bluuebunny/crossref_metadata_2025 huggingface dataset:
Stabilized Multivariate Tests ‐ the Inclusion of Missing Values
Authors: Kropf S. , Läuter J. , Glimm E.
Published: May 2007

In two recent papers, LÄUTER (1996) and LÄUTER, GLIMM, and KROPF (1996) have proposed a new class of exact tests for multivariate normal data with an inherent structure. These tests are based on the construction of scores that have a spherical distribution. The principle can be adapted to a variety of different situations, and it supports exact tests with small samples of high‐dimensional data.

In this paper, an enhancement of that theory will be given regarding the problem of missing data. It provides a new mathematical understanding of mean imputation techniques, and it is also the basis for a modified principal component missing data algorithm described here.
On Robust Linear Regression of Hepatic Extraction of Insulin
Authors: Aboukalam M. A. F.
Published: May 2007

In classical linear regression model for analysis of medical data concerning hepatic extraction of insulin and c‐peptide the fundamental assumption is that the subjects involved are of a similar nature. In reality, if this assumption is violated then the precision of the results is questionable. This paper suggests a robust alternative to overcome this problem. It is observed that the robustification may be a better option to determine an optimal quantity of insulin which minimizes the risk of damage associated with diabatic treatments.
Tests of Independence and Zero Correlations Among P Random Variables
Authors: Wilcox Rand R.
Published: May 2007

Suppose it is desired to determine whether there is an association between any pair of p random variables. A common approach is to test H0 : R = I, where R is the usual population correlation matrix. A closely related approach is to test H0 : Rpb = I, where Rpb is the matrix of percentage bend correlations. In so far as type I errors are a concern, at a minimum any test of H0 should have a type I error probability close to the nominal level when all pairs of random variables are independent. Currently, the Gupta‐Rathie method is relatively successful at controlling the probability of a type I error when testing H0: R = I, but as illustrated in this paper, it can fail when sampling from nonnormal distributions. The main goal in this paper is to describe a new test of H0: Rpb = I that continues to give reasonable control over the probability of a type I error in the situations where the Gupta‐Rathie method fails. Even under normality, the new method has advantages when the sample size is small relative to p. Moreover, when there is dependence, but all correlations are equal to zero, the new method continues to give good control over the probability of a type I error while the Gupta‐Rathie method does not. The paper also reports simulation results on a bootstrap confidence interval for the percentage bend correlation.
Methods for the Analyses of Case‐Cohort Studies
Authors: Volovics Alexander , Van Brandt Piet A. Den
Published: May 2007

Case‐cohort and nested case‐control sampling methods have recently been introduced as a means of reducing cost in large cohort studies. The asymptotic distribution theory results for relative rate estimation based on Cox type partial or pseudolikelihoods for case‐cohort and nested case‐control studies have been accounted for. However, many researchers use (stratified) frequency table methods for a first or primary summarization of the most important evidence on exposure‐disease or dose‐response relationships, i.e. the classical Mantel‐Haenszel analyses, trend tests and tests for heterogeneity of relative rates. These can be followed by exponential failure time regression methods on grouped or individual data to model relationships between several factors and response. In this paper we present the adaptations needed to use these methods with case‐cohort designs, illustrating their use with data from a recent case‐cohort study on the relationship between diet, life‐style and cancer. We assume a very general setup allowing piecewise constant failure rates, possible recurrent events per individual, independent censoring and left truncation.
Incomplete Split‐Block Designs
Authors: Hering Franz , Mejza Stanislaw
Published: May 2007

The paper deals with modelling of experiments carried out in incomplete split‐block designs. Moreover, the characterization of the design with respect to a general balance property is given. Also, some statistical properties of the design are examined. The problems considered are illustrated with examples.
Disentangling Intervention and Temporal Effects in Longitudinal Designs Using Latent Curve Analysis
Authors: Raykov Tenko
Published: May 2007

This article is concerned with an approach to disconfounding effects in repeated measure designs with multiple groups. An extension of latent curve analysis (MEREDITH and TISAK, 1990; RAO, 1958, 1965) is described. The method permits estimation and testing of intervention effects separately from temporal effects. It is based on restricted factor analysis of individual change profiles and utilizes basis curves representing group patterns of change. The approach is illustrated on data from a two‐group intervention study.
The Propensity Score in the Analysis of Therapeutic Studies
Authors: Graf Erika
Published: May 2007

A method for reducing bias in observational studies proposed by ROSENBAUM and RUBIN (1983, 1984) is discussed with a view to applications in studies designed to compare two treatments. The data are stratified on a function of covariates, called the propensity score. The propensity score is the conditional probability of receiving a specific treatment given a set of observed covariates. Some insight into how this kind of stratification works in theory is given. Within strata, the treatment groups are comparable with respect to the distribution of covariates incorporated into the score, hence a corresponding stratified analysis can be considered. The method is different from other strategies in that the sub‐classes are not intended to comprise patients with similar prognosis. In practice, estimated grouped scores are used. Problems concerning the interpretation of the proposed stratified approach are illustrated by an application in oncology, and the results are compared to those from an analysis in a standard regression model.
The Analysis of Correlated Binary Outcomes Using Multivariate Logistic Regression
Authors: Gauvreau Kimberlee , Pagano Marcello
Published: May 2007

