bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sample size considerations in observational health care quality studies
Authors: Normand Sharon‐Lise T. , Zou Kelly H. 
Published: August 2002

AbstractA common objective in health care quality studies involves measuring and comparing the quality of care delivered to cohorts of patients by different health care providers. The data used for inference involve observations on units grouped within clusters, such as patients treated within hospitals. Unlike cluster randomization trials where often clusters are randomized to interventions to learn about individuals, the target of inference in health quality studies is the cluster. Furthermore, randomization is often not performed and the resulting biases may invalidate standard tests. In this paper, we discuss approaches to sample size determination in the design of observational health quality studies when the outcome is binary. Methods for calculating sample size using marginal models are briefly reviewed, but the focus is on hierarchical binomial models. Sample size in unbalanced clusters and stratified designs are characterized. We draw upon the experiences that have arisen from a study funded by the Agency for Healthcare Research and Quality involving assessment of quality of care for patients with cardiovascular disease. If researchers are interested in comparing clusters, hierarchical models are preferred. Copyright © 2002 John Wiley & Sons, Ltd.
Country estimates of maternal mortality: an alternative model
Authors: Hakkert Ralph 
Published: August 2002

AbstractEver since the publication of country level estimates of maternal mortality for 1990 by WHO and UNICEF, there has been some degree of controversy about these estimates. The recent publication of a 1995 revision, based on the modification of the multivariate model used for 1990, has not managed to put this controversy to rest. Countries with national estimates of their own have generally protested against the higher figures resulting from the multivariate modelling approach used by WHO and UNICEF, but some experts have also objected to the model itself. As a result of earlier discussions with the WHO/UNICEF team, some adjustments were incorporated into their model, notably the age standardization of maternal mortality ratios (MMRs) and proportions maternal among deaths of females of reproductive age (PMDF) of demographic and health surveys (DHS) direct sisterhood data, as the use of unstandardized values was shown to cause systematic biases. However, a model feature that continued to be controversial was the use of the PMDF as the dependent variable. As will be shown in this paper, the use of this dependent variable has a number of conceptual and practical disadvantages, such as its dependence on non‐maternal deaths and the need for separate projections of births and deaths of women of reproductive age, in order to convert the estimated PMDF into a more conventional MMR. The latter greatly increases the uncertainty of the resulting MMR estimates, even though this additional variance is ignored in the WHO/UNICEF estimates of confidence intervals. On balance, the MMR, while also subject to some legitimate objections, is still considered preferable as an independent variable. This paper therefore derives alternative country estimates for 1995 based on a multivariate model of the MMR. The model is shown to lead to smaller root mean square relative errors of the MMR estimates. While the overall number of maternal deaths estimated worldwide is very similar to the number reached by WHO/UNICEF, there are major disagreements with respect to particular countries. Finally, a discussion is included on the appropriate way to incorporate the DHS direct sisterhood data, as this affects the results substantially. Copyright © 2001 John Wiley & Sons, Ltd.
Meta‐analyses in systematic reviews of randomized controlled trials in perinatal medicine: comparison of fixed and random effects models
Authors: Villar José , Mackey Maria Eugenia , Carroli Guillermo , Donner Allan 
Published: August 2002

AbstractThere is a need for empirical work comparing the random effects model with the fixed effects model in the calculation of a pooled relative risk in the meta‐analysis in systematic reviews of randomized controlled trials. Such comparisons are particularly important when trial results are heterogeneous. We considered 84 independent meta‐analyses in which each trial included a set of different women/newborns. These meta‐analyses were included in systematic reviews published in the Cochrane Library's pregnancy and childbirth module. Twenty‐one of these 84 meta‐analyses demonstrated statistical heterogeneity at p<0.10. The random effects model estimates showed wider confidence intervals, particularly in those meta‐analyses showing heterogeneity in the trial results. The summary relative risk for the random effects model tended to show a larger protective treatment effect than the fixed effects model in the heterogeneous meta‐analyses. In this set of meta‐analyses, statistical evaluation of publication bias cannot be shown to account for heterogeneity. Our empirical conclusion is that there may be opposing effects if the random effects model is used in the meta‐analysis of clinical trials showing heterogeneity in the results: stronger treatment effects reflected in the summary relative risk, but wider confidence intervals about this summary measure. Copyright © 2001 John Wiley & Sons, Ltd.
Administrative and artificial censoring in censored regression models
Authors: Joffe Marshall M. 
Published: August 2002

