bluuebunny/crossref_metadata_2025 huggingface dataset:
The sequential structure of odour mixture component intensity judgements
Authors: Gregson Robert A. M.
Published: August 2011

The use of linear multivariable time‐series modelling, to disentangle sequential stimulus and response processes, is illustrated on a task involving judgements of the intensity of odour mixture components. A satisfactory fit of a model with no more than two lags is shown; the same model can represent diverse behaviour by internal parameter changes. The fundamental contrast between this dynamic approach and traditional static psychophysics is noted.
Paired comparison experiments involving all possible pairs
Authors: Sirotnik Barbara W. , Beaver Robert J.
Published: August 2011

The analysis of paired comparison experiments using the tie and order model due to Davidson & Beaver is extended to account for the inclusion of pairs of identical items in the experiment (design 1). It is shown that in testing for order effects, the asymptotic relative efficiency of design 1 to design 2, which includes the distinct ordered pairs, is always greater than one in non‐trivial cases.
Asymptotically distribution‐free methods for the analysis of covariance structures
Authors: Browne M. W.
Published: August 2011

Methods for obtaining tests of fit of structural models for covariance matrices and estimator standard errors which are asymptotically distribution free are derived. Modifications to standard normal theory tests and standard errors which make them applicable to the wider class of elliptical distributions are provided. A random sampling experiment to investigate some of the proposed methods is described.
A note on the consistency of estimators in the analysis of moment structures
Authors: Shapiro A.
Published: August 2011

This paper is concerned with the consistency of estimators in the analysis of moment structures. An example is given where in spite of identifiability of the parameters the associated estimator is inconsistent. Consistency is shown to hold under the additional condition of compactness of the parameter space.
The weak Borda effect is an unsatisfactory index of plurality/majority disagreement
Authors: Gillett Raphael
Published: August 2011

As an index of the propensity of the plurality voting procedure to produce an outcome which conflicts with the wishes of the majority, the likelihood of the weak Borda effect is flawed and misleading. It is recommended that researchers discontinue using the quantity for this purpose, since it is possible to obtain directly the likelihood of plurality/majority disagreement.
The effect of signal probability on the slope of the receiver operating characteristic given by the rating procedure
Authors: Treisman Michel , Faulkner Andrew
Published: August 2011

Signal detection theory (SDT) requires that the slope of the receiver operating characteristic (ROC) is independent of the probability of signal and noise. But it has been shown that when the rating procedure is applied to detection, the slope of the receiver operating characteristic may increase as a function of the probability of the signal (Schulman & Greenberg, 1970). This presents a serious problem for signal detection theory. This problem is examined in relation to a recent theory of criterion setting (Treisman & Williams, 1984), and an explanation for the effect of signal probability on ROC slope is derived which is compatible with SDT. Further data on the relation between signal probability and ROC slope are reported.
Fitting linear models to ordinal responses
Authors: Stirling W. Douglas
Published: August 2011

The distribution of an ordinal response can be modelled as a grouping of an underlying quantitative variable whose mean is a linear function of explanatory variables. Possible distributional assumptions about the underlying quantitative response are compared. An iteratively reweighted least squares algorithm for parameter estimation in these models is described in detail and variances and tests of hypotheses are given. Two data sets are analysed to illustrate the methods.
Item parameter estimation via minimum logit chi‐square
Authors: Baker Frank B.
Published: August 2011

The minimum logit chi‐square procedure was used in the item parameter estimation stage of the Birnbaum joint estimation paradigm. Simulated item response data for 36 data sets were analysed via this approach. Overall, the results yielded by the minimum chi‐square procedure compared very favourably with the results yielded by the LOGIST computer program for these data sets. As would be expected, test length, sample size and match of the test difficulty to the ability of the examinees all had an impact upon the level of agreement of the estimates with the underlying item parameter values. The empirical results suggest that in this context the minimum logit‐square procedure yields acceptable item parameter estimates.
The validity of the linear model as a basis for extracting principal components from psychological variables
Authors: Seddon G. M. , Moore B. G.
Published: August 2011

The investigation was concerned with the principal components analysis of compound variables which do not conform to the linear model. It was conducted using artificial data in which measures on compound variables were derived by multiplying and dividing the scores on the components, rather than adding and subtracting them. The results indicate that using the linear model leads to these variables being resolved just as accurately as variables which do comply with the linear model. However, the correct factor pattern is not always achieved using the Varimax criterion for rotating the principal components.
A class of stochastic procedures for the assessment of knowledge
Authors: Falmagne J.‐Cl. , Doignon J.‐P.
Published: August 2011

