bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nonstoichiometric polyelectrolyte complex of carboxymethylcellulose and N‐methylated poly(2‐vinylpyridine): Formation of a gel‐like structure
Authors: Vishalakshi B. , Ghosh Soumyadeb 
Published: June 2003

AbstractThe formation of polyelectrolyte complexes between carboxymethylcellulose and N‐methylated poly(2‐vinylpyridine), at a nonstoichiometric mixing ratio, was studied. Various methods, such as viscometry, turbidimetry, electrophoresis, and optical spectroscopy, were used to investigate the complexes with respect to their composition, structure, and stability in aqueous systems of different ionic strengths. A gel‐like structure was proposed for the nonstoichiometric polyelectrolyte complexes. Two steps of complex formation—ionic bond formation followed by its rearrangement—were identified. The conformational change of the polyelectrolyte chains in the complexes, responsible for the slower and latter step, was followed by viscometry, and the results were interpreted on the basis of a model proposed for the kinetics of swelling of hydrogels. A similarity was found between the kinetics of diffusion of polymer segments responsible for the swelling of a macrogel of a nonionic polymer and the rearrangement of ionic bonds leading to the formation of a nonstoichiometric polyelectrolyte complex el. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2288–2295, 2003
Building sustainable science curriculum: Acknowledging and accommodating local adaptation
Authors: Barab Sasha Alexander , Luehmann April Lynn 
Published: June 2003

AbstractA core challenge facing science educators is how to develop and support the implementation of project‐based, technology‐rich science curriculum that is consistent with international calls for a “new approach” to science education while at the same time meeting the everyday needs of classroom teachers. In this article, we discuss the challenges of scaling out university‐developed, project‐based curricula, providing a contextualizing frame for the articles that constitute this current issue of Science Education. Specifically, we overview (1) what constitutes and why implement inquiry‐based, project‐focused learning environments, (2) the role of integrating technology to support their implementation, (3) the value of engaging in design experiments for their development, (4) the importance of allowing for local adaptation, and (5) the process of curricular diffusion. In our thinking, the process of dissemination is not simply “rubber‐stamping” the same program into multiple contexts; rather, the process of large‐scale adoption involves additional, individual teacher‐directed design, fitting, and adaptation for local circumstances. © 2003 Wiley Periodicals, Inc. Sci Ed 87:454–467, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/sce.10083
Research towards an expanded understanding of inquiry science beyond one idealized standard
Authors: Songer Nancy Butler , Lee Hee‐Sun , McDonald Scott 
Published: June 2003

AbstractThe work presented builds on a multiyear effort to study the implementation and adaptation of Kids as Global Scientists (KGS), an inquiry‐based, technology‐rich middle school learning environment enacted simultaneously in hundreds of classrooms across the nation. Two groups of teachers participated in this study. One group consists of “maverick” teachers: those distributed across the nation that find us and customize our program to their needs without systematic professional development. This group of teachers tends to work in schools with a relatively rich fund of resources and supports. Another group—urban teachers—resulted from a recent partnership between KGS and teachers from a large, high‐poverty urban school district. We provide these teachers with targeted professional development to help them overcome constraints common to their schools. This study provides profiles of both maverick and urban teachers, and then examines teacher and student data from five focus classrooms that were successful in implementing KGS. In all cases, successful classrooms were defined as those where students made significant positive gains on open‐ended and multiple‐choice assessments. The focus classrooms consisted of three classrooms from urban teachers in high‐poverty environments and two classrooms from maverick teachers in middle‐class suburban environments. The paper discusses the need for research that provides multiple exemplars of classroom science inquiry that are realized through large‐scale enactments responsive to diverse learning environments. © 2003 Wiley Periodicals, Inc. Sci Ed 87:490–516, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/sce.10085
WISE design for knowledge integration
Authors: Linn Marcia C. , Clark Douglas , Slotta James D. 
Published: June 2003

