bluuebunny/crossref_metadata_2025_split huggingface dataset:
Long‐term effectiveness of grain protectants and structural treatments against Liposcelis decolor (Pearman) (Psocoptera: Liposcelididae), a pest of stored products
Authors: Nayak Manoj K , Collins Patrick J , Pavic Hervoika 
Published: November 2002

AbstractNumerous strains of the psocid pest, Liposcelis decolor (Pearman) were collected from farms and central storages and interbred to form three representative strains from three major grain‐growing states of Australia: Queensland, South Australia and New South Wales. These were tested against the grain protectants and structural treatments currently registered for use in Australia. Recently, L decolor has become an important pest of stored grain in Australia, particularly in the eastern and southern parts. There is no published information available on management of this pest and the current pest‐management strategy, based predominantly on phosphine fumigation, has failed to control infestations of this pest in numerous grain storages in Australia. Alternative methods of control such as use of contact insecticides were explored in the present work to supplement phosphine fumigation to manage this new pest. From eight grain protectants tested as admixtures, only chlorpyrifos‐methyl, bioresmethrin plus piperonyl butoxide, and fenitrothion were found to provide long term (3–9 months) protection against all three strains of L decolor. Chlorpyrifos‐methyl gave the best protection, providing a minimum of 7.5 to a maximum of 9 months protection, depending on the strains tested. Three structural treatments, azamethiphos, azamethiphos plus carbaryl and permethrin provided long‐term control (8–9 months) of all three strains of L decolor on galvanised steel surfaces, with permethrin delivering 9 months protection against all strains. However, all of these treatments failed to provide long‐term control of any strains on concrete surfaces. We conclude that chlorpyrifos‐methyl as a grain admixture can be incorporated into fumigation strategies to optimise the control of L decolor infestations. Structural treatments, such as permethrin can be used to support a fumigation strategy in storages made of galvanised steel.© 2002 Society of Chemical Industry
Cheap control tracking performance for non‐right‐invertible systems
Authors: Woodyatt A. R. , Seron M. M. , Freudenberg J. S. , Middleton R. H. 
Published: November 2002

AbstractThere exists a well‐known fundamental limitation upon the achievable setpoint tracking performance of a non‐right‐invertible plant. This limitation manifests itself, for example, in the cost associated with the cheap control tracking problem. In this paper, we provide a new interpretation of this limitation. We show that the cheap control cost may be decomposed into the sum of two terms. The first of these depends upon certain non‐minimum phase zeroes that include the non‐minimum phase plant zeroes. The second term depends upon the extent to which the plant direction varies with frequency. To state these results, we first develop a co‐ordinate transformation that may be used to define the notion of frequency dependent plant direction and to display the relevant non‐minimum phase zeroes. We also show that the cheap control cost is connected to an integral relation that constrains the performance of any stable closed‐loop system (not necessarily under cheap control) for which the plant has a single control input and two performance outputs. Copyright © 2002 John Wiley & Sons, Ltd.
Guaranteed cost inequalities for robust stability and performance analysis
Authors: Bernstein Dennis S. , Osburn Scot L. 
Published: November 2002

AbstractIn this paper, we formulate robust stability and performance bounds in terms of guaranteed cost inequalities. We derive new guaranteed cost bounds for plants with real structured uncertainty, and we reformulate them as linear matrix inequalities (LMIs). In particular, we obtain a shifted linear bound and a shifted inverse bound, and give LMI forms for a shifted bounded real bound, a shifted Popov bound, a shifted linear bound and a shifted inverse bound. Several examples are used to compare the shifted bounds with their unshifted counterparts and to make comparisons among these new bounds and vertex LMI bounds. Copyright © 2002 John Wiley & Sons, Ltd.
Adaptive/robust time‐varying stabilization of second‐order non‐holonomic chained form with input uncertainties
Authors: Ma B. L. , Tso S. K. , Xu W. L. 
Published: November 2002