The knowledge state of an individual with respect to a particular body of information is conceptualized as the set of all the questions that this individual is capable of solving. The goal of an assessment procedure is to identify, by a sequence of appropriately chosen questions, the individual's state among all possible ones. A deterministic procedure is conceivable, but not realistic, in that it does not account for possible inconsistencies in the observed responses. Such inconsistencies may arise from careless errors or lucky guesses from the subject, but may also be of a more fundamental character. A stochastic framework is developed here, in which an individual ‘state’ is formalized as a distribution on the set of all possible knowledge states. On each trial, the assessor has a likelihood function on the set of knowledge states which provides the basis for selecting the question to be asked on that trial. The response is assumed to depend on the individual ‘state’. The question asked and the response observed are used to update the likelihood function. Several examples of questioning rules and of updating rules are discussed, which lead to Markov processes. A central problem is to describe conditions ensuring that the latent distribution corresponding to the subject's ‘state’ can be estimated. We show that, under general conditions, the ‘state’ of a subject is uncoverable if the latent distribution is concentrated on a particular knowledge state.
Selecting a stimulus set with prescribed structure from empirical confusion frequencies
Authors: Heiser Willem J.
Published: August 2011

The problem of selecting a subset of stimuli when empirical confusion frequencies are given is discussed for a case in which a quartet of letter pairs must be found with maximum similarity within pairs and minimum similarity between pairs. As a preliminary step the Shepard–Luce model is fitted; a non‐metric three‐dimensional scaling analysis provides confirmation of the validity of the actually selected pairs.
Estimating generalizability in systematic observation studies
Authors: Plewis Ian
Published: August 2011

This paper considers different ways of estimating variance components, and hence of estimating generalizability coefficients, with particular application to systematic observation studies which use time sampling. Recent work on multilevel models is reviewed and these models are shown to have advantages over other methods for data of this type. The ideas are applied to a recent study of children observed in infant school classes.
A new alternative to the ANOVA F and new results on James's second‐order method
Authors: Wilcox Rand R.
Published: August 2011

A new procedure is proposed for testing the hypothesis that the means of J independent normal distributions are equal. Extensive simulations indicate that the new procedure always gives the experimenter more control over the probability of a Type I error than does the Brown–Forsythe or Welch adjusted degree of freedom techniques. For equal and reasonably large sample sizes the Welch procedure might be preferred, however, because it can have substantially more power, and it provides adequate though liberal control over Type I errors. However, Welch's procedure cannot always be recommended for reasons described in the paper. For unequal sample sizes both the Welch and Brown–Forsythe procedures are known to be unsatisfactory in certain practical situations, while the new procedure has Type I error probabilities that are much closer to the nominal level. Moreover, the new procedure seems to give conservative results provided the sample sizes in each group are greater than or equal to 10. New results are also reported on James's second order method. Although computationally more tedious, James's procedure is recommended for general use.
Time resolution of clocks: Effects on reaction time measurement—Good news for bad clocks
Authors: Ulrich Rolf , Giray Markus
Published: August 2011

This paper investigates the measurement of reaction times (RTs) with clocks of limited time resolution. The questions raised are: (a) What is the relationship between measured and true RT? (b) Are mean and variance of measured RT biased, and if so, (c) how does this bias depend on the clock's time resolution? (d) Is it possible to correct this bias? It is concluded that the bias is practically negligible even if the time resolution of a clock is only 30 ms. The results show that a clock of limited time resolution biases mean and variance of measured RT. Furthermore it is shown that the effect of time resolution on detecting a true mean RT difference is negligible if the variance of true RT is relatively large. Formulae are provided to correct the bias of mean and variance of measured RT. In addition the implication of time resolution on measured RT for paired observations is analysed. It is shown that the product moment correlation coefficient but not the covariance of paired RT measures is affected by time resolution. A correction formula to remove the bias on the product moment correlation coefficient is provided.
Computer‐intensive correlational analysis: Bootstrap and approximate randomization techniques
Authors: Rasmussen Jeffrey Lee
Published: August 2011

Computer‐intensive statistical techniques have been suggested as alternatives to standard parametric analysis due to their freedom from normal‐theory assumptions. Two such techniques that may be used for correlational analysis are bootstrap and approximate randomization tests. These techniques were compared with the parametric Pearson's r under composite‐normal conditions in which the test of significance of Pearson's r is known to possess overly liberal Type I error rates. Results indicated that the approximate randomization test had Type I error rates that closely followed the parametric approach. The bootstrap, however, showed good control of the Type I error rates, except on small sample sizes.
Multiple choice tests: Power, length and optimal number of choices per item
Authors: Andrés A. Martín , del Castillo J.D. Luna
Published: August 2011

In an earlier paper (Martín Andrés & Luna del Castillo, 1989), three statistical tests for assigning a mark for a student in multiple choice tests were set out. In the present paper, the authors give the power of all three tests, for the purpose of selecting the best one for each particular case. They also give the formulae for determining the minimum number of questions (sample size) for an examination with k alternatives (only one of which is the correct answer), to satisfy given requirements about the number of students one wishes to pass or fail undeservedly (formulae which are also valid for giving any other mark, or for deciding the student's level of knowledge with given exactitude).

Finally, the authors prove that, under certain very general conditions, it is better to set questions with k = 3 alternative answers, whilst under another criterion, the value k = 2 is to be preferred.

