bluuebunny/crossref_metadata_2025_split huggingface dataset:
Orthogonal Procrustes Rotation Maximizing Congruence
Authors: Brokken Frank B. 
Published: January 2006

Procedures for assessing the invariance of factors found in data sets using different subjects and the same variables are often using the least squares criterion, which appears to be too restrictive for comparing factors.Tucker's coefficient of congruence, on the other hand, is more closely related to the human interpretation of factorial invariance than the least squares criterion. A method maximizing simultaneously the sum of coefficients of congruence between two matrices of factor loadings, using orthogonal rotation of one matrix is presented. As shown in examples, the sum of coefficients of congruence obtained using the presented rotation procedure is slightly higher than the sum of coefficients of congruence using Orthogonal Procrustes Rotation based on the least squares criterion.
Canonical/Redundancy Factoring Analysis
Authors: DeSarbo Wayne S. 
Published: January 2006

The interrelationships between two sets of measurements made on the same subjects can be studied by canonical correlation. Originally developed by Hotelling [1936], the canonical correlation is the maximum correlation between linear functions (canonical factors) of the two sets of variables. An alternative statistic to investigate the interrelationships between two sets of variables is the redundancy measure, developed by Stewart and Love [1968]. Van Den Wollenberg [1977] has developed a method of extracting factors which maximize redundancy, as opposed to canonical correlation.A component method is presented which maximizes user specified convex combinations of canonical correlation and the two nonsymmetric redundancy measures presented by Stewart and Love. Monte Carlo work comparing canonical correlation analysis, redundancy analysis, and various canonical/redundancy factoring analyses on the Van Den Wollenberg data is presented. An empirical example is also provided.
Structural Analysis of Covariance and Correlation Matrices
Authors: Jöreskog Karl G. 
Published: January 2006

A general approach to the analysis of covariance structures is considered, in which the variances and covariances or correlations of the observed variables are directly expressed in terms of the parameters of interest. The statistical problems of identification, estimation and testing of such covariance or correlation structures are discussed.Several different types of covariance structures are considered as special cases of the general model. These include models for sets of congeneric tests, models for confirmatory and exploratory factor analysis, models for estimation of variance and covariance components, regression models with measurement errors, path analysis models, simplex and circumplex models. Many of the different types of covariance structures are illustrated by means of real data.
Least-Squares Theory Based on General Distributional Assumptions with an Application to the Incomplete Observations Problem
Authors: Van Praag B. M. S. , Dijkstra T. K. , Van Velzen J. 
Published: January 2006

The linear regression model y=β′x+ ε is reanalyzed. Taking the modest position that β′x is an approximation of the “best” predictor of y we derive the asymptotic distribution of b and R2, under mild assumptions.The method of derivation yields an easy answer to the estimation of β from a data set which contains incomplete observations, where the incompleteness is random.
Stepwise Variable Selection in Factor Analysis
Authors: Kano Yutaka , Harada Akira 
Published: January 2006

It is very important to choose appropriate variables to be analyzed in multivariate analysis when there are many observed variables such as those in a questionnaire. What is actually done in scale construction with factor analysis is nothing but variable selection.In this paper, we take several goodness-of-fit statistics as measures of variable selection and develop backward elimination and forward selection procedures in exploratory factor analysis. Once factor analysis is done for a certain number p of observed variables (the p-variable model is labeled the current model), simple formulas for predicted fit measures such as chi-square, GFI, CFI, IFI and RMSEA, developed in the field of the structural equation modeling, are provided for all models obtained by adding an external variable (so that the number of variables is p + 1) and for those by deleting an internal variable (so that the number is p − 1), provided that the number of factors is held constant.A program SEFA (Stepwise variable selection in Exploratory Factor Analysis) is developed to actually obtain a list of the fit measures for all such models. The list is very useful in determining which variable should be dropped from the current model to improve the fit of the current model. It is also useful in finding a suitable variable that may be added to the current model. A model with more appropriate variables makes more stable inference in general.The criteria traditionally often used for variable selection is magnitude of communalities. This criteria gives a different choice of variables and does not improve fit of the model in most cases.
Linear Relations among k Sets of Variables
Authors: Van de Geer John P. 
Published: January 2006

