A Model and Questionnaire of Language Identity in Iran: A Structural Equation Modelling Approach
ERIC Educational Resources Information Center
Khatib, Mohammad; Rezaei, Saeed
2013-01-01
This study consisted of three main phases including the development of a hypothesised model of language identity in Iran, developing and validating a questionnaire based on this model and finally testing the model based on the questionnaire data. In the first phase of this research, a hypothesised model of language identity in Iran was developed…
Paper to Electronic Questionnaires: Effects on Structured Questionnaire Forms
NASA Technical Reports Server (NTRS)
Trujillo, Anna C.
2009-01-01
With the use of computers, paper questionnaires are being replaced by electronic questionnaires. The formats of traditional paper questionnaires have been found to effect a subject's rating. Consequently, the transition from paper to electronic format can subtly change results. The research presented begins to determine how electronic questionnaire formats change subjective ratings. For formats where subjects used a flow chart to arrive at their rating, starting at the worst and middle ratings of the flow charts were the most accurate but subjects took slightly more time to arrive at their answers. Except for the electronic paper format, starting at the worst rating was the most preferred. The paper and electronic paper versions had the worst accuracy. Therefore, for flowchart type of questionnaires, flowcharts should start at the worst rating and work their way up to better ratings.
ERIC Educational Resources Information Center
Waller, Niels G.; And Others
1991-01-01
The structural and external validity of the Tridimensional Personality Questionnaire (TPQ) and the relations among TPQ lower-order and higher-order scales and those of the Multidimensional Personality Questionnaire were examined. Results for 1,236 adults support the TPQ's validity but indicate its failure to operationalize portions of the…
Selective Mutism Questionnaire: Measurement Structure and Validity
ERIC Educational Resources Information Center
Letamendi, Andrea M.; Chavira, Denise A.; Hitchcock, Carla A.; Roesch, Scott C.; Shipon-Blum, Elisa; Stein, Murray B.
2008-01-01
The psychometric properties of the Selective Mutism Questionnaire (SMQ) are evaluated using a clinical sample of children with selective mutism (SM). The study shows that SMQ is useful in determining the severity of a child's nonspeaking behaviors, the scope of these behaviors and necessary follow up assessment.
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…
The Structure and Validity of the Multidimensional Social Support Questionnaire
ERIC Educational Resources Information Center
Hardesty, Patrick H.; Richardson, George B.
2012-01-01
The factor structure and concurrent validity of the Multidimensional Social Support Questionnaire, a brief measure of perceived social support for use with adolescents, was examined. Findings suggest that four dimensions of perceived social support may yield more information than assessments of the unitary construct of support. (Contains 8 tables…
A Structural Examination of the Learning Experiences Questionnaire
ERIC Educational Resources Information Center
Tokar, David M.; Buchanan, Taneisha S.; Subich, Linda M.; Hall, Rosalie J.; Williams, Christine M.
2012-01-01
The underlying factor structure of the Learning Experiences Questionnaire (LEQ; Schaub, 2004) was examined using data from 742 male and female college-age respondents. The LEQ items reflect a variety of learning experiences (generated based on Bandura's (1986, 1997) four sources of self-efficacy perceptions) that might occur in each of Holland's…
The Bilevel Structure of the Outcome Questionnaire-45
ERIC Educational Resources Information Center
Bludworth, Jamie L.; Tracey, Terence J. G.; Glidden-Tracey, Cynthia
2010-01-01
The structure of the Outcome Questionnaire-45 (Lambert et al., 2001) was examined in a sample of 1,100 university counseling center clients using confirmatory factor analysis. Specifically, the relative fit of 1-factor, 3-factor orthogonal, 3-factor oblique, 4-factor hierarchical, and 4-factor bilevel models were examined. Although the 3-factor…
Structural Equation Model Trees
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
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…
Equational Sentence Structure in Eskimo.
ERIC Educational Resources Information Center
Hofmann, Th. R.
A comparison of the syntactic characteristics of mathematical equations and Eskimo syntax is made, and a proposal that Eskimo has a level of structure similar to that of equations is described. P:t performative contrast is reanalyzed. Questions and speculations on the formal treatment of this type of structure in transformational grammar, and its…
A structural equation model of residents’ attitudes for tourism development
Dong-Wan Ko; William P. Stewart
2002-01-01
This study tests the structural equation model between residents’ perceived tourism impacts and attitudes toward host community. The model consisted of five latent constructs and nine path hypotheses and is based upon 732 mailback questionnaires returned by residents of Cheju Island, Korea, a major domestic tourism destination. It was found that residents’ ‘community satisfaction’ was closely related to ‘perceived positive’
ERIC Educational Resources Information Center
Cui, Lixia; Lin, Wenwen; Oei, Tian P. S.
2011-01-01
This study investigated cross-cultural differences in the factor structure and psychometric properties of the Young Schema Questionnaire (short form; YSQ-SF). The participants were 712 Chinese undergraduate students. The total sample was randomly divided into two sub-samples. Exploratory Factor Analysis (EFA) was conducted on questionnaire results…
Factors contributing to posttraumatic growth: a proposed structural equation model.
Cadell, Susan; Regehr, Cheryl; Hemsworth, David
2003-07-01
With the current shift to include positive outcomes of trauma, this research was designed to explore factors that allow growth to occur. Structural equation modeling was used to test a model for understanding posttraumatic growth. A sample (N = 174) of bereaved HIV/AIDS caregivers completed questionnaires. Spirituality, social support, and stressors were found to have a positive relationship with growth. Facilitation of posttraumatic growth is crucial to all helping professions. PMID:12921208
ERIC Educational Resources Information Center
Sun, Huaping; Hernandez, Diley
2012-01-01
This study investigates the structural invariance of the Achievement Goal Questionnaire (AGQ) in American, Chinese, and Dutch college students. Using confirmatory factor analyses (CFA), the authors found evidence for the four-factor structure of achievement goals in all three samples. Subsequent multigroup CFAs supported structural invariance of…
Structural Analysis of the Resident Assistant Cultural Diversity Questionnaire
ERIC Educational Resources Information Center
Johnson, Vanessa D.; Kang, Young-Shin; Thompson, George F.
2011-01-01
This study investigated the five-factor structure of the Resident Assistant Cultural Diversity (RACD) instrument, which assesses resident assistant (RA) confidence in addressing issues of cultural diversity in college and university residence halls. The instrument has five components that explore RA confidence: (1) belief in the need for cultural…
Equations relating structure functions of all orders
Hill, R J
2001-01-01
The hierarchy of exact equations are given that relate two-spatial-point velocity structure functions of arbitrary order with other statistics. Because no assumption is used, the exact statistical equations can apply to any flow for which the Navier-Stokes equations are accurate and no matter how small the number of samples in the ensemble. The exact statistical equations can be used to verify DNS computations and to detect their limitations because if DNS data are used to evaluate the exact statistical equations, then the equations should balance to within numerical precision, otherwise a computational problem is indicated. The equations allow quantification of the approach to local homogeneity and to local isotropy. Testing the balance of the equations allows detection of scaling ranges for quantification of inertial-range exponents. The second-order equations lead to Kolmogorov's equation. All higher-order equations contain a statistic composed of one factor of the two-point difference of the pressure grad...
ERIC Educational Resources Information Center
Alkherainej, Khaled
2012-01-01
The factor structure and agreement among commonly used questionnaires for identifying children at risk for developmental disability and autism spectrum disorders between the ages of 36 and 66 months were studied. The Age and Stages Questionnaires (ASQ), the Ages and Stages Questionnaire: Social Emotional (ASQ: SE), and the Social Communication…
Factor Structure of the Children's Behavior Questionnaire in Children with Williams Syndrome
ERIC Educational Resources Information Center
Leyfer, Ovsanna; John, Angela E.; Woodruff-Borden, Janet; Mervis, Carolyn B.
2012-01-01
To examine the factor structure of temperament in 5-10-year-olds with Williams syndrome, an exploratory factor analysis was conducted on the responses of parents of 192 children on the children's behavior questionnaire. Four factors were identified. Two corresponded to factors reported for typically developing children: effortful control and…
Temperament Factor Structure in Fragile X Syndrome: The Children's Behavior Questionnaire
Roberts, Jane E.; Tonnsen, Bridgette L.; Robinson, Marissa; McQuillin, Samuel D.; Hatton, Deborah D.
2014-01-01
Early patterns of temperament lay the foundation for a variety of developmental constructs such as self-regulation, psychopathology, and resilience. Children with fragile X syndrome (FXS) display unique patterns of temperament compared to age-matched clinical and non-clinical samples, and early patterns of temperament have been associated with later anxiety in this population. Despite these unique patterns in FXS and recent reports of atypical factor structure of temperament questionnaires in Williams Syndrome (Leyfer, John, Woodruff-Borden, & Mervis, 2012), no studies have examined the latent factor structure of temperament scales in FXS to ensure measurement validity in this sample. The present study used confirmatory factor analysis to examine the factor structure of a well-validated parent-reported temperament questionnaire, the Children's Behavior Questionnaire (Rothbart, Ahadi, Hershey, & Fisher, 2001), in a sample of 90 males with FXS ages 3-9 years. Our data produced a similar, but not identical, three-factor model that retained the original CBQ factors of negative affectivity, effortful control, and extraversion/surgency. In particular, our FXS sample demonstrated stronger factor loadings for fear and shyness than previously reported loadings in non-clinical samples, consistent with reports of poor social approach and elevated anxiety in this population. Although the original factor structure of the Children's Behavior Questionnaire is largely retained in children with FXS, differences in factor loading magnitudes may reflect phenotypic characteristics of the syndrome. These findings may inform future developmental and translational research efforts. PMID:24380785
Factor Structure and Convergent Validity of the Aggression Questionnaire in an Offender Population
Tamra Y. Williams; Jenine C. Boyd; Michele A. Cascardi; Norman Poythress
1996-01-01
The study examined whether the 4-factor structure of the Aggression Questionnaire (AQ; A. Buss & M. Perry, 1992), consisting of Physical Aggression, Verbal Aggression, Hostility, and Anger, would replicate in an offender population. The AQ and Novaco's Anger Scale (NAS; R. Novaco, 1994) were administered to 200 adult offenders. The results of a confirmatory analysis suggested that the 4-factor model
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…
2009-01-01
Background Self-reported data are a common source of information about drug exposure. Modes of data collection differ considerably and the questionnaire's structure may affect prevalence estimates. We compared the recall of medication use evaluated by means of two questionnaires differing in structure and length. Methods Drug utilization was assessed by two alternative versions of a questionnaire (A – 4 pages, including specific questions for 12 indications/pharmacological groups and one question for "other medicines"; B – 1 page, including 1 open-ended question to cover overall drug consumption). Each of 32 classes in a private University in Maputo, Mozambique, was randomly assigned questionnaire A (233 participants) or B (276 participants). Logistic regression (allowing for clustering by classroom) was used to compare the two groups in terms of socio-demographic characteristics and medication used during the previous month. Results Overall, 67.4% of the subjects had used at least one drug during the previous month. The following prevalences were greater among participants completing questionnaire A: use of drugs from two or more pharmacological groups (60.5% vs. 34.4%, p < 0.001), use of two or more drugs (66.2% vs. 43.0%, p < 0.001), and use of antibiotics (14.6% vs. 6.9%, p = 0.001), antifungals (9.4% vs. 4.0%, p = 0.013), antiparasitics (5.6% vs. 1.8%, p = 0.031) and antacids (8.6% vs. 3.6%, p = 0.024). Information about duration of treatment and medical advice was more complete with version A. Conclusion The indication/drug-specific questions (questionnaire A) revealed a significantly higher prevalence of use of medicines – antibiotics, antifungals, antiparasitics and antacids – without compromising the completeness of the information. PMID:19563651
Assessment of structured physical examination skills training using a retro-pre-questionnaire
2013-01-01
Purpose: The effectiveness of physical examination skills (PES) training is very rarely assessed using the “post-then-pre” approach. In this study, a retro-pre-questionnaire was used to study the effect of structured physical examination skills training (SPEST) imparted to second-year undergraduate medical students. Methods: KIST Medical College (KISTMC) affiliated to Tribhuvan University Nepal admitted its first batch of MBBS students in November 2008. The university curriculum recommends the involvement of Medicine and Surgery Departments in PES training, but the methods for teaching and assessment are not well defined. KISTMC has made training more structured and involved the Medicine, Surgery, Gynaecology and Obstetrics, Orthopaedics, ENT, Ophthalmology, Paediatrics, and Family Medicine Departments. SPEST includes the teaching/learning of basic PES for 210 minutes once a week for 28 weeks. Self-assessment is done by using a retro-pre-questionnaire at the end of the last session of training, and these data are analysed using SPSS. Results: Out of 100 students, 98 participated in the objective structured clinical examination (OSCE); 82 completed the retro-pre-questionnaire. Forty-six skills representing various systems were selected for inclusion in the retro-pre-questionnaire from among the many skills taught in different departments. The average perceived skills score (maximum score, 46×4=184) before training was 15.9 and increased to 116.5 after training. The increase was statistically significant upon the application of a paired t-test. Conclusion: The students perceived that their level of skills improved after the training. The retro-pre- instrument seems to be useful for assessing the learners’ self-reported changes in PES after training if a large number of skills need to be assessed. However, it should be noted that although a retro-pre-questionnaire may reveal valuable information, it is not a substitute for an objective measure or gold standard. PMID:24498473
Barnacle Equivalence Structure in Relativistic Wave Equations
M. A. K. Khalil
1978-01-01
Relativistic wave equations for spin s particles (-i beta \\\\cdot partial + m) psi = 0 transforming under a representation Lambda mapsto T(Lambda) of SL(2, C), can have structural properties that make them physically equivalent to similar wave equations. This equivalence extends to all the standard external field interactions. There are T(Lambda)'s which cannot lead to theories different from simpler
Psychometric properties and factor structure of an L2 reading motivation questionnaire.
Kim, Hee-jung; Choi, Sunhee
2014-01-01
The purpose of this study is to investigate the psychometric properties and factor structure of a popular second language reading motivation questionnaire developed by Mori (2002). 550 first year high school students in Korea answered the 30-item questionnaire which consists of statements indicating different degrees of English reading motivation. Exploratory factor analysis was conducted with principal axis factoring and promax rotation, which yielded a four-factor solution. The factors included 'Intercultural and Intellectual Orientation', 'Reading Efficacy', 'Intrinsic Motivation', and 'Negative Attitudes'. The results supported the multidimensionality of the construct of L2 reading motivation, but could not replicate the nine factor structure which was originally proposed by Mori. The implications for further research on L2 reading motivation and development of a more valid L2 reading scale are discussed. PMID:24704649
Factor Structure of the Iranian Version of 12-Item General Health Questionnaire
Rahmati Najarkolaei, Fatemeh; Raiisi, Fatemeh; Rahnama, Parvin; Gholami Fesharaki, Mohammad; Zamani, Omid; Jafari, Mohammad Reza; Montazeri, Ali
2014-01-01
Background: The 12-Item General Health (GHQ-12) questionnaire is one of the most commonly used instruments in screening studies on mental health. Objectives: The current study aimed to examine the factor structure of the GHQ-12 questionnaire among the students in Iran. Materials and Methods: It was a cross-sectional study in which 428 university students were recruited and completed the GHQ-12. Reliability of the GHQ-12 was evaluated using the Cronbach's alpha and the split-half method by applying the Spearman-Brown coefficient. Factor structure of the questionnaire was extracted by exploratory factor analysis (EFA). Confirmatory factor analysis (CFA) was conducted to assess how well the EFA extracted model fitted the observed data. Results: The mean age of the participants was 22.83 years (SD = 3.09). Most of them were female (56.1%) and 81% were unemployed. The Cronbach’s alpha coefficient for the Iranian version of GHQ-12 was 0.85. Using the split-half method, the alpha for the social dysfunction was found to be 0.77; it was 0.76 for the psychological distress. The principal component analysis revealed a two-factor structure for the questionnaire including social dysfunction and psychological distress that explained 48% of the observed variances. The confirmatory factor analysis was showed fit for the data. Conclusions: The current study findings confirm that the Iranian version of GHQ-12 has a good factor structure and is a reliable and valid instrument to measure psychological distress and social dysfunction. PMID:25593708
Oh, Woon Yong; Lee, Ji Woong; Lee, Chong Eon; Ko, Moon Seok; Jeong, Jae Hong
2009-12-01
In this study, a structured survey questionnaire was used to determine consumers' preferences and behavior with regard to horse meat at a horse meat restaurant located in Jeju, Korea, from October 1 to December 24, 2005. The questionnaire employed in this study consisted of 20 questions designed to characterize six general attributes: horse meat sensory property, physical appearance, health condition, origin, price, and other attributes. Of the 1370 questionnaires distributed, 1126 completed questionnaires were retained based on the completeness of the answers, representing an 82.2% response rate. Two issues were investigated that might facilitate the search for ways to improve horse meat production and marketing programs in Korea. The first step was to determine certain important factors, called principal components, which enabled the researchers to understand the needs of horse meat consumers via principal component analysis. The second step was to define consumer segments with regard to their preferences for horse meat, which was accomplished via cluster analysis. The results of the current study showed that health condition, price, origin, and leanness were the most critical physical attributes affecting the preferences of horse meat consumers. Four segments of consumers, with different demands for horse meat attributes, were identified: origin-sensitive consumers, price-sensitive consumers, quality and safety-sensitive consumers, and non-specific consumers. Significant differences existed among segments of consumers in terms of age, nature of work, frequency of consumption, and general level of acceptability of horse meat. PMID:20163664
Wang, Li; Zhang, Hua; Yuan, Wei-An; Wang, Yi-Xing; Tang, Jie; Cui, Chen; Zeng, Jin; Miao, Ping; Jiang, Jian
2014-11-01
By reviewing research contents of patient-reported outcome (PRO) and discussing Chinese medicine (CM) theories related to chronic liver disease (CLD), we have followed international PRO questionnaire development specification, combined CM theories such as uniformed spirit and body, correspondence between human and the universe, yin in property and yang in function of Gan, and seven emotions, and constructed theoretical structure of PRO questionnaire of treating CLD, including four major areas as physiology, psychology, independence, and society and nature. Of them, the physiological field contained six aspects such as blood deficiency, yin deficiency, bleeding, disorder of qi movement, improper transformation and transportation of Pi-Wei, and abnormal biliary excretion. The psychological field contained two aspects: Gan-related emotions and general disease related emotions. The independence field contained two aspects: daily life and study and work. The field of society and nature contains three aspects: social relations, social environment, and natural adaptability. PMID:25566635
Evaluation of adherence to oral antiviral hepatitis B treatment using structured questionnaires
Giang, Leesa; Selinger, Christian P; Lee, Alice Unah
2012-01-01
AIM: To assess adherence rates to nucleos(t)ide analogues (NUCs) therapy in patients with chronic hepatitis B virus infection and determine factors associated with adherence. METHODS: The questionnaire study was conducted in the liver clinics at Concord Repatriation General Hospital. All patients who were currently taking one or more NUCs were asked to complete a structured, self-administered 32-item questionnaire. Adherence was measured using visual analogue scales. The patient’s treating clinician was also asked to assess their patient’s adherence via a structured questionnaire. RESULTS: A total of 80 patients completed the questionnaire. Sixty six percent of the patients (n = 49) reported optimal adherence whilst 25 (33.8%) graded their adherence to NUCs as suboptimal. Thirty four (43%) patients reported to have omitted taking their NUCs sometime in the past. Recent non-adherence was uncommon. Amongst the patients who reported skipping medications, the most common reason cited was ”forgetfulness“ (n = 27, 56.25%). Other common reasons included: ran out of medications (n = 5, 10.42%), being too busy (n = 4, 8.33%) and due to a change in daily routine (n = 5, 10.42%). Patients who reported low adherence to other prescription pills were also more likely to miss taking NUCs (P = 0.04). Patients who were under the care of a language-discordant clinician were also more likely to report suboptimal adherence to NUCs (P = 0.04). CONCLUSION: Adherence rates were much less than that expected by the physician and has potential adverse affect on long term outcome. Communication and education appear central and strategies need to be implemented to improve ongoing adherence. PMID:22400085
Structural equation model for investigating factors affecting delay in Indian construction projects
Hemanta Doloi; Anil Sawhney; K. C. Iyer
2012-01-01
The rapid growth of the Indian construction sector over the last few decades and recurring failure in on-time delivery highlight the need for a systematic analysis of the factors influencing delay. A theoretical structural equation model representing the influence of four key latent variables on project delays in the Indian construction industry has been developed. Data collected from a questionnaire
Nicholls, Elaine E.; Hill, Susan; Foster, Nadine E.
2012-01-01
Background: The Revised Illness Perceptions Questionnaire (IPQ-R) is commonly used to measure illness perceptions. We tested whether the structure of the IPQ-R was appropriate for use with primary care musculoskeletal pain patients. Methods: Confirmatory (C) and exploratory (E) factor analyses (FA) were used to test whether the structure of the IPQ-R was supported for patients with knee pain (n = 393), hand pain (n = 2113) and back pain (n = 1591). CFA was used to test whether the timeline acute/chronic, timeline cyclical, consequences, personal control, treatment control, illness coherence and emotional representation dimensions of the IPQ-R were distinct; EFA was used to explore potential structure for patients’ views on the cause of their condition. Results: Goodness-of-fit indices for the CFA were below our criteria for good model fit. Removal of six items from the model improved model fit, but our criteria for good model fit was still not achieved. An interpretable factor solution could not be determined for the causal items on the questionnaire. Conclusions: Our data show limited evidence that the seven dimensions of the IPQ-R are distinct. A clear structure for the causal items was not determined. Further work is needed to develop the IPQ-R for use with primary care musculoskeletal pain patients. PMID:22891727
Argyrides, Marios; Kkeli, Natalie; Kendeou, Panayiota
2014-06-01
The current study aimed to confirm the factor structure and reliability of the newly translated Greek version of the Sociocultural Attitudes Towards Appearance Questionnaire-3 (SATAQ-3) among 1753 Greek-Cypriot high school students. Results of the structural equation modeling indicated a very good fit with the original four-factor structure of the SATAQ-3 for both males and females. The Cronbach's alpha coefficients for the four subscales were .92 for 'Internalization-General', .82 for 'Internalization-Athlete', .94 for 'Pressure' and .88 for 'Information'. Further analyses showed no significant differences between BMI categories with respect to the Internalization-General, Internalization-Athlete and Information factors but there were significant differences on the Pressure factor. The findings of the current study support the existence of the original four-factor structure of the SATAQ-3. The validity and reliability results of the Greek version of the SATAQ-3 support its use in Greek-speaking countries or populations. PMID:24958653
Bakhla, Ajay Kumar; Verma, Vijay; Hembram, Mahesh; Praharaj, Samir Kumar; Sinha, Vinod Kumar
2013-01-01
Background: As there are no instruments to measure psychological wellness or distress in visually impaired students, we studied internal consistency and factor structure of GHQ-12 in visually impaired children. Materials and Methods: Internal consistency analysis (Cronbach's alpha and item total correlation) and exploratory factor analysis (principal component analysis) were carried out to identify factor structure of 12-item general health questionnaire (GHQ-12). Results: All items of GHQ-12 were significantly associated with each other and the Cronbach's alpha coefficient for the scale was 0.7. On analysis of principal component, three-factor solution was found that accounted for 47.92% of the total variance. The factors included, ‘general well-being’, ‘depression’ and ‘cognitive’, with Cronbach's alpha coefficients being 0.70, 0.59, and 0.34, respectively. Conclusion: Our study findings suggest GHQ-12 is a reliable with adequate internal consistency scale and multidimensional factor structure in visually impaired students. PMID:25013310
Spinhoven, Philip; Penninx, Brenda W; Hickendorff, Marian; van Hemert, Albert M; Bernstein, David P; Elzinga, Bernet M
2014-09-01
To study the psychometric properties of the Childhood Trauma Questionnaire-Short Form (CTQ-SF), we determined its dimensional structure, measurement invariance across presence of emotional disorders, the association of the CTQ-SF with an analogous interview-based measure (CTI) across presence of emotional disorders, and the incremental value of combining both instruments in determining associations with severity of psychopathology. The sample included 2,308 adults, ages 18-65, consisting of unaffected controls and chronically affected and intermittently affected persons with an emotional disorder at Time 0 (T0) or 4 years later at T4. Childhood maltreatment was measured at T0 with an interview and at T4 with the CTQ-SF. At each wave, patients were assessed for Diagnostic and Statistical Manual of Mental Disorders (4th ed., or DSM-IV; American Psychiatric Association, 1994)-based emotional disorders (Composite Interview Diagnostic Instrument) and symptom severity (Inventory of Depressive Symptomatology, Beck Anxiety Inventory, Fear Questionnaire). Besides the correlated original 5-factor solution, an indirect higher order and direct bifactorial model also showed a good fit to the data. The 5-factor solution proved to be invariant across disordered-control comparison groups. The CTQ-SF was moderately associated with the CTI, and this association was not attenuated by disorder status. The CTQ-SF was more sensitive in detecting emotional abuse and emotional neglect than the CTI. Combined CTQ-SF/CTI factor scores showed a higher association with severity of psychopathology. We conclude that although the original 5-factor model fits the data well, results of the hierarchical analyses suggest that the total CTQ scale adequately captures a broad dimension of childhood maltreatment. A 2-step measurement approach in the assessment of childhood trauma is recommended in which screening by a self-report questionnaire is followed by a (semi-)structured diagnostic interview. PMID:24773037
Structural Equation Modeling in Behavioral Research
April 27, 2012 10:00 AM - 11:00 AM + Add to Outlook Calendar Date and Time: Friday, April 27th, 10:00-11:00am, EPS/7107 Lecturer: Natalia Frishman, MD PhD Candidate Iowa State University Print This Page Structural Equation Modeling in Behavioral Research News
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.
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,…
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
Exploring the factor structure of the Food Cravings Questionnaire-Trait in Cuban adults
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
Toll, Benjamin A.; McKee, Sherry A.; Martin, Daniel J.; Jatlow, Peter; O’Malley, Stephanie S.
2008-01-01
The Medication Adherence Questionnaire (MAQ) is a scale used to evaluate adherence to medications. The present study assessed the factor structure and validity of the MAQ with cigarette smokers. A principal components analysis was conducted on MAQ scores from a sample of smokers presenting for treatment in a clinical trial of naltrexone and nicotine patch for smoking cessation (N=385). Indices of convergent and predictive validity were tested using electronic medication caps for naltrexone, nicotine patch counts, plasma drug levels of naltrexone, and treatment outcomes. The principal components analysis revealed two factors. Factor 1, labeled “unintentional nonadherence,” measured the extent to which individuals were nonadherent because they were careless or forgot to take their medications. Factor 2, labeled “purposeful nonadherence,” assessed nonadherence related to purposefully stopping medication use after feeling better or worse. Only the second factor was shown to have good convergent and predictive validity. Specifically, this factor was related to pill-taking behavior measured with electronic medication caps and drug plasma levels and nicotine patch use based on nicotine patch count data, and it was associated with smoking cessation outcome. Thus the purposeful nonadherence factor of the MAQ may be used as a brief screening tool for medication adherence with cigarette smokers seeking treatment. Information obtained with this questionnaire could be used to counsel patients regarding the importance of medication adherence. PMID:17454716
Llewellyn, Clare H; van Jaarsveld, Cornelia H M; Johnson, Laura; Carnell, Susan; Wardle, Jane
2011-10-01
The objective of this study was to develop a parent-report psychometric measure of infant appetite during the period of exclusive milk-feeding. Constructs and items for the Baby Eating Behaviour Questionnaire (BEBQ) were derived from an existing psychometric measure validated for older ages, the Children's Eating Behaviour Questionnaire, supplemented by a review of the literature on milk-feeding behaviours. Cognitive interviewing with a sample of mothers (n=10) was used to refine the questions. The factor structure of the 18-item BEBQ was assessed in infants (one per family) from the Gemini twin birth cohort (n=2402 families). Principal Component Analysis identified four distinct appetitive constructs, all of which had good internal reliability: 'enjoyment of food' (Cronbach's ?=0.81), 'food responsiveness' (?=0.79), 'slowness in eating' (?=0.76), and 'satiety responsiveness' (?=0.73). A single item assessing 'general appetite' correlated with all of the constructs. The BEBQ is the first standardised measure of infant appetite designed to characterise appetitive traits that might confer susceptibility to excess weight gain. PMID:21672566
Barron, David; Swami, Viren; Towell, Tony; Hutchinson, Gerard; Morgan, Kevin D
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
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
2013-01-01
Background The Otitis Media-6 questionnaire (OM-6) is the most frequently used instrument to measure health related quality of life in children with otitis media. The main objectives of this study are 1) to translate and cross-culturally adapt the OM-6 into Danish, and 2) to assess important psychometric properties including structural validity and interpretability of the OM-6 in a Danish population of children suffering from otitis media. Methods The OM-6 was translated and cross-culturally adapted according to international guidelines. A longitudinal validation study enrolled 491 children and their families, and the measurement properties of the OM-6 were evaluated using the Cosmin taxonomy. The properties assessed were construct and structural validity (confirmatory factor analysis) including internal consistency, reproducibility (test-retest reliability and smallest detectable change), responsiveness and interpretability. Results A total of 435 children were eligible to participate in the study. Analyses of structural validity and internal consistency indicated that parent appraisal of hearing and speech problems may be problematic. Both scales showed similarly good test-retest reliability and construct validity, were able to discriminate between diagnostic subgroups and responsive to change. Cut-off values of 16.7 and 30.0 were found to represent minimal important change for the patients. Conclusions The Danish version of the OM-6 is a reliable, valid, responsive and interpretable questionnaire to measure quality of life in children with otitis media. This study sheds light on possible weaknesses of the instrument that needs to be acknowledged in the utilization of the instrument. However, despite these issues our results support the continuing use of OM-6 as a 1-factor functional health scale with a separate global health rating. Furthermore, indications of values representing minimal important change as perceived by the respondent are presented. PMID:24257471
Grilo, Carlos M.; Henderson, Kathryn E.; Bell, Robert L.; Crosby, Ross D.
2012-01-01
Objective The Eating Disorder Examination-Questionnaire (EDE-Q) is increasingly used in studies with bariatric surgery patients although little is known about psychometric properties of this self-report measure in this clinical group. The current study evaluated the factor structure and construct validity of the EDE-Q in bariatric surgery candidates. Methods Participants were a consecutive series of 174 obese bariatric surgery candidates who completed the EDE-Q and a battery of behavioral and psychological measures. Results Confirmatory factor analysis (CFA) revealed an inadequate fit for the original EDE-Q structure but revealed a good fit for an alternative structure suggested by recent research with obese samples. CFA supported a 7-item, 3-factor structure; the three factors were interpreted as dietary restraint, shape/weight overvaluation, and body dissatisfaction. The three factors converged with other relevant collateral measures. Conclusions These factor analytic findings, which replicate recent findings from studies with diverse obese samples, demonstrated convergent validity. Implications of these findings for clinical assessment and research with bariatric surgery patients are discussed. PMID:23229951
On the evaluation of structural equation models
Richard P. Bagozzi; Youjae Yi
1988-01-01
Criteria for evaluating structural equation models with latent variables are defined, critiqued, and illustrated. An overall\\u000a program for model evaluation is proposed based upon an interpretation of converging and diverging evidence. Model assessment\\u000a is considered to be a complex process mixing statistical criteria with philosophical, historical, and theoretical elements.\\u000a Inevitably the process entails some attempt at a reconcilation between so-called
COVARIANCE STRUCTURE OF PARABOLIC STOCHASTIC PARTIAL DIFFERENTIAL EQUATIONS
Larsson, Stig
COVARIANCE STRUCTURE OF PARABOLIC STOCHASTIC PARTIAL DIFFERENTIAL EQUATIONS ANNIKA LANG, STIG LARSSON, AND CHRISTOPH SCHWAB Abstract. In this paper parabolic random partial differential equations and parabolic sto- chastic partial differential equations driven by a Wiener process are considered. A deter
Generalized Ideal Gas Equations for Structureful Universe
Shahid N. Afridi; Khalid Khan
2006-09-04
We have derived generalized ideal gas equations for a structureful universe consisting of all forms of matters. We have assumed a universe that contains superclusters. Superclusters are then made of clusters. Each cluster can be further divided into smaller ones and so on. We have derived an expression for the entropy of such a universe. Our model is rather independent of the geometry of the intermediate clusters. Our calculations are valid for a non-interacting universe within non-relativistic limits. We suggest that structure formation can reduce the expansion rate of the universe.