The results are compared with the equivalent classic methods.
Comparisons with a control in two‐way and one‐way designs, and determining whether the most effective treatment has been selected with probability 1‐α
Authors: Wilcox Rand R.
Published: August 2011

This paper deals with three problems related to comparing independent treatment groups to a control. The first goal is to extend Dunnett's solution to two‐way designs. Let μjk (j = 1, …, J; k = 1, …, K) be the means of JK independent normal distributions. Percentage points of the multivariate t distribution are supplied that provide two‐sided 1–α simultaneous confidence intervals for μjk – μjk (j = 1, …, J – 1; k = 1, …, K) when the variances and sample sizes are equal. Next, approximate methods for handling both unequal variances and unequal sample sizes are suggested and studied via simulations. A new two‐stage procedure is also described where the probability coverage is at least 1–α and the length of the confidence intervals are fixed in advance by the experimenter, even when the variances are unequal. Using real data, implications of the new results are illustrated for situations where a researcher is interested in performing multiple comparisons with the ‘best’ treatment group, where ‘best’ is defined to be the treatment group with the largest mean. In particular, the results in this paper can be used to determine whether the most effective of several treatments was correctly identified with probability 1–α.
Lines, regression and some relations between slopes and intercepts considered from a geometric viewpoint
Authors: Runcie Dennis , Neggers Joseph , Hsia W. S.
Published: August 2011

Recently, Valentine, Wilding & Mohindra (1984) argued that the negative correlation between slopes and intercepts sometimes found in memory‐scanning tasks can be explained on purely statistical grounds. Because theory underlying the memory‐scanning literature is so emphatic in stating that this should not be so, a more exhaustive examination of other possibilities was undertaken. In this paper we consider a more geometric approach and observe that the geometric properties of the transformation x → x + t determine the correlations obtainable from the variables ‘slope’ and ‘intercept’ associated with the kinds of data given in memory scan experiments. The family of lines produced are naturally negatively correlated for good geometric reasons. Even though our observations do not contradict the conclusions obtained by Valentine et al., our method is sufficiently different to be considered in its own right. It is hoped that the geometric considerations of the type presented here may find application in interpreting data obtained from families of regression lines representing runs of experiments.
Non‐parametric analysis of covariance based on predicted medians
Authors: Wilcox Rand R.
Published: August 2011

A common problem is comparing two independent treatment groups in terms of some random variable Y when there is some covariate X. Typically the comparison is made in terms of E(Y|X). However, highly skewed distributions occur in psychology (Micceri, 1989), and so a better method might be to compare the two groups in terms of the median of Y given X, say M(Y|X). For the jth group, assume that M(Y|X) = βjX + αj. The βs and αs can be estimated with the Brown‐Mood procedure, but there are no results on how one might test H0:β1 = β2 or H0:α1 = α2. Let and be the estimates of α and β, respectively. One of the more obvious approaches is to use a jackknife estimate of the variance of and then assume that the resulting test statistics have a standard normal distribution. This approach was found to be unsatisfactory. Some alternative procedures were considered, some of which gave good results when testing H0:α1 = α2, but they were too conservative, in terms of Type I errors, when testing H0:β1 = β2. Still another procedure was considered and found to be substantially better than all others. The new procedure is based on a modification of the Brown‐Mood procedure and a bootstrap estimate of the standard errors. Some limitations of the new method are noted.
Population comparisons based on an extreme fraction of the sample: A caveat
Authors: Gillett Raphael
Published: August 2011

Population comparisons based on the mean of a fixed number of the highest (lowest) sample values have been shown to be biased when the samples are of different sizes. The present study demonstrates that, surprisingly, the bias persists even when the mean is based on a fixed proportion, rather than a fixed number, of the highest (lowest) sample values. Although the magnitude of the effect is considerably diminished, it can still produce problems in statistical surveys and in applied settings, e.g. personnel selection. Methods of correcting the bias are outlined.
A comparison of four methods of calculating standard errors of maximum‐likelihood estimates in the analysis of covariance structure
Authors: Dolan Conor V. , Molenaar Peter C. M.
Published: August 2011

Four methods of calculating standard errors (SEs) in the analysis of covariance structure using normal theory maximum‐likelihood estimation, namely LISREL SEs, SEs derived from the exact Hessian, SEs derived from the finite difference approximation to the Hessian using exact gradients, and SEs derived from the update of the Hessian obtained during quasi‐Newton optimization, are compared.

Two comparisons are made. The first is based on 30 data sets simulated according to an orthogonal common factor model. The second is based on the analysis of a well known data set concerning the stability of alienation.