AbstractAdaptive and robust time‐varying control schemes are constructed to stabilize second‐order non‐holonomic chained form in the presence of input uncertainties. The proposed control schemes guarantee that all the state variables converge to zero asymptotically in spite of input uncertainties, and are applied to the stabilization of a planar rigid body driven by active force and torque with unknown inertia and geometric parameters. The basic idea of the proposed stabilization schemes is to first convert the non‐holonomic system into a linear time‐varying form by time‐varying co‐ordinate transformation, and then design control laws to stabilize the converted linear time‐varying system. Copyright © 2002 John Wiley & Sons, Ltd.
Robust stabilization of a class of uncertain system via block decomposition and VSC
Authors: Loukianov Alexander G. , Castillo‐Toledo B. , Dodds Stephen 
Published: November 2002

AbstractIn this paper, a block decomposition procedure for sliding mode control of a class of nonlinear systems with matched and unmatched uncertainties, is proposed. Based on the nonlinear block control principle, a sliding manifold design problem is divided into a number of sub‐problems of lower dimension which can be solved independently. As a result, the nominal parts of the sliding mode dynamics is linearized. A discontinuous feedback is then used to compensate the matched uncertainty. Finally, a step‐by‐step Lyapunov technique and a high gain approach is applied to obtain hierarchical fast motions on the sliding manifolds and to achieve the robustness property of the closed‐loop system motion with respect to unmatched uncertainty. Copyright © 2002 John Wiley & Sons, Ltd.
Analysis of censored and incomplete survival data using flowgraph models
Authors: Yau C. Lillian , Huzurbazar Aparna V. 
Published: November 2002

AbstractMulti‐state stochastic models are widely used to model stages of disease progression in survival analysis. This paper develops flowgraph models for data analysis in survival analysis. We illustrate these methods using data from a study of diabetic retinopathy consisting of 277 subjects with insulin‐dependent (type I) diabetes mellitus (IDDM). These data were collected at the Eye‐Kidney Clinic of the Barbara Davis Center for Childhood Diabetes at the University of Colorado Health Sciences Center. Copyright © 2002 John Wiley & Sons, Ltd.
The origin of DNA replication and Fieller's problem
Authors: Truong Young K. , Scott Rona S. , Vos Jean‐Michel H. 
Published: November 2002

AbstractThe paper considers the statistical problem of estimating the origin of DNA replication within the human ribosomal DNA (rDNA) locus and the issue of assessing the standard error of the estimate. Based on mapping the cumulative replication index (CRI), two different modelling schemes are suggested and investigated. The statistical problem of constructing a confidence interval for the origin of DNA replication is related to Fieller's problem of obtaining a confidence interval for the ratio of two normal means. Standard normal theory, the delta and bootstrap methods are used to estimate the standard error of the estimate of the origin of DNA replication, as well as the variation of the replication rate. Copyright © 2002 John Wiley & Sons, Ltd.
Statistical estimation of parameters in a disease transmission model: analysis of a Cryptosporidium outbreak
Authors: Brookhart M. Alan , Hubbard Alan E. , van der Laan Mark J. , Colford John M. , Eisenberg Joseph N. S. 
Published: November 2002

AbstractPopulation dynamic models, commonly used tools in the study of epidemics and other complex population processes, are implicit non‐linear mathematical equations. Inference based on such models can be difficult due to the problems associated with high dimensional parameters that may be non‐identified and complex likelihood functions that are difficult to maximize. To address a problem of non‐identifiability due to collinearity of parameter estimates in a mathematical model of the 1993 Milwaukee Cryptosporidium parvum outbreak, we examined the utility of a constrained profile likelihood approach. This method was used to study two parameters of interest from the mathematical model: (i) the rate of secondary transmission; (ii) the proportional increase in primary transmission due to water treatment failure. The estimated values of these parameters were shown to depend strongly on poorly understood aspects of Cryptosporidium epidemiology such as asymptomatic proportion and the population immune status. Our analysis demonstrated that the combination of a disease transmission model and a constrained profile likelihood procedure provides an effective approach for inference and estimation of important parameters regulating infectious disease outbreaks. Copyright © 2002 John Wiley & Sons, Ltd.
The analysis of multivariate interval‐censored survival data
Authors: Kim Mimi Y. , Xue Xiaonan 
Published: November 2002