Williams, Matthew J; Dalgleish, Tim; Karl, Anke; Kuyken, Willem
2014-06-01
The five facet mindfulness questionnaire (FFMQ; Baer, Smith, Hopkins, Krietemeyer, & Toney, 2006) and the self-compassion scale (SCS; Neff, 2003) are widely used measures of mindfulness and self-compassion in mindfulness-based intervention research. The psychometric properties of the FFMQ and the SCS need to be independently replicated in community samples and relevant clinical samples to support their use. Our primary aim was to establish the factor structures of the FFMQ and SCS in individuals with recurrent depression in remission, since mindfulness-based cognitive therapy (MBCT) was developed as a treatment for preventing depressive relapse. In order to determine the consistency across populations, we examined the factor structures of the FFMQ and SCS in 3 samples: (1) a convenience sample of adults, (2) a sample of adults who practice meditation, and (3) a sample of adults who suffer from recurrent depression and were recruited to take part in a trial of MBCT. Confirmatory factor analyses (CFAs) showed that a 4-factor hierarchical model of the FFMQ best fits the community sample and the clinical sample but that a 5-factor hierarchical model of the FFMQ best fits the meditator sample. CFA did not endorse the SCS 6-factor hierarchical structure in any of the 3 samples. Clinicians and researchers should be aware of the psychometric properties of the FFMQ to measure mindfulness when comparing meditators and nonmeditators. Further research is needed to develop a more psychometrically robust measure of self-compassion. PMID:24490681
Gross, Georgina M; Mellin, Juliann; Silvia, Paul J; Barrantes-Vidal, Neus; Kwapil, Thomas R
2014-10-01
Schizotypy is a multidimensional construct that captures the expression of schizophrenic symptoms and impairment from subclinical levels to full-blown psychosis. The present study examined the comparability of the factor structure of 2 leading psychometric measures of schizotypy: the Wisconsin Schizotypy Scales (WSS) and the Schizotypal Personality Questionnaire (SPQ). Both the SPQ and WSS purportedly capture the multidimensional structure of schizotypy; however, whether they are measuring comparable factors has not been empirically demonstrated. This study provided support for a 2-factor model with positive and negative factors underlying the WSS; however, contrary to previous findings, the best fit for the SPQ was for a 4-factor model using confirmatory factor analysis, and a 2-factor model using exploratory factor analysis. The WSS factors were relatively distinct, whereas those underlying the SPQ showed high overlap. The WSS positive and SPQ cognitive-perceptual factors appeared to tap comparable constructs. However, the WSS negative and SPQ interpersonal factors appeared to tap somewhat different constructs based on their correlation and their patterns of associations with other schizotypy dimensions and the Five-Factor Model-suggesting that the SPQ interpersonal factor may not adequately tap negative or deficit schizotypy. Although the SPQ offers the advantage over the WSS of having a disorganization factor, it is not clear that this SPQ factor is actually distinct from positive schizotypy. Existing measures should be used with caution and new measures based on a priori theories are necessary to further understand the factor structure of schizotypy. PMID:25314229
Fournier, Jay C.; DeRubeis, Robert J.; Beck, Aaron T.
2013-01-01
Background This study examines the structure of the Personality Belief Questionnaire (PBQ), a self-report instrument designed to assess dysfunctional beliefs associated with personality pathology, as proposed by the cognitive theory of personality dysfunction. Methods The PBQ was examined using exploratory factor analysis with responses from 438 depressed outpatients, and confirmatory factor analysis with responses from 683 treatment-seeking psychiatric outpatients. All participants were assessed for personality disorder using a standard clinical interview. The validity of the resulting factor structure was assessed in the combined sample (N=1121) by examining PBQ scores for patients with and without personality disorder diagnoses. Results Exploratory and confirmatory analyses converged to indicate that the PBQ is best described by 7 empirically identified factors: 6 assess dysfunctional beliefs associated with forms of personality pathology recognized in DSM-IV. Validity analyses revealed that those diagnosed with a personality disorder evidenced a higher average score on all factors, relative to those without these disorders. Subsets of patients diagnosed with specific DSM-IV personality disorders scored higher, on average, on the factor associated with their respective diagnosis, relative to all other factors. Conclusions The pattern of results has implications for the conceptualization of personality pathology. To our knowledge, no formal diagnostic or assessment system has yet systematically incorporated the role of dysfunctional beliefs into its description of personality pathology. The identification of dysfunctional beliefs may not only aid in case conceptualization, but may provide unique targets for psychological treatment. Recommendations for future personality pathology assessment systems are provided. PMID:21910933
ERIC Educational Resources Information Center
Ang, Rebecca P.
2007-01-01
Bryant and Smith [(2001). Refining the architecture of aggression: A measurement model for the Buss-Perry Aggression Questionnaire. "Journal of Research in Personality," 35, 138-167] refined the 29-item Aggression Questionnaire and obtained a 12-item short form of the AQ that has yet to be validated with samples outside of North America and…
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…
ERIC Educational Resources Information Center
Thombs, Brett D.; Bernstein, David P.; Lobbestael, Jill; Arntz, Arnoud
2009-01-01
Objective: The 28-item Childhood Trauma Questionnaire-Short Form (CTQ-SF) has been translated into at least 10 different languages. The validity of translated versions of the CTQ-SF, however, has generally not been examined. The objective of this study was to investigate the factor structure, internal consistency reliability, and known-groups…
ERIC Educational Resources Information Center
Chiu, Chung-Yi; Jochman, Joseph; Fujikawa, Mayu; Strand, David; Cheing, Gladys; Lee, Gloria; Chan, Fong
2014-01-01
Purpose: To examine the factorial structure of the "Coping Strategy Questionnaire"-24 (CSQ-24) in a sample of Canadians with chronic musculoskeletal pain. Method: The sample included 171 workers' compensation clients (50.9% men) recruited from outpatient rehabilitation facilities in Canada. Mean age of participants was 42.45 years…
Suicidal ideation in adolescents: A structural equation modeling approach.
Choi, Jung-Hyun; Yu, Mi; Kim, Kyoung-Eun
2014-06-19
The purpose of this study is to test a model linking adolescents' experience of violence and peer support to their happiness and suicidal ideation. The participants were high school students in Seoul, and in Kyungi, and Chungnam Provinces in Korea. The Conflict Tactics Scale, School Violence Scale, Oxford Happiness Inventory, and Suicidal Ideation Questionnaire were administered to just over 1000 adolescents. The model was tested using a path analysis technique within structural equation modeling. The model fit indices suggest that the revised model is a better fit for the data than the original hypothesized model. The experience of violence had a significant negative direct effect and peer support had a significant positive direct effect on their happiness. Happiness had a significant negative effect and the experience of violence had a significant positive effect on suicidal ideation. These findings demonstrate the fundamental importance of reducing exposure of violence to adolescents, and that increasing peer support and their happiness may be the key to adolescent suicidal ideation prevention. PMID:24943997
Atomic Structure Schrdinger equation has approximate solutions for multi-
Zakarian, Armen
Atomic Structure SchrÃ¶dinger equation has approximate solutions for multi- electron atoms, which indicate that all atoms are like hydrogen Atomic Structure SchrÃ¶dinger equation has approximate solutions 3s 3p 3d Energy hydrogen multi-electron #12;Atomic Structure Â· orbitals are populated by electrons
Use of structural equation modeling in counseling psychology research
Ruth E. Fassinger
1987-01-01
Structural equation modeling (multivariate analysis with latent variables, also called causal modeling or covariance structure analysis) is a valuable methodological tool for use in counseling psychology research. Essentially the broad framework that subsumes many well-known proce- dures (e.g., multiple linear regression, factor analysis, path analysis), structural equation modeling allows for analysis of causal patterns among unobserved variables represented by multiple
A Framework for Structural Equation Models in General Pedigrees
Nathan J. Morris; Robert C. Elston; Catherine M. Stein
2010-01-01
Background\\/Aims: Structural Equation Modeling (SEM) is an analysis approach that accounts for both the causal relationships between variables and the errors associated with the measurement of these variables. In this paper, a framework for implementing structural equation models (SEMs) in family data is proposed. Methods: This framework includes both a latent measurement model and a structural model with covariates. It
Learning Structural Equation Models for fMRI
Amos J. Storkey; Enrico Simonotto; Heather Whalley; Stephen Lawrie; Lawrence Murray; David Mcgonigle
2006-01-01
Structural equation models can be seen as an extension of Gaussian belief net- works to cyclic graphs, and we show they can be understood generatively as the model for the joint distribution of long term average equilibrium activity of Gaus- sian dynamic belief networks. Most use of structural equation models in fMRI involves postulating a particular structure and comparing learnt
Sandra C. Paivio; Kenneth M. Cramer
2004-01-01
Objective:The aims of this study were to examine (1) the psychometric properties of the Childhood Trauma Questionnaire [CTQ; Bernstein, D., Fink, L., Handelsman, L., Foote, J., Lovejoy, M., Wenzel, K., Sapareto, E., & Ruggiero, J. (1994). Initial reliability and validity of a new retrospective measure of child abuse and neglect. American Journal of Psychiatry, 151, 1132–1136; Bernstein, D., & Fink,
The Home Situations Questionnaire-PDD Version: Factor Structure and Psychometric Properties
ERIC Educational Resources Information Center
Chowdhury, M.; Aman, M. G.; Scahill, L.; Swiezy, N.; Arnold, L. E.; Lecavalier, L.; Johnson, C.; Handen, B.; Stigler, K.; Bearss, K.; Sukhodolsky, D.; McDougle, C. J.
2010-01-01
Background: The Home Situations Questionnaire (HSQ) is a caregiver-rated scale designed to assess behavioural non-compliance in everyday settings that has been used in several studies in typically developing children. Currently there is no accepted measure of behavioural non-compliance in children with pervasive developmental disorders (PDDs).…
Moniek M. Kuile; A. Corry G. Linssen; Philip Spinhoven
1993-01-01
This study was conducted to develop a comprehensive Multidimensional Locus of Pain Control questionnaire (MLPC) and to examine how locus of pain control is related to pain appraisals, pain coping strategies, and adjustment to chronic pain. Subjects were 170 chronic headache patients. By means of factor analysis, four subscales were derived: an Internal, a Chance, a Physician, and a Medication
ERIC Educational Resources Information Center
Rudasill, Kathleen Moritz; Foust, Regan Clark; Callahan, Carolyn M.
2007-01-01
Gifted students report that they are often perceived differently than nonidentified students (Cross, Coleman, & Stewart, 1993); thus, they employ social coping strategies to manipulate the visibility of their giftedness. The Social Coping Questionnaire (SCQ; Swiatek, 1995) was designed to assess these strategies. This study's purpose was to…
ERIC Educational Resources Information Center
Paivio, Sandra, C.; Cramer, Kenneth, M.
2004-01-01
Objective: The aims of this study were to examine (1) the psychometric properties of the Childhood Trauma Questionnaire [CTQ; Bernstein, D., Fink, L., Handelsman, L., Foote, J., Lovejoy, M., Wenzel, K., Sapareto, E., & Ruggiero, J. (1994). Initial reliability and validity of a new retrospective measure of child abuse and neglect. American Journal…
Component Structure, Reliability, and Stability of Lawrence's Self-Esteem Questionnaire (LAWSEQ)
ERIC Educational Resources Information Center
Rae, Gordon; Dalto, Georgia; Loughrey, Dolores; Woods, Caroline
2011-01-01
Lawrence's Self-Esteem Questionnaire (LAWSEQ) was administered to 120 Year 1 pupils in six schools in Belfast, Northern Ireland. A principal components analysis indicated that the scale items were unidimensional and that the reliability of the scores, as estimated by Cronbach's alpha, was satisfactory ([alpha] = 0.73). There were no differences…
Fermionic covariant prolongation structure theory for supernonlinear evolution equation
Cheng Jipeng [School of Mathematical Sciences, Capital Normal University, Beijing 100048 (China); Department of Mathematics, University of Science and Technology of China, Hefei 230026 (China); Wang Shikun [College of Mathematics and Information Science, Henan University, Kaifeng 475004 (China); KLMM, AMSS, Chinese Academy of Sciences, Beijing 100080 (China); Wu Ke [School of Mathematical Sciences, Capital Normal University, Beijing 100048 (China); KLMM, AMSS, Chinese Academy of Sciences, Beijing 100080 (China); Zhao Weizhong [School of Mathematical Sciences, Capital Normal University, Beijing 100048 (China); Institute of Mathematics and Interdisciplinary Science, Capital Normal University, Beijing 100048 (China)
2010-09-15
We investigate the superprincipal bundle and its associated superbundle. The super(nonlinear)connection on the superfiber bundle is constructed. Then by means of the connection theory, we establish the fermionic covariant prolongation structure theory of the supernonlinear evolution equation. In this geometry theory, the fermionic covariant fundamental equations determining the prolongation structure are presented. As an example, the supernonlinear Schroedinger equation is analyzed in the framework of this fermionic covariant prolongation structure theory. We obtain its Lax pairs and Baecklund transformation.
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…
Goodness of Fit Criteria in Structural Equation Models.
ERIC Educational Resources Information Center
Schumacker, Randall E.
Several goodness of fit (GOF) criteria have been developed to assist the researcher in interpreting structural equation models. However, the determination of GOF for structural equation models is not as straightforward as that for other statistical approaches in multivariate procedures. The four GOF criteria used across the commonly used…
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…
Drug prescription practices in Brazil: a structural equation model
Wagner Junior Ladeira; Marlon Dalmoro; Alisson Eduardo Maehler; Clécio Falcão Araujo
2011-01-01
Purpose – The paper's aim is to analyze the functional relationships between factors related to the prescription of medical drugs in Brazil. Design\\/methodology\\/approach – A survey was conducted among 232 medical doctors in Brazil. Data were collected using a structured questionnaire. Five hypotheses on the factors impacting drug prescription were proposed, and the constructs were validated using a set of
Modeling Attitude toward Statistics by a Structural Equation
ERIC Educational Resources Information Center
Escalera-Chávez, Milka Elena; García-Santillán, Arturo; Venegas-Martínez, Francisco
2014-01-01
In this study, we examined whether the constructs of usefulness, motivation, likeness, confidence, and anxiety influence the student's attitude towards statistics. Two hundred ninety eight students enrolled in the private university were surveyed by using the questionnaire proposed by Auzmendi (1992). Data analysis was done by structural…
Sensitivity of rocky planet structures to the equation of state
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.
Shock wave structure for generalized Burnett equations
NASA Astrophysics Data System (ADS)
Bobylev, A. V.; Bisi, M.; Cassinari, M. P.; Spiga, G.
2011-03-01
Stationary shock wave solutions for the generalized Burnett equations (GBE) [A. V. Bobylev, "Generalized Burnett hydrodynamics," J. Stat. Phys. 132, 569 (2008)] are studied. Based on the results of Bisi et al. ["Qualitative analysis of the generalized Burnett equations and applications to half-space problems," Kinet. Relat. Models 1, 295 (2008)], we choose a unique (optimal) form of GBE and solve numerically the shock wave problem for various Mach numbers. The results are compared with the numerical solutions of Navier-Stokes equations and with the Mott-Smith approximation for the Boltzmann equation (all calculations are done for Maxwell molecules) since it is believed that the Mott-Smith approximation yields better results for strong shocks. The comparison shows that GBE yield certain improvement of the Navier-Stokes results for moderate Mach numbers.
Validating a tourism development theory with structural equation modeling
Yooshik Yoon; Dogan Gursoy; Joseph S. Chen
2001-01-01
This study attempts to examine the structural effects of four tourism-impact factors on total impact and on local residents’ support for tourism development. To achieve the above goal, five research hypotheses are proposed. Three hundred and four questionnaires from a mail survey of randomly selected residents from the Norfolk\\/Virginia Beach\\/Newport News area were analyzed. A confirmatory factor analysis and structural
Alternative bi-Hamiltonian structures for WDVV equations of associativity
NASA Astrophysics Data System (ADS)
Kalayci, J.; Nutku, Y.
1998-01-01
The WDVV equations of associativity in two-dimensional topological field theory are completely integrable third-order Monge-Ampère equations which admit bi-Hamiltonian structure. The time variable plays a distinguished role in the discussion of Hamiltonian structure, whereas in the theory of WDVV equations none of the independent variables merits such a distinction. WDVV equations admit very different alternative Hamiltonian structures under different possible choices of the time variable, but all these various Hamiltonian formulations can be brought together in the framework of the covariant theory of symplectic structure. They can be identified as different components of the covariant Witten-Zuckerman symplectic 2-form current density where a variational formulation of the WDVV equation that leads to the Hamiltonian operator through the Dirac bracket is available.
Integrable structures for a generalized Monge-Ampère equation
NASA Astrophysics Data System (ADS)
Verbovetsky, A. M.; Vitolo, R.; Kersten, P.; Krasil'shchik, I. S.
2012-05-01
We consider a third-order generalized Monge-Ampère equation uyyy - u{xxy/ 2 } + uxxxuxyy = 0, which is closely related to the associativity equation in two-dimensional topological field theory. We describe all integrable structures related to it: Hamiltonian, symplectic, and also recursion operators. We construct infinite hierarchies of symmetries and conservation laws.
USING STRUCTURAL EQUATION MODELING TO INVESTIGATE RELATIONSHIPS AMONG ECOLOGICAL VARIABLES
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...
A general non-linear multilevel structural equation mixture model
Kelava, Augustin; Brandt, Holger
2014-01-01
In the past 2 decades latent variable modeling has become a standard tool in the social sciences. In the same time period, traditional linear structural equation models have been extended to include non-linear interaction and quadratic effects (e.g., Klein and Moosbrugger, 2000), and multilevel modeling (Rabe-Hesketh et al., 2004). We present a general non-linear multilevel structural equation mixture model (GNM-SEMM) that combines recent semiparametric non-linear structural equation models (Kelava and Nagengast, 2012; Kelava et al., 2014) with multilevel structural equation mixture models (Muthén and Asparouhov, 2009) for clustered and non-normally distributed data. The proposed approach allows for semiparametric relationships at the within and at the between levels. We present examples from the educational science to illustrate different submodels from the general framework. PMID:25101022
The relativistic equations of stellar structure and evolution
K. S. Thorne
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.
A general non-linear multilevel structural equation mixture model.
Kelava, Augustin; Brandt, Holger
2014-01-01
In the past 2 decades latent variable modeling has become a standard tool in the social sciences. In the same time period, traditional linear structural equation models have been extended to include non-linear interaction and quadratic effects (e.g., Klein and Moosbrugger, 2000), and multilevel modeling (Rabe-Hesketh et al., 2004). We present a general non-linear multilevel structural equation mixture model (GNM-SEMM) that combines recent semiparametric non-linear structural equation models (Kelava and Nagengast, 2012; Kelava et al., 2014) with multilevel structural equation mixture models (Muthén and Asparouhov, 2009) for clustered and non-normally distributed data. The proposed approach allows for semiparametric relationships at the within and at the between levels. We present examples from the educational science to illustrate different submodels from the general framework. PMID:25101022
Jackson, Todd; Chen, Hong
2010-09-01
There is considerable evidence that mass media portrayals of body image contribute to body dissatisfaction, yet the assessment of perceived media influences has been examined fleetingly in highly populated, non-Western cultures, particularly among young males. This research examined the factor structure of the Sociocultural Attitudes Towards Appearance Questionnaire-3 (SATAQ-3) among adolescent boys in China. In an initial exploratory factor analysis (N=719), a four factor solution emerged with components reflecting General Pressure-Internalization, Sources of Appearance Information, Pressure-Internalization of an Athletic Ideal, and Pressure to be Thin. Subsequently, confirmatory factor analyses in a new sample (n=749) assessed fits of the derived four factor model, a three factor variant, and alternatives reflecting "Western" and "Malay" SATAQ-3 solutions. The derived four factor solution had the most acceptable structure across several fit indices. Patterns of correlation with other self-report measures also provided preliminary support for the validity of the derived solution. PMID:20800561
Impact of organizational structure on nurses’ job satisfaction: A questionnaire survey
A. WILLEM; M. BUELENS; I. DE JONGHE
2005-01-01
Background Nurses’ job satisfaction is an important issue because of its impact on the quality of the nursing job. Therefore, it receives a lot of attention in the international nursing literature but insight into the sources of nurses’ job satisfaction is yet insufficient, in particular for sources related to organizational structure. ObjectivesWe contribute by investigating the relationship between the organizational
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…
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…
Fast integral equation solvers in computational electromagnetics of complex structures
W. C. Chew; H. Y. Chao; T. J. Cui; C. C. Lu; S. Ohnuki; Y. C. Pan; J. M. Song; S. Velamparambil; J. S. Zhao
2003-01-01
This paper reviews the recent progress of fast integral equation solvers at the Center for Computational Electromagnetics and Electromagnetics laboratory, University of Illinois at Urbana-Champaign. We will demonstrate the ability to solve a variety of electromagnetic problems for complex structures and low-frequency structures as well as large scale scattering problems with over 10 million unknowns.
Anne W. Riley; Lisa M. Lyman; Georg Spiel; Manfred Döpfner; Maria J. Lorenzo
2006-01-01
\\u000a Abstract\\u000a \\u000a \\u000a Background\\u000a Attention-deficit\\/hyperactivity disorder (ADHD) in children affects every member of the family. Practical tools are needed\\u000a to assess the effects of ADHD on families to better understand and address the level of stress, strain and burden that families\\u000a experience.\\u000a \\u000a \\u000a \\u000a \\u000a Objective\\u000a To provide the preliminary reliability, validity and factor structure of the Family Strain Index (FSI), a 6-item parent-report\\u000a questionnaire.
On third Poisson structure of KdV equation
Gorsky, A.; Marshakov, A.; Orlov, A. [Inst. of Theoretical Physics, Moscow (Russian Federation)] [and others
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.
On integrable structures for a generalized Monge-Ampere equation
Paul Kersten; Iosif Krasil'shchik; Alexander Verbovetsky; Raffaele Vitolo
2011-01-01
We consider a 3rd-order generalized Monge-Ampere equation u_yyy - u_xxy^2 + u_xxx u_xyy = 0 (which is closely related to the associativity equation in the 2-d topological field theory) and describe all integrable structures related to it (i.e., Hamiltonian, symplectic, and recursion operators). Infinite hierarchies of symmetries and conservation laws are constructed as well.
Post-partum blues among Korean mothers: a structural equation modelling approach.
Chung, Sung Suk; Yoo, Il Young; Joung, Kyoung Hwa
2013-08-01
The objective of this study was to propose the post-partum blues (PPB) model and to estimate the effects of self-esteem, social support, antenatal depression, and stressful events during pregnancy on PPB. Data were collected from 249 women post-partum during their stay in the maternity units of three hospitals in Korea using a self-administered questionnaire. A structural equation modelling approach using the Analysis of Moments Structure program was used to identify the direct and indirect effects of the variables on PPB. The full model had a good fit and accounted for 70.3% of the variance of PPB. Antenatal depression and stressful events during pregnancy had strong direct effects on PPB. Household income showed indirect effects on PPB via self-esteem and antenatal depression. Social support indirectly affected PPB via self-esteem, antenatal depression, and stressful events during pregnancy. PMID:23009567
ERIC Educational Resources Information Center
Makikangas, Anne; Feldt, Taru; Kinnunen, Ulla; Tolvanen, Asko; Kinnunen, Marja-Liisa; Pulkkinen, Lea
2006-01-01
This study provides new knowledge about the factor structure of the 12-item General Health Questionnaire (GHQ-12; D. Goldberg, 1972) through the application of confirmatory factor analysis to longitudinal data, thereby enabling investigation of the factor structure, its invariance across time, and the rank-order stability of the factors. Two…
Covariant symplectic structure of the complex Monge-Ampère equation
NASA Astrophysics Data System (ADS)
Nutku, Y.
2000-04-01
The complex Monge-Ampère equation is invariant under arbitrary holomorphic changes of the independent variables with unit Jacobian. We present its variational formulation where the action remains invariant under this infinite group. The new Lagrangian enables us to obtain the first symplectic 2-form for the complex Monge-Ampère equation in the framework of the covariant Witten-Zuckerman approach to symplectic structure. We base our considerations on a reformulation of the Witten-Zuckerman theory in terms of holomorphic differential forms. The first closed and conserved Witten-Zuckerman symplectic 2-form for the complex Monge-Ampère equation is obtained in arbitrary dimension and for all cases elliptic, hyperbolic and homogeneous. The connection of the complex Monge-Ampère equation with Ricci-flat Kähler geometry suggests the use of the Hilbert action principle as an alternative variational formulation. However, we point out that Hilbert's Lagrangian is a divergence for Kähler metrics and serves as a topological invariant rather than yielding the Euclideanized Einstein field equations. Nevertheless, since the Witten-Zuckerman theory employs only the boundary terms in the first variation of the action, Hilbert's Lagrangian can be used to obtain the second Witten-Zuckerman symplectic 2-form. This symplectic 2-form vanishes on shell, thus defining a Lagrangian submanifold. In its derivation the connection of the second symplectic 2-form with the complex Monge-Ampère equation is indirect but we show that it satisfies all the properties required of a symplectic 2-form for the complex elliptic, or hyperbolic Monge-Ampère equation when the dimension of the complex manifold is 3 or higher. The complex Monge-Ampère equation admits covariant bisymplectic structure for complex dimension 3, or higher. However, in the physically interesting case of n=2 we have only one symplectic 2-form. The extension of these results to the case of complex Monge-Ampère-Liouville equation is also presented.
Fonseca-Pedrero, Eduardo; Compton, Michael T; Tone, Erin B; Ortuño-Sierra, Javier; Paino, Mercedes; Fumero, Ascensión; Lemos-Giráldez, Serafín
2014-08-13
The main goal of this study was to examine the cross-cultural invariance of the factor structure of the Schizotypal Personality Questionnaire (SPQ) (Raine, 1991) in two large samples of Spanish and American young adults. The final sample was made up of 2313 college students (508 men, 22%). Their mean age was 20.5 years (S.D.=3.2). The results indicated that the Stefanis et al. (2004) four-factor model yielded the best goodness-of-fit indices compared to alternative models. Moreover, the results support configural, metric, and partial measurement invariance of the covariances of the SPQ across the two samples. The finding of measurement equivalence across cultures provides essential evidence of construct validity for the schizotypy dimensions and of the cross-cultural validity of SPQ scores. The finding of comparable dimensional structures in cross-cultural samples lends further support to the continuum model of schizotypy and schizophrenia spectrum disorders. Future studies should continue to examine the validity of scores on the SPQ and other schizotypy measures and their variation or consistency across cultures. PMID:25412981
Fonseca-Pedrero, Eduardo; Compton, Michael T; Tone, Erin B; Ortuño-Sierra, Javier; Paino, Mercedes; Fumero, Ascensión; Lemos-Giráldez, Serafín
2014-12-30
The main goal of this study was to examine the cross-cultural invariance of the factor structure of the Schizotypal Personality Questionnaire (SPQ) (Raine, 1991) in two large samples of Spanish and American young adults. The final sample was made up of 2313 college students (508 men, 22%). Their mean age was 20.5 years (S.D.=3.2). The results indicated that the Stefanis et al. (2004) four-factor model yielded the best goodness-of-fit indices compared to alternative models. Moreover, the results support configural, metric, and partial measurement invariance of the covariances of the SPQ across the two samples. The finding of measurement equivalence across cultures provides essential evidence of construct validity for the schizotypy dimensions and of the cross-cultural validity of SPQ scores. The finding of comparable dimensional structures in cross-cultural samples lends further support to the continuum model of schizotypy and schizophrenia spectrum disorders. Future studies should continue to examine the validity of scores on the SPQ and other schizotypy measures and their variation or consistency across cultures. PMID:25632419
Berg, Kelly C.; Swanson, Sonja A.; Stiles-Shields, E. Colleen; Eddy, Kamryn T.; Peterson, Carol B.; Le Grange, Daniel
2013-01-01
Objective The purpose of this investigation was to compare the latent structures of the interview (EDE) and questionnaire (EDE-Q) versions of the Eating Disorder Examination. Methods Participants were 280 children, adolescents, and young adults seeking eating disorder treatment. Two separate latent structure analyses (LSAs) were conducted; one used variables from the EDE as indicators and the other used the corresponding variables from the EDE-Q as indicators. Results The EDE and EDE-Q models both yielded four-class solutions. Three of the four classes from the EDE-Q model demonstrated moderate to high concordance with their paired class from the EDE model. Using the EDE-Q to detect the EDE, the sensitivity and specificity of measuring certain classes varied from poor (18.6%) to excellent (93.7%). The overall concordance was moderate (?=.49). Discussion These data suggest that LSAs using the EDE and EDE-Q may be directly compared; however, differences between results may represent inconsistencies in response patterns rather than true differences in psychopathology. PMID:23375185
Consistent Partial Least Squares for nonlinear structural equation models.
Dijkstra, Theo K; Schermelleh-Engel, Karin
2014-10-01
Partial Least Squares as applied to models with latent variables, measured indirectly by indicators, is well-known to be inconsistent. The linear compounds of indicators that PLS substitutes for the latent variables do not obey the equations that the latter satisfy. We propose simple, non-iterative corrections leading to consistent and asymptotically normal (CAN)-estimators for the loadings and for the correlations between the latent variables. Moreover, we show how to obtain CAN-estimators for the parameters of structural recursive systems of equations, containing linear and interaction terms, without the need to specify a particular joint distribution. If quadratic and higher order terms are included, the approach will produce CAN-estimators as well when predictor variables and error terms are jointly normal. We compare the adjusted PLS, denoted by PLSc, with Latent Moderated Structural Equations (LMS), using Monte Carlo studies and an empirical application. PMID:24306555
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…
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…
Equations for Mix Design of Structural Lightweight Concrete
M. Abdullahi; B. S. Mohammed
Equations for mix design of structural lightweight concrete are presented. Conventionally, mix design of concrete is conducted using the tabular data and charts in standards. This requires extra efforts of understanding the data in the code and interpolations are often required when intermediate values are needed. The process is also liable to human error as data may be erroneously taken
Using Fixed Thresholds with Grouped Data in Structural Equation Modeling
ERIC Educational Resources Information Center
Koran, Jennifer; Hancock, Gregory R.
2010-01-01
Valuable methods have been developed for incorporating ordinal variables into structural equation models using a latent response variable formulation. However, some model parameters, such as the means and variances of latent factors, can be quite difficult to interpret because the latent response variables have an arbitrary metric. This limitation…
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…
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…
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…
Structure-Preserving Model Order Reduction of RCL Circuit Equations
Freund, Roland W.
Structure-Preserving Model Order Reduction of RCL Circuit Equations Roland W. Freund Department of Mathematics, University of California at Davis, One Shields Avenue, Davis, CA 95616, U.S.A. freund compute reduced-order models that represent Pad´e #12;2 Roland W. Freund or matrix-Pad´e approximations [5
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…
Habitat fragmentation and reproductive success: a structural equation modelling approach
Helle, Samuli
Habitat fragmentation and reproductive success: a structural equation modelling approach Eric Le on the effects of habitat fragmentation, whereby habitat is lost and the spatial configuration of remaining habitat patches is altered, on individual breeding per- formance. However, we still lack consensus of how
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…
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.
Dynamic Structural Equation Models for Tracking Cascades Over Social Networks
Pratt, Vaughan
of the topology plays a crucial role for several reasons e.g., when social media advertisers select a small setDynamic Structural Equation Models for Tracking Cascades Over Social Networks Brian Baingana and leveraging the sparse connectivity inherent to social networks, edge weights are estimated by minimizing
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…
Interactions of Latent Variables in Structural Equation Models.
ERIC Educational Resources Information Center
Bollen, Kenneth A.; Paxton, Pamela
1998-01-01
Provides a discussion of an alternative two-stage least squares (2SLS) technique to include interactions of latent variables in structural equation models. The method requires selection of instrumental variables, and rules for selection are presented. An empirical example and Statistical Analysis System programs are presented. (SLD)
Equivalent Structural Equation Models: A Challenge and Responsibility
ERIC Educational Resources Information Center
Raykov, Tenko; Marcoulides, George A.
2007-01-01
Relevant aspects of the example provided by Raykov and Marcoulides (2001) are emphasized, specifically the distinctiveness of infinitely many members of its sequence of equivalent structural equation models. This emphasis appears to be needed in light of recent statements by Markus (2002), whose intended counterexamples do not present a…
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…
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…
Principles and practice in reporting structural equation analyses
Roderick P. McDonald; Moon-Ho Ringo Ho
2002-01-01
Principles for reporting analyses using structural equation modeling are reviewed, with the goal of supplying readers with complete and accurate information. It is recommended that every report give a detailed justification of the model used, along with plausible alternatives and an account of identifiability. Nonnormality and missing data problems should also be addressed. A complete set of parameters and their
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…
Peirce, Jessica M.; Burke, Christopher K.; Stoller, Kenneth B.; Neufeld, Karin J.; Brooner, Robert K.