AbstractScaling research‐based curriculum to the multitude of science teaching standards and contexts has proven difficult in the past. To respond to the challenge, the Web‐based Inquiry Science Environment (WISE) offers designers a technology‐enhanced, research‐based, flexibly adaptive learning environment. The learning environment can incorporate new features such as modeling tools or hand‐held devices. Using WISE, design teams can create projects that bend but do not break when customized to support new school contexts and state standards. WISE curriculum projects are created by diverse design teams that include classroom teachers, technologists, discipline experts, pedagogy researchers, and curriculum designers. WISE inquiry projects incorporate Internet materials and build on the commitments and talents of teachers as well as the constraints and opportunities of their classroom contexts rather than imposing new practices without concern for past successes. These design teams create projects that incorporate diverse features of the WISE learning environment to form specific patterns that are then combined into whole projects. We refer to the whole projects as implementing curriculum design patterns for student activities. The projects are tested to determine how the curriculum design patterns promote knowledge integration, then reviewed by WISE researchers and revised accordingly (see M. C. Linn, P. Bell, & E. A. Davis, in press, Internet Environments for Science Education). Hillsdale, NJ: Erlbaum.). The most successful projects become part of the WISE library. This paper describes WISE design team practices, features of the WISE learning environment, and patterns of feature use in current library projects. The success of WISE in classrooms illustrates how flexibly adaptive projects can meet the needs of diverse teachers. Variation amongst library projects shows that designers can support inquiry with a wide variety of activities. Taken together, the library of projects and the success of students learning from them suggest that sustainable curricular innovations require extensive opportunities for customization and flexibly adaptive designs. © 2003 Wiley Periodicals, Inc. Sci Ed 87:517–538, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/sce.10086
REML and ML estimation for clustered grouped survival data
Authors: Lam K. F. , Ip David 
Published: June 2003

AbstractClustered grouped survival data arise naturally in clinical medicine and biological research. For example, in a randomized clinical trial, the variable of interest is the time to occurrence of a certain event with or without a new treatment and the data are collected from possibly correlated subjects from independent clusters. However it is sometimes impossible or too expensive to monitor the experimental subjects continuously. The subjects are examined regularly and the continuous survival data are thus grouped into a discrete time scale. With such a design, researchers are mainly interested in the effectiveness of the new treatment as well as the correlation among subjects from the same cluster, namely the intracluster correlation. This paper suggests a random effects approach to the estimation of the regression parameter with various choices of regression model and also the dependence parameter which characterizes the intracluster correlation. Time dependent covariates can be accommodated in the proposed model, and the estimation procedure will not be further complicated with large cluster sizes. The proposed method is applied to the data from the Diabetic Retinopathy Study, the objective of which is to evaluate the effectiveness of laser photocoagulation in delaying or preventing the onset of blindness in the left and right eyes of individuals with diabetes‐associated retinopathy. The intracluster correlation using a grouped proportional hazards regression model can be estimated and the relationship between the regression parameter estimates based on the random effects approach and the marginal approach using a dynamic logistic regression model are discussed. Results from a simulation study of the proposed method are also presented. Copyright © 2003 John Wiley & Sons, Ltd.
Confidence limits for the ratio of two rates based on likelihood scores: non‐iterative method
Authors: Graham P. L. , Mengersen K. , Morton A. P. 
Published: June 2003

AbstractThis paper describes a method for creating a confidence interval for the ratio of rates using the score statistic. This non‐iterative and easy to apply procedure produces confidence intervals that are suitable for use with Poisson data and simulation results indicate that it is close to the nominal level for a wide range of scenarios. Copyright © 2003 John Wiley & Sons, Ltd.
Implications of genetic traits on vaccine efficacy
Authors: Murthy B. N. 
Published: June 2003

AbstractLiterature on genetic screening in the community suggests that people having specific genotypes may either get or protect from infection, for example, malaria, human papiloma virus, and haemophilic influenza, for which vaccines are either already developed or being targeted. In such a situation, the evaluation of the efficacy of vaccine in the community needs to be examined with caution. In this paper, I present a method for the estimation of vaccine efficacy (VE) in the presence of genetic traits/component (θ) and the sample size required to estimate the 95 per cent CI with a given relative width for the estimated vaccine efficacy. Considering true efficacy ranging from 40 to 80 per cent and the possible values of the genetic component (θ) ranging from 0 to 60 per cent, the VE was estimated. The 95 per cent confidence intervals (CI) for the estimated VE for relative widths (R) 1.0 and 0.1 were computed. The sample sizes required for each of the unvaccinated and vaccinated cohorts were computed for estimating the 95 per cent CI for given incidence rates in the unvaccinated (Iu) cohort. In the presence of genetic traits I found that the VE was consistently overestimated. There existed change in the location as well as the asymmetry of the 95 per cent CIs over the point estimate of VE. The sample size required for estimating 95 per cent CI of VE was substantially reduced, resulting in savings. The more the genetic component (θ) affecting disease in the community, the more the savings in sample size. I examined the above estimators for (i) VE, (ii) 95 per cent CI for VE and (iii) sample size required for estimating 95 per cent CI of VE using the real‐life data from the Haemophilus influenzae type b vaccine trial conducted in Finland and the global genetic structure of encapsulated H. influenza. Because of escalated VE and large savings in sample size for estimating the 95 per cent CI for VE, I recommend that the design should consider the genetic component that causes/protects from infection/disease for the evaluation of efficacy of vaccine in the field. Copyright © 2003 John Wiley & Sons, Ltd.
Comparing HLA antigen frequencies between two groups of patients
Authors: Follmann Dean A. 
Published: June 2003

