bluuebunny/crossref_metadata_2025_split huggingface dataset:
Moment calculation method for digital vision chip
Authors: Ishii Idaku , Komuro Takashi , Ishikawa Masatoshi 
Published: December 2002

AbstractRecently, an interesting general‐purpose digital vision chip has been realized by integrating a photodetector (PD) and a processing element (PE) directly connected for each pixel on a single chip. This paper proposes bit plane (BP) feature decomposition as a realization of the idea of feature calculation that is suited to a massively parallel processing structure integrated on the digital vision chip. Moment calculation based on the method is discussed. An evaluation of the digital vision chip using the proposed calculation method is presented, and its effectiveness is demonstrated. © 2002 Wiley Periodicals, Inc. Syst Comp Jpn, 34(1): 89–97, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.1187
Teleconference system composed of super‐high‐definition image system and B‐ISDN
Authors: Wada Minoru , Hashimoto Tsutomu , Matsumura Yasushi , Matsuda Tetsuya , Komori Masaru , Takahashi Takashi , Minato Kotaro , Tokutomi Yoshihiro , Takeda Hiroshi 
Published: December 2002

AbstractThis paper describes a system to carry out a medical conference between two remote places. Most kinds of medical images for a patient with circulatory‐organ disease are filed in a super‐high‐definition image system, and the quality of these images and the maneuverability of the system were evaluated by medical experts. The results show that the qualities of all of the images and the maneuverability of the system satisfy the medical requirements. Further, a wide‐band ISDN which has this system at two terminals in remote places has been constructed. The delay time, protocol analysis, and subjective evaluation of this system have been obtained, showing its good feasibility. © 2002 Wiley Periodicals, Inc. Syst Comp Jpn, 34(1): 98–110, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.1188
Comparison of tests for categorical data from a stratified cluster randomized trial
Authors: Dobbins Timothy A. , Simpson Judy M. 
Published: December 2002

AbstractTwo features commonly exhibited by randomized trials of health promotion interventions are cluster randomization and stratification. Ignoring correlations between individuals within clusters can lead to an inflated type I error rate and hence a P‐value which overstates the significance of the result. This paper compares several methods for analysing categorical data from a stratified cluster randomized trial. We propose an extension of a method from survey sampling that uses the design effect to reduce the effective sample size. We compare this with three methods from Zhang and Boos that extend the standard Cochran–Mantel–Haenszel (CMH) statistic by using appropriate covariance matrices, and with a bootstrap method. The comparison is based on empirical type I error rates from a simulation study, in which the number of clusters randomized is small, as in most public health intervention studies. The method that performs consistently well is one of the Zhang and Boos extensions of the standard CMH statistic. Copyright © 2002 John Wiley & Sons, Ltd.
A graphical sensitivity analysis for clinical trials with non‐ignorable missing binary outcome
Authors: Hollis Sally 
Published: December 2002

AbstractMany clinical trials are analysed using an intention‐to‐treat (ITT) approach. A full application of the ITT approach is only possible when complete outcome data are available for all randomized subjects. In a recent survey of clinical trial reports including an ITT analysis, complete case analysis (excluding all patients with a missing response) was common. This does not comply with the basic principles of ITT since not all randomized subjects are included in the analysis. Analyses of data with missing values are based on untestable assumptions, and so sensitivity analysis presenting a range of estimates under alternative assumptions about the missing‐data mechanism is recommended. For binary outcome, extreme case analysis has been suggested as a simple form of sensitivity analysis, but this is rarely conclusive. A graphical sensitivity analysis is proposed which displays the results of all possible allocations of cases with missing binary outcome. Extension to allow binomial variation in outcome is also considered. The display is based on easily interpretable parameters and allows informal examination of the effects of varying prior beliefs. Copyright © 2002 John Wiley & Sons, Ltd.
A comparison of confidence interval methods for the intraclass correlation coefficient in cluster randomized trials
Authors: Ukoumunne Obioha C. 
Published: December 2002

