bluuebunny/crossref_metadata_2025_split huggingface dataset:
Surface potential images of self‐assembled monolayers patterned by organosilanes: ab initio molecular orbital calculations
Authors: Saito N. , Hayashi K. , Sugimura H. , Takai O. , Nakagiri N. 
Published: October 2002

AbstractSelf‐assembled monolayers (SAMs) with different function terminal groups were prepared on substrates of n‐type silicon by chemical vapour deposition (CVD) from n‐octadecyltrimethoxysilane (ODS: H3C(CH2)17Si(OCH3)3), heptadecafluoro‐1,1,2,2‐tetrahydro‐decyl‐1‐trimethoxysilane (FAS: F3C(CF2)7 (CH2)2Si(OCH3)3), n‐(6‐aminohexyl)aminopropyltrimethoxysilane (AHAPS: H2N(CH2)6NH(CH2)3 Si(OCH3)3) and 4‐(chloromethyl)phenyltrimethoxysilane [CMPS: H2ClC(C6H4)Si(OCH3)3]. The sample surfaces covered with ODS‐SAM were irradiated under a reduced pressure of 10 Pa with vacuum ultraviolet (VUV) light through a photomask. Then, the irradiated areas with the ODS‐SAM removed were covered with another SAM by CVD. Surface potential images of the patterned areas were measured by Kelvin probe force microscopy (KPFM) and explained by ab initio molecular orbital (MO) calculations. The KPFM measurements showed that the surface potential contrasts of the FAS‐, AHAPS‐ and CMPS‐SAMs against the ODS‐SAM were about −170, +50 and −30 mV, respectively. The surface potentials as a function of area occupied by a molecule were predicted using the respective dipole moments perpendicular to substrates, which were obtained by the ab initio MO calculations. The predicted surface potentials of the FAS‐, CMPS‐ and AHAPS‐SAMs approximately agreed with the measured values at areas of about 1.5, 1.6 and 0.6 nm2 per molecule. The ab initio MO calculations also showed differences in surface potentials appearing due to the differences in Fermi levels of the respective SAMs. Copyright © 2002 John Wiley & Sons, Ltd.
XPS and theoretical studies of the electronic structure of FeX and NiX (X = Al, Si, P)
Authors: Shabanova I. N. , Mitrochin Y. S. , Terebova N. S. , Nebogatikov N. M. 
Published: October 2002

AbstractFor the stoichiometric compounds FeX and NiX (X = Si, Al, P) the x‐ray photoelectron spectra of valence bands are obtained and calculations of their electronic structure are carried out by the tight‐binding linear muffin‐tin orbital atomic sphere approximation method (TB‐LMTO‐ASA). A satisfactory agreement between the x‐ray photoelectron spectra and the calculated density‐of‐states curves is obtained. It is shown that with an increase of the second‐component p‐electrons, hybridization of d(metal) and p(X) electrons decreases, the probability of d–p resonance increases and the contribution of p(X) states near Ef increases. Copyright © 2002 John Wiley & Sons, Ltd.
Study by Monte‐Carlo simulation of resolution improvement by energy filtering in Bio‐TEM
Authors: Suga H. , Kouzuki T. , Shimizu R , Kotera M. 
Published: October 2002

AbstractAn electron microscope for observing biological samples at atmospheric pressure has been proposed. The major principle of the present instrument is that a biological sample is set in a conventional transmission electron microscope (TEM) beamline but it is isolated from a high vacuum by upper‐ and lower bulkheads. As indicated by an electron trajectory simulation, a clear image could be obtained if the bulkhead was 100 nm thick beryllium foil. In the present study, the feasibility of the image resolution improvement is examined by energy filtering of the transmitted electrons. Copyright © 2002 John Wiley & Sons, Ltd.
Influence of PMAA‐graft‐PEO copolymers on the formation of thin ZnO films from aqueous solutions
Authors: Hoffmann Rudolf , Fuchs Tobias , Niesen Thomas P. , Bill Joachim , Aldinger Fritz 
Published: October 2002

