Home About us Contact
|
Home About us Contact | ||
|
|
||
Invariance
Kinds of Invariance Terms modified by Invariance Selected AbstractsGrade-Level Invariance of a Theoretical Causal Structure Predicting Reading Comprehension With Vocabulary and Oral Reading FluencyEDUCATIONAL MEASUREMENT: ISSUES AND PRACTICE, Issue 3 2005Paul Yovanoff This research investigates the relative importance of vocabulary and oral reading fluency as measurement dimensions of reading comprehension as the student passes from elementary to high school. Invariance of this model over grades 4 through 8 is tested using two independent student samples reading grade-level appropriate passages. Results from structural equation modeling indicate that the model is not invariant across grade levels. Vocabulary knowledge is a significant and constant predictor of overall reading comprehension irrespective of grade level. While significant, fluency effects diminish over grades, especially in the later grades. Lack of grade level invariance was obtained with both samples. Results are discussed in light of vertically linked reading assessments, adequate yearly progress, and instruction. [source] An Application of Score Equity Assessment: Invariance of Linkage of New SAT® to Old SAT Across Gender GroupsJOURNAL OF EDUCATIONAL MEASUREMENT, Issue 2 2006Jinghua Liu The College Board's SAT® data are used to illustrate how the score equity assessment (SEA) can help inform the program about equatability. SEA is used to examine whether the content change(s) to the revised new SAT result in differential linking functions across gender groups. Results of population sensitivity analyses are reported on the linkage of the new SAT critical reading (CR) prototype to an old SAT verbal (OV). Based on the criteria used in this study, population invariance was achieved with respect to gender groups. [source] Invariance and factorial modelsJOURNAL OF THE ROYAL STATISTICAL SOCIETY: SERIES B (STATISTICAL METHODOLOGY), Issue 2 2000P. McCullagh Two factors having the same set of levels are said to be homologous. This paper aims to extend the domain of factorial models to designs that include homologous factors. In doing so, it is necessary first to identify the characteristic property of those vector spaces that constitute the standard factorial models. We argue here that essentially every interesting statistical model specified by a vector space is necessarily a representation of some algebraic category. Logical consistency of the sort associated with the standard marginality conditions is guaranteed by category representations, but not by group representations. Marginality is thus interpreted as invariance under selection of factor levels (I -representations), and invariance under replication of levels (S -representations). For designs in which each factor occurs once, the representations of the product category coincide with the standard factorial models. For designs that include homologous factors, the set of S -representations is a subset of the I -representations. It is shown that symmetry and quasi-symmetry are representations in both senses, but that not all representations include the constant functions (intercept). The beginnings of an extended algebra for constructing general I -representations is described and illustrated by a diallel cross design. [source] An Efficient Taper for Potentially Overdifferenced Long-memory Time SeriesJOURNAL OF TIME SERIES ANALYSIS, Issue 2 2000Clifford M. Hurvich We propose a new complex-valued taper and derive the properties of a tapered Gaussian semiparametric estimator of the long-memory parameter d, (,0.5, 1.5). The estimator and its accompanying theory can be applied to generalized unit root testing. In the proposed method, the data are differenced once before the taper is applied. This guarantees that the tapered estimator is invariant with respect to deterministic linear trends in the original series. Any detrimental leakage effects due to the potential noninvertibility of the differenced series are strongly mitigated by the taper. The proposed estimator is shown to be more efficient than existing invariant tapered estimators. Invariance to kth order polynomial trends can be attained by differencing the data k times and then applying a stronger taper, which is given by the kth power of the proposed taper. We show that this new family of tapers enjoys strong efficiency gains over comparable existing tapers. Analysis of both simulated and actual data highlights potential advantages of the tapered estimator of d compared with the nontapered estimator. [source] A Note on the ,Invariance of Market Innovation to the Number of Firms'*BULLETIN OF ECONOMIC RESEARCH, Issue 1 2000Yuki Iidaka This note disputes the claim by Sah and Stiglitz (Rand Journal of Economics, 1987, pp. 98,108) that their strong invariance result holds in a wide range of situations. [source] Testing Measurement Invariance Using Item Response Theory in Longitudinal Data: An IntroductionCHILD DEVELOPMENT