AbstractThis paper considers a marginal approach for the analysis of the effect of covariates on multivariate interval‐censored survival data.Interval censoring of multivariate events can occur when the events are not directly observable but are detected by periodically performing clinical examinations or laboratory tests. The method assumes the marginal distribution for each event is based on a discrete analogue of the proportional hazards model for interval‐censored data. A robust estimator for the covariance matrix is developed that accounts for the correlation between events. A simulation study comparing the performance of this method and a midpoint imputation approach indicates the parameter estimates from the proposed method are less biased. Furthermore, even when the events are only modestly correlated, ignoring the correlation can result in erroneous variance estimators. The method is illustrated using data from an ongoing clinical trial involving subjects with systemic lupus erythematosus. Copyright © 2002 John Wiley & Sons, Ltd.
A hierarchical Poisson mixture regression model to analyse maternity length of hospital stay
Authors: Wang K. , Yau Kelvin K. W. , Lee Andy H. 
Published: November 2002

AbstractInpatient length of stay (LOS) is often considered as a proxy of hospital resource consumption. Using statewide obstetrical delivery data, a two‐component Poisson mixture model provides a reasonable fit to the heterogeneous LOS distribution. Adopting the generalized linear mixed model (GLMM) approach, random effects are introduced to the two‐component Poisson mixture regression model to account for the inherent correlation of patients clustered within hospitals. An EM algorithm is developed for the joint estimation of regression coefficients and variance component parameters. Related diagnostic measures for assessing model adequacy are derived. When applying the method to analyse maternity LOS, appropriate risk factors for the short‐stay and long‐stay subgroups can be identified from the respective Poisson components. In addition, predicted random hospital effects enable the comparison of relative efficiencies among hospitals after adjustment for patient case‐mix and health provision characteristics. Copyright © 2002 John Wiley & Sons, Ltd.
Selecting the best method to evaluate bronchodilation when analysing bronchodilator studies
Authors: Goedhart Dick M. , Zanen Pieter 
Published: November 2002

AbstractChanges in lung function (that is, FEV1) are commonly expressed as a percentage of the predicted value. The question is whether this parameter is best suited for statistical analysis. A total of 2199 bronchodilation tests were selected and pre‐ and post‐dilator FEV1, age, height and sex extracted. Predicted FEV1 values, the difference between pre‐ and post‐dilator FEV1 and the change as percentage of predicted or baseline FEV1 were calculated. The latter parameters were subjected to analysis of variance and pre‐ and post‐dilator FEV1 to analysis of covariance. The statistical power of these four approaches and the residual structure were used to select the best approach. Analysis of variance of the change as percentage of predicted and covariance analysis of pre‐ and post‐dilator FEV1 offers the best performance. The residuals of the analysis of variance showed a funnel shaped structure. The latter causes residual heterogeneity, resulting in a loss of power and deviations between the actual and nominal α‐level. This is not taken into account when calculating sample sizes using the standard equations, which implicitly assume lack of these problems. Analysis of covariance does not suffer from these problems. The best way to evaluate bronchodilation in trials is to use analysis of covariance. Copyright © 2002 John Wiley & Sons, Ltd.
Alternatives to the hazard ratio in summarizing efficacy in time‐to‐event studies: an example from influenza trials
Authors: Keene Oliver N. 
Published: November 2002

AbstractEstimates of the efficacy of new medicines are key to the investigation of their clinical effectiveness. The most widely recommended approach to summarizing time‐to‐event data from clinical trials is to use a hazard ratio. When the proportional hazards assumption is questionable, a hazard ratio depends on the length of patient follow‐up. Hazard ratios do not directly translate into differences in times to events and therefore can present difficulties in interpretation. This paper describes an area where summary by hazard ratio would seem unsuitable and explores alternative estimates of efficacy. In particular, the difference in median time to event between treatments can provide a useful and consistent measure of efficacy. Methods of calculating confidence intervals for differences in medians for censored time‐to‐event will be described. Accelerated failure time models provide a useful alternative approach to proportional hazards modelling. Estimates of the ratio of the median time to event between treatments are directly available from these models. One of the reasons given for summarizing time‐to‐event studies by a hazard ratio is to facilitate meta‐analyses. The bootstrap estimate of standard error for difference in median in each trial can provide a method for combining results based on summary statistics. Copyright © 2002 John Wiley & Sons, Ltd.
Evaluating mixed stains with contributors of different ethnic groups under the NRC‐II Recommendation 4.1
Authors: Fung Wing K. , Hu Yue‐Qing 
Published: November 2002