AbstractThe microstructure of ZnO thin films was characterized by atomic force microscopy (AFM) and scanning electron microscopy (SEM). The ZnO films were deposited on bare silicon as well as on Si wafers modified with self‐assembled monolayers (SAMs) by the thermohydrolysis of zinc salts from aqueous solution with the addition of water‐soluble copolymers. The influence of polymethacrylic acid partially grafted with polyethylenoxide side‐chains on the morphology of the thin films was investigated.X‐ray photoelectron spectroscopy (XPS) was carried out to determine the composition of the thin films. A comparison of the position of the O 1s peak in as‐deposited and annealed films suggests that the copolymer remains attached to the precipitated ZnO particles. After calcination at 723 K the copolymer is completely removed, yielding ZnO films with a thickness of ∼70 nm. Copyright © 2002 John Wiley & Sons, Ltd.
Compositional analysis of SiOxNy:H films by heavy‐ion ERDA: the problem of radiation damage
Authors: Bohne W. , Fuhs W. , Röhrich J. , Selle B. , Sieber I. , del Prado A. , San Andrés E. , Mártil I. , González‐Díaz G. 
Published: October 2002

AbstractFilms of SiOxNy:H were deposited at room temperature on Si substrates by the electron cyclotron resonance (ECR) plasma method. By varying the flow rates of the precursor gases SiH4, O2 and N2, the whole composition range between pure silicon oxide and nitride could be covered. Heavy‐ion elastic recoil detection analysis (HI‐ERDA) with a 150 MeV 86Kr ion beam and time‐of‐flight (ToF) mass separation was applied to determine the absolute atomic concentrations of all film components, including hydrogen. Additionally, the bonding configuration of the films was studied by infrared (IR) spectroscopy. Extended ion beam exposure was found to decrease the intensity of the N–H phonon band as well as the nitrogen and hydrogen concentrations. By storing the ion scattering data event by event and by recalculating a zero‐dose composition, this effect was taken into account. The corrected HI‐ERDA results revealed clear relations to the deposition parameters (e.g. the O2/SiH4 flow ratio). The hydrogen incorporated in the films turned out to be bonded predominantly to nitrogen. The damage effects were strongest in the medium composition range. They were found to scale with the relative concentration of SiO2N2‐type basic tetrahedrons, suggesting that this bonding configuration is most sensitive against irradiation during the HI‐ERDA measurement. Copyright © 2002 John Wiley & Sons, Ltd.
Characterization of lead–titanium–oxygen compounds by static SIMS
Authors: Aubriet Frédéric , Poleunis Claude , Bertrand Patrick 
Published: October 2002

AbstractPb–Ti–O thin films, lead titanate powder, lead monoxide, titanium dioxide and a stoichiometric PbO–TiO2 mixture were investigated by time‐of‐flight (ToF) SIMS. The nature of the numerous PbxOy+/−, TixOy+/− and PbxTix,Oy+/− ionic species generated by 15 keV Ga+ primary ion bombardment analysed by ToF‐SIMS allowed the identification of the involved metal–oxygen system. The detection of PbxTix,Oy+/− mixed metal ions was specific to lead titanate (film and powder). Indeed, these species were not observed when the PbO–TiO2 stoichiometric mixture was examined. Consequently, they allowed unambiguous molecular identification of the Pb–Ti–O investigated system. Copyright © 2002 John Wiley & Sons, Ltd.
Free‐electron metal alloys: a study by high‐energy XPS
Authors: Abel Marie‐Laure , Tsakiropoulos Panos , Watts John F. , Matthew James A. D. 
Published: October 2002