A method for analyzing correlated binary outcomes when the responses are distinct measurements made simultaneously on a single individual is presented. This extension of univariate logistic regression allows us to model the dependence of the responses on a set of covariates while estimating the degree of association among them. For the case of two dichotomous outcomes, a form of the cumulative bivariate logistic distribution proposed by Gumbel is used to characterize their joint probabilities in terms of logistic marginal probabilities and the correlation coefficient of the responses. The model is then extended to accommodate three or more dichotomous outcomes. A two‐step approximation to fitting the multivariate logistic model is also described.
Analysis of Repeated Measurements with Ante‐Dependence Covariance Models
Authors: Macchiavelli Raúl E. , Moser E. Barry
Published: May 2007

This paper considers the use of ante‐dependence models in problems with repeated measures through time. These are conditional regression models which reflect the dependence of a measure on some of the previous observations from the same subject. We present maximum likelihood estimators of the covariance matrix and procedures for selecting the order of ante‐degendence based on penalized like‐lihoods. Extensions to missing data situations are discussed.

We propose Wald‐type test statistics and apply them in two situations common in experiments with repeated measures: one with pre‐study observations and another one with small sample size relative to the number of time periods. In these examples, tests assuming ante‐dependence find effects which are not detected using competing procedures.
Selection of Tree‐Biased Classifiers with the Bootstrap 632+ Rule
Authors: Merler Stefano , Furlanello Cesare
Published: May 2007

This paper introduces a novel model selection procedure for tree‐based classifiers. The method is based on the bootstrap 632+ rule recently proposed by Efron and Tibshirani. The rule allows selecting compact, non‐overfitting classification trees by weighting the contributions of the resubstitution and standard bootstrap estimated error. The proposed method is applied in a medical entomology problem for modeling the risk of parasite presence.
A Likelihood Approach to Analysing Longitudinal Bivariate Binary Data
Authors: Chan Jennifer S. K. , Kuk Anthony Y. C. , Bell James
Published: May 2007

To study the effect of methadone treatment in reducing multiple drug use, say heroin and benzodiazepines while controlling for their possible interaction, we analyse the results of urine drug screens from patients in treatment at a Sydney clinic in 1986. Weekly tests are either positive or negative for each type of drug and a bivariate binary model was developed to analyse such repeated bivariate binary outcomes. It models simultaneously the logit of each type of drug use and their log odds ratio linearly in some covariates. The serial correlation within subject is accounted for by including the ‘previous outcome’ of both drugs and their interaction as covariates. Our main conclusion is that drug use is reduced over time and the interaction between dose and time effects is not significant. It also suggests that while methadone maintenance is effective in reducing heroin use (CHAN et al., 1995), it does not suppress non‐opioid drug use. Concerning the association between the two drugs, it is found that the present strength of their association depends on the previous outcomes only through a measure of concordance. The proposed model has a tractable likelihood function and so a full likelihood analysis is possible. It can be easily extended to incorporate mixture effects. The EM algorithm is used for the estimation of parameters in the mixture model and model selection can be based on the Akaike Information Criterion.
Test Statistics for Three‐Factor Interaction in 2 × 2 × 2 Contingency Tables
Authors: Mannan M. , Nassar R.
Published: May 2007

A Monte Carlo simulation was conducted in order to determine the size and power of two proposed tests (the covariance and correlation tests) for three‐factor interaction in 2 × 2 × 2 contingency tables. Results were compared to the log‐odds ratio test statistic. Simulation showed the correlation test to be more conservative than the covariance test, but less so than the log‐odds ratio test. However, the correlation test was the most powerful among the three tests.
Bayesian Neural Network Models for Censored Data
Authors: Faraggi David , Simon R. , Yaskil E. , Kramar A.
Published: May 2007

Neural networks are considered by many to be very promising tools for classification and prediction. The flexibility of the neural network models often result in over‐fit. Shrinking the parameters using a penalized likelihood is often used in order to overcome such over‐fit. In this paper we extend the approach proposed by FARAGGI and SIMON (1995a) to modeling censored survival data using the input‐output relationship associated with a single hidden layer feed‐forward neural network. Instead of estimating the neural network parameters using the method of maximum likelihood, we place normal prior distributions on the parameters and make inferences based on derived posterior distributions of the parameters. This Bayesian formulation will result in shrinking the parameters of the neural network model and will reduce the over‐fit compared with the maximum likelihood estimators. We illustrate our proposed method on a simulated and a real example.
Using a Normal Approximation to Test for the Binomial Distribution
Authors: Sun Ping , Madden Laurence V.
Published: May 2007

The commonly used method to test for the binomial distribution is thex2‐test. In this paper, we introduce an alternative method to test for the binomial distribution. SupposeNis the number of sample groups withnindividuals each,xijis thejth sample inith group, a Bernoulli variable with parameter and VVI=s2/[m(1 ‐m)/n]. Then it is well know that the asymptotic distribution of the statistic (N‐ 1) VVI isx2(N‐ 1) under the hypothesisp1= p2= … = pN.Here we find that VVI has an asymptotic normal distributionN(1, 2(1 ‐ 1/n)/(N‐ 1)). Unlike thex2‐statistic, the variance of the normal test statistic is a function ofn.This method is convenient in detecting spatial patterns and dispersion in the study of diseased organisms (e.g., plants) in field samples.
Confidence Limits on the Ratio of the Mean Failure Times Based on Paired Exponential Observations
Authors: Lui Kung‐Jong
Published: May 2007

