bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sulphur segregation on free and oxidized NiAl(001)
Authors: Rivoaland L. , Maurice V. , Bacos M.‐P. , Marcus P. 
Published: October 2002

AbstractAuger electron spectroscopy (AES), low‐energy electron diffraction (LEED) and X‐ray photoelectron spectroscopy (XPS) data on the segregation of sulphur at the surface of an NiAl(001) single crystal and at the interface with alumina thin films are reported. The results show that sulphur segregates at the free metallic surface. The amount of segregated sulphur decreases with increasing aluminium content of the surface. Although the segregation of aluminium is favoured thermodynamically, segregation kinetics and diffusion coefficients measured at 700, 750, 800 and 850°C [D = 0.15 exp(−2 18 000/RT)] show that the segregation of sulphur is favoured kinetically. Saturation of the metallic surface with an amorphous alumina layer formed at room temperature blocks the segregation of sulphur. However, in the initial stages of oxidation at 950°C where the transient θ alumina grows by cationic transport and injection of vacancies at the interface, sulphur segregates at the interface between the alumina thin films and the metallic substrate as measured by XPS. Copyright © 2002 John Wiley & Sons, Ltd.
Epitaxial growth of CaSi2 on Si(111)
Authors: Schöpke A. , Würz R. , Schmidt M. 
Published: October 2002

AbstractThin Ca films were evaporated on Si(111) under ultrahigh vacuum conditions and annealed in the temperature range 200–650°C. The interdiffusion of Ca and Si was examined by ex situ Auger depth profiling. In situ monitoring of the Si 2p core‐level shift by x‐ray photoelectron spectroscopy was employed to study the silicide formation process. The formation temperature of CaSi2 films on Si(111) was found to be ∼350°C. Epitaxial growth takes place at ≥400°C. The morphology of the films, observed by atomic force microscopy, was correlated with their crystallinity as analysed by x‐ray diffraction. Copyright © 2002 John Wiley & Sons, Ltd.
XPS study of fresh and oxidized (Pb,Ge)Te surfaces
Authors: Yashina L. V. , Kobeleva S. P. , Neudachina V. S. , Shatalova T. B. , Zlomanov V. P. 
Published: October 2002

AbstractThe oxidation of (Pb,Ge)Te crystal surfaces at ambient temperature and humidity was studied by means of XPS in a time range from minutes to months. Vacuum‐cleaved crystal was used for the experiment. It was found that Ge in a PbTe lattice occupies two different positions. At one of them, donor behaviour is revealed and the concentration of donor atoms increases at temperatures lower than those of the cubic–rhombohedral phase transition. It was found that oxidation takes place even after a few minutes of air exposure. Germanium atoms oxidize entirely to oxidation state +4, this being followed by slow oxidation of tellurium atoms from oxidation state −2 to +4. After a long air exposure, significant surface enrichment in Pb was observed. Copyright © 2002 John Wiley & Sons, Ltd.
Study of thin oxide films by ellipsometry and ARXPS
Authors: Tichopádek P. , Nebojsa A. , Čechal J. , Bábor P. , Jurkovič P. , Navrátil K. , Šikola T. 
Published: October 2002

AbstractIn the paper the application of a simple spectroscopic ellipsometer for ex situ and in situ studies on SiO2 films (including native oxides on Si) is reported. It is shown that the ellipsometer is a reliable tool for the monitoring of chemical etching of SiO2 films with thicknesses of >10 nm. When the films become thinner, the results are strongly influenced by the contamination and roughness of their surface layers. The concentration profiles of these ultrathin films (<10 nm) were analysed by angle‐resolved XPS. Further, the ability of the ellipsometer to monitor the removal of native oxides on an Si(111) surface by thermal flashing under ultrahigh vacuum conditions is demonstrated as well. Copyright © 2002 John Wiley & Sons, Ltd.
An electrochemical cell for study by XPS of lithium intercalation in oxide films
Authors: Castle J. E. , Guascito M. R. , Salvi A. M. , Decker F. 
Published: October 2002