2011-01-01
Posttraumatic stress disorder (PTSD) diagnosis requires first identifying a traumatic event, but very few studies have evaluated methods of potential traumatic event assessment and their impact on PTSD diagnosis. We compared a behaviorally-specific comprehensive multiple-item traumatic event measure to a single-item measure to determine their impact on traumatic event identification and subsequent PTSD diagnosis. In a within-subject, counterbalanced design, the Traumatic Life Events Questionnaire (TLEQ; Kubany et al., 2000) was compared to the single-question traumatic event assessment in the Structured Clinical Interview for DSM-IV (SCID; First, Spitzer, Gibbon, & Williams, 1998) in 129 participants in opioid dependence treatment. The TLEQ produced a 9-fold higher rate of traumatic events reported by the participants as compared to the SCID. As a result, PTSD diagnoses in the sample increased to 33% after the TLEQ measure from 24% after the SCID. The increase in potential traumatic event identification and PTSD diagnosis was greater in women than men. This study provides strong support for the use of comprehensive traumatic event assessments to measure traumatic events and PTSD diagnoses, particularly in women. PMID:19485675
ERIC Educational Resources Information Center
Uz Bas, Asli; Yurdabakan, Irfan
2012-01-01
The present study aimed to evaluate the factor structure of the Reactive-Proactive Aggression Questionnaire (RPQ) with Turkish children, and to investigate gender, grade-level, and socioeconomic status (SES) differences in reactive and proactive aggression. Participants consisted of 1,081 Turkish children (544 boys and 537 girls) aged 9 to 14…
The Rivermead Post Concussion Symptoms Questionnaire
Seb Potter; Eleanor Leigh; Derick Wade; Simon Fleminger
2006-01-01
Objective To investigate the factor structure of the Rivermead Post Concussion Symptoms Questionnaire (RPQ) among individuals seen as\\u000a part of routine follow-up following traumatic brain injury.\\u000a \\u000a \\u000a \\u000a Methods RPQ data from 168 participants was examined (mean age 35.2, SD 14.3; 89% with post traumatic amnesia duration < 24 hours)\\u000a six months after admission to an Accident & Emergency Department following TBI. Structural equation modelling was
Bjarte Sanne; Torbjørn Torsheim; Einar Heiervang; Kjell Morten Stormark
2009-01-01
Objective: To test Goodman’s theoretical 5-factor model of the Strengths and Difficulties Questionnaire (SDQ) in an analysis of the Norwegian parent (P) and teacher (T) versions of the questionnaire. Method: The T-SDQ was analyzed for 8,999 (95.4% of all) children in primary school grades 2–4 in Bergen, Norway, whereas the P-SDQ was examined for 6,430 children (68.2%). Main analyses were
Chung, Min-Huey; Liu, Wen-I; Lee, Hui-Ling; Hsu, Nanly
2013-01-01
Few studies have examined relationships among neurophysiological, psychological, and behavioral factors with regard to their effects on sleep quality. We used a structure equation model to investigate behavioral and psychological factors that influence neurophysiological regulation of sleep in shift workers. Using a cross-sectional study design, we tested the model with a sample of 338 female nurses working rotating shifts at an urban regional hospital. The Morningness-Eveningness Questionnaire (MEQ) and short-form Menstrual Distress Questionnaire (MDQ) were used to measure neurophysiological factors involved in morningness-eveningness and menstrual distress. The Sleep Hygiene Awareness and Practice Scale (SHAPS) and Profile of Mood States Short Form (POMS-SF) were completed to measure behavioral factors of sleep hygiene practices and psychological factors of mood states. In addition, the Pittsburgh Sleep Quality Index (PSQI) measured participant's self-reported sleep quality. The results revealed that sleep hygiene practices and mood states mediated the effects of morningness-eveningness and menstrual distress on sleep quality. Our findings provide support for developing interventions to enhance sleep hygiene and maintain positive mood states to reduce the influence of neurophysiological factors on sleep quality among shift workers. PMID:24278145
Weker, H; Rudzka-Ka?toch, Z
1999-01-01
On the basis of available publications and obligatory legal regulations regarding the organisation of collective feeding patterns in Social Service Health Centres a questionnaire study was established to examine the way milk kitchen function in Poland. The study covered 533 milk kitchen centres (in hospitals, orphanages and crèches) from February to December 1997. The afore-mentioned study analysed the general characteristics of the milk kitchen centre, its type of work, supervisory methods and the personnel's hygiene. From the results of this research it can be concluded that the organisational structure of the milk centres was appropriate, appliances and equipment in the majority centres were adequate but basis utensils were insufficient. It is obvious that dietetic feeding methods for this particular group of children are insufficiently applied. Only 22.2% of the centres apply the recommended proposals i.e. without boiling, without pasteurisation, ready for consumption when preparing, infant formulae, follow-up formulae and other mixed products. Work hygiene and health quality of production in the milk kitchen centres is subject to systematic controls by competent individuals from the State Sanitary Inspection services. In the years 1995-96, 72 samples of infant food that mainly came from hospital milk kitchen centres were taken due to the poor microbiological quality of the food. The considerable changes that have taken place over the last few years as far as infant feeding is concerned, for example, the promotion of breast-feeding, taking advantage of prepared dietetic products for infants (infant formulae, follow-up formulae, vegetable products, fruits, vegetable-meat products, cereal products) require changes at the organisational level of infant collective feeding which was confirmed by the afore-mentioned study. PMID:10523939
Specification, evaluation, and interpretation of structural equation models
Richard P. Bagozzi; Youjae Yi
We provide a comprehensive and user-friendly compendium of standards for the use and interpretation of structural equation\\u000a models (SEMs). To both read about and do research that employs SEMs, it is necessary to master the art and science of the\\u000a statistical procedures underpinning SEMs in an integrative way with the substantive concepts, theories, and hypotheses that\\u000a researchers desire to examine.
2010-01-01
Background The use of structural equation modeling and latent variables remains uncommon in epidemiology despite its potential usefulness. The latter was illustrated by studying cross-sectional and longitudinal relationships between eating behavior and adiposity, using four different indicators of fat mass. Methods Using data from a longitudinal community-based study, we fitted structural equation models including two latent variables (respectively baseline adiposity and adiposity change after 2 years of follow-up), each being defined, by the four following anthropometric measurement (respectively by their changes): body mass index, waist circumference, skinfold thickness and percent body fat. Latent adiposity variables were hypothesized to depend on a cognitive restraint score, calculated from answers to an eating-behavior questionnaire (TFEQ-18), either cross-sectionally or longitudinally. Results We found that high baseline adiposity was associated with a 2-year increase of the cognitive restraint score and no convincing relationship between baseline cognitive restraint and 2-year adiposity change could be established. Conclusions The latent variable modeling approach enabled presentation of synthetic results rather than separate regression models and detailed analysis of the causal effects of interest. In the general population, restrained eating appears to be an adaptive response of subjects prone to gaining weight more than as a risk factor for fat-mass increase. PMID:20433707
Testing Multivariable Covariance Structure and Means Hypotheses via Structural Equation Modeling.
ERIC Educational Resources Information Center
Raykov, Tenko
2001-01-01
Presents a didactic collection of covariance and mean structure hypotheses that can be tested using a widely applicable and easy to use structural equation modeling approach. The method is useful when the goal is to examine the observed multivariable structure or test hypotheses regarding interrelationships in measures and when large samples are…
Extended Navier–Stokes equations, ultrasonic absorption and shock structure
NASA Astrophysics Data System (ADS)
Emanuel, G.
2015-01-01
The Navier-Stokes (N-S) equations for a steady or unsteady, compressible, continuum flow are modified. The extension is based on a Stokesian fluid with a single nonlinear term in an isotropic stress, rate-of-deformation relation. This is the simplest possible nonlinear extension that also satisfies the second law of thermodynamics. The transport coefficient of this term is referred to as the third viscosity coefficient. In the extended version, the momentum and energy equations each contain a nonlinear term that is proportional to this new coefficient. These terms are significant only when the velocity gradient is extremely large. They are inconsequential, e.g., in a laminar boundary layer. Nevertheless, there are flows where the extended version of the N-S equations is relevant. The first of these is an ultrasonic, unsteady, one-dimensional flow, which is used for evaluating the bulk viscosity. In this case, the linearized N-S equations become singular as the ultrasonic frequency increases toward infinity. When the frequency is sufficiently large, nonlinear terms in the extended N-S equations need to be retained. The terms that are proportional to the third viscosity coefficient increase in importance, relative to linear terms, as the fourth power of the frequency. A second example is shock wave structure. A model is established and numerically solved for the normalized density derivative. Results are compared with corresponding measurements for argon when the upstream Mach number is 1.058 and 1.23. Good agreement between the extended N-S predictions and measurements is obtained for both Mach numbers with a single, but extremely small, value for the third viscosity coefficient. An important difference between conventional and extended N-S shock structure solutions is that the extended-model solution depends on the upstream pressure, whereas the conventional solution does not.
Zamolodchikov's Tetrahedron Equation and Hidden Structure of Quantum Groups
Vladimir V. Bazhanov; Sergey M. Sergeev
2005-10-10
The tetrahedron equation is a three-dimensional generalization of the Yang-Baxter equation. Its solutions define integrable three-dimensional lattice models of statistical mechanics and quantum field theory. Their integrability is not related to the size of the lattice, therefore the same solution of the tetrahedron equation defines different integrable models for different finite periodic cubic lattices. Obviously, any such three-dimensional model can be viewed as a two-dimensional integrable model on a square lattice, where the additional third dimension is treated as an internal degree of freedom. Therefore every solution of the tetrahedron equation provides an infinite sequence of integrable 2d models differing by the size of this "hidden third dimension". In this paper we construct a new solution of the tetrahedron equation, which provides in this way the two-dimensional solvable models related to finite-dimensional highest weight representations for all quantum affine algebra $U_q(\\hat{sl}(n))$, where the rank $n$ coincides with the size of the hidden dimension. These models are related with an anisotropic deformation of the $sl(n)$-invariant Heisenberg magnets. They were extensively studied for a long time, but the hidden 3d structure was hitherto unknown. Our results lead to a remarkable exact "rank-size" duality relation for the nested Bethe Ansatz solution for these models. Note also, that the above solution of the tetrahedron equation arises in the quantization of the "resonant three-wave scattering" model, which is a well-known integrable classical system in 2+1 dimensions.
The local Callan-Symanzik equation: structure and applications
Florent Baume; Boaz Keren-Zur; Riccardo Rattazzi; Lorenzo Vitale
2014-12-03
The local Callan-Symanzik equation describes the response of a quantum field theory to local scale transformations in the presence of background sources. The consistency conditions associated with this anomalous equation imply non-trivial relations among the $\\beta$-function, the anomalous dimensions of composite operators and the short distance singularities of correlators. In this paper we discuss various aspects of the local Callan-Symanzik equation and present new results regarding the structure of its anomaly. We then use the equation to systematically write the n-point correlators involving the trace of the energy-momentum tensor. We use the latter result to give a fully detailed proof that the UV and IR asymptotics in a neighbourhood of a 4D CFT must also correspond to CFTs. We also clarify the relation between the matrix entering the gradient flow formula for the $\\beta$-function and a manifestly positive metric in coupling space associated with matrix elements of the trace of the energy momentum tensor.
The local Callan-Symanzik equation: structure and applications
NASA Astrophysics Data System (ADS)
Baume, Florent; Keren-Zur, Boaz; Rattazzi, Riccardo; Vitale, Lorenzo
2014-08-01
The local Callan-Symanzik equation describes the response of a quantum field theory to local scale transformations in the presence of background sources. The consistency conditions associated with this anomalous equation imply non-trivial relations among the ?-function, the anomalous dimensions of composite operators and the short distance singularities of correlators. In this paper we discuss various aspects of the local CallanSymanzik equation and present new results regarding the structure of its anomaly. We then use the equation to systematically write the n-point correlators involving the trace of the energy-momentum tensor. We use the latter result to give a fully detailed proof that the UV and IR asymptotics in a neighbourhood of a 4D CFT must also correspond to CFTs. We also clarify the relation between the matrix entering the gradient flow formula for the ?-function and a manifestly positive metric in coupling space associated with matrix elements of the trace of the energy momentum tensor.
The local Callan-Symanzik equation: structure and applications
Baume, Florent; Rattazzi, Riccardo; Vitale, Lorenzo
2014-01-01
The local Callan-Symanzik equation describes the response of a quantum field theory to local scale transformations in the presence of background sources. The consistency conditions associated with this anomalous equation imply non-trivial relations among the $\\beta$-function, the anomalous dimensions of composite operators and the short distance singularities of correlators. In this paper we discuss various aspects of the local Callan-Symanzik equation and present new results regarding the structure of its anomaly. We then use the equation to systematically write the n-point correlators involving the trace of the energy-momentum tensor. We use the latter result to give a fully detailed proof that the UV and IR asymptotics in a neighbourhood of a 4D CFT must also correspond to CFTs. We also clarify the relation between the matrix entering the gradient flow formula for the $\\beta$-function and a manifestly positive metric in coupling space associated with matrix elements of the trace of the energy momentum tens...
NASA Technical Reports Server (NTRS)
Guruswamy, Guru P.; Byun, Chansup
1993-01-01
A computational procedure is presented to study fluid-structural interaction problems for three-dimensional aerospace structures. The flow is modeled using the three-dimensional unsteady Euler/Navier-Stokes equations and solved using the finite-difference approach. The three dimensional structure is modeled using shell/plate finite-element formulation. The two disciplines are coupled using a domain decomposition approach. Accurate procedures both in time and space are developed to combine the solutions from the flow equations with those of the structural equations. Time accuracy is maintained using aeroelastic configuration-adaptive moving grids that are computed every time step. The work done by aerodynamic forces due to structural deformations is preserved using consistent loads. The present procedure is validated by computing the aeroelastic response of a wing and comparing with experiment. Results are illustrated for a typical wing-body configuration.
Structure of the field equations in N = 1 chiral supergravity
M. Tsuda; T. Shirafuji
1996-10-16
We study the structure of linearized field equations in $N = 1$ chiral supergravity (SUGRA) with a complex tetrad, as a preliminary to introducing additional auxiliary fields in order that the supersymmetry (SUSY) algebra close off shell. We follow the first-order formulation we have recently constructed using the method of the usual $N = 1$ SUGRA. In particular, we see how the real and imaginary parts of the complex tetrad are coupled to matter fields in the weak field approximation. Starting from the linearized (free) theory of $N = 1$ chiral SUGRA, we then construct a Lagrangian which is invariant under local SUSY transformations to zeroth order of the gravitational constant, and compare the results with the linearized field equations.
2014-01-01
Background Early feeding practices lay the foundation for children’s eating habits and weight gain. Questionnaires are available to assess parental feeding but overlapping and inconsistent items, subscales and terminology limit conceptual clarity and between study comparisons. Our aim was to consolidate a range of existing items into a parsimonious and conceptually robust questionnaire for assessing feeding practices with very young children (<3 years). Methods Data were from 462 mothers and children (age 21–27 months) from the NOURISH trial. Items from five questionnaires and two study-specific items were submitted to a priori item selection, allocation and verification, before theoretically-derived factors were tested using Confirmatory Factor Analysis. Construct validity of the new factors was examined by correlating these with child eating behaviours and weight. Results Following expert review 10 factors were specified. Of these, 9 factors (40 items) showed acceptable model fit and internal reliability (Cronbach’s ?: 0.61-0.89). Four factors reflected non-responsive feeding practices: ‘Distrust in Appetite’, ‘Reward for Behaviour’, ‘Reward for Eating’, and ‘Persuasive Feeding’. Five factors reflected structure of the meal environment and limits: ‘Structured Meal Setting’, ‘Structured Meal Timing’, ‘Family Meal Setting’, ‘Overt Restriction’ and ‘Covert Restriction’. Feeding practices generally showed the expected pattern of associations with child eating behaviours but none with weight. Conclusion The Feeding Practices and Structure Questionnaire (FPSQ) provides a new reliable and valid measure of parental feeding practices, specifically maternal responsiveness to children’s hunger/satiety signals facilitated by routine and structure in feeding. Further validation in more diverse samples is required. PMID:24898364
ERIC Educational Resources Information Center
Forde, David R.; Baron, Stephen W.; Scher, Christine D.; Stein, Murray B.
2012-01-01
This study examines the psychometric properties of the Childhood Trauma Questionnaire short form (CTQ-SF) with street youth who have run away or been expelled from their homes (N = 397). Internal reliability coefficients for the five clinical scales ranged from 0.65 to 0.95. Confirmatory Factor Analysis (CFA) was used to test the five-factor…
ERIC Educational Resources Information Center
Aguado, Jaume; Campbell, Alistair; Ascaso, Carlos; Navarro, Purificacion; Garcia-Esteve, Lluisa; Luciano, Juan V.
2012-01-01
In this study, the authors tested alternative factor models of the 12-item General Health Questionnaire (GHQ-12) in a sample of Spanish postpartum women, using confirmatory factor analysis. The authors report the results of modeling three different methods for scoring the GHQ-12 using estimation methods recommended for categorical and binary data.…
ERIC Educational Resources Information Center
Okech, David
2012-01-01
Objectives: Using baseline and second wave data, the study evaluated the measurement and structural properties of parenting stress, personal mastery, and economic strain with N = 381 lower income parents who decided to join and those who did not join in a child development savings account program. Methods: Structural equation modeling mean and…
A Double-Structure Structural Equation Model for Three-Mode Data
ERIC Educational Resources Information Center
Gonzalez, Jorge; De Boeck, Paul; Tuerlinckx, Francis
2008-01-01
Structural equation models are commonly used to analyze 2-mode data sets, in which a set of objects is measured on a set of variables. The underlying structure within the object mode is evaluated using latent variables, which are measured by indicators coming from the variable mode. Additionally, when the objects are measured under different…
Structural equation modeling of mediation and moderation with contextual factors
Little, Todd D.; Card, N. A.; Bovaird, James A.; Preacher, K. J.; Crandall, C. S.
2007-01-01
a105 ?Chapter9?Little? ? 2007/2/12 ? 15:58 ? page 207 ? #1 a105 a105 a105 a105 a105 CHAPTER NINE Structural Equation Modeling of Mediation and Moderation With Contextual Factors Todd D. Little University of Kansas Noel A. Card University of Arizona... relationships are de- scribed in terms such as indirect influences, distal vs. proximal causes, interme- diate outcomes, and ultimate causes; all of which share the concept of mediation. Similarly, researchers must often consider that an observed relationship...
A semiparametric Bayesian approach for structural equation models.
Song, Xin-Yuan; Pan, Jun-Hao; Kwok, Timothy; Vandenput, Liesbeth; Ohlsson, Claes; Leung, Ping-Chung
2010-06-01
In the development of structural equation models (SEMs), observed variables are usually assumed to be normally distributed. However, this assumption is likely to be violated in many practical researches. As the non-normality of observed variables in an SEM can be obtained from either non-normal latent variables or non-normal residuals or both, semiparametric modeling with unknown distribution of latent variables or unknown distribution of residuals is needed. In this article, we find that an SEM becomes nonidentifiable when both the latent variable distribution and the residual distribution are unknown. Hence, it is impossible to estimate reliably both the latent variable distribution and the residual distribution without parametric assumptions on one or the other. We also find that the residuals in the measurement equation are more sensitive to the normality assumption than the latent variables, and the negative impact on the estimation of parameters and distributions due to the non-normality of residuals is more serious. Therefore, when there is no prior knowledge about parametric distributions for either the latent variables or the residuals, we recommend making parametric assumption on latent variables, and modeling residuals nonparametrically. We propose a semiparametric Bayesian approach using the truncated Dirichlet process with a stick breaking prior to tackle the non-normality of residuals in the measurement equation. Simulation studies and a real data analysis demonstrate our findings, and reveal the empirical performance of the proposed methodology. A free WinBUGS code to perform the analysis is available in Supporting Information. PMID:20533410
Questionnaire Development Resources
Resources made available by DCEG for use in developing study questionnaires. Includes questionnaires reviewed and approved by DCEG’s Technical Evaluation Committee, as well as non-reviewed questionnaire modules to be used as starting points for development.
Structural Equation Modeling: Applications in Ecological and Evolutionary Biology Research
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.
The Interface Between Theory and Data in Structural Equation Models
Grace, James B.; Bollen, Kenneth A.
2006-01-01
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, for representing general concepts. In simple terms, composite variables specify the influences of collections of other variables and can be helpful in modeling general relationships 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 influences of suites of variables are often of interest.
NASA Astrophysics Data System (ADS)
Papanikolaou, Dimitrios; Papanikolaou, Ioannis; Diakakis, Michalis; Deligiannakis, Georgios
2013-04-01
In the face of a growing number of natural disasters and the increasing costs associated with them, Europe and Greece in particular, have devoted significant efforts and resources in natural hazards mitigation during the last decades. Despite the significant legislative efforts (e.g. 1998/22/EC, 2001/792/EC, 2007/60/EC Directives, 3013/2002 Act) and even though a number of steps has been taken towards improving civil protection, recent catastrophic events have illustrated the weaknesses of current approaches. In particular, in Greece, events such as the 1999 Athens earthquake, the 2007 and 2009 wildfires have shown the inadequacy of prevention and mitigation practices. Given the enhanced civil protection responsibilities, given by the Greek national law (Acts 3013/2002, 3852/2010) to local authorities in Greece, this work analyses and evaluates the existing structure and current management framework under which local authorities function and examines their risk mitigation practices. We conducted the largest questionnaire survey regarding Civil Protections issues, among the municipalities of Greece. To this aim, this work used a innovative online tool to assess current framework. Therefore, a network connecting civil protection departments of municipalities was developed, based on an Internet platform that acted also as a communication tool. Overall, we had feedback either online or offline from 125 municipalities across the country (representing more than one/third of the total municipalities of Greece). Through this network, municipal civil protection officials completed surveys designed to obtain and quantify information on several aspects of civil protection practices and infrastructure. In particular, the examined factors included: (i) personnel and equipment, (ii) inter-agency cooperation, (iii) training, (iv) compliance with existing regulations and (v) persistent problems encountered by civil protection departments, that prevent the effectiveness of current practices. Responses showed that civil protection personnel lack adequate training and expertise, many are overstretched with several duties, while several prevention actions are carried out by seasonal or voluntary staff. Approximately half of the heads of civil protection offices do not hold a university degree, only 27% have a relevant scientific background (geoscientists or engineers) and more than half of them are elected members and not permanent staff, implying that no continuity is secured. Inter-agency cooperation is shown to be poor and organizational learning from international practices not adequate. Half of the municipalities report that the authorization processes are too slow so that prevention actions particularly regarding forest fires are severely delayed. Existing regulations are not followed by a significant portion of municipalities since 19% have not established a civil protection office and 23% have not compiled an action plan yet. Existing action plans lack important information, present no spatial data and are predominantly catalogues and tables of information regarding authorised personnel and equipment. Overall, underfunding, poor coordination of the different actors involved, lack of training and understaffing, lack of proper equipment and several other issues are held responsible by officials for preventing effectiveness of current practices. Finally, the EU emergency number 112 is widely unknown (87%). This work was held under the LIFE+ project "Local Authorities Alliance for Forest Fire Prevention - LIFE08/ENV/GR/000553" which is implemented with the contribution of the LIFE financial instrument of the European Community.
Structure detection of semiparametric structural equation models with Bayesian adaptive group lasso.
Feng, Xiang-Nan; Wang, Guo-Chang; Wang, Yi-Fan; Song, Xin-Yuan
2015-04-30
Structural equation models (SEMs) are widely recognized as the most important statistical tool for assessing the interrelationships among latent variables. This study develops a Bayesian adaptive group least absolute shrinkage and selection operator procedure to perform simultaneous model selection and estimation for semiparametric SEMs, wherein the structural equation is formulated using the additive nonparametric functions of observed and latent variables. We propose the use of basis expansions to approximate the unknown functions. By introducing adaptive penalties to the groups of basis expansions, the nonlinear, linear, or non-existent effects of observed and latent variables in the structural equation can be automatically detected. A simulation study demonstrates that the proposed method performs satisfactorily. This paper presents an application of revealing the observed and latent risk factors of diabetic kidney disease. Copyright © 2015 John Wiley & Sons, Ltd. PMID:25640461
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 managers so that they can allocate resources to improve these practices to get better performance.
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…
Kamel Jedidi; Harsharanjeet S. Jagpal; Wayne S. DeSarbo
1997-01-01
Two endemic problems face researchers in the social sciences (e.g., Marketing, Economics, Psychology, and Finance): unobserved heterogeneity and measurement error in data. Structural equation modeling is a powerful tool for dealing with these difficulties using a simultaneous equation framework with unobserved constructs and manifest indicators which are error-prone. When estimating structural equation models, however, researchers frequently treat the data as
Structure of solutions of the buoyancy -- drag equation
NASA Astrophysics Data System (ADS)
Bouquet, Serge; Falize, Emeric; Gandeboeuf, Pierre; Pailhoriès, Pierre
2008-04-01
In this paper, the well-known buoyancy-drag equation (BDE) is studied. This equation describes the non linear regime of Rayleigh -- Taylor instabilities and also the structure of the mixing zone where both fluids are present. Analytical solutions of the BDE are derived for time-dependent accelerations, ?(t), of the form ?(t) ˜ t^n where the exponent n can be positive, negative or zero. It is shown, first, that the width, h(t), of the mixing zone behaves like hn(t) ˜ t^n+2 and, second, provided the initial conditions satisfy some constraints, the special solution hn(t) is an attractor for t going to infinity. On the other hand, the behavior of the asymtotic solutions for ?(t) ˜ t^n is examined in terms of the drag coefficient, Cd, that is present in the drag force (proportional to the square of the derivative dh/dt) in the right hand side of the BDE. Critical values for this coefficient are derived analytically and it is shown that the asymptotic behaviors are strongly dependent on the value of Cd. These results are also evidenced from numerical simulations achieved with the CLAWPACK numerical package.
The algebraic structure behind the derivative nonlinear Schrödinger equation
NASA Astrophysics Data System (ADS)
França, G. S.; Gomes, J. F.; Zimerman, A. H.
2013-08-01
The Kaup-Newell (KN) hierarchy contains the derivative nonlinear Schrödinger equation (DNLSE) amongst others interesting and important nonlinear integrable equations. In this paper, a general higher grading affine algebraic construction of integrable hierarchies is proposed and the KN hierarchy is established in terms of an \\hat{s\\ell }_2 Kac-Moody algebra and principal gradation. In this form, our spectral problem is linear in the spectral parameter. The positive and negative flows are derived, showing that some interesting physical models arise from the same algebraic structure. For instance, the DNLSE is obtained as the second positive, while the Mikhailov model as the first negative flows. The equivalence between the latter and the massive Thirring model is also explicitly demonstrated. The algebraic dressing method is employed to construct soliton solutions in a systematic manner for all members of the hierarchy. Finally, the equivalence of the spectral problem introduced in this paper with the usual one, which is quadratic in the spectral parameter, is achieved by setting a particular automorphism of the affine algebra, which maps the homogeneous into principal gradation.
Structural equation models of VMT growth in US urbanised areas.
Ewing, Reid; Hamidi, Shima; Gallivan, Frank; Nelson, Arthur C.; Grace, James B.
2014-01-01
Vehicle miles travelled (VMT) is a primary performance indicator for land use and transportation, bringing with it both positive and negative externalities. This study updates and refines previous work on VMT in urbanised areas, using recent data, additional metrics and structural equation modelling (SEM). In a cross-sectional model for 2010, population, income and freeway capacity are positively related to VMT, while gasoline prices, development density and transit service levels are negatively related. Findings of the cross-sectional model are generally confirmed in a more tightly controlled longitudinal study of changes in VMT between 2000 and 2010, the first model of its kind. The cross-sectional and longitudinal models together, plus the transportation literature generally, give us a basis for generalising across studies to arrive at elasticity values of VMT with respect to different urban variables.
Appendix B: Questionnaire B1: Questionnaire
. Where was the study child born? City ST ___ ___ Country 6. What is the child's sex? Male Female 7. HowAppendix B: Questionnaire B1: Questionnaire #12;Do not write in this space To protect your child/her as the "study child". This page, which includes his/her personal information, will be separated from the rest
Two-vortex structure of electron, nonlocality and Dirac equation
S. C. Tiwari
2012-01-20
The dimensionless electromagnetic coupling constant $\\alpha=e^2 /\\hbar c$ may have three interpretations: as the well known ratio between the electron charge radius $e^2/mc^2$ and the Compton wavelength of electron $\\lambda_c= \\hbar /mc$, as a ratio of two angular momenta since Planck constant has the dimension of angular momentum, and two flux quanta $e$ and $hc/e$. The anomalous part of the electron magnetic moment together with the unified picture of the three interpretations of $\\alpha$ is suggested to have deep physical significance. The electric charge is proposed to be a new quantum of flux such that a two-vortex structure of electron is envisaged. In analogy with quantum conditions we postulate sub-quantum conditions applicable in a region of the order of $\\lambda_c$ replacing $\\hbar$ by a universal constant $f=e^2 /2\\pi c$ and apply it to Dirac equation in internal space that gives rise to the anomalous magnetic moment of electron. Dirac spinor and 2-spinor representation for vortex structure of electron in the single particle Dirac framework are discussed. The role of sub-quantum rules and the internal variables for developing the present ideas is also debated. A critical discussion on the past attempts to give fundamental importance to magnetism and flux quantum is given to delineate the new ideas in the present work.
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.
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
2014-01-01
Objective: To investigate the association between posttreatment motivation to change as measured by the Readiness to Change Questionnaire Treatment Version and drinking outcomes 9 months after the conclusion of treatment for alcohol problems. Method: Data from 392 participants in the United Kingdom Alcohol Treatment Trial were used to fit structural equation models investigating relationships between motivation to change pre- and posttreatment and 5 outcomes 9 months later. The models included pathways through changes in drinking behavior during treatment and adjustment for sociodemographic information. Results: Greater posttreatment motivation (being in action vs. preaction) was associated with 3 times higher odds of the most stringent definition of positive outcome (being abstinent or entirely a nonproblem drinker) 9 months later (odds ratio = 3.10, 95% confidence interval [1.83, 5.25]). A smaller indirect effect of pretreatment motivation on this outcome was seen from pathways through drinking behavior during treatment and posttreatment motivation (probit coefficient = 0.08, 95% confidence interval [0.03, 0.14]). A similar pattern of results was seen for other outcomes evaluated. Conclusion: Posttreatment motivation to change has hitherto been little studied and is identified here as a clearly important predictor of longer term treatment outcome. PMID:25244390
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…
Eugenia Fabra Florit; Luis E. Vila Lladosa
2007-01-01
Independent single-equation models and structural equation models are used to analyze both direct and indirect impacts of\\u000a education length, and of the match between education and employment, on job satisfaction after controlling for individual-specific\\u000a and job-specific attributes, including health status and wages. The main results show that: (1) education\\/job mismatches,\\u000a both in level and domain, reduce utility from work irrespective
Using structural equation modeling to investigate relationships among ecological variables
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 0.1258. Natural variability had a positive direct effect on biodiversity of magnitude 0.5347 and a negative indirect effect mediated through growth potential of magnitude -0.1105 yielding a positive total effects of magnitude 0.4242. Sediment contamination had a negative direct effect on biodiversity of magnitude -0.1956 and a negative indirect effect on growth potential via biodiversity of magnitude -0.067. Biodiversity had a positive effect on growth potential of magnitude 0.8432, and growth potential had a positive effect on biodiversity of magnitude 0.3398. The correlation between biodiversity and growth potential was estimated at 0.7658 and that between sediment contamination and natural variability at -0.3769.
How motivation affects academic performance: a structural equation modelling analysis.
Kusurkar, R A; Ten Cate, Th J; Vos, C M P; Westers, P; Croiset, G
2013-03-01
Few studies in medical education have studied effect of quality of motivation on performance. Self-Determination Theory based on quality of motivation differentiates between Autonomous Motivation (AM) that originates within an individual and Controlled Motivation (CM) that originates from external sources. To determine whether Relative Autonomous Motivation (RAM, a measure of the balance between AM and CM) affects academic performance through good study strategy and higher study effort and compare this model between subgroups: males and females; students selected via two different systems namely qualitative and weighted lottery selection. Data on motivation, study strategy and effort was collected from 383 medical students of VU University Medical Center Amsterdam and their academic performance results were obtained from the student administration. Structural Equation Modelling analysis technique was used to test a hypothesized model in which high RAM would positively affect Good Study Strategy (GSS) and study effort, which in turn would positively affect academic performance in the form of grade point averages. This model fit well with the data, Chi square = 1.095, df = 3, p = 0.778, RMSEA model fit = 0.000. This model also fitted well for all tested subgroups of students. Differences were found in the strength of relationships between the variables for the different subgroups as expected. In conclusion, RAM positively correlated with academic performance through deep strategy towards study and higher study effort. This model seems valid in medical education in subgroups such as males, females, students selected by qualitative and weighted lottery selection. PMID:22354335
Structural Equation Modeling for Analyzing Erythrocyte Fatty Acids in Framingham
Pottala, James V.; Djira, Gemechis D.; Espeland, Mark A.; Larson, Martin G.; Harris, William S.
2014-01-01
Research has shown that several types of erythrocyte fatty acids (i.e., omega-3, omega-6, and trans) are associated with risk for cardiovascular diseases. However, there are complex metabolic and dietary relations among fatty acids, which induce correlations that are typically ignored when using them as risk predictors. A latent variable approach could summarize these complex relations into a few latent variable scores for use in statistical models. Twenty-two red blood cell (RBC) fatty acids were measured in Framingham (N = 3196). The correlation matrix of the fatty acids was modeled using structural equation modeling; the model was tested for goodness-of-fit and gender invariance. Thirteen fatty acids were summarized by three latent variables, and gender invariance was rejected so separate models were developed for men and women. A score was developed for the polyunsaturated fatty acid (PUFA) latent variable, which explained about 30% of the variance in the data. The PUFA score included loadings in opposing directions among three omega-3 and three omega-6 fatty acids, and incorporated the biosynthetic and dietary relations among them. Whether the PUFA factor score can improve the performance of risk prediction in cardiovascular diseases remains to be tested. PMID:24959197
Structural equation modeling for analyzing erythrocyte fatty acids in Framingham.