This paper discusses interval estimation for the ratio of the mean failure times on the basis of paired exponential observations. This paper considers five interval estimators: the confidence interval using an idea similar to Fieller's theorem (CIFT), the confidence interval using an exact parametric test (CIEP), the confidence interval using the marginal likelihood ratio test (CILR), the confidence interval assuming no matching effect (CINM), and the confidence interval using a locally most powerful test (CIMP). To evaluate and compare the performance of these five interval estimators, this paper applies Monte Carlo simulation. This paper notes that with respect to the coverage probability, use of the CIFT, CILR, or CIMP, although which are all derived based on large sample theory, can perform well even when the number of pairs n is as small as 10. As compared with use of the CILR, this paper finds that use of the CIEP with equal tail probabilities is likely to lose efficiency. However, this loss can be reduced by using the optimal tail probabilities to minimize the average length when n is small (<20). This paper further notes that use of the CIMP is preferable to the CIEP in a variety of situations considered here. In fact, the average length of the CIMP with use of the optimal tail probabilities can even be shorter than that of the CILR. When the intraclass correlation between failure times within pairs is 0 (i.e., the failure times within the same pair are independent), the CINM, which is derived for two independent samples, is certainly the best one among the five interval estimators considered here. When there is an intraclass correlation but which is small (<0.10), the CIFT is recommended for obtaining a relatively short interval estimate without sacrificing the loss of the coverage probability. When the intraclass correlation is moderate or large, either the CILR or the CIMP with the optimal tail probabilities is preferable to the others. This paper also notes that if the intraclass correlation between failure times within pairs is large, use of the CINM can be misleading, especially when the number of pairs is large.
A Two‐Way Analysis of Covariance Model for Classification of Stability Data
Authors: Ahn Hongshik , Chen James J. , Lin Tsae‐Yun D.
Published: May 2007

This paper proposes a procedure for testing and classifying data with multiple factors. A two‐way analysis of covariance is used to classify the differences among the batches as well as another factor such as package type and/or product strength. In the test procedure, slopes and intercepts of the main effects are tested using a combination of simultaneous and sequential F‐tests. Based on the test procedure results, the data are classified into one of four different groups. For each group, shelf life can be calculated accordingly. We examine if the procedure produces satisfactory control of the probability of a Type I error and the power of detecting the difference of degradation rates and intercepts for different nominal levels. The method is evaluated with a Monte Carlo simulation study. The proposed procedure is compared with the current FDA procedure using real data.
A Note on Circular Nonparametrical Classification
Authors: Ackermann Hanns
Published: May 2007

Following the linear approach by Stoller a circular discriminant analytical method is described. Marginally, following Ling, a simple method is mentioned to find clusters on a circle. Both methods are distribution‐free and invariant under rotation.
Comparing the Powers of the Wald‐Wolfowitz and Kolmogorov‐Smirnov Tests
Authors: Magel Rhonda C. , Wibowo Sasmito H.
Published: May 2007

The Wald‐Wolfowitz test and the Kolmogorov‐Smirnov test are two well‐known tests which can be used to test for differences between two population distributions, where these distributions could differ in means, variances or shapes. This paper compares the simulated power of the Wald‐Wolfowitz test to that of the Kolmogorov‐Smirnov test in several situations. Differences in location only, differences in variance only, and differences in both location and variance are considered. In most cases, equal sample sizes of 10 and 20 are used.
Pairwise Comparisons Using Trimmed Means or M‐Estimators when Working with Dependent Groups
Authors: Wilcox Rand R.
Published: May 2007

For J dependent groups, let θj, j = 1, …, J, be some measure of location associated with the jth group. A common goal is computing confidence intervals for the pairwise differences, θj — θk, j < k, such that the simultaneous probability coverage is 1 — α. If means are used, it is well known that slight departures from normality (as measured by the Kolmogorov distance) toward a heavy‐tailed distribution can substantially inflate the standard error of the sample mean, which in turn can result in relatively low power. Also, when distributions differ in shape, or when sampling from skewed distributions with relatively light tails, practical problems arise when the goal is to obtain confidence intervals with simultaneous probability coverage reasonably close to the nominal level. Extant theoretical and simulation results suggest replacing means with trimmed means. The Tukey‐McLaughlin method is easily adapted to the problem at hand via the Bonferroni inequality, but this paper illustrates that practical concerns remain. Here, the main result is that the percentile t bootstrap method, used in conjunction with trimmed means, gives improved probability coverage and substantially better power. A method based on a one‐step M‐estimator is also considered but found to be less satisfactory.
Overlapping Clusters of Tuberculosis Contacts: An Improved Sampling Strategy
Authors: Osahan Sukhminder S.
Published: May 2007

