bluuebunny/crossref_metadata_2025_split huggingface dataset:
Development of ultrahigh vacuum floating‐type low‐energy ion gun with differential pumping facilities for high‐resolution depth profiling
Authors: Mizuhara Y. , Bungo T. , Nagatomi T. , Takai Y. , Suzuki S. , Kikuchi K. , Sato T. , Uta K. 
Published: January 2005

AbstractAn ultrahigh vacuum floating‐type low‐energy ion gun (UHV‐FLIG) with a differential pumping system was developed. The developed UHV‐FLIG ensured high ion current densities of ∼45 and ∼20 µA cm−2 for Ar+ ions of 300 and 100 eV, respectively, under the UHV condition of the analysis chamber below ∼4 × 10−6 Pa. The application of the developed UHV‐FLIG to Auger electron spectroscopy (AES) sputter depth profiling of a GaAs/AlAs superlattice material revealed that the ultimate high depth resolution of ∼1.0 nm was achieved by sputter etching using 100 eV Ar+ ions. The present results confirmed that lowering the primary energy of Ar+ ions to 100 eV is still significantly effective for achieving higher depth resolution in sputter depth profiling. Copyright © 2005 John Wiley & Sons, Ltd.
Deconvolution of SIMS depth profiles of As multiple delta layers in silicon
Authors: Lee J. W. , Kim K. J. , Kim H. K. , Moon D. W. 
Published: January 2005

AbstractWe investigated the deconvolution of SIMS depth profiles of arsenic multiple delta layers in silicon. Two samples with spacings of 50 and 5/10 nm between the arsenic‐doped silicon delta layers of thickness 1.0 and 0.5 nm, respectively, were used for the study. Time‐of‐flight SIMS analysis with sputtering of 0.5 keV Cs+ at 45° incident angle has been performed to obtain the SIMS depth profile. We observed five clearly separated peaks in the 50 nm spacing sample but eight poorly separated peaks in the 5/10 nm spacing sample. After deconvolution, however, we could obtain very thin and sharp clearly separated peaks in both samples. The separability of the overlapping peaks was much improved, especially in the region of 5 nm spacing. An improvement in depth resolution by a factor of ∼3 and a gain in maximum peak intensity by a factor of ∼4 were achieved. We could not find any significant loss or gain of peak intensity during the deconvolution procedure. The physical validity of the deconvolution method is supported by non‐destructive medium‐energy ion scattering spectroscopy analysis, which can measure the thickness of the arsenic‐doped silicon delta layer in a silicon matrix quantitatively. Copyright © 2005 John Wiley & Sons, Ltd.
Study of solid/solid interface by transmitted x‐ray reflectivity
Authors: Inoue Koji , Kitahara Amane , Matsushita Kiyohiko , Kikkawa Hiroyuki , Nakabayashi Fumitomo , Ageishi Naoya , Terauchi Hikaru , Sakata Osami , Takahashi Isao 
Published: January 2005

AbstractIn this paper, we demonstrate investigations of metal thick layer/semiconductor interfaces (Au/Si and Ga/GaAs) by x‐ray reflectivity under transmission geometry (TXR), which could not be performed by conventional x‐ray reflectivity due to the macroscopic thickness and surface roughness of the overlayers. We obtain precise electron density by using the two maxima in diffuse scattering of TXR caused by the Fresnel transmission function (the so‐called Yoneda wings). From in situ TXR measurements of Ga/GaAs with elevating temperature, the onset of structural variation at the interface is found to be 520 K. Such an interfacial variation at an extraordinarily low temperature agrees with an ex situ SEM study of an etched GaAs surface. Copyright © 2005 John Wiley & Sons, Ltd.
Fluorine Kα x‐ray fluorescence spectra of LuF3 and NaF using synchrotron radiation
Authors: Kaibuchi Kazuki , Nagasono Mitsuru , Liu Zhenlin , Koja Yusuke , Fukushima Akiko , Shin Shik , Takahashi Hideyuki , Kawai Jun 
Published: January 2005