The finite difference and exact SEs are identical to at least four places of decimals. Little difference is observed between the remaining SEs.
A composite stopping rule for multinomial subset selection
Authors: Chen Pinyuen , Hsu Lifang
Published: August 2011

The paper studies a sequential procedure R for selecting a random size subset that contains the multinomial cell which has the largest cell probability. The stopping rule of the proposed procedure R is the composite of the stopping rules of curtailed sampling, inverse sampling, Ramsey–Alam sampling, and the truncation of fixed‐sample‐size procedure. A property on the worst configuration is shown, and it is employed in computing the procedure parameters that guarantee certain probability requirements. Tables of these procedure parameters, the corresponding probability of correct selection, the expected sample size, and the expected subset size are given for comparison.
Bayesian analysis of stochastic constraints in structural equation models
Authors: Lee Sik‐Yum
Published: August 2011

Structural equation models are analysed in the presence of stochastic constraints. Based on a Bayesian perspective, a prior distribution on nuisance parameters in the unknown covariance matrix of error measurements with stochastic constraints is considered. An iterative procedure is implemented to produce the various Bayesian estimates with stochastic constraints. A simulation study is conducted to illustrate the accuracy and behaviour of this Bayesian approach. A real‐life example is provided to illustrate the theory.
Alternatives to traditional analysis of covariance
Authors: Rutherford Andrew
Published: August 2011

Traditional analysis of covariance (ANCOVA) assumptions beyond those required for analysis of variance (ANOVA) are described as unnecessary. The problem posed by the most common violation of traditional ANCOVA: heterogeneity of dependent variable on covariate regression coefficients across treatments is considered, as is the relationship between linear modelling and ANCOVA. The amelioration of problems due to covariate‐treatment covariation by heterogeneous regression ANCOVA is described and illustrated in terms of a hypothetical experiment. Subsequently, various parametric alternatives to the traditional ANCOVA are presented in terms of the types of analyses they provide. Finally, the theoretical issue of the relationship between the psychological model and the mathematical model is considered briefly.
Robust generalizations of classical test reliability and Cronbach's alpha
Authors: Wilcox Rand R.
Published: August 2011

This paper describes a general class of reliability measures that contains the classical‐test‐theory measure as a special case. A particular member of this class is suggested for applied work, and some of its properties are studied. A lower bound for this new measure of reliability is derived which is a robust analogue of Cronbach's alpha. Here the term ‘robust’ is being used to describe a measure of reliability that is relatively insensitive to small fluctuations in the tails of the distributions under study. The idea is that the value of a parameter, intended to reflect reliability, should be determined by the bulk of the distribution associated with whatever is being measured. If, for example, a test is considered unreliable when test scores have a normal distribution, it should not be possible to make the test appear to be reliable with a trivial change in the tails of the distributions. It is illustrated that Cronbach's alpha does not have this characteristic. In statistical jargon, Cronbach's alpha is not a resistant measure of reliability, while the reverse is true for the new measure of reliability introduced here. Included in this paper is a method for computing a confidence interval for the new lower bound.
The analysis of proximity matrices through sums of matrices having (anti‐)Robinson forms
Authors: Hubert Lawrence , Arabie Phipps
Published: August 2011

A least‐squares strategy is developed for representing a symmetric proximity matrix containing similarity or dissimilarity values between each pair of objects from some given set, as an approximate sum of a small number of symmetric matrices having the same size as the original but which satisfy certain simple order constraints on their entries. The primary class of constraints considered are of the Robinson (or anti‐Robinson) type, where the entries in such a matrix, subject to a suitable row/column ordering, never increase (or decrease) when moving away from a main diagonal entry within any row or column. Matrices satisfying either the Robinson or anti‐Robinson condition can be viewed as defining certain restricted collections of possibly overlapping subsets along with an associated measure of ‘compactness’ or ‘salience’ for each; these subsets and their compactness or salience indices form the basis for helping explain the patterning of entries in the initial proximity matrix as now reflected by the matrix sum. A number of empirical examples based on well‐known published data sets are used as illustrations of how such reconstructions might be carried out and interpreted. Finally, several other types of matrix order constraints are mentioned briefly, along with a few corresponding numerical examples, to show how alternative structures also can be considered using the same type of computational strategy as in the (anti‐)Robinson case.
Factor analysis of variables with 2, 3, 5 and 7 response categories: A comparison of categorical variable estimators using simulated data
Authors: Dolan Conor V.
Published: August 2011

Two estimators in the factor analysis of categorical items are studied, the weighted least squares function implemented in the tandem PRELIS‐LISREL 7 and a generalized least squares function implemented in LISCOMP. Of main interest is the performance of these estimators in relatively small samples (200 to 400) and the comparison of their performance with the normal theory maximum likelihood estimator given an increasing number of response categories. The evaluation of the performance of these estimators concerns the variability of the parameter estimates, the bias of the parameter estimates, the distribution of the parameter estimates and the χ2 goodness‐of‐fit statistics. The model used in the simulation is an 8‐indicator single common factor model. The effect of model size (12‐ and 16‐indicator models) on the categorical item estimator of LISREL 7 is investigated briefly.