AbstractIn an extension of previous work on charge redistribution phenomena in aluminium transition metals alloys, high‐energy x‐ray photoelectron spectroscopy (XPS) was performed on alloys prepared with elements having sp‐dominated band structure, specifically aluminium, magnesium and silicon, and the alloys Al–2.5Mg, Al–25Mg, Al–10Si and Al–50Si have been investigated. This work was performed using an ESCA300 spectrometer fitted with a Cr Kβ source (hν = 5946.7 eV).Examination of the final‐ and initial‐state Auger parameters shows that very little variation occurs in the alloys compared with pure elemental solids and that the values obtained are very close to being within experimental error. Examination of the plasmon energies and intensities, however, shows that the main variations are obtained for alloys forming a discrete phase upon alloying (intermetallic phase) as opposed to alloys forming solid solutions or those precipitating pure metallic phases on cooling. The Al–25Mg alloy contains the Al3Mg2 (β) phase. This phase contributes towards the variation of the effective cell volume of Mg and Al compared with the pure metals and is consistent with an increase and a decrease of their respective plasmon energies. Copyright © 2002 John Wiley & Sons, Ltd.
Passivity and its breakdown on stainless steels and alloys
Authors: Qiu J. H. 
Published: October 2002

AbstractThe service reliability of stainless steels and alloys is predominantly determined by the chemical stability of an ultrathin passive film on their surfaces. The thickness, composition and structure of such an ultrathin oxide film are all influenced by the alloy composition and the nature of the environments they are exposed to. Surface analysis of passive films formed on different grades of stainless steels under different conditions showed that chromium was significantly enriched in the surface film whereas nickel was not present in the oxidized state. Breakdown of passivity either due to mechanical damage or due to chemical attack often leads to localized corrosion in the form of pitting, crevice corrosion and stress corrosion cracking. This paper discusses the corrosion resistance characteristics of stainless steels and alloys in the context of surface film properties. Copyright © 2002 John Wiley & Sons, Ltd.
Nanoscale surface characterization of conducting and non‐conducting materials with STM and contact SFM: some problems and solutions
Authors: Zhdan Peter A. 
Published: October 2002

AbstractMethods of scanning tunnelling microscopy (STM) and of contact scanning force microscopy (CSFM) are widely used in many academic and industrial laboratories for nanoscale surface characterization of conducting and insulating materials. These techniques allow for very high (atomic) resolution to be achieved in different environments—vacuum, air and liquids—not to mention their ability to evaluate quantitatively selected surface features, including statistical analysis of corrugations, which permits roughness parameters to be determined on the nano‐ and microscale. Many CSFM systems are used now in industrial research laboratories, quality assurance and control departments where precise surface feature dimensioning of roughness analysis is critical for product development or process control. Each STM and CSFM user comes up against these tasks regularly during his/her daily work, therefore thorough understanding of the main principles, advantages and limitations of specific operation modes is the basis for appropriate setting of the experiments and for interpretation of acquired STM and CSFM data.Here, using a variety of experimental results obtained in our laboratory during the last few years for a number of different conducting and non‐conducting materials, some principal questions and problems related to the practical aspects of STM and CSFM are reviewed and discussed in detail: requirements for samples to be studied and their preparation for investigation, optimization of the experimental set‐up and acquisition parameters for different environments; and correct interpretation of the acquired experimental data. We hope that practical recommendations given in this paper will be useful to new users of STM and CSFM, introducing them to this field and helping in their experimental work, especially when studying ‘difficult’ samples. Copyright © 2002 John Wiley & Sons, Ltd.
Using in situ AFM to investigate corrosion and passivation of duplex stainless steels
Authors: Yang X. F. , Castle J. E. 
Published: October 2002

AbstractThis paper reports in situ atomic force microscopy (AFM) and SEM studies of the corrosion of duplex stainless steels. The results showed selective dissolution of the duplex structure, with one rapidly dissolving phase and one slowly dissolving phase. Electron probe microanalysis (EPMA) measurements showed that the weak phase contained more Cr and Mo and the resistance phase contained more Ni, which was used to assign these phases to ferrite and austenite, respectively. Copper deposition experiments showed that the resistant phase was more noble and acted as the cathode. The mode of dissolution was apparently modified after polarization of the steel in the passive range. Copyright © 2002 John Wiley & Sons, Ltd.
A practical approach for comparing means of two groups without equal variance assumption
Authors: Wang Hansheng , Chow Shein‐Chung 
Published: October 2002