AbstractThe F Kα x‐ray fluorescence spectrum of LuF3 is excited by monochromated synchrotron radiation and a satellite peak is observed at the higher energy side of the F Kα1, 2 lines. The intensity of this peak depends on the incident x‐ray energy; the presence of the threshold energy to excite the satellite proves that the satellite is assigned to Kα3, 4 due to the transition 1s−12p−1→ 2p−2. The Kα3, 4/Kα1, 2 intensity ratio for LuF3 is 0.20, which is significantly weaker than that for NaF (0.46). It is observed that the Kα1, 2 line width of LuF3 is significantly broader than that for NaF. Copyright © 2005 John Wiley & Sons, Ltd.
Development of photoelectron spectro‐holography apparatus
Authors: Ishii Hideshi , Mamaishin Shuichi , Tamura Keiji , Chu Wei‐Guo , Owari Masanori , Doi Makoto , Tsukamoto Katsumi , Takahashi Sadayuki , Iwai Hideo , Watanabe Katsumi , Kobayashi Hideo , Kita Yoshiteru , Yamazui Hiromichi , Taguchi Masami , Shimizu Ryuichi , Nihei Yoshimasa 
Published: January 2005

AbstractWe improved the photoelectron spectro‐holography apparatus for high‐speed and high‐energy photoelectron detection. The combination of an aperture for ±1.4° acceptance angle at the diffraction plane and a 64‐channel detector realized the high‐speed XPS and rapid x‐ray photoelectron diffraction (XPED) measurements Furthermore, high‐energy XPS and XPED measurements excited by Cu Kα have been performed. Copyright © 2005 John Wiley & Sons, Ltd.
Surface structure analysis of Zr‐O/W(100) at high temperature by x‐ray photoelectron diffraction
Authors: Tamura Keiji , Amano Mikiya , Chu Wei‐guo , Ishii Hideshi , Owari Masanori , Kawano Takashi , Nagatomi Takakiyo , Takai Yoshizo , Oshima Chuhei , Shimizu Ryuichi , Nihei Yoshimasa 
Published: January 2005

AbstractTemperature dependence of the surface structure of Zr‐O/W(100) was obtained by low‐energy electron diffraction observation to check the phase transition of the surface. After flashing the Zr‐O/W(100) to 1500 K, the c(2 × 4) + c(4 × 2) double‐domain structure was clearly observed at room temperature. This surface changed to the p(1 × 1) phase over 1300 K, accompanied by a decrease in the work function. The temperature dependence of the work function was obtained from the shift of the energy distributions of secondary electrons. The reversible phase transition of the Zr‐O/W(100) surface and the decrease in the work function of 2 eV at high temperature were checked. X‐ray photoelectron diffraction (XPD) measurements at 1500 K have been performed to investigate the surface structure at the working temperature of the Zr‐O/W(100) electron emitter. The O1s XPED pattern included some patterns that can be regarded as the influence of Zr–O complexes on the W(100) surface. Copyright © 2005 John Wiley & Sons, Ltd.
Wedge‐shaped and flat cross‐sections for quantitative characterization of the electrostatic potential distributions across p‐n junctions by electron holography
Authors: Wang Zhouguang , Kato Takeharu , Hirayama Tsukasa , Kato Naoko , Sasaki Katsuhiro , Saka Hiroyasu 
Published: January 2005

AbstractBoth flat and wedge‐shaped cross‐sectional specimens were fabricated by focused ion beam (FIB) milling of the same implanted Si/Si p‐n junction sample. The junction potential distributions in both kinds of specimens were examined by using electron holography, and their differences were compared. Some parameters needed for characterizing junction potential distributions quantitatively, such as the thickness of the electrically dead layer on the surface, can be obtained only from wedge‐shaped cross‐sections, and it is shown that the two‐dimensional potential distributions in practical semiconductor devices can be measured accurately only by combining the results obtained using both of these specimen geometries. Copyright © 2005 John Wiley & Sons, Ltd.
Ultimate sized nano‐dots formed by electron beam‐induced deposition using an ultrahigh vacuum transmission electron microscope
Authors: Tanaka M. , Shimojo M. , Han M. , Mitsuishi K. , Furuya K. 
Published: January 2005

AbstractWe have successfully fabricated nano‐dots containing tungsten or gold from metal‐organic gas sources by electron beam‐induced deposition in an ultrahigh vacuum transmission electron microscope. The size of the dots can be controlled by changing the time for irradiation and the partial pressure of the precursor. The smallest particle size fabricated from W(CO)6 is ∼1.5 nm in diameter, which is close to the theoretical resolution limit. Copyright © 2005 John Wiley & Sons, Ltd.
Transmission electron microscopy observation of the structure of TiO2 nanotube and Au/TiO2 nanotube catalyst
Authors: Akita Tomoki , Okumura Mitsutaka , Tanaka Koji , Ohkuma Kayoko , Kohyama Masanori , Koyanagi Tsuguo , Date Masakazu , Tsubota Susumu , Haruta Masatake 
Published: January 2005