PERSPECTIVES, Issue 1 2010Roger E. Millsap Abstract, Item response theory (IRT) consists of a set of mathematical models for the probabilities of various responses to test items as a function of item and person characteristics. In longitudinal data, changes in measured variables can only be interpreted if important psychometric features of the measured variables are assumed invariant across time. Measurement invariance is invariance in the relation of a measure to the latent variable underlying it. Measurement invariance in longitudinal studies concerns invariance over time, and IRT provides a useful approach to investigating longitudinal measurement invariance. Commonly used IRT models are described, along with the representation of measurement invariance in IRT. The use of IRT for investigating invariance is then described, along with practical considerations in using IRT for this purpose. Conceptual issues, rather than technical details, are emphasized throughout. [source] Factorial Invariance Within Longitudinal Structural Equation Models: Measuring the Same Construct Across TimeCHILD DEVELOPMENT PERSPECTIVES, Issue 1 2010Keith F. Widaman Abstract, Charting change in behavior as a function of age and investigating longitudinal relations among constructs are primary goals of developmental research. Traditionally, researchers rely on a single measure (e.g., scale score) for a given construct for each person at each occasion of measurement, assuming that measure reflects the same construct at each occasion. With multiple indicators of a latent construct at each time of measurement, the researcher can evaluate whether factorial invariance holds. If factorial invariance constraints are satisfied, latent variable scores at each time of measurement are on the same metric and stronger conclusions are warranted. This article discusses factorial invariance in longitudinal studies, contrasting analytic approaches and highlighting strengths of the multiple-indicator approach to modeling developmental processes. [source] Barycentric Coordinates on SurfacesCOMPUTER GRAPHICS FORUM, Issue 5 2010Raif M. Rustamov This paper introduces a method for defining and efficiently computing barycentric coordinates with respect to polygons on general surfaces. Our construction is geared towards injective polygons (polygons that can be enclosed in a metric ball of an appropriate size) and is based on replacing the linear precision property of planar coordinates by a requirement in terms of center of mass, and generalizing this requirement to the surface setting. We show that the resulting surface barycentric coordinates can be computed using planar barycentric coordinates with respect to a polygon in the tangent plane. We prove theoretically that the surface coordinates properly generalize the planar coordinates and carry some of their useful properties such as unique reconstruction of a point given its coordinates, uniqueness for triangles, edge linearity, similarity invariance, and smoothness; in addition, these coordinates are insensitive to isometric deformations and can be used to reconstruct isometries. We show empirically that surface coordinates are shape-aware with consistent gross behavior across different surfaces, are well-behaved for different polygon types/locations on variety of surface forms, and that they are fast to compute. Finally, we demonstrate effectiveness of surface coordinates for interpolation, decal mapping, and correspondence refinement. [source] Position-Invariant Neural Network for Digital Pavement Crack AnalysisCOMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 2 2004Byoung Jik Lee This system includes three neural networks: (1) image-based neural network, (2) histogram-based neural network, and (3) proximity-based neural network. These three neural networks were developed to classify various crack types based on the subimages (crack tiles) rather than crack pixels in digital pavement images. These spatial neural networks were trained using artificially generated data following the Federal Highway Administration (FHWA) guidelines. The optimal architecture of each neural network was determined based on the testing results from different sets of the number of hidden units, learning coefficients, and the number of training epochs. To validate the system, actual pavement pictures taken from pavements as well as the computer-generated data were used. The proximity value is determined by computing relative distribution of crack tiles within the image. The proximity-based neural network effectively searches the patterns of various crack types in both horizontal and vertical directions while maintaining its position invariance. The final result indicates that the proximity-based neural network produced the best result with the accuracy of 95.2% despite its simplest neural network structure with the least computing requirement. [source] Measurement Equivalence Using Generalizability Theory: An Examination of Manufacturing Flexibility