bluuebunny/crossref_metadata_2025_split huggingface dataset:
Exploring policy options with a behavioral climate–economy model
Authors: Fiddaman Thomas S. 
Published: September 2002

AbstractMany integrated energy–economy–climate models have been developed to address climate change policy. While these models are quite varied in scope, most share a common core of economic optimization and equilibrium assumptions. By contrast, system dynamics models of energy–economy interactions focus on disequilibrium dynamics, with behavioral decision rules and explicit stocks and flows of capital, labor, resources and money. This article tests climate policies using a system dynamics model that includes many features missing from economic models. Among these are endogenous technological change and boundedly rational decision making. Energy requirements are embodied in capital, and energy production capacity depends on explicit capital stocks. The search for optimal policies is decoupled from other decisions, and uses criteria that are fair across generations. Earlier experiments with the model, briefly reported here, indicate that these features greatly alter policy outcomes. The model is used to test a family of emissions permit and tax policies like the Kyoto Protocol under a range of assumptions. Uncertainty is included in the analysis through Monte Carlo simulation. Results suggest that nearly all policy options are a net benefit, and that the landscape for policy choice is more forgiving than generally supposed. However, implementation remains a critical issue, and the viability of tradeable permits is questionable. Carbon tax policies are found to outperform fixed emissions permits in nearly all circumstances. The model used in this article is available at https://metasd.com/2014/07/free/. Copyright © 2002 John Wiley & Sons, Ltd.
Cloudy skies: assessing public understanding of global warming
Authors: Sterman John D. , Sweeney Linda Booth 
Published: September 2002

AbstractSurveys show that most Americans believe global warming is real. But many advocate delaying action until there is more evidence that warming is harmful. The stock and flow structure of the climate, however, means “wait and see” policies guarantee further warming. Atmospheric CO2 concentration is now higher than any time in the last 420,000 years, and growing faster than any time in the past 20,000 years. The high concentration of CO2 and other greenhouse gases (GHGs) generates significant radiative forcing that contributes to warming. To reduce radiative forcing and the human contribution to warming, GHG concentrations must fall. To reduce GHG concentrations, emissions must fall below the rate at which GHGs are removed from the atmosphere. Anthropogenic CO2 emissions are now roughly double the removal rate, and the removal rate is projected to fall as natural carbon sinks saturate. Emissions must therefore fall by more than half even to stabilize CO2 at present record levels. Such reductions greatly exceed the Kyoto targets, while the Bush administration's Clear Skies Initiative calls for continued emissions growth. Does the public understand these physical facts? We report experiments assessing people's intuitive understanding of climate change. We presented highly educated graduate students with descriptions of greenhouse warming drawn from the IPCC's nontechnical reports. Subjects were then asked to identify the likely response to various scenarios for CO2 emissions or concentrations. The tasks require no mathematics, only an understanding of stocks and flows and basic facts about climate change. Overall performance was poor. Subjects often select trajectories that violate conservation of matter. Many believe temperature responds immediately to changes in CO2 emissions or concentrations. Still more believe that stabilizing emissions near current rates would stabilize the climate, when in fact emissions would continue to exceed removal, increasing GHG concentrations and radiative forcing. Such beliefs support “wait and see” policies, but violate basic laws of physics. We discuss implications for education and public policy. Copyright © 2002 John Wiley & Sons, Ltd.
Identification of significant host factors for HIV dynamics modelled by non‐linear mixed‐effects models
Authors: Wu Hulin , Wu Lang 
Published: September 2002

AbstractNon‐linear mixed‐effects models are powerful tools for modelling HIV viral dynamics. In AIDS clinical trials, the viral load measurements for each subject are often sparse. In such cases, linearization procedures are usually used for inferences. Under such linearization procedures, however, standard covariate selection methods based on the approximate likelihood, such as the likelihood ratio test, may not be reliable. In order to identify significant host factors for HIV dynamics, in this paper we consider two alternative approaches for covariate selection: one is based on individual non‐linear least square estimates and the other is based on individual empirical Bayes estimates. Our simulation study shows that, if the within‐individual data are sparse and the between‐individual variation is large, the two alternative covariate selection methods are more reliable than the likelihood ratio test, and the more powerful method based on individual empirical Bayes estimates is especially preferable. We also consider the missing data in covariates. The commonly used missing data methods may lead to misleading results. We recommend a multiple imputation method to handle missing covariates. A real data set from an AIDS clinical trial is analysed based on various covariate selection methods and missing data methods. Copyright © 2002 John Wiley & Sons, Ltd.
Analysis of the ratio of marginal probabilities in a matched‐pair setting
Authors: Nam Jun‐mo , Blackwelder William C. 
Published: September 2002