A two stage without replacement strategy is proposed for estimating the population mean of overlapping clusters of contacts of tuberculosis cases. This sampling strategy is an improvement over the two sampling strategies proposed by SINGH (1988). A numerical illustration is provided by taking two populations of tuberculosis contacts from New York City; the percentage gain in efficiency varies from 3.70 to 24.99. The proposed improved sampling strategy may be useful to other contagious diseases in the different fields of biomedical sciences or similar situations in other fields.
A Generalized Allometric Model for Determining Length‐Weight Relationship
Authors: Venugopalan R. , Prajneshu
Published: May 2007

Well‐known allometric model is critically reviewed for determining the length‐weight relationship. Procedure to be followed for applying this model under the assumption of multiplicative as well as additive error is discussed. The possibility of autocorrelations in error term is explored. It has been demonstrated that the usual allometric relationship does not always work satisfactorily. Accordingly, a generalization of this model is studied in detail. As an illustration, this generalized version of allometric model is used to determine the length‐weight relationship of some data on the Indian pearl oyster.
Prediction of Growth: A Hierarchical Bayesian Approach
Authors: Arjas Elja , Liu Liping , Maglaperidze Niko
Published: May 2007

A nonparametric hierarchical growth curve model is proposed. Different levels in the model hierarchy are intended to correspond to different sources of variation in an individual's growth. The nonparametric character of the model offers considerable flexibility in fitting the growth curves to empirical data. Here the emphasis is on prediction, and for this purpose the adopted Bayesian inferential approach seems particularly natural and efficient. A Markov chain Carlo method is used to perform the numerical computations. As an illustration of the techniques, we consider the growth of children, during their first two years.
A Technical Note on the Power Determination for Fisher's Combination Test
Authors: Wassmer Gernot
Published: May 2007

In a recent paper, Banik, Köhne, and Bauer (1996) investigated the use of Fisher's combination test for two stage sampling in terms of its power as compared to the optimal test in the pooled sample. The distributional assumptions corresponded to the application of paired comparisons and parallel groups t tests in the classical nonadaptive scenario. Allowing early stopping in favor of H0, as described in Bauer and Köhne (1994), modifies this test procedure and possibly reduces the sample size. For power calculations they noted a technical problem in integration arising from function singularities. This note provides a technically feasible solution for power calculations in these and other cases using SAS/IML software. Some results, e.g. concerning a potential gain in power when allowing for early stopping are presented.
A Stochastic Process and Generalized Distributions for the Study of Oviposition Evolution of a Parasite
Authors: Janardan K. G.
Published: May 2007

This paper considers a generalized birth process {Xm(t), t > 0} and presents a new stochastic model for the number of eggs laid by a parasite on a host. Also, given an underlying distribution for the number of visits between parasites and a host, this distribution is generalized by the distribution of the number of eggs per visit laid on the host. If a certain number of eggs are already present on the host, a parasite such as a Japanese weevil, may avoid oviposition in subsequent visits (see JANARDAN (1980)) to the same host. A class of generalized distributions are presented to model such situations. The case of a single egg laying parasite and a Poisson distribution for the number of visits of the parasite to the same host yields a distribution of particular interest. In order to develop this model, certain lemmas are derived. Finally a characteristic property of this stochastic model is presented.
Linear Discriminant Functions for Stationary Time Series
Authors: Krzyśko Mirosłw , Wołński Waldemar
Published: May 2007

Optimal classification rules based on linear functions which maximize the Chernoff distance, or the Morisita distance, or the Kullback‐Leibler distance are studied here. We obtain an expression for the optimal linear discriminant function and show that the resulting linear procedure belongs to the Anderson‐Bahadur admissible class. For the comparison of discriminant rules we use some index which is the measure of the accuracy of a given class of discriminant procedures. The asymptotic form of the discriminant function is also studied.
Computing Projections into Cones Generated by a Matrix
Authors: Frick H.
Published: May 2007

A method is described for computing orthogonal projections into finitely generated cones. This method can be used to solve nonnegative least squares approximation problems, to find the multivariate onesided Maximum Likelihood estimator and also determines the most stringent somewhere most powerful test of Schaafsma. The gist of the procedure is the unconstrained maximization of a numerically simple function. This function has a global maximum and allows an uncomplicated maximum search since local maxima do not exist. The maximum can be obtained after a finite number of iterations.
Interval Estimation for Ratios in Bioequivalence Trials
Authors: Chen Keh‐Wei , Li Gang , Sun Yanqing , Chow Shein‐Chung
Published: May 2007

The problem for assessment of equivalence in variability of bioavailability between two drug products is considered. An exact confidence region for the ratio between intrasubject variabilities is derived when the intersubject variance is known. When the intersubject variance is unknown, a large sample approximation is considered. The proposed method for assessing equivalence in variability of bioavailability appears to be asymptotically uncorrelated with the sample mean ratio for average bioavailabilty. As a result, the proposed method in conjunction with the sample mean ratio method can be utilized for assessing population bioequivalence. An example concerning a bioequivalence trial with 24 healthy volunteers is presented to illustrate the proposed method.
Engineering bacteria for production of rhamnolipid as an agent for enhanced oil recovery
Authors: Wang Qinhong , Fang Xiangdong , Bai Baojun , Liang Xiaolin , Shuler Patrick J. , Goddard William A. , Tang Yongchun
Published: May 2007