The results indicate that in the ideal circumstances of the simulation study, 200 is too small a sample size to justify the use of large sample statistics associated with these estimators.
A note on the attenuation of correlation
Authors: Bedrick Edward J.
Published: August 2011

We study the attenuation of a correlation coefficient when one of the underlying measurement variables is categorized. We show that the attenuation depends critically on the distribution of the underlying latent variable, and on the scores assigned to the categories. Practical implications of these results are discussed.
Iterative projection strategies for the least‐squares fitting of tree structures to proximity data
Authors: Hubert Lawrence , Arabie Phipps
Published: August 2011

A least squares optimization strategy is first reviewed and applied to the task of fitting a given collection of symmetric proximity values defined between the objects from one set by a collection of reconstructed proximity values, satisfying a fixed set of constraints, generated from some specified graph‐theoretic structure, such as an ultrametric or an additive tree, selected for representing the objects. Our method uses itcrative projection on to closed convex sets defined by the collection of given constraints characterizing the structural representation specified, and in contrast to least squares optimization methods that impose such constraints through the use of penalty functions, avoids the use of the latter, as well as the implementation of any gradient‐based optimization technique. Secondly, just as various penalty‐function/ gradient‐based optimization techniques have been turned into heuristic search strategies for such particular structures of interest as ultrametrics or additive trees, the use of iterative projection is suggested as a general heuristic search strategy for locating the best structural representations to impose in the first place, where the collection of constraints used may vary over the course of the optimization process. Our evaluation of the expected results uses several data sets previously analysed in the literature. Finally, several other applications of iterative projection as a heuristic optimization technique are discussed, including the consideration of data beyond that of a single symmetric proximity matrix (for example, extensions to two‐mode proximity matrices, i.e. between two distinct object sets, and to three‐way proximity matrices either symmetric or not), and to representations based on sums of matrices where each is constrained separately to conform to some desired representational structure.
A two‐stage estimation of structural equation models with continuous and polytomous variables
Authors: Lee Sik‐Yum , Poon Wai‐Yin , Bentler P. M.
Published: August 2011

This paper develops a computationally efficient procedure for analysis of structural equation models with continuous and polytomous variables. A partition maximum likelihood approach is used to obtain the first stage estimates of the thresholds and the polyserial and polychoric correlations in the underlying correlation matrix. Then, based on the joint asymptotic distribution of the first stage estimator and an appropriate weight matrix, a generalized least squares approach is employed to estimate the structural parameters in the correlation structure. Asymptotic properties of the estimators are derived. Some simulation studies are conducted to study the empirical behaviours and robustness of the procedure, and compare it with some existing methods.
A latent trait and a latent class model for mixed observed variables
Authors: Moustaki Irini
Published: August 2011

Latent variable models are widely used in social sciences in which interest is centred on entities such as attitudes, beliefs or abilities for which there exist no direct measuring instruments. Latent modelling tries to extract these entities, here described as latent (unobserved) variables, from measurements on related manifest (observed) variables. Methodology already exists for fitting a latent variable model to manifest data that is either categorical (latent trait and latent class analysis) or continuous (factor analysis and latent profile analysis).

In this paper a latent trait and a latent class model are presented for analysing the relationships among a set of mixed manifest variables using one or more latent variables. The set of manifest variables contains metric (continuous or discrete) and binary items. For the latent trait model the latent variables are assumed to follow a multivariate standard normal distribution. Our method gives maximum likelihood estimates of the model parameters and standard errors of the estimates by analysing the data as they are without using any underlying variables. The mixed latent trait and latent class models are fitted using an EM algorithm.

To illustrate the use of the mixed model three data sets have been analysed. Two of the data sets contain five memory questions, the first on Thatcher's resignation and the second on the Hillsborough football disaster; these five questions were included in British Market Research Bureau International August 1993 face‐to‐face omnibus survey. The third data set is from the 1991 British Social Attitudes Survey; the questions which have been analysed are from the environment section.
Robust mean and covariance structure analysis
Authors: Yuan Ke‐Hai , Bentler Peter M.
Published: August 2011

Covariance structure analysis is used to evaluate hypothesized influences among unmeasured latent and observed variables. As implemented, it is not robust to outliers and bad data. Several robust methods in model fitting and testing are proposed. These include direct estimation of M‐estimators of structured parameters and a two‐stage procedure based on robust M‐ and S‐estimators of population covariances. The large sample properties of these estimators are obtained. The equivalence between a direct M‐estimator and a two‐stage estimator based on an M‐estimator of population covariance is established when sampling from an elliptical distribution. Two test statistics are presented in judging the adequacy of a hypothesized model; both are asymptotically distribution free if using distribution free weight matrices. So these test statistics possess both finite sample and large sample robustness. The two‐stage procedures can be easily adapted into standard software packages by modifying existing asymptotically distribution free procedures. To demonstrate the two‐stage procedure, S‐estimator and M‐estimators under different weight functions are calculated for some real data sets.
An unbiased errors‐in‐variables approach to detecting unconscious cognition
Authors: Klauer Karl Christoph , Draine Sean C. , Greenwald Anthony G.
Published: August 2011

Greenwald, Klinger and Schuh (1995) have proposed a regression approach for detecting unconscious cognition. An errors‐in‐variables approach is presented that corrects for measurement error in the predictor and takes into account that the latent predictor variable is assumed to be non‐negative. The new approach requires the same input as the uncorrected regression analysis and provides consistent estimates of regression weights as well as valid statistical tests of their significance. In particular, the method yields a consistent estimate of the regression intercept that provides critical evidence for unconscious cognition. A simulation study illustrates these aspects of the new technique. Several data sets are then reanalysed by means of the new method.
Effects of temperature and near-substrate plasma density on the structural and electrical properties of dc sputtered germanium thin films
Authors: Pollock Kristin M. , Kaufman-Osborn Tobin , Hiltrop Jonas , Doyle James R.
Published: August 2011