AbstractA TiO2 nanotube catalyst was synthesized and observed by analytical transmission electron microscopy (TEM) combined with scanning transmission electron microscopy (STEM) and electron energy‐loss spectroscopy (EELS). It was revealed that the crystalline structure of the TiO2 nanotube is different from that of anatase and rutile TiO2. It was found that gold nanoparticles could be supported successfully on the TiO2 nanotube when applied using the deposition precipitation method. The catalytic activity of an Au/TiO2 nanotube for CO oxidation and H2 oxidation was examined and found to be different from Au on anatase or and rutile TiO2 catalyst. Copyright © 2005 John Wiley & Sons, Ltd.
Cost‐effectiveness analysis when the WTA is greater than the WTP
Authors: Willan Andrew R. , O'Brien Bernie J. , Leyva Rina A. 
Published: January 2005

AbstractThe incremental cost effectiveness ratio has long been the standard parameter of interest in the assessment of the cost‐effectiveness of a new treatment. However, due to concerns with interpretability and statistical inference, authors have suggested using the willingness‐to‐pay for a unit of health benefit to define the incremental net benefit as an alternative. The incremental net benefit has a more consistent interpretation and is amenable to routine statistical procedures. These procedures rely on the fact that the willingness‐to‐accept compensation for a loss of a unit of health benefit (at some cost saving) is the same as the willingness‐to‐pay for it. Theoretical and empirical evidence suggest, however, that in health care the willingness‐to‐accept is about twice as much as the willingness‐to‐pay. We use Bayesian methods to provide a statistical procedure for the cost‐effectiveness comparison of two arms of a randomized clinical trial that allows the willingness‐to‐pay and the willingness‐to‐accept to have different values. An example is provided. Copyright © 2001 John Wiley & Sons, Ltd.
Group sequential test strategies for superiority and non‐inferiority hypotheses in active controlled clinical trials
Authors: Wang Sue‐Jane , James Hung H. M. , Tsong Yi , Cui Lu 
Published: January 2005

AbstractIn a group sequential active controlled clinical trial, the study hypothesis may be a superiority hypothesis that an experimental treatment is more effective than the active control therapy or a non‐inferiority hypothesis that the treatment is no worse than the active control within some non‐inferiority range. When it is necessary to plan for testing the superiority and the non‐inferiority hypotheses, we propose an adaptive group sequential closed test strategy by which the sample size is planned for testing superiority and is to be increased for showing non‐inferiority given that it is deemed more plausible than superiority based on the observed sample path during the course of the trial. The proposed adaptive test strategy is valid in terms of having the type I error probability maintained at the targeted α level for both superiority and non‐inferiority. It has power advantage or sample size saving over the traditional group sequential test designed for testing either superiority only or non‐inferiority only. Copyright © 2001 John Wiley & Sons, Ltd.
Meta‐analysis of binary data: which within study variance estimate to use?
Authors: Chang Bei‐Hung , Waternaux Christine , Lipsitz Stuart 
Published: January 2005

AbstractWe applied a mixed effects model to investigate between‐ and within‐study variation in improvement rates of 180 schizophrenia outcome studies. The between‐study variation was explained by the fixed study characteristics and an additional random study effect. Both rate difference and logit models were used. For a binary proportion outcome pi with sample size ni in the ith study, (p̂i(1−p̂i)ni)−1 is the usual estimate of the within‐study variance σ2i in the logit model, where p̂i is the sample mean of the binary outcome for subjects in study i. This estimate can be highly correlated with logit(p̂i). We used (p̄i(1−p̄)ni)−1 as an alternative estimate of σ2i, where p̄ is the weighted mean of p̂i's. We estimated regression coefficients (β) of the fixed effects and the variance (τ2) of the random study effect using a quasi‐likelihood estimating equations approach. Using the schizophrenia meta‐analysis data, we demonstrated how the choice of the estimate of σ2i affects the resulting estimates of β and τ2. We also conducted a simulation study to evaluate the performance of the two estimates of σ2i in different conditions, where the conditions vary by number of studies and study size. Using the schizophrenia meta‐analysis data, the estimates of β and τ2 were quite different when different estimates of σ2i were used in the logit model. The simulation study showed that the estimates of β and τ2 were less biased, and the 95 per cent CI coverage was closer to 95 per cent when the estimate of σ2i was (p̄(1−p̄)ni)−1 rather than (p̂i(1−p̂)ni)−1. Finally, we showed that a simple regression analysis is not appropriate unless τ2 is much larger than σ2i, or a robust variance is used. Copyright © 2001 John Wiley & Sons, Ltd.
A note on the distribution of the number of vaccinated infected under non‐random mixing conditions
Authors: Hernández‐Suárez Carlos M. 
Published: January 2005