AbstractX‐ray photoelectron spectroscopy (XPS) is used to determine valence states of thin films. When used to elucidate the effects of electrochemical intercalation of ions in oxide films, the information required is the valence state of multivalence ions. To ensure that this information is not compromised by surface reoxidation, we have developed an in situ electrochemical cell for use with aprotic and anhydrous electrolytes. This cell has been used to study lithium intercalation in thin oxide layers built up on induim tin oxide (ITO)‐coated glass slides. Samples can be exposed for intercalation of lithium (or de‐intercalation), rinsed, dried and transferred within the vacuum of the spectrometer for characterization. The cell is designed to be withdrawn into a nacelle when not in use so as not to interfere with the normal use of the spectrometer. We have shown that the lithium electrode remains in good condition throughout storage periods. The successful use of the prototype cell gives an opportunity to develop the cell for related electrochemical studies in non‐aqueous electrolytes. Copyright © 2002 John Wiley & Sons, Ltd.
Rapid chemical and structural characterization of metastable thin‐film libraries by a combination of electron probe microanalysis and scanning x‐ray diffraction
Authors: Cremer R. , Richter S. 
Published: October 2002

AbstractThe increasing complexity of modern coatings leads to the demand for a cost‐effective tool for the development of new products in the advanced materials industry. One possible approach to this question is the adaptation of combinatorial methods to the specific requirements of the coatings industry.In this paper, the deposition and characterization of two‐dimensionally laterally graded (Ti,Al,Si)N hard coatings deposited by a triple cathode magnetron sputtering arrangement is presented. The three cathodes, equipped with aluminium, silicon and titanium targets, respectively, were adjusted at a low angle to the surface. Additionally, a system of apertures was mounted between the cathodes. The relation between composition and structure of the resulting materials library was investigated by a combination of electron probe microanalysis (EPMA) and scanning x‐ray diffraction. Copyright © 2002 John Wiley & Sons, Ltd.
Coating of Ti–6Al–4V alloy substrates with Ti–N films by reactive d.c. sputtering
Authors: Sonoda T. , Watazu A. , Zhu J. , Shi W. , Kamiya A. , Kato K. , Asahina T. 
Published: October 2002

AbstractThe coating of Ti–6Al–4V alloy substrates with Ti–N films by reactive d.c. sputtering in an Ar–N2 gas mixture was examined to improve not only the blood compatibility but also the hardness and thereby the abrasion resistance of the alloy. The effects of discharge voltage on the formation of the Ti–N film were investigated. Under visual observation, the films deposited at various voltages appeared to be uniform and adhesive, whereas their colour tone varied with the voltage and the films obtained under a voltage of >400 V looked yellow‐gold. With SEM, the surface of the films deposited under various voltages were observed to consist of fine particles. According to AES, the Ti/N ratio in the depth direction was nearly constant in each of the films. On the basis of x‐ray diffraction, it was concluded that a Ti2N phase was formed predominantly in films deposited at 350 V whereas a TiN phase was formed predominantly in films deposited at a voltage of >400 V and the crystallinity of these phases was developed by heating the substrates to >400°C. Furthermore, it was found that the Vickers hardness Hv reached >2400 for films deposited at a voltage of >400 V onto the substrates and heated to >400°C. Therefore it was expected that the Ti–N films deposited onto the alloy substrates heated to >400°C under a voltage of >400 V could serve to improve not only the blood compatibility but also the hardness and thereby the abrasion resistance of the alloy. Copyright © 2002 John Wiley & Sons, Ltd.
STM and XRD studies of the adsorption and assembling structures of phthalocyanine and porphyrin
Authors: Lei S. B. , Wang J. , Dong Y. H. , Wang C. , Wan L. J. , Bai C. L. 
Published: October 2002