Rhamnolipid as a potent natural biosurfactant has a wide range of potential applications, including enhanced oil recovery (EOR), biodegradation, and bioremediation. Rhamnolipid is composed of rhamnose sugar molecule and β‐hydroxyalkanoic acid. The rhamnosyltransferase 1 complex (RhlAB) is the key enzyme responsible for transferring the rhamnose moiety to the β‐hydroxyalkanoic acid moiety to biosynthesize rhamnolipid. Through transposome‐mediated chromosome integration, the RhlAB gene was inserted into the chromosome of the Pseudomonas aeruginosa PAO1‐rhlA− and Escherichia coli BL21 (DE3), neither of which could produce rhamnolipid. After chromosome integration of the RhlAB gene, the constitute strains P. aeruginosa PEER02 and E. coli TnERAB did produce rhamnolipid. The HPLC/MS spectrum showed that the structure of purified rhamnolipid from P. aeruginosa PEER02 was similar to that from other P. aeruginosa strains, but with different percentage for each of the several congeners. The main congener (near 60%) of purified rhamnolipid from E. coli TnERAB was 3‐(3‐hydroxydecanoyloxy) decanoate (C10–C10) with mono‐rhamnose. The surfactant performance of rhamnolipid was evaluated by measurement of interfacial tension (IFT) and oil recovery via sand‐pack flooding tests. As expected, pH and salt concentration of the rhamnolipid solution significantly affected the IFT properties. With just 250 mg/L rhamnolipid (from P. aeruginosa PEER02 with soybean oil as substrate) in citrate–Na2HPO4, pH 5, 2% NaCl, 42% of oil otherwise trapped was recovered from a sand pack. This result suggests rhamnolipid might be considered for EOR applications. Biotechnol. Bioeng. 2007; 98: 842–853. © 2007 Wiley Periodicals, Inc.
Cadmium removal from contaminated soil by thermally responsive elastin (ELPEC20) biopolymers
Authors: Lao U Loi , Chen Alin , Matsumoto Mark R. , Mulchandani Ashok , Chen Wilfred
Published: May 2007

Cadmium contamination of soil is a major concern in the biosphere. Beyond the suite of available physico‐chemical treatment methods, green and more efficient technologies are desired to reduce cadmium and other heavy metal contaminants to acceptable levels. Elastin‐like polypeptides (ELP) composed of a polyhistidine domain (ELPH12) can be used as an environmentally benign chelating agent for ex situ soil washing. However, ELPH12 is relatively non‐selective. A biopolymer with metal‐binding domains that have stronger affinity, capacity, and selectivity would have distinct advantages. The aim of this work is to investigate the use of a new generation of ELP biopolymer, ELPEC20, containing synthetic phytochelatin (EC) as the metal‐binding domain for ex situ soil washing. ELPEC20 was shown to bind cadmium more effectively and selectively than ELPH12. The binding constant of ELPEC20 is an order of magnitude higher and the binding capacity is fivefold higher than ELPH12. In contrast to ELPH12, no decrease in cadmium binding was observed in the presence of other competing metal ions. The improved selectivity and binding capacity provided by ELPEC20 were directly reflected in the enhanced cadmium extraction efficiency from contaminated soil. In batch washing studies up to 62% of the bound cadmium was removed by ELPEC20 while less than 12% was removed by ELPH12. Cadmium was removed not only from the exchangeable fraction but also the oxidizable fraction. The high‐affinity binding sites of ELPEC20 also results in very rapid extraction with complete removal achieved within 1 h, suggesting that ELPEC20 could be used as part of a rapid (short retention time) technology with minimum possibility for the biodegradation of biopolymers. Biotechnol. Bioeng. 2007;98: 349–355. © 2007 Wiley Periodicals, Inc.
Self‐expanding intracoronary stent for symptomatic myocardial bridging
Authors: Ahmed S. Hinan , Khawaja Shazib N. , Husain Nadeem M. , Panayiotou Hercules
Published: May 2007

Myocardial bridging has been recognized as a potential cause of symptoms of angina, arrhythmias and even infarction. Various treatment strategies including beta‐blockers, surgery and more recently intra‐coronary stents have been used to manage bridging. We report a novel case of use of self‐expanding stent for myocardial bridging in a patient with symptoms of angina and ischemia on nuclear imaging. We further present the 18‐month follow up showing minima in‐stent stenosis. To our knowledge, this is the first report of using a self‐expanding stent in myocardial bridging. The use of self‐expanding stents could be a potential treatment for symptomatic myocardial bridging. © 2007 Wiley‐Liss, Inc.
Flow Characteristics and Shannon Entropy Analysis of Dense‐Phase Pneumatic Conveying of Pulverized Coal with Variable Moisture Content at High Pressure
Authors: Liang C. , Zhao C.‐S. , Chen X.‐P. , Pu W.‐H. , Lu P. , Fan C.‐L.
Published: May 2007