AbstractStatistical methods for testing and interval estimation of the ratio of marginal probabilities in the matched‐pair setting are considered in this paper. We are especially interested in the situation where the null value is not one, as in one‐sided equivalence trials. We propose a Fieller‐type statistic based on constrained maximum likelihood (CML) estimation of nuisance parameters. For a series of examples, the significance level of the CML test is satisfactorily close to the nominal level, while a Wald‐type test is anticonservative for reasonable sample sizes. We present formulae for approximate power and sample size for the CML and Wald tests. The matched design is seen to have a clear advantage over the unmatched design in terms of asymptotic efficiency when the two responses of the pair are highly positively correlated. We recommend the CML method over the Wald method, especially for small or moderate sample sizes. Published in 2002 by John Wiley & Sons, Ltd.
Combining regression and association modelling for longitudinal data on bacterial carriage
Authors: Ekholm Anders , Jokinen Jukka , Kilpi Terhi 
Published: September 2002

AbstractA longitudinal data set, from the Finnish Otitis Media (FinOM) Studies, reporting carriage or non‐carriage of Streptococcus pneumoniae at 2, 3, 4, 5, 6, 9, 12, 15 and 18 months of age of 329 children living in Tampere, Finland, is analysed. A logistic regression model on five time varying explanatory variables is fitted. The temporal association between presence at different ages is measured by dependence ratios and the structure of these is shown to be well described by a model indicating that roughly 10 per cent of the children are not susceptible to the bacteria, while for those that are susceptible, carriage status at a future observation age is conditionally independent of past observed statuses, given the present status. The dependence ratios between carriage at adjacent observation ages decay exponentially with age. Maximum likelihood estimates are obtained for the parameters of the full model, which is the combination of the marginal logistic regression and the association models. The parameter estimates of the full model, strengthened by non‐testable Markov assumptions, are used for assessing the median duration of carriage and the acquisition rate as functions of age. Copyright © 2002 John Wiley & Sons, Ltd.
A Bayesian space varying parameter model applied to estimating fertility schedules
Authors: Assunção Renato M. , Potter Joseph E. , Cavenaghi Suzana M. 
Published: September 2002

AbstractWe propose a spatial generalized linear model (GLM) to analyse the vital rates for small areas. In each small area, we have a response vector and covariates to explain its variability. The statistical methodology is based on a spatial Bayesian approach and it allows the covariates' parameters of the generalized linear model to vary smoothly on space. Hence, the effect of a covariate on the response varies depending on the random variables measurement location. Our model is an extension of disease mapping models allowing the space–covariate interaction to be modelled in a natural way and giving space a position of intrinsic interest. We introduce the model in the context of fertility curve estimation. In each small area, we have a curve describing the variation of fertility rates by age modelled by Coale's fertility model, which implies a GLM in each area. A simulation shows the advantages of our approach. In addition, the paper applies the procedure to census data used to study the diffusion of low fertility behaviour in Brazil. Copyright © 2002 John Wiley & Sons, Ltd.
Modelling HIV viral rebound using non‐linear mixed effects models
Authors: Fitzgerald Anthony P. , DeGruttola Victor G. , Vaida Florin 
Published: September 2002

Abstract Individuals infected with the human immunodeficiency virus type 1 (HIV‐1) who initiate antiretroviral therapy typically experience a marked decline in concentrations of HIV‐1 RNA in plasma. Often, however, viral rebound occurs within the first year of treatment and this rebound may be associated with resistance to antiretroviral therapy. For this reason, it is important to study the patterns of virological response of HIV‐1 RNA to treatment. In particular, there is interest in the relationship between the lowest level of plasma HIV‐1 RNA attained after initiation of therapy (nadir value) and the time until rebound. To investigate this question, we implement a simple and flexible non‐linear mixed effects model for the trajectory of the HIV‐1 RNA until rebound. This model is also consistent with biological insights into the effects of treatment. We also show how the problem of censoring of HIV‐1 RNA values at the lower limit of assay quantification can be addressed using a multiple imputation scheme. The algorithm is simple to implement and is based on accessible software. Our application makes use of data from clinical trial 315 conducted by the AIDS Clinical Trials Group (ACTG 315). We find a strong relationship between HIV‐1 RNA nadir and time to rebound, with potentially important consequences for the management of HIV‐infected individuals. Copyright 2002 John Wiley & Sons, Ltd.
Comparison of bandwidth selection methods for kernel smoothing of ROC curves
Authors: Zhou Xiao‐Hua , Harezlak Jaroslaw 
Published: September 2002

