bluuebunny/crossref_metadata_2025 huggingface dataset:
Estimating risk and rate levels, ratios and differences in case‐control studies
Authors: King Gary , Zeng Langche
Published: August 2002

Classic (or ‘cumulative’) case‐control sampling designs do not admit inferences about quantities of interest other than risk ratios, and then only by making the rare events assumption. Probabilities, risk differences and other quantities cannot be computed without knowledge of the population incidence fraction. Similarly, density (or ‘risk set’) case‐control sampling designs do not allow inferences about quantities other than the rate ratio. Rates, rate differences, cumulative rates, risks, and other quantities cannot be estimated unless auxiliary information about the underlying cohort such as the number of controls in each full risk set is available. Most scholars who have considered the issue recommend reporting more than just risk and rate ratios, but auxiliary population information needed to do this is not usually available. We address this problem by developing methods that allow valid inferences about all relevant quantities of interest from either type of case‐control study when completely ignorant of or only partially knowledgeable about relevant auxiliary population information. Copyright © 2002 John Wiley & Sons, Ltd.
On the use of Cox regression in the presence of an irregularly observed time‐dependent covariate
Authors: de Bruijne Mattheus H. J. , le Cessie Saskia , Kluin‐Nelemans Hanneke C. , van Houwelingen Hans C.
Published: August 2002

We consider the joint modelling of longitudinal and event time data. The longitudinal data are irregularly collected and the event times are subject to right censoring. Most methods described in the literature are quite complex and do not belong to the standard statistical tools. We propose a more practical approach using Cox regression with time‐dependent covariates. Since the longitudinal data are observed irregularly, we have to account for differences in observation frequency between individual patients. Therefore, the time elapsed since last observation (TEL) is added to the model. TEL and its interaction with the time‐dependent covariate show a strong effect on the hazard. The latter indicates that older recordings have less impact than recent recordings. Pros and cons of this methodology are discussed and a simulation study is performed to study the effect of TEL on the hazard. The fitted Cox model serves as a starting point for the prediction of future patient's events. Our method is applied to a study on chronic myeloid leukaemia (CML) with longitudinal white blood cell counts (WBC) as time‐dependent covariate and patient's death as event. Copyright © 2001 John Wiley & Sons, Ltd.
Modelling cause‐specific hazards with radial basis function artificial neural networks: application to 2233 breast cancer patients
Authors: Boracchi Patrizia , Biganzoli Elia , Marubini Ettore
Published: August 2002

The clinical course of a disease is often characterized by the possible occurrence of different types of events acting in a competing way. From a statistical point of view this translates into the need of modelling the dependence of cause‐specific hazards as a function of covariates. Generalized linear models with Poisson error have previously been adopted for the analysis of competing risks as a function of discrete covariates. In the present paper an artificial neural network extension for the flexible joint estimation of cause‐specific hazards depending on both discrete and continuous covariates is proposed. This approach is based on radial basis function networks which have the advantage of allowing parameter estimation by the adoption of standard software for generalized linear models. We have applied this method to data from 2233 breast cancer patients to investigate the effects of age, tumour size, number of metastatic axillary nodes, histology and tumour site on cause‐specific hazards for intra‐breast tumour recurrences and distant metastases. The adoption of a radial basis function network made it possible to highlight effects that were not considered by previous analyses of the same data. Copyright © 2001 John Wiley & Sons, Ltd.
Estimation of bivariate measurements having different change points, with application to cognitive ageing
Authors: Hall Charles B. , Ying Jun , Kuo Lynn , Sliwinski Martin , Buschke Herman , Katz Mindy , Lipton Richard B.
Published: August 2002

Longitudinal studies of ageing make repeated observations of multiple measurements on each subject. Change point models are often used to model longitudinal data. We demonstrate the use of Bayesian and profile likelihood methods to simultaneously estimate different change points in the longitudinal course of two different measurements of cognitive function in subjects in the Bronx Aging Study who developed Alzheimer's disease (AD). Analyses show that accelerated memory decline, as measured by Buschke Selective Reminding, begins between seven and eight years before diagnosis of AD, while decline in performance on speeded tasks as measured by WAIS Performance IQ begins slightly more than two years before diagnosis, significantly after the decline in memory. Copyright © 2001 John Wiley & Sons, Ltd.
Prediction of survival and opportunistic infections in HIV‐infected patients: a comparison of imputation methods of incomplete CD4 counts
Authors: Molenberghs Geert , Williams Paige L. , Lipsitz Stuart R.
Published: August 2002