A family of solutions for linear relations among k sets of variables is proposed. It is shown how these solutions apply for k = 2, and how they can be generalized from there to k ≥ 3.The family of solutions depends on three independent choices: (i) to what extent a solution may be influenced by differences in variances of components within each set; (ii) to what extent the sets may be differentially weighted with respect to their contribution to the solution—including orthogonality constraints; (iii) whether or not individual sets of variables may be replaced by an orthogonal and unit normalized basis.Solutions are compared with respect to their optimality properties. For each solution the appropriate stationary equations are given. For one example it is shown how the determinantal equation of the stationary equations can be interpreted.
Circumplex Models for Correlation Matrices
Authors: Browne Michael W. 
Published: January 2006

Structural models that yield circumplex inequality patterns for the elements of correlation matrices are reviewed. Particular attention is given to a stochastic process defined on the circle proposed by T. W. Anderson. It is shown that the Anderson circumplex contains the Markov Process model for a simplex as a limiting case when a parameter tends to infinity.Anderson's model is intended for correlation matrices with positive elements. A replacement for Anderson's correlation function that permits negative correlations is suggested. It is shown that the resulting model may be reparametrzed as a factor analysis model with nonlinear constraints on the factor loadings. An unrestricted factor analysis, followed by an appropriate rotation, is employed to obtain parameter estimates. These estimates may be used as initial approximations in an iterative procedure to obtain minimum discrepancy estimates.Practical applications are reported.
SAS Macro Programs for Statistical Graphics
Authors: Friendly Michael 
Published: January 2006

The purpose of this announcement is to describe a collection of general macro programs for statistical graphics for use with the SAS System that have been made available in conjunction with the book, SAS system for statistical graphics, first edition (Friendly, 1991). The primary goals of the book are to survey the kinds of graphic displays that are useful for different questions and data, and to show how can these displays be done with the SAS System. It emphasizes displays that reveal aspects of data not easily captured in numerical summaries or tabular formats and diagnostic displays that help determine if assumptions of an analysis are met.All of the programs use keywords for the required and optional parameters and supply default values where possible to parameters not specified when the macro is invoked.
A Comparison of Three Simple Test Theory Models
Authors: Ramsay J. O. 
Published: January 2006

In very simple test theory models such as the Rasch model, a single parameter is used to represent the ability of any examinee or the difficulty of any item. Simple models such as these provide very important points of departure for more detailed modeling when a substantial amount of data are available, and are themselves of real practical value for small or even medium samples. They can also serve a normative role in test design.As an alternative to the Rasch model, or the Rasch model with a correction for guessing, a simple model is introduced which characterizes strength of response in terms of the ratio of ability and difficulty parameters rather than their difference. This model provides a natural account of guessing, and has other useful things to contribute as well. It also offers an alternative to the Rasch model with the usual correction for guessing. The three models are compared in terms of statistical properties and fits to actual data. The goal of the paper is to widen the range of “minimal” models available to test analysts.
Tail-Measurability in Monotone Latent Variable Models
Authors: Ellis Jules L. , Junker Brian W. 
Published: January 2006

We consider latent variable models for an infinite sequence (or universe) of manifest (observable) variables that may be discrete, continuous or some combination of these. The main theorem is a general characterization by empirical conditions of when it is possible to construct latent variable models that satisfy unidimensionality, monotonicity, conditional independence, and tail-measurability. Tail-measurability means that the latent variable can be estimated consistently from the sequence of manifest variables even though an arbitrary finite subsequence has been removed. The characterizing, necessary and sufficient, conditions that the manifest variables must satisfy for these models are conditional association and vanishing conditional dependence (as one conditions upon successively more other manifest variables). Our main theorem considerably generalizes and sharpens earlier results of Ellis and van den Wollenberg (1993), Holland and Rosenbaum (1986), and Junker (1993). It is also related to the work of Stout (1990).The main theorem is preceded by many results for latent variable models in general—not necessarily unidimensional and monotone. They pertain to the uniqueness of latent variables and are connected with the conditional independence theorem of Suppes and Zanotti (1981). We discuss new definitions of the concepts of “true-score” and “subpopulation,” which generalize these notions from the “stochastic subject,” “random sampling,” and “domain sampling” formulations of latent variable models (e.g., Holland, 1990; Lord & Novick, 1968). These definitions do not require the a priori specification of a latent variable model.
False‐positive results in neonatal screening for cystic fibrosis based on a three‐stage protocol (IRT/DNA/IRT): Should we adjust IRT cut‐off to ethnic origin?
Authors: Cheillan D. , Vercherat M. , Chevalier‐Porst F. , Charcosset M. , Rolland M. O. , Dorche C. 
Published: January 2006