Experiments consisting of dense‐phase pneumatic conveying of pulverized coal using nitrogen were carried out in an experimental test facility, with a conveying pressure of up to 4 MPa. The influences of the conveying differential pressure, the coal moisture content, the gas volume flow rate and the superficial velocity, on the solid‐gas ratios, were investigated. The Shannon entropy analysis of the pressure fluctuation time series was developed to reveal the flow characteristics. By investigation of the distribution of the Shannon entropy at different conditions, the flow stability and the evolutional tendency of Shannon entropy, in different regimes and regime transition processes, were revealed, and the relationship between Shannon entropy and the flow regime was also established. The results indicate that the solid‐gas ratio and the Shannon entropy rise with increases in conveying differential pressure. The solid‐gas ratio and the Shannon entropy reveal preferable correlation with the superficial gas velocity. Shannon entropy is different for different flow regimes, and can be used to identify the flow regimes. Both the mass flow rate and the Shannon entropy, decrease with increases in moisture content. Shannon entropy analysis is a feasible approach to researching the characteristics of the flow regime, the flow stability and the flow regime transitions in dense‐phase pneumatic conveying systems, at high pressure.
Polymorphism of N,N′′‐Diacetylbiuret Studied by Solid‐State 13C and 15N NMR Spectroscopy, DFT Calculations, and X‐ray Diffraction
Authors: Macholl Sven , Lentz Dieter , Börner Frank , Buntkowsky Gerd
Published: May 2007

The molecular configuration and crystal structure of solid polycrystalline N,N′′‐diacetylbiuret (DAB), a potential nitrogen‐rich fertilizer, have been analyzed by a combination of solid‐ and liquid‐state NMR spectroscopy, X‐ray diffraction, and DFT calculations. Initially a pure NMR study (“NMR crystallography”) was performed as available single crystals of DAB were not suitable for X‐ray diffraction. Solid‐state 13C NMR spectra revealed the unexpected existence of two polymorphic modifications (α‐ and β‐DAB) obtained from different chemical procedures. Several NMR techniques were applied for a thorough characterization of the molecular system, revealing chemical shift anisotropy (CSA) tensors of selected nuclei in the solid state, chemical shifts in the liquid state, and molecular dynamics in the solid state. Dynamic NMR spectroscopy of DAB in solution revealed exchange between two different configurations, which raised the question, is there a correlation between the two different configurations found in solution and the two polymorphic modifications found in the solid state?

By using this knowledge, a new crystallization protocol was devised which led to the growth of single crystals suitable for X‐ray diffraction. The X‐ray data showed that the same symmetric configuration is present in both polymorphic modifications, but the packing patterns in the crystals are different. In both cases hydrogen bonds lead to the formation of planes of DAB molecules. Additional symmetry elements, a two‐fold screw in the case of α‐DAB and a c‐glide plane in the case of β‐DAB, lead to a more symmetric (α‐DAB) or asymmetric (β‐DAB) intermolecular hydrogen‐bonding pattern for each molecule.
A CE assay for the detection of agonist‐stimulated adenylyl cyclase activity
Authors: Cunliffe Jennifer M. , Whorton Matthew R. , Sunahara Roger K. , Kennedy Robert T.
Published: May 2007

A CE assay was developed for the detection of adenylyl cyclase (AC) activity stimulated at the AC and G protein‐coupled receptor (GPCR) level. In the assay, cell membranes overexpressing GPCR and/or AC were incubated with modulators and substrate ATP to produce cAMP in a dose‐dependent manner. In both the CE‐UV and a radiochemical assay, the addition of forskolin (FSK) resulted in a two‐ to three‐fold maximum increase in AC activity with EC50s of 4.2 ± 0.7 and 2.4 ± 0.7 μM, respectively, demonstrating that similar results were obtained by both assays. GPCR activation was also detected using cell membranes overexpressing AC and the β2‐adrenergic receptor (β2AR) fused to the stimulatory G protein. Terbutaline (β2AR agonist) increased the basal rate of cAMP formation 1.7 ± 0.1‐fold resulting in an EC50of 62 ± 10 nM. The assay's ability to detect antagonists is demonstrated by the expected right‐shifted EC50of terbutaline by the β2AR antagonist propranolol. The CE‐UV assay offers advantages over the traditional radioactivity assay in terms of safety and labor.
DRIVE – The Future of Automotive Power: Fuel Cells Perspective
Authors: Düsterwald H. G. , Günnewig J. , Radtke P.
Published: May 2007

The automotive propulsion technology market is likely to experience significant change over the next 10 to 15 years, with today's incumbent internal combustion engines (ICE) coming under attack from a multitude of alternative technologies. In the short term, these will mainly be hybrid drive trains. In the longer term, fuel cells may emerge as the strongest challengers. New fuels like natural gas, biodiesel, and hydrogen will challenge the current dominance of oil‐based fuels. The McKinsey DRIVE study assesses the perspectives of conventional and alternative power trains and their world market potential over the next 15 years, deriving implications for OEMs, suppliers, and the fuel industry.
Restructuring health services in Canada: Challenges for policy makers, planners and managers in the eighties
Authors: Crichton Anne
Published: May 2007

Is downsizing the latest jargon word applied to rationalization, a new concept or a different manifestation of a long term trend in health services management? At present, Canada is struggling to implement feasible reductions of expansionary pressures in the health care system. While provincial governments tend to see the issue as one of controlling chronic excess demand, federal government is still concerned to ensure free access to care on an equitable basis. Thus the problems of downsizing can be expressed by the provinces in terms of an ideological struggle with an unfeeling central government which does not understand their problems; although all know they are really about the feasibility of continuing to provide a service to meet demand.