Pottala, James V; Djira, Gemechis D; Espeland, Mark A; Ye, Jun; Larson, Martin G; Harris, William S
2014-01-01
Research has shown that several types of erythrocyte fatty acids (i.e., omega-3, omega-6, and trans) are associated with risk for cardiovascular diseases. However, there are complex metabolic and dietary relations among fatty acids, which induce correlations that are typically ignored when using them as risk predictors. A latent variable approach could summarize these complex relations into a few latent variable scores for use in statistical models. Twenty-two red blood cell (RBC) fatty acids were measured in Framingham (N = 3196). The correlation matrix of the fatty acids was modeled using structural equation modeling; the model was tested for goodness-of-fit and gender invariance. Thirteen fatty acids were summarized by three latent variables, and gender invariance was rejected so separate models were developed for men and women. A score was developed for the polyunsaturated fatty acid (PUFA) latent variable, which explained about 30% of the variance in the data. The PUFA score included loadings in opposing directions among three omega-3 and three omega-6 fatty acids, and incorporated the biosynthetic and dietary relations among them. Whether the PUFA factor score can improve the performance of risk prediction in cardiovascular diseases remains to be tested. PMID:24959197
Breeding Algebraic Structures An Evolutionary Approach to Inductive Equational Logic Programming
Fernandez, Thomas
Breeding Algebraic Structures Â An Evolutionary Approach to Inductive Equational Logic Programming semantics. 1 INTRODUCTION The aim of concept learning is to induce a description of a concept from a set equations and the induced con- cept descriptions are first-order equational theories. We have implemented
The viscous Cahn-Hilliard equation: Morse decomposition and structure of the global attractor
The viscous Cahn-Hilliard equation: Morse decomposition and structure of the global attractor M-dimensional viscous Cahn{Hilliard equation is established by explicit energy calculations. Strong non- degeneracy Introduction In this paper, we consider the viscous Cahn{Hilliard equation (1 )t = [f() 2 + t]; (1.1) where f
Moreira, Helena; Martins, Teresa; Gouveia, Maria João; Canavarro, Maria Cristina
2015-01-01
The Experiences in Close Relationships-Relationship Structures questionnaire (ECR-RS) is one of the most recent measures of adult attachment. This instrument provides a contextual assessment of attachment-related anxiety and avoidance by measuring these dimensions in various close relationships (mother, father, partner, friend). To further explore its psychometric properties and cross-cultural adequacy, this study presents the validation of the ECR-RS in a sample of Portuguese community individuals (N = 236). The Portuguese version showed adequate reliability and construct validity. The original 2-factor structure was confirmed through confirmatory factor analysis. The ECR-RS is a psychometrically robust measure of attachment, representing an important advance in the measurement of adult attachment. PMID:25175516
Critical Missing Equation of Quantum Physics for Understanding Atomic Structures
Xiaofei Huang
2013-11-01
This paper presents an optimization approach to explain why and how a quantum system evolves from an arbitrary initial state to a stationary state, satisfying the time-independent Schr\\"{o}dinger equation. It also points out the inaccuracy of this equation, which is critial important in quantum mechanics and quantum chemistry, due to a fundamental flaw in it conflicting with the physical reality. The some directions are suggested on how to modify the equation to fix the problem
Critical Missing Equation of Quantum Physics for Understanding Atomic Structures
Huang, Xiaofei
2015-01-01
This paper presents an optimization approach to explain why and how a quantum system evolves from an arbitrary initial state to a stationary state, satisfying the time-independent Schr\\"{o}dinger equation. It also points out the inaccuracy of this equation, which is critial important in quantum mechanics and quantum chemistry, due to a fundamental flaw in it conflicting with the physical reality. The some directions are suggested on how to modify the equation to fix the problem
Conversion of Questionnaire Data
Powell, Danny H [ORNL] [ORNL; Elwood Jr, Robert H [ORNL] [ORNL
2011-01-01
During the survey, respondents are asked to provide qualitative answers (well, adequate, needs improvement) on how well material control and accountability (MC&A) functions are being performed. These responses can be used to develop failure probabilities for basic events performed during routine operation of the MC&A systems. The failure frequencies for individual events may be used to estimate total system effectiveness using a fault tree in a probabilistic risk analysis (PRA). Numeric risk values are required for the PRA fault tree calculations that are performed to evaluate system effectiveness. So, the performance ratings in the questionnaire must be converted to relative risk values for all of the basic MC&A tasks performed in the facility. If a specific material protection, control, and accountability (MPC&A) task is being performed at the 'perfect' level, the task is considered to have a near zero risk of failure. If the task is performed at a less than perfect level, the deficiency in performance represents some risk of failure for the event. As the degree of deficiency in performance increases, the risk of failure increases. If a task that should be performed is not being performed, that task is in a state of failure. The failure probabilities of all basic events contribute to the total system risk. Conversion of questionnaire MPC&A system performance data to numeric values is a separate function from the process of completing the questionnaire. When specific questions in the questionnaire are answered, the focus is on correctly assessing and reporting, in an adjectival manner, the actual performance of the related MC&A function. Prior to conversion, consideration should not be given to the numeric value that will be assigned during the conversion process. In the conversion process, adjectival responses to questions on system performance are quantified based on a log normal scale typically used in human error analysis (see A.D. Swain and H.E. Guttmann, 'Handbook of Human Reliability Analysis with Emphasis on Nuclear Power Plant Applications,' NUREG/CR-1278). This conversion produces the basic event risk of failure values required for the fault tree calculations. The fault tree is a deductive logic structure that corresponds to the operational nuclear MC&A system at a nuclear facility. The conventional Delphi process is a time-honored approach commonly used in the risk assessment field to extract numerical values for the failure rates of actions or activities when statistically significant data is absent.
Measuring Metacognition in Cancer: Validation of the Metacognitions Questionnaire 30 (MCQ-30)
Cook, Sharon A.; Salmon, Peter; Dunn, Graham; Fisher, Peter
2014-01-01
Objective The Metacognitions Questionnaire 30 assesses metacognitive beliefs and processes which are central to the metacognitive model of emotional disorder. As recent studies have begun to explore the utility of this model for understanding emotional distress after cancer diagnosis, it is important also to assess the validity of the Metacognitions Questionnaire 30 for use in cancer populations. Methods 229 patients with primary breast or prostate cancer completed the Metacognitions Questionnaire 30 and the Hospital Anxiety and Depression Scale pre-treatment and again 12 months later. The structure and validity of the Metacognitions Questionnaire 30 were assessed using factor analyses and structural equation modelling. Results Confirmatory and exploratory factor analyses provided evidence supporting the validity of the previously published 5-factor structure of the Metacognitions Questionnaire 30. Specifically, both pre-treatment and 12 months later, this solution provided the best fit to the data and all items loaded on their expected factors. Structural equation modelling indicated that two dimensions of metacognition (positive and negative beliefs about worry) were significantly associated with anxiety and depression as predicted, providing further evidence of validity. Conclusions These findings provide initial evidence that the Metacognitions Questionnaire 30 is a valid measure for use in cancer populations. PMID:25215527
Carrard, Isabelle; Lien Rebetez, Marie My; Mobbs, Olivia; Van der Linden, Martial
2015-03-01
The Eating Disorder Examination-Questionnaire (EDE-Q) is a self-report questionnaire that is widely used to investigate the core features of eating disorders. The EDE-Q is derived from the Eating Disorder Examination, a semi-structured interview considered as the "gold standard" in the assessment of eating disorders. To verify the factor structure of both instruments, originally composed of four subscales, factor analyses have been conducted with various samples. Heterogeneous results were found. Because no study had investigated the factor structure of the EDE-Q in individuals with binge eating disorder, the goal of our study was to fill this gap. We started with a review of the studies on the EDE and EDE-Q factor structure to decide which models to compare. Among 21 studies that were identified, three models had been replicated several times. We compared these three models-a 22-item, 3-factor model, a brief 7-item, 3-factor model and a brief 8-item, 1-factor model-in two samples of participants, one with threshold and subthreshold criteria for binge eating disorder (N = 116) and one without eating disorders (N = 161). Confirmatory factor analysis revealed a good fit for the brief 7-item, 3-factor model for both populations, whereas other solutions were not acceptable. Cronbach's alpha coefficients of the three factors were acceptable to good, ranging between 0.714 and 0.953. The group with binge eating disorder symptoms had significantly higher scores for each factor. This brief 7-item instrument might be useful for screening or short interventions. PMID:25194301
Montero-Marin, Jesús; Piva Demarzo, Marcelo Marcos; Pereira, Joao Paulo; Olea, Marina; García-Campayo, Javier
2014-01-01
Background The training to become a dentist can create psychological distress. The present study evaluates the structure of the ‘Perceived Stress Questionnaire’ (PSQ), its internal consistency model and interrelatedness with burnout, anxiety, depression and resilience among dental students. Methods The study employed a cross-sectional design. A sample of Spanish dental students (n?=?314) completed the PSQ, the ‘Goldberg Anxiety and Depression Scale’ (GADS), ‘Connor-Davidson Resilience Scale’ (10-item CD-RISC) and ‘Maslach Burnout Inventory-Student Survey’ (MBI-SS). The structure was estimated using Parallel Analysis from polychoric correlations. Unweighted Least Squares was the method for factor extraction, using the Item Response Theory to evaluate the discriminative power of items. Internal consistency was assessed by squaring the correlation between the latent true variable and the observed variable. The relationships between the PSQ and the other constructs were analysed using Spearman’s coefficient. Results The results showed a PSQ structure through two sub-factors (‘frustration’ and ‘tenseness’) with regard to one general factor (‘perceived stress’). Items that did not satisfy discriminative capacity were rejected. The model fit were acceptable (GFI?=?0.98; RSMR?=?0.06; AGFI?=?0.98; NFI?=?0.98; RFI?=?0.98). All the factors showed adequate internal consistency as measured by the congeneric model (?0.91). High and significant associations were observed between perceived stress and burnout, anxiety, depression and resilience. Conclusions The PSQ showed a hierarchical bi-factor structure among Spanish dental students. Using the questionnaire as a uni-dimensional scale may be useful in perceived stress level discrimination, while the sub-factors could help us to refine perceived stress analysis and improve therapeutic processes. PMID:24466330
Efficient solution of eigenvalue equations of optical waveguiding structures
Emmanuel Anemogiannis; Elias N. Glytsis; Thomas K. Gaylord
1994-01-01
A general numerical method is presented that is capable of extracting all the zeros of a complex equation. This method allows accurate determination of the complex propagation constants of general multilayer optical and microwave planar waveguides, the computation of energy states and their lifetimes of semiconductor heterostructures, and the roots of complex transcendental equations from other scientific disciplines. The method
Compact and noncompact structures for nonlinear fractional evolution equations
Zaid M. Odibat
2008-01-01
This Letter deals with compact and noncompact solutions for nonlinear evolution equations with time-fractional derivatives. We present a reliable approach of the homotopy perturbation method to handle nonlinear fractional evolution equations. The validity of the approach is verified through illustrative examples. New exact solitary wave and compacton solutions are developed. The proposed technique could lead to a promising approach for
2012-01-01
Background The Recalled Parental Rearing Behavior questionnaire (FEE, [1,2]) assesses perceived parental rearing behavior separately for each parent. An ultra-short screening version (FEE-US) with the same three scales each for the mother and the father is reported and factor-analytically validated. Methods N = 4,640 subjects aged 14 to 92 (M = 48.4 years) were selected by the random-route sampling method. The ultra-short questionnaire version was derived from the long version through item and factor analyses. In a confirmatory factor analysis framework, the hypothesized three-factorial structure was fitted to the empirical data and tested for measurement invariance, differential item functioning, item discriminability, and convergent and discriminant factorial validity. Effects of gender or age were assessed using MANOVAs. Results The a-priori hypothesized model resulted in mostly adequate overall fit. Neither gender nor age group yielded considerable effects on the factor structure, but had small effects on means of raw score sums. Factorial validities could be confirmed. Scale sums are well-suited to rank respondents along the respective latent dimension. Conclusion The structure of the long version with the factors Rejection & Punishment, Emotional Warmth, and Control & Overprotection could be replicated for both father and mother items in the ultra-short screening version using confirmatory factor analyses. These results indicate that the ultra-short screening version is a time-saving and promising screening instrument for research settings and in individual counseling. However, the shortened scales do not necessarily represent the full spectrum covered by the full-scale dimensions. PMID:23134704
Habitat fragmentation and reproductive success: a structural equation modelling approach.
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 of habitat amount vs. habitat configuration in landscape ecology that may have bearing on biological conclusions. PMID:23550698
ERIC Educational Resources Information Center
Smith, Dennis W.; Lee, Jay T.; Colwell, Brian; Stevens-Manser, Stacey
2008-01-01
In response to the problem of adolescent smoking and limited appropriate cessation resources, this study examined the pattern and structure of the American Lung Association, Why Do You Smoke? (WDS) to determine its appropriateness for use in youth smoking cessation programs. The WDS is used to help smokers identify primary motivations for using…
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…
ERIC Educational Resources Information Center
Stoel, Reinoud D.; Garre, Francisca Galindo; Dolan, Conor; van den Wittenboer, Godfried
2006-01-01
The authors show how the use of inequality constraints on parameters in structural equation models may affect the distribution of the likelihood ratio test. Inequality constraints are implicitly used in the testing of commonly applied structural equation models, such as the common factor model, the autoregressive model, and the latent growth…
Progress in Integrated Fluid/Structure/Controls Computations Using High Fidelity Equations
NASA Technical Reports Server (NTRS)
Guruswamy, Guru P.; VanDalsem, William R. (Technical Monitor)
1995-01-01
Aeroelasticity that 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 aircraft which can experience complex flow/structure interactions. Supersonic transports can experience vortex induced aeroelastic oscillations whereas subsonic transports 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. Using these high fidelity methods, design quantities such as structural stresses can be directly computed. Computations using these high fidelity equations require state-of-the-art large computational resources. This paper will describe the transition from potential equations to Euler/Navier-Stokes equations for fluids and from modal equations to finite element equations for structures. Complexities associated with grids for moving control surfaces will be discussed. All contents of the paper will be limited to those already presented at domestic conferences within U.S. such as those sponsored by AIAA. It will not include any materials related to HPCCP computational work.
An EM Algorithm for Fitting Two-Level Structural Equation Models
ERIC Educational Resources Information Center
Liang, Jiajuan; Bentler, Peter M.
2004-01-01
Maximum likelihood is an important approach to analysis of two-level structural equation models. Different algorithms for this purpose have been available in the literature. In this paper, we present a new formulation of two-level structural equation models and develop an EM algorithm for fitting this formulation. This new formulation covers a…
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…
System Characteristics, Satisfaction and E-Learning Usage: A Structural Equation Model (SEM)
ERIC Educational Resources Information Center
Ramayah, T.; Lee, Jason Wai Chow
2012-01-01
With the advent of the Internet, more and more public universities in Malaysia are putting in effort to introduce e-learning in their respective universities. Using a structured questionnaire derived from the literature, data was collected from 250 undergraduate students from a public university in Penang, Malaysia. Data was analyzed using AMOS…
Fixed- and random-effects meta-analytic structural equation modeling: examples and analyses in R.
Cheung, Mike W-L
2014-03-01
Meta-analytic structural equation modeling (MASEM) combines the ideas of meta-analysis and structural equation modeling for the purpose of synthesizing correlation or covariance matrices and fitting structural equation models on the pooled correlation or covariance matrix. Cheung and Chan (Psychological Methods 10:40-64, 2005b, Structural Equation Modeling 16:28-53, 2009) proposed a two-stage structural equation modeling (TSSEM) approach to conducting MASEM that was based on a fixed-effects model by assuming that all studies have the same population correlation or covariance matrices. The main objective of this article is to extend the TSSEM approach to a random-effects model by the inclusion of study-specific random effects. Another objective is to demonstrate the procedures with two examples using the metaSEM package implemented in the R statistical environment. Issues related to and future directions for MASEM are discussed. PMID:23807765
Chan, Raymond C K; Qing, Yonghong; Wu, Qiuping; Shum, David
2010-06-01
This study aimed to examine the latent structure of the Chinese version of the Comprehensive Assessment of Prospective Memory (CAPM) using confirmatory factor analysis. A total of 264 healthy Chinese participants (118 men and 146 women) took part in the study and their ages ranged from 17 to 90 years. There was no gender effect upon the frequency of prospective memory (PM) forgetting but age and education were found to be correlated significantly with these frequencies in the current sample. Results of the study also showed that the model with the best fit had a tripartite structure which consisted of a general memory factor (with all items loading on it) plus a basic activities of daily living as well as an instrumental activities of daily living factor. Furthermore, this tripartite model was robust across subgroups with respect to gender, education, and age. These findings provide support for the construct validity of the original CAPM and demonstrate its utility in another culture. PMID:20155572
Development and Validation of the Cognitive Behavioral Physical Activity Questionnaire.
Schembre, Susan M; Durand, Casey P; Blissmer, Bryan J; Greene, Geoffrey W
2014-08-27
Abstract Purpose . Develop and demonstrate preliminary validation of a brief questionnaire aimed at assessing social cognitive determinants of physical activity (PA) in a college population. Design . Quantitative and observational. Setting . A midsized northeastern university. Subjects . Convenience sample of 827 male and female college students age 18 to 24 years. Measures . International Physical Activity Questionnaire and a PA stage-of-change algorithm. Analysis . A sequential process of survey development, including item generation and data reduction analyses by factor analysis, was followed with the goal of creating a parsimonious questionnaire. Structural equation modeling was used for confirmatory factor analysis and construct validation was confirmed against self-reported PA and stage of change. Validation analyses were replicated in a second, independent sample of 1032 college students. Results . Fifteen items reflecting PA self-regulation, outcome expectations, and personal barriers explained 65% of the questionnaire data and explained 28.6% and 39.5% of the variance in total PA and moderate-to-vigorous-intensity PA, respectively. Scale scores were distinguishable across the stages of change. Findings were similar when the Cognitive Behavioral Physical Activity Questionnaire (CBPAQ) was tested in a similar and independent sample of college students (40%; R(2) moderate-to-vigorous-intensity PA = .40; p < .001). Conclusion . The CBPAQ successfully explains and predicts PA behavior in a college population, warranting its incorporation into future studies aiming at understanding and improving on PA behavior in college students. PMID:25162324
Pukrop, R; Gentil, I; Steinbring, I; Steinmeyer, E
2001-10-01
The Dimensional Assessment of Personality Pathology-Basic Questionnaire (DAPP-BQ) assesses 18 traits to provide a systematic representation of the overall domain of personality disorders. We tested the cross-cultural stability of the prediction that four higher-order factors (Emotional Dysregulation, Dissocial Behavior, Inhibitedness, and Compulsivity) underlie the 18 basic traits. A total of 81 patients who were primarily treated for an Axis II personality disorder and N = 166 healthy control patients completed the German version of the DAPP-BQ. Results clearly confirmed cross-cultural stability of the postulated four-factor structure in both samples, accounting for 74.7% (clinical sample), and 65.7% (nonclinical sample) of the total variance. All four higher-order factors showed specific correlational relationships with dimensional assessments of DSM-IV personality disorders. PMID:11723879
John, Ime A; Lawoko, Stephen
2010-01-01
Abstract: Background: There has been increased advocacy to involve healthcare providers in the prevention of intimate partner violence (IPV) through screening for it in healthcare. Yet, only one in ten providers screen for IPV, suggesting barriers. Understanding the readiness of healthcare providers to screen for IPV is therefore paramount. The Domestic Violence Healthcare Provider Survey Scales (DVHPSS) is a previously validated, comprehensive scale to study readiness of healthcare providers to screen for IPV. However, an understanding of its usefulness in the Sub-Saharan African context remains elusive. The current study undertook to examine the structural validity of the DVHPSS in Nigeria. Methods: Exploratory factor analysis and Cronbach's Alpha were run to reveal the factorial structure and reliability of the instrument/subscales respectively. Established thresholds were used to determine significant factor loadings and alphas coefficient. Results: A six factor model emerged, with 2 factors similar to the original scale, another two differing slightly and a further two factors resulting from a splitting up of the original combination of victim/provider safety to having distinct victim and provider safety subscales. Conclusions: With slight modifications, the DVHPSS can be use to study IPV screening among Nigerian healthcare professionals. Introducing screening protocols could promote better understanding of crucial questions that were lost in the analysis. PMID:21483202
Hamiltonian structure of propagation equations for ultrashort optical pulses
Amiranashvili, Sh.; Demircan, A. [Weierstrass Institute for Applied Analysis and Stochastics, Mohrenstrasse 39, D-10117 Berlin (Germany)
2010-07-15
A Hamiltonian framework is developed for a sequence of ultrashort optical pulses propagating in a nonlinear dispersive medium. To this end a second-order nonlinear wave equation for the electric field is transformed into a first-order propagation equation for a suitably defined complex electric field. The Hamiltonian formulation is then introduced in terms of normal variables, i.e., classical complex fields referring to the quantum creation and annihilation operators. The derived z-propagated Hamiltonian accounts for forward and backward waves, arbitrary medium dispersion, and four-wave mixing processes. As a simple application we obtain integrals of motion for the pulse propagation. The integrals reflect time-averaged fluxes of energy, momentum, and photons transferred by the pulse. Furthermore, pulses in the form of stationary nonlinear waves are considered. They yield extremal values of the momentum flux for a given energy flux. Simplified propagation equations are obtained by reduction of the Hamiltonian. In particular, the complex electric field reduces to an analytic signal for the unidirectional propagation. Solutions of the full bidirectional model are numerically compared to the predictions of the simplified equation for the analytic signal and to the so-called forward Maxwell equation. The numerics is effectively tested by examining the conservation laws.
2014-01-01
Background This study aimed to clarify how community mental healthcare systems can be improved. Methods We included 79 schizophrenic patients, aged 20 to 80 years, residing in the Tokyo metropolitan area who regularly visited rehabilitation facilities offering assistance to psychiatric patients and were receiving treatment on an outpatient basis. No subjects had severe cognitive disorders or were taking medication with side effects that could prevent the completion of questionnaires. Questionnaires included items related to quality of life, self-efficacy, self-esteem, psychosis based on the Behavior and Symptom Identification Scale, health locus of control, and socio-demographic factors. We performed multiple linear regression analysis with quality of life as the dependent variable and, based on covariance structural analysis, evaluated the goodness of fit of the resulting structural equations models. Results Self-efficacy, self-esteem, and degree of psychosis significantly impacted quality of life. Marital status, age, and types of medications also influenced quality of life. Multiple linear regression analysis revealed psychiatric symptoms (Behavior and Symptom Identification Scale-32 [daily living and role functioning] (Beta?=??0.537, p?structural analysis, the resulting model was found to exhibit reasonable goodness of fit. Conclusions Self-efficacy had an especially strong and direct impact on QOL. Therefore, it is important to provide more positive feedback to patients, provide social skills training based on cognitive behavioral therapy, and engage patients in role playing to improve self-efficacy and self-concept. PMID:25101143
Solving Differential Equations in Developmental Models of Multicellular Structures Expressed
Prusinkiewicz, Przemyslaw
Anabaena. Reference P. Federl and P. Prusinkiewicz: Solving differential equations in developmental models with a developmental model of the multicellular bacterium Anabaena. 1 Introduction Recent advances in genetics have solution by revisiting the diffusion-based developmental model of the blue-green alga Anabaena catenula [1
On the coherent structures of the Nizhnik-Novikov-Veselov equation
NASA Astrophysics Data System (ADS)
Lou, Sen-yue
2000-11-01
A variable separation approach is used to obtain exact solutions of high-dimensional nonlinear physical models. Taking the Nizhnik-Novikov-Veselov (NNV) equation as a simple example, we show that a high-dimensional nonlinear physical model may have quite rich localized coherent structures. For the NNV equation, the richness of the localized structures caused by the entrance of two variable-separated arbitrary functions. For some special selections of the arbitrary functions, it is shown that the localized structures of the NNV equation may be dromions, lumps, breathers, instantons and ring solitons, etc.
F. Quesada Pereira; J. L. Gomez Tornero; D. Cañete Rebenaque; J. Pascual Garcia; A. Alvarez Melcon
2005-01-01
An efficient numerical implementation of the integral equation technique (IE) has been developed for the analysis of the electrical characteristics of finite microstrip structures. The technique formulates a volume version of the IE for the finite dielectric objects and a standard surface IE technique for the metallic areas. The system of integral equations formulated is solved with special numerical techniques
Incompatibility of the Shuttleworth equation with Hermann’s mathematical structure of thermodynamics
NASA Astrophysics Data System (ADS)
Bottomley, D. J.; Makkonen, Lasse; Kolari, Kari
2009-01-01
We show that three independent derivations of the Shuttleworth equation, arguably the second most important equation in surface physics, are inconsistent with Hermann's mathematical structure of thermodynamics [R. Hermann, Geometry, Physics and Systems, Marcel Dekker Inc., New York, USA, 1973 (Chapter 6)]. The possible implications of this result are discussed.
Parabolic Equations of a Quasi-Homogeneous Structure
Samuil D. Eidelman; Anatoly N. Kochubei; Stepan D. Ivasyshen
\\u000a We start from the case of a 2®<\\/font\\u000a>b\\u000a\\\\overrightarrow {2b}\\u000a-parabolic equation of the form (1.1.10), of the first order with respect to the variable t, with bounded coefficients, that\\u000a is the equation \\u000a \\u000a \\u000a\\u000a\\u000a\\u000a\\u000a\\u000aLN (t,x,¶<\\/font\\u000a>t ,¶<\\/font\\u000a>x )u(t,x): = ( I¶<\\/font\\u000a>t -<\\/font\\u000a> å<\\/font\\u000a>||<\\/font\\u000a> k ||<\\/font\\u000a> \\\\leqslant 2b ak (t,x)¶<\\/font\\u000a>xk )u(t,x) = f(t,x),
Bringing It All Together: Modeling Intervention Processes Using Structural Equation Modeling.
ERIC Educational Resources Information Center
Hennessy, Michael; Greenberg, Judith
1999-01-01
Describes the integration of programmatic theory and structural equation modeling to serve as the basic intellectual machinery for designing and evaluating behavioral interventions. Illustrates this integration with the example of a program to reduce sexual risk taking. (SLD)
Non-standard Construction of Hamiltonian Structures and of the Hamilton-Jacobi equation
M. Herrera; S. A. Hojman
2000-08-10
Examples of non-standard construction of Hamiltonian structures for dynamical systems and the respective Hamilton-Jacobi (H-J) equations, without using Lagrangians, are presented. Alternative H-J equations for Euler top are explicitly exhibited and solved. We demonstrate that some stability criterion, relating the slope of a Casimir function parametrized by the Lagrange multiplier to critical point type, depends on the used Hamiltonian structure and it is inadequate for this reason.
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.
On the coherent structures of the Nizhnik-Novikov-Veselov equation
S.-y. Lou
2000-01-01
A variable separation approach is used to obtain exact solutions of high-dimensional nonlinear physical models. Taking the Nizhnik-Novikov-Veselov (NNV) equation as a simple example, we show that a high-dimensional nonlinear physical model may have quite rich localized coherent structures. For the NNV equation, the richness of the localized structures caused by the entrance of two variable-separated arbitrary functions. For some
On the coherent structures of the Nizhnik–Novikov–Veselov equation
Sen-yue Lou
2000-01-01
A variable separation approach is used to obtain exact solutions of high-dimensional nonlinear physical models. Taking the Nizhnik–Novikov–Veselov (NNV) equation as a simple example, we show that a high-dimensional nonlinear physical model may have quite rich localized coherent structures. For the NNV equation, the richness of the localized structures caused by the entrance of two variable-separated arbitrary functions. For some
PTSD QUESTIONNAIRE Participant's Name _____________________________________
New Mexico, University of
PTSD QUESTIONNAIRE Participant's Name _____________________________________ Instructions a bit Extremely 1. Repeated, disturbing memories, thoughts, or images of a stressful military experience from the past? 2. Repeated disturbing dreams of a stressful military experience from the past? 3
Basics of Developing Questionnaires
NSDL National Science Digital Library
Carter McNamara
Whether developing questions for questionnaires or interviews or focus groups, there are certain guidelines that help to ensure that respondents provide information that is useful and can later be analyzed. This resource offers advice on developing questions for interviews or focus groups. It contains basics conducting the interviews, providing directions to respondents as well as guidelines for composing the content and wording of the questionnaire. This resource is aimed for use in workshops/conferences and is intended for novice evaluators.
Exploiting chordal structure in systems of polynomial equations
Cifuentes Pardo, Diego Fernando
2014-01-01
Chordal structure and bounded treewidth allow for efficient computation in linear algebra, graphical models, constraint satisfaction and many other areas. Nevertheless, it has not been studied whether chordality might also ...
Age-structured Trait Substitution Sequence Process and Canonical Equation
Sylvie Méléard; Viet Chi Tran
2007-01-01
We are interested in a stochastic model of trait and age-structured population undergoing mutation and selection. We start with a continuous time, discrete individual-centered population process. Taking the large population and rare mutations limits under a well-chosen time-scale separation condition, we obtain a jump process that generalizes the Trait Substitution Sequence process describing Adaptive Dynamics for populations without age structure.
R-Matrices and Hamiltonian Structures for Certain Lax Equations
NASA Astrophysics Data System (ADS)
Wu, Chao-Zhong
2013-04-01
In this paper a list of R-matrices on a certain coupled Lie algebra is obtained. With one of these R-matrices, we construct infinitely many bi-Hamiltonian structures for each of the two-component BKP and the Toda lattice hierarchies. We also show that, when such two hierarchies are reduced to their subhierarchies, these bi-Hamiltonian structures are reduced correspondingly.
Inverse diffraction grating of Maxwell's equations in biperiodic structures.
Bao, Gang; Cui, Tao; Li, Peijun
2014-02-24
Consider a time-harmonic electromagnetic plane wave incident on a perfectly conducting biperiodic surface (crossed grating). The diffraction is modeled as a boundary value problem for the three-dimensional Maxwell equation. The surface is assumed to be a small and smooth deformation of a planar surface. In this paper, a novel approach is developed to solve the inverse diffraction grating problem in the near-field regime, which is to reconstruct the surface with resolution beyond Rayleigh's criterion. The method requires only a single incident field with one polarization, one frequency, and one incident direction, and is realized by using the fast Fourier transform. Numerical results show that the method is simple, efficient, and stable to reconstruct biperiodic surfaces with subwavelength resolution. PMID:24663798
Analysis of particular phononic structures using single integral equations
Fadoulourahmane Seydou; Ramani Duraiswami; Nail A. Gumerov
2003-01-01
A fast method for determining phononic (and photonic) bandgaps in composite materials is developed. It is known that in the propagation of waves in a 3D medium containing N scatterers arranged periodically, there exist refractive indices for which such structures have bandgaps, i.e., frequencies for which no waves can propagate inside. Our task is to find the frequencies that generate
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…
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…
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…
Risto Rajala; Mika Westerlund
2010-01-01
The paper presents a hierarchical construct PLS structural equation model to analyze mobile advertisement acceptance. Hypotheses are established and tested about the hierarchical structure and the effects of the factors that precede consumers' behavioral intention to accept mobile advertisement. The results suggest that valuable content and trust in advertisers are key predictors of mobile device users' acceptance of mobile advertising.
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…
Electromagnetic wave propagation in periodic structures: Bloch wave solution of Maxwell's equations
Ze Zhang; Sashi Satpathy
1990-01-01
We examine the propagation of electromagnetic waves in periodic dielectric structures by solving the vector Maxwell equations with the plane-wave method. Contrary to experimental reports, as well as results of scalar-wave calculations, we do not find a true gap extending throughout the Brillouin zone in the fcc structure. However, there is a depletion in the photon density of states, seemingly
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,…
Magnetic Fields and Large Scale Structure in a hot Universe. I. General Equations
E. Battaner; E. Florido; J. Jimenez-Vicente
1997-10-06
We consider that no mean magnetic field exists during this epoch, but that there is a mean magnetic energy associated with large-scale magnetic inhomogeneities. We study the evolution of these inhomogeneities and their influence on the large scale density structure, by introducing linear perturbations in Maxwell equations, the conservation of momentum-energy equation, and in Einstein field equations. The primordial magnetic field structure is time independent in the linear approximation, only being diluted by the general expansion, so that $\\vec{B}R^2$ is conserved in comoving coordinates. Magnetic fields have a strong influence on the formation of large-scale structure. Firstly, relatively low fields are able to generate density structures even if they were inexistent at earlier times. Second, magnetic fields act anisotropically more recently, modifying the evolution of individual density clouds. Magnetic flux tubes have a tendency to concentrate photons in filamentary patterns.
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.
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
McGuire, Brian E.; Morrison, Todd G.; Barker, Lynne A.; Morton, Nicholas; McBrinn, Judith; Caldwell, Sheena; Wilson, Colin F.; McCann, John; Carton, Simone; Delargy, Mark; Walsh, Jane
2014-01-01
Aims: This study sought to address two questions: (1) what is the inter-rater reliability of the Dysexecutive Questionnaire (DEX) when completed by patients, their significant others, and clinicians; and (2) does the factor structure of the DEX vary for these three groups? Methods: We obtained DEX ratings for 113 patients with an acquired brain injury from two brain injury services in the UK and two services in Ireland. We gathered data from two groups of raters—“significant others” (DEX-SO) such as partners and close family members and “clinicians” (DEX-C), who were psychologists or rehabilitation physicians working closely with the patient and who were able to provide an opinion about the patient’s level of everyday executive functioning. Intra-class correlation coefficients and their 95% confidence intervals were calculated between each of the three groups (self, significant other, clinician). Principal axis factor (PAF) analyses were also conducted for each of the three groups. Results: The factor analysis revealed a consistent one-factor model for each of the three groups of raters. However, the inter-rater reliability analyses showed a low level of agreement between the self-ratings and the ratings of the two groups of independent raters. We also found low agreement between the significant others and the clinicians. Conclusion: Although there was a consistent finding of a single factor solution for each of the three groups, the low level of agreement between significant others and clinicians raises a question about the reliability of the DEX. PMID:25346668
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.
Testing strong factorial invariance using three-level structural equation modeling
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
NATIONAL INSTITUTES OF HEALTH Diet History Questionnaire Today's date: MONTH DAY YEAR |___|___| 0 0 1 1 2 2 3 3 4 5 6 7 8 01 Jan 02 Feb 03 Mar 04 Apr 05 May 06 Jun 07 Jul 08 Aug 09 Sep 10 Oct 11 Nov 12
Questionnaire typography and production.
Gray, M
1975-06-01
This article describes the typographic principles and practice which provide the basis of good design and print, the relevant printing processes which can be used, and the graphic designer's function in questionnaire production. As they impose constraints on design decisions to be discussed later in the text, the various methods of printing and production are discussed first. PMID:15677172
The Depression Coping Questionnaire.
ERIC Educational Resources Information Center
Kleinke, Chris L.
College students (N=396), chronic pain patients (N=319), and schizophrenic veterans (N=43) completed the Depression Coping Questionnaire (DCQ) and the Beck Depression Inventory (BDI). Factor analysis of the DCQ identified eleven coping responses: social support, problem solving, self-blame/escape, aggression, indulgence, activities, medication,…
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.
NASA Astrophysics Data System (ADS)
Velayutham, Sunitadevi; Aldridge, Jill M.
2013-04-01
The primary aim of this study was two-fold: 1) to identify salient psychosocial features of the classroom environment that influence students' motivation and self-regulation in science learning; and 2) to examine the effect of the motivational constructs of learning goal orientation, science task value and self-efficacy in science learning on students' self-regulation in science classrooms. Data collected from 1360 science students in grades 8, 9 and 10 in five public schools in Perth, Western Australia were utilized to validate the questionnaires and to investigate the hypothesized relationships. Structural Equation Modeling analysis suggested that student cohesiveness, investigation and task orientation were the most influential predictors of student motivation and self-regulation in science learning. In addition, learning goal orientation, task value and self-efficacy significantly influenced students' self-regulation in science. The findings offer potential opportunities for educators to plan and implement effective pedagogical strategies aimed at increasing students' motivation and self-regulation in science learning.
Biological fitness and the Price Equation in class-structured populations.