AbstractAdministrative censoring, in which potential censoring times are known even for subjects who fail, is common in clinical and epidemiologic studies. Nonetheless, most statistical methods for failure‐time data do not use the information contained in these potential censoring times. Robins has proposed two approaches for using this information to estimate parameters in an accelerated failure‐time model; the methods generally require the analyst to treat as censored some subjects whose failure time is observed. This paper provides a rationale for this ‘artificial censoring’, discusses some of its consequences, and illustrates some of these points with data from a randomized trial of breast cancer screening. Copyright © 2001 John Wiley & Sons, Ltd.
On determination of sample size in hierarchical binomial models
Authors: Zou Kelly H. , Normand Sharon‐Lise T. 
Published: August 2002

AbstractWe consider a two‐ and a three‐stage hierarchical design containing the effects of k clusters with n units per cluster. In the two‐stage model, the conditional distribution of the discrete response Yi is assumed to be independent binomial with mean nθi (I=1,…,k). The success probabilities, θi's, are assumed exchangeable across the k clusters, each arising from a beta distribution. In the three‐stage model, the parameters in the beta distribution are assumed to have independent gamma distributions. The size of each cluster, n, is determined for functions of θi. Lengths of central posterior intervals are computed for various functions of the θi's using Markov chain Monte Carlo and Monte Carlo simulations. Several prior distributions are characterized and tables are provided for n with given k. Methods for sample size calculations under the two‐ and three‐stage models are illustrated and compared for the design of a multi‐institutional study to evaluate the appropriateness of discharge planning rates for a cohort of patients with congestive heart failure. Copyright © 2001 John Wiley & Sons, Ltd.
Large packaged application software maintenance: a research framework
Authors: Gable Guy G. , Chan Taizan , Tan Wui‐Gee 
Published: August 2002

AbstractThis paper seeks to stimulate research on large application package software maintenance by presenting a tentative framework for future research in the area, partially instantiating that framework with examples from the papers in this special issue of the Journal of Software Maintenance and Evolution, highlighting other specific areas of research need and neglect, and posing a long list of related research questions. The user‐organization‐centric research framework captures relevant and interacting factors that can impact maintenance strategy, including software‐source, support‐source, and organizational and environmental contexts. These are viewed from the perspectives of four key stakeholders in the new distributed maintenance arrangement. In addition to the user‐organization, stakeholders include the software vendor, third‐party service providers, and society. Key messages from the paper include: maintenance generates benefits as well as costs; all stakeholders must have a lifecycle‐wide view of maintenance costs and benefits; there is value in understanding all stakeholder perspectives; various software and related support sourcing alternatives have substantial maintenance incidence implications (incidence of costs, benefits, and responsibilities); and maintenance knowledge sourcing decisions should be made in the light of lifecycle‐wide maintenance knowledge requirements. Copyright © 2001 John Wiley & Sons, Ltd.
Coping with aliasing in the GNU Eiffel Compiler implementation
Authors: Zendra Olivier , Colnet Dominique 
Published: August 2002

AbstractThis paper reports our experience about aliasing in the implementation of SmallEiffel, the GNU Eiffel Compiler. The SmallEiffel compiler source code makes intensive use of aliasing in order to achieve very good performance. We explain how aliasing can be handled in a safer way, and how helpful the design by contract capabilities of the Eiffel language have been. The Singleton pattern appears to be crucial in implementing alias provider objects. We propose an efficient implementation of this pattern made easy by some Eiffel idioms. This technique, which requires no language modification, is very appropriate for compilation, but can also be applied to a much wider range of applications. We show the performance impact of string aliasing both in terms of memory footprint and execution time. Copyright © 2001 John Wiley & Sons, Ltd.
Adjuvant treatment of brain metastases
Authors: Lohr Frank , Pirzkall Andrea , Hof Holger , Fleckenstein Katharina , Debus Jürgen 
Published: August 2002