In evaluating the risk of mortality or development of opportunistic infections in HIV‐infected patients, the number of CD4 lymphocyte cells per cubic millimetre of blood is widely recognized as one of the best available predictors of such future events. However, its usefulness is limited by the incompleteness and variability of such CD4 measurements during follow‐up. Because of these limitations, analysis of such data requires the missing measurements to be ‘filled in’ or the patients without them to be excluded. We consider multiple imputation of CD4 values based partly on information from other health status measures such as haemoglobin, as well as on the event status of interest. These alternative health status measures are also considered as possible independent predictors of survival endpoints. Our work is motivated by a cohort of 1530 patients enrolled in two AIDS clinical trials. We compare our approach to other strategies such as basing evaluation of risk on baseline CD4, the last measured CD4 before an event, or a time‐dependent covariate based on carrying the last CD4 value forward; we conclude with a strong recommendation for multiple imputation. Copyright © 2002 John Wiley & Sons, Ltd.
Sample size re‐estimation in cluster randomization trials
Authors: Lake Stephen , Kammann Erin , Klar Neil , Betensky Rebecca
Published: August 2002

Cluster randomization trials in which families are the unit of allocation are commonly adopted for the evaluation of disease prevention interventions. Sample size estimation for cluster randomization trials depends on parameters that quantify the variability within and between clusters and the variability in cluster size. Accurate advance estimates of these nuisance parameters may be difficult to obtain and misspecification may lead to an underpowered study. Since families are typically recruited over time, we propose using a portion of the data to estimate the nuisance parameters and to re‐estimate sample size based on the estimates. This extends the standard internal pilot study methods to the setting of cluster randomization trials. The effect of this design on the power, significance level and sample size is analysed via simulation and is shown to provide a flexible and practical approach to cluster randomization trials. Copyright © 2002 John Wiley & Sons, Ltd.
Construction of a single global scale for multi‐item assessments of the same variable
Authors: Svensson Elisabeth
Published: August 2002

Complex health‐related concepts are commonly measured by means of multi‐item scales or questionnaires. As the item scales of an instrument cover different aspects of the same variable, a single global response value is required of the concept to be measured. In this paper, different approaches that take into account the non‐metric properties of ordered categorical data when aggregating multi‐item scales into global scaling were suggested. A single score of equally important items is easily defined by the median. When the multi‐items are constructed to identify the most serious sign of a particular state, the maximum categorical level of the items could be an appropriate single score of the variable. By means of the joint response scheme over two aspects of the same variable, a global scale with an optional number of ordered categories could be defined. Some of the multi‐item scales of the Short‐Form Health Survey (SF‐36) and Euro‐QoL were used for illustrations to the proposed approaches. Copyright © 2001 John Wiley & Sons, Ltd.
How should meta‐regression analyses be undertaken and interpreted?
Authors: Thompson Simon G. , Higgins Julian P. T.
Published: August 2002

Appropriate methods for meta‐regression applied to a set of clinical trials, and the limitations and pitfalls in interpretation, are insufficiently recognized. Here we summarize recent research focusing on these issues, and consider three published examples of meta‐regression in the light of this work. One principal methodological issue is that meta‐regression should be weighted to take account of both within‐trial variances of treatment effects and the residual between‐trial heterogeneity (that is, heterogeneity not explained by the covariates in the regression). This corresponds to random effects meta‐regression. The associations derived from meta‐regressions are observational, and have a weaker interpretation than the causal relationships derived from randomized comparisons. This applies particularly when averages of patient characteristics in each trial are used as covariates in the regression. Data dredging is the main pitfall in reaching reliable conclusions from meta‐regression. It can only be avoided by prespecification of covariates that will be investigated as potential sources of heterogeneity. However, in practice this is not always easy to achieve. The examples considered in this paper show the tension between the scientific rationale for using meta‐regression and the difficult interpretative problems to which such analyses are prone. Copyright © 2002 John Wiley & Sons, Ltd.
Designing linked micromap plots for states with many counties
Authors: Carr Daniel B.
Published: August 2002

This paper describes the design of linked micromap plots for showing county estimates on a state by state basis. The linked micromap template was specifically developed to represent spatially indexed statistical summaries. Each plot shows regional names, spatial patterns and statistical patterns while linking them all together. Thus the design is useful for communicating summaries from a host of health and environmental studies. The specific design challenge in this paper is to create one‐page plots for the states with 60 to 120 counties. While the county names and micromaps take up substantial space, the three examples demonstrate that there is sufficient space to represent two variables. The basic design has the potential for showing more. Consequently the new designs are suitable for presenting sophisticated summaries. Copyright © 2001 John Wiley & Sons, Ltd.
A multiple imputation strategy for incomplete longitudinal data
Authors: Landrum Mary Beth , Becker Mark P.
Published: August 2002