DimensionsDECISION SCIENCES, Issue 4 2008Manoj K. Malhotra ABSTRACT As the field of decision sciences in general and operations management in particular has matured from theory building to theory testing over the past two decades, it has witnessed an explosion in empirical research. Much of this work is anchored in survey-based methodologies in which data are collected from the field in the form of scale items that are then analyzed to measure latent unobservable constructs. It is important to assess the invariance of scales across groups in order to reach valid, scientifically sound conclusions. Because studies have often been conducted in the field of decision sciences with small sample sizes, it further exacerbates the problem of reaching incorrect conclusions. Generalizability theory can more effectively test for measurement equivalence in the presence of small sample sizes than the confirmatory factor analysis (CFA) tests that have been conventionally used for assessing measurement equivalency across groups. Consequently, we introduce and explain the generalizability theory (G-theory) in this article to examine measurement equivalence of 24 manufacturing flexibility dimension scales that have been published in prior literature and also compare and contrast G-theory with CFA. We show that all the manufacturing flexibility scales tested in this study were invariant across the three industry SIC groups from which data were collected. We strongly recommend that G-theory should always be used for determining measurement equivalence in empirical survey-based studies. In addition, because using G-theory alone does not always reveal the complete picture, CFA techniques for establishing measurement equivalence should also be invoked when sample sizes are large enough to do so. Implications of G-theory for practice and its future use in operations management and decision sciences research are also presented. [source] Cardiac anxiety in people with and without coronary atherosclerosis,DEPRESSION AND ANXIETY, Issue 10 2008Craig D. Marker Ph.D. Abstract Many studies have shown that cardiac anxiety when occurring in the absence of coronary artery disease is common and quite costly. The Cardiac Anxiety Questionnaire (CAQ) is an 18-item self-report measure that assesses anxiety related to cardiac symptoms. To better understand the construct of cardiac anxiety, a factor analysis was conducted on CAQ data from 658 individuals who were self or physician-referred for electron beam tomographic screening to determine whether clinically significant coronary atherosclerosis was present. A four-factor solution was judged to provide the best fit with the results reflecting the following factor composition: heart-focused attention, avoidance of activities that bring on symptoms, worry or fear regarding symptoms, and reassurance-seeking. Factorial invariance across groups was also assessed to determine whether the factor structure of the CAQ was similar in individuals with and without clear evidence of coronary atherosclerosis. The factor structure of the CAQ did not differ between the two groups. However, the group without coronary atherosclerosis had significantly higher mean scores on their attention and worry/fear factors suggesting that people without a diagnosed cardiac condition pay more attention to and worry more about their cardiac-related symptoms than those people who have coronary atherosclerosis. Depression and Anxiety 2007. Published 2007 Wiley-Liss, Inc. [source] Perception of audiovisual rhythm and its invariance in 4- to 10-month-old infantsDEVELOPMENTAL PSYCHOBIOLOGY, Issue 4 2006David J. Lewkowicz Abstract This study investigated the perception of complex audiovisual rhythmic patterns in 4-, 6-, 8-, and 10-month-old human infants. In Experiment 1, we first habituated infants to an event in which an object could be seen and heard bouncing in a rhythmic fashion. We then tested them to determine if they would detect a relative temporal pattern change produced by rearranging the intrapattern intervals. Regardless of age, infants successfully detected the pattern change. In Experiment 2, we asked whether infants also can extract rhythmic pattern invariance amid tempo variations. Thus, we first habituated infants to a particular rhythmic pattern but this time varying in its tempo of presentation across trials. We then administered one test trial in which a novel rhythm was presented at a familiar tempo and another test trial in which a familiar rhythm was presented at a novel tempo. Infants detected both types of changes indicating that they perceived the invariant rhythm and that they did so despite the fact that they also detected the varying tempo. Overall, the findings demonstrate that infants between 4 and 10 months of age can perceive and discriminate complex audiovisual temporal patterns on the basis of relative temporal differences and that they also can learn the invariant nature of such patterns. © 2006 Wiley Periodicals, Inc. Dev Psyshobiol 48: 288,300, 