bluuebunny/crossref_metadata_2025_split huggingface dataset:
Estimating the size of an illicit‐drug‐using population
Authors: Simeone Ronald , Holland Lynn , Viveros‐Aguilero Roman 
Published: September 2003

AbstractThis paper describes a new method for estimating the size of an illicit‐drug‐using population. It is designed to overcome certain limitations of registry‐based techniques that require both comprehensive site coverage and unique case identifiers, and which do not typically provide estimates of the number of drug users who are currently active. The approach involves collecting retrospective self‐report data on the careers of individuals who appear at drug treatment programmes. A model is developed that corrects for the selection bias introduced by the sampling plan, and which allows us to estimate the rate at which drug users generate treatment admission events during spells of use. The size of the drug‐using population is estimated by dividing the estimated total number of treatment admissions that are generated during some fixed interval of time by the estimated rate at which individuals generate such events. The technique is tested in a series of simulation studies which demonstrate that accurate estimates of the size of the drug using population can be obtained in this manner. Analytical expressions for confidence intervals about the population estimates are derived as part of the exercise. Limitations of the approach and other potential applications are discussed. Copyright © 2003 John Wiley & Sons, Ltd.
The CUSCORE test and the q‐interval in cluster analyses of colon cancer and of lymphoma among asbestos workers
Authors: Chen R. , Froom P. 
Published: September 2003

AbstractExposure to a carcinogen is likely to be reflected by temporal clustering of cancer cases among the community members. Detection of such clustering is a complicated task in general and more so in a small workplace community with low turnover rate. In this study we applied the CUSCORE test and the q‐interval statistic to lymphoma and colon cancer death data among 2200 asbestos workers. The CUSCORE test was applied in order to identify clusters, and the q‐interval was used to provide clues related to the cause of the cluster. We also evaluated and tested the data according to the standardized mortality ratio (SMR). Significant increases in both colon cancer and lymphoma among asbestos workers in Israel (1987–1997) were demonstrated by the CUSCORE test but not so by the SMR. The fact that an apparent clustering was observed from the pattern of the q‐intervals leads to the conclusion that the detected clusters are real. Copyright 2003 John Wiley & Sons, Ltd.
Minimizing predictability while retaining balance through the use of less restrictive randomization procedures
Authors: Berger Vance W. , Ivanova Anastasia , Deloria Knoll Maria 
Published: September 2003

AbstractThe interpretation of between‐group comparisons is facilitated by the creation of treatment groups that are similar to each other in baseline composition. To prevent treatment effects from being confounded with time effects, most trials use restricted randomization to force balance. An unintended consequence of these restrictions is that they create patterns that allow for the prediction of future treatment allocations, and hence selection bias, especially in unmasked trials. In fact, the more restrictive the allocation procedure, the greater the potential for selection bias. It was decided, in the context of a recent clinical trial comparing two dosing schedules of paclitaxel and carboplatin for advanced stage IIIB/IV non‐small‐cell lung cancer, that the randomized block procedure could not simultaneously protect sufficiently against both selection and chronological bias. In this paper we detail our development of the maximal procedure. The maximal procedure takes as input the extent of chronological bias allowed by the randomized block procedure, then matches it, but does so with fewer restrictions. This feature makes the maximal procedure more resistant to selection bias than the randomized block procedure is. Published in 2003 by John Wiley & Sons, Ltd.
Consequences of exposure measurement error for confounder identification in environmental epidemiology
Authors: Budtz‐Jørgensen Esben , Keiding Niels , Grandjean Philippe , Weihe Pal , White Roberta F. 
Published: September 2003