AbstractIn countries with multiple racial or ethnic groups, it is not uncommon that contributors to a mixed stain or a DNA mixture belong to different ethnic origins. This paper derives a general formula for evaluating the likelihood ratio in such situations based on the commonly adopted Recommendation 4.1 of the U.S. Second National Research Council Report on the evaluation of DNA evidence. The restrictive Hardy–Weinberg assumption is not taken in this paper. Our formula generalizes the results of Fung and Hu for a single ethnic group, and of Weir et al. under the Hardy–Weinberg law for a single, and Fukshansky and Bär for multiple ethnic groups. The effect of different ethnic groups of contributors to the interpretation of mixtures is illustrated through the analysis of the Simpson case. Copyright © 2002 John Wiley & Sons, Ltd.
The study of long‐term HIV dynamics using semi‐parametric non‐linear mixed‐effects models
Authors: Wu Hulin , Zhang Jin‐Ting 
Published: November 2002

AbstractModelling HIV dynamics has played an important role in understanding the pathogenesis of HIV infection in the past several years. Non‐linear parametric models, derived from the mechanisms of HIV infection and drug action, have been used to fit short‐term clinical data from AIDS clinical trials. However, it is found that the parametric models may not be adequate to fit long‐term HIV dynamic data. To preserve the meaningful interpretation of the short‐term HIV dynamic models as well as to characterize the long‐term dynamics, we introduce a class of semi‐parametric non‐linear mixed‐effects (NLME) models. The models are non‐linear in population characteristics (fixed effects) and individual variations (random effects), both of which are modelled semi‐parametrically. A basis‐based approach is proposed to fit the models, which transforms a general semi‐parametric NLME model into a set of standard parametric NLME models, indexed by the bases used. The bases that we employ are natural cubic splines for easy implementation. The resulting standard NLME models are low‐dimensional and easy to solve. Statistical inferences that include testing parametric against semi‐parametric mixed‐effects are investigated. Innovative bootstrap procedures are developed for simulating the empirical distributions of the test statistics. Small‐scale simulation and bootstrap studies show that our bootstrap procedures work well. The proposed approach and procedures are applied to long‐term HIV dynamic data from an AIDS clinical study. Copyright © 2002 John Wiley & Sons, Ltd.
Optimal designs of two‐stage studies for estimation of sensitivity, specificity and positive predictive value
Authors: McNamee Roseanne 
Published: November 2002

AbstractThe cost efficiency of estimation of sensitivity, specificity and positive predictive value from two‐stage sampling designs is considered, assuming a relatively cheap test classifies first‐stage subjects into several categories and an expensive gold standard is applied at stage two. Simple variance formulae are derived and used to find optimal designs for a given cost ratio. The utility of two‐stage designs is measured by the reduction in variances compared with one‐stage simple random designs. Separate second‐stage design is also compared with proportional allocation (PA). The maximum percentage reductions in variance from two‐stage designs for sensitivity, specificity and positive predictive value estimation arePper cent, (1‐P) per cent andW, respectively, wherePis the population prevalence of disease andWthe population percentage of test negatives. The optimum allocation of stage‐two resources is not obvious: the optimum proportion of true cases at stage two may even be less than under PA. PA is near optimal for sensitivity estimation in most cases when prevalence is low, but inefficient compared with the optimal scheme for specificity. Copyright © 2002 John Wiley & Sons, Ltd.
Adjustment for misclassification in studies of familial aggregation of disease using routine register data
Authors: Andersen Elisabeth Wreford , Andersen Per Kragh 
Published: November 2002