SummarySince 1979, newborn screening for cystic fibrosis (CF) has been possible by measuring immunoreactive tryspinogen (IRT) in blood spots. In France, a programme based on a three‐stage strategy (IRT/DNA/IRT) started in 2002. In the Rhône‐Alpes area, the positive screening rate (i.e. the proportion of samples sent for genotyping) observed after the first IRT measurement was higher than the expected rate (0.65% versus 0.50%), without a greater CF incidence. We hypothesized that the IRT reference range could differ according to the ethnic origin of the newborns. 35 141 newborns were studied and divided into two groups: European ethnic group 26 324 (75%) and North African ethnic group 8817 (25%). 243 positive newborns were identified: 146 (60%) in the European ethnic group and 97 (40%) in the North African ethnic group. Three CF patients and 11 unaffected heterozygotes were found in the European group, but no mutations were found in the North African group. Mean IRT values and the percentage of IRT values over the cut‐off were significantly higher in the North African group than in the European group (mean IRT = 21.17 μg/L and 19.74 μg/L, p < 0.0001; %IRT > cut‐off = 1.1% and 0.5%, respectively). For the positive screened newborns, term and IRT mean were comparable, whereas birth weight was higher in the North African ethnic group. These results lead us to conclude that (i) newborns from families of North African origin have higher IRT values and (ii) most of the positive screened newborns in this population could be considered as ‘false positives’. These conclusions could explain, in part, the large variations seen in the positive screening rate in the French CF neonatal screening and raise the question whether it is relevant to adapt cut‐off to ethnic origin of the newborns.
Identification of a common novel mutation in Saudi patients with argininosuccinic aciduria
Authors: Al‐Sayed M. , AlAhmed S. , Alsmadi O. , Khalil H. , Rashed M. S. , Imtiaz F. , Meyer B. F. 
Published: January 2006

SummaryWe have identified a common novel mutation (Q354X) in the argininosuccinate lyase (ASL) gene in Saudi patients with argininosuccinic aciduria (ASAuria; McKusick 207900). The two index patients were siblings, had a neonatal onset of the disease and were diagnosed based on the clinical presentation and confirmed by analysis of their dried blood spots (DBS) by tandem mass spectrometry (MS/MS). The ASL gene was then analysed by direct sequencing. A further 28 patients with a confirmed diagnosis of ASAuria based on MS/MS of their DBS were tested by sequencing for the presence of the Q354X mutation. This mutation was found in 14 out of the 28 patients (50%) tested. Our work indicates that the Q354X allele is common, may account for 50% of the abnormal ASL genes in the Saudi population, and is likely to be associated with the neonatal form of the disease. We recommend that all patients diagnosed with ASAuria in Saudi Arabia or of Arab origin be tested for this mutation and for Q116X, which has been described previously. In addition, further analysis is needed to identify other underlying disease mutations for ASAuria in the Saudi population.
Search for mutations in SLC1A5 (19q13) in cystinuria patients
Authors: Brauers E. , Vester U. , Zerres K. , Eggermann T. 
Published: January 2006

SummaryTo elucidate whether SLC1A5 is involved in the aetiology of cystinuria, we screened two non‐type I cystinuria families without detectable mutations inSLC7A9 (and SLC3A1) but compatible with linkage to 19q13 for genomic variants in SLC1A5. Despite evidence for an involvement of SLC1A5 in the aetiology of cystinuria, we could not identify any mutation in this gene in the two families. With SLC1A5, a further candidate gene for cystinuria can be excluded as being involved in the pathogenesis of this disease in these two families. Of course, there remains the possibility that other genes are involved in cystinuria; further molecular studies will clarify the complex nature of this disorder.
Genetic variants of transferrin in the diagnosis of protein hypoglycosylation
Authors: Albahri Z. , Marklová E. , Vaníček H. , Minxová L. , Dédek P. , Skálová S. 
Published: January 2006

