bluuebunny/crossref_metadata_2025_split huggingface dataset:
Surface chemistry study of RuO2/IrO2/TiO2 mixed‐oxide electrodes
Authors: Barison Simona , Daolio Sergio , Fabrizio Monica , Battisti Achille De 
Published: January 2004

AbstractDSA® metal oxide electrodes such as the RuO2/IrO2/TiO2 mixed system are widely studied for their excellent electrocatalytic activity. In order to understand their catalytic properties, the comprehension of the surface chemistry involved during electrochemical treatments is crucial. With this aim, RuO2/IrO2/TiO2 mixed‐oxide electrodes having various noble metal contents were studied by means of secondary ion mass spectrometry (SIMS). In particular, cathodic and anodic polarization and O2 evolution reactions were carried out to test the electrode behaviour and SIMS analyses were performed after all these treatments. In this way, surface changes induced by electrochemical treatments and depending on electrode composition were widely investigated by SIMS, revealing, for example, the presence of hydration or preferential dissolution phenomena induced by electrochemical processing. Copyright © 2004 John Wiley & Sons, Ltd.
Ab initio calculations of proton affinities of glycine, proline, cysteine and phenylalanine: comparison with the experimental values obtained using an electrospray ionisation ion trap mass spectrometer
Authors: Pepe C. , Rochut S. , Paumard J.‐P. , Tabet J.‐C. 
Published: January 2004

AbstractThe proton affinities of four characteristic amino acids, glycine, proline, cysteine and phenylalanine, have been calculated using three different types of wave function, HF, DFT and MP2. These wave functions were combined with several basis sets using the valence double‐ or triple‐ξ with polarisation functions, and included or not a diffuse d function on heavy atoms. Calculations were carried out using Gaussian 98 on a LINUX system (2 GHz, 2 GB of RAM). The calculated results have been compared with the experimental values obtained using Cooks' kinetic method, in particular on an electrospray ionisation ion trap mass spectrometer. An excellent agreement was found between the experimental values and the theoretical results obtained using the B3P86/6‐31+G*//B3LYP/6‐31G* level. Copyright © 2004 John Wiley & Sons, Ltd.
Glass‐chip‐based sample preparation and on‐chip trypic digestion for matrix‐assisted laser desorption/ionization mass spectrometric analysis using a sol–gel/2,5‐dihydroxybenzoic acid hybrid matrix
Authors: Lin Ya‐Shiuan , Yang Chin‐Hsiung , Chen Yu‐Chie 
Published: January 2004

AbstractA glass‐chip‐based sample preparation method for matrix‐assisted laser desorption/ionization mass spectrometric (MALDI‐MS) analysis of tryptic digests of proteins and intact cells is described. A MALDI matrix, 2,5‐dihydroxybenzoic acid (2,5‐DHB), was hybridized with sol–gels to generate a sol–gel‐derived material. Taking advantage of the characteristics of sol–gels, the sol–gel‐derived material readily adhered to the surface of a glass chip through covalent bonding. Only one step of sample preparation, deposition of the sample solution on the glass chip, was required before MALDI‐MS analysis. Because 2,5‐DHB was homogeneously dispersed on the sol–gel network structure, good spot‐to‐spot reproducibility was obtained in MALDI analysis using this approach and the analyte signals were uniform throughout the chip. The modified glass chips were robust and effective for at least 1 week. This glass‐chip‐based matrix preparation method provides a straightforward approach to developing techniques for analyzing the on‐chip enzymatic digestion of proteins and intact cells of microorganisms. Cytochrome C and Escherichia coli were used as analytes to demonstrate the feasibility of this approach. The products of the on‐chip enzymatic digests were identified through protein database searches. Copyright © 2004 John Wiley & Sons, Ltd.
Rapid screening for S‐adenosylmethionine‐dependent methylation products by enzyme‐transferred isotope patterns analysis
Authors: Wan Wei , Zhao Gang , Al‐Saad Khalid , Siems William F. , Zhou Zhaohui Sunny 
Published: January 2004