Germanium thin films were deposited by dc reactive magnetron sputtering as a function of substrate temperature and ion flux using an unbalanced magnetron with an external magnetic field. The ion flux and energy distribution were measured using a retarding field energy analyzer (RFEA), a flat probe with a guard ring, and cylindrical Langmuir probes. The RFEA ion flux, the flat probe saturation currents, and the ion densities inferred from the cylindrical probe data are in very good agreement over a wide range of plasma densities, which were varied both by the external coil current and discharge power. The RFEA ion energy distributions are in good agreement with the plasma potentials inferred from the cylindrical probes, and suggest that the nonuniformity of the plasma in the vicinity of the substrate holder should be considered in the interpretation of probe results in these systems. The deposited films were characterized by x-ray diffraction, Raman spectroscopy, optical transmission, resistivity, and Hall effect measurements. Under low ion bombardment conditions, an abrupt onset of the crystalline phase with respect to temperature is observed in the Raman and x-ray diffraction measurements, and the crystal quality increases with increasing temperature above the transition temperature. The transition is also accompanied by a sharp decrease in film resistivity. The microcrystalline films have a strong preferential orientation in the (220) direction, and are p type with carrier densities in the range 1018 cm−3 and mobilities in the range 15–30 cm2/V-s. The structural and electronic properties of the films are sensitive to the ion flux. Near the transition temperature the effects of increasing ion flux can be attributed to the small temperature rise that accompanies the higher plasma density. At higher temperatures the increased ion flux results in a more random crystallographic orientation, with significantly lower carrier concentrations and only slightly lower carrier mobilities, implying either a reduction in acceptor defect density and/or the creation of compensating n-type defects.
Changing Incentives to Publish
Authors: Franzoni Chiara , Scellato Giuseppe , Stephan Paula
Published: August 2011

National incentive policies relate to increases in research article submissions and publications in
Science
.
Minimizing the Mischief of Mineralocorticoids
Authors: Boxer Rebecca S.
Published: August 2011

Reversing the adverse effects of mineralocorticoids in mice may have important implications for human heart health
Understanding the Regulatory Pathway One Video at a Time
Authors: Robinson Rebecca , Bailey Alexander M. , Ibrahim Samir
Published: August 2011

Online instruction guides scientists through the regulatory process for complex regenerative medicine products.
Reduced Antibody Responses to the Pandemic (H1N1) 2009 Vaccine after Recent Seasonal Influenza Vaccination
Authors: Choi Yoon Seok , Baek Yun Hee , Kang Wonseok , Nam Seung Joo , Lee Jino , You Sooseong , Chang Dong-Yeop , Youn Jong-Chan , Choi Young Ki , Shin Eui-Cheol
Published: August 2011

The vaccination program against the 2009 pandemic H1N1 influenza virus (2009 H1N1) provided a unique opportunity to determine if immune responses to the 2009 H1N1 vaccine were affected by a recent, prior vaccination against seasonal influenza virus. In the present study, we studied the immune responses to the 2009 H1N1 vaccine in subjects who either received the seasonal influenza virus vaccination within the prior 3 months or did not. Following 2009 H1N1 vaccination, subjects previously given a seasonal influenza virus vaccination exhibited significantly lower antibody responses, as determined by hemagglutination inhibition assay, than subjects who had not received the seasonal influenza virus vaccination. This result is compatible with the phenomenon of “original antigenic sin,” by which previous influenza virus vaccination hampers induction of immunity against a new variant. Our finding should be taken into account for future vaccination programs against pandemic influenza virus outbreaks.
Detection of Mycoplasma genitalium-Reactive Cervicovaginal Antibodies among Infected Women
Authors: Iverson-Cabral Stefanie L. , Manhart Lisa E. , Totten Patricia A.
Published: August 2011

Mycoplasma genitalium-reactive cervicovaginal IgA and IgG antibodies were detected in 51.9% and 70.4% of 27 infected women and 22.2% and 18.5% of 27 uninfected controls, respectively. The predominance of MgpB- and MgpC-reactive antibodies at the site of infection is consistent with their hypothesized role in selecting antigenic variants during persistent infection.
The Genome of Yoka Poxvirus
Authors: Zhao Guoyan , Droit Lindsay , Tesh Robert B. , Popov Vsevolod L. , Little Nicole S. , Upton Chris , Virgin Herbert W. , Wang David
Published: August 2011