AbstractFor diseases that involve the immune system, the alleles of the human leukocyte antigen (HLA) complex can play a major role. For example, if responsiveness to therapy is immunologically mediated, one would think that responders and non‐responders might tend to have different HLA alleles. However, comparing the frequencies between the two groups of patients at each allele can introduce a substantial multiple comparisons problem as the number of alleles is large. This paper proposes an efficient two‐stage procedure for identifying alleles that may mediate response. In the first‐stage, the distribution of all alleles for the patients are compared to a reference population and a few alleles are selected. These candidate alleles are then compared between the two groups of patients using a modest Bonferroni correction. The two‐stage procedure strongly controls the type I error rate as the first‐stage selection is statistically independent of the second‐stage tests. We analyse a cohort of patients with bone marrow failure who are classified as responders or non‐responders to immunosuppressive therapy. Published in 2003 by John Wiley & Sons, Ltd.
Comparing longitudinal binary outcomes in an observational oral health study
Authors: Shelton Brent J. , Gilbert Gregg H. , Lu Zhenmei , Bradshaw Patrick , Chavers L. Scott , Howard George 
Published: June 2003

AbstractObservational studies continue to be recognized as viable alternatives to randomized trials when making treatment group comparisons, in spite of drawbacks due mainly to selection bias. Sample selection models have been proposed in the economics literature, and more recently in the medical literature, as a method to adjust for selection bias due to observed and unobserved confounders in observational studies. Application of these models has been limited to cross‐sectional observational data and to outcomes that are continuous in nature. In this paper we extend application of these models to include longitudinal studies and binary outcomes. We apply a two‐stage probit model using GEE to account for correlated longitudinal binary chewing difficulty outcomes. Chewing difficulty was measured every six months during a 24‐month period between two groups of subjects: those either receiving or not receiving dental care. Dental care use was measured at six‐month intervals as well. Results from our proposed model are compared to results using a standard GEE model that ignores the potential selection bias introduced by unobserved confounders. In this application, accounting for selection bias made a major difference in the substantive conclusions about the outcomes of interest. This is due in part to an adverse selection phenomenon in which those most in need of treatment (and consequently most likely to benefit from it) are actually the ones least likely to seek treatment. Our application of sample selection models to binary longitudinal observational outcome data should serve as impetus for increased utilization of this promising set of models to other health outcomes studies. Copyright © 2003 John Wiley & Sons, Ltd.
Bias correction of two‐state latent Markov process parameter estimates under misclassification
Authors: Rosychuk Rhonda J. , Thompson Mary E. 
Published: June 2003

AbstractA discretely observed two‐state process may misclassify the state of an unobservable continuous‐time, two‐state Markov process. We examine the behaviour of maximum likelihood transition probability estimates as functions of known misclassification probabilities. Since maximum likelihood estimators are not available in closed form, we provide two alternatives for bias‐adjusted estimation. In the case of large samples, the asymptotic bias is quantified and estimators are constructed iteratively using transition counts and specified misclassification probabilities. For finite samples, we provide an approximation based on partial derivatives. Estimators that are bias‐adjusted to a first approximation are easily constructed and may serve well when misclassification probabilities are known to be small. Simulation studies reveal the effect of misclassification on estimation. Repeated diagnostic testing data illustrate the approaches. Copyright © 2003 John Wiley & Sons, Ltd.
EASYLOCAL++: an object‐oriented framework for the flexible design of local‐search algorithms
Authors: Di Gaspero Luca , Schaerf Andrea 
Published: June 2003

AbstractLocal search is a paradigm for search and optimization problems, which has recently evidenced to be very effective for a large number of combinatorial problems. Despite the increasing interest of the research community in this subject, there is still a lack of a widely‐accepted software tools for local search.We propose EASYLOCAL, an object‐oriented framework for the design and the analysis of local‐search algorithms. The abstract classes that compose the framework specify and implement the invariant part of the algorithm and are meant to be specialized by concrete classes that supply the problem‐dependent part. The framework provides the full control structures of the algorithms, and the user has only to write the problem‐specific code. Furthermore, the framework comes with some tools that simplify the analysis of the algorithms.The architecture of EASYLOCAL provides a principled modularization for the solution of combinatorial problems by local search and helps the user by deriving a neat conceptual scheme of the application. It also supports the design of combinations of basic techniques and/or neighborhood structures.The framework has been tested in some applicative domains and has proved to be flexible enough in the implementation of algorithms for the solution of various scheduling problems. Copyright © 2003 John Wiley & Sons, Ltd.
Trends in the Design, Manufacture and Evaluation of Wind Turbine Blades
Authors: Veers Paul S. , Ashwill Thomas D. , Sutherland Herbert J. , Laird Daniel L. , Lobitz Donald W. , Griffin Dayton A. , Mandell John F. , Musial Walter D. , Jackson Kevin , Zuteck Michael , Miravete Antonio , Tsai Stephen W. , Richmond James L. 
Published: June 2003