Longitudinal studies are commonly used to study processes of change. Because data are collected over time, missing data are pervasive in longitudinal studies, and complete ascertainment of all variables is rare. In this paper a new imputation strategy for completing longitudinal data sets is proposed. The proposed methodology makes use of shrinkage estimators for pooling information across geographic entities, and of model averaging for pooling predictions across different statistical models. Bayes factors are used to compute weights (probabilities) for a set of models considered to be reasonable for at least some of the units for which imputations must be produced, imputations are produced by draws from the predictive distributions of the missing data, and multiple imputations are used to better reflect selected sources of uncertainty in the imputation process. The imputation strategy is developed within the context of an application to completing incomplete longitudinal variables in the so‐called Area Resource File. The proposed procedure is compared with several other imputation procedures in terms of inferences derived with the imputations, and the proposed methodology is demonstrated to provide valid estimates of model parameters when the completed data are analysed. Extensions to other missing data problems in longitudinal studies are straightforward so long as the missing data mechanism can be assumed to be ignorable. Copyright © 2001 John Wiley & Sons, Ltd.
Bayesian model selection: analysis of a survival model with a surviving fraction
Authors: Seltman Howard , Greenhouse Joel , Wasserman Larry
Published: August 2002

We describe a methodology for model comparison in a Bayesian framework as applied to survival with a surviving fraction. This is illustrated using a case study of a randomized and controlled clinical trial investigating time until recurrence of depression. Posterior distributions are simulated using Metropolis‐within‐Gibbs Markov chain methods. Models reflecting the effects of covariates on the log odds of being in the surviving fraction, the log of the hazard rate, as well as both and neither are compared. Bayes factors for comparing the models are obtained by using the bridge sampling method of calculating normalizing constants. Copyright © 2001 John Wiley & Sons, Ltd.
Relative risk estimation and inference using a generalized logrank statistic
Authors: Mehrotra Devan V. , Roth Arthur J.
Published: August 2002

When comparing two survival distributions with proportional hazard functions, the logrank test is optimal for testing the null hypothesis that the constant hazard ratio (relative risk) is one. In this paper, we focus on (i) testing for departures from a relative risk other than one, and (ii) estimation of the relative risk. The standard tool to address both (i) and (ii) is the Cox proportional hazards model. However, the performance of the Cox model can be less than optimal with small samples. We show why this is the case, and propose a simple alternative method of estimation and inference based on a generalized logrank (GLR) statistic. While the GLR and Cox model approaches are asymptotically similar, empirical results reveal that the GLR approach is notably more efficient than the Cox model when the number of subjects is small (< 100 subjects per treatment group). An example based on survival times of cervical cancer patients is used to illustrate the proposed methodology. Copyright © 2001 John Wiley & Sons, Ltd.
Understanding neural networks using regression trees: an application to multiple myeloma survival data
Authors: Faraggi David , LeBlanc Michael , Crowley John
Published: August 2002

Neural networks are becoming very popular tools for analysing data. It is however quite difficult to understand the neural network output in terms of the original covariates or input variables. In this paper we provide, using readily available software, an easy way of understanding the output of the neural network using regression trees. We focus on the problem in the context of censored survival data for patients with multiple myeloma, where identifying groups of patients with different prognosis is an important aspect of clinical studies. The use of regression trees to help understand neural networks can be easily applied to uncensored situations. Copyright © 2001 John Wiley & Sons, Ltd.
Mixed multivariate generalized linear models for assessing lower‐limb arterial stenoses
Authors: Cengiz Mehmet A. , Percy David F.
Published: August 2002

Experiments and observational studies often involve gathering information on several response variables, enabling us to model their dependence on observable predictor variables. Despite associations between the response variables, they are often analysed separately using general and generalized linear models. This paper investigates applications of multivariate regression analysis to improve the accuracy of predictions and decisions, in the specific context of diagnosing arterial stenoses in human legs. Two basic models are developed for this application, using (i) four binary responses and (ii) a mixture of two binary and two normal responses. The results clearly demonstrate the potential advantages offered by this approach. Copyright © 2001 John Wiley & Sons, Ltd.
A hierarchical regression approach to meta‐analysis of diagnostic test accuracy evaluations
Authors: Rutter Carolyn M. , Gatsonis Constantine A.
Published: August 2002

An important quality of meta‐analytic models for research synthesis is their ability to account for both within‐ and between‐study variability. Currently available meta‐analytic approaches for studies of diagnostic test accuracy work primarily within a fixed‐effects framework. In this paper we describe a hierarchical regression model for meta‐analysis of studies reporting estimates of test sensitivity and specificity. The model allows more between‐ and within‐study variability than fixed‐effect approaches, by allowing both test stringency and test accuracy to vary across studies. It is also possible to examine the effects of study specific covariates. Estimates are computed using Markov Chain Monte Carlo simulation with publicly available software (BUGS). This estimation method allows flexibility in the choice of summary statistics. We demonstrate the advantages of this modelling approach using a recently published meta‐analysis comparing three tests used to detect nodal metastasis of cervical cancer. Copyright © 2001 John Wiley & Sons, Ltd.
An extension of the continual reassessment method using decision theory
Authors: Leung Denis Heng‐Yan , Wang You‐Gan
Published: August 2002