AbstractA Correction has been published for this article in Statistics in Medicine 23(18) 2004, 2935. This study compared different methods for assigning confidence intervals to the analysis of variance estimator of the intraclass correlation coefficient (ρ). The context of the comparison was the use of ρ to estimate the variance inflation factor when planning cluster randomized trials. The methods were compared using Monte Carlo simulations of unbalanced clustered data and data from a cluster randomized trial of an intervention to improve the management of asthma in a general practice setting. The coverage and precision of the intervals were compared for data with different numbers of clusters, mean numbers of subjects per cluster and underlying values of ρ. The performance of the methods was also compared for data with Normal and non‐Normally distributed cluster specific effects. Results of the simulations showed that methods based upon the variance ratio statistic provided greater coverage levels than those based upon large sample approximations to the standard error of ρ. Searle's method provided close to nominal coverage for data with Normally distributed random effects. Adjusted versions of Searle's method to allow for lack of balance in the data generally did not improve upon it either in terms of coverage or precision. Analyses of the trial data, however, showed that limits provided by Thomas and Hultquist's method may differ from those of the other variance ratio statistic methods when the arithmetic mean differs markedly from the harmonic mean cluster size. The simulation results demonstrated that marked non‐Normality in the cluster level random effects compromised the performance of all methods. Confidence intervals for the methods were generally wide relative to the underlying size of ρsuggesting that there may be great uncertainty associated with sample size calculations for cluster trials where large clusters are randomized. Data from cluster based studies with sample sizes much larger than those typical of cluster randomized trials are required to estimate ρ with a reasonable degree of precision. Copyright © 2002 John Wiley & Sons, Ltd.
A weighted Kaplan–Meier estimator for matched data with application to the comparison of chemotherapy and bone‐marrow transplant in leukaemia
Authors: Galimberti Stefania , Sasieni Peter , Valsecchi Maria Grazia 
Published: December 2002

AbstractStudies on the comparison of transplantation with respect to standard therapy present a number of statistical challenges: they are usually not randomized, often retrospective (based on registry data) and the treatment assignment is time dependent (waiting time to transplant). Matching on known prognostic factors and waiting time to transplant can be used to select appropriate samples for the analysis. When a variable number of patients treated with conventional therapy matches each transplanted patient, the standard estimating and testing procedures need to be modified in order to account for the fact that matched data are highly stratified, with strata containing a few, possibly censored, observations. A weighted version of the Kaplan–Meier estimator, which accounts for a variable proportion of matching, is proposed and its statistical properties are studied. The problem of the comparison of the survival experience in the two treatment groups is also considered. Two tests, based on the distance between the survival estimates calculated at a prefixed time point, are examined and their behaviour is evaluated through simulations. The procedures proposed here are applied to data collected from an Italian study whose aim was the evaluation of bone marrow transplant, as compared to intensive chemotherapy, in the cure of paediatric acute lymphoblastic leukaemia. Copyright © 2002 John Wiley & Sons, Ltd.
Multicollinearity in prognostic factor analyses using the EORTC QLQ‐C30: identification and impact on model selection
Authors: Van Steen Kristel , Curran Desmond , Kramer Jocelyn , Molenberghs Geert , Van Vreckem Ann , Bottomley Andrew , Sylvester Richard 
Published: December 2002

AbstractClinical and quality of life (QL) variables from an EORTC clinical trial of first line chemotherapy in advanced breast cancer were used in a prognostic factor analysis of survival and response to chemotherapy. For response, different final multivariate models were obtained from forward and backward selection methods, suggesting a disconcerting instability. Quality of life was measured using the EORTC QLQ‐C30 questionnaire completed by patients. Subscales on the questionnaire are known to be highly correlated, and therefore it was hypothesized that multicollinearity contributed to model instability. A correlation matrix indicated that global QL was highly correlated with 7 out of 11 variables. In a first attempt to explore multicollinearity, we used global QL as dependent variable in a regression model with other QL subscales as predictors. Afterwards, standard diagnostic tests for multicollinearity were performed. An exploratory principal components analysis and factor analysis of the QL subscales identified at most three important components and indicated that inclusion of global QL made minimal difference to the loadings on each component, suggesting that it is redundant in the model. In a second approach, we advocate a bootstrap technique to assess the stability of the models. Based on these analyses and since global QL exacerbates problems of multicollinearity, we therefore recommend that global QL be excluded from prognostic factor analyses using the QLQ‐C30. The prognostic factor analysis was rerun without global QL in the model, and selected the same significant prognostic factors as before. Copyright © 2002 John Wiley & Sons, Ltd.
Use of the mean, hot deck and multiple imputation techniques to predict outcome in intensive care unit patients in Colombia
Authors: Pérez Adriana , Dennis Rodolfo J. , Gil Jacky F. A. , Rondón Martín A. , López Adriana 
Published: December 2002

AbstractA cohort of intensive care unit (ICU) patients in 20 Colombian ICUs is used to describe the application of three imputation techniques: single, hot deck and multiple imputation. These strategies were used to impute the missing data in the variables used to construct APACHE II scores, a scoring system for the ICU patients that provides an unbiased standardized estimate of the probability of hospital death. Imputed APACHE II scores were then used in the APACHE II model to estimate adjusted hospital mortality rates. The area under the receiver operating characteristic (ROC) curve was used to compare imputation strategies with respect to predictive power. While statistically significant differences were found for the area under the ROC curve, these differences were not clinically significant. Copyright © 2002 John Wiley & Sons, Ltd.
Predicting time to prostate cancer recurrence based on joint models for non‐linear longitudinal biomarkers and event time outcomes
Authors: Pauler Donna K. , Finkelstein Dianne M. 
Published: December 2002

