration, but also because of difficulties that arise in parameter estimation when using conventional solution procedures. In this paper we present a framework for discussing composites and demonstrate how the use of partially-reduced-form models can help to overcome some of the parameter estimation and evaluation problems associated with models containing composites. Diagnostic procedures for evaluating the most appropriate and effective use of composites are illustrated with an example from the ecological literature. It is argued that an ability to incorporate composite variables into structural equation models may be particularly valuable in the study of natural systems, where concepts are frequently multifaceted and the influence of suites of variables are often of interest. ?? Springer Science+Business Media, LLC 2007.

  10. On the relationship between modifications to the Raychaudhuri equation and the canonical Hamiltonian structures

    NASA Astrophysics Data System (ADS)

    Singh, Parampreet; Soni, S. K.

    2016-06-01

    The problem of obtaining canonical Hamiltonian structures from the equations of motion, without any knowledge of the action, is studied in the context of the spatially flat Friedmann, ‘Robertson’, and Walker models. Modifications to the Raychaudhuri equation are implemented independently as quadratic and cubic terms of energy density without introducing additional degrees of freedom. Depending on their sign, modifications make gravity repulsive above a curvature scale for matter satisfying strong energy conditions, or more attractive than in the classical theory. The canonical structure of the modified theories is determined by demanding that the total Hamiltonian be a linear combination of gravity and matter Hamiltonians. In the quadratic repulsive case, the modified canonical phase space of gravity is a polymerized phase space with canonical momentum as inverse a trigonometric function of the Hubble rate; the canonical Hamiltonian can be identified with the effective Hamiltonian in loop quantum cosmology. The repulsive cubic modification results in a ‘generalized polymerized’ canonical phase space. Both the repulsive modifications are found to yield singularity avoidance. In contrast, the quadratic and cubic attractive modifications result in a canonical phase space in which canonical momentum is nontrigonometric and singularities persist. Our results hint at connections between the repulsive/attractive nature of modifications to gravity arising from the gravitational sector and polymerized/non polymerized gravitational phase space.

  11. Actinide electronic structure based on the Dirac equation and density functional theory

    NASA Astrophysics Data System (ADS)

    Wills, John M.; Mattsson, Ann E.

    2013-03-01

    Density functional theory (DFT) provides a formally predictive basis for predicting the structural properties of actinides. Although available approximations to the exchange/correlation functional provide accurate predictions for many materials, they fail qualitatively and sometimes quantitatively when applied to actinides. Major contributors to this deficiency are an inadequate treatment of confinement physics and an incomplete treatment of relativity in the underlying equations. The development of a functional correctly incorporating confinement physics with a proper treatment of relativity would provide definitive, internally consistent predictions of actinide properties. To enable the development of such a functional and quantify the predictions of currently available functionals, we have developed an efficient first-principles electronic structure method based on the Dirac equation. Results are compared with current methods, and the implications for relativistic density functionals discussed. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  12. An extended structure-based model based on a stochastic eddy-axis evolution equation

    NASA Technical Reports Server (NTRS)

    Kassinos, S. C.; Reynolds, W. C.

    1995-01-01

    We have proposed and implemented an extension of the structure-based model for weak deformations. It was shown that the extended model will correctly reduce to the form of standard k-e models for the case of equilibrium under weak mean strain. The realizability of the extended model is guaranteed by the method of its construction. The predictions of the proposed model were very good for rotating homogeneous shear flows and for irrotational axisymmetric contraction, but were seriously deficient in the case of plane strain and axisymmetric expansion. We have concluded that the problem behind these difficulties lies in the algebraic constitutive equation relating the Reynolds stresses to the structure parameters rather than in the slow model developed here. In its present form, this equation assumes that under irrotational strain the principal axes of the Reynolds stresses remain locked onto those of the eddy-axis tensor. This is correct in the RDT limit, but inappropriate under weaker mean strains, when the non-linear eddy-eddy interactions tend to misalign the two sets of principal axes and create some non-zero theta and gamma.

  13. Temperature and thermodynamic structure of Einstein's equations for a cosmological black hole

    NASA Astrophysics Data System (ADS)

    Bhattacharya, Krishnakanta; Majhi, Bibhas Ranjan

    2016-07-01

    It is expected that the cosmological black holes are the closest realistic solutions of gravitational theories and they evolve with time. Moreover, the natural way of defining thermodynamic entities for the stationary ones is not applicable in the case of a time dependent spacetime. Here we confine our discussion within the Sultana-Dyer metric, which is a cosmological black hole solution of Einstein's gravity. In the literature, there exist two expressions of horizon temperature—one is time dependent and the other does not depend on time. To single out the correct one we find the temperature by studying the Hawking effect in the tunneling formalism. This leads to time dependent structure. After identifying the correct one, Einstein's equations are written on the horizon and we show that this leads to the first law of thermodynamics. In this process the expressions for horizon entropy and energy, obtained earlier by explicit calculations, are being used. This provides the evidence that Einstein's equations have thermodynamic structure even for a cosmological black hole spacetime. Moreover, this study further clarifies the correctness of the expressions for the thermodynamic quantities, like temperature, entropy, and internal energy.

  14. Structural equation modeling versus marginal structural modeling for assessing mediation in the presence of posttreatment confounding.

    PubMed

    Moerkerke, Beatrijs; Loeys, Tom; Vansteelandt, Stijn

    2015-06-01

    Inverse probability weighting for marginal structural models has been suggested as a strategy to estimate the direct effect of a treatment or exposure on an outcome in studies where the effect of mediator on outcome is subject to posttreatment confounding. This type of confounding, whereby confounders of the effect of mediator on outcome are themselves affected by the exposure, complicates mediation analyses and necessitates apt analysis strategies. In this article, we contrast the inverse probability weighting approach with the traditional path analysis approach to mediation analysis. We show that in a particular class of linear models, adjustment for posttreatment confounding can be realized via a fairly standard modification of the traditional path analysis approach. The resulting approach is simpler; by avoiding inverse probability weighting, it moreover results in direct effect estimators with smaller finite sample bias and greater precision. We further show that a particular variant of the G-estimation approach from the causal inference literature is equivalent with the path analysis approach in simple linear settings but is more generally applicable in settings with interactions and/or noncontinuous mediators and confounders. We conclude that the use of inverse probability weighting for marginal structural models to adjust for posttreatment confounding in mediation analysis is primarily indicated in nonlinear models for the outcome. PMID:25751514

  15. Stability of discontinuity structures described by a generalized KdV-Burgers equation

    NASA Astrophysics Data System (ADS)

    Chugainova, A. P.; Shargatov, V. A.

    2016-02-01

    The stability of discontinuities representing solutions of a model generalized KdV-Burgers equation with a nonmonotone potential of the form φ( u) = u 4- u 2 is analyzed. Among these solutions, there are ones corresponding to special discontinuities. A discontinuity is called special if its structure represents a heteroclinic phase curve joining two saddle-type special points (of which one is the state ahead of the discontinuity and the other is the state behind the discontinuity).The spectral (linear) stability of the structure of special discontinuities was previously studied. It was shown that only a special discontinuity with a monotone structure is stable, whereas special discontinuities with a nonmonotone structure are unstable. In this paper, the spectral stability of nonspecial discontinuities is investigated. The structure of a nonspecial discontinuity represents a phase curve joining two special points: a saddle (the state ahead of the discontinuity) and a focus or node (the state behind the discontinuity). The set of nonspecial discontinuities is examined depending on the dispersion and dissipation parameters. A set of stable nonspecial discontinuities is found.

  16. A determinant-based criterion for working correlation structure selection in generalized estimating equations.

    PubMed

    Jaman, Ajmery; Latif, Mahbub A H M; Bari, Wasimul; Wahed, Abdus S

    2016-05-20

    In generalized estimating equations (GEE), the correlation between the repeated observations on a subject is specified with a working correlation matrix. Correct specification of the working correlation structure ensures efficient estimators of the regression coefficients. Among the criteria used, in practice, for selecting working correlation structure, Rotnitzky-Jewell, Quasi Information Criterion (QIC) and Correlation Information Criterion (CIC) are based on the fact that if the assumed working correlation structure is correct then the model-based (naive) and the sandwich (robust) covariance estimators of the regression coefficient estimators should be close to each other. The sandwich covariance estimator, used in defining the Rotnitzky-Jewell, QIC and CIC criteria, is biased downward and has a larger variability than the corresponding model-based covariance estimator. Motivated by this fact, a new criterion is proposed in this paper based on the bias-corrected sandwich covariance estimator for selecting an appropriate working correlation structure in GEE. A comparison of the proposed and the competing criteria is shown using simulation studies with correlated binary responses. The results revealed that the proposed criterion generally performs better than the competing criteria. An example of selecting the appropriate working correlation structure has also been shown using the data from Madras Schizophrenia Study. Copyright © 2015 John Wiley & Sons, Ltd. PMID:26626276

  17. Development of gender- and age group-specific equations for estimating body weight from anthropometric measurement in Thai adults

    PubMed Central

    Chittawatanarat, Kaweesak; Pruenglampoo, Sakda; Trakulhoon, Vibul; Ungpinitpong, Winai; Patumanond, Jayanton

    2012-01-01

    Background Many medical procedures routinely use body weight as a parameter for calculation. However, these measurements are not always available. In addition, the commonly used visual estimation has had high error rates. Therefore, the aim of this study was to develop a predictive equation for body weight using body circumferences. Methods A prospective study was performed in healthy volunteers. Body weight, height, and eight circumferential level parameters including neck, arm, chest, waist, umbilical level, hip, thigh, and calf were recorded. Linear regression equations were developed in a modeling sample group divided by sex and age (younger <60 years and older ≥60 years). Original regression equations were modified to simple equations by coefficients and intercepts adjustment. These equations were tested in an independent validation sample. Results A total of 2000 volunteers were included in this study. These were randomly separated into two groups (1000 in each modeling and validation group). Equations using height and one covariate circumference were developed. After the covariate selection processes, covariate circumference of chest, waist, umbilical level, and hip were selected for single covariate equations (Sco). To reduce the body somatotype difference, the combination covariate circumferences were created by summation between the chest and one torso circumference of waist, umbilical level, or hip and used in the equation development as a combination covariate equation (Cco). Of these equations, Cco had significantly higher 10% threshold error tolerance compared with Sco (mean percentage error tolerance of Cco versus Sco [95% confidence interval; 95% CI]: 76.9 [74.2–79.6] versus 70.3 [68.4–72.3]; P < 0.01, respectively). Although simple covariate equations had more evidence errors than the original covariate equations, there was comparable error tolerance between the types of equations (original versus simple: 74.5 [71.9–77.1] versus 71.7 [69.2

  18. Professional identity acquisition process model in interprofessional education using structural equation modelling: 10-year initiative survey.

    PubMed

    Kururi, Nana; Tozato, Fusae; Lee, Bumsuk; Kazama, Hiroko; Katsuyama, Shiori; Takahashi, Maiko; Abe, Yumiko; Matsui, Hiroki; Tokita, Yoshiharu; Saitoh, Takayuki; Kanaizumi, Shiomi; Makino, Takatoshi; Shinozaki, Hiromitsu; Yamaji, Takehiko; Watanabe, Hideomi

    2016-01-01

    The mandatory interprofessional education (IPE) programme at Gunma University, Japan, was initiated in 1999. A questionnaire of 10 items to assess the students' understanding of the IPE training programme has been distributed since then, and the factor analysis of the responses revealed that it was categorised into four subscales, i.e. "professional identity", "structure and function of training facilities", "teamwork and collaboration", and "role and responsibilities", and suggested that these may take into account the development of IPE programme with clinical training. The purpose of this study was to examine the professional identity acquisition process (PIAP) model in IPE using structural equation modelling (SEM). Overall, 1,581 respondents of a possible 1,809 students from the departments of nursing, laboratory sciences, physical therapy, and occupational therapy completed the questionnaire. The SEM technique was utilised to construct a PIAP model on the relationships among four factors. The original PIAP model showed that "professional identity" was predicted by two factors, namely "role and responsibilities" and "teamwork and collaboration". These two factors were predicted by the factor "structure and function of training facilities". The same structure was observed in nursing and physical therapy students' PIAP models, but it was not completely the same in laboratory sciences and occupational therapy students' PIAP models. A parallel but not isolated curriculum on expertise unique to the profession, which may help to understand their professional identity in combination with learning the collaboration, may be necessary. PMID:26930464

  19. Structural equation modeling of disability in women with fibromyalgia or multiple sclerosis.

    PubMed

    Phillips, Lorraine J; Stuifbergen, Alexa K

    2009-02-01

    Structural equation modeling (SEM), a popular statistical technique for analysis of multivariate data in the social sciences, is increasingly being used in the behavioral and clinical sciences. SEM is appropriate for posing complex models that evaluate the direct and indirect influence of several variables on one or more outcome variables. A biosocial model of disability, the Disablement Process Model, lends itself to evaluation by SEM. Using SEM, this study examined predictors of disability (Age, Education, Duration of Illness, and Economic Adequacy Functional Limitations, Depressive Symptoms, and Social Support) separately in women with multiple sclerosis (MS) and women with fibromyalgia syndrome (FMS) and compared the respective models across groups. Data were analyzed with Analysis of Moment Structures (Amos) 7.0. Problems identified in initial confirmatory model testing included collateral correlated errors, a negative error variance, and poor performance of the disability indicators. After specifying well-fitting confirmatory models for each group, a structural model for the larger FMS group was estimated. Model refinement resulted in the reversal of the path between Depressive Symptoms and Social Support. Further model revisions were based on comparative fit statistics and theoretical logic. The structural model developed from the FMS sample required minimal changes to fit the MS sample. The multisample model explained greater variance in disability in women with FMS than in women with MS. Social support and depressive symptoms mediated the effect of functional limitations on disability. Interventions that target modifiable characteristics, such as depression and social support, may improve outcomes such as disability. PMID:19150972

  20. Thermodynamic and structural properties of strongly coupled plasma mixtures from the perturbative HNC-equation

    SciTech Connect

    Kang, H.S.; Ree, F.H.

    1997-12-01

    Recently, we developed the perturbative hypernetted-chain (PHNC) integral equation which can predict reliable thermodynamic and structural data for a system of particles interacting with either short range or long range (Coulomb) potential. The present work extends this earlier work to mixtures. This is done by employing a reference potential which is designed to satisfy a thermodynamic consistency on the isothermal compressibility as described in the next section. We test the present theory in Sec. III by applying it to plasma mixtures interacing with either an unscreened or a screened Coulomb potential. We made comparisons of results from the present theory with those from the best available theory, i.e., Rosenfeld`s density functional theory (DFT). The DFT was shown to give internal energy with three to five fignre accuracy compared to a wide range of Monte Carlo data. Meanwhile, small deviations of excess internal energy from the so-called ``liner mixing rule`` (LMR) are better predicted by a less sophiscated theory like the hypernetted- chain (HNC) equation. This rule relates thermodynamics of an unscreened mixture to those for individual components in a strongly coupled regime where the potential energy of a constituent particle is much larger than its kinetic energy. We also apply the present theory to a H{sub 2} + H mixture interacting with Morse potentials. For this sytem, comparison of thermodynamic properties and radial distribution functions from the present theory will be made with those from another successful theory of dense fluid, i.e., the HMSA equation of Zerah and Hansen.

  1. Structural equation models to estimate risk of infection and tolerance to bovine mastitis

    PubMed Central

    2013-01-01

    Background One method to improve durably animal welfare is to select, as reproducers, animals with the highest ability to resist or tolerate infection. To do so, it is necessary to distinguish direct and indirect mechanisms of resistance and tolerance because selection on these traits is believed to have different epidemiological and evolutionary consequences. Methods We propose structural equation models with latent variables (1) to quantify the latent risk of infection and to identify, among the many potential mediators of infection, the few ones that influence it significantly and (2) to estimate direct and indirect levels of tolerance of animals infected naturally with pathogens. We applied the method to two surveys of bovine mastitis in the Walloon region of Belgium, in which we recorded herd management practices, mastitis frequency, and results of bacteriological analyses of milk samples. Results and discussion Structural equation models suggested that, among more than 35 surveyed herd characteristics, only nine (age, addition of urea in the rations, treatment of subclinical mastitis, presence of dirty liner, cows with hyperkeratotic teats, machine stripping, pre- and post-milking teat disinfection, and housing of milking cows in cubicles) were directly and significantly related to a latent measure of bovine mastitis, and that treatment of subclinical mastitis was involved in the pathway between post-milking teat disinfection and latent mastitis. These models also allowed the separation of direct and indirect effects of bacterial infection on milk productivity. Results suggested that infected cows were tolerant but not resistant to mastitis pathogens. Conclusions We revealed the advantages of structural equation models, compared to classical models, for dissecting measurements of resistance and tolerance to infectious diseases, here bovine mastitis. Using our method, we identified nine major risk factors that were directly associated with an increased risk of

  2. Brain Emotion Systems, Personality, Hopelessness, Self/Other Perception, and Gambling Cognition: A Structural Equation Model.

    PubMed

    Iliceto, Paolo; D'Antuono, Laura; Bowden-Jones, Henrietta; Giovani, Eleni; Giacolini, Teodosio; Candilera, Gabriella; Sabatello, Ugo; Panksepp, Jaak

    2016-03-01

    The aim of this study was to explore the relations between gambling, brain emotion systems, personality, self/other perception, and hopelessness in an Italian community. Dimensions of gambling, positive and negative emotions, self/other perception, personality and hopelessness were assessed in a community sample of 235 adults aged 19-59 years. Two structural models were tested. We found a significant correlation between problem gambling and impulsivity, which in association with aggressivity and negative personality dimensions may help explain the psychopathology factor, i.e. a latent variable involving neurotic personality, hopelessness, high sensation seeking, low metacognitive responsiveness, and disorganized patterns of interpersonal relationships. These results contribute to develop a theoretical framework of gambling in relation with personality factors and provide a new approach for clinical intervention of problem gambling that relies on a solid multidimensional perspective. PMID:25894294

  3. Subdivision based isogeometric analysis technique for electric field integral equations for simply connected structures

    NASA Astrophysics Data System (ADS)

    Li, Jie; Dault, Daniel; Liu, Beibei; Tong, Yiying; Shanker, Balasubramaniam

    2016-08-01

    The analysis of electromagnetic scattering has long been performed on a discrete representation of the geometry. This representation is typically continuous but not differentiable. The need to define physical quantities on this geometric representation has led to development of sets of basis functions that need to satisfy constraints at the boundaries of the elements/tessellations (viz., continuity of normal or tangential components across element boundaries). For electromagnetics, these result in either curl/div-conforming basis sets. The geometric representation used for analysis is in stark contrast with that used for design, wherein the surface representation is higher order differentiable. Using this representation for both geometry and physics on geometry has several advantages, and is elucidated in Hughes et al. (2005) [7]. Until now, a bulk of the literature on isogeometric methods have been limited to solid mechanics, with some effort to create NURBS based basis functions for electromagnetic analysis. In this paper, we present the first complete isogeometry solution methodology for the electric field integral equation as applied to simply connected structures. This paper systematically proceeds through surface representation using subdivision, definition of vector basis functions on this surface, to fidelity in the solution of integral equations. We also present techniques to stabilize the solution at low frequencies, and impose a Calderón preconditioner. Several results presented serve to validate the proposed approach as well as demonstrate some of its capabilities.

  4. Numerical solutions of Navier-Stokes equations for the structure of a trailing vortex

    NASA Technical Reports Server (NTRS)

    Jain, A. C.

    1977-01-01

    The structure and decay of a trailing vortex were analyzed during the numerical solutions of the full Navier-Stokes equations. Unsteady forms of the governing equations were recast in terms of circulation, vorticity, and stream function as dependent variables, and a second upwind finite difference scheme was used to integrate them with prescribed initial and boundary conditions. The boundary conditions at the outer edge and at the outflow section of the trailing vortex were considered. Different models of the flow were postulated, and solutions were obtained describing the development of the flow as integration proceeds in time. A parametric study was undertaken with a view to understanding the various phenomena that may possibly occur in the trailing vortex. Using the Hoffman and Joubert law of circulation at the inflow section, the results of this investigation were compared with experimental data for a Convair 990 wind model and a rectangular wing. With an exponentially decaying law of circulation at the inflow section and an adverse pressure gradient at the outer edge of the trailing vortex, solutions depict vortex bursting through the sudden expansion of the core and/or through the stagnation and consequent reversal of the flow on the axis. It was found that this bursting takes place at lower values of the swirl ratio as the Reynolds number increases.

  5. Correlation structure and variable selection in generalized estimating equations via composite likelihood information criteria.

    PubMed

    Nikoloulopoulos, Aristidis K

    2016-06-30

    The method of generalized estimating equations (GEE) is popular in the biostatistics literature for analyzing longitudinal binary and count data. It assumes a generalized linear model for the outcome variable, and a working correlation among repeated measurements. In this paper, we introduce a viable competitor: the weighted scores method for generalized linear model margins. We weight the univariate score equations using a working discretized multivariate normal model that is a proper multivariate model. Because the weighted scores method is a parametric method based on likelihood, we propose composite likelihood information criteria as an intermediate step for model selection. The same criteria can be used for both correlation structure and variable selection. Simulations studies and the application example show that our method outperforms other existing model selection methods in GEE. From the example, it can be seen that our methods not only improve on GEE in terms of interpretability and efficiency but also can change the inferential conclusions with respect to GEE. Copyright © 2016 John Wiley & Sons, Ltd. PMID:26822854

  6. From patterns to causal understanding: Structural equation modeling (SEM) in soil ecology

    USGS Publications Warehouse

    Eisenhauer, Nico; Powell, Jeff R; Grace, James B.; Bowker, Matthew A.

    2015-01-01

    In this perspectives paper we highlight a heretofore underused statistical method in soil ecological research, structural equation modeling (SEM). SEM is commonly used in the general ecological literature to develop causal understanding from observational data, but has been more slowly adopted by soil ecologists. We provide some basic information on the many advantages and possibilities associated with using SEM and provide some examples of how SEM can be used by soil ecologists to shift focus from describing patterns to developing causal understanding and inspiring new types of experimental tests. SEM is a promising tool to aid the growth of soil ecology as a discipline, particularly by supporting research that is increasingly hypothesis-driven and interdisciplinary, thus shining light into the black box of interactions belowground.

  7. The Cusp Catastrophe Model as Cross-Sectional and Longitudinal Mixture Structural Equation Models

    PubMed Central

    Chow, Sy-Miin; Witkiewitz, Katie; Grasman, Raoul P. P. P.; Maisto, Stephen A.

    2015-01-01

    Catastrophe theory (Thom, 1972, 1993) is the study of the many ways in which continuous changes in a system’s parameters can result in discontinuous changes in one or several outcome variables of interest. Catastrophe theory–inspired models have been used to represent a variety of change phenomena in the realm of social and behavioral sciences. Despite their promise, widespread applications of catastrophe models have been impeded, in part, by difficulties in performing model fitting and model comparison procedures. We propose a new modeling framework for testing one kind of catastrophe model — the cusp catastrophe model — as a mixture structural equation model (MSEM) when cross-sectional data are available; or alternatively, as an MSEM with regime-switching (MSEM-RS) when longitudinal panel data are available. The proposed models and the advantages offered by this alternative modeling framework are illustrated using two empirical examples and a simulation study. PMID:25822209

  8. IT vendor selection model by using structural equation model & analytical hierarchy process

    NASA Astrophysics Data System (ADS)

    Maitra, Sarit; Dominic, P. D. D.

    2012-11-01

    Selecting and evaluating the right vendors is imperative for an organization's global marketplace competitiveness. Improper selection and evaluation of potential vendors can dwarf an organization's supply chain performance. Numerous studies have demonstrated that firms consider multiple criteria when selecting key vendors. This research intends to develop a new hybrid model for vendor selection process with better decision making. The new proposed model provides a suitable tool for assisting decision makers and managers to make the right decisions and select the most suitable vendor. This paper proposes a Hybrid model based on Structural Equation Model (SEM) and Analytical Hierarchy Process (AHP) for long-term strategic vendor selection problems. The five steps framework of the model has been designed after the thorough literature study. The proposed hybrid model will be applied using a real life case study to assess its effectiveness. In addition, What-if analysis technique will be used for model validation purpose.

  9. OpenMx 2.0: Extended Structural Equation and Statistical Modeling.

    PubMed

    Neale, Michael C; Hunter, Michael D; Pritikin, Joshua N; Zahery, Mahsa; Brick, Timothy R; Kirkpatrick, Robert M; Estabrook, Ryne; Bates, Timothy C; Maes, Hermine H; Boker, Steven M

    2016-06-01

    The new software package OpenMx 2.0 for structural equation and other statistical modeling is introduced and its features are described. OpenMx is evolving in a modular direction and now allows a mix-and-match computational approach that separates model expectations from fit functions and optimizers. Major backend architectural improvements include a move to swappable open-source optimizers such as the newly written CSOLNP. Entire new methodologies such as item factor analysis and state space modeling have been implemented. New model expectation functions including support for the expression of models in LISREL syntax and a simplified multigroup expectation function are available. Ease-of-use improvements include helper functions to standardize model parameters and compute their Jacobian-based standard errors, access to model components through standard R $ mechanisms, and improved tab completion from within the R Graphical User Interface. PMID:25622929

  10. A Comparison of Methods for Estimating Quadratic Effects in Nonlinear Structural Equation Models

    PubMed Central

    Harring, Jeffrey R.; Weiss, Brandi A.; Hsu, Jui-Chen

    2012-01-01

    Two Monte Carlo simulations were performed to compare methods for estimating and testing hypotheses of quadratic effects in latent variable regression models. The methods considered in the current study were (a) a 2-stage moderated regression approach using latent variable scores, (b) an unconstrained product indicator approach, (c) a latent moderated structural equation method, (d) a fully Bayesian approach, and (e) marginal maximum likelihood estimation. Of the 5 estimation methods, it was found that overall the methods based on maximum likelihood estimation and the Bayesian approach performed best in terms of bias, root-mean-square error, standard error ratios, power, and Type I error control, although key differences were observed. Similarities as well as disparities among methods are highlight and general recommendations articulated. As a point of comparison, all 5 approaches were fit to a reparameterized version of the latent quadratic model to educational reading data. PMID:22429193

  11. High Pressure Structures and Equations of State of HIO3 and HI3 O8

    NASA Astrophysics Data System (ADS)

    Zaug, Joseph; Stavrou, Elissaios; Little, Brian; Bastea, Sorin; Crowhurst, Jonathan

    Knowledge of high-pressure thermodynamic properties of iodine containing oxides and acids is important toward improving the accuracy of semi-empirical predictions of extreme condition explosive and combustive chemistry of iodine containing formulations. Here we report on the synthesis of explosive chemical products HIO3 and HI3O8 and on the structures and isotropic equations of state up to 35 and 45 GPa respectively. EOS model parameters are provided including parametrized exponential-6 interatomic potential values used to conduct thermochemical calculations of iodine containing reactants. This work was performed under the auspices of the U.S. Department of Energy jointly by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  12. The relationship between market orientation and performance in the hospital industry: a structural equations modeling approach.

    PubMed

    Raju, P S; Lonial, S C; Gupta, Y P; Ziegler, C

    2000-06-01

    There is general consensus in the research literature that market orientation is related to organizational performance. This study examines this relationship in the hospital industry. One unique feature of this study is that both market orientation and performance are conceptualized as being multi-dimensional constructs. Hence the technique of Structural Equations Modeling (SEM) is used to examine the relationship. Analyses were based on market orientation and performance data obtained from 175 hospitals in a five-state region of the United States. The SEM results confirm the multi-dimensional nature of both market orientation and performance, and the strong relationship between the constructs. Interestingly, this relationship is found to be much stronger for smaller hospitals than for larger hospitals. Implications for the hospital industry are discussed. PMID:10907326

  13. Perceptions of ambiguously unpleasant interracial interactions: a structural equation modeling approach.

    PubMed

    Marino, Teresa L; Negy, Charles; Hammons, Mary E; McKinney, Cliff; Asberg, Kia

    2007-11-01

    Despite a general consensus in the United States that overtly racist acts are unacceptable, many ambiguous situations in everyday life raise questions of whether racism has influenced a person's behavior in an interracial encounter. The authors of the present study sought to (a) examine simultaneously an array of variables thought to be related to perceived racism and (b) investigate how the contribution of these variables may differ with respect to the asymmetry hypothesis, which suggests that acts of discrimination from a dominant person toward a subordinate person will be viewed as more biased than if the situation were reversed. The authors used a dual structural equation modeling approach. Results indicated that ethnic identity significantly predicted perceived racism. In addition, the extent to which cognitive interpretation style significantly predicted perceived racism depended on the ethnicity of participants involved in the interaction. PMID:18044276

  14. Students attitude towards calculus subject: A case-study using structural equation modeling

    NASA Astrophysics Data System (ADS)

    Awang, Noorehan; Hamid, Nur Nadiah Abd.

    2015-10-01

    This study was designed to assess the attitude of Bumiputera students towards mathematics. The instrument used to measure the attitude was Test of Mathematics Related Attitude (TOMRA). This test measures students' attitudes in four criteria: normality of mathematics (N), attitudes towards mathematics inquiry (I), adoption of mathematics attitude (A) and enjoyment of mathematics lessons (E). The target population of this study was all computer science and quantitative science students who enrolled in a Calculus subject at UiTM Negeri Sembilan. Confirmatory Factor Analysis was carried out and the inter-relationship among the four criteria was analyzed using Structural Equation Modeling. The students scored high in E, moderately in A and relatively low in N and I.