AbstractIn this paper we compared four non‐parametric kernel smoothing methods for estimating an ROC curve based on a continuous‐scale test. All four methods produced a smooth ROC curve of the test. The difference in these four methods lay with the way they chose their bandwidth parameters. To assess the relative performance of the four bandwidth selection methods, we conducted a simulation study using different underlying distributions, along with varied sample sizes. The results from our simulation study suggested that the kernel smoothing method originally proposed by Altman and Léger for estimation of the distribution function was the best choice for estimation of an ROC curve. We illustrated these methods with a real example. Copyright © 2002 John Wiley & Sons, Ltd.
On the assessment of adverse drug reactions from spontaneous reporting systems: the influence of under‐reporting on odds ratios
Authors: van der Heijden Peter G. M. , van Puijenbroek Eugène P. , van Buuren Stef , van der Hofstede Jacques W. 
Published: September 2002

AbstractA well‐known problem in spontaneous reporting systems (SRSs) for adverse drug reactions (ADRs) is under‐reporting, that is, the problem that not all occurrences of ADRs are reported to the SRS. We look at the question of how to draw statistical conclusions from analyses of SRS data using reporting odds ratios. We will show that certain under‐reporting problems play no role in assessing ADRs from SRSs: the results from the analyses turn out to be biased by some specific under‐reporting problems, but not by others. SRS data can be particularly useful for the assessment of drug–drug interactions. If the assumption holds that there is an under‐reporting problem for a first drug, and an under‐reporting problem for a second drug, but that these two under‐reporting problems do not influence each other, then reporting odds ratios estimated from SRSs are useful for signalling drug–drug interactions in the ADR‐experiencing population. Similar results hold for covariate–drug interactions. We illustrate our results using two examples. Copyright © 2002 John Wiley & Sons, Ltd.
Tests for 2×K contingency tables with clustered ordered categorical data
Authors: Jung Sin‐Ho , Kang Seung‐Ho 
Published: September 2002

AbstractOrdered categorical data summarized in a 2×K table usually consist of two‐sample multinomial or K‐sample binomial observations. In analysing these data, we usually assign scores to the K columns and perform a testing for the equality of two multinomial distributions in the former case and no trend among K binomial proportions in the latter case. Among the most popular score tests are the Wilcoxon rank sum test and the Armitage's linear trend test. In this paper we extend the score tests to be used for clustered data under diverse study designs. Our methods do not require correct specification of the dependence structure within clusters. The proposed tests are based on the asymptotic normality for large number of clusters and are a generalization of the standard tests used for independent data. Simulation studies are conducted to investigate the finite‐sample performance of the new methods. The proposed methods are applied to real‐life data. Copyright © 2001 John Wiley & Sons, Ltd.
Competing risks analysis of patients with osteosarcoma: a comparison of four different approaches
Authors: Tai Bee‐Choo , Machin David , White Ian , Gebski Val 
Published: September 2002

AbstractIn failure time studies involving a chronic disease such as cancer, several competing causes of mortality may be operating. Commonly, the conventional statistical technique of Kaplan–Meier, which is only meaningfully interpreted by assuming independence of failure types and the censoring mechanism, is employed in clinical research involving competing risks data. Some authors have advocated the use of a cause‐specific cumulative incidence function which takes into account the existence of other events within a competing risks framework, without making any assumption about independence. Lunn and McNeil have proposed an approach based on an extension of the Cox proportional hazards regression, which enables direct comparisons between failure types. We have extended this approach to estimate cause‐specific cumulative incidence. As it is often not easy to follow competing risks methodology in the literature, this paper sets out systematically the assumptions made and the steps taken to implement four different methods of analysing competing risks data using cumulative incidence rates or the Kaplan–Meier estimates of cause‐specific failure probabilities. The data obtained from a randomized trial of patients with osteosarcoma were used to compare these four approaches. As illustrated using the osteosarcoma data, the estimates of the classical Kaplan–Meier methods have larger numerical values than the cause‐specific cumulative incidence. On the other hand, estimates of the cause‐specific cumulative incidence rates from the conventional method and the modified Cox method are highly comparable. Copyright © 2001 John Wiley & Sons, Ltd.
Estimating probability of non‐response to treatment using mixture distributions
Authors: Pavlic Maja , Brand Richard J. , Cummings Steven R. 
Published: September 2002

AbstractRepeat measurements of patient characteristics are often used to assess response to treatment. In this paper we discuss a normal mixture model for the observed change in the characteristic of interest in treated patients. The methods described can be used to estimate the overall proportion of non‐response to treatment and also the probability that a patient has not responded to treatment given his or her observed change. The model parameters are estimated using maximum likelihood, and the delta method is used to construct a pointwise confidence band for the conditional probability that a patient is a non‐responder to treatment. The work was initially motivated by analysis issues in the Fracture Intervention Trial (FIT), a randomized trial of the osteoporosis drug alendronate, and the method is illustrated with data from that study. We also evaluate key aspects of the estimation procedure with two simulation studies. In the first, the data generation model is the assumed normal mixture model, and in the second, the data are generated according to a shifted and scaled central t‐distribution model suggested by the FIT data. Copyright © 2001 John Wiley & Sons, Ltd.
On tests of the overall treatment effect in meta‐analysis with normally distributed responses
Authors: Hartung Joachim , Knapp Guido 
Published: September 2002