AbstractWe report here an isotopic labeling and mass spectrometric method to rapidly identify S‐adenosylmethionine (AdoMet)‐dependent methylation products. In the presence of CH3‐ and CD3‐labeled AdoMet, a methyl transfer product appears as a doublet separated by 3 Da in a mass spectrum, while other compounds show their normal isotopic distribution. Based on this unique isotopic pattern, methylation product(s) can be easily detected even from a mixture of cellular components. To validate our method, the product of human thiopurine methyltransferase (TPMT, EC 2.1.1.67) has been successfully identified from both an in vitro assay and a whole‐cell assay. This method is generally applicable to AdoMet‐dependent transmethylation and other group‐transfer reactions, and constitutes the first example of a general strategy of enzyme‐transferred isotope patterns (ETIPs) analysis. Copyright © 2004 John Wiley & Sons, Ltd.
[2H/H] Isotope ratio analyses of [2H5]cholesterol using high‐temperature conversion elemental analyser isotope‐ratio mass spectrometry: determination of cholesterol absorption in normocholesterolemic volunteers
Authors: Godin Jean‐Philippe , Richelle Myriam , Metairon Sylviane , Fay Laurent‐Bernard 
Published: January 2004

AbstractThis paper validates the use of high‐temperature conversion elemental analyser isotope‐ratio mass spectrometry (TC‐EA/IRMS) for measuring the [2H/H] enrichment of plasma [2H5]cholesterol. From a molecular point of view, the free cholesterol is initially separated from plasma by thin‐layer chromatography (TLC) and then injected onto the TC‐EA reactor which converts cholesterol molecules into CO and H2 gases. The slope of the curve of the experimental mole percent excess (MPE(exp.)) versus MPE(theor.) was very close to 1, demonstrating that no significant isotopic fractionation was observed during all processing of the samples (i.e., isolation of plasma free cholesterol by TLC and pyrolysis in the TC‐EA reactor). Excellent linearity (r2 = 0.9994, n = 4) of δ (‰) of [2H/H] isotopic measurements versus mole percent (MP) was assessed over the range 0 to 0.1 MP. The precision of the [2H/H] measurement, evaluated with two calibration points processed with TLC, was δ2HV‐SMOW = −192.5 ± 3.4‰ and δ2HV‐SMOW = −136.9 ± 2.9‰. The standard deviations of the within‐assay and between‐assay repeatabilities of the analytical process, evaluated using the quality control (QC) of plasma samples, were 4.6 and 6.1‰, respectively. Plant sterols are known to reduce cholesterol absorption and therefore were used as a positive control in a clinical study performed with normocholesterolemic volunteers. This present method produces biological results consistent with those already reported in the literature. Copyright © 2004 John Wiley & Sons, Ltd.
Oligomeric carbon and siloxane series observed by matrix‐assisted laser desorption/ionisation and laser desorption/ionisation mass spectrometry during the analysis of soot formed in fuel‐rich flames
Authors: Apicella Barbara , Ciajolo Anna , Millan Marcos , Galmes Carolina , Herod Alan A. , Kandiyoti Rafael 
Published: January 2004

AbstractOligomeric carbon and siloxane series have been observed by matrix‐assisted laser desorption/ionisation mass spectrometry (MALDI‐MS), during the analysis of the dichloromethane (DCM)‐soluble fractions of condensable material recovered from fuel‐rich flames. Laser desorption (LD) spectra showed a pattern of oligomeric dimethyl‐siloxane structures with a spacing of 74 u. The siloxane series appears to have originated as contamination of samples by silicone oil used to lubricate connections of polymer tubing. This was confirmed by extracting silicone tubing and silicone grease with DCM followed by MALDI‐MS analysis. A series of peaks with a mass spacing of 24 u was also observed, superimposed on the continuum of unresolved organic ions. This oligomeric series appears to correspond to polycyclic aromatics separated by (mainly) ethylene bridges. Thus LD‐MS appears to have revealed a series of soot precursors, intermediate between polycyclic aromatics and particulate soot, which was not detected by MALDI‐MS. More detailed work is necessary to define these species with precision. Copyright © 2004 John Wiley & Sons, Ltd.
Advantages of derivatization by osmium tetroxide and 2,2′‐bipyridine for matrix‐assisted laser desorption/ionization post‐source decay fragment ion analysis of peptides
Authors: Šedo O. , Novotná K. , Havel J. 
Published: January 2004