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
Thermodynamics and structure of a two-dimensional electrolyte by integral equation theory
Aupic, Jana; Urbic, Tomaz, E-mail: tomaz.urbic@fkkt.uni-lj.si [Faculty of Chemistry and Chemical Technology, University of Ljubljana, Ašker?eva 5, SI-1000 Ljubljana (Slovenia)] [Faculty of Chemistry and Chemical Technology, University of Ljubljana, Ašker?eva 5, SI-1000 Ljubljana (Slovenia)
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.
ERIC Educational Resources Information Center
Yeh, Yu-Chen; Lin, Sunny S. J.; Tseng, Yin-Hsing; Hwang, Fang-Ming
2012-01-01
This study constructed a questionnaire, named "Lifestyle Change in Regard to Problematic Internet Use (LC-PIU)," for helping school psychologists detect early indications of PIU-related lifestyle changes in university populations. Our focus is on all university students who use the Internet, not users who already show dependent symptoms. The…
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."
Questioning Newton's second law: What is the structure of equations of motion?
Claus Lämmerzahl; Patricia Rademaker
2009-04-30
Interactions are explored through the observation of the dynamics of particles. On the classical level the basic underlying assumption in that scheme is that Newton's second law holds. Relaxing the validity of this axiom by, e.g., allowing for higher order time derivatives in the equations of motion would allow for a more general structure of interactions. We derive the structure of interactions by means of a gauge principle and discuss the physics emerging from equations of motion of higher order. One main result is higher order derivatives induce a zitterbewegung. As a consequence the main motion resulting from the second order equation of motion is rather robust against modifications. The gauge principle leads to a gauge field with the property of a space metric. We confront this general scheme with experimental data.
Questioning Newton's second law: What is the structure of equations of motion?
Lämmerzahl, Claus
2009-01-01
Interactions are explored through the observation of the dynamics of particles. On the classical level the basic underlying assumption in that scheme is that Newton's second law holds. Relaxing the validity of this axiom by, e.g., allowing for higher order time derivatives in the equations of motion would allow for a more general structure of interactions. We derive the structure of interactions by means of a gauge principle and discuss the physics emerging from equations of motion of higher order. One main result is higher order derivatives induce a zitterbewegung. As a consequence the main motion resulting from the second order equation of motion is rather robust against modifications. The gauge principle leads to a gauge field with the property of a space metric. We confront this general scheme with experimental data.
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.
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…
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…
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…
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…
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…
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…
Eight Myths About Causality and Structural Equation Kenneth A. Bollen and Judea Pearl
California at Los Angeles, University of
Chapter 15 Eight Myths About Causality and Structural Equation Models Kenneth A. Bollen and Judea accumulated. A variety of misunderstandings and myths about the nature of SEMs and their role in causal by presenting eight myths about causality and SEMs in the hope that this will lead to a more accurate
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…
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,…
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…
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…
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…
ERIC Educational Resources Information Center
Macho, Siegfried; Ledermann, Thomas
2011-01-01
The phantom model approach for estimating, testing, and comparing specific effects within structural equation models (SEMs) is presented. The rationale underlying this novel method consists in representing the specific effect to be assessed as a total effect within a separate latent variable model, the phantom model that is added to the main…
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…
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…
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…
Hypothesis Testing and Model Comparison in Two-Level Structural Equation Models.
ERIC Educational Resources Information Center
Lee, Sik-Yum; Song, Xin-Yuan
2001-01-01
Demonstrates the use of the well-known Bayes factor in the Bayesian literature for hypothesis testing and model comparison in general two-level structural equation models. Shows that the proposed method is flexible and can be applied to situations with a wide variety of nonnested models. (SLD)
Gary K. Leak; Laura L. Finken
2011-01-01
Research examining the connection between religiousness and prejudice has used scales exclusively as proxies for the underlying constructs. Scholars in the psychology of religion, however, are ultimately concerned about the nature of religious constructs and their relationships with other variables, and the use of scales provides only indirect information concerning these constructs. To overcome this limitation, structural equation modeling (SEM)
Testing a Structural Equation Model of Partnership Program Implementation and Parent Involvement
ERIC Educational Resources Information Center
Sheldon, Steven B.
2005-01-01
Structural equation modeling was used to test a model of the relations between the implementation and results of programs of school, family, and community partnerships in elementary schools. The model included school demographic measures, key elements of school organization and processes, partnership program quality, and parent involvement. Data…
NONLINEAR WAVE EQUATIONS ARISING IN MODELING OF SOME STRAIN-HARDENING STRUCTURES
Wei, Dongming
strain theory. The examples include some rods and Euler-type beams in the form of a single stainlessNONLINEAR WAVE EQUATIONS ARISING IN MODELING OF SOME STRAIN-HARDENING STRUCTURES DONGMING WEI of heat treated metals that satisfy the power-law stress- strain relationship in the framework of small
Implications of Recent Developments in Structural Equation Modeling for Counseling Psychology.
ERIC Educational Resources Information Center
Quintana, Stephen M.; Maxwell, Scott E.
1999-01-01
Reviews recent developments in structural equation modeling (SEM). Discusses issues critical to designing and evaluating SEM studies and recent technological developments. Examines innovations in applying SEM to different research contexts and designs. Also discusses procedures for redressing common problems and misunderstandings in the…
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…
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…
David A. Caughey
2005-01-01
The efficient symmetric Gauss-Seidel (SGS) algorithm for solving the Euler equations of inviscid, compressible flow on structured grids, developed in collaboration with Jameson of Stanford University, is extended to unstructured grids. The algorithm uses a nonlinear formulation of an SGS solver, implemented within the framework of multigrid. The earlier form of the algorithm used the natural (lexicographic) ordering of the
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…
A PROBABILISTIC APPROACH FOR EVALUATING THE SENSITIVITY TO FAKE DATA IN STRUCTURAL EQUATION MODELING
Luigi Lombardi; Massimiliano Pastore
2009-01-01
In this paper we address the issue of evaluating the sensitivity of goodness-of-fit indices in structural equation modeling when fake data are considered in three different factorial models with vary- ing sample sizes (n= 50, 100 and 200). The sensitivity evaluation is carried out by means of a simulation procedure which combines a standard Monte Carlo approach and a new
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…
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…
12?Structural Equation Modeling in Management Research: A Guide for Improved Analysis
Larry J. Williams; Robert J. Vandenberg; Jeffrey R. Edwards
2009-01-01
A large segment of management research in recent years has used structural equation modeling (SEM) as an analytical approach that simultaneously combines factor analysis and linear regression models for theory testing. With this approach, latent variables (factors) represent the concepts of a theory, and data from measures (indicators) are used as input for statistical analyses that provide evidence about the
Level-Specific Evaluation of Model Fit in Multilevel Structural Equation Modeling
ERIC Educational Resources Information Center
Ryu, Ehri; West, Stephen G.
2009-01-01
In multilevel structural equation modeling, the "standard" approach to evaluating the goodness of model fit has a potential limitation in detecting the lack of fit at the higher level. Level-specific model fit evaluation can address this limitation and is more informative in locating the source of lack of model fit. We proposed level-specific test…
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…
Approximations to the Distributions of Fit Indexes for Misspecified Structural Equation Models.
ERIC Educational Resources Information Center
Ogasawara, Haruhiko
2001-01-01
Derives approximations to the distributions of goodness-of-fit indexes in structural equation modeling with the assumption of multivariate normality and slight misspecification of models. Also derives an approximation to the asymptotic covariance matrix for the fit indexes by using the delta method and develops approximations to the densities of…
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…
Standards-Based Evaluation and Teacher Career Satisfaction: A Structural Equation Modeling Analysis
ERIC Educational Resources Information Center
Conley, Sharon; Muncey, Donna E.; You, Sukkyung
2005-01-01
Structural equation modeling was used to assess the plausibility of a conceptual model specifying hypothesized linkages among perceptions of characteristics of standards-based evaluation, work environment mediators, and career satisfaction and other outcomes. Four comprehensive high schools located in two neighboring counties in southern…
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.…
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…
Equivalence and Differences between Structural Equation Modeling and State-Space Modeling Techniques
ERIC Educational Resources Information Center
Chow, Sy-Miin; Ho, Moon-ho R.; Hamaker, Ellen L.; Dolan, Conor V.
2010-01-01
State-space modeling techniques have been compared to structural equation modeling (SEM) techniques in various contexts but their unique strengths have often been overshadowed by their similarities to SEM. In this article, we provide a comprehensive discussion of these 2 approaches' similarities and differences through analytic comparisons and…
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…
ERIC Educational Resources Information Center
Lee, Sik-Yum; Song, Xin-Yuan; Tang, Nian-Sheng
2007-01-01
The analysis of interaction among latent variables has received much attention. This article introduces a Bayesian approach to analyze a general structural equation model that accommodates the general nonlinear terms of latent variables and covariates. This approach produces a Bayesian estimate that has the same statistical optimal properties as a…
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…
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…
Juline Elaine Mills
2002-01-01
The objective of this research was to develop a survey instrument and structural equation model of customer satisfaction (e-satisfaction) with travel Websites. The study proposed that customer satisfaction with a travel Website is determined by the customer's experience at the travel Website. Customer experience at the travel Website is in turn a function of three higher-order constructs, travel Website interface,
Evaluating Small Sample Approaches for Model Test Statistics in Structural Equation Modeling
ERIC Educational Resources Information Center
Nevitt, Jonathan; Hancock, Gregory R.
2004-01-01
Through Monte Carlo simulation, small sample methods for evaluating overall data-model fit in structural equation modeling were explored. Type I error behavior and power were examined using maximum likelihood (ML), Satorra-Bentler scaled and adjusted (SB; Satorra & Bentler, 1988, 1994), residual-based (Browne, 1984), and asymptotically…
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.…
An Assessment of the Use of Partial Least Squares Structural Equation Modeling in Marketing Research
Joe F. Hair; Marko Sarstedt; Christian M. Ringle; Jeannette A. Mena
2012-01-01
Most methodological fields undertake regular critical reflections to ensure rigorous research and publication practices, and, consequently, acceptance in their domain. Interestingly, relatively little attention has been paid to assessing the use of partial least squares structural equation modeling (PLS-SEM) in marketing research?despite its increasing popularity in recent years. To fill this gap, we conducted an extensive search in the 30
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…
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…
Women's Path into Science and Engineering Majors: A Structural Equation Model
ERIC Educational Resources Information Center
Camp, Amanda G.; Gilleland, Diane; Pearson, Carolyn; Vander Putten, Jim
2009-01-01
The intent of this study was to investigate the adequacy of Weidman's (1985, 1989) theoretical undergraduate socialization model as an empirical-based causal model pertaining to women's career path choice into a science or engineering (SE) major via structural equation modeling. Data were obtained from the Beginning Postsecondary Students…
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…
N. H. Tenneij; Chris K. W. Schotte; Damiaan A. J. P. Denys; Megen van H. J. G. M; Herman G. M. Westenberg
2003-01-01
In patients with obsessive-compulsive disorder, personality disorders are not many times assessed according to DSM-IV criteria. The purpose of the present study is to examine the prevalence of personality disorders diagnosed according to the DSM-IV in a severely disordered OCD popula- tion (n = 65) with three different methods of assessing personality disor- ders (structured interview, questionnaire, and clinical diagnoses).
Tooze, Janet A; Troiano, Richard P; Carroll, Raymond J; Moshfegh, Alanna J; Freedman, Laurence S
2013-06-01
Systematic investigations into the structure of measurement error of physical activity questionnaires are lacking. We propose a measurement error model for a physical activity questionnaire that uses physical activity level (the ratio of total energy expenditure to basal energy expenditure) to relate questionnaire-based reports of physical activity level to true physical activity levels. The 1999-2006 National Health and Nutrition Examination Survey physical activity questionnaire was administered to 433 participants aged 40-69 years in the Observing Protein and Energy Nutrition (OPEN) Study (Maryland, 1999-2000). Valid estimates of participants' total energy expenditure were also available from doubly labeled water, and basal energy expenditure was estimated from an equation; the ratio of those measures estimated true physical activity level ("truth"). We present a measurement error model that accommodates the mixture of errors that arise from assuming a classical measurement error model for doubly labeled water and a Berkson error model for the equation used to estimate basal energy expenditure. The method was then applied to the OPEN Study. Correlations between the questionnaire-based physical activity level and truth were modest (r = 0.32-0.41); attenuation factors (0.43-0.73) indicate that the use of questionnaire-based physical activity level would lead to attenuated estimates of effect size. Results suggest that sample sizes for estimating relationships between physical activity level and disease should be inflated, and that regression calibration can be used to provide measurement error-adjusted estimates of relationships between physical activity and disease. PMID:23595007
Tooze, Janet A.; Troiano, Richard P.; Carroll, Raymond J.; Moshfegh, Alanna J.; Freedman, Laurence S.
2013-01-01
Systematic investigations into the structure of measurement error of physical activity questionnaires are lacking. We propose a measurement error model for a physical activity questionnaire that uses physical activity level (the ratio of total energy expenditure to basal energy expenditure) to relate questionnaire-based reports of physical activity level to true physical activity levels. The 1999–2006 National Health and Nutrition Examination Survey physical activity questionnaire was administered to 433 participants aged 40–69 years in the Observing Protein and Energy Nutrition (OPEN) Study (Maryland, 1999–2000). Valid estimates of participants’ total energy expenditure were also available from doubly labeled water, and basal energy expenditure was estimated from an equation; the ratio of those measures estimated true physical activity level (“truth”). We present a measurement error model that accommodates the mixture of errors that arise from assuming a classical measurement error model for doubly labeled water and a Berkson error model for the equation used to estimate basal energy expenditure. The method was then applied to the OPEN Study. Correlations between the questionnaire-based physical activity level and truth were modest (r = 0.32–0.41); attenuation factors (0.43–0.73) indicate that the use of questionnaire-based physical activity level would lead to attenuated estimates of effect size. Results suggest that sample sizes for estimating relationships between physical activity level and disease should be inflated, and that regression calibration can be used to provide measurement error–adjusted estimates of relationships between physical activity and disease. PMID:23595007
Regina J. Eisenbach
1995-01-01
Item wording effects were investigated using scenarios depicting a fictitious leader's behavior, 496 respondents, and a questionnaire containing regular, polar opposite, negated polar opposite, and negated regular item versions. Oblique-rotated exploratory factor-analytic results showed clear item wording factors; confirmatory factor-analytic results showed the item formats to yield separate wording factors but that the regular items had substantially more trait variance
Hamilton, Michael P.
Problem Description:Problem Description: Biotic and Abiotic Regulators of Soil RespirationBiotic and Abiotic Regulators of Soil Respiration Proposed Solution:Proposed Solution: Structural Equation Modeling: an Integrated ApproachStructural Equation Modeling: an Integrated Approach Understanding Soil Respiration: an
Developing Written Questionnaires: Determining if Questionnaires Should be Used
NSDL National Science Digital Library
Daniel R. Zalles
This module provides a strategy for determining whether a written questionnaire is an appropriate means of gathering data to meet the goals of an evaluation. The authors define which conditions are suitable for using questionnaires.
General features and master equations for structurization in complex dusty plasmas
Tsytovich, V. N., E-mail: tsytov@lpi.ru [Russian Academy of Science, General Physics Institute (Russian Federation); Morfill, G. E., E-mail: gem@mpe.mpg.de [Max Planck Institute for Extraterrestrial Physics (Germany)
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.
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.
Hamiltonian Structures and Integrability for a Discrete Coupled KdV-Type Equation Hierarchy
NASA Astrophysics Data System (ADS)
Zhao, Hai-Qiong; Zhu, Zuo-Nong; Zhang, Jing-Li
2011-05-01
Coupled Korteweg-de Vries (KdV) systems have many important physical applications. By considering a 4 × 4 spectral problem, we derive a discrete coupled KdV-type equation hierarchy. Our hierarchy includes the coupled Volterra system proposed by Lou et al. (e-print arXiv:0711.0420) as the first member which is a discrete version of the coupled KdV equation. We also investigate the integrability in the Liouville sense and the multi-Hamiltonian structures for the obtained hierarchy.
Asymptotics, structure, and integration of sound-proof atmospheric flow equations
Rupert Klein
2009-01-01
Relative to the full compressible flow equations, sound-proof models filter acoustic waves while maintaining advection and\\u000a internal waves. Two well-known sound-proof models, an anelastic model by Bannon and Durran’s pseudo-incompressible model,\\u000a are shown here to be structurally very close to the full compressible flow equations. Essentially, the anelastic model is\\u000a obtained by suppressing ?\\u000a t\\u000a \\u000a ? in the mass continuity
Integro-differential equations and the stability of neural networks with dendritic structure.
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
L. V. Laperashvili; H. B. Nielsen
1999-12-05
The quantum field theory describing electric and magnetic charges and revealing a dual symmetry was developed in the Zwanziger formalism. The renormalization group (RG) equations for both fine structure constants - electric $\\alpha$ and magnetic $\\tilde \\alpha$ - were obtained. It was shown that the Dirac relation is valid for the renormalized $\\alpha $ and $\\tilde \\alpha$ at the arbitrary scale, but these RG equations can be considered perturbatively only in the small region: $0.25 \\stackrel{<}{\\sim} \\alpha, \\tilde \\alpha \\stackrel{<}{\\sim} 1$ with $\\tilde \\alpha$ given by the Dirac relation: $\\alpha {\\tilde \\alpha}$ = 1/4.
Ovchinnikov, Yu. N., E-mail: ovc@itp.ac.ru [Max-Planck Institute for Physics of Complex Systems (Germany)
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.
A Finite-Volume Method for Nonlinear Nonlocal Equations with a Gradient Flow Structure
NASA Astrophysics Data System (ADS)
Carrillo, José A.; Chertock, Alina; Huang, Yanghong
2015-01-01
We propose a positivity preserving entropy decreasing finite volume scheme for nonlinear nonlocal equations with a gradient flow structure. These properties allow for accurate computations of stationary states and long-time asymptotics demonstrated by suitably chosen test cases in which these features of the scheme are essential. The proposed scheme is able to cope with non-smooth stationary states, different time scales including metastability, as well as concentrations and self-similar behavior induced by singular nonlocal kernels. We use the scheme to explore properties of these equations beyond their present theoretical knowledge.
Solution of quadratic matrix equations for free vibration analysis of structures.
NASA Technical Reports Server (NTRS)
Gupta, K. K.
1973-01-01
An efficient digital computer procedure and the related numerical algorithm are presented herein for the solution of quadratic matrix equations associated with free vibration analysis of structures. Such a procedure enables accurate and economical analysis of natural frequencies and associated modes of discretized structures. The numerically stable algorithm is based on the Sturm sequence method, which fully exploits the banded form of associated stiffness and mass matrices. The related computer program written in FORTRAN V for the JPL UNIVAC 1108 computer proves to be substantially more accurate and economical than other existing procedures of such analysis. Numerical examples are presented for two structures - a cantilever beam and a semicircular arch.
Wu, Jiun-Yu
2011-10-21
Conventional statistical methods assuming data sampled under simple random sampling are inadequate for use on complex survey data with a multilevel structure and non-independent observations. In structural equation modeling (SEM) framework, a...
The Toronto Empathy Questionnaire
Spreng, R. Nathan; McKinnon, Margaret C.; Mar, Raymond A.; Levine, Brian
2008-01-01
In order to formulate a parsimonious tool to assess empathy, we used factor analysis on a combination of self-report measures to examine consensus and developed a brief self-report measure of this common factor. The Toronto Empathy Questionnaire (TEQ) represents empathy as a primarily emotional process. In three studies, the TEQ demonstrated strong convergent validity, correlating positively with behavioral measures of social decoding, self-report measures of empathy, and negatively with a measure of Autism symptomatology. Moreover, it exhibited good internal consistency and high test-retest reliability. The TEQ is a brief, reliable, and valid instrument for the assessment of empathy. PMID:19085285
Questionnaire Translation and Questionnaire Validation: Are They the Same?
ERIC Educational Resources Information Center
Griffee, Dale T.
The purpose of this paper is to give evidence for the thesis that if teachers using a questionnaire as a data collection instrument have the questionnaire items translated from one language into another, they cannot assume that the translated items are valid simply because they were translated. Even if the original questionnaire items were…
Paris-Sud XI, Université de
Travelling waves in a nonlocal reaction-diffusion equation as a model for a population structured by a space variable and a phenotypical trait Matthieu Alfaro 1 , Jérôme Coville 2 and Gaël Raoul 3 . Abstract We consider a nonlocal reaction-diffusion equation as a model for a population structured by a space
ERIC Educational Resources Information Center
McCoach, D. Betsy
2003-01-01
Structural equation modeling (SEM) refers to a family of statistical techniques that explores the relationships among a set of variables. Structural equation modeling provides an extremely versatile method to model very specific hypotheses involving systems of variables, both measured and unmeasured. Researchers can use SEM to study patterns of…
Guides & Reports for Questionnaire Design
Applied Research Program (ARP) staff use a variety of methods to develop and test questionnaires, including established Questionnaire Design Principles, empirical methods such as Cognitive Testing and psychometric methods such as Item Response Theory Modeling.
Diet History Questionnaire: International Applications
ARP staff adapted the Diet History Questionnaire (DHQ) for use by Canadian populations in collaboration with the Alberta Cancer Board. This questionnaire takes into account the different food fortification polices of the US and Canada.
ATBC Study - Questionnaires and Forms
Skip to Main Content Home Contact Us Links Study Details Questionnaires & Forms Current Projects ATBC Study Bibliography Study Investigators & Collaborators Proposal Review & Collaboration Research Consortium Projects Questionnaires & Forms Baseline
The Claustrophobia Questionnaire.
Radomsky, A S; Rachman, S; Thordarson, D S; McIsaac, H K; Teachman, B A
2001-01-01
The content and psychometric properties of the Claustrophobia Questionnaire (CLQ) are described. An earlier version of the CLQ was developed to test the hypothesis that claustrophobia is comprised of two distinct but related fears--the fear of suffocation and the fear of restriction [J. Anxiety Disord. 7 (1993) 281.]. The scale was used to assess patients undergoing the magnetic resonance imaging (MRI) procedure [J. Behav. Med. 21 (1998) 255.] and in participants with panic disorder [J. Abnorm. Psychol. 105 (1996) 146; Taylor, S., Rachman, S., & Radomsky, A. S. (1996). The prediction of panic: a comparison of suffocation false alarm and cognitive theories. Unpublished data.]. On the basis of these studies, we decided to revise and shorten the CLQ, collect normative data, and provide information on the scale's predictive and discriminant validity as well as its internal consistency and test-retest reliability. This was done through a set of four interconnected studies that included psychometric analyses of undergraduate and community adult questionnaire responses and behavioural testing. Results indicate that the CLQ has good predictive and discriminant validity as well as good internal consistency and test-retest reliability. The CLQ appears to be a reliable and sensitive measure of claustrophobia and its component fears. We encourage the use of the CLQ in a variety of clinical and research applications. The scale is provided in this paper for public use. PMID:11474815
ERIC Educational Resources Information Center
Armey, Michael F.; Fresco, David M.; Moore, Michael T.; Mennin, Douglas S.; Turk, Cynthia L.; Heimberg, Richard G.; Kecmanovic, Jelena; Alloy, Lauren B.
2009-01-01
Depressive rumination, as assessed by Nolen-Hoeksema's Response Styles Questionnaire (RSQ), predicts the onset, chronicity, and duration of depressed mood. However, some RSQ items contain depressive content and result in a heterogeneous factor structure. After the a priori elimination of items potentially confounded with depressed item content,…
Global Bifurcation Structure and Parameter Dependence of the Hodgkin-Huxley Equations
NASA Astrophysics Data System (ADS)
Pan, Zhenxing; Doi, Shinji
The Hodgkin-Huxley (HH) equations of a squid giant axon are the most important mathematical model in electrophysiology and biology, and are also important in the development of various biologically inspired intelligent devices such as artificial neuron device and neural networks. The HH equations, however, include various constants or parameters whose values were determined based on physiological experiments, and thus the values possess inherent ambiguities. Also, the ‘constants’ are not really constant but change temporally. Thus, in this paper, we study the effects of the change of the constants or parameters on the dynamics of the HH equations and consider the parameter dependence and sensitivity of the equations; we study the bifurcation structure of the HH equations by changing their various parameters. In particular, we take the voltage-dependency of the dynamics of so-called gating variables as typical bifurcation parameters and show that the HH dynamics is very sensitive to the steady-state functions but not sensitive to the time ‘constants’ of gating variables.
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…
Quantum structure emerging from the transformation design of the Dirac equation
Lin, De-Hone, E-mail: dhlin@mail.nsysu.edu.tw
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.
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.
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.
NASA Astrophysics Data System (ADS)
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.
Liza S. Rovniak; Eileen S. Anderson; Richard A. Winett; Robert S. Stephens
2002-01-01
This study used a prospective design to test a model of the relation between social cognitive variables and physical activity\\u000a in a sample of 277 university students. Social support, self-efficacy, outcome expectations, and self-regulation were measured\\u000a at baseline and used to predict physical activity 8 weeks later. Results of structural equation modeling indicated a good\\u000a fit of the social cognitive
Implicit SUPG solution of Euler equations using edge-based data structures
Lucia Catabriga; Alvaro L. G. A. Coutinho
2002-01-01
In this work we present an implicit, edge-based implementation of the semi-discrete SUPG formulation with shock-capturing for the Euler equations in conservative variables. By disassembling the resulting finite element matrices into their edge contributions, sparse matrix coefficients, residuals and matrix-vector products needed in Krylov-update techniques are computed based on edge data structures. The resulting solution method requires less memory and
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.
Jennifer E. Johnson; Gary M. Burlingame; Joseph A. Olsen; D. Robert Davies; Robert L. Gleave
2005-01-01
This study examined the definitional and statistical overlap among 4 key group therapeutic relationship constructs—group climate, cohesion, alliance, and empathy—across member-member, member-group, and member-leader relationships. Three multilevel structural equation models were tested using self-report measures completed by 662 participants from 111 counseling center and personal growth groups. As hypothesized, almost all measures of therapeutic relationship were significantly correlated. Hypothesized 1-factor,
The Trauma Outcome Process Assessment Model: A Structural Equation Model Examination of Adjustment
Susan E. Borja; Jennifer L. Callahan
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 internalizing distress (e.g., anxiety, depression), externalizing distress (e.g., aggression), and recovery outcomes following traumatic events.
Estimation of health effects of prenatal methylmercury exposure using structural equation models
Budtz-Jørgensen, Esben; Keiding, Niels; Grandjean, Philippe; Weihe, Pal
2002-01-01
Background Observational studies in epidemiology always involve concerns regarding validity, especially measurement error, confounding, missing data, and other problems that may affect the study outcomes. Widely used standard statistical techniques, such as multiple regression analysis, may to some extent adjust for these shortcomings. However, structural equations may incorporate most of these considerations, thereby providing overall adjusted estimations of associations. This approach was used in a large epidemiological data set from a prospective study of developmental methyl-mercury toxicity. Results Structural equation models were developed for assessment of the association between biomarkers of prenatal mercury exposure and neuropsychological test scores in 7 year old children. Eleven neurobehavioral outcomes were grouped into motor function and verbally mediated function. Adjustment for local dependence and item bias was necessary for a satisfactory fit of the model, but had little impact on the estimated mercury effects. The mercury effect on the two latent neurobehavioral functions was similar to the strongest effects seen for individual test scores of motor function and verbal skills. Adjustment for contaminant exposure to poly chlorinated biphenyls (PCBs) changed the estimates only marginally, but the mercury effect could be reduced to non-significance by assuming a large measurement error for the PCB biomarker. Conclusions The structural equation analysis allows correction for measurement error in exposure variables, incorporation of multiple outcomes and incomplete cases. This approach therefore deserves to be applied more frequently in the analysis of complex epidemiological data sets. PMID:12513702
Cosmological structure formation under MOND: a new numerical solver for Poisson's equation
NASA Astrophysics Data System (ADS)
Llinares, Claudio; Knebe, Alexander; Zhao, Hongsheng
2008-12-01
We present a novel solver for an analogue to Poisson's equation in the framework of modified Newtonian dynamics (MOND). This equation is highly non-linear and hence standard codes based upon tree structures and/or fast Fourier transforms in general are not applicable; one needs to defer to multigrid relaxation techniques. After a detailed description of the necessary modifications to the cosmological N-body code AMIGA (formerly known as MLAPM) we utilize the new code to revisit the issue of cosmic structure formation under MOND. We find that the proper (numerical) integration of a MONDian Poisson's equation has some noticeable effects on the final results when compared against simulations of the same kind but based upon rather ad hoc assumptions about the properties of the MONDian force field. Namely, we find that the large-scale structure evolution is faster in our revised MOND model leading to an even stronger clustering of galaxies, especially when compared to the standard ? cold dark matter paradigm.
Ridge Structural Equation Modeling with Correlation Matrices for Ordinal and Continuous Data*
Yuan, Ke-Hai; Wu, Ruilin; Bentler, Peter M.
2011-01-01
This paper develops a ridge procedure for structural equation modeling (SEM) with ordinal and continuous data by modeling polychoric/polyserial/product-moment correlation matrix R. Rather than directly fitting R, the procedure fits a structural model to Ra = R + aI by minimizing the normal-distribution-based discrepancy function, where a > 0. Statistical properties of the parameter estimates are obtained. Four statistics for overall model evaluation are proposed. Empirical results indicate that the ridge procedure for SEM with ordinal data has better convergence rate, smaller bias, smaller mean square error and better overall model evaluation than the widely used maximum likelihood procedure. PMID:21506947
The quantum group, Harper equation and structure of Bloch eigenstates on a honeycomb lattice
NASA Astrophysics Data System (ADS)
Eliashvili, M.; Japaridze, G. I.; Tsitsishvili, G.
2012-10-01
The tight-binding model of quantum particles on a honeycomb lattice is investigated in the presence of a homogeneous magnetic field. Provided the magnetic flux per unit hexagon is a rational of the elementary flux, the one-particle Hamiltonian is expressed in terms of the generators of the quantum group Uq(sl2). Employing the functional representation of the quantum group Uq(sl2), the Harper equation is rewritten as a system of two coupled functional equations in the complex plane. For the special values of quasi-momentum, the entangled system admits solutions in terms of polynomials. The system is shown to exhibit a certain symmetry allowing us to resolve the entanglement, and a basic single equation determining the eigenvalues and eigenstates (polynomials) is obtained. Equations specifying the locations of the roots of polynomials in the complex plane are found. Employing numerical analysis, the roots of polynomials corresponding to different eigenstates are solved and diagrams exhibiting the ordered structure of one-particle eigenstates are depicted.
Subdiffusive master equation with space-dependent anomalous exponent and structural instability.
Fedotov, Sergei; Falconer, Steven
2012-03-01
We derive the fractional master equation with space-dependent anomalous exponent. We analyze the asymptotic behavior of the corresponding lattice model both analytically and by Monte Carlo simulation. We show that the subdiffusive fractional equations with constant anomalous exponent ? in a bounded domain [0,L] are not structurally stable with respect to the nonhomogeneous variations of parameter ?. In particular, the Gibbs-Boltzmann distribution is no longer the stationary solution of the fractional Fokker-Planck equation whatever the space variation of the exponent might be. We analyze the random distribution of ? in space and find that in the long-time limit, the probability distribution is highly intermediate in space and the behavior is completely dominated by very unlikely events. We show that subdiffusive fractional equations with the nonuniform random distribution of anomalous exponent is an illustration of a "Black Swan," the low probability event of the small value of the anomalous exponent that completely dominates the long-time behavior of subdiffusive systems. PMID:22587063
Subdiffusive master equation with space-dependent anomalous exponent and structural instability
NASA Astrophysics Data System (ADS)
Fedotov, Sergei; Falconer, Steven
2012-03-01
We derive the fractional master equation with space-dependent anomalous exponent. We analyze the asymptotic behavior of the corresponding lattice model both analytically and by Monte Carlo simulation. We show that the subdiffusive fractional equations with constant anomalous exponent ? in a bounded domain [0,L] are not structurally stable with respect to the nonhomogeneous variations of parameter ?. In particular, the Gibbs-Boltzmann distribution is no longer the stationary solution of the fractional Fokker-Planck equation whatever the space variation of the exponent might be. We analyze the random distribution of ? in space and find that in the long-time limit, the probability distribution is highly intermediate in space and the behavior is completely dominated by very unlikely events. We show that subdiffusive fractional equations with the nonuniform random distribution of anomalous exponent is an illustration of a “Black Swan,” the low probability event of the small value of the anomalous exponent that completely dominates the long-time behavior of subdiffusive systems.
Manuel de Leon; Juan Carlos Marrero; D. Martin de Diego
2009-11-13
In this paper, we study the underlying geometry in the classical Hamilton-Jacobi equation. The proposed formalism is also valid for nonholonomic systems. We first introduce the essential geometric ingredients: a vector bundle, a linear almost Poisson structure and a Hamiltonian function, both on the dual bundle (a Hamiltonian system). From them, it is possible to formulate the Hamilton-Jacobi equation, obtaining as a particular case, the classical theory. The main application in this paper is to nonholonomic mechanical systems. For it, we first construct the linear almost Poisson structure on the dual space of the vector bundle of admissible directions, and then, apply the Hamilton-Jacobi theorem. Another important fact in our paper is the use of the orbit theorem to symplify the Hamilton-Jacobi equation, the introduction of the notion of morphisms preserving the Hamiltonian system; indeed, this concept will be very useful to treat with reduction procedures for systems with symmetries. Several detailed examples are given to illustrate the utility of these new developments.