  15. Analyzing average and conditional effects with multigroup multilevel structural equation models

    PubMed Central

    Mayer, Axel; Nagengast, Benjamin; Fletcher, John; Steyer, Rolf

    2014-01-01

    Conventionally, multilevel analysis of covariance (ML-ANCOVA) has been the recommended approach for analyzing treatment effects in quasi-experimental multilevel designs with treatment application at the cluster-level. In this paper, we introduce the generalized ML-ANCOVA with linear effect functions that identifies average and conditional treatment effects in the presence of treatment-covariate interactions. We show how the generalized ML-ANCOVA model can be estimated with multigroup multilevel structural equation models that offer considerable advantages compared to traditional ML-ANCOVA. The proposed model takes into account measurement error in the covariates, sampling error in contextual covariates, treatment-covariate interactions, and stochastic predictors. We illustrate the implementation of ML-ANCOVA with an example from educational effectiveness research where we estimate average and conditional effects of early transition to secondary schooling on reading comprehension. PMID:24795668

  16. High Pressure Structures and Equations of State of HIO3 and HIO3 O8

    NASA Astrophysics Data System (ADS)

    Zaug, Joseph; Stavrou, Elissaios; Little, Brian; Bastea, Sorin; Crowhurst, Jonathan; Chemical Energetics Collaboration

    Knowledge of high-pressure thermodynamic properties of iodine containing oxides and acids is important toward improving the accuracy of semi-empirical predictions of extreme condition explosive and combustive chemistry of iodine containing formulations. Here we report on the synthesis of explosive chemical products HIO3 and HIO3O8 and on the structures and isotropic equations of state up to 35 and 45 GPa respectively. EOS model parameters are provided including parametrized exponential-6 interatomic potential values used to conduct thermochemical calculations of iodine containing reactants. This work was performed under the auspices of the U.S. Department of Energy jointly by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  17. Maternal, Infant Characteristics, Breastfeeding Techniques, and Initiation: Structural Equation Modeling Approaches

    PubMed Central

    Htun, Tha Pyai; Lim, Peng Im; Ho-Lim, Sarah

    2015-01-01

    Objectives The aim of this study was to examine the relationships among maternal and infant characteristics, breastfeeding techniques, and exclusive breastfeeding initiation in different modes of birth using structural equation modeling approaches. Methods We examined a hypothetical model based on integrating concepts of a breastfeeding decision-making model, a breastfeeding initiation model, and a social cognitive theory among 952 mother-infant dyads. The LATCH breastfeeding assessment tool was used to evaluate breastfeeding techniques and two infant feeding categories were used (exclusive and non-exclusive breastfeeding). Results Structural equation models (SEM) showed that multiparity was significantly positively associated with breastfeeding techniques and the jaundice of an infant was significantly negatively related to exclusive breastfeeding initiation. A multigroup analysis in the SEM showed no difference between the caesarean section and vaginal delivery groups estimates of breastfeeding techniques on exclusive breastfeeding initiation. Breastfeeding techniques were significantly positively associated with exclusive breastfeeding initiation in the entire sample and in the vaginal deliveries group. However, breastfeeding techniques were not significantly associated with exclusive breastfeeding initiation in the cesarean section group. Maternal age, maternal race, gestations, birth weight of infant, and postnatal complications had no significant impacts on breastfeeding techniques or exclusive breastfeeding initiation in our study. Overall, the models fitted the data satisfactorily (GFI = 0.979–0.987; AGFI = 0.951–0.962; IFI = 0.958–0.962; CFI = 0.955–0.960, and RMSEA = 0.029–0.034). Conclusions Multiparity and jaundice of an infant were found to affect breastfeeding technique and exclusive breastfeeding initiation respectively. Breastfeeding technique was related to exclusive breastfeeding initiation according to the mode of birth. This

  18. Integrating occupancy models and structural equation models to understand species occurrence

    PubMed Central

    Joseph, Maxwell B.; Preston, Daniel L.; Johnson, Pieter T. J.

    2016-01-01

    Understanding the drivers of species occurrence is a fundamental goal in basic and applied ecology. Occupancy models have emerged as a popular approach for inferring species occurrence because they account for problems associated with imperfect detection in field surveys. Current models, however, are limited because they assume covariates are independent (i.e., indirect effects do not occur). Here, we combined structural equation and occupancy models to investigate complex influences on species occurrence while accounting for imperfect detection. These two methods are inherently compatible because they both provide means to make inference on latent or unobserved quantities based on observed data. Our models evaluated the direct and indirect roles of cattle grazing, water chemistry, vegetation, nonnative fishes, and pond permanence on the occurrence of six pond-breeding amphibians, two of which are threatened: the California tiger salamander (Ambystoma californiense), and the California red-legged frog (Rana draytonii). While cattle had strong effects on pond vegetation and water chemistry, their overall effects on amphibian occurrence were small compared to the consistently negative effects of nonnative fish. Fish strongly reduced occurrence probabilities for four of five native amphibians, including both species of conservation concern. These results could help to identify drivers of amphibian declines and to prioritize strategies for amphibian conservation. More generally, this approach facilitates a more mechanistic representation of ideas about the causes of species distributions in space and time. As shown here, occupancy modeling and structural equation modeling are readily combined, and bring rich sets of techniques that may provide unique theoretical and applied insights into basic ecological questions. PMID:27197402

  19. Integrating occupancy models and structural equation models to understand species occurrence.

    PubMed

    Joseph, Maxwell B; Preston, Daniel L; Johnson, Pieter T J

    2016-03-01

    Understanding the drivers of species occrrece s a fundamenal goal in basic and applied ecology. Occupancy models have emerged as a popular approach for inferring species occurrence because they account for problems associated with imperfect detection in field surveys. Current models, however, are limited because they assume covariates are independent (i.e., indirect effects do not occur). Here, we combined structural equation and occupancy models to investigate complex influences on species occurrence while accounting for imperfect detection. These two methods are inherently compatible because they both provide means to make inference on latent or unobserved quantities based on observed data. Our models evaluated the direct and indirect roles of cattle grazing, water chemistry, vegetation, nonnative fishes, and pond permanence on the occurrence of six pond-breeding amphibians, two of which are threatened: the California tiger salamander (Ambysloma californiense) and the California red-legged frog (Rana draytonil). While cattle had strong effects on pond vegetation and water chemistry, their overall effects on amphibian occurrence were small compared to the consistently negative effects of nonnative fish. Fish strongly reduced occurrence probabilities for four of five native amphibians, including both species of conservation concern. These results could help to identify drivers of amphibian declines and to prioritize strategies for amphibian conservation. More generally, this approach facilitates a more mechanistic representation of ideas about the causes of species distributions in space and time. As shown here, occupancy modeling and structural equation modeling are readily combined, and bring rich sets of techniques that may provide unique theoretical and applied insights into basic ecological questions. PMID:27197402

  20. Structure-function hierarchies and von Kármán-Howarth relations for turbulence in magnetohydrodynamical equations.

    PubMed

    Basu, Abhik; Naji, Ali; Pandit, Rahul

    2014-01-01

    We generalize the method of A. M. Polyakov, [ Phys. Rev. E 52 6183 (1995)] for obtaining structure-function relations in turbulence in the stochastically forced Burgers equation, to develop structure-function hierarchies for turbulence in three models for magnetohydrodynamics (MHD). These are the Burgers analogs of MHD in one dimension [ Eur. Phys. J. B 9 725 (1999)], and in three dimensions (3DMHD and 3D Hall MHD). Our study provides a convenient and unified scheme for the development of structure-function hierarchies for turbulence in a variety of coupled hydrodynamical equations. For turbulence in the three sets of MHD equations mentioned above, we obtain exact relations for third-order structure functions and their derivatives; these expressions are the analogs of the von Kármán-Howarth relations for fluid turbulence. We compare our work with earlier studies of such relations in 3DMHD and 3D Hall MHD. PMID:24580182

  1. Ab initio studies of equations of state and chemical reactions of reactive structural materials

    NASA Astrophysics Data System (ADS)

    Zaharieva, Roussislava

    subject of studies of the shock or thermally induced chemical reactions of the two solids comprising these reactive materials, from first principles, is a relatively new field of study. The published literature on ab initio techniques or quantum mechanics based approaches consists of the ab initio or ab initio-molecular dynamics studies in related fields that contain a solid and a gas. One such study in the literature involves a gas and a solid. This is an investigation of the adsorption of gasses such as carbon monoxide (CO) on Tungsten. The motivation for these studies is to synthesize alternate or synthetic fuel technology by Fischer-Tropsch process. In this thesis these studies are first to establish the procedure for solid-solid reaction and then to extend that to consider the effects of mechanical strain and temperature on the binding energy and chemisorptions of CO on tungsten. Then in this thesis, similar studies are also conducted on the effect of mechanical strain and temperature on the binding energies of Titanium and hydrogen. The motivations are again to understand the method and extend the method to such solid-solid reactions. A second motivation is to seek strained conditions that favor hydrogen storage and strain conditions that release hydrogen easily when needed. Following the establishment of ab initio and ab initio studies of chemical reactions between a solid and a gas, the next step of research is to study thermally induced chemical reaction between two solids (Ni+Al). Thus, specific new studies of the thesis are as follows: (1) Ab initio Studies of Binding energies associated with chemisorption of (a) CO on W surfaces (111, and 100) at elevated temperatures and strains and (b) adsorption of hydrogen in titanium base. (2) Equations of state of mixtures of reactive material structures from ab initio methods. (3) Ab initio studies of the reaction initiation, transition states and reaction products of intermetallic mixtures of (Ni+Al) at elevated

  2. Factors that Affect Mathematics-Science (MS) Scores in the Secondary Education Institutional Exam: An Application of Structural Equation Modeling

    ERIC Educational Resources Information Center

    Yavuz, Mustafa

    2009-01-01

    Discovering what determines students' success in the Secondary Education Institutional Exam is very important to parents and it is also critical for students, teachers, directors, and researchers. Research was carried out by studying the related literature and structural equation modeling techniques. A structural model was created that consisted…

  3. Race/Ethnicity and Social Capital among Middle- and Upper-Middle-Class Elementary School Families: A Structural Equation Model

    ERIC Educational Resources Information Center

    Caldas, Stephen J.; Cornigans, Linda

    2015-01-01

    This study used structural equation modeling to conduct a first and second order confirmatory factor analysis (CFA) of a scale developed by McDonald and Moberg (2002) to measure three dimensions of social capital among a diverse group of middle- and upper-middle-class elementary school parents in suburban New York. A structural path model was…

  4. Analysis of Narrative Discourse Structure as an Ecologically Relevant Measure of Executive Function in Adults

    ERIC Educational Resources Information Center

    Cannizzaro, Michael S.; Coelho, Carl A.

    2013-01-01

    This study examined the narrative discourse production and executive function (EF) abilities of 46 neuro-typical adults (18-98 years old). Two questions were addressed: Is the analysis of narrative structure sensitive to changes associated with aging? & What is the relationship between measures of narrative structure and EF? Narratives were…

  5. On the mathematical and geometrical structure of the determining equations for shear waves in nonlinear isotropic incompressible elastodynamics

    NASA Astrophysics Data System (ADS)

    Saccomandi, Giuseppe; Vitolo, Raffaele

    2014-08-01

    Using the theory of 1 + 1 hyperbolic systems we put in perspective the mathematical and geometrical structure of the celebrated circularly polarized waves solutions for isotropic hyperelastic materials determined by Carroll [Acta Mechanica 3, 167-181 (1967)]. We show that a natural generalization of this class of solutions yields an infinite family of linear solutions for the equations of isotropic elastodynamics. Moreover, we determine a huge class of hyperbolic partial differential equations having the same property of the shear wave system. Restricting the attention to the usual first order asymptotic approximation of the equations determining transverse waves we provide the complete integration of this system using generalized symmetries.

  6. Full Equations (FEQ) model for the solution of the full, dynamic equations of motion for one-dimensional unsteady flow in open channels and through control structures

    USGS Publications Warehouse

    Franz, Delbert D.; Melching, Charles S.

    1997-01-01

    The Full EQuations (FEQ) model is a computer program for solution of the full, dynamic equations of motion for one-dimensional unsteady flow in open channels and through control structures. A stream system that is simulated by application of FEQ is subdivided into stream reaches (branches), parts of the stream system for which complete information on flow and depth are not required (dummy branches), and level-pool reservoirs. These components are connected by special features; that is, hydraulic control structures, including junctions, bridges, culverts, dams, waterfalls, spillways, weirs, side weirs, and pumps. The principles of conservation of mass and conservation of momentum are used to calculate the flow and depth throughout the stream system resulting from known initial and boundary conditions by means of an implicit finite-difference approximation at fixed points (computational nodes). The hydraulic characteristics of (1) branches including top width, area, first moment of area with respect to the water surface, conveyance, and flux coefficients and (2) special features (relations between flow and headwater and (or) tail-water elevations, including the operation of variable-geometry structures) are stored in function tables calculated in the companion program, Full EQuations UTiLities (FEQUTL). Function tables containing other information used in unsteady-flow simulation (boundary conditions, tributary inflows or outflows, gate settings, correction factors, characteristics of dummy branches and level-pool reservoirs, and wind speed and direction) are prepared by the user as detailed in this report. In the iterative solution scheme for flow and depth throughout the stream system, an interpolation of the function tables corresponding to the computational nodes throughout the stream system is done in the model. FEQ can be applied in the simulation of a wide range of stream configurations (including loops), lateral-inflow conditions, and special features. The

  7. Solving the Helmholtz equation in conformal mapped ARROW structures using homotopy perturbation method.

    PubMed

    Reck, Kasper; Thomsen, Erik V; Hansen, Ole

    2011-01-31

    The scalar wave equation, or Helmholtz equation, describes within a certain approximation the electromagnetic field distribution in a given system. In this paper we show how to solve the Helmholtz equation in complex geometries using conformal mapping and the homotopy perturbation method. The solution of the mapped Helmholtz equation is found by solving an infinite series of Poisson equations using two dimensional Fourier series. The solution is entirely based on analytical expressions and is not mesh dependent. The analytical results are compared to a numerical (finite element method) solution. PMID:21368995

  8. A structural equation model of plant species richness and its application to a coastal wetland

    USGS Publications Warehouse

    Grace, J.B.; Pugesek, B.H.

    1997-01-01

    Studies of plant species richness have often emphasized the role of either community biomass (as an indicator of density effects) or abiotic factors. In this article we present a general model that simultaneously examines the relative importance of abiotic and density effects. General and specific models were developed to examine the importance of abiotic conditions, disturbance, and community biomass on plant species richness. Models were evaluated using structural equation modeling based on data from 190 plots across a coastal marsh landscape. The accepted model was found to explain 45% of the observed variation in richness, 75% of biomass, and 65% of light penetration. Model results indicate that abiotic conditions have both direct effects on the species pool and indirect effects on richness mediated through effects on biomass and shading. Effects of disturbance were found to be indirect via biomass. Strong density effects on richness were indicated by the results, and canopy light penetration was found to be a better predictor of richness than was biomass. Overall, it appears that richness in this coastal landscape is controlled in roughly equal proportions by abiotic influences on the species pool and density effects, with disturbance playing a lesser role. The structure of the general model presented should be applicable to a wide variety of herbaceous plant communities.

  9. The Dirac equation in electronic structure calculations: Accurate evaluation of DFT predictions for actinides

    SciTech Connect

    Wills, John M; Mattsson, Ann E

    2012-06-06

    Brooks, Johansson, and Skriver, using the LMTO-ASA method and considerable insight, were able to explain many of the ground state properties of the actinides. In the many years since this work was done, electronic structure calculations of increasing sophistication have been applied to actinide elements and compounds, attempting to quantify the applicability of DFT to actinides and actinide compounds and to try to incorporate other methodologies (i.e. DMFT) into DFT calculations. Through these calculations, the limits of both available density functionals and ad hoc methodologies are starting to become clear. However, it has also become clear that approximations used to incorporate relativity are not adequate to provide rigorous tests of the underlying equations of DFT, not to mention ad hoc additions. In this talk, we describe the result of full-potential LMTO calculations for the elemental actinides, comparing results obtained with a full Dirac basis with those obtained from scalar-relativistic bases, with and without variational spin-orbit. This comparison shows that the scalar relativistic treatment of actinides does not have sufficient accuracy to provide a rigorous test of theory and that variational spin-orbit introduces uncontrolled errors in the results of electronic structure calculations on actinide elements.

  10. A structural equation modelling approach examining the pathways between safety climate, behaviour performance and workplace slipping

    PubMed Central

    Swedler, David I; Verma, Santosh K; Huang, Yueng-Hsiang; Lombardi, David A; Chang, Wen-Ruey; Brennan, Melayne; Courtney, Theodore K

    2015-01-01

    Objective Safety climate has previously been associated with increasing safe workplace behaviours and decreasing occupational injuries. This study seeks to understand the structural relationship between employees’ perceptions of safety climate, performing a safety behaviour (ie, wearing slip-resistant shoes) and risk of slipping in the setting of limited-service restaurants. Methods At baseline, we surveyed 349 employees at 30 restaurants for their perceptions of their safety training and management commitment to safety as well as demographic data. Safety performance was identified as wearing slip-resistant shoes, as measured by direct observation by the study team. We then prospectively collected participants’ hours worked and number of slips weekly for the next 12 weeks. Using a confirmatory factor analysis, we modelled safety climate as a higher order factor composed of previously identified training and management commitment factors. Results The 349 study participants experienced 1075 slips during the 12-week follow-up. Confirmatory factor analysis supported modelling safety climate as a higher order factor composed of safety training and management commitment. In a structural equation model, safety climate indirectly affected prospective risk of slipping through safety performance, but no direct relationship between safety climate and slips was evident. Conclusions Results suggest that safety climate can reduce workplace slips through performance of a safety behaviour as well as suggesting a potential causal mechanism through which safety climate can reduce workplace injuries. Safety climate can be modelled as a higher order factor composed of safety training and management commitment. PMID:25710968

  11. Structural Equation Modeling Highlights the Potential of Kim-1 as a Biomarker for Chronic Kidney Disease

    PubMed Central

    Gardiner, Lesley; Akintola, Adebayo; Chen, Gang; Catania, Jeffrey M.; Vaidya, Vishal; Burghardt, Robert C.; Bonventre, Joseph V.; Trzeciakowski, Jerome; Parrish, Alan R.

    2012-01-01

    Background Chronic kidney disease (CKD) is a major public health problem, and despite continued research in the field, there is still a need to identify both biomarkers of risk and progression, as well as potential therapeutic targets. Structural equation modeling (SEM) is a family of statistical techniques that has been utilized in the fields of sociology and psychology for many years; however, its utilization in the biological sciences is relatively novel. SEM's ability to investigate complex relationships in an efficient, single model could be utilized to understand the progression of CKD, as well as to develop a predictive model to assess kidney status in the patient. Methods Fischer 344 rats were fed either an ad libitum diet or a calorically restricted diet, and a time-course study of kidney structure and function was performed. EQS, a SEM software package, was utilized to generate five CKD models of the Fisher 344 rat and identify relationships between measured variables and estimates of kidney damage and kidney function. Results All models identified strong relationships between a biomarker for CKD, kidney injury molecule-1 (Kim-1) and kidney damage, in the Fischer 344 rat CKD model. Models also indicate a strong relationship between age and renal damage and dysfunction. Conclusion SEM can be used to model CKD and could be useful to examine biomarkers in CKD patients. PMID:22269876

  12. Dual transcriptional activator and repressor roles of TBX20 regulate adult cardiac structure and function

    PubMed Central

    Sakabe, Noboru J.; Aneas, Ivy; Shen, Tao; Shokri, Leila; Park, Soo-Young; Bulyk, Martha L.; Evans, Sylvia M.; Nobrega, Marcelo A.

    2012-01-01

    The ongoing requirement in adult heart for transcription factors with key roles in cardiac development is not well understood. We recently demonstrated that TBX20, a transcriptional regulator required for cardiac development, has key roles in the maintenance of functional and structural phenotypes in adult mouse heart. Conditional ablation of Tbx20 in adult cardiomyocytes leads to a rapid onset and progression of heart failure, with prominent conduction and contractility phenotypes that lead to death. Here we describe a more comprehensive molecular characterization of the functions of TBX20 in adult mouse heart. Coupling genome-wide chromatin immunoprecipitation and transcriptome analyses (RNA-Seq), we identified a subset of genes that change expression in Tbx20 adult cardiomyocyte-specific knockout hearts which are direct downstream targets of TBX20. This analysis revealed a dual role for TBX20 as both a transcriptional activator and a repressor, and that each of these functions regulates genes with very specialized and distinct molecular roles. We also show how TBX20 binds to its targets genome-wide in a context-dependent manner, using various cohorts of co-factors to either promote or repress distinct genetic programs within adult heart. Our integrative approach has uncovered several novel aspects of TBX20 and T-box protein function within adult heart. Sequencing data accession number (http://www.ncbi.nlm.nih.gov/geo): GSE30943. PMID:22328084

  13. Tolman-Oppenheimer-Volkoff equations and their implications for the structures of relativistic stars in f(T) gravity

    NASA Astrophysics Data System (ADS)

    Kpadonou, A. V.; Houndjo, M. J. S.; Rodrigues, M. E.

    2016-07-01

    We investigate in this paper the structures of neutron and quark stars in f(T) theory of gravity where T denotes the torsion scalar. Attention is attached to the TOV type equations of this theory and numerical integrations of these equations are performed with suitable EoS. We search for the deviation of the mass-radius diagrams for power-law and exponential type correction from the TT gravity. Our results show that for some values of the input parameters appearing in the considered models, f(T) theory promotes more the structures of the relativistic stars, in consistency with the observational data.

  14. Significant progress in solution of nonlinear equations at displacement of structure and heat transfer extended surface by new AGM approach

    NASA Astrophysics Data System (ADS)

    Akbari, M. R.; Ganji, D. D.; Nimafar, M.; Ahmadi, A. R.

    2014-12-01

    In this paper, we aim to promote the capability of solving two complicated nonlinear differential equations: 1) Static analysis of the structure with variable cross section areas and materials with slope-deflection method; 2) the problem of one dimensional heat transfer with a logarithmic various surface A( x) and a logarithmic various heat generation G( x) with a simple and innovative approach entitled "Akbari-Ganji's method" (AGM). Comparisons are made between AGM and numerical method, the results of which reveal that this method is very effective and simple and can be applied for other nonlinear problems. It is significant that there are some valuable advantages in this method and also most of the differential equations sets can be answered in this manner while in other methods there is no guarantee to obtain the good results up to now. Brief excellences of this method compared to other approaches are as follows: 1) Differential equations can be solved directly by this method; 2) without any dimensionless procedure, equation(s) can be solved; 3) it is not necessary to convert variables into new ones. According to the aforementioned assertions which are proved in this case study, the process of solving nonlinear equation(s) is very easy and convenient in comparison to other methods.

  15. Structure borne noise analysis using Helmholtz equation least squares based forced vibro acoustic components

    NASA Astrophysics Data System (ADS)

    Natarajan, Logesh Kumar

    This dissertation presents a structure-borne noise analysis technology that is focused on providing a cost-effective noise reduction strategy. Structure-borne sound is generated or transmitted through structural vibration; however, only a small portion of the vibration can effectively produce sound and radiate it to the far-field. Therefore, cost-effective noise reduction is reliant on identifying and suppressing the critical vibration components that are directly responsible for an undesired sound. However, current technologies cannot successfully identify these critical vibration components from the point of view of direct contribution to sound radiation and hence cannot guarantee the best cost-effective noise reduction. The technology developed here provides a strategy towards identifying the critical vibration components and methodically suppressing them to achieve a cost-effective noise reduction. The core of this technology is Helmholtz equation least squares (HELS) based nearfield acoustic holography method. In this study, the HELS formulations derived in spherical co-ordinates using spherical wave expansion functions utilize the input data of acoustic pressures measured in the nearfield of a vibrating object to reconstruct the vibro-acoustic responses on the source surface and acoustic quantities in the far field. Using these formulations, three steps were taken to achieve the goal. First, hybrid regularization techniques were developed to improve the reconstruction accuracy of normal surface velocity of the original HELS method. Second, correlations between the surface vibro-acoustic responses and acoustic radiation were factorized using singular value decomposition to obtain orthogonal basis known here as the forced vibro-acoustic components (F-VACs). The F-VACs enables one to identify the critical vibration components for sound radiation in a similar manner that modal decomposition identifies the critical natural modes in a structural vibration. Finally

  16. Conceptual Structure of the Symptoms of Adult ADHD According to the "DSM-IV" and Retrospective Wender-Utah Criteria

    ERIC Educational Resources Information Center

    Glockner-Rist, Angelika; Pedersen, Anya; Rist, Fred

    2013-01-01

    Objective: Adult "Diagnostic and Statistical Manual of Mental Disorders" (4th ed.; "DSM-IV") and retrospective childhood Wender-Utah ADHD criteria are implemented in self-report measures to assess adult ADHD and its required onset in childhood. Yet their dimensional structure and relationship to adult ADHD depressivity is still…

  17. On the structure of the master equation for a two-level system coupled to a thermal bath

    NASA Astrophysics Data System (ADS)

    de Vega, Inés

    2015-04-01

    We derive a master equation from the exact stochastic Liouville-von-Neumann (SLN) equation (Stockburger and Grabert 2002 Phys. Rev. Lett. 88 170407). The latter depends on two correlated noises and describes exactly the dynamics of an oscillator (which can be either harmonic or present an anharmonicity) coupled to an environment at thermal equilibrium. The newly derived master equation is obtained by performing analytically the average over different noise trajectories. It is found to have a complex hierarchical structure that might be helpful to explain the convergence problems occurring when performing numerically the stochastic average of trajectories given by the SLN equation (Koch et al 2008 Phys. Rev. Lett. 100 230402, Koch 2010 PhD thesis Fakultät Mathematik und Naturwissenschaften der Technischen Universitat Dresden).

  18. Factor Structure of the Primary Scales of the Inventory of Personality Organization in a Nonclinical Sample Using Exploratory Structural Equation Modeling

    ERIC Educational Resources Information Center

    Ellison, William D.; Levy, Kenneth N.

    2012-01-01

    Using exploratory structural equation modeling and multiple regression, we examined the factor structure and criterion relations of the primary scales of the Inventory of Personality Organization (IPO; Kernberg & Clarkin, 1995) in a nonclinical sample. Participants (N = 1,260) completed the IPO and measures of self-concept clarity, defenses,…

  19. Estimating GFR in Adult Patients with Hematopoietic Cell Transplant: Comparison of Estimating Equations with an Iohexol Reference Standard

    PubMed Central

    Pao, Emily; Schoch, Gary; Gooley, Ted; Schwartz, George J.