AbstractMatrix‐assisted laser desorption/ionization—post‐source decay (MALDI‐PSD) fragment ion analysis is frequently used for peptide sequence determination. PSD fragmentation is often changed or improved in terms of, e.g., sequence coverage, after derivatization. In this work, the influence of modification by an osmium tetroxide‐bipyridine reagent (Os,bipy) on the MALDI‐PSD behaviour of peptides is studied. The reagent modifies peptides specifically at tryptophan residues and oxidizes methionine to methionine sulfone and cysteine to cysteic acid. As a result the masses of some of the fragments are specifically shifted in case of peptides containing a methionine by +32 Da and, in cases of peptides containing a cysteine residue, by +48 Da. In addition, due to the change in protonation properties of a peptide after oxidation, fragments containing cysteic acid are in most cases totally suppressed. This effect significantly facilitates peptide sequence determination. Improvement of MALDI‐TOFMS and PSD analysis after the reaction with Os,bipy is demonstrated for examples involving derivatives of humanin, a novel neuroprotective peptide. Copyright © 2004 John Wiley & Sons, Ltd.
Formation of [MH]− and [M2H]2− ions in the electrospray ionization mass spectra of dicarboxylated polyethylene glycols
Authors: Frańska Magdalena , Zgoła Agnieszka , Rychłowska Joanna , Szymański Andrzej , Łukaszewski Zenon , Frański Rafał 
Published: January 2004

AbstractThe negative‐ion electrospray mass spectrometric behavior of dicarboxylated polyethylene glycols (CPEGCs) is discussed. Both [MH]− and [M2H]2− ions were observed. It was found that the ratio [M2H]2−/[MH]− is affected by oxyethylene chain length, solvent polarity, analyte concentration and applied cone voltage. Copyright © 2004 John Wiley & Sons, Ltd.
Adaptation to life after surgical removal of the bladder—an application of graphical Markov models for analysing longitudinal data
Authors: Hardt J. , Petrak F. , Filipas D. , Egle U. T. 
Published: January 2004

AbstractGraphical Markov models have been developed particularly for the analysis of observational data. They allow the control of various background variables when analysing theoretically relevant associations. This paper demonstrates the application and some advantages of graphical Markov models in comparison to conventional statistical analyses. The aim of the study was to identify patients at risk for developing decreased health‐related quality of life (QoL) after cystectomy and to explore the influence of coping on QoL in this situation. Therefore, the method was applied to analyse the data of a prospective study, in which 81 patients with bladder cancer were interviewed pre‐operatively and in a 1‐year follow‐up. QoL was assessed both times, and two basic coping strategies (active and depressive) were measured preoperatively. The explanatory variables of theoretical interest were active and depressive coping strategies. As a result of the analysis, relevant proportions of variance in the development of QoL could be explained by the suggested model (60 per cent in mental component, 40 per cent in physical component of QoL). Active coping was positively related to QoL, depressive coping negatively. These effects were linear in the physical component of QoL, moderated by working status and the type of urinary diversion in the mental component of QoL. Copyright © 2004 John Wiley & Sons, Ltd.
Admissible two‐stage designs for phase II cancer clinical trials
Authors: Jung Sin‐Ho , Lee Taiyeong , Kim KyungMann , George Stephen L. 
Published: January 2004

AbstractIn a typical two‐stage design for a phase II cancer clinical trial for efficacy screening of cytotoxic agents, a fixed number of patients are initially enrolled and treated. The trial may be terminated for lack of efficacy if the observed number of tumour responses after the first stage is too small, thus avoiding treatment of patient with inefficacious regimen. Otherwise, an additional fixed number of patients are enrolled and treated to accumulate additional information on efficacy as well as safety. The minimax and the so‐called ‘optimal’ designs by Simon have been widely used, and other designs have largely been ignored in the past for such two‐stage cancer clinical trials. Recently Jung et al. proposed a graphical method to search for compromise designs with features more favourable than either the minimax or the optimal design. In this paper, we develop a family of two‐stage designs that are admissible according to a Bayesian decision‐theoretic criterion based on an ethically justifiable loss function. We show that the admissible designs include as special cases the Simon's minimax and the optimal designs as well as the compromise designs introduced by Jung et al. We also present a Java program to search for admissible designs that are compromises between the minimax and the optimal designs. Copyright © 2004 John Wiley & Sons, Ltd.
Testing non‐inferiority (and equivalence) between two diagnostic procedures in paired‐sample ordinal data
Authors: Lui Kung‐Jong , Zhou Xiao‐Hua 
Published: January 2004