AbstractThis paper discusses the misclassification that occurs when relying solely on routine register data in family studies of disease clustering. A register study of familial aggregation of schizophrenia is used as an example. The familial aggregation is studied using a regression model for the disease in the child including the disease status of the parents as a risk factor. If all the information is found in the routine registers then the disease status of the parents is only known from the time when the register started and if this information is used unquestioningly the parents who have had the disease before this time are misclassified as disease‐free. Two methods are presented to adjust for this misclassification: regression calibration and an EM‐type algorithm. These methods are used in the schizophrenia example where the large effect of having a schizophrenic mother hardly shows any signs of bias due to misclassification. The methods are also studied in simulations showing that the misclassification problem increases with the disease frequency. Copyright © 2002 John Wiley & Sons, Ltd.
Updating of covariates and choice of time origin in survival analysis: problems with vaguely defined disease states
Authors: Liestøl Knut , Andersen Per Kragh 
Published: November 2002

AbstractThis paper discusses survival analysis based on updated covariates with focus on proportional hazard regression in situations where some disease states may be vaguely defined. Analyses of a trial in liver cirrhosis are used to motivate the discussion. We use problems caused by inclusion of recordings from unscheduled follow‐ups to illustrate the importance of appropriate coding of covariates and describe how such problems may be approached using appropriately ‘lagged’ covariates. The choice of time origin is discussed with emphasis on situations where disease initiation is difficult to define. Simulations are used to assess the effect of an erroneously specified time origin. It is argued that age or calendar time may frequently be sensible time variables. Copyright © 2002 John Wiley & Sons, Ltd.
Power and sample size for DNA microarray studies
Authors: Lee Mei‐Ling Ting , Whitmore G. A. 
Published: November 2002

AbstractA microarray study aims at having a high probability of declaring genes to be differentially expressed if they are truly expressed, while keeping the probability of making false declarations of expression acceptably low. Thus, in formal terms, well‐designed microarray studies will have high power while controlling type I error risk. Achieving this objective is the purpose of this paper. Here, we discuss conceptual issues and present computational methods for statistical power and sample size in microarray studies, taking account of the multiple testing that is generic to these studies. The discussion encompasses choices of experimental design and replication for a study. Practical examples are used to demonstrate the methods. The examples show forcefully that replication of a microarray experiment can yield large increases in statistical power. The paper refers to cDNA arrays in the discussion and illustrations but the proposed methodology is equally applicable to expression data from oligonucleotide arrays. Copyright © 2002 John Wiley & Sons, Ltd.
Studies of mitochondrial DNA, allozyme and morphometric variation in a house mouse hybrid zone
Authors: HAUFFE HEIDI C. , FRAGUEDAKIS-TSOLIS STELLA , MIROL PATRICIA M. , SEARLE JEREMY B. 
Published: November 2002

An unusual chromosomal hybrid zone of the house mouse, Mus musculus domesticus, exists in Upper Valtellina, Northern Italy, consisting of four Robertsonian (Rb) races and the standard (all-acrocentric, or 2n = 40) race, all hybridizing freely within 10 km2. The hybrid zone in Valtellina provides an excellent opportunity to study the role of Rb fusions in reproductive isolation and speciation. This hybrid zone has already been well studied for the distribution of Rb fusions and the fertility of hybrids, but in order to understand the dynamics of the zone, a basic understanding of the origin and genetic similarity of the chromosomal races is necessary. This paper presents the results of three different methods of measuring genetic differentiation: multivariate analysis of morphological traits and analyses of allozyme variation and mitochondrial DNA sequences. The standard race is clearly distinguishable from the three Rb races by all three methods, but the Rb races are not distinguishable from one another. This provides strong evidence for our previous suggestions that the well-established Rb races in Valtellina are closely related, and that the standard race was introduced into the valley more recently from a distant source. The fact that the Rb races are indistinguishable is also consistent with our hypothesis that a within-village speciation event involving two of the races (Hauffe & Searle, 1992) was a recent occurrence. The low level of allozyme heterozygosity among the Rb races suggests that these populations are the products of at least one bottleneck. The present article substantially extends earlier studies and provides the first detailed morphological and molecular analysis of this complex hybrid zone.