The primary goal of a phase I trial is to find the maximally tolerated dose (MTD) of a treatment. The MTD is usually defined in terms of a tolerable probability, q*, of toxicity. Our objective is to find the highest dose with toxicity risk that does not exceed q*, a criterion that is often desired in designing phase I trials. This criterion differs from that of finding the dose with toxicity risk closest to q*, that is used in methods such as the continual reassessment method. We use the theory of decision processes to find optimal sequential designs that maximize the expected number of patients within the trial allocated to the highest dose with toxicity not exceeding q*, among the doses under consideration. The proposed method is very general in the sense that criteria other than the one considered here can be optimized and that optimal dose assignment can be defined in terms of patients within or outside the trial. It includes as an important special case the continual reassessment method. Numerical study indicates the strategy compares favourably with other phase I designs. Copyright © 2002 John Wiley & Sons, Ltd.
Competitive advantage: logical and philosophical considerations
Authors: Powell Thomas C.
Published: August 2002

Strategic management theories invoke the concept of competitive advantage to explain firm performance, and empirical research investigates competitive advantage and describes how it operates. But as a performance hypothesis, competitive advantage has received surprisingly little formal justification, particularly in light of its centrality in strategy research and practice. As it happens, the core hypothesis—that competitive advantage produces sustained superior performance—finds little support in formal deductive or inductive inference, and the leading theories of competitive advantage incorporate refutation barriers that preclude meaningful empirical tests. This article explores the logical and philosophical foundations of the competitive advantage hypothesis, locating its philosophical foundations in the epistemologies of Bayesian induction, abductive inference and an instrumentalist, pragmatic philosophy of science. Copyright © 2001 John Wiley & Sons, Ltd.
An examination into the causal logic of rent generation: contrasting Porter's competitive strategy framework and the resource‐based perspective
Authors: Spanos Yiannis E. , Lioukas Spyros
Published: August 2002

In this study we revisit some fundamental questions that are increasingly at the heart of current strategic management discourse regarding the relative impact of industry and firm‐specific factors on sustainable competitive advantage. We explore this issue by referring to respective assertions of two major perspectives that dominate the literature over the last two decades: the Porter framework of competitive strategy and the more recent resource‐based view of the firm. A composite model is proposed which elaborates upon both perspectives' divergent causal logic with respect to the conditions relevant for firm success.

Empirical findings suggest that industry and firm specific effects are both important but explain different dimensions of performance. Where industry forces influence market performance and profitability, firm assets act upon accomplishments in the market arena (i.e., market performance), and via the latter, to profitability. The paper concludes with directions for future research that will seek to integrate both content and process aspects of firm behavior. Copyright © 2001 John Wiley & Sons, Ltd.
Cultural entrepreneurship: stories, legitimacy, and the acquisition of resources
Authors: Lounsbury Michael , Glynn Mary Ann
Published: August 2002

We define cultural entrepreneurship as the process of storytelling that mediates between extant stocks of entrepreneurial resources and subsequent capital acquisition and wealth creation. We propose a framework that focuses on how entrepreneurial stories facilitate the crafting of a new venture identity that serves as a touchstone upon which legitimacy may be conferred by investors, competitors, and consumers, opening up access to new capital and market opportunities. Stories help create competitive advantage for entrepreneurs through focal content shaped by two key forms of entrepreneurial capital: firm‐specific resource capital and industry‐level institutional capital. We illustrate our ideas with anecdotal entrepreneurial stories that range from contemporary high‐technology accounts to the evolution of the mutual fund industry. Propositions are offered to guide future empirical research based on our framework. Theoretically, we aim to extend recent efforts to synthesize strategic and institutional perspectives by incorporating insights from contemporary approaches to culture and organizational identity. Copyright © 2001 John Wiley & Sons, Ltd.
Customer value analysis in a heterogeneous market
Authors: DeSarbo Wayne S. , Jedidi Kamel , Sinha Indrajit
Published: August 2002

In recent years, customer value has become a major focus among strategy researchers and practitioners as an essential element of a firm's competitive strategy. Many firms have been interested in Customer Value Analysis (CVA) which involves a structural analysis of the antecedent factors of perceived value (i.e., perceived quality and perceived price) to assess their relative importance in the perceptions of their buyers. We develop a statistical approach for performing CVA utilizing a recursive simultaneous equation model that is formulated to accommodate buyer heterogeneity. In particular, the proposed finite‐mixture methodology allows one to estimate the relative effects and integration rules of perceived value drivers at the market segment level, as well as to simultaneously determine the (unknown) segments themselves. We demonstrate the utility of the proposed methodology via an actual commercial application involving a large electric utility company. Finally, we discuss the contributions of our research from the perspective of firm strategy and how it may be extended in the future. Copyright © 2001 John Wiley & Sons, Ltd.
The survival of new domestic and foreign‐owned firms
Authors: Mata José , Portugal Pedro
Published: August 2002