AbstractFor the meta‐analysis of controlled clinical trials or epidemiological studies, in which the responses are at least approximately normally distributed, a refined test for the hypothesis of no overall treatment effect is proposed. The test statistic is based on a direct estimation function for the variance of the overall treatment effect estimator. As outcome measures, the absolute and the standardized difference between means are considered. In simulation studies it is shown that the proposed test keeps the prescribed significance level very well in contrast to the commonly used tests in the fixed effects and random effects model, respectively, which can become very liberal. Furthermore, just for using the proposed test it is not necessary to choose between the fixed effects and the random effects approach in advance. Copyright © 2001 John Wiley & Sons, Ltd.
A multiple imputation method for missing covariates in non‐linear mixed‐effects models with application to HIV dynamics
Authors: Wu Hulin , Wu Lang 
Published: September 2002

AbstractWe propose a three‐step multiple imputation method, implemented by Gibbs sampler, for estimating parameters in non‐linear mixed‐effects models with missing covariates. Estimates obtained by the proposed multiple imputation method are compared to those obtained by the mean‐value imputation method and the complete‐case method through simulations. We find that the proposed multiple imputation method offers smaller biases and smaller mean‐squared errors for the estimates of covariate coefficients compared to other two methods. We apply the three missing data methods to modelling HIV viral dynamics from an AIDS clinical trial. We believe that the results from the proposed multiple imputation method are more reliable than that from the other two commonly used methods. Copyright © 2001 John Wiley & Sons, Ltd.
Is sense of coherence a mediator between adversity and psychological well‐being in adults?
Authors: Gana Kamel 
Published: September 2002

AbstractThe role and status of sense of coherence (SOC) in psychological functioning are still unclear. A conceptual model in which sense of coherence mediates the relationship between adverse experiences and psychological well‐being was developed and estimated using structural equation modeling. Data was obtained from a sample of 193 adults (30–85 years old). The mediating role of sense of coherence was demonstrated by using the rationale and procedure suggested by Holmbeck. The buffering effect of sense of coherence was demonstrated through multi‐group analyses (weak vs. strong SOC groups). Copyright © 2001 John Wiley & Sons, Ltd.
Self‐esteem, stress and cigarette smoking in adolescents
Authors: Byrne D. G. , Mazanov J. 
Published: September 2002

AbstractBoth high stress and low self‐esteem have been consistently, though independently, reported to relate to aspects of adolescent smoking behaviour. Recent work on self‐esteem, however, suggests that adequate provision of this attribute may protect the individual adolescent from unpleasant dysphoric or harmful behavioural states. In line with this suggestion, the present study sought to extend this to the area of adolescent smoking behaviour. While independent associations were confirmed there was not strong support for a protective effect of self‐esteem on adolescent smoking in the face of stressor exposure. A modest sex effect was evident but not of sufficient magnitude to allow firm conclusions. Nonetheless, the results were tempting enough to indicate further investigation. Copyright © 2001 John Wiley & Sons, Ltd.
Influence of hypothalamically induced restlessness under fasted and fed conditions on plasma levels of glucose, free fatty acids and total cholesterol
Authors: Kojima Kyoji , Mohamed Souher , Fujimaru Yasuaki , Mori Yoshinobu , Kaname Hitoshi , Sumida Yasuhisa , Kinukawa Naoko , Tashiro Nobutada 
Published: September 2002

AbstractInfluence of hypothalamically induced emotional behavior on plasma levels of epinephrine (E), norepinephrine (NE), glucose, cortisol, free fatty acids (FFA) and total cholesterol (T‐C) were examined in cats under both fasted and fed conditions. Restlessness was evoked intermittently for 6 h by electrical stimulation of the anteromedial hypothalamus (AMH). Blood was sampled immediately before, 1 h after and 6 h after the start of stimulation. Both E and glucose levels in the restlessness group increased markedly after 1 h and then tended to decrease after 6 h in fasted and fed states. In the restlessness group the NE level increased after 1 h and further increased after 6 h and cortisol level increased markedly, whether cats were fasted or fed. The FFA level in the fasted restlessness group showed no change while it increased in the fasted control group after 6 h. By contrast, the FFA level in the fed restlessness group significantly increased after 6 h while no change was observed in the fed control group. The T‐C level decreased only under the fasted condition in both restlessness and control groups. These results indicated that AMH‐induced restlessness elicited marked sympatho‐adrenal activation and hyperglycemia whether cats were fasted or fed while the behavior showed a different pattern in the response of plasma FFA between fasted and fed conditions. Copyright © 2001 John Wiley & Sons, Ltd.