2006. [source] Relating streamflow characteristics to specialized insectivores in the Tennessee River Valley: a regional approach,ECOHYDROLOGY, Issue 4 2008Rodney R. Knight Abstract Analysis of hydrologic time series and fish community data across the Tennessee River Valley identified three hydrologic metrics essential to habitat suitability and food availability for insectivorous fish communities in streams of the Tennessee River Valley: constancy (flow stability or temporal invariance), frequency of moderate flooding (frequency of habitat disturbance), and rate of streamflow recession. Initial datasets included 1100 fish community sites and 300 streamgages. Reduction of these datasets to sites with coexisting data yielded 33 sites with streamflow and fish community data for analysis. Identification of critical hydrologic metrics was completed using a multivariate correlation procedure that maximizes the rank correlation between the hydrologic metrics and fish community resemblance matrices. Quantile regression was used to define thresholds of potential ranges of insectivore scores for given values of the hydrologic metrics. Increased values of constancy and insectivore scores were positively correlated. Constancy of streamflow maintains wetted perimeter, which is important for providing habitat for fish spawning and increased surface area for invertebrate colonization and reproduction. Site scores for insectivorous fish increased as the frequency of moderate flooding (3 times the median annual streamflow) decreased, suggesting that insectivorous fish communities respond positively to less frequent disturbance and a more stable habitat. Increased streamflow recession rates were associated with decreased insectivore scores. Increased streamflow recession can strand fish in pools and other areas that are disconnected from flowing water and remove invertebrates as food sources that were suspended during high-streamflow events. Copyright © 2008 John Wiley & Sons, Ltd. [source] Testing for criticality in ecosystem dynamics: the case of Amazonian rainforest and savanna fireECOLOGY LETTERS, Issue 7 2010Salvador Pueyo Ecology Letters (2010) 13: 793,802 Abstract We test for two critical phenomena in Amazonian ecosystems: self-organized criticality (SOC) and critical transitions. SOC is often presented in the complex systems literature as a general explanation for scale invariance in nature. In particular, this mechanism is claimed to underlie the macroscopic structure and dynamics of terrestrial ecosystems. These would be inextricably linked to the action of fire, which is conceived as an endogenous ecological process. We show that Amazonian savanna fires display the scale-invariant features characteristic of SOC but do not display SOC. The same is true in Amazonian rainforests subject to moderate drought. These findings prove that there are other causes of scale invariance in ecosystems. In contrast, we do find evidence of a critical transition to a megafire regime under extreme drought in rainforests; this phenomenon is likely to determine the time scale of a possible loss of Amazonian rainforest caused by climate change. [source] Mass invariance of population nitrogen flux by terrestrial mammalian herbivores: an extension of the energetic equivalence ruleECOLOGY LETTERS, Issue 9 2008Christopher W. Habeck Abstract According to the energetic equivalence rule, energy use by a population is independent of average adult body mass. Energy use can be equated with carbon flux, and it has been suggested that population fluxes of other materials, such as nitrogen and phosphorus, might also be independent of body mass. We compiled data on individual nitrogen deposition rates (via faeces and urine) and average population densities of 26 species of mammalian herbivores to test the hypothesis of elemental equivalence for nitrogen. We found that the mass scaling of individual nitrogen flux was opposite to that of population density for the species in our dataset. By computing the product of individual nitrogen flux and average population density for each species in our dataset, we found that population-level nitrogen flux was independent of species mass, averaging c. 3.22 g N ha,1 day,1. Results from this analysis can be used to understand the influence of mammalian herbivore communities on nitrogen cycling in terrestrial ecosystems. [source] The dimensionality of alcohol use disorders and alcohol consumption in a cross-national perspectiveADDICTION, Issue 2 2010Guilherme Borges ABSTRACT Aims To replicate the finding that there is a single dimension trait in alcohol use disorders and to test whether the usual 5+ drinks for men and 4+ drinks for women and other measures of alcohol consumption help to improve alcohol use disorder criteria in a series of diverse patients from emergency departments (EDs) in four countries. Design Cross-sectional surveys of patients aged 18 years and older that reflected consecutive arrival at the ED. The Composite International Diagnostic