    2015-01-01

    Background and objectives Formal evaluation of kidney function before and after hematopoietic cell transplant is important to determine conditioning regimens, type of transplant, and medication dosing. Serum creatinine and estimating equations may not accurately assess kidney function. Design, study, participants, & measurements Existing estimating equations for GFR were compared with an iohexol measure of GFR in a prospective cohort study of 50 patients undergoing hematopoietic cell transplant and subsequent care at the Fred Hutchinson Cancer Research Institute from 2009 to 2013. Patients underwent iohexol GFR, serum creatinine, and cystatin C determination at baseline and day 100 posthematopoietic cell transplant. Iohexol GFR measurements were compared with the CKD Epidemiology Collaboration, Inker CKD Epidemiology Collaboration cystatin C with and without serum creatinine, Modification of Diet in Renal Disease, and Cockcroft–Gault estimating equations using Bland–Altman analysis and McNemar’s test. The iohexol measurements were also compared with blood samples collected simultaneously on filter paper. Results Mean differences between iohexol GFR and eGFR on the basis of Bland–Altman analyses ranged from −20.6 to +15.4 ml/min per 1.73 m2 at baseline and −12.7 to +12.9 ml/min per 1.73 m2 at day 100. The CKD Epidemiology Collaboration and Modification of Diet in Renal Disease estimating equations classified 64% of patients with a GFR<90 at baseline compared with 38% by iohexol GFR (P=0.003 and P<0.01, respectively). No statistically significant differences were seen at day 100. The filter paper GFR had a mean difference of 0 at baseline and 5.9 at day 100. Additionally, 21%–37% and 57%–89% of eGFRs were within 10% and 30%, respectively, of the iohexol GFR at baseline, and 16%–34% and 72%–84% were within 10% and 30%, respectively, of the iohexol GFR at day 100; 98% of the filter paper estimates at baseline were within 30%, and 46% were within 10

  20. Age effect on subcortical structures in healthy adults

    PubMed Central

    Goodro, Matt; Sameti, Mohammad; Patenaude, Brian; Fein, George

    2012-01-01

    Cross-sectional age effects in normal control volunteers were investigated in 8 subcortical structures: lateral ventricles, thalamus, caudate, putamen, pallidum, hippocampus, amygdala and nucleus accumbens. Two hundred and twenty six control subjects, ranging in age from 19 to 85 years, were scanned on a 1.5T GE system (n = 184) or a 3.0T Siemens system (n = 42). Cranium-size adjusted subcortical structure volumes were estimated using FSL’s FIRST software, which is fully automated. Significant age effects were found for all volumes when the entire age range was analyzed, however the older subjects (60–85 years of age) showed a stronger correlation between age and structural volume for the ventricles, hippocampus, amygdala and accumbens than middle-aged (35–60 years of age) subjects. Middle-aged subjects were studied at both sites, and age effects in these groups were comparable, despite differences in magnet strength and acquisition systems. This agreement lends support to the validity of the image analysis tools and procedures used in the present study. PMID:22863654

  1. Connecting Athletes' Self-Perceptions and Metaperceptions of Competence: a Structural Equation Modeling Approach.

    PubMed

    Cecchini, Jose A; Fernández-Rio, Javier; Méndez-Giménez, Antonio

    2015-06-27

    This study explored the relationships between athletes' competence self-perceptions and metaperceptions. Two hundred and fifty one student-athletes (14.26 ± 1.89 years), members of twenty different teams (basketball, soccer) completed a questionnaire which included the Perception of Success Questionnaire, the Competence subscale of the Intrinsic Motivation Inventory, and modified versions of both questionnaires to assess athletes' metaperceptions. Structural equation modelling analysis revealed that athletes' task and ego metaperceptions positively predicted task and ego self-perceptions, respectively. Competence metaperceptions were strong predictors of competence self-perceptions, confirming the atypical metaperception formation in outcome-dependent contexts such as sport. Task and ego metaperceptions positively predicted athletes' competence metaperceptions. How coaches value their athletes' competence is more influential on what the athletes think of themselves than their own self-perceptions. Athletes' ego and task metaperceptions influenced their competence metaperceptions (how coaches rate their competence). Therefore, athletes build their competence metaperceptions using all information available from their coaches. Finally, only task-self perfections positively predicted athletes' competence self-perceptions. PMID:26240662

  2. Coaching competency and satisfaction with the coach: a multi-level structural equation model.

    PubMed

    Myers, Nicholas D; Beauchamp, Mark R; Chase, Melissa A

    2011-02-01

    The purpose of this initial predictive validity study was to determine the ability of measures derived from the Athletes' Perceptions of Coaching Competency Scale II - High School Teams (APCCS II-HST) to predict satisfaction with the head coach. Specification of the statistical model was informed by the mediational model of coach-athlete interactions. The technical quality of the satisfaction measure was evaluated before testing the predictive validity of the coaching competency measures. Data were collected from athletes of seven sports. Athlete observations (N = 748) were clustered within teams (G = 74). Multi-group confirmatory factor analyses (CFA) provided evidence for factorial invariance of a reduced version of the satisfaction measure by athlete gender. Multi-level CFA provided evidence of model-data consistency for a reduced version of the satisfaction measure. Multi-level structural equation modelling provided evidence for the ability of latent coaching competency to positively predict latent satisfaction at both the athlete level (technique competency and motivation competency) and the team level (coaching competency) and for close model-data fit. Implications of this study include: that the APCCS II-HST should be viewed as a replacement for the Coaching Competency Scale when the intended population is appropriate; a preliminary multi-level measurement model for satisfaction with one's coach that should be considered as a potential starting point in subsequent studies; and empirical support for a key relationship proposed in the mediational model of coach-athlete interactions. PMID:21184342

  3. The Decision Making Ecology of placing a child into foster care: A structural equation model.

    PubMed

    Graham, J Christopher; Dettlaff, Alan J; Baumann, Donald J; Fluke, John D

    2015-11-01

    The Decision Making Ecology provided a framework for empirically testing the impact of Case, Caseworker and Organizational factors on the decision to place children in out-of-home care. The structural equation model we developed fit the data extremely well, indicating a complex relationship between the variables. The main findings indicate that Case factors, even as aggregated to the worker level, were of most importance: Percent Removed was increased in part by greater average Risk being assessed and more families on a worker's caseload being Low Income. Furthermore, removal rates were increased by lower proportions of Hispanic families on the caseload, as well as lower organizational support, and a perception of manageable workload and sufficient resources. Individual factors, i.e., variables characterizing the caseworkers themselves, were not found to directly influence the placement decision, including workers' own race/ethnicity, though various orders of mediated effects were indicated, and these are detailed. Interrelationships between variables that affect case, caseworker and organizational factors are discussed along with implications for practice. PMID:25861871

  4. Predictors of Quality of Life in Portuguese Obese Patients: A Structural Equation Modeling Application

    PubMed Central

    Vilhena, Estela; Pais-Ribeiro, José; Silva, Isabel; Cardoso, Helena; Mendonça, Denisa

    2014-01-01

    Living with obesity is an experience that may affect multiple aspects of an individual's life. Obesity is considered a relevant public health problem in modern societies. To determine the comparative efficacy of different treatments and to assess their impact on patients' everyday life, it is important to identify factors that are relevant to the quality of life of obese patients. The present study aims to evaluate, in Portuguese obese patients, the simultaneous impact of several psychosocial factors on quality of life. This study also explores the mediating role of stigma in the relationship between positive/negative affect and quality of life. A sample of 215 obese patients selected from the main hospitals in Portugal completed self-report questionnaires to assess sociodemographic, clinical, psychosocial, and quality of life variables. Data were analysed using structural equation modeling. The model fitted the data reasonably well, CFI = 0.9, RMSEA = 0.06. More enthusiastic and more active patients had a better quality of life. Those who reflect lower perception of stigma had a better physical and mental health. Partial mediation effects of stigma between positive affect and mental health and between negative affect and physical health were found. The stigma is pervasive and causes consequences for psychological and physical health. PMID:24693421

  5. Mediation Analysis With Intermediate Confounding: Structural Equation Modeling Viewed Through the Causal Inference Lens

    PubMed Central

    De Stavola, Bianca L.; Daniel, Rhian M.; Ploubidis, George B.; Micali, Nadia

    2015-01-01

    The study of mediation has a long tradition in the social sciences and a relatively more recent one in epidemiology. The first school is linked to path analysis and structural equation models (SEMs), while the second is related mostly to methods developed within the potential outcomes approach to causal inference. By giving model-free definitions of direct and indirect effects and clear assumptions for their identification, the latter school has formalized notions intuitively developed in the former and has greatly increased the flexibility of the models involved. However, through its predominant focus on nonparametric identification, the causal inference approach to effect decomposition via natural effects is limited to settings that exclude intermediate confounders. Such confounders are naturally dealt with (albeit with the caveats of informality and modeling inflexibility) in the SEM framework. Therefore, it seems pertinent to revisit SEMs with intermediate confounders, armed with the formal definitions and (parametric) identification assumptions from causal inference. Here we investigate: 1) how identification assumptions affect the specification of SEMs, 2) whether the more restrictive SEM assumptions can be relaxed, and 3) whether existing sensitivity analyses can be extended to this setting. Data from the Avon Longitudinal Study of Parents and Children (1990–2005) are used for illustration. PMID:25504026

  6. Determinants of Phubbing, Which is the Sum of Many Virtual Addictions: A Structural Equation Model

    PubMed Central

    Karadağ, Engi̇n; Tosuntaş, Şule Betül; Erzen, Evren; Duru, Pinar; Bostan, Nalan; Şahi̇n, Berrak Mizrak; Çulha, İLKAY; Babadağ, Burcu

    2015-01-01

    Background and Aims Phubbing can be described as an individual looking at his or her mobile phone during a conversation with other individuals, dealing with the mobile phone and escaping from interpersonal communication. In this research, determinants of phubbing behavior were investigated; in addition, the effects of gender, smart phone ownership and social media membership were tested as moderators. Methods To examine the cause–effect relations among the variables of the theoretical model, the research employs a correlational design. Participants were 409 university students who were selected via random sampling. Phubbing was obtained via the scales featuring mobile phone addiction, SMS addiction, internet addiction, social media addiction and game addiction. The obtained data were analyzed using a correlation analysis, multiple linear regression analysis and structural equation model. Results The results showed that the most important determinants of phubbing behavior are mobile phone, SMS, social media and internet addictions. Discussion Although the findings show that the highest correlation value explaining phubbing is a mobile phone addiction, the other correlation values reflect a dependency on the phone. Conclusions There is an increasing tendency towards mobile phone use, and this tendency prepares the basis of phubbing. PMID:26014669

  7. A multilevel cross-lagged structural equation analysis for reciprocal relationship between social capital and health.

    PubMed

    Yu, Ge; Sessions, John G; Fu, Yu; Wall, Martin

    2015-10-01

    We investigated the reciprocal relationship between individual social capital and perceived mental and physical health in the UK. Using data from the British Household Panel Survey from 1991 to 2008, we fitted cross-lagged structural equation models that include three indicators of social capital vis. social participation, social network, and loneliness. Given that multiple measurement points (level 1) are nested within individuals (level 2), we also applied a multilevel model to allow for residual variation in the outcomes at the occasion and individual levels. Controlling for gender, age, employment status, educational attainment, marital status, household wealth, and region, our analyses suggest that social participation predicts subsequent change in perceived mental health, and vice versa. However, whilst loneliness is found to be significantly related to perceived mental and physical health, reciprocal causality is not found for perceived mental health. Furthermore, we find evidence for reverse effects with both perceived mental and physical health appearing to be the dominant causal factor with respect to the prospective level of social network. Our findings thus shed further light on the importance of social participation and social inclusion in health promotion and aid the development of more effective public health policies in the UK. PMID:26277109

  8. Bayesian model comparison of nonlinear structural equation models with missing continuous and ordinal categorical data.

    PubMed

    Lee, Sik-Yum; Song, Xin-Yuan

    2004-05-01

    Missing data are very common in behavioural and psychological research. In this paper, we develop a Bayesian approach in the context of a general nonlinear structural equation model with missing continuous and ordinal categorical data. In the development, the missing data are treated as latent quantities, and provision for the incompleteness of the data is made by a hybrid algorithm that combines the Gibbs sampler and the Metropolis-Hastings algorithm. We show by means of a simulation study that the Bayesian estimates are accurate. A Bayesian model comparison procedure based on the Bayes factor and path sampling is proposed. The required observations from the posterior distribution for computing the Bayes factor are simulated by the hybrid algorithm in Bayesian estimation. Our simulation results indicate that the correct model is selected more frequently when the incomplete records are used in the analysis than when they are ignored. The methodology is further illustrated with a real data set from a study concerned with an AIDS preventative intervention for Filipina sex workers. PMID:15171804

  9. Executive functions, impulsivity, and inhibitory control in adolescents: A structural equation model.

    PubMed

    Fino, Emanuele; Melogno, Sergio; Iliceto, Paolo; D'Aliesio, Sara; Pinto, Maria Antonietta; Candilera, Gabriella; Sabatello, Ugo

    2014-01-01

    Background. Adolescence represents a critical period for brain development, addressed by neurodevelopmental models to frontal, subcortical-limbic, and striatal activation, a pattern associated with rise of impulsivity and deficits in inhibitory control. The present study aimed at studying the association between self-report measures of impulsivity and inhibitory control with executive function in adolescents, employing structural equation modeling. Method. Tests were administered to 434 high school students. Acting without thinking was measured through the Barratt Impulsiveness Scale and the Dickman Impulsivity Inventory, reward sensitivity through the Behavioral Activation System, and sensation seeking through the Zuckerman-Kuhlman-Aluja Personali- ty Questionnaire. Inhibitory control was assessed through the Behavioral Inhibition System. The performance at the Wisconsin Card Sorting Task indicated executive function. Three models were specified using Sample Covariance Matrix, and the estimated parameters using Maximum Likelihood. Results. In the final model, impulsivity and inhibitory control predicted executive function, but sensation seeking did not. The fit of the model to data was excellent. Conclusions. The hypothesis that inhibitory control and impulsivity are predictors of executive function was supported. Our results appear informative of the validity of self-report measures to examine the relation between impulsivity traits rather than others to regulatory function of cognition and behavior. PMID:25157298

  10. [Antecedents and consequences of workplace bullying: a longitudinal analysis with a structural equation model].

    PubMed

    Carretero Domínguez, Noelia; Gil-Monte, Pedro Rafael; Luciano Devis, Juan Vicente

    2011-11-01

    Most studies focusing on the antecedents and consequences of workplace bullying have used a cross-sectional design, which impedes determining the causality of the relationships. In the present work, we analyzed, by means of structural equation models, the relationship between workplace bullying and some variables that are considered antecedents (interpersonal conflicts, role ambiguity, role conflict, and workplace social support) or consequences (health complaints and inclination to absenteeism from work) of this phenomenon. Multicenter study with two phases. The sample consisted of 696 employees from 66 centers. Workplace bullying was assessed by means of the "Mobbing-UNIPSICO" questionnaire, and the other variables with frequency scales. The cross-sectional models indicated a significant association between role conflict, workplace social support, and workplace bullying in both study periods. Concerning the longitudinal relationships, only workplace social support was a significant predictor of workplace bullying, which, in turn, was a cross-sectional and longitudinal predictor of workers' health complaints. Our results show the mediating effect of workplace bullying between certain work conditions and health complaints, and it is recommendable to replicate these findings in a multi-occupational sample. PMID:22047848

  11. Connecting Athletes’ Self-Perceptions and Metaperceptions of Competence: a Structural Equation Modeling Approach

    PubMed Central

    Cecchini, Jose A.; Fernández-Rio, Javier; Méndez-Giménez, Antonio

    2015-01-01

    This study explored the relationships between athletes’ competence self-perceptions and metaperceptions. Two hundred and fifty one student-athletes (14.26 ± 1.89 years), members of twenty different teams (basketball, soccer) completed a questionnaire which included the Perception of Success Questionnaire, the Competence subscale of the Intrinsic Motivation Inventory, and modified versions of both questionnaires to assess athletes’ metaperceptions. Structural equation modelling analysis revealed that athletes’ task and ego metaperceptions positively predicted task and ego self-perceptions, respectively. Competence metaperceptions were strong predictors of competence self-perceptions, confirming the atypical metaperception formation in outcome-dependent contexts such as sport. Task and ego metaperceptions positively predicted athletes’ competence metaperceptions. How coaches value their athletes’ competence is more influential on what the athletes think of themselves than their own self-perceptions. Athletes’ ego and task metaperceptions influenced their competence metaperceptions (how coaches rate their competence). Therefore, athletes build their competence metaperceptions using all information available from their coaches. Finally, only task-self perfections positively predicted athletes’ competence self-perceptions. PMID:26240662

  12. Pesticide residue transfer in Thai farmer families: using structural equation modeling to determine exposure pathways.

    PubMed

    Liu, Hanhua; Hanchenlaksh, Chalalai; Povey, Andrew C; de Vocht, Frank

    2015-01-01

    Use of pesticides in agriculture may lead to downstream exposure of farmers' families to pesticide residues inadvertently taken home. Identification of the independent contribution of different exposure pathways from the farmer to their children can provide clear targets to reduce exposure of farmers' children. Individual contributions of different pesticide transfer exposure pathways were investigated using structural equation modeling methods, and the benefits of these methods compared to standard multiple regression are described. A total of 72 Thai families, consisting of a farmer, a spouse, and a child, participated in this study. Family members completed a questionnaire and self-collected three spot morning urine samples in the spraying season. Urine samples were analyzed for diethyl phosphate, diethyl thiophosphate, diethyl dithiophosphate, dimethyl phosphate, dimethyl thiophosphate, and dimethyl dithiophosphate. A path model was developed based on an a priori hypothesized framework to examine the individual contributions of different exposure pathways that may directly or indirectly affect transfer of pesticide residues from farmers to their children. Transfer from the farmer to the child occurs indirectly, primarily through transfer to the spouse in the first instance, but also through contamination of the home environment. Clear targets for interventions are directly the reduction of farmers' take-home exposures and indirectly frequent cleaning of the home to avoid buildup of pesticide residues. PMID:25407029

  13. Testing a theory of aircraft noise annoyance: a structural equation analysis.

    PubMed

    Kroesen, Maarten; Molin, Eric J E; van Wee, Bert

    2008-06-01

    Previous research has stressed the relevance of nonacoustical factors in the perception of aircraft noise. However, it is largely empirically driven and lacks a sound theoretical basis. In this paper, a theoretical model which explains noise annoyance based on the psychological stress theory is empirically tested. The model is estimated by applying structural equation modeling based on data from residents living in the vicinity of Amsterdam Airport Schiphol in The Netherlands. The model provides a good model fit and indicates that concern about the negative health effects of noise and pollution, perceived disturbance, and perceived control and coping capacity are the most important variables that explain noise annoyance. Furthermore, the model provides evidence for the existence of two reciprocal relationships between (1) perceived disturbance and noise annoyance and (2) perceived control and coping capacity and noise annoyance. Lastly, the model yielded two unexpected results. Firstly, the variables noise sensitivity and fear related to the noise source were unable to explain additional variance in the endogenous variables of the model and were therefore excluded from the model. And secondly, the size of the total effect of noise exposure on noise annoyance was relatively small. The paper concludes with some recommended directions for further research. PMID:18537376

  14. Handling Missing Data With Multilevel Structural Equation Modeling and Full Information Maximum Likelihood Techniques.

    PubMed

    Schminkey, Donna L; von Oertzen, Timo; Bullock, Linda

    2016-08-01

    With increasing access to population-based data and electronic health records for secondary analysis, missing data are common. In the social and behavioral sciences, missing data frequently are handled with multiple imputation methods or full information maximum likelihood (FIML) techniques, but healthcare researchers have not embraced these methodologies to the same extent and more often use either traditional imputation techniques or complete case analysis, which can compromise power and introduce unintended bias. This article is a review of options for handling missing data, concluding with a case study demonstrating the utility of multilevel structural equation modeling using full information maximum likelihood (MSEM with FIML) to handle large amounts of missing data. MSEM with FIML is a parsimonious and hypothesis-driven strategy to cope with large amounts of missing data without compromising power or introducing bias. This technique is relevant for nurse researchers faced with ever-increasing amounts of electronic data and decreasing research budgets. © 2016 Wiley Periodicals, Inc. PMID:27176912

  15. Testing hypotheses in evolutionary ecology with imperfect detection: capture-recapture structural equation modeling.

    PubMed

    Cubaynes, Sarah; Doutrelant, Claire; Grégoire, Arnaud; Perret, Philippe; Faivre, Bruno; Gimenez, Olivier

    2012-02-01

    Studying evolutionary mechanisms in natural populations often requires testing multifactorial scenarios of causality involving direct and indirect relationships among individual and environmental variables. It is also essential to account for the imperfect detection of individuals to provide unbiased demographic parameter estimates. To cope with these issues, we developed a new approach combining structural equation models with capture-recapture models (CR-SEM) that allows the investigation of competing hypotheses about individual and environmental variability observed in demographic parameters. We employ Markov chain Monte Carlo sampling in a Bayesian framework to (1) estimate model parameters, (2) implement a model selection procedure to evaluate competing hypotheses about causal mechanisms, and (3) assess the fit of models to data using posterior predictive checks. We illustrate the value of our approach using two case studies on wild bird populations. We first show that CR-SEM can be useful to quantify the action of selection on a set of phenotypic traits with an analysis of selection gradients on morphological traits in Common Blackbirds (Turdus merula). In a second case study on Blue Tits (Cyanistes caeruleus), we illustrate the use of CR-SEM to study evolutionary trade-offs in the wild, while accounting for varying environmental conditions. PMID:22624306

  16. Perievent Panic Attack and Depression after the World Trade Center Disaster: A Structural Equation Model Analysis

    PubMed Central

    Adams, Richard E.; Boscarino, Joseph A.

    2011-01-01

    Research suggests that perievent panic attacks – panic attacks in temporal proximity to traumatic events – are predictive of later mental health status, including the onset of depression. Using a community sample of New York City residents interviewed 1 year and 2 years after the World Trade Center Disaster, we estimated a structural equation model (SEM) using pre-disaster psychological status and post-disaster life events, together with psychosocial resources, to assess the relationship between perievent panic and later onset depression. Bivariate results revealed a significant association between perievent panic and both year-1 and year-2 depression. Results for the SEM, however, showed that perievent panic was predictive of year-1 depression, but not year-2 depression, once potential confounders were controlled. Year-2 stressors and year-2 psychosocial resources were the best predictors of year-2 depression onset. Pre-disaster psychological problems were directly implicated in year-1 depression, but not year-2 depression. We conclude that a conceptual model that includes pre- and post-disaster variables best explains the complex causal pathways between psychological status, stressor exposure, perievent panic attacks, and depression onset two years after the World Trade Center attacks. PMID:21957721

  17. Identifying determinants of nations' wetland management programs using structural equation modeling: An exploratory analysis

    USGS Publications Warehouse

    La Peyre, M.K.; Mendelssohn, I.A.; Reams, M.A.; Templet, P.H.; Grace, J.B.

    2001-01-01

    Integrated management and policy models suggest that solutions to environmental issues may be linked to the socioeconomic and political Characteristics of a nation. In this study, we empirically explore these suggestions by applying them to the wetland management activities of nations. Structural equation modeling was used to evaluate a model of national wetland management effort and one of national wetland protection. Using five predictor variables of social capital, economic capital, environmental and political characteristics, and land-use pressure, the multivariate models were able to explain 60% of the variation in nations' wetland protection efforts based on data from 90 nations, as defined by level of participation, in the international wetland convention. Social capital had the largest direct effect on wetland protection efforts, suggesting that increased social development may eventually lead to better wetland protection. In contrast, increasing economic development had a negative linear relationship with wetland protection efforts, suggesting the need for explicit wetland protection programs as nations continue to focus on economic development. Government, environmental characteristics, and land-use pressure also had a positive direct effect on wetland protection, and mediated the effect of social capital on wetland protection. Explicit wetland protection policies, combined with a focus on social development, would lead to better wetland protection at the national level.

  18. Unified field theory from the classical wave equation: Preliminary application to atomic and nuclear structure

    NASA Astrophysics Data System (ADS)

    Múnera, Héctor A.

    2016-07-01

    It is postulated that there exists a fundamental energy-like fluid, which occupies the flat three-dimensional Euclidean space that contains our universe, and obeys the two basic laws of classical physics: conservation of linear momentum, and conservation of total energy; the fluid is described by the classical wave equation (CWE), which was Schrödinger's first candidate to develop his quantum theory. Novel solutions for the CWE discovered twenty years ago are nonharmonic, inherently quantized, and universal in the sense of scale invariance, thus leading to quantization at all scales of the universe, from galactic clusters to the sub-quark world, and yielding a unified Lorentz-invariant quantum theory ab initio. Quingal solutions are isomorphic under both neo-Galilean and Lorentz transformations, and exhibit nother remarkable property: intrinsic unstability for large values of ℓ (a quantum number), thus limiting the size of each system at a given scale. Unstability and scale-invariance together lead to nested structures observed in our solar system; unstability may explain the small number of rows in the chemical periodic table, and nuclear unstability of nuclides beyond lead and bismuth. Quingal functions lend mathematical basis for Boscovich's unified force (which is compatible with many pieces of evidence collected over the past century), and also yield a simple geometrical solution for the classical three-body problem, which is a useful model for electronic orbits in simple diatomic molecules. A testable prediction for the helicoidal-type force is suggested.

  19. [Structural equation model in the study of risk factors in the maintenance of binge eating].

    PubMed

    Bastianelli, A; Vicentini, M; Spoto, A; Vidotto, G

    2007-01-01

    This study investigated, in a sample of 483 adolescent girls, a number of risk factors associated with Binge Eating (BE) disorder, i.e. negative feelings, dieting behaviour, social influence and body dissatisfaction. Participants completed the following questionnaires: Bulimia Test, Depression Questionnaire, Dieting Self-Efficacy Measure, Dieting Success, Dieting Status Measure, Dutch Eating Behavior Questionnaire, Eating Disorder Inventory, Positive and Negative Affect Scale Revised, Rosenberg Self-Esteem Scale and Socio-cultural Attitudes Towards Appearance Questionnaire. Structural equation modeling was used in the data analysis to verify the hypothesized relations among the variables, with the aim of identifying the main predictors of BE. This methodology explains the correlation between the considered variables, and determines, using quantitative good fit indexes, both the strength of the correlations and the plausibility of the causal links between the hypothesized factors. Our findings confirm that negative feelings (Negative Affect) are the primary predictor for the maintenance of BE and highlight the significant role played by Social Influence. While Dieting Behaviour is not a primary predictor for the maintenance of BE it appears to influence it through its link with Negative Affect. PMID:18575358

  20. Linking impulsivity to dysfunctional thought control and insomnia: a structural equation model.

    PubMed

    Schmidt, Ralph E; Gay, Philippe; Ghisletta, Paolo; VAN DER Linden, Martial

    2010-03-01

    According to cognitive models of insomnia, excessive mental activity at bedtime may be viewed as an important impediment to the process of falling asleep. A further assumption of these models is that 'cognitive arousal' may be perpetuated and exacerbated by counterproductive strategies of thought management. As yet, little is known about factors that may predispose people to rely on these strategies when confronted with thoughts that keep them awake at night. This study examined the relations between impulsivity, use of different thought-control strategies and insomnia severity. A sample of 391 university students completed the UPPS Impulsive Behavior Scale, the Thought Control Questionnaire Insomnia-Revised and the Insomnia Severity Index. Correlation analyses revealed that two facets of impulsivity (urgency and lack of perseverance), two strategies of thought control (aggressive suppression and worry) and insomnia severity were positively associated. Follow-up structural equation modeling analyses showed that the two mentioned thought-control strategies mediated the effects of the two facets of impulsivity on sleep problems. These findings extend existing cognitive accounts of insomnia by suggesting how predisposing and perpetuating factors may be related: specific personality traits may incline individuals to respond with dysfunctional thought-control strategies to unwanted mental activity at night. PMID:19659917

  1. The impact of culture and employee-focused criteria on productivity: A structural equation modelling approach

    NASA Astrophysics Data System (ADS)

    Ab Hamid, Mohd Rashid; Mustafa, Zainol; Mohd Suradi, Nur Riza; Idris, Fazli; Abdullah, Mokhtar

    2013-04-01

    Culture and employee-focused criteria are important factors for the success of any organization. These factors have to be aligned with the productivity initiatives in the organization in order to gear ahead for excellence. Therefore, this article investigated the impact of culture and employee-focused criteria on productivity in Higher Education Institutions (HEIs) in Malaysia using intangible indicators through core values. The hypothesized relationship was tested using Structural Equation Modeling (SEM) with the PLS estimation technique. 429 questionnaires were returned from the target population. The results of the modelling revealed that the PLS estimation confirmed all the hypotheses tested as in the hypothesized model. The results generally support significant relationships between culture values, employee-focused values and productivity-focused values. The study also confirmed the mediating role of employee-focused values for the relationship between culture values and productivity-focused values. In conclusion, the empirically validated results supported the adequacy of the hypothezised model of the impact of culture and employee-focused criteria on productivity in HEI through value-based indicators.

  2. Sample Size Requirements for Structural Equation Models: An Evaluation of Power, Bias, and Solution Propriety

    PubMed Central

    Wolf, Erika J.; Harrington, Kelly M.; Clark, Shaunna L.; Miller, Mark W.

    2015-01-01

    Determining sample size requirements for structural equation modeling (SEM) is a challenge often faced by investigators, peer reviewers, and grant writers. Recent years have seen a large increase in SEMs in the behavioral science literature, but consideration of sample size requirements for applied SEMs often relies on outdated rules-of-thumb. This study used Monte Carlo data simulation techniques to evaluate sample size requirements for common applied SEMs. Across a series of simulations, we systematically varied key model properties, including number of indicators and factors, magnitude of factor loadings and path coefficients, and amount of missing data. We investigated how changes in these parameters affected sample size requirements with respect to statistical power, bias in the parameter estimates, and overall solution propriety. Results revealed a range of sample size requirements (i.e., from 30 to 460 cases), meaningful patterns of association between parameters and sample size, and highlight the limitations of commonly cited rules-of-thumb. The broad “lessons learned” for determining SEM sample size requirements are discussed. PMID:25705052

  3. Reconstruction of vibroacoustic responses of a highly nonspherical structure using Helmholtz equation least-squares method.