AbstractBefore adopting a new diagnostic procedure, which is more convenient and less expensive than the standard existing procedure, it is essentially important to assess whether the diagnostic accuracy of the new procedure is non‐inferior (or equivalent) to that of the standard procedure. In this paper, we consider the situation where test responses are on an ordinal scale with more than two categories. We give two definitions of non‐inferiority, one in terms of the probability of correctly identifying the case for a randomly selected pair of a case and a non‐case over all possible cut‐off points, and the other in terms of both the sensitivity and specificity directly. On the basis of large sample theory, we develop two simple test procedures for detecting non‐inferiority. We further conduct Monte Carlo simulation to evaluate the finite sample performance of these test procedures. We note that the two asymptotic test procedures proposed here can actually perform reasonably well in a variety of situations even when the numbers of studied subjects from the diseased and non‐diseased populations are not large. To illustrate the use of the proposed test procedures, we include an example of determining whether the diagnostic accuracy of using a digitized film is non‐inferior to that of using a plain film for screening breast cancer. Finally, we note that the extension of these results to accommodate the case of detecting (two‐sided) equivalence is simply straightforward. Copyright © 2004 John Wiley & Sons, Ltd.
Stochastic model for non‐standard case–cohort design
Authors: Hsiu‐Hsi Chen Tony , Yen Ming‐Fang , Shiu Ming‐Neng , Tung Tao‐Hsin , Wu Hui‐Min 
Published: January 2004

AbstractApplication of case–cohort design to multi‐state disease progression in epidemiological studies has been barely addressed. To estimate multi‐state disease natural history, we proposed non‐homogeneous exponential regression stochastic model to accommodate the data requiring a non‐standard case–cohort design. We allowed transition rates to vary with time by modelling the time of transitions between two states with Weibull distribution. The exponential regression model was used to assess the effect of patient‐specific covariates on multi‐state disease progressions. This method was successfully applied to two epidemiological applications. The first application was to elucidate the effect of betel quids, smoking and alcohol on three‐state disease progression, from normal, through leukoplakia and finally to oral cancer. The second application was to extend the three‐state to a five‐state model to estimate transition rates from normal to diminutive adenoma to small adenoma to large adenoma and finally to invasive carcinoma of the colon and rectum. Finally, an index for assessing the treatment efficacy for pre‐cancerous lesion was developed by comparing transition probabilities derived from the proposed model with the probabilities of malignant transformation after a medical regime. Copyright © 2004 John Wiley & Sons, Ltd.
Analysis of testicular cancer data using a frailty modelwith familial dependence
Authors: Moger Tron A. , Aalen Odd O. , Heimdal Ketil , Gjessing Håkon K. 
Published: January 2004

AbstractPreviously published papers have indicated a fairly strong familial dependence intesticular cancer patients. This is particularly evident in brothers. We have applied a frailty model with familial dependence to family data on brothers of testicular cancer patients from the Norwegian Radium Hospital. The model is a two‐level frailty, with variation in susceptibility at both the family and the individual level. Specifically, the frailty variable is assumed to be compound Poisson distributed to allow individuals to be non‐susceptible. The underlying Poisson parameter is gamma distributed to model how testicular cancer is distributed among families. This is an extension of a previous compound Poisson frailty model developed for individual testicular cancer data, and an alternative to traditional modelling of survival time family data. The likelihood construction and ascertainment problems are looked at in detail. To avoid ascertainment bias, the likelihood is based on the probability of observing the disease status for each brother in a family, given that at least one brother is ascertained. The estimated relative risk for brothers is 7.4. This paper expands on a previous analysis of the data by using a frailty model, which makes it possible to examine how the cancer is distributed among families. The estimated gamma‐shaped parameter is 0.151 (95 per cent confidence interval 0.078–0.294), and this indicates that in order to obtain the high relative risks observed for brothers of testicular cancer patients, the distribution of susceptibility has to be strongly skewed among the families. The vast majority of families have a very low risk and a small proportion have a high risk. In addition, a quantity similar to the relative risk is derived to show that the susceptibility is skewly distributed also if the Poisson parameter is Bernoulli or stable distributed. This indicates that the results are valid also if other distributions are used to model familial dependence in the compound Poisson frailty model. Copyright © 2004 John Wiley & Sons, Ltd.
Two‐sample scale tests for comparison of metabolic rates for styrene in previously exposed and unexposed groups
Authors: Chen Chu‐Chih , Wu Kuen‐Yuh , Balakrishnan N. 
Published: January 2004