Interview Core was used to obtain a diagnosis of DSM-IV alcohol dependence and alcohol abuse; quantity and frequency of drinking and drunkenness as well as usual number of drinks consumed during the last year. Setting Participants were 5195 injured and non-injured patients attending seven EDs in four countries: Argentina, Mexico, Poland and the United States (between 1995,2001). Findings Using exploratory factor analyses alcohol use disorders can be described as a single, unidimensional continuum without any clear-cut distinction between the criteria for dependence and abuse in all sites. Results from item response theory analyses showed that the current DSM-IV criteria tap people in the middle,upper end of the alcohol use disorder continuum. Alcohol consumption (amount and frequency of use) can be used in all EDs with the current DSM-IV diagnostic criteria to help tap the middle,lower part of this continuum. Even though some specific diagnostic criteria and some alcohol consumption variables showed differential item function across sites, test response curves were invariant for ED sites and their inclusion would not impact the final (total) performance of the diagnostic system. Conclusions DSM-IV abuse and dependence form a unidimensional continuum in ED patients regardless of country of survey. Alcohol consumption variables, if added, would help to tap patients with more moderate severity. The DSM diagnostic system for alcohol use disorders showed invariance and performed extremely well in these samples. [source] Grade-Level Invariance of a Theoretical Causal Structure Predicting Reading Comprehension With Vocabulary and Oral Reading FluencyEDUCATIONAL MEASUREMENT: ISSUES AND PRACTICE, Issue 3 2005Paul Yovanoff This research investigates the relative importance of vocabulary and oral reading fluency as measurement dimensions of reading comprehension as the student passes from elementary to high school. Invariance of this model over grades 4 through 8 is tested using two independent student samples reading grade-level appropriate passages. Results from structural equation modeling indicate that the model is not invariant across grade levels. Vocabulary knowledge is a significant and constant predictor of overall reading comprehension irrespective of grade level. While significant, fluency effects diminish over grades, especially in the later grades. Lack of grade level invariance was obtained with both samples. Results are discussed in light of vertically linked reading assessments, adequate yearly progress, and instruction. [source] Complex-valued multidirectional associative memoryELECTRICAL ENGINEERING IN JAPAN, Issue 1 2007Masaki Kobayashi Abstract Hopfield model is a representative associative memory. It was improved to Bidirectional Associative Memory (BAM) by Kosko and to Multidirectional Associative Memory (MAM) by Hagiwara. They have two layers or multilayers. Since they have symmetric connections between layers, they ensure convergence. MAM can deal with multiples of many patterns, such as (x1,x2,,), where xm is the pattern on layer m. Copyright © 2004 Wiley Periodicals, Inc. Noest, Hirose, and Nemoto proposed complex-value Hopfield model. Lee proposed complex-valued Bidirectional Associative Memory. Zemel proved the rotation invariance of complex-valued Hopfield model. It means that the rotated pattern in also stored. In this paper, the complex-valued Multidirectional Associative Memory is proposed. The rotation invariance is also proved. Moreover it is shown by computer simulation that the differences of angles of given patterns are automatically reduced. At first we define complex-valued Multidirectional Associative Memory. Then we define the energy function of network. With the energy function, we prove that the network ensures convergence. Next, we define the learning law and show the characteristic of recall process. The characteristic means that the differences of angles of given patterns are automatically reduced. Especially we prove the following theorem. In the case that only a multiple of patterns is stored, if patterns with different angles are given to each layer, the differences are automatically reduced. Finally, we investigate whether the differences of angles influence the noise robustness. It is found to reduce the noise robustness, because the input to each layer becomes small. We show this by computer simulations. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 159(1): 39,45, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20387 [source] Developmental maturation of ionotropic glutamate receptor subunits in rat vestibular nuclear neurons responsive to vertical linear accelerationEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 11 2008Suk-King Lai Abstract We investigated the maturation profile of subunits of ionotropic glutamate receptors in vestibular nuclear neurons that were activated by sinusoidal linear acceleration along the vertical plane. The otolithic origin of Fos expression in these neurons was confirmed as a marker of functional activation when labyrinthectomized and/or stationary control rats contrasted by showing sporadically scattered Fos-labeled neurons in the vestibular nuclei. By double immunohistochemistry for Fos and one of the receptor subunits, otolith-related neurons that expressed either ,-amino-3-hydroxy-5-methyl-4-isoxazole-propionate or N -methyl- d -aspartate subunits were first identified in the medial vestibular nucleus, spinal vestibular nucleus and Group x by postnatal day (P)7, and in the lateral vestibular nucleus and Group y by P9. No double-labeled neurons were found in the superior vestibular nucleus. Within each vestibular subnucleus, these double-labeled neurons constituted ,90% of the total Fos-labeled neurons. The percentage of Fos-labeled neurons expressing the GluR1 or NR2A subunit showed developmental invariance in all subnuclei. For Fos-labeled neurons expressing the NR1 subunit, similar invariance was observed except that, in Group y, these neurons decreased from P14 onwards. For Fos-labeled neurons expressing the GluR2, GluR2/3, GluR4 or NR2B subunit, a significant decrease was found by the adult stage. In particular, those expressing the GluR4 subunit showed a two- to threefold decrease in the medial vestibular nucleus, spinal vestibular nucleus and Group y. Also, those expressing the NR2B subunit showed a twofold decrease in Group y. Taken together, the postsynaptic expression of ionotropic glutamate receptor subunits in different vestibular subnuclei suggests that glutamatergic transmission within subregions plays differential developmental roles in the coding of gravity-related vertical spatial information. [source] Factorial structure and cross-cultural invariance of the Oral Impacts on Daily PerformancesEUROPEAN JOURNAL OF ORAL SCIENCES, Issue 3 2009A. N. Åstrøm The issue of cross-cultural construct validation and measurement invariance of the Oral Impacts on Daily Performances (OIDP) questionnaire is important. Using confirmatory factor analysis (CFA), this study evaluated a proposed three-factor structure of the OIDP questionnaire in Tanzanian adolescents and adults and assessed whether this model would be replicated in Ugandan adolescents. Between 2004 and 2007, OIDP data were collected from 1,601 Tanzanian adolescents, 1,031 Tanzanian adults, and 1,146 Ugandan adolescents. Model generation analysis was restricted to Tanzanian adolescents, and the model achieved was tested, without modification, in Tanzanian adults and in Ugandan adolescents. A modified three-factor solution with cross-loadings improved the fit of the OIDP model to the data compared with a one-factor model and the original three-factor model within the Tanzanian [comparative fit index (CFI) = 0.99] and Ugandan (CFI = 0.98) samples. Cross-validation in Tanzanian adults provided a reasonable fit (CFI = 0.98). Multiple-group CFA demonstrated acceptable fit [,2 = 140.829, degrees of freedom (d.f.) = 24, CFI = 0.98] for the unconstrained model, whereas unconstrained and constrained models were statistically significantly different. Factorial validity was confirmed for the three-factor OIDP model. The results provide evidence for cross-cultural equivalence of the OIDP, suggesting that this measure is comparable, at least to some extent, across Tanzanian and Ugandan adolescents. [source] Morningness in German and Spanish students: a comparative studyEUROPEAN JOURNAL OF PERSONALITY, Issue 4 2007Christoph Randler Abstract Humans show pronounced individual differences in circadian orientation. Transcultural comparisons are interesting since biological (or environmental) factors together with cultural ones may contribute to differences in morningness,eveningness. We compared Spanish and German undergraduates using the Composite Scale of Morningness (CSM) to assess circadian preferences. Confirmatory and multiple groups confirmatory factor analysis were used to assess factor structure and structural invariance across countries. The results showed that a three-factor model of morningness best characterises the CSM structure of both samples. Partial factorial invariance (factor loadings) across countries was demonstrated for the factors ,morningness' and ,morning alertness'. Scores of both factors were higher in German students. Potential cultural and biological explanations for the differences are discussed. Copyright © 2007 John Wiley & Sons, Ltd. [source] The five-factor personality inventory: cross-cultural generalizability across 13 countriesEUROPEAN JOURNAL OF PERSONALITY, Issue 5 2003A. A. Jolijn Hendriks In the present study, we investigated the structural invariance of the Five-Factor Personality Inventory (FFPI) across a variety of cultures. Self-report data sets from ten European and three non-European countries were available, representing the Germanic (Belgium, England, Germany, the Netherlands, USA), Romance (Italy, Spain), and Slavic branches (Croatia, Czech Republic, Slovakia) of the Indo-European languages, as well as the