    PubMed

    Lu, Huancai; Wu, Sean F

    2009-03-01

    The vibroacoustic responses of a highly nonspherical vibrating object are reconstructed using Helmholtz equation least-squares (HELS) method. The objectives of this study are to examine the accuracy of reconstruction and the impacts of various parameters involved in reconstruction using HELS. The test object is a simply supported and baffled thin plate. The reason for selecting this object is that it represents a class of structures that cannot be exactly described by the spherical Hankel functions and spherical harmonics, which are taken as the basis functions in the HELS formulation, yet the analytic solutions to vibroacoustic responses of a baffled plate are readily available so the accuracy of reconstruction can be checked accurately. The input field acoustic pressures for reconstruction are generated by the Rayleigh integral. The reconstructed normal surface velocities are validated against the benchmark values, and the out-of-plane vibration patterns at several natural frequencies are compared with the natural modes of a simply supported plate. The impacts of various parameters such as number of measurement points, measurement distance, location of the origin of the coordinate system, microphone spacing, and ratio of measurement aperture size to the area of source surface of reconstruction on the resultant accuracy of reconstruction are examined. PMID:19275312

  4. A structural equation analysis of family accommodation in pediatric obsessive-compulsive disorder.

    PubMed

    Caporino, Nicole E; Morgan, Jessica; Beckstead, Jason; Phares, Vicky; Murphy, Tanya K; Storch, Eric A

    2012-01-01

    Family accommodation of symptoms is counter to the primary goals of cognitive-behavioral therapy for pediatric obsessive-compulsive disorder (OCD) and can pose an obstacle to positive treatment outcomes. Although increased attention has been given to family accommodation in pediatric OCD, relatively little is known about associated child and parent characteristics, and their mediating/moderating effects. This study examined a structural equation model of parent and child variables related to parent reports of family accommodation. Sixty-one children with OCD (ages 6-17 years, 39% female) and their parents were recruited from a university-based clinic. They were administered clinician- and parent-rated measures of child OCD symptom severity, OCD-specific impairment, internalizing problems, and externalizing problems as well as parent anxiety, depression, empathy, consideration of future consequences, and accommodation. Results generally supported the hypothesized model. Family accommodation mediated the relationship between OCD symptom severity and parent-rated functional impairment; child internalizing problems mediated the relationship between parent anxiety and family accommodation; and parent empathy and consideration of future consequences interacted to predict family accommodation. Child externalizing problems were significantly associated with family accommodation but neither of these two variables was associated with parent depression. Findings suggest that reductions in family accommodation might be maximized by routinely screening for comorbid psychopathology in children with OCD and their parents, and using prescriptive or modular approaches to intervention. Directions for future research are discussed. PMID:21842196

  5. Financial Literacy of Young Adults: The Importance of Parental Socialization

    ERIC Educational Resources Information Center

    Jorgensen, Bryce L.; Savla, Jyoti

    2010-01-01

    This article tests a conceptual model of perceived parental influence on the financial literacy of young adults. Structural equation modeling was used to test whether (a) parents were perceived to influence young adults' financial knowledge, attitudes, and behaviors and (b) the degree to which young adults' financial attitudes mediated financial…

  6. Value Preferences Predicting Narcissistic Personality Traits in Young Adults

    ERIC Educational Resources Information Center

    Gungor, Ibrahim Halil; Eksi, Halil; Aricak, Osman Tolga

    2012-01-01

    This study aimed at showing how the value preferences of young adults could predict the narcissistic characteristics of young adults according to structural equation modeling. 133 female (59.6%) and 90 male (40.4%), total 223 young adults participated the study (average age: 25.66, ranging from 20 to 38). Ratio group sampling method was used while…

  7. Investigating perturbed pathway modules from gene expression data via structural equation models

    PubMed Central

    2014-01-01

    Background It is currently accepted that the perturbation of complex intracellular networks, rather than the dysregulation of a single gene, is the basis for phenotypical diversity. High-throughput gene expression data allow to investigate changes in gene expression profiles among different conditions. Recently, many efforts have been made to individuate which biological pathways are perturbed, given a list of differentially expressed genes (DEGs). In order to understand these mechanisms, it is necessary to unveil the variation of genes in relation to each other, considering the different phenotypes. In this paper, we illustrate a pipeline, based on Structural Equation Modeling (SEM) that allowed to investigate pathway modules, considering not only deregulated genes but also the connections between the perturbed ones. Results The procedure was tested on microarray experiments relative to two neurological diseases: frontotemporal lobar degeneration with ubiquitinated inclusions (FTLD-U) and multiple sclerosis (MS). Starting from DEGs and dysregulated biological pathways, a model for each pathway was generated using databases information biological databases, in order to design how DEGs were connected in a causal structure. Successively, SEM analysis proved if pathways differ globally, between groups, and for specific path relationships. The results confirmed the importance of certain genes in the analyzed diseases, and unveiled which connections are modified among them. Conclusions We propose a framework to perform differential gene expression analysis on microarray data based on SEM, which is able to: 1) find relevant genes and perturbed biological pathways, investigating putative sub-pathway models based on the concept of disease module; 2) test and improve the generated models; 3) detect a differential expression level of one gene, and differential connection between two genes. This could shed light, not only on the mechanisms affecting variations in gene

  8. Wing-Body Aeroelasticity Using Finite-Difference Fluid/Finite-Element Structural Equations on Parallel Computers

    NASA Technical Reports Server (NTRS)

    Byun, Chansup; Guruswamy, Guru P.

    1993-01-01

    This paper presents a procedure for computing the aeroelasticity of wing-body configurations on multiple-instruction, multiple-data (MIMD) parallel computers. In this procedure, fluids are modeled using Euler equations discretized by a finite difference method, and structures are modeled using finite element equations. The procedure is designed in such a way that each discipline can be developed and maintained independently by using a domain decomposition approach. A parallel integration scheme is used to compute aeroelastic responses by solving the coupled fluid and structural equations concurrently while keeping modularity of each discipline. The present procedure is validated by computing the aeroelastic response of a wing and comparing with experiment. Aeroelastic computations are illustrated for a High Speed Civil Transport type wing-body configuration.

  9. Spatially inhomogeneous structures in the solution of Fisher-Kolmogorov equation with delay

    NASA Astrophysics Data System (ADS)

    Aleshin, S. V.; Glyzin, S. D.; Kaschenko, S. A.

    2016-02-01

    We consider the problem of density wave propagation in a logistic equation with delay and diffusion (Fisher-Kolmogorov equation with delay). A Ginzburg-Landau equation was constructed in order to study the qualitative behavior of the solution near the equilibrium state. The numerical analysis of wave propagation shows that for a sufficiently small delay this equation has a solution similar to the solution of a classical Fisher-Kolmogorov equation. The delay increasing leads to existence of the oscillatory component in spatial distribution of solutions. A further increase of delay leads to destruction of the traveling wave. That is expressed in the fact that undamped spatio-temporal fluctuations exist in a neighborhood of the initial perturbation. These fluctuations are close to the solution of the corresponding boundary value problem with periodic boundary conditions. Finally, when the delay is sufficiently large we observe intensive spatio-temporal fluctuations in the whole area of wave propagation.

  10. Meta-Analytic Methods of Pooling Correlation Matrices for Structural Equation Modeling under Different Patterns of Missing Data

    ERIC Educational Resources Information Center

    Furlow, Carolyn F.; Beretvas, S. Natasha

    2005-01-01

    Three methods of synthesizing correlations for meta-analytic structural equation modeling (SEM) under different degrees and mechanisms of missingness were compared for the estimation of correlation and SEM parameters and goodness-of-fit indices by using Monte Carlo simulation techniques. A revised generalized least squares (GLS) method for…

  11. Review of Sample Size for Structural Equation Models in Second Language Testing and Learning Research: A Monte Carlo Approach

    ERIC Educational Resources Information Center

    In'nami, Yo; Koizumi, Rie

    2013-01-01

    The importance of sample size, although widely discussed in the literature on structural equation modeling (SEM), has not been widely recognized among applied SEM researchers. To narrow this gap, we focus on second language testing and learning studies and examine the following: (a) Is the sample size sufficient in terms of precision and power of…

  12. Three Approaches to Using Lengthy Ordinal Scales in Structural Equation Models: Parceling, Latent Scoring, and Shortening Scales

    ERIC Educational Resources Information Center

    Yang, Chongming; Nay, Sandra; Hoyle, Rick H.

    2010-01-01

    Lengthy scales or testlets pose certain challenges for structural equation modeling (SEM) if all the items are included as indicators of a latent construct. Three general approaches to modeling lengthy scales in SEM (parceling, latent scoring, and shortening) have been reviewed and evaluated. A hypothetical population model is simulated containing…

  13. Study of Factors Preventing Children from Enrolment in Primary School in the Republic of Honduras: Analysis Using Structural Equation Modelling

    ERIC Educational Resources Information Center

    Ashida, Akemi

    2015-01-01

    Studies have investigated factors that impede enrolment in Honduras. However, they have not analysed individual factors as a whole or identified the relationships among them. This study used longitudinal data for 1971 children who entered primary schools from 1986 to 2000, and employed structural equation modelling to examine the factors…

  14. An Empirical Test of Tinto's Integration Framework for Community Colleges Using Structural Equation Modeling

    ERIC Educational Resources Information Center

    Santos-George, Arlene A.

    2012-01-01

    This dissertation empirically tested Tinto's student integration theory through structural equation modeling using a national sample of 2,847 first-time entering community college students. Tinto theorized that the more academically and socially integrated a student is to the college environment, the more likely the student will persist…

  15. Modeling the Relationships among Topical Knowledge, Anxiety, and Integrated Speaking Test Performance: A Structural Equation Modeling Approach

    ERIC Educational Resources Information Center

    Huang, Heng-Tsung Danny

    2010-01-01

    Thus far, few research studies have examined the practice of integrated speaking test tasks in the field of second/foreign language oral assessment. This dissertation utilized structural equation modeling (SEM) and qualitative techniques to explore the relationships among topical knowledge, anxiety, and integrated speaking test performance and to…

  16. Accuracy in Parameter Estimation for Targeted Effects in Structural Equation Modeling: Sample Size Planning for Narrow Confidence Intervals

    ERIC Educational Resources Information Center

    Lai, Keke; Kelley, Ken

    2011-01-01

    In addition to evaluating a structural equation model (SEM) as a whole, often the model parameters are of interest and confidence intervals for those parameters are formed. Given a model with a good overall fit, it is entirely possible for the targeted effects of interest to have very wide confidence intervals, thus giving little information about…

  17. Socioeconomic Status and Asian American and Pacific Islander Students' Transition to College: A Structural Equation Modeling Analysis

    ERIC Educational Resources Information Center

    Museus, Samuel D.; Vue, Rican

    2013-01-01

    The purpose of this study is to examine socioeconomic differences in the interpersonal factors that influence college access among Asian Americans and Pacific Islanders (AAPIs). Data on 1,460 AAPIs from the Education Longitudinal Study (ELS: 02/06) were analyzed using structural equation modeling techniques. Findings suggest that parental…

  18. Perceived Social Relationships and Science Learning Outcomes for Taiwanese Eighth Graders: Structural Equation Modeling with a Complex Sampling Consideration

    ERIC Educational Resources Information Center

    Jen, Tsung-Hau; Lee, Che-Di; Chien, Chin-Lung; Hsu, Ying-Shao; Chen, Kuan-Ming

    2013-01-01

    Based on the Trends in International Mathematics and Science Study 2007 study and a follow-up national survey, data for 3,901 Taiwanese grade 8 students were analyzed using structural equation modeling to confirm a social-relation-based affection-driven model (SRAM). SRAM hypothesized relationships among students' perceived social relationships in…

  19. Do Test Design and Uses Influence Test Preparation? Testing a Model of Washback with Structural Equation Modeling

    ERIC Educational Resources Information Center

    Xie, Qin; Andrews, Stephen

    2013-01-01

    This study introduces Expectancy-value motivation theory to explain the paths of influences from perceptions of test design and uses to test preparation as a special case of washback on learning. Based on this theory, two conceptual models were proposed and tested via Structural Equation Modeling. Data collection involved over 870 test takers of…

  20. Modeling Latent Growth Curves With Incomplete Data Using Different Types of Structural Equation Modeling and Multilevel Software

    ERIC Educational Resources Information Center

    Ferrer, Emilio; Hamagami, Fumiaki; McArdle, John J.

    2004-01-01

    This article offers different examples of how to fit latent growth curve (LGC) models to longitudinal data using a variety of different software programs (i.e., LISREL, Mx, Mplus, AMOS, SAS). The article shows how the same model can be fitted using both structural equation modeling and multilevel software, with nearly identical results, even in…

  1. A Model for Integrating Fixed-, Random-, and Mixed-Effects Meta-Analyses into Structural Equation Modeling

    ERIC Educational Resources Information Center

    Cheung, Mike W.-L.

    2008-01-01

    Meta-analysis and structural equation modeling (SEM) are two important statistical methods in the behavioral, social, and medical sciences. They are generally treated as two unrelated topics in the literature. The present article proposes a model to integrate fixed-, random-, and mixed-effects meta-analyses into the SEM framework. By applying an…

  2. The Best of Both Worlds: Factor Analysis of Dichotomous Data Using Item Response Theory and Structural Equation Modeling

    ERIC Educational Resources Information Center

    Glockner-Rist, Angelika; Hoijtink, Herbert

    2003-01-01

    Both structural equation modeling (SEM) and item response theory (IRT) can be used for factor analysis of dichotomous item responses. In this case, the measurement models of both approaches are formally equivalent. They were refined within and across different disciplines, and make complementary contributions to central measurement problems…

  3. Are Teachers' Approaches to Teaching Responsive to Individual Student Variation? A Two-Level Structural Equation Modeling

    ERIC Educational Resources Information Center

    Rosário, Pedro; Núñez, José Carlos; Vallejo, Guilermo; Paiva, Olímpia; Valle, António; Fuentes, Sonia; Pinto, Ricardo

    2014-01-01

    In the framework of teacher's approaches to teaching, this study investigates the relationship between student-related variables (i.e., study time, class absence, domain knowledge, and homework completion), students' approaches to learning, and teachers' approaches to teaching using structural equation modeling (SEM) with two…

  4. Structural Equation Modeling (SEM) for Satisfaction and Dissatisfaction Ratings; Multiple Group Invariance Analysis across Scales with Different Response Format

    ERIC Educational Resources Information Center

    Mazaheri, Mehrdad; Theuns, Peter

    2009-01-01

    The current study evaluates three hypothesized models on subjective well-being, comprising life domain ratings (LDR), overall satisfaction with life (OSWL), and overall dissatisfaction with life (ODWL), using structural equation modeling (SEM). A sample of 1,310 volunteering students, randomly assigned to six conditions, rated their overall life…

  5. Maximum Likelihood Methods in Treating Outliers and Symmetrically Heavy-Tailed Distributions for Nonlinear Structural Equation Models with Missing Data

    ERIC Educational Resources Information Center

    Lee, Sik-Yum; Xia, Ye-Mao

    2006-01-01

    By means of more than a dozen user friendly packages, structural equation models (SEMs) are widely used in behavioral, education, social, and psychological research. As the underlying theory and methods in these packages are vulnerable to outliers and distributions with longer-than-normal tails, a fundamental problem in the field is the…

  6. Structural Equation Analyses of Clinical Subpopulation Differences and Comparative Treatment Outcomes: Characterizing the Daily Lives of Drug Addicts.

    ERIC Educational Resources Information Center

    Aiken, Leona S.; And Others

    1994-01-01

    Used structural equation modeling for comparative treatment outcome research conducted with heterogeneous clinical subpopulations within large multimodality treatment settings. Evaluated effect of early period of treatment on daily lives of 486 clients in 2 drug abuse treatment modalities (methadone maintenance and outpatient counseling).…

  7. Regression Levels of Selected Affective Factors on Science Achievement: A Structural Equation Model with TIMSS 2011 Data

    ERIC Educational Resources Information Center

    Akilli, Mustafa

    2015-01-01

    The aim of this study is to demonstrate the science success regression levels of chosen emotional features of 8th grade students using Structural Equation Model. The study was conducted by the analysis of students' questionnaires and science success in TIMSS 2011 data using SEM. Initially, the factors that are thought to have an effect on science…

  8. Factor Structure and Psychometric Properties of the Anxiety Sensitivity Index in a Sample of Croatian Adults

    ERIC Educational Resources Information Center

    Jurin, Tanja; Jokic-Begic, Natasa; Korajlija, Anita Lauri

    2012-01-01

    Anxiety sensitivity (AS) refers to a person's tendency to fear anxiety-related symptoms due to the belief that these symptoms may have harmful consequences. The most widely used operationalization of AS in adults is the Anxiety Sensitivity Index (ASI). The factor structure, gender stability, and psychometric properties of the ASI in a sample of…

  9. Adult Daughters' Family Structure and the Association between Reciprocity and Relationship Quality

    ERIC Educational Resources Information Center

    Schwarz, Beate

    2006-01-01

    The study explores whether family structure is a moderator of the associations between help exchange, reciprocity of this exchange, and the quality of the mother and adult daughter relationship. A total of 183 daughters (mean age = 42.13; SD = 4.91) are either in first marriage (n = 87), living with a new partner after divorce (n = 77), or…

  10. Mind-Reading in Young Adults with ASD: Does Structure Matter?

    ERIC Educational Resources Information Center

    Ponnet, Koen; Buysse, Ann; Roeyers, Herbert; De Clercq, Armand

    2008-01-01

    This study further elaborates on the mind-reading impairments of young adults with autism spectrum disorder (ASD). The hypothesis is that differences in mind-reading abilities between subjects with ASD and control subjects become more apparent when they have to infer thoughts and feelings of other persons in a less structured or more chaotic…

  11. Adult Participation in Undergraduate Education: The Effect of State-Level Structural Factors.

    ERIC Educational Resources Information Center

    Jung, Jong-Chul; Cervero, Ronald M.; Valentine, Thomas

    2003-01-01

    Composite state-level data from four national sets were used to compare 1991 and 1997 higher education participation of adults over 24. Variations in state structural factors significantly affected participation variance. Factors at one point in time substantially affected future participation. State policymakers had an influence on access and…

  12. Structural Relationships between Social Activities and Longitudinal Trajectories of Depression among Older Adults

    ERIC Educational Resources Information Center

    Hong, Song-Iee; Hasche, Leslie; Bowland, Sharon

    2009-01-01

    Purpose: This study examines the structural relationships between social activities and trajectories of late-life depression. Design and Methods: Latent class analysis was used with a nationally representative sample of older adults (N = 5,294) from the Longitudinal Study on Aging II to classify patterns of social activities. A latent growth curve…

  13. Participation Structure and Incidental Focus on Form in Adult ESL Classrooms

    ERIC Educational Resources Information Center

    Nassaji, Hossein

    2013-01-01

    This study examined the role of incidental focus on form (FonF) in adult English-as-a-second-language classrooms. Specifically, it explored the extent to which the amount, type, and effectiveness of FonF were related to differences in classroom participation structure, that is, the organization of classroom talk within which FonF may occur. The…

  14. Factor Structure Invariance of the Kaufman Adolescent and Adult Intelligence Test across Male and Female Samples

    ERIC Educational Resources Information Center

    Immekus, Jason C.; Maller, Susan J.

    2010-01-01

    Multisample confirmatory factor analysis (MCFA) and latent mean structures analysis (LMS) were used to test measurement invariance and latent mean differences on the Kaufman Adolescent and Adult Intelligence Scale[TM] (KAIT) across males and females in the standardization sample. MCFA found that the parameters of the KAIT two-factor model were…

  15. Household Structure, Coupling Constraints, and the Nonpartner Victimization Risks of Adults

    ERIC Educational Resources Information Center

    Yule, Carolyn; Griffiths, Elizabeth

    2009-01-01

    Victimization studies consistently find that household structure influences the risk of personal and property victimization among adult household members, with those in "traditional" homes enjoying the most protection from victimization and lone parents experiencing the greatest vulnerability. Drawing on the concept of "coupling constraints,"…

  16. White matter structures associated with loneliness in young adults

    PubMed Central

    Nakagawa, Seishu; Takeuchi, Hikaru; Taki, Yasuyuki; Nouchi, Rui; Sekiguchi, Atsushi; Kotozaki, Yuka; Miyauchi, Carlos Makoto; Iizuka, Kunio; Yokoyama, Ryoichi; Shinada, Takamitsu; Yamamoto, Yuki; Hanawa, Sugiko; Araki, Tsuyoshi; Hashizume, Hiroshi; Kunitoki, Keiko; Sassa, Yuko; Kawashima, Ryuta

    2015-01-01

    Lonely individuals may exhibit dysfunction, particularly with respect to social empathy and self-efficacy. White matter (WM) structures related to loneliness have not yet been identified. We investigated the association between regional WM density (rWMD) using the UCLA Loneliness Scale in 776 healthy young students aged 18–27 years old. Loneliness scores were negatively correlated with rWMD in eight clusters: the bilateral inferior parietal lobule (IPL), right anterior insula (AI), posterior temporoparietal junction (pTPJ), left posterior superior temporal sulcus (pSTS), dorsomedial prefrontal cortex (dmPFC), and rostrolateral prefrontal cortex (RLPFC). The bilateral IPL, right AI, left pSTS, pTPJ, and RLPFC were strongly associated with Empathy Quotient (EQ), whereas the bilateral IPL, right AI, left pTPJ, and dmPFC were associated with General Self-Efficacy Scale (GSES) score. The neural correlates of loneliness comprise widespread reduction in WMD in areas related to self- and social cognition as well as areas associated with empathy and self-efficacy. PMID:26585372

  17. White matter structures associated with loneliness in young adults.

    PubMed

    Nakagawa, Seishu; Takeuchi, Hikaru; Taki, Yasuyuki; Nouchi, Rui; Sekiguchi, Atsushi; Kotozaki, Yuka; Miyauchi, Carlos Makoto; Iizuka, Kunio; Yokoyama, Ryoichi; Shinada, Takamitsu; Yamamoto, Yuki; Hanawa, Sugiko; Araki, Tsuyoshi; Hashizume, Hiroshi; Kunitoki, Keiko; Sassa, Yuko; Kawashima, Ryuta

    2015-01-01

    Lonely individuals may exhibit dysfunction, particularly with respect to social empathy and self-efficacy. White matter (WM) structures related to loneliness have not yet been identified. We investigated the association between regional WM density (rWMD) using the UCLA Loneliness Scale in 776 healthy young students aged 18-27 years old. Loneliness scores were negatively correlated with rWMD in eight clusters: the bilateral inferior parietal lobule (IPL), right anterior insula (AI), posterior temporoparietal junction (pTPJ), left posterior superior temporal sulcus (pSTS), dorsomedial prefrontal cortex (dmPFC), and rostrolateral prefrontal cortex (RLPFC). The bilateral IPL, right AI, left pSTS, pTPJ, and RLPFC were strongly associated with Empathy Quotient (EQ), whereas the bilateral IPL, right AI, left pTPJ, and dmPFC were associated with General Self-Efficacy Scale (GSES) score. The neural correlates of loneliness comprise widespread reduction in WMD in areas related to self- and social cognition as well as areas associated with empathy and self-efficacy. PMID:26585372

  18. Factors contributing to academic achievement: a Bayesian structure equation modelling study

    NASA Astrophysics Data System (ADS)

    Payandeh Najafabadi, Amir T.; Omidi Najafabadi, Maryam; Farid-Rohani, Mohammad Reza

    2013-06-01

    In Iran, high school graduates enter university after taking a very difficult entrance exam called the Konkoor. Therefore, only the top-performing students are admitted by universities to continue their bachelor's education in statistics. Surprisingly, statistically, most of such students fall into the following categories: (1) do not succeed in their education despite their excellent performance on the Konkoor and in high school; (2) graduate with a grade point average (GPA) that is considerably lower than their high school GPA; (3) continue their master's education in majors other than statistics and (4) try to find jobs unrelated to statistics. This article employs the well-known and powerful statistical technique, the Bayesian structural equation modelling (SEM), to study the academic success of recent graduates who have studied statistics at Shahid Beheshti University in Iran. This research: (i) considered academic success as a latent variable, which was measured by GPA and other academic success (see below) of students in the target population; (ii) employed the Bayesian SEM, which works properly for small sample sizes and ordinal variables; (iii), which is taken from the literature, developed five main factors that affected academic success and (iv) considered several standard psychological tests and measured characteristics such as 'self-esteem' and 'anxiety'. We then study the impact of such factors on the academic success of the target population. Six factors that positively impact student academic success were identified in the following order of relative impact (from greatest to least): 'Teaching-Evaluation', 'Learner', 'Environment', 'Family', 'Curriculum' and 'Teaching Knowledge'. Particularly, influential variables within each factor have also been noted.

  19. Establishing components of community satisfaction with recycled water use through a structural equation model.

    PubMed

    Hurlimann, Anna; Hemphill, Elizabeth; McKay, Jennifer; Geursen, Gus

    2008-09-01

    The use of recycled water is being promoted through policy in many parts of the world with the aim of achieving sustainable water management. However there are some major barriers to the success of recycled water use policies and their instruments, in particular for potable reuse schemes. One of these barriers can be a lack of community support. Despite the critical nature of community attitudes to recycled water to the success of projects, they are often little understood. Further information is required to ensure the successful implementation of recycled water policy and to ensure sustainable management of water resources is achieved. The aim of this paper is to establish the key components of community satisfaction with recycled water. This was investigated through a case study of the Mawson Lakes population in South Australia, where recycled water is used for non-potable purposes through a dual water supply system (the 'recycled water system'). This paper reports results from a survey of 162 Mawson Lakes residents. A structural equation model (SEM) was developed and tested to explain and predict components of community satisfaction with recycled water use (for non-potable use) through the dual water supply system. Results indicate the components of satisfaction with recycled water use were an individual's positive perception of: the Water Authority's communication, trust in the Water Authority, fairness in the recycled water system's implementation, quality of the recycled water, financial value of the recycled water system, and risk associated with recycled water use (negative relationship). The results of this study have positive implications for the future management and implementation of recycled water projects in particular through dual water supply systems. The results indicate to water authorities and water policy developers guiding principles for community consultation with regards to the management of recycled water projects. PMID:17662519

  20. The relationship between quality management practices and organisational performance: A structural equation modelling approach

    NASA Astrophysics Data System (ADS)

    Jamaluddin, Z.; Razali, A. M.; Mustafa, Z.

    2015-02-01

    The purpose of this paper is to examine the relationship between the quality management practices (QMPs) and organisational performance for the manufacturing industry in Malaysia. In this study, a QMPs and organisational performance framework is developed according to a comprehensive literature review which cover aspects of hard and soft quality factors in manufacturing process environment. A total of 11 hypotheses have been put forward to test the relationship amongst the six constructs, which are management commitment, training, process management, quality tools, continuous improvement and organisational performance. The model is analysed using Structural Equation Modeling (SEM) with AMOS software version 18.0 using Maximum Likelihood (ML) estimation. A total of 480 questionnaires were distributed, and 210 questionnaires were valid for analysis. The results of the modeling analysis using ML estimation indicate that the fits statistics of QMPs and organisational performance model for manufacturing industry is admissible. From the results, it found that the management commitment have significant impact on the training and process management. Similarly, the training had significant effect to the quality tools, process management and continuous improvement. Furthermore, the quality tools have significant influence on the process management and continuous improvement. Likewise, the process management also has a significant impact to the continuous improvement. In addition the continuous improvement has significant influence the organisational performance. However, the results of the study also found that there is no significant relationship between management commitment and quality tools, and between the management commitment and continuous improvement. The results of the study can be used by managers to prioritize the implementation of QMPs. For instances, those practices that are found to have positive impact on organisational performance can be recommended to

  1. Structural equation modeling of the inflammatory response to traffic air pollution

    PubMed Central

    Baja, Emmanuel S.; Schwartz, Joel D.; Coull, Brent A.; Wellenius, Gregory A.; Vokonas, Pantel S.; Suh, Helen H.

    2015-01-01

    Several epidemiological studies have reported conflicting results on the effect of traffic-related pollutants on markers of inflammation. In a Bayesian framework, we examined the effect of traffic pollution on inflammation using structural equation models (SEMs). We studied measurements of C-reactive protein (CRP), soluble vascular cell adhesion molecule-1 (sVCAM-1), and soluble intracellular adhesion molecule-1 (sICAM-1) for 749 elderly men from the Normative Aging Study. Using repeated measures SEMs, we fit a latent variable for traffic pollution that is reflected by levels of black carbon, carbon monoxide, nitrogen monoxide and nitrogen dioxide to estimate its effect on a latent variable for inflammation that included sICAM-1, sVCAM-1 and CRP. Exposure periods were assessed using 1-, 2-, 3-, 7-, 14- and 30-day moving averages previsit. We compared our findings using SEMs with those obtained using linear mixed models. Traffic pollution was related to increased inflammation for 3-, 7-, 14- and 30-day exposure periods. An inter-quartile range increase in traffic pollution was associated with a 2.3% (95% posterior interval (PI): 0.0–4.7%) increase in inflammation for the 3-day moving average, with the most significant association observed for the 30-day moving average (23.9%; 95% PI: 13.9–36.7%). Traffic pollution adversely impacts inflammation in the elderly. SEMs in a Bayesian framework can comprehensively incorporate multiple pollutants and health outcomes simultaneously in air pollution–cardiovascular epidemiological studies. PMID:23232970

  2. Cognitive indicators of social anxiety in youth: a structural equation analysis.

    PubMed

    Rudy, Brittany M; Davis, Thompson E; Matthews, Russell A

    2014-01-01

    Previous studies have demonstrated significant relationships among various cognitive variables such as negative cognition, self-efficacy, and social anxiety. Unfortunately, few studies focus on the role of cognition among youth, and researchers often fail to use domain-specific measures when examining cognitive variables. Therefore, the purpose of the present study was to examine domain-specific cognitive variables (i.e., socially oriented negative self-referent cognition and social self-efficacy) and their relationships to social anxiety in children and adolescents using structural equation modeling techniques. A community sample of children and adolescents (n=245; 55.9% female; 83.3% Caucasian, 9.4% African American, 2% Asian, 2% Hispanic, 2% "other," and 1.2% not reported) completed questionnaires assessing social cognition and social anxiety symptomology. Three latent variables were created to examine the constructs of socially oriented negative self-referent cognition (as measured by the SONAS scale), social self-efficacy (as measured by the SEQSS-C), and social anxiety (as measured by the SPAI-C and the Brief SA). The resulting measurement model of latent variables fit the data well. Additionally, consistent with the study hypothesis, results indicated that social self-efficacy likely mediates the relationship between socially oriented negative self-referent cognition and social anxiety, and socially oriented negative self-referent cognition yields significant direct and indirect effects on social anxiety. These findings indicate that socially oriented negative cognitions are associated with youth's beliefs about social abilities and the experience of social anxiety. Future directions for research and study limitations, including use of cross-sectional data, are discussed. PMID:24411119

  3. Species richness and soil properties in Pinus ponderosa forests: A structural equation modeling analysis

    USGS Publications Warehouse

    Laughlin, D.C.; Abella, S.R.; Covington, W.W.; Grace, J.B.