AbstractA common situation in vaccine efficacy (VE) estimation is dealing with non‐randomly mixing populations, which may subject vaccinated and unvaccinated individuals to a different infection pressure. These conditions may lead to a bias in VE estimates. The derivation of the statistical distribution of the number of vaccinated and infected out of a sample of n infections in a VE trial is essential to develop estimates and their properties. For randomly mixing populations, it has been shown recently that this follows a hypergeometric distribution for ‘all/nothing’ vaccines, whereas it is a non‐central hypergeometric distribution for ‘leaky’ ones. Here it is shown that these distributions still hold under non‐random mixing conditions, provided that mixing preferences and contact rates are independent of vaccination status. These conditions are met when vaccine and placebo are randomized. Copyright © 2001 John Wiley & Sons, Ltd.
Use of odds ratio or relative risk to measure a treatment effect in clinical trials with multiple correlated binary outcomes: data from the NINDS t‐PA stroke trial
Authors: Lu Mei , Tilley Barbara C. 
Published: January 2005

AbstractIn clinical trials, when a single outcome is not sufficient to describe the underlying concept of interest, it may be necessary to compare treatment groups on multiple correlated outcomes. A global test based on a logit link function provides an estimate of the odds ratio for assessing a common treatment effect among correlated binary outcomes. In this paper we extend the use of generalized estimating equations (GEE) to calculate a common relative risk from correlated binary outcomes based on a log link function. In the context of global tests, we discuss the equivalence and difference between logit and log links and their estimates. We also derive a formula for calculating a common risk difference between two treatment groups based on multiple correlated binary outcomes with categorical covariates, assuming the asymptotic equivalency between the logit and log‐linear links. We discuss the statistical tools to be used in choosing between the logit and log links when models on different links yield contrasting results. Examples using data from the NINDS t‐PA Stroke Trials are provided. We conclude, in a study of correlated binary outcomes, that the choice of the logit or log link could be based on a comparison of goodness‐of‐link. Copyright © 2001 John Wiley & Sons, Ltd.
Group comparisons involving missing data in clinical trials: a comparison of estimates and power (size) for some simple approaches
Authors: Miller Michael E. , Morgan Timothy M. , Espeland Mark A. , Emerson Scott S. 
Published: January 2005

AbstractWhen using ‘intent‐to‐treat’ approaches to compare outcomes between groups in clinical trials, analysts face a decision regarding how to account for missing observations. Most model‐based approaches can be summarized as a process whereby the analyst makes assumptions about the distribution of the missing data in an attempt to obtain unbiased estimates that are based on functions of the observed data. Although pointed out by Rubin as often leading to biased estimates of variances, an alternative approach that continues to appear in the applied literature is to use fixed‐value imputation of means for missing observations. The purpose of this paper is to provide illustrations of how several fixed‐value mean imputation schemes can be formulated in terms of general linear models that characterize the means of distributions of missing observations in terms of the means of the distributions of observed data. We show that several fixed‐value imputation strategies will result in estimated intervention effects that correspond to maximum likelihood estimates obtained under analogous assumptions. If the missing data process has been correctly characterized, hypothesis tests based on variances estimated using maximum likelihood techniques asymptotically have the correct size. In contrast, hypothesis tests performed using the uncorrected variance, obtained by applying standard complete data formula to singly imputed data, can provide either conservative or anticonservative results. Surprisingly, under several non‐ignorable non‐response scenarios, maximum likelihood based analyses can yield equivalent hypothesis tests to those obtained when analysing only the observed data. Copyright © 2001 John Wiley & Sons, Ltd.
Optimal estimation of transposition rates of insertion sequences for molecular epidemiology
Authors: Tanaka Mark M. , Rosenberg Noah A. 
Published: January 2005