We compare the survival of new domestic and foreign‐owned firms. We analyze the determinants of the survival of new firms and investigate whether foreignness accounts for significant differences in the survival of new foreign and new domestic firms. We find survival to be determined by ownership advantages, size and growth strategies, the internal organization of firms, and by industry characteristics such as economies of scale, and industry entry and growth. After controlling for these characteristics, we find that domestic and foreign firms do not exhibit different chances of survival, that they respond in similar fashions to the determinants of survival and display identical time patterns of exit. Copyright © 2002 John Wiley & Sons, Ltd.
Pace, rhythm, and scope: process dependence in building a profitable multinational corporation
Authors: Vermeulen Freek , Barkema Harry
Published: August 2002

Many potential benefits of foreign expansion have been identified in the literature, yet empirical support that multinational firms perform better than domestic firms is mixed. This paper takes a longitudinal perspective and argues that how much a firm benefits from having foreign subsidiaries depends on its process of internationalization. We argue that a firm's capacity to absorb expansion is subject to constraints: some expansion patterns increase profitability less than others, owing to diseconomies of time compression. We hypothesize that the speed of internationalization, the spread of the geographical and product markets entered, and the irregularity of the expansion pattern negatively moderate a firm's increase in profitability resulting from international expansion. Model estimations based on panel data raised strong support for these predictions. Copyright © 2002 John Wiley & Sons, Ltd.
Impact of experience on maintenance skills
Authors: Jørgensen Magne , Sjøberg Dag I. K.
Published: August 2002

This study reports results from an empirical study of 54 software maintainers in the software maintenance department of a Norwegian company. The study addresses the relationship between amount of experience and maintenance skills. The findings were, amongst others, as follows. (1) While there may have been a reduction in the frequency of major unexpected problems from tasks solved by very inexperienced to medium experienced maintainers, additional years of general software maintenance experience did not lead to further reduction. More application specific experience, however, further reduced the frequency of major unexpected problems. (2) The most experienced maintainers did not predict maintenance problems better than maintainers with little or medium experience. (3) A simple one‐variable model outperformed the maintainers' predictions of maintenance problems, i.e. the average prediction performance of the maintainers seems poor. An important reason for the weak correlation between length of experience and ability to predict maintenance problems may be the lack of meaningful feedback on the predictions. Copyright © 2002 John Wiley & Sons, Ltd.
Design, implementation and evolution of object oriented frameworks: concepts and guidelines
Authors: van Gurp J. , Bosch J.
Published: August 2002

Object‐oriented frameworks provide software developers with the means to build an infrastructure for their applications. Unfortunately, frameworks do not always deliver on their promises of reusability and flexibility. To address this, we have developed a conceptual model for frameworks and a set of guidelines to build object oriented frameworks that adhere to this model. Our guidelines focus on improving the flexibility, reusability and usability (i.e. making it easy to use a framework) of frameworks. Copyright © 2001 John Wiley & Sons, Ltd.
From broadcast television to Internet audio/video: techniques and tools for VCR‐style interactivity
Authors: Makofske David B. , Almeroth Kevin C.
Published: August 2002

One of the new applications evolving in the Internet is streaming audio/video. A major reason for its growing popularity is interest in the compelling new services that become possible. Prototype services are being developed which are new to the Internet but offer the same look, feel, and functionality that have traditionally only been found in services delivered via other communication medium, e.g. broadcast television. In addition, the Internet is evolving to offer ‘value‐added’ services, like streaming audio/video with VCR‐style interactivity and embedded hyperlinks. We are poised both on seeing the development of new paradigms for interacting with audio/video, and on seeing the merging of broadcast television and Internet‐based broadcasts. Before this process can be considered successful, a number of technical challenges, derived from the various ways in which content is physically delivered, must be solved. In this paper, we focus on the value‐added service of VCR interactivity. VCR interactivity has long been a challenge for both broadcast television and streamed Internet audio/video. The challenge is how to provide individualized playout for content being streamed to a large group of users using one‐to‐many delivery. While some new companies are starting to offer devices which provide this kind of service for broadcast television, there are still numerous technical challenges for the Internet‐based version of a similar service. This paper has a three‐fold objective. First, we describe the types of services available in the traditional broadcast infrastructure and compare these to the types of services that are deployed or possible in Internet‐based services. Second, we describe our attempts to implement some of the more challenging and novel service types. In particular, we examine client‐based control of programs streamed over the Internet to tens, thousands, or even millions of users. Finally, we discuss the impact of these services on the protocols and applications used to support Internet‐based, multi‐party conferencing. Copyright © 2001 John Wiley & Sons, Ltd.
Transparent adaptation of sharing granularity in MultiView‐based DSM systems
Authors: Niv Nitzan , Schuster Assaf
Published: August 2002