AbstractIn this paper we consider two‐groups of i.i.d. normally distributed random variables (N(μx,σx2) and N(μy,σy2)) without assuming equal variance (σx2 = σy2). We propose a simple method for constructing confidence bounds based on Howe's approximation I. Its applications in parallel clinical trial (testing H0 : μx‐μy=0 versus H1 : μx‐μy<0) and parallel bioequivalence (BE) trial (testing H0:∣μx‐μy∣δ versus H1:∣μx‐μy∣<δ) are studied. Sample size calculation formulae for both cases are derived. Their performances are evaluated by simulation. Our study shows that the proposed procedure can control type I error satisfactorily compared with Cochran–Cox's and Satterthwaite's approximations while maintaining a relatively high power. The proposed approach is not only simple for constructing the confidence limit, but also provides a simple and accurate formula for sample size calculation. Copyright © 2002 John Wiley & Sons, Ltd.
Mechanistic modelling in large case‐control studies of lung cancer risk from smoking
Authors: Heidenreich W. F. , Wellmann J. , Jacob P. , Wichmann H. E. 
Published: October 2002

AbstractThe two‐step clonal expansion (TSCE) model is applied to large case‐control studies, frequency matched for age, which allow estimation of the RR of lung tumour risk caused by smoking. For estimating background hazard rates, mortality data from the study areas are used to supplement the case‐control data. Two approaches are used to analyse the data, based on the unconditional and the conditional likelihoods. They are demonstrated to give nearly identical results. Some model diagnostics are performed and demonstrate a good model fit. Our results indicate that smoking acts on the promotion and transformation parameters, but not on the initiation parameter of the TSCE model. The fitted relative risk of current smokers peaks between ages 50 and 60 years. The relative risk of male ex‐smokers decreases strongly with time since end of exposure, but does not reach the risk of non‐smokers, and does not decrease as much as for female ex‐smokers. Copyright © 2002 John Wiley & Sons, Ltd.
The ebb and flow of the NHS waiting list: how do recruitment and admission affect event‐based measures of the length of ‘time‐to‐admission’?
Authors: Armstrong Paul W. 
Published: October 2002

AbstractThe likelihood of admission is reported in England as the percentage of elective episodes occurring within a certain time, for example, within three months of the date of enrolment on the waiting list. This event‐based measure is calculated from cross‐sectional data: the denominator is the number of elective episodes occurring in a specified calendar period, and the numerator is the number found to have enrolled on the waiting list less than three months previously. Now the number of elective episodes occurring within three months reflects the likelihood of admission and the numbers eligible to be admitted. If there is any increase in the likelihood of admission or in the number of people exposed to that likelihood then there will be an increase in the number of elective episodes found to have enrolled on the waiting list less than three months previously. Thus the numerator used by the Government Statistical Service accurately reflects conditions during the calendar period and within the enrolment cohorts of interest. The Government Statistical Service also needs a denominator so the episodes observed 0–2, 3–5, 6–8, 9–11 etc. months after enrolment are added as an indication of the number of people that could have been admitted within three months. This denominator implies that the number of people eligible for admission from the 3–5 month waiting time category is the same as the number surviving admission from the 0–2 month waiting time category but, during the period of interest, these two groups of people belong to cohorts that were recruited to the waiting list quite independently. As a result, this denominator will be too big if the number surviving to the end of one waiting time category is bigger than the number eligible for admission from the next and it will be too small if the number surviving to the end of one waiting time category is smaller than the number eligible for admission from the next. The event‐based measure assumes that the waiting list is stationary and closed and only gives unbiased estimates under these conditions. This paper describes three alternative measures which recognize that the number of people recruited or admitted may vary from one quarter to the next. It uses Department of Health data to assess the size of the error if the event‐based measure is used in these circumstances. Copyright © 2002 John Wiley & Sons, Ltd.
On changing a long‐term clinical trial midstream
Authors: Wittes Janet 
Published: October 2002