AbstractOutbreaks of infectious disease can be confirmed by identifying clusters of DNA fingerprints among bacterial isolates from infected individuals. This procedure makes assumptions about the underlying properties of the genetic marker used for fingerprinting. In particular, it requires that each fingerprint changes sufficiently slowly within an individual that isolates from separate individuals infected by the same strain will exhibit similar or identical fingerprints. We propose a model for the probability that an individual's fingerprint will change over a given period of time. We use this model together with published data in order to estimate the fingerprint change rate for IS6110 in human tuberculosis, obtaining a value of 0.0139 changes per copy per year. Although we focus on insertion sequences (IS), our method applies to other fingerprinting techniques such as pulsed‐field gel electrophoresis (PFGE). We suggest sampling intervals that produce the least error in estimates of the fingerprint change rate, as well as sample sizes that achieve specified levels of error in the estimate. Copyright © 2001 John Wiley & Sons, Ltd.
Residual mass histology in testicular cancer: development and validation of a clinical prediction rule
Authors: Steyerberg Ewout W. , Vergouwe Yvonne , Jan Keizer H. , Habbema J. Dik F. ,   for the ReHiT study group
Published: January 2005

AbstractAfter chemotherapy for metastatic non‐seminomatous testicular cancer, surgical resection is a generally accepted treatment to remove remnants of the initial metastases, since residual tumour may still be present (mature teratoma or viable cancer cells). In this paper, we review the development and external validation of a logistic regression model to predict the absence of residual tumour. Three sources of information were used. A quantitative review identified six relevant predictors from 19 published studies (996 resections). Second, a development data set included individual data of 544 patients from six centres. This data set was used to assess the predictive relationships of five continuous predictors, which resulted in dichotomization for two, and a log, square root, and linear transformation for three other predictors. The multiple logistic regression coefficients were reduced with a shrinkage factor (0.95) to improve calibration, based on a bootstrapping procedure. Third, a validation data set included 172 more recently treated patients. The model showed adequate calibration and good discrimination in the development and in the validation sample (areas under the ROC curve 0.83 and 0.82). This study illustrates that a careful modelling strategy may result in an adequate predictive model. Further study of model validity may stimulate application in clinical practice. Copyright © 2001 John Wiley Sons, Ltd.
Cumulative logit models for ordinal data: a case study involving allergic rhinitis severity scores
Authors: Lunn David J. , Wakefield Jon , Racine‐Poon Amy 
Published: January 2005

AbstractOrdered categorical data arise in numerous settings, a common example being pain scores in analgesic trials. The modelling of such data is intrinsically more difficult than the modelling of continuous data due to the constraints on the underlying probabilities and the reduced amount of information that discrete outcomes contain. In this paper we discuss the class of cumulative logit models, which provide a natural framework for ordinal data analysis. We show how viewing the categorical outcome as the discretization of an underlying continuous response allows a natural interpretation of model parameters. We also show how covariates are incorporated into the model and how various types of correlation among repeated measures on the same individual may be accounted for. The models are illustrated using longitudinal allergy data consisting of sneezing scores measured on a four‐point scale. Our approach throughout is Bayesian and we present a range of simple diagnostics to aid model building. Copyright © 2001 John Wiley & Sons, Ltd.
Randomized clinical trials with added rescue medication: some approaches to their analysis and interpretation
Authors: White Ian R. , Bamias Christina , Hardy Pollyanna , Pocock Stuart , Warner Jacquie 
Published: January 2005

AbstractPatients in some randomized clinical trials may start additional non‐randomized medication because of an exacerbation of symptoms or insufficient therapeutic effect. Typically this rescue medication reduces the observed treatment effect in intention‐to‐treat analysis. We discuss methods of analysis which take account of rescue medication in order to achieve a more meaningful comparison of the randomized treatments, focusing on trials with a repeated quantitative outcome. Ignoring all data after rescue is likely to be biased because rescued patients are a highly selected group. Instead we propose using methods based on ranks or multilevel models. The rank‐based methods assume that rescued patients have especially bad underlying outcomes. The multilevel regression model relates a patient's outcome to allocated treatment and rescue status at each time, and requires correct modelling of all prognostic factors which predict starting rescue medication and of the covariance between outcomes measured at different times. We also describe sensitivity analyses over a range of possible models for the effect of rescue medication. We illustrate these methods in a trial in Parkinson's disease. It appears that adjustment for rescue medication will not radically alter the randomized treatment comparison unless rescue medication is substantially imbalanced between randomized groups and has a substantial effect on the outcome. Copyright © 2001 John Wiley & Sons, Ltd.