SummaryHuman transferrin (Tf) shows genetic polymorphisms, which may interfere in the screening of congenital disorders of glycosylation (CDG). Isoelectric focusing followed by direct immunofixation was used for Tf analysis in controls and several groups of patients. Equivocal results in one case have been recognized as a rare Tf CD variant. A higher incidence of some genetic variants has been reported in connection with certain diseases; of the seven Tf phenotypes detected in our set of samples, an apparently higher frequency of Tf C1C2 variant found in some groups of patients was not significant.
Kinetic characterization of human hydroxyacid–oxoacid transhydrogenase: Relevance toD‐2‐hydroxyglutaric and γ‐hydroxybutyric acidurias
Authors: Struys E. A. , Verhoeven N. M. , Ten Brink H. J. , Wickenhagen W. V. , Gibson K. M. , Jakobs C. 
Published: January 2006

SummaryWe investigated the presence of hydroxyacid–oxoacid transhydrogenase (HOT), which catalyses the cofactor‐independent conversion of γ‐hydroxybutyrate (GHB) to succinic semialdehyde coupled to reduction of 2‐ketoglutarate (2‐KG) to D‐2‐hydroxyglutarate (D‐2‐HG), in human liver extracts employing [2H6]GHB and 2‐KG as substrates. We measured incorporation of 2H in D‐[2H]2‐HG using GC‐MS analyses, providing evidence for HOT activity in humans. Kinetic characterization of HOT was undertaken in forward and reverse directions. We employed [2H6]GHB and [2H4]2‐KG as cosubstrates in order to develop a HOT activity assay in cultured human fibroblasts derived from patients with D‐2‐hydroxyglutaric aciduria. HOT activity was quantified in this system by the measurement of D‐[2H5]2‐HG production. Fibroblasts derived from patients with D‐2‐hydroxyglutaric aciduria showed normal HOT activities. Our results provide the first demonstration and preliminary kinetic characterization of HOT activity in human tissues.
Increased HVA detected on organic acid analysis in a patient with Costello syndrome
Authors: Bowron A. , Scott J. G. , Brewer C. , Weir P. 
Published: January 2006

SummaryUrine organic acid analysis is routinely performed to investigate inborn errors of metbolism; however, interpretation can be difficult owing to the detection of compounds derived from other disease states or from nonpathological causes. We describe the finding of elevated homovanillc acid (HVA) on urine organic acid analysis which was not associated with medication or a neuroendocrine tumour but with Costello syndrome.
First‐trimester enzymatic and molecular prenatal diagnosis of mevalonic aciduria
Authors: Rolland M. O. , Cuisset L. , Le Bozec J. , Guffon N. , VianeySaban C. 
Published: January 2006

SummaryPrenatal diagnosis was offered to a family at risk of mevalonic aciduria. A chorionic villus sample was obtained and both mevalonate kinase activity and mutation analysis were done. An affected fetus was diagnosed.
Effect of copper and diethyldithiocarbamate combination therapy on the macular mouse, an animal model of Menkes disease
Authors: Kodama H. , Sato E. , Gu Y.‐H. , Shiga K. , Fujisawa C. , Kozuma T. 
Published: January 2006