Yoka poxvirus was isolated almost four decades ago from a mosquito pool in the Central African Republic. Its classification as a poxvirus is based solely upon the morphology of virions visualized by electron microscopy. Here we describe sequencing of the Yoka poxvirus genome using a combination of Roche/454 and Illumina next-generation sequencing technologies. A single consensus contig of ∼175 kb in length that encodes 186 predicted genes was generated. Multiple methods were used to show that Yoka poxvirus is most closely related to viruses in the
Orthopoxvirus
genus, but it is clearly distinct from previously described poxviruses. Collectively, the phylogenetic and genomic sequence analyses suggest that Yoka poxvirus is the prototype member of a new genus in the family
Poxviridae
.
A ZORA-DFT and NLMO study of the one-bond fluorine–X indirect nuclear spin-spin coupling tensors for various VSEPR geometries
Authors: Perras Frédéric A. , Bryce David L.
Published: August 2011

Zeroth-order regular approximation (ZORA) density functional theory (DFT) calculations of one-bond X–19F indirect nuclear spin-spin coupling (J) tensors were performed on a series of fluorine-containing compounds covering several valence shell electron pair repulsion (VSEPR) theory geometries for which J, by symmetry, is not required to be axially symmetric. The calculations show that the antisymmetric components of J are only of the same order of magnitude as the principal components of the symmetric J-coupling tensor for a few geometries, and that in cases of approximate axial symmetry along the bond, J remains nearly axially symmetric with its unique component along the bond. In general, different species having the same nominal geometry tend to have similar tensor orientations, magnitudes of anisotropy of J relative to the isotropic coupling constant, as well as the same dominant contributions from the different coupling mechanisms. Structures are also systematically modified to determine how the tensor components depend on geometrical parameters. The isotropic coupling constants are subsequently interpreted using a natural localized molecular orbital (NLMO) approach. Our results could prove to be useful for future experimental characterizations of J tensors in systems having symmetry properties that do not force J to be axially symmetric or coincident with the dipolar coupling tensor.
Nuclear magnetic resonance and mass spectrometry studies of 2′,3′,5′-O-triacetylguanosine self-assembly in the presence of alkaline earth metal ions (Ca2+, Sr2+, Ba2+)
Authors: Kwan Irene C.M. , She Yi-Min , Wu Gang
Published: August 2011

We report structural determination of cation-templated self-assembly of a guanosine derivative, 2′,3′,5′-O-triacetylguanosine (TAG), in the presence of three alkaline earth metal ions (Ca2+, Sr2+, and Ba2+) in CDCl3. Using a combination of nuclear magnetic resonance (NMR) and electrospray ionization mass spectrometry (ESI-MS) methods, we have found that TAG molecules form discrete octamers in the form of [TAG]8M2+ (M2+ = Ca2+, Sr2+, and Ba2+), which is composed of two G-quartets and a sandwiched metal ion. We have determined the ability of the three alkaline earth metal ions to promote TAG self-assembly (relative binding affinity) to be Sr2+ ≫ Ba2+ > Ca2+. More importantly, we have used two-dimensional (2D) NMR methods to determine the structural details of [TAG]8Sr2+. In particular, we found that each octamer consists of an all-anti G-quartet stacking on top of an all-syn G-quartet in a tail-to-head fashion with a twist angle of 45° between the two G-quartets. This TAG octamer structure represents a unique case quite different from other lipophilic guanosine octamers reported in the literature.
Phosphorus-31 and vanadium-51 solid-state nuclear magnetic resonance spectroscopy of β-vanadyl phosphate — Effects of homo- and heteronuclear spin-spin, electrostatic, and paramagnetic interactions
Authors: Eichele Klaus , Grimmer Arnd-Rüdiger
Published: August 2011

Field-dependent 31P solid-state NMR studies demonstrate that the line shape in spectra of β-VOPO4 depends on 51V–31P direct and indirect spin-spin interactions (M2 (51V, 31P) = 101(23) × 106 rad2 s–2, 2Jiso (51V, 31P) = 48(5) Hz) and, to a lesser extent, on 31P chemical shift anisotropy (δiso = –10.4(2), Ω = δ11 – δ33 = 22(2) ppm) and 31P–31P interactions (M2 (31P, 31P) = 6.7(1) × 106 rad2 s–2). In contrast, homonuclear dipolar interactions play an important role for the field and spinning rate dependent 31P spin-lattice relaxation via paramagnetic impurities (T1 = 20–60 s). Vanadium-51 magic-angle spinning NMR spectra indicate a sizeable chemical shift anisotropy (δiso = –754(1), δ11 = –336(10), δ22 = –344(6), δ33 = –1581(8) ppm) and nuclear quadrupole interaction (χ = 1.5(1) MHz, η = 0.35(5)); the principal axis systems of both interactions are clearly not coincident, with an angle of 35(5)° between the greatest component of the electric field gradient tensor and δ33.
Distinct cardiac and renal effects of ETAreceptor antagonist and ACE inhibitor in experimental type 2 diabetes
Authors: Zoja Carla , Cattaneo Sara , Fiordaliso Fabio , Lionetti Vincenzo , Zambelli Vanessa , Salio Monica , Corna Daniela , Pagani Chiara , Rottoli Daniela , Bisighini Cinzia , Remuzzi Giuseppe , Benigni Ariela
Published: August 2011