AbstractClinical triallists are often reluctant to alter the protocol or the design of an ongoing study in part because of concern that changes may affect the integrity of the study. This paper encourages considering changes in long‐term clinical trials when the medical environment changes or when the accruing data from the trial lead to questioning the assumptions underlying the original design. One must make such changes in a way that will not cast doubt on the integrity of the trial. An important aspect of the design is choice of sample size. Methodology for sample size recalculation has matured over the decade. Several techniques are now available for the usual types of endpoints – continuous, discrete and time‐to‐failure – as well as for longitudinal analysis. Published papers describe the choices of variance at the time of recalculation, approaches to estimation and testing at the end of the study, and the time of recalculation. In a study with a sponsor, a Data Safety Monitoring Board (DSMB) and an Executive Committee, one or more of these three groups is responsible for recommending increases in sample size when the accruing data indicate that the assumed variance underestimated the true variance. Sometimes a statistician independent of all three bodies performs the relevant calculations and sends the recommendation to the sponsor. This paper argues that the DSMB should not generally be the responsible body because knowledge of treatment effect can place it in an uncomfortable position. Copyright © 2002 John Wiley & Sons, Ltd.
Regulatory perspectives on data monitoring
Authors: O'Neill Robert T. 
Published: October 2002

AbstractData monitoring is a critical component of the conduct of clinical trials that provide the evidence of efficacy and safety of investigational drugs. These trials may be conducted either by a pharmaceutical sponsor or by the government, especially those large trials that assess the impact of therapies on serious morbidity and/or mortality. While not extensive, I will review a regulatory history of FDA's evolving concerns and positions on data monitoring. I will review the key aspects of data monitoring and interim analysis of clinical trials contained in the recently published International Conference on Harmonization's statistical guidance as well as some other issues being considered for a draft guidance on data monitoring. Finally, some suggestions for improving and enhancing tools and statistical methods for monitoring clinical trials for safety assessment will be offered. This latter area deserves more consideration by statisticians than it has received to date. Published in 2002 by John Wiley & Sons, Ltd.
The role of covariates in estimating treatment effects and risk in long‐term clinical trials
Authors: Ford Ian , Norrie John 
Published: October 2002

AbstractThis paper reviews previously published work showing that the impact of including covariates in models used to estimate the magnitude of treatment effects in long‐term clinical trials is different from what would be predicted from results for the normal linear model. Typically, models with and without covariates cannot simultaneously be valid. A case is made for the use of data from clinical trials to model the future risk and potential benefits of treatment in individual subjects. The methods and results are illustrated using data from the West of Scotland Coronary Prevention Study. Copyright © 2002 John Wiley & Sons, Ltd.
Subgroup analysis, covariate adjustment and baseline comparisons in clinical trial reporting: current practiceand problems
Authors: Pocock Stuart J. , Assmann Susan E. , Enos Laura E. , Kasten Linda E. 
Published: October 2002

AbstractClinical trial investigators often record a great deal of baseline data on each patient at randomization. When reporting the trial's findings such baseline data can be used for (i) subgroup analyses which explore whether there is evidence that the treatment difference depends on certain patient characteristics, (ii) covariate‐adjusted analyses which aim to refine the analysis of the overall treatment difference by taking account of the fact that some baseline characteristics are related to outcome and may be unbalanced between treatment groups, and (iii) baseline comparisons which compare the baseline characteristics of patients in each treatment group for any possible (unlucky) differences. This paper examines how these issues are currently tackled in the medical journals, based on a recent survey of 50 trial reports in four major journals. The statistical ramifications are explored, major problems are highlighted and recommendations for future practice are proposed. Key issues include: the overuse and overinterpretation of subgroup analyses; the underuse of appropriate statistical tests for interaction; inconsistencies in the use of covariate‐adjustment; the lack of clear guidelines on covariate selection; the overuse of baseline comparisons in some studies; the misuses of significance tests for baseline comparability, and the need for trials to have a predefined statistical analysis plan for all these uses of baseline data. Copyright © 2002 John Wiley & Sons, Ltd.