Semito-Hamitic (Israel) and Altaic (Hungary, Japan) language families. Each data set was subjected to principal component analysis, followed by varimax rotation and orthogonal Procrustes rotation to optimal agreement with (i) the Dutch normative structure and (ii) an American large-sample structure. Three criteria (scree test, internal consistency reliabilities of the varimax-rotated components, and parallel analysis) were used to establish the number of factors to be retained for rotation. Clear five-factor structures were found in all samples except in the smallest one (USA, N,=,97). Internal consistency reliabilities of the five components were generally good and high congruence was found between each sample structure and both reference structures. More than 80% of the items were equally stable within each country. Based on the results, an international FFPI reference structure is proposed. This reference structure can facilitate standardized communications about Big Five scores across research programmes. Copyright © 2003 John Wiley & Sons, Ltd. [source] Test of Nyborg's General Trait Covariance (GTC) model for hormonally guided development by means of structural equation modelingEUROPEAN JOURNAL OF PERSONALITY, Issue 3 2003Martin Reuter Nyborg's General Trait Covariance (GTC) model for hormonally guided development investigates the influence of gonadal hormones and fluid intelligence on body build, achievement, and socioeconomic variables. According to the model, testosterone should be negatively related to height, fat/muscle ratio, intelligence, income, and education. It is conceived that this influence should be determined to a great extent by mutual relationships between these variables. The model was tested by means of structural equation modeling (SEM) in a sample of 4375 males who had served in the United States Armed Forces. The results largely confirm Nyborg's androtype model but in addition reflect the relationships between the variables included in a quantitative causal manner. It could be shown that testosterone has a negative influence on crystallized intelligence and that this effect is mainly mediated by the negative influence of testosterone on education. An additional multiple group analysis testing for structural invariance across age groups revealed that the mediating role of education is more pronounced in old veterans. Copyright © 2002 John Wiley & Sons, Ltd. [source] Construct validity and generalizability of the Carver,White behavioural inhibition system/behavioural activation system scalesEUROPEAN JOURNAL OF PERSONALITY, Issue 5 2001Luigi Leone The factorial structure and invariance of the BIS/BAS scales of Carver and White were assessed across three samples from the USA, UK, and Italy. Previous validation studies of the BIS/BAS scales relied on individual samples drawn from English-speaking populations only and failed to formally assess generalizability. The current study shows that the four-factor structure proposed by Carver and White,i.e. one BIS and three BAS facets,achieved satisfactory psychometric properties in all three samples and that measurement invariance was obtained across countries. Latent mean differences due to gender and country were also investigated. Theoretical issues concerning the validity of the BIS/BAS scales are addressed. Copyright © 2001 John Wiley & Sons, Ltd. [source] PERSPECTIVE: EVOLUTION AND DETECTION OF GENETIC ROBUSTNESSEVOLUTION, Issue 9 2003J. Arjan G. M. de Visser Abstract Robustness is the invariance of phenotypes in the face of perturbation. The robustness of phenotypes appears at various levels of biological organization, including gene expression, protein folding, metabolic flux, physiological homeostasis, development, and even organismal fitness. The mechanisms underlying robustness are diverse, ranging from thermodynamic stability at the RNA and protein level to behavior at the organismal level. Phenotypes can be robust either against heritable perturbations (e.g., mutations) or nonheritable perturbations (e.g., the weather). Here we primarily focus on the first kind of robustness,genetic robustness,and survey three growing avenues of research: (1) measuring genetic robustness in nature and in the laboratory; (2) understanding the evolution of genetic robustness; and (3) exploring the implications of genetic robustness for future evolution. [source] Generalization of Schrödinger invariance.FORTSCHRITTE DER PHYSIK/PROGRESS OF PHYSICS, Issue 5-7 2009Applications to Bose-Einstein condensation Abstract The symmetries of non-linear Schrödinger equations with power-law non-linearities are investigated. It is shown that Galilei invariance can be extended to Schrödinger invariance if the coupling constant(s) in non-linearity is treated as dimensionful quantity. This is used to find a new non-stationary solutions from given stationary ones. [source] Gauged supergravities in various spacetime dimensions,FORTSCHRITTE DER PHYSIK/PROGRESS OF PHYSICS, Issue 8 2007M. Weidner Abstract In this