AbstractUsing scanning tunnelling microscopy (STM) and x‐ray diffraction (XRD), the assembling behaviour of substituted phthalocyanine and porphyrin on both hydrophobic and hydrophilic surfaces was investigated. Copper (II) 2,3,9,10,16,17,23,24‐octakis(octyloxy)‐29H,31H‐phthalocyanine (denoted as CuPcOC8) and 21,23‐dihydro‐5,10,15,20‐tetrakis[4‐(tetradecyloxy)phenyl]porphyrin (TTPP) molecules adsorb stably on a highly oriented pyrolytic graphite (HOPG) surface, yielding high‐resolution STM images. The results illustrate that alkyl molecular anchors can be used as a generalized approach for immobilization of organic molecules on hydrophobic surfaces. The XRD results show that on a hydrophilic substrate CuPcOC8 and TTPP form completely different assembled structures from those on a HOPG surface, which indicates that the polarity of the substrate has substantial effects on the assembling behaviour of organic molecules. Copyright © 2002 John Wiley & Sons, Ltd.
Preparation and characterization of Langmuir–Blodgett‐type arachidate films
Authors: Mohai M. , Kiss É. , Tóth A. , Szalma J. , Bertóti I. 
Published: October 2002

AbstractMetal arachidate Langmuir–Blodgett (LB) films with Pb2+ and Cd2+ cations and varying numbers of monomolecular layers (2 and 4 monolayers, ML) were deposited on trimethylsilylated glass substrates. The arachidate salt formation was commenced during the film deposition from a water‐based solution. The extent of salt formation and the build‐up of the LB layer were evaluated by quantitative XPS.The completeness of the salt formation was assessed by the atomic ratio of the carboxylic (‐COO‐)‐type carbon component with C 1s binding energy at ∼288.5 eV to that of the selected line of the actual cation.The surface coverage of the glass substrate by the LB film was assessed by calculations based on a substrate–overlayer model using the XPS MultiQuant program. According to this model, the attenuation of the Si 2p photoelectron signal from the substrate by the 2 and 4 ML LB films (with 56 and 112 Å thickness, respectively) was calculated and compared with the measured intensities, enabling the completeness of the layer to be evaluated. The layer thickness values calculated from the measured intensity of the layer constituents reflected accurately the thickness derived from the geometry of the arachidate molecule, confirming both the adequacy of the model and the accuracy of the measurement.In agreement with earlier results it was confirmed that salt‐based LB films are fairly stable under high vacuum conditions, although slow decomposition of lead arachidate films was detected during prolonged x‐ray irradiation. Copyright © 2002 John Wiley & Sons, Ltd.
Use and limitations of electron flood gun control of surface potential during XPS: two non‐homogeneous sample types
Authors: Baer D. R. , Engelhard M. H. , Gaspar D. J. , Lea A. S. , Windisch C. F. 
Published: October 2002

AbstractThe ability of charge compensation methods to control surface potential is examined for two types of non‐homogenous samples: a small conducting dot on an insulating substrate and an insulating thin film on a conductive substrate. Results demonstrate that two newer types of charge compensation systems have improved performance in relation to some previous flood gun systems, while reaffirming the concept that a primary objective of charge compensation is to find conditions for which the surface potential of the specimen is as uniform as possible. However, experiments involving both flood gun use and specimen grounding demonstrate that peak broadening and shifting can occur when two (or more) potentials are present in the region of analysis. Finally, the ability of interface charge to shift specimen potentials and measured binding energies demonstrates fundamental limitations to the absolute accuracy of binding energy measurements, but also remind us that charging phenomena can be used to obtain important information about the sample. Copyright © 2002 John Wiley & Sons, Ltd.
Investigation of sulphur diffusion at the CdS/CdTe interface of thin‐film solar cells
Authors: Gibson P. N. , Baker M. A. , Özsan M. E. 
Published: October 2002