Diabetic nephropathy is associated with cardiovascular morbidity. Angiotensin-converting enzyme (ACE) inhibitors provide imperfect renoprotection in advanced type 2 diabetes, and cardiovascular risk remains elevated. Endothelin (ET)-1 has a role in renal and cardiac dysfunction in diabetes. Here, we assessed whether combination therapy with an ACE inhibitor and ETAreceptor antagonist provided reno- and cardioprotection in rats with overt type 2 diabetes. Four groups of Zucker diabetic fatty (ZDF) rats were treated orally from 4 (when proteinuric) to 8 mo with vehicle, ramipril (1 mg/kg), sitaxsentan (60 mg/kg), and ramipril plus sitaxsentan. Lean rats served as controls. Combined therapy ameliorated proteinuria and glomerulosclerosis mostly as a result of the action of ramipril. Simultaneous blockade of ANG II and ET-1 pathways normalized renal monocyte chemoattractant protein-1 and interstitial inflammation. Cardiomyocyte loss, volume enlargement, and capillary rarefaction were prominent abnormalities of ZDF myocardium. Myocyte volume was reduced by ramipril and sitaxsentan, which also ameliorated heart capillary density. Drug combination restored myocardial structure and reestablished an adequate capillary network in the presence of increased cardiac expression of VEGF/VEGFR-1, and significant reduction of oxidative stress. In conclusion, in type 2 diabetes concomitant blockade of ANG II synthesis and ET-1 biological activity through an ETAreceptor antagonist led to substantial albeit not complete renoprotection, almost due to the ACE inhibitor. The drug combination also showed cardioprotective properties, which however, were mainly dependent on the contribution of the ETAreceptor antagonist through the action of VEGF.
A Corotational Finite Element Method Combined with Floating Frame Method for Large Steady‐State Deformation and Free Vibration Analysis of a Rotating‐Inclined Beam
Authors: Tsai Ming Hsu , Lin Wen Yi , Zhou Yu Chun , Hsiao Kuo Mo
Published: August 2011

A corotational finite element method combined with floating frame method and a numerical procedure is proposed to investigate large steady‐state deformation and infinitesimal‐free vibrationaround the steady‐state deformation of a rotating‐inclined Euler beam at constant angular velocity. The element nodal forces are derived using the consistent second‐order linearization of the nonlinear beam theory, the d′Alembert principle, and the virtual work principle in a current inertia element coordinates, which is coincident with a rotating element coordinate system constructed at the current configuration of the beam element. The governing equations for linear vibration are obtained by the first‐order Taylor series expansion of the equation of motion at the position of steady‐state deformation. Numerical examples are studied to demonstrate the accuracy and efficiency of the proposed method and to investigate the steady‐state deformation and natural frequency of the rotating beam with different inclined angle, angular velocities, radius of the hub, and slenderness ratios.
Age-Related Long-Term Functional Results after Riboflavin UV A Corneal Cross-Linking
Authors: Caporossi Aldo , Mazzotta Cosimo , Baiocchi Stefano , Caporossi Tomaso , Denaro Rosario
Published: August 2011

Purpose. To report a comparative prospective long-term functional analysis after Riboflavin UV A corneal cross-linking (CXL) in three different age groups of patients affected by progressive keratoconus (KC).Methods. Functional analysis comprised paediatric patients (≤18 years) included 152 eyes (29.5%); intermediate group (19–26 years) 286 eyes (55.4%), and adults (≥27 years) 78 eyes (15.1%). CXL was performed according to the Siena protocol by using the Vega CBM (Caporossi-Baiocchi-Mazzotta) X linker (CSO, Florence, Italy) at Siena University by the same authors. Pre- and post-op examinations included UCVA, BSCVA, corneal topography, and surface aberrometry (CSO Eye Top, Florence, Italy), at 48 months followup.Results. At 48 months followup paediatrics, intermediate, and adult patients showed a mean gain in UCVA of +0.2, +0.14 and +0.12 Snellen lines. BSCVA gained by a mean of +0.21, +0.2, and +0.1 Snellen lines.Kmaxwas reduced by a mean value of −0.9 D, −0.6 D, and −0.5 D, respectively. Coma values improved by a mean of −0.45 μm, −0.91 μm, and −0.19 μm, respectively. Treatment ensured a long-term keratoconus stabilization in over 90% of treated patients.Conclusion. According to our long-term comparative results, epithelium-off Riboflavin UV A cross-linking should be the first choice therapy of progressive KC, particularly in paediatric age and patients under 26 years.
Asymptotical Stability of Nonlinear Fractional Differential System with Caputo Derivative
Authors: Zhang Fengrong , Li Changpin , Chen YangQuan
Published: August 2011

This paper deals with the stability of nonlinear fractional differential systems equipped with the Caputo derivative. At first, a sufficient condition on asymptotical stability is established by using a Lyapunov‐like function. Then, the fractional differential inequalities and comparison method are applied to the analysis of the stability of fractional differential systems. In addition, some other sufficient conditions on stability are also presented.