Rusli, Bin Nordin; Edimansyah, Bin Abdin; Naing, Lin
2008-01-01
Background The relationships between working conditions [job demand, job control and social support]; stress, anxiety, and depression; and perceived quality of life factors [physical health, psychological wellbeing, social relationships and environmental conditions] were assessed using a sample of 698 male automotive assembly workers in Malaysia. Methods The validated Malay version of the Job Content Questionnaire (JCQ), Depression Anxiety Stress Scales (DASS) and the World Health Organization Quality of Life-Brief (WHOQOL-BREF) were used. A structural equation modelling (SEM) analysis was applied to test the structural relationships of the model using AMOS version 6.0, with the maximum likelihood ratio as the method of estimation. Results The results of the SEM supported the hypothesized structural model (?2 = 22.801, df = 19, p = 0.246). The final model shows that social support (JCQ) was directly related to all 4 factors of the WHOQOL-BREF and inversely related to depression and stress (DASS). Job demand (JCQ) was directly related to stress (DASS) and inversely related to the environmental conditions (WHOQOL-BREF). Job control (JCQ) was directly related to social relationships (WHOQOL-BREF). Stress (DASS) was directly related to anxiety and depression (DASS) and inversely related to physical health, environment conditions and social relationships (WHOQOL-BREF). Anxiety (DASS) was directly related to depression (DASS) and inversely related to physical health (WHOQOL-BREF). Depression (DASS) was inversely related to the psychological wellbeing (WHOQOL-BREF). Finally, stress, anxiety and depression (DASS) mediate the relationships between job demand and social support (JCQ) to the 4 factors of WHOQOL-BREF. Conclusion These findings suggest that higher social support increases the self-reported quality of life of these workers. Higher job control increases the social relationships, whilst higher job demand increases the self-perceived stress and decreases the self-perceived quality of life related to environmental factors. The mediating role of depression, anxiety and stress on the relationship between working conditions and perceived quality of life in automotive workers should be taken into account in managing stress amongst these workers. PMID:18254966
Structure and decay constant of the {rho} meson within the Bethe-Salpeter equation
Wang, Z. G. [Department of Physics, North China Electric Power University, Baoding 071003 (China); Wan, S. L. [Department of Modern Physics, University of Science and Technology of China, Hefei 230026 (China)
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.
The evolution of anisotropic structures and turbulence in the multi-dimensional Burgers equation
S. N. Gurbatov; A. Yu. Moshkov; A. Noullez
2008-08-20
The goal of the present paper is the investigation of the evolution of anisotropic regular structures and turbulence at large Reynolds number in the multi-dimensional Burgers equation. We show that we have local isotropization of the velocity and potential fields at small scale inside cellular zones. For periodic waves, we have simple decay inside of a frozen structure. The global structure at large times is determined by the initial correlations, and for short range correlated field, we have isotropization of turbulence. The other limit we consider is the final behavior of the field, when the processes of nonlinear and harmonic interactions are frozen, and the evolution of the field is determined only by the linear dissipation.
NASA Astrophysics Data System (ADS)
Nosov, Victor V.; Lukin, Vladimir P.; Nosov, Evgeny V.; Torgaev, Andrey V.
2014-11-01
Coherent structures (topological solitons) indoors had been simulated by numerical solving of hydrodynamics equations. "Indoors" means inside the closed volume without the external direct wind influence and without the exchange of internal and external medium through the borders. Results of six boundary value problems are demonstrated: spectrograph pavilion and telescope dome of large astronomical telescopes (LSVT and BTA), cubic room, flat square cuvette, square section tube, parietal turbulence (thermals). The solitary large vortices (coherent structures, topological solitons) are observed indoors. The scenes of air motion as a result of simulation of coherent structures with identical boundary conditions are the practically same as the scenes, independently previously registered at experiments by us (indoors LSVT and BTA).
Nestler, Steffen
2014-05-01
Parameters in structural equation models are typically estimated using the maximum likelihood (ML) approach. Bollen (1996) proposed an alternative non-iterative, equation-by-equation estimator that uses instrumental variables. Although this two-stage least squares/instrumental variables (2SLS/IV) estimator has good statistical properties, one problem with its application is that parameter equality constraints cannot be imposed. This paper presents a mathematical solution to this problem that is based on an extension of the 2SLS/IV approach to a system of equations. We present an example in which our approach was used to examine strong longitudinal measurement invariance. We also investigated the new approach in a simulation study that compared it with ML in the examination of the equality of two latent regression coefficients and strong measurement invariance. Overall, the results show that the suggested approach is a useful extension of the original 2SLS/IV estimator and allows for the effective handling of equality constraints in structural equation models. PMID:24033324
Maruta, Toshimasa; Yamate, Taketo; Iimori, Makio; Kato, Masaaki; Livesley, W John
2006-01-01
The Dimensional Assessment of Personality Pathology, Basic Questionnaire (DAPP-BQ) was developed to assess 18 personality traits that provide a systematic representation of personality disorder. This study investigates the reliability and validity of the Japanese version of the DAPP-BQ and the relationship between the DAPP-BQ and Revised NEO Personality Inventory (NEO-PI-R) in a heterogeneous general population sample (n = 1485). Internal consistency (coefficient alpha) and test-retest reliability over a 3-week period was satisfactory for all scales. Factor analysis yielded 4 factors labeled "emotional dysregulation," "dissocial behavior," "inhibition," and "compulsivity" that accounted for 76.0% of the total variance. Subsequently, we investigated the relationships between the 18 dimensions and the 5 dimensions of the NEO-PI-R in a second heterogeneous general population sample (n = 717). Combined factor analysis of the 2 scales again yielded 4 factors accounting for 70.4% of the total variance. Finally, we used multiple regression analyses to examine the extent to which the 5 NEO-PI-R scales could be used to predict individual DAPP-BQ scales. These indicated that the NEO-PI-R does not have content that covers some DAPP-BQ dimensions, especially conduct problems, narcissism, and stimulus seeking. PMID:17067879
Cognitive Biases Questionnaire for Psychosis
Peters, Emmanuelle R.
2014-01-01
Objective: The Cognitive Biases Questionnaire for psychosis (CBQp) was developed to capture 5 cognitive distortions (jumping to conclusions, intentionalising, catastrophising, emotional reasoning, and dichotomous thinking), which are considered important for the pathogenesis of psychosis. Vignettes were adapted from the Cognitive Style Test (CST),1 relating to “Anomalous Perceptions” and “Threatening Events” themes. Method: Scale structure, reliability, and validity were investigated in a psychosis group, and CBQp scores were compared with those of depressed and healthy control samples. Results: The CBQp showed good internal consistency and test-retest reliability. The 5 biases were not independent, with a 2-related factor scale providing the best fit. This structure suggests that the CBQp assesses a general thinking bias rather than distinct cognitive errors, while Anomalous Perception and Threatening Events theme scores can be used separately. Total CBQp scores showed good convergent validity with the CST, but individual biases were not related to existing tasks purporting to assess similar reasoning biases. Psychotic and depressed populations scored higher than healthy controls, and symptomatic psychosis patients scored higher than their nonsymptomatic counterparts, with modest relationships between CBQp scores and symptom severity once emotional disorders were partialled out. Anomalous Perception theme and Intentionalising bias scores showed some specificity to psychosis. Conclusions: Overall, the CBQp has good psychometric properties, although it is likely that it measures a different construct to existing tasks, tentatively suggested to represent a bias of interpretation rather than reasoning, judgment or decision-making processes. It is a potentially useful tool in both research and clinical arenas. PMID:23413104
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 conducted for an autoregressive model with 5 latent variables (brain regions), each defined by 3 indicators (successive activity time bins). A series of simulations were then run by generating data from an existing pool of 51 typical readers (aged 7.5-12.5 years). Sample sizes ranged between 20 and 1,000 participants and for each sample size 1,000 replications were run. Results were evaluated using chi-square Type I errors, model convergence, mean RMSEA (root mean square error of approximation) values, confidence intervals of the RMSEA, structural path stability, and D-Fit index values. Results suggested that 70 to 80 participants were adequate to model relationships reflecting close to not so close fit as per MacCallum et al.'s recommendations. Sample sizes of 50 participants were associated with satisfactory fit. It is concluded that structural equation modeling is a viable methodology to model complex regional interdependencies in brain activation in pediatric populations. PMID:25435589
Hsu, Hsien-Yuan
2011-02-22
Two Monte Carlo studies were conducted to investigate the sensitivity of fit indices in detecting model misspecification in multilevel structural equation models (MSEM) with normally distributed or dichotomous outcome variables separately under...
Tice, Julie Anne Goodwin
1996-01-01
This research used structural equation modeling to test the construct validity of measures I I ion, and work of four global constructs: trait socialization, self-concept, organizational socialization' concept. Using measurement model procedures...
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.
Health belief structural equation model predicting sleep behavior of employed college students.
Knowlden, Adam P; Sharma, Manoj
2014-01-01
Adequate sleep comprising 7 to 8 hours per day is vital for health and effective functioning for all adults. The purpose of this study was to specify a health belief model to measure and predict the sleep behavior of employed college students. A 52-item instrument was developed with acceptable validity and reliability. A cross-sectional, convenience sample of 188 students was recruited for this study. Structural equation modeling was used to build models. The health belief model explained 34% of the variance in sleep behavior, with perceived severity, perceived barriers, cues to action, and self-efficacy identified as significant predictors. PMID:25167067
The Attitudes to Ageing Questionnaire: Mokken Scaling Analysis
Shenkin, Susan D.; Watson, Roger; Laidlaw, Ken; Starr, John M.; Deary, Ian J.
2014-01-01
Background Hierarchical scales are useful in understanding the structure of underlying latent traits in many questionnaires. The Attitudes to Ageing Questionnaire (AAQ) explored the attitudes to ageing of older people themselves, and originally described three distinct subscales: (1) Psychosocial Loss (2) Physical Change and (3) Psychological Growth. This study aimed to use Mokken analysis, a method of Item Response Theory, to test for hierarchies within the AAQ and to explore how these relate to underlying latent traits. Methods Participants in a longitudinal cohort study, the Lothian Birth Cohort 1936, completed a cross-sectional postal survey. Data from 802 participants were analysed using Mokken Scaling analysis. These results were compared with factor analysis using exploratory structural equation modelling. Results Participants were 51.6% male, mean age 74.0 years (SD 0.28). Three scales were identified from 18 of the 24 items: two weak Mokken scales and one moderate Mokken scale. (1) ‘Vitality’ contained a combination of items from all three previously determined factors of the AAQ, with a hierarchy from physical to psychosocial; (2) ‘Legacy’ contained items exclusively from the Psychological Growth scale, with a hierarchy from individual contributions to passing things on; (3) ‘Exclusion’ contained items from the Psychosocial Loss scale, with a hierarchy from general to specific instances. All of the scales were reliable and statistically significant with ‘Legacy’ showing invariant item ordering. The scales correlate as expected with personality, anxiety and depression. Exploratory SEM mostly confirmed the original factor structure. Conclusions The concurrent use of factor analysis and Mokken scaling provides additional information about the AAQ. The previously-described factor structure is mostly confirmed. Mokken scaling identifies a new factor relating to vitality, and a hierarchy of responses within three separate scales, referring to vitality, legacy and exclusion. This shows what older people themselves consider important regarding their own ageing. PMID:24892302
Structure properties of one-mode collaboration network model based on rate equation approach
NASA Astrophysics Data System (ADS)
Wang, Long; Ma, Yinghong
2014-12-01
The rate equation approach is very useful to describe the dynamic structure property of collaboration network, especially in calculating the node degree distribution and the joint degree distribution, and considering the correlation of node degrees. In this paper, we referee the two-mode collaboration network model (RDP), and translate it into one-mode RDP model. By the rate-equation approach, we study the node degree distribution in the one-mode RDP model (RDP) with numerical simulations verifying the feasibility of the model. It is proved that the node degree distribution of the model is a right-skewed power-law like distribution with the exponent ? in interval (1,3]. For the large enough node degree k, it can be proved that the node degree distribution is approximately power-law distribution. The joint degree distribution are also got by utilizing rate-equation approach and the node degree distribution. Through the joint degree distribution, we find that the correlation relationship of node degrees is nontrivial correlation relationship among the degrees of connected nodes that formed by spontaneously. Finally we get the clustering coefficient of the RDP model by calculating the mathematical expectation of degree distribution.
JOB EVALUATION QUESTIONNAIRE ANSWER SHEET
Amin, S. Massoud
JOB EVALUATION QUESTIONNAIRE ANSWER SHEET DO NOT WRITE IN THIS SPACE N.C. Date Received Reclass New Starting Date in Class Yes No NA (NA if Temporary Job) Notice # Effective Date If Reclassified IS TO BE USED WITH THE JOB EVALUATION QUESTIONNAIRE (BA 802) ONLY FOR POSITIONS COVERED BY CIVIL SERVICE
Implementation of an Adaptive Questionnaire
Petri Nokelainen; Markku Niemivirta; Jaakko Kurhila; Miikka Miettinen; Henry Tirri
2001-01-01
An adaptive on-line questionnaire, named EDUFORM 1 , is based on Bayesian statistical techniques that both optimize the number of propositions presented to each respondent and create an individual learner profile. Adaptive graphical user interface is generated partially (propositions of the questionnaire, collaborative actions and links to resources) and computational part totally with Bayesian computational techniques. The preliminary results show
Killing-Yano equations with torsion, worldline actions and G-structures
NASA Astrophysics Data System (ADS)
Papadopoulos, G.
2012-06-01
We determine the geometry of the target spaces of supersymmetric non-relativistic particles with torsion and magnetic couplings, and with symmetries generated by the fundamental forms of G-structures for G = U(n), SU(n), Sp(n), Sp(n) · Sp(1), G2 and Spin(7). We find that the Killing-Yano equation, which arises as a condition for the invariance of the worldline action, does not always determine the torsion coupling uniquely in terms of the metric and fundamental forms. We show that there are several connections with skew-symmetric torsion for G = U(n), SU(n) and G2 that solve the invariance conditions. We describe all these compatible connections for each of the G-structures and explain the geometric nature of the couplings.
Romdhani, Hela; Hwang, Heungsun; Paradis, Gilles; Roy-Gagnon, Marie-Helene; Labbe, Aurelie
2015-02-01
There is increasing interest in the joint analysis of multiple genetic variants from multiple genes and multiple correlated quantitative traits in association studies. The classical approach involves testing univariate associations between genotypes and phenotypes and correcting for multiple testing that results in loss of power to detect associations. In this paper, we propose modeling complex relationships between genetic variants in candidate genes and measured correlated traits using structural equation models (SEM), taking advantage of prior knowledge on clinical and genetic pathways. We adopt generalized structured component analysis (GSCA) as an approach to SEM and develop a single association test between multiple genetic variants in a gene and a set of correlated traits, taking into account all available data from other genes and other traits. The performance of this test is investigated by simulations. We apply the proposed method to the Quebec Child and Adolescent Health and Social Survey (1999) data to investigate genetic associations with cardiovascular disease-related traits. PMID:25558046
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.
Chen, Gang; Glen, Daniel R; Saad, Ziad S; Paul Hamilton, J; Thomason, Moriah E; Gotlib, Ian H; Cox, Robert W
2011-12-01
Vector autoregression (VAR) and structural equation modeling (SEM) are two popular brain-network modeling tools. VAR, which is a data-driven approach, assumes that connected regions exert time-lagged influences on one another. In contrast, the hypothesis-driven SEM is used to validate an existing connectivity model where connected regions have contemporaneous interactions among them. We present the two models in detail and discuss their applicability to FMRI data, and their interpretational limits. We also propose a unified approach that models both lagged and contemporaneous effects. The unifying model, structural vector autoregression (SVAR), may improve statistical and explanatory power, and avoid some prevalent pitfalls that can occur when VAR and SEM are utilized separately. PMID:21975109
Kim, Min-Geun; Jang, Hong-Lae [National Creative Research Initiatives Center for Isogeometric Optimal Design and Department of Naval Architecture and Ocean Engineering, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 151-744 (Korea, Republic of)] [National Creative Research Initiatives Center for Isogeometric Optimal Design and Department of Naval Architecture and Ocean Engineering, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 151-744 (Korea, Republic of); Cho, Seonho, E-mail: secho@snu.ac.kr [National Creative Research Initiatives Center for Isogeometric Optimal Design and Department of Naval Architecture and Ocean Engineering, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 151-744 (Korea, Republic of)] [National Creative Research Initiatives Center for Isogeometric Optimal Design and Department of Naval Architecture and Ocean Engineering, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 151-744 (Korea, Republic of)
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.
Guidelines for a graph-theoretic implementation of structural equation modeling
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 an updated definition of the SEM process that subsumes the historical matrix approach under a graph-theory implementation. The implementation is also designed to permit complex specifications and to be compatible with various estimation methods. Finally, they are meant to foster the use of probabilistic reasoning in both retrospective and prospective considerations of the quantitative implications of the results.
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.
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.
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.
Multidisciplinary Treatment Planning Questionnaire
Multidisciplinary care, which incorporates Multidisciplinary Treatment Planning (MTP), is increasingly being adopted within oncology care settings with the intent of enhancing the quality of care delivered to patients. However, what is not known is its impact on improving patient outcomes and the quality of care being delivered. A targeted review of the literature was conducted to examine the organization and operation of the Multidisciplinary Care (MDC) team structure1. Findings revealed that a variety of implementation models exist within the health care system.
Ponce, J; Garrigues, V; Agréus, L; Tabaglio, E; Gschwantler, M; Guallar, E; Tafalla, M; Nuevo, J; Hatlebakk, J
2012-01-01
Background Response to treatment among primary care patients with gastro-oesophageal disease (GERD) is variable. Aim The GERD Management Project (GMP) evaluated the effectiveness of a structured management approach to GERD vs. standard treatment (usual care). Methods Data from five cluster-randomised clinical trials in adult primary care patients with symptoms of GERD were pooled. The structured pathway was based on the self-administered GERD Questionnaire (GerdQ) and was compared with standard treatment. Results 1734 patients were enrolled (structured treatment, n = 834; standard treatment, n = 900). The difference in the mean GerdQ score change from baseline favoured the structured pathway (?0.61; 95% CI: ?0.88, ?0.34; p < 0.001). The odds ratio for an indication for treatment revision at the end of follow-up (structured vs. standard treatment) was 0.39 (95% CI: 0.29, 0.52; p = 0.001). Conclusions Management of primary care patients with GERD can be improved by systematic stratification of patients using a patient management tool such as the GerdQ. PMID:22805293
Development of uncertainty-based work injury model using Bayesian structural equation modelling.
Chatterjee, Snehamoy
2014-01-01
This paper proposed a Bayesian method-based structural equation model (SEM) of miners' work injury for an underground coal mine in India. The environmental and behavioural variables for work injury were identified and causal relationships were developed. For Bayesian modelling, prior distributions of SEM parameters are necessary to develop the model. In this paper, two approaches were adopted to obtain prior distribution for factor loading parameters and structural parameters of SEM. In the first approach, the prior distributions were considered as a fixed distribution function with specific parameter values, whereas, in the second approach, prior distributions of the parameters were generated from experts' opinions. The posterior distributions of these parameters were obtained by applying Bayesian rule. The Markov Chain Monte Carlo sampling in the form Gibbs sampling was applied for sampling from the posterior distribution. The results revealed that all coefficients of structural and measurement model parameters are statistically significant in experts' opinion-based priors, whereas, two coefficients are not statistically significant when fixed prior-based distributions are applied. The error statistics reveals that Bayesian structural model provides reasonably good fit of work injury with high coefficient of determination (0.91) and less mean squared error as compared to traditional SEM. PMID:24111548
Development of high vorticity structures in incompressible 3D Euler equations
Agafontsev, D S; Mailybaev, A A
2015-01-01
We perform the systematic numerical study of high vorticity structures that develop in the 3D incompressible Euler equations from generic large-scale initial conditions. We observe that a multitude of high vorticity structures appear in the form of thin vorticity sheets (pancakes). Our analysis reveals the self-similarity of the pancakes evolution, which is governed by two different exponents $e^{-t/T_{\\ell}}$ and $e^{t/T_{\\omega}}$ describing compression in the transverse direction and the vorticity growth respectively, with the universal ratio $T_{\\ell}/T_{\\omega} \\approx 2/3$. We relate development of these structures to the gradual formation of the Kolmogorov energy spectrum $E_{k}\\propto\\, k^{-5/3}$, which we observe in a fully inviscid system. With the spectral analysis we demonstrate that the energy transfer to small scales is performed through the pancake structures, which accumulate in the Kolmogorov interval of scales and evolve according to the scaling law $\\omega_{\\max} \\propto \\ell^{-2/3}$ for th...
2007-01-01
Background For effective deterrence methods, individual, systemic and situational factors that make an athlete or athlete group more susceptible to doping than others should be fully investigated. Traditional behavioural models assume that the behaviour in question is the ultimate end. However, growing evidence suggests that in doping situations, the doping behaviour is not the end but a means to an end, which is gaining competitive advantage. Therefore, models of doping should include and anti-doping policies should consider attitudes or orientations toward the specific target end, in addition to the attitude toward the 'tool' itself. Objectives The aim of this study was to empirically test doping related dispositions and attitudes of competitive athletes with the view of informing anti-doping policy developments and deterrence methods. To this end, the paper focused on the individual element of the drug availability – athlete's personality – situation triangle. Methods Data were collected by questionnaires containing a battery of psychological tests among competitive US male college athletes (n = 199). Outcome measures included sport orientation (win and goal orientation and competitiveness), doping attitude, beliefs and self-reported past or current use of doping. A structural equation model was developed based on the strength of relationships between these outcome measures. Results Whilst the doping model showed satisfactory fit, the results suggested that athletes' win and goal orientation and competitiveness do not play a statistically significant role in doping behaviour, but win orientation has an effect on doping attitude. The SEM analysis provided empirical evidence that sport orientation and doping behaviour is not directly related. Conclusion The considerable proportion of doping behaviour unexplained by the model suggests that other factors play an influential role in athletes' decisions regarding prohibited methods. Future research, followed by policy development, should incorporate these factors to capture the complexity of the doping phenomenon and to identify points for effective anti-doping interventions. Sport governing bodies and anti-doping organisations need to recognise that using performance enhancements may be more of a rational, outcome optimizing behaviour than deviance and consider offering acceptable alternative performance-enhancing methods to doping. PMID:17996097
Biktashev, Vadim N.
The Asymptotic Structure of the Hodgkin-Huxley Equations Rebecca Suckley 1 and Vadim N. Biktashev 1 correspondence should be addressed. Abstract We analyse the asymptotic structure of the Hodgkin-Huxley system approaches. 1 Introduction Fifty years ago, Hodgkin & Huxley (1952) suggested a system of di#11;erential
R. Rajkhowa; J. K. Sarma
2012-09-19
We present particular and unique solutions of Dokshitzer- Gribov- Lipatov- Altarelli-Parisi (DGLAP) evolution equation for gluon structure function in leading order (LO) and obtain t and x-evolutions of gluon structure function at small-x. The results are compared with a recent global parameterization.
Physical Activity Questionnaire Search Results
The Brunel Lifestyle Physical Activity Questionnaire a4 If you add together each session of pre-planned physical activity that you engage in during a normal week, how much time would you estimate that you spend in total?
Alcaraz, Saül; Viladrich, Carme; Torregrosa, Miquel
2013-01-01
When assessing team environments in youth sport, participants often spend substantial time responding to lots of items in questionnaires, causing a lack of efficiency (i.e. time and effort) and a decrease of data quality. The purpose of this work was to create short-forms of the questionnaires PeerMCYSQ, SCQPeer, TEOSQ, and also to analyse the existing short-form of the SCQCoach. In Study 1 we developed the short-forms of the instruments. We shortened the questionnaires by using both theory driven and data-driven criteria. In Study 2, we used also qualitative and quantitative data with the aim of validating the short-forms. Finally, in Study 3 we tested the last version of the short-forms and sought evidences concerning their criterion validity. The results showed evidence that supports the psychometric merit of these short-forms: (a) significantly less missing values were obtained; (b) all the factors obtained alpha values above .70; (c) confirmatory factor analyses demonstrated that the short-forms fitted the hypothesized models well; (d) correlations between variables were coherent with expectations, and (e) structural equation modeling results showed significant paths consistent with previous literature. On average, our participants only spent a third of the time used to complete the original questionnaires. PMID:24230940
Powell, Danny H [ORNL] [ORNL; Elwood Jr, Robert H [ORNL] [ORNL
2011-01-01
The questionnaire is the instrument used for recording performance data on the nuclear material protection, control, and accountability (MPC&A) system at a nuclear facility. The performance information provides a basis for evaluating the effectiveness of the MPC&A system. The goal for the questionnaire is to provide an accurate representation of the performance of the MPC&A system as it currently exists in the facility. Performance grades for all basic MPC&A functions should realistically reflect the actual level of performance at the time the survey is conducted. The questionnaire was developed after testing and benchmarking the material control and accountability (MC&A) system effectiveness tool (MSET) in the United States. The benchmarking exercise at the Idaho National Laboratory (INL) proved extremely valuable for improving the content and quality of the early versions of the questionnaire. Members of the INL benchmark team identified many areas of the questionnaire where questions should be clarified and areas where additional questions should be incorporated. The questionnaire addresses all elements of the MC&A system. Specific parts pertain to the foundation for the facility's overall MPC&A system, and other parts pertain to the specific functions of the operational MPC&A system. The questionnaire includes performance metrics for each of the basic functions or tasks performed in the operational MPC&A system. All of those basic functions or tasks are represented as basic events in the MPC&A fault tree. Performance metrics are to be used during completion of the questionnaire to report what is actually being done in relation to what should be done in the performance of MPC&A functions.
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.
Silveira, Marise Fagundes; Marôco, João P; Freire, Rafael Silveira; Martins, Andréa Maria Eleutério de Barros Lima; Marcopito, Luiz Francisco
2014-06-01
This study aimed to estimate the prevalence of impact of oral health conditions on physical and psychosocial dimensions among adolescents and to identify factors associated with severity of impact. The impact of oral health status was assessed by the instrument Oral Health Impact Profile (OHIP-14). The covariates were: socioeconomic status, habits and health care, use of dental services, and normative conditions of oral health. Structural equation modeling was performed, and 15.6% of adolescents reported impact in at least one dimension of the OHIP-14. The dimensions that showed the highest prevalence of impact were psychological distress (11.8%) and physical pain (6.6%). The number of teeth needing dental treatment, number of filled teeth, and CPI significantly affected severity of impact. In this adolescent population, unfavorable socioeconomic conditions were associated with reduced use of dental services, associated in turn with precarious oral health conditions and increased severity of impact. PMID:25099041
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
Attitudes toward medication and the clinical variables in schizophrenia: Structural equation models
Rossi, Alessandro; Pacifico, Roberta; Stratta, Paolo
2009-01-01
Objective: Our study uses data from a large clinical trial to further dissect the contributors attitude toward antipsychotic medication measured with the Drug Attitude Inventory (DAI) in schizophrenia. Method: A total of 227 consecutive outpatients (140 males, 87 females) with schizophrenia or schizoaffective disorder according to DSM-IV criteria were evaluated. Structural equation models (SEM) were used to examine the relationship between attitudes toward medication as measured with the DAI and clinical variables assessed by Positive and Negative Syndrome Scale (PANSS) and Global Assessment of Functioning (GAF). Results: Among four models, the data better fit a model in which attitudes toward medication (DAI-30) was predicted by PANSS Positive and Insight measures, and GAF (goodness-of-fit = 0.99). Conclusion: The data best fit a model where the most complex interaction of insight measures and positive symptoms does predict attitudes toward medication. PMID:19936173
Analyzing average and conditional effects with multigroup multilevel structural equation models
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
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.
Adams, Richard E; Boscarino, Joseph A
2011-02-01
Studies suggest that perievent panic attacks are predictive of future posttraumatic stress disorder (PTSD). Using a population of New York City residents interviewed after the World Trade Center Disaster, the authors measured event exposure, perievent panic, potential confounding, mediating variables, and PTSD. When they estimated a structural equation model, with other stressor events, psychological resources, and Year 1 and Year 2 PTSD as latent variables and adjusted for confounders, the association between perievent panic and Year 2 PTSD was not significant. Results revealed that perievent panic was predictive of Year 1 PTSD, but not Year 2 PTSD. Year 2 stressors and Year 2 psychosocial resources were the best predictors of Year 2 PTSD. PMID:21351165
C. Senthil Kumar; R. Radha; M. Lakshmanan
2009-01-01
In this paper, using a novel approach involving the truncated Laurent expansion in the Painlevé analysis of the (2+1) dimensional K-dV equation, we have trilinearized the evolution equation and obtained rather general classes of solutions in terms of arbitrary functions. The highlight of this method is that it allows us to construct generalized periodic structures corresponding to different manifolds in
Tanaka, Noriko; Huttenhower, Curtis; Nosho, Katsuhiko; Baba, Yoshifumi; Shima, Kaori; Quackenbush, John; Haigis, Kevin M.; Giovannucci, Edward; Fuchs, Charles S.; Ogino, Shuji
2010-01-01
The CpG island methylator phenotype (CIMP-high, CIMP1) is a distinct phenotype associated with microsatellite instability (MSI) and BRAF mutation in colon cancer. Recent evidence suggests the presence of KRAS mutation-associated CIMP subtype (CIMP-low, CIMP2). We used cluster analysis, principal component analysis (PCA), and structural equation modeling (SEM), a novel strategy, to decipher the correlation structure of CpG island hypermethylation. Using a database of 861 colon and rectal cancers, DNA methylation at 16 CpG islands [CACNA1G, CDKN2A (p16/ink4a), CHFR, CRABP1, HIC1, IGF2, IGFBP3, MGMT, MINT-1, MINT-31, MLH1, NEUROG1, p14 (CDKN2A/arf), RUNX3, SOCS1, and WRN] was quantified by real-time PCR. Tumors were categorized into three groups: Group 1 with wild-type KRAS/BRAF (N = 440); Group 2 with mutant KRAS and wild-type BRAF (N = 308); and Group 3 with wild-type KRAS and mutant BRAF (N = 107). Tumors with mutant KRAS/BRAF (N = 6) were excluded. In unsupervised hierarchical clustering analysis, all but six markers (CACNA1G, IGF2, RUNX3, MGMT, MINT-1, and SOCS1) were differentially clustered with CIMP-high and CIMP-low according to KRAS and BRAF status. In SEM, the correlation structures between CIMP, locus-specific CpG island methylation, and MSI differed according to KRAS and BRAF status, which was consistent with PCA results. In conclusion, KRAS and BRAF mutations appear to differentially influence correlation structure of CpG island methylation. Our novel data suggest two distinct perturbations, resulting in differential locus-specific propensity of CpG methylation. PMID:21037082
High-pressure structural behavior and equation of state of NaZnF{sub 3}
Yakovlev, Sergey, E-mail: s.yakovlev@tnw.utwente.n [Bragg Institute, Australian Nuclear Science and Technology Organisation, 1 PBM, Menai, NSW 2234 (Australia); Avdeev, Maxim [Bragg Institute, Australian Nuclear Science and Technology Organisation, 1 PBM, Menai, NSW 2234 (Australia); Mezouar, Mohamed [ID-27, European Synchrotron Radiation Facility (ESRF), 6 rue Jules Horowitz, PB220, 38043 Grenoble CEDEX (France)
2009-06-15
We report the results of density functional theory ab-initio calculations and monochromatic synchrotron X-ray diffraction study carried out for orthorhombic NaZnF{sub 3} in the pressure range 0-40 GPa. Perovskite-to-postperovskite phase transition was anticipated by first-principles computations and then observed in high-pressure diamond anvil cell synchrotron diffraction experiment between 14 and 22 GPa. Above 25 GPa postperovskite structure (CaIrO{sub 3} type, space group Cmcm) coexists with another phase, yet unidentified. On decompression, pure postperovskite-type structure was found to be stable down to 4 GPa; below this pressure sample contained both perovskite and postperovskite modifications. Fit of experimental P-V data to the third-order Birch-Murnaghan equation of state gave bulk moduli, K{sub P,0} 64.98+-2.67 and 69.88+-3.69 GPa for perovskite and postperovskite modifications, respectively. Both phases demonstrated strong anisotropy of compressibility. For postperovskite NaZnF{sub 3}, the highest compression was observed along the direction perpendicular to the planes of ZnF{sub 6} octahedra arrangement. - Graphical Abstract: Fit of P-V data obtained from high-pressure X-ray diffraction study of perovskite and postperovskite NaZnF{sub 3} to the third-order Birch-Murnaghan equation of state (solid line). Open and closed symbols represent experimental data corresponding to compression and decompression, respectively. Bulk moduli, K{sub 0,P}, of perovskite and postperovskite phases are 64.98+-2.67 and 69.88+-3.69 GPa.
Huber, Claudia; Kunz, Miriam; Artelt, Cordula; Lautenbacher, Stefan
2010-01-01
BACKGROUND/OBJECTIVE: It is known that maladaptive attentional and emotional mechanisms of pain processing – as indicated by constructs such as pain hypervigilance, pain-related anxiety and pain catastrophizing – play an important role in the development and maintenance of chronic pain conditions. However, little is known to date about the potential risk factors for these forms of maladaptive processing. The aim of the present study was to shed more light on this issue. A very comprehensive set of predictor variables was examined in healthy pain-free subjects. METHOD: Participants were 92 young and healthy subjects (mean [± SD] age 26.99±6.90 years; 47 men, 45 women). Maladaptive attentional and emotional mechanisms of pain processing were assessed by self-report measures of pain hypervigilance, pain-related anxiety and pain catastrophizing, as well as by a dot-probe task. The comprehensive set of predictor variables included measures of affective and bodily distress (depression, anxiety and somatization), experimental pain sensitivity, and cortisol reactivity. Directed relationships were estimated by using structural equation modelling. RESULTS: Structural equation modelling revealed a significant path from affective and bodily distress to self-reported maladaptive attentional and emotional pain processing. In contrast, the paths from pain sensitivity and cortisol reactivity did not reach the level of significance. CONCLUSION: These results support the position that anxiety and depression, as well as somatization, contribute to the aberrance of attentional and emotional mechanisms of pain processing. Surprisingly, the assumption of a close relationship between these maladaptive mechanisms of pain processing and pain sensitivity could not be confirmed. PMID:20808968
Pennig, Sibylle; Schady, Arthur
2014-01-01
In some regions the exposure to railway noise is extremely concentrated, which may lead to high residential annoyance. Nonacoustical factors contribute to these reactions, but there is limited evidence on the interrelations between the nonacoustical factors that influence railway noise annoyance. The aims of the present study were (1) to examine exposure-response relationships between long-term railway noise exposure and annoyance in a region severely affected by railway noise and (2) to determine a priori proposed interrelations between nonacoustical factors by structural equation analysis. Residents (n = 320) living close to railway tracks in the Middle Rhine Valley completed a socio-acoustic survey. Individual noise exposure levels were calculated by an acoustical simulation model for this area. The derived exposure-response relationships indicated considerably higher annoyance at the same noise exposure level than would have been predicted by the European Union standard curve, particularly for the night-time period. In the structural equation analysis, 72% of the variance in noise annoyance was explained by the noise exposure (L(den)) and nonacoustical variables. The model provides insights into several causal mechanisms underlying the formation of railway noise annoyance considering indirect and reciprocal effects. The concern about harmful effects of railway noise and railway traffic, the perceived control and coping capacity, and the individual noise sensitivity were the most important factors that influence noise annoyance. All effects of the nonacoustical factors on annoyance were mediated by the perceived control and coping capacity and additionally proposed indirect effects of the theoretical model were supported by the data. PMID:25387535
NASA Astrophysics Data System (ADS)
Radha, R.; Lakshmanan, M.