AbstractDiffusion of atoms across the CdS/CdTe interface during post‐deposition annealing is thought to have an important effect on the performance of CdS/CdTe‐based solar cells. Thin‐film solar cell samples were annealed at 400°C for three different times. The samples were etched sequentially in a bromine/methanol solution and then examined with Auger depth profiling and X‐ray diffraction. Profiling showed the as‐deposited samples to have little or no interfacial mixing, but annealing even for a short time caused diffusion of sulphur into the CdTe material. As the annealing times lengthened, the concentration of sulphur in the CdTe increased. X‐ray diffraction measurements indicated that the CdS layer rapidly crystallized into its hexagonal Greenockite modification, but with lattice parameters increased by 0.8%. This changed little with annealing time. The CdTe near the interface appeared to have a modified but well‐defined cubic structure with respect to reference CdTe, as indicated by splitting of the diffraction peaks, denoting the growth of a CdTexSy interfacial layer. This layer increased in thickness with annealing time and most probably has a stoichiometry within the range CdTeS0.04–CdTe0.88S0.12. Copyright © 2002 John Wiley & Sons, Ltd.
Pigment effects on ink–polymer bonding
Authors: West Robin H. 
Published: October 2002

AbstractPigment electrical properties are shown to influence the adhesion strength of ink bonding to ionomer polymer films exposed briefly to high relative humidity. Weakening of the ink/polymer interface is caused by the rapid formation of an interphase region that contains sodium ions and nitrate‐containing species. Replacing organic pigments with titanium dioxide inhibits the formation of the interphase region. A model based on electric field formation between counter‐ions and field attenuation from the pigment dielectric constant is proposed for the interphase formation. The model is tested using inks with mixed pigments and a direct correlation is found between nitrate enrichment in the interphase and relative electric field strength at the interface. Copyright © 2002 John Wiley & Sons, Ltd.
Replacing the no‐effect level (NOEL) with bounded effect levels (OBEL and LEBEL)
Authors: Hansson Sven Ove 
Published: October 2002

AbstractFrom experiments or epidemiological studies designed to search for a particular toxic effect, it is in general possible to determine an upper bound for that effect. This observed bounded effect level (OBEL) is defined for both positive and negative experiments. It is non‐zero even for negative experiments, and it is inversely related to the size of the exposed group. The OBEL can be used to determine the linearly extrapolated bounded effect level (LEBEL) for various effect doses. Contrary to no‐observed‐effect' levels (NOELs), LEBEL values are designed to protect against type II (false negative) errors. It is proposed that LEBEL values replace NOELs as a tool for decision‐making. Copyright © 2002 John Wiley & Sons, Ltd.
Interval estimation of generalized odds ratio in data with repeated measurements
Authors: Lui Kung‐Jong 
Published: October 2002

AbstractWhen the underlying responses are on an ordinal scale, the generalized odds ratio (GOR), defined as the ratio of the proportions of concordant and discordant pairs, is a useful index to summarize the difference between two stochastically ordered distributions of an ordinal categorical variable. We discuss interval estimation of the GOR for ordinal data with repeated measurements. On the basis of the Dirichlet‐multinomial model, we develop three asymptotic interval estimators of the GOR using Wald's test statistic, a logarithmic transformation, and a method analogous to Fieller's theorem, respectively. To evaluate and compare the finite‐sample performance of these estimators, we apply Monte Carlo simulation. We find that when the number of subjects per group is not large, the coverage probability of interval estimator using Wald's test statistic is likely to be less than the desired confidence level. By contrast, the coverage probability of the other two estimators are approximately equal to or larger than the desired confidence level. When the number of subjects per group is small and the intraclass correlation between repeated measurements within subjects is large, we note that applying the interval estimator derived from a method analogous to Fieller's theorem can lose efficiency. We also note that the interval estimator using the logarithmic transformation is generally preferable to the other two estimators with respect to both the coverage probability and the average length. Finally, on the basis of a few preliminary simulations, we do find some robustness for all the estimators developed here. We include an example comparing the inflammation grade after lung transplant between surgeries to illustrate the use of the proposed interval estimators. Copyright 2002 John Wiley & Sons, Ltd.
Clinical trials in the new millennium
Authors: DeMets David L. 
Published: October 2002