The present economic recession enables provincial governments to appeal to their voters for support in a new way. Earlier, the appeal was to consumers to become involved in health service organization management and this policy succeeded, to a degree, where there were flourishing grass roots communities; albeit that the service continued to be driven by professionals. Now the appeal is to taxpayers for their strong support in cost cutting. This has been more successful. Provincial governments are now permitted to ‘touch the untouchables’, that is to downsize the medical profession and previously sacrosanct health care institutions. They also are exploring the feasibility of introducing a two‐tier system which would provide basic care for everyone and extra care for those able to pay, thus side‐stepping federal conditions. By reorganizing support in this way, provincial governments have extended the range of policy choices, and two types of planning, the rational and the political, have now become combined into strategic management activity.
Identification of novel Runx2 targets in osteoblasts: Cell type‐specific BMP‐dependent regulation of Tram2
Authors: Pregizer Steven , Barski Artem , Gersbach Charles A. , García Andrés J. , Frenkel Baruch
Published: May 2007

Runx2 is an osteoblast master transcription factor and a target for bone morphogenetic protein (BMP) signaling, but our knowledge of events downstream of Runx2 is limited. In this study, we used ChIP Display to discover seven novel genomic regions occupied by Runx2 in living MC3T3‐E1 osteoblastic cells. Six of these regions are found within or up to 1‐kb away from annotated genes, but only two are found within 5′‐gene flanking sequences. One of the newly identified Runx2 target genes is Tram2, whose product facilitates proper folding of type I collagen. We demonstrate that Tram2 mRNA is suppressed in non‐osteoblasts when Runx2 is over‐expressed, and that this suppression is alleviated upon treatment with BMP‐2. Moreover, we show that BMP‐induced Runx2 expression in the C3H10T1/2, ST2, C2C12, and MC3T3‐E1 cell lines coincides with an increase in Tram2 mRNA levels. Thus, Runx2 may regulate Tram2 expression in a BMP‐dependent manner, and Tram2 may participate in the overall osteogenic function of Runx2. Among the other Runx2 target genes discovered in this study are Lnx2, an intracellular scaffolding protein that may play a role in Notch signaling, and Tnfrsf12a, a Tumor Necrosis Factor receptor family member that influences both osteoblast and osteoclast differentiation. Expanding our knowledge of Runx2 target genes, and manipulation of these genes, are warranted to better understand the regulation of osteoblast function and to provide opportunities for the development of new bone anabolics. J. Cell. Biochem. 102: 1458–1471, 2007. © 2007 Wiley‐Liss, Inc.
Helicobacter pylori as a class I carcinogen: Physiopathology and management strategies
Authors: Vogiatzi Paraskevi , Cassone Marco , Luzzi Ida , Lucchetti Chiara , Otvos Laszlo , Giordano Antonio
Published: May 2007

The gram‐negative bacterium Helicobacter pylori is known as a persistent colonizer of the human stomach, and probably less known is that it is also involved in extraintestinal diseases. Public awareness of its contribution in the development of gastric cancer is less than 15 years old. The efficacy of the current therapies based on antibiotics against H. pylori has been limited by difficulties such as antibiotic resistance and recurrence. As a consequence, the development of promising vaccines was prompted as the best preventive measure. Unfortunately, so far vaccines failed the transition from animal models to human trials. This keynote presentation is to provide a bird's eye view of H. pylori‐related gastric diseases, including gastric cancer, with a synthesis of the molecular mechanisms involved, and an exhaustive presentation and discussion of the current therapeutic guidelines and future strategies for prevention or therapy. J. Cell. Biochem. 102: 264–273, 2007. © 2007 Wiley‐Liss, Inc.
Molecular mechanics (MM4) study of amines
Authors: Chen Kuo‐Hsiang , Lii Jenn‐Huei , Fan Yi , Allinger Norman L.
Published: May 2007

The MM4 force field has been extended to include aliphatic amines. About 20 amines have been examined to obtain a set of useful molecular mechanics parameters for this class. The vibrational spectra of seven amines (172 frequencies) calculated by MM4 have an overall rms error of 27 cm−1, compared with corresponding MM4 value of 24 cm−1 for alkanes. The rms and signed average errors of the moments of inertia of nine simple amines compared with the experimental data were 0.18% and −0.004%, respectively. The heats of formation of 30 amines were also studied. The MM4 weighted standard deviation is 0.41 kcal/mol, compared with experiment. Electronegativity effects occur in the hydrocarbon portion of an amine from the nitrogen, and are accounted for by including electronegativity induced changes in bond lengths and angles, and induced dipole–dipole interactions in the molecule. Negative hyperconjugation results from the presence of the lone pair of electrons on nitrogen, and leads to the Bohlmann bands in the infrared, and also to strong and unusual geometric changes in the molecules (Bohlmann effect), all of which are fairly well accounted for. The conformational energies in amines appear to be less straightforward than those for most other classes of molecules, apparently because of the Bohlmann effect, and these are probably not yet completely understood. In general, the agreement between the MM4 calculated results and the available data is reasonably good. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2007
All‐atom de novo protein folding with a scalable evolutionary algorithm
Authors: Verma Abhinav , Gopal Srinivasa M. , Oh Jung S. , Lee Kyu H. , Wenzel Wolfgang
Published: May 2007