AbstractStatistical analysis procedure in two‐sample treatment difference, as well as alternative hypothesis, may play a central role in statistical inference, especially in small sample size case. In this paper, simple non‐parametric two‐sample permutation tests for scale difference based on the Hodges–Lehmann estimator are reformulated, and are applied to a study examining whether previous styrene exposure increases (thus a one‐sided alternative hypothesis rather than a two‐sided one) the human liver's metabolic ability to convert styrene into styrene oxide, in which a three‐compartment physiologically based pharmacokinetic (PBPK) model was used to compare the estimated metabolic constant κamong the previously exposed and unexposed groups. Contrary to the previous conclusion, the proposed tests for scale difference identified from a mixed‐effects model showed a significant result. Copyright © 2004 John Wiley & Sons, Ltd.
Electronic monitoring of variation in drug intakes can reduce bias and improve precision in pharmacokinetic/pharmacodynamic population studies
Authors: Vrijens Bernard , Goetghebeur Els 
Published: January 2004

AbstractPopulation pharmacokinetic (PK) and pharmacodynamic (PD) studies evaluate drug concentration profiles and pharmacological effects over time when standard drug dosage regimens are assigned. They constitute a scientific basis for the determination of the optimal dosage of a new drug. Population PK/PD analyses can be performed on relatively few measures per patient enabling the study of a sizable sample of patients who take the drug over a possibly long period of time. We expose the problem of bias in PK/PD estimators in the presence of partial compliance with assigned treatment as it occurs in practice. We propose to solve this by recording accurate data on a number of previous dose timings and using timing‐explicit hierarchical non‐linear models for analysis. In practice, we rely on electronic measures of an ambulatory patient's drug dosing histories. Especially for non‐linear PD estimation, we found that not only bias can be reduced, but higher precision can also be retrieved from the same number of data points when irregular drug intake times occur in well‐controlled studies. We apply methods proposed by Mentré et al. to investigate the information matrix for hierarchical non‐linear models. This confirms that a substantial gain in precision can be expected due to irregular drug intakes. Intuitively, this is explained by the fact that regular takers experience a relatively small range of concentrations, which makes it hard to estimate any deviation from linearity in the effect model. We conclude that estimators of PK/PD parameters can benefit greatly from information that enters through greater variation in the drug exposure process. Copyright © 2004 John Wiley & Sons, Ltd.
Binary latent variable modelling and its applicationin the study of air pollution in Hong Kong
Authors: Hu Z. G. , Wong C. M. , Thach T. Q. , Lam T. H. , Hedley A. J. 
Published: January 2004

AbstractA binary latent variable is constructed to account for the correlation between multiple binary outcomes and is treated as a dependent variable in modelling for covariate effects. This modelling method is similar to the structural equation modelling. Three models are considered: (1) all covariates affecting the binary latent variable directly; (2) some covariates affecting the binary latent variable while other affecting the manifestation of the binary outcomes; and (3) no covariates are included. Gibbs sampling, a special case of the Markov Chain Monte Carlo method, is used to estimate the parameters in the models. Simulation studies show that this method is valid and reliable in estimating covariate effects. But Model (1) fitted the data best with lowest value in the deviance information criteria. The method is illustrated by applying it to the data analysis of an environmental air pollution study. The results show that air pollution (i.e. the most versus the least polluted district) (odds ratio 1.20; 95% confidence interval 0.97–1.49; p=0.102), smoking (relative to not smoking) (2.75; 2.21–3.41; p < 0.001) and mosquito coil use (relative to non‐use) (1.27; 0.99–1.62; p=0.058) had an impact on the respiratory health of male adults in Hong Kong. Copyright © 2004 John Wiley & Sons, Ltd.
The WebDAV property design
Authors: Whitehead E. James , Goland Yaron Y. 
Published: January 2004

AbstractThis paper provides a detailed description of the general design space for metadata storage capabilities. The design space considers issues of metadata identification, typing and representation, dynamic behavior, predefined and user‐defined metadata, schema discovery/update, operations, API packaging/marshalling, searching, and versioning. The design space is used to structure a retrospective analysis of the three major alternative metadata designs considered during the design of the WebDAV distributed authoring protocol. Deployment experience with WebDAV properties is also discussed, with the most successful use occurring in custom client/server pairs and in protocol extensions. Copyright © 2004 John Wiley & Sons, Ltd.