AbstractWind turbine blades continue to be the target of technological improvements by the use of better designs, materials, manufacturing, analysis and testing. As the size of turbines has grown over the past decade, designers have restrained the associated growth in blade weight to less than would have been possible through simple scaling‐up of past approaches. These past improvements are briefly summarized. Manufacturing trends and design drivers are presented, as are the ways these design drivers have changed. Issues related to blade material choices are described, first for the currently dominant glass fibre technology and then for the potential use of carbon fibres. Some possible directions for future blade design options are presented, namely new planforms, aerofoils and aeroelastic tailoring. The significant improvement in sophistication of stress analysis and full‐scale blade testing are also discussed. Copyright © 2003 John Wiley & Sons, Ltd.
Wind power and the conditions at a liberalized power market
Authors: Morthorst P. E. 
Published: June 2003

AbstractWind power is undergoing a rapid development nationally as well as globally and in a number of countries covers an increasing part of the power supply. At the same time an ongoing liberalization of power markets is taking place and to an increasing extent the owners of wind power plants will themselves have to be responsible for trading the power at the spot market and financially handling the balancing. In the western part of Denmark (Jutland/Funen area), wind‐generated power from time to time covers almost 100% of total power consumption. Therefore some examples are chosen from this area to analyse in more detail how well large amounts of wind power in the short‐term are handled at the power spot market. It turns out that there is a tendency that more wind power in the system in the short run leads to relatively lower spot prices, while less wind power implies relatively higher spot prices, although, with the exception of December 2002, in general no strong relationship is found. A stronger relationship is found at the regulating market, where there is a fairly clear tendency that the more wind power produced, the higher is the need for down‐regulation, and, correspondingly, the less wind power produced, the higher is the need for up‐regulation. In general for the Jutland/Funen area the average cost of down‐regulation is calculated as 1·2 c€/kWh regulated for 2002, while the cost of up‐regulation amounts to 0·7 c€/kWh regulated. Copyright © 2003 John Wiley & Sons, Ltd.
Wind Resource Estimation—An Overview
Authors: Landberg Lars , Myllerup Lisbeth , Rathmann Ole , Petersen Erik Lundtang , Jørgensen Bo Hoffmann , Badger Jake , Mortensen Niels Gylling 
Published: June 2003

AbstractThis article gives an overview of the different ways the wind resource at a site can be estimated. Eight separate ways have been identified. Each of these will be described in some detail, and advantages and disadvantages of each of them will be discussed. Copyright © 2003 John Wiley & Sons, Ltd.
Short‐term Prediction—An Overview
Authors: Landberg Lars , Giebel Gregor , Nielsen Henrik Aalborg , Nielsen Torben , Madsen Henrik 
Published: June 2003

AbstractThis article gives an overview of the different methods used today for predicting the power output from wind farms on the 1–2 day time horizon. It describes the general set‐up of such prediction systems and also gives examples of their performance. Copyright © 2003 John Wiley & Sons, Ltd.
Quantifying shade using a standard environment
Authors: Langman V.A. , Rowe M. , Forthman D. , Langman N. , Black J. , Walker T. 
Published: June 2003

AbstractThe purpose of this study was to quantify the thermal microclimate provided by a shade structure in the African elephant enclosure at Zoo Atlanta. The hypothesis was that the interior of a weather instrument shelter (a Stevenson screen) would provide the maximum environmental shielding and the coolest possible ambient conditions without artificial heating or cooling. The ambient conditions inside the Stevenson screen were compared with the ambient conditions in the shaded and nonshaded sections of the exhibit to quantify the extremes possible under the environmental conditions. The Stevenson screen reduced the radiant heat load by 766 W m−2. The shade structure in the elephant enclosure reduced the radiant heat load by 278 W m−2, which was 37% of the total possible reduction represented by the interior of the Stevenson screen. The longwave radiant heat was 10% greater in the direct sun and 37% greater in the shaded area than the shortwave radiant heat. The shade structure reduced the shortwave radiant heat by 254 W m−2 or 43%, but only reduced the longwave radiant heat by 24Wm−2 or 3%. Shade structures alone may not provide adequate protection from radiant heat for captive species. A cool microclimate in an artificial enclosure should be designed to reduce all sources of radiant heat. Zoo Biol 22:253–260, 2003. © 2003 Wiley‐Liss, Inc.