AbstractNon‐differential measurement error in the exposure variable is known to attenuate the dose–response relationship. The amount of attenuation introduced in a given situation is not only a function of the precision of the exposure measurement but also depends on the conditional variance of the true exposure given the other independent variables. In addition, confounder effects may also be affected by the exposure measurement error. These difficulties in statistical model development are illustrated by examples from a epidemiological study performed in the Faroe Islands to investigate the adverse health effects of prenatal mercury exposure. Copyright © 2003 John Wiley & Sons, Ltd.
A simulation‐based confidence band for drug concentrations in blood: an application to a clinical phase I trial
Authors: Yafune Akifumi , Ishiguro Makio 
Published: September 2003

AbstractSince drug concentrations in blood are usually related to the effectiveness and toxicity, a confidence band for the drug concentrations gives useful information for the treatment. This paper proposes a simulation‐based approach for constructing confidence bands for drug concentrations in blood. The confidence band covers the whole profile of the drug concentrations with a specified probability. The proposed approach presupposes that actual concentrations of a subject fluctuate randomly around a curve specified by an appropriate pharmacokinetic model and the subject‐specific pharmacokinetic parameters. The confidence band is constructed by taking into account both the random fluctuations of the actual concentrations and the statistical uncertainty of the parameter estimates. The proposed approach is applied to a simulation study and an actual phase I trial. Copyright © 2003 John Wiley & Sons, Ltd.
Bayesian analysis of structural equation models with dichotomous variables
Authors: Lee Sik‐Yum , Song Xin‐Yuan 
Published: September 2003

AbstractStructural equation modelling has been used extensively in the behavioural and social sciences for studying interrelationships among manifest and latent variables. Recently, its uses have been well recognized in medical research. This paper introduces a Bayesian approach to analysing general structural equation models with dichotomous variables. In the posterior analysis, the observed dichotomous data are augmented with the hypothetical missing values, which involve the latent variables in the model and the unobserved continuous measurements underlying the dichotomous data. An algorithm based on the Gibbs sampler is developed for drawing the parameters values and the hypothetical missing values from the joint posterior distributions. Useful statistics, such as the Bayesian estimates and their standard error estimates, and the highest posterior density intervals, can be obtained from the simulated observations. A posterior predictive p‐value is used to test the goodness‐of‐fit of the posited model. The methodology is applied to a study of hypertensive patient non‐adherence to medication. Copyright © 2003 John Wiley & Sons, Ltd.
Estimating regression models with unknown break‐points
Authors: Muggeo Vito M. R. 
Published: September 2003

AbstractThis paper deals with fitting piecewise terms in regression models where one or more break‐points are true parameters of the model. For estimation, a simple linearization technique is called for, taking advantage of the linear formulation of the problem. As a result, the method is suitable for any regression model with linear predictor and so current software can be used; threshold modelling as function of explanatory variables is also allowed. Differences between the other procedures available are shown and relative merits discussed. Simulations and two examples are presented to illustrate the method. Copyright © 2003 John Wiley & Sons, Ltd.
A chain of evidence with mixed comparisons: models for multi‐parameter synthesis and consistency of evidence
Authors: Ades A. E. 
Published: September 2003

AbstractMulti‐parameter evidence synthesis is a generalization of meta‐analysis in which several parameters are estimated jointly. Here this approach is applied to a common form of data structure in which mixed pairwise comparisons are made between treatments in a ‘chain of evidence’ structure. The data set investigated here, which first appeared in the confidence profile method literature, features three types of data relating to thrombolytic treatment following acute myocardial infarction. There is information on reperfusion (coronary patency) following treatment, information on survival in reperfused and non‐reperfused patients (conditional survival), and independent information on the effect of treatment on survival without specifying reperfusion state (overall survival). The objective of this study is to explore models for combining these three types of evidence within a single model, and some of the evidence consistency issues that arise. Bayesian Markov chain Monte Carlo methods are used to fit two models. The first, proposed in the confidence profile literature, assumes there are no differences between studies in baseline effects (equal study effects). The second model assumes fixed treatment effects but allows for study differences in baseline reperfusion and conditional survival rates by assuming random study effects. The equal study effects model fits the data poorly, and cross‐validation shows that the overall survival evidence is not consistent with the reperfusion and conditional survival evidence under this model. The evidence appears to be consistent within the more loosely structured random study effects model, but results are sensitive to prior assumptions about the between‐study variance. The inconsistency between the three evidence types relates to overall survival, rather than to the effect of treatment on survival. Multi‐parameter evidence synthesis, with suitable checks for evidence consistency, can be used to help determine whether chains of evidence ‘add up’ epidemiologically within an overall model, and to construct parameter distributions for an entire model simultaneously, consistent with all the available data. Copyright © 2003 John Wiley & Sons, Ltd.
On the non‐inferiority of a diagnostic test based on paired observations
Authors: Lu Ying , Jin Hua , Genant Harry K. 
Published: September 2003