    2007-01-01

    Question: How are the effects of mineral soil properties on understory plant species richness propagated through a network of processes involving the forest overstory, soil organic matter, soil nitrogen, and understory plant abundance? Location: North-central Arizona, USA. Methods: We sampled 75 0.05-ha plots across a broad soil gradient in a Pinus ponderosa (ponderosa pine) forest ecosystem. We evaluated multivariate models of plant species richness using structural equation modeling. Results: Richness was highest at intermediate levels of understory plant cover, suggesting that both colonization success and competitive exclusion can limit richness in this system. We did not detect a reciprocal positive effect of richness on plant cover. Richness was strongly related to soil nitrogen in the model, with evidence for both a direct negative effect and an indirect non-linear relationship mediated through understory plant cover. Soil organic matter appeared to have a positive influence on understory richness that was independent of soil nitrogen. Richness was lowest where the forest overstory was densest, which can be explained through indirect effects on soil organic matter, soil nitrogen and understory cover. Finally, model results suggest a variety of direct and indirect processes whereby mineral soil properties can influence richness. Conclusions: Understory plant species richness and plant cover in P. ponderosa forests appear to be significantly influenced by soil organic matter and nitrogen, which are, in turn, related to overstory density and composition and mineral soil properties. Thus, soil properties can impose direct and indirect constraints on local species diversity in ponderosa pine forests. ?? IAVS; Opulus Press.

  4. A structural equation model analysis of postfire plant diversity in California shrublands

    USGS Publications Warehouse

    Grace, J.B.; Keeley, J.E.

    2006-01-01

    This study investigates patterns of plant diversity following wildfires in fire-prone shrublands of California, seeks to understand those patterns in terms of both local and landscape factors, and considers the implications for fire management. Ninety study sites were established following extensive wildfires in 1993, and 1000-m2 plots were used to sample a variety of parameters. Data on community responses were collected for five years following fire. Structural equation modeling (SEM) was used to relate plant species richness to plant abundance, fire severity, abiotic conditions, within-plot heterogeneity, stand age, and position in the landscape. Temporal dynamics of average richness response was also modeled. Richness was highest in the first year following fire, indicating postfire enhancement of diversity. A general decline in richness over time was detected, with year-to-year variation attributable to annual variations in precipitation. Peak richness in the landscape was found where (1) plant abundance was moderately high, (2) within-plot heterogeneity was high, (3) soils were moderately low in nitrogen, high in sand content, and with high rock cover, (4) fire severity was low, and (5) stands were young prior to fire. Many of these characteristics were correlated with position in the landscape and associated conditions. We infer from the SEM results that postfire richness in this system is strongly influenced by local conditions and that these conditions are, in turn, predictably related to landscape-level conditions. For example, we observed that older stands of shrubs were characterized by more severe fires, which were associated with a low recovery of plant cover and low richness. These results may have implications for the use of prescribed fire in this system if these findings extrapolate to prescribed burns as we would expect. ?? 2006 by the Ecological Society of America.

  5. Impact of adiposity on cardiac structure in adult life: the childhood determinants of adult health (CDAH) study

    PubMed Central

    2014-01-01

    Background We have examined the association between adiposity and cardiac structure in adulthood, using a life course approach that takes account of the contribution of adiposity in both childhood and adulthood. Methods The Childhood Determinants of Adult Health study (CDAH) is a follow-up study of 8,498 children who participated in the 1985 Australian Schools Health and Fitness Survey (ASHFS). The CDAH follow-up study included 2,410 participants who attended a clinic examination. Of these, 181 underwent cardiac imaging and provided complete data. The measures were taken once when the children were aged 9 to 15 years, and once in adult life, aged 26 to 36 years. Results There was a positive association between adult left ventricular mass (LVM) and childhood body mass index (BMI) in males (regression coefficient (β) 0.41; 95% confidence interval (CI): 0.14 to 0.67; p = 0.003), and females (β = 0.53; 95% CI: 0.34 to 0.72; p < 0.001), and with change in BMI from childhood to adulthood (males: β = 0.27; 95% CI: 0.04 to 0.51; p < 0.001, females: β = 0.39; 95% CI: 0.20 to 0.58; p < 0.001), after adjustment for confounding factors (age, fitness, triglyceride levels and total cholesterol in adulthood). After further adjustment for known potential mediating factors (systolic BP and fasting plasma glucose in adulthood) the relationship of LVM with childhood BMI (males: β = 0.45; 95% CI: 0.19 to 0.71; p = 0.001, females: β = 0.49; 95% CI: 0.29 to 0.68; p < 0.001) and change in BMI (males: β = 0.26; 95% CI: 0.04 to 0.49; p = 0.02, females: β = 0.40; 95% CI: 0.20 to 0.59; p < 0.001) did not change markedly. Conclusions Adiposity and increased adiposity from childhood to adulthood appear to have a detrimental effect on cardiac structure. PMID:24980215

  6. Constancy of Adult Personality Structure in Males: Longitudinal, Cross-Sectional and Times-of-Measurement Analyses.

    ERIC Educational Resources Information Center

    McCrae, Robert R.; And Others

    1980-01-01

    The invariance of factor structures in the Guilford Zimmerman Temperament Survey is clearly evident. Basic personality structure appears little affected by social and historical change. Results favor the stability model for objectively measured personality traits in adult males. (JAC)

  7. The Polish version of the Body Image Avoidance Questionnaire: an exploratory structural equation modeling approach.

    PubMed

    Brytek-Matera, Anna; Rogoza, Radosław

    2016-03-01

    The objective of the study was to validate a Polish version of the Body Image Avoidance Questionnaire (BIAQ). The study included 115 participants with no diagnosis (control group) (Mage = 20.53, SD = 1.80) on which we have based factor analyses, 48 participants diagnosed with anorexia nervosa (Mage = 18.69, SD = 3.52) and 39 participants diagnosed with bulimia nervosa (Mage = 22.28, SD = 3.80). In the current study, we have run confirmatory factor analysis; however, the analysis did not fit the data (CFI = 0.81, RMSEA = 0.09). Three-factor solution (number of factors were chosen basing on parallel analysis and MAP) was assessed using exploratory structural equation modeling approach (extraction: Maximum Likelihood; rotation: Geomin) which appeared to fit the data well (CFI = 0.90, RMSEA = 0.07). Validation with the clinical sample was performed using multi-group ESEM. Since the models achieved only configural level of invariance, we have examined the structure of clinical group with next ESEM model (CFI = 0.95, RMSEA = 0.05). To evaluate internal consistency, we have employed Omega (ω) and Cronbach's α with bootstrapped 95 % confidence interval (95 % CI). The first factor (food and weight preoccupation) was 0.79 (95 % CI = 0.74-0.83), for second factor (social activities) was 0.86 (95 % CI = 0.81-0.90), and for third factor (clothing) was 0.84 (95 % CI = 0.79-0.87). Convergent validity was assessed by correlating the Eating Disorder Inventory and the Body Attitude Test scores. The results have shown that the Polish version of the BIAQ fulfilled basic psychometric criteria and may be used for evaluation of body image avoidance behaviors among Polish women. PMID:26183601

  8. Nonlocal Symmetries, Explicit Solutions, and Wave Structures for the Korteweg-de Vries Equation

    NASA Astrophysics Data System (ADS)

    Ma, Zheng-Yi; Fei, Jin-Xi

    2016-08-01

    From the known Lax pair of the Korteweg-de Vries (KdV) equation, the Lie symmetry group method is successfully applied to find exact invariant solutions for the KdV equation with nonlocal symmetries by introducing two suitable auxiliary variables. Meanwhile, based on the prolonged system, the explicit analytic interaction solutions related to the hyperbolic and Jacobi elliptic functions are derived. Figures show the physical interaction between the cnoidal waves and a solitary wave.

  9. The structure of coping among older adults living with HIV/AIDS and depressive symptoms.

    PubMed

    Hansen, Nathan B; Harrison, Blair; Fambro, Stacy; Bodnar, Sara; Heckman, Timothy G; Sikkema, Kathleen J

    2013-02-01

    One-third of adults living with HIV/AIDS are over the age of 50. This study evaluated the structure of coping among 307 older adults living with HIV/AIDS. Participants completed 61 coping items and measures of anxiety, depression, loneliness, and coping self-efficacy. Exploratory factor analyses retained 40 coping items loading on five specific first order factors (Distancing Avoidance, Social Support Seeking, Self-Destructive Avoidance, Spiritual Coping, and Solution-Focused Coping) and two general second order factors (Active and Avoidant Coping). Factors demonstrated good reliability and validity. Results suggest that general coping factors should be considered with specific factors when measuring coping among older adults. PMID:22453164

  10. A special purpose symbolic manipulation program for the derivation of the equations of motion for large flexible structures

    NASA Technical Reports Server (NTRS)

    Hale, A. L.; Meirovitch, L.

    1977-01-01

    This paper outlines a computer program especially tailored to the task of deriving explicit equations of motion for structures with point-connected substructures. The special purpose program is written in FORTRAN and is designed for performing the specific algebraic operations encountered in the derivation of explicit equations of motion. The derivation is by the Lagrangian approach. Using an orderly kinematical procedure and a discretization and/or truncation scheme, it is possible to write the kinetic and potential energy of each substructure in a compact vector-matrix form. Then, if each element of the matrices and vectors encountered in the kinetic and potential energy is a known algebraic expression, the computer program performs the necessary operations to evaluate the kinetic and potential energy of the system explicitly. Lagrange's equations for small motions about equilibrium can be deduced directly from the explicit form of the system kinetic and potential energy.

  11. Cognitive aging on latent constructs for visual processing capacity: a novel structural equation modeling framework with causal assumptions based on a theory of visual attention

    PubMed Central

    Nielsen, Simon; Wilms, L. Inge

    2015-01-01

    We examined the effects of normal aging on visual cognition in a sample of 112 healthy adults aged 60–75. A testbattery was designed to capture high-level measures of visual working memory and low-level measures of visuospatial attention and memory. To answer questions of how cognitive aging affects specific aspects of visual processing capacity, we used confirmatory factor analyses in Structural Equation Modeling (SEM; Model 2), informed by functional structures that were modeled with path analyses in SEM (Model 1). The results show that aging effects were selective to measures of visual processing speed compared to visual short-term memory (VSTM) capacity (Model 2). These results are consistent with some studies reporting selective aging effects on processing speed, and inconsistent with other studies reporting aging effects on both processing speed and VSTM capacity. In the discussion we argue that this discrepancy may be mediated by differences in age ranges, and variables of demography. The study demonstrates that SEM is a sensitive method to detect cognitive aging effects even within a narrow age-range, and a useful approach to structure the relationships between measured variables, and the cognitive functional foundation they supposedly represent. PMID:25642206

  12. State-dependent neutral delay equations from population dynamics.

    PubMed

    Barbarossa, M V; Hadeler, K P; Kuttler, C

    2014-10-01

    A novel class of state-dependent delay equations is derived from the balance laws of age-structured population dynamics, assuming that birth rates and death rates, as functions of age, are piece-wise constant and that the length of the juvenile phase depends on the total adult population size. The resulting class of equations includes also neutral delay equations. All these equations are very different from the standard delay equations with state-dependent delay since the balance laws require non-linear correction factors. These equations can be written as systems for two variables consisting of an ordinary differential equation (ODE) and a generalized shift, a form suitable for numerical calculations. It is shown that the neutral equation (and the corresponding ODE--shift system) is a limiting case of a system of two standard delay equations. PMID:25117688

  13. Weyl-Euler-Lagrange equations on twistor space for tangent structure

    NASA Astrophysics Data System (ADS)

    Kasap, Zeki

    2016-06-01

    Twistor spaces are certain complex three-manifolds, which are associated with special conformal Riemannian geometries on four-manifolds. Also, classical mechanic is one of the major subfields for mechanics of dynamical system. A dynamical system has a state determined by a collection of real numbers, or more generally by a set of points in an appropriate state space for classical mechanic. Euler-Lagrange equations are an efficient use of classical mechanics to solve problems using mathematical modeling. On the other hand, Weyl submitted a metric with a conformal transformation for unified theory of classical mechanic. This paper aims to introduce Euler-Lagrage partial differential equations (mathematical modeling, the equations of motion according to the time) for the movement of objects on twistor space and also to offer a general solution of differential equation system using the Maple software. Additionally, the implicit solution of the equation will be obtained as a result of a special selection of graphics to be drawn.

  14. High-Accuracy Finite Difference Equations for Simulation of Photonic Structures

    SciTech Connect

    Hadley, G.R.

    1999-04-23

    Progress towards the development of such algorithms as been reported for waveguide analysis'-3and vertical-cavity laser simulation. In all these cases, the higher accuracy order was obtained for a single spatial dimension. More recently, this concept was extended to differencing of the Helmholtz Equation on a 2-D grid, with uniform regions treated to 4th order and dielectric interfaces to 3'd order5. No attempt was made to treat corners properly. In this talk I will describe the extension of this concept to allow differencing of the Helmholtz Equation on a 2-D grid to 6* order in uniform regions and 5* order at dielectric interfaces. In addition, the first known derivation of a finite difference equation for a dielectric comer that allows correct satisfaction of all boundary conditions will be presented. This equation is only accurate to first order, but as will be shown, results in simulations that are third-order-accurate. In contrast to a previous approach3 that utilized a generalized Douglas scheme to increase the accuracy order of the difference second derivative, the present method invokes the Helmholtz Equation itself to convert derivatives of high order in a single direction into mixed

  15. Complex interactions among biocontrol agents, pollinators, and an invasive weed: a structural equation modeling approach.

    PubMed

    Swope, Sarah M; Parker, Ingrid M

    2012-12-01

    Herbivores, seed predators, and pollinators can exert strong impacts on their host plants. They can also affect the strength of each other's impact by modifying traits in their shared host, producing super- or sub-additive outcomes. This phenomenon is especially relevant to biological control of invasive plants because most invaders are attacked by multiple agents. Unfortunately, complex interactions among agents are rarely studied. We used structural equation modeling (SEM) to quantify the effect of two biocontrol agents and generalist pollinators on the invasive weed Centaurea solstitialis, and to identify and quantify the direct and indirect interaction pathways among them. The weevil Eustenopus villosus is both a bud herbivore and a predispersal seed predator; the fly Chaetorellia succinea is also a predispersal seed predator; Apis mellifera is the primary pollinator. We conducted this work at three sites spanning the longitudinal range of C. solstitialis in California (USA) from the coast to the Sierra Nevada Mountains. SEM revealed that bud herbivory had the largest total effect on the weed's fecundity. The direct effect of bud herbivory on final seed set was 2-4 times larger in magnitude than the direct effect of seed predation by both agents combined. SEM also revealed important indirect interactions; by reducing the number of inflorescences plants produced, bud herbivory indirectly reduced the plant's attractiveness to ovipositing seed predators. This indirect, positive pathway reduced bud herbivory's direct negative effect by 11-25%. In the same way, bud herbivory also reduced pollinator visitation, although the magnitude of this pathway was relatively small. E. villosus oviposition deterred C. succinea oviposition, which is unfortunate because C. succinea is the more voracious of the seed predators. Finally, C. succinea oviposition indirectly deterred pollinator visitation, thereby enhancing its net effect on the plant. This study demonstrates the

  16. Structural Equation Model Analysis of the Length of Hospital Stay Following Lumbar Spine Surgery

    PubMed Central

    Kanaan, Saddam F; Waitman, Russell L; Yeh, Hung-Wen; Arnold, Paul M; Burton, Douglas C; Sharma, Neena K

    2015-01-01

    Background context Length of hospital stay (LOS) after lumbar spine surgery (LSS) can be affected by many factors. However, few studies have evaluated predictors of LOS, and all have used limited number of variables as predictors. Purpose To identify pre-surgical, surgical, and post-surgical predictors of LOS following LSS. Study Design/Setting Retrospective review of consecutive patients who had LSS at the (Blinded) Hospital from October, 2008 to April, 2012. Patient Sample 593 patients who underwent LSS consisting of laminotomy, laminectomy, or arthrodesis. Outcome Measures Dependent variable: LOS. Multiple pre-surgical, surgical, and post-surgical variables were extracted from patients’ medical records and considered as possible predictors (independent variables) of LOS. Methods Potential predictors that were significantly correlated with LOS were used as indicators to construct three latent factors; pre-surgical, surgical, and post-surgical, which were in turn used to predict LOS in a structural equation model (SEM). Results The average LOS was 4.01±2.73 days. The pre-surgical factor was indicated by age (61.97±14.49 years), prior level of function (60.5% were totally independent), prior hemoglobin level (13.70±1.36 mg/dl), and use of assistive devices (60% were assistive device users). The surgical factor was indicated by severity of illness (50.2% had minor disease severity), presence of complications (1.9%), and stay in an intensive care unit (4.0%). The post-surgical factor was indicated by post-surgical walking distance (166.43±175.75 feet), level of assistance during walking (5.18±0.81 out of 7 points), balance scores (6.18 ±1.82 out of 10 points), and bed mobility and transfer dependency scores (9.81± 1.99 out of 14 points). These three latent factors explained 47% of variation in LOS. Conclusion Post-surgical factors predicted the highest variation in LOS in comparison to pre-surgical and surgical factors and should be taken into consideration

  17. The Neo Personality Inventory-Revised: Factor Structure and Gender Invariance from Exploratory Structural Equation Modeling Analyses in a High-Stakes Setting

    ERIC Educational Resources Information Center

    Furnham, Adrian; Guenole, Nigel; Levine, Stephen Z.; Chamorro-Premuzic, Tomas

    2013-01-01

    This study presents new analyses of NEO Personality Inventory-Revised (NEO-PI-R) responses collected from a large British sample in a high-stakes setting. The authors show the appropriateness of the five-factor model underpinning these responses in a variety of new ways. Using the recently developed exploratory structural equation modeling (ESEM)…

  18. The paths leading from attachment to ageism: a structural equation model approach.

    PubMed

    Bodner, Ehud; Cohen-Fridel, Sara

    2014-01-01

    The study introduces a model in which attachment patterns serve as predictors, empathy and fear of death as mediators, and ageism as the predicted variable. Data were collected from young adults (N = 440). Anxious attachment was directly and positively correlated with ageism, and also indirectly and positively by the mediator "fear of death." Avoidant attachment was indirectly and negatively correlated with ageism by the mediator "empathy". It is suggested that interventions for reducing ageist attitudes among younger adults would focus on existential fears, as well as on empathic ability, according to the attachment tendencies of these individuals. PMID:24758211

  19. Electrodynamic field equations for composite superconducting structures in the mixed state

    SciTech Connect

    Coffey, M.W.

    1997-08-01

    Governing vector partial differential equations for the linear electrodynamic response of an isotropic type-II superconductor in the mixed state are derived. A continuum theory of vortex motion is used, and two-fluid effects are also accounted for. The governing equation is sufficiently general to reduce to either normal metal or dielectric material results in special limits. The complex-valued conductivity tensor of the mixed state is made explicit, and is also discussed for an anisotropic superconductor. The theory is illustrated with a planar superconducting waveguide problem, wherein the complex propagation constant, phase velocity, and surface impedance are obtained.

  20. Analytic structure of two 1D-transport equations with nonlocal fluxes

    NASA Astrophysics Data System (ADS)

    Baker, Gregory R.; Li, Xiao; Morlet, Anne C.

    We replace the flux term in Burger's equation by two simple alternates that contain contributions depending globally on the solution. In one case, the term is in the form of a hyperbolic equation where the characteristic speed is nonlocal, and in the other the term is in conservation form. In both cases, the nonanalytic is due to the presence of the Hilbert transform. The equations have a loose analogy to the motion of vortex sheets. In particular, they both form singularities in finite time in the absence of viscous effects. Our motivation then is to study the influence of viscosity. In one case, viscosity does not prevent singularity formation. In the other, we can prove solutions exist for all time, and determine the likely weak solution as viscosity vanishes. An interesting aspect of our work is that singularity formation can be viewed as the motion of singularities in the complex physical plane that reach the real axis in finite time. In one case, the singularity is a pole and causes the solution to blow up when it reaches the real axis. In the other, numerical solutions and an asymptotic analysis suggest that the weak solution contains a square root singularity that reaches the real axis in finite time, and then propagates along it. We hope our results will spur further interest in the role of singularities in the complex spatial plane in solutions to transport equations.

  1. Complex structures and zero-curvature equations for σ-models

    NASA Astrophysics Data System (ADS)

    Bykov, Dmitri

    2016-09-01

    We construct zero-curvature representations for the equations of motion of a class of σ-models with complex homogeneous target spaces, not necessarily symmetric. We show that in the symmetric case the proposed flat connection is gauge-equivalent to the conventional one.

  2. Structural and Functional Rich Club Organization of the Brain in Children and Adults

    PubMed Central

    Grayson, David S.; Ray, Siddharth; Carpenter, Samuel; Iyer, Swathi; Dias, Taciana G. Costa; Stevens, Corinne; Nigg, Joel T.; Fair, Damien A.

    2014-01-01

    Recent studies using Magnetic Resonance Imaging (MRI) have proposed that the brain’s white matter is organized as a rich club, whereby the most highly connected regions of the brain are also highly connected to each other. Here we use both functional and diffusion-weighted MRI in the human brain to investigate whether the rich club phenomena is present with functional connectivity, and how this organization relates to the structural phenomena. We also examine whether rich club regions serve to integrate information between distinct brain systems, and conclude with a brief investigation of the developmental trajectory of rich-club phenomena. In agreement with prior work, both adults and children showed robust structural rich club organization, comprising regions of the superior medial frontal/dACC, medial parietal/PCC, insula, and inferior temporal cortex. We also show that these regions were highly integrated across the brain’s major networks. Functional brain networks were found to have rich club phenomena in a similar spatial layout, but a high level of segregation between systems. While no significant differences between adults and children were found structurally, adults showed significantly greater functional rich club organization. This difference appeared to be driven by a specific set of connections between superior parietal, insula, and supramarginal cortex. In sum, this work highlights the existence of both a structural and functional rich club in adult and child populations with some functional changes over development. It also offers a potential target in examining atypical network organization in common developmental brain disorders, such as ADHD and Autism. PMID:24505468

  3. Structural and functional rich club organization of the brain in children and adults.

    PubMed

    Grayson, David S; Ray, Siddharth; Carpenter, Samuel; Iyer, Swathi; Dias, Taciana G Costa; Stevens, Corinne; Nigg, Joel T; Fair, Damien A

    2014-01-01

    Recent studies using Magnetic Resonance Imaging (MRI) have proposed that the brain's white matter is organized as a rich club, whereby the most highly connected regions of the brain are also highly connected to each other. Here we use both functional and diffusion-weighted MRI in the human brain to investigate whether the rich club phenomena is present with functional connectivity, and how this organization relates to the structural phenomena. We also examine whether rich club regions serve to integrate information between distinct brain systems, and conclude with a brief investigation of the developmental trajectory of rich-club phenomena. In agreement with prior work, both adults and children showed robust structural rich club organization, comprising regions of the superior medial frontal/dACC, medial parietal/PCC, insula, and inferior temporal cortex. We also show that these regions were highly integrated across the brain's major networks. Functional brain networks were found to have rich club phenomena in a similar spatial layout, but a high level of segregation between systems. While no significant differences between adults and children were found structurally, adults showed significantly greater functional rich club organization. This difference appeared to be driven by a specific set of connections between superior parietal, insula, and supramarginal cortex. In sum, this work highlights the existence of both a structural and functional rich club in adult and child populations with some functional changes over development. It also offers a potential target in examining atypical network organization in common developmental brain disorders, such as ADHD and Autism. PMID:24505468

  4. Exploring the factor structure of the Food Cravings Questionnaire-Trait in Cuban adults

    PubMed Central

    Rodríguez-Martín, Boris C.; Molerio-Pérez, Osana

    2014-01-01

    Food cravings refer to an intense desire to eat specific foods. The Food Cravings Questionnaire-Trait (FCQ-T) is the most commonly used instrument to assess food cravings as a multidimensional construct. Its 39 items have an underlying nine-factor structure for both the original English and Spanish version; but subsequent studies yielded fewer factors. As a result, a 15-item version of the FCQ-T with one-factor structure has been proposed (FCQ-T-reduced; see this Research Topic). The current study aimed to explore the factor structure of the Spanish version for both the FCQ-T and FCQ-T-reduced in a sample of 1241 Cuban adults. Results showed a four-factor structure for the FCQ-T, which explained 55% of the variance. Factors were highly correlated. Using the items of the FCQ-T-reduced only showed a one-factor structure, which explained 52% of the variance. Both versions of the FCQ-T were positively correlated with body mass index (BMI), scores on the Food Thoughts Suppression Inventory and weight cycling. In addition, women had higher scores than men and restrained eaters had higher scores than unrestrained eaters. To summarize, results showed that (1) the FCQ-T factor structure was significantly reduced in Cuban adults and (2) the FCQ-T-reduced may represent a good alternative to efficiently assess food craving on a trait level. PMID:24672503

  5. Reelin Exerts Structural, Biochemical and Transcriptional Regulation Over Presynaptic and Postsynaptic Elements in the Adult Hippocampus

    PubMed Central

    Bosch, Carles; Muhaisen, Ashraf; Pujadas, Lluís; Soriano, Eduardo; Martínez, Albert

    2016-01-01

    Reelin regulates neuronal positioning and synaptogenesis in the developing brain, and adult brain plasticity. Here we used transgenic mice overexpressing Reelin (Reelin-OE mice) to perform a comprehensive dissection of the effects of this protein on the structural and biochemical features of dendritic spines and axon terminals in the adult hippocampus. Electron microscopy (EM) revealed both higher density of synapses and structural complexity of both pre- and postsynaptic elements in transgenic mice than in WT mice. Dendritic spines had larger spine apparatuses, which correlated with a redistribution of Synaptopodin. Most of the changes observed in Reelin-OE mice were reversible after blockade of transgene expression, thus supporting the specificity of the observed phenotypes. Western blot and transcriptional analyses did not show major changes in the expression of pre- or postsynaptic proteins, including SNARE proteins, glutamate receptors, and scaffolding and signaling proteins. However, EM immunogold assays revealed that the NMDA receptor subunits NR2a and NR2b, and p-Cofilin showed a redistribution from synaptic to extrasynaptic pools. Taken together with previous studies, the present results suggest that Reelin regulates the structural and biochemical properties of adult hippocampal synapses by increasing their density and morphological complexity and by modifying the distribution and trafficking of major glutamatergic components. PMID:27303269

  6. New method for computation of band structures in 1D photonic crystals based on the Fresnel equations

    NASA Astrophysics Data System (ADS)

    Roshan Entezar, S.

    2013-02-01

    In this paper, we present a new method for calculation of band structure in one-dimensional bilayer photonic crystals, based on the Fresnel equations. We derive a new relation to obtain the band structure without using the Floquet theorem. It is shown that this relation can be simplified under the assumption that the single-path phase-shift acquired through the individual layers of the photonic crystal be equal to ? . The results obtained by our method are compared with the ones obtained from the transfer matrix method to show that they are exactly identical.

  7. Phase stability, electronic structure and equation of state of cubic TcN from first-principles calculations

    NASA Astrophysics Data System (ADS)

    Song, T.; Ma, Q.; Sun, X. W.; Liu, Z. J.; Fu, Z. J.; Wei, X. P.; Wang, T.; Tian, J. H.

    2016-09-01

    The phase transition, electronic band structure, and equation of state (EOS) of cubic TcN are investigated by first-principles pseudopotential method based on density-functional theory. The calculated enthalpies show that TcN has a transformation between zincblende and rocksalt phases and the pressure determined by the relative enthalpy is 32 GPa. The calculated band structure indicates the metallic feature and it might make cubic TcN a better candidate for hard materials. Particular attention is paid to the predictions of volume, bulk modulus and its pressure derivative which play a central role in the formulation of approximate EOSs using the quasi-harmonic Debye model.

  8. Individual, Interpersonal, and Structural Power: Associations With Condom Use in a Sample of Young Adult Latinos.

    PubMed

    Stokes, Lynissa R; Harvey, S Marie; Warren, Jocelyn T

    2016-01-01

    Interviews were conducted with 480 sexually active Latino young adults from four rural counties in Oregon. We examined relationships between three levels of power (individual, interpersonal, and structural) and consistent condom use. Condom use self-efficacy and sexual decision-making, examples of individual and interpersonal measures of power, respectively, were associated with increased odds of consistent condom use among both men and women. Among men only, increasing relationship control, an interpersonal measure of power, was associated with lower odds of consistent condom use. Among women only, increasing medical mistrust, a structural measure of power, was associated with increased odds of consistent condom use. PMID:25868753

  9. Equation of State and Structure of Electrostatic Colloidal Crystals: Osmotic Pressure and Scattering Study

    NASA Astrophysics Data System (ADS)

    Reus, V.; Belloni, L.; Zemb, T.; Lutterbach, N.; Versmold, H.