AbstractBiological markers that are both sensitive and specific for tumour regrowth or metastasis are increasingly becoming available and routinely monitored during the regular follow‐up of patients treated for cancer. Obtained by a simple blood test, these markers provide an inexpensive non‐invasive means for the early detection of recurrence (or progression). Currently, the longitudinal behaviour of the marker is viewed as an indicator of early disease progression, and is applied by a physician in making clinical decisions. One marker that has been studied for use in both population screening for early disease and for detection of recurrence in prostate cancer patients is PSA. The elevation of PSA levels is known to precede clinically detectable recurrence by 2 to 5 years, and current clinical practice often relies partially on multiple recent rises in PSA to trigger a change in treatment. However, the longitudinal trajectory for individual markers is often non‐linear; in many cases there is a decline immediately following radiation therapy or surgery, a plateau during remission, followed by an exponential rise following the recurrence of the cancer. The aim of this article is to determine the multiple aspects of the longitudinal PSA biomarker trajectory that can be most sensitive for predicting time to clinical recurrence. Joint Bayesian models for the longitudinal measures and event times are utilized based on non‐linear hierarchical models, implied by unknown change‐points, for the longitudinal trajectories, and a Cox proportional hazard model for progression times, with functionals of the longitudinal parameters as covariates in the Cox model. Using Markov chain Monte Carlo sampling schemes, the joint model is fit to longitudinal PSA measures from 676 patients treated at Massachusetts General Hospital between the years 1988 and 1995 with follow‐up to 1999. Based on these data, predictive schemes for detecting cancer recurrence in new patients based on their longitudinal trajectory are derived. Copyright © 2002 John Wiley & Sons, Ltd.
Modelling tooth emergence data based on multivariate interval‐censored data
Authors: Bogaerts K. , Leroy R. , Lesaffre E. , Declerck D. 
Published: December 2002

AbstractStudies on emergence of (permanent) teeth are published regularly in the dental literature. Besides descriptive statistics (mean or median values) on emergence times, comparisons between boys and girls are of interest. Gender comparisons are intersubject analyses, but also intrasubject questions, like ‘Is there a left–right symmetry with respect to the mean (median) emergence times?’ are of interest. Studies on emergence times most often are faced with interval‐censored data. We will extend a GEE‐type test proposed by Husteret al.for bivariate right‐censored data to the multivariate setting with interval‐censored data. Central to our paper is to provide appropriate statistical models to resolve some dental questions on emergence. The analyses are based on data from the longitudinal Signal‐Tandmobiel study. Copyright © 2002 John Wiley & Sons, Ltd.
Global goodness‐of‐fit tests in logistic regression with sparse data
Authors: Kuss Oliver 
Published: December 2002

AbstractThe logistic regression model has become the standard analysing tool for binary responses in medical statistics. Methods for assessing goodness‐of‐fit, however, are less developed where this problem is especially pronounced in performing global goodness‐of‐fit tests with sparse data, that is, if the data contain only a small numbers of observations for each pattern of covariate values. In this situation it has been known for a long time that the standard goodness‐of‐fit tests (residual deviance and Pearson chi‐square) behave unsatisfactorily ifp‐values are calculated from the χ2‐distribution. As a remedy in this situation the Hosmer–Lemeshow test is frequently recommended; it relies on a new grouping of the observations to avoid sparseness, where this grouping depends on the estimated probabilities from the model. It has been shown, however, that the Hosmer–Lemeshow test also has some deficiencies, for example, it depends heavily on the calculating algorithm and thus different implementations might lead to different conclusions regarding the fit of the model. We present some alternative tests from the statistical literature which should also perform well with sparse data. Results from a simulation study are given which show that there exist some goodness‐of‐fit tests (for example, the Farrington test) that have good properties regarding size and power and that even outperform the Hosmer–Lemeshow test. We illustrate the various tests with an example from dermatology on occupational hand eczema in hairdressers. Copyright © 2002 John Wiley & Sons, Ltd.
Simplifying a prognostic model: a simulation study based on clinical data
Authors: Ambler Gareth , Brady Anthony R. , Royston Patrick 
Published: December 2002

AbstractPrognostic models are designed to predict a clinical outcome in individuals or groups of individuals with a particular disease or condition. To avoid bias many researchers advocate the use of full models developed by prespecifying predictors. Variable selection is not employed and the resulting models may be large and complicated. In practice more parsimonious models that retain most of the prognostic information may be preferred. We investigate the effect on various performance measures, including mean square error and prognostic classification, of three methods for estimating full models (including penalized estimation and Tibshirani's lasso) and consider two methods (backwards elimination and a new proposal called stepdown) for simplifying full models. Simulation studies based on two medical data sets suggest that simplified models can be found that perform nearly as well as, or sometimes even better than, full models. Optimizing the Akaike information criterion appears to be appropriate for choosing the degree of simplification. Copyright © 2002 John Wiley & Sons, Ltd.
Regional differences in sympathetic purinergic transmission along the length of the mouse vas deferens
Authors: Knight D. , D'Arbe M. , Liang S. , Phillips W.D. , Lavidis N.A. 
Published: December 2002