SummaryMenkes disease (MD) is a neurodegenerative disorder characterized by a copper deficiency in the brain. It is caused by the defective intestinal absorption of copper resulting from a deficiency of a copper‐transporting ATPase, ATP7A. This gives rise to an accumulation of copper in the intestine. The copper deficiency in the brain of MD patients cannot be improved by copper injections, because the administered copper accumulates at the blood–brain barrier and is not transported across to the neurons. To resolve this problem, we investigated the effect of a combination therapy of copper and sodium diethyldithiocarbamate (DEDTC), a lypophilic chelator, in an animal model of MD, the macular mouse. Four‐week‐old macular mice treated with 50 μg of CuCl2 on the 7th day after birth were used. Experimental mice were given a subcutaneous injection of CuCl2 (4 μg) and an intraperitoneal injection of DEDTC (0.2 mg/g body weight) twice a week for 4 weeks and then sacrificed. Copper concentrations and cytochrome‐c oxidase activity in the brains of treated mice were higher than those of control macular mice, which received only copper or saline. The ratios of brain noradrenaline to dopamine and of adrenaline to dopamine were also increased by the treatment, suggesting that the activity of dopamine β‐hydroxylase, a copper‐dependent enzyme, was improved by the treatment. Liver and renal function tests showed no abnormalities in the treated mice, although copper concentrations in the kidneys of treated mice were higher than those of control macular mice. These results suggest that DEDTC facilitates the passage of copper across the blood–brain barrier and that the combination therapy of copper and DEDTC may be an effective treatment for the neurological disturbances suffered by patients with MD.
Predicting the phenylalanine blood concentration from urine analyses. An approach to noninvasive monitoring of patients with phenylketonuria
Authors: Langenbeck U. , Baum F. , Mench‐Hoinowski A. , Luthe H. , Behbehani A. W. 
Published: January 2006

SummaryThe need for regular blood‐drawing in the management of chronic metabolic disorders may negatively influence the compliance of patients and their parents; noninvasive analytical procedures could well alleviate this burden. Using data obtained in six adult probands with phenylketonuria, we evaluate the feasibility of noninvasive prediction of phenylalanine blood concentrations from analysis of phenylalanine and creatinine in urine. Cross‐validated regression equations correct for the significant inter‐individual variation of phenylalanine fractional excretion rates. With sensitive and specific enzymatic assays for phenylalanine and creatinine, the accuracy of this noninvasive procedure may also become clinically satisfactory for the purpose of self‐monitoring.
Mutation detection in four candidate genes (OXA1L, MRS2L, YME1L and MIPEP) for combined deficiencies in the oxidative phosphorylation system
Authors: Coenen M. J. H. , Smeitink J. A. M. , Smeets R. , Trijbels F. J. M. , van den Heuvel L. P. 
Published: January 2006

SummaryMitochondria are the main energy‐producing organelles of the cell. Five complexes embedded in the mitochondrial inner membrane, together constituting the oxidative phosphorylation (OXPHOS) system, comprise the final steps in cellular energy production. Many patients with a mitochondrial defect suffer from a so‐called combined deficiency, meaning that the enzymatic activities of two or more complexes of the OXPHOS system are decreased. Numerous mutations have been described in nuclear genes that are involved in the functioning of a single complex of the OXPHOS system. However, little attention has been paid to patients with a deficiency of more than one complex of this particular system. In this study we have investigated four nuclear genes (OXA1L, MRS2L, YME1L and MIPEP) that might be involved in the pathology of combined enzymatic deficiencies of the OXPHOS system. Based on the results of yeast knockouts of these four proteins, we have sequenced the open reading frame of OXA1L in eight patients with an enzymatic deficiency of complexes I and IV. MRS2L, YME1L and MIPEP have been sequenced in three patients with a combined defect of complexes III and IV. No mutations were detected in these patients, showing that at least in these patients the OXPHOS system deficiency cannot be explained by a mutation in these four genes.
Pulmonary hypertension—A new manifestation of mitochondrial disease
Authors: Barclay A. R. , Sholler G. , Christodolou J. , Shun A. , Arbuckle S. , Dorney S. , Stormon M. O. 
Published: January 2006

SummaryMitochondrial respiratory chain (RC) abnormalities in children can present as multiorgan disease, including liver failure, usually within the first year of life. Cardiorespiratory complications have previously been described in association with RC defects; however, to our knowledge no cases of pulmonary hypertension have been described. We discuss two patients with proven mitochondrial RC liver disease who developed severe pulmonary hypertension, one subsequent to cadaveric orthotopic liver transplantation, the second in the neonatal period. It is our contention that pulmonary hypertension should now be included as another potential manifestation of paediatric mitochondrial disease.