    1997-04-01

    Electrostatically stabilized aqueous suspensions of bromopolystyrene particles have been studied by scattering and osmotic pressure measurements. We investigated their structure and the interparticle interactions as a function of the volume fraction at very low salinity of the order of micromole/l. At slow crystallization speed we observe perfect crystals, body centrered cubic crystals by light scattering for volume fractions between 0.04 and 0.7% and face centrered cubic crystals by Ultra Small Angle X ray Scattering (USAXS) for higher volume fractions (2 12%). After shear the crystal displays other structures. At low volume fractions (0.1 0.3%), some reflexions disappear by light scattering whereas a strong diffuse “prepeak" appears before the first Bragg peak for higher concentrations (2 12%) evidenced by USAXS. This “prepeak" can be attributed to defects in the crystal. Osmotic pressures have been measured by difference between the hydrostatic pressure in the solution and in the reservoir separated by an hemipermeable membrane. The experimental data are very well reproduced by the Poisson Boltzmann Cell (PBC) theory which shows that the interaction between particles is purely repulsive. No attractive contribution has been experimentally detected. By calculating the mean square displacement of a particle inside its cage from the eccentric PBC model, we have verified that the Lindemann criterion for the existence of crystals (against melting) is satisfied. This study has allowed to determine the equation of state of an electrostatical colloidal crystal and is equivalent to an ultraprecise force/distance measurement between latex particles since the measured forces are of the order of 10^{-12} N for distances of the order of 4000 Å. Des suspensions aqueuses de particules de bromopolystyrène ont été caractérisées par diffusion de lumière, diffusion de rayons X aux petits angles et par des mesures de pression osmotique. Nous avons ainsi étudié leur

  10. Phase Equilibria, Morphologies of Microphase Separation, and Interfacial Structures of Polymer Systems Studied by Equations of State

    NASA Astrophysics Data System (ADS)

    Liu, Honglai; Xu, Hui; Chen, Houyang; Peng, Changjun; Hu, Ying

    Polymer blends or copolymers have multiscale complex structures that can be used as templates to prepare various complex materials. To regulate the mesoscale structures of these polymer blends or copolymers, there are three fun damental problems: What is the physical condition of the microphase separation needed to form materials with desired compositions and mesoscale structures in dif ferent domains? How do these compositions and mesoscale structures evolve during the preparation period? How does the morphology change in the interfacial region? Many experimental measurements, computer simulation methods, and theories have been developed. However, most of them are only suitable for individual tasks. In re cent years, we have developed theoretical methods based on equations of state that can be used comprehensively to study the multiscale structure of polymer systems, including the phase diagrams, the morphologies and evolution of microphase sepa ration, the densities and composition profiles in different domains, and the molecular configurations in the interfacial region. The molecular parameters of the equation of state or the Helmholtz function model can be determined from the pressure, volume, temperature, and miscibility data of polymers, which ensures the practical applica bility of the methods.

  11. Wing-Body Aeroelasticity Using Finite-Difference Fluid/Finite-Element Structural Equations on Parallel Computers

    NASA Technical Reports Server (NTRS)

    Byun, Chansup; Guruswamy, Guru P.; Kutler, Paul (Technical Monitor)

    1994-01-01

    In recent years significant advances have been made for parallel computers in both hardware and software. Now parallel computers have become viable tools in computational mechanics. Many application codes developed on conventional computers have been modified to benefit from parallel computers. Significant speedups in some areas have been achieved by parallel computations. For single-discipline use of both fluid dynamics and structural dynamics, computations have been made on wing-body configurations using parallel computers. However, only a limited amount of work has been completed in combining these two disciplines for multidisciplinary applications. The prime reason is the increased level of complication associated with a multidisciplinary approach. In this work, procedures to compute aeroelasticity on parallel computers using direct coupling of fluid and structural equations will be investigated for wing-body configurations. The parallel computer selected for computations is an Intel iPSC/860 computer which is a distributed-memory, multiple-instruction, multiple data (MIMD) computer with 128 processors. In this study, the computational efficiency issues of parallel integration of both fluid and structural equations will be investigated in detail. The fluid and structural domains will be modeled using finite-difference and finite-element approaches, respectively. Results from the parallel computer will be compared with those from the conventional computers using a single processor. This study will provide an efficient computational tool for the aeroelastic analysis of wing-body structures on MIMD type parallel computers.

  12. The Hamiltonian structure of Dirac's equation in tensor form and its Fermi quantization

    NASA Technical Reports Server (NTRS)

    Reifler, Frank; Morris, Randall

    1992-01-01

    Currently, there is some interest in studying the tensor forms of the Dirac equation to elucidate the possibility of the constrained tensor fields admitting Fermi quantization. We demonstrate that the bispinor and tensor Hamiltonian systems have equivalent Fermi quantizations. Although the tensor Hamiltonian system is noncanonical, representing the tensor Poisson brackets as commutators for the Heisenberg operators directly leads to Fermi quantization without the use of bispinors.

  13. Spectral structure across the syllable specifies final-stop voicing for adults and children alike

    PubMed Central

    Nittrouer, Susan; Lowenstein, Joanna H.

    2008-01-01

    Traditional accounts of speech perception generally hold that listeners use isolable acoustic “cues” to label phonemes. For syllable-final stops, duration of the preceding vocalic portion and formant transitions at syllable’s end have been considered the primary cues to voicing decisions. The current experiment tried to extend traditional accounts by asking two questions concerning voicing decisions by adults and children: (1) What weight is given to vocalic duration versus spectral structure, both at syllable’s end and across the syllable? (2) Does the naturalness of stimuli affect labeling? Adults and children (4, 6, and 8 years old) labeled synthetic stimuli that varied in vocalic duration and spectral structure, either at syllable’s end or earlier in the syllable. Results showed that all listeners weighted dynamic spectral structure, both at syllable’s end and earlier in the syllable, more than vocalic duration, and listeners performed with these synthetic stimuli as listeners had performed previously with natural stimuli. The conclusion for accounts of human speech perception is that rather than simply gathering acoustic cues and summing them to derive strings of phonemic segments, listeners are able to attend to global spectral structure, and use it to help recover explicitly phonetic structure. PMID:18177167

  14. Spectral structure across the syllable specifies final-stop voicing for adults and children alike.

    PubMed

    Nittrouer, Susan; Lowenstein, Joanna H

    2008-01-01

    Traditional accounts of speech perception generally hold that listeners use isolable acoustic "cues" to label phonemes. For syllable-final stops, duration of the preceding vocalic portion and formant transitions at syllable's end have been considered the primary cues to voicing decisions. The current experiment tried to extend traditional accounts by asking two questions concerning voicing decisions by adults and children: (1) What weight is given to vocalic duration versus spectral structure, both at syllable's end and across the syllable? (2) Does the naturalness of stimuli affect labeling? Adults and children (4, 6, and 8 years old) labeled synthetic stimuli that varied in vocalic duration and spectral structure, either at syllable's end or earlier in the syllable. Results showed that all listeners weighted dynamic spectral structure, both at syllable's end and earlier in the syllable, more than vocalic duration, and listeners performed with these synthetic stimuli as listeners had performed previously with natural stimuli. The conclusion for accounts of human speech perception is that rather than simply gathering acoustic cues and summing them to derive strings of phonemic segments, listeners are able to attend to global spectral structure, and use it to help recover explicitly phonetic structure. PMID:18177167

  15. Using structural equation modeling to construct calibration equations relating PM2.5 mass concentration samplers to the federal reference method sampler

    NASA Astrophysics Data System (ADS)

    Bilonick, Richard A.; Connell, Daniel P.; Talbott, Evelyn O.; Rager, Judith R.; Xue, Tao

    2015-02-01

    The objective of this study was to remove systematic bias among fine particulate matter (PM2.5) mass concentration measurements made by different types of samplers used in the Pittsburgh Aerosol Research and Inhalation Epidemiology Study (PARIES). PARIES is a retrospective epidemiology study that aims to provide a comprehensive analysis of the associations between air quality and human health effects in the Pittsburgh, Pennsylvania, region from 1999 to 2008. Calibration was needed in order to minimize the amount of systematic error in PM2.5 exposure estimation as a result of including data from 97 different PM2.5 samplers at 47 monitoring sites. Ordinary regression often has been used for calibrating air quality measurements from pairs of measurement devices; however, this is only appropriate when one of the two devices (the "independent" variable) is free from random error, which is rarely the case. A group of methods known as "errors-in-variables" (e.g., Deming regression, reduced major axis regression) has been developed to handle calibration between two devices when both are subject to random error, but these methods require information on the relative sizes of the random errors for each device, which typically cannot be obtained from the observed data. When data from more than two devices (or repeats of the same device) are available, the additional information is not used to inform the calibration. A more general approach that often has been overlooked is the use of a measurement error structural equation model (SEM) that allows the simultaneous comparison of three or more devices (or repeats). The theoretical underpinnings of all of these approaches to calibration are described, and the pros and cons of each are discussed. In particular, it is shown that both ordinary regression (when used for calibration) and Deming regression are particular examples of SEMs but with substantial deficiencies. To illustrate the use of SEMs, the 7865 daily average PM2.5 mass

  16. Simvastatin and artesunate impact the structural organization of adult Schistosoma mansoni in hypercholesterolemic mice.

    PubMed

    Alencar, Alba Cristina Miranda de Barros; Santos, Thais da Silva; Neves, Renata Heisler; Lopes Torres, Eduardo José; Nogueira-Neto, José Firmino; Machado-Silva, José Roberto

    2016-08-01

    Experimental data have shown that simvastatin and artesunate possess activity against Schistosoma mansoni worms in mice fed standard chow. However, little is known regarding the roles of these drugs in mice fed high-fat chow. We have extended past studies by measuring the effects of these drugs on the structural organization of adult schistosomes in hypercholesterolemic mice. For this purpose, mice were gavaged with either simvastatin or artesunate at nine weeks post-infection and were euthanized by cervical dislocation at two weeks post-treatment. Adult worms were then collected and examined by conventional light microscopy, morphometry and confocal laser scanning microscopy. Plasma total cholesterol and worm reduction rates were significantly increased in mice fed high-fat chow compared with their respective control groups. Simvastatin and artesunate caused changes in the tegument, tubercles, and reproductive system (testicular lobes, vitelline glands and ovarian cells), particularly when administered to mice fed high-fat chow. In particular, the tegument and tubercles were significantly thinner in artesunate-treated worms in mice fed high-fat chow compared with mice fed standard chow. This study thus demonstrated that simvastatin and artesunate have several novel effects on the structural organization of adult worms. Together, these results show, for the first time, that simvastatin and artesunate display antischistosomal activity in hypercholesterolemic mice. PMID:27228897

  17. Systematic Review of Structural and Functional Neuroimaging Findings in Children and Adults with CKD

    PubMed Central

    Reiser, Kathryn A.; Detre, John A.; Schultz, Robert T.; Herrington, John D.; Davatzikos, Christos; Doshi, Jimit J.; Erus, Guray; Liu, Hua-Shan; Radcliffe, Jerilynn; Furth, Susan L.; Hooper, Stephen R.

    2013-01-01

    Summary CKD has been linked with cognitive deficits and affective disorders in multiple studies. Analysis of structural and functional neuroimaging in adults and children with kidney disease may provide additional important insights into the pathobiology of this relationship. This paper comprehensively reviews neuroimaging studies in both children and adults. Major databases (PsychLit, MEDLINE, WorldCat, ArticleFirst, PubMed, Ovid MEDLINE) were searched using consistent search terms, and studies published between 1975 and 2012 were included if their samples focused on CKD as the primary disease process. Exclusion criteria included case reports, chapters, and review articles. This systematic process yielded 43 studies for inclusion (30 in adults, 13 in children). Findings from this review identified several clear trends: (1) presence of cerebral atrophy and cerebral density changes in patients with CKD; (2) cerebral vascular disease, including deep white matter hyperintensities, white matter lesions, cerebral microbleeds, silent cerebral infarction, and cortical infarction, in patients with CKD; and (3) similarities in regional cerebral blood flow between patients with CKD and those with affective disorders. These findings document the importance of neuroimaging procedures in understanding the effect of CKD on brain structure, function, and associated behaviors. Results provide a developmental linkage between childhood and adulthood, with respect to the effect of CKD on brain functioning across the lifespan, with strong implications for a cerebrovascular mechanism contributing to this developmental linkage. Use of neuroimaging methods to corroborate manifest neuropsychological deficits or perhaps to indicate preventive actions may prove useful to individuals with CKD. PMID:23723341

  18. Systematic review of structural and functional neuroimaging findings in children and adults with CKD.

    PubMed

    Moodalbail, Divya G; Reiser, Kathryn A; Detre, John A; Schultz, Robert T; Herrington, John D; Davatzikos, Christos; Doshi, Jimit J; Erus, Guray; Liu, Hua-Shan; Radcliffe, Jerilynn; Furth, Susan L; Hooper, Stephen R

    2013-08-01

    CKD has been linked with cognitive deficits and affective disorders in multiple studies. Analysis of structural and functional neuroimaging in adults and children with kidney disease may provide additional important insights into the pathobiology of this relationship. This paper comprehensively reviews neuroimaging studies in both children and adults. Major databases (PsychLit, MEDLINE, WorldCat, ArticleFirst, PubMed, Ovid MEDLINE) were searched using consistent search terms, and studies published between 1975 and 2012 were included if their samples focused on CKD as the primary disease process. Exclusion criteria included case reports, chapters, and review articles. This systematic process yielded 43 studies for inclusion (30 in adults, 13 in children). Findings from this review identified several clear trends: (1) presence of cerebral atrophy and cerebral density changes in patients with CKD; (2) cerebral vascular disease, including deep white matter hyperintensities, white matter lesions, cerebral microbleeds, silent cerebral infarction, and cortical infarction, in patients with CKD; and (3) similarities in regional cerebral blood flow between patients with CKD and those with affective disorders. These findings document the importance of neuroimaging procedures in understanding the effect of CKD on brain structure, function, and associated behaviors. Results provide a developmental linkage between childhood and adulthood, with respect to the effect of CKD on brain functioning across the lifespan, with strong implications for a cerebrovascular mechanism contributing to this developmental linkage. Use of neuroimaging methods to corroborate manifest neuropsychological deficits or perhaps to indicate preventive actions may prove useful to individuals with CKD. PMID:23723341

  19. Beyond narrative: Is there an implicit structure to the way in which adults organise their discourse?

    PubMed

    Whitworth, Anne; Claessen, Mary; Leitão, Suze; Webster, Janet

    2015-06-01

    Understanding the structure of discourse in healthy adults is fundamental to the assessment and diagnosis of discourse level impairments in clinical populations and the development of effective treatment regimes. Exploring discourse genre in healthy speakers that extend beyond the traditional narrative is equally paramount in facilitating maximum impact of clinical interventions in everyday speaking contexts. This study aimed to characterise the discourse of 30 healthy adult speakers across three age groups (20-39, 40-59 and 60+ years) and four discourse genres (recount, procedural, exposition and narrative), drawing on discourse frameworks used in classroom teaching. A clinically useful discourse protocol and analytic procedure using SALT was developed that profiled the macrostructure and key aspects of linguistic microstructure of the different genres, exploring coherence and cohesion within and across genre in a systematic manner. Analyses considered whether there were differences in coherence and cohesion among the different age groups, different genres and specific topics. Results showed that, while individual variability was present, healthy adults structured their discourse consistently, adhering to the frameworks described in the developmental literature, across all four genres. Significant age differences were only seen in the amount of information contained in the body of the discourse (i.e. events, steps or statements offered) with older participants offering less information. This dataset will enable comparisons to be drawn with clinical populations to determine the utility and the feasibility of the use of this framework for diagnosis and intervention. PMID:25774761

  20. Electrophysiological responses to argument structure violations in healthy adults and individuals with agrammatic aphasia

    PubMed Central

    Kielar, Aneta; Meltzer-Asscher, Aya; Thompson, Cynthia

    2012-01-01

    Sentence comprehension requires processing of argument structure information associated with verbs, i.e. the number and type of arguments that they select. Many individuals with agrammatic aphasia show impaired production of verbs with greater argument structure density. The extent to which these participants also show argument structure deficits during comprehension, however, is unclear. Some studies find normal access to verb arguments, whereas others report impaired ability. The present study investigated verb argument structure processing in agrammatic aphasia by examining event-related potentials associated with argument structure violations in healthy young and older adults as well as aphasic individuals. A semantic violation condition was included to investigate possible differences in sensitivity to semantic and argument structure information during sentence processing. Results for the healthy control participants showed a negativity followed by a positive shift (N400-P600) in the argument structure violation condition, as found in previous ERP studies (Friederici & Frisch, 2000; Frisch, Hahne, & Friederici, 2004). In contrast, individuals with agrammatic aphasia showed a P600, but no N400, response to argument structure mismatches. Additionally, compared to the control groups, the agrammatic participants showed an attenuated, but relatively preserved, N400 response to semantic violations. These data show that agrammatic individuals do not demonstrate normal real-time sensitivity to verb argument structure requirements during sentence processing. PMID:23022079

  1. The solution of linear systems of equations with a structural analysis code on the NAS CRAY-2

    NASA Technical Reports Server (NTRS)

    Poole, Eugene L.; Overman, Andrea L.

    1988-01-01

    Two methods for solving linear systems of equations on the NAS Cray-2 are described. One is a direct method; the other is an iterative method. Both methods exploit the architecture of the Cray-2, particularly the vectorization, and are aimed at structural analysis applications. To demonstrate and evaluate the methods, they were installed in a finite element structural analysis code denoted the Computational Structural Mechanics (CSM) Testbed. A description of the techniques used to integrate the two solvers into the Testbed is given. Storage schemes, memory requirements, operation counts, and reformatting procedures are discussed. Finally, results from the new methods are compared with results from the initial Testbed sparse Choleski equation solver for three structural analysis problems. The new direct solvers described achieve the highest computational rates of the methods compared. The new iterative methods are not able to achieve as high computation rates as the vectorized direct solvers but are best for well conditioned problems which require fewer iterations to converge to the solution.

  2. Structured group psychotherapy in adults with attention deficit hyperactivity disorder: results of an open multicentre study.

    PubMed

    Philipsen, Alexandra; Richter, Harald; Peters, Julia; Alm, Barbara; Sobanski, Esther; Colla, Michael; Münzebrock, Mirka; Scheel, Corinna; Jacob, Christian; Perlov, Evgeniy; Tebartz van Elst, Ludger; Hesslinger, Bernd

    2007-12-01

    Attention deficit hyperactivity disorder (ADHD) is a serious mental disorder that often persists in adulthood. In a pilot study, a structured skills training group program for adult ADHD led to significant symptomatic improvements. The present study evaluated the program's effectiveness, feasibility, and patient acceptability in a multicenter setting. Seventy-two adult ADHD patients were assigned to 13 two-hour weekly sessions at 4 different therapy sites. The therapy was well tolerated and led to significant improvements of ADHD, depressive symptoms, and personal health status (p < 0.001). The factors treatment site and medication did not contribute to the overall improvement. Patients regarded the program topics "behavioral analyses," "mindfulness," and "emotion regulation" as the most helpful. In this multicenter study, the therapy program showed therapist-independent effects and seemed to be disorder-specific. This warrants the effort of organizing further controlled studies. PMID:18091195

  3. Effects of increasing physical activity on foot structure and ankle muscle strength in adults with obesity

    PubMed Central

    Zhao, Xiaoguang; Tsujimoto, Takehiko; Kim, Bokun; Katayama, Yasutomi; Wakaba, Kyousuke; Wang, Zhennan; Tanaka, Kiyoji

    2016-01-01

    [Purpose] The purpose of this study was to examine the effects of increasing physical activity on foot structure and ankle muscle strength in adults with obesity and to verify whether the rate of change in foot structure is related to that in ankle muscle strength. [Subjects and Methods] Twenty-seven adults with obesity completed a 12-week program in which the intensity of physical activity performed was gradually increased. Physical activity was monitored using a three-axis accelerometer. Foot structure was assessed using a three-dimensional foot scanner, while ankle muscle strength was measured using a dynamometry. [Results] With the increasing physical activity, the participants’ feet became thinner (the rearfoot width, instep height, and girth decreased) and the arch became higher (the arch height index increased) and stiffer (the arch stiffness index increased); the ankle muscle strength also increased after the intervention. Additionally, the changes in the arch height index and arch stiffness index were not associated with changes in ankle muscle strength. [Conclusion] Increasing physical activity may be one possible approach to improve foot structure and function in individuals with obesity.

  4. The equation of state at finite temperature: Structure and composition of protoneutron stars

    NASA Astrophysics Data System (ADS)

    Burgio, G. F.; Baldo, M.; Chen, H.; Schulze, H.-J.

    2016-01-01

    We study the hadron-quark phase transition at finite temperature in the interior of protoneutron stars, combining the equation of state obtained within the Brueckner-Hartree-Fock approach for hadronic matter with the MIT bag and the Dyson-Schwinger models for quark matter. We discuss the dependence of the results on different nuclear three-body forces and on details of the quark model. We find that a maximum mass exceeding two solar masses can be obtained with a strong three-body force and suitable parameter values in the Dyson-Schwinger model.

  5. Network community structure alterations in adult schizophrenia: identification and localization of alterations

    PubMed Central

    Lerman-Sinkoff, Dov B.; Barch, Deanna M.

    2015-01-01

    A growing body of literature suggests functional connectivity alterations in schizophrenia. While findings have been mixed, evidence points towards a complex pattern of hyper-connectivity and hypo-connectivity. This altered connectivity can be represented and analyzed using the mathematical frameworks provided by graph and information theory to represent functional connectivity data as graphs comprised of nodes and edges linking the nodes. One analytic technique in this framework is the determination and analysis of network community structure, which is the grouping of nodes into linked communities or modules. This data-driven technique finds a best-fit structure such that nodes in a given community have greater connectivity with nodes in their community than with nodes in other communities. These community structure representations have been found to recapitulate known neural-systems in healthy individuals, have been used to identify novel functional systems, and have identified and localized community structure alterations in a childhood onset schizophrenia cohort. In the present study, we sought to determine whether community structure alterations were present in an adult onset schizophrenia cohort while stringently controlling for sources of imaging artifacts. Group level average graphs in healthy controls and individuals with schizophrenia exhibited visually similar network community structures and high amounts of normalized mutual information (NMI). However, testing of individual subject community structures identified small but significant alterations in community structure with alterations being driven by changes in node community membership in the somatosensory, auditory, default mode, salience, and subcortical networks. PMID:26793435

  6. Network community structure alterations in adult schizophrenia: identification and localization of alterations.

    PubMed

    Lerman-Sinkoff, Dov B; Barch, Deanna M

    2016-01-01

    A growing body of literature suggests functional connectivity alterations in schizophrenia. While findings have been mixed, evidence points towards a complex pattern of hyper-connectivity and hypo-connectivity. This altered connectivity can be represented and analyzed using the mathematical frameworks provided by graph and information theory to represent functional connectivity data as graphs comprised of nodes and edges linking the nodes. One analytic technique in this framework is the determination and analysis of network community structure, which is the grouping of nodes into linked communities or modules. This data-driven technique finds a best-fit structure such that nodes in a given community have greater connectivity with nodes in their community than with nodes in other communities. These community structure representations have been found to recapitulate known neural-systems in healthy individuals, have been used to identify novel functional systems, and have identified and localized community structure alterations in a childhood onset schizophrenia cohort. In the present study, we sought to determine whether community structure alterations were present in an adult onset schizophrenia cohort while stringently controlling for sources of imaging artifacts. Group level average graphs in healthy controls and individuals with schizophrenia exhibited visually similar network community structures and high amounts of normalized mutual information (NMI). However, testing of individual subject community structures identified small but significant alterations in community structure with alterations being driven by changes in node community membership in the somatosensory, auditory, default mode, salience, and subcortical networks. PMID:26793435

  7. Some Mathematical Structures Including Simplified Non-Relativistic Quantum Teleportation Equations and Special Relativity

    SciTech Connect

    Woesler, Richard

    2007-02-21

    The computations of the present text with non-relativistic quantum teleportation equations and special relativity are totally speculative, physically correct computations can be done using quantum field theory, which remain to be done in future. Proposals for what might be called statistical time loop experiments with, e.g., photon polarization states are described when assuming the simplified non-relativistic quantum teleportation equations and special relativity. However, a closed time loop would usually not occur due to phase incompatibilities of the quantum states. Histories with such phase incompatibilities are called inconsistent ones in the present text, and it is assumed that only consistent histories would occur. This is called an exclusion principle for inconsistent histories, and it would yield that probabilities for certain measurement results change. Extended multiple parallel experiments are proposed to use this statistically for transmission of classical information over distances, and regarding time. Experiments might be testable in near future. However, first a deeper analysis, including quantum field theory, remains to be done in future.

  8. Static aeroelastic analysis of wings using Euler/Navier-Stokes equations coupled with improved wing-box finite element structures

    NASA Technical Reports Server (NTRS)

    Guruswamy, Guru P.; MacMurdy, Dale E.; Kapania, Rakesh K.

    1994-01-01

    Strong interactions between flow about an aircraft wing and the wing structure can result in aeroelastic phenomena which significantly impact aircraft performance. Time-accurate methods for solving the unsteady Navier-Stokes equations have matured to the point where reliable results can be obtained with reasonable computational costs for complex non-linear flows with shock waves, vortices and separations. The ability to combine such a flow solver with a general finite element structural model is key to an aeroelastic analysis in these flows. Earlier work involved time-accurate integration of modal structural models based on plate elements. A finite element model was developed to handle three-dimensional wing boxes, and incorporated into the flow solver without the need for modal analysis. Static condensation is performed on the structural model to reduce the structural degrees of freedom for the aeroelastic analysis. Direct incorporation of the finite element wing-box structural model with the flow solver requires finding adequate methods for transferring aerodynamic pressures to the structural grid and returning deflections to the aerodynamic grid. Several schemes were explored for handling the grid-to-grid transfer of information. The complex, built-up nature of the wing-box complicated this transfer. Aeroelastic calculations for a sample wing in transonic flow comparing various simple transfer schemes are presented and discussed.

  9. Molly and Equations in A[2]: A Case Study of Apprehending Structure

    ERIC Educational Resources Information Center

    Simpson, Adrian; Stehlikova, Nada

    2004-01-01

    This paper explores one student's attempt to apprehend an abstract mathematical structure (similar to Z[99]). We discuss Karmiloff-Smith's theory of representational redescription as a model for the development of structural understanding and contrast this with existing process-object theories. We use two cycles in Molly's movement from an action…

  10. The effects of indefinite nonlinear boundary conditions on the structure of the positive solutions set of a logistic equation

    NASA Astrophysics Data System (ADS)

    Ramos Quoirin, Humberto; Umezu, Kenichiro

    2014-12-01

    We investigate a semilinear elliptic equation with a logistic nonlinearity and an indefinite nonlinear boundary condition, both depending on a parameter λ. Overall, we analyze the effect of the indefinite nonlinear boundary condition on the structure of the positive solutions set. Based on variational and bifurcation techniques, our main results establish the existence of three nontrivial non-negative solutions for some values of λ, as well as their asymptotic behavior. These results suggest that the positive solutions set contains an S-shaped component in some case, as well as a combination of a C-shaped and an S-shaped components in another case.

  11. Structural changes underlying compensatory increase of diffusing capacity after left pneumonectomy in adult dogs.

    PubMed Central

    Hsia, C C; Fryder-Doffey, F; Stalder-Nayarro, V; Johnson, R L; Reynolds, R C; Weibel, E R

    1993-01-01

    To determine if the functional compensation in diffusing capacity of the remaining lung following pneumonectomy is due to structural growth, we performed morphometric analysis of the right lung in three adult foxhounds approximately 2 yr after left pneumonectomy (removal of 42% of lung) and compared the results to those in normal adult dogs previously studied by the same techniques. Diffusing capacity was calculated by an established morphometric model and compared to physiologic estimates at peak exercise in the same dogs after pneumonectomy. The major structural changes after left pneumonectomy are hyperinflation of the right lung, alveolar enlargement, and thinning of the alveolar-capillary tissue barrier. These changes confer significant functional compensation for gas exchange by reducing the overall resistance to O2 diffusion. The magnitude of compensation in diffusing capacity estimated either morphometrically or physiologically is similar. In spite of morphometric and physiologic evidence of functional compensation, there is no evidence of significant growth of structural components. After pneumonectomy, morphometric estimates of diffusing capacity are on average 23% higher than physiologic estimates in the same dogs at peak exercise. We conclude that the previously reported large differences between morphometric and physiologic estimates of diffusing capacity reflects the presence of large physiologic reserves available for recruitment. Images PMID:8349815

  12. Structured data-sparse approximation to high order tensors arising from the deterministic Boltzmann equation

    NASA Astrophysics Data System (ADS)

    Khoromskij, Boris N.