AbstractSince the introduction of the randomized clinical trial (RCT) over 50 years ago, this method has become the corner stone for evaluating new pharmacologic or biologic agents with many disease areas benefiting. There are numerous examples demonstrating beneficial interventions as well as others either not beneficial or harmful. Statistical methodology for clinical trials has grown rapidly. Advances in information technology for data collection have allowed trials to be conducted around the world. Academia, industry and government have worked in partnership to conduct RCTs. Despite these many RCT achievements, the most interesting and challenging era of clinical trials lies ahead of us. With the human genome now sequenced, we face a new set of challenges to transform vast amounts of data into useful information. The post‐genomics era will better identify the disease mechanism and thus help design better treatments, and be more selective in screening patients, yielding more efficient clinical trials. For some areas of medicine, such as medical devices, standards of acceptance and regulatory approval are changing. Other areas, such as medical procedures and alternative medicines, are generally not well evaluated and could benefit greatly from a wider use of RCT methodology. As the ICH guidelines facilitate and encourage international clinical trials, the scientific and ethical dimension of conducting trials in Third World countries are raised. For example, Western society's best standard of care may not be available or affordable to these countries as the control Western investigators should not exploit patients in the Third World. Those and many other challenges face us in the decade ahead. It is truly an exciting time with new opportunities for the RCT to contribute to medicine and health care or prevention. Copyright © 2002 John Wiley & Sons, Ltd.
Advanced issues in the design and conduct of randomized clinical trials: the bigger the better?
Authors: Warlow Charles 
Published: October 2002

AbstractLarge trials provide more precise estimates of treatment effects than small trial (how good is the treatment?) and they may allow a few sensible and pre‐defined sub‐group analyses (for whom does the treatment work best?). But large trials will not get done unless they are simple and as part of normal clinical practice as possible. Copyright © 2002 John Wiley & Sons, Ltd.
Policy developments in regulatory approval
Authors: Temple Robert 
Published: October 2002

AbstractAlthough radical changes in drug regulation are rare (e.g., the Federal Food, Drug and Cosmetic Act of 1938 and the 1962 amendment to the Act creating an effectiveness requirement), regulations and guidance do evolve significantly in the face of new problems and accumulating experience. Recent changes have been driven by the Food and Drug Administration Modernization Act (FDAMA), user fee legislation, the International Conference on Harmonization, recent safety related drug withdrawals, and concerns about trial ethics and investigator conflict of interest.FDAMA and guidance developed in response to it has helped circumstances in which FDA would rely on a single study to support effectiveness and the circumstances in which surrogate endpoints could support approval. An ICH Document ‘Choice of control group and related design issues in clinical trials’ focussed attention on the ethics of placebo controls (acceptable, even if there is existing therapy, when the placebo‐treated patient will suffer no irreversible injury) and the design of ‘equivalence’ or ‘non‐inferiority’ trials.There has been greatly increased attention to obtaining good dose‐response information and to assessing need for modifying treatment in demographic (age, gender, race) and concomitant disease (renal or hepatic function abnormalities) subgroups, and in assessing drug–drug interactions.Other important trends are increasing reliance on non‐U.S. data, increasing numbers of FDA‐industry meetings during drug development, and new focus on risk assessment and risk management. Published in 2002 by John Wiley & Sons, Ltd.
Issues in the meta‐analysis of cluster randomized trials
Authors: Donner Allan , Klar Neil 
Published: October 2002

AbstractMeta‐analyses involving the synthesis of evidence from cluster randomization trials are being increasingly reported. These analyses raise challenging methodologic issues beyond those raised by meta‐analyses which include only individually randomized trials. In this paper we review and comment on a selected number of these issues, including problems of study heterogeneity, difficulties in estimating design effects from individual trials and the choice of statistical methods. Copyright © 2002 John Wiley & Sons, Ltd.