AbstractContraction of the smooth muscle in the mouse vas deferens is elicited by sympathetic nerves releasing at least two neurotransmitters, adenosine triphosphate (ATP) and noradrenaline (NA). Several studies have indicated the presence of regional variation in the purinergic and noradrenergic contributions to sympathetic nerve‐evoked contractions in rodent vasa deferentia. We examined the relative contribution of ATP and NA to neurotransmission and contraction at the prostatic and epididymal ends of the mouse vas deferens. The success rate of recording excitatory junction currents (EJCs, extracellular indication of ATP release) from varicosities at the prostatic end of the vas deferens was eight times greater than for varicosities located at the epididymal end. Both regions of the vas deferens responded similarly to focal application of NA and ATP. Furthermore, the relative density and distribution of P2X1‐receptor mRNA and anti‐P2X1 immunostaining did not differ between the two regions. Our results suggest that most varicosities located at the epididymal end of the vas deferens are releasing an insufficient amount of ATP to evoke detectable EJCs. Synapse 47:225–235, 2003. © 2002 Wiley‐Liss, Inc.
Creation, expression, and characterization of a constitutively active mutant of the human serotonin 5‐HT6 receptor
Authors: Purohit Anil , Herrick‐Davis Katharine , Teitler Milt 
Published: December 2002

AbstractThe serotonin 5‐HT6 receptor, a G‐protein‐coupled receptor, displays high affinity for antipsychotic, antidepressant, and psychotropic drugs. We created a constitutively active form of the human 5‐HT6 receptor in order to probe the molecular domains of receptor activation and to determine if inverse agonist activities of antipsychotic drugs contribute to their clinical profile. Previous studies from our laboratory support a critical role for the c‐terminal region of the third intracellular loop (il3) in the activation of Gq‐coupled serotonin receptors. In the present study, PCR‐based mutagenesis was used to mutate serine 267 (S6.34) in the c‐terminal region of il3 to lysine (S267K). The native and S267K 5‐HT6 receptors were expressed in COS‐7 cells to study the functional effects of the mutation. The S267K receptor shows 10‐fold higher affinity for serotonin than the native receptor and demonstrates agonist‐independent activity. Clozapine decreased the basal activity of the S267K receptor to vector control levels. Therefore, we can conclude that the S267K mutation renders the 5‐HT6 receptor constitutively active and that clozapine is an inverse agonist at the mutant 5‐HT6 receptor. These results indicate that the c‐terminal region of il3 of the Gs‐coupled 5‐HT6 receptor is a key domain for G‐protein coupling, similar to the Gq‐coupled 5‐HT receptors. The inverse agonist action of clozapine indicates that drugs displaying competitive antagonist activity at native 5‐HT6 receptors may display inverse agonist activity at the constitutively activated form of the receptor. Synapse 47:218–224, 2003. © 2002 Wiley‐Liss, Inc.
Regional infusions of serotonin into the striatum and memory consolidation
Authors: Prado‐Alcalá Roberto A. , Ruiloba María Isabel , Rubio Laura , Solana‐Figueroa Rafael , Medina Cristina , Salado‐Castillo Rigoberto , Quirarte Gina L. 
Published: December 2002

AbstractLesions, temporal inactivation, electrical stimulation and administration of drugs that antagonize synaptic activity of the striatum lead to significant deficits of memory. Also, it has been shown that interruption of dopaminergic, GABAergic, or cholinergic activity in discrete areas of this structure is sufficient to disrupt cognitive functions. In spite of the known interactions among dopamine, GABA, acetylcholine, and serotonin, there is a notable scarcity of data germane to the participation of striatal serotonin in learning and memory. It was important, therefore, to investigate the possible involvement of serotonin in cognition. In light of the differential distribution of serotonergic elements within the striatum, a prediction was made that focal injections of serotonin into distinctive regions would produce dissimilar effects on memory. Rats were trained in a one‐trial step‐through inhibitory avoidance task and a retention test was carried out 24 h later. Posttraining injections of serotonin into the dorsal and ventral aspects of the posterior region produced strong amnesia compared to similar injections into the dorsal and ventral aspects of the anterior region. The present findings support the hypothesis that striatal serotonergic activity is involved in memory functions and also provide further evidence of neurochemical heterogeneity within the striatum regarding memory consolidation. Synapse 47:169–175, 2003. © 2002 Wiley‐Liss, Inc.