    2007-09-01

    We develop efficient data-sparse representations to a class of high order tensors via a block many-fold Kronecker product decomposition. Such a decomposition is based on low separation-rank approximations of the corresponding multivariate generating function. We combine the Sinc interpolation and a quadrature-based approximation with hierarchically organised block tensor-product formats. Different matrix and tensor operations in the generalised Kronecker tensor-product format including the Hadamard-type product can be implemented with the low cost. An application to the collision integral from the deterministic Boltzmann equation leads to an asymptotical cost O(n^4log^beta n) - O(n^5log^beta n) in the one-dimensional problem size n (depending on the model kernel function), which noticeably improves the complexity O(n^6log^beta n) of the full matrix representation.

  13. The Incorporation of Truncated Fourier Series into Finite Difference Approximations of Structural Stability Equations

    NASA Technical Reports Server (NTRS)

    Hannah, S. R.; Palazotto, A. N.

    1978-01-01

    A new trigonometric approach to the finite difference calculus was applied to the problem of beam buckling as represented by virtual work and equilibrium equations. The trigonometric functions were varied by adjusting a wavelength parameter in the approximating Fourier series. Values of the critical force obtained from the modified approach for beams with a variety of boundary conditions were compared to results using the conventional finite difference method. The trigonometric approach produced significantly more accurate approximations for the critical force than the conventional approach for a relatively wide range in values of the wavelength parameter; and the optimizing value of the wavelength parameter corresponded to the half-wavelength of the buckled mode shape. It was found from a modal analysis that the most accurate solutions are obtained when the approximating function closely represents the actual displacement function and matches the actual boundary conditions.

  14. The hierarchical factor structure of the WAIS-R for alcoholic adults.

    PubMed

    Blaha, J; Mandes, E

    1993-09-01

    A Wherry (1984) hierarchical factor solution was obtained on the WAIS-R subtest intercorrelations for 108 alcoholic adults. An ability arrangement consistent with Vernon's (1950) structure-of-intellect paradigm was found. This ability hierarchy consisted of a strong general intelligence (g) factor defined by all 11 subtests, which accounted for 49% of the variance. The primary level of the ability hierarchy consisted of spatial-perceptual-mechanical (k:m), Freedom from Distractibility (FD), and Verbal Comprehension (VC) factors. Those respective factors accounted for 86%, 4%, and 3% of the total subtest variance. PMID:8254084

  15. Full equations utilities (FEQUTL) model for the approximation of hydraulic characteristics of open channels and control structures during unsteady flow

    USGS Publications Warehouse

    Franz, Delbert D.; Melching, Charles S.

    1997-01-01

    The Full EQuations UTiLities (FEQUTL) model is a computer program for computation of tables that list the hydraulic characteristics of open channels and control structures as a function of upstream and downstream depths; these tables facilitate the simulation of unsteady flow in a stream system with the Full Equations (FEQ) model. Simulation of unsteady flow requires many iterations for each time period computed. Thus, computation of hydraulic characteristics during the simulations is impractical, and preparation of function tables and application of table look-up procedures facilitates simulation of unsteady flow. Three general types of function tables are computed: one-dimensional tables that relate hydraulic characteristics to upstream flow depth, two-dimensional tables that relate flow through control structures to upstream and downstream flow depth, and three-dimensional tables that relate flow through gated structures to upstream and downstream flow depth and gate setting. For open-channel reaches, six types of one-dimensional function tables contain different combinations of the top width of flow, area, first moment of area with respect to the water surface, conveyance, flux coefficients, and correction coefficients for channel curvilinearity. For hydraulic control structures, one type of one-dimensional function table contains relations between flow and upstream depth, and two types of two-dimensional function tables contain relations among flow and upstream and downstream flow depths. For hydraulic control structures with gates, a three-dimensional function table lists the system of two-dimensional tables that contain the relations among flow and upstream and downstream flow depths that correspond to different gate openings. Hydraulic control structures for which function tables containing flow relations are prepared in FEQUTL include expansions, contractions, bridges, culverts, embankments, weirs, closed conduits (circular, rectangular, and pipe

  16. Implications of a New Ab-Initio H-He Equation of State for Giant Planet Structure (Invited)

    NASA Astrophysics Data System (ADS)

    Hubbard, W. B.

    2013-12-01

    I report results from a continuing study of the structure and evolution of hydrogen-dominated giant planets with masses of ~ 100 to 600 Earth masses (collaboration with B. Militzer and J. Fortney). Our initial study is of the radii and cooling history of giant planets in this mass range, assuming simplified isentropic structures and constant hydrogen-helium mixing ratio; no heavier elements are included. Unlike in previous studies, our equation of state is thermodynamically consistent, tied to an absolute entropy scale, and based on a full density-functional molecular-dynamics simulation of a strongly interacting hydrogen-helium fluid. We reference our suite of models to an equivalent suite calculated using the widely-used equation of state of Saumon, Chabrier, and Van Horn (1995, ApJ. Suppl. 99:713; SCVH). Our models cover an entropy range from 7 Boltzmann constants per electron (similar to the entropy in the atmospheres of Jupiter and Saturn) up to about 12 Boltzmann constants per electron (comparable to the entropy in the atmospheres of the hottest giant exoplanets), thus permitting a general treatment of cooling models for giant planets. To infer giant-planet "metallicity" (astrophysical term for the object's fractional content of elements heavier than H-He), particularly for exoplanets, one relies on measurement of the giant planet's mean radius, which decreases as the metallicity rises. However the mean radius depends not only on metallicity, but also on the object's mean entropy, its rotation, and on uncertainties in the equation of state. For H-He objects in the mass range we have studied, all of these effects can increase or decrease the mean radius by up to a few tenths of a Jupiter radius (R_J). Importantly, the new equation of state causes low-entropy giant-planets such as Jupiter and Saturn to shrink in comparison to SCVH models by up to 0.08 R_J. Thus one might infer that Jupiter and Saturn are of lower metallicity than SCVH models would imply, unless

  17. The Importance of Isomorphism for Conclusions about Homology: A Bayesian Multilevel Structural Equation Modeling Approach with Ordinal Indicators

    PubMed Central

    Guenole, Nigel

    2016-01-01

    We describe a Monte Carlo study examining the impact of assuming item isomorphism (i.e., equivalent construct meaning across levels of analysis) on conclusions about homology (i.e., equivalent structural relations across levels of analysis) under varying degrees of non-isomorphism in the context of ordinal indicator multilevel structural equation models (MSEMs). We focus on the condition where one or more loadings are higher on the between level than on the within level to show that while much past research on homology has ignored the issue of psychometric isomorphism, psychometric isomorphism is in fact critical to valid conclusions about homology. More specifically, when a measurement model with non-isomorphic items occupies an exogenous position in a multilevel structural model and the non-isomorphism of these items is not modeled, the within level exogenous latent variance is under-estimated leading to over-estimation of the within level structural coefficient, while the between level exogenous latent variance is overestimated leading to underestimation of the between structural coefficient. When a measurement model with non-isomorphic items occupies an endogenous position in a multilevel structural model and the non-isomorphism of these items is not modeled, the endogenous within level latent variance is under-estimated leading to under-estimation of the within level structural coefficient while the endogenous between level latent variance is over-estimated leading to over-estimation of the between level structural coefficient. The innovative aspect of this article is demonstrating that even minor violations of psychometric isomorphism render claims of homology untenable. We also show that posterior predictive p-values for ordinal indicator Bayesian MSEMs are insensitive to violations of isomorphism even when they lead to severely biased within and between level structural parameters. We highlight conditions where poor estimation of even correctly specified

  18. Networks involved in olfaction and their dynamics using independent component analysis and unified structural equation modeling.

    PubMed

    Karunanayaka, Prasanna; Eslinger, Paul J; Wang, Jian-Li; Weitekamp, Christopher W; Molitoris, Sarah; Gates, Kathleen M; Molenaar, Peter C M; Yang, Qing X

    2014-05-01

    The study of human olfaction is complicated by the myriad of processing demands in conscious perceptual and emotional experiences of odors. Combining functional magnetic resonance imaging with convergent multivariate network analyses, we examined the spatiotemporal behavior of olfactory-generated blood-oxygenated-level-dependent signal in healthy adults. The experimental functional magnetic resonance imaging (fMRI) paradigm was found to offset the limitations of olfactory habituation effects and permitted the identification of five functional networks. Analysis delineated separable neuronal circuits that were spatially centered in the primary olfactory cortex, striatum, dorsolateral prefrontal cortex, rostral prefrontal cortex/anterior cingulate, and parietal-occipital junction. We hypothesize that these functional networks subserve primary perceptual, affective/motivational, and higher order olfactory-related cognitive processes. Results provided direct evidence for the existence of parallel networks with top-down modulation for olfactory processing and clearly distinguished brain activations that were sniffing-related versus odor-related. A comprehensive neurocognitive model for olfaction is presented that may be applied to broader translational studies of olfactory function, aging, and neurological disease. PMID:23818133

  19. Structural equation modeling and nested ANOVA: Effects of lead exposure on maternal and fetal growth in rats

    SciTech Connect

    Hamilton, J.D. ); O'Flaherty, E.J.; Shukla, R.; Gartside, P.S. ); Ross, R. )

    1994-01-01

    This study provided an assessment of the effects of lead on early growth in rats based on structural equation modeling and nested analysis of variance (ANOVA). Structural equation modeling showed that lead in drinking water (250, 500, or 1000 ppm) had a direct negative effect on body weight and tail length (i.e., growth) in female rats during the first week of exposure. During the following 2 weeks of exposure, high correlation between growth measurements taken over time resulted in reduced early postnatal growth. By the fourth week of exposure, reduced growth was not evident. Mating began after 8 weeks of exposure, and exposure continued during gestation. Decreased fetal body weight was detected when the effects of litter size, intrauterine position, and sex were controlled in a nested ANOVA. Lead exposure did not appear to affect fetal skeletal development, possibly because lead did not alter maternal serum calcium and phosphorus levels. The effect of lead on individual fetal body weight suggests that additional studies are needed to examine the effect of maternal lead exposure on fetal development and early postnatal growth. 24 refs., 4 figs., 6 tabs.

  20. Application of Structural Equation Models for Elucidating the Ecological Drivers of Anopheles sinensis in the Three Gorges Reservoir

    PubMed Central

    Duo-quan, Wang; Lin-hua, Tang; Heng-hui, Liu; Zhen-cheng, Gu; Xiang, Zheng

    2013-01-01

    Objective To identify the major ecological drivers for malaria vector density using the structural equation model (SEM) in the Three Gorges Reservoir. Method An 11-year longitudinal surveillance of malaria vector as well as its related ecological factors was carried out in the Three Gorges Reservoir. The Delphi method was used to identify associated ecological factors. The structural equation model was repeatedly corrected and improved by the corrected index, combined with the actual situation. The final model was defined by relative simplicity, best fitting as well as the practicality. Result The final model indicated that the direct effects of temperature, livestock, humidity, and breeding on the vector were 0.015, −0.228, 0.450, 0.516 respectively, their total effects on the vector were 0.359, −0.112, 0.850, and 0.043 through different pathways. Conclusion SEM was effective and convenient in elucidating the mechanism by which malaria vector dynamics operated in this study. It identified that the breeding had the highest direct effect on vector and played a key role for mediating effect of temperature and humidity. PMID:23935887

  1. Analysis of Causal Relationships by Structural Equation Modeling to Determine the Factors Influencing Cognitive Function in Elderly People in Japan

    PubMed Central

    Kimura, Daisuke; Nakatani, Ken; Takeda, Tokunori; Fujita, Takashi; Sunahara, Nobuyuki; Inoue, Katsumi; Notoya, Masako

    2015-01-01

    The purpose of this study is to identify a potentiality factor that is a preventive factor for decline in cognitive function. Additionally, this study pursues to clarify the causal relationship between the each potential factor and its influence on cognitive function. Subjects were 366 elderly community residents (mean age 73.7 ± 6.4, male 51, female 315) who participated in the Taketoyo Project from 2007 to 2011. Factor analysis was conducted to identify groupings within mental, social, life, physical and cognitive functions. In order to detect clusters of 14 variables, the item scores were subjected to confirmatory factor analysis. We performed Structural Equation Modeling analysis to calculate the standardization coefficient and correlation coefficient for every factor. The cause and effect hypothesis model was used to gather two intervention theory hypotheses for dementia prevention (direct effect, indirect effect) in one system. Finally, we performed another Structural Equation Modeling analysis to calculate the standardization of the cause and effect hypothesis model. Social participation was found to be activated by the improvement of four factors, and in turn, activated “Social participation” acted on cognitive function. PMID:25658829

  2. Adaptive Modulation of Adult Brain Gray and White Matter to High Altitude: Structural MRI Studies

    PubMed Central

    Zhang, Jiaxing; Zhang, Haiyan; Li, Jinqiang; Chen, Ji; Han, Qiaoqing; Lin, Jianzhong; Yang, Tianhe; Fan, Ming

    2013-01-01

    The aim of this study was to investigate brain structural alterations in adult immigrants who adapted to high altitude (HA). Voxel-based morphometry analysis of gray matter (GM) volumes, surface-based analysis of cortical thickness, and Tract-Based Spatial Statistics analysis of white matter fractional anisotropy (FA) based on MRI images were conducted on 16 adults (20–22 years) who immigrated to the Qinghai-Tibet Plateau (2300–4400 m) for 2 years. They had no chronic mountain sickness. Control group consisted of 16 matched sea level subjects. A battery of neuropsychological tests was also conducted. HA immigrants showed significantly decreased GM volumes in the right postcentral gyrus and right superior frontal gyrus, and increased GM volumes in the right middle frontal gyrus, right parahippocampal gyrus, right inferior and middle temporal gyri, bilateral inferior ventral pons, and right cerebellum crus1. While there was some divergence in the left hemisphere, surface-based patterns of GM changes in the right hemisphere resembled those seen for VBM analysis. FA changes were observed in multiple WM tracts. HA immigrants showed significant impairment in pulmonary function, increase in reaction time, and deficit in mental rotation. Parahippocampal and middle frontal GM volumes correlated with vital capacity. Superior frontal GM volume correlated with mental rotation and postcentral GM correlated with reaction time. Paracentral lobule and frontal FA correlated with mental rotation reaction time. There might be structural modifications occurred in the adult immigrants during adaptation to HA. The changes in GM may be related to impaired respiratory function and psychological deficits. PMID:23874692

  3. Testis structure and function in a nongenetic hyperadipose rat model at prepubertal and adult ages.

    PubMed

    França, L R; Suescun, M O; Miranda, J R; Giovambattista, A; Perello, M; Spinedi, E; Calandra, R S

    2006-03-01

    There are few data for hormonal levels and testis structure and function during postnatal development in rats neonatally treated with monosodium L-glutamate (MSG). In our study, newborn male pups were ip injected with MSG (4 mg/g body weight) every 2 d up to 10 d of age and investigated at prepubertal and adult ages. Plasma levels of leptin, LH, FSH, prolactin, testosterone (T), corticosterone, and free T4 (FT4) were measured. MSG rats displayed elevated circulating levels of corticosterone and hyperadiposity/hyperleptinemia, regardless of the age examined; conversely, circulating prolactin levels were not affected. Moreover, prepubertal MSG rats revealed a significant (P < 0.05) reduction in testis weight and the number of Sertoli (SC) and Leydig cells per testis. Leptin plasma levels were severalfold higher (2.41 vs. 8.07; P < 0.05) in prepubertal MSG rats, and these animals displayed plasma LH, FSH, T, and FT4 levels significantly decreased (P < 0.05). Taken together, these data indicate that testis development, as well as SC and Leydig cell proliferation, were disturbed in prepubertal MSG rats. Adult MSG rats also displayed significantly higher leptin plasma levels (7.26 vs. 27.04; P < 0.05) and lower (P < 0.05) LH and FSH plasma levels. However, T and FT4 plasma levels were normal, and no apparent alterations were observed in testis structure of MSG rats. Only the number of SCs per testis was significantly (P < 0.05) reduced in the adult MSG rats. In conclusion, although early installed hyperadipose/hyperleptinemia phenotype was probably responsible for the reproductive axis damages in MSG animals, it remains to be investigated whether this condition is the main factor for hypothalamus-pituitary-gonadal axis dysfunction in MSG rats. PMID:16339210

  4. Communication: multireference equation of motion coupled cluster: a transform and diagonalize approach to electronic structure.

    PubMed

    Nooijen, Marcel; Demel, Ondřej; Datta, Dipayan; Kong, Liguo; Shamasundar, K R; Lotrich, V; Huntington, Lee M; Neese, Frank

    2014-02-28

    The novel multireference equation-of-motion coupled-cluster (MREOM-CC) approaches provide versatile and accurate access to a large number of electronic states. The methods proceed by a sequence of many-body similarity transformations and a subsequent diagonalization of the transformed Hamiltonian over a compact subspace. The transformed Hamiltonian is a connected entity and preserves spin- and spatial symmetry properties of the original Hamiltonian, but is no longer Hermitean. The final diagonalization spaces are defined in terms of a complete active space (CAS) and limited excitations (1h, 1p, 2h, …) out of the CAS. The methods are invariant to rotations of orbitals within their respective subspaces (inactive, active, external). Applications to first row transition metal atoms (Cr, Mn, and Fe) are presented yielding results for up to 524 electronic states (for Cr) with an rms error compared to experiment of about 0.05 eV. The accuracy of the MREOM family of methods is closely related to its favorable extensivity properties as illustrated by calculations on the O2-O2 dimer. The computational costs of the transformation steps in MREOM are comparable to those of closed-shell Coupled Cluster Singles and Doubles (CCSD) approach. PMID:24588141

  5. Communication: Multireference equation of motion coupled cluster: A transform and diagonalize approach to electronic structure

    SciTech Connect

    Nooijen, Marcel; Huntington, Lee M.; Demel, Ondřej; Datta, Dipayan; Kong, Liguo; Shamasundar, K. R.; Lotrich, V.; Neese, Frank

    2014-02-28

    The novel multireference equation-of-motion coupled-cluster (MREOM-CC) approaches provide versatile and accurate access to a large number of electronic states. The methods proceed by a sequence of many-body similarity transformations and a subsequent diagonalization of the transformed Hamiltonian over a compact subspace. The transformed Hamiltonian is a connected entity and preserves spin- and spatial symmetry properties of the original Hamiltonian, but is no longer Hermitean. The final diagonalization spaces are defined in terms of a complete active space (CAS) and limited excitations (1h, 1p, 2h, …) out of the CAS. The methods are invariant to rotations of orbitals within their respective subspaces (inactive, active, external). Applications to first row transition metal atoms (Cr, Mn, and Fe) are presented yielding results for up to 524 electronic states (for Cr) with an rms error compared to experiment of about 0.05 eV. The accuracy of the MREOM family of methods is closely related to its favorable extensivity properties as illustrated by calculations on the O{sub 2}–O{sub 2} dimer. The computational costs of the transformation steps in MREOM are comparable to those of closed-shell Coupled Cluster Singles and Doubles (CCSD) approach.

  6. Distribution of cuticular proteins in different structures of adult Anopheles gambiae.

    PubMed

    Zhou, Yihong; Badgett, Majors J; Bowen, John Hunter; Vannini, Laura; Orlando, Ron; Willis, Judith H

    2016-08-01

    Anopheles gambiae devotes over 2% (295) of its protein coding genes to structural cuticular proteins (CPs) that have been classified into 13 different families plus ten low complexity proteins not assigned to families. Small groups of genes code for identical proteins reducing the total number of unique cuticular proteins to 282. Is the large number because different structures utilize different CPs, or are all of the genes widely expressed? We used LC-MS/MS to learn how many products of these genes were found in five adult structures: Johnston's organs, the remainder of the male antennae, eye lenses, legs, and wings. Data were analyzed against both the entire proteome and a smaller database of just CPs. We recovered unique peptides for 97 CPs and shared peptides for another 35. Members of 11 of the 13 families were recovered as well as some unclassified. Only 11 CPs were present exclusively in only one structure while 43 CPs were recovered from all five structures. A quantitative analysis, using normalized spectral counts, revealed that only a few CPs were abundant in each structure. When the MS/MS data were run against the entire proteome, the majority of the top hits were to CPs, but peptides were recovered from an additional 467 proteins. CP peptides were frequently recovered from chitin-binding domains, confirming that protein-chitin interactions are not mediated by covalent bonds. Comparison with three other MS/MS analyses of cuticles or cuticle-rich structures augmented the current analysis. Our findings provide new insights into the composition of different mosquito structures and reveal the complexity of selection and utilization of genes coding for structural cuticular proteins. PMID:27179905

  7. Structural homology of identified motoneurones in larval and adult stages of hemi- and holometabolous insects.

    PubMed

    Breidbach, O; Kutsch, W

    1990-07-15

    The set of neurones innervating the dorsal longitudinal muscles was studied with cobalt and nickel backfills in: (1) larval and adult locusts (Schistocerca gregaria and Locusta migratoria), (2) the larval and adult beetle (Zophobas morio), and (3) various segments of these insect species. In all specimens 11 neurones were encountered, which can be subdivided into a group of 7 motoneurones that stem from the next anterior ganglion and 4 neurones located in the ganglion of the segment containing the muscles. The latter group comprises 2 contralateral and 2 medial somata, of which one is a dorsal unpaired median neurone. The results were analysed under different aspects. This neural set and the basic structure of the dendritic fields is similar in: (1) different segments (serial homology), (2) the larval stage and imago of the same species with or without a pronounced metamorphosis (ontogeny), and (3) the studied hemi- and holometabolous insects (phylogeny). Our results support the notion that the structure of these neurones is conserved irrespectively of changes in the periphery and strategy of postembryonic development. PMID:2398139

  8. Structural Stigma and Hypothalamic-Pituitary-Adrenocortical Axis Reactivity in Lesbian, Gay, and Bisexual Young Adults

    PubMed Central

    Hatzenbuehler, Mark L.; McLaughlin, Katie A.

    2013-01-01

    Background Youth exposed to extreme adverse life conditions have blunted cortisol responses to stress. Purpose To examine whether growing up in highly stigmatizing environments similarly shapes stigmatized individuals’ physiological responses to identity-related stress. Methods We recruited 74 lesbian, gay, and bisexual young adults (mean age=23.68) from 24 states with varying levels of structural stigma surrounding homosexuality. State-level structural stigma was coded based on several dimensions, including policies that exclude sexual minorities from social institutions (e.g., same-sex marriage). Participants were exposed to a laboratory stressor, the Trier Social Stress Test (TSST), and neuroendocrine measures were collected. Results LGB young adults who were raised in highly stigmatizing environments as adolescents evidenced a blunted cortisol response following the TSST compared to those from low-stigma environments. Conclusions The stress of growing up in environments that target gays and lesbians for social exclusion may exert biological effects that are similar to traumatic life experiences. PMID:24154988

  9. Organizational Support and Volunteering Benefits for Older Adults

    ERIC Educational Resources Information Center

    Tang, Fengyan; Choi, Eunhee; Morrow-Howell, Nancy

    2010-01-01

    Purpose: This study tested a theoretical model of volunteering benefits and examined the mechanism through which volunteering benefits older adults. Design and Methods: This is a 2-wave study of 253 older adult volunteers serving in 10 volunteer programs. Older volunteers completed the mailed surveys in 2005 and 2006. Structural equation modeling…

  10. Impact of Choice on Social Outcomes of Adults with ASD

    ERIC Educational Resources Information Center

    Mehling, Margaret H.; Tassé, Marc J.

    2015-01-01

    This study explores social outcomes for adults with autism spectrum disorder (ASD) in comparison to adults with developmental disabilities other than ASD by investigating the relationships between the constructs Social Participation and Relationships, Social Determination, and Personal Control. Structural equation modeling (SEM) was used to test a…

  11. A Comparison of Normal and Elliptical Estimation Methods in Structural Equation Models.

    ERIC Educational Resources Information Center

    Schumacker, Randall E.; Cheevatanarak, Suchittra

    Monte Carlo simulation compared chi-square statistics, parameter estimates, and root mean square error of approximation values using normal and elliptical estimation methods. Three research conditions were imposed on the simulated data: sample size, population contamination percent, and kurtosis. A Bentler-Weeks structural model established the…

  12. Structural Equation Model of the Consumer-Directed Theory of Empowerment in a Vocational Rehabilitation Context

    ERIC Educational Resources Information Center

    Kosciulek, John F.

    2005-01-01

    One model that is potentially useful in the rehabilitation field is the Consumer-Directed Theory of Empowerment (CDTE; Kosciulek, 1999a). However, additional empirical data are needed to further develop and critically evaluate the CDTE. To accomplish this task, the purpose of this study was to test the hypothesized structural model CDTE in a…

  13. Examination of the Factor Structure of the Schizotypal Personality Questionnaire among British and Trinidadian Adults

    PubMed Central

    Barron, David; Swami, Viren; Hutchinson, Gerard

    2015-01-01

    Much debate in schizotypal research has centred on the factor structure of the Schizotypal Personality Questionnaire (SPQ), with research variously showing higher-order dimensionality consisting of two to seven dimensions. In addition, cross-cultural support for the stability of those factors remains limited. Here, we examined the factor structure of the SPQ among British and Trinidadian adults. Participants from a White British subsample (n = 351) resident in the UK and from an African Caribbean subsample (n = 284) resident in Trinidad completed the SPQ. The higher-order factor structure of the SPQ was analysed through confirmatory factor analysis, followed by multiple-group analysis for the model of best fit. Between-group differences for sex and ethnicity were investigated using multivariate analysis of variance in relation to the higher-order domains. The model of best-fit was the four-factor structure, which demonstrated measurement invariance across groups. Additionally, these data had an adequate fit for two alternative models: (a) 3-factor and (b) modified 4-factor model. The British subsample had significantly higher scores across all domains than the Trinidadian group, and men scored significantly higher on the disorganised domain than women. The four-factor structure received confirmatory support and, importantly, support for use with populations varying in ethnicity and culture. PMID:25699263

  14. Post-equinox observations of Uranus: Berg's evolution, vertical structure, and track towards the equator

    NASA Astrophysics Data System (ADS)

    de Pater, Imke; Sromovsky, L. A.; Hammel, Heidi B.; Fry, P. M.; LeBeau, R. P.; Rages, Kathy; Showalter, Mark; Matthews, Keith

    2011-09-01

    We present observations of Uranus taken with the near-infrared camera NIRC2 on the 10-m W.M. Keck II telescope, the Wide Field Planetary Camera 2 (WFPC2) and the Wide Field Camera 3 (WFC3) on the Hubble Space Telescope (HST) from July 2007 through November 2009. In this paper we focus on a bright southern feature, referred to as the "Berg." In Sromovsky et al. (Sromovsky, L.A., Fry, P.M., Hammel, H.B., Ahue, A.W., de Pater, I., Rages, K.A., Showalter, M.R., van Dam, M. [2009]. Icarus 203, 265-286), we reported that this feature, which oscillated between latitudes of -32° and -36° for several decades, suddenly started on a northward track in 2005. In this paper we show the complete record of observations of this feature's track towards the equator, including its demise. After an initially slow linear drift, the feature's drift rate accelerated at latitudes ∣ θ∣ < 25°. By late 2009 the feature, very faint by then, was spotted at a latitude of -5° before disappearing from view. During its northward track, the feature's morphology changed dramatically, and several small bright unresolved features were occasionally visible poleward of the main "streak." These small features were sometimes visible at a wavelength of 2.2 μm, indicative that the clouds reached altitudes of ˜0.6 bar. The main part of the Berg, which is generally a long sometimes multipart streak, is estimated to be much deeper in the atmosphere, near 3.5 bars in 2004, but rising to 1.8-2.5 bars in 2007 after it began its northward drift. Through comparisons with Neptune's Great Dark Spot and simulations of the latter, we discuss why the Berg may be tied to a vortex, an anticyclone deeper in the atmosphere that is visible only through orographic companion clouds.

  15. Querying databases of trajectories of differential equations: Data structures for trajectories

    NASA Technical Reports Server (NTRS)

    Grossman, Robert

    1989-01-01

    One approach to qualitative reasoning about dynamical systems is to extract qualitative information by searching or making queries on databases containing very large numbers of trajectories. The efficiency of such queries depends crucially upon finding an appropriate data structure for trajectories of dynamical systems. Suppose that a large number of parameterized trajectories gamma of a dynamical system evolving in R sup N are stored in a database. Let Eta is contained in set R sup N denote a parameterized path in Euclidean Space, and let the Euclidean Norm denote a norm on the space of paths. A data structure is defined to represent trajectories of dynamical systems, and an algorithm is sketched which answers queries.

  16. Multi-Center Electronic Structure Calculations for Plasma Equation of State

    SciTech Connect

    Wilson, B G; Johnson, D D; Alam, A

    2010-12-14

    We report on an approach for computing electronic structure utilizing solid-state multi-center scattering techniques, but generalized to finite temperatures to model plasmas. This approach has the advantage of handling mixtures at a fundamental level without the imposition of ad hoc continuum lowering models, and incorporates bonding and charge exchange, as well as multi-center effects in the calculation of the continuum density of states.

  17. Impact of Family Structure on Parental Attitudes Toward the Economic Support of Adult Children Over the Transition to Adulthood

    ERIC Educational Resources Information Center

    Aquilino, William S.

    2005-01-01

    This research explored the influence of family structure on midlife parents' attitudes toward the economic support of adult children and measured change in those attitudes as their oldest child moved from adolescence to young adulthood. Results suggest that family structure has long-term effects on parents' attitudes toward financial obligations…

  18. Problems involved in the specification and interpretation of quantitative structure-activity relationships. Part 1: A modified type of structure-activity equations.