In this paper we propose a mechanism that provides distributed shared memory (DSM) systems with a flexible sharing granularity. The size of the shared memory units is dynamically determined by the system during runtime. This size can range from that of a single variable up to the size of the entire shared memory space. During runtime, the DSM transparently adapts the granularity to the memory access pattern of the application in each phase of its execution. This adaptation, called ComposedView, provides efficient data sharing in software DSM while preserving sequential consistency. Neither complex code analysis nor annotation by the programmer or the compiler are required. Our experiments indicate a substantial performance boost (up to 80% speed‐up improvement) when running a large set of applications using our method, compared to running these benchmark applications with the best fixed granularity. Copyright © 2001 John Wiley & Sons, Ltd.
View‐based process elicitation: a user's perspective
Authors: Tassé Josée , Madhavji Nazim H.
Published: August 2002

Software process models are considered important for a number of purposes, such as assessment, improvement and customization. In order to obtain a complete model of a process, it is often necessary to gather relevant information from different sources (agents, documents, observations, etc.). One problem with this is that different sources may give inconsistent information about the same process. Resolving such conflicts can be difficult and arduous. This paper describes a user's perspective of a prototype tool, called V‐elicit, which helps in eliciting process models based on information from multiple sources. In V‐elicit, the information gathered from each source is entered separately as ‘views’, each of which is checked for internal consistency. Following this, common elements across the views are identified, and inconsistencies amongst them are flagged. As the elicitor, aided by the system, resolves these conflicts, the final (merged) model is automatically built. These features are illustrated through an example elicitation of a requirements engineering process. Copyright © 2001 John Wiley & Sons, Ltd.
Adaptation to creation: progress of organizational learning and increasing complexity of learning systems
Authors: Unnikrishnan Nair K.
Published: August 2002

A brief survey of organizational learning literature shows that understanding of how organizations learn has proceeded along two streams: one based on progress function or learning/experience curve effect, and the other as a process facilitating organizational adaptation and growth, and development and sustenance of competitiveness. This latter stream presents three phases of evolution: initially it considered learning as adaptation through search and problem solving, followed by attempts at conceptualization of learning as an organization‐wide, holistic phenomenon, and finally focusing on development of systems, processes, training tools, capabilities, etc., for building learning organizations. Learning is now understood as the development of organizational generative capabilities with a wide response range. The article identifies that the understanding of organizational learning from learning as adaptation to information processing and knowledge creation systems capable of generating a wide range of response patterns exhibits an underlying link of increasing complexity. This in turn holds an interesting correspondence to Boulding's hierarchy of systems. The article discusses the implications of this correspondence for research and practice. Copyright © 2001 John Wiley & Sons, Ltd.
Effect of 5‐HT on binding of [11C] WAY 100635 to 5‐HT1A receptors in rat brain, assessed using in vivo microdialysis and PET after fenfluramine
Authors: Hume Susan , Hirani Ella , Opacka‐Juffry Jolanta , Myers Ralph , Townsend Claire , Pike Victor , Grasby Paul
Published: August 2002

By using a combination of positron emission tomography (PET) and postmortem tissue dissection, the effect of increased endogenous serotonin on specific binding of [11C]WAY 100635 to the 5‐HT1A receptor was investigated in rat brain in vivo. The binding studies were complemented by in vivo microdialysis to monitor 5‐HT levels in similarly treated isoflurane‐anaesthetised rats, with the dialysis probe locations corresponding to two of the tissues sampled for specific binding of the radioligand. Fenfluramine treatment (10 mg/kg i.p.) resulted in a ∼5‐fold increase in extracellular 5‐HT in medial prefrontal cortex and a ∼15‐fold increase in lateral hippocampus, maximal at ∼40 min after injection. PET scan duration was either 60 or 90 min, beginning 30 min after fenfluramine injection. The specific binding of [11C]WAY 100635 was reduced by 10–20% in hippocampus, which showed highest binding in control animals. Specific binding, however, was unaffected in both prefrontal cortex and midbrain raphe, each additional high binding regions. The minimal effects are consistent with a low baseline occupancy of the 5‐HT1A receptor by 5‐HT in vivo, so that only a large change in endogenous agonist concentration will affect radioligand binding. This implies that utilisation of [11C]WAY 100635 in human PET to quantify 5‐HT1A receptor expression can be extended to pathology where synaptic 5‐HT levels are altered as a consequence of the disease state. Synapse 41:150–159, 2001. © 2001 Wiley‐Liss, Inc.
Process integration using the design structure matrix
Authors: Browning Tyson R.
Published: August 2002