review article we study the gaugings of extended supergravity theories in various space-time dimensions. These theories describe the low-energy limit of non-trivial string compactifications. For each theory under consideration we review all possible gaugings that are compatible with supersymmetry. They are parameterized by the so-called embedding tensor which is a group theoretical object that has to satisfy certain representation constraints. This embedding tensor determines all couplings in the gauged theory that are necessary to preserve gauge invariance and supersymmetry. The concept of the embedding tensor and the general structure of the gauged supergravities are explained in detail. The methods are then applied to the half-maximal (N = 4) supergravities in d = 4 and d = 5 and to the maximal supergravities in d = 2 and d = 7. Examples of particular gaugings are given. Whenever possible, the higher-dimensional origin of these theories is identified and it is shown how the compactification parameters like fluxes and torsion are contained in the embedding tensor. [source] Abelian and non-abelian D-brane effective actionsFORTSCHRITTE DER PHYSIK/PROGRESS OF PHYSICS, Issue 9 2004P. Koerber Abstract In this Ph.D. thesis, accepted at the Vrije Universiteit Brussel, we review and elaborate on a method to find the D-brane effective action, based on BPS equations. Firstly, both for the Yang-Mills action and the Born-Infeld action it is shown that these configurations are indeed BPS, i.e. solutions to these equations saturate a Bogomolny bound and leave some supersymmetry unbroken. Next, we use the BPS equations as a tool to construct the D-brane effective action and require that (a deformation of) these equations should still imply the equations of motion in more general cases. In the abelian case we managed to calculate all order in ,, four-derivative corrections to the effective action and the BPS equations while in the non-abelian case we obtained the effective action up to order ,,4. Furthermore, we discuss a check based on the spectrum of strings stretching between intersecting branes. Finally, this Ph.D. thesis also discusses the construction of a boundary superspace which would be the first step to use the method of Weyl invariance in N = 2 superspace in order to again construct the D-brane effective action. A more detailed summary of each section can be found in the introduction. [source] Field theory on a non-commutative plane: a non-perturbative studyFORTSCHRITTE DER PHYSIK/PROGRESS OF PHYSICS, Issue 5 2004F. Hofheinz Abstract The 2d gauge theory on the lattice is equivalent to the twisted Eguchi,Kawai model, which we simulated at N ranging from 25 to 515. We observe a clear large N scaling for the 1- and 2-point function of Wilson loops, as well as the 2-point function of Polyakov lines. The 2-point functions agree with a universal wave function renormalization. The large N double scaling limit corresponds to the continuum limit of non-commutative gauge theory, so the observed large N scaling demonstrates the non-perturbative renormalizability of this non-commutative field theory. The area law for the Wilson loops holds at small physical area as in commutative 2d planar gauge theory, but at large areas we find an oscillating behavior instead. In that regime the phase of the Wilson loop grows linearly with the area. This agrees with the Aharonov-Bohm effect in the presence of a constant magnetic field, identified with the inverse non-commutativity parameter. Next we investigate the 3d ,,4 model with two non-commutative coordinates and explore its phase diagram. Our results agree with a conjecture by Gubser and Sondhi in d = 4, who predicted that the ordered regime splits into a uniform phase and a phase dominated by stripe patterns. We further present results for the correlators and the dispersion relation. In non-commutative field theory the Lorentz invariance is explicitly broken, which leads to a deformation of the dispersion relation. In one loop perturbation theory this deformation involves an additional infrared divergent term. Our data agree with this perturbative result. We also confirm the recent observation by Ambjø rn and Catterall that stripes occur even in d = 2, although they imply the spontaneous breaking of the translation symmetry. [source] Test of the CPT symmetry using laser spectroscopy on antiprotonic atomsFORTSCHRITTE DER PHYSIK/PROGRESS OF PHYSICS, Issue 2-3 20032Article first published online: 26 FEB 200, D. Horváth Antiprotons stopped in helium get trapped in long-living orbits making possible to study their atomic transitions via laser spectroscopy. These measurements started at CERN, Geneva, 10 years ago at the Low Energy Antiproton Ring and now continue at CERN's Antiproton Decelerator. The main result of the ASACUSA experiment is an improvement in the measurement of the antiproton mass and charge, which tests the CPT invariance when compared with those of the proton. [source] | ||||||||||||||||||||||||||||||||||||||||