bluuebunny/crossref_metadata_2025_split huggingface dataset:
A comparison of methods for adaptive sample size adjustment
Authors: Friede Tim , Kieser Meinhard 
Published: August 2002

AbstractIn fixed sample size designs, precise knowledge about the magnitude of the outcome variable's variance in the planning phase of a clinical trial is mandatory for an adequate sample size determination. Wittes and Brittain introduced the internal pilot study design that allows recalculation of the sample size during an ongoing trial using the estimated variance obtained from an interim analysis. However, this procedure requires the unblinding of the treatment code. Since unblinding of an ongoing trial should be avoided whenever possible, there should be some benefit of this design compared with blinded sample size recalculation procedures to justify the unveiling of the treatment code. In this paper, we compare several sample size recalculation procedures with and without unblinding. The simulation results indicate that the procedures behave similarly. In particular, breaking of the blind is not required for an efficient sample size adjustment. We also compare these pure sample size adaptation procedures with study designs which additionally allow for early stopping. Evaluation of the cumulative distribution function of the resulting sample sizes shows that the option for early stopping may lead to lower expectation but generally to a higher variability. The procedures are illustrated by an example of a trial in the treatment of depression. Copyright © 2001 John Wiley & Sons, Ltd.
Analysis of ulcer data using hierarchical generalized linear models
Authors: Lee Youngjo , Nelder John A. 
Published: August 2002

AbstractIn multi‐centre clinical trials, heterogeneities in individual hospital treatment effects can be modelled as random effects. Estimates of the individual hospital treatment effects and estimate of the mean treatment effect, allowing for the presence of overall hospital differences, are required, together with some measure of their uncertainty. Systematic inferences from the hierarchical‐likelihood are now possible, using hierarchical generalized linear models. We show how to construct profile likelihoods for the treatment effects of individual hospitals. Copyright © 2002 John Wiley & Sons, Ltd.
Complete imputation of missing repeated categorical data: one‐sample applications
Authors: West Colin P. , Dawson Jeffrey D. 
Published: August 2002

AbstractLongitudinal studies with repeated measures are often subject to non‐response. Methods currently employed to alleviate the difficulties caused by missing data are typically unsatisfactory, especially when the cause of the missingness is related to the outcomes. We present an approach for incomplete categorical data in the repeated measures setting that allows missing data to depend on other observed outcomes for a study subject. The proposed methodology also allows a broader examination of study findings through interpretation of results in the framework of the set of all possible test statistics that might have been observed had no data been missing. The proposed approach consists of the following general steps. First, we generate all possible sets of missing values and form a set of possible complete data sets. We then weight each data set according to clearly defined assumptions and apply an appropriate statistical test procedure to each data set, combining the results to give an overall indication of significance. We make use of the EM algorithm and a Bayesian prior in this approach. While not restricted to the one‐sample case, the proposed methodology is illustrated for one‐sample data and compared to the common complete‐case and available‐case analysis methods. Copyright © 2002 John Wiley & Sons, Ltd.
Cure model analysis in cancer: an application to data from the Children's Cancer Group
Authors: Sposto Richard 
Published: August 2002

AbstractThe most commonly used statistical methods for evaluating treatment or prognostic effects on cancer outcome – the logrank test and Cox regression analysis – rely on the proportional hazards (PH) assumption in that they have maximal power in this circumstance. Implicitly, these methods emphasize covariate effects on failure times rather than their effects on the proportion of long‐term survivors (‘cures’), which may be of equal or primary interest. In paediatric cancer, treatment has progressed dramatically in recent decades, and in many diagnoses cures are obtained in a large fraction of patients. A primary focus of clinical research is therefore the achievement of cure. Parametric cure model (PCM) analysis, introduced 50 years ago, is arguably better suited to the analytic requirements of clinical research in paediatric and other cancers where cure is achieved. In this paper two classes of PCMs are described and used to analyse examples from the Children's Cancer Group. These are compared to analyses using Cox regression analysis. Results from PCM analyses are similar or identical to Cox regression analysis when the PH assumption is appropriate. When it is not, PCMs can provide a coherent way to investigate and report covariate effects on the proportion cured separately from their effect on time to failure. Despite their reliance on explicit parametric forms, PCMs often provide a good description of cancer outcome, and are insensitive to lack of fit provided that follow‐up is sufficient. Copyright © 2002 John Wiley & Sons, Ltd.
Stress levels in nursing staff working in oncology
Authors: Escot C. , Artero S. , Gandubert C. , Boulenger J. P. , Ritchie K. 
Published: August 2002

AbstractCare of cancer patients may be a source of considerable stress. As part of a large scale longitudinal study of the interaction of biological, psychological and environmental factors in determining patient outcome, the mental and physical health status of 37 members of the nursing staff of a cancer hospital was examined. The study identifies risk factors for stress, professional ‘burn‐out’ and psychiatric morbidity. An assessment questionnaire also examined work time, work organization, relationships with colleagues, identification of stressful situations, and treatment of pain. Each subject completed three scales designed to measure stress and psychiatric morbidity: the Nursing Stress Scale, the Maslasch Burnout Inventory and the General Health Questionnaire. Item analysis suggested that stress is primarily related to inadequate training, lack of time to deal with the psychological component of care giving especially terminal care, and relationship difficulties with other medical staff. Multiple analysis of correspondence indicated that in the face of stress, risk factors for professional burnout are high psychiatric symptomatology, lack of information at the time of diagnosis, poor perceived health, relationship difficulties with patients and their families, and work uncertainties. Copyright © 2001 John Wiley & Sons, Ltd.
Cognitive processes involved in the appraisal of stress
Authors: Guillet Laurent , Hermand Danièle , Mullet Etienne 
Published: August 2002

AbstractFour experiments were organized around a central question: What is the form of relationship between estimated stress level on the one hand and situation strain, personal resources and social support, on the other? The first experiment examined the form of the relationship between estimated level of stress, situation strain and personal resources. The participants were students. They integrated situation strain and personal resources information in a non‐additive way. In particular, the effect of personal resources on the estimated level of stress varied as a function of the level of situation strain considered. When the situation strain was low, the stress level related with this circumstance largely depended on the personal resources of the individual. When the situation strain was high, the stress level related with this circumstance was much less dependent on the personal resources of the individual. The second experiment replicated these results among first‐aid workers, fire‐fighters and persons that had recently been injured. The third and fourth experiments replicated these results in various conditions differing as regards the level of social support. Copyright © 2002 John Wiley & Sons, Ltd.
Finding the right mix: franchising, organizational learning, and chain performance
Authors: Sorenson Olav , Sørensen Jesper B. 
Published: August 2002

AbstractFranchising provides an increasingly important vehicle for entrepreneurial wealth creation and accounts for a large and growing share of business in the retail and service sectors. Chains—which operate in dispersed markets—most frequently use this form of governance. These firms must balance the centralization and standardization required for efficiency with the adaptation needed for success in varied local markets. By adopting an organizational learning perspective, we argue that the mix of company‐owned and franchised units affects this balance, thereby influencing chain performance. In particular, the different incentives facing company managers and the entrepreneurs that manage franchises encourage distinct patterns of organizational learning. Franchised establishments provide better opportunities for the firm to learn through experimentation; however, companies find it easier to diffuse this information and enforce standards through their company‐owned units. Analyses of franchised restaurant chains in the United States provide empirical evidence of this trade‐off. Copyright © 2001 John Wiley & Sons, Ltd.
The effects of CEO equity ownership and firm diversification on risk taking
Authors: Eisenmann Thomas R. 
Published: August 2002

AbstractThis research explores the effects of CEO equity ownership and corporate diversification on firms' risk‐taking and risk avoidance behaviors. Hypotheses regarding these effects are tested through econometric analysis of mergers in the U.S. cable television industry. Risk taking and avoidance are measured as horizontal expansion through acquisitions and as the divestiture of assets, respectively, in the face of increasing environmental turbulence. Copyright © 2002 John Wiley & Sons, Ltd.
Activity theory and the design of educational systems: examining the mediational importance of conversationa
Authors: Jenlink Patrick M. 
Published: August 2002

AbstractEducational systems design, largely communicative in nature, depends on discourse as a semiotic tool for mediation within the cognitive, cultural, and creative activities essential to overcoming deep sociohistorical patterns woven into the fabric of society. The use of activity theory as a framework for understanding the mediational importance of conversation in educational systems design represents a sociocultural and inquiry‐oriented perspective that illuminates the relationship of design as a human activity system and the sociocultural context in which the design activity unfolds. As in Banathy's idealized concept of social systems design the importance of conversation is acknowledged in activity theory. Likewise, the importance of language as a symbol‐based mediational tool connects systems design and activity theory. Essential to the design of human activity systems, such as educational systems, is the ability of participants to acknowledge the dialectical contradictions that have emerged in their past or present activity system(s), while also acknowledging the importance of creating dialogical relationships toward the goal of designing new systems.Design conversation and systems language underlie the socially constructed process of educational systems design. The framework of activity theory suggests that mediational artifacts such as language and discourse do not exist inside or outside of individual consciousness; rather they reside on the borderline between oneself as designer and the others who are also designers and users. From this perspective one has to take and use cultural artifacts (i.e., design conversation and systems language), to appropriate these artifacts with the intentions of the designer and the design community.This paper will examine the mediational importance of conversation in the design of human activity systems that are educative and intentioned as learning systems. The paper will first examine activity theory and human activity systems, seeking to make connections between the systemic nature of activity theory as drawn from sociocultural learning theory and human activity systems grounded in social systems design. The paper will then examine educational systems design, viewing design as post‐epistemological in nature. Design conversation is then deconstructed to create an understanding of how this type of discourse draws from other genres or types of discourse such as dialogue, discussion, dialectic, ethical and critical discourse. The paper will then elaborate on design conversation as activity through an activity theory framework, demonstrating the dynamic relationship between participants, purpose, mediational artifacts, community, design work, and sociocultural rules governing design. The author will conclude with reflections on the mediational importance of design conversation in transcending dualisms that challenge social change. Copyright © 2001 John Wiley & Sons, Ltd.
Relationship between blockade of dopamine transporters by oral methylphenidate and the increases in extracellular dopamine: Therapeutic implications
Authors: Volkow Nora D. , Wang Gene‐Jack , Fowler Joanna S. , Logan Jean , Franceschi Dinko , Maynard Laurence , Ding Yu‐Shin , Gatley Samuel J. , Gifford Andrew , Zhu Wei , Swanson James M. 
Published: August 2002

AbstractMethylphenidate (Ritalin) is an effective drug in the treatment of attention deficit hyperactivity disorder. However, the doses required therapeutically vary significantly between subjects and it is not understood what determines these differences. Since methylphenidate's therapeutic effects are in part due to increases in extracellular DA secondary to blockade of dopamine transporters (DAT), the variability could reflect differences in levels of DAT blockade. Here we used PET to assess if for a given dose of methylphenidate the differences in DAT blockade account for the variability in methylphenidate‐induced increases in extracellular DA. Ten healthy adult subjects were tested before and 60 min after oral methylphenidate (60 mg) with PET to estimate DAT occupancy (with [11C]cocaine as the radioligand) and levels of extracellular DA (with [11C]raclopride as the D2 receptor radioligand that competes with endogenous DA for binding to the receptor). Methylphenidate significantly blocked DAT (60 ± 11%) and increased extracellular DA in brain (16 ± 8% reduction in [11C]raclopride binding in striatum). However, the correlation between methylphenidate‐induced DAT blockade and DA increases was not significant. These results indicate that for a given dose of methylphenidate, individual differences in DAT blockade are not the main source for the intersubject variability in MP‐induced increases in DA. This finding suggests that individual differences in response to MP are due in part to individual differences in DA release, so that for an equivalent level of DAT blockade, MP would induce smaller DA changes in subjects with low than with high DA cell activity. Synapse 43:181–187, 2002. © 2002 Wiley‐Liss, Inc.
Effects of fasting and intermittent fasting on rat hepatocarcinogenesis induced by diethylnitrosamine
Authors: Rocha Noeme Sousa , Barbisan Luís Fernando , de Oliveira Maria Luiza Cotrim , de Camargo João Lauro Viana 
Published: August 2002

AbstractThe influences of fasting on DEN‐initiation and of intermittent fasting (IF) on the rat liver chemical carcinogenesis process were evaluated in a 52‐week long assay. Three groups of adult male Wistar rats were used: Groups 1 to 3 were treated with a single i.p. injection of 200 mg/kg of diethylnitrosamine (DEN). Group 2 was submitted to 48 h fasting prior to DEN treatment. After the 4th week, Group 3 was submitted to IF, established as 48 h weekly fasting during 48 weeks, while Groups 1 and 2 were fed ad libitum until the 52nd week. All animals were submitted to 70% partial hepatectomy and sacrificed at the 3rd and 52nd weeks, respectively. Fasting prior to DEN‐initiation did not influence the development of altered foci of hepatocytes (AFHs) and of hepatic nodules (Group 2 vs. Group G1). IF inhibited the development of preneoplastic lesions, since this dietary regimen decreased the number and the size of glutathione S‐transferase (GST‐P) positive foci and the number and size of liver nodules (Group G3 vs. Group G1). The inhibitory effect of IF was also reflected in the development of clear and basophilic cell foci. These results indicate that long‐term IF regimen exerts an anti‐promoting effect on rat hepatocarcinogenesis induced by DEN. Teratogenesis Carcinog. Mutagen. 22:129–138, 2002. © 2002 Wiley‐Liss, Inc.
Versatility and specificity in flavoenzymes: Control mechanisms of flavin reactivity
Authors: Miura Retsu 
Published: August 2002

AbstractFlavoenzymes are characterized by their remarkable versatility and strict specificity. The former can be grasped when flavoenzymes are treated as a whole, while the latter refers to each flavoenzyme in which the broad versatility of flavin is specifically controlled. The versatility stems from the variety of the redox, ionic, and electronic states that the flavin ring system can adopt. Versatility of flavoenzymes is reflected in their classification, which has generally been based on substrates and reactions catalyzed. A different classification is presented according to the number of electrons transferred in the reductive and oxidative half reactions. Specificity of each flavoenzyme is understood in terms of the regulatory mechanism of the broad reactive potentiality of flavin. The elements of this regulatory mechanism include hydrogen‐bonding network, electrostatic effect, charge‐transfer interaction, positioning between a substrate/ligand and flavin, and modulation of resonance hybridization, each of which is explained with relevant examples provided mainly by studies from the author’s group. © 2001 John Wiley & Sons, Inc. and The Japan Chemical Journal Forum Chem Rec 1:183–194, 2001
Transformation of organic molecules on the low‐valent {M(Ph2PCH2CH2PPh2)2} moiety derived from trans‐[M(N2)2(Ph2PCH2CH2PPh2)2] or related complexes (M = MO, W)
Authors: Seino Hidetake , Mizobe Yasushi , Hidai Masanobu 
Published: August 2002

AbstractA zero‐valent {M(Ph2PCH2CH2PPh2)2} moiety (M = Mo, W) generated in situ by dissociation of the N2 ligands in trans‐[M(N2)2(Ph2PCH2CH2PPh2)2] can activate π‐accepting organic molecules including isocyanides and nitriles, which undergo the electrophilic attack caused by a strong π‐donation from a zero‐valent metal center. Cleavage of a variety of C–X bonds (X = H, C, N, O, P, halogen) also occurs at their electron‐rich sites through oxidative addition to form reactive intermediates, which subsequently degradate to yield smaller molecules either bound to or dissociated from the metal center. The mechanism is substantiated unambiguously by isolation of numerous intermediate stages. © 2001 John Wiley & Sons, Inc. and The Japan Chemical Journal Forum Chem Rec 1:349–361, 2001
Use of imposex (pseudohermaphroditism) as indicator of the occurrence of organotin compounds in Portuguese coastal waters—Sado and Mira estuaries
Authors: Pessoa M. F. , Fernando A. , Oliveira J. S. 
Published: August 2002

AbstractOrganotin compounds, including tributyltin (TBT), are a class of the most toxic xenobiotics occurring in aquatic systems. High concentration levels in waters and sediments are mainly due to their extensive use as biocides and high persistence when present in sediments under anaerobic conditions. Toxicity studies have revealed the acute effects of TBT for aquatic organisms at concentrations as low as 1 μg/L, and the induction of imposex at levels below 0.5 ng/L TBT (as Sn). At 20 ng/L TBT (as Sn) causes sterility and is followed with the disappearance of the most sensitive neogastropods on a given shore. Imposex is the most sensitive response of all known pathological conditions for nontarget organisms following an exposure to tributyltin. In this study results are discussed that were obtained from two monitoring sites with different anthropogenic background using imposex monitoring as an indicator of TBT concentrations, as well as chemical analysis of tissue ofHinia (=Nassarius) reticulata(L.) (Gastropoda). © 2001 John Wiley & Sons, Inc. Environ Toxicol 16: 234–241, 2001
Channel estimation in narrowband wireless communication systems
Authors: Arslan Hüseyin , Bottomley Gregory E. 
Published: August 2002

AbstractChannel estimation is an integral part of standard adaptive receiver designs used in narrowband, digital wireless communication systems. In this tutorial paper, commonly used approaches to channel estimation are reviewed. Both time‐invariant and time‐varying channels are considered. For time‐varying channels, both pilot symbol interpolation and data‐directed channel tracking are considered. Applications include the Global System for Mobile communications, the Enhanced Data rates for Global Evolution system, and another Time‐Division Multiple‐Access system known as Telecommunications Industry Association/Electronics Industry Association/Interim Standard—136 (TIA/EIA/IS‐136 or IS‐136). Copyright © 2001 John Wiley & Sons, Ltd.
A survey of multiuser/multisubchannel detection schemes based on recurrent neural networks
Authors: Engelhart Achim , Teich Werner G. , Lindner Jürgen , Jeney Gábor , Imre Sándor , Pap László 
Published: August 2002

AbstractMultiuser/multisubchannel detection schemes based on a recurrent neural network (RNN) structure are a promising alternative to conventional detection schemes, both in terms of performance and complexity. This paper gives an overview of different approaches that make use of the results of RNN research for multiuser/multisubchannel detection. The detectors' results are compared with the results of conventional detection schemes in simulations of the uplink of a DS‐CDMA packet transmission system. Copyright © 2002 John Wiley & Sons, Ltd.
Resource management in power‐controlled cellular wireless systems
Authors: Xiao Mingbo , Shroff Ness B. , Chong Edwin K. P. 
Published: August 2002

AbstractThe efficient management of wireless resource is essential to the success of wireless systems. While power control is traditionally considered as a means to counteract the detrimental effects of channel fading, it is also a flexible mechanism to provide Quality of Service to individual users, and can be used as a platform for radio resource management. In this paper, we review the developments of distributed power control and related resource management problems in cellular wireless systems. We highlight the feasibility issue in a power‐controlled system, which enables us to push the system toward high efficiency, and prevent the system from collapsing at the same time. Considering the unique features of multimedia traffic to be supported in future wireless systems, we also review power and rate control schemes proposed for wireless data, and present a framework for utility‐based power control as a possible candidate for distributed power control of multimedia wireless systems. Copyright © 2001 John Wiley & Sons, Ltd.