A process, as a kind of system, derives its added value from the relationships among its elements (e.g., activities). For a group of activities to be truly integrated (versus merely aggregated), the flow of deliverables among them must be well defined, agreed to, and committed to. Engineering processes are especially complex because of the large number of interdependencies among the activities, as many types of information flow to many destinations. A process model of what actually flows must be extracted from the existing, implicit way work really gets done. Since this requires getting “close” to where work is actually done, it is beyond the ability of a single, centralized group to build the entire model. Instead, a number of process “puzzle pieces” must be integrated into a single process model that will have more holistic descriptive, analytical, and prescriptive value. (The systems engineering “V” model applies to processes as well as to products.) This paper applies a powerful technique for representing and analyzing complex processes, thedesign structure matrix(DSM). The paper shows how to use the DSM to display both internal and external inputs and outputs, thereby defining the “edges” of the process puzzle pieces so they can be assembled to form large, integrated processes where value can flow. Process definition and integration is akin to “mapping the genome” of how work is efficiently and effectively accomplished across disciplines and organizations. It is an important enabler of process understanding and improvement. © 2002 Wiley Periodicals, Inc. Syst Eng 5: 180–193, 2002
Semi‐active control of seismic response of tall buildings with podium structure using ER/MR dampers
Authors: Qu W. L. , Xu Y. L.
Published: August 2002

A tall building with a large podium structure under earthquake excitation may suffer from a whipping effect due to the sudden change of building lateral stiffness at the top of the podium structure. This paper thus explores the possibility of using electrorheological (ER) dampers or magnetorheological (MR) dampers to connect the podium structure to the tower structure to prevent this whipping effect and to reduce the seismic response of both structures. A set of governing equations of motion for the tower–damper–podium system is first derived, in which the stiffness of the member connecting the ER/MR damper to the structures is taken into consideration. Based on the principle of instantaneous sub‐optimal active control, a semi‐active sub‐optimal displacement control algorithm is then proposed. To demonstrate the effectiveness of semi‐active control of the system under consideration, a 20‐storey tower structure with a 5‐storey podium structure subjected to earthquake excitation is finally selected as a numerical example. The results from the numerical example imply that, as a kind of intelligent control device, ER/MR dampers can significantly mitigate the seismic whipping effect on the tower structure and reduce the seismic responses of both the tower structure and the podium structure. Copyright © 2001 John Wiley & Sons, Ltd.
Viscous damper development and future trends
Authors: Lee D. , Taylor D. P.
Published: August 2002

Viscous dampers can protect structures against wind excitation, blast and earthquakes. Viscous damper technology originated with military and aerospace applications. Approximately 10 years ago it was found that the same fluid viscous dampers that protect missiles against nuclear attack and guard submarines against near‐miss underwater explosions could also protect buildings, bridges and other structures from destructive shock and vibration. This paper describes fluid damper technology, analysis considerations, installation methods and development work in progress. Copyright © 2001 John Wiley & Sons, Ltd.
Protective action of propolis on the rat colon carcinogenesis
Authors: Bazo Ana Paula , Rodrigues Maria Aparecida Marchesan , Sforcin José Maurício , de Camargo João Lauro Viana , Ribeiro Lúcia Regina , Salvadori Daisy Maria Fávero
Published: August 2002

Propolis is a honeybee product with several biological and therapeutical properties. Its effect on the process of colon carcinogenesis and DNA damage were evaluated in the male Wistar rats using the aberrant crypt foci (ACF) assay and the comet assay, respectively. For both tests, animals were treated with the colon carcinogen 1,2 dimethylhydrazine (DMH, 40 mg/kg, s.c.) for 2 weeks (two injections/week) in order to induce both DNA damage and ACF. The animals were divided into groups that received propolis (ethanolic extract) at three different doses (10, 30, and 90 mg/kg b.w., by gavage), either simultaneously or after DMH treatment. For the comet assay, peripheral blood samples were collected 4 h after the last DMH treatment. All animals were sacrificed at the 5th week for evaluation of ACF. The results show that only the intermediate dose (30 mg/kg) of propolis, administered after DMH initiation, is significantly associated to a smaller number of aberrant crypts in the distal colon. No effect on DNA damage in peripheral blood cells, however, was verified by the comet assay. These data suggest that propolis has a protective influence on the process of colon carcinogenesis, suppressing the development of preneoplastic lesions, and probably exerts no protection against the initiation of carcinogenesis.Teratogenesis Carcinog. Mutagen. 22:183–194, 2002.© 2002 Wiley‐Liss, Inc.
Technology‐rich inquiry science in urban classrooms: What are the barriers to inquiry pedagogy?*
Authors: Songer Nancy Butler , Lee Hee‐Sun , Kam Rosalind
Published: August 2002