The search for efficient and predictive methods to describe the protein folding process at the all‐atom level remains an important grand‐computational challenge. The development of multi‐teraflop architectures, such as the IBM BlueGene used in this study, has been motivated in part by the large computational requirements of such studies. Here we report the predictive all‐atom folding of the forty‐amino acid HIV accessory protein using an evolutionary stochastic optimization technique. We implemented the optimization method as a master‐client model on an IBM BlueGene, where the algorithm scales near perfectly from 64 to 4096 processors in virtual processor mode. Starting from a completely extended conformation, we optimize a population of 64 conformations of the protein in our all‐atom free‐energy model PFF01. Using 2048 processors the algorithm predictively folds the protein to a near‐native conformation with an RMS deviation of 3.43 Å in <24 h. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2007
Merging multiconfigurational wavefunctions and correlation functionals to predict magnetic coupling constants
Authors: Pérez‐Jiménez Ángel J. , Pérez‐Jordá José M. , Moreira Ibério de P. R. , Illas Francesc
Published: May 2007

We study the performance of different approaches that combine multiconfigurational wavefunctions with correlation functionals for the calculation of magnetic coupling constants of several materials and molecules. The systems under study include four antiferromagnetic materials: NiO, KNiF3, K2NiF4 and La2CuO4; two biradicals: α‐4‐Dehydrotoluene and 1,1′,5,5′‐Tetramethyl‐6,6′‐dioxo‐3,3′‐biverdazyl; two molecular complexes: [Cu2Cl6]−2 and Copper(II) acetate monohidrate; and the prototypical H‐He‐H system. On average, the best results are obtained with a recently proposed method [Phys. Rev. A 75, 012503 (2007)] that estimates the correlation energy of density functionals from a pair of alternative spin densities built from the natural orbitals and occupation numbers of the multiconfigurational wavefunction. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2007
A self‐contained and portable density functional theory library for use in Ab Initio quantum chemistry programs
Authors: Sałek Paweł , Hesselmann Andreas
Published: May 2007

A major unresolved problem of density functional theory is the yet unknown exchange‐correlation functional, which leads to a proliferation of its less or more successful approximations. A practical implementation of these numerous functionals can present a substantial challenge particularly if the higher order functional derivatives are required. We present a systematic method of functional implementation. The method allows a clean handling of a large number of functionals in a mutually independent way. We developed an extensive set of automatic test routines to facilitate functional and derivative testing with respect to the implementation correctness and numerical stability. An integral part of the presented solution is a program for automatic code generation from analytical formulas that uses only freely available tools. Code for evaluation of functionals and their first, second, third, and fourth derivatives can be generated, which accelerates the development, implementation, and testing of new functionals. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2007
Information theoretical measures to analyze trajectories in rational molecular design
Authors: Hamacher K.
Published: May 2007

We develop a new methodology to analyze molecular dynamics trajectories and other time series data from simulation runs. This methodology is based on an information measure of the difference between distributions of various data extract from such simulations. The method is fast as it only involves the numerical integration/summation of the distributions in one dimension while avoiding sampling issues at the same time. The method is most suitable for applications in which different scenarios are to be compared, e.g. to guide rational molecular design. We show the power of the proposed method in an application of rational drug design by reduced model computations on the BH3 motif in the apoptosis inducing BCL2 protein family. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2007
Parallel DFT gradients using the Fourier Transform Coulomb method
Authors: Baker Jon , Wolinski Krzysztof , Pulay Peter
Published: May 2007

The recently described Fourier Transform Coulomb (FTC) algorithm for fast and accurate calculation of Density Functional Theory (DFT) gradients (Füsti‐Molnar, J Chem Phys 2003, 119, 11080) has been parallelized. We present several calculations showing the speed and accuracy of our new parallel FTC gradient code, comparing its performance with our standard DFT code. For that part of the total derivative Coulomb potential that can be evaluated in plane wave space, the current parallel FTC gradient algorithm is up to 200 times faster in total than our classical all‐integral algorithm, depending on the system size and basis set, with essentially no loss in accuracy. Proposed modifications should further improve the overall performance relative to the classical algorithm. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2007
Early sonographic assessment of Budd‐Chiari syndrome after orthotopic liver transplantation
Authors: Zhang Bu‐lin , Hu Bing , Zhu Jia‐an
Published: May 2007

Budd‐Chiari syndrome is a rare vascular complication of liver transplantation that may result in loss of the graft and a high mortality risk. Therefore, early diagnosis is extremely important to allow preservation of the graft and improve the prognosis. We describe the sonographic findings in a patient in whom Budd‐Chiari syndrome occurred 2 days after orthotopic liver transplantation. © 2007 Wiley Periodicals, Inc. J Clin Ultrasound, 2007
Vasculogenic impotence as a symptom in late‐onset Buerger's disease
Authors: Yavas Ulas Savas , Calisir Cuneyt , Kaya Tamer
Published: May 2007

Buerger's disease, or thromboangiitis obliterans, is a nonatherosclerotic, noninflammatory, segmentally occlusive disease of unclear etiology. We report a case of late‐onset Buerger's disease in a 57‐year‐old man with erectile dysfunction, an uncommon symptom that occurred shortly after intermittent claudication. © 2007 Wiley Periodicals, Inc. J Clin Ultrasound, 2007