AbstractNon‐inferiority of a diagnostic test to the standard or the optimum test is a common issue in medical research. Often we want to determine if a new diagnostic test is as good as the standard reference test. Sometimes we are interested in an inexpensive test that may have an acceptably inferior sensitivity or specificity. While hypothesis testing procedures and sample size formulae for the equivalence of sensitivity or specificity alone have been proposed, very few studies have discussed simultaneous comparisons of both parameters. In this paper, we present three different testing procedures and sample size formulae for simultaneous comparison of sensitivity and specificity based on paired observations and with known disease status. These statistical procedures are then used to compare two classification rules that identify women for future osteoporotic fracture. Simulation experiments demonstrate that the new tests and sample size formulae give the appropriate type I and II error rates. Differences between our approach and the approach of Lui and Cumberland are discussed. Copyright © 2003 John Wiley & Sons, Ltd.
Heterogeneity and transferring practices: implementing flow manufacturing in multiple plants
Authors: Maritan Catherine A. , Brush Thomas H. 
Published: September 2003

AbstractAdopting new practices to develop capabilities and enhance competitiveness is a goal for many firms. This study of a corporate initiative to implement flow manufacturing in multiple plants highlights some elements of the interaction between the content of a complex practice, the sources of the practice knowledge, and the characteristics and competitive priorities of the recipients of the practice. Heterogeneity among the plants, stemming from both differences in resource endowments and differences in choices made by managers, presents challenges to achieving firm‐wide distinctiveness. Copyright © 2003 John Wiley & Sons, Ltd.
Doing the right thing and knowing the right thing to do: why the whole is greater than the sum of the parts
Authors: Makadok Richard 
Published: September 2003

AbstractThis paper models the joint impact of two determinants of profitable resource advantages: the accuracy of managers' expectations about the future value of a resource, and the severity of agency problems that cause managers' interests to diverge from those of shareholders. While the impact of each of these factors on resource‐investment decisions has been considered in isolation, their joint interaction effect has never been examined. The model generates the following set of testable hypotheses: Managers of firms with agency problems will, on average, tend to under‐invest (relative to what shareholders would ideally like them to do) in resources of uncertain value. This under‐investment will be most severe for those resources where managers' information indicates a low expected value (i.e., risky bets), and will actually be reversed (i.e., over‐investment) for those resources where managers' information indicates a high expected value (i.e., safe bets). Two levers can be used to reduce the degree of this under‐investment: reducing the severity of the agency problems, or improving the accuracy of managers' expectations. Based on their interaction effect, these two levers are shown to be complementary in the sense that they work better together at reducing under‐investment than either one does in isolation. Therefore, future research on the genesis of competitive advantage should examine agency and governance issues along with, not apart from, resource‐based issues. Copyright © 2003 John Wiley & Sons, Ltd.
The organizational routines factor market paradox
Authors: Knott Anne Marie 
Published: September 2003

AbstractThe resource‐based view (RBV) of strategy holds that superior organizational routines can be a source of value if and only if there is an isolating mechanism preventing their diffusion throughout industry. Generally this isolating mechanism is taken to be the tacitness of the routines. However, the existence of franchises, a market for organizational routines, poses a challenge to this RBV—if the routine is to be conveyed across a market, it can't be tacit. This paper examines the necessary and sufficient conditions of the RBV to find the weak link leading to the paradox of explicit, yet valuable franchise routines. Copyright © 2003 John Wiley & Sons, Ltd.
An asymmetry‐based view of advantage: towards an attainable sustainability
Authors: Miller Danny 
Published: September 2003