What are the barriers to technology‐rich inquiry pedagogy in urban science classrooms, and what kinds of programs and support structures allow these barriers to be overcome? Research on the pedagogical practices within urban classrooms suggests that as a result of many constraints, many urban teachers' practices emphasize directive, controlling teaching, that is, the “pedagogy of poverty” (Haberman, 1991), rather than the facilitation of students' ownership and control over their learning, as advocated in inquiry science. On balance, research programs that advocate standards‐based or inquiry teaching pedagogies demonstrate strong learning outcomes by urban students. This study tracked classroom research on a technology‐rich inquiry weather program with six urban science teachers. The teachers implemented this program in coordination with a district‐wide middle school science reform. Results indicated that despite many challenges in the first year of implementation, students in all 19 classrooms of this program demonstrated significant content and inquiry gains. In addition, case study data comprised of twice‐weekly classroom observations and interviews with the six teachers suggest support structures that were both conducive and challenging to inquiry pedagogy. Our work has extended previous studies on urban science pedagogy and practices as it has begun to articulate what role the technological component plays either in contributing to the challenges we experienced or in helping urban science classrooms to realize inquiry science and other positive learning values. Although these data outline results after only the first year of systemic reform, we suggest that they begin to build evidence for the role of technology‐rich inquiry programs in combating the pedagogy of poverty in urban science classrooms. © 2002 John Wiley & Sons, Inc. J Res Sci Teach 39: 128‐150, 2002
Description and mission evaluation of the Hungarian case‐control surveillance of congenital abnormalities, 1980–1996
Authors: Czeizel Andrew E. , Rockenbauer Magda , Siffel Csaba , Varga Erika
Published: August 2002

Background

The Hungarian Case‐Control Surveillance of Congenital Abnormalities was established in 1980. This article describes how the Hungarian Case‐Control Surveillance of Congenital Abnormalities was first organized and is currently maintained. The baseline statistics are provided and potential venues of postmarketing surveillance of drug teratogenicity and other public health tasks and research are proposed.

Methods

Cases with congenital abnormalities and patient controls with Down syndrome were selected from the Hungarian Congenital Abnormality Registry. Population controls without congenital abnormalities were selected from the National Birth Registry on the basis of three matching criteria: sex, week of birth, and district of parent's residence. Three sources of information concerning drug exposures, maternal disorders, and pregnancy complications, among others, were used: (1) prospective and medically recorded data from antenatal care logbooks and discharge summaries; (2) retrospective maternal self‐reported data obtained with a structured questionnaire in all the three study groups; and (3) data collected by regional nurse in house visits to nonrespondent cases and patient controls. Twenty‐five congenital abnormality groups were evaluated. During the 17‐year period of data collection, 22,843 cases, 38,151 population controls, and 834 patient controls were incorporated into the data set, constituting the largest population‐based case‐control data set of congenital abnormalities to date.

Results

Demographic features of pregnant women and informative offspring are presented along with the distribution of 25 main groups of congenital abnormalities.

Conclusions

This system is appropriate for postmarketing the surveillance of drug teratogenicity, for the improvement of congenital abnormality diagnosis, to get informed consent, to have a communication with parents and to provide material for research. Teratology 63:176–185, 2001. © 2001 Wiley‐Liss, Inc.
Using Midsemester Student Feedback and Responding to It
Authors: Lewis Karron G.
Published: August 2002

Getting midsemester feedback from your students can help faculty make changes before it's too late.
Acute toxicity, mutagenicity, and estrogenicity of bisphenol‐A and other bisphenols
Authors: Chen Min‐Yu , Ike Michihiko , Fujita Masanori
Published: August 2002

Although abundant data are available on the toxicity of bisphenol‐A (2,2‐bis (4‐hydroxydiphenyl)propane; BPA), little is known about the toxicities of the structurally similar compounds, namely bisphenols (BPs). A variety of BPs were examined for their acute toxicity against Daphnia magna, mutagenicity, and estrogenic activity using the Daphtoxkit (Creasel Ltd.), the umu test system, and the yeast two‐hybrid system, respectively, in comparison with BPA. BPA was moderately toxic to D. magna (48‐h EC50 was 10 mg/l) according to the current U.S. EPA acute toxicity evaluation standard, and it was weakly estrogenic with 5 orders of magnitude lower activity than that of the natural estrogen 17β‐estradiol in the yeast screen, while no mutagenicity was observed. All seven BPs tested here showed moderate to slight acute toxicity, no mutagenicity, and weak estrogenic activity as well as BPA. Some of the BPs showed considerably higher estrogenic activity than BPA, and others exhibited much lower activity. Among the tested BPs, two compounds, i.e., bisphenol‐S (bis(4‐hydroxydiphenyl)sulfone) and bis(4‐hydroxyphenyl)sulfide, have never been reported for their estrogenic activity previously. © 2002 by Wiley Periodicals, Inc. Environ Toxicol 17: 80–86, 2002