1994-09-01
In this article, a singularity structure analysis of a (2+1)-dimensional generalized Korteweg-de Vries equation studied originally by Boiti et al., admitting a weak Lax pair, is carried out and it is proven that the system satisfies the Painlevé property. Its bilinear form is constructed in a natural way from the P analysis and then it is used to generate ``multidromion'' solutions (exponentially decaying solutions in all directions). The same analysis can be extended to construct the multidromion solutions of the generalized Nizhnik-Novikov-Veselov (NNV) equation from which the NNV equation follows as a special case.
Michael E. Hyland; Sidney H. Irvine; Clive Thacker; Peter L. Dann; Ian Dennis
1989-01-01
The factor structure of the Stunkard-Messick Eating Questionnaire (SMEQ) differs from that of the Dutch Eating Behavior Questionnaire\\u000a (DEBQ). Using students and members of a weight watchers club, we factor-analyzed responses to the SMEQ and produced a solution\\u000a which was different from that obtained by Stunkard and Messick, but which had some similarities to the factor structure of\\u000a the DEBQ.
Parallel workflows for data-driven structural equation modeling in functional neuroimaging.
Kenny, Sarah; Andric, Michael; Boker, Steven M; Neale, Michael C; Wilde, Michael; Small, Steven L
2009-01-01
We present a computational framework suitable for a data-driven approach to structural equation modeling (SEM) and describe several workflows for modeling functional magnetic resonance imaging (fMRI) data within this framework. The Computational Neuroscience Applications Research Infrastructure (CNARI) employs a high-level scripting language called Swift, which is capable of spawning hundreds of thousands of simultaneous R processes (R Development Core Team, 2008), consisting of self-contained SEMs, on a high performance computing system (HPC). These self-contained R processing jobs are data objects generated by OpenMx, a plug-in for R, which can generate a single model object containing the matrices and algebraic information necessary to estimate parameters of the model. With such an infrastructure in place a structural modeler may begin to investigate exhaustive searches of the model space. Specific applications of the infrastructure, statistics related to model fit, and limitations are discussed in relation to exhaustive SEM. In particular, we discuss how workflow management techniques can help to solve large computational problems in neuroimaging. PMID:19876406
A structural equation model of plant species richness and its application to a coastal wetland
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.
ODEion--a software module for structural identification of ordinary differential equations.
Gennemark, Peter; Wedelin, Dag
2014-02-01
In the systems biology field, algorithms for structural identification of ordinary differential equations (ODEs) have mainly focused on fixed model spaces like S-systems and/or on methods that require sufficiently good data so that derivatives can be accurately estimated. There is therefore a lack of methods and software that can handle more general models and realistic data. We present ODEion, a software module for structural identification of ODEs. Main characteristic features of the software are: • The model space is defined by arbitrary user-defined functions that can be nonlinear in both variables and parameters, such as for example chemical rate reactions. • ODEion implements computationally efficient algorithms that have been shown to efficiently handle sparse and noisy data. It can run a range of realistic problems that previously required a supercomputer. • ODEion is easy to use and provides SBML output. We describe the mathematical problem, the ODEion system itself, and provide several examples of how the system can be used. Available at: http://www.odeidentification.org. PMID:24467754
Wills, John M [Los Alamos National Laboratory; Mattsson, Ann E [Sandia National Laboratories
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.
Parallel Workflows for Data-Driven Structural Equation Modeling in Functional Neuroimaging
Kenny, Sarah; Andric, Michael; Boker, Steven M.; Neale, Michael C.; Wilde, Michael; Small, Steven L.
2009-01-01
We present a computational framework suitable for a data-driven approach to structural equation modeling (SEM) and describe several workflows for modeling functional magnetic resonance imaging (fMRI) data within this framework. The Computational Neuroscience Applications Research Infrastructure (CNARI) employs a high-level scripting language called Swift, which is capable of spawning hundreds of thousands of simultaneous R processes (R Development Core Team, 2008), consisting of self-contained SEMs, on a high performance computing system (HPC). These self-contained R processing jobs are data objects generated by OpenMx, a plug-in for R, which can generate a single model object containing the matrices and algebraic information necessary to estimate parameters of the model. With such an infrastructure in place a structural modeler may begin to investigate exhaustive searches of the model space. Specific applications of the infrastructure, statistics related to model fit, and limitations are discussed in relation to exhaustive SEM. In particular, we discuss how workflow management techniques can help to solve large computational problems in neuroimaging. PMID:19876406
Stromswold, Karin
© K. Stromswold, 2003 Perinatal Factors Questionnaire (Singleton Version) 1 PERINATAL FACTORS & DEVELOPMENT QUESTIONNAIRE (Singleton Version) Person completing questionnaire: Today's date: Mailing Address E completing this questionnaire, please contact Ellyn Sheffield by phone (732-445-5231) or email (sheffield
Using Presence Questionnaires in Reality Using Presence Questionnaires in Reality
Slater, Mel
, Ernest Catena, Sima Arman, Mel Slater Department of Computer Science University College London Gower different presence question- naires can distinguish between real and virtual experiences. One group of 10 subjects were given two different presence questionnaires in randomised order: the Witmer and Singer
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 accuracy and convergence of the numerical routines in the model are demonstrated for the case of laboratory measurements of unsteady flow in a sewer pipe. Verification of the routines in the model for field data on the Fox River in northeastern Illinois also is briefly discussed. The basic principles of unsteady-flow modeling and the relation between steady flow and unsteady flow are presented. Assumptions and the limitations of the model also are presented. The schematization of the stream system and the conversion of the physical characteristics of the stream reaches and a wide range of special features into function tables for model applications are described. The modified dynamic-wave equation used in FEQ for unsteady flow in curvilinear channels with drag on minor hydraulic structures and channel constrictions determined from an equivalent energy slope is developed. The matrix equation relating flows and depths at computational nodes throughout the stream system by the continuity (conservation of mass) and modified dynamic-wave equations is illustrated for four sequential examples. The solution of the matrix equation by Newton's method is discussed. Finally, the input for FEQ and the error messages and warnings issued are presented.
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.
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
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).
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, the dominant F-VAC responsible for acoustic radiation are decomposed into the natural modes of a vibrating structure, and the critical vibration modes responsible for the dominant F-VAC are identified. Experimental validation for this technology was conducted using a baffled square plate and a scaled model vehicle cabin subject to a point force excitation inside a fully anechoic chamber.
Psychometric validation of the Dysexecutive Questionnaire (DEX).
Shaw, Simone; Oei, Tian P S; Sawang, Sukanlaya
2015-03-01
This study reported on the validation of the psychometric properties, the factorability, validity, and sensitivity of the Dysexecutive Questionnaire (DEX) in 3 clinical and nonclinical samples. A mixed sample of 997 participants-community (n = 663), psychiatric (depressed [n = 92] and anxious [n = 122]), and neurologically impaired (n = 120)-completed self-report questionnaires assessing executive dysfunction, depression, anxiety, stress, general self-efficacy, and satisfaction with life. Before analyses the data were randomly split into 2 subsets (A and B). Exploratory factor analysis performed on Subset A produced a 3-factor model (Factor 1: Inhibition, Factor 2: Volition, and Factor 3: Social Regulation) in which 15 of the original 20 items provided a revised factor structure that was superior to all other structures. A series of confirmatory factor analyses performed on Subset B confirmed that this revised factor structure was valid and reliable. The revised structure, labeled the DEX-R, was found to be a reliable and valid tool for assessing behavioral symptoms of dysexecutive functioning in mixed community, psychiatric, and neurological samples. (PsycINFO Database Record (c) 2015 APA, all rights reserved). PMID:25602692
ERIC Educational Resources Information Center
de Guzman, Allan B.; Jimenez, Benito Christian B.; Jocson, Kathlyn P.; Junio, Aileen R.; Junio, Drazen E.; Jurado, Jasper Benjamin N.; Justiniano, Angela Bianca F.
2013-01-01
Anchored on the key constucts of Ajzen's Theory of Planned Behavior (1985), this paper seeks to test a model that explores the influence of knowledge, attitude, and caring behavior on nursing students' behavioral intention toward geriatric care. A five-part survey-questionnaire was administered to 839 third and fourth year nursing students from a…
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.
School of Informatics Course Questionnaire
Koehn, Philipp
return your completed feedback form to the course lecturer or directly to the Informatics Teaching: http://www.inf.ed.ac.uk/admin/ITO/questionnaires You can also provide feedback directly to your Evaluation Please rate the course according to the following attributes, on a scale from 1 to 5. Workload
Physical Activity Questionnaire Search Results
The Physical Activity Questionnaire for Elderly Japanese (PAQ-EJ) 1 Over 7 typical days, how often did you take a walk or ride a bicycle on errands such as going to or from a store or taking children to school?
Efficiency of split questionnaire surveys
James O. Chipperfield; David G. Steel
2011-01-01
We consider a general design that allows information for different patterns, or sets, of data items to be collected from different sample units, which we call a Split Questionnaire Design (SQD). While SQDs have been historically used to accommodate constraints on respondent burden, this paper shows they can also be an efficient design option. The efficiency of a design can
Exit Interview Questionnaire Employee's Name
Oyet, Alwell
Exit Interview Questionnaire Employee's Name: Department/Unit: Position Title: Date Hired Good Poor Very Poor Comments: #12;Job satisfaction Very High High Average Low Very Low Comments: Overall satisfaction with Memorial as an employer Very High High Average Low Very Low Comments: Overall
Physical Activity Questionnaire Search Results
Global Physical Activity Questionnaire (GPAQ) 13 Do you do any moderate-intensity sports, fitness or recreational (leisure) activities that causes a small increase in breathing or heart rate such as brisk walking, cycling, swimming, volleyball) for at least 10 minutes continuously?
Energy Balance Survey: Adult Questionnaire
The Physician Survey of Practices on Diet, Physical Activity, and Weight Control -- Adult Questionnaire is sponsored by the National Cancer Institute in collaboration with the Office of Behavioral and Social Sciences Research, the National Institute of Child Health and Human Development, the National Institute of Diabetes and Digestive and Kidney Diseases, and the Centers for Disease Control and Prevention.
Physical Activity Questionnaire Search Results
Neighborhood Physical Activity Questionnaire (NPAQ) A1 In a USUAL WEEK, do you cycle in or around your new neighbourhood or new local area to get to or from somewhere (such as cycling to a shop or to public transport) or for recreation, health or fitness (including cycling with your dog)?
Lifestyle Questionnaire Patient Name:______________________________________ Date:_________________
:_________________ If it is determined that surgery is appropriate for you, this questionnaire will help us provide the best treatment for some activities after surgery. Please fill this form out completely and turn in to your technician. Please do not hesitate to contact us with any questions. 1. After surgery, would you be interested
ERIC Educational Resources Information Center
Willoughby, Michael; Vandergrift, Nathan; Blair, Clancy; Granger, Douglas A.
2007-01-01
This study introduces a novel application of structural equation modeling (SEM) for the analysis of cortisol data that are collected using a pre-post-post design. By way of an extended example, an SEM model is developed that permits an examination of both the overall level of cortisol, as well as changes in cortisol (reactivity and regulation), as…
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…
ERIC Educational Resources Information Center
Bandalos, Deborah L.
1997-01-01
Monte Carlo methods were used to study the accuracy and utility of estimators of overall error and error due to approximation in structural equation modeling. Effects of sample size, indicator reliabilities, and degree of misspecification were examined. The rescaled noncentrality parameter also was examined. Choosing among competing models is…
ERIC Educational Resources Information Center
Byrne, Barbara M.
2001-01-01
Uses a confirmatory factor analytic (CFA) model as a paradigmatic basis for the comparison of three widely used structural equation modeling computer programs: (1) AMOS 4.0; (2) EQS 6; and (3) LISREL 8. Comparisons focus on aspects of programs that bear on the specification and testing of CFA models and the treatment of incomplete, nonnormally…
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…
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…
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…
ERIC Educational Resources Information Center
Enders, Craig K.
2002-01-01
Proposed a method for extending the Bollen-Stine bootstrap model (K. Bollen and R. Stine, 1992) fit to structural equation models with missing data. Developed a Statistical Analysis System macro program to implement this procedure, and assessed its usefulness in a simulation. The new method yielded model rejection rates close to the nominal 5%…
ERIC Educational Resources Information Center
Ogasawara, Haruhiko
2007-01-01
Higher-order approximations to the distributions of fit indexes for structural equation models under fixed alternative hypotheses are obtained in nonnormal samples as well as normal ones. The fit indexes include the normal-theory likelihood ratio chi-square statistic for a posited model, the corresponding statistic for the baseline model of…
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…
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…
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…
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…
Stephen G. West; Irwin Sandler; David R. Pillow; Louise Baca; Joanne C. Gersten
1991-01-01
Describes a generative study of processes which may lead to symptomatology in children who have experienced the death of a parent. Based on existing literature, four putative mediating variables were identified: parental demoralization, family warmth, negative family events, and positive stable family events. Structural equation modeling techniques were used to compare several potential causal models involving these variables. The results
ERIC Educational Resources Information Center
Rindskopf, David
2012-01-01
Muthen and Asparouhov (2012) made a strong case for the advantages of Bayesian methodology in factor analysis and structural equation models. I show additional extensions and adaptations of their methods and show how non-Bayesians can take advantage of many (though not all) of these advantages by using interval restrictions on parameters. By…
Pediatric Health-Related Quality of Life: A Structural Equation Modeling Approach
Villalonga-Olives, Ester; Kawachi, Ichiro; Almansa, Josué; Witte, Claudia; Lange, Benjamin; Kiese-Himmel, Christiane; von Steinbüchel, Nicole
2014-01-01
Objectives One of the most referenced theoretical frameworks to measure Health Related Quality of Life (HRQoL) is the Wilson and Cleary framework. With some adaptions this framework has been validated in the adult population, but has not been tested in pediatric populations. Our goal was to empirically investigate it in children. Methods The contributory factors to Health Related Quality of Life that we included were symptom status (presence of chronic disease or hospitalizations), functional status (developmental status), developmental aspects of the individual (social-emotional) behavior, and characteristics of the social environment (socioeconomic status and area of education). Structural equation modeling was used to assess the measurement structure of the model in 214 German children (3–5 years old) participating in a follow-up study that investigates pediatric health outcomes. Results Model fit was ?2?=?5.5; df?=?6; p?=?0.48; SRMR ?=?0.01. The variance explained of Health Related Quality of Life was 15%. Health Related Quality of Life was affected by the area education (i.e. where kindergartens were located) and development status. Developmental status was affected by the area of education, socioeconomic status and individual behavior. Symptoms did not affect the model. Conclusions The goodness of fit and the overall variance explained were good. However, the results between children' and adults' tests differed and denote a conceptual gap between adult and children measures. Indeed, there is a lot of variety in pediatric Health Related Quality of Life measures, which represents a lack of a common definition of pediatric Health Related Quality of Life. We recommend that researchers invest time in the development of pediatric Health Related Quality of Life theory and theory based evaluations. PMID:25415751
Is Structural Equation Modeling Advantageous for the Genetic Improvement of Multiple Traits?
Valente, Bruno D.; Rosa, Guilherme J. M.; Gianola, Daniel; Wu, Xiao-Lin; Weigel, Kent
2013-01-01
Structural equation models (SEMs) are multivariate specifications capable of conveying causal relationships among traits. Although these models offer insights into how phenotypic traits relate to each other, it is unclear whether and how they can improve multiple-trait selection. Here, we explored concepts involved in SEMs, seeking for benefits that could be brought to breeding programs, relative to the standard multitrait model (MTM) commonly used. Genetic effects pertaining to SEMs and MTMs have distinct meanings. In SEMs, they represent genetic effects acting directly on each trait, without mediation by other traits in the model; in MTMs they express overall genetic effects on each trait, equivalent to lumping together direct and indirect genetic effects discriminated by SEMs. However, in breeding programs the goal is selecting candidates that produce offspring with best phenotypes, regardless of how traits are causally associated, so overall additive genetic effects are the matter. Thus, no information is lost in standard settings by using MTM-based predictions, even if traits are indeed causally associated. Nonetheless, causal information allows predicting effects of external interventions. One may be interested in predictions for scenarios where interventions are performed, e.g., artificially defining the value of a trait, blocking causal associations, or modifying their magnitudes. We demonstrate that with information provided by SEMs, predictions for these scenarios are possible from data recorded under no interventions. Contrariwise, MTMs do not provide information for such predictions. As livestock and crop production involves interventions such as management practices, SEMs may be advantageous in many settings. PMID:23608193
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
Is structural equation modeling advantageous for the genetic improvement of multiple traits?
Valente, Bruno D; Rosa, Guilherme J M; Gianola, Daniel; Wu, Xiao-Lin; Weigel, Kent
2013-07-01
Structural equation models (SEMs) are multivariate specifications capable of conveying causal relationships among traits. Although these models offer insights into how phenotypic traits relate to each other, it is unclear whether and how they can improve multiple-trait selection. Here, we explored concepts involved in SEMs, seeking for benefits that could be brought to breeding programs, relative to the standard multitrait model (MTM) commonly used. Genetic effects pertaining to SEMs and MTMs have distinct meanings. In SEMs, they represent genetic effects acting directly on each trait, without mediation by other traits in the model; in MTMs they express overall genetic effects on each trait, equivalent to lumping together direct and indirect genetic effects discriminated by SEMs. However, in breeding programs the goal is selecting candidates that produce offspring with best phenotypes, regardless of how traits are causally associated, so overall additive genetic effects are the matter. Thus, no information is lost in standard settings by using MTM-based predictions, even if traits are indeed causally associated. Nonetheless, causal information allows predicting effects of external interventions. One may be interested in predictions for scenarios where interventions are performed, e.g., artificially defining the value of a trait, blocking causal associations, or modifying their magnitudes. We demonstrate that with information provided by SEMs, predictions for these scenarios are possible from data recorded under no interventions. Contrariwise, MTMs do not provide information for such predictions. As livestock and crop production involves interventions such as management practices, SEMs may be advantageous in many settings. PMID:23608193
Modelling Pathways to Rubisco Degradation: A Structural Equation Network Modelling Approach
Tétard-Jones, Catherine; Gatehouse, Angharad M. R.; Cooper, Julia; Leifert, Carlo; Rushton, Steven
2014-01-01
‘Omics analysis (transcriptomics, proteomics) quantifies changes in gene/protein expression, providing a snapshot of changes in biochemical pathways over time. Although tools such as modelling that are needed to investigate the relationships between genes/proteins already exist, they are rarely utilised. We consider the potential for using Structural Equation Modelling to investigate protein-protein interactions in a proposed Rubisco protein degradation pathway using previously published data from 2D electrophoresis and mass spectrometry proteome analysis. These informed the development of a prior model that hypothesised a pathway of Rubisco Large Subunit and Small Subunit degradation, producing both primary and secondary degradation products. While some of the putative pathways were confirmed by the modelling approach, the model also demonstrated features that had not been originally hypothesised. We used Bayesian analysis based on Markov Chain Monte Carlo simulation to generate output statistics suggesting that the model had replicated the variation in the observed data due to protein-protein interactions. This study represents an early step in the development of approaches that seek to enable the full utilisation of information regarding the dynamics of biochemical pathways contained within proteomics data. As these approaches gain attention, they will guide the design and conduct of experiments that enable ‘Omics modelling to become a common place practice within molecular biology. PMID:24498339
A GENERAL PANEL MODEL WITH RANDOM AND FIXED EFFECTS: A STRUCTURAL EQUATIONS APPROACH
Bollen, Kenneth A.; Brand, Jennie E.
2011-01-01
Fixed and random effects models for longitudinal data are common in sociology. Their primary advantage is that they control for time-invariant omitted variables. However, analysts face several issues when they employ these models. One is the uncertainty of whether to apply the fixed effects (FEM) versus the random effects (REM) models. Another less discussed issue is that the FEM and REM models as usually implemented might be insufficiently flexible. For instance, the effects of variables, including the latent time-invariant variable, might change over time rather than be constant as in the usual FEM and REM. The latent time-invariant variable might correlate with some variables and not others. Lagged endogenous variables might be necessary. Alternatives that move beyond the classic FEM and REM models are known, but they involve different estimators and software that make these extended models difficult to implement and to compare. This paper presents a general panel model that includes the standard FEM and REM as special cases. In addition, it provides a sequence of nested models that provide a richer range of models that researchers can easily compare with likelihood ratio tests and fit statistics. Furthermore, researchers can implement our general panel model and its special cases in widely available structural equation models (SEMs) software. The paper is oriented towards applied researchers with most technical details given in the appendix and footnotes. An extended empirical example illustrates our results. PMID:21769157
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
Network inference of AP pattern formation system in D.melanogaster by structural equation modeling
NASA Astrophysics Data System (ADS)
Aburatani, S.; Toh, H.
2014-03-01
Within the field of systems biology, revealing the control systems functioning during embryogenesis is an important task. To clarify the mechanisms controlling sequential events, the relationships between various factors and the expression of specific genes should be determined. In this study, we applied a method based on Structural Equation Modeling (SEM), combined with factor analysis. SEM can include the latent variables within the constructed model and infer the relationships among the latent and observed variables, as a network model. We improved a method for the construction of initial models for the SEM calculation, and applied our approach to estimate the regulatory network for Antero-Posterior (AP) pattern formation in D. melanogaster embryogenesis. In this new approach, we combined cross-correlation and partial correlation to summarize the temporal information and to extract the direct interactions from the gene expression profiles. In the inferred model, 18 transcription factor genes were regulated by not only the expression of other genes, but also the estimated factors. Since each factor regulated the same type of genes, these factors were considered to be involved in maternal effects or spatial morphogen distributions. The interpretation of the inferred network model allowed us to reveal the regulatory mechanism for the patterning along the head to tail axis in D. melanogaster.
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
Stress and Resilience in Functional Somatic Syndromes – A Structural Equation Modeling Approach
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 (?2(21) ?=?48.808, p<.001, CFI ?=?.995, TLI ?=?.992, RMSEA ?=?.021, 90% CI [.013.029]) and prospective analyses (?2(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
Modeling motor connectivity using TMS/PET and structural equation modeling
Laird, Angela R.; Robbins, Jacob M.; Li, Karl; Price, Larry R.; Cykowski, Matthew D.; Narayana, Shalini; Laird, Robert W.; Franklin, Crystal; Fox, Peter T.
2010-01-01
Structural equation modeling (SEM) was applied to positron emission tomographic (PET) images acquired during transcranial magnetic stimulation (TMS) of the primary motor cortex (M1hand). TMS was applied across a range of intensities, and responses both at the stimulation site and remotely connected brain regions covaried with stimulus intensity. Regions of interest (ROIs) were identified through an activation likelihood estimation (ALE) meta-analysis of TMS studies. That these ROIs represented the network engaged by motor planning and execution was confirmed by an ALE meta-analysis of finger movement studies. Rather than postulate connections in the form of an a priori model (confirmatory approach), effective connectivity models were developed using a model-generating strategy based on improving tentatively specified models. This strategy exploited the experimentally-imposed causal relations: (1) that response variations were caused by stimulation variations, (2) that stimulation was unidirectionally applied to the M1hand region, and (3) that remote effects must be caused, either directly or indirectly, by the M1hand excitation. The path model thus derived exhibited an exceptional level of goodness (?2=22.150, df = 38, P = 0.981, TLI=1.0). The regions and connections derived were in good agreement with the known anatomy of the human and primate motor system. The model-generating SEM strategy thus proved highly effective and successfully identified a complex set of causal relationships of motor connectivity. PMID:18387823
A critical review of questionnaires for assessing pain-related disability
Richard W. Millard
1991-01-01
Standardized questionnaires offer a practical and cost-effective means for measuring moderate disability. Fourteen questionnaires that can be used for assessing pain-related disability are reviewed in this article. Their comparative attributes are summarized. Most of the questionnaires obtain information about specific activities of daily living. They vary in terms of structure, content, and intended applications. Psychometric theory provides the optimal method
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)…
The Verbalizer-Visualizer Questionnaire: a review.
Antonietti, A; Giorgetti, M
1998-02-01
The psychometric properties of Richardson's 1977 Verbalizer-Visualizer Questionnaire have been studied by analyzing papers in which this questionnaire was employed. Such review showed that the Verbalizer-Visualizer Questionnaire does not measure a unidimensional construct and does not predict the actual use of mental imagery in thinking. Further, a lack of long-term reliability of the questionnaire emerged. In conclusion, use of the questionnaire to assess the verbal-visual cognitive style appears questionable. PMID:9530739
Structural equation modeling of the proximal–distal continuum of adherence drivers
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 by about a quarter of respondents (24% and 23%, respectively). A smaller percentage of respondents had osteoporosis (17%), diabetes (15%), asthma (13%), or other cardiovascular disease (8%). Three independent variables were significantly associated with the three proximal adherence drivers: perceived disease severity, knowledge about the medication, and perceived value of nutraceuticals. Both perceived immunity to side effects and patient engagement was significantly associated with perceived need for medications and perceived medication concerns. Conclusion Testing the proximal–distal continuum of adherence drivers shed light on specific areas where adherence dialogue and enhancement should focus. Our results can help to inform the design of future adherence interventions as well as the content of patient education materials and adherence reminder letters. For long-term medication adherence, patients need to autonomously and intrinsically commit to therapy and that, in turn, is more likely to occur if they are both informed (disease and medication knowledge and rationale, disease severity, consequences of nonadherence, and side effects) and motivated (engaged in their care, perceive a need for medication, and believe the benefits outweigh the risks). PMID:23204839
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
A Structural Equation Model Analysis of Relationships among ENSO, Seasonal Descriptors and Wildfires
Slocum, Matthew G.; Orzell, Steve L.
2013-01-01
Seasonality drives ecological processes through networks of forcings, and the resultant complexity requires creative approaches for modeling to be successful. Recently ecologists and climatologists have developed sophisticated methods for fully describing seasons. However, to date the relationships among the variables produced by these methods have not been analyzed as networks, but rather with simple univariate statistics. In this manuscript we used structural equation modeling (SEM) to analyze a proposed causal network describing seasonality of rainfall for a site in south-central Florida. We also described how this network was influenced by the El Niño-Southern Oscillation (ENSO), and how the network in turn affected the site’s wildfire regime. Our models indicated that wet and dry seasons starting later in the year (or ending earlier) were shorter and had less rainfall. El Niño conditions increased dry season rainfall, and via this effect decreased the consistency of that season’s drying trend. El Niño conditions also negatively influenced how consistent the moistening trend was during the wet season, but in this case the effect was direct and did not route through rainfall. In modeling wildfires, our models showed that area burned was indirectly influenced by ENSO via its effect on dry season rainfall. Area burned was also indirectly reduced when the wet season had consistent rainfall, as such wet seasons allowed fewer wildfires in subsequent fire seasons. Overall area burned at the study site was estimated with high accuracy (R2 score = 0.63). In summary, we found that by using SEMs, we were able to clearly describe causal patterns involving seasonal climate, ENSO and wildfire. We propose that similar approaches could be effectively applied to other sites where seasonality exerts strong and complex forcings on ecological processes. PMID:24086670
Kapetanovic, Suad; Griner, Ray; Zeldow, Bret; Nichols, Sharon; Leister, Erin; Gelbard, Harris A.; Miller, Tracie L.; Hazra, Rohan; Mendez, Armando J.; Malee, Kathleen; Kammerer, Betsy; Williams, Paige L.
2014-01-01
Objective To examine the relationship between markers of vascular dysfunction and neurodevelopmental outcomes in perinatally HIV-infected (PHIV+) and perinatally HIV-exposed but uninfected (PHEU) youth. Design Cross-sectional design within a prospective, 15-site US-based cohort study. Methods Neurodevelopmental outcomes were evaluated in relation to nine selected vascular biomarkers in 342 youth (212 PHIV+, 130 PHEU). Serum levels were assessed for adiponectin, C-reactive protein (CRP), fibrinogen, interleukin-6 (IL-6), soluble vascular cell adhesion molecule-1 (sVCAM-1), E-selectin (sE-selectin), monocyte chemoattractant protein (sMCP-1), intercellular adhesion molecule-1 (sICAM-1), and P-selectin (sP-selectin). The Wechsler Intelligence Scale for Children-Fourth Edition (WISC-IV) was administered at entry, yielding a Full-Scale IQ score, and four index scores. Factor analysis was conducted to reduce the biomarkers to fewer factors with related biological roles. Structural equation models (SEMs) were used to measure associations between resulting factors and WISC-IV scores. Results Mean participant age was 11.4 years, 54% were female, 70% black. The nine biomarkers were clustered into three factor groups: F1 (fibrinogen, CRP, and IL-6); F2 (sICAM-1 and sVCAM-1); and F3 (MCP-1, sP-selectin, and sE-selectin). Adiponectin showed little correlation with any factor. SEMs revealed significant negative association of F1 with WISC-IV processing speed score in the total cohort. This effect remained significant after adjusting for HIV status and other potential confounders. A similar association was observed when restricted to PHIV+ participants in both unadjusted and adjusted SEMs. Conclusion Aggregate measures of fibrinogen, CRP, and IL-6 may serve as a latent biomarker associated with relatively decreased processing speed in both PHIV+ and PHEU youth. PMID:24670521
A structural equation model analysis of postfire plant diversity in California shrublands
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.
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.
Dang, Bich N.; Westbrook, Robert A.; Black, William C.; Rodriguez-Barradas, Maria C.; Giordano, Thomas P.
2013-01-01
Introduction Analogous to the business model of customer satisfaction and retention, patient satisfaction could serve as an innovative, patient-centered focus for increasing retention in HIV care and adherence to HAART, and ultimately HIV suppression. Objective To test, through structural equation modeling (SEM), a model of HIV suppression in which patient satisfaction influences HIV suppression indirectly through retention in HIV care and adherence to HAART. Methods We conducted a cross-sectional study of adults receiving HIV care at two clinics in Texas. Patient satisfaction was based on two validated items, one adapted from the Consumer Assessment of Healthcare Providers and Systems survey (“Would you recommend this clinic to other patients with HIV?) and one adapted from the Delighted-Terrible Scale, (“Overall, how do you feel about the care you got at this clinic in the last 12 months?”). A validated, single-item question measured adherence to HAART over the past 4 weeks. Retention in HIV care was based on visit constancy in the year prior to the survey. HIV suppression was defined as plasma HIV RNA <48 copies/mL at the time of the survey. We used SEM to test hypothesized relationships. Results The analyses included 489 patients (94% of eligible patients). The patient satisfaction score had a mean of 8.5 (median 9.2) on a 0- to 10- point scale. A total of 46% reported “excellent” adherence, 76% had adequate retention, and 70% had HIV suppression. In SEM analyses, patient satisfaction with care influences retention in HIV care and adherence to HAART, which in turn serve as key determinants of HIV suppression (all p<.0001). Conclusions Patient satisfaction may have direct effects on retention in HIV care and adherence to HAART. Interventions to improve the care experience, without necessarily targeting objective clinical performance measures, could serve as an innovative method for optimizing HIV outcomes. PMID:23382948
Satoshi Fujii; Ryuichi Kitamura
2000-01-01
A structural equations model system which represents the effects of transportation control measures on commuters’ daily activity patterns after work hours is presented. A commuter’s daily activity after work till going to sleep is defined in terms of variables that indicate time use and travel. These variables are the endogenous variables of the structural equations model system. The parameters of
Design of psychosocial factors questionnaires: a systematic measurement approach
Vargas, Angélica; Felknor, Sarah A
2012-01-01
Background Evaluation of psychosocial factors requires instruments that measure dynamic complexities. This study explains the design of a set of questionnaires to evaluate work and non-work psychosocial risk factors for stress-related illnesses. Methods The measurement model was based on a review of literature. Content validity was performed by experts and cognitive interviews. Pilot testing was carried out with a convenience sample of 132 workers. Cronbach’s alpha evaluated internal consistency and concurrent validity was estimated by Spearman correlation coefficients. Results Three questionnaires were constructed to evaluate exposure to work and non-work risk factors. Content validity improved the questionnaires coherence with the measurement model. Internal consistency was adequate (?=0.85–0.95). Concurrent validity resulted in moderate correlations of psychosocial factors with stress symptoms. Conclusions Questionnaires´ content reflected a wide spectrum of psychosocial factors sources. Cognitive interviews improved understanding of questions and dimensions. The structure of the measurement model was confirmed. PMID:22628068
Continuum Schwinger-Dyson Equations and Universal Structures in Two-Dimensional Quantum Gravity
Masafumi Fukuma; Hikaru Kawai; Ryuichi Nakayama
1991-01-01
We study the continuum Schwinger-Dyson equations for nonperturbative two-dimensional quantum gravity coupled to various matter fields. The continuum Schwinger-Dyson equations for the one-matrix model are explicitly derived and turn out to be a formal Virasoro condition on the square root of the partition function, which is conjectured to be the tau function of the KdV hierarchy. Furthermore, we argue that
N. Nettelmann; B. Holst; A. Kietzmann; M. French; R. Redmer; D. Blaschke
2008-06-06
The equation of state of hydrogen, helium, and water effects interior structure models of giant planets significantly. We present a new equation of state data table, LM-REOS, generated by large scale quantum molecular dynamics simulations for hydrogen, helium, and water in the warm dense matter regime, i.e.for megabar pressures and temperatures of several thousand Kelvin, and by advanced chemical methods in the complementary regions. The influence of LM-REOS on the structure of Jupiter is investigated and compared with state-of-the-art results within a standard three-layer model consistent with astrophysical observations of Jupiter. Our new Jupiter models predict an important impact of mixing effects of helium in hydrogen with respect to an altered compressibility and immiscibility.