AbstractThe resource‐based view of the firm postulates that sustainable abnormal rents can accrue to firms having valuable, rare, inimitable, non‐substitutable resources and capabilities. Given these criteria, sustainable resources are hard to attain. Our study of some two dozen firms shows how some of them were able to overcome this dilemma by building not so much on resources and capabilities as on asymmetries. Asymmetries are typically skills, processes, or ‘assets’ a firm's competitors do not and cannot copy at a cost that affords economic rents. They are rare, inimitable and non‐substitutable, although not connected to any engine of value creation, and, in fact, often act as liabilities. By discovering and reconceptualizing these asymmetries, embedding them within a complementary organizational design, and leveraging them across appropriate market opportunities, many firms were able to turn asymmetries into sustainable capabilities. Copyright © 2003 John Wiley & Sons, Ltd.
Corporate effects and dynamic managerial capabilities
Authors: Adner Ron , Helfat Constance E. 
Published: September 2003

AbstractCorporate effects in variance decomposition capture heterogeneity of business performance derived from factors internal to firms at the corporate level. Most estimates of corporate effects do not include effects associated with fluctuations in returns over time, except insofar as the fluctuations affect the average corporate return for the time period in question. Exclusion of the time‐varying dimension of the corporate effect makes it difficult to fully understand the effect of corporate strategy and the actions of corporate managers, particularly in response to a changing environment. The evidence in this article shows that within a single industry, where managers face the same external environment, time‐varying corporate effects associated with corporate level managerial decisions are statistically significant. We introduce the concept of dynamic managerial capabilities to underpin the finding of heterogeneity in managerial decisions and firm performance in the face of changing external conditions. Copyright © 2003 John Wiley & Sons, Ltd.
The payments perspective: micro‐foundations of resource analysis
Authors: Lippman Steven A. , Rumelt Richard P. 
Published: September 2003

AbstractProblems in the micro‐foundations of neoclassical theory, especially in partial equilibrium analysis, are being imported into the resource‐based view. This paper critiques neoclassical theory and proffers new concepts more suited to strategy scholars. In particular, we develop the concepts of simple rents, rent sensitivity analysis, and the payments perspective. Copyright © 2003 John Wiley & Sons, Ltd.
Evaluation of the Degree of Starch Gelatinization by a New Enzymatic Method
Authors: Di Paola Romina D. , Asis Ramon , Aldao Mario A. J. 
Published: September 2003

AbstractIn this work, a new enzymatic method is proposed to evaluate the degree of starch gelatinization in starchy food and feed. The procedure developed is based on the fact that the gelatinization process enhances the chemical reactivity of inert starch granules towards amylolytic enzymes. Aqueous suspensions of maize starch were treated at different temperatures to obtain different degrees of gelatinization, from 25 °C (control without gelatinization) until 95 °C. Heated samples were then incubated with a glucoamylase. The enzymatic activity was measured by the glucose released during the digestion time by using a standard glucose oxidase method. The initial velocity value of the enzymatic reaction (Vi) was selected as the parameter to quantify the degree of starch gelatinization (DG). Changes in granule morphology and the starch available for hydrolysis were evaluated by photomicrographs. The new method was standardized and compared with DSC and viscosity measurements in order to check its efficiency, considering the DG observed by photomicrographs. A good agreement was observed between the DG calculated by Vi and by DSC (correlation coefficient r = 0, 97), thus Vi reflect the degree of starch gelatinization as well as DSC. These results show that the developed enzymatic procedure is an effective method to evaluate the DG in starchy foods and feeds.
Starch Paste Stickiness is a Relevant Native Starch Selection Criterion for Wet‐end Paper Manufacturing
Authors: Blennow Andreas , Bay‐Smidt Anne Mette , Leonhardt Peter , Bandsholm Ole , Madsen Marianne H. 
Published: September 2003