    PubMed

    Mager, H; Barth, A

    1979-01-01

    It has been demonstrated that ordinary regression coefficients of a quantitative structure-activity equation depend strongly on the scaling both of the biological parameter and the explanatory variables (regressors). Even in the case of only two regressors this fact may lead to challengable interpretations regarding the relative performances of the explanatory variables, say physicochemical parameters. The use of standardized variables and, consequently, of standardized regression coefficients is proposed in order to get a better insight into the mechanistic features of the mode of action of the congeneric series under investigation. The procedure has been illustrated with examples adapted from the literature. PMID:396534

  19. The consequences of ignoring measurement invariance for path coefficients in structural equation models

    PubMed Central

    Guenole, Nigel; Brown, Anna

    2014-01-01

    We report a Monte Carlo study examining the effects of two strategies for handling measurement non-invariance – modeling and ignoring non-invariant items – on structural regression coefficients between latent variables measured with item response theory models for categorical indicators. These strategies were examined across four levels and three types of non-invariance – non-invariant loadings, non-invariant thresholds, and combined non-invariance on loadings and thresholds – in simple, partial, mediated and moderated regression models where the non-invariant latent variable occupied predictor, mediator, and criterion positions in the structural regression models. When non-invariance is ignored in the latent predictor, the focal group regression parameters are biased in the opposite direction to the difference in loadings and thresholds relative to the referent group (i.e., lower loadings and thresholds for the focal group lead to overestimated regression parameters). With criterion non-invariance, the focal group regression parameters are biased in the same direction as the difference in loadings and thresholds relative to the referent group. While unacceptable levels of parameter bias were confined to the focal group, bias occurred at considerably lower levels of ignored non-invariance than was previously recognized in referent and focal groups. PMID:25278911

  20. Factorial Structure and Measurement Invariance of the PANAS in Spanish Older Adults.

    PubMed

    Buz, José; Pérez-Arechaederra, Diana; Fernández-Pulido, Ramón; Urchaga, David

    2015-01-01

    Developmental theories suggest age-related changes in the structure of affect. Paradoxically, the internal structure of the Positive and Negative Affect Schedule (PANAS; Watson, Clark, & Tellegen, 1988) has not been tested in Spanish older adults by means of confirmatory factor analysis (CFA) despite it is the most widely used measure of emotional well-being in later life. The aim of this study was to examine competing models of the internal structure of the Spanish version of the PANAS, its measurement invariance, reliability, and external validity. Participants were a representative sample of 585 community-dwelling people aged 60 and over, who also completed depression, loneliness and life satisfaction measures. Results showed that the orthogonal two-factor model with correlated errors (RMSEA = .057, 90% CI [.051, .063], SRMR = .084, CFI = .97, NNFI = .97) was the best fitting solution. Measurement invariance analyses confirmed that the two-independent factor structure can be used across young-old and very old people, as well as in both males and females. It showed good reliability (PA: α = .93, NA: α = .83), criterion, convergent and discriminant validity (p < .01). Our discussion highlights the role of age and culture in the experience and expression of emotions. PMID:26054863

  1. Inverse material identification in coupled acoustic-structure interaction using a modified error in constitutive equation functional

    NASA Astrophysics Data System (ADS)

    Warner, James E.; Diaz, Manuel I.; Aquino, Wilkins; Bonnet, Marc

    2014-09-01

    This work focuses on the identification of heterogeneous linear elastic moduli in the context of frequency-domain, coupled acoustic-structure interaction (ASI), using either solid displacement or fluid pressure measurement data. The approach postulates the inverse problem as an optimization problem where the solution is obtained by minimizing a modified error in constitutive equation (MECE) functional. The latter measures the discrepancy in the constitutive equations that connect kinematically admissible strains and dynamically admissible stresses, while incorporating the measurement data as additional quadratic error terms. We demonstrate two strategies for selecting the MECE weighting coefficient to produce regularized solutions to the ill-posed identification problem: 1) the discrepancy principle of Morozov, and 2) an error-balance approach that selects the weight parameter as the minimizer of another functional involving the ECE and the data misfit. Numerical results demonstrate that the proposed methodology can successfully recover elastic parameters in 2D and 3D ASI systems from response measurements taken in either the solid or fluid subdomains. Furthermore, both regularization strategies are shown to produce accurate reconstructions when the measurement data is polluted with noise. The discrepancy principle is shown to produce nearly optimal solutions, while the error-balance approach, although not optimal, remains effective and does not need a priori information on the noise level.

  2. Inverse Material Identification in Coupled Acoustic-Structure Interaction using a Modified Error in Constitutive Equation Functional

    PubMed Central

    Warner, James E.; Diaz, Manuel I.; Aquino, Wilkins; Bonnet, Marc

    2014-01-01

    This work focuses on the identification of heterogeneous linear elastic moduli in the context of frequency-domain, coupled acoustic-structure interaction (ASI), using either solid displacement or fluid pressure measurement data. The approach postulates the inverse problem as an optimization problem where the solution is obtained by minimizing a modified error in constitutive equation (MECE) functional. The latter measures the discrepancy in the constitutive equations that connect kinematically admissible strains and dynamically admissible stresses, while incorporating the measurement data as additional quadratic error terms. We demonstrate two strategies for selecting the MECE weighting coefficient to produce regularized solutions to the ill-posed identification problem: 1) the discrepancy principle of Morozov, and 2) an error-balance approach that selects the weight parameter as the minimizer of another functional involving the ECE and the data misfit. Numerical results demonstrate that the proposed methodology can successfully recover elastic parameters in 2D and 3D ASI systems from response measurements taken in either the solid or fluid subdomains. Furthermore, both regularization strategies are shown to produce accurate reconstructions when the measurement data is polluted with noise. The discrepancy principle is shown to produce nearly optimal solutions, while the error-balance approach, although not optimal, remains effective and does not need a priori information on the noise level. PMID:25339790

  3. Structure of the Ninetyeast Ridge North of the Equator, Eastern Indian Ocean.

    NASA Astrophysics Data System (ADS)

    Gopala Rao, D.; Sreekrishna, K.; Levchenko, O.; W. Sager, W.; Paul, C.

    2008-12-01

    The Ninetyeast Ridge in the eastern Indian Ocean is an aseismic volcanic ridge that marks the Keruguelen hotspot trace between 35°S and 17°N, depicting significant changes in morphology and crust/lithosphere structure. Age progression, younger ages in the south to older ages, 90 Ma (anomaly 34) in the north of the ridge has been reported from linear magnetic anomalies adjoining the ridge and rocks drilled from it during the DSDP/ODP cruises. The bathymetric expression of it is visible up to Lat. 10°N but seismic reflection data indicate its buried anticlinal shape beneath the Bengal Fan, extending up to about Lat.17°N. Gravity anomalies are strongly positive over the exposed segment of the ridge but are subdued over the buried portion. A prominent break in the continuity of the Sunda-trench gravity low reflects that the ridge impinges upon the island arc and seismic reflection data indicate that the ridge approaches close to the trench. The crest of the ridge consists of numerous peaks and sediment filled basins. The sediments are likely to be volcnoclastic and/or shallow water carbonates depending upon submarine to sub- aerial conditions of the parts of the ridge overlain by hemi-pelagic to turbidites of varied thickness. Seismic sequences of the sediments are < 2 km, < 6 km and > 6 km over the ridge, along the eastern flank and on the western flank respectively. The velocity structure of the sedimentary sequences, from top to bottom, consists of 1.6 to 1.9, 2.4 to 2.7, 3.2 to 3.4, 4.5 to 4,6 and 5.2 to 5.7 km/s layers along the western flank, 1.7 to 2.0, 2.3 to 3.2 and 4.6 to 5.7 km/s of Quaternary, pre-Miocene and pre-Paleocene respectively over the crest of the ridge and 2.3, 2.9 and 4.8 km/s velocity along the eastern flank of the ridge underlain by 6.4 km/s velocity oceanic layer 2. Tight folds and closely spaced faults (normal and reverse), some of them extending to the basement and deforming the crust of the ridge, have been imaged seismically. The en

  4. The evidence-based practice readiness survey: a structural equation modeling approach for a Greek sample.

    PubMed

    Patelarou, Athina E; Dafermos, Vasilis; Brokalaki, Hero; Melas, Christos D; Koukia, Evmorfia

    2015-06-01

    The present study reports on the translation, cultural adaptation and validation of the Evidence-Based Practice Readiness Survey into the Greek language. Back-translation strategy for cross-cultural research was used to translate the questionnaire into Greek. The psychometric measurements that were performed included: reliability coefficients and explanatory factor analysis using a Varimax Rotation and Principal Components Method. In a further step, confirmatory analysis of the principal components was conducted. The internal consistency of the Greek Evidence-Based Practice Readiness Survey version, as assessed by the Cronbach's alpha coefficient, showed satisfactory results. The value for alpha was found equal to 0.85. The explanatory and confirmatory factor analysis demonstrated a four-factor structure of the tool. PMID:26057651

  5. Brain structure and cognitive correlates of body mass index in healthy older adults

    PubMed Central

    Bolzenius, Jacob D.; Laidlaw, David H.; Cabeen, Ryan P.; Conturo, Thomas E.; McMichael, Amanda R.; Lane, Elizabeth M.; Heaps, Jodi M.; Salminen, Lauren E.; Baker, Laurie M.; Scott, Staci E.; Cooley, Sarah A.; Gunstad, John; Paul, Robert H.

    2014-01-01

    Obesity, commonly measured with body mass index (BMI), is associated with numerous deleterious health conditions including alterations in brain integrity related to advanced age. Prior research has suggested that white matter integrity observed using diffusion tensor imaging (DTI) is altered in relation to high BMI, but the integrity of specific white matter tracts remains poorly understood. Additionally, no studies have examined white matter tract integrity in conjunction with neuropsychological evaluation associated with BMI among older adults. The present study examined white matter tract integrity using DTI and cognitive performance associated with BMI in 62 healthy older adults (20 males, 42 females) aged 51 to 81. Results revealed that elevated BMI was associated with lower fractional anisotropy (FA) in the uncinate fasciculus, though there was no evidence of an age by BMI interaction relating to FA in this tract. No relationships were observed between BMI and other white matter tracts or cognition after controlling for demographic variables. Findings suggest that elevated BMI is associated with lower structural integrity in a brain region connecting frontal and temporal lobes and this alteration precedes cognitive dysfunction. Future studies should examine biological mechanisms that mediate the relationships between BMI and white matter tract integrity, as well as the evolution of these abnormalities utilizing longitudinal designs. PMID:25448431

  6. Brain structure and cognitive correlates of body mass index in healthy older adults.

    PubMed

    Bolzenius, Jacob D; Laidlaw, David H; Cabeen, Ryan P; Conturo, Thomas E; McMichael, Amanda R; Lane, Elizabeth M; Heaps, Jodi M; Salminen, Lauren E; Baker, Laurie M; Scott, Staci E; Cooley, Sarah A; Gunstad, John; Paul, Robert H

    2015-02-01

    Obesity, commonly measured with body mass index (BMI), is associated with numerous deleterious health conditions including alterations in brain integrity related to advanced age. Prior research has suggested that white matter integrity observed using diffusion tensor imaging (DTI) is altered in relation to high BMI, but the integrity of specific white matter tracts remains poorly understood. Additionally, no studies have examined white matter tract integrity in conjunction with neuropsychological evaluation associated with BMI among older adults. The present study examined white matter tract integrity using DTI and cognitive performance associated with BMI in 62 healthy older adults (20 males, 42 females) aged 51-81. Results revealed that elevated BMI was associated with lower fractional anisotropy (FA) in the uncinate fasciculus, though there was no evidence of an age by BMI interaction relating to FA in this tract. No relationships were observed between BMI and other white matter tracts or cognition after controlling for demographic variables. Findings suggest that elevated BMI is associated with lower structural integrity in a brain region connecting frontal and temporal lobes and this alteration precedes cognitive dysfunction. Future studies should examine biological mechanisms that mediate the relationships between BMI and white matter tract integrity, as well as the evolution of these abnormalities utilizing longitudinal designs. PMID:25448431

  7. The Relationships between Individualism, Nationalism, Ethnocentrism, and Authoritarianism in Flanders: A Continuous Time-Structural Equation Modeling Approach.

    PubMed

    Angraini, Yenni; Toharudin, Toni; Folmer, Henk; Oud, Johan H L

    2014-01-01

    This article analyzes the relationships among nationalism (N), individualism (I), ethnocentrism (E), and authoritarianism (A) in continuous time (CT), estimated as a structural equation model. The analysis is based on the General Election Study for Flanders, Belgium, for 1991, 1995, and 1999. We find reciprocal effects between A and E and between E and I as well as a unidirectional effect from A on I. We furthermore find relatively small, but significant, effects from both I and E on N but no effect from A on N or from N on any of the other variables. Because of its central role in the N-I-E-A complex, mitigation of authoritarianism has the largest potential to reduce the spread of nationalism, ethnocentrism, and racism in Flanders. PMID:26745672

  8. Periodic structures in the Franck-Hertz experiment with neon: Boltzmann equation and Monte-Carlo analysis

    NASA Astrophysics Data System (ADS)

    White, R. D.; Robson, R. E.; Nicoletopoulos, P.; Dujko, S.

    2012-05-01

    The Franck-Hertz experiment with neon gas is modelled as an idealised steady-state Townsend experiment and analysed theoretically using (a) multi-term solution of Boltzmann equation and (b) Monte-Carlo simulation. Theoretical electron periodic electron structures, together with the `window' of reduced fields in which they occur, are compared with experiment, and it is explained why it is necessary to account for all competing scattering processes in order to explain the observed experimental `wavelength'. The study highlights the fundamental flaws in trying to explain the observations in terms of a single, assumed dominant electronic excitation process, as is the case in text books and the myriad of misleading web sites.

  9. Structural parameters of glycine zwitterion hydration from the data of the integral equation method in the RISM approach

    NASA Astrophysics Data System (ADS)

    Fedotova, M. V.; Kruchinin, S. E.

    2012-12-01

    The structural parameters of glycine zwitterion in water were studied by means of the integral equation method in the framework of the RISM approximation. According to calculations, five water molecules are located in the nearest environment of the -NH{3/+} group, and two of them are the H-bonded with this group. At the same time, six water molecules are located in the nearest environment of the -COO- group, and three of them are the H-bonded with this group. The average number of water molecules in the first hydration shell of -CH2 group is four. It has been shown that the probability of hydrogen bond formation between water molecules and the hydrogen atom H1 of the -NH{3/+} group is low, and there is no H-bonding between water molecules and the nitrogen atom the -NH{3/+} group.

  10. Making things happen: reciprocal relationships between work characteristics and personal initiative in a four-wave longitudinal structural equation model.

    PubMed

    Frese, Michael; Garst, Harry; Fay, Doris

    2007-07-01

    The authors used the frameworks of reciprocal determinism and occupational socialization to study the effects of work characteristics (consisting of control and complexity of work) on personal initiative (PI)--mediated by control orientation (a 2nd-order factor consisting of control aspiration, perceived opportunity for control, and self-efficacy) and the reciprocal effects of PI on changes in work characteristics. They applied structural equation modeling to a longitudinal study with 4 measurement waves (N = 268) in a transitional economy: East Germany. Results confirm the model plus 1 additional, nonhypothesized effect. Work characteristics had a synchronous effect on PI via control orientation (full mediation). There were also effects of control orientation and of PI on later changes in work characteristics: As predicted, PI functioned as partial mediator, changing work characteristics in the long term (reciprocal effect); unexpectedly, there was a 2nd reciprocal effect of an additional lagged partial mediation of control orientation on later work characteristics. PMID:17638467

  11. A multilevel structural equation modeling analysis of vulnerabilities and resilience resources influencing affective adaptation to chronic pain.

    PubMed

    Sturgeon, John A; Zautra, Alex J; Arewasikporn, Anne

    2014-02-01

    The processes of individual adaptation to chronic pain are complex and occur across multiple domains. We examined the social, cognitive, and affective context of daily pain adaptation in individuals with fibromyalgia and osteoarthritis. By using a sample of 260 women with fibromyalgia or osteoarthritis, we examined the contributions of pain catastrophizing, negative interpersonal events, and positive interpersonal events to daily negative and positive affect across 30days of daily diary data. Individual differences and daily fluctuations in predictor variables were estimated simultaneously by utilizing multilevel structural equation modeling techniques. The relationships between pain and negative and positive affect were mediated by stable and day-to-day levels of pain catastrophizing as well as day-to-day positive interpersonal events, but not negative interpersonal events. There were significant and independent contributions of pain catastrophizing and positive interpersonal events to adaptation to pain and pain-related affective dysregulation. These effects occur both between persons and within a person's everyday life. PMID:24120460

  12. Using bifactor exploratory structural equation modeling to examine global and specific factors in measures of sports coaches' interpersonal styles.

    PubMed

    Stenling, Andreas; Ivarsson, Andreas; Hassmén, Peter; Lindwall, Magnus

    2015-01-01

    In the present work we investigated distinct sources of construct-relevant psychometric multidimensionality in two sport-specific measures of coaches' need-supportive (ISS-C) and controlling interpersonal (CCBS) styles. A recently proposed bifactor exploratory structural equation modeling (ESEM) framework was employed to achieve this aim. In Study 1, using a sample of floorball players, the results indicated that the ISS-C can be considered as a unidimensional measure, with one global factor explaining most of the variance in the items. In Study 2, using a sample of male ice hockey players, the results indicated that the items in the CCBS are represented by both a general factor and specific factors, but the subscales differ with regard to the amount of variance in the items accounted for by the general and specific factors. These results add further insight into the psychometric properties of these two measures and the dimensionality of these two constructs. PMID:26388808

  13. Using bifactor exploratory structural equation modeling to examine global and specific factors in measures of sports coaches' interpersonal styles

    PubMed Central

    Stenling, Andreas; Ivarsson, Andreas; Hassmén, Peter; Lindwall, Magnus

    2015-01-01

    In the present work we investigated distinct sources of construct-relevant psychometric multidimensionality in two sport-specific measures of coaches' need-supportive (ISS-C) and controlling interpersonal (CCBS) styles. A recently proposed bifactor exploratory structural equation modeling (ESEM) framework was employed to achieve this aim. In Study 1, using a sample of floorball players, the results indicated that the ISS-C can be considered as a unidimensional measure, with one global factor explaining most of the variance in the items. In Study 2, using a sample of male ice hockey players, the results indicated that the items in the CCBS are represented by both a general factor and specific factors, but the subscales differ with regard to the amount of variance in the items accounted for by the general and specific factors. These results add further insight into the psychometric properties of these two measures and the dimensionality of these two constructs. PMID:26388808

  14. Effect of isomeric structures of branched cyclic hydrocarbons on densities and equation of state predictions at elevated temperatures and pressures.

    PubMed

    Wu, Yue; Bamgbade, Babatunde A; Burgess, Ward A; Tapriyal, Deepak; Baled, Hseen O; Enick, Robert M; McHugh, Mark A

    2013-07-25

    The cis and trans conformation of a branched cyclic hydrocarbon affects the packing and, hence, the density, exhibited by that compound. Reported here are density data for branched cyclohexane (C6) compounds including methylcyclohexane, ethylcyclohexane (ethylcC6), cis-1,2-dimethylcyclohexane (cis-1,2), cis-1,4-dimethylcyclohexane (cis-1,4), and trans-1,4-dimethylcyclohexane (trans-1,4) determined at temperatures up to 525 K and pressures up to 275 MPa. Of the four branched C6 isomers, cis-1,2 exhibits the largest densities and the smallest densities are exhibited by trans-1,4. The densities are modeled with the Peng-Robinson (PR) equation of state (EoS), the high-temperature, high-pressure, volume-translated (HTHP VT) PREoS, and the perturbed chain, statistical associating fluid theory (PC-SAFT) EoS. Model calculations highlight the capability of these equations to account for the different densities observed for the four isomers investigated in this study. The HTHP VT-PREoS provides modest improvements over the PREoS, but neither cubic EoS is capable of accounting for the effect of isomer structural differences on the observed densities. The PC-SAFT EoS, with pure component parameters from the literature or from a group contribution method, provides improved density predictions relative to those obtained with the PREoS or HTHP VT-PREoS. However, the PC-SAFT EoS, with either set of parameters, also cannot fully account for the effect of the C6 isomer structure on the resultant density. PMID:23815675

  15. Effect of Isomeric Structures of Branched Cyclic Hydrocarbons on Densities and Equation of State Predictions at Elevated Temperatures and Pressures

    SciTech Connect

    Wu, Yue; Bamgbade, Babatunde A; Burgess, Ward A; Tapriyal, Deepak; Baled, Hseen O; Enick, Robert M; McHugh, Mark

    2013-07-25

    The cis and trans conformation of a branched cyclic hydrocarbon affects the packing and, hence, the density, exhibited by that compound. Reported here are density data for branched cyclohexane (C6) compounds including methylcyclohexane, ethylcyclohexane (ethylcC6), cis-1,2-dimethylcyclohexane (cis-1,2), cis-1,4-dimethylcyclohexane (cis-1,4), and trans-1,4-dimethylcyclohexane (trans-1,4) determined at temperatures up to 525 K and pressures up to 275 MPa. Of the four branched C6 isomers, cis-1,2 exhibits the largest densities and the smallest densities are exhibited by trans-1,4. The densities are modeled with the Peng–Robinson (PR) equation of state (EoS), the high-temperature, high-pressure, volume-translated (HTHP VT) PREoS, and the perturbed chain, statistical associating fluid theory (PC-SAFT) EoS. Model calculations highlight the capability of these equations to account for the different densities observed for the four isomers investigated in this study. The HTHP VT-PREoS provides modest improvements over the PREoS, but neither cubic EoS is capable of accounting for the effect of isomer structural differences on the observed densities. The PC-SAFT EoS, with pure component parameters from the literature or from a group contribution method, provides improved density predictions relative to those obtained with the PREoS or HTHP VT-PREoS. However, the PC-SAFT EoS, with either set of parameters, also cannot fully account for the effect of the C6 isomer structure on the resultant density.

  16. High-resolution protein structure determination starting with a global fold calculated from exact solutions to the RDC equations.

    PubMed

    Zeng, Jianyang; Boyles, Jeffrey; Tripathy, Chittaranjan; Wang, Lincong; Yan, Anthony; Zhou, Pei; Donald, Bruce Randall

    2009-11-01

    We present a novel structure determination approach that exploits the global orientational restraints from RDCs to resolve ambiguous NOE assignments. Unlike traditional approaches that bootstrap the initial fold from ambiguous NOE assignments, we start by using RDCs to compute accurate secondary structure element (SSE) backbones at the beginning of structure calculation. Our structure determination package, called RDC-PANDA: (RDC-based SSE PAcking with NOEs for Structure Determination and NOE Assignment), consists of three modules: (1) RDC-EXACT: ; (2) PACKER: ; and (3) HANA: (HAusdorff-based NOE Assignment). RDC-EXACT: computes the global optimal solution of backbone dihedral angles for each secondary structure element by exactly solving a system of quartic RDC equations derived by Wang and Donald (Proceedings of the IEEE computational systems bioinformatics conference (CSB), Stanford, CA, 2004a; J Biomol NMR 29(3):223-242, 2004b), and systematically searching over the roots, each of which is a backbone dihedral varphi- or psi-angle consistent with the RDC data. Using a small number of unambiguous inter-SSE NOEs extracted using only chemical shift information, PACKER: performs a systematic search for the core structure, including all SSE backbone conformations. HANA: uses a Hausdorff-based scoring function to measure the similarity between the experimental spectra and the back-computed NOE pattern for each side-chain from a statistically-diverse rotamer library, and drives the selection of optimal position-specific rotamers for filtering ambiguous NOE assignments. Finally, a local minimization approach is used to compute the loops and refine side-chain conformations by fixing the core structure as a rigid body while allowing movement of loops and side-chains. RDC-PANDA: was applied to NMR data for the FF Domain 2 of human transcription elongation factor CA150 (RNA polymerase II C-terminal domain interacting protein), human ubiquitin, the ubiquitin-binding zinc

  17. The Literacy Equation: Competence = Capability? National Conference of the Australian Council for Adult Literacy Conference Papers (Queensland, Australia, November 7-9, 1996).

    ERIC Educational Resources Information Center

    Queensland Council for Adult Literacy, Red Hill (Australia).

    Papers from the 19th Adult Literacy Conference convened by the Australian Council for Adult Literacy include: "A Little to the Right on Writing" (Brendan Bartlett, Margaret Fletcher); "Deconstructing the 'Australian Language and Literacy Policy'" (Helen Beazley); "Comparing Content-Centered and Learner-Centered Approaches in School Mathematics:…

  18. Cognitive ability, acquiescence, and the structure of personality in a sample of older adults.

    PubMed

    Lechner, Clemens M; Rammstedt, Beatrice

    2015-12-01

    Acquiescence, or the tendency to respond to descriptions of conceptually distinct personality attributes with agreement/affirmation, constitutes a major challenge in personality assessment. The aim of this study was to shed light on cognitive ability as a potential source of individual differences in acquiescent responding. We hypothesized that respondents with lower cognitive ability exhibit stronger acquiescent response tendencies than respondents with higher cognitive ability and that this leads to problems in establishing the Big Five structure by means of principal component analyses (exploratory factor analysis was not applicable to these data) in the former group. Further, we hypothesized that after controlling for acquiescence by using mean-corrected instead of raw item scores, the Big Five structure holds even among respondents with lower cognitive ability. Analyses in a sample of 1,071 German adults aged 56 to 75 years using the Digit Symbol Substitution Test as a measure of cognitive ability and the BFI-10, a 10-item abbreviated version of the Big Five Inventory, as a measure of personality, corroborated these hypotheses. These findings suggest that lower cognitive ability and age-related declines in cognitive functioning more specifically are associated with higher acquiescence, which in turn leads to problems in establishing the Big Five structure among individuals with lower cognitive ability that should be addressed by controlling for acquiescence. PMID:26011482

  19. Evidence of Left Inferior Frontal–Premotor Structural and Functional Connectivity Deficits in Adults Who Stutter

    PubMed Central

    Horwitz, Barry; Ostuni, John; Reynolds, Richard; Ludlow, Christy L.

    2011-01-01

    The neurophysiological basis for stuttering may involve deficits that affect dynamic interactions among neural structures supporting fluid speech processing. Here, we examined functional and structural connectivity within corticocortical and thalamocortical loops in adults who stutter. For functional connectivity, we placed seeds in the left and right inferior frontal Brodmann area 44 (BA44) and in the ventral lateral nucleus (VLN) of the thalamus. Subject-specific seeds were based on peak activation voxels captured during speech and nonspeech tasks using functional magnetic resonance imaging. Psychophysiological interaction (PPI) was used to find brain regions with heightened functional connectivity with these cortical and subcortical seeds during speech and nonspeech tasks. Probabilistic tractography was used to track white matter tracts in each hemisphere using the same seeds. Both PPI and tractrography supported connectivity deficits between the left BA44 and the left premotor regions, while connectivity among homologous right hemisphere structures was significantly increased in the stuttering group. No functional connectivity differences between BA44 and auditory regions were found between groups. The functional connectivity results derived from the VLN seeds were less definitive and were not supported by the tractography results. Our data provide strongest support for deficient left hemisphere inferior frontal to premotor connectivity as a neural correlate of stuttering. PMID:21471556

  20. Predictive Validity of the American College of Cardiology/American Heart Association Pooled Cohort Equations in Predicting All-Cause and Cardiovascular Disease-Specific Mortality in a National Prospective Cohort Study of Adults in the United States.

    PubMed

    Loprinzi, Paul D; Addoh, Ovuokerie

    2016-06-01

    The predictive validity of the Pooled Cohort risk (PCR) equations for cardiovascular disease (CVD)-specific and all-cause mortality among a national sample of US adults has yet to be evaluated, which was this study's purpose. Data from the 1999-2010 National Health and Nutrition Examination Survey were used, with participants followed up through December 31, 2011, to ascertain mortality status via the National Death Index probabilistic algorithm. The analyzed sample included 11,171 CVD-free adults (40-79 years of age). The 10-year risk of a first atherosclerotic cardiovascular disease (ASCVD) event was determined from the PCR equations. For the entire sample encompassing 849,202 person-months, we found an incidence rate of 1.00 (95% CI, 0.93-1.07) all-cause deaths per 1000 person-months and an incidence rate of 0.15 (95% CI, 0.12-0.17) CVD-specific deaths per 1000 person-months. The unweighted median follow-up duration was 72 months. For nearly all analyses (unadjusted and adjusted models with ASCVD expressed as a continuous variable as well as dichotomized at 7.5% and 20%), the ASCVD risk score was significantly associated with all-cause and CVD-specific mortality (P<.05). In the adjusted model, the increased all-cause mortality risk ranged from 47% to 77% based on an ASCVD risk of 20% or higher and 7.5% or higher, respectively. Those with an ASCVD score of 7.5% or higher had a 3-fold increased risk of CVD-specific mortality. The 10-year predicted risk of a first ASCVD event via the PCR equations was associated with all-cause and CVD-specific mortality among those free of CVD at baseline. In this American adult sample, the PCR equations provide evidence of predictive validity. PMID:27180122