Donggen Wang; Fion Yuk Ting Law
2007-01-01
The objective of this paper is to contribute an empirical study to the literature on transportation impacts of Information\\u000a and Communications Technologies (ICT). The structural equation model (SEM) is employed to analyze the impacts of ICT usage\\u000a on time use and travel behavior. The sample is derived from the travel characteristic survey conducted in Hong Kong in 2002.\\u000a The usage
Carolyn E. Ievers-Landis; Rachel Neff Greenley; Chris Burant; Elaine Borawski
2006-01-01
\\u000aPurpose: To examine the roles of cognitive social maturity and life change events in a structural equation model (SEM) to explain adolescents' use of marijuana, tobacco, and alcohol. Methods: Data were derived from 1322 9th and 10th graders in a HIV prevention study. Students completed a survey of their cognitive social maturity, recent life events and substance use habits. A
Michael Schönberger; Jennie Ponsford; John Olver; Michael Ponsford; Markus Wirtz
2011-01-01
BackgroundTraumatic brain injury (TBI) can cause lasting functional changes and lead to unemployment. The purpose of this study was to create and test a structural equation model (SEM) of the prediction of functional and employment outcome after TBI.MethodsParticipants were 949 individuals with predominantly moderate to severe TBI (74% males, median age 25.7 years) who attended a follow-up interview 1 year
Doubling versus non-doubling of equations and phase space structure in one-hermitean-matrix models
P. M. S. Petropoulos
1991-01-01
In the framework of the saddle-point approximation, we analyse the phase structure of one-hermitean-matrix models with non-even interaction potential. This enables us to reconsider the issue of the doubling phenomenon: the boundaries of the phase space are shown to correspond to critical behaviours with doubling of equations, when the eigenvalue density varrho(lambda) vanishes as the (m - 1\\/2)th power of
R. Radha; M. Lakshmanan
1994-01-01
In this article, a singularity structure analysis of a (2+1)-dimensional generalized Korteweg–de Vries equation studied originally by Boiti etal., admitting a weak Lax pair, is carried out and it is proven that the system satisfies the Painleve´ property. Its bilinear form is constructed in a natural way from the P analysis and then it is used to generate ‘‘multidromion’’ solutions
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 powerful insights that can be gained from the SEM approach in understanding the multiple direct and indirect interactions among agents and pollinators and their effects on an invasive weed. Such an approach may improve our ability to manage weeds with biocontrol agents by identifying pathways that could be exploited by future agents and minimizing the possibility of interference with established agents. PMID:23387114
Family burden in inherited ichthyosis: creation of a specific questionnaire
2013-01-01
Background The concept of individual burden, associated with disease, has been introduced recently to determine the “disability” caused by the pathology in the broadest sense of the word (psychological, social, economic, physical). Inherited ichthyosis belong to a large heterogeneous group of Mendelian Disorders of Cornification. Skin symptoms have a major impact on patients’ Quality of Life but little is known about the burden of the disease on the families of patients. Objectives To develop and validate a specific burden questionnaire for the families of patients affected by ichthyosis. Methods Two steps were required. First, the creation of the questionnaire which followed a strict methodological process involving a multidisciplinary team and families. Secondarily, the validation of the questionnaire, including the assessment of its reliability, external validity, reproducibility and sensitivity, was carried out on a population of patients affected by autosomal recessive congenital ichthyosis. A population of parents of patients affected by ichthyosis was enrolled to answer the new questionnaire in association with the Short Form Q12 questionnaire (SF-12) and a clinical severity score was filled for each patient. Results Ninety four families were interviewed to construct the verbatim in order to create the questionnaire and a cognitive debriefing was realized. The concept of burden could be structured around five components: “economic”, “daily life”, “familial and personal relationship”, “work”, and “psychological impact”. As a result, “Family Burden Ichthyosis” (FBI) reproducible questionnaire of 25 items was created. Forty two questionnaires were analyzable for psychometric validation. Reliability (Cronbach’s alpha coefficient?=?0.89), reflected the good homogeneity of the questionnaire. The correlation between mental dimensions of the SF-12 and the FBI questionnaire was statistically significant which confirmed the external validity. The mean FBI score was 71.7?±?18.8 and a significant difference in the FBI score was shown between two groups of severity underlining a good sensitivity of the questionnaire. Conclusions The internal and external validity of the “FBI” questionnaire was confirmed and it is correlated to the severity of ichtyosis. Ichthyoses, and other chronic pathologies, are difficult to assess by clinical or Quality of Life aspects alone as their impact can be multidimensional. “FBI” takes them all into consideration in order to explain every angle of the handicap generated. PMID:23414570
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.
High-Accuracy Finite Difference Equations for Simulation of Photonic Structures
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
NASA Astrophysics Data System (ADS)
Jiang, Bin; Zhang, Yejin; Wang, Yufei; Zheng, Wanhua
2012-08-01
We present the Dirichlet-to-Neumann wave vector eigen equation (DtN-WVEE) method to calculate the band structure of photonic crystal (PhC) with dispersive and lossy materials, and then use finite-difference time-domain method to verify the validity of the results of the DtN-WVEE method. Since the material is lossy with a non-zero imaginary part of epsilon, the wave vector of PhC band structure also has a non-zero imaginary part which results in the reduction of the intensity of the mode. We further present the band structure which gives the relationship among the normalized frequency, the real part of the wave vector, and the imaginary part of the wave vector. To our knowledge, the band structure of lossy PhC has not been well studied yet, and our results can be useful in designing the devices using surface plasmon polariton effect.
The higher grading structure of the WKI hierarchy and the two-component short pulse equation
NASA Astrophysics Data System (ADS)
França, G. S.; Gomes, J. F.; Zimerman, A. H.
2012-08-01
A higher grading affine algebraic construction of integrable hierarchies, containing the Wadati-Konno-Ichikawa (WKI) hierarchy as a particular case, is proposed. We show that a two-component generalization of the Schäfer-Wayne short pulse equation arises quite naturally from the first negative flow of the WKI hierarchy. Some novel integrable nonautonomous models are also proposed. The conserved charges, both local and nonlocal, are obtained from the Riccati form of the spectral problem. The loop-soliton solutions of the WKI hierarchy are systematically constructed through gauge followed by reciprocal Bäcklund transformation, establishing the precise connection between the whole WKI and AKNS hierarchies. The connection between the short pulse equation with the sine-Gordon model is extended to a correspondence between the two-component short pulse equation and the Lund-Regge model.
Thermodynamic structure of Lanczos-Lovelock field equations from near-horizon symmetries
Kothawala, Dawood; Padmanabhan, T. [IUCAA, Post Bag 4, Ganeshkhind, Pune - 411 007 (India)
2009-05-15
It is well known that, for a wide class of spacetimes with horizons, Einstein equations near the horizon can be written as a thermodynamic identity. It is also known that the Einstein tensor acquires a highly symmetric form near static, as well as stationary, horizons. We show that, for generic static spacetimes, this highly symmetric form of the Einstein tensor leads quite naturally and generically to the interpretation of the near-horizon field equations as a thermodynamic identity. We further extend this result to generic static spacetimes in Lanczos-Lovelock gravity, and show that the near-horizon field equations again represent a thermodynamic identity in all these models. These results confirm the conjecture that this thermodynamic perspective of gravity extends far beyond Einstein's theory.
Senior High School Questionnaire. Appendix C.
ERIC Educational Resources Information Center
Welch, Wayne W.; And Others
This was developed in collaboration with the White Bear Lake Senior High School Evaluation Committee to evaluate the school's flexible module scheduling program. It includes a questionnaire about the school and its program and a questionnaire form for interviews in the community. Part I of the high school questionnaire has 25 questions about the…
A Brief Guide to Questionnaire Development
NSDL National Science Digital Library
Robert Frary
This comprehensive guide leads the user step-by-step through questionnaire creation. Topics include preliminary considerations, writing the questionnaire items, issues that may come up when giving the questionnaire, statistical considerations, and references for further reading. This resource is intended for novice and professional evaluators.
A Temperament Questionnaire for Early Adult Life
Alexander Thomas; Mary Mittelman; Stella Chess; Sam J. Korn; Jacob Cohen
1982-01-01
The construction of a temperament questionnaire for early adult life is described, utilizing the nine categories of the New York Longitudinal Study. A correlation matrix of the nine categories, as generated from the 140 item questionnaire, and a factor analysis are reported, and the significance of the factor is discussed. The questionnaire was administered to 70 young adult subjects of
Confirmatory factor analysis of the equity preference questionnaire
Brian K. Miller
2009-01-01
Purpose – The purpose of this paper is to provide an analysis of the factor structure of the equity preference questionnaire (EPQ). Design\\/methodology\\/approach – Individual level data are collected from two samples (n1=382, n2=455) and subjected to confirmatory factor analysis of an a priori two-factor structure for equity sensitivity. Sample two is randomly split and one half subjected to structural
Determinant Structure of the Rational Solutions for the Painlev\\\\'e IV Equation
Kenji Kajiwara; Yasuhiro Ohta
1997-01-01
Rational solutions for the Painlev\\\\'e IV equation are investigated by Hirota bilinear formalism. It is shown that the solutions in one hierarchy are expressed by 3-reduced Schur functions, and those in another two hierarchies by Casorati determinant of the Hermite polynomials, or by special case of the Schur polynomials.
NASA Technical Reports Server (NTRS)
Peters, C.
1979-01-01
A statistical model on normal mixtures which takes into account the organization of LANDSAT agricultural data into fields which are homogeneous as to crop type is presented. Likelihood equations for the parameters of the model are derived which may be solved iteratively as in UHMLE.
Electronic structure and equation of state data of warm dense gold.
Renaudin, P; Recoules, V; Noiret, P; Clérouin, J
2006-05-01
Equation of state data and electrical resistivity of warm dense gold were measured in the internal energy range 8 - 12 MJ/kg. Experimental results were compared with quantum molecular dynamics simulations. The theoretical results match well the experimental data, allowing a detailed interpretation of the theoretical thermodynamic properties and frequency-dependent conductivities. PMID:16803046
Contrast structures for a quasilinear Sobolev-type equation with unbalanced nonlinearity
NASA Astrophysics Data System (ADS)
Bykov, A. A.; Nefedov, N. N.; Sharlo, A. S.
2014-08-01
The existence of a solution to a generalized Kolmogorov-Petrovskii-Piskunov equation is proved and its asymptotic expansion of the internal transition layer type is constructed. The convergence of the asymptotics is proved by applying the asymptotic comparison principle developed for a new class of problems.
Ryan, Travis A; Bailey, Alastair; Fearon, Pasco; King, John
2013-01-01
Objectives The UK's Improving Access to Psychological Therapies (IAPT) programme uses the Patient Health Questionnaire Depression Scale (PHQ-9; Kroenke, Spitzer, & Williams, 2001, J. Gen. Intern. Med., 16, 606) and Generalized Anxiety Disorder Scale (GAD-7; Spitzer et al., 2006, Arch. Intern. Med., 166, 1092) to assess patients' symptoms of depression and anxiety respectively. Data are typically collected via telephone or face-to-face; however, no study has statistically investigated whether the questionnaires' items operate equivalently across these modes of data collection. This study aimed to address this omission. Methods & Results Questionnaire data from patients registered with an IAPT service in London (N = 23,672) were examined. Confirmatory factor analyses suggested that unidimensional factor structures adequately matched observed face-to-face and telephone data for the PHQ-9 and GAD-7. Invariance analyses revealed that while the PHQ-9 had equivalent factor loadings and latent means across data collection methods, the GAD-7 had equivalent factor loadings but unequal latent means. In support of the scales' convergent validity, positive associations between scores on the PHQ-9 and GAD-7 emerged. Conclusions With the exception of the GAD-7's latent means, the questionnaires' factor loadings and latent means were equivalent. This suggests that clinicians may meaningfully compare PHQ-9 data collected face-to-face and by telephone; however, such comparisons with the GAD-7 should be done with caution. Practitioner points The PHQ-9 and GAD-7's factor loadings were equivalent across data collection methods. Only the PHQ-9's latent means were equivalent across data collection methods. Clinicians may be confident collecting PHQ-9 data by telephone and face-to-face and, then, comparing such data. Caution is recommended when determining clinical effectiveness using telephone and face-to-face GAD-7 data. More psychometric research is warranted. PMID:24117915
THE VISCOUS CAHN-HILLIARD EQUATION: MORSE DECOMPOSITION AND STRUCTURE OF THE GLOBAL ATTRACTOR
M. GRINFELD; A. NOVICK-COHEN
1999-01-01
In this paper we establish a Morse decomposition of the stationary solutions of the one-dimensional viscous Cahn{Hilliard equation by explicit en- ergy calculations. Strong non-degeneracy of the stationary solutions is proven away from turning points and points of bifurcation from the homogeneous state and the dimension of the unstable manifold is calculated for all station- ary states. In the unstable
Thermodynamic structure of field equations near apparent horizon for radiating black holes
NASA Astrophysics Data System (ADS)
Papnoi, Uma; Govender, Megan; Ghosh, Sushant G.
2014-10-01
We study the intriguing analogy between gravitational dynamics of the horizon and thermodynamics for the case of nonstationary radiating spherically symmetric black holes both in four dimensions and higher dimensions. By defining all kinematical parameters of nonstationary radiating black holes in terms of null vectors, we demonstrate that it is possible to interpret the Einstein field equations near the apparent horizon in the form of a thermodynamical identity T dS = dE+P dV.
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.
Kinetic Formulation of the Kohn-Sham Equations for ab initio Electronic Structure Calculations
NASA Astrophysics Data System (ADS)
Mendoza, M.; Succi, S.; Herrmann, H. J.
2014-08-01
We introduce a new connection between density functional theory and kinetic theory. In particular, we show that the Kohn-Sham equations can be reformulated as a macroscopic limit of the steady-state solution of a suitable single-particle kinetic equation. We derive a Boltzmann-like equation for a gas of quasiparticles, where the potential plays the role of an external source that generates and destroys particles, so as to drive the system towards its ground state. The ions are treated as classical particles by using either the Born-Oppenheimer dynamics or by imposing concurrent evolution with the electronic orbitals. In order to provide quantitative support to our approach, we implement a discrete (lattice) kinetic model and compute the exchange and correlation energies of simple atoms and the geometrical configuration of the methane molecule. Moreover, we also compute the first vibrational mode of the hydrogen molecule, with both Born-Oppenheimer and concurrent dynamics. Excellent agreement with values in the literature is found in all cases.
Development of a Questionnaire Assessing School Physical Activity Environment
ERIC Educational Resources Information Center
Robertson-Wilson, Jennifer; Levesque, Lucie; Holden, Ronald R.
2007-01-01
This study was designed to develop the Questionnaire Assessing School Physical Activity Environment (Q--SPACE) based on student perceptions. Twenty-eight items rated on 4-point Likert scales were administered to 244 middle school students in 9 schools. Exploratory factor analysis was used to evaluate the underlying structure of the items and 2…
The Development and Evaluation of the Academic Entitlement Questionnaire
ERIC Educational Resources Information Center
Kopp, Jason P.; Zinn, Tracy E.; Finney, Sara J.; Jurich, Daniel P.
2011-01-01
Validity evidence was gathered for the Academic Entitlement Questionnaire (AEQ). After reviewing entitlement literature, items were written to cover the breadth of academic entitlement. Results provide evidence for the substantive, structural, and external aspects of validity of the AEQ. Implications for research and use of the AEQ are discussed.…
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 ?. 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 ?, 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.
Kramer, A.; Assadian, O.; Helfrich, J.; Krüger, C.; Pfenning, I.; Ryll, S.; Perner, A.; Loczenski, B.
2013-01-01
From January to May 2012, 1,860 hospitals throughout Germany received a questionnaire encompassing 77 items. Additionally, 300 outpatient care services and 310 nursing homes for elderly in Berlin also received a 10-item questionnaire asking on their implemented infection control practices. All questionnaires were anonymous. A total of 229 completed questionnaires from hospitals, 14 questionnaires from outpatient care services, and 16 questionnaires from nursing homes were eligible for further analysis. The lack of Infection Control physicians was identified as the largest issue. In hospitals sized 400–999 beds a gap of 71%, and in hospitals sized ?1,000 beds a gap of 17% was reported. Depending on the number of hospital beds, 13–29% of hospitals sized ?100 beds reported not havening one infection control nurse. Since based on the number of beds in larger institutions or in facilities caring for high-risk patients several infection control nurses may be required, the deficiency in infection control nurses may even be higher, particularly in secondary and tertiary care facilities. Furthermore, the analysis revealed that the legal requirements for surveillance and reporting of notifiable infectious diseases have not yet been implemented in 11% of the facilities. The implementation of antibiotic strategies did show significant gaps. However, deficiencies in the implemented measures for the prevention of surgical site infections were less frequent. Yet 12% of the participants did not have a dedicated infection control concept for their surgical services. Eight percent of hospitals were not prepared for an outbreak management and 10% did not have established regulations for wearing surgical scrubs. Deficiencies in waste disposal and the control of air-conditioning systems were also noted. Based on the results of this survey, conclusions on the optimal resource allocation for further improvement of patient safety may be drawn. While all participating nursing homes had some sort of infection control consultation, this only applied to 12 out of 16 outpatient nursing services. However, all 16 nursing services worked on the basis of an implemented infection control plan. Though legally binding hygiene recommendations have not yet been implemented for nursing homes, the necessity of infection control to assure patient safety has obviously been recognised throughout these services. PMID:23967397
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-arch shapes), dam failures, floodways, and underflow gates (sluice and tainter gates). The theory for computation of the hydraulic characteristics is presented for open channels and for each hydraulic control structure. For the hydraulic control structures, the theory is developed from the results of experimental tests of flow through the structure for different upstream and downstream flow depths. These tests were done to describe flow hydraulics for a single, steady-flow design condition and, thus, do not provide complete information on flow transitions (for example, between free- and submerged-weir flow) that may result in simulation of unsteady flow. Therefore, new procedures are developed to approximate the hydraulics of flow transitions for culverts, embankments, weirs, and underflow gates.
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…
Development and Preliminary Validation of Chinese Preschoolers’ Eating Behavior Questionnaire
Zhang, Yuhai; Wang, Baoxi; Sun, Lijun; Shang, Lei
2014-01-01
Background The objective of this study was to develop a questionnaire for caregivers to assess the eating behavior of Chinese preschoolers. Methods To assess children’s eating behaviors, 152 items were derived from a broad review of the literature related to epidemiology surveys and the assessment of children’s eating behaviors. All of these items were reviewed by 50 caregivers of preschoolers and 10 experienced pediatricians. Seventy-seven items were selected for use in a primary questionnaire. After conducting an exploratory factor analysis and a variability analysis on the data from 313 preschoolers used to evaluate this primary questionnaire, we deleted 39 of these 77 items. A Chinese Preschoolers’ Eating Behavior Questionnaire (CPEBQ) was finally established from the remaining 38 items. The structure of this questionnaire was explored by factor analysis, and its reliability, validity and discriminative ability were evaluated with data collected from caregivers of 603 preschoolers. Results The CPEBQ consisted of 7 dimensions and 38 items. The 7 dimensions were food fussiness, food responsiveness, eating habit, satiety responsiveness, exogenous eating, emotional eating and initiative eating. The Cronbach’s ? coefficient for the questionnaire was 0.92, and the test-retest reliability was 0.72. There were significant differences between the scores of normal-weight, overweight and obese preschoolers when it was referred to food fussiness, food responsiveness, eating habits, satiety responsiveness and emotional eating (p<0.05). Differences in caregiver’s education levels also had significant effects on scores for food fussiness, eating habits and exogenous eating (p<0.05). Conclusions The CPEBQ satisfies the conditions of reliability and validity, in accordance with psychometric demands. The questionnaire can be employed to evaluate the characteristics of Chinese preschoolers’ eating behaviors; therefore, it can be used in child health care practice and research. PMID:24520359
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 the compositional effect is offset by another effect such as higher interior entropy. On the other hand, our new models for high-entropy exoplanets are few tenths of R_J larger than SCVH models at the same entropy. In summary, the new equation of state yields corrections (with respect to SCVH) to planetary structure that are comparable to other important corrections such as rotation and deviations from constant entropy. For studies of the planets Jupiter and Saturn, where new interior-structure data from the Juno and Cassini missions are in prospect, the advanced equation of state will be necessary to accurately derive important quantities such as core mass and mantle enrichment in heavy elements.
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
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
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
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.
Developing a Questionnaire on Attitude towards School
ERIC Educational Resources Information Center
Seker, Hasan
2011-01-01
The purpose of the present study was to develop a questionnaire to assess student attitudes towards school by describing the factors that affect these attitudes. For this purpose, a sample of 362 (11-13 years-old) elementary-school students was used. Both exploratory and confirmatory factor analyses were carried out. The questionnaire consists of…
Applying Learning Strategy Questionnaires: Problems and Possibilities
ERIC Educational Resources Information Center
Schellings, Gonny
2011-01-01
This article discusses measuring learning strategies by means of questionnaires. In "multi-method" research, in which think-aloud measures are compared with questionnaires, low or moderate correlations are found. A conclusion often drawn is that learners are not able to verbally report on their learning activities. Alternative explanations concern…
Questionnaire Design: Asking Questions with a Purpose
NSDL National Science Digital Library
Ellen Taylor-Powell
This short document guides the user through the stages of creating and implementing an effective questionnaire. The types of questions and how they should be worded are addressed, and many good examples of the different types of questions that could go into a questionnaire are presented. This resource is intended for novice evaluators.
ORIGINAL PAPER The Broad Autism Phenotype Questionnaire
van Lambalgen, Michiel
ORIGINAL PAPER The Broad Autism Phenotype Questionnaire Robert S. E. Hurley Æ Molly Losh Æ Morgan Phenotype Questionnaire (BAPQ), was administered to 86 parents of autistic individuals and 64 community@med.unc.edu J. S. Reznick Department of Psychology, University of North Carolina, Chapel Hill, NC 27599
. Introduction LNG FEM, short for the linear graded finite element method (FEM), is a free software package in the finite element method. We hope it triggers more interest and discoveries both in academia and in industry structures [16, 24, 26], and for construction of linear finite element solutions for elliptic boundary value
ERIC Educational Resources Information Center
Lay, Jinn-Guey; Chi, Yu-Lin; Hsieh, Yeu-Sheng; Chen, Yu-Wen
2013-01-01
Understanding the usage of the geographic information system (GIS) among geography teachers is a crucial step in evaluating the current dissemination of GIS knowledge and skills in Taiwan's educational system. The primary contribution of this research is to further our understanding of the factors that affect teachers' GIS usage. The structural…
I-Li LU
In scientic research, data acquired in time-series and cross-sectional form or from experiments with repeated measures often exhibit strong association in the response variables. The phenomenon sometime may be explained by theoretical reasoning or can be attributed to the existence of some structural relations that linked the variables together. When latter is alleged, one usually attempts to discover the underlying
Ecological Modelling 192 (2006) 385409 Exploring ecological patterns with structural equation
Arhonditsis, George B.
2006-01-01
in revised form 26 May 2005; accepted 18 July 2005 Available online 3 October 2005 Abstract Structural development, while both direct and indirect effects and measurement errors are considered. Given dynamics; Water quality management 1. Introduction ". . .Thinking only in terms of directly observable vari
Toward a Model of Motivated Vocabulary Learning: A Structural Equation Modeling Approach
ERIC Educational Resources Information Center
Tseng, Wen-Ta; Schmitt, Norbert
2008-01-01
This study presents a structural model that integrates vocabulary knowledge and motivation with six latent variables: the initial appraisal of vocabulary learning experience, self-regulating capacity of vocabulary learning, strategic vocabulary learning involvement, mastery of vocabulary learning tactics, vocabulary knowledge, and postappraisal of…
Nooijen, Marcel; Demel, Ond?ej; 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
NASA Astrophysics Data System (ADS)
Neufeld, M.; Walgraef, D.; San Miguel, M.
1996-12-01
We investigate a pattern-forming system close to a Hopf bifurcation with broken translational symmetry. In one-dimensional geometries, its evolution is governed by two coupled complex Ginzburg-Landau equations which describe the amplitude of the counterpropagating traveling waves that develop beyond the instability. The convective and absolute instabilities of the possible steady states are analyzed. In the regime of strong cross coupling, where traveling waves are favored by the dynamics, the results of previous analysis are recovered. In the weak cross-coupling regime, where standing waves are favored by the dynamics, traveling waves nevertheless appear, in the absence of noise, between the uniform steady state and the standing-wave patterns. In this regime, standing waves are sustained by spatially distributed external noise for all values of the bifurcation parameter beyond the Hopf bifurcation. Hence, the noise is not only able to sustain spatiotemporal patterns, but also to modify pattern selection processes in regimes of convective instability. In this weak coupling regime we also give a quantitative statistical characterization of the transition between deterministic and noise-sustained standing waves when varying the bifurcation parameter. We show that this transition occurs at a noise-shifted point and it is identified by an apparent divergence of a correlation time and the saturation of a correlation length to a value given by the system size.
NASA Astrophysics Data System (ADS)
Nooijen, Marcel; Demel, Ond?ej; Datta, Dipayan; Kong, Liguo; Shamasundar, K. R.; Lotrich, V.; Huntington, Lee M.; Neese, Frank
2014-02-01
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.
Burgers' Equation Burgers' equation
Gardner, Carl
Burgers' Equation Burgers' equation ut + uux = uxx is the simplest PDE that models the more complicated Navier-Stokes equa- tions (viscous fluid dynamics, boundary layers, etc.). The inviscid Burgers of ideal gas dynamics (shock and rarefaction waves). The inviscid Burgers' equation ut + uux = 0
ERIC Educational Resources Information Center
Moulding, Richard; Anglim, Jeromy; Nedeljkovic, Maja; Doron, Guy; Kyrios, Michael; Ayalon, Ariel
2011-01-01
The study aimed to examine the factor structure of the Obsessive Beliefs Questionnaire (OBQ), the most widely used measure of dysfunctional beliefs in obsessive-compulsive disorder (OCD). Multiple exploratory methods (exploratory factor analysis, cluster analysis by variable, multidimensional scaling) were used to examine the questionnaire.…
The Prospective and Retrospective Memory Questionnaire (PRMQ): Normative data and latent
Crawford, John R.
The Prospective and Retrospective Memory Questionnaire (PRMQ): Normative data and latent structure The Prospective and Retrospective Memory Questionnaire (PRMQ; Smith, Della Sala, Logie, & Maylor, 2000±275 # 2003 Psychology Press Ltd http://www.tandf.co.uk/journals/pp/09658211.html DOI:10
Psychometric Properties of the Portuguese Version of the Quality of Life Questionnaire (QOL-Q)
ERIC Educational Resources Information Center
Albuquerque, Cristina P.
2012-01-01
Background: This study analyzes the psychometric properties of the Portuguese version of the Quality of Life Questionnaire (QOL-Q; Quality of Life Questionnaire Manual--1993 Manual and 2004 Revision. 2004, IDS Publishing Company, Worthington, OH; Schalock & Keith 2004). Method: The analysis of the factorial structure was carried out on a sample of…
NASA Astrophysics Data System (ADS)
Vuilleumier, Rodolphe; Seitsonen, Ari; Sator, Nicolas; Guillot, Bertrand
2014-09-01
First-principle molecular dynamics (FPMD) calculations have been performed to evaluate the physical properties of liquid calcium carbonate (CaCO3), which are up to now poorly known. The liquid structure, the density, the atomic vibration motions, the diffusion coefficients of calcium and carbonate ions and the electrical conductivity have been evaluated. As compared with silicate melts, molten CaCO3 is characterized by a low density (?2.25 g/cm3 at 1623 K and 0.5 GPa), a viscosity almost as low as that of water (?5 mPa s), and a high conductivity (?200 S/m). In using the FPMD calculations for benchmark, an empirical force field has been developed for predicting the properties of molten CaCO3 at any state point in the liquid stability field. This force field is implemented into a classical molecular dynamics (MD) code, much cheaper in computer time, and the equation of state and the phase diagram of the liquid phase have been obtained. The evolutions of the self diffusion coefficients, viscosity, and the electrical conductivity with pressure and temperature have been investigated and the results fitted with analytical forms. It is shown that the Stokes-Einstein equation, expressing the viscosity as a function of diffusion motion, is well followed, and that the Nernst-Einstein equation relating the electrical conductivity to the diffusion coefficients of charge carriers leads to an accurate prediction of the conductivity, provided that a constant correcting factor is applied. Consequently, viscosity and electrical conductivity of the liquid are found to be anticorrelated with each other and can be described by a simple law; ? = A/?0.9 (where A = 1.905, ? is in S/m, and ? in Pa s).
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.
Integrable Structure of Conformal Field Theory II.Q-operator and DDV equation
Vladimir V. Bazhanov; Sergei L. Lukyanov; Alexander B. Zamolodchikov
1997-01-01
: This paper is a direct continuation of [1] where we began the study of the integrable structures in Conformal Field Theory.\\u000a We show here how to construct the operators ${\\\\bf Q}_{\\\\pm}(\\\\lambda)$ which act in the highest weight Virasoro module and commute\\u000a for different values of the parameter ?. These operators appear to be the CFT analogs of the Q -
Mahdi Abbasi; Nadereh Golshan Ebrahimi; Mahdi Nadali; Masood Khabazian Esfahani
Molecular stress function theory with new strain energy function is used to analyze transient extensional viscosity data of\\u000a seven low-density polyethylene (LDPE) melts with various molecular structures as published by Stadler et al. (Rheol Acta 48:479–490,\\u000a 2009) Pivokonsky et al. (J Non Newton Fluid Mech 135:58–67, 2006) and Wagner et al. (J Rheol 47(3):779–793, 2003). The new strain energy function
Multi-Center Electronic Structure Calculations for Plasma Equation of State
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.
Gross, James J.
Berkeley Expressivity Questionnaire The Berkeley Expressivity Questionnaire assesses three facets-reports, peer ratings, and behavior. Journal of Personality and Social Psychology, 72, 435-448. Other references include: Gross, J.J. (2000). The Berkeley Expressivity Questionnaire. In J. Maltby, C.A. Lewis, & A
S. Ian Robertson
2004-01-01
A sample of 202 students filling in a student evaluation of teaching (SET) questionnaire were asked to complete another questionnaire asking about the specific reasons for awarding a score to the specific SET questionnaire items. The aim was to find out what influenced students' judgements on those items. It was found that students' interpretation of some questions differed from the
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
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. PMID:25339790
Psychometric properties of the Questionnaire for Secondary Traumatization
Weitkamp, Katharina; Daniels, Judith K.; Klasen, Fionna
2014-01-01
Background During the past several years, there has been a growing interest in the negative effects that providing therapy may have on therapists. Of special interest is a phenomenon called secondary traumatization, which can arise while working with traumatized clients. To develop a simple screening tool for secondary traumatization, a quantitative assessment instrument was constructed using a data-driven approach based on qualitative interviews with affected trauma therapists as well as experienced supervisors in trauma therapy. Objective The aim of the current study was to analyze the psychometric properties of the newly developed Questionnaire for Secondary Traumatization (FST) acute and lifetime version and to determine the most appropriate scoring procedure. Method To this end, three independent samples of psychotherapists (n=371), trauma therapists in training (n=80), and refugee counselors (n=197) filled out an online questionnaire battery. Data structure was analyzed using factor analyses, cluster analyses, and reliability analyses. Results Factor analyses yielded a six-factor structure for both the acute and the lifetime version with only a small number of items loading on differing factors. Cluster analyses suggested a single scale structure of the questionnaire. The FST total score showed good internal consistencies across all three samples, while internal consistency of the six extracted factors was mixed. Conclusion With the FST, a reliable screening instrument for acute and lifetime secondary traumatization is now available which is free of charge and yields a sum score for quick evaluation. The six-factor structure needs to be verified with confirmatory factor analyses. PMID:24427450
Dai, Chao-Qing; Wang, Yan
2014-01-01
The spatiotemporal nonlinear Schrödinger equation with power-law nonlinearity in -symmetric potentials is investigated, and two families of analytical three-dimensional spatiotemporal structure solutions are obtained. The stability of these solutions is tested by the linear stability analysis and the direct numerical simulation. Results indicate that solutions are stable below some thresholds for the imaginary part of -symmetric potentials in the self-focusing medium, while they are always unstable for all parameters in the self-defocusing medium. Moreover, some dynamical properties of these solutions are discussed, such as the phase switch, power and transverse power-flow density. The span of phase switch gradually enlarges with the decrease of the competing parameter k in -symmetric potentials. The power and power-flow density are all positive, which implies that the power flow and exchange from the gain toward the loss domains in the cell. PMID:24983624
Snyder, James
2014-01-01
Objective?Demonstrate multivariate multilevel survival analysis within a larger structural equation model. Test the 3 hypotheses that when confronted by a negative parent, child rates of angry, sad/fearful, and positive emotion will increase, decrease, and stay the same, respectively, for antisocial compared with normal children. This same pattern will predict increases in future antisocial behavior.?Methods?Parent–child dyads were videotaped in the fall of kindergarten in the laboratory and antisocial behavior ratings were obtained in the fall of kindergarten and third grade.?Results?Kindergarten antisocial predicted less child sad/fear and child positive but did not predict child anger given parent negative. Less child positive and more child neutral given parent negative predicted increases in third-grade antisocial behavior.?Conclusions?The model is a useful analytic tool for studying rates of social behavior. Lack of positive affect or excess neutral affect may be a new risk factor for child antisocial behavior. PMID:24133296