AbstractThe correct choice of selection and quality criteria is critical for most starch applications. In this study, a set of different potato starches, selected for a large variation in natural phosphate content and final viscosity, was cationised and tested in a laboratory scale wet‐end paper manufacturing process. Analysis of further parameters expected to be critical for processing, including amylose content and starch granule size, was also performed. Since no significant correlation was found between any of these parameters and paper processing, further attempts were made to find structural or physico‐chemical explanations for the paper processing performance. Hence, several additional parameters of the starches were determined including amylopectin chain length pattern, phosphate substitution, molecular size distribution, pasting‐texture properties and fragility of the gelatinised granules. Among these parameters, the best correlation found to paper filler retention was stickiness of the starch as measured by texture analysis. The starches that performed best in the paper trials showed rapid granule bursts that could be readily estimated from the width of the pasting curve peaks. Light microscopy of non‐soluble remnant starch obtained after gelatinisation of starch under dilute conditions revealed a high proportion of broken granular structures. It is hypothesised that the degree of phosphorylation, together with a hitherto unknown molecular parameter that is related to starch granule fragility, determines starch paste stickiness, which in turn is an important parameter for wet‐end paper manufacturing.
Mechanical Properties of White Salted Noodles from Near‐isogenic Wheat Lines with Different wx Protein‐Deficiency
Authors: Ishida Nanako , Miura Hideho , Noda Takahiro , Yamauchi Hiroaki 
Published: September 2003

AbstractFlour with a low amylose content produces a desirable texture in white salted noodles (WSN). In order to understand the impact of amylose content on noodle texture, flours of similar quality but different starch characteristics must be compared and analyzed because the characteristics of the protein contained in the flour also affect the mechanical properties of WSN. In this study, eight genotypes of near‐isogenic wheat with different compositions of the Wx‐proteins involved in amylose synthesis were used to study the relationship between the mechanical properties of WSN and their amylose content in starch. Results of the study indicated that the breaking force/breaking deformation value of WSN made from the eight lines decreased and that softer noodles were obtained when the amylose content was lower. The gels made from flours and starches of the eight lines decreased in maximum compression stress, in line with the lowering of amylose content. These results show that the mechanical properties of WSN are determined primarily by the amylose content of the flour and the properties of the starch gel. Sensory evaluations of the WSN indicated that the noodles from the flours of single‐null types, which lack either the Wx‐B1 or Wx‐D1 proteins, and doublenull types, which lack the Wx‐A1 and Wx‐D1 proteins, especially the latter, had desirable textures.
Effect of Amylose Content on Gelatinization, Retrogradation and Pasting Properties of Flours from Different Cultivars of Thai Rice
Authors: Varavinit Saiyavit , Shobsngob Sujin , Varanyanond Warunee , Chinachoti Pavinee , Naivikul Onanong 
Published: September 2003

AbstractPresently, rice cultivars are categorized according to amylose content into three groups: low, medium and high amylose content cultivars. The correlation of amylose content with gelatinization properties, retrogradation, and pasting properties of eleven cultivars of Thai rice were investigated. Rice flour was prepared from milled rice by the wet grinding process. Onset (To), peak (Tp) and conclusion (Tc) temperatures of gelatinization, (determined by DSC) were found to be highly positively correlated with amylose levels. This correlation could be used for prediction of amylose content of rice flour. Low amylose starch could also be characterized by low degree of retrogradation (%R). The data obtained from RVA‐viscograms (peak viscosity, breakdown, setback, and pasting temperature) can be used only for characterization of the group of low amylose starches (waxy rice). It was demonstrated that low amylose rice starch provided the highest peak viscosity and breakdown and the lowest setback and pasting temperature among the groups investigated.