AbstractWith an incidence of 15/105 in the general population, brain metastases constitute a serious, debilitating complication in cancer patients. The majority of those patients suffer from more than one metastasis, but up to 30% to 40% present with a solitary lesion. Whole‐brain radiotherapy (WBRT) extends median survival from 1 to 2 months for treatment with steroids only, to 4 to 6 months in most series. However, long‐term survival (>1–2 years) is observed in up to 10% of patients with favorable prognostic factors, such as solitary lesions, good Karnofsky performance status, and absence of extracranial disease. For those patients, individually optimized treatment is worthwhile. For good‐prognosis patients with controlled extracranial disease, surgery in combination with postoperative WBRT should be considered, especially when fast relief of symptoms is mandated. For surgically inaccessible solitary lesions below a size threshold of approximately 30 ccm, stereotactic radiosurgery (RS), although never compared to surgery in a randomized fashion, seems to yield comparable results and is the treatment of choice for more than one lesion in appropriately selected patients. Nevertheless, a number of questions concerning the optimal treatment regimens for brain metastases remain. These mainly concern the radiation dose, need for a combination of RS and WBRT, relative timing of different treatment modalities, and maximum number of brain metastases that can reasonably be treated with RS when long‐term progression‐free survival is the goal. However, RS is definitely an excellent option for salvage and palliation in patients with short life expectancy, as it is simultaneously noninvasive and cost‐effective, with short hospitalization times. Semin. Surg. Oncol. 20:50–56, 2001. © 2001 Wiley‐Liss, Inc.
Role of endoscopy in the staging of esophageal and gastric cancer
Authors: Messmann Helmut , Schlottmann Klaus 
Published: August 2002

AbstractProgress in instrumentation and clinical research continues to expand the potential utility of endoscopic ultrasound (EUS) in the treatment of esophageal and gastric cancer. This review focuses on the role of EUS in the staging and treatment planning of patients with esophageal and gastric cancer. Semin. Surg. Oncol. 20:78–81, 2001. © 2001 Wiley‐Liss, Inc.
Life on the Web
Authors: Pandzic Igor S. 
Published: August 2002

AbstractWith an increasing number of companies and research centers producing Virtual Characters aimed specifically for the Internet, the Web may soon become very much alive with all sorts of interesting and useful creatures guiding us, giving information or simply trying to sell us something. IGOR PANDZIC tries to predict the possible applications for Virtual Characters in the context of the Web, analyzes the technical requirements to enable these applications and provides a comparative review of currently available technologies with respect to the outlined requirements. Copyright © 2001 John Wiley & Sons, Ltd.
NMDA antagonist effects on striatal dopamine release: Positron emission tomography studies in humans
Authors: Kegeles Lawrence S. , Martinez Diana , Kochan Lisa D. , Hwang Dah‐Ren , Huang Yiyun , Mawlawi Osama , Suckow R. F. , Van Heertum Ronald L. , Laruelle Marc 
Published: August 2002

AbstractPrevious brain imaging studies with [11C]raclopride have suggested that the psychotogenic effects of the noncompetitive N‐methyl‐D‐aspartate antagonist ketamine in humans might be mediated by increased dopamine (DA) release and increased stimulation of DA D2 receptors in the striatum. The goal of the present study was to assess the effect of ketamine on D2 receptor availability in subregions of the striatum (dorsal caudate, DCA; dorsal putamen, DPU; ventral striatum, VST) in humans. Ten healthy subjects were studied twice. In a first group of five subjects, PET scanning was obtained twice for 90 min during bolus plus constant infusion of [11C]raclopride. No significant differences were observed in [11C]raclopride specific‐to‐nonspecific activity ratios (V) measured during an early interval (30–50 min) and late interval (70–90 min), confirming that a state of sustained equilibrium had been established from 30–90 min (end of infusion). In a second group of five subjects, a similar experiment was performed twice, except that ketamine was administered beginning at 50 min (0.12 mg/kg i.v. bolus followed by 0.65 mg/kg/h i.v. infusion for 70 min). Raclopride V measured before ketamine (30–50‐min interval) was compared to [11C]raclopride V measured during ketamine infusion (70–90‐min interval). Ketamine induced a robust dissociative state. However, no significant differences were observed in D2 receptor availability measured before and during the ketamine infusion (n = 10) in any of the regions examined (DCA, DPU, and VST). These data fail to demonstrate an effect of ketamine on [11C]raclopride BP and are consistent with microdialysis studies in rodents and nonhuman primates which reported only small effects of acute NMDA receptor blockade on extracellular striatal DA concentration. Synapse 43:19–29, 2002. © 2002 Wiley‐Liss, Inc.
Ketamine alters the availability of striatal dopamine transporter as measured by [11C]β‐CFT and [11C]β‐CIT‐FE in the monkey brain
Authors: Tsukada Hideo , Nishiyama Shingo , Kakiuchi Takeharu , Ohba Hiroyuki , Sato Kengo , Harada Norihiro 
Published: August 2002

AbstractThe effects of ketamine anesthesia on the binding of [11C]‐labeled cocaine analogs, [11C]β‐CFT (2β‐carbomethoxy‐3β‐(4‐fluorophenyl)tropane) and [11C]β‐CIT‐FE (N‐(2‐fluoroethyl)‐2β‐carbomethoxy‐3β‐(4‐iodophenyl)tropane), to the striatal dopamine transporter (DAT) were evaluated in the monkey brain using positron emission tomography (PET). We sequentially measured the kinetics of these labeled compounds in the brains of five young‐adult male rhesus monkeys (Macaca mulatta) in the conscious state, followed by those under ketamine anesthesia with continuous infusion (3 and 10 mg/kg/h). After intravenous injection, [11C]β‐CFT and [11C]β‐CIT‐FE were predominantly accumulated in the striatum in both conscious and ketamine‐anesthetized states. In the conscious state, the striatal uptake of [11C]β‐CFT and [11C]β‐CIT‐FE continuously increased with time up to 91 min after injection. Continuous infusion of ketamine‐induced higher levels of uptake of [11C]β‐CFT and [11C]β‐CIT‐FE into the brain in a dose‐dependent manner as compared with conscious state, and kinetic analysis with metabolite‐corrected arterial input function indicated that the binding potentials (BP = k3/k4) of both compounds were elevated by ketamine. Not only [11C]β‐CIT‐FE but also [11C]β‐CFT reached the equilibrium state of specific binding in the striatum within 40–50 min after injection. The present results demonstrated that ketamine significantly alters the DAT availability as measured with [11C]β‐CFT and [11C]β‐CIT‐FE in the brain. Synapse 42:273–280, 2001. © 2001 Wiley‐Liss, Inc.
Internalization and trafficking of opioid receptor ligands in rat cortical neurons
Authors: Lee Mao‐Cheng , Cahill Catherine M. , Vincent Jean‐Pierre , Beaudet Alain 
Published: August 2002

AbstractThe binding, internalization, and trafficking of the fluorescently labeled opioid peptides Fluo‐dermorphin and Fluo‐deltorphin were quantitatively studied by confocal microscopy in primary cortical neurons in culture. Specific binding of these selective ligands to neurons naturally expressing mu (μ) and delta (δ) opioid receptors (OR), respectively, resulted in their internalization into neuronal somas and processes, as indicated by the persistence of fluorescent labeling following removal of cell surface binding by hypertonic acid wash. This internalization was receptor‐specific, as the fluorescent signal was completely abolished when the cells were concomitantly incubated with the opioid receptor antagonist naloxone. It also was clathrin‐dependent, as it was totally prevented by the endocytosis inhibitor phenylarsine oxide. Accordingly, internalized ligands were detected inside small, endosome‐like vesicles. These labeled vesicles accumulated within nerve cell bodies between 5–30 min of incubation with the fluorescent ligands. This accumulation was abolished after treatment with the antitubular agent nocodazole, suggesting that it was due to a microtubule‐dependent, retrograde transport of the internalized ligands from processes to the soma. By contrast, there was no change in the compartmentalization of internalized μOR or δOR, as assessed by immunocytochemistry, suggesting that the latter were recycled locally. The present results provide the first demonstration of receptor‐mediated internalization of opioid peptides in cultured neurons. It is proposed that their retrograde transport into target cells might be involved in mediating some of the long‐term, transcriptional effects of opioids. Synapse 43:102–111, 2002. © 2001 Wiley‐Liss, Inc.
Differential distribution of cAMP‐specific phosphodiesterase 7A mRNA in rat brain and peripheral organs
Authors: Miró X. , Pérez‐Torres S. , Palacios J.M. , Puigdomènech P. , Mengod G. 
Published: August 2002

AbstractWe investigated the regional distribution and cellular localization of mRNA coding for the cAMP‐specific phosphodiesterase 7A (PDE7A) in rat brain and several peripheral organs by in situ hybridization histochemistry. The regional expression of two splice variants, PDE7A1 and PDE7A2, was examined by RT‐PCR using RNA extracted from several brain regions. PDE7A mRNA was found to be widely distributed in rat brain in both neuronal and nonneuronal cell populations. The highest levels of hybridization were observed in the olfactory bulb, olfactory tubercle, hippocampus, cerebellum, medial habenula nucleus, pineal gland, area postrema, and choroid plexus. Positive hybridization signals were also detected in other areas, such as raphe nuclei, temporal and entorhinal cortex, pontine nuclei, and some cranial nerve motor nuclei. Both mRNA splice forms were differentially distributed in several areas of the brain with the striatum expressing only PDE7A1 and the olfactory bulb and spinal cord expressing PDE7A2 exclusively. In peripheral organs the highest levels of PDE7A hybridization were seen in kidney medulla, although testis, liver, adrenal glands, thymus, and spleen also presented high hybridization signal. These results are consistent with PDE7A being involved in the regulation of cAMP signaling in many brain functions. The consistent colocalization with PDE4 mRNAs suggests that PDE7A could have an effect on memory, depression, and emesis. The results offer clear anatomical and functional systems in which to investigate future specific PDE7 inhibitors. Synapse 40:201–214, 2001. © 2001 Wiley‐Liss, Inc.
Effect of endogenous dopamine on extrastriatal [11C]FLB 457 binding measured by PET
Authors: Okauchi Takashi , Suhara Tetsuya , Maeda Jun , Kawabe Kouichi , Obayashi Shigeru , Suzuki Kazutoshi 
Published: August 2002

AbstractCentral dopaminergic systems are known to be implicated in the pathophysiology of schizophrenia and recent in vivo dopamine receptor imaging studies have focused on the measurement of extrastriatal dopamine receptor. However, there are only a limited number of ligands that can measure the low‐density D2 receptor in extrastriatal regions and their sensitivity to endogenous dopamine in extrastriatal regions has not yet been fully examined. In this study, the effect of endogenous dopamine on the extrastriatal binding of [11C]FLB 457 was examined in the rhesus monkey after facilitation with 1 mg/kg of methamphetamine (MAP) and was compared with the effect on the striatal binding of [11C]raclopride. The indices of receptor binding were obtained by four methods using cerebellum as a reference region. The bindings of [11C]FLB 457 in the frontal cortex, temporal cortex, and thalamus were not significantly changed after MAP treatment, while the striatal binding of [11C]raclopride was decreased by more than 20%. These results suggest that [11C]FLB 457 is not sensitive to endogenous dopamine in the extrastriatal regions of rhesus monkeys, despite a sufficient dose of MAP to decrease the binding of [11C]raclopride in the striatum. Synapse 41:87–95, 2001. © 2001 Wiley‐Liss, Inc.
On the damping adjustment factors for earthquake response spectra
Authors: Naeim F. , Kircher C. A. 
Published: August 2002

AbstractDamping adjustment factors for converting 5%‐damped earthquake response spectra to other damping levels are evaluated in this paper. The evaluation is based on statistical analysis of spectra of 1047 horizontal components of earthquake ground shaking recorded between 1933 and 1994. The dependency of damping adjustment factors to response period is studied. Results of the evaluation are compared to the damping adjustment factors embodied in the current seismic design code provisions and guidelines which are based on the spectrum amplification factors of Newmark and Hall. Copyright